Title of Invention

CONE CLUTCH FOR CONTINUOUSLY VARIABLE TRANSMISSION

Abstract A cone clutch system tor contmuous varIable transmISSIon comprising a belt member torque ramp and fly mass sensor actuators~ a fixed half pulley mounted on a shaft, the axial movement of the fixed half pulley being arrested on the shaft, but free to rotate about the said shaft~ the torque ramp connecting a moveable half pulley and the said shaft~ the belt member being held between the said half pulleys at a diameter Da by a clamping force Fa, characterized in that the movable half pulley and fixed half pulley are connected with relative axial movement alone, the ratio change taking place by the axial movement of the moveable half pulley with respect to the fixed half pulley during which the movable half pulley rotates relative to the said shaft due to the torque ramp, the fixed half pulley, during ratio change, also rotating with the movable half pulley relative to the said shaft.
Full Text

The cunent invention relates to sensor-actuator for continuously variable transmission. It specifically deals with power sensor-actuator for cone clutches, for generating the necessary clamping force, used in v-belt based continuously variable transmission.
Cone clutches are power transmission units working on the principles of friction drive. It consists of conical surfaces held together with a clamping force. The friction between the contacting surfaces allows the power transmission between them. Figure I shows a typical example of v-belt based continuously variable transmission that uses such a cone clutch. The friction between each of the half pulley and v-belt surface along with the clamping force P is used for power transfer between the pulley and the belt. The clamping force between the conical surfaces can be generated using a variety of sensor-actuators such as fly mass, torque ramp, compression spring, torsion spring or a combination of these.
Torque ramp sensor-actuator is used in cone clutch to sense the shaft torque and provide clamping force proportional to the torque. Torque ramp sensor-actuator is a helical surface at an angle to the shaft axis, where the tangential force due to torque transfer generates a reaction force having axial component. The magnitude of the axial component is proportional to the angle and the shaft torque.
Fly masses sensor-actuators are used to sense and generate clamping force proportional to the shaft speed. Generally these fly masses are free or pivoted. The fly masses are subjected to centrifugal force proportional to the square of the shaft speed. At a given position of the moveable sheave the roller masses contact the moveable sheave at curved surface. The normal reaction due to centrifugal force at this contact generates an axial force component, based on the contact angle, which is used for torque transmission between the belt and the pulley.
Figure 2 shows a typical cone clutch arrangement that uses torque ramp sensor-actuator to generate the clamping force for a v-belt continuously variable transmission. In such designs the torque ramp. 1 is placed between the moveable half pulley 4 and the shaft 2 of the cone clutch C hence responding to half the shaft torque. The moveable half pulley 4 is also free to rotate on shaft 2 supported by any known means (say bushes). The fixed half pulley 5 is integrated to shaft 2, by any known means (say welding), so half the shaft torque flows directly between them. The v-belt member 6 is held between the fixed half pulley 5 and the moveable half pulley 4 with a clamping force F. The different ratios of torque transmission are achieved by varying the mean diameter for belt operation D. This is achieved by axially moving the moveable half pulley 4 with respect to the fixed half pulley 5. The torque transmission has to take place through an angular contact at torque ramp 1, for a given belt diameter D, in order to generate a proportional clamping force F. The axial motion requirement of the moveable half pulley 4 along with the angular contact requirement for torque transmission results in the angular rotation of the moveable half pulley 4 with respect to shaft 2 as it moves axially during ratio shift.
Figure 3 shows a typical cone clutch arrangement that uses fly mass sensor-actuator to generate the clamping force for a v-belt continuously variable transmission. In such

designs the fly mass 8 is placed between the moveable half pulley 9 and the shaft 10 of the cone clutch CI hence responding to shaft speed. The moveable half pulley 9 is also free to rotate on shaft 10 supported by any known means (say bushes). The fixed half pulley 11 is integrated to shaft 10 temporarily or permanently, by any known means (say welding). The v-belt member 12 is held between the fixed half pulley 11 and the moveable half pulley 9 with a clamping force Fl. The different ratios of torque transmission are achieved by varying the mean diameter for belt operation Dl. This is achieved by axially moving the moveable half pulley 9 with respect to the fixed half pulley 11. The axial position of the moveable half pulley 9 with respect to fixed half pulley 11 determines the radial position of the fly mass 8 contacting the moveable half pulley 9 at angular surface S and shaft 10 at angular surface SI. the centrifugal force CF on the fly mass is balanced by the normal reactions at the angular contacts at surface S and surface SI. The normal reaction at surface S also has an axial component Fl that is used for clam.ping the belt 12 between moveable half pulley 9 and the fixed half pulley 11.
The major disadvantage of the above system is that the clamping force F generated by any of these sensor-actuators is proportional to either shaft speed or shaft torque. Combination of torsion or a compression spring with such a sensor-actuator only helps to modify the clamping force characteristics over the moveable half pulley travel. There is a need for controlling the transmission ratio of the CVT in relation to shaft power rather than shaft speed or shaft torque alone. The existing sensor-actuators are not capable of sensing the shaft power, which is a function of both shaft speed and shaft torque. A combination of the existing torque sensor-actuator and fly mass sehsdf-actuator is not possible as there is a relative rotational motion between the fixed half pulley and the moveable half pulley in the case of the existing torque sensor-actuator, which is not possible in the fly mass sensor-actuator.
The present invention was made in this situation so as to have a power sensor-actuator that generates an axial clamping force that is function of both the shaft speed and the shaft torque. Figure 4 and figure 5 show an embodiment of the invention for the following explanation. In this embodiment the fly masses 8a are considered as non-pivoted type rollers. In this design the axial position of the fixed half pulley 5a is arrested with respect to shaft 2a but it is free to rotate about the shaft 2a. The torque ramp la connects the moveable half pulley 4a and the shaft 2a. The innovative part of the design is connecting the moveable half pulley 4a and fixed half pulley 5a with relative axial motion alone, removing the relative rotational motion using any known arrangement 4b such as splines or slots with roller followers. The belt member 6a ^s held between the moveable half pulley 4a and the fixed half pulley 5a at a diameter Da with a clamping force Fa. The ratio change takes place'by axially moving the moveable half pulley 4a with respect to fixed half pulley 5a. As the moveable half pulley 4a moves axially, during ratio shift, it rotates relative to the shaft 2a due to torque ramp la. The fixed half pulley 5a also rotates along with the moveable half pulley 4a relative to the shaft 2a .The torque flow path between the fixed half pulley 5 a and the shaft 2a is through the spline 4b and the torque ramp la. The fly mass 8a is in contact the surface 4d, on the moveable half pulley 4a, at 4c and surface 2b, on the shaft end of the torque ramp la, at 2c. For a given

diameter Da of the belt member 6a the axial position of the moveable half pulley 4a with respect to fixed half pulley 5a is fixed. The shaft torque, torque ramp angle at this position along with the diameter of action determines the axial clamping force Fta proportional to shaft torque contributing to Fa. At the same position the shaft speed, fly mass weight along with the contact angles at 4c and 2c determine the axial clamping force Fsa proportional to shaft speed contributing to Fa. During ratio shift there is no relative motion between the fixed half pulley 5a and the moveable half pulley 4a hence restricting the fly mass path as 2-dimensional with respect to the fixed half pulley 5a. The additional use of torsion or compression spring CS can be used to fine-tune the axial force Fa characteristic along the moveable half pulley 4a's travel. Hence the invention is capable of generating different axial clamping force at a given shaft speed for different shaft torque and vice versa. Hence this invention allows tuning the axial clamping force as per the shaft power requirements.
This innovative solution allows the clamping force, necessary for efficient torque transmission by the cone clutch with out smearing the belt member as the relative motion between the half pulleys is removed during ratio shift. The clamping force is not a function of the shaft torque or shaft speed alone but a function of shaft power.



We Claim:
1. A cone clutch system for continuous variable transmission comprising a belt member; torque ramp and fly mass sensor actuators; a fixed half pulley mounted on a shaft, the axial movement of the fixed half pulley being arrested on the shaft, but fi-ee to rotate about the said shaft; the torque ramp connecting a moveable half pulley and the said shaft; the belt member being held between the said half pulleys at a diameter Da by a clamping force Fa, characterized in that the movable half pulley and fixed half pulley are connected with relative axial movement alone, the ratio change taking place by the axial movement of the moveable half pulley with respect to the fixed half pulley during which the movable half pulley rotates relative to the said shaft due to the torque ramp, tihe fixed half pulley, during ratio change, also rotating with the movable half pulley relative to the said shaft.
2.A cone clutch system for continuous variable transmission substantially as herein described with reference to and as illustrated in Figs.4 and 5 of the accompanying drawings.

Documents:


Patent Number 259217
Indian Patent Application Number 832/CHE/2004
PG Journal Number 10/2014
Publication Date 07-Mar-2014
Grant Date 03-Mar-2014
Date of Filing 20-Aug-2004
Name of Patentee TVS MOTOR COMPANY LIMITED
Applicant Address JAYALAKSHMI ESTATES, NO 8,HADDOWS ROAD, CHENNAI-600 006
Inventors:
# Inventor's Name Inventor's Address
1 MOHAN GANGADURAI JAYALAKSHMI ESTATES, NO 8,HADDOWS ROAD, CHENNAI-600 006.
2 HARIKRISHNAN NAGARAJAN JAYALAKSHMI ESTATES, NO.8, HADDOWS ROAD, CHENNAI-600 006.
PCT International Classification Number F16H 15/30
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA