WO2003060331A1

WO2003060331A1 - Electrically controlled valve and brake-assisting servo motor comprising such a valve

Info

Publication number: WO2003060331A1
Application number: PCT/FR2002/004552
Authority: WO
Inventors: Thierry Pasquet
Original assignee: Robert Bosch Gmbh
Priority date: 2001-12-31
Filing date: 2002-12-24
Publication date: 2003-07-24
Also published as: AU2002364879A1; FR2834324A1; FR2834324B1

Abstract

Disclosed is an electrically controlled valve, particularly a pneumatic valve, configured as a flat structure and comprising a plate (P) made of several parallel layers, i.e. one electricity conducting layer (1) forming a first electrode (E1), at least one intermediate dielectric layer (I1, I2) applied against one side of the first electrode, a second electrode (E2) formed by another electricity conducting layer (2) applied against the dielectric layer (I2) on the side lying across from the first electrode, and at least one supporting layer (3) located on the side of the second electrode which lies across from the dielectric layer. The inventive valve also comprises at least one outlet (4) crossing the supporting layer and the second electrode. The first electrode is provided with a flexible tongue (9) closing the outlet or letting a fluid circulate in a released position. Movement of the tongue is controlled by applying sufficient voltage between the electrodes (E1, E2).

Description

_V A _LVE WITH ELECTRICAL _CONTROL AND BRAKE SUPPORT SERVOMOTOR COMPRISING SUCH A VALVE

The invention relates to a valve, in particular pneumatic, 5 with electrical control.

Many types of electrically operated valves are known, provided by at least one electromagnetic coil. Such valves generally work satisfactorily but are relatively heavy and bulky due to the electromagnetic coil, with a response time which needs to be reduced. Their consumption of electric current is not negligible, and parasitic electromagnetic waves can appear during the operation of these valves.

The invention aims, above all, to provide a valve

- pneumatic with electric control whose size and weight

15 are reduced and whose electric current consumption is low, in particular less than 100 mA (milliamps). It is also desirable that the response time be very short, in particular less than 5 ms.

(Milliseconds). .

According to the invention, a pneumatic valve with control

20 electric is characterized in that it has a flattened structure and that it comprises a plate consisting of several parallel layers, namely an electrically conductive layer forming a first electrode, at least one intermediate dielectric layer applied

^• against one face of the first electrode; a second electrode formed

25 by another conductive layer of applied electricity, against the dielectric layer on the opposite side A- first electrode, and at least ^a support layer on the side of the second electrode opposite to the dielectric layer, at least one through passage the support layer and

. the second electrode, while a flexible tab is provided in the

30 first electrode to close the passage or to be removed from it and let ^' circulate a fluid, in particular air, the movement of the tongue being controlled by application of a sufficient electric voltage between the electrodes.

Preferably, in the absence of electrical voltage between the

35 electrodes, the tongue is moved away from the outlet of the -passage and the valve is open, the valve being closed by application of the • electrical voltage between the electrodes.

Advantageously, the first electrode, located towards the outside of the plate, is connected to ground while the high voltage is applied to the electrode located within the plate. The tongue may have a rectangular shape, adjoining the layer by a short side serving as a hinge, and cut along its two long sides and the other short side.

The invention also relates to flexible membrane comprising a set of valves as defined above, characterized in that it comprises several layers corresponding to those of the valves, and that in the membrane are cut a plurality of tabs corresponding to as many passages, each tab and associated passage constituting an elementary valve.

Preferably, the valves of the membrane are arranged in a matrix in rows and columns. Addressing means can be provided for individually controlling each, elementary valve of the membrane, or by groups of valves.

A particularly interesting application of such a membrane relates to a pneumatic assistance booster for a motor vehicle braking installation.

The assistance booster comprises a rigid casing traversed by a rod constituting a manual control member, the casing being internally separated into two chambers by a movable partition in the direction of the axis of the rod, the partition comprising a rigid skirt fixed to the rod and connected along its outer contour to the inner wall of the envelope by a bellows made of deformable flexible material allowing axial movements of the 'skirt, and is. characterized by the fact that the rigid skirt is provided. openings, and formed for example by a grid, and a membrane as defined above is applied and held against the rigid skirt.

The booster may include a second membrane disposed against an end wall.

Advantageously, the booster comprises a control assembly comprising: - a circuit in which is stored the law characteristic of the deceleration of the vehicle as a function of the pressure in the master cylinder and supplying from an input value corresponding to the pressure measured in the master cylinder a signal representing the desired deceleration;

a circuit in which the law of deceleration of the vehicle is stored as a function of the stroke of the pedal, this circuit providing as output a desired deceleration value established according to the measured stroke of the brake pedal;

- And a comparator circuit having two inputs connected respectively to the outputs of the above circuits and which provides, on an output line, a target deceleration corresponding to the absolute maximum value chosen between the input signals;

- And means for determining a stroke error of the actuator rod from the comparator output signal.

The control assembly may include a subtracting circuit providing an error signal equal to the difference between the target deceleration and a calculated deceleration, and a circuit which converts the deceleration error signal into a drag error signal. ^'' by dividing the deceleration error signal by the vehicle mass. ^'

Preferably, the assembly includes circuits for converting the halftone error signal into a target stroke signal of the actuator rod, and a subtractor circuit whose input receives the measured value of the stroke of the actuator rod. and another input the target stroke value, this subtracting circuit providing on its output a rod stroke error signal for controlling the diaphragm valves and ensuring the correction of the position of the actuator bulkhead and of the rod .

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 embodiments described in detail with reference to the accompanying drawings, but which are in no way limiting. On these drawings:

Fig. l is a ^• schematic perspective view, with parts broken away, of a pneumatic valve according to the invention.

Fig.2 is a vertical section of the valve of Fig.l in the open state. - Fig.3 shows, similarly to Fig.2, the valve in the closed state.

Fig.4 is a partial schematic plan view of a membrane comprising a plurality of valves according to the invention.

Fig. 5 is a schematic section of an assistance booster braking system using at least one diaphragm of the type in Fig. 4.

Fig.6, finally, is the diagram of a control assembly of a pneumatic brake booster for a motor vehicle comprising in its movable partition a membrane with valves. Referring to Fig.l, one can see a pneumatic valve V, electrically operated, having a flattened structure. The representation of Fig.l is made on an enlarged scale. The thickness e of the valve is less than 10 mm and preferably less than 5 mm. The valve V comprises a plate P formed from several parallel layers. An electrically conductive layer 1 forms a first electrode E1 which, in the example shown, constitutes the upper wall of the plate P. The layer 1 is generally metallic. El will hereinafter be designated as the upper electrode. Of course, the plate P could have an arrangement other than horizontal, according to which the electrode El would no longer constitute the upper face of P.

At least one electrically insulating intermediate layer, forming a dielectric, is disposed on one side of the electrode El. Advantageously, the dielectric intermediate layer comprises a first layer II of reduced thickness applied directly against the face of the electrode El and a second dielectric layer 12 of significantly greater thickness, preferably three times greater than that of layer II, applied against the face of II remote from the electrode El.

Another electrically conductive layer 2, in particular metallic, forms a second electrode E2 separated from the electrode El by at least part of the dielectric layers II, 12. Advantageously, the electrode E2 is embedded in the layer 12 which includes a part I2a located between E2 and II, and a part I2b located on the other side of E2.

The distance h (FIG. 3) between the facing faces of the electrodes E1 and E2 is reduced, in particular equal to, or of the order of 0.2 mm.

At least one support layer 3, thicker than the dielectric layer 12, is disposed on the side of the second electrode E2 opposite the first electrode El.

The dielectric layers II, 12 and the support layer 3 can be produced with suitable plastic sheets. A passage 4 passes through the support layer 3, the second electrode E2 and the dielectric layer 12. The passage 4 may include a frustoconical entry 5 provided in the support 3 with its large base located on the side opposite the electrode E2.

The passage 4 passes through the second electrode E2, and the parts I2b, I2a of the layer 12 surrounding this electrode, following a circular hole 6 which opens into a recess 7, for example with a rectangular contour, provided in the layer 12 and opening on layer II. The diameter D of the hole 6 is small, in particular equal to, or of the order of 0.5 mm.

The recess 7 is produced only over a fraction of the thickness of the part I2a so that a dielectric coating 8 remains in the bottom of the recess 7 on the second electrode 2.

A flexible tab 9 of rectangular shape is cut along its two long sides and a short side in the first electrode E1 and in the layer II. The tongue 9 is attached to the electrode El by the other short side 10 which is not cut, which serves as a hinge. The tongue 9 is located above the circular hole 6 which is located substantially in line with the center of the tongue. The contour of the tongue 9 is parallel to the contour of the recess 7 but situated slightly inside this contour so that a slot 11 exists between the three cut sides of the tongue and the rest of the electrode El The width of the slot 11 is generally less than 1 mm.

In the rest position illustrated in Figs. 1 and 2, the tongue 9 is in the plane of the electrode El and the part of the layer II located under the tongue 9 is spaced from the bottom of the recess 7 so that a gas, in particular air entering the passage 4 can escape through the recess 7 and the slot 11 on the side of the plate P opposite the entry of the passage-4.

The electrodes E1, E2 are connected by electrical conductors 12, 13 schematically shown, and by a switching device not shown, to a source of high voltage DC not shown. Preferably, the electrode E1 which constitutes one of the external faces of the plate P is connected to ground, while the electrode E2, electrically insulated, is connected to the high direct voltage.

The operation of the valve, or valve, of Figs. l to 3 is as follows. In the absence of voltage applied between the electrodes E1 and E2, the tongue 9 occupies its rest position and a stream of gas entering through the passage 4 can escape through the recess 7 and the slot 11, on the side opposite to the support 3 as illustrated by arrows in Fig. 2. The tongue 9 can flex on the side opposite to the support 3 as illustrated in phantom in Fig.2 to release a larger passage section for a high flow.

The valve V is closed by applying a high continuous voltage, in particular of the order of 4500 volts, between the electrodes

E1 and E2 which causes an electrostatic attraction between the electrodes and the application of the tongue 9 against the bottom of the recess

7. The circular hole 6 is then closed, as well as the valve V.

It is possible to control the closing or opening of valve V at will. The response time is very short and can be less than 5 ms, while the current consumption is very low, less than 100 mA (100 milliamps ).

In Fig.4 a set of pneumatic valves V is formed in a flexible membrane M having a multilayer structure identical to that shown in Figs.1-3. The membrane M therefore ^" comprises a first conductive layer corresponding to the electrode El, one or more dielectric layers, a second conductive layer corresponding to the second electrode E2 preferably embedded in a dielectric layer, and a support layer corresponding to layer 3 of Fig. 2.

In the membrane M, on the side of the electrode El, are cut a plurality of tongues 9 corresponding to as many passages 6 and valves V. Preferably the tongues 9 are arranged in a matrix with lines and columns intersecting at right angles . The electrodes of the elementary valves V. of the membrane M can be placed individually, or in groups, under high voltage by means of a not shown addressing, of known type, ^' by lines or lines. ^• - columns, in particular with transistors.

The membrane M thus constitutes an electrically controlled variable porosity membrane. The porosity may be zero, which corresponds to an impermeable membrane, all the valves V being closed. Maximum porosity is obtained with all V valves in the open position. Intermediate porosity values are possible depending on the addressing provided for controlling the diaphragm valves V. An advantageous application of a valve V and a membrane

M according to the invention relates to a pneumatic brake booster of known type, for example by FR 2 658 466 or EP 0 662 894. Fig.5 illustrates such a booster 14 using membranes Ml, M2 according to the invention.

The booster 14 comprises a rigid casing 15 delimited by two front walls 15a, 15b. The casing .15 is crossed axially by a rod 16 constituting a manual control member. The displacement of the rod 16 can be controlled by the driver of the vehicle, who presses on a brake pedal 17 connected by an articulation to one end of the rod 16.

The envelope 15 is internally separated into two chambers 14a, 14b by a partition 18 movable in the direction of the axis of the rod

16, and orthogonal to this rod. The partition 18 comprises a rigid skirt 19 fixed to the rod 16. The rigid skirt 19 is provided with openings 01, and is formed for example by a grid.

A membrane Ml, similar to the membrane M of Fig.4 with valves V not visible in Fig.5, is fixed against the rigid skirt 19. A bellows 20 is hermetically connected to the outline of the membrane Ml and to the inner wall of the casing 15. The bellows 20 of flexible deformable material allows axial movements of the skirt 19.

The chamber 14a is permanently connected by a nozzle 15c to a source of vacuum creating a relative vacuum in the chamber 14a. ^•

The valves of the membrane M1 are controlled all together by the simultaneous application of a high voltage Ul between the electrodes El and E2 of each valve.

At rest, no tension. is applied between the electrodes of the valves of the membrane Ml; the valves are therefore open and the chambers 14a, 14b communicate and are both under the same relative depression. No pneumatic assistance force is then exerted on the rod 16.

The chamber 14b is closed at its end, remote from the partition 18 by a wall 21 which comprises a rigid support element 21a provided with openings 02, for example formed by a grid. A membrane

M2 similar to that shown in Fig.4, with valves V (not visible in Fig.5), is fixed against the rigid element 21a.

The rod 16 passes in leaktight and sliding fashion through a sleeve 22 fixed to the center of the element 21a and of the membrane M2.

All the valves of the membrane M2 are controlled simultaneously by applying a high voltage U2 between the electrodes of each valve. The wall 15b has a central tube 23 which surrounds the rod 16 and leads to the atmosphere. An air filter 24 is advantageously provided at the inlet of the tube 23 to stop dust and particles contained in the air.

In the absence of voltage between the electrodes of the membrane M2, the valves of this membrane are open and the space 25 between the walls 21 and l ^" 5b communicates with the chamber 14b.

It should be noted that the membrane M1 can be provided alone, without the membrane M2 which would be replaced by one or more conventional valves provided in a full wall 21. In addition, the membrane Ml and the skirt 19 could be replaced by a wall in which at least one controlled solenoid valve would be provided allowing either to communicate, or to isolate, the chambers located on each side.

The operation of the servomotor 14 of Fig.5 is as follows.

At rest the voltage Ul is zero while U2 is a high voltage ensuring the closing of the valves of the membrane M2. The chambers 14a and 14b communicate and are in a relative vacuum, the chamber 14b being isolated from the space 25 and from the atmosphere. No pneumatic force is exerted on the rigid skirt 19 nor transmitted to the rod 16.

When the driver controls braking by pressing the pedal 17, the start of movement of the rod 16 is detected by means not shown which bring the voltage Ul to a high voltage value so that the valves of the membrane Ml are close and the chambers 14a, 14b are separated from each other.

Preferably for a short time the valves of the membrane M2 remain closed by maintaining the high voltage U2 until the closing of the valves of the membrane M1 is confirmed.

The voltage U2 is then lowered to zero to ensure the opening of the valves of the membrane M2. The atmospheric pressure is admitted into the chamber 14b while the chamber 14a is still under relative vacuum and the high voltage Ul is maintained on Ml. The pressure difference which is exerted on the partition 18 generates a pneumatic assistance force which is transmitted to the rod 16.

When there is stabilization of the braking with maintenance of the pedal 17 in a determined position, U2 is brought to high voltage to ensure the closing of the valves of the membrane M2 and to stop the admission of air at atmospheric pressure into the room 14b. So that the braking ceases (brake release) when the pedal 17 is released, the voltage Ul is lowered to zero. The valves of Ml open and allow the pressure balance between the chambers 14a and

14b and the recoil of the partition 18 and of the rod 16. U2 is maintained at high voltage and the valves of M2 remain closed.

Advantageously, the axial position of the partition 18 and therefore of the rod 16 can be detected by sensors, in particular capacitive or impedance sensors, formed between the partition 18 and at least one from the end end walls 15a, 21a, 15b of the servomotor. Conventionally, the rod 16, at its end remote from the pedal 17, transmits the force to a piston 26, generally the primary piston of a master cylinder..tandem MCT which supplies brake fluid under pressure to the brakes such as B of the different wheels of the vehicle. In the rest position of the booster, the volume of the chamber 14a is preferably relatively large, in particular at least three times greater than the volume of the chamber 14b, to constitute a reserve of relative vacuum.

Referring to Fig.6 we can see the diagram of a control assembly of the servomotor 14 of Fig 5. The servomotor and the master cylinder are represented schematically by a block 27 with two inputs connected to lines 28, 29. The line 28 transmits a signal obtained from a sensor not shown, representing the force Fv exerted by the driver on the pedal 17. the ^'line 29 transmits, from a not-shown sensor, a signal representing the stroke Sv pedal 17.

An output line 30 of block 27 transmits a signal representative of the braking pressure Pm measured in the master cylinder.

Another output line 31 of the block 27 transmits a signal Sm corresponding to the measured stroke of the rod 16.

The signal Pm from line 30 is supplied to the input of a circuit 32 in which is stored the law characteristic of the deceleration γ of the vehicle plotted on the ordinate, as a function of the pressure P in the master cylinder plotted on the abscissa. From the input value Pm supplied by the line 30, the circuit 32 provides at output on a line 33 a signal, representing the desired deceleration γPc (or target deceleration) of the vehicle corresponding to the pressure value Pm. Line 31 supplies the signal Sm to an input of a circuit 34 in which the law of deceleration γ of the vehicle is stored, plotted on the ordinate, as a function of the stroke S of the pedal plotted on the abscissa. Circuit 34 provides at output a desired deceleration value γSc

5 based on the Sm race.

Lines 33 and 35 are each connected to an input of a comparator circuit 36 which provides, on an output line 37, a target deceleration γc corresponding to the absolute maximum value chosen between γPc and γSc. Line 37 is connected to an input of a subtractor circuit 38.

Another input of this circuit 38 receives, via a line 39, a signal representing the calculated deceleration γcalc. of the vehicle .

The calculated deceleration is obtained from speed sensors (not shown) provided on each of the four wheels of the vehicle 15. and connected to a circuit 40 which delivers, on four outputs Vavd, Vavg, Vard and Varg, the values of the speeds. the right front wheel, the left front wheel, the right rear wheel and the left rear wheel, respectively. These values are supplied to an evaluation circuit 41 which establishes, from the four wheel speed values, a reference speed value 20 Vref. of the vehicle delivered on an output line 42.

This value Vref. is provided. at the entrance of a circuit. differentiator with respect to time 43 whose output, connected to line 39, delivers the calculated acceleration γcalc.

The subtractor circuit 38 provides a 5 on an output line 44 _. error signal εγ equal to the _. difference between the target deceleration γc and. the calculated deceleration γcalc. : εγ = γtarget - γcalc.

Line .44 is connected to the input of a circuit 45 P.I.D

(Proportional Integral Derivative) which provides on an output line 46 the

30 deceleration error signal. This signal is sent to the input of a circuit 47 which converts the deceleration error signal into a signal

. drag error εT by dividing the deceleration error signal by the mass M of the vehicle. The halftone force corresponds to the sum of the forces of friction against the ground of the tires of the vehicle wheels. 5 A line 48 transmits the raster error signal εT to a set 49 of four circuits (not shown in detail), which determine from the signal εT the liquid pressure to be established in each wheel brake. A Pcible signal is established by weighting the fluid pressure values for each wheel brake.

The signal Pcible is delivered on a line 50 at the input of a circuit 51 suitable for converting the signal Pcible into a target race signal Scib. of the actuator rod 16. This Scib signal. is supplied on an output line 52 at the input of a subtractor circuit 53, another input of which receives by a line 54 the measured value of the stroke Sm.

The circuit 53 provides on its output 55 an error signal εS of the stroke of the rod 16, sent to the input of a control circuit PD 56 (proportional derivative) which supplies, on its output 57, the signal for order the diaphragm M2 of the servomotor 14 and ensure the position correction of the partition 18 and of the rod 16.

Claims

1. Valve, in particular pneumatic, electrically controlled, characterized in that it has a flattened structure and that it comprises a plate (P) consisting of several parallel layers, namely a layer (1) conductive of the electricity forming a first electrode (E1), at least one intermediate dielectric layer (11,12) applied against one face of the first electrode, a second electrode (E2) formed by another layer (2) conducting electricity applied against the dielectric layer (12) on the side opposite the first electrode, and at least one support layer (3) located on the side of the second electrode opposite to the dielectric layer, at least one passage (4) passing through the support layer and the second electrode, while a flexible tongue (9) is provided in the first electrode to close the passage, or to be separated from it and allow a fluid to circulate, the displacement of the tongue being controlled by applying sufficient electrical voltage between the electrodes.

2. Valve according to claim 1, characterized in that in the absence of electrical voltage between the electrodes (El, E2), the tongue (9) is spaced from the outlet of the passage (4) and the valve is. open, the valve being closed by applying the electrical voltage between the electrodes.

3. Valve according to claim 1 or 2, characterized in that the first electrode (El), located towards the outside of the plate, is connected to ground while the high voltage is applied to the electrode (E2) located within the plate.

4. Valve according to one of claims 1 to 3, characterized in that the tongue (9) has a rectangular shape, adjoining the layer (1) by a short side (10) serving as a hinge, and cut according to its two long sides and the other short side.

5. Valve according to one of the preceding claims, characterized in that the second electrode (E2) is embedded in a dielectric layer (12) separated into a part (I2a) between the second electrode (E2) and a dielectric layer (II) applied against the first electrode (El), and a part (I2b) located on the other side of the second electrode (E2).

6. Valve according to one of the preceding claims, characterized in that the distance (h) between the facing faces of the electrodes (El, E2) is of the order of 0.2 mm.

7. Valve according to one of the preceding claims, characterized in that the passage (4) which passes through the second electrode (E2) opens into a recess (7) and that a dielectric coating (8) remains in the bottom of the recess (7) on the second electrode (E2), the contour of the tongue (9) being parallel to the contour of the recess (7) but situated inside this contour. .

8. Valve according to claim 7, characterized in that in the rest position the tongue (9) is in the plane of the electrode (El) and the part of the dielectric layer (II) located under the tongue ^' ( 9) is moved away from the bottom of the recess (7).

9. Flexible membrane comprising a set of valves according to one of the preceding claims, characterized in that it comprises several layers corresponding to those of the valves, and that in the membrane are cut a plurality of tabs (9) corresponding to as many passages, each tab and associated passage constituting an elementary valve (V).

10. Membrane according to claim 9, characterized in that the valves (V) of the membrane are arranged in a matrix in rows and columns.

11. Pneumatic booster for motor vehicle braking installation, comprising a rigid casing (15) traversed by a rod (16) constituting a manual control member, and internally separated into two chambers (14a, 14b) by a partition (18) movable in the direction of the axis of the rod (16), the partition (18) comprising a rigid skirt (19) fixed to the rod (16) and connected along its outer contour to the inner wall of the envelope (15) by a bellows (20) made of flexible deformable material allowing axial movements of the skirt (19), in which the rigid skirt (19) is provided with openings (01), and a membrane (Ml) according to claim 9 or 10 is applied and held against the rigid skirt (19).

12. Booster according to claim 11, wherein a second membrane (M2) according to claim 9 or 10 is disposed against an end wall (21a) of the booster provided with openings (02).

13. Booster according to claim 11 or 12, comprising a control assembly comprising:

- a circuit (32) in which the law characteristic of the deceleration (γ) of the vehicle is stored as a function of the pressure (P) in the master cylinder and providing from an input value (Pm) corresponding to the pressure measured in the master cylinder a signal representing the desired deceleration (γPc);

- a circuit (34) in which the deceleration law (γ) of the vehicle is stored as a function of the stroke (S) of the pedal, this circuit (34) providing as output a desired deceleration value (γSc) established by after the measured stroke (Sm) of the rod (16) of the actuator; - And a comparator circuit (36) having two inputs respectively connected to the outputs of the above circuits (32, 34) and which provides, on an output line (37), a target deceleration (γc) corresponding to the absolute maximum value chosen between the input signals (γPc, γSc) and means (38, 45, 47, 49, 51, 53) for determining a stroke error (εS) of the rod (16) from the comparator output signal ( 36).

14. Servomotor according to claim 13, characterized in that it comprises a subtractor circuit (38) providing at output (44) a deceleration error signal (εγ) equal to the difference between the target deceleration (γc) and a calculated deceleration (γcalc.), and a circuit (47) which converts the deceleration error signal into a drag error signal (εT) by dividing the deceleration error signal by the mass (M) of the vehicle .

15. Booster according to claim 14, characterized in that it comprises circuits (49, 51) for converting the drag error signal (εT) into a target stroke signal (Scib.) Of the rod (16 ) of servomotor, and a subtractor circuit (53), one input of which receives the measured value (Sm) of the rod (16) of the servomotor and another input of which the target stroke value (Scib.), which subtractor circuit (53) provides on its output (55) a rod stroke error signal (εS) to control the diaphragm valves (M2) and to correct the position of the partition (18) of the actuator (14) and of the rod (16).