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 closing element axially movably arranged in a valve housing, which is capable of opening or closing a valve passage in the valve housing, which is formed in a valve seat, and comprising a magnetic armature provided for electromagnetic actuation of the valve closing element and a spring element which is arranged in a through-bore of the sleeve-shaped valve housing such that the valve closing element remains in a position lifted from the valve seat in the electromagnetically unactuated home position of the magnetic armature, wherein a plunger piston (3) which delays the movement of the valve closing element (4) is arranged between the valve seat (8) and the magnetic armature (7), which is axially movably received with radial clearance (S) within a fluid chamber (6) of the valve housing (1), characterized in thatthat the plunger (3) is formed directly on the valve closing element (4), which is connected to a valve tappet (5) which, under the action of the spring element (2), rests against the end face of the magnetic armature (7).

Description

The invention relates to an electromagnetic valve, in particular for slip-controlled motor vehicle braking systems, according to the preamble of claim 1. From DE 10 2015 221 465 A1, an electromagnetic solenoid valve that is open in the non-excited state is already known. It consists of a magnetic armature for actuating a valve closing element, which can be actuated against the action of a return spring, in a tubular valve housing. The housing has a pressure medium passage in a valve seat, which is closed when the magnetic armature is energized by the valve closing element. However, this design has the disadvantage that an undesirable switching noise is generated when the valve closing element strikes the valve seat. From US 2011 / 0 198 522 A1, an electromagnetic valve is known which comprises a valve plunger movably arranged in a valve housing, wherein the valve plunger is able to open or close a valve passage in the valve housing which is formed in a valve seat, and with a magnetic armature provided for electromagnetic actuation of the valve plunger and a spring element which is arranged in a through-bore of the sleeve-shaped valve housing such that the valve closing element remains in a position lifted from the valve seat in the electromagnetically unactuated home position of the magnetic armature, wherein the valve plunger has a guide section which is axially movably received within a fluid chamber of the valve housing and has radial play to the through-bore of the sleeve-shaped valve housing, whereby the guide section delays a movement of the valve plunger when switching the electromagnetic valve. The object of the present invention is to provide an electromagnetic valve of the type mentioned above that does not have the aforementioned disadvantage. Furthermore, the reduction of switching noise should not only be effective in the electromagnetically initiated closing direction of the electromagnetic valve, but should also enable noiseless switching back of the electromagnetic valve when the excitation current is switched off. This problem is solved according to the invention with an electromagnetic valve according to the features of claim 1. Further features and advantages of the invention are explained below by means of a description of several exemplary embodiments with reference to drawings. Figure 1 shows a first advantageous embodiment of the solenoid valve in longitudinal section with a plunger arranged directly between the valve closing element and a valve plunger in a fluid chamber located in the lower section of the valve housing; Figure 2 shows an enlarged section of the solenoid valve according to Figure 1 in the area of ​​the plunger in the electromagnetically unexcited resting position; Figure 3 shows the solenoid valve according to Figure 2 in its electromagnetically closed switching position; Figure 4 shows a further embodiment of the invention in the switched-off state of the solenoid valve, in which the fluid chamber with the plunger is integrated away from the valve closing element in the upper section of the valve housing adjacent to the magnetic armature, which is designed as a magnetic core; Figure 5 shows the embodiment according to Figure 4 in the electromagnetically initiated position of the plunger. Fig. 1 shows a significantly enlarged view of a solenoid valve open in the electromagnetically unexcited state in longitudinal section, which is preferably used for slip-controlled hydraulic motor vehicle braking systems. The solenoid valve has a valve closing element 4 arranged axially movable in a valve housing, which is able to open or close a valve passage 9 in the valve housing 1, which is formed in a valve seat 8, as well as a magnetic armature 7 provided for electromagnetic actuation of the valve closing element 4 and a spring element 2, which is arranged in a through-bore 11 of the sleeve-shaped valve housing 1 such that the valve closing element 4 remains in the electromagnetically unactuated basic position of the magnetic armature 7, in a position lifted from the valve seat 8. As shown in the illustration, the magnetic armature 7 is received within an austenitic cap 19, which is preferably welded to the thick-walled, tubular valve housing 1, the so-called housing top part, which ensures secure attachment in a valve receiving bore of a valve receiving body. The dome-shaped closed cap 16 is preferably produced by deep drawing of thin sheet metal, while the contour of the tubular valve housing 1 is manufactured by cold forming or cold extrusion from a steel blank which has a ferritic material structure to represent the magnetic core 13. On both sides of the valve seat 8, which is designed as a press-fit part, a pressure port 17, 18 opens into the lower valve housing 1, which, as shown in the illustration, is designed as a longitudinal groove on the left above the valve seat 8 and as a vertically extending central bore below the valve seat 8. In the illustrated, electromagnetically non-excited valve position, the valve closing element 4 remains at a distance from the valve seat 8 that releases the valve passage 9 in the valve seat 8, so that an unimpeded hydraulic connection between the pressure ports 17, 18 opening into the lower valve housing 1 on both sides of the valve seat 8 is ensured. In contrast, in the electromagnetically excited valve position, the valve closing element 4 closes the valve passage 9 in the valve seat 8, whereby it must be ensured that the valve closing element 4 contacts the valve seat 8 with the lowest possible impact velocity and is not audibly perceptible. Therefore, according to the invention, a plunger 3 is arranged between the valve seat 8 and the magnetic armature 7 to decelerate the valve closing element 4 in the direction of the valve seat 8 as well as in the opposite direction, and is axially movable within a fluid chamber 6 of the valve housing 1 with minimal radial clearance S. In Figures 1, 2 to 3, the plunger 3 is formed in a compact design directly on the valve closing element 4. It is frictionally connected to a valve tappet 5, the end of which, under the action of the spring element 2, rests against the end face of the magnetic armature 7. For the purpose of this frictional connection, the plunger 3 is provided with a blind bore 15 centrally on the end face facing away from the valve closing element 4. The end of the valve tappet 5 facing away from the magnetic armature 7 is frictionally fixed in this bore. As can be seen from Fig. 1, Fig. 2 to Fig. 3, the plunger 3 is attached to the valve tappet 5, which is arranged between the magnetic armature 7 and the valve closing element 4, by means of an interference fit. The plunger 5 has a significantly smaller diameter than the plunger 3 to form the fluid chamber 6, so that the fluid chamber 6 is realized in the form of an annular space directly in the through bore 11 of the valve housing 1 in a space-saving manner. According to Fig. 1, Fig. 2 to Fig. 3, the through-bore 11 in the area of ​​the fluid chamber 6 has a diameter increased by the radial clearance S of the plunger 3, wherein a throttling gap 10 is provided between the plunger 3 and the fluid chamber 6 for controlled fluid exchange, which is defined by the immersion depth of the plunger 3 into the fluid chamber 6 and the radial clearance S of the plunger 3 in the fluid chamber 6. At the same time, the plunger 3 in Fig. 1, Fig. 2 to Fig. 3 assumes a centering function for the valve closing element 4, since the plunger 3 has radial projections 14 on its outer surface outside the fluid chamber 6, which are guided along the inner wall of the valve housing 1 for the precise alignment of the valve closing element 4 on the valve seat 8. In all illustrated embodiments, the fluid chamber 6 is bounded on the end face facing away from the plunger 3 by a shoulder 12 formed in the through-bore 11, the inner diameter of which is adapted to the diameter of the valve tappet 5 to allow clearance for its passage. For the basic positioning of the valve closing element 4 in its position lifted from the valve seat 8, the spring element 2 is clamped between a collar 20 on the valve tappet 5 and the shoulder 12 in the through-bore 11. In Fig. 4 and Fig. 5, the collar 20 takes over the function of the plunger and the through-bore 11 serves as a fluid chamber between the shoulder 12 and the collar 20, from which fluid exchange is ensured via a throttle gap 10 formed as a longitudinal groove on the outer surface of the collar 20. Fig. 2 shows a position of the plunger 3 with a minimal volume intake V1 in the fluid chamber 6, since the valve closing element 4 attached to the plunger 4 is lifted from the valve seat 8. As soon as the valve closing element 4 is lowered towards the valve seat 8 by means of electromagnetic actuation, the fluid located between the two pressure ports 17, 18 in the valve housing 1 must be drawn into the fluid chamber 6 via the throttle gap 10 to compensate for the volume change. This results in a deceleration of the plunger 3 towards the valve seat 8, whereby the valve closing element 4 closes the valve passage 9 in the valve seat 8 with reduced momentum. The resulting stop damping can be variably and thus precisely adjusted by selecting the gap S and its length L. Fig. 3 shows the valve closing element 3 in its closed position at the valve seat 8, whereby the volume intake V2 in the fluid chamber 6 is at its maximum. As soon as the valve closing element 4 moves away from its valve seat 8 after completion of the electromagnetic actuation, fluid volume must now be displaced in the opposite direction from the fluid chamber 6 via the throttle gap 10 into the space of the valve housing 1 located between the two pressure seals 17, 18. This results in a deceleration of the valve closing element 4 as it lifts off the valve seat 8, so that the magnetic armature 7 engages the cap 16 with reduced momentum. In Fig. 4 and Fig. 5, the operating principle described above is applied identically, but with the difference that for the fluid chamber 6, the volume intake V1, V2 is exchanged via the longitudinal groove formed as a throttling gap 10 on the collar 20. With the exception of Fig. 4 and Fig. 5, in all other embodiments the plunger 3 is formed on the valve closing element 4, which is positioned in a manufacturing-friendly manner between the valve housing upper part and the valve housing lower part. Reference symbol list 1 Valve housing 2 Spring element 3 Plunger piston 4 Valve closing element 5 Valve tappet 6 Fluid chamber 7 Magnetic armature 8 Valve seat 9 Valve passage 10 Throttle gap 11 Through bore 12 Shoulder 13 Magnetic core 14 Projection 15 Blind bore 16 Cap 17 Pressure port 18 Pressure port

Claims

An electromagnetic valve, particularly for slip-controlled motor vehicle braking systems, comprising a valve closing element axially movably arranged in a valve housing, which is capable of opening or closing a valve passage in the valve housing, which is formed in a valve seat, and comprising a magnetic armature provided for electromagnetic actuation of the valve closing element and a spring element which is arranged in a through-bore of the sleeve-shaped valve housing such that the valve closing element remains in a position lifted from the valve seat in the electromagnetically unactuated home position of the magnetic armature, wherein a plunger (3) which delays the movement of the valve closing element (4) is arranged between the valve seat (8) and the magnetic armature (7), which is axially movably received with radial clearance (S) within a fluid chamber (6) of the valve housing (1), characterized in thatthat the plunger (3) is formed directly on the valve closing element (4), which is connected to a valve tappet (5) which, under the action of the spring element (2), rests against the end face of the magnetic armature (7). Electromagnetic valve according to claim 1, characterized in that the fluid chamber (6) is formed directly in the through-bore (11) of the valve housing (1), for which purpose the through-bore (11) in the area of ​​the fluid chamber (6) has a diameter increased by the radial clearance (S) of the plunger (3). Electromagnetic valve according to claim 2, characterized in that a throttle gap (10) is provided between the plunger piston (3) and the fluid chamber (6), which is defined by the immersion depth of the plunger piston (3) into the fluid chamber (6) and the radial clearance (S) of the plunger piston (3) in the fluid chamber (6). Electromagnetic valve according to claim 1, characterized in that the fluid chamber (6) is limited on the end face facing away from the plunger (3) by a shoulder (12) formed in the through bore (11), the inner diameter of which is adapted to the diameter of the valve plunger (5) for the passage of the valve plunger (5) with clearance. Electromagnetic valve according to claim 1, characterized in that the plunger (3) outside the fluid chamber (6) has radial projections (14) on its outer surface which are guided along the inner wall of the valve housing (1) to align the valve closing element (4) with the valve seat (8). Electromagnetic valve according to claim 1, characterized in that the plunger (3) is provided on the end face facing away from the valve closing member (4) with a blind bore (15) in which the end of the valve plunger (5) facing away from the magnetic armature (7) is frictionally fixed.

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