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 (4) arranged in a valve housing (14) which is capable of opening or closing a valve passage (10) in a valve seat (11), a magnetic armature (2) provided for actuating the valve closing element (4), a damping element (3) arranged between the magnetic armature (2) and a magnetic core (5), and a return spring (8) arranged between the magnetic armature (2) and the magnetic core (5) fixed in the valve housing (14), wherein the damping element (3) has an elastically deformable sleeve section (7) which extends into a space (9) provided between the magnetic armature (2) and the magnetic core (5), characterized in that the outer surface of the resilient sleeve section (7) has a partial cross-sectional reduction.wherein the cross-sectional weakening is produced by several holes (15) or distributed transverse slots (12) evenly distributed around the circumference of the sleeve section (7).

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 US 2007 / 0 069 166 A1, an electromagnetic valve of the type described is already known, which has an elastically deformable damping element between the magnetic armature and the magnetic core closing the valve housing to reduce switching noise. This damping element is designed as a rubber stop and is fixed to the magnetic core under the action of a return spring contained in the magnetic armature.

[0003] However, the use of a rubber stop has disadvantages in terms of technical feasibility and durability; in particular, a deterioration of the material properties must be expected in long-term operation, which can permanently impair the damping effect of the rubber stop.

[0004] Furthermore, an electromagnetic valve is known from DE 10 2010 031 275 A1, which comprises a valve plunger arranged in a valve housing, which is configured to open or close a valve passage in a valve seat, with a magnetic armature provided for actuating the valve plunger, with a damping element arranged between the magnetic armature and a magnetic core, and with a return spring arranged between the magnetic armature and the magnetic core fixed in the valve housing, wherein the damping element has an elastically deformable sleeve section which extends into an intermediate space provided between the magnetic armature and the magnetic core.

[0005] The object of the present invention is now to implement an electromagnetic valve of the specified type in a cost-effective manner using the simplest possible functional means, which does not have the aforementioned disadvantages.

[0006] This problem is solved according to the invention with an electromagnetic valve according to the features of claim 1.

[0007] Further features and advantages of the invention will become apparent from the following description of several exemplary embodiments based on the Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6 to Fig. 7 stands out.

[0008] They show: Fig. 1. In longitudinal section, the basic structure of the solenoid valve according to the invention, Fig. 2 a diagram to illustrate the mode of operation of the solenoid valve according to the invention, Fig. 3 starting from the Fig. 1 the essential details of the invention in longitudinal section in a partial view of the solenoid valve, the damping element of which is positively engaged in the magnetic armature, Fig. 4 a perspective representation of the in Fig. 3 illustrated details, Fig. 5 a further embodiment of the solenoid valve according to the invention, the damping element of which is positively engaged in the magnetic armature, Fig. 6 a further embodiment of the solenoid valve according to the invention, the damping element of which is force-fitted into the magnetic core, Fig. Figure 7 shows a further constructive design variant of the damping element in a perspective view before adjustment in the magnetic armature using a suitable tool.

[0009] The invention relates to an electromagnetic valve that is closed in its home position and is preferably used in slip-controlled motor vehicle braking systems.

[0010] According to the chosen principal representation according to Fig. The solenoid valve comprises a valve closing element designed as a valve tappet 4, which, under the action of a return spring 8 arranged between a magnetic armature 2 and a magnetic core 5, is capable of closing a valve passage 10 in a valve seat 11. To release the valve passage 10, the magnetic armature 2, connected to the valve tappet 4, is electromagnetically actuated in the direction of the magnetic core 5 by means of a magnetic coil in a manner known per se. A damping element 3 arranged between the magnetic armature 2 and the magnetic core 5 ensures, during the electromagnetic actuation of the magnetic armature 2, an effective reduction of the valve switching noise and precise maintenance of a residual air gap provided between the magnetic armature 2 and the magnetic core 5. The damping element 3 consists of a material that does not conduct magnetic flux, in particular an austenitic steel.

[0011] In order to keep the noise level as low as possible when switching the solenoid valve, the invention provides that the damping element 3 has an elastically deformable sleeve section 7 which extends into an intermediate space 9 provided between the magnetic armature 2 and the magnetic core 5.

[0012] The Fig. Figure 1 discloses the elastic sleeve section 7 formed on the damping element 3 in a schematic representation, with reference to the diagram according to [reference] to clarify the operating principle. Fig. Reference is made to 2. Further details and constructive variants of the invention are set forth in the Fig. 3, Fig. 4, Fig. 5, Fig. 6 to Fig. 7 can be seen.

[0013] Before going into the Fig. 3, Fig. 4, Fig. 5, Fig. 6 to Fig. Reference is made to details disclosed in section 7; first, the diagram should be shown. Fig. 2 will be explained, along whose abscissa the magnetic armature stroke S to the contact point A of the damping element 3 on the magnetic core 5 is shown, while along the ordinate the spring force curve F and the magnetic force curve F Magnet has been applied.

[0014] The straight line, which initially rises only slightly in the direction of the point of attachment A, illustrates the characteristic course of the spring force F8 for the return spring 8 with increasing magnetic armature stroke S for an electromagnetic valve known from the introductory description.

[0015] Upon reaching the contact point A, the further course of the straight line takes the form of a significantly increasing buckling characteristic due to the high spring stiffness of the sleeve section 7, so that a striking noise of the magnetic armature 2 on the magnetic core 5 is avoided.

[0016] Upon reaching the characteristic curve inflection point, the sum force F resulting from the return spring 8 and the sleeve section 7 is thus generated from the contact point A due to the spring-elastic deformation of the sleeve section 7. 7,8 The kinetic energy of the magnetic armature 2 is considerably absorbed by the damping element 3, so that the area of ​​spring work W shown below the steep characteristic curve F corresponds to the elastically deformed sleeve section 7.

[0017] Since the damping element 3 has a higher spring stiffness than the spring stiffness of the return spring 8, a considerable increase in force only occurs shortly before reaching the residual air gap, as a result of the deformation of the sleeve section 7 clamped between the magnetic armature 2 and the magnetic core 5, which advantageously allows a reduction of the residual air gap in order to exert a sufficiently large restoring force on the magnetic armature 2 after completion of the electromagnetic excitation of the magnetic armature 2.

[0018] The design of the spring-loaded sleeve section 7 thus has the advantage that, in conjunction with the parallel-connected return spring 8, a significantly higher spring stiffness is achieved in the area of ​​small air gaps and therefore high effective magnetic forces between the magnetic armature 2 and the magnetic core 5. In contrast, at the beginning of the stroke of the magnetic armature 2, the spring-loaded sleeve section 7 is ineffective, and the return spring 8, which is advantageously designed for low stiffness, can act alone due to the smaller magnetic force gradient.

[0019] The following section summarizes the other constructive design variants based on the Fig. 3, Fig. 4, Fig. 5, Fig. 6 to Fig. 7 explains, according to which, starting from the Fig. 1 the Fig. 3, Fig. 4, Fig. 5, Fig. 6 to Fig. Figure 7 illustrates that the damping element 3 in the area of ​​the elastically deformable sleeve section 7 has a projection 6, the axial extent of which after elastic end deformation or compression corresponds to the dimension of a residual air gap required to limit the magnet armature stroke in the space 9.

[0020] The damping element 3 is fixed in a longitudinal bore 1, which is oriented according to the Fig. 1, 3 to 5 and 7 in the magnetic armature 2 or according to the Fig. 6 is arranged centrally in the magnetic core 5. Preferably, the damping element 3 is supported in Fig. 1, Fig. 3, Fig. 4 and Fig. 7 form-fitting at the bottom of the longitudinal bore 1, while the damping element 3 is in the Fig. 5 and Fig. 6 is fixed in the longitudinal bore 1 by means of a sliding press fit. In order for the damping element 3 to be force-fitted in the longitudinal bore 1, the frictional force acting in the sliding press fit must necessarily be at least as large as the mechanical and hydraulic forces acting on the damping element 3 during valve switching.

[0021] In the Fig. 1, Fig. 3, Fig. 5 and Fig. 6 shows that, based on the selected partial view of the solenoid valve in longitudinal section, the cylindrical return spring 8 is predominantly contained lengthwise within the damping element 3, so that only a few coils of the return spring 8 protrude from the resilient sleeve section 7, which are arranged according to the Fig. 1, 3 to 5 on the magnetic core 5 closing the valve housing 14 or according to the Fig. 6, due to the reversed mounting of the damping element 3 in conjunction with the return spring 8 in a longitudinal bore 1 of the magnetic core 5, supported on the magnetic armature 2. In all embodiments, the longitudinal bore 1 has a clearance fit in the area of ​​the sleeve section 7, so that the sleeve section 7 can deform elastically without hindrance.

[0022] The further Fig. 4 and Fig. Figure 7 shows in a perspective view some suitable designs of the sleeve section 7, which is resiliently attached to the rigid sleeve-shaped end section of the damping element 3.

[0023] Conceptually, in all figures, the sleeve section 7 in the area of ​​the sleeve shell has a local cross-sectional weakening in order to achieve the desired spring stiffness, which according to the Fig. 3, Fig. 4, Fig. 5 to Fig. 6 preferably designed as transverse slots 12 arranged one below the other in the sleeve jacket and laterally offset from each other.

[0024] Another practical design for weakening the cross-section of the sleeve jacket is shown by the Fig. 7, wherein instead of several transverse slots 12 the sleeve shell is provided with several holes 15 arranged one below the other in the sleeve shell, which are preferably produced by a stamping tool in analogy to the transverse slots 12.

[0025] Furthermore, in the Fig. 7 outlines the use of a tool 13 for compressing the damping element 3 to the required projection 6, which must be adjusted precisely as a measure for the residual air gap between the magnetic core 5 and the magnetic armature 3. As shown in the Fig. As can be seen from 7, the protrusion 6 on the magnetic armature 2, which determines the residual air gap, results from the elastic springback of the sleeve section 7 after the upsetting of the sleeve section 7.

[0026] The one in Fig. The revealed adjustment of the residual air gap enables a reduction in the force tolerances for the sleeve cut 7 on the damping element 3, thus allowing the use of simple sheet metal of deep-drawing quality that does not meet spring steel specifications. This allows optimal utilization of a material with low elastic properties and eliminates plastic deformation of the damping element 3 due to any tolerances in the installation space within the longitudinal bore 1. Reference symbol list 1 longitudinal bore 2 magnetic anchors 3 damping element 4 valve tappets 5 magnetic core 6 overhang 7 Sleeve section 8 Return spring 9 space 10 passage 11 Valve seat 12 cross slots 13 tools 14 Valve housings 15 holes

Claims

An electromagnetic valve, particularly for slip-controlled motor vehicle braking systems, comprising a valve closing element (4) arranged in a valve housing (14) which is capable of opening or closing a valve passage (10) in a valve seat (11), a magnetic armature (2) provided for actuating the valve closing element (4), a damping element (3) arranged between the magnetic armature (2) and a magnetic core (5), and a return spring (8) arranged between the magnetic armature (2) and the magnetic core (5) fixed in the valve housing (14), wherein the damping element (3) has an elastically deformable sleeve section (7) which extends into a space (9) provided between the magnetic armature (2) and the magnetic core (5), characterized in that the outer surface of the resilient sleeve section (7) has a partial cross-sectional reduction.wherein the cross-sectional weakening is produced by several holes (15) or distributed transverse slots (12) evenly distributed around the circumference of the sleeve section (7). Electromagnetic valve according to claim 1, characterized in that the sleeve section (7) extends with a projection (6) into the space (9), the axial extent of which, after elastic compression, corresponds to the dimension of a residual air gap required to limit the magnet armature stroke in the space (9). Electromagnetic valve according to claim 1 or 2, characterized in that the damping element (3) is fixed in a longitudinal bore (1) which is arranged centrally either in the magnetic armature (2) or in the magnetic core (5). Electromagnetic valve according to claim 3, characterized in that the damping element (3) is fixed section by section in the longitudinal bore (1) by means of a sliding press fit, wherein the frictional force effective in the sliding press fit is at least as large in magnitude as the mechanical and hydraulic forces acting on the damping element (3) during valve switching. Electromagnetic valve according to one of claims 1 to 4, characterized in that the return spring (8) is received within the damping element (3). Electromagnetic valve according to claim 1, characterized in that the sleeve section (7) has a spring stiffness which is greater in magnitude than the spring stiffness of the return spring (8). Electromagnetic valve according to claim 2, characterized in that the protrusion (6) determining the residual air gap results from an elastic springback of the sleeve section (7) after a plastic deformation of the sleeve section (7). Electromagnetic valve according to claim 7, characterized in that the plastic deformation is carried out by upsetting the sleeve section (7) by means of an axially supplied tool (13). Electromagnetic valve according to claim 1, characterized in that the damping element (3) is made from a sheet metal which is preferably deformable by deep drawing.

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