JPH0315822Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) This invention relates to a fuel injection pump used in a diesel engine, and is particularly aimed at improving the control sleeve.

(Prior Art) A fuel injection pump having a variable prestroke mechanism is known, for example, from Japanese Utility Model Application No. 114875/1983. Pumping conditions for injection according to this example are shown in FIGS. 5-7.

5 to 7, a plunger barrel 3 is fixed to the pump body 1, and a plunger 4 is slidably inserted into the plunger barrel 3.
This plunger 4 is configured to reciprocate in response to the rotation of the engine. A fuel intake/discharge hole 24 and a control inclined groove 26 are formed in the portion of the plunger 4 facing the fuel reservoir chamber 18, and a control sleeve 17 in which a cut-off hole 28 is formed in the radial direction is provided above the plunger 4. It is slidably fitted on the outside. A control rod 29 is provided perpendicularly to the control sleeve 17, and an engaging portion 3 protrudes radially from the control rod 29.
6 or engagement groove 2 formed in the control sleeve 17;
2 is engaged. Therefore, when the control rod 29 is rotated, the engaging portion 36 rotates together with the control rod 29, and the rotation of the engaging portion 36 causes the control sleeve 7 to move up and down.
The relative position of the plunger 4 and the control sleeve 17 in the vertical direction changes, and the prestroke of the plunger 4, which is the dimension of the control sleeve 17 and the fuel intake/discharge hole 24, can be adjusted.

As shown in FIG. 5, the fuel is delivered by moving the plunger 4 upwards and opening the fuel intake/discharge hole 24 into the control sleeve 1.
7, the injection (pressure feeding of fuel) is started, and as shown in FIG.
The control sleeve 17 has a control inclined groove 26 communicating with the control sleeve 17.
By communicating with the cut-off port 28, injection (completion of pressure feeding of fuel) is completed.

(Problem to be Solved by the Invention) However, even after the end of the pumping of fuel, the plunger 4 is displaced upward, and as a result, the control inclined groove 26 passes through the cut-off port 28 and the control sleeve 17 The control inclined groove 26
is closed, the upper part of the control inclined groove 26 protrudes from the control sleeve 17, and the fuel reservoir chamber 1 is closed.
However, if the pre-stroke is particularly large and the control sleeve 17 is close to the lower surface 5a of the valve housing 5, the escape route for the high-pressure oil becomes narrow, the discharge of the return fuel is restricted, and the internal pressure of the injection pipe becomes There was a problem in which the fuel was rising and secondary injection occurred.

Therefore, in this invention, the fuel injection system has a variable pre-stroke mechanism that can smoothly discharge the returned fuel after cut-off and prevent secondary injection, regardless of the position of the control sleeve. The challenge is to provide pumps.

(Means for Solving Problems) The gist of this invention is to slide a control sleeve having a cut-off hole onto a plunger that reciprocates and rotates and has a suction and exhaust hole and an inclined groove that communicate with a communication hole. A control rod is connected to the control sleeve so as to be movable, and rotation of the control rod changes the relative position of the plunger and the control sleeve in the axial direction, thereby moving the control sleeve upward. Sometimes, in a fuel injection pump having a variable pre-stroke mechanism that is close to or in contact with the lower end surface of the valve housing, a radial groove communicating with the inner hole is formed on the upper surface of the control sleeve, so that the upward stroke of the plunger Even when the suction/discharge hole and the inclined groove are cut off from communicating with the cut-off hole, the upper part of the inclined groove protrudes from the control sleeve,
The return fuel can be discharged from the protrusion through the groove into the fuel reservoir chamber.

(Function) Therefore, regardless of the position of the control sleeve, the return fuel after cut-off is discharged from the groove formed on the upper surface of the control sleeve, so that the internal pressure of the injection pipe is not increased even temporarily, and the return fuel is discharged. The cause of the subsequent injection can be eliminated, and the above object can be achieved.

(Example) Hereinafter, an example of this invention will be described with reference to the drawings.

1 to 4, the row type fuel injection pump has a vertical hole 2 formed in a pump body 1 corresponding to the number of cylinders of the engine, and a plunger barrel 3 is inserted into the pump body 1 within this vertical hole 2. Insert is fixed,
A plunger 4 is inserted into the plunger barrel 3 so as to be rotatable and reciprocating. The upper end of the plunger 4 is inserted into a valve housing 5 that is fixed to the pump body 1. A delivery valve 6 is provided in the valve housing 5, and the fuel pressure is maintained between the delivery valve 6 and the plunger 4. A chamber 7 is formed, and a fuel outlet 8 is formed above the delivery valve 6 and the plunger 4.

Further, the lower end of the plunger 4 is in contact with a cam 10 formed on a camshaft 9 via a tappet 11, and the camshaft 9 is connected to the engine and rotates.
The plunger 4 is moved by the cam 1 in cooperation with the spring 12.
The plunger 4 is configured to reciprocate along the contour of the arrow. Furthermore, a face portion 13 is formed on this plunger 4, and this face portion 13
engages with the injection amount adjusting sleeve 14 in a manner that restricts the direction of rotation, and the sleeve 14 engages with the projection 15.
The plunger 4 is engaged with an injection amount adjustment rod 16 via the injection amount adjustment rod 16, and by moving this injection amount adjustment rod 16, the plunger 4 can be rotated.

The plunger 4 has a fuel intake/discharge hole 24 formed in its radial direction and open to the fuel reservoir chamber 18, and a communication hole 24 formed in its central axis direction to communicate the fuel intake/discharge hole 24 with the fuel pressure chamber 7. Hole 2
5. It has an inclined groove 26 formed on its outer surface and a vertical groove 27 that communicates the inclined groove 26 with the opening of the fuel intake/discharge hole 24.

The control sleeve 17 is connected to the plunger barrel 3.
It is arranged in a fuel storage chamber 18 surrounded by
The plunger 4 is fitted externally within this fuel reservoir chamber 18, and the fuel inlet 2 is connected to the fuel reservoir chamber 18 through a horizontal hole 19 formed in the pump body 1.
It leads to 0. In addition, the control sleeve 17
As shown in FIGS. 2 to 4, a vertical guide groove 21 is formed at the rear thereof, and a horizontal engagement groove 22 is formed at the front thereof. 3 are engaged with each other, and a control rod 29, which will be described later, is inserted into the engagement groove 22.

Furthermore, a cut-off hole 28 that communicates with the inner hole 31 in the radial direction is formed in the middle of the control sleeve 17, and the upper surface 17a is cut out at an angle on both sides except for the center part, so that the cross section is triangular. A groove 30 is formed in the radial direction of this upper surface 17a. Even if the control sleeve 17 moves upward to the maximum (maximum prestroke) and contacts the lower surface 5a of the valve housing 5 in this groove 30, the inner hole 31 of the control sleeve 17 and the fuel reservoir are connected to each other through the groove 30. A state of communication with the chamber 18 is maintained.

Therefore, as shown in FIG. 1, when the plunger 4 is initially rising from the bottom dead center, the fuel intake/discharge hole 24 opens into the fuel reservoir chamber 18, and the fuel pressure chamber 7 and the fuel The reservoir chamber 18 and the fuel intake/discharge hole 2
4 and 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. From this state, the plunger 4
further rises and the fuel intake/discharge hole 24 is positioned above the lower surface of the control sleeve 17, the fuel intake/discharge hole 24 is closed by the inner surface of the control sleeve 17, and the pressure of the fuel in the fuel pressure chamber 7 decreases. It rises, opens the delivery valve 6, and sends out fuel from the fuel outlet 8. The dimension from the bottom dead center of the plunger 4 to when the fuel intake/discharge hole 24 is closed is the pre-stroke of the plunger 4, and
Injection begins when the is closed. Then, when the plunger 4 further rises and the 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 are connected to the communication hole 25, the fuel intake/discharge hole 24, the vertical groove 27, and the inclined groove. 26 and the cut-off hole 28, 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, the delivery valve 6 is closed, and the injection starts. The oil supply for this purpose is completed.

Further, the plunger 4 is raised, and the control inclined groove 26 passes through the cut-off hole 28 and is again closed by the control sleeve 17, but the upper part of the control inclined groove 26 and the vertical hole 27 is closed by the control sleeve 1.
7 and enters the fuel reservoir chamber 18 through the groove 30.
Even if the prestroke is at its maximum and the fuel is in close proximity to or in contact with the lower surface 5a of the valve housing 5, the return fuel can flow out from the groove 30 into the fuel reservoir chamber 18 without resistance. It is something.

The effective stroke of pressure feeding for injection can be adjusted by rotating the plunger 4 with the injection adjustment rod 16, and the prestroke can be adjusted by rotating the control sleeve 17 up and down with the control rod 29 described below. It can be adjusted by moving.

The control rod 29 is inserted into the horizontal hole 19, has a bearing rotatably supported by the pump body 1, is connected to an actuator such as a step motor, and is rotated by the actuator. Further, as shown in FIG. 2, 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.
An engagement shaft 33 is inserted into 2. The 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 connected to the control sleeve 1 from the window portion 32.
7 side and engages with the engagement groove 22 of the control sleeve 17. Further, an adjustment rod portion 37 is formed integrally with the main body portion 34 on the opposite side of the engagement shaft 33, and this adjustment rod portion 37 is inserted through a center hole 39 formed in the cap screw 38. The cap screw 38 is attached to the window portion 32.
and the engagement shaft 3 through the washer 40.
The main body part 34 of No. 3 is held down.

(Effects of the invention) As described above, according to this invention, even if the control sleeve approaches or comes into contact with the lower surface of the valve housing, the fuel returned after the end of pressure-feeding for injection
Since the groove formed on the upper surface of the control sleeve allows sufficient discharge, secondary injection does not occur.

Further, it has the advantage that it is only necessary to form grooves on the upper surface of the control sleeve without changing the dimensions of other components.

[Brief explanation of drawings]

Figure 1 is a sectional view showing an embodiment of this invention, Figure 2 is a sectional view showing an embodiment of this invention.
The figure is an exploded perspective view of the control sleeve, control rod, and engagement shaft. Figure 3 is a plan view of the control sleeve. Figure 4 is a sectional view of the control sleeve. Figures 5 to 7 are of the conventional example. It is an explanatory view showing a pressure feeding state for injection. 4... Plunger, 17... Control sleeve, 2
9...Control rod, 30...Groove.

Claims (1)

[Claims for Utility Model Registration] The plunger 4 has a suction and exhaust hole 24 that reciprocates and rotates and communicates with the communication hole 25 and an inclined groove 26.
A control sleeve 17 having a cut-off hole 28 is slidably fitted onto the outside of the control sleeve 17.
A control rod 29 is connected to the plunger 4, and the relative position of the plunger 4 and the control sleeve 17 in the axial direction is changed by rotation of the control rod 29.
In a fuel injection pump having a variable pre-stroke mechanism that approaches or abuts the lower end surface of the valve housing when the control sleeve 17 moves upward, a radial groove on the upper surface of the control sleeve 17 that communicates with the inner hole 31 is provided. A groove 30 is formed so that the suction/discharge hole 24 and the inclined groove 2 are formed during the upward stroke of the plunger 4.
6 is cut off from communication with the cut-off hole 28, the upper part of the inclined groove 26 protrudes from the control sleeve 17, and the return fuel can be discharged from the protrusion through the groove 30 into the fuel reservoir chamber. and fuel injection pump.