Electric pump and electric pump manufacturing method

Abstract

An electric pump (100) comprises: a pump unit (10) that discharges a liquid; a motor unit (20) that rotates a drive shaft (1) to drive the pump unit (10); a housing (40) that houses the pump unit (10) and the motor unit (20); a bushing (71) and a ball bearing (73) that are provided in the housing (40) and rotatably support the drive shaft (1); and an oil seal (72) that is provided in the housing (40) and is in sliding contact with an outer circumferential surface of the drive shaft (1), wherein the oil seal (72) is positioned between the bushing (71) and the ball bearing (73).

Description

Electric pump and method for manufacturing an electric pump

[0001] The present invention relates to an electric pump and a method for manufacturing an electric pump.

[0002] Japanese Unexamined Patent Application Publication No. 2013-64395 discloses an electric pump unit that supports an intermediate portion of a motor shaft by a second bearing composed of two adjacent deep-groove ball bearings.

[0003] In the motor portion of an electric pump, when the gap between the motor rotor and the stator is uneven, the motor rotor is attracted toward the side with a narrower gap, resulting in an uneven load and causing the drive shaft connected to the motor rotor to tilt.

[0004] However, if the distance between the two bearings that support the drive shaft at the intermediate portion is short, these two bearings may not sufficiently suppress the tilting of the drive shaft, and there is a risk that the motor rotor cannot be stably held.

[0005] An object of the present invention is to suppress the tilting of a drive shaft.

[0006] According to an aspect of the present invention, there is provided an electric pump including: a pump section that discharges a liquid; a motor section that rotates a drive shaft to drive the pump section; a housing that houses the pump section and the motor section; a first bearing and a second bearing provided in the housing to rotatably support the drive shaft; and a seal ring provided in the housing and in sliding contact with an outer peripheral surface of the drive shaft, the seal ring being disposed between the first bearing and the second bearing.

[0007] It is a figure which shows the electric pump which concerns on embodiment of this invention. It is explanatory drawing of a sliding bearing press-fitting process. It is explanatory drawing of a seal ring press-fitting process. It is explanatory drawing of a drive shaft press-fitting process.

[0008] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0009] The electric pump 100 is mounted on a vehicle and used as a pump to discharge coolant (liquid) to cool equipment mounted on the vehicle, or as a pump to discharge oil (liquid) to lubricate gears mounted on the vehicle. The electric pump 100 may also be used as a fluid pressure supply source to discharge working fluid (liquid) to drive equipment, and may be mounted on industrial machinery other than vehicles. The electric pump 100 can be used to discharge liquids with lubricating properties, such as oil, including when used to discharge coolant or working fluid.

[0010] As shown in Figure 1, the electric pump 100 comprises a pump unit 10 for discharging liquid, a motor unit 20 for rotating the drive shaft 1 to drive the pump unit 10, a control unit 30 for controlling the motor unit 20, and a housing 40 for housing the pump unit 10, the motor unit 20, and the control unit 30. In the electric pump 100, the control unit 30, the motor unit 20, and the pump unit 10 are arranged in this order from the top in Figure 1. Hereafter, the axial, radial, and circumferential directions of the drive shaft 1 will also be simply referred to as "axial direction," "radial direction," and "circumferential direction."

[0011] The pump section 10 is an internal gear pump and includes an inner rotor 11 through which the drive shaft 1 is inserted and connected, and an outer rotor 12 provided outside the inner rotor 11. The inner rotor 11 and the outer rotor 12 are housed in the pump housing 51 of the housing 40, are eccentrically positioned relative to each other, and are covered by the pump cover 66 of the housing 40. The center of the inner rotor 11 is coaxially positioned so as to overlap with the drive shaft 1, and the center of the outer rotor 12 is offset from the drive shaft 1. The inner rotor 11 has multiple external teeth (not shown), and the outer rotor 12 has multiple internal teeth (not shown) that slide against the external teeth. The number of teeth of the external teeth and internal teeth are different, and the pump chamber 13 is partitioned by adjacent external teeth of the inner rotor 11 and internal teeth of the outer rotor 12. Multiple pump chambers 13 are formed in the pump section 10.

[0012] The motor unit 20 includes an annular stator 21 and a motor rotor 24 positioned radially inward of the stator 21. The motor unit 20 is an electric motor, and the drive shaft 1 also serves as the rotation axis of the motor unit 20 as an electric motor.

[0013] The stator 21 has an annular stator core 22 installed so as to surround the motor rotor 24, and coils 23 wound around the stator core 22. The stator core 22 is constructed by laminating a plurality of electromagnetic steel sheets. Coils 23 corresponding to the three phases of drive current are formed in the stator core 22 as U-phase coils, V-phase coils, and W-phase coils, and the ends of the coil wiring extending from the coils 23 are connected to the control unit 30.

[0014] The motor rotor 24 has a rotor core 25 connected to the outer circumferential surface of the drive shaft 1 and rotating together with the drive shaft 1, and a plurality of permanent magnets (not shown) provided on the rotor core 25, and is press-fitted onto the drive shaft 1. The motor rotor 24 is press-fitted onto the drive shaft 1 from the base end 1b side (upper side in Figure 1) of the drive shaft 1 while receiving a press-fitting load at the tip 1a of the drive shaft 1.

[0015] The control unit 30 includes an electronic component 31, a substrate 32 on which the electronic component 31 is mounted and to which the coil 23 of the motor unit 20 is connected, and a heat dissipation unit 33 that dissipates heat from the substrate 32, and controls the current supplied to the stator 21 to drive the motor unit 20.

[0016] The housing 40 includes a motor housing 41 that houses the motor unit 20, a pump housing 51 that houses the pump unit 10, a cover 61 that covers the opening 42 of the motor housing 41, and a pump cover 66 that covers the pump unit 10 housed in the pump housing 51. The electric pump 100 also includes a bush 71 and a ball bearing 73 as first and second bearings provided within the housing 40 to rotatably support the drive shaft 1, and an oil seal 72 provided within the housing 40 as a seal ring that slides against the outer circumferential surface of the drive shaft 1.

[0017] The motor housing 41 is made of a metal material (for example, an aluminum alloy or a steel material) and has an opening 42 that opens at one end in the axial direction (upper side in Figure 1) and a bottom surface 43 that forms the outer surface at the other end in the axial direction (lower side in Figure 1). The bush 71 as the first bearing constitutes the bearing on the side of the opening 42 of the housing 40 that is closer to the oil seal 72, and the ball bearing 73 as the second bearing constitutes the bearing on the side of the bottom surface 43 of the housing 40 that is closer to the oil seal 72. The bush 71 as the first bearing constitutes a sliding bearing, and the ball bearing 73 as the second bearing constitutes a rolling bearing.

[0018] The motor housing 41 further includes a motor housing recess 44 that accommodates the motor unit 20 and a through hole 45 through which the drive shaft 1 is inserted. The motor housing recess 44 includes a first housing recess 44a with an opening 42 formed therein, and a second housing recess 44c that extends axially from the first bottom surface 44b of the first housing recess 44a toward the bottom surface 43, forming an annular space. The outer circumferential surface of the stator core 22 fits into the inner circumferential surface of the second housing recess 44c, thereby positioning the stator 21 radially through the radial positioning of the stator core 22.

[0019] The insertion hole 45 is formed in a cylindrical portion 44e that protrudes axially from the center of the second bottom surface 44d of the second receiving recess 44c. The insertion hole 45 penetrates the cylindrical portion 44e axially, and the inner and outer circumferences of the cylindrical portion 44e are arranged to gradually decrease in diameter toward the opening 42 side of the motor housing 41. The inner circumference of the cylindrical portion 44e decreases in diameter in stages toward the opening 42 side, and accordingly, the outer circumference of the cylindrical portion 44e also decreases in diameter in stages toward the opening 42 side.

[0020] The insertion hole 45 includes a bush housing portion 46 as a sliding bearing housing portion that houses a bush 71 which rotatably supports the drive shaft 1, an oil seal housing portion 47 which is formed to be larger in diameter than the bush housing portion 46 and houses an oil seal 72 which slides against the outer surface of the drive shaft 1, and a ball bearing housing portion 48 which is formed to be larger in diameter than the oil seal housing portion 47 and houses a ball bearing 73 which is a bearing that rotatably supports the drive shaft 1.

[0021] The bush housing portion 46 is formed in a cylindrical shape, and the oil seal housing portion 47 and the ball bearing housing portion 48 are formed as recesses for housing the oil seal 72 and the ball bearing 73, respectively. The oil seal housing portion 47 has a bottom surface 47a facing the oil seal 72 from the axial direction and an inner circumferential surface 47b connected to the bottom surface 47a, and is formed in a concave shape toward the opening 42 side of the motor housing 41. The ball bearing housing portion 48 has a bottom surface 48a facing the outer ring 731 of the ball bearing 73 from the axial direction and an inner circumferential surface 48b connected to the bottom surface 48a, and is formed in a concave shape toward the opening 42 side of the motor housing 41.

[0022] A bush 71 and an oil seal 72 are press-fitted into the bush housing 46 and the oil seal housing 47, respectively, and a ball bearing 73 is placed in the ball bearing housing 48. The outer ring 731 of the ball bearing 73 is clearance-fitted against the inner circumferential surface 48b of the ball bearing housing 48, and the inner ring 732 of the ball bearing 73 is press-fitted onto the drive shaft 1.

[0023] The bush housing 46, the oil seal housing 47, and the ball bearing housing 48 are arranged in this order. Therefore, the oil seal 72 is positioned between the bush 71 and the ball bearing 73. This allows the distance between the bush 71 and the ball bearing 73 to be increased, thereby suppressing tilting of the drive shaft 1. The bush 71, oil seal 72, and ball bearing 73 are arranged around the middle section of the drive shaft 1.

[0024] The bush housing 46, the oil seal housing 47, and the ball bearing housing 48 are arranged in this order from the opening 42 side of the housing 40 in the axial direction. The bush housing 46 opens at the tip surface 44f of the cylindrical portion 44e, and the oil seal housing 47 is formed axially continuous with the bush housing 46. The ball bearing housing 48 is formed axially continuous with the oil seal housing 47 and opens at the bottom surface 43 of the motor housing 41.

[0025] The rotor core 25 of the motor rotor 24 has a recess 25a, which forms a bottomed cylindrical shape. The recess 25a opens toward the pump section 10, and the bush 71 is positioned inside the recess 25a by inserting the bush housing section 46.

[0026] As a result, the bush 71 is positioned near the axial center position C of the rotor core 25, making it less likely for the drive shaft 1 to tilt. Also, since the bush 71 has a small outer diameter, the outer diameter of the rotor core 25 can be reduced. The bush 71 is positioned in the axial direction, overlapping with the axial center position C of the rotor core 25.

[0027] The pump housing 51 has a pump housing recess 52 for housing the pump unit 10 and a through hole 53 that penetrates the bottom of the pump housing recess 52 and through which the drive shaft 1 is inserted, and is fixed to the bottom surface 43 of the motor housing 41.

[0028] The pump housing 51 is made of a metal material (for example, an aluminum alloy or steel) and is fixed to the motor housing 41 by fastening members (not shown). The pump housing recess 52 opens to the outer surface on the side opposite to the motor housing 41 in the axial direction (lower side in Figure 1), and the center of the pump housing recess 52 is offset from the center of the insertion hole 45 of the motor housing 41. The insertion hole 53 penetrates the center of the bottom of the pump housing recess 52 and is formed to be coaxial with the insertion hole 45 of the motor housing 41.

[0029] A gap 80 is formed between the inner circumferential surface of the insertion hole 53 and the outer circumferential surface of the drive shaft 1, and the pump housing recess 52 that houses the pump unit 10 and the ball bearing housing 48 that houses the ball bearing 73 are in communication with each other through the gap 80. Liquid flows into the gap 80 from the pump chamber 13 of the pump unit 10 through the gap between the inner rotor 11 and the bottom of the pump housing recess 52.

[0030] Therefore, liquid flows from the pump housing recess 52 of the pump housing 51 into the ball bearing housing 48 of the motor housing 41 through the gap 80, thereby lubricating the ball bearing 73. Furthermore, even if liquid flows into the ball bearing housing 48, the oil seal 72 prevents the liquid from flowing out of the ball bearing housing 48 into the motor housing recess 44 through the bush housing 46.

[0031] The cover 61 is fixed to the motor housing 41 by fastening members (not shown) and houses the control unit 30. The pump cover 66 is fixed to the pump housing 51 by fastening members (not shown) and covers the pump housing recess 52. The pump cover 66 has a shaft housing portion 66a that houses the tip portion 1a of the drive shaft 1, and the tip portion 1a housed in the shaft housing portion 66a is positioned so as not to come into contact with the pump cover 66.

[0032] The drive shaft 1 has a large-diameter portion 2 and a small-diameter portion 3 which is smaller in diameter than the large-diameter portion 2. The small-diameter portion 3 is formed on the tip end 1a side (lower side in Figure 1), and the large-diameter portion 2 is formed on the base end 1b side (upper side in Figure 1). A magnet 67 is provided at the base end 1b so as not to come into contact with the electronic components 31 and substrate 32 of the control unit 30. Changes in magnetism caused by the magnet 67 are detected by the control unit 30 and used to calculate the rotation angle and rotation speed of the drive shaft 1.

[0033] The bush 71 and oil seal 72 slide against the outer circumferential surface of the large diameter portion 2, and a ball bearing 73 is press-fitted into it. The inner circumferential surface of the through hole 53 faces the outer circumferential surface of the large diameter portion 2. The small diameter portion 3 is inserted into the through hole 11a of the inner rotor 11. The small diameter portion 3 has a flat portion 3a that forms a two-sided width, and the flat portion 3a is in surface contact with the through hole 11a.

[0034] In the electric pump 100 configured in this way, under the control of the control unit 30, the motor rotor 24 of the motor unit 20 rotates integrally with the drive shaft 1, thereby transmitting the rotational torque of the drive shaft 1 to the inner rotor 11 and driving the pump unit 10. In the pump unit 10, the outer teeth of the inner rotor 11 slide against the inner teeth of the outer rotor 12, causing the inner rotor 11 and outer rotor 12 to rotate, and consequently the pump chamber 13 to repeatedly expand and contract. In the expanded region (suction region) where the pump chamber 13 expands, liquid is drawn in through a suction port (not shown) formed in the pump cover 66, and in the contracted region (discharge region) where the pump chamber 13 contracts, liquid is discharged to the outside through a discharge port (not shown) formed in the pump cover 66.

[0035] Next, the manufacturing method of the electric pump 100 configured in this way will be explained using Figures 2 to 4.

[0036] In the sliding bearing press-fitting process shown in Figure 2, the bush 71 is press-fitted into the bush housing 46 of the motor housing 41 (housing 40). Compared to rolling bearings, the bush 71 is advantageous in terms of bearing size and cost considering the bearing load, and assembly is also easier as the press-fitting load is smaller. By using the bush 71 in one of the two bearings, the bush 71 and the ball bearing 73, assembly is also improved.

[0037] The bush 71 is press-fitted into the motor housing 41 to which the stator 21 is assembled. The bush 71 is press-fitted into the bush housing 46 from the opening 42 side of the motor housing 41, so that the end of the bush 71 positioned on the opening 42 side of the motor housing 41 is flush with the tip surface 44f (see Figure 1). The bush 71 can be press-fitted to a desired depth (axial position) using a press-fitting jig with a flange that contacts the tip surface 44f. The bush 71 may also be press-fitted into the bush housing 46 from the bottom surface 43 side of the motor housing 41. Press-fitting can be performed using a fluid pressure cylinder, and may also be performed by impact.

[0038] In the seal ring press-fitting process shown in Figure 3, the oil seal 72 is press-fitted into the oil seal housing 47 of the motor housing 41 (housing 40). The oil seal 72 is press-fitted into the oil seal housing 47 from the bottom surface 43 side of the motor housing 41 until the oil seal 72 contacts the bottom surface 47a of the oil seal housing 47. The oil seal 72 is press-fitted into the motor housing 41 to which the stator 21 and bush 71 are assembled.

[0039] In the drive shaft press-fitting process shown in Figure 4, with the ball bearing 73 positioned in the ball bearing housing 48, the drive shaft 1 is passed through the bush 71 and oil seal 72, which are press-fitted into the motor housing 41 (housing 40), and then press-fitted into the inner ring 732 of the ball bearing 73.

[0040] In other words, since the bush 71 and oil seal 72 slide against the drive shaft 1, the bush 71 and oil seal 72 only need to pass the drive shaft 1 through them, and then the drive shaft 1 is press-fitted into the inner ring 732.

[0041] In this way, with the cylindrical load receiver 90 in contact with the inner ring 732 of the ball bearing 73 from the bottom surface 43 side of the motor housing 41, the drive shaft 1 can be press-fitted into the inner ring 732 while the load receiver 90 receives the press-fitting load. The drive shaft 1 is press-fitted into the inner ring 732 of the ball bearing 73 with the motor rotor 24 assembled to it.

[0042] If a ball bearing is used instead of the bushing 71, the oil seal 72 is positioned between the two bearings, the ball bearing and the ball bearing 73, making it difficult to press-fit the inner ring of the ball bearing onto the shaft during the manufacturing process.

[0043] In this case, if the ball bearing is pre-pressed onto the drive shaft 1, it becomes possible to press the drive shaft 1 onto the ball bearing 73 in the same manner as in Figure 4. However, in this case, since the two bearings are pressed onto the drive shaft 1 separately, it is a time-consuming process.

[0044] On the other hand, the bush 71 is also press-fitted separately from the ball bearing 73. However, since the bush 71 is smaller and lighter than the ball bearing, it is easy to handle and the press-fitting load can be small. Further, since the bush 71 may be press-fitted into the motor housing 41, the drive shaft 1 as an assembly is also lighter than the case where the ball bearing is press-fitted into the drive shaft 1 in advance.

[0045] In the present embodiment, since the drive shaft 1 may be press-fitted into the inner ring 732 of the ball bearing 73 after passing through the bush 71 and the oil seal 72, the assemblability is improved.

[0046] Note that either the bush 71 or the oil seal 72 may be press-fitted first, or they may be press-fitted simultaneously. Further, the ball bearing 73, the oil seal 72, and the bush 71 may be arranged in this order from the opening 42 side of the housing 40. In this case, the drive shaft 1 can be press-fitted from the bottom surface 43 side of the motor housing 41. In this case, the ball bearing 73 constituting the rolling bearing corresponds to the first bearing, and the bush 71 constituting the sliding bearing corresponds to the second bearing. Even in this case, since the distance between the bush 71 and the ball bearing 73 can be increased, the tilting of the drive shaft 1 can be suppressed, and the assemblability is also improved by adopting the bush 71 for one of the two bearings of the bush 71 and the ball bearing 73.

[0047] Hereinafter, the configuration, operation, and effects of the embodiment of the present invention will be summarized and described.

[0048] The electric pump 100 includes a pump unit 10 that discharges a liquid, a motor unit 20 that rotates a drive shaft 1 to drive the pump unit 10, a housing 40 that houses the pump unit 10 and the motor unit 20, a bush 71 as a first bearing provided in the housing 40 and rotatably supporting the drive shaft 1, a ball bearing 73 as a second bearing, and an oil seal 72 as a seal ring provided in the housing 40 and slidably contacting the outer peripheral surface of the drive shaft 1. The oil seal 72 is disposed between the bush 71 and the ball bearing 73.

[0049] With this configuration, by placing the oil seal 72 between the bush 71 and the ball bearing 73, the distance between the bush 71 and the ball bearing 73 can be increased compared to when the bush 71 and the ball bearing 73 are adjacent to each other, thereby suppressing the tilting of the drive shaft 1.

[0050] In the electric pump 100, the bush 71, which serves as the first bearing, is a sliding bearing.

[0051] With this configuration, since the bush 71, which serves as the first bearing, is a sliding bearing, it is advantageous in terms of bearing size and cost considering the bearing load compared to the case of a rolling bearing. Furthermore, assembly is easier because the press-fit load is smaller, improving ease of assembly.

[0052] The motor unit 20 has a bottomed cylindrical rotor core 25 with a recess 25a formed therein, and the bush 71 is positioned inside the recess 25a.

[0053] With this configuration, the bush 71 can be positioned near the axial center position C of the rotor core 25, making it less likely for the drive shaft 1 to tip over. Also, since the bush 71 has a small outer diameter, the outer diameter of the rotor core 25 can be reduced.

[0054] In the manufacturing method of the electric pump 100, the electric pump 100 comprises a pump unit 10 for discharging liquid, a motor unit 20 for rotating a drive shaft 1 to drive the pump unit 10, and a housing 40 for housing the pump unit 10 and the motor unit 20. The housing 40 has a bush housing 46 as a sliding bearing housing for housing a bush 71 as a sliding bearing that rotatably supports the drive shaft 1, an oil seal housing 47 as a seal ring housing for housing an oil seal 72 which is formed to be larger in diameter than the bush housing 46 and slides against the outer circumferential surface of the drive shaft 1, and a ball bearing housing 48 which is formed to be larger in diameter than the oil seal housing 47 and houses a ball bearing 73 which is a bearing that rotatably supports the drive shaft 1. The bush housing 46, the oil seal housing 47, and the ball bearing housing 48 are arranged in this order. The method for manufacturing the electric pump 100 includes the steps of: press-fitting a bush 71 into a bush housing 46 of the housing 40; press-fitting an oil seal 72 into an oil seal housing 47 of the housing 40; and, with a ball bearing 73 positioned in a ball bearing housing 48, passing the drive shaft 1 through the bush 71 and oil seal 72 which are press-fitted into the housing 40, and then press-fitting it into the inner ring 732 of the ball bearing 73.

[0055] With this configuration, the drive shaft 1 can be passed through the bush 71 and oil seal 72 before being press-fitted into the inner ring 732 of the ball bearing 73, thus improving ease of assembly.

[0056] Although embodiments of the present invention have been described above, these embodiments only represent a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

[0057] This application claims priority based on Japanese Patent Application No. 2025-007455, filed with the Japan Patent Office on January 20, 2025, and all contents of that application are incorporated herein by reference.

Claims

1. An electric pump comprising: a pump section for discharging liquid; a motor section for driving the pump section by rotating a drive shaft; a housing for housing the pump section and the motor section; a first bearing and a second bearing provided within the housing for rotatably supporting the drive shaft; and a seal ring provided within the housing for sliding contact with the outer circumferential surface of the drive shaft, wherein the seal ring is positioned between the first bearing and the second bearing.

2. An electric pump according to claim 1, wherein the first bearing or the second bearing is a sliding bearing.

3. An electric pump according to claim 2, wherein the motor section has a rotor core formed in a bottomed cylindrical shape by a recess, and the sliding bearing is disposed within the recess.

4. A method for manufacturing an electric pump, wherein the electric pump comprises: a pump section for discharging liquid; a motor section for rotating a drive shaft to drive the pump section; and a housing for housing the pump section and the motor section, wherein the housing includes: a sliding bearing housing section for housing a sliding bearing that rotatably supports the drive shaft; a seal ring housing section formed to be larger in diameter than the sliding bearing housing section and for housing a seal ring that slides against the outer surface of the drive shaft; and a bearing housing section formed to be larger in diameter than the seal ring housing section and for housing a bearing that rotatably supports the drive shaft, wherein the sliding bearing housing section, the seal ring housing section, and the bearing housing section are arranged in this order, and the manufacturing process includes: pressing the sliding bearing into the sliding bearing housing section of the housing; and pressing the seal ring into the seal ring housing section of the housing. A method for manufacturing an electric pump, comprising the steps of: placing the bearing in the bearing housing, passing the drive shaft through the sliding bearing and seal ring which are press-fitted into the housing, and then press-fitting the drive shaft into the inner ring of the bearing.

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