Oil Pump

Abstract

An oil pump includes an inner rotor, an outer rotor, an outer ring, and a pump housing including a suction port and a discharge port, and including a first seal land formed between a terminal end section of the suction port and a start end section of the discharge port, and moreover including a rotor chamber that houses the inner rotor, the outer rotor, and the outer ring. In swing of an angle from an initial position to a final position of the outer ring, a final position eccentric axis connecting a rotation center of the inner rotor and a rotation center of the outer rotor is turnable in an area of an angle exceeding 90 degrees on the suction port side with respect to an initial position eccentric axis.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a discharge amount variable oil pump mounted on a vehicle engine or the like, the oil pump being capable of further increasing a discharge amount variable rate and further reducing unnecessary work in the engine and the pump, thereby improving fuel efficiency.

2. Description of the Related Art

There have been various discharge amount variable oil pumps. Among the oil pumps, there is an oil pump including a rotor of an inscribed type. In general, in an inscribed gear type oil pump, an inner rotor including external teeth and an outer rotor including inner teeth rotate while meshing with each other. Spaces called cells are formed between the teeth of the inner rotor and the teeth of the outer rotor.

In the rotating motion of the inner rotor and the outer rotor, while a rotation angle is in a range of 180 degrees of 360 degrees, the oil pump sucks oil according to an increase in the volume of the cells. While the rotation angle is in the remaining range of 180 degrees, the oil pump discharges the oil according to a decrease in the volume of the cells. In a normal inscribed teeth oil pump, which is not the variable capacity type, a suction port is arranged in a phase where the volume of the cells increases and a discharge port is arranged in a phase where the volume of the cells decreases.

In the discharge amount variable oil pump, in order to move the outer rotor along a predetermined track, an adjusting member is provided. The outer rotor is turnably amounted on the adjusting member. A rotation center of the outer rotor is moved by swinging the adjusting member. As the oil pump of this type, there are oil pumps disclosed in WO2010/013625, Japanese Patent Application Laid-Open No. H10-169571, Japanese Patent Application Laid-Open No. H08-159046, and Japanese Patent Application Laid-Open No. 2008-298026.

Specifically, paragraph 0006 of WO2010/013625 mentions that “A locker lever that actuates the adjustment ring 14 is swingably supported in the casing portion 1. By swinging the locker lever, a rotation axis of the outer rotor 4 moves 90 degrees in a direction on the opposite side of the inner rotor 3 in a state in which the inner side row of teeth 24′ and the outer side row of teeth 24 mesh with each other. Due to this movement, a positional relation between the low pressure port 8 and the high pressure port 9 with respect to the ring gear set 5 of the inner rotor 3 and the outer rotor 4 changes to make it possible to adjust a discharge amount of the pump from a maximum discharge amount to zero.”

Paragraph 0037 of Japanese Patent Application Laid-Open No. H10-169571 mentions that “The adjustment ring 14 rotates in the rotating direction D of the inner rotor 3 by a relatively small angle γ in a state in which the two rows of teeth 24 and 24′ of the adjustment gear 20 are continuously meshed with each other. Consequently, when the root circle 15 of the adjustment ring 14 and the root circle 16 of the inner side row of teeth 24′ rotate with respect to each other without slipping, first, the rotation axis of the outer rotor moves 90 degrees from a position shown in FIG. 1A to a position shown in FIG. 1B around the rotation axis of the inner rotor 3 in a direction opposite to a rotating position of the inner rotor 3. The position shown in FIG. 1B is a zero position of the pump. In an ideal case, fluid is not discharged in this position. In the zero position, the groove ports 8 and 9 extend symmetrically on both sides of complete and open meshing positions.”

Paragraph 0023 of Japanese Patent Application Laid-Open No. H08-159046 mentions that “According to such swing movement of the cam ring 5, a rotation center position of the outer rotor 4 rotatably held in the cam ring 5 revolves 90 degrees in the clockwise direction with the teeth height of the inscribed gear pump set as a revolving diameter and with the rotation center position of the inner rotor 3 set as a revolving center. The capacity of the oil transfer reservoir section 11 on the terminal end vicinity 22 of the suction region 21 is minimized.”

Paragraph 0055 of Japanese Patent Application Laid-Open No. 2008-298026 mentions that “When the pump revolution rate further rises, the pump discharge pressure acting on the adjustment ring 7 further increases. Therefore, as shown in FIG. 11, the adjustment ring 7 further rotates in the counterclockwise direction and rotates to an angle of approximately 30 degrees resisting a spring force of the spring member 27.

Therefore, the center point E of the outer rotor 5 moves approximately 90 degrees. An eccentric direction from the inner rotor 4 is in an angle position of approximately 90 degrees. Therefore, the capacity of the pump chamber 10 is substantially equal when the pump chamber 10 passes the seal land section 15 from the suction chamber 11 to the discharge chamber 12 and when the pump chamber 10 passes the seal land section 16 from the discharge chamber 12 to the suction chamber 11. A pump discharge amount is minimized.”

WO2010/013625 to Japanese Patent Application Laid-Open No. 2008-298026 disclose an operation explained below in order to change a discharge capacity of the oil pump. FIGS. 6A and 6B are schematic diagrams for explaining the contents of WO2010/013625 to Japanese Patent Application Laid-Open No. 2008-298026. When the discharge capacity of the oil pump is maximized, a suction port “a” is arranged in a phase where the volume of the cells increases and a discharge port “b” is arranged in a phase where the volume of the cells decreases. The position of an outer rotor “c” in this case is set as an initial position (see FIG. 6A). An eccentric axis k at this point is perpendicular in FIG. 6A.

The eccentric axis k in a final position is tilted an angle θ₀ with respect to the eccentric axis k in the initial position. A position of the eccentric axis k tilted 90 degrees is set as the final position of the outer rotor “c”. A suction amount and a discharge amount of a moving cell are substantially equal on the insides of both of the discharge port “b” and the suction port “a”. Therefore, a suction amount and a discharge amount are offset and oil does not flow. Consequently, the discharge capacity can be theoretically reduced to zero. As explained above, in WO2010/013625 to Japanese Patent Application Laid-Open No. 2008-298026, when the discharge capacity of the oil pump is theoretically reduced to zero, it is a technical common sense to tilt the eccentric axis k 90 degrees (see FIG. 6B).

That is, in WO2010/013625 to Japanese Patent Application Laid-Open No. 2008-298026, when the eccentric axis k tilts 90 degrees with respect to the initial position, according to the rotation by an inner rotor “d” and the outer rotor “c”, a sucking amount and a discharging amount of the passing oil in the cell are substantially equal on the insides of the discharge port “b” and the suction port “a”. That is, a suction amount and a discharge amount of the oil by the cell are substantially equal and offset. The oil stops flowing.

However, when the applicant actually tilted the eccentric axis 90 degrees and conducted an experiment, a result indicating that the oil of approximately 25% flowed with respect to a maximum discharge amount was obtained. Therefore, a variable rate of a discharge amount is 75% and is not zero. This means that improvement of fuel efficiency decreases because variable width of the discharge capacity decreases.

As explained above, there is a cause that the discharge capacity of the oil pump cannot actually be reduced to zero even if the eccentric axis k is tilted 90 degrees. This cause is explained below. First, in the pump, the oil in a flowing state is always about to continue to flow in a forward direction from a suction side to a discharge side. If the engine continues to be operated, the oil necessarily flows in the forward direction.

The oil has mass. The oil flowing in the forward direction in the pump maintains a flowing state in the forward direction with the inertia of the oil. Even if action in a backflow direction occurs in the pump (when the eccentric axis exceeds 90 degrees), if the action is very small, the oil continues to flow in the forward direction without changing the flowing direction. Therefore, even if the eccentric axis k is turned 90 degrees, although the discharge amount decreases, the flow of the oil in the forward direction does not decrease to zero. The oil discharge of the pump is continued.

As an example of the cause that the discharge capacity of the oil pump does not decrease to zero even if the eccentric axis k is tilted 90 degrees, there is cavitation that occurs in the pump. When the eccentric axis k turns 90 degrees, the arrangement changes to arrangement shown in FIG. 6B. A configuration shown in FIG. 6B is vertically symmetric with respect to the eccentric axis k.

In a state in which the eccentric axis k turns 90 degrees and is arranged horizontally (see FIG. 6B), seal lands (partitioning sections) are arranged on both upper and lower side with respect to the eccentric axis k. When the inner rotor and the outer rotor rotates counterclockwise in such a state, a discharge operation is performed on a side below the eccentric axis k horizontally arranged on the discharge port “b” side of the pump because the volume of the cells gradually decreases. A suction operation is performed on a side above the eccentric axis k because the volume of the cells gradually increases.

In this case, in a process in which the volume of the cells decreases, the oil is surely discharged by the decrease in the volume of the cells. That is, in the discharge port “b”, in a contraction process of the cell that moves counterclockwise, the oil in the cell is substantially completely discharged. On the other hand, in an expansion process of the cell that moves counterclockwise in the discharge port “b”, the oil is sometimes not sufficiently filled in the cell having increased volume. In particular, as rotation speed of the rotors increases, an air gap portion not filled with the oil tends to occur in a part of the cell.

Further, while the volume of the cell that move counterclockwise continues to increase, when a part of the cell reaches the seal land where the oil is absent, the cell cannot suck the oil and a vacuum area occurs in the cell. In this way, in particular, when the cell moves while increasing the volume rapidly, inflow of the oil less easily performed and the vacuum area increases. As a result, a large number of air bubbles (very small vacuum bubbles) are generated from the oil in the cell.

This phenomenon is so-called cavitation. Even if a part of the cell is present in the discharge port “b”, the cell cannot suck the oil because of the large number of air bubbles. In particular, probability of cavitation occurrence increases when the cell starts to cross the seal land section and, in addition, the volume of the cell increases.

Therefore, in the related art, in a state in which the eccentric axis k turns 90 degrees, on the discharge port “b” side, an oil discharge amount by the cell is larger than a suction amount in an oil discharge operation of the cell in which the volume decreases and an oil suction operation of the cell in which the volume increases. As a result, a discharge amount and a suction amount of the oil in the discharge port “b” are not equal and are not fully offset.

Moreover, since the discharge amount of the oil by the cell in the discharge port “b” is larger than the suction amount, even if the eccentric axis k turns 90 degrees, an oil discharge amount decreases as a whole. The oil continues to flow in the forward direction. The flow does not stop. An expected variable rate of the discharge amount cannot be expected. Therefore, it is an object of the present invention (a technical problem to be solved) to further increase the variable rate of the discharge amount in an operation for rotating the eccentric axis and changing the discharge amount.

SUMMARY OF THE INVENTION

Therefore, the inventor earnestly carried out researches in order to solve the problems and solved the problems according to embodiments of the present invention explained below.

According to a first aspect of the present invention, there is provided an oil pump including: an inner rotor including outer teeth; an outer rotor including inner teeth that form, together with the outer teeth, cells, and rotating while having a predetermined eccentricity amount with respect to a rotation center of the inner rotor; an outer ring that swings, with respect to a rotation center of the inner rotor, a rotation center of the outer rotor along a track circle having the eccentricity amount as a radius; and a pump housing including a suction port and a discharge port, and including a first seal land formed between a terminal end section of the suction port and a start end section of the discharge port, and moreover including a rotor chamber that houses the inner rotor, the outer rotor, and the outer ring. In swing of an angle from an initial position to a final position of the outer ring, a final position eccentric axis connecting the rotation center of the inner rotor and the rotation center of the outer rotor is turnable in an area of an angle exceeding 90 degrees on the suction port side with respect to an initial position eccentric axis.

According to a second embodiment of the present invention, in the oil pump according to the first embodiment, in the swing from the initial position to the final position of the outer ring, the final position eccentric axis connecting the rotation center of the inner rotor and the rotation center of the outer rotor is turnable in an area of an angle exceeding 90 degrees to an angle of 150 degrees on the suction port side with respect to the initial position eccentric axis.

According to a third embodiment of the present invention, in the oil pump according to the first embodiment, in the swing from the initial position to the final position of the outer ring, the final position eccentric axis connecting the rotation center of the inner rotor and the rotation center of the outer rotor is turnable in an area of an angle of 100 degrees to 140 degrees on the suction port side with respect to the initial position eccentric axis.

In the present invention, in the swing from the initial position to the final position of the outer ring, the final position eccentric axis connecting the rotation center of the inner rotor and the rotation center of the outer rotor is turnable in the area of the angle exceeding 90 degrees to the suction port side with respect to the initial position eccentric axis. Therefore, when the eccentric axis of the inner rotor and the outer rotor is the final position eccentric axis, it is possible to further reduce the discharge amount and increase the variable rate of the discharge capacity to approximately 80% or more. Therefore, it is possible to reduce useless work of the pump and improve fuel efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a main part enlarged sectional view showing an initial position of an outer ring, an outer rotor, and an inner rotor of the present invention;

FIG. 1B is an enlarged view showing the configuration in the vicinity of a fan-shaped turning track;

FIG. 2 is a main part enlarged sectional view showing a final position of the outer ring, the outer rotor, and the inner rotor of the present invention;

FIG. 3 is a schematic diagram showing a configuration in the present invention;

FIG. 4 is a graph showing characteristics of the present invention and the related art;

FIG. 5A is a main part enlarged sectional view of a state in which a phase of the outer rotor of the present invention is rotated 90 degrees in a clockwise direction with respect to an initial position eccentric axis;

FIG. 5B is a view of a state in which the inner rotor and the outer rotor turn by a small angle in the state shown in FIG. 5A;

FIG. 5C is an “α” part enlarged view of FIG. 5B;

FIG. 6A is a schematic diagram showing an initial position state of the outer rotor in the related art; and

FIG. 6B is a schematic diagram showing a final position state of the outer rotor in the related art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention is explained below with reference to the drawings. An oil pump according to the embodiment of the present invention mainly includes, as shown in FIGS. 1A to 3, a pump housing A, an inner rotor 3, an outer rotor 4, an outer ring 5, and an operation unit 9. In the pump housing A, a rotor chamber 1 is formed. In a bottom surface section of the rotor chamber 1, a shaft hole 11, into which a driving shaft for pump driving is inserted, is formed. A suction port 12 and a discharge port 13 are formed around the shaft hole 11. Seal lands are formed between the suction port 12 and the discharge port 13.

The seal lands are formed in two places in the rotor chamber 1. One of the seal lands is located between a terminal end section 12b of the suction port 12 and a start end section 13a of the discharge port 13. The seal land is referred to as first seal land 14.

The other seal land is located between a terminal end section 13b of the discharge port 13 and a start end section 12a of the suction port 12. The seal land is referred to as second seal land 15. In the pump housing A, an operation chamber 2 leading to the rotor chamber 1 is formed and an operation projecting section 51 of the outer ring 5 (to be described later) is arranged. The inner rotor 3, the outer rotor 4, and the outer ring 5 are internally mounted in the rotor chamber 1.

The inner rotor 3 is a gear formed in a trochoid shape or a substantially trochoid shape. A plurality of outer teeth 31 are formed in the inner rotor 3 (see FIGS. 1A to 3). A boss hole 32 for the driving shaft is formed in a center position in the diameter direction of the inner rotor 3. A driving shaft 33 is pierced through and fixed in the boss hole 32. The boss hole 32 is formed in a non-circular shape. The driving shaft is fixed to the inner rotor 3 by press-fitting of a shaft fixing section having substantially the same shape as the boss hole 32 or by fixing means having width across flat or the like. The inner rotor 3 rotates according to rotation driving of the driving shaft.

The outer rotor 4 is formed in an annular shape. A plurality of inner teeth 41 are formed on the inner circumferential side of the outer rotor 4. The number of the outer teeth 31 of the inner rotor 3 is smaller than the number of the inner teeth 41 of the outer rotor 4 by one. A plurality of cells (inter-teeth spaces) S are formed by the outer teeth 31 of the inner rotor 3 and the inner teeth 41 of the outer rotor 4.

A rotation center of the inner rotor 3 is represented as Pa. The position of the rotation center Pa is immobile with respect to the rotor chamber 1. A rotation center of the outer rotor 4 is represented as Pb. An imaginary line connecting the rotation center Pa and the rotation center Pb is referred to as eccentric axis. As the eccentric axis, an initial position eccentric axis La and a final position eccentric axis Lx are present according to the positions of the outer rotor 4 and the outer ring 5.

A distance between the rotation center Pa of the inner rotor 3 and the rotation center Pb of the outer rotor 4 is referred to as eccentricity amount e. A track circle having the rotation center Pa of the inner rotor 3 as a center and having the eccentricity amount e as a radius is formed. According to operation of the outer ring 5, the rotation center Pb of the outer rotor 4 moves along a fan-shaped arc, which is a portion of the track circle, from an initial position state to a final position state (see FIG. 1B). An arc-shaped track portion of the rotation center Pb in this case is referred to as fan-shaped turning track Q.

The outer ring 5 is formed in a substantially annular shape. The operation projecting section 51 formed to project outward in the diameter direction from a predetermined place of an outer circumferential side surface 5a of the outer ring is provided. A wrapping inner circumference section 52 functioning as a round through-hole is formed on the inward side of the outer ring 5. The outer ring 5 is swung in the rotor chamber 1 by the operation unit 9 (to be described later) via the operation projecting section 51. The operation projecting section 51 is arranged in the operation chamber 2 and can swing in the operation chamber 2.

The wrapping inner circumference section 52 is formed as a circular inner wall surface. The inner diameter of the wrapping inner circumference section 52 is substantially the same as the outer diameter of the outer rotor 4. Specifically, the inner diameter of the wrapping inner circumference section 52 is slightly larger than the outer diameter of the outer rotor 4. The outer rotor 4 is inserted into the wrapping inner circumference section 52 with a clearance provided between the wrapping inner circumference section 52 and the outer rotor 4 such that the outer rotor 4 is smoothly rotatable.

The position of a diameter center Pc of the wrapping inner circumference section 52 of the outer ring 5 coincides with the position of the rotation center Pb of the outer rotor inserted into the wrapping inner circumference section 52 (see FIG. 2). The outer ring 5 is arranged in the rotor chamber 1. The outer rotor 4 is arranged in the wrapping inner circumference section 52 to rotatably support the outer rotor 4 and swing the outer rotor 4 along the fan-shaped turning track Q via the operation unit 9 (see FIGS. 1A to 2).

The outer ring 5 is internally mounted in the rotor chamber 1 of the pump housing A. The outer ring 5 is swingable in the rotor chamber 1. Therefore, the rotor chamber 1 is formed slightly wider than the external shape of the outer ring 5. A space for the outer rotor 4 to swing is provided in addition. The outer ring 5 is swung by the operation unit 9. However, a track of the swing is determined. The diameter center Pc of the wrapping inner circumference section 52 swings along the fan-shaped turning track Q.

In the present invention, an initial position and a final position are present for the inner rotor 3 and the outer rotor 4. The initial position refers to a position of the inner rotor 3, the outer rotor 4, and the outer ring 5 at the time when a largest cell Sa having a largest capacity among the plurality of cells S formed by the inner rotor 3 and the outer rotor 4 is located on the first seal land 14. In the initial position, the number of revolutions of the engine is mainly in a low revolution area. An eccentric axis connecting the rotation center Pa of the inner rotor 3 and the rotation center Pb of the outer rotor 4 in the initial position is referred to as initial position eccentric axis La (see FIG. 1A).

The final position refers to a position of the outer ring 5, the inner rotor 3, and the outer rotor 4 at the time when the outer ring 5 swings from the initial position to the maximum, the rotation center Pb of the outer rotor 4 moves on the fan-shaped turning track Q, and the position of the largest cell Sa moves to the maximum. The number of revolutions of the engine is in a medium revolution area and a high revolution area. An eccentric axis connecting the rotation center Pa of the inner rotor 3 and the rotation center Pb of the outer rotor 4 in the final position is referred to as final position eccentric axis Lx (see FIG. 2).

An angle of swing from the initial position eccentric axis La to the final position eccentric axis Lx of the outer rotor 4 actually swung by the outer ring 5 is represented as θ and an angle of swing of the operation projecting section 51 of the outer ring 5 at this point is represented as θa. The angle θa is markedly smaller than the angle θ.

That is, only by slightly swinging the operation projecting section 51 of the outer ring 5 with the operation unit 9, a maximum swing angle of the outer rotor 4, that is, an angle formed by the initial position eccentric axis La and the final position eccentric axis Lx can be set extremely large. Specifically, when a swing angle of the operation projecting section 51 can be set to approximately 15 degrees, the angle formed by the initial position eccentric axis La and the final position eccentric axis Lx of the outer rotor 4 can be set to approximately 120 degrees (see FIGS. 1A and 2).

When the outer ring 5 actually swings from the initial position to the final position, the eccentric axis swings in an area of the angle θ formed by the initial position eccentric axis La and the final position eccentric axis Lx. In this way, the eccentric axis swings in the area of the angle θ. The angle θ is an angle exceeding 90 degrees. That is, the angle θ does not include 90 degrees. Therefore, the angle θ formed by the initial position eccentric axis La and the final position eccentric axis Lx is an obtuse angle.

As a range of the angle θ, the angle θ exceeds 90 degrees and is equal to or smaller than approximately 150 degrees. In this embodiment, when the angle θ of the final position eccentric axis Lx is approximately 150 degrees with respect to the initial position eccentric axis La, the largest cell Sa is present within an area of the suction port 12. The range of the angle θ is sometimes limited to enable the final position eccentric axis Lx to turn in an area of an angle of approximately 100 degrees to approximately 140 degrees on the suction port 12 side with respect to the initial position eccentric axis La. In the present invention, an optimum angle θ of the final position eccentric axis Lx with respect to the initial position eccentric axis La is set to approximately 120 degrees. Consequently, the oil pump of the present invention operates as explained below.

First, the oil pump sucks the oil a little from the start end section 12a side of the suction port 12. When the cell S passes a position of the largest cell Sa, the oil pump discharges a large amount of the oil to the inside of the suction port 12. The oil pump discharges the oil a little between a position close to the start end section 13a side of the discharge port 13 and a position where the cell S is the smallest cell Sb. When the oil passes this position, the oil pump sucks a large amount of the oil from the discharge port 13. As a discharge amount, the oil equal to or smaller than 20% of a maximum discharge amount flows in the forward direction. Consequently, it is possible to set the variable rate to approximately 80% or higher (see FIG. 4).

In the operation projecting section 51 of the outer ring 5, a first pressure receiving surface 51a is formed in one side of a swinging direction and a second pressure receiving surface 51b is formed on the other side. An elastic pressing section 8 provided in the operation chamber 2 elastically presses the second pressure receiving surface 51b and generates a load for always setting the outer ring 5 and the outer rotor 4 in the initial position.

A first oil path 21 and a second oil path 22 are provided between the operation unit 9 and the operation chamber 2. Hydraulic pressures can be respectively applied to the first pressure receiving surface 51a and the second pressure receiving surface 51b of the operation projecting section 51 in the operation chamber 2 by the operation unit 9. The operation projecting section 51 is swung by hydraulic pressure control of the operation unit 9 according to a pressure difference between the hydraulic pressures applied to the first pressure receiving surface 51a and the second pressure receiving surface 51b of the operation projecting section 51 and an elastic pressing force of the elastic pressing section 8. Consequently, the operation unit 9 swings the outer ring 5 (see FIGS. 1A to 3).

An operation for guiding the swing of the outer ring 5 is performed by a plurality of tooth mark sections 6 provided between the rotor chamber 1 and the outer ring 5. The tooth mark sections 6 include outer side position tooth marks 6b formed in the rotor chamber 1 and inner side position tooth marks 6a formed on the outer circumferential side surface of the outer ring 5. As the operation unit 9 for the outer ring 5, specifically, a solenoid valve or the like is used. In the figure, reference numeral 7 denotes seal sections, which play a role of shutting off a space between the rotor chamber 1 and the outer ring 5.

FIG. 5A shows a state in which, in the present invention, an eccentric axis Lm connecting the rotation center Pa of the inner rotor 3 and the rotation center Pb of the outer rotor 4 moves 90 degrees in the clockwise direction with respect to the initial position eccentric axis La and a phase of the outer rotor 4 shifts. In this case, naturally, the position of the diameter center Pc of the wrapping inner circumference section 52 of the outer ring 5 and the position of the rotation center Pb of the outer rotor 4 coincide with each other. According to the shift of the phase, the largest cell Sa crosses the initial position eccentric axis La on the eccentric axis Lm that moves in the clockwise direction (see FIG. 5A).

Immediately after the start of the engine, first, as shown in FIG. 1A, the rotation center Pb of the outer rotor 4 is in the position of the initial state and largest cell Sa crosses the initial position eccentric axis La on the initial position eccentric axis La. In this case, the oil flows in the forward direction from the suction port 12 to the discharge port 13. The flow of the oil in the forward direction is maintained even if the eccentric axis Lm moves 90 degrees in the clockwise direction with respect to the initial position eccentric axis La.

That is, since the oil has mass, the oil is about to continue to flow in the forward direction with the inertia of the oil. The oil has power to flow in the forward direction. When the phase of the outer rotor 4 shifts and the cell S performs operations for discharging and sucking the oil within the range of the discharge port 13, the power is added to the discharge operation, a discharge amount of the oil exceeds a suction amount, and, eventually, the flow in the forward direction of the oil is maintained.

As the eccentric axis Lm approaches the final position eccentric axis Lx, contraction of the volume of the cell S within the range of the discharge port 13 disappears, the discharge of the oil is stopped, and, on the contrary, expansion of the volume of the cell S increases, and only suction of the oil is performed. Therefore, a backflow of a part of the oil from the discharge port 13 to the suction port occurs. There is no flow in the forward direction at a predetermined angle exceeding 90 degrees.

The operation explained above can also be explained by application of occurrence of cavitation (see FIGS. 5B and 5C). That is, when the eccentric axis Lm turns 90 degrees and the phase of the outer rotor 4 shifts, the inner rotor 3 and the outer rotor 4 become vertically symmetrical with respect to the eccentric axis Lm. The first seal land 14 and the second seal land 15 are arranged on both upper and lower sides of the eccentric axis Lm.

The inner rotor 3 and the outer rotor 4 rotate counterclockwise, whereby the volume of the cell S gradually decreases and the oil is discharged on a side below the eccentric axis Lm horizontally arranged within the range of the discharge port 13. The volume of the cell S gradually increases and the oil is sucked on a side above the eccentric axis Lm (see (α) of FIG. 5B).

In this case, in a process in which the volume of the cell S decreases, the oil is surely discharged by a reduced amount of the volume of the cell S. However, in a process in which the volume of the cell S increases and the oil is about to be sucked, the oil is not sufficiently filled in the cell S. In particular, as the rotating speed of the rotors increases, an air gap portion not filled with the oil tends to occur in a part of the cell S.

Further, while the volume of the cell S moving counterclockwise increases, when the cell S starts to cross the second seal land 15 where the oil is absent, the cell S cannot sufficiently absorb the oil. A vacuum area occurs in the cell S. As the cell S moves, the vacuum area continues to increase and a large number of air bubbles q, that is, cavitation occurs (see FIG. 5C).

When a crossing portion of the cell S and the second seal land 15 further increases, a larger number of air bubbles q occur. Even if a negative pressure in the cell S increases, the large number of air bubbles q prevent suction of the oil and oil suction of the cell S decreases. Consequently, within the range of the discharge port 13, an oil discharge amount by the cell S exceeds a suction amount or only a discharging operation is performed and the flow of the oil in the forward direction is maintained.

Although the flow of the oil in the forward direction is maintained, a total discharge amount of the pump decreases. As a result, the eccentric axis Lm is turned exceeding 90 degrees with respect to the initial position eccentric axis La. Therefore, a turning range of the eccentric axis Lm in which the discharge amount can be further reduced increases. It is possible to obtain a large variable rate.

In the second embodiment, in the swing of the outer ring from the initial position to the final position, the final position eccentric axis connecting the rotation center of the inner rotor and the rotation center of the outer rotor is turnable in the area of the angle exceeding 90 degrees to the angle of 150 degrees to the suction port side with respect to the initial position eccentric axis. Therefore, in a process in which the engine changes from the low revolution area to the high revolution area, a position change of the cell having the maximum capacity from the initial position eccentric axis to the final position eccentric axis is performed in the range of the angle exceeding 90 degrees to 150 degrees. Consequently, it is possible to set the variable rate of the discharge amount of the oil higher than the variable rate in the past. Further, it is possible to change the variable rate of the discharge amount of the oil to a desired value by changing the turning angle of the outer ring.

In the third embodiment, in the swing from the initial position to the final position of the outer ring, the final position eccentric axis connecting the rotation center of the inner rotor and the rotation center of the outer rotor is turnable in the area of the angle of 100 degrees to 140 degrees to the suction port side with respect to the initial position eccentric axis. Consequently, it is possible to highly accurately set the variable rate of the discharge amount of the oil. Further, it is possible to change the variable rate of the discharge amount of the oil to a desired value by changing the turning angle of the outer ring.

Claims

1. An oil pump comprising: an inner rotor including outer teeth;an outer rotor including inner teeth that form, together with the outer teeth, cells, and rotating while having a predetermined eccentricity amount with respect to a rotation center of the inner rotor;an outer ring that swings, with respect to a rotation center of the inner rotor, a rotation center of the outer rotor along a track circle having the eccentricity amount as a radius; anda pump housing including a suction port and a discharge port, and including a first seal land formed between a terminal end section of the suction port and a start end section of the discharge port, and moreover including a rotor chamber that houses the inner rotor, the outer rotor, and the outer ring, whereinin swing of an angle from an initial position to a final position of the outer ring, a final position eccentric axis connecting the rotation center of the inner rotor and the rotation center of the outer rotor is turnable in an area of an angle exceeding 90 degrees on the suction port side with respect to an initial position eccentric axis.

2. The oil pump according to claim 1, wherein, in the swing from the initial position to the final position of the outer ring, the final position eccentric axis connecting the rotation center of the inner rotor and the rotation center of the outer rotor is turnable in an area of an angle exceeding 90 degrees to an angle of 150 degrees on the suction port side with respect to the initial position eccentric axis.

3. The oil pump according to claim 1, wherein, in the swing from the initial position to the final position of the outer ring, the final position eccentric axis connecting the rotation center of the inner rotor and the rotation center of the outer rotor is turnable in an area of an angle of 100 degrees to 140 degrees on the suction port side with respect to the initial position eccentric axis.