Automobile Inspection Technology

Chapter 33 Vehicle Inspection Technology (9)
The same measurement is made one round trip.The difference between the two measurement results on the same side of the vehicle shall not be greater than 2dB, and the greater of the average of the two sound levels on each side shall be taken as the maximum noise level of the vehicle under test.If only one sound level meter is used for measurement, the same measurement should be carried out 4 times, that is, 2 times for each side.

50. The amount of external noise from a vehicle running at a constant speed.The vehicle uses the usual gears, keeps the throttle opening stable, and drives through the measurement area at a constant speed of [-]km/h.The use of the sound level meter, the reading of data and the measurement results are the same as the measurement of the external noise of the accelerated driving vehicle.

②车内噪声测量。车内噪声测量通常在人耳附近布置测点。话筒方向朝前。驾驶室内噪声测点位置示意图见图5-53。客车测点还应加上车厢中部及最后排座的中间的位置，测点可参考图5-53布置。53驾驶室内噪声测点的位置测量车辆以常用挡位50km/h以上的不同车速等速行驶时的车内噪声。用声级计“慢”挡测量A、C。

(Section [-]) Vehicle speedometer detection

[-]. Overview of speedometer
The speedometer is an instrument that indicates the speed of the car. It is generally combined with the odometer, also known as the speedometer.The speedometer generally transmits the speed of the vehicle to the speedometer through the speed sensor, so that it can indicate the speed of the vehicle.

While driving, the driver uses the speedometer to understand and grasp the speed of the vehicle, which requires that the speedometer should have a certain accuracy and can reflect the actual speed of the vehicle as accurately as possible.However, the speedometer may produce an indication after a long period of use
error.

Errors between the speed indicated by the speedometer and the actual speed may be caused by factors such as sensor and speedometer manufacturing and assembly errors, performance degradation of the speedometer, or tire wear and tire pressure that do not meet the regulations.

The commonly used magnetoelectric speedometer shows the speed of the car through the swing of the pointer.In the speedometer, there are turntables with pointer shafts, rotating shafts with permanent magnets, bearings, hairsprings and other parts. The rotating shafts are driven by flexible shafts. connect.Due to the natural wear and tear of these parts during use, as well as the magnetic changes of the magnetic elements, the indication error of the speedometer will be caused.

If the indication error of the speedometer is large, it is difficult for the driver to accurately grasp the speed of the vehicle, which may lead to traffic accidents.Therefore, in order to ensure driving safety, the indication error of the speedometer is listed as one of the necessary inspection items in the automobile safety inspection.The device that detects the error indicated by the speedometer is called a speedometer test bench.

[-]. Speedometer testing equipment

Beside this there is

Connect to the power outlet

1. Speedometer test bench
The speedometer test bench is the main equipment used to test the speedometer, and there are two types: standard type and driving type.

The speedometer testing platform and the brake testing platform are combined to form a multifunctional compound testing platform.

The standard speedometer test bench itself does not have a driving device, and its roller is driven to rotate by the driving wheel of the car to be tested.The standard speedometer test bench is shown in Figure 5-54.

The motor-driven speedometer testing platform is shown in Figure 5-55. It has a driving device, and uses a roller to drive the driven wheels of the vehicle to be tested to rotate and drive the speedometer to indicate the speed of the vehicle.

2. Detection principle

When testing, the driving wheel of the car is placed on the drum, and the engine drives the wheel to rotate through the transmission system, and the wheel drives the drum to rotate by means of friction.The rotating drum is equivalent to the moving road.The driving wheel is rotated on the roller to simulate the actual state of the car when driving on the road.The tachometer generator (that is, the speed sensor, which is more commonly used now is a photosensitive tube, Hall sensor, etc.) is driven by the end of the drum.The voltage from the tachogenerator (or the number of pulses from the photosensitive tube, hall sensor, etc.) increases with the increase of the drum speed, and the drum speed is proportional to the vehicle speed, so the voltage of the tachogenerator is proportional to the vehicle speed.Or use a pulse signal generator, install it at one end of the drum, and send the electrical signal corresponding to the rotating speed of the drum to the speed indicating device.Because there is no slippage between the wheel and the drum, the linear speed of the wheel and the drum is the same.The linear speed of the drum can be calculated by adjusting the rotating speed of the drum through the diameter of the drum and the speed sensor, which is the actual driving speed of the wheel.

If the diameter of the roller of the speedometer testing table and the rotating speed of the roller are known, the linear velocity of the roller of the speedometer testing table can be obtained by the following formula:

Three, speedometer detection method

The speedometer indication error is measured by the relative error size, which is defined as:
Av=(v table - real) / real X100%
In the formula, v table——refers to the speed value indicated by the speedometer (km/h);

vReal——refers to the actual driving speed value of the vehicle, and the measurement value of a measuring device with high precision is often used as the actual vehicle speed value (km/h).

There are usually two methods of speedometer calibration: road test method and indoor bench test method.The road test method is that the car passes through a test road section of a predetermined length at a constant speed at different speeds, measures the time for passing the road section, and then calculates the actual speed, and compares it with the speedometer indication value in the cab to find out the speed at different speeds. Speedometer indication error.The bench test method is carried out on a drum speedometer test bench.

GB7258-2004对车速表允许误差范围规定为+20%-0，即当实际车速为40km/h时，车速表的指示值为48-40km/h为合格。

From a safety point of view, the reading of the speedometer should not be less than the actual speed of the vehicle.In GB7258-2004 "Technical Conditions for Motor Vehicle Operation Safety", Appendix A "Speedometer Inspection Method" stipulates that the speedometer inspection should be carried out on the speedometer inspection platform.During detection, the vehicle to be detected is driven onto the speedometer detection platform and the roller of the detection platform is driven to rotate.

(Section [-]) Detection of automobile headlights

The luminous intensity of the headlights is insufficient, and the driver cannot clearly identify the situation in front of the car when driving at night; the improper direction of the beam of the headlights may cause the oncoming driver to be dazzled.During the use of the headlight, the bulb will gradually age, and the luminous efficiency will decrease; the reflector will also gradually become darker, and the light-gathering performance will deteriorate.At the same time, the vibration of the motor vehicle during driving will also cause the position of the headlight of the car to change, thereby changing the irradiation position of the headlight beam.Therefore, the luminous intensity and beam irradiation direction of the headlight must comply with the provisions of GB7258-2004 "Technical Conditions for Motor Vehicle Operation Safety" to ensure the safety of driving at night.

[-]. Overview of headlights
The headlight is composed of a bulb, a reflector and a light distribution mirror.The surface shape of the reflector is a rotating parabola. When the filament is outside the focal point, the light is reflected by the reflector to form a parallel beam and shoot to the distance; the light distribution mirror is the transparent glass at the front of the lamp. The required light distribution performance.

The number of headlights installed on the car generally has two lamps and four lamps.The two-lamp system headlamps are both far and low beam double beam lamps, which are symmetrically installed on both sides of the front of the car; the four lamp system headlamps, two on each side, and the two installed on the outside are far and low beam dual beam lamps , the two mounted on the inside are high-beam single-beam lights.

The characteristics of headlights include luminous intensity, beam irradiation direction and light distribution characteristics.

1. Luminous intensity
Luminous intensity is a measure of how strong a light source emits light in a given direction, and its unit is candela, represented by the symbol cd.According to the regulations of the international standard unit SI, if a light source emits monochromatic radiation with a frequency of 540X1012Hz in a given direction, and the radiation intensity in this direction is 1/683W per steradian, then the light source in the given direction The luminous intensity is 1cd.

When the light emitted by the headlamp (light source) hits the object to be illuminated, the brightness of the light-receiving surface changes.The physical quantity to measure the brightness of the light-receiving surface is illuminance, and the unit is lux, which is represented by the symbol LX.Under the condition that the luminous intensity of the headlight (light source) is constant, the farther the illuminated object is from the light source, the worse the degree of illumination and the smaller the illuminance.If the luminous intensity is represented by J(cd), the illuminance is represented by ￡(Lx), and the distance between the headlight (light source) and the illuminated object is S(m), then the relationship between the three is E=I/S2. : The illuminance is proportional to the luminous intensity of the light source by 5000, and is inversely proportional to the square of the distance from the illuminated object to the light source by 4000 (called the inverse quadratic method). The fitting situation between the change curve and the theoretical 5 curve.It can be seen that when the distance exceeds 56m, the measured value is basically consistent with the theory, and the farther the distance is, the more accurate the measured crystallite value is; when the distance is 3000m, an error of about 5% left and 3(M) right occurs.However, due to the limitation of the measurement site, when using the headlight tester to detect the headlights, the measurement distances usually used are 15m, 1m, and 3m. According to the above formula, the illuminance measured at this distance is converted into the front The illuminance at 1m in front of the lamp is converted into luminous intensity for indication.

2. Direction of irradiation
If the brightest place of the headlight is taken as the center of the beam, then the beam irradiation direction is measured by the deviation of the center from the horizontal and vertical coordinate axes.

3. Light distribution characteristics

At present, the headlights of double tungsten filament bulbs produced at home and abroad are divided into two different light distribution systems: American type and European type.

(1) American light distribution (SAE method)

Figure 5-57 The beam irradiation direction is symmetrical because of the light shape distribution of the low beam, and this light distribution system is also called symmetrical light distribution.This type of headlight adopts ordinary twin-filament bulbs, and the positions of the filaments are shown in Figure 5-58.The high-beam filament is at the focal point and has more power; the low-beam filament is offset up and to the right (looking from the bulb to the reflector) and has less power.

When the high beam is used, the light emitted by the filament is reflected by the reflector, and then parallel to the distance along the optical axis, as shown in Figure 5-58; when the low beam is used, the light that hits the reflector h61 is reflected by the reflector After that, it shoots to the right and bottom of the headlight axis, that is, it shoots to the road surface; after the light that hits the reflector and 61C1 is reflected, it shoots to the top and left, that is, the distance/m.

(2) European light distribution (ECE mode)

Because of the asymmetric distribution of the light shape of the low beam, this light distribution system is also called asymmetrical light distribution.This type of headlamp adopts a double-filament bulb with a light distribution screen, and its filament position is shown in Figure 5-59.The high-beam filament is at the focal point of the reflector; the low-beam filament moves to the front of the focus along the optical axis, and a light distribution screen is arranged below it, and the upper half of the light emitted by the low-beam filament shoots to the
The upper part of the reflector is reflected into a beam of light that is inclined to the road surface, while the light distribution screen can cover the light in the lower part so that it cannot be directed to the lower part of the reflector, so there is no upward reflection. May cause glare of light.The beam irradiation situation is shown in Figure 5-59(a).When the high beam is used, the light distribution screen does not work, and the reflected beam is still directed forward, as shown in Figure 5-59(b).

Because the headlight bulb with light distribution screen has good anti-glare effect, it meets the ECE standard formulated by the Economic Commission for Europe. It is an ideal light distribution and has been recognized by the world.It is stipulated in GB4599-1994 that the light distribution performance of the dipped beam should be the asymmetrical light distribution shown in Figure 5-60.The light distribution performance shall be measured on the vertical light distribution screen passing the HV point 25m before the reference center of the headlamp.On the light distribution screen, the low beam should produce an obvious light and dark cut-off line, the horizontal part of which is on the left side of the line, and the right side is a 15° oblique line from the horizontal line, or a 45° upward oblique line until the vertical distance from the horizontal line is 25cm and turns to the horizontal of polylines.In order to achieve the above light distribution, the light distribution screen inside the headlight bulb is usually made asymmetrical, and the left edge of the light distribution screen is inclined at 15°.

The area melon is an obvious dark area. The N50L point in this area indicates the position of the eyes of the oncoming vehicle driver at a distance of 50m. Since the illuminance value of the light at this point is very low (the maximum value is 0.3lx), it can avoid oncoming vehicles. The dazzle of the driver.

Recently, a more excellent light shape has been developed abroad, and its low beam light shape is shown in Figure 5-61.The light and dark cut-off line is Z-shaped, so it is called Z-shaped light distribution, which can not only avoid the glare of oncoming vehicles v drivers, but also prevent the glare of oncoming pedestrians and non-motor vehicle users, and further ensure the driving of cars at night safety.

[-]. Headlight inspection items and standards
In the inspection process of automobile headlights, from the perspective of safe driving, its luminous intensity and beam irradiation direction are mandatory inspection items.According to the provisions of GB7258-2004 "Technical Conditions for Motor Vehicle Operation Safety", the requirements that should be met are as follows:

1. Basic requirements
①Under normal conditions of use, the beam irradiation position of the motor vehicle headlamp should remain stable.

②Motor vehicles equipped with headlights should have high and low beam conversion devices, and when the high beam changes to low beam, all high beams should be able to go out at the same time.The headlights on the same motor vehicle do not allow the left and right far and low beams to be switched on.

③When the headlights with far and low beams are arranged side by side, the low beams should be on the upper side, and in other cases, the low beams should be on the outside.

④ The dipped beams of all headlights are not allowed to dazzle.

⑤ The headlights installed on automobiles (except three-wheeled automobiles) shall comply with the provisions of GB4599-1994 "Light Distribution Performance of Automobile Headlights".

2. Headlight beam irradiation position

(1) Check the irradiation position of the low beam beam of the headlamp
When the headlight is irradiated on the screen at a distance of 10m, the height of the corner or the midpoint of the cut-off line of the low beam beam of the passenger car headlight should be 0.7H-0.9H (H is the height of the reference center of the headlight, the same below) , other motor vehicles (except tractor transport units) should be 0.6H-0.8H.For motor vehicles (except for motor vehicles equipped with one headlamp), the horizontal position of the low beam beam of the headlamp is not allowed to deviate more than 170mm to the left, and not more than 350mm to the right.

(2) Check the irradiation position of the high beam of the headlight and the single beam of the high beam

When the headlight is irradiated on the screen at a distance of 10m, it is required to be at the height of the beam center of the screen from the ground, which is

0.9H-1.0H, and 0.8H-0.95H for other motor vehicles; for motor vehicles (except for motor vehicles equipped with one headlamp), the horizontal position of the high-beam beam of the headlamp is required, and the deviation of the left lamp to the left is not allowed to exceed 170mm , the deviation to the right is not allowed to exceed 350mm, and the deviation of the right lamp to the left or right is not allowed to exceed 350mm.

(3) Detection method

When detecting the irradiation position of the headlamp beam, the detection method used shall meet the following requirements:

① Screen method: that is, check on the screen.The inspection site should be flat, and the screen should be perpendicular to the site.The vehicle to be inspected should be carried out under the conditions of no load, normal tire pressure and one driver.Park the vehicle in front of the screen and make it perpendicular to the screen so that the reference center of the headlights is 10m away from the screen, determine on the screen the horizontal reference line that is equal to the distance H from the reference center of the headlights to the ground, and the longitudinal center plane of the vehicle is at The projection on the screen is the reference center position line of the left and right headlights.Measure the offset values ​​of the horizontal and vertical irradiation azimuths of the left and right far and near beams respectively.

②Inspection with a headlamp calibration device: Put the vehicle under inspection against the headlamp calibration device at a specified distance, and measure the offset values ​​of the horizontal and vertical irradiation orientations of the left and right far and near beams from the screen of the headlamp calibration device.

③ When inspecting motor vehicle safety technology, it is advisable to use a headlight tester to test the irradiation position of the headlight beam.

3. High beam luminous intensity
The high-beam luminous intensity of each headlamp of a motor vehicle shall meet the requirements in Table 5-22.When testing, its power system should be in charging state.

Note: For motor vehicles with four-lamp system, if two symmetrical lamps meet the requirements of the two-lamp system, it is considered qualified.

[-]. Detection method of headlights

1. Use the screen method to detect the beam irradiation position of the headlight

Under the specified detection conditions, place a special screen 10m away from the headlight and make it perpendicular to the ground.The screen is drawn with three vertical lines and three horizontal lines.The vertical line is aligned with the longitudinal center line of the vehicle, and the vertical lines V left to V left and V right to V right on both sides are respectively aligned with the center line of the left and right headlights.The horizontal line hh is at the same height as the center of the headlamp of the inspected vehicle, and the height from the ground is H (mm). H1=1.0H (for passenger cars); the second horizontal line is at the same height as the upper limit of the center of the low beam beam of the headlamp of the inspected vehicle, and the height from the ground is H2=0.9H (for passenger cars) .The standard stipulates that the deviation range of the center height of the far and low beam beams is divided into

They are 0.1H and 0.2H (for passenger cars), that is, the lower values ​​are 0.9H and 0.7H respectively.

When testing, first cover the headlight on one side, and first test the low beam of the uncovered headlight. According to the testing standard, the corner of the low light and dark cut-off line or the center of the beam should be illuminated at a height of H2, H2-0.2H Two horizontal lines and two vertical lines with a distance of S/2+170mm, S/2-350mm (to the left lamp) or S/2+350mm, S/2-170mm (to the right lamp) from the vertical line VV , otherwise it indicates that the deflection of the low beam beam exceeds the standard, as shown in Figure 5-62.Generally speaking, when detecting and adjusting the beam irradiation direction, the detection and adjustment of the low beam is mainly used for the far and near double beam lights.Because the quality of the light bulb is manufactured and the low beam adjustment is qualified, the high beam beam is generally also qualified; if the low beam beam is adjusted to pass, the direction of the high beam beam is unqualified after review, and the bulb should be replaced.

Figure 5-62 Use the screen to detect the irradiation position of the headlight beam
(End of this chapter)