JPH0351901B2 - - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a fuel injection pump, particularly for a diesel internal combustion engine.

[Technical background of the invention]

A fuel injection pump of this type is described, for example, in German Patent Publication No. DD-PS 130 873. In the case of the pump described there, the additional outlet hole has a relatively small cross section and acts as a throttle valve, through which a portion of the fuel can flow out of the pump chamber at the beginning of the supply. It is configured. It is intended that the feed characteristics decrease sharply with a decrease in the rotational speed of the camshaft.

[Problem to be solved by the invention]

An object of the present invention is to provide a fuel injection pump having an additional outlet hole as described above, which can continuously vary the start of fuel injection over a wide range, has a simple structure, and has a valve provided at the outlet hole. An object of the present invention is to develop a fuel injection pump that can maintain operation of the fuel injection pump even when trouble occurs.

[Means for solving problems]

According to the invention, this object comprises a piston guide and a piston movably installed inside the piston guide, a pump chamber being defined by the piston guide and the piston, the pump chamber being a fuel injection chamber. The piston guide is configured to be connectable to the engine through a pipe, the piston guide having at least one inlet hole opening into the pump chamber in the region of the bottom dead center of the piston and from this inlet hole in the direction of the inner dead center. an outlet hole spaced a short distance apart, the piston being provided with a control lip to control the amount of fuel injected; A valve is provided, the valve closure of which is held in a rest position by a locking means to effectuate the release of fuel, and when the locking means is released the valve closure is held under the pressure of the released fuel stream. This is accomplished by a fuel injection pump which is then moved to an operating position to close the valve and stop the discharge of fuel through the outlet hole, supplying fuel in the pump chamber to the engine through the fuel injection pipe.

The invention is based on the idea that if this outlet hole is controlled by a rapidly closing valve, the start of the injection can be varied continuously within wide limits. The required valve closing time is then considered to be on the order of 0.5 milliseconds. According to the invention, it is possible to realize a valve of this type that closes very quickly, in which the valve closing body flows out of this hole in order to close the valve which is restrained in the rest position by the locking means. Fuel pressure is used.

The locking means for restraining the valve closure in the rest position with the outlet hole open can also be pneumatically or hydraulically controlled, but electromagnetically operated locking means are preferred. This is because the electromagnet can be energized by a reverse current surge, thus further reducing the valve closing time.

Any desired other positioning elements can be used to reset the valve closure to the rest position. During the suction stroke of the pump piston, the pump chamber approaches vacuum.
Because it contributes to the opening movement of the valve closure and there is sufficient time to open the valve during the suction stroke, a simple return spring can be used to reset the valve closure.

The distance between the outlet hole and the inlet hole is not in itself essential to the principles of the invention. However, in order to minimize the deformation of the valve as much as possible, the latest possible start of injection ensures that the piston almost reaches the outlet hole or partially reaches it when the valve closing body is switched into the operating position (closing position). Care should be taken to select the distance to cover the In fact, high pump pressures can be prevented from acting on the valve closing body in this way.

[Embodiments of the invention]

The present invention will now be described in detail with reference to embodiments shown in the accompanying drawings.

A pump piston 11 is movably arranged in the piston guide 10, which, during its working stroke, carries fuel from the pump chamber 12 via the valve 13 into the fuel injection pipe 1.
4. Inject into the inside. The inlet hole 15 is connected to the piston guide 1
0 and opens into the pump chamber 12 in the bottom dead center area of the piston as shown. Furthermore, the piston guide 10 has an additional outlet hole 16, which is offset in the direction of the inner (top) dead center. The outlet hole 16 can be controlled by a valve generally designated 20. The container 21 of this valve 20 is
A valve seat 22 with a taper opening towards the outlet hole 16 is mounted directly on the piston guide 10 so as to be arranged concentrically with the outlet hole 16 . The conical valve body acts as a valve closing body 23 on which a stem 24 is formed, which extends into a bore in the valve housing 21 . In the figure, this valve closing body 23 is in its rest position (valve open position)
, in which the outlet hole 16
is virtually open. This is because fuel can be discharged from the pump chamber 12 through this outlet hole 16 and through the opening section 26 of the valve, the hole 25 and the duct 27.

In this rest position, the valve closing body 23 is restrained by locking means generally indicated at 30. This locking means 30 consists of an electromagnet 31 having an iron core 32, a wire ring 33, and a movable piece 34. An adjusting screw 35 is attached to this movable piece 34, and the screw protrudes into a hole 36 in the iron core 32, and the valve closing body 2
Acts as a stop for the stem 24 of No. 3. Two springs 37 firmly supported on a base fixed to the iron core hold the movable piece 34 in the illustrated position even when the electromagnet 31 is not energized and its restraining force is not generated.

The operating modes of the illustrated fuel injection pump will now be described in detail. In the description, the valve closing body 2
It is assumed that 3 initially occupies the rest position shown and is restrained in this position by the force of the energized electromagnet 31. During the delivery stroke of the pump piston, the inlet hole 15 is closed first. However, fuel from the pump chamber 12 can flow out via the outlet hole 16 and pass through the conical valve closure body 23, so that initially no fuel is released into the fuel injection pipe 14 even when the inlet hole 15 is closed. The flow of discharged fuel creates a closing force on the valve closing body 23 in the valve closing direction F. However, this closing force is not sufficient to overcome the force of the electromagnet 31, so the valve 20 initially remains open.

Depending on the rotational speed and other important parameters, the electromagnet 31 is deenergized at a given time. The locking means blocking the valve closing body 23 in the rest position is thereby released. Then, the magnetic force rapidly decreases and becomes smaller than the force in the closing direction acting on the valve closing body 23, and the closing force is applied to the spring 37.
The valve closing body 23 is displaced in the closing direction against the force. The opening cross-section 26 is thereby reduced, the pressure acting in this area increases and therefore the closing force also increases as a result. The valve closing body 23 is therefore switched to its operating position (closed position), and in that position the valve closing body 23 is seated in a sealing manner on the valve seat 22. Fuel will then no longer flow out of the pump chamber 12 through the outlet hole 16 and injection will begin.
The outlet hole 16 communicating with the valve container 21 is then closed.

Then the pump piston 11 starts its operation (compression)
At the end of the stroke, the valve 13 is opened and fuel is forced into the fuel injection pipe 14 from the pump chamber 12. The end of the injection takes place in the usual manner via a control lip on the pump piston 11 and a control hole in the piston guide 10. At the end of the injection, there is only a slight pressure in the pump chamber 12 and the spring 37 therefore resets the movable piece 34 to the position shown and therefore also closes the valve closure 23.
from the operating position to the rest position. Furthermore, this reset movement causes the re-energized electromagnet 3
1 and by the creation of a vacuum in the pump chamber 12 during the suction stroke of the pump reset 11. Therefore, after each injection, the valve closing body 2
3 is again restrained in its rest position. This electromagnetically acting locking means is released only on the next actuation stroke of the pump piston 11 by deenergizing the electromagnet or by applying a reverse surge current, so that the valve closing time is further reduced.

The distance A between the inlet hole 15 and the outlet hole 16 is such that, at the latest start of injection, the pump piston 11 almost reaches the position of the outlet hole 16 when the valve closure body 23 is switched to its operating position, or selected at a distance that partially covers the area. In this way, it can be ensured that the valve closing body 23 is not acted upon by high pump pressures for any too long period of time. Furthermore, in this case the latest start of the injection is not determined by the edge of the outlet hole 16, but by the closing action of the valve 20.

According to experiments, a valve closing time of 0.5 milliseconds or less could be obtained by this invention. Only these short valve closing times allow the pump piston 11 to move between the upper edge of the inlet hole 15 and the upper edge of the outlet hole 16, allowing a continuous change in the start of the injection. Such a short valve closing time cannot be achieved by an electromagnetically operated slide closing the outlet hole 16 transversely to the direction of discharge. A device of this type with a slide for closing the outlet hole 16 should therefore be considered for two-point adjustment of the start of the injection.

In the illustrated embodiment of the invention, the valve 20 is mounted directly on the piston guide 10.
Of course, a structure in which this valve 20 is connected to the outlet hole via a duct is also possible. however,
This loss of flow in the duct will increase the valve closure time. It is therefore preferable to mount the valve as close to the outlet hole as possible.

In the illustrated embodiment, the spring 37 is connected to the valve closing body 2.
3 to the rest position. However, additional electromagnets or other hydraulic or pneumatic positioning elements can also be used.

Of course, the locking means can be of other designs. It is also possible to envisage a locking means with a positioning device which is moved into the path of movement of the stem 24, in particular transverse to the direction of movement of the valve closing body.

〔Effect of the invention〕

As described above, according to the present invention, by rapidly opening and closing the flow of fuel discharged through the outlet hole 16 using a valve, it is possible to continuously change the start of fuel injection over a wide range. . This is because the valve that shuts off the flow of fuel discharged through the outlet hole 16 is closed using the pressure of the fuel flow flowing through the outlet hole 16, and the valve closing body is closed by electromagnetic force. A conventional driven electromagnetic valve cannot close such a quick time, and therefore it is impossible to continuously change the start of fuel injection over a wide range as in the present invention.

Furthermore, in the present invention, when the valve 20 fails, it becomes impossible to adjust the start of fuel injection, and the pump cannot operate at its best, but it is possible to continue operating as a fuel injection pump. The start of fuel injection is controlled by the upper edge of the outlet hole 16 if the valve closure body 23 of the valve 20 remains in the illustrated rest position, discharging fuel via the outlet hole 16. Conversely, if valve 20 fails and remains closed continuously, the start of fuel injection is controlled by the upper edge of inlet hole 15. Therefore, failure of valve 20 will not render the entire pump inoperable.

The fuel injection pump according to the invention therefore makes it possible to easily adapt to the different operating conditions of diesel internal combustion engines.

[Brief explanation of drawings]

The figure is a sectional view of a portion of a fuel injection pump according to an embodiment of the present invention. 10...Piston guide body, 11...Pump piston, 12...Pump chamber, 13...Valve, 14...
fuel injection pipe, 15...inlet hole, 16... outlet hole,
20... Valve, 21... Valve container, 22... Valve seat, 2
3... Valve closing body, 24... Stem, 30... Locking means, 31... Electromagnet, 32... Iron core, 33...
Winding wire, 34...movable piece, 37...spring.

Claims (1)

[Scope of Claims] 1. Comprising a piston guide body 10 and a piston 11 movably installed inside the piston guide body 10, the pump chamber 1 is provided by the piston guide body 10 and the piston 11.
2 is defined, and this pump chamber 12 is connected to the fuel injection pipe 1
4, said piston guide 10 has at least one inlet hole 15 opening into the pump chamber 12 in the region of the bottom dead center of the piston 11 and in the direction of the inner dead center. In a fuel injection pump, the piston 11 is provided with a control lip to control the amount of fuel injected, the piston 11 having an outlet hole 16 at a small distance from the inlet hole 15; A valve 20 is provided for controlling the release of fuel flowing through the valve 20, the valve closure body 23 of which is held in a rest position by means of a locking means 30 to effect the release of fuel, when the locking means 30 is released. The valve closure body 23 is moved into the operating position by the pressure of the ejected fuel flow to close the valve and stop the ejection of fuel through the outlet hole, allowing the fuel in the pump chamber 12 to pass through the fuel injection pipe 14. A fuel injection pump characterized by supplying the engine. 2. The fuel injection pump according to claim 1, wherein the valve closing body 23 is held at the rest position by the electromagnetic force of the energized electromagnet 31. 3. Fuel injection pump according to claim 2, characterized in that the current flowing through the electromagnet 31 is interrupted or reversed for releasing the locking means 30. 4. Any one of claims 1 to 5, characterized in that during the suction stroke of the pump piston 11, the valve closing body 23 is switched from the operating position to the rest position by means of a reset positioning element 37. The fuel injection pump according to item 1. 5. The fuel injection pump according to claim 1, wherein the positioning element for resetting the valve closing body 23 is a spring 37. 6 The distance A between the inlet hole 15 and the outlet hole 16 is
The distance is chosen such that in the latest case of the start of injection, the piston 11 has almost reached the outlet hole 16 or has reached a position where it partially covers it when the valve closing body 23 is switched into its operating position. A fuel injection pump according to any one of claims 1 to 5, characterized in that: 7 The container 21 of the valve 20 is directly connected to the piston guide 10
A valve closing body 23 configured as a cone is mounted on the valve seat 22, which is arranged concentrically with the outlet hole 16 and has a taper opening in the direction of the outlet hole 16.
Claims 1 to 6 include a stem 24 which extends into the container 21 of the valve and is mechanically connected to a movable piece 34 of an electromagnet 31. The fuel injection pump according to any one of paragraphs.