Active and passive vehicle safety. The best cars for comfort The most comfortable Chinese cars

The study of the working conditions of drivers indicates the significant importance of the parameters of the internal environment in the car. These parameters are only more or less likely to comply with the established standards, which allows us to extend the concept of reliability to the system that provides the conditions for the habitability of people in the car. In some cases, operational observations are indirect evidence of its insufficient reliability. According to the results of a survey of a large number of professional drivers about the influence of internal environmental factors, the temperature regime in the cab was negatively assessed (hot in summer, cold in winter) - 49% of drivers; the presence of toxic substances (air pollution by exhaust gases) - 60%; vibration influence - 45%, noise -

56% of surveyed drivers.

1.13.1. Climate comfort

Abnormal climatic conditions in the car cabin have a harmful effect on the health of the driver and are one of the reasons contributing to the occurrence of an accident. Under the influence of high or low temperature in the cab, the driver's attention is dulled, visual acuity decreases, reaction time increases, fatigue sets in quickly, errors and miscalculations appear that can lead to an accident.

One of the requirements of occupational safety and health is to exclude the possibility of penetration into the driver's cab of spent

gases that contain a number of toxic components, including carbon monoxide. Depending on the proportion of carbon monoxide in the air and the duration

the driver's work in such an atmosphere, the impact is different.

The most characteristic signs of minor poisoning are drowsiness, fatigue, intellectual passivity, impaired

spatial coordination of movements, errors in determining the distance and an increase in the latent period during sensorimotor reactions. Studies have shown that only a small

amount of carbon monoxide to make some people feel intoxicated, intoxicated, headache, drowsiness and disorientation, i.e. such deviations that can lead to an exit from the road, an unexpected turn of the steering wheel, falling asleep.

Carbon monoxide is sucked into the passenger compartment along with exhaust gases in case of technical malfunctions of the car. Deprived of any odor and color, carbon monoxide remains perfectly clean for a long time.

inconspicuous. At the same time, a working person is poisoned three times faster than a person who is at rest.

It should be borne in mind that carbon monoxide enters the driver's workplace also along with exhaust gases emitted by engines of other vehicles. This is especially dangerous for drivers of passenger cars - taxis, city buses and trucks, systematically working in conditions of heavy and dense traffic Vehicle in cities whose highways are filled with exhaust gases.

Studies of the air environment in driver's cabins and passenger compartments of buses have shown that in some cases the content of carbon monoxide reaches 125 mg/m3, which is several times higher than the maximum permissible concentration for working area driver. Therefore, long-term driving of a car exceeding 8 hours in urban conditions is extremely dangerous due to the possibility of poisoning the driver with carbon monoxide.

Conditions in which a person does not experience overheating or hypothermia, sudden movement of air and other unpleasant sensations can be considered thermally comfortable. Comfortable conditions in winter period somewhat different from the same conditions in the summer, which is associated with the use of different clothes by a person. The main factors that determine the thermal state of a person are temperature, humidity and air velocity, temperature and properties of the surfaces surrounding a person. With various combinations of these factors, it is possible to create equally comfortable conditions in the summer and winter periods of operation. In view of the variety of features of heat exchange between the human body and the external environment, the choice of a single criterion that characterizes comfortable conditions and is a function of environmental parameters is a difficult task. Therefore, comfortable conditions are usually expressed as a set of indicators that limit individual parameters: temperature, humidity, air speed, maximum air temperature difference in the body and outside it, temperature of surrounding surfaces (floor, walls, ceiling), radiation level, air supply to a confined space (body , cabin) per person per unit time or air exchange rate.

Comfortable values of air temperature and humidity recommended by various researchers differ somewhat. Yes, Institute of Hygiene

performing light work, the air temperature in winter

20...22°C, in summer +23...25°C at its relative humidity of 40...60%.

Permissible air temperature is +28°C at the same humidity and low speed (about 0.1 m/s).

According to the results of French researchers, for light winter work, an air temperature of +18 ... 20 ° C is recommended with a humidity of 50 ... 85%, and

for summer +24...28 °С at air humidity 35...65%.

According to other foreign data, car drivers must work with more low temperatures(+15...17°С during the winter period of operation and

18...20°C in summer) at a relative air humidity of 30...60% and

the speed of its movement is 0.1 m/s. In addition, the temperature difference between the outside air and inside the body during the summer period should not exceed 10 ° C. The temperature difference inside the limited volume of the body in order to avoid human colds should not exceed 2 ... 3 ° C.

Depending on the working conditions, in order to ensure comfortable conditions, the temperature in winter can be taken equal to + 21 ° С with mild

work, +18.5°C for moderate, +16°C for severe.

At present, microclimatic conditions on cars are regulated in Russia.

So, for cars, the air temperature in the cab (body) in summer should not be higher than +28 C, in winter (at an outside temperature of -20 ° C) - at least + 14 ° C. V summer time when the car is moving at a speed of 30

km/h, the difference between the internal and external air temperatures at the level of the driver's head should not be more than 3°С at an external temperature of +28°С and more than 5°С at an external temperature of +40°С. In winter time in the zone

positioning of the legs, belt and head of the driver should ensure the temperature is not lower than +15°C at an outside temperature of -25°C and not lower than +10°C at an outside temperature of -40°C.

Humidity in the cabin should be 30 ... 70%. The supply of fresh air to the cabin must be at least 30 m3/h per person, the speed of air movement in the cabin and the passenger compartment is 0.5...1.5 m/s. The maximum concentration of dust in the cabin (cabin) should not exceed 5 mg/m3.

Ventilation system devices must create an excess pressure of at least 10 Pa in a closed cabin.

The maximum concentration of dust in the cabin (cabin) should not exceed 5 mg/m3.

The maximum permissible concentrations of harmful substances in the air of the working areas of the passenger compartment and the cab of the car are regulated by GOST R 51206 - 98 for cars, in particular: carbon monoxide (CO) - 20 mg / m3; nitrogen oxides in terms of NO2 – 5 mg/m3; total hydrocarbons (Сn Нm) – 300 mg/m3; acrolein (С2Н3СНО) – 0.2 mg/m3.

The concentration of gasoline vapors in the cabin and cabin of the vehicle should not exceed 100 mg/m3.

The temperature regime in the cabin (body) can be approximately

calculated according to the heat balance equation, according to which the air temperature in the cabin (body) remains constant:

The flow of heat into the cabin from various sources. V

In most cases, the heat balance of the cabin (cabin) is determined by a number of factors, the main of which are: the number of people in the cabin (cabin) and

quantity of heat

QH coming from them; quantity of heat,

coming through transparent barriers

(mainly from

solar radiation) and opaque fences

(quantity of heat,

coming from the engine

Qeng, transmissions

QTP, hydraulic equipment

electrical equipment fan.

In this way,

QEO) and together with outside air

QVN supplied

ΣQi  QCh  QCh  QP.O  QNP.O  QDV  QTR  QGO  QEO  QVN  0

It should be noted that the heat balance terms included in the equation should be taken into account algebraically, i.e. with a positive sign when heat is released into the cabin and with a negative sign when it is removed from the cabin. Obviously, the heat balance condition is met if the amount of heat entering the cabin is equal to the amount of heat removed from it.

Temperature conditions and air mobility in the cabins of vehicles are provided by heating, ventilation and air conditioning systems.

Currently, there are various ventilation and heating systems for cabins and car interiors, differing in layout and design. individual nodes. The most economical and widely used

modern cars is a heating system that uses the heat liquid cooling engine. The combination of heating systems and general ventilation of the cabin allows you to increase the efficiency of the entire complex of devices for ensuring the microclimate in the cabin throughout the year.

Heating and ventilation systems differ mainly in the location of the air intake on the outer surface of the car, the type of fan used and its location relative to the radiator

heater (at the inlet or outlet of the radiator), the type of radiator used (tubular-lamellar, tubular-tape, with an intensified surface, matrix, etc.), control method

the operation of the heater, the presence or absence of a bypass air duct,

recirculation channel, etc.

The intake of air from outside the cab into the heater is carried out in the place of the minimum dust content of the air and the maximum dynamic pressure,

occurring while the vehicle is in motion. In trucks, the air intake is located on the cab roof. Water-repellent partitions, blinds and covers are installed in the air intake,

powered from inside the cab.

An axial fan is used to provide air supply to the cabin and overcome the aerodynamic resistance of the radiator and air ducts.

radial, diametrical, diagonal or other type. Currently, the most widely used double-console radial fan, as it has a relatively small size with a large

performance.

DC motors are used to drive the fan. The speed of rotation of the electric motor and, accordingly, the fan impeller is regulated by a two- or three-stage variable resistor included in the power supply circuit of the electric motor.

The heat output of the heater and its

aerodynamic drag. To increase the efficiency of heat transfer from the radiator, the shape of its channels through which air moves is complicated, various turbulators are used.

A decisive role in the effective uniform distribution of temperatures and air velocities in the cabin is played by the air distributor. The air distributor nozzles are made in various shapes: rectangular,

round, oval, etc. They are placed in front of the windshield, near the door windows, in the center of the instrument panel, at the driver's feet and in other places determined by the requirements for the distribution of fresh air

flows in the cab.

In the nozzles, various dampers, rotary shutters,

control plates, etc. The drive for dampers and rotary shutters is most often located directly in the air distributor housing.

Air ducts to the air distributor are made of sheet steel, rubber hoses, corrugated plastic pipes, etc. V

some cars use cabin parts, the cavity of the instrument panel as air ducts. However, such a design of air ducts is irrational, since tightness is not ensured and air consumption increases. Vehicle traffic safety is largely

depends on reliable and effective protection of the windshield from fogging and freezing, which is achieved by uniform blowing of warm air and heating to a temperature above the dew point.

Such glass protection is structurally simple, does not impair its optical properties, but requires an increase in the ventilation system performance and a high heat capacity of the glass. The effectiveness of glass jet protection against

fogging is determined by the temperature and air velocity at the outlet of the nozzle located in front of the glass edge. The higher the air velocity at the outlet of the nozzle, the lower the temperature in the glass zone differs from

temperature at the nozzle exit.

The layout of the ventilation and heating system depends on the design of the vehicle, cab, individual components and their placement.

At present, air conditioners have become widespread - devices for

artificial cooling of the air entering the cabin (body). According to the principle of operation, air conditioners are divided into compression, air-cooled, thermoelectric and evaporative. Automatic control of the heater operation mode of some vehicles is carried out by changing the flow rate of liquid or air through the heater radiator. With automatic control by changing

air flow parallel to the radiator, a bypass air channel is made, in which a controlled damper is installed.

As already noted, an important place in the ventilation system of the cabin (body)

the car is occupied by cleaning the ventilation air from dust.

The most common way is to clean the ventilation air using filters made of cardboard, synthetic fiber materials,

modified polyurethane foam, etc. However, in order to effectively use such filters, which are characterized by low dust capacity, with fewer maintenance,

dust concentration at the filter inlet. For preliminary air purification, inertial type dust separators are installed at the inlet to the filter with continuous removal of trapped dust.

The basic principles of ventilation air dedusting are based on the use of one or more mechanisms for the deposition of dust particles from the air: the inertial separation effect and the effects of engagement and

deposition.

Inertial sedimentation is carried out with the curvilinear movement of dusty air under the action of centrifugal and Coriolis forces. On the

The settling surface is discarded by particles whose mass or velocity are significant and cannot follow the flow line around the obstacle along with the air. Inertial settling is manifested and

when the obstacles are the filling elements of filters made of fibrous materials, the ends of flat sheets of inertial louvered grilles, etc.

When dusty air moves through the porous partition of the particle,

suspended in the air, linger on it, and the air completely passes through it. Studies of the filtration process are aimed at establishing the dependence of dust collection efficiency and aerodynamic resistance on the structural characteristics of porous partitions, dust properties and air flow regime.

The process of air purification in fibrous filters occurs in two stages.

At the first stage, particles are deposited in a clean filter without structural changes in the porous partition. In this case, changes in the thickness and composition of the dust layer are not significant and can be neglected. At the second stage, continuous structural changes in the dust layer and further deposition of particles in a significant amount occur. This changes the dust collection efficiency of the filter and its aerodynamic resistance, which complicates the calculation of the filtration process. The second stage is complex and little studied; under operating conditions, it is this stage that determines the efficiency of the filter, since the first stage is very short-lived. Of the variety of filter materials used in the filters of the cabin ventilation air dedusting system, three groups can be distinguished: woven from natural, synthetic and mineral fibers; non-woven - felt, paper, cardboard, needle-punched materials, etc.; cellular - polyurethane foam, sponge rubber, etc.

For the manufacture of filters, materials of organic origin and artificial are used. Organic materials include cotton, wool. They have low heat resistance, high moisture capacity. A common disadvantage of all filter materials of organic origin is their susceptibility to putrefactive processes and the negative effects of moisture. Synthetic and mineral materials include: nitron, which has a high resistance to temperatures, acids and alkalis; chlorane having low heat resistance but high chemical resistance; capron, characterized by high resistance to abrasion; oxalon having high heat resistance; glass fiber and asbestos, which are distinguished by high heat resistance, etc. The filter material made of lavsan has high rates of dust-catching, strength and regeneration parameters.

Wide application in filters with pulsed air purge during filter regeneration has received non-woven needle-punched polyester

filter materials. These materials are obtained by compacting the fibers, followed by stitching or needle punching.

The disadvantage of such filter materials is the passage of more

fine dust particles through the holes formed by the needles.

A significant disadvantage of filters made of any filter material is the need to replace them or Maintenance with the aim of

regeneration (recovery) of the filter material. Partial filter regeneration can be carried out directly in the ventilation system by blowing back the filter material with purified air from the vehicle cabin or by local jet air blowing

from compressor with pre-cleaning compressed air from water vapor and oil.

Design of filters made of woven or non-woven filter media

for cabin ventilation systems should have a maximum filtration surface at minimum sizes and aerodynamic drag. Installing the filter in the cabin and changing it should be convenient and ensure reliable tightness around the filter perimeter.

1.13.2. Vibration comfort

From the point of view of reaction to mechanical excitations, a person is a kind of mechanical system. At the same time, various internal organs and individual parts of the human body can be considered as masses interconnected by elastic bonds with the inclusion of parallel resistances.

Relative movements of parts of the human body lead to stresses in the ligaments between these parts and mutual impact and pressure.

Such a viscoelastic mechanical system has natural frequencies and rather pronounced resonant properties. resonant

the frequencies of individual parts of the human body are as follows: head - 12 ... 27 Hz,

throat - 6 ... 27 Hz, chest - 2 ... 12 Hz, legs and arms - 2 ... 8 Hz, lumbar spine - 4 ... 14 Hz, abdomen - 4 ... 12 Hz. The degree of harmful effects of vibrations on the human body depends on the frequency, duration and direction of vibration, individual characteristics of a person.

Long fluctuations of a person with a frequency of 3 ... 5 Hz adversely affect the vestibular apparatus, the cardiovascular system and cause motion sickness. Oscillations with a frequency of 1.5 ... 11 Hz cause disorders due to resonant vibrations of the head, stomach, intestines and, ultimately, the whole body. With fluctuations with a frequency of 11 ... 45 Hz, vision deteriorates, nausea and vomiting occur, and the normal activity of other organs is disrupted. Fluctuations with a frequency of more than 45 Hz cause damage to the vessels of the brain, a disorder of blood circulation and higher nervous activity occurs, followed by the development of a vibration disease. Since vibration under constant exposure has an adverse effect on the human body, it is normalized.

The general approach to normalizing vibration is to limit the vibration acceleration or vibration velocity measured at the driver's workplace to

depending on the direction of the vibration, its frequency and duration.

Note that the smooth running of the machine is characterized by general vibration,

transmitted through the supporting surfaces to the body of a seated person. Local vibration is transmitted through the hands of a person from the controls of the machine, and its influence is less significant.

The dependence of the mean square value of the vertical

vibration acceleration az of a seated person as a function of the oscillation frequency at its constant vibration loading is shown in fig. 1.13.1 (curves of "equal thickening"), from which it can be seen that in the frequency range f = 2 ... 8 Hz, the sensitivity of the human body to vibration increases.

The reason for this lies precisely in the resonant vibrations of various parts of the human body and its internal organs. Most curves

"equal thickening" obtained by exposing the human body to harmonic vibration. With random vibration, the curves of "equal thickening" in different frequency ranges have a common character, but

quantitatively different from harmonic vibration.

Hygienic assessment of vibration is carried out by one of three methods:

frequency (spectral) analysis; integral estimate by frequency and

"dose of vibration".

In the case of separate-frequency analysis, the normalized parameters are the root-mean-square values of vibration velocity V and their logarithmic levels Lv or vibration acceleration az for local vibration in octave frequency bands, and for general vibration - in octave or one-third octave frequency bands. When normalizing vibration, "equal thickening" curves were first taken into account in ISO 2631-78. The standard establishes the permissible mean square values of vibration acceleration in one-third octave bands

frequencies in the range of geometric mean frequencies of 1...80 Hz at various durations of vibration action. ISO 2631-78 provides for the evaluation of both harmonic and random vibration. In this case, the direction of the general vibration is usually estimated along the axes of the orthogonal coordinate system (x - longitudinal, y - transverse, z - vertical).

Rice. 1.13.1. Equal Condensation Curves for Harmonic Vibration:

1 - threshold of sensations; 2 - the beginning of discomfort

A similar approach to vibration regulation is used in GOST

12.1.012-90, the provisions of which are the basis for determining the criterion and indicators of the smooth running of cars.

The concept of “safety” was introduced as a criterion for smooth running, not

causing health problems for the driver.

Ride ratings are usually assigned according to the output value, which is the vertical vibration acceleration az or the vertical vibration velocity Vz determined from the driver's seat. It should be noted here that when assessing the vibration load on a person, the vibration acceleration is the preferred output value. For sanitary standardization and control, the vibration intensity is estimated by the root mean square

az value

vertical vibration acceleration, as well as its logarithmic

Threshold RMS vertical

vibration acceleration.

RMS value az

called "controlled"

parameter", and the smoothness of the machine is determined with constant vibration in the frequency range of 0.7 ... 22.4 Hz.

In the integral assessment, a frequency-corrected value of the controlled parameter is obtained, which takes into account the ambiguity of human perception of vibration with a different spectrum

frequencies. Frequency-corrected value of the controlled parameter az

and its logarithmic level

determined from expressions:

~ ∑ (k zi a zi) ;

 10 lg ∑100.1(Lazi  Lkzj) ,

– root mean square value of the controlled parameter

and its logarithmic level in the i-th octave or one-third octave band;

- weighting factor for the root mean square value

controlled parameter and its logarithmic level in the i-th band

kzi i ; n is the number of bands in the normalized frequency range.

The values of the weight coefficients are given in Table 1.13.1.

Table 1.13.1

The average value of the frequency of a third octave and

One third octave frequency band

Octave Bandwidth

octave bands

According to sanitary standards, with a shift duration of 8 hours and general vibration, the standard mean square value of vertical vibration acceleration is 0.56 m/s2, and its logarithmic level is 115 dB.

When determining the vibration load on a person using the vibration spectrum, the normalized indicators are the root mean square value of vibration acceleration or its logarithmic level in one-third octave and octave frequency bands.

Permissible values of spectral indicators of vibration load per person are given in Table. 1.13.2.

Table 1.13.2

Sanitary standards for spectral indicators of vibration load for vertical vibration acceleration

geometric

Standard average

quadratic value

Regulatory

logarithmic

one-third octave frequency value

vibration acceleration

and octave

third octave

frequency band

Octave

frequency band

third octave

frequency band n

In the case of applying the integral and separate-frequency methods for assessing the vibration load on a person, one can come to different results. As a priority, it is recommended to use the method of separate-frequency (spectral) assessment of the vibration load.

At present, normative indicators of the smoothness of the movement of machines, such as vibration accelerations and

vibration velocities in the vertical and horizontal planes, set differentially for different vibration frequencies.

The latter are grouped into seven octave bands with an average geometric frequency from 1 to 63 Hz (Table 1.13.3.).

Table 1.13.3

Normative indicators of the smoothness of the movement of transport vehicles

Parameter

Vibration velocity,

Average geometric oscillation frequency, Hz

1 2 4 8 16 31,5 6

vertical horizontal Vibration acceleration, m/s2: vertical horizontal

On a number of special wheeled and tracked vehicles operated in difficult road conditions, where the amplitudes of the microprofile are significant, it is difficult to ensure the values of the ride smoothness indicators regulated for transport technology. Therefore, for such machines, standard indicators of smooth running are set at a lower level (Table 1).

Table 1.13.4

Normative indicators of smoothness for machines operating in difficult road conditions

Acceleration in the workplace

driver - (operator)

Vertical:

root mean square maximum from episodic

tremors

maximum from rotary shocks

Horizontal RMS

Transport traction

Ride comfort standards for trucks, buses, cars, trailers and semi-trailers are defined for three types of sections of the NAMI polygon:

I – cement dynamometric road with r.m.s. value of roughness heights 0.006 m;

II - cobblestone paved road without potholes with RMS

roughness values 0.011 m;

III - cobblestone road with potholes with r.m.s. roughness values of 0.029 m.

Vehicle smoothness standards established by OST 37.001.291-84,

are given in table. 1.13.5, 1.13.6, 1.13.7.

To improve the smooth running of cars, the following measures are used:

The choice of the layout scheme of the car, ensuring the independence of oscillations on the front and rear suspension sprung mass of the machine;

The choice of the optimal characteristics of the elasticity of the suspension;

Ensuring the optimal ratio of rigidity of the front and rear suspensions of the car;

Reducing the mass of unsprung parts;

Suspension of the cab and driver's seat of a truck and road train.

Table 1.13.5

Limit technical standards smooth running of trucks

Corrected values of vibration accelerations on seats, m/s2, no more

horizontal

RMS values of vertical

vibration accelerations in

road vertical

al longitudinal

characteristic points of the sprung part, m/s2, no more

Table 1.13.6

Limit technical standards for smooth running of passenger cars

The corrected values of vibration accelerations on the driver's seats and

Road type

passengers, m/s2, no more

vertical horizontal

Table 1.13.7

Limit technical standards for the smooth running of buses

Corrected values of vibration accelerations on bus seats, m/s2, no more

urban other types

driver passengers driver and passengers

1.13.3. Acoustic comfort

Various noises occur in the cab of the car, which adversely affect the driver's performance. First of all, the auditory function suffers, but noise phenomena, having cumulative properties (i.e., properties to accumulate in the body), depress the nervous system, while psychophysiological functions change, the speed and accuracy of movements are significantly reduced. Noise causes negative emotions, under its influence the driver develops absent-mindedness, apathy, memory impairment. The impact of noise on a person can be subdivided depending on the intensity and spectrum of noise into the following groups:

Very strong noise with levels of 120 ... 140 dB and above - regardless of the spectrum, it can cause mechanical damage to the hearing organs and cause severe damage to the body;

Strong noise with levels of 100 ... 120 dB at low frequencies, above 90 dB at medium frequencies and above 75 ... 85 dB at high frequencies - causes irreversible changes in the hearing organs, and with prolonged exposure it can be

the cause of a number of diseases and, first of all, the nervous system;

Noise at lower levels of 60 ... 75 dB at medium and high frequencies has a harmful effect on the nervous system of a person engaged in work that requires concentrated attention, to which work belongs

car driver.

Sanitary standards divide noise into three classes and set an acceptable level for them:

Class 1 - low-frequency noise (the largest components in the spectrum are located below the frequency of 350 Hz, above which the levels decrease) with an allowable level of 90 ... 100 dB;

Class 2 - mid-frequency noise (the highest levels in the spectrum

located below the frequency of 800 Hz, above which the levels decrease) with an allowable level of 85 ... 90 dB;

Class 3 - high-frequency noise (the highest levels in the spectrum are located above the frequency of 800 Hz) with an allowable level of 75 ... 85 dB.

Thus, the noise is called low-frequency when the oscillation frequency is not

more than 400 Hz, mid-frequency - 400 ... 1000 Hz, high-frequency - more

1000 Hz. At the same time, according to the frequency of the spectrum, noise is classified into broadband, including almost all frequencies of sound pressure (the level is measured in dBA), and narrow-band (the level is measured in dB).

Although the frequency of acoustic sound vibrations is in the range of 20 ... 20,000

Hz, its normalization in dB is carried out in octave bands with a frequency of 63 ...

8000 Hz constant noise. The characteristic of intermittent and broadband noise is equivalent in energy and perception

human ear sound level in dBA.

Permissible levels of internal noise for vehicles according to

GOST R 51616 - 2000 are given in table. 1.13.8.

It should be noted that the permissible levels of internal noise in the cabin or saloon are set regardless of whether there is one source here.

noise or more. Obviously, if the sound power emitted by one source satisfies the maximum permissible sound pressure level at the workplace, then when installing several such sources

the indicated maximum allowable level will be exceeded due to the sum of their effects. As a result, the overall noise level is determined by the law of energy summation.

Table 1.13.8

Permissible levels of internal noise of vehicles

Permissible

motor vehicle

Cars and buses for the transport of passengers

sound level, dB A

M 1, except for wagon models or

half-bonnet body layout

M 1 - models with wagon or 80

semi-bonnet body layout.

M 3 , except models with

the location of the engine in front of or next to the place

driver: 78 in the driver's workplace 80 in the passenger area of class II buses 82

in the passenger area of class I buses

Models with arrangement 80

engine in front of or next to the driver's seat:

at the driver's workplace and in the passenger 80

indoors

Vehicles for the transport of goods

N1 gross weight up to 2 t 80

N1 GVW from 2 to 3.5 t 82

N3 , except models,

intended for international and 80

intercity transportation

Models for international and 80

intercity transportation

Trailers designed for the transport of passengers 80

Total noise level, dBA, from several identical sources

LΣ  L1  10 lg⋅ n ,

L1 – noise level of one source, dBA;

n is the number of noise sources.

With the simultaneous action of two sources with different sound pressure levels, the total noise level

LΣ  La  ∆L ,

– the largest of the two summed noise levels;

∆L – additive depending on the difference in noise levels between two sources

∆L values

depending on the difference between the noise levels of the two sources

> Lb) are given below:

La − Lb , dBA…..0 1
∆L , dBA…...3 2.5

Obviously, if the noise level of one source is higher than that of another by

8 ... 10 dBA, then the noise of a more intense source will prevail, since

in this case, the addition ∆L

very small.

The total noise level of sources of different intensity is determined by the expression

−0.1∆L1,n 

Σ  1  10 log 1  10

 ...  10 ,

L1 - the highest noise level of one of the sources;

∆L1, 2 − L1 − L2 ;

∆L1.3  L1 − L3 ; ∆L1,n  L1 − Ln ⋅ L2 , L3 ,...., Ln 

Noise levels

2nd, 3rd, ..., nth sources, respectively). Calculation of the noise level, dB A,

with a change in the distance to the source is performed by the formula

Lr  Lu − 201gr − 8 ,

– source noise level; r is the distance from the noise source to

the object of his perception,

The general noise of a moving car is the sum of the noise generated by the engine, units, car body and its components, noise auxiliary equipment and tire rolling, as well as noise from the air flow.

Noise in a particular source is generated by certain physical phenomena, among which the most characteristic in a car are:

impact interaction of bodies; friction of surfaces; forced vibrations of solid bodies; vibration of parts and assemblies; pressure pulsation in pneumatic and hydraulic systems.

In general, vehicle noise sources can be divided into the following:

Mechanical - engine internal combustion, body parts,

transmission, suspension, panels, tires, tracks, exhaust system;

Hydromechanical - torque converters, fluid couplings, hydraulic pumps,

hydraulic motors;

Electromagnetic - generators, electric motors;

Aerodynamic - intake and exhaust system of an internal combustion engine, fans.

Noise has a complex structure and is made up of noise from individual sources. The most intense sources of noise are:

structural engine noise (mechanical and combustion noise), intake and system noise, exhaust system and exhaust system noise, cooling fan noise, transmission noise, tire rolling noise (tire noise), body noise. Many years of research have established that the main sources of noise in a car include an internal combustion engine, transmission elements, tires, and aerodynamic noise. Body panels are a secondary source of noise. Additional sources include noise from engine attachments, some transmission elements, electric motors, heaters, window blowing, slamming doors, etc.

The listed sources generate mechanical and acoustic vibrations, different in frequency and intensity. The nature of the frequency spectrum

disturbances is very difficult to analyze due to the overlap and frequency interconnection of work processes and disturbances from transmission elements, running gear, aerodynamic processes, etc.,

and also in view of the fact that many sources are both causative agents of mechanical and acoustic vibrations. In the vibration spectra of the main transmission units and noise, mainly

harmonic components from the main excitation sources

(engine and transmission).

The dynamic interaction of parts of the vehicle's assemblies generates vibrational energy, which, propagating from vibration sources,

creates the sound field of a car, tractor, i.e. car noise.

In accordance with this, the following ways can be outlined to reduce the intensity of noise:

Reducing the vibration activity of aggregates, i.e. decrease in the level of vibrational energy generated in the source;

Taking measures to reduce the intensity of fluctuations in the way of their

distribution;

Impact on the process of radiation and transmission of vibrations to attached parts, i.e. reduction of their vibroacoustic activity.

Reducing the vibration activity of the source is achieved by improving the kinematic properties of vehicle systems and selecting parameters mechanical systems so that their resonant frequencies are

as far as possible from the frequency range containing the operating frequencies of the units, as well as reducing to a minimum the levels of oscillations at the reference points and minimizing the amplitudes of forced oscillations. Noise reduction can be achieved by creating a low noise process

combustion, improving the vibroacoustic characteristics of body parts, assemblies, introducing damping into their design, improving the design and manufacturing quality of movable

parts, increasing the acoustic efficiency of intake and exhaust silencers, etc.

Fight against noise and vibrations during their distribution in the process

radiation and transmission of vibrational energy to attached parts and

aggregates can be carried out by "detuning" the system of bearing elements from resonant states by means of vibration isolation, vibration damping and vibration damping.

Vibration isolation - the choice of such parameters of mechanical systems that provide localization of vibrations in a certain area of the car without

its further distribution.

Vibration damping - the use of systems that actively dissipate the energy of vibrations of vibrating surfaces, as well as the use of materials with a large decrement

attenuation.

Vibration damping is the use in units tuned to a certain frequency and shape of vibrations, systems operating in antiphase.

Suppression of noise at the very source of its occurrence is an active method of noise suppression and the most radical means of combating noise. However, in many cases this method, for one reason or another, is not

can be applied. Then you have to resort to passive methods of noise protection - this is vibration damping of surfaces, sound absorption, sound insulation.

Soundproofing refers to the reduction of sound (noise) entering the receiver due to reflection from obstacles in the transmission path. The soundproofing effect always occurs when the passage of sound

waves through the interface between two different media. The greater the energy of the reflected waves, the less the energy of the transmitted ones and, consequently, the greater the soundproofing ability of the interface between the media. The more sound energy is absorbed by the barrier, the higher its sound-absorbing

ability.

Noise caused by medium and high frequency vibrations is transmitted to the cabin mainly through the air. To reduce this transmission, a special

pay attention to sealing the cabin, identifying and eliminating acoustic holes (acoustic holes). Acoustic holes can be through and non-through slots, technological holes, areas with

low sound insulation, significantly worsening the overall sound insulation of the structure.

From the point of view of the characteristics of the transmission of sound energy, there are

large and small acoustic openings. A large acoustic hole is characterized by a large ratio of the linear dimensions of the hole to the length of the sound wave incident on the hole compared to unity. In practice, we can assume that sound waves pass through a large acoustic hole according to the laws of geometric acoustics, and the sound energy passed through the hole is proportional to its area. Each hole category has one or more effective methods their elimination.

To determine effective ways to reduce noise, it is necessary to know the most intense sources of noise, to carry out their separation, as well as

determine the need and magnitude of reducing the levels of each of them.

Having the results of separation of sources and their levels, it is possible to determine the sequence of finishing the car in terms of noise.

Control questions

1. For what purpose is the safety of the design of vehicles regulated?

2. What are the main properties that determine the safety of the design of vehicles

3. By what criteria is the impact of active vehicle safety on road safety determined?

4. What is the relationship between vehicle weight and risk

injury in an accident for its passengers?

5. What determines the width of the dynamic corridor during curvilinear motion?

6. What are the size classes for cars sold in Europe?

with GOST R 52051-2003?

8. What forces act on a car accelerating uphill?

9. What changes in the technical condition of the car affect its traction dynamics and how?

10. What is the dynamic factor of a car?

11. What is called transverse stability car?

12. What is called the longitudinal stability of the car?

13. What is directional stability car?

14. What are the main technical requirements (test methods)

apply to the braking properties of vehicles?

15. What standards regulate the stability and controllability of vehicles as properties of active safety?

16. What types of stability tests do you know?

17. What indicators are evaluated during the "stabilization" test?

18. What types of car steering exist?

19. For what technical reasons is it possible to lose control of the car?

20. What is the stopping distance of a car?

21. How a Type 0 test is carried out brake systems Vehicle?

22. What indicators determine the requirements for tires and wheels?

23. Specify the main characteristics of coupling devices.

24. What devices are used for information support of vehicles?

25. What technical requirements apply to lighting and light signaling devices?

In some cases, operational observations are indirect evidence of its insufficient reliability. According to the results of a survey of 4 drivers of this car about the influence of internal environmental factors, the temperature regime in the cab was negatively assessed (hot in summer, cold in winter) - 75% of drivers; the presence of toxic substances (air pollution with exhaust gases) - 75%; influence of vibrations - 75%, noise - 75%.

A survey was also conducted on the state of noise in the car interior and 100% of the respondents stated the presence of mid-frequency noise from the low quality of the interior plastic, which causes increased irritation during the trip, although they do not exceed noise class 2 according to GOST R 51616 - 2000.

Based on the above, I conclude that the driver's comfort in the car is significantly low, which leads to a decrease in the active safety of the car.

3. Vehicle passive safety systems

Passive safety includes many elements, and one of the main ones is the seat belt. The second most important element of passive safety is the car body. Its front or rear part should, by crushing, dissipate the released impact energy as much as possible, and the central part of the body should provide as much space as possible for the passengers of the car to survive. Interior materials should not only be pleasant to the touch and pleasing to the eye, if necessary, they should soften the blow as much as possible. At the same time, they should not crack, so that their fragments do not cause additional damage to passengers.

After the impact, the car's gas tank must not ignite or crack in order to avoid spilling fuel on the road. Great importance is attached to doorways and locks. As accident statistics show, the most severe injuries, often incompatible with life, are received by passengers who fell out of the opened car doors. At the same time, after an accident, locks and doors should open easily without the use of additional equipment to ensure quick and timely evacuation of people in the cabin.

Composed of a number of factors, often contradictory, passive safety serves to achieve one main task - in the event of an accident, regardless of its severity, to do everything possible to save the lives of people in the car.

Based on the study of the safety of the ZAZ 1102 car by the magazine Autoreview No. 3 of 2004. "The hood as a murder weapon"

(A crash test of this car was carried out. The nature and severity of the damage received by Tavria left no doubt about the outcome of the collision for this car.

The front part of Tavria was thoroughly crumpled - 62 cm on the left side. At the same time, the entire front part noticeably shifted to the left, two solid folds appeared on the roof - the body went like a screw. Crashed and thrown out on impact windshield, the driver's door jammed in the opening.

The base of the A-pillar shifted back by 33 cm, to which the spare wheel contributed - it advanced part of the engine shield into the cabin, and the hard plastic instrument panel shifted back and cracked slightly to the left of the center, forming sharp injury-prone edges. With the steering column and the driver's seat, miracles happened at all. The column moved to the right so that wheel it turned out to be almost in the middle and at the same time it shifted inward by 14 cm. The left seat moved forward by 13 cm, and in addition it was strongly skewed to the left. This happened due to the fact that the power structure of the floor of the body in the area of \u200b\u200bfastening the front seats turned out to be too flimsy - the floor went in waves, bent the seat slide, and they opened up without holding the seat. Together with the deformation of the floor, this reduced the space for the feet and legs, and in addition, after the dummy bounced back, his head missed the headrest, which is fraught with damage to the cervical vertebrae.

It is also unpleasant that the locks-latches of the rear seat back from the impact opened up and allowed it to fold. The decoded data from the dummy's sensors showed that the total level of overloads that acted on the dummy's head for 20 ms turned out to be higher than the permissible one.)

Imagine our surprise when, while watching high-speed filming, we saw a strange and terrible picture: the hard object that the driver hit his head turned out to be ... the hood! Even during the first inspection of the body, we noticed that the emergency latch of the hood on the left side did not work. The right hook did its job, and the left hook just came off "with meat" upon impact! In general, this is not surprising - the hook is cantilevered to the motor shield, and in the event of a collision, all spot welding points (there are four of them) worked to break away. The hook came off already after 30 milliseconds, and over the next 60 ms, the sharp edge of the hood pierced the windshield, which led to its sweeping out of the opening and shifted into the cabin towards the dummy. The high-speed filming footage clearly shows how the mannequin hit its face on the sharp edge of the hood. And this despite the fact that the belts were tightened as much as is hardly possible during normal driving.

An analysis of the residual deformation of the car body showed that Tavria has a weaker power structure of the body, seat and steering column.

COMFORTABILITY

The comfort of the car determines the time during which the driver is able to drive the car without fatigue. An increase in comfort is facilitated by the use of automatic transmission, speed controllers (cruise control), etc. Currently, vehicles are equipped with adaptive cruise control. It not only automatically maintains the speed at a given level

not, but also, if necessary, reduces it up to a complete stop of the car.

3 Passive vehicle safety

BODY

It provides acceptable loads on the human body from a sharp deceleration in an accident and saves the space of the passenger compartment after the deformation of the body.

In a severe accident, there is a risk that the engine and other components can enter the driver's cab. Therefore, the cabin is surrounded by a special "safety grid", which is an absolute protection in such cases. The same stiffening ribs and bars can be found in the doors of the car (in case of side collisions). This also includes areas of energy repayment.

In a severe accident, there is a sharp and unexpected deceleration to a complete stop of the car. This process causes huge overloads on the bodies of passengers, which can be fatal. It follows from this that it is necessary to find a way to "slow down" the deceleration in order to reduce the load on the human body. One way to solve this problem is to design areas of destruction that dampen the energy of a collision in the front and rear parts of the body. The destruction of the car will be more severe, but the passengers will remain intact (and this is compared to the old "thick-skinned" cars, when the car got off with a "light fright", but the passengers received severe injuries). AAAAAAAAAAAAAAAAAAAAAAAAAAA

The design of the body provides that in the event of a collision, the parts of the body are deformed, as it were, separately. Plus, high-tensioned metal sheets are used in the design. This makes the car more rigid, and on the other hand allows it to be not so heavy.

SEAT BELTS

At first, cars were equipped with two-point belts that “held” riders by the stomach or chest. In less than half a century, engineers realized that the multi-point design is much better, because in the event of an accident it allows you to distribute the pressure of the belt on the surface of the body more evenly and significantly reduce the risk of injury to the spine and internal organs. In motorsport, for example, four-, five- and even six-point seat belts are used - they keep the person in the seat “tightly”. But on the “citizen”, because of their simplicity and convenience, three-point ones took root.

In order for the belt to work properly for its purpose, it must fit snugly against the body. Previously, belts had to be adjusted, adjusted to fit. With the advent of inertial belts, the need for “manual adjustment” has disappeared - in the normal state, the coil rotates freely, and the belt can wrap around a passenger of any build, it does not hinder actions, and every time a passenger wants to change the position of the body, the strap always fits snugly to the body. But at the moment when “force majeure” comes, the inertial coil will immediately fix the belt. In addition, on modern machines squibs are used in the belts. Small explosive charges detonate, pulling the belt, and he presses the passenger to the back of the seat, preventing him from hitting.

Seat belts are one of the most effective means of protection in an accident.

So cars must be equipped with seat belts, if attachment points are provided for this. The protective properties of belts largely depend on their technical condition. Belt malfunctions, in which the vehicle is not allowed to be operated, include tears and abrasions of the fabric tape of the straps visible to the naked eye, unreliable fixation of the tongue of the strap in the lock or the absence of automatic ejection of the tongue when the lock is unlocked. For inertia-type seat belts, the webbing of the webbing must be freely retracted into the coil and blocked when sudden movement car at a speed of 15 - 20 km / h. Belts that have experienced critical loads during an accident in which the car body has received serious damage are subject to replacement.

AIRBAGS

One of the most common and effective safety systems in modern cars (after seat belts) are air cushions. They began to be widely used already in the late 70s, but it was not until a decade later that they really took their rightful place in the safety systems of most manufacturers' cars.

They are located not only in front of the driver, but also in front of the front passenger, as well as from the sides (in the doors, pillars, etc.). Some car models have their forced shutdown due to the fact that people with heart problems and children may not be able to withstand their false operation.

Today, airbags are commonplace not only in expensive cars, but also on small (and relatively inexpensive) cars. Why are airbags needed? And what are they?

Airbags have been developed for both drivers and passengers on front seat. For the driver, the pillow is usually installed on the steering, for the passenger - on dashboard(depending on design).

The front airbags are deployed when an alarm is received from the control unit. Depending on the design, the degree of filling of the pillow with gas may vary. The purpose of the front airbags is to protect the driver and passenger from injury by solid objects (engine body, etc.) and glass fragments in frontal collisions.

Side airbags are designed to reduce damage to vehicle occupants in a side impact. They are installed on the doors or in the backs of the seats. In the event of a side impact, external sensors send signals to the central airbag control unit. This makes it possible for some or all of the side airbags to deploy.

Here is a diagram of how the airbag system works:

Studies of the effect of airbags on the likelihood of driver death in frontal collisions have shown that it is reduced by 20-25%.

If the airbags have deployed or been damaged in any way, they cannot be repaired. The entire airbag system must be replaced.

The driver's airbag has a volume of 60 to 80 liters, and the front passenger - up to 130 liters. It is easy to imagine that when the system is triggered, the interior volume decreases by 200-250 liters within 0.04 seconds (see figure), which gives a considerable load on the eardrums. In addition, a pillow flying at a speed of more than 300 km / h is fraught with a considerable danger to people if they are not fastened with a seat belt and nothing delays the inertial movement of the body towards the pillow.

Fatigue is a condition that has arisen under the influence of the work done and affects the level of performance.

Fatigue is a complex and varied phenomenon. Often it does not directly affect the performance of labor activity, but manifests itself in a different way. For example, labor operations that used to be performed easily, without any tension, automatically, after a few hours of work require additional effort, special attention. The rate of fatigue development depends on many factors: dynamic and static adaptation, visual comfort, working environment, etc.

Fatigue has a decisive influence on the driver's ability to navigate correctly, quickly and safely in a traffic situation. Decreased performance due to fatigue is not a purely physiological phenomenon. As numerous studies have shown, an important role in the processes of fatigue belongs to psychological factors, the tension of the human nervous system.

In the practice of the driver of a car (tractor) there are:

Natural fatigue, the effects of which disappear the next day;

Excessive fatigue arising from improper organization of work;

A harmful fatigue, the effects of which do not disappear on the second day, but imperceptibly accumulate and remain unconscious for a long time, until they suddenly appear.

The main factors causing driver fatigue and other deviations during work are as follows:

Duration of continuous driving of the car (tractor);

The psycho-physiological state of the driver before leaving for a flight or leaving for a shift;

Driving a car (tractor) at night;

Monotony and monotony of driving;

Working conditions at the driver's workplace.

The most objective evidence of driver fatigue when driving a car is the number of accidents depending on the duration of movement and other conditions associated with fatigue. A clear dependence of the number of road accidents and accidents on the duration of work has been established.

The driver's psychophysiological state before departure has no less influence on the driver's fatigue. It worsens from lack of sleep and the load of the driver before starting work (mental stress, conflict unnerving environment, mental trauma).

Increased driver fatigue occurs when driving at night.

With monotonous and monotonous movement, a particularly dangerous type of fatigue occurs, which causes a inhibited state of the higher nervous activity of the driver and can lead to weakness, drowsiness and falling asleep at the wheel. This condition occurs as a result of prolonged repetition of the same action.

No less important factors that accelerate fatigue are the working conditions at the driver’s workplace (working position, rhythm and pace of work, work breaks), the microclimate at the driver’s workplace (temperature, pressure, air humidity, gas pollution, lighting, radiation) and noise and vibration levels.

One of the main criteria when choosing a car, which guides 90% of buyers, is just the level of comfort. It is both simple and difficult to define what comfort is at the same time, because it is still impossible to formulate exactly what it is. And only in general terms it can be noted that comfort is what makes our life easier, more convenient.

With regard to cars, manufacturers have brought some of their developments into a separate group, which is called the comfort system. In fact, almost all the advantages of a single car can be attributed to these: visibility, landing, simplicity - all this, you see, creates one or another level of comfort. Nevertheless, in order to figure out what it is - the comfort of modern cars, we decided on a very rough, but at the same time understandable classification of comfort systems:

Immediate comfort systems;
Comfort systems

What are immediate comfort systems?

What can we attribute to the first group? What does the motorist constantly face? Of course, this is the driver's seat. A huge number of innovative systems and technologies are aimed at making the landing of the driver, and the passenger, as convenient as possible. As a result, modern cars instead of banal mechanical seat adjustments, they are equipped with electric ones. The more you pay, the higher the level of comfort. That is why BMW equips the luxury versions of its cars with seats with variable geometry. For example, the lateral support of the seats changes, their length increases so that the legs are as little as possible in tension. Or, for example, a position memory system driver's seat- why not a comfort system? Therefore, comfort is also different from comfort.

TO direct systems comfort, that is, what is used constantly and is already considered in the order of things, can be attributed to or, etc. All this also creates a high level of comfort and is in constant use. You can list the systems indefinitely, since everything that is done in the car is done for the comfort of those who will be in this car.

Comfort systems

What is meant by this group? For example, there is a car with basic system comfort, which we talked about earlier: automatic transmission, power steering, etc. Comfort systems are those that are not used constantly, but only under certain conditions. For example, a system that is connected only when the driver enters the track. On the one hand, the car already has a high level of comfort, but it is possible to make movement even more comfortable with the help of such systems that operate under certain circumstances, under certain conditions.

In addition to cruise control, we can also mention the control system, intelligent system, etc.

The main rule of comfort

All innovative systems that are being introduced into cars, in fact, only cloud the mind of a person, and he, seeing how many useful options one car has, turns away from the one that has a simpler package, but at the same time is more comfortable.

What are the main comfort criteria that should be followed? This is not at all, in the form of heated wipers, remote start of a car, or. Yes, all this is certainly important, but there are systems that are decisive. These include characteristics, because it is very important how the car behaves on the road. For example, it may be crammed with electronics that supposedly increase comfort, but the part will be designed in such a way that each hole will penetrate into the cabin. Yes, with this state of affairs, you do not want any latest technology, you will be ready to give everything for quality undercarriage. From the same considerations, noise-vibration-sound insulation can be considered. Comfort is unimaginable without silence. Engine characteristics, the same automatic transmission that we mentioned are the main and main parameters that affect the comfort of a car, and all the rest electronic systems These are just small additions to what already exists.