GB1586044A

GB1586044A - Electro-magnetically operable valves

Info

Publication number: GB1586044A
Application number: GB995078A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1977-03-15
Filing date: 1978-03-14
Publication date: 1981-03-18
Also published as: JPS53115933A; DE2711140A1

Description

(54) IMPROVEMENTS IN OR RELATING TO ELECTRO-MAGNETICALLY OPERABLE VALVES (71) We, ROBERT BOSCH GMBH, a German Company of Postfach 50, 7 Stuttgart 1, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This present invention relates to electromagnetically operable valves.

In one form of electro-magentically operable solenoid valve a pole surface of an armature is reduced by recesses for leaf springs for guiding and centering the armature. This has the disadvantage that the number of ampere-turns required to move the armature into its pulledin position has to be increased, resulting in a higher current consumption and heating the solenoid coil to a higher temperature.

According to the present invention there is provided an electro-magnetically operable valve in which an armature which carries movable valve members is urged by a spring into a normal or released position from which it can be displaced by magnetic force upon energisation of a coil and is guided and centered by means of leaf springs which are received in cut-away recesses in its end faces, and in which an annular pole shoe engaging one end face of the armature covers the recesses in that end face.

An electro-magnetically operable solenoid valve embodying the present invention can have the advantage that the required number of ampere-turns can be reduced. When using such a valve as a three-port, three position solenoid valve, the force/travel characteristic can then be substantially level or horizontal. Valve devices of this type involve the problems of reconciling the spring forces with the magentic forces. In each case allowance must be made, owing to the effect of hysteresis, for a certain range of variation in the magnetic forces and the spring forces.

Pressure medium forces of changing magnitude, frictional forces, and the effects of dimensional tolerances result in a relatively wide variation in these forces. Furthermore, it is advantageous, at least for many purposes, if the valve stroke is not too small, in order to ensure that a certain minimum cross-sectional area is available for the flow of pressure medium.

Therefore, a further advantage of a solenoid valve embodying the present invention is that, with a force/travel characteristic of the magnet which is as flat as possible, the spring characteristic can be readily chosen in order to promote reliable movement of the armature into its terminal positions with relatively large crosssectional areas for flow-through of a pressure medium, and also into its central position.

Finally, it is an advantage if, in the vicinity of the terminal position of the armature to which the armature is moved magnetically, the attractive force of the magent is attenuated in the end region of the stroke of the armature.

The invention will be further described by way of example with reference to the accompanying drawing which is an axial sectional view of one embodiment of the invention: A solenoid valve 1 is arranged between a connection II leading to a pressure-responsive device, a connection I leading to a source of pressure, and a connection III leading to a relief point 4. The source of pressure can be a pump 3, and the pressure-responsive device can be a brake cylinder 2. A coil 5 is mounted on a coil carrier 6 and the latter is in turn slipped onto a tubular shell 7 which is connected to a non-magnetic ring 8 by, for example, welding. An outer tube 9' forms part of the magnetic circuit for a magnetic field set up on energisation of the coil 5.

The tubular shell 7 with the ring 8, a yoke 9, and an inlet valve seat 12 secured in the latter, are rigidly connected to one another. This device accommodates an armature assembly comprising basically a ring 11 and an armature 13. The ring 11 and the armature 13 are interconnected by way of lower and upper leaf springs 16 and 17 respectively. The leaf springs 16, 17 are accommodated in cut-away recesses in the end faces of the armature. The leaf springs 16 and 17 are made from resilient, nonmagnetic spring material and are generally annular and have circular or spiral tongues. Part of a tongue of each spring is fitted to the armature 13, for example by a weld, so as to centre the armature whilst allowing sufficient freedom of movement.Preferably each spring 16, 17 is fixed to the ring 11, for example by a weld, to form an assembly which can be inspected before being assembled into the complete valve. A spacer ring 18 is located between the upper leaf spring 17 and an end member 10 having a seat 14 for the outlet valve. The end member 10 is retained in the tubular shell 7 by means of a flange 15 formed on the tubular shell.

A valve closure member 20, 22 of an inlet valve 12, 20, 22 and a valve closure member 21, 23 of an outlet valve 14, 21, 23, are fitted in a multi-stepped bore provided in the armature 13.

The two aforementioned valve closure members comprise balls 20, 21, each let into, and secured in, a respective ball holder 22 and 23.

The ball holder 22 of the inlet valve closure member 20, 22 normally abuts against a shoulder 24 of a bore 19 of armature 13. The closure member 20, 22 is thereby raised from the valve seat 12, and the inlet valve 12, 20,22 is open.

A spring 25 acts between the valve closure member 20, 22 and a ring 26 which is secured in the armature 13 by means of a further ring having a shoulder 27. The shoulder 27 has a cut-away portion, whereby an axial gap 28 is formed between the cut-away portion and the ring 26 to accommodate the ball holder 23. The ball holders 22 and 23 are provided with axial openings 22' and 23' for the passage of pressure medium. One end of a valve spring 29 of the outlet valve 14, 21,23, extending within the spring 25, abuts against the ball holder 23 and its other end abuts against the ball holder 22.

For the purpose of accommodating the leaf springs 16 and 17 respectively, one end of the armature 13 is provided with a cut-away portion 30 and its pole surface 13' is provided with a cut-away portion 31. The cut-away portion 31 on the pole surface 13' is covered by an annular pole shoe 32, so that a full uninterrupted annular surface is again produced as the pole face of the armature 13.

An intermediate disc 34 is placed onto an annular cut-away portion 33 in the yoke 9. An annular wall 35 of the cut-away portion 33 is thereby located opposite an outer edge 36 of the pole shoe 32 to provide a shunt part of the magnetic circuit in this region.

A spring 37 is arranged below the armature 13 and, together with the leaf springs 16 and 17 applying a restoring force, urges the pole shoe 32 and the armature 13 upwardly so that the outlet valve 14, 21, 23 is normally closed and the inlet valve 12, 20, 22 is normally open when the magnet is de-energized. This spring 37 is fitted in a recess 38 in the pole shoe 32. A cylindrical shoulder 39 is formed on the other side of the pole shoe 32 and its external diameter corresponds approximately to the internal diameter of a cut-away portion 13" in the armature.

The solenoid valve 1 operates as follows: When the device is in its normal or released position when the coil 5 is not energised, the pressure-responsive device 2 communicates with the source 3 of pressure through the hollow armature 13 and through the openings 22' and 23' in the ball holders 22 and 23. The armature 13 is drawn downwardly when the coil 5 is energised to a first value of current level, the leaf springs 16 and 17 being resiliently deformed and the spring 37 compressed. The spring 25 expands so that the valve closure member 21, 23 of the outlet valve 14, 21, 23 remains on its seat 14 until the valve closure member 20, 22 of the inlet valve 12, 20, 22 has engaged its seat 12 and the inlet valve 12, 20, 22 has been closed.

Upon a further stroke of the armature 13 as a result of an increase in the current through the coil 5, the valve closure member 21, 23 of the outlet valve is moved off its seat 14 by the ring 27 and the outlet valve 14, 21, 23 is thus opened. The pressure medium in the pressureresponsive device 2 can now expand towards the relief point 4.

The armature 13 is not subjected to any friction during movement thereof, since it is mounted in a frictionless manner by means of the leaf springs 16 and 17. The force/travel characteristic is substantially level or horizontal by virtue of the magnetic shunt between the cut-away portion 33 and the rim 36 of the pole shoe 32. The number of ampere-turns required for switching the valve can be reduced by virtue of the enlarged pole surface provided by the pole shoe 32.

Having regard to the provision of Section 9 of the Patents Act 1949 attention is directed to the claims of our prior Patent No. 1,501,506.

WHAT WE CLAIM IS: 1. An electro-magnetically operable valve in which an armature which carries movable valve members is urged by a spring into a normal or released position from which it can be displaced by magnetic force upon energisation of a coil and is guided and centered by means of leaf springs which are received in cut-away recesses in its end faces, and in which an annular pole shoe engaging one end face of the armature covers the recesses in that end face.

2. A valve as claimed in Claim 1, in which an outer rim of the pole shoe provides a shunt part of a magnetic circuit including the armature and a housing.

3. A valve as claimed in Claim 1 or 2, in which the internal annular region of the annular pole shoe has a cylindrical shoulder extending therefrom whose side facing the armature has an external diameter substantially corresponding to the internal diameter of a recess in the armature, and the other side of the pole shoe has a recess for receiving part of the spring urging the armature into the normal or released position.

4. A valve as claimed in any of Claims 1 to 3 which is a 3-position valve which is arranged between a pressure-responsive device, a source of pressure and a relief point, and in which the armature accommodates two valve closure

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

fixed to the ring 11, for example by a weld, to form an assembly which can be inspected before being assembled into the complete valve. A spacer ring 18 is located between the upper leaf spring 17 and an end member 10 having a seat

14 for the outlet valve. The end member 10 is retained in the tubular shell 7 by means of a flange 15 formed on the tubular shell.

A valve closure member 20, 22 of an inlet valve 12, 20, 22 and a valve closure member 21,

23 of an outlet valve 14, 21, 23, are fitted in a multi-stepped bore provided in the armature 13.

The two aforementioned valve closure members comprise balls 20, 21, each let into, and secured in, a respective ball holder 22 and 23.

The ball holder 22 of the inlet valve closure member 20, 22 normally abuts against a shoulder 24 of a bore 19 of armature 13. The closure member 20, 22 is thereby raised from the valve seat 12, and the inlet valve 12, 20,22 is open.

A spring 25 acts between the valve closure member 20, 22 and a ring 26 which is secured in the armature 13 by means of a further ring having a shoulder 27. The shoulder 27 has a cut-away portion, whereby an axial gap 28 is formed between the cut-away portion and the ring 26 to accommodate the ball holder 23. The ball holders 22 and 23 are provided with axial openings 22' and 23' for the passage of pressure medium. One end of a valve spring 29 of the outlet valve 14, 21,23, extending within the spring 25, abuts against the ball holder 23 and its other end abuts against the ball holder 22.

For the purpose of accommodating the leaf springs 16 and 17 respectively, one end of the armature 13 is provided with a cut-away portion 30 and its pole surface 13' is provided with a cut-away portion 31. The cut-away portion 31 on the pole surface 13' is covered by an annular pole shoe 32, so that a full uninterrupted annular surface is again produced as the pole face of the armature 13.

An intermediate disc 34 is placed onto an annular cut-away portion 33 in the yoke 9. An annular wall 35 of the cut-away portion 33 is thereby located opposite an outer edge 36 of the pole shoe 32 to provide a shunt part of the magnetic circuit in this region.

A spring 37 is arranged below the armature 13 and, together with the leaf springs 16 and 17 applying a restoring force, urges the pole shoe 32 and the armature 13 upwardly so that the outlet valve 14, 21, 23 is normally closed and the inlet valve 12, 20, 22 is normally open when the magnet is de-energized. This spring 37 is fitted in a recess 38 in the pole shoe 32. A cylindrical shoulder 39 is formed on the other side of the pole shoe 32 and its external diameter corresponds approximately to the internal diameter of a cut-away portion 13" in the armature.

The solenoid valve 1 operates as follows: When the device is in its normal or released position when the coil 5 is not energised, the pressure-responsive device 2 communicates with the source 3 of pressure through the hollow armature 13 and through the openings 22' and 23' in the ball holders 22 and 23. The armature 13 is drawn downwardly when the coil 5 is energised to a first value of current level, the leaf springs 16 and 17 being resiliently deformed and the spring 37 compressed. The spring 25 expands so that the valve closure member 21, 23 of the outlet valve 14, 21, 23 remains on its seat 14 until the valve closure member 20, 22 of the inlet valve 12, 20, 22 has engaged its seat 12 and the inlet valve 12, 20, 22 has been closed.

Upon a further stroke of the armature 13 as a result of an increase in the current through the coil 5, the valve closure member 21, 23 of the outlet valve is moved off its seat 14 by the ring 27 and the outlet valve 14, 21, 23 is thus opened. The pressure medium in the pressureresponsive device 2 can now expand towards the relief point 4.

The armature 13 is not subjected to any friction during movement thereof, since it is mounted in a frictionless manner by means of the leaf springs 16 and 17. The force/travel characteristic is substantially level or horizontal by virtue of the magnetic shunt between the cut-away portion 33 and the rim 36 of the pole shoe 32. The number of ampere-turns required for switching the valve can be reduced by virtue of the enlarged pole surface provided by the pole shoe 32.

Having regard to the provision of Section 9 of the Patents Act 1949 attention is directed to the claims of our prior Patent No. 1,501,506.

WHAT WE CLAIM IS: 1. An electro-magnetically operable valve in which an armature which carries movable valve members is urged by a spring into a normal or released position from which it can be displaced by magnetic force upon energisation of a coil and is guided and centered by means of leaf springs which are received in cut-away recesses in its end faces, and in which an annular pole shoe engaging one end face of the armature covers the recesses in that end face.
2. A valve as claimed in Claim 1, in which an outer rim of the pole shoe provides a shunt part of a magnetic circuit including the armature and a housing.
3. A valve as claimed in Claim 1 or 2, in which the internal annular region of the annular pole shoe has a cylindrical shoulder extending therefrom whose side facing the armature has an external diameter substantially corresponding to the internal diameter of a recess in the armature, and the other side of the pole shoe has a recess for receiving part of the spring urging the armature into the normal or released position.
4. A valve as claimed in any of Claims 1 to 3 which is a 3-position valve which is arranged between a pressure-responsive device, a source of pressure and a relief point, and in which the armature accommodates two valve closure

members which are movable towards one another and relative to the armature and which are urged away from one another by means of a valve spring arranged in the armature.
5. An electro-magnetically operable valve constructed and arranged and adapted to be operated substantially as hereinbefore particularly described with reference to and as illustrated in the accompanying drawing.