JPH02102361A - Control device for fuel injection for diesel engine - Google Patents

Abstract

PURPOSE:To enable the function of fail-safe to be secured in case of abnormalities by providing a control sleeve opening and/or closing a spill port, and thereby concurrently arranging a solenoid valve for a fuel return line communicating a low pressure feed pump chamber with a plunger chamber. CONSTITUTION:When a plunger 7 is rotated while being reciprocated, fuel sucked in a plunger chamber 12 from a feed pump chamber 5 through a suction line 6 is fed with pressure to an injection nozzle from a distribution port 31 through a delivery valve 32. A control sleeve 21 which opens and/or closes a spill port formed on a plunger is fit in the circumferential surface of the plunger 8. The control sleeve 21 is interlocked with an accelerator via a control lever and the like. By this a fuel return line 13 is formed, which communicates the fuel chamber 5 with the plunger chamber 12, and a high speed responding type solenoid valve 14 is arranged on the halfway so that the fuel injection completion timing is thereby adjusted by opening the aforesaid valve 14.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel injection control device for a diesel engine.

(Prior Art) As a fuel injection device for a diesel engine, there is a distribution type fuel injection pump that electronically controls fuel injection timing, fuel injection amount, etc. (see, for example, Japanese Utility Model Application No. 1988-192534).

To explain this with reference to FIG. 7, 1 is a pump housing, 2 and 3 are a low-pressure side feed pump and a high-pressure side plunger pump driven by a drive shaft 4, and the fuel sucked by the feed pump 2 from a fuel inlet (not shown) is It is supplied to a feed pump chamber 5 in the housing 1 and sent to the plunger pump 3 via a suction passage 6 that opens into the feed pump chamber 5.

The plunger 7 of the plunger pump 3 has suction grooves 8 of the same number as the shillings of the engine formed at the tip, and a 7-eighth cam 9 having the same number of cam ridges at the other end.
The eighth cam 9 rotates together with the drive shaft 4 and reciprocates by a predetermined cam lift over the rollers 11 disposed on the roller ring 10.

Therefore, the plunger 7 reciprocates while rotating, and the fuel sucked into the plunger chamber 12 from the suction groove 8 due to this rotation and reciprocation is delivered from a distribution boat for each cylinder (not shown) that communicates with the plunger chamber 12. It is pumped through a valve to an injection nozzle facing the combustion chamber.

In order to control the fuel injection timing and injection amount, a fuel return passage 13 is formed that communicates the feed pump chamber 5 and the plunger chamber 12, and a fast-response type solenoid valve 14 is provided in the middle of this fuel return passage 13. is interposed.

This electromagnetic valve 14 opens the plunger chamber 12 when the valve is opened, and is closed for a predetermined period during the discharge stroke of the plunger pump 3 according to the operating conditions of the engine by a drive pulse.

Fuel injection is started by closing the solenoid valve 14 during the pressure feeding stroke of the plunger 7, and injection is ended by opening the solenoid valve 14. Therefore, depending on the closing timing of the solenoid valve 14, the fuel injection start timing can be changed. The injection amount is controlled according to the valve closing period.

(Problem to be Solved by the Invention) However, in such a fuel injection control device for a diesel engine, since the solenoid valve 14 has the function of both starting and stopping fuel pumping, in the unlikely event that the solenoid valve 14 There was a problem in that if an incorrect signal was input to the valve and the valve remained closed, a large amount of fuel would be injected even if the accelerator was in the fully closed position.

The present invention aims to solve such problems.

(Means for Solving the Problems) This invention includes a plunger that reciprocates while rotating in synchronization with engine rotation, and when the plunger operates, fuel is sucked from a low-pressure feed pump chamber into the plunger chamber to each cylinder. In a fuel injection control system for a diesel engine, a solenoid valve is installed in the fuel return passage that communicates the low-pressure feed pump chamber formed in the pump housing with the plunger chamber, and the end timing of fuel injection is adjusted by opening the solenoid valve. A spill port is formed that passes through the plunger and opens at the surface of the plunger in order to communicate the plunger chamber with the feed pump chamber, and a control sleeve for opening and closing the spill port is slidably fitted onto the plunger, and the control sleeve is fitted into the plunger. The system is designed to adjust the fuel injection start timing in conjunction with the accelerator.

(Operation) When the control sleeve closes the spill port due to the compression stroke of the plunger, the pressure in the plunger chamber increases and fuel injection begins. When the solenoid valve opens, the high-pressure plunger chamber is released into the low-pressure feed pump chamber, stopping fuel injection. This makes it possible to finely control the fuel injection amount and injection timing by operating the control sleeve in accordance with the accelerator opening degree and operating the solenoid valve in accordance with various operating conditions.

Even in the unlikely event that the operation of the solenoid valve is disturbed due to an erroneous signal from the control circuit, the amount of fuel injection that can be supplied can be mechanically limited via a control sleeve that is linked to the accelerator opening, thereby ensuring the 7-air-save 7PIi performance.

(Example) The present invention will be described in detail below based on the accompanying drawings. Note that the same components as those of the conventional example are given the same reference numerals.

As shown in FIG. 1, the plunger 7 of the plunger pump 3 has a suction groove 8 formed at its tip with the same number as the cylinders of the engine, and a 7-eighth cam 9 having the same number of cam ridges formed at the other end. While rotating together with the drive shaft, the seven-eighth cam 9 rides over the rollers 11 disposed on the roller ring 10 and reciprocates by a predetermined cam lift. As the plunger 7 reciprocates while rotating, the fuel sucked into the plunger chamber 12 from the feed pump chamber 5 through the suction passage 6 and the suction groove 8 is transferred to the distribution boat 31 for each cylinder that communicates with the plunger chamber 12. The fuel is forced to pass through the delivery valve 32 and to the injection nozzle facing the combustion chamber.

A spill port 22 that communicates the plunger chamber 12 and the low-pressure feed pump chamber 5 is opened on the circumferential surface of the plunger 8, and a funnel sleeve 2 that opens and closes this spill port 22 is opened.
1 is slidably fitted.

When the plunger 7 strokes toward the compression side of the plunger chamber 12, the spill port 22 is closed by the control sleeve 21, thereby increasing the pressure in the plunger chamber 12, and the timing of starting fuel injection changes depending on the position of the control sleeve 21. .

As shown in FIG. 2, the control sleeve 21 is interlocked with the accelerator via a tension lever 26, a spring 27, a control lever 28, and the like.

As shown in Figure 3, the fuel injection timing is determined by the feed pump 3.
Advance angle control is also performed by rotating the roller ring 10 of the timer piston 35, which operates in accordance with the discharge pressure. A high pressure chamber 36 and a low pressure chamber 37 are defined at both ends of the timer piston 35, and the oil pressure guided to each oil chamber 36, 37 is adjusted to move the timer piston 35 to the spring 3.
A timing control valve 38 is provided which operates against the timing control valve 9.

A position sensor 34 that detects the stroke position of the control sleeve 21 in conjunction with the tension lever 26 is provided, and a device that controls the timing control valve 38 includes a control unit that processes the detection signal of the position sensor 34; It consists of a drive circuit and
In cooperation with the operation of the control sleeve 21, the timer piston 35 is driven to finely adjust the fuel injection start timing.

A fuel return passage 13 communicating between the feed pump chamber 5 and the plunger chamber 12 is formed, and a high-speed response type solenoid valve 14 is interposed in the middle of the fuel return passage 13.

This electromagnetic valve 14 opens the plunger chamber 12 when the valve is opened, and is closed for a predetermined period during the discharge stroke of the plunger pump 3 according to the operating conditions of the engine by a drive pulse.

The injection ends by opening the solenoid valve 14 during the pressure feeding stroke of the blunt 7, and therefore the fuel injection start timing is controlled by the valve closing timing of the solenoid valve 14, and the injection amount is controlled according to the valve closing period. be.

The device that controls the electromagnetic valve 14 includes a sensor that detects operating parameters such as engine speed, a control unit that processes the detection signal, and a drive circuit.

It is constructed as described above, and its operation will be explained next.

As shown in FIG. 4, when the control sleeve 21 closes the spill port 22 during the compression stroke of the plunger 7, pressure builds up in the plunger chamber 12 and fuel injection starts. ends.

The amount of fuel is increased mainly by the timing when the control sleeve 21 closes the spill hole 22, but movement of the control sleeve 21 alone is not sufficient to control the injection amount optimally in response to changes in operating conditions such as engine speed. Fine control is performed by controlling the opening timing of the electromagnetic valve 14.

Further, the fuel injection start timing changes due to the movement of the control sleeve 21, but the position of the control sleeve 21 is detected by the position sensor 34, and the timing is corrected to the optimum timing by the timing control valve 38 and the timer piston 35.

Even in the unlikely event that the operation of the solenoid valve 14 is disturbed due to an erroneous signal from the control circuit, the control sleeve 21 will slide in conjunction with the accelerator, move to the right in the figure as the accelerator opening degree decreases, and move the plunger 7. Since the timing of closing the spill hole 22 is delayed during the stroke and the amount of fuel injection that can be supplied is limited, the 7-in-1 operation can be ensured.

Next, another embodiment shown in FIG. 5 will be described. A main valve 41 is interposed in the middle of the fuel return passage 13 communicating with the plunger chamber 12, and a back pressure chamber 43 is formed behind the main valve 41. A fuel return passage 13 communicating with this back pressure chamber 43 is formed, and a pilot solenoid valve 42 is provided in the middle of the fuel return passage 13.

During the compression stroke of the plunger 7, the plunger chamber 12 and the back pressure chamber 43 are maintained at equal pressure through the orifice 45 formed in the main valve 41, and the pressure in the back pressure chamber 43 is reduced by opening the pilot solenoid valve 42. When released, the main valve 41 opens against the spring 46 and fuel injection stops.

In this case, the pilot solenoid valve 42 can be made smaller, and the high pressure generated in the plunger chamber 12 can be maintained with less power consumption.

In addition, as shown in FIG. 6, the control sleeve 21
A shaft 49 is rotatably connected to the shaft 49 with a predetermined moment arm via a ballge coint 48,
A control lever 50 that is linked to the accelerator is connected to one end of this shaft 49, and as the accelerator opening increases, the shaft 49 rotates and slides the control sleeve 21 to the left in the figure to determine when to start fuel injection. It is starting to be faster.

A rotational position sensor 50 is provided in the middle of the shaft 49,
The sliding position of the hunt roll sleeve 21 is detected.

(Effects of the Invention) As described above, according to the present invention, a spill port that opens on the surface of the plunger and a control sleeve that opens and closes this spill port are provided, and this control sleeve is linked to the accelerator to determine when to start fuel injection. A solenoid valve is installed in the fuel return passage that communicates the low-pressure feed pump chamber and the plunger chamber formed in the pump housing, and the end timing of fuel injection is adjusted by opening the solenoid valve. The solenoid valve operates in conjunction with the sleeve to perform fine-grained control according to driving conditions, and even if the solenoid valve control signal is disrupted, the amount of fuel injection that can be supplied is controlled in conjunction with the accelerator opening. Mechanically limited by sleeve
8% capacity can be secured.

[Brief explanation of the drawing]

FIGS. 1, 2, and 3 are sectional views showing one embodiment of the present invention, and FIG. 4 is a diagram for explaining the operation. MS Fig. 5 and Fig. 6 are sectional views showing other embodiments, respectively. Fig. 7 is a sectional view showing a conventional example. DESCRIPTION OF SYMBOLS 1... Pump housing, 5... Feed pump chamber, 7... Plunger, 9... 7 Acecam, 11...
...Roller, 12...Plunger chamber, 13...Fuel return passage, 14...Solenoid valve, 21...Control sleeve, 22...Spill port.

Claims (1)

[Claims] It is equipped with a plunger that rotates and reciprocates in synchronization with the engine rotation, and a plunger chamber that sucks fuel from the low-pressure feed pump chamber and distributes it to each cylinder by the operation of the plunger, and the plunger chamber and the low-pressure feed pump chamber are connected. A spill port is formed that penetrates the plunger and opens on its circumference, and a control sleeve that opens and closes this spill port is slidably fitted to the plunger, and this control sleeve is linked to the accelerator to inject fuel. In addition to adjusting the start timing, a solenoid valve is installed in the fuel return passage that communicates the low-pressure feed pump chamber and the plunger chamber formed in the pump housing, and the end timing of fuel injection is adjusted by opening the solenoid valve. A fuel injection control device for a diesel engine characterized by: