JPS6211327Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a pressure accumulation type fuel injection device for an internal combustion engine.

In a conventional pressure accumulation type fuel injection system, the following equation holds true, where Q is the injection amount, ΔP is the pressure in the pressure accumulation chamber minus the valve closing pressure, β is the bulk elasticity coefficient of the fuel, and V is the volume of the pressure accumulation chamber.

ΔP=β・Q/V……(1) In this case, V has the following requirements.

(1) Large enough to avoid excessive pressure at the maximum injection amount; (2) Small enough to ensure the minimum injection amount;
It is difficult to obtain a V that satisfies the above requirements at the same time.

The present invention was developed in view of the above circumstances, and its purpose is to make it possible to change the volume of the pressure accumulation chamber according to the internal pressure, so that when the injection amount is small, the pressure accumulation The purpose is to reduce the volume V of the chamber to ensure a minimum injection amount, and when the injection amount is large, the volume V of the pressure accumulation chamber is also increased to avoid excessive pressure at the maximum injection amount.

EMBODIMENT OF THE INVENTION Hereinafter, the pressure accumulation type fuel injection device based on this invention is demonstrated with reference to drawings.

In the drawing, 6 is a valve body, and a nozzle part 7 is fitted to the lower end of the valve body 6, and a head member 8 is fitted to the upper end of the valve body 6.

A guide portion 9 is formed in the lower part of the head member 8, and a piston member 10 is slidably provided on this guide portion 9, and the piston member 10 also extends against the inner circumferential surface of the valve body 6. It is made to be able to slide freely. An upper spring 1 is interposed between the piston member 10 and the head member 8. In the drawing, 11 is a needle, and the lower end of the needle 11 is slidably inserted into the hole 12 of the nozzle part 7.

A spring receiver 5 is fixed to the needle 11, a valve member 3 is slidably provided to the needle 11, and a lower spring 4 is interposed between the spring receiver 5 and the valve member 3. be.

A fuel supply passage 12 is formed in the head member 8, and the supply passage 12 opens at the lower end surface of the guide portion 9, and the supply passage 12 is connected to the discharge side of the jerk pump. Further, a punch hole 13 is formed in the head member 8.

A chamber 14 is formed in the nozzle part 7,
The chamber 14 communicates with a pressure accumulating chamber 16 via a guide hole 15, and the nozzle portion 7 is provided with a spout 15 communicating with the chamber 14.

The valve member 3 is biased by the lower spring 4, and the peripheral edge 20 of the recess 19 of the valve member 3 is in contact with the lower surface of the piston member 10 to form a pressure chamber 18, and these are connected to the supply path. 12 and the pressure accumulation chamber 16, and these constitute a check valve 17.

Thus, the fuel pumped by the jerk pump enters between the valve member 3 and the piston member 10 through the oil supply hole 12, causes the piston member 10 to rise against the upper spring 1, and the fuel enters the pressure accumulation chamber 16. As the pressure within the pressure accumulation chamber 16 increases, the piston member 10 and the valve member 3 rise.

Next, the injection process begins, and at the same time as the pressure on the jerk pump side is released, the needle 11 rises and injection starts. As the pressure within the pressure accumulation chamber 16 decreases, the piston member 10 and the valve member 3 descend.

When the pressure in the pressure accumulation chamber 16 becomes below the standard value,
The needle 1 is moved by the resultant force of the lower springs 1 and 4.
1 descends and the injection ends.

The volume V of the pressure accumulator 16 is a function of the pressure P in the pressure accumulator: V=VO+AP...(2) If the valve closing pressure is PC, P=PC+ΔP...(3) From (2) and (3), V=VO+A (PC + ΔP) ...(4) If V at valve closing pressure is Vc, then Vc = VO + Apc
...(5) From (4) and (5) V=Vc+AΔP ...(6) From (1) and (6) ΔP=β・Q/(Vc+AΔP)
...(7) The above is shown in a graph as shown in Figure 4. However, V in equation (1) was set to V=Vc.

In the drawing, A is equation (1) and B is equation (2).

The present invention has been described in detail above, and the piston member 10 is provided in the valve body 6 and is slidably guided by the guide portion 9 of the head member 8 to form the pressure accumulation chamber 16 in the valve body 6. A valve member 3 having a concave portion 19 on the upper surface of the needle 11 provided in the pressure accumulating chamber 16
is slidably provided, a lower spring 4 is interposed between the valve member 3 and a spring receiver 5 provided on the needle 11, and an upper spring 1 is interposed between the head member 8 and the piston member 10. Since the valve member 3 is pressed against the piston member 10 by the upper and lower springs 1 and 4 to form a pressure chamber 18 consisting of a recess, and the fuel supply path 12 is opened in the pressure chamber 18, the volume of the pressure accumulation chamber 16 is can be changed according to this internal pressure, so when the injection amount is small, the volume V of the pressure accumulation chamber 16 is also reduced, ensuring the minimum injection amount, and when the injection amount is large, the Accumulator chamber 1
The volume V of No. 6 is also increased, and excessive pressure at the time of maximum injection amount can be avoided.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of an embodiment of the present invention;
FIG. 3 is an explanatory view of the same operation, and FIG. 4 is a diagram showing the relationship between the differential pressure ΔP between the pressure accumulation chamber and the valve opening pressure and the injection amount Q. 1 is an upper spring, 10 is a piston member, 3
1 is a valve member, 4 is a lower spring, 11 is a needle, 16 is a pressure accumulation chamber, and 18 is a pressure chamber.

Claims (1)

[Scope of utility model registration request] A piston member 10 is provided in the valve body 6 and is slidably guided by the guide portion 9 of the head member 8 to form a pressure accumulation chamber 16 within the valve body 6. , a valve member 3 having a recess 19 on the upper surface is slidably provided, a lower spring 4 is interposed between the valve member 3 and a spring support 5 provided on the needle 11, and the head member 8 and the piston member 10 are connected to each other. With the upper spring 1 interposed between them,
A pressure accumulation type fuel injection characterized in that a valve member 3 is pressed against a piston member 10 by lower springs 1 and 4 to form a pressure chamber 18 consisting of a recess, and a fuel supply path 12 is opened in the pressure chamber 18. Device.