FR2826425A1 - Valve for electro-rheological fluid used in anti-lock braking installation in motor vehicle, uses tension applied to electrodes that define passage for fluid to control fluid flow through valve - Google Patents

Abstract

The valve to control an electro-rheological fluid, has a body (1) with inlet (2) and outlet (3) for the fluid flow, and a means of regulating (R) flow through the valve. The regulator comprises electrodes (A1,A2) delimiting the passage (8) for the fluid in the body of the valve, and connections (C1,C2) to an electrical source to create an adjustable electric field between the electrodes.

Description

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VALVE FOR ELECTRO-RHEOLOGICAL FLUID, BRAKING SYSTEM AND PUMP COMPRISING SUCH VALVES.

 The invention relates to a valve, for electrorheological fluid, which comprises a valve body with at least one inlet and one outlet for the fluid and means for adjusting the flow rate of fluid passing through the valve.

 An electro-rheological fluid is a fluid composed of particles of organic inorganic composite polymer, these particles being dispersed in an electrically insulating liquid, for example of the silicone type.

 To control a flow of liquid, electromagnetic valves are known. They are frequently used in various hydraulic installations, in particular in braking installations for motor vehicles, or in dynamic chassis control installations for a vehicle (ESP). The electromagnetic valves can be of the drawer type allowing proportional control, or of the ball type operating in all or nothing or proportional. The electromagnetic coils used in these valves are bulky and heavy. In addition, the electromagnetic fields produced during operation create parasites which can be harmful to the operation of other components of a motor vehicle.

 More particularly, in the case of a braking installation for a motor vehicle with anti-lock braking system (ABS), two valves are provided for each wheel, ie eight valves for a passenger vehicle. This results in a significant weight for the group of valves.

 In addition, the operation of the electromagnetic valves is relatively noisy.

 The object of the invention is, above all, to provide a valve which makes it possible to avoid the problems of electromagnetic compatibility, and which is compact and of reduced weight, while having a quieter operation than an electromagnetic valve .

 It is further desirable that the valve remain simple and economical in construction.

 According to the invention, a valve for electro-rheological fluid, which comprises a valve body with at least one inlet and one outlet for

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 the fluid and means for adjusting the flow rate of fluid passing through the valve, is characterized in that the adjusting means comprise at least two electrodes delimiting the passage of the fluid in the valve body, and means for electrically connecting the electrodes to a voltage source to create an adjustable electric field between the electrodes.

 The viscosity of an electro-rheological liquid increases as a function of the electric field to which it is subjected. It is thus possible, by adjusting the electric field existing between the electrodes, to regulate the flow rate passing through the valve. The electro-rheological liquid can practically solidify for high electric fields (for example of the order of 2 to 3 MV / mm) in which case the flow rate becomes practically zero.

 No element being in movement in the valve, the operation is particularly silent. The size is reduced and the operation does not cause electromagnetic emissions.

 The valve body can be electrically conductive, in particular metallic, and comprise at least one cylindrical bore, the inlet of the valve being provided towards an axial end of the bore and the outlet towards the other axial end; an electrically conductive core, with an outside diameter less than the diameter of the bore, is held fixed coaxially with the bore by electrically insulating means so that an annular passage for the fluid is defined between the external surface of the core and the surface internal bore; the valve body constitutes a first electrode, while the core constitutes the second electrode.

 Generally, the valve body is connected to ground while the core has a connection for connection to an adjustable high voltage.

 According to another possibility, each electrode comprises parallel lamellae, the lamellae of one electrode being arranged opposite the lamellae of the other electrode and defining between them passages for the fluid. Advantageously, each electrode comprises a plate in which the lamellae are cut in part and folded down at right angles to the plate, the lamellae of the two electrodes being nested and kept at a distance from each other. Such a valve may include a parallelepiped insulating body ensuring the maintenance of the electrodes formed by the lamellae, the fluid inlet being provided on

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 a face of the body perpendicular to the strips and the outlet being provided on the opposite face of the body.

 A compact set of valves may comprise a metal parallelepiped block in which are drilled several bores of parallel axes, in particular situated in the same plane, each bore being equipped with a coaxial core maintained by electrically insulating means so that a passage annular for the fluid is defined in each bore between the internal surface of this bore and the corresponding core, the block being connected to ground and each core being connected to an electrical potential specific to this core.

 The invention also relates to a hydraulic braking installation for a motor vehicle in which the liquid is an electro-rheological liquid and the control of the flow of liquid in the various pipes of the installation is ensured by valves comprising electrodes delimiting the passage of the fluid in the valve body and means for electrical connection of the electrodes to a source of electrical voltage.

 The invention also relates to a pump for electro-rheological fluid comprising a cylinder and a piston reciprocating in the cylinder, a fluid inlet and an outlet for delivery, and means for controlling the inlet. and of the outlet in synchronism with the movements of the piston, this pump being characterized in that each means for controlling the inlet and the outlet comprises a valve as defined above, to the exclusion of any valve.

The invention consists, apart from the arrangements set out above, of a certain number of other arrangements which will be more explicitly discussed below in connection with exemplary embodiments described with reference to the attached drawings, but which are not in no way limiting. In these drawings:
Fig. l is a schematic sectional view with part cut away of a valve for electro-rheological liquid according to the invention.

 Fig. 2 is a diagram illustrating the state of the electrorheological liquid subjected to a relatively weak electric field.

 Fig. 3 is a diagram similar to FIG. 2 showing the state of the liquid subjected to a larger electric field.

 Fig. 4 is a schematic perspective view of a drilled block.

 Fig. 5 is a schematic perspective view of a variant of

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 valve for electro-rheological liquid.

 Fig. 6 is a schematic section of a pump without valve for electro-rheological liquid.

 Fig. 7 is a partial diagram of an automobile braking installation.

 Fig. 8 and Fig. 9 finally, are simplified diagrams of braking circuits on a motor vehicle.

 As illustrated in Figs. 2 and 3, an electro-rheological fluid is composed of particles p of organic inorganic composite polymer, these particles being dispersed in an electrically insulating liquid L, for example of the silicone type. The shear force of the fluid (and therefore its viscosity) varies in accordance with the amplitude of the electric field to which the fluid is subjected. In a zero electric field, the viscosity of the fluid is low and the fluidity is good. The viscosity increases with the amplitude of the electric field passing through the fluid. The response time for variations in viscosity as a function of variations in the electric field is very rapid, for example of the order of a millisecond.

 Referring to Fig. l, we can see a valve V for electro-rheological fluid. This valve comprises a valve body 1 with an inlet 2 and an outlet 3 for the fluid. Means for adjusting the flow rate R passing through the valve comprise two electrodes A1, A2 delimiting the passage of the fluid in the body 1. Electrical connection means C1, C2 are provided for connecting the electrodes Al, A2 to the terminals of a source of adjustable voltage U to create an adjustable electric field between the electrodes Al, A2.

 The body 1 is electrically conductive, generally metallic, and comprises at least one cylindrical bore 4 closed at one end and opening onto one face of the body 1 at its other end.

The inlet 2 of the valve is provided towards an axial end of the bore 4, namely the open end according to FIG. l, while the outlet 3 is provided towards the other end, namely the blind end according to the example shown. The diameter of bore 4 is equal to Dl.

 An electrically conductive core, generally metallic, is formed by a cylinder of diameter D2 less than Dl. The core 5 is kept fixed coaxially with the bore 4. Towards its two axial ends, the core 5 is cleavage along extensions 5a, 5b of diameter less than D2; annular clearances are thus created at entry 2 and exit 3. Extension 5a, located

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 on the side of the open end of the bore 4, is itself extended by a coaxial part 5c of smaller diameter engaged in an insulating centering washer 6 blocked in the bore 4. The lower extension 5b is engaged in a another insulating washer 7 bearing against the bottom of the blind bore 4.

 An annular passage 8 of sufficient section is thus defined between the core 5 and the internal surface of the bore 4 for the flow of the fluid from the inlet 2 to the outlet 3.

 The valve body 1 constitutes the first electrode A1 by the internal surface of the bore 4, while the core 5 constitutes the second electrode A2, by its external cylindrical surface.

 The connection means C1 is constituted by an electric wire 9 connecting the body 1 to the ground. The connection means C2 consists of an electric wire 10, surrounded by an insulating sheath, connected to the source U of adjustable high voltage. The voltage to which the core 5 can be brought relative to the mass is several thousand volts (several kilovolts). The electric field E to which the fluid is subjected in the annular space 8 can vary, for example, from 0 kV / mm to 5 kV / mm or more.

 For a zero electric field between the core 5 and the body 1, the viscosity of the electro-rheological fluid is low and the flow rate passing through the valve V is maximum. For a high electric field, the viscosity of the fluid is higher and the flow rate is reduced.

 Fig. 2 schematically illustrates the state of the electrorheological fluid for a voltage E = 300 V applied between the core 5 and the internal surface of the bore 4. The voltage is relatively low and the particles p of the fluid remain relatively spaced between the electrodes which allows a relatively high flow rate.

 Fig. 3 represents the state for a higher voltage applied between the electrodes 5 and 4, for example a voltage of 1000 V. The particles p form denser rows between the electrodes 4 and 5 which corresponds to an increase in viscosity and to a decrease in the flow of liquid passing through the valve.

 For an even higher electric field, one can practically solidify the fluid and cancel the flow.

 Fig. 4 schematically shows a set of eight valves of an anti-lock braking group (ABS) of a braking installation for a motor vehicle, the liquid of which is an electro-rheological liquid.

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 The assembly includes a metal block B in the form of a rectangular parallelepiped in which eight blind holes 4 are drilled with parallel axes located in the same plane, parallel to the large faces of the parallelepiped. The inlet 2 and the outlet 3 for each bore 4 are provided on the same large face 11 of the block B. Each bore 4 is equipped with a coaxial core 5. The block B is connected to ground. The core 5 of each bore 4 is connected to a source of electrical voltage specific to this core.

 Eight V1-V8 valves are thus produced with a minimum space requirement and can operate silently. Two valves are assigned to each of the vehicle's four wheels.

 Fig. 5 is a diagram of another exemplary embodiment of the valve V. The electrodes A1, A2 respectively comprise lamellas 12, 13 rectangular, parallel, arranged facing each other and defining between them rectilinear passages 14 for the fluid.

 Each electrode advantageously comprises a rectangular plate 15, 16 in which the slats 12, 13 which are adjoining the plate by one of their long sides are partially cut, and which are folded down at right angles to this plate.

 In the case of the plate 15, each strip 12 forms with a strip 17 of the plate a right dihedral, one end of which is free and the other end of which is secured, by a small side of the strip 17, to a transverse blade 18 perpendicular to the longitudinal direction of the slats 12. The blade 18 projects by an extension 18a allowing an electrical connection.

 According to the arrangement of FIG. 5, the plate 15 is located above the plate 16 and the electrode Al corresponding to the plate 15 will be designated as the upper electrode, the electrode A2 being the lower electrode.

 The plate 16 comprises bands 19, similar to the bands 17 of the plate 15, which form with the lamellae 13 straight dihedrons of which one end situated on the side of the blade 18 is free while the other end is integral with a blade transverse 20 by the short side of the bands 19.

 The slats 12 are folded down, that is to say towards the plate 16, while the slats 13 are folded up, that is to say towards the plate 15. Preferably, the transverse spacing between the slats 12 and 13 is regular.

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 The transverse blade 20 of the plate 16 has an extension 20a for the electrical connection.

 The plates 15, 16 with their strips 12, 13 are enclosed and maintained in an insulating parallelepipedic body 21 forming a housing.

The extensions 18a, 20a protrude through openings provided in one face of this housing. The fluid inlet is provided on a face 21a of the housing perpendicular to the strips 12, 13, in the direction of the arrow F perpendicular to the face 21a. The fluid outlet is provided on the face of the housing opposite to 21a.

 Fig. 6 is a diagram of a pump 22 for an electrorheological fluid comprising a cylinder 22a, and a piston 23 driven (by a means not shown) in reciprocating movement in the cylinder 22a. A fluid intake pipe 24 opens into the working chamber of the pump 22. A delivery pipe 25 also opens into this working chamber.

 The pump 22 is devoid of any inlet and outlet valve. On the other hand, a valve Va for electro-rheological fluid, of the type described with reference to FIG. l or Fig. 5, is installed on the pipe 24. Similarly, a similar valve Vr is installed on the delivery pipe 25.

 The valves Va and Vr are controlled in synchronism with the movements of the piston 23. When the piston 23 moves in a direction which corresponds to an increase in the volume of the working chamber of the pump 22 the valve Va is open, this is that is to say that the electric field between the electrodes of this valve is brought to the zero value while the valve Vr is in a state which brakes to the maximum or which blocks the backflow, the electric field between the electrodes of this valve being carried at its maximum value.

 During the reverse movement of the piston 23, causing a reduction in the volume of the working chamber, the valve Vr is open while the valve Va goes into the closed state, under maximum electric field.

 This results in particularly silent operation. In addition, manufacture is simplified, in particular with respect to a pump with a valve housed in the pump piston, which requires complicated machining.

 Fig. 7 schematically shows part of a braking installation with electro-rheological fluid comprising a pump 22 without a valve and equipped on its intake pipe with a

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 valve Va and on its delivery line a valve Vr similar to that shown in FIG. 5, the connections of the electrodes to the voltage source not being shown. The displacements of the piston 23 are controlled by a connecting rod 26 and an eccentric 27.

 A single disc brake 28 has been shown with a brake shoe cylinder 29. An inlet pipe 30 for pressurized fluid and a pipe 31 for discharging the fluid are connected to the cylinder 29. A valve V'1 and a valve V'2 similar to those illustrated in FIG. 5 are provided respectively on the lines 30 and 31 and are controlled to ensure the modulation of the pressure in the cylinder 29. A similar connection is provided for the other three wheels of the vehicle. The master cylinder MC is also shown in the diagram in FIG. 7.

 In general, two independent braking circuits are provided in a braking installation, either by half of the front / rear circuit as illustrated in FIG. 8, either with cross circuits as illustrated in FIG. 9.

 The valves according to the invention make it possible to produce pressure modulation systems for space-saving electro-rheological fluid with silent operation, particularly advantageous for braking installations in particular of the ABS type or for dynamic chassis control systems (ESP).

Claims (9)

 CLAIMS 1. Valve, for electro-rheological fluid, which comprises a valve body with at least one inlet and one outlet for the fluid and means for adjusting the flow rate of fluid passing through the valve, characterized in that the means for adjustment (R) comprise at least two electrodes (Al, A2) delimiting the passage (8; 14) of the fluid in the valve body, and means for electrical connection (Cl, C2) of the electrodes to a voltage source to create an adjustable electric field between the electrodes. 2. Valve according to claim 1, characterized in that the valve body (1) is electrically conductive and comprises at least one cylindrical bore (4), the inlet (2) of the valve being provided towards an axial end of the bore and the outlet (3) towards the other axial end, that an electrically conductive core (5), of outside diameter (D2) smaller than the diameter (dal) of the bore (4), is kept fixed coaxially to the bore by electrically insulating means (6,7) so that an annular passage (8) for the fluid is defined between the external surface of the core and the internal surface of the bore, the body (1) of valve constituting a first electrode, while the core (5) constitutes the second electrode. 3. Valve according to claim 2, characterized in that the valve body (1) is connected to ground while the core (5) has a connection for connection to an adjustable high voltage. 4. Valve according to claim 1, characterized in that each electrode (Al, A2) comprises lamellae (12,13) parallel, the lamellae of one electrode being arranged opposite the lamellae of the other electrode and defining between they passages (14) for the fluid. 5. Valve according to claim 4, characterized in that each electrode comprises a plate (15,16) in which the slats (12, 13) are cut in part and folded down at right angles to the plate, the slats ( 12,13) of the two electrodes being nested and kept at a distance from each other. <Desc / Clms Page number 10> 6. Valve according to claim 4 or 5, characterized in that it comprises a parallelepipedic body (21) insulating ensuring the maintenance of the electrodes (Al, A2) formed by the lamellae (12,13), the entry of the fluid being provided on a face (21a) of the body perpendicular to the lamellae and the outlet being provided on the opposite face of the body. 7. Valve assembly according to claim 2, characterized in that it comprises a metal parallelepiped block (B) in which are drilled several bores (4) of parallel axes, each bore being equipped with a coaxial core (5 ) maintained by electrically insulating means so that an annular passage for the fluid is defined in each bore between the internal surface of this bore and the corresponding core, the block (B) being connected to the ground and each core (5) being connected to an electrical potential specific to this nucleus. 8. Hydraulic braking installation for a motor vehicle, characterized in that the liquid is an electro-rheological liquid and that the control of the flow of liquid in the various pipes of the installation is ensured by valves (V; V1-V8; Va, Vr; V'l, V'2) comprising electrodes (Al, A2) delimiting the passage of the fluid in the valve body and means for electrically connecting the electrodes to a source of electric voltage. 9. Pump for electro-rheological fluid comprising a cylinder (22a) and a piston (23) reciprocating in the cylinder, a fluid inlet (24) and an outlet (25) for delivery, and means for controlling the input and the output in synchronism with the movements of the piston, characterized in that each means for controlling the input and the output comprises a valve (Va, Vr) according to one of claims 1 to 6, excluding any valve.