Wheel Speed Sensing Device for Two Wheeler

Field of the invention

The present invention relates to "Wheel Speed Detecting Device for Two Wheeler". In particular this invention relates to wheel speed detecting device for a motorcycle having anti lock braking system.

Background of the invention

Generally, wheel speed sensing is done with pickup coils (or sensors) and a disc. As a background art wheel speed detecting device, the "Wheel Speed Detecting device" disclosed in 848/MUM/2000 has been known. Fig.7 of the above mentioned patent is a view explaining the pulsar ring of the wheel speed sensing device mounted on the rear and front wheel of a motorcycle. In a wheel speed detecting device the disc is provided with slots at predetermined certain pitches on a pitch circle drawn in a radially inward circumferential position spaced at a predetermined distance from an outer edge of the disc.

The standard speed sensing disc has multiple slots defined which are parallel to outer diameter of the disc at each respective point. The sensitive face of the sensor is placed in proximity to the disc such that the sensitive face is parallel to the disc having slots in it.

Usually for a better sensitivity the sensor's sensitive face is made rectangular since there is a manufacturing constraint which is associated with circular sensitive face.

When the sensor with its sensitive face being rectangular in shape (or having some edge), the said sensor is constrained to be placed close to the disc such that one of its edge is parallel to the slots provided in the disc. The above mentioned constraint leaves a limited area for sensor mounting. However the problem arises when the sensor mounting in that direction is not feasible because of several reasons, such as placement of other nearby components at the rear side of the motorcycle which partially obstructs the area.

In order to be able to rotate the sensor face or edge about an axis vertical to its face, the sensor has to be moved on the disc parallel to the circumference of the disc, which leads to the problem like requirement of longer sensor cable routing, straining and bending of the sensor cable.

Hence the objective of the present invention is to overcome the above problems associated with the prior arts.

Summary of the invention:

The present invention has been devised in view of the above difficulties and it is therefore an object of the present invention is to provide flexibility in mounting orientation of the speed sensing element or sensor such that the sensor's sensitive face or edge is parallel to the edge of the slot on the disc.

Another objective of the present invention is to facilitate mounting of the sensing element or sensor on the two-wheeler so that obstruction of other components is minimized.

Another objective of the present invention is to facilitate mounting of the sensing element or sensor on the two-wheeler so that wiring (or sensor cable) routing for the sensor is simplified, avoiding unnecessary or excess looping.

Another objective of the present invention is to locate the sensor which will render it easy for assembling and servicing.

Further objective of the present invention is to make the wheel speed detecting device cost effective and this objective is achieved by reduction in length of sensor cable and other associated advantages in manufacturing.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

Brief Description of the Drawings:

The invention in its preferred embodiments will be more particularly described by reference to the accompanying drawings, in which like parts are designated by the same numerals in the various figures and in which:

Fig. 1 illustrates a motorcycle;

Fig. 2 shows one of the embodiment according to the present invention.

Fig. 3 shows second embodiment according to the present invention.

Fig. 4 shows third embodiment according to the present invention.

Detailed Description of the Invention:

The present invention relates to wheel speed detecting device for a motorcycle.

Referring to figure. 1, a motorcycle comprises of a frame (101), front fork (102) attached to a pivot tube (103) of the vehicle frame, a front wheel (104) attached to these front forks (102), a handle bar (105) connected to the front forks (102), a fuel tank (106) attached so as to straddle an upper part of the vehicle frame, a seat (107) attached to the upper rear portion of the vehicle frame, an engine unit (108) attached to the lower front section of the vehicle frame, a swing arm (109) attached to a lower rear section of the vehicle frame, suspended by a rear shock absorber (not shown in the drawing) from the vehicle frame and a rear wheel (110) attached to a rear end of swing arm (109). The intake system of the engine comprises of a carburettor, intake duct and an air cleaner. The exhaust system of the engine comprises of exhaust pipe and a muffler. The motorcycle is also provided with a side cover (111) for covering a side section of the vehicle frame, a seat cover for covering a rear section of the vehicle frame below the seat, a front fender (112) for covering an upper part of the front wheel (104), and a rear fender (113) for covering an upper part of the rear wheel (110). The drive from the engine (108) is transmitted from the engine to the driven wheel sprocket mounted on the rear wheel hub mounted on the rear wheel assembly.

To measure the wheel speed, a sensing element (114) (hereinafter is referred to as sensor) is attached to the disc brake mounting structure as a stationary element and a rotating element hereinafter referred to as disc (115,116) is mounted to the wheel (110, 104) such that wheel (110,104) and the said disc (115,116) rotate together. The sensor (114) sensitive face is placed parallel to the plane of the disc (115).

Referring to figure.2, the said disc (115) is provided with uniformly spread out slots (201), which are skewed at a predefined angle. The said wheel speed sensing disc (115) slots (201) are not parallel to the outer diameter of the disc (115) at each respective location but an angle to it. The angle is specific to application and the construction. Angle can be either in clockwise or in counterclockwise and the maximum angle is limited by the constructional feasibility of the disc (115).

When the sensor (114) sensitive face requires to be placed parallel to the plane of the disc (115), the new acquired orientation of the sensor (114) is the rotated orientation of the slots (201) which are provided in the disc (115).

The slots (201) provided in the disc (115) are cut through. The said slots (201) are defined by a set of radii and a set of tangent lines. The length of the slots along the radial direction is defined by an inner circle (1) and a outer circle (2) concentric to outermost diameter of the said disc (115).

An imaginary defined circle (3) having radius less than circle (1) and circle (2) is drawn concentric to outermost diameter of the disc (115), a pair of tangent lines (203 and 204) are drawn to said imaginary circle (3) passing beyond the outermost diameter of the disc (115). The intersection point of the inner circle (1) and the outer circle (2) with the tangent line forms a nearly trapezoidal cut through slot (201) in the disc (115). The same is repeated throughout the disc to form required number of slots and to leave a required amount of metal strip (202) between slots (201) to space them equally. The skewing of the slot (201) is done considering that one of the edges of the sensing face should align with the edge of the skewed slot (201), in order to maximize the output response of the said sensor (114).

The said disc (115) is made of a material which has lower magnetic reluctance than the surrounding interconnecting parts such that when the said sensor (114) is placed

in proximity to the face of the disc (115), it produces electrical or similar signals corresponding to the rotation of the disc (115). The said sensor (114) may be combined with additional circuitry to provide pulsed output with frequency corresponding to wheel speed.

In the case of sensing element being variable reluctance sensor, the output of the sensor would be voltage induced across the coils which corresponds to the rate of change of flux through the sensor coil.

In the case of sensing element being magneto resistive sensor, the output of the sensor is measured by means of changed resistance of the magneto resistive sensor.

In another preferred embodiment shown in figure. 3 of the present invention, two imaginary circles (5 and 6) having radius less than inner circle (301) and outer circle (302) are drawn concentric to outermost diameter of the disc (115) and pair of tangent lines (304 and 305) is drawn to said imaginary circles (5 and 6) passing beyond the outermost diameter of the disc. The intersection point of the inner circle (301) and outer circle (302) with the tangent line (304,305) forms a rectangular cut through slot whose edges are completely rounded off to form an elongated circular slot (303) in the disc (115).

In yet another preferred embodiment shown in figure. 4 of the present invention, two imaginary circles (7 and 8) having radius less than inner circle (401) and outer circle (402) are drawn concentric to outermost diameter of the disc (115) and pair of tangent lines (404 and 405) is drawn to said imaginary circles (7 and 8) passing beyond the outermost diameter of the disc. The intersection point of the inner circle (401) and outer circle (402) with the tangent line (404,405) forms a rectangular shaped metal strip (403). The same is repeated throughout the disc to leave a required amount of trapezoidal shaped slots (406) between metal strips (403) to space them equally. It is also possible to convert the metal strips (403) part as cut through slot and the slot (406) as metal strip, rest remaining the same.

The invention being thus 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 spirit and scope of the 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 claims.

We Claim:
1. A wheel speed detecting device adopted in a two wheeler having a front and a rear wheel comprising:

a sensor mounted on a body side of the vehicle and facing one of the said front wheel and rear wheel; and

a disc mounted on a wheel side of the vehicle and co-axially with an axle of one of said front wheel and rear wheel, wherein the disc is formed with skewed slots such that it is parallel to the edge of the sensor face.

2. A wheel speed detecting device as claimed in claim 1, wherein the said skewed slots are preferably cut through slots.

3. A wheel speed detecting device as claimed in claim 1, wherein the said skewed slots are spread out uniformly throughout the surface of the disc.

4. A wheel speed detecting device as claimed in claim 1, wherein the said slots are skewed either in clockwise or anticlockwise direction.

5. A wheel speed detecting device as claimed in claim 1, wherein the said skewed slots are preferably parallelograms in shape.

6. A wheel speed detecting device as claimed in claim 1, wherein the said skewed slots are preferably trapezoidal in shape.

7. A wheel speed detecting device as claimed in claim 1, wherein the said disc is preferably made up of material whose magnetic reluctance is lower than the surrounding interconnecting parts.

8. A wheel speed detecting device as claimed in claim 1, wherein the said slots are preferably elongated circular slots.