WO2001063119A2

WO2001063119A2 - Injection device

Info

Publication number: WO2001063119A2
Application number: PCT/DE2001/000453
Authority: WO
Inventors: Marcus Parche
Original assignee: Robert Bosch Gmbh
Priority date: 2000-02-24
Filing date: 2001-02-06
Publication date: 2001-08-30
Also published as: WO2001063119A3; DE10008542A1

Abstract

The invention relates to an injection device comprising a pressure generator (12), an injector (14) that is coupled to said pressure generator (12), a control valve (106), an actuating element (36) for actuating the control valve (106) and a coupler (100, 102, 40, 42). The effect of the actuating element (36) can be transmitted to the control valve (106) by means of said coupler which is provided with at least two coupler chambers (100, 102) that are connected to each other.

Description

Injector

State of the art

The invention relates to an injection device with a pressure generator, an injector coupled to the pressure generator, a control valve, an actuating element for actuating the control valve and a coupler, via which the action of the actuating element can be transferred to the control valve.

A generic injection device is known. It is used as a single-pump injection system, particularly in diesel engines with direct injection. A generic injection device can be designed as a "pump-nozzle unit (PDE)". An integrated solenoid valve, for example, is used as the control element in the electronically controlled pump-nozzle unit. The solenoid valve and the nozzle form a unit that is built directly into the cylinder head of the diesel engine. Each engine cylinder is supplied by its own injection module. The pump-nozzle unit is driven by an injection cam on the engine camshaft via a tappet and a rocker arm. A pump-nozzle unit with a solenoid valve works in such a way that the solenoid valve is open when not energized. This allows free passage from the pump system to the low-pressure area of the system, which makes it possible to fill the pump chamber during the suction stroke of the pump piston and to allow the fuel to flow back during the delivery stroke. Activating the solenoid valve during the delivery stroke of the pump cylinder closes this "bypass". This leads to a build-up of pressure in the high-pressure range and, after the nozzle opening pressure has been exceeded, fuel being sprayed off at the injection nozzle.

It has also already been proposed to use a piezo actuator as an actuating element. Piezo actuators that operate a control valve have several advantages over solenoid valves. For example, a piezo actuator offers a high switching speed. Furthermore, a piezo actuator is infinitely adjustable through the appropriate selection of the control parameters. Small injection quantities can thus be achieved, which is particularly useful for a pre-injection. However, since the stroke of a piezo actuator is too small for use in a pump nozzle unit without further measures, it is necessary to enlarge it by means of a hydraulic coupler. However, this increases the space required for the entire control system. By using a piezo actuator instead of a solenoid valve, it was possible to reduce the space requirement, but the need for a hydraulic coupler largely negated this advantage.

Advantages of the invention The injection device according to the invention builds on the injection device of the prior art according to claim 1 in that the coupler has at least two interconnected coupler spaces. This separation of the hydraulic coupler into two subsystems allows a free spatial arrangement of the two subsystems in the pump nozzle unit. This means that the components can be arranged at locations where space is available due to other structural constraints, which means that overall a flexible and space-saving arrangement can be selected.

The control element is preferably a piezo actuator. As has already been described, especially when using a piezo actuator is due to its small size

Hubes a hydraulic coupler useful. Since a piezo actuator has a small design in comparison to other control elements, the invention is particularly advantageous when using a piezo actuator.

It is preferred that the first coupler space is arranged near the actuating element, that the second coupler space is arranged near the control valve and that the control valve is arranged near the injector. The control valve can thus be installed, for example, in the shaft of the pump nozzle unit and the space available there can be used. Outside of the shaft, therefore, only the already small actuating element and the first coupler space have to be accommodated. The overall dimension of the entire pump-nozzle unit is consequently reduced. A further advantage in the arrangement mentioned is that no high-pressure bore has to be provided from the pump chamber to a control valve arranged outside the shaft. The connection between the shaft and the components arranged outside the shaft components can only be made with low pressure components. In this way, the hydraulic damage volume is reduced and cheaper components can be used. The reduction in the hydraulic damage volume can be used to improve the hydraulic efficiency.

The pressure generator preferably has an essentially cylindrical pump piston, the direction of movement of the actuating element being perpendicular, parallel or inclined to the axis of the pump piston. Due to the fact that very different arrangements of the actuating element are possible, which can have a very compact design anyway, very flexible arrangements and thus an optimal use of the available space are possible.

The control valve can be a seat valve or a slide valve. At this point, too, you are variable; the invention is not limited to a particular type of valve with regard to its use.

The control element is preferably infinitely adjustable. In this way, for example, a seat valve can be brought into any intermediate position. In these cases, the valve seat acts as a hydraulic throttle, which can be used to set the pressure level on the injector. The high level of a control signal in connection with the control frequency of the control element accordingly allows a pressure curve control that can be individually adapted to the respective operating conditions of the internal combustion engine.

The invention is based on the surprising finding that the size of a pump-nozzle unit is divided into two due to the separation of the hydraulic coupler. bound coupler space can be significantly reduced. Furthermore, the hydraulic damage volume of the pump nozzle unit can be reduced by the same measure, which enables the hydraulic efficiency to be increased.

drawing

The invention will now be explained by way of example with reference to the drawing.

Figure 1 shows schematically an overview of a system with a pump-nozzle unit;

Figure 2 shows a pump-nozzle unit with a piezo actuator and a hydraulic coupler;

Figure 3 shows schematically an arrangement according to the invention;

Figure 4 shows an injection device according to the present invention.

Description of the exemplary embodiments

FIG. 1 schematically shows a structure in which a pump-nozzle unit 10 according to the invention is used. The pump-nozzle unit comprises a hydraulic pressure generator 12, an injector 14 which flows into a combustion chamber (not shown) and a control unit 16 for determining the pressure applied to the injector 14. The pump-nozzle unit 10 is removed from a tank 72 by a Preliminary pump 74 is supplied with fuel via a filter 76. Furthermore, a fuel return 78 between the pump nozzle Unit 10 and the tank 72 provided. The control unit 16 is controlled by an electronic control device 80. The pressure generator 12 has a piston 18 which is movably guided. A support sleeve 23 is connected to the piston 18 and comprises a circumferential collar 24. On this collar 24 is a compression spring 26 which is clamped between the support sleeve 23 and the housing of the pump-nozzle unit 10. A plunger 28, which can be actuated by the camshaft 82 of an internal combustion engine, acts on the end of the piston 18 on which the support sleeve 23 is arranged. This device forces the piston 18 against the restoring force of the compression spring 26 on a lifting movement.

In Figure 2, a pump-nozzle unit 10 is shown so that the basic processes during the injection process can be described. It should be noted, however, that the illustration according to FIG. 2 is a pump-nozzle unit 10 with a single coupling space 44, in contrast to the solution according to the invention, in which two coupler spaces are provided. However, the illustration according to FIG. 2 is equally suitable for explaining the basic structure and the basic processes which are also relevant for the invention. In particular, the features of the pump-nozzle unit 10 according to FIG. 2 in combination with other features of the invention can be essential for the invention.

FIG. 2 again shows the pressure generator 12 with its piston 18, which is movably guided in a cylinder 20 of a housing 22. The piston 18 projects from one end of the cylinder 20. There, it has a fixed support sleeve 23 with a horizontally circumferential collar 24. A compression spring 26 rests on this collar 24, which is located between the support sleeve 23 and the housing 22 is clamped. A plunger 28 acts on this end of the piston 18. This device forces the piston 18 against the restoring force of the compression spring 26 on a lifting movement. The cylinder 20 is filled with fuel, which comes under high pressure as a result of the stroke movement of the piston 18, provided that the control unit 16 is in its illustrated, unactuated rest position. In this rest position, a pressure medium connection between the high pressure and the low pressure leading part of the pump nozzle unit 10 is blocked.

The control unit 16 is also arranged in the housing 22 and comprises a valve member 34 slidably mounted in a control bore 32, an externally controllable piezoelectric actuator 36 and a hydraulic translator 38 for transmitting the stroke movement of the actuator 36 to the valve member 34 FIG. 2, the longitudinal axis of the control bore 32 is arranged parallel to the longitudinal axis of the pressure generator 12. Likewise, a vertical arrangement or an arrangement with any other angle is conceivable.

The translator 38 has two pistons 40 and 42 with differently sized pressure surfaces, which protrude into a pressure chamber 44 designed as a coupling space and filled with pressure medium. The piston 40 facing the actuator 36 has the larger pressure area of the two pistons 40, 42 in order to translate the relatively small stroke movement of the actuator 36 into a larger deflection movement of the valve member 34. The pistons 40 and 42 can each be formed in one piece with the components assigned to them.

A first channel 48 leads from the control bore 32 to the injector 14. Another channel 46 connects the cylinder 20 with the first channel. The control bore 32 has an enlarged inner diameter in the region in which the first channel 48 connects, the diameter transitions being designed as a chamfer. The lower chamfer forms the valve seat 50, which can be closed by the valve member 34. The latter is printed in the direction of the valve open by a valve spring 54, which is supported at the closed end of the control bore 32 and at the end face of the valve member 34. A supply channel 55, which carries fuel under low pressure, opens into the control bore 32 in the area of the installation space of the valve spring 54.

In the illustrated, non-actuated (de-energized) position of the valve member 34, the valve seat 50 is opened, so that there is a pressure medium connection between the supply channel 55 and the first channel 48. This serves, for example, for the initial filling of the device 10 with fuel or to compensate for leakage-related losses, for example after the device 10 has not been operated for a long time.

The supply channel 55 connects the two end regions of the control bore 32 to one another by means of a branch 58. In the case of the movement of the valve member 34, no pressure differences which inhibit this movement can form as a result.

The valve member 34 consists of the closing body 60, the end of which forms a chamfer for controlling the two valve seats 50. Furthermore, the valve member 34 has a guide piston 62 which enables the valve member 34 to move in the control bore 32 without tilting. The diameter of the

Guide piston 62 is matched to the diameter of the control bore 32. A pressure build-up in the injector 14 takes place by electrical actuation of the actuator 36. Due to the electrical actuation, this produces a stroke movement which it transmits to the piston 40. The liquid displaced by the piston 40 in the pressure chamber 44 likewise forces the piston 42 to perform a stroke movement, the ratio of the two stroke movements being inversely proportional to the ratio of the pressure areas of the two pistons 40, 42. In the maximally deflected state, the valve member 34 rests with its closing member 60 on the valve seat 50 and seals it. Through this measure, the

Pressure medium connection between the supply channel 55 and the first channel 48 interrupted.

The pressure prevailing in the cylinder 20 is also present at the injector 14. As soon as the pressure level exceeds a value determined by the pretensioning of a closing spring 68 of the injector 14, a needle 70 acted upon by this closing spring 68 opens. The needle opens injection openings of the injector 14 which cannot be seen in the illustration, so that the injection process takes place in the combustion chamber of an internal combustion engine ,

The injection process is ended by a pressure reduction in the injector 14. For this purpose, the actuation of the actuator 36 is withdrawn, as a result of which the valve member 34 moves back into the rest position shown. The valve seat 50 opens so that a pressure relief of the injector 14 takes place via the pressure medium connection between the outlet 48 and the supply channel 55.

The stroke movement of the actuator 36 can be regulated continuously between zero and a maximum value by the height of the control signal. The valve member 34 accordingly forms a so-called pro in connection with the continuously switching actuator 36 portionalventil. This can be placed in any intermediate position. In these cases, the valve seat 50 acts as a hydraulic throttle, which determines the pressure level in the injector 14. The level of the control signal in connection with the control frequency of the actuator 36 accordingly allows a pressure curve control that can be individually adapted to the respective operating conditions of the internal combustion engine.

The characteristic particularity of the invention can now be described on the basis of the above description of a pump-nozzle unit with a hydraulic coupler which has only one coupler space.

In Figure 3, the basic arrangement for hydraulic coupling according to the invention is shown schematically. The hydraulic coupler is implemented by forming a first coupler space 100 and a second coupler space 102. The two coupler spaces 100, 102 are connected to one another by a line 108 or a bore. A first piston 40 is provided in the first coupler space 100 and is actuated by the piezo actuator 36. The piezo actuator 36 is controlled by a control device 80. The first piston 40 in the first coupler space 100 is operated by a reset element, e.g. a spring 104, pressed against the piezo actuator 36. The reset element can be arranged in the coupler space 100 or outside the coupler space 100. A second piston 42 is provided in the second coupler chamber 102 and actuates a valve 106 by means of the hydraulically mediated movement. The counterforce against the hydraulic stroke of the second piston 42 is applied by an elastic element, not shown, of the control valve 106.

FIG. 4 shows a pump nozzle unit 10 according to the invention. A control device 80 controls a piezo actuator 36 on. This acts mechanically on a first piston 40, which projects into a first coupler space 100 of a hydraulic coupler. The force of a spring 104 counteracts the stroke of the piston 40. The coupler space 100 is connected to a second coupler space 102 via a line 108, which is designed, for example, as a bore. A second piston 42 projects into this and actuates a valve 106. The valve 106 is shown here in terms of switching technology. It can be constructed, for example, in the manner or similar to the valve according to FIG. 2. A spring 110, which is arranged on the valve 106, generates the counterforce for the second piston 42.

The pressure generator 12 has a piston 20 which is movably guided in the housing of the pump-nozzle unit. The piston 18 protrudes with one of its ends out of the housing of the pump nozzle unit 10 and is subjected to a force there, preferably as described in connection with FIGS. 1 and 2, by a compression spring 36. This force is the counterforce for a force that is applied, for example, by a plunger. This tappet is preferably actuated by the camshaft of an internal combustion engine. Due to the movement of the piston 18, the high pressure is made available for the injection, which ultimately causes a needle 70 in the injector 14 to rise against the force of a closing spring 68.

It can be seen from the illustration in FIG. 4 that the various components of the pump nozzle unit 10 can be arranged in an advantageous manner. Thus, the first coupler space 100 is arranged in the vicinity of the piezo actuator 36, while the second coupler space 102 is arranged in the control valve 106. In this way, a flexible arrangement of the two components of the hydraulic coupler is possible. This leads to ultimately to a compact design of the entire pump nozzle unit. It should also be emphasized that the control valve 106 is in the vicinity of the injector 14. The high-pressure system of the pump-nozzle unit is therefore small in comparison to the arrangement according to FIG. 2, which leads to a low hydraulic damage volume. Ultimately, the efficiency of the pump nozzle unit 10 can thus be improved.

This system also maintains an advantageous ability of a hydraulic coupler: it is suitable for compensating for temperature expansions within the system.

The preceding description of the exemplary embodiments according to the present invention serves only for illustrative purposes

Purposes and not for the purpose of limiting the invention. Various changes and modifications are possible within the scope of the invention without leaving the scope of the invention and its equivalents.

Claims

Expectations

1. Injection device with a pressure generator (12), an injector (14) coupled to the pressure generator (12), a control valve (106), an actuating element (36) for actuating the control valve (106) and a coupler (100, 102, 40 , 42), via which the action of the control element (36) can be transmitted to the control valve (106), characterized in that the coupler (100, 102, 40, 42) has at least two interconnected coupler spaces (100, 102).

2. Injection device according to claim 1, characterized in that the adjusting element (36) is a piezo actuator.

3. Injection device according to one of the preceding claims, characterized in that the first coupler space 100 is arranged in the vicinity of the actuating element (36), that the second coupler space (102) is arranged in the vicinity of the control valve (106) and that Control valve (106) is arranged in the vicinity of the injector (14).

4. Injection device according to one of the preceding claims, characterized in that the pressure generator (12) has a substantially cylindrical pump piston (18) and that the direction of movement of the actuating element (36) is perpendicular to the axis of the pump piston (18).

5. Injection device according to one of claims 1 to 3, characterized in that the pressure generator (12) has a substantially cylindrical pump piston (18) and that the direction of movement of the actuating element (36) is parallel to the axis of the pump piston (18).

6. Injection device according to one of claims 1 to 3, characterized in that the pressure generator (12) has a substantially cylindrical pump piston (18) and that the direction of movement of the actuating element (36) is inclined to the axis of the pump piston (18).

7. Injection device according to one of the preceding claims, characterized in that the control valve (106) is a seat valve.

8. Injection device according to one of claims 1 to 6, characterized in that the control valve (106) is a slide valve.

9. Injection device according to one of the preceding claims, characterized in that the adjusting element (36) is infinitely adjustable.