Electric supercharger

Abstract

This electric supercharger is provided with: a compressor; and a motor part having a motor housing engaged with the compressor in the axial direction and applying torque to the compressor impeller, in which a gap region in which the compressor and the motor housing face each other in the axial direction with a gap therebetween is provided at the engagement part of the compressor and the motor housing.

Description

Technical Field

[0001] This disclosure relates to electric superchargers. Background Technology

[0002] Conventionally, it is known that there are electric boosters with a configuration in which a compressor and a motor that applies torque to the impeller of the compressor are connected in the direction of rotation (see Patent Document 1 below). In such electric boosters, heat generated in the compressor due to the insulated compression of the gas is generated, and a portion of this heat is conducted from the compressor to the motor side.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2009-024576 Summary of the Invention

[0004] However, if a large amount of heat is conducted from the compressor to the motor, it causes the motor temperature to rise, and the motor's operating performance may decrease due to the heat. Furthermore, the heat from the compressor is ultimately handled by the cooling system that cools the motor, thus increasing the load on that system. Therefore, this disclosure describes an electric booster that suppresses the movement of heat from the compressor to the motor.

[0005] One aspect of the electric booster disclosed herein includes: a compressor; and a motor unit having a motor housing that engages with the compressor in the direction of the rotation axis and applies torque to the impeller of the compressor. A gap region is provided at the junction of the compressor and the motor housing, in which the compressor and the motor housing are separated by a gap and are opposite each other in the direction of the rotation axis.

[0006] According to this disclosure, an electric booster can be provided that suppresses the movement of heat from the compressor to the motor section. Attached Figure Description

[0007] Figure 1 This is a cross-sectional view showing the implementation of the electric supercharger.

[0008] Figure 2 It is an enlarged representation Figure 1 A cross-sectional view of a portion of an electric supercharger.

[0009] Figure 3 This is a diagram showing the mating surface of the motor housing that is connected to the compressor, viewed from the axial direction.

[0010] Figure 4 This is a diagram showing a deformed example of the mating surface of the motor housing that is connected to the compressor, viewed from the axial direction. Detailed Implementation

[0011] The purpose of this disclosure is as follows [1] to [7].

[0012] [1] An electric booster includes: a compressor; and a motor unit having a motor housing that engages with the compressor in the direction of rotation axis and applies torque to the impeller of the compressor, wherein a gap region is provided at the joint between the compressor and the motor housing, in which the compressor and the motor housing are separated by a gap and are opposite each other in the direction of rotation axis.

[0013] [2] According to the electric booster described in [1], the radial position of the outermost portion of the gap region is the same as or further outward than the radial position of the diffuser outlet of the compressor, and is the same as or further outward than the radial position of the outermost portion of the scroll member of the compressor.

[0014] [3] According to the electric booster described in [1] or [2], the radial position of the diffuser outlet of the compressor is closer to the inner circumference than the radial position of the outermost circumference portion of the gap region, and closer to the outer circumference than the radial position of the innermost circumference portion of the gap region.

[0015] [4] The electric booster according to any one of [1] to [3], wherein the gap region is divided into a plurality of parts in the circumferential direction.

[0016] [5] The electric booster according to any one of [1] to [4], wherein the projected area of ​​the gap region projected in the direction of the rotation axis is more than 40% of the projected area of ​​the entire joint projected in the direction of the rotation axis.

[0017] [6] According to any one of [1] to [5], a cooling air flow path is formed in the motor housing, the cooling air flow path connects the outside of the motor housing with the space of the bearing housing the motor part, and allows cooling air to flow through the bearing, and the gap region is set at a position that does not overlap with the cooling air flow path when viewed from the direction of the rotation axis.

[0018] [7] According to any one of [1] to [6], the electric booster has: a compressor housing; and a diffuser plate that forms a diffuser between itself and the compressor housing and engages with the motor housing at the joint, the diffuser plate being made of stainless steel.

[0019] Hereinafter, the electric supercharger 1 according to the embodiments of the present disclosure will be described with reference to the accompanying drawings. In the drawings, the same or equivalent elements are labeled with the same reference numerals, and repeated descriptions are omitted. Also, in the drawings, some feature parts are exaggerated, so the dimensional ratios of different parts may vary between different drawings. Furthermore, in the following description, when simply referred to as "axial," "radial," and "circumferential," they respectively refer to the direction of the rotation axis 15 of the electric supercharger 1 (rotation axis H direction), the radial direction, and the circumferential direction. Additionally, in the rotation axis H direction, the turbine 2 side of the electric supercharger 1 (in... Figure 1 The left side (middle) is simply referred to as the "turbine side," and the compressor's three sides (in) Figure 1 The right side (in the middle) is referred to as the "compressor side".

[0020] Figure 1 This is a cross-sectional view showing the electric supercharger 1. Figure 2 This is an enlarged cross-sectional view showing a portion thereof. The electric supercharger 1 in this embodiment is an electrically assisted turbocharger mounted on a fuel cell vehicle. The electric supercharger 1 supplies the generated compressed air to the fuel cell stack 91, thereby increasing the oxygen content associated with the chemical reactions at the fuel cell stack 91.

[0021] The electric supercharger 1 includes a turbine 2 and a compressor 3. The electric supercharger 1 also includes a motor section 20 disposed between the turbine 2 and the compressor 3, and an inverter section 30 that supplies power to the motor section 20.

[0022] The turbine 2 includes a turbine housing 4 and a turbine impeller 6 housed within the turbine housing 4. The turbine housing 4 has a vortex member 12 extending circumferentially around the turbine impeller 6. Additionally, the turbine housing 4 is provided with an exhaust gas inlet 8 and an exhaust gas outlet 10. The compressor 3 includes a compressor housing 5 and a compressor impeller 7 housed within the compressor housing 5. The compressor housing 5 has a vortex member 13 extending circumferentially around the compressor impeller 7. Additionally, the compressor housing 5 is provided with an intake inlet 9 and an outlet 11. The compressor 3 is configured as a centrifugal compressor, and the compressor impeller 7 discharges air axially introduced from the intake inlet 9 radially outward toward the vortex member 13.

[0023] Furthermore, the electric supercharger 1 includes a rotating shaft 15 that connects the turbine impeller 6 and the compressor impeller 7. That is, the turbine impeller 6 is provided at one end of the rotating shaft 15, and the compressor impeller 7 is provided at the other end of the rotating shaft 15. The turbine impeller 6, the rotating shaft 15, and the compressor impeller 7 are integrally formed to constitute a rotating body 19 that rotates about the rotation axis H.

[0024] The motor unit 20 includes a motor 21 and a motor housing 23 for housing the motor 21. The motor 21 is, for example, a brushless AC motor, having a rotor 27 as a rotating component and a stator 29 as a stationary component. The rotor 27 is fixed to the rotating shaft 15 and located between the turbine impeller 6 and the compressor impeller 7. The stator 29 is configured to surround the rotor 27 and is fixed to the motor housing 23.

[0025] Additionally, the rotating shaft 15 extends axially through the motor housing 23. At each through portion of the rotating shaft 15, a pair of radial bearings 42 and 43 are provided in the motor housing 23 to support the rotating shaft 15. The radial bearing 42 on the turbine side is located between the motor 21 and the turbine impeller 6. The radial bearing 43 on the compressor side is located between the motor 21 and the compressor impeller 7. Furthermore, a thrust bearing 45 for the rotating shaft 15 is provided in the motor housing 23. The thrust bearing 45 is located between the radial bearing 43 and the compressor impeller 7. The radial bearings 42 and 43 and the thrust bearing 45 are air bearings.

[0026] The inverter section 30 is connected to the motor section 20 via connector 31. The inverter section 30 includes an inverter housing 33 disposed outside the motor housing 23, and an inverter body 35 and a bus 37 housed within the inverter housing 33. The inverter body 35 is electrically connected to the stator 29 of the motor 21 via the bus 37 and connector 31.

[0027] In this electric supercharger 1, exhaust gas from the fuel cell stack 91 flows into the turbine housing 4 through the exhaust gas inlet 8. The exhaust gas then flows into the turbine impeller 6 through the vortex member 12, causing the turbine impeller 6 to rotate about the rotation axis H. The exhaust gas then flows out of the turbine housing 4 through the exhaust gas outlet 10. While the turbine impeller 6 rotates as described above, the compressor impeller 7 rotates via the rotation shaft 15. The rotating compressor impeller 7 draws in external air through the intake port 9. This air is compressed by the compressor impeller 7 and the vortex member 13 and discharged from the outlet 11. The compressed air discharged from the outlet 11 is supplied to the aforementioned fuel cell stack 91.

[0028] When the torque of the rotating shaft 15 is insufficient, the motor 21 applies torque to the rotating shaft 15 to compensate for the deficiency. That is, a magnetic field is generated around the stator 29 by supplying current from the inverter body 35 to the coils of the stator 29. Through this magnetic field, a circumferential force acts on the permanent magnet of the rotor 27, which in turn applies torque to the rotating shaft 15.

[0029] Next, the structure near the joint 50 between the compressor 3 and the motor 20 will be described. Figure 2 This is an enlarged cross-sectional view showing the area near the joint 50. Figure 3This is a view of the mating surface 23a of the motor housing 23, which is connected to the compressor 3, viewed axially. In addition to the compressor housing 5 and compressor impeller 7 described above, the compressor 3 also includes a diffuser plate 51. The diffuser plate 51 is located between the compressor housing 5 and the motor housing 23. The diffuser plate 51 engages with the turbine side of the compressor housing 5 and with the compressor side of the motor housing 23. A diffuser 53 is formed in the region radially outer of the compressor impeller 7, which is axially held by the diffuser plate 51 and the compressor housing 5. The material of the diffuser plate 51 is, for example, a metal with low thermal conductivity such as stainless steel. In this embodiment, the diffuser plate 51 is made of stainless steel.

[0030] The aforementioned radial bearing 43 and thrust bearing 45, located around the rotating shaft 15, are mounted on the motor housing 23. A cooling air flow path 55 is formed in the motor housing 23. The cooling air flow path 55 connects the outside of the motor housing 23 to the bearing housing space 52. The bearing housing space 52 is the space that houses the radial bearing 43 and the thrust bearing 45. The cooling air flow path 55 allows cooling air supplied from a cooling air source (not shown) outside the motor section 20 to flow to the radial bearing 43 and the thrust bearing 45. The radial bearing 43 and the thrust bearing 45 are cooled by this cooling air. After passing through the radial bearing 43 and the thrust bearing 45, the cooling air passes through the interior of the motor housing 23 and is finally discharged from the exhaust gas outlet 10 along with the exhaust gas from the turbine 2. In addition, as another structure for cooling the motor 21, a cooling water flow path 56 (see reference) is provided in the motor housing 23. Figure 1 The cooling water flow path 56 is formed in a spiral shape inside the outer wall of the motor housing 23, and the motor 21 is cooled by the flow of cooling water supplied from an external cooling water source (not shown).

[0031] At the junction 50 between the diffuser plate 51 and the motor housing 23, a gap region 57 is provided in which the diffuser plate 51 and the motor housing 23 are axially opposed, with a gap G between them. More specifically, in the junction 50, the diffuser plate 51 and the motor housing 23 are engaged when the mating surface 23a of the motor housing 23 is in contact with the mating surface 51a of the diffuser plate 51. Furthermore, a recess 59 is present on the mating surface 23a of the motor housing 23. The recess 59 is formed by slightly recessing a portion of the mating surface 23a towards the turbine side. The bottom surface 59a of the recess 59 forms a plane orthogonal to the axial direction and is axially opposed to the mating surface 51a of the diffuser plate 51, with the aforementioned gap G. The size of the gap G is, for example, approximately 1 mm. The region in the junction 50 where the recess 59 is present is the aforementioned gap region 57. The recess 59 in... Figure 3 It is shown by the shading in the middle.

[0032] Viewed axially, the gap region 57 extends in a circumferential band along an arc centered on the axis of rotation H, with a specified radial width. Viewed axially, the gap region 57 is positioned where it does not overlap with the cooling airflow path 55. The radial position of the outermost peripheral portion 57a ​​of the gap region 57 is further outward than the radial position 61 of the diffuser 53 outlet. Furthermore, the radial position of the outermost peripheral portion 57a ​​is further inward than the radial position 62 of the outermost peripheral portion of the scroll member 13 of the compressor 3. The radial position of the outermost peripheral portion 57a ​​may also be the same as the radial position 61 of the diffuser 53 outlet, or it may be the same as the radial position 62 of the outermost peripheral portion of the scroll member 13 of the compressor 3.

[0033] In addition, the radial position 61 of the outlet of the diffuser 53 is closer to the inner circumference than the radial position of the outermost peripheral portion 57a ​​of the gap region 57, and closer to the outer circumference than the radial position of the innermost peripheral portion 57b of the gap region 57.

[0034] Furthermore, within the diffuser 53, there is theoretically a point where the compressed air reaches its highest pressure. For example... Figure 2 As shown, when the radial position of this part is indicated by reference numeral 63, the axial flow path width of the diffuser 53 is constant on the inner circumferential side compared to the radial position 63. The axial flow path width of the diffuser 53 widens from the radial position 63 toward the outlet of the diffuser 53 (radial position 61). This radial position 63 is on the inner circumferential side compared to the radial position of the outermost circumferential portion 57a ​​of the gap region 57, and on the outer circumferential side compared to the radial position of the innermost circumferential portion 57b of the gap region 57.

[0035] Additionally, near the outermost periphery of the joint 50, an O-ring 67 is provided, sandwiched between the diffuser plate 51 and the motor housing 23. This O-ring 67 prevents compressed air and the like from leaking to the outside through the joint 50. The outermost periphery portion 57a ​​of the gap region 57 is located on the inner periphery side of the gap region 57, which is closer to the position of the O-ring 67.

[0036] The projected area of ​​the gap region 57 in the axial direction is preferably 40% or more of the projected area of ​​the entire joint 50 in the axial direction. In this case, the projected area of ​​the entire joint 50 refers to the sum of the projected area of ​​the gap region 57 and the projected areas of all portions of the diffuser plate 51 that contact the motor housing 23. Furthermore, the projected area of ​​the gap region 57 corresponds to... Figure 3 The area of ​​the shaded region (recess 59) in the diagram. Additionally, as... Figure 4 As shown, the gap region 57 can also be divided into multiple parts in the circumferential direction. Figure 4 In the example, the gap region 57 is divided into two parts in the circumferential direction, but the gap region 57 can also be divided into more than three parts.

[0037] The effects of the electric supercharger 1 described above will be explained. In this electric supercharger 1, the diffuser plate 51 of the compressor 3 and the motor housing 23 of the motor unit 20 are axially joined at the joint 50. In the compressor 3, heat is generated due to the insulated compression of air. If most of this heat is conducted to the motor unit 20, it causes the temperature of the motor 21 to rise, and there is a possibility that the operating performance of the motor 21 will decrease due to the heat. In addition, it leads to an increase in the load on the cooling system, including the cooling air flow path 55 and the cooling water flow path 56.

[0038] In contrast, in the electric supercharger 1, a gap region 57 is provided in the joint 50, where the diffuser plate 51 and the motor housing 23 are separated by a gap G in the axial direction. The presence of this gap G reduces heat conduction from the diffuser plate 51 to the motor housing 23, thus suppressing the movement of heat from the compressor 3 to the motor unit 20. Therefore, the reduction in continuous operating performance of the motor 21 due to temperature is suppressed. Furthermore, the load on the cooling system used to cool the motor unit 20 can be reduced.

[0039] Furthermore, as described above, by setting the projected area of ​​the gap region 57 in the axial direction to more than 40% of the projected area of ​​the entire joint 50 in the axial direction, the aforementioned effects can be effectively obtained.

[0040] In addition, as described above, the material of the diffuser plate 51 is a metal with low thermal conductivity, such as stainless steel, so that even in the part where the diffuser plate 51 contacts the motor housing 23, the movement of heat from the compressor 3 to the motor unit 20 can be suppressed.

[0041] Here, the pressure of the compressed air within the compressor 3 is greatest near the radial position 61 at the outlet of the diffuser 53. Therefore, the temperature caused by the insulated compression of the air is also considered to be highest near the radial position 61. In contrast, the radial position of the outermost peripheral portion 57a ​​of the gap region 57 is further outward than the radial position 61 at the outlet of the diffuser 53, and further inward than the radial position 62 of the outermost peripheral portion of the scroll member 13. Thus, when the aforementioned radial position 61 is particularly likely to be high-temperature, the gap region 57 extends outward beyond the radial position 61. As a result, heat conduction from the diffuser plate 51 to the motor housing 23 can be reduced more efficiently.

[0042] Furthermore, the radial position 61 of the diffuser 53 outlet is closer to the inner circumference than the radial position of the outermost peripheral portion 57a ​​of the gap region 57, and closer to the outer circumference than the radial position of the innermost peripheral portion 57b of the gap region 57. In this way, the gap region 57 exists in a manner that radially spans the aforementioned radial position 61, which is particularly likely to be a high temperature area, thereby more efficiently reducing heat conduction from the diffuser plate 51 to the motor housing 23.

[0043] Furthermore, the radial position 63 where the air compressed by the compressor 3 reaches its highest pressure is theoretically located closer to the inner periphery than the radial position of the outermost peripheral portion 57a ​​of the gap region 57, and closer to the outer periphery than the radial position of the innermost peripheral portion 57b of the gap region 57. Thus, theoretically, the gap region 57 exists in a manner that radially spans the aforementioned radial position 63, which is particularly likely to become a high-pressure and high-temperature region, thereby more efficiently reducing heat conduction from the diffuser plate 51 to the motor housing 23.

[0044] Furthermore, assuming that the cooling air flow path 55 and the recess 59 are arranged in an axially overlapping manner in the motor housing 23, the space between the cooling air flow path 55 and the bottom surface 59a of the recess 59 becomes thinner. In contrast, in the electric supercharger 1, when viewed axially, the gap region 57 is provided at a position that does not overlap with the cooling air flow path 55, thus ensuring sufficient wall thickness of the motor housing 23 in the portion where the cooling air flow path 55 is provided. Additionally, in this portion, there is no gap region 57, and the diffuser plate 51 contacts the motor housing 23, but most of the heat moving from the diffuser plate 51 to the motor housing 23 is removed by the cooling air through the cooling air flow path 55.

[0045] Starting from the above embodiments, this disclosure can be implemented in various ways with various modifications and improvements based on the knowledge of those skilled in the art. Furthermore, variations can be constructed using the technical aspects described in the above embodiments. The structures of various embodiments, etc., can also be appropriately combined for use. For example, in one embodiment, the gap region 57 is provided by forming a recess 59 on the mating surface 23a of the motor housing 23, but the gap region can also be provided by forming a recess on the mating surface 51a of the diffuser plate 51.

[0046] Explanation of reference numerals in the attached figures

[0047] 1… Electric booster; 3… Compressor; 20… Motor section; 23… Motor housing; 50… Joint; 51… Diffuser plate; 53… Diffuser; 55… Cooling air flow path; 57… Gap area; 57a… Outermost peripheral part; 57b… Innermost peripheral part; 61… Radial position of diffuser outlet; 62… Radial position of outermost peripheral part of scroll component; G… Gap; H… Rotation axis.

Claims

1. An electric supercharger characterized by, Possessing: a compressor; and a motor portion having a motor case joined to the compressor in a direction of a rotational axis and applying a torque to an impeller of the compressor, a gap region in which the compressor and the motor case are spaced apart from each other in the direction of the rotational axis is provided at a joint portion of the compressor and the motor case.

2. The electric supercharger according to claim 1, characterized in that a radial position of an outermost portion of the gap region is the same as or outward of a radial position of a diffuser outlet of the compressor, and is the same as or inward of a radial position of an outermost portion of a scroll of the compressor.

3. The electric supercharger according to claim 1, characterized in that a radial position of a diffuser outlet of the compressor is inward of a radial position of an outermost portion of the gap region, and is outward of a radial position of an innermost portion of the gap region.

4. The electric supercharger according to claim 1, characterized in that the gap region is divided into a plurality in a circumferential direction.

5. The electric supercharger according to claim 1, characterized in that a projected area of the gap region projected in the direction of the rotational axis is 40% or more of a projected area of the joint portion as a whole projected in the direction of the rotational axis.

6. The electric supercharger according to claim 1, characterized in that a cooling air flow path is formed in the motor case, the cooling air flow path communicating an outside of the motor case with a space in which a bearing of the motor portion is housed and allowing cooling air for cooling the bearing to flow, the gap region is provided at a position not overlapping the cooling air flow path, as viewed in the direction of the rotational axis.

7. The electric supercharger according to claim 1, characterized in that the compressor has: a compressor housing; and a diffuser plate forming a diffuser between the compressor housing and the motor case and joined to the motor case at the joint portion, the diffuser plate is made of stainless steel. ​

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