JP2013064395A - Electric pump unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric pump unit capable of reducing inclinations of a motor shaft and a motor rotor, by enhancing bearing support rigidity of a bearing device.SOLUTION: A pump body 6 is constituted of a pump housing 8 and a pump plate 9 arranged on the front end side of the pump housing 8. A motor housing 7 incorporated with a pump driving electric motor 4 is fixed to the rear end side of the pump housing 8. The bearing device 17 for supporting the motor shaft 18 has a first bearing 21 arranged in a closed-end hole 9b formed on a rear face of the pump plate 9 and supporting a front end part of the motor shaft 18, and a second bearing 22 formed in the pump housing 8, arranged inside a cylindrical bearing support portion 15 extending in the motor housing 7 and supporting a middle part of the motor shaft 18. A pump rotor 12 is arranged between the first bearing 21 and the second bearing 22.

Description

  The present invention relates to an electric pump unit used as a hydraulic pump for supplying hydraulic pressure to a transmission (transmission) of an automobile, for example.

  Hydraulic pressure is supplied to the vehicle's transmission by a hydraulic pump. However, in order to save energy, the vehicle is stopped when the vehicle is stopped, so-called idle stop (idling stop) is secured. In order to do so, an electric hydraulic pump is used.

  Since an electric hydraulic pump for an automobile transmission is mounted in a limited space of a vehicle body, it is required to be compact, and to be light and reduce costs. In order to meet such a demand, an electric pump unit in which a pump, an electric motor for driving a pump, and a controller for the electric motor are incorporated in a common unit housing has been proposed (for example, see Patent Document 1).

  In such a conventional electric pump unit, a motor housing is connected to the rear side of a pump main body constituting the pump, and the electric motor and the controller are incorporated in a sealed motor chamber formed in the motor housing. The electric motor is disposed on the front side (pump main body side) in the motor chamber, and a controller board is fixed to the rear end surface of the electric motor. A plurality of electrical components (electrical components and electronic components) such as capacitors and FETs constituting the controller are attached to the substrate.

  The electric motor includes a motor rotor fixed to a free end portion on the rear side of a pump drive motor shaft supported by a bearing device, and a motor stator fixed to a motor housing. A pump chamber is formed inside the pump body. The pump body is formed with a cylindrical bearing holding portion extending into the motor housing, and a motor shaft bearing device is provided inside the bearing holding portion. The front part of the motor shaft enters the pump chamber, and the pump rotor of the pump is fixed to the front free end part. When the pump is an internal gear pump, an inner gear which is an inner pump rotor is fixed to the front end portion of the motor shaft.

  The bearing device includes two single-row deep groove ball bearings arranged side by side in the axial direction. An oil seal for sealing between the pump chamber and the bearing device is provided in the bearing holding portion of the pump body.

  In this electric pump unit, the two rolling bearings of the bearing device are adjacent to each other in order to reduce the size. Thus, the motor shaft is supported on the motor rotor side and is cantilevered with the pump rotor side being a free end. In order to reduce costs, the two rolling bearings are single row deep groove ball bearings, and the ball bearings are fitted with a clearance between the bearing holding portion and the motor shaft to reduce assembly costs.

  When the pump is an internal gear pump, the oil suction port and the oil discharge port are formed at symmetrical positions of the pump housing corresponding to the meshing portion of the inner gear and the outer gear which is the outer pump rotor.

JP 2010-116914 A

  In the conventional electric pump unit described above, when the pump is operated, the oil suction port of the pump chamber is at a low pressure, but the oil discharge port is at a high pressure. For this reason, radial force acts on the front end portion (end portion on the pump housing side) of the cantilevered motor shaft to which the inner gear is fixed. As described above, the single row deep groove ball bearing in which the two rolling bearings of the bearing device are arranged side by side is a clearance fit, so that the bearing support rigidity is low and the motor shaft is inclined. Due to the tilt of the motor shaft, the inner gear tilts and rotates in contact with the motor housing. For this reason, there exists a possibility that noise may generate | occur | produce and abrasion may generate | occur | produce in a motor rotor and a motor housing.

  An object of the present invention is to provide an electric pump unit that can solve the above-described problems, increase the bearing support rigidity of the bearing device, and reduce the inclination of the motor shaft and the motor rotor.

  An electric pump unit according to the present invention includes a pump housing in which a pump main body of a pump that sucks and discharges fluid includes a pump chamber in which a pump rotor is housed, and a pump rate provided on one end side of the pump housing. A motor housing having a pump drive electric motor built in is fixed to the other end side of the pump housing, and the electric motor is supported by a bearing device and rotationally drives the pump rotor; and the motor shaft In the electric pump unit comprising a motor rotor fixed to the end portion of the motor housing and a motor stator fixed to the motor housing, the bearing device is disposed in a bottomed hole formed in the pump plate. A first bearing for supporting a pump housing side end of the motor shaft, and the pump A second bearing that is formed inside a cylindrical bearing holding portion that is formed in the housing and extends into the motor housing and supports an intermediate portion of the motor shaft, and the pump rotor includes the first bearing and the second bearing. It is arranged between the second bearing.

  Since the pump housing side end of the motor shaft, which has conventionally been a free end, is supported by the first bearing, the bearing support rigidity is increased accordingly. Thereby, the inclination of the motor shaft and the pump rotor can be reduced.

  Further, the first bearing can be provided without changing the axial dimension by providing the first bearing arrangement space function to the pump plate which has not been conventionally used as the arrangement space of the motor shaft. it can. Thereby, bearing support rigidity can be improved, without changing the dimension of an axial direction.

  The first bearing is preferably a sliding bearing.

  The first bearing is a plain bearing like a bush, so it can be installed in a small space, and the pump plate can easily secure the installation location such as suction port, discharge port, suction hole, discharge hole, etc. Can do.

  The pump rotor is composed of an outer gear and an inner gear. The inner gear is fixed to the motor shaft in a state in which axial and radial movements are restricted, and the second bearing is a rolling unit provided with an inner ring, an outer ring, and rolling elements. It is a bearing, and it is preferable that the inner ring is fitted on the motor shaft.

  When the inner gear is fixed to the motor shaft in a state where the axial direction and the radial direction movement are restricted, the backlash of the motor shaft is suppressed. Further, since the inner ring of the second bearing supporting the intermediate portion of the motor shaft is fitted to the motor shaft, the bearing support rigidity can be further increased. Thereby, the shake of a pump rotor or a motor rotor can be suppressed.

  In addition to the inner ring being fitted to the motor shaft, the outer ring of the second bearing is fitted to the bearing holding portion of the pump housing, so that the bearing support rigidity can be further increased.

  The outer ring of the second bearing can be a clearance fit. In this case, the first bearing is formed of a cylindrical metal member, the motor shaft is clearance-fitted to the first bearing, and the outer ring of the second bearing. Is preferably fitted to the bearing holding portion, and the shaft center of the motor shaft is assembled to the discharge port side with respect to the shaft center of the metal member.

  That is, instead of assembling so that the tip of the motor shaft (the fitting portion to the first bearing) is located at the center of the first bearing, the pump plate is placed so that the tip of the motor shaft is close to the discharge port side. On the other hand, it is preferable that the pump housing is assembled and assembled, and in this way, the sound pressure of the low frequency sound generated when the pump rotor is rotationally driven can be reduced.

  According to the electric pump unit of the present invention, as described above, the bearing support rigidity of the bearing device can be increased, and the inclination of the motor shaft and the pump rotor can be reduced.

FIG. 1 is a longitudinal sectional view of a main part of an electric pump unit showing a first embodiment of the present invention. FIG. 2 is a longitudinal sectional view of a main part of an electric pump unit showing a second embodiment of the present invention. FIG. 3 is a longitudinal sectional view of a main part of an electric pump unit showing a third embodiment of the present invention. FIG. 4 is a diagram schematically showing a preferred example of how to assemble the electric pump unit according to the first embodiment of the present invention. FIG. 5 is a diagram for explaining the operational effects of the assembly method shown in FIG. FIG. 6 is a diagram for explaining the problem of the assembly method compared with the assembly method shown in FIG. 4.

  Hereinafter, an embodiment in which the present invention is applied to an electric pump unit for an automobile transmission will be described with reference to the drawings.

  FIG. 1 is a longitudinal sectional view of a main part of an electric pump unit showing a first embodiment of the present invention. In the following description, the left side of FIG.

  In the electric pump unit (1), a pump (3) for sucking and discharging oil, an electric motor (4) for driving the pump, and a controller (5) for the electric motor (4) are integrated in the unit housing (2). It is built in. In this example, the pump (3) is an internal gear pump, and the motor (4) is a sensorless control DC brushless motor having a three-phase winding.

  The unit housing (2) includes a pump body (6) of the pump (3), and a motor housing (7) incorporating an electric motor (4) and a controller (5).

  The pump body (6) includes a rear pump housing (8) and a front pump plate (9). The pump housing (8) has a thick plate shape that extends in a direction perpendicular to the front-rear direction, and a pump chamber (10) having an open front is formed at the center thereof. A pump plate (9) is fixed to the front surface of the pump housing (8) via an O-ring (47), and the front surface of the pump chamber (10) is closed. An outer gear (11), which is an outer pump rotor, is rotatably accommodated in the pump chamber (10), and an inner gear (12), which is an inner pump rotor that meshes with the outer gear (11), is disposed inside the outer gear (11). The pump housing (8) and the pump plate (9) are made of, for example, an aluminum alloy.

  The motor housing (7) includes a cylindrical synthetic resin motor case (13) and a disc-shaped lid (14) fixed to the rear end of the motor case (13). The front end of the motor case (13) is fixed to the rear surface of the pump housing (8) via an O-ring (48). The pump plate (9), the pump housing (8), and the motor case (13) have a plurality of connecting portions (9a), (8a), and (13a) that are integrally formed so as to protrude radially outward from the outer periphery thereof. The parts are secured to each other by bolts (16). The rear end opening of the motor case (13) is closed by the lid (14).

  The electric motor (4) has a motor shaft (18) which is a pump drive shaft extending in the front-rear direction. The motor shaft (18) is supported by the bearing device (17). The bearing device (17) includes a first bearing (21) that supports the front end portion (end portion on the pump housing side) of the motor shaft (18), and a second bearing that supports the front and rear intermediate portions of the motor shaft (18). 22).

  The second bearing (22) is composed of two deep groove ball bearings (51) and (52) adjacent to each other in the front-rear direction. Each of the deep groove ball bearings (51) (52) is a grease-lubricated sealed type, and includes an inner ring (51a) (52a), an outer ring (51b) (52b), and a plurality of balls (rolling elements) (51c) ( 52c) and a pair of seals (51d) and (52d).

  The motor shaft (18) is formed in a stepped shape. The front part of the motor shaft (18) penetrates the central part of the pump housing (8) and enters the pump chamber (10), and the front end part is a bottomed hole provided on the rear surface of the pump plate (9). (9b).

  The first bearing (21) is a cylindrical bush (cylindrical metal member), and is fixed to the bottomed hole (9b) on the rear surface of the pump plate (9) with an interference fit. The front end portion of the motor shaft (18) is fitted into the first bearing (21) with a clearance fit. Thereby, the inner peripheral surface of the first bearing (21) (bush) and the outer peripheral surface of the front end portion of the motor shaft (18) are slidable to constitute a slide bearing.

  A cylindrical bearing holding portion (15) having a smaller diameter than the motor case (13) is integrally formed at the center of the rear end surface of the pump housing (8) and extends into the motor case (13).

  The inner ring (51a) (52a) of each deep groove ball bearing (51) (52) is fitted into the motor shaft (18), and the outer ring (51b) (52b) of each deep groove ball bearing (51) (52). ) Is fitted into the bearing holder (15).

  Between the second bearing (22) and the inner gear (12), an oil seal (20) that seals between the bearing holder (15) and the motor shaft (18) is disposed.

  The inner gear (12) is fitted near the front end of the motor shaft (18) so as to contact the rear surface of the pump plate (9). The inner gear (12) is fixed to the motor shaft (18) in a state where axial movement and radial movement are restricted by this interference fit (press-fit).

  A motor rotor (23) constituting the motor (4) is fixed to a rear end portion (motor housing side end portion) of the motor shaft (18) protruding rearward from the bearing holding portion (15). The motor rotor (23) is provided with a synthetic resin permanent magnet holding member (25) fixed on the outer periphery of the cylindrical rotor body (24), and the holding member (25) is equally divided in the circumferential direction. And a segment-shaped permanent magnet (26).

  A motor stator (27) constituting the motor (4) is fixed to the inner periphery of the motor case (13) facing the motor rotor (23). In the stator (27), an insulator (synthetic resin insulator) (29) is incorporated in a stator core (28) made of laminated steel sheets, and a coil (30) is wound around the insulator (29). In this example, the stator (27) is molded integrally with the inner periphery of the motor case (13).

  The rotor body (24) includes a cylindrical portion (24a) facing the motor stator (27), and a flange portion extending radially outward from the rear end of the motor shaft (18) and integrated with the cylindrical portion (24a). (24b) and the cross-sectional shape is a U-shape.

  The board (31) of the controller (5) is fixed to the rear end of the insulator (29), and the component (32) constituting the controller (5) is attached to the board (31). Although only one component (32) attached to the front surface of the substrate (31) is shown in FIG. 1, the component is disposed at a predetermined position on at least one of the front surface and the rear surface of the substrate (31). The component (32) shown in FIG. 1 is, for example, an electrolytic capacitor.

  The stator core (28) is formed by integrally forming pole portions (tooth portions) (28b) projecting radially inward at a plurality of locations equally dividing the inner periphery of the annular portion (28a) in the circumferential direction. The tip of each pole portion (28b) extends on both sides in the circumferential direction, and its inner peripheral surface forms one cylindrical surface.

  The insulator (29) is composed of a pair of front and rear halves (33) (34). Each half body (33) (34) is formed of a synthetic resin such as PPS (polyphenylene sulfide resin), for example, and the stator core (28) excluding the outer peripheral surface of the annular portion (28a) and the inner peripheral surface of the pole portion (28b). It is incorporated into the stator core (28) from both the front and rear sides so as to cover the surface. Each half (33) (34) is formed with a coil mounting portion (33a) (34a) that covers a portion excluding the inner peripheral surface of the pole portion (28b) of the stator core (28). In each pole part (28b) of the stator core (28), the coil (30) is wound around the part covered with the coil mounting parts (33a) (34a) of both halves (33) (34). Substrate projections (34b) extending rearward are integrally formed at a plurality of locations equally dividing the radially outer portion of the coil mounting portion (34a) of the rear half (34) in the circumferential direction. A metal female screw member (35) having a female screw formed on the inner periphery is embedded inside the rear end of each protrusion (34b).

  The motor case (13) is integrated with the stator (27) by molding a synthetic resin such as PA66 (polyamide 66) on the outer peripheral side of the stator (27) using a mold. The stator (27) except for the inner peripheral surface of the pole portion (28b) of the stator core (28), the inner peripheral surface of the coil mounting portion (33a) (34a) of the insulator (29), and the rear end surface of the protrusion (34b). Is covered with a motor case (13). A connector (37) having a plurality of pins (36) is integrally formed on the outer periphery of the motor case (13).

  The lid (14) is made of synthetic resin and is fixed to the rear end of the motor case (13) by an appropriate means such as heat welding.

  The substrate (31) of the controller (5) is fixed to the insulator (29) by a screw (39) screwed to the female screw member (35) of the protrusion (34b) of the insulator (29). Although not shown, a plurality of bus bars are incorporated in the molded body of the insulator (29) and the motor case (13), and the coils (30) of the stator (27) are electrically connected to each other using these bus bars. And electrically connected to the substrate (31). The pin (36) of the connector (37) is also electrically connected to the substrate (31).

  The oil suction port (on the opposite wall of the pump housing (8) and the pump plate (9) corresponding to the meshing part of the inner gear (12) and the outer gear (11) of the pump (3) (the lower meshing part in this example) 40) (41) is formed. The oil discharge port (42) is formed on the opposing wall of the pump housing (8) and the pump plate (9) corresponding to the meshing part (in this example, the meshing part on the upper side) of the inner gear (12) and the outer gear (11) of the pump (3). ) (43) is formed. The pump plate (9) has an oil suction hole (44) communicating with the oil suction port (41) and an oil discharge hole (45) communicating with the oil discharge port (43). An oil relief groove (46) is formed in the wall of the pump housing (8) facing the pump chamber (10) to communicate the hole (19) through which the motor shaft (18) is inserted and the oil suction port (40). ing.

  When the pump (3) is driven by the electric motor (4) and the inner gear (12) and the outer gear (11) rotate, the oil suction ports (40) (41) are at low pressure and the oil discharge ports (42) (43 ) Becomes high pressure. For this reason, the inner gear (12) receives a force in the radial direction (downward in this example).

  In the embodiment described above, the front and rear intermediate portions of the motor shaft (18) are supported by the second bearing (22), and the front end portion of the motor shaft (18) is supported by the first bearing (21). Therefore, the bearing support rigidity is improved, and the motor shaft (18) is prevented from tilting even when a radial force due to hydraulic pressure acts on the inner gear (12), which causes the pump (3) to fall. Can be suppressed, and noise and wear can be reduced.

  In addition, the first bearing (21) is a sliding bearing such as a bush, so that it can be installed in a small space. The pump plate (9) has an oil suction port (41) and an oil discharge port (43). In addition, installation locations such as the oil suction hole (44) and the oil discharge hole (45) can be easily secured.

  Further, since the inner gear (12) is fitted to the motor shaft (18), the movement of the motor shaft (18) in the axial direction is restricted, and play is suppressed. Therefore, the outer ring (51b) (52b) of each deep groove ball bearing (51) (52) may be loosely fitted to the bearing holding part (15), and a circlip is provided between the outer rings (51b) (52b). There is no need. For this reason, the bearings (51) and (52) can be easily assembled and the assemblability is improved. However, in order to further improve the bearing support rigidity, the outer rings (51b) and (52b) of the deep groove ball bearings (51) and (52) can be fitted into the bearing holding portion (15).

  FIG. 2 is a longitudinal sectional view of a main part of an electric pump unit showing a second embodiment of the present invention. In the second embodiment, the configuration of the rotating part including the bearing device is different from that of the first embodiment. In the following, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In this embodiment, the bearing device (61) that supports the motor shaft (60) of the electric motor (4) includes a first bearing (63) that supports the front end portion of the motor shaft (60), and the motor shaft (60). The first bearing (63) is the same bush as in the first embodiment, and the second bearing (64) is a single deep groove ball bearing. It is said that.

  The motor shaft (60) has a columnar shape as compared with the stepped shape of the first embodiment. Further, the axial length of the motor shaft (60) is shorter than that of the first embodiment because the second bearing (64) is a single deep groove ball bearing.

  The bearing holding part (62) formed integrally with the pump housing (8) includes a front thick part (62a) and a rear thin part (62b). The thick part (62a) has a smaller inner diameter and a larger outer diameter than the thin part (62b). An inward flange portion (62c) is provided on the inner periphery of the boundary portion between the thick portion (62a) and the thin portion (62b).

  The second bearing (64) is disposed on the inner periphery of the thick wall portion (62a), and the oil seal that seals between the bearing holding portion (62) and the motor shaft (60) on the inner periphery of the thin wall portion (62b). (65) is arranged. The interference of the oil seal (65) is slightly smaller than that of the first embodiment.

  The second bearing (64) is disposed so as to sandwich the inner gear (12) (pump rotor) between the first bearing (63). The second bearing (64) is an open type deep groove ball bearing having an inner ring (64a), an outer ring (64b), and a plurality of balls (rolling elements) (64c), and the inner ring (64a) is a motor shaft (60). The outer ring (64b) is fit into the thick wall portion (62a) of the bearing holding portion (62).

  The motor shaft (60) is connected to the inner gear (12) by a knock pin (66) at a portion near the front end. The knock pin (66) is a coupling member for coupling the motor shaft (60) and the inner gear (12) so that they rotate integrally and do not move relative to each other in the axial direction. The inner gear (12) is fixed to the motor shaft (60) in a restricted state. As the coupling member, a pin such as a spy roll pin or a key can be used instead of the knock pin (66).

  The motor rotor (67) is fixed to the rear end (motor housing side end) of the motor shaft (60), and the motor stator (27) is provided at the same position as in the first embodiment. The rotor body (68) of the motor rotor (67) is integrated with the cylindrical portion (68a) extending radially outward from the rear end of the motor shaft (61) and the cylindrical portion (68a) facing the motor stator (27). And a flanged portion (68b). Since the axial length of the motor shaft (60) is shorter than that of the first embodiment, the rotor body (68) has a flange portion (68b) that is substantially in the axial direction of the cylindrical portion (68a). (The cross-sectional shape is I-type).

  In the second embodiment, as in the first embodiment, the second bearing (64) supports the front and rear intermediate portions of the motor shaft (60), and the front end of the motor shaft (60) is the first bearing. (63), the bearing support rigidity is improved, and the motor shaft (60) is prevented from tilting even when a radial force due to hydraulic pressure is applied to the inner gear (12). As a result, the pump (3) can be prevented from falling down, and noise and wear can be reduced. Moreover, since the inner and outer rings (64a) and (64b) of the second bearing (64) are interference fits, the bearing support rigidity is further improved.

  Further, since the motor shaft (60) and the inner gear (12) are coupled by the knock pin (66), the movement of the motor shaft (60) in the axial direction is restricted, and play is suppressed.

  Further, since the flange portion (68b) of the rotor body (68) is fixed to the substantially central portion in the axial direction of the cylindrical portion (68a), the flange portion (24b) is fixed to the rear end portion of the cylindrical portion (24a). The balance is better than that of the first embodiment, and the vibration of the motor rotor (67) can be prevented.

  The bearing holding part (62) has a thin part (62b) at its rear part in order to avoid interference with the motor rotor (67). The front part that does not interfere with the motor rotor (67) is the thick part (62a). Since the outer ring (64b) of the second bearing (64) is fitted into the thick part (62a), a sufficient allowance can be secured between the bearing holding part (62) and the outer ring (64b). . Therefore, it is not necessary to implement separate measures against disconnection (such as prevention of axial movement using a circlip). Further, since the rigidity is increased by the inward flange portion (62c), the deformation of the bearing holding portion (62) when the oil seal (65) is press-fitted is prevented, and the interference is stabilized.

  FIG. 3 is a longitudinal sectional view of a main part of an electric pump unit showing a third embodiment of the present invention. In the third embodiment, the configuration of the bearing device including the oil seal is different from that of the second embodiment. Hereinafter, the same reference numerals are given to the same configurations as those of the first and second embodiments, and the description thereof will be given. Is omitted.

  The bearing device (71) of this embodiment includes a first bearing (73) and a second bearing (74), as in the first and second embodiments.

  The bearing holding part (72) formed integrally with the pump housing (8) is composed of a front thick part (72a) and a rear thin part (72b), and the thick part (72a) The inner diameter is equal to the thin part (72b), and the outer diameter is larger than the thin part (72b). An inward flange portion (72c) is provided at the front end of the thick portion (72a). An oil seal (75) is arranged inside the thick part (72a), and a second bearing (74) is arranged inside the thin part (72b).

  The first bearing (73) is a bush similar to the first and second embodiments, and the second bearing (74) includes an inner ring (74a), an outer ring (74b), and a plurality of balls (rolling elements) (74c). And a grease lubricated sealed deep groove ball bearing having a pair of seals (74d).

  The second bearing (74) is disposed so as to sandwich the inner gear (12) (pump rotor) and the oil seal (75) between the first bearing (73). In the second bearing (74), the inner ring (74a) is fitted into the middle part of the motor shaft (60), and the outer ring (74b) is fitted into the thin part (72b) of the bearing holding part (72). Yes.

  In the third embodiment, the positional relationship between the oil seal (75) and the second bearing (74) is reversed from that of the second embodiment, so that the second bearing (74) is connected to the motor shaft. (60) Arranged near the rear end, the distance between the first bearing (73) and the second bearing (74) is larger than in the second embodiment. Thereby, the bearing support rigidity is further enhanced.

  The motor rotor (67) is the same as in the second embodiment, and the cross-sectional shape is an I-type, which is advantageous in preventing the motor rotor (67) from shaking.

  In the first embodiment, the outer rings (51b) and (52b) of the two deep groove ball bearings (51) and (52) constituting the second bearing (22) and the bearing holding portion of the pump housing (8) ( 15) is a clearance fit, and the first bearing (21) and the tip of the motor shaft (18) are also a clearance fit. An example of a preferred assembly method in this case is shown in FIG.

  In FIG. 4, the shaft center (18a) of the motor shaft (18) is assembled to the discharge port side with respect to the shaft center (21a) of the first bearing (21). The size of the gap formed by the clearance fit is actually about several tens of μm (for example, about 20 μm on the first bearing (21) side and about 10 μm on the second bearing (22) side). In FIG. 4, the gap is schematically shown exaggerated.

  As shown in FIG. 6 (a), the above assembly is normally performed so that the tip of the motor shaft (18) is positioned at the center between the suction port (41) and the discharge port (43). While the shaft center (21a) of (21) and the shaft center (18a) of the motor shaft (18) coincide with each other, as shown in FIGS. 4 and 5 (a), the motor shaft (18 ), The suction port side hydraulic pressure is smaller than the discharge port side hydraulic pressure when hydraulic pressure is applied. Side clearance> Discharge port side clearance.

  The pump (3) in the electric pump unit (1) according to the present invention is a pump that operates when the vehicle stops idling and the engine stops, and there are no parts to drive other than the pump (3). If the sound pressure generated from the pump (3) is large, the driver may feel uncomfortable. Therefore, it is necessary to reduce the level of sound generated by the pump (3).

  When assembled as shown in FIG. 6 (a), the shaft center (18a) of the motor shaft (18) and the shaft center (21a) of the first bearing (21) coincide with each other when no hydraulic pressure is applied. When the hydraulic pressure is applied, the discharge port side becomes a high pressure, so that the tip of the motor shaft (18) is pushed to the suction port side as shown in FIG. 6 (b). As a result, the first bearing (21) and the motor shaft (18) may slide on the suction port side, and this sliding noise may increase the low frequency (281 to 2245 Hz) sound pressure.

  On the other hand, when assembled as shown in FIG. 5 (a), the hydraulic pressure is not applied and the discharge port side is approached in advance, and when the hydraulic pressure is applied, the discharge port side becomes high pressure. As shown in FIG. 5 (b), the tip of the motor shaft (18) is pushed to the suction port side. At this time, the gap increases on the discharge port side where the gap is small. If this gap is 10 μm or more, an oil film is formed, and the motor shaft (18) and the first bearing (21) rotate without rubbing each other. Thereby, the low frequency (281-2245 Hz) sound pressure resulting from the sliding sound between a motor shaft (18) and a 1st bearing (21) can be reduced.

  In order to obtain a gap as shown in FIG. 5A, for example, a load of 5 to 30 N may be applied to the motor shaft (18) so as to approach the discharge port side.

  This assembly can reduce low-frequency sound, reduce variation in assembly position, and reduce fluctuations in sound pressure. Also, friction between the first bearing (21) and the motor shaft (18) As a result, the durability can be improved.

  In each of the above embodiments, the first bearings (21), (63), and (73) of the bearing devices (17), (61), and (71) are bushes as slide bearings, and the second bearings (22), (64), and (74). However, the present invention is not limited to this, and the first bearing may be a rolling bearing, and the second bearing may be a rolling bearing other than the deep groove ball bearing. When the first bearing is a rolling bearing, a needle roller bearing is preferable. The needle roller bearing includes, for example, a cylindrical outer ring, a plurality of needle rollers arranged along the inner diameter surface of the outer ring, and a cage that holds the plurality of needle rollers. The outer ring is press-fitted and fixed to the peripheral wall of the bottomed hole (9b). By using a needle roller bearing as the first bearing instead of a ball bearing, it becomes easy to use a rolling bearing and to secure the assemblability and the port space.

  The overall configuration of the electric pump unit and the configuration of each unit are not limited to those of the above-described embodiment, and can be changed as appropriate.

  Moreover, this invention is applicable also to electric pump units other than the electric pump unit for transmissions.

(1): Electric pump unit, (3): Pump, (4): Electric motor, (6): Pump body, (7): Motor housing, (8): Pump housing, (9): Pump plate, ( 9b): Bottomed hole, (10): Pump chamber, (11): Outer gear, (12): Inner gear (pump rotor), (15): Bearing holding part, (17): Bearing device, (18): Motor Shaft, (21): First bearing, (22): Second bearing, (23): Motor rotor, (27): Motor stator, (51) (52): Deep groove ball bearing (rolling bearing), (51a) (52a): Inner ring, (51b) (52b): Outer ring, (51c) (52c): Ball (rolling element), (60): Motor shaft, (61): Bearing device, (62): Bearing holder, (63): First bearing, (64): Second bearing, (64a): Inner ring, (64b): Outer ring, (64c): Ball (rolling element), (67): Motor rotor, (71): Bearing device , (72): Bearing holding part, (73): First bearing, (74): Second bearing, (74a): Inner ring, (74b): Outer ring, (74c): Ball (rolling element)

Claims (5)

A pump main body of a pump that sucks and discharges fluid includes a pump housing in which a pump chamber accommodating a pump rotor is formed, and a pump rate provided on one end side of the pump housing, and the other end of the pump housing A motor housing with a built-in electric motor for driving the pump is fixed to the side, and the electric motor is supported by a bearing device and rotationally drives the pump rotor, and is fixed to the end of the motor shaft on the motor housing side An electric pump unit comprising a motor rotor and a motor stator fixed to the motor housing;
The bearing device includes a first bearing disposed in a bottomed hole formed in the pump plate and supporting a pump housing side end portion of the motor shaft, and a cylinder formed in the pump housing and extending into the motor housing. And a second bearing that supports an intermediate portion of the motor shaft, and the pump rotor is disposed between the first bearing and the second bearing. An electric pump unit characterized by that.   The electric pump unit according to claim 1, wherein the first bearing is a slide bearing.   The pump rotor is composed of an outer gear and an inner gear, and the inner gear is fixed to the motor shaft in a state in which axial movement and radial movement are restricted, and the second bearing includes an inner ring, an outer ring, and a rolling element. The electric pump unit according to claim 1, wherein the inner ring is fitted into an intermediate portion of the motor shaft.   The electric pump unit according to claim 3, wherein an outer ring of the second bearing is fitted into the bearing holding portion.   The first bearing is formed of a cylindrical metal member, the motor shaft is fitted into the first bearing, and the outer ring of the second bearing is fitted into the bearing holding portion. 4. The electric pump unit according to claim 3, wherein the shaft center is assembled to the discharge port side with respect to the shaft center of the metal member.

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