Valve mechanism with a variable valve opening diameter

Abstract

A valve mechanism with a variable valve opening cross section disposed in a passageway of an internal combustion engine and has a gas exchange valve that is acted on by the force of a valve spring and can be slid back and forth in the axial direction inside a guide by a valve control unit. Coaxial to the gas exchange valve is a seal valve acted on by the force of a coupling spring and can be slid back and forth in the axial direction by the valve control unit. The position of the seal valve in relation to the gas exchange valve in the axial direction can be changed by an adjusting unit.

Description

The invention relates to a valve mechanism with a variable valve opening cross section with the features mentioned in the preamble to claim 1.

PRIOR ART

It is known to use internal combustion engines as the drive engine in motor vehicles. In these engines, an air-fuel mixture is compressed and ignited in a working chamber. The energy produced by this is converted into mechanical work. It is known to supply air and the air-fuel mixture to the working chamber by means of valves (inlet valves) and to evacuate the combustion products from the working chamber by means of valves (outlet valves). Controlling these valves is of considerable importance in determining the efficiency of the internal combustion engine. In particular, the control of the valves controls the gas exchange in the working chamber.

In addition to a camshaft control, another known method is to use an electrohydraulic valve control. The electrohydraulic valve control offers the possibility of a variable or completely variable valve control so that it is possible to optimize the gas exchange and consequently to increase the motor efficiency of the internal combustion engine.

The electrohydraulic valve control includes a hydraulically actuatable control valve, whose control valve piston actuates a valve body of the inlet and outlet valves and moves it toward a valve seat (valve seat ring) (closing of the valve) or moves it away from the seat (opening of the valve). The control valve can be actuated by controlling the pressure of a hydraulic medium. The pressure control in this connection is executed by means of solenoid valves incorporated into the hydraulic circuit. In order to be able to achieve as optimal a gas exchange as possible, it is desirable to achieve the highest possible switching speeds of the control valve. Because of these high switching speeds, the valve body of the inlet and outlet valves strikes the valve seat ring at high speed. On the one hand, this generates noise, and on the other hand, the valve partners experience a relatively high degree of wear.

For example, the subject of EP 0 455 761 B1 is a hydraulic valve control device for an internal combustion engine. The fundamental technical principal of this embodiment lies in moving an engine valve by means of a controlled pressure of a hydraulic fluid. This embodiment includes the provision that an electronic control unit triggers a solenoid valve, which in turn controls the movement of a reservoir piston that changes of the stroke of the engine valve.

EP 0 512 698 A1 describes an adjustable valve system for an internal combustion engine. This embodiment is an example of a mechanical valve control by means of the cams of a rotating camshaft.

The subject of U.S. Pat. No. 4,777,915 is an electromagnetic valve control system for an internal combustion engine. A similar embodiment of an electromagnetic valve control is known from EP 0 471 614 A1. In these embodiments, the valve is moved back and forth into different positions through the use of electromagnetic force. The electromagnets are disposed inside a housing part of the cylinder head, in two different regions. The alternating activation of the electromagnets moves the valve alternatively into two end positions that respectively correspond to the open position and the closed position of the valve. In these end positions of the valve, the opening to allow the passage of the air-fuel mixture into the combustion chamber is open the widest it can go or is completely closed.

Another embodiment is known from EP 0 551 271 B1. This embodiment is a valve mechanism with a disk valve, which is disposed in a passageway of an internal combustion engine. The fundamental principle of this embodiment lies in dividing the valve disk in two, where the first half of the valve disk executes only part of the stroke of the other half of the valve disk.

A particular disadvantage of these embodiments for valve control is the high cost of manufacturing and assembling the valve mechanism due to its complex design. This has a negative effect on the costs of manufacture and assembling. Furthermore, these embodiments require extremely high speeds and powerful forces for valve control, resulting in an inevitable increase in susceptibility to malfunction of the valve control due to a considerable wear on the parts of the valve mechanism.

ADVANTAGES OF THE INVENTION

The valve mechanism according to the invention, with the characterizing features of the main claim, has the advantage over the prior art of achieving a variable valve opening cross section through the use of simple means. The fact that a seal valve is disposed coaxial to the gas exchange valve, is acted on by the force of a coupling spring, and can be slid back and forth in an axial direction by the valve control unit, wherein the position of the seal valve in relation to the gas exchange valve in the axial direction can be adjusted by means of an adjusting unit, which is essentially comprised of a regulating valve and a working cylinder that contains a regulating piston that can be slid by means of a working medium, produces a valve mechanism that has a simple design and functions in a reliable, durable fashion. The advantage of the invention is particularly comprised in that a variable valve opening cross section can be produced, wherein each individual valve can be separately regulated. It is also possible to regulate all of the outlet and inlet valves together or separately by cylinder. The variable valve opening cross section can advantageously be produced with the valve mechanism according to the invention, without producing high speeds and without powerful forces so that this valve mechanism has an extremely low susceptibility to malfunction. Due to its simple design, the valve mechanism according to the invention can be inexpensively manufactured and assembled. The invention advantageously achieves a variable valve control that makes it possible to optimize the gas exchange and consequently to increase the motor efficiency of the internal combustion engine.

A preferred embodiment of the invention provides that the valve control unit is a camshaft.

Another preferred embodiment of the invention provides that the gas exchange valve has a rotationally symmetrical basic design and is comprised of a valve shaft, the lower end of which has a valve disk supported on it.

Another preferred embodiment of the invention provides that the valve disk has a conical circumference surface, which constitutes the sealing seat of the gas exchange valve.

Furthermore, a preferred embodiment of the invention provides that in the closed position of the valve mechanism, the sealing seat of the gas exchange valve respectively rests directly against a sealing seat of the seal valve and against a valve seat ring of the cylinder head.

Another preferred embodiment of the invention provides that the seal valve is comprised of a bushing-shaped supporting body, which is disposed so that it can slide axially back and forth inside a guide of the cylinder head.

These advantageous embodiments of the invention permit the supply of the air-fuel mixture to be regulated in a highly precise manner and thus achieve a higher efficiency of the internal combustion engine.

Other advantageous embodiments of the invention ensue from the features disclosed in the dependent claims.

DRAWINGS

The invention will be explained in detail below in an exemplary embodiment in conjunction with the accompanying drawings.

FIG. 1 shows a section through a cylinder head, with the valve mechanism according to the invention and

FIG. 2 shows a perspective view of a seal valve of the valve mechanism according to the invention;

FIG. 3 shows a connection diagram of a hydraulic adjusting unit of the regulating slide valve of the valve mechanism according to the invention and

FIG. 4 is a sectional depiction of a regulating valve of a hydraulic adjusting unit of the regulating slide valve of the valve mechanism according to the invention.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

In the four Figs., the individual parts of the valve mechanism according to the invention are depicted schematically and are only shown with the components that are essential to the invention. The same parts of the valve mechanism according to the invention are given the same reference numerals in the Figs. and as a rule, are only described once.

FIG. 1 shows the valve mechanism according to the invention in its position in the cylinder head 18 of an internal combustion engine. The valve mechanism has a gas exchange valve 12, which is acted on by the force of a valve spring 16. The gas exchange valve 12 can be slid back and forth inside a guide, wherein the sliding motion is produced by a valve control unit. In a preferred embodiment of the invention, a camshaft (not shown) is provided as the valve control unit.

The gas exchange valve 12 has a rotationally symmetrical basic design and is comprised of a valve shaft 14, the lower end of which has a valve disk 20 supported on it. FIG. 1 shows the valve mechanism in the closed position of the gas exchange valve 12. In this position, the sealing seat 28 of the gas exchange valve 12 respectively rests directly against a sealing seat 30 of the seal valve 10 and against a valve seat ring 22 of the cylinder head 18.

The design and function of gas exchange valves 12 are generally known in and of themselves, so there is no need to discuss them in detail in the context of the current specification.

The invention provides that a seal valve 10 is disposed coaxial to the gas exchange valve 12. The seal valve 10 is acted on by the force of a coupling spring 24 and can be slid axially back and forth. The camshaft that controls the sliding motion of the gas exchange valve 12 also produces the sliding motion of the seal valve 10.

FIG. 2 shows a perspective view of the seal valve 10. The seal valve 10 is essentially comprised of a supporting body 40 and a sealing body 38. The supporting body 40 of the seal valve 10 is bushing-shaped and is contained so that it can slide axially back and forth inside a guide of the cylinder head 18. At the bottom end, the seal valve 10 is provided with a cylindrical sealing body 38 whose outer surface constitutes the sealing seat 30. The sealing seat 38 is connected to the supporting body 40 by means of connecting rods 42.

A stop disk 26 is fastened to the supporting body 40 in the vicinity of its top end. In order to facilitate assembly, this stop disk 26 is comprised of two parts. The two parts of the stop disk 26 are encompassed by a clamping ring 36, which holds them together.

The connection between the sealing body 38 and the supporting body 40 is designed so that sufficient space remains for the air or air-fuel mixture flowing through. Both for the inlet and for the outlet of air or of the air-fuel mixture, this advantageously provides for a through opening inside the seal valve 10 large enough to permit an unhindered flow of this medium.

FIG. 3 shows a connection diagram for a hydraulic adjusting unit with a regulating valve 44, which can be used to regulate the position of the seal valve 10 in relation to the gas exchange valve 12 by means of a regulating piston 46, which is disposed in a sliding fashion inside a working cylinder 52. The regulating valve 44, which is embodied in the form of an intrinsically known 3-way valve, has three separate working chambers, which permit the hydraulic fluid to flow into the working chamber 52 and permit the hydraulic fluid to flow back out of the working chamber 52 or completely shut off the flow of the hydraulic fluid. To this end, the sliding of the regulating valve 44 can bring the working chambers of the regulating valve 44 into three different switched positions A, B, C.

FIG. 4 shows a sectional view of the design of a regulating valve 44 of the hydraulic adjusting unit.

The regulating valve 44 is comprised of a housing 56 with three connections. The connections, respectively, are a pressure connection 60, a return line 54, and a cylinder connection 58. Pressure generated by an oil pump 50 supplies the hydraulic fluid to the regulating valve 44 via the pressure connection 60. The return line 54 permits the hydraulic fluid to flow from the regulating valve 44 to the oil tank 48 (not shown here). The cylinder connection 58 communicates with the working cylinder 52 of the adjusting unit and is used to supply the hydraulic fluid to the working cylinder 52 and to drain hydraulic fluid from the working cylinder 52. The cylinder connection 58 is disposed on the one side of the regulating valve 44, approximately in its middle. The pressure connection 60 and the return line 56 are disposed on opposite sides of the regulating valve 44, close to its respective upstream and downstream ends.

An adjusting pin 90 is supported so that it can be slid axially in the housing 88 of the regulating valve 44. The adjusting pin 90 is connected at one of its ends to a stroke drive unit 84, which generates an axial sliding motion of the adjusting pin 90. The adjusting pin 90 is continuously acted on by the force of a spring 78, which presses a stop connected to the adjusting pin 90 against a support 86 of the housing 88 of the regulating valve 44. At the opposite end of the adjusting pin 90, it is supported so that it can slide in a bore of a sealing seat support 72 of the housing 88 of the regulating valve 44.

A first driver disk 64 and a second driver disk 66 are fastened to the adjusting pin 90 spaced apart from each other. The first driver disk 64 serves to support a first seal valve 68 and the second driver disk 66 serves to support a second seal valve 70, wherein both of the seal valves 68, 70 are supported so that they can slide axially on the adjusting pin 90 and a compression spring 80 is disposed between the two seal valves 68, 70, whose force presses the seal valves 68, 70 into contact with their respective associated driver disks 64, 66. The first seal valve 68 has a conical outer surface, which corresponds to a sealing seat 74 of the housing 88 of the regulating valve 44. The second seal valve 70 also has a conical outer surface, which corresponds to a sealing seat 76 of the sealing seat support 72 of the regulating valve 44.

The valve mechanism shown in FIGS. 1 and 2 functions in the following manner:

The valve control unit, which is a camshaft (not shown) in a preferred embodiment of the invention, can either open or close the gas exchange valve 12. As in a conventional valve gear mechanism, the camshaft pushes down the valve shaft 14 of the gas exchange valve 12 and thus controls the course of movement of the gas exchange valve 12. In this connection, all known methods can be used, which are based on the technical principles of a bucket tappet, a tilting lever, a drag lever, and the like.

The camshaft 44 works against the restoring force of the valve spring 16, which is supported against the cylinder head 18 and against the valve disk 20 that moves along with the gas exchange valve 12. The rotation of the camshaft 44 pushes the gas exchange valve 12 downward, and the sealing seat 28 of the gas exchange valve 12 lifts up from the valve seat ring 22.

The coupling spring 24, which is subjected to a certain degree of initial stress, causes the seal valve 10 to move along with it. The coupling spring 24 is supported against the valve disk 20 and the stop disk 26, which is connected to the seal valve 10. As a result, the sealing seat 28 of the seal valve 10 is pressed against the sealing seat 28 of the gas exchange valve 12. Since an annular gap seal is provided between the sealing body 38 and the valve seat ring 22, only a very slight air quantity (leakage) can travel into the combustion chamber 32.

The gas exchange valve 12 and therefore also the seal valve 10 follow the course of the cam until the stop disk 26 comes into contact with the regulating slide valve 34.

In its starting position, the regulating slide valve 34 can be adjusted in relation to the gas exchange valve 12 in the axial direction of the valve shaft 14. The regulating slide valve 34 here can only be adjusted by means of a corresponding adjusting unit, a preferred embodiment of which, in the form of a hydraulic adjusting unit, is shown in detail in FIGS. 3 and 4. Otherwise, the position of the regulating slide valve 34 inside the valve mechanism remains fixed, even when external forces act on it. There is also the possibility of embodying the adjusting unit in an electric or pneumatic form.

As soon as the stop disk 26 comes into contact with the regulating slide valve 34, then the seal valve 10 can execute no further movement in the opening direction of the gas exchange valve 12. Since the camshaft moves the gas exchange valve 12 further, the sealing seat 28 of the gas exchange valve 12 lifts up from the sealing seat 30 of the seal valve 10, which allows air to travel into the combustion chamber 32. The coupling spring 24 is compressed in the process of this.

If the gas exchange valve 12 is following the closing flank of the camshaft, then the valve spring 16 pushes the gas exchange valve 12 in the closing direction. The sealing seat 28 of the gas exchange valve 12 comes to rest against the sealing seat 30 of the seal valve 10. The seal valve 10 is carried along with the gas exchange valve until the sealing seat 28 of the gas exchange valve 12 comes to rest against the valve seat ring 22 and the gas exchange valve 12 is closed.

The gas exchange valve 12 and consequently also the seal valve 10 follow the course of the cam on the camshaft 44. At a particular moment, the stop disk 26 that is connected to the seal valve 10 comes into contact with the regulating slide valve 34 (state shown in FIG. 1). Then the seal valve 10 can no longer follow the course of the cam on the camshaft 44. The gas exchange valve 12 lifts up from the seal valve 10 and air can travel into the combustion chamber.

Axial shifting of the position of the regulating slide valve 34 by means of an adjusting unit can be used to set when the sealing seat 28 of the gas exchange valve 12 lifts up from the sealing seat 30 of the seal valve 10. This advantageously makes it possible to regulate the opening cross section of the gas exchange valve 12 and consequently also the quantity of the air traveling into the combustion chamber 32.

The hydraulic adjusting unit of the seal valve 10, which is shown in the form of a connection diagram in FIG. 3, functions as follows:

The regulating piston 46 is connected to the regulating slide valve 34 and, like it, can slide in the axial direction of the valve shaft 14 of the gas exchange valve 12. The sliding is executed with the aid of a hydraulic fluid, which travels under a particular pressure into the working cylinder 52 of the adjusting unit in which the regulating piston 46 is contained in a sliding fashion.

If the regulating valve 44 is in the third switched position C, then hydraulic fluid travels into the working cylinder 52 of the adjusting unit. An oil pump 50 supplies the hydraulic fluid through the supply line 54 and into the working cylinder 52. The regulating piston 46 moves upward in the axial direction of the valve shaft 14. This results in the fact that the stop disk 26 (FIG. 1) comes into contact with the regulating slide valve 34 earlier. The seal valve 10 therefore executes a shorter motion so that the valve opening cross section is increased.

FIG. 3 shows the regulating valve 44 of the adjusting unit in the first switched position A. In this first switched position A of the regulating valve 44, hydraulic fluid can travel out of the working cylinder 52 via the return line 56 into the oil tank 48. If the contact disk 26 rests against the regulating slide valve 34, then the prestressing force of the coupling spring 24 acts on the regulating slide valve 34 and presses it downward as long as the regulating valve 44, is in the first switched position A. It is also possible to provide an additional spring between the valve disk 20 and the regulating slide valve 34, which exerts a permanent prestressing force on the regulating slide valve 34. Since the regulating slide valve 34 is now in a lower position, in the next actuation by the camshaft, the stop disk 26 comes into contact with the regulating slide valve 34 at a later point in time. The seal valve 10 thus executes a longer movement so that the valve opening cross section is reduced.

If the regulating valve 44 is disposed in the second switched position B, then the flow of the hydraulic fluid through the working chamber is stopped in both directions. As a result, no hydraulic fluid can flow into the working cylinder 52 and also, no hydraulic fluid can flow out of the working cylinder 52. The position of the regulating piston 46 therefore remains constant.

A preferred embodiment of the invention provides that the regulating valve 44 can be electrically triggered. In this case, the regulating valve 44 is designed so that it is always in the first switched position A without a being supplied with current. This results in the fact that when the regulating valve 44 is without current, the regulating piston 46 is pressed downward and consequently sets the opening cross section of the gas exchange valve 12 to the minimal possible value.

The regulating valve 44 of the adjusting unit of the seal valve 10 shown in FIG. 4 functions as follows:

The hydraulic fluid travels via the pressure connection 60 into the housing 88 of the regulating valve 44. The prestressing force of the spring 78 presses the stop 82 connected to the adjusting pin 90 against the support 86 of the housing 88. The first driver disk 64 lifts the first seal valve 68, which is movably supported on the adjusting pin 90, up from the sealing seat 74 of the housing 88. At the same time, the spring 88 presses the second seal valve 70 against the sealing seat 76 of the sealing seat support 72 of the regulating valve 44.

The fluid can travel from the working cylinder 52 of the adjusting unit, through the cylinder connection 62, and into the return line 56. At the same time, the connection between the pressure connection 60 and the cylinder connection 62 is closed. This corresponds to the first switched position A according to FIG. 3.

The stroke drive unit 84, whose design is known per se to one skilled in the art and is therefore not shown in detail, can exert a force on the adjusting pin 90 in the axial direction.

The exertion of a particular force of the stroke drive unit 84 on the adjusting pin 90 causes the adjusting pin 90 to move in the axial direction. The force of the stroke drive unit 84 that must be exerted in order to bring about this movement depends respectively on the prestressing forces of the spring 78 and the compression spring 80 against which the stroke drive unit 84 must work. The switched position B of the regulating valve 44 (FIG. 3) is achieved by selecting the drive force of the stroke drive unit 84 so that the adjusting pin 90 moves until the compression spring 80 presses the first seal valve 68 against the first sealing seat 74. In this case, the second driver disk 66 has not yet lifted the second seal valve 70 up from the sealing seat 76 of the sealing seat support 72. In this switched position B of the regulating valve 44, the two connections are closed so that no hydraulic fluid can flow.

In order to reach the switched position C of the regulating valve 44 according to FIG. 3, the force that the stroke drive unit 84 exerts on the adjusting pin 90 must be increased. The second driver disk 66 lifts the second seal valve 70 up from the sealing seat of the sealing seat support 72. In this switched position C of the regulating valve 44, hydraulic fluid can travel from the pressure connection 60 into the cylinder connection 62.

In order to achieve the switched positions A, B, and C according to FIG. 3 of the regulating valve 44, it is necessary that the spring forces of the spring 78 and the compression spring 80 as well as the force to be exerted by the stroke drive unit 84 to be precisely matched to one another.

The invention advantageously makes it possible to regulate the opening cross sections of the gas exchange valves 12 of an internal combustion engine either individually or in groups through the use of one adjusting unit. As a result, the embodiment according to the invention is particularly inexpensive.

Claims

1-24. (canceled)

25. In a valve mechanism with a variable valve opening cross section, wherein the valve mechanism is disposed in a passageway of an internal combustion engine and has a gas exchange valve that is acted on by the force of a valve spring and can be slid back and forth in the axial direction inside a guide by a valve control unit, the improvement comprising, a seal valve (10) coaxial to the gas exchange valve (12), acting on the seal valve (10), the seal valve being axially slidable back and forth by the valve control unit, an adjusting unit operable to change the position of the seal valve (10) in relation to the gas exchange valve (12) in the axial direction, the adjusting unit being essentially comprised of a regulating valve (44) and a working cylinder (52) that contains a regulating piston (46) that can be slid by means of a working medium.

26. The valve mechanism according to claim 25, wherein the valve control unit is a camshaft.

27. The valve mechanism according to claim 25, wherein the gas exchange valve (12) has a rotationally symmetrical basic design and is comprised of a valve shaft (14), the upper end of which has a valve disk (20) supported on it.

28. The valve mechanism according to claim 27, wherein the valve disk (20) has a conical circumference surface, which constitutes the sealing seat (28) of the gas exchange valve (12).

29. The valve mechanism according to claim 25, wherein, in the closed position of the valve mechanism, the sealing seat (28) of the gas exchange valve (12) respectively rests directly against a sealing seat (30) of the seal valve (10) and against a valve seat ring (22) of the cylinder head (18).

30. The valve mechanism according to claim 25, wherein the seal valve (10) comprises of a bushing-shaped supporting body (40), which is supported so that it can slide axially back and forth inside a guide of the cylinder head (18).

31. The valve mechanism according to claim 25, wherein the seal valve (10) comprises a bushing-shaped supporting body (40) constituting the guide of the gas exchange valve (12), inside of which guide the gas exchange valve (12) can slide back and forth in the axial direction.

32. The valve mechanism according to claim 25, wherein, at its bottom end, the seal valve (10) has a cylindrical sealing body (38) whose outer surface constitutes the sealing seat (30).

33. The valve mechanism according to claim 25, wherein the seal valve (10) comprises a supporting body (40), and wherein the sealing body (38) is connected to the supporting body (40) by means of connecting rods (42).

34. The valve mechanism according to claim 25, wherein the seal valve (10) comprises a support body, and a stop disk (26) fastened to the supporting body (40) of the seal valve, close to its top end.

35. The valve mechanism according to claim 34, wherein the stop disk (26) is comprised of two parts.

36. The valve mechanism according to claim 35, wherein the two parts of the stop disk (26) are encompassed by a clamping ring (36).

37. The valve mechanism according to claim 25, wherein the working medium of the adjusting unit is a hydraulic fluid.

38. The valve mechanism according to claim 25, wherein the regulating valve (44) is electrically triggered.

39. The valve mechanism according to claim 25, wherein the working medium of the adjusting unit is a hydraulic fluid, wherein the regulating valve (44) is electrically triggered, the regulating valve (44) being operable to produce three different switched positions (A, B, C), of which the first switched position (A) opens the return flow of hydraulic fluid and the third switched position (C) opens the inflow of hydraulic fluid, while the second switched position (B) shuts off the flow of the hydraulic fluid.

40. The valve mechanism according to claim 39, wherein the regulating valve (44) can trigger a working cylinder (52), which contains the regulating piston (46) in a sliding fashion, wherein the regulating piston (46) is connected to the regulating slide valve (34) of the valve mechanism.

41. The valve mechanism according to claim 40, wherein the regulating valve (44) is essentially comprised of a housing (88) that has a central working chamber (92) with three connections, wherein an adjusting pin (90) that can slide axially is disposed inside the working chamber (92).

42. The valve mechanism according to claim 41, wherein the three connections of the central working chamber, respectively, are a pressure connection (60), a return line (56), and a cylinder connection (58).

43. The valve mechanism according to claim 42, wherein the pressure connection (60) is connected to an oil pump (50), the return line (56) is connected to an oil tank (48), and the cylinder connection (58) is connected to a working cylinder (52) of the adjusting unit.

44. The valve mechanism according to claim 43, wherein the adjusting pin (90) is acted on by the force of a spring (78) and is connected to a stroke drive unit (84).

45. The valve mechanism according to claim 44, wherein further comprising a first driver disk (64) and a second driver disk (66) fastened to the adjusting pin (90) spaced apart from each other and serve to support a first seal valve (68) and a second seal valve (70), wherein both of the seal valves (68, 70) are supported on the adjusting pin (90) in an axially sliding fashion and a compression spring (80) is disposed between the two seal valves (68, 70), whose force can bring the seal valves (68, 70) into contact with their respective associated driver disks (64, 66).

46. The valve mechanism according to claim 45, wherein the first seal valve (68) has a conical outer surface, which corresponds to a sealing seat (74) of the housing (88), and the second seal valve (70) has a conical outer surface, which corresponds to a sealing seat (76) of the sealing seat support (72) of the regulating valve (44).

47. The valve mechanism according to claim 45, wherein characterized in that the through openings of the working chamber (92) to the return line (56) and/or to the pressure connection (50) can be closed depending on the axial position of the adjusting pin (90).

48. The valve mechanism according to claim 25, wherein the motor oil that is present can be used as the hydraulic fluid of the adjusting unit.