OIL PUMP

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. § 119 to Japanese Patent Application 2017-235279, filed on Dec. 7, 2017, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to an oil pump, and in particular, to an oil pump having an inner rotor and an outer rotor.

BACKGROUND DISCUSSION

In the related art, an oil pump equipped with an inner rotor and an outer rotor has been known (see, e.g., JP 2008-308991A (Reference 1)).

Reference 1 discloses an oil pump equipped with an inner rotor having external teeth, an outer rotor having internal teeth that engage with the external teeth of the inner rotor, and a housing that accommodates the inner rotor and the outer rotor. The housing of the oil pump of Reference 1 is formed with an inlet port that guides oil into a pump chamber between the external teeth and the internal teeth, an outlet port which guides the oil to the outside of the pump chamber, and a discharge hole that guides bubbles contained in the oil to the outside of the pump chamber. In the oil pump of Reference 1, the discharge hole is configured to communicate with the pump chamber in a state where the pump chamber and the outlet port communicate with each other.

In the oil pump of Reference 1, the discharge hole, which guides the bubbles contained in the oil to the outside of the pump chamber, is configured to communicate with the pump chamber in a state where the pump chamber and the outlet port communicate with each other. For this reason, when the pump chamber and the outlet port communicate with each other, the bubbles separated from the oil are disturbed by the flow of the outflow oil, and as a result, the effect of removing the bubbles from the discharge hole deteriorates. Therefore, there is a need for an oil pump capable of effectively removing bubbles contained in oil.

Thus, a need exists for an oil pump which is not susceptible to the drawback mentioned above.

SUMMARY

An oil pump according to an aspect of this disclosure includes: an inner rotor including external teeth; an outer rotor including internal teeth that engage with the external teeth of the inner rotor; a housing configured to accommodate the inner rotor and the outer rotor; an inlet port formed in the housing and configured to guide oil into a pump chamber between the external teeth and the internal teeth; an outlet port formed in the housing and configured to guide the oil to the outside of the pump chamber; and a discharge hole formed in the housing and configured to guide bubbles contained in the oil to the outside of the pump chamber, in which the discharge hole is provided to communicate with the pump chamber earlier than a timing when the pump chamber and the outlet port communicate with each other, and the outlet port is provided to communicate with the pump chamber later than a timing when the pump chamber has a maximum volume.

In the oil pump according to the aspect of this disclosure, the pump chamber and the discharge hole communicate with each other before the pump chamber and the outlet port communicate with each other as described above, so that bubbles may be discharged from the discharge hole, and as a result, it is possible to inhibit the bubbles separated from the oil from being disturbed by a flow of the oil from the pump chamber toward the outlet port. In addition, since the pump chamber and the outlet port communicate with each other after the timing when the pump chamber has the maximum volume, the pressure in the pump chamber may be increased while the volume of the pump chamber is decreased from the state where the pump chamber has the maximum volume. Therefore, the bubbles may be discharged from the discharge hole by the increased pressure. Therefore, the bubbles may be more efficiently discharged from the discharge hole, it is possible to effectively remove the bubbles contained in the oil. Here, there are water, NO_x(nitrogen oxide), HC (hydrocarbon), and the like as substances that degrade an engine. It has been known that if water, NO_x, and HC are contained in the oil, the oil is degraded due to chemical reactions between water, NO_x, and HC. In the oil pump of this disclosure, it is possible to effectively remove water, NO_x, and HC contained as bubbles in oil, and as a result, it is possible to effectively inhibit degradation of oil.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and additional features and characteristics of this disclosure will become more apparent from the following detailed description considered with the reference to the accompanying drawings, wherein:

FIG. 1 is a view illustrating an oil pump according to a first embodiment;

FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1;

FIG. 3A is a view illustrating a state where an opening of an inlet port is closed with respect to a pump chamber;

FIG. 3B is a view illustrating a state where the pump chamber has a maximum volume;

FIG. 3C is a view illustrating a state where the pump chamber and a discharge hole communicate with each other;

FIG. 3D is a view illustrating a state where the pump chamber and an opening of an outlet port begin to communicate with each other;

FIG. 4 is a view illustrating a simulation result of pressure in the pump chamber of the oil pump according to the first embodiment;

FIG. 5 is an enlarged view of a portion from −20 degrees to 20 degrees in FIG. 4;

FIG. 6 is a view illustrating an oil pump according to a second embodiment;

FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. 6;

FIG. 8A is a view illustrating a state where bubbles are collected at an end of a groove portion; and

FIG. 8B is a view illustrating a state where bubbles are introduced into the groove portion.

DETAILED DESCRIPTION

Hereinafter, embodiments will be described with reference to the drawings.

First Embodiment

A configuration of an oil pump 100 according to a first embodiment will be described with reference to FIGS. 1 to 5.

The oil pump 100 according to the first embodiment is mounted in an automobile (not illustrated) having an engine. The oil pump 100 serves to pump oil (lubricant) in an oil pan and supply (pump) the oil to the periphery of a piston of the engine and to moving parts (sliding parts) such as a crank shaft.

(Configuration of Oil Pump)

As illustrated in FIG. 1, the oil pump 100 has a housing 10, an inner rotor 11, and an outer rotor 12. The inner rotor 11 has external teeth 111. The outer rotor 12 has internal teeth 121 that engage with the external teeth 111 of the inner rotor 11. Pump chambers 13 are formed between the external teeth 111 of the inner rotor 11 and the internal teeth 121 of the outer rotor 12.

The housing 10 accommodates the inner rotor 11 and the outer rotor 12 so that the inner rotor 11 and the outer rotor 12 are rotatable. The housing 10 has an inlet port 14 that guides oil into the pump chamber 13 between the external teeth 111 and the internal teeth 121. In addition, the housing 10 has an outlet port 15 that guides the oil to the outside of the pump chamber 13. As illustrated in FIG. 2, the housing 10 includes a first portion 10a and a second portion 10b. The inner rotor 11 and the outer rotor 12 are accommodated between the first portion 10a and the second portion 10b. The housing 10 is made of an aluminum alloy.

The inner rotor 11 is configured to be rotated by a rotating shaft 112. The rotating shaft 112 is rotated by an operation of the engine. A rotation center of the inner rotor 11 is eccentric only by a predetermined degree with respect to a rotation center of the outer rotor 12. When the inner rotor 11 is rotated in a direction of the arrow R (clockwise), the outer rotor 12 is rotated in the same direction. During the rotation, the external teeth 111 of the inner rotor 11 and the internal teeth 121 of the outer rotor 12 mesh with each other at a portion where a distance between the inner rotor 11 and the outer rotor 12 is short. In contrast, because the number of external teeth 111 of the inner rotor 11 is smaller by one than the number of internal teeth 121, a gap (pump chamber 13) is formed between the external teeth 111 and the internal teeth 121 at a portion where the distance is long. In addition, the pump chamber 13 is expanded or contracted simultaneously with the rotation in the direction of the arrow R, so that a pumping function is created. Therefore, as a volume of the pump chamber 13 is increased, the oil is sucked into the pump chamber 13. In addition, as the volume of the pump chamber 13 is decreased, the oil in the pump chamber 13 is ejected to the outside.

The inlet port 14 has an opening 141 at a portion where the pump chamber 13 is gradually expanded. The inlet port 14 is connected to the oil pan, so that the oil is supplied from the oil pan. The outlet port 15 has an opening 151 at a portion where the pump chamber 13 is gradually contracted. The outlet port 15 is connected to oil supply destinations of respective parts in the engine. As illustrated in FIG. 2, the inlet port 14 and the outlet port 15 are formed in a concave shape in an inner surface of the housing 10 (a surface opposite to a side at which the inner rotor 11 and the outer rotor 12 are rotatably fitted). In addition, the inlet port 14 and the outlet port 15 are formed in the housing 10 so as to have predetermined flow path shapes.

In the first embodiment, the housing 10 has a discharge hole 16 that guides bubbles contained in the oil to the outside of the pump chamber 13. As illustrated in FIG. 2, the discharge hole 16 communicates with the outside of the housing 10. Specifically, an opening 161 of the discharge hole 16 communicates with the gap between the rotating shaft 112 and the housing 10. Therefore, the bubbles discharged from the discharge hole 16 are discharged to the outside of the housing 10.

As illustrated in FIG. 1, the discharge hole 16 is formed to be opened at a position which is closer in a radial direction to the rotating shaft 112 than the opening 151 of the outlet port 15. In addition, the discharge hole 16 is formed to be opened at the portion which is closer in the radial direction to the rotating shaft 112 than the opening 141 of the inlet port 14. The opening 161 of the discharge hole 16 is formed to be connected to the pump chambers 13 in the vicinity of tooth bottoms of the external teeth 111 of the inner rotor 11.

In the first embodiment, the inlet port 14 is provided to be closed earlier than the timing when the pump chamber 13 has a maximum volume. Specifically, the inlet port 14 is provided to be closed earlier than the timing when the pump chamber 13 has the maximum volume so that pressure in the pump chamber 13 becomes pressure that generates bubbles. For example, in a state where the pump chamber 13 has the maximum volume, the pressure in the pump chamber 13 is configured to be lower than vapor pressure of water at a room temperature (about 25° C.). In addition, the outlet port 15 is provided to communicate with the pump chamber 13 later than the timing when the pump chamber 13 has the maximum volume.

In the first embodiment, the discharge hole 16 is provided to communicate with the pump chamber 13 earlier than the timing when the pump chamber 13 and the outlet port 15 communicate with each other. Specifically, the discharge hole 16 is formed to be opened at a position, between the opening 141 of the inlet port 14 and the opening 151 of the outlet port 15, which is closer to the opening 151 of the outlet port 15 than the opening 141 of the inlet port 14. In addition, the discharge port 16 is provided to communicate with the pump chamber 13 later than the timing when the pump chamber 13 has the maximum volume. A region where the outlet port 15 and the pump chamber 13 communicate with each other and a region where the discharge hole 16 and the pump chamber 13 communicate with each other partially overlap with each other. That is, the pump chamber 13 communicates with the discharge hole 16 first. Thereafter, the pump chamber 13 communicates with the outlet port 15 in the state where the pump chamber 13 communicates with the discharge hole 16. Further, the pump chamber 13 communicates with the outlet port 15 even after the communication between the pump chamber 13 and the discharge hole 16 is closed.

As illustrated in FIG. 3A, the communication between the inlet port 14 and the pump chamber 13 is closed earlier than the timing when the pump chamber 13 (hatched area) has the maximum volume. That is, the opening 141 of the inlet port 14 is formed to be terminated at a position opposite in a rotation direction to the position at which the pump chamber 13 has the maximum volume. When the pump chamber 13 (hatched area) is rotated in the direction of the arrow R from the state in FIG. 3A, the pump chamber 13 has the maximum volume in the state in FIG. 3B. In this case, the pump chamber 13 does not communicate with any one of the inlet port 14, the outlet port 15, and the discharge hole 16.

When the pump chamber 13 is rotated in the direction of the arrow R from the state in FIG. 3B, the pump chamber 13 communicates with the discharge hole 16 in the state in FIG. 3C. In this case, the pump chamber 13 does not communicate with the inlet port 14 and the outlet port 15. That is, in the state in FIG. 3C, the pump chamber 13 communicates with the discharge hole 16, so that the bubbles are discharged from the discharge hole 16.

When the pump chamber 13 is rotated in the direction of the arrow R from the state in FIG. 3C, the pump chamber 13 communicates with the outlet port 15 in the state in FIG. 3D. In this case, the pump chamber 13 does not communicate with the inlet port 14. In addition, the pump chamber 13 communicates with the discharge hole 16. Thereafter, when the pump chamber 13 is rotated in the direction of the arrow R, the communication between the pump chamber 13 and the discharge hole 16 is terminated.

(Explanation of Pressure in Pump Chamber of Oil Pump)

FIGS. 4 and 5 illustrate a relationship between a rotation angle (degree) of the inner rotor 11 and pressure (kPa) in the pump chamber 13 in the oil pump 100 of the first embodiment. A position at which the rotation angle of the inner rotor 11 is 0 degree is a closing timing position in the related art. In addition, the pressure in the pump chamber 13 is pressure relative to atmosphere. As illustrated in FIG. 4, the pressure in the pump chamber 13 is increased in a range in which the rotation angle of the inner rotor 11 varies from about 20 degrees to 40 degrees. In this case, the pressure in the pump chamber 13 is increased up to a maximum of 12 Mpa. That is, it is possible to eject the oil with high pressure by retarding the opening timing of the outlet port 15. In addition, since the pressure in the pump chamber 13 is increased, the discharge hole 16 is provided in this region to make it possible to efficiently discharge the bubbles.

As illustrated in FIG. 5, when the suction timing is closed 10 degrees earlier, the pressure in the pump chamber 13 is decreased, so that absolute pressure in the pump chamber 13 becomes equal to or lower than 3 kPa which is lower than the atmospheric pressure. 3 kPa is pressure at which water boils at 25° C. Therefore, in the pump chamber 13, water, which is an impurity, is educed as gas.

Effect of First Embodiment

The following effects may be obtained in the first embodiment.

In the oil pump 100 of the first embodiment, bubbles may be efficiently discharged from the discharge hole 16, as a result, it is possible to effectively remove bubbles contained in oil. In addition, in the oil pump 100 of the present embodiment, it is possible to effectively remove water, NO_x(nitrogen oxide), and HC (hydrocarbon) contained in oil as bubbles, and as a result, it is possible to effectively inhibit degradation of oil.

In the first embodiment, the bubbles may be discharged from the discharge hole 16 immediately before the oil is ejected from the opening 151 of the outlet port 15 after the oil is sucked into the pump chamber 13 from the inlet port 14. Therefore, it is possible to efficiently discharge the bubbles from the discharge hole 16 without causing turbulence of the oil in the pump chamber 13.

In the first embodiment, the pump chamber 13 is further expanded after the oil is sucked into the pump chamber 13 from the inlet port 14, and as a result, it is possible to decrease the pressure in the pump chamber 13. Therefore, unnecessary substances such as water dissolved, as a liquid, in the oil may be educed (vaporized) as bubbles, and as a result, it is possible to easily discharge unnecessary substances such as water as bubbles from the discharge hole 16.

In the first embodiment, unnecessary substances dissolved in the oil may be assuredly educed (vaporized) as bubbles, and as a result, it is possible to effectively remove unnecessary substances from the oil.

In the first embodiment, the bubbles, which are moved toward the inside of the pump chamber 13 due to an influence of centrifugal force because the bubbles have a smaller specific weight than the oil, may be easily discharged from the discharge hole 16 opened at the inside of the pump chamber 13.

Second Embodiment

Next, a second embodiment will be described with reference to FIG. 6 to FIGS. 8A and 8B. In the second embodiment, a configuration in which groove portions 113 are formed in the inner rotor 11 unlike the first embodiment will be described as an example. In addition, in the drawings, constituent elements identical to the constituent elements in the first embodiment are denoted by the same reference numerals as the constituent elements in the first embodiment.

An oil pump 200 according to the second embodiment is mounted in an automobile (not illustrated) having an engine. The oil pump 200 serves to pump oil (lubricant) in an oil pan and supply (pump) the oil to the periphery of a piston of the engine and to moving parts (sliding parts) such as a crank shaft.

(Configuration of Oil Pump)

As illustrated in FIG. 6, the oil pump 200 has a housing 10, an inner rotor 11, and an outer rotor 12. The inner rotor 11 has external teeth 111. The outer rotor 12 has internal teeth 121 that engage with the external teeth 111 of the inner rotor 11. Pump chambers 13 are formed between the external teeth 111 of the inner rotor 11 and the internal teeth 121 of the outer rotor 12.

The inner rotor 11 is configured to be rotated by a rotating shaft 112. The inner rotor 11 is rotated in a direction of the arrow R (clockwise). The outer rotor 12, which engages with the inner rotor 11, is rotated together with the inner rotor 11.

In the second embodiment, the inner rotor 11 has the groove portions 113 formed in tooth bottom portions 111a of the external teeth 111. In addition, the groove portions 113 are formed in the tooth bottom portions 111a of the multiple external teeth 111, respectively. As illustrated in FIG. 7, the groove portions 113 are provided in both end surfaces of the inner rotor 11 in the direction of the rotating shaft. In addition, the groove portion 113 is formed to have a larger cross-sectional area than a bubble. For example, the groove portion 113 has a depth and a width of several millimeters.

In the second embodiment, as illustrated in FIG. 6, the housing 10 has a discharge hole 16 that guides bubbles contained in the oil to the outside of the pump chamber 13. The discharge hole 16 communicates with the outside of the housing 10. Specifically, an opening 161 of the discharge hole 16 communicates with a gap between the rotating shaft 112 and the housing 10. Therefore, the bubbles discharged from the discharge hole 16 are discharged to the outside of the housing 10.

In the second embodiment, the outlet port 15 is provided to communicate with the pump chamber 13 later than the timing when the pump chamber 13 has a maximum volume. In addition, the discharge hole 16 is provided to communicate with the pump chamber 13 earlier than the timing when the pump chamber 13 and the outlet port 15 communicate with each other. In addition, the discharge hole 16 is formed to be opened at a position, in a radial direction, which overlaps with the groove portion 113 but does not overlap with the pump chamber 13. That is, the pump chamber 13 and the discharge hole 16 are configured to communicate with each other through the groove portion 113.

The groove portion 113 of the inner rotor 11 is formed in an arc shape when viewed in the rotating shaft. In addition, the groove portion 113 of the inner rotor 11 is formed such that both ends of the groove portion 113 are connected to the pump chamber 13. As illustrated in FIGS. 8A and 8B, as the inner rotor 11 rotates, the oil is moved by centrifugal force from the arc-shaped groove portion 113 into the pump chamber 13. In this case, the oil flows out from one end of the groove portion 113, so that attractive force is generated at the other end. Further, bubbles 20, which are moved to the tooth bottom portion 111a of the inner rotor 11, are drawn into the groove portion 113. That is, the bubbles 20 are introduced into the arc-shaped groove portion 113 by a pump-priming effect. The groove portion 113 and the discharge hole 16 communicate with each other in a state where the bubbles 20 are collected in the groove portion 113, so that the bubbles are discharged from the discharge hole 16.

The other configurations of the second embodiment are identical to those of the first embodiment.

Effect of Second Embodiment

The following effects may be obtained in the second embodiment.

Similar to the first embodiment, in the second embodiment, it is possible to effectively remove the bubbles contained in the oil.

In the second embodiment, the bubbles 20, which are moved toward the inside of the pump chamber 13 due to an influence of centrifugal force because the bubbles have a smaller specific weight than the oil, may be collected in the groove portion 113 provided in the tooth bottom portion 111a of the inner rotor 11. Therefore, the groove portion 113 and the discharge hole 16 communicate with each other, so that the bubbles may be easily discharged.

In the second embodiment, the bubbles 20 may be smoothly guided into the groove portion 113, so that the bubbles 20 may be effectively collected in the groove portion 113.

In the second embodiment, the oil in the groove portion 113 is discharged into the pump chamber 13 from one end of the groove portion 113, so that the bubbles may be guided to be sucked into the groove portion 113 from the other end of the groove portion 113, and as a result, it is possible to more effectively collect the bubbles in the groove portion 113.

In the second embodiment, the discharge hole 16 and the pump chamber 13 are not directly connected to each other, and as a result, it is possible to inhibit the oil in the pump chamber 13 from being discharged from the discharge hole 16.

The other effects of the second embodiment are identical to those of the first embodiment.

Modified Example

Further, it should be considered that all of the disclosed embodiments are illustrative in all aspects but not limitative. The scope of the embodiments disclosed here are defined by the appended claims instead of the description of the embodiments and includes all alterations (modified examples) within the meanings and scope equivalent to the claims.

For example, in the first and second embodiments, an example in which the embodiment disclosed here is applied to the oil pump for supplying oil (lubricant) to the engine (internal combustion engine) has been described, but the embodiment disclosed here is not limited thereto. For example, the embodiment disclosed here may be applied to an oil pump for supplying an AT fluid (AT oil) to an automatic transmission (AT) that automatically switches a gear ratio in accordance with a rotational speed of an internal combustion engine. In addition, the embodiment disclosed here may be applied to an oil pump for supplying a lubricant to a sliding portion in a continuously variable transmission (CVT) capable of changing a gear ratio continuously without a stage unlike the AT (multistage transmission) that performs the gear shift operation by changing a combination of gears. In addition, the embodiment disclosed here may be applied to an oil pump for supplying power steering oil to a power steering device that performs steering (operates a steering device) in a vehicle.

In the first and second embodiments, the configuration in which the oil pump is rotationally operated by the operation of the engine has been described as an example, but the embodiment disclosed here is not limited thereto. In the embodiment disclosed here, the oil pump may be rotationally operated by an electric motor.

In the first and second embodiments, the configuration in which the outer rotor is driven by driving the inner rotor has been described as an example, but the embodiment disclosed here is not limited thereto. In the embodiment disclosed here, the inner rotor may be driven by driving the outer rotor.

In the first and second embodiments, the configuration in which the pump chamber and the outlet port communicate with each other in the state where the pump chamber and the discharge hole communicate with each other has been described as an example, but the embodiment disclosed here is not limited thereto. In the embodiment disclosed here, the pump chamber and the outlet port may communicate with each other after the pump chamber and the discharge hole are closed. Further, the pump chamber and the outlet port may communicate with each other at the same time when the pump chamber and the discharge hole is closed.

In the first and second embodiments, the configuration in which the inlet port is closed earlier than the timing when the pump chamber has the maximum volume has been described as an example, but the embodiment disclosed here is not limited thereto. In the present embodiment, the inlet port may be closed at the timing when the pump chamber has the maximum volume.

In the first and second embodiments, the configuration in which the discharge holes are provided at both sides of the housing in the direction of the rotating shaft has been described as an example, but the embodiment disclosed here is not limited thereto. In the present embodiment, the discharge hole may be provided at one side of the housing in the direction of the rotating shaft.

In the second embodiment, the configuration in which the groove portions are provided at both sides of the inner rotor in the direction of the rotating shaft has been described as an example, but the embodiment disclosed here is not limited thereto. In the present embodiment, the groove portion may be provided at one side of the inner rotor in the direction of the rotating shaft.

In the first and second embodiments, the example in which the oil pump is mounted in a vehicle such as an automobile having an engine has been described, but the embodiment disclosed here is not limited thereto. For example, the present embodiment may be applied to an oil pump mounted in facility equipment other than the vehicle having the internal combustion engine. In addition, a gasoline engine, a diesel engine, a gas engine, and the like may be applied as the internal combustion engine.

In the oil pump according to the aspect of this disclosure, it is preferable that the discharge hole is formed to be opened at a position, between an opening of the inlet port and an opening of the outlet port, and closer to the opening of the outlet port than the opening of the inlet port.

With this configuration, the bubbles may be discharged from the discharge hole immediately before the oil is ejected from the opening of the outlet port after the oil is drawn into the pump chamber from the inlet port, and as a result, it is possible to efficiently discharge the bubbles from the discharge hole without causing turbulence of the oil in the pump chamber.

In the oil pump according to the aspect of this disclosure, it is preferable that the inlet port is provided to be closed earlier than the timing when the pump chamber has the maximum volume.

With this configuration, the pump chamber is further expanded after the oil is sucked into the pump chamber from the inlet port, and as a result, it is possible to decrease the pressure in the pump chamber. Therefore, unnecessary substances dissolved, as a liquid, in the oil may be educed (vaporized) as bubbles, and as a result, it is possible to easily discharge the unnecessary substances as bubbles from the discharge hole.

In the oil pump according to the aspect of this disclosure, it is preferable that the discharge hole is formed to be opened at a position closer to a rotating shaft of the inner rotor than the opening of the outlet port in a radial direction of the inner rotor.

In the oil pump according to the aspect of this disclosure, it is preferable that the inner rotor has groove portions provided in tooth bottom portions of the external teeth.

With this configuration, the bubbles, which are moved toward the inside of the pump chamber due to an influence of centrifugal force because the bubbles have a smaller specific weight than the oil, may be collected in the groove portion provided in the tooth bottom portion of the inner rotor, and as a result, it is possible to easily discharge the bubbles as the groove portion and the discharge hole communicate with each other.

In this disclosure, the following configurations may be conceived regarding the oil pump according to one aspect.

That is, in the configuration in which the groove portions are provided in the inner rotor, a groove portion of the inner rotor may be formed in an arc shape when viewed in a direction of the rotating shaft of the inner rotor.

With this configuration, the bubbles may be smoothly guided into the groove portion, and as a result, it is possible to effectively collect the bubbles in the groove portion.

In the configuration in which the groove portions are provided in the inner rotor, the groove portion of the inner rotor may be formed such that both ends of the groove portion in a rotation direction of the inner rotor are connected to the pump chamber.

With this configuration, the oil in the groove portion is discharged into the pump chamber from one end of the groove portion, so that the bubbles may be guided to be sucked into the groove portion from the other end of the groove portion, and as a result, it is possible to more effectively collect the bubbles in the groove portion.

In the configuration in which the groove portions are provided in the inner rotor, the discharge hole may be opened at a position, in a radial direction of the inner rotor, which overlaps with the groove portion but does not overlap with the pump chamber.

With this configuration, the discharge hole and the pump chamber are not directly connected to each other, and as a result, it is possible to inhibit the oil in the pump chamber from being discharged from the discharge hole.

In the configuration in which the inlet port is provided to be closed earlier the timing when the pump chamber has the maximum volume, the inlet port is provided to be closed earlier than the timing when the pump chamber has the maximum volume so that the pressure in the pump chamber becomes a pressure that generates bubbles.

With this configuration, unnecessary substances dissolved in the oil may be assuredly educed (vaporized) as bubbles, and as a result, it is possible to effectively remove the unnecessary substances from the oil.

The principles, preferred embodiment and mode of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby.

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Priority Claims (1)