The working principle of the fuel injection pump is that two sets of opposed plungers are installed on the impeller in the pump. When the impeller is driven by the engine, the plunger also rotates. As the convex part of the cam ring presses the plunger, the plunger It acts like a pump to pressurize the diesel to the oil hole in the center of the impeller. At this time, the diesel sent out fills the inlet of the distributor, and then the cylinders are sprayed in sequence.
Since the number of revolutions of two sets of plunger systems (or one set of plunger systems) increases in proportion to the number of cylinders, this type of injection pump is limited by the number of cylinders and the maximum speed.

With the development of diesel engine technology, a single-type fuel injection pump (called a single pump or a pump nozzle) has emerged. It actually "zeroes" the above two types of fuel injection pumps. Cylinder fuel injection is performed by separate injection units (unit pumps or pump nozzles).

Oil absorption process:
The plunger is driven by the cam of the camshaft. When the convex part of the cam leaves the plunger, the plunger moves down under the action of the plunger spring, the volume of the oil chamber increases, and the pressure decreases. When the oil inlet is exposed, the fuel in the low-pressure oil chamber flows into the pump cavity along the oil inlet.
Oil pumping process: When the plunger of the cam lifts the plunger, the volume in the pump cavity decreases and the pressure increases, and the fuel flows back to the low pressure oil cavity along the radial oil hole on the plunger sleeve. When going up to completely plug the radial oil hole on the plunger sleeve, the pressure on the pump cavity increases rapidly; when this pressure overcomes the pre-tightening force of the outlet valve spring, the outlet valve moves up; when the outlet valve is on When the pressure reducing ring belt leaves the valve seat, the high-pressure diesel is pumped into the high-pressure oil pipe and injected into the cylinder through the injector.

Oil return process:
As the plunger continues to move up, when the chute on the plunger communicates with the radial oil hole on the plunger sleeve, the fuel in the pump cavity passes through the axial oil passage, oblique oil passage and column The oil hole on the plug sleeve flows back to the low-pressure oil chamber and the pump oil stops.

Take the plunger injection pump as an example to see how the "pump" works:
The fuel injection pump requires a power source to run, and the camshaft at the lower part is driven by the engine crank gear.

The key part of the fuel injection pump is the plunger. If a syringe commonly used in hospitals is used as an analogy, the movable stopper is called the plunger, and the syringe is called the plunger sleeve. Assuming a spring is installed inside the needle to press against the post One end of the plug and the other end of the plunger contact the camshaft. When the camshaft rotates once, the plunger will move up and down once in the plunger sleeve. This is the basic movement of the fuel injection pump plunger.

The plunger and plunger sleeve are very precise machining parts. There is an inclined groove on the plunger body. There is a small hole in the plunger sleeve called the suction port. This suction port is filled with diesel oil. When the plunger inclined groove faces the suction port, the diesel oil enters the plunger sleeve and the plunger is camshaft When pushed to a certain height, the inclined groove of the plunger is staggered with the suction port, and the suction port is closed, so that the diesel can neither be sucked in nor pressed out. When the plunger continues to rise, the diesel is pressed, and the diesel pressure will open in one direction when it reaches a certain level. The valves swarmed out into the fuel injection nozzle, and then entered the cylinder combustion chamber from the fuel injection nozzle.

It should be particularly pointed out here that diesel engines have oil inlet and return pipes. The oil inlet pipe is easy to understand. So what is the purpose of the oil return pipe? The original plunger discharged a certain amount of diesel at a time, and only a part of it was injected into the cylinder, and the remaining part was leaked through the oil return hole, and the fuel injection amount was adjusted by increasing or decreasing the returned oil amount.

When the plunger rises to the "top dead center" and moves down, the plunger inclined groove will meet the suction port again, and the diesel is sucked into the plunger sleeve, and the above action is repeated again. Each group of in-line fuel injection pump corresponds to one cylinder. There are 4 groups of piston systems for 4 cylinders, so the volume is relatively large, and it is mostly used in medium-sized cars and above. For example, diesel engines on buses and trucks generally use in-line fuel injection pumps.

Fuel injection pumps on passenger cars and light-duty diesel engines are generally distributed, with the advantages of small size, light weight, and few parts and simple structure. It is pressurized with two sets of plunger systems (or one set of plunger systems), and diesel is sent to each injector separately.

For a single pump, the fuel injection pump and the fuel injector are connected by a short high-pressure oil pipe. For the pump nozzle, the fuel injection pump and the fuel injector are combined into one body and directly installed on the cylinder head of the diesel engine. Driven by an overhead camshaft. Their biggest advantage is that they can reduce or eliminate the pressure wave effect in the high pressure oil pipe during the flow and injection of diesel. Because this pressure wave will prevent the fuel injection system from matching well with the load and speed, and will increase as the length of the high-pressure pipe increases.

Therefore, by shortening the length of the high-pressure fuel pipe (design idea of ​​the fuel injection pump) or simply not using the high-pressure fuel pipe (design idea of ​​the pump nozzle), reducing the high-pressure volume between the plunger and the fuel injection nozzle, you can get a value close to that specified by the cam profile Oil supply law. In particular, pump nozzles have been applied to General Motors more than a decade ago, and now have precise control of electronic technology to improve their performance.

Zhejiang Yongling Hydraulic Machine Co , Ltd . is a professional China manufacturer and supplier of    Oil Pumps  . View and purchase oil pump products, welcome to visit: https://www.china-vanepump.com/product/sqp-series-vane-pumps-with-lower-noise/sqp1-vane-oil-pump-with-lower-noise.html