FR2738204A1 - Anti-lock braking pressure control system for two wheel vehicle, e.g. motorcycle - Google Patents

Abstract

The ABS system includes a sensor (51) which detects movement of an element (3R) which is actuated during braking. The open loop control system (52), has a device (M1) for calculating fundamental relationships so as to drive a control unit (5) on the basis of the output signal of the sensor (51). The control system (52) effects open loop control of the unit (5) as a function of the output of the sensor (M1). The system (52) has a correction unit (M2) which corrects the fundamental relationship on the basis of time variation in the speed of braking action.

Description

APPARATUS FOR CONTROLLING A BRAKING PRESSURE,
EQUIPPED WITH A VEHICLE BRAKING SYSTEM
The present invention relates to an apparatus for controlling a brake pressure, fitted to a vehicle braking system in which a control device is actuated according to the operation of a brake actuation member, and a brake. hydraulic is operated by a master cylinder driven by the control device.

 Control devices associated with such a vehicle braking system, which control the braking pressure as a function of an operating force or an operating stroke of the brake actuating member, are for example well known. according to Japanese patents n Hei 2-279450 and Hei 2262456 subject to public inspection.

 In the control device exposed by the reference publication mentioned first, a hydraulic control means is interposed between the master cylinder and a wheel brake, and the position of a control slide of said hydraulic control means is controlled as a function of an operating force of the brake actuating member, to vary the magnitude of the braking pressure. In the control device exposed by the publication cited in the second place, a plurality of hydraulic control valves, interposed between the master cylinder and a wheel brake, are controlled as a function of a difference existing between an operating stroke of the brake actuator, and a deceleration of the vehicle.

 However, the aforementioned conventional control devices require a large number of complicated sensors and control devices for controlling a brake pressure.

The adoption of such conventional control units is for example difficult, for the braking system of a motorized two-wheeled vehicle of the scooter type or of a similar type, concerning both the sizing and the costs.

 The present invention is the fruit of the foregoing considerations, and aims to provide a braking pressure control device which is simple in structure and of low cost, and which can deliver braking pressure with high linearity for an operating stroke of the brake actuating member.

 To achieve the above object, in a vehicle braking system in which a control device is actuated according to the operation of a brake actuating member, and a hydraulic brake is actuated by a master cylinder driven by the device control, the control device according to the invention is characterized in that it comprises a maneuvering stroke detector means, for detecting an operating stroke of the brake actuating member; and an open-loop control means, having a basic functional ratio calculating means, which calculates a fundamental functional ratio for driving the control device on the basis of the output signal of the maneuver stroke detector means, the control means in open loop carrying out an open loop control of said device as a function of the output signal of the means for calculating fundamental functional ratios.

 Optionally, the control device according to the invention can be such that the open-loop control means has a first means of correcting functional ratios, for correcting the fundamental functional ratio on the basis of a rate of variation over time of the maneuvering stroke.

 Optionally, the control device according to the invention can also be such that the open-loop control means has a second functional ratio correction means, for correcting the fundamental functional ratio with a view to compensating for a hysteresis in the pressure of braking provided by the master cylinder, generated between the instant at which the operating stroke increases and the instant at which the operating stroke decreases.

 Optionally, the control device according to the invention can also be such that the open-loop control means has a third means for correcting functional ratios, for correcting the fundamental functional ratio at the instant at which the vehicle speed is low. just before a stop.

 Optionally, the control device according to the invention may, moreover, be such that the brake actuating member is connected both to the control device and to a mechanical brake, by means of cables, and the means open-loop control device has a fourth means for correcting functional ratios, for correcting the fundamental functional ratio as a function of slack in said cables.

The invention will now be described in more detail, by way of non-limiting example, with reference to the appended drawings in which
Figure 1 is an overall side elevation of a motorized two-wheeled vehicle
Figure 2 is a view seen in the direction of arrow 2 in Figure 1
Figure 3 is an embodiment of a braking system
Figure 4 is a longitudinal section of a first cable damper
Figure 5 is a longitudinal section of a second cable damper
Figure 6 is a side elevation from the right of a control device (seen in the direction of arrow 6 in Figure 7)
Figure 7 is a section along line 7-7 of Figure 6 ;;
Figure 8 is a side elevation from the left of the control device (seen in the direction of arrow 8 in Figure 7)
Figure 9 is a section along line 9-9 of Figure 7
Figure 10 is a section along line 10-10 of Figure 7
Figure 11 is a section along line 11-11 of Figure 6
Figure 12 is a section along line 12-12 of Figure 6
Figure 13 is a section along line 13-13 of Figure 8
Figure 14 is a section along line 14-14 of Figure 8
Figure 15 is a block diagram of an anti-lock brake control system
FIG. 16 is an explanatory diagram of the operation of the interlocked brakes;
FIG. 17 is an explanatory diagram of the operation of the anti-lock brakes
Figure 18 is an explanatory graph of the operation of the interlocked brakes
FIG. 19 is an explanatory diagram of the operation of the anti-lock brakes
FIG. 20 is an explanatory diagram of the operation of the interlocked brakes
FIG. 21 is an explanatory graph of the operation of a means for calculating fundamental auxiliary quantities
Figure 22 is an explanatory graph of the operation of an input speed correcting means;
FIG. 23 is an explanatory graph of the operation of a corrective hold-release means
FIG. 24 is an explanatory graph of the operation of a means for correcting the speed of the vehicle; and
Figure 25 is an explanatory graph of the operation of a setting correction means.

As illustrated in Figures 1 to 3, a front wheel brake BF (which is a hydraulically operated disc brake) is mounted, as a hydraulic wheel brake, on a front wheel
WF of a motorized two-wheeled vehicle V of the scooter type, fitted with an oscillating type engine block P. A known mechanical brake
Rear wheel BR, developing a braking force proportional to the operating stroke of an actuating link 1, is mounted on a rear wheel WR as a mechanical wheel brake. Handles 2F and 2R are respectively provided at the two ends situated to the right and to the left of a handlebar. A first brake lever 3F pivotally attached to the rightmost region of the handlebars fulfills the function of a first brake actuating member which can be operated by the right hand of the driver grasping the handle 2F. 3RV brake lever provided in the extreme left region of the handlebars, acts as a second brake actuation member which can be operated by the driver's left hand grasping the 2R handle.

 The first brake lever 3F and the brake BF of the front wheel are connected to each other by means of a first transmission system 4Fl capable of transmitting the actuating force of said first lever 3F to said brake BF . The second brake lever 3RS and the actuation rod 1 assigned to the brake BR of the rear wheel, are connected to each other by means of a second transmission system 4R capable of mechanically transmitting the force actuation of said second lever 3R to said brake BR. In addition, intermediate zones of the two transmission systems 4F and 4R are connected to a control device 5. The braking force of the brake BF of the front wheel and that of the brake BR of the rear wheel can be adjusted under the action. of the control device 5.

 A first cable damper 241 is mounted on a first push-pull cable 251 connecting, to each other, the first brake lever 3F and the control device 5, while a second cable damper 242 is mounted on a second push-pull cable 252 connecting the second brake lever 3R and said device 5. The shock absorbers 241 and 242 of the cables are respectively arranged on the right side and on the left side of a pipe descending from the frame of the vehicle. A battery 53 occupies a position overlying the first shock absorber 241 located on the right, while an electronic control unit 52 overhangs the second shock absorber 242 located on the left.

 In FIGS. 1 and 2, the reference numeral 56 designates a reservoir of a master cylinder 26 integrated in the control device 5, as described below; the reference numeral 57 indicates a purge valve for the expulsion of air contained in the upper end of a duct 27 extending from the master cylinder 26 to the brake BF of the front wheel (see FIG. 3); reference numeral 45 relates to a third push-pull cable, starting from said device 5 and reaching the brake BR of the rear wheel; and reference numeral 58 relates to a fuel tank.

 The following description, referring to FIG. 4, relates to the structural arrangement of the first cable damper 24.

 The first push-pull cable 251 consists of an outer sheath 291 connected to the first braking lever 3F of an outer sheath 291 'connected to the control device 5, and an inner rope 301 inserted, in a movable manner, in said sheaths 291 and 291 '. The first cable damper 241 comprises a cylindrical housing 31 connected to the vehicle frame a movable cylindrical part 32 inserted, with relative axial movement, in said housing 31 of the damper; a fixed cylindrical part 33 which is permanently set inside said housing 31, and by means of which the moving part 32 performs relative sliding; a sliding part 34 inserted into the housing 31 with relative axial movement, and provided with a collar 34a designed to abut against a collar 32a of the movable part 32; and two springs 35 compressed between the collar 32a of the moving part 32, and a collar 33a of the fixed part 33.

 An end region of one, 291, of the outer sheaths is secured to the flange 33a of the fixed part 33, while an end region of the other outer sheath 291 'is fixed to the flange 32a of the moving part 32 The two springs 35 thus develop a biasing force acting in directions suitable for moving the outer sheaths 291 and 291 'away from each other.

 A first load-sensing switch 381, secured to one of the extreme sides of the housing 31 of the shock absorber, is in abutment against one of the ends of the moving part 32 which projects beyond one of the ends of said housing 31. When the braking input power, coming from the first braking lever 3F drops below a predetermined load range while the moving part 32 completes a stroke having the effect of compressing the springs 35 in response to a pulling movement of the first push-pull cable 251, the first load detector switch 381 engages within a predetermined range of the aforementioned stroke.

 This point will now be described in more detail. When the actuation force of the first brake lever 3F increases beyond a predetermined value, that is to say when the tensile force of the inner rope 301 exceeds a predetermined value in the direction of an arrow A, the moving part 32 slides in the direction of the fixed part 33, by compressing the springs 35, under the action of a load having the effect of bringing the two outer sheaths 291 and 291 'closer to each other. As a result, the moving part 32 causes the first load detector switch 381 to engage.

 As illustrated in FIG. 5, the second cable damper 242 has, basically, the same structural arrangement as the first cable damper 241. The constituent parts identical to those of the first damper 241 are identified by the same reference numerals, are not the subject of detailed explanations in the present brief, and are only illustrated in the figure. The only difference between the second damper 242 and the first damper 241 is that two elastic frustoconical washers 36 are interposed between the flange 34a of the sliding part 34, and the flange 32a of the moving part 32.

 When the load, induced by the second brake lever 3R and having the effect of pulling an inner rope 302 from the second push-pull cable 252 in the direction of arrow A, is included in the predetermined range, a second switch 382 detector loads starts. Since a load is imposed on the second switch 382 by the frustoconical elastic washers 36, the elastic constant of which is low, it becomes possible to increase a variation in load when the input stroke is small, and to maintain relatively low a load loss based on failure to use the cable damper. It is possible to reduce an ineffective stroke, so as not to induce a notion of incompatibility in the feeling of braking.

 I1 should be described below, with reference to FIGS. 6 to 10, the structural arrangement of the control device 5.

 The control device 5 is provided with a first planetary gear mechanism 61; a second planetary gear mechanism 62; an electromagnetic brake 7 fulfilling the function of a planetary wheel braking means; and a motor 8 which can rotate forwards and backwards.

 A casing 9 of the control device 5 consists of a first element 10 on which the motor 8 is mounted, and a second element 11 which is coupled to the first element 10, and on which the electromagnetic brake 7 is mounted according to the same axis as the axis of rotation of the motor 8. A rotary shaft 7a of the electromagnetic brake 7 and a rotary shaft 8a of the motor 8 are arranged on the same axis, and face each other in respective extreme regions.

 The first planetary gear mechanism 61, which is located on the outer periphery of the rotary shaft 8a of the motor 8, comprises a first toothed ring 161 surrounding the outer periphery of the aforementioned end region of the shaft 8a of the motor 8; a first planetary wheel 171 formed on the end region of said shaft 8a; a plurality of first planet gears 181 meshing, both in the first ring 161 and in the first planetary wheel 171; and a first planet carrier 191 which supports the first planet gears 181 with the possibility of rotation. In the first mechanism 61, the first planetary wheel 171 can be rotated by actuating the motor 8.

 The second planetary gear mechanism 62 comprises a second ring gear 162, surrounding the outer periphery of the above-mentioned end region of the rotary shaft 7a of the electromagnetic brake 7; a second planetary wheel 172 shaped on the end region of said shaft 7a; a plurality of second planet gears 182 meshing both in the second ring gear 162 and in the second planetary wheel 172; and a second planet carrier 192 offering a rotary support to said second planet gears 182. In the second mechanism 62, the electromagnetic brake 7 can brake and interrupt the rotation of the second planetary wheel 172.

 The first and second toothed rings 161, 162 are one and the same piece and are sandwiched radially by the first and second planet gears 181, 182, with relative rotational faculty between the first and second satellite doors 191, 192. The fact of providing the first and second rings 161, 162 in the form of a single piece makes it possible to reduce the number of constituent elements, and to obtain the reduced dimensioning of the control device.

 A first control shaft 201 and a second control shaft 202 are installed in front of the rotary shaft 7a of the electromagnetic brake 7 and in front of the rotary shaft 8a of the motor 8, parallel to said rotary shafts 7a and 8a. A cylindrical part is machined at the inner end of the first control shaft 201, and the outer periphery of the inner end of the second control shaft 202 is adjusted, with relative rotation, in the inner periphery of said cylindrical part, if although the first and second shafts 201, 202 are arranged coaxially on a common axis parallel to the axes of the first and second mechanisms 61, 62 with planetary gears.

 As an observation of FIGS. 7 and 9 reveals, a first toothed sector 481, acting as a first control member, is subject to the first control shaft 201 and is engaged with a driven pinion 491 integral with the first satellite carriers 191. A piston striker 43, intended to actuate the master cylinder 26 described below, is similarly secured to the first control shaft 201.

 The master cylinder 26 is provided with a cylindrical body 39 fixed to the casing 9 of the control device 5; a piston 40 slidingly adjusted in the cylindrical body 39, so that its front face is opposite a pressure chamber 41; and a return spring 42 housed inside the pressure chamber 41 and having the effect of biasing said piston 40 backwards (to the right in FIG. 9).

The conduit 27, communicating with the chamber 41, is connected to the anterior end of the cylindrical body 39.

 The striker 43 of the piston abuts against the rear end of said piston 40 projecting from the rear end of the cylindrical body 39. When the first toothed sector 481 occupies its position in solid lines in FIG. 9, a sealing gasket 44 in the form cup, placed on the piston 40, is in a position suitable for opening an expansion orifice 39a formed in the cylindrical body 39; and the first sector 481 can turn slightly anticlockwise from the position in solid lines above (direction retraction of the piston 40), to its position in broken lines in which it abuts against a stopper 10a by which its rotary movement is prevented. An angle of rotation, between said position in solid lines and said position in broken lines, is adjusted taking into account the position of the detent orifice 39a and variations involved in the precision of machining of each toothing, so that, when the first sector 481 abuts against the cleat 10a, and the piston 40 reaches its retraction limit, the lining 44 placed on said piston 40 opens suddenly on said orifice 39a, and does not retract a great distance away from this orifice 39a.

 When the first control shaft 201 has pushed the piston 40 through the striker 43, said piston 40 moves to one side implying a reduction in the volume of the pressure chamber 41 and the resulting hydraulic pressure, prevailing in said chamber 41 , acts on the brake BF of the front wheel via the conduit 27.

 As described above, the fact that the first and second control shafts 201, 202 are arranged coaxially on a common axis, parallel to the axes of the first and second mechanisms 61, 62 with planetary gears, makes it possible to provide the control device 5, a compact embodiment compared to the case in which the shafts 201 and 202 are, one and the other, on different axes. The master cylinder 26 is moreover interposed between the rotation surface of the first toothed sector 481 wedged on the first shaft 201 and that of a second toothed sector 482 wedged on the second shaft 202, so as to cut the two shafts 201 , 202, which makes it possible to effectively exploit the dead space in the control device 5, and to give a compact arrangement to the master cylinder 26.

 FIGS. 6, 11 and 12 show a connection between the first push-pull cable 251, connected to the first braking lever 3F and the first control shaft 201 extending outwards from the first element 10 of the casing . A bushing 61 is adjusted for relative rotation on the outer periphery of the first shaft 201, an upper arm 62 and a lower arm 63 being welded to this bushing 61. An adjustment arm 64 is also fixed, using a bolt 65, at the outer periphery of the first shaft 201. The first cable 251 is connected to the upper end of the upper arm 62, by means of a cable tie 66.

 An adjustment bolt 68, pivotally attached to the lower end of the lower arm 63 by means of a pin 67, passes through a tenon 69 bearing in an intermediate region of the adjustment arm 64, and an adjustment nut 70 is engaged by thread with the upper end of said bolt 68. A helical spring is adjusted on the outer periphery of the bolt 68 and urges the pin 69 so that this pin comes into abutment against a curvilinear surface 70a, formed at the the lower end of the adjusting nut 70.

 Consequently, the lower arm 63 integrating with the upper arm 62 is connected to the adjustment arm 64 by means of the adjustment bolt 68, so that, when said upper arm 62 is rotated by the first cable 251 of push-pull, the first control shaft 201 rotates under the action of the lower arm 63, the bolt 68 and the arm 64. A rotation respectively imparted to the adjusting nut 70 at the rate of half a revolution complete, to vary the relative angle of the lower arm 63 and the adjustment arm 64, allows to adjust the phase of the first control shaft 201, at will and with precision, so that the striker 43 of the piston, provided on said first shaft 201, can be adjusted precisely until its position in solid lines in FIG. 9.

 As evidenced by an observation of Figures 7 and 10, the second toothed sector 482, fulfilling the function of a second control member, is supported in relative rotation by the second control shaft 202 and is engaged with a driven pinion 492 secured to the second planet carrier 192. A retaining zone 50a, shaped at the end of a control arm 50 secured to the second control shaft 202, is adjusted in an oblong hole 48a. The area 50a and the oblong hole 48a constitute a dead-stroke mechanism. In order to limit a rotation of the second toothed sector 482 in a clockwise direction considering FIG. 10, the second element 11 of the casing has a stopper lla capable of providing a stop for said second toothed sector.

 Figures 6, 13 and 14 show a connection between the second push-pull cable 252, connected to the second brake lever 3Rl and the second control shaft 202 extending outward from the second element 11 of the housing. An arm 73 is fixed to the second shaft 202 by means of a bolt 72 and two cable ties 75, 76 are pivotally connected to said arms 73 by means of a pin 74. The attachment cable 75 is connected to the inner cable 302 of the second push-pull cable 252, which comprises said cable 302 and an outer sheath 292 '; the cable tie 76 is connected, in turn, to a third inner cable 47 of the third push-pull cable 45, consisting of said cable 47 and an outer sheath 46.

The first 4F transmission system transmitting the actuating force of the first 3F brake lever to the brake
BF of the front wheel, is composed of the first push-pull cable 251 including the first shock absorber 241, the master cylinder 26 and the duct 27. The second 4R transmission system, transmitting the actuation force of the second lever braking 3R to the brake BR of the rear wheel, consists of the second push-pull cable 252 including the second damper 242, and the third push-pull cable 45.

 An angular sensor 51 is fixed to the outer end of the second control shaft 202 starting from the control device 5, in order to detect an operating stroke of the second brake lever 3R. As illustrated in FIG. 3, a front wheel speed sensor 54 and a rear wheel speed sensor 55 are mounted, respectively, on the front wheel WF and on the rear wheel WR. The engagement and release of the electromagnetic brake 7 in the control device 5, as well as the direction of rotation of the motor 8 and the maneuvering stroke of the latter, are controlled by the electronic control unit 52. Detected values coming from first and second switches 381, 382 load detectors, the angular sensor 51, the front wheel speed sensor 54 and the rear wheel speed sensor 55, are introduced into the unit 52.

 FIG. 15 is a block diagram of a control system intended to drive the brake BF of the front wheel, via the control device 5, as a function of the operation of the second brake lever 3R connected to the brake BR of Rear wheel. During the operation of the second lever 3Rw the braking force of the brake BR of the rear wheel is amplified by the braking force of the brake BF of the front wheel and, in this way, an auxiliary quantity is determined by operating speed control of rotation of the motor 8 provided in the control device 5.

 The control system under consideration comprises a means M1 for calculating fundamental auxiliary quantities (means for calculating fundamental functional ratios); means M2 for correcting the input speed (first means for correcting functional ratios); means M3 correcting hold-release (second means correcting functional reports); means M4 for correcting the vehicle speed (third means for correcting functional ratios); and a means M5 for correcting the adjustment (fourth means for correcting functional ratios).

 The means M1 for calculating fundamental auxiliary quantities calculates a fundamental auxiliary value, expressed by a functional ratio of the motor 8, on the basis of a rotation angle O of the second control shaft 202 (that is to say of an operating stroke S of the second brake lever 3R) detected by the angular sensor 51.

 For example, when the second braking lever 3R is tightly pressed inwards, the input speed correction means M2 corrects the fundamental auxiliary quantity (fundamental functional ratio), both on the basis of the travel of maneuver S detected by the angular sensor 51, and the shape of / dt of the variation in time of the maneuvering stroke 0, so that a braking force, proportional to the speed of actuation of the braking lever , can be developed to provide an adequate braking sensation.

 On the basis of the maneuvering stroke e detected by the angular sensor 51, the hold-release correction means M3 corrects the auxiliary quantity when it is detected that the second brake lever 3RK, once grasped, is held or has been released , so as to compensate for a hysteresis in the braking pressure generated between forward and backward strokes of the piston 40 in the master cylinder 26.

 To improve the braking sensation just before stopping the motorized two-wheeled vehicle V, the vehicle speed correction means M4 corrects the auxiliary quantity on the basis of a vehicle speed V, detected on the basis of the signal output of the front wheel speed sensor 54.

 When the braking force of the brake BR of the rear wheel decreases concomitantly with a release of the second and third cables 252, 45 of push-pull connecting, to each other, the second brake lever 3R and said brake BR of the rear wheel, the adjustment correction means M5 corrects the auxiliary quantity in order to correspondingly reduce the braking force of the brake BF of the front wheel.

 The functions of the means M1 to M5 will be described in more detail on the subject of the operation of the present embodiment.

 The description below relates to the operation of the embodiment having the structural arrangement described above.

When the input actuating power, coming from the first or second braking lever 3F or 3Rx is below the predetermined value, a braking force of the brake
BF or BR of the front or rear wheel is obtained by said first or second brake lever, without actuation of the control device 5. When the first and second switches 381, 382 load detectors are triggered, the operation of the motor 8 is interrupted by the electronic control unit 52, then the electromagnetic brake 7 is deactivated to allow free rotation of the second planetary wheel 172.

In this condition, when only the first brake lever 3F is actuated, the first control shaft 201 rotates jointly with a pulling movement of the first push-pull cable 251, so that a hydraulic pressure is delivered by the master cylinder 26 and acts on the brake
BF of the front wheel via the conduit 27, so that a braking force is applied to said brake of the front wheel. At this stage, the rotational force which has been applied to the first control shaft 201 is transmitted to the first satellite carriers 191, from the first toothed sector 481, by the input of the driven pinion 491.

 When the motor 8 is off, the first planetary wheel 171 is stationary, and the second brake lever 3R is not in the brake actuation state, the second planet carrier 192 integrated in the second mechanism 62 at the planetary gear is also stationary, so that the rotation of the first planet carrier 191 is transmitted to the second planet wheel 172 by means of the first planet gears 181, the first and second toothed rings 161, 162 and, moreover, via the second planet gears 182, thus causing a crazy rotation of the second planetary wheel 172. Consequently, the operation of the first brake lever 3F does not imply an actuation of the brake BR of the rear wheel as long as the motor 8 and the electromagnetic brake 7 are not in operation.

 When the motor 8 and the electromagnetic brake 7 are both off, and when only the second braking lever 3R is operated, a braking force is developed in the rear brake BR following a mechanical transmission of the brake actuation force via the second 4R transmission system At this stage, even if the second control shaft 202 is rotated by a pulling movement of the second push-pull cable 252, the engine 8 is out of function, the first planetary wheel 171 is stationary and the first planet carrier 191 is also stationary since the first brake lever 3F is not in the brake actuation state, so that a rotation of the first and second toothed rings 161, 162 is prohibited by the first planet gears 181.As a result, the rotation of the second planet carrier 192 is transferred to the second planetary wheel 172 by the int intermediate the second planet gears 182, thus causing a crazy rotation of this second planetary wheel 172. In this way, the operation of the second brake lever 3R does not result in an operation of the brake BF of the front wheel as long as the motor 8 and the electromagnetic brake 7 are both off.

 When the input actuating power, emanating from the first or second brake lever 3F or 3RT has exceeded the predetermined value, the control device 5 is actuated to interlock and activate the brakes BFS BR of the front and rear wheels. When the first and second switches 381, 382 load detectors are engaged, the motor 8 is actuated by the electronic control unit 52 and the electromagnetic brake 7 comes into operation, that is to say that the second planetary wheel 172 is braked.

 It is then assumed that the second braking lever 3R has been actuated by an actuating force exceeding the predetermined value. As illustrated in FIG. 16, when a rotation is imparted to the motor 8 while the second planetary wheel 172 is braked by the electromagnetic brake 7, the first and second planet carriers 191, 192 are rotated in mutually opposite directions and the second toothed sector 482 is driven, by the driven pinion 492 integral with the second planet carrier 192, in a clockwise direction when considering FIG. 16. However, because the rotation of the second toothed sector 482 is prevented by the latter coming into abutment against the stopper îîa, the first planet carrier 191, rotating under the effect of the resulting reaction force, causes the first sector 481 to rotate under the action of the first driven pinion 491, counterclockwise, considering FIG. 16. Therefore, the master cylinder 26 comes into operation and generates a braking pressure involving actuation of the brake BF of the front wheel.

 At this stage, as the retaining zone 50a of the control arm 50 is housed with play in the oblong hole 48a, the rotation of the second toothed sector 482, conditioned by an actuation of the control device 5, does not affect the rotation of the second control shaft 202 resulting from the operation of the second brake lever 3R During the interlocked operation of the BFI BR brakes of the front and rear wheels, the actuation of the device 5 is controlled as a function of the output signal of the angular sensor 51 detecting the angle of rotation of the second shaft 202.

 These considerations will now be described with reference to FIG. 18. When the second brake lever 3R is actuated, the rear brake BR comes into operation under the action of the second and third cables 252, 45 of push-pull , in order to generate a braking force on the rear wheel WR. When the maneuvering force imposed on the second 3RV lever is increased and when the second load detector switch 382, which is integrated in the second cable damper 242, comes into operation, the control device 5 comes into operation, as well as the brake BF of the front wheel. Therefore, the distribution of the braking force follows an ideal distribution curve.

 At this stage, in the absence of the dead-stroke mechanism, comprising the retaining zone 50a of the control arm 50 and the oblong hole 48a of the second toothed sector 482, the braking force of the rear wheel WR represents, after actuation of the control device 5, the sum of the force induced by the driver from the second brake lever 3Rl and an increment (hatched area in FIG. 18) based on the actuation of said device 5; in this way, as symbolized by a dotted line, the braking force of the rear wheel WR becomes excessive and deviates amply from the ideal distribution curve, hence a greater probability of blocking the rear wheel WR. however, the braking force of the rear wheel WR is only represented by the force induced by the driver, so that an appropriate adjustment of the actuating stroke of the device 5, in order to adjust the braking force of the WF front wheel, makes it easy to obtain a distribution characteristic of the braking force close to the ideal distribution curve. It is also possible to contribute to improving the feeling of braking.

The description below, mainly referring to FIGS. 20 to 25, relates to the control of a braking force (auxiliary quantity) generated, in the brake BF of the front wheel, during an operation of the second brake lever 3R
In FIG. 20, when the second braking lever 3R is grasped inwardly in order to increase the operating stroke of this lever, and when the second load detector switch 382, integrated in the second, comes into operation cable damper 242, the motor 8 and the electromagnetic brake 7 come into action, in the control device 5, to initiate an auxiliary control. At this instant, a fundamental auxiliary quantity f (e), intended to control the number of full turns of the motor 8, is adjusted so as to increase as the operating stroke 8 increases as a function of the angle of rotation e of the second control shaft 202 (that is to say of the operating stroke e of the second brake lever 3R), as illustrated in FIG. 21.

 When the control device 5 causes the piston 40 to advance into the master cylinder 26, a predetermined reaction force is applied until the cup-shaped seal 44 passes the expansion port 39a and up to that a braking pressure is generated, but the increasing auxiliary quantity, in FIG. 21, when the second load detector switch 382 is engaged, represents an absorption component of the aforementioned reaction force.

 A fundamental auxiliary quantity f (S) proportional to the operating stroke e is calculated by the means M1 for calculating fundamental auxiliary quantities and, on the basis of this fundamental auxiliary quantity f (e), an open-loop control of the motor 8 operates in the control device 5. In this way, it is not only possible to easily obtain a braking sensation with high linearity, by generating a braking pressure proportional to the operating stroke B of the second braking lever 3R ; but it is also possible to simplify the control system thanks to the open-loop control, and to reduce the number of detector means, which makes it possible to contribute to the reduction of costs.

 In a range of correction of the input speed [zone (A) in FIG. 20], from the moment at which the second load detector switch 382 activates and until the operating stroke e reaches a predetermined value in FIG. 20, the input speed correction means M2 corrects the fundamental auxiliary quantity f (8) as a function of a time offset value dS / dt of the operating stroke 0. As illustrated in the Figure 22, the magnitude of the auxiliary quantity corrected by the correction means M2 is determined by KDVSTRK x dB / dt or by KDVSTRK x (de / dt) 2, both on the basis of a constant KDVSTRK and the value time difference dS / dt of the maneuvering stroke 0.

 When the second brake lever 3R initiates its maneuver, it is grasped with such firmness that the time offset value of / dt of the maneuvering stroke e usually becomes large, and the total auxiliary quantity increases as the auxiliary quantity corrector KDVSTRK x dS / dt is added to the fundamental auxiliary quantity f (S) in the range of correction of the input speed. Thus, when the second brake lever 3R is strongly gripped, it is possible to correct the auxiliary force of the brake BF of the front wheel in the direction of increase, in order to increase the braking force at the initial stage of braking, and therefore to improve the braking sensation. The correction of the input speed is terminated after the maneuvering stroke has increased until it leaves zone (A), which makes it possible to prevent the application of excessive auxiliary force in the region of a large maneuvering stroke 6 (area of large auxiliary force).

 In FIG. 20, in a zone (B) in which the maneuvering stroke e passes from an increase state to a hold and decrease state, the hold-release correction means M3 corrects the auxiliary quantity so as to compensate for the hysteresis of the master cylinder 26. More specifically, when the piston 40 has moved, in the master cylinder 26, from the condition of increase in the braking pressure (implying an advance of the piston) up to the condition of reduction of the braking pressure (implying a stopping and a retraction of said piston), the braking pressure does not immediately decrease immediately after the retraction of the piston 40, following a play affecting various parts of the master cylinder 26 or more deformations of elastic parts such as the cup-shaped seal 40, but it decreases with a slight delay. Consequently, a hysteresis occurs in the braking pressure between the instant at which the piston 40 advances in the master cylinder 26, and the instant at which it reverses. Thus, it is necessary to compensate for said hysteresis in order to obtain a braking sensation with high linearity.

 In FIG. 23 (B), in the case where the maneuvering stroke e varies along a line -OO-, if the value of the variation of this stroke e per unit of time is designated by AS, an operational average EAS of four continuous additions of the variation value A0 is indicated by a line -AA-. When the operational average AB takes a positive value, it is estimated that the operating stroke e is in the increasing state and the hold-release mark, illustrated in FIG. 23 (C), is then set to "0 ". On the other hand, when the operational average EAE takes a negative value, it is estimated that the maneuvering stroke e is in the declining state and the hold-release mark is then set to" 1 ".

 As shown in FIG. 23 (A), an auxiliary quantity (dotted line) in the state of increase of the operating stroke 0, and an auxiliary quantity (dashed line) in the state of decrease of said stroke 8, are previously set in accordance with hysteresis characteristics of the cylinder master 26. When the maneuvering stroke 9 increases as the second braking lever 3Rl is actuated, the hold-release mark is on "0" and, therefore, the auxiliary quantity coincides with the auxiliary quantity in the decreasing state of the stroke 0, which is symbolized by a dotted line. Then, when the hold-release mark changes to "1" during hold or release of said second lever 3RT the auxiliary quantity is modified to pass from that marked by a dotted line to that symbolized by a dashed line, in order to compensate for the hysteresis. At this stage, to prevent an abrupt variation of the auxiliary quantity, the auxiliary quantity is reduced according to a rate of variation has preset in a zone (D).

 When the second brake lever 3R is again gripped inwards and when this results in a new change to "0" of the hold-release mark, the auxiliary quantity is changed from that indicated by a dashed line to the one marked with a dotted line. At this stage, the auxiliary quantity is increased at a rate of variation ss preset in an area (E), in order to prevent an abrupt variation of this quantity. The absolute value here of the aforementioned variation rate, in the state of increase of the operating stroke 8, is set larger than the absolute value lai a | from the aforementioned variation rate to the state of decrease of said stroke 0.

The corrective auxiliary quantity, supplied by the hold-release correcting means M3, is designated by
OFFCBS.

 In FIG. 20, the vehicle speed correction means M4 decreases the auxiliary quantity in a zone (C) in which the speed V of the vehicle decreases, and in which said vehicle is about to stop. More specifically, as illustrated in FIG. 24, when the speed V of the vehicle reaches an auxiliary reduction speed, the correcting means M4 decreases the auxiliary quantity and, when the speed V of the vehicle has reached an auxiliary interruption speed, the quantity auxiliary is brought to zero, which makes it possible to reduce the braking force just before stopping the vehicle and thus achieve a smooth stop of said vehicle.

In addition, since the auxiliary quantity takes the value zero before the second load detector switch 382 goes off in order to interrupt the operation of the control device 5, there is a reduction in the transmitted reaction force to the second braking lever 3R when said device S stops operating when said second switch 382 trips, which makes it possible to improve the feeling produced by said lever.

The second and third push-pull cables 252, 45, connecting the second braking lever 3R and the brake BR of the rear wheel to one another, tend to relax due to an elongation due to a secular variation , or as a result of wear of the brake shoe in said brake
BR. Such release of the second and third cables 252, 45 is accompanied by a progressive weakening of the braking force of the brake BR of the rear wheel. It is nevertheless difficult for the driver to become aware of such loosening of the cables 252, 45, since there is no weakening of the braking force of the brake BF of the front wheel which is actuated, by the control device 5, in interlocking with the brake BR of the rear wheel. In addition, in the event of an abrupt reduction in the braking force of the brake BF of the front wheel, resulting for example from a failure of the device 5, if the braking force of the brake BR of the rear wheel is in the weakened state following a loosening of the second and third cables 252, 45, the total braking force varies suddenly before and after the failure, causing a feeling of inadequacy on the part of the driver.

 The above problems are solved by detecting the amount of slack in the second and third push-pull cables 252, 45 and decreasing the auxiliary magnitude as the amount of slack increases, then interrupting assistance when the magnitude of the slack reaches a predetermined increase value, by using the adjustment correction means M5, as illustrated in FIG. 25. The magnitude of the slack corresponding to the interruption of the assistance is set smaller than the amount of slack corresponding to the operation of an indicator which detects the slack of the second and third cables 252, 45, then triggers an alert. This makes it possible to warn the driver, even before the indicator operates, of a slack affecting the second and third cables 252, 45.

 The slack in the second and third push-pull cables 252, 45 can be detected on the basis of a deviation of the angle of rotation S (that is to say of the operating stroke 0) of the second shaft. command 202 at the instant of activation of the second load detector switch 382. More particularly, when the second and third cables 252, 45 are in the normal slack-free state, the angle of rotation 8 is deemed to have the value 00 at the stage of activation of the second switch 382 and, when the second and third cables 252, 45 are released, the angle of rotation, detected when the second switch 382 is engaged, then passes to a value 01 differing from the above-mentioned value e0. In this way, once the difference 0 - o is calculated, this difference can be coordinated with the amount of play in the second and third cables 252, 45.

In conclusion, the nominal drive performance of the motor 8, in the control device 5, is given by the following equations
CBSORG = CBSSTR x (f (8) + KDVSTRK x (d8 / dt)) ... (1),
performance
nominal = KCBS x (KCBAFDJ x CBSORG + OFFCBS) ... (2).

 In equation (1), the auxiliary quantity CBSORG is calculated by adding the fundamental auxiliary quantity f (S) calculated on the basis of FIG. 21 and the corrective auxiliary quantity KDVSTRK x (dS / dt) calculated on the basis of the Figure 22, then multiplying the sum by an increase value CBSSTR.

 In equation (2), the nominal performance is calculated idea, as final functional ratio, by multiplying the auxiliary quantity CBSORG by an auxiliary correction coefficient KCBAFDJ calculated on the basis of figure 25; then adding to the product obtained, or subtracting from this product, the corrective hold-release quantity (see Figure 23); then multiplying the result by a KCBS coefficient intended to establish the functional ratio between 0% and 100%.

 The description below concerns the case in which an anti-lock braking command must be executed.

 If the tendency of a wheel to lock up is detected on the basis of the output signal from the front wheel speed sensor 54 and that of the rear wheel speed sensor 55, the electronic control unit 52 puts the electromagnetic brake 7 in operation and triggers the operation of the motor 8 in the direction opposite to that of the aforementioned operation in interlocked mode. Consequently, as illustrated in FIG. 17, the first and second planet carriers 191, 192 are rotated in directions opposite to each other and opposite to the direction of the above-mentioned interlocked operating mode; the first toothed sector 481 is driven clockwise in FIG. 17, while the second toothed sector 482 is driven counterclockwise. At this stage, the rotation of the first sector 481 is directly reflected on the first control shaft 201 , by forcing this shaft 201 to rotate in a proper direction to weaken the braking force of the front wheel WF. On the other hand, the rotation of the second toothed sector 482 is passed on to the second control shaft 202 since the retaining zone 50a of the control arm 50 abuts against an end region of the oblong hole 48a of said second sector, thus inciting the second shaft 202 to rotate in a direction suitable for weakening the braking force of the rear wheel WR.

 Repetitive engagement and tripping of the control device 5, in accordance with the wheel slip coefficients, make it possible to carry out an anti-lock braking control in order to effectively prevent a wheel lock (s).

 Furthermore, in the first and second transmission systems 4Fl 4R, the first and second dampers 241, 242 of the cables are interposed, respectively, between the control device 5 and the first brake lever 3Fl and between said device 5 and the second brake lever 3R. When the braking force must be increased again in anti-lock braking control mode, the motor 8 is put out of operation and it thus becomes possible to exploit the reaction force stored in the shock absorbers 241, 242. , it is possible to prevent the force from the control device 5 from being directly applied to the first lever 3F or to the second lever 3R during the execution of the anti-lock braking command, and thus to obtain a good feeling of operation.

 Thanks to the presence of the stopper stopper 10a (see FIG. 9) limiting the rotary range of the first toothed sector 481 connected to the master cylinder 26, the control device 5 used in the present embodiment can exert the effects described below. -after.

 In FIG. 19, for example, when the speed of the front wheel WF becomes lower than the speed of the chassis of the vehicle beyond a predetermined value, the anti-lock braking control is initiated and the angle of rotation of the first sector toothed 481 decreases in a direction suitable for weakening the braking force by actuation of the control device 5, from which it follows that the braking force of the front wheel WF also decreases. When the angle of rotation of the first sector 481 decreases, the piston 40 housed in the master cylinder 26 moves back while obeying the striker 43 of said piston and, immediately after the seal 44 in the form of a bowl has opened the orifice detent 39a in Figure 9, the first sector 481 abuts against the stopper 10a, by which its rotation is prevented.

 At this stage, as indicated by a dotted line in FIG. 19, if we admit the absence of the stopper 10a, the first toothed sector 481 continues its rotation and the reaction force of the first brake lever 3F increases similarly up to a substantial value, which results in a degradation of the feeling provided by the lever. Furthermore, when the control device 5 is actuated to rotate the first sector 481 in the direction of an increase in the braking force, the seal 44 of the piston 40, configured in a bowl, closes the orifice trigger 39a so as to delay the instant of generation of a braking pressure in the pressure chamber 41, hence a degradation of the sensitivity.

 Thus, in the present embodiment, the rotation of the first toothed sector 481 in the direction of recoil of the piston 40 is prevented by the stopper 10a, so that, when said first sector 481 is driven by actuation of the device control 5 to cause a further increase in the braking force, it is possible to rapidly advance the piston 40 in order to generate a braking force, and consequently to avoid a degradation of the sensitivity.

 According to the invention, as explained above, the means for calculating fundamental functional ratios calculates a fundamental functional ratio for driving the control device on the basis of an operating stroke of the brake actuating member, detected by the maneuver stroke detector means, and the open loop control means performs an open loop control of the control device on the basis of the fundamental functional ratio thus calculated; in this way, not only is it possible to easily obtain a braking sensation with high linearity, by generating a braking pressure proportional to the operating stroke of the brake actuating member, but it is also possible to simplify the control system thanks to the open-loop control, and to reduce the number of detection means, thereby contributing to a reduction in costs.

 According to the invention, since the first means for correcting functional ratios, integrated in the open-loop control means, optionally corrects the fundamental functional ratio on the basis of a course variation over time in the race. maneuver, it is possible to vary the magnitude of the braking force in proportion to the speed of operation of the brake actuating member, and thus obtain an advantageous braking sensation.

 According to the invention, since the second means for correcting functional ratios, integrated in the open-loop control means, optionally corrects the fundamental functional ratio in order to compensate for a hysteresis in the braking pressure supplied by the master cylinder , it is possible to reduce the difference created, in the braking force, between the instant at which the operating stroke of the brake actuating member increases, and the instant at which it decreases, and thus obtain a braking sensation with higher linearity.

 According to the invention, as the third means for correcting functional ratios, integrated into the open-loop control means, optionally corrects the fundamental functional ratio when the vehicle speed is low just before stopping said vehicle, it is possible to weaken the braking force at the instant directly preceding the stopping of the vehicle, and consequently cause a smooth stopping of said vehicle.

 According to the invention, the fact that the fourth means for correcting fundamental ratios, integrated in the open-loop control means, corrects facllltativenent the fundamental functional relationship as a function of the extent of the slack in the cables, makes it possible to weaken the force of braking of the hydraulic brake, when the braking force of the mechanical brake decreases as the amount of slack in the cables increases, thus offering the driver the possibility of detecting the increase in the magnitude of the slack cables.

 Although the foregoing detailed description relates to an embodiment of the present invention, it goes without saying that numerous modifications can be made, without departing from the scope of the invention.

Claims (5)

- CLAIMS  1. A brake pressure control apparatus, fitted to a vehicle braking system in which a control device (5) is actuated as a function of the operation of a brake actuation member (3R), and a hydraulic brake (BF) is actuated by a master cylinder (26) driven by the control device (5), apparatus characterized in that it comprises a means (51) for maneuver stroke detection, for detecting a stroke operation of the brake actuation member (3R); and an open loop control means (52), having fundamental functional ratio calculating means (M1), which calculates a fundamental functional ratio to drive the controller (5) based on the output signal of the means (51 ) maneuver stroke detector, the open loop control means (52) performing an open loop control of said device (5) as a function of the output signal of the means (M1) calculating fundamental functional ratios.  2. Apparatus according to claim 1, characterized in that the open loop control means (52) has a first means (M2) correcting functional ratios, to correct the fundamental functional ratio on the basis of a variation pattern during the time of the maneuvering race.  3. Apparatus according to claim 1, characterized in that the open loop control means (52) has a second means (M3) correcting functional ratios, to correct the fundamental functional ratio in order to compensate for a hysteresis in the pressure brake supplied by the master cylinder (26), generated between the instant at which the operating stroke increases and the instant at which the operating stroke decreases.  4. Apparatus according to claim 1, characterized in that the open loop control means (52) has a third means (M4) correcting functional ratios, to correct the fundamental functional ratio at the time at which the speed (V ) of the vehicle is weak just before a stop.  5. Apparatus according to claim 1, characterized in that the brake actuation member (3R) is connected both to the control device (5) and to a mechanical brake (BR) I via cables (252, 45), and the open loop control means (52) has a fourth functional ratio correcting means (M5), for correcting the fundamental functional relationship as a function of slack in said cables (252, 45).