Gives You An Easy Idea Of How The Injectors Work!
In 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. The injection time and fuel injection volume are controlled by the auxiliary plunger, the injection needle valve, the injection needle valve return spring, the injection needle valve damper, and the 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 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 18MPa, the upward thrust generated by the fuel on the cone surface of the injection needle valve is greater than the preload force of the return spring of the injection needle valve, and the injection needle valve will be jacked up to start pre-injection.
(2) The 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, which prevents the injection needle valve from continuing to move upwards and restricts the amount of fuel pre-injection. 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 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 fuel injection and pre-fuel injection, 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 injection needle valve is reset under the action of the injection needle valve return spring, and the auxiliary plunger is injecting 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 cavity is filled with oil. When the descending section of the cam contacts 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 oil passage (connected to the oil inlet pipe) flows to the high-pressure oil chamber through the electromagnetic control valve until the high-pressure oil chamber is filled, so as to prepare for the next fuel injection.
