WO2010066533A1

WO2010066533A1 - Actuating element of an electromagnetic actuating unit of a hydraulic valve

Info

Publication number: WO2010066533A1
Application number: PCT/EP2009/065150
Authority: WO
Inventors: Jens Hoppe; Ali Bayrakdar
Original assignee: Schaeffler Kg
Priority date: 2008-12-10
Filing date: 2009-11-13
Publication date: 2010-06-17
Also published as: DE102008061396A1

Abstract

The invention relates to an actuating element (22) of an electromagnetic actuating unit (1) of a hydraulic valve, said actuating element comprising at least one armature (13) which is arranged in the actuating unit (1) in a longitudinally displaceable manner, and a push rod (14) firmly connected to the armature (13). The push rod is made of a metal or a metal alloy and is at least partially hardened by means of a strain-hardening process.

Description

Name of the invention

Actuating element of an electromagnetic actuator of a

hydraulic valve

description

Field of the invention

The invention relates to an actuating element of an electromagnetic actuating unit of a hydraulic valve, which has at least one armature which is displaceably arranged in the adjusting unit, and a push rod fixedly connected to the armature.

Such directional control valves are used in internal combustion engines, for example for controlling hydraulic camshaft adjusters or switchable cam followers. The directional control valves consist of an electromagnetic actuator and a hydraulic section. At least one inlet connection, at least one working connection and a tank connection are formed on the hydraulic section. By means of the electromagnetic actuator unit specific connections of the hydraulic section can be hydraulically connected to each other and thus the pressure medium flows are directed.

For the use of a directional control valve for controlling a camshaft adjuster, the hydraulic valve is normally designed as a 4/3 proportional directional control valve. Such a proportional valve is disclosed for example in DE 199 56 160 A1. In this embodiment, the electromagnetic actuator is fixedly connected to the valve portion. The electromagnetic actuator is composed in this case of a first magnetic yoke, a coil, a second magnetic yoke, a housing, an actuator and a connection element which receives an electrical connector, which serves to power the coil together. The actuator consists of an armature and a push rod. The hydraulic section consists of a valve housing and a control piston arranged axially displaceable therein. The valve housing is arranged within a receiving opening of the second magnetic yoke and fixedly connected thereto. On the outer circumferential surface of the valve housing four annular grooves are formed, which serve as pressure medium connections. In the Nutgründen the annular grooves openings are formed, whereby pressure fluid can reach into the interior of the valve housing. 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. Furthermore, ring grooves are likewise formed on the control piston, via which adjacent pressure medium connections can be connected to one another.

The coil, the first and the second magnetic yoke are arranged coaxially within the housing of the electromagnetic actuator. The first and the second yoke are offset from each other in the axial direction. In the region between the first and the second magnetic yoke is located radially within the magnetic yokes of the armature, which is surrounded in the radial direction of the coil. The armature, the housing, the first and the second magnetic yoke form a flux path for the magnetic flux lines, which are caused by energizing the coil.

By energizing the coil, the armature is urged in the direction of the second magnetic yoke, wherein this movement is transmitted by means of the anchor rod attached to the control piston. This is now moved against a spring supported on the valve housing in the axial direction. The push rod is arranged in a receptacle of the armature and firmly connected thereto. This is realized in that the push rod is made with excess to the recording and pressed into it, so that a frictional connection between the armature and the push rod is formed. Thus, the armature and the push rod form an actuating element, which can be displaced by energizing the coil in the axial direction and the control piston of the hydraulic section is actuated, that is positioned within the valve housing of the hydraulic section.

Another such directional control valve, a so-called central valve, is disclosed in DE 10 2006 031 517 A1. In this embodiment, the hydraulic section is configured separately from the electromagnetic actuator and accommodated in a cavity of a camshaft, wherein the hydraulic section rotates with the camshaft during operation of the internal combustion engine. The actuator is fixed in place on a cylinder head cover or cylinder head. The positioning is again effected by an actuating element which comprises an armature and a push rod connected thereto. In this case, the adjusting movement of the armature by means of the push rod, which is pressed into a receptacle of the armature, transmitted to the control piston of the valve section.

Directional valves for controlling switchable cam followers are usually designed as switching valves. Such a switching valve is, in one embodiment known as a 3/2-way valve, for example from DE 102 52 431 A1. The electromagnetic actuator in turn consists of a housing, an actuating element, consisting of an armature and a push rod, a connection element, a first and a second yoke. The function and design of the electromagnetic actuator are largely analogous to that of the proportional valve.

In this case, an inlet connection, a working connection and a tank connection are formed on the hydraulic section. The working connection communicates via a respective valve seat designed as opening with both the inlet and the tank connection. Within the valve housing, a control piston is further arranged, on which two closing elements are formed. Each closing element can, depending on the position of the control piston within the valve housing, block or release the pressure medium flow through one of the valve seats. Depending on the axial position of the control piston so the working port can selectively with the inlet port or connected to the tank connection. The axial position of the control piston is in turn set via the axial position of the actuating element relative to the second magnetic yoke.

In DE 100 51 614 A1, a further electromagnetic actuating unit of a proportional valve is disclosed. In this case, an armature guide sleeve is arranged within a magnetic yoke, in which an actuating element, consisting of an armature and a push rod, is received axially displaceable. The armature guide sleeve is pot-shaped with a bottom and a cylindrical see section with a cylindrical inner surface. The cylindrical inner circumferential surface serves to guide the armature, wherein the bottom limits the axial travel of the armature in an axial direction. The friction between the armature and the armature guide sleeve has a significant influence on the characteristics of the hydraulic valve, especially on the hysteresis occurring. Advantageously, low frictional forces. For this reason, friction-reducing measures, such as formations of the armature or bearing elements between these components are provided in the prior art. For example, it may be provided to provide the anchor with a sliding coating, such as Teflon. Between the bottom of the armature guide sleeve and the armature flush with the inner circumferential surface, a closed cavity is formed. This cavity can on the one hand, act by a negative pressure occurring in this, inhibiting movement of the armature away from the ground. Furthermore, leaking oil entering this cavity can inhibit axial movement of the anchor to the ground. In DE 100 51 614 A1 is proposed to solve this problem to provide the anchor with axial holes or axially extending grooves on the outer circumferential surface to allow pressure equalization between the cavities before and behind the anchor. Also in this embodiment, the push rod is force-fit pressed into a receptacle of the armature.

On the push rod of the known actuators act during operation high frictional forces. To avoid excessive wear the pushrods hardened, resulting in high additional costs and increased manufacturing costs.

Summary of the invention

The invention is therefore based on the object to avoid these disadvantages and thus to provide an actuating element of an electromagnetic actuator of a directional control valve, whereby the production cost is minimized and its manufacturing costs to be reduced.

According to the invention the object is achieved in that the push rod consists of a metal or a metal alloy, wherein the push rod is at least partially cured by means of a work hardening process. The actuating element of an electromagnetic actuating unit of a hydraulic valve comprises at least one armature and a push rod. The armature moves under the influence of a magnetic field, which is caused by energizing a coil of the actuator. The push rod is firmly connected to the armature, so that they move these components as a unit. In this case, the push rod bears against a control piston of the hydraulic section of the hydraulic valve. Thus, the actuator is moved relative to this when changing the energization of the coil, wherein the push rod transmits this movement to the control piston. The push rod is usually fitted in a receptacle of the armature, which is made with excess to the receptacle and pressed into it, whereby a non-positive connection between the two components is produced. Alternatively, fabric or form-locking connection methods are conceivable. The push rod may be partially hollow. From the resulting mass reduction of the actuator, the response of the actuator can be significantly improved. In applications in which the push rod is exposed to high loads, such as special central valve applications, the push rod can also be solid, ie formed without cavities. The push rod can for example, consist of a light metal, such as aluminum. Thus, the weight of the actuator is significantly reduced. In addition, it can be provided that the push rod is made of a non-magnetizable material, such as a non-magnetizable steel or aluminum.

After the production of the push rod this is subjected to a work hardening process. In this case, the material of the push rod is briefly applied to the desired locations with a force, so that a cold deformation, that is, a deformation significantly below the recrystallization takes place. The plastic deformation increases the dislocation density (number of lattice defects) within the material, thus increasing the hardness of the sites applied with the force. It can be provided that one end of the push rod engages a control piston and the surface of the push rod is hardened in this contact region by means of the work hardening process. It can be provided that the end of the push rod is formed hemispherical during the work hardening process, whereby lateral forces from the frictional contact with the control piston, axial offsets and tilting can be compensated.

Alternatively or additionally, it may be provided that the push rod is mounted displaceably in the setting unit and that the bearing surface of the push rod is hardened by means of the work hardening process. By hardening the outer surface, at least the portions of the outer surface that are highly stressed, the life of the actuator is significantly increased. Furthermore, the wear is reduced, so that there is no danger that peeled off by the push rod parts within the actuator affect their functionality. In one development of the invention, provision can be made for a projection to be formed on an outer surface of the push rod. In this case, an outer surface of the projection may be hardened.

This projection can serve as a stop, for example, which limits the press-in path of the push rod into the receptacle of the armature. Alternatively or In addition, this projection can also serve as a stop with respect to one of the magnetic yokes. The projection in this case limits the displacement of the actuating element during operation of the electromagnetic actuator in that it comes to rest on the magnetic yoke. Thus, measures for curing the anchor can be dispensed with. The projection may be formed, for example, as a circumferential in the direction of the push rod rotating disk.

The use of a strain hardening process to locally increase the hardness of the pushrod is an economical alternative to the otherwise usually fully hardened or coated pushrods. With this process, furthermore, only the areas of the surface of the pushrod that are stressed during operation of the actuator can be hardened. so that, for example, the assembly of the push rod to the anchor makes us easier and less error prone.

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

FIG. 1 shows an electromagnetic actuating unit of a hydraulic valve with a first actuating element according to the invention in longitudinal section,

2 shows an electromagnetic actuator of a hydraulic valve with a second actuator according to the invention in longitudinal section.

Detailed description of the drawing FIG. 1 shows an electromagnetic actuating unit 1 of a hydraulic valve with a first embodiment according to the invention of an actuating element 20 in longitudinal section. The electromagnetic actuator 1 has a bobbin 2, which carries a coil 4 consisting of several turns of a suitable wire, which is at least partially surrounded by an encapsulation 5 of non-magnetizable material. A first magnetic yoke 6 has a disk-shaped and a sleeve-shaped section 6a, 6b, wherein the sleeve-shaped section in FIG. 6b extends into the interior of the bobbin 2. The sleeve-shaped portion 6b engages in a cavity radially inside the bobbin 2, wherein the outer diameter is adapted to the inner diameter of the bobbin 2. The disc-shaped section 6a abuts the coil body 2 or the encapsulation 5 in the axial direction and thus determines the axial position of the first magnetic yoke 6.

The bobbin 2 is further arranged in a cup-shaped housing 7, in the bottom of a receiving opening 8 is provided. In the receiving opening 8, a second magnetic yoke 9 is received, which projects into the coil body 2 in the axial direction. In this case, the open ends 10 of the first and second magnetic yoke 6, 9 are axially opposite one another via an air gap 11.

The first and second magnetic yokes 6, 9 delimit an armature space 12, in which an axially displaceable actuating element 20 is arranged. The actuating element 20 comprises an armature 13 and a push rod 14 fixedly connected to the armature 13. The push rod 14 is partially disposed in a receptacle 21 of the armature 13 and extends through an opening 15 formed on the second magnetic yoke 9, one end of the push rod 14 in the assembled state of the actuating unit 1 rests against a partially shown control piston 3 of the hydraulic section of the hydraulic valve, not shown otherwise. Thus, by energizing the coil 4, the actuating element 20 is displaced and thus the control piston 3 of the directional control valve is actuated. Within the opening 15, a sliding sleeve 16 is provided in order to minimize friction losses at this point. During operation, the energization of the control unit 1 is regulated, whereby a magnetic field within the control unit 1 is generated. The first magnetic yoke 6, the housing 7, the second magnetic yoke 9 and the armature 13, which consist of magnetizable materials serve as a flow path, which is completed by the air gap 11 between the armature 13 and the first and second magnetic yoke 6, 9. When current flows through the coil 4 acts on the armature 13, a force in the direction of the second magnetic yoke 9, which is dependent on the amount of current to the coil 4. By balancing the magnetic force acting on the armature 13, and a spring force acting on the control piston 3, the armature 13 and thus the control piston 3 can be positioned in any position between two extreme positions.

The armature 13 is provided with axially extending bores 18 which are open on both axial side surfaces of the armature 13. The holes 18 thus connect two cavities 19 which are arranged in the axial direction of the armature 13 and are separated from it. During the movement of the armature 13, a pressure equalization between the cavities 19 can take place via the bores 18 and lubricant present in the actuating unit 1 can be exchanged. Thus, the friction between the armature 13 and the first yoke 6 and the hysteresis of the current-path characteristic of the actuator 1 is reduced.

The push rod 14 is in the embodiment shown in Figure 1 solid, ie not hollow, formed. Thus, high forces can be transmitted without deforming the push rod 14. The push rod 14 is frictionally secured in the receptacle 21 of the armature 13. This can be achieved, for example, by making the push rod 14 slightly oversized with the receptacle 21 and pressing it into it. On the outer circumferential surface of the substantially cylindrically executed push rod 14, a projection 17 in the form of a circumferential in the circumferential direction of the push rod 14 disc is formed. The projection 17 serves as a travel limit during the pressing of the push rod 14 in the receptacle 21. Furthermore, the projection 17 serves as a stop against the second magnetic yoke 9 during operation of the actuator 1. Thus, it is prevented that the armature 13 over a large area on the second yoke 9 comes to rest. Thus, adhesion forces are reduced due to the lubricant present in the setting unit 1 upon contact of the projection 17 on the second magnetic yoke 9.

FIG. 2 shows push rod 14 of a second embodiment of an actuating element 20 according to the invention in longitudinal section. In contrast to the first embodiment, this push rod 14 is hollow, like a blind hole, formed, whereby the weight of the actuating element 20 is reduced. Furthermore, no projection 17 is formed on the lateral surface of the push rod 14, which leads to a further reduction of the weight of the push rod 14.

The ends of the push rods 14 shown in Figures 1 and 2, which protrude from the actuator 1, are in the assembled state of the hydraulic valve at a facing this end of the control piston 3. By energizing the coil 4, the push rod 14 moves the control piston 3 against the force of a spring, not shown. In this case, a bearing surface of the tappet rod slides along the sliding sleeve 16. These highly stressed portions of the surface of the tappet rod 14 are hardened by means of a work hardening process. In this case, the material of the push rod is briefly subjected to a force at the desired locations, so that cold deformation, that is to say a deformation significantly below the recrystallization temperature, takes place. By this plastic deformation, the dislocation density (number of lattice defects) within the material increases, so that the hardness of the sites applied with the force is increased.

The push rod 14 is advantageously made of a nichtmagnetisierba- ren material on the one hand not to disturb the magnetic field generated by the coil 4 and on the other hand to prevent magnetizable particles collected from the lubricating / pressure fluid of the internal combustion engine and introduced into the actuator 1 whereby the sliding surfaces of the sliding sleeve 16, the push rod 14, the armature 13 or the first and second magnetic yoke 6, 9 can be damaged.

The push rod 14 is made of a suitable metal or a suitable metal alloy. For example, non-magnetizable steels can be used, as a result of which a high resistance force of the push rod 14 can be achieved with respect to forces acting on it. Furthermore, light metals may be provided, for example aluminum or magnesium, whereby the weight of the push rod 14 is reduced and thus the response speed of the actuator 1 or its hysteresis behavior is positively influenced.

reference numeral

1 actuator

2 bobbins

3 control piston

4 coil

5 reversion

6 first magnetic yoke

6a disc-shaped section

6b sleeve-shaped section

7 housing

8 receiving opening

9 second yoke

10 end

11 air gap

12 anchor room

13 anchors

14 pushrod

15 opening

16 sliding sleeve

17 lead

18 hole

19 cavity

20 actuator

21 recording

Claims

claims

An actuating element (22) of an electromagnetic actuating unit (1) of a hydraulic valve, which has at least one armature (13) which is longitudinally displaceable in the actuating unit (1) and a push rod (14) fixedly connected to the armature (13), characterized in that the push rod (14) consists of a metal or a metal alloy, wherein the push rod (14) is at least partially cured by means of a work hardening process.

2. Actuating element (22) according to claim 1, characterized in that one end of the push rod (14) acts on a control piston (3) and the surface of the push rod (14) is hardened in this contact region by means of the work hardening process.

3. Actuator (22) according to claim 2, characterized in that this end of the push rod (14) is formed hemispherical during the work hardening process.

4. Actuating element (22) according to claim 1, characterized in that the push rod (14) in the adjusting unit (1) is displaceably mounted and the bearing surface of the push rod (14) is hardened by means of the work hardening process.