FIELD OF INVENTION:
The present invention relates to a modular electro-hydraulic assist gear-shift system used in an earth moving machine.
BACKGROUND OF INVENTION:
The present invention relates to a modular electro-hydraulic assist gear-shift system used in an earth moving machine, for example a Back hoe loader, involving gear selection through electrical switch, the signal from which is sent to a hydraulic shift unit through an electronic control module, which energizes solenoid to effect selection of the required gear.
In conventional gear shift pattern the gears are selected with manually operated lever. In Back hoe loaders while loading operator has to command three operations i.e. loader bucket control, steering wheel and gear shift lever. The operator can command at the most only two functions at a time. This results in loss of shovel productivity.
Other disadvantage of the conventional system is that during normal road plying of machine, frequent shift of gears through lever results in operator fatigue.
Also, movement of lever for gear shifting requires additional space in cabin.
Apart from above, in the current system, noise and heat perforates into the cabin due to the cut out in the floor which results in operator discomfort.
Another prevailing design available is an automated manual transmission with the shifting devices integrated into the transmission, making it bespoke and unique. The disadvantage of this system is that it is integral to the transmission unit and hence is expensive to make and replace. The present invention is directed to overcome one or more of the problems identified above.

Therefore, in view of the disadvantages stated above, the main objective of the present invention is to describe a modular effortless gear shifting using an electro-hydraulic assist shift mechanism and thereby enhancing loader productivity.
Another important objective is to deploy modular shift units whereby a decision can be made at the end of the base gearbox production line, to either fit a manual stick shift module or an electro-hydraulic assist module, thereby increasing standardization and reducing investment.
With this invention, the further objective is also to increase the leg space and enhance operator comfort inside the cabin of the machine.
We shall now describe the invention with reference to accompanying drawings which are given for the sake of illustration, but do not restrict the scope of present invention.
Referring to drawings:-
Fig. 1 shows the electro-hydraulic system of the present invention.
Fig. 2 shows the gear operating pattern of the present invention.
According to present invention there is provided the salient features of improved modular gear shift unit given in accompanied Fig. 1.
As illustrated in Figure 1, the electro-hydraulic system includes an electrical switch (7) for manual gear selection being mounted on the steering column in the cabin of the machine. This electrical switch (7) operates on 12V machine electrical systems and sends signal directly to electronic control unit (5) through electrical wiring harness. The electronic control unit 5 through wiring harness, is further connected with the gear shift unit (8). It is intended to control the automated gear-shift unit (8) fitted to the gearbox. Electronic control unit works as per the logical programmed inputs entered through a software.

This unit comprises of two pistons - fore / aft piston (9) and cross gate piston (10), which controls the gear shift finger (11) movement within the unit. The shift finger (11), in the unit, moves in two planes, fore/aft and cross gate. The piston movement takes place with the fluid flow through pump (1) from the gearbox. Three solenoids (2), (3) and (4) attached with the hydraulic shift unit controls the fluid flow to the pistons and return fluid goes to sump (6). The three solenoids are termed, even-gears (4), odd-gears (3) and cross-gate (2). Position of the shift finger (11) in the unit is monitored with two rotary angle sensors. One sensor is used to monitor the fore/aft direction and the other for cross gate.
The machine operator selects the required gear by rotating the electrical switch (7) which further sends power signal to Electronic Control Unit (5). Electronic Control Unit (5) works as per programmed logical input and sends electrical signals to the respective solenoid valve. Solenoid valve attached with the unit opens and closes the respective ports for the fluid flow which in turn makes the respective pistons to move forward and backward.
I Gear
As illustrated in Figure 2, the machine operator selects the 1st gear by rotating the electrical switch (7) one step in clockwise direction which sends signal to Electronic control unit (5). The electronic control unit (5) further sends electrical signals to odd gear solenoid valve (3). The hydraulic power through valve makes fore / aft piston (9) to move in fore position. This in turn moves the gear shift finger (11) in forward direction and hence selects 1st gear.
II Gear
The machine operator selects the 2nd gear by rotating the electrical switch (7) two steps in clockwise direction which sends signal to Electronic control unit (5). The electronic control unit (5) further sends electrical signals to even gear solenoid valve (4). The hydraulic power through valve makes fore / aft piston (9) to move in aft position. This in turn moves the gear shift finger (11) in backward direction and hence selects the 2nd gear.

III Gear
The machine operator selects the 3rd gear by rotating the electrical switch (7) three steps in clockwise direction which sends signal to electronic control unit (5). The electronic control unit (5) further sends electrical signals to odd gear solenoid valve (3) and cross gate solenoid valve (2). The hydraulic power through cross-gate solenoid (2) moves the shift finger from 1/2 neutral plane to 3/4 neutral plane and odd gear solenoid valve (4) makes fore / aft piston (9) to move in fore position This in turn moves the gear shift finger (11) in forward direction in 3/4 plane and hence selects the 3rd gear.
IV Gear
The machine operator selects the 4th gear by rotating the electrical switch (7) four steps in clockwise direction which sends signal to electronic control unit (5). The electronic control unit 5 further sends electrical signals to even gear solenoid valve (4) and cross gate solenoid valve (2). The hydraulic power through cross-gate solenoid (2) moves the shift finger from 1/2 neutral plane to 3/4 neutral plane and even gear solenoid valve (3) makes fore / aft piston (9) to move in aft position. This in turn moves the gear shift finger (11) in backward direction in 3/4 plane and hence selects the 4th gear.
When the cross-gate solenoid is off, a spring returns the shift finger to the 1/2 plane providing the finger is in the centre of the 'H Gate*.
• 1st gear, Neutral - Odd gears
• 2nd gear, Neutral - Even gears
• 3rd gear, Neutral - Cross gate - Odd gears
• 4th gear, Neutral - Cross gate - Even gears
As the respective piston moves, the rotary angle sensors monitor the position of shift finger and sends signal to the Electronic control unit (5). The electronic control unit (5) which works on the basis of programmed logic takes these signals from two sensors as an input to

select the solenoid valve for further movement of the finger (11). This is to ensure actual movement of finger (11) to avoid any malfunctioning of the system.