Patent ID: 12244207

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG.1is a schematic cross-sectional view of a drive unit100. The drive unit100is a unit for directly or indirectly controlling driving of a vehicle (not shown) such as an electric vehicle or a hybrid vehicle using a rotating electrical machine11. The direct drive control using the rotating electrical machine11is, for example, a control mode in which a torque generated by the rotating electrical machine11is converted into a driving force of the vehicle. The indirect drive control using the rotating electrical machine11is, for example, a control mode in which the rotating electrical machine11is used for power generation, and a part or all of electric power generated by the power generation is used to generate a driving force of the vehicle. The drive unit100of the present embodiment is mounted on a series hybrid electric vehicle. Therefore, the drive unit100controls the driving of the vehicle directly and indirectly.

As shown inFIG.1, the drive unit100includes the rotating electrical machine11and an inverter12that controls an operation of the rotating electrical machine11in an outer housing10. In addition to the rotating electrical machine11and the inverter12, the drive unit100is configured integrally with members (not shown) such as gears constituting a speed reducer and a rotation sensor.

The outer housing10is a housing that forms an outer shell of the drive unit100. The rotating electrical machine11, the inverter12, and the like are accommodated in the outer housing10, thereby being integrated as the drive unit100. A flow path (hereinafter, referred to as a refrigerant flow path)14through which a refrigerant13that cools a heating element such as the rotating electrical machine11and the inverter12flows is provided in the outer housing10. The refrigerant13is a fluid such as a liquid or a gas supplied for cooling, and is, for example, cooling water, other cooling liquid or air, and the like. The refrigerant13flows through the refrigerant flow path14and the like, thereby cooling each part accommodated in the outer housing10, such as the rotating electrical machine11, the inverter12, and other heating elements (not shown). In the present embodiment, the refrigerant13is a cooling liquid that circulates between radiators (not shown).

The rotating electrical machine11is a motor, a generator, or a motor generator that operates as a motor and a generator. The rotating electrical machine11may include two or more motors that operate as a motor, a generator, or a motor generator. In the present embodiment, the rotating electrical machine11includes two motors, that is, a first motor20and a second motor25. For this reason, the inverter12includes a first inverter12athat controls the first motor20and a second inverter12bthat controls the second motor25.

The first motor20is a driving motor (electric motor). Therefore, the vehicle equipped with the drive unit100travels by converting a torque generated by the first motor20into a driving force. Electric power for driving the first motor20is supplied from a battery (not shown). The first motor20includes an inner housing21, a stator22, and a rotor23.

The inner housing21is a cylindrical member that fixes the stator22by a method such as shrink fitting. In the present embodiment, the inner housing21has a cylindrical shape. The inner housing21includes a refrigerant flow path24(seeFIG.2and the like) that communicates with the refrigerant flow path14of the outer housing10therein. That is, the refrigerant flow path24is a flow path (passage) through which the refrigerant13flows. A structure of the inner housing21and a structure of the refrigerant flow path24of the inner housing21(hereinafter referred to as the refrigerant flow path24of the first motor20) will be described in detail later.

The rotor23is attached to the outer housing10and is inserted into a central portion of the stator22when the drive unit100is formed. The rotor23is rotatable with respect to the inner housing21and the stator22even after being inserted into the stator22. Since the stator22is a unit through which a current flows to control the first motor20, the stator22is at least one of heat generation factors of the first motor20.

The second motor25is a power generation motor (generator). The second motor25is connected to an engine (internal combustion engine) (not shown) and is driven by the engine. The electric power generated by the second motor25is accumulated in a battery that supplies electric power to the first motor20. The second motor25can consume the electric power of the battery by idling.

The second motor25is different in use from the first motor20, but has the same basic structure as the first motor20. That is, the second motor25includes an inner housing26, a stator27, and a rotor28. The inner housing26is a cylindrical member that fixes the stator27by a method such as shrink fitting, and has a cylindrical shape in the present embodiment. The inner housing26includes a refrigerant flow path29(seeFIG.12and the like) that communicates with the refrigerant flow path14of the outer housing10therein. That is, the refrigerant flow path29is a flow path through which the refrigerant13flows. The refrigerant flow path29of the inner housing26(hereinafter, referred to as the refrigerant flow path29of the second motor25) has substantially the same basic structure as the refrigerant flow path24of the inner housing21. A structure of the refrigerant flow path29of the second motor25will be described in detail later together with a coupling structure of the first motor20and the second motor25. The rotor28is attached to the outer housing10and is rotatable even after being inserted into the stator27. Since the stator27is a unit through which a current flows to control the second motor25, the stator27is at least one of heat generation factors of the second motor25.

The inner housing21of the first motor20and the inner housing26of the second motor25are integrated by being coupled with a coupling pipe30. For this reason, the inner housing21of the first motor20and the inner housing26of the second motor25as a whole constitute an inner housing of the rotating electrical machine11. That is, the inner housing of the rotating electrical machine11includes a first housing and a second housing. The first housing is the inner housing21of the first motor20, accommodates the stator22as a first stator and the rotor23as a first rotor, and has the refrigerant flow path24. The second housing is the inner housing26of the second motor accommodates the stator27as a second stator and the rotor28as a second rotor, and has the refrigerant flow path29.

In addition to integrating the inner housings21and26as described above, the coupling pipe30couples the refrigerant flow path24of the first motor20and the refrigerant flow path29of the second motor25. In the present embodiment, the refrigerant13flowing into the outer housing10flows into the refrigerant flow path24of the first motor20after passing through the refrigerant flow path14to cool the inverter12. Thereafter, the refrigerant13flows through the refrigerant flow path24of the first motor20and flows out to the coupling pipe30. Therefore, a connection portion between the refrigerant flow path14of the outer housing10and the first motor20is an inlet (hereinafter referred to as an inlet α) of the refrigerant13in the refrigerant flow path24of the first motor20. A connection portion between the coupling pipe30and the first motor20is an outlet (hereinafter referred to as an outlet β) of the refrigerant13in the refrigerant flow path24of the first motor20. That is, in the refrigerant flow path24of the first motor20, the inlet α is an introduction port of the refrigerant13, and the outlet β is a discharge port of the refrigerant13.

The refrigerant13flows into the refrigerant flow path29of the second motor25through the coupling pipe30, flows through the refrigerant flow path29of the second motor25, and then flows out to the refrigerant flow path14of the outer housing10. Therefore, a connection portion between the coupling pipe30and the second motor25is an inlet (hereinafter referred to as an inlet γ) of the refrigerant13in the refrigerant flow path29of the second motor25. A connection portion between the refrigerant flow path14of the outer housing10and the second motor25is an outlet (hereinafter referred to as an outlet δ) of the refrigerant13in the refrigerant flow path29of the second motor25. That is, in the refrigerant flow path29of the second motor25, the inlet γ is an introduction port of the refrigerant13, and the outlet δ is a discharge port of the refrigerant13.

That is, the coupling pipe30linearly couples the outlet β of the inner housing21and the inlet γ of the inner housing26without waste. Accordingly, the coupling pipe30connects the refrigerant flow path24of the first motor20and the refrigerant flow path29of the second motor25.

In the present embodiment, rotation axes of the first motor20and the second motor25are parallel to each other. As shown inFIG.1, a direction of the rotation axes of the first motor20and the second motor25is defined as a Z direction, and an X direction and a Y direction are defined so as to form a right-handed system with reference to the Z direction. Further, as shown inFIG.1, for convenience of explanation, the refrigerant flow path14connected to the first motor20and the refrigerant flow path14connected to the second motor25are parallel to each other in the vicinity of the connection portions thereof. A connection direction of the refrigerant flow path14to the first motor20and the second motor25is defined as the Y direction.

[Structure of Inner Housing and Refrigerant Flow Path]

FIG.2is a perspective view of the inner housing21. AlthoughFIG.2shows the inner housing21of the first motor20, the inner housing26of the second motor25also has the same structure. As shown inFIG.2, the inner housing21of the first motor20has a double pipe structure including an inner pipe31and an outer pipe32, and the refrigerant flow path24of the first motor20is formed between the inner pipe31and the outer pipe32.

The inner pipe31is a substantially cylindrical member, and has a flange portion33at one end. The flange portion33is provided with a fastening portion34. Therefore, the flange portion33constitutes a mounting surface to the outer housing10. The flange portion33also functions as a positioning member of the outer pipe32. That is, when the outer pipe32is attached to the inner pipe31by engagement, screwing, or other methods, an end of the outer pipe32abuts against the flange portion33of the inner pipe31. Accordingly, a relative position between the inner pipe31and the outer pipe32in the Z direction is determined. The fastening portion34is a portion of the flange portion33that has screw holes for fastening the inner housing21to the outer housing10. The stator22is accommodated and fixed in the inner pipe31.

Hereinafter, among circumferential surfaces of the inner pipe31, a circumferential surface in contact with the stator22is referred to as an inner circumferential surface, and a circumferential surface in contact with the outer pipe32is referred to as an outer circumferential surface. Similarly, among circumferential surfaces of the outer pipe32, a circumferential surface on the outer circumferential surface side of the inner pipe31is referred to as an inner circumferential surface, and a circumferential surface forming an outer periphery of the inner housing21is referred to as an outer circumferential surface. For convenience of explanation, in the inner circumferential surface of the inner pipe31, the inner circumferential surface on the positive side in the X direction is referred to as a right inner circumferential surface36, and the inner circumferential surface on the negative side in the X direction is referred to as a left inner circumferential surface37. A surface at the end of the inner housing21is referred to as an end surface. In the present embodiment, for convenience, an end surface of the inner pipe31on the positive side in the Z direction where the flange portion33is provided is referred to as “one end surface38”, and an end surface on the negative side in the Z direction is referred to as “the other end surface39”.

The outer pipe32is attached to an outside of the inner pipe31so as to cover the outer circumferential surface of the inner pipe31. Further, when the outer pipe32is attached to the inner pipe31, the inner circumferential surface of the outer pipe32abuts against the outer circumferential surface of the inner pipe31except for a portion where the refrigerant flow path24is formed. For this reason, the refrigerant flow path24is kept watertight and airtight to the extent that the refrigerant13does not leak at least. The outer pipe32has a connecting pipe40connected to the refrigerant flow path14of the outer housing10at the inlet α of the refrigerant13. The connecting pipe40may be referred to as a bulge.

FIG.3is a perspective view of the inner pipe31. The inner pipe31has a series of grooves41along the outer circumferential surface. The grooves41are formed to surround the outer circumferential surface of the inner pipe31. Adjacent ones of the grooves41are separated by wall portions42due to the encirclement or the like. The wall portions42separate the one end surface38and the other end surface39from the grooves41. Top portions43(ridge portions) of the wall portions42abut against the inner circumferential surface of the outer pipe32. When the outer pipe32is attached to the inner pipe31, the refrigerant flow path24is formed by the inner circumferential surface of the outer pipe32, the grooves41, and the wall portions42.

FIG.4is a side view of the inner pipe31.FIG.5is a side view of the inner pipe31as viewed from another direction. As shown inFIGS.4and5, the refrigerant flow path24is formed so as to spirally circulate along the outer circumferential surface of the inner pipe31from the inlet α to the outlet β. The refrigerant flow path24is provided in substantially the entire range (hereinafter referred to as a heat generation range45) in which heat is generated due to the presence of the stator22in the Z direction. For this reason, as indicated by dashed arrows, when the refrigerant13flows through the refrigerant flow path24, the entire stator22is cooled at least.

FIG.6is an explanatory view showing a detailed configuration of the refrigerant flow path24. As shown inFIG.6, hereinafter, a position of the refrigerant flow path24along the outer circumferential surface is represented by an angle in a plane (XY plane direction) perpendicular to the Z direction with reference to a position of the inlet α. An angle indicating a position in the refrigerant flow path24is referred to as an angular position. In the present embodiment, as shown inFIG.6, angular positions of the inlet α and the outlet β of the refrigerant13in the refrigerant flow path24are separated from each other, and an angular position of the inlet α is 0 degrees, whereas an angular position of the outlet β is 900 degrees. For this reason, the angular positions of the inlet α and the outlet β are separated by 180 degrees.

Regarding the angular positions of the inlet α and the outlet β, the term “separated” means that the inlet α and the outlet β are located at substantially different angular positions in consideration of sizes of the inlet α and the outlet β, a range in which the refrigerant13located at the inlet α and the outlet β cools the stator22, and the like. A structure of the refrigerant flow path24described in detail below is a structure for effectively cooling the accommodated stator22and the like even when the inlet α and the outlet β are separated. Therefore, it can be said that the positions of the inlet α and the outlet β are substantially separated from each other as long as a cooling effect of a part or the whole of the stator22is enhanced by adopting the structure of the refrigerant flow path24.

In addition, as the angular positions of the inlet α and the outlet β are separated, the structure of the refrigerant flow path24is more effective in relation to the cooling effect. When the inlet α and the outlet β are separated from each other by, for example, 10 degrees or more, a cooling performance improvement effect due to the structure of the refrigerant flow path24can be sufficiently expected. For example, when the inlet α and the outlet β are separated by 45 degrees or more, the cooling performance improvement effect due to the structure of the refrigerant flow path24tends to become remarkable. When the inlet α and the outlet β are separated by, for example, 90 degrees or more, the cooling performance improvement effect due to the structure of the refrigerant flow path24is particularly remarkable. In a case where a structure other than the refrigerant flow path24is adopted, the cooling effect is most likely to be reduced when the inlet α and the outlet β are separated by 180 degrees. For this reason, in a case where the inlet α and the outlet β are separated by 180 degrees, when the structure of the refrigerant flow path24is adopted, the cooling effect is most improved.

As shown inFIG.6, the refrigerant flow path24includes a first flow path51and a second flow path52. In the present embodiment, the refrigerant flow path24includes a third flow path53in addition to the first flow path51and the second flow path52.

The first flow path51is formed along the one end surface38of the inner housing21from the inlet α, and is formed such that a width along the circumferential surface increases along a flow direction of the refrigerant13. In particular, in the present embodiment, the first flow path51is provided in a range extending around the circumferential surface of the inner housing21from the inlet α.

The expression “formed along the one end surface38” means that a part or the whole of a first round closest to the one end surface38is included as a constituent element in the refrigerant flow path24surrounding the circumferential surface of the inner housing21. In the present embodiment, the first flow path51is a portion of the refrigerant flow path24corresponding to the first round from the inlet α, that is, a portion having an angular position of 0 degrees to 360 degrees. In particular, in the first flow path51, the wall portion42and the top portion43thereof on the one end surface38side are formed parallel to the one end surface38. Therefore, in a narrower sense, the first flow path51is formed along the one end surface38even when considering a positional relation between the one end surface38and the wall portion42forming the first flow path51.

The flow direction of the refrigerant13in the refrigerant flow path24is a direction along the refrigerant flow path24from the inlet α to the outlet β. In the first flow path51, the flow direction of the refrigerant13is a positive direction (direction from 0 degrees to 360 degrees) of a lower angular position with respect to the inlet α.

The “width along the circumferential surface” refers to a length in the Z direction, that is, an interval between the wall portions42(particularly, top portions43) in the Z direction. As shown inFIG.6, the first flow path51is formed such that the width along the circumferential surface gradually increases as the angular position increases from 0 degrees. As indicated by a dashed line inFIG.6, when the inlet α and the outlet β are coupled by a spiral flow path having a uniform width, the flow path is defined as a reference flow path55. A width along a circumferential surface of the reference flow path55is defined as a reference width. At this time, the first flow path51has a shape obtained by expanding the flow path with the reference width, that is, the reference flow path55in a direction (positive direction in the Z direction) of the one end surface38of the inner housing21. The reference width that is the width of the reference flow path55is determined according to an allowable pressure loss of the refrigerant13at the inlet α and the outlet β.

The second flow path52is formed along the other end surface39of the inner housing21, and is formed such that the width along the circumferential surface decreases toward the outlet β along the flow direction of the refrigerant13. In particular, in the present embodiment, the second flow path52is provided in a range extending around the circumferential surface of the inner housing26from the outlet R.

The expression “formed along the other end surface39” means that a part or the whole of a last round closest to the other end surface39is included as a constituent element in the refrigerant flow path24surrounding the circumferential surface of the inner housing21. In the present embodiment, the second flow path52is the last round of the refrigerant flow path24reaching the outlet β, that is, a portion having an angular position of 540 degrees to 900 degrees. In particular, in the second flow path52, the wall portion and the top portion43thereof on the other end surface39side are formed parallel to the other end surface39. Therefore, in a narrower sense, the second flow path52is formed along the other end surface39even when considering a positional relation between the other end surface39and the wall portion42forming the second flow path52.

The flowing direction of the refrigerant13in the second flow path52is a direction along the outlet β from an angular position of 540 degrees. As shown inFIG.6, the second flow path52is formed such that the width along the circumferential surface gradually decreases as the angular position increases from the angular position of 540 degrees to the outlet β. In particular, the second flow path52has a shape obtained by expanding the reference flow path55, which is the flow path with the reference width, in a direction (negative direction in the Z direction) of the other end surface39of the inner housing21.

The third flow path53is a flow path of the refrigerant13that is provided between the first flow path51and the second flow path52and couples the first flow path51and the second flow path52. The third flow path53is formed to have a uniform width along the circumferential surface. The width of the third flow path53is formed to be narrower than a width of a widest portion of the first flow path51and narrower than a width of a widest portion of the second flow path52. In the present embodiment, as indicated by hatching inFIG.6, the third flow path53is a portion at an angular position of 360 degrees to 540 degrees. In particular, in the present embodiment, the width of the third flow path53is equal to the reference width which is the width of the reference flow path55. The structure of the third flow path53contributes to suppression of the pressure loss of the refrigerant13, particularly to minimization of the pressure loss.

A boundary between the first flow path51and the third flow path53and a boundary between the second flow path52and the third flow path53are formed by straight lines along a circumferential direction of the inner housing21. Furthermore, in the present embodiment, the boundary between the first flow path51and the second flow path52is also formed by a straight line along the circumferential direction of the inner housing21. The straight line corresponds to the wall portion42when the reference flow path55is formed. In this way, the boundaries of the first flow path51, the second flow path52, and/or the third flow path53are formed by the straight lines in order to reduce the pressure loss of the refrigerant13and further improve the cooling performance by substantially conforming to the reference flow path55.

[Action of Refrigerant Flow Path]

Hereinafter, the action of the refrigerant flow path24configured as described above will be described in comparison with a refrigerant flow path of a comparative example.

FIG.7is an explanatory view showing a configuration of the refrigerant flow path60of the comparative example. In the comparative example, the configuration of the inner housing21other than the refrigerant flow path60, such as the angular positions of the inlet α and the outlet β of the refrigerant13, is the same as that of the inner housing21of the present embodiment. As shown inFIG.7, the refrigerant flow path60of the comparative example is configured to surround the circumferential surface of the inner housing21by a parallel flow path61and an inclined flow path62. The parallel flow path61is a flow path of the refrigerant13and is parallel to the one end surface38and the other end surface39. A width of the parallel flow path61along the circumferential surface is uniform. The inclined flow path62is a flow path of the refrigerant13provided at a connection portion of the parallel flow path61, and is formed to be inclined with respect to the parallel flow path61. A width of the inclined flow path62in a direction perpendicular to the flow direction of the refrigerant13is the same as that of the parallel flow path61.

As shown inFIG.7, in a case where the refrigerant flow path60is formed by the parallel flow path61, a portion where the refrigerant flow path is not formed (hereinafter referred to as a flow path non-forming portion65) is generated in the heat generation range45according to a separation angle between the inlet α and the outlet β. Of course, the refrigerant flow path60can also be formed by formally extending the parallel flow path61to the flow path non-forming portion65prior to the outlet β, but in such a formal flow path, the refrigerant13stays, and thus a substantial cooling effect is significantly reduced. For this reason, the extended portion of the formal parallel flow path61cannot be said to be a substantial refrigerant flow path.

FIG.8is an explanatory view showing an inner surface temperature of the inner housing21employing the refrigerant flow path60of the comparative example. (A) ofFIG.8shows a temperature distribution of the left inner circumferential surface37when the refrigerant flow path60of the comparative example is adopted. (B) ofFIG.8shows a temperature distribution of the right inner circumferential surface36when the refrigerant flow path60of the comparative example is adopted. InFIG.8, a portion having a higher density (black) indicates a higher temperature.

As shown inFIG.8, when the refrigerant flow path60of the comparative example is adopted, a significant high-temperature portion66exceeding an allowable limit is generated on the right inner circumferential surface36and the left inner circumferential surface37. The high-temperature portion66corresponds to the flow path non-forming portion65. That is, in the refrigerant flow path60of the comparative example, the flow path non-forming portion65is inevitably formed, and as a result, the high-temperature portion66is generated. For this reason, in the refrigerant flow path60of the comparative example, there is a failure that the first motor20is not sufficiently cooled.

FIG.9is an explanatory view showing an inner surface temperature of the inner housing21employing the refrigerant flow path24according to the present embodiment. (A) ofFIG.9shows a temperature distribution of the left inner circumferential surface37when the refrigerant flow path24of the present embodiment is adopted. (B) ofFIG.9shows a temperature distribution of the right inner circumferential surface36when the refrigerant flow path24of the present embodiment is adopted. InFIG.9, a portion having a higher density (black) indicates a higher temperature.

As indicated by a dashed line inFIG.9, the significant high-temperature portion66is generated in the refrigerant flow path60of the comparative example, whereas the high-temperature portion66is not generated when the refrigerant flow path24according to the present embodiment is adopted. Therefore, the refrigerant flow path24according to the present embodiment can sufficiently cool the first motor20.

As described above, the reason why the refrigerant flow path24according to the present embodiment can sufficiently cool the first motor20without generating the high-temperature portion66is that the refrigerant flow path24includes at least the first flow path51and the second flow path52.

Specifically, the first flow path51has a structure in which the width thereof gradually increases from the inlet α. For this reason, since the refrigerant flow path24includes the first flow path51, the refrigerant flow path24has a structure in which the flow path non-forming portion65is not formed at the end at least on the one end surface38side in the heat generation range45. The second flow path52has a structure in which the width thereof gradually decreases toward the outlet β. For this reason, since the refrigerant flow path24includes the second flow path52, the refrigerant flow path24has a structure in which the flow path non-forming portion65is not formed at the end at least on the other end surface39side in the heat generation range45.

Therefore, since the refrigerant flow path24includes the first flow path51and the second flow path52, the refrigerant flow path24has a structure in which the flow path non-forming portion65is not formed and almost the entire heat generation range45is cooled by the refrigerant13. As a result, compared to the refrigerant flow path60of the comparative example in which the flow path non-forming portion65is generated due to the separation between the inlet α and the outlet β, the refrigerant flow path24according to the present embodiment can cool almost the entire heat generation range45by the refrigerant13flowing therethrough. For this reason, the refrigerant flow path24according to the present embodiment can sufficiently cool the first motor20.

FIG.10is an explanatory view showing a flow velocity of the refrigerant13in the refrigerant flow path24according to the present embodiment. InFIG.10, a portion having a higher density (black) indicates a higher flow velocity, and a portion having a lower density (white) indicates a lower flow velocity. However, a white band at an angular position of more than 90 degrees is merely a missing part of data due to simulation settings, and does not indicate that the flow velocity of the refrigerant13is low.

As shown inFIG.10, in the refrigerant flow path24, due to a relation between structures to be satisfied by the first flow path51and the third flow path53, the connection portion therebetween becomes a steep contraction portion71in which the width along the circumferential direction is suddenly contracted. In the refrigerant flow path24, due to the relation between the structures to be satisfied by the third flow path53and the second flow path52, the connection portion therebetween becomes a steep expansion portion72in which the width along the circumferential direction is suddenly expanded.

In general, when a flow path of a fluid is rapidly contracted or rapidly expanded, a velocity (flow velocity) of the fluid is locally and remarkably decreased in the portion, and a large pressure loss occurs. However, in the refrigerant flow path24, the structures of the first flow path51and the second flow path52prevent a local and remarkable velocity decrease in the vicinity of the steep contraction portion71and the steep expansion portion72. As a result, in the refrigerant flow path24, the pressure loss in the steep contraction portion71and the steep expansion portion72is suppressed, and sufficient cooling performance is realized including the steep contraction portion71and the steep expansion portion72.

Specifically, since the first flow path51is formed such that the width thereof gradually increases, the refrigerant13flows through the first flow path51from the inlet α, and thus the velocity thereof gradually decreases over a long distance. For this reason, also in the first flow path51whose width is increased with respect to the reference flow path55, the refrigerant13diffuses to almost every corner. For example, as shown inFIG.10, in the steep contraction portion71which is the end of the first flow path51, the refrigerant13is easily diffused to corners. As a result, a portion on the one end surface38side in the heat generation rang45is sufficiently cooled by the structure of the first flow path51.

In the first flow path51, the velocity of the refrigerant13decreases, but a change in velocity is gentle, and a locally large decrease in flow velocity does not occur. For this reason, an energy loss proportional to the square of the velocity of the refrigerant13can be suppressed. As a result, a change in pressure of the refrigerant13in the first flow path51becomes gentle, and no significant pressure loss occurs in the first flow path51.

Thereafter, the velocity of the refrigerant13is reduced by passing through the first flow path51, and the refrigerant13reaches the steep contraction portion71in a state of high diffusibility. Accordingly, the refrigerant13can flow into the third flow path53without large energy loss at the steep contraction portion71. That is, the refrigerant flow path24reduces the pressure loss at the steep contraction portion71by the structure of the first flow path51.

Similar to the first flow path51, since the second flow path52is formed such that the width thereof gradually decreases, the refrigerant13flows through the second flow path2toward the outlet β, and thus the velocity thereof gradually increases over a long distance. For this reason, also in the second flow path52whose width is increased with respect to the reference flow path55, the refrigerant13diffuses to almost every corner. For example, as shown inFIG.10, in the steep expansion portion72which is the beginning of the second flow path52, the refrigerant13is easily diffused to corners. As a result, a portion on the other end surface39side in the heat generation rang45is sufficiently cooled by the structure of the second flow path52. In particular, since the refrigerant flow path24is formed in a spiral shape, the flow direction of the refrigerant13in the steep expansion portion72is inclined toward the other end surface39. For this reason, the refrigerant13flowing in from the third flow path53flows in a direction of the wall portion42parallel to the other end surface39. As a result, the refrigerant13easily diffuses to the corners of the steep expansion portion72. In this way, since the refrigerant13is easily diffused also in the steep expansion portion72, a local velocity decrease and a pressure loss in the steep expansion portion72or in the vicinity thereof are suppressed.

In the second flow path52, the velocity of the refrigerant13changes (increases), but the change in velocity is gentle, and a locally large change in flow velocity does not occur. For this reason, an energy loss proportional to the square of the velocity of the refrigerant13can be suppressed. As a result, a change in pressure of the refrigerant13in the second flow path52becomes gentle, and no significant pressure loss occurs in the second flow path52.

As described above, the refrigerant flow path24is configured to suppress the pressure loss of the refrigerant13by the first flow path51and the second flow path52, and the effect of suppressing the pressure loss is remarkable to the extent that the pressure loss is suppressed better than the refrigerant flow path60of the comparative example. That is, in comparison with the pressure loss of the refrigerant13, the pressure loss of the refrigerant13at the outlet β of the refrigerant flow path24according to the present embodiment is smaller than the pressure loss of the refrigerant13at the outlet β of the refrigerant flow path60of the comparative example.

FIG.11is a graph schematically showing changes in flow velocity and temperature of the refrigerant13. As shown inFIG.11, in the refrigerant flow path24, the velocity of the refrigerant13is low and the temperature thereof is high in the vicinity of the steep expansion portion72. For this reason, the steep expansion portion72and the vicinity thereof are the most severe environment for the cooling performance of the first motor20, and are likely to reach a high temperature. However, as shown inFIG.9, the temperature does not become extremely high even in the portion corresponding to the steep expansion portion72, and the right inner circumferential surface36and left inner circumferential surface37that abut against the stator22as a whole are sufficiently cooled by the refrigerant flow path24.

[Coupling Structure of First Motor and Second Motor]

FIG.12is an explanatory view showing a configuration of a refrigerant flow path of the entire rotating electrical machine11. As shown inFIG.12, the refrigerant flow path24of the first motor20extends from the inlet α in the positive direction of the Z direction in a right-handed spiral and reaches the outlet β. On the other hand, the refrigerant flow path29of the second motor25extends from the inlet γ in the negative direction of the Z direction in a left-handed spiral and reaches the outlet δ. That is, the refrigerant flow path24of the first motor20and the refrigerant flow path29of the second motor25are different in helicity (or chirality), and are spirally wound in opposite directions. As described above, in a case where the refrigerant flow path24of the first motor20and the refrigerant flow path29of the second motor25are formed in a spiral shape in which the two refrigerant flow paths24and29are wound in opposite directions to each other, the refrigerant flow path24of the first motor20and the refrigerant flow path29of the second motor25can be linearly connected to each other in a shortest length by the coupling pipe30without providing a needlessly long connecting pipe. For this reason, the first motor20and the second motor25are disposed in a space-saving manner, and a compact rotating electrical machine11is provided. In addition, in a case where the refrigerant flow path24of the first motor20and the refrigerant flow path29of the second motor25are formed in a spiral shape in which the two refrigerant flow paths24and29are wound in opposite directions to each other, it is possible to easily align respective attachment surfaces of the first motor20and the second motor25with respect to the outer housing10, and it is easy to arrange the first motor20and the second motor25in a space-saving manner compared to a case where the respective attachment surfaces are not aligned.

The refrigerant flow path29of the second motor25is formed in a spiral shape that is wound in a reverse direction with respect to the refrigerant flow path24of the first motor20as described above, but the basic structure thereof is the same as that of the refrigerant flow path24of the first motor20. The inner housing26of the second motor25is formed by an inner pipe81and an outer pipe82, similar to the inner housing21of the first motor20. The refrigerant flow path29of the second motor25is formed on an outer circumferential surface of the inner pipe81. In the inner pipe81, an end surface on the positive side in the Z direction where a flange portion is provided is one end surface83, and an end surface on the negative side in the Z direction is the other end surface84.

The refrigerant flow path29of the second motor25includes a first flow path91and a second flow path92. In the present embodiment, the refrigerant flow path29of the second motor25further includes a third flow path93. The first flow path91is formed along the one end surface83of the inner housing26, and is formed such that a width along the circumferential surface increases along the flow direction of the refrigerant13. The second flow path92is formed along the other end surface84of the inner housing26from the inlet γ, and is formed such that a width along the circumferential surface decreases toward the outlet δ along the flow direction of the refrigerant13. The third flow path93is formed between the first flow path91and the second flow path92so that the width along the circumferential surface is uniform, and couples the first flow path91and the second flow path92. That is, the refrigerant flow path29of the second motor25is formed in the same manner as the refrigerant flow path24of the first motor20except that the refrigerant flow path29is wound in a reverse direction.

In a case where the drive unit100is provided with a rotating electrical machine in which a plurality of motors are arranged in a compact manner as in the rotating electrical machine11, the refrigerant flow path14of the outer housing10is preferably formed as shown inFIG.1, for example. That is, in order to form the drive unit100in a compact manner, it is preferable that the refrigerant flow paths14of the outer housing10couples the respective portions constituting the drive unit100by substantially the shortest route. However, when the refrigerant flow path14of the outer housing10is formed in this manner, the inlet and the outlet of the refrigerant to each of motors constituting the rotating electrical machine are separated from each other. When the drive unit100is configured to be particularly compact, the inlet and the outlet of the refrigerant flow path in each of the motors constituting the rotating electrical machine are separated by about 180 degrees. This is as shown inFIG.1and the like by the inlet α and the outlet β of the refrigerant flow path24of the first motor20and the inlet γ and the outlet δ of the refrigerant flow path29of the second motor25.

On the other hand, considering only the cooling performance of the first motor20, it is desirable that the inlet α and the outlet β of the refrigerant flow path24of the first motor20are not separated from each other so that the flow path non-forming portion65is substantially not formed. The same applies to the second motor25. That is, considering only the cooling performance for each of the motors constituting the rotating electrical machine, it is desirable that the inlet and the outlet of the refrigerant flow path are not substantially separated. However, in consideration of the cooling performance of the first motor20and/or the second motor25alone, the redundancy of the refrigerant flow path14of the outer housing10results in a disadvantage that the drive unit100cannot be configured compactly.

Therefore, according to the present embodiment, the structures of the refrigerant flow path24and the refrigerant flow path29, and the coupling structures thereof are the best structures that enable the drive unit100to be formed as compact as possible with respect to the flow path of the refrigerant13, and further maximize the cooling performance of the first motor20and the second motor25.

[First Modification]

In the above embodiment, in addition to the first flow path51and the second flow path52, the refrigerant flow path24of the first motor20includes the third flow path53coupling the first flow path51and the second flow path52. Further, in addition to the first flow path91and the second flow path92, the refrigerant flow path29of the second motor25also includes a third flow path93coupling the first flow path91and the second flow path92. However, the third flow paths53and93may be omitted in consideration of cooling performance, pressure loss, and the like. Also in this case, the same effects as those of the refrigerant flow path24and the like according to the above embodiment can be obtained.

FIG.13is an explanatory view showing a configuration of a refrigerant flow path95according to a first modification. The refrigerant flow path95of the modification is a refrigerant flow path in which the third flow path53in the refrigerant flow path24of the first motor20is omitted and the first flow path51and the second flow path52are directly coupled. In the refrigerant flow path85of the modification, a range of an angular position of 0 degrees (inlet α) to 360 degrees or 180 degrees is a range formed along the one end surface38and formed such that the width along the circumferential surface increases along the flow direction of the refrigerant13. Therefore, in the refrigerant flow path85of the modification, the range of 0 degrees to 360 degrees or 180 degrees is the first flow path51.

Similarly, in the refrigerant flow path85of the modification, a range of an angular position of 180 degrees or 360 degrees to 540 degrees (outlet β) is a range formed along the other end surface39and formed such that the width along the circumferential surface decreases toward the outlet β along the flow direction of the refrigerant13. Therefore, in the refrigerant flow path the range of 180 degrees or 360 degrees to 540 degrees (outlet β) is the second flow path52.

The range of the angular position of 180 degrees to 360 degrees satisfies a condition for the first flow path51by being grasped integrally with the first flow path51, and satisfies a condition for the second flow path52by being grasped integrally with the second flow path52, as described above. For this reason, the range of the angular position of 180 degrees to 360 degrees can belong to both the first flow path51and the second flow path52. In addition, since the width along the circumferential direction is larger than that of the reference flow path55, it is different from the third flow paths53and93. Therefore, the range of the angular position of 180 degrees to 360 degrees belongs to one or both of the first flow path51and the second flow path52.

[Second Modification]

In the above embodiment, the refrigerant flow path24of the first motor20includes the third flow path53, and the refrigerant flow path29of the second motor25includes the third flow path93. The third flow paths53and93are provided over half the circumference of the inner housings21and26. However, the number of turns of the third flow paths53and93can be freely changed by adaptation in accordance with an allowable pressure loss (hereinafter referred to as an allowable pressure loss), dimensions of the inlets α and γ and the outlets13and6, and the like.

FIG.14is an explanatory diagram showing a configuration of a refrigerant flow path96according to a second modification. As shown inFIG.14, for example, when the allowable pressure loss is large and a relatively large pressure loss is allowable, the number of turns of the third flow paths53and93can be increased. Conversely, when the allowable pressure loss is small and only a relatively small pressure loss is allowable, the number of turns of the third flow paths53and93can be reduced (seeFIG.13).

Note that changing the number of turns of the third flow paths53and93is synonymous with changing the number of turns of the refrigerant flow paths24and29. The number of turns of the third flow paths53and93correlates with the width of the third flow paths53and93and a spiral angle (pitch) formed by the third flow paths53and93and the refrigerant flow paths24and29, and by determining one of these, the other parameters are automatically determined. Therefore, as in the second modification, instead of changing the number of turns of the third flow paths53and93, the width of the third flow paths53and93or the spiral angle formed by the third flow paths53and93and the refrigerant flow paths24and29may be changed. The allowable pressure loss is appropriately determined according to, for example, the dimensions of the stators22and27.

As described above, a rotating electrical machine11according to the present embodiment and the modifications includes an inner housing21(26) that is a cylindrical housing. The inner housing21(26) that is a cylindrical housing includes a refrigerant flow path24(29) configured to allow a refrigerant13to flow therethrough, an inlet α (γ) configured to allow the refrigerant13to flow into the refrigerant flow path24(29), and an outlet β (δ) configured to allow the refrigerant13to flow out of the refrigerant flow path24(29). The refrigerant flow path24is formed so as to spirally surround around a circumferential surface of the inner housing21(26). In addition, the refrigerant flow path24(29) includes a first flow path51(91) that is formed along one end surface38(83) of the inner housing21(26) and formed such that a width along the circumferential surface increases along a flow direction of the refrigerant13from the inlet α (γ), and a second flow path52(92) that is formed along the other end surface39(84) of the inner housing21(26) and formed such that a width along the circumferential surface decreases toward the outlet β (δ) along the flow direction of the refrigerant13.

As described above, in a case where the refrigerant flow path24(29) is provided in the inner housing21(26) of the rotating electrical machine11and the refrigerant flow path24(29) includes the first flow path51(91) and the second flow path52(92), a flow path non-forming portion65is substantially not formed even when the inlet α (γ) and the outlet β (δ) of the refrigerant13are separated from each other. The first flow path51(91) and the second flow path52(92) suppress a local decrease in velocity of the refrigerant13and an increase in pressure loss, and obtain sufficient cooling performance almost entirely. Thus, in the refrigerant flow path24(29), the first flow path51(91) and the second flow path52(92) allow substantially the entire heat generation range45to be cooled by the refrigerant13flowing through the refrigerant flow path24(29). Therefore, in the rotating electrical machine11in which the refrigerant flow path24(29) including the first flow path51(91) and the second flow path52(92) is formed, cooling performance is improved and necessary cooling performance is obtained.

In the rotating electrical machine11according to the above embodiment and the modifications, the inlet α (γ) and the outlet β (δ) of the refrigerant13are provided at positions at which the inlet α (γ) and the outlet β (δ) of the refrigerant13are separated from each other in a circumferential direction of the inner housing21(26). For this reason, an effect of improving the cooling performance is particularly remarkable.

In the rotating electrical machine11according to the embodiment and the modifications, the refrigerant flow path24(29) includes a third flow path53(93) having a uniform width between the first flow path51(91) and the second flow path52(92). Since the width of the third flow path53(93) is uniform, the velocity reduction and the pressure loss of the refrigerant13flowing through the refrigerant flow path24(29) are reduced. Therefore, since the refrigerant flow path24(29) includes the third flow path53(93), the required sufficient cooling effect can be easily obtained while satisfying an allowable pressure loss condition.

In the rotating electrical machine11according to the embodiment and the modifications, the width of the third flow path53(93) is narrower than a width of a widest portion of the first flow path51(91) and narrower than a width of a widest portion of the second flow path52(92). This structure is particularly likely to suppress pressure loss. As a result, the required sufficient cooling effect can be particularly easily obtained while satisfying the allowable pressure loss condition.

In the rotating electrical machine11according to the embodiment and the modification, when a flow path connecting the inlet α (γ) and the outlet β (δ) with a uniform width determined according to an allowable pressure loss of the refrigerant13is defined as a reference flow path55, the first flow path51(91) has a shape obtained by expanding the reference flow path55in a direction of the one end surface38(83) of the inner housing21(26). The second flow path52(92) has a shape obtained by expanding the reference flow path55in a direction of the other end surface39(84) of the inner housing21(26). When the reference flow path55is formed and the reference flow path surrounds the inner housing21(26), the flow path non-forming portion65is inevitably formed. In contrast, as described above, the first flow path51(91) and the second flow path52(92) each have a shape obtained by expanding the reference flow path55in the directions of the one end surface38(83) and the other end surface38(84), respectively. For this reason, in the refrigerant flow path24(29), a portion of the flow path non-forming portion65generated when the reference flow path55is formed becomes the first flow path51(91) and the second flow path52(92). As a result, the rotating electrical machine11is more reliably cooled.

In the rotating electrical machine11according to the embodiment and the modifications, a boundary between the first flow path51(91) and the third flow path53(93) and a boundary between the second flow path52(92) and the third flow path53(93) are formed by straight lines along a circumferential direction of the inner housing21(26). Accordingly, the third flow path53(93) is a flow path generally conforming to the reference flow path As a result, the pressure loss of the refrigerant13in the third flow path53(93) is reduced, and the cooling performance is further enhanced.

In the rotating electrical machine11according to the embodiment and the modifications, the first flow path51(91) is provided in a range extending around the circumferential surface of the inner housing21(26) from the inlet α (γ). The second flow path52(92) is provided in a range extending around the circumferential surface of the inner housing21(26) from the outlet β (δ). A range of one round from the inlet α (γ) and a range of one round from the outlet β (δ) are particularly prone to the generation of the flow path non-forming portion65. Therefore, when the first flow path51(91) is provided in the range of at least one round from the inlet α (γ) and the second flow path52(92) is provided in the range of at least one round from the outlet β (δ), the cooling performance of the rotating electrical machine11is easily improved.

However, the first flow path51(91) may be provided beyond the range of one round from the inlet α (γ), and the second flow path52(92) may be provided within the range of one round from the outlet β (δ). When there are other circumstances, such as when the third flow path53(93) is not provided as shown inFIG.13, the first flow path51(91) and/or the second flow path52(92) may not be provided in the entire range of one round.

In the rotating electrical machine11according to the embodiment and the modifications, the inner housing21(26) includes the inner housing21that is a first housing, the inner housing26that is a second housing, and a coupling pipe30. The inner housing21that is the first housing accommodates a stator22as a first stator and a rotor23as a first rotor, and has the refrigerant flow path24. The inner housing26that is the second housing accommodates a stator27as a second stator and a rotor28as a second rotor, and has the refrigerant flow path29. The coupling pipe30linearly couples the outlet β of the inner housing21that is the first housing and the inlet γ of the inner housing26that is the second housing without waste. For this reason, the rotating electrical machine11incorporating two motors is configured to be compact while maintaining the cooling performance thereof. Further, the cost of the rotating electrical machine11is additionally reduced.

In the rotating electrical machine11according to the embodiment and the modifications, the refrigerant flow path29of the inner housing26that is the second housing is formed in a spiral shape that is wound in a reverse direction with respect to the refrigerant flow path24of the inner housing21that is the first housing. In this way, when the two refrigerant flow paths24and29to be coupled are formed in a spiral shape in which the two refrigerant flow paths24and29are wound in opposite directions to each other, the rotating electrical machine11incorporating two motors is easily configured to be particularly compact while maintaining the cooling performance thereof.

Although the embodiment of the present invention has been described above, configurations described in the embodiment and the modification are only a part of application examples of the present invention, and are not intended to limit the technical scope of the present invention.

For example, the first motor20may be a power generation motor, and the second motor25may be a driving motor. Further, both the first motor20and the second motor25may be driving motors, and both the first motor20and the second motor25may be power generation motors. The rotating electrical machine11may include only one of the first motor20and the second motor25.

In the above embodiment, the refrigerant flow path24is formed by the grooves41provided in the outer circumferential surface of the inner pipe31. Alternatively, the refrigerant flow path24can be formed by providing similar grooves in the inner circumferential surface of the outer pipe32. The refrigerant flow path24may be formed by providing grooves in both the outer circumferential surface of the inner pipe31and the inner circumferential surface of the outer pipe32. The same applies to the refrigerant flow path29.

In the embodiment and the modifications, in the refrigerant flow path24, the width of the first flow path51smoothly increases, and the width of the second flow path52smoothly decreases. However, the widths of the first flow path51and the second flow path52may be changed stepwise, for example. Also in the case where the widths of the first flow path51and the second flow path52change stepwise, it is possible to obtain the same effects as those of the above embodiment and the like. However, it is preferable that the widths of the first flow path51and the second flow path52change as smoothly as possible as in the above embodiment and the like. The same applies to the refrigerant flow path29.