JP6950537B2 - Oil pump - Google Patents

Description

The present invention relates to an inscribed gear type oil pump.

As disclosed in Patent Document 1, an inscribed gear type oil pump is known.
The inscribed gear type oil pump has an inner rotor fixed to a drive shaft and having external teeth, and an outer rotor having internal teeth. The outer rotor is housed in a pump chamber formed in a pump case. The inner rotor is housed inside the outer rotor so that its center of rotation is eccentric from the center of the outer rotor. When the inner rotor is rotated with the rotation of the drive shaft, the volume of the working chamber formed between the internal teeth and the external teeth changes. Due to the change in the volume of the working chamber, the oil introduced into the working chamber is discharged from the suction port to the discharge port side.

Japanese Unexamined Patent Publication No. 2013-249803

In the inscribed gear type oil pump, since the discharge port side has a higher pressure than the suction port side, the portion of the plurality of operating chambers communicating with the discharge port has a higher pressure. Due to this pressure difference, a force in the direction of being pressed against the discharge port side acts on the outer rotor.

Further, in an inscribed gear type oil pump, a clearance is provided between the inner peripheral surface of the pump chamber and the outer peripheral surface of the outer rotor in order to suppress friction due to mutual contact. Similarly, a clearance is also provided between the internal teeth and the external teeth at the positions where the internal teeth of the outer rotor and the external teeth of the inner rotor mesh with each other. Therefore, when a force in the direction of being pressed against the discharge port side acts on the outer rotor, the position of the outer rotor may move to the discharge port side as compared with the case where the force does not act.

In the inscribed gear type oil pump, when the outer rotor is not moved to the discharge port side, the working chamber and the discharging port do not communicate with each other when the volume of the working chamber is maximum. However, when the position of the outer rotor is moved to the discharge port side, the operating chamber may communicate with the discharge port. At this time, there is a problem that oil flows back from the discharge port to the operating chamber and a pulsating sound is generated.

The oil pump for solving the above problems includes a pump case in which a cylindrical pump chamber, a suction port for introducing oil into the pump chamber, and a discharge port for discharging oil from the pump chamber are formed, and the above. An outer rotor housed in a pump chamber and having internal teeth and an outer rotor provided inside the outer rotor and meshing with the internal teeth are provided and driven with a point eccentric to the center of the outer rotor as the center of rotation. An internal gear type oil pump having an inner rotor fixed to a shaft, and the outer rotor has an elliptical outer shape.

According to the above configuration, since the outer rotor has an elliptical shape, when a force pressing the outer rotor against the discharge port side is applied, the minor axis of the ellipse is more elliptical than when it faces the discharge port side. When the long axis of the outer rotor faces the discharge port side, the center of the outer rotor is separated from the discharge port. That is, when a force pressing the outer rotor against the discharge port side is acting, the center of the outer rotor moves away from the discharge port as the long axis approaches the discharge port side as the outer rotor rotates. In other words, the outer rotor can rotate while being displaced so that the locus of the center draws a substantially ellipse. As a result, the outer rotor does not stay at a position where oil may flow back from the discharge port to the operating chamber, and the generation of pulsating noise due to the backflow of oil can be reduced.

The figure which shows the cross-sectional structure about one Embodiment of an oil pump. The front view which shows the outer rotor of the oil pump which concerns on the same embodiment.

Hereinafter, an embodiment of the oil pump will be described with reference to FIGS. 1 and 2.
FIG. 1 shows the cross-sectional structure of the oil pump 10. The oil pump 10 is an inscribed gear type oil pump, and includes an inner rotor 21 fixed to a drive shaft 23 and an outer rotor 22 that meshes with the inner rotor 21. The oil pump 10 is mounted on the internal combustion engine and supplies the oil in the oil pan to each part of the engine. The drive shaft 23 is provided so as to rotate in conjunction with the crankshaft of the internal combustion engine.

The pump case 11 of the oil pump 10 is formed with a cylindrical pump chamber 15 in which the inner rotor 21 and the outer rotor 22 are housed.
The pump case 11 is open with a suction port 12 for introducing oil into the pump case 11. The pump case 11 is formed with a suction passage 13 that connects the suction port 12 and the pump chamber 15.

The pump case 11 is opened with a discharge port 18 for discharging oil from the inside of the pump case 11. The pump case 11 is formed with a discharge passage 17 that connects the discharge port 18 and the pump chamber 15.

As shown in FIG. 1, the suction passage 13 and the discharge passage 17 are arranged on both sides of the center of the pump chamber 15.
The outer rotor 22 is housed in the pump chamber 15 so as to be rotatable in the pump chamber 15. Inside the outer rotor 22, an inner rotor 21 fixed to the drive shaft 23 is housed.

The inner rotor 21 has 10 external teeth. The outer rotor 22 has internal teeth that mesh with the external teeth of the inner rotor 21. The outer rotor 22 is formed with 11 internal teeth, which is one more than the external teeth.

In FIG. 1, the rotation direction of the inner rotor 21 that rotates with the rotation of the drive shaft 23 is indicated by an arrow. The drive shaft 23 is arranged so that the center of rotation of the inner rotor 21 is eccentric from the center of the pump chamber 15 and the outer rotor 22. Therefore, the volume of the working chamber, which is the space between the inner teeth of the outer rotor 22 and the outer teeth of the inner rotor 21, changes with the rotation of the inner rotor 21 and the outer rotor 22.

As shown in FIG. 1, a suction port 14 which is an annular groove communicating with the suction passage 13 is formed on the inner surface of the pump case 11 and the side surface of the pump chamber 15. The suction port 14 is a semicircular region on the suction passage 13 side in the pump chamber 15, and the volume of the working chamber, which is a space between the inner teeth of the outer rotor 22 and the outer teeth of the inner rotor 21, gradually increases. It is formed in the range. Similarly, on the side surface of the pump chamber 15, a discharge port 16 which is an annular groove communicating with the discharge passage 17 is formed. The discharge port 16 is a semicircular region on the discharge passage 17 side in the pump chamber 15, and the volume of the operating chamber, which is a space between the inner teeth of the outer rotor 22 and the outer teeth of the inner rotor 21, gradually decreases. It is formed in the range.

When the inner rotor 21 and the outer rotor 22 have the rotation angles shown in FIG. 1, the operating chamber 31 located between the end portion 14B of the suction port 14 and the start end portion 16A of the discharge port 16 is the suction port 14 and the operating chamber 31. It does not communicate with the discharge port 16. The operating chamber 31 is located at a position where the volume between the internal teeth and the external teeth is maximized.

As shown in FIG. 2, the outer rotor 22 has an elliptical outer shape. The outer rotor 22 has an elliptical cross-sectional contour, and the length D1 of the major axis is longer than the length D2 of the minor axis. In FIG. 2, a two-dot chain line shows a circle whose diameter is equal to the length D1 of the major axis. Further, the length D1 of the major axis of the outer rotor 22 is shorter than the diameter of the pump chamber 15. As shown in FIG. 1, a gap is formed between the inner peripheral surface of the pump chamber 15 and the outer peripheral surface of the outer rotor 22, and a clearance is provided so that the outer rotor 22 can rotate in the pump chamber 15. ing. The elliptical outer rotor 22 shown in FIG. 2 is a schematic one and does not show the magnitude relationship between the actual long axis and the short axis.

The operation and effect of this embodiment will be described.
While the oil pump 10 is being driven, a force that pushes the outer rotor 22 against the discharge port 16 side acts due to the pressure difference between the suction port 14 side and the discharge port 16 side. Since the outer rotor 22 of the oil pump 10 has an elliptical outer shape, the long axis of the ellipse is the discharge port 16 as compared with the case where the outer rotor 22 is rotating so that the short axis of the ellipse faces the discharge port 16. The center of the outer rotor 22 is separated from the discharge port 16 when the outer rotor 22 is rotated so as to face the side.

That is, when a force pressing the outer rotor 22 against the discharge port 16 side is acting, the center of the outer rotor 22 is the discharge port 16 as the long axis approaches the discharge port 16 side as the outer rotor 22 rotates. Get away from. Further, as the long axis moves away from the discharge port 16 side as the outer rotor 22 rotates, the center of the outer rotor 22 approaches the discharge port 16. In other words, the outer rotor 22 can rotate in the pump chamber 15 while being displaced so that the locus of the center draws a substantially ellipse.

Here, when the outer rotor 22 is pressed against the discharge port 16, the operating chamber 31 located between the end portion 14B of the suction port 14 and the start end portion 16A of the discharge port 16 is the discharge port. May communicate with 16. In this regard, according to the oil pump 10 of the present embodiment, the outer rotor 22 can rotate while shifting the inside of the pump chamber 15 so that the locus of the center draws a substantially elliptical shape. Therefore, depending on the rotation angle of the outer rotor 22. Can eliminate the communication between the operating chamber 31 located between the end portion 14B of the suction port 14 and the start end portion 16A of the discharge port 16 and the discharge port 16. That is, the outer rotor 22 does not stay at a position where oil may flow back from the discharge port 16 to the operating chamber 31 located between the end portion 14B of the suction port 14 and the start end portion 16A of the discharge port 16. , It is possible to reduce the generation of pulsating noise due to the backflow of oil from the discharge port 16 to the operating chamber 31.

This embodiment can be modified and implemented as follows. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
In the above embodiment, the inner rotor 21 has 10 outer teeth and the outer rotor 22 has 11 internal teeth. The number of external teeth and internal teeth is not particularly limited. It suffices that "n + 1" internal teeth are provided for "n" external teeth (n is a positive integer).

-As the shapes of the external teeth and the internal teeth, for example, those having a trochoidal curve, an involute curve, or a cycloid curve can be adopted.
The size of the difference between the length D1 of the major axis and the length D2 of the minor axis in the outer rotor 22 formed in an elliptical shape can be appropriately changed. For example, the larger the clearance that the outer rotor 22 can move in the radial direction in the pump chamber 15, the larger the difference between the length D1 of the major axis and the length D2 of the minor axis, thereby increasing the difference between the length D1 of the major axis and the length D2 of the minor axis. The locus becomes easy to draw an ellipse, and it becomes easy to eliminate the communication between the operating chamber 31 and the discharge port 16 located between the end portion 14B of the suction port 14 and the start end portion 16A of the discharge port 16.

10 ... Oil pump, 11 ... Pump case, 12 ... Suction port, 13 ... Suction passage, 14 ... Suction port, 14B ... End part, 15 ... Pump chamber, 16 ... Discharge port, 16A ... Start part, 17 ... Discharge passage, 18 ... Discharge port, 21 ... Inner rotor, 22 ... Outer rotor, 23 ... Drive shaft, 31 ... Operating chamber.

Claims (1)

A pump case in which a cylindrical pump chamber, a suction port for introducing oil into the pump chamber, and a discharge port for discharging oil from the pump chamber are formed, and a pump case housed in the pump chamber and provided with internal teeth. An outer rotor and an inner rotor provided inside the outer rotor and having external teeth that mesh with the internal teeth and fixed to the drive shaft with a point eccentric to the center of the outer rotor as the center of rotation. An internal gear type oil pump that has
An oil pump having an elliptical outer shape of the outer rotor.

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