JPS5815618B2 - Intensive pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a pump piston that reciprocates and simultaneously rotates under the control of a cam and is used as a distributor, and furthermore, the pump piston is distributed on the circumferential surface of a pump cylinder surrounding the pump piston. A pump piston that changes the amount of fuel delivered into an arranged delivery passage by controlling the opening of a depressurizing passage that discharges from the pump working chamber to the suction chamber; The present invention relates to a fuel injection pump for an internal combustion engine of the type having constant maintenance means.

In the case of known fuel injection pumps, the fuel quantity is regulated by means of a variable throttle in the suction channel leading to the pump working chamber.

In the case of this pump, during part-load operation, a high underpressure is created in the pump working chamber and the connected passage during the suction stroke.

This causes vapor lock, uneven injection and cavitation damage.

To avoid this drawback, patent no. 12 of the Federal Republic of Germany
In the fuel injection pump according to No. 06205, a check valve with a depressurizing piston is provided in each injection conduit (conduit between the control point and the injection nozzle), and further control of the check valve and the injection conduit is provided. It is known that during the suction stroke the connecting channel between the pump and the pump is closed off from the pump work chamber and is depressurized via the connecting pipe into the pump suction chamber.

However, such an arrangement uneconomically requires the provision of two separate control points, an additional duct and an expensive pressure relief valve for each injection conduit, which is therefore expensive. This has the disadvantage of becoming.

It is an object of the present invention to eliminate the disadvantages of the known fuel injection pumps mentioned above, namely to achieve a high delivery efficiency or high pressure and fuel delivery rate by simple means and with a suitable arrangement at low costs. It is an object of the present invention to provide an injection pump of the type mentioned at the outset, in which, despite its large size, negative pressure formation and thus cavitation damage and non-uniform injection are avoided.

In order to solve this problem, according to the invention, a depressurization channel is provided starting from the end face of the pump piston and extending around the circumference of the pump piston in order to reduce and keep constant the fuel pressure in the delivery channel leading to the injection location. a first passageway portion leading to a first outlet opening formed in the surface and a second outlet opening formed in the circumferential surface of the pump piston and axially adjacent said first outlet opening to the pump piston; a second passageway portion leading to a third outlet opening formed in the circumferential surface, the connecting passageway bringing said first outlet opening and said second outlet opening into communication during the delivery stroke of the pump piston; is provided in the wall of the pump cylinder, the connecting duct being assigned each time to a delivery duct and always connected to the delivery duct, the first outlet opening being connected to the suction of the pump piston. After the rotational position of the pump piston that introduces the start of the stroke, it is closed off during the suction stroke by the wall of the pump cylinder, in which case the third outlet opening is closed in the area of the pump piston and the suction chamber filled with fuel. a control slide which is sealed and slidably arranged on the pump piston and correspondingly opens or closes in the axial direction by a control lip on the control slide and furthermore in a second passage section of the pressure relief passage; A non-return valve is arranged which opens towards the third outlet opening, and the distribution hole in the third control part is opened immediately after the start of the suction stroke of the pump piston and also in the direction of the lower discharge opening in the second control part. It closes earlier than the radial holes in the pressure passage portion, and furthermore, the distribution hole and the radial hole are controlled to open simultaneously during the delivery stroke.

An advantage of the invention is that during the suction stroke of the pump piston, underpressure only occurs in the region of the upper depressurization channel section that is connected to the pump working chamber.

Pressure oscillations occurring in the delivery channel and the injection conduit connected thereto are in this case eliminated via only one central pressure relief valve, at which the average pressure can be maintained constantly.

Furthermore, even after the depressurization channel has been opened, a constant pressure is maintained in the pump chamber and its connection with the central pressure relief valve during the delivery stroke.

A further advantage is that, after closing the distribution bore, the delivery channel can be depressurized even during the start of the suction stroke of the pump piston, even after the pump piston has reached top dead center at the beginning of the suction stroke. Since the distribution hole is kept open for a precisely defined predetermined period of time, a predetermined amount of fuel can be returned to the pump working chamber.

This makes it possible to additionally reduce the residual fuel volume in the delivery channel and the injection conduit.

According to another advantageous embodiment of the invention, the drive cam for the pump piston has a rest period at its uppermost point.

As a result, the pressure in the delivery passage is further depressurized and pressure oscillations are eliminated before the start of the suction stroke.

The described configuration advantageously makes it possible, despite the high delivery efficiency, without the formation of underpressure and thus avoids cavitation damage and non-uniform injection.

The invention will now be explained with reference to the illustrated embodiment.

In the housing 1 of the fuel injection pump, a piston 2 works in a cylinder 4 consisting of a sleeve 3 fixedly inserted into the housing.

The piston 2, configured as a distributor, sequentially supplies fuel to several cylinders of the internal combustion engine.

For this purpose, the piston is caused to rotate and at the same time reciprocate as indicated by the arrow in FIG. It is crimped by a spring (not shown).

The transmission of rotational movement between the cam disk 6 and the piston 2 takes place via a pin 8 which engages in a groove 9 provided in the piston skirt 10.

During each suction stroke of the piston 2, the fuel supply to the working chamber 12, which is closed between the pump piston and the cylinder 4, is carried out through the inlet passage 13, the supply hole 14 and the working chamber 1.
This is done through one of the longitudinal grooves 15 extending from 2.

A depressurization channel is arranged in the longitudinal axis of the piston, which depressurization channel starts from the end face of the pump piston 2 and opens into a first outlet opening 41 formed in the circumferential surface of the pump piston. a third outlet formed in the circumference of the pump piston from the passage portions 17, 22 and a second outlet opening 42 formed in the circumference of the pump piston and axially adjacent to said first outlet opening 41; It consists of a second passage section 24, 18, 20.degree. 23 leading to an opening 43.

The initial blind hole section 19 of the lower depressurization passage section 18 based on the piston skirt 10 has a larger diameter than the end section 20 .

A radial hole 22 opens into the upper depressurization channel section 17 and serves as a distribution hole.

The lower depressurization passage section 18 also has a radial hole 23 in the end section 20 and a lateral hole 24 in the blind hole section 19, which allow control from the piston. Cooperatively with a slide 26, this control slide is axially movable on the pump piston 2 as a function of load and rotational speed by means not shown in detail.

The depressurization channel section 18 is closed by a pin 27 screwed in from the piston skirt, and depending on the screwing depth of this pin, the spring 28 can be subjected to an initial spring force of varying strength.

Of course, it is also possible to press-fit other suitable pins.

The spring 28 holds the ball 30 at the end portion 2 at the blind hole portion 19.
0 towards the opening, thereby closing this opening in a fluid-tight manner.

The distribution bore 22 and the radial direction 23 can communicate by means of a U-shaped connecting channel 32 provided in the sleeve 3 .

One fuel delivery conduit 33 branches off from this connection channel, leading to an injection nozzle (not shown).

These delivery conduits and connecting channels are arranged on the circumference of the pump piston depending on the number and sequence of cylinders to be supplied of the internal combustion engine.

The mode of operation of the fuel injection pump is as follows: driven by the cam disk 6, the pump piston performs a rotational and reciprocating movement as already mentioned, the piston being in a downward movement during the suction stroke. , inflow passage 13,
Fuel is sucked into the working chamber 12 from the suction chamber 16 via the feed hole 14 and a longitudinal groove 15 provided on the upper circumference of the pump piston.

During this process, the distribution holes 22, the radial holes 23 and the connecting passages 3
The connection with 2 is closed.

During the delivery stroke, the fuel flows through the upper depressurizing passage section 1γ,
The fuel flows via the distribution bore 22 , the connecting channel 32 and the delivery channel 33 to a nozzle (not shown), and on the other hand, the communication between the radial bore 23 and the connecting channel 32 is open, so that the fuel also flows into the sphere 30 . Access is possible into the lower depressurization channel section 18 via a check valve consisting of a non-return valve.

In this case, the first control part consisting of the control slide 26 and the transverse bore 24 is closed, so that the delivered fuel exclusively reaches the nozzle.

Depending on the position of the control slide 26, the first control is opened sooner or later before the piston reaches top dead center, so that fuel flows out into the suction chamber via the check valve 30 and the transverse bore 24. do.

Upon reaching top dead center, the distribution hole 22 forming the third control section
Communication between the piston and the connecting passage 32 is closed by rotation of the piston.

The relationship between the opening time of this third control section and the other control sections is the same as that of the second control section.
The schematic diagram in the figure shows the piston stroke curve in the course of the rotary movement of the piston.

In this diagram, the symbol ■ indicates the duration of communication between the distribution hole 22 and the connection passage 32 in the third control section.

For this third control section, the communication duration (2) between the radial hole 23 and the connection passage 32 is the same at the beginning of opening and remains open longer than the third control section, and moreover, it extends over almost the entire suction stroke. It's open.

Due to the closing of the third control before the start of the suction stroke, no negative pressure is created in the connecting channel 32, the delivery channel 33 and the lower pressure relief channel section 18 due to the piston movement.

After the third control is closed, ie at the end of the delivery, the pressure wave occurring in the injection conduit can be removed via the check valve 30.

In particular, a uniform depressurization in the delivery channel and the injection conduit is achieved, defined by the rebound pressure of the check valve 30.

Furthermore, the central valve maintains a constant pressure in the pump chamber and the bore connected thereto as soon as the transverse bore 24 is opened by the control slide.

By varying the initial spring force of spring 28, it is possible to define the pressure that is to be maintained in the delivery conduit after nozzle closure.

This arrangement prevents negative pressures caused by the suction stroke and causing non-uniform injection, as well as pressures that arise in the delivery passage and injection conduit due to pressure oscillations and causing cavitation damage and non-uniform injection. Avoided.

By making the opening time in the third control part last until a little after the pump piston reaches top dead center, residual fuel in the delivery passage 33 can be additionally removed for a short period of time immediately after the start of the suction stroke. A predetermined amount of fuel can be withdrawn for mitigation.

In another embodiment, the cam controlling the movement of the pump piston may have a short rest period R during which the piston is stationary at top dead center, again allowing additional residual fuel to be added as described above. can be taken out, thus eliminating pressure oscillations in the delivery system.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal sectional view of a fuel injection pump according to the present invention;
FIG. 2 is a diagram showing the opening times of the individual controls plotted with respect to the stroke curve of the pump piston. 1...Casing, 2...Piston,
3...Sleeve, 4...Cylinder, 6
...Cam disc, 7...Roller, 8...
...Pin, 9...Groove, 10...Piston skirt, 12...Working chamber, 14...
... Supply hole, 15 ... Vertical groove, 16 ...
... Suction chamber, 17, 18... Depressurization passage part,
19...Blind hole portion, 20...Terminal portion, 22, 23...Radial hole, 24...
・Horizontal hole, 26...Control slider, 27...
... Pin, 28 ... Spring, 30 ...
・Check valve, 32... Connection passage, 33...
・Delivery conduit.

Claims (1)

[Claims] 1. A pump piston that reciprocates and simultaneously rotates while being controlled by a cam and is used as a distributor, and is delivered into delivery passages distributed around the circumference of the pump cylinder surrounding the pump piston. Internal combustion of the type having a pump piston whose fuel quantity is varied by controlling the opening of a depressurizing passage leading from the pump working chamber to the suction chamber, and means for reducing and keeping constant the fuel pressure in the delivery passage leading to the injection point. In fuel injection pumps for engines, in order to reduce and keep constant the fuel pressure in the delivery passage leading to the injection point, the depressurization passage comprises:
A first outlet opening 41 starting from the end face of said pump piston 2 and leading to a first outlet opening 41 formed in the circumference of the pump piston.
from a second outlet opening 42 formed in the circumferential surface of the pump piston and axially adjacent to said first outlet opening 41 to a third outlet opening formed in the circumferential surface of the pump piston. a second passageway portion 24 leading to an outlet opening 43;
18, 20, 23, and a connecting passage 32 is provided in the wall of the pump cylinder, which communicates the first outlet opening 41 and the second outlet opening 42 during the delivery stroke of the pump piston. , the connecting channel 32 is assigned in each case to a delivery channel 33 and is always connected to the delivery channel, and the first outlet opening 41 is connected to the pump piston, which introduces the start of the suction stroke of the pump piston. After the pivoted position, it is closed during the suction stroke by the wall of the pump cylinder, in which case the third outlet opening 43 is sealed to said pump piston in the area of the pump piston and the suction chamber 16 filled with fuel. and is opened or closed by a control lip on the control slide 26 in response to a relative axial movement with the slidably arranged control slide 26, and furthermore in the second passage section 18, 20 of the depressurization passage. Check valve 28°30 that opens toward the third outlet opening 43
is arranged, and furthermore, the distribution hole 22 in the third control part 22° 32 is opened immediately after the start of the suction stroke of the pump piston and at the radius of the lower depressurization channel section 18 in the second control part 23° 32. A fuel injection pump for an internal combustion engine, characterized in that the distribution hole 22 and the radial hole 23 close earlier than the directional hole 23, and the distribution hole 22 and the radial hole 23 are controlled to open simultaneously during the delivery stroke.