EP1430201A1

EP1430201A1 - Method for operating an electrohydraulic valve control system of an internal combustion engine, computer program and control and regulating device for operating an internal combustion engine

Info

Publication number: EP1430201A1
Application number: EP02747175A
Authority: EP
Inventors: Hans Schlembach; Hermann Gaessler; Udo Diehl; Karsten Mischker; Rainer Walter; Ulf Pischke; Andreas Baumann; Hurbert Schweiggart; Gerhard Filp; Bernd Rosenau; Jürgen Ulm; Uwe Hammer; Thomas Mocken; Sevan Tatiyosyan; Jürgen Schiemann; Christian Grosse; Volker Beuche; Stefan Reimer; Simon Kieser
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2001-08-08
Filing date: 2002-05-28
Publication date: 2004-06-23
Anticipated expiration: 2022-05-28
Also published as: JP4047807B2; DE50204345D1; EP1430201B1; WO2003016682A1; KR20040019008A; JP2004538416A; KR100852805B1; DE10138881A1; US20040069255A1

Abstract

The invention relates to an electrohydraulic valve control system (10) of an internal combustion engine, comprising at least one actuator (24) which acts on a gas exchange valve (38). Said actuator, in turn, comprises at least one working chamber (30) which is connected to a high-pressure hydraulic accumulator (16) for actuating the actuator (24) in such a way that it moves from a first position to a second position, and which is separated from a low-pressure return line (56). In order to actuate the actuator (24) in such a way that it moves back from the second position into the first position, the working chamber (30) is connected to the low-pressure return line (56) and is separated from the high-pressure hydraulic accumulator (16). In order to easily maintain the pressure constant or to cause a pressure drop in the high-pressure hydraulic accumulator (16), the working chamber (30) is simultaneously connected to the high-pressure hydraulic accumulator (16) and to the low-pressure return line (56).

Description

Method for operating an electro-hydraulic valve control of an internal combustion engine, computer program and control and regulating device for operating an internal combustion engine

State of the art

The invention first relates to a method for operating an electrohydraulic valve control of an internal combustion engine, with at least one actuator working on a gas exchange valve with at least one working space, which is connected to actuate the actuator from a first position to a second position with a high-pressure hydraulic accumulator and from a low pressure -Return separated and connected to actuate the actuator from the second position to the first position back to the low pressure return and separated from the high pressure hydraulic accumulator.

Such a process is known from the market. Electro-hydraulic valve controls of internal combustion engines enable the control of the gas exchange valves regardless of the position of the crankshaft or the camshaft. This enables, among other things, gasoline savings and improvements in the emission characteristics of an internal combustion engine. In an electrohydraulic valve control known from the market, the shaft of the gas exchange valve is connected to a hydraulic actuator. This has two working spaces on both sides of the piston end faces, which are of different sizes. The small end face is constantly subjected to high pressure from a high-pressure hydraulic accumulator, which in turn is fed by a hydraulic pump. The large end face of the piston is also optionally connected to the high-pressure hydraulic accumulator or to a low-pressure return. Depending on the result, a force result that opens or closes the gas exchange valve.

In the known method, the amount of hydraulic fluid that flows from the high-pressure hydraulic accumulator via the actuator to the low-pressure return and is used to actuate the actuator can vary widely. The amount of fluid conveyed by the hydraulic pump into the high-pressure hydraulic accumulator can also vary, for example when the hydraulic pump is driven directly by the internal combustion engine and then there is a speed-dependent delivery rate of the hydraulic pump.

In order to be able to achieve a relatively constant pressure associated with the operating point in the high-pressure hydraulic accumulator, an overpressure or pressure control valve has been provided so far, for example, which discharges hydraulic fluid from the high-pressure hydraulic accumulator when a certain pressure is exceeded. Regulation of the delivery rate by the hydraulic pump is also known. Dynamic pressure peaks in the high-pressure hydraulic accumulator can also be passively smoothed, for example, by a large volume of the high-pressure hydraulic accumulator. However, the measures with which the pressure in the high-pressure hydraulic accumulator can be kept constant are relatively complex and sometimes react only sluggishly to pressure changes in the high-pressure hydraulic accumulator. A large-scale high-pressure hydraulic accumulator for smoothing pressure peaks is also disadvantageous, since usually little space is usually available in the engine compartment, for example of motor vehicles. The same disadvantage also results from a pressure control valve.

The present invention therefore has the task of developing a method of the type mentioned in the introduction _{/ in} such a way that the pressure in the high-pressure hydraulic accumulator can be kept constant in a simple manner.

In a method of the type mentioned at the outset, this object is achieved in that a

Maintaining constant pressure or lowering the pressure in the high-pressure hydraulic accumulator is achieved by connecting the work space to the high-pressure hydraulic accumulator and the low-pressure return at the same time.

Advantages of the invention

The measure according to the invention enables a direct connection from the high-pressure hydraulic accumulator to the low-pressure return, without additional components, such as, for. B. a pressure control valve are necessary. To make this possible, an operating state is expressly permitted in which the work area is connected to the high-pressure hydraulic accumulator and the low-pressure return of the electrohydraulic valve control at the same time. Results, for example. By a sensor found the need to remove hydraulic fluid from the high pressure ^"" ^ raulikspeicher, the pressure in this To be able to keep constant, this can be done according to the invention in a simple manner via the work space to the low-pressure return.

Since the switching valves usually used have a short response time and highly dynamic switching behavior, short-term fluctuations in the pressure in the high-pressure hydraulic accumulator can also be smoothed out. A pressure control valve can therefore be dispensed with on the one hand by the method according to the invention. Furthermore, the high-pressure hydraulic accumulator can be made smaller. This saves costs in the manufacture of the electro-hydraulic valve control and the electro-hydraulic valve control requires less installation space.

Advantageous developments of the invention are specified in the subclaims.

In a first development, it is stated that, in order to keep the pressure in the high-pressure hydraulic accumulator constant or to lower it, the working space of an actuator is simultaneously connected to the high-pressure hydraulic accumulator and the low-pressure return, the associated gas exchange valve of which is just closed. This development of the method according to the invention is particularly useful when the actuation of the actuator and the opening of the gas exchange valve are carried out by applying the full high pressure. In the closed idle state of the gas exchange valve, a pressure is therefore usually present in the working space of the actuator which is lower than the full high pressure of the high-pressure hydraulic accumulator.

When the high-pressure hydraulic accumulator is connected to the low-pressure return via the working space of the actuator however, there is a pressure in the working space of the accumulator that is below the full pressure in the high-pressure hydraulic accumulator. The closed rest position of the gas exchange valve is thus not influenced by this connection of the work space at the same time as the high-pressure hydraulic accumulator and the low-pressure return.

It is particularly preferred if the working space of an actuator is simultaneously connected to the high-pressure hydraulic accumulator and the low-pressure return to keep the pressure constant or reduce the pressure in the high-pressure hydraulic accumulator, the associated gas exchange valve of which cannot open precisely due to a high internal cylinder pressure. This effectively prevents an undesired opening of the gas exchange valve in the case of an actuator which is “sensitive” to pressure fluctuations in the work space.

It is also possible that the working space of an actuator, which is to be moved from the first position to the second position, is connected to the high-pressure hydraulic accumulator immediately before the separation from the low-pressure return, and / or the working space of an actuator, which is moved from the second position to be moved to the first position, is connected to the low-pressure return immediately before the separation from the high-pressure hydraulic accumulator.

In this case, an actuation of the actuator that is intended in any case is used to discharge hydraulic fluid from the high-pressure hydraulic accumulator. This is made possible by a shift in the time at which the connection of the work space with the low-pressure return or the high-pressure hydraulic accumulator takes place. Thus there is an overlap of the periods in which the Working space is connected to the low pressure return and the high pressure hydraulic accumulator. This makes it possible to integrate pressure maintenance or pressure reduction in the high-pressure hydraulic accumulator into the normal operation of an actuator.

Particularly preferred is that further development of the method according to the invention in which the working space of an actuator is then temporarily connected to the high-pressure hydraulic accumulator and the low-pressure return line at the same time when the internal combustion engine is operated at a low speed. This development takes into account the fact that a lower pressure in the high-pressure hydraulic accumulator is generally advantageous at low speed. Since such a targeted reduction in pressure in the high-pressure hydraulic accumulator was previously not possible, the actuation strategy of the actuator had to be changed instead at low engine speeds. This can be omitted in the method further developed according to the invention.

In another development, it is proposed that the constant pressure or pressure reduction be combined by a simultaneous connection of the working space of an actuator with the low-pressure return and the high-pressure hydraulic accumulator with a control or regulation of the delivery rate by a hydraulic pump. While the above-mentioned connection of the work space can influence the pressure in the high-pressure hydraulic accumulator very quickly and highly dynamically, the control or regulation of the delivery rate by the hydraulic pump enables a long-term and quantitatively significant adjustment of the pressure in the high-pressure hydraulic accumulator.

The method according to the invention is particularly preferred when the actuator has two working spaces, which are separated by different sizes and acting in opposite ^directions' pressure surfaces on a piston, and one working space is constantly subjected to high pressure and the other work chamber with the high pressure hydraulic accumulator and the low pressure return can be connected. Actuators of this type can be used to achieve very short switching times, which facilitates the implementation of the method according to the invention.

In order to avoid cavitation when the hydraulic fluid flows out of the working space toward the low-pressure return, the hydraulic fluid can also flow from the working space into a low-pressure hydraulic accumulator in the method according to the invention. The pressure difference when the hydraulic fluid flows out is thus reduced, which counteracts the formation of cavitation.

The invention also relates to a computer program which is suitable for carrying out the method according to one of the preceding claims when it is executed on a computer. It is particularly preferred if the computer program is stored on a memory, in particular on a flash memory or a ferrite RAM.

The invention further relates to a control and regulating device for operating an internal combustion engine, which is connected at least to a first control valve and a second control valve of an electrohydraulic valve control, with which a working space of an actuator of a gas exchange device is connected to a high-pressure hydraulic accumulator or a low-pressure return can be.

In order to simplify the structure of the electro-hydraulic valve control, it is proposed that Steuer- and Regelgerac is suitable for performing the above method. It is particularly preferred if it is provided with a computer program of the type mentioned above.

drawing

Below is a particularly preferred one

Embodiment of the invention explained in detail with reference to the accompanying drawings. The drawing shows:

Figure 1 is a schematic representation of an electro-hydraulic valve control of an internal combustion engine;

FIG. 2 shows a diagram in which the pressure curve in a high-pressure hydraulic accumulator from FIG. 1 is shown over time; and

Figure 3 is a diagram showing the pressure in the high pressure hydraulic accumulator of Fig. 1 over a speed of the internal combustion engine.

Description of the embodiment

In Fig. 1, an electrohydraulic valve control system bears the reference number 10 overall. It first comprises a reservoir for hydraulic fluid, which in the present case bears reference number 12 and which can be the oil sump of the internal combustion engine. The hydraulic fluid is conveyed from the hydraulic reservoir 12 into a high-pressure hydraulic accumulator 16 by a controllable high-pressure hydraulic pump 14. A hydraulic line 18 leads from the high-pressure hydraulic accumulator 16 via a pressure control valve 20 to a solenoid valve 22. The hydraulic line 18 leads from the solenoid valve 22 to an actuator 24. This is a hydraulic cylinder with a double-acting piston 26. The piston 26 is guided in a housing 28. In Fig. 1 above the piston 26, a first working space 30 is formed between the latter and the housing 28. This is connected to the solenoid valve 22. 1, a second working space 32 is formed between the piston 26 and the housing 28. This is connected via a branch line 33 to that section of the hydraulic line 18 which lies between the high-pressure hydraulic accumulator 16 and the solenoid valve 22.

The upper end face 34 of the piston 26 in FIG. 1 is overall larger than the lower end face 36 of the piston 26 in FIG. 1, which delimits the second working space 32. The piston 26 is therefore a so-called "differential piston". The piston 26 is connected to a gas exchange valve 38. This comprises a valve rod 40 and a valve element 42. An opening (without reference number) of a combustion chamber 44 can be closed or opened by the valve element 42. The combustion chamber 44 is present in an engine block 46 of an internal combustion engine (without reference numerals).

From the first working chamber 30 of the actuator 24, a hydraulic line 48 leads via a second solenoid valve 50 to a low-pressure hydraulic accumulator 52. This is in turn connected via a pressure control valve 54 to a low-pressure return 56, which finally leads back to the hydraulic reservoir 12. A hydraulic line 58 also leads from the first working space 30 of the actuator 24 back to the high-pressure hydraulic accumulator 16 via a pressure control valve 60. The two solenoid valves 22 and 50 are actuated by solenoid actuators 62 and 64 and are each pressed into their rest position by a compression spring 66 and 68, respectively. The first solenoid valve 22 is closed in its idle switching position 70, in which the magnetic actuator 62 is not energized, whereas it is open in the actuated switching position 72. In contrast, the second solenoid valve 50 is open in its idle switching position 74 and closed in the actuated switching position in which the magnetic actuator 64 is energized. This switch position bears the reference number 76.

The electro-hydraulic valve control 10 also includes a control and regulating device 78. This is connected on the output side to the magnetic actuators 62 and 64. It can also control the hydraulic pump 14. On the input side, the control and regulating device 78 is connected to a pressure sensor 80, which detects the pressure in the high-pressure hydraulic accumulator 16. Furthermore, the control and regulating device 78 is connected to a speed sensor for the crankshaft of the internal combustion engine. This speed sensor bears the reference number 82.

The electro-hydraulic valve control 10 is operated as follows (the method described below is stored as a computer program on a ferrite RAM (not shown) in the control and regulating device 78): In order to open the gas exchange valve 38, the piston 26 in FIG move down. This is achieved by energizing the second solenoid valve 50 from the rest position 74 and thus closing it. The connection between the first working space 30 and the low-pressure hydraulic accumulator 52 is thus interrupted.

The control unit 78 then energizes the magnetic actuator 62 of the first solenoid valve 22, see above that this solenoid valve 22 moves from its closed rest position 70 into the open switch position 72. The first working space 30 is thus connected to the high-pressure hydraulic accumulator 16. Essentially, the hydraulic pressure also prevailing in the high-pressure hydraulic accumulator 16 is set in the first working space 30.

Since the lower end face 36 is smaller than the upper end face 34 of the piston 26, however, the same pressure prevails in both working spaces 30 and 32 of the actuator 24, namely essentially the pressure prevailing in the high-pressure hydraulic accumulator 16, a resultant force results in Fig. 1 down, so that the piston 26 moves in this direction. As a result, the valve rod 40 and the valve element 42 are also moved downward in FIG. 1, that is to say the gas exchange valve 38 is opened.

If the gas exchange valve 38 is to be closed again, the first solenoid valve 22 is first de-energized by the control and regulating device 78, so that it is pressed from the open switch position 72 by the compression spring 66 into the closed switch position 70. The connection between the high-pressure hydraulic accumulator 16 and the first working space 30 is thus interrupted again.

Then the second solenoid valve 50 is de-energized by the control and regulating device 78, so that it moves due to the compression spring 68 from the closed switching position 76 into the open rest position 74. The first working space 30 is now connected to the low-pressure hydraulic accumulator 52 again. Thus, the pressure in the first working space 30 drops until a resultant force occurs, which moves the piston 26 up again. As a result, the gas exchange valve 38 closes. If control device 78 is now informed via pressure sensor 80 that the pressure in high-pressure hydraulic accumulator 16 is higher than a target pressure, control device 78 controls first solenoid valve 22 into its open switch position 72, whereas the second solenoid valve 50 remains in its open rest position 74. It is assumed that the internal combustion engine is in an operating state in which the gas exchange valve 38, which is connected to the actuator 24, is to remain closed. By said actuation of the first solenoid valve 22, there is now a direct connection from the high-pressure hydraulic accumulator 16 via the first solenoid valve 22, the first working chamber 30 and the second solenoid valve 50 to the low-pressure hydraulic accumulator 52.

By means of an appropriate design of the hydraulic lines 18 and 48 it can be achieved that in this state the pressure in the first working space 30 never becomes so high that an undesired movement of the piston 26 is induced. Due to the direct connection from the high-pressure hydraulic accumulator 16 to the low-pressure hydraulic accumulator 52, hydraulic fluid can flow from the high-pressure hydraulic accumulator 16 directly to the low-pressure hydraulic accumulator 52 without this leading to actuation of the actuator 24. The pressure in the high-pressure hydraulic accumulator 16 can thus be specifically reduced or kept constant.

If the gas exchange valve 38 is to be reliably prevented from opening during this state, the direct connection between the high-pressure hydraulic accumulator 16 and the low-pressure hydraulic accumulator 52 is preferably established when the valve element 42 is pressed into its closed position due to a high pressure prevailing in the combustion chamber 44 becomes. The outflow of hydraulic fluid from the high-pressure hydraulic accumulator 16 to the low-pressure hydraulic accumulator 52 is terminated simply by the first solenoid valve 22 being de-energized by the control and regulating device 78, so that it returns to its closed rest position 70. The pressure prevailing in the low-pressure hydraulic accumulator 52 is then set again in the first working space 30.

The electro-hydraulic valve control 10 can, however, be operated in another way in order to keep the pressure in the high-pressure hydraulic accumulator 16 constant or to lower it:

The connection of the high-pressure hydraulic accumulator 16 to the low-pressure hydraulic accumulator 52 can thus be coupled to an actuation of the actuator 24. When the actuator 24 is actuated in such a way that the gas exchange valve 38 opens, the solenoid valve 22 can, for example, immediately before the energization of the magnetic actuator 64 of the second solenoid valve 50, as a result of which it moves from its open rest position 74 to the closed switching position 76 Rest position 70 can be controlled in the actuated and open switch position 72.

Thus, shortly before the second solenoid valve 50 is closed, there is a direct connection between the high-pressure hydraulic accumulator 16 and the low-pressure hydraulic accumulator 52, through which hydraulic fluid can flow out of the high-pressure hydraulic accumulator 16. In the same way, if the gas exchange valve 38 is to be closed again, immediately before the magnetic actuator 62 of the first magnetic valve 22 is de-energized, as a result of which it returns from its open switching position 72 to the closed rest position 70, the second solenoid valve 50 can already be brought from its closed switching position 76 into the open rest position 74.

This also results in a short-term direct connection from the high-pressure hydraulic accumulator 16 to the low-pressure hydraulic accumulator 52 and further to the low-pressure return line 56, through which hydraulic fluid flows out of the high-pressure hydraulic accumulator 16 and the pressure in the latter can thus be kept constant or reduced.

Such short-term actuation of the valves and such a short-term direct connection between the high-pressure hydraulic accumulator 16 to the low-pressure return line 56 can keep the pressure in the high-pressure hydraulic accumulator 16 constant, as can be seen from FIG. 2. The amount of fluid to be discharged is controlled by the duration of the direct connection. In this figure, the pressure is dashed without a corresponding actuation of the solenoid valves 22 and 50, that pressure curve which can be produced by a corresponding actuation of the solenoid valves 22 and 50 is shown in a solid line.

If the internal combustion engine is operated at a low speed, this is detected by the speed sensor 82 and a corresponding signal is sent to the control and regulating device 78. This can then control the solenoid valves 22 and 50 so that the pressure in the high-pressure hydraulic accumulator 16 is reduced. Typically, the operating pressure is reduced from the usual 200 bar to approximately 50 bar. If the speed rises again, a direct fluid connection between the high-pressure hydraulic accumulator 16 and the low-pressure return is avoided, so that the pressure in the high-pressure hydraulic accumulator 16 again due to the continuous delivery by the high-pressure hydraulic pump 14 increases. The relationship between the engine speed n and the pressure P in the high-pressure hydraulic accumulator 16 is shown in FIG. 3. The pressure setting in the high-pressure hydraulic accumulator 16 can, if necessary, be supported by a corresponding control of the high-pressure hydraulic pump 14.

Claims

Expectations

1. Method for operating an electrohydraulic valve control (10) of an internal combustion engine, with at least one actuator (24) working on a gas exchange valve (38) with at least one working space (30), which for actuating the actuator (24) from a first position into a second position connected to a high-pressure hydraulic accumulator (16) and separated from a low-pressure return line (56) and connected to the low-pressure return line (56) for actuation of the actuator (24) from the second position back to the first position and is separated from the high-pressure hydraulic accumulator (16), characterized in that a constant pressure or a pressure reduction in the high-pressure hydraulic accumulator (16) is brought about by the fact that the working space (30) simultaneously with the high-pressure hydraulic accumulator (16) and the low-pressure Return (56) is connected.

2. The method according to claim 1, characterized in that for maintaining the pressure constant or lowering the pressure in the high-pressure hydraulic accumulator (16), the working space (30) of an actuator (24) is simultaneously connected to the high-pressure hydraulic accumulator (16) and the low-pressure return (56) whose associated gas exchange valve (38) is just closed.

3. The method according to claim 2, characterized in that for maintaining the pressure constant or lowering the pressure in the high-pressure hydraulic accumulator (16), the working space (30) of an actuator (24) is simultaneously connected to the high-pressure hydraulic accumulator (16) and the low-pressure return (56) whose associated gas exchange valve (38) cannot open precisely because of a high pressure in the combustion chamber (44).

4. The method according to any one of the preceding claims, characterized in that the working space (30) of an actuator (24), which is to be moved from the first position to the second position, immediately before the separation from the low-pressure return (56) with the High-pressure hydraulic accumulator (16) is connected, and / or the working space (30) of an actuator (24), which is to be moved from the second position to the first position, immediately before the separation from the high-pressure hydraulic accumulator (16) with the low pressure -Return (56) is connected.

5. The method according to any one of the preceding claims, characterized in that the working space (30) of an actuator (24) is then temporarily connected simultaneously to the high-pressure hydraulic accumulator (16) and the low-pressure return (56) when the internal combustion engine with less Speed is operated.

6. The method according to any one of the preceding claims, characterized in that the hydraulic pump (14) additionally controls or regulates the delivery rate.

7. The method according to any one of the preceding claims, characterized in that the actuator (24) has two working spaces (30, 32), which by differently sized and oppositely acting pressure surfaces (34, 36) on a piston (26) are separated from each other, and one working space (32) is constantly pressurized and the other working space (30) with the high-pressure hydraulic accumulator (16) and the Low pressure return (56) can be connected.

8. The method according to any one of the preceding claims, characterized in that the hydraulic fluid flows from the working space (30) into a low-pressure hydraulic accumulator (52).

9. Computer program, characterized in that it is suitable for performing the method according to one of the preceding claims when it is executed on a computer.

10. Computer program according to claim 9, characterized in that it is stored on a memory, in particular on a flash memory or a ferrite RAM.

11. Control and regulating device (78) for operating an internal combustion engine, which is connected to at least a first control valve (22) and a second control valve (50) of an electrohydraulic valve control (10), with which a working space (30) of an actuator ( 24) a gas exchange valve (38) with a high-pressure hydraulic accumulator (16) or one

Low-pressure return line (56) can be connected, characterized in that it is suitable for carrying out the method according to one of claims 1 to 8.

12. Control and regulating device (78) according to claim 11, characterized in that it is provided with a computer program according to one of claims 9 or 10.