Valve construction

[0002] The invention relates to a valve construction having a housing within which are at least two ports and a slide movable between positions in which at least one of the ports is selectively open or closed.

[0003] Valves are known in the art for the most varied uses. They have at least two connections and a slide which is movable to and fro between at least two setting positions, wherein the slide seals at least one connection in one setting position and opens it in the other setting position. Positioning means to perform the positioning function and sealing means to perform the sealing function of the slide are also provided.

[0004] An electromagnetic injection valve for fuels is known from U.S. Pat. No. 4,679,000, in which a slide opens the communication between two connections in one setting position and closes it in the other setting position. By control of an electromagnetic actuating device the slide is brought into the closed position, the front end thereof coming into contact with a corresponding seal seat. Thus the electromagnetic actuating device on the one hand produces the positioning force and on the other hand produces the sealing force onto the slide. In the closed position the slide is clamped by means of a piezoelectric element. In this known valve the electromagnetic actuating device is of relatively large construction since on the one hand it must provide a relatively large adjustment distance of the slide and on the other hand it must apply a relatively great sealing force in the closed position.

[0005] The object of the invention, therefore, is to improve the known valve so that it can be set more effectively and more reliably.

[0006] According to the invention this object is achieved by the characterising feature of claim 1, in that the positioning means have a positioning actuator and the sealing means have a sealing actuator which can be control led separately from one another. Thus the “positioning” and “sealing” functions of the slide during the valve operation can be achieved by a plurality of separate actuators. In this case each actuator can be optimally designed for its function, particularly with regard to adjustment distance and adjusting force. Thus a comparatively large adjustment distance with a small adjusting force will be required of the positioning actuator, whilst the requirements are the reverse for the sealing actuator, namely a small adjustment distance and a relatively great adjusting force.

[0007] FIG. 1 shows a schematic representation of a first embodiment,

[0008] FIG. 2 shows a schematic representation of a second embodiment,

[0009] FIG. 3 shows a schematic representation of a third embodiment,

[0010] FIG. 4 shows a schematic representation of a fourth embodiment,

[0011] FIGS. 5ato 5cshow control characteristics of the valve according to a first control arrangement, and

[0012] FIGS. 6ato 6cshow control characteristics according to a second control arrangement.

[0013] A 3/2-way valve is shown in FIG. 1. This valve has a housing H within which is a passage P in communication with three spaced ports or connections 1, 2, and 3. The port 1 is a pressure connection, the port 2 is an equipment connection, and the port 3 is an air exhaust connection. A slide 4 is accommodated in the passage P and is movable to and fro between two setting positions, whereby in the illustrated setting position the slide closes the exhaust air connection 3 and establishes communication between the equipment connection 1 and the pressure connection 2 and in the other setting position it opens the exhaust air connection 3 and in this way establishes communication between the equipment connection 1 and the exhaust air connection 3.

[0014] Positioning or slide actuating means for performing the positioning function are also connected to the slide 4, these positioning means being formed by a positioning actuator 5aand an elastic element, particularly a first spring element 5b. In order to perform the sealing function sealing means are provided which comprise a sealing actuator 6aand a second spring element 6b. In the illustrated embodiment both the positioning actuator 5aand the sealing actuator 6aare formed by a piezoelectric bending tongue clamped on one end.

[0015] By corresponding charging with voltage the positioning actuator 5ais energised so that it displaces the slide 4 towards the left against the force of the spring element 5b. At the same time the sealing actuator 6ais energised in such a way that it neutralises or relieves the sealing force exerted by the second spring element 6bon the slide. The restoring of the sealing actuator 6aand thus the exerting of the sealing force takes place after displacement of the slide 4 by the second spring element 6b. The two actuators 5a, 6amust not transmit any further forces to the slide after the displacement of the slide 4. This has the great advantage that no so-called “creeping” can take place in the actuators formed by the bending tongues. This creeping can occur particularly when a bending tongue must be deflected for a relatively long time, since it is then possible for slipping of the adhesive layer in thee actuator to occur.

[0016] The two end or setting positions of the slide 4 are advantageously delimited by two stops 7, 8.

[0017] In contrast to the positioning actuator 5a, the sealing actuator 6amerely requires a short adjustment distance. In order to be able to compensate for any manufacturing tolerances, the spring force of the second spring element 6bis set by an adjusting screw 9.

[0018] The slide 4 has a seal 4a, particularly an elastic coating, which comes into operative connection with a corresponding connection and is provided on a lateral surface of the slide which is disposed transversely with respect to the direction of movement of the slide.

[0019] The second embodiment which is shown in FIG. 2 again shows a 3/2-way valve, but in this case the exhaust air connection 3′ is disposed transversely with respect to the equipment connection 1 and to the pressure connection 2 on another side of the valve. The slide 4 is again movable to and fro between two positions by means of a positioning actuator 5a. The sealing means are formed by a second spring element 6band a sealing actuator 6′a, the sealing actuator 6′abeing provided as an armature which can be operated electromagnetically.

[0020] Thus for displacement of the slide 4 the sealing actuator 6′ais first of all actuated in order to neutralise or relieve the spring force of the second spring element 6b, so that the positioning actuator 5acan then be controlled. In the illustrated embodiment the positioning actuator 5ais again formed by a piezoelectric bending tongue which is clamped on one end to the housing and on the opposite end to the slide, restoring of the slide 4 being achieved by the spring force present in the positioning actuator 5a. However, in this construction it is possible for the “creeping” described above to occur.

[0021] In the illustrated embodiment the exhaust air connection 3′ is disposed perpendicular to the equipment connection 1 and to the pressure connection 2. This has the advantage that the system pressure which presses the slide from the interior onto the exhaust air connection 3′ only acts when the slide 4 has not yet been displaced. As soon as the slide is slightly lifted off from the exhaust air connection 3′ the pressure drops and thus so does the force on the positioning actuator 5a. This force then acts against the positioning actuator 5awhich is constructed as a piezoelectric bending tongue and which can reach the highest force with minimal deflection.

[0022] By comparison with FIG. 2 the embodiment according to FIG. 1 has the disadvantage that the compressive force on the exhaust air connection 3 acts as a normal force on the frictional force of the slide 4, all the more so over a longer path.

[0023] The third embodiment which is illustrated in FIG. 3 shows a 2/2-way valve in which only an equipment connection 1 and a pressure connection 2 is provided, wherein the slide 4 opens the pressure connection 2 in one setting position and closes it in the other setting position.

[0024] The positioning movement of the slide 4 is achieved here by an electromagnetic positioning actuator 5′awhich in turn co-operates with a first spring element 5b.

[0025] The sealing force is produced by a piezoelectric bending strip 6awhich is designed to increase a positioning force on both sides. In the illustrated embodiment the sealing actuator 6aoperates without an additional spring element against the slide 4. The necessary spring force can then be produced for example by pretensioning of the sealing actuator.

[0026] The fourth embodiment which is illustrated in FIG. 4 again corresponds by its outer connections to the 3/2-way valve illustrated in FIG. 1. The positioning means are formed by a positioning actuator 5aconstructed as a piezoelectric bending tongue and first spring element 5b. The sealing force is produced by a spring element 6b, whilst neutralising or relieving of this sealing force is effected by way of a sealing actuator 6aconstructed as a stack piezo. A lever 10 is used to increase the deflection of the sealing actuator 6a.

[0027] The illustrated side 4′ has a bore 4′bthrough which the medium is passed in the open state, i.e. when the equipment connection is in communication with the pressure connection 2. The particular advantage with this construction of the slide 4 is that small pressure-filled volumes are produced in the valve so that the time required for the build-up of pressure is short.

[0028] Within the scope of the invention the elements illustrated in the individual embodiments are interchangeable with one another. What is special about all the embodiments is that the “positioning” function and the “sealing” function are carried out by two actuators which are separate from one another. Whereas the positioning actuator requires the greatest possible adjustment path and the sealing actuator requires the greatest possible sealing force, each actuator can therefore be optimally designed for its function. Since the positioning actuator and the sealing actuator act in different directions on the slide 4, 4′, the functions can also be clearly separated from one another. In some cases the sealing actuator also performs a function of clamping the slide as well as the sealing function.

[0029] Three curve traces are shown in FIGS. 5ato 5c, FIG. 5 showing the control of the entire valve as seen from outside. FIGS. 5ashows the control of the positioning actuator and 5bshows the control of the sealing actuator. In all three cases the control voltage U is shown relative to the time t. In order to open the valve during a time period from t₁to t₂, first of all the sealing actuator is operated at the time t₁. The positioning actuator is actuated simultaneously or with some time delay.

[0030] Because of the autonomous return of the slide when the sealing force is neutralised, in order to close the valve at the time t₂it is merely necessary to control the sealing actuator.

[0031] In the bistable control of the valve which is illustrated in FIGS. 6ato 6ban electrical impulse is used in each case to alternate between the “open” and “closed” positions. In order with a pulse to change to the respective other valve state, the respective last position of the valve (open or closed) must be stored temporarily in a memory. When a signal arrives, depending upon the contents of the memory both the actuators are operated for opening of the valve or only the sealing actuator is operated for closing it.