Electrically Operated Valves For Delivering Fluid Under Pressure

Abstract

An electrically operated valve comprises a distributor having a slide operative to selectively place a fluid actuated device in communication with a source of pressurised fluid, or with a fluid outlet. The slide is actuated by an electrodynamic motor in response to a control signal, whereby the fluid pressure in the device is dependent on the signal.

Description

FIELD OF THE INVENTION

The present invention relates to electrically operated valves.

SUMMARY OF THE INVENTION

According to the present invention, there is provided in an electrically operated valve for delivering a fluid pressure governed by a control signal, feed pipe means, means defining an outlet, a distributor, said distributor having slide means selectively placing the feed pipe means in communication with a source of fluid under pressure or with the outlet, means subjecting the slide means to an axial force dependent on pressure within an associated fluid-actuated device and an electrodynamic motor, said motor having a winding through which flows a current governed by the control signal, the said winding constituting the moving part of the electrodynamic motor and being connected to the slide means,

In one embodiment of the invention, the force acting on the winding and the force dependent on the pressure in the associated device are opposite in direction so as to balance each other at least partially; the pressure in the associated device is then an increasing function of the control signal.

In another embodiment of the invention, the force acting on the winding and the force dependent on the pressure in the associated device act in the same direction, the valve having means for applying to the slide means a force opposite in direction to the foregoing two forces; the pressure in the associated device is in this case a decreasing function of the control signal. This embodiment of the invention is particularly useful in preventing wheel lock on a motor vehicle, the electrically operated valve being interposed between the pressure source and a brake cylinder of a braked wheel, the control winding being energised by a signal having a mean intensity dependent on, for instance, the degree of wheel slip.

Preferably, the valve has a chamber connected to the feed pipe, within which chamber a transmission or thrust member connected to the slide means and smaller in section than the latter is mounted with freedom to move.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which:

FIG. 1 is a section of one embodiment of a valve in accordance with the invention;

FIG. 2 is a section, to an enlarged scale, of a portion of a valve; and

FIGS. 3 to 7 are sections showing details of other embodiments of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1, an electrically operated valve has a distributor comprising a body 1 containing a bore 2 within which is a movable slide 3. The slide 3 has annular grooves 4 and 5 between bearing portions 6, 7 and a bearing thrust member 8; a passage 9, connected to a pressure source, and an outlet passage 10, connected to a vent, open into the grooves 4 and 5, respectively. The pressure source consists of a hydraulic accumulator 11, charged from a tank 12 by a pump 13, and maintaining a pressure P higher than that which normally exists in a fluid actuated device 15. An intermediate feed pipe passage 14 is connected to the device 15, represented diagrammatically by a ram. According to the position of the slide 3, the passage 14 is either closed by the intermediate bearing portion 7 or partially or fully in communication with either the groove 4 or the groove 5. One end of the bore 2 opens into a chamber 16 of the same section, and which is connected to the passage 14 by a passage 17.

When axial force (F) is applied to the end of the slide 3 remote from the chamber 16, the slide 3 moves to the right (as viewed in FIG. 1), placing the passage 14 in communication with the passage 9 and hence with the high-pressure source. The pressure which then acts in the device 15 and hence in the chamber 16 acts as a fluid actuated device that tends to move the slide 3 towards the left. There is finally established in the device 15 a pressure (P.sub.u) proportional to F, its value here being F/S, where S is the cross-sectional area of the end face of the bearing portion 8. Any variation in the force F or pressure P.sub.u results in displacement of the slide 3 so as to alter the ratio of the pressure differentials between the passage 14 and the grooves 4 and 5, that is to say between the pressure source and the vent, in a direction corresponding to the restoration of equilibrium.

The slide 3 is actuated by an electrodynamic motor; in other words the motor applies the force F to the slide 3. The motor incorporates a permanent magnet 18 mounted between a pole piece 19 and the end wall of a pot-shaped magnetic yoke 20 so as to define, in conjunction with the pole piece 19, an annular gap 21; the yoke 20 is fixed to the body 1 of the distributor.

Mounted within the gap 21 is a winding 22 supported on a cup 23. The cup 23 is biased against the end of the slide 3 by a spring 24; a spring 25 mounted within the chamber 16, acts in opposition to the spring 24 whereby, when a control signal is zero, the slide is located in an equilibrium position in which the axial surface of the bearing portion 7 which faces towards the groove 5 lies in the transverse plane of that position of the generator line of the passage 14 which is nearest to the groove 5 (as shown in FIG. 2).

In this way, in the absence of current in the winding 22, the pressure in the connection to the deivce 15 is zero; but when current is passed through the winding 22 in the appropriate direction, the winding tends to move axially, towards the right (as viewed in FIG. 1), exerting on the slide 3 a force F which is proportional to the mean strength of current I.sub.m passing through the winding. The pressure in the device 15 is ultimately proportional to this mean current strength I.sub.m.

In the embodiment shown in FIG. 3, the magnet 18 is replaced by a ring magnet 18', fitted around an H-sectioned member 34, in which the limbs of the member 34 are of unequal length, an annular air gap 21 being defined between the shorter limb of the member 34 and a ring 35.

In the embodiment shown in FIG. 4, the magnet 18 is replaced by a coil 36. In this case, a current which varies with the signal can be passed through the coil 36 and/or the winding 22.

In the embodiment of FIG. 5, the winding 22 is fixed on a drum 26 slidable to an axial hub 27, fixed to the pole piece 19. The drum 26 is connected by two or more levers 28, pivotally mounted at 29 on the body 1, to a cup 30, biased against the slide 3 by a spring 24. The pivot 29 is nearer to the pivotal connection between the levers 28 and the cup 20 than to the pivotal connection between the levers 28 and the drum 26. In use, current is passed through the winding 22 whereby the winding and the drum 26 move to the left as viewed in FIG. 5; this movement is transmitted via the levers 28 to the cup 30 (and hence to the slide 3) with amplitude reduced, that is to say with the force increased, i.e. with a mechanical advantage.

The embodiment of FIG. 6 is generally similar to that shown in FIG. 1 except that the cup 23 is hooked over the slide 3. Additionally, a thrust pin 31 extends axially through the pole piece 19, the cup 20 and the magnet 18, which is ring-shaped for this purpose, and bears against the slide 3. In the absence of current, the pressure P.sub.u in the device 15 is proportional to a force (f) exerted on the pin 31; when current of mean strength I.sub.m is passed through the winding 22 in a sense to move the winding 22 to the left as viewed in FIG. 6, it exerts on the slide 3 a force F proportional to I.sub.m and opposite in direction to the force f. The pressure P.sub.u falls and becomes proportional to f - F, that is to say that the value by which it falls is proportional to I.sub.m.

In the embodiment shown in FIG. 7, the bore 2 is connected to a chamber 16 by an aperture through which a thrust pin 32 extends. Equilibrium is established when the value of the force F is equal to s.P.sub.u, s being the cross-sectional area of the pin 33. The force F is thus smaller than the value it will have in the embodiment in FIG. 1.

In the embodiment shown in FIG. 1, the spring 24 can be pre-stressed as to bring the slide 3 into a position in which the passages 9 and 14 are in communication even at maximum pressure. Then, the winding 22 being arranged to be energized so as to be subjected to a force directed towards the left as viewed in FIG. 1, the pressure in the device 15 would have a value P in the absence of current in the winding 22, but, with current flowing through that winding, would fall by an amount related linearly to the mean strength of that current.

Claims

What is claimed is:

1. In an electrically operated valve for delivering a fluid pressure governed by a control signal,

a. feed pipe means,

b. means defining an outlet,

c. a fluid pressure source,

d. a distributor connected to said fluid pressure source and said feed pipe and outlet means,

e. said distributor having slide means selectively placing the feed pipe means in communication with said source of fluid under pressure and with the outlet,

f. a fluid actuated device associated with said distributor,

g. means subjecting the slide means to a first axial force dependent on pressure within said associated fluid-actuated device, and

h. an electrodynamic motor, having a winding through which flows a current governed by the control signal, the said winding constituting the moving part of the electrodynamic motor and being connected to the slide means to apply a second axial force thereto.

2. A valve as claimed in claim 1, in which the electrodynamic motor includes

a permanent magnet.

3. A valve as claimed in claim 1, in which the electrodynamic motor comprises

one fixed winding for creating a magnetic field, and

one moving winding.

4. A valve as claimed in claim 1, in which the force acting on the winding and the force dependent on the pressure in said associated device act in opposite directions so as to cancel each other out at least partially.

5. A valve as claimed in claim 4, further comprising

linking means connecting the winding to the slide means, said linking means applying a mechanical advantage to the slide means.

6. A valve as claimed in claim 1, in which the force acting on the winding and the force dependent on the pressure in said associated device act in the same direction, said valve further comprising

means exerting a force on the slide means opposite in direction to the other forces.

7. A valve as claimed in claim 6, in which the means exerting the opposite force comprises

a spring.

8. A valve as claimed in claim 7, in which the spring is pre-stressed and exerts sufficient force on the slide means to retain the slide means in a position in which the feed pipe means is in communication with the source of fluid under pressure, even when the pressure in the associated device is at a maximum, the said force being insufficient to hold the slide means in the said position once the force acting on the winding has reached a predetermined value.

9. A valve as claimed in claim 1, in which the said means subjecting the slide means to a force dependent on the pressure in the associated device comprises

means defining a chamber in communication with the feed pipe means, and

a movable thrust member, the thrust member being smaller in section that the slide means, one end portion of the thrust member being received in said chamber, and the other end of the thrust member being movable with the slide means.

10. A valve as claimed in claim 9, in which the said other end of the thrust member bears against the slide means.