Drive unit

Abstract

To provide a drive unit that can increase drive power.SOLUTION: A drive unit 100 includes an electric motor 2 and a torque converter 3. The electric motor 2 is configured to drive a drive wheel via the torque converter 3. The electric motor 2 has a characteristic that output torque becomes large as revolution speed increases in a range from stopping to a specific revolution speed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a drive unit.

Background Art

[0002] In a conventional electric vehicle, torque from an electric motor is transmitted to drive wheels via a speed reducer and a differential gear. For example, in the electric vehicle disclosed in Patent Document 1, a speed reducer is directly connected to the motor, and torque is transmitted from this speed reducer to the drive wheels via a differential gear. Note that an embedded magnet type synchronous motor is used as the electric motor that is the drive source of this electric vehicle. This embedded magnet type synchronous motor can obtain maximum torque from a stop.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an electric vehicle as described above, there is a demand for improving the driving force. Therefore, an object of the present invention is to provide a drive unit capable of improving the driving force.

Means for Solving the Problems

[0005] A drive unit according to an aspect of the present invention includes a torque converter and an electric motor. The electric motor is configured to drive drive wheels via the torque converter. The electric motor has a characteristic that the output torque increases as the rotational speed increases in a range from a stop to a predetermined rotational speed.

[0006] In this configuration, torque from the electric motor is output to the drive wheels via a torque converter, thereby improving the driving force. In this drive unit, the load torque when the electric motor is stopped is very small because the electric motor outputs torque to the torque converter. Therefore, the electric motor in this drive unit does not need to output maximum torque from a standstill, as is the case with electric motors used in conventional electric vehicles. Accordingly, the electric motor in this drive unit has the characteristic that the output torque increases as the rotational speed increases, within the range from a standstill to a predetermined rotational speed. In this way, the drive unit uses an electric motor with more appropriate characteristics.

[0007] Preferably, the electric motor has the characteristic that, in a range above a predetermined rotational speed, the output torque decreases as the rotational speed increases.

[0008] Preferably, the electric motor has a rotor that does not contain magnets and a stator. With this configuration, since the electric motor does not have magnets, there is no need to reduce the induced voltage at high rotational speeds. As a result, field weakening control can be eliminated. [Effects of the Invention]

[0009] According to the present invention, the driving force can be improved. [Brief explanation of the drawing]

[0010] [Figure 1] Schematic diagram of the drive unit. [Figure 2] A graph showing the characteristics of an electric motor. [Figure 3] Cross-sectional view of a torque converter. [Figure 4] Cross-sectional view of the impeller hub. [Figure 5] Cross-sectional view of the impeller hub. [Figure 6] Enlarged view of the power output section. [Figure 7] Enlarged view of the power output section. [Figure 8] Enlarged view of the power output section. [Figure 9] A cross-sectional view of the drive unit showing the first cooling channel. [Figure 10] Cross-sectional view of the side wall of the torque converter case. [Figure 11] Cross-sectional view of the side wall of the torque converter case. [Figure 12] A schematic diagram of the drive unit related to a modified example. [Modes for carrying out the invention]

[0011] The drive unit according to this embodiment will be described below with reference to the drawings. Figure 1 is a schematic diagram of the drive unit according to this embodiment. In the following description, the axial direction refers to the direction in which the rotation axis O of the electric motor 2 and the torque converter 3 extends. The circumferential direction refers to the circumferential direction of a circle centered on the rotation axis O, and the radial direction refers to the radial direction of a circle centered on the rotation axis O.

[0012] [Drive unit 100] As shown in Figure 1, the drive unit 100 is a unit for driving the drive wheels 101. The drive unit 100 comprises an electric motor 2, a torque converter 3, a power output unit 4, a switching mechanism 8, an input shaft 5, an output shaft 6, a torque converter case 7, and a first cooling passage 9a (see Figure 9). This drive unit 100 is mounted, for example, in an electric vehicle.

[0013] <Electric Motor 2> The electric motor 2 is configured to drive the drive wheels 101 via the torque converter 3. In other words, the torque output by the electric motor 2 is transmitted to the drive wheels 101 via the torque converter 3.

[0014] Figure 2 is a graph showing the characteristics of electric motor 2 (relationship between rotational speed and torque). The solid line in Figure 2 is the torque curve showing the characteristics of electric motor 2 in this embodiment. The dashed line in Figure 2 is the torque curve showing the characteristics of an electric motor used as a power source in a conventional electric vehicle.

[0015] As shown by the solid line in FIG. 2, the electric motor 2 has a characteristic that the output torque increases as the rotational speed increases in the range from a stop state (rotational speed 0) to a predetermined rotational speed n. That is, the electric motor 2 does not output the maximum torque from the stop state. Note that in the electric motor 2, the torque at the time of rotational speed 0 is less than or equal to half of the maximum torque.

[0016] Also, the electric motor 2 has a characteristic that the output torque decreases as the rotational speed increases in the range higher than the predetermined rotational speed n. The electric motor 2 outputs the maximum torque at the predetermined rotational speed n. Note that, although not particularly limited, for example, the predetermined rotational speed n is about 20 to 40% of the maximum rotational speed Nmax of the electric motor 2.

[0017] As shown in FIG. 1, the electric motor 2 has a motor case 21, a stator 22, and a rotor 23. The electric motor 2 in the present embodiment is a so-called inner rotor type motor. The motor case 21 is fixed to a vehicle body frame or the like and is non-rotatable.

[0018] The stator 22 is fixed to the inner peripheral surface of the motor case 21. The stator 22 is non-rotatable. The stator 22 has a stator core 221 and a coil 222. The stator core 221 is configured by laminating a plurality of electromagnetic steel sheets. The coil 222 is wound around the stator core 221. Specifically, the coil 222 is wound around the teeth portion of the stator core 221.

[0019] The rotor 23 rotates around the rotation axis O. The rotor 23 is arranged inside the stator 22 in the radial direction. The rotor 23 does not have a permanent magnet. The rotor 23 can be, for example, a cage type rotor. The electric motor 2 can be an induction motor. Note that, as will be described later, the electric motor 2 rotates in the same direction both when the vehicle moves forward and when it moves backward. For this reason, the electric motor 2 rotates only in the forward rotation direction and does not rotate in the reverse rotation direction.

[0020] <Torque converter 3> The torque converter 3 is positioned at a distance from the electric motor 2 in the axial direction. The power output unit 4 is positioned between the torque converter 3 and the electric motor 2. In the axial direction, the electric motor 2, power output unit 4, and torque converter 3 are arranged in that order.

[0021] The rotation axis O of the torque converter 3 substantially coincides with the rotation axis O of the electric motor 2. The torque converter 3 receives power input from the electric motor 2. The torque converter 3 then amplifies the power (torque) from the electric motor 2 and outputs it to the power output unit 4.

[0022] As shown in Figure 3, the torque converter 3 includes a cover 31, an impeller 32, a turbine 33, a stator 34, and a one-way clutch 36. The torque converter 3 also further includes a centrifugal clutch 37.

[0023] The torque converter 3 is positioned such that the impeller 32 faces the electric motor 2 side (left side in Figure 3) and the cover 31 faces the opposite side of the electric motor 2 (right side in Figure 3). This torque converter 3 is housed in a torque converter case 7. A working fluid is supplied to the torque converter 3. The working fluid is, for example, hydraulic oil.

[0024] The cover 31 receives power from the electric motor 2. The cover 31 rotates due to the power from the electric motor 2. The cover 31 is fixed to the input shaft 5 extending from the electric motor 2. For example, the cover 31 has spline holes, and the input shaft 5 spline-fits into the spline holes of the cover 31. As a result, the cover 31 rotates integrally with the input shaft 5. The cover 31 is positioned to cover the turbine 33.

[0025] The cover 31 has a disc portion 311, a cylindrical portion 312, and a cover hub 313. The disc portion 311 has an opening in the center. The cylindrical portion 312 extends from the outer peripheral end of the disc portion 311 toward the electric motor 2. The disc portion 311 and the cylindrical portion 312 are made of a single component.

[0026] The cover hub 313 is fixed to the inner circumference end of the disc portion 311. In this embodiment, the cover hub 313 is made of a separate component from the disc portion 311, but it may also be made of the same component as the disc portion 311.

[0027] The cover hub 313 has a first boss portion 313a, a first flange portion 313b, and a protruding portion 313c. The first boss portion 313a, the first flange portion 313b, and the protruding portion 313c are made of a single component.

[0028] The first boss portion 313a is cylindrical and has a spline hole. The input shaft 5 is spline-fitted to this first boss portion 313a. The first boss portion 313a is rotatably supported in the torque converter case 7 via a bearing member 102. Therefore, in the axial direction, the first boss portion 313a extends from the first flange portion 313b to the side opposite the electric motor 2.

[0029] The first flange portion 313b extends radially outward from the first boss portion 313a. More specifically, the first flange portion 313b extends radially outward from the end of the first boss portion 313a on the electric motor 2 side. The disc portion 311 is fixed to the outer peripheral end of this first flange portion 313b.

[0030] The projection 313c extends axially from the first flange portion 313b. The projection 313c extends toward the electric motor 2. The projection 313c extends from the outer peripheral end of the first flange portion 313b. The projection 313c is cylindrical. This projection 313c has a plurality of through holes 313d. Working fluid is discharged from the torque converter 3 through these through holes 313d.

[0031] The impeller 32 rotates integrally with the cover 31. The impeller 32 is fixed to the cover 31. The impeller 32 has an impeller shell 321, a plurality of impeller blades 322, an impeller hub 323, and a plurality of supply channels 324.

[0032] The impeller shell 321 is fixed to the cover 31. Multiple impeller blades 322 are attached to the inner surface of the impeller shell 321.

[0033] The impeller hub 323 is attached to the inner circumferential end of the impeller shell 321. In this embodiment, the impeller hub 323 is made of the same component as the impeller shell 321, but it may be made of a separate component from the impeller shell 321.

[0034] The impeller hub 323 has a second boss portion 323a and a second flange portion 323b. The second boss portion 323a is cylindrical, shaft It extends in the direction. The second boss portion 323a is rotatably supported by the torque converter case 7 via the bearing member 103 (see Figure 9). The fixed shaft 104 moves within the second boss portion 323a. shaft It extends in that direction. Furthermore, this fixed shaft 104 is cylindrical, and the output shaft 6 passes through this fixed shaft 104. shaft It extends in the direction. The fixed shaft 104 also extends from, for example, the transmission case 40 or the torque converter case 7. The fixed shaft 104 is non-rotatable.

[0035] The supply channel 324 is formed in the impeller hub 323. More specifically, the supply channel 324 is formed in the second flange portion 323b. The supply channel 324 extends radially outward from the inner circumferential surface of the impeller hub 323. The supply channel 324 opens into the torus T. The torus T is the space enclosed by the impeller 32 and the turbine 33.

[0036] The supply channel 324 is closed in the axial direction. That is, the supply channel 324 is a through-hole extending radially within the impeller hub 323. As shown in Figure 4, the supply channel 324 extends radially. The supply channel 324 is inclined radially outward, opposite to the direction of rotation. Note that the supply channel 324 is not limited to extending in a straight line; for example, as shown in Figure 5, the supply channel 324 may extend in a curved shape.

[0037] As shown in Figure 3, the turbine 33 is positioned opposite the impeller 32. More specifically, the turbine 33 faces the impeller 32 in the axial direction. Power from the impeller 32 is transmitted to the turbine 33 via the working fluid.

[0038] The turbine 33 has a turbine shell 331, a plurality of turbine blades 332, and a turbine hub 333. The turbine blades 332 are fixed to the inner surface of the turbine shell 331.

[0039] The turbine hub 333 is fixed to the inner circumference end of the turbine shell 331. For example, the turbine hub 333 is fixed to the turbine shell 331 by rivets. In this embodiment, the turbine hub 333 is made of a separate component from the turbine shell 331, but it may be made of the same component as the turbine shell 331.

[0040] The output shaft 6 is attached to the turbine hub 333. More specifically, the output shaft 6 is spline-fitted to the turbine hub 333. The turbine hub 333 rotates integrally with the output shaft 6.

[0041] The turbine hub 333 has a third boss portion 333a and a third flange portion 333b. The third boss portion 333a and the third flange portion 333b are made of a single component.

[0042] The third boss portion 333a is cylindrical and has a spline hole. The output shaft 6 is spline-fitted to this third boss portion 333a. The third boss portion 333a extends axially from the third flange portion 333b toward the side opposite to the electric motor 2. That is, the third boss portion 333a extends axially from the third flange portion 333b toward the cover hub 313.

[0043] The third boss portion 333a is positioned radially apart from the projection portion 313c. That is, radially, the projection portion 313c is positioned outside the third boss portion 333a. A bearing member 35 is positioned between the third boss portion 333a and the projection portion 313c. In the absence of the bearing member 35, the outer circumferential surface of the third boss portion 333a and the inner circumferential surface of the projection portion 313c face each other.

[0044] A fluid passage is formed between the tip of the third boss portion 333a and the cover hub 313 through which the working fluid flows. In this embodiment, a plurality of notches 333c are formed at the tip of the third boss portion 333a. The notches 333c extend radially from the tip of the third boss portion 333a. The working fluid is discharged from the torque converter 3 through these notches 333c and through holes 313d.

[0045] The third flange portion 333b extends radially outward from the third boss portion 333a. More specifically, the third flange portion 333b extends radially outward from the end of the third boss portion 333a on the electric motor 2 side. The turbine shell 331 is fixed to the outer peripheral end of this third flange portion 333b by rivets or the like.

[0046] The stator 34 is configured to rectify the hydraulic fluid returning from the turbine 33 to the impeller 32. The stator 34 is rotatable around the rotation axis O. For example, the stator 34 is supported on a fixed shaft 104 via a one-way clutch 36. The stator 34 is positioned axially between the impeller 32 and the turbine 33.

[0047] The stator 34 includes a disc-shaped stator carrier 341 and a plurality of stator blades 342 attached to its outer circumferential surface.

[0048] The one-way clutch 36 is positioned between the fixed shaft 104 and the stator 34. The one-way clutch 36 is configured to allow the stator 34 to rotate in the forward direction. On the other hand, the one-way clutch 36 prevents the stator 34 from rotating in the reverse direction. Power (torque) is amplified by this stator 34 and transmitted from the impeller 32 to the turbine 33.

[0049] The centrifugal clutch 37 is attached to the turbine 33. The centrifugal clutch 37 rotates integrally with the turbine 33. The centrifugal clutch 37 is configured to connect the cover 31 and the turbine 33 by the centrifugal force generated by the rotation of the turbine 33. In detail, the centrifugal clutch 37 is configured to transmit power from the cover 31 to the turbine 33 when the turbine 33 reaches a predetermined rotational speed or higher.

[0050] The centrifugal clutch 37 has a plurality of centrifugal elements 371 and a friction material 372. The friction material 372 is attached to the outer circumferential surface of the centrifugal elements 371. The centrifugal elements 371 are arranged to be movable in the radial direction. However, the centrifugal elements 371 are arranged to be immovable in the circumferential direction. Therefore, the centrifugal elements 371 rotate together with the turbine 33 and move radially outward due to centrifugal force.

[0051] When the rotational speed of the turbine 33 exceeds a predetermined speed, the centrifugal element 371 of the centrifugal clutch 37 moves radially outward, and the friction material 372 frictionally engages with the inner circumferential surface of the cylindrical portion 312 of the cover 31. As a result, the centrifugal clutch 37 turns on, and power from the cover 31 is transmitted to the turbine 33 via the centrifugal clutch 37. Even when the centrifugal clutch 37 is turned on, the working fluid can still flow through the centrifugal clutch 37.

[0052] When the rotational speed of the turbine 33 falls below a predetermined speed, the centrifugal element 371 moves radially inward, and the frictional engagement between the friction material 372 and the inner circumferential surface of the cylindrical portion 312 of the cover 31 is released. As a result, the centrifugal clutch 37 is turned off, and power from the cover 31 is not transmitted to the turbine 33 via the centrifugal clutch 37. In other words, power from the cover 31 is transmitted to the impeller 32 and then to the turbine 33 via the working fluid.

[0053] <Input axis 5> As shown in Figures 1 and 3, the input shaft 5 extends from the electric motor 2. More specifically, the input shaft 5 extends from the rotor 23 of the electric motor 2. The input shaft 5 extends toward the torque converter 3. The axis of rotation of the input shaft 5 is substantially collinear with the axis of rotation of the electric motor 2 and the axis of rotation of the torque converter 3.

[0054] The input shaft 5 inputs power from the electric motor 2 to the torque converter 3. The tip of the input shaft 5 is attached to the cover hub 313 of the torque converter 3. The input shaft 5 rotates integrally with the rotor 23 of the electric motor 2. The input shaft 5 extends inside the output shaft 6. The input shaft 5 is solid. The input shaft 5 has a communication passage 51 at its tip. The communication passage 51 extends axially and opens toward the first cooling passage 9a.

[0055] <Output shaft 6> The output shaft 6 outputs power from the torque converter 3. The output shaft 6 outputs power from the torque converter 3 to the power output unit 4. The output shaft 6 extends from the torque converter 3 toward the electric motor 2.

[0056] The output shaft 6 is cylindrical. The input shaft 5 extends inside this output shaft 6. One end of the output shaft 6 (the right end in Figure 3) is attached to the turbine 33 of the torque converter 3. The other end of the output shaft 6 is rotatably supported, for example, by the transmission case 40 via a bearing member or the like.

[0057] <Power output section 4> As shown in Figure 1, the power output unit 4 is positioned axially between the electric motor 2 and the torque converter 3. The power output unit 4 is housed within the transmission case 40. The power output unit 4 outputs power from the torque converter 3 to the drive wheels 101. More specifically, the power output unit 4 outputs power from the torque converter 3 to the drive wheels 101 via the differential gear 109. As will be described later, the power output unit 4 does not output power in neutral mode.

[0058] As shown in Figure 6, the power output unit 4 has a first gear train 41 and a second gear train 42. The power output unit 4 outputs power from either the first gear train 41 or the second gear train 42. The first gear train 41 outputs power from the torque converter 3 in a first rotation direction. The second gear train 42 outputs power from the torque converter 3 in a second rotation direction. The second rotation direction is the opposite direction of rotation to the first rotation direction.

[0059] The first rotation direction is the direction of rotation when the vehicle moves forward. The second rotation direction is the direction of rotation when the vehicle moves backward. Therefore, when power is transmitted to the drive wheels 101 via the first gear train 41, the vehicle moves forward. On the other hand, when power is transmitted to the drive wheels 101 via the second gear train 42, the vehicle moves backward.

[0060] The first gear train 41 has a first gear 41a and a second gear 41b that mesh with each other. The first gear 41a is supported so as to be rotatable relative to the output shaft 6. When the ring gear 82 of the switching mechanism 8, which will be described later, meshes with it, the first gear 41a rotates integrally with the output shaft 6.

[0061] The second gear 41b is supported by the drive shaft 43. The second gear 41b rotates integrally with the drive shaft 43. The second gear 41b outputs power from the first gear 41a to the drive shaft 43.

[0062] The second gear train 42 has a third gear 42a, a fourth gear 42b, and a fifth gear 42c. The second gear train 42 has one more gear than the first gear train 41. The third gear 42a is supported so as to be rotatable relative to the output shaft 6. The third gear 42a rotates integrally with the output shaft 6 when the ring gear 82 of the switching mechanism 8, which will be described later, engages with it.

[0063] The fourth gear 42b meshes with the third gear 42a. The fourth gear 42b is supported by a counter shaft (not shown). The fourth gear 42b may rotate integrally with the counter shaft or relative to the counter shaft.

[0064] The fifth gear 42c meshes with the fourth gear 42b. The fifth gear 42c is supported by the drive shaft 43. The fifth gear 42c rotates integrally with the drive shaft 43. The fifth gear 42c outputs power from the third gear 42a to the drive shaft 43.

[0065] The gear ratio in the first gear train 41 is different from the gear ratio in the second gear train 42. More specifically, the gear ratio in the second gear train 42 is greater than the gear ratio in the first gear train 41.

[0066] The power output unit 4 can be in one of three states: first output mode, second output mode, or neutral mode. In first output mode, the power output unit 4 outputs power via the first gear train 41. In second output mode, the power output unit 4 outputs power via the second gear train 42. In neutral mode, the power output unit 4 does not output power from the torque converter 3.

[0067] <Switching mechanism> The switching mechanism 8 is configured to switch the state of the power output unit 4 to one of the following: first output mode, second output mode, or neutral mode. The switching mechanism 8 includes a clutch hub 81, a ring gear 82, and a lever 83.

[0068] The clutch hub 81 is attached to the output shaft 6. The clutch hub 81 rotates integrally with the output shaft 6. The clutch hub 81 may be composed of one component with the output shaft 6, or it may be composed of separate components. The clutch hub 81 has multiple teeth on its outer circumferential surface.

[0069] The ring gear 82 has multiple teeth on its inner circumference. The ring gear 82 is always meshed with the clutch hub 81 and rotates together with the clutch hub 81. In other words, the ring gear 82 rotates together with the output shaft 6. The ring gear 82 is positioned to be movable in the axial direction.

[0070] As shown in Figure 6, the ring gear 82 can mesh with the clutch hub 81 and engage with the first gear 41a. In detail, the first gear 41a has a first cylindrical portion 411 that protrudes in the axial direction. The first cylindrical portion 411 has a plurality of teeth on its outer circumferential surface. The ring gear 82 meshes with the outer circumferential surface of this first cylindrical portion 411.

[0071] In this way, the ring gear 82 engages with the clutch hub 81 and the first cylindrical portion 411, causing the power output unit 4 to enter the first output mode. That is, power from the output shaft 6 is output via the first gear train 41.

[0072] As shown in Figure 7, the ring gear 82 can mesh with the clutch hub 81 and engage with the third gear 42a. In detail, the third gear 42a has a second cylindrical portion 421 that protrudes in the axial direction. The second cylindrical portion 421 has multiple teeth on its outer circumferential surface. The ring gear 82 meshes with the outer circumferential surface of this second cylindrical portion 421.

[0073] In this way, the ring gear 82 engages with the clutch hub 81 and the second cylindrical portion 421, causing the power output unit 4 to enter the second output mode. That is, power from the output shaft 6 is output via the second gear train 42.

[0074] As shown in Figure 8, the ring gear 82 can be in a state where it engages only with the clutch hub 81. In this way, when the ring gear 82 engages only with the clutch hub 81 and not with both the first cylindrical portion 411 and the second cylindrical portion 421, the power output unit 4 enters a neutral mode. That is, power from the output shaft 6 is not output to the drive wheel 101.

[0075] Lever 83 is connected to the ring gear 82. Lever 83 extends from the ring gear 82 to the outside of the transmission case 40. Lever 83 is operated by the driver. By operating lever 83, the ring gear 82 can be moved axially. This causes the ring gear 82 to engage with the clutch hub 81 and the first cylindrical portion 411, or with the clutch hub 81 and the second cylindrical portion 421, or with the clutch hub 81 only. As a result, the switching mechanism 8 can switch the state of the power output unit 4 to one of the first output mode, the second output mode, or the neutral mode.

[0076] <Torque converter case 7> As shown in Figure 9, the torque converter case 7 houses the torque converter 3. In this embodiment, the torque converter case 7 is made of the same component as the transmission case 40, but it may be made of separate components.

[0077] The torque converter case 7 has a side wall portion 71, an outer wall portion 72, and a plurality of heat dissipation fins 73. The side wall portion 71 is positioned to face the cover 31 of the torque converter 3. The side wall portion 71 is positioned perpendicular to the rotation axis O.

[0078] In the axial direction, the torque converter 3 is located on one side of the side wall 71 (the left side in Figure 9). On the other hand, the other side of the side wall 71 (the right side in Figure 9) is in contact with the outside air. In other words, no heat source components are located on the other side of the side wall 71.

[0079] A cover 31 is rotatably attached to the center of the side wall portion 71 via a bearing member 102. The side wall portion 71 is made of a material with high specific heat and thermal conductivity so that it can quickly absorb a large amount of heat from the working fluid flowing in the first cooling channel 9a and dissipate it to the atmosphere. For example, the side wall portion 71 is made of magnesium or aluminum.

[0080] The outer wall portion 72 is positioned to face the outer circumferential surface of the torque converter 3. The outer wall portion 72 is composed of a single component with the side wall portion 71, but it may be composed of separate components. The outer wall portion 72 extends from the outer circumferential end of the side wall portion 71 toward the electric motor 2. The outer wall portion 72 extends substantially parallel to the rotation axis O. The tip of the outer wall portion 72 (the end on the electric motor 2 side) is inclined radially inward. The material of the outer wall portion 72 can be the same as that of the side wall portion 71.

[0081] The heat dissipation fins 73 are formed on the side wall portion 71. The heat dissipation fins 73 extend from the side wall portion 71 to the side opposite the torque converter 3 (right side in Figure 9). The heat dissipation fins 73 are attached to the side wall portion 71 to efficiently dissipate heat from the working fluid flowing through the first cooling channel 9a. The thermal conductivity of the heat dissipation fins 73 is preferably equal to or higher than that of the side wall portion 71, but is not particularly limited. For example, the heat dissipation fins 73 are made of magnesium, aluminum, or copper.

[0082] <First cooling channel 9a> The first cooling channel 9a is a channel for cooling the working fluid discharged from the torque converter 3. The first cooling channel 9a extends within the torque converter case 7. In this embodiment, the first cooling channel 9a is formed only in the upper half of the torque converter case 7.

[0083] The first cooling channel 9a extends from the center of the side wall 71 to the outer periphery, and then extends axially along the outer wall 72 beyond the torque converter 3. The first cooling channel 9a is in communication with the working fluid reservoir 91.

[0084] As shown in Figure 10 or Figure 11, the first cooling channel 9a has multiple paths within the side wall 71. In this embodiment, the first cooling channel 9a is divided into two paths within the side wall 71. The first cooling channel 9a does not extend in a straight line from the center to the outer periphery within the side wall 71, but rather extends in a meandering manner.

[0085] The first cooling channel 9a may have multiple paths within the outer wall portion 72. In this embodiment, for example, the first cooling channel 9a is divided into three paths within the outer wall portion 72. The first cooling channel 9a extends linearly in the axial direction within the outer wall portion 72, but it may also extend in a meandering manner.

[0086] <Working fluid reservoir> As shown in Figure 9, the drive unit 100 is equipped with a working fluid reservoir 91. The working fluid reservoir 91 is positioned in the axial direction, in cooperation with the side wall 71, to sandwich the torque converter 3. That is, in the axial direction, the working fluid reservoir 91, torque converter 3, and side wall 71 are arranged in that order. The working fluid reservoir 91 is located inside the transmission case 40. The working fluid reservoir 91 is located above the rotating shaft O.

[0087] The working fluid reservoir 91 contains the working fluid supplied to the torque converter 3. The working fluid reservoir 91 has a supply hole 92 on its bottom surface. The working fluid discharged from this supply hole 92 is supplied to the torque converter 3 via a flow path 106 between the fixed shaft 104 and the second boss portion 323a of the impeller hub 323.

[0088] Specifically, the rotation of the impeller 32 of the torque converter 3 generates centrifugal force, which supplies the working fluid in the flow path 106 into the torus T via the supply flow path 324. The working fluid discharged from the torque converter 3 then flows through the connecting passage 51 to the first cooling flow path 9a. The working fluid cooled by flowing through the first cooling flow path 9a is then returned to the working fluid reservoir 91.

[0089] <Operation> In the drive unit 100 configured as described above, when the vehicle is moving forward, the power output unit 4 is in first output mode. As a result, the power input from the electric motor 2 to the torque converter 3 is output to the drive wheels 101 via the first gear train 41 of the power output unit 4. On the other hand, when the vehicle is moving backward, the power output unit 4 is in second output mode. As a result, the power input from the electric motor 2 to the torque converter 3 is output to the drive wheels 101 via the second gear train 42 of the power output unit 4. In this way, the rotation direction of the electric motor 2 and the torque converter 3 is constant when the vehicle is moving forward and backward. For this reason, the drive unit 100 can amplify torque not only when moving forward but also when moving backward.

[0090] [Differentiation] Although embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications are possible without departing from the spirit of the invention.

[0091] Variation 1 In the above embodiment, the impeller 32 has a supply passage 324, but the configuration is not limited to this. That is, the impeller 32 does not have to have a supply passage 324. In this case, as shown in Figure 12, the drive unit 100 may further include an oil pump 12.

[0092] The oil pump 12 is configured to supply oil into the torque converter 3. The oil pump 12 rotates integrally with the electric motor 2 or the torque converter 3. More specifically, the oil pump 12 is mounted on the impeller 32 so as to rotate integrally with the impeller 32. More specifically, the oil pump 12 is mounted on the impeller hub 323 of the impeller 32. The oil pump 12 is, for example, a positive displacement pump.

[0093] Variation 2 In the above embodiment, the switching mechanism 8 switches the state of the power output unit 4 by operating the lever 83, but the configuration of the switching mechanism 8 is not limited to this. For example, the switching mechanism 8 can also switch the state of the power output unit 4 by electronic control or the like.

[0094] Variation 3 The electric motor 2 may be a synchronous motor. In this case, the characteristics of the electric motor 2 in the above embodiment can be achieved by controlling the current flowing through the coils of the stator 22 of the electric motor 2. [Explanation of Symbols]

[0095] 2 Electric motor 22 stata 23 Rotors 3 Torque converter 100 Drive Unit

Claims

1. Torque converter and, An electric motor, which is the sole power source and is configured to drive the drive wheels via the torque converter, Equipped with, The aforementioned electric motor, in the range from stopped to a predetermined rotational speed, increases in rotational speed. It has the characteristic of increasing output torque as it progresses. Drive unit.

2. The electric motor, in a range higher than the predetermined rotational speed, It has the characteristic of decreasing output torque as a result. The drive unit according to claim 1.

3. The electric motor has a rotor that does not contain magnets and a stator. The drive unit according to claim 1 or 2.

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