GB2039000A

GB2039000A - Solenoid valve

Info

Publication number: GB2039000A
Application number: GB7942160A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1978-12-23
Filing date: 1979-12-06
Publication date: 1980-07-30
Also published as: DE2856113A1; JPS5586981A; GB2039000B

Abstract

The armature (31) of a solenoid valve is supported via a plunger arrangement (30, 32) on two membrane springs (14, 15) which are arranged at axially opposite sides of the coil (12) and whose outer peripheries are clamped to the coil housing (3) by cover plates (16, 17). The closure member (25) of a double- seated valve (23) is operatively associated with one end of the plunger arrangement (30, 32). The wide spacing of the membrane springs (14, 15) ensures accurate play-free guidance of the armature 31. Inlet air can flow from an inlet passage having an inlet seat (24) to a service port (27) and exhaust air can flow from the latter to an outlet passage having an outlet seat (22) from where it flows through the membrane (15), over the coil and through the membrane (14) to an outlet non- return valve (28), the membranes being of multi-spiral configuration to allow great flexibility thereof and to provide flow passages for the exhausting air. <IMAGE>

Description

SPECIFICATION Solenoid valve The invention relates to a solenoid valve.

In a solenoid valve known from German Patent Specification No. 12 72 666, friction-free guidance and centring of the armature is effected by means of two membrane springs, both of which are arranged on the same side of the solenoid housing. Consequently, the distance between them is relatively short, and tilting of the arumature is not, with certainty, prevented.

Moreover, the valve itself is arranged in the armature, and is consequently very expensive.

The present invention provides a solenoid valve having a coil through which an electric current may be passed and which is centrally arranged in a coil housing, and in which there is arranged an armature, which is movable under magnetic and resilient forces and which controls the closure member of a double-seated valve arranged at one end of the coil housing, and which is centrally located by two membrane springs, which are arranged at axially opposite sides of the coil with their outer peripheries clamped with respect to the coil housing and with their centres clampled to a plunger arrangement securely inserted in the armature, a free end of the plunger arrangement being operatively associated with the closure member of the double-seated valve.

The wide spacing of the membrane springs ensures accurate guidance of the armature. The closure member of the valve is operated by a plunger, which, at the same time, can also securely clamp one membrane spring against a shoulder and is therefore directly responsible for guidance of the armature. The number of structural elements is thereby substantially reduced. If the armature stroke is equally distributed about the mid-position of the displacement of the membrane springs, the overall elastic force of the diaphragm springs operates to assist both the attracting and releasing movements of the armature. Optimal utilisation of magnetic force and current strength is thereby achieved, and very rapid action is ensured.

Such rapid-acting solenoid valves are preferably used in anti-wheel lock systems of pneumatic brakes. In this connection, according to a further feature of the invention, it is an advantage if the cross-section of an outlet valve seat connection is larger than that of an inlet valve seat connection.

In this way, the outlet pressure gradient can be matched to the inlet pressure gradient in order to permit rapid lowering of pressure in the event of anti-locking action.

The invention is further described, by way of example, with reference to the drawings, in which Figure 1 is a longitudinal section of a 3/2-way solenoid valve in accordance with the invention, Figure 2 is a similar view of a 4/2-way solenoid valve, and Figure 3 is a plan view, to a smaller scale, of a membrane spring.

A solenoid valve comprises an electro-magnet portion 1 and a valve portion 2. The magnet portion 1 is housed in an electro-housing 3, which, comprises a hollow cylinder, inside which there are two shoulders 4 and 5. each of which is abutted by a respective plate 6, 7. Each plate 6, 7 has a central hole 8, 9 and an eccentric axial orifice 10, 11 for the passage of air. The two plates 6 and 7 accommodate between them a coil 12 of the electro-magnet, and the lower plate 6 in the drawing has, additionally, a core portion 1 3.

The plate 6, the magnet housing 3 and the plate 7 form the magnetic flux return path for the magnetic flux circuit. On the outer surfaces of the plates 6 and 7 remote from the coil 12 there is provided a respective membrane spring 14, 15, whose flexible portions 14', 15' are spirally arranged, as is evident from Figure 3. The length of the flexible portions thereby achieved permits, on the one hand, the necessary axial displacement of the armature 31, and yet, on the other hand, makes available a sufficiently large flow cross section for the passage of air.

Over the outer face of each of the membrane springs 14, 15 there is placed a respective cover plate 16, 1 7, and, for the purpose of clamping the cover plates 16, 17, the membrane springs 14, 15, and the plates 6 and 7, the magnet housing 3 is flanged over at its ends 18 and 19. The membrane springs 14 and 15 are thereby clamped in the housing 3 without additional fastening means.

The cover plate 17, adjacent to the valve portion 3, has an opening 20 for the power supply conductors to the coil 12, and has, on its inside surface, an outlet-valve seat 22, whose flow cross-section forms an outlet connection of a double-seated valve 23, an inlet connection of whose inlet-valve seat 24 lies opposite the outlet connection, a closure member 25 being arranged between the outlet seat 22 and the inlet seat 24.

A valve chamber 26, for receiving the closure member 25, is provided with a service connection 27. The flow cross-section of the outlet connection is larger than that of the inlet connection.

The other cover plate 16 is provided with a non-return valve 28, which controls a connection 29 to the outside atmosphere in such a manner as to prevent the ingress of foreign matter into the magnet housing 3.

One end of a plunger 30, whose other end is press-fitted into one end of the armature 31, is riveted centrally to the membrane spring 14. A valve plunger 32, having a shoulder 34, which clamps the membrane spring 1 5 against the armature 31, is press-fitted into the other end of the armature. The other end of the valve plunger 32 is rigidly connected to the closure member 25 of the double-seated valve 23, or a spring 35, shown by broken lines, may be provided, which spring 35 presses the closure member 25 against the valve plunger 32. For precise stroke adjustment, it is possible to compensate for manufacturing tolerances by the insertion of a correspondingly thick packing shim between the shoulder 34 and the armature 31. Clamping of the membranes to the plungers 30, 32 ensures accurate guidance, with zero play.

Lastly, a spring 36, for influencing the movement of the armature 31, is used, and is arranged between the plate 6 and the armature 31. The purpose of this spring 36 is to force the two membrane springs 14 and 15 5 away from their mid-positions, in a direction towards the inlet seat 24, in order that the closure member 25 may close the latter when the magnet is in its neutral (that is, deenergised) state. Without the spring 36, the two membrane springs 14 and 15 would retain the armature 31 in such a position that, relative to the position of the inlet seat 24 and the outlet seat 22, the armature movement would be distributed equally about the mid-point of the possible displacement of the membrane springs.

In this way, the resilient bias of the two membrane springs 14 and 15 operates to assist both the attracting and the releasing movements of the armature; on the attraction of the armature 31, first of all the movement is assisted by the resilient bias of the membrane springs 14 and 15, and, when the mid-position is passed, the brakes are applied. On the release of the armature 31, the membrane springs 14 and 15 press it back to the mid-position, from which, under the force of the spring 36, and against the force of the membrane springs 14 and 15, it attains its initial position. In this way, fast armature attraction and release times are achieved.

The air flowing from the outlet connection passes over the coil 12, flowing, as its does, through the membranes 14 and 15 and the axial orifices 10 and 11. The coil 12 is thereby cooled.

The widely spaced membrane springs 14 and 15 ensure accurate guidance of the armature and provide optimal resistance to possible transverse forces of the armature. The spriral coil configuration of the membrane springs 14 and 15 permits the flexible portions 14', 15', to be very long; soft suspension is thereby achieved.

The described Figure 1 shows a 3/2-way solenoid valve. This may be converted, if necessary, to a 2/2-way solenoid valve by replacing the valve portion 2, without modification of the electro-magnet portion 1. Such a 4/2-way solenoid valve is shown in Figure 2. Here, a 4/2 way valve portion 42 has an inlet 43, two service connections 44 and 45, and an outlet. All other parts correspond to those of Figure 1.

The solenoid valve according to the present invention has a very rapid action. It is, therefore, preferably usable in anti-wheel locking systems in motor vehicles. It is important that the cross section of the outlet seat 22 is greater than that of the inlet seat 24, so that the outlet pressure gradient is matched to the inlet pressure gradient, and rapid lowering of pressure is possible in the event of anti-locking action.

Claims

1. A solenoid valve, having a coil through which an electric current may be passed and which is centrally arranged in a coil housing, and in which there is arranged an armature, which is movable under magnetic and resilient forces and which controls the closure member of a double-seated valve arranged at one end of the coil housing, and which is centrally located by two membrane springs, which are arranged at axially opposite sides of the coil with their outer peripheries clamped with respect to the coil housing and with their centres clamped to a plunger arrangement securely inserted in the armature, a free end of the plunger arrangement being operatively associated with the closure member of the double-seated valve.

2. A solenoid valve according to claim 1, in which the armature movement is equally distributed about the mid-point of the displacement of the membrane springs.

3. A solenoid valve according to claim 1 or 2, in which the two membrane springs are of spiral configuration.

4. A solenoid valve according to claim 1, 2 or 3, in which the outer periphery of each of the membrane springs is clamped against a respective shoulder in the coil housing, by a respective cover plate, and the coil housing is provided with a flange at each of its ends engaging over a respective cover plate.

5. A solenoid valve according to any of claimsl to 4, for pneumatic operation, on which a compressed-air inlet connection, a compressed-air outlet connection, and a service connection are arranged at one end of the coil housing and a connection to the outside atmosphere is provided at the other end of the coil housing, air which is to be discharged being guided inside the coil housing past the coil and through the membrane springs.

6. A solenoid valve according to claim 5, in which the flow cross-section of the outlet seat of the valve is larger than the flow cross-section of the inlet seat.

7. A solenoid valve according to claim 5 or 6, when appendant to Claim 4, in which the cover plate adjacent to the valve carries the outlet connection of the double-seated valve, and the other cover plate, remote from the valve, is provided with a non-return valve for outside air.

8. A solenoid valve according to any of claims 1 to 7, in which the valve is constructed selectively as a 2/2-way, 3/2-way or 4/2-way valve.

9. A solenoid valve constructed substantially as herein described with reference to and as illustrated in the drawings.