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Patent Searching and Data


Title:
GEARSHIFT
Document Type and Number:
WIPO Patent Application WO/2012/077045
Kind Code:
A1
Abstract:
The invention concerns a gearshift (10) for a transmission of a vehicle, in particular for a powershift transmission of a mining or agricultural vehicle. The gearshift (10) includes a body (12) containing a valve bank (14) having a number of outlets (20, 22). The outlets (20, 22) are, in use, in fluid communication with actuators on the transmission responsible for selecting different transmission ratios. The gearshift (10) further includes a selector (28) for controlling the flow of fluid to different valve outlets (20, 22). The selector (28) is movable between a number of positions which allow different fluid flow paths through the valve bank (14) in order to activate and deactivate different actuators. By allowing fluid flow to different actuators, different gear ratios in the transmission are selected. The invention also concerns a method of controlling a gearshift (10) for a transmission of a vehicle.

Inventors:
AUCAMP PAULUS JOHANNES (ZA)
Application Number:
PCT/IB2011/055481
Publication Date:
June 14, 2012
Filing Date:
December 06, 2011
Export Citation:
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Assignee:
AGRICULTURAL AND IND MECHANISATION GROUP PROPRIETARY LTD (ZA)
AUCAMP PAULUS JOHANNES (ZA)
International Classes:
F16H59/04
Foreign References:
US4119119A1978-10-10
US3522867A1970-08-04
DE8802280U11988-04-07
Attorney, Agent or Firm:
SPOOR & FISHER et al. (0001 Pretoria, ZA)
Download PDF:
Claims:
CLAIMS

1. A gearshift for a transmission of a vehicle, the gearshift including a body, a valve bank having a number of outlets which, in use, are in fluid communication with actuators on the transmission responsible for selecting different transmission ratios, and a selector for controlling the flow of fluid to different valve outlets, the selector being movable between a number of positions which allow different fluid flow paths through the valve bank in order to activate and deactivate different actuators depending on the valve outlets to which fluid is supplied, thereby engaging and disengaging different gear ratios in the transmission.

2. A gearshift according to claim 1 , wherein the selector runs on top of the valve bank and is slidable between its different positions.

3. A gearshift according to either claim 1 or 2, wherein the selector has a number of activating formations which in use interact with selection pins located on the valve bank in order to direct the flow of fluid to different valve outlets depending on which selection pin or combination of selection pins is activated.

4. A gearshift according to claim 3, wherein a different selection pin or combination of selection pins is activated in each of the positions of the selector, thereby selecting different fluid flow paths in each of the selector positions.

5. A gearshift according to either claim 3 or 4, wherein the activating formations protrude from a surface of the selector, which in use is a bottom surface facing the top of the valve bank, towards the top of the valves where the selection pins are located so that when the activating formations press the selection pins downwards fluid flow is cut off to the outlets associated with the depressed selection pins.

6. A gearshift according to claim 5, wherein each valve outlet has a corresponding selection pin.

7. A gearshift according to any one of claims 1 to 6, wherein the valve bank includes a number of distribution valves, each valve having one inlet and two outlets.

8. A gearshift according to any one of claims 1 to 7, wherein the selector is connected to a gear lever such that in use the selector is moved between its different positions by means of the gear lever.

9. A gearshift according to any one of claims 1 to 8, including a park brake valve having an outlet which, in use, is in fluid communication with a park brake actuator for activating a park brake of the vehicle, wherein the park brake is automatically activated when fluid flow is cut off to the park brake outlet and automatically released when fluid is supplied to the park brake outlet.

10. A gearshift according to claim 9, wherein fluid flow to all of the outlets of the valve bank is cut off when the selector is in its neutral position, thereby discharging the corresponding actuators in order to disengage all gear ratios in the transmission and to activate the park brake.

11. A gearshift according to claim 10, wherein fluid is supplied to the park brake outlet when the selector is in any position other than neutral,

moved out of neutral.

12. A gearshift according to any one of claims 1 to 10, including a starter valve for activating the engine starter motor, wherein the starter valve is obstructed from being activated when the selector is in any position other than neutral.

13. A gearshift according to claim 12, including a cam which is movable between a receiving position wherein the starter valve may be activated and an obstructing position wherein the starter valve is prevented from being activated.

14. A gearshift according to claim 13, wherein the cam is connected to the selector so that it rotates as the selector is moved between its different positions, thereby ensuring that the cam only moves into its receiving position when the selector is in neutral.

15. A gearshift according to either claim 13 or 14, including a reverse switch which is automatically activated when the selector is moved from its neutral position to a reverse position, wherein the reverse switch includes a runner following the cam so that rotation of the cam activates the switch.

16. A gearshift according to any one of clams 1 to 15, wherein the fluid is air so that the gearshift controls the transmission of the vehicle pneumatically.

17. A method of operating a gearshift for a transmission of a vehicle, the method including:

supplying fluid to a valve bank including a number of outlets which in use are in fluid communication with actuators on the transmission responsible for selecting different transmission ratios;

selecting different fluid flow paths through the valve bank by moving a selector between different positions;

activating and deactivating different actuators depending on the position of the selector in order to engage and/or disengage different gear ratios in the transmission.

18. A method according to claim 17, inciuding supplying fluid to a starter valve and activating the starter valve manually.

19. A method according to claim 18, including preventing activation of the starter valve while the selector is in any position other than neutral.

20. A method according to any one of claims 17 to 19, wherein the step of selecting different fluid flow paths includes depressing and releasing different selection pins on the valve bank by moving the selector between its different positions.

21. A method according to claim any one of claims 17 to 20, including cutting off fluid to a park brake valve outlet, which is in use in fluid communication with a park brake actuator for applying a park brake of the vehicle, when the selector is in its neutral position.

22. A method according to claim 21 , including supplying fluid to the park brake valve outlet for releasing the park brake so that the vehicle may be driven when the selector is in any position other than neutral.

23. A method according to any one of claims 17 to 22, including cutting off fluid flow to all of the valve outlets when the selector is in a neutral position, thereby discharging all of the corresponding actuators in order to disengage all of the gear ratios in the transmission.

24. A method according to any one of claims 17 to 23, wherein the gearshift is a gearshift according to any one of claims 1 to 16.

Description:
GEARSHIFT

BACKGROUND TO THE INVENTION

This invention relates to a gearshift. In particular, but not exclusively, this invention relates to a gearshift for a powershift transmission of a mining or agricultural vehicle.

In the fields of mining and agricultural vehicles the use of solenoid activated hydraulic powershift transmissions are well known. These transmissions generally include solenoids which are electrically activated by manipulating a gearshift whenever gear selection is done. One disadvantage of using the known electrically activated transmissions is that fireproof certification is generally problematic as many electrical components used in these systems do not comply with stringent fireproof requirements. This is particularly problematic when using the transmissions in vehicles which are intended for use underground, for example in mines where safety is one of the main concerns. A further problem with electrically activated transmissions is experienced whenever maintenance or servicing procedures have to be carried out. These procedures generally require equipment such as computers to service and calibrate these efe.ctrica.liy activated transmissions. In rural areas the necessary equipment is not always at hand, thus resulting in unnecessary downtime of the vehicle.

It is an object of this invention to alleviate at least some of the problems experienced with existing electrically activated powershift transmissions.

It is a further object of this invention to provide a gearshift that will be a useful alternative to existing gearshifts.

SUMMARY OF THE INVENTION

According to the invention there is provided a gearshift for a transmission of a vehicle, the gearshift including a body, a valve bank having a number of outlets which, in use, are in fluid communication with actuators on the transmission responsible for selecting different transmission ratios, and a selector for controlling the flow of fluid to different valve outlets, the selector being movable between a number of positions which allow different fluid flow paths through the valve bank in order to activate and deactivate different actuators depending on the valve outlets to which fluid is supplied, thereby engaging and disengaging different gear ratios in the transmission.

The selector preferably runs on top of the valve bank and may be slidable between its different positions.

The selector may have a number of activating formations which in use interact with selection pins located on the valve bank in order to direct the flow of fluid to different valve outlets depending on which selection pin or combination of selection pins is activated. In the preferred embodiment a different selection pin or combination of selection pins is activated in each of the positions of the selector, thereby selecting different fluid flow paths in each of the selector positions.

Preferably, the activating formations protrude from a surface of the selector, which in use is a bottom surface facing the top of the valve bank, towards the top of the valves where the selection pins are located so that when the activating formations press the selection pins downwards fluid flow is cut off to the outlets associated with the depressed selection pins.

Each valve outlet may have a corresponding selection pin.

The valve bank preferably includes a number of distribution valves, each valve may have one inlet and two outlets.

The selector is preferably connected to a gear lever such that in use the selector is moved between its different positions by means of the gear lever.

The gearshift may include a park brake valve having an outlet which, in use, is in fluid communication with a park brake actuator for activating a park brake of the vehicle, wherein the park brake is automatically activated when fluid flow is cut off to the park brake outlet and automatically released when fluid is supplied to the park brake outlet.

Preferably, fluid flow to ali of the outlets of the valve bank is cut off when the selector is in its neutral position, thereby discharging the corresponding actuators in order to disengage all gear ratios in the transmission and to activate the park brake.

In the preferred embodiment, fluid is supplied to the park brake outlet when the selector is in any position other than neutral, thereby releasing the park brake automatically when the selector is moved out of neutral. The gearshift may include a starter valve for activating the engine starter motor, wherein the starter valve is obstructed from being activated when the selector is in any position other than neutral.

The gearshift may further include a cam which is movable between a receiving position wherein the starter valve may be activated and an obstructing position wherein the starter valve is prevented from being activated. Preferably, the cam is connected to the selector so that it rotates as the selector is moved between its different positions, thereby ensuring that the cam only moves into its receiving position when the selector is in neutral.

The gearshift may also include a reverse switch which is automatically activated when the selector is moved from its neutral position to a reverse position, wherein the reverse switch includes a runner following the cam so that rotation of the cam activates the switch.

The fluid is preferably air so that the gearshift controls the transmission of the vehicle pneumatically.

According to another aspect of the invention there is provided a method of operating a gearshift for a transmission of a vehicle, the method including: - supplying fluid to a valve bank including a number of outlets which in use are in fluid communication with actuators on the transmission responsible for selecting different transmission ratios;

selecting different fluid flow paths through the valve bank by moving a selector between different positions;

activating and deactivating different actuators depending on the position of the selector in order to engage and/or disengage different gear ratios in the transmission.

The method may include the step of supplying fluid to a starter valve and activating the starter valve manually. Activation of the starter valve is preferably prevented while the selector is in any position other than neutral.

The step of selecting different fluid flow paths preferably includes depressing and releasing different selection pins on the valve bank by moving the selector between its different positions.

The method may include cutting off fiuid to a park brake valve outlet which is in use in fluid communication with a park brake actuator for applying a park brake of the vehicle when the selector is in neutral.

The method preferably includes supplying fluid to the park brake valve outlet for releasing the park brake so that the vehicle may be driven when the selector is in any position other than neutral.

The method may include cutting off fluid flow to all of the valve outlets when the selector is in a neutral position, thereby discharging all of the corresponding actuators in order to disengage all of the gear ratios in the transmission.

The method is preferably carried out using the gearshift according to the first aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:

Figure 1 shows a left side perspective view of a gearshift according to the invention; Figure 2 shows a right side perspective view of the gearshift of Figure 1 ; and

Figure 3 shows a rear perspective view of the gearshift of Figures 1 and 2.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

Figure 1 shows a gearshift 10 according to the invention. In use, the gearshift 10 is used to activate a powershift transmission of a vehicle pneumatically. Although in this description the invention will be described as a pneumatic gearshift it must be understood that a fluid other than air may also be used. For example, it is envisaged that in an alternative embodiment the gearshift 10 could also activate a powershift transmission hydraulically.

Returning to the illustrated embodiment, the gearshift 10 has a body 12 holding a valve bank 14 which has a number of distribution valves 16. In this embodiment the valve bank 14 includes three valves 16.1 , 16.2 and 16.3. Each valve has an inlet 18 and two outlets 20 and 22 which are in fluid communication with corresponding actuators on the transmission responsible for selecting different transmission ratios. In the preferred embodiment the actuators are pneumatically activated solenoids which in turn activate hydraulic clutch packs in the transmission in order to select different transmission ratios. A person skilled in the art of powershift transmissions will be familiar with the way in which the different transmission ratios are selected and accordingly it will not be discussed in any detail.

Air flow through the different valves 16 is controlled by a control mechanism 24 including a gear lever 26 which is movable between a number of different positions in order to direct air flow to different valves outlets 20, 22. It should be clear that by manipulating the gear lever 26 between its different positions the driver may change the gear ratios in the transmission as a result of different fluid flow paths activating different solenoids. In the preferred embodiment the gear lever 26 has five different positions namely first gear, second gear, third gear, neutral and reverse. It is envisaged that in an alternative embodiment the gear lever 26 may have a sixth position which corresponds to fourth gear.

As shown in Figure 1 the gear lever 26 is mounted on the end of a locating shaft 28 which is attached to the body 12 by means of bushings 30.1 and 30.2. The shaft 28 is located rotatably in the bushings 30 to allow it to rotate as the lever 20 is rotated. Also attached to the shaft 28 is a connecting member 32 which in turn drives a selector 34. The selector 34 is movable in a channel 36 which in use extends substantially horizontally between two guides 38 located on top of the valve bank 14. Fasteners 40 are used to connect the guides 38 and valves 16 to the body 12. In order to translate the rotational movement of the lever 26 into linear movement of the selector 34 in the channel 36, linkages 42 are connected between the selector by and connecting member 32 by means of fasteners 44. In the preferred embodiment the linkages 42 are bolted to the connecting member 32 and selector 34 so that they may rotate about a longitudinal axis of the bolts 44 as the selector is moved.

By moving the gear lever 26 between its different positions, the selector is moved along the channel 36 (shown in Figure 2) between different positions wherein air flow is allowed to different valve outlets. The selector 34 has activating formations (not shown in the drawings) located on a surface which is in use a bottom surface. The activating formations extend towards the valves 16 and interact with corresponding selection pins (not shown in the drawings) located on the valves in order to activate and deactivate the valves 16 as the selector slides along the channel 36 between its various positions. In the preferred embodiment each valve 16 has two selection pins, one associated with each valve outlet 20 and 22. in the preferred embodiment the valves 16 in the valve bank 14 are normally open valves and in order to stop air flow to a particular valve outlet the corresponding selection pin has to be depressed, i.e. pressed downwards, by the corresponding activating formation located on the selector 34. It should be clear that air flow to the valve outlet or combination of valve outlets corresponding to the selection pin or combination of selection pins which is depressed is prevented. In contrast, air flow is allowed to the outlet or combination of outlets corresponding to the selection pin or combination of selection pins which is released, i.e. not depressed, thereby activating the solenoid or solenoids in fluid connection with the outlet(s).

The selector 34 is also used to control the activation and deactivation of a park brake of the vehicle by controlling air flow to a park brake outlet on the valve bank. Again, the park brake outlet is in fluid connection with a park brake solenoid responsible for activating and deactivating the park brake. The gearshift is designed so that air supply to the valve outlets is cut off upon activation of the park brake, thereby discharging all of the solenoids in order to disengage all gears in the transmission. It must be understood that upon activation of the park brake the vehicle will also be brought to a standstill.

As a safety precaution the park brake may only be activated when the gearshift is in its neutral position i.e. when the gear lever 26 is positioned in a generally vertical direction as shown in the figures. In the preferred embodiment the park brake is activated automatically upon movement of the gear iever 26 and accordingly the selector 34 into their neutral positions in order to bring the vehicle to a complete standstill every time the transmission is shifted into neutral. From the above description it should be clear that ail of the selection pins are activated i.e. depressed when the selector 34 and therefore the gearshift 0 are in neutral.

The advantage of activating the park brake prior to shifting the transmission into reverse is that the direction of travel of the vehicle cannot be changed without first bringing the vehicle to a standstill. A person skilled will understand that this feature protects the transmission against damage.

In the preferred embodiment the park brake is automatically released whenever the gear lever 26 is moved out off its neutral position by allowing air flow to the park brake outlet.

The gearshift 10 further includes a starter valve 46 mounted to the body 12 and in fluid communication with the engine starter motor. In the illustrated embodiment the starter valve 46 is manually operated and the driver must activate it in order to start the vehicle's engine. As a safety precaution the starter valve 46 is prevented from being activated while the gearlever 26 is in any position other than neutral. This is achieved by mounting a cam 48 on the shaft 28 in such a manner that it rotates with the gear lever between a receiving position wherein the starter valve may be activated and an obstructing position wherein the starter valve is obstructed from being activated. As shown in Figure 3 the cam 48 has a recess 50 which is oriented to receive a portion 52 of the starter valve 46 when the cam is in its receiving position i.e. when the gear lever is in its neutral position. It should be clear that when the gear lever 26 is moved into any position other than neutral, the cam will automatically move into its obstructing position wherein the recess 50 is not aligned with the starter valve portion 52 and, as a result, the starter valve cannot be activated.

The gearshift 10 also includes a reverse switch 54 which has a runner 56 following the cam 48. The reverse switch 54 may be used to activate an indicator for indicating to people in the vicinity of the vehicle that the vehicle is reversing.

The layout of the valves 16 and in particular the valve outlets 20 and 22 in combination with the activating formations on the selector 34 are designed so that the reverse solenoid cannot be activated without the gearshift 10 first having been put into neutral. In other words, the gear lever 26 cannot be moved into its reverse position without first having been moved into its neutral position wherein the park brake is automatically activated.

It should further be understood that the gearshift 10 illustrated in the drawings will generally be used in mining and agricultural vehicles and will be run off the vehicle's existing air supply.