FIELD OF INVENTION
[0001] The present invention relates to a two-wheeler and more particularly to installation of a speed sensor in an internal combustion engine of the said two-wheeler.
BACKGROUND OF INVENTION
[0002] In a typical two-wheeled vehicle, speed is measured through .sensor fitted on wheel. This often leads to erratic speed indication due to dirt/water accumulation and also for such a system a long cable is required which gets strained due to front fork oscillation under full bump condition.
[0003] To avoid these failure modes, it is required to package speed sensor in a dirt free area. However, it is difficult to directly mount the speed sensor on engine due to many layout constraints. One of the reasons being that a speed sensor cannot be assembled from top side of crankcase, since for servicing requirement of the engine; engine needs to be removed from frame. Hence, if the speed sensor is assembled at top, it may break during engine replacement due to collision with the frame.
[0004] In addition, Speed sensor cannot be assembled from top side of crankcase since breather circuit has been provided in the top zone that requires a larger space; the space required being a function of the cylinder volume. Also, using top side of crankcase is not preferable because that location is more suitable for starter motor. Speed sensor assembly from rear side of crankcase is also not preferable since it may interfere with the kick-starter assembly zone.

[0005] Furthermore, speed sensor cannot be assembled to sense gear teeth in radial direction since the gears, which are in constant mesh with drive shaft, are floating gears. Hence, a system is required wherein the speed sensor can be assembled in such a way that it can sense the speed in all the positions of the floating gear.
SUMMARY OF THE INVENTION
[0006] To obviate the above limitations as described in the background of the invention, the current invention discloses a speed sensor mounted inside the crankcase with a dummy gear added inside the gearbox, and speed sensor sensing the gear RPM of the dummy gear along the axial direction.
[0007] Due to addition of dummy gear, it is possible to take signal from floating gear also. In the current invention, it is easy to service speed sensor by just removing few outside parts. In the present invention, dismounting of engine from frame for servicing the speed sensor is not required.
[0008] In the current invention, dummy gear is packaged below the drive shaft and between crankcases. The dummy gear herein described is driven by drive shaft gear. In the current invention, speed sensor can be assembled / removed from both the crankcase left (CCL) side or crankcase right (CCR) side depending on engine layout. •> Furthermore, in the disclosed invention, speed sensor is not directly visible from outside hence, it is safe from outside stones and mud thus safer than the location as described in the prior art.

BRIEF DESCRIPTION OF DRAWINGS
Figure 1 illustrates a typical two-wheeler.
Figure 2 illustrates the internal combustion engine of the two-wheeler.
Figure 3 illustrates the sectional view of engine along plane A-A'.
Figure 4 illustrates the sectional view of engine along plane A-A' during floating gear condition.
Figure 5 illustrates the perspective view of engine cut section.
DETAILED DESCRIPTION OF THE INVENTION
[0009] The following description describes a mechanism to calculate vehicle speed . by installing a speed sensor as per the current invention, at a preferred location to obviate the problems associated with the prior art. It is required that the installation of speed sensor provides a safe location for the speed sensor where the speed sensor is protected against any mud or water entry that may otherwise interfere with the sensitivity of the said speed sensor.
[00010] Figure 1 shows a rider seat 1, exhaust muffler 2, rear wheel 3, vehicle stand 4, rider footrest 5, vehicle rear brake paddle 6, exhaust pipe 7, front wheel 8, engine 9, vehicle 10 and pillion rider footrest 11. The engine 9 as shown in the Figure 1 is a motorcycle engine, but the current invention is not limited to only a motorcycle engine but is applicable to any internal combustion engine.

[00011] Figure 2 shows the perspective view of the engine 9 shown in Figure 1. Figure 2 shows cylinder head 21, cylinder block 22, crankcase 23 and cut section plane A-A'. For further description of the current invention, a section plane along the line A-A' is taken. This section plane-A-A' accommodates the gear location and the speed sensor and hence it clearly shows the position and sensing direction of the disclosed speed sensor.
[00012] Figure 3 shows a fork gear shift 31, cam gear shift 32, clutch assembly 33, 1st gear 34-A, 2nd gear 34-B, 3rd gear 34-C, 4th gear 34-D, 5th gear 34-E, dummy gear 35, speed sensor 36, drive shaft assembly 37, 5th driven gear 38. The fork gearshift 31 slides on the cam gearshift-32 and is used for changing the gear position. The engine 9 as disclosed in the current invention has mainly five gear positions clearly illustrated in the Figure 3 as 1st gear 34-A, 2nd gear 34-B, 3rd gear 34-C, 4th gear 34-D, and 5th gear 34-E.
[00013] As further explained further in Figure 5, the dummy gear 35 is positioned in the crankcase in such a way that the crankshaft 52 is coupled to the countershaft assembly 53 that in turn is coupled to the drive shaft assembly 55 and the rotation of crankshaft 52 drives the idler gear 57.
[00014] The coupling of gears on the crankshaft 52, countershaft assembly 53, cam gear shift 54 and drive shaft assembly 55 is maintained in such a way that whenever the crankshaft 52 rotates, the idler gear 57 also rotates and vice versa.

[00015] Figure 4 shows drive shaft assembly 37, floating position of 5th driven gear 41, and dummy gear in mesh with floating gear 42. As disclosed in the Figure 4, the idler gear 57 is positioned in such a way that the idler gear 57 is coupled with the rotating gear in both floating position and non-floating position. Thereby, the current position and mechanism of coupling of the speed sensor provides an accurate vehicle speed also during the gearshift.
[00016] Figure 5 shows the perspective view of the cut section of the engine 9. Figure 5 shows cylinder head 21, cylinder block 22, balancer shaft assembly 51, crankshaft 52, countershaft assembly 53, cam gearshift 54, drive shaft, assembly 55, arm gearshift 56, idler gear 57, speed sensor 36 and crankcase-LH 59. The speed sensor 36 is located inside the crankcase and below the idler gear 57 that provides enough protection and safety for the speed sensor.
[00017] In addition, it is to be noted that the in the current invention, the speed
sensor 36 senses the idler gear speed in the axial direction. The speed sensor 36 is
installed in a plane in such a way that it senses the teeth of the idler gear in a
perpendicular direction of the plane of the gear.
■. ■' [00018] Due to addition of idler gear 57, it is possible to take vehicle speed signal
input from floating gear as well. The current, location of speed sensor 36 provides
easiness in service in which minimum number of parts required to be rfemoved. There is
no need to dismount the whole engine from frame for servicing of speed sensor in the
current invention.

[00019] The idler gear 57 is packaged below the drive shaft assembly 55 and between crankcase-LH 59. Idler gear 57 in the current invention is driven by drive shaft gear on the drive shaft assembly 55. The freedom to assemble speed sensor 36 in the current invention provides approach for speed sensor 36 either from crankcase left side or crankcase right side depending on layout. Another advantage of the current location and mounting of speed sensor 36 being that the speed sensor is not directly visible from outside. For measuring the speed, the current disclosed speed sensor 36 takes input pulses from the teeth of idler gear 57 along the axial direction.

We claim:
1. An internal combustion engine (9) comprising:
a cylinder block (22) which accommodates a piston within a cylinder and due to combustion of fuel inside the cylinder, the reciprocating motion of the piston is converted into rotational motion through a crankshaft (52);
a counter shaft assembly (53) which is mechanically coupled to the said crankshaft (52) and is driven by the said crankshaft (52);
a drive shaft assembly (55) wherein a gear on the said counter shaft assembly (53) is mechanically coupled to a gear on the said drive shaft assembly (55) so as to drive the said drive shaft assembly (55); the drive shaft being further mechanically coupled to a vehicle wheel (3) through a sprocket;
an idler gear (57) which is further mechanically coupled to a gear of the said drive shaft assembly (55) in such a way so that the idler gear (57) is driven by the said drive shaft (55);
wherein a speed sensor (36) is located at a pre-determined distance from the said idler gear (57) in an axial direction with respect to the said idler gear (57); the speed sensor (36) being further used to detect speed of rotation of the said wheel (3) of a vehicle (10).

2. The internal combustion engine as claimed in Claim 1 wherein the speed sensor (36) is press fit into the crankcase LH (59) inner surface.
3. The internal combustion engine as claimed in Claim 1 wherein the speed sensor (36) is rigidly fastened using suitable fasteners on the crankcase LH (59) inner surface.