JP2014015888A - Electric pump unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric pump unit which increases mechanical efficiency and suppresses reduction of volume efficiency.SOLUTION: On a face facing an outer gear 11 of an internal gear pump 3 of a pump body 5, grooves 21, 22 are provided at positions not including a boundary portion between a discharge port 20 and a suction port 19. The grooves 21, 22 reduce friction resistance. Providing the grooves 21, 22 at positions not including the boundary portion between the discharge port 20 and the suction port 19 prevents oil leak.

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.

  Oil pressure is supplied to the vehicle's transmission by a hydraulic pump, but for vehicles that perform so-called idle stop (idling stop) that stops the engine when the vehicle is stopped from the standpoint of energy saving, etc., ensure that the hydraulic pressure is supplied to the transmission even during idle stop. 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 and an electric motor for driving a pump 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 the pump body constituting the pump, and the electric motor is built in a sealed motor chamber formed in the motor housing.

  When the pump is an internal gear pump, an oil suction port and an 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. When the pump is operating, the suction port in the pump chamber is at a low pressure, but the discharge port is at a high pressure.

Japanese Patent Laid-Open No. 2008-231982

  In the conventional electric pump unit described above, raising the efficiency of the electric pump is an issue. Pump efficiency is represented by the product of mechanical efficiency and volumetric efficiency (pump efficiency = mechanical efficiency × volumetric efficiency). The mechanical efficiency can be improved by widening the side clearance (the gap formed between the internal gear pump and the surface of the pump body facing the internal gear pump). However, in this case, oil leakage increases and the volumetric efficiency decreases, and mechanical efficiency and volumetric efficiency are usually in conflict.

  An object of the present invention is to provide an electric pump unit that improves mechanical efficiency and suppresses a decrease in volumetric efficiency.

  An electric pump unit according to the present invention includes a pump housing in which a pump chamber accommodating an inscribed gear pump is formed, a pump body having a pump rate provided on one end side of the pump housing, and fixed to the other end side of the pump housing. And an electric pump unit comprising a motor housing incorporating a pump driving electric motor, and a groove on the surface of the pump body facing the inscribed gear pump, avoiding a boundary between the discharge port and the suction port. Is formed.

  By forming a groove on the surface of the pump body facing the inscribed gear pump, the contact area between the pump body and the inscribed gear pump is reduced, and the frictional resistance is reduced, thereby improving the mechanical efficiency. When a groove is provided at the boundary between the discharge port and the suction port, an oil leakage path from the discharge port to the suction port through the groove may be formed. By forming the groove while avoiding the boundary between the discharge port and the suction port, an increase in oil leakage due to the provision of the groove is suppressed, and a decrease in volumetric efficiency is suppressed.

  The groove is preferably relatively small on the discharge side and relatively large on the suction side.

  According to the electric pump unit of the present invention, as described above, it is possible to improve the mechanical efficiency and suppress the decrease in the volumetric efficiency.

FIG. 1 is a longitudinal sectional view of a main part of an electric pump unit showing an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1 and shows a main part of the internal gear pump. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1 and shows a main part of the pump plate. FIG. 4 is a diagram showing an example of the cross-sectional shape of the groove.

  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. In the following description, the left side of FIG.

  In the electric pump unit (1), an internal gear pump (3) for sucking and discharging oil and an electric motor (4) for driving the pump are integrally incorporated in a unit housing (2).

  The unit housing (2) is composed of a pump body (5) incorporating an internal gear pump (3) and a motor housing (6) incorporating a motor (4).

  The pump body (5) includes a rear pump housing (7) and a front pump plate (8). The pump housing (7) has a thick plate shape that extends in a direction orthogonal to the front-rear direction, and a pump chamber (9) having an open front is formed at the center thereof. A pump plate (8) is fixed to the front surface of the pump housing (7) via an O-ring (10), and the front surface of the pump chamber (9) is closed. An outer gear (11) that is an outer pump rotor is rotatably accommodated in the pump chamber (9), and an inner gear (12) that is an inner pump rotor that meshes with the outer gear (11) is disposed inside the outer gear (11). The pump housing (7) and the pump plate (8) are made of, for example, an aluminum alloy.

  The motor (4) has a motor shaft (13) which is a pump drive shaft extending in the front-rear direction. The motor shaft (13) is formed in a stepped shape and is supported by left and right rolling bearings (14) and (15). The front part of the motor shaft (13) penetrates the central part of the pump housing (7) and enters the pump chamber (9).

  An oil seal (16) for sealing between the pump housing (7) and the motor shaft (13) is disposed between the left rolling bearing (14) and the inner gear (12). The inner gear (12) is fitted into the front end of the motor shaft (13) so as to rotate integrally with the motor shaft (13).

  A motor rotor (17) constituting the motor (4) is integrally provided on the motor shaft (13), and the motor (4) is constituted on the inner periphery of the motor housing (6) facing the motor rotor (17). The motor stator (18) is fixed.

  When the rotational force of the motor (4) is transmitted to the internal gear pump (3), as shown in FIG. 2, the outer gear (11) and the inner gear (12) move in the directions indicated by arrows A1 and A2, respectively. The oil (fluid) is sucked and discharged by the volume change of the pump chamber (9) formed between the tooth surfaces of the inner teeth and the outer teeth.

  As shown in FIG. 3, the pump plate (8) is formed with a crescent-shaped intake port (19) and a crescent-shaped discharge port (20).

  In the pump chamber (9), as the outer gear (11) and the inner gear (12) rotate, a low pressure portion (9a) is formed on the suction side and a high pressure portion (9b) is formed on the discharge side, and the pump plate (8) Oil is fed through the formed suction port (19) and discharge port (20).

  When the internal gear pump (3) is driven by the motor (4) and the outer gear (11) and the inner gear (12) rotate, the suction port (19) has a low pressure and the discharge port (20) has a high pressure.

  In the electric pump unit (1) of this embodiment, as shown in FIG. 3, grooves (21) and (22) are formed on the surface of the pump plate (8) facing the outer gear (11). The grooves (21) and (22) have one suction-side groove (21) provided in an arc shape along the outer periphery of the suction port (19) and an arc shape so as to follow the outer periphery of the discharge port (20). There is one discharge-side groove (22) provided in the. Each groove (21) (22) faces the outer peripheral edge of the outer gear (11). In FIG. 3, the surface (8a) facing the outer gear (11) of the pump plate (8) and the outer gear (11) have less oil leakage when the gap (side clearance) between them is narrowed. Excellent efficiency. However, in this case, the mechanical efficiency decreases due to the frictional resistance caused by the contact. The suction-side groove (21) and the discharge-side groove (22) can reduce the frictional resistance, thereby obtaining the same effect as widening the side clearance.

  A boundary portion of a required size is provided between the discharge port (20) and the suction port (19), and the suction side groove (21) and the discharge side groove (22) Is provided to avoid. When a groove is provided at the boundary between the discharge port (20) and the suction port (19), an oil leakage path from the discharge port (20) to the suction port (19) can be formed. There is sex. Therefore, the grooves (21) and (22) are formed avoiding the boundary between the discharge port (20) and the suction port (19), so that oil leakage caused by providing the grooves (21) and (22) can be prevented. The increase is suppressed and the decrease in volumetric efficiency is suppressed.

  The cross-sectional shapes of the suction side groove (21) and the discharge side groove (22) may be rectangular as shown in FIG. 4 (a), and as shown in FIG. 4 (b), A trapezoidal shape in which inclined surfaces (21a) and (22a) are formed on both sides may be used, and as shown in FIG. 4 (c), the inclined surfaces (21b and 22b) may be arcuate.

  The planar shape of the suction side groove (21) and the discharge side groove (22) is not particularly limited, and the suction side groove (21) and the discharge side groove (22) are provided symmetrically. May be. In the illustrated example, the discharge-side groove (22) is relatively small, and the suction-side groove (21) is relatively large.

  When the discharge port (20) having a high pressure is compared with the suction port (19) having a relatively low pressure, oil leakage from the discharge port (20) becomes relatively large. Therefore, oil leakage from the discharge port (20) is suppressed by relatively reducing the discharge side groove (22). Even if the groove (21) on the suction side is relatively large, the increase in oil leakage is small. In this way, a decrease in volumetric efficiency due to oil leakage is suppressed. On the other hand, by increasing the size of the grooves (21) and (22), the same effect as widening the side clearance can be obtained, which is advantageous in improving the mechanical efficiency. Therefore, the suction side groove (21) is made relatively larger than the discharge side groove (22), so that the pump efficiency is higher than that in which the grooves are the same size on the discharge side and the suction side. = Mechanical efficiency x volumetric efficiency can be increased.

  Each of the suction-side groove (21) and the discharge-side groove (22) is a single groove that is long in the circumferential direction, but not a single groove. It is good also as a groove | channel.

  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): Internal gear pump, (4): Electric motor, (5): Pump body, (6): Motor housing, (7): Pump housing, (8): Pump plate , (9): Pump chamber, (11): Outer gear, (12): Inner gear, (13): Motor shaft, (19): Suction port, (20): Discharge port, (21): Suction side groove, (22): Groove on the discharge side

Claims (2)

A pump housing in which a pump chamber containing an internal gear pump is formed, a pump body having a pump rate provided at one end of the pump housing, and an electric motor for driving the pump fixed to the other end of the pump housing. In the electric pump unit having a built-in motor housing,
An electric pump unit characterized in that a groove is formed on a surface of the pump body facing the outer gear of the internal gear pump so as to avoid a boundary portion between a discharge port and a suction port.   2. The electric pump unit according to claim 1, wherein the groove is relatively small on the discharge side and relatively large on the suction side.

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