Two-speed transmission for electric vehicles

Abstract

This two-step transmission for an electric automobile comprises: a planetary gear mechanism 16 disposed coaxially between an input shaft 10 and an output shaft 12; a friction brake 28; and a friction clutch 26. A first speed is implemented by engagement of the friction brake 28, and a one-to-one second speed is implemented by engagement of the friction clutch 26. An electric actuator 30 for switching between the first speed and the second speed comprises an electric control motor 32, a torque–thrust conversion mechanism 36, and a pusher 34. The torque–thrust conversion mechanism 36 is formed from: an inner-side cylindrical screw 40 that is driven to rotate by the control motor 32; and an outer-side cylindrical nut 42 that is screwed onto the cylindrical screw 40 and joined so as to move axially as a single body with the pusher 34. The control motor 32 can comprise an electromagnetic brake for retaining engagement of the friction brake 28 and the friction clutch 26. Axial-direction thrust can also be transmitted by the swinging of an arm 316.

Description

[Technical field]

[0001] The present invention relates to a two-speed transmission for an electric vehicle. [Background technology]

[0002] In electric vehicles (EVs), even in hybrid vehicles that switch between or share the engine and electric motor, and even in vehicles that run purely on the driving force of the electric motor, it has been common to transmit the power of the electric motor to the axle without a separate transmission on the rotating shaft, and to only have a reduction gear that reduces the rotation of the drive motor to an appropriate rotation speed suitable for driving. This is because electric motors can generate driving torque from a zero-rotation range, so the usable rotation range is wide, and because the simple structure is an important selling point of EVs, there is no need to install a transmission that complicates the structure.

[0003] However, there are merits to using a transmission in an EV, and that is that even if it is an electric type, it is difficult to maintain high efficiency in the entire rotation range, and in particular, efficiency deteriorates in the high rotation range, making it impossible to obtain a high vehicle speed. To improve this, various types of systems have been proposed in which a two-stage transmission is placed between the drive motor and the reduction gear. In this system, in the high rotation range where efficiency deteriorates, the high gear ratio side of the two-stage transmission is used to reduce the rotation speed of the drive motor and operate the drive motor with high efficiency, thereby obtaining a high vehicle speed. As this type of two-stage transmission, various types have been proposed that use a planetary gear mechanism as a speed change mechanism, and set the planetary gear mechanism so as to provide a relatively low gear ratio in the first speed, and set the planetary gear mechanism so as to provide a relatively high gear ratio in the second speed. Among them, an electric actuator for switching between the first speed dog clutch (or friction clutch) and the second speed friction clutch, which is composed of an armature made of a soft magnetic material, a spring, and an electromagnetic coil, has been proposed (Patent Document 1). That is, in first gear, the dog clutch is engaged by the armature under spring force, and in second gear, the dog clutch (or friction clutch) is disengaged by driving the armature by an electromagnetic coil, thereby engaging the friction clutch for second gear.

[0004] Another type of electric actuator has been proposed, which includes an electric rotary control motor, a torque-thrust conversion mechanism that is made up of an inner diameter side piston equipped with an outer peripheral thread that screws into the inner peripheral thread of the worm wheel via a worm, and converts the rotation (torque) of the control motor into axial thrust of the piston by the torque-thrust conversion mechanism, thereby switching between a first speed friction clutch and a second speed friction clutch (Patent Document 2). In the technology of Patent Document 2, the rotation of the worm by the control motor is transmitted to the worm wheel, and the rotation of the worm wheel is converted into axial back and forth movement of the piston, selectively driving the first and second friction clutches, and switching between first speed and second speed is possible by a planetary gear mechanism. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6545921 [Patent Document 2] Patent No. 6028507 Summary of the Invention [Problem to be solved by the invention]

[0006] The technology of Patent Document 1 uses a dog clutch as the first gear, and the first gear can be maintained by the spring force, which saves the power consumption of the actuator. However, when changing from the second gear to the first gear, the dog clutch cannot be synchronized as it is, so control such as torque increase is required to avoid gear change shock, and regenerative control is not possible due to the torque increase, which is disadvantageous in terms of fuel consumption. In addition, for smooth switching operation, precise control of the engagement capacity is necessary at the beginning of clutch switching, but in the control of the armature by the electromagnetic coil, it is not possible to respond to this due to the characteristics of the electromagnetic attractive force that increases uniquely and rapidly as the distance is shortened.

[0007] The torque-thrust conversion method in Patent Document 2 does not cause shift shocks like those of a dog clutch, and the torque control of the control motor allows for appropriate control of the engagement capacity of the friction clutch according to the driving state, eliminating the above-mentioned drawbacks of the dog clutch method. However, the torque-thrust conversion method in Patent Document 2 converts the rotation of the worm on the outer diameter side into the linear motion of the piston on the inner diameter side, and this method requires a support mechanism for the rolling and thrust of the rotating worm against the housing. Although this configuration is not described in Patent Document 2, it would be common technical knowledge to adopt an angular ball bearing that can receive rolling and thrust, but due to the structure of the worm wheel located on the outer diameter side, the angular ball bearing must be large. The adoption of an angular ball bearing increases not only the outer diameter of the transmission but also its shaft length, making it unsuitable for EV parts where miniaturization is strongly desired.

[0008] The present invention aims to solve the problems described above. The present invention also aims to provide a structure suitable for miniaturization of a planetary gear type two-speed transmission equipped with a torque-thrust conversion mechanism driven by an electric rotary control motor, and is particularly intended to achieve miniaturization and power saving. [Means for solving the problem]

[0009] The two-speed transmission in a vehicle using an electric drive motor for driving wheels according to the present invention comprises: A two-speed transmission for an electric vehicle using an electric rotary drive motor for driving wheels, Housing and an input shaft supported by the housing and connected to an electric rotary drive motor; an output shaft supported by the housing and connected to a wheel side; a first gear mechanism including gears that mesh with each other to obtain a first speed ratio between the input shaft and the output shaft when the first gear mechanism is connected to the input shaft; a second gear mechanism including gears that mesh with the input shaft when the second gear mechanism is connected to the input shaft to obtain a second speed ratio that is higher than the first speed ratio but rotates in the same direction as the output shaft; a first multi-plate friction clutch that, when engaged, transmits rotation of the input shaft to the first gear mechanism to obtain a first speed change ratio; a second multi-plate friction clutch arranged coaxially with and spaced apart from the first multi-plate friction clutch in the axial direction, and configured to transmit rotation of the input shaft to a second gear mechanism when engaged, thereby obtaining a second speed change ratio; an actuator for selectively engaging the first multi-plate friction clutch and the second multi-plate friction clutch, The actuator comprises a control motor which is a torque source, meshing gears for transmitting torque, screw-engaged inner diameter member and outer diameter member for converting torque into thrust, a thrust transmission member for transmitting thrust, and a clutch pressing member (pusher) which presses the first multi-plate friction clutch and / or the second multi-plate friction clutch for fastening by thrust, and the inner diameter member is adapted to receive torque from the torque transmission gears, and the outer diameter member is slidably supported in the housing while being prevented from rotating, in order to convert the torque applied to the inner diameter member into thrust.

[0010] A set of actuators can be used for selectively engaging the first and second multi-plate friction clutches, and in this case, the clutch pressing member is moved back and forth in the axial direction together with the outer diameter member via the thrust transmission member to selectively engage the first and second multi-plate friction clutches. The outer diameter member and the thrust transmission member can be configured as a double cylinder consisting of an inner cylindrical portion and an outer cylindrical portion that are concentric with the central axis of the transmission, and a radial wall portion that connects them together, and the inner cylindrical portion is screwed into the inner diameter member on the outside of the first and second multi-plate friction clutches on the central axis, and the outer cylindrical portion is slidably fitted into the inner peripheral surface of the housing while facing the first or second multi-plate friction clutch located on the adjacent side, and the clutch pressing member is connected integrally to the outer cylindrical portion so as to be located between the first and second multi-plate friction clutches.

[0011] In another embodiment in which one set of actuators is used for both fastening the first and second multi-plate friction clutches, the thrust transmission member can be rotated (swinged) back and forth by the axial back and forth movement of the outer diameter member, and the clutch pressing member can selectively fasten the first and second multi-plate friction clutches by the back and forth rotation of the thrust transmission member. The thrust transmission member is configured as a swing arm pivotally attached to the housing at one end and loosely fitted in the outer diameter member (nut) at the other end at a diametrically opposed position, and the clutch pressing member is pivotally attached to the swing arm at a diametrically opposed position and is located between the opposing surfaces of the multi-plate friction clutch and the second multi-plate friction clutch, and the back and forth rotation of the swing arm by the axial back and forth movement of the internal thread member causes the clutch pressing member to directly face the first multi-plate friction clutch or the second multi-plate friction clutch and fasten it.

[0012] The first gear mechanism and the second gear mechanism can be configured as a planetary gear type speed change mechanism. In the planetary gear type speed change mechanism, an input shaft is arranged coaxially with an output shaft in a housing, and three rotating elements are provided: a carrier supporting a pinion, and two gears with different numbers of teeth meshing with the pinion, two of which are connected to the input shaft and the output shaft, respectively. The first and second multi-plate friction clutches are arranged relative to the three rotating elements and the housing so that a first speed change ratio is obtained between the input and output shafts by engaging the first multi-plate friction clutch and disengaging the second multi-plate friction clutch by the thrust transmission member, thereby configuring the planetary gear type speed change mechanism as the first gear mechanism, and a second speed change ratio is obtained between the input and output shafts in the same rotation direction but by disengaging the first multi-plate friction clutch and engaging the second multi-plate friction clutch by the thrust transmission member, thereby configuring the planetary gear type speed change mechanism as the second gear mechanism. In addition, without using a planetary gear type transmission mechanism, the first gear mechanism and the first gear mechanism planetary gear can be constructed from meshing spur gears to obtain a first speed change ratio, and the second gear mechanism can be constructed from meshing spur gears to obtain a second speed change ratio.

[0013] In addition, two sets of actuators can be provided, the first set being used to engage and disengage a first multi-plate friction clutch for setting the first gear ratio, and the second set being used to engage and disengage a second multi-plate friction clutch.

[0014] The two-stage transmission of the present invention may further include an electromagnetic brake for selectively braking the rotating shaft of the control motor. The electromagnetic brake can maintain the first and second multi-plate friction clutches in their engaged states under low rotational torque of the control motor by braking and restraining the rotating shaft of the control motor when the first and second multi-plate friction clutches are engaged, respectively. The first and second multi-plate friction clutches can be re-engaged by braking the rotating shaft of the control motor at regular time intervals.

[0015] Furthermore, in the present invention, when the first speed change ratio and the second gear mechanism are changed by selectively engaging the first multi-plate friction clutch and the second multi-plate friction clutch, a one-way clutch can be installed in parallel with the multi-plate friction clutch that contributes to the first speed change ratio. Effect of the Invention

[0016] In the two-speed transmission of the present invention, the torque-thrust conversion mechanism of the meshing screw type in the actuator controlled by the electric motor for changing the gear ratio of the planetary gear mechanism rotates an inner diameter member (screw) and axially moves an outer diameter member (nut), thereby switching between the first and second multi-plate friction clutches. Since the rotating inner diameter member has a small diameter, the torque-thrust conversion mechanism can be made compact, and the thrust generated in the inner diameter member can be reduced, allowing a simple bearing mechanism to be adopted. In addition, it is possible to control the switching of the friction clutch and friction brake appropriately according to the operating state, without compromising the advantage of electric motor control, which is power saving.

[0017] By making the inner diameter member and the outer diameter member in the torque-thrust conversion mechanism into a double cylindrical shape with an inner and outer side, and locating the screw-threaded portion between the inner shape portion of the outer diameter member and the inner diameter member on the outside of the first multi-plate friction clutch and the second multi-plate friction clutch, the axial length of the axial installation portion of the torque-thrust conversion mechanism can be reduced, thereby achieving miniaturization.

[0018] Furthermore, by equipping the control motor with an electromagnetic brake, it is possible to keep the first multi-plate friction clutch and the second multi-plate clutch engaged, the normal torque of the control motor can be minimized, power can be saved, heat generation by the motor can be suppressed, and the cooling device can be simplified.

[0019] In addition, by using a one-way clutch in combination with the switching operation, the multi-plate clutch can be engaged during coasting, allowing gear changes to be performed without shock and without the need to increase torque. This can then be used for power regeneration, resulting in power savings and increased efficiency.

[0020] By providing two sets of actuators and engaging the first multi-plate friction clutch and the second multi-plate friction clutch, respectively, it is possible to eliminate the idling period during which the pusher moves between the first multi-plate friction clutch and the second multi-plate friction clutch in the case of the switching type, thereby reducing the power required for the control motor and making it possible to omit the one-way clutch. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic diagram showing a wheel drive train of an electric vehicle according to the present invention. [Diagram 2] FIG. 2 is a skeleton diagram showing the overall structure of a two-speed transmission according to an embodiment of the present invention. [Diagram 3] FIG. 3 is a schematic diagram of an example of a one-way clutch used in the two-speed transmission of FIG. 2, taken along line III-III of FIG. [Figure 4]FIG. 4 is a schematic enlarged view of the portion indicated by A in FIG. 2, and shows a schematic diagram of the screwing state between the cylindrical screw and the cylindrical nut in the torque-axial thrust conversion mechanism. [Diagram 5] FIG. 5 is a schematic enlarged view of the portion indicated by B in FIG. 2, and shows a schematic spline connection between the pusher and the housing. [Figure 6] FIG. 6 is an explanatory diagram of the operation of the actuator of FIG. 2, where (A) shows the original position of the actuator, (B) shows the friction brake engagement position, and (C) shows the friction clutch engagement position. [Figure 7] FIG. 7 is a graph showing the relationship between the rotation angle of the control motor and the stroke amount of the pusher. [Figure 8] FIG. 8 is an explanatory diagram of an embodiment in which a switching drive portion of a pusher is elastically deformed when switching between a friction clutch and a friction brake. [Figure 9] FIG. 9 is an explanatory diagram of engagement and disengagement of the one-way clutch, friction brake, and friction clutch at each stage in an embodiment of the present invention. [Figure 10] FIG. 10 is a flow chart for explaining the operation of the control circuit when the control motor does not have an electromagnetic brake. [Figure 11] FIG. 11 is a schematic diagram of a control motor having an electromagnetic brake. [Figure 12] FIG. 12 is a cross-sectional view taken along line XII-XII in FIG. [Figure 13] FIG. 13 is a schematic timing diagram illustrating the friction clutch and friction brake re-engagement operation by an electromagnetic brake, where (A) shows the operation of the electromagnetic brake and (B) shows the operation of the solenoid. [Figure 14A] FIG. 14A is a part of a flowchart for explaining the operation of the control circuit when the control motor is equipped with an electromagnetic brake. [Figure 14B] FIG. 14B is the remainder of the flow chart that follows FIG. [Figure 15] FIG. 15 is a cross-sectional view of the two-speed transmission of FIG. 2 when it is implemented in an actual machine. [Figure 16]FIG. 16 is a schematic detailed view of the ball screw mechanism in FIG. [Figure 17] FIG. 17 is a skeleton diagram that shows in outline the entirety of a two-speed transmission that switches between first and second speeds by a swing arm. [Figure 18] FIG. 18 is a schematic front view of the swing arm (a cross-sectional view taken along the line XVIII-XVIII in FIG. 17). [Figure 19] 19 is a schematic diagram of spline engagement between the screw member and the nut member in FIG. 17 (a cross-sectional view taken along the line IXX-IXX in FIG. 17). [Figure 20] FIG. 20 is a skeleton diagram that shows in outline the entirety of a two-speed transmission in which friction clutches for first and second speeds are switched by two sets of swing arms. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] [Overall configuration] FIG. 1 shows a schematic diagram of the drive train of an electric vehicle of the present invention, in which 2 indicates a drive motor, which is an electric motor for driving, 4 indicates the two-speed transmission of the present invention, 6 indicates a reduction gear, 8 indicates a differential gear, and 9 indicates wheels. The two-speed transmission 4 has an input shaft 10 to the drive motor 2 and an output shaft 12 to the reduction gear 6. The reduction gear 6 is configured by housing meshing gears in a housing, and is installed to reduce the high rotation speed of the drive motor 2 to a rotation speed suitable for driving by the wheels 9. In the case of a normal electric vehicle that does not have the two-speed transmission 4, the reduction ratio of the reduction gear 6 is set to a value of about 3.5, which is suitable for operating the drive motor 2 in a highly efficient rotation speed range during regular low-speed driving, but with this setting, the rotation speed of the electric motor increases too much during high-speed driving, deteriorating the efficiency of the electric motor and making it impossible to drive at high speeds, so the two-speed transmission 4 is installed. In this invention, the transmission 4 is equipped with a planetary gear mechanism, and in this embodiment, the first speed is set by reducing the speed with the sun gear input and the carrier output (reduction ratio is, for example, 1.6), and the second speed is set by directly connecting the input and output (speed ratio 1.0). If the reduction ratio of the reducer 6 is assumed to be 2.2, the total reduction ratio is 1.6 x 2.2 = 3.52, which is approximately the total reduction ratio of a conventional case without a two-speed transmission. In addition, when operating in second speed, the total reduction ratio is 2.2 x 1.0 = 2.2, and since the reduction ratio is smaller, in the high vehicle speed operating range, the drive motor 2 can be operated in a low rotational speed range with good efficiency compared to the low vehicle speed operating range, and high-speed operation is possible.

[0023] Figure 2 is a skeleton diagram showing the basic configuration of the two-speed transmission 4 and the reduction gear 6 in the drive train of Figure 1. In this two-speed transmission, the output shaft 12 is cylindrical and is arranged coaxially with the central input shaft 10 (connected to the output shaft 2-1 of the drive motor 2), i.e., they share a common center of rotation.

[0024] The two-speed transmission 4 includes a planetary gear mechanism 16 arranged in a housing 14. The planetary gear mechanism 16 includes three rotating elements: a carrier 20 configured by axially supporting a plurality of pinions 18 arranged at intervals in the circumferential direction so as to be freely rotatable; a sun gear 22 that shares a common center of rotation with the carrier 20 and meshes with the pinions 18; and a ring gear 24 that shares a common center of rotation with the carrier 20 and meshes with the pinions 18. The sun gear 22 is connected to the input shaft 10, and the carrier 20 is connected to the output shaft 12. Furthermore, the planetary gear mechanism 16 includes a multi-plate friction clutch (hereinafter simply referred to as a friction clutch) 26, a one-way clutch 27, and a multi-plate friction brake (hereinafter simply referred to as a friction brake) 28 as fastening elements. In the first gear (coast), the ring gear 24 is fastened to the housing 14 by the one-way clutch 27, and the carrier 20 on the output shaft 12 side is set to the reduction ratio of 1.6 described above with respect to the sun gear 28 on the input shaft 10 side, and in the second gear, the sun gear 28 and the carrier 20 are connected by the friction clutch 26, so that the input shaft 10 and the output shaft 12 rotate together, and the speed change ratio is 1.0, which is an increase from the first gear. In the first gear, in drive, the one-way clutch 27 fastens the ring gear 24 to the housing 14 as described above to transmit power, but when the driver releases the accelerator pedal and coasts (decels), the fastening of the one-way clutch 27 to the housing 14 is released, but in this case, the friction brake 28 is fastened, so that the fastening of the ring gear 24 to the housing 14 is ensured, and the first gear coasting can be continued without any shock. This operation of the one-way clutch 27 will be described later.

[0025] Also, the one-way clutch 27 achieves the function of ensuring torque transmission during the idling period in the switching operation of the friction clutch 26 and the friction brake 28. That is, in this embodiment, the friction clutch 26 and the friction brake 28 are installed apart in the axial direction, and the friction clutch 26 and the friction brake 28 are switched and engaged by a pusher 34 described below moving back and forth in the axial direction, so that during the switching, both the friction clutch 26 and the friction brake 28 are inevitably in a non-engaged state, albeit momentarily, but during the idling period, particularly when switching from first to second speed, the one-way clutch 27 can be useful in ensuring the torque of the output shaft and preventing shift shock.

[0026] The planetary gear mechanism 16 may be a double pinion type with pinions of different diameters. In this case, the carrier supporting the pinion and gears (sun gears or ring gears) with different numbers of teeth that mesh with the different diameter portions of the pinions become the three rotating elements of the planetary gear mechanism.

[0027] The multi-plate friction clutch 26 and the multi-plate friction brake 28 are arranged concentrically with the central axis of the two-speed transmission 4 and spaced apart in the axial direction. As is well known, the friction clutch 26 includes a drive disk 26-1 (axially slidable relative to a clutch drum 26-4 rotating integrally with the sun gear 22) that rotates integrally with the input shaft 10, i.e., the sun gear 22, and a driven disk 26-2 (axially slidable relative to a clutch drum (inner drum 66 shown in FIG. 14) fixed to the carrier 20 by spline engagement) that rotates integrally with the carrier 20, and a thrust bearing 26-3 on the side of the drive disk 26-1 adjacent to the friction brake 28. As is also well known, the friction brake 28 includes a drive disk 28-1 (axially slidable relative to the housing 14 by spline engagement) that is axially movable but non-rotatably connected to the inner periphery of the housing 14 by spline engagement, and a driven disk 28-2 that is axially movable but connected to the ring gear 24 by spline engagement so as to rotate integrally with the ring gear 24.

[0028] The configurations of the planetary gear mechanism 16, the friction clutch 26, and the friction brake 28 in the actual device will be described later with reference to FIG.

[0029] In this embodiment, the one-way clutch 27 may be of a type in which a cam 27-2 held by a retaining ring 27-1 shown in FIG. 3 is held by a garter spring 27-3, although this is not limitative. The one-way clutch is not limited to this type, and may be, for example, a roller type. In the first speed of the two-speed transmission 4, the one-way clutch 27 restricts the rotation of the ring gear 24 (counterclockwise direction f in FIG. 3) relative to the housing 14 during drive operation. Furthermore, in the coasting operation, the one-way clutch 27 allows the ring gear 24 to rotate freely relative to the housing 14 (clockwise direction g in FIG. 3).

[0030] In the two-speed transmission 4 of this embodiment, first gear drive (during non-coasting operation) is performed by disengaging the friction clutch 26 and restraining the ring gear 24 against the housing 14 with the one-way clutch 27, and the friction brake 28 is in a no-clearance state (however, fastening torque = 0) between the drive disk 28-1 and the driven disk 18-2 so that fastening torque can be generated immediately when transitioning to first gear coasting operation where the one-way clutch 27 spins freely, and second gear (both coasting and non-coasting operation) is performed by engaging the friction clutch 26 (the one-way clutch 27 causes the ring gear 24 to spin freely against the housing 14). That is, in the first gear, the friction brake 28 has no clearance between the drive disk 28-1 and the driven disk 18-2 (the engagement torque of the friction brake 28 is generated only during coasting), and in the second gear, the friction clutch 26 has no clearance between the drive disk 26-1 and the driven disk 26-2, and generates an engagement torque regardless of whether the vehicle is in non-coasting or coasting. An actuator 30 is provided for switching the friction clutch 26 and the friction brake 28 in this way.

[0031] The actuator 30 includes a control motor 32 which is an electric rotary motor, a pusher (pressing member of the present invention) 34 which selectively engages the friction brake 28 (a first multi-plate friction clutch associated with the first speed in the present invention) and the friction clutch 26 (a second multi-plate friction clutch associated with the second speed in the present invention), a torque-thrust conversion mechanism 36 which converts the rotational torque of the control motor 32 into thrust (axial back and forth movement of the pusher 34), and a power transmission mechanism 38 which transmits the rotation of the control motor 32 to the torque-thrust conversion mechanism 36. The torque-thrust conversion mechanism 36 is composed of a cylindrical screw 40 (an inner diameter member of the present invention) and a cylindrical nut 42 (corresponding to an outer diameter member of the present invention) which are screwed together. In this embodiment, the cylindrical nut 42 is formed as a double cylinder including a central screw portion 42-1a, a disk-shaped portion 42-1 extending in the radial direction, and a cylindrical portion 42-2 extending in the axial direction from the disk-shaped portion (radial wall portion) 42-1, and the cylindrical portion 42-2 is movable only in the axial direction on the inner periphery of the housing 14 (the rotation direction is restricted), so that the cylindrical nut 42 can move in the axial direction by rotating the cylindrical screw 40. In order to make the cylindrical nut 42 movable only in the axial direction, as shown in FIG. 5, the cylindrical portion 42-2 of the cylindrical nut 42 has a spline 42-2a on the outer periphery, and the spline 42-2a meshes with a spline 14-1 on the inner periphery of the housing 14, so that the cylindrical nut 42 can move in the axial direction relative to the housing 14, but is restricted by the housing 14 in the rotation direction, so that the cylindrical nut 42 can move back and forth in the axial direction by rotating the cylindrical screw 40. 4 shows a schematic diagram of the engagement between the cylindrical screw 40 and the cylindrical nut 42, with the external thread 40-1 of the cylindrical screw 40 engaged with the internal thread 40-2 of the cylindrical nut 42, and since the cylindrical nut 42 is restricted from rotating and can only move in the axial direction, the rotation of the cylindrical screw 40 by the control motor 32 is converted into the axial movement of the cylindrical nut 42 (torque-thrust conversion) according to the lead angle. The torque-thrust conversion generates a thrust force in the cylindrical screw 40, but to counter the thrust force, thrust bearings 43a, 43b are installed between the opposing surfaces of the housing on both sides of the cylindrical screw 40 as shown in FIG.The pusher 34 is formed in an annular shape as a whole, and includes an annular disk portion 34-1 integrally connected to the cylindrical portion 42-2 at its outer circumferential end, and a friction brake drive portion 34-3a and a friction clutch drive portion 34-3b provided at the inner circumferential end of the annular disk portion 34-1 so as to face the friction clutch 26 and the friction brake 28, respectively, in the axial direction. The friction clutch drive portion 34-3b is disposed opposite to a thrust bearing 26-3 located on the drive disk side of the friction clutch 26 closest to the friction brake 28. The thrust bearing 26-3 is disposed so as not to impair the rotation of the friction clutch 26 (carrier 20) against a thrust force applied from the friction clutch drive portion 34-3b of the fixed pusher 34 in the rotation direction. The friction brake drive portion 34-3a is located opposite to the drive disk 28-1 of the friction brake 28 closest to the friction clutch 26. In this embodiment, the axial sliding during torque-thrust conversion is borne by the cylindrical portion 42-2, and the structure in which the pusher 34 is attached to the cylindrical portion 42-2 is a mechanism that combines torque-thrust conversion and thrust transmission.

[0032] In the above-described configuration of the actuator 30, the forward and reverse rotational motion of the cylindrical screw 40 is converted into a linear motion in the left and right axial direction of the cylindrical nut 42 that is screwed onto the cylindrical screw 40 and prevented from rotating, and this linear motion is transmitted to the pusher 34 via the cylindrical portion 42-2 of the cylindrical nut 42, and a switching operation between the friction clutch 26 and the friction brake 28 is performed by the friction brake drive unit 34-3a and the friction clutch drive unit 34-3b. The switching operation will be described in detail later.

[0033] In FIG. 2, the rotational power transmission mechanism 38 in the two-speed transmission 4 is composed of a drive spur gear 44 fixed to the output shaft 32-1 of the control motor 32, and a driven spur gear 46 meshing with the drive spur gear 44 and fixed to the cylindrical screw 40 coaxially with the central axis of the transmission. The forward and backward rotation of the control motor 32 is transmitted to the cylindrical screw 40 via the rotational power transmission mechanism 38. The control motor 32 does not have an electromagnetic brake in this embodiment, but can be equipped with an electromagnetic brake as described later. Since the rotational power transmission mechanism 38 in this embodiment is composed of spur gears 44, 44, the thrust force superimposed on the cylindrical screw 40 of the torque-thrust conversion mechanism 36 by the driven spur gear 46 is overwhelmingly smaller than that of the worm mechanism in the cited document 2, and therefore there is an advantage that no heavy load is placed on the thrust bearings 43a, 43b.

[0034] The reduction gear 6 includes an input shaft 6-1, an output shaft 6-2, a relay gear set (comprising a gear 6-3 on the output shaft 12 of the two-speed transmission 4 and a gear 6-4 on the input shaft 6-1 meshing therewith), and a gear set for shifting (comprising a gear 6-5 on the input shaft 6-1 and a gear 6-6 on the output shaft 6-2 meshing therewith), and the reduction gear 6 is capable of obtaining the above-mentioned total reduction ratio of 2.2 between the output shaft 12 of the two-speed transmission 4 and the output shaft 6-2 of the reduction gear 6. The output shaft 6-2 of the reduction gear 6 is connected to the differential 8.

[0035] [Clutch and brake switching by actuator] Next, the switching operation between the friction clutch 26 and the friction brake 28 by the actuator 30 will be described with reference to Figs. 6 and 7. The actuator 30 has some parts that are slightly different or modified from those in Fig. 2, but this is merely for the sake of convenience of explanation and is essentially the same. Mindicates the midpoint of the pusher 34 between the friction clutch 26 and the friction brake 28 (corresponding to the coordinate origin in FIG. 7), and the pusher 34 is located midway between the friction clutch 26 and the friction brake 28. In FIG. 7, the horizontal coordinate axis indicates the rotation angle of the rotary shaft 32-1 of the control motor 32, and the vertical coordinate axis indicates the stroke amount of the pusher 34. The forward rotation of the control motor 32 moves the pusher 34 to the right in FIG. 6, and the stroke amount value increases to the positive side in FIG. 7, and the reverse rotation of the control motor 32 moves the pusher to the left, and the stroke amount value increases to the negative side in FIG. 7. The midpoint L in FIG. 6(A) M At the center of the friction clutch 26 (corresponding to the origin of the coordinate system in FIG. 7), the pusher 34 leaves a clearance of Ccr+St / 2 between itself and the opposing end of the friction clutch 26 (the thrust bearing 26-3 on the closest side), and a clearance of Bcr+St / 2 between itself and the opposing end of the friction brake 28. Here, Ccr is the midpoint L required to prevent drag torque from being generated between the friction clutch 26 when the friction clutch 26 is idling (to prevent drag from being generated between the drive disk 26-1 and the driven disk 26-2). M The clearance value Bcr from the midpoint L required to prevent drag torque from being generated in the friction brake 28 when the friction brake 28 is idling (to prevent drag from being generated between the drive disk 28-1 and the driven disk 28-2). M , and St is a margin for preventing drag torque from being generated in either the friction clutch 26 or the friction brake 28.

[0036] Midpoint L of Figure 6(A) M When the pusher 34 moves to the right by St / 2 due to the forward rotation of the output shaft 32-1 of the control motor 32 from here, the clearance with the friction brake 28 becomes Bcr, and when it is moved further to the right by Bcr from here, as shown in FIG. 6(B), the friction brake drive section 34-3a of the pusher 34 comes into contact with the adjacent drive plate 28-1 of the friction brake 28, and the drive disk 28-1 and driven disk 28-2 of the friction brake 28 come into complete contact (no clearance) although there is no torque. At this point, the engagement of the friction brake 28 (switching to first speed) is completed by increasing the forward rotation torque of the control motor 32. In this state, when the pusher 34 reaches the midpoint LM This is a state in which the pusher 34 has moved Bcr+St / 2 to the right from the friction brake 28, and on the opposite side, a gap of Ccr+Bcr+St (corresponding to the target stroke amount b of the pusher 34 for switching from the friction brake 28 to the friction clutch 26) is created between the friction clutch drive unit 34-3b of the pusher 34 and the friction clutch 26.

[0037] In order to change from the first gear to the second gear, it is necessary to switch the friction brake 28 from the engaged state to the disengaged state in FIG. 6(B) and to bring the friction clutch 26 to engagement. At this time, the pusher 34 moves to the left by Bcr+Ccr+St due to the negative rotation of the output shaft 32-1 of the control motor 32, and the friction clutch drive unit 34-3b of the pusher 34 comes into contact with the proximal thrust bearing 26-3 of the friction clutch 26, and the engagement of the friction clutch 26 is completed by increasing the negative rotation torque of the control motor 32. This state is shown in FIG. 6(C), and the clearance between the friction brake drive unit 34-3a of the pusher 34 and the friction brake 28 at this time is also Bcr+Ccr+St (the target stroke amount a of the pusher 34 for switching from the friction clutch 26 to the friction brake 28).

[0038] [Increasing fastening force through elastic deformation during fastening] In the switching operation between the friction clutch 26 and the friction brake 28 by the pusher 34 shown in FIG. 6, when the friction brake drive unit 34-3a and the friction clutch drive unit 34-3b engage with the opposing portions of the friction clutch 26 and the friction brake 28, the pusher 34 can be moved so that the engagement becomes deeper. In this case, if the annular disk portion 34-1 is drawn in an exaggerated manner in FIG. 8, it is deformed with respect to the base portion where it joins with the cylindrical portion 42-2 as shown by imaginary line 34-1' when the friction brake drive portion 34-3a contacts the friction brake 28, and as shown by imaginary line 34-1" when the friction clutch drive portion 34-3b contacts the friction clutch 26. These deformations are within the range of elastic limit, but the friction clutch 26 and the friction brake 28 can be reliably fastened by the elastic force. In this case, if the elastic deformation amount on the drive center in the case of FIG. 6(B) is Dcr and the elastic deformation amount on the drive center in the case of FIG. 6(C) is Dbr, the target stroke amounts a and b of the friction clutch 26 and the friction brake 28 in FIG. 6(B) and FIG. 6(C) are respectively as follows: a=Bcr+Ccr+St+Dcr b=Bcr+Ccr+St+Dbr The size is .

[0039] [Shifting action of two-speed transmission] Next, the shifting operation of the two-speed transmission 4 of this embodiment will be described. The shifting operation is shown in Fig. 8, where ◯ indicates the engagement operation and × indicates the disengagement operation. This two-speed transmission 4 realizes the above-mentioned two gear ratios of the first and second speeds, as well as a reverse gear. The vehicle state can be broadly divided into a drive state (drive) in which the drive motor generates positive torque to accelerate the vehicle, and a deceleration state (coast) in which the drive motor regenerates and generates negative torque to decelerate the vehicle. Below, the operation when the gear stage and the drive and coast states are combined will be described.

[0040] When driving at 1st speed During first speed driving, the pusher 34 takes the rightward position in Fig. 6(B), the pusher 34 has no clearance with respect to the friction brake 28, is not engaged with the friction clutch 26, and the clearance is maximum. Although the pusher 34 has no clearance with respect to the friction brake 28, the control motor 32 is controlled according to the flowchart in Fig. 10 described later so as not to generate an engaging torque, and the friction brake 28 is not engaged. In the case of the operation shown in Figs. 13 and 14B described below using a control motor 32 equipped with an electromagnetic clutch described below, during first speed driving, the friction clutch 26 is held in an engaged state by the electromagnetic clutch, and therefore when the electromagnetic clutch is in an engaged state, the friction brake 28 is in an engaged state. However, since the electromagnetic clutch performs a re-gripping operation, during re-gripping the friction brake 28 becomes a non-engaged operation (X), and the one-way clutch 27 in an engaged state becomes an engaged operation (O) that ensures power transmission during re-gripping.

[0041] In FIG. 2, the input rotation / torque during first speed driving (drive motor torque is positive) enters the input shaft 10 from the drive motor 2 and rotates the sun gear 22. The ring gear 24 is stopped due to the rotation restriction imposed by the one-way clutch 27 (the engagement operation of the one-way clutch 27 is indicated by a circle in FIG. 9). That is, the one-way clutch 27 functions such that the cam 27-2 in FIG. 3 prevents the ring gear 24 from rotating counterclockwise. As a result, in FIG. 2, the sun gear 22 rotates the carrier 20, and torque and rotation can be transmitted to the output shaft 12. The output shaft 12 transmits the torque and rotation as a driving force to the wheels 9 via the reduction gear 6 and the differential 8, accelerating the vehicle. As is well known, the gear ratio of first speed is Zs / (Zs+Zr) (reduction) when the number of teeth of the sun gear 22 is Zs and the number of teeth of the ring gear 24 is Zr.

[0042] When decelerating in 1st gear (coast) During first speed deceleration (coasting), the pusher 34 is in the rightward position in Fig. 6(B) (the pusher 34 is in contact with the friction brake 28), and the torque of the control motor 32 is controlled as described below so as to generate an appropriate engagement torque, rather than a torque-free state as occurs during first speed driving. Therefore, the friction brake 28 is engaged (circle in Fig. 9).

[0043] The input rotation / torque during first speed deceleration enters the carrier 20 from the output shaft 12 in the opposite direction to that during driving, and the pinion 18 is subjected to torque in the direction that rotates the sun gear 22 and ring gear 24. Because the torque input to the ring gear 24 is in the idling direction of the one-way clutch 27 (a state in which cam 27-2 is not effective due to clockwise rotation in FIG. 3), idling of the ring gear 24 is prevented by engaging the friction brake 28. This allows the rotation from the wheels 9 to be directly transmitted to the drive motor 2, and the drive motor generates negative torque through power regeneration, transmitting torque in the negative direction to the wheels 9, decelerating the vehicle.

[0044] Second speed drive During second speed driving, the pusher 34 takes the leftward position in FIG. 6(c), and an appropriate torque is applied from the control motor 32, so the friction clutch 26 is engaged (circle in FIG. 9), and the friction brake 28 is disengaged. The input rotation / torque during second speed driving enters the input shaft 10 from the drive motor 2, and rotates the clutch drum connected and fitted to the sun gear shaft. The clutch drum rotates at the same speed as the drive motor 2 through the engaged friction clutch 26 to the carrier 20. Since the carrier shaft is also integrated with the carrier 20, the carrier 20 rotates the output shaft 12 at the same speed as the drive motor 2 (the gear ratio is 1.0, which is a relative increase in speed compared to the first speed). At this time, the ring gear 24 receives torque in the idling direction of the one-way clutch 27, and rotates at the same speed as the drive motor 2 because the friction brake 28 is disengaged.

[0045] When decelerating in 2nd gear (coast) The friction clutch 26 is engaged (see FIG. 9), and the friction brake 28 is disengaged, which is the same as in second speed driving.

[0046] The input rotation / torque during second speed deceleration flows in the opposite direction to that during driving. The rotation goes from the output shaft 12 to the carrier 20, the carrier shaft, and through the engaged friction clutch 26 to the sun gear shaft and the driving motor 2, so that the negative torque due to the power regeneration of the driving motor is transmitted to the wheels 9 during second speed non-driving, and the vehicle decelerates appropriately.

[0047] When reversing When in reverse, the input rotation / torque is such that as the drive motor 2 rotates in the reverse direction, the rotation / torque in the reverse direction enters the sun gear 22, and the torque is applied to the ring gear 24 in the direction that reverses the rotation through the carrier 20. Since the ring gear 24 receives torque in the direction that causes the one-way clutch 27 to spin freely, the friction brake 28 is engaged (Figure 9) to prevent the ring gear 24 from spinning freely. This transmits the reverse torque and rotation of the drive motor to the wheels 9.

[0048] [Actuator control (without electromagnetic brake)] Next, the control logic of the control motor 32 in the actuator 30 for the switching operation between the first and second speeds will be described with reference to the flowchart in FIG. 10. The operation during reverse will not be described in the flowchart. A control circuit by a microcomputer for controlling the speed change of the control motor 32 is indicated by 47 in FIG. 2. The control circuit 47 receives signals from the accelerator opening, the vehicle speed, the position sensor of the rotary shaft 32-1 of the control motor 32, and other sensors, and controls the control motor 32 by software stored inside. Note that in the following description, the position of the pusher 34 relative to the friction brake 28 and the friction clutch 26, i.e., the calculation of the required stroke amount of the pusher 34 will not be specifically described, but it can be grasped by a well-known method from the detection value of the position sensor of the rotary shaft 32-1 provided on the control motor 32.

[0049] In FIG. 10, step 100 indicates input of accelerator opening and vehicle speed signals to know the driving state of the vehicle. In step 102, it is determined whether or not the gear is not being changed based on the accelerator opening and vehicle speed signal information. If it is determined that the gear is being changed, the process proceeds to step 104, where it is determined whether or not the gear is being changed from first gear to second gear. If it is determined that the gear is being changed from first gear to second gear, the pusher 34 is initially in contact with the friction brake 28 (first gear) as shown in FIG. 6B, and the clearance b with respect to the friction clutch 26 is b=Ccr+Bcr+St, which is the target stroke amount of the pusher 34. From here, in order to change to second gear, the pusher 34 needs to be moved leftward from the position shown in FIG. 6B until the friction clutch 26 is engaged by the reverse rotation of the control motor 32, and the pusher 34 has no clearance with the friction clutch 26, i.e., the target stroke amount is obtained. In the next step 106, the control motor current value for moving the pusher 34 is output to the control motor 32 (a value which rotates the control motor 32 in the negative direction but is as small as possible as a torque value that can move the pusher 34 and does not generate an engagement force in the friction clutch 26) until it is determined in step 108 that the deviation δb=0 from the target stroke amount b, that is, until the pusher 34 comes into contact with the friction clutch 26 as shown in Fig. 6(C). If it is determined in step 108 that δb=0, the process proceeds to step 110, where the engagement force (torque of the control motor 32) required to engage the friction clutch 26 in that operating state is calculated, which is converted into a required current value in step 112, and a current command is output from the control circuit 47 to the control motor 32 in step 114.

[0050] When the gear change operation from first to second gear is completed in this manner, in the next execution of the routine of FIG. 10, the process proceeds to steps 100 and 102. Since the answer to step 102 is yes, the process proceeds to step 116. Since the current gear is second gear, the answer to step 116 is no, so the process proceeds to step 110. In this case, the torque required for the control motor 32 to maintain the engagement of the friction clutch 26 in the driving state determined by the accelerator opening and vehicle speed input in step 100 is calculated. In step 112, the required current value is calculated. In step 114, an instruction to operate the control motor 32 is issued (the required current value calculated in step 112 is output).

[0051] When shifting from the second speed to the first speed, the process proceeds from steps 100 and 102 to step 104, and because the result is negative, the process proceeds to step 118. At this time, the pusher 34 is in a state where there is no clearance with respect to the friction clutch 26 as shown in FIG. 6(C). In order to shift from this point to the first speed, it is necessary to move the pusher 34 to the right in the figure by the target stroke amount of a=Ccr+Bcr+St until the friction brake 28 is engaged, and the output of the control motor current value for moving the pusher 34 to the control motor 32 (the control motor 32 is rotating in the forward direction, but the torque value is as small as possible to move the pusher 34 and does not generate an engagement force in the friction clutch 26) is continued until the deviation δa=0 from the target stroke amount a is determined in step 120, that is, until the pusher 34 assumes a state of no clearance with respect to the friction brake 28 as shown in FIG. 6(B). If it is determined in step 120 that δa=0, that is, if the pusher 34 has reached a state of no clearance with respect to the friction brake 28, the process proceeds to step 122, where the torque of the control motor 32 is set to zero. The current value also becomes zero (step 112), and the process proceeds to step 114, where an instruction to that effect is given. That is, in the first speed driving state, the one-way clutch 27 is involved in the power transmission, and the friction brake 28 is not involved in the power transmission, so the torque is set to zero.

[0052] When the shift operation from second gear to first gear is completed in this manner (the pusher 34 has reached a state where there is no clearance between the friction brake 28), the next routine proceeds from steps 100 and 102 to step 116, and then to step 118, where it is determined whether or not the vehicle is coasting (coasting at first gear). If the vehicle is not coasting even in first gear, the determination at step 118 is negative, and the routine proceeds to the aforementioned step 122, where the torque of the friction brake 28 is maintained at zero.

[0053] When the driver releases the accelerator pedal in first gear and the vehicle coasts, the process goes through steps 100, 102, and 116, and because a positive determination is made in step 118, the process proceeds to step 124, where a friction torque at which the friction brake 28 will not slip is calculated from the torque of the drive motor 32 required according to the driving state in first gear coasting from the accelerator opening and vehicle speed, and in step 112 a current value of the control motor 32 corresponding to this friction torque is calculated, and in step 114 this current value is output from the control circuit 47 to the control motor 32. In the coasting state, the one-way clutch 27 rotates idly, but because an appropriate friction torque is instantly applied from the control motor 32 to the friction brake 28, which has already arrived at a position with no clearance with respect to the friction brake 28, a smooth transition to coasting can be made without a deceleration shock.

[0054] [Actuator control (with electromagnetic brake)] In the embodiment of the present invention, the control motor 32 in FIG. 2 may be equipped with an electromagnetic brake. By providing the control motor 32 with an electromagnetic brake, the friction brake 28 and the friction clutch 26 can be engaged and held without torque drive by the control motor 32, and the power consumption of the control motor 32 can be reduced. As shown in FIG. 11, the electromagnetic brake 48 is provided on the output shaft 32-1 and includes an annular drive plate 50 made of a weak magnetic material, an annular brake shoe 52, a plurality of springs 54 arranged in the circumferential direction, and a solenoid (electromagnetic coil) 56. The output shaft 32-1 includes an outer circumferential spline 32-1a (FIG. 12) at the mounting portion of the drive plate 50, and the spline 32-1a is fitted into a spline hole 50-1 of the drive plate 50. The drive plate 50 is axially slidable relative to the output shaft 32-1, but is fixed in the rotational direction. The electromagnetic brake 48 is engaged by de-energizing (OFF) the solenoid 56 (see Figure 13). At this time, under the force of the spring 54, the drive plate 50 engages the brake shoe 52 with the engaging portion 58 on the motor housing side, and the output shaft 32-1 of the control motor 32 is restrained and stopped.

[0055] The electromagnetic brake 48 is disengaged by energizing (ON) the solenoid 56 (see FIG. 13), at which time the drive plate 50 is displaced axially toward the solenoid 56 against the spring 54 by electromagnetic force, the brake shoe 52 releases the output shaft 32-1 of the control motor 32, and the rotation of the output shaft 32-1 of the control motor 32 can be transmitted to the actuator 30. The output shaft 32-1 of the control motor 32 rotates all the time, but a large torque is applied only when the friction clutch 26 and the friction brake 28 are engaged; otherwise, the control motor 32 can be operated with the minimum torque required to perform the stroke motion of the pusher 34, thereby reducing the overall power consumption.

[0056] The operation of switching between first and second speeds when the control motor 32 is equipped with an electromagnetic brake 48 will be explained with reference to the flowcharts of Figures 13 and 14B. The main part of this operation is that the friction clutch 26 and the friction brake 28 are held engaged by the electromagnetic brake 48 without relying on the rotational torque of the control motor 32. In the following explanation of the flowchart, the same processing steps as those in Figure 10 are given the same reference numerals (100s), and duplicate explanations are omitted as much as possible and simplified as much as possible, and processing not explained in Figure 10 is given the reference numerals in the 200s and will be explained in detail. After the accelerator opening signal and the vehicle speed signal are input in step 100, in the case of a shift from first to second gear, in step 200, the solenoid 56 (FIG. 11) of the electromagnetic brake 48 is energized to disengage the electromagnetic brake 48 (see FIG. 13), and the rotation of the rotary shaft 32-1 of the control motor 32 is made capable of being transmitted to the actuator 30 side, and the process proceeds to steps 104, 106, and 108. When the pusher 34 is in the state of abutting against the friction brake 28 in FIG. 6(b) and moves to the left as shown in FIG. 6(C) in which the pusher 34 abuts against the friction clutch 26 (thrust bearing 26-3), that is, when the movement of the target stroke b of the pusher 34 for shifting to first gear is completed, the determination in step 108 is affirmative (δb=0), and the above-mentioned steps 110, 112, The process of 114 is performed, the required torque of the control motor 32 is calculated, and the friction clutch 26 can be engaged with the required torque.

[0057] In this way, when the torque required to maintain engagement is obtained in the friction clutch 26 and the shift operation to the second speed is completed, the routine immediately following step 100 proceeds to step 102, and then to step 202, where it is determined whether the electromagnetic brake 48 is engaged. Since the electromagnetic brake 48 is initially not engaged (the solenoid 56 is energized (ON) in step 200), the routine proceeds to step 204, where the electromagnetic brake 48 is engaged (i.e., the solenoid 56 in FIG. 11 is de-energized (OFF)). The engagement of the electromagnetic brake 48 restrains the motor rotating shaft 32-1, and the engaged state of the friction clutch 26 engaged as shown in FIG. 6(C) can be maintained without relying on the rotation torque of the control motor 32. In the next step 206, it is determined whether the current speed is the first speed. Since the current speed is the second speed, the determination is negative, and the routine proceeds to step 208, where it is determined whether the gear ratio of the second speed is normal. That is, if the engagement torque of friction clutch 26 by engagement of electromagnetic brake 48 is normal, the pusher 34 maintains its contact state with friction clutch 26 in Fig. 6(C), and if the engagement torque decreases, the contact state is released and pusher 34 shifts toward friction brake 28, so that an abnormality can be determined from the detection position of rotating shaft 32-1 of control motor 32. If there is no abnormality in the second speed gear ratio, the process proceeds to step 210, where it is determined whether or not a predetermined time Tsec has elapsed since the last engagement of electromagnetic brake 48, and if the predetermined time Tsec has not elapsed, the process loops to step 208, and the engaged state of friction clutch 26 by electromagnetic brake 48 is maintained. If it is determined in step 208 that a predetermined time Tsec has elapsed since the last engagement of the electromagnetic brake 48, or if it is determined in step 208 that the second gear ratio is abnormal, the process proceeds to step 212, where the electromagnetic brake 48 is temporarily disengaged (solenoid 56 is energized (ON)), and in step 214, an operation command is issued to the control motor 32 to set the torque value to the maximum value (MAX) in the negative rotation direction (the leftward direction in FIG. 6(C) which reduces the clearance between the pusher 34 and the friction clutch 26). In the next step 215, a wait is performed for a time τsec required for the friction clutch 26 to be returned to the engaged state even if it was once disengaged.13 is a schematic diagram showing the re-engagement operation of the friction clutch 26 in second gear, in which the electromagnetic brake 48 is disengaged every Tsec and the control motor rotates in the negative direction (for a duration of τ) at the maximum torque. Even if Tsec has not been reached, if it is determined in step 208 that the second gear ratio is abnormal, the friction clutch 26 is immediately re-engaged.

[0058] In the case of shifting from second gear to first gear, the process goes from step 100 to step 102, and in step 200, the electromagnetic brake 48 is disengaged to enable the rotation of the control motor 32 to be transmitted to the actuator 30, and then proceeds to steps 104, 118, and 120, where an operation command for the control motor 32 is issued to move the pusher 34 to the right (the control motor 32 rotates forward) from the state in FIG. 6(C) in which the pusher 34 is in contact with the friction clutch 26, which is the current position of the pusher 34, toward the friction brake 28. Then, the movement of the pusher 34 by the target value a for shifting to first gear is completed, and the deviation δa=0 is reached. When the friction brake 28 is engaged, in step 122, the torque value of the friction brake 28 is set to zero, and the process goes to steps 112 and 114, where an instruction current=0 is issued, and although the pusher 34 has no clearance with the friction brake 28, the torque applied to the friction brake 28 is zero.

[0059] In this way, when the shift operation to the first speed is completed, the process goes from step 100 to step 102, and the electromagnetic brake 48 is engaged (the solenoid 56 is de-energized (OFF)) by the processing of the above-mentioned steps 202 and 204, the friction brake 28 has no clearance with the pusher 34, and the torque applied to the friction brake 28 is maintained at 0. In the next step 206, since the current speed is the first speed, the determination is affirmative, and the process proceeds to step 216, where it is determined whether or not the gear ratio of the first speed is abnormal. That is, if the gear ratio of the first speed is normal, and if the holding position of the pusher 34 with respect to the friction brake 28 by the electromagnetic brake 48 is normal, it is in an abutting state, and if the position of the pusher 34 is released from the abutting state with the friction brake 28 and shifts toward the friction clutch 26 side, it can be determined that the gear ratio of the first speed is abnormal from the detection value of the rotating shaft 32-1 of the control motor 32. If there is no abnormality in the first gear ratio, the process proceeds to step 218, where it is determined whether or not a predetermined time Tsec has elapsed since the last application of the electromagnetic brake 48, and if the predetermined time Tsec has not elapsed, the process loops to step 216. If it is determined in step 218 that the predetermined time Tsec has elapsed since the last application of the electromagnetic brake 48, or if it is determined in step 216 that the first gear ratio is abnormal, the process proceeds to step 220, where the electromagnetic brake 48 is disengaged (the solenoid 56 is excited), and the constrained state of the rotating shaft 32-1 of the control motor 32 by the electromagnetic brake 48 is released, and in step 222, a current value is calculated that maximizes the torque value (MAX) in the forward direction of the control motor 32 (the rightward direction in FIG. 6C that reduces the clearance between the pusher 34 and the friction brake 28), and the current value is instructed to the control motor 32 until the predetermined time τsec in step 215 has elapsed. The operation of re-engaging the friction brake 28 is similar to that of Fig. 13, and involves disengaging the electromagnetic brake 48 every Tsec and performing forward rotation (continuation time τ) at the maximum torque of the control motor. Also, even if Tsec has not been reached, if an abnormality is determined in step 216, the friction brake 28 is immediately re-engaged during first speed coasting.

[0060] 13 and 14B, in first gear, regardless of whether the vehicle is in drive or coast mode, the friction brake 28 is held engaged by engaging the electromagnetic brake 48, and since control for engaging the friction brake is not performed when the vehicle transitions to the coast mode as in the embodiment of FIG. 10, the control can be simplified, power can be saved, and the driver can feel the deceleration, improving drivability. That is, in this control, the friction brake 28 is held engaged in first gear regardless of whether the vehicle is in drive or coast mode, but during re-engagement (τ in FIG. 13), the friction brake 28 is not engaged, and the one-way clutch 27 is engaged to ensure power transmission while the friction brake 28 is not engaged.

[0061] 14A-14B, the friction brake 28 is held engaged during first gear coasting by the electromagnetic brake 48, and the friction clutch 26 is held engaged during second gear by the electromagnetic brake 48, so that the rotational torque of the control motor 32 during this time is minimum and the solenoid 56 of the electromagnetic brake 48 is not energized, thereby realizing power saving. Also, the friction clutch 26 and the friction brake 28 are re-engaged only by energizing (ON) the solenoid 56 of the electromagnetic brake 48 and setting the control motor 32 to maximum torque during the instant (τ) when the electromagnetic brake 48 is not engaged (see FIG. 13), so that the reliability of the engagement and maintenance operation of the friction clutch 26 and the friction brake 28 by the electromagnetic brake 48 can be ensured without substantially impairing the total power saving.

[0062] 11 in which the solenoid 56 is energized and excited when the electromagnetic brake 48 is not engaged (when the torque of the control motor 32 is being transmitted to the actuator 30) and the solenoid 56 is not energized when the electromagnetic brake 48 is engaged (during operation to maintain the engagement torque) as shown in the flowchart of Figures 14A-14B, as described above, is preferable from the viewpoint of saving power consumption. However, it is possible in some cases to adopt an electromagnetic brake of a type that is not engaged when the solenoid is not energized and is engaged when the solenoid is energized.

[0063] [2-speed transmission actual configuration] Fig. 15 shows an example of the configuration of the two-speed transmission of Fig. 2 as an actual machine, and parts having the same functions are given the same reference numerals as in Fig. 2. The central axis of the input shaft 10 is indicated by 10a, and both ends are supported by angular ball bearings 62, 64 on the upright wall portion 14-3 of the housing 14. The cylindrical output shaft 12 is supported coaxially with the input shaft 10 by an angular ball bearing 65 and the like. The planetary gear mechanism 16 includes a carrier 20 and a sun gear 22, and the carrier 20 supports a pinion 18, which meshes with the sun gear 22 on the inside and meshes with a ring gear 24 on the outside, by a pinion pin 67. The sun gear 22 is fitted with the input shaft 10 on the inner periphery side by a spline 10-1, and rotates integrally with the input shaft 10.

[0064] The friction clutch 26 is composed of an inner drum 66 that rotates integrally with the carrier 20 together with the pinion pin 67, a driven plate 26-2 that is spline-fitted to the spline 66-1 of the inner drum 66, an outer drum 26-4 (fixed to the sun gear 22) that rotates integrally with the sun gear 22, a drive plate 26-1 (together with the driven plate 26-2 to form a clutch pack) that is spline-fitted to the inner circumferential spline 67 of the outer drum 26-4 and is arranged alternately with the driven plate 26-2, and a thrust bearing 26-3 provided on the side of the clutch pack furthest from the outer drum 68.

[0065] The friction brake 28 is composed of a driven plate 28-2 that is spline-fitted with the outer peripheral spline 24-1 of the ring gear 24, which also serves as the inner drum, an outer drum portion 14-2 that is an integral connecting part of a part of the housing (housing 14 in Figure 2), and a drive plate 28-1 (which together with the driven plate 28-2 forms a clutch pack) that is spline-fitted with the inner peripheral spline 14-2a of the outer drum portion 14-2 and is arranged alternately in the axial direction with respect to the driven plate 28-2.

[0066] One-way clutch 69 is disposed between the inner periphery of ring gear 24 and the outer periphery of an annular protrusion 14-3 on the inner periphery side formed on outer drum 14-2 which is an integral part of housing 14 (FIG. 2) of friction brake 28. Since the arrangement between the inner periphery and the outer periphery is reversed from that of one-way clutch 27 shown in FIG. 3, one-way clutch 69 has an opposite orientation between locked and idling compared to one-way clutch 27, but the operation itself is the same.

[0067] The actuator 30 for switching the friction clutch 26 and the friction brake 28 includes a control motor 32, a pusher 34, a torque-thrust conversion mechanism 36, and a rotational power transmission mechanism 38. The rotational power transmission mechanism 38 includes a drive-side spur gear 44 and a driven-side spur gear 46. The torque-thrust conversion mechanism 36 includes a cylindrical screw 40 (inner diameter member) and a cylindrical nut 42A screwed onto the cylindrical screw 40 (in this embodiment, the cylindrical nut 42A is simply a screwed part with the cylindrical screw 40, and functions as an outer diameter member of the present invention by being integrated into a double cylindrical body described below), and the cylindrical nut 42A is integrally connected to form a double cylindrical body including a disk portion 42A-1 and a cylindrical portion 42A-2 for restricting rotation and allowing it to slide relative to the housing 14. In order to be integrated with the cylindrical nut 42A, the disk portion 42A-1 is fitted with the outer circumferential spline of the cylindrical nut 42A in the inner circumferential spline hole of the lower end flange portion 42A-1a, and is fixed to the cylindrical nut 42A by a snap ring 80, so that the cylindrical nut 42A is integrated as a double cylinder. In this actual structure, the cylindrical screw 40 and the cylindrical nut 42A are screwed together via a ball 72 installed in an infinite circulation path between them, which is a well-known ball nut mechanism (Figure 15 is a schematic diagram, but see the detailed diagram in Figure 16). The cylindrical screw 40 is rotatably supported on the input shaft 10 by a bush 74. Thrust bearings 43a and 43b are arranged on both sides of the cylindrical screw 40 to receive thrust. The pusher 34 is an annular press-molded product made of a plate material, and the outer circumferential cylindrical portion 34-2 is spline-fitted with the cylindrical portion 42-2 of the cylindrical nut 42, so that it can move in the axial direction, but is constrained in the rotational direction and is locked by a snap ring 82. The pusher 34 is integrally connected to the cylindrical nut 42A, and the cylindrical nut 42A and the pusher 34 can move in the axial direction (transmit thrust) by rotating the cylindrical screw 40. The pusher 34 has a radially intermediate portion formed as an annular protrusion that faces the friction clutch 26 via a thrust bearing 26-3, and this annular protrusion functions as a friction clutch drive portion 34-3b (see FIG. 6). Furthermore, the inner end portion of the pusher 34 in the radial direction is formed to extend in the axial direction toward the friction brake 28, and this axially extending portion functions as a friction brake drive portion 34-3a.This allows switching between the friction clutch 26 and the friction brake 28 to be performed by moving the pusher 34 left and right in the axial direction.

[0068] 15, since the input shaft 10 is supported on the housing by the angular bearings 62, 64 at both ends, the centering of the input shaft 10 can be easily and reliably achieved with sufficient accuracy, the rolling support of the inner cylindrical screw 40 in the torque-thrust conversion mechanism 36 on the input shaft 10 can be reliably achieved by a simple mechanism called the bush 74, and the restriction of the axial left and right movement of the outer cylindrical nut 42A can also be achieved with sufficient thrust resistance by a simple support structure called the thrust bearings 43a, 43b. Therefore, while suppressing the axial dimension of the torque-thrust conversion mechanism 36, the torque-thrust conversion mechanism 36 for switching between the engagement and disengagement of the friction clutch 26 and the friction brake 28 can be ensured to operate stably for a long period of time without incurring excessive costs.

[0069] 16 shows an example of the details of the ball nut mechanism, in which the balls 72 are arranged in close contact with each other between the external thread 40a of the cylindrical screw 40 and the internal thread 42A-a of the cylindrical nut 42A, which form an infinite circulation track, and a circulation path 84 is formed in the cylindrical nut 42, which is provided in an angular range of approximately 180 degrees in the cylindrical nut 42A, and which opens in a tangential direction to the thread that accommodates the balls 72, and this opening becomes a ball discharge part or an introduction part depending on the direction of rotation, thereby forming an infinite circulation track for the balls 72. The structure of the ball nut mechanism described above is an example, and any suitable one available on the market can be used. [Embodiment equipped with swing arm actuator for two-speed shifting]

[0070] 17 to 19 show a spur gear type two-speed change mechanism 300 instead of a planetary gear mechanism for two-speed change, and clutch switching is performed by a swing arm type actuator. The same reference symbols are used for parts with the same configuration and function. The spur gear type two-speed change mechanism 300 achieves the function of transmitting the rotation of a rotary drive motor 2, which is an electric motor, to wheels 9 via a reducer 6 and a differential gear 8 at a speed change ratio according to the vehicle speed. The spur gear type two-speed change mechanism 300 includes a first-speed gear set 301 and a second-speed gear set 302, the first-speed gear set 301 being composed of a pair of meshing input side spur gear 301-1 and output side spur gear 302-2, and the second-speed gear set 302 being composed of a pair of meshing input side spur gear 302-1 and output side spur gear 302-2, respectively. As explained for the embodiment in Figure 2, the gear ratio between the input side spur gear 301-1 and the output side spur gear 302-2 in the first speed gear set 301, including the gear ratio of the reducer 6, is set to the desired gear ratio for first speed operation (low vehicle speed), and the gear ratio between the input side spur gear 302-1 and the output side spur gear 302-2 in the second speed gear set 302 is set to the desired gear ratio for second speed operation (high vehicle speed), so that the wheels 9 are driven by the drive motor 2.

[0071] The spur gear type two-speed change mechanism 300 further includes a first-speed friction clutch 304 as a multiple-plate friction clutch, and a second-speed friction clutch 306 as a multiple-plate friction clutch arranged on the transmission input shaft 10 coaxial with the rotary shaft 2-1 of the rotary drive motor 2 with some space therebetween. The first-speed friction clutch 304 includes a driving-side clutch plate 304-1 fixed for rotational connection on the output shaft 2-1 thereof, and a driven-side clutch plate 304-2 fixed for rotational connection to an input spur gear 301-1 of the first-speed gear set 301. The second-speed friction clutch 306 includes a driving-side clutch plate 306-1 fixed for rotational connection on the transmission input shaft 10, and a driven-side clutch plate 306-2 fixed for rotational connection to an input spur gear 302-1 of the second-speed gear set 302.

[0072] An actuator 308 is provided for switching between a first-gear friction clutch 304 and a second-gear friction clutch 306. The actuator 308 is similar to the embodiment of FIG. 1-16 in that it includes a control motor 32 (FIG. 18) that is an electric rotary motor. In this embodiment, the actuator 308 includes a torque-thrust conversion mechanism 310 that converts the rotation torque of the control motor 32 into thrust, and is functionally common to the torque-thrust conversion mechanism 36 of FIG. 1-16, but is composed of an inner diameter side screw member 312 (inner diameter member of the present invention) and an outer diameter side nut member 314 (outer diameter member of the present invention). The actuator 308 further includes a swing arm 316 (thrust transmission member of the present invention) for transmitting thrust, a ring-shaped pusher 318 (pressing member of the present invention) for selectively engaging the friction clutch 304 for first gear and the friction clutch 306 for second gear, and a control motor 320 for transmitting the rotation of the control motor 32 to the torque-thrust conversion mechanism 310.

[0073] 18, in the neutral state, the swing arm 316 forms an annular body 316-1 coaxial with the transmission input shaft 10, a tongue 316-2 at the upper end of the annular body 316-1, and a pair of ears 316-3 extending downward from the annular body 316-1 in parallel with the upper end tongue 316-2 at diametrically opposed positions of the upper end tongue 316-2. The upper end tongue 316-2 of the swing arm 316 is pivotally attached to the housing 14 (arm pivot attachment portion 14-4) by an arm support pin 322, and the swing arm 316 is configured to be swingable around the central axis of the arm support pin 322, which is the transmission central axis (parallel to the paper surface of FIG. 17), i.e., a rotation center perpendicular to the transmission central axis (perpendicular to the paper surface of FIG. 17). 17, the pair of pusher support pins 324 are disposed at diametrically opposed positions, and the inner end of each pusher support pin 324 is fitted into the pusher 318 from its outer circumferential surface, while the outer end is fitted into the annular body portion 316-1 of the swing arm 316, whereby the pusher 318 is supported so as to be swingable at a certain angle relative to the swing arm 316 about a center line perpendicular to the central axis of the transmission. Such a support structure for the swing arm 316 enables the pusher 318 to perform a switching operation between the 1st-speed gear friction clutch 304 and the 2nd-speed gear friction clutch 306. That is, by rotating the swing arm 316 clockwise around the arm support pin 322 from the upright position of the swing arm 316 shown in FIG. 17, the pusher 318 is driven toward the friction clutch 304 for first gear, and the friction clutch 304 for first gear is engaged via the thrust bearing 326. Conversely, by rotating the swing arm 316 counterclockwise around the arm support pin 322, the pusher 318 is driven toward the friction clutch 306 for second gear, and the friction clutch 304 for second gear is engaged via the thrust bearing 328. In such a switching operation between the friction clutch 304 for first gear and the friction clutch 306 for second gear, the pusher 310 is initially somewhat inclined due to its pivoting structure around the pusher support pin 320, but due to the pivoting support structure of the pusher 310 relative to the arm 316 by the pusher support pin 324, the position of the pusher 310 relative to the swinging arm 316 is eventually corrected, and the pusher 310 can be engaged with the opposing clutch surface in an upright position.

[0074] The screw member 312 on the inner diameter side and the nut member 314 on the outer diameter side constituting the torque-thrust conversion mechanism 310 are located on the opposite side of the fulcrum of the swing arm 316 with respect to the housing, sandwiching the friction clutch 304 for the first gear and the friction clutch 306 for the second gear. In this embodiment, the screw member 314 is a solid rod-like member extending parallel to the central axis of the clutches 304, 306, and both ends are rotatably supported by the housing through bearings 330. The screw member 312 and the nut member 314 can also be configured as a ball screw similar to that shown in FIG. 16. As shown in FIG. 19, the outer periphery of the nut member 314 is fitted with the spline hole 14-5a in the nut attachment portion 14-5 of the housing while preventing rotation, so that the rotation of the screw member 312 is converted into a linear movement in the axial direction of the nut member 314. In order to obtain the swinging motion of the swinging arm 316 from the linear motion of the nut member 314, the cylindrical nut member 314 has a drive pin 332 fixed thereto at a diametrically opposed position in a longitudinal middle portion thereof as shown in Fig. 17 and Fig. 18, and a pin hole 334 extending elongatedly in the longitudinal direction of the arm 316 is formed in the ear portion 316-3 of the swinging arm 316, and the free end of the drive pin 332 from the nut member 314 is loosely fitted into the pin hole 334. In the neutral position of the swinging arm 316 shown in Fig. 17 and Fig. 18, the pin hole 328 has a clearance above and below the drive pin 332, and this clearance portion realizes the rotation of the swinging arm 316 accompanying the axial back and forth linear movement of the screw member 312 due to the rotation of the central screw 314, and in turn, the switching operation of the first-speed gear friction clutch 304 and the second-speed gear friction clutch 306 due to the back and forth movement of the pusher 318.

[0075] 18, the power transmission mechanism 320 for transmitting the rotation of the control motor 32 to the central screw 314 is composed of a worm gear 340 connected to the rotating shaft of the control motor 32, and a worm wheel 342 fixed on the central screw 314 and meshing with the worm gear 340. The rotation of the control motor 32 is transmitted to the central screw 314 via the meshing worm gear 340 and worm wheel 342, and the nut member 314 is moved in the axial direction by the rotation of the central screw 312. The axial movement of the nut member 314 causes a swinging motion of the arm 316, thereby realizing the switching operation of the first-speed gear friction clutch 304 and the second-speed gear friction clutch 306 described above.

[0076] A one-way clutch 348 is provided between the input side (driving motor 2 side) and output side (input side of 1st speed gear set 301) of 1st speed friction clutch 304. The operation of one-way clutch 348 is the same as that in the flowchart of Fig. 9, and in 1st speed drive, one-way clutch 348 is locked and engagement torque of 1st speed friction clutch 304 is set to 0, and the torque of driving motor 2 is transmitted to 1st speed gear set 301 via one-way clutch 348. Also, during 1st speed coasting, engagement torque is applied to 1st speed friction clutch 304, preventing idling of one-way clutch 348.

[0077] In this embodiment, the inner diameter side screw member 312 is solid, so the torque-thrust conversion mechanism can be made more compact, which contributes to cost reduction. Also, the axial force of the screw member 312 can be maintained by the self-locking function of the worm gear 320, so the electromagnetic brake 48 described in Figures 11 and 14A and 14B becomes unnecessary, which provides an advantage in terms of cost. [An embodiment in which the actuator is independent for two-speed shifting]

[0078] FIG. 20 shows a modified embodiment of the embodiment shown in FIGS. 17 to 19, characterized in that the actuators for the first gear friction clutch 304 and the second gear friction clutch 306 are made independent and a dedicated first gear friction clutch drive arm 350 and a dedicated second gear friction clutch drive arm 352 are used, respectively. The basic structure of the friction clutch drive arms 350, 352 is similar to that of the swing arm 316 in the embodiment of Figs. 17-19, but the differences are as follows: (a) a first-speed gear pusher 354 (and a thrust bearing 355) is supported on the first-speed gear friction clutch drive arm 350, and a second-speed gear pusher 356 (and a thrust bearing 358) is supported on the second-speed gear friction clutch drive arm 352; (b) a dedicated torque-thrust conversion mechanism 360 (comprised of a central screw 362 and a nut 364) is provided for the swing of the first-speed gear friction clutch drive arm 350, and a dedicated torque-thrust conversion mechanism 366 (comprised of a central screw 368 and a nut 370) is provided for the swing of the second-speed gear friction clutch drive arm 352; and (c) A rotation control motor 372 and a worm mechanism 374 are provided for the torque-thrust conversion mechanism 360 dedicated to the friction clutch for first gear, and a rotation control motor 376 and a worm mechanism 378 are provided for the torque-thrust conversion mechanism 366 dedicated to the friction clutch for second gear.

[0079] In this embodiment, since dedicated actuators (friction clutch drive arm 350 for 1st gear and friction clutch drive arm 352 for 2nd gear) are provided for the friction clutch 304 for 1st gear and the friction clutch 306 for 2nd gear, respectively, it is possible to design so that there is no idle time when switching between the friction clutch 304 for 1st gear and the friction clutch 306 for 2nd gear, and the one-way clutch 27 (Fig. 1, etc.), 69 (Fig. 16) is unnecessary, which is also advantageous in reducing the shock of gear shifting. In addition, since there is no idle time when switching, the moving distance of the pusher is shortened, and the control motor can be made accordingly smaller. [Explanation of symbols]

[0080] 2...Drive motor 4...2-speed transmission 10...Input shaft 12...Output shaft 14. Housing 16...Planetary gear mechanism 20…Career 22…Sun gear 24…Ring gear 26…Friction clutch 27...One-way clutch 28…Friction brake 30…Actuator 32...Control motor 32-1…Control motor output shaft 34... Pusha 34-3a…Friction brake drive part of pusher 34-3b…Pusher friction clutch drive section 36...Torque-thrust conversion mechanism 38...Power transmission mechanism 40... Cylindrical screw (inner diameter member of the present invention) 42... Cylindrical nut (outer diameter member of the present invention) 43a, 43b...Thrust bearing 44…Drive spur gear 46…Driven spur gear 48...Electromagnetic brake 52...Brake shoe a…Target stroke amount of pusher for 2-1 shifting b…Target stroke of pusher for 1-2 shift

[0081] 300…Spur gear type two-speed transmission 301...1st gear set 301-1…Input spur gear 301-2…Output spur gear 302...2-speed gear set 302-1…Input spur gear 302-2…Output spur gear 304...Friction clutch for 1st gear 306...Friction clutch for 2nd gear 308...Actuator 310...Torque-thrust conversion mechanism 312...Thread member (inner diameter member of the present invention) 314... Nut member (outer diameter member of the present invention) 316... Swing arm (thrust transmission member of the present invention) 318... Pusha 320...Control motor 322…Arm support pin 324…Pusher support pin 332…Arm drive pin 334...Drive pin hole 350...Friction clutch drive arm for 1st gear 352...Friction clutch drive arm for 2nd gear 354…1st gear pusher 356...2nd gear pusher 360…Torque-thrust conversion mechanism for 1st gear 362...Torque-thrust conversion mechanism for 2nd gear

Claims

1. 1. A two-speed transmission for an electric vehicle using an electric rotary drive motor for driving wheels, comprising: Housing and an input shaft supported by the housing and connected to an electric rotary drive motor; an output shaft supported by the housing and connected to a wheel side; a first gear mechanism including gears that mesh with each other to obtain a first speed ratio between the input shaft and the output shaft when the first gear mechanism is connected to the input shaft; a second gear mechanism including gears that mesh with the input shaft when the second gear mechanism is connected to the input shaft to obtain a second speed ratio that rotates in the same direction as the output shaft but is a higher gear ratio than the first speed; a first multi-plate friction clutch that, when engaged, transmits rotation of the input shaft to the first gear mechanism to obtain a first speed change ratio; a second multi-plate friction clutch arranged coaxially with and spaced apart from the first multi-plate friction clutch in the axial direction, and configured to transmit rotation of the input shaft to a second gear mechanism when engaged, thereby obtaining a second speed change ratio; an actuator for selectively engaging the first multi-plate friction clutch and the second multi-plate friction clutch, The actuator comprises a control motor which is a torque source, meshing gears for transmitting torque, inner diameter member and outer diameter member which screw together to convert torque into thrust, a thrust transmission member for transmitting thrust, and a clutch pressing member which presses the first multi-plate friction clutch and / or the second multi-plate friction clutch for fastening by thrust, wherein the inner diameter member is adapted to receive torque from the torque transmission gear, and the outer diameter member is slidably supported in the housing to convert the torque applied to the inner diameter member into thrust.

2. In the invention described in claim 1, a set of actuators is shared for engaging a first multi-plate friction clutch and a second multi-plate friction clutch, and the clutch pressing member moves back and forth in the axial direction integrally with the outer diameter member via a thrust transmission member, thereby selectively engaging the first multi-plate friction clutch and the second multi-plate friction clutch.

3. In the invention described in claim 2, the outer diameter member and the thrust transmission member are configured as a double cylindrical body consisting of an inner cylindrical portion and an outer cylindrical portion concentric with the central axis of the transmission and a radial wall portion connecting these together, the inner cylindrical portion is screwed with the inner diameter member outside the first multi-plate friction clutch and the second multi-plate friction clutch on the central axis, and the outer cylindrical portion is slidably fitted onto the inner circumferential surface of the housing while facing the first multi-plate friction clutch or the second multi-plate friction clutch located on the adjacent side, and the clutch pressing member is fixed to the outer cylindrical portion so as to be located between the first multi-plate friction clutch and the second multi-plate friction clutch.

4. In the invention described in claim 3, the clutch pressing member is composed of a press-formed annular plate extending radially between the first multi-plate friction clutch and the second multi-plate friction clutch, is integrally connected to the outer cylindrical portion at its outer circumferential end, and is provided with a press-formed portion at its inner circumferential end for pressing one of the first multi-plate friction clutch and the second multi-plate friction clutch, and is provided with a press-formed portion at an intermediate portion for pressing the other of the first multi-plate friction clutch and the second multi-plate friction clutch.

5. In the two-speed transmission according to the invention as claimed in claim 4, the inner peripheral portion of the clutch pressing member is engaged with the outer peripheral portion with some elastic deformation in the axial direction to thereby perform the fastening operation of the first multi-plate friction clutch and the second multi-plate friction clutch.

6. In the invention described in claim 1, a set of actuators is shared for engaging a first multi-plate friction clutch and a second multi-plate friction clutch, and the thrust transmission member rotates (swings) back and forth due to the axial back and forth movement of the outer diameter member, and the clutch pressing member selectively engages the first multi-plate friction clutch and the second multi-plate friction clutch due to the back and forth rotation of the thrust transmission member. This two-speed transmission for an electric vehicle selectively engages

7. In the invention described in claim 6, the thrust transmission member is pivotally attached to the housing at one end, and is configured as a swing arm that is loosely fitted into the internal thread member at a diametrically opposed position at the other end sandwiching the first multi-plate friction clutch and the second multi-plate friction clutch, and the clutch pressure member is pivotally attached to the swing arm at a diametrically opposed position and is located between the opposing surfaces of the multi-plate friction clutch and the second multi-plate friction clutch, and the forward and backward rotation of the swing arm due to the forward and backward axial movement of the internal thread member causes the clutch pressure member to directly face the first multi-plate friction clutch or the second multi-plate friction clutch while engaging it.

8. In the invention of claim 2 or 4, an input shaft is disposed coaxially with the output shaft within a housing, and the transmission includes three rotating elements: a carrier supporting a pinion, and two gears having different numbers of teeth that mesh with the pinion, and a planetary gear type transmission mechanism is provided in which the input shaft and the output shaft are respectively connected to two of the three rotating elements. The first and second multi-plate friction clutches are disposed relative to the three rotating elements and the housing so that a first speed change ratio is obtained between the input and output shafts by engaging the first multi-plate friction clutch and disengaging the second multi-plate friction clutch by the thrust transmission member, thereby configuring a planetary gear type transmission mechanism as the first gear mechanism, and a second speed change ratio is obtained between the input and output shafts by disengaging the first multi-plate friction clutch and engaging the second multi-plate friction clutch by the thrust transmission member, thereby configuring a planetary gear type transmission mechanism as the second gear mechanism. This is a two-speed transmission.

9. In the invention described in claim 8, the first multi-plate friction clutch contributes to forming the first gear ratio by reducing the speed between the input and output shafts by connecting one of the two rotating elements that are not the carrier in the planetary gear type transmission mechanism to the housing (brakes the housing), and the second multi-plate friction clutch contributes to forming the second gear ratio by rotating the rotating elements between the input and output shafts as one unit, and a two-speed transmission equipped with a one-way clutch arranged in parallel with the first multi-plate friction clutch for transmitting driving torque between the output shaft and the housing.

10. 5. A two-speed transmission for an electric vehicle according to claim 2 or 4, wherein the first gear mechanism is composed of meshing spur gears for obtaining a first speed change ratio, and the second gear mechanism is composed of meshing spur gears for obtaining a second speed change ratio.

11. 11. A two-speed transmission for an electric vehicle according to claim 10, further comprising a one-way clutch disposed in parallel between the first gear mechanism and an input side and an output side thereof for transmitting driving torque.

12. 2. A two-speed transmission for an electric vehicle according to claim 1, wherein two sets of the actuators are provided, the first actuator being involved in engaging and disengaging a first multi-plate friction clutch for setting a first speed change ratio, and the second actuator being involved in engaging and disengaging a second multi-plate friction clutch.

13. In the invention described in claim 12, in each actuator, the thrust transmission member is pivotally attached to the housing at one end, and is configured as a swing arm loosely fitted into the outer diameter member at a diametrically opposed position at the other end sandwiching a first multi-plate friction clutch in the first set and a second multi-plate friction clutch in the second set, and the clutch pressure member is pivotally attached to the swing arm at a diametrically opposed position, and the forward and backward rotation of the swing arm due to the axial forward and backward movement of the outer diameter member causes the clutch pressure member to engage the first multi-plate friction clutch in the first set and the second multi-plate friction clutch in the second set.

14. 2. A two-speed transmission according to claim 1, wherein the meshing gears for transmitting torque are constituted by a pair of spur gears.

15. 2. A two-speed transmission according to claim 1, wherein the gears for torque transmission are constituted by a worm on the control motor side and a wheel meshing with the worm.

16. 2. A two-speed transmission according to claim 1, wherein the internally threaded member and the externally threaded member have a large number of balls disposed therebetween in close contact with each other so as to circulate infinitely.

17. 2. A two-speed transmission according to claim 1, further comprising an electromagnetic brake for braking the rotating shaft of the control motor to hold the first multi-plate friction clutch and / or the second multi-plate friction clutch in the engaged state.

18. 18. A two-speed transmission according to claim 17, wherein the first multi-plate friction clutch and / or the second multi-plate friction clutch are re-engaged by braking the rotating shaft of the control motor at predetermined time intervals.

19. 19. A two-speed transmission according to claim 17 or 18, wherein the electromagnetic brake brakes the rotating shaft of the control motor when it is not energized.

20. 12. A two-speed transmission according to claim 9 or 11, wherein the one-way clutch is locked and the electromagnetic brake is not engaged when driving at a first gear ratio, and the one-way clutch is free and the electromagnetic brake is engaged when coasting at the first gear ratio.

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