EP1937944A1

EP1937944A1 - Hydraulic directional valve

Info

Publication number: EP1937944A1
Application number: EP06793340A
Authority: EP
Inventors: Jens Hoppe; Andreas Röhr
Original assignee: Schaeffler KG
Current assignee: IHO Holding GmbH and Co KG
Priority date: 2005-10-12
Filing date: 2006-09-07
Publication date: 2008-07-02
Also published as: CN101287894B; CN101287894A; KR20080048530A; US20080245983A1; US7959128B2; JP2009511837A; DE102005048732A1; KR101292388B1; WO2007042361A1

Abstract

The invention relates to an electromagnetic actuating unit (10) of a hydraulic directional valve (9) having an armature (18) which is arranged such that it can be axially displaced within an armature space (30) and having a pole core (29) which is arranged in a receptacle (27a) and delimits the armature space (30) in a movement direction of the armature (18). Means are proposed for avoiding deposits on a guide face of the armature (18), as a result of which the dynamics and the response behaviour of the actuating unit (10) are increased and hysteresis effects and the risk of a functional disruption of the actuating unit are minimized.

Description

Name of the invention

Hydraulic directional valve

description

Field of the invention

The invention relates to an electromagnetic actuator of a hydraulic directional control valve with an armature which is arranged axially displaceably within an armature space and a pole core, which is arranged in a receptacle and limits the armature space in a direction of movement of the armature.

Such directional control valves are used in internal combustion engines, for example for the control of hydraulic Nockenwellenverstellem. The directional control valves consist of an electromagnetic actuator and a valve section. The valve section represents the hydraulic section of the directional control valve, wherein at least one inlet connection, at least one working connection and a tank connection are formed on the latter. By means of the electromagnetic actuating unit, certain connections of the valve section can be hydraulically connected to one another and thus the pressure medium flows can be directed.

Such directional control valves may be integrally formed, wherein the electromagnetic actuator is fixedly connected to the valve portion. In these cases, the directional control valve is positioned in a receptacle formed, for example, on a cylinder head or a cylinder head cover, and connected via pressure medium lines to the pressure chambers of the camshaft adjuster. In a further embodiment, the electromagnetic setting unit and the valve portion are designed as separate components, wherein the valve portion is arranged radially within an inner rotor of the camshaft adjuster. It is conceivable, for example, to arrange the valve section within a receptacle which is connected to the inner rotor, a camshaft or a drive. extension of the camshaft is formed. The valve portion is arranged coaxially with the camshaft and the inner rotor in this case and rotates together with these about the common axis of rotation.

In the axial direction to the valve portion, the electromagnetic Stellein- unit is arranged, which is fixedly fixed, for example, to a chain case or the like. The electromagnetic actuator controls the axial position of a push rod, which in turn controls the axial position of a control piston of the valve portion.

For the use of a directional control valve for controlling a camshaft adjuster, this is normally designed as a 4/3 or 4/2 proportional directional control valve. Such a proportional valve is known for example from DE 102 1 1 467 A1. The electromagnetic actuator in this case consists of a magnetic yoke (pole core), a coil, a housing, an armature and a connecting element, which receives an electrical plug connection, which serves to supply power to the coil.

The coil and the pole core are arranged coaxially with each other within the housing of the electromagnetic actuator. Within the coil, an armature space is formed, which is bounded in the radial direction by the Umsphtzung of the coil and in the axial direction at one end of the housing and the other end of the received in the armature space pole core. Within the armature space an axially displaceable armature is arranged, on which a push rod is fixed, which engages through an opening of the pole core and is supported in this opening in the radial direction. The armature, the housing and the pole core form a flux path for the magnetic flux lines, which are caused by energizing the coil.

The valve section consists of a valve housing and a control piston arranged axially displaceable therein. The valve housing is designed as a central screw, which is arranged within an inner rotor of a camshaft adjuster and rotatably connected to a camshaft. On the inner rotor is rotatably mounted to this outer rotor angeord- net, which is in the illustrated embodiment by means of a chain drive in drive connection with a crankshaft.

On the outer lateral surface of the valve housing, a plurality of pressure medium connections are formed, which serve as inlet, outlet connection and working connections. The working connections communicate with counteracting pressure chambers formed within the camshaft adjuster. In the interior of the valve housing, a control piston is arranged axially displaceable, wherein the outer diameter of the control piston is adapted to the inner diameter of the valve housing. On the outer circumferential surface of the control piston annular grooves are formed, via which adjacent pressure medium connections can be connected to each other.

By energizing the coil, the armature is urged in the direction of the pole core, wherein this movement is transmitted by means of an anchor rod attached to the control piston. This is now moved in the axial direction against a spring supported on the valve housing, whereby the pressure medium flow is controlled from the inlet port to one of the working ports and from the other working port to the drain port. As a result, the pressure chambers of the camshaft adjuster pressure medium to be supplied or discharged therefrom, whereby the phase angle of the camshaft can be varied to form a crankshaft.

In order to ensure a smooth axial displacement of the armature during operation, it is provided the armature space to supply a small amount of lubricant. This is achieved by allowing low leakage of engine oil into the actuator. During the life of the actuator, the low circulation of lubricant in the actuator results in deposits, such as aged engine oil, or debris settling on the tread of the armature or oil sludge accumulating within the actuator. This leads to a deteriorated response of the actuator, higher hysteresis and lower dynamics and can lead to the terminals of the armature and thus the failure of the actuator and thus the camshaft adjuster. Summary of the invention

The invention is therefore based on the object to avoid these disadvantages and thus to provide an electromagnetic actuator, which permanently has a high response and high dynamics with low hysteresis, the life increases and costs and production costs are reduced or at least not increased should.

According to the invention, the object is achieved in that at least one outflow channel is provided which communicates with both the armature space and with the exterior of the setting unit.

Furthermore, it can be provided that with the armature, a push rod is connected, which extends through an opening in the pole core and is radially supported by this.

An armature space of the setting unit is at least partially surrounded in the radial direction and in the axial direction by a coil, which can be energized via a connecting element. Within the armature space an axially displaceable armature is arranged, which is mounted on a the outer contour of the armature adapted guide surface. The axial position of the armature within the armature space can be adjusted by energizing the coil targeted. The guide surface may be formed, for example, by an armature guide sleeve which is at least partially supported by a reversion of the coil, or by the reversion itself. In an axial direction of the armature, preferably in a direction facing the valve portion, the armature space is bounded by a pole core. The pole core is arranged in a receptacle which can be formed, for example, by the armature guide sleeve, the encapsulation of the coil or in a housing which at least partially surrounds the actuating unit. The pole core, for example, by means of a press fit in the recording rotatably and fixedly secured. The actuator is secured by means formed on the housing retaining tabs on a surrounding structure, such as a chain case, wherein the Retaining tabs are arranged and designed such that the actuating unit can be mounted only in one orientation to the surrounding structure.

The movement of the armature is transmitted by means of a plunger rod connected to this on a control piston of an axially arranged actuator unit valve section. In this case, the push rod passes through an opening formed on the pole core, in which the push rod is radially supported and axially guided. In order to achieve a high response dynamics and low hysteresis effects, it is provided to supply the armature space with a small amount of lubricant, in the form of engine oil, during operation of the internal combustion engine. According to the invention, it is proposed to form an outflow at the setting unit, via which the engine oil in the armature space can be led out of the setting unit. As a result, a flushing effect occurs within the armature space. This prevents deposits on the guide surface or the armature, for example aged engine oil or foreign bodies, from depositing. Furthermore, foreign matter, for example, original dirt of the internal combustion engine or abrasion, flushed out of the actuator and prevents accumulation of oil sludge within the actuator. As a result, the movement of the armature in the armature space against a lower resistance and there is no risk of jamming of the armature. The response and dynamics of the armature movement remain permanently high and hysteresis effects and the risk of failures are significantly reduced.

In a concretization of the invention it is provided that the drainage channel opens at a geodetically lowest point in the anchor space. Characterized in that the mouth of the drainage channel is provided in the armature space at a point at which the engine oil in the control unit collects due to gravity, the actuator is emptied functionally reliable in the most critical phases, the operating pauses of the internal combustion engine. In these phases of operation, the engine oil is not continuously circulated because the armature does not move. Deposition effects are preferably carried out in these phases. The complete, autonomous emptying of the actuator eliminates this risk.

In an advantageous development of the invention, it is provided that the outflow channel opens into a chain box.

In the case of chain-driven camshaft adjusters the actuator passes through a flange portion of a chain box. In order to prevent the engine oil discharged from the setting unit from getting into the engine compartment of a vehicle, it must be ensured that it is returned without leakage to the crankcase of the internal combustion engine. An inexpensive solution is achieved in that the drainage channel also extends through the opening of the flange portion of the chain box and opens into the interior thereof.

In a concretization of the invention is provided to form the drainage channel as a drain hole in the pole core. Alternatively it can be provided to form the drainage channel between the pole core and a wall of the receptacle of the pole core. It can be provided that the outflow channel is formed as an axial groove on an outer circumferential surface of the pole core or on an inner circumferential surface of a wall of the receptacle. Alternatively, the pole core can be fastened non-positively within a receiving opening of a housing, wherein the drainage channel is formed as an annular channel between the pole core and the receptacle and a recess on an inner circumferential surface of the receiving opening, a recess on the outer lateral surface of the PoI- core or a housing opening with the Outside the actuator communicates.

The proposed embodiments represent cost-effective or cost-neutral solutions to be implemented, which do not or hardly increase the production cost. During the manufacture of the components, the drainage channel may be taken into account by minor modifications to the production tool. Furthermore, it can be provided that the setting unit controls a directional valve designed as a central valve, wherein the directional control valve is arranged radially inside an inner rotor of a device for variably setting the control times of an internal combustion engine.

Brief description of the drawings

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

1 shows a camshaft adjuster mounted on a camshaft with a central valve designed as a directional control valve in longitudinal section,

2a shows a first embodiment of an actuating unit according to the invention in longitudinal section,

FIG. 2b shows a plan view of the setting unit according to the invention from FIG. 2a along the arrow IIB,

3a shows a further embodiment of an actuating unit according to the invention in longitudinal section,

FIG. 3b shows a plan view of the setting unit according to the invention from FIG. 3a along the arrow HIB,

FIG. 4 a shows a further embodiment of an actuating unit according to the invention in longitudinal section,

4b shows a plan view of the setting unit according to the invention from FIG. 4a along the arrow IVB, FIG. 5a shows a further embodiment of an actuating unit according to the invention in longitudinal section,

FIG. 5b shows a plan view of the setting unit according to the invention from FIG. 5a along the arrow VB,

FIG. 6a shows a further embodiment of an actuating unit according to the invention in longitudinal section,

Figure 6b is a plan view of the actuator according to the invention from Figure 6a along the arrow VIB.

Detailed description of the drawing

FIG. 1 shows a camshaft adjuster 1, which is arranged on a drive-side end of a camshaft 2. The camshaft adjuster 1 consists of an inner rotor 3, an outer rotor 4 and two side covers 5. The inner rotor 3 is rotatably connected to the camshaft 2 and arranged coaxially with the outer rotor 4. The side covers 5 limit the camshaft adjuster 1 in the axial direction. On an inner circumferential surface of the outer rotor 4 recesses 6 are provided which are limited by the outer rotor 4, the inner rotor 3 and the side covers 5 pressure-tight. On an outer circumferential surface of the inner rotor 3 wings 7 are arranged, each wing 7 engages in one of the recesses 6 and divides them into two oppositely acting pressure chambers.

A formed on an outer circumferential surface of the outer rotor 4 sprocket 8, the outer rotor 4 is in driving connection with a crankshaft, not shown. Via a hydraulic adjusting device formed by the pressure chambers and the wings 7, the torque transmitted to the outer rotor 4 of the crankshaft is transmitted to the inner rotor 3 and thus the camshaft 2. By pressure medium supply or removal to or from individual Pressure chambers can be adjusted or maintained a phase angle between the outer rotor 4 and the inner rotor 3 within a certain angular range. As a result, the phase angle of the camshaft 2 relative to the crankshaft is variably adjustable within a certain range. The design of such camshaft adjuster 1 and its operation are well known to the skilled person and described for example in DE 103 55 502 A1.

For controlling the phase position of the camshaft 2 relative to the crankshaft, a hydraulic directional valve 9 is provided, which consists of an electromagnetic actuator 10 and a valve portion 1 1. The directional control valve 9 is formed as a central valve, wherein the valve portion 11 is disposed radially within the inner rotor 3 and coaxially thereto and can either rotate about the common axis of rotation with this or stand still.

The valve portion 1 1 is composed of a valve housing 12 and a control piston 13, wherein the valve portion 1 1 is disposed within the hollow camshaft 2. The essentially hollow-cylindrical valve housing 12 has two working ports A, B, an inlet connection P and two outlet connections T. Within the valve housing 12, the control piston 13 is received axially displaceable. By properly positioning the control piston 13 relative to the valve housing 12, each of the working ports A, B can be connected to either the inlet port P or the drain port T. The working ports A, B are connected via pressure medium lines 14 with the pressure chambers in hydraulic communication. By suitable positioning of the control piston 13 within the valve housing 12 can selectively pressure chambers of the camshaft adjuster 1 is supplied to pressure medium and discharged therefrom and thus the phase angle of the camshaft 2 are adjusted relative to the crankshaft.

The still to be explained in more detail electromagnetic actuator 10 is arranged in the axial direction of the camshaft 2 and the valve portion 1 1. In the illustrated embodiment, the actuator 10 passes through a Flanschab- cut 15b of a chain case 15 with this is screwed on retaining tabs 16 stationary and rotationally fixed. In this case, a plurality of retaining tabs 16 are provided, which are arranged such that the adjusting unit 10 can be mounted only in a defined orientation to the chain case 15. The outer diameter of the adjusting unit 10 encompassing housing 26 is adapted to the inner diameter of the opening of the flange portion 15b, wherein at the sealing point between the components, a first sealing element 15a is arranged. By means of a push rod 17, the axial movement of an armature 18 can be transmitted to the control piston 13 and this are thus displaced in the axial direction against the force of a spring element 19. As a result, the hydraulic connections between the working ports A, B, the inlet port P and the outlet ports T can be controlled in a targeted manner and thus influenced the phase position of the camshaft 2 relative to the crankshaft.

Based on Figure 2a, the structure of the electromagnetic actuator 10 and its operation is explained below.

The electromagnetic actuating unit 10 has a coil body 20 and a connecting element 21 formed integrally therewith. The bobbin 20 carries a coil 22 consisting of several turns of a suitable wire and is at least partially surrounded by a reversion 23 of non-magnetizable material. On the camshaft side facing away from the bobbin 20, a magnetic yoke 24 is arranged, which has a disc-like and a sleeve-like portion 24a, 24b in the illustrated embodiment. The sleeve-like portion 24b engages in a cavity radially within the encapsulation 23 of the coil 22, wherein the outer diameter of the inner diameter of the encapsulation 23 is adapted. The plate-like section 24a abuts the encapsulation 23 in the axial direction and thus determines the axial position of the magnetic yoke 24. Alternatively, it is also conceivable to integrate the sleeve-like section 24b in the production of the encapsulation 23. Radially within the sleeve-like portion 24b and the encapsulation 23 is a cup-shaped armature guide sleeve 25 is arranged, the open end of the camshaft 2 faces and extending in the axial direction on the Spulen- body 20 and the encapsulation 23 addition. The open end of the armature guide sleeve 25 extends annularly outward.

The bobbin 20 is further arranged in a cup-shaped housing 26, in the bottom of a receiving opening 27 is provided. The open end of the armature guide sleeve 25 extends in the radial direction between the bottom of the housing 26 and the encapsulation 23, wherein a second sealing element 28 is provided which seals a sealing point between the armature guide sleeve 25 and the housing 26.

The receiving opening 27 is part of a receptacle 27 a in which a pole core 29 is received. In the illustrated embodiment, the pole core 29 is secured by means of a press fit with the receiving opening 27 on the housing 26 and projects into the armature guide sleeve 25 in the axial direction.

The armature guide sleeve 25 and the pole core 29 define an armature space 30, in which an axially displaceable armature 18 is arranged. The push rod 17 connected to the armature 18 extends through an opening 32 formed on the pole core 29, one end of the push rod 17 abutting against the control piston 13 in the mounted state of the control unit 10. Within the opening 32, as shown in Figure 2a, a sliding sleeve 33 may be provided to minimize friction losses at this point.

During operation of the internal combustion engine, a control unit regulates the energization of the actuating unit 10, as a result of which a magnetic field within the actuating unit 10 is generated. The pole core 29, the housing 26, the magnetic yoke 24 and the armature 18 serve as a flow path, which is completed by an air gap between the armature 18 and the pole core 29. In this case, a force acts in the direction of the pole core 29 on the armature 18, which depends on the height of the Energization of the coil 22 is. By balancing the magnetic force acting on the armature 18, and the spring force acting on the control piston 13, the armature 18 and thus the control piston 13 can be positioned in any position between two extreme positions.

Both in the pole core 29 and in the armature 18 axially extending holes 34a, 34b are formed. By means of the pressure compensation bores 34a in the armature 18, a pressure equalization between the spaces in front of and behind the armature 18 can take place during a displacement of the armature 18 in the armature space 30. About the leakage holes 34b in the pole core 29 of the armature space 30 is supplied pressurized with leakage oil. By this supply of lubricant in the armature space 30, the friction between the armature 18 and the armature guide sleeve 25 is reduced and thus minimizes the response time and the hysteresis of the actuator 10.

If the lubricant in the armature space 30 is not constantly exchanged, there is a risk that deposits deposited on the armature bearing surfaces in the lubricant will settle, or that oil sludge accumulates in the setting unit 10. These foreign bodies can cause the response of the actuator 10 is deteriorated, to a terminal of the armature 18 in the armature guide sleeve 25 and thus to a malfunction of the directional control valve. 9

In order to ensure a constant drainage of the lubricant from the setting unit 10, in the embodiment shown in FIGS. 2a and 2b the armature guide sleeve 25 is at the geodetically lowest point, ie at the point where the lubricant collects due to gravity Outflow channel 35 formed in the form of an axial groove 35a. Alternatively, the axial groove 35a may be formed on an outer circumferential surface of the pole core 29, which in turn is provided at the geodetically lowest point of the armature guide sleeve 25. The axial groove 35 a connects the armature space 30 with the exterior of the setting unit 10. In the actuator 10 entering lubricant collects, especially during the breaks of the internal combustion engine, at the point where the axial groove 35a opens into the armature space 30, whereby this can be returned to the chain case 15. Advantageously, either the Ankerführungs- sleeve 25 or the armature 18 is provided with axially extending indentations or bulges, so that behind the armature 18 existing engine oil can reach the axial groove 35a. As a result, aged engine oil, oil sludge and foreign matter leak out of the actuator 10, whereby the response and the dynamics of the actuator 10 can be kept permanently high level, hysteresis minimized and the reliability can be increased.

Since the lubricant can completely run out of the actuator 10 during the pauses of the internal combustion engine, the armature 18 or the armature guide sleeve 25 is advantageously provided with a sliding layer which provides a runflat property of the armature 18 in the armature guide sleeve 25 to prevent wear at this point.

FIGS. 3 a and 3 b show a further embodiment of an adjusting unit 10 according to the invention, which is designed similarly to the setting unit 10 illustrated in FIGS. 2 a and 2 b. In contrast, in this embodiment, a part of the guide surface of the armature 18 is formed by the pole core 29. The drainage channel 35 is designed in the form of a drain hole 35b formed on the pole core 29, which opens into the chain case 15 on the one hand, at the geodetically lowest point of the armature space 30, in these and the other end.

In a further embodiment according to the invention, which is illustrated in FIGS. 4 a and 4 b, part of the guide surface of the armature 18 is again formed by an axially extending section of the pole core 29. The inner diameter of the portion of the armature guide sleeve 25, which rests against the bottom of the housing 26, is made slightly larger than the outer diameter of the pole core 29. As a result, a drain channel 35 formed as an annular channel 35c is formed, which via an annular opening with the interior of the Anchor guide sleeve 25, in particular at a geodetically deepest Position of the armature space 30, communicates. The diameter of the annular channel 35c rises steadily along its axial extent, starting from the annular opening, up to a maximum value. Via a recess 36 on the inner lateral surface of the receiving opening 27 of the housing 26, the annular channel 35c can communicate with the exterior of the actuating unit 10. Alternatively, the annular channel 35c can communicate with the exterior of the actuating unit 10 via a recess 36 on the outer circumferential surface of the pole core 29. In both cases, the recess 36 is again arranged at the geodetically lowest point of the annular channel 35c.

FIGS. 5a and 5b show an alternative embodiment to that shown in FIGS. 4a and 4b, in which the annular channel 35c communicates with the exterior of the actuator 10 via a housing opening 37 formed in the bottom of the housing 26. The housing opening 37 is again formed at the geodetically lowest point of the annular channel 35c.

Figures 6a and 6b show a further embodiment of an actuating unit 10 according to the invention in which between the pole core 29 and the armature guide sleeve 25 in turn an annular channel 35c is formed, via which the pressure medium is fed to a housing opening 37. The housing opening 37 is formed in this case on the cylindrical portion of the housing 26, wherein between the bottom of the housing 26 and the encapsulation 23, a radially extending channel 38 is formed which communicates with both the annular channel 35c and with the housing opening 37. The channel 38 opens at the geodätisch lowest point of the annular channel 35c in this and the housing opening 37 is disposed below this mouth region.

All embodiments have in common that an outflow channel 35 is provided, which opens at the geodetically lowest point in the armature space 30 and connects it to the exterior of the actuating unit 10, preferably with the interior of a chain box 15. In the armature space 30 entering lubricant now passes continuously, especially during the breaks of the internal combustion engine, back into the chain case 15 whereby the danger deposits, such as aged engine oil or debris within the armature guide sleeve 25 is eliminated and thus the reliability of the actuator 10 is ensured.

reference numeral

1 camshaft adjuster

2 camshaft

3 inner rotor

4 outer rotor

5 side covers

6 recess

7 wings

8 sprocket

9 way valve

10 setting unit

11 valve section

12 valve housing

13 control piston

14 pressure medium line

15 chains boxes

15a first sealing element

15b flange section

16 holding tab

17 pushrod

18 anchors

19 spring element

20 bobbins

21 connection element

22 coil

23 encapsulation

24 magnetic yoke

24a disc-like section

24b sleeve-like section

25 anchor guide sleeve

26 housing

27 receiving opening 27a recording

28 second sealing element

29 polkernels

30 Anchor space 32 opening

33 sliding sleeve

34a Pressure compensation hole

34b leakage hole

35 outflow channel 35a axial groove

35b drainage hole

35c ring channel

36 recess

37 housing opening 38 channel

A work connection

B work connection

P inlet connection

T drain connection

Claims

claims

1. Electromagnetic actuator (10) of a hydraulic directional control valve (9) with - an armature (18) which is arranged axially displaceable within an armature space (30) and

- A pole core (29) which is arranged in a receptacle (27 a) and the armature space (30) in a direction of movement of the armature (18) delimited, characterized in that - at least one outflow channel (35) is provided which is connected both to the Anchor space (300) and with the exterior of the actuator (10) communicates.

2. Electromagnetic actuator (10) according to claim 1, characterized in that with the armature (18) has a push rod (17) is connected, which extends through an opening (32) in the pole core (29) and radially supported by this becomes.

3. Electromagnetic actuator (10) according to claim 1, characterized in that the outflow channel (35) opens at a geodetically lowest point in the armature space (30).

4. Electromagnetic actuator (10) according to claim 1, characterized in that the outflow channel (35) opens into a chain case (15).

5. Electromagnetic actuator (10) according to claim 1, characterized in that the outflow channel (35) as a drain hole (35b) in the pole core (29) is formed.

6. Electromagnetic actuator (10) according to claim 1, characterized in that the outflow channel (35) between the pole core (29) and a wall of the receptacle (27a) of the pole core (29) is formed.

7. Electromagnetic actuator (10) according to claim 6, characterized in that the outflow channel (35) as an axial groove (35a) on an outer circumferential surface of the pole core (29) is formed.

8. Electromagnetic actuator (10) according to claim 6, characterized in that the outflow channel (35) as an axial groove (35c) on an inner circumferential surface of a wall of the receptacle (27a) is formed.

9. Electromagnetic actuator (10) according to claim 6, characterized in that the pole core (29) is positively secured within a receiving opening (27) of a housing (26), wherein the discharge channel (35) as an annular channel (35c) between the pole core ( 29) and the receptacle (27a) is formed and via a recess (36) on an inner circumferential surface of the receiving opening (27), a recess (36) on the outer circumferential surface of the pole core (29) or a housing opening (37) with the exterior of the actuating unit (10) communicates.

10. Electromagnetic actuator (10) according to claim 1, characterized in that the adjusting unit (10) controls a control valve designed as a central valve, wherein the directional control valve is arranged radially within an inner rotor of a device for variably setting the timing of an internal combustion engine.