FIELD OF INVENTION:

The invention generally relates to the field of automotive parts. More particularly embodiments of the invention relates to a switch back arrangement for a ratio shifter of a multi speed axle.

BACKGROUND:

A two speed axle is a very significant automotive component of the auto industry. The two speed axle has two predefined ratio positions. Selection of the first position of the ratio results in the increased speed for that selected ratio. Selecting the second position of ratio provides the increased torque on demand. The two speed axle briefly described herein above has the advantages of increasing the fuel efficiency of the vehicle fitted with the two speed axle and reducing the turnaround time. The ratio shift is triggered through a ratio changeover switch. The ratio changeover shift is coupled to a shifter unit. The turning ON/OFF of the ratio changeover switch is communicated to the shifter unit, which then performs the ratio shift.

A ratio shift can be from a high speed to a low speed and vice versa. The shift from high speed to low speed normally occurs through a mechanical engagement of the sun gear in the clutch plate. However, there may be a failure of the mechanical engagement of the sun gear in the clutch plate. On such instance, where there could be a failure in the mechanical arrangement is the downgrade motion of the vehicle. During the down grade motion, the rpm of the vehicle wheel is high and the vehicle speed can be reduced either by the transmission or through activation of brakes. An attempt to initiate Low Speed ratio shift from High Speed ratio during the downgrade motion may result in improper engagement of sun gear with the clutch plate. Such improper engagement can cause the vehicle to attain a neutral state causing no effect of transmission gear shift & eventually leading to over speed of the vehicle. Shifting of the vehicle to the neutral provides a setback for activation of braking. However, For Continuous down hill performance engine braking is the only safest option as Applying Brake continuously will cause "FADE" due to overheating of the liner and eventually the brake may be lost!!!.

Hence, there is a need for a mechanism that eliminates the safety risk associated with the attempt of the Low Speed Ratio shift from High Speed Ratio of a two speed axle during the Down grade drive.

SUMMARY OF THE INVENTION

An aspect of the present invention is to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below.

Accordingly, an aspect of the present invention is to provide a switch back arrangement for a multi-speed axle for the ratio shift attempt from high speed ratio to low speed ratio during the Down garde drive of the vehicle, the arrangement comprising: a shifter unit for shifting the ratio between high speed to a low speed and vice versa due to the Toggle switch trigger mechanism associated with it, a Toggle switch is triggered by the driver in the cabin initiates the ratio shift by opening the solenoid valve to release the compressed air in the shifter unit, wherein the Shifter shaft initiates the ratio shift during the shift of speed from high to low and switch back to the original position during the shift of speed form low to high again based on the toggle switch trigger by driver, a Toggle switch for initiating the switch back of the shifter unit is coupled to a solenoid, and a quick release valve, a source of air which is coupled to the solenoid valve, and a timer mechanism is coupled to the solenoid valve & the Switch sensor of the Shifter unit which provides the confirmation of the physical shift of the Shifter shaft in shifter unit, wherein the timer mechanism is initiated upon receipt of a signal from the Toggle switch and is triggered following a preset time, wherein, during failure of the ratio shift ( i.e. if there is no positive shift confirmation by the switch sensor within the specified time), the timer mechanism forces the solenoid to shut off using the quick release valve, thereby forcing the release of air from the source to the shifter unit, wherein the air inflow from the source through the air valve into the shifter unit causes the ratio to shift back to the previous position.

Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS:

The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 shows a representative circuit of a switch back arrangement according to an embodiment of the invention.

Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.

SUMMARY OF THE INVENTION:

One aspect of the invention provides a switch back arrangement for improper ratio shifts during abnormal driving conditions of a vehicle. The switch back arrangement includes a timer mechanism for resetting an improper ratio shift. A timer mechanism acts a feedback mechanism and is coupled to pre-existing means of shift indicator. The timer mechanism is initiated subsequent to lapse of a preset time interval. A solenoid arrangement coupled to the timer mechanism is activated after the lapse of the preset time interval to initiate reset of the ratio shift. The switch back arrangement is a failsafe arrangement for eliminating improper ratio shift, enhancing vehicle performance and preventing premature brake fade.

DETAILED DESCRIPTION OF THE INVENTION:

Various embodiments of the invention provide a switchback arrangement for a ratio shift of a two speed axle. FIG. l shows a representative circuit of a switch back arrangement according to an embodiment of the invention. 101 is a shifter unit of a two speed axle (Two Speed axle is not shown in FIG1). A sensor switch 102 is provided on the shifter unit 101. The Toggle switch 105 initiates the ratio shift and the shift in the ratio are indicated by an indicator 103 mounted on the vehicle. The switch sensor 102 is coupled to a power source 104. A Toggle switch 105 is connected to the power source 104. The mechanism 109 is responsible for initiating the switch back, in an embodiment of the invention. The Toggle switch 105 is operable coupled to a solenoid arrangement 106. The solenoid arrangement 106 is coupled to a source of air 107. The movement of a solenoid (not shown) within the solenoid arrangement 106 facilitates release of air from the source 107.

A timer mechanism 109 is coupled to the Switch sensor 102, the Toggle switch 105 and the solenoid arrangement 106. The timer mechanism 109 is initiated upon receipt of a signal from the Toggle switch 105. In one embodiment of the invention, non availability of signal at switch sensor 102 after within the specified time of Toggle Switch 105 actuation is an improper shift of the ratio. The timer mechanism 109 is triggered only subsequent to a preset time. In one instance, the preset time is the time required for shift of the ratio. Upon failure of the ratio shift, the timer mechanism 109 forces the solenoid arrangement 106 to shut off and stops the release of air from the source 107. A quick release valve 108 connected to the Shifter Unit 101 releases the air to from the shifter unit 101. The withdrawal of air inflow from the source 107 through the air valve 106 into the shifter unit 101, causes the ratio to shift back to the previous position.

Described herein below are few conditions under which the switch back arrangement as described briefly herein above functions.

Condition 1: shift during the plain road or uphill (shift from high speed to low speed): An operator pulls the toggle switch. The pulling of the toggle switch results in the movement of the solenoid. The movement of the solenoid enables opening of the valve. The opening of the valve facilitates inflow of air into the shifter unit. The inflow of air into the shifter unit increases the pressure resulting in shift of the position of the shifter shaft. The change in the position of the shifter shaft enables physical contact of the shaft with a sensor switch leading to activation of the sensor switch. The activation of the sensor switch is indicated through an indicator bulb connected to the sensor switch.

Condition 2: shift during the plain road or uphill (shift from low speed to high speed): An operator pushes the toggle switch. The pushing of the toggle switch results in the deactivation of the solenoid. The deactivation of the solenoid enables closing of the valve. The closing of the valve facilitates release of air with the help of quick release valve from the shifter unit. The quick release of air from the shifter unit decreases the pressure resulting in shift back of the position of the shifter shaft at the earliest. The shift back of the shifter shaft disables the physical contact of the shaft with the sensor switch leading to deactivation of the sensor switch. The deactivation of the sensor switch causes switching off of the indicator bulb.

Condition 3: shift during the downhill or down grade (shift from high speed to low speed): An operator pulls the toggle switch. The pulling of the toggle switch results in the movement of the solenoid. The movement of the solenoid enables opening of the valve. The opening of the valve facilitates inflow of air into the shifter unit. The inflow of air into the shifter unit increases the pressure resulting in shift of the position of the shifter shaft. A timer mechanism is connected to both the activation switch and the switch sensor. The timer mechanism is set to a predetermined value of time. Subsequent to the activation of the switch by the operator, if the switch sensor is not triggered within the set value of time, the timer mechanism forces the deactivation of the solenoid causing the release of the air pressure and repositioning of the shifter to the original speed or high speed ratio. In one example of the invention, if the solenoid switch is activated and if within 5 seconds the shifting is not done, then the timer mechanism shuts off the solenoid causing the shifter to go back to the original position. The timer mechanism will get deactivated at the instance of activation of the switch sensor. Alternatively, the timer mechanism can also get deactivated at the instance of the operator pushing the activation switch position back to the high speed ratio position. In another instance of implementation of invention, say during the down grade, If the position of the shifter is interim due to the air pressure on one side and resistance of shift from the other side due to the increased wheel speed caused by the down grade, then the timer mechanism clock is activated as soon as the driver pulls the toggle switch. As soon as the time difference exceeds the time set in the timer mechanism, the timer mechanism will rest the position of the Shifter by closing the circuit.
The invention provides a switch back arrangement for improper ratio shifts during abnormal driving conditions of a vehicle. The switch back arrangement includes a timer mechanism for resetting an improper ratio shift. Timer mechanism acts a feedback mechanism and is coupled to pre-existing means of shift indicator. The timer mechanism is initiated subsequent to lapse of a preset time interval. A solenoid arrangement coupled to the timer mechanism is activated after the lapse of the preset time interval to initiate reset of the ratio shift. The switch back arrangement is a failsafe arrangement for eliminating improper ratio shift, enhancing vehicle performance and preventing premature brake fade. The foregoing description of the invention has been set for merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to person skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.

WE CLAIM:

1. A switch back arrangement for a multi-speed axle, the arrangement comprising:

a shifter unit for shifting the ratio between high speed to a low speed and vice versa due to the spring mechanism associated with it;

a sensor switch is provided on the shifter unit, wherein the sensor switch initiates the ratio shift during the shift of speed from high to low and switch back to the original position during the shift of speed form low to high; a Toggle switch for initiating the switch back of the shifter unit, the Toggle switch is coupled to a solenoid, and a quick release valve; a source of air which is coupled to the solenoid of the Toggle switch,

and a timer mechanism is coupled to the solenoid of the Toggle switch, wherein the timer mechanism is initiated upon receipt of a signal from the sensor switch and is triggered following a preset time, wherein, during failure of the ratio shift, the timer mechanism forces the solenoid to shut off and there by release of air from the source to the shifter unit by using the quick release valve, and withdrawal of air inflow from the source through the Shut off of the Solenoid valve into the shifter unit causes the ratio to shift back to the previous position.

2. The arrangement of claim 1, wherein the Toggle Switch movement detection triggers the Solenoid switch to facilitate the release of air from the source.

3. The arrangement of claim 1, further comprising:

4. an indicator for indicating the contact of the shifter Shaft of the Shuifter unit with the sensor switch when the speed is shifted from high to low.

5. The arrangement of claim 1, further comprising

a power source which supplies power to the Switch Sensor and the Toggle switch.

6. The arrangement of claim 1, wherein the shifter unit is at interim position, the timer mechanism is activated by pulling a toggle switch, and the timer clock performs the function of shutting down the solenoid after the expiration of the preset time causing the shifter to go back to the original position.

7. The arrangement of claim 1, wherein the timer mechanism is automatically stopped as soon as the switch sensor gets sensed or the push of the toggle switch from the low speed to the high speed.

8. The arrangement of claim 1, wherein the solenoid arrangement coupled to the timer mechanism is activated after the lapse of the preset time interval to initiate reset of the ratio shift.

9. The arrangement of any of the preceding claims eliminates improper ration shift, enhancing vehicle performance and preventing impulsive brake fade.

10. The switch back arrangement for a multi-speed axle substantially as herein described with reference to the above mentioned description and accompanying drawings.