WO2010066534A1

WO2010066534A1 - Actuating element of an electromagnetic actuating unit of a hydraulic valve

Info

Publication number: WO2010066534A1
Application number: PCT/EP2009/065151
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: DE102008061397A1

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 (11) in a longitudinally displaceable manner, and a push rod (14) which is firmly connected to the armature and is produced by means of an extrusion pressing 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 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 fixedly attached to 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 to it. In this case, the adjusting movement of the armature is transmitted to the control piston of the valve section by means of the push rod, which is pressed into a receptacle of the armature.

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 actuating unit in turn consists of a housing, an actuating element, consisting of an armature and a push rod, a connecting element, a first and a second magnetic 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, the working connection can thus be selectively connected to the inlet connection or 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 cup-shaped with a bottom and a cylindrical portion formed with a cylindrical inner circumferential 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 occurring hysteresis. 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 surface of the armature, 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 non-positively pressed into a receptacle of the armature.

A disadvantage of the proposed embodiment, the high production costs, which by the machining production and post-processing of caused by a non-magnetizable material push rod.

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 is made by means of an extrusion process. In this method, a blank, such as a piece of wire, is urged by a punch so that the material begins to flow below its melting temperature and fills a mold that is formed as a negative to the desired shape of the push rod.

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 these components move as a unit. In this case, the push rod abuts 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 use of an extrusion molding process for the production of the push rod is a cost-effective alternative to the push rods usually produced by means of machining processes. On the other hand, the production takes place in this way with a significantly higher clock frequency. At the same time, additional structures can be made on the pushrod by simply fitting the mold so that they are formed during the molding process.

In addition, it can be provided that an outer surface of the push rod is hardened in the region of a bearing surface and / or in the region of a contact surface to a control piston. 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 additionally, this projection can also serve as a stop with respect to one of the magnet 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 protrusion may be formed, for example, as a circumferential disk in the circumferential direction of the push rod.

In addition, it can be provided that an outer surface of the push rod is at least partially hardened by means of a work hardening process. This increase in surface hardness can be done, for example, during the extrusion process or in a subsequent step. In this case, the push rod is plastically deformed below the recrystallization temperature, whereby its hardness increases. Advantageously, the push rod is at least partially hollow, whereby the weight of the push rod is reduced and thus the dynamics of the actuator is increased. Through the use of an extrusion process for the production of the push rod, the cavity can be formed without additional steps during the formation of the push rod. Unlike machining methods, no subsequent shaping, for example drilling, is necessary. Thus, more material can be saved.

Advantageously, the push rod is made of a light metal, for example 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.

In one development of the invention, it can be provided that the surface of the push rod is at least partially provided with a hardness-increasing coating, so that the wear on the push rod is reduced.

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 an electromagnetic actuator of a hydraulic valve with an actuator according to the invention in longitudinal section,

FIG. 2 shows a longitudinal section through a push rod of a second embodiment of the actuating element according to the invention,

Figure 3 shows a longitudinal section through a push rod of another embodiment of the invention the actuating element.

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-magnetisable 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 disk-shaped section 6a abuts against the bobbin 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 reception 8, a second magnetic yoke 9 is accommodated, 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 arranged in a receptacle 21 of the armature 13 and extends through an opening 15 formed on the second magnet yoke 9, one end of which Push rod 14 rests in the assembled state of the actuating unit 1 on a partially shown control piston 3 of the hydraulic section of the hydraulic valve, not shown otherwise. Thus, the actuator 20 is displaced by energizing the coil 4 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 Anchor 13 can take place via the holes 18, a pressure equalization between the cavities 19 and replaced in the actuator 1 existing lubricant. Thus, the friction between the armature 13 and the first yoke 6 and the hysteresis of the current-displacement curve of the actuator unit 1 is reduced.

The push rod 14 is solid in the embodiment shown in Figure 1, i. not hollow, trained. 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, the anchor 13 is prevented over a large area on the second magnetic 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 a 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, 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.

FIG. 3 shows push rod 14 of a further embodiment of an actuating element 20 according to the invention in longitudinal section. In contrast to the first embodiment, this push rod 14 is in the area which in the Receiving 21 of the armature 13 engages hollow, while the rest of the part is solid. Thus, the weight of the push rod 14 is reduced, at the same time high forces can be transmitted to the control piston 3 due to the high rigidity of the part of the push rod 14, which is arranged outside the receptacle 21. Furthermore, the pressing of the push rod 14 is facilitated in the receptacle 21. The engaging in the receptacle 21 end of the push rod 14 is provided with an insertion phase 22.

The push rods 14 shown in FIGS. 1 to 3 are produced by means of an extrusion process. For this purpose, a blank, such as a piece of wire, a suitable material by means of a punch is pressurized so that the material begins to flow below its melting temperature and a shape that is a negative of the desired shape of the push rod 14 fills. The advantage of this method is the surface quality that can be achieved by this method, which makes complicated and costly post-treatment steps unnecessary. Furthermore, complex structures, for example the projection 17 or the insertion phase 22, can be realized cost-effectively during the extrusion molding process. At the same time, a work hardening of the surface can take place during the production process, which increases the life of the push rod 14. Alternatively or additionally, further methods curing the surface of the push rod 14 can be carried out, for example by applying suitable coatings, laser hardening or further work hardening methods. Advantageously, only the highly stressed parts of the surface, such as the bearing surface in the region of the sliding sleeve 16, the contact surface to the control piston 3 and or the projection 17 are hardened. 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 be, 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, whereby a high resistance force of the push rod 14 can be achieved with respect to these forces acting. 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

22 introduction phase

Claims

claims

An actuating element (20) of an electromagnetic actuating unit (1) of a hydraulic valve which has at least one armature (13) which is displaceably arranged in the actuating unit (1) and a push rod (14) fixedly connected to the armature (13), characterized in that the push rod (14) is made by means of an extrusion molding process.

Second actuating element (20) according to claim 1, characterized in that an outer surface of the push rod (14) is at least partially cured by means of a work hardening process.

3. Actuating element (20) according to claim 1, characterized in that an outer surface of the push rod (14) is hardened in the region of a bearing surface.

4. Actuating element (20) according to claim 1, characterized in that an outer surface of the push rod (14) is hardened in the region of a contact surface to a control piston (3).

5. Actuator (20) according to claim 1, characterized in that on an outer surface of the push rod (14) has a projection (17) is formed.

6. Actuator (20) according to claim 5, characterized in that an outer surface of the projection (17) is hardened.

7. actuating element (20) according to claim 1, characterized in that the push rod (14) is at least partially hollow.

8. actuating element (20) according to claim 1, characterized in that the push rod (14) consists of a non-magnetizable material.

9. actuating element (20) according to claim 1, characterized in that the push rod (14) consists of a light metal.

10. Actuating element (20) according to claim 1, characterized in that the surface of the push rod (14) is at least partially provided with a hardness-increasing coating.