Actuator for powered vehicle closure

A power closure actuator for powering a movable closure includes an output member configured to drive movement of the movable closure, a motor coupled through a gear reduction to drive the output member, and an integrated brake-clutch unit having an input configured to receive drive power from the electric motor. The brake-clutch unit provides independent braking and clutching between the electric motor and the output member via an electric brake actuator and an electric clutch actuator, respectively. Brake and clutch portions of the brake-clutch unit act on a rotor, and brake force can be maintained on the rotor without powering the brake actuator. A clutch disc is biased disengaged from the rotor. The integrated brake-clutch unit provides a drive state between the electric motor and the output member when the brake portion is released concurrently with the clutch portion establishing a power coupling between the clutch disc and the rotor.

BACKGROUND

The invention relates to powered vehicle closures and particularly actuators provided for opening and/or closing a closure in an automotive application including, but not limited to, truck end gates or “tailgates,” vehicular rear hatches, lift gates, trunks, and side entry doors.

SUMMARY

In one aspect, the invention provides a power closure actuator for powering a movable closure. The power closure actuator includes an output member configured to drive movement of the movable closure, an electric motor coupled through at least one gear reduction stage to drive the output member, and an integrated brake-clutch unit. The integrated brake-clutch unit has an input configured to receive drive power from the electric motor. The integrated brake-clutch unit provides independent braking and clutching action between the electric motor and the output member via an electric brake actuator and an electric clutch actuator, respectively. A brake portion of the integrated brake-clutch unit includes a rotor having a first portion operable to receive a brake force from a brake member in an absence of electrical power to the electric brake actuator. A clutch portion of the integrated brake-clutch unit includes a clutch disc rotatable with the input, the clutch disc selectively providing a power coupling with a second portion of the rotor, the clutch disc and the rotor being biased to a disengaged state in the absence of electrical power to the electric clutch actuator. The integrated brake-clutch unit provides a drive state between the electric motor and the output member when the brake portion is released concurrently with the clutch portion establishing the power coupling.

In yet another aspect, the invention provides a method of powering a movable closure with a power closure actuator, an output member of which is coupled to drive movement of the movable closure. The power closure actuator is provided in a first state in which an electric motor that provides the driving force of the power closure actuator is off. In the first state, a clutch disc of an integrated brake-clutch unit provided between the electric motor and the output member is biased to a disengaged state with respect to a rotor of the integrated brake-clutch unit, and electrical power to an electric clutch actuator that selectively moves the clutch disc is absent. Also, in the first state, a brake member, the movement of which is controlled by an electric brake actuator, applies a brake force to the rotor while electrical power to the electric brake actuator is absent. A first signal is provided to a controller to initiate powered movement of the movable closure with the power closure actuator. In response to the first signal, the controller provides a second signal to the electric clutch actuator to establish a power coupling between the clutch disc and the rotor, and provides a third signal to the electric brake actuator to retract the brake member from the rotor to release the brake force, thus putting the integrated brake-clutch unit into a drive state. With the integrated brake-clutch unit in the drive state, the controller provides a fourth signal to energize the electric motor so that driving force from the electric motor is transferred through the integrated brake-clutch unit, and through at least one gear reduction stage to the output member to open or close the movable closure.

In yet another aspect, the invention provides a power closure actuator for powering a movable closure. The power closure actuator includes an electric motor having an output, and a controller in command of the motor. A drivetrain is provided between the motor output and an output member of power closure actuator, the drivetrain including a brake operable to selectively apply a brake force to the drivetrain. An operator force sensor is provided in the drivetrain and configured to detect a force on the output member applied from the closure both due to gravitational force on the closure resulting from vehicle inclination and due to a user-applied force on the closure. A controller is configured to release the brake in response to the operator force sensor detecting a value that corresponds to a force on the closure at or above a predetermined force, the controller configured to disregard the gravitational force so that the predetermined force corresponds only to the user-applied force on the closure.

DETAILED DESCRIPTION

FIGS. 1 to 2Billustrate a power closure actuator, or simply, “actuator20” which may be actuated to produce forces applied as opening and/or closing forces for selectively opening and/or closing a power closure such as a vehicle closure (e.g., a vehicle entry door, hatch, tailgate or end gate, decklid or trunk, and the like). The actuator20includes an electric motor24having an output shaft, which in the illustrated construction is embodied as a worm28operatively meshed with a worm gear32in a first gearbox36. The first gearbox36, along with several additional subassemblies as described further herein, forms part of a drivetrain between the motor24and an output shaft40. The output shaft40, which is one exemplary form of an actuator output member, defines a central axis A. The central axis A is shared with the remainder of the drivetrain, aside from the motor24and the worm28, although other constructions are optional as shown inFIGS. 4, 5, and 6. A linkage44is secured to the output shaft40and operable by rotation of the output shaft40to perform an opening and/or closing articulation. In the event that the actuator20is supported to move with the closure, the linkage44can be secured to the vehicle body structure (e.g., door frame, truck bed, or pillar). However, in other constructions, the actuator20is fixed to the vehicle body structure and the linkage44is secured to the closure. The closure is selectively released from the vehicle body by a separate latching device (not illustrated), which can be powered or manually operable.

As illustrated inFIG. 3A, the actuator20is fixed to the vehicle body structure (e.g., roof) and the linkage44is secured to the closure50, which is in the form of a liftgate. As illustrated inFIG. 3B, the actuator20is fixed to the vehicle body structure and the linkage44is secured to the closure50, which is in the form of a liftgate. As illustrated inFIG. 3C, the actuator20is fixed to the closure50, which is in the form of a liftgate, and the linkage44is secured to the vehicle body structure. As illustrated inFIG. 3D, the actuator20is fixed to the closure50, which is in the form of a sliding side door, and the linkage44is secured to the vehicle body structure. As illustrated inFIG. 3E, the actuator20is fixed to the vehicle body structure (e.g., floor) and the linkage44is secured to the closure50, which is in the form of a sliding side door. As illustrated inFIG. 3F, the actuator20is fixed to the vehicle body structure (e.g., truck bed) and the linkage44is secured to the closure50, which is in the form of a tailgate. As illustrated inFIG. 3G, the actuator20is fixed to the closure50, which is in the form of a tailgate, and the linkage44is secured to the vehicle body structure. As illustrated inFIG. 3H, the actuator20is fixed to the vehicle body structure and the linkage44is secured to the closure50, which is in the form of a swinging side entry door, in particular a driver's side door.

Returning now toFIGS. 1 to 2B, the motor24of the actuator20defines a central axis of rotation B that is arranged at a skew angle with respect to the central axis A. A housing54of the motor24is secured to a first intermediate housing58, also forming the housing of the first gearbox36. The first intermediate housing58is in turn secured to a second intermediate housing62containing an electromagnetic brake with integrated clutch (EMBIC) unit66and a slip clutch70. The second intermediate housing62is in turn secured to an output housing or cap80, also forming the housing of a second gearbox76. The various housings54,58,62,80can be secured to each other in various ways, for example by interfacing flanges with a plurality of threaded fasteners. One or both of the first and second gearboxes36,76can include a planetary gear set. The second intermediate housing62can have opposing axial ends sandwiched axially between the first intermediate housing58and the output housing80. The output housing80surrounds a portion of the output shaft40and is secured to a distal end (opposite the motor24) of the second intermediate housing62(e.g., with a plurality of threaded fasteners). Any or all of the housing attachments can be made by alternate means besides threaded fasteners, either in lieu of or in addition to threaded fasteners. The output shaft40is supported for rotation by one or multiple bearings84, for example rolling element bearings, along its length. Additional sections of the drivetrain are supported for rotation by additional bearings in any or all of the aforementioned housings.

In general functional terms, the motor24provides input torque in a prescribed direction for opening or closing the closure50to one or more gear reduction stages (e.g., of the first gearbox36), an output of which transmits an amplified torque (at reduced speed) to an input of the EMBIC unit66. The EMBIC unit66controls whether or not a driving connection is established between the motor24and the output shaft40, and more particularly between the first gearbox36and the slip clutch70. As a separate function, the EMBIC unit66also controls whether or not a braking force is applied on the drivetrain. Specific functions of the EMBIC unit66are covered in further detail below with reference toFIGS. 7A to 7C. Regardless of the state of the EMBIC unit66, the slip clutch70provides a fully passive mechanism limiting abusive loads from being transmitted to the components of the drivetrain, including the motor24and the various gear reduction stages. The slip clutch70, as described in further detail below with reference toFIGS. 9 to 11, transmits torque only up to a prescribed torque threshold and automatically slips to break the continuity of the drivetrain above the prescribed torque threshold. As shown in the cross-section ofFIG. 5, a magnet (e.g., magnet ring88A) and Hall sensor88B form a Hall sensor assembly88operable to detect rotational position change (e.g., on an output side of the slip clutch70) of the drivetrain during operation. The Hall sensor assembly88is one example of a position sensor, although others may be appreciated as suitable replacements, that can detect position and/or speed of the output shaft40or other components of the drivetrain having a fixed relationship therewith (i.e., downstream of the EMBIC unit66and the slip clutch70). Additionally noted inFIG. 1is the location of an operator force sensor92, which is described in further detail below with reference to the cross-section ofFIG. 8. The sensor92is incorporated into the drivetrain downstream of the slip clutch70, for example within the second gearbox76, although the operator force sensor92is located in other locations in alternate constructions. In a working closure application of the actuator20in which the actuator20operates to perform a power open and/or power close function for the closure50, such a system additionally includes a controller96in signal communication with the motor24, the EMBIC unit66, the Hall sensor assembly88, and the operator force sensor92. The controller96can be integrated into the actuator20or provided elsewhere within a vehicle. The controller96, which can include a microprocessor and memory for storing executable instructions, can be implemented in whole or part as a vehicle body control module or may be in signal communication with a body control module.

Through the EMBIC unit66, the actuator20can exhibit three distinct drivetrain states including: drive, neutral (or “freewheel”), and brake as shown inFIGS. 7A to 7C. In the drive state, input and output sides of the EMBIC unit66are connected for driving. The at-rest (i.e., no power) state of the EMBIC unit66is a state in which the brake is engaged and the clutch is disengaged. Thus, transition from the at-rest state to the drive state involves actuating two separate internal actuators of the EMBIC unit66, the first actuator being an electromagnetic brake coil104, and the second actuator being an electromagnetic clutch coil108. Because the at-rest state is the brake state, the EMBIC unit66passively (without any supply of power) holds the output shaft40, and thus the closure50, fixed in a given position. Thus, the EMBIC unit66, along with the controller96, enables an infinite check/stop and hold feature for the closure50in any position throughout the movement range of the closure50, rather than relying on fixed-position detents (e.g., typical door detents used to hold a vehicle entry door in one of a few preselected positions). The passive nature of the EMBIC unit brake avoids electrical power drain (e.g., from a main vehicle battery that powers the actuator20) in the event the operator desires to leave the closure50in a partly or fully open state for a length of time (e.g., during loading/unloading). The brake of the EMBIC unit66may also provide a stronger holding force than conventional door detents in some constructions such that the closure50is less likely to move from the desired position (e.g., by wind or other incidental forces). During times of powered output from the motor24to the output shaft40for power opening or power closing, the brake coil104is actuated to release the brake and the clutch coil108is actuated to close/couple the clutch. The EMBIC unit66of the illustrated embodiment is constructed according to the following description, although other embodiments are envisioned, including but not limited to those shown inFIGS. 4B and 4C, shown in the drawings alongside a schematic representation (FIG. 4A) of the actuator20according to the construction ofFIGS. 1 to 2B. In the variation ofFIG. 4B, the central axis is broken into two parallel axes A, A′ with a connecting drivetrain75between the components on the respective axes (e.g., additional transfer gears, belt, chain, etc.).FIG. 4Cillustrates a construction in which the motor24that acts as the seminal drive source of the actuator20is arranged with its axis along the same axis as the EMBIC unit66, the output shaft40, and the other components therebetween. Thus, aspects of the present disclosure may be adapted to various package sizes and shapes as necessary to meet the needs of a particular closure application.

Referring particularly toFIGS. 6 to 7C, an input member112and an output shaft114are concentrically arranged along the central axis A of the EMBIC unit66. Although a portion of the output shaft114is received through the entire EMBIC unit66and through a hollow portion of the input member112, there is no driving connection directly from the input member112to the output shaft114. The input member112can be formed as an axially extended portion of a gear of the gearbox36. A clutch member, particularly clutch disc116, is secured to the input member112for rotation therewith. For example, a flange portion of the input member112can be bonded, pinned, screwed, etc. together with an axial end wall of the clutch disc116. The clutch disc116is arranged to form one axial end of a body of the EMBIC unit66, which can be cylindrical in shape. A radially outer portion of the clutch disc116can include an axial extension portion that extends toward an output end (left as shown) of the EMBIC unit66. A rotor member, particularly rotor disc118, is fixed for rotation with the output shaft114, e.g., by spline, key, bonding, etc. As illustrated, a radially inner portion of the rotor disc118can include an axial extension portion that extends toward the output end of the EMBIC unit66. A hub120extends at least partially around the rotor disc118(e.g., axial extension portion of the rotor disc118) and supports the brake and clutch coils104,108. Radial clearance may be provided between the rotor disc118and the radially surrounding portion of the hub120. The hub120is arranged to form the other axial end of the EMBIC unit body, opposite the clutch disc116. A bearing130supports the hub120on the output shaft114, and the hub120is also maintained out of engagement with the clutch disc116. Thus, the hub120is rotatably separate from both the EMBIC unit output (provided cooperatively by the output shaft114and the rotor disc118) and the EMBIC unit input (provided cooperatively by the input member112and the clutch disc116).

A brake member, particularly a brake sleeve124, radially surrounds at least a portion of the brake coil104. The brake sleeve124is slidably supported on a guide125. The guide125, which has a T-shaped cross section on each side of the axis A, also acts to direct the required magnetic flux for the electromagnetic coil(s)104,108. The brake sleeve124is positioned axially between a radial flange portion of the hub120and the rotor disc118. The brake sleeve124is biased toward the input end of the EMBIC unit66(right as shown, and thus toward the clutch disc116and away from the hub120) by one or more brake springs122positioned between the hub120and the brake sleeve124. The bias force from the brake spring122urges the brake sleeve124against the rotor disc118, particularly a first axial end surface thereof as shown. For example, the brake sleeve124may press upon the first portion of the rotor disc118through one or more friction discs126. Because the rotor disc118is fixed for rotation with the output shaft114, the output shaft114is thus braked by the brake sleeve124from the force in the brake spring122. Thus, the brake spring122maintains brake engagement at-rest in a state in which there is no power draw by the brake coil104, or more broadly no power being supplied to the actuator120overall. Electrical current powering the brake coil104causes the brake sleeve124to be attracted to the brake coil104, urging the brake sleeve124to overcome the bias of the brake spring122and release the brake as shown inFIG. 7B(e.g., by releasing the friction discs126). This converts the EMBIC unit66from the at-rest brake state to the neutral or freewheel state. Under circumstances that the controller96determines that the EMBIC unit66is to be bypassed so that the closure50can be freely opened and closed by the user rather than under power of the motor24, the brake coil104is energized to achieve the neutral state ofFIG. 7B. In the neutral state, a human operator can open and close the closure50without resistance of the actuator20(i.e., with the feel of a conventional un-powered closure).

With respect to the clutch, the rotor disc118has a portion (e.g., a second axial end surface) defining a friction surface in selective contact with a mating and co-facing friction surface of the clutch disc116to close/couple the clutch of the EMBIC unit66. A clutch spring128normally biases the two mating friction surfaces of the clutch disc116and the rotor disc118apart from each other, for example defining an axial space therebetween, so that the clutch is open or decoupled and torque is not transferrable from the input member112and the clutch disc116to the rotor disc118and the output shaft114. Electrical current powering the clutch coil108causes the clutch disc116to be attracted to the clutch coil108(right as shown, same attraction direction as the brake coil104on the brake sleeve124) to overcome the bias of the clutch spring128and close/couple the clutch by bringing the friction surfaces of the clutch disc116and the rotor disc118together. The clutch disc116may move alone or the input member112may move with the clutch disc116. Under circumstances that the controller96determines that the motor24is to drive the output shaft40through the EMBIC unit66to perform a powered opening or powered closing of the closure50, the brake coil104is energized to release the brake and concurrently the clutch coil108is energized to close/couple the clutch and achieve the drive state ofFIG. 7C. This state of the EMBIC unit66is maintained throughout operation of the motor24to perform the powered opening or the powered closing.

In use of the closure50, for example on a vehicle, the vehicle operator may provide an input to a designated input device132, for example a mechanical sensor (e.g., button, switch, dial, etc. either integrated with or separate from a handle on the closure50) or a touch sensor (e.g., a touch pad or touch screen having resistive or capacitive sensing). The operator input device132can be one of a plurality of operator input devices132, and the operator input device(s) can be positioned on the closure50, on the vehicle body, on a control panel of the vehicle interior, and/or on a vehicle key fob having a wireless connection to the vehicle. Example operator input devices132are shown throughoutFIGS. 3A to 3H. The input can be received by the controller96, for example, via one or more signals from any one of the above mentioned input devices, and in response the controller96can signal the brake coil104to power off and release the EMBIC unit brake66. Depending on the controller logic and/or the type of input from the operator, the EMBIC unit66can either remain in the neutral state, or further be actuated to establish the drive state by a signal from the controller96to power on the clutch coil108. In addition to the operator input mechanisms described above, the actuator20can further be configured to respond (i.e., perform a change of state such as a change of state of the EMBIC unit66and/or a change in motor operation such as speed and/or direction) to an operator force applied to the closure50, in particular a pushing or pulling force in the opening or closing direction of the closure50. However, enabling the actuator20via the controller96to make an appropriate determination for response is significantly challenged by the potentially diverse static conditions of the vehicle. In particular, a vehicle having the closure50cannot reasonably be expected to have use only in a flat or level orientation with respect to earth. Rather, normal use of the vehicle will typically include various states of pitch in which the front of the vehicle is higher or lower than the rear, and roll in which the left side of the vehicle is higher or lower than the right side. In the context of this application, pitch and roll do not refer to dynamic motion of the vehicle, but rather the static inclination of the vehicle having the vehicle closure50, as considered with respect to earth.

To overcome the above mentioned difficulties, the actuator20includes force sensing capability that enables the controller96to differentiate force on the closure50applied by an operator, i.e., a human user, from force on the closure50applied by gravitational forces on the closure50in the opening/closing direction of the closure50due to vehicle inclination. Thus, the response of the actuator20to user-applied force on the closure50is independent of vehicle inclination so as to provide consistent and repeatable effort for the user. The force sensing referred to above utilizes the operator force sensor92briefly introduced above with respect toFIG. 1. A first exemplary embodiment of the operator force sensor92is shown in further detail inFIG. 8. As shown there, the sensor92includes a housing, either a separate housing or in this case a portion of the end housing80. A rotary element138is positioned within the housing80. Although the rotary element138may have limited rotational freedom within the housing80, the rotary element138forms an otherwise fixed component (e.g., ring gear) of a gear reduction stage (e.g., planetary gear set) in the second gearbox76. In particular, the housing80and the rotary element138are engaged with complementary shapes that allow only a limited amount of relative rotation therebetween (e.g., less than 20 degrees, or less than 15 degrees). For example, as illustrated, the inside of the housing80and the outside of the rotary element138form a spline engagement that is loose-fitting, having intentional circumferential clearance between mating spline portions. The housing80that houses the sensor92may be fixed to or integral with the other actuator housing(s)54,58,62. The rotary element138includes at least one radial protuberance138A received in a radial extension space or cavity136of the housing80. The illustrated construction includes two such protuberances138A, diametrically opposed. One or more springs142are arranged against each radial protuberance138A in the cavity136. In the illustrated example, each spring142forms a loop from which two legs extend so that one leg is positioned on each side of the radial protuberance138A of the rotary element138. The springs142can be secured to and/or retained by a spring housing144within or extended from the cavity136. As shown inFIG. 2A, each spring142is held within a spring housing144formed in the adjacent second intermediate housing62. The springs142urge the rotary element138to a central position within its limited range of rotational travel in the housing80so that it has available travel in both directions with respect to the housing80. However, in response to forces, more particularly torque in a rotational application, applied to the output shaft40(e.g., when the EMBIC unit66is in the braked state), the rotary element138of the operator force sensor92may rotate with respect to the housing80. In other words, the operator force sensor92is located in the drivetrain at a position downstream of the brake of the EMBIC unit66.

The operator force sensor92is an absolute position sensor. The sensor92is operable to track the position of the radial protuberance138A of the rotary element138, such as the deviation from a central position as biased by the springs142. The sensor92can be implemented as a Hall effect sensor assembly including a Hall effect sensor element (i.e., circuit)148secured to the housing80and a magnet150secured to the rotary element138. The sensor element150can be located at least partially within a radial extension space or cavity146separate from the cavities136in which the biased radial protuberances138A are located, and the magnet150can be supported on or in a portion (e.g., optionally radially protruded, and optionally extending into the cavity146) of the rotary element138separate from the biased radial protuberances138A. The sensor element148provides an output is in communication with the controller96and operable to detect torque in the drivetrain resulting from applied force on the closure50(e.g., by a human user pushing or pulling on the closure50). Gravitational force in the opening-closing direction of the closure50is also sensed by the sensor element148, but the gravitational component is configured to be segregated and neglected so that uniformity can be provided in effort on the closure to achieve a prescribed response of the actuator20. In other words, for a car door or other closure, its own weight will not add to or subtract from the needed operator effort to trigger the controller threshold for operating the actuator20. The controller96may for example perform a time-based comparison of output signal(s) from the sensor element148in order to identify an output signal change corresponding to the change in force or “force delta” applied from the closure50to the operator force sensor92. The initial or static signal from the sensor element148is categorized as gravitational force (if any) due to inclination, and this amount, which is either positive or negative due to its directional nature, is subtracted from a subsequent force measurement of the sensor element148. In some constructions, the segregation of forces can be confirmed or accomplished via an inclinometer on board the vehicle and provided in communication with the controller96. For example, if the controller96is programmed with an algorithm that takes into consideration a mass of the closure, then inclination data can be used to calculate a gravitational force that the closure imparts to the actuator20at the output shaft40.

A prescribed response of the actuator20can be a release of the brake and/or release of the brake, coupling of the clutch, and actuation of the motor24, and/or if the motor24is already operating, changing speeds of the motor24, including stopping of the motor24. In an example where the motor24is running, the controller96, on the basis of the operator force sensor92, may slow down the motor speed when operator force is applied to the closure50in a direction opposite the motor-driven direction and/or the controller96, on the basis of the operator force sensor92, may speed up the motor speed or transition to the neutral state of the drivetrain when operator force is applied to the closure50in the motor-driven direction. Although these operations are available for utilizing the operator force sensor92, the controller logic may utilize less than all of these potential operations, or may use certain operations in conjunction with or as a back-up to another sensor or primary controller logic. For example, the actuator20can include a separate position sensor, rotary encoder or the like (e.g., the Hall sensor assembly88) that enables the controller96to track the relationship between speed and electric current to the motor24, and this speed/current relationship is utilized as the primary means to detect and respond to forces applied to the closure50during powered open/close operations by the motor24.

FIG. 8Aillustrates another operator force sensor92′ generally similar to the operator force sensor92except as otherwise noted. In this construction, there is a single radial protuberance138A, which both carries the magnet150and is directly biased by the springs142′. Thus, the housing80′ includes only one radial cavity136to accommodate the entire operator force sensor92′. The springs142′ in this construction are coil springs arranged along an axis perpendicular to a radial line from the axis A (although both springs142′ are offset from this radial line, such that the springs142′ are not arranged exactly tangential). Various spring types and arrangements may be utilized. A spring pocket144extends as a sub-cavity from the cavity136on each side of the radial protuberance138A.

FIG. 8Billustrates an operator force sensor292according to another exemplary construction that can be incorporated in the actuator20. Like the sensor92ofFIG. 8, the operator force sensor292includes a housing280and a rotary element238. In particular, reference is made to the above description of the operator force sensors92,92′, particularly the basic configuration of the housing236and the rotary element238, which are most similar to those ofFIG. 8A. However, rather than having a Hall effect sensor element coupled with the controller96and operable to obtain a measure of torque, the operator force sensor292includes sensor elements248in the form of pressure sensors situated between the housing280and the rotary element238(e.g., flanking the radial protuberance238A of the rotary element238in the corresponding cavity236of the housing280) to obtain a measure of torque applied therebetween. Although referred to herein as the rotary element238, it should be noted that the configuration of the operator force sensor292may provide very little clearance and minimal or no measurable rotation of the rotary element238. Thus, the term rotary element within the context of an operator force sensor may refer to the fact that the element is not directly restrained by or fixed to the housing280such that torque exerted on the rotary element238is borne by the sensor elements248and not directly reacted by the housing280. In other words, the sensor elements248are operatively positioned between the housing280and the rotary element238so as to observe such torque.

FIG. 8Cillustrates an operator force sensor392according to another exemplary construction that can be incorporated in the actuator20. Like the sensor92ofFIG. 8, the operator force sensor392includes a housing380and a rotary element338. In particular, reference is made to the above description of the operator force sensors92,92′,292with respect to the basic configuration of the housing380and the rotary element338. However, rather than having a Hall effect sensor element or pressure sensors coupled with the controller96and operable to obtain a measure of torque, the operator force sensor392includes sensor elements348in the form of strain gauges (i.e., strain gauge circuits) situated on the spring(s)342that bias the rotary element338with respect to the housing380(e.g., centering the radial protuberance338A in the cavity336). The springs342can be linear springs, each having at least one surface that experiences strain (measurable elastic deformation) during rotary displacement of the rotary element338. The spring surfaces having the strain gauges342mounted thereon can be flat surfaces. The strain measured correlates to torque applied therebetween. Because the sensor elements348are integrated with the springs342, the additional housing cavity146is not required.

Thus, regardless of the exact type of sensor element(s) or transducer(s) (e.g., strain gauge, pressure sensor, Hall effect or other position detector, etc.), the operator force sensors92,92′,292are torque sensors configured to detect torque resulting from operator force applied in the opening/closing direction of the closure50.

Turning toFIGS. 9-11, the slip clutch70of the power closure actuator drivetrain is shown in further detail. As shown, the slip clutch70includes an input shaft114, a housing156, and an output shaft158. Although referred to as the input shaft114with respect to the description of the slip clutch70, the input shaft114can be the same shaft as the output shaft114of the EMBIC unit66, either provided as a single monolithic element, or separate elements fixedly secured to rotate together. The housing156may be of plastic material construction. The input shaft114extends out of a first end of the housing156. The input shaft114may have a fixed rotational relationship with the motor24, at least when the EMBIC unit66is in the driving state. When there is no slip in the slip clutch70(i.e., torque between the input and output shafts114,158does not exceed a threshold amount), the input and output shafts114,158also have a fixed rotational relationship and in fact rotate together as one. However, there is no torque-transmitting connection or engagement directly between the input shaft114and the output shaft158. The shafts114,158may have no direct interface therebetween. In other constructions (seeFIG. 13), the interface between the shafts114,158is a rotational journal interface by which an end of the input shaft114is rotatably supported in an aperture formed in the output shaft158or vice versa. A clutch pack forms the torque-transmitting connection between the input of the slip clutch70(e.g., the input shaft114of the illustrated construction) and the output of the slip clutch70(e.g., collectively defined by the housing156and the output shaft158in the illustrated construction). The housing156and the output shaft158in all circumstances rotate together as one, for example being splined or keyed together, manufactured integrally, etc. The threshold torque that induces slip between the input and output shafts114,158is determined by the clutch pack, which includes integral preload springs. The slip clutch70includes two sets of clutch members or discs, including stationary plates in the form of flat washers178and rotating clutch members in the form of Belleville disc springs180. So that similar contact is established between each flat washer to Belleville disc spring interface, each Belleville disc spring180is arranged to have the outer perimeter thereof in contact with the adjacent flat washer178. As such, there are two Belleville disc springs180positioned between each adjacent pair of flat washers178. The flat washers178have an outer perimeter shaped complementary to an inner periphery of the housing156so that the flat washers178are rotationally locked to the housing156. On the other hand, the Belleville disc springs180have a non-circular inner periphery (e.g., two opposing flat sides180A forming a “double-D” shape) complementary to the outer surface of the clutch input, which in the slip clutch70is cooperatively formed by the input shaft114and a bushing184fixed therewith. One or more apertures178A in the flat washers178(e.g., positioned at the radial distance of the point of contact with the Belleville disc springs180) can contain a quantity of grease for lubricating the mating friction surfaces of the slip clutch70. As shown, each of the three flat washers178includes three equally-spaced grease-containing apertures178A. In other constructions, the slip clutch70is a dry clutch in which the clutch pack is not bathed in oil or lubricated with grease. A nut170is threaded onto the bushing184to set the preload in the clutch pack by at least partially deflecting the Belleville disc springs180. The nut170thusly provides adjustability or the ability to tune the torque transmission limit of the slip clutch70. However, the nut170may be utilized only in initial manufacturing and/or testing, and may subsequently be crimped or otherwise permanently fixed to the input shaft114so that the clutch preload is fixed for the useful life of the actuator20. Although other configurations are optional, the Belleville disc spring180on one axial end of the clutch pack is in direct contact with the nut170, and the Belleville disc spring180on the opposite axial end of the clutch pack is in direct contact with an axial end surface within the housing156. During operation, when net torque between the input and output sides, applied in either direction, exceeds the prescribed threshold, frictional forces between the flat washers178and the Belleville disc springs180are overcome and the excess torque is not transmitted, thus protecting the mechanical components of the drivetrain from exposure to such torque.

FIGS. 12-14illustrate a slip clutch70′ according to another exemplary embodiment. The slip clutch70′ performs the same function as the slip clutch70in the drivetrain of the actuator20, and thus the following description of the slip clutch70′ is focused on aspects of the construction that differ from the slip clutch70ofFIGS. 9-11. Like reference numbers are used where applicable. In the slip clutch70′, rather than the clutch pack including integral preload springs, a separate clutch spring166is provided to bear on the clutch pack. In particular, the alternating sets of clutch members or discs, particularly stationary wear plates162and rotating wear plates164with friction discs163therebetween. The clutch spring166exerts a bias force on the clutch pack and presses an axial end of the clutch pack against an axially abutting interior surface of the housing156. The clutch spring166is embodied here as one or more wave springs, but various types of springs may be used in alternate constructions. Each of the stationary wear plates162is nested into the housing156so as to be rotationally locked therewith. Each of the rotating wear plates164is rotationally locked with the input shaft114. As illustrated, the rotating wear plates164have a star-shaped central aperture for mating engagement with a star-shaped outer profile of the bushing184′ that is rotationally locked with the input shaft114(e.g., splined or keyed therewith). The stationary and rotating wear plates162,164are in frictional contact through the intervening friction discs163. As with the clutch70, the nut170can be permanently fixed once the preload is set prior to final assembly of the actuator20. The nut170of the slip clutch70′ is threaded onto the input shaft114and is operable to indirectly (e.g., via a washer172) exert a preload on the clutch pack to squeeze the wear plates162,164and the friction discs163together. Although not shown, the housing156can have a multi-piece construction, for example, including a separate end cap to cooperate to close the open end of the housing156where the nut170is located. As mentioned briefly above, the input shaft114has a reduced diameter end portion114A that is rotatably received within a concentric end bore158A of the output shaft158such that a journal bearing is provided therebetween—there being no torque transmitted here between the shafts114,158.

The EMBIC unit66of the preceding disclosure is one example of an integrated brake-clutch unit, particularly one in which both the brake and clutch functions are achieved through electromagnetic coils. However,FIGS. 15-18illustrate another embodiment of an integrated brake-clutch unit266that is operable as a replacement for the EMBIC66in the actuator20of the preceding disclosure. Similar to the EMBIC66, the brake-clutch unit266ofFIGS. 15-18requires actuation of both the brake and clutch portions in order to establish a driving connection. As such, the actuator20can exhibit three distinct drivetrain states including: drive, neutral (or “freewheel”), and brake according to the corresponding states of the brake-clutch unit266. In the drive state, input and output sides of the brake-clutch unit266are connected for driving. Transition from the at-rest state to the drive state may involve actuating two separate actuators of the brake-clutch unit266, the first actuator being a brake actuator204(e.g., electric motor with worm drive output204A), and the second actuator being an electromagnetic clutch coil208similar to the coil108of the EMBIC unit66. Like the EMBIC unit66, the brake-clutch unit266can have an at-rest state in which the brake is engaged so that the brake-clutch unit266passively (without any supply of power) holds the output shaft40, and thus the closure50, fixed in a given position. To enable powered output from the motor24to the output shaft40for power opening or power closing, the brake actuator204is actuated to release the brake, and the clutch coil208is actuated to close/couple the clutch. As such, similar benefits as those of the EMBIC unit66may be enjoyed. However, the brake portion of the brake-clutch unit266is equipped to be bi-stable rather than biased in one direction to the brake-engaged state. Thus, the brake-clutch unit266can have a second at-rest state in which the clutch is open or decoupled to be in a non-torque-transmitting state, and the brake is left disengaged without continuous actuation of the brake actuator204. In such a state, the actuator20is imperceptible to the user in that it poses no added interference or obstruction to the user manually operating the attached closure. The brake-clutch unit266of the illustrated embodiment is constructed according to the following description, although other embodiments are envisioned.

Concentrically arranged along the central axis A of the brake-clutch unit266are an input member212and an output shaft214. Although a portion of the output shaft214is received within the hollow input member212, there is no driving connection directly therebetween. A clutch member, particularly clutch disc216, is secured to the input member212for rotation therewith. The clutch disc216is arranged to form one axial end of a body of the brake-clutch unit266, which can be cylindrical in shape. A rotor member, particularly rotor disc218, is fixed for rotation with the output shaft214, e.g., by spline, key, bonding, etc. As illustrated, both a radially outer portion and a radially inner portion of the rotor disc218can extend axially toward the output end of the brake-clutch unit266. A hub220is situated at least partially around the axially-extended inner portion of the rotor disc218and supports the clutch coil208. Radial clearance may be provided between the rotor disc218and the radially surrounding portion of the hub220. The hub220is coupled with extension arms of a guide housing225that forms the other axial end of the brake-clutch unit body, opposite the clutch disc216. The guide housing225also supports the brake actuator204, which is positioned away from the axis A. The hub220is maintained out of engagement with the rotor disc218. Thus, the hub220is rotatably separate from both the input and the output of the brake-clutch unit output.

A brake member, particularly brake sleeve224, is arranged about and movable along the axis A. The brake sleeve224can be guided for axial movement by the guide housing225, although a guide pin227is also shown extending from the hub220through a guide aperture229in the brake sleeve224. A friction member (e.g., disc)226is provided on one or both of the brake sleeve224and a corresponding contact portion of the rotor disc218such that the friction member226receives an axial pressing force for braking the rotor disc218and the output shaft214when the brake is in the actuated position (closing the gap which is shown inFIG. 18). The brake sleeve224is unbiased, thus eliminating the brake spring122of the prior embodiment. Rather, a screw member235is engaged with the brake sleeve224such that rotation of the screw member235about the axis A, which is driven by the worm drive output204A through a gear portion of the screw member235, drives the brake sleeve224which acts as a lead screw nut guided by the guide housing225and the guide pin227. The screw member235is rotatably supported on the output shaft214by one or more bearings. The brake actuator204is not back-drivable through the worm drive output204A, thus the brake will remain in the brake-engaged state even without continued energization of the brake actuator204, following an actuation to the brake-engaged state. Reverse actuation of the brake actuator204causes reverse rotation of the screw member235and reverse axial movement of the brake sleeve224to disengage the rotor disc218and release the brake as best shown inFIG. 18. As long as the clutch remains unactuated, the brake release converts the brake-clutch unit266from the brake state to the neutral or freewheel state, both of which are at-rest or de-energized states of the actuator20. Under circumstances that the controller96determines that the brake-clutch unit266is to be bypassed so that the closure50can be freely opened and closed by the user rather than under power of the motor24, the brake is released to achieve the neutral state, and this is accomplished by a momentary, rather than continuous, energization of the brake actuator204.

In order to use the power of the actuator20to operate an attached closure, a power coupling must be established through the brake-clutch unit266by engaging the clutch portion thereof. With respect to the clutch, the rotor disc218has a portion (e.g., a second axial end surface opposite that of the brake-engaging axial end surface) defining a friction surface in selective contact with a mating and co-facing friction surface of the clutch disc216to close/couple the clutch of the brake-clutch unit266. A clutch spring228normally biases the two mating friction surfaces of the clutch disc216and the rotor disc218apart from each other, for example defining an axial space therebetween as shown inFIGS. 17 and 18, so that the clutch is open or decoupled and torque is not transferrable from the input member212and the clutch disc216to the rotor disc218and the output shaft214. Electrical current powering the clutch coil208causes the clutch disc216to be attracted to the clutch coil208(right as shown) to overcome the bias of the clutch spring228and close/couple the clutch by bringing the friction surfaces of the clutch disc216and the rotor disc218together. The clutch disc216may move alone or the input member212may move with the clutch disc216. Under circumstances that the controller96determines that the motor24is to drive the output shaft40through the brake-clutch unit266to perform a powered opening or powered closing of the closure50, the brake actuator204is energized to release the brake (unless it is already in the brake-released state) and concurrently the clutch coil208is energized to close/couple the clutch and achieve the drive state. This state of the brake-clutch unit266is maintained throughout operation of the motor24to perform the powered opening or the powered closing.