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 (4) arranged in a valve housing (3) which is capable of opening or closing a valve passage in a valve seat (5) of the valve housing (3), a magnetic armature (1, 2) provided for actuating the valve tappet (4), and a return spring (11) for positioning the valve tappet (4) in a basic position opening the valve passage, wherein the magnetic armature (1, 2) is multi-part, consisting of a first and a second armature (1, 2) which are arranged coaxially and relatively movable relative to each other in the valve housing (3), wherein, depending on the magnitude of the electromagnetic excitation of the magnetic armature, either a magnetic force component is effective on the first armature (1) which lifts the valve tappet (4) from the valve seat (5),or in the opposite direction a magnetic force component moving the valve tappet (4) onto the valve seat (5) can be generated on the second armature (2). characterized in that the second armature (2) can be mechanically actuated by a driver (6) which is rigidly connected to the first armature (1).

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 2014 225 251 A1, an electromagnetic valve of the type specified is already known, comprising a valve tappet movably arranged in a valve housing, which is able to open or close a valve passage in a valve seat of the valve housing, a magnetic armature provided for actuating the valve tappet, and a return spring for positioning the valve tappet in a basic position opening the valve passage, for which purpose the return spring is supported against a stop in the valve housing.

[0003] Furthermore, US Patent 2010 / 0213758A1 discloses a solenoid valve for motor vehicle braking systems, comprising a valve tappet arranged in a valve housing, which is capable of opening or closing a valve passage in a valve seat of the valve housing, a magnetic armature provided for actuating the valve tappet, and a return spring for positioning the valve tappet in a home position opening the valve passage. The magnetic armature is multi-part, consisting of a first and a second armature, which are arranged coaxially and relatively movable relative to each other in the valve housing. Depending on the magnitude of the electromagnetic excitation of the magnetic armature, either a magnetic force component that lifts the valve tappet from the valve seat acts on the first armature, or, conversely, a magnetic force component that moves the valve tappet onto the valve seat can be generated on the second armature.

[0004] The object of the present invention is now to further develop and improve the solenoid valve of the specified type in a cost-effective manner using the simplest possible functional means, such that with minimal electromagnetic excitation both sensitive pressure control in the sense of minimizing the valve flow rate is possible and, if necessary, complete valve opening can be achieved by increasing the excitation current.

[0005] This problem is solved according to the invention for the solenoid valve of the type specified by the features of claim 1, according to which a new constructive and functional design of the magnetic armature is now presented, which includes a closing magnetic force component, but at the same time enables a complete opening of the valve with low holding current.

[0006] Further features and advantages of the invention will become apparent from the following description of an exemplary embodiment with reference to a drawing.

[0007] The Fig. Figure 1 shows the invention by means of a longitudinal section through an electromagnetic valve which has two independently actuated armatures 1, 2 which are in the basic position in the valve housing 3 by means of two springs 11, 13 in the electromagnetically de-energized state.

[0008] The solenoid valve has an inlet-side valve passage located in a valve seat 5 of the valve housing 3. This passage is opened by means of a valve tappet 4 arranged on an armature 2 under the action of two return springs 11, 13, as long as a valve coil 10 mounted on the valve housing 3 is inactive. Depending on the magnitude of the electric current, the valve coil 10 can hydraulically connect a valve outlet 14 located above the valve seat 5 in the valve housing 3 to the variably adjustable valve passage of the valve seat 5.

[0009] In the present embodiment, a magnetic core 12 inserted into the valve housing 3 is pressed into an austenitic connecting tube as a sealing plug, which is welded as part of the valve housing 3 to a thick-walled, magnetic flux-conducting tube body of the valve housing 3, which ensures secure fastening in a valve receiving bore of a valve receiving body.

[0010] According to the invention, the magnetic armature is constructed in multiple parts, consisting of a first and a second armature 1, 2, both of which are arranged coaxially and relatively movable to each other in the valve housing 3, in order to exert a magnetic force component on the first armature 1, lifting the valve tappet 4 from the valve seat 5, depending on the magnitude of the electromagnetic excitation of the magnetic armature, or to be able to generate a magnetic force component on the second armature 2, moving the valve tappet 4 onto the valve seat 5, for fine control of the hydraulic flow using a small electromagnetic current in the opposite direction.

[0011] A sleeve-shaped driver 6 is arranged between the first and second armatures 1, 2, which surrounds the first armature 1 on its outer surface by means of an interference fit. Below the first armature 1, the driver 6 has a first axial stop 7 at its radially inwardly angled sleeve end, directed towards the annular inner end face 8 of the thick-walled valve housing 3. The axial stop 7 enables simple basic positioning of the first armature 1 in the valve housing 3 during the electromagnetically unexcited position of the first armature 1, for which purpose according to the Fig. 1 the axial stop 7 is supported on the inner end face 8 which acts as a magnetic pole.

[0012] Furthermore, the driver 6 has a second axial stop 9 on the inner circumference of the radially inwardly angled sleeve end, which interacts with an end face formed on the second armature 2 in such a way that in the electromagnetically excited position of the first armature 1 the valve tappet 4 can be lifted from its valve seat 5.

[0013] To enable the precise, independent positioning of the two armatures 1 and 2 within the valve housing 3, the return spring is designed in two parts: a first spring 11, located between the magnetic core 12 and the first armature 1, and a second spring 13, clamped between the second armature 1 and a guide section 15 located above the valve seat 5 within the valve housing 3. This second spring guides the valve tappet 4 precisely towards the valve seat 5. The second spring 13 has a lower spring stiffness than the first spring 11, so only small actuating forces are required to move the valve tappet 4 towards the valve seat 5 against the force exerted by the second spring 13.

[0014] In the electromagnetically non-excited state, the two armatures 1, 2 are positioned in the valve housing 3 under the pressure of the two springs 11, 13 in a position in which the valve tappet 4 keeps the valve seat 5 permanently open.

[0015] In order to achieve the highest possible magnetic saturation with a low excitation current, the second armature 2 includes a thin-walled ring disk section, through whose central opening the valve tappet 4 extends into the second armature 2.

[0016] The second anchor 2 is fixed to the valve tappet 4 in a simple manner by means of an interference fit, wherein the second anchor 2 is axially movable in the cavity of the first, essentially cap-shaped anchor 1 due to a clearance fit with its cylindrical extension.

[0017] The second armature 2 is therefore combined with the first armature 1 to form a compact, integrated magnetic armature assembly. For this purpose, the second armature 2 is designed as a plunger piston, which is telescopically mounted inside the pot-shaped, and thus hollow, first armature 1. This design results in optimal magnetic flux transmission because the nesting of both armatures 1 and 2, due to small radial gap dimensions, provides a large-area transition between them. This ensures that the magnetic flux transmission between the two armatures 1 and 2 is largely independent of the stroke between them.

[0018] The Fig.Figure 1 shows the solenoid valve in the electromagnetically de-energized state, in which the two armatures 1 and 2 are held independently of each other in the illustrated basic position by their respective springs 11 and 13. Due to the action of the first spring 11, the first armature 1 remains in a position in which the driver 6 rests with its outer axial stop 7 against the inner end face 8 of the valve housing 3, while the inner axial stop 9 of the driver 6 is a distance of a precisely adjustable drive stroke X from the lower end face of the annular disc section formed on the second armature 2.

[0019] In order to switch the solenoid valve in a position regulating the hydraulic flow at the valve seat 5, a slight electromagnetic excitation of the second armature 2, which is rigidly connected to the valve tappet 4, is sufficient due to the small residual air gap RLS2 provided between the inner end face 8 and the second armature 2, the magnetic force of which opposes the hydraulic inlet pressure at the valve seat 5 and the force of the second spring 13.

[0020] Under the influence of the small excitation current generated by the valve coil 10, the magnetic force generated at the second armature 2 is therefore dominant over the magnetic force acting in the opposite direction at the first armature 1, so that the valve tappet 4 is moved towards the valve seat 5 with low energy consumption for hydraulic pressure control.

[0021] Due to the larger residual air gap RLS1, which is provided structurally between the first armature 1 and the magnetic core 12, the magnetic force generated at the first armature 1 is generally smaller than the opposing force of the first spring 11 when the excitation current is low, so that the second armature 2, independently of the first armature 1, can move the valve tappet 4 sensitively towards the valve seat 5 against the hydraulic pressure acting on the valve tappet 4 from below at the inlet side of the valve seat 5.

[0022] As soon as the electromagnetic current acting on the first armature 1 is increased so that its magnetic force exceeds the force of the first spring 11, the second armature 2, which remains under magnetic excitation, enters magnetic saturation and is raised by a maximum of the drive stroke X together with the first armature 1 in the direction of the magnetic core 12.

[0023] Consequently, the valve tappet 4, which is rigidly connected to the second armature 2, also moves away from the valve seat 5 until, after a defined working stroke, the first armature 1 comes into contact with the magnetic core 12. As the magnetic armature stroke increases, the magnetic force of the first armature 1 increases towards the magnetic core 12 due to the decreasing residual air gap RLS1, while the magnetic force of the second armature 2 decreases due to the increasing residual air gap RLS2, so that the valve opening stroke increases steadily until the first armature 1 makes contact with the magnetic core 12.

[0024] To ensure that under all operating conditions the magnetic force of the first armature 1 is greater than the opposing magnetic force of the second armature 2 under increased excitation current, the pole area between the first armature 1 and the magnetic core 12 is chosen to be larger than the pole area between the inner end face 8 and the second armature 2.

[0025] The solenoid valve presented here in different switching positions is characterized by oppositely acting magnetic surfaces of two telescopically arranged armatures 1, 2, which are coordinated with each other in such a way that, with increasing excitation current in the valve coil 10, a reversal of direction of the magnetic armature takes place as desired or required, depending on the respective resulting magnetic force.

[0026] Furthermore, the presented solenoid valve enables hydraulically pressure-assisted release of the valve passage in the electromagnetically unactuated state as soon as the inlet pressure at the valve seat 5 is greater than the outlet pressure at the valve outlet 14.

[0027] Depending on the excitation current and the hydraulic pressure, the solenoid valve can be operated as an analogously controlled inlet valve (inlet pressure is greater than the outlet pressure) or as a digitally opening outlet valve if the outlet pressure at the valve outlet 14 exceeds the inlet pressure at the valve seat 5.

[0028] In summary, the presented solenoid valve has the following advantages: - Low spring forces result in a lower opening current in the comfort control range. - Reducing the spring force reduces the lateral force effect, resulting in less wear on the valve seat and tappet. - Important parameters, such as the armature stroke and the residual air gap RLS1, RLS2, can be set during valve assembly. - The solenoid valve can be used as both an electromagnetically normally open and an electromagnetically normally closed inlet and outlet valve, preferably in slip-controlled brake systems, the latter variant requiring only an arrangement of the second spring 13 between the two armatures 1, 2. Reference symbol list 1 anchor 2 anchors 3 Valve housings 4 valve tappets 5 valve seat 6 drive wheels 7 Axial stop 8 Inner end face 9 Axial stop 10 Valve coil 11 spring 12 magnetic cores 13 spring 14 Valve outlet 15 Leadership section

Claims

An electromagnetic valve, particularly for slip-controlled motor vehicle braking systems, comprising a valve tappet (4) arranged in a valve housing (3) which is capable of opening or closing a valve passage in a valve seat (5) of the valve housing (3), a magnetic armature (1, 2) provided for actuating the valve tappet (4), and a return spring (11) for positioning the valve tappet (4) in a basic position opening the valve passage, wherein the magnetic armature (1, 2) is multi-part, consisting of a first and a second armature (1, 2) which are arranged coaxially and relatively movable relative to each other in the valve housing (3), wherein, depending on the magnitude of the electromagnetic excitation of the magnetic armature, either a magnetic force component is effective on the first armature (1) which lifts the valve tappet (4) from the valve seat (5),or in the opposite direction a magnetic force component moving the valve tappet (4) onto the valve seat (5) can be generated on the second armature (2). characterized in that the second armature (2) can be mechanically actuated by a driver (6) which is rigidly connected to the first armature (1). Electromagnetic valve according to claim 1, characterized in that, for the basic positioning of the first armature (1) in the valve housing (3), the driver (6) has a first axial stop (7) on its outer circumference, which in the electromagnetically unexcited position of the first armature (1) is supported on an inner end face (8) of the valve housing (3) acting as a magnetic pole surface. Electromagnetic valve according to claim 1 or 2, characterized in that the driver (6) has a second axial stop (9) on its inner circumference, which interacts positively with a stop (10) formed in the area of ​​the second armature (2) such that in the electromagnetically excited position of the first armature (1) the valve plunger (4) is completely lifted from its valve seat (5). Electromagnetic valve according to one of claims 1 to 3, characterized in that the return spring is designed in two parts, consisting of a first spring (11) which is arranged between the magnetic core (12) and the first armature (1), and with a second spring (13) which is clamped between the second armature (2) and a guide section (15) formed in the valve housing (3) which centers the valve tappet (4) in the direction of the valve seat at an axial distance to the valve seat (5). Electromagnetic valve according to claim 4, characterized in that the second armature (2) is combined with the first armature (1) to form an integrated magnetic armature assembly, for which one of the two armatures (1, 2) is designed as a plunger piston, which is received at least partially axially movable in one of the two armatures (1, 2) designed as hollow pistons. Electromagnetic valve according to claim 5, characterized in that the second armature (2) is designed as a plunger piston, which is guided axially movable section by section within the first armature (1) designed as a hollow piston by means of a clearance fit. Electromagnetic valve according to claim 5, characterized in that the driver (6) is designed as a sleeve which is fixed to the outer circumference of the first armature (1), wherein the sleeve is angled radially inwards at the sleeve end facing away from the first armature (1) to form the two stops (7, 9) which interact positively with the second armature (2). Electromagnetic valve according to one of claims 1 to 7, characterized in that the end face of the first armature (1) facing away from the second armature (2) is spaced apart from the end face (8) of the magnetic core (12) by an adjustable first residual air gap (RLS1). Electromagnetic valve according to claim 2, characterized in that the end face of the second armature (2) facing away from the first armature (1) is spaced apart from the inner end face (8) of the valve housing (3) by an adjustable second residual air gap (RLS2). Electromagnetic valve according to claims 8 and 9, characterized in that the first residual air gap (RLS1) is smaller than the second residual air gap (RLS2). Electromagnetic valve according to claim 4, characterized in that the second armature (2) is connected to the valve plunger (4) by means of an interference fit, and that in the electromagnetically unexcited, valve-opening basic position the second armature (2) remains against the end face of the first armature (1) under the action of the second spring (13). Electromagnetic valve according to claim 4, characterized in that, in the electromagnetically excited state, the valve plunger (4) can be actuated in the direction of the valve seat (5) by means of a magnetic force acting on the second armature (2), which is greater and opposite to the second spring (13). Electromagnetic valve according to claim 4, characterized in that, in the electromagnetically excited state, by means of a magnetic force acting on the first armature (2) which is greater and opposite to the first spring (11), the first armature (1) as well as the second armature (2) can be moved in the direction of the magnetic core (12) after overcoming a defined drive stroke (X) of the drive (6). Electromagnetic valve according to claim 4, characterized in that the second spring (13) has a lower spring stiffness compared to the first spring (11).

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