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.
Everyone has it driver there is a special opinion about the comfort of the car. For one, comfort is a unique hydraulic suspension, for another, air conditioning, and for others, powerful audio and video systems please. Another of the innovations car tuning- this . For lovers of the unusual tuning you can see recommendations on how to do it yourself on the AutoNovator website LED backlight
, which gives not only aesthetic pleasure, but has practical significance. 
Also, someone, creating comfort in the cabin, covers it with heat-insulating materials so that in winter the summer temperature is always maintained inside. Many drivers evaluate car comfort soundproofing and vibration car. Loud music lovers always get annoyed when noise motor or road noise drowns out musical sounds.
But, surprisingly and not paradoxically, it is a comfortable car that becomes potentially dangerous. Automakers, in their desire to make a beautiful toy out of a car, with a mass of additional accessories, thereby render a disservice to car owners. Statistics and expert data confirm this idea and warn of an increase in the number of accidents in a number of comfortable cars. Swedish researchers, analyzing this problem, came to the conclusion that drivers will experience great difficulty in driving the machine. According to scientists, cars equipped with a soundproofing system are in demand among young people. drivers with little driving experience. The young men in this case belonged to the road noise as a distraction that prevented them from listening to music in the salon car. However, the opinion of professional drivers regarding noise on the road is different. They believe that in isolation from noise it is difficult for the car to have an idea of what is happening around, and it is impossible to fully assess the situation on the road. Professionals believe that all sounds coming from outside into the cabin signal danger and are therefore useful in the process of driving. By the sounds coming, you can determine the quality of the engine, on which road, with what surface it is driving automobile which car is approaching to overtake.
Therefore, Swedish scientists issued an appeal to automakers not to create for drivers vacuum conditions. Noise plays, as it turned out, not only a negative role. Road noise reminds driver that he rides on the road to car instead of lying at home on the couch and listening to music. By the way, scientists from Sweden were supported by people from public organizations of the visually impaired and the blind, for whom cars with a weak engine sound are dangerous.
Of course, as they say, you can’t forbid living beautifully. It is always pleasant and easy to ride in comfort when cheerful music is playing, it is frosty outside, and there is a tropical climate in the cabin. And you don’t think at all about what is happening on the road there, and what awaits you around the next turn ...
The study of the working conditions of drivers indicates the significant importance of the parameters of the internal environment in the car. These parameters only with greater or lesser probability correspond to 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 a 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 cause some people to experience a burning sensation, intoxication, 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 when technical malfunctions 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 showed that in some cases the content of carbon monoxide reaches 125 mg/m3, which is several times higher than the maximum permissible concentration for the driver's working area. 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 are somewhat different from the same conditions in 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 limited room (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 should work at lower temperatures (+15...17°C in the winter period 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. In summer, when driving a car 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 cabin 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. IN
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, which differ in the layout and design of individual units. The most economical and widely used
modern cars is a heating system that uses the heat of liquid cooling of the 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-plate, 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 rotational speed 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. IN
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 protection of glass is structurally simple, does not impair its optical properties, but requires an increase in the performance of the ventilation system 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 outlet.
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 the efficiency of dust collection 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 back blowing the filter material with purified air from the vehicle cabin or by local jet air blowing
from a compressor with preliminary purification of 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 with minimum dimensions and aerodynamic resistance. 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, rib cage- 2 ... 12 Hz, legs and arms - 2 ... 8 Hz, lumbar spine - 4 ... 14 Hz, stomach - 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
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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 rates 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:
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~ ∑ (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
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 heavy road conditions, where the amplitudes of the microprofile are significant, it is difficult to ensure the values of the 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 for 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 loud 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 indoor noise levels for vehicles on
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 general level noise 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 total noise of a moving vehicle is made up of the noise generated by the engine, aggregates, the vehicle body and its components, the noise of auxiliary equipment and tire rolling, as well as the 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 due to 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 transmitted 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.
test 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 braking distances 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 are the technical requirements for lighting and light signaling devices?
If the car is not comfortable, then after traveling especially for a long distance or in case of standing idle in traffic jams, it will cause you fatigue and irritation. Russian roads, unfortunately, leave much to be desired and not all brands of cars can boast of comfort and convenience.
But it must be admitted that most modern cars have become better in terms of reliability, quality and comfort. However, there are models that have a huge advantage over other brands in terms of comfort. We offer you our rating of the most comfortable cars. selected for comfort while driving, sound insulation, the convenience of the driver's seat and front passenger seat. We intentionally excluded compact small cars from our list, sports cars and convertibles, which, by definition, cannot be perfectly comfortable due to their size or design features.
Also familiarized with best cars for convenience, you can also find out if these models, as well as what kind they have, by clicking on the photo or model name.
A6 is very convenient and comfortable. A trip in this car will appeal to even the most experienced driver.
This year's new Impala model has become modern big sedan. Spacious interior, comfortable, quiet and pleasant to drive. Draw attention to the large and spacious front seats. They are pleasant to the touch and perfectly support the lower back and unload the back, which allows you to comfortably cover long distances.
One of best sedans on the market. Space and comfortthe main merit of computer engineersChrysler. The top trim is the best. Management of all functions of the car is very convenient. Various amenities, luxury items and silence during the trip will not let you get tired behind the wheel. The car is especially ideal on the highway, where you will not hear the loud work of the engine and the sound of tires.See also:
The highest comfort available in the car maximum configuration. The cabin is quiet. Noise comes from
climate control ventilation. Also, some noise will bother you for several minutes after starting the engine in cold weather. After warming up, you will not hear the sound of the motor. front seats correct form and very comfortable, thanks to the support of the lower back. It is worth noting that it leather seats hold your back better than fabric chairs. Plus, cloth-trimmed seats are somewhat stiffer than leather, which can lead to fatigue during long traffic jams.See also:
Complete silence in the cabin. Even at high speed, no wind noise is heard. The interior of the Lexus ES is thought out to the smallest detail.
Comfort is maximum. Expensive interior trim pleasantly surprises with its textures. The ES models have very quiet engines and expensive noise insulation. The seats are distinguished by their comfort thanks to their width and balanced softness.Reliability Rating
Lexus LS The flagship sedan provides both driver and passengers with comfort and a relaxing ride over any distance. The LS on the road won't be a problem on any road. Noise isolation is top notch. Absorption of extraneous noise is perfect. The smooth running of the car and excellent handling are the main advantage of this model. All seats are very comfortable and luxurious.