Vane pump

FIELD OF THE INVENTION

This invention relates to a vane pump, and in particular to a vane pump which is suitable for supplying oil pressure to a power steering device of a vehicle.

BACKGROUND OF THE INVENTION

A vehicle such as an automobile is provided with a power steering device which uses oil pressure. Conventionally, to supply this oil pressure, a vane pump is used such as is shown in FIG.

13

and FIG.

14

.

The vane pump houses a cam ring

30

, a rotor

31

and vanes

32

which form a pump cartridge

3

in the inner circumference of a body

107

. The cam ring

30

and rotor

31

are disposed between a cover

106

tightened to the body

107

and a side plate

108

fixed to the inner circumference of the body

107

.

The rotor

31

is joined to a drive shaft

50

′ which passes through the body

107

. A pulley is joined to a base end

50

′B of the drive shaft

50

′, and the pulley is connected with an engine. The drive shaft

50

′ drives the rotor

31

and vanes

32

. The drive shaft

50

′ is supported by a bearing

120

provided in the body

107

and a bearing

121

provided in the cover

106

. A tip end

50

′A on the bearing

121

side of the drive shaft

50

′ is housed inside the cover

106

without penetrating the cover

106

.

A ring groove

52

is formed at a predetermined position on the outer circumference of the drive shaft

50

′, and a cir clip

33

engages with the ring groove

52

. The relative displacement of the rotor

31

and drive shaft

50

′ in the axial direction is thereby regulated, and the rotor

31

is joined to the drive shaft

50

′.

When a force acts on the drive shaft

50

′ in such a direction as to push it away from the body

107

, the cir clip

33

comes in contact with the rotor

31

which slides on the side plate

108

, and the displacement of the drive shaft

50

′ in the axial direction is thereby regulated.

A high pressure chamber

101

formed between the inner circumference of the body

107

and the side plate

108

, a passage

111

connecting the high pressure chamber

101

and a flowrate control valve

4

, an intake connector

105

connecting with the outside of the body

107

, and a low pressure passage

109

for recirculating excess hydraulic fluid in the flowrate control valve

4

to the pump cartridge

3

, are provided inside the body

107

.

Hydraulic fluid is supplied under pressure from the pump cartridge

3

via a connecting hole in the side plate

108

, and the required amount of hydraulic fluid is supplied to the power steering device via the passage

111

and flowrate control valve

4

.

Surplus flowrate from the flowrate control valve

4

and hydraulic fluid from the intake connector

105

flow into the cover

106

via the low pressure passage

109

. The hydraulic fluid is sent to an intake area of the pump cartridge

3

via branch passages

102

,

102

formed in the cover

106

. As the cover

106

comprises the branch passages

102

,

102

, it is formed by demolding using a core. A thick part

106

A of predetermined thickness is formed between the branch passages

102

and a contact surface of the cover

106

with the rotor

31

and vanes

32

, and strength is thereby ensured.

Hydraulic fluid which has leaked from the end face of the cam ring

30

, and from a gap between the rotor

31

and the side plate

108

flows back to the low pressure passage

109

from the outer circumference of the bearing

120

via a drain passage

112

inclined at a predetermined angle to the drive shaft

50

′.

However, in the aforesaid prior art, the drive shaft

50

′ is supported by the bearing

120

in the body

107

and the bearing

121

in the cover

106

. Therefore, when the vane pump is assembled, an assembly step must be provided to press the bearing

121

into the cover

106

. The contact surfaces between the cover

106

and the body

107

also must be finished with a predetermined surface precision in order to ensure orthogonality of the cover

106

and drive shaft

50

′ and concentricity of the bearing

121

and drive shaft

50

′. Therefore, the number of machining steps increases, machining time increases, and production costs rise.

The displacement of the drive shaft

50

′ to the right-hand side of

FIG. 13

is restricted by the cir clip

33

, and when it displaces to the left-hand side, the end

50

′A of the drive shaft

50

′ comes in contact with the inner circumference of the cover

106

. Therefore, the depth of the hole into which the bearing

121

is inserted requires to be strictly controlled. As machining is necessary after casting the cover

106

, the number of machining steps and machining time increase, and production costs increase.

As shown in

FIG. 14

, the positional relationship of the cam ring

30

and side plate

108

is determined by a pair of dowel pins

42

,

42

which pass through the cam ring

30

and side plate

108

. The dowel pins

42

are pressed into positioning holes, not illustrated, formed on the surface of the cover

106

on which the rotor

31

and vanes

32

slide. Therefore, the number of machining steps and machining time increase in order to ensure machining precision of this hole.

The vane pump having the aforesaid construction is assembled by assembling each component sequentially to the body

107

or cover

106

, so the number of assembly steps increases. Further, automation of assembly steps is difficult, and productivity cannot be improved.

This invention, which was conceived in view of the aforesaid problems, largely reduces the number of steps used in assembling the vane pump by reducing the steps for machining the cover, and thereby improves productivity. It is a further object of the invention to provide a vane pump whereof the assembly can be automated.

DISCLOSURE OF THE INVENTION

This invention provides a vane pump comprising:

a cam ring comprising a rotor joined to a drive shaft and vanes provided in the rotor such that they are free to move in or out,

a body supporting the drive shaft and housing the cam ring,

a side plate on which are symmetrically provided first low pressure ports corresponding to an intake area of the cam ring and a high pressure port corresponding to a discharge area and connected to a high pressure chamber in the body,

an intake chamber formed between an inner circumference of the body and an upper outer circumference of the cam ring connecting with a low pressure passage for leading hydraulic fluid from the outside,

a branch passage formed between the inner circumference of the body and the upper outer circumference of the cam ring connecting the first low pressure ports of the side plate with the intake chamber, and

a cover comprising an end face joined to an open end face of the body which comes in contact with one end face of the cam ring, wherein second low pressure ports are symmetrically arranged as depressions at positions corresponding to the intake area of the cam ring, and a low pressure distributing groove provided as a depression connected to the intake chamber which splits into two along the upper outer circumference of the cam ring towards the second low pressure ports, and

a pin implanted in the side plate whereof a tip extends by a predetermined amount from the open end face of the body towards the cover, wherein

a throughhole is formed in the cam ring through which the pin passes,

a concave part of predetermined depth is formed in the cover which engages with the tip of the pin, and

an escape hole of predetermined depth for housing a tip end of the drive shaft is formed in the end face of the cover at a position corresponding to the drive shaft.

When the rotor housed inside the cam ring is driven, on one end face of the cam ring, hydraulic fluid in the intake chamber connected to the low pressure passage is aspirated from the second low pressure port via low pressure distributing branch grooves in the cover end face, while on the other end face, it is aspirated to the intake area of the cam ring from between the first low pressure port of the side plate and the end face of the cam ring via branch passages connected to the intake chamber.

Hydraulic fluid discharged from the discharge area of the cam ring is supplied under pressure to the outside through the flowrate control valve from the high pressure chamber in the body via the side plate. Hydraulic fluid is supplied to the second low pressure port from the cover side via the low pressure distributing branch grooves formed in the end face of the cover.

As this vane pump is provided with the pin in the side plate, when the throughhole of the cam ring is penetrated by the pin and the rotor and vanes are housed within the inner circumference of the cam ring, the side plate and pump cartridge can be assembled in a one-piece construction. When this side plate and pump cartridge housed together inside the body in a one-piece construction are inserted in the body and the cover is joined to the body, the intake chamber and branch passages can be formed easily. As the pin that extends from the open end face of the body engages with the concave part of the cover, the side plate and cam ring can be attached to the body in a predetermined positional relationship.

One end of the drive shaft extending from the end face of the body is housed in the escape hole formed in the end face of the cover and does not come in contact with the cover. Therefore, it is not necessary to provide a bearing or pin in the cover as is required in the aforesaid prior art. Therefore, the number of steps and time required to machine the cover are reduced, the number of parts is reduced, and ease of assembly is improved. It is moreover easy to automate assembly steps.

According to an aspect of this invention, at least one set of the pin is symmetrically provided in the side plate, plural througholes for passing the pins through are formed in the cam ring, and plural concave parts joined to tips of the pins in the end face of the cover are symmetrically formed relative to the drive shaft supported by the body.

At least one set of pins which are implanted symmetrically about the axis in the side plate respectively pass through in the cam ring, and the side plate and cam ring are joined together in a predetermined positional relationship. When the side plate and cam ring are assembled in the body, and the cover is joined to the body, plural concave parts formed in the end face of the cover engage with the pins, and the side plate and cam ring can easily be positioned in a predetermined positional relationship relative to the body. Therefore ease of assembly is improved, and the assembly steps can easily be automated.

According to another aspect of this invention, the pin is pressed into a hole formed in the side plate. The aforesaid pin is fixed, and there is no need to fix the pin to the cover as is required in the aforesaid prior art. Therefore, construction of the cover is simplified, production costs can be kept low, and ease of assembly is enhanced.

According to yet another aspect of this invention, the drive shaft is joined to the rotor in an axial direction by a cir clip, the drive shaft comprises a small diameter part having a predetermined diameter on the cover side and a large diameter part having a larger diameter than the small diameter part on the body side, the large diameter part is supported by the body, a step is formed between the small diameter part and the large diameter part, and a shoulder part is provided which comes in contact with the step at an end of a shaft hole in the body.

The drive shaft is joined to the rotor in the axial direction by the cir clip in the small diameter part, and axial displacement in such a direction as to push the drive shaft away from the body is restricted. Due to this, the drive shaft does not fall off the body.

As displacement of the drive shaft in the axial direction towards the cover is restricted by the shoulder part provided in the body, the tip end of the drive shaft does not come in contact with the cover. Therefore, there is no need to provide a means to restrict axial displacement of the drive shaft in the cover as is required in the aforesaid prior art. Therefore the construction of the cover is simplified, the number of parts and number of machining steps are reduced, and production costs can be reduced.

When the drive shaft is inserted into the bearing in the body from the small diameter part side, the step is stopped by the shoulder part. Due to this, the special positioning means is unnecessary, and assembly steps can easily be automated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a cross-sectional view of a vane pump showing one embodiment of this invention.

FIG. 2

is a view taken in the direction of the arrow A of FIG.

1

.

FIG. 3

shows a cover. (A) is a left side view of

FIG. 1

, (B) is a cross-sectional view taken along a line B—B in (A), and (C) is a side view of (A).

FIG. 4

shows the cover. (A) is a front view of the cover from the side of a body, and (B) is a cross-sectional view taken along a line D—D in (A).

FIG. 5

shows the body alone and is a view taken in the direction of the arrow A of FIG.

1

.

FIG. 6

is a cross-sectional view taken along a line E—E of FIG.

5

.

FIG. 7

is a cross-sectional view taken along a line F—F of FIG.

5

.

FIG. 8

is a cross-sectional view taken along a line G—G of FIG.

5

.

FIG. 9

shows a side plate. (A) is a front view, and (B) is a cross-sectional view taken along a line H—H of (A).

FIG. 10

shows a cam ring. (A) is a front view, and (B) is a cross-sectional view taken along a line J—J of (A).

FIG. 11

is a partial enlarged view of

FIG. 1

showing an area near a step of the drive shaft.

FIG. 12

is a schematic explanatory drawing of the steps involved in assembling the vane pump. (A) shows a shaft assembly step, (B) shows a pump cartridge assembly step, (C) shows a cover assembly step, and (D) shows a step for tightening the cover to the body. (B-

1

), (B-

2

) show pump cartridge sub-assembly steps. (B-

1

) shows a dowel pin insertion step, and (B-

2

) shows a pump cartridge and side plate assembly step.

FIG. 13

is a cross-sectional view of a vane pump according to the prior art.

FIG. 14

is a view taken in the direction of the arrow Z of FIG.

13

.

PREFERRED EMBODIMENTS OF THE INVENTION

The invention will now be described in more detail with reference to the attached drawings.

FIG.

1

-

FIG. 11

show one embodiment of a vane pump of this invention.

In FIG.

1

and

FIG. 2

, a body

1

supports a drive shaft

50

to which a pulley

51

is joined at a base end

50

B. A valve hole housing a flowrate control valve

4

is provided in the body

1

.

The body

1

houses a pump cartridge

3

comprising a side plate

8

and a cam ring

30

housing a rotor

31

free to rotate, the pump cartridge

3

being inserted from an open end face

1

A of body

1

. A cover

2

is joined to the open end face

1

A.

A shaft hole

100

passes substantially through the center of the body

1

. The drive shaft

50

that passes through the shaft hole

100

is supported by a bearing metal

18

fixed to the inner circumference of the shaft hole

100

.

As shown in FIG.

1

and

FIG. 11

, the rotor

31

engages with splines

53

provided on a tip end

50

A side of the drive shaft

50

. Its rotation relative to the drive shaft

50

is restricted, but its relative displacement in the axial direction is permitted.

The pulley

51

is joined to the base end

50

B which extends to the right-hand side of FIG.

1

and

FIG. 11

from the body

1

. The pulley

51

is connected to an engine via a belt, not shown, and the drive shaft

50

rotates the rotor

31

due to the drive force of the engine.

The flowrate control valve

4

is housed in the valve hole formed on the pulley

51

side in the body

1

so that it is effectively perpendicular to the drive shaft

50

, as shown in FIG.

2

. Hydraulic fluid whereof the flowrate is regulated is supplied under pressure to the outside of the vane pump from a discharge port, not shown, and is supplied for example to a power steering device.

In

FIG. 1

, the body

1

is formed so that the tip end

50

A of the drive shaft

50

opposite to the pulley

51

extends by a predetermined length from the open end face

1

A of the body

1

. A concave space is formed in the body

1

from the open end face

1

A, and the pump cartridge

3

and side plate

8

being housed in this space. The cover

2

which is formed by diecasting is tightened to the open end face

1

A of the body

1

.

The pump cartridge

3

comes in contact with an end face

2

A of the cover

2

opposite to the body

1

. The side plate

8

is interposed between the pump cartridge

3

and a base of the inner circumference of the body

1

which is formed in a concave shape. The cam ring

30

in the pump cartridge

3

is gripped between the side plate

8

and cover

2

.

The pump cartridge

3

comprises the rotor

31

which engages with splines

53

on the drive shaft

50

inside the cylindrical cam ring

30

, and vanes

32

supported by the rotor

31

which slide on the inner circumference of the cam ring

30

as shown in FIG.

2

.

As shown in

FIG. 10

, a pair of engaging holes

30

A,

30

A are symmetrically formed in the cam ring

30

. A pair of dowel pins

42

,

42

have one of their ends fixed in holes

84

,

84

in the side plate

8

which is substantially disk-shaped as shown in FIG.

9

. When the dowel pins

42

,

42

are passed through the engaging holes

30

A,

30

A, the rotation of the cam ring

30

is restricted, and the pump cartridge

3

and side plate

8

are joined in a predetermined positional relationship. The side plate

8

is formed by sintering or the like.

A discharge area of the pump cartridge

3

faces a high pressure port

81

in the side plate

8

, and is connected with the high pressure chamber

12

in the body

1

in a predetermined positional relationship. Likewise, an intake area of the pump cartridge

3

is connected with first and second low pressure ports

82

,

6

A formed in the side plate

8

and cover

2

(

FIG. 9

,

FIG. 4

) in a predetermined positional relationship. Due to this, the inner circumference of the cam ring

30

can aspirate hydraulic fluid substantially uniformly from both sides in the axial direction.

In

FIG. 1

, the lower part of a cylindrical intake connector

5

joined to the upper part of the body

1

connects with a low pressure passage

9

formed substantially parallel to the drive shaft

50

. The left-hand side of this low pressure passage

9

in the figure also opens into an upper position in the base of the concave space of the body

1

.

An intake chamber

10

is formed between the upper inner circumference of the concave space of the body

1

and the upper outer circumference of the cam ring

30

and side plate

8

. The low pressure passage

9

which opens into the base of the inner circumference of the concave space connects with the intake chamber

10

, and the right-hand side of the low pressure passage

9

connects with a bypass side of the flowrate control valve

4

which discharges surplus flowrate. Surplus flowrate from the flowrate control valve

4

and low pressure hydraulic fluid supplied from the intake connector

5

are combined, and flow into the intake chamber

10

formed in the body

1

via the low pressure passage

9

.

The high pressure chamber

12

connected to the high pressure port

81

of the side plate

8

, is connected to the flowrate control valve

4

via a passage

11

which slopes upwards as shown in FIG.

1

. Hydraulic fluid which has leaked from the pump cartridge

3

flows toward the pulley

51

along the drive shaft

50

, and is led to the low pressure passage

9

via a drain passage

19

provided from the lower end of the intake connector

5

to the drive shaft

50

. The axial line of this drain passage

19

is formed in a line with the intake connector

5

in a plane substantially perpendicular to the drive shaft

50

.

The side plate

8

interposed between the base of the concave space of the body

1

and the pump cartridge

3

is formed by a disk-shaped member as shown in FIG.

9

(A), (B). An end face

8

A comes in contact with the body

1

, and an end face

8

B comes in contact with the cam ring

30

.

Hence, as described hereabove, the pair of high pressure ports

81

,

81

are formed symmetrically in the side plate

8

on either side of the drive shaft

50

at a position corresponding to the discharge area of the cam ring

30

.

A pair of steps at positions distant by 90° from the high pressure ports

81

,

81

in a circumferential direction are formed on the surface

8

B which comes in contact with the cam ring

30

and on which the rotor

31

and vanes

32

slide. The steps form low pressure ports

82

,

82

, which are first low pressure ports. These low pressure ports

82

are formed in a gap between the cam ring

30

and side plate

8

, and connect with the intake chamber

10

surrounding the upper outer circumference of the cam ring

30

and side plate

8

.

As shown in

FIG. 2

, hydraulic fluid aspirated from the low pressure passage

9

open to the part above the cam ring

30

to the intake chamber

10

, is led to the low pressure ports

82

,

82

opening between the cam ring

30

and side plate

8

via branch passages

13

,

13

along the outer circumference of the cam ring

30

.

Branch passages

13

are on the opening side of a concave space

1

C of predetermined internal diameter engaging with the outer circumference of the side plate

8

. These branch passages

13

are formed between an inner wall

1

D formed on the inner circumference of the body

1

and the upper outer circumference of the cam ring

30

, as shown in FIG.

5

-FIG.

7

. The widths of these branch passages

13

become progressively larger towards the intake chamber

10

as shown in FIG.

6

and

FIG. 7

(f

1

>f

2

).

On the side plate

8

side of the cam ring

30

, hydraulic fluid which has flowed into the intake chamber

10

via the branch passages

13

,

13

is distributed to the left and right along the cam ring

30

. This hydraulic fluid is aspirated almost uniformly into the intake area of the cam ring

30

from the left and right of

FIG. 2

via the low pressure ports

82

.

A substantially annular vane back pressure groove

83

of predetermined depth is formed in the end face

8

B of the side plate

8

so as to lead back pressure to the bases of the vanes

32

.

Branch grooves

6

,

6

of predetermined depth are formed as low pressure distributing grooves in the end face

2

A of the cover

2

from a position facing the low pressure passage

9

opening into the body

1

along the outer circumference of the cam ring

30

in contact with the end face

2

A.

As shown in FIG.

4

(A), the branch grooves

6

,

6

are formed from a position

9

′ facing the low pressure passage

9

up to the horizontal direction (left-right direction in the figure) spanning an escape hole

24

. The escape hole

24

is formed at a predetermined depth so that the tip end

50

A of the drive shaft

50

does not come in contact with the end face

2

A. The branch grooves

6

,

6

extend further in a substantially horizontal direction from their lower ends to the escape hole

24

. These extension grooves are formed at a predetermined depth as the pair of low pressure ports

6

A,

6

A facing the intake area of the cam ring

30

. These low pressure ports

6

A,

6

A comprise the second low pressure ports.

Therefore, hydraulic fluid from the intake chamber

10

is distributed to the left and right from the upper part along the branch grooves

6

,

6

. This hydraulic fluid is aspirated substantially uniformly from the left-right direction of

FIG. 4

to the intake area of the cam ring

30

via the pair of low pressure ports

6

A,

6

A.

Due to the branch passages

13

,

13

formed between the upper outer circumference of the cam ring

30

and the inner circumference of the body

1

, the low pressure ports

82

,

82

formed as steps in the side plate

8

and the branch grooves

6

,

6

formed in the cover

2

, the pump cartridge aspirates hydraulic fluid substantially uniformly to both sides of the axial direction of the low pressure ports

82

,

82

and the low pressure ports

6

A,

6

A formed in a horizontal direction.

As in the case of the side plate

8

, a substantially circular vane back pressure groove

23

is also formed in the end face

2

A of the cover

2

at a position corresponding to the base ends of the vanes

32

in the rotor

31

. Due to this, back pressure can be led to the base ends of the vanes

32

via the vane back pressure groove

83

in the side plate

8

.

The body

1

and cover

2

are tightened by bolts. As shown in FIG.

5

and

FIG. 7

, plural bolt seats

7

comprising bolt holes

41

are arranged at a predetermined interval on the outer circumference of the open end face

1

A of the body

1

. Bolt holes

21

are formed in the cover

2

at positions corresponding to the bolt holes

41

. The cover

2

is tightened to the body

1

by screwing bolts passing through the bolt holes

21

of the cover

2

into the bolt holes

41

.

A loop-shaped seal ring groove

14

of predetermined depth is formed in the inner circumference of the opening end face

1

A, as shown in FIG.

5

. As shown in FIG.

1

and

FIG. 2

, a loop-shaped low pressure seal ring

15

is embedded in the seal ring groove

14

, and pressed in and gripped between the end face

2

A of the cover

2

and the seal ring groove

14

. The low pressure seal ring

15

seals hydraulic fluid in the low pressure intake chamber

10

and the branch passages

13

,

13

.

An end face

1

B, which is lower by a height h

2

than the open end face

1

A, is partially formed on the inside of the seal ring groove

14

facing the intake chamber

10

and branch passages

13

, as shown in FIG.

6

-FIG.

8

.

The four bolt seats

7

which are formed at predetermined positions are higher by a height h1 than the open end face

1

A, as shown in FIG.

8

. The bolt seats

7

extend toward the cover

2

. When bolts, not shown, which pass through the bolt holes

21

formed in the cover

2

, are screwed into the bolt holes

41

in the bolt seats

7

, the end face

2

A of the cover

2

comes in contact with the body

1

only at the plural bolt seats

7

. When the seal ring

15

is pushed into and gripped between the end face

2

A and the seal ring groove

14

, the inside of the body

1

is sealed from the outside. A gap h1 depending on the extending height of the bolt seats

7

is formed between the end face

1

A of the body

1

and the end face

2

A of the cover

2

, so that the seal ring

15

is exposed to the outside between the bolt seats

7

. The end face

1

B is not formed near the lower outer circumference of the cam ring

30

, but the lower outer circumference of the cam ring

30

supports the internal circumference of the seal ring

15

.

Next, a ring groove

52

engaging with a cir clip

33

and a spline

53

for restricting relative rotation with the rotor

31

are formed on the drive shaft

50

driving the rotor

31

in sequence from the tip end

50

A extending towards the escape hole

24

of the cover

2

, as shown in FIG.

1

.

The ring groove

52

and splines

53

at the tip end

50

A are formed with a predetermined outer diameter. The base end

50

B side of the drive shaft

50

is supported in the body

1

by a bearing

18

. The base end

50

B side of the drive shaft

50

which is joined to the pulley

51

is formed of a part

55

having a larger outer diameter than a small diameter part

54

. A step

56

is formed between this large diameter part

55

and small diameter part

54

.

The step

56

is situated more to the right than the side plate

8

in

FIG. 1

, FIG.

11

. The small diameter part

54

of the drive shaft

50

passes through an axial hole

80

in the side plate

8

.

A shoulder part