JPH0368216B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a fuel injection pump for an internal combustion engine having an adjusting piston useful for adjusting injection timing, wherein one end surface of the adjusting piston forms a working chamber, and the working chamber is A pressure source or a depressurization chamber can be connected in the adjusting piston via a control slide arranged coaxially with respect to the adjusting piston, and the control slide is always connected at one end side to the pressure source, Moreover, the pressure of the pressure source can be varied as a function of the rotational speed, and the control slider
The force generated by said pressure supports a support surface located outside the adjusting piston and which is adjusted in relation to the operating parameters by means of an adjusting device between two end points. Relates to types that are loaded against the force of a spring. This type of injection pump is covered by U.S. Patent No.
4037574, in which the control of the adjusting piston is carried out by means of a control slide, which can be adjusted against the force of a return spring by means of a fluid pressure that is dependent on the rotational speed. be.
The resting point of the return spring is a slider, the position of which can be changed in dependence on the load between the two stops. In this case, early adjustment of the injection timing is reduced due to the increasing load. Furthermore, the slide is loaded with an adjustable spring, which makes it possible to influence the load-related characteristics of the injection timing modification.

In the fuel injection pump according to the invention, the regulating device comprises:
It is characterized by a stationary step motor whose support surface is adjusted via a threaded spindle, by means of which the injection timing can be adjusted in the usual manner as a function of the rotational speed, and in addition, Corrective actions can be carried out during the injection timing adjustment optionally in relation to the operating parameters. A step motor adjusts the spring supports to any intermediate position. By providing a stopper, an emergency operation function is ensured without any damage to the internal combustion engine operated by the fuel injection pump when the electrically controlled injection timing corrective action is stopped. There is.

The invention will be explained below with reference to the exemplary embodiments shown.

Only a portion of the fuel injection pump is shown in the drawing. A pin 2 is engaged in the cam drive 1, for example in the roller ring of a distribution injection pump or in the cam plate of a radial piston injection pump, which pin is adapted to adjust the injection timing in a known manner by means of an adjusting piston 3. be manipulated for. The adjusting piston 3 is slidably arranged in a closed cylinder 4 and forms a working chamber 6 within the cylinder by one end face 5 of the adjusting piston. Starting from the other end face 7 and coaxially to the adjusting piston axis, a blind bore 8 is provided, which transitions into a bore 10 at its bottom end;
By means of the bore 10 the blind bore 8 is connected to a recess 11 formed in the wall of the cylinder 4. The recess 11 is constantly connected to the pump suction chamber 12 and is supplied with a pressure liquid, the pressure of which is varied as a function of the rotational speed.

A control slide 14 is arranged in the blind bore 8 , whose end face 15 forms a pressure chamber 16 in the blind bore 8 . The control slide has an annular groove 18 by which a slide part 19 is formed on the pressure chamber side. The annular groove connects the cylinder 4 through the hole or cutout 20.
It is connected to a closed depressurization chamber 21 by the other end face 7 of the regulating piston 3 within. The end face 22 of the control slide, which protrudes into the depressurization chamber, is connected to the adjusting device 2.
4 is loaded by a spring 23 which is supported at The adjusting device 24 is adjustable in the direction of movement of the adjusting piston 3 by means of a step motor 25, and the maximum approach to the adjusting piston 3 is at the stop 26.
limited by. The step motor adjusts the position of the spindle 27 and thus of the adjustment device via a thread in the spindle 27 which supports the adjustment device 24. Of course, other suitable electrically controlled adjustment mechanisms can also be used.

A connecting channel 29 branches off from the blind hole 8 and leads to the working chamber 6 . The opening of the connecting channel 29 in the wall of the blind hole 8 can be closed by a slider part 19.

During operation of the device described above, the end face 1 of the control slider
5 is loaded with a pressure dependent on the rotational speed and is further displaced against the spring 23 by the increasing pressure. During such a sliding movement, the slide part 19 opens the connecting channel 29, so that pressure liquid can flow from the pressure chamber 16 into the working chamber 6. This means that the adjusting piston, which slides under the action of a pressure fluid, connects the inlet of the connecting channel to the slider part 1.
This continues until it is covered again by 9. Conversely, when the pressure of the pressurized liquid decreases, the spring 23 pushes back the control slide, so that the connecting channel 29 is now connected to the annular channel 18 and also to the depressurization chamber 21 .
Therefore, by depressurizing the working chamber 6, the regulating piston
It is slid in a different direction until the opening of the connecting channel is again covered by the slider part 19. That is, the adjusting piston 3 is connected to the control slide 14
follows the movement of In this case, the return movement of the adjusting piston is additionally produced by a return spring 31, which is arranged between the end face 7 of the adjusting piston and the corresponding end face delimiting the cylinder 4; In general, however, the force is provided by an injection torque which moves the adjusting piston 3 to the left. In this case, if the support plate 24 is not adjusted, under the action of the spring 23 and the pressure chamber 1
Under the influence of a speed-dependent pressure in 6, a speed-related adjustment of the injection timing is obtained. The adjustment properties are influenced in this case by the configuration of the spring 23, for example by an additional spring or a spring 30 arranged concentrically with the spring 23. The spring 30 is preferably supported on the stationary stop 26 and the spring 2
3 serves as the main return spring if the preload is not adjusted. In addition to this rotational speed-related regulation, a number of other operating parameters of the internal combustion engine, for example the load, can then be influenced by varying the return force of the spring 23 or by adjusting the regulating device 24. Alternatively, corrections that take operational parameters such as temperature into consideration are superimposed. By using step motors here, a different influence and evaluation of the individual operating parameters is possible. In a simple form, a step motor can be additionally integrated into the existing design of the injection timing adjustment device, in particular for adjusting the injection timing for starting and warming up the internal combustion engine by means of a relatively large stroke of the step motor. can also be controlled in any format.

The advantage of step motors is that they are capable of performing limited calculated adjustment steps, thus obtaining very precise adjustment of the member to be adjusted without having to detect the actual position of this member. That's true. The switching steps are calculated and regulated, for example, by an electrical control device in combination with the detection element. This is well known and therefore will not be explained here. In particular, when the step motor moves the spindle, the advantage is obtained that the position of the part is held by a self-locking effect if the step motor is not controlled, which occurs during the control and adjustment of the injection pump. This is particularly advantageous in the case of adjusting elements which are subjected to such high return forces. Therefore, the use of step motors is not limited to injection timing adjustment.

[Brief explanation of drawings]

The drawing is a partial longitudinal sectional view of a fuel injection pump according to the invention. DESCRIPTION OF SYMBOLS 1...Cam drive device, 2...Pin, 3...Adjustment piston, 4...Cylinder, 5...End face, 6...
Working chamber, 7... end face, 8... blind hole, 10... hole,
11... Notch, 12... Pump suction chamber, 14
... Control slider, 15 ... End face, 16 ... Pressure chamber, 18 ... Annular groove, 19 ... Slider part,
20... Notch, 21... Depressurization chamber, 22... End face, 23... Spring, 24... Adjustment device, 25...
Step motor, 26...stopper, 27...spindle, 29...connection passage, 30...spring, 3
1...Return spring.

Claims (1)

[Scope of Claims] 1. A fuel injection pump for an internal combustion engine having a regulating piston useful for adjusting injection timing, wherein one end surface of the regulating piston forms a working chamber, and the working chamber is located within the regulating piston. A pressure source or a depressurization chamber can be connected via a control slide coaxially arranged with respect to the adjusting piston, and the control slide is always connected at one end to a pressure source, and the pressure source The pressure of can be varied as a function of the rotational speed, and furthermore the control slide is located outside the adjusting piston and can be moved between the two end points of the adjusting device by the force generated by said pressure. of the type in which the adjusting device 2 is loaded against the force of a spring supported on a support surface which is adjusted in relation to the operating parameters by
Fuel injection pump for an internal combustion engine, characterized in that 4 is a stationary step motor 25 whose support surface is adjusted via a threaded spindle. 2. Internal combustion engine according to claim 1, wherein the end point of the adjusting device 24 on the side of the adjusting piston is designed as a stop 26, which stop is also designed as a stop for the extreme position of the control slide. Fuel injection pump. 3. Fuel injection pump for internal combustion engines according to claim 2, in which an additional return spring 30 is arranged between the stationary stop 26 and the adjusting piston.