JPH0437261Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a fuel injection pump used in a diesel engine or the like, and particularly relates to the structure of a delivery valve thereof.

[Technical background of the invention]

A conventional fuel injection pump for a diesel engine has a cylinder 11, a valve seat 12, and a valve holder 13 attached to a pump body 10, and a plunger 1 accommodated in the cylinder 11, as shown in FIG.
4 is reciprocated by a drive cam (not shown) to draw fuel from the fuel reservoir 15 into the plunger chamber 16 and forcefully send this fuel to the discharge valve chamber 18 in the valve holder 13 through the valve hole 17 formed in the valve seat 12. From this discharge valve chamber 18, the fuel is supplied to the injection valve via an injection pipe (not shown). In this case, the delivery valve 20 is placed in the valve hole 17.
The delivery valve 20 is provided with a valve hole 17 by a spring 21 housed in the discharge valve chamber 18.
The pressure of the fuel pressurized in the plunger chamber 16 pushes the delivery valve 20 to open the valve hole 17.

The conventional delivery valve 20 described above includes a conical valve seat portion 22 that approaches and separates from the opening of the valve hole 17 on the discharge valve chamber side;
A flange-shaped relief piston portion 23 that advances into the valve hole 17 to open and close the valve hole 17, and a partial cut portion 24 formed in the relief piston portion 23.
The protrusions 25 , which protrude radially, are connected to the valve hole 17 .
A fuel passage 26 is formed between these protrusions 25...
It is equipped with a sliding guide part 27 that ensures...
In this case, when the delivery valve 20 is pushed by the pressure of the fuel pressurized in the plunger chamber 16 and the relief piston part 23 exceeds the opening on the discharge valve chamber side of the valve hole 17, the valve hole 17 is moved from the plunger chamber 16 to the valve hole 17.
The fuel pumped through the protrusions 25, the fuel passages 26, and the partial cut portions 24 is sent into the discharge valve chamber 18.

[Problems with background technology]

In the above conventional structure, the cut amount of the partial cut portion 24 formed on the relief piston portion 23 is small, about several microns, so a location with good machinability is selected and the conventional method is as shown in FIGS. 5 to 7. , was formed on the extension line of the protrusion 25 formed on the sliding guide part 27.

However, in recent years, with the increase in fuel injection pressure, it is required to increase the suction amount by the delivery valve 20 in order to prevent secondary injection in high load operating ranges, and to prevent abnormal injection in low load operating ranges. Therefore, it is required to increase the cut amount of the partial cut portion 24 to about several tens of microns.

However, when the partial cut part 24 is formed on the extension line of the protrusion part 25 as in the conventional case, the fuel passing through the partial cut part 24 is obstructed by the protrusion part 25 on the extension line, bypasses this protrusion part 25, and enters the second part. The flow becomes curved as shown by the arrow in Figure 5. Such a curved detour flow tends to generate air bubbles near the partial cut portion 24, and these air bubbles are crushed by secondary waves and cause erosion in the toilet seat portion 22, resulting in reduced reliability such as poor airtightness. invite

Therefore, even if the cutting amount of the partial cutting section 24 is increased, highly accurate operation cannot be expected.

[Purpose of invention]

This invention was developed under these circumstances, and is a fuel injection pump that corrects the curved detour flow, prevents the generation of bubbles, and improves reliability as the fuel injection pressure increases. The purpose is to provide.

[Summary of the idea]

In order to achieve the above object, the present invention aims to avoid the partial cut part of the relief piston part from being on the extension line of the protrusion part formed on the sliding guide part, and to avoid the part cut part of the relief piston part from extending in the same circumferential direction as the fuel passage formed between these protrusion parts. It is characterized by being formed on an extension line of this fuel passage so as to be located at.

[Example of idea]

The present invention will be explained below based on an embodiment shown in FIGS. 1 to 3.

In this embodiment, the pump body 10, cylinder 11, valve seat 12, valve holder 13, and plunger 14 may have the same structure as the conventional one shown in FIG. 4 and subsequent figures, so their explanation will be omitted.

The partial cut portion 1 formed in the flange-like relief piston portion 23 of the delivery valve 20 is connected to the radially arranged protrusions 25 in the sliding guide portion 27.
... is formed at a position that coincides in the axial direction with respect to the fuel passage 26 secured therebetween.

According to the configuration of this embodiment, when the delivery valve 20 is slightly lifted and the fuel flows through the partial cut portion 1, the partial cut portion 1 and the fuel passage 26 are connected in a straight line, so that the flow of the fuel is prevented. is the first
It becomes approximately linear as shown by the arrow in the figure. As a result, air bubbles are not generated near the partial cut portion 1, and therefore erosion is not generated near the valve seat portion 22, and the valve seat portion 22 is seated on the valve seat 12 while maintaining highly accurate airtightness.

Therefore, even if the cut amount of the partial cut portion 1 is increased to increase the fuel flow rate, the protrusion 25 will not interfere. This makes it possible to increase the amount of suction back in a high-load operating range as the fuel injection pressure increases, and to prevent abnormal injection in a low-load operating range.

[Effect of idea]

As described above, according to the present invention, since the partial cut portion and the fuel passage are connected linearly, the fuel flow through the partial cut portion becomes substantially linear. As a result, the generation of air bubbles near the partial cut portion is eliminated, and therefore erosion is prevented from occurring near the valve seat portion, so that the valve seat portion maintains highly accurate airtightness and improves reliability.

[Brief explanation of drawings]

1 to 3 show an embodiment of the present invention, in which FIG. 1 is a sectional view of the valve seat and delivery valve in an assembled state, FIG. 2 is a view taken along the line - in FIG. 1,
Fig. 3 is a sectional view taken along the line - in Fig. 2, Fig. 4 and the following show the conventional structure, Fig. 4 is an overall sectional view, and Fig. 5 is a sectional view of the assembled state of the valve seat and delivery valve. 6 is a view taken along the line -- in FIG. 5, and FIG. 7 is a sectional view taken along the line -- in FIG. 6. 10...Pump body, 11...Cylinder, 1
2...Valve seat, 13...Valve holder, 14...Plunger, 16...Plunger chamber, 17...Valve hole, 18...Discharge valve chamber, 20...Delivery valve, 2
2...Valve seat portion, 23...Relief piston, 25
...Protrusion part, 26...Fuel passage, 27...Sliding guide part, 1...Partial cut part.

Claims (1)

[Scope of Claim for Utility Model Registration] A fuel injection pump that operates a delivery valve provided in a valve hole with the pressure of fuel pressurized in a plunger chamber, and pressure-feeds the fuel in the plunger chamber to the discharge valve chamber through the valve hole. The delivery valve has a valve seat portion that comes into contact with and separates from the opening of the valve hole on the discharge valve chamber side, a flange-type relief piston portion that slides within the valve hole, and a flange-type relief piston portion that slides within the valve hole. a sliding guide portion comprising a plurality of protrusions arranged in a radial direction and extending in the axial direction, and forming a plurality of fuel passages extending in the axial direction between the protrusions; and a circumferential surface of the relief piston portion; In the fuel injection pump, the fuel injection pump is provided with a partial cut portion that cooperates with the fuel passage of the sliding guide portion to establish continuity between the plunger chamber and the discharge valve chamber when the delivery valve is slightly lifted. A fuel injection pump characterized in that the partial cut portion formed in the piston portion is located in the same circumferential direction as the fuel passage formed in the sliding guide portion and is formed on an extension line of this fuel passage.