JPS59218359A - Fuel-injection pump - Google Patents

Abstract

PURPOSE:To prevent both secondary injection at high load and abnormal injection at low load from occurring, by installing such a piston that is slidably fitted inside a hydraulic cylinder and simultaneously comes into contact with a spring keeper, in case of a fuel injection valve for an internal-combustion engine. CONSTITUTION:Enregizing force of a needle valve spring 4 is adjusted by an adjust screw 3 via a spring keeper 10. On the top of a body 1, there is provided with a cylinder 9 in which pistons 11 and 12 are slidably fitted. Fuel enters an oil sump 31 by way of an oil hole 30 and pushes a needle valve 6 upward against the energizing force of the needle valve spring 4, then injected into the cylinder from a nozzle hole 32. In time of low load, there is a clearance l, making valve opening pressure into being low but in time of high load, the clearance lcomes to zero by movements of these pistons 11 and 12 whereby the valve opening pressure goes up. Thus both of abnormal injection at low load and seconday injection at high speed are preventable.

Description

DETAILED DESCRIPTION OF THE INVENTION An example of a conventional automatic fuel injection valve for a diesel engine is shown in FIG. In the figure, 1 is the main body, 2 is the nozzle, 3 is the adjustment screw, 4 is the needle valve spring, 5 is the push rod, 6 is the needle valve, 7 is the lower spring holder, 8 is the lock nut sb, and the fuel is removed as shown by the arrow. Supplied. The opening pressure of the needle valve 6 is adjusted by an adjusting screw 3, and since the adjusting screw 3 is fixed by a lock nut 8, the opening pressure cannot be changed during operation. Generally, as the load and rotation speed of the L roller increases, the fuel pressure increases and the fluctuating pressure in the injection path also increases. Therefore, in order to improve the sharpness of injection and prevent secondary injection, the amount of suction back into the injection pump discharge valve has generally been increased or the valve opening pressure has been increased. However, in this method, the valve opening pressure must be set high from the beginning in order to prevent secondary injection under high loads. This has the disadvantage that, at low loads, the abnormal injection region becomes wider due to intermittent injection or irregular injection, and the region where normal injection is performed becomes narrower.

The present invention was made in view of the above, and an object of the present invention is to provide a fuel injection valve that prevents both secondary injection under high load and abnormal injection under low load, and achieves normal injection in the entire load range. shall be.

An embodiment of the present invention will be described below with reference to FIG. 2, which is a sectional view taken along the axis of the needle valve. In the same figure, the nozzle 2 is firmly fastened to the main body 1 by a cap nut 33, and the needle valve 6 is slidably guided inside the nozzle 2 in an oil-tight manner. The needle valve 6 is biased by the needle valve spring 4 via the push rod 5 and the lower spring receiver 7, and the tip of the needle valve 6 is normally pressed against the nozzle seat 2a by this biasing force. The biasing force of the needle valve spring 4 is adjusted by the adjusting screw 3 via a spring retainer 10 that is slidably fitted into the adjusting screw 3. This adjustment screw 3 is the lock nut 8
Fixed by The upper part of the spring retainer 10 has a nut 19 for adjusting the gap 1 between the spring retainer 10 and the upper surface of the adjusting screw 3, and a lock nut 20 for fixing the nut 19. A cylinder 9 is provided on the upper surface of the main body 1, and pistons 11 and 12 are slidably fitted inside the cylinder 9. piston 1
1 , 12 and the cylinder 9 are provided with fluid chambers 13 , 14 , and below the piston 11 is an atmospheric chamber 15 that communicates with the atmosphere through a hole 16 . A passage 11a and a groove 11 that communicate with and 14.
b is provided. Furthermore, a lid 21 having an inlet hole 23 for working fluid is provided at the upper end of the cylinder 9.
The pistons 11, 12 and the lid 21 are integrated into the cylinder 9 and are fixed to the main body 1 with bolts 22 as complete parts.

The cylinder 9 also has a piston stopper 18 and an atmosphere release hole 1.
7 below.

In the above device, fuel pumped from a fuel injection pump (not shown) passes through the oil reservoir 30 and enters the oil reservoir 31, pushes up the needle valve 6 against the biasing force of the needle valve spring 4, and pushes the seat portion 2a open. , and is injected into the cylinder from the nozzle 32 through the nozzle chamber 34. The biasing force of the needle valve spring 4 is the fuel pressure that starts pushing up the needle valve 6, that is, the valve opening pressure, which is normally 300 Kf/
/c/I is adjusted with the adjustment screw 3,
It is fixed with a lock nut 8. If the valve opening pressure is set to this level, irregular injection or intermittent injection will not occur even under low load.

On the other hand, during high-load operation, the working fluid that has entered the fluid chamber 13 through the inlet hole 23 from the controller (not shown) flows into the piston 1.
It acts on the upper surface of the piston 12 and enters the fluid chamber 14 through the passage 11a and the groove 11b, and also acts on the upper surface of the piston 12. This fluid pressure is applied to the needle valve spring 4 which is pushing down the needle valve 6.
Since the biasing force of piston 11 is set larger than that of
, 12 are pushed down, the spring holder 10 is lowered, the needle valve spring 4 is compressed by the gap l, the urging force on the needle valve 6 increases, and the valve opening pressure of the seat portion 2a increases.

The above-mentioned clearance e is set so as to increase the valve opening pressure necessary to prevent secondary injection.

As mentioned above, when the load is low, the gap e exists and the valve opening pressure is low, but when the load is high, the movement of the pistons 11 and 12 makes the gap l become ze 1, and the valve opening pressure increases by this amount. becomes.

The present invention is constructed as described above, and the present invention has the following advantages.

In high-pressure injection systems, the valve-opening pressure is increased as one of the measures to prevent secondary injection, but this high valve-opening pressure increases during low-load operation.
This causes irregular injection or intermittent injection, which impedes the stable rotation of the engine. Further, during low load operation, the fuel pressure is relatively low and secondary injection does not occur.

The present invention prevents irregular and intermittent injection by not guiding the working fluid to the inlet hole during low-load operation, that is, by leaving a gap l and setting the valve opening pressure low using only the biasing force of the needle valve spring. When the load increases to a certain extent and irregular and intermittent injection no longer occurs even with high valve opening pressure, introduce working fluid into the inlet hole,
The biasing force of the needle valve spring 4 is increased by setting the clearance l to zero to increase the valve opening pressure and prevent secondary injection.

In this way, even with a high-pressure injection system, normal injection can be performed over the entire operating range, resulting in stable engine operation and highly durable engine operation with less dirt.

Furthermore, since the cylinder incorporating the piston is mounted on the upper part of the main body 1, the structure is small and compact, and the installation space in the engine is small, and it is possible to obtain a large valve opening pressure.

[Brief explanation of the drawing]

FIG. 1 is a sectional view taken along the axis of a needle valve showing one example of a conventional fuel injection valve for a diesel engine, and FIG. 2 is a view corresponding to FIG. 1 showing one embodiment of the present invention. 1...Body, 2...Nozzle, 4...Needle valve spring, 6
... Needle valve, 9... Cylinder, 10... Spring holder,
11, 12...piston iris

Claims (1)

[Claims] In a fuel injection valve that opens a needle valve against the elasticity of a side valve spring due to the pressure of fuel oil and injects the fuel into a cylinder, the needle valve is slidably fitted into the valve body and has one end connected to the needle valve. a spring holder that comes into contact with the upper end of the spring; a fluid pressure cylinder that is attached to the top of the main body; and a fluid pressure cylinder that is slidably fitted into the fluid pressure cylinder and has one end that comes into contact with the spring holder and is inserted into the cylinder. A fuel injection pump comprising: a piston that moves the spring holder against the elasticity of the needle valve spring by means of a working fluid introduced into the fuel injection pump.