JPS6255455A - Fuel injection pump - Google Patents

Abstract

PURPOSE:To reduce noise for an idling operation by allowing a plunger speed to be in a low an constant speed range for the first half of a cam desk which reciprocates the plunger, and also by allowing the plunger speed to be in a high speed range for the latter half so as to permit a delivery valve to be an isotactic pressure one. CONSTITUTION:The rotation of a rotating shaft 1 allows a roller holder 8 which has a roller ball 9, to rotate. A plunger 6 having a cam desk 7 reciprocates right and left at a speed corresponding to the surface shape of the cam desk while the ball 9 slides on the cam desk 7. For the cam rotating angle from O to theta1, a plunger speed is st at a low an constant one where an injection suitable for an idling operation is effected. For the cam rotating angle from theta1 to theta2, the plunger speed will be maximum and then is decelerated toward the cam angle theta3. From that time on, the speed is accelerated until the cam rotates upto a reference position. Fuel is injected at a high injection rate for the angle range from theta1 to theta3 so as to secure the necessary power. A delivery valve 20 is set up in such a way that a fuel injection nozzle is allowed to maintain a residual pressure more than 1/3 of the injection nozzle is allowed to maintain a residual pressure more than 1/3 of the injection starting pressure. This configuration permits the injection to start easily preventing noise for the idling operation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel injection pump that supplies fuel to an internal combustion engine through a fuel injection nozzle. The purpose is to obtain a fuel injection pump that can be secured.

(Prior Art) In a conventional fuel injection pump, for example, the Utility Model Application Publication No. 58-1 is used as a device having an injection rate control function for the above purpose.
There is one disclosed in Japanese Patent No. 13869. The technology disclosed herein uses control circuits and actuators to
By controlling the plunger axial position of the control sleeve, the position of the cam can be changed according to the operating conditions of the internal combustion engine, thereby reducing noise in the idle operating range and ensuring output in other ranges. This is what I did. Therefore, this fuel injection pump has to have an electronic control circuit, which has the problem of making it expensive.

(Object of the Invention) Fuel injection by the fuel injection pump starts when the pressure inside the injection pipe reaches the injection start pressure of the injection nozzle. To do this, the plunger must be lifted by a predetermined amount after starting pressure feeding, and the volumes of the pressurizing chamber and the injection pipe must be reduced until the injection starting pressure can be obtained. This lift amount is determined by determining the delivery valve, the length of the injection pipe, and the injection start pressure.

The present invention was developed in view of the above-mentioned conventional problems, and it is possible to maintain the residual pressure in the injection pipe high using an equal pressure valve and increase the pressure in the injection pipe to the injection starting pressure within a small rotation range of the cam. It is an object of the present invention to provide a fuel injection pump capable of achieving a low injection rate in an idling operation region and a high injection rate in other regions.

(Structure of the Invention) The present invention includes a cam disk that is rotationally driven and rotates and reciprocates a plunger according to the shape of the cam surface, pressurizes and distributes intake fuel, and supplies it to an internal combustion engine through a fuel injection nozzle. In the fuel injection pump, the cam has a characteristic in which, depending on the cam rotation angle, the front stage part has a low plunger speed and a substantially constant speed region, and the rear stage part has a high speed region, and the delivery valve is an equal pressure valve.

By configuring as described above, it is possible to increase the residual pressure in the fuel injection pipe that communicates the fuel injection pump and the fuel injection nozzle, and the pressure inside the injection pipe is adjusted to start the injection from the injection nozzle from the time when the plunger lift is small. It is possible to increase the pressure.

Thereby, injection can be started at a low speed and in a substantially constant speed region, and a state of low injection rate can be obtained.

Therefore, it is possible to reduce noise in the idle operating range.

Since fuel injection continues even in the high-speed region when the injection amount is large, it becomes possible to inject fuel at a high injection rate and obtain the necessary output in other regions.

The reason why the present invention has the above cam shape and uses an equal pressure valve to increase the residual pressure is that a distribution fuel injection pump that uses a face cam must supply fuel to all cylinders in one revolution of the cam. Moreover, since it is necessary to provide an area for the plunger lift O for timer advance angle control, the cam angle that can be used for injection is ((360°/number of cylinders)).
- timer controlled cam angle], and the cam angle at the start of injection cannot be delayed.

(Example of the invention) The present invention will be explained below based on a first embodiment.

FIG. 1 is a sectional view showing the configuration of a fuel injection pump according to the present invention, and FIG. 2 is an explanatory diagram of the cam shape of the present invention.

The fuel in the fuel tank is sent to the suction space 4 in the pump housing 3 by the oil feed pump 2 driven by the engine via the drive shaft 1, and the pressure in the suction space 4 is controlled by the engine rotation by a regulating pulp (not shown). The pressure is controlled according to the number. A pump/distribution plunger 6 is fitted into the barrel 5 fixed to the pump housing 3, and the pump housing 3, the barrel 5, and the plunger 6 form a pressurizing chamber 14. A cam disk 7 is fixed to the base of the plunger 6, and the cam disk 7 and the drive shaft 1 are coupled in the rotation direction via a driving disk (not shown).

A cam surface (described later) having a number of ridges equal to the number of cylinders of the engine is formed on the cam disk 7, and this cam surface is pressed and held against the roller 9 of the roller holder 8 by a plunger spring (not shown). As a result, the plunger 6 rotates as the drive shaft 1 rotates, and moves reciprocally by the cam surface of the cam disk 7 and the transfer guide action of the roller 9, thereby suctioning, pressurizing, distributing, and force-feeding fuel.

The plunger 6 has the same number of suction grooves 12 as the number of engine cylinders, a cut-off port 13, a pressurizing chamber 14, and a cut-off boat 13.
A communication hole 15 communicating with the communication hole 15 and a distribution groove 16 communicating with the communication hole 15 are provided, and the control sleeve 11 is slidably fitted therein.

A pressure passage 19, which is formed through the pump housing 3 and the barrel 5 and in which the delivery valve 20 is arranged, is formed at a position where it communicates with the distribution groove 1.6 at a predetermined timing,
It communicates with each cylinder via a fuel injection pipe (not shown).

The delivery valve 20 uses an equal pressure valve known in Japanese Patent Application Laid-Open No. 58-51267, etc., and in this embodiment, it maintains a residual pressure of 1/3 or more of the injection start pressure of the fuel injection nozzle, for example, 35% to 75%. Set the relief valve inside the equal pressure valve.

The control sleeve 11 is controlled by a control lever 21 of a known governor mechanism to take a position suitable for the load, and controls the injection amount in conjunction with the cutoff boat 13.

Next, the shape of the cam surface of the cam disk 7 will be explained with reference to FIG. In the figure, the dashed-dotted line is the plunger speed characteristic,
The solid line shows the plunger lift versus cam rotation angle characteristic. The shape of the cam surface is such that the plunger speed is approximately constant at approximately 0.25 M/SEC between the rotation angle of the cam disc 7 from 0 (reference position) to θ1, and the cam angle is set to the range required during idle operation. The angle should be set so that the desired injection amount can be obtained. This plunger speed corresponds to a speed range in which an injection rate that does not deteriorate the combustion state and allows slow combustion to be obtained.

In addition, the plunger speed is increased between θ1 and θ2, and e2
The plunger speed is set to be the fastest at this time, and the speed at this time is approximately 0.65 to 0.7 M/SEC.

From then on, the direction is decreased at e3, and thereafter the direction is increased to the reference position. This plunger speed corresponds to a speed range in which the necessary and sufficient injection rate can be obtained to obtain the necessary output. As a result, the plunger lift characteristics become as shown by the solid line in FIG.

Next, the operation will be explained.

When the plunger 6 is in the suction stroke in which it moves to the left in the figure as the drive shaft 1 rotates, the fuel oil in the suction space 4 passes through the suction passage 18 and enters the pressurized chamber 14 via the suction groove 12. is inhaled.

When the plunger 6 moves to the right in the figure, the fuel oil in the pressurizing chamber 14 is pressurized and sent out from the distribution groove 16 to the pressure feeding passage 19, and is then forced into the injection nozzle provided in each cylinder via the delivery valve 20. be done. Injection starts when the pressure of the fuel oil exceeds the injection start pressure of the injection nozzle. The number of pressure feeding passages 19 is the same as the number of cylinders, and they are equally spaced in the circumferential direction, and as the plunger 6 rotates and reciprocates, fuel is supplied to each cylinder from the injection nozzle in a predetermined order. The fuel injection ends when the cut-off boat 13 comes off the edge of the control sleeve 11 and opens into the suction space 4, and the fuel in the pressurized chamber 14 flows out into the suction space 4.

At this time, the residual pressure inside the injection pipe is set to 1/3 or more of the injection start pressure of the injection nozzle, so the pressure inside the injection pipe can reach the injection start pressure of the injection nozzle from the time when the plunger lift is small, and the cam It is possible to increase the pressure in the pipe to the injection start pressure within the low speed and constant speed rotation range, making it possible to inject fuel at low speed and at a constant speed, and even at a low injection rate in the idling range. fuel injection and noise reduction.

When the injection amount increases, fuel injection continues even in the high speed range, making it possible to inject fuel at a high injection rate and ensure the necessary output in other ranges.

In the present invention, the plunger speed in the constant speed region is set to 0.25 M/SEC, but other speeds may be used as long as the speed allows slow combustion without deteriorating the combustion state. , maximum speed 0.65~0
．． 7 M/SEC, but other speeds may be used as long as the output can be ensured.

(Effects of the Invention) As explained above, according to the present invention, the cam shape of the cam disk has a region in which the plunger speed is low and constant in the front stage portion with respect to the cam rotation angle, and a region in which the plunger speed is high in the rear stage portion. Since the set pressure of the equal pressure valve is configured to be at least a predetermined ratio to the injection start pressure, the internal pressure of the injection pipe can be increased to the injection start pressure with a small rotation angle, which makes it possible to improve the cam design. The degree of freedom can be increased, and the injection start time can be brought forward while maintaining a low speed section, reducing engine noise in the 4J idle range.
This has excellent effects in that it is possible to secure output in other areas, and it is possible to obtain a high-performance fuel injection pump with an extremely simple configuration and low cost.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the configuration of a fuel injection pump. FIG. 2 is an explanatory diagram of the cam surface shape in one embodiment of the present invention. 6...Plunger, 7...Cam disc, 8...
Roller holder, 9...roller. Patent applicant: Diesel Kiki Co., Ltd. Agent Patent attorney: Nobuo Sunako 1st
Figure + F4

Claims (2)

[Claims] (1) A fuel injection pump equipped with a cam disk that is rotationally driven and that rotates and reciprocates a plunger according to the shape of a cam surface, pressurizes and distributes intake fuel and supplies it to an internal combustion engine via a fuel injection nozzle. The cam has a characteristic that the front stage part has a low plunger speed and a substantially constant speed region, and the rear stage part has a high speed region with respect to the cam rotation angle,
A fuel injection pump characterized in that a delivery valve is an equal pressure valve. (2) The fuel injection pump according to claim 1, wherein the set pressure of the equal pressure valve is set to 35% or more and 75% or less of the injection start pressure of the fuel injection nozzle.