The electric fuel pump is a device that continuously sucks the fuel out of the fuel tank and provides fuel with specified pressure and flow to the fuel system.

 

Classification of Electric Fuel Pumps

 

According to different installation positions, electric fuel pumps can be divided into two types: built-in type and external type.

 

• Built-in type: installed in the fuel tank, it has the advantages of low noise, less air resistance, less leakage, and simpler pipeline installation.
• External type: connected in series in the oil pipeline outside the fuel tank, the advantages are easy layout and large installation freedom, but it is noisy and prone to air resistance.

 

According to different fuel pump structures, it can be divided into turbine type, roller type, gear type, rotor type, side groove type and other types.

 

At present, most electric fuel pumps used in electronically controlled gasoline injection systems are built-in turbo pumps installed in the fuel tank. The built-in electric fuel pump has the advantages of low noise, less air resistance, less leakage, and simpler installation pipeline, etc., and is more widely used. Some models also have a small fuel tank in the fuel tank, and the fuel pump is placed in the small fuel tank, which can prevent the fuel around the fuel pump from moving around the fuel pump when the fuel tank is insufficient, causing the fuel pump to inhale air and generate gas. resistance.

 

External electric fuel pumps mostly adopt the ball type, which is connected in series to the fuel pipeline outside the fuel tank. The advantage is that it is easy to arrange and has a large degree of freedom in installation, but it is noisy and the fuel supply system is prone to air resistance, so it is only used in a few models.

 

Construction of electric fuel pump

 

1) Roller electric fuel pump

It is mainly composed of fuel pump motor, roller pump, oil delivery valve and so on.

 

The roller type electric fuel pump is generally installed outside the fuel tank. Because of its large output pressure fluctuations, a damping shock absorber must be installed at the fuel outlet.

 

①The roller pump is mainly composed of rollers and rotors. The rotor is eccentric and placed in the pump casing. The fuel pump is driven by a DC motor. When the rotor rotates, the rollers located in the rotor groove are pressed tightly by centrifugal force. On the inner surface of the pump housing, it acts as a seal to the surroundings, and a working chamber is formed between two adjacent rollers.

 

During the operation of the fuel pump, after the working chamber turns over the oil outlet, its volume continues to increase, forming With a certain degree of vacuum, when it turns to communicate with the oil inlet, the fuel is inhaled; and after the working chamber that is full of fuel turns over the oil inlet, its volume decreases continuously, so that the pressure of the fuel increases, and the pressurized fuel flows through The electric motor is output from the oil outlet.

 

②Pressure-limiting valve function: It works when the oil pressure of the system is too high, so as to avoid damage to the pipeline due to too high oil pressure.

 

③One-way check valve function: When the oil pump is not running, the valve is closed to prevent the fuel in the pipeline from flowing back into the fuel tank, making it difficult to start the car next time.

 

(2) Turbo pump

 

The turbo electric fuel pump is mainly composed of a motor, a turbo pump, an oil outlet valve (one-way valve), a pressure relief valve (safety valve), etc. Before the fuel in the fuel tank enters the fuel inlet chamber in the fuel pump, it first passes through the filter screen filter. The motor and the blades are integrated and sealed in the same housing.

 

The turbo pump is mainly composed of impeller, vane, pump housing and pump cover (as shown in Figure 2-1-5), and the impeller is installed on the rotor shaft of the fuel pump motor. When the motor is energized, the motor drives the impeller to rotate. Under the action of centrifugal force, the blades in the small groove around the impeller cling to the pump casing and bring the fuel from the oil inlet chamber to the oil outlet chamber.

 

As the fuel in the fuel inlet chamber is continuously taken away, a certain degree of vacuum is formed, and the fuel in the fuel tank is sucked through the fuel inlet; while the fuel in the fuel outlet chamber continues to increase, the fuel pressure rises, when the oil pressure reaches a certain value , then top open the oil outlet valve to output through the oil outlet. The delivery valve and pressure relief valve function the same as the turbo pump electric fuel pump.

 

The Role of the Electric Fuel Pump 

 

1. At present, the fuel pump of most models is installed in the fuel tank of the car. The fuel pump driven by electricity is composed of three parts: the pump body, the permanent magnet motor and the casing.

 

2. Fuel flows through the inside of the electric fuel pump, cooling the armature of the permanent magnet motor, also called wet fuel pump.

 

3. The additional function of the fuel pump is completed by the safety valve and check valve. The safety valve can prevent the oil pipe from breaking or the fuel pump from being damaged due to excessive pressure rise when the fuel pipe is blocked.

 

4. The purpose of setting the check valve is to seal the oil circuit and maintain a certain residual pressure in the fuel system when the fuel pump stops working, so that the engine can be started easily next time.

 

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