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

Abstract

Electromagnetic valve, in particular for slip-controlled motor vehicle braking systems, comprising a first and a second valve closing element (1; 2) arranged in a valve housing (3), which are coaxially arranged in the valve housing (3) and are each capable of opening or closing a valve passage (6; 12) in a first and a second valve seat (7; 13), respectively, comprising a magnetic armature (8) which forms a self-contained assembly with the first valve closing element (1) and which can be applied to the second, sleeve-shaped valve closing element (2) under the action of a return spring (17), comprising a magnetic core (16) in the valve housing on which a spring end of the return spring (17) facing away from the assembly is supported, comprising a pressure medium inlet (18) opening into the valve housing (3) and a pressure medium outlet (19),wherein the first valve closing element (1) is able to open the first valve passage (12) located in the second valve closing element (2) depending on the electromagnetic excitation of a valve coil attachable to the valve housing (3), wherein the second valve closing element (2) is electromagnetically actuated to release the second valve seat (7), characterized in that the second valve closing element (2) is attached to a solenoid (10) which is fixed between the solenoid armature (8) and the second valve seat (7) on the first valve closing element (1).

Description

[0001] The invention relates to an electromagnetic valve, in particular for slip-controlled motor vehicle braking systems, according to the preamble of claim 1.

[0002] An electromagnetic valve of the type described is already known from DE 10 2005 014 100 A1, comprising a first and a second valve closing element arranged in a valve housing. These elements are coaxially arranged within the valve housing, similar to a two-stage valve, and are capable of opening or closing both a first and a second valve passage. The second valve closing element is located below the first valve closing element in a guide sleeve that is fixed within the valve housing. A compression spring, subject to manufacturing tolerances, is clamped between the second valve closing element and a stop located on the guide sleeve. This spring exerts force on the second valve closing element in the direction of the first valve closing element, enabling it to lift the second valve closing element from its valve seat. Consequently, the valve requires a correspondingly complex design.

[0003] Furthermore, US Patent 2004 / 0035472A1 discloses an electromagnetic valve with two valve closing elements, wherein a first valve closing element is able to close a first valve passage in the second valve closing element, wherein both valve closing elements are electromagnetically actuated by means of a coil encompassing the solenoid valve, and the two valve closing elements therefore either consist entirely of magnetizable material or contain at least a part of this material.

[0004] Furthermore, an electromagnetic valve is known from the subsequently published DE 10 2015 213 284 A1 in which the use of a compression spring with tolerances can be avoided by manufacturing the tension and compression spring as a longitudinally elastic plunger.

[0005] The object of the present invention is therefore to design an electromagnetic valve of the type specified in a cost-effective and compact manner using the simplest possible functional means, which is why the previously required compression spring should be eliminated.

[0006] This problem is solved according to the invention for the solenoid valve of the type specified by the features of claim 1.

[0007] Further features and advantages of the invention will become apparent from the description of several exemplary embodiments below.

[0008] They show: Fig. 1 A longitudinal section view of an electromagnetic valve, the two valve closing elements of which can be actuated exclusively electromagnetically to release the valve seats, Fig. 2 the solenoid valve after Fig. 1 in an electromagnetically excited switching position of the magnetic armature, in which the first valve closing element is lifted from its valve seat, while the second valve closing element remains on its valve seat, Fig. 3 the solenoid valve after Fig. 1 in an electromagnetically excited switching position of the second valve closing element connected to a lifting magnet, which is lifted from its valve seat under the action of the lifting magnet.

[0009] The Fig. Figures 1 to 3 each show, at a considerable magnification, a longitudinal section of a solenoid valve with a multi-part valve housing 3. The lower and upper housing sections are preferably formed as thin-walled sleeves 5 using a deep-drawing process. The central, particularly thick-walled housing section is preferably formed as a tube 4 by chipless forming. The upper sleeve 5 adjoins the solid tube 4, which is manufactured, for example, as a cold-forged part. The upper sleeve 5 is closed by a plug-shaped magnetic core 16. The magnetic core 16 also preferably consists of a cost-effective and sufficiently precisely manufactured cold-forged part, which is laser-welded to the outer circumference of the sleeve 5. Below the magnetic core 16, a magnetic armature 8 is located in the valve housing 3. This armature is also manufactured very cost-effectively from a round or polygonal profile by cold forging or extrusion.

[0010] As shown in the illustration, in the valve's basic position, the magnetic armature 8, which has the first valve closing element 1, closes the first valve seat 13 arranged in a second valve closing element 2 under the direct action of a return spring 17, which determines the size of the first valve passage 12.

[0011] As a result of the action of the return spring 17 on the first valve closing element 1, in the illustrated, electromagnetically unexcited valve position, the second valve closing element 2 closes a (second) valve seat 7 provided in the lower sleeve 5 of the valve housing 3, which has a (so-called second) valve passage 6, the openable passage cross-section of which is considerably larger than the electromagnetically openable opening cross-section of the (first) valve passage 12 arranged in the second valve closing element 2.

[0012] In all illustrated embodiments, at least one pressure medium inlet channel 18 opens laterally into the lower sleeve 5 at the level of the second valve closing element 2. The pressure medium outlet 19, opening perpendicularly into the lower sleeve 5, is located below the second valve closing element 2. The pressure medium enters the lower sleeve 5 via the two pressure medium inlets 18, which are shown as horizontal channels in the lower sleeve 5. Fig. 2, Fig. 3 The pressure medium flow shown proceeds in the direction of both valve closing elements 1, 2, so that inlet-side pressure medium, after passing through a ring filter 9, reaches the two valve seats 13, 7 via the shortest route.

[0013] To keep the size, weight, and material usage as low as possible, the second valve closing element 2 is designed as a hollow plunger which, in conjunction with a precisely guided solenoid 10 in the valve housing 3, is directed towards its valve seat 7. As can be seen from the Fig. As can be clearly seen from Figures 1 to 3, the valve housing 3 consists of a thick-walled tube 4 with different wall thicknesses and two thin-walled sleeves 5 with constant wall thickness, between which the tube 4 is fixed, wherein in the lower sleeve 5 the second valve seat 7, which has the second, generously dimensioned valve passage 6, is preferably fixed as a separate ring disc component instead of an integrated design.

[0014] In the figures, the return spring 17 is predominantly mounted centrally within the magnetic armature 8 in a particularly compact design. For this purpose, the magnetic armature 8 has a blind bore adapted to the diameter of the return spring 17, at the bottom of which the return spring 17 rests with its end facing away from the magnetic core 16. The magnetic armature 8 preferably carries the spherical first valve closing element 1 in a positive-locking connection. This first valve closing element interacts with the first valve seat 7 integrated within the second valve closing element 2. The first valve passage 12 is directly connected to the first valve seat 7 within the second valve closing element 2. This first valve passage 12 typically has a significantly smaller opening cross-section than the second valve passage 6 located in the second valve seat 13, acting as a pilot stage.

[0015] In order to eliminate the need for a compression spring with tolerances for actuating the second valve closing element 2, the invention provides that the second valve closing element 2 can be actuated exclusively electromagnetically to release the second valve seat 7, for which purpose the second valve closing element 2 is rigidly connected to the solenoid 10, which is guided directly between the closing head of the second valve closing element 2 and the first valve closing element 1 in the tube 4.

[0016] The second valve closing element 2, connected to the lifting magnet 10, can thus be lifted from the second valve seat 7 in a simplified manner by means of a conventional valve coil extending from the magnetic core 16 to the tube 4, which is required anyway for actuating the magnetic armature 8. A diagram of the valve coil has been omitted.

[0017] Preferably the solenoid 10 is designed as a ring solenoid, in the central opening of which the second valve closing element 2 is fixed in a simple yet precise manner, which is designed as a hollow plunger for the further formation of the valve passage 12 adjoining the first valve seat 13.

[0018] For miniaturization and optimal design of the magnetic circuit, the solenoid 10 is funnel-shaped and widened towards the magnetic armature 8. The end section of the magnetic armature 8 facing the solenoid 10 is at least partially received in the funnel-shaped opening of the solenoid 10. For this purpose, the end section of the magnetic armature 8 is adapted to the funnel-shaped contour of the solenoid 10 in the form of an armature cone 11. At its conical end, the first valve closing element 1 is received. In the electromagnetically unexcited home position, the first valve closing element 1, together with the armature cone 11, is drawn into the funnel-shaped contour of the solenoid 10 by the action of the return spring 17, thereby closing the first valve seat 13 located in the second valve closing element 2.

[0019] Between the funnel-shaped contour of the solenoid 10 and the armature cone 11 is an air gap 14, which can be bridged by the magnetic flux of the valve coil and which, due to the selected funnel geometry, enables optimal magnetic contact. As a result of the geometric overlap between the armature cone 11 and the funnel-shaped solenoid 10, a significantly high magnetic flux density is achieved both for the closed valve and for lifting the second valve closing element 2 from its valve seat 13, as soon as the second valve closing element 2 is hydraulically pressure-compensated.

[0020] Both the magnetic armature 8 and the lifting magnet 10 are guided with minimal radial play in the valve housing 3, so that the magnetic flux can be transmitted with negligible power loss via a minimal gap 20 provided between the tube 4 and the lifting magnet 10 as well as via a minimal gap 20 between the tube 4 and the magnetic armature 8.

[0021] According to the explained constructive design of the air gap 14 and the radial gaps 20, the required magnetic flux for the magnetic armature 8 as well as the lifting magnet 10 can thus be optimally represented for all switching positions.

[0022] Furthermore, instead of a longitudinal channel arranged on the outer surface of the solenoid 10, at least one longitudinal channel 15 is now provided between the solenoid 10 and the second valve closing element 2. This channel is designed as a notch or groove milled into the inner surface of the solenoid 10 and is permanently connected to the pressure medium inlet 18 opening into the valve housing 3. The internal longitudinal channel 15 significantly improves the magnetic contact between the valve housing 3 and the solenoid 10 by maintaining the minimum radial gap 20.

[0023] The Fig. Figure 2 shows the first valve closing element 1 in a position lifted from the first valve seat 13 as a result of electromagnetic excitation of the magnetic armature 8 initiated by the valve coil. In this position, the longitudinal channel 15 connects the pressure medium inlet 18 via the valve passage 12 in the second valve closing element 2 to a pressure medium outlet 19 adjacent to the second valve seat 7 in the valve housing 3, as long as the second valve closing element 2 remains at its valve seat 13 due to its hydraulically unbalanced state. The arrows shown are intended to illustrate the flow direction of the pressure medium, the completed direction of movement of the magnetic armature 8, and the direction of movement yet to be completed by the lifting magnet 10.

[0024] As from the Fig. As can be seen from Figure 3, only after hydraulic pressure compensation does the lifting magnet 10, which is under the influence of the magnetic circuit, lift the second valve closing element 2 from its valve seat 13, so that, according to the arrow representation, a direct hydraulic connection between the pressure medium inlet 18 and the pressure medium outlet 19 is subsequently established via the open large valve passage 6 in the shortest possible way.

[0025] The solenoid 10 is made of a low-alloy, soft magnetic steel to make the best possible use of the magnetic forces, in which the second valve closing element 2, made of a tempered, high-alloy steel, is adjusted by means of a sliding press fit for the precise adjustment of the air gap 14 provided between the magnetic armature 8 and the solenoid 10.

[0026] Regarding the results from the Fig. The following can be determined from the operating principle of the depicted solenoid valve, which can be seen in points 1 to 3: In the Fig. In the electromagnetically non-excited valve position shown in 1, both valve closing elements 1, 2 assume their valve closing positions as a result of the closing force of the return spring 17.

[0027] According to the Fig. 2. The magnetic armature 8 remains in contact with the magnetic core 16 as a result of a stroke movement initiated electromagnetically by the valve coil. This causes the first valve closing element 1 to move away from the first valve seat 7 integrated in the second valve closing element 2, as long as the second valve closing element 2 is not hydraulically pressure-balanced. Therefore, the valve closing element 2 is initially still subjected to a hydraulic pressure differential in the closing direction and thus rests against the second valve seat 13. Consequently, in this state, the hydraulic fluid can only reach the hydraulic fluid outlet 19 in a throttled manner via the orifice-shaped valve passage 12 in the first valve seat 7.

[0028] After hydraulic pressure equalization has been achieved, the prerequisite is created in a relatively simple way for the second valve closing element 2 to lift off from the second valve seat 13 by the magnetic field of the valve coil acting on the lifting solenoid 10 and to open the large, unobstructed cross-section in the second valve passage 6. Fig. Figure 3 illustrates the end position of the lifting magnet 10, which is brought towards the magnetic core 16, and on whose spherical valve closing element 1 the raised second valve closing element 2 with its integrated valve seat 7 is supported.

[0029] With the termination of the electromagnetic excitation, the direction of movement of the magnetic armature 8 and the lifting magnet 10 reverses due to the action of the return spring 17, so that both valve closing elements 1, 2 again move analogously to Fig. 1 assume their closed switching positions at both valve seats 7,13. Reference symbol list 1 Valve closing element 2 valve closing elements 3 Valve housings 4 pipe 5 Sleeve 6 valve passage 7 valve seat 8 magnetic anchors 9 ring filters 10 lifting magnet 11 anchor cones 12 Valve passage 13 Valve seat 14 air gap 15 Longitudinal channel 16 magnetic cores 17 Return spring 18 Pressure medium inlet 19 Pressure medium outlet 20 gaps

Claims

[1] Electromagnetic valve, in particular for slip-controlled motor vehicle braking systems, comprising a first and a second valve closing element (1; 2) arranged in a valve housing (3), which in a coaxial arrangement in the valve housing (3) each have a valve passage (6; 12) in a first and in a second valve seat (7;13) able to open or close, with a magnetic armature (8) which forms an independently manageable assembly with the first valve closing element (1), which can be applied to the second, sleeve-shaped valve closing element (2) under the action of a return spring (17), with a magnetic core (16) in the valve housing, on which a spring end of the return spring (17) facing away from the assembly is supported, with a pressure medium inlet (18) opening into the valve housing (3) and a pressure medium outlet (19), wherein the first valve closing element (1) is able to open the first valve passage (12) located in the second valve closing element (2) depending on the electromagnetic excitation of a valve coil attachable to the valve housing (3), wherein the second valve closing element (2) is electromagnetically actuated to release the second valve seat (7), ; characterized by, that the second valve closing element (2) is attached to a lifting magnet (10) which is fixed between the magnet armature (8) and the second valve seat (7) on the first valve closing element (1). [2] Solenoid valve according to claim 1, characterized by , that the second valve closing element (2) connected to the lifting magnet (10) can be lifted off the second valve seat (7) by means of the valve coil attached to the valve housing (3). [3] Solenoid valve according to claim 1, characterized by , that the lifting magnet (10) is designed as a ring magnet, in whose central opening the second valve closing element (2) is fixed. [4] Solenoid valve according to claim 3, characterized by , that the second valve closing element (2) is designed as a hollow plunger to accommodate the valve passage (12) adjoining the first valve seat (13). [5] Solenoid valve according to claim 1, characterized by, that the lifting magnet (10) is funnel-shaped in the direction of the magnetic armature (8), and that the magnetic armature (8) with its end section facing the lifting magnet (10) is received at least partially in the funnel-shaped opening of the lifting magnet (10) in the manner of a diving magnet. [6] Solenoid valve according to claim 5, characterized by , that the end section of the magnetic armature (8) is adapted to the funnel-shaped contour of the lifting magnet (10) in the form of an armature cone (11), which at its conical end receives the first valve closing element (1), which together with the armature cone (11) in the electromagnetically unexcited basic position, under the action of the return spring (17), immerses into the funnel-shaped opening of the lifting magnet (10) and closes the first valve seat (13) arranged in the second valve closing element. [7] Solenoid valve according to claim 6, characterized by, that an air gap (14) which can be bridged by the magnetic flux of a valve coil is provided between the funnel-shaped opening of the lifting magnet (10) and the armature cone (11). [8] Solenoid valve according to claim 1, characterized by , that a longitudinal channel (15) is provided between the lifting magnet (10) and the second valve closing element (2) designed as a hollow plunger, which establishes a hydraulic connection between a pressure medium inlet (18) opening into the valve housing (3) and the first valve closing element (1) cooperating with the first valve seat (13). [9] Solenoid valve according to claim 8, characterized by , that in a position of the first valve closing element (1) lifted from the first valve seat (13) the longitudinal channel (15) connects the pressure medium inlet (18) via the valve passage (12) in the second valve closing element (2) with a pressure medium outlet (19) adjacent to the second valve seat (7) in the valve housing (3). [10] Solenoid valve according to claim 8, characterized by , that the longitudinal channel (15) is formed by a notch or groove milled into the inner shell of the lifting magnet. [11] Solenoid valve according to claim 1, characterized by , that the lifting magnet (10) is made of a low-alloy, soft magnetic steel in which the second valve closing element (2) made of a tempered, high-alloy steel is adjusted by means of a sliding press fit for the precise adjustment of an air gap (14) provided between the magnetic armature (8) and the lifting magnet (10).

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