JPH09228915A - Injection pressure control device for fuel injection pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain durability of an injection pump by suppressing arm abnormal increase of forced feed fuel pressure (injection pressure) in a high pressure chamber, without accompaniment of output decrease due to decreasing of a fuel injection amount. SOLUTION: A device comprises a check valve 39 provided in a plunger 8 to be opened when a fuel pressure in a high pressure chamber is increased to a prescribed value or more, a port 40 introducing fuel passing through the check valve 39 to an operating chamber 37 in a control sleeve 16, a subsleeve 31 moving a fuel injection amount to an increasing side in accordance with a fuel amount introduced to the operating chamber 37 and a plunger side sleeve side each fuel return passage 41, 42 returning fuel in the operating chamber 37 to a low pressure chamber after ending a forced feed of fuel.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a fuel injection control device for a fuel injection pump.

[0002]

2. Description of the Related Art To improve the performance of diesel engines,
It is effective to improve the fuel injection pressure. However, due to the durability of the plunger drive cam and the pressure resistance of the pump casing,
There is an upper limit to the maximum fuel injection pressure setting. Moreover, in actuality, considering the manufacturing variations of the fuel injection pump, the fuel injection nozzle, and the like, it is not possible to set the maximum fuel injection pressure to the maximum limit. Further, if a part of the nozzle injection hole is blocked due to the inclusion of foreign matter, the fuel injection pressure will rise abnormally, and the durability of the injection pump and the nozzle may be reduced.

As a technique for preventing such an abnormal rise in fuel injection pressure and maintaining the durability of the injection pump,
There is a fuel injection pump described in Japanese Utility Model Publication No. 61-152767. This is to control the maximum fuel injection pressure by providing a check valve that opens when the pressure-feed fuel pressure in the high-pressure chamber exceeds a predetermined value and returning a part of the pressure-feed fuel to the low-pressure chamber through this check valve. Is.

[0004]

However, in such a conventional technique, the operation delay of the check valve (opening →
(Closed) causes the fuel to return to the low pressure chamber more than necessary (more than the amount necessary to return the fuel pressure in the high pressure chamber to a predetermined value), resulting in a decrease in fuel injection amount and a decrease in output and deterioration of drivability. There is a risk.

Therefore, according to the present invention, it is possible to suppress the abnormal increase in the pressure-feed fuel pressure (injection pressure) in the high pressure chamber and maintain the durability of the injection pump without the output reduction due to the decrease in the fuel injection amount. Has an aim.

[0006]

In order to achieve the above object, in the invention according to claim 1, in a fuel injection pump in which fuel is pressure-fed by a plunger, a means for detecting a fuel pressure in a plunger high pressure chamber, and a plunger high pressure When the fuel pressure in the chamber reaches a predetermined value, a means for bypassing the fuel in the plunger high pressure chamber to the pump chamber and a means for correcting the fuel injection amount to be increased according to the fuel amount bypassed at this time are provided. There is. According to the second aspect of the present invention,
A check valve provided in the plunger that opens when the fuel pressure in the high-pressure chamber exceeds a specified value, a port that introduces the fuel that has passed through this check valve into the working chamber in the control sleeve, and this working chamber A second control sleeve for moving the fuel injection amount to the increasing side according to the introduced fuel amount;
A fuel return passage is provided for returning the fuel in the working chamber to the low pressure chamber after the completion of the pressure feeding of the fuel. Further, in the invention according to claim 3, the fuel injection pump reciprocates following the face cam by rotating in synchronization with engine rotation, and a plunger high pressure chamber that expands and contracts due to reciprocating movement of the plunger. From the plunger high pressure chamber, which communicates with the same number of intake slits as the number of cylinders engraved on the outer peripheral surface of the plunger to guide the fuel to be sucked into the plunger high pressure chamber, and which communicates with the distribution slit engraved on the outer peripheral surface of the plunger. A distribution port for guiding the discharged fuel to each cylinder, and a control sleeve for releasing the fuel discharged from the high pressure chamber of the plunger by opening a cutoff port opened on the outer peripheral surface of the plunger at the end of the pressure feeding of the fuel. Further, in the invention according to claim 4, the second control sleeve according to claim 2 is provided with an elastic body urged so as to move the fuel injection amount to the reduction amount side.

[0007]

[Operation] A part of the pressure-feed fuel is returned to the low-pressure chamber through a check valve that opens when the pressure-feed fuel pressure in the high-pressure chamber exceeds a predetermined value, and at the same time, the control sleeve is used to increase the fuel injection amount with the returned fuel amount. Is moved, the injected fuel pressure can be controlled without lowering the output due to the decrease in the fuel injection amount, and the durability of the pump and the nozzle can be maintained.

[0008]

1 is a block diagram of an embodiment of the present invention. Except for part A of the present invention, a known electronically controlled distributed fuel injection pump [Ryoji Kihara, diesel passenger vehicle, ( Grand Prix Publishing Co., Ltd. (1984), P130-
141 ”]. As shown in FIG. 1, in a distributed fuel injection pump provided in a diesel engine, fuel is sucked by a feed pump 3 driven by a drive shaft 2, and the feed pump 3
The fuel supplied from the pump chamber 5 to the pump chamber 5 is sent to the high-pressure plunger pump 7 through the suction port 6. The plunger 8 of the plunger pump 7 is rotationally driven by the drive shaft 2 via the joint 29 in synchronism with engine rotation at a speed half the engine speed.

A cam disk 9 fixed to the plunger 8.
Has the same number of face cams 10 as the number of cylinders of the engine, and reciprocates the plunger 8 by a predetermined cam lift against the spring 19 every time the rollers 12 rotate and get over the rollers 12. Due to the rotary reciprocating motion of the plunger 8, the fuel sucked into the plunger high pressure chamber 4 from the suction port 6 through the suction slit 17 formed in the plunger 8 passes from the distribution port 13 to the injection valve (not shown) through the delivery valve 14. Pumped.

The plunger 8 moves to the right side in the drawing and moves from the plunger high pressure chamber 4 through the distribution slit 18 to the distribution port 1.
When the opening portion of the cutoff port 15 exceeds the right end portion of the control sleeve 16 in the drawing in the process of pumping the fuel to 3, the fuel that has been pumped is released to the low pressure pump chamber 5.

The fuel injection amount is determined by the position of the control sleeve 16 that opens and closes the cutoff port 15 formed in the plunger 8. That is, when the control sleeve 16 is displaced to the right in the figure, the fuel injection end timing is delayed and the fuel injection amount is increased, and when it is displaced to the left in the figure, the fuel injection end timing is advanced and the fuel injection amount is decreased. is there.

A rotary solenoid 21 is provided as an electronically controlled governor for automatically adjusting the position of the control sleeve 16. The rotary solenoid 21 is the rotor 2
Ball 2 that is eccentrically provided at the tip
The control sleeve 16 is linearly moved in the axial direction of the plunger 8 via 3.

A control unit (not shown) provided as control means for the rotary solenoid 21 sets the control voltage of the rotary solenoid 21 as map information in advance, and inputs various detection signals such as accelerator opening, engine speed, engine water temperature and the like. An appropriate fuel injection amount is calculated according to the detected operating conditions, and the calculated fuel injection amount is converted into a control voltage for the rotary solenoid 21 and output.

The fuel injection timing is adjusted by rotating the face cam 10 relative to the roller 12 via the roller ring 11 by the timer piston 25. By adjusting the hydraulic pressure difference acting on both ends of the timer piston 25 via the timing control valve 26, the timer piston 25 is moved to rotate the roller ring 11, and the time when the face cam 10 rides on the roller 12 is changed. It is like this. In addition,
In FIG. 1, the timer piston 25, the feed pump 3 and the like show a cross section rotated by 90 degrees.

The details of the A section will be described with reference to FIG. The plunger 8 is formed with a cut-off port 15 that determines the fuel injection end timing depending on the position relative to the control sleeve 16. The control sleeve 16 is supported by a ball 23 eccentrically provided at the tip of a rotor 22 which is a rotary shaft of the rotary solenoid 21.
The position of the control sleeve 16 is displaced according to the rotation angle of. In the fuel injection, when the opening of the cut-off port 15 moves to the right side of the plunger 8 and exceeds the right end of the control sleeve 16, the plunger high pressure chamber 4 (not shown) has been pressure-fed to the distribution port 13. The fuel is terminated by opening it through the cutoff port 15 to the low pressure pump chamber 5.

Therefore, when the control sleeve 16 is relatively displaced rightward with respect to the plunger 8, the fuel injection end timing is delayed and the fuel injection amount is increased. Conversely, when the control sleeve 16 is displaced leftward, the fuel injection is performed. The end timing is advanced and the fuel injection amount is reduced.

A sub-sleeve 31 and a spring 33 are inserted into the control sleeve 16, and the right end portion of the spring 33 in the figure is fixed by a seat 35.
The seat 35 is fixed to the control sleeve 16 by screwing, for example. A working chamber 37 is formed between the control sleeve 16 and the sub sleeve 31.

The plunger 8 is provided with a check valve 39 that opens when the fuel pressure in the plunger high pressure chamber 4 reaches a predetermined value or more, and the fuel passing through the check valve 39 is introduced into the working chamber 37. A port 40 is provided. Further, after the fuel injection is completed, a plunger side fuel return passage 41 is provided in the plunger 8 and a sleeve side fuel return passage 42 is provided in the control sleeve 16 in order to return the fuel in the working chamber 37 to the low pressure pump chamber 5. Has been.

The operation will be described below with reference to FIG.
During fuel pressure feeding (injection), when the fuel pressure in the plunger high pressure chamber 4 exceeds the valve opening pressure of the check valve 39, the check valve 39 opens and the fuel in the plunger high pressure chamber 4 passes through the port 40, It is introduced into the working chamber 37.

Due to the fuel introduced into the working chamber 37, the sub-sleeve 31 is displaced to the right side in the figure, that is, to the side where the fuel injection amount is increased. The displacement amount of the sub sleeve 31, that is, the increase correction amount of the fuel injection amount changes according to the amount of fuel introduced into the working chamber 37 (in FIG. 3). Therefore, it is possible to prevent the fuel injection pressure from rising abnormally, and the durability of the injection pump and the fuel nozzle (not shown) is not reduced.

As described above, since the sub-sleeve 31 is moved to the side of increasing the fuel injection amount according to the amount of fuel returned from the high pressure chamber to the working chamber 37, the fuel injection amount does not decrease and the output decreases. It is possible to prevent the deterioration of drivability due to.

After the completion of the pressure feeding (on the right in FIG. 3), the movement of the plunger 8 causes the plunger-side fuel return passage 41 and the sleeve-side fuel return passage 42 to communicate with each other, and the fuel in the working chamber 37 returns to the pump chamber 5. , The sub sleeve 31 is the spring 3
It is pushed back to the initial position by 3 to prepare for the next pressure feeding start.

[0023]

As described above, according to the present invention, the means for detecting the fuel pressure in the plunger high pressure chamber and the fuel in the plunger high pressure chamber when the fuel pressure in the plunger high pressure chamber reaches a predetermined value. Since the structure is provided with means for bypassing to the pump chamber and means for increasing and correcting the fuel injection amount in accordance with the amount of fuel bypassed at this time, as shown in FIG. Without being accompanied, it is possible to suppress an abnormal increase in the pressure-feed fuel pressure (injection pressure) in the high-pressure chamber and maintain the durability of the injection pump.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a detailed view of a main part (A part in FIG. 1) of the embodiment.

FIG. 3 is an explanatory diagram of an operation of the embodiment.

FIG. 4 is an explanatory diagram showing an effect of the present invention.

[Explanation of symbols]

 4 Plunger high pressure chamber 8 Plunger 16 Control sleeve 22 Rotor 23 Ball 31 Sub sleeve 33 Spring 35 Seat 37 Working chamber 39 Check valve 40 Port 41 Plunger side fuel return passage 42 Sleeve side fuel return passage

Claims (4)

[Claims] 1. A fuel injection pump for pumping fuel by a plunger, means for detecting a fuel pressure in a high pressure chamber of a plunger, and when the fuel pressure in the high pressure chamber of a plunger reaches a predetermined value,
An injection pressure control device for a fuel injection pump, comprising: a means for bypassing the fuel in the plunger high pressure chamber to the pump chamber; and a means for correcting the fuel injection amount by increasing the amount of fuel bypassed at this time. 2. A check valve, which is provided in the plunger and opens when the fuel pressure in the high pressure chamber reaches a predetermined value or more, and a port for introducing the fuel passing through the check valve into the working chamber in the control sleeve. A second control sleeve for moving the fuel injection amount to the increasing side according to the amount of fuel introduced into the working chamber, and a fuel return passage for returning the fuel in the working chamber to the low pressure chamber after the completion of the pressure feeding of the fuel. An injection pressure control device for a distributed fuel injection pump. 3. The fuel injection pump comprises a plunger that reciprocates following a face cam by rotating in synchronization with engine rotation, a plunger high pressure chamber that expands and contracts due to reciprocating movement of the plunger, and an outer peripheral surface of the plunger. A port that communicates with the same number of intake slits as the number of engraved cylinders to guide the fuel drawn into the plunger high pressure chamber, and a distribution slit that is engraved on the outer peripheral surface of the plunger communicates the fuel discharged from the plunger high pressure chamber. 2. A distribution port for guiding each cylinder, and a control sleeve for releasing fuel discharged from the high pressure chamber of the plunger by opening a cut-off port opened on the outer peripheral surface of the plunger at the end of fuel pressure feeding. Alternatively, the injection pressure control device of the fuel injection pump described in 2. 4. The injection pressure of a fuel injection pump, wherein the second control sleeve according to claim 2 is provided with an elastic body that is urged to move the fuel injection amount to the reduction side. Control device.