JP2013015111A - Electric oil pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electric oil pump whose operating noise can be reduced and which is highly efficient by using an optimal gear specification and an optimal rotating speed in accordance with a required flow rate.SOLUTION: The electric oil pump includes: an inner gear 1 that has external teeth on an outer circumference thereof; an outer gear 2 that has internal teeth on an inner circumference thereof and is configured to mesh with the inner gear; a case 3 that has a gear housing in which the two gears are housed; and a plate that includes an intake port and a discharge port, both of which communicate with a volume chamber 10 corresponding to an opposing space of the two gears, and that covers up one side of the gear housing. The inner gear and the outer gear are configured to eccentrically mesh with each other. The two gears are disposed so that a center-to-center spacing of the same gears may be smaller than an eccentric amount which is determined by a tooth profile represented by the following expression: Eccentric amount=(Tip diameter of inner gear (maximum diameter)-Root diameter of inner gear (minimum diameter))/4 and such that a gap of a sealing point formed by the two gears may smaller than a gap of a sealing point determined by tooth profiles of the inner gear and the outer gear.

Description

  The present invention relates to an electric oil pump comprising an inner gear, an internal gear pump that has an outer gear that meshes with the inner gear in an eccentric state, and that sucks and discharges oil, and an electric motor that drives the pump. Is.

  In recent years, as fuel economy improvement and exhaust gas regulations for automobiles have been strengthened, as a technology that is relatively simple and has a large effect on improving fuel consumption and reducing exhaust gas, the engine is stopped when the automobile is temporarily stopped or at low speeds, and the vehicle restarts. Adoption of an idle stop system that restarts the engine at times is increasing. In idle stop technology, in order to reduce the start shock immediately after engine restart, it is necessary to drive the electric oil pump during idle stop to generate pressure in the transmission or to fill the transmission with oil. There is a need to reduce the operating noise of the electric oil pump during idling stop while reducing the start shock.

  As disclosed in Patent Document 1, as a means for suppressing the operation sound of the electric oil pump, the gear specification of the electric oil pump is adopted by using a gear having a discharge flow rate as large as possible as required by the pump. There is disclosed a method for controlling the motor rotation speed so as to be equal to or lower than the threshold value of the operating sound required from the mounted vehicle while ensuring the flow rate.

JP 2008-115718 A

  However, the invention of Patent Document 1 employs a gear specification in which the discharge flow rate per rotation is as large as possible and suppresses the motor rotation speed, so that the volumetric efficiency of the pump is lowered and the actual work of the pump with respect to the motor output is reduced. There has been a problem that the pump efficiency has deteriorated. Furthermore, there is a problem in that heat generation increases due to an increase in gear specifications and an increase in load on the pump unit and an increase in current in the motor unit. Further, in order to solve this problem, it is necessary to increase the motor output, which leads to an increase in motor size, and it has been difficult to reduce the size of the electric oil pump.

  The present invention has been made to solve such a problem, adopts a gear specification in which the discharge flow rate per rotation is as large as possible, can reduce the operation noise without lowering the rotation speed, and is required. The objective is to obtain a high-efficiency electric oil pump by using the optimum gear specifications and rotation speed that match the flow rate.

The electric oil pump according to the present invention includes a motor unit that drives the pump, a pump unit shaft that is coupled to a shaft of the motor unit, both ends of which are axially supported, and is fitted into the pump unit shaft, and has external teeth on the outer periphery. An inner gear, an outer gear having inner teeth on the inner periphery so as to mesh with the inner gear, a case having a gear housing portion that accommodates both gears, and a suction port that communicates with a volume chamber that is an opposing space of the both gears; Eccentricity determined from the tooth profile represented by the following equation, the distance between the centers of the two gears provided with a discharge port, including a plate that closes one side of the gear housing, and engaged in an eccentric state,
Eccentricity = (Inner gear tooth tip diameter (maximum diameter) −Inner gear tooth root diameter (minimum diameter)) / 4
Both gears are arranged such that the gap between the seal points formed by the two gears is smaller than the gap between the seal points determined by the tooth shapes of the inner gear and the outer gear.

The electric oil pump according to the present invention includes a motor unit that drives the pump, an inner gear that is inserted into one end of a shaft of the motor unit and has outer teeth on the outer periphery, and an inner tooth on the inner periphery so as to mesh with the inner gear. An outer gear, a case having a gear storage portion for storing both gears, and a suction port and a discharge port communicating with a volume chamber that is a space opposed to the both gears, and one side of the gear storage portion is provided. The amount of eccentricity determined from the tooth profile represented by the following equation for the distance between the centers of the two gears provided with a closing plate and meshed in an eccentric state,
Eccentricity = (Inner gear tooth tip diameter (maximum diameter) −Inner gear tooth root diameter (minimum diameter)) / 4
Both gears are arranged such that the gap between the seal points formed by the two gears is smaller than the gap between the seal points determined by the tooth shapes of the inner gear and the outer gear.

  According to this invention, by arranging both gears so that the distance between the centers of both gears is smaller than the eccentricity determined from the tooth profile, and bringing the seal point closer, the clearance between the gears at the seal point is reduced and the discharge pressure fluctuations Since the amplitude of gear vibration due to vibration can be reduced and the contact noise of the gear can be reduced, the gear specification can be changed to a size with a large flow rate, and the operating noise of the electric oil pump can be reduced without reducing the rotational speed. it can.

  Moreover, since the amplitude at the time of gear vibration can be suppressed, the impact at the time of gear contact can be reduced, and the durability improvement of the gear tooth surface can be expected.

  In addition, by shifting the center position of both gears so as to be smaller than the amount of eccentricity determined by the gear tooth profile, the clearance near the seal point is reduced, and oil from the discharge side to the suction side near the seal point is reduced. Leakage can be reduced and pump performance can be improved.

  In addition, the gear specifications are increased and the operating noise can be reduced without reducing the number of revolutions, so that the optimum gear specifications and the optimum number of revolutions can be used according to the required flow rate. Efficiency can be expected.

It is sectional drawing which shows the structure of the electric oil pump which concerns on Embodiment 1 of this invention. It is the figure which looked at the cross section in the aa line | wire of FIG. 1 in the arrow direction. It is sectional drawing which shows the structure of the electric oil pump which concerns on Embodiment 2 of this invention. It is arrangement | positioning explanatory drawing of the inner gear and outer gear of a general electric oil pump.

Embodiment 1 FIG.
1 and 2 are views showing the structure of an electric oil pump according to Embodiment 1 of the present invention.
The internal gear type electric oil pump includes an inner gear 1 having outer teeth on the outer periphery, and a constant eccentric amount arranged so as to mesh with the inner gear 1 at a meshing point A. Is inserted into a gear housing portion 3a provided in the case 3, and one side of the gear housing portion 3a is closed by a plate 4 having a suction port 4a and a discharge port 4b. The part is composed. The suction port 4a and the discharge port 4b communicate with the volume chamber 10 which is a space facing the inner gear 1 and the outer gear 2 through the suction opening 4d and the discharge opening 4e, respectively.

  The inner gear 1 is fitted into a pump portion shaft 5 supported at both ends by a bearing 6 provided on the case 3 and a bearing 7 provided on the plate 4 by H cut or the like. In addition, a brushless motor or the like is used as the motor unit 8 that drives the oil pump, and the pump unit shaft 5 and the motor unit shaft 9 are fitted with an H cut or the like to constitute an electric oil pump. . In addition, suction opening portions 3d and 4d and discharge opening portions 3e and 4e are provided in the gear housing portion upper surface 3c and the plate upper surface 4c facing the both end surfaces of the gear. Further, the case 3, the plate 4 and the motor 8 are fixed by screws or the like (not shown).

First, a general internal gear type electric oil pump shown in FIG. 4 will be described. In addition, the description of each component is abbreviate | omitted by attaching | subjecting the code | symbol same as FIG. 1 to each component of the general internal gear type electric oil pump shown in FIG. Here, the rotation center of the inner gear 1 is Oi, and the rotation center of the outer gear 2 is Oo. The inner gear 1 and the outer gear 2 have a constant eccentricity C (distance between Oi and Oo) as expressed by the following equation so that the inner gear 1 and the outer gear 2 mesh with each other.
Eccentricity C = (Inner gear tooth tip diameter (maximum diameter) −Inner gear tooth root diameter (minimum diameter)) / 4
The inner gear 1 and the outer gear 2 are meshed at a meshing point A, and the suction part and the discharge part are sealed at a seal point B on the opposite side of the meshing point A. At the seal point B, A minute clearance D (for example, about 80 μm) is provided. The clearance D is determined by the tooth shapes of the inner gear 1 and the outer gear 2,
Clearance D = (outer gear tooth tip diameter (minimum diameter) + outer gear tooth root diameter (maximum diameter)) / 2-inner gear tooth tip diameter (maximum diameter)
However, D> 0
It is a value represented by

  The operation principle of a general internal gear pump will be described with reference to FIG. By applying a voltage to the motor unit 8 that is a pump drive source, the inner gear 1 rotates via the motor unit shaft 9 and the pump unit shaft 5, and the outer gear 2 that meshes with the inner gear 1 at the meshing point A meshes. Both gears rotate. At this time, the volumes of the plurality of volume chambers 10 constituted by the inner gear 1 and the outer gear 2 are changed, and oil is sucked and discharged.

  In the suction stroke, the volume of the volume chamber 10 increases with rotation, so that the volume chamber 10 is filled with oil through the suction port 4a and the suction opening 4d. In the discharge stroke, the volume increases with rotation. As the volume of the chamber 10 decreases, the oil filled in the volume chamber 10 is pushed out, and the oil is discharged through the discharge opening 4e and the discharge port 4b.

  At this time, a load is generated in the inner gear 1 and the outer gear 2 in the direction of the double arrow F in FIG. 4 due to the differential pressure between the suction portion and the discharge portion. This load changes due to the pressure pulsation of the pump. From this, it is considered that the inner gear 1 and the outer gear 2 vibrate with the width of the clearance D at the seal point B during the pump operation, which causes an increase in operating noise.

  On the other hand, in the first embodiment of the present invention, the center of the gear housing 3a is connected in the direction in which the distance between the centers of both gears becomes smaller than the eccentric amount C determined by the tooth profile, as shown in FIG. 2, for example, Oo and Oi. It is shifted by a minute amount E (for example, 50 μm) in the direction of 45 degrees with respect to the line, and the center of the outer gear 2 is arranged so as to be Oo ′ from the outer gear center Oo determined from the tooth shapes of the inner gear 1 and the outer gear 2. The clearance is reduced. The position of the outer gear center Oo ′ described above is a position where the distance between the centers Oi to Oo ′ <the eccentricity C (the distance between Oi to Oo) of both gears, and is 45 with respect to the line connecting Oo and Oi. It is not limited to the direction of the degree. Therefore, the clearance at the seal point B is (DE). FIG. 2B is an enlarged view of the central portion of FIG.

  In the first embodiment, since the above structure is adopted, the clearance at the seal point B is (DE), and the clearance at the seal point B is set to about 40% with respect to a general internal gear pump. Therefore, it is possible to suppress the amplitude at the time of gear vibration due to the pump operation, and it is possible to reduce the operation noise by about 3 to 5 dBA when securing the pump characteristics with the same pressure and the same flow rate. It has been verified.

  In general, it is known that the amount of fluid leakage from the minute gap is proportional to the cube of the gap, but in the above structure, the clearance at the seal point B is about 40%. Since the amount of oil leakage from the sealing point is reduced to about 6% as compared with a general internal gear type pump, it is possible to improve the pump efficiency.

Embodiment 2. FIG.
The configuration of the second embodiment will be described with reference to FIG. In the second embodiment of the present invention, the motor unit 8 that is a drive source for driving the pump, the inner gear 1 that has outer teeth fitted on one end of the motor unit shaft 11, and the meshing point A with the inner gear 1. The outer gear 2 provided with a constant eccentric amount C so as to be meshed with each other and having inner teeth on the inner periphery is inserted into the gear housing portion 3a provided on the case 3, and the suction port 4a and the discharge port 4b Is sandwiched by the plate 4 provided with the motor part 8, the case 3, and the plate 4 are fixed by screws or the like. At this time, as in the first embodiment, the center of the gear housing 3a is shifted in the direction in which the distance between the centers of both gears becomes smaller than the eccentricity C, and the clearance of the seal point B composed of the inner gear 1 and the outer gear 2 is the center of the outer gear. The configuration is reduced.

  In the second embodiment, the operation noise is reduced and the pump efficiency is improved as in the first embodiment, and a portion for fitting the pump portion shaft and the motor portion shaft becomes unnecessary, so that the size can be reduced. It becomes.

In the first and second embodiments, the gap (one side) between the outer periphery of the outer gear 2 and the gear housing 3a is generally set to 50 to 75 μm, but should be set to a small value of 30 to 55 μm. As a result, the amplitude of the outer gear 2 can be further reduced, so that the operating noise can be further reduced. Further, it has been experimentally confirmed that the lower limit value of the gap at this time needs to be 30 μm in consideration of resistance to minute foreign matters contained in the oil.

1 inner gear, 2 outer gear,
3 Case, 3a Gear housing,
3c top surface of gear housing, 3d suction opening,
3e discharge opening, 4 plates,
4a Intake port, 4b Discharge port,
4c top surface of plate, 4d suction opening,
4e discharge opening, 5 pump shaft,
6 bearings, 7 bearings,
8 Motor part, 9 Motor part shaft,
10 Volume chamber, 11 Motor part shaft.

Claims (4)

A motor unit that drives the pump, a pump unit shaft that is fitted to the shaft of the motor unit and is supported at both ends, an inner gear that is fitted to the pump unit shaft and has external teeth on the outer periphery, and meshes with the inner gear An outer gear having inner teeth on the inner periphery, a case having a gear housing for housing both gears, and a suction port and a discharge port communicating with a volume chamber that is a space opposed to the both gears. In an electric oil pump that includes a plate that closes one side of a storage portion and is arranged so that the inner gear and the outer gear are engaged with each other in an eccentric state, a tooth profile represented by the following equation is a distance between the centers of the two gears The amount of eccentricity determined from
Eccentricity = (Inner gear tooth tip diameter (maximum diameter) −Inner gear tooth root diameter (minimum diameter)) / 4
An electric oil pump characterized in that the both gears are arranged so as to be smaller and the gap between the seal points formed by the both gears is reduced. A motor unit that drives the pump, an inner gear that is inserted into one end of the shaft of the motor unit and has outer teeth on the outer periphery, an outer gear that has inner teeth on the inner periphery so as to mesh with the inner gear, and stores both gears A case provided with a gear housing portion, and a suction port and a discharge port communicating with a volume chamber that is a space opposite to the two gears, and a plate that closes one side of the gear housing portion, the inner gear and the outer gear, Is the amount of eccentricity determined by the tooth profile represented by the following equation for the distance between the centers of the two gears in the electric oil pump arranged to mesh in an eccentric state,
Eccentricity = (Inner gear tooth tip diameter (maximum diameter) −Inner gear tooth root diameter (minimum diameter)) / 4
An electric oil pump characterized in that the both gears are arranged so as to be smaller and the gap between the seal points formed by the both gears is reduced. The electric oil pump according to claim 1 or 2, wherein a gap between an outer periphery of the outer gear and the gear housing portion is set to 30 to 55 µm. The clearance (clearance) D of the seal point determined from the tooth profile of the inner gear and the outer gear is:
Clearance D = (outer gear tooth tip diameter (minimum diameter) + outer gear tooth root diameter (maximum diameter)) / 2-inner gear tooth tip diameter (maximum diameter)
However, D> 0
It is represented by these. The electric oil pump as described in any one of Claims 1-3 characterized by the above-mentioned.

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