JP3149207B2 - Variable displacement vane pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable displacement vane pump applied to a power steering device and the like.

[0002]

2. Description of the Related Art In general, a power steering apparatus for an automobile or the like is known which is provided with a variable displacement vane pump in which the amount of eccentricity of a cam ring with respect to a rotor is changed so as to make a discharge flow variable. 60-11107
No. 9, etc.).

The conventional variable displacement vane pump includes a rotor for supporting a plurality of vanes slidably in a radial direction inside a pump body one end of which is closed by a rear cover;
A center of the rotor and a cam ring provided eccentrically rotatable are accommodated, and the pump discharge fluid discharged from a pump chamber between the rotor and the cam ring is supplied to a control valve of a power steering. The cam ring is eccentrically rotated with respect to the rotor using the differential pressure across the orifice of the discharge fluid to control the pump discharge flow rate irrespective of the rotation speed of the rotor.

Further, the pump discharge fluid is introduced between a rear cover and a side plate interposed between the rear cover and the cam ring, and presses the side plate by the high pressure of the discharge fluid to form the cam ring. To ensure the sealing performance of the pump chamber and improve the pump volumetric efficiency.

[0005]

However, in the conventional variable displacement vane pump, a sufficient sealing property of the pump chamber is secured by pressing the side plate in the cam ring direction by the pump discharge pressure as described above. However, since the pump discharge pressure acts on the entire side surface of the side plate, the pressing force of the side plate against the cam ring is increased. Therefore, a large frictional resistance is generated between the cam ring and the side plate, and the smooth eccentric rotation of the cam ring is hindered. Consequently, pump control responsiveness of the discharge flow rate is deteriorated to be controlled at a constant relative relationship between the pump speed, the hysteresis of the discharge flow rate as indicated by the broken line in FIG. 8 increases.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems. In particular, the present invention has a pressure receiving portion formed between a side plate and a rear cover for introducing a discharge pressure of a pump. At a position deviated to the pump discharge side,
It is characterized in that it is formed smaller than the area inside the outer diameter of the cam ring . Further, the outer diameter of the side plate and the outer diameter of the rotor are substantially the same.

[0007]

According to the present invention having the above-described structure, the pump discharge pressure is biased toward the pump discharge side instead of the entire side surface of the side plate.
Area of the outer-diameter side of the part of the region only means that the cam ring
Since it acts on a pressure receiving area smaller than that, the pressing force of the side plate against the cam ring is reduced, and the cam ring can always be smoothly and eccentrically rotated.

Further, by making the outer diameter of the side plate substantially equal to the outer diameter of the rotor, the side plate receiving the pump discharge pressure can be prevented from slidingly contacting the cam ring. Occasional frictional resistance is reduced, and the cam ring can be smoothly eccentrically rotated.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic structural view showing an embodiment of a variable displacement vane pump according to the present invention, FIG. 2 is a sectional view showing a main part of the variable displacement vane pump, a part of which is omitted, and FIG. FIG. In these figures, reference numeral 1 denotes a pump body. A drive shaft 2 is rotatably supported by the pump body 1, and a rotor 3 is connected to the drive shaft 2 so as to be able to rotate integrally. The rotor 3 has a plurality of slots 4 radially formed on an outer peripheral side thereof, and a vane 5 is slidably accommodated in the slots 4.

Reference numeral 6 denotes a cam ring.
In the figure, the upper end is pivotally supported on the pump body 1 by a pin 7. This cam ring 6 has a circular inner cam surface (inner circumference).
The rotor 3 provided with the vane 5 is accommodated in the internal space of the rotor 3. An arm 9 extends radially outward from the lower end of the cam ring 6 in the figure, and the arm 9 is connected to a control mechanism 10.

The control mechanism 10 is arranged at the lower end of the pump body 1 in the figure. The control mechanism 10 has a substantially cylindrical casing 11 (see FIG. 2) as shown in detail in FIG.
5 ), a pair of left and right cylinders 12, 13 formed in
The cylinder includes a pair of left and right pistons 14 and 15 slidably and opposed to each other in the cylinders 12 and 13, and compression springs 16 and 17 for urging the pistons 14 and 15 toward the arm 9. 12,13
Are closed by stoppers 18 and 19. Note that pressing members 20 and 21 are fixed to the tips of the pistons 14 and 15, and the pressing members 20 and 21 are brought into contact with the side surfaces of the arm 9. The strokes of the pistons 14 and 15 are regulated by the ends 18a and 19a of the stoppers 18 and 19.

Reference numeral 22 denotes a plurality of grooves formed on the side surface of the pump body 1 and the side plate 23 on the rotor 3 side. The grooves 22 communicate with the bottom 4a of the slot 4 (see FIG. 5). And among these concave grooves 22,
A hydraulic passage 24 is provided in the groove 22 located in the discharge area of the pump.
One end of the hydraulic passage 25 communicates with the groove 22 located in the suction area of the pump (see FIG. 7).

The other end of one hydraulic passage 24 is connected to a pump discharge passage 27 extending from a discharge port 26, and one of the cylinders 1 is connected via a branch passage 28.
3 (see FIG. 1 ). And the branch passage 28
An orifice 29 is provided in the hydraulic passage 24 between the connection point of the hydraulic passage 24 and the connection point of the hydraulic passage 24 to the pump discharge passage 27 (see FIG. 3). The other hydraulic passage 2
5 has the other end connected to the other cylinder 12 and to the discharge port 26 via the branch passage 30 (see FIG. 1 ).

Reference numeral 31 denotes an oil suction port. The oil suction port 31 communicates with a pump chamber 34 located in a pump suction area via a suction chamber 32 and a suction passage 33 (see FIGS. 4 and 5). ). On the other hand, the pump chamber 34 in the pump discharge area communicates with the discharge chamber 35 and the discharge port 26 (see FIGS. 2 and 3).

3 to 5, reference numeral 36 denotes an O-ring for sealing the joint surface between the side plate 23 and the rear cover 37. An O-ring 38 for forming a pressure receiving portion is disposed inside the O-ring 36. . This O-ring 3 for forming a pressure receiving portion
Reference numeral 8 denotes O so that the minute gap between the side plate 23 and the rear cover 37 (the pressure receiving portion 39 shown by meshes in FIG. 4) in the inner portion thereof corresponds to a partial region on the pump discharge side.
It is arranged eccentrically with respect to the ring 36. That is,
The pressure receiving portion 39 extends over the entire corresponding area on the side of the cam ring 6.
However, it is arranged offset to the pump discharge side. The pressure receiving portion 39 partitioned by the pressure receiving portion forming O-ring 38 has an outer diameter within the outer diameter of the cam ring 6 as shown in FIGS.
It is formed smaller than the area on the side. Also, this pressure receiving part
In 39, the hydraulic passage 24 after passing through the orifice 29 is opened, and one end of the pump discharge passage 27 is opened.

Reference numeral 40 denotes an O-ring for partitioning the hydraulic passage. The O-ring 40 is arranged on the outer peripheral side of the hydraulic passage 24 formed in the side plate 23, seals the space between the rear cover 37 and the side plate 23, and allows the high-pressure fluid (oil) in the hydraulic passage 24 before passing through the orifice 29. ) Is prevented from flowing into the pressure receiving portion 39 and the pump discharge passage 27.

In FIG. 1, O ₁ is the center of rotation of the rotor 3, and O ₂ is the center of the inner peripheral cam surface 8 of the cam ring 6. 3 and 5, reference numeral 1a denotes a center body which constitutes a part of the pump body 1. The width of the center body 1a is slightly larger than the width of the cam ring 6.

According to the structure of the above embodiment, the vane 5
When the rotor 3 rotates counterclockwise in FIG. 1, the rotor 3 is pressed against the inner peripheral cam surface 8 by centrifugal force and slides on the inner peripheral cam surface 8.
It slides back and forth in the slot 4. Therefore, the branch passage 30,
The discharge oil introduced into the bottom 4a of the slot 4 through the hydraulic passage 25 and the concave groove 22 in the pump suction area is pressurized by the vane 5 descending in the slot 4 in the pump discharge area. Then, the oil pressurized at the bottom 4a of the slot 4 functioning as a pump chamber is supplied to the control mechanism 10 on the right side in FIG. introduced <br/> the cylinder 13, the pump discharge passage 2 through the orifice 29 to further
7. As shown in FIG.
The hydraulic pressure on the downstream side of the orifice 29 is introduced into the pressure receiving portion 39.
Is done.

As a result, the hydraulic pressure P ₁ in the hydraulic passage 24 and the branch passage 28 before passing through the orifice 29 is higher than the hydraulic pressure (pump discharge pressure) P ₂ in the hydraulic passage 24 after passing through the orifice 29. It is higher by the pressure drop (ΔP = P ₁ −P ₂ ) due to the orifice 29. The differential pressure across the orifice 29 in the hydraulic passage 24 (ΔP = P ₁ −P ₂ )
Increases as the pump rotation speed increases and the amount of oil discharged from the bottom 4a of the slot 4 increases.

On the other hand, the hydraulic pressure (pump discharge pressure) P ₂ after passing through the orifice 29 is introduced into the left cylinder 12 in FIG. 1 through the branch passage 30 and the hydraulic passage 25. Pressure difference across the orifice 29 (Δ
As P) increases, the pressure difference acting on the pistons 14, 15 also increases.

When the pressure difference (.DELTA.P) acting on the pistons 14, 15 exceeds a predetermined value, the force pressing the right piston 15 in FIG. 1 leftward in FIG. Is greater than the force pressing rightward in FIG. Therefore, the cam ring 6 is rotated by the control mechanism 10 from the maximum eccentric position shown in FIGS. 1 and 2 in a direction (clockwise direction in the drawing) in which the eccentric amount e is reduced. At this time, the pump discharge pressure acts on the pressure receiving portion 39 of the side plate 23, and the pressure acting on the pressure receiving portion 39 opposes the pressure acting on the side surface of the side plate 23 on the rotor 3 side. Since the pressure receiving area is limited to correspond to a partial area on the pump discharge side, the side plate 23
Is smaller than the conventional example. Therefore, the frictional resistance between the cam ring 6 and the side plate 23 is reduced, and a smooth eccentric rotation of the cam ring 6 can be obtained. Then, the pump discharge amount changes according to the rotation amount (θ) of the cam ring 6. The pressure receiving area of the pressure receiving portion 39 is such that even if the pump discharge pressure acts on the side plate 23, sufficient adhesion between the side plate 23 and the cam ring 6, that is, the sealing property of the pump chamber 34 is not impaired. Needless to say.

When the pump discharge amount is equal to or less than a predetermined value, that is, when the differential pressure (ΔP) across the orifice 29 is equal to or less than a predetermined value, the cam ring 6 is held at the maximum eccentric position shown in FIGS. ing.

When such a variable displacement vane pump is applied to a power steering device of an automobile, it is possible to adjust the amount of oil supplied to the power steering device according to the running state of the vehicle, that is, the engine speed. Become.

As described above, in the present embodiment, the pressure receiving portion 39 of the side plate 23 is limited to a part of the area on the pump discharge side, so that the force for pressing the side plate 23 against the cam ring 6 is more than that of the conventional example. Pump chamber 34
, The frictional resistance generated between the side plate 23 and the cam ring 6 can be reduced, and the eccentric rotation of the cam ring 6 can be smoothly performed. As a result, the control response of the pump discharge amount is improved, and the hysteresis of the discharge flow rate is sufficiently reduced as shown by the solid line in FIG.

In this embodiment, the bottom 4a of the slot 4
The hydraulic pressure taken out from the hydraulic system via the hydraulic passage 24 is controlled by the control mechanism 1
Since the control mechanism 10 is operated by using the pressure difference (ΔP) before and after the orifice 29 provided in the hydraulic passage 24, the orifice 29 does not need to be provided in the pump discharge passage 27. In comparison, the pump work amount corresponding to the differential pressure (ΔP) across the orifice 29 can be reduced. As a result, an increase in the pump internal pressure can be suppressed, the power consumption of the pump can be reduced, and an increase in the oil temperature can also be effectively suppressed.

FIG. 9 shows an embodiment corresponding to claim 2 of the present invention. That is, in the present embodiment, the pump body 1
The rear cover 37 is fixed via a center body 41 to the high rigidity pump body 1 and the rear cover 3.
The cam ring 6 is accommodated between the cam ring 6 and the cam ring 7 so as to be eccentrically rotatable. The cam ring 6 has one end pivotally connected to the pump body 1 and the rear cover 37 by a pin 7.

In this embodiment, a concave portion 42 substantially concentric with the drive shaft 2 and substantially the same diameter as the rotor 3 is formed on the side surface of the rear cover 37 on the cam ring 6 side, and the side plate 43 is slid in the concave portion 42. Housed so that you can do it.

The side plate 43 has an outer diameter substantially equal to the outer diameter of the rotor 3 and is engaged with the inner peripheral surface of the concave portion 42 with a small gap. The side plate 43 has an outer periphery and a concave portion 42.
The seal members 44 and 45 are accommodated on the bottom side (the left side in the figure) of. These seal members 44 and 45 seal the gap between the rear cover 37 and the side plate 23. One of the seal members 45 is eccentric with respect to the drive shaft 2 by a predetermined amount as shown in FIG. It is arranged.

The pump discharge pressure is introduced into the area partitioned by the seal members 44 and 45 via the pump discharge passage 27 and the oil passage 46. As a result, the hatched portion shown in FIG. 10 functions as the pressure receiving portion 39, and the pump discharge pressure acts on the pressure receiving portion 39. Where inside
Member 45, whose pressure is low, may be biased toward the pump suction side
The pressure receiving section 39 is located on the pump discharge side as a whole.
Is biased toward. In addition, the pressure receiving part 39 is a side plate 4
The area thereof is determined so that the high pressure acting on the side surface of the rotor 3 on the rotor 3 side and the pressure acting on the pressure receiving portion 39 are pressure-balanced.

In FIG. 9, reference numeral 47 denotes a guide pin. The guide pin 47 has a function of preventing rotation of the side plate 43 and a function of guiding the side plate 43 to move in the axial direction. Reference numeral 48 denotes an oil reservoir formed in the pressure receiving portion 39 of the side plate 43 (see FIG. 10).
9 is an oil suction port. The seal member 44 includes a Teflon ring 50 and a backup ring 51, and the seal member 45 normally uses an O-ring.

According to the structure of the above-described embodiment, when the pump operates, the side plate 43 is held at a position where the pressures acting on both sides thereof are balanced. 43 and rotor 3
Can be maintained at a constant value at all times, and high-pressure oil is prevented from leaking from the gap between the side plate 43 and the rotor 3 to the low-pressure side.
Problems such as seizure of the rotor 3 and the rotor 3 can be prevented.

Further, according to the structure of this embodiment, the cam ring 6
Is housed between the highly rigid pump body 1 and the rear cover 37, even if the pressure in the pump chamber 34 increases.
An increase in the amount of clearance between the rear cover 37 and the cam ring 6 and between the cam ring 6 and the pump body 1 can be suppressed.

As described above, in this embodiment, the outer diameter of the side plate 43 responsive to the pressure is formed to be substantially the same as the outer diameter of the rotor 3, so that the side plate 43 and the cam ring 6 are in sliding contact with each other. The friction force acting on the cam ring 6 during the operation of the pump does not increase. Therefore, the eccentric rotation of the cam ring 6 can be smoothed similarly to the embodiment, and the control response of the pump discharge amount is improved. The present invention is not limited to the configuration of each of the above embodiments. For example, the present invention is also applied to a vane pump in which a cam ring has a structure in which the inner and outer circumferences are eccentric, and the entire cam ring is rotated to obtain a variable discharge amount. it can.

[0035]

As apparent from the above description, according to the present invention, according to the variable displacement vane pump according to the present invention, a pressure receiving portion for introducing the pump discharge pressure is especially formed between the side plate and the rear cover, a pump discharge To the position offset to the side,
Since the cam ring is formed smaller than the area inside the outer diameter, the pressing force of the side plate against the cam ring is reduced, the frictional resistance is reduced, and the cam ring can always be smoothly and eccentrically rotated. As a result, the control response of the pump discharge flow rate is improved.

Further, by making the outer diameter of the side plate substantially equal to the outer diameter of the rotor, the side plate receiving the pump discharge pressure can be prevented from slidingly contacting the cam ring. The frictional resistance generated at the time of movement can be reduced, the cam ring can always be smoothly and eccentrically rotated, and the control response of the pump discharge flow rate can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of a variable displacement vane pump according to the present invention.

FIG. 2 is a cross-sectional view of a main part of the embodiment (a cross-sectional view along line AA in FIG. 5).

FIG. 3 is a vertical cross-sectional view showing the same embodiment (a cross-sectional view along line BB in FIG. 6).

FIG. 4 is a sectional view taken along the line CC of FIG. 5;

FIG. 5 is a sectional view taken along line DD of FIG. 6;

FIG. 6 is a front view of the variable displacement vane pump according to the embodiment.

FIG. 7 is a sectional view taken along the line EE in FIG. 5;

FIG. 8 is a characteristic diagram showing a comparison between a discharge flow rate hysteresis of the present embodiment and a conventional example.

FIG. 9 is a longitudinal sectional view of a variable displacement vane pump showing another embodiment of the present invention.

FIG. 10 is a front view of a side plate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pump body, 3 ... Rotor, 5 ... Vane, 6 ... Cam ring, 23, 43 ... Side plate, 37 ... Rear cover, 39 ... Pressure receiving part.

Continuation of the front page (56) References JP-A 1-139095 (JP, U) JP-A 57-162983 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F04C 15 / 04 321 F04C 2/344 331

Claims (2)

(57) [Claims] A pump body having one end closed by a rear cover, a rotor housed inside the pump body and supporting a plurality of vanes so as to be slidable in a radial direction;
A cam ring provided so as to be rotatable eccentrically with respect to the center of the rotor, and a side plate disposed on a side surface of the rear cover on the cam ring side; the pressure receiving portion is formed between the rear cover by introducing a discharge pressure of the pump, pump ejection
At the position deviated to the exit side, the surface inside the outer diameter of the cam ring
A variable displacement vane pump characterized by being formed smaller than the product . 2. The variable displacement vane pump according to claim 1, wherein an outer diameter of said side plate is substantially equal to an outer diameter of said rotor.