GB2220302A

GB2220302A - Electromagnetically actuated valve

Info

Publication number: GB2220302A
Application number: GB8914852A
Authority: GB
Inventors: Roger Labouesse
Original assignee: Solex SA
Current assignee: Solex SA
Priority date: 1988-06-29
Filing date: 1989-06-28
Publication date: 1990-01-04
Anticipated expiration: 2009-06-28
Also published as: GB8914852D0; DE8907897U1; FR2633694B1; GB2220302B; ES2013568A6; IT8948145A0; FR2633694A1; IT1231625B

Abstract

The valve, which can be used especially on an air delivery channel to an internal-combustion engine, comprises a housing in which a rotor assembly (14) can rotate between a first position and a second position. A return spring (56) stresses the assembly towards a position in which the spring closes an air outlet (15b). The assembly is brought into the valve open position by exciting a coil (20) for generating an axial magnetic field, associated with a magnetic circuit having a tubular stator (28) surrounding the coil (20) and a calliper (54) secured to the rotor assembly, the stator and the calliper having interacting teeth (30, 44) such that the magnetic circuit has a minimum reluctance in the valve open position. <IMAGE>

Description

tIAS ELEOTFICALLY CONTROLLED V^T 5TE t The invention relates to electrically controlled valves, often called solenoid valves, of the type comprising a housing equipped with inlet and outlet passages and an assembly movable between a first position, in which it puts the passages in communication with one another, and a second position, in which it separates the passages, this assembly being urged - towards one of the positions via a return spring and being brought into the other position by magnetic-field generation means when these are fed.

The invention has an especially important, although not sole use in the feed systems of an internalcombustion engine of the injection or carburation type.

The feed systems of the engine of vehicles equipped with electrical feed accessories, such as an air conditioner, power-assisted steering, high-power lighting, etc. must often include an air delivery channel branched off on the throttle actuated by the driver. This channel is equipped with a valve controlled by a circuit sensitive to the speed of the engine. When the latter is idling, the circuit controls the valve in order to admit a sufficient air flow to prevent the speed from falling below a specific value in the event of an overload of the engine attributable, for example, to the activation of an accessory. The increase of the air flow in turn causes an increase in the fuel flow.

Some of the electrically controlled valves employed for these uses have an assembly movable in translational motion. But in many cases, it is necessary to use a valve with a rotary assembly in order to obtain the desired accuracy of adjustment. At the present time, solenoid valves with a rotary assembly have complex windings of a construction comparable to that of the windings of an electric motor and of high bulk. Those of the valves where the winding is carried by the movable assembly also require relatively fragile sliding contacts.

An object of the present invention is to provide an electrically controlled valve which satisfies practical requirements better than those previously known, particularly in that it is of low bulk, in that the means making it possible to generate the electrical control torque are of low cost and have only a small bulk, and in that the rotary assembly has an inertia compatible with the conventional uses.

To achieve this, the invention provides a valve of the type defined above, wherein the control magnetic-field generation means comprise a fixed coil for generating an axial magnetic field, associated with a magnetic circuit having a tubular stator sur rounding th coil and a rotor belonging to the rotary assembly, the stator and the rotor having interacting teeth, the cut-out of which is such that the magnetic circuit has a minimum reluctance in the said other position.

The stator can consist, in particular, of a tube having at least one tooth delimited circumferentially by two edges of differing depth, two circumferentially successive edges of differing depth being connected by means of an oblique part; the tooth or each tooth of the rotor is cut out so as to come to bear over the entire height of the edge associated with the tooth and over a fraction of the oblique part when the assembly is in the said other position.

In practice, the stator generally has two teeth and the rotor then consists of a calliper likewise having two teeth. To avoid the risks of adhesion attributable to the residual magnetization of the magnetic circuit, a thin layer of non-ferromagnetic conductive material is advantageously provided on one of the fixed and movable teeth, so as to form a flux gap on the magnetic circuit when the assembly is in the said other position.

The mean passage flow through a solenoid valve is in which the inventionlwirl generally be controlled by applying to the coil electrical pulses of variable cyclic ratio and of a fixed or variable frequency. When the solenoid valve is used in a feed system of an internal-combustion engine, the moment of inertia of the rotary assembly is generally given a value sufficient to ensure that the movable assembly assumes a mean position of equilibrium which is a function of the cyclic ratio of the current pulses (at the constant intensity of these pulses), even for a low frequency generally of between 50 and 100 Hz. The position of the solenoid valve, and therefore the flow passing through it, can thus be controlled by modulating the width of the pulses applied to the magnetic-field generation means.

One embodiment of this invention trill be described now by way oQ example with reference to the accomtanying drawings :In j.Jhich: - Figure 1 shows a solenoid valve in which the invention is embodied in section along the line I-I ot Figure 2: - Figure 2 is a front view of the solenoid valve in the direction of the arrow II in Figure 1; - Figure 3 is a diagrammatic perspective view showing the essential components of the ferromagnetic circuit of the solenoid valve of Figures 1 and 2; - Figure 4 is a developed diagram showing the form of the teeth of the stator.

The solenoid valve shown diagrammatically in Figures 1 and 2 comprises a housing 10 composed of several assembled parts, for example made of an aluminium-based alloy. This housing carries a stop element 12, on which bears and rotates a rotary assembly 14 which can be considered as consisting of a motive part belonging to the magnetic circuit of the field-generating means and of a fluid-flow control part.

The housing can be regarded as comprising a rear part containing the motive part of the rotary assembly 14 and a front part 17 delimiting a chamber receiving the control part. The front part is pierced with inlet and outlet passages 1Sa and 15b.

The rear part of the housing is composed of a sleeve 26 and of a bottom 16, through which pass insulated feed wires 18 for a coil 20 of the solenoid type carried by a plastic mandrel 22. Interposed between the coil 20 and a lateral sleeve 26 belonging to the housing 10 and fastened to the bottom by means of screws is a tubular stator 28 made of ferromagnetic material and retained in terms of rotation relative to the housing.

This tubular stator 28 bears at the rear on the bottom 16. At the front, it has a special cut-out intended for forming teeth projecting axially forwards relative to the mandrel 22 of the coil 20. A flux-closing piece of ferromagnetic material 29 is placed inside the mandrel 22.

In the embodiment illustrated, shown more clearly in Figures 3 and 4, it can be seen that the tubular stator 28 has two teeth. Each tooth 30 can be considered as limited by a front edge 32, a circumferential edge 34 located markedly beyond the mandrel 22, an oblique breadth 36 intersecting the level of the end face of the mandrel, and a rear edge 38 which is extended axially towards the inside of the coil beyond the front edge 32.

Two successive teeth 34 are connected by means of a circumferential edge 40 starting from a rear edge 38, followed by a step and by an oblique part 42 meeting the front edge.

This arrangement gives the lines of force of the magnetic field generated by the coil 20 a form different from that which they would normally have. The field generated by a solenoid normally has lines of force, each of which is contained completely in a plane passing through the axis of the coil. Because of the presence of the teeth 30 and their interaction with teeth 44 which are carried by the rotary assembly and which will be mentioned later, within the teeth the lines of force assume an inclination which causes them to pass through the front edges 32, particularly when the teeth 44 of the rotary assembly are against the front edges 32.

To prevent the teeth from remaining adhering to one another in this position, a thin layer 46 of nonferromagnetic material is advantageously provided on the front edges 32; this flux gap can also be provided by means of a stop device.

The motive part of the rotary assembly 14 comprises a core 48 of ferromagnetic material, onto which is fitted a rod 50 which belongs to the flow control means and which bears on the stop 12. The core 48 rotates on a ball 52 made of insulating material and bearing against the piece 29, onto which it is laid by means of the stop 12. Fastened to the core is a calliper-like rotor 54 terminating in the two teeth 44 interacting with the teeth 30 of the stator. The teeth 44 have such a form that the reluctance of the magnetic circuit is at a minimum when they are laid against the front edges of the teeth 30 (as represented by broken lines in Figure 4) and at a maximur when they are in the vicinity of the rear edges 38.

In this case, a return spring must be provided in order to move the teeth away from the position shown in Figure 4 and bring them towards the position where they are represented by unbroken lines in Figure 2. In the embodiment illustrated, this return spring 56 also constitutes a shutter, the front part of the rotary assembly 14 having a construction similar to that des French cribed and claimed in the applicant'sAPatent Application FR.8801577. The spring 56 consists of a spirally wound leaf, the outer end of which is fastened to the housing by means of a rod 58 and the inner end of which is engaged in a slot of the rod 50 belonging to the rotary assembly.

In the instance illustrated, the return spring 56 has, at rest, such a form that it tends to lay itself against the crifice 15b, thereby driving the rotary assembly towards the position represented by unbroken lines in Figure 2 and opposite that of Figure 4. When the coil 20 is fed permanently, on the contrary, it brings the rotary assembly into the position shown in Figure 4, the spring 56 then assuming the position represented by dot-and-dash lines in Figure 2 and exposing a maximum passage cross-section.

It can be seen that such a valve is closed at rest. When it is fed with current pulses typically having a frequency of 50 to 100 Hz and a cyclic ratio of 20 to 80%, the movable assembly assumes an intermediate mean position of equilibrium which is a function of the cyclic ratio and which makes it possible to adjust the flow passing through the solenoid valve.

The invention is not limited to the particular embodiment illustrated and described by way of example.

On the contrary, it can have many alternative embodiments relating both to the means of controlling passage crosssection and to the composition and number of teeth of the magnetic circuit.

Claims

1. An electrically controlled valve comprising a housing equipped with inlet and outlet passages and an assembly rotatable between a first position, in which it puts the passages in communication with one another, and a second position, in which it separates the passages, this assembly being urged towards one of the positions by a return spring and being brought into the other position by the action of magnetic-field generation means when they are energised wherein the control magnetic-field generation means comprise a fixed coil for generating an axialnagpetic-field, associated with a magnetic circuit having a tubular stator surrounding the coil and a rotor belonging to the rotary assembly, the stator and the rotor having interacting teeth, the cut-out of which is such that the magnetic circuit has a minimum flux gap in the axial direction and therefore a minimum reluctance, in the said other position.

2. An electrically controlled valve comprising a housing equipped with inlet and outlet passages and an assembly rotatable between the first position, in which it puts the passages in communication with one another, and a second position, in which it separates the passages, this assembly being urged towards one of the positions by a return spring and being brought into the other position by the action of magnetic-field generation means when they are energised wherein the control magnetic-field generation means comprise a fixed coil for generating an axial magnetic field, associated with a magnetic circuit having a tubular stator surrounding the coil and a rotor belonging to the rotary assembly, the stator and the rotor having interacting teeth, the cut-out of which is such that the magnetic circuit has a minimum reluctance in the said other position, and in that the stator consists of a tube having at least one longitudinally directed tooth delimited circumferentially by two edges of differing depth, two circumferentially successive edges being connected by means of an oblique part.

3. A valve according to claim 2, wherein the tooth or each tooth of the rotor is cut out so as to come to bear over the entire height of the associated edge of the tooth or of each tooth of the stator and over a fraction of the oblique part when the assembly is in the said other position.

4. A valve according to claim 1, claim 2 or claim 3 wherein the stator has two teeth, and in that the rotor consists of a calliper likewise having two teeth.

5. A valve according to any one of the preceding claims wherein a thin layer of non-ferromagnetic material is provided on one of the fixed and movable teeth in order to form a flux gap when the assembly is in the said other position.

6. A valve according to any one of the preceding claims, wherein the rotary assembly has a moment of inertia such that it assumes a mean position of equilibrium when the coil is fed with current pulses having a variable cyclic ratio at a frequency of between 50 and 100 Hz.

7. A valve according to any one of the preceding claims wherein the return spring consists of a spiral spring fastened to the rotary assembly and to the housing and arranged so as to lay itself against at least one of the passages and close it in one of the two end positions of the rotary assembly.

8. An electrically controlled valve substantially as described hereinbefore with reference to and as illustrated in the accompanying drawings.