JPS6146459A - Fuel jet pump of internal combustion engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The invention relates to a fuel injection pump for internal combustion engines, in particular for high-speed diesel engines, which is limited by a plunger guided in a barrel and by a sylansha. a pump working chamber which is filled with fuel during the suction stroke of the plunger and connected to the injection nozzle during the discharge stroke of the syringer; and an adjustment slider slidable in the axial direction along the plunger. opens or closes at least one pressure relief opening provided on the outer circumferential surface of the syringe and connected to the pump working chamber; A control edge for controlling the flow rate is formed by the radial side of an inner annular groove provided on the adjusting slide and open towards the plunger, which annular groove is connected to an outflow passage leading to the outside. Regarding the format of

PRIOR ART AND DISADVANTAGES In fuel injection pumps of this type, the discharge stroke of the plunger and thus the injection process is such that, when the plunger slides, the pressure relief opening or control hole provided in the plunger is pushed over the control edge of the annular groove. and ends by connecting with the annular groove.

As a result, the pump working chamber is depressurized and the remaining fuel quantity in the pump working chamber flows out during the residual stroke of the plunger via the depressurization opening and the outflow channel into the suction chamber of the fuel injection pump. This discharge control process takes place so quickly that it has already ended before the injection valve or nozzle needle of the injection nozzle closes again. In high-speed diesel engines, in order to obtain the highest injection pressure, a backflow restrictor is installed between the pump work chamber and several injection valves, but no valves are installed, so the injection valves When not yet closed, the combustion gases in the engine combustion chamber may cause a portion of the fuel to flow back from the discharge conduit leading to each injector into the pump working chamber via the backflow restriction. As a result, during the next injection process, the injection amount is reduced and the start of injection is delayed.

Therefore, the object of the present invention is to provide a fuel injection system for an internal combustion engine that can reliably avoid the above-mentioned inconvenient backflow of fuel and can always guarantee a predetermined injection amount and injection start timing. is to provide a pump.

Means for Solving the Problem In order to solve this problem, the present invention provides a fuel injection pump of the type mentioned at the beginning, in which the outflow passage is operated at least when the control slider starts controlling the opening of the pressure relief opening. The bong 70 was closed off by a pressure control member that maintained a predetermined pressure in the chamber and the injection conduit supplied with fuel from the bong 70 working chamber.

Effects of the Invention With the structure of the present invention, backflow of fuel can be avoided with simple means. By means of the pressure control element according to the invention, the pressure maintained in the pump working chamber at the beginning of the discharge control process between the opening of the pressure relief opening by means of the adjustable slider and the closing of the nozzle needle in the injection valve is determined by the pressure of the combustion gases. The pressure is so high that fuel cannot flow back through the backflow restrictor.

Embodiments The claims 2 to 10 describe advantageous embodiments of the fuel injection pump according to the invention.

If configured as described in claim 2,
The sliding piston can utilize a storage volume into which the quantity of fuel to be discharged is forced against the pressure of the compression spring.

Further, when configured as described in claim 6, such an outflow hole can prevent the discharge of the storage volume and thus the pressure control member from gradually becoming inactive. The discharge of the storage volume and thus the gradual deactivation of the pressure control element means that, due to the space, the pressure spring cannot be set too strongly and the fuel quantity to be discharged is forced out again before the pressure relief opening is closed. It is brought about by being During each discharge control process, the given storage volume is then filled further until the slide piston compresses the pressure spring and contacts the casing bottom and the pressure control element becomes inactive. By suitably arranging the outlet holes relative to the stroke of the sliding piston, the maximum storage volume is limited. Excess fuel quantity flows out via the outflow hole into the suction chamber of the fuel injection pump. The outflow hole is also at the same time,
Configured as claimed in claim 4, characterized by a relatively precise regulation of the pressure maintained by the pressure control valve,
Via the connecting hole, the spring chamber is connected to a suction chamber of the fuel injection pump, which is filled with fuel and which surrounds the piston housing.

The amount of fuel flowing out through the throttle cross section during sliding of the sliding piston dampens the piston movement and thus improves the pressure characteristics of the pressure control element.

Advantageous embodiments of the invention are obtained by the features of patent claims 7 and 8.

With this embodiment, a sufficiently high pressure is generated in the pump work chamber at the start of the injection control process according to the invention, and on the other hand, the fuel can be depressurized unhindered after closing the nozzle needle in the injection valve. It is set to allow outflow through the opening.

Embodiment In the distribution type fuel injection pump schematically shown in longitudinal section in FIG. 1, as is well known, the plunger 10 is driven by a drive device (not shown) via a cam plate 11, and performs both reciprocating motion and rotational motion. , is supposed to be done. The plunger 10 slides in a barrel 12 which is closed at one end and delimits a pump working chamber 13 in this barrel 12 . The barrel 12 is held within a pump casing 14, which has a suction chamber 15 and has a suction chamber 15.
, this suction chamber 15 surrounds the cam plate 11 and the plunger portion protruding from the barrel. The suction chamber 15 is filled with fuel by a feed pump (not shown). The fuel enters in this case via the inlet 16 .

The plunger 10 has a centrally extending axial bore 18 which opens at an end face 17 of the plunger 10 which delimits the pump working chamber 13 . The axial hole 18 is connected to a lateral hole 19 which is connected to an annular groove 20 provided on the outer circumferential surface of the plunger 10.
It is open to From the annular groove 20 extends a distribution longitudinal groove 2 , 1 which cooperates with a discharge or injection conduit 22 extending inside the pump housing 14 . The injection lines 22 are distributed over the entire circumference of the barrel 12, the number of injection lines 22 corresponding to the number of cylinders of the associated internal combustion engine.

During high-speed operation of the diesel engine, each injection line 22 leads to the associated injection nozzle via a backflow throttle.

Vertical grooves 23 extend from the end face of the plunger 10 , and via these vertical grooves 23 the pump working chamber 13 is connected to the suction hole 24 during each suction stroke of the plunger 10 . The suction hole 24 extends from the suction chamber 15 into the barrel 12 and further through the barrel wall. The suction hole 24 can be closed by a solenoid valve 25.

The section of the plunger protruding into the suction chamber 15 is provided with an adjusting slide 26 that slides axially along this section, which adjusts the adjusting rod 27 by means of a centrifugal governor in a known manner. is operated through the pump to control the discharge stroke, as well as the maximum discharge amount and the end of injection. The adjusting slide 26 has an inner annular groove 28 that opens towards the outer circumferential surface of the plunger 10 and cooperates with a transverse bore 29 provided in the plunger 10 . This horizontal hole 29
is connected to the axial bore 18 and thus always connected to the pump working chamber 13. This allows the axial hole 18
and the transverse bore 29 form a pressure relief opening for the menzo working chamber 13, which pressure relief opening is closed by an adjusting slide 26 and, depending on the adjustment of the adjusting slide 26, a small or large stroke movement of the plunger 10. Released at distance. In this case, the left-hand side surface of the annular groove 28 in FIG. 1 forms a control edge. The annular groove 28 has an outflow channel 30 which opens into the suction chamber 15 and is configured as a radial bore.
This outflow passage 30 is connected to the pressure control member 3
1,311 (see Figures 2 and 6). The pressure control member 31.31 is connected to the adjustment slider 26
A predetermined pressure is maintained in the pump working chamber 13 until the nozzle needle in the injection nozzle is closed for a short time at the start of the opening control of the pressure relief opening.

In the embodiment shown in FIG. 2, the pressure control element 31 has a sliding piston 32 with a pressure spring 33, which seats in the opening of the outlet channel 30. This slide piston 3
2 is guided in a casing formed by an adjusting slide 26. In the embodiment shown in FIG. 2, the adjustment slider 26 has a blind hole 34, and an outflow passage 30 opens at the bottom of the blind hole 34.

In the blind hole 34 the sliding stone 32 is guided in an axially slidable manner and is pressed against the bottom of the blind hole 34 by means of a pressure spring 33 . At the other end of the compression spring 33,
It is supported by a closing member 35 that closes the blind hole 34. An axial bore 36 is provided in the closing member 35, via which the spring chamber is connected to the suction chamber. The axial bore 36 has a defined throttle cross section. A radial hole 37 is opened in the blind hole 34 between the bottom of the blind hole 34 and the closing member 35 . The axial length of the slide piston 32 is such that in its rest position the slide piston 32 closes the radial bore 37 in its rest position and in the position in which it abuts the bottom of the blind bore 34 .

The mode of action of the pressure control element 31 is as follows.During the discharge stroke of the plunger 10, fuel is pumped via the injection line 22 to the injection nozzle, where it is injected into the respective cylinder of the internal combustion engine. The discharge stroke ends as soon as the pressure relief opening transverse hole 29 passes the control edge of the annular groove 28 during the stroke movement of the plunger 10. When the closing control process is introduced during the residual stroke of the plunger 10, fuel flows from the working chamber 13 of the bong 70 through the outlet passage 30 through the pressure relief opening formed by the axial hole 18 and the transverse hole 29.
There, the slide piston 32 is moved against the force of the compression spring 33 while filling the storage volume. On the other hand, the rear side of the sliding piston 32 is also stressed by the pressure in the suction chamber 15, so that a defined pressure determined by the dimensions of the pressure spring 33 is required to move the sliding piston 32. The shift pressure of the sliding piston 32 is now set in such a way that a predetermined pressure is maintained in the pump working chamber 13 at least as soon as the discharge control process is started and until the time when the nozzle needle reliably closes the injection nozzle again. By maintaining a predetermined pressure, it is reliably avoided that fuel flows back through the backflow restriction into the discharge conduit 22 and the pump working chamber 13 by the combustion gases of the engine when the nozzle needle is still open. When the sliding piston 32 is pushed back by the outflowing fuel quantity until the radial bore 37 opens, a larger quantity of fuel enters this radial bore 37.
Flows into the suction chamber 15 via. This determines the maximum storage volume that can be released by the sliding stone 32. Depending on the distance of the radial hole 37 from the bottom of the blind hole 34, the maximum storage volume is determined as follows:
With the start of the movement in the opposite direction, the pressure relief opening is pushed back into the pump working chamber 13 until it is closed again.

In the embodiment shown in FIG. 6, the pressure control element 311 is formed by a non-return valve 38 which closes the outflow channel 30, which check valve 38 is configured as a spherical check valve in the embodiment shown. has been done.

The check valve 38 is integrated into the adjusting slider 26, and for this purpose the adjusting slider 26 has a blind hole 39, the bottom of which forms a valve seat 40 for the ball 41. . The valve closing spring 42 is supported on the one hand by the ball 41 and on the other hand by a closing member 43 which closes the blind hole 39 . Closing member 43 is similar to closing member 35 shown in FIG.
of the same type and for the same purpose, it has an axial bore 44 with a defined throttle cross section. The valve interior is connected via this axial hole 44 to the suction chamber 15 of the fuel injection pump.

The outflow channel 30 is designed as a throttle, the throttle cross section being such that a sufficiently high pressure is maintained in the pump work chamber 13 at the start of the discharge control process and that the fuel passes through the check valve 38 after closing the nozzle needle in the injection valve. It is set up so that it can flow out through.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing a part of the fuel injection pump, FIG. 2 is a longitudinal sectional view showing a first embodiment of the pressure control member, and FIG. 3 is a longitudinal sectional view showing a second embodiment of the pressure control member. It is a diagram. 10... Shira/Ja, 11... Cam board, 12...
Barrel, 13... Pump working chamber, 14... Pump casing, 15... Suction chamber, 16... Inflow section, 1
7... End face, 18... Axial hole, 19... Lateral hole, 20... Annular groove, 21... Distribution vertical groove, 22...
・Injection conduit, 23... Vertical groove, 24... Suction hole, 2
5... Solenoid valve, 26... Adjustment slider, 27...
Adjustment rod, 28... Annular groove, 29... Lateral hole, 30
...Outflow passage, 31.31...Pressure control member, 32
...Slide piston, 33...Crimp spring, 34.
... blind hole, 35 ... closing member, 36 ... axial hole,
37... Radial hole, 38... Check valve, 39...
Blind hole, 40... Valve seat, 41... Ball, 42... Valve closing spring, 43... Closing member, 44... Axial hole

Claims (1)

[Claims] 1. A fuel injection pump for an internal combustion engine, which has a barrel (1
2) a plunger (10) guided within;
The plunger (10
) is filled with fuel during the suction stroke of the plunger (10)
The pump working chamber (
13) and an adjustment slider (26) that is slidable in the axial direction along the plunger (10), the adjustment slider being provided on the outer peripheral surface of the plunger (10) and disposed in the pump working chamber ( Depending on the stroke position of the plunger (10), at least one pressure relief opening connected to the pressure relief opening (13) is opened or closed depending on the stroke position of the plunger (10), in which case the control edge of the adjustment slide (26) which controls the pressure relief opening is connected to the adjustment slide (26) and is formed by the radial side surface of an inner annular groove (28) that is open toward the plunger (10);
In the type in which the annular groove is connected to an outflow passage (30) leading to the outside, the outflow passage (30) comprises:
A pressure control element (31) that maintains a predetermined pressure in the pump working chamber (13) and the injection conduit (22) supplied with fuel from the pump working chamber, at least at the start of the opening control of the pressure relief opening by the adjusting slide (26). , 31) for an internal combustion engine, characterized in that the pump is closed by 2. Fuel injection according to claim 1, characterized in that the pressure control element (31) has a sliding piston (32) with a pressure spring (33), which seats in the opening of the outflow channel (30). Pump 3. A sliding piston (32) is guided in a casing which also receives a pressure spring (33), and in the sliding range of the sliding piston (32) an outflow hole extending through the piston casing opens radially. The fuel injection pump according to claim 2, wherein: 4. Claim 1, in which a connecting hole passes through the housing wall into the spring chamber of the housing surrounding the compression spring (33), the connecting hole having a defined throttle cross section. The fuel injection pump according to item 2 or 6. 5. The axial length of the slide piston (32) is set such that the outflow hole is closed by the slide piston (32) when the slide piston is seated at the opening of the outflow passage (30). , a fuel injection pump according to claim 3. 6. 6. Fuel injection pump according to claim 3, wherein the housing is formed by the adjusting slide (26) itself. 7. 2. Fuel injection pump according to claim 1, wherein the pressure control member (31^I) is formed by a check valve (38) closing the outflow passage (30). 8. 8. Fuel injection pump according to claim 7, characterized in that a throttle is arranged in series with the check valve (38), said throttle being formed by the outflow channel (30) itself. 9. 9. Fuel injection pump according to claim 7, wherein the check valve (38) is integrated into the adjusting slide (26). 10. According to the patent claim, a connecting channel having a defined throttle cross section and leading to the outside opens into the valve chamber, which receives the valve closing element (41) and the valve closing spring (42). Fuel injection pump according to scope item 9