Electromagnetic actuator for a hydraulic directional control valve

Abstract

Electromagnetic actuator for a hydraulic directional control valve, comprising: - a housing (08) with which the actuating unit can be attached opposite the directional control valve, - a coil (01) arranged in a coil former (03), - an anchor (09) which is arranged to be axially displaceable in the actuating unit, - and a seal (13, 24) between the housing (08) and the coil body (03), which has a circumferential circular groove (27) for receiving the seal (24), characterized in that the coil body (3) has a holder (26, 28) for holding the seal (24) during assembly of the actuating unit, wherein: - the holder (26, 28) is formed by an undercut (28) of an inner wall of the groove (27), into which the seal (24) can be inserted by elastic deformation, - the coil body (03) has a hollow cylindrical basic shape (21) and the support (26, 28) is formed on a base surface of the hollow cylindrical basic shape (21), - the anchor (09), a yoke (04) and a pole core (07) are arranged in the cavity of the hollow cylindrical base form (21), - and the inner wall of the groove (27) is formed segmentally with respect to its direction of rotation.

Description

[0001] The invention relates to an electromagnetic actuator for a hydraulic directional control valve, which can be adjusted by the actuator. Such directional control valves are used, for example, in internal combustion engines to control hydraulic camshaft adjusters.

[0002] From DE 103 00 974 A1, a proportional solenoid valve for a camshaft adjustment device for motor vehicles is known. The proportional solenoid valve has a valve housing in which a piston is slidable and which has several ports through which hydraulic oil can be supplied. The proportional solenoid valve further comprises an electromagnet element with which the piston can be adjusted via a plunger. In one embodiment of the proportional solenoid valve, the housing of the electromagnet element is provided with a recess on its end face into which one end of the housing of the valve element projects. An annular groove is located in the bottom of the recess, which receives a sealing ring. The housing of the valve element rests against this sealing ring on its end face. However, this seal does not provide a seal for components within the electromagnet element.Therefore, the housing of the electromagnetic part must ensure a complete seal, otherwise hydraulic oil may leak from the electromagnetic part.

[0003] DE 102 11 467 A1 discloses a camshaft adjuster with an electromagnet designed as a pressing proportional magnet. The proportional magnet has a magnetic armature that is fixedly mounted on an armature plunger, which passes through a hollow core and bears with a free end face against a control piston or a part rigidly connected to it. The magnetic armature and a coil body of the proportional magnet are not sealed against the control piston, so the sealing of the proportional magnet must be achieved entirely by a housing of the proportional magnet.

[0004] DE 101 53 019 A1 discloses an electromagnet, particularly suitable as a proportional magnet for actuating a hydraulic valve. The electromagnet comprises a hollow cylindrical coil body, bounded by an upper pole shoe and a lower pole shoe, and is enclosed by a magnet housing. The coil body exerts a magnetic force on a magnetic armature, which transmits the magnetic force via a pushrod to actuate the valve. The coil body is sealed from the valve by a non-magnetizable metal tube; however, a further seal is required via the housing of the proportional magnet.

[0005] A known solution for sealing a coil former against a housing of an electromagnetic actuator that does not fully enclose it is to use a liquid seal. However, such liquid seals are subject to significant process fluctuations depending on factors such as humidity, pot life, temperature, and chemical changes during process interruptions, meaning that ensuring reliable operation of the liquid seal is only possible with considerable effort.

[0006] DE 10 2005 048 732 A1 relates to an electromagnetic actuator for a hydraulic directional control valve. The actuator comprises an armature that is axially displaceable within an armature chamber and a pole piece that is arranged in a receptacle and limits the armature chamber in one direction of movement of the armature. The actuator also includes a coil, which is preferably overmolded with a non-magnetizable material to form a coil former. This former has a hollow cylindrical shape that is positively fitted into a housing of the actuator. The housing does not completely enclose the components of the directional control valve, necessitating a sealing element between the coil former and the housing. A disadvantage of this solution is that installing the seal for mounting the actuator is complex, particularly to ensure long-term functionality.

[0007] Fig. Figure 1 shows a further electromagnetic actuator according to the prior art in a cross-sectional view. This actuator is designed for controlling a hydraulic directional control valve configured as a central valve, which is arranged radially within an inner rotor of a device for the variable adjustment of the valve timing of an internal combustion engine. The actuator comprises a coil 01, which is electrically supplied via a plug-in contact 02 and is arranged within a coil former 03, which is formed, for example, by a housing assembled and bonded together or by overmolding the coil 01 with a plastic. The magnetic field generated by the coil 01 is transmitted via a soft iron circuit, consisting of a yoke 04, a yoke plate 06, a pole piece 07, and a housing 08, to a movably mounted magnetic armature 09.The magnetic field exerts a magnetic force on the magnetic armature 09 via an air gap between the pole core 07 and the magnetic armature 09. This force is transmitted via a push pin 11 to a piston of the central valve (not shown). The actuator is attached to the central valve or to a housing surrounding the central valve via a flange 12 of the housing 08. Hydraulic oil from the central valve flows through the housing 08 into the area of ​​the magnetic armature 09. Since the actuator is not completely enclosed by the housing 08, a seal 13 is required between the coil former 03 and the housing 08. The seal 13 is designed as a flat-faced, single-piece seal, for example in the form of an O-ring or a profiled sealing ring, which is inserted into a groove in the coil former 03. The cross-sectional area of ​​the seal 13 is significantly smaller than the diameter of its ring shape.Because of this relationship, the seal 13 is mechanically unstable on its own, so that during the assembly of the coil body 03 into the housing 08 the seal 13 can partially or completely escape from the groove in the coil body 03, making the assembly prone to failure.

[0008] Another electromagnetic actuating unit is described in US 4 453 700 A. US 3 310 283 A shows the sealing of two pipeline flanges, in which an O-ring is inserted into a groove.

[0009] The object of the present invention is, starting from the in Fig. 1 electromagnetic actuator shown, therein to provide a solution for sealing the coil body of an electromagnetic actuator, which enables easy and safe mounting of the actuator.

[0010] The aforementioned problem is solved by an electromagnetic actuating unit according to the attached claim 1.

[0011] The actuating unit according to the invention serves to adjust a hydraulic directional control valve, for example, for the variable adjustment of the valve timing of an internal combustion engine. The actuating unit comprises a housing with which the actuating unit is attached to the directional control valve. Attachment to the directional control valve can be direct or indirect via a housing surrounding the directional control valve. In the case of a hydraulic directional control valve for adjusting the valve timing of an internal combustion engine, the actuating unit can, for example, be designed such that its housing can be attached to a timing chain cover coaxially with the camshaft. The housing is formed, for example, by a housing assembled and bonded together, or it can be manufactured by overmolding the coil with a plastic or another non-magnetic material. The actuating unit according to the invention further comprises a coil arranged in a coil former.The coil former at least partially encloses the coil. The electromagnetic field generated by the coil acts on an armature that is axially displaceable within the actuator. To prevent the hydraulic fluid of the directional control valve, which, for example, flows through a portion of the armature to the coil former, from escaping the actuator, the actuator includes a seal between the coil former and the housing. The coil former has a circumferential circular groove to receive the seal. Therefore, the housing does not need to completely enclose the coil former. According to the invention, the coil former has a holder for retaining the seal.The holder ensures that the seal is held in the coil body at least during the assembly of the actuator, so that when the coil body is inserted into the housing the seal remains in its intended position, even if it is not yet fixed against the housing by pressure.

[0012] The coil former has a circumferential circular groove to accommodate the seal. This groove allows the seal's shape to be fixed, thus facilitating its retention by the holder. The holder is formed on the inner wall of the groove. To create the holder, the inner wall is undercut, thereby altering its circumference. When held in place, the seal, due to its elasticity, is forced into the circumferential area of ​​the undercut wall, thus ensuring its retention. The seal is attached to the holder by being elastically deformed and pushed over the portion of the inner wall that is not undercut, whereupon, due to its elasticity, the seal remains in the undercut area of ​​the inner wall.

[0013] A particular advantage of the actuator is that a simple design modification to the coil former allows for significantly easier assembly of the actuator. The production costs for such an actuator are considerably reduced.

[0014] The holder is preferably designed for a form-fit, force-fit, or material-fit retention of the seal and can therefore be adapted to the specific requirements of the actuator, for example, by a special shape or by incorporating an adhesive to hold the seal. The holder can be designed, for instance, so that the seal is clamped onto or into the holder. Often, seals made of an elastic material are used that are inherently suitable for clamping into or onto the holder.

[0015] The holder is preferably formed integrally with the coil former. Alternatively, the holder can be attached to the coil former after its manufacture, for example, by attaching connecting elements or by applying an adhesive. The actuating unit according to the invention can be designed such that the seal is attached to the coil former during its manufacture using the holder, or that the seal is attached to the coil former during the assembly of the actuating unit. The holder can be designed for either a detachable or a permanent hold of the seal.

[0016] The holder according to the invention is preferably designed to hold a seal formed by a circular sealing ring. Sealing rings are available in many designs and have proven effective for many types of seals. Furthermore, a circular sealing ring can be held particularly easily and securely by the holder. O-rings or profile sealing rings, which ensure a reliable seal, are especially suitable for this purpose.

[0017] The coil former has a hollow cylindrical shape. This shape accommodates a coil wound in the form of a hollow cylinder, which is preferred for most applications. An electrical connection, for example, is attached to the hollow cylindrical shape. The holder for the seal is formed on one of the two annular base surfaces of the hollow cylindrical shape. Apart from the holder, the base surface is preferably flat. The armature, a yoke, and a pole piece are located within the hollow cylindrical shape, i.e., in the cavity. Such an arrangement has proven successful in the prior art and is particularly suitable for an electromagnetic actuating unit according to the invention.

[0018] The housing of the actuating unit according to the invention is preferably designed such that it positively engages the coil former with its outer surface and the flat base surface having the holder. Accordingly, the housing provides a cylindrical interior space whose size is adapted to the coil former. This allows the coil former to be mounted in the housing by pressing it into the housing. When the coil former is fully pressed into the housing, its flat base surface having the holder abuts a corresponding flat surface of the housing, so that the held seal is pressed against this surface of the housing, creating a seal between the housing and the coil former.

[0019] The undercut preferably has an inwardly curved shape into which, for example, an O-ring can snap, and can be formed on either the smaller or the larger of the two cylindrical surfaces of the groove. In the first case, the seal is brought onto or into the undercut by elastic expansion, and in the second case by elastic contraction.

[0020] It is not necessary for the groove to extend over the entire circumference of the seal. Likewise, it is not necessary for the retaining element to extend over the entire circumference of the seal. For example, the inner wall of the groove forming the retaining element can be interrupted. In this case, the inner wall is formed segmentally with respect to the circumference of the seal, i.e., with respect to the circumferential direction of the groove. This segmented design facilitates easy demolding of the coil body during its manufacture, particularly when it is produced by an injection molding process. The segments of the inner wall are preferably evenly distributed along the circumferential direction of the groove and each has an equal-sized gap between them.

[0021] The segments of the inner wall can also be designed as segments of a ring, arranged on the base of a coaxial cylindrical recess in the coil former. The groove is formed between the inner surface of the recess and the ring segments.

[0022] Further advantages, details, and embodiments of the present invention will become apparent from the following description of a preferred embodiment, with reference to the drawing. The drawing shows: Fig. 1 an electromagnetic actuator for a hydraulic directional control valve according to the state of the art; Fig. 2 a coil body of a preferred embodiment of the electromagnetic actuating unit according to the invention; and Fig. 3 den in Fig. 2 shown coil bodies with a sealing ring.

[0023] Fig. Figure 1 shows an electromagnetic actuator for a hydraulic directional control valve for variable adjustment of the timing of an internal combustion engine, as is known from the prior art and has already been discussed in the introductory description.

[0024] Fig. Figure 2 shows a perspective view of a coil former of the electromagnetic actuating unit according to the invention for a hydraulic directional control valve. This embodiment of the actuating unit is particularly suitable for actuating a hydraulic directional control valve designed as a central valve, which is arranged radially within an inner rotor of a device for the variable adjustment of the valve timing of an internal combustion engine. Such an actuating unit is also referred to as a central solenoid and serves for camshaft adjustment. The coil former shown initially comprises a hollow cylindrical base body 21 in which a coil (not shown) is arranged. The coil former is manufactured by overmolding the coil with plastic. This provides electrical insulation for the coil and insulation against the hydraulic medium.Furthermore, the coil former has an electrical connection 22, which is attached to one of the two base surfaces of the base body 21 and through which the coil can be energized. On the base surface opposite the connection 22, the base body 21 has a coaxial cylindrical recess 23, which extends over approximately half the diameter of the annular shape of the base surface of the base body 21. The depth of the recess 23 is only a few millimeters and is dimensioned such that a seal 24 (shown in . ) can be accommodated. Fig. 3) in an undeformed state, when arranged in the recess 23, projects beyond it and thus forms a sealing contact with the housing 08 (shown in Fig. 1) can build.

[0025] Six ring segments 26 are arranged on the bottom surface of the recess 23. The ring represented by the ring segments 26 is arranged coaxially to the recess 23 and has a diameter that is approximately equal to the average of the diameter of the cavity of the base body 21 and the diameter of the recess 23.

[0026] The ring segments 26 are evenly distributed over the ring they represent and, in the embodiment shown here, are each of the same size. Likewise, the six spaces between the ring segments 26 are of the same size.

[0027] The segmentation of the ring segments 26 simplifies the production of a coil former. The coil former, consisting of the base body 21, the electrical connection 22, and the ring segments 26 in the recess 23, is manufactured as a single piece from an injection-molded plastic part. The segmentation of the ring segments 26 facilitates demolding from the injection mold required for injection molding. Demolding can also be achieved or facilitated by other means, thus eliminating the need for segmentation.

[0028] The height of the ring segments 26 is dimensioned such that they do not project beyond the cylindrical recess 23. A groove 27 is formed between the outer circumference of the ring segments 26 and the inner wall of the recess 23, in which the seal 24 (shown in Fig. 3) can be accommodated. A bulge 28 is formed on the outer circumferential surface of the ring segments 26, which serves to retain the seal 24. The bulge 28 is aligned in the direction of the axis of rotation of the base body 21 and the ring represented by the ring segments 26, as well as the groove 27. The bulge 28 can be created by subsequently undercutting the ring segments 26 or by forming it during injection molding.

[0029] Fig. 3 shows the one in Fig. Figure 2 shows a coil body in a different perspective view, in which the seal 24 is inserted into the groove 27. The seal 24 is an O-ring made of an elastic material. The inner diameter of the O-ring is smaller than the diameter of the ring represented by the ring segments 26 when the seal 24 is undeformed. In particular, the diameter of the O-ring 24 is smaller than the diameter of the ring segments 26 in a region upstream of the bulge 28. The diameter of the ring formed by the ring segments 26 in the region of the bulge 28 can be dimensioned to be equal to or slightly larger than the inner diameter of the seal 24.The described design of the diameter of the seal 24 and the diameter of the ring formed by the ring segments 26 in the area before and within the bulge 28 serves to ensure that a force is required to deform the seal 24, in particular to increase its inner diameter, when inserting it into the groove 27. As soon as the seal 24 reaches the area of ​​the bulge 28 during insertion into the groove 27, it partially or completely relaxes, so that its inner diameter decreases again. If the seal 24 is then to be removed from the groove 27, a force must first be applied to deform the seal 24, in particular to increase its inner diameter, in order to move it over the bulge 28. If this force is not applied, the seal 24 is held in the groove 27 by the ring segments 26 and their bulge 28.This holding function of the ring segments 26 with their curvature 28 is particularly important during the assembly of the coil body into the housing 08 (shown in . Fig.1) of importance. Under normal conditions, the seal 24 cannot leave its intended position due to its retention by the ring segments 26 with their curvature 28. This ensures that when the coil former is inserted into the housing 08, the seal 24 does not leave the groove 27, but instead abuts the housing 08 at the intended position, where it is pressed against the housing 08, thus creating a seal between the coil former and the housing 08. Once the coil former is mounted in the housing 08, the retention of the seal 24 by the ring segments 26 with their curvature 28 is generally irrelevant, as the seal 24 is fixed by being pressed against the housing 08. However, the groove 27 continues to ensure that the seal 24 retains its circular shape and does not leave its intended position. Reference symbol list 01 Coil 02 Plug contact 03 Coil body 04 Joch 05 - 06 Jochplatte 07 Pole core 08 Housing 09 Magnetic armature 10 - 11 Pushpin 12 flange 13 Seal 14 - 15 - 16 - 17 - 18 - 19 - 20 - 21 hollow cylindrical base body 22 electrical connection 23 cylindrical recesses 24 Seal 25 - 26 ring segments 27 Nut 28 Curvature

Claims

[1] Electromagnetic actuator for a hydraulic directional control valve, comprising: - a housing (08) with which the actuating unit can be attached opposite the directional control valve, - a coil (01) arranged in a coil former (03), - an anchor (09) which is arranged to be axially displaceable in the actuating unit, - and a seal (13, 24) between the housing (08) and the coil body (03), which has a circumferential circular groove (27) for receiving the seal (24), characterized in that the coil body (3) has a holder (26, 28) for holding the seal (24) during assembly of the actuating unit, wherein: - the holder (26, 28) is formed by an undercut (28) of an inner wall of the groove (27), into which the seal (24) can be inserted by elastic deformation, - the coil body (03) has a hollow cylindrical basic shape (21) and the support (26, 28) is formed on a base surface of the hollow cylindrical basic shape (21), - the anchor (09), a yoke (04) and a pole core (07) are arranged in the cavity of the hollow cylindrical base form (21), - and the inner wall of the groove (27) is formed segmentally with respect to its direction of rotation. [2] Electromagnetic actuating unit according to claim 1, characterized by , that the holder (26, 28) is designed for a form-fit, force-fit or material-fit holding of the seal (24). [3] Electromagnetic actuating unit according to claim 1 or 2, characterized by , that the holder (26, 28) is designed to hold a seal (24) formed by a circular sealing ring. [4] Electromagnetic actuating unit according to claim 3, characterized by, that the holder (26, 28) is designed to hold a seal (24) formed by an O-ring or by a profile sealing ring. [5] Electromagnetic actuating unit according to claim 1, characterized by , that the coil body (03) with its outer surface and the flat base surface having the support (26, 28) is positively engaged with the housing (08). [6] Electromagnetic actuating unit according to claim 1, characterized by , that the undercut has an inwardly curved shape (28). [7] Electromagnetic actuating unit according to claim 1, characterized by , that the segments of the inner wall of the groove (27) are evenly distributed over its direction of rotation and each has an intermediate space. [8] Electromagnetic actuator according to claim 7, characterized by, that the segments of the inner wall of the groove (27) are formed as ring segments (26) which are arranged in a coaxial cylindrical recess (23) of the coil body (03), wherein the groove (27) is formed between the inside of the shell of the cylindrical recess (23) and the ring segments (26). [9] Electromagnetic actuator according to any one of claims 1 to 8, characterized by , that the coil body (03) is formed by a plastic overmolding of the coil (01). [10] Electromagnetic actuator according to any one of claims 1 to 9, characterized by , that it is designed for positioning a hydraulic directional control valve designed as a central valve, which is arranged radially within an inner rotor of a device for the variable adjustment of the timing of an internal combustion engine.

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