A TRANSMISSION CONTROL SYSTEM AND A METHOD FOR CONTROLLING TRANSMISSION FOR CLUTCH PEDAL FREE OPERATION
FIELD OF THE INVENTION
The present invention relates to a transmission control system. In particular, the present invention relates to the transmission control system which uses only speed sensors to control the transmission system of the vehicle.
BACKGROUND OF THE INVENTION
Generally, for a tractor employed with a transmission system having wet clutch, requires various sensors and switches for clutch pedal free gear transmission. For every gear shift in tractor, clutch engagement has to be modulated based on the selected gear due to variation in gear ratio for different gears. The transmission control system of the tractor modulates the clutch engagement/disengagement based on the signals from various sensors and switches.
US Patent No. 4648290 discloses a semi-automatic mechanical transmission system and method for controlling same. The transmission system includes a shaft selector lever which may be moved forward or rearward from the centered position thereof to select upshifts and downshifts, respectively, and a central processing unit receiving input signals from the selector lever and which will sense multiple movements of the shift select lever in a given direction and interpret same as request for multiple or skip shifts in said direction. The control also includes a display comprised of three sections, a currently engaged gear ratio section a maximum permissible consecutive upshift indicating section and a maximum permissible consecutive downshift indicating section. The central processing unit includes circuitry and logic rules to process input signals to determine the currently permissible gear ratios and will indicate said gear ratios, in the form of maximum permissible upshifts and downshifts, at said display, and will also execute only the lesser of the maximum permissible number of consecutive upshifts or downshifts or the number of consecutive upshifts or downshifts selected by the operator. The present patent discloses that the

control system uses the lever position sensor and other various sensors for controlling the transmission shift.
US Patent No. 4722248 discloses a vehicular transmission shift control system is provided for effecting automatic shifting between a group of sequentially related forward gear ratios provided by the transmission that includes a logic member operative to receive and process an engine speed signal and a gear ratio position signal and to provide an output control signal to a shift actuator that is operative to enable automatic shifting between the sequentially related forward gear ratios whenever the lowest sequentially related forward gear ratios of the group is manually engaged by an operator of the vehicle. The present patent discloses that the control system utilises the signals from the position sensor, input speed sensor and also output speed sensor.
Therefore, there is need in art to provide a control system which utilises only speed sensors to control transmission system and reduces the complexity of the control system. This leads to cost reduction and ease of maintenance also.
OBJECTIVE OF THE INVENTION
The primary object of the invention is to provide a hassle free transmission control system with clutch pedal free operation for utility vehicles.
Another object of the present invention is to provide a transmission control system with clutch pedal free operation using speed sensors and eliminating the need of various position sensors for detecting the selected gear.
Still another object of the present invention is to provide a cost effective transmission control system having clutch pedal free operation with reduced complexity.
SUMMARY OF THE INVENTION
The present invention provides a transmission control system for clutch pedal free operation, comprising of: an engine (101); a clutch unit (102), wherein the clutch unit (102) comprises of a forward clutch pack and a reverse clutch pack; a transmission system

(103), said transmission system (103) is operatively coupled with the said clutch unit (102); a fluid system (104), said fluid system (104) is in communication with the transmission system (103) for cooling and/or lubrication purpose, wherein the fluid system (104) is a hydraulic fluid system; a fluid valve block (105), said fluid valve block (105) is in contact with the fluid system (104) fluidically, wherein the fluid valve block (105) comprises of a forward valve and a reverse valve, said forward valve supplies or drain pressurised fluid to or from the forward clutch pack and said reverse valve supplies or drain pressurised fluid to or from the reverse clutch pack; an electronic control unit (106), said electronic control unit (106) sends an appropriate signals to the fluid valve block (105), wherein the appropriate signals is a modulated pressure signals, said appropriate signals are appropriated by means of input from a plurality of sensors and a gear shift switch (109).
Said plurality of sensors are, a first sensor (107) and a second sensor (108). Wherein said plurality of sensors are speed sensors. The first sensor (107) measures speed of engine (101) and sends measured speed signal to the electronic control unit (106). The second sensor (108) measures speed of the transmission unit (103) and sends measured speed signal to the electronic control unit (106). The gear shift switch (109) is positioned appropriately along with a mechanical speed shift lever. The gear shift switch (109) is a digital switch, wherein the gear shift switch (109) is pressed whilst gear shifting. Upon triggering the gear shift switch (109) whilst shifting gears, said gear shift switch (109) sends appropriate signals to disengage the clutch in the clutch unit (102).
Based on the signals received by the electronic control unit (106) from the gear shift switch (109), either the forward or the reverse clutch pack will be engaged/disengaged by means of supply/drain of fluid from the fluid system (104) through the forward or the reverse valve respectively.
This method and system of transmission control eliminates the additional requirement of sensors. This system also eliminates the requirement of various position sensors. Reduced number of sensors in the system reduces the cost of the said transmission control system drastically. The present invention also allows the operator to shift from any high speed ratio to any low speed ratio and vice-versa without any hassle.

BRIEF DESCRIPTION OF THE DIAGRAMS
Figure 1 shows the schematic block diagram of the transmission control system.
Figure 2 illustrates the modulation curve diagram of the present invention.
While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention as embodied by the "A transmission control system and a method
for controlling transmission for clutch pedal free operation", succinctly fulfils the above-
mentioned need(s) in the art. The present invention has objective(s) arising as a result of
the above-mentioned need(s), said objective(s) being enumerated below. In as much as
the objective(s) of the present invention are enumerated, it will be obvious to a person
skilled in the art that, the enumerated objective(s) are not exhaustive of the present
invention in its entirety, and are enclosed solely for the purpose of illustration. Further, the
present invention encloses within its scope and purview, any structural alternative(s) and/or
any functional equivalent(s) even though, such structural alternative(s) and/or any
functional equivalent(s) are not mentioned explicitly herein or elsewhere, in the present
disclosure. The present invention therefore encompasses also, any
improvisation(s)/modification(s) applied to the structural alternative(s)/functional alternative(s) within its scope and purview. The present invention may be embodied in other specific form(s) without departing from the spirit or essential attributes thereof.
Throughout this specification, the use of the word "comprise" and variations such as "comprises" and "comprising" may imply the inclusion of an element or elements not specifically recited.

The present invention provides a transmission control system for clutch pedal free operation, comprising of: an engine (101); a clutch unit (102) adjacent to the engine (101), wherein the clutch unit (102) comprises of a forward clutch pack and a reverse clutch pack, said forward clutch pack and reverse clutch pack is a wet clutch pack; a transmission system (103), said transmission system (103) is operatively coupled with the clutch unit (102), wherein the transmission system (103) is a mechanical transmission system; a fluid system (104), said fluid system (104) is in communication with the transmission system (103) for cooling and/or lubrication purpose, wherein the fluid system (104) is hydraulic fluid system; a fluid valve block (105), said fluid valve block (105) is in contact with the fluid system (104) fluidically, wherein the fluid valve block (105) comprises of a forward valve and a reverse valve, wherein the forward valve and the reverse valve is a pressure proportional control valve, said forward valve supplies or drain pressurised fluid to or from the forward clutch pack and said reverse valve supplies or drain pressurised fluid to or from the reverse clutch pack; and an electronic control unit (106), said electronic control unit (106) sends an appropriate signals to the fluid valve block (105), wherein the appropriate signals is a modulated pressure signals, said appropriate signals are appropriated by means of input from a plurality of sensors, a gear shift switch (109) and/or a stored data.
Said plurality of sensors are, a first sensor (107) and a second sensor (108). Wherein said plurality of sensors are speed sensors. The first sensor (107) measures speed of the engine (101) and sends measured speed signal to the electronic control unit (106). The second sensor (108) measures speed of the transmission unit (103) and sends measured signal to the electronic control unit (106). Said gear shift switch (109) is positioned appropriately along with a mechanical speed shift lever. The gear shift switch (109) is a digital switch, wherein the gear shift switch (109) is pressed whilst gear shifting. Upon triggering the gear shift switch (109) whilst shifting gears, said gear shift switch (109) sends appropriate signals to disengage the clutch in the clutch unit (102).
Said stored data is the datas pertaining to the optimum performance of the vehicle.
A method for controlling the transmission system for clutch pedal free operation, comprising of,

• shifting the mechanical speed shift lever by the operator of the vehicle;
• triggering the gear shift switch (109) whilst shifting the mechanical speed shift lever by the operator of the vehicle;
• sending signals from the gear shift switch (109) to the electronic control unit (106) to disengage the clutch pack in the clutch unit (102) in order to shift the gear from the operating gear to a selected operating gear;
• measuring the speed of the engine (101) and the speed of the transmission unit (103) by means of the first sensor (107) and the second sensor (108) respectively;
• transmitting the measured speed signals, from the first sensor (107) and the second sensor (108), to the electronic control unit (106);
• estimating the operating speed ratio with respect to the received measured speed signals by the electronic control unit (106);
• inferring the selected operating gear, said selected operating gear is inferred by comparing the operating speed ratio with the stored data, by the electronic control unit (106);
• modulating the pressure signals, said pressure signals are modulated on the basis of inferred selected operating gear and received signals from gear shift switch (109), first sensor (107) and second sensor (108) , by the electronic control unit (106);
• conveying the modulated pressure signals from the electronic control unit (106) to the fluid valve block (105);
• controlling the clutch unit (102), said clutch unit is controlled by the fluid valve block (105), wherein the fluid valve block (105) communicate the fluid to the clutch unit (102) apt to the conveyed modulated pressure signals; and
• adjusting the speed ratio and/or changing the direction of operation of the vehicle, appropriate to the selected operating gear by means of the mechanical speed shift lever.
Upon receiving the signals from the gear shift switch (109), the electronic control unit (106) conveys the appropriate modulated pressure signals to the fluid valve block (105). The

fluid valve block (105) removes the fluid from the clutch unit (102) to disengage the clutch pack and shifts the gear from operating gear to the selected operating gear.
The electronic control unit (106) estimates the operating speed ratio according to the speed signals received from the first sensor (107) and the second sensor (108). Furthermore, the electronic control unit (106) infers the selected operating gear by comparing the operating speed ratio from the stored data. On the basis of the inferred selected operating gear, the electronic control unit (106) sends appropriate modulated pressure signals to the fluid valve block (105). The fluid valve block (105) communicates the fluid to the clutch unit (102) to control the clutch pack and adjust the operating speed ratio of the vehicle appropriate to the selected operating gear.
In an embodiment of the present invention, the vehicle is operating in the forward direction, the operator of the vehicle shift the gear from the operating gear to the selected operating gear by triggering the gear shift switch (109) whilst shifting the mechanical speed lever. The gear shift switch (109) send the signals to the electronic control unit (106). The electronic control unit (106) conveys the modulated pressure signals to the forward valve in the fluid valve block (105). The forward valve removes the fluid from the forward clutch pack and sends back the fluid to the fluid system (104), to disengage the clutch for easy shift of the gear. Upon selecting the selected operating gear, the speed signals from the first sensor (107) and the second sensor (108) are transmitted to the electronic control unit (106). The electronic control unit (106) estimates the operating speed ratio on the basis of the received signals. Furthermore, the electronic control unit (106) infers the selected operating gear by comparing the operating speed ratio with the stored data. The electronic control unit (106) modulates the pressure signals on the basis of the inferred selected operating gear, estimated operating speed ratio and/or signals from the gear shift switch (109). The modulated pressure signals is conveyed from the electronic control unit (106) to the forward valve in the fluid valve block (105). The fluid valve block (105) appropriately communicates the fluid from the fluid system (104) to the forward clutch pack in the clutch unit (102) and adjust the operating speed ratio appropriate to the selected operating gear.

In an another embodiment of the present invention, the vehicle is operating in the reverse direction, the operator of the vehicle shift the gear from the operating gear to the selected operating gear by triggering the gear shift switch (109) whilst shifting the mechanical speed lever. The gear shift switch (109) send the signals to the electronic control unit (106). The electronic control unit (106) conveys the modulated pressure signals to the reverse valve in the fluid valve block (105). The reverse valve removes the fluid from the reverse clutch pack and sends back the fluid to the fluid system (104), to disengage the clutch for easy shift of the gear. Upon selecting the selected operating gear, the speed signals from the first sensor (107) and the second sensor (108) are transmitted to the electronic control unit (106). The electronic control unit (106) estimates the operating speed ratio on the basis of the received signals. Furthermore, the electronic control unit (106) infers the selected operating gear by comparing the operating speed ratio with the stored data. The electronic control unit (106) modulates the pressure signals on the basis of the inferred selected operating gear, estimated operating speed ratio and/or signals from the gear shift switch (109). The modulated pressure signals is conveyed from the electronic control unit (106) to the reverse valve in the fluid valve block (105). The fluid valve block (105) appropriately communicates the fluid from the fluid system (104) to the reverse clutch pack in the clutch unit (102) and adjust the operating speed ratio appropriate to the selected operating gear.
In an yet another embodiment of the present invention, the vehicle is operating in the forward direction, the operator of the vehicle shifts the gear from the forward operating gear to the reverse selected operating gear by triggering the gear shift switch (109) whilst shifting the mechanical speed lever. The gear shift switch (109) send the signals to the electronic control unit (106). The electronic control unit (106) conveys the modulated pressure signals to the forward valve in the fluid valve block (105). The forward valve removes the fluid from the forward clutch pack and sends back the fluid to the fluid system (104), to disengage the clutch for easy shift of the gear. Upon selecting the reverse selected operating gear, the speed signals from the first sensor (107) and the second sensor (108) are transmitted to the electronic control unit (106). The electronic control unit (106) estimates the operating speed ratio on the basis of the received signals. Furthermore, the electronic control unit (106) infers the selected operating gear by

comparing the operating speed ratio with the stored data. The electronic control unit (106) modulates the pressure signals on the basis of the inferred selected operating gear, estimated operating speed ratio and/or signals from the gear shift switch (109). The modulated pressure signals is conveyed from the electronic control unit (106) to the reverse valve in the fluid valve block (105). The fluid valve block (105) appropriately communicates the fluid from the fluid system (104) to the reverse clutch pack in the clutch unit (102) and adjust the operating speed ratio appropriate to the reverse selected operating gear.
In an another embodiment of the present invention, the vehicle is operating in the reverse direction, the operator of the vehicle shifts the gear from the reverse operating gear to the forward selected operating gear by triggering the gear shift switch (109) whilst shifting the mechanical speed lever. The gear shift switch (109) send the signals to the electronic control unit (106). The electronic control unit (106) conveys the modulated pressure signals to the reverse valve in the fluid valve block (105). The reverse valve removes the fluid from the reverse clutch pack and sends back the fluid to the fluid system (104), to disengage the clutch for easy shift of the gear. Upon selecting the forward selected operating gear, the speed signals from the first sensor (107) and the second sensor (108) are transmitted to the electronic control unit (106). The electronic control unit (106) estimates the operating speed ratio on the basis of the received signals. Furthermore, the electronic control unit (106) infers the selected operating gear by comparing the operating speed ratio with the stored data. The electronic control unit (106) modulates the pressure signals on the basis of the inferred selected operating gear, estimated operating speed ratio and/or signals from the gear shift switch (109). The modulated pressure signals is conveyed from the electronic control unit (106) to the forward valve in the fluid valve block (105). The fluid valve block (105) appropriately communicates the fluid from the fluid system (104) to the forward clutch pack in the clutch unit (102) and adjust the operating speed ratio appropriate to the forward selected operating gear.
The method and system of transmission control of the present invention eliminates the additional requirement of sensors. This system also eliminates the requirement of various position sensors. Since less sensors are used cost of the control system is drastically

reduced. The present invention also allow the operator to shift from any high speed ratio to any low speed ratio and vice-versa without any hassle.
It will be apparent to a person skilled in the art that the above description is for illustrative purposes only and should not be considered as limiting. Various modifications, additions, alterations, and improvements without deviating from the spirit and the scope of the invention may be made by a person skilled in the art.