Transmission system for a work vehicle

A transmission system for a work vehicle includes a transmission. The transmission includes one or more input shafts, one or more output shafts, and shafts disposed in-between. The transmission includes gear sets disposed on the shafts, wherein the gear sets include intermediate gear sets. The transmission includes clutches disposed along the shafts, wherein each of the clutches is configured to selectively couple a respective gear set of the gear sets corresponding to a respective power flow path of the transmission. The transmission also includes a forward coupler and a reverse coupler each disposed on one of the shafts. The transmission system also includes a controller configured to receive a signal indicative of a shuttle shift, and in response to receiving the signal, instruct the clutches to stop rotation of the intermediate gear sets and subsequently shuttle shift between forward and reverse directions.

BACKGROUND

The disclosure relates generally to a transmission system for a work vehicle.

Transmissions are used in agricultural and construction equipment to transmit power from power sources, such as internal combustion engines, to equipment for accomplishing a desired task. For example, transmissions are used to transmit power to wheels and/or tracks of a work vehicle. A powershift transmission is a transmission that controls the application and release of multiple clutches to maintain a torque path through the transmission while switching between gears. A powershift transmission may include a power shuttle unit (e.g., a power shuttle transmission) to enable the work vehicle to shuttle between forward and reverse directions within a short duration. The power shuttle transmission usually includes multi-plate clutches to shift between forward and reverse directions. However, these multi-plate clutches may be subjected to high relative speeds within the clutches (e.g., between counter-rotating plates of forward and reverse clutches), which may result in high parasitic losses due to clutch drag.

BRIEF DESCRIPTION

In one embodiment, a transmission system for a work vehicle includes a transmission, which includes one or more input shafts coupled to an input, one or more output shafts coupled to a load, a plurality of shafts disposed between the one or more input shafts and the one or more output shafts. The transmission includes a plurality of gear sets disposed on the plurality of shafts, wherein the plurality of gear sets include intermediate gear sets. The transmission includes a plurality of clutches disposed along the plurality of shafts, wherein each of the plurality of clutches is configured to selectively couple a respective gear set of the plurality of gear sets corresponding to a respective power flow path of the transmission. The transmission also includes a forward coupler disposed on one of the plurality of shafts and a reverse coupler disposed on one of the plurality of shafts. The transmission system also includes a controller communicatively coupled to the plurality of clutches, the forward coupler, and the reverse coupler, wherein the controller is configured to receive a signal indicative of a shuttle shift, and in response to receiving the signal, instruct the plurality of clutches to stop rotation of the intermediate gear sets and subsequently swap engagement of the forward coupler and the reverse coupler to shuttle shift between forward and reverse directions.

In another embodiment, a method for shuttle shifting a work vehicle, via a controller, includes receiving a signal indicative of a shuttle shift, and in response to receiving the signal, instructing a plurality of clutches to stop rotation of intermediate gear sets of a plurality of gear sets disposed on a plurality of shafts, wherein the plurality of shafts are disposed between one or more input shafts coupled to an input and one or more output shafts coupled to a load, and each of the plurality of clutches is configured to selectively couple a respective gear set of the plurality of gear sets corresponding to a respective power flow path of a transmission of the work vehicle. The method also includes subsequently instructing swapping engagement of a forward coupler and a reverse coupler to shuttle shift between forward and reverse directions, and instructing modulating the one or more output shafts during the shuttle shift.

In a further embodiment, an apparatus includes at least one non-transitory memory storing instructions for execution by a processor. The instructions include instructions to receive a signal indicative of a shuttle shift. The instructions include instructions to a plurality of clutches to stop rotation of intermediate gear sets of a plurality of gear sets disposed on a plurality of shafts of a transmission, wherein the plurality of clutches are disposed along the plurality of shafts disposed between one or more input shafts coupled to an input and one or more output shafts coupled to a load, wherein each of the plurality of clutches is configured to selectively couple a respective gear set of the plurality of gear sets corresponding to a respective power flow path of the transmission. The instructions also include instructions to swap engagement of a forward coupler and a reverse coupler to shuttle shift between forward and reverse directions and instructions to modulate a pressure applied to a respective output clutch of the plurality of clutches to modulate rotation of the one or more output shafts during the shuttle shift.

DETAILED DESCRIPTION

A transmission using clutches (e.g., forward and reverse clutches) to shuttle between forward and reverse directions may have counter-rotating plates in the clutches. Such counter rotating plates may result in high parasitic losses due to clutch drag. This disclosure relates to a transmission that uses forward and reverse couplers, synchronizers, or both, in place of forward and reverse clutches. In general, synchronizers may drag much less than clutches, and couplers may have substantially no drag. As such, the disclosed transmission may have a reduced parasitic loss as compared to a conventional transmissions that uses clutches for shuttling between forward and reverse directions.

With the foregoing in mind,FIG. 1is a side view of an embodiment of a work vehicle10that may employ a transmission system. The work vehicle10may be any suitable type of loader, tractor, grader, backhoe, forklift, agricultural vehicle, or any other suitable work vehicle that utilizes a transmission. The work vehicle10has a body12that typically houses an engine, transmission, and power train. Further, the work vehicle10has a cabin14where an operator may sit or stand to operate the work vehicle10. The work vehicle10has two front wheels16and two rear wheels18that rotate to move the work vehicle10. The engine of the work vehicle10may drive the front wheels16and/or the back wheels18using a transmission. For example, a full powershift transmission system may transfer power from the engine to the front wheels16and/or the back wheels18. While the wheels16and18are illustrated inFIG. 1, the wheels16and/or wheels18may be tracks.

FIG. 2is a block diagram of an embodiment of a transmission system20that may be used in the work vehicle10ofFIG. 1. An engine22(e.g., an internal combustion engine) provides power to drive a transmission24of the transmission system20. The transmission24may include a hydraulic system, a planetary gear unit, seals and gaskets, a torque converter, a modulator, sensor(s), other suitable components, or a combination thereof. Output from the transmission24drives a load26, such as the wheels of the work vehicle. The transmission system20furthers include a controller28configured to control various systems and units within the transmission24. As illustrated, the controller28includes one or more memory devices30and one or more processors32. For example, the one or more memory devices30may include volatile memory, such as random access memory (RAM), and/or non-volatile memory, such as read-only memory (ROM), optical drives, hard disc drives, solid-state drives, or a combination thereof. Additionally, the one or more processors32may include one or more application specific integrated circuits (ASICs), one or more field programmable gate arrays (FPGAs), one or more general purpose processors, or any combination thereof. Furthermore, the term processor is not limited to just those integrated circuits referred to in the art as processors, but broadly refers to computers, processors, microcontrollers, microcomputers, programmable logic controllers, ASICs, and other programmable circuits. The one or more memory devices30(e.g., non-transitory computer-readable medium/memory circuitry) may store one or more sets of instructions (e.g., processor-executable instructions) to operate the transmission24. In operation, the controller28uses the one or more processors32to execute instructions stored in the one or more memory devices30to control the transmission24. For example, the controller28may receive instructions to cause various clutches to be engaged/disengaged to cause gear ratio changes while the work vehicle10is moving (e.g., at different speeds).

FIG. 3is a schematic diagram of an embodiment of a transmission24that may be used within the transmission system20ofFIG. 2. In the following descriptions, an axial direction40pointing toward an input42is referred to as “front”, whereas an axial direction44pointing toward a load or output46is referred to as “rear”. The input42may be a motor or the engine22and the load or output46may be the load26as shown inFIG. 2. In the illustrated embodiment, the transmission24includes an input shaft or a first shaft48, a second shaft50, a third shaft52, a fourth shaft54, and an output shaft56, that are parallel to one another. The input shaft48is driven by the input42, and a shaft58is selectively fixedly coupled to the input shaft48by a clutch IN1. A shaft60is selectively fixedly coupled to the second shaft50by a clutch IN2. A shaft62and a shaft64are selectively fixedly coupled to the second shaft50by a forward-reverse coupler66. The forward-reverse coupler66includes a forward coupler F and a reverse coupler R, such that the shaft62may be selectively fixedly coupled to the second shaft50by the reverse coupler R, and the shaft64may be selectively fixedly coupled to the second shaft50by the forward coupler F. In some embodiments, one or both of the forward and reverse couplers F and R may include synchronizer(s) (e.g., a forward synchronizer for the forward coupler F, a reverse synchronizer for the reverse coupler R, or both). A shaft68is selectively fixedly coupled to the third shaft52by a clutch MID1, and a shaft70is selectively fixedly coupled to the fourth shaft54by a clutch MID2. A shaft72is selectively fixedly coupled to the output shaft56by a clutch OUT2, and a shaft74is selectively fixedly coupled to the output shaft56by a clutch OUT1.

The transmission24includes shafts disposed between the input shaft48and the output shaft56, such as the second, third, and fourth shafts50,52, and54. Arranged between the input shaft48and the output shaft56along the axial direction pointing toward the rear44, are six gear sets G1, G2, G3, G4, G5, and G6that are each formed by respective gears76/78,80/82,84/86/88,90/92/94,96/98/100, and102/104. In the illustrated embodiment, the gear set G1is referred to as a front gear set77, the gear sets G3, G4, and G5are referred to as intermediate gear sets81, and the gear set G6is referred to as a rear gear set97. The gears76and78are fixedly coupled to the shaft58and the second shaft50, respectively, the gears80and82are fixedly coupled to the input shaft48and the shaft60, respectively, and the gears84and88are fixedly coupled to the shafts62and68, respectively, while the gear86is coupled to both the gears84and88. The gear86may be an idler gear (e.g., a gear wheel that is inserted between two or more other gear wheels) that may be used to change the direction of rotation of the output shaft56. The gears90,92, and94are fixedly coupled to the shafts64,68, and70, respectively, the gears96,98, and100are fixedly coupled to the third shaft52, the fourth shaft54, and the shaft72, respectively, and the gears102and104are fixedly coupled to the fourth shaft54and the shaft74, respectively. The clutches IN1and IN2are disposed between the gear sets G1and G2, the forward-reverse coupler66is disposed between the gear sets G3and G4, the clutches MID1and MID2are disposed between the gear sets G4and G5, and the clutches OUT2and OUT1are disposed between the gear sets G5and G6. The clutches IN1and IN2are fixedly coupled to the input shaft48and the second shaft50, respectively, the clutches MID1and MID2are fixedly coupled to the shafts52and54, respectively, and the clutches OUT1and OUT2are fixedly coupled to the output shaft56.

In addition, the transmission24ofFIG. 3may include one or more speed sensors, each configured to output a respective signal indicative of the rotational speed of a respective shaft. The speed sensor(s) may include reflective sensor(s), interrupter sensor(s), optical sensor(s), magnetic sensor(s), Hall-effect sensor(s), other suitable types of sensor(s), or a combination thereof. The speed sensor(s) may continuously, periodically, or upon receiving an instruction from the controller28, measure and output signals indicative of rotational speed to the controller28. Based on the signals from the speed sensor(s), the controller28may determine the rotational speed of respective shaft(s) of the transmission24and may determine whether respective clutch(es) of the transmission24are locked-up. For example, the speed sensor(s) may measure and output signals indicative of rotational speeds of the respective shaft(s), such that the controller28may determine that the respective shaft(s) have stopped rotation. Furthermore, the speed sensor(s) may measure and output signals indicative of rotational speeds of the shaft74and the output shaft56, such that the controller28may determine that the clutch OUT1is locked-up (e.g., the shaft74and the output shaft56are rotating at the same or substantially the same speed).

The clutches described herein may be any suitable type(s) of clutch(es) including dry clutch(es), wet clutch(es), single/multi plate clutch(es), centrifugal clutch(es), pneumatic or hydraulic clutch(es), electromagnetic clutch(es), or any combination thereof. Each of the clutches may be configured to selectively couple a gear to a shaft or selectively couple a shaft to another shaft upon receiving a control signal from the controller (e.g., the controller28). The couplers described herein may be any suitable type(s) of coupler(s) including gear coupler(s), disc coupler(s), jaw coupler(s), another suitable coupler(s), or any combination thereof. In addition, a coupler may include a synchronizer (e.g., a coupler having a synchronizer is referred to as a “synchronizer”). The synchronizers described herein may be any suitable type(s) of synchronizer(s) including single-cone synchronizer(s), dual-cone synchronizer(s), triple-cone synchronizer(s), another suitable type of synchronizer(s), or any combination thereof. Each of the couplers may be configured to selectively allow engagement of gears, engagement of a gear and a shaft, or engagement of shafts (e.g., synchronizing the rotation speeds of the respective engaging components) upon receiving a control signal from the controller (e.g., the controller28).

The described system of gears and shafts can be actuated with the clutches (IN1, IN2, MID1, MID2, OUT1, OUT2) and the forward-reverse coupler66to achieve different gear ratios (e.g., speeds) between the input shaft48and the output shaft56in forward and reverse directions. For example, the clutches and the forward-reverse coupler66may be controlled (e.g., via the controller28) to control the engagement/disengagement of each clutch and the forward-reverse coupler66with their respective gear(s) and/or shaft(s) to transfer power along different power flow paths to achieve different speeds in forward and reverse directions as discussed more inFIG. 4.

FIG. 4is an embodiment of a shift diagram corresponding to gear ratio changes within the transmission ofFIG. 3, with eight forward speeds from Speeds1to8and eight reverse speeds from Speeds1to8. Here, the forward and reverse Speeds1to8are illustrated in successive rows, with each speed achievable via a power flow path through the transmission ofFIG. 3. For example, forward Speed1may be achieved by engaging the forward coupler F of the forward-reverse coupler66and the clutches IN1, MID1, and OUT1(e.g., designated as ‘X’), forward Speed2may be achieved by engaging the forward coupler F of the forward-reverse coupler and the clutches IN2, MID1, and OUT1, and so on with the engaged clutches designated with an “X”. Reverse Speed1may be achieved by engaging the reverse coupler R of the forward-reverse coupler and the clutches IN1, MID1, and OUT1(e.g., designated as ‘X’), reverse Speed2may be achieved by engaging the reverse coupler R of the forward-reverse coupler and the clutches IN2, MID1, and OUT1, and so on with the engaged clutches designated with an “X”. The gears in the transmission24are arranged such that when power-shifts are performed from forward Speed1to Speed8and from reverse Speed1to Speed8(e.g., down the rows), the total gear ratio (e.g., speed of the input shaft divided by the speed of the output shift) of the transmission decreases. Furthermore, a portion of the concepts described herein is focused on providing power-shuttle operation by using coupler(s) and/or synchronizer(s) (e.g., the forward-reverse coupler66) in place of clutches (e.g., a forward clutch and a reverse clutch) to reduce parasitic losses attributed to clutch drag and/or to reduce potential for clutch plate flutter. It may be appreciated that synchronizers may drag much less than multi-plate clutches, and couplers may have substantially no drag, and neither synchronizers nor couplers are susceptible to flutter.

FIG. 5is a flow chart of an embodiment of a method120for performing a shuttle shift using the transmission ofFIG. 3to transition the work vehicle from driving in a first direction to a second direction, opposite to the first direction. The first direction and the second direction may be forward and reverse directions, respectively, or vice versa. As set forth inFIG. 4, the controller may engage/disengage respective clutches (IN1, IN2, MID1, MID2, OUT1, OUT2) and the forward-reverse coupler of the transmission ofFIG. 3to drive the work vehicle in any of the forward Speeds1to8or any of the reverse Speeds1to8. The method120may be applied to perform shuttle shifting between any of the forward Speeds1to8and any of the reverse Speeds1to8.

One or more of the steps of the method120may be executed by the controller. The method120may include instructing the engine and the transmission to drive (step122) the work vehicle in a first direction (e.g., forward direction). The controller may instruct the transmission to engage clutches and forward-reverse coupler corresponding to a particular speed in the first direction. For example, for forward Speed3, the controller may instruct the transmission to engage the clutches IN1, MID2, and OUT1, and the forward coupler F. The method120may include receiving (step124) a signal indicative of a shuttle shift. For example, the controller may receive a signal in response to an operator or a driver of the work vehicle signaling a shuttle shift (e.g., via a shuttle-shift lever). In some embodiment, step124may be omitted.

The method120includes instructing the transmission to disconnect the intermediate gear sets81(e.g., the gear sets G3, G4, and G5) from the input42. The controller may instruct the transmission to disengage at least one clutch disposed on the respective power flow path to disconnect the intermediate gear sets81from the input42. For example, if the engine drives the work vehicle at forward Speed3, the forward coupler F is engaged, and step126may include instructing the transmission to disengage the clutch IN1and engage the clutch MID1to stop rotation of the second shaft50. The disengagement of the clutch IN1(e.g., disengagement of at least one clutch) disconnects the input shaft48from the second shaft50, such that rotation of the input shaft48does not drive the second shaft50to rotate with the input shaft48, which in turn also disconnects the intermediate gear sets81from the input42.

The method120includes instructing the transmission to stop (step128) rotation of the intermediate gear sets81(e.g., the gear sets G3, G4, and G5) and modulate the output shaft56. The controller may instruct the transmission to engage and/or disengage respective clutches to stop rotations of the intermediate gear sets81(e.g., the gear sets G3, G4, and G5), which in turn stops rotations of the associated shafts (e.g., the second, third, and fourth shafts50,52, and54), such that the forward-reverse coupler66may be shifted between the forward coupler F and the reverse coupler R. The controller may instruct the transmission to engage at least two clutches (e.g., clutches disposed on different power flow paths) to stop rotation of the intermediate gear sets81. For example, while the clutch MID2is engaged, the engagement of the clutch MID1induces a conflict between the clutches, and thus causes the third and fourth shafts52and54to stop rotation. As the third shaft52stops rotation, the second shaft50also stops rotation because the second shaft50has been disconnected from the input42and remains connected to the third shaft52via the clutch MID1, the shaft68, the gear92, the gear90, the shaft64, and the forward coupler F. As such, by disengaging the clutch IN1and engaging the clutch MID1(while the clutch MID2is engaged), the intermediate gear sets81(e.g., the gear sets G3, G4, and G5) and the associated shafts (e.g., the second, third, and fourth shafts50,52, and54) stop rotation.

It should be noted that even if the intermediate gear sets81and the associated shafts have stopped rotation, the output shaft56may still be rotating due to the inertia of the load. The controller may instruct the transmission to modulate the output shaft56by instructing the respective output clutch to apply a braking torque to the output shaft56. For example, when shifting from forward Speed3to a reverse speed, the controller may instruct the transmission to modulate the pressure applied to the clutch OUT1, such that the torque transmitted by the clutch OUT1is controlled, to provide braking to the output shaft56(e.g., to decelerate the rotation speed of the output shaft56at a controlled rate to provide a suitable rate of deceleration of the work vehicle).

The method120includes instructing the transmission to shift (step130) the forward-reverse coupler66between the forward coupler F and the reverse coupler R and modulate the output shaft56. Once the second shaft50stops rotation, the controller may instruct the transmission to shift the forward-reverse coupler66. For example, for shifting from a forward direction to a reverse direction, the controller may instruct the transmission to disengage the forward coupler F and engage the reverse coupler R. At the same time, the controller may continue to instruct the transmission to modulate the output shaft to continue decelerating the work vehicle.

The method120includes instructing the transmission to engage and/or disengage respective clutches to drive (step132) the work vehicle in a second direction (e.g., opposite to the first direction) and modulate the output shaft56. For example, for reverse Speed3, while the reverse coupler R is engaged, the controller may instruct the transmission to maintain engagement of the clutch MID2, disengage the clutch MID1, engage the clutch IN1, and continue to modulate the pressure applied to the clutch OUT1. As such the work vehicle may start accelerating in the second direction (e.g., reverse Speed3). To minimize the amount of energy absorbed by the clutch OUT1and OUT2, the controller may wait to instruct the transmission to accelerate in the second direction until the rotation speed of the output shaft56is close to zero. During the period that the work vehicle decelerates to a substantially zero speed (e.g., the output shaft56has a substantially zero rotation per minute (rpm)) and accelerates in the second direction (e.g., in reverse Speed3), the controller may continue modulating the output shaft56to ensure a smooth shuttle shift transition. The controller may instruct the transmission to modulate the output shaft56till the output clutch is locked-up (e.g., the shaft74and the output shaft56are rotating at the same or substantially the same speed). To the extent, the clutch OUT1may be viewed as an inching clutch that provides torque to the output shaft56to decelerate and accelerate the work vehicle smoothly throughout the shuttle shift.

FIG. 6is a schematic diagram of another embodiment of a transmission that may be used within the transmission system ofFIG. 2. In the following descriptions, the axial direction40pointing toward an input150is referred to as “front”, whereas an axial direction44pointing toward a load or output152is referred to as “rear”. The input150may be a motor or the engine22and the load or output152may be the load26as shown inFIG. 2. In the illustrated embodiment, the transmission25includes an input shaft or a first shaft154, a second shaft156, a third shaft158, a fourth shaft160, and an output shaft162, that are parallel to one another. To the extent that the second shaft156rotates with the input shaft154, the second shaft156may also be considered as an input shaft. The transmission25includes shafts disposed between the input shaft154and the output shaft162(e.g., the second, third, and fourth shafts156,158, and160, and shafts disposed thereon, such as shafts164,166,168,170,172,174,176,180, and182). The input shaft154is driven by the input150. Arranged on the second shaft156, a shaft164is selectively fixedly coupled to the second shaft156by a clutch C, a shaft166is selectively fixedly coupled to the second shaft156by a clutch B, and a shaft168is selectively fixedly coupled to the shaft166by a reverse coupler or synchronizer R. As illustrated, the second shaft156is an inner shaft that is concentrically disposed within the shafts164and166, and the shaft166is an inner shaft that is concentrically disposed within the shaft168.

Arranged on the third shaft158, a shaft170is selectively fixedly coupled to the third shaft158by a clutch A, a shaft172is selectively fixedly coupled to the shaft170by a forward synchronizer or coupler F, and a shaft174is selectively fixedly coupled to the shaft172by a clutch IN2. Also arranged on the third shaft158, a shaft176is selectively fixedly coupled to the shaft174by a clutch2&7, and a shaft178is selectively fixedly coupled to the shaft174by a clutch1&8. As illustrated, the third shaft158is an inner shaft that is concentrically disposed within the shafts170,172, and174, and the shaft174is an inner shaft that is concentrically disposed within the shafts176and178.

Arranged on the fourth shaft160, shafts180and182are selectively fixedly coupled to the fourth shaft160by a clutch IN1and a clutch3&6, respectively. A shaft184is selectively fixedly coupled to the fourth shaft160by a clutch H, and a shaft186is selectively fixedly coupled to the shaft184by a clutch L. As illustrated, the fourth shaft160is an inner shaft that is concentrically disposed within the shafts180and182, and the shaft184is an inner shaft that is concentrically disposed with the shaft186. To the extent that the shaft184rotates with the output shaft162, the shaft184may also be considered as an output shaft.

Arranged between the input shaft154and the output shaft162along the axial direction pointing toward the rear44, are ten gear sets G1, G2, G3, G4, G5, G6, G7, G8, G9, and G10that are each formed by respective gears188/190,192/194,196/198,200/202,204/206/208,210/212,214/216,218/220,222/224, and226/228. In the illustrated embodiment, the gear sets G1and G2are referred to as front gear sets189, the gear sets G5, G6, G7, G8, and G9are referred to as intermediate gear sets205, and the gear set G10is referred to as a rear gear set227. The gears188and190are fixedly coupled to the input shaft154and the second shaft156, respectively, the gears192and194are fixedly coupled to the second shaft156and the third shaft158, respectively, and the gears196and198are fixedly coupled to the shafts164and170, respectively. The gears200and202are fixedly coupled to the shafts166and170, respectively, and the gears204,206, and208are fixedly coupled to the shafts168,172, and180, respectively. The gears210and212are fixedly coupled to the shaft176and the fourth shaft160, respectively, the gears214and216are fixedly coupled to the shafts174and182, respectively, and the gears218and220are fixedly coupled to the shaft178and the fourth shaft160, respectively. The gears222and224are fixedly coupled to the shafts174and186, respectively, and the gears226and228are fixedly coupled to the shaft184and the output shaft162, respectively. The clutches C and A are disposed between the gear sets G2and G3, the reverse coupler or synchronizer R and the forward synchronizer or coupler F are disposed between the gear sets G4and G5, the clutches B, IN2and IN1are disposed between the gear sets G5and G6, the clutches2&7and3&6are disposed between the gear sets G6and G7, and the clutches1&8, H, and L are disposed between the gear sets G8and G9.

In addition, the transmission25ofFIG. 6may include one or more speed sensors, each configured to output a respective signal indicative of the rotational speed of a respective shaft. The speed sensor(s) may include reflective sensor(s), interrupter sensor(s), optical sensor(s), magnetic sensor(s), Hall-effect sensor(s), other suitable types of sensor(s), or a combination thereof. The speed sensor(s) may continuously, periodically, or upon receiving an instruction from the controller28, measure and output signals indicative of rotational speed to the controller28. Based on the signals from the speed sensor(s), the controller28may determine the rotational speed of respective shaft(s) of the transmission25and may determine whether respective clutch(es) of the transmission25are locked-up. For example, the speed sensor(s) may measure and output signals indicative of rotational speeds of the respective shaft(s), such that the controller28may determine that the respective shaft(s) have stopped rotation. Furthermore, the speed sensor(s) may measure and output signals indicative of rotational speeds of the shaft186and the shaft184, such that the controller28may determine that the clutch L is locked-up (e.g., the shaft186and the shaft184are rotating at the same or substantially the same speed). The speed sensor(s) may measure and output signals indicative of rotational speeds of the fourth shaft160and the shaft184, such that the controller28may determine that the clutch H is locked-up (e.g., the fourth shaft160and the shaft184are rotating at the same or substantially the same speed).

The clutches described herein may be any suitable type(s) of clutch(es) including dry clutch(es), wet clutch(es), single/multi plate clutch(es), centrifugal clutch(es), pneumatic or hydraulic clutch(es), electromagnetic clutch(es), or any combination thereof. Each of the clutches may be configured to selectively couple a gear to a shaft or selectively couple a shaft to another shaft upon receiving a control signal from the controller (e.g., the controller28). The couplers described herein may be any suitable type(s) of coupler(s) including gear coupler(s), disc coupler(s), jaw coupler(s), another suitable coupler(s), or any combination thereof. In addition, a coupler may include a synchronizer (e.g., a coupler having a synchronizer is referred to as a “synchronizer”). The synchronizers described herein may be any suitable type(s) of synchronizer(s) including single-cone synchronizer(s), dual-cone synchronizer(s), triple-cone synchronizer(s), another suitable type of synchronizer(s), or any combination thereof. Each of the couplers may be configured to selectively allow engagement of gears, engagement of a gear and a shaft, or engagement of shafts (e.g., synchronizing the rotation speeds of the respective engaging components) upon receiving a control signal from the controller (e.g., the controller28).

The described system of gears and shafts can be actuated with the clutches (C, A, B, IN2, IN1,2&7,3&6,1&8, H, and L) and the coupler and/or synchronizer F and R to achieve different gear ratios (e.g., speeds) between the input shaft154and the output shaft162in forward and reverse directions. For example, the clutches and the coupler(s) and/or synchronizer(s) may be controlled (e.g., via the controller28) to control engagement and/or disengagement of each clutch and the coupler(s) and/or synchronizer(s) with their respective gear(s) and/or shaft(s) to transfer power along different power flow paths to achieve different speeds in forward and reverse directions as discussed more inFIG. 7.

FIG. 7is another embodiment of a shift diagram corresponding to gear ratio changes within the transmission ofFIG. 6, with twenty-four forward speeds from Speeds1to24and twenty-four reverse speeds from Speeds1to24. Here, the forward and reverse Speeds1to24are illustrated in successive rows, with each speed achievable via a power flow path through the transmission ofFIG. 6. For example, forward Speed1may be achieved by engaging the forward synchronizer or coupler F and the clutches A, IN1,1&8, and L (e.g., designated as ‘X’), forward Speed2may be achieved by engaging the forward synchronizer or coupler F and the clutches B, IN1,1&8, and L, and so on with the engaged clutches designated with an “X”. Reverse Speed1may be achieved by engaging the reverse coupler or synchronizer R and the clutches A, IN1,1&8, and L (e.g., designated as ‘X’), reverse Speed2may be achieved by engaging the reverse coupler or synchronizer R and the clutches B, IN1,1&8, and L, and so on with the engaged clutches designated with an “X”. It should be noted that for some speeds, the clutches are designated as “Opt”, which indicates that the clutch may be engaged, but the clutch is not in the torque path. The gears in the transmission are arranged such that when power-shifts are performed from forward Speed1to Speed24and from reverse Speed1to Speed24(e.g., down the rows), the total gear ratio (e.g., speed of the input shaft divided by speed of the output shaft) of the transmission decreases. Furthermore, a portion of the concepts described herein is focused on providing power-shuttle operation by using coupler(s) and/or synchronizer(s) (e.g., the forward synchronizer or coupler F and the reverse coupler or synchronizer R) in place of clutches (e.g., a forward clutch and a reverse clutch) to reduce parasitic losses attributed to clutch drag and/or reduce potential for clutch plate flutter. It may be appreciated that synchronizers may drag much less than multi-plate clutches, and couplers may have substantially no drag, and neither synchronizers nor couplers are susceptible to flutter.

The method120shown inFIG. 5may also be performed using the transmission ofFIG. 6to shuttle shift between forward and reverse speeds. As set forth inFIG. 7, the controller28may engage and/or disengage the respective clutches (IN1, IN2,1&8,2&7,3&6, L, and H) and the forward and reverse couplers or synchronizers F and R of the transmission ofFIG. 6to drive the work vehicle10in any of the forward Speeds1to24or any of the reverse Speeds1to24. The method120may be applied to perform shuttle shifting between any of the forward Speeds1to24and any of the reverse Speeds1to24.

In step122, the controller may instruct the transmission ofFIG. 6to engage respective clutches and forward and reverse couplers or synchronizers F and R to drive the work vehicle at a corresponding speed in a first direction. For example, for forward Speed16, the controller may instruct the transmission to engage the clutches A, IN2,3&6, and H, and the forward coupler or synchronizer F. In step124, the controller may receive a signal in response to an operator or a driver of the work vehicle signaling a shuttle shift (e.g., via a shuttle-shift lever). In some embodiments, step124may be omitted.

In step126, the controller may instruct the transmission to disconnect the intermediate gear sets205(e.g., the gear sets G5, G6, G7, G8, and G9) from the input150. The controller may instruct the transmission to disengage at least one clutch disposed on the respective power flow path (e.g., clutches A, B, and/or C depending on the power flow path) to disconnect the intermediate gear sets205from the input150. For example, the controller may instruct the transmission to disengage the clutches A, B, and C to disconnect the shafts170,164, and166and the gear sets G3and G4from the second and third shafts156and158, such that rotation of the input shaft154does not drive rotation of the shafts170,164, and166and the gear sets G3and G4, the intermediate gear sets205, and the associated shafts (e.g., the fourth shaft160and the shafts168,172,174,176,178,180,182, and186).

In step128, the controller may instruct the transmission to stop rotation of the intermediate gear sets205(e.g., the gear sets G5, G6, G7, G8, and G9) and modulate the output shaft162. The controller may instruct the transmission to disengage at least one clutch (e.g., clutches disposed before the rear gear set227toward the axial direction44) to disconnect the intermediate gear sets205from the load or output152. The controller may instruct the transmission to engage at least three clutches (e.g., clutches disposed on different power flow paths) to stop rotation of the intermediate gear sets205and the associated shafts. For example, the controller may instruct the transmission to disengage the clutches L and H to disconnect the intermediate gear sets205and the associated shafts from the output shaft162, and engage at least three of the clutches IN1, IN2,1&8,2&7, and3&6to stop rotation of the intermediate gear sets205in the transmission. The engagement of at least three of the clutches IN1, IN2,1&8,2&7, and3&6induce conflicts among the clutches, and thus cause the intermediate gear sets205(e.g., the gear sets G5, G6, G7, G8, and G9) and the associated shafts to stop rotation. It should be noted that the shaft184and the output shaft162may still rotate due to the inertia of the load. Thus, in step128, the controller may instruct the transmission to modulate the pressure applied to an output clutch (e.g., the clutch L or the clutch H) to provide braking to the output shaft162(e.g., to decelerate the rotation speed of the shaft184and thus decelerating the rotation speed of the output shaft162at a controlled rate to provide a suitable rate of deceleration of the work vehicle).

In step130, once the shafts168and172stop rotation, the shafts166and170also stop rotation because the forward coupler or synchronizer F or the reverse coupler or synchronizer R is still engaged, and the controller may instruct the transmission to shift between the forward coupler or synchronizer F and the reverse coupler or synchronizer R. For example, to shuttle shift from a forward direction (e.g., a first direction) to a reverse direction (e.g., a second direction), the controller may instruct the transmission to disengage the forward coupler or synchronizer F and engage the reverse coupler or synchronizer R. At the same time, the controller may instruct the transmission to continue modulating the output shaft (e.g., modulating a pressure applied to an output clutch, the clutch L or the clutch H) to continue decelerating the work vehicle.

In step132, the controller may instruct the transmission to engage and/or disengage respective clutches to drive the work vehicle in the second direction (e.g., opposite to the first direction) and modulate the output shaft162(e.g., modulating a pressure applied to an output clutch, the clutch L or the clutch H). For example, for reverse Speed1, while the reverse coupler or synchronizer R is engaged, the controller may instruct the transmission to maintain disengagements of the clutch B and C, engage the clutch A, engage or maintain engagement of the clutch IN1, disengage or maintain disengagement of the clutch IN2, the clutch2&7, and the clutch3&6, engage or maintain engagement of the clutch1&8, and continue to modulate the pressure applied to the clutch L. As such the work vehicle may start accelerating in the second direction (e.g., reverse Speed1). To minimize the amount of energy absorbed by the clutch L, the controller may wait to instruct the transmission to drive the work vehicle in the second direction until the rotation speed of the output shaft162is close to zero. During the period that the work vehicle decelerates to a substantially zero speed (e.g., the output shaft162has a substantially zero rotation per minute (rpm)) and accelerates in the second direction (e.g., in reverse Speed1), the controller may continue modulating the output shaft162(e.g., modulating a pressure applied to an output clutch, the clutch L or the clutch H) to ensure a smooth shuttle shift transition. The controller may instruct the transmission to modulate the output shaft162till the clutch L is locked-up (e.g., the shaft186and the shaft184are rotating at the same or substantially the same speed). To the extent, the clutch L may be viewed as an inching clutch that provides torque to the output shaft162to decelerate and accelerate the work vehicle smoothly throughout the shuttle shift.

In some embodiments, some steps of the method120may be generally applicable to the controller (e.g., the controller28) performing stationary shuttling (e.g., disengaging one of the couplers or synchronizers and engaging the other coupler or synchronizer while the work vehicle10is stationary) using the transmission ofFIG. 6. For example, in step128, the controller may engage at least three of the clutches IN1, IN2,1&8,2&7, and3&6to stop rotation of most of the components in the transmission between the input and output shafts154and162. However, this combination of clutches may already be engaged to stop rotation of the components while the work vehicle is stationary, to prevent creep of the work vehicle that could otherwise occur caused by clutch drag.

In some embodiments, the transmission ofFIG. 6may include a forward coupler F and a reverse coupler R (e.g., as opposed to a coupler and a synchronizer), and the parasitic losses is reduced as compared to a transmission including a coupler and a synchronizer. If both the forward coupler F and the reverse coupler R are in their neutral positions, and the input shaft154is rotating, there is no way to force shafts166and170to stop to allow engaging the forward coupler F or the reverse coupler R without clashing. The controller may be configured to ensure that at least one of the forward coupler F and the reverse coupler R is not in neutral position. The controller may instruct the transmission to maintain engagement of at least one of the forward coupler F and the reverse coupler R at all times.

In some embodiments, the transmission ofFIG. 6may include a forward synchronizer F and a reverse synchronizer R (as opposed to a coupler and a synchronizer, or both couplers). In some embodiments, such as the illustrated embodiment shown inFIG. 6, the transmission may include a forward synchronizer F and a reverse coupler R (as opposed to two couplers or two synchronizers). In these two cases, the controller does not need to specifically instruct the transmission to circumvent the situation that both the forward and reverse couplers F and R are in neutral positions, as set forth above. In the case of a forward synchronizer F and a reverse coupler R, the controller may instruct the transmission to shift from neutral to reverse by instructing the transmission to engage the forward synchronizer F, thus stopping rotation of the shafts166and170, then engage the reverse coupler R and disengage the forward synchronizer F. Using a reverse coupler R may minimize drag losses when driving in forward direction. Furthermore, the controller may instruct the transmission to shift both the forward synchronizer F and the reverse coupler R to neutral positions while the work vehicle is in neutral or park position to reduce parasitic losses during stationary power take off (PTO) operation. Still in some embodiments, the transmission ofFIG. 6may include a forward coupler F and a reverse synchronizer R (as opposed to a forward synchronizer F and a reverse coupler R).