FR2551409A1 - ANTI-SKATING BRAKING SYSTEM FOR VEHICLES - Google Patents

Abstract

A MODULATOR PISTON 6 ASSEMBLY IN THE GENERAL SHAPE OF A DUMBBELL AND INCLUDES A FIRST 7 AND A SECOND 9 MODULATOR PISTONS EQUIPPED WITH A SOLIDAR ROD 10 CARRYING AN ISOLATION BLOCK THAT CAN BE APPLIED TO A 16 SEAT CARRIED BY THE FIRST PISTON 7. A FIRST, SECOND AND THIRD MODULATOR CHAMBERS 23, 24, 41 ARE LIMITED BY THE MODULATOR PISTON ASSEMBLY SO THAT WHEN IT LEAVES ITS NORMAL POSITION, THE VOLUMES OF THE FIRST AND THIRD CHAMBERS 23, 41 INCREASE AND THAT OF THE SECOND 24 DECREASES. A MASTER CYLINDER 28 IS PERMANENTLY CONNECTED TO THE SECOND CHAMBER 24 AND TO THE FIRST CHAMBER 23 AND A NORMALLY CLOSED DISCHARGE VALVE 35, 36 IS INTERPOSED BETWEEN THE INPUT 31 OF THE MASTER CYLINDER AND THE THIRD CHAMBER 41. DURING A SKATE SIGNAL, VALVE 35,36 OPENS AND FLUID FLOWS FROM SECOND CHAMBER 24 TO THIRD 41 ISOLATION VALVE 14, 16 CLOSES AND FIRST CHAMBER 23 EXPANDS TO RELEASE BRAKE PRESSURE OF WHEEL. A PISTON 51 IS DESIGNED TO DELIVER FLUID FROM THE THIRD CHAMBER 41 TO THE INPUT OF VALVE 35, 36 AND WHEN THE SKATING SIGNAL ENDS, THIS PISTON RETURNS FLUID FROM THE THIRD CHAMBER 41 TO THE SECOND 24.

Description

The invention relates to anti-skid braking systems for

vehicles.

  There have been many prior proposals for such systems. Most of these fall broadly into the following types In

  a first type, the wheel brakes are connected to a reservoir used to relieve the brake pressure.

  In a second type, a support chamber is connected to a reservoir In a third type, the wheel brakes are connected to an expansion chamber and in a fourth, an accumulator is connected to a

  so as to push upside down against the cylinder maltre.

  Associated with each of these known types are drawbacks The use of a separate reservoir or expansion chamber, to which fluid is sent from the brakes or from a support chamber considerably increases the development of the piping of the system it is generally also considered undesirable to react a large force on the brake pedal in the event of a slip signal.

  of these systems can be difficult to drain.

  To try to overcome the drawbacks of the types of existing systems, we now have

imagined another type of system.

  According to one aspect of the invention, in an anti-skid braking system for vehicles, a modulator assembly comprises a modulator housing, a modulator piston assembly which can move axially in a housing bore, the piston assembly 30 modulator and the bore of the housing having the desired shape to define first, second and third modulator chambers, limiting portions of the modulator piston assembly so that when the modulator piston assembly moves in one direction starting from its normal position, the volumes of the first and third chambers are both increased while the volume of the second chamber is reduced, the first chamber is connected to a wheel brake, the second chamber is connected to a master cylinder and the third chamber is connected to the second chamber by a normally closed expansion valve, responding to a slip sensor, a normally open isolation valve is connected between the p first chamber and the second chamber and designed to close in response to a slip state signal, means being provided for bringing fluid from the third to the

  second chamber when the skating signal ends.

  On reception of a slip state signal, the expansion valve opens so as to allow fluid to arrive from the second chamber to the third chamber and thus bring the modulator piston assembly out of its normal position. to expand the volume of the first chamber connected to the wheel brake so as to

  release the brake pressure from the wheel brake.

  Since there is no need for an external reservoir, the complications associated with this can be avoided. As will be explained below 9, this makes it possible to place a pump working chamber of the fluid return means. , away from the modulator housing if desired with only one connection per pipe. Preferably, the isolation valve is closed by a relative movement of two parts of the modulating piston assembly in response to expansion

initial of the third bedroom.

  A particular advantage of a system 30 according to the invention is that by making the effective pressure areas of the modulator piston assembly which are exposed in the second and third chambers practically equal, little fluid reaction is applied. to the master cylinder during the expansion of fluid or lcrs of a new brake application, since the average variation in volume of the fluid transferred from the

  second to third chamber or vice versa varies very little when the piston assembly goes back and forth.

  In order to tune "the system, the effective pressure areas can be made slightly uneven if desired. In particular, when there is a need to reduce the wheel brake pressure to zero, it may be desirable to have the effective pressure area of the modulator piston assembly 10 which is exposed to the third chamber is greater

  than the one exposed in the second bedroom.

  the master cylinder can be a hydrostatic master cylinder or a power valve.

  In a preferred arrangement, the modulator piston assembly has a general dumbbell shape, comprising opposite end parts connected by a central part of reduced diameter which passes in leaktight manner through a partition of the modulator housing, the second and third chambers are defined at opposite ends of the modulator piston assembly and the first chamber is an adjacent annular chamber

  at the partition and surrounding the reduced diameter portion.

  The modulating piston is preferably urged towards its normal position by elastic means 25 which urge the modulating piston assembly in the

  meaning to reduce the volume of the third chamber.

  In the preferred arrangement mentioned last, the elastic means are advantageously placed in an annular additional chamber 30 located on the side opposite the annular chamber relative to the partition, the annular additional chamber being connected to the atmosphere or containing

low pressure fluid.

  The means serving to bring fluid 35 from the third to the second chamber when the slip signal ends preferably comprise a pump piston actuated by an eccentric of a drive shaft, the pump piston being normally kept out of cooperation with the eccentric by a piston biasing means but being urged to cooperate with the eccentric, when fluid is supplied to the third chamber, by the increase in

  fluid pressure in the third chamber.

  the inlet and outlet valves of the pump are preferably both located in the modulator assembly but the working chamber of the pump can be located at a distance from the pump if desired and connected by a single pipe hydraulic to a valve chamber of the modulator assembly, located between the inlet and outlet valves of the pump Since there is only one hydraulic connection between the working chamber of the pump and the pump valve, the pump working chamber can be located,

  in the vehicle, in any suitable position where there is a suitable means of driving the pump.

  The drive means can be a vehicle wheel, the propulsion engine, an electric motor or a transmission, etc. This way of placing the working chamber of the pump at a distance from the valve chamber of the pump can be applied not only to systems according to the first aspect of the invention but more generally. Thus, according to a second aspect of the invention, a traction control braking system for vehicles includes a modulator assembly provided with a chamber to which fluid is estiamenated in response to a slip state signal coming from a sensor, a pump valve chamber situated inside the modulator assembly and connected to the chamber thereof by a pump inlet valve, a pump outlet valve housed inside the assembly modulator and a pump working chamber remote from the modulator assembly and connected to the pump valve chamber by a single hydraulic hose. Two embodiments of the invention will now be described, by way of example only, with reference to the appended drawings in which: FIG. 1 is a section through an autonomous assembly of modulator, pump and detector slippage, the modulator piston assembly being shown in its normal position and FIG. 2 is a similar view of a modulator assembly and a remotely located pump drive assembly, combined with a detector

skating.

  As shown in FIG. 1, a modulator casing 1 is provided with a bore passing through step 2 inclined relative to a second bore passing through step 3 and closed at its lower end by a threaded plug 4 'Bore 2 is partitioned into an upper portion of bore 3 and a lower portion of bore 4 by a partition 5 A set of modulating piston 69 practically in the form of a dumbbell, can slide in bore 2 and comprises a first modulating piston 7 provided with '' a frustoconical perforation 8 and a second modulating piston 9 with which forms a rod 10 which passes axially through the partition 5 and through the perforation 8 of the first modulating piston 7 The first and 30 second modulating pistons 7, 9 are sealed vis-à-vis the wall of the bore 2 by respective O-rings 11, 12 and the rod 10 is made tight vis-à-vis the wall 5 by an O-ring 13 o A frustoconical part 14 of the rod 35 10, spaced from its extremity é free at t 9 te 15, plays the r 8 le of an isolation valve intended to cooperate with an isolation valve seal 16 carried by the first modulating piston 7, the Seal 16 being held in place by a member joint retainer 17 In the normal state of the modulator assembly, when there is no slip signal, a projection 18 of the second piston 9 abuts against a fixed inserted element 19 and the piston 9 is retained in this position by a coil compression spring 20 acting between the partition 5 and the piston 9. 10 A skirt 21 of the first modulating piston abuts against the partition 5 so as to define the normal position of the first modulating piston 7, the piston 7 being biased towards this position by a compression spring 22 acting between the head 15 and the retaining member 17 It will be seen in FIG. 1 that the isolation valve defined by the elements 14 and 16 is thus designed to be opened in the normal state of the modulator assembly so as to ensure e unrestricted communication between a first modulator chamber 23 defined in the bore part 4 between the wall 5 and the first piston 7 and a second modulator chamber 24 defined in the bore part 4 between the first piston

modulator 7 and the plug 4 '.

  the first modulator chamber 23 25 is permanently connected to a wheel brake 25 through an orifice 26 and a brake hose 27 and the second modulator chamber 24 is permanently connected to a master cylinder 28 which can be a my hydrostatic cylinder or a power valve, through the median of an inclined perforation 29, of a perforation parallel to the bore 2, of an inlet orifice 31 and

a brake hose 32.

  Thus, in the normal state of the modulator assembly, the wheel brake is actuated in the normal way by a fluid pressure coming from the master cylinder 28 passing through the open isolation valve 14, 16, The element inserted 19 is fixed by screwing, by its upper end, to the body 33 of a

  solenoid 34, the body 33 playing the role of a plug 5 for closing the upper end of the bore 2.

  The inserted element 19 is provided with an axial passing bore 34 comprising a constriction which plays the role of expansion valve seat for the application of an expansion valve shutter 36 carried by the armature 37 of the solenoid In the normal non-excited state of the solenoid 34, the armature is biased downwards by a spring 38

  so as to keep the expansion valve 35, 36 closed.

  The upper head 8 of the expansion valve 35, 36 is permanently connected to the master cylinder and to the second modulator chamber 24 by diametrical perforations 39 of the inserted element 19, an annular chamber 39 'and

  a perforation 40 connected to the inlet orifice 31.

  A third modulator chamber 41 is defined in the bore 2 between the second modulator piston 9 and the inserted element 19 and communicates with the lower side of the valve seat 35, since the valve seat 35 is normally closed , there cannot normally be a flow from inlet 31 to the

room 41.

  The inserted element 19 is provided with two external annular recesses in which are placed respective one-way annular seals 42, 43 which allow the fluid to flow along the wall of the bore 2, of the third chamber. modulator 41 to 30 the perforation 40 As will be explained below, the one-way seal 42 plays the role of a pump inlet valve and the seal 43 plays the role of an outlet valve of a pump used to recover the fluid brought to the

  third modulator chamber 41.

  In the second bore 3 of the housing

  a drive shaft 44 is mounted with an eccentric ring

  pump plate 45, the shaft 44 rotating in spaced bearings 46, 47 and carrying at its inner end a rotor 48 of an optical sensor assembly 49 used to measure the speed of the shaft The shaft 44 can be driven by a vehicle wheel, via any suitable centering link such as a toothed belt The eccentric ring 45 can rotate freely on a bearing 50 mounted eccentrically on the shaft 44 A pump piston 51 is housed in a bore 52 extending transversely to the bore 3 to define a pump working chamber 53 at the lower end of the bore 52, blocked by a piston seal 54 The piston 51 is normally kept out of cooperation with the ring 54 by a compression spring 55. The working chamber 53 of the pump is permanently connected to bore 2 by a perforation 56 which is connected to bore 2 at a location

  intermediate between one-way joints-42 and 43.

  An electronic control unit, not shown, is connected to the optical sensor assembly 49 and to the solenoid 34 by a plug and socket connection 57. The control unit operates in a conventional manner by controlling the output of the assembly. of an optical sensor for detecting an excessive deceleration of the shaft 44, 25 indicating an imminent slip situation A slip signal is generated when such a situation is detected and in response to the slip signal, the solenoid

34 is excited.

  We will now describe the operation 30 of the assembly of FIG. 1 Normally, in the absence of a slip signal, the isolation valve 14, 16 is open as shown, the expansion valve 35, 36 is closed and the modulating pistons 7, 9 are in the positions shown in which the volumes of the first and third chambers, 23 and 41 respectively, are practically minimized and the volume of the chamber 24 is practically maximized When the master cylinder 28 is put into action, the brake is applied, as explained above, by the fluid supplied passing through the open isolation valve 14, 16. An important advantage of the arrangement is that in the event of a sudden braking effort by the driver, the isolation valve 14, 16 does not close under the

  transient fluid pressure forces, since the two pistons 7, 9 are applied to stops.

  When the electronic control unit detects an imminent slip state based on the signals from the optical sensor 49, the solenoid 34 is excited, moving the armature 37 upwards so as to open the expansion valve seat 35 and allowing the fluid to start flowing from the second modulator chamber 24 to the third modulator chamber 41 via the perforations 29, 30, 40 and 39 The initial movement of the second modulator piston 9 downwards, at the fluid inlet into the third modulator chamber 41, causes the isolation valve 14, 16 to close, the first modulator piston initially remaining in cooperation with the wall 5 under the action of the spring 22 The closure of the isolation valve 14, 25 16 isolates the first modulator chamber 23 from the second modulator chamber 24 and thus isolates the wheel brake 25 from the supply so that as the pistons 7, 9 move towards the low in unison, with the fluid conti as it flows from chamber 24 to chamber 41, the first modulator chamber 23 expands so as to reduce the pressure of the wheel brake, chamber 58, in which the spring 20 is placed, is connected to the atmosphere to allow movement of the piston 9 Finally, the modulator piston assembly 6 35 reaches a new equilibrium position in which the sum of the pressure and spring forces applied

to set 6 is balanced.

  In the drawings, the diameter of the pistons 7 and 9 are equal but if it is necessary to reduce the pressure of the wheel brake to zero, it is desirable to increase the diameter of the piston 9 relative to that of the piston 7 to increase the effective area of

  pressure of the piston 9 exposed to the chamber 41.

  An advantage of this arrangement and in particular an advantage of the practically equal diameter of the pistons 7 and 9 is that a small variation in volume of fluid is felt at the master cylinder 28 by the supply of fluid to the chamber 41 because the volume total fluid in chambers 24 and 41 remains practically

  constant when the modulator piston assembly moves.

  Thus, the driver will not feel a violent reaction

on the brake pedal.

  during the initial supply of fluid to the third modulator chamber 41, a certain quantity of fluid exceeds the one-way seal 42 and arrives via the perforation 56 in the working chamber of the pump, so as to move the piston pump 51 upwards and apply it to the ring 45, and then the pump is capable of pumping fluid from the third chamber 25 41, passing the seals 42, 43, towards the chamber 39 ', the fluid returning to the chamber 41 passing through the expansion valve seat 35 which is open. It will be understood that as the piston 51 moves upwards, fluid is sucked from the chamber 41 via the seal 30 42 and that '', during the downward movement of the piston 51, fluid is discharged from the perforation 56 by passing the seal 43 which plays the r 8 of a pump outlet valve This pumping action causes a certain vibration which will probably be felt by the driver's foot but this will be useful when indicating the presence nce of a situation

of imminent skating.

  When the wheel speed has recovered sufficiently for the electronic control unit to end the slip signal, the solenoid 34 is de-energized so that the expansion valve 35, 36 closes The pump continues to operate by pumping of fluid from the third modulation chamber 41 to the perforation 39 but this time the fluid flows through the passage 40 and returns to the second modulator chamber 10 24 passing through the perforations 309 29 Thus fluid is gradually returned by the pump piston 51, from chamber 41 to chamber 24 and as the chamber 41 decreases in volume the chamber 24 expands so that the net variation in volume at the master cylinder 15 is zero or very small As a result of the pumping action , the modulator pistonl assembly 6 moves upwards, reducing the volume of the first modulator chamber 23 so as to restore the wheel brake pressure At the final stage of pumping fluid from chamber 41, the first The piston 7 again applies to the wall 5 and the isolation valve 140 16 reopens again connecting the master cylinder 28 to the wheel brake 25 o Once the piston stop 18 applies again to the inserted element 19 under the force 25 of the fluid pressure in the chamber 24 and of the spring, it is no longer possible to suck fluid from the chamber 41 When, at the desired moment, the driver releases the brakes, the piston pump 51 moves downward under the force of the spring 55 which is sufficient to cause the fluid to be pumped again, by going beyond the joint 43, towards the master cylinder pipe 329 allowing the spring 55 to retract the piston of pump 51 in

moving it away from the ring 45.

  It will be understood that with this arrangement, by which the third modulator chamber 41 expands at the same time as the second modulator chamber 24 contracts, when the modulator piston assembly 6 moves downward in response to a signal skating, an external tank is not necessary and the modulating piston assembly can be housed inside a

single bore 2 of the housing.

  Since there is only one fluid connection, the perforation 56 in FIG. 1, between the working chamber 53 of the pump and the bore in which the pump valve seals 42 are located and 43, it is possible to arrange the working chamber of the pump at a distance from the modulating piston assembly, as in the arrangement of FIG. 2, described below. In FIG. 2, the parts corresponding to those of FIG. 1 bear corresponding references. However, reference has only been made to the main parts. In the present case, the drive assembly 44, $ 5, 51 of the pump and the optical sensor 49 are arranged under the form of an assembly 1 'which is intended to be mounted at a distance from the casing 1 containing the modulator assembly, but connected to the latter by a single hydraulic brake pipe 56 and by an electrical conductor 57 coming from the optical sensor 49 It will be understood that the fact of providing two units connected by a single hydraulic hose e and an electrical conductor helps to house the assemblies in a vehicle. For example, the modulator assembly can be closely associated with the master cylinder and the small unit 1 ′ can be accommodated more easily at the location of a wheel or other source of drive

tree 44.

  In the arrangement of FIG. 2, a set of flow regulating valve 58 is disposed between the working chamber 53 of the pump and the brake pipe 56 so as to regulate the flow rate at which fluid is pumped by the pump, from chamber 41 to chamber 24, when the wheel brake pressure is reapplied, and thus regulate the speed of this application. Any suitable type of flow regulator can be used. The regulating valve indicated is described in detail in the publication document of the patent application GB 2 045 372 A The regulator is

  intended to take account of any variations in the flow rate of the pump with the speed of the impeller.

  Another difference between the arrangement of FIG. 2 and that of FIG. 1 is that in FIG. 2, there is provided a flow restrictor 59 to pocket sudden variations in the flow rate passing through the passage 34 The restrictor 59 comprising a spring-loaded bowl with edges

bottlenecks.

  It will be understood that the regulating valve 58 and the throttle 59 can also apply to the arrangement of FIG. 1.

  Although the valve of the relief valve 26 has been shown to be actuated by a solenoid 34 in response to the output of an optical sensor 49, it would be possible to actuate the expansion valve 25 by means of a mechanism steering wheel responding to deceleration such as that described in patent GB 2,029

914 B.

  It will also be understood that the shape and arrangement of the first, second and third modulator chambers 23 can be significantly modified,

  24, 41 while still obtaining a similar result.

  Although the pump inlet and outlet valves are formed by one-way seals

  42, 43, it would obviously be possible to use other one-way valve structures.

  In a complete brake system, there will usually be several sets of modulator, their inlet orifices 31 being connected to a common master cylinder 28 which can of course be a master cylinder in tandem, in which case certain orifices 31 would be connected to a different output from

my master cylinder.

Claims (6)

  1 Anti-skid braking system for vehicles comprising a braked modulator assembly between a master cylinder and a wheel brake, the modulator assembly comprising a modulator housing and a piston 5 modulator assembly which can move axially in a housing bore , system characterized by the fact that the modulating piston assembly (6) and the bore (2) of the casing have the desired shape - opeu to define a first, a second and a third: e chambers of -odulator L ( 253 249 41) limiting i O parts of 1-assembly of modulating piston so that u'lo Se: 3 em-l-Se ó 'se' oistl od 5 ulateu 'r moves in uni direction en - rtar, -'tn sa -: we N in'male 9 the volumes of the first (23) and three H (4 '1 3 hours) are Ctos deuz increased while qua e voum' 12 deu-irme rchaenrbre (24) es- t dimilnue, qua la) are linked to the wheel brake (25), Oua 'La de ul?, u -1 î 2 St connected to the master cylinder f 2 f 3') er rîE_ (-j -i M c 4 e (41) is - linked to second h =? i- -t 'i 3 ç r rl e' 5 5 i 6 normally C- 3 r Ca 3: J del-seîw - ,; e (35 e C al dage (48, 49), quilune 0 O vave a ' '*' - "6) nma lemen 'o Lr Yerte ests branchée"' es -> J eec 1 hambres and concte pour se fe;  4 j -n if gal Or, _ 5 'state of skating, and that (, in S 45 5156, i''provided to bring fluid from the it isi>, the Ellesiêm room when the signal of skate-a re Dr'n; -e sslon claim 1, characterized _oa 3 s-rc D teo ar rce '' "by the fact that the isolation wave is designed to be closed by the reactive movement of two parts (7 s, 9) of the modulating piston assembly in response to an ilial expansion of the third chamber   3 System according to June of claims 1 and 2,   characterized by the fact that the effective pressure areas   of the modulating piston assembly which are exposed respectively to the second and third chambers are made substantially equal.   4 System according to one of claims 1 to 3,   characterized by the fact that the modulating piston assembly has the general shape of a dumbbell comprising opposite end parts (7, 9) connected by a central part (10) of reduced diameter which passes in leaktight manner through a partition ( 5) the modulator housing, that the second and third chambers are defined at opposite ends   of the modulating piston assembly and that the first chamber is an annular chamber (23) adjacent to the partition 10 and surrounding the reduced diameter portion (10).   System according to one of claims 1 to 4,   characterized in that the modulator piston assembly is biased towards its normal position by elastic means (20) which bias the modulator piston assembly 15 in the desired direction to reduce the volume of the third chamber. 6 System according to claim 5, characterized in that the elastic means are placed in an annular additional chamber (58) located on the opposite side 8 20 to the annular chamber relative to the partition, the annular additional chamber being connected to the 'atmosphere or   containing low pressure fluid.   7 System according to one of claims 1 to 6,   characterized by the fact that the means serving to return fluid from the third to the second chamber when the slip signal ends comprise a pump piston (51) actuated by an eccentric (45) of a drive shaft ( 44), the pump piston normally being kept out of cooperation with the eccentric by means of piston solenoid30 (55) but being pushed to cooperate with the eccentricwhen fluid is brought to the third chamber, by the increase fluid pressure in this third bedroom.   8 System according to one of claims 1 to 7, 35 characterized in that the inlet valves (42) and   pump outlet (43) are both located in the modulator assembly, the working chamber (53) of the pump being located remotely from the modulator assembly and connected by a single hydraulic hose (56) a valve chamber of the modulator assembly, located between the inlet and outlet valves of the pump.