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

Abstract

An electromagnetic valve, particularly for slip-controlled motor vehicle braking systems, comprising a first and a second valve closing element (2, 3) arranged in a valve housing (1), which are coaxially arranged in the valve housing (1) and are capable of opening or closing a first and a second valve passage (4, 5), respectively, with a pressure medium inlet (6) and a pressure medium outlet (7) opening into the valve housing (1), wherein the first valve closing element (2) is capable of opening or closing the first valve passage (4) located in the second valve closing element (3) depending on the excitation of an electromagnet, and wherein the second valve closing element (3) releases the second valve passage (5) under the influence of a return spring (8) in the open position of the first valve passage (4), so that a pressure medium present in the pressure medium inlet (6) flows along a flow path within the valve housing (1),in which the first and second valve passages (4, 5) are located, the pressure medium flows to the pressure medium outlet (7), the valve closing elements (2, 3) being arranged in a cage (9) axially displaceable relative to the valve housing (1), one of the valve closing elements (2, 3) being fixedly arranged in the cage (9), and a tension spring (17) being clamped between the valve closing elements (2, 3), under the influence of which the valve closing elements (2, 3) are held in the cage (9) in a relative position in which the first valve passage (4) is open, and the return spring (8) being effectively arranged between the valve housing (1) and the cage (9), characterized in that the first valve closing element (2) is fixedly arranged in the cage (9).

Description

[0001] The invention relates to an electromagnetic valve, in particular for slip-controlled motor vehicle braking systems, having a first and a second valve closing body arranged in a valve housing, which, in a coaxial arrangement in the valve housing, are capable of opening or closing a first and a second valve passage, having a pressure medium inlet opening into the valve housing and a pressure medium outlet, wherein the first valve closing body is capable of opening or closing the first valve passage located in the second valve closing body depending on the excitation of an electromagnet, and wherein the second valve closing body, under the influence of a return spring in the open position of the first valve passage, releases the second valve passage, so that a pressure medium present in the pressure medium inlet 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 an electromagnetic valve is described in DE 10 2011 080 176 A1. The first valve closing body is held in a driver by the force of a tension spring. The driver is guided in a guide sleeve, with the lower edge of the driver resting on the second valve closing body. This is held in the open position by a return spring that rests on an inward-facing flange of the guide sleeve. When the electromagnet is actuated, an actuating force acts on the first valve closing body, which is displaced in the closing direction and, due to the restraint, takes the driver with it. Since the driver is supported on the second valve closing body, it is also displaced in the closing direction against the force of the return spring until the second valve passage is closed.If the actuating force is further increased, the first valve closing body moves against the first valve passage, compressing the tension spring and leaving the driver behind. Since the second valve closing body rests against the second valve passage, the return spring is no longer compressed as the first valve closing body approaches the first valve passage. The switching point for the approach of the first valve closing body to the first valve passage is determined by the preload of the tension spring and the tension state of the return spring reached when the second valve passage closes. Beyond the tension state reached, the return spring makes no further contribution to influencing the closing movement of the first valve closing body to close the first valve passage.

[0003] From WO 99 / 43 523 A1, an electromagnetic valve for slip-controlled braking systems is known, comprising a valve housing, within which a first and a second valve closing body are arranged, which, in a coaxial arrangement in the valve housing, are capable of opening or closing a first and a second valve passage, with a pressure medium inlet opening into the valve housing and a pressure medium outlet, wherein the first valve closing body is capable of opening or closing the first valve passage located in the second valve closing body depending on the excitation of an electromagnet, and wherein the second valve closing body, under the influence of a return spring in the open position of the first valve passage, releases the second valve passage, wherein the valve closing bodies are arranged in a cage which is axially displaceable relative to the valve housing,wherein the second valve closing body is fixedly arranged in the cage and a tension spring is clamped between the second valve closing body and the cage.,

[0004] The invention is therefore based on the task of better utilizing the two springs to determine the switching behavior of the valve.

[0005] To achieve the object, it is therefore proposed that the valve closing bodies are arranged in a cage which is axially displaceable relative to the valve housing, wherein one of the valve closing bodies is arranged fixedly in the cage and a tension spring is clamped between the valve closing bodies, under the influence of which the valve closing bodies are held in the cage in a relative position in which the first valve passage is open, and that the return spring is effectively arranged between the valve housing and the cage, wherein according to the invention the first valve closing body is arranged fixedly in the cage.

[0006] This means that when the first valve passage closes, not only the tension spring is effective, but the return spring is also further compressed. Both springs thus cooperate during the closing movement of the first valve closing body to close the first valve passage. The tension spring can thus be designed somewhat weaker; in particular, its preload does not need to be too high, resulting in a weight saving and, secondly, a reduced risk of spring breakage.

[0007] To ensure that the second valve passage is closed when the valve is operated, the tension spring has a preload.

[0008] In order to easily create a cage, it is formed by a one-piece stepped sleeve.

[0009] The second valve closing body has an outwardly directed collar, the underside of which rests against a step of the stepped sleeve and on the upper side of which the tension spring is supported.

[0010] In order to be able to fasten the first valve closing body to the cage after the second valve closing body and the tension spring have been inserted therein, the first valve closing body is provided with a base which is pressed into the upper, wide end of the stepped sleeve.

[0011] There, the stepped sleeve has an outward-facing flange on which the return spring is supported.

[0012] Preferably, the valve housing has a free space for receiving the cage and the return spring and is connected to a magnetic core of the electromagnet in such a way that the magnetic core covers the free space.

[0013] In the free space there is a step on which the return spring is supported.

[0014] On its circumference, the sleeve has indentations which form an inner diameter which corresponds to the collar diameter of the second valve closing body, so that the latter is guided therein.

[0015] The invention will be explained in more detail below using an exemplary embodiment. The figures show: Fig. 1 the electromagnetic valve according to the invention with two valve passages in the open valve basic position, in which both valve passages are open, Fig. 2 an enlarged view of the valve passages with two valve closing bodies arranged in a cage and Fig. 3 Perspective view of the cage.

[0016] The Fig. 1 shows a longitudinal section through an electromagnetic valve, such as is preferably used in slip-controlled motor vehicle braking systems. The electromagnetic valve has a first and a second valve closing body 2, 3 arranged in a valve housing 1, which, in a coaxial arrangement, can open or close a first and a second valve passage 4, 5. Furthermore, a transverse bore functioning as a pressure medium inlet 6 is located radially to the longitudinal axis of the valve above the second valve passage 5 in the valve housing 1, and a pressure medium outlet 7 is located in the longitudinal axis of the valve below the second valve passage 5, wherein the first valve closing body 2 can close the first valve passage 4 located in the second valve closing body 3 depending on the excitation of an electromagnet.The second valve closing body 3 releases the second valve passage 5 under the influence of a return spring 8 in the open position of the first valve passage 4, so that a pressure medium present in the pressure medium inlet 6 reaches the pressure medium outlet 7 along a flow path within the valve housing 1, in which the first and second valve passages 4, 5 are located on the valve longitudinal axis.

[0017] The solenoid valve is designed in such a way that in the electromagnetically non-energized valve basic position both valve passages 4, 5 (as shown in the Fig. 1 and Fig. 2) are fully open.

[0018] The valve arrangement is as follows: The first and second valve closing bodies 2, 3 are arranged in a cage 9 formed by a stepped sleeve. The first valve closing body 2 has a base 10, to which a pin with a dome-shaped end 11 is connected, which faces the second valve passage 5 in the second valve closing body 3. The base 10 is immovably clamped into the upper end of the cage 9 (shown in the illustration).

[0019] The second valve closing body 3 consists of a cylinder 12 with a continuous longitudinal bore 13 and an outwardly projecting collar 14. The cylinder 12 is guided in the lower end of the cage 9, which here has a narrower cross-section than its upper end, so that a limited axial movement of the cylinder 12 relative to the cage 9 is possible. In the illustrated lower position of the second valve closing body 3, in which the first valve passage 4 is open, the collar 14 rests on a step 15 between the lower, narrower region and the upper, wider region of the cage 9. The lower end of the cylinder 12 points beyond the lower end of the cage 9 in order to be able to come into closing contact with a sleeve 16 arranged in the pressure medium outlet 7, which forms the second valve passage 5.

[0020] A tension spring 17 is inserted between the collar 14 of the second valve closing body 3 and the base 10, which has a preload, whereby the first valve passage 4 is kept open.

[0021] As long as this preload is not exceeded by forces acting on the second valve closing body 3, the cage 9 acts with the two valve closing bodies 2, 3 as a structural unit.

[0022] This unit is inserted into the free space 18 of the valve housing 1, which has a step 19. Also located in the free space 18 is the return spring 8, which is arranged outside the cage 9 and coaxial with it. The return spring 8 is supported on the one hand by the step 19 and on the other hand by an outward-facing flange 20 at the upper end of the cage 9.

[0023] The electromagnetic actuation of the valve is realized as follows: A magnetic core 21 is designed as a solid tubular part, into the lower end of which the valve housing 1 is inserted.

[0024] Above the magnetic core 21 is a cylindrical armature 22 within a cap 23 in the form of a sleeve closed on one side, which is placed over the magnetic core and connected to it in a pressure-tight manner. A coil (not shown here) is located around the cap 23. When current flows through it, it magnetizes the armature 22, so that it is attracted to the magnetic core.

[0025] To transmit the movement of the armature 22 to the valve, a plastic push rod 24 is located in the through-bore of the magnetic core 21, which rests on the armature 22 on one side and on the base 10 on the other. To ensure unhindered volume equalization of the fluid volume above and below the magnetic core 21, the push rod 24 is provided with longitudinal grooves.

[0026] Several of the Fig. The valves shown in Figure 1 are installed in a valve block (not shown here) that has hydraulic connections to the wheel brake cylinders and a master brake cylinder of a vehicle braking system. The valve block is provided with pressure fluid channels so that the pressure fluid inlet 6 is connected to the master brake cylinder and the pressure fluid outlet 7 is connected to one of the wheel brake cylinders.

[0027] The valve can be set to three switching positions. Fig. In the illustration shown in Figure 2, the valve is open because the electromagnet is not energized: The tension spring 17 presses the second valve closing body 3 downward so that the first valve passage 4 formed therein is opened. The return spring 8 presses the cage 9 upward so that the second valve closing body 3 is lifted off the second valve passage 5.

[0028] When the magnet is slightly excited up to an amount of 700 to 900 mA (depending on the design of the springs and the electromagnet), the push rod 24 presses on the base 10, which - because it is firmly arranged in the cage 9 - takes the cage 9 with it, whereby the soft return spring 8 is compressed until the second valve closing body 3 sits on the second valve passage 5. This blocks its cross-section. However, the first valve passage 4 remains open because the force exerted by the electromagnet is not sufficient to overcome the preload of the tension spring 17, so that a connection continues to exist between the wheel brake cylinder and the master brake cylinder. Even if the electromagnet is excited again, this situation initially remains because the applied force is not sufficient to compress the tension spring 17. Only when a current of approx.1000 mA is reached, this is sufficient for the force exerted on the cage 9 by means of the push rod 24 to cause it to be moved further downwards against the force of the tension spring 17 and the return spring 8, whereby the first valve closing body 2 approaches the second valve closing body 3 sitting on the second valve passage 5, until the first valve passage 4 is also closed.

[0029] The current required to close the first valve passage 4 is thus determined by the preload of the tension spring 17 and the preload of the return spring 8 which causes the second valve passage 5 to close.

[0030] If, after the electromagnetically initiated closure of both valve passages 4, 5, the first valve passage 4 is to be opened again, the electromagnet is deactivated so that the first valve closing body 2, as a result of the action of the return spring 8 and the tension spring 17, can lift off the second valve closing body 3, which is still closing the second valve passage 5. For this to happen, the restoring forces of the return and tension springs 8, 17 must be greater than the hydraulic forces acting on the first valve closing body 2. As a result of a hydraulic force of the pressure medium present in the valve housing 1 acting on the second valve closing body 3, the second valve closing body 3 remains at the second valve passage 5 as long as the hydraulic force is greater than the spring force of the return spring 8. In the present exemplary embodiment, the pressure of the pressure medium corresponds to the pressure of the master brake cylinder present in the pressure medium inlet 6.

[0031] Since the first valve closing body 2 is lifted off the second valve closing body 3, the hydraulic force acting on the second valve closing body 3 can be reduced by the escape of pressure medium via the first valve passage 4 to the pressure medium outlet 7 to such an extent that the spring force of the return spring 8 for lifting the second valve closing body 3 off the second valve passage 5 predominates, whereby finally the second valve passage 5 is also released and the valve basic position according to Fig. 2 is reached again.

[0032] In the electromagnetically closed state of both valve passages 4, 5, the magnetic force of the electromagnet must be at least as large as the spring forces caused by the tension spring 17 and the return spring 8, taking into account the hydraulic force acting on the second valve closing body 3 in the valve opening direction, wherein in the electromagnetically closed state of both valve passages 4, 5, the working air gap A between the magnetic core 21 of the electromagnet and the armature 22 is advantageously a minimum.

[0033] The solenoid valve is thus constructed in such a way that it advantageously has the smallest working air gap A when the greatest magnetic force is required, so that a reliable shut-off of the high wheel brake pressure present in the pressure medium outlet 7 is ensured.

[0034] Likewise, at the smallest required magnetic force, if the solenoid valve is starting from the Fig. 2 is to be switched to an intermediate position, the working air gap A is initially at its largest, so that, as a result of the selected design, electromagnetic valve switching of large valve strokes with low magnetic force requirements is possible.

[0035] When switching to the intermediate position, the magnetic force required to reduce the initially large working gap A can be small, since only the low spring force of the weak return spring 8 has to be overcome. With a reduced working gap A, the magnetic force required can be easily increased to overcome the combined force formed by the tension spring and return spring 8.

[0036] The Fig.Figure 3 shows a perspective view of the cage 9 in the form of a stepped cylinder. The previously mentioned sections of the cage 9 are provided with the corresponding reference numerals. The central section of the wall of the cage 9 has inwardly directed indentations 25, which rest against the collar 14 and thus laterally support the second valve closing body 3. Furthermore, openings 26 are provided in the wall, which allow the flow of brake fluid. List of reference symbols 1 valve housing 2 1. Valve closing body 3 2. Valve closing body 4 1. Valve passage 5 2. Valve passage 6 Pressure medium inlet 7 Pressure medium outlet 8 Return spring 9 Cage 10 sockets 11 End 12 cylinders 13 Longitudinal bore 14 collars 15th level 16 sleeve 17 Tension spring 18 open space 19th level 20 flange 21 Magnetic core 22 anchors 23 Cap 24 push rod 25 impressions 26 openings

Claims

[1] Electromagnetic valve, in particular for slip-controlled motor vehicle braking systems, with a first and a second valve closing body (2, 3) arranged in a valve housing (1), which, in a coaxial arrangement in the valve housing (1), are capable of opening or closing a first and a second valve passage (4, 5), with a pressure medium inlet (6) opening into the valve housing (1) and a pressure medium outlet (7), wherein the first valve closing body (2) is capable of opening or closing the first valve passage (4) located in the second valve closing body (3) depending on the excitation of an electromagnet, and wherein the second valve closing body (3) releases the second valve passage (5) under the influence of a return spring (8) in the open position of the first valve passage (4), so that a pressure medium present in the pressure medium inlet (6) along a flow path within the valve housing (1),in which the first and second valve passages (4, 5) are located, reaches the pressure medium outlet (7), wherein the valve closing bodies (2, 3) are arranged in a cage (9) which is axially displaceable relative to the valve housing (1), wherein one of the valve closing bodies (2, 3) is fixedly arranged in the cage (9) and a tension spring (17) is clamped between the valve closing bodies (2, 3), under the influence of which spring the valve closing bodies (2, 3) are held in the cage (9) in a relative position in which the first valve passage (4) is open, and that the return spring (8) is effectively arranged between the valve housing (1) and the cage (9), , characterized by that the first valve closing body (2) is fixedly arranged in the cage (9). [2] Solenoid valve according to claim 1, characterized by that the tension spring (17) has a pre-tension. [3] Solenoid valve according to one of the preceding claims, characterized bythat the cage (9) is formed by a one-piece stepped sleeve. [4] Solenoid valve according to claim 3, characterized by that the second valve closing body (3) has an outwardly directed collar (14) which rests with its underside against a step (15) of the stepped sleeve and on the upper side of which the tension spring (17) is supported. [5] Solenoid valve according to claim 4, characterized by that the first valve closing body (2) has a base (10) which is pressed into the upper, wide end of the stepped sleeve. [6] Solenoid valve according to claim 5, characterized by that the stepped sleeve has at its upper end an outwardly directed flange (20) on which the return spring (8) is supported. [7] Solenoid valve according to one of the preceding claims, characterized bythat the valve housing (1) has a free space (18) for receiving the cage (9) and the return spring (8) and is connected to a magnetic core (21) of the electromagnet, wherein the magnetic core (21) covers the free space (18). [8] Solenoid valve according to one of the preceding claims, characterized by that the cage (9) has indentations (25) on its circumference, which form an inner diameter which corresponds to the diameter of the collar (14) of the second valve closing body (3), so that the latter is guided in the cage (9).

Images