JPH0210289Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a fuel injection pump for a diesel engine, and in particular, to a fuel injection pump for cutting off fuel sucked into a high pressure chamber when the starter switch is turned off or during fail-safe operation. The present invention relates to a fuel injection pump having a solenoid valve.

[Background of the idea]

During the intake stroke of the plunger, which rotates and reciprocates in synchronization with the rotation of the internal combustion engine, relatively low-pressure fuel is introduced from the low-pressure side into the high-pressure chamber, and during the compression stroke of the plunger, the low-pressure fuel is increased in pressure and discharged to each cylinder of the internal combustion engine. In addition, with fuel injection pumps in which the fuel passage leading to the high pressure chamber is closed by a fuel cutoff solenoid valve while the starter switch is off or in a fail-safe situation, if the starter switch is accidentally turned off while driving, Since the fuel supply to the high pressure chamber is cut off, the pressure inside the fuel introduction passage between the fuel cutoff solenoid valve and the high pressure chamber becomes negative, and the fuel cutoff solenoid valve will not open even if the starter switch is turned on next time. Therefore, there is a risk that an engine whose combustion has been interrupted due to fuel cutoff may not be able to restart. Such a problem may also occur when the starter switch is turned off after the vehicle has stopped and then turned on again immediately after that. Furthermore, the fuel cutoff electromagnetic valve is closed by the failsafe, and a similar phenomenon may occur when the failsafe operation is canceled.

The reason why the fuel introduction passage between the fuel cutoff solenoid valve and the high pressure chamber becomes negative pressure is because the engine cannot be stopped immediately even if the fuel cutoff solenoid valve is closed and the fuel supply to the high pressure chamber is interrupted. This is because the plunger reciprocates and only a very small amount of fuel is introduced into the high pressure chamber during the suction stroke of the plunger.

[Purpose of invention]

The purpose of this invention is to provide a diesel engine that prevents negative pressure from remaining in the fuel introduction passage between the solenoid valve and the high pressure chamber even if the plunger moves back and forth when the fuel cutoff solenoid valve is closed. Our purpose is to provide fuel injection pumps.

[Structure of the idea]

In the present invention, a pressure relief passage is formed in the plunger to communicate the fuel passage between the solenoid valve and the high pressure chamber with the low pressure side only at a predetermined period of the compression stroke.

〔Example〕

FIG. 1 shows an embodiment of a fuel injection pump according to the present invention, where reference numeral 1 denotes a fuel injection pump, in which low-pressure fuel introduced from an input port 5 by a fuel pump 3 is supplied to a low-pressure chamber 7 on the low-pressure side. The fuel is introduced into the high pressure chamber 15 by the plunger 11, which rotates and slides back and forth in synchronization with the rotation of the shaft 9, and is made to be highly pressurized, and is then sent from the injection valve provided in each cylinder to the combustion chamber of each cylinder via the delivery valve 17. The configuration is such that fuel is injected and excess fuel is exhausted from the exhaust port 19.

Here, numeral 21 is a fuel cutoff solenoid valve,
When the starter switch 22 is turned on, the solenoid valve 21 is opened in response to the starter switch 22 and the low pressure chamber 7 and high pressure chamber 1 are opened.
When the starter switch 22 is turned off, the solenoid valve 21 is closed and the fuel passage 23 is closed. It is also designed to be closed during failsafe conditions. In addition, plunger 11
is fitted into the cylinder block 12, so that the high pressure chamber 15 is defined within the cylinder block 12.

The fuel injection amount is determined by sliding a spill ring 25 that is slidably fitted on the circumferential surface of the plunger 11 using a linear solenoid 27, and setting the positional relationship between the right end surface of the spill ring 25 and the spill port 11a of the plunger 11. It is determined as follows. On the other hand, the injection timing is determined by intermittently opening and closing a solenoid valve 29 as a timing control valve to control the pressure inside the timer 31, thereby appropriately setting the positional relationship between the roller 33 and the cam plate 35. , by controlling the timing at which the plunger 11 starts moving to the right.

Linear solenoid 27 and therefore spill ring 2
5 is detected by the spill position sensor 37, and the position of the timer piston 39 is detected by the timer position sensor 41. Further, the engine rotation speed is detected by a rotation speed sensor 45 that is provided facing the gear 43 fixed to the shaft 9 and outputs a pulse signal according to the rotation speed of the gear 43. Furthermore, the amount of depression of the accelerator pedal 47 is detected by an accelerator sensor 49.

Each of these sensors and each of the above-mentioned sensors is connected to a control circuit 51, and upon receiving signals from these sensors, the control circuit 51 calculates and determines the fuel injection amount and injection timing, and according to the calculation results. The control signal is supplied to the linear solenoid 27 and the electromagnetic valve 29. Further, in response to a signal from the starter switch 22 or in response to a failsafe signal, an opening/closing control signal is supplied to the fuel cutoff electromagnetic valve 21.

The plunger 11 has a shape as shown in FIG. 2, and fuel introduction grooves 11b corresponding to the number of cylinders are formed on the outer peripheral surface of one end defining the high pressure chamber 15 at predetermined angle intervals, in this example, at 90 degree intervals. (four cylinders), and this groove 11b is formed over a predetermined length in the fuel cutoff electromagnetic valve 21 and the high pressure chamber 1 during the intake stroke shown in FIG. 3a.
5, the low pressure fuel in the low pressure chamber 7 is introduced into the high pressure chamber 15.

On the other hand, at one of the four angular positions where the fuel introduction groove 11b is formed, this groove 1
Fuel distribution port 1 is located on the circumferential surface spaced apart from 1b by a predetermined distance.
Only one 1c is open. In addition, the above-mentioned spill port 11a (Fig. 3a
) is penetrated perpendicularly to the axis. These spill ports 11a and distribution ports 11
b communicates with a fuel passage 11d (see FIG. 3b) that is bored in the axial direction of the plunger 11.
Then, at a predetermined time in the compression stroke shown in FIG. 3b, the distribution port 11c is opened to the delivery valve 17
The inner circumferential surface 1 in the cylinder block 12 is communicated with
The high-pressure fuel in the high-pressure chamber is distributed and injected via the delivery valve 17, so that the high-pressure fuel in the high-pressure chamber is distributed and injected through the delivery valve 17. Furthermore, at a predetermined time in the compression stroke shown in FIG.
The high-pressure fuel is discharged to the low-pressure chamber 7, and the injection is completed.

Furthermore, referring to FIG. 2, at each angular position intermediate between the angular positions where the fuel introduction grooves 11b are carved, grooves 11b extending in the axial direction start from a position near the terminal end of the groove 11b. A pressure relief groove 11e is formed, and the terminal end of the groove 11e is connected to a pressure relief group 11f formed on the outer circumferential surface of the plunger 11 at a position that constantly communicates with the low pressure chamber 7.
These grooves 11e and groups 11f form pressure relief passages. Then, at a predetermined time in the compression stroke shown in FIG. Therefore, the fuel passage 23a is connected to the groove 11c and the group 1
It communicates with the low pressure chamber 7 via 1f.

In the fuel injection pump configured in this way, the starter switch may be accidentally turned off while the engine is rotating, and the fuel cutoff solenoid valve 21 may close, or the solenoid valve 21 may close due to a fail-safe operation.
Even if the fuel passage 23 is closed, the electromagnetic valve 21 is closed at a predetermined time between each suction stroke of the plunger, which rotates and reciprocates for a while after the fuel injection is interrupted, that is, at a predetermined time in the compression stroke. Since the fuel passage 23a between the high pressure chamber 15 and the low pressure chamber 7 is communicated with the low pressure chamber 7 via the groove 11e and the group 11f, negative pressure generated in the fuel passage 23a during the intake stroke can be removed. Therefore, when the starter switch is turned on again or after a failure recovery, the solenoid valve 21 is opened quickly and reliably, and fuel can be continuously injected. Furthermore, when the groove 11e faces the fuel distribution passage 18, this fuel distribution passage 18 communicates with the low pressure chamber 7, thereby removing the residual pressure in the passage 18, so that the pressure in each distribution passage 18 is equalized. This improves the accuracy of fuel injection timing and injection amount.

[Effect of idea]

According to the present invention, a pressure relief passage is formed in the plunger to communicate the fuel passage between the fuel cutoff electromagnetic valve and the high pressure chamber with the low pressure side at a predetermined time during the compression stroke of the plunger, so that the starter switch can be accidentally activated. Even if the fuel cut-off solenoid valve is closed due to a failsafe, the negative pressure in the fuel passage generated during the intake stroke can be removed, without using a cut-off solenoid valve that generates a large electromagnetic force. The solenoid valve can be opened and closed quickly and reliably when the starter switch is turned on again or after a failure recovery.

The present invention can be applied to a type of injection pump that discharges high-pressure fuel using a spill solenoid valve placed facing a high-pressure chamber instead of a spill ring, or to a type of injection pump that uses a mechanical governor to adjust the spill ring position. can also be applied.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of the fuel injection pump according to the present invention, Fig. 2 is a perspective view showing the shape of its plunger, and Figs. 3 a to 3 d explain various operations in the suction stroke and compression stroke. FIG. 3 is an enlarged sectional view of the vicinity of the plunger. 1...Fuel injection pump, 7...Low pressure chamber, 11...
... Plunger, 11a ... Spill port, 11b
...Fuel introduction groove, 11c...Distribution port, 11
d...Fuel passage, 11e...Pressure relief groove, 11f
...Pressure relief group, 15... Hyperbaric chamber, 17...
... Delivery valve, 21 ... Solenoid valve for fuel cutoff,
23... Fuel passage, 25... Spill ring.

Claims (1)

[Scope of utility model registration request] During the suction stroke of a plunger that rotates and reciprocates in synchronization with the rotation of the internal combustion engine, relatively low-pressure fuel is introduced from the low-pressure side into the high-pressure chamber, and during the compression stroke of the plunger, the low-pressure fuel in the high-pressure chamber is increased in pressure to increase the pressure of the internal combustion engine. In a fuel injection pump for a diesel engine, in which a fuel passage leading to the high pressure chamber is closed by a fuel cutoff solenoid valve at a predetermined time, the solenoid valve and the high pressure chamber are closed at a predetermined time during the compression stroke. A fuel injection pump for a diesel engine, characterized in that a pressure relief passage is formed in the plunger to communicate a fuel passage therebetween with the low pressure side.