WO2024090184A1

WO2024090184A1 - Electric fluid pump

Info

Publication number: WO2024090184A1
Application number: PCT/JP2023/036603
Authority: WO
Inventors: 直嗣北山; 雅道藤川
Original assignee: Ntn株式会社
Priority date: 2022-10-26
Filing date: 2023-10-06
Publication date: 2024-05-02
Also published as: JP2024063595A

Abstract

An electric oil pump (electric fluid pump) 1 comprises: a motor unit 2; a pump unit 3; an intake-side flow path (intake-side counter port 65) through which oil before compressed by the pump unit 3 flows; an ejection-side flow path (ejection-side counter port 66) through which oil after compressed by the pump unit 3 flows; a relief conduit 67 making the intake-side counter port 65 and the ejection-side counter port 66 communicate with each other; and a relief valve 71 disposed inside the relief conduit 67 and opened when a fluid pressure of the ejection-side flow path becomes a prescribed value or more. The relief conduit 67 and the relief valve 71 are disposed in a region between the motor unit 2 and the pump unit 3 in an axial direction.

Description

Electric Fluid Pump

The present invention relates to an electric fluid pump.

In recent years, automobiles and other vehicles may use an electric oil pump to supply oil to various parts of the vehicle. For example, vehicles equipped with an idling stop mechanism (a mechanism that automatically stops the engine when the vehicle is stopped) and hybrid vehicles are equipped with an electric oil pump that supplies oil pressure to the transmission when the engine is stopped.

In a hydraulic circuit that includes an electric oil pump, for example, the hydraulic pressure is maintained at an appropriate level by controlling the output of the motor section based on the hydraulic pressure detected by a hydraulic sensor and adjusting the pump discharge pressure. In this case, however, a hydraulic sensor is required, and complex control is required to vary the output of the motor section based on the detection results of the hydraulic sensor.

For example, the following Patent Document 1 shows an electric oil pump having a relief valve. As shown in FIG. 9, this electric oil pump includes an electric motor 103 having a motor stator 101 and a motor rotor 102, a pump 106 having an inner rotor 104 and an outer rotor 105, a motor housing 107 that houses the electric motor 103, and a housing 109 having a pump housing 108 that houses the pump 106, and a pump plate 110 fixed to one axial side (left side in the figure) of the housing 109. As shown in FIG. 10, the pump plate 110 is provided with a crescent-shaped port 111 on the suction side and a crescent-shaped port 112 on the discharge side, and these crescent-

shaped ports

111, 112 are respectively connected to a suction port 113 and a discharge port 114. The pump plate 110 is provided with a valve mounting hole 115 that connects the two crescent-

shaped ports

111, 112. A relief valve 116 is arranged inside the valve mounting hole 115 in a reciprocating manner.

When the inner rotor 104 of the pump 106 is driven to rotate by the electric motor 103, oil is sucked in from the suction port 113 and enters the space between the inner rotor 104 and the outer rotor 105 via the crescent-shaped port 111 on the suction side. The oil compressed in this space is discharged from the discharge port 114 via the crescent-shaped port 112 on the discharge side.

At this time, when the oil pressure in the crescent-shaped port 112 on the discharge side reaches or exceeds a predetermined value, the relief valve 116 moves backward (to the right in Figure 10) due to this oil pressure, and both crescent-

shaped ports

111, 112 communicate via the valve mounting hole 115. As a result, oil flows from the crescent-shaped port 112 on the discharge side through the valve mounting hole 115 into the crescent-shaped port 111 on the suction side, and the oil pressure in the crescent-shaped port 112 on the discharge side, i.e., the discharge pressure of the oil from the discharge port 114, decreases. As described above, the discharge pressure of the electric oil pump is maintained below a predetermined value through mechanical control by the relief valve 116, eliminating the need for hydraulic sensors or complex control.

JP 2008-215087 A

However, in the above electric oil pump, the relief valve 116 is provided on the pump plate 110, which is located on the axially opposite side of the pump 106 from the electric motor 103 (the left side in Figure 9), which leads to an increase in the size of the pump plate 110 and therefore the size of the electric oil pump.

In addition, in the above electric oil pump, the electric motor 103 and the oil flow path are separated, so there is little hope of the oil providing any cooling effect to the electric motor 103.

The present invention aims to make the electric fluid pump more compact and improve the cooling efficiency of the motor section.

The present invention made to solve the above problems is an electric fluid pump having a motor section, a pump section provided on one axial side of the motor section and driven by the motor section, an intake side flow path through which fluid before being compressed by the pump section flows, a discharge side flow path through which fluid compressed by the pump section flows, a relief pipeline connecting the discharge side flow path and the intake side flow path, and a relief valve disposed in the relief pipeline and opened when fluid pressure in the discharge side flow path reaches or exceeds a predetermined value,
The relief pipe and the relief valve are disposed in an axial region between the motor section and the pump section.

In this way, the present invention focuses on the fact that there is dead space between the motor section and the pump section in the axial direction, and places the relief line and relief valve in this dead space. This increases the efficiency of component placement within the electric fluid pump, and allows the electric fluid pump to be made more compact. Also, by providing a relief line between the motor section and the pump in the axial direction, the relief line is located closer to the motor section than in the conventional product shown in Figure 9, making it easier for the motor section to be cooled by the fluid flowing through the relief line.

In an electric fluid pump, when a discharge port and a suction port are provided on one axial side of the pump section, the fluid pressure in the discharge port and the suction port presses the pump section against the housing from one axial side. Therefore, by providing a counter port on the other axial side of the pump section (the opposite side to the discharge port and the suction port), the fluid pressure in the discharge port and the fluid pressure in the counter port are offset in the axial direction, reducing the force with which the pump section is pressed against the housing.

The pump plate 110 of the conventional electric oil pump shown in Figures 9 and 10 is provided with an intake port 113, a discharge port 114, and a mounting surface 117 for mounting to an object. The intake port 113 and the discharge port 114 are open in the mounting surface 117. In this electric oil pump, the mounting surface 117 is provided so as to be parallel to the rotation axis of the electric motor 103, but depending on the object to which it is to be mounted, the mounting surface may be provided so as to be perpendicular to the rotation axis of the electric motor 103. Therefore, the shape of the pump plate 110 needs to be changed according to the arrangement of the mounting surface 117. In this electric oil pump, a valve mounting hole 115 (relief pipe) and a relief valve 116 are provided inside the pump plate 110, so that the arrangement of the valve mounting hole 115 and the relief valve 116 provided inside the pump plate 110 needs to be changed in accordance with the change in the shape of the pump plate 110.

Therefore, when the electric fluid pump has a suction port and a discharge port provided on one axial side of the pump section, and a suction side counter port and a discharge side counter port provided axially between the motor section and the pump section, it is preferable to connect the relief line to the suction side counter port and the discharge side counter port. By providing the relief valve on the counter port side rather than on the suction port and discharge port side in this way, even if the shape or arrangement of the mounting surface where the suction port and discharge port open is changed, the arrangement of the relief line and the relief valve is not affected, and there is no need to change the arrangement of the relief line and the relief valve.

The above electric oil pump preferably includes a housing having a motor housing section that houses the motor section on its inner circumference, a pump housing section that houses the pump section on its inner circumference, and a relief pipe, all integrally formed as a single component. This allows heat to be easily transferred between the relief pipe and the pump section and the motor section via the housing, which is an integral part, thereby further enhancing the cooling effect of the motor section.

The electric oil pump may have, for example, a motor rotor provided in the motor section, a pump rotor provided in the pump section, a rotating shaft that rotates integrally with the motor rotor and the pump rotor, a plain bearing that supports the rotating shaft, and a seal member that is disposed between the motor section and the plain bearing, and the relief pipe and the relief valve may be configured to be disposed on the outer periphery of the plain bearing or the seal member.

The above electric fluid pump can be used, for example, as an electric oil pump for pumping oil.

As described above, the present invention makes it possible to make the electric fluid pump more compact and improve the cooling efficiency of the motor section.

8 is a cross-sectional view of the electric oil pump according to the embodiment of the present invention, taken along line II in FIG. 7 . 2 is a cross-sectional view taken along line II-II in FIG. 1 . FIG. 2 is a perspective view of the electric oil pump. 4 is a cross-sectional view taken along line IV-IV in FIG. 1 . 2 is a cross-sectional view taken along line VV in FIG. 1 . FIG. 13 is a perspective view of the counter port and the relief line. 7 is a cross-sectional view taken along line VII-VII in FIG. FIG. 4 is a perspective view showing another example of the electric oil pump of the present invention. FIG. 1 is a cross-sectional view of a conventional electric oil pump. 10 is a cross-sectional view taken along line XX in FIG. 9.

The following describes an embodiment of the present invention with reference to the drawings.

The electric fluid pump of this embodiment is an electric oil pump that mainly supplies hydraulic pressure to the transmission while the engine is stopped. The electric oil pump draws oil from an oil reservoir at the bottom of the transmission case, and then discharges the oil to pump it into the transmission, thereby ensuring the necessary hydraulic pressure and amount of lubricating oil within the transmission.

FIG. 1 shows an electric oil pump 1 of this embodiment. This electric oil pump 1 has a motor section 2, a pump section 3 driven by the motor section 2, a controller 4 that controls the motor section 2, and a housing 5 that houses the motor section 2, the pump section 3, and the controller 4. This electric oil pump 1 is an integrated mechanical and electrical type with a built-in controller 4, but is not limited to this, and the electric oil pump 1 may also be a separate mechanical and electrical type that does not have a controller. Each member or element will be described in detail below.

In the following description, the direction parallel to the axis O of the motor unit 2 is referred to as the "axial direction," and the radial direction of a circle centered on the axis O is referred to as the "radial direction" (the "inner diameter direction" and "outer diameter direction" also refer to the inner diameter direction and outer diameter direction of the circle). In addition, the circumferential direction of a circle centered on the axis O is referred to as the "circumferential direction."

The motor section 2 is, for example, a three-phase brushless DC motor. The motor section 2 has a stator 21 and a rotor 22. The stator 21 has a number of coils evenly arranged in the circumferential direction, specifically, coils corresponding to the three phases U-phase, V-phase, and W-phase. The rotor 22 has a number of magnets 23 evenly arranged in the circumferential direction. The stator 21 and the rotor 22 are arranged with a small radial gap between them. The rotating shaft 6 is fixed to the inner circumference of the rotor 22.

The pump section 3 is disposed on one axial side of the motor section 2 (the right side in the figure). The pump section 3 is a rotary pump that pumps oil by rotating. As shown in FIG. 2, the pump section 3 of this embodiment is a trochoid pump having an inner rotor 31 on which multiple external teeth 31a are formed, and an outer rotor 32 on which multiple internal teeth 32a are formed. The inner rotor 31 and the outer rotor 32 are formed of, for example, an iron-based metal or a copper-based metal. The inner rotor 31 is disposed on the inner diameter side of the outer rotor 32. The outer rotor 32 is in an eccentric position with respect to the inner rotor 31. Some of the internal teeth 32a of the outer rotor 32 mesh with some of the external teeth 31a of the inner rotor 31. If the number of teeth of the inner rotor 31 is n, the number of teeth of the outer rotor 32 is (n+1). The outer peripheral surface 32b of the outer rotor 32 and the inner peripheral surface 55a of the housing 5 into which it fits are both cylindrical surfaces. The outer rotor 32 is rotatably arranged on the inner circumference of the housing 5 so as to rotate in conjunction with the rotation of the inner rotor 31.

The rotating shaft 6 is rotatably supported relative to the housing 5 via a bearing 7 (see FIG. 1). For example, a plain bearing or a rolling bearing can be used as the bearing 7, and in this embodiment, a plain bearing, particularly a sintered oil-impregnated bearing, is used. The bearing 7 is fixed to the inner periphery of the housing 5, for example, by press-fitting. In this case, it is preferable that the bearing 7 is made of a material that has a linear expansion coefficient close to that of the housing 5 into which it is press-fitted, and that has excellent sliding properties. For example, if the housing 5 is made of an aluminum alloy, the bearing 7 is preferably made of a copper-based metal (a metal containing copper as the main component).

The inner rotor 31 (pump rotor) of the pump section 3 is fixed to the end of the rotating shaft 6 on one axial side (the right side in FIG. 1), and the rotor 22 (motor rotor) of the motor section 2 is fixed to the end of the rotating shaft 6 on the other axial side (the left side in FIG. 1). This allows the rotating shaft 6, the inner rotor 31, and the rotor 22 to rotate together. The rotating shaft 6 and either or both of the inner rotor 31 and the rotor 22 may be integrally formed as a single component. A seal member 8 is disposed between the bearing 7 and the motor section 2. The seal member 8 has a seal lip that slides against the outer circumferential surface of the rotating shaft 6. This seal member 8 prevents oil from leaking from the pump section 3 to the motor section 2. Oil from the pump section 3 is supplied to the sliding contact portion between the bearing 7 and the rotating shaft 6.

The controller 4 is disposed on the other axial side of the motor unit 2 (the left side in FIG. 1). The controller 4 has a board perpendicular to the axial direction and multiple electronic components mounted on the board. These electronic components form a control circuit that controls the driving of the motor unit 2. The controller 4 is supplied with power from an external power source via a connector.

The housing 5 has a central housing 51, a pump cover 52 provided on one axial side of the central housing 51 (right side in FIG. 1), a controller housing 53 provided on the other axial side of the central housing 51 (left side in FIG. 1), and a controller cover 54 provided on the other axial side of the controller housing 53 (left side in FIG. 1). The central housing 51, pump cover 52, controller housing 53, and controller cover 54 are integrated together by fastening them together with bolts, for example.

The central housing 51 has a roughly cylindrical pump accommodating section 55 that accommodates the pump section 3 on its inner periphery, a roughly cylindrical motor accommodating section 56 that accommodates the motor section 2 on its inner periphery, and an intermediate section 57 provided in the axial direction of these sections. The outer circumferential surface 32b of the outer rotor 32 is fitted into the cylindrical inner circumferential surface 55a of the pump accommodating section 55, thereby allowing the outer rotor 32 to rotate freely around its own axis. The stator 21 of the motor section 2 is fixed to the cylindrical inner circumferential surface of the motor accommodating section 56.

The pump cover 52 is a flat member that covers the pump section 3 from one axial side (the right side in FIG. 1). The pump cover 52 is provided with a mounting surface 52a for mounting the electric oil pump 1 to a mounting target part (the transmission case in this embodiment). The mounting surface 52a in the illustrated example is a flat surface that is provided on the end face of the pump cover 52 on one axial side (the right side in FIG. 1) and is perpendicular to the axial direction. With the mounting surface 52a in close contact with the transmission case, the pump cover 52 and the transmission case are fastened together, for example with bolts, to fix the electric oil pump 1 to the transmission case.

The controller housing 53 is cylindrical. The controller cover 54 covers the opening on the other axial side of the controller housing 53 (the left side in FIG. 1). The controller 4 is housed in the space formed inside the controller housing 53 and the controller cover 54. The controller cover 54 is provided with a number of fins 54a (see FIG. 3).

The central housing 51 is integrally formed as a single component, for example, by casting, cutting, or a combination of these. The central housing 51, pump cover 52, controller housing 53, and controller cover 54 are formed from a metal material that is a conductor and has good thermal conductivity, for example, an aluminum alloy. Alternatively, one or more of the central housing 51, pump cover 52, controller housing 53, and controller cover 54 may be formed from another metal material (for example, an iron-based metal or a copper-based metal) or resin.

The pump cover 52 is formed with an intake side intermediate port 61, a discharge side intermediate port 62, an intake port 63 and a discharge port 64. The intake side intermediate port 61 and the discharge side intermediate port 62 are both provided adjacent to one axial side of the pump section 3 (the right side in FIG. 1). The intake side intermediate port 61 opens to a portion (suction space) of the space between the inner rotor 31 and the outer rotor 32 where the spatial volume expands with rotation. The discharge side intermediate port 62 opens to a portion (compression space) of the space between the inner rotor 31 and the outer rotor 32 where the spatial volume narrows with rotation. As shown in FIG. 4, the intake side intermediate port 61 and the discharge side intermediate port 62 are both arc-shaped (crescent-shaped) extending in the circumferential direction, and are provided at positions that are approximately symmetrical with respect to the diameter direction (the vertical straight line passing through the center of rotation in FIG. 4). One end of the suction port 63 opens to the suction side intermediate port 61, and the other end of the suction port 63 opens to the mounting surface 52a (see FIG. 1). One end of the discharge port 64 opens to the discharge side intermediate port 62, and the other end of the discharge port 64 opens to the mounting surface 52a.

The above-mentioned suction side intermediate port 61, suction port 63, and suction side counter port 65 form a suction side flow path through which oil flows before being compressed in the pump section 3. The above-mentioned discharge side intermediate port 62, discharge port 64, and discharge side counter port 66 form a discharge side flow path through which oil compressed in the pump section 3 flows.

In the middle portion 57 of the central housing 51, a suction side counter port 65 and a discharge side counter port 66, and a relief pipe 67 that communicates between them are formed. The suction side counter port 65 and the discharge side counter port 66 are both provided adjacent to the other axial side (left side in FIG. 1) of the pump section 3. The suction side counter port 65 opens to a portion (suction space) of the space between the inner rotor 31 and the outer rotor 32 where the spatial volume expands with rotation. The discharge side counter port 66 opens to a portion (compression space) of the space between the inner rotor 31 and the outer rotor 32 where the spatial volume narrows with rotation. It opens to the meshing portion of the inner rotor 31 and the outer rotor 32. As shown in FIG. 5, the suction side counter port 65 and the discharge side counter port 66 are both arc-shaped (crescent-shaped) extending in the circumferential direction, and are provided at positions that are approximately symmetrical with respect to the diameter direction (the vertical straight line passing through the center of rotation in FIG. 5). The suction side counter port 65 is shaped and positioned so as to overlap the suction side intermediate port 61 when viewed from the axial direction, and the discharge side counter port 66 is shaped and positioned so as to overlap the discharge side intermediate port 62 when viewed from the axial direction.

As shown in FIG. 6, the relief pipe 67 has a valve accommodating portion 67a, a suction side connection portion 67b, and a discharge side connection portion 67c. The suction side connection portion 67b connects the valve accommodating portion 67a to the suction side counter port 65. The discharge side connection portion 67c connects the valve accommodating portion 67a to the discharge side counter port 66. In the illustrated example, the valve accommodating portion 67a is a straight (cylindrical) pipe. The side (inner peripheral surface) of the valve accommodating portion 67a is connected to the suction side counter port 65 by the suction side connection portion 67b. The end (end closer to the axis O) of the valve accommodating portion 67a is connected to the discharge side counter port 66 by the discharge side connection portion 67c. In the illustrated example, the suction side connection portion 67b and the discharge side connection portion 67c are each made up of two straight (cylindrical) pipes that intersect with each other. In this way, the valve housing portion 67a, the suction side connection portion 67b, and the discharge side connection portion 67c are each formed as a straight line, and therefore can be easily formed in the central housing 51 by machining using a drill or the like. Note that the configuration of the relief line 67 is not limited to the above, and for example, the suction side connection portion 67b or the discharge side connection portion 67c, or both, may be formed as one or three or more straight lines.

As shown in FIG. 7, the valve housing portion 67a has a larger diameter than the discharge side connection portion 67c that is connected to its end. Therefore, a step is provided at the boundary between the valve housing portion 67a and the discharge side connection portion 67c, and a seal surface 67d is provided at the inner diameter end of this step. The seal surface 67d has a tapered surface shape similar to the tapered surface 71a provided at the tip of the relief valve 71.

A relief valve 71 is accommodated in the valve housing portion 67a of the relief pipe 67. In this embodiment, the opening on the outside side of the valve housing portion 67a is closed by a cover member 72, and a spring 73 is arranged in a compressed state between the cover member 72 and the relief valve 71. The elastic force of the spring 73 presses the relief valve 71 against the seal surface 67d of the relief pipe 67, closing this portion, thereby blocking the suction side counter port 65 and the discharge side counter port 66. Note that the configuration of the relief valve is not limited to the poppet valve as described above, and may be, for example, a spool valve or a ball valve.

In the electric oil pump 1, the bearing 7 and the seal member 8 are provided between the motor section 2 and the pump section 3 in the axial direction (see FIG. 1). In other words, the motor section 2 and the pump section 3 need to be spaced apart in the axial direction in order to secure space for arranging the bearing 7 and the seal member 8. Therefore, a dead space is created between the motor section 2 and the pump section 3 and on the outer periphery of the bearing 7 and the seal member 8. In the electric oil pump 1, the relief pipe 67 and the relief valve 71 are arranged in the axial region between the motor section 2 and the pump section 3 (the middle section 57 of the central housing 51), which is the dead space, specifically on the outer periphery of the bearing 7 or the seal member 8 (the outer periphery of the bearing 7 in the illustrated example). This increases the efficiency of component arrangement within the electric oil pump 1, and allows the electric oil pump 1 to be made smaller.

Incidentally, a rolling bearing can also be used as the bearing 7 that supports the rotating shaft 6. However, because rolling bearings are usually lubricated with grease, it becomes necessary to place a seal member 8 between the rolling bearing (bearing 7) and the pump section 3 to prevent mixing with the oil pumped by the pump section 3. In other words, the arrangement of the bearing 7 and the pump section 3 is reversed in the axial direction from that shown in FIG. 1. In this case, because the seal member 8 is placed close to the pump section 3, it becomes difficult to secure space for providing a relief pipe 67 on its outer periphery.

Therefore, in this embodiment, a plain bearing is used as the bearing 7. Since the plain bearing can be lubricated by the oil in the pump section 3, the bearing 7 can be arranged close to the other axial side of the pump section 3 (the left side in the figure). In this case, a seal member 8 for preventing oil from entering the motor section 2 is arranged between the bearing 7 and the motor section 2 as shown in FIG. 1. Generally, a plain bearing has a smaller radial dimension than a rolling bearing, so by arranging the plain bearing (bearing 7) close to the pump section 3 as described above, it becomes easier to ensure space for providing a relief pipe 67 on its outer periphery, which facilitates the design of the electric oil pump 1, and in particular the design of the relief pipe 67.

Furthermore, the above electric oil pump 1 may require a change in the arrangement of the mounting surface 52a to be provided on the pump cover 52 depending on the object to which it is to be attached. For example, in this embodiment, as shown in Figures 1 and 3, the mounting surface 52a is perpendicular to the axial direction, but as shown in Figure 8, the mounting surface 52a may be parallel to the axial direction. In this way, the shape of the pump cover 52 varies greatly depending on the arrangement of the mounting surface 52a. In this case, if a relief valve 71 and a relief line 67 are provided inside the pump cover 52, it becomes necessary to reconsider the arrangement of the relief valve 71 and the relief line 67 provided inside the pump cover 52 every time the shape of the pump cover 52 is changed.

In the above electric oil pump 1, the relief line 67 and the relief valve 71 are provided in the central housing 51, which is provided with the

counter ports

65, 66, rather than in the pump cover 52, which is provided with the suction port 63 and the discharge port 64. This makes it easier to make design changes, since there is no need to change the position of the relief line 67 and the relief valve 71 even if the shape of the pump cover 52 is changed.

In the electric oil pump 1 having the above configuration, when the motor section 2 is driven, the inner rotor 31 rotates, and the meshed outer rotor 32 rotates, causing the space formed between the teeth of the two to expand and contract as the rotor rotates. As a result, oil collected in the oil reservoir inside the transmission case is sucked into the pump section 3 via the suction port 63 and the suction side intermediate port 61 (see arrow A in Figure 1), and the oil compressed by the pump section 3 is discharged via the discharge side intermediate port 62 and the discharge port 64 (see arrow B in Figure 1) and supplied to the transmission.

The oil compressed by the pump section 3 as described above is not only supplied to the discharge side intermediate port 62 and the discharge port 64 as described above, but also to the discharge side counter port 66. At this time, if the oil pressure at the discharge side counter port 66 is below a predetermined value, the relief valve 71 is pressed against the seal surface 67d by the biasing force of the spring 73, and the relief valve 71 is maintained in a closed state. In this way, because the relief line 67 is blocked by the relief valve 71 being closed, the oil at the discharge side counter port 66 does not flow into the suction side counter port 65 via the relief line 67.

On the other hand, if the oil pressure at the discharge side counter port 66 exceeds a predetermined value, the oil pressure pushes the relief valve 71 against the biasing force of the spring 73, the relief valve 71 moves away from the seal surface 67d, and the discharge side counter port 66 and the suction side counter port 65 communicate with each other via the relief line 67 (see dotted line in FIG. 7). As a result, the oil at the discharge side counter port 66 flows into the suction side counter port 65 via the relief line 67 (see dotted arrow C in FIG. 7), and the oil pressure at the discharge side counter port 66 drops. Then, when the oil pressure at the discharge side counter port 66 falls below a predetermined value, the relief valve 71 is pressed against the seal surface 67d by the biasing force of the spring 73, and the relief line 67 is shut off again. As a result, the oil pressure at the discharge side flow path is maintained within an appropriate range (below a predetermined value).

As described above, by providing the electric oil pump 1 with a relief valve 71 and mechanically controlling the oil pressure with this relief valve 71, the oil pressure can be maintained within an appropriate range without the need for complex control.

In the above electric oil pump 1, as shown in FIG. 1, a relief pipe 67 is disposed in the axial region between the motor section 2 and the pump section 3. In this case, the relief pipe 67 and the motor section 2 are disposed relatively close to each other, so that the motor section 2 is easily cooled through the housing 5 by the oil flowing through the relief pipe 67. In particular, in this embodiment, the motor accommodating section 56 of the housing 5 to which the stator 21 of the motor section 2 is fixed and the intermediate section 57 in which the relief pipe 67 is formed are integrally formed as a single component from metal (e.g., aluminum alloy), so that heat from the stator 21 is easily transferred to the relief pipe 67, further improving cooling efficiency.

When the relief valve 71 is closed, no oil flows through the relief line 67, so the cooling effect described above is hardly obtained. However, in the electric oil pump 1, the more the driving force of the motor section 2 is increased and the discharge pressure of the pump section 3 is raised, the more heat is generated by the stator 21 of the motor section 2. When the discharge pressure of the pump section 3 increases in this way, the relief valve 71 opens and oil flows through the relief line 67, so that the motor section 2 is cooled by the oil flowing through the relief line 67. In other words, when the driving force of the motor section 2 increases and the amount of heat generated by the stator 21 increases, the relief valve 71 opens and oil flows through the relief line 67, so that the cooling effect described above can be obtained when cooling is particularly necessary.

The electric oil pump 1 described above can also be used for applications where it is not necessary to provide a relief valve 71. In this case, the process of forming the relief line 67 (valve accommodating portion 67a, suction side connection portion 67b, and discharge side connection portion 67c) in the intermediate portion 57 of the central housing 51 can be omitted, and a central housing 51 without a relief line 67 can be formed. In this case, there is no need to change any other configuration of the electric oil pump 1.

In addition, the electric oil pump 1 can also use the suction side flow path (suction port 63, suction side intermediate port 61, suction side counter port 65) as a discharge side flow path, and the discharge side flow path (discharge port 64, discharge side intermediate port 62, discharge side counter port 66) as a suction side flow path.

The present invention is not limited to the above embodiment. Other embodiments of the present invention will be described below, but duplicate explanations of points similar to the above embodiment will be omitted.

In the above embodiment, the suction port 63 and the discharge port 64 are provided on one axial side of the pump section 3 (right side in FIG. 1), and the

counter ports

65 and 66 are provided on the other axial side of the pump section 3 (left side in FIG. 1). However, conversely, the suction port 63 and the discharge port 64 may be provided on the other axial side of the pump section 3 (left side in FIG. 1), and the

counter ports

65 and 66 may be provided on one axial side of the pump section 3 (right side in FIG. 1). In this case, the suction side intermediate port 61, the suction port 63, the discharge side intermediate port 62, the discharge port 64, and the relief pipe 67 are provided in the axial region between the motor section 2 and the pump section 3, specifically in the intermediate section 57 of the central housing 51. The relief pipe 67 is provided at a position that communicates the suction port 63 and the discharge port 64, or the suction side intermediate port 61 and the discharge side intermediate port 62.

In the above embodiment, the housing 5 is made of an aluminum alloy, and the outer rotor 32 of the pump section 3 is made of an iron-based metal or a copper-based metal. In this case, the difference in hardness between the two is relatively large, so the amount of wear on the housing 5 increases, the gap between the housing 5 and the outer rotor 32 increases, and the amount of oil leakage increases, which leads to a decrease in the oil discharge characteristics (flow rate relative to pump pressure at each rotation speed). In addition, because the housing 5 and the outer rotor 32 come into contact and slide, a decrease in pump efficiency is unavoidable due to the sliding resistance at this time.

Therefore, it is preferable that the hardness of at least the part of the housing 5 that slides against the outer rotor 32, i.e., the inner surface of the pump housing 55, is made equal to the hardness of the outer rotor 32 of the pump section 3. For example, it is preferable that the difference in hardness between them is HRB5 or less. Specifically, by subjecting the inner surface of the pump housing 55 of the housing 5 to a treatment (coating, surface treatment, heat treatment, etc.), the hardness of this part can be made equal to the hardness of the outer rotor 32 made of iron or copper-based metal (for example, HRB60 or higher). When the housing 5 is made of an aluminum alloy, anodizing can be applied as a treatment for increasing the hardness as described above. Anodizing is particularly preferable because it not only increases the hardness but also improves the sliding properties. In addition, the pump housing 55 may be subjected to a heat treatment (for example, T6 treatment) to increase the hardness of the pump housing 55 itself. In addition to the above-mentioned treatment to increase hardness, the housing 5 may also be subjected to surface modification (e.g., molybdenum disulfide shot) to improve sliding properties.

As described above, by making the hardness of the pump housing 55 equal to that of the outer rotor 32, wear of the pump housing 55 due to sliding contact with the outer rotor 32 can be suppressed. This makes it possible to suppress an increase in the clearance between the outer rotor 32 and the pump housing 55 due to wear, and an increase in the amount of oil leakage that accompanies this, and therefore a decrease in pump efficiency can be suppressed.

Furthermore, the above-mentioned surface treatment may be applied not only to the inner circumferential surface of the pump housing 55, but also to other areas where the inner rotor 31 and the outer rotor 32 slide, such as the end faces of the pump cover 52 and the central housing 51 that face the end faces of the inner rotor 31 and the outer rotor 32.

Also, a sliding bearing (e.g., a sintered oil-impregnated bearing) may be interposed between the inner peripheral surface of the pump housing 55 and the outer peripheral surface of the outer rotor 32. For example, a cylindrical sliding bearing is fixed to the inner peripheral surface of the pump housing 55 by press-fitting or the like, and this sliding bearing is in sliding contact with the outer peripheral surface of the outer rotor 32. The sliding bearing is made of an iron-based or copper-based metal. The hardness of the sliding bearing is equivalent to the hardness of the outer rotor 32, and the hardness difference with the outer rotor 32 is, for example, HRB5 or less. When the outer rotor 32 is made of an iron-based or copper-based metal, it is desirable that the hardness of the sliding bearing is equivalent to or greater than HRB60. In this way, by sliding the housing 5 and the outer rotor 32 via the sliding bearing, the material of the pump housing 55 is not limited, and it can be applied regardless of whether it is made of metal or resin. In particular, by forming the plain bearing from a sintered oil-impregnated bearing, the oil impregnated inside seeps into the sliding contact area between the plain bearing and the outer rotor 32, thereby improving sliding properties.

The present invention can be applied not only to electric oil pumps that pump oil, but also to electric pumps that pump liquids other than oil.

1. Electric oil pump (electric fluid pump)
2 Motor section 3 Pump section 4 Controller 5 Housing 6 Rotating shaft 7 Bearing 8 Seal member 21 Stator 22 Rotor 31 Inner rotor 32 Outer rotor 51 Central housing 52 Pump cover 52a Mounting surface 53 Controller housing 54 Controller cover 55 Pump accommodating section 56 Motor accommodating section 57 Intermediate section 61 Suction side intermediate port 62 Discharge side intermediate port 63 Suction port 64 Discharge port 65 Suction side counter port 66 Discharge side counter port 67 Relief pipe 67a Valve accommodating section 67b Suction side connecting section 67c Discharge side connecting section 67d Seal surface 71 Relief valve 72 Lid member 73 Spring

Claims

A motor unit;
a pump section provided on one axial side of the motor section and driven by the motor section;
a suction side flow path through which fluid before being compressed in the pump portion flows;
a discharge side flow path through which the fluid compressed in the pump portion flows;
a relief pipe connecting the discharge side flow path and the suction side flow path;
a relief valve disposed in the relief line and opened when the fluid pressure in the discharge side flow path reaches or exceeds a predetermined value,
The relief pipe and the relief valve are disposed in an axial region between the motor portion and the pump portion.
a suction port and a discharge port provided on one axial side of the pump portion;
a suction side counter port and a discharge side counter port provided between the motor section and the pump section in the axial direction,
2. The electric fluid pump according to claim 1, wherein the relief line is connected to the suction counter port and the discharge counter port.
a housing integrally formed as one piece;
3. The electric fluid pump according to claim 1, wherein the housing has a motor accommodating portion that accommodates the motor portion on an inner periphery thereof, a pump accommodating portion that accommodates the pump portion on an inner periphery thereof, and the relief pipe.
A motor rotor provided in the motor unit;
A pump rotor provided in the pump section;
a rotating shaft that rotates integrally with the motor rotor and the pump rotor;
A plain bearing for supporting the rotating shaft;
a seal member disposed between the motor portion and the sliding bearing,
3. The electric fluid pump according to claim 1, wherein the relief pipe and the relief valve are disposed on an outer periphery of the sliding bearing or the seal member.
The electric fluid pump according to claim 1 or 2 is an electric oil pump for pumping oil.