TECHNICAL FIELD
[0001] 'The present subject matter relates generally to a two-or three-wheeled vehicle and more particularly, but not exclusively, to an antilock braking system (ABS) for the two-or three-wheeled vehicle.
BACKGROUND
[0002] Generally, Anti-lock braking system (ABS) are used in automobiles as safety devices. The ABS ensures that the wheels consistently maintain tractive contact with the ground surface when brakes are applied by the driver of the automobile. In general, ABS pervents the wheels of the vehicle from being locked up thereby ensuring the wheels never cease to rotate helping in avoiding skidding of the wheels. Further, the ABS also offers improved vehicle control and reduces distance generally taken to stop the vehicle on a dry or slippery surface when the ; brakes are applied by the driver. [0003] Conventionally, ABS units are provided in bigger automobiles, for example, cars that run in considerably high speeds. However, as the safety norms to be followed in automobiles has increased substantially over the last few years, the need for ABS units in almost all type of automobiles including two-wheeled vehicles was found very much unavoidable, for example, the European Commission has imposed a mandatory legislation for all new motorcycles above 125cc to include an ABS unit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The detailed description is described with reference to the accompanying
figures. In the figures, the left-most digit(s) of a reference number identifies the
figure in which the reference number first appears. The same numbers are used
throughout the drawings to reference like features and components.
[0005] FIG. 1(a) illustrates a scooter type vehicle, in accordance with an
embodiment of the present subject matter.
[0006] FIG. 1 (b) illustrates a rear brake assembly of a straddle type vehicle, in
accordance with an embodiment of the present subject matter.
[0007] FIG. 2 (a) illustrates a wheel assembly for a two-wheeled vehicle, in
accordance with an embodiment of the present subject matter.

[0008] FIG. 2 (b) illustrates a brake panel assembly for a two-wheeled vehicle,
in accordance with an embodiment of the present subject matter.
[0009] FIG. 3 (a) illustrates an antilock braking system (ABS), in accordance
with a first embodiment of the present subject matter.
[00010] FIG. 3 (b) illustrates an antilock braking system (ABS), in accordance
with a second embodiment of the present subject matter.
DETAILED DESCRIPTION
[00011] Generally motorcycles are known to include antilock braking system (ABS) units. On such motorcycles, the ABS unit continuously monitors the speed of the wheels using wheel speed sensors. This enables the ABS unit to quickly act in case one of the wheel locks during slippery conditions by controlling the braking pressure delivered to the wheels thereby optimizing the braking effect. This largely enables maintaining the maneuverability and vehicle stability during running conditions, especially in adverse running conditions. [00012] Generally, during wheel lock-up condition, control of the two-wheeled vehicle is affected as the engine inertia tends to delay the wheels' ability to roll-up to vehicle speed. Further, during such wheel lock-up condition, the wheels of the two-wheeled vehicle starts to skid thereby increasing braking distance and retarding steerability of the vehicle. Wheel lock-up condition may cause panic in rider's mind leading to over-application of the brakes, which eventually causes the rider to lose control over the vehicle.
[00013] However, in case of a vehicle fitted with an ABS unit, the impending wheel lockup is detected and the ABS unit, generally a hydraulic electronic control unit (HECU) enables control of braking operation, for example, may initiate an operating sequence to hold, increase and decrease brake pressure necessary to bring the vehicle back to normal braking condition. Such ABS units generally takes over when ever panic and human error occurs. Under most circumstances, two-wheelers fitted with such HECU units ensures antilock braking by not only improving stopping distance under wheel lock-over conditions, but simultaneously allowing the rider of the two-wheeled vehicle to retain control and steerability,

[00014] The conventionally known ABS fitted two-wheelers, includes several other:components other than an HECUMInl for optimally functioning the ABS under panic braking conditions. Such other components includes a hydraulic modulator device that houses the HECU unit, plurality of bundy tubes connecting the hydraulic modulator with brake fluid dispensing cylinders, master cylinder assembly, one or more disc plates capable of being fitted to front and/or rear wheels, caliper assembly fitted to each disc plate, and brake fluids. [00015] In most two-wheeled vehicles, mounting of HECU unit and the other associated components is challenging and has not been as simple as it is in the case of a four-wheeled vehicle. This is because, a two-wheeled vehicle has a body frame that do not completely cover all the components of the vehicle and many components are exposed outside atmosphere and are not covered. Moreover, choosing an optimal mounting location for the HECU unit is a challenge because the motorcycle, for example, a step-through type vehicle is already packaged with several components and it is often difficult to accommodate the HECU unit. Further, there is always a challenge to accommodate the HECU unit in a location that is less exposed to outside atmosphere, for example, any location that prevents entry of dirt particles or other pollutants.
[00016] Moreover, addition of such components associated with ABS functionality to two-wheeled vehicles tend to increase the gross weight of the two-wheeled vehicle. More particularly, in two-wheeled vehicles below a certain engine size arid capacity, for example, in the segment of under 150cc of engine size, the addition of such components could eventually make such two-wheeled vehicles to add unnecessary weight and which in turn could increase the cost. [00017] Further, the conventionally known ABS units are deviced to work suitably with two-wheeled vehicles containing front and/or rear disc brake assemblies. Though there are no hard and fast rules as to decide on which type of two wheeler to be provided with a disc brake assembly, not all two-wheeled vehicles are provided with brake assemblies controlled by hydraulically operated disc plates. Such decisions are generally based on one or more factors, for example, the engine capacity, wheel base, wheel diameter, maximum power output, segment of riders and so on. Thus, under stringent regulatory conditions, when all segment of vehicles are mandated to include certain safety components

such as ABS units, it is pertinent that all types of two-wheeled vehicles, with or without'disc brake assemblies to include antilock braking abilities. [00018] The present subject matter is aimed at overcoming the above mentioned problems. In an embodiment, the present subject matter relates to a stepthrough type vehicle. In an embodiment, the present subject matter provides an antilock braking system (ABS) comprising one or more actuator unit(s), one or more wheel speed sensor(s) functionally connected and controlled by at least one electronic . control unit (ECU). In another embodiment, the ABS of the present subject matter is capable of being provided to a straddle type two-wheeled vehicle, a three-wheeled vehicle and the like.
[00019] In an embodiment, the present subject matter provides an ABS for two-or three-wheeled vehicle provided with drum brake assemblies. In one embodiment, the ABS of the present subject matter involves least complexity and is capable of being accommodated on any two-or three-wheeled vehicle, both at the time of manufacturing and as an accessory fitment. The ABS of the present subject matter in addition to providing an enhanced flexibility, ensures improved safety for vehicle with drum brake assemblies, for instance, even under conditions when the brake shoes wear out. The cost involved in providing the ABS of the present subject matter is substantially less as it involves least number of parts and are primarily operated mechanically and/or electro mechanically. Moreover, the ABS of the present subject matter is easy to assemble as it includes components that are less in complexity.
[00020] Typically, the one or more wheel speed sensor of the ABS provides information to the one or more ECU when a condition, for example, a wheel lock is impending. In an embodiment, the ABS includes one or more actuator units, for example, a linear actuator mounted on a brake panel anchor plate and connected to a brake cam lever suitably. In another embodiment, the one more actuator units can be a rotary actuator including a stepper motor, or a servomotor or the like. In yet another embodiment, the one or more actuator units can be selected from the group consisting of a hydroelectric, electro-pneumatic, and electric actuators. In an embodiment, the one or more actuator units are supported by means of one or more spring elements.
[00021] In a first embodiment, the linear actuator is capable of pulling or pushing the brake cam lever. For instance, by pulling or pushing the brake cam

lever, the linear actuator augments or opposes a brake input force that is transmitted from the rider input point, for instance, a brake pedal or a brake hand lever to one or more brake shoes disposed on a brake panel assembly. In an embodiment, during normal braking operation, the ABS of the present subject matter ensures that the linear actuator does not intervene in the normal functioning of the front and rear brake assemblies of the two-or three-wheeled vehicle. [00022] Further, in one embodiment, when the ECU receives signals from the one or more wheel speed sensor(s) indicating impending wheel lock, the ABS of the present subject matter includes the ECU to suitably control the one or more linear actuators to perform one or more actions. For instance, a first action of the linear actuator is capable of initially locking the brake cam lever in a first position and prevents any further transfer of rider's brake input force to the brake shoes. In an embodiment, the first action of the linear actuator is a hold action. The ABS of the present subject matter enables the linear actuator to perform a second action, for example, a release action, when the linear actuator opposes and releases the braking force exerted by the brake shoes by moving the brake cam lever in a direction opposite to the braking direction. In another embodiment, the ABS of the present subject matter enables the linear actuator to perform a third action, for example, an augmentation action, when the linear actuator partially allows further increase in braking force through the brake cam lever when the ECU determines that the impending wheel lock situation has improved.
[00023] In yet another embodiment, the one or more actuator unit(s) of the ABS of the present subject matter includes a rotary actuator, for instance, a stepper motor or servomotor. In an embodiment, the rotary actuator of the present subject matter is mounted on the brake panel anchor plate and functionally connected to the brake cam assembly. In an embodiment, the rotary actuator of the present subject matter is operatively connected to the ECU, which receives one or more signals from the one or more wheel speed sensor(s):
[00024] In an embodiment, during normal braking operation, the rotary actuator of the ABS, allows the brake cam actuated by means of actuation of a brake cam through a brake pedal or a brake hand lever to push a plurality of brake shoes apart from each other and against a brake drum.
[00025] In an embodiment, the rotary actuator is activated to hold the brake cam in position by means of holding torque to prevent the brake cam from further

pushing the plurality of brake shoes thereby limiting the brake torque, whenever the ECU receives wheel speed signal indicating impending wheel lock-up. Further, in an embodiment, the activation of the rotary actuator of the AB.S enables avoiding wheel locking tendency. In another embodiment, if the wheel locking tendency is not substantially reduced, the rotary actuator enters a second phase, for example, a release phase, during when, the rotary actuator is activated to apply an opposite-torque on the brake cam to limit the pushing force generated by the plurality of brake shoes against the brake drum. This ensures that the brake torque is reduced to avoid wheel-locking tendency.
[00026] In another embodiment, when the ECU receives the signal that the wheel speed is recovered to vehicle speed, the rotary actuator of the ABS enters a third phase, for example, a braking phase, during when the rotary actuator is activated to reduce the applied torque substantially closer to its holding torque, thereby allowing a substantial amount of braking. Further, the rotary actuator is also activated to release its holding-torque. This allows the brake cam to apply maximum braking force, if the wheel remains in unlock condition. In an embodiment, the ABS ensures that the actuation cycle continues until the vehicle is brought to a complete halt.
[00027] These and other advantages of the present subject matter would be described in greater detail in conjunction with the figures in. the following description.
[00028] FIG. 1(a) illustrates a scooter type vehicle 100, in accordance with an embodiment of the present subject matter. In an embodiment, the scooter type vehicle 100 includes step-through structure enabling easy access to the rider. The step-through structure of the vehicle 100 includes a chassis frame structure 112 having a main tube 130 downwardly disposed from a handlebar assembly. In an embodiment, the vehicle 100 includes an engine 126 rearwardly disposed underneath a seat structure of the vehicle 100. In an embodiment, the engine 126 is a single cylinder four stroke horizontal engine 126 disposed substantially adjoining a rear wheel 108. Further, in one embodiment, the head tube of the chassis structure 112 is disposed substantially downward and forward towards a front wheel 124, with a front fork assembly 132 receiving the head tube. In an embodiment, the front wheel 124 includes a brake panel assembly 104. In an embodiment, the brake panel assembly 104 includes a drum brake assembly

having a plurality of brake shoes enabling retarding vehicle motion whenever the brake forces are supplied by the rider through actuation of a hand brake lever or a brake pedal. In an embodiment, a plurality of brake cables 128 are appropriately connected to the brake panel assembly 104 to enable actuation of brake forces when the rider actuates the hand brake lever or the brake pedal. [00029] FIG. 1 (b) illustrates a straddle type vehicle 101, in accordance with an embodiment of the present subject matter. In an embodiment, the straddle type vehicle 101 of the present subject matter includes a rear brake assembly 102 coupled to the rear wheel 108. In an embodiment, the rear wheel 108 of the vehicle is decelerated and stopped when necessary by the rider of the vehicle with the help of the rear brake assembly 102. In an embodiment, the rear brake assembly 102 is a drum brake assembly. For example, in vehicles, especially in motorcycles, the rear brake assembly 102 involves the rear brake assembly 102 that is controlled by a rear brake actuating member that is foot operated. In another embodiment, the rear brake assembly 102 is controlled by the hand brake lever. For example, the rear brake actuating member is connected to the rear wheel 108 through the rear brake assembly 102. In one embodiment, the rear brake assembly 102 is connected to the chassis frame 112 of the vehicle. The chassis frame 112 is provided with a rider footrest that enables the rider to comfortably rest the foot on the rider footrest and operate the rear brake actuating member to decelerate the vehicle.
[00030] In one embodiment, the rear brake assembly 102 is mounted on the chassis frame 112 on one end and to the brake panel assembly 104 on the other end. In an embodiment, the brake panel assembly 104 is mounted on to a wheel hub 106 of the rear wheel 108. In an embodiment, the wheel hub 106 houses a rear axle (not shown) that is driven when the vehicle is in motion. For example, coupling the brake panel assembly 104 to the wheel hub 106 ensures that the braking forces from the rear brake assembly 102 are transmitted to the wheel hub 106 by the brake panel assembly 104 to achieve the required deceleration of the vehicle.
[00031] In one embodiment, the brake panel assembly 104 is mounted with a fixed chassis member 110, for example, a swing arm 110 for transferring braking forces received from the rear brake assembly 102 to the chassis frame 112. In an embodiment, when the rider operates the rear brake actuating member, braking

forces are transmitted by the rear brake assembly 102 to the brake panel assembly 104, which in turn is transmitted to the wheel hub 106 for effecting vehicle deceleration. For example, the brake panel assembly 104 includes a brake panel, which along with the wheel hub 106 forms a space therebetween that accommodates a plurality of brake shoes 116. The brake shoes 116 establish contact with the wheel hub 106 whenever braking forces are received to effect the required deceleration.
[00032] FIG. 2 (a) illustrates a wheel assembly 124 for a two-wheeled vehicle, in accordance with an embodiment of the present subject matter. In an embodiment, the wheel assembly 124 is a front wheel assembly 124. The wheel assembly 124 includes the wheel hub 106 that is disposed centrally enabling mounting of the brake panel assembly 104. The construction of the brake panel assembly 104 is described in reference to Fig. 2 (b). The brake panel assembly 104 includes a brake cam lever 122 that is capable of being actuated whenever the rider applies brake forces for decelerating the vehicle. The brake cam lever 122 is capable of further actuating a brake cam 120 that causes the brake to be applied on the front or rear drum brake assembly of the vehicle.
[00033] FIG. 2 (b) illustrates a brake panel assembly 104 for a two-wheeled vehicle, in accordance with an embodiment of the present subject matter. In one embodiment, the brake panel assembly 104 includes a cam lever 122 that is capable of actuating a cam 120. In one embodiment, the cam lever 122 is coupled to the rear brake assembly 102 of the vehicle 100 at one end and to the cam 120 at another end. For example, in one embodiment, the rear brake assembly 102 transmits braking forces to the cam lever 122 causing the cam lever 122 to actuate. The actuation of the cam lever 122 causes angular displacement of the cam lever 122 towards an axial center line of a brake panel 114 of the brake panel assembly 104. For example, when the rider of the vehicle operates the rear brake actuating member (shown in Fig. 2), the rear brake assembly 102 forces the cam lever 122 to rotate in a direction towards a front side of the vehicle, and when the rear brake actuating member is released by the rider, the rear brake assembly 102 releases the cam lever 122 to rotate in a direction away from the front side of the vehicle.
[00034] In one embodiment, the actuation of the cam lever 122 by the rear brake assembly 102 causes a corresponding actuation of the cam 120 that is coupled to

the cam lever 122 .and disposed through a circumferential opening on the brake panel 114/F^exaMpife;. when the cam lever 122 is actuated, the cam 120 rotates in an anti-clockwise direction, and when the cam lever 122 is released, the cam 120 rotates in a clockwise direction. In an embodiment, the anti-clockwise direction rotation of the cam 120 causes the cam 120 to displace a plurality of brake shoes 116 towards an inner surface (not shown) of the wheel hub 106. [00035] In one embodiment, the outward displacement of the plurality of brake shoes 116 by the anti-clockwise rotation of the cam 120 causes the plurality of brake shoes 116 to establish contact with the inner surface of the wheel hub 106 and thereby enabling the rear brake assembly 102 to effect the rotating wheel hub 106 to decelerate thereby bringing the vehicle to a temporary halt. In an embodiment, the displacement of the plurality of brake shoes 116 are controlled by a plurality of brake shoe springs. In one embodiment, the plurality of brake shoes 116 are fixed centrally to the brake panel 114 enabling the brake shoes 116 to rotate in respect of the fixed joint on the brake panel 114. [00036] In one embodiment, each brake shoe of the plurality of brake shoes 116 includes a brake lining 118. For example, the brake lining 118 is generally made of any material that is rigid and exhibits maximum resistance to heat. Further, the material of the brake lining 118 also has high coefficient of friction. In an embodiment, for example, the brake lining 118 is fixed on each brake shoe 116 using any generally known adhesive. In an embodiment, the material of the brake lining 118 however rigid and tough it may be tends to wear over prolonged usage. [00037] FIG. 3 (a) illustrates an antilock braking system (ABS) 300-1, in accordance with a first embodiment of the present subject matter. The ABS 300-1 of the present subject matter, includes a first actuator unit 302 mounted on a brake panel anchor plate 304 of the brake panel assembly 104. The first actuator unit 302 is communicatively connected to a first ECU (not shown) in such a manner that the first actuator unit 302 is capable of sending and receiving signals to and from the first ECU. Similarly, the first ECU unit is communicatively coupled with a first wheel speed sensor unit (not shown) for receiving signals whenever an impending wheel lock-up is detected by the wheel speed sensor unit In an embodiment, the first ECU unit sends appropriate control signals to the first actuator unit 302 whenever the impending wheel lock-up signal is received from the wheel speed sensor unit. Similarly, whenever the wheel speed sensor unit

sends an improvement signal after overcoming the wheel lock-up condition, the first ECU unit receives such signal and sends appropriate control command to the first actuator unit 302 for allowing normal braking action.
[00038] In an embodiment, the first actuator unit 302 is a linear actuator 302. The linear actuator 302 is mounted on to the brake panel anchor plate 304 by means of one or more actuator mounting1 elements 310. In an embodiment, the linear actuator 302 is coupled to the brake cam lever 122 through an actuator link element 308. The actuator link element 308, in an embodiment, is movably hinged to the brake cam lever 122 at a hinge joint 306. In an embodiment, during normal braking conditions, the rider of the vehicle applies brake forces through the hand brake lever or the brake pedal. The actuation of the hand brake lever or the brake pedal causes application of brake forces transmitted through one or more brake cables 128. In an embodiment, the one or more brake cables 128 is called as a first brake actuation component. In another embodiment, the brake forces can be transmitted through one or more brake rod(s) instead of the brake-cables 128, especially in case of straddle type two-wheeled vehicles. In this embodiment, the one or more brake rod(s) is also referred to as the first brake actuation component. In an embodiment, the brake cables 128 are connected to a free end of the brake cam lever 122, such that the actuation of the brake cables 128 causes the brake cam lever 122 to angularly displace from its initial position. In an embodiment, the angular displacement of the brake cam lever 122 occurs about the brake cam 120 as the brake cam lever 122 is movably coupled to the brake cam 120. [00039] In an embodiment, during the normal braking condition of the vehicle, the actuator 302 do not intervene in the functioning of the brake cam lever 122 and allows the actuation of the brake cam 120 by the brake cam lever 122 that leads to centripetal displacement of one or more brake shoes 116. The displacement of the brake shoes 116 causes the brake lining 118 to establish contact against an inner surface of the brake drum.
[00040] In an embodiment, if the wheel lock-up condition has not reduced beyond a predetermined limit, the first ECU continues to send wheel lock prevention signals to the actuator 302 that leads the actuator 302 to enter the release phase. During the release phase, the actuator 302 applies an opposite torque on the brake cam lever 122 causing the brake cam lever 122 to displace in a direction opposite to the normal braking direction. This causes the release of the

brake force exerted by the plurality of brake shoes 116. Further, in one embo