Electric vehicle

Abstract

The present invention realizes an electric vehicle comprising a structure with which it is possible to reliably lock the rotation of a driving wheel when the vehicle stops. In a state in which torque with which a vehicle-stop position can be maintained is output by a driving motor 4 of each of one or more driving devices 2 among a plurality of driving devices 2, the output torque of a driving motor 4 of the remaining driving device 2 among the plurality of driving devices 2 is set to 0, as a result of which a pressing surface of an engagement element of a reverse input blocking clutch 6 of the remaining driving device 2 is brought into contact with a pressed surface, and then the output torque of a driving motor 4 of one or a plurality of the driving devices 2 among the one or more driving devices 2 is set to 0, as a result of which a pressing surface of an engaging element of a reverse input blocking clutch 6 of the one or of each of the plurality of driving devices 2 is brought into contact with a pressed surface.

Description

electric vehicles

[0001] The present disclosure relates to an electric vehicle using an electric motor as a drive source.

[0002] In response to the recent trend toward reducing the use of fossil fuels, research into electric vehicles has progressed and some electric vehicles have been put into practical use. For example, Japanese Patent Application Laid-Open No. 2000-010631 describes an electric vehicle equipped with a drive motor for each running wheel.

[0003] The electric vehicle described in JP 2000-010631 A uses an electric motor as the drive motor, which has a parking brake function to prevent the vehicle from moving when stopped, regardless of external forces or the inclination angle of the road surface.

[0004] WO 2023 / 085395 discloses a reverse input disconnection clutch that can be used as a parking brake. The reverse input disconnection clutch described in WO 2023 / 085395 includes a pressed member, an input member, an output member, an engagement element, and a biasing member.

[0005] In the reverse input cutoff clutch described in WO 2023 / 085395, when rotational torque is input to the input member, the input-side engaging portion of the input member engages with the input-side engaged portion of the engager, causing the engager to move in a direction away from the pressed surface of the pressed member, and engaging the output-side engaged portion of the output member with the output-side engaging portion of the output member, thereby transmitting the rotational torque input to the input member to the output member. On the other hand, when rotational torque is reversely input to the output member, the engager moves in a direction approaching the pressed surface, and the pressing surface of the engager is pressed against the pressed surface, frictionally engaging the pressing surface with the pressed surface. The biasing member elastically biases the engager in a direction approaching the pressed surface.

[0006] By connecting the input member constituting this reverse input cutoff clutch to the drive motor side of the electric vehicle described in JP 2000-010631 A and connecting the output member to the wheels of the electric vehicle, it is possible to prevent the vehicle from moving when stopped, regardless of external forces or the inclination angle of the road surface. In other words, the reverse input cutoff clutch constitutes a parking brake.

[0007] JP 2000-010631 A International Publication No. 2023 / 085395

[0008] However, if the reverse input cut-off clutch described in WO 2023 / 085395 is applied to the parking brake provided for each running wheel of the electric vehicle described in JP 2000-010631 A, when the output torque of all drive motors of multiple drive units is simultaneously set to zero (power supply to the drive motors is simultaneously stopped) when the electric vehicle stops, depending on the inclination of the road surface at the stopping position, the weight of the transported goods, etc., the engaging element may move in a direction approaching the pressed surface, and the rotational torque reversely input to the output member may be transmitted to the input member via the engaging element before the pressing surface frictionally engages with the pressed surface. As a result, it may not be possible to reliably lock the rotation of the drive wheels.

[0009] The present disclosure aims to realize an electric vehicle that can reliably lock the rotation of its wheels when the vehicle is stopped.

[0010] An electric vehicle according to one aspect of the present disclosure includes a plurality of drive units.

[0011] Each of the plurality of drive devices includes a drive motor, a drive wheel, and a reverse input cutoff clutch.

[0012] The reverse input disconnect clutch is disposed in a torque transmission path from the drive motor to the drive wheels.

[0013] The reverse input disconnecting clutch includes a pressed member, an input member, an output member, an engaging element, and a biasing member.

[0014] The pressed member has a pressed surface on its inner circumferential surface.

[0015] The input member has an input-side engaging portion disposed radially inside the pressed surface, is disposed coaxially with the pressed surface, and is connected to the drive motor.

[0016] The output member has an output side engaging portion arranged radially inward of the input side engaging portion on the radial inside of the pressed surface, arranged coaxially with the pressed surface, and connected to the drive wheel side.

[0017] The engaging element has a pressing surface facing the pressed surface, an input side engaged portion that can engage with the input side engaging portion, and an output side engaged portion that can engage with the output side engaging portion, and is arranged so that it can move radially (in the direction toward or away from the pressing surface).

[0018] The biasing member elastically biases the engaging element in a direction in which the engaging element approaches the pressed surface.

[0019] When rotational torque is input from the drive motor to the input member, the reverse input cutoff clutch moves the engaging element away from the pressed surface based on the engagement of the input-side engaging portion with the input-side engaged portion, thereby engaging the output-side engaged portion with the output-side engaging portion, thereby transmitting the rotational torque input to the input member to the output member (unlock mode). On the other hand, when rotational torque is reversely input from the drive wheel to the output member, the reverse input cutoff clutch moves the engaging element toward the pressed surface, causing the pressing surface to frictionally engage with the pressed surface, thereby preventing rotation of the output member (lock mode).

[0020] In particular, in an electric vehicle according to one aspect of the present disclosure, immediately after the rotation speeds of the drive wheels of all of the plurality of drive units decrease to or below a predetermined threshold, while the drive motor of at least one of the plurality of drive units outputs a torque sufficient to maintain a parked position, the output torque of the drive motor of the remaining drive units of the plurality of drive units is set to zero, thereby causing the pressing surfaces of the engagers of the reverse input cutoff clutches of the remaining drive units to contact the pressed surfaces, i.e., placing the reverse input cutoff clutch in a state in which it can be quickly switched to a locked mode. Thereafter, the output torque of the drive motor of one or more drive units of the at least one drive unit is set to zero, thereby causing the pressing surfaces of the engagers of the reverse input cutoff clutches of the one or more drive units to contact the pressed surfaces, i.e., placing the reverse input cutoff clutch in a state in which it can be quickly switched to a locked mode.

[0021] In an electric vehicle according to one aspect of the present disclosure, the output torque of the drive motors of the remaining drive units is set to zero one by one or simultaneously, and the pressing surface of the engagement element of the reverse input cut-off clutch is brought into contact with the pressed surface.

[0022] In an electric vehicle according to one aspect of the present disclosure, the output torque of all of the remaining drive units is set to zero, thereby bringing the pressing surfaces of the engaging members of all of the reverse input cut-off clutches of the remaining drive units into contact with the pressed surfaces, and then the output torque of the drive motor of at least one of the drive units (including the one or more drive units) is set to zero one by one or simultaneously, bringing the pressing surfaces of the engaging members of the reverse input cut-off clutch into contact with the pressed surfaces.

[0023] In an electric vehicle according to one aspect of the present disclosure, the order of the plurality of drive devices that sets the output torque of the drive motor to zero can be changed depending on the stopping situation, i.e., the order of the plurality of drive devices that is to be the at least one drive device, the drive devices that are to be the remaining drive devices, and the drive devices that are to be the one or more drive devices can be changed as appropriate.

[0024] In an electric vehicle according to one aspect of the present disclosure, when the electric vehicle is parked on a slope, the at least one drive unit is an upper drive unit whose drive wheels are in contact with the upper part of the slope, and the remaining drive unit is a lower drive unit whose drive wheels are in contact with the lower part of the slope. That is, when the electric vehicle is parked on a slope, the upper drive unit outputs a torque sufficient to maintain the parked position, and the output torque of the drive motor of the lower drive unit is set to zero, thereby causing the pressing surface of the engagement element of the reverse input cutoff clutch of the lower drive unit to contact the pressed surface, and then the output torque of the drive motor of the upper drive unit is set to zero, thereby causing the pressing surface of the engagement element of the upper drive unit to contact the pressed surface.

[0025] In an electric vehicle according to one aspect of the present disclosure, when the lower drive unit is composed of a plurality of drive units, the output torque of the drive motors of the plurality of lower drive units is set to zero one by one or simultaneously, and the pressing surface of the engagement element of the reverse input cutoff clutch is brought into contact with the pressed surface. Then, after the pressing surface of the engagement element of the reverse input cutoff clutch is brought into contact with the pressed surface for all of the lower drive units, the output torque of the drive motor of the upper drive unit is set to zero, and the pressing surface of the engagement element of the upper drive unit is brought into contact with the pressed surface.

[0026] In an electric vehicle according to one embodiment of the present disclosure, when the upper drive unit is composed of multiple drive units, the output torque of the drive motor of the lower drive unit can be set to zero, and after the pressing surface of the engaging element of the reverse input cut-off clutch of the lower drive unit is brought into contact with the pressed surface, the output torque of the drive motors of the multiple upper drive units can be set to zero one by one in sequence or simultaneously.

[0027] In an electric vehicle according to an aspect of the present disclosure, the electric vehicle further includes at least one steering wheel that can be steered about a pivot axis that extends in a vertical direction, in addition to the drive wheels, and the plurality of drive units are configured with two drive units. In this case, when stopping the electric vehicle, a steering angle is applied to the at least one steering wheel in a direction that suppresses rotation due to a yaw moment.

[0028] In the electric vehicle according to one aspect of the present disclosure, each of the plurality of drive units has a reducer disposed in the torque transmission path, specifically, between the drive motor and the reverse input cutoff clutch or between the reverse input cutoff clutch and the drive wheels.

[0029] According to an electric vehicle according to one aspect of the present disclosure, the rotation of the drive wheels can be reliably locked when the vehicle is stopped.

[0030] FIG. 1 is a plan view schematically illustrating an electric vehicle according to a first embodiment of the present disclosure. FIG. 2 is an end view of a reverse input cutoff clutch of a drive unit constituting the electric vehicle according to the first embodiment, viewed from the output member side. FIG. 3 is a side view as viewed from the X-X cross section of FIG. 2. FIG. 4 is a Y-Y cross section of FIG. 3, with the biasing member omitted. FIG. 5 is a view similar to FIG. 4, showing a state in which rotational torque is input to the input member. FIG. 6 is a view similar to FIG. 4, showing a state in which rotational torque is reversely input to the output member. FIG. 7 is a flowchart showing operations performed when the electric vehicle according to the first embodiment is stopped. FIG. 8 is a view corresponding to FIG. 7, showing a first modified example of the first embodiment. FIG. 9 is a view corresponding to FIG. 7, showing a second modified example of the first embodiment. FIG. 10 is a view corresponding to FIG. 7, showing a third modified example of the first embodiment. FIG. 11 is a side view schematically illustrating an electric vehicle according to a second embodiment of the present disclosure. FIG. 12 is a flowchart showing operations performed when the electric vehicle according to the second embodiment is stopped. FIG. 13 is a plan view schematically showing an electric vehicle according to a third example of an embodiment of the present disclosure. FIG. 14 is a flowchart showing the operation of the electric vehicle according to the third example when it is stopped. FIG. 15(A) is a diagram corresponding to FIG. 13 showing a first modified example of the third example, and FIG. 15(B) is a diagram corresponding to FIG. 13 showing a second modified example of the third example. FIG. 16 is a plan view schematically showing an electric vehicle according to a fourth example of an embodiment of the present disclosure. FIG. 17 is a flowchart showing the operation of the electric vehicle according to the fourth example when it is stopped. FIG. 18 is a plan view schematically showing an electric vehicle according to a fifth example of an embodiment of the present disclosure. FIG. 19 is a flowchart showing the operation of the electric vehicle according to the fifth example when it is stopped.

[0031] First Example A first example of an embodiment of the present disclosure will be described with reference to FIGS. 1 to 7. FIG.

[0032] The electric vehicle 1 of this example includes a vehicle that uses electricity as an energy source and is driven by an electric motor. The electric vehicle 1 of this example is widely applicable to various electric vehicles, and can be applied not only to self-driving vehicles but also to electric vehicles driven by humans. Self-driving vehicles include automated guided vehicles and robotic cars used in industrial applications, as well as autonomous buses, taxis, and passenger cars that can be used on public roads and transport passengers. The electric vehicle 1 of this example will be described below with reference to an example in which it is applied to an automated guided vehicle that transports goods in a factory, warehouse, or the like.

[0033] <Overall Structure of Electric Vehicle> The electric vehicle 1 includes a plurality of drive units 2. Each of the plurality of drive units 2 includes a drive motor 4, drive wheels 5, and a reverse input cutoff clutch 6.

[0034] The number of drive units 2 is determined appropriately depending on the type of electric vehicle 1. Therefore, the plurality of drive units 2 may be configured with two, three, four, five or more drive units. The electric vehicle 1 may also be provided with one or more non-drive wheels other than the drive wheels 5.

[0035] In the electric vehicle (automated guided vehicle) 1a to which this example is applied, the plurality of drive units 2 are configured by four drive units 2a to 2d. The electric vehicle 1a does not have any non-drive wheels.

[0036] The plurality of drive units 2 are supported by a vehicle body 3. In the electric vehicle 1a, the four drive units 2a to 2d are supported at four locations on the front, rear, left and right sides of the vehicle body 3.

[0037] A position-controllable electric motor can be used as the drive motor 4. Examples of the position-controllable electric motor include a servo motor and a stepping motor.

[0038] The drive wheels 5 are rotationally driven by the drive motor 4 via a reverse input cutoff clutch 6. Each of the multiple drive units 2 can have one drive wheel 5 or multiple drive wheels 5. That is, each of the multiple drive units 2 can be configured so that one drive wheel 5 is rotationally driven by one drive motor 4. Alternatively, each of the multiple drive units 2 can be configured so that multiple drive wheels 5 are rotationally driven by one drive motor 4. In the electric vehicle 1a, each of the drive units 2a to 2d has one drive wheel 5.

[0039] The reverse input blocking clutch 6 is arranged in the torque transmission path from the drive motor 4 to the drive wheels 5, and transmits torque input from the drive motor 4 side to the drive wheels 5 side, but does not transmit torque reversely input from the drive wheels 5 side to the drive motor 4 side.

[0040] The drive device 2 may further include, as an optional component, a reducer 7 arranged in a torque transmission path from the drive motor 4 to the drive wheels 5. The reducer 7 reduces the speed of the output rotation of the drive motor 4 (increases the output torque) and transmits it to the drive wheels 5.

[0041] There are no particular limitations on the type of reducer 7. The reducer 7 can be configured, for example, as a planetary gear reducer, a parallel shaft gear reducer, a friction roller reducer, a multi-stage reducer or a stepless reducer whose reduction ratio is changeable, or the like.

[0042] The reducer 7 can be arranged in the torque transmission path from the drive motor 4 to the drive wheels 5, between the drive motor 4 and the reverse input cutoff clutch 6, or between the reverse input cutoff clutch 6 and the drive wheels 5. In the electric vehicle 1a, the reducer 7 is arranged between the reverse input cutoff clutch 6 and the drive wheels 5.

[0043] The plurality of drive units 2 can be controlled by an electronic control unit (ECU) (not shown) of the electric vehicle 1 or other control device. Specifically, the direction of travel, travel speed, and turning angle of the electric vehicle 1 can be controlled by adjusting the rotation speed and rotation direction of each of the drive wheels 5 of the plurality of drive units 2 using a control device of the electric vehicle 1.

[0044] <Structure of Reverse Input Disconnect Clutch> The reverse input disconnect clutch 6 includes a pressed member 8 , an input member 9 , an output member 10 , an engaging element 11 , and a biasing member 12 .

[0045] In this specification, unless otherwise specified, the axial direction, radial direction, and circumferential direction refer to the axial direction, radial direction, and circumferential direction of the reverse input cutoff clutch 6. In this example, the axial direction, radial direction, and circumferential direction of the reverse input cutoff clutch 6 coincide with the axial direction, radial direction, and circumferential direction of the input member 9, coincide with the axial direction, radial direction, and circumferential direction of the pressed surface 13, and coincide with the axial direction, radial direction, and circumferential direction of the output member 10. Furthermore, one axial side refers to the input member 9 side (the right side in FIG. 3 ), and the other axial side refers to the output member 10 side (the left side in FIG. 3 ).

[0046] The pressed member 8 has an inner peripheral surface to be pressed 13. The pressed member 8 is supported and fixed to a structural element that does not rotate even when the electric vehicle 1 is running, such as the chassis, body, or frame of the electric vehicle 1, or a member supported and fixed to any of these, or is provided integrally with the structural element and its rotation is restricted.

[0047] The pressed surface 13 constitutes a surface that comes into contact with the pressing surface 26 of the engaging element 11 when the engaging element 11 moves in a direction approaching the pressed surface 13. The pressed surface 13 has a circular ring shape when viewed from the axial direction, and in this example, has a cylindrical surface shape whose inner diameter does not change in the axial direction, although this is not limited to this.

[0048] The input-side engaging portion 14 of the input member 9 and the output-side engaging portion 21 of the output member 10 are disposed radially inside the pressed surface 13. The input-side engaging portion 14, the output-side engaging portion 21, and the engaging element 11 are capable of rotating around the central axis of the pressed surface 13 radially inside the pressed surface 13.

[0049] The input member 9 has an input side engaging portion 14 arranged radially inside the pressed surface 13 , arranged coaxially with the pressed surface 13 , and connected to the drive motor 4 side.

[0050] That is, the input member 9 is rotatably supported relative to the structural element and is rotationally driven by the drive motor 4. The input member 9 is connected, for example, to the output shaft of the drive motor 4, or to the output shaft of the reducer 7 when the reducer 7 is disposed between the drive motor 4 and the reverse input cutoff clutch 6. In this example, the input member 9 is connected to the output shaft of the drive motor 4.

[0051] The input-side engaging portion 14 is provided at a portion radially outwardly displaced from the rotation center O of the input member 9, and has a portion that engages with the input-side engaged portion 27 of the engager 11. The input-side engaging portion 14 is configured so that its radially inner surface 18 engages (contacts) with the radially inner surface 29 of the input-side engaged portion 27 as the input member 9 or the engager 11 rotates. In this example, the radially inner surface 18 of the input-side engaging portion 14 constitutes the portion that engages with the input-side engaged portion 27.

[0052] The input member 9 may have any structure as long as it has an input-side engaging portion 14 that can engage with the input-side engaged portion 27 of the engaging element 11, is connected to the drive motor 4, and can input rotational torque from the drive motor 4. In this example, the input member 9 has a base portion 15 and an input shaft portion 16 in addition to the input-side engaging portion 14.

[0053] The substrate portion 15 has an end face shape that is substantially circular when viewed in the axial direction.

[0054] The input shaft portion 16 protrudes axially from the center of one axial side surface of the base portion 15. The input shaft portion 16 is connected to the output shaft of the drive motor 4 or the reducer 7 so as to be able to transmit torque, or is configured integrally with the output shaft of the drive motor 4 or the reducer 7.

[0055] In this example, the input side engaging portion 14 protrudes toward the other axial side from a portion of the side surface of the base plate portion 15 that is radially outwardly spaced from the rotation center O.

[0056] The shape of the input-side engaging portion 14 is not limited as long as it is configured to engage with the input-side engaged portion 27 of the engaging element 11. The number of input-side engaging portions 14 is determined according to the number of engaging elements 11, and when the engaging element 11 is configured with a plurality of engaging elements 11, the input-side engaging portion 14 is also configured with a plurality of input-side engaging portions 14.

[0057] In this example, the engaging elements 11 are configured with two engaging elements 11. Therefore, the input side engaging portion 14 is configured with two input side engaging portions 14 to match the number of engaging elements 11. The two input side engaging portions 14 are arranged at two radially opposite positions on the other axial side surface of the base portion 15, and are spaced apart from each other in the radial direction of the input member 9. Furthermore, each input side engaging portion 14 has a shape that is symmetrical in the circumferential direction.

[0058] In this example, each input-side engaging portion 14 has an end face shape that is generally fan-shaped or trapezoidal, with its circumferential width increasing radially outward when viewed from the axial direction. The radially inner surfaces 18 of the two input-side engaging portions 14 are formed by flat surfaces that are parallel to each other, and the radially outer surface 19 of each input-side engaging portion 14 has the same cylindrical contour shape as the outer circumferential surface of the base portion 15. The two circumferential side surfaces 20 of each input-side engaging portion 14 are formed by flat surfaces that incline in directions that move away from each other radially outward.

[0059] The output member 10 has an output-side engaging portion 21 that is arranged radially inward of the input-side engaging portion 14 on the radially inner side of the pressed surface 13, and is arranged coaxially with the pressed surface 13 and connected to the drive wheel 5. In other words, the output member 10 is also arranged coaxially with the input member 9.

[0060] The output member 10 is rotatably supported by the pressed member 8 or the structural element. The output member 10 is connected, for example, to the drive shaft of the drive wheels 5, or, if a reducer 7 is disposed between the reverse input cutoff clutch 6 and the drive wheels 5, to the input shaft of the reducer 7. In other words, the output member 10 is configured to output rotational torque to the drive wheels 5 as it rotates. In this example, the output member 10 is connected to the input shaft of the reducer 7.

[0061] The output side engaging portion 21 is located radially inward of the input side engaging portion 14, and forms a portion that engages with the output side engaged portion 28 as the output member 10 or the engaging element 11 rotates, i.e., is positioned in a position where a portion of it can engage with the output side engaged portion 28 of the engaging element 11.

[0062] The structure of the output member 10 is arbitrary as long as it has an output side engaging portion 21 that can engage with the output side engaged portion 28 of the engager 11, is connected to the drive wheels 5, and can output rotational torque to the drive wheels 5. In this example, the output member 10 has an output shaft portion 22 in addition to the output side engaging portion 21.

[0063] The output shaft portion 22 is provided in a portion adjacent to the other axial side of the output side engagement portion 21, and is connected to the drive wheel 5 side, i.e., the input shaft of the drive wheel 5 or the input shaft of the reducer 7 so as to be able to transmit torque, or is formed integrally with the input shaft of the drive wheel 5 or the input shaft of the reducer 7.

[0064] The output side engaging portion 21 protrudes from the center of a side surface on one axial side of the output shaft portion 22 toward one axial side.

[0065] The shape of the output-side engaging portion 21 is not limited as long as it is configured to have a portion that engages with the output-side engaged portion 28. Furthermore, the number of portions of the output-side engaging portion 21 that engage with the output-side engaged portion 28 is determined according to the number of engaging elements 11, and when the engaging element 11 is configured with a plurality of engaging elements 11, the output-side engaging portion 21 is also configured with a plurality of engaging portions. Note that even when the engaging element is configured with a single engaging element, the output-side engaging portion can have a plurality of engaging portions.

[0066] In this example, the output side engaging portion 21 is configured to have portions that engage with two output side engaged portions 28 in accordance with the number of the engaging pieces 11 .

[0067] In this example, the output-side engaging portion 21 has a substantially rectangular or oval end face shape when viewed in the axial direction, and protrudes toward one axial side from the center of one axial end face of the output shaft portion 22. In other words, the distance from the rotation center O of the output member 10 to the outer circumferential surface of the output-side engaging portion 21, which is the portion that engages with the output-side engaged portion 28, is not constant in the circumferential direction. Therefore, the output-side engaging portion 21 has a cam function.

[0068] More specifically, the outer peripheral surface of the output-side engaging portion 21 is composed of two parallel flat surfaces 24 and two partially cylindrical convex surfaces 25. Therefore, the distance from the rotation center O of the output member 10 to the outer peripheral surface of the output-side engaging portion 21 is not constant in the circumferential direction. Each of the two convex surfaces 25 is composed of a partially cylindrical surface centered on the rotation center O of the output member 10.

[0069] The output-side engaging portion 21 is plane-symmetrical with respect to an imaginary plane that passes through the rotation center O of the output member 10 and is perpendicular to the flat surface 24. Furthermore, the output-side engaging portion 21 is plane-symmetrical with respect to an imaginary plane that passes through the rotation center O of the output member 10 and is parallel to the flat surface 24.

[0070] In this example, the output side engaging portion 21 is disposed between the output side engaged portions 28 of the two engaging elements 11 in the portion between the two input side engaging portions 14 .

[0071] The engaging element 11 has a pressing surface 26 facing the pressed surface 13, an input side engaged portion 27 that can engage with the input side engaging portion 14, and an output side engaged portion 28 that can engage with the output side engaging portion 21, and is arranged so that it can move radially, i.e., in a first direction which is the direction towards or away from the pressing surface 26 relative to the pressed surface 13.

[0072] The engaging element 11 may be constituted by one engaging element 11 or by two or more engaging elements 11.

[0073] In this example, the engaging element 11 is configured by two engaging elements 11. Each engaging element 11 has a function as an engaging element 11.

[0074] The radial direction with respect to the engaging element 11 is the direction of approach and distance of the pressing surface 26 relative to the pressed surface 13, and corresponds to the direction indicated by arrow A in Fig. 4. The width direction with respect to the engaging element 11 is the direction perpendicular to both the direction of approach and distance of the pressing surface 26 relative to the pressed surface 13 and the axial direction of the input member 9, and corresponds to the direction indicated by arrow B in Fig. 4. In this example, the radial direction with respect to the engaging element 11 is referred to as the first direction, and the width direction with respect to the engaging element 11 is referred to as the second direction.

[0075] The engaging element 11 has a substantially semicircular end face shape when viewed from the axial direction, and has a shape that is symmetrical with respect to the width direction.

[0076] The pressing surface 26 is provided on the radially outer surface of the engaging element 11 facing the pressed surface 13. The pressing surface 26 is configured as a partially cylindrical convex curved surface having a radius of curvature equal to or smaller than the radius of curvature of the pressed surface 13, preferably smaller than the radius of curvature of the pressed surface 13. The pressing surface 26 can be provided at one location (including the entirety) or at two or more locations on the radially outer surface of the engaging element 11. In this example, the pressing surface 26 is configured as two pressing surfaces 26 provided at two locations on the radially outer surface of the engaging element 11 that are spaced apart from each other in the circumferential direction. In this example, each pressing surface 26 is configured as a partially cylindrical convex curved surface having a radius of curvature smaller than the radius of curvature of the pressed surface 13.

[0077] In this example, the portion of the radially outer surface of the engaging element 11 that is circumferentially deviated from the two pressing surfaces 26 is located radially inward of an imaginary circle that is centered on the central axis of the input member 9 and that is tangent to the two pressing surfaces 26, when viewed from the axial direction. In other words, when the two pressing surfaces 26 are in contact with the pressed surface 13, the portion that is circumferentially deviated from the two pressing surfaces 26 does not contact the pressed surface 13.

[0078] The pressing surface 26 preferably has a surface property that has a higher coefficient of friction with the pressed surface 13 than the other parts of the engaging part 11. The pressing surface 26 can be formed integrally with the other parts of the engaging part 11, or can be formed by the surface of a friction material fixed to the other parts of the engaging part 11 by sticking, bonding, or the like.

[0079] The input-side engaged portion 27 has any structure that can engage with the input-side engaging portion 14 as the input member 9 or the engaging element 11 rotates, and is disposed at any position that can engage with the input-side engaging portion 14. The input-side engaging portion 27 can be configured, but is not limited to, a through-hole that penetrates the engaging element 11 in the axial direction and opens on both side surfaces of the engaging element 11, a hole that opens on one axial side of the engaging element 11, or a recess that extends radially inward from the radially outer surface of the engaging element 11. In this example, the input-side engaged portion 27 is provided in a radially intermediate portion of the widthwise center of the engaging element 11. More specifically, but not limited to, the input-side engaged portion 27 has a substantially arch-shaped outline when viewed axially, and is configured as a through-hole that penetrates axially through a radially intermediate portion at the widthwise center of the engaging element 11.

[0080] The input-side engaged portion 27 has a size that allows the input-side engaging portion 14 to be loosely inserted therein. Therefore, with the input-side engaging portion 14 inserted inside the input-side engaged portion 27, there is a gap between the input-side engaging portion 14 and the inner surface of the input-side engaged portion 27 in both the width direction and the radial direction of the engaging element 11. Therefore, the input-side engaging portion 14 can be displaced relative to the input-side engaged portion 27 in the rotational direction of the input member 9, and the input-side engaged portion 27 can be displaced relative to the input-side engaging portion 14 in the radial direction of the engaging element 11.

[0081] In this example, of the inner surfaces of the input side engaged portion 27, the radially inner surface 29 facing radially outward is composed of a flat surface perpendicular to the first direction, and the radially outer surface 30 of the inner surfaces of the input side engaged portion 27 facing radially inward is composed of a curved surface having an approximately arc-shaped contour when viewed from the axial direction.

[0082] The output-side engaged portion 28 has any structure that can engage with the output-side engaging portion 21 as the output member 10 or the engaging element 11 rotates, and is disposed at any position that can engage with the output-side engaging portion 21. The output-side engaging portion 28 can be configured by, but is not limited to, the radially inner surface of the engaging element 11, or a recess extending radially outward from the radially inner surface of the engaging element 11. In this example, the output-side engaged portion 28 is provided at the widthwise center of the radially inner surface of the engaging element 11.

[0083] In this example, the engaging element 11 has, on its radially inner surface, a flat surface portion 31 that is perpendicular to the radial direction of the engaging element 11, and has two protrusions 32 that protrude radially inward at two locations on the flat surface portion 31 in the width direction of the engaging element 11. The output-side engaged portion 28 is formed by a portion of the flat surface portion 31 that is located between the two protrusions 32 in the width direction. In this example, the width dimension of the output-side engaged portion 28, i.e., the distance between the two protrusions 32, is larger than the width dimension of the flat surface 24 of the output-side engaging portion 21.

[0084] In the reverse input cutoff clutch 6 of this example, the pressing surfaces 26 of the two engaging elements 11 are oriented radially opposite to each other, and the flat surface portions 31 are opposed to each other. Each engaging element 11 is arranged radially inward of the pressed member 8 so as to be movable in a first direction, which is the radial direction of each engaging element 11 and corresponds to the direction in which the pressing surfaces 26 move toward and away from the pressed surfaces 13. Furthermore, the two input-side engaging portions 14 of the input member 9 arranged on one axial side are axially inserted into the input-side engaged portions 27 of the two engaging elements 11, and the output-side engaging portion 21 of the output member 10 arranged on the other axial side is axially inserted between the output-side engaged portions 28 of the two engaging elements 11. In other words, the two engaging elements 11 are arranged so that the output-side engaging portion 21 is sandwiched from the radially outer side by the output-side engaged portions 28.

[0085] When the two engaging elements 11 are positioned radially inside the pressed member 8, the inner diameter dimension of the pressed member 8 and the radial dimension of the engaging elements 11 are regulated so that there is a gap in at least one of the areas between the pressed surface 13 and the two pressing surfaces 26, and between the tip surfaces of the two combinations of convex portions 32 formed by the two convex portions 32 of the two engaging elements facing each other.

[0086] The biasing member 12 elastically biases the engaging element 11 in a direction approaching the pressed surface 13. The biasing member 12 can be made of a spring such as a leaf spring, a coil spring, or a disc spring, or an elastic material such as rubber, elastomer, or synthetic resin. The number of biasing members 12 is not particularly limited and is determined appropriately depending on the number of engaging elements 11. The biasing member 12 can be arranged, without being limited thereto, between the radial inner surfaces of two engaging elements 11, or between an engaging element 11 and the output member 3, more specifically, between the output-side engaging portion 21 and the output-side engaged portion 28, or the like.

[0087] In this example, the biasing member 12 is composed of two biasing members 12 arranged at two positions in the width direction between the radially inner surfaces of the two engaging elements 11, and each biasing member 12 is composed of a compression coil spring. A protrusion 32 is inserted into the inside of each biasing member 12 at both ends in the extension direction. This prevents each biasing member 12 from falling out from between the two engaging elements 11.

[0088] In this example, the elastic force of the two biasing members 12 to restore its original shape elastically biases the two engaging elements 11 in a direction that brings them closer to the pressed surface 13. As a result, when no torque is applied to either the input member 9 or the output member 10, the pressing surfaces 26 of the two engaging elements 11 come into contact with the pressed surface 13.

[0089] When the biasing member 12 is disposed between the output member 10 and the engaging element 11, one or more biasing members 12 can be disposed between the output member 10 and the engaging element 11. For example, in this example, when the biasing member 12 is configured by a leaf spring, one biasing member 12 can be sandwiched between the output side engaging portion 21 and the output side engaged portion 28 for each engaging element 11.

[0090] By keeping the pressing surface 26 in contact with the pressed surface 13 by the biasing member 12 when no torque is applied to either the input member 9 or the output member 10, when a rotational torque is reversely input to the output member 10, it is possible to quickly increase the surface pressure at the contact portion between the pressing surface 26 and the pressed surface 13 without having to reduce the gap between the pressing surface 26 and the pressed surface 13. In other words, the reverse input cutoff clutch 6 can be quickly switched to the locked mode.

[0091] <Operation of Reverse Input Cutoff Clutch> When rotational torque is input to the input member 9 from the drive motor 4 side, the input side engaging portion 14 engages with the input side engaged portion 27, causing the engager 11 to move in a direction away from the pressed surface 13 and engaging the output side engaged portion 28 with the output side engaging portion 21. As a result, the reverse input cutoff clutch 6 transmits the rotational torque input to the input member 9 to the output member 10 (unlock mode).

[0092] Specifically, when a rotational torque is input from the drive motor 4 to the input member 9, the engaging element 11 moves in a direction away from the pressed surface 13, regardless of the rotational direction of the input member 9. More specifically, as shown in Fig. 5 , the input-side engaging portion 14 rotates inside the input-side engaged portion 27 in the rotational direction of the input member 9 (counterclockwise in the example of Fig. 5 ).

[0093] This reduces the gap between the radial inner surface 18 of the input side engaging portion 14 and the radial inner surface 29 of the input side engaged portion 27, and brings the radial inner surface 18 of the input side engaging portion 14, or the connection portion between the radial inner surface 18 and the circumferential side surface 20, into contact with the radial inner surface 29 of the input side engaged portion 27.

[0094] When the input member 9 rotates further from this state, the radially inner surface 18 of the input-side engaging portion 14 or the connecting portion presses the radially inner surface 29 of the input-side engaged portion 27 radially inward, causing the engaging element 11 to move in a direction away from the pressed surface 13. That is, the engaging element 11 moves radially inward based on engagement with the input member 9, and the output-side engaged portion 28 of the engaging element 11 engages with the output-side engaging portion 21 of the output member 10. In this example, the two engaging elements 11 move radially inward, that is, in a direction approaching each other, based on engagement with the input member 9, so that the radially inner surfaces of the two engaging elements 11 approach each other, and the output-side engaged portions 28 of the two engaging elements 11 clamp the output-side engaging portion 21 of the output member 10 from both radial sides.

[0095] In this example, the output member 10 is rotated so that the flat surface 24 of the output side engaging portion 21 is parallel to the flat surface portion 31 of the engaging element 11, and the output side engaging portion 21 and the output side engaged portion 28 of the engaging element 11 are engaged without rattle. Due to the engagement between the output side engaging portion 21 and the output side engaged portion 28, the rotational torque input to the input member 9 is transmitted to the output member 10 via the engaging element 11.

[0096] In contrast, when a rotational torque is reversely input from the drive wheel 5 side to the output member 10, the engaging element 11 moves in a direction approaching the pressed surface 13, causing the pressing surface 26 to frictionally engage with the pressed surface 13. As a result, the reverse input cutoff clutch 6 prevents the rotation of the output member 10 (lock mode).

[0097] Specifically, when a rotational torque is input in reverse from the input shaft of the reducer 7 to the output member 10, the engaging element 11 moves in a direction approaching the pressed surface 13, regardless of the rotational direction of the output member 10. More specifically, as shown in Fig. 6 , the output-side engaging portion 21 rotates radially inside the output-side engaged portion 28 of the engaging element 11 in the rotational direction of the output member 10 (clockwise in the example of Fig. 6 ). A part of the output-side engaging portion 21, in this example, a connection portion (corner portion) between the flat surface 24 and the convex curved surface 25 on the outer peripheral surface of the output-side engaging portion 21, presses the output-side engaged portion 28 radially outward, and the engaging element 11 moves in a direction approaching the pressed surface 13.

[0098] That is, based on the engagement with the output member 10, the engaging element 11 moves radially outward, i.e., in a direction away from each other, and the pressing surface 26 of the engaging element 11 comes into contact with the pressed surface 13 and frictionally engages with the pressed surface 13. As a result, the engaging element 11 is stretched (sandwiched) between the output-side engaging portion 21 and the pressed member 8, and the rotational torque input in reverse to the output member 10 is completely blocked and is not transmitted to the input member 9.

[0099] In the electric vehicle 1 of this example, in each drive unit 2, a reverse input cutoff clutch 6 is arranged in the torque transmission path from the drive motor 4 to the drive wheels 5, and is configured to function to transmit torque input from the drive motor 4 side to the drive wheels 5 side, but not to transmit torque reversely input from the drive wheels 5 side to the drive motor 4 side.

[0100] In order to enable the above operation, the size of the gap between each component of the reverse input cutoff clutch 6 is adjusted. In particular, when the pressing surface 26 of the engaging element 11 is in contact with the pressed surface 13, a gap is set to exist between the radially inner surface 18 of the input-side engaging portion 14 and the radially inner surface 29 of the input-side engaged portion 27.

[0101] The dimensions and shapes of each part of the pressed member 8, the input member 9, the output member 10, and the two engaging elements 11 are not limited to these, but can be regulated so as to satisfy the following relationships, for example.

[0102] As the output member 10 rotates in a predetermined direction (for example, the clockwise direction in FIG. 4), the two pressing surfaces 26 are pressed against the pressed surface 13, and as the input member 9 rotates in a direction opposite to the predetermined direction (for example, the counterclockwise direction in FIG. 4), the input side engaging portion 14 and the input side engaged portion 27 are engaged (a part of the input side engaging portion 14 is in contact with the input side engaged portion 27). In this state, the contact portion P ｉｎ and a first distance D which is a distance in the second direction between the center of rotation O of the input member 9 and the １ For example, the contact point P between the output side engaging portion 21 and the output side engaged portion 28 can be set arbitrarily. ｏｕｔcan be made smaller than the second distance D2 in the second direction from the rotation center O of the output member 10 (D １ <D ２ ). Alternatively, the first distance D １ The second distance D ２ can be made larger than (D １ >D ２ In this example, as shown in FIG. １ The second distance D ２ (D １ <D ２ ).

[0103] In addition, when a rotational torque is input in reverse to the output member 10 and the two pressing surfaces 26 of the engaging element 11 are in contact with the pressed surface 13, the contact portion C between the output side engaging portion 21 and the output side engaged portion 28 １ and one of the two pressing surfaces 26 (the position of the contact portion C １ ) the contact portion C between the pressing surface 26 and the pressed surface 13 ２ Regarding the relationship between the contact point C1 and the imaginary line L connecting the contact point C1 and the rotation center O of the output member 10, the contact point C1 can be positioned closer to the rotation center O of the output member 10 in the first direction than the imaginary line L (below the imaginary line L in FIG. 6), or can be positioned farther from the rotation center O of the output member than the imaginary line L (above the imaginary line L in FIG. 6). In this example, as shown in FIG. 6, the contact point C1 can be positioned closer to the rotation center O of the output member 10 than the imaginary line L (above the imaginary line L in FIG. 6). １ is positioned closer to the rotation center of the output member than the imaginary line L.

[0104] In this example, the first distance D １ and the second distance D ２ and the contact point C with the virtual line L １ The positional relationship of the first distance D １ The second distance D ２ (D １ <D ２ ), and contact portion C １ is positioned closer to the rotation center of the output member 3 than the virtual straight line L. Alternatively, for example, the first distance D １ The second distance D ２ is larger than (D １>D ２ ) and contact portion C １ is positioned closer to the rotation center of the output member 3 than the virtual line L, or the first distance D １ The second distance D ２ (D １ <D ２ ), and contact portion C １ is positioned on the side farther from the rotation center of the output member 3 than the virtual line L, or the first distance D １ The second distance D ２ is larger than (D １ >D ２ ) and contact portion C １ can be positioned farther from the rotation center of the output member 3 than the virtual straight line L.

[0105] <Control when electric vehicle is stopped> Hereinafter, control for reliably locking the rotation of the drive wheels 5 of the multiple drive units 2 when stopping the electric vehicle 1 of this example, regardless of the stopping state of the electric vehicle 1, will be described with reference to FIG. 7 which shows an example of control.

[0106] In the electric vehicle 1 of this example, when the vehicle is stopped, for example, immediately after the rotation speeds of all the drive wheels 5 of the multiple drive units 2 decrease and fall below a predetermined threshold value Rs, the drive motor 4 of at least one of the multiple drive units 2 outputs a torque sufficient to maintain the stopped position, and the output torque of the drive motor 4 of the remaining drive units 2 of the multiple drive units 2 is set to zero, thereby bringing the pressing surface 26 of the engaging element 11 of the reverse input cut-off clutch 6 of the remaining drive units 2 into contact with the pressed surface 13, and then the output torque of the drive motor 4 of one or more drive units 2 of the at least one drive unit 2 (drive unit 2 that is outputting a torque sufficient to maintain the stopped position using the drive motor 4) is set to zero, thereby bringing the pressing surface 26 of the engaging element 11 of the reverse input cut-off clutch 6 of the one or more drive units 2 into contact with the pressed surface 13.

[0107] The threshold value Rs of the rotation speed of the drive wheels 5, which is the criterion for determining whether to start control when the electric vehicle 1 is stopped, can be set to a value at which the electric vehicle 1 is considered to be substantially stopped. For example, but not limited to, the threshold value Rs can be set to the rotation speed when the traveling speed of the electric vehicle 1 is 1 km / h or less. The threshold value Rs can also be set to 0.

[0108] When it is determined based on conditions such as output signals from various sensors that the rotation speeds of all drive wheels 5 of the plurality of drive units 2 have fallen below threshold value Rs, the drive motor 4 of at least one of the plurality of drive units 2 outputs torque sufficient to maintain the parked position. By maintaining the electric vehicle 1 in the parked position, the drive wheels 5 of the remaining drive units 2 of the plurality of drive units 2 (drive units 2 that are not outputting torque sufficient to maintain the parked position from their drive motors 4) are also prevented from rotating, and the output torque of the drive motors 4 of the remaining drive units 2 is set to zero (power supply to the drive motors 4 is stopped). This causes the biasing force of the biasing member 12 to bring the pressing surface 26 of the engaging element 11 of the reverse input cutoff clutch 6 of the remaining drive unit 2 into contact with the pressed surface 13. This enables the reverse input cutoff clutch 6 of the remaining drive unit 2 to be quickly switched to the locked mode.

[0109] After the pressing surfaces 26 of the engaging elements 11 of the reverse input cutoff clutches 6 of the remaining drive units 2 are brought into contact with the pressed surface 13, the output torque of the drive motors 4 of one or more drive units 2 of the at least one drive unit 2 (drive units 2 in a state in which torque is being output by the drive motor 4) is set to zero, whereby the biasing force of the biasing member 12 causes the pressing surfaces 26 of the engaging elements 11 of the reverse input cutoff clutches 6 of the one or more drive units 2 to come into contact with the pressed surface 13. This brings the reverse input cutoff clutches 6 of the one or more drive units 2 into a state in which they can be quickly switched to the locked mode.

[0110] In this case, the output torque of the drive motors 4 of the remaining drive units 2 can be set to 0 one by one or simultaneously, so that the pressing surface 26 of the engaging element 11 of the reverse input cut-off clutch 6 can be brought into contact with the pressed surface 13.

[0111] Furthermore, by setting the output torque of all of the remaining drive units 2 to zero, the pressing surfaces 26 of the engaging elements 11 of all of the reverse input disconnection clutches 6 of the remaining drive units 2 are brought into contact with the pressed surfaces 13, and then the output torque of the drive motor 4 of at least one drive unit 2 (the drive unit 2 that is outputting torque sufficient to maintain the stopped position using the drive motor 4) can be set to zero one by one or simultaneously, thereby bringing the pressing surfaces 25 of the engaging elements 11 of the reverse input disconnection clutch 6 into contact with the pressed surfaces 13.

[0112] In the electric vehicle (automated guided vehicle) 1a to which this example is applied, first, when the rotation speeds of all drive wheels 5 of four drive units 2a to 2d fall below threshold value Rs, immediately thereafter, while the drive motors 4 of three of the four drive units 2a, 2b, and 2d output torque sufficient to maintain the parked position, the output torque of the drive motor 4 of the remaining drive unit 2c is set to 0, thereby bringing the pressing surface 26 of the engaging element 11 of the reverse input cut-off clutch 6 of the remaining drive unit 2c into contact with the pressed surface 13.

[0113] Specifically, torque sufficient to maintain the vehicle at a stopped position is output (S1-1) by the drive motors 4 of the front left drive unit 2a, the front right drive unit 2b, and the rear right drive unit 2d, which correspond to at least one of the four drive units 2a to 2d supported at four positions on the front, rear, left, and right sides of the vehicle body 3. This prevents the drive wheels 5 of the drive units 2a, 2b, and 2d from rotating.

[0114] For drive units 2a, 2b, and 2d, the drive motor 4 outputs a torque sufficient to prevent rotation of the drive wheels 5, thereby maintaining the parked position of the electric vehicle 1. This also prevents rotation of the drive wheels 5 of the rear left drive unit 2c, which corresponds to the remaining drive unit 2 of the four drive units 2a to 2d (the drive unit 2 that is not outputting a torque sufficient to maintain the parked position via the drive motor 4). In this state, the output torque of the drive motor 4 of drive unit 2c is set to zero (S1-2). When the output torque of the drive motor 4 of drive unit 2c is set to zero, the engaging element 11 of the reverse input cutoff clutch 6 of drive unit 2c moves toward the pressed surface 13 due to the biasing force of the biasing member 12, bringing the pressing surface 26 into contact with the pressed surface 13. This allows the reverse input cutoff clutch 6 of drive unit 2c to be quickly switched to the locked mode (S1-3).

[0115] Next, of the three drive units 2a, 2b, and 2d, the two front drive units 2a and 2b continue to output torque sufficient to maintain the stopped position using the drive motor 4 (S2-1). As a result, the rotation of the drive wheels 5 of the two front drive units 2a and 2b continues to be prevented.

[0116] For the left rear drive unit 2c, the reverse input cutoff clutch 6 is maintained in a state in which it can be quickly switched to the lock mode, or the reverse input cutoff clutch 6 is quickly switched to the lock mode. That is, for the left rear drive unit 2, when the drive wheels 5 attempt to rotate, if a rotational torque is reversely input to the output member 10 of the reverse input cutoff clutch 6, the surface pressure between the pressing surface 26 and the pressed surface 13 quickly increases, and the reverse input cutoff clutch 6 of the drive unit 2c quickly switches to the lock mode. As a result, for the drive unit 2c, the rotation of the drive wheels 5 connected to the output member 10 via the reducer 7 so as to be able to transmit torque is prevented.

[0117] For the two front drive units 2a, 2b, the drive motor 4 outputs a torque sufficient to prevent rotation of the drive wheels 5, and for the left rear drive unit 2c, the reverse input cutoff clutch 6 is maintained in a state in which it can be quickly switched to lock mode, and is switched to lock mode as necessary, thereby maintaining the parked position of the electric vehicle 1. This also prevents rotation of the drive wheels 5 of the right rear drive unit 2d, which corresponds to one or more of the at least one drive unit 2. In this state, the output torque of the drive motor 4 of the drive unit 2d is set to zero (S2-2). When the output torque of the drive motor 4 of the drive unit 2d is set to zero, the engaging element 11 of the reverse input cutoff clutch 6 of the drive unit 2d moves toward the pressed surface 13 due to the biasing force of the biasing member 12, bringing the pressing surface 26 into contact with the pressed surface 13. This allows the reverse input cutoff clutch 6 of the drive unit 2d to be quickly switched to lock mode (S2-3).

[0118] Next, of the two front drive units 2a, 2b, the right front drive unit 2b continues to output torque by the drive motor 4 sufficient to maintain the stopped position (S3-1). As a result, the rotation of the drive wheels 5 of the right front drive unit 2b continues to be prevented.

[0119] In this state, the two rear drive units 2c and 2d are also ready to switch quickly to the lock mode or have already switched to the lock mode, thereby preventing the rotation of the drive wheels 5 of the two rear drive units 2c and 2d.

[0120] For the right front drive unit 2b, the drive motor 4 outputs a torque sufficient to prevent rotation of the drive wheels 5, and for the two rear drive units 2c and 2d, the reverse input cutoff clutch 6 is switched to lock mode as necessary to maintain the parked position of the electric vehicle 1, thereby preventing rotation of the drive wheels 5 of the left front drive unit 2a, which corresponds to one or more of the at least one drive unit 2. In this state, the output torque of the drive motor 4 of the drive unit 2a is set to zero (S3-2). When the output torque of the drive motor 4 of the drive unit 2a is set to zero, the engaging element 11 of the reverse input cutoff clutch 6 of the drive unit 2a moves toward the pressed surface 13 due to the biasing force of the biasing member 12, bringing the pressing surface 26 into contact with the pressed surface 13. This allows the reverse input cutoff clutch 6 of the drive unit 2a to be quickly switched to the lock mode (S3-3).

[0121] Next, the output torque of the drive motor 4 of the right front drive unit 2b, which corresponds to one or more drive units 2 of the at least one drive unit 2, is set to 0 (S4-1). As a result, the engaging element 11 of the reverse input cutoff clutch 6 of the drive unit 2b moves in a direction approaching the pressed surface 13 due to the biasing force of the biasing member 12, and the pressing surface 26 comes into contact with the pressed surface 13. In other words, the reverse input cutoff clutch 6 of the drive unit 2b is brought into a state in which it can be quickly switched to the lock mode (S4-2).

[0122] When the output torque of the drive motor 4 of the right front drive unit 2b is set to 0, the left front drive unit 2a, the left rear drive unit 2c, and the right rear drive unit 2d are also ready to switch to the lock mode immediately or have already switched to the lock mode. Therefore, the operation of setting the output torque of the drive motor 4 of the drive unit 2b to 0 can be performed while the electric vehicle 1 is maintained in a parked position and while the drive wheels 5 of the right front drive unit 2d are not rotating.

[0123] The magnitude of the torque output by the drive motors 4 of the drive units 2a, 2b, and 2d to maintain the parked position is not particularly limited and can be determined arbitrarily as long as it can maintain the parked position of the electric vehicle 1. For example, the magnitude of the torque can be calculated based on the load amount obtained by a weight sensor, the inclination angle of the road surface obtained by an inclination sensor, etc. Alternatively, the magnitude of the torque can be a predetermined value determined in advance by experiment, calculation, etc. based on the number of drive units 2, or a predetermined value set in advance regardless of the number of drive units 2.

[0124] According to the electric vehicle 1 (1a) of this example, when stopping, for each of the plurality of drive units 2 (2a-2d), the engaging element 11 of the reverse input cutoff clutch 6 can be moved toward the pressed surface 13 by the biasing force of the biasing member 12, thereby bringing the pressing surface 26 into contact with the pressed surface 13, while the drive wheels 5 connected to the output member 10 of the reverse input cutoff clutch 6 so as to be capable of transmitting torque directly or via the reducer 7 are prevented from rotating. Therefore, when the electric vehicle 1 (1a) is stopped, it is possible to reliably prevent the occurrence of a phenomenon in which the rotational torque reversely input from the drive wheels 5 to the output member 10 is transmitted to the input member 9 via the engaging element 11 before the pressing surface 26 of the engaging element 11 frictionally engages with the pressed surface 13. In other words, according to the electric vehicle 1 (1a) of this example, the rotation of the drive wheels 5 can be reliably locked when stopping.

[0125] In the electric vehicle 1 of this example, the order in which the drive units 2 set the output torque of the drive motors 4 to 0 is not limited to this example and can be any order. Also, in the electric vehicle 1 of this example, the output torque of the drive motors 4 can be set to 0 simultaneously for multiple drive units 2 depending on the parking position of the vehicle.

[0126] For example, in a first modified example of the first example shown in FIG. 8 , in an electric vehicle 1 a to which this example is applied, first, of the four drive units 2 a to 2 d, the drive motors 4 of the front left drive unit 2 a, the front right drive unit 2 b, and the rear right drive unit 2 d output torque sufficient to maintain the vehicle in a stopped position (S1-1), and in this state, the output torque of the drive motor 4 of the rear left drive unit 2 c is set to 0 (S1-2), and its reverse input cut-off clutch 6 is brought into a state in which it can be quickly switched to the lock mode (S1-3).

[0127] Next, for the left front drive unit 2a and the right rear drive unit 2d, the drive motor 4 continues to output torque sufficient to maintain the stopped position (S2-1). In this state, the output torque of the drive motor 4 of the right front drive unit 2b, which is located diagonally opposite the left rear drive unit 2c whose output torque of the drive motor 4 was just set to zero, is set to zero (S2-2), and the reverse input cutoff clutch 6 is set to a state in which it can be quickly switched to the lock mode (S2-3).

[0128] Furthermore, for the right rear drive unit 2d, the drive motor 4 continues to output torque sufficient to maintain the stopped position (S3-1). In this state, the output torque of the drive motor 4 of the left front drive unit 2a is set to 0 (S3-2), and its reverse input cutoff clutch 6 is brought into a state in which it can be quickly switched to the lock mode (S3-3).

[0129] Finally, the output torque of the drive motor 4 of the right rear drive unit 2d, which is located diagonally opposite the left front drive unit 2a whose output torque of the drive motor 4 was just set to 0, is set to 0 (S4-1). As a result, the reverse input cutoff clutch 6 of the right rear drive unit 2d is brought into a state in which it can be quickly switched to the lock mode (S4-2).

[0130] 9 , in an electric vehicle 1a, as in the first example, the output torque of the drive motors 4 of the four drive units 2a-2d is set to zero in the order of the left rear drive unit 2c and the right rear drive unit 2d, thereby enabling the reverse input cutoff clutches 6 of these drive units to be quickly switched to the locked mode (S1-1 to S2-3). In the second example, the output torque of the drive motors 4 of the two front drive units 2a, 2b is then simultaneously set to zero (S3-1). As a result, the reverse input cutoff clutches 6 of the two front drive units 2a, 2b are simultaneously enabled to be quickly switched to the locked mode (S3-2).

[0131] 10, in an electric vehicle 1a, of the four drive units 2a to 2d, the drive motors 4 of the two front drive units 2a and 2b output torque sufficient to maintain the vehicle in a parked position (S1-1), while simultaneously setting the output torque of the drive motors 4 of the two rear drive units 2c and 2d to zero (S1-2). As a result, the reverse input cutoff clutches 6 of the two rear drive units 2c and 2d are simultaneously placed in a state in which they can be quickly switched to the lock mode (S1-3).

[0132] Next, the output torque of the drive motors 4 of the two front drive units 2a, 2b is simultaneously set to 0 (S3-1), thereby simultaneously bringing the two front drive units 2a, 2b into a state in which they can be quickly switched to the lock mode (S3-2).

[0133] Second Example A second example of the embodiment of the present disclosure will be described with reference to FIGS. 11 and 12. FIG.

[0134] In the electric vehicle 1 of this example, the order of the drive units 2 that set the output torque of the drive motor 4 to zero can be changed depending on the parking situation. In other words, the order of the drive units 2 that set at least one drive unit 2 (the drive unit 2 that outputs enough torque to maintain the parking position using the drive motor 4) can be changed as appropriate. The order of the drive units 2 that set the output torque of the drive motor 4 to zero can be changed as appropriate.

[0135] More specifically, in the electric vehicle 1 of this example, when the electric vehicle 1 is parked on a slope, at least one of the plurality of drive units 2 (the drive unit 2 that outputs torque sufficient to maintain the parked position through the drive motor 4) is the upper drive unit 2 whose drive wheels 5 are in contact with the upper part of the slope, and the remaining drive units 2 (the drive units 2 that do not output torque sufficient to maintain the parked position through the drive motor 4) are the lower drive units 2 whose drive wheels 5 are in contact with the lower part of the slope. In other words, when the electric vehicle 1 is parked on a slope, while the upper drive unit 2 outputs torque sufficient to maintain the parked position, the output torque of the drive motor 4 of the lower drive unit 2 is set to zero, thereby bringing the pressing surface 26 of the engaging element 11 of the reverse input cutoff clutch 6 of the lower drive unit 2 into contact with the pressed surface 13, and then the output torque of the drive motor 4 of the upper drive unit 2 is set to zero, bringing the pressing surface 26 of the engaging element 11 of the upper drive unit into contact with the pressed surface 13. The condition of the slope (the tilt direction and tilt angle of the electric vehicle 1) can be acquired by, for example, an inclination sensor.

[0136] When the upper drive unit 2 is composed of multiple drive units 2, by setting the output torque of the drive motor 4 of the lower drive unit 2 to zero, the pressing surface 26 of the engaging element 11 of the reverse input cut-off clutch 6 of the lower drive unit 2 is brought into contact with the pressed surface 13, and then the output torque of the drive motors 4 of the multiple upper drive units 2 can be set to zero one by one in sequence or simultaneously.

[0137] In the electric vehicle 1b to which this example is applied, the order in which the drive units 2a to 2d are configured to set the output torque of the drive motor 4 to zero is changed according to the stopping situation, as follows: Specifically, when the electric vehicle 1b is stopped on a slope, the drive motor 4 of the upper drive unit 2 whose drive wheels 5 are in contact with the upper part of the slope outputs a torque sufficient to maintain the stopped position, while the output torque of the drive motor of the lower drive unit 2 whose drive wheels 5 are in contact with the lower part of the slope is set to zero, so that the reverse input cutoff clutch 6 of the lower drive unit 2 can be quickly switched to the lock mode.

[0138] The electric vehicle 1b is equipped with four drive units 2a to 2d supported at four locations on the front, rear, left, and right sides of the vehicle body 3, and an inclination sensor 33 that measures the tilt direction and tilt angle of the electric vehicle 1b. The inclination sensor 33 is attached to the vehicle body 3.

[0139] When the electric vehicle 1b is stopped and the rotation speeds of all the drive wheels 5 of the drive units 2a to 2d become equal to or less than the threshold value Rs, the tilt direction and tilt angle of the electric vehicle 1b are measured by the tilt sensor 33, and it is determined which part of the vehicle body 3 is positioned on the upper side based on the measurement results of the tilt sensor 33 (S1).

[0140] For example, assume that the front side of the vehicle body 3 is located on the upper side and the rear side of the vehicle body 3 is located on the lower side. In this case, the upper drive unit 2 is composed of a left front drive unit 2a and a right front drive unit 2b, and the lower drive unit 2 is composed of a left rear drive unit 2c and a right rear drive unit 2d.

[0141] After the determination, for the two rear drive units 2c, 2d corresponding to the lower drive units 2, the output torque of the drive motor 4 is set to 0 in the order of the left rear drive unit 2c and the right rear drive unit 2d, thereby enabling their reverse input cutoff clutches 6 to be quickly switched to the locked mode (S2-1 to S3-3). After that, for the two front drive units 2a, 2b corresponding to the upper drive units 2, the output torque of the drive motor 4 is set to 0 in the order of the left front drive unit 2a and the right front drive unit 2b, thereby enabling their reverse input cutoff clutches 6 to be quickly switched to the locked mode (S4-1 to S5-2).

[0142] However, there is no particular limitation as to which of the left and right drive units 2a to 2d the output torque of the drive motor 4 is set to zero, and the opposite of this example is also possible. Furthermore, the output torque of the drive motor 4 of multiple drive units can be set to zero simultaneously. That is, while the drive motor 4 of the two upper drive units 2 (e.g., the front drive units 2a and 2b) outputs a torque sufficient to maintain the vehicle in a stopped position, the output torque of the drive motor 4 of the two lower drive units 2 (e.g., the rear drive units 2c and 2d) can be set to zero simultaneously. Additionally or alternatively, the reverse input cutoff clutches 6 of the two lower drive units 2 can be set to a state in which they can be quickly switched to the lock mode, and then the output torque of the drive motors 4 of the two upper drive units 2 can be set to zero simultaneously.

[0143] When the vehicle is stopped with the rear side of the vehicle body 3 positioned on the upper side and the front side of the vehicle body 3 positioned on the lower side, the output torque of the drive motors 4 of the two front drive units 2a, 2b is set to 0 one by one in sequence or simultaneously, while the drive motors 4 of at least the two rear drive units 2c, 2d are outputting torque sufficient to maintain the stopped position. After that, the output torque of the drive motors 4 of the two rear drive units 2c, 2d is set to 0 one by one in sequence or simultaneously.

[0144] The electric vehicle 1 of this example can also be applied when parked on a slope that slopes in the left-right direction. When the electric vehicle 1 is parked with one side (left or right) of the vehicle body 3 positioned at the top and the other side (right or left) of the vehicle body 3 positioned at the bottom, the drive motors 4 of at least two drive units 2 on one side output torque sufficient to maintain the parked position, and the output torques of the drive motors 4 of two drive units 2 on the other side are set to zero one by one or simultaneously. Then, the output torques of the drive motors 4 of two drive units 2 on one side are set to zero one by one or simultaneously.

[0145] Furthermore, the electric vehicle 1 of this embodiment can also be used when parked on a slope that is inclined both in the longitudinal and lateral directions. In this case, the output torque of the drive motor 4 can be reduced to zero, starting from the drive unit 2 located at the top.

[0146] In the electric vehicles 1 of this example, including the electric vehicle 1b, when parked on a slope, it is possible to effectively prevent the electric vehicle 1 from rotating about its center of gravity due to the yaw moment acting on the electric vehicle 1. The other configurations and effects of the second example are the same as those of the first example.

[0147] Third Example A third example of the embodiment of the present disclosure will be described with reference to FIGS. 13 and 14. FIG.

[0148] In the electric vehicle 1 of this example, the number of drive units 2 is changed from that of the electric vehicle 1 of the first example. The electric vehicle 1 of this example includes two drive units 2, each connected to one drive wheel 5.

[0149] For example, an electric vehicle 1c to which this example is applied includes two drive units 2a and 2b. The two drive units 2a and 2b are supported at two locations, one on the left and one on the right, of a vehicle body 3. Each of the drive units 2a and 2b is configured to rotate one drive wheel 5 using one drive motor 4 via a reverse input cutoff clutch 6 and a reducer 7.

[0150] When the electric vehicle 1c starts to stop, first, the drive motor 4 of one drive unit 2a, which corresponds to at least one of the plurality of drive units 2 of the two drive units 2a, 2b, outputs a torque sufficient to maintain the stopped position (S1-1), and then the output torque of the drive motor 4 of the other drive unit 2b, which corresponds to the other of the plurality of drive units 2, is set to 0 (S1-2).This allows the reverse input cutoff clutch 6 of the other drive unit 2b to be quickly switched to the lock mode (S1-3).

[0151] Next, the output torque of the drive motor 4 of one drive unit 2a, which corresponds to one or more drive units 2 among the at least one drive unit 2, is set to 0 (S2-1). As a result, the reverse input cutoff clutch 6 of the one drive unit 2a is brought into a state in which it can be quickly switched to the lock mode (S2-2).

[0152] The order in which the output torque of the drive motor 4 of the drive devices 2a and 2b is set to 0 can be reversed.

[0153] The electric vehicle 1 of this example may be provided with non-drive wheels that are not driven to rotate by the drive motor.

[0154] For example, in a first modification of the second example shown in Fig. 15(A), an electric vehicle 1c includes a non-driven wheel 34 supported via a fork in the center of the vehicle body 3 in the left-right direction, at a position offset in the front-rear direction from the portion where the two drive units 2a, 2b are supported. The fork is a member for supporting the non-driven wheel 34 and includes a top mount supported on the vehicle body 3 so as to be rotatable about a pivot shaft extending in the up-down direction, and two blades bent downward from both sides of the top mount in the width direction. The non-driven wheel 34 is disposed to extend horizontally and is supported so as to be rotatable about an axis whose ends are supported by the two blades.

[0155] 15(B), an electric vehicle 1c includes two non-drive wheels 34a that are supported for rotation about axles 35 that extend in the left-right direction. The axles 35 are supported on a portion of the vehicle body 3 that is offset in the front-rear direction from the portion where the two drive units 2a, 2b are supported.

[0156] The other configurations and effects of the third example are the same as those of the first example.

[0157] Fourth Example A fourth example of the embodiment of the present disclosure will be described with reference to FIGS. 16 and 17. FIG.

[0158] The electric vehicle 1 of this example further includes, in addition to the drive wheels 5, at least one steering wheel 36 that can be steered about a turning axis that extends in the vertical direction, and the multiple drive units 2 are configured with two drive units 2. When the electric vehicle 1 of this example stops, a steering angle is applied to the at least one steering wheel 36 in a direction that suppresses rotation due to yaw moment. Any means can be used to apply the steering angle, and a steering motor 37, for example, can be used. The at least one steering wheel 36 can be configured with a single steering wheel 36, but the electric vehicle 1 of this example can also be configured with a configuration that includes multiple steering wheels 36.

[0159] For example, in an electric vehicle 1d to which this example is applied, two drive units 2a and 2b are supported at two locations on the left and right sides of the vehicle body 3.

[0160] In the electric vehicle 1d, at least one steering wheel 36 is configured as a single steering wheel 36 supported in the center in the left-right direction at a portion of the vehicle body 3 that is offset in the front-rear direction from the portion where the two drive units 2a, 2b are supported. The steering wheel 36 is configured to be able to impart a desired steering angle based on driving a steering motor 37.

[0161] When the electric vehicle 1d starts to stop, first, a steering angle is applied to the steering wheels 36 in a direction that suppresses rotation of the electric vehicle 1d due to the yaw moment (S1-1). Specifically, the steering wheels 36 are turned in a direction other than the direction of a tangent T to the turning axis of an imaginary circle C that is centered on the center of gravity G of the electric vehicle 1d and passes through the turning axis. In the electric vehicle 1d, the steering wheels 36 are turned in the direction of a normal N to the turning axis of the imaginary circle C.

[0162] After applying a steering angle to the steering wheels 36 in a direction that suppresses rotation due to the yaw moment, the procedure for setting the output torque of the drive motors 4 of the two drive units 2a, 2b to zero is basically the same as the procedure in the electric vehicle 1c to which the third example is applied.

[0163] That is, while the drive motor 4 of one of the two drive units 2a, 2b is outputting a torque sufficient to maintain the parked position, the output torque of the drive motor 4 of the other drive unit 2b is set to 0 to enable quick switching to the lock mode (S2-1 to S2-3). After that, the output torque of the drive motor 4 of the other drive unit 2a is set to 0 to enable quick switching to the lock mode (S3-1 to S3-2). However, the order in which the output torque of the drive motor 4 of the drive units 2a, 2b is set to 0 can be reversed.

[0164] According to the electric vehicles 1 of this example, including the electric vehicle 1d, it is possible to effectively prevent the electric vehicle 1c from rotating about the center of gravity G due to the yaw moment acting on the electric vehicle 1. The other configurations and effects of the fourth example are similar to those of the first and third examples.

[0165] Fifth Example A fifth example of the embodiment of the present disclosure will be described with reference to FIGS. 18 and 19. FIG.

[0166] In the electric vehicle 1 of this example, the number of drive units 2 is changed from that of the electric vehicle 1 of the first example. The electric vehicle 1 of this example is equipped with a plurality of drive units 2, and each drive unit 2 is connected to a plurality of drive wheels 5. In this example, the basic control of the electric vehicle 1 when stopped is the same as in the first example.

[0167] For example, an electric vehicle 1e to which this example is applied includes two drive units 2e and 2f. The two drive units 2e and 2f are provided at two locations, one at the front and one at the rear, of a vehicle body 3. Each of the drive units 2e and 2f is configured to rotate two drive wheels 5a using one drive motor 4.

[0168] The two drive wheels 5a extend in the left-right direction and are connected to both axial ends of a drive shaft 38 that is rotatably supported on the vehicle body 3 so as to be able to transmit torque.

[0169] The drive shaft 38 is configured to be rotatably driven by the drive motor 4 via the reverse input cutoff clutch 6 and the reducer 7. That is, each of the drive units 2e and 2f includes the reverse input cutoff clutch 6 and the reducer 7 in the torque transmission path from the drive motor 4 to the drive shaft 38.

[0170] When the electric vehicle 1e starts to stop, first, the drive motor 4 of one of the two drive units 2e, 2f outputs a torque sufficient to maintain the parked position, and the output torque of the drive motor 4 of the other drive unit 2f is set to zero to enable quick switching to the lock mode (S1-1 to S1-3). After that, the output torque of the drive motor 4 of one of the drive units 2e is set to zero to enable quick switching to the lock mode (S2-1 to S2-2). However, the order in which the output torque of the drive motors 4 of the drive units 2e, 2f is set to zero can be reversed.

[0171] The other configurations and effects of the fifth example are the same as those of the first example.

[0172] The first to fifth examples of the embodiment of the present disclosure and their modified examples can be implemented in any suitable combination as long as no contradiction occurs.

[0173] REFERENCE SIGNS LIST 1, 1a, 1b, 1c, 1d, 1e Electric vehicle 2a, 2b, 2c, 2d, 2e, 2f Drive device 3 Vehicle body 4 Drive motor 5, 5a Drive wheel 6 Reverse input cut-off clutch 7 Reducer 8 Pressed member 9 Input member 10 Output member 11 Engager 12 Urging member 13 Pressed surface 14 Input side engaging portion 15 Base plate portion 16 Input shaft portion 18 Radially inner surface 19 Radially outer surface 20 Circumferential side surface 21 Output side engaging portion 22 Output shaft portion 24 Flat surface 25 Convex curved surface 26 Pressing surface 27 Input side engaged portion 28 Output side engaged portion 29 Radially inner surface 30 Radially outer surface 31 Flat surface portion 32 Convex portion 33 Inclination sensor 34, 34a Non-driving wheel 35 Axle 36 Steering wheel 37 Steering motor 38 Drive shaft

Claims

1. An electric vehicle having a plurality of drive units, each of the plurality of drive units having a drive motor, a drive wheel, and a reverse input cutoff clutch arranged in a torque transmission path from the drive motor to the drive wheel, wherein the reverse input cutoff clutch includes: a pressed member having a pressed surface on its inner circumferential surface; an input member having an input side engaging portion arranged radially inside the pressed surface, arranged coaxially with the pressed surface and connected to the drive motor; an output member having an output side engaging portion arranged radially inside the pressed surface and more radially inside than the input side engaging portion, arranged coaxially with the pressed surface and connected to the drive wheel; an engager having a pressing surface facing the pressed surface, an input side engaged portion engageable with the input side engaging portion, and an output side engaged portion engageable with the output side engaging portion, arranged radially movable; and an urging member that elastically urges the engager in a direction approaching the pressed surface. When a rotational torque is input to the input member from the drive motor side, the input side engaging portion engages with the input side engaged portion, and the engaging piece moves in a direction away from the pressed surface, and the output side engaged portion engages with the output side engaging portion, thereby transmitting the rotational torque input to the input member to the output member, whereas when a rotational torque is input in reverse to the output member from the drive wheel side, the engaging piece moves in a direction approaching the pressed surface, and the pressing surface is frictionally engaged with the pressed surface, thereby preventing the rotation of the output member.an electric vehicle in which, immediately after the rotation speeds of all of the drive wheels of the plurality of drive units have decreased to below a predetermined threshold, the drive motor of at least one of the plurality of drive units outputs a torque sufficient to maintain a parked position, and the output torque of the drive motor of the remaining drive units of the plurality of drive units is set to zero, thereby bringing the pressing surface of the engagement element of the reverse input cutoff clutch of the remaining drive unit into contact with the pressed surface; and then, the output torque of the drive motor of one or more drive units of the at least one drive unit is set to zero, thereby bringing the pressing surface of the engagement element of the reverse input cutoff clutch of the one or more drive units into contact with the pressed surface.

2. The electric vehicle according to claim 1, wherein the output torque of the drive motors of the remaining drive devices is set to zero one by one or simultaneously, causing the pressing surface of the engagement element of the reverse input cutoff clutch to contact the pressed surface.

3. The electric vehicle according to claim 2, wherein the output torque of all of the remaining drive units is set to zero, thereby causing the pressing surfaces of the engagement elements of all of the reverse input cutoff clutches of the remaining drive units to contact the pressed surfaces, and then the output torque of the drive motor of at least one of the drive units is set to zero one by one or simultaneously, causing the pressing surfaces of the engagement elements of the reverse input cutoff clutch to contact the pressed surfaces.

4. The electric vehicle according to claim 1 or 3, wherein the order of the drive units among the plurality of drive units in which the output torque of the drive motor is set to zero is changed depending on the stopping state of the vehicle.

5. An electric vehicle as described in claim 1 or 3, wherein, when stopping on a slope, immediately after the rotation speeds of all of the drive wheels of the plurality of drive units decrease to below the threshold, at least one of the drive units becomes an upper drive unit whose drive wheels are in contact with the upper part of the slope, and the remaining drive units become lower drive units whose drive wheels are in contact with the lower part of the slope.

6. An electric vehicle according to any one of claims 1 to 4, further comprising a steering wheel that can be steered around a vertically extending pivot axis in addition to the drive wheels, wherein the plurality of drive units are made up of two drive units, and wherein, when stopping, a steering angle is applied to the steering wheel in a direction that suppresses rotation due to yaw moment.

7. The electric vehicle according to any one of claims 1 to 6, wherein each of the plurality of drive units has a reducer disposed in the torque transmission path.

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