Patent ID: 12208680

DETAILED DESCRIPTION

A power take-off (PTO) assembly with a disconnect clutch and a bi-directional pump for use with a hydraulic system is described herein. The PTO assembly may be coupled to a transmission via a shaft (e.g., an output shaft) such that the PTO assembly may be receive rotational input when the shaft is rotating (either via a prime mover or via wheel rotation, as during a tow operation). The bi-directional pump provides lubricant to the hydraulic system when the prime mover (e.g., an internal combustion engine or electric motor) coupled to the transmission is shut down by pumping fluid from a sump to transmission components. To achieve this functionality, the disconnect clutch is configured to passively disconnect the bi-directional pump from the transmission when the prime mover is in operation and mechanically connect the bi-directional pump to the transmission when the prime mover is shut down. Pump disconnection and connection is achieved using a hydraulic circuit that passively permits and inhibits fluid flow to a clutch piston according to fluid pressure in the hydraulic system. The disconnect clutch, when engaged, allows rotational energy to be transmitted from the transmission shaft to the bi-directional pump. When disengaged, rotational power is not transmitted to the bi-directional pump. Consequently, the transmission is lubricated while the transmission shaft is rotating and the engine or other suitable prime mover coupled to the transmission is shut down.

The PTO assembly described herein may be used in any number of suitable systems such as a transmission. An exemplary transmission system with a PTO assembly is shown inFIG.1. A schematic diagram of an exemplary hydraulic circuit in a PTO assembly is depicted inFIG.2. Illustrations of an exemplary PTO assembly and hydraulic system are shown inFIGS.3,4,5A, and5B. Methods of operation for the passively actuated PTO assembly are depicted in flowcharts inFIGS.6and7. A use-case scenario for operation of the passively actuated hydraulic circuit in the PTO assembly is shown in a timing diagram depicted inFIG.8.

FIG.1depicts a transmission system100. The transmission system100in the illustrated example, may be included in an electric drive unit102of a vehicle104such as an electric vehicle (EV) (e.g., a battery electric vehicle (BEV)), although alternative examples are possible such as hybrid electric vehicles (HEV) that utilize an internal combustion engine for propulsion and/or recharging of an energy storage device. Further, in other examples the transmission system may be utilized in a vehicle powertrain which solely utilizes an internal combustion engine as the prime mover.

The electric drive unit102generates motive power for vehicle propulsion. The vehicle104may be an on-highway vehicle such as a sedan or truck or an off-highway vehicle such as a material handling, mining, or railway vehicle. More generally, the vehicle104may be a light, medium, or heavy duty vehicle, for instance.

The electric drive unit102may include an electric machine106(e.g., traction motor). However, another suitable prime mover may be used in place of the electric machine106such as an internal combustion engine or hydraulic motor, in other examples. The electric machine106may include components such as a rotor and a stator that electromagnetically interact during operation to generate motive power. Further in one example, the electric machine may be a motor-generator which is designed to generate electrical energy during regeneration operation.

The electric machine106may be electrically coupled to one or more energy storage device(s)108(e.g., one or more traction batteries, capacitor(s), fuel cell(s), combinations thereof, and the like) by way of an inverter110when the machine is designed as alternating current (AC) machine. However, a direct current (DC) electric machine may be used in alternate examples.

Arrows114denote the electrical connection between the electric machine106, the inverter110, and the energy storage device(s)108. The inverter110may be designed to convert direct current (DC) to AC and vice versa. In one use-case example, the electric machine106and the inverter110may be three-phase devices which can achieve greater efficiency when compared to other types of motors. However, motors and inverters designed to operate using an alternate number of phases have been envisioned.

The electric machine106may be rotationally coupled to the transmission system100. Further, the transmission system100may include a multi-speed transmission116(e.g., a multi-speed gearbox) with multiple assemblies. When the multi-speed transmission is used in an EV it may be referred to as an electric multi-speed transmission. However, in other examples, the transmission may be a single speed transmission.

The multi-speed transmission116may include one or more clutch assemblies, such as a higher-lower range clutch assembly118and a multi-speed clutch assembly120. The higher-lower range clutch assembly118may be positioned downstream of the multi-speed clutch assembly120. The higher-lower range clutch assembly118may include a higher range clutch122positioned coaxial to an output shaft124and a lower range clutch126positioned coaxial to a first layshaft128. However, in another example, the higher range clutch may be positioned coaxial to the first layshaft and the lower range clutch may be positioned coaxial to the output shaft. It will be understood, that other clutch architectures in the transmission may be used. For instance, the number, positioning, and/or type of clutches used in the transmission may be altered to meet different end-use design goals.

The higher range clutch122as well as the other clutches described herein may be friction clutches (e.g., wet friction clutches). The friction clutches described herein may be operated with varying amounts of engagement (e.g., continuously adjusted through the clutch's range of engagement) of friction plates and spacers. Further, the friction clutches described herein may be wet friction clutches through which lubricant is routed to increase clutch longevity. Specifically, oil may be routed between the friction plates prior to, during, and/or after engagement in order to reduce degradation of the friction plates long term. The higher range clutch122and the other clutches described herein may be adjusted via hydraulic, pneumatic, and/or electro-mechanical actuators. For instance, hydraulically operated pistons may be used to induce clutch engagement/disengagement. However, solenoids may be used for electro-mechanical clutch actuation, in other examples. Using friction clutches allows power interruptions during shifting transients to be reduced, thereby increasing transmission performance. However, other types of clutches such as dog clutches may be used in the transmission, in other examples.

In the friction clutch example, the higher range clutch122includes an inner carrier130and an outer carrier132. The inner carrier130has a first set of plates mounted thereto and the outer carrier132has a second set of plates mounted thereto. These plates may frictionally engage when the clutch is closed to permit torque transfer from the inner carrier130to the outer carrier132. Conversely, when the clutch is open the plates may be frictionally disengaged. As such, the clutch may be in an engaged state when it is closed and a disengaged state when it is open. The outer carrier132may be fixedly coupled to a gear134that is fixedly coupled to the output shaft124. A bearing136may serve as the rotational connection between the inner carrier130and the output shaft124. The bearing136as well as the other bearings described herein may include an inner race, an outer race, and roller elements (e.g., cylindrical rollers, tapered rollers, balls, and the like). The inner clutch carriers depicted inFIG.1are shown coupled to a single bearing. However, it will be understood that the clutch carriers may be coupled to multiple bearings, in other examples. Further, the inner carrier130is fixedly coupled to a gear138which meshes with a gear140coupled to the first layshaft128.

Again in the friction clutch example, the lower range clutch126includes an inner carrier142and an outer carrier144which each have different sets of plates mounted thereto and functions in the similar manner to the higher range clutch122with regard to plate engagement and disengagement. The other friction clutches of the multi-speed transmission116described herein also includes plates the function in a similar manner and repeated description of the plates is omitted for brevity. The inner carrier142may be fixedly coupled to a gear146that meshes with the gear134. Conversely, the outer carrier144may be fixedly coupled to the gear140that meshes with the gear138and a gear148.

In the illustrated example, the higher and lower range clutches122and126are axially offset along their rotational axes150and151. In this way, the transmission's space efficiency is increased when compared to clutches that have the same position along their respective rotational axes. However, in other examples, the higher and lower range clutches may have alternate axial positions.

As illustrated, the output shaft124may include two mechanical interfaces152which are designed to mechanically attach to downstream driveline components such as shafts, joints, and the like that transfer mechanical power to drive axle assemblies154which may each include a differential, axle shafts (e.g., half shafts), drive wheels, and the like. This mechanical power transfer is denoted via arrows155. In other examples, the output shaft124may include one mechanical interface or more than two mechanical interfaces.

The output shaft124may further include a PTO gear set125. The output shaft124may be removably coupled to a gear111which meshes with a gear113. Gear113may be coupled, either fixedly or removably, to a PTO assembly112or included therein. The PTO assembly112may be referred to as a ground driven PTO assembly that is driven via rotation of the output shaft124, during towing for example. Towing operating as described herein is an operating condition where the prime mover is not in operation and vehicle drive wheels are rotating due to the vehicle104being attached to a tow vehicle (e.g., tow truck). However, in alternate examples, the PTO assembly112may be driven by another shaft in the transmission116. The PTO assembly112provides fluid (e.g., lubricant) to a hydraulic system127which in turn provides fluid to components in the transmission with fluid demands for lubrication and/or actuation such as the clutches, bearings, and the like. Arrow129denotes the fluidic connection between the PTO assembly112and the hydraulic system127which is expanded upon herein with regard toFIGS.2-5B. It will be understood that the PTO gear set125may be incorporated into the PTO assembly112and the PTO assembly may be formed as a unit that is removably coupled to the output shaft124. In this way, the PTO assembly112may be efficiently incorporated into the transmission at a later stage in the manufacturing process, when compared to PTOs that are attached to the transmission at upstream locations. Designing the PTO assembly and gears as a monolithic unit allows, the applicability of the PTO assembly to be expanded while increasing the transmission's functional capabilities.

In some examples, the multi-speed clutch assembly120includes two or more clutches arranged on a second layshaft156and a third layshaft158. To elaborate, in the illustrated example, a first pair of clutches which includes a first gear clutch160and a third gear clutch162are positioned coaxial to the third layshaft158and a second pair of clutches which includes a second gear clutch164and a fourth gear clutch165are positioned coaxial to the second layshaft156.

The second gear clutch164may include an inner carrier166and an outer carrier167. The inner carrier166may be fixedly coupled to the gear148that meshes with the gear140. The outer carrier167may be fixedly coupled to the second layshaft156.

The fourth gear clutch165may include an inner carrier168and an outer carrier169. The inner carrier168may be fixedly coupled to a gear170that meshes with a gear171on the first layshaft128. The outer carrier169may be again fixedly coupled to the second layshaft156.

The first gear clutch160may include an inner carrier172and an outer carrier173. The inner carrier172may be fixedly coupled to a gear174that is rotationally coupled to the gear140as denoted via curved line178. In other words, the gear174may mesh with the gear140. However, in other examples, the gear174may be coupled to the gear140via a mechanical coupling such as one or more gears, shafts, joints, and the like. The inner carrier172may be fixedly coupled to the third layshaft158.

The third gear clutch162may include an inner carrier175and an outer carrier176. The inner carrier175may be fixedly coupled to a gear177that is rotationally coupled to a gear179on the first layshaft128as denoted via curved line180. In other words, the gear177may mesh with the gear179. However, in other examples, the gear177may be coupled to the gear179via a mechanical coupling such as one or more gears, shafts, joints, and the like. The inner carrier175may be fixedly coupled to the third layshaft158.

The multi-speed transmission116further includes, in the illustrated example, an input assembly181that includes an input shaft182with a gear183and a gear184fixedly coupled thereto. The gear183meshes with a gear185fixedly coupled to the third layshaft158. The gear185is rotationally coupled to a gear186that is fixedly coupled to the second layshaft156as denoted via curved line187.

In other words, the gear185may mesh with the gear186. However, in other examples, the gear185may be coupled to the gear186via a mechanical coupling such as one or more gears, shafts, joints, and the like. Further, the gear184meshes with a gear188on an electric machine interface shaft189. In turn, the electric machine interface shaft189is coupled to a rotor shaft in the electric machine106.

Input shaft182further includes a gear107fixedly coupled thereto. Gear107may mesh with a gear197, which may be fixedly or removably coupled to a pump191(e.g., charging pump). As such, the electric machine106may provide rotational power to the pump191. The pump191may provide pressurized fluid (e.g., lubricant such as mineral based and/or synthetic oil) to clutches for actuation and/or lubrication as well as bearings and/or other components in the transmission with fluid demands.

A second electric machine198may additionally be coupled to the multi-speed transmission116, in one example, via a gear199that meshes with the gear184. However, in other examples, the second electric machine198may be omitted from the electric drive unit102.

The output shaft124may be arranged below the layshafts128,156,158as well as an input shaft182. In this way, the transmission achieves a desired drop that has applicability in a wide range of vehicles. However, the output shaft may be positioned above at least one of the layshafts, in other examples.

The multi-speed transmission116may further include bearings147that are coupled to inner carriers of the clutches and the corresponding shafts that are coaxial to the inner carriers. In this way, the inner carriers can independently rotate with regard to the shafts when the clutches are disengaged.

The vehicle104may further include a control system190with a controller192as shown inFIG.1. The controller192may include a microcomputer with components such as a processor193(e.g., a microprocessor unit), input/output ports, an electronic storage medium194for executable programs and calibration values (e.g., a read-only memory chip, random access memory, keep alive memory, a data bus, and the like). The storage medium may be programmed with computer readable data representing instructions executable by a processor for performing the methods and control techniques described herein as well as other variants that are anticipated but not specifically listed.

The controller192may receive various signals from sensors195coupled to various regions of the vehicle104and the multi-speed transmission116. For example, the sensors195may include a pedal position sensor designed to detect a depression of an operator-actuated pedal such as an accelerator pedal and/or a brake pedal, a speed sensor at the transmission output shaft, energy storage device state of charge (SOC) sensor, clutch position sensors, and the like. Motor speed may be ascertained from the amount of power sent from the inverter to the electric machine. An input device145(e.g., accelerator pedal, brake pedal, drive mode selector, combinations thereof, and the like) may further provide input signals indicative of an operator's intent for vehicle control.

Upon receiving the signals from the various sensors195ofFIG.1, the controller192processes the received signals, and employs various actuators196of vehicle and/or transmission components to adjust the components based on the received signals and instructions stored on the memory of controller192. For example, the controller192may receive an accelerator pedal signal indicative of an operator's request for increased vehicle acceleration. In response, the controller192may command operation of the inverter110to adjust electric machine mechanical power output and increase the power delivered from the electric machine106to the multi-speed transmission116. The controller192may, during certain operating conditions, be designed to send commands to the clutches122,126,160,162,164,165, to engage and disengage the clutches. For instance, a control command may be sent to the higher range clutch122and in response to receiving the command, an actuator in the clutch may adjust the clutch based on the command for clutch engagement or disengagement. The other controllable components in the vehicle may function in a similar manner with regard to sensor signals, control commands, and actuator adjustment, for example.

An axis system is provided inFIG.1as well asFIGS.2-5B, for reference. The z-axis may be a vertical axis (e.g., parallel to a gravitational axis), the x-axis may be a lateral axis (e.g., horizontal axis), and/or the y-axis may be a longitudinal axis, in one example. However, the axes may have other orientations, in other examples.

The multi-speed transmission116may be designed to operate with an equal number of forward and reverse driving gear modes. For instance, in the illustrated example, the transmission has eight forward and reverse gear modes. However, it will be appreciated that the transmission may be designed with a different number of gear modes which may be symmetric in some cases. For instance, the transmission may have two, three, four, or sixteen forward and/or reverse gear modes.

To operate the multi-speed transmission116in a reverse drive mode the electric machine106may spin the rotor shaft in an opposite direction as the forward drive mode. Designing the electric machine106in this manner allows the compactness of the transmission to be reduced when compared to transmissions with mechanical reverse assemblies. However, in other examples, the transmission may include a mechanical reverse that decreases the system's space efficiency.

The transmission116is described as one possible exemplary embodiment and that other configurations of exemplary transmission systems with other configurations of clutches, gears, and/or shafts are possible without departing from the scope of this disclosure. For instance, the electric machine106and/or the electric machine198may be replaced with internal combustion engine(s), in one example. In other examples, the multi-speed transmission may provide motive power to a first drive axle assembly while an internal combustion engine provides motive power to a second drive axle assembly. Still further, in other embodiments, an internal combustion engine may be provided to recharge the energy storage device(s)108. However, it will be understood, that when the transmission is used in an all-electric vehicle, the system may be simplified thereby reducing manufacturing costs and the chance of component failure.

FIG.2schematically illustrates a hydraulic system200and a passive hydraulic actuation circuit201in a PTO assembly203. It will be understood that the PTO assembly203and the hydraulic system200depicted inFIG.2as well as the other PTO assemblies described herein may be included in the transmission system depicted inFIG.1or another suitable system.

The hydraulic system200may include multiple hydraulic devices and a relief valve216in fluidic communication a fluid reservoir (e.g., a lubricant sump). The hydraulic system200may receive fluid (e.g., lubricant such as oil) from the sump. The hydraulic system200may act to provide fluid to component(s)214(e.g., transmission components) with lubricant demands while the prime mover (e.g., the electric machine106ofFIG.1or an internal combustion engine) is shut down. As described herein, prime mover shut down is an operating condition where the prime mover is not generating and/or transferring mechanical power to downstream components. During prime mover shut down, while a pump205(e.g., lubricant pump) is not in operation, and while the transmission output shaft (e.g., output shaft124) or other suitable shaft to which the PTO assembly, is rotating (during vehicle towing, for instance) the PTO assembly203is designed to provide lubricant to the component(s)214by way of the hydraulic system200. In this way, the system (e.g., transmission) is lubricated over a wider range of operating conditions, thereby increasing system longevity when compared to systems which are not designed to lubricate components during towing. The pump205may be in fluidic communication with a hydraulic line256at a junction254, the hydraulic line256being in fluidic communication with the hydraulic component(s)214(e.g., transmission system components).

In some examples, the PTO assembly203includes a disconnect clutch206(e.g., a passively actuated disconnect clutch) and a bi-directional pump208. Additionally, the PTO assembly203may include a hydraulically actuated valve202(e.g., pressure port). The hydraulically actuated valve202may allow for use of pressurized lubricant within the hydraulic system200to passively actuate the valve, as opposed to manually actuated valves, or actively controlled valves (e.g., solenoid valves) that demand programmatic control logic. For instance, when the pressure of the fluid applied to the valve202is greater than a threshold value, the valve transitions into an open position where pressurized fluid can travel from a pump (e.g., a transmission pressure pump) in the transmission or other suitable system, to the valve202via an inlet line207, then through the valve202, and subsequently to a hydraulic actuator204in the disconnect clutch206. Conversely, when the lubricant pressure applied to the valve drops below the threshold value the valve transitions into a closed position where pressurized fluid flow through the valve is inhibited.

Further, the bi-directional pump208allows for lubricant to be pumped from a sump210to the hydraulic system (e.g., a transmission lubrication system) via rotation of a pump input shaft244in either direction. Thus, the bi-directional pump208may provide lubricant to the transmission during operations, such as towing, in which prime mover is shutdown the output shaft is rotating in either a forward or a reverse direction as opposed to a uni-directional pump which may allow for lubricant to be pumped in only one of the two directions. Further, it will be appreciated that the pump input shaft244may be rotationally coupled to a transmission shaft such as an output shaft.

The passive hydraulic actuation circuit201is designed to initiate engagement/disengagement of the disconnect clutch206based on the lubricant pressure within the hydraulic system200. To expound, shutting down and turning on of the prime mover alters pressure within the circuit to engage and disengage the disconnect clutch206, respectively. This passive actuation circuit reduces need for other actuators such as solenoids or manual actuators that may increase system complexity and increase time demanded to prepare the vehicle for certain operations, such as towing operation, if desired.

The passive hydraulic actuation circuit201routes hydraulic fluid (e.g., e.g., mineral based and/or synthetic oil) to control various hydraulic components. To elaborate the passive hydraulic actuation circuit201uses fluid pressure to engage and disengage (or sustain engagement and disengagement of) the disconnect clutch206. To accomplish this fluid routing, the passive hydraulic actuation circuit201may include multiple fluid distribution components, which may include valves, lines, conduits, and the like.

In the example illustrated inFIG.2, the hydraulic system200includes the hydraulically actuated valve202in fluidic communication with the hydraulic actuator204. Pressure within the hydraulic actuator204determines actuation of the disconnect clutch206. The operational state of the bi-directional pump208is dependent upon actuation state (engaged vs. disengaged) of the disconnect clutch206.

The hydraulic system200may be configured to hydraulically actuate multiple clutches and/or supply lubricant to multiple hydraulic devices (e.g., hydraulic pumps), each in fluidic communication with a respective hydraulically actuated valve.

The bi-directional pump208, which in some examples, may be a bi-directional fixed displacement hydraulic lubricant pump. The bi-directional pump208may be in fluidic communication with and may receive lubricant from the sump210via a pick-up line248. Further, the bi-directional pump208may be a positive displacement hydraulic pump having a housing and a pumping device (e.g., a reciprocating piston (e.g., check-ball piston pump) or rotary device) designed to deliver a pressurized lubricant during each cycle, for instance. Check valves,228and230, in a rectifying setup enable the bi-directional pump208to provide lubrication with rotation in either direction, in the illustrated example. However, other pump setups that enable bi-directional functionality may be used in other example.

The hydraulic system200may further include a relief valve216in fluidic communication with the sump210, as indicated via fluid return line250. The relief valve216, in the illustrated example, is a hydraulically controlled valve designed for selectively discharging lubricant back to the sump210when the pressure in the outlet line256is above a threshold value. In this way, overpressure conditions, such as during cold starts, in the hydraulic system200can be avoided, if desired. The relief valve216is shown including a spring217that dictates the pressure at which the valve opens. In this way, the relief valve216may be passively controlled (e.g., opened and/or closed) to avoid over pressure conditions in passive hydraulic actuation circuit201. However, relief valves with alternate constructions have been contemplated. The pressure in the hydraulic system200may refer to the pressure of the fluid downstream of a junction254.

The bi-directional pump208pressurizes and flows lubricant to the component(s)214via the outlet line256, respectively. Further, the bi-directional pump208may be in fluidic communication with the actuation line246. In this way, the bi-directional pump is able to open the valve202and allow fluidic communication between the hydraulic system and the hydraulic actuator.

Further, in one example, lubricant may be returned from the hydraulically actuated valve202to the sump210via a drain line258, passing through a check valve220and a flow restrictor242before returning to the sump210.

In some examples, the hydraulic actuator204may include a hydraulic chamber270, an actuation piston272, and a spring240. The hydraulic actuator204may actuate the disconnect clutch206. Although the disconnect clutch206and the hydraulic actuator204are separately illustrated inFIG.2, the clutch actuator may be incorporated in the disconnect clutch, as will be described further below. The actuation piston272may be axially slidable in the hydraulic chamber270. In some examples, the disconnect clutch206may include be a hydraulically actuated dog clutch. However, other types of hydraulically operated clutches may be used in other examples.

Pressurized fluid may be supplied to the hydraulic chamber270from the hydraulically actuated valve202via a hydraulic supply line280when the valve202is open and permitting fluid flow therethrough. Additionally, the hydraulically actuated valve202may be in fluidic communication with the actuation line246. Further, the outlet line256may be in fluidic communication with one or more lubricated components of the transmission via one or more additional lubricant lines.

The disconnect clutch206is designed to engage when the lubricant pressure in the hydraulic chamber270drops below a threshold value (e.g., a positive non-zero value) to place the actuation piston272is in a retracted position. The disconnect clutch206may be designed to disengage when the lubricant pressure in the hydraulic chamber270is above the threshold value and the actuation piston272is in an extended position as a result of hydraulic pressure in the hydraulic chamber270causing the actuation piston272to move into the extended position and the spring240to compress. As will be described in greater detail herein, reduction of pressure in the hydraulic chamber270may reduce force on the spring240, causing the spring240to return the actuation piston272to the retracted position, thereby engaging the disconnect clutch206.

As indicated above, the hydraulically actuated valve202is designed to passively supply pressurized lubricant to the hydraulic actuator204when the fluid pressure applied to the valve rises above a threshold value (e.g., a positive non-zero value), and thus the valve202transitions into an open configuration where lubricant flow is permitted between a main circuit in the hydraulic system (which may feed the clutch control system) and the hydraulic actuator204. The hydraulically actuated valve202may include a spring282that compresses when the valve202is transitioned into the open configuration. When actuated, the hydraulically actuated valve202permits pressurized fluid flow from the main circuit (which also feeds the clutch control system) in the hydraulic system through the hydraulically actuated valve202and into the hydraulic supply line280. Lubricant may actively flow through the hydraulically actuated valve202while the prime mover is in operation and causes the lubricant pump205to generate lubricant flow above a threshold pressure. Thus, the disconnect clutch206may be disengaged while the prime mover is in operation and vice versa.

When the prime mover of the vehicle is switched from an operational state to a shutdown state, system pressure from the transmission drops below a threshold and the spring240returns the hydraulic actuator204to a position that engages the disconnect clutch206. Subsequently, the bi-directional pump208flows pressurized fluid to the component(s)214as well as to the valve202. When the fluid pressure applied to the valve202surpasses the threshold value, the valve is closed, thereby inhibiting fluid flow from the main circuit to the hydraulic actuator204. To elaborate, fluid that remains in the lines is drained to the sump210via the flow restrictor242(e.g., throttle valve) to enable evacuation of fluid in order to retract the hydraulically actuated valve202.

Further, engagement of the disconnect clutch206actives the bi-directional pump208by enabling the transfer of rotational energy from a transmission shaft (e.g., transmission output shaft) to the pump input shaft244of the bi-directional pump208. Rotation of the pump input shaft244in turns rotates the bi-directional pump208, thereby allowing lubricant to be drawn from the sump210and delivered to the component(s)214for lubrication. A first port224(e.g., an inlet) of the bi-directional pump208may be in fluidic communication with the first pair of check valves228and a second port226(e.g., outlet) of the bi-directional pump208may be in fluidic communication with the second pair of check valves230. The first pair of check valves228may be configured to allow flow of lubricant from the sump towards the outlet226. The second pair of check valves230may be configured to allow flow of lubricant from the outlet226towards outlet line256. The pairs of check valves allow the pump to receive rotational input in opposing directions and supply lubricant to downstream components. Lubricant may then flow into an oil cooler212before passing another check valve232and then flowing to component(s)214in the system, such as the transmission system. The oil cooler212may be configured to control temperature of the lubricant supplied to the component(s)214when the prime mover is shut down and the bi-directional pump is providing lubrication to the transmission, for instance. Conversely, when the prime mover is operating, a transmission cooler may be used to control the temperature of the lubricant, in some examples. However, in other examples, the oil cooler may be positioned in a different location or be omitted from the system.

Additionally, when the prime mover is switched from a shutdown state to an operational state, the pressure of the lubricant flow generated by the bi-directional pump208increases. As a result, lubricant flows through actuation line246to the hydraulically actuated valve202, passing through a check valve222. Check valve222and other check valves described herein allow one way flow of lubricant when the pressure upstream of the valve exceed a threshold associated with the valve. For example, check valve232allows flow of lubricant from the bi-directional pump208to a junction254but not from the junction254towards the bi-directional pump208. The check valves228and230may be included in a bi-directional pump assembly231.

Hydraulic system200may further include a pressure sensor262(e.g., a pressure switch which may be configured to provide feedback to a controller (e.g., a transmission control unit) which indicates whether the bi-directional pump208is disconnected (e.g., generating 0 bar), when the prime mover is in operation.

Now referring toFIGS.3-5B, an example of a PTO assembly335that may be included in a system300, such as a transmission, is shown. Further, the PTO assembly shown inFIG.3may share at least some similarities with the PTO assembly described with regard toFIG.2. Redundant description of the overlapping features is omitted for brevity.

The multi-speed transmission300includes a housing302with a prime mover interface shaft with an interface306that is profiled to attach a shaft of a prime mover.

In the illustrated example, the housing302includes multiple sections: a first section310and a second section308that are attached to one another via fasteners312and/or other suitable attachments. However, other housing contours may be used in other examples.

The system300may further include a sump322that houses lubricant such as oil for use by other components of the system300. The lubricant may be used for component lubrication and/or component actuation (e.g., clutch actuation). The housing302at least partially encloses an input assembly, a range clutch assembly, and a multi-speed clutch assembly, in some examples.

The PTO assembly335include a bi-directional pump324that is configured to pump lubricant to a hydraulic system (e.g., the hydraulic system200, shown inFIG.2). Pressurized lubricant from the transmission or other suitable system may enter the PTO assembly335via a supply line330. Lubricant may drain from the PTO assembly via a drain line338. The bi-directional pump324may be configured to, when activated, draw lubricant from the sump322via a pick-up line328and deliver the lubricant to downstream components via an outlet port332.

A PTO housing337may at least partially surround and retain the components in the PTO assembly335. The PTO housing337may efficiently attach to the housing section308using fasteners336and/or other suitable attachment devices.

A mechanical output interface314is further included in the system300. The output interface314may be provided on an end of a transmission output shaft. The mechanical output interface314may be positioned below the electric machine interface. In this way, the transmission may achieve a desired amount of drop. However, other transmission input and output interface arrangements have been contemplated.

A pump316(e.g., charging pump) may further be included in the system300. The pump316may be driven by a shaft (e.g., an input shaft) in the system300, in one example. The pump316is designed to provide pressurized fluid (e.g., lubricant such as oil) to components of the transmission such as clutches for actuation and/or lubrication, bearings, and the like, in one example. Pressure provided by the pump316is also delivered towards the PTO assembly335in order to open a disconnect of the PTO assembly335(e.g., disconnect clutch206). The lubricant pump may be a suitable type of pump such as a positive displacement pump. In this way, a space efficient transmission unit with lubricant pump functionality may be achieved, if desired. A-A′ denotes the cutting plane for the cross-sectional views depicted inFIGS.4-5B.

FIG.4illustrates a cross-sectional view of the PTO assembly335that is coupled to an output shaft410of the transmission300via a PTO gear set400. The transmission may include the output shaft410that is coupled to other components within the transmission such as gears, shafts, and clutches. However, as previously discussed, the PTO assembly335may be coupled to another suitable shaft in the transmission or incorporated into another system.

The output shaft410may have the mechanical output interface314attached thereto or incorporated therein. The mechanical output interface314may be profiled to mechanically attach to downstream driveline components such as shafts, joints, and the like that transfer mechanical power to drive axles. Drive axles may be coupled to wheels of the vehicle such that when the output shaft rotates, the wheels rotate. Consequently, during operations in which a prime mover is not providing power to the transmission300, such as during a tow operation, the output shaft may rotate as a consequence of the wheels rotating. Such rotation of the output shaft may in turn lead to rotation of other components of the transmission, such as gears within the PTO gear set400as well as other shafts and gears of the transmission. Without power from the prime mover, a lubricant pump installed on the transmission may not provide lubrication to the transmission and without lubrication, rotation of components of the transmission may cause frictional wear and degradation. The PTO driven hydraulic pump system utilizes the rotation of the output shaft to provide lubrication to the transmission during such operations.

The PTO gear set400may include a second gear412that is directly coupled to or formed integrally with the output shaft410. For instance, the gear412and the shaft410may be manufactured together via machining, casting, combinations thereof, and the like. However, in other examples, the gear412may be splined, attached via fasteners, press-fit, combinations thereof, and the like to the shaft410. Bearings424may support and facilitate rotation of the output shaft410. Further, the output shaft410may include splines425which facilitate efficient attachment to another section of the output shaft that extends from the transmission enclosure. The bearings424may reside in the PTO housing337.

The second gear412may mesh with a first gear414. The first gear414and other components herein described may be contained within the PTO housing337. The first gear414may be fixedly coupled or incorporated into a shaft415. Bearings422, retained in the PTO housing337, are coupled to the shaft415and permit rotation thereof. In the illustrated example, the shaft415includes an opening417in which an extension419of a disconnect clutch432is positioned. The extension419specifically axially protrudes from a flange421which include a first toothed face474. The extension419may axially slidable within the shaft415. To accomplish this functionality, the shaft415and the extension419may each include axially extending splines that are mated with one another. As such, the shaft may include interior splines.

A hydraulic actuator in the form of an actuation piston423is further included in the disconnect clutch432and protrudes from the flange421in the opposite axial direction as the extension419. The actuation piston423mates with a recess in a section427of the disconnect clutch432that includes a flange429. The flange429includes a second toothed face476that is designed to engage with the first toothed face474and permit torque transfer therethrough when the clutch is engaged.

A hydraulic chamber431is formed in the recess of clutch section427. The hydraulic chamber receives lubricant for clutch actuation, as expanded upon herein with regard toFIGS.5A and5B. A seal433may be provided around the actuation piston423to reduce the chance of oil leakage from the hydraulic chamber431.

Bearings420may be positioned between the clutch section427and a section435of the PTO housing337. In this way, the disconnect clutch is able to rotate within the housing. The housing section435may be adjacent to (e.g., directly coupled to) the bi-directional pump324. The bearings420may be axially spaced apart to enable a lubricant supply line544to extend therebetween and connect with the hydraulic chamber431.

A stop437may be retained within the shaft415. A spring532may be axially delimited via the stop437. The stop437allows the spring532to be compressed when the disconnect clutch432is disengaged. In the illustrated example, the spring532is arranged in a cavity of the extension419. In this way, the space efficiency of the clutch actuator is increased. However, in other examples, the spring may be positioned external to the extension419. A seal439may circumferentially surround the stop437to reduce the chance of oil leakage.

Rotational axes490,491,492of the output shaft410, the shaft415, and the bi-directional pump324, respectively are provided for reference. It will be understood that the axes491,492are aligned with one another, in the illustrated example, to increase PTO assembly compactness. However, in alternate examples, the axes may not be aligned with one another.

The disconnect clutch432may be passively engaged and disengaged, as is further described below. The PTO assembly335, including the bi-directional pump324, may be coupled to the transmission, as is further described below. In brief, lubricant (e.g., natural and/or synthetic oil) stored within a sump450(e.g., the sump322ofFIG.3) may be pumped into a port562(e.g., inlet) of the bi-directional pump324via a pick-up line452(e.g., pick-up line328ofFIG.3). Fluid (e.g., lubricant) may then be pumped out of the bi-directional pump324(via a port560) to hydraulic system456via fluid line454. Fluid within the hydraulic system456may be directed via one or more fluid lines, conduits, and the like towards components458of the hydraulic system, indicated by arrow460.

In the illustrated example, the disconnect clutch432is a dog clutch. To elaborate, the disconnect clutch432is a dog clutch with a first toothed face474and a second toothed face476. The first toothed face474is rotationally coupled to the first gear414and the second toothed face476is rotationally coupled to an input shaft478of the bi-directional pump324. As such, mating of the toothed interfaces, during clutch engagement enables rotational energy to be transferred from the PTO gear set400to the bi-directional pump324. Conversely, during clutch disengagement, the toothed interfaces are spaced away from one another, thereby inhibiting rotational energy transfer between the PTO gear set400and the bi-directional pump324. However, in alternate examples the dog clutch may include splined interfaces or another suitable type of clutch may be utilized such as a friction clutch. The dog clutch may exhibit greater space efficiency and reliability when compared to other types of clutches, such as friction clutches.

The PTO assembly335may be formed as an interconnected unit that is able to be efficiently moved into positioned and coupled to the transmission housing. To elaborate, the PTO housing337may include fasteners479that extend therethrough and are profiled to attach to the transmission housing. Consequently, the PTO assembly335is capable being efficiency incorporated into the transmission at a later stage in manufacturing, when compared to PTOs that are attached to other transmission shafts such as the input shaft. As a result, the manufacturing process achieves greater adaptability and the PTO assembly may be used in a wider variety of transmissions, thereby increasing customer appeal. However, other PTO assembly constructions have been contemplated.

FIGS.5A and5Billustrate the PTO assembly335in different configurations.FIG.5Aspecifically depicts the PTO assembly335with the disconnect clutch432disengaged andFIG.5Bconversely depicts the PTO assembly335with the disconnect clutch432engaged.

As shown inFIG.5Athe disconnect clutch432is disengaged. Clutch disengagement occurs when the prime mover, connected to the transmission, is in operation and the transmission pump (which may be driven by the prime mover) is supplying pressurized fluid to the transmission. The disconnect clutch hydraulic actuator416includes a hydraulically actuated valve502in the depicted embodiment. However, other actuator configurations may be used in other embodiments. Further, the valve502includes a sleeve514(e.g., spool) in the illustrated example. The sleeve514is positioned in a cavity of the PTO housing337and axially translates therein during valve actuation. Various hydraulic passages, lines, and the like are fluidly coupled to the cavity in which the sleeve514resides to enable lubricant routing to be altered based on the sleeve's position. To expound, a first inlet port518(in fluidic communication with the hydraulic system) is fluidly coupled to a sleeve actuation chamber517(e.g., a hydraulic chamber) via a check valve516. It will be specifically understood, that an actuation line may be in fluidic communication with the inlet port518and a lubricant conduit in the hydraulic system. As such, when the lubricant pressure in the hydraulic system surpasses the check valve threshold, lubricant travels into the sleeve actuation chamber517. A second inlet port512is additionally fluidly coupled to the sleeve cavity. In the illustrated example, the second inlet port512is in fluidic communication with the hydraulic system and receives lubricant therefrom as denoted via arrow519. To expound, the arrow519may represent a transmission lubricant supply line for the valve502.

FIG.5Ashows the valve502in an open position. The valve502transitions into the open position when pressure in the sleeve actuation chamber517exerts a force on the sleeve514that is greater than a constant of a spring510, coupled to the sleeve, and therefore urges the sleeve in an axial direction (leftward in the frame of reference ofFIG.5A). When the sleeve is in a position which compresses the spring510, lubricant is allowed to flow from the second inlet port512to the hydraulic chamber431by way of the lubricant supply line544.

A portion of the spring510(including a first end) may be positioned in a recess in the sleeve514to increase assembly compactness. Further, the spring510is delimited at a second end via a detent in the PTO housing section435. A first land521in the sleeve514allows the second portion to be selectively blocked. Further, a second land523in the sleeve514allows the sleeve actuation chamber517to be fluidly separated from the path of lubricant which travels between the second inlet portion512and the lubricant supply line544. The disconnect clutch hydraulic actuator416may further include a return line525with a check valve520positioned therein. The check valve520opens when the pressure in the lubricant supply line544exceeds a threshold pressure (e.g., 20 bar, in one use-case example). In this way, overpressure conditions in the hydraulic chamber may be avoided, if desired.

In turn, pressurized lubricant will flow from the lubricant supply line544into the hydraulic chamber431with the actuation piston423positioned therein. As previously indicated, when the chamber pressure exceeds a threshold, the actuation piston423moves the disconnect clutch432into a disengaged position where the toothed faces474and476are decoupled and spaced apart from one another. In this way, the disconnect clutch432is passively disengaged when the pressure of the lubricant in the hydraulic system surpasses a threshold pressure. Torque transfer from the gear414to the bi-directional pump324is inhibited when the disconnect clutch432is disengaged. A drain540may allow drainage of lubricant from the PTO assembly335into the sump. Specifically, in the illustrated example, the drain540is in fluidic communication with a passage541within the sleeve514that is aligned with the return line525, when the valve502is closed (as shown inFIG.5B). However, alternate drain passage arrangements may be used in alternate examples.

Conversely,FIG.5Bshows the disconnect clutch432in an engaged configuration, during prime mover shutdown. During these conditions, the hydraulically actuated valve502is closed and inhibiting lubricant flow from the second inlet port512to the lubricant supply line544. Therefore, lubricant flow into the hydraulic chamber431of the disconnect clutch hydraulic actuator416is inhibited when the hydraulically actuated valve502is closed and therefore the forces acting upon the actuation piston423drops and consequently, with the actuation piston423axially moves into a neutral position in which the toothed faces474,476are mated and the disconnect clutch432is consequently engaged.

With the disconnect clutch432engaged, rotational torque is able to be transferred from the gear414to the bi-directional pump324via the input shaft478, as described above. Lubricant is consequently pumped from the sump450to the hydraulic system456via the bi-directional pump324. The lubricant enters the pump via the port562and exits the pump via port560.

It will be appreciated that due to the configuration of the disconnect clutch hydraulic actuator, the bi-directional pump324will continue to provide lubricant to the transmission until the lubricant pump drives by the prime mover generate a lubricant pressure greater than a threshold value. As such, both the bi-directional pump and the lubrication pump may be concurrently operated for a brief duration after prime mover start up. However, once the lubricant pressure surpasses the threshold, the bi-directional pump is passively disconnected. In this way, the chance of the transmission not receiving a target amount of lubricant during prime mover start up is decreased, thereby increasing transmission longevity.

FIG.6depicts a method600for a PTO assembly and hydraulic system. The method600occurs when the prime mover transitions from an operation state to a shut down state. The method600may be carried out by a PTO assembly and/or hydraulic system such as any of the previously described PTO assemblies and hydraulic systems or combinations thereof. However, in other examples, the method600may be implemented in other suitable PTO assemblies and/or hydraulic systems. At least a portion of the steps in the method are passively implemented based on lubricant pressure within the hydraulic system. To elaborate, step602is an active step that is carried out in response to operator interaction with the vehicle and steps604-612are passive actions that occur as a consequence of the active step602.

Prior to the start of method600, the prime mover is in operation and driving the transmission lubrication pump. As such, during prime mover operation, pressurized lubricant is directed from the hydraulic system to a disconnect clutch in the PTO assembly. Further, while the prime mover is operating, pressurized lubricant from the system flows through a hydraulically actuated valve (e.g., hydraulically actuated valve502ofFIGS.5A and5B) and into a chamber (e.g., chamber431ofFIGS.5A and5B) of a disconnect clutch hydraulic actuator (e.g., disconnect clutch hydraulic actuator416), sustaining the disconnect clutch (e.g., disconnect clutch432) in a disengaged position by moving a piston (e.g., actuation piston423ofFIGS.5A and5B). Disengagement of the disconnect clutch inhibits mechanical power transfer from the transmission to a bi-directional pump.

At602, the method600includes shutting down the prime mover (e.g., electric machine106ofFIG.1). Instructions for carrying out prime mover shut down may be executed by a controller and may be stored on a memory of the controller. Method600then proceeds to604.

At604, the method600includes decreasing the pressure in the hydraulic system as a result of the prime mover shutting down. Method600then proceeds to606.

At606, the method600includes closing the hydraulically actuated valve in response to the hydraulic system pressure falling below a threshold pressure. To elaborate, the hydraulically actuated valve closes due to a return spring (e.g., return spring510) urging a sleeve (e.g., sleeve514) of the hydraulically actuated valve to a neutral position, the neutral position being a closed position which inhibits lubricant delivery to the disconnect clutch actuator. Method600then proceeds to608.

At608, the method600includes decreasing the pressure in the chamber of the disconnect clutch actuator. Without system pressure entering the hydraulic system, the pressure within the chamber drops below a threshold. Method600then proceeds to610.

At610, the method600includes returning the piston to a neutral position. Method600then proceeds to612. At612, the method600includes engaging the disconnect clutch, as a result of the piston returning to the neutral position, to activate the bi-directional pump. Engagement of the disconnect clutch rotationally couples a bi-directional PTO pump (e.g., bi-directional pump324) to an output shaft of a transmission via a PTO gear set. The bi-directional PTO pump therefore pumps lubricant from a sump to the transmission of the vehicle when the output shaft rotates, such as during a tow operation on which one or more wheels are in contact with a ground surface (e.g., a road). The PTO gear set may be part of a PTO that derives rotation from rotation of the output shaft, thereby allowing rotation of components of the hydraulic system (e.g., the bi-directional pump) when the disconnect clutch is engaged and the output shaft is rotating. The method600ends after612.

FIG.7depicts another method700for the PTO assembly and lubrication system. The method700occurs when the prime mover transitions from a shut down state to an operation state. The method700is carried by the assembly and system used to implement the method600. Further, at least a portion of the steps in the method700are passively implemented based on lubricant pressure within the hydraulic system. To elaborate, step702is an active step that is carried out in response to operator interaction with the vehicle and steps704-712are passive actions that occur as a consequence of the active step702.

Prior to the start of method700, the prime mover is shut down and the bi-directional pump in the PTO assembly therefore delivers lubricant to the transmission when the output shaft is rotating (e.g., during towing or when the prime mover in non-operational and the vehicle is coasting). The hydraulically actuated valve is therefore in a closed position prior to the start of method700. During prime mover shutdown, the hydraulic system pressure is below the threshold for actuation of the hydraulically actuated valve.

At702, the method700includes starting the prime mover. Instructions for starting the prime mover may be executed by a controller and stored on a memory of the controller. Once the prime mover is in operation, the lubricant pressure in the hydraulic system rises but the hydraulically actuated valve remains closed thereby inhibiting oil flow to the disconnect clutch actuator. Method700then proceeds to704.

At704, the method700includes increasing lubricant pressure within the actuation line above a threshold pressure. Method700then proceeds to706. At706, the method700includes passively actuating the hydraulically actuated valve due to a sleeve within the hydraulically actuated valve transitioning from a closed position into an open position. Method700then proceeds to708.

At708, the method700includes flowing pressurized fluid through the valve in the disconnect clutch actuator. The system pressure may maintain the actuated position of the hydraulically actuated valve even when fluid pressure decreases. Method700then proceeds to710.

At710, the method700includes the flowing pressurized fluid into the hydraulic chamber to move the piston of the disconnect clutch actuator, initiating disengagement of the disconnect clutch. To elaborate, the fluid exerts a force on the piston, the force being above the threshold for the piston to compress the spring of the disconnect clutch actuator. The piston moving and the spring compression initiates disengagement of the disconnect clutch. The method700then proceeds to712.

At712, the method700includes the deactivating the bi-directional pump in response to disconnect clutch disengagement. Therefore, with the disconnect clutch disengaged, power transfer from a PTO input shaft to the bi-directional pump is inhibited. As such, the bi-directional pump does not pump lubricant. After712, the method ends.

FIG.8illustrates a timing diagram800of a use-case scenario for a PTO assembly and hydraulic system, such as any of the previously described PTO assemblies and hydraulic systems or combinations thereof. In each graph, time is indicated on the abscissa and increases from left to right. The ordinate for plot802indicates an operational state of a disconnect clutch (“Engaged” and “Disengaged”). Engaged indicates that the clutch permits rotational energy transfer therethrough and disengaged denotes that rotational energy transfer through the clutch is inhibited. While the clutch is engaged, the bi-directional pump is driven by rotation of transmission output shaft that may be brought about via towing operation or when the prime mover is non-operational but coasting. The ordinate for plot804indicates an operational state of the hydraulically actuated valve (“Open” and “Closed”). The ordinate for plot806indicates an operation state of the prime mover (“On” and “Off”). The ordinate for plot808indicates hydraulic system pressure, where the pressure increases along the ordinate from zero towards the arrow.

At t0, the prime mover is off, the disconnect clutch is engaged, the hydraulically actuated valve is in a closed position, and system pressure is zero. At t1, the prime mover is transitions from off to on. Between t1 and t2, system pressure increases. At t2, lubricant pressure passes the threshold810. Between t2 and t3, the hydraulically actuated valve state switches from closed to open, then the disconnect clutch switches from engaged to disengaged. At t3, the prime mover transitions from on to off, causing the system pressure to then drop below the threshold810at t4. When the system pressure drops below the threshold, the valve switches back to a closed position and the clutch again engages. From t4 to t5, system pressure decreases to zero.

The technical effect of the operating methods of the passive hydraulically actuated PTO assembly herein described is to efficiently provide lubricant to a transmission with a prime mover either powered on or powered off. A lubricant pump coupled to the transmission may lubricate the transmission when the prime mover is in operation and a PTO assembly may lubricate the transmission when the prime mover is shut down and wheels are rotating, such as during a tow operation or during conditions where the prime mover is not operational. Lubricating the transmission during such tow operation and other modes where the prime mover is shut down or non-operational but the transmissions is receiving rotational input may reduce degradation of the transmission. The passive nature of the hydraulic circuit allows for transmission lubrication without operator input or need for separate components such as a lube pump, if desired.

FIGS.3,4,5A, and5Bare drawn approximately to scale, aside from the schematically depicted components, though other relative component dimensions may be used in other embodiments.

FIGS.1-5Bshow example configurations with relative positioning of the various components. If shown directly contacting each other, or directly coupled, then such elements may be referred to as directly contacting or directly coupled, respectively, at least in one example. Similarly, elements shown contiguous or adjacent to one another may be contiguous or adjacent to each other, respectively, at least in one example. As an example, components laying in face-sharing contact with each other may be referred to as in face-sharing contact. As another example, elements positioned apart from each other with only a space there-between and no other components may be referred to as such, in at least one example. As yet another example, elements shown above/below one another, at opposite sides to one another, or to the left/right of one another may be referred to as such, relative to one another. Further, as shown in the figures, a topmost element or point of element may be referred to as a “top” of the component and a bottommost element or point of the element may be referred to as a “bottom” of the component, in at least one example. As used herein, top/bottom, upper/lower, above/below, may be relative to a vertical axis of the figures and used to describe positioning of elements of the figures relative to one another. As such, elements shown above other elements are positioned vertically above the other elements, in one example. As yet another example, shapes of the elements depicted within the figures may be referred to as having those shapes (e.g., such as being circular, straight, planar, curved, rounded, chamfered, angled, or the like). Additionally, elements co-axial with one another may be referred to as such, in one example. Further, elements shown intersecting one another may be referred to as intersecting elements or intersecting one another, in at least one example. Further still, an element shown within another element or shown outside of another element may be referred as such, in one example. In other examples, elements offset from one another may be referred to as such.

The invention will be further described in the following paragraphs. In one aspect, a power take-off (PTO) assembly is provided that comprises a bi-directional pump in fluidic communication with a fluid reservoir and a hydraulic system; and a passively actuated disconnect clutch configured to mechanically disconnect the bi-directional pump from a transmission when a prime mover is in operation and mechanically connect the bi-directional pump to the transmission when the prime mover is shut down.

In another aspect, a method is provided that comprises during prime mover operation, directing fluid from a hydraulic system to a disconnect clutch to sustain disengagement or initiate disengagement of the disconnect clutch and inhibit mechanical power transfer between a transmission and a bi-directional pump that is in fluidic communication with the hydraulic system; and during prime mover shutdown, inhibiting fluid delivery to the disconnect clutch to transition the disconnect clutch into an engaged position that permits mechanical power transfer between the transmission and the bi-directional pump. The method may further comprise, in one example, during a transition from the engaged position to a disengaged position of the disconnect clutch, sustaining engagement of the disconnect clutch until a pump causes a fluid pressure in an actuation line to rise above a threshold value and a hydraulically actuated valve permits fluid flow to the disconnect clutch.

In yet another example, a power take-off (PTO) assembly is provided that comprises a bi-directional pump in fluidic communication with a sump and a hydraulic system for a multi-speed transmission; a hydraulically actuated dog clutch that mechanically connects and disconnects the multi-speed transmission from the PTO pump; and a hydraulically actuated valve that permits and inhibits oil flow to an actuation piston in the hydraulically actuated dog clutch; wherein when the hydraulically actuated valve is open and permitting oil flow that is above a threshold pressure to the actuation piston, the actuation piston disengages the hydraulically actuated dog clutch; and wherein when the hydraulically actuated valve is closed and inhibiting oil flow to the actuation piston, the actuation piston engages the hydraulically actuated dog clutch.

In any of the aspects or combinations of the aspects, the passively actuated disconnect clutch may include a first toothed face that is coupled to a first gear that meshes with a second gear that is coupled to an output shaft that includes an output interface.

In any of the aspects or combinations of the aspects, the passively actuated disconnect clutch may include a second toothed face that is coupled to a shaft in the bi-directional pump.

In any of the aspects or combinations of the aspects, the PTO assembly may further comprise a hydraulically actuated valve that is in fluidic communication with a hydraulic actuator of the passively actuated disconnect clutch.

In any of the aspects or combinations of the aspects, the hydraulically actuated valve may include an actuation line that is hydraulically coupled to an outlet line of the bi-directional pump.

In any of the aspects or combinations of the aspects, the outlet line may be in fluidic communication with one or more lubricated components.

In any of the aspects or combinations of the aspects, when a pressure of a fluid in the actuation line is above a threshold pressure, the hydraulically actuated valve may permit pressurized fluid flow to the passively actuated disconnect clutch and disengage the passively actuated disconnect clutch; and when the pressure of the fluid in the actuation line is below a threshold pressure, the hydraulically actuated valve may inhibit pressurized fluid flow to the passively actuated disconnect clutch and engage the passively actuated disconnect clutch.

In any of the aspects or combinations of the aspects, the PTO assembly may further comprise a first pair of check valves in fluidic communication with a first port of the bi-directional pump.

In any of the aspects or combinations of the aspects, the PTO assembly may further comprise a second pair of check valves in fluidic communication with a second port of the bi-directional pump.

In any of the aspects or combinations of the aspects, the prime mover may be an internal combustion engine.

In any of the aspects or combinations of the aspects, the prime mover may be an electric motor.

In any of the aspects or combinations of the aspects, the transmission may be a multi-speed transmission that includes two or more clutches.

In any of the aspects or combinations of the aspects, a fluid in the fluid reservoir may be oil.

In any of the aspects or combinations of the aspects, mechanical power may be transferred from an output shaft of the transmission to the bi-directional pump.

In any of the aspects or combinations of the aspects, the hydraulically actuated valve may be actuated via an actuation line that may be in fluidic communication with the hydraulic system.

In any of the aspects or combinations of the aspects, the hydraulic system may include a pump that is driven by a prime mover.

In any of the aspects or combinations of the aspects, the prime mover may be a traction motor.

In another representation, a ground driven power take-off box is provided that includes a passive hydraulically actuated disconnect clutch that is configured to rotationally disconnect a lubricant pump from a mechanical input when a prime mover is in operation and configured to rotationally connect the lubricant pump and the mechanical input when the prime mover is shutdown.

While various embodiments have been described above, it should be understood that they have been presented by way of example, and not limitation. It will be apparent to persons skilled in the relevant arts that the disclosed subject matter may be embodied in other specific forms without departing from the spirit of the subject matter. The embodiments described above are therefore to be considered in all respects as illustrative, not restrictive. As such, the configurations and routines disclosed herein are exemplary in nature, and that these specific examples are not to be considered in a limiting sense, because numerous variations are possible. For example, the above technology can be applied to powertrains that include different types of propulsion sources including different types of electric machines and/or internal combustion engines. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein.

As used herein, the term “approximately” is construed to mean plus or minus five percent of the range, unless otherwise specified.

The following claims particularly point out certain combinations and sub-combinations regarded as novel and non-obvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.