In the process of automobile use, with the extension of use time (or the increase of mileage), its parts are gradually worn, corroded, deformed and aged, and the lubricating oil deteriorates, which makes the clearance of the mating pair larger, causing loose movement, vibration, ringing, air leakage, water leakage and oil leakage. , leading to the decline of automobile technical performance. The core of automobile maintenance work (or automobile maintenance work) is to "maintain" the technical condition of the automobile. That is, the purpose of sorting out and testing this paragraph through cleaning and editing can be divided into two categories: safety and environmental protection testing and comprehensive performance testing.
(1) Safety and environmental protection inspection. Safety and environmental protection testing refers to the regular and irregular safety operation and environmental protection testing of automobiles. The purpose is to establish a safety and pollution monitoring system without disassembling the vehicle, to ensure that the vehicle has the required appearance and good safety performance, to limit the degree of environmental pollution of the vehicle, and to make it run in a safe, efficient and low-pollution working condition.
(2) Comprehensive performance test. Comprehensive performance testing is the comprehensive performance testing of automobiles in specified and irregular periods. The purpose is to determine the working ability and technical status of running vehicles, find out the parts and causes of faults or hidden dangers, implement quality supervision on maintenance vehicles, and establish a quality monitoring system to ensure that vehicles have good safety, reliability, power, economy, exhaust purification and noise pollution, so as to create greater economic and social benefits. Edit this paragraph | Return to top FAQ 1. Automobile technical condition: the sum of the parameter values quantitatively measured to represent the appearance and performance of the automobile at a certain moment.
2. Automobile inspection: inspection and measurement to determine the technical condition or working ability of the automobile.
3, automobile diagnosis: in the case of not disassembling (or only disassembling a few small parts), determine the technical condition of the automobile or find out the fault parts and causes for detection, analysis and judgment.
4. Automobile diagnosis parameters include working process parameters, accompanying process parameters and geometric parameters.
5. Selection principles of diagnostic parameters: sensitivity, singleness, stability, information and economy. Six diagnostic criteria: country, industry, place and enterprise.
7. Composition of diagnostic parameter standard: initial value Pf, allowable value Pd and limit value Pn.
8. Classification of measurement errors: absolute and relative according to the expression method of measurement errors, systematic, random and negligent according to the law of measurement errors, and static and dynamic according to the state of measurement errors.
9. Absolute error is the difference between the measured value and the measured value; The relative error is the ratio of the absolute error of the measured value to the true value of the measured value, expressed as a percentage.
10. Generally, the allowable value that the maximum citation error can't exceed is used as the scale to divide the accuracy level. Common accuracy grades are 0. 1, 0.2, 0.5, 1.0, 1.5, 2.0, 2.5, 5.0.
1 1. System error: when the same quantity is measured for many times under the same measurement condition, the magnitude and sign of the measurement error remain unchanged or change according to a certain law; Random ~: When the same value is measured many times under the same measurement conditions, the magnitude and sign of the error change in an unpredictable way ~
12, engine assembly (cylinder pressure gauge); Chassis assembly (toe box); Measuring tools and instruments (electrolyte densimeter, high frequency discharge fork)
13. detection station type: according to service function (safety ~ maintenance ~ comprehensive ~); Comprehensive testing stations are divided by function (Grade A, Grade B and Grade C); Safety ~: Regularly check the items related to safety and environmental protection in the vehicle to ensure the safe driving of the vehicle and reduce the pollution to the allowable limit; Maintenance ~: from the point of view of vehicle use and maintenance, responsible for testing the technical status of vehicles before and after maintenance; Comprehensive ~: It can not only undertake the safety and environmental protection inspection of vehicle management department, but also undertake the technical condition diagnosis of vehicle use and maintenance enterprises, and also undertake the performance test and parameter test in scientific research or teaching; A-class station: it can fully undertake the task of testing station; Bilibili: able to detect the technical condition and maintenance quality of vehicles in use; Class C station: capable of testing the technical condition of vehicles in use.
14. Vehicle data input and safety device detection station: this station not only inputs vehicle data into the login microcomputer and sends it to the main control microcomputer of the detection line, but also visually checks the lights and safety devices on the upper part of the vehicle, which can be referred to as L station for short. Sideslip braking speedometer station: It consists of sideslip detection, axle load detection, braking detection and speedometer detection, and is called ABS station for short. Lighting tail gas station: mainly composed of headlight detection, tail gas detection, smoke detection and horn sound level detection, abbreviated as HX~. The underbody inspection station is called P~ for short. This station is a visual inspection of the bottom of the vehicle. Inspectors manually check whether the connection between the chassis device and the engine is firm and reliable, and whether there are any phenomena such as bending, loosening, oil leakage, water leakage and electric leakage.
15, the percentage of axle braking force and axle load = (left wheel braking force+right wheel ~)/axle load * 100%.
16, ABS station inspection program: 1) Four-wheel vehicle (rear drive, rear parking): sideslip-front brake-rear brake-parking brake-speedometer 2) Four-wheel vehicle (front drive, front parking): sideslip-front brake-parking brake-speedometer-rear brake 3) Four-wheel vehicle (rear brake 3)
17, the oscilloscope can display the waveform of voltage changing with time, and it is a multi-purpose automobile testing equipment. It can be used to display the waveforms of electrical fire system, electronic components, high-pressure oil pipe of diesel engine and abnormal noise of engine. Its basic function is to display the change of voltage with time. Besides observing the change of state, it can also detect voltage, frequency and pulse width.
18, cylinder tightness is related to the technical conditions of cylinder, cylinder head, cylinder gasket, piston, piston ring and intake and exhaust valves; The diagnostic parameters of cylinder sealing mainly include cylinder compression pressure, crankcase leakage, cylinder leakage, cylinder leakage rate and intake pipe vacuum.
19, cylinder pressure gauge detection conditions: the engine runs to the normal working temperature. The starter is used to drive the engine to run with all spark plugs or fuel injectors removed, and its rotation speed should comply with the original factory regulations.
Diagnostic parameter standard: the pressure of each cylinder of the engine is not less than 85% of the original design value, and the difference between the pressure of each cylinder and the average pressure of each cylinder is not more than 8% of that of the gasoline engine. Diesel engine shall not exceed10%; The cylinder pressure after engine overhaul shall conform to the original design regulations, and the difference between the cylinder pressure of gasoline engine and the average pressure of each cylinder shall not exceed 8%, and that of diesel engine shall not exceed 10%.
20. After the FA contact is closed, the second closing oscillation occurs first, and then the secondary voltage gradually becomes zero from a negative value.
2 1. Types of abnormal engine noise: mainly mechanical noise, combustion noise, aerodynamic noise and electromagnetic noise. (1) Mechanical abnormal sound is mainly the impact and vibration caused by the damage of the mating surface after the mating clearance of the motion pair is too large. (2) Abnormal combustion noise is mainly caused by abnormal engine combustion. (3) The abnormal aerodynamic noise is mainly caused by the airflow vibration at the air inlet, air outlet and running fan of the engine. (4) Abnormal electromagnetic sound is mainly caused by the alternating change of magnetic field in engines, motors and some electromagnetic devices, which causes the vibration of some parts or parts of the machinery. The influencing factors of engine abnormal sound are speed, temperature, load and lubrication condition; When the gasoline engine is overheated, it often produces ignition knocking sound (deflagration or surface ignition); When the temperature of diesel engine is too low, it will often produce sparking sound (rough workmanship).
22. Crankshaft main bearing noise: 1) Phenomenon: When the car accelerates or the engine suddenly accelerates, the engine makes a heavy and powerful metal knocking sound, or "just, just, just". In severe cases, the engine block vibrates greatly, and the noise increases with the increase of engine speed and load, and the noise is generated on the crankshaft and crankshaft shaft. 2) Reason: (1) The fixing screw of crankshaft main bearing cover is loose; (2) The running-in metal of crankshaft main bearing burns out or falls off; (3) Excessive wear of crankshaft main bearing and journal, and excessive wear of axial thrust device, resulting in excessive radial and axial clearance; (4) The crankshaft bending is not corrected, so the fit clearance between the main bearing and the journal has to be increased when assembling the engine; (5) The oil pressure is too low, the viscosity is too small or the oil is deteriorated.
23. Crankshaft connecting rod bearing ring: 1) Phenomenon: When the car accelerates, the engine suddenly accelerates and the engine makes a "clang, clang". "Bang" continuous obvious, light and short metal knocking sound (main feature); When the connecting rod bearing is seriously loose, obvious noise can be heard at idle speed, and the oil pressure is reduced; When the engine temperature changes, the noise does not change obviously; The noise increases with the increase of engine speed and load, and the noise is generated in the upper part of the crankcase; When a single cylinder is on fire, the noise is obviously weakened or disappeared, but it reappears when the fire is resumed, that is, there is a phenomenon of noise "on the cylinder". 2) Cause: (1) The fixing bolt of crankshaft connecting rod bearing cover is loose or broken; (2) The running-in reducing metal of crankshaft connecting rod bearing is burnt out or falls off; (3) Excessive wear of crankshaft connecting rod bearing or journal leads to excessive radial clearance; (4) The oil passage through the connecting rod journal in the crankshaft is blocked; (5) High oil pressure, low viscosity or oil deterioration.
24. The swimming angle of transmission system is the sum of the swimming angles of clutch, transmission, universal transmission and drive axle, also known as the total swimming angle of transmission system. Detection methods include experience inspection and instrument inspection; Instrument detection includes pointer and digital; The pointer detector consists of pointer, dial and measuring wrench, and the digital detector consists of inclination sensor and measuring instrument. Test steps of empirical test method: the empirical test method can check the running angle of the transmission system in sections, and then add the surge angles of each section to get the total running angle of the transmission system. (1) Inspection of the deviation angle between the clutch and the transmission: The clutch area is in the combined state, hang the transmission in the gear to be inspected, release the parking brake, and then turn the flange or parking brake disc on the transmission output shaft from one extreme position to another by hand under the vehicle. The rotation angle between the two extreme positions is the deviation angle from the clutch to the transmission output end in this gear. Hang into each gear in turn, and you can get the swimming angle under each gear. (2) Check the swimming angle of the universal drive: set up the drive axle, tighten the parking brake, and then turn the flange of the drive axle from one extreme position to the other by hand under the car. The included angle between the two extreme positions is the swimming angle of the universal drive. (3) Inspection of the swing angle of the drive axle: release the parking brake, put the transmission in neutral position, the drive axle touches the ground or is in braking state, and then turn the flange of the drive axle from one extreme position under the vehicle to another extreme position, and the angle between the two extreme positions is the swing angle of the drive axle. The above three sections are the swimming angles of the transmission system.
25. The function of the inclination sensor is to convert the inclination of the sensor housing swimming with the transmission shaft into electric oscillation with corresponding frequency.
26. Swimming Angle Reference: Clutch and Transmission
27. Excessive free travel of the steering wheel: 1) Phenomenon: The car is stationary and the two front wheels keep moving in a straight line. Gently turn the steering wheel back and forth, feeling that the swimming angle is very large; 2) Reason: (1) Loose connection between steering wheel and steering shaft; (2) The meshing part of the driving part and the driven part in the steering wheel is loose or the bearings of the driving part and the driven part are loose; (3) The connection between the vertical arm shaft of the steering gear and the vertical arm is loose; (4) The ball joint of the longitudinal and transverse steering rods is loose; (5) The connection between the longitudinal and transverse steering arm and the steering knuckle is loose; (6)
28. Heavy steering: 1) Phenomenon: When the driver turns the steering wheel left and right while driving, he feels heavy and laborious and has no sense of righting; When the car turns or turns around at a low speed, it is more laborious to turn the steering wheel; 2) Reason (1) Insufficient tire pressure (2) Excessive preload of the bearing of the steering gear driving part or tight fit between the driven part (vertical arm shaft) and the bushing (3) Too tight engagement adjustment between the driving part and the driven part of the steering gear (4) No oil or lack of oil in the steering gear (5) Too tight fit or lack of oil between the steering knuckle and the kingpin (6) Oil or damage to the steering knuckle thrust bearing (7). The ball joint of the transverse steering tie rod is adjusted too tightly or is short of oil (8). The steering shaft connected with the steering wheel is bent or its sleeve is sunken, which causes the deformation of the front cross beam and the frame when the kingpin is scraped (9) too inward or the front wheel is negative outward (10), resulting in inaccurate positioning of the front wheel.
29. Automatic deviation: 1) Phenomenon: the car automatically runs to one side while driving. You must hold the steering wheel hard to keep driving straight. 2) Reason: (1) The pressure of the two front tires is unequal, the diameters are different or the car is unevenly stressed. (2) The tightness of the hub bearing or hub oil seal of the two front wheels is different. (3) The camber angle, caster angle and toe angle of the two front wheels are unequal or the toe-in distribution of the front wheels is uneven. (4) The deflection or elasticity of the left and right leaf springs are different. (5) The axle tube or frame of the rear axle is bent on a horizontal plane. (6) The wheelbase on both sides of the frame is not equal. (7) The wheels at both ends of the front wheel and the rear wheel axle have unilateral braking or unilateral braking delay. (8) The toe-in of the front wheel is too small or negative. (9) The road arch is too large or there is crosswind.
30. The detection of wheel alignment includes the detection of steering wheel (usually front wheel) and the detection of non-steering wheel (usually rear wheel). The detection of steering wheel and non-steering wheel positioning, that is, the detection of front wheel and rear wheel positioning, is collectively called four-wheel positioning detection. Front wheel alignment includes front wheel camber, front wheel toe-in, caster angle and caster angle, which is an important diagnostic parameter to evaluate the stability of straight driving, handling stability and the technical condition of front axle and steering system. Rear wheel positioning mainly includes rear wheel camber and toe-in, which can be used to evaluate the linear driving stability and technical condition of rear axle.
3 1, static detection method; In the stationary state of the automobile, according to the direct or indirect geometric relationship between the wheel rotation plane and the wheel positioning, the geometric angle of the wheel positioning is measured with special testing equipment. The commonly used detection equipment includes bubble level, optics, laser, electronic and microcomputer front wheel aligner or four-wheel aligner; Dynamic detection method: when the car is driving at a certain speed, it uses detection equipment to detect the lateral force caused by wheel positioning or the wheel side slip caused by it.
32. According to the applicable vehicle range, the bubble level wheel locator can be divided into two types: one is suitable for large, medium and small cars, and the other is suitable for small cars. The former generally consists of a level, a bracket, a turntable (also known as a goniometer), etc. The latter generally consists of a level and a turntable. The turntable is generally composed of a fixed disk, a movable disk, a sector ruler, a cursor pointer, a lock pin and a plurality of balls, and the balls are installed between the fixed disk and the movable disk.
33. Detection of the maximum steering angle of the front wheel: refers to the angles of the left and right steering limit positions when the front wheel is in a straight-line driving position. Because the steering gear and longitudinal tie rod of some cars are arranged on one side of the frame, in order to prevent tire abrasion, the maximum turning angle from left to right is not equal. The detection method is as follows: (1) After finding the straight driving position of the front wheel, set the sector scale of the turntable at zero and fix it; (2) Turn the steering wheel, turn the front wheel to the limit position on both sides, read and record the angle value from the sector scale, and compare it with the value specified by the original factory. The maximum angle of the front wheel that does not meet the requirements can be adjusted by adjusting the limit screw on the steering knuckle until it meets the requirements. (3) Turn the steering wheel and turn the front wheel to the limit position on the other side. The maximum angle of the front wheel on the other side can be measured in the same way as above, and adjusted as needed.
34. The items that can be detected by the four-wheel alignment instrument include: front wheel toe, front wheel camber, caster angle, caster angle, rear wheel toe, rear wheel camber, wheel track, wheelbase, rear wheel axle thrust angle and left-right wheelbase difference.
35. The amount of free rotation of the steering wheel refers to the swimming angle measured by gently shaking the steering wheel left and right when the steering wheel of the car keeps moving in a straight line. Steering force of steering wheel refers to the circumferential force acting on the outer edge of steering wheel under certain driving conditions.
Diagnostic parameter standard: 1) Free turning amount of steering wheel: The maximum free turning amount of steering wheel of motor vehicle shall not be greater than the left or right angle from the middle position. (1) The motor vehicle with the maximum design speed greater than or equal to 100km/h is 10 degree (2) The motor vehicle with the maximum design speed less than 100km/h (except for three-wheeled agricultural transport vehicles) is 15 degree (3) Three-wheeled agricultural transport vehicles are. 2) Steering force of steering wheel: When the motor vehicle runs on a flat, hard, dry and clean cement or asphalt pavement, it will travel from a straight line to a circular line with a diameter of 24m within 5s at a speed of 10km/h, and the maximum tangential force applied to the outer edge of the steering wheel shall not be greater than 245N N.
36. Wheel dynamic imbalance: Even a wheel that is statically balanced, that is, a wheel whose center of gravity coincides with the center of rotation, may be dynamically unbalanced.
37. Causes of wheel imbalance: 1) The axis of hub and brake drum (disc) is not accurately positioned during machining, resulting in large machining error, large casting error of non-machined surface, heat treatment deformation, and uneven deformation or wear during use. 2) The quality of hub bolts is uneven, the hub mass distribution is uneven or the radial circular runout is too large. 3) The tire mass distribution is uneven, the size or shape error is too large, and it is deformed or worn unevenly during use. 4) Tire repair: the inflation nozzles of twin tires are not separated by 180 degrees, and the inflation nozzles of single tires are not separated by 180 degrees. 5) When the wheel hub, brake drum, tire bolt, rim, inner tube, liner and tire are disassembled and reassembled into tires, the accumulated unbalanced mass or shape and position deviation is too large, which destroys the original balance.
38. Types of wheel balancing machines: static wheel balancing machines and dynamic wheel balancing machines according to functions; According to the measurement method, the vehicle type and vehicle type are separated ~; According to the form of wheel balancer shaft, there are soft wheels and hard wheels ~
39. The principle of detecting the static imbalance of wheels with on-board wheel balancer: If the wheels scattered on the ground are unbalanced, the up-and-down vibration generated during rotation is transmitted to the sensing head, adjustable strut and sensor in the base of the detection device through the knuckle or suspension. The electric signal changed by the sensor controls the strong point flash to indicate the position of the wheel unbalance point, and the input indicator is only the unbalance degree. When the sensor transmits downward force, the time-frequency flashing light will light up, and the lowest point of the illuminated wheel is the unbalanced point. The greater the mass of the unbalanced point, the greater the force on the sensor, the greater the converted electric quantity, and the greater the value indicated by the indicating device.
40. The principle of detecting wheel dynamic imbalance with vehicle wheel balancer is the same as that of static imbalance, except that the sensor head is fixed on the brake floor to detect lateral vibration. The lateral vibration is transmitted to the sensor in the base through the sensor head and the adjustable strut, and the electric signal converted by the sensor controls the strong point flash to indicate the position of the wheel unbalance point, and is input into the indicating device to indicate the wheel unbalance degree.
4 1, the balance weight of wheel dynamic balancing machine is also called counterweight, and there are usually two types: clamping type and pasting type.
42. Braking deviation: 1) Phenomenon: When the vehicle is braked, the driving direction of the vehicle is skewed; When the car brakes suddenly, the car will shake its head or tail. 2) Reason: (1) The friction plates of the left and right wheel brake shoes are made of different materials or have different old and new degrees; (2) The contact areas, contact positions or braking gaps between the friction plates of the left and right wheel brake shoes and the brake drum are different; (3) The technical conditions of the left and right wheel brake cylinders are different, resulting in different action time or different opening force; (4) The tension of the return springs of the left and right wheel brake shoes is different. ...............................
43, driving wheel output power detection, namely chassis dynamometer. The purpose of chassis dynamometer. First, in order to obtain the output power or driving force of the driving wheel, so as to evaluate the dynamic performance of the automobile; The second is to compare the output power of the driving wheel with the output power of the engine flywheel to find out the transmission efficiency, so as to judge the technical status of the chassis transmission system.
44. Types of chassis dynamometer: According to the different forms of dynamometer, it can be divided into hydraulic type, electric type and eddy current type; According to the cooling mode of dynamometer, it can be divided into air-cooled, water-cooled and oil-cooled types. According to the bearing capacity of the roller device, it can be divided into small (~ 3t), medium (3 ~ 6), large (6 ~ 10) and extra large (10 ~).
45. The automobile fuel consumption meter is generally composed of sensors and measuring display instruments, which are connected by cables and divided into volumetric (diaphragm, measuring tube and piston) and mass type. The sensor of four-piston automobile fuel consumption meter consists of flow measurement mechanism and signal conversion mechanism.
46. Installation method: connect the fuel consumption meter sensor in series on the fuel supply pipeline of the fuel system: the carburetor gasoline engine should be connected in series between the gasoline pump and the carburetor; The diesel engine should be connected in series between the diesel filter and the diesel pump, and the fuel returning from the high-pressure oil return pipe and the low-pressure oil return pipe should be connected between the fuel consumption meter sensor and the fuel injection pump to avoid repeated metering; The electronically controlled fuel injection engine should be connected in series between the fuel filter and the fuel distribution pipe, and the fuel flowing back to the fuel tank from the fuel pressure regulator through the oil return pipe should be connected between the fuel consumption meter sensor and the fuel distribution pipe to avoid repeated metering.
47. Schematic diagram of gas separator; When the fuel mixed with gas enters the float chamber of the gas separator, the gas will force the oil level in the float chamber to drop, so that the needle valve will open and the gas will be discharged into the atmosphere. The fuel entering the sensor from the oil outlet pipe has no gas, which improves the measurement accuracy.
48. The sideslip test bench is a kind of test equipment to measure the lateral slip of the front wheel of an automobile and judge whether it is qualified or not. Can be divided into skateboard and drum. The main purpose of sideslip test bench is to know whether toe-in and camber are appropriate. The skateboard test-bed is to measure the front wheel side slip by using the principle that the skateboard can slide sideways under the action of lateral force. The influence of front camber (or negative camber) on skateboard, whether the vehicle is moving forward or backward, its sideslip amount is equal and its sideslip direction is the same; The front wheel toe-in (or negative toe-in) acts on the skateboard. When the vehicle moves forward and backward, although the sideslip amount is equal, the sideslip direction is opposite.
49. According to the national standard, use the sideslip test bench to detect the front wheel sideslip, and its value is not more than 5m/km; Motor vehicles can use braking distance, braking deceleration and braking force to test braking performance, and if one of them meets the requirements, it will be judged as qualified.
50. Check the technical condition of the rear axle; In addition to some cars, the rear wheels also have toe-in and camber, and quite a few cars have no positioning. The sideslip test bench can be used to test whether the rear axle is bent or deformed and whether the hub bearing is loose. The method is as follows. 1) make the rear wheel of the car pass back and forth from the skateboard of the sideslip test bench. If both sideslip readings are zero, this means that the rear axle is not bent. 2) If the two sideslip readings are not zero, and the sideslip readings after passing through the side skateboard are equal and the sideslip directions are opposite, it means that the rear axle is bent in the horizontal plane. If the skateboard slides outward when moving forward and inward when moving backward, it means that the rear axle end bends forward on the horizontal plane. B. If the skateboard slides inward when moving forward, it will slide outward when moving backward, that is, the rear end will bend backward in the horizontal plane. 3) If the two sideslip readings are not zero, the sideslip readings are equal but the sideslip direction is the same after the side skateboard moves back and forth, indicating that the rear axle is bent in the vertical plane. If the skateboard slides outward, it means that the rear axle end is bent upward in the vertical plane. If the skateboard slides inward, it means that the rear axle end bends downward in the vertical plane. 4.
5 1. The braking deceleration can be divided into stable braking deceleration, average deceleration and fully issued average deceleration according to different testing, values and calculation methods. For the braking performance of road test, the fully released average deceleration FMDD is used as the evaluation index.
52. Disadvantages of the road test method: (1) The road test method can only measure the braking performance of the whole vehicle, but the difference of braking performance of each wheel can be qualitatively analyzed from towing and stamping, and quantitative data cannot be obtained. (2) For vehicles with unqualified braking performance, the specific parts of the fault are not diagnosed. (3) The length of braking distance and the size of braking deceleration often vary with the driver's operation method, road conditions and the situation of cars, horses and pedestrians, and the repeatability is poor. (4) In addition to road conditions, the road test will also be limited by climatic conditions. And the risk of accidents. (5) The road test method consumes oil and wears tires, which has adverse effects on all parts of the vehicle. This test-bed is fast, economical, safe, not limited by external natural conditions, good test repeatability, and can quantitatively indicate the braking force or braking distance of each wheel, so it is widely used.
53. Types of brake test-bed: according to the measuring principle of the test-bed, it can be divided into reaction type and inertia type, drum type and flat type according to the types of wheels supported by the test-bed, braking force type, braking distance type and multifunctional type according to the different test parameters of the test-bed, mechanical type, hydraulic type and electric type according to the different ways in which the measuring device of the test-bed transmits signals to the indicating device, and single shaft type, double shaft type and multi-shaft type according to the number of shafts that can be measured at the same time.
54. The measuring device of the reaction drum brake test-bed consists of a force measuring lever, a force measuring sensor and a force measuring spring; The driving device consists of a motor, a reducer and a chain drive.
55. The braking coordination time refers to the time from the beginning of pedal action to the deceleration (or braking force) of the vehicle reaching 75% of the specified average deceleration.