What are the functions and characteristics of automobile gasoline pump?

The installation classification of fuel pump is divided into traditional structure and electric fuel pump. At present, cars use electric gasoline pumps, which are driven by a small motor that uses direct current. The function of the automobile oil pump is very simple, that is, to pump the fuel from the fuel tank and provide continuous, stable and sufficient pressure for the fuel injectors, fuel pipes and other components.

The earliest automobile manufacturer that used gasoline pump was Buick Automobile Manufacturing Company in the United States. Most electric fuel pumps are installed in the fuel tank and sealed by the fuel tank cover. If installed on the engine or chassis, the noise will be very loud, and there will be hidden dangers such as oil leakage (fear of bottoming out) and air intake. Therefore, external installation is not used. The advantages of built-in oil pump are large pumping capacity and stable oil supply.

Specific analysis of the function of gasoline pump

There are many types of electric gasoline pumps, such as drum type and vane type. The structure is as follows, consisting of a buffer, a check valve and a motor. Both ends of the oil pump are respectively provided with an oil inlet and an oil outlet, and one side of the oil inlet is provided with a power plug.

When the oil pump is energized, the motor in the middle of the casing runs at high speed, and the motor speed is controlled by the engine speed. When idling and accelerating, the motor speed is different, but the oil pump pressure is not wireless, and the maximum pressure is about 400KPa. If the pressure is too high, the tubing is easy to break.

Due to the centrifugal force generated by rotor selection, the roller is thrown out and sealed on the shell wall to generate pressure. When the volume of the oil inlet on the pump body becomes larger and larger, the fuel is sucked into the oil pump and the pressurized gasoline flows out from the oil outlet.

Characteristics of gasoline pump

1, which will not be affected by air pressure and parts wear.

In the past, mechanical diaphragm pumps were used for gasoline pumps. The gasoline pump is driven by an eccentric wheel on the camshaft of the engine. The camshaft of diesel engine is installed in the crankcase, and the camshaft of gasoline engine is installed on the cylinder head. The eccentric wheel drives the rocker arm, the rocker arm drives the diaphragm to pull down, and the diaphragm compresses the spring. At this time, the gap above the diaphragm becomes larger, which generates negative pressure and sucks fuel from the oil inlet. Because the outlet valve is closed, fuel is stored in the space above the diaphragm.

Due to the continuous operation of the camshaft, the eccentric wheel continuously drives and leaves the rocker arm of the oil pump to complete the oil supply process. In a diesel engine, it is not called a gasoline pump, but a fuel transfer pump, which has the same function as a gasoline pump.

The disadvantage of this kind of oil pump is that the oil pressure will be affected by the vacuum degree, especially the air leakage is serious and the oil pressure fluctuates abnormally. After the camshaft is used for a period of time, the height of some eccentric wheels will be consumed due to wear, and the driving force of the oil pump rocker arm is insufficient.

If an electric oil pump is used, this problem will not exist, because the oil pump rotor is in contact with gasoline, which will not cause wear and tear, and is only responsible for providing pressure. The oil pressure is regulated by the oil pressure regulator, regardless of the atmospheric pressure.

2. The control of gasoline pump is controlled by electronic control unit.

The control circuit of the gasoline pump is mainly determined by the ignition switch and ECU, as shown in the following figure. The oil pump relay consists of two coils (L 1 and L2), in which L2 is controlled by the ignition switch, which controls the operation of the oil pump during starting. L 1 is controlled by the engine electronic control unit. After starting, the engine speed ne signal is transmitted to the electronic control unit to keep the oil pump running.

The oil pump will work as long as the engine is running. If the engine stops running, the interrupted signal will make the transistor VT non-conductive, the relay L 1 will not work, and the oil pump will not work. Even if the engine is not started, the vt control circuit will open as long as the key switch is turned on. Generally, the oil pump will run for 3-5 seconds before stopping, and the pressure in the pipeline is preset.

The rotational speed of the oil pump is determined by the applied voltage. Under the condition of high engine speed and heavy load, the oil supply is large, which can speed up the rotation speed of the oil pump. When the engine is idling under light load, it does not need such a high oil supply, which can reduce the rotation speed of the oil pump and avoid unnecessary energy waste. If the crankshaft position sensor is not used to detect the engine speed, a speed control mechanism should be set in the oil pump.

There is a diagnostic terminal Fp of the oil pump in the diagnostic socket, which can be used to judge the relay. When the ignition switch is turned on (the engine is not started), the Fp and +B terminals are short-circuited by wires, and the oil pump will run.

Summary and suggestions

The gasoline pump in the electronically controlled fuel injection system provides oil pressure for the whole system. If the frequency of use is high and the load of the oil pump is heavy, it is easy to cause problems. When testing the fuel system, we can learn from some common fault phenomena and maintenance experience. For example, if the fault position appears in the control circuit of the oil pump, the circuit can be repaired first, and then the fuel pressure can be detected if there is no problem in the circuit, with emphasis on the oil pressure regulator integrated on the oil pump, because the size of the oil pressure regulator is directly related to the concentration of the mixed gas, which will lead to the oil pump not working normally.

The most important feature of automobile gasoline pump is that it can not only control the oil pump with the control unit, but also avoid the wear and heat caused by the rotation of the oil pump. It is precisely because of these advantages that electric oil pumps are widely used in automobiles.