EP0399991B1 - Process and device for controlling the movement of a hydraulically actuated valve - Google Patents

Description

The invention relates to a method and a device for controlling the stroke of a hydraulically actuated valve with a drive element which delimits a drive chamber in the valve housing and is pressure or spring-loaded in the closing direction and a pressure generating unit.

A device of this type has become known, for example, from EP-A-0328602, in which a gas exchange chamber is controlled by a valve of an injection valve that opens outward into the cylinder of an internal combustion engine. Compressed gases are removed from the cylinder during a work cycle, stored temporarily and blown into the cylinder of the internal combustion engine together with the fuel introduced into the valve-side gas exchange chamber in the following cycle.

For adapting the control times of the blowing device to different engine parameters such as load or speed, design variants have become known from EP-A-0328602, which allow a control of the stroke speed of the valve needle or a change of the needle stroke. In comparison to the versions without a variable needle stroke, this results in advantages with regard to the operation of the engine at low loads or at full load, whereby the positive influence on the emission behavior of the internal combustion engine should be mentioned above all.

In the known embodiment for controlling the valve lift, a piston is used as the drive element of the valve needle, which has a shoulder that forms an annular space with the housing of the valve. System pressure from a metering device is applied to this annular space via a check valve. As soon as the piston of the injection valve moves downwards and the valve opens, the annulus is reduced, the fuel is displaced from it and injected into the valve-side gas exchange chamber via a check valve. However, the valve of the injection valve opens only to the extent that it corresponds to the injection quantity conveyed by the metering device, as a result of which an amount of valve lift that increases with increasing engine load can be realized. With this simultaneous control, the needle stroke of the injection valve is therefore proportional to the amount of fuel injected.

For optimal adaptation of the control times of injection valves but also injection valves to the load and / or speed state of an internal combustion engine, however, an individual adjustment of the stroke, the opening and the closing time of the valve, regardless of the injection quantity, would be necessary, which by the known devices or Procedure can not be realized.

The object of the invention is to propose a method and a device with which the stroke of a hydraulically actuated valve can be varied continuously for each individual working cycle independently of the valve's control times, production-related tolerances and temperature-related changes in length on the valve or on the valve housing having no influence should have on the valve stroke.

This object is achieved in that a flying adjustment piston guided in a cylinder is provided, which delimits a pressure chamber in the cylinder and separates the pressure chamber from the drive chamber in the valve housing, and that the pressure generating unit has a high-pressure line leading from a valve into the pressure chamber and a has a low-pressure line which is controlled by a further valve and leads into the drive chamber, the adjusting piston abutting a stop in the cylinder when the valve is at maximum stroke.

According to the invention it is provided in the claimed method that when the valve is closed, a drive chamber located between a drive element of the valve and a flying adjusting piston is acted upon with low pressure, so that the adjusting piston lifts off a stop until a valve controlling the low pressure is closed, as a result of which a certain stroke is defined that the adjusting piston is acted upon by valve under high pressure, whereby the adjusting piston up to its stop moved and the valve is opened due to the incompressible medium in the drive chamber, and that the valve controlling the low pressure is opened, whereby the drive chamber is emptied and the valve is closed by the closing force applied to the drive member. Advantageously, the opening and closing times of the valve and independently of its stroke can be steplessly controlled via the valves in the high-pressure line and in the low-pressure line. Both a piston guided in a cylinder and a diaphragm which is pressure or spring-loaded in the closing direction of the valve are conceivable as the drive element for the valve. With the help of the stop in the cylinder, against which the adjusting piston rests at the beginning of each individual working cycle, the starting position of the flying adjusting piston is practically redefined for each working cycle, so that production-related tolerances and temperature-related changes in length can be compensated for.

An embodiment of the invention provides that the valve housing and the cylinder containing the adjusting piston are made in one piece, the valve axis and the axis of the adjusting piston coinciding. However, other design variants are also conceivable, it only being necessary to ensure that the adjusting piston is arranged between the drive chamber and the pressure chamber and the volume of the drive chamber can be varied by the adjusting piston.

When designing the low-pressure part of the device, several design variants are conceivable, it being provided in particular that an electromagnetically operable two-way valve is arranged in the low-pressure line connected to the pressure generating unit via a reducing valve, a return line with a pressure-maintaining device being arranged between the reducing valve and two-way valve. Via the return line arranged between the reducing valve and the two-way valve, the excess fuel which is present after an opening and closing operation of the valve can be returned from the drive space into the fuel tank.

It is also conceivable that the pressure maintaining device is designed as a bladder accumulator. In all versions there must be a low pressure part and a high part pressure part of the pressure generating unit only a pressure difference overcoming the closing force of the valve is present.

It is further provided that an electromagnetically actuated three-way valve is arranged in the high-pressure line, one output of which is connected to the pressure chamber and the other output of which leads to a return line in which a throttle is arranged. With this valve, the pressure chamber is pressurized with high pressure, whereby the valve is opened due to the incompressible medium between the flying piston and the drive element of the valve, or the pressure chamber is relieved into a fuel tank.

A particularly advantageous application of the invention is the control of an injection valve of an internal combustion engine, the outward opening valve controlling a gas exchange chamber which is arranged in the valve housing and which is connected to the pressure generating unit via a metering device. Advantageously, the metering of the fuel quantity injected into the gas exchange chamber can thus take place completely independently of the valve control.

Another advantageous application of the device according to the invention in an injection valve of an internal combustion engine provides that the inward opening valve controls a fuel chamber arranged in the valve housing, which is connected to the pressure generating unit via a pressure line.

• Fig. 1 eine Vorrichtung zur Steuerung des Hubes eines hydraulisch betätigbaren Ventiles, im speziellen eines Einblaseventiles einer Brennkraftmaschine in schematischer Darstellung,
• Fig. 2 eine Ausführungsvariante nach Fig. 1,
• Fig. 3 eine Ausführungsvariante zur Steuerung eines Einspritzventils einer Brennkraftmaschine,
• Fig. 3a eine Ausführungsvariante nach Fig. 3 sowie
• Fig. 4 ein Steuerdiagramm eines Ventiles nach der Erfindung.

The invention is explained in more detail below with reference to drawings. Show it:

• 1 shows a device for controlling the stroke of a hydraulically actuated valve, in particular an injection valve of an internal combustion engine, in a schematic illustration,
• 2 shows an embodiment variant according to FIG. 1,
• 3 shows an embodiment variant for controlling an injection valve of an internal combustion engine,
• Fig. 3a shows an embodiment of Fig. 3 and
• Fig. 4 is a control diagram of a valve according to the invention.

The device for controlling the stroke of a valve shown in FIG. 1 shows a blow-in valve 1, the outward opening valve 2 of which can be actuated via a web 3 with a drive member or piston 4 which is spring-loaded in the closing direction. A cylinder 6, in which a flying adjusting piston 7 is guided, is formed in one piece with the valve housing 5. The adjusting piston 7, which is axially freely movable up to a stop 8 in the cylinder 6, separates a drive chamber 9, limited by the piston 4, in the valve housing 5 from the pressure chamber 10 in the cylinder 6. The valve axis 2 'and the axis 7' of the adjusting piston 7 coincide in this embodiment variant. The valve 2 is closed here by a spring 11, however, in the sense of the invention, the space 12 accommodating the spring 11 could also be pressurized.

The pressure generating unit 13 of the device has a high-pressure pump 15 connected to a fuel tank 14, the pressure of which can be adjusted via a throttle valve 16. Excess fuel is fed into the fuel tank 14 via a return 17. The pressure generating unit 13 has a high-pressure line 18 which supplies the pressure chamber 10 in the cylinder 5 via an electromagnetically actuated three-way valve 19. In a switching position of the three-way valve 19, the pressure chamber 10 can be relieved into the fuel tank 14 via a return 29 with a throttle 30. Furthermore, the pressure generating unit supplies a low-pressure line 21 via a one-way reducing valve 20, which is connected to the drive chamber 9 via an electromagnetically actuated two-way valve 22. Arranged between the reducing valve 20 and the two-way valve 22 is a return line 23 with a pressure maintaining device, which is designed here as a pressure maintaining valve 24 and has a connecting line 25 to the fuel tank 14.

A line 26 branching off from the pressure line 18 leads to a metering device 27, with which the fuel is metered for the gas exchange chamber 28 arranged in the valve housing 5.

The mode of operation will now be explained in more detail with reference to FIGS. 1 and 4, which shows the control diagram of the device. The considered points in time 0 to 5 are on the The abscissa of the diagram is shown. Curve I represents the stroke of the injection valve, curve II represents the stroke of the adjusting piston 7 from the stop 8; curve III the switching of the three-way valve 19, the pressure chamber being acted upon with high pressure in the position H and being relieved in the R position. Curve IV represents the switching positions of the two-way valve 22, where O means open and S means closed.

Time 0:

Before the start of the stroke adjustment cycle, the two-way valve 22 and the three-way valve 19 are switched in such a way that the high pressure (20 to 100 bar) generated by the pump 15 is still applied to the pressure chamber 10 and is therefore in contact with the flying adjusting piston 7, which thereby rests on its stop 8 is held. The injection valve 2 is already closed by the force of the spring 11.

Time 1:

At time 1, the three-way valve 19 is switched so that the connection between the pressure chamber 10 and the pump 15 is interrupted and the return 29 for the fuel still in the pressure chamber 10 is released into the fuel tank 14 via the throttle 30. As a result, the pressure in the pressure chamber 10 drops, so that the pressure (2 to 10 bar) present in the drive chamber 9 on the lower side of the flying adjusting piston 7 comes into play and this begins to lift up from the stop 8.

In the embodiment according to FIG. 1, the amount of fuel required for this flows through the one-way reducing valve 20, the high pressure generated by the pump 15 being reduced to the low pressure mentioned. It should be noted that the pressure control valve 24 in the return line 23 should be set so that it is not yet opened when the low pressure is present.

Time 2:

At time 2, the two-way valve 22 is blocked. The lifting process of the adjusting piston 7 is thus ended. The period between times 1 and 2 determines this in the drive room 9 filled fuel volume, thus the size of the stroke carried out by the adjusting piston 7 and consequently the stroke of the valve 2 in the injection valve 1.

Time 3:

At time 3, the return 29 is closed by the three-way valve 19 and the pressure chamber 10 is connected to the high-pressure line 18. The high pressure is thus applied to the top of the adjusting piston 7. Since the two-way valve 22 is closed, the amount of fuel in the drive chamber 7 remains constant and, due to its largely incompressibility, causes a quasi-rigid connection of the adjusting piston 7 with the piston 4. The force of the spring 11 is overcome by the high pressure and this with the piston 4 the web 3 connected valve 2 of the injection valve 1 opened. This process is complete when the adjusting piston 7 reaches its stop 8. Valve 2 thus reaches its maximum stroke in this cycle and remains in this position until time 4. The period between times 3 and 4 therefore represents the injection and recharge time of the injection valve 1.

Time 4:

At time 4, the two-way valve 22 opens. As a result, the fuel located in the drive chamber 9 can flow out via the pressure-maintaining valve 24. While the high-pressure adjusting piston 7 maintains its position, the piston 4 is moved upwards by the spring 11 and the injection valve 1 is thereby closed. In the embodiment according to FIG. 1, the pressure-maintaining valve 24 is opened by the fuel pressure generated by the valve spring in the low-pressure line 21, and thus the fuel displaced by the piston 4 is discharged into the fuel tank 14.

Time 5:

After valve 2 is closed, a cycle is completed and the initial state (time 0) is restored, so that the next cycle can begin.

With the dashed curves I ', II' and IV 'in slide slide Fig. 4, the situation at an earlier closing of the two-way valve 22 at time 2' and thus less stroke of the valve 2 and the adjusting piston 7 is shown.

The embodiment of FIG. 2 differs from that of FIG. 1 only in that the pressure maintaining device is designed as a bladder accumulator 31. In this embodiment, the bladder accumulator 31 supplies the amount of fuel required to raise the adjusting piston 7 at the time 1. The pressure reducing valve 20 opens only when the amount of fuel in the bladder accumulator 31, and thus the pressure in the low-pressure part, drops below a certain minimum value as a result of leaks in the low-pressure part.

2, the spring 11 overcomes the counterpressure of the bladder accumulator 31 at time 4 and the displaced fuel volume is absorbed by the latter.

In the embodiment according to FIG. 3, the device for controlling the valve lift is used in an injection valve 32. 1 and 2 corresponding components are provided with the same reference numerals. An inward opening valve 2 is provided here, which controls a fuel chamber 33 arranged in the valve housing 5. A connection to the pressure generating unit 13 is established via the line 26. In this embodiment variant, the pressure chamber 10 is arranged between the drive chamber 9 and the fuel chamber 33, as a result of which the adjusting piston 7, which can move up to the stop 8, must have a passage 34 for the web 3 of the valve 2.

However, an embodiment variant according to FIG. 3a is also conceivable, in which the cylinder 6 with the adjusting piston 7 is arranged laterally on the valve housing 5, as a result of which the bushing 34 is omitted. The axis of the adjusting piston 7 'and the valve axis 2' are arranged normal to each other here. The stop 8 for the adjusting piston 7 can be formed directly by the wall of the valve housing 5.

In the case of an injection valve of this type, the amount of fuel injected is advantageously determined via the opening duration and the stroke of the valve. A smaller stroke results in smaller injection quantities better atomization, with longer injection times, better fuel processing can be achieved.

Claims (8)

1. A device for controlling the lift of a hydraulically operated valve comprising an actuating element bounding an actuating chamber in the valve cage, which element is pressure-loaded or spring-loaded in closing direction, and further comprising a pressure-generating unit, wherein is provided a flying setting plunger (7) guided in a cylinder (6), which bounds a pressure chamber (10) in the cylinder (6) and separates the pressure chamber (10) from the actuating chamber (9), in the valve cage (5), and wherein is provided that the pressure-generating unit (13) have a high-pressure line (18) controlled by a valve (19) and leading into the pressure chamber (10), as well as a low-pressure line (21) controlled by a another valve (22) and leading into the actuating chamber (9), the setting plunger (7) being pressed against a stop (8) in the cylinder (6) at maximum lift of the valve (2).

2. A Device according to claim 1, wherein the valve cage (5) and the cylinder (6) containing the setting plunger (7) are integrated in one piece, such that the valve axis (2′) and the axis (7′) of the setting plunger (7) coincide.

3. A device according to claim 1, wherein is provided a solenoid-controlled two-way valve (22), which is located in the low pressure line (21) connected to the pressure-generating unit (13) via a reducing valve (20), a return line (23) with a pressure-maintaining element (24; 31) being included between the reducing valve (20) and the two-way valve (22).

4. A device according to claim 3, wherein the pressure-maintaining element is configured as a pressure-tank (31) with an air cushion.

5. A device according to claim 1, wherein a solenoid-controlled three-way valve (19) is located in the high-pressure line (18), one of whose outlet is connected to the pressure chamber (10) while the other one leads to a return line (29) containing a throttle (30).

6. A device according to any of claims 1 to 5, for control of a fuel/gas injection valve of an internal combustion engine, wherein the valve (2), which opens outwardly, controls a gas exchange chamber (28) located in the valve cage (5) which chamber (28) is connected to the pressure-generating unit (13) via a metering device (27).

7. A device according to any of claims 1 to 5, for control of a fuel injection valve of an internal combustion engine, wherein the valve (2), which opens inwardly, controls a fuel chamber (33) located in the valve cage (5), which chamber (33) is connected to the pressure-generating unit (13) via a pressure line (26).

8. A method for controlling the lift of a hydraulically operated valve whose actuating element is pressure-loaded or spring-loaded in closing direction, wherein an actuating chamber, which is situated between an actuating element of the valve and a flying setting plunger, is subjected to low pressure in the closed position of the valve, such that the setting plunger is lifted from a stop, until a valve controlling the low pressure is closed, which will define a given lift, and wherein the setting plunger is subjected to high pressure via the control of a valve, such that the setting plunger is moved until it reaches its stop and the valve is forced open by the incompressible medium in the actuating chamber, and finally, wherein the low pressure control valve is opened, such that the actuating chamber is emptied and the valve is closed by the closing force acting on the actuating element.

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