Electric vehicle having powertrain with reaction centrifugal clutch

Abstract

The invention provides an electric vehicle with a powertrain having a reaction centrifugal clutch. An electric vehicle includes an electric drive motor, a transmission, and a centrifugal clutch. The centrifugal clutch is drivingly coupled in a torque transfer path between the electric drive motor and the transmission. The centrifugal clutch includes a first friction plate, a second friction plate, a biasing member, and a counterweight. The first friction plate is rotatable about an axis. The second friction plate is rotatable about the axis and axially movable relative to the first friction plate. The second friction plate is configured to frictionally engage the first friction plate to transfer torque therebetween. The biasing member biases the second friction plate toward the first friction plate. A counterweight assembly is coupled to the second friction plate and is configured to apply a balancing gravity on the second friction plate away from the first friction plate in response to a rotational speed of the second friction plate exceeding a predetermined rotational speed.

Description

Technical Field

[0001] The present disclosure relates to electric vehicles, and more particularly to powertrain systems for electric vehicles. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0003] A typical vehicle has a prime mover (e.g., an internal combustion engine or an electric motor) whose output is coupled to a transmission via a coupling device. In some cases, the coupling device is a torque converter (i.e., a fluid coupling). In other cases, the coupling device is a friction clutch, which can be manually or automatically actuated.

[0004] refer to Figure 1 A typical internal combustion engine (ICE) has a torque curve 110 that generally increases with engine output speed (RPM) within a useful range. Conventional wisdom in the field of vehicle powertrains is that slippage of the friction clutch between the prime mover and the transmission at high RPM reduces power delivered to the wheels, thereby reducing overall vehicle performance. Therefore, some vehicles (such as, for example, Top Fuel drag racing vehicles) are equipped with a centrifugal friction clutch that couples the ICE to the transmission so that increasing engine speed increases the torque holding capacity 114 of the friction clutch to inhibit slippage of the friction clutch as the engine's torque output increases.

[0005] However, reference Figure 2 A typical electric motor for a battery electric vehicle (BEV) has a torque curve 210 that starts at maximum torque and remains substantially constant until relatively high RPM, at which point the output torque begins to decrease.

[0006] Furthermore, high-performance transmissions can change gear ratios in milliseconds, and electric motors typically have greater rotational inertia than ICEs. Therefore, it can be difficult to match the rotational speed of the electric motor to the rotational speed of the transmission input during a shift event. For example, Figure 3 is a graph illustrating electric motor output rotational speed 310, transmission input speed 314, and vehicle wheel rotational speed 318 during transmission shift events 322, 326, and 330 when a typical friction clutch couples the electric motor to the transmission. Figure 3 In FIG, since there is no slip in the friction clutch, the electric motor output rotational speed 310 and the transmission input speed 314 are substantially similar. However, it has been found that these rapid shift events 322, 326, 330 may result in sudden spikes 334, 338, 342 in rotational speed 318, which may cause wheel slip and reduced traction.

[0007] The present disclosure addresses these and other problems with typical friction clutches in the powertrain of electric motor-driven vehicles. Summary of the Invention

[0008] This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features.

[0009] In one form, the present disclosure provides an electric vehicle including an electric drive motor, a transmission, and a centrifugal clutch. The transmission is switchable between multiple gear ratios. The centrifugal clutch is drivingly coupled in a torque transmission path between the electric drive motor and the transmission. The centrifugal clutch includes a first friction plate, a second friction plate, a biasing member, and a counterweight. The first friction plate is rotatable about an axis. The second friction plate is rotatable about the axis and axially movable relative to the first friction plate. The second friction plate is configured to frictionally engage the first friction plate to transmit torque therebetween. The biasing member applies a biasing force to the second friction plate, the biasing force biasing the second friction plate in a first axial direction toward the first friction plate. The counterweight assembly is coupled to the second friction plate and is configured to apply a counterweight force on the second friction plate in a second axial direction away from the first friction plate in response to a rotational speed of the second friction plate exceeding a predetermined rotational speed.

[0010] According to various alternative forms that can be used alone or in any combination with the electric vehicle of the above paragraph: the centrifugal clutch also includes a base member, the base member is connected to the second friction plate for common rotation therewith about the axis, wherein the second friction plate is movable along the axis relative to the base member; the biasing member biases the second friction plate axially away from the base member and toward the first friction plate; the counterweight assembly is connected to the base member via a first pivot connection and is connected to the second friction plate via a second pivot connection; the counterweight assembly includes a counterweight, a pivot member and a transmission member and a second end of the transfer member is coupled to the second friction plate and the second end of the transfer member is coupled to the pivot member at the second pivot connection; the first friction plate is coupled to the input end of the transmission for common rotation therewith, and the base member is coupled to the output end of the electric drive motor for common rotation therewith; the balancing weight is configured to be less than the biasing force for all operating speeds of the motor; the centrifugal clutch is configured to have a biasing force for the All operating speeds of the motor exceed the torque holding capacity of the torque output of the motor, but slip between the first friction plate and the second friction plate is allowed in response to a torque disturbance caused by shifting a gear ratio of the transmission; the electric vehicle further includes a control module configured to shift the transmission between gear ratios; the control module is configured to receive signals from a plurality of sensors and actively control the motor output torque in response to the signals received from the plurality of sensors to actively control the amount of slip of the centrifugal clutch during shifting of the transmission; the centrifugal clutch is configured to have a torque holding and a centrifugal clutch configured to have a torque holding capacity that allows slipping between the first and second friction plates at the predetermined torque output of the motor corresponding to the shift points of the transmission.

[0011] In another embodiment, the present disclosure provides an electric vehicle including an electric drive motor, a transmission, and a centrifugal clutch. The transmission is switchable between multiple gear ratios. The centrifugal clutch is drivingly coupled in a torque transmission path between the electric drive motor and the transmission. The centrifugal clutch includes a first friction plate, a second friction plate, a biasing member, and a counterweight assembly. The first friction plate is rotatable about an axis. The second friction plate is rotatable about the axis and axially movable relative to the first friction plate. The second friction plate is configured to frictionally engage the first friction plate to transmit torque therebetween. The biasing member applies a biasing force to the second friction plate, the biasing force biasing the second friction plate in a first axial direction toward the first friction plate. The counterweight assembly is coupled to the second friction plate and configured to apply a counterweight force on the second friction plate in a second axial direction away from the first friction plate in response to a rotational speed of the second friction plate exceeding a predetermined rotational speed. The centrifugal clutch is configured to have torque holding capability exceeding the torque output of the motor for all operating speeds of the motor, but to allow slip between the first and second friction plates in response to torque disturbances caused by shifting a gear ratio of the transmission.

[0012] According to various alternative forms that can be used alone or in any combination with the electric vehicle of the above paragraph: the centrifugal clutch further includes a base member coupled to the second friction plate for common rotation therewith about the axis, wherein the second friction plate is movable relative to the base member along the axis; the counterweight assembly includes a counterweight and a pivot member, the counterweight coupled to the pivot member, the pivot member coupled to the base member via a first pivot connection and to the second friction plate via a second pivot connection; the counterweight assembly further includes a transfer member, wherein a first end of the transfer member is coupled to the second friction plate and a second end of the transfer member is coupled to the pivot member at the second pivot connection; the second friction plate is axially located between the base member and the first friction plate; the electric vehicle further includes a control module configured to shift the transmission between the plurality of gear ratios, wherein the control module is configured to receive signals from a plurality of sensors and actively control the motor output torque in response to the signals received from the plurality of sensors to actively control the amount of slip of the centrifugal clutch during shifting of the transmission.

[0013] In yet another form, the present disclosure provides an electric vehicle comprising an electric drive motor, a transmission, and a centrifugal clutch. The transmission is shiftable between a plurality of gear ratios. The centrifugal clutch is drivingly coupled in a torque transmission path between the electric drive motor and the transmission. The centrifugal clutch includes a first friction plate, a second friction plate, a biasing member, and a counterweight assembly. The first friction plate is rotatable about an axis. The second friction plate is rotatable about the axis and axially movable relative to the first friction plate. The second friction plate is configured to frictionally engage the first friction plate to transmit torque therebetween. The biasing member applies a biasing force to the second friction plate, the biasing force biasing the second friction plate in a first axial direction toward the first friction plate. The counterweight assembly is coupled to the second friction plate and configured to apply a counterweight force on the second friction plate in a second axial direction away from the first friction plate in response to a rotational speed of the second friction plate exceeding a predetermined rotational speed. The centrifugal clutch is configured to have a torque holding capacity exceeding the torque output of the motor for all operating speeds of the motor, but to allow slip between the first friction plate and the second friction plate in response to a torque disturbance caused by shifting a gear ratio of the transmission. The centrifugal clutch includes a base member that is coupled to the output end of the electric drive motor for common rotation therewith. The counterweight assembly includes a counterweight, a pivot member, and a transfer member. The counterweight is coupled to the pivot member. The pivot member is coupled to the base member via a first pivot connection and to the transfer member via a second pivot connection. A first end of the transfer member is coupled to the second friction plate, and a second end of the transfer member is coupled to the pivot member at the second pivot connection.

[0014] According to an alternative form that can be used with the electric vehicle of the above paragraph: the electric vehicle may also include a control module, which is configured to cause the transmission to shift between the multiple gear ratios, wherein the control module is configured to receive signals from multiple sensors and actively control the motor output torque in response to the signals received from the multiple sensors to actively control the slip amount of the centrifugal clutch during shifting of the transmission.

[0015] Further areas of applicability will become apparent from the description provided herein.It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order that the present disclosure may be better understood, various forms of the present disclosure will now be described by way of example with reference to the accompanying drawings, in which:

[0017] Figure 1 is a graph showing typical internal combustion engine torque and conventional centrifugal clutch torque capacity versus motor speed;

[0018] Figure 2 is a graph showing typical electric motor torque and conventional centrifugal clutch torque capacity versus motor speed;

[0019] Figure 3 is a graph showing electric motor output rotational speed, transmission input speed, and wheel rotational speed versus time during a transmission shift event when a typical friction clutch couples the electric motor to the transmission;

[0020] Figure 4 is a schematic perspective view of a vehicle according to the teachings of the present disclosure;

[0021] Figure 5 According to the teachings of this disclosure Figure 4 A schematic diagram of a powertrain of a vehicle including an electric motor, a transmission, and a centrifugal clutch;

[0022] Figure 6 yes Figure 5 A schematic perspective view of a centrifugal clutch;

[0023] Figure 7 yes Figure 5 A schematic partial cross-sectional view of a portion of a centrifugal clutch;

[0024] Figure 8 It shows Figure 5 The torque output of the motor and Figure 5 A graph showing the relationship between the torque capacity of the centrifugal clutch and the motor speed;

[0025] Figure 9 is shown during a transmission shift event Figure 5 a graph showing the relationship between the electric motor output rotational speed, the transmission input speed and the wheel rotational speed of the powertrain and time;

[0026] Figure 10 According to the teachings of this disclosure Figure 4 a schematic diagram of a powertrain of a second configuration of a vehicle;

[0027] Figure 11 According to the teachings of this disclosure Figure 4 a schematic diagram of a powertrain of a third configuration of a vehicle;

[0028] Figure 12 According to the teachings of this disclosure Figure 4 A schematic diagram of a powertrain of a third configuration of a vehicle; and

[0029] Figure 13 According to the teachings of this disclosure Figure 4 a schematic diagram of a powertrain of a third configuration of a vehicle;

[0030] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. DETAILED DESCRIPTION

[0031] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0032] refer to Figure 4 , a vehicle 410 is shown. The vehicle 410 includes a drivetrain 414 configured to provide power to at least one set of wheels (e.g., wheels 418) to propel the vehicle 410. In one form, for example, the vehicle may be a rear wheel drive (RWD) vehicle, although other configurations such as front wheel drive (FWD), all wheel drive (AWD), or four wheel drive (4WD) may be used.

[0033] In another form, vehicle 410 may include more than one instance of drivetrain 414. In one such form, each drivetrain 414 provides power to a dedicated set of wheels 418. In yet another form, each drivetrain 414 may provide power to a dedicated one of wheels 418.

[0034] Although a passenger car is shown, vehicle 410 may be any suitable type of vehicle, including, but not limited to, a racing car, an off-road vehicle, a truck, a recreational vehicle (RV), or a military vehicle. Although not specifically shown, those skilled in the art will appreciate that the powertrain 414 of the present disclosure may also be suitable for non-vehicle applications, such as, for example, farm or industrial equipment.

[0035] In the example provided, vehicle 410 is an electric vehicle and includes a vehicle power storage unit 422 (e.g., a vehicle battery or a hydrogen tank and fuel cell). Vehicle power storage unit 422 provides electricity to drivetrain 414, and drivetrain 414 converts the electricity into mechanical power to drive wheels 418. In another form, not specifically shown, vehicle 410 can be a hybrid vehicle such that an internal combustion engine can also provide power to the same wheels 418. In yet another form, vehicle 410 can be configured such that an internal combustion engine (not shown) can provide power to one set of wheels 418, while drivetrain 414 can provide power to a different set of wheels 418.

[0036] refer to Figure 5 , the powertrain 414 includes an electric motor 510, a centrifugal clutch 514, and a transmission 518. The electric motor 510 may be a vehicle power storage unit 422 ( Figure 4 ) any suitable type of electric motor that receives electricity and converts the electricity into rotational power. The electric motor 510 includes a motor output 522 and is configured to rotate the motor output 522. The motor output 522 is coupled to a clutch input 524 of the centrifugal clutch 514. The clutch output 528 of the centrifugal clutch 514 is coupled to a transmission input 532 of the transmission 518. The transmission output 536 of the transmission 518 is coupled to the wheels 418 ( Figure 4 ) is configured to drive wheels 418 to propel the vehicle 410 ( Figure 4 ).

[0037] In one form, the transmission output 536 may be coupled to a propeller shaft (not shown) that is connected to the vehicle 410 ( Figure 4 ) provides power to a drive axle (not shown) of the vehicle 410, which may optionally include a differential (not shown), but other configurations may be used. In another form, the transmission output 536 may be directly coupled to a drive axle (not shown) or wheels 418 ( Figure 4 ) is a special wheel in the .

[0038] The centrifugal clutch 514 is configured to couple the motor output 522 to the transmission input 532 to provide rotational power therebetween.

[0039] The transmission 518 can be any suitable transmission and includes a transmission gear set 540 having a plurality of gear ratios disposed between a transmission input 532 and a transmission output 536. The transmission 518 can include an actuator 544 coupled to the transmission gear set 540 and configured to select one or more gear ratios of the transmission gear set 540. The actuator 544 can be any suitable type of actuator. In one form, the actuator 544 is a manual shifter that is physically and manually moved between gear ratios by an operator (not shown). In another form, the actuator 544 is an electric or hydraulic actuator controlled by a controller 548 to switch between gear ratios automatically or in response to input from an operator (not shown).

[0040] refer to Figure 6 and Figure 7, the centrifugal clutch 514 includes a clutch input 524, a clutch output 528, and a clutch mechanism 552, all of which are rotatable about a central axis 556. The clutch input 524 and the clutch output 528 are coaxially disposed about the central axis 556. The clutch mechanism 552 is configured to transmit torque between the clutch input 524 and the clutch output 528 in a manner that reduces the torque capacity of the centrifugal clutch 514 at higher rotational speeds (i.e., revolutions per minute; "RPM") based on the rotational speed.

[0041] The clutch mechanism 552 includes a housing 558, at least one input friction plate (e.g., input friction plate 560, also referred to as a pressure plate), at least one output friction plate (e.g., output friction plate 564), at least one counterweight assembly (e.g., counterweight assembly 568), and at least one biasing member (e.g., biasing member 572). The housing 558 is coupled to the clutch input end 524 for common rotation about a central axis 556. Each input friction plate (e.g., input friction plate 560) is coupled to the housing 558 for common rotation about the central axis 556, but is axially movable relative to the housing 558. Each output friction plate (e.g., output friction plate 564) is coupled to the clutch output end 528 for common rotation about the central axis 556.

[0042] In the example provided, the housing 558 includes a first base member 710, a second base member 714, and at least one connecting member 718, although other configurations may be used. The first base member 710 is directly coupled to the clutch input 524 for common rotation therewith, such as via welds, bolts, rivets, splines, etc. The second base member 714 is axially spaced from the first base member 710 and fixedly coupled thereto by a plurality of connecting members 718.

[0043] In the example provided, there are a plurality of connecting members 718, each of which is a cylindrical shaft and is spaced apart from one another in a circumferential direction about the central axis 556. One end of each connecting member 718 is coupled to the first base member 710, and the other end is coupled to the second base member 714. The connecting members 718 are configured to inhibit axial movement of the second base member 714 relative to the first base member 710 and to couple the second base member 714 to the first base member 710 for common rotation. In an alternative configuration, not specifically shown, the plurality of connecting members 718 may be replaced by a single connecting member that forms a generally drum-shaped or cylindrical shape about the central axis 556.

[0044] The clutch input 524 and the clutch output 528 are configured to be generally rotatable relative to one another, and the input friction plates 560 and the output friction plates 564 are configured to frictionally couple the clutch input 524 to the clutch output 528 for common rotation about the axis 556. Thus, the clutch input 524 and the clutch output 528 may rotate relative to one another if the input friction plates 560 and the output friction plates 564 are spaced apart from one another or if a torque difference therebetween exceeds the friction torque holding capacity of the engagement between the input friction plates 560 and the output friction plates 564.

[0045] Thus, the clutch mechanism 552 can operate in a coupled condition, in which substantially all torque is transferred between the clutch input 524 and the clutch output 528, and in a slipping mode, in which some, but not all, of the torque is transferred between the clutch input 524 and the clutch output 528. In some forms, the clutch mechanism 552 can optionally be configured to also operate in a disengaged mode, in which the input friction plates 560 and the output friction plates 564 are disengaged from one another and do not transfer torque.

[0046] In the example provided, a single input friction plate 560 and a single output friction plate 564 are used, but other configurations may be used. In the example provided, the output friction plate 564 is axially fixed to the clutch output end 528, but other configurations may be used. The side of the input friction plate 560 facing the output friction plate 564 includes friction material 722 (e.g., one or more friction pads) attached thereto. The side of the output friction plate 564 facing the input friction plate 560 includes friction material 726 (e.g., one or more friction pads) attached thereto. Thus, the contact between the friction materials 722, 726 of the input friction plate 560 and the output friction plate 564 allows the input friction plate 560 to frictionally couple to the output friction plate 564.

[0047] In an alternative arrangement, not specifically shown, the output friction plates 564 may be axially movable relative to the clutch output 528 .

[0048] In another alternative configuration, not specifically shown, more than one input friction plate and more than one output friction plate may be used. In this configuration, the input friction plates are coupled to the clutch input 524 for common rotation about the central axis 556 but are axially movable relative to the clutch input 524, and the output friction plates are coupled to the clutch output 528 for common rotation about the central axis 556 but are axially movable relative to the clutch input 524. In this configuration, the input friction plates and the output friction plates are positioned in an alternating manner along the axial direction.

[0049] Returning to the example provided, the output friction plate 564 can be located axially between the first base member 710 and the input friction plate 560. The input friction plate 560 can be located axially between the output friction plate 564 and the second base member 714. The clutch output end 528 can extend axially through the aperture 730 in the second base member 714 and the aperture 734 in the input friction plate 560 to couple to the output friction plate 564 for common rotation, such as via a weld, bolts, rivets, splines, etc.

[0050] Each biasing member 572 biases the input friction plate 560 and the output friction plate 564 into engagement with each other. In the example provided, each biasing member 572 is mounted between the housing 558 (e.g., mounted to the second base member 714) and the input friction plate 560 to act on the input friction plate 560 to bias the input friction plate 560 in an axial direction toward the output friction plate 564.

[0051] In the example provided, the biasing member 572 comprises a coil spring, but other configurations may be used, such as other types of springs or resilient materials. The force applied by the biasing member 572 may optionally be adjustable. In the example provided, the adjustment screw 576 threadably engages the second base member 714 and is between the second base member 714 and the biasing member 572, such that turning the adjustment screw 576 in one direction compresses the biasing member 572 between the second base member 714 and the input friction plate 560 to increase the biasing force. Accordingly, turning the adjustment screw 576 in the opposite direction decreases the biasing force.

[0052] Each counterweight assembly 568 is configured such that, during rotation of the clutch mechanism 552, the counterweight assembly 568 applies a force in a direction that counteracts the biasing force from the biasing member 572. Each counterweight assembly 568 is configured such that the force applied thereby increases as the rotational speed of the clutch mechanism 552 increases.

[0053] In the example provided, the counterweight assembly 568 includes a counterweight 610, a pivot body 614, and a transfer member 618. The counterweight 610 is mounted to the pivot body 614. The pivot body 614 is coupled to the second base member 714 for common rotation therewith about the central axis 556. The pivot body 614 is coupled to the second base member 714 at a first pivot location 622 such that the pivot body 614 can pivot relative to the housing 558 about the first pivot location 622 while rotating with the housing 558 about the central axis 556. The counterweight 610 is positioned relative to the first pivot location 622 such that rotation of the housing 558 about the central axis 556 generates a centrifugal force on the counterweight 610 in a radially outward direction relative to the central axis 556.

[0054] The counterweight 610 can be any suitable component coupled to the pivot body 614 and having sufficient mass to generate the centrifugal force. In the example provided, the counterweight 610 can be removable, and different mass counterweights can be interchangeably coupled to the pivot body 614 to adjust the centrifugal force. In other forms, the counterweight 610 can be permanently coupled to the pivot body 614 and / or integrally formed therewith.

[0055] One end of the transfer member 618 is rigidly coupled to the input friction plate 560. The opposite end of the transfer member 618 is coupled to the pivot body 614 at a second pivot location 626, allowing the pivot body 614 to pivot relative to the transfer member 618. The second pivot location 626 is positioned such that the centrifugal force causing the pivot body 614 to pivot about the first pivot location 622 is converted into a force that pulls the transfer member 618 in an axial direction away from the output friction plate 564. Thus, as the rotational speed of the housing 558 increases, the total force acting on the input friction plate 560 in an axial direction toward the output friction plate 564 decreases, and thus, the friction force coupling the input friction plate 560 to the output friction plate 564 decreases.

[0056] refer to Figure 8 , showing an electric motor 510 ( Figure 5 ) of the torque output 810 and the centrifugal clutch 514 ( Figures 5 to 7 )'s torque capacity 814 (also referred to as torque holding capability) and the motor's rotational speed (i.e., the rotational speed of the motor output 522; Figure 5 The torque output 810 starts at substantially maximum torque and is substantially constant for most speeds, but then decreases above a threshold speed 818.

[0057] The mass of the counterweight 610 ( Figure 7 ), the geometry of the pivot body 614 ( Figure 7 ) and the biasing force of the biasing member 572 ( Figure 7 ) is configured such that the torque capacity 814 decreases as the motor speed increases above a threshold speed 818.

[0058] In the example provided, the mass of the counterweight 610 ( Figure 7 ), the geometry of the pivot body 614 ( Figure 7 ) and the biasing force of the biasing member 572 ( Figure 7 ) can be configured so that the torque capacity 814 decreases over the entire motor speed range, but other configurations can be used, such as remaining substantially constant for lower motor speeds and then decreasing for higher motor speeds.

[0059] In one form, the mass of the counterweight 610 ( Figure 7), the geometry of the pivot body 614 ( Figure 7 ) and the biasing force of the biasing member 572 ( Figure 7 ) can be configured such that the torque capacity 814 remains greater than or equal to the torque capacity of the electric motor 510 ( Figure 5 ) torque output 810.

[0060] In another form, the mass of the counterweight 610 ( Figure 7 ), the geometry of the pivot body 614 ( Figure 7 ) and the biasing force of the biasing member 572 ( Figure 7 ) can be configured such that the torque capacity 814 remains greater than the torque capacity of the electric motor 510 ( Figure 5 ) torque output 810.

[0061] In the example provided, the mass of the counterweight 610 ( Figure 7 ), the geometry of the pivot body 614 ( Figure 7 ) and the biasing force of the biasing member 572 ( Figure 7 ) can be configured so that the torque capacity 814 remains greater than that of the electric motor 510 ( Figure 5 ) of the torque output 810, but within a predetermined torque range of the torque output 810 at the predetermined motor speed. In other words, the input friction plates 560 and the output friction plates 564 can be configured to never fully disengage. The predetermined motor speed corresponds to the transmission 518 ( Figure 5 ) shift point and can be a range of motor speeds. In other words, the predetermined motor speed is the speed at which the transmission 518 is configured to shift to a higher gear (e.g., first gear to second gear, or second gear to third gear, etc.).

[0062] In one form, the predetermined motor speed is equal to or greater than the threshold rotational speed 818 , although other configurations, including being less than the threshold rotational speed 818 , may be used.

[0063] The predetermined torque range is configured such that the clutch mechanism 552 ( Figure 7 ) is configured to connect the clutch input 524 ( Figure 7 ) is connected to the clutch output 528 ( Figure 7 ) in the transmission 518 ( Figure 5 ) maintains a constant gear ratio for the electric motor 510 ( Figure 5) (or at least all speeds below the predetermined motor speed) without slipping. However, the predetermined torque range is configured such that a torque disturbance (e.g., an inertia pulse) caused by shifting the transmission 518 between gear ratios (e.g., from a lower gear to a higher gear) causes the torque difference between the clutch input 524 and the clutch output 528 to exceed the torque capacity 814. Thus, the clutch mechanism 552 is configured to slip in response to a torque disturbance caused by shifting the transmission 518 at the predetermined motor speed.

[0064] In one form, the torque capacity 814 may be set to be configured to achieve a desired tradeoff between a number of related performance requirements (e.g., maintaining tire traction, achieving consistent shift speeds, minimizing clutch slip to improve system efficiency and clutch wear, and smoothing power delivery across shifts, etc.).

[0065] In one form, for example, the torque capacity 814 can be set to achieve a predetermined clutch slip range such that the inertia pulse causes the clutch to slip without losing traction at the tire. In another form, the clutch capacity 814 can be set to allow slip of the centrifugal clutch 514, but minimize the amount of time the centrifugal clutch 514 is slipping to improve system efficiency and clutch wear, and can optionally allow some slip of the tire (i.e., vehicle wheel 418), but less than would occur with a non-slip clutch.

[0066] In another form, sensors 580, 582 can be used to determine the speed and / or torque at various locations within the system, and the controller 548 can be configured to use a closed-loop motor control algorithm to enhance clutch behavior. In other words, the controller 548 can actively control the amount of slip of the centrifugal clutch 514 by actively controlling the output torque of the motor 510. In one such example, sensors can detect or be used to determine the speed of the motor output 522 and the speed of the transmission input 532. In this example, if the controller 548 determines that the clutch capacity 814 is less than expected, the controller 548 can use a closed-loop motor control algorithm to actively reduce the motor torque to reduce the duration of the shift and smoothly relock the clutch. This algorithm can optionally be combined with estimating the clutch capacity using measured speed and / or torque feedback signals to adapt the control and characterize the mechanical performance of the clutch.

[0067] In an alternative form, the clutch mechanism 552 may be configured to slip to a certain extent immediately prior to a shift event and regain full coupling after the shift occurs.

[0068] refer to Figure 9, shows the motor output rotational speed 910 (e.g., the rotational speed of the motor output 522; Figure 5 ), the transmission input speed 914 (eg, the rotational speed of the transmission input 532 ; Figure 5 ) and wheel rotation speed 918 (e.g., wheel 418 ( Figure 4 ) or the speed of the transmission output 536; Figure 5 ) versus time. When the motor output rotational speed 910 smoothly transitions (e.g., decreases) during the shift events 934, 938, 942 compared to the transmission input speed 914, the clutch mechanism 552 ( Figure 7 ) can be slipped Figure 9 By comparing Figure 9 The curve graph and Figure 3 As can be seen from the graph, the vehicle 410 ( Figure 4 ) utilizing the powertrain system 414 discussed herein ( Figure 5 ) significantly reduces disturbances in wheel rotational speed 918 (eg, disturbances 922 , 926 , and 930 ) during these shift events 934 , 938 , 942 .

[0069] refer to Figure 10 , an alternative configuration of a drivetrain 1010 is shown. Drivetrain 1010 is similar to drivetrain 414 except as otherwise shown or described herein. Accordingly, similar components are identified with similar reference numerals, and only the differences are described in detail herein. In the example provided, drivetrain 1010 includes an electric motor 510, a motor output 522, a centrifugal clutch 514, a clutch input 524, and a clutch output 528, all arranged substantially similarly to those described above. In drivetrain 1010, transmission 518 is optionally replaced with a gear reduction gearbox 1014, which can provide a single-speed gear reduction between input 1018 and output 1022 of gear reduction gearbox 1014. Input 1018 is drivingly coupled to clutch output 528 to receive torque therefrom, and can optionally be directly coupled thereto. Output 1022 is drivingly coupled to a single wheel 418. In configurations where the optional gear reduction gearbox 1014 is not included, the clutch output 528 may be drivingly coupled to the wheels 418 .

[0070] In the example provided, another instance of the drivetrain 1010 would be configured to drive a different wheel 418. For example, the rear wheels 418 and / or the front wheels could be driven by a corresponding instance of the drivetrain 1010.

[0071] refer to Figure 11, an alternative configuration of a drivetrain 1110 is shown. Except as otherwise shown or described herein, the drivetrain 1110 is similar to the drivetrain 1010. Therefore, similar components are identified with similar reference numerals, and only the differences are described in detail herein. In the example provided, the drivetrain 1110 includes an electric motor 510, a motor output 522, a centrifugal clutch 514, a clutch input 524, and a clutch output 528 substantially similar to the arrangement described above and may optionally include the gear reduction gearbox 1014 arranged above. The drivetrain 1110 also includes a disconnect clutch 1114 located in the torque transfer path between the electric motor 510 and the wheels 418. In the example provided, the disconnect clutch 1114 drivingly couples the motor output 522 to the clutch input 524.

[0072] In an alternative configuration, not specifically shown, disconnect clutch 1114 can drivingly couple clutch output 528 to input 1018. In yet another alternative configuration, not specifically shown, disconnect clutch 1114 can drivingly couple output 1022 to wheels 418. In yet another alternative configuration, not specifically shown, without gear reduction gearbox 1014, disconnect clutch 1114 can drivingly couple clutch output 528 to wheels 418.

[0073] The disconnect clutch 1114 can act as an overspeed protection mechanism. In normal operation, the disconnect clutch 1114 can be opened at high vehicle speeds and closed at lower vehicle speeds to prevent the electric motor 510 from being backdriven by the wheels 418 at speeds greater than the speed for which the electric motor 510 is designed. In the event that the disconnect clutch 1114 does not operate as intended, the centrifugal clutch 514 can act as a backup device to protect the electric motor 510 at high speeds. In this configuration, the centrifugal clutch 514 can be fully disengaged or simply allowed to slip to protect the electric motor 510.

[0074] refer to Figure 12, an alternative configuration of a drivetrain 1210 is shown. Except as otherwise shown or described herein, the drivetrain 1210 is similar to the drivetrain 414. Accordingly, similar components are identified with similar reference numerals, and only the differences are described in detail herein. In the example provided, the drivetrain 1210 includes an electric motor 510, a motor output 522, a centrifugal clutch 514, a clutch input 524, and a clutch output 528, substantially similar to the arrangement described above. The clutch output 528 is drivingly coupled to the transmission 1214 (e.g., an electrically variable transmission) via the input 1218 of the transmission 1214. The output 1222 of the transmission 1214 is drivingly coupled to the wheels 418 in any suitable manner, similar to the transmission output 536 (discussed above). Figure 5 ). Powertrain 1210 also includes at least one additional prime mover drivingly coupled to the transmission via an additional input of transmission 1214.

[0075] The additional prime mover can be an additional electric motor or an internal combustion engine. In the example provided, the additional electric motor 1226 is drivingly coupled to an additional input 1230 of the transmission 1214, and the internal combustion engine 1234 is drivingly coupled to another input 1238 of the transmission 1214, but other configurations can be used. The additional electric motor 1226 can be coupled to the input 1230 of a centrifugal clutch 1242. The centrifugal clutch 1242 can be similar to the centrifugal clutch 514.

[0076] In an alternative configuration not specifically shown, the additional electric motor 1226 is omitted, and the transmission 1214 is driven only by the electric motor 510 and the internal combustion engine 1234. In another alternative configuration not shown, the internal combustion engine 1234 is omitted, and the transmission 1214 is driven only by the two electric motors 510 and 1226.

[0077] refer to Figure 13 , an alternative configuration of a powertrain 1310 is shown. Powertrain 1310 is similar to powertrain 414 except as otherwise shown or described herein. Accordingly, similar components are identified with similar reference numerals, and only the differences are described in detail herein. In the example provided, powertrain 1310 includes an electric motor 510, a motor output 522, a centrifugal clutch 514, a clutch input 524, and a clutch output 528, substantially similar to the arrangement described above. Powertrain 1310 also includes an internal combustion engine 1314, a summing gear set 1318, and a transmission 1322.

[0078] The summing gear set 1318 can be any suitable set of gears, belts, chains, or the like configured to sum torque inputs from more than one input and output the sum of the torques to a common output. In the example provided, the summing gear set 1318 has a first input 1326, a second input 1330, and an output 1334. The first input 1326 is drivingly coupled to the clutch output 528. The second input 1330 is drivingly coupled to the output 1338 of the internal combustion engine 1314. The output 1334 is drivingly coupled to the input 1342 of the transmission 1322. The transmission 1322 can be any suitable transmission and can be similar to the transmission 518 discussed above. Figure 5 The output 1346 of the transmission 1322 is drivingly coupled to the wheels 418 in any suitable manner, similar to the transmission output 536 discussed above. Figure 5 In this configuration, the electric motor 510 can provide power at low speeds (e.g., when starting off), and the centrifugal clutch 514 can disengage or slip at high speeds while the internal combustion engine 1314 can still provide power.

[0079] Thus, the teachings of the present disclosure provide an electric vehicle that provides smooth operation during transmission shifts while also allowing for various hybrid powertrains.

[0080] Unless otherwise expressly indicated herein, all numerical values ​​indicating mechanical / thermal properties, composition percentages, dimensions and / or tolerances or other characteristics when describing the scope of the present disclosure should be understood as modified by the word "about" or "approximately." Such modification is desirable for various reasons, including: industrial practice; material, manufacturing and assembly tolerances; and testing capabilities.

[0081] As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical "or", and should not be construed to mean "at least one of A, at least one of B, and at least one of C."

[0082] In this application, the terms "controller" and / or "module" may refer to, be part of, or include: an application-specific integrated circuit (ASIC); a digital, analog, or mixed analog / digital discrete circuit; a digital, analog, or mixed analog / digital integrated circuit; a combinatorial logic circuit; a field-programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system on a chip.

[0083] The term memory is a subset of the term computer-readable medium. The term computer-readable medium, as used herein, does not encompass transient electrical or electromagnetic signals propagated through a medium (such as on a carrier wave); thus, the term computer-readable medium may be considered to be both tangible and non-transitory. Non-limiting examples of non-transitory tangible computer-readable media are non-volatile memory circuits (such as flash memory circuits, erasable programmable read-only memory circuits, or mask read-only circuits), volatile memory circuits (such as static random access memory circuits or dynamic random access memory circuits), magnetic storage media (such as analog or digital magnetic tape or hard drives), and optical storage media (such as CDs, DVDs, or Blu-ray discs).

[0084] The apparatus and methods described in this application may be implemented partially or completely by a special-purpose computer created by configuring a general-purpose computer to perform one or more specific functions embodied in a computer program. The functional blocks, flow chart components, and other elements described above serve as software specifications that can be translated into a computer program through routine work by a technician or programmer.

[0085] The description of the present disclosure is merely exemplary in nature and, thus, variations that do not depart from the essence of the disclosure are intended to be within the scope of the present disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure.

[0086] According to the present invention, an electric vehicle is provided, which comprises: an electric drive motor; a transmission, the transmission being switchable between a plurality of gear ratios; and a centrifugal clutch, the centrifugal clutch being drivingly coupled in a torque transmission path between the electric drive motor and the transmission, the centrifugal clutch comprising: a first friction plate, the first friction plate being rotatable about an axis; a second friction plate, the second friction plate being rotatable about the axis and being axially movable relative to the first friction plate, the second friction plate being configured to frictionally engage the first friction plate to transmit torque therebetween; and a biasing member, the biasing member applying a biasing force to the second friction plate. and a first gear configured to bias the second friction plate in a first axial direction toward the first friction plate; and a second gear configured to bias the second friction plate in a first axial direction toward the first friction plate; and a second gear configured to bias the second friction plate in a first axial direction toward the first friction plate in response to a rotational speed of the second friction plate exceeding a predetermined rotational speed.

[0087] According to one embodiment, the centrifugal clutch further includes a base member coupled to the second friction plate for common rotation therewith about the axis, wherein the second friction plate is movable relative to the base member along the axis.

[0088] According to one embodiment, the counterweight assembly includes a counterweight and a pivot member, the counterweight being coupled to the pivot member, the pivot member being coupled to the base member via a first pivot connection and to the second friction plate via a second pivot connection.

[0089] According to one embodiment, the counterweight assembly further comprises a transfer member, wherein a first end of the transfer member is coupled to the second friction plate, and a second end of the transfer member is coupled to the pivot member at the second pivot connection.

[0090] According to one embodiment, the second friction plate is located axially between the base member and the first friction plate.

[0091] According to one embodiment, the present invention is further characterized by a control module configured to shift the transmission between the plurality of gear ratios, wherein the control module is configured to receive signals from a plurality of sensors and actively control motor output torque in response to the signals received from the plurality of sensors to actively control the amount of slip of the centrifugal clutch during shifting of the transmission.

[0092] 18. The electric vehicle of claim 17, wherein the first and second gears are connected in a direction of rotation of the at least one wheel support member, the at least one wheel support member being connected in a direction of rotation of the at least one wheel support member. The electric vehicle of claim 17, wherein the at least one wheel support member is connected in a direction of rotation of the at least one wheel support member. and a second cam which is adapted to move the first and second friction plates relative to each other in an axial direction away from the first friction plate.

[0093] According to one embodiment, the present invention is further characterized by a control module configured to shift the transmission between the plurality of gear ratios, wherein the control module is configured to receive signals from a plurality of sensors and actively control motor output torque in response to the signals received from the plurality of sensors to actively control the amount of slip of the centrifugal clutch during shifting of the transmission.

Claims

1. An electric vehicle comprising: electric drive motor; a transmission capable of shifting between a plurality of gear ratios; as well as a centrifugal clutch drivingly coupled in a torque transfer path between the electric drive motor and the transmission, the centrifugal clutch comprising: a first friction plate, the first friction plate being rotatable about an axis; a second friction plate rotatable about the axis and axially movable relative to the first friction plate, the second friction plate being configured to frictionally engage the first friction plate to transmit torque therebetween; a biasing member that applies a biasing force to the second friction plate, the biasing force biasing the second friction plate in a first axial direction toward the first friction plate; and A counterweight assembly is coupled to the second friction plate and is configured to apply a counterweight force on the second friction plate in a second axial direction away from the first friction plate in response to a rotational speed of the second friction plate exceeding a predetermined rotational speed.

2. The electric vehicle of claim 1, wherein the centrifugal clutch further comprises a base member coupled to the second friction plate for common rotation therewith about the axis, wherein the second friction plate is movable relative to the base member along the axis. 3 . The electric vehicle of claim 2 , wherein the biasing member axially biases the second friction plate away from the base member and toward the first friction plate. 4 . The electric vehicle of claim 2 , wherein the counterweight assembly is coupled to the base member via a first pivot connection and to the second friction plate via a second pivot connection.

5. The electric vehicle according to claim 4, wherein the counterweight assembly includes a counterweight, a pivot member and a transfer member, wherein the counterweight is connected to the pivot member and the pivot member is connected to the base member at the first pivot connection, wherein the first end of the transfer member is connected to the second friction plate, and the second end of the transfer member is connected to the pivot member at the second pivot connection. 6 . The electric vehicle of claim 2 , wherein the first friction plate is coupled to an input of the transmission for common rotation therewith, and the base member is coupled to an output of the electric drive motor for common rotation therewith. 7 . The electric vehicle of claim 1 , further comprising a control module configured to shift the transmission between gear ratios.

8. The electric vehicle of claim 7, wherein the control module is configured to receive signals from a plurality of sensors and actively control motor output torque in response to the signals received from the plurality of sensors to actively control the slip amount of the centrifugal clutch during gear shifting of the transmission.

9. The electric vehicle of any one of claims 1 to 8, wherein the counterweight force is configured to be less than the biasing force for all operating speeds of the motor.

10. The electric vehicle of any one of claims 1 to 8, wherein the centrifugal clutch is configured to have a torque holding capability exceeding the torque output of the motor for all operating speeds of the motor, but to allow slip between the first friction plate and the second friction plate in response to a torque disturbance caused by shifting a gear ratio of the transmission.

11. The electric vehicle of claim 10, wherein the centrifugal clutch includes a base member coupled to an output of the electric drive motor for common rotation therewith, wherein the counterweight assembly comprises a counterweight, a pivoting member and a transmission member, wherein the counterweight is coupled to the pivoting member, wherein the pivot member is coupled to the base member via a first pivot connection and to the transfer member via a second pivot connection, Wherein a first end of the transfer member is coupled to the second friction plate, and a second end of the transfer member is coupled to the pivot member at the second pivot connection.

12. An electric vehicle according to any one of claims 1 to 8, wherein the centrifugal clutch is configured to have a torque holding capability that exceeds the torque output of the motor for all operating speeds of the motor, but within a predetermined torque range of the torque output at a predetermined motor speed, wherein the predetermined motor speed corresponds to a shift point of the transmission, and the predetermined torque range is configured such that a torque disturbance due to the shift causes the centrifugal clutch to slip in response to shifting the transmission.

13. The electric vehicle according to any one of claims 1 to 8, wherein the centrifugal clutch is configured to have a torque holding capability that allows slippage between the first friction plate and the second friction plate at a predetermined torque output of the motor corresponding to a shift point of the transmission.

14. The electric vehicle of any one of claims 1 to 6, further comprising a control module configured to shift the transmission between gear ratios.

15. The electric vehicle of claim 14, wherein the control module is configured to receive signals from a plurality of sensors and actively control motor output torque in response to the signals received from the plurality of sensors to actively control the slip amount of the centrifugal clutch during gear shifting of the transmission.

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