Power control system with stall prevention clutch modulation function

A control system for a work vehicle includes a power source including an engine and at least one electric motor configured to generate power; a transmission including a plurality of clutches coupled together and configured for selective engagement to transfer the power from the engine and the at least one electric motor along a power flow path to drive an output shaft of a powertrain according to a plurality of transmission modes; and a controller coupled to the power source and the transmission. The controller has a processor and memory architecture configured to: monitor an electric motor speed of the at least one electric motor; and generate and execute, when the electric motor speed is less than a first predetermined stall speed threshold, a clutch modulation command for the transmission such that at least one clutch of the plurality of clutches along the power flow path is partially engaged.

CROSS-REFERENCE TO RELATED APPLICATION(S)

Not applicable.

STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE DISCLOSURE

This disclosure generally relates a control system for a work vehicle, and more specifically to a power control system for a transmission and an electric motor of the work vehicle.

BACKGROUND OF THE DISCLOSURE

In the agriculture, construction and forestry industries, work vehicles, including wheel loaders, may be utilized to perform a number of different tasks. Modern work vehicles may use power from multiple power sources, including both a traditional engine (e.g., an internal combustion engine) and one or more continuously variable power sources (CVP) (e.g., an electric motor) to provide useful power. In various applications, the powertrain of the work vehicle may use power selectively provided solely by either power source or in combined form via an infinitely variable transmission (IVT) or continuously variable transmission (CVT) according to modes. Moreover, each mode may have one or more gear (or speed) ratios as clutches are selectively engaged and disengaged to vary the power flow path. Some operating conditions may provide challenges for certain modes of one or both types of power sources.

SUMMARY OF THE DISCLOSURE

The disclosure provides a power control system for a work vehicle.

In one aspect, the disclosure provides a control system for a work vehicle. The system includes a power source including an engine and at least one electric motor configured to generate power; a transmission including a plurality of clutches coupled together and configured for selective engagement to transfer the power from the engine and the at least one electric motor along a power flow path to drive an output shaft of a powertrain of the work vehicle according to a plurality of transmission modes; and a controller coupled to the power source and the transmission. The controller has a processor and memory architecture configured to: monitor an electric motor speed of the at least one electric motor; and generate and execute, when the electric motor speed is less than a first predetermined stall speed threshold, a clutch modulation command for the transmission such that at least one clutch of the plurality of clutches along the power flow path is partially engaged.

In another aspect, the disclosure provides a controller for a work vehicle with an engine and at least one electric motor configured to generate power and a transmission with a plurality of clutches coupled together and configured for selective engagement to transfer the power from the engine and the at least one electric motor along a power flow path to drive an output shaft according to a plurality of transmission modes. The controller includes a processor and memory architecture configured to: monitor an electric motor speed of the at least one electric motor; and generate and execute, when the electric motor speed is less than a first predetermined stall speed threshold, a clutch modulation command for the transmission such that at least one clutch of the plurality of clutches along the power flow path is partially engaged.

In a further aspect, the disclosure provides a method of operating a powertrain of a work vehicle with an engine and at least one electric motor configured to generate power and a transmission with a plurality of clutches coupled together and configured for selective engagement to transfer the power from the engine and the at least one electric motor along a power flow path to drive an output shaft according to a plurality of transmission modes. The method includes monitoring, with a controller, an electric motor speed of the at least one electric motor; and generating and executing, at the controller, a clutch modulation command for the transmission such that at least one clutch of the plurality of clutches along the power flow path is partially engaged when the electric motor speed is less than a first predetermined stall speed threshold

DETAILED DESCRIPTION

The following describes one or more example embodiments of the disclosed power control system, powertrain, or vehicle, as shown in the accompanying figures of the drawings described briefly above. Various modifications to the example embodiments may be contemplated by one of skill in the art.

Typically, work vehicles, such as those in the agriculture, construction and forestry industries, may include a power control system implemented with a powertrain having an engine and one or more additional power sources, such as one or more electric motors, that individually and collectively provide power via a transmission to drive the vehicle and perform work functions. For example, the power control system may implement one or more split modes in which power from the engine and electric motor are combined in the transmission to provide output torque; one or more direct drive modes in which power from only the engine provides the output torque; and one or more series modes in which power from primarily the electric motor provides the output torque. Such a transmission may be considered a hybrid transmission, an infinitely variable transmission (IVT), or an electrical infinitely variable transmission (eIVT); and such a powertrain may be considered a hybrid, IVT, or eIVT powertrain. Within each mode, the clutches of the transmission may be manipulated to provide or more gear or speed ratios.

During typical operation, the power control system may be subject to relatively heavy loads, including loads that may stop and slow the work vehicle, despite the application of torque. In certain modes, particularly in series modes (e.g., in which the output torque is provided by one or more of the electric motors), the reduction in speed of the vehicle may slow the electric motor to a value that is less than the electric motor stall speed. Typically, upon reaching the stall speed, the controller may derate the electric motor to avoid heat management issues. As such, in these situations, the electric motor may not be able to provide the desired torque for the work vehicle, thereby potentially impacting vehicle performance and efficiency.

However, according to the present disclosure, the power control system is configured to implement a clutch modulation function in certain conditions to suitably address the potential impact of a slowing electric motor. In one example, the conditions associated with the clutch modulation function may include the current mode of the transmission and/or the current electric motor speed. In particular, the clutch modulation function may be implemented when the transmission mode is a series mode and when the current electric motor speed is approaching, fallen below, or at the electric motor stall speed. Upon implementation, the power control system may generate commands to modulate at least one of the clutches in the transmission, particularly one of the clutches in the power flow path of the transmission that couples the electric motor to the output shaft. In one example, the power control system may implement the clutch modulation by dithering the selected clutch (e.g., rapid increase and decreases in the resultant pressure at the clutch), while in other examples, the power control system may implement the clutch modulation by targeting an intermediate or partially engaged resultant pressure at the clutch. The clutch modulation function operates to partially decouple the electric motor from the transmission such that the electric motor may obtain and/or maintain speeds that are above the electric motor stall speed and avoid or mitigate the resulting derating, thereby maintaining torque capability of the electric motor. As such, the present disclosure may enable a power control system with an electric motor stall prevention clutch modulation function that provides consistent and reliable performance and efficiency, particularly without needing to size a larger motor for high torque, low speed applications. Additional details will be provided below.

Referring toFIG.1, a work vehicle100may include or otherwise implement a power control system102that executes a clutch modulation function to ensure appropriate electric motor speed and torque capability, thereby providing consistent and smooth operation of the work vehicle100. The view ofFIG.1generally reflects the work vehicle100as a tractor. It will be understood, however, that other configurations in the agricultural, construction, and/or forestry industries may be possible, including configurations as a wheel loader. It will further be understood that the disclosed powertrain106may also be used in non-work vehicles and non-vehicle applications (e.g., fixed-location power installations). In one example, the power control system102may be considered to include or otherwise interact with a controller104, a powertrain106, and one or more sensors110supported on the chassis112of the work vehicle100.

Generally, the powertrain106includes one or more sources of power, such as an engine114(e.g., a diesel engine) and/or one or more continuously variable power sources (CVPs)116a,116b. Typically, the CVPs116a,116bare electric motors and will be referred to below as such. However, in other embodiments, the CVPs116a,116bmay be other continuously variable power sources, such as hydraulic motors. The electric motors116a,116bmay be associated with or otherwise incorporate one or more power components that condition, store, and/or convert power to and/or from the motors116a,116b. Such power components may include one or more sensors, controllers, batteries and/or inverters (e.g., semiconductor devices with insulated-gate bipolar transistors (IGBTs)). As noted above, if unaddressed, a reduction of speed of the electric motor116a,116b(particularly motor116bcoupled to selectively drive transmission118) may result in a derating of the torque capability to avoid heat issues in the IGBTs. The clutch modulation function operates to identify and address these conditions to prevent undue heating of the power components, derating of the electric motors116a,116b(e.g., a reduction in torque capability), and ensure consistent and efficient operation of the powertrain106, as described in greater detail below.

The powertrain106further includes a transmission118that transfers power from the power sources114,116a,116bto a suitable driveline coupled to one or more driven wheels (or tracks)120to enable propulsion of the work vehicle100. The wheels120interact directly with a support surface and are responsible for vehicle100movement and tractive effort. The transmission118may also supply power to drive other vehicle systems, components, or implements. The transmission118may include various gears, shafts, clutches, and other power transfer elements that may be operated in a variety of ranges representing selected output speeds and/or torques. As described in greater detail below, the power control system102is used to implement the clutch modulation function at one or more conditions within the powertrain106.

Generally, the controller104implements operation of the power control system102, powertrain106, and other aspects of the vehicle100, including any of the functions described herein. The controller104may be configured as computing devices with associated processor devices and memory architectures, as hydraulic, electrical or electro-hydraulic controllers, or otherwise. As such, the controller104may be configured to execute various computational and control functionality with respect to the vehicle100. The controller104may be in electronic, hydraulic, or other communication with various other systems or devices of the vehicle100, including via a CAN bus (not shown). For example, the controller104may be in electronic or hydraulic communication with various actuators, sensors, and other devices within (or outside of) the vehicle100.

In some embodiments, the controller104may be configured to receive input commands and to interface with an operator via a human-machine interface or operator interface122, including typical steering, acceleration, velocity, transmission, and wheel braking controls, as well as other suitable controls. The operator interface122may be configured in a variety of ways and may include one or more joysticks, various switches or levers, one or more buttons, a touchscreen interface that may be overlaid on a display, a keyboard, a speaker, a microphone associated with a speech recognition system, or various other human-machine interface devices. The controller104may also receive inputs from one or more sensors110associated with the various system and components of the work vehicle100, as discussed in greater detail below. As also discussed below, the controller104may implement the power control system102based on these inputs to generate suitable commands for the powertrain106, particularly with respect to the clutch modulation function.

As noted above, the work vehicle100may include one or more sensors (generally represented by sensor110) in communication to provide various types of feedback and data with the controller104in order to implement the functions described herein, as well as functions typical for a work vehicle100. In certain applications, sensors110may be provided to observe various conditions associated with the work vehicle100. In one example, the sensors110may provide information associated with the power control system102to implement the clutch modulation function. The sensors110may include kinematic sensors that collect information associated with the position and/or movement of the work vehicle100, such as one or more directional sensors and/or one or more ground speed sensors. Additional sensors (or otherwise, sources or data) may provide or include sources of powertrain data, including data sufficient to determine the current or anticipated mode of the transmission118, information associated with the positions and states of one or more transmission clutch elements, and torque and/or speed information associated with the electric motors116a,116b, engine114, and/or elements of the transmission118. In particular, the sensors110may collect information associated with the current motor speed, clutch element speeds, transmission output speed, ground speed, and the like, e.g., directly or derived from other parameters.

As described in greater detail below, the power control system102operates to implement the clutch modulation function to prevent electric motor stall. The clutch modulation function is particularly useful in a hybrid powertrain system (e.g., with electric motor and engine power sources). An example powertrain106is depicted and discussed below with reference toFIG.2as implementing aspects of the power control system102, and subsequently, additional details about the power control system102implementing the clutch modulation function are provided with reference toFIG.3.

Referring toFIG.2and as introduced above, the power control system102may be considered to include powertrain106and the controller104, which is in communication with the various components of the powertrain106and additionally receives information from various vehicle systems and/or sensors110(FIG.1). As also noted above, the powertrain106may include one or more power sources114,116a,116b. In particular, the powertrain106may include the engine114, which may be an internal combustion engine of various known configurations; and further the powertrain106may also include the first electric motor116aand the second electric motor116b, which may be connected together by a conduit and/or other power components116c. The powertrain106includes the transmission118that transfers power from the engine114, first electric motor116a, and/or electric motor116bto an output shaft230. As described below, the transmission118includes a number of gearing, clutch, and control assemblies to suitably drive the output shaft230at different speeds in multiple directions. Generally, in one example, the transmission118of powertrain106for implementing the power control system102may be any type of infinitely variable transmission arrangement.

The engine114may provide rotational power via an engine output element, such as a flywheel, to an engine shaft130according to commands from the controller104based on the desired operation. The engine shaft130may be configured to provide rotational power to a gear132. The gear132may be enmeshed with a gear134, which may be supported on (e.g., fixed to) a shaft136. The shaft136may be substantially parallel to and spaced apart from the engine shaft130. The shaft136may support various components of the powertrain106as will be discussed in detail.

The gear132may also be enmeshed with a gear138, which is supported on (e.g., fixed to) a shaft140. The shaft140may be substantially parallel to and spaced apart from the engine shaft130, and the shaft140may be connected to the first electric motor116a. Accordingly, mechanical power from the engine (i.e., engine power) may transfer via the engine shaft130, to the enmeshed gears132,138, to the shaft140, and to the first electric motor116a. The electric motor116amay convert this power to an alternate form (e.g., electrical power) for transmission over the conduit116cto the second electric motor116b. This converted and transmitted power may then be re-converted by the second electric motor116bfor mechanical output along a shaft142. As introduced above, various control devices (not shown) may be provided to regulate such conversion, transmission, re-conversion, and so on. Also, in some embodiments, the shaft142may support a gear144(or other similar component). The gear144may be enmeshed with and may transfer power to a gear146. The gear144may also be enmeshed with and may transfer power to a gear148. Accordingly, power from the second electric motor116bmay be divided between the gear146and the gear148for transmission to other components as will be discussed in more detail below. The powertrain106may further include a variator150that represents one example of an arrangement that enables an infinitely variable power transmission between the engine114and electric motors116a,116band the output shaft230. As discussed below, this arrangement further enables the power control system102in which mechanical energy from the engine114may be used to boost the electric power in a series mode. Other arrangements of the variator150, engine114, and electric motors116a,116bmay be provided.

In some embodiments, the variator150may include at least two planetary gearsets. In some embodiments, the planetary gearset may be interconnected and supported on a common shaft, such as the shaft136, and the planetary gearsets152,160may be substantially concentric. In other embodiments, the different planetary gearsets152,160may be supported on separate, respective shafts that are nonconcentric. The arrangement of the planetary gearsets may be configured according to the available space within the work vehicle100for packaging the powertrain106.

As shown in the embodiment ofFIG.2, the variator150may include a first planetary gearset (i.e., a “low” planetary gearset)152with a first sun gear154, first planet gears and associated carrier156, and a first ring gear158. Moreover, the variator150may include a second planetary gearset (i.e., a “high” planetary gearset)160with a second sun gear162, second planet gears and associated carrier164, and a second ring gear166. The second planet gears and carrier164may be directly attached to the first ring gear158. Also, the second planet gears and carrier164may be directly attached to a shaft168having a gear170fixed thereon. Moreover, the second ring gear166may be directly attached to a gear172. As shown, the shaft168, the gear170, and the gear172may each receive and may be substantially concentric to the shaft136. Although not specifically shown, it will be appreciated that the powertrain106may include various bearings for supporting these components concentrically. Specifically, the shaft168may be rotationally attached via a bearing to the shaft136, and the gear172may be rotationally attached via another bearing on the shaft168.

On the opposite side of the variator150(from left to right inFIG.2), the gear148may be mounted (e.g., fixed) on a shaft174, which also supports the first and second sun gears154,162. In some embodiments, the shaft174may be hollow and may receive the shaft136. A bearing (not shown) may rotationally support the shaft174on the shaft136substantially concentrically. Furthermore, the first planet gears and associated carrier156may be attached to a gear176. The gear176may be enmeshed with a gear178, which is fixed to a shaft180. The shaft180may be substantially parallel to and spaced apart from the shaft136.

As noted above, the powertrain106may be configured for delivering power (from the engine114, the first electric motor116a, and/or the second electric motor116b) to the output shaft230or other output component via the transmission118. The output shaft230may be configured to transmit this received power to wheels of the work vehicle100, to a power take-off (PTO) shaft, to a range box, to an implement, or other component of the work vehicle100.

The powertrain106may have a plurality of selectable modes, such as direct drive modes, split path modes, and series modes. In a direct drive mode, power from the engine114may be transmitted to the output shaft230, and power from the second electric motor116bmay be prevented from transferring to the output shaft230. In a split path mode, power from the engine114and the second electric motor116bmay be summed by the variator150, and the summed or combined power may be delivered to the output shaft230. Moreover, in a series mode, power from the second electric motor116bmay be transmitted to the output shaft230and power from the engine114may be generally prevented from transferring to the output shaft230. The powertrain106may also have different speed modes in one more of the direct drive, split path, and series modes, and these different speed modes may provide different angular speed ranges for the output shaft230. The powertrain106may switch between the plurality of modes to maintain suitable operating efficiency. Furthermore, the powertrain106may have one or more forward modes for moving the work vehicle100in a forward direction and one or more reverse modes for moving the work vehicle100in a reverse direction. The powertrain106may implement different modes and speeds, for example, using a control assembly182. The control assembly182may include one or more selectable transmission components. The selectable transmission components may have first positions or states (engaged positions or states), in which the respective device transmits effectively all power from an input component to an output component. The selectable transmission components may also have a second position or states (disengaged positions or states), in which the device prevents power transmission from the input to the output component. The selectable transmission components may have third positions or states (partially engaged or modulated positions or states), in which the respective device transmits only a portion of the power from an input component to an output component. Unless otherwise noted, the term “engaged” refers to the first position or state in which effectively all of the power is transferred, whereas “partially engaged”, “modulated”, or “dithered” specifically refers to only the partial transfer of power, albeit potentially with different characteristics. The selectable transmission components of the control assembly182may include one or more wet clutches, dry clutches, dog collar clutches, brakes, synchronizers, or other similar devices. The control assembly182may also include an actuator for actuating the selectable transmission components between the first, second, and third positions.

As shown inFIG.2, the control assembly182may include a first clutch184, a second clutch186, a third clutch188, a fourth clutch190, and a fifth clutch192. Also, the control assembly182may include a forward directional clutch194and a reverse directional clutch196.

In one example, the first clutch184may be mounted and supported on a shaft198. Also, the first clutch184, in an engaged position, may engage the gear146with the shaft198for rotation as a unit. The first clutch184, in a disengaged position, may allow the gear146to rotate relative to the shaft198. Also, a gear200may be fixed to the shaft198, and the gear200may be enmeshed with the gear170that is fixed to the shaft168. The reverse directional clutch196may be supported on the shaft198(i.e., commonly supported on the shaft198with the first clutch184). The reverse directional clutch196may engage and, alternatively, disengage the gear200and a gear202. The gear202may be enmeshed with an idler gear204, and the idler gear204may be enmeshed with a gear206. The forward directional clutch194may be supported on gear206, which is in turn supported on the shaft136, to selectively engage shaft168. Thus, the forward directional clutch194may be concentric with both the shaft168and the shaft136. The second clutch186may be supported on the shaft180. The second clutch186may engage and, alternatively, disengage the shaft180and a gear208. The gear208may be enmeshed with a gear210. The gear210may be fixed to and mounted on a countershaft212. The countershaft212may also support a gear214. The gear214may be enmeshed with a gear216, which is fixed to the output shaft230.

The third clutch188may be supported on a shaft218. The shaft218may be substantially parallel and spaced at a distance from the shaft180. Also, a gear220may be fixed to and supported by the shaft218. The gear220may be enmeshed with the gear172as shown. The third clutch188may engage and, alternatively, disengage the gear220and a gear222. The gear222may be enmeshed with the gear210. The fourth clutch190may be supported on the shaft180(in common with the second clutch186). The fourth clutch190may engage and, alternatively, disengage the shaft180and a gear224. The gear224may be enmeshed with a gear226, which is mounted on and fixed to the countershaft212. Additionally, the fifth clutch192may be supported on the shaft218(in common with and concentric with the third clutch188). The fifth clutch192may engage and, alternatively, disengage the shaft218and a gear228. The gear228may be enmeshed with the gear226.

The different transmission modes of the powertrain106will now be discussed. Like the embodiments discussed above, the powertrain106may have at least one at least one split path mode in which power from the engine114and one or more of the electric motors116a,116bare combined. Also, the powertrain106may additionally have a direct drive mode and/or and at least one generally series mode (i.e., electric motor-only mode).

In some embodiments, engaging the first clutch184and the second clutch186may place the powertrain106in a first forward mode. Generally, this mode may be a series mode (i.e., electric motor-only mode). In this mode, mechanical power from the engine114may flow via the shaft130, the gear132, the gear138, and the shaft140to the first electric motor116a. The first electric motor116amay convert this input mechanical power to electrical or hydraulic power and supply the converted power to the second electric motor116b. Also, power from the engine114that flows via the shaft130, the gear132, and the gear134to the shaft136is nominally prevented from being input into the variator150. Moreover, mechanical power from the second electric motor116bmay rotate the shaft142and the attached gear144. This power from the electric motor116bmay rotate the gear148for rotating the first sun gear154. The power may also rotate the gear146, which may transfer across the first clutch184to the shaft198, to the gear200, to the gear170, to the shaft168, to the second planet gears and associated carrier164, to the first ring gear158. In other words, in this mode, power from the second from the electric motor116b116bmay drivingly rotate two components of the variator150(the first sun gear154and the first ring gear158), and the power may be summed and re-combined at the first planet gears and associated carrier156. The re-combined power may transfer via the gear176and the gear178to the shaft180. Power at the shaft180may be transferred across the second clutch186to the gear208, to the gear210, along the countershaft212, to the gear214, to the gear216, and ultimately to the output shaft230. In some embodiments, the series mode may provide the output shaft230with relatively high torque at low angular speed output. Thus, this mode may be referred to as a creeper mode in some embodiments. Furthermore, as will become evident, the first clutch184may be used only in this mode; therefore, the first clutch184may be referred to as a “creeper clutch”. In other words, the second electric motor116brotates the first sun gear154and the first ring gear158, and the power from the second electric motor116brecombines at the first planet gears and carrier156as a result.

In some embodiments, engaging the forward directional clutch194and the second clutch186may place the powertrain106in a first forward directional mode. This mode may be a split path mode in which the variator150sums power from the second electric motor116band the engine114and outputs the combined power to the output shaft230. Specifically, power from the second electric motor116bis transmitted from the shaft142, to the gear144, to the gear148, to the shaft174, to drive the first sun gear154. Also, power from the engine114is transmitted to the shaft130, to the gear132, to the gear134, to the shaft136, to the gear206, through the forward directional clutch194, to the shaft168, to the second planet gears and associated carrier164to the first ring gear158. Combined power from the second electric motor116band the engine114is summed at the first planet gears and the associated carrier156and is transmitted via the gear176and the gear178to the shaft180. Power at the shaft180may be transferred across the second clutch186to the gear208, to the gear210, along the countershaft212, to the gear214, to the gear216, and ultimately to the output shaft230.

Additionally, in some embodiments, engaging the forward directional clutch194and the third clutch188may place the powertrain106in a second forward directional mode as a further split path mode. Specifically, power from the second electric motor116bmay be transmitted from the shaft142, to the gear144, to the gear148, to the shaft174, to drive the second sun gear162. Also, power from the engine114is transmitted to the shaft130, to the gear132, to the gear134, to the shaft136, to the gear206, through the forward directional clutch194, to the shaft168, to the second planet gears and associated carrier164. Combined power from the second electric motor116band the engine114may be summed at the second ring gear166, and may be transmitted to the gear172, to the gear220, through the third clutch188, to the gear222, to the gear210, to the countershaft212, to the gear214, to the gear216, and ultimately to the output shaft230.

In addition, in some embodiments, engaging the forward directional clutch194and the fourth clutch190may place the powertrain106in a third forward directional mode as a further split path mode. Specifically, power from the second electric motor116bis transmitted from the shaft142, to the gear144, to the gear148, to the shaft174, to drive the first sun gear154. Also, power from the engine114is transmitted to the shaft130, to the gear132, to the gear134, to the shaft136, to the gear206, through the forward directional clutch194, to the shaft168, to the second planet gears and associated carrier164, to the first ring gear158. Combined power from the second electric motor116band the engine114is summed at the first planet gears and the associated carrier156and is transmitted via the gear176and the gear178to the shaft180. Power at the shaft180may be transferred across the fourth clutch190to the gear210, to the gear226, along the countershaft212, to the gear214, to the gear216, and ultimately to the output shaft230.

Moreover, in some embodiments, engaging the forward directional clutch194and the fifth clutch192may place the powertrain106in a fourth forward directional mode as a further split path mode. Specifically, power from the second electric motor116bmay be transmitted from the shaft142, to the gear144, to the gear148, to the shaft174, to drive the second sun gear162. Also, power from the engine114is transmitted to the shaft130, to the gear132, to the gear134, to the shaft136, to the gear206, through the forward directional clutch194, to the shaft168, to the second planet gears and associated carrier164. Combined power from the second electric motor116band the engine114may be summed at the second ring gear166, and may be transmitted to the gear172, to the gear220, through the fifth clutch192, to the gear228, to the gear226, to the countershaft212, to the gear214, to the gear216, and ultimately to the output shaft230.

The powertrain106may also have one or more reverse modes for driving the work vehicle100in the opposite (reverse) direction from those modes discussed above. In some embodiments, the powertrain106may provide a reverse series mode, which corresponds to the forward series mode discussed above in which the first clutch184and the second clutch186may be engaged such that the second electric motor116bdrives the shaft142and the other downstream components in the opposite direction from that described above to move the work vehicle100in reverse.

Moreover, the powertrain106may have a plurality of split path reverse directional modes. In some embodiments, the powertrain106may provide reverse directional modes that correspond to the forward directional modes discussed above; however, the reverse directional clutch196may be engaged instead of the forward directional clutch194to achieve the reverse modes.

Accordingly, the powertrain106may provide a first reverse directional mode by engaging the reverse directional clutch196and the second clutch186. As such, power from the second electric motor116bmay be transmitted from the shaft142, to the gear144, to the gear148, to the shaft174, to drive the first sun gear154. Also, power from the engine114may be transmitted to the shaft130, to the gear132, to the gear134, to the shaft136, to the gear206, to the idler gear204, to the gear202, through the reverse directional clutch196, to the gear200to the gear170, to the shaft168, to the second planet gears and associated carrier164to the first ring gear158. Combined power from the second electric motor116band the engine114may be summed at the first planet gears and the associated carrier156and may be transmitted via the gear176and the gear178to the shaft180. Power at the shaft180may be transferred across the second clutch186to the gear208, to the gear210, along the countershaft212, to the gear214, to the gear216, and ultimately to the output shaft230.

The powertrain106may also provide a second reverse directional mode by engaging the reverse directional clutch196and the third clutch188. As such, power from the second electric motor116bmay be transmitted from the shaft142, to the gear144, to the gear148, to the shaft174, to drive the second sun gear162. Also, power from the engine114may be transmitted to the shaft130, to the gear132, to the gear134, to the shaft136, to the gear206, to the idler gear204, to the gear202, through the reverse directional clutch196, to the gear200, to the gear170, to the shaft168, to the second planet gears and associated carrier164. Combined power from the second electric motor116band the engine114may be summed at the second ring gear166, and may be transmitted to the gear172, to the gear220, through the third clutch188, to the gear222, to the gear210, to the countershaft212, to the gear214, to the gear216, and ultimately to the output shaft230.

In addition, in some embodiments, engaging the reverse directional clutch196and the fourth clutch190may place the powertrain106in a third reverse directional mode. Specifically, power from the second electric motor116bmay be transmitted from the shaft142, to the gear144, to the gear148, to the shaft174, to drive the first sun gear154. Also, power from the engine114may be transmitted to the shaft130, to the gear132, to the gear134, to the shaft136, to the gear206, to the idler gear204, to the gear202, through the reverse directional clutch196, to the gear200, to the gear170to the shaft168, to the second planet gears and associated carrier164, to the first ring gear158. Combined power from the second electric motor116band the engine114may be summed at the first planet gears and the associated carrier156and may be transmitted via the gear176and the gear178to the shaft180. Power at the shaft180may be transferred across the fourth clutch190to the gear210, to the gear226, along the countershaft212, to the gear214, to the gear216, and ultimately to the output shaft230.

Moreover, in some embodiments, engaging the reverse directional clutch196and the fifth clutch192may place the powertrain106in a fourth reverse directional mode. Specifically, power from the second electric motor116bmay be transmitted from the shaft142, to the gear144, to the gear148, to the shaft174, to drive the second sun gear162. Also, power from the engine114may be transmitted to the shaft130, to the gear132, to the gear134, to the shaft136, to the gear206, to the idler gear204, to the gear202, through the reverse directional clutch196, to the gear200, to the gear170, to the shaft168, to the second planet gears and associated carrier164. Combined power from the second electric motor116band the engine114may be summed at the second ring gear166, and may be transmitted to the gear172, to the gear220, through the fifth clutch192, to the gear228, to the gear226, to the countershaft212, to the gear214, to the gear216, and ultimately to the output shaft230.

Furthermore, the powertrain106may provide one or more direct drive modes, in which power from the engine114is transferred to the output shaft230and power from the second electric motor116bis prevented from transferring to the output shaft230. Specifically, engaging the second clutch186, the third clutch188, and the forward directional clutch194may provide a first forward direct drive mode. As such, power from the engine114may transfer from the shaft130, to the gear132, to the shaft136, to the gear206, through the forward directional clutch194, to the second planet gears and carrier164, and to the first ring gear158. Moreover, with the second and third clutches186,188engaged, the second ring gear166and the first planet gears and carrier156lock in a fixed ratio to the countershaft212and, thus, the output shaft230. This effectively constrains the ratio of each side of the variator150and locks the engine speed directly to the ground speed of the work vehicle100by a ratio determined by the tooth counts of the engaged gear train. In this scenario, the speed of the sun gears154,162is fixed and the sun gears154,162carry torque between the two sides of the variator150. Furthermore, the first electric motor116aand the second electric motor116bmay be unpowered.

Similarly, engaging the fourth clutch190, the fifth clutch192, and the forward directional clutch194may provide a second forward direct drive mode. Furthermore, engaging the second clutch186, the third clutch188, and the reverse directional clutch196may provide a first reverse direct drive mode. Also, engaging the fourth clutch190, the fifth clutch192, and the reverse directional clutch196may provide a second reverse direct drive mode. As introduced above, the controller104is coupled to control various aspects of the power control system102, including the engine114and transmission118to implement the engine throttle shift function.

Referring now also toFIG.3, a dataflow diagram illustrates an embodiment of the power control system102implemented by the controller104, engine114, and transmission118to execute the clutch modulation function for motor stall prevention and/or mitigation. Generally, the controller104may be considered a vehicle controller, a dedicated controller, or a combination of engine and/or transmission controllers. With respect to the power control system102ofFIG.3, the controller104may be organized as one or more functional units or modules240,242(e.g., software, hardware, or combinations thereof). As can be appreciated, the modules240,242shown inFIG.3may be combined and/or further partitioned to carry out similar functions to those described herein. As an example, each of the modules240,242may be implemented with processing architecture such as a processor244and memory246, as well as suitable communication interfaces. For example, the controller104may implement the modules240,242with the processor244based on programs or instructions stored in memory246. In some examples, the consideration and implementation of the clutch modulation function by the controller104are continuous, e.g., constantly active. In other examples, the activation of the engine throttle shift function may be selective, e.g., enabled or disabled based on input from the operator or other considerations. In any event, the engine throttle function may be enabled and implemented by the power control system102, as described below.

Generally, the controller104may receive input data in a number of forms and/or from a number of sources, including sensors110, although such input data may also come in from other systems or controllers, either internal or external to the work vehicle100. This input data may represent any data sufficient to operate the motors116a,116b, engine114, and/or transmission118, particularly any data sufficient to carry out the clutch modulation function described below.

In one example, the controller104may be considered to include a transmission control module240and a motor control module242. In general, the transmission control module240is configured to generate clutch commands to operate the transmission118based on various types of data, including ground speed and operator input, as shown. The clutch commands may be generated at “shift points” in which the commands result in the clutches (e.g., clutches184,184,188,190,192,194,196ofFIG.2) of the transmission118providing a new gear or speed ratio at the output (e.g., shaft230ofFIG.2). Such operation may be implemented based on one or more shift schedules stored in memory246. As described below, the transmission control module240may also implement at least a portion of the clutch modulation function.

In general, the motor control module242may generate commands to operate one or more of the motors116a,116b, including commands associated with the typical operation of the motors116a,116b, such as speed commands, shut downs, timings, etc. The motor commands may be based on a number of factors, including the current motor speed. Other parameters impacting the motor commands generated by the motor control module242may include operational parameters and operator input via the operator interface122(FIG.1), as well as the current and intended mode or gear ratio commanded by the transmission control module240. In some example, the motor commands may be generated based on a predetermined operational schedule stored in memory246.

During typical operation (e.g., without the clutch modulation function), the transmission control module240generates commands for the various clutches of the transmission118to implement the scheduled transmission mode such that selected clutches are fully engaged or fully disengaged; and the motor control module242generates associated motor commands, particularly speed commands. As described below, the motor control module242and/or the transmission control module240may implement the clutch modulation function to improve the powertrain performance under certain conditions.

In particular, during operation, the motor control module242may received clutch mode commands (on which the clutch commands for the transmission118are based) in order to monitor the current mode of the transmission118. In one example, the motor control module242may identify and/or be notified when the transmission118is in a series mode, e.g., when the output torque of the transmission118is being provided by the second motor116b. The motor control module242may also monitor the motor speed, e.g., the speed of electric motor116bin the example ofFIG.2. Other parameters may be considered, such as output or ground speed. In any event, the motor control module242may determine when the conditions of the powertrain106are such that the second motor116b(and/or other motors116a) may be approaching or fallen below a stall speed threshold, typically as a result of a slowing vehicle100or transmission118. In other words, the motor control module242may identify when the vehicle100has encountered a situation in which the counterforce on the vehicle100or transmission118is slowing the motor116b, such as when engaging a heavy load or traveling up a steep incline that may result in motor stall.

Generally, the stall speed threshold is the speed threshold at which the motor may be adversely impacted by the inability to rotate properly, such as upon asymmetric phase or winding usage. Typically, the motor control module242(and/or other module or system) may derate or reduce the torque capability of the subject motor in these conditions to avoid heat issues. The stall speed threshold may be based on the size or type of the motor. In one example, the stall speed threshold may be 25 rpms, 50 rpms, 100 rpms, 250 rpms or 500 rpms, although any suitable stall speed threshold may be considered.

Reference is briefly made toFIG.4A, which is an example data representation250of motor performance in view of motor speed. In particular, the representation250ofFIG.4Adepicts electric motor torque capability (Nm) as a function of electric motor speed (RPM). The representation250further depicts various reference speeds260,262,264,266. Reference speed260is the electric motor maximum speed; reference speed262is the electric motor base speed; reference speed264is the stall speed threshold; and reference speed266is a further stall speed threshold. As shown, the torque capability is maximum in between the stall speed threshold264and the electric motor base speed262. At speeds above the electric motor base speed262, the torque capability decreases, including decreasing until reaching the electric motor maximum speed260. At speeds below the stall speed threshold264, the electric motor is derated, as reflected by the decrease in torque capability. The torque capability continues to decrease from the stall speed threshold264until the further stall speed threshold266, at which the decreased torque capability is maintained at a constant value. As described below, the clutch modulation function attempts to maintain the electric motor at speeds above the stall speed threshold (e.g., threshold264) to maximize the torque capability of the electric motor.

Returning toFIG.3and as discussed above, the motor control module242may monitor the motor speed relative to a stall speed threshold in order to identify a motor stall condition, and upon identification, the motor control module242may generate motor stall prevention commands for the transmission control module240. In one example, the motor control module242particularly monitors the electric motor116b, which as referenced below is responsible for providing the torque to the transmission118in the series mode. As noted above, in some examples, the motor control module242may only generate the motor stall prevention commands when the transmission is in a series mode, although in other examples, the motor control module242may generate the motor stall prevention commands for the transmission control module240independently of the clutch mode, e.g., in modes other than series modes.

Upon receipt of the motor stall prevention commands, the transmission control module240may generate modified clutch commands (e.g., clutch commands with clutch modulation commands for at least one clutch) in accordance with the clutch modulation function in order to address the potential stall of motor116b. Generally, the clutch commands generated according to the clutch modulation function operate to “modulate” (or partially engage) an otherwise engaged clutch within the power flow path of the transmission118. For example, in the first forward mode described above with reference toFIG.2, which is also a series mode, the clutch commands may operate to modulate the first clutch184that couples the second motor116bto other portions of the transmission118. In another example, in the first forward mode described above with reference toFIG.2, the clutch commands may operate to modulate the second clutch186that couples the second motor116bto other portions of the transmission118. In further examples, both clutches184,186may be modulated. Generally, the transmission control module242may select the clutch or clutches most suitable for modulation, e.g., clutch or clutches that may accommodate the heat or friction of the clutch slip associated with modulation.

The clutch modulation operates to at least partially decouple the electric motor116bfrom the slowing transmission118. In particular, a power flow clutch (e.g., clutch184) is allowed to slip such that the clutch element on the input side of the power flow path (e.g., on the side of the electric motor116b) is allowed to move at a higher speed than the opposite clutch element on the output side (e.g., on the side of the output shaft230).

The clutch modulation may be implemented in various ways. In one example, the clutch modulation may occur by dithering the selected clutch (e.g., a regular and rapid increase and decreases over a defined bandwidth relative to a mean of the resultant pressure at the clutch). Such dithering may be increasing or decreasing step forms, sawtooth forms, sinusoidal forms, and/or other shapes or functions (e.g., as an open loop function). In an example, upon initiating clutch modulation with dithering, the controller104may initially command the clutch torque to drop from an engaged pressure to a reduced clutch pressure lower than a normal or engaged clutch pressure. The reduced clutch pressure may be a function of a schedule or determined as a function of motor speed or output speed. The clutch pressure may subsequently stepped up and down (e.g., to oscillate or alternate) at approximately equal amplitudes. The resulting mean clutch pressure may increase or decrease with the motor speed and terminate when the motor speed reaches a sufficient value. In other examples, the power control system may implement the clutch modulation by targeting an intermediate or partially engaged resultant pressure at the clutch (e.g., as a closed loop function).

As a result of the clutch modulation, the electric motor116bmay be able to reach and/or maintain a speed above the stall speed threshold. The controller104may continue to monitor the parameters and maintain the clutch modulation until the conditions are such that the clutch modulation function is no longer necessary. In particular, the controller104may terminate the clutch modulation function when the ground speed or transmission output speed is greater than the stall speed threshold of the electric motor116b. At that point, the motor control module242may terminate the motor stall prevention commands resulting in the clutch modulation function, and the transmission control module240may generate clutch commands such that previously modulated clutch (e.g., clutch184) is fully engaged, e.g., normal or nominal operation. Additional details will be provided below.

Reference is now made toFIG.4B, which is a data representation270depicting powertrain parameters prior to, during, and subsequent to implementation of the stall prevention clutch modulation function. In particular, the data representation270depicts respective relative magnitudes of the various parameters on the vertical axis as a function of time on the horizontal axis.

The data representation270includes a first line272reflecting the transmission output speed (e.g., at output shaft230) over time; a second line274reflecting the clutch torque (e.g., for the clutch associated with the clutch modulation function, such as clutch184) over time; a third line276reflecting the relative clutch element speed (e.g., representing the amount of clutch slip) over time; a fourth line278reflecting the electric motor speed (e.g., electric motor116b) over time; a fifth line280reflecting the delivered or current electric motor torque capability over time; a sixth line282reflecting the command or desired electric motor torque over time; a seventh line or reference point284reflecting the initiation of the clutch modulation function; an eighth line286reflecting an effective or mean clutch torque (e.g., for the modulated clutch torque of line274); and a ninth line or reference point288reflecting the point at which the transmission output speed272exceeds the electric motor speed278.

As shown, the clutch modulation function is initiated (represented at point284) when the transmission output speed272is relatively low (e.g., at a stall speed threshold). Prior to point284, the clutch torque274is fully engaged such that the relative clutch element speed276is approximately zero; and since the transmission output speed272is approximately zero, the clutch torque274is fully engaged, and the electric motor speed278is relatively low, the electric motor delivered torque280is less than the desired electric motor torque282. In other words, prior to implementing the clutch modulation function at point284, the electric motor may not be delivering the desired torque.

At point284, the clutch modulation function is initiated, and in particular, the clutch (e.g., clutch184) is subject to dither. As the clutch is dithered, the clutch torque274is initially reduced and subsequently undergoes relatively quick increases and decreases about an average amplitude or magnitude286, such that the relative clutch element speed276is increased (e.g., clutch slip occurs), which in turn enables the electric motor speed278to increase. As shown, the delivered torque280increases as the electric motor speed278increases.

At point288, the output speed272of the transmission is such that full engagement of the clutch would no longer result in the electric motor having a speed278that would stall the electric motor. As a result, the stall prevention modulation function may be terminated and the clutch torque274may be such that the clutch is fully engaged, e.g., such that the relative clutch element speed276is reduced to zero. Subsequently, the electric motor continues to increase in speed278and continues to deliver the requested torque280.

The power control system discussed herein may further be embodied as a method for controlling a powertrain of a work vehicle. In particular, the method includes initiating, monitoring, with a controller, an electric motor speed of the at least one electric motor; and generating and executing, at the controller, a clutch modulation command for the transmission such that at least one of the plurality of clutches along the power flow path is partially engaged when the electric motor speed is less than a first predetermined stall speed threshold. The generating and executing step may include generating and executing the clutch modulation command such that the at least one clutch is dithered. Further. the generating and executing step may include generating and executing the clutch modulation command such that the at least one clutch is subject to repeated modulations in clutch pressure between higher and lower amplitudes. The method may be terminated when the electric motor speed exceeds the first predetermined stall speed threshold.

Accordingly, the present disclosure provides a power control system and method for a work vehicle powertrain having an engine and at least one electric motor generating power conditioned by a transmission such as an eIVT. In particular, the power control system and method provide improved performance and efficiency, specifically in low speed, high torque applications.

Also, the following examples are provided, which are numbered for easier reference.

1. A control system for a work vehicle comprising: a power source including an engine and at least one electric motor configured to generate power; a transmission including a plurality of clutches coupled together and configured for selective engagement to transfer the power from the engine and the at least one electric motor along a power flow path to drive an output shaft of a powertrain of the work vehicle according to a plurality of transmission modes; and a controller coupled to the power source and the transmission, the controller having a processor and memory architecture configured to: monitor an electric motor speed of the at least one electric motor; and generate and execute, when the electric motor speed is less than a first predetermined stall speed threshold, a clutch modulation command for the transmission such that at least one clutch of the plurality of clutches along the power flow path is partially engaged.

2. The control system of example 1, wherein the controller is configured to generate and execute the clutch modulation command such that the at least one clutch is dithered.

3. The control system of example 1, wherein the controller is configured to generate and execute the clutch modulation command such that the at least one clutch is subject to repeated modulations in clutch pressure between higher and lower amplitudes.

4. The control system of example 1, wherein the controller is configured to generate and execute the clutch modulation command such that the at least one clutch is subject to repeated modulations in clutch pressure between higher and lower amplitudes.

5. The control system of example 4, wherein the controller is configured to generate and execute the clutch modulation command such that the repeated modulation occurs subsequent to an initial drop in clutch pressure at an initiation of the clutch modulation command.

6. The control system of example 5, wherein the controller is configured to continue the repeated modulation about a mean resultant clutch pressure that increases as the electric motor speed increases.

7. The control system of example 1, wherein, upon generation and execution of the clutch modulation command, the controller is configured to continue to monitor the electric motor speed and to terminate the clutch modulation command when the electric motor speed exceeds the first predetermined stall speed threshold.

8. The control system of example 1, wherein the plurality of transmission modes includes a series mode in which the output shaft of the powertrain is driven primarily by power from the at least one electric motor and a split mode in which the output shaft of the power is driven by combined power from the engine and the at least one electric motor, and wherein the controller is configured to generate and execute the clutch modulation command when the electric motor speed is less than the first predetermined stall speed threshold and the transmission is operating in the series mode.

9. The control system of example 1, wherein the transmission is an electrical infinitely variable transmission (eIVT).

10. A controller for a work vehicle with an engine and at least one electric motor configured to generate power and a transmission with a plurality of clutches coupled together and configured for selective engagement to transfer the power from the engine and the at least one electric motor along a power flow path to drive an output shaft according to a plurality of transmission modes, the controller comprising: a processor and memory architecture configured to: monitor an electric motor speed of the at least one electric motor; and generate and execute, when the electric motor speed is less than a first predetermined stall speed threshold, a clutch modulation command for the transmission such that at least one clutch of the plurality of clutches along the power flow path is partially engaged.

11. The controller of example 10, wherein the processor and memory are further configured to generate and execute the clutch modulation command such that the at least one clutch is dithered.

12. The controller of example 10, wherein the processor and memory are further configured to generate and execute the clutch modulation command such that the at least one clutch is subject to repeated modulations in clutch pressure between higher and lower amplitudes.

13. The controller of example 10, wherein the processor and memory are further configured such that the at least one clutch is subject to repeated modulations in clutch pressure between higher and lower amplitudes.

14. The controller of example 13, wherein the processor and memory are further configured such that the repeated modulation occurs subsequent to an initial drop in clutch pressure at an initiation of the clutch modulation command.

15. The controller of example 14, wherein the processor and memory are further configured to continue the repeated modulation about a mean resultant clutch pressure that increases as the electric motor speed increases.

For convenience of notation, “component” may be used herein, particularly in the context of a planetary gear set, to indicate an element for transmission of power, such as a sun gear, a ring gear, or a planet gear carrier. Further, references to a “continuously” variable transmission, power train, or power source will be understood to also encompass, in various embodiments, configurations including an “infinitely” variable transmission, power train, or power source.

In the discussion below, various example configurations of shafts, gears, and other power transmission elements are described. It will be understood that various alternative configurations may be possible, within the spirit of this disclosure. For example, various configurations may utilize multiple shafts in place of a single shaft (or a single shaft in place of multiple shafts), may interpose one or more idler gears between various shafts or gears for the transmission of rotational power, and so on.

As will be appreciated by one skilled in the art, certain aspects of the disclosed subject matter can be embodied as a method, system (e.g., a work machine control system included in a work machine), or computer program product. Accordingly, certain embodiments can be implemented entirely as hardware, entirely as software (including firmware, resident software, micro-code, etc.) or as a combination of software and hardware (and other) aspects. Furthermore, certain embodiments can take the form of a computer program product on a computer-usable storage medium having computer-usable program code embodied in the medium.

As will be appreciated by one skilled in the art, aspects of the disclosed subject matter can be described in terms of methods, systems (e.g., control or display systems deployed onboard or otherwise utilized in conjunction with work machines), and computer program products. With respect to computer program products, in particular, embodiments of the disclosure may consist of or include tangible, non-transitory storage media storing computer-readable instructions or code for performing one or more of the functions described throughout this document. As will be readily apparent, such computer-readable storage media can be realized utilizing any currently-known or later-developed memory type, including various types of random access memory (RAM) and read-only memory (ROM). Further, embodiments of the present disclosure are open or “agnostic” to the particular memory technology employed, noting that magnetic storage solutions (hard disk drive), solid state storage solutions (flash memory), optimal storage solutions, and other storage solutions can all potentially contain computer-readable instructions for carrying-out the functions described herein. Similarly, the systems or devices described herein may also contain memory storing computer-readable instructions (e.g., as any combination of firmware or other software executing on an operating system) that, when executed by a processor or processing system, instruct the system or device to perform one or more functions described herein. When locally executed, such computer-readable instructions or code may be copied or distributed to the memory of a given computing system or device in various different manners, such as by transmission over a communications network including the Internet. Generally, then, embodiments of the present disclosure should not be limited to any particular set of hardware or memory structure, or to the particular manner in which computer-readable instructions are stored, unless otherwise expressly specified herein.

As used herein, the term module refers to any hardware, software, firmware, electronic control component, processing logic, and/or processor device, individually or in any combination, including without limitation: application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. The term module may be synonymous with unit, component, subsystem, sub-controller, circuitry, routine, element, structure, control section, and the like.