JPH0410380Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Application of the Invention) The present invention relates to a fuel injection pump used in an internal combustion engine such as a diesel engine, and particularly relates to a fuel injection pump equipped with a variable prestroke mechanism.

(Prior Art) A fuel injection pump having a variable pre-stroke mechanism has been known, for example, as proposed in Japanese Utility Model Application No. 58-114875. The fuel pumping process for fuel injection in this invention will be explained below based on FIGS. 1 to 3.

1 to 3, a lower plunger barrel 3 is fixed to the pump body 1, a plunger 4 is slidably inserted into the lower plunger barrel 3, and the plunger 4 is connected to an engine (not shown).
The lower plunger barrel 3 receives the rotational driving force of
It reciprocates within the upper plunger barrel 5 and forces the fuel within the fuel pressure chamber 7 upward in the figure and injects it from an injection nozzle (not shown).

The plunger 4 includes a radial fuel suction/discharge hole 24 opening into the fuel reservoir chamber 18, a communication hole 25 formed in the central axis direction so as to communicate the fuel suction/discharge hole 24 and the fuel pressure chamber 7, and It has a control inclined groove 26 formed on the outer surface, and a vertical groove 27 that communicates the control inclined groove 26 with the opening of the fuel intake/discharge hole 24 .

Further, a control sleeve 17 having a cut-off hole 28 formed therethrough in the radial direction is slidably fitted onto the plunger 4. The cut-off hole 28 is arranged in a vertical positional relationship such that it can communicate with the control inclined hole 26 according to the movement of the plunger 4 in the vertical direction.

The control sleeve 17 has a fuel reservoir 18 surrounded by the lower plunger barrel 3.
The plunger 4 is disposed inside the fuel reservoir chamber 18 and externally fitted onto the plunger 4. In addition, the fuel reservoir chamber 18
communicates with the fuel inlet 20 via a horizontal hole 19 formed in the pump body 1.

A control rod 29 is provided perpendicularly to the control sleeve 17, and an engaging portion 36 protruding radially from the control rod 29 is engaged with an engaging groove 22 formed in the control sleeve 17. There is.

Therefore, when the control rod 29 is rotated in the forward and reverse directions as shown by the arrows in FIG. 1, the engaging portion 36 rotates together with the control rod 29. The control sleeve 17 moves up and down due to the movement, and the relative position of the plunger 4 and the control sleeve 17 in the vertical direction changes. The pre-stroke of the plunger 4, defined as the dimension between the two positions, can be adjusted.

That is, the dimension from the bottom dead center of the plunger 4 to when the fuel intake/discharge hole 24 is closed is
This is the pre-stroke, and injection begins when the fuel intake/discharge hole 24 is closed (FIG. 1).

In actual fuel delivery, as shown in FIG. 1, the plunger 4 is raised, its fuel intake/discharge hole 24 is closed by the control sleeve 17, and injection (fuel feeding) is started. Next, as shown in FIG. 2, the control inclined groove 26 communicating with the fuel intake/discharge hole 24 communicates with the cut-off hole 28 of the control sleeve 17, so that the cut-off hole 28, the control inclined groove 26, the vertical groove 27, and the fuel The cut-off hole 28 and the fuel pressure chamber 7 communicate with each other via the intake/discharge hole 24 and the communication hole 25, and injection (pressure feeding of fuel) is completed.

However, as shown in FIG. 3, even after the end of the fuel pumping, the plunger 4 is displaced upward, and as a result, the control inclined groove 26 passes through the cut-off hole 28 and the control sleeve 17 When the inclined groove 26 is closed, the upper part of the control inclined groove 26 protrudes from the control sleeve 17 and communicates with the fuel reservoir chamber 18. However, especially when setting a large prestroke, the control sleeve 17 is connected to the upper plunger barrel 5. If it is close to the lower surface 5a, the cross-sectional area of the high-pressure fuel escape flow path becomes small, and the discharge amount of the returned fuel is restricted, causing a problem in which the internal pressure of the injection pipe increases temporarily and secondary injection occurs. Was.

(Purpose of the invention) In view of the above-mentioned problems, the present invention has developed a pre-stroke system that allows the returned fuel after cut-off to be smoothly discharged regardless of the position of the control sleeve and prevents secondary injection. An object of the present invention is to provide a fuel injection pump having a variable mechanism.

(Means for solving the problem) That is, the present invention includes a control sleeve slidably fitted onto a reciprocating plunger, a control rod connected to the control sleeve, and rotation of the control rod. In a fuel injection pump having a pre-stroke variable mechanism that adjusts a pre-stroke by changing the relative position in the axial direction between the plunger and the control sleeve, the fuel is placed on the lower surface of the upper plunger barrel opposite to the upper surface of the control sleeve. Provide a cut-off groove,
This fuel injection pump discharges the returned fuel after cutoff from this groove, thereby eliminating the cause of secondary injection without even temporarily increasing the internal pressure of the injection pipe.

(Embodiment) Next, an example in which an embodiment of the present invention is applied to a row-type fuel injection pump will be described with reference to FIGS. 4 to 6. However, the same parts as in FIGS. 1 to 3 are given the same reference numerals.

First, as shown in FIG. 4, vertical holes 2 corresponding to the number of cylinders of the engine are formed in the pump body 1, and the lower plunger barrel 3 is inserted into the vertical holes 2.
is inserted and fixed into the pump body 1, and the plunger 4 is inserted into the lower plunger barrel 3 so as to be rotatable and reciprocating.

The upper end of the plunger 4 is inserted into the upper plunger barrel 5 fixed to the pump body 1 via the lower plunger barrel 3, and a delivery valve 6 is provided in the upper plunger barrel 5.
A fuel pressure chamber 7 is formed between the pump and the plunger 4, and a fuel outlet 8 is formed above the delivery valve 6.

Further, the lower end of the plunger 4 is in contact with a cam 10 provided on a camshaft 9 via a tappet 11. This camshaft 9 is connected to an engine, is rotationally driven by the engine, and has a spring 12.
along the periphery of the cam 10 in cooperation with the plunger 4
are brought into contact with each other, and this is made to reciprocate in the vertical direction in the figure.

Furthermore, this plunger 4 has a face portion 13.
The face portion 13 engages with the injection amount adjustment sleeve 14 in such a manner as to restrict its rotational direction, and the injection amount adjustment sleeve 14 is connected to the injection amount adjustment rod via a protrusion 15. By moving the plunger 16, the plunger 4 can be rotated.

Note that the effective stroke of pressure feeding for injection can be adjusted by rotating the plunger 4 using the injection amount adjusting rod 16.

Furthermore, as shown in an enlarged view in FIG. 5, a fuel cut-off groove 50 is formed by cutting out the lower surface of the upper plunger barrel 5 over a necessary cross-sectional area, and in the state shown in FIG. The control inclined groove 26 or vertical groove 27 can communicate with the fuel reservoir chamber 18.

The control sleeve 17 has a longitudinal guide groove 21 at its rear and a transverse engagement groove 22 at its front.
The guide pin 23 provided on the lower plunger barrel 3 is engaged with the guide groove 21, and the control rod 29 is engaged with the engagement groove 22.
An engaging portion 36 is inserted therein.

This control rod 29 is inserted into the horizontal hole 19, is rotatably supported by the pump body 1 via a bearing, and is connected to an actuator (not shown) such as a step motor to be connected to the actuator. It shall be driven by the

Further, as shown in FIG. 6, the control rod 29 has a window 32 formed therethrough in the diametrical direction of the control rod 29 and facing the control sleeve 17. 33
Insert. This engagement shaft 33 has a disc-shaped main body 34, which is rotatably fitted into a step 35 formed in the window 32.

Further, this engagement shaft 33 is formed with an engagement portion 36 integrally with the main body portion 34, and this engagement portion 36 is eccentric with respect to the main body portion 34 and is located at the window portion 32.
It protrudes toward the control sleeve 17 from above and engages with the engagement groove 22 of the control sleeve 17.

Further, on the opposite side of the engagement shaft 33 from the engagement part 36, an adjustment rod part 37 is formed integrally with the main body part 34, and a center hole 39 formed in the cap screw 38 is formed integrally with the main body part 34.
This cap screw 38
is screwed into the window portion 32 and presses down the main body portion 34 of the engagement shaft 33 via a washer 40.

The pre-stroke described above can be adjusted by moving the control sleeve 17 up and down using the control rod 29.

The operation of the above configuration will be explained.

First, when the plunger 4 shown in FIG. Since the fuel pressure chamber 7 and the fuel pressure chamber 7 are in communication with each other through the communication hole 25, the pressure of the fuel in the fuel pressure chamber 7 does not increase, and the delivery valve 6 remains closed.

When the plunger 4 further rises from this state and the fuel intake/discharge hole 24 comes to be located above the lower surface of the control sleeve 17, this fuel intake/discharge hole 24
is closed by the inner surface of the control sleeve 17, and at this time the injection begins, and the pressure of the fuel in the fuel pressure chamber 7 rises, opening the delivery valve 6 and sending out fuel from the fuel outlet 8. .

Then, when the plunger 4 further rises and the control inclined groove 26 communicates with the cut-off hole 28 of the control sleeve 17, the fuel pressure chamber 7 and the fuel reservoir chamber 18
The communication hole 25, the fuel intake and exhaust hole 24, the vertical groove 27,
The fuel in the fuel pressure chamber 7 is communicated with the control inclined groove 26 and the cutoff hole 28 through the path, and the fuel in the fuel pressure chamber 7 escapes to the fuel reservoir chamber 18, the pressure of the fuel in the fuel pressure chamber 7 decreases, and the delivery valve 6 is opened. It is closed and oil supply for injection ends.

Further, the plunger 4 rises and the control inclined groove 26 passes through the cut-off hole 28 and is again closed by the control sleeve 17.
At this time, since the upper parts of the control inclined groove 26 and the longitudinal groove 27 come out from the upper part of the control sleeve 17 and communicate with the fuel cut-off groove 50, it is assumed that the pre-stroke is the maximum and the control sleeve 17 is connected to the upper plunger barrel. 5, a sufficient discharge cross-sectional area is ensured, and the returned fuel can flow out from the fuel cut-off groove 50 into the fuel reservoir chamber 18 without resistance.

(Effects) As explained above, according to the present invention, even if the control sleeve is preset so as to be close to the lower surface of the upper plunger barrel, the fuel returned after the end of pressure feeding for injection can be transferred to the upper plunger barrel. The fuel can be sufficiently discharged from the cut-off groove formed in the fuel cut-off groove, so secondary injection does not occur. Further, since this is different from processing such as providing a raised portion for forming a groove on the upper surface of the control sleeve, the control sleeve can be made smaller and lighter.

[Brief explanation of the drawing]

1 to 3 are explanatory diagrams sequentially showing the pumping states for fuel injection in a conventional fuel injection pump, FIG. 4 is a longitudinal sectional view of an embodiment of the present invention, and FIG.
The figure is an enlarged sectional view of the control sleeve 17 portion, and FIG. 6 is an exploded perspective view of the control sleeve 17 and control rod 29 portions. 1...Pump body, 2...Vertical hole, 3...Lower plunger barrel, 4...Plunger, 5...Upper plunger barrel, 6...Delivery valve, 7...Fuel pressure chamber, 8...Fuel outlet, 9...Camshaft, 10...Cam, 11...Tappet, 12...Spring, 1
3...Face portion, 14...Sleeve for adjusting injection amount, 15...Protrusion, 16...Rod for adjusting injection amount, 17...Control sleeve, 18...Fuel reservoir chamber, 19...Horizontal hole, 20... ...Fuel inlet, 21...
Guide groove, 22... Engagement groove, 23... Guide pin, 2
4... Fuel intake and exhaust hole, 25... Communication hole, 26... Control inclined groove, 27... Vertical groove, 28... Cut-off hole, 29... Control rod, 32... Window, 33... Section Combined shaft, 34...Main body, 3
5... Step part, 36... Engaging part, 37... Adjustment rod part, 38... Holding screw, 39... Center hole, 40
... Washer, 50 ... Groove for fuel cut-off.

Claims (1)

[Scope of Claim for Utility Model Registration] An upper plunger that injects fuel by reciprocating within the upper plunger barrel having a fuel pressure chamber, and a fuel intake/discharge hole communicating with the fuel pressure chamber, and a vertical groove communicating with the fuel intake/discharge hole. a plunger having a control inclined groove, the plunger being provided in a fuel reservoir chamber adjacent to the fuel pressure chamber and slidably fitted onto the plunger to open and close the fuel intake/discharge hole; a control sleeve formed with a cut-off hole that can communicate with the plunger; and a control rod connected to the control sleeve, and the rotation of the control rod changes the relative position of the plunger and the control sleeve in the axial direction. In a fuel injection pump having a variable pre-stroke mechanism adapted to adjust a pre-stroke, on the lower surface of the upper plunger barrel opposite to the upper surface of the control sleeve, from the upper end of the control sleeve past the cut-off hole of the control sleeve. A fuel injection pump characterized in that a fuel cut-off groove is formed facing the fuel reservoir chamber and communicating with the control inclined groove or vertical groove of the protruding plunger.