JP2947306B2 - Fuel injection pump discharge valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge valve of a fuel injection pump for a diesel engine.

[0002]

2. Description of the Related Art Conventionally, as disclosed in Japanese Utility Model Laid-Open No. 55-41545, a fuel injection pump for a diesel engine has been designed to improve the abnormal injection amount characteristic in a low speed region due to high-pressure injection of fuel. There is known a fuel injection pump in which a cut-out shape of a suction-back collar formed at a tip of a discharge valve of a fuel injection pump is improved.

[0003]

However, according to such a discharge valve of a conventional fuel injection pump, the residual pressure (residual pressure) in the injection pipe connecting the fuel injection valve and the discharge valve of the internal combustion engine is reduced. When the internal combustion engine is operated at moderate acceleration, the residual pressure abruptly changes at the boundary between the positive pressure and the negative pressure, causing the injection amount to change. There is a problem that the characteristics are deteriorated and a surge or the like is easily generated.

In the case where the boundary between the positive and negative pressures in the injection pipe is shifted toward the high load region by changing the shape of the suction return collar described in Japanese Utility Model Laid-Open No. 55-41545, the low speed and low load region is required. The residual pressure increases, and the residual pressure level difference between the cylinders tends to be large due to fuel leakage or the like. Therefore, there is a problem that uneven injection is caused and vibration is easily generated in the internal combustion engine.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem. The present invention makes it possible to control the residual pressure level of an injection pipe in a low-speed low-load region and to reduce the residual pressure in a low-load region to a medium-load region. It is an object of the present invention to provide a discharge valve of a fuel injection pump in which a sudden change is prevented to improve a fuel injection amount characteristic.

[0006]

A discharge valve of a fuel injection pump according to the present invention is connected to an injection pipe for guiding fuel to a fuel injection valve of an internal combustion engine, and is introduced into the injection pipe. A discharge valve for controlling fuel pressure, a valve holder having an inner hole communicating with the injection pipe, a cylindrical valve seat provided in the inner hole, and guiding fuel to the inner hole; A valve body slidably provided on the inner peripheral wall, having a cylindrical body at an end, and shutting off fuel by seating on the valve seat; and a valve body provided in the inner hole and closing the valve body in a valve closing direction. And a rod slidably mounted on the inner peripheral wall of the cylindrical body, and a second biasing means provided in the cylindrical body and biasing the rod toward the injection pipe. And the rod is the circle A locking member for locking the rod so as not to fall off from the body, and a valve provided in the inner hole, the valve being capable of locking the rod when a movement amount of the valve body in a valve opening direction reaches a predetermined amount. With a stopper,
As the fuel pressure rises, the valve body moves in the valve opening direction against the first biasing means until the rod comes into contact with the valve stopper, and after the rod comes into contact with the valve stopper, the fuel pressure further increases. When the pressure rises, the valve body further moves in the valve opening direction against the second urging means.

[0007]

According to the discharge valve of the fuel injection pump of the present invention, the valve body and the rod move in the valve opening direction against the first urging means in response to a rise in the fuel pressure at a low load or a medium load. The rod abuts the valve stopper without remaining pressure in the injection pipe changing to negative pressure while maintaining positive pressure due to the movement of the valve body, and stops the movement of the valve body after the rod abuts. I do. While the movement of the valve body is stopped, the residual pressure increases as the load increases. Further, when the valve body moves in the valve opening direction again against the urging forces of the first urging means and the second urging means under a high load, the increase in the residual pressure is attenuated.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show an embodiment in which the present invention is applied to an in-line fuel injection pump for a multi-cylinder diesel engine. A camshaft 2 interlocking with a diesel engine is inserted into a pump housing 1, and a cam portion 3 of several cylinders of the diesel engine is formed on the camshaft 2. The pump element 6 is actuated via the roller 4 and the tappet 5 according to the cam ridge shape of the cam portion 3.

The pump element 6 comprises a cylinder 8 fixed to the pump housing 1 and a plunger 10 reciprocating up and down in the cylinder 8. The fuel high-pressure chamber 11 formed in the cylinder 8 facing the upper end of the plunger 10 is connected to a delivery valve 13 described later. When the fuel pressure in the high-pressure fuel chamber 11 exceeds a predetermined value, the delivery valve 13 overcomes the urging set pressure of the compression coil spring 14 and pushes up the valve body 36 to inject fuel into the injection pipe.

A notch groove 18 formed on the outer periphery of the plunger 10 faces the inner peripheral wall surface of the cylinder 8. Then, when the feed hole 20 faces the notch groove 18 after the fuel pressure feeding, the fuel is released from the notch groove 18 to the feed hole 20 and the fuel feeding is completed. A center portion of the camshaft 2 inserted in the longitudinal direction inside the pump housing 1 is supported by a center bearing 22, and the center bearing bottom surface 22a is supported by an inner peripheral wall surface 1b of the housing skirt portion 1a. The cover plate 24 is fixed to the bottom surface 1c of the housing skirt 1a by screws 32.

As shown in FIG. 1, the delivery valve 13
The valve body 36 is inserted into the holder bore 35a of the holder 35.
The valve seat 37 is inserted, and the valve body 36 is urged by the compression coil spring 14 in the valve closing direction. Valve body 36 slidable in valve seat 37
Has a sliding portion 39, a cylindrical portion 40, and an annular convex portion 41 formed between the sliding portion 39 and the cylindrical portion 40.
The compression coil spring 14 is disposed on one spring seat 41b. Then, the seat surface 41 a of the annular convex portion 41 is pressed against the tip of the valve seat 37. Valve stopper 42
The shim 53 provided on the spring seat 42 a adjusts the set load of the compression coil spring 14 and
Is determined.

A compression coil spring 43 and a rod 44 are housed in the cylindrical portion 40 of the valve body 36. The rod 44 slidable in the cylindrical portion 40 is
6 and a small diameter portion 47, and a through hole 49 is formed in the axial direction. The compression coil spring 43 is adjusted to a predetermined initial load by a shim 50 disposed on the bottom surface 40a in the cylindrical portion 40, and urges the rod 44 toward the injection pipe. Collar 51 fixed to the tip of cylindrical portion 40 by screwing
Locks the large diameter portion 46 of the rod 44 to prevent the rod 44 and the compression coil spring 43 from jumping out of the cylindrical portion 40.

The position of the valve stopper 42 arranged at the end of the holder bore 35a on the injection pipe side is adjusted by a shim 52 for adjusting the pre-lift A. And the holder inner hole 3
The fuel introduced into the cylinder 5a passes through a not-shown injection pipe through a through hole 35b from a through hole 42b formed with a slope in the valve stopper 42, and is provided in a cylinder of a diesel engine. Supplied to

As for the procedure for assembling the delivery valve 13, first, the shim 5 is inserted into the cylindrical portion 40 of the valve body 36.
0, the compression coil spring 43 and the rod 44 are arranged, and the collar 51 is screwed to the opening of the cylindrical portion 40.
Next, after the shim 52, the valve stopper 42, the shim 53, and the compression coil spring 14 are sequentially inserted into the holder inner hole 35a, the valve body 36 and the valve seat 37 are inserted.
Is disposed in the holder inner hole 35a.

According to the delivery valve 13 of this embodiment,
When increasing the fuel injection amount of a diesel engine, first,
The valve body 36 rises together with the rod 44 against the urging force of the compression coil spring 14 from the position shown in FIG. The distal end of the rod 44 is
, The valve body 36 and the rod 44 stop rising. Next, when the injection amount further increases and the fuel pressure acting in the valve opening direction of the valve body 36 becomes larger than the urging set pressure of the compression coil spring 14 and the compression coil spring 43, the outer periphery of the rod 44 is moved by the cylindrical portion 40. While sliding, the valve body 36 starts to rise again.

The timing at which the valve body 36 stops rising is adjusted by a pre-lift A provided between the rod 44 and the valve stopper 42. The timing at which the valve body 36 starts to rise above the pre-lift A is adjusted by the set load of the compression coil spring 43.
In the present embodiment, the pre-lift A is set so that the rise of the valve body 36 stops before the residual pressure in the injection pipe becomes a negative pressure. The set load of the compression coil spring 43 is adjusted so that the body 36 starts rising above the pre-lift A. As a result, the residual pressure in the injection pipe is always maintained at a positive pressure, and stable fuel injection becomes possible.

FIG. 3 shows the relationship between the fuel injection amount, the valve lift amount, the valve effective suction and retraction amount, and the residual pressure in the injection pipe in the middle speed range of the diesel engine, and FIG. 4 shows the relationship between the rotation speed of the internal combustion engine and the injection amount. Show. The conventional example, with the increase of the injection quantity q, the valve lift amount H _V increases, the injection quantity q
The relatively small low injection amount range for the rate of increase in the valve effective suck-back amount V _E than the rate of increase in the injection quantity q is increased, the injection pipe residual pressure P _r is lowered. Then, the injection tube residual pressure P _r
Is injected in the injection quantity q ₁ tract residual pressure P _r = 0, and becomes a negative pressure state which is not further shown. Then, when the increase rate of the valve effective suck-back amount V _E becomes smaller than the rate of increase of the injection quantity q,
Injection pipe residual pressure P _r begins to rise, returns to the positive pressure state again becomes the injection pipe residual pressure P _r = 0 when the injection quantity q _2.

[0018] In contrast, in the present embodiment, since the injection pipe residual pressure P _r is increasing the valve lift amount H _V in the injection quantity q ₃ before a positive pressure to 0 to stop the injection pipe residual pressure P decrease of _r can be suppressed even when the injection quantity q ₃ or more. Then, the injection pipe residual pressure P _r between the injection quantity q ₃ and the injection quantity q ₄ holds a positive pressure, valve lift H _V in the injection quantity q ₄ is increased again, due to this, and the valve effective suck-back the amount is increased, but increased the percentage injection pipe residual pressure P _r is also once is attenuated, the ratio of injection amount relative to the valve effective suck-back amount is increased again for a large. Accordingly, the injection pipe residual pressure P _r from the low injection amount region to the high injection amount region is always held at a positive pressure.

As described above, the delivery valve 13 according to the above-described embodiment improves the fuel injection amount characteristic in the in-line type fuel injection pump. The effect of the quantity characteristic can be obtained. In the above embodiment, the outer peripheral surface of the large-diameter portion 46 of the rod 44 and the inner peripheral surface of the cylindrical portion 40 are sliding portions.
According to the present invention, the outer peripheral surface of the small diameter portion of the rod and the inner peripheral surface of the collar may be used as the sliding portion. Further, when the collar 51 is fixed to the cylindrical portion 40, the collar 51 can be fixed by press fitting instead of screwing.

[0020]

As described above, according to the discharge valve of the fuel injection pump of the present invention, the valve lift of the discharge valve is controlled in a stepwise manner to maintain the residual pressure in the injection pipe in a positive pressure state. Therefore, there is an effect that abnormal fuel injection such as secondary injection and illegal fuel injection can be reduced, and good fuel injection amount characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a discharge valve of a fuel injection pump according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a fuel injection pump according to an embodiment of the present invention.

FIG. 3 is a characteristic diagram showing a relationship among a valve lift amount, a fuel injection amount, a residual pressure in an injection pipe, and a valve effective suction / return amount of a discharge valve of a fuel injection pump according to an embodiment of the present invention and a conventional example.

FIG. 4 is a characteristic diagram showing a relationship between a rotation speed and an injection amount of an internal combustion engine according to an embodiment of the present invention and a conventional example.

[Description of Signs] 13 Delivery valve (discharge valve) 14 Compression coil spring (first biasing means) 35 Holder (valve holder) 35a Holder inner hole (inner hole) 36 Valve body 37 Valve seat 40 Cylindrical part (cylindrical body) 42 valve stopper 43 compression coil spring (second biasing means) 44 rod 51 collar (locking member)

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F02M 59/46

Claims (1)

(57) [Claims] 1. A discharge valve connected to an injection pipe for guiding fuel to a fuel injection valve of an internal combustion engine and controlling a pressure of fuel introduced into the injection pipe, the valve having an inner hole communicating with the injection pipe. A holder, a cylindrical valve seat provided in the inner hole and guiding fuel to the inner hole, a valve body slidably provided on an inner peripheral wall of the valve seat, having a cylindrical body at an end portion, and the valve A valve body for shutting off fuel by sitting on a seat; a first urging means provided in the inner hole for urging the valve body in a valve closing direction; and slidably on an inner peripheral wall of the cylindrical body. A rod to be attached; a second urging means provided in the cylinder, for urging the rod toward the injection pipe; and a locking member for locking the rod so that the rod does not fall off the cylinder. And provided in the inner hole A valve stopper capable of locking the rod when the amount of movement of the valve body in the valve opening direction reaches a predetermined amount, wherein the rod stops until the rod comes into contact with the valve stopper as fuel pressure increases. (1) The valve body moves in the valve opening direction against the urging means, and when the fuel pressure further increases after the rod comes into contact with the valve stopper, the valve body moves against the second urging means. A discharge valve for a fuel injection pump, which further moves in a valve opening direction.