Electromagnetic hydraulic valve

Abstract

Electromagnetic hydraulic valve comprising an electromagnetic actuator (12) for positioning a piston (20) of the hydraulic valve (10) which is axially displaceably received in a valve bushing (14) of the hydraulic valve (10) along a longitudinal axis (18) of the valve bushing (14), wherein the piston (20) is used to open and / or close ports (P, A, T) of the valve bushing (14) allowing flow through them, wherein the valve bushing (14) has at least one compensating opening (64) which establishes a flowable connection with a tank connection (TL2), and wherein the hydraulic valve (10) has a compensating channel (66) for discharging fluid, which is connected to the compensating opening (64) allowing flow through it, characterized in that the compensating channel (66) is predominantly spirally extended in the given installation space along the longitudinal axis (18) so that an optimal length-cross-section ratio is achieved.

Description

The invention relates to an electromagnetic hydraulic valve of the type specified in the preamble of claim 1. Electromagnetic hydraulic valves are well-known. They are used, for example, for the hydraulic control of a clutch in an automatic transmission of a motor vehicle. The hydraulic valves have an axially movable piston in a valve bushing, which is designed to open and / or close ports. The piston is moved axially by means of an electromagnetic actuator. The hydraulic valve is designed to allow hydraulic fluid to flow through it. The hydraulic fluid is introduced into the valve via a supply port and can flow out again via a reservoir port. The hydraulic fluid flows into the consumer via a consumer port and from there back into the hydraulic valve. During piston movement, the volume in the magnet chamber changes, calculated by multiplying the cross-sectional area of ​​the tappet by the stroke. To compensate for this tappet stroke volume, the magnet chamber is connected to the tank via at least one equalization channel. During the oscillating movement of the fluid in the compensation channel, dirt particles can enter the magnetic chamber. There they accumulate and can lead to premature valve failure. It has been shown that it is advantageous to make the compensating channel leading to the tank connection in the hydraulic valve as long as possible. For example, a compensating connection currently used is offset by 180° to the tank connection and lies in the same cross-sectional plane of the valve bushing. However, this requires a sometimes complex design solution for a venting connection. Patent US 9,423,045 B2 describes a hydraulic valve whose compensating channel is spirally shaped in a cross-sectional plane of the valve bushing. The compensating channel extends exclusively in the radial and circumferential directions. The greatest possible longitudinal extent of the compensating channel is further achieved by extending it circumferentially in a wave-like pattern. The disadvantage is that the longitudinal extent in the circumferential direction is limited because the compensating channel extends over a single cross-sectional plane. Therefore, the object of the present invention is to provide an improved electromagnetic hydraulic valve in whose operation the aforementioned disadvantages are eliminated. The problem is solved according to the invention by a hydraulic valve having the features of claim 1. Advantageous embodiments with expedient and non-trivial further developments of the invention are specified in the respective dependent claims. An electromagnetic hydraulic valve according to the invention comprises an electromagnetic actuator for positioning a piston of the hydraulic valve, which is axially displaceable along a longitudinal axis of the valve bushing within a valve bushing. The piston is used to open and / or close ports of the valve bushing, allowing flow through them. The valve bushing has at least one compensating port, which establishes a flow-through connection to a tank port. For fluid discharge, the hydraulic valve has a compensating channel, which is connected to the compensating port, allowing flow through it. According to the invention, the compensating channel is predominantly spirally extended along the longitudinal axis within the given installation space, resulting in an optimal length-to-cross-sectional ratio.The advantage lies in the creation of a very long compensation channel within the given installation space, as the length of the compensation channel depends on the number of turns resulting from the spiral shape along the longitudinal axis. The higher the number of turns, the longer the compensation channel can be. The installation space of the hydraulic valve is not increased by the creation of the compensation channel. In one embodiment of the hydraulic valve according to the invention, the compensating channel is formed in an end section of the valve bushing, which is opposite the electromagnetic actuator, so that the fluid can flow from a chamber formed between the end section and the electromagnetic actuator into and out of the compensating channel via the shortest possible path, thus ensuring a short reaction time, in other words a fast reaction of the hydraulic valve unaffected by the fluid flow. In a further embodiment, the compensating channel is formed using a channel element. This offers the advantage of designing the compensating channel with an element independent of the valve bushing. The compensating channel could, for example, be designed as a spiral groove extending along the longitudinal axis of the valve bushing. However, this would eliminate the possibility of adjusting the length of the spiral channel to the requirements of the hydraulic valve. Similarly, the width of the compensating channel could no longer be adjusted. Furthermore, the manufacturing of the channel element is significantly simpler than manufacturing the compensating channel within the valve bushing due to its improved handling. Therefore, the advantage of the channel element independent of the valve bushing lies in its cost-effective manufacturing and the high degree of variability in the compensating channel geometry. In a particularly cost-effective and simple solution, the channel element is designed in the form of a spiral element, for example, a spiral spring similar to a compression spring. For secure positioning, a groove can be provided in the end section, where the spiral channel is preferably formed, in which the spiral spring is arranged. The spiral spring would then be supported against the edge regions of the groove. This is a simple and cost-effective way to create a large-scale equalization channel. In a further embodiment of the hydraulic valve according to the invention, the channel element is made of spring steel or plastic. Spring steel has the advantage that the channel element can be expanded considerably, i.e., deformed significantly, for example, during assembly, and then, after assembly and thus upon release from the deformed state, regains its original shape and can fit snugly against the valve bushing, particularly its outer surface. A channel element made of plastic, on the other hand, is particularly cost-effective to manufacture and reduces weight. A particularly advantageous feature is the design of a channel section of the compensating channel extending axially from the second end of the valve bushing. The valve bushing is typically pressed into the pole element of the electromagnetic actuator. To allow the fluid to easily flow directly from the volume formed between the valve bushing and the armature into the spiral channel section of the compensating channel, and vice versa, at least one axially extending channel section of the compensating channel is provided. In a further embodiment, the channel floor of the equalization channel, at least in the area of ​​a second channel section in which the channel element is arranged, is unevenly designed, such that steps are formed in which the channel element can be received. The advantage is that the channel element is prevented from slipping or shifting, as it is held in position between the steps. In a further embodiment, a gap is formed between the channel element and a surface that radially delimits the channel element. Thus, when the piston moves, any air that accumulates does not escape via the compensation channel but rather through the gap. The fluid follows the geometry of the channel element, while the air escapes through the gap formed between the channel element and the surface and therefore has no influence on the fluid flow. The compensating channel can be manufactured cost-effectively if the surface is an inner surface of a pole element of the electromagnetic actuator. The pole element of the electromagnetic actuator is hollow cylindrical, and the valve bushing is typically pressed into it. Utilizing the existing inner surface of the hollow cylindrical shape allows the compensating channel to be formed on the outer circumference of the valve bushing. This, in turn, results in the largest possible diameter for the windings of the spiral compensating channel. Compensation channel section as well as for cost-effective production, since an outer wall of the compensation channel is already formed using the inner surface. Typically, the valve bushing has an annular collar in the area of ​​the tank connection, which serves to axially delimit the tank connection from the pole element or the electromagnetic actuator. For the cost-effective manufacture of the hydraulic valve according to the invention, a collar of the valve bushing facing the electromagnetic actuator can be used for axial support of the channel element, such that the channel element is arranged to bear against the annular collar. To further extend the compensation channel, the channel element is designed to extend axially in a first section and radially in a second section. For this purpose, a collar can be formed on the valve bushing such that the channel element can be arranged extending radially between the collar and a wall of the pole element. The hydraulic valve according to the invention is characterized in particular by the fact that hardly any dirt particles from the tank connection can enter the electromagnetic actuator. Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. The features and combinations of features mentioned above in the description, as well as those mentioned below in the figure description and / or shown in the figures alone, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention. Identical or functionally equivalent elements are assigned identical reference numerals. For the sake of clarity, it is possible that the elements are not provided with their reference numerals in all figures, without, however, losing their association. Figure 1 shows a longitudinal section of an electromagnetic hydraulic valve according to the invention in a first embodiment.2 in a perspective longitudinal section the hydraulic valve according to Fig. 1, Fig. 3 in a perspective view a valve bushing of the hydraulic valve, Fig. 4 in a longitudinal section the hydraulic valve according to the invention in a second embodiment, Fig. 5 in a longitudinal section the hydraulic valve according to the invention in a third embodiment and Fig. 6 in a longitudinal section the hydraulic valve according to the invention in a fourth embodiment. An electromagnetic hydraulic valve 10 according to the invention for a clutch (not shown) of an automatic transmission of a motor vehicle (not shown) is designed in a first embodiment according to Fig. 1. The hydraulic valve 10 is shown in Fig. 1 in a first position, which is characterized by the absence of current to an electromagnetic actuator 12 of the hydraulic valve 10. The hydraulic valve 10 has a valve bushing 14, which is designed for connection to hydraulic ports, a supply port P through which hydraulic fluid can be supplied to the hydraulic valve 10, a consumer port A, and a tank port T. A piston 20, which is axially displaceable along a longitudinal axis 18 of the valve bushing 14, is movably received in a receiving opening 16 formed in the valve bushing 14. The valve bushing 14 is rotationally symmetrical with respect to the longitudinal axis 18. The piston 20 is designed for the controllable flow through the hydraulic connections P, A, and T. It has a control groove 21 extending around its circumference, which has a first control edge 22 and a second control edge 24. The first control edge 22 serves to establish a flow-through connection between the supply connection P and the consumer connection A. The second control edge 24 serves to establish a flow-through connection between the consumer connection A and the tank connection T. To provide the flow-through connections, the valve bushing 14 has flow-through openings arranged serially along the longitudinal axis 18, completely penetrating the valve bushing 14, wherein a first flow-through opening 26 is connected to the supply port P, a second flow-through opening 28 to the consumer port A, and a third flow-through opening 30 to the The tank connection T is assigned. A filter screen 32 is accommodated in the first flow opening 26, which serves to filter a hydraulic fluid flowing through the hydraulic valve 10, which is supplied to the hydraulic valve 10 via the supply connection P. It should be noted that the sequence and number of connections are not limited to the illustrated embodiment. For example, further consumer connections can be provided, and the arrangement of the connections is variable depending on the application. To position the piston 20 into further positions, the electromagnetic actuator 12 is designed with an axially movable armature 34, which assumes its axial position when the electromagnetic actuator 12 is energized. Fig. 1 shows the electromagnetic actuator 12 in the unenergized state and the armature 34 in a rest position. The electromagnetic actuator 12 comprises, in addition to the armature 34, a pole element 82 enclosing the armature 34, a coil 86 at least partially encompassing the pole element 82, and a plug element 88 for connecting the electromagnetic actuator 12 to a power source for supplying power. At its anchor end 36, which faces the piston 20, the anchor 34 has a cover element 38 for covering a central bore 40 of the anchor 34, through which it is connected to the piston 20, touching it. Thus, when the armature 34 moves, the piston 20 also performs an axial movement. The central bore 40 of the armature 34 serves to equalize pressure between a first chamber 42 facing away from the piston 20 and a second chamber 44 facing the piston 20. Therefore, the cover element 38 has a further recess 46. This pressure equalization is necessary for the rapid axial movement of the piston 20. The piston 20 has a significantly reduced diameter DR on its tappet 48, which faces the armature 34, compared to the diameter D of its control section 49. A sealing element 50 is provided, which is designed to receive the tappet 48. The receiving opening 16 has a cover-shaped end element 54 at a first end 52 of the valve bushing 14, which is designed facing away from the anchor 34. This end element forms a leakage opening 56 for the drainage of leakage fluid. The system is designed for hydraulic fluids. The leakage opening 56 provides a flow-through connection between the receiving opening 16 and a first leakage tank connection TL1. The leakage opening 56 serves to drain the leakage fluid, particularly during movement of the piston 20. To control the movement of the piston 20 during displacement, a preload element 58 is arranged between the piston 20 and the end element 54. In this embodiment, the preload element 58 is designed in the form of a spiral element. The preload element 58 is supported at one end by a first shoulder 60 of the end element 54 and at the other end by a second shoulder 62 of the piston 20. In order to compensate for the stroke volume of the plunger 48, particularly when the piston 20 moves towards the armature 34 to create a flow connection between the consumer port A and the tank port T, the valve bushing 14 has a compensating port 64 between the third flow opening 30 adjacent to the actuator 12 and the electromagnetic actuator 12, which provides a flow-through connection between the hydraulic valve 10 and a tank port TL2. This volume equalization must be achieved, otherwise a vacuum could form. The volume equalization takes place between the second chamber 44 and the tank connection TL2. Equalizing fluid thus flows from the hydraulic valve 10 via the equalization port 64 and vice versa. Fig. 2 shows, for further explanation, the hydraulic valve 10 according to Fig. 1 in a perspective longitudinal section. The compensating opening 64 is associated with a compensating channel 66, which is designed for the discharge and supply of fluid from the second chamber 44. The compensating channel 66 extends longitudinally along the longitudinal axis 18 and spirally in the circumferential direction; that is, the compensating channel 66 is predominantly spirally elongated, resulting in an optimal length-to-cross-sectional ratio. In the three illustrated embodiments, the compensating channel 66 is designed with the aid of an annular groove 68 and a channel element 74 received in the groove 68. The compensating channel 66 could also be designed... For example, it could also be designed with the aid of a further groove formed in a spiral shape within the groove 68. Alternatively, the groove 68 itself could be formed in the form of a spiral winding around the end section of the valve bushing 14. To realize the compensation channel 66, the valve bushing 14 has the annular groove 68 at its end section facing the electromagnetic actuator 12. A second end 70 of the valve bushing 14 extends axially from a second end 70 facing away from the first end 52. The first channel section 72, extending and opening into the groove 68, serves as the entry point for the fluid into the groove 68. In other words, in this first embodiment, the compensating channel 66 comprises at least one channel section extending predominantly in the axial direction, the first channel section 72, and a second channel section 73 extending axially and circumferentially. The second channel section 73 includes the groove 68 and the channel element 74. The direction of fluid flow is indicated by the arrows 76, as can also be seen in Fig. 3. The channel element 74 is received in the groove 68, and this element is used to create the channel walls 77. This channel element 74 is designed in the form of a spiral element – ​​in this case, a spiral spring. The overall length of the compensating channel 66 depends on the number of turns of the channel element 74. In other words, increasing the number of turns leads to a longer overall length of the compensating channel 66. The compensating channel 66 is formed between an outer surface 78 of the valve bushing 14 and an inner surface 80 of the hollow cylindrical pole element 82 of the electromagnetic actuator 12, wherein the channel element 74 is predominantly arranged between the outer surface 78 and the inner surface 80. To extend the compensating channel 66, a radially extending, annular collar 92 is provided in the area of ​​the groove 68, wherein a receiving space 94 is created between the pole element 82 forming the inner surface 80 and the collar 92, in which the channel element 74 is positioned extending radially from the groove 68. The hydraulic valve 10 according to the invention in a second embodiment is shown in section in Fig. 4. The compensating channel 66 extends in the radial direction. As can be seen, in this embodiment the channel element 74 extends in a first section in the axial direction and in a second section in the radial direction. In the radial direction, the channel element 74 is arranged in the receiving space 94 between a wall 84 of the pole element 82 and the collar 92. The channel element 74 is positioned close to the outer surface 78 of the groove 68. A small gap 96 is formed between the outer surface 78 and the channel element 74. This gap 96 allows air that occurs in the equalization channel to escape from the equalization channel 66, while the fluid follows the channel geometry towards the equalization opening 64. Slippage of the channel element 74 can be reduced by making the channel base 90 of the compensating opening 64 uneven, at least in the second channel section 73. In other words, steps are formed that must be overcome during the installation of the channel element 74. In this particular embodiment, the channel element 74 is made of spring steel, which, after installation, fits snugly against the outer surface 78 of the part of the end section intended for channel formation. However, within the scope of the invention, it is also conceivable to manufacture the channel element 74 from plastic or other suitable materials. Furthermore, the round cross-sectional shape and spring-like properties of the channel element 74 are not mandatory. The hydraulic valve 10 according to the invention in a third embodiment is shown in partial view in Fig. 5. The compensating channel 66 extends exclusively in the axial direction. The hydraulic valve 10 according to the invention in a fourth embodiment is shown in part in Fig. 6. The compensating channel 66 extends exclusively in the axial direction. A collar 97 is formed on the pole element 82 to allow for a further extension of the compensating channel 66. QUOTES INCLUDED IN THE DESCRIPTION This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature US 9,423,045 B2

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Claims

Electromagnetic hydraulic valve comprising an electromagnetic actuator (12) for positioning a piston (20) of the hydraulic valve (10) which is axially displaceably mounted in a valve bushing (14) of the hydraulic valve (10) along a longitudinal axis (18) of the valve bushing (14), wherein the piston (20) is used to open and / or close ports (P, A, T) of the valve bushing (14) allowing flow through them, wherein the valve bushing (14) has at least one compensating opening (64) which establishes a flowable connection with a tank connection (TL2), and wherein the hydraulic valve (10) has a compensating channel (66) for discharging fluid, which is connected to the compensating opening (64) allowing flow through it, characterized in that the compensating channel (66) is predominantly spirally extended in the given installation space along the longitudinal axis (18) so that an optimal length-cross-section ratio is achieved. Electromagnetic hydraulic valve according to claim 1, characterized in that the compensating channel (66) is formed in an end section of the valve bushing (14) which is opposite the electromagnetic actuator (12). Electromagnetic hydraulic valve according to claim 1 or 2, characterized in that the compensating channel (66) is formed by means of a channel element (74). Electromagnetic hydraulic valve according to claim 3, characterized in that the channel element (74) is designed in the form of a spiral element. Electromagnetic hydraulic valve according to claim 3 or 4 characterized in that the channel element (74) is made of spring steel or plastic. Electromagnetic hydraulic valve according to one of claims 1 to 5, characterized in that the compensating channel (66) has a channel section (72) extending axially from the second end (70) of the valve bushing (14). Electromagnetic hydraulic valve according to one of claims 3 to 6, characterized in that the channel element (74) is arranged in a groove (68) formed in the end section. Electromagnetic hydraulic valve according to claim 7, characterized in that a channel floor (90) of the compensating channel (66) is unevenly designed at least in the area of ​​a second channel section (73) in which the channel element (74) is arranged, such that steps are formed between which the channel element (74) can be received. Electromagnetic hydraulic valve according to one of claims 3 to 8, characterized in that a gap (96) is formed between the channel element (74) and a surface (80) that limits the channel element (74) in a radial direction. Electromagnetic hydraulic valve according to one of claims 3 to 9, characterized in that the channel element (74) is arranged to support itself on an annular collar (92) of the valve bushing (12). Electromagnetic hydraulic valve according to claim 10, characterized in that the channel element (74) is designed to extend in a first section in the axial direction and in a second section in the radial direction.

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