During the working process, the injection process of the pump injector can be divided into two stages: pre-injection and main injection, or it can be divided into pre-injection, pre-injection end, main injection, main injection end, and high pressure oil chamber 5 processes of oil intake.
Injection time and amount are controlled by auxiliary plunger, injection needle valve, injection needle valve return spring, injection needle valve damper and solenoid control valve.
(1) Pre-injection.
When the straight section of the cam is in contact with the rocker arm, the electronic control system supplies power to the solenoid control valve, moves the solenoid control valve needle valve to the left, and cuts off the passage between the high pressure oil chamber and the low pressure oil passage. At the same time, the pump oil column Under the action of the dfsk rocker arm, the plug moves downward against the elastic force of the return spring of the pump oil plunger, so that the oil pressure in the high-pressure oil chamber rises rapidly.
When the oil pressure rises to 18 MPa, the upward thrust generated by the fuel on the cone surface of the injection needle valve is greater than the pre-tightening force of the return spring of the injection needle valve, and the injection needle valve will be jacked up to start pre-injection.
(2) Pre-injection ends.
After the pre-injection starts, the injection needle valve continues to move upwards. When the cam turns over 1/3 of the injection stroke, the lower end of the injection needle valve damper enters the injection needle valve damper hole, and the top of the injection needle valve The fuel can only flow into the return spring cavity of the injection needle valve through a small gap.
In this way, a so-called "hydraulic washer" is formed on the top of the injection needle valve to prevent the injection needle valve from continuing to move upwards, so that the amount of fuel pre-injection is restricted.
As the pump oil plunger continues to move downwards, the oil pressure in the high-pressure oil chamber continues to rise. When the oil pressure reaches the specified value, after the auxiliary plunger moves downward under the action of high-pressure fuel, the volume of the high-pressure oil chamber suddenly Increase, the fuel pressure drops instantly.
At this time, the upward thrust on the cone in the middle of the injection needle valve decreases, and the injection needle valve resets under the action of the return spring of the Geely EC7 injection needle valve (the elastic force increases due to the compression of the auxiliary plunger), and the pre-injection The oil is over.
(3) After the main injection and pre-injection ends.
The pump oil plunger continues to move downward, causing the oil pressure in the high-pressure oil chamber to rise rapidly. When the oil pressure rises to greater than the pre-injection oil pressure (30MPa), the injection needle valve moves upward and the main injection starts. Because the fuel oil pressure in the high-pressure oil chamber rises extremely fast, the oil pressure in the high-pressure oil chamber will continue to rise to about 205MPa.
(4) The main fuel injection ends.
When the electronic control system stops supplying power to the solenoid control valve, the solenoid control valve needle valve moves to the right under the action of the solenoid control needle valve return spring, connecting the high pressure oil chamber and the low pressure oil passage.
At this time, the fuel in the high-pressure fuel chamber flows to the low-pressure fuel passage through the electromagnetic control valve, the fuel pressure in the high-pressure fuel chamber drops, the fuel injection needle valve is reset under the action of the return spring of the fuel injection needle valve, and the auxiliary plunger is spraying The oil passage between the high-pressure oil chamber and the return spring of the injection needle valve is closed under the action of the return spring of the oil needle valve, and the main fuel injection ends.
(5) The high-pressure oil chamber enters the oil.
When the descending section of the cam is in contact with the rocker arm, the pump oil plunger moves upward under the action of the pump oil plunger return spring, and the high-pressure oil chamber generates a vacuum due to the increase in volume.
At this time, the fuel in the low-pressure fuel passage (connected to the fuel inlet pipe) flows to the high-pressure fuel chamber through the electromagnetic control valve until the high-pressure fuel chamber is filled, so as to prepare for the next fuel injection.
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