GB2214587A - Anti wheel lock device - Google Patents

Description

j 1 - ANTI-LOCK CONTROLLER FOR VEHICLE r) n -1.

, i_ 1 458 1 The present invention relates to an anti-lock controller for a vehicle, and particularly, to an improvement of an anti-lock controller for a vehicle, comprising a flywheel rotatably and axially displaceably disposed to surround an output shaft which is driven in operative association with a wheel to be braked by a wheel brake, a clutch arrangement adapted to normally transmit a driving torque of the output shaft to the flywheel and to slip so as to permit overrunning of the flywheel when an angular deceleration greater than a given value is produced in the wheel during braking, a cam mechanism operated in response to the overrunning of the flywheel to provide an axial displacement to the flywheel, the clutch arrangement and the cam mechanism being interposed between the output shaft and the flywheel, and a -modulator operated to control the braking force of the wheel brake by-the axial displacement of the flywheel.

In such conventional anti-lock controller, the clutch arrangement is comprised of only a constant-torque clutch which As always constant in torque (for-example, see Japanese Patent Application Laid-open No. 181758/86).

In the-controllers constructed as described above, the timing for restoring of the modulator, i.e., the timing for recovery of the braking force and the time required for restoring of the speed of the flywheel to the speed of the C; - 2 output shaft are both determined by the transmission torque of the constant-torque clutch.

Thereupon, if the transmission torque of the constanttorque clutch is set at a relatively low level as shown in Fig. 11 to assure a suf f icient time required f or the wheel to be restored again to the vehicle speed from the start of operation of the modulator when driving on a road surface having a lower friction coefficient, the timing for restoring of the modulator is advantageously late. However, when the wheel speed approaches the vehicle speed as a result of controlling of the braking force, the time required for the speed of the flywheel to be restored to the speed of the output shaft is prolonged according to an increase in friction coefficient of a road surface. This results in a disadvantageie-E4- that points of second and subsequent operations of the modulator are delayed, i.e. a point of control of the braking force is delayed, as shown in FIG.12, this increasing the slip ratio.

On the other hand, if the transmission torque of the constant-torque clutch is set at a relatively high level, the time required for the speed of the flywheel to be restored to the speed of the output shaft is shortened, as shown in Fig.11, but the timing for restoring of the modulator is too early in a _road surface having a lower friction coefficient and hence, the wheel tends to become locked.

Therefore, to provide a good anti-lock controlling at all times in correspondence to the variation in friction coefficient of the road surface, it is required that the timing for restoring of the modulator is as late as 3 possible, and the time required for the speed of the flywheel to be restored to the speed of the output shaft is shortened as much as possible.

It is an object of the present invention to provide an anti-lock controller of the type described above, in which such requirements can be satisfied.

To achieve the above object, according to the present invention, there is provided an anti-lock controller for a vehicle, comprising a flywheel rotatably and axially displaceably disposed to surround an output shaft which is driven in operative association with a wheel to be braked by a wheel brake, a clutch arrangement adapted to normally transmit a driving torque of the output shaft to the flywheel and to slip so as to permit overrunning of the flywheel when an angular deceleration greater than a given value is produced in the wheel during braking, a cam mechanism operated in response to the overrunning of the flywheel to provide an axial displacement to the flywheel, the clutch arrangement and the cam mechanism being interposed between the output shaft and the flywheel, and a modulator operated to control the braking force of the wheel brake by the axial displacement of the flywheel, wherein the clutch arrangement is constructed so that the transmission torque is smallest when the flywheel overruns relative to the output shaft, and the transmission torque is increased, depending upon the driving torque of the output shaft,.when the output shaft drives the flyweel.

With the above construction, when the flywheel overruns 4- relative to the output shaft to operate the modulator, thereby controlling the braking force, the timing for restoring of the modulator can be sufficiently late, because a slippage is produced in the clutch arrangement with a smallest transmission torque. When the wheel speed approaches the vehicle speed with controlling of the braking force, the output shaft drives the flywheel and hence, in the clutch arrangement, the transmission torque is increased depending upon the driving torque of the output shaft. Consequently, the restoring of the speed of the flywheel to the speed of the output shaft can be hastened. Accordingly, a good anti-lock controlling is always possible in correspondence to the variation in friction coefficient of the road surface.

An embodiment of the invention will now be described way of example and with reference to the accompanying drawings, in which:- Fig.1 is a schematic plan view of a motorcycle equipped with a braking device having an anti-lock controller according to one embodiment of the present invention; Fig.2 is a longitudinal sectional-side view of a relevant portion of the braking device having the anti-lock controller; Fig.3 is a sectional views taken along lines III-III I - and IV and IV in Fig.2; Fig-4 is an enlarged view in longitudinal section of the anti-lock controller in Fig.3; M D - Fig.5 is a sectional view taken along a line V-V in Fig. 2; Fig. 4; Fig.6 is a sectional view taken along a line VI-VI in Fig.7 is a plan view of a drive cam plate in a cam mechanism; Fig.8 is a sectional view taken along a line VIII-117III in Fig.4; Fig.9 is a graph illustrating a relationship among the speed of a wheel, the speed of a flywheel and the braking force with respect to the time during an anti-lock controlling; Fig.10 is a graph illustrating the braking forcecontrolling timing according to the present embodiment; Fig.11 is a graph similar to Fig.9 but according to the prior art controller; and

Fig.12 is a graph similar to Fig.10 and according to the prior art controller.

Referring first to Fig.1, a motorcycle 1 comprises a pair of left and right front wheel brakes 3f, 3f for braking a front wheel 2f, and a single re-ar wheel brake 3r for braking a rear wheel 2r. The front wheel brakes 3f, 3f are operated by an output hydraulic pressure produced by a front master cylinder 5f operated by a brake lever 4. The rear wheel brake 2r. is operated by an output hydraulic pressure produced by a rear master cylinder 5r operated by a brake pedal 6.

- 6 LO L5 Particularly, the hydraulic braking pressure of the front wheel brakes 3f, Sf is controlled by an anti-lock controller 7.

Referring to Figs.2 and 3, a hub 8 of the front wheel 2f is rotatably supported on an axle 10 through a pair of bearings 11 and 11'. The axle 10 has its opposite ends removably secured to lower ends of a pair of left and right front forks 9, 9 by a holder 121 and a bolt/nut 122, respectively. Each of the pair of front wheel brakes 3f, 3f disposed on the opposite sides of the front wheel 2f comprises a brake disk 12 secured to an end face of the hub 8, and a brake caliper 14 disposed astride the brake disk 12 and supported on the front fork 9 through a bracket 13. The brake caliper 14, when an output hydraulic pressure is supplied to-its input port 14a from the front master cylinder 5f, is operated to grip the brake disk 1-2, thus applying a braking force to the front wheel 2f.

An anti-lock controller 7 is interposed in a hydraulic pressure conduit 15 as a braking-oil passage connecting an output port 5fa in the front master cylinder 5f with an input port 14a in each brake caliper 14.

The anti-lock controller 7, as shown in Figs. 2-8, primarily comprises a hydraulic pump 16 operated when braking, a modulator 17 interposed on the way of the hydraulic pressure conduit 15 and having a control hydraulic oil chamber 18 into which a pressure discharged f rom the hydraulic punp 16 is introduced, a normally-closed pressure discharge valve 20 interposed in a communication passage between the control hydraulic oil chamber 18 and oil reservoir 19, and an inertia type wheel angular 7 is deceleration sensor 21 which detects an angular deceleration of the front wheel f greater than a given value to close the pressure discharge valve 20. These components are arranged in a casing 22.

The casing 22 is constructed with open ends of its cupshaped inner case 22a and outer case 22b fitted to each other. A radially outward extending extension 22c is integrally formed on an end wall of the outer case 22b. Except for the extension 22c, the casing 22 is disposed so that it may be contained in a recess 8a formed on a left end face of the hub 8. The outer case 22b is supported at the central portion of its end wall on a left end of a cylindrical shaft 24 fitted over an outer peripehry of the axle 10 and is connected to the front fork 9 through detent means so that it is prevented from being rotated about the axle 10. The detent means may be any one and for example, is suitably a bolt 25 (see Fig.2) for securing the bracket 13 to the front fork 9.

The hydraulic pump 16 comprises a cam shaft 26 disposed in parallel to the axle 10, a push rod 27 disposed with its inner end opposed to an eccentric cam 26a formed on the cam shaft 26, a pump piston 28 abutting against an outer end of the push rod 27, an operation piston 29 abutting against an outer end of the pump piston - 28, a return spring 30 for biasing the push rod 27 away from the eccentric cam 26a.

The push rod 27 and the pump piston 28 are slidably received in a first cylinder bore 33 provided in the extension 22c to define an inlet chamber 31 and an outlet chamber 32 therearound, respectively. A plug 34 is fitted in 8 - an outer end of the first cylinder bore 33 to define a pump chamber 35 between the plug and the pump piston 28. The operation piston 29 is slidably received in the plug 34 to define a hydraulic oil chamber 36.

The inlet chamber 31 communicates with the oil reservoir 19 through a conduit 37 and with the pump chamber 35 through an intake valve 38. The pump chamber 35 communicates with the outlet chamber 32 through a unidirectional sealing member 39 having a discharge valve function. The hydraulic oil chamber 36 is connected to an upstream pipe 15a of the hydraulic pressure conduit 15 to normally communicate with the output port 5fa of the front master cylinder 5f.

As shown in Fig.5, the cam shaft 26 is supported on an end wall of the outer case 22b through a pair of bearings 40 and 401 and is driven from the front wheel 2f through a speed increasing device 42 which will be described hereinafter.

A meter driving gear 49 is secured to an outer end of the cam shaft 26 and meshed with a driven gear 50 connected to an input shaft of a speed meter 51 for the motorcycle.

Referring to Fig. 2, the modulator 17 is comprised of a pressure-reducing piston 46, a stationary piston 47 which receives one end of thia pressurereducing piston 46 to provide a retreat limit therefor, and a return spring 48 for biasing the pressure-reducing piston 46 in a direction to abut against the stationary piston 47. The pistons 46 and 47 are slidably received in a second cylinder bore 52 which is provided in the extension 22c adjacent the first cylinder 2_ - 9 bore 33.

In the second cylinder bore 52, the pressure-reducing piston 46 defines a control hydraulic oil chamber 18 between an inner end face of the second cylinder bore, and an output hydraulic oil camber 55 between the stationary piston 47, and the stationary piston 47 defines an input hydraulic oil chamber 54 around its outer periphery. The input hydraulic oil chamber 54 communicates with the hydraulic oil chamber 36 in the hydraulic pump 16, and the output hydraulic oil chamber 55 is connected to a downstream pipe 15b of the hydraulic pressure conduit 15 to normally communicate with the input ports 14a of the front wheel brakes 3f, 3f. The control hydraulic oil chamber 18 communicates with the outlet chamber 32 in the hydraulic pump 16 through an oil passage 57.

The stationary piston 47 comprises a valve chamber 58 normally communicating with the input hydraulic oil chamber 54, and a valve bore 59 which permits the valve chamber 58 to communicate with the output hydraulic oil chamber 55. Contained in the valve chamber 58 are a valve member 60 for opening and closing the valve bore 59, and a valve spring 61 for biasing the valve member 60 in a closing direction. A valve- opening stem 62 for opening the valve member 60 is mounted on one end face of the pressure-reducing piston 46 to project therefrom and adapted to maintain the valve meber 60 in an opened state when the pressure- reducing piston 46 is located at its retreat limit.

An outer opening of the second cylinder bore 52 is closed by an end plate 63 secured to the extension 22c, and - 1 the stationary piston 47 is always held at a location to abut against the end plate 63 by a resilient force of the return spring 48 or a hydraulic pressure introduced into the input and output hydraulic oil chambers 54 and 55.

The hydraulic pump 16 and the modulator 17 are disposed behind the front fork 9 as the brake caliper 14 is.

Referring to Fig.4, the pressure discharge valve 20 is comprised of a valve seat member 65 fitted in a stepped cylinder bore 64 in the outer case 22b, and a valve member 67 slidably received in the valve seat member 65 to open and close a valve bore 66 therein. The valve seat member 65 defines an inlet chamber 68 in a smaller diameter portion of the stepped cylinder bore 64 and an oulet chamber 69 in a larger diameter portion of the bore 64- Both the chambers 68 and 69 communicate with each other through the valve bore 66. The inlet chamber 68 communicates with the control hydraulic oil chamber 18 in the modulator 17 through an oil passage 70, while the outlet chamber 69 communicates with the inlet chamber 31 in the hydraulic pump 16 through an oil passage 16. Eventually, the outlet chamber 69 communicates with the oil reservoir 19.

Referring to Figs.4 and 5, the wheel angular deceleration sensor_21 comprises a flywheel 72 rotated from the front wheel 2f through the speed increasing device 45, a cam mechanism 73 for converting an overrunning of the flywheel 72 into an axial displacement, and an output lever mechanism 74 capable of operating the pressure discharge valve 20 -in response to the axial movement of the flywheel 72. These components are all disposed within the casing 22.

The speed increasing device 45 is comprised of a cuplike input member"75 disposed within the casing 22 with its opened end turned toward the outer case 22b, a ring gear 76 formed at the opened end of the input member 75, a first planetary gear 78 1 secured to an inner end of the cam shaft 26 and meshed with the ring gear 76, a single or a plurality of second planetary gear or gears 78 2 which is or are supported on a stub shaft 77 projecting on the end wall of the outer case 22b through a bearing Ill and which is or are meshed with the ring gear 76, a sun gear 79 concurrently meshed with both the first and second planetary gears 78 and 78 2' and an output shaft 42 spline-connected to the sun gear 79. The output shaft 42 is supported on the cylindrical shaft 24 through an angular contact bearing 85 so that it cannot be axially moved.

The seco nd planetary gear 78 2 is intended to provide a proper meshing of the first planetary gear 78 1 with the ring gear 76 and the sun gear 79 to maintain the concentricity of the ring gear 76 and the sun gear 79 and insure a transmitting effect of the speed increasing device 45, but can be omitted when the supporting rigidity of the ring gear 76 and the sun gear 79 is sufficiently high.

The input member 75 is supported on the cylindrical shaft 24 through ball bearings 123 at a boss 75a formed at a central portion of its end wall, so that it cannot be axially moved. The boss 75a is connected to the hub 8 of the front wheel 2f through an overload clutch 128.

The.overload clutch 128 comprises a clutch pin 126 slidably received in each of a plurality of support holes (only one of which is shown in Fig.4) surrounding the center of the boss 75a of the input member 75 and opened in an outer surface thereof, and a spring 127 mounted in compression in the support hole 125 for resiliently biasing the clutch pin 126 to project from the outer surface of the boss 75a. The clutch pin 126 has its leading semi-spherical end 126a engaged in a tapered clutch hole 124 in an end face of the hub 8. Thus, when a rotating torque greater than a specified value is applied between the hub 8 and the input member 75, the clutch pin 126 is moved away from the clutch hole 124 against a set load of the spring 127, thereby preventing the transmission of an overload.

The flywheel 72 is disposed to surround the output shaft 42 and is connected to the output shaft 42 through the cam mechanism 73 and a clutch arrangement 80.

Referring to Figs.4, 6 and 7, the cam mechanism 73 is comprised of a drive cam plate 82 supported on the output shaft 42 through angular contact bearings 86 and 861 so that it cannot be axially moved, a follower or driven cam plate 83 integrally formed on the flywheel 72 and opposed to the drive cam plate 82, and a plurality of thrust balls 84, 84 - anuularly arranged between both the cam plates 82 and 83.

Opposed portions of the drive and driven cam plates 82 -and 83 are formed with tapered surfaces f I and f 2 increasing in diameter toward a constant-torque clutch 80a which will be described hereinafter, respectively. Each of the tapered surfaces f I and f 2 is provided with a plurality of cam recesses 82a, 83a which are engaged by the thrust balls 84, 84 - 13 20.

The recess 82a of the drive cam plate 82 has its bottom surface inclined to decrease in depth in a direction R of rotation of the output shaft 42, while the recess 83a of the follower cam plate 83 has its bottom surface inclined to increase in depth in such rotational direction R. Hence, in a normal case where the drive cam plate 82 drives the follower cam plate 83, the thrust ball 84 engages the deepest portions of the two cam recesses 82a and 83a to merely transmit the rotating torque received by the drive cam plate 82 from the output shaft 42 to the follower cam plate 83, there being no relative rotation between the two cam plates 82 and 83. On the other hand, however, when the follower cam plate 83 overruns the drive cam plate 82, a relative rotation occurs between the cam plates 82 and 83, causing the thrust ball 84 to roll along the inclined bottom surfaces of the cam recessees 82a and 83a. This applies a thrust force to the cam plates 82 and 83, thereby axially displacing the follower cam plate 83 away from the drive cam plate 82.

The engagement of thrust balls 84 in the cam recesses 82a and 83a provided on the tapered surfaces f I and f 2 of the drive and follower cam plates 82 and 83 as described above enables the drive cam plate 82 to support the follower cam plate 83 through the thrust balls 84 in thrust and radial directions, maintaining the flywheel 72 out of contact with the output shaft 42. Therefore, it is not necessary to provide lubrication between the output shaft 42 and the flywheel 72.

The clutch arrangement 80 is comprised of the constant- 14 torque clutch 80a and a unidirectional variable-torque clutch 80b which are interposed in parallel -to each other between the output shaft 42 and the drive cam plate 82.

The constant-torque clutch 80a includes an annular friction clutch plate 87 which has its inner peripheral edge slidably spline-connected to the output shaft 42. A lining 87a is added to the friction clutch plate 87 and opposed to the drive cam plate on the opposite side from the follower cam plate 83. To urge the lining 87a into engagement with the drive clutch plate 87, a clutch spring 99 is mounted in compression between the friction clutch plate 87 and a seat plate 98 locked to the end of the output shaft 42.

The unidirectional variable-torque clutch 80b, as shown in Fig.8, is comprised of a clutch inner 101 fitted over the output shaft 42, a clutch outer 102 relatively rotatably fitted to an inner peripheral surface of a boss of the drive cam plate 82, and a plurality of sprags 103, 103 --arranged circumferentially between opposed peripheral surfaces of the clutch inner and outer 101 and 102. The sprags 103 are held by a retainer 104 for righting and tilting-down movements. The clutch outer 102 has a single cut 105 so that it may be radially expanded and normally, it is maintained in contact with the boss inner surface of the drive cam plate 82 by its own light resilient expanding force. The sprags 103, 103 --- are tilted down and moved away from the clutch inner and outer 101 and 102 (into a clutch-off condition) when the clutch outer 102 is intended to rotate-more rapidly than the clutch inner 161 in a direction of rotation of the output shaft 42, and are righted to provide an expanding 1 Q!.:

force to the clutch outer 102 when the clutch inner 101 is intended to rotate more rapidly than the clutch outer 102. An increasing of the expanding force for the clutch outer 102 results in an increased friction force between the clutch outer 102 and the drive cam plate 82.

The flywheel 72 has a boss 72a projecting toward the side opposite from the cam mechanism 73. An urging ring- 89 for operating the output lever mechanism 74 is mounted around an inner periphery of the boss 72a through an angular contact bearing 88. The urging ring 89 is also disposed so as not to contact with the output shaft 42.

As shown in Figs.4 and 8, the output lever mechanism 74 includes a support post 90 mounted in projection on an inner end face of the outer case 22b at a place intermediate the axle 10 and the pressure discharge valve 20, and a lever 91 supported on a neck portion 90a at a leading end of the support post 90 for swinging movement in an axial direction of the axle 10. The lever 91 is comprised of a first longer arm 91a extending from the support post 90 around the output shaft 42, and a second shorter arm 91b extending from the support post 90 toward the pressure discharge valve 20. An abutment 93 is raised in an angular form on an intermediate portion of the first arm 91a to abut against an outer surface of the urging ring 89.

A control spring 94 is interposed between a leading end of the first arm 91a and the outer case 22b, and a leading end of the second arm 91b is disposed to urge an outer end of the valve member 67 of the pressure discharge valve 20.

A resilient force of the control spring 94 acts on the k lever 91 to urge the abutment 93 of the first arm gla against the urging ring 89 and normally against the valve member 67 of the pressure discharge valve 20 to maintain a valve-closed condition. An urging force received by the urging ring 89 from the control spring 94 acts on the drive can plate 89 through the flywheel 72, the follower cam plate 89 and the thrust balls 84, thereby applying an approaching force to the cam plates 82 and 83 and applying a frictionengaging force to the friction clutch plate 87 and the drive cam plate 82.

The friction-engaging force is set such that a slippage is produced in the friction clutch plate 87 when a rotating torque greater than a given value acts between the friction clutch plate 87 and the flywheel 72.

For preventing the falling of the control spring 94 and for restricting the path of swinging movement of the lever 91, a guide rod 100 is fixedly mounted on the outer case 22b and passed through the control spring 94 and the lever 91.

The support shaft 90 is constructed in an adjustable manner so that a proper gap g may be provided between a fulcrum portion of the support shaft 90, i.e., a base of the neck portion 90a and the lever 91 to assure the closed state of the pressure dischar_qe valve 20 provided by the second arm 91b even during oscillatign of the lever 91. More specifically, the support shaft 90 has a threaded portion 90b threadedly connected into a side wall of the outer case 22b to project outside the side wall, with a lock nut 92 threadedly fitted over an outer end of the threaded portion 90b. Thus, if the lock nut 92 is loosened to properly turn 17 the threaded portion 90b, the effective length of the support shaft 90 can be increased or decreased, so that the fulcrum point of the support shaft 90 for the lever 91 can be adjusted. After adjustment, tightening of the lock nut 92 allows the support shaft 90 to be fixed to the outer case 22b.

The threaded portion 90b and the lock nut 92 are exposed outside the casing 22 and designed to easily perform a maintenance by use of a special tool. Specifically, the lock nut 92 is formed into a circular shape and provided at its end face with a tool groove 95 which can be engaged by only a special screw driver which bypasses an outer end of the threaded portion 90b.

The tool groove 96 of the threaded portion 90b may be a usual one which may be engaged by a usual screw driver.

An 0-ring 97 for sealing the outer case 22b is mounted on a portion of the support shaft 90 which is passed through the outer case 22b.

The operation of this embodiment will be described below.

When a vehicle is travelling, the rotation of the front wheel 2f is transmitted from the hub 8 through the overload clutch 128 to the input member 75 and further to the output shaft 42 with increases in speed provided by the ring gear 76, the first and second planetary gears 78 1 and 78 2 and the sun gear 79, and then, via the friction clutch plate 87 and the cam mechanism 73 to the flywheel 72 to drive the latter.

Hence, the flywheel 72 rotates at a speed higher than that of the front wheel 2f and consequently, the flywheel 72 has - 18 is a large rotating inertia. At the same time, the cam shaft 26 and the speed meter 51 are also driven by the rotation of the first planetary gear 78 l' Now, if the front master cylinder 5f is operated to brake the front wheel 2f, an output hydraulic pressure therefrom is transmitted, sequentially via the upstream pipe 15a of the hydraulic pressure conduit 15, the hydraulic oil chamber 36 in the hydraulic pump 16, the input hydraulic oil chamber 54 in the modulator 17, the valve chamber 58, the valve bore 59, the output hydraulic oil chamber 55 and the downstream pipe 15b of the hydraulic pressure conduit 15 to the front brakes 3f, 3f, thereby applying a braking force to the front wheel 2f.

On the other hand, in the hydraulic pump 16, the output hydraulic pressure from the front master cylinder 5f has been introduced into the hydraulic oil chamber 36 and hence, a reciprocal motion is provided to the pump piston 28 by an urging effect provided by such hydraulic pressure on the operation piston 29 and a lift effect provided by the eccentric cam 26a on the push rod 27. In an intake stroke in which the pump piston 28 moves toward the push rod 27, the intake valve 38 is opened, permitting an oil in the oil reservoir 19 to be drawn from the conduit 37 through the inlet chamber 31 into the pump chamber-35. In a discharge stroke in which the pump piston 28 moves toward the operation piston 29, the unidirectional sealing member 39 is operated to be opened, permitting the oi.1 in the pump chamber 35 to be pumped into the outlet chamber 32 and further through the oil passage 57 into the control R 19 1 hydraulic oil chamber 18 in the modulator 17. When each of the'pressures in the outlet chamber 32 and in the control hydraulic oil chamber 18 is increased up to a predetermined value, the pump piston 28 is held at the location ofabutment against the plug 34 by the pressure in the outlet chamber 32.

Now, the control hydraulic oil chamber 18 in the modulator 17 is originally placed out of communication with the oil reservoir 19 by closing of the pressure discharge valve 20, so that the hydraulic pressure supplied from the hydraulic pump 16 into the control hydraulic oil chamber 18 acts directly on the pressure-reducing piston 46 to force it to its retreated position, and the valve-opening rod 62 maintains the valve member 60 opened, permitting passing of the output hydraulic pressure from the front master cylinderSf therethrough.

Accordingly, in a usual braking condition, the braking force applied to the front brakes 3f, 3f is proportional to the output hydraulic pressure produced from the front master cylinder 5f.

When an angular deceleration is produced in the front wheel 2f with such braking, the flywheel 72 which has sensed this angular deceleration intends to overrun relative to the output shaft 42 by an inertia thereof. Specifically, it intends to produce a relative rotation of the both cam plates 82 and 83. In a stage free from a locking possibility of the front wheel 2f, however, the angular deceleration of the front wheel 2f is lower, and the relative rotation of the cam plates 82 and 83 is restrained by a set load of the - 20 control spring 94 for biasing the lever 91 toward the cam plates 82 and 83.

However, when the front wheel 2f is about to become locked due to an excessive braking force or a reduction in friction coefficient of a road surface, a rapid increase in angular deceleration of the front wheel 2f therewith causes the relative rotation to be produced in the cam plates 82 and 83, so that a thrust force generated by rolling of the thrust balls 84 exceeds the set load of the control spring 94 to provide an axial displacement to the follower cam plate 83 and the flywheel 72. Then, the lever 91, after reduction of the gap g between the support shaft 90, swings about the support shaft 90 to compress the return spring 94, so that the second arm 91b of the lever 91 is moved-away from the valve member 67. Consequently, the pressure discharge valve 20 is brought into a closed state.

When the rotating torque by the inertia of the flywheel 72 exceeds a specified transmission torque of the friction clutch plate 87 after axial displacement of the flywheel 72, a slippage is produced between the drive cam plate 82 and the friction clutch plate 87, allowing the flywheel 72 to be overrun relative to the output shaft 42. At this time, the unidirectional variable-torque clutch 80b is brought into the clutch-off state and hence, the overrunning of the flywheel cannot be prevented in any way. Accordingly, by setting the transmission torque of the constanttorque clutch 80a at a smaller level, a sufficient valve-closing time for the pressure discharge valve 20 can be provided to accomodate to a road surface of a lower friction 1 21 - 1 coef f icient When the pressure discharge valve 20 becomes opened, the hydraulic pressure in the control hydraulic oil chamber 18 is discharged into the oil reservoir 19 via the oil passage 70, the inlet chamber 68, the valve bore 66, the outlet chamber 69, the oil passage 71, the inlet chamber 31 in the hydraulic pump 16, and the conduit 37, so that the pressure reducing piston 46 is moved toward the control hydraulic oil chamber 18 by the hydraulic pressure in the output hydraulic oil chamber 55 against the force of the return spring 48, thereby retreating the valve-opening rod 62 to close the valve member 60, thus cutting off the communication between the input and output hydraulic oil chamber 54 and 55 and increasing the volume of the output hgydraulic oil chamber 55. As a result, the hydraulic braking pressure acting on the front brakes 3f, 3f is reduced to control the braking force for the front wheel 2f.

When the speed of the front wheel 2f approaches to the vehicle speed with the control of the braking force, the output shaft 42 is brought into an attitude to drive the flywheel 72. Hence, in the unidirectional variabletorque clutch 80b, righting of the sprags 103, 103 --- cause the clutch outer 102 to be expanded, so that the friction force between the clutch outer 102 and the drive cam plate 82 increases according to the driving torque of the output shaft 42. Thus, the transmitted torque from the output shaft 42 to the drive cam plate 82 is a sum of the transmision torque of the constant- torque clutch 80a and the transmission torque of the unidirectional variable-torque - 22 clutch 80b. Accordingly, however small the transmission torque of the constant-torque clutch 80a is, the speed of rotation of the drive cam plate 82 and thus the flywheel 72 can be quickly restored to that of the output shaft 42 (see Fig.9). As a result, the thrust force of the cam mechanism 73 on the lever 91 is releasd, permitting the lever 91 to be returned to the original position by the force of the control spring 94 to bring the pressure discharge valve 20 into the closed state.

When the pressure discharge valve 20 has been closed, the hydraulic pressure discharged from the hydraulic pump 16 is immediately confined in the control hydraulic oil chamber 18, and the pressure-reducing piston 46 is retreated toward the output hydraulic oil chamber 55 to boost the chamber 55, thus recovering the braking force.

When the front wheel_2f is about to become locked again with recovery of the braking force, the above-described operation is repeated, but restoring of the rotation of the flywheel 72 to the speed of rotation of the output shaft when recovery of the rotation of the front wheel 2f is quickly performed. Therefore, even in second and subsequent antilock controllings, the opening point for the pressure_ discharge valve 20, i.e., the controlling point for the braking force is regularized, and the rate of slippare is stabilized, enabling the anti-lock controlling to be always efficiently conducted.

41 1 1 It is to be clearly understood that there are no particular features of the foregoing specification, or of any claims appended hereto, which are at present regarded as being essential to the performance of the present invention, and that any one or more of such features or combinations thereof may therefore be included in, added to, omitted from or deleted from any of such claims if and when amended during the prosecution of this application or in thefiling or prosecution of any divisional application based thereon. Furthermore the manner in which any of such features of the specification or claims are described or defined may be amended, broadened. or otherwise modified inany manner which falls within the knowledge of a person skilled in the relevant art, for example so as to encompass, either implicitly or explicitly, equivalents or generalisations thereof.

24 - 4

Claims (2)

1. Claims: 1. An anti-lock controller for a vehicle, comprising a flywheel

   rotatably and axially displaceably disposed to surro.und an output shaft which is driven in operative association with a wheel to be braked by a wheel brake, a clutch arrangement adapted to normally transmit a driving torque of said output shaft to said flywheel and to slip so as to permit overrunning of said flywheel when an angular deceleration greater than a given value is produced in the wheel during braking, a cam mechanism operated in response to the overrunning of said flywheel to provide an axial displacement to said flywheel, said clutch arrangement and said cam mechanism being interposed between said output shaft and the flywheel, and a modulator operated to control the braking force of said wheel brake by the axial displacement of said flywheel, wherein said clutch arrangement is constructed so that the transmission torque is smallest when said flywheel overruns relative to said output shaft, and-the transmission torque is increased, depending upon the driving torque of said output shaft, when said output shaft drives said flyweel.
2. 2. An anti- lock controller for a vehicle according to claim 1, wherein said clutch arrangement is comprised of a constant-torque clutch which is always constant in torque,and a unidirectional variable-torque clutch which is brought into a clutch-off state when said flywheel overruns relative to said output shaft, and which has a transmission torque increased depending upon the driving torque of said output shaft when said output shaft drives said flywheel, said i' f r.

   - clutches being interposed in parallel between said output shaft and said-flywheel.

   Published 1989 at The Patent Office, State House, 56'71 High Holborn, LondanWClR4TP. Further copies maybe obtained from The Patent Office. Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con. 1/87