TECHNICAL FIELD

[0001] The present subject matter relates to braking system for vehicles and more particularly to a self-cleaning drum brake system.

BACKGROUND

[0002] Generally, two major types of brake systems are used on vehicles, viz. the disc brake system and the drum brake system. The drum brake systems are being used for a long time because of its reliability and its cost-effectiveness. However, there is shift from drum brake systems to disc brake system as the engine capacity and vehicle speeds are increasing, as there is a need for effective braking.

[0003] Still, the drum brake systems are used in vehicles with low speed applications. For example, drum brake system is used in two-wheeled and three-wheeled vehicles, which run at low speeds. The drum brake system comprises a brake drum and at least one brake shoe provided with frictional liner that engages with an inner surface of the brake drum. Either mechanical or hydraulic mechanism is used for actuating the brake for making the liner of the brake shoe to come in contact with the brake drum. Upon actuation, the liners of the brake shoe come in contact with the drum and the frictional contact between the brake shoe and the inner wall of brake drum reduces the rotational speed of the wheel.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The detailed description of the present subject matter is described with reference to the accompanying figures. Same numbers are used throughout the drawings to reference like features and components.

[0005] Fig. 1 illustrates a left side view of an exemplary two-wheeled motor vehicle, in accordance with an embodiment of the present subject matter.

[0006] Fig. 2 (a) depicts a brake drum assembly, in accordance with the embodiment depicted in Fig. 1. [0007] Fig. 2 (b) depicts an enlarged view of a brake drum, in accordance with another embodiment of the present subject matter.

[0008] Fig. 2 (c) depicts another enlarged view of the brake drum, in accordance with the embodiment depicted tin Fig. 2 (b).

[0009] Fig. 3 depicts an enlarged view of another brake drum and a cross sectional view of a brake drum, in accordance with another embodiment of the present subject matter.

DETAILED DESCRIPTION

[00010] Generally, in vehicles, a brake system is used either to slow down or to stop the moving vehicle. In two-wheeled or three-wheeled vehicles, a drum brake system is employed so as to be used as at least one of the braking systems. The drum brake system is installed on either a front wheel or a rear wheel or on all the wheels of the vehicle. Conventionally, a rear wheel is installed with a drum brake system and the users are habituated to actuate the rear wheel brake. This makes the rear brake an essential active safety feature of the vehicle, which is the drum brake system.

[00011] Generally, the drum brake includes a brake drum having inner wall that surrounds the brake shoes. The inner wall is the inner circumferential wall of the brake drum. When the brake is actuated, the liners of the brake shoes come in contact with the inner wall of the brake drum. Frictional forces acting between the brake shoes and the brake drum surface will slow down the rotation of the wheel and eventually bring the wheel to a stop.

[00012] Generally, the brake shoes are provided with the frictional material that provides balance of friction characteristics and brake noise control. The brake noise control is influenced by a formation of debris in the brake drum system. Especially, mud entry into the drum brake system forms a thin layer on either brake shoe or on the inner surface brake drum. Further, wear out of the liners of the brake shoe or of the drum liner or both forms a thin layer on the brake liners. Especially, during the rainy season water may also enter into the brake drum system that mixes up with debris formed due to wear out, thereby forming a layer on the brake liners. Therefore, upon actuation of brake, the brake shoe and brake drum do not come in direct contact with each other due to the formation of debris on the brake liner thereby resulting in poor brake performance and in most of the cases generating brake noise. Generally, frequent cleaning (manual) of the brake shoe liners reduces the aforementioned problems. However, the cleaning process requires removal of the brake shoes from the drum brake assembly, which is tedious, expensive, and time taking.

[00013] Generally, provision of grooves on brake drum surface is known in the art that is used for removal of debris when the vehicle is in running condition. However, the provision of grooves known in the art would remove the brake shoe liner. Subsequently, this results in excess removal of the brake shoe liner from the brake liner surface leading to reduced life of the brake shoe liners. Therefore, frequency of replacement of brake shoes is increased thereby cost and time for the maintenance is affected.

[00014] Thus, there is a need for providing a brake drum system that addresses the aforementioned and other problems of the prior art.

[00015] Hence, it is an object of the present subject matter to provide an improved brake drum system. The brake drum system comprises of a brake drum that is provided with plurality of grooves on the inner circumferential surface of the brake drum. Further, each of the plurality of grooves includes two faces, wherein at least one face of the two faces is having a tapered cross section forming a wedge shaped profile thereby forming a dovetail, a parallelogram, or a trapezoidal shaped groove. Further, the at least one face of the two faces of the groove is a trailing face with respect to direction of rotation of the wheel. The trailing face is disposed at an acute angle with respect to a radial line, wherein the radial line is passing through an inner edge of the trailing face. In other words, the trailing face is having a tapered cross-section forming the dovetail, the parallelogram, or the trapezoidal shaped groove. In one embodiment, any known regular or irregular geometric shaped groove with aforementioned trailing face profile section is provided.

[00016] According to an additional aspect of the present subject matter, the grooves are provided along lateral direction of the brake drum and are obliquely disposed in a helical direction. This enables gradual engagement of the trailing edge of the groove over the brake liner surface so that any chip-off or damage of brake liner surface or of friction material is minimized.

[00017] It is one aspect that the trailing face is at an acute angle with respect to a radial line passing through an inner edge (radially inner edge) of the trailing face. The trailing face is extending obliquely and radially outward from the inner edge in a direction opposite to the direction of rotation) of the brake drum. The trailing face is extending in a direction, which is diagonal to both radially outward direction and a direction opposite to tangential direction of rotation.

[00018] It is an aspect of the present subject matter that the plurality of grooves are disposed at a helix angle, extending in a lateral direction of the brake drum to enable at least a portion of an wedge shaped profile of the groove to be in contact with the brake shoe. It is a feature of the present subject matter that the friction torque variations caused due to improper engagement of grooves with the frictional liners is reduced due to at least a portion of the wedge shaped profile of the groove being in contact with the brake shoe.

[00019] In an embodiment, the grooves are disposed at a helix angle to further improve the contact area.

[00020] It is another aspect of the present subject matter that the trailing face of the groove, which is provided with a dovetail or a parallelogram or a trapezoidal cross section, forms a wedge shaped profile. The wedge comes in contact with the brake shoe liner during actuation of the brake. This enables optimum removal of brake liner from the brake shoe liner surface, to self-clean debris formed on the brake shoe liner of the brake drum system by shaving. Thus, it is another feature of the present subject matter that the wedge shaped profile is optimally provided to avoid any excessive shaving of frictional liner.

[00021] It is another feature of the present subject matter that the plurality of grooves enable reduction of noise, at the same time provides the advantage of improved braking.

[00022]

[00023] Further aspect being, the friction torque variations are also reduced. It is an additional feature of the present subject matter that the brake drum system is capable of self-cleaning of debris or dirt.

[00024] It is an advantage of the present subject matter that the requirement for frequent manual cleaning of the brake drum is eliminated.

[00025] It is another advantage of the present subject matter that a substantially stable frictional coefficient characteristic required for braking are maintained due to continuous cleaning thereby providing improved braking as compared to the conventional system, over life. This also improves drivability and safety.

[00026] It is yet another advantage of the present subject matter that the groove cross section is adaptable depending on the type of vehicle or the terrain where the vehicle is operated, providing flexibility to deploy on different types two-wheeled and threeD wheeled vehicles.

[00027] It is an additional aspect of the present subject matter that in a side view one end of a first groove over laps with at least a portion of an opposite end of an adjacent groove. This aids in maintaining at least a portion of the liner of the brake shoe to be always in contact with at least one groove.

[00028] It is yet another feature of the present subject matter that the essence of the invention is also adaptable to the frictional liners of the brake shoe of the brake drum system. [00029] The aforesaid and other advantages of the present subject matter would be described in greater detail in conjunction with the figures in the following description.

[00030] Fig. 1 illustrates a left side view of a two-wheeled vehicle, in accordance with an embodiment of the present subject matter. The vehicle 100 comprises a frame assembly 105 extending from a front portion towards a rear portion of the vehicle 100. A power unit 110 is mounted on the frame assembly 105 of the vehicle 100. The power unit 110 includes at least one of an internal combustion (IC) engine or a traction motor. In an embodiment, the power unit 110 is a four-stroke single cylinder type IC engine. The power unit 110 includes a starter system. Particularly, the starter system includes an electric start system or a mechanical kick-start system or both that are employed with power unit 110 provided with the IC engine. Through a transmission system 115, a rear wheel 120 is functionally coupled to the power unit 110. The transmission system 115 may include a fixed gear chain drive or continuously variable transmission (CVT) or an automatic manual transmission (AMT) or a multi-speed manual control gearbox system. A rear fender 125 covers at least a portion of the rear wheel 120. Further, one or more rear suspension spring and damper system(s) 130 functionally connect the rear wheel 120 to the frame assembly 105.

[00031] A head tube of the frame assembly 105 is rotatably supported by a steering shaft (not shown). A handle bar assembly 135 is connected to the steering shaft. One or more front suspension spring and damper system(s) 140 rotatably support a front wheel 145 and connect the front wheel 145 to the steering shaft. A front fender 150 covers at least a portion of the front wheel 145. A seat assembly 155 is supported by a portion of the frame assembly 105. The fuel tank 160 is disposed in anterior portion of the seat assembly 155 and upwardly of the power unit 110.

[00032] The vehicle 100 comprises a front drum brake assembly 200 disposed at the front wheel 145 and an actuating lever 170 is provided on the handle bar assembly 135. The rear wheel 120 is provided with another drum brake assembly (not shown) that is actuated by a hand-operated lever or a leg operated lever.

[00033] The vehicle 100 includes a transmission cover 165 covering at least a portion of the transmission 115. Plurality of panels 175A and 175B are disposed longitudinally and downwardly from the seat assembly 155. The internal combustion engine of the power unit 110 will be supplied with air fuel mixture supplied by a fuel tank (not shown) and an air induction system (not shown) that are coupled through a carburetor or a fuel injection system (not shown). The vehicle 100 comprises an auxiliary power source (not shown) that includes a battery or a hydrogen cell or a fuel cell or the like. Further, the traction motor of the power unit 110 is powered by the auxiliary power source mounted on the vehicle 100.

[00034] Further, the vehicle 100 includes various electronic, electrical, and mechanical systems such as a vehicle control unit, an anti-lock braking system, or a synchronous braking system. Also, an electrical starter system, a headlamp 180, and a tail lamp 185 are provided on the vehicle.

[00035] Fig. 2 (a) illustrates a perspective view of the drum brake assembly 200. The drum brake assembly 200 comprises of anchor plate member 205 that supports plurality of brake shoes 210A, 210B. The brake shoes 210A, 210B are arc shaped and each of the shoes 21 OA, 210B are provided with a frictional liner 210AA, 210BA. One end of the brake shoes 210 are mounted on a pin 215 that is rigidly connected to the anchor member 205. On the other end, a cam member 220 is rotatably supported by the anchor plate member 205 and rigidly connected to a lever 225 in order to provide angular movement therebetween. Further, a brake drum 300 is en-casted or affixed to a hub portion (not shown) of the wheel 145 to secure angular movement between them. Therefore, the anchor plate member 205 is a stationary part, while the brake drum 300 rotates along with the wheel.

[00036] The brake drum 300 comprises a circumferential wall 305 that is capable of enclosing the plurality shoes 21 OA, 210B in circumferential direction. Further, the inner circumferential wall 305 of the brake drum 300 is provided with plurality of grooves 310 extending in a lateral direction that are disposed in helical direction, wherein the grooves are extending from one lateral end to other lateral end of the brake drum 300. Each groove of the plurality of grooves 310 comprises a trailing face 310T (shown in Fig. 2 (c)), which is with respect to direction of rotation of the wheel, having a wedge shaped profile P. The plurality of grooves 310 are provided with a cross section including a trapezoidal, a parallelogram, or a dovetail shape, wherein the trailing face 310T is having the wedge shaped profile P.

[00037] The brake shoes 21 OA, 210B are connected to each other through plurality of springs 226 that enable restoration to normal state. In normal state of the brake shoes 21 OA, 210B, free ends of the arc shaped shoes 210 are in contact with a flat surface of the cam member 220. The springs 226 hold the brake shoes 210A, 210B in the normal state. Actuation of brake will enable rotation of the lever 225 that will rotate the cam member 220, which will push the brake shoes 21 OA, 210B apart from each other thereby moving the brake shoes 21 OA, 210B towards the inner circumferential surface 305 of the brake drum 300. Further, the frictional liners 210AA, 210BA provided on the brake shoes 210A, 210B come in contact with the inner circumferential surface 305 of the brake drum 300. This creates a friction between the frictional liners 210AA, 210BA and brake drum 300, resulting in reducing the speed of the rotation of the wheel. When the brake actuation lever is released, the springs 226 will retract the brake shoes 21 OA, 210B to the normal condition.

[00038] Therefore, when the brake is applied, the frictional liners 210AA, 210BA of the brake shoes 210A, 210B come in contact with plurality of grooves 310 provided on the inner circumferential surface 305resulting in optimal shaving of the frictional liners 210AA, 210BA of the brake shoes. The shaving of the frictional liners 210AA, 210BA by the inner edge E (shown in Fig. 2 (c)) of the wedge shaped profile P of the groove removes and cleans any dirt or debris formed on the brake liner surface 210AA, 210BA whenever brake is actuated. [00039] Fig. 2 (b) depicts an enlarged view of a brake drum 300, in accordance with the embodiment of the present subject matter depicted in Fig. 2

(a) . In an embodiment, one end of a first groove 310 over laps with at least a portion of an opposite end of a second groove 320 that is adjacent to the first groove 310, when viewed from sideward. The helix angle Θ (shown in Fig. 2 (b)) of the grooves 310 enables achieving of aforementioned aspect, which is overlapping of the first groove 310 with the second groove 320 (shown in Fig. 2

(b) ) when viewed from sideward. Viewed in axial direction AD, which is vehicle sideward direction, the reference line L drawn parallel to the axis of the brake drum 300 cuts through the first groove 310 and also through the second groove 320 thereby providing gradual engagement. Thus, gradual engagement of the inner edge E of the wedge shaped profile P of the trailing face of the plurality of grooves 310 with the frictional liners 210AA, 210BA enables minimization of any chip-off or damage of the frictional liners 210AA, 210BA. Further, wear rate of frictional liners 210AA, 210BA is also minimized. Furthermore, the provision of one end of the first groove 310 over lapping with at least a portion of the opposite end of the second groove 320 enables at least a portion of the grooves 310, 320 to be in contact with the frictional liners-simultaneously.

[00040] The brake drum 300 is en-casted with a wheel and disposed at the wheel hub. The present embodiment comprises of plurality of grooves, which are collectively referred as D310D, that extend from one end of the brake drum 300 to other end on the inner circumferential surface of the brake drum 300. Further, the grooves 310 are obliquely disposed. Actuation of brake will enable the frictional liner 210AA, 210BA provided on the brake shoes 210A, 210B (as shown in Fig. 2 (a)) to come in contact with the inner circumferential surface 305 of the brake drum. Therefore, the plurality of grooves 310 provided on the brake drum 300 will enable shaving of the debris on the brake liner 210AA, 210BA (as shown in Fig. 2 (a)) of the brake shoes 210A, and 210B. This will enable self-cleaning of the debris or dirt or both that is accumulated over the frictional liners 210AA, [00041] The plurality of grooves 310 is disposed at a helix angle Θ. A tangent B-BD of the groove 310 makes a helix angle Θ with respect to an axis A- AD that is parallel to the wheel axis. The helix angle Θ and length of the groove define the number of grooves provided on the brake drum 300. For example, with a helix angle Θ at 60 degrees, the number of grooves provided will be equivalent to six for a brake drum having 30 millimeters of width. Therefore, the helix angle Θ depends upon the number of grooves, drum diameter and drum width, and equals to an inverse of the ratio of angular advancement of the groove (angular pitch) and axial advancement of the groove (brake drum width). In other words, the number of grooves is equal to 360 degrees divided by angular pitch of the grooves.

[00042] Fig. 2 (c) depicts another enlarged view of the brake drum 300, in accordance with the embodiment depicted in Fig. 2 (b). In a preferred embodiment, each of the plurality of grooves 310 comprises of at least two faces 310L, 310T extending in a lateral direction of the vehicle 100, wherein the groove(s) 310 are disposed at a helix angle. For example, the groove depicted in Fig. 2 (c) comprises of a leading face 310L and a trailing face 310T. The leading face 310L and the trailing face 310T are with respect to a direction of rotation DR of the brake drum 300 that is due to the rotational motion of wheel caused due to the movement of vehicle 100.

[00043] At least the trailing face 310T of the two faces 310L, 310T is having a tapered profile P. In other words, the trailing face 310T is disposed at an angle, which forms a wedge shaped profile P. In present embodiment, the groove 310 is having a parallelogram cross-section as shown in Fig. 2 (c). In another embodiment, the groove 310 has a dovetail cross-section as shown in Fig. 3. Further, the trailing face 310T is inclined at an acute angle with respect to radial line of the brake drum 300 passing through inner edge of the trailing face 310T, wherein the inner edge is in proximity to the center of the brake drum 300. The trailing face 310T acts as a wedge that will enable effective removal of the dirt or debris from the frictional liners 210AA, 210BA of the brake shoes 210A, 210B. Further, the angle of inclination of trailing face 310T is in the range of 0-30 degree for optimal functioning of the brake drum assembly.

[00044] Fig. 3 depicts an enlarged view of the brake drum and a cross-sectional view of a groove taken for a brake drum at axis X-XD, in accordance with another embodiment of the present subject matter. The depicted groove is having a dovetail cross-section. In the present embodiment, a leading face 410L and a trailing face 410T of the groove 410 are provided with tapered profile, wherein the trailing face 410T is inclined at an acute angle a. The radial line R-RD of the brake drum 400 passing through the inner edge E of the trailing face 410T and center of the drum (not shown). Further, the leading face 410L is inclined at an acute angle β with respect to the radial line R-RD passing through an inner edge ED of the leading face 410L.

[00045] Furthermore, the trailing face 410T is extending obliquely and radially outward from the inner edge E in a direction that is opposite to the direction of rotation DR of the brake drum 400. The obliquely extending trailing face 410T forms the wedge shaped profile P that engage with the frictional liners during actuation of the brake thereby enabling in self-cleaning of the friction liners of brake shoes. A further effect of the self-cleaning is, minimizing the brake noise problem.

[00046] Thus, as depicted in Fig. 3, a first axis T-TD passing along the trailing face 410T is disposed at an acute angle a with respect to the radial line R-RD passing through the inner edge E of the trailing face 410T. Furthermore, a second axis L-LD passing along the leading face 410L is disposed at an acute angle β with respect to the radial line R-RD passing through an inner edge ED of the leading face 410L. In the present embodiment, the groove 410 is having a dovetail cross-section. The trailing face 410T is extending obliquely, which is at an acute angle a with the radial line R-RD , and a radially outward in a direction opposite to the direction of rotation DR of the wheel.

[00047] As depicted in Fig. 3, the wedge shaped cross-section is provided on both the leading face 410L and the trailing face 410T. This enables self-cleaning of frictional liners when the wheel is rotating in forward direction and also in the reverse direction. The acute angle(s) α, β are preferably in the range of 0-30 degrees to enable optimal removal of debris and also to minimize chip-off and damage of the frictional liners.

[00048] The trailing face 410T and the leading face 410L are depicted in accordance to the direction of rotation DR of the wheel 145. The trailing face 410T and the leading face 410L would interchange when the direction of rotation of the wheel 145 or 120 or both changes. To sum up, in the present embodiment, the self-cleaning of the frictional liners 210AA, 210BA occurs during rotation of the wheel 145 in either of the directions.

[00049] In the present embodiment, the groove 410 is provided with the leading edge ED and the trailing edge E that are obliquely disposed. In another embodiment as depicted in Fig. 2 (c), the leading edge ED and the trailing edge E of the grooves are obliquely disposed to each other. In other words, gap between the leading edge 410L and trailing edge 410T of the grooves is kept either constant or is variable depending on the application.

[00050] It is to be understood that the aspects of the embodiments are not necessarily limited to the features described herein. Many modifications and variations of the present subject matter are possible in the light of above disclosure. The present invention is thus briefly described. It will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the present invention.