Model essay entitled "Inspection and Maintenance of Hybrid Electric Vehicles"
Abstract: At present, the hybrid vehicles that have been successfully developed and put into use are mainly hybrid vehicles with internal combustion engines and batteries, which are called hybrid vehicles. First of all, with the improvement of automobile electronic control, especially the development of hybrid electric vehicles, pure electric vehicles and fuel cell vehicles in the future, the main faults of automobiles will appear in the circuit. When faced with complex and chaotic automobile circuits, it is only after having excellent theoretical knowledge that it is possible to sort out and understand them, and to further form a correct diagnosis idea and find a correct maintenance method. As we know, different hybrid electric systems have different structures and working principles, which makes the detection and maintenance methods of different hybrid electric vehicles very different.
Keywords: hybrid electric vehicle, testing, maintenance
The English word for Hybrid Electric Vehicle is "hybrid electric vehicle" or "HEV" for short. According to the recommendation of the Technical Committee of Electric Vehicles of the International Electromechanical Commission, a hybrid vehicle refers to a vehicle that uses two or more energy storage devices, energy sources or converters as the driving energy, and at least one vehicle that can provide electric energy is called a hybrid vehicle. At present, the hybrid vehicles that have been successfully developed and put into use are mainly hybrid vehicles with internal combustion engines and batteries, which are called hybrid vehicles. The hybrid vehicle described in this paper is also limited to this kind of hybrid vehicle.
The so-called hybrid vehicle (hereinafter referred to as hybrid vehicle) refers to the traditional internal combustion engine and electric motor (battery) as power sources, and uses two systems of heat energy and electric energy to drive the vehicle. The internal combustion engine used in hybrid electric vehicle can be gasoline engine or diesel engine, and the electrical system used includes high-efficiency enhanced motor, generator and battery. The combined use of the two systems makes both the internal combustion engine and the motor run in the high-efficiency area economically, and the output power is relatively stable. Fuel provides most of the energy needed for vehicle operation, and the auxiliary power unit, namely the power battery, makes the vehicle have better power and economy through the motor.
I. Overview of Inspection and Maintenance of Hybrid Electric Vehicles
Automobile maintenance work is mainly divided into maintenance, mechanical maintenance, electrical and electronic control system maintenance, sheet metal and painting. For a hybrid electric vehicle, the main difference between it and a traditional internal combustion engine vehicle lies in the addition of an electric drive system, which makes the already complicated electronic control system more complicated, and the maintenance of electrical appliances and electronic control systems is self-evident. Due to the addition of electric drive system and the corresponding transformation of the original internal combustion engine vehicle structure, it is determined that hybrid electric vehicles will inevitably produce new and unique fault types. Some maintenance experience, diagnosis ideas and detection methods that were originally suitable for traditional internal combustion engine vehicles may no longer be suitable for hybrid electric vehicles. Therefore, as maintenance personnel, if they stick to the rules, rely on experience and do not pay attention to the study of theoretical knowledge and the cultivation of diagnostic thinking, they will soon be eliminated. So how should we face the next challenge?
First of all, with the improvement of automobile electronic control, especially the development of hybrid electric vehicles, pure electric vehicles and fuel cell vehicles in the future, the main faults of automobiles will appear in the circuit. When faced with complex and chaotic automobile circuits, it is only after having excellent theoretical knowledge that it is possible to sort out and understand them, and to further form a correct diagnosis idea and find a correct maintenance method.
Secondly, observe more and compare more. On the basis of mastering relevant theoretical knowledge, we should return to practice, observe more and compare more. Carefully observe the structure of the car, carefully compare its similarities and differences with the traditional internal combustion engine car, and the theory is closely related to practice.
Again, sum up frequently. Hybrid electric vehicles are bound to have unique fault types different from the existing traditional internal combustion engine vehicles, which should be recorded in detail and carefully analyzed and summarized in maintenance practice, so as to form a set of effective maintenance methods suitable for hybrid electric vehicles over time.
Second, the detection and maintenance of hybrid electric vehicles
As we know, different hybrid electric systems have different structures and working principles, which makes the detection and maintenance methods of different hybrid electric vehicles very different. Taking Toyota Prius hybrid vehicle as an example, this paper briefly introduces the inspection and maintenance of hybrid vehicle.
1, Precautions for Inspection and Maintenance of Prius Hybrid Vehicle
The Prius uses a high-voltage circuit. The rated voltage of the power battery pack is 20 1.6V, and the voltage generated (or used) by the generator and motor is 500 V. In the circuit system of the Prius, the wiring harness and connectors of the high-voltage circuit are orange, and the high-voltage parts such as batteries are affixed with warning signs of "high voltage". Attention! Don't touch these wires. Paper format. In the process of maintenance, we must strictly follow the correct operation steps. In the process of maintenance (such as installing or disassembling parts, inspecting vehicles, etc.). ), we must pay attention to the following points:
(1) When operating the high-voltage system, turn off the vehicle power switch first;
(2) Wear insulating gloves (before wearing insulating gloves, be sure to check that the gloves are not damaged, even if the eye of the needle is big, there can be no cracks, no signs of aging and no wet);
(3) Disconnect the negative cable of the auxiliary battery (before checking the fault code, it is necessary to save or record the fault code, because the fault code of disconnecting the negative cable of the battery will be cleared, just like the traditional diesel locomotive);
(4) Remove the maintenance plug and put it in the pocket for safekeeping, so as to prevent other personnel from mistakenly putting the maintenance plug back in its original place and causing accidents;
(5) Do not operate the power switch after unplugging the maintenance plug, otherwise the hybrid ECU may be damaged.
(6) Before other operations, leave the vehicle for at least 5 minutes after removing the maintenance plug, because it takes at least 5 minutes for the high-voltage capacitor in the frequency converter to discharge;
(7) When working on high-voltage system, warning signs should be placed in conspicuous places to remind others to pay attention to safety;
(8) Don't carry any metal objects or other conductors with you, so as not to accidentally drop them and cause short circuit;
(9) Remove any high-voltage wiring and immediately wrap it with insulation substitutes to ensure its complete insulation;
(10) Make sure to tighten the high-pressure screw terminal according to the specified torque. Too much or too little torque may lead to failure;
(1 1) After completing the operation of the high-voltage system, before reinstalling and overhauling, it should be confirmed again that there are no parts or tools left around the working platform, the high-voltage terminals are tightened and the connectors are plugged in. Paper format.
2. Basic maintenance procedures of Prius
(1) The vehicle enters the workshop.
(2) Analyze the faults described by each household.
(3) Connect the intelligent diagnostic instrument II to the diagnostic socket of the vehicle.
(4) Read fault codes and frozen frame data and record them. If there is a fault code related to CAN communication system, check and repair CAN communication first.
(5) Clear the fault code.
(6) Confirmation of fault symptoms. If the fault does not appear, simulate the fault symptoms; If there is a fault, please check the fault code and related data flow for relevant information.
(7) Conduct basic inspection and consult relevant information.
(8) Fault diagnosis is carried out according to fault phenomena, fault codes, relevant data streams and other detection means to find out the cause of the fault.
(9) Troubleshooting.
(10) Confirm the troubleshooting.
3. Inspection and maintenance of hybrid control system of Prius hybrid vehicle.
(1) Before operating the control system of the hybrid electric vehicle, it is necessary to understand the composition and working principle of the control system of the hybrid electric vehicle, combine the circuit diagram and relevant maintenance materials, and strictly follow the operation steps in the manual.
(2) Relevant inspection of Prius hybrid power system
① Check the frequency converter.
Check the fault code; Clear the fault code; Wear insulating gloves; Turn off the power switch; Remove the maintenance plug; Remove the inverter cover and disconnect terminals A and B. ..
Turning the power switch to the IG position will produce the fault code of the interlocking switch system; Measure the voltage with a voltmeter and the resistance with an ohmmeter at the harness side.
② Check the converter (operate with insulating gloves)
If the warning light, main warning light and charging warning light of the hybrid system are on at the same time, please check the fault code and troubleshoot accordingly.
③ Check the speed sensor.
Measure the resistance between terminals with an ohmmeter, and the value should meet the standard value, otherwise replace the transaxle assembly.
④ Check the temperature sensor.
Measure the resistance between terminals with an ohmmeter, and the resistance should meet the standard value, otherwise replace the transaxle assembly.
⑤ Check the accelerator pedal position signal.
Turn the power switch to the IG position; Measure the voltage of the corresponding terminal in the connector B of the control ECU of the hybrid electric vehicle with a voltmeter, which should meet the standard value, otherwise replace the accelerator pedal connecting rod assembly.
4. Inspection and maintenance of battery system of Prius hybrid vehicle.
The battery system of Prius hybrid electric vehicle is mainly composed of the following parts: power battery pack, 12V auxiliary battery, battery ECU, cooling system, current sensor, main relay of maintenance plug system, etc.
Power battery pack: Prius adopts Ni-MH power battery pack, which has the characteristics of high power density and long service life. The battery pack is composed of 28 battery modules connected in series, and each module is composed of 6 cells 1V or 2V connected in series. Therefore, the whole battery pack *** 168 single cells can get a high voltage of 20 1.6V in paper format.
Battery ECU: The function of battery ECU is to detect the state of charge (SOC), temperature, voltage, current and leakage of battery pack, and send these information to HV ECU. The battery ECU is also responsible for controlling the operation of the cooling fan to ensure that the battery pack is within the normal temperature range.
Battery cooling system: The battery cooling system consists of a cooling fan, an air temperature sensor, three temperature sensors in the battery and ventilation pipes. Three temperature sensors and an air temperature sensor detect the air inlet temperature of the battery and the air inlet at any time. If the temperature rises to a certain value, the battery ECU will start the cooling fan until the temperature drops to a specified value, thus keeping the temperature of the battery pack within the normal range.
Maintenance plug: The maintenance plug is located between the 19 module and the 20th module of the battery pack. Removing the maintenance plug before inspection or maintenance can cut off the high-voltage circuit in the middle of the battery pack and ensure the safety of personnel during maintenance.
System main relay (SMR): The function of the system main relay is to turn on and off the power supply of the high-voltage circuit according to the instruction of the high-voltage ECU. The system main relay * * * consists of three relays, two of which are located at the positive pole, namely SMR 1 and SMR2, and one is located at the negative pole, namely SMR3. When the circuit is connected, SMR 1 and SMR3 work, then SMR2 works and SMR 1 closes.
Auxiliary battery: Prius adopts 12V maintenance-free battery, which is similar to the traditional automobile battery, and the negative electrode is also grounded through the body. This kind of battery is very sensitive to high voltage. When charging, remove it from the car and charge it with Toyota's special charger. Ordinary chargers have no special voltage control function, which may damage the battery.
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