Combined Brake System for Motorcycle

Field of the Invention:

The present invention relates to "Combined brake system for Motorcycle" and more particularly this invention relates to mounting of combined braking system unit in a typical two wheeled motorcycle having a tubular frame construction.

Background of the Invention:

In most of the present two wheeler braking systems, both front and rear brakes are independently operated i.e. application of front brake force will activate only front wheel brake and rear brake force will activate only rear wheel brake. Rear brake force application is limited, because of dynamics of vehicle during braking. Due to load transfer to front wheel during braking, further increase in rear brake force will result in skidding rather than stopping the vehicle. Vehicle controlling becomes difficult and stopping distance will be more, thereby resulting in poor braking performance due to wheel skidding. So typically in a combined brake system the available braking force is completely utilized by distributing it to front and rear brake, thereby the stopping distance is minimized in two wheelers. So, there is a limitation on rear brake application, for the safety of the rider. To increase the safety of rider front and rear brakes are combined with a hydraulic means. This hydraulic pressure distributor controls the braking pressure required for front and rear brakes. Pressure control valve has two input pressures from front and rear brake inputs and the output is two different pressures to activate front and rear brakes. The application of rear brake will apply both front and rear brakes and front brake application is independent. The brake feel and performance depends the location of pressure control valve in the vehicle layout. Therefore the present invention aims at providing an optimal location for combined brake system on two-wheeler.

Summary of the Invention:

An object of the present invention is to substantially overcome the problems or defects or drawbacks encountered in the prior art mentioned above and to adapt a combined brake system (referred as CBS also) in a two wheeled motorcycle having a tubular frame construction with least modifications in comparison to the existing tubular frame construction without having a provision for CBS unit.

Another object of the present invention is to optimize the brake performance by minimizing brake fluid losses in brake hoses.

Another object of the present invention is to provide an excellent brake feel or brake performance for the rider.

Another object of the present invention is to locate the CBS unit in such a way which will render it easy for servicing without the need for removing any nearby parts.

Further object of the present invention is to mount the CBS unit in a way, wherein the mounting system can be removed from the frame easily.

Further object of the present invention is to avoid welding of the CBS mounting system, to the frame.

Further object of the present invention is to provide the CBS unit mounting system as a separate kit thereby enabling the customer to upgrade the existing vehicle for CBS unit without any major modifications.

Further object of the present invention is to provide a mounting system for CBS unit such that it avoids damages to contact paint portion of the frame.

Yet another object of the present invention is to utilize the existing free space available within the vehicle body frame, wherein the CBS unit can be located.

The nature and further characteristic features of the present invention will be made clearer from the following description made with reference to the accompanying drawings.

Brief description of the Drawings:

The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein

Figure 1 illustrates a conventional motorcycle.

Figure 2 shows is a right side view of the motorcycle according to the first embodiment of the present invention.

Figure 3 shows the CBS unit location on the motorcycle according to the present invention.

Detailed Description of the Drawings:

In a combined braking system front brake application will activate only front brake, during this operation pressurized brake fluid flows through pressure control valve (PCV) to reach front brake caliper. Application of rear brake activates both front and rear brakes that is both rear and front brakes are combined by distributing the applied rear brake pressure by hydraulic pressure control valve in predetermined ratio. During combined braking operation, the rear brake control pedal/lever will actuate rear brake master cylinder (Rear M/C). PCV distributes the pressurized brake fluid to the front and rear brakes in predetermined ration.

In the non-combined braking system two wheelers the front and rear brake hydraulic paths can be optimized independently for best brake feel and performance. But, in two-wheeler motorcycle layout with combined braking system, optimization of rear brake hydraulic path will affect the front brake hydraulic path, finally resulting in poor overall braking feel. In this invention, combined braking unit location for two wheeler motorcycle layout is optimized for better brake feeland performance which depends on the factors like hydraulic pipe wall material properties and construction, the brake fluid hydraulic path length, number of bends and direction changes in hydraulic path, radius of bent the hydraulic path and hydraulic head differences of inter locking unit, brake calipers and master cylinders.

A preferred embodiment of the present invention will be described hereunder with reference to the accompanying drawings.

First, with reference to Figure 1 a motorcycle comprises of a frame (101), front fork (102) attached to a pivot tube (201) of the vehicle frame, a front wheel (103) attached to these front forks (102), a handle bar (104) connected to the front forks (102), a fuel tank (105) attached so as to straddle an upper part of the vehicle frame, a seat (106) attached to the upper rear portion of the vehicle frame, an engine unit (107) attached to the lower front section of the vehicle frame, a swing arm (108) attached to a lower rear section of the vehicle frame, suspended by a rear shock absorber (not shown) from the vehicle frame and a rear wheel attached to a rear end of swing arm (108). The intake system of the engine comprises of a fuel air metering device such as a carburettor (109), 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 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 (110) for covering an upper part of the front wheel (103), and a rear fender (111) for covering an upper part of the rear wheel (112). The drive from the engine (107) is transmitted from the engine to the driven wheel sprocket mounted on the rear wheel hub mounted on the rear wheel assembly.

As shown in Figure 2, with the side covers open, the body frame of the motorcycle includes a head pipe/ steering pivot/pivot tube (201) at the front end of the body frame. From the top portion of the head pipe (201) one main tube (202) extends backwards and obliquely downwards. Both sides of the lower portion of the main tube is provided with a bracket (203) for rear engine mounting. A tube centre stand (204) is disposed horizontally at the lower portion of the main tube (201), extending outward through an opening on the two sides of the bracket (203).

From the lower portion of the head pipe a pair of left and right down tubes (205) extends obliquely downward and backward, while extending parallel in the direction towards the rear engine mounting bracket (203). The end portion of the said down tubes (205) is welded to the said tube centre stand (204). From the portion where the main tube starts descending, a pair of upper tubes (206) extends backward and slightly upward towards the rear side of the upper tubes (206) with respect to the horizontal direction.

A pair of side tubes (207) extending from a middle portion of the rear engine bracket (203) and extending backward and upward, while extending parallel in a direction so as to get welded with the end rear portion of the upper tubes (206). The pair of left and right body frame components such as the down tubes (205) and upper tubes (206) as mentioned above are firmly interconnected with a plurality of horizontal bridges stretching between the pair of pipes and along the width of the vehicle body.
Two reinforcing members (211,212), one between the front end portions of the main tube (202) and down tubes (205) and the other just below the rear end of the upper tubes (206).

Referring to figure 3 and according to one embodiment of the present invention CBS unit (301) is located in the vicinity of the oblique portion of the main tube (202) of the motorcycle. This CBS unit (301) location is surrounded by other motorcycle elements like engine air cleaner case etc.

At this particular said location the ratio of front brake hydraulic circuit length to rear hydraulic circuit length is preferably in the range of 0.9 to 1.1. The said hoses are connected to the CBS unit through banjo bolts. The said banjo bolts can be provided both in horizontal or vertical direction as per the requirement. In another aspect of the invention, the CBS system is provided with a mounting system arrangement which avoids welding of the bracket to the frame. The said mounting system has at least two brackets. Both the brackets are hat shaped ones. The bigger bracket wraps the main tube of the frame for approximately 200 degree and the other small bracket partially wraps the main tube frame for approximately 30 degree. Both the said brackets have extended flat ends. The said bigger bracket is provided with welded nut and the said smaller bracket is provided with a hole. A cushion member is interposed between the said hat shaped brackets. Two bolts are used for clamping the brackets. The said mounting arrangement is a removable one and avoids damages to the paint surfaces of the frame. This mounting arrangement since removable can be provided as separate kit to the customer, whereby the customer can upgrade his vehicle to mount CBS unit to its frame.

We claim:

1. A motorcycle provided with a combined brake system (CBS) having a front fork supporting a front wheel of a motorcycle is supported to be rotatable by a head pipe located at a front end portion of a body frame of the motorcycle, at least one main tube extending from upper portion of the head tube obliquely downward and backward, at least one down tube extending obliquely from lower portion of the head tube towards back and a CBS unit is disposed in the vicinity of the oblique portion of the main tube.

2. A motorcycle provided with a combined brake system as claimed in claim 1 wherein the CBS unit is substantially covered by the side cover(s).

3. A motorcycle provided with a combined brake system as claimed in claim 1 wherein the ratio of front brake hydraulic circuit length to rear brake hydraulic circuit length is preferably in the range of 0.9 to 1.1.

4. A motorcycle provided with a combined brake system as claimed in claim 1 wherein the CBS unit is surrounded by engine assembly, fuel tank assembly, battery box, air cleaner case or like parts.

5. A motorcycle provided with a combined brake system as claimed in claim 3 wherein the said engine assembly comprises an engine, a transmission unit and fuel air metering device.

6. A motorcycle provided with a combined brake system as claimed in claim 1 wherein the said CBS unit is a hydraulic one.

7. A motorcycle provided with a combined brake system as claimed in claim 1 wherein CBS unit mounting arrangement comprises at least two hat shaped brackets wrapped around the frame, a cushion member interposed between the brackets and the frame and at least two bolts for clamping the brackets.

8. A motorcycle provided with a combined brake system as claimed in claim 6 wherein CBS unit is mounted to the one of the brackets.

9. A motorcycle provided with a combined brake system as claimed in claim 1 wherein CBS unit is provided with banjo bolts for input and output hoses.