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 tappet axially movable in a valve housing, which is capable of opening or closing a valve passage in the valve housing formed in a valve seat, and comprising a magnetic armature provided for actuating the valve tappet, which is actuated by a return spring, whereby the valve tappet remains in a position lifted from the valve seat in the electromagnetically unactuated home position of the magnetic armature, away from a magnetic core area formed in the valve housing, characterized in that an elastic element (7) is arranged between the magnetic armature (6) and the valve tappet (3), which is subjected to tension and thus stretched exclusively in the electromagnetically initiated closing position of the valve tappet (3).

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] From DE 10 2015 221 465 A1, an electromagnetic solenoid valve that is open in the non-excited state is already known, consisting of a magnetic armature for actuating a valve plunger that can be actuated against the action of a return spring in a tubular valve housing, which has a pressure medium passage in a valve seat that is closed when the magnetic armature is energized by the valve plunger. The valve plunger extends through the helical return spring, which is supported in the magnetic core area of ​​the valve housing.

[0003] However, this design has the disadvantage that a so-called residual air gap is required between the magnetic core and the magnetic armature to transmit the magnetic force to the valve tappet in the closing direction. Without this residual air gap, and thus without sufficient axial clearance between the magnetic armature and the magnetic core, the effective closing force on the valve tappet would be impaired, potentially leading to leakage. To compensate for tolerances and form deviations, this residual air gap cannot currently be reduced to the extent desirable for optimal efficiency of the magnetic drive.

[0004] From DE 10 2015 206 647 A1, an electromagnetic valve is known, comprising a valve housing, magnetic armature, axially movable valve closing element, a spring between the closing element and the armature, and a counteracting compression spring supported on the magnetic core, as well as a pressure medium inlet and outlet which are connected to each other via the plunger-shaped closing element upon excitation. The spring arranged between the valve closing element and the magnetic armature is designed as a tension spring, which is fixed section by section to both the magnetic armature and the valve closing element in order to lift the valve closing element from the valve seat. The tension spring enables a pulling movement of the valve closing element during lifting.

[0005] The object of the present invention is now to create an electromagnetic valve of the type mentioned above that does not have the aforementioned disadvantage.

[0006] This problem is solved for an electromagnetic valve of the type specified according to the invention by the features characterizing claim 1, in that the magnetic armature can be brought to a stop against the magnetic core area of ​​the valve housing by means of an elastic element generating the required closing force on the valve plunger, thereby significantly increasing the magnetic holding force and thus the efficiency of the magnetic drive.

[0007] Further features and advantages of the invention are explained below with reference to the description of an exemplary embodiment using a drawing.

[0008] The Fig. Figure 1 shows a significantly enlarged view of a longitudinal section of an open solenoid valve in the non-excited electromagnetic state, which is preferably used for slip-controlled motor vehicle braking systems.

[0009] The solenoid valve has a magnetic armature 6, acting against the action of a return spring 4, for actuating a valve tappet 3 in a valve housing 1, which is guided within a dome-shaped end section 5 fixed to the valve housing 1, wherein the magnetic armature 6, upon electromagnetic excitation, moves the valve tappet 3 in the direction of a valve seat 2 formed in the valve housing 1 in order to close the pressure medium passage provided therein.

[0010] For this purpose, the valve tappet 3 extends by means of its tappet section within a central passage in the valve housing 1 through the helical return spring 4 in the direction of the valve seat 2, which is frictionally fixed in the valve housing 1. In the present embodiment, the return spring 4 is supported with its first spring end against a shoulder provided in the area of ​​the passage, which is formed by a bore step 13, while the end of the return spring 4 facing away from the end face rests against the magnetic armature 6.

[0011] As shown in the illustration, the magnetic armature 6 is thus received within the austenitic, sleeve-shaped end section 5, which is welded to the thick-walled, tubular valve housing 1, which ensures secure attachment in a valve receiving bore of a block-shaped valve receiving body.

[0012] The dome-shaped closed end section 5 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 circuit.

[0013] On both sides of the valve seat 2, a pressure port 14 opens into the valve housing 1, which, as shown in the illustration, is designed as a transverse channel to the right of the valve seat 2 and as a horizontal channel to the left of the valve seat 2, wherein the pipe section of the valve housing 1 accommodates, for example, a ring filter 15 in the area of ​​the transverse channel and a plate filter 16 in the area of ​​the vertical channel.

[0014] In the illustrated, electromagnetically non-excited valve position, the valve tappet 3 remains at a distance from the valve seat 2 that allows the passage of pressure medium in the valve seat 2, so that an unimpeded hydraulic connection between the pressure ports 14 opening into the valve housing 1 on both sides of the valve seat 2 is ensured.

[0015] In contrast, in the electromagnetically excited valve position, the valve tappet 3 closes the pressure medium passage in the valve seat 2, whereby it must be ensured that the valve seat 2 remains unchanged in its position in the valve housing 1.

[0016] To significantly increase the efficiency of the magnetic drive, the invention provides that the magnetic armature 6 is brought to a stop against the magnetic core area 12 of the valve housing 1, for which purpose an elastic element 7 is arranged between the magnetic armature 6 and the valve tappet 3, which is axially stretched only in the electromagnetically initiated closed position of the valve tappet 3. The elastic element is preferably designed as a simple tension spring 7, which is rigidly connected at one end 9 of its first coil to the magnetic armature 6 and at the other end 9 of its second coil to the valve tappet 3.

[0017] To ensure the most compact design possible, the magnetic armature 6 has a stepped through-bore 10 in which the elastic element, designed as a tension spring 7, is arranged in a space-saving manner. At the same time, the end of the valve tappet 3 facing away from the valve seat 2 extends into the tension spring 7, so that the valve tappet 3 is partially contained within the tension spring 7.

[0018] The tension spring 7 has several spring coils which are preferably frictionally fixed at one end in the through-bore 10 of the magnetic armature 6 and at the other end on the valve tappet 3, for this purpose the two diametrical spring coil ends 9 have a radial elastic deformation in the direction of the wall of the through-bore 10 as well as in the direction of the end of the valve tappet 3, which establishes the secure force transmission in the through-bore 10 and on the circumference of the valve tappet end section extending into the tension spring 7.

[0019] To adjust the closing force transmitted from the magnetic armature 6 via the tension spring 7 to the valve tappet 3, the valve seat 2 is axially displaceable in the valve housing 1, for which purpose the valve seat 2 is designed as a bushing which is fixed in the tubular valve housing 1 by means of a press fit.

[0020] In the illustrated basic position of the valve tappet 3, lifted from the valve seat 2, the tension spring 7 is compressed to the length of the spring block, while in the electromagnetically initiated closing position of the valve tappet 3 on the valve seat 2 (not illustrated), the tension spring 7 arranged between the magnetic armature 6 and the valve tappet 3 is axially stretched to generate the closing force in such a way that an axial gap or residual air gap provided between the magnetic armature 6 and the magnetic core section 12 for the purpose of increasing the magnetic holding force is completely bridged, so that the magnetic armature 6 remains with its end face on the end face of the magnetic core section 12.

[0021] By energizing the valve coil 8, the magnetic armature 6 is electromagnetically moved towards the magnetic core 12. This causes the end of the valve tappet 3 facing the valve seat 2 to initially contact the valve seat 2. Then, due to the magnetic force generated by the valve coil 8, which significantly exceeds the force exerted by the tension spring 7, the tension spring 7 is stretched under tensile stress until the magnetic armature 6 contacts the magnetic core 12. The closing force of the valve tappet 3 results from the bridged residual air gap and the spring rate of the tension spring 7. Reference symbol list 1 Valve housing 2 Valve seat 3 valve tappets 4 Return spring 5 Final section 6 magnetic anchors 7 Tension spring 8 valve coil 9 spring coil end 10 through holes 11 plate filters 12 Magnetic core area 13th drilling stage 14 Pressure connection 15 ring filters

Claims

[1] Electromagnetic valve, in particular for slip-controlled motor vehicle braking systems, with a valve tappet axially movable in a valve housing, which is able to open or close a valve passage in the valve housing formed in a valve seat, and with a magnetic armature provided for actuating the valve tappet, which is actuated by a return spring, whereby the valve tappet remains in the electromagnetically unactuated home position of the magnetic armature, away from a magnetic core area formed in the valve housing, in a position lifted from the valve seat, characterized by , that an elastic element (7) is arranged between the magnetic armature (6) and the valve tappet (3), which is subjected to tensile stress and thus stretched exclusively in the electromagnetically initiated closing position of the valve tappet (3). [2] Solenoid valve according to claim 1, characterized by, that the elastic element is designed as a tension spring (7) which is firmly connected on the one hand with its first spring coil end (9) to the magnetic armature (6) and on the other hand with its second spring coil end (9) to the valve tappet (3). [3] Solenoid valve according to claim 2, characterized by , that the magnetic armature (6) is provided with a stepped through-bore (10) in which the elastic element designed as a tension spring (7) is arranged, into which the end of the valve tappet (3) facing away from the valve seat (2) extends centrally. [4] Solenoid valve according to claim 3, characterized by, that several spring coil ends (9) of the tension spring (7) are frictionally fixed both within the through-bore (10) of the magnetic armature (6) and at the end of the valve tappet (3), for which the spring coil ends (9) exhibit a radial elastic deformation in the direction of the wall of the through-bore (10) as well as in the direction of the end of the valve tappet (3). [5] Solenoid valve according to claim 2, characterized by , that the valve seat (2) in the valve housing (1) is axially displaceable in order to adjust the closing force transmitted from the magnetic armature (6) via the tension spring (7) to the valve tappet (3). [6] Solenoid valve according to claim 5, characterized by , that the valve seat (2) is designed as a bushing which is fixed in the tubular valve housing (1) by means of a press fit. [7] Solenoid valve according to claim 2, characterized by, that in the electromagnetically initiated closing position of the valve tappet (3) on the valve seat (2) the tension spring (7) arranged between the magnetic armature (6) and the valve tappet (3) is axially stretched in such a way that an axial gap provided between the magnetic armature (6) and the magnetic core area (12) is completely bridged, so that the magnetic armature (6) remains with its end face on the end face of the magnetic core area (12). [8] Solenoid valve according to claim 2, characterized by , that in the basic position of the valve tappet (3) lifted from the valve seat (2) the tension spring (7) is compressed to the length of the spring block.

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