Drive unit

Abstract

The present invention provides a drive unit including a motor that transfers electric power to and from an inverter and a housing that accommodates the motor, wherein a bearing pivotably supporting a rotor constituting the motor is supported by the housing; the bearing is disposed at a position on the radially inner side of a coil end, which is the portion of the coil that protrudes from a stator constituting the motor, thereby forming a ring-shaped inner space in the housing, said coil being installed on the stator; and a portion of a busbar electrically connecting the coil end with the inverter is disposed in the inner space.

Description

Drive unit

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

[0002] JP2012-143019A discloses a configuration in which a bus bar that connects a coil end extending axially from a stator of a motor and an inverter is disposed on the outer diameter side of the coil end.

[0003] However, when the motor is housed in a housing, the portion of the housing that interferes with the bus bar must protrude in the radial direction, which reduces the on-board efficiency.

[0004] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a drive unit that has a bus bar that is compactly accommodated near a motor, thereby improving on-board efficiency.

[0005] According to one aspect of the present invention, there is provided a drive unit including a motor that exchanges power with an inverter and a housing that accommodates the motor. In the drive unit, a bearing that supports a rotor constituting the motor is supported by the housing, and the bearing is positioned radially inward of a coil end that is a portion of a coil assembled to a stator constituting the motor that protrudes from the stator, thereby forming a ring-shaped internal space in the housing. A portion of a bus bar that electrically connects the coil end and the inverter is positioned in the internal space.

[0006] Fig. 1 is a cross-sectional view and a partially enlarged view of the drive unit of this embodiment. Fig. 2 is a schematic view of the drive unit of this embodiment as viewed from the axial direction (a cross-sectional view taken along line A-A in Fig. 1). Fig. 3 is a perspective view of the drive unit of this embodiment (a perspective view taken along line A-A in Fig. 1). Fig. 4 is a schematic view of a modified example of this embodiment as viewed from the axial direction.

[0007] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0008] Fig. 1 is a cross-sectional view and a partially enlarged view of the drive unit 1 of this embodiment. Fig. 2 is a schematic view of the drive unit 1 of this embodiment as seen from the axial direction (a cross-sectional view taken along line A-A in Fig. 1). Fig. 3 is a perspective view of the drive unit 1 of this embodiment (a cross-sectional view taken along line A-A in Fig. 1).

[0009] The drive unit 1 of this embodiment is composed of a motor 2 (a stator 21 and a rotor 22), an inverter 3, a housing 4, and the like.

[0010] The drive unit 1 of this embodiment is mounted on an electric vehicle or a hybrid vehicle and functions as an electric motor that drives the wheels. The drive unit 1 also functions as a generator that receives driving force from the rotation of the wheels and generates electricity (regenerative power). The drive unit 1 may also be used as a drive unit for devices other than automobiles, such as various electrical appliances or industrial machines.

[0011] The housing 4 has a cylindrical shape and accommodates the motor 2 and the inverter 3. A partition plate 43 is arranged in the housing 4 to divide the interior of the housing 4 in the axial direction. The partition plate 43 divides the housing 4 into a first accommodation section 41 that accommodates the motor 2 and a second accommodation section 42 that accommodates the inverter 3.

[0012] An opening 411 is arranged in the wall surface of the first housing portion 41 on the opposite side of the partition plate 43 in the axial direction, and a rotor shaft 222 (described later) protrudes from the opening 411 .

[0013] The motor 2 includes a stator 21 formed in an annular shape, and a rotor 22 rotatably mounted inside the stator 21 .

[0014] The outer peripheral surface of the stator 21 is fixed by shrink fitting or the like while in contact with the inner surface of the housing 4 (first accommodating portion 41). The stator 21 has coils of flat wire, for example, having a rectangular cross section, in slots (not shown). Of the two axial ends of the stator 21, a coil end 23A extends from the end closest to the partition plate 43, and a coil end 23B extends from the opposite end.

[0015] The rotor 22 includes a rotor core 221 that is ring-shaped when viewed in the axial direction, and a rotor shaft 222 that supports the rotor core 221 .

[0016] The base end of the rotor shaft 222 in the axial direction is rotatably supported by a bearing 5A (bearing portion), and the tip end of the rotor shaft 222 is rotatably supported by a bearing 5B (bearing portion). Note that in addition to the bearings 5A and 5B, any bearing such as a metal bearing (slide bearing) or a thrust bearing can be used as the bearing portion.

[0017] Bearing 5A is supported by a ring-shaped support portion 412 arranged on the main surface of partition plate 43 on the side facing first housing portion 41, and bearing 5B is supported by a ring-shaped support portion 413 arranged in a position facing opening 411 of first housing portion 41. The end of rotor shaft 222 on the bearing 5B side protrudes from housing 4, and when drive unit 1 is mounted on a vehicle, this protruding portion is coupled to a transmission or the like mounted on the vehicle. Note that if the connection portion of the transmission with rotor shaft 222 is rotatably supported by the above-mentioned bearing portion or the like, bearing 5B may be omitted.

[0018] As shown in FIG. 1 etc., the coil end 23A and the bearing 5A (support portion 412) are arranged in positions where they overlap each other in the axial direction, and the coil end 23A is arranged so as to wrap around the periphery of the bearing 5A (support portion 412).

[0019] Furthermore, the outer diameter of the bearing 5A (support portion 412) is set smaller than the inner diameter of the coil end 23A. Therefore, a ring-shaped internal space 414 is formed between the bearing 5A (support portion 412) and the coil end 23A. Note that the support portion 412 is not limited to a shape that covers the outer periphery of the bearing 5A as shown in FIG. 1 etc., but may be configured to support the bearing 5A from the axial direction and have a diameter that is substantially the same as the diameter of the bearing 5A.

[0020] In place of the partition plate 43, for example, multiple beams may be arranged to extend from the same position as the bearing 5A (support portion 412) in the axial direction of the inner wall of the housing 4 and connect to the bearing 5A (support portion 412), and the beams may be arranged so that, when viewed from the axial direction, they extend radially from the bearing 5A (support portion 412) as the center and connect to the inner wall of the housing 4, thereby supporting the bearing 5A (support portion 412).

[0021] As shown in FIGS. 2 and 3, bus bars 6 (bus bar 6U, bus bar 6V, bus bar 6W) are arranged in internal space 414.

[0022] The bus bar 6 is made of a material with high electrical conductivity, such as copper (Cu), and is formed in a flat plate shape.

[0023] The bus bar 6 is arranged in the internal space 414 and includes a main body 61 having an arc shape that curves in the same direction as the coil end 23A when viewed from the axial direction, a pair of first connection portions 62 that extend axially from different positions (for example, both circumferential ends) of the main body 61 in the circumferential direction of the stator 21 and have a shape that bends radially outward from the stator 21 midway, and whose tips extending radially outward are connected to the coil end 23A by welding or the like, and a second connection portion 63 that extends axially from a position between the pair of first connection portions 62 in a direction away from the stator 21 and is electrically connected to the inverter 3 (Figure 1) outside the internal space 414.

[0024] The coils (coil ends 23A, 23B) and bus bars 6 preferably have a rectangular cross-sectional shape, but may also have a circular cross-sectional shape. In this case, a crimp terminal (not shown) may be attached to the tip of the second connection portion 63, and the crimp terminal may be connected to the inverter 3 side (connection terminal 31).

[0025] By making the main body 61 arc-shaped as shown in Figures 2 and 3, the bus bar 6 can be efficiently arranged in the internal space 414 without interfering with the coil end 23A and the bearing 5A (support portion 412).

[0026] Furthermore, by arranging the second connection portion 63 between the pair of first connection portions 62, the busbar 6 has a circumferentially symmetrical shape, and current is dispersed from the second connection portion 63 toward the pair of first connection portions 62, thereby suppressing local heat generation in the busbar 6.

[0027] The stator 21 is assembled with multiple U-phase coils, V-phase coils, and W-phase coils arranged in order in the circumferential direction, and therefore the coil ends 23A include the U-phase coil ends 23A, the V-phase coil ends 23A, and the W-phase coil ends 23A.

[0028] One end of each of the multiple U-phase coils, one end of each of the multiple V-phase coils, and one end of each of the multiple W-phase coils are connected in parallel to a neutral bus bar 6N (Figure 3), and the neutral bus bar 6N (Figure 3) is positioned, for example, on the inner side of the coil end 23A.

[0029] The other ends of the multiple U-phase coils are connected in parallel at one of two parallel connection points. The other ends of the multiple V-phase coils and the other ends of the multiple W-phase coils are also connected in parallel in the same manner as the other ends of the multiple U-phase coils.

[0030] Therefore, one of the pair of first connection portions 62 of the U-phase busbar 6U is connected to one of the parallel connection points of the U-phase coil ends 23A, and the other of the pair of first connection portions 62 is connected to the other parallel connection point of the U-phase coil ends 23A. The V-phase busbar 6V (first connection portion 62) and the W-phase busbar 6W (first connection portion 62) are connected to coil ends 23A of the same phase, similar to the U-phase busbar 6U.

[0031] 2, the U-phase busbar 6U, the V-phase busbar 6V, and the W-phase busbar 6W are arranged so that their circumferential centers (e.g., second connection portions 63) divide the internal space 414 into approximately three circumferential portions. This allows the U-phase busbar 6U, the V-phase busbar 6V, and the W-phase busbar 6W to be arranged efficiently without interfering with each other. Furthermore, because the connection positions between the busbars 6 and the coil ends 23A are approximately uniform in the circumferential direction, localized heat generation in the coil ends 23A can be suppressed.

[0032] In addition, if there is one parallel connection point for each of the other ends of the U-phase coil, the other ends of the multiple V-phase coils, and the other ends of the multiple W-phase coils, the number of first connection portions 62 of the busbar 6 for each phase may be one.

[0033] As shown in FIG. 1 , the partition plate 43 has an insertion hole 431 through which the second connection portion 63 is inserted, and the tip of the second connection portion 63 inserted through the insertion hole 431 is connected by welding or the like to a connection terminal 31 extending from the inverter 3 (the three-phase AC side of the semiconductor power module that performs power conversion between DC power and three-phase AC power).

[0034] Although not shown, the partition plate 43 is formed with an insertion hole 431 through which the second connection portion 63 of the U-phase bus bar 6U is inserted, an insertion hole 431 through which the second connection portion 63 of the V-phase bus bar 6V is inserted, and an insertion hole 431 through which the second connection portion 63 of the W-phase bus bar 6W is inserted. The three insertion holes 431 are arranged at positions that divide the rotor shaft 222 into approximately three equal parts in the circumferential direction around the rotor shaft 222. Correspondingly, extending from the inverter 3 are connection terminals 31 that connect to the second connection portion 63 of the U-phase bus bar 6U, connection terminals 31 that connect to the second connection portion 63 of the V-phase bus bar 6V, and connection terminals 31 that connect to the second connection portion 63 of the W-phase bus bar 6W.

[0035] 1 , it is preferable to fill the insertion hole 431 after the second connection portion 63 has been inserted with a filler material 432 having insulating properties and high thermal conductivity, such as epoxy resin. This reduces the heat transfer from the first accommodating portion 41 to the second accommodating portion 42 (inverter 3) via air, and allows the filler material 432 to absorb the heat propagating through the second connection portion 63, thereby reducing the transfer of heat generated in the stator 21 to the inverter 3 via the second connection portion 63.

[0036] In the second housing portion 42, the inverter 3 is attached, for example, to the inner side surface of the second housing portion 42. The inverter 3 is preferably disposed adjacent to a flow path through which a refrigerant that cools the motor 2 flows. Note that this embodiment also includes a configuration in which the inverter 3 is disposed outside the housing 4.

[0037] [Modification] Fig. 4 is a schematic diagram of a modification of the present embodiment as viewed from the axial direction. In this modification, the parallel connection points of the U-phase coil ends 23A (not shown), the V-phase coil ends 23A (not shown), and the W-phase coil ends 23A (not shown) are unevenly distributed to the right of the coil ends 23A in Fig. 4. The parallel connection points of each phase are arranged, for example, clockwise in the circumferential direction in the following order: one of the parallel connection points of the U-phase coil ends 23A, one of the parallel connection points of the V-phase coil ends 23A, the other of the parallel connection points of the U-phase coil ends 23A, one of the parallel connection points of the W-phase coil ends 23A, the other of the parallel connection points of the V-phase coil ends 23A, and the other of the parallel connection points of the W-phase coil ends 23A.

[0038] The U-phase busbar 6U, the V-phase busbar 6V, and the W-phase busbar 6W are arranged unevenly in a position on the right side of the internal space 414 in Fig. 4. Furthermore, the U-phase busbar 6U and the W-phase busbar 6W are arranged radially inward of the stator 21 (coil end 23A) relative to the V-phase busbar 6V.

[0039] Furthermore, the other of the two circumferential ends of the U-phase busbar 6U intersects with one of the two circumferential ends of the V-phase busbar 6V in the circumferential direction, and the other of the two circumferential ends of the V-phase busbar 6V intersects with one of the two circumferential ends of the W-phase busbar 6W in the circumferential direction.

[0040] As a result, the left side of the internal space 414 in FIG. 4 becomes an empty space, allowing other components to be placed therein.

[0041] In addition, in the partition plate 43, the insertion holes 431 for inserting the second connection portions 63 of the U-phase busbar 6U, the insertion holes 431 for inserting the second connection portions 63 of the V-phase busbar 6V, and the insertion holes 431 for inserting the second connection portions 63 of the W-phase busbar 6W can be positioned unevenly on the right side in the case of Figure 4, so that the left side of the partition plate 43 (second accommodating portion 42 (Figure 1)) also becomes empty space, and other components can be placed therein.

[0042] Furthermore, by arranging the inverter 3 (not shown in FIG. 4) in the second accommodating section 42 (FIG. 1) so that it is close to, for example, the V-phase bus bar 6V in the radial and circumferential directions, the length of the second connecting section 63 that enters the second accommodating section 42 can be shortened, thereby reducing electrical loss accordingly.

[0043] The length of the radially extending portion of the first connection portion 62 of the U-phase busbar 6U, the length of the radially extending portion of the first connection portion 62 of the V-phase busbar 6V, and the length of the radially extending portion of the first connection portion 62 of the W-phase busbar 6W may be set to be different from one another. This makes it possible to arrange the U-phase busbar 6U, the V-phase busbar 6V, and the W-phase busbar 6W at different radial positions and overlap one another in the circumferential direction while avoiding contact (short-circuiting) with one another.

[0044] [Effects of this embodiment] According to the drive unit 1 of this embodiment, in the drive unit 1 including the motor 2 that exchanges power with the inverter 3 and the housing 4 that accommodates the motor 2, the bearing portion (bearing 5A) that supports the rotor 22 that constitutes the motor 2 is supported by the housing 4, and the bearing portion (bearing 5A) is positioned radially inward of the coil end 23A, which is the portion of the coil assembled to the stator 21 that protrudes from the stator 21 that constitutes the motor 2, so that a ring-shaped internal space 414 is formed in the housing 4, and a portion of the bus bar 6 that electrically connects the coil end 23A and the inverter 3 is positioned in the internal space 414.

[0045] With the above configuration, components that connect the coil end 23A and the inverter 3, such as the bus bar 6, do not protrude to the outer periphery of the coil end 23A (stator 21), and by avoiding radial protrusion of the housing 4 due to this protrusion, the on-board efficiency of the drive unit 1 can be improved.

[0046] In this embodiment, the coil end 23A includes a first coil end (U-phase coil end 23A), a second coil end (V-phase coil end 23A) through which a current flows that is out of phase with the current flowing through the first coil end (U-phase coil end 23A), and a third coil end (W-phase coil end 23A) through which a current flows that is out of phase with the current flowing through the first coil end (U-phase coil end 23A) and the second coil end (V-phase coil end 23A). The bus bar 6 is connected to the first coil end (U-phase coil end 23A) and the second coil end (V-phase coil end 23A). the first bus bar (bus bar 6U) connected to the second coil end (V-phase coil end 23A) and insulated from the third coil end (W-phase coil end 23A) and the third coil end (W-phase coil end 23A); the second bus bar (bus bar 6V) connected to the second coil end (V-phase coil end 23A) and insulated from the third coil end (W-phase coil end 23A) and the first coil end (U-phase coil end 23A); and the third bus bar (bus bar 6W) connected to the third coil end (W-phase coil end 23A) and insulated from the first coil end (U-phase coil end 23A) and the second coil end (V-phase coil end 23A).

[0047] With the above configuration, the bus bars 6 (bus bars 6U, bus bars 6V, bus bars 6W) can be efficiently arranged in the circumferential direction in the internal space 414.

[0048] In this embodiment, the busbar 6 includes a main body 61 that is disposed in the internal space 414 and has an arc shape that curves in the same direction as the coil end 23A when viewed from the axial direction, a pair of first connection portions 62 that extend axially from different positions on the main body 61 in the circumferential direction of the stator 21 and have a shape that bends radially outward from the stator 21 midway, with the tips extending radially outward connecting to the coil end 23A, and a second connection portion 63 that extends axially from a position between the pair of first connection portions 62 in a direction away from the stator 21 and is electrically connected to the inverter 3 outside the internal space 414.

[0049] With the above configuration, the busbars 6 can be efficiently arranged in the circumferential direction in the internal space 414. Furthermore, the current flowing from the inverter 3 to the second connection portion 63 is dispersed in the main body 61 so as to flow to the two first connection portions 62, thereby reducing localized heat generation in the busbars 6.

[0050] In this embodiment, a plurality of bus bars 6 are arranged in the internal space 414, and among the plurality of arranged bus bars 6, the length of the radially extending portion of the first connection portion 62 of one of a pair of adjacent bus bars 6 (e.g., bus bar 6U or bus bar 6W) is different from the length of the radially extending portion of the first connection portion 62 of the other of the pair of adjacent bus bars 6 (e.g., bus bar 6V).

[0051] In the above configuration, one of a pair of adjacent bus bars 6 (for example, bus bar 6U or bus bar 6W) and the other of a pair of adjacent bus bars 6 (for example, bus bar 6V) can be arranged at different positions in the radial direction of stator 21 and can be arranged to intersect with each other in the circumferential direction of stator 21. This allows the bus bars 6 to be unevenly arranged at specific positions in the circumferential direction of internal space 414, thereby increasing the degree of freedom in setting the connection positions with inverter 3.

[0052] In this embodiment, three bus bars 6 are arranged in the internal space 414, and the circumferential centers (first connection portions 62) of the three bus bars 6 (bus bar 6U, bus bar 6V, bus bar 6W) are arranged at positions that divide the internal space 414 into approximately equal thirds.

[0053] With the above configuration, the bus bars 6 can be efficiently arranged in the circumferential direction in the internal space 414. In particular, by arranging the neutral bus bar 6N (which forms the inner side surface of the coil end 23A in this embodiment) connected to the bus bars 6 at different radial positions, arrangement efficiency can be improved. Furthermore, current can be supplied to the coil end 23A approximately uniformly in the circumferential direction, which can suppress localized heat generation in the coil end 23A.

[0054] In this embodiment, the housing 4 is capable of accommodating the inverter 3 together with the motor 2 , and the inverter 3 is disposed at a different position from the motor 2 in the axial direction and adjacent to the internal space 414 .

[0055] With the above configuration, the drive unit 1 accommodating the inverter 3 can be made compact.

[0056] In this embodiment, the housing 4 is capable of accommodating the inverter 3 together with the motor 2, and includes a partition plate 43 that divides the space accommodating the motor 2 (first accommodating section 41) and the space accommodating the inverter 3 (second accommodating section 42) in the axial direction and to which a bearing section (bearing 5A) is attached, and the partition plate 43 has an insertion hole 431 through which the second connection section 63 is inserted.

[0057] The above configuration allows the coils (coil ends 23A) arranged on the stator 21 to be connected over a short distance to the inverter 3 (semiconductor power module). Also, heat transfer from the motor 2 to the inverter 3 through the air can be reduced.

[0058] In this embodiment, the insertion hole 431 through which the second connection portion 63 is inserted is filled with a filling material 432 (for example, epoxy resin) having insulating and thermally conductive properties.

[0059] With the above configuration, the transfer of heat through the air from the first accommodating section 41 (motor 2) to the second accommodating section 42 (inverter 3) is reduced, and the heat propagating through the second connecting section 63 is absorbed by the filling material 432, thereby reducing the transfer of heat generated in the stator 21 that is transferred to the inverter 3 via the second connecting section 63.

[0060] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

Claims

1. A drive unit including a motor which receives and transmits power to and from an inverter, and a housing which accommodates the motor, wherein a bearing portion which supports a rotor constituting the motor is supported by the housing, the bearing portion is disposed at a position radially inward of a coil end which is a portion of a coil assembled to a stator constituting the motor and which protrudes from the stator, thereby forming a ring-shaped internal space in the housing, and a portion of a bus bar which electrically connects the coil end and the inverter is disposed in the internal space.

2. A drive unit as described in claim 1, wherein the coil ends include a first coil end, a second coil end through which a current of a different phase from the current flowing in the first coil end flows, and a third coil end through which a current of a different phase from the current flowing in the first coil end and the current flowing in the second coil end flows, and the bus bars include a first bus bar connected to the first coil end and insulated from the second coil end and the third coil end, a second bus bar connected to the second coil end and insulated from the third coil end and the first coil end, and a third bus bar connected to the third coil end and insulated from the first coil end and the second coil end.

3. The drive unit described in claim 1, wherein the bus bar includes: a main body that is disposed in the internal space and has an arc shape that curves in the same direction as the coil ends when viewed in the axial direction; a pair of first connection portions that extend axially from different positions on the main body in the circumferential direction of the stator and have a shape that bends radially outward of the stator midway, with tips extending radially outward connecting to the coil ends; and a second connection portion that extends axially from a position between the pair of first connection portions in a direction away from the stator and electrically connects to the inverter outside the internal space.

4. A drive unit as described in claim 3, wherein a plurality of bus bars are arranged in the internal space, and the length of a radially extending portion of the first connection portion of one of a pair of adjacent bus bars among the plurality of arranged bus bars is different from the length of a radially extending portion of the first connection portion of the other of the pair of adjacent bus bars.

5. A drive unit as described in claim 3, wherein three bus bars are arranged in the internal space, and the circumferential centers of the three bus bars are arranged at positions that divide the internal space into thirds approximately equally.

6. A drive unit according to claim 1, wherein the housing is capable of accommodating the inverter together with the motor, the inverter being disposed at a different position from the motor in the axial direction and adjacent to the internal space.

7. A drive unit as described in claim 3, wherein the housing is capable of accommodating the inverter together with the motor, includes a partition plate that axially divides a space accommodating the motor and a space accommodating the inverter, and includes a partition plate to which the bearing portion is attached, and the partition plate is formed with an insertion hole through which the second connection portion is inserted.

8. A drive unit according to claim 7, wherein the insertion hole through which the second connection portion is inserted is filled with a filling material having insulating properties and thermal conductivity.

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