Electric unit

Abstract

The present invention provides an electric unit that suppresses heat transfer from the transaxle case to the power control unit, while also preventing the overall unit from becoming larger. [Solution] An electric unit 1 comprises a transaxle case 3 housing a transaxle including a motor and gear train, and a PCU case 2 housing a power control unit 4 that controls the power supplied to the motor, with the PCU case 2 having a cylindrical connecting portion 3b protruding from the transaxle case 3. The PCU case 2 has an opening 2e that opens toward the space inside the connecting portion 3b and is fixed to the end of the connecting portion 3b. At least a part of the power control unit 4 is positioned inside the connecting portion 3b and is fixed to the PCU case 2 with a predetermined gap between it and the transaxle case 3.

Description

Technical Field

[0001] This invention relates to an electric unit including a transaxle containing a motor and a gear train, and a power control unit for controlling the motor.

Background Art

[0002] Patent Document 1 describes an integrated electric unit in which a PCU case for housing a power control unit for controlling a motor is fixed to the upper part of a transaxle case housing a transaxle including a motor and a differential mechanism. In order to suppress the influence of radiant heat from the transaxle case, such as the partition part which is the upper surface of the transaxle case, on the power control unit, a cylindrical connection part protruding upward from the transaxle case is provided, ribs having a heat dissipation function are provided inside the connection part, and the PCU case is fixed to the upper end of the connection part. The ribs are arranged in a lattice pattern within the inner region of the connection part, and the tip ends thereof are configured to protrude outside the connection part.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the electric unit described in Patent Document 1, in order to suppress the influence of radiant heat from the partition part which is the upper surface of the transaxle case on the power control unit, in the vertical direction of the electric unit, the transaxle case, the ribs, and the PCU case are arranged in this order. That is, providing ribs between the transaxle case and the PCU case is an essential configuration. Therefore, there is a possibility that the electric unit may become larger in size.

[0005] This invention was made in view of the above-mentioned technical problems, and aims to provide an electric unit that suppresses the transfer of heat from the transaxle case to the power control unit, while also suppressing an increase in the overall size of the unit. [Means for solving the problem]

[0006] To achieve the above objective, this invention provides an electric unit comprising a transaxle case housing a transaxle including a motor and a gear train, and a PCU case housing a power control unit for controlling the power supplied to the motor, wherein the PCU case has a cylindrical connecting portion protruding from the transaxle case, and the PCU case has an opening that opens toward the space inside the connecting portion and is fixed to the end of the connecting portion, and at least a part of the power control unit protrudes toward the inside of the connecting portion and is fixed to the PCU case with a predetermined gap between it and the transaxle case. [Effects of the Invention]

[0007] According to this invention, a transaxle case housing a transaxle including a motor and gear train, and a PCU case housing a power control unit are connected via a connection portion protruding from the transaxle case. The power control unit is fixed to the PCU case. Therefore, the heat transferred from the transaxle case to the connection portion is dissipated by the connection portion, thereby reducing the amount of heat transferred from the transaxle case to the PCU case by heat conduction. As a result, the amount of heat transferred to the power control unit fixed to the PCU case can be reduced.

[0008] Furthermore, the PCU case has an opening that faces the space inside the connection section, and at least a portion of the power control unit protrudes inward towards the connection section and is fixed to the PCU case. In other words, the connection section has the function of connecting the transaxle case and the PCU case, and the function of dissipating heat transferred from the transaxle case, as well as the function of housing the power control unit. Therefore, since there is no need to provide a heat dissipation section or the like between the transaxle case and the power control unit, the electric unit can be made smaller.

[0009] Furthermore, the power control unit is fixed to the PCU case such that a predetermined gap is maintained between the power control unit located inside the connection point and the transaxle case. In other words, an air layer with a low heat transfer coefficient is interposed between the power control unit and the transaxle case. Therefore, heat transfer from the transaxle case to the power control unit can be suppressed. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic cross-sectional view showing an example of an electric unit in an embodiment of this invention. [Modes for carrying out the invention]

[0011] This invention will be described based on the embodiments shown in the figures. Note that the embodiments described below are merely examples of how the present invention can be implemented and do not limit the invention.

[0012] The electric unit in this embodiment of the invention can be applied to a vehicle having a transaxle that includes a motor that functions as a driving force source and a gear train that transmits the torque of the motor to the drive wheels. Figure 1 shows an enlarged cross-sectional view illustrating an example of the electric unit in this embodiment of the invention. The electric unit 1 shown in Figure 1 is constructed by combining a PCU case 2 that houses a power control unit (hereinafter referred to as PCU) 4 that controls the motor, and a transaxle case 3 that houses the aforementioned transaxle.

[0013] In the example shown in Figure 1, the PCU4 is composed of, for example, a converter that steps up or down the output voltage of an energy storage device (not shown) and an inverter that converts the DC voltage of the energy storage device to an AC voltage. The PCU4 may also include other electronic components, such as a DC-DC converter that adjusts the voltage applied to electrical equipment of auxiliary equipment installed in the vehicle. In Figure 1, the PCU4 comprises four components: a first component 4a, a second component 4b, a third component 4c, and a fourth component 4d.

[0014] The PCU case 2 comprises a mounting plate 2a, a cylindrical first side wall portion 2b extending upward from the outer peripheral edge of the mounting plate 2a in Figure 1, a substantially tapered second side wall portion 2c extending downward from near the outer peripheral edge of the mounting plate 2a in Figure 1, and a flange portion 2d protruding outward from the lower end of the second side wall portion 2c. The flange portion 5a of the cover 5, which has a trapezoidal cross-section, is fixed to the upper end of the first side wall portion 2b by bolts (not shown), for example, and the first component 4a of the PCU 4 is positioned on the upper surface of the mounting plate 2a in Figure 1 within the upper space 6 surrounded by the cover 5 and the mounting plate 2a and second side wall portion 2c of the PCU case 2.

[0015] On the other hand, a cylindrical connecting portion 3b is formed on the top plate portion 3a of the transaxle case 3 so as to extend upward in Figure 1, and the upper end of the connecting portion 3b is fixed to the flange portion 2d of the PCU case 2 by a bolt (not shown), for example. As a result, a housing portion 7 is formed between the PCU case 2 and the transaxle case 3, in which the second component 4b, third component 4c, and fourth component 4d of the PCU 4 are housed.

[0016] Specifically, the housing section 7 is formed by the internal space 3c of the connection section 3b of the transaxle case 3 and an opening 2e formed on the inside of the second side wall section 2c of the PCU case 2 that opens toward the internal space 3c. In the housing section 7, the second component 4b of the PCU 4 is directly attached to the lower surface of the mounting plate 2a of the PCU case 2 in Figure 1, within the opening 2e of the PCU case 2.

[0017] The third component 4c of the PCU4 has a flange-shaped fastening portion 4e that protrudes from one of its sides toward the connection portion 3b of the transaxle case 3, and the fastening portion 4e is fixed to a part of the flange portion 2d of the PCU case 2 by a bolt 8 via a buffer 4f. The buffer 4f is preferably made of an elastic resin material, so that the buffer 4f can function as a heat insulating material and a cushioning material. In this way, the third component 4c is not in direct contact with the second component 4b, and is supported only by the flange portion 2d of the PCU case 2 via the buffer 4f.

[0018] The fourth component 4d of the PCU4 is slightly smaller in width compared to the second component 4b and the third component 4c. Specifically, the fourth component 4d is mounted on the lower surface of the third component 4c in Figure 1, maintaining a predetermined gap between it and the top plate portion 3a of the transaxle case 3. In this way, at least a portion of the PCU4 is housed so as to protrude toward the internal space 3c of the connection portion 3b of the transaxle case 3, and predetermined gaps are maintained between the PCU4 and the connection portion 3b of the transaxle case 3, and between the PCU4 and the top plate portion 3a of the transaxle case 3.

[0019] In the example shown in Figure 1, a stepped portion 3d is formed on the top plate portion 3a of the transaxle case 3 to match the shape of the fourth component 4d of the PCU 4, which is positioned opposite it. In other words, a part of the top plate portion 3a of the transaxle case 3 protrudes into the interior of the housing portion 7. This allows the PCU 4 to be offset downward relative to the transaxle case 3, thereby enabling miniaturization of the electric unit 1.

[0020] As described above, the electric unit 1 is composed of a motor that functions as a driving force source and a transaxle that includes a gear train that transmits the motor's torque to the drive wheels. Therefore, for example, while the vehicle is running, the motor generates heat due to copper losses caused by energizing the motor's coils and iron losses caused by the rotation of the motor's rotor. In addition, each gear constituting the gear train generates heat due to frictional forces corresponding to the sliding of the tooth surfaces when the gear train transmits torque.

[0021] As described above, the heat generated by the motor and gear train while the vehicle is running is transferred to the transaxle case 3, as shown by the thick arrows in Figure 1, and eventually conducted to the top plate portion 3a of the transaxle case 3. In this situation, in the electric unit 1 according to this embodiment of the invention, the connection portion 3b of the transaxle case 3 functions as a heat dissipation portion. Therefore, the heat transferred from the motor and gear train to the top plate portion 3a of the transaxle case 3 is dissipated from the connection portion 3b, as shown by the thin arrows in Figure 1. As a result, the amount of heat transferred from the transaxle case 3 to the PCU case 2 is reduced, and consequently, thermal damage to the first component 4a and second component 4b of the PCU 4, which are in direct contact with the mounting plate 2a of the PCU case 2, can be suppressed.

[0022] Also, as described above, there is a predetermined gap between the top plate portion 3a of the transaxle case 3 and the fourth component 4d of the PCU 4, and the air intervening in the gap has a low heat transfer coefficient. Therefore, the heat (radiant heat) radiated from the top plate portion 3a of the transaxle case 3 can be suppressed from being transmitted to the PCU 4. As a result, the heat resistance (heat capacity) of the PCU 4 can be reduced, and the degree of freedom in selecting components of the electric unit 1 can be increased, so that the cost of the electric unit 1 can be reduced.

[0023] In addition, when the buffer 4f is formed of a resin elastic member as described above, the buffer 4f can function as a heat insulating material and a cushioning material. In this case, the amount of heat transmitted to the PCU case 2, which has decreased due to heat radiation from the connecting portion 3b, is further reduced by the buffer 4f when being transmitted to the third component 4c of the PCU 4. Therefore, damage to the third component 4c due to heat can be further suppressed.

[0024] Furthermore, the PCU case 2 has an opening 2e that opens toward the internal space 3c of the connecting portion 3b, and the PCU 4 is fixed to the PCU case 2 such that at least a part of it protrudes toward the internal space 3c of the connecting portion 3b. That is, the connecting portion 3b has a function of connecting the transaxle case 3 and the PCU case 2, a function of radiating the heat transmitted from the transaxle case 3, and in addition, a function of housing the PCU 4. Therefore, there is no need to provide a heat radiating portion or the like between the transaxle case 3 and the PCU 4, and the electric unit 1 can be miniaturized.

[0025] Furthermore, the PCU 4 is fixed to the PCU case 2 such that a predetermined gap is formed between the PCU 4 provided inside the connecting portion 3b and the transaxle case 3. Thereby, an air layer with a low heat transfer coefficient intervenes between the PCU 4 and the transaxle case 3, so that heat transfer from the transaxle case 3 to the PCU 4 can be suppressed.

[0026] It should be noted that the present invention is not limited to the embodiments described above, and may be modified as appropriate within the scope of the configuration described in the claims. For example, instead of bolts, the flange portion 5a of the cover 5 may be fixed to the first side wall portion 2b of the PCU case 2 by welding or other appropriate method. Similarly, the flange portion 2d of the PCU case 2 may be fixed to the connection portion 3b of the transaxle case 3 by welding or other appropriate method. In addition, the buffer 4f may be omitted in order to reduce the number of parts. In that case, the fastening portion 4e can be made of a high-strength heat-resistant resin to provide the fastening portion 4e with heat insulation and cushioning functions. [Explanation of symbols]

[0027] 1 Electric Unit 2 PCU cases 2e opening 3 Transaxle Case 3a Top panel 3b Connection 3c interior space 4. Power Control Unit (PCU) 4a First component 4b Second component 4c Third component 4d 4th component 4e Fastening section 7. Storage area

Claims

[Claim 1] An electric unit comprising a transaxle case housing a transaxle including a motor and gear train, and a PCU case fixed to the transaxle case housing a power control unit that controls the power supplied to the motor, It is equipped with a cylindrical connecting portion that protrudes from the transaxle case, The PCU case has an opening that faces the space inside the connection portion and is fixed to the end of the connection portion. At least a portion of the power control unit is positioned inside the connection portion and fixed to the PCU case with a predetermined gap between it and the transaxle case. An electric unit characterized by the following features.

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