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

Abstract

An electromagnetic valve, particularly for hydraulic, wheel-slip-controlled motor vehicle braking systems, comprising a first and a second valve closing element arranged in a valve housing, each capable of opening or closing a valve passage in a first and a second valve seat in the valve housing, comprising a magnetic armature which, under the action of a return spring, is removed from a magnetic core in the valve housing, on which a spring end of the return spring facing away from the magnetic armature is supported, and comprising a pressure medium inlet and a pressure medium outlet connected to the valve housing, between which the two valve closing elements with their associated valve seats are arranged, characterized in that, in the electromagnetically unactuated state of the magnetic armature (2), both valve closing elements (8, 10) are closed by means of the return spring (4) and a valve spring (11) arranged between the two valve closing elements (8, 10).10) are lifted from their valve seats (14, 15).

Description

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

[0002] From DE 10 2005 048 880 A1, an electromagnetic valve of the type described is already known, comprising a first and a second valve closing element arranged in a valve housing, which are capable of opening or closing a first and a second valve passage in the valve housing, respectively. The second valve closing element, designed as a differential pressure-dependent check valve, is located in a parallel circuit below the first, electromagnetically actuated valve closing element.

[0003] However, the check valve has the disadvantage that it is only absolutely leak-proof at large pressure differences, and that undesirable leaks can occur at small pressure differences.

[0004] Therefore, the object of the present invention is to improve an electromagnetic valve of the type specified by the simplest possible functional means in such a way that, regardless of the magnitude of the pressure difference, the second valve closing element seals in its closed position without leakage occurring at its valve seat.

[0005] This problem is solved according to the invention for the solenoid valve of the type specified by the features of claim 1.

[0006] Further features and advantages of the invention will become apparent below from the description of an exemplary embodiment with reference to several drawings.

[0007] They show: Fig. 1. An overall view of a solenoid valve in longitudinal section in an electromagnetically de-energized basic position, which is provided with two valve closing elements to be actuated successively in order to form a two-stage valve, Fig. 2 that out Fig. 1 known solenoid valve in a partially electromagnetically closed position, in which the first valve closing element in the associated first valve seat keeps the large flow cross-section closed, while the second valve closing element keeps the relatively small flow cross-section open in its associated second valve seat, Fig. 3 that out Fig. 1 known solenoid valve in its electromagnetically completely closed switching position, in which both valve closing elements securely close the associated two valve seats solely depending on the maximum completed magnetic armature stroke.

[0008] The Fig. Figures 1 to 3 each show, at a considerable magnification, a two-stage solenoid valve in longitudinal section with a multi-part valve housing 3, the upper housing area of ​​which is preferably manufactured as a thin-walled sleeve using a deep-drawing process. The lower, particularly thick-walled valve housing 6 forms a further part of the valve housing assembly. The sleeve-shaped valve housing 3 is preferably bonded to the thick-walled valve housing 6 and is closed by a plug-shaped magnetic core 5. The magnetic core 5 preferably consists of a cost-effective and sufficiently precisely manufactured cold-forged part, which is preferably laser-welded to the outer circumference of the sleeve-shaped valve housing 3. A magnetic armature 2 is guided in the valve housings 3 and 6 below the magnetic core 5. This armature can also be manufactured very cost-effectively from a round or polygonal profile, for example, by cold forging or extrusion.A return spring 4 is clamped between the magnetic armature 2 and the magnetic core 5 for the basic positioning of the two valve closing elements 8, 10 in the open valve basic position.

[0009] The thick-walled valve housing 6 contains the two valve closing elements 8, 10 in a coaxial arrangement for two-stage actuation, each of which is able to open or close a valve passage in a first as well as in a second valve seat 14, 15.

[0010] The second valve closing element 8 is attached to a plunger 7 extending through the passage opening of the first valve seat 14, which is formed centrally on the end face of the magnetic armature 2 facing away from the magnetic core 5, while the first valve closing element 10 is formed on a sleeve 12 extending through the passage opening of the first valve seat 14, which is guided on the plunger 7.

[0011] The first valve closing element 10 is essentially designed as an annular disc seat valve with a larger diameter than the second valve closing element 8, and has the second valve seat 15 in the central opening of the annular disc. The central opening provided for the passage of pressure medium through the second valve seat 15 adjoins a vertical annular channel 13 provided sectionally between the sleeve 12 and the plunger 7, which is connected via at least one transverse bore 16 in the sleeve 12 to the pressure medium inlet A opening into the valve housing 3.

[0012] The second valve closing element 8 is essentially designed as a poppet valve with a smaller diameter than the first valve closing element 10, which is aligned concentrically to the second valve seat 15 arranged in the first valve closing element 10 by means of the plunger 7 guided in the sleeve 12. The contour of the second valve closing element 8 can be designed as a sphere, cone, or plate if desired or required.

[0013] As shown in the illustration, the valve is in its basic position after Fig. 1 In the electromagnetically unactuated state of the magnetic armature 2, the return spring 4 and a valve spring 11, which is arranged between the two valve closing elements 8, 10, lift both valve closing elements 8, 10 from their valve seats 14, 15, so that an unimpeded hydraulic connection is established between the pressure medium inlet A connected to the valve housing 6 and a pressure medium outlet B. The valve spring 11 is designed as a compression spring, which is clamped in a compact design between the first valve closing element 10 and a spring stop 9 formed on the second valve closing element 8.

[0014] The Fig. Figure 2 shows the solenoid valve in an electromagnetically initiated partial stroke of the magnetic armature 2 as a result of a current-carrying valve coil 1, whereby the first valve seat 14 is closed by the first valve closing element 10 and the second valve seat 15 is initially still released unchanged by the second valve closing element 8 under the action of the valve spring 11.

[0015] The Fig. Figure 3 finally shows an electromagnetically initiated maximum stroke of the magnetic armature 2, whereby, in addition to the first valve seat 14 closed by the first valve closing element 10, the second valve seat 15 is also closed by the second valve closing element 8 against the action of the valve spring 11.

[0016] The presented two-stage design of the solenoid valve eliminates the need for the differential pressure-dependent check valve known from the prior art. The complete tightness of the closed second valve element 8 is now guaranteed independently of the pressure differential due to the mechanical connection between the pressure medium inlet A and the pressure medium outlet B with the plunger 7 formed on the magnetic armature 2.

[0017] The two-stage design also has the advantage that the solenoid valve can be switched with small currents, since the return spring 4, located between the magnetic armature 2 and the magnetic core 5, only needs to have a small spring force. If the pressure p A The pressure at pressure medium inlet A is greater than the pressure p. BIn the pressure medium outlet B, the pressure differential assists in lifting the large valve closing element 10 from its valve seat 14. A high spring force is not required for this. If the pressure p B Since the pressure medium outlet B is larger than the pressure medium inlet A, the large flow opening in the first valve seat 14 is closed by the first valve closing element 10 due to the low spring force of the return spring 4. The comparatively large spring force of the valve spring 11 then keeps the small flow opening in the second valve seat 15 open. Because the valve spring 11 is supported between the first valve closing element 10 and the spring stop 9 of the second valve closing element 8, which is rigidly connected to the magnetic armature 2 via the plunger 7, the return spring 4 can be implemented with a low spring force.

[0018] When the presented solenoid valve is used as a wheel-side brake pressure modulation valve (so-called inlet valve) in a wheel-slip-controlled brake system, in the electrically de-energized state of the valve coil 1, during a hydraulic pressure build-up from the direction of the pressure medium outlet B to the pressure medium inlet A, the first valve closing element 10 is closed by the pressure difference (p B > p A ) against the spring force of the return spring 4, it is pressed against its valve seat 14 and closes its large flow opening. Flow through the small flow opening in the second valve seat 15 is still possible, since the high spring force of the valve spring 11 prevents the second valve closing element 8 from closing the small flow opening in the second valve seat 15.

[0019] During pressure reduction in the normal braking mode of the brake system (valve coil 1 is not energized), the first valve closing element 10 is closed by the pressure difference (pA > p B The valves are opened, allowing flow through both flow openings into the valve seats 14 and 15. This allows the wheel brake pressure to be quickly reduced from the pressure medium inlet A to the pressure medium outlet B.

[0020] In order to enable a reduction of wheel brake pressure in anti-lock braking mode via a further brake pressure modulation valve (so-called exhaust valve) on the wheel outlet side, the valve coil 1 is electrically energized and the presented solenoid valve according to the invention (so-called inlet valve) is completely closed via the maximum magnetic armature stroke.

[0021] For the targeted increase in wheel brake pressure required after the reduction of wheel brake pressure, the small flow orifice in the second valve seat 15 is opened by means of individual current pulses from the valve coil 1, and a defined quantity of hydraulic fluid can flow through the valve. The large flow orifice of the first valve seat 14 is controlled by the differential pressure (p B > pA ) closed.

[0022] In the case of a damaged brake line in the brake system, the solution according to the invention makes it possible to completely isolate the affected wheel brake from the brake system by tightly sealing both flow openings in the valve seats 14, 15, thereby effectively preventing the emptying of a brake fluid reservoir connected to the brake system. The tightness of the solenoid valve is ensured by the [missing information - likely a specific feature or component] in the Fig. 1-3 schematically depicted design ensures, regardless of the level of system pressure in the brake system. Reference symbol list 1 valve coil 2 magnetic anchors 3 Valve housings 4 Return spring 5 magnetic core 6 Valve housings 7 pestles 8 valve closing elements 9 Spring stop 10 valve closing elements 11 Valve spring 12 sleeve 13 Ring channel 14 Valve seat 15 Valve seat 16 transverse bore

Claims

[1] Electromagnetic valve, in particular for hydraulic, wheel slip-controlled motor vehicle braking systems, comprising a first and a second valve closing element arranged in a valve housing, each of which is capable of opening or closing a valve passage in a first and a second valve seat in the valve housing, comprising a magnetic armature which is removed from a magnetic core in the valve housing by the action of a return spring, on which a spring end of the return spring facing away from the magnetic armature is supported, and comprising a pressure medium inlet and a pressure medium outlet connected to the valve housing, between which the two valve closing elements with their associated valve seats are arranged, characterized by, that in the electromagnetically unactuated state of the magnetic armature (2) by means of the return spring (4) and a valve spring (11) arranged between the two valve closing elements (8, 10) both valve closing elements (8, 10) are lifted from their valve seats (14, 15). [2] Solenoid valve according to claim 1, characterized by , that by an electromagnetically initiated partial stroke of the magnetic armature (2) the first valve seat (14) is closed by the first valve closing element (10) and the second valve seat (15) is released unchanged by the second valve closing element (8) under the action of the valve spring (11). [3] Solenoid valve according to claim 1, characterized by , that by an electromagnetically initiated maximum stroke of the magnetic armature (2) the first valve seat (14) is closed by the first valve closing element (10) as well as the second valve seat (15) is closed by the second valve closing element (8) against the action of the valve spring (11). [4] Solenoid valve according to claim 1, characterized by , that the second valve closing element (8) is attached to a plunger (7) extending through the passage opening of the first valve seat (14), which is rigidly formed in the center of the end face of the magnetic armature (2) facing away from the magnetic core (5). [5] Solenoid valve according to claim 4, characterized by , that the first valve closing element (10) is attached to a sleeve (12) extending through the passage opening of the first valve seat (14), which is guided along the outer surface of the plunger (7). [6] Solenoid valve according to claim 5, characterized by , that the first valve closing element (10) is essentially designed as an annular disc seat valve with a diameter larger than that of the second valve closing element (8), which has the second valve seat (15) in the center of the annular disc. [7] Solenoid valve according to claim 6, characterized by, that an opening provided for the passage of pressure medium in the second valve seat (15) adjoins an annular channel (13) provided section by section between the sleeve (12) and the plunger (7), which is connected via at least one transverse bore (16) in the sleeve (12) to the pressure medium inlet (A) opening into the valve housing (3). [8] Solenoid valve according to claim 5, characterized by , that the second valve closing element (8) is essentially designed as a seat valve with a smaller diameter than the first valve closing element (10), which is aligned concentrically to the second valve seat (15) arranged in the first valve closing element (10) by means of the plunger (7) guided in the sleeve (12). [9] Solenoid valve according to claim 1, characterized by, that the valve spring (11) is designed as a compression spring which is clamped between the first valve closing element (10) and a spring stop (9) formed on the second valve closing element (8). [10] Solenoid valve according to claim 1, characterized by , that the contour of the second valve closing element (8) is designed as a sphere, cone or plate.

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