Solenoid valve, especially for slip-controlled motor vehicle braking systems

Abstract

An electromagnetic valve, particularly for slip-controlled motor vehicle braking systems, comprising a valve housing (1) in which a first and a second valve closing element (7, 8) are arranged coaxially, which are capable of opening or closing a first and a second valve passage (5, 6), wherein the first valve passage (5) has a smaller cross-section than the second valve passage (6), comprising a pressure medium inlet (13) and a pressure medium outlet (19) opening into the valve housing (1), wherein the first valve closing element (7) is capable of opening or closing the first valve passage (5) located in the second valve closing element (8) depending on the electromagnetic excitation of a valve coil, and wherein the second valve closing element (8) releases the second valve passage (6) under the influence of a valve spring (17) exclusively when the first valve passage (5) is in the open position.so that a pressure medium present in the pressure medium inlet (13) flows along a flow path within the valve housing (1), in which the first and second valve passages (5, 6) are located, to the pressure medium outlet (19), characterized in that the valve spring (17) is arranged between the first and the second valve closing elements (7, 8) and is attached to them in such a way that a tensile connection between the valve closing elements (7, 8) is established.

Description

[0001] The invention relates to an electromagnetic valve, in particular for slip-controlled motor vehicle braking systems, with a valve housing in which a first and a second valve closing element are arranged coaxially, which are capable of opening or closing a first and a second valve passage, wherein the first valve passage has a smaller cross-section than the second valve passage, with a pressure medium inlet and a pressure medium outlet opening into the valve housing, wherein the first valve closing element is capable of opening or closing the first valve passage located in the second valve closing element depending on the electromagnetic excitation of a valve coil, and wherein the second valve closing element, under the influence of a valve spring, releases the second valve passage exclusively in the open position of the first valve passage.so that a pressure medium present in the pressure medium inlet flows along a flow path within the valve housing, in which the first and second valve passages are located, to the pressure medium outlet.

[0002] Such a solenoid valve is described in DE 102 52 231 A1 and works as follows: The solenoid valve is normally closed (de-energized). It opens when the valve's electromagnet is energized, causing a magnetic armature connected to the first valve closing element to be pulled against a magnet.

[0003] This simultaneously opens the first valve passage in the second valve closing body, allowing pressure medium to initially flow from the pressure medium inlet to the pressure medium outlet.

[0004] Since the cross-section of the first valve passage is small, pressure equalization occurs only slowly. The first valve closing element is subjected to pressure from both the inlet and outlet of the valve, and because the second valve passage has a larger cross-section than the first, the pressure at the outlet initially pushes the first valve closing element against the second passage, thus keeping it closed until pressure equalization has occurred.

[0005] The first valve closing element is loaded by a valve spring that works against the pressure at the pressure medium inlet.

[0006] After the first valve passage has been opened and pressure equalization gradually occurs, there is a certain point at which the total pressure force on the first valve closing element becomes smaller than the force of the valve spring, so that it lifts the second valve closing element from the second valve passage and opens it.

[0007] The pressure medium is then rapidly discharged through the large cross-section of the second valve passage.

[0008] Such a two-stage design of the valve allows for a smooth opening process.

[0009] The valve spring is designed as a compression spring and is applied from below, i.e. against a surface that is directed towards the second valve passage, against a collar on the second valve closing element.

[0010] To provide support for the valve spring opposite the collar, a sleeve is located on the magnetic armature. This sleeve engages under the collar and has an inward-facing shoulder against which the valve spring is supported. Therefore, an additional component, namely the sleeve, is required to create support for the valve spring.

[0011] The invention is based on the objective of continuing to implement a smooth switching process - as explained above - while achieving a simpler valve design.

[0012] The invention is solved by arranging the valve spring between the first and the second valve closing element and attaching it to them in such a way that a tensile connection is created between the valve closing elements.

[0013] In contrast to the prior art, the valve spring is thus used as a tension spring rather than a compression spring. This has the advantage that an additional component that provides support for the valve spring can be omitted.

[0014] Preferably, the valve spring is designed such that it has a minimum stroke and a maximum stroke, wherein the minimum stroke is present when the first valve closing element is in contact with the first valve passage, and the maximum stroke is present when the first valve closing element is spaced away from the second valve closing element and the second valve closing element is in contact with the second valve passage, and that the spring characteristic of the valve spring is arranged such that the spring force in the maximum stroke is less than a predetermined holding force, which is determined from the pressure differential value at the second valve element, related to the cross-sectional difference of the second and first valve passages, when the second valve element is in a position where the second valve passage is still closed but no pressure equalization between the inlet pressure and the outlet pressure has yet taken place, but is greater than a release force.which is determined from the pressure differential value at the second valve body, related to the cross-sectional difference of the second and first valve passages, in which the second valve passage is in a position where the second valve passage is still closed, but because of the open first valve passage at least a partial pressure equalization between the inlet pressure and the outlet pressure has already taken place.

[0015] This adjustment of the valve spring means that its spring force is insufficient to pull the second valve closing element in until pressure equalization has occurred. Instead, the second valve closing element initially remains in its closed position at the second valve passage.

[0016] Only when a certain pressure equalization has taken place and the total pressure force on the second valve closing element has decreased, is the spring tension able to lift the second valve closing element from the second valve passage and open it.

[0017] To secure the valve spring, it is proposed that the magnetic armature has a first socket on its side facing the second valve closing body and a second socket on the end face of the second valve closing body opposite this socket, with the valve spring being attached to one of the sockets at each of its ends.

[0018] The fastening is particularly easy to achieve if the valve spring is a cylindrical spring and the bases each have a cylindrical shape and the ends of the valve spring are placed on the bases.

[0019] No further fastening means are necessary if the inner diameter of the valve spring is slightly smaller than the outer diameter of the bases, so that the inside of the valve spring is held in frictional contact with the outer surface of the bases.

[0020] The difference between the inner diameter of the cylindrical spring and the outer diameters of the bases must be chosen so that the frictional connection provides a greater fastening force than the release force.

[0021] The invention further provides that the second valve closing element is manufactured as a turned part from free-cutting steel.

[0022] Furthermore, the invention provides that the valve housing is made in one piece, the open sleeve end of which, facing away from the second valve passage, is closed by a plug acting as a magnetic core, which is designed as a cold-forged or flow-forged part.

[0023] The invention is explained in more detail below using an exemplary embodiment. The single figure shows a longitudinal section through a valve according to the invention.

[0024] The solenoid valve thus has a one-piece, thin-walled valve housing 1, manufactured using a deep-drawing process. This housing accommodates the upper end of a separate retaining collar 2, which is attached to the outer circumference of the valve housing by laser welding and is manufactured, for example, as a cold-forged part by chipless forming. The essentially disc-shaped retaining collar 2 is designed as a crimping die on its outer circumference, so that its circumferential undercut allows it to be pressed into a stepped receiving bore of a block-shaped valve carrier (not shown) along with the assembled valve housing 1. During the pressing-in process, the soft material of the valve carrier is displaced into the undercut for fastening and sealing purposes.

[0025] A sleeve 9, forming an extension of the valve housing 1, is attached to the lower end of the retaining collar 2. Above the retaining collar 2, the open end section of the sleeve-shaped valve housing 1 is closed with a plug 14, which simultaneously functions as a magnetic core. The plug 14 is also a cost-effective and sufficiently precisely manufactured cold-forged part, which is laser-welded to the valve housing 1 around its outer circumference. Below the plug 14 is a magnetic armature 4, which is also manufactured very cost-effectively from a round or polygonal profile by cold forging or extrusion. In the valve's initial position, the magnetic armature 4, under the action of a closing spring 16, closes a first valve passage 5, located in a second valve closing element 8, together with the first valve closing element 7 attached to the magnetic armature 4.The second valve closing element 8 is in the sleeve 9, which below the second valve closing element 8 holds a valve seat body 10 through which a second valve passage 6 runs.

[0026] For this purpose, the first valve closing element 7 is expediently designed as a valve ball 11 and riveted into a recess in an end face of a base 20 on the end face of the magnetic armature 4. The second valve closing element 8 is designed as a hollow cylinder. Under the action of a valve spring 17, it is biased in the closing direction against a second valve passage 6.

[0027] As a result of the action of the closing spring 16 arranged between the plug 14 and the magnetic armature 4, the valve ball 11, which acts as a valve closure, remains in the valve's basic position as shown in the illustration, at the second valve passage 6 provided at the lower end of the valve, the cross-sectional area of ​​which is considerably larger than the opening cross-section of the first valve passage 5.

[0028] The pressure medium inlet 13, which is essentially designed as a transverse channel in the valve carrier, continues via a cavity in the valve carrier to a punched transverse bore 18 in the sleeve 9, so that inlet-side pressure medium is directly adjacent to the second valve closing element 8.

[0029] The second valve passage 6 is provided for the mechanical relief of the valve housing 1 in a disc- or sleeve-shaped valve seat body 10, which is held on the inner wall of the sleeve 9 by means of an interference fit. The valve seat body 10 is made of a wear-resistant metal.

[0030] In contrast to the prior art design, the valve spring 17 is not designed as a compression spring, but as a tension spring.

[0031] The magnetic armature 4 has a central extension in the form of a base 20, at the free end of which the valve ball 11 is pressed into a recess. The base 20 tapers slightly conically but has a cylindrical foot.

[0032] The second valve closing element 8 also has a base 23 at its end facing the magnetic armature 4, which has a cylindrical surface through whose center the first valve passage 5 runs.

[0033] The front face of the base 23 is slightly conically drawn inwards, thus forming a valve seat 24 which can be occupied by the valve ball 11 in order to block the first valve passage 5.

[0034] The valve spring 17 is designed as a cylindrical spring and has an inner diameter that is slightly smaller than the diameters of the two bases 20, 23, so that its ends can be pressed onto them, creating a frictional connection that ensures a firm connection of the valve spring 17 between the magnetic armature 4 and the second valve closing element 8.

[0035] The valve spring 17 has a certain preload, so that the valve ball 11 is placed on the valve seat 24 with a slight pressure and keeps it closed.

[0036] When the valve opens, the magnetic armature 4 is magnetized and pulled against the magnetic core (plug 14) by the force of a closing spring 16. Since the second valve closing element 8 is subjected to pressure at the valve inlet in the closing direction, the preload of the valve spring is insufficient to pull it along. Instead, the second valve closing element 8 remains in its valve seat at the second valve passage 6.

[0037] Now, hydraulic fluid can flow from the hydraulic fluid inlet 13 to the hydraulic fluid outlet 19 below the second valve passage 6 via the first valve passage 5, which has a small cross-section. However, since this presents a hydraulic resistance, pressure equalization occurs only slowly.

[0038] At a certain point, however, a pressure will be present at the pressure medium outlet 19 that balances the pressure at the pressure medium inlet, thus reducing the total pressure force on the second valve closing element 8 and enabling the valve spring 17 to pull the second valve closing element 8 against the first valve closing element 7. While the first valve passage 5 is closed, the second valve passage 6 is simultaneously opened, so that in the second phase of pressure medium equalization a large cross-section is available, which promotes rapid pressure equalization. Reference symbol list 1 Valve housing 2 retaining collars 4 magnetic anchors 5 first valve passage 6 second valve passage 7 first valve closing element 8 second valve closing body 9 sleeve 10 valve seat bodies 11 Valve ball 13 Pressure medium inlet 14 plugs 16 Locking spring 17 Valve spring 18 transverse bore 19 Pressure medium outlet 20 sockets 23 sockets 24 valve seat

Claims

[1] Electromagnetic valve, in particular for slip-controlled motor vehicle braking systems, comprising a valve housing (1) in which a first and a second valve closing element (7, 8) are arranged coaxially, which are capable of opening or closing a first and a second valve passage (5, 6), wherein the first valve passage (5) has a smaller cross-section than the second valve passage (6), comprising a pressure medium inlet (13) and a pressure medium outlet (19) opening into the valve housing (1), wherein the first valve closing element (7) is capable of opening or closing the first valve passage (5) located in the second valve closing element (8) depending on the electromagnetic excitation of a valve coil, and wherein the second valve closing element (8) releases the second valve passage (6) under the influence of a valve spring (17) exclusively when the first valve passage (5) is open,so that a pressure medium present in the pressure medium inlet (13) flows along a flow path within the valve housing (1), in which the first and second valve passages (5, 6) are located, to the pressure medium outlet (19), , characterized by , that the valve spring (17) is arranged between the first and the second valve closing element (7, 8) and is attached to them in such a way that a tensile connection is established between the valve closing elements (7, 8). [2] Solenoid valve according to claim 1, characterized by, that the valve spring (17) has a minimum stroke and a maximum stroke, wherein the minimum stroke is present when the first valve closing element (7) is in contact with the first valve passage (5), and the maximum stroke is present when the first valve closing element (7) is spaced away from the second valve closing element (8) and the second valve closing element (8) is in contact with the second valve passage (6), and that the spring characteristic of the valve spring (17) is arranged such that the spring force in the maximum stroke is less than a predetermined holding force, which is determined from the pressure differential value at the second valve closing element (8) related to the cross-sectional difference of the second and first valve passages (5, 6), in which the latter is in a position where the second valve passage (6) is still closed but no pressure equalization between the inlet pressure and the outlet pressure has yet taken place, but is greater than a release force,which is determined from the pressure differential value at the second valve closing element (8) related to the cross-sectional difference of the second and first valve passages (5, 6), in which the latter is in a position where the second valve passage (6) is still closed but, due to the open first valve passage (5), at least a partial pressure equalization between the inlet pressure and the outlet pressure has already taken place. [3] Solenoid valve according to claim 1 or 2, characterized by , that the magnetic armature (4) has a first base (20) on its side facing the second valve closing body (8) and the end face of the second valve closing body opposite the base has a second base (23), wherein the valve spring (17) is attached with its ends to each of the bases (20, 23). [4] Solenoid valve according to claim 3, characterized by, that the valve spring (17) is a cylindrical spring, that the bases (20, 23) each have a cylindrical shape and the ends of the valve spring (17) are placed on the bases (20, 23). [5] Solenoid valve according to claim 4, characterized by , that the inner diameter of the valve spring (17) is slightly smaller than the outer diameters of the bases (20, 23), so that the inside of the valve spring (17) is held in frictional contact with the outer surface of the bases (20, 23). [6] Solenoid valve according to claim 5, characterized by that the frictional connection provides a greater fastening force than the loosening force. [7] Solenoid valve according to any one of the preceding claims, characterized by , that the second valve closing element (8) is manufactured as a turned part from free-cutting steel. [8] Solenoid valve according to any one of the preceding claims, characterized by, that the valve housing (1) is made in one piece, the open sleeve end of which is closed by a plug (14) acting as a magnetic core, which is designed as a cold-forged or flow-forged part.

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