EP1797285B1 - Device for modifying the timing of gas exchange valves in an internal combustion engine - Google Patents

Description

Field of the invention

The invention relates to a method for controlling a device for changing the timing of gas exchange valves of an internal combustion engine according to the preamble of claim 1.

In internal combustion engines, camshafts are used to actuate the gas exchange valves. Camshafts are mounted in the internal combustion engine such that cams attached to them abut cam followers, for example cup tappets, drag levers or rocker arms. If a camshaft is rotated, the cams roll on the cam followers, which in turn actuate the gas exchange valves. Due to the position and the shape of the cams thus both the opening duration and the opening amplitude but also the opening and closing times of the gas exchange valves are set.

Modern engine concepts go to design the valve train variable. On the one hand, valve lift and valve opening duration should be variable, up to the complete shutdown of individual cylinders. For this purpose, concepts such as switchable cam followers or electrohydraulic or electric valve actuations are provided. Furthermore, it has been found to be advantageous to be able to influence the opening and closing times of the gas exchange valves during operation of the internal combustion engine. In this case, it is particularly desirable to be able to influence the opening or closing times of the inlet or outlet valves separately, in order, for example, to adjust a defined valve overlap in a targeted manner. By the attitude the opening and closing times of the gas exchange valves in dependence on the current map range of the engine, for example, the current speed or the current load, the specific fuel consumption can be lowered, the exhaust behavior positively influenced, the engine efficiency, the maximum torque and the maximum power can be increased.

The described variability of the valve timing is achieved by a relative change in the phase angle of the camshaft to the crankshaft. The camshaft is usually via a chain, belt, gear drive or equivalent drive concepts in drive connection with the crankshaft. Between the driven by the crankshaft chain, belt or gear drive and the camshaft, a device for changing the timing of an internal combustion engine, hereinafter also called camshaft adjuster, mounted, which transmits the torque from the crankshaft to the camshaft. In this case, this device is designed such that during operation of the internal combustion engine, the phase angle between the crankshaft and camshaft securely held and, if desired, the camshaft can be rotated in a certain angular range relative to the crankshaft.

In internal combustion engines, each with a camshaft for the intake and the exhaust valves, these can each be equipped with a camshaft adjuster. As a result, the opening and closing times of the intake and exhaust valves can be shifted in time relative to one another and the valve overlaps can be adjusted in a targeted manner.

The seat of modern camshaft adjuster is usually located at the drive end of the camshaft. The camshaft adjuster can also be arranged on an intermediate shaft, a non-rotating component or the crankshaft. It consists of a driven by the crankshaft, a fixed phase relation to this holding drive wheel, a driving connection with the camshaft standing output part and a torque transmitting from the drive wheel to the output part adjusting mechanism. The drive wheel may, in the case of a not arranged on the crankshaft camshaft adjuster be designed as a chain, belt or gear and is driven by means of a chain, a belt or a gear drive from the crankshaft. The adjustment mechanism can be operated electrically, hydraulically or pneumatically.

Two preferred embodiments of hydraulically adjustable camshaft adjusters are the so-called Axialkolbenversteller and Rotationskolbenversteller.

In the Axialkolbenverstellern the drive wheel is connected to a piston and this with the output part via helical gears in combination. The piston separates a cavity formed by the driven part and the drive wheel into two pressure chambers arranged axially to each other. If now one pressure chamber is acted upon by pressure medium while the other pressure chamber is connected to a tank, the piston shifts in the axial direction. The axial displacement of the piston is translated by the helical gears in a relative rotation of the drive wheel to the output part and thus the camshaft to the crankshaft.

A second embodiment of hydraulic phaser are the so-called rotary piston adjuster. In these, the drive wheel is rotatably connected to a stator. The stator and a rotor are arranged concentrically with each other, wherein the rotor is positively, positively or materially, for example by means of a press fit, a screw or welded connection with a camshaft, an extension of the camshaft or an intermediate shaft connected. In the stator, a plurality of circumferentially spaced cavities are formed which extend radially outward from the rotor. The cavities are limited pressure-tight in the axial direction by side cover. In each of these cavities, a wing connected to the rotor extends, dividing each cavity into two pressure chambers. By selectively connecting the individual pressure chambers with a pressure medium pump or with a tank, the phase of the camshaft can be adjusted or held relative to the crankshaft.

To control the camshaft adjuster sensors detect the characteristics of the engine, such as the load condition and the speed. These data are supplied to an electronic control unit, which controls the supply and the outflow of pressure medium to the various pressure chambers after comparing the data with a characteristic field of the internal combustion engine.

In order to adjust the phase position of the camshaft relative to the crankshaft, one of the two counteracting pressure chambers of a cavity with a pressure medium pump and the other are connected to the tank in hydraulic camshaft adjusters. The inlet of pressure medium to a chamber in conjunction with the flow of pressure medium from the other chamber moves the pressure chambers separating piston in the axial direction, whereby in Axialkolbenverstellern on the helical gears, the camshaft is rotated relative to the crankshaft. In Rotationskolbenverstellern is caused by the pressurization of a chamber and the pressure relief of the other chamber, a displacement of the wing and thus directly a rotation of the camshaft to the crankshaft. To keep the phase position both pressure chambers are either connected to the pressure medium pump or separated from both the pressure medium pump and the tank.

The control of the pressure medium flows to and from the pressure chambers by means of a control valve, usually a 4/3-proportional valve. A valve housing is provided with one connection each for the pressure chambers (working connection), a connection to the pressure medium pump and at least one connection to a tank. Within the substantially hollow cylindrical valve housing an axially displaceable control piston is arranged. The control piston can be brought by means of an electromagnetic actuator against the spring force of a spring element axially in any position between two defined end positions. The control piston is further provided with annular grooves and control edges, whereby the individual pressure chambers can be selectively connected to the pressure medium pump or the tank. Likewise, a position of the control piston may be provided, in which the pressure medium chambers are separated from both the pressure medium pump and the pressure medium tank.

In the DE 100 64 222 A1 such a device is shown. This is a device in rotary piston design. A standing in drive connection with the camshaft stator is rotatably mounted on a rotatably connected to a camshaft rotor. The stator is formed with recesses open to the rotor. In the axial direction of the device side covers are provided, which limit the device. The recesses are pressure sealed by the rotor, the stator and the side cover and thus form pressure chambers. In the outer circumferential surface of the rotor axial grooves are introduced, in which wings are arranged which extend into the recesses. The wings are designed such that they divide the pressure chambers into two oppositely acting pressure chambers. By supplying or discharging pressure medium to and from the pressure chambers, the phase position of the camshaft can be selectively held or adjusted relative to the crankshaft.

In the side covers two locking pins are arranged, which are acted upon by means of a spring means with a force in the direction of the rotor. In the end face of the rotor, which faces the locking pins, circumferentially extending grooves are mounted. The grooves are arranged and designed such that in a defined middle position, both locking pins engage in a respective groove when none of the grooves is acted upon by pressure medium. Each pin abuts a peripheral end of the respective groove. The rotor is thus locked relative to the stator whereby a relative rotation is prevented. About first and second pressure medium lines, the pressure medium chambers can be filled with pressure medium. If a first pressure medium chamber filled with pressure medium, so also an end face of a locking pin is acted upon with pressure medium. As a result, the corresponding pin is pressed into the receiving bore of the side cover and allows an adjustment of the rotor relative to the stator in one direction. In this case, the other groove, in which the other Verrieglungspin still engages, so designed such that an adjustment of the rotor from the center position is made possible up to a maximum value. Accordingly, the adjustment of the rotor relative to the stator runs in the other direction. The device is equipped with a compensating spring which is fixed at one end to the rotor and at the other end to the stator and compensates for the drag torque which the camshaft exerts on the rotor.

In DE 198 53 670 A1 a control valve is shown which serves to control the flow of pressure medium to the pressure chambers depending on the current load state of the internal combustion engine. The control valve consists of an actuating unit, a substantially hollow cylindrical valve housing and a substantially hollow cylindrical control piston, which is received axially displaceable within the valve housing. On the valve housing two working ports, an inlet and a drain port are formed. The adjusting unit can be, for example, an electromagnet, which shifts the control piston against the force of a spring by applying a control current via a push rod. Depending on the position of the control piston inside the valve housing, the inlet connection is connected to one of the two working connections and the tank connection to the other working connection or the working connections are disconnected from the inlet or outlet connection. As a result, pressure medium is supplied to a pressure chamber, while pressure medium flows out of the other pressure chamber, which causes a change in the phase position of the camshaft to the crankshaft.

A serious disadvantage of this control valve in conjunction with a camshaft adjuster with center-position locking is the fact that in the de-energized state of the pressure medium connection is connected to one of the two working ports. In the case of a malfunction of the actuator so pressure medium is directed to one of the two pressure chambers and at the same time to one of the two pins. As a result, the camshaft adjuster, depending on the configuration of the control valve, is rotated into one of the two maximum positions after the actuating unit fails and this phase position is maintained over the entire operation of the internal combustion engine. Because the center position in which the phaser is locked in a depressurized state of the device, is selected such that the internal combustion engine in this phase position of the camshaft relative to the crankshaft good start and running properties, resulting from a maximum phase shift relative to the center position worse start and running characteristics of the internal combustion engine.

Summary of the invention

The invention is therefore based on the object to avoid these disadvantages and thus to propose a method by which the camshaft can be brought relative to the crankshaft in a phase position in which the hydraulic actuator is in a position in which this is either locked or in it is automatically brought into the locked position during the first revolution of the camshaft upon restart, without a piston or wing abutting an end stop.
Furthermore, a method is to be proposed, whereby the adjusting device is brought into the locked position when the parking position is not locked.

• Anfahren und Halten einer definierten Phasenlage ϕ+X°KW,
• Ausschalten der Zündung,
• Einstellen der zweiten oder vierten Steuerstellung (130, 132), um die Phasenlage ϕ+X°KW zu halten, bis die Drehzahlsensorik die Drehzahl n=0 meldet,
• Detektieren der Drehzahl n über eine Drehzahlsensorik,
• Halten der eingenommenen Steuerstellung (130, 132) für eine vorbestimmte Zeitspanne,
• nach Ablauf der Zeitspanne Deaktivieren der Stelleinheit (112).

The object is achieved according to the invention in that the following method steps are carried out in the order listed during the stopping process of the internal combustion engine:

• Approaching and holding a defined phase position φ + X ° KW,
• Switching off the ignition,
• Setting the second or fourth control position (130, 132) to maintain the phase position φ + X ° CA until the speed sensor system reports the speed n = 0,
• Detecting the rotational speed n via a rotational speed sensor system,
• Holding the assumed control position (130, 132) for a predetermined period of time,
• after expiration of the time period deactivating the actuator (112).

By this method, the adjusting device is brought into a phase position during the stopping process, which deviates from the center locking position by an amount X ° crankshaft (KW). The sign of X depends on the adjustment direction of the adjusting device, if this is not sufficiently filled with pressure medium. For example, if the device is equipped with no compensating spring or a compensating spring which has a low torque on the system rotor stator, the torque is smaller than the drag torque of the rotating camshaft, this phase position is relative to the center locking position in the early direction. In the event that the compensation spring torque is greater and opposite to the camshaft drag torque, this phase position is late relative to the center locking position. through the process steps. After issuing the ignition, that control position is to be assumed which prevents the actuator from moving into the middle position until a rotational speed sensor system signals the rotational speed n = 0. Subsequently, the assumed control position is held for a defined period of time. This is necessary because the speed sensor system in the last revolution of the camshaft / crankshaft already reports the rotational speed n = 0 and due to the alternating torques the actuator can be moved via the center position in the undesired position. By this holding time relaxation effects of the internal combustion engine are also intercepted, for example, relax piston or the like, whereby also the wrong position can be taken.

• Einstellen der ersten Steuerstellung
• Detektion der Drehzahl n der Kurbelwelle oder der Nockenwelle,
• ist die Drehzahl n>0: Detektion des Druckmitteldrucks p,
• ist der Druckmitteldruck p größer als ein vorbestimmter Wert: Einstellen von Steuerstellungen nach dem in der Steuereinheit abgelegtem Kennfeld,

In a further development of the invention, it is provided that the following method steps are carried out in the order listed during the startup process:

• Setting the first control position
• Detection of the speed n of the crankshaft or the camshaft,
• is the speed n> 0: detection of the fluid pressure p,
• is the pressure medium pressure p greater than a predetermined value: setting of control positions according to the stored in the control unit map,

This ensures that the lock is achieved in the unlocked state, and the lock can be canceled only when the fluid pressure has reached a certain value and thus a sufficient pressure medium supply of the device is ensured. As a result, a striking of a piston or wing is prevented, which would be the case with an unlocked, not sufficiently supplied with pressure means device.

Brief description of the drawings

Figur 1

einen Längsschnitt durch eine hydraulische Stellvorrichtung,

Figur 2

einen Querschnitt durch eine hydraulische Stellvorrichtung nach Figur 1,

Figur 3

ein Flussdiagramm für ein Verfahren zum Starten einer Brennkraftmaschine mit einer erfindungsgemäßen Vorrichtung zur Veränderung der Steuerzeiten von Gaswechselventilen,

Figur 4

eine schematische Darstellung einer erfindungsgemäßen Vorrichtung zur Veränderung der Steuerzeiten von Gaswechselventilen einer Brennkraftmaschine,

Figur 5a

einen Längsschnitt durch ein Steuerventil einer erfindungsgemäßen Vorrichtung zur Veränderung der Steuerzeiten von Gaswechselventilen einer Brennkraftmaschine in einer ersten Steuerstellung,

Figur 5b

einen Längsschnitt durch das Steuerventil aus Figur 5a in einer zweiten Steuerstellung,

Figur 5c

einen Längsschnitt durch das Steuerventil aus Figur 5a in einer dritten Steuerstellung,

Figur 5d

einen Längsschnitt durch das Steuerventil aus Figur 5a in einer vierten Steuerstellung,

Figur 6

in einem Diagramm den Volumenstrom vom Zulaufanschluss zu den Druckkammern in Abhängigkeit von der Stellung des Steuerkolbens relativ zum Ventilgehäuse,

Figur 7

ein Flussdiagramm für ein Verfahren zum geregelten Abschalten einer Brennkraftmaschine mit einer erfindungsgemäßen Vorrichtung zur Veränderung der Steuerzeiten von Gaswechselventilen und

Figur 8

eine schematische Darstellung einer Vorrichtung zur Veränderung der Steuerzeiten von Gaswechselventilen einer Brennkraftmaschine aus dem Stand der Technik.

Further features of the invention will become apparent from the following description and from the drawings, in which embodiments of the invention are shown in simplified form. Show it:

FIG. 1

a longitudinal section through a hydraulic actuator,

FIG. 2

a cross section through a hydraulic adjusting device according to FIG. 1 .

FIG. 3

a flowchart for a method for starting an internal combustion engine with a device according to the invention for changing the timing of gas exchange valves,

FIG. 4

a schematic representation of a device according to the invention for changing the timing of gas exchange valves of an internal combustion engine,

FIG. 5a

a longitudinal section through a control valve of a device according to the invention for changing the timing of gas exchange valves of an internal combustion engine in a first control position,

FIG. 5b

a longitudinal section through the control valve FIG. 5a in a second control position,

FIG. 5c

a longitudinal section through the control valve FIG. 5a in a third control position,

FIG. 5d

a longitudinal section through the control valve FIG. 5a in a fourth control position,

FIG. 6

in a diagram, the volume flow from the inlet port to the pressure chambers in dependence on the position of the control piston relative to the valve housing,

FIG. 7

a flowchart for a method for the controlled shutdown of an internal combustion engine with a device according to the invention for changing the timing of gas exchange valves and

FIG. 8

a schematic representation of a device for changing the timing of gas exchange valves of an internal combustion engine from the prior art.

Detailed description of the drawing

The Figures 1 and 2 show a hydraulic adjusting device 1 a of a device 1 for changing the timing of gas exchange valves of an internal combustion engine. The adjusting device 1a consists essentially of a stator 2 and a concentrically arranged rotor 3. A drive wheel 4 is rotatably connected to the stator 2 and formed in the illustrated embodiment as a sprocket. Also conceivable are embodiments of the drive wheel 4 as a belt or gear. The stator 2 is rotatably mounted on the rotor 3, wherein on the inner circumferential surface of the stator 2 in the illustrated embodiment, five circumferentially spaced recesses 5 are provided. The recesses 5 are bounded in the radial direction by the stator 2 and the rotor 3, in the circumferential direction of two side walls 6 of the stator 2 and in the axial direction by a first and a second side cover 7, 8. Each of the recesses 5 is sealed pressure-tight manner in this way. The first and second side covers 7, 8 are connected to the stator 2 by means of connecting elements 9, for example screws.

On the outer circumferential surface of the rotor 3 axially extending vane grooves 10 are formed, wherein in each vane groove 10, a radially extending vane 11 is arranged. In each recess 5, a wing 11 extends, wherein the wings 11 in the radial direction on the stator 2 and in the axial direction of the side covers 7, 8 abut. Each wing 11 divides a recess 5 in two mutually opposed pressure chambers 12, 13. In order to ensure a pressure-tight abutment of the wings 11 on the stator 2, 11 leaf spring elements 15 are mounted between the groove bases 14 of the wing grooves 10 and the wings, which the wing 11 in Apply a force to the radial direction.

By means of first and second pressure medium lines 16, 17, the first and second pressure chambers 12, 13 are connected via a control valve, not shown, with a likewise not shown pressure medium pump or a tank, also not shown. As a result, an actuator is formed, which allows a Relatiwerdrehung of the stator 2 relative to the rotor 3. It is provided that either all the first pressure chambers 12 are connected to the pressure medium pump and all second pressure chambers 13 to the tank or the exact opposite configuration. If the first pressure chambers 12 are connected to the pressure medium pump and the second pressure chambers 13 are connected to the tank, then the first pressure chambers 12 expand at the expense of the second pressure chambers 13. This results in a displacement of the wings 11 in the circumferential direction, in the direction indicated by the first arrow 21. By moving the vanes 11, the rotor 3 is rotated relative to the stator 2.

In the illustrated embodiment, the stator 2 is driven by the crankshaft by means of a chain drive (not shown) acting on its drive wheel 4. Also conceivable is the drive of the stator 2 by means of a belt or gear drive. The rotor 3 is non-positively, positively or materially, for example, by means of press fit or by a screw connection by means of a central screw, connected to a camshaft, not shown. From the relative rotation of the rotor 3 relative to the stator 2, as a result of the supply and discharge of pressure medium to and from the pressure chambers 12, 13, resulting in a phase shift between the camshaft and crankshaft. By selective introduction and discharge of pressure medium into the pressure chambers 12, 13, the control times of the gas exchange valves of the internal combustion engine can thus be selectively varied.

The pressure medium lines 16, 17 are designed in the illustrated embodiment as substantially radially arranged bores extending from a central bore 22 of the rotor 3 to the outer circumferential surface. Within the central bore 22, a central valve, not shown, can be arranged, via which the pressure chambers 12, 13 can be selectively connected to the pressure medium pump or the tank. Another possibility is to arrange a pressure medium distributor within the central bore 22, which connects the pressure medium lines 16, 17 via pressure medium channels and annular grooves with the terminals of an externally mounted control valve.

The substantially radially extending side walls 6 of the recesses 5 are provided with formations 23 which extend in the circumferential direction in the recesses 5. The formations 23 serve as a stop for the wings 11 and ensure that the pressure chambers 12, 13 can be supplied with pressure medium, even if the rotor 3 occupies one of its two extreme positions relative to the stator 2, in which the wings 11 on one of the side walls. 6 issue.

With insufficient supply of pressure medium of the device 1, for example during the starting phase of the internal combustion engine, the rotor 3 is due to the alternating and drag torque which exerts the camshaft on this uncontrolled relative to the stator 2 moves. In a first phase, the drag torques of the camshaft urge the rotor relative to the stator in a circumferential direction opposite to the direction of rotation of the stator until they abut the side walls 6. In the following, the alternating moments, which exerts the camshaft on the rotor 3 to a swinging back and forth of the rotor 3 and thus the wing 11 in the recesses 5, until at least one of the pressure chambers 12, 13 is completely filled with pressure medium. This leads to greater wear and noise developments in the device 1. To prevent this, two locking elements 24 are provided in the device 1. Each locking element 24 consists of a cup-shaped piston 26, which is arranged in an axial bore 25 of the rotor 3. The piston 26 is acted upon by a spring 27 in the axial direction with a force. The spring 27 is supported in the axial direction on the one side on a venting element 28 and is disposed with its axial end facing away from inside the pot-shaped executed piston 26.

In the first side cover 7 per link element 24, a link 29 is formed such that the rotor 3 can be locked relative to the stator 2 in a position corresponding to the position during the start of the internal combustion engine. In this position, the piston 26 are urged in insufficient supply of pressure medium of the device 1 by means of the springs 27 in the scenes 29. Furthermore, means are provided to push the piston 26 with sufficient supply of the device 1 with pressure medium in the axial bores 25 and thus cancel the lock. This is usually accomplished with pressure medium, which is passed through pressure medium lines, not shown, into a recess 30, which is formed on the cover-side end face of the piston 26. Corresponds to the phase position φ, which corresponds to the starting position of the internal combustion engine, a center position of the wings 11 between the respective side walls 6, so can a locking of the hydraulic actuator 1a be accomplished in this position by the use of two locking elements 24 and adapted scenes 29.

In order to be able to derive leakage oil from the spring chamber of the axial bore 25, the venting element 28 is provided with axially extending grooves, along which the pressure medium can be directed to a bore in the second side cover 8.

FIG. 8 shows a device 101 for changing the timing of gas exchange valves of an internal combustion engine of the prior art. This consists of a hydraulic actuator 102 and a control valve 103rd
The adjusting device 102 consists of a pressure chamber 104, which is subdivided by a displaceable element 105 into two counteracting pressure chambers 106, 107. The displaceable element 105 is non-rotatably connected to the camshaft or the crankshaft, while the other component is non-rotatably connected to the pressure chamber 104. The displaceable element 105 is immovably connected to two scenes 108, 109. Furthermore, 110 and 111 respectively denotes a locking pin, wherein these are fixedly mounted to the pressure chamber 104. Each link 108, 109 is each associated with a Verrieglungspin 110, 111. Alternatively, the locking pins 110, 111 can move with the element 105 and the scenes 108, 109 may be formed in a stationary to the pressure chamber 104 component.

The control valve 103 consists of an actuating unit 112, a first spring element 113 and a valve body 114. The actuating unit 112 may be designed, for example, in the form of an electric or hydraulic actuating unit 112. In the following, without limitation of generality, an electric actuator 112 is assumed, which is designed as an electromagnet. On the valve body 114, a first working port A, a second working port B, an inflow port P and a drain port T are formed. The first working port A is connected via a first pressure medium line 115 with the first pressure chamber 106 and the second working port B via a second Pressure medium line 116 with the second pressure chamber 107 in conjunction. Furthermore, the outlet connection T is connected to a pressure medium reservoir 117. Via a pressure medium pump 118, a filter 119 and a check valve 120, the inlet port P is subjected to pressure medium. Via a third pressure medium line 121, the first link 108 is in communication with the first pressure medium line 115. Similarly, the second link 109 is connected via a fourth pressure medium line 122 in connection with the second pressure medium line 116. The first and second link 108, 109 are each as a groove formed, wherein the dimension thereof in the direction of movement of the movable member 105 is greater than that of the respective Verrieglungspins 110, 111. Both locking pins 110, 111 engage in the illustrated center position of the displaceable element 105 in the respective link 108, 109 and are in the direction of the movable member 105 disposed at one end of the respective groove.

By means of the adjusting unit 112, the valve against the spring force of the first spring element 113 in a second, a third and a fourth control position 130, 131, 132 are brought. If the valve is located in the second control position 130, which is the case for low to no energization of the setting unit 112, the second working connection B is connected exclusively to the inflow connection P and the first working connection A is connected exclusively to the outflow connection T.
If the valve is in the third control position 131, which is the case with low to medium energization of the setting unit 112, both working connections A, B are connected neither to the inlet connection P nor to the outlet connection T. Alternatively it can be provided that both working ports A, B are connected exclusively to the inlet port P to compensate for leakage losses.
If the valve is in the fourth control position 132, which is the case with average to maximum current supply of the actuating unit 112, the first working port A is connected exclusively to the inflow port P and the second working port B is connected exclusively to the outflow port T.

During controlled operation of the internal combustion engine, the control valve 103 is brought into the second control position 130 in order to achieve an adjustment of the movable element 105 in the direction of late, characterized by the second arrow 126. Pressure medium is passed from the inlet port P via the second working port B and the second pressure medium line 116 to the second pressure chamber 107. At the same time 122 pressure medium is passed into the second gate 109 via the fourth pressure medium line. As a result, the second locking pin 111 is urged against the force of a second spring 129 from the second link 109. At the same time, the first pressure chamber 106 is connected to the pressure medium reservoir 117 via the first pressure medium line 115 and the discharge port T. As a result of the outflow of pressure medium from the first pressure chamber 106 and the inflow of pressure medium to the second pressure chamber 107, the movable element 105 is displaced in the direction of late. At the same time, the first and the second gate 108, 109 are also moved late. In this case, the first locking pin 110 moves within the first link 108, while the second locking pin 111 is located outside of the second link 109.
In order to maintain a phase angle φμ of the hydraulic actuator 102, the control valve 103 is brought into the third control position 131. Both working ports A, B are connected neither to the supply P nor to the drain port T. There is no inflow or outflow of pressure medium to or from the pressure chambers 106, 107 instead and the phase position φ is kept constant.
In order to achieve an adjustment of the movable element 105 in the direction early, characterized by the third arrow 128, the control valve 103 is brought into the fourth control position 132. Pressure medium is passed from the inlet port P via the first working port A and the first pressure medium line 115 to the first pressure chamber 106. At the same time, pressure medium is conducted into the first slide 108 via the third pressure medium line 121. As a result, the first locking pin 110 is urged against the force of a first spring 127 from the first link 108. At the same time, the second pressure chamber 107 is connected via the second pressure medium line 116 and the discharge port T to the pressure medium reservoir 117. By the flow of pressure medium from the second pressure chamber 107 and the inlet of pressure medium to the first pressure chamber 106, the movable member 105 is shifted toward early. At the same time, the first and second scenery 108, 109 are also moved early. In this case, the second locking pin 111 moves within the second link 109, while the first locking pin 110 is located outside the first link 108.
When the movable member 105 is moved from a position different from that in FIG FIG. 8 shown center position deviates over the center position, so locks the locking pin 110, 111, which is not acted upon with pressure medium in the respective backdrop 108, 109 a. At the same time, the other locking pin 110, 111 is acted upon by pressure medium so that it is outside the gate 108, 109. The movement is limited only by the latched locking pin 110, 111.
Is the hydraulic actuator 102 in the in FIG. 8 shown middle position and the device 101 is not supplied with sufficient pressure medium, which is the case for example when starting the internal combustion engine, then both locking pins are engaged in 110, 111 in the respective link 108, 109. In this case, the locking pins 110, 111 are arranged and the scenes 108, 109 designed such that the Verrieglungspins 110, 111 are located at the ends of the scenes 108, 109 which are furthest apart. As a result, the movable element 105 is fixed relative to the pressure chamber 104. Alternatively, the locking pins 110, 111 may be at the ends of the scenes 108, 109 that are closest to each other. In this alternative embodiment, the first slide 108 would have to be acted upon by the second pressure medium line 116 and the second slide 109 by the first pressure medium line 115 with pressure medium. Also conceivable is an action on the scenes 108, 109 via the respective pressure chamber 106, 107, for example by means of a worm groove.

During the stopping process of the internal combustion engine, there is the possibility that the displaceable element 105 is positioned in a late position relative to the center position. When restarting the device 101 is not yet sufficiently filled with pressure medium. Due to the drag torque of the camshaft, the element 105 is driven in the direction of the late stop 133 and strikes there at. This leads to increased wear of the components and unpleasant noise.

If the actuator 112 of the control valve 103 fails, the power supply is interrupted, for example, by a defect in the electromagnet or the power connections, the control valve 103 is set in the second control position 130. As a result, the second locking pin 111 is unlocked and the camshaft is retarded relative to the crankshaft. This has the consequence that the starting and running characteristics of the internal combustion engine, which in the in FIG. 8 center position are optimal, deteriorate.

The schematically illustrated hydraulic adjusting device 102 may be, for example, an axial piston adjuster or a rotary piston adjuster. In the following, only the embodiment of a rotary piston adjuster is to be treated without limiting the generality. The pressure chamber 104 corresponds to the recesses 5 FIG. 1 , The movable member 105 the wings 11. The locking pins 110, 111 may in the embodiment of FIG. 1 either in a side cover of the rotary piston adjuster or in the rotor of the rotary piston adjuster within a bore, preferably a blind hole. The respective scenes 108, 109 are formed in the respective other component.

In FIG. 4 a device 101 according to the invention is shown schematically, analogously to FIG. 8. This is mostly with the in FIG. 8 shown identical, which is why the same reference numerals have been used for the same components. The difference of the device 101 according to the invention is that the control valve 103 additionally has a first control position 140. The first control position 140 is activated when the actuator 112 assumes a state corresponding to a low to no energization. The first spring element 113 ensures in this case that the first control position 140 is reached. In this position, neither the first nor the second working port A, B is connected to the inlet port P. Depending on the configuration of the Hydraulic actuator 102 can now either the first or the second working port A, B are connected to the drain port T, while the other working port A, B does not communicate with the drain port T. Also conceivable is an embodiment in which, in the first control position 140, the first and the second working port A, B communicate neither with the inlet port P nor with the outlet port T or both working ports A, B communicate exclusively with the outlet port T.
In addition to the first control position 140, the control valve 103 also has the in FIG. 8 shown second, third and fourth control positions 103, 131.132, wherein the second control position 130 at a low to medium energization, the third control position 131 at a medium to high energization and the fourth control position 132 at a high to maximum current, the actuator 112 occupied becomes.
In the event of a defect of the actuator 112 or an error in the power supply, the control valve 103 automatically enters the first control position 140, wherein the switching valve 103 holds this position until the repair of the actuator 112 and their power supply. After a restart of the internal combustion engine 102, the movable member 105 is moved regardless of its position on switching off the internal combustion engine due to the drag and alternating torques in the middle position due to the insufficient pressure medium supply. There, both locking pins 110, 111 in the respective link 108, 109 einriegeln, whereby the position of the movable member 105 is fixed in the pressure chamber 104. Due to the configuration of the first control position 140, no pressure medium is supplied to the pressure chambers 106, 107 and thus to the scenes 108, 109 during operation of the internal combustion engine. This has the consequence that the movable element 105 is held stationary relative to the pressure chamber 104 and thus the phase angle φ between the camshaft and crankshaft is kept constant in the emergency running position in which the internal combustion engine has good starting and running properties.

The FIGS. 5a to 5d The valve body 114 is designed substantially hollow-cylindrical, wherein in the outer circumferential surface of which are formed three axially spaced annular grooves 143, 144, 145. The valve body 114 has a valve body 114 , Each of the annular grooves 143 to 145 is a port of the valve, wherein the axially outer annular grooves 143, 145, the working ports A, B and the middle annular groove 144, the inlet port P. A drain port T is through an opening in an end face of the valve housing 141 executed. Each of the annular grooves 143 to 145 is connected to the inner of the valve housing 141 via first radial openings 146. Within the valve housing 141, a substantially hollow cylindrical executed control piston 142 is arranged axially displaceable. The control piston 142 is acted upon by a second spring element 147 on one end face and by a push rod 148 of the setting unit 112 on the opposite end face. By energizing the actuator 112, the control piston 142 can be moved against the force of the second spring element 147 in an arbitrary position between a first and a second end stop 149, 150.
The control piston 142 is provided with a first and a second annular web 151, 152. The outer diameter of the annular ribs 151, 152 are adapted to the inner diameter of the valve housing 141. Furthermore, in the control piston 142 between the frontal end, on which engages the push rod 148, and the second annular web 152 second radial openings 146a are formed, whereby the interior of the control piston 142 is in communication with the interior of the valve housing 141. The first and the second annular web 151, 152 are formed and arranged on the outer circumferential surface of the control piston 142, that control edges 153 to 156 in dependence on the position of the control piston 142 relative to the valve housing 141, a connection between the inlet port P and the working ports A, B. enables or blocks and enables or blocks a connection between the working ports A, B and the drain port T. The outer diameter of the control piston 142 is in the areas between the push rod 148 and the second annular rib 152 and between the first annular rib 151 and the second annular rib 152 made smaller than the inner diameter of the valve housing 141. As a result, a fourth annular groove 157 is formed between the first and the second annular rib 151, 152. Within the fourth annular groove 157, a third annular rib 158 is formed. The outer diameter of the third annular web 158 is adapted to the inner diameter of the valve housing 141. Furthermore, the third annular web 158 is positioned such that in the first control position 140 of the control valve 103 it blocks the connection between the feed port P and the second working port B.

FIG. 5a shows the first control position 140 of the control valve 103, in which the control piston 142 is acted upon by the actuating unit 112 via the push rod 148 with a force between a minimum force and a small F ₁ . The plunger-side end face of the control piston 142 is located in a region between the first end stop 149 (displacement distance = 0 mm) and a displacement path S ₁ . The connection between the inlet connection P and the second working connection B is blocked by the third annular web 158 and the connection between the inlet connection P and the first working connection A through the first annular web 151. Furthermore, the connection between the second working port B and the discharge port T is blocked by means of the second annular web 152, while pressure fluid can flow from the first working port A to the discharge port T. Since the pressure medium flow to both locking pins 110, 111 and to both pressure chambers 106, 107 is blocked, no active adjustment can take place in the first control position 140. By the connection of the first pressure chamber 106 with the reservoir 11, this is emptied. Depending on the position of the hydraulic actuator 102, the movable member 105 is immediately, or after a certain time required to empty the second pressure chamber 107 due to leakage driven due to drag or alternating torques of the camshaft in the center position and locked there permanently ,
This control position corresponds to a configuration of the control valve 103 in which the actuator 112 is de-energized and consequently the control piston 142 is displaced by means of the second spring element 147 to the first end stop 149 is, the displacement is thus zero. In this position, the valve is when the actuator 112 is defective or their power supply is interrupted.

FIG. 5b shows the second control position 130 of the control valve 103, in which the control piston 142 is acted upon by the adjusting unit 112 via the push rod 148 with a force between a small force F ₁ and an average force F ₂ , wherein F ₂ > F ₁ . As a result, the control piston 142 is displaced by a distance S ₁ to S ₂ from the push rod-side first end stop 149, S ₂ > S ₁ . The first ring land 151 further blocks the connection between the first working port A and the inflow port P while still allowing pressure fluid to flow from the first working port to the drain port T. Furthermore, the second annular rib 152 blocks the connection between the second working port B and the drain port T, while both the second and the third annular ribs 152, 158 release a connection between the inflow port P and the second working port B. In this position, pressure medium is supplied via the second working port B, the second and fourth pressure medium line 116, 122 of the second pressure chamber 107 and the second link 109, whereby the second locking pin 111 is unlocked and the hydraulic adjusting device 102 retards the direction. At the same time, pressure medium flows from the first pressure chamber 106 via the first pressure medium line 115 to the first working port A and from there to the discharge port T.

FIG. 5c shows the third control position 131 of the control valve 103, in which the control piston 142 is acted upon by the adjusting unit 112 via the push rod 148 with a force between a middle F ₂ and a large force F ₃ , wherein F ₃ > F ₂ . As a result, the control piston 142 is displaced by a distance S ₂ to S ₃ from the push rod-side first end stop 149, S ₃ > S ₂ . In this position of the switching valve, the first and the second annular web 151, 152 block the connections between the working ports A, B and the inlet port P and the connections between the working ports A, B and the drain port T. In this position of the control valve 103 is neither pressure means to the pressure chambers 106, 107, nor can Pressure fluid from the pressure chambers 106, 107 drain. This control position thus corresponds to a holding position in which the phase angle φ between the camshaft and the crankshaft is kept constant.

FIG. 5d shows the fourth control position 132 of the control valve 103, in which the control piston 142 is acted upon by the adjusting unit 112 via the push rod 148 with a force between a large force F ₃ and a maximum force F ₄ , wherein F ₄ > F ₃ . As a result, the control piston 142 is displaced by a distance S ₃ to S ₄ from the push rod-side first end stop 149, S ₄ > S ₃ . In this configuration, the first ring land 151 blocks communication between the first work port A and the drain port T, while the communication between the port port P and the first work port A is released from both the first ring land 151 and the third land land 158. Furthermore, the connection between the inlet connection P and the second working connection B is blocked by the second annular web 152, while pressure medium can reach the interior of the control piston 142 and from there to the discharge connection T via the second working connection B and the second radial openings 146a. In this position, the control valve 103 pressure medium from the second pressure chamber 107 via the second pressure medium line 116 to the second working port B and from there to the drain port T is passed. At the same time via the first working port A, the first pressure medium line 115 and the third pressure medium line 121 pressure medium to the first pressure chamber 106 and the first slide 108 passed. Thereby, the first locking pin 110 is unlocked and the hydraulic actuator 102 moves to early.

By using the described 4/4-way valve, as the control valve 103 of the device 101 according to the invention, no additional modules, such as additional control valves needed to represent a device 101 with center-position locking, which starts automatically in a locked center position, wherein an abutment of the element 105 (wing with Vane adjusters) stops at a stop. Neither the space, nor the manufacturing or assembly costs are compared to the in the Technique described embodiment increases. At the same time the device 101 is brought in case of failure of the actuator 112 in the center position and locked there until the repair of the actuator 112.

FIG. 6 represents the volume flow from the inlet port T to the pressure chambers 106, 107 as a function of the duty cycle of the actuator 112. The actuator 112 may be supplied with a voltage, wherein either zero volts or a maximum value is applied. The duty cycle indicates the proportion of the time in which the maximum value of the voltage is present at the setting unit 112. The higher the duty cycle, the higher the force exerted by the actuator 112 via the push rod 148 on the control piston 142. Thus, the duty cycle is a measure of the displacement of the spool 142 within the valve housing 141 relative to the first end stop 149.
In a first region in which the duty cycle lies between zero and a first value TV 1, the control valve 103 assumes the first control position 140. In this control position 140, the connections between the inlet connection P and the working connections A, B are blocked, the volume flow is apart from leakage flows 0.
If the duty cycle lies between a first value TV 1 and a second value TV 2, the control valve 103 is in the second control position 130. Pressure medium can reach the second working port B from the inlet port P, while the connection between the inlet port P and the first working port A Is blocked. The volumetric flow increases steadily as the duty cycle increases from a first value TV 1 to a third value TV 3, while when increasing further up to the second value TV 2 it steadily decreases and finally near the value TV 2 it is close to zero. Advantageously, only the area between TV3 and TV2 is used for the second control position 130.
In a third range between the value TV 2 and a value TV 4, duty cycles which are in this range are referred to below as the hold duty ratio, the duty cycle is the volume flow almost zero. This area corresponds to the third control position 131 of the control valve 103, in the two working ports A, B are not in communication with the inlet port P.
If the value of the duty cycle, starting from the value TV 4, is further increased to 100%, then the volume flow from the feed port P to the pressure chamber 106, 107 initially increases steadily. The volume flow can rise steadily up to a duty factor of 100%, or, for design reasons, can go through a maximum. This area corresponds to the fourth control position 132 of the control valve 103, is conducted in the pressure medium from the inlet port P to the first working port A, while the connection between the inlet port P and the second working port B is blocked.

In addition to the advantage that in case of failure of the actuator 112 at a restart of the internal combustion engine, the hydraulic actuator 102 is locked in a central position and this lock is held, the device 101 of the invention allows for intact actuator 112 locking the hydraulic actuator 102 in the center position when switching off the internal combustion engine or a positioning of the hydraulic actuator 102 such that upon restart of the internal combustion engine, the hydraulic actuator 102 is brought into the center position and locked there. This has the advantage that during the starting operation, in which the device 101 is not yet sufficiently filled with pressure medium, the hydraulic adjusting device 102 is securely locked in the center position, whereby a striking of the displaceable element 105 is avoided on a side wall of the pressure chamber 104, whereby increased wear and noise is avoided.

$$\mathrm{TV}\mathrm{2}\mathrm{=}{\mathrm{TV}}_{\mathrm{Halte}}\mathrm{-}\mathrm{Y}\mathrm{2}\mathrm{,}$$

$$\mathrm{TV}\mathrm{3}\mathrm{=}{\mathrm{TV}}_{\mathrm{Halte}}\mathrm{-}\mathrm{Y}\mathrm{3.}$$

To operate the internal combustion engine, the different duty cycles, in particular TV1 to TV3 and the hold duty cycle TV _{hold must be known to} the engine control unit. The hold duty ratio is determined by the engine control unit as standard and stored in a memory unit. For the determination of TV1, TV2 and TV3 two possibilities are conceivable.
About the structural design and the consequent valve characteristics TV1, TV2 and TV3 can in direct dependence on the holding load ratio TV _hold be determined. The difference angle Y ₁ . Y ₂ and Y ₃ are permanently stored in a memory unit. The engine control unit determines the hold duty ratio TV _hold at an early stage of the operation of the internal combustion engine. For TV1, TV2 and TV3 then: $$\mathrm{TV}\mathrm{1}\mathrm{=}{\mathrm{TV}}_{\mathrm{holding}}\mathrm{-}\mathrm{Y}\mathrm{1}\mathrm{.}$$

$$\mathrm{TV}\mathrm{2}\mathrm{=}{\mathrm{TV}}_{\mathrm{holding}}\mathrm{-}\mathrm{Y}\mathrm{2}\mathrm{.}$$

$$\mathrm{TV}\mathrm{3}\mathrm{=}{\mathrm{TV}}_{\mathrm{holding}}\mathrm{-}\mathrm{Y}\mathrm{Third}$$

A second way is to have TV1 and TV2, optionally after each restart, determined by the engine control unit and store in the map. To determine TV1 and TV3, the camshaft angle signals and crankshaft angle signals can be used. Above all, the relative phase angle of the two waves and the temporal change of the phase position can be used for this purpose. For example, the following method can be used. A ramp of the duty cycle of 0% is increased. The value TV1 is reached when an adjustment operation starts (at this point, one of the pressure chambers 106, 107 and a lock pin 110, 111 is pressurized and the hydraulic actuator is displaced, which can be detected via camshaft angle sensors and crankshaft angle sensors). The value TV3 is reached when a maximum adjustment speed is exceeded. TV2 is reached when the phase position is kept constant. The determined values are then stored in a memory.

FIG. 7 FIG. 12 shows a flowchart of a method for controlling the device 101 according to the invention during a stopping operation of the internal combustion engine, by which the hydraulic adjusting device 102 is brought into a position in which it is either locked or in a position after the stop of the internal combustion engine the restart of the internal combustion engine is moved directly to the center position and locked there.
When initiating the stopping process of the internal combustion engine, the rotational speed n> zero. The phase angle φ between the camshaft and the crankshaft is with Help the control valve 103 brought into a Abstellphasenlage which differs by a defined amount X of the locking phase position φ _center . The Abstellphasenlage is for a device 101, which is designed without compensation spring, relative to the locking phase position φ _center shifted towards early. The same applies to a device 101 which is equipped with a compensation spring, but whose torque is smaller than the drag torque of the camshaft. For a device 101 with a compensation spring, which exerts a torque which is greater than the drag torque of the camshaft, the parking phase is relative to the locking phase position φ _center shifted late. If the predetermined Abstellphasenlage is reached, the ignition is turned off and the value of the duty cycle is set such that this phase φ is held securely. In the case of setting a postponed Abstellphasenlage the duty cycle is therefore between TV 2 and 100%, in the case of a Abstellphasenlage which is relative to the Verrieglungsphasenlage φ _center moved late between TV 4 and TV3. This duty cycle is maintained until the speed sensors report zero speed. Thereafter, the set duty cycle is held for a certain period Y before finally the actuator 112 is kept de-energized. The hold time of Y prevents the locking pins 110, 111 from being unlocked during the last revolution of the engine during which the speed sensor is already at n = 0, and the movable member 105 is unlocked at the center position due to pressure fluctuations due to the alternating moments is pushed.
The hydraulic actuator 102 is now, either due to the last revolution of the crankshaft, in the locked state or in a position in which it is automatically and immediately driven into the locked position either by the drag torque of the camshaft or the torque of the compensation spring when starting the internal combustion engine ,

FIG. 3 shows a flowchart of a method for starting an internal combustion engine with a device 101 according to the invention, by which it is ensured that an existing or a manufactured during the first revolution of the crankshaft locking of the movable member 105 is held until the oil pressure within the internal combustion engine has risen to a value needed for the safe operation of the device 101. At the beginning of the starting process, the speed n and the duty cycle is zero. As long as the speed sensor reports a speed n = zero, the duty cycle is kept between zero% and the value TV 1. If the speed sensor reports a speed> zero, the value of an oil pressure sensor is read out. As long as the value of the oil pressure p is less than a certain minimum value p _min , which is necessary to safely operate the device 101 according to the invention, the value of the duty cycle is kept between zero% and the value TV 1. Exceeds the oil pressure p the predetermined pressure, the device 101 goes into controlled operation and the duty cycle is adjusted depending on the load condition of the machine between TV 3 and 100%.

The aforementioned embodiments are only exemplary. Of course, the working connections A, B are interchangeable. Also included in the scope of the invention are devices 101 with central position locking of the hydraulic actuator 102, wherein only one locking pin can engage in a slide or a stepped link. Also devices with any locking phasing with one or more locking pins. When considering the volume flows and the connections between different connections of the switching valve, pressure losses due to leakage were neglected. <B> reference numerals </ b> 1 contraption 102 hydraulic actuator 1a hydraulic actuator 103 control valve 2 stator 104 pressure chamber 3 rotor 105 element 4 drive wheel 106 first pressure chamber 5 recesses 107 second pressure chamber 6 Side wall 108 first backdrop 7 first side cover 109 second backdrop 8th second side cover 110 first locking pin 9 connecting element 111 second locking pin 10 vane 112 actuator 11 wing 113 first spring element 12 first pressure chamber 114 valve body 13 second pressure chamber 115 first pressure medium line 14 groove base 116 second pressure medium line 15 Leaf spring element 117 Pressure fluid reservoir 16 first pressure medium line 118 Hydraulic pump 17 second pressure medium line 119 filter 21 first arrow 120 check valve 22 central bore 121 third pressure medium line 23 formations 122 fourth pressure medium line 24 locking element 126 second arrow 25 axial bore 127 first spring 26 piston 128 third arrow 27 feather 129 second spring 28 A vent 130 second control position 29 scenery 131 third control position 30 recess 132 fourth control position 101 contraption 133 late stop 140 first control position 141 valve housing 142 spool 143 ring groove 144 ring groove 145 ring groove 146 first radial openings 146a second radial openings 147 second spring element 148 pushrod 149 first end stop 150 second end stop 151 first ring bridge 152 second ring bridge 153 first control edge 154 second control edge 155 third control edge 156 fourth control edge 157 fourth ring groove 158 third ringbridge P inflow connection T drain connection A first work connection B second work connection φ phasing φ _middle Locking phase X amount Y ₁ difference angle Y ₂ difference angle Y ₃ difference angle TV _hold holding duty p _min oil pressure

Claims (2)

1. Method for controlling a device (101) for varying the control times of gas exchange valves for an internal combustion engine with

   - a hydraulic actuation device (102) which has two reciprocally acting pressure chambers (106, 107),

   - a phase position (ϕ) of a camshaft in relation to a crankshaft being capable of being held or varied in a controlled way by means of the supply and discharge of pressure medium to and from the pressure chambers (106, 107),

   - and with a control valve (103) with two working connections (A, B), with an outflow connection (T) and with an inflow connection (P), the first working connection (A) communicating with the first pressure chamber (106), the second working connection (B) with the second pressure chamber (107) and the outflow connection (T) with a tank, and the inflow connection (P) being acted upon with pressure medium,

   - the control valve (103) being capable of being brought into four control positions (103, 131, 132, 140) by means of an actuation unit (112),

   - in a first control position (140) of the control valve (103), neither the first working connection (A) nor the second working connection (B) communicating with the inflow connection (P),

   - in a second control position (130) of the control valve (103), the first working connection (A) communicating with the outflow connection (T) and the second working connection (B) communicating with the inflow connection (P),

   - in a third control position (131) of the control valve (103), the first and the second working connection (A, B) communicating neither with the outflow connection (T) nor with the inflow connection (P), or the first and the second working connection (A, B) communicating solely with the inflow connection (P),

   - in a fourth control position (132) of the control valve (103), the second working connection (B) communicating with the outflow connection (T) and the first working connection (A) communicating with the inflow connection (P), characterized in that the following method steps are carried out in the order listed during the operation of stopping the internal combustion engine,

   - assumption and holding of a defined phase position ϕ + X°KW,

   - switch-off of the ignition,

   - setting of the second or fourth control position (130, 132) in order to hold the phase position ϕ + X°KW until the rotational-speed sensor arrangement communicates the rotational speed n = 0,

   - detection of the rotational speed n via a rotational-speed sensor arrangement,

   - holding of the assumed control position (130, 132) for a predetermined timespan,

   - after the expiry of the timespan, deactivation of the actuation unit (112).
2. Method according to Claim 1, characterized in that the following method steps are carried out in the order listed during the operation of starting,

   - setting of the first control position,

   - detection of the rotational speed n of the crankshaft or of the camshaft,

   - if the rotational speed is n > 0: detection of the pressure-medium pressure p,

   - if the pressure-medium pressure p is higher than a predetermined value: setting of control positions according to the characteristic diagram filed in the control unit.

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