Pump equipment with plural rotary pumps and method for assembling same

CROSS REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of Japanese Patent Application No. H.10-112436 filed on Apr. 22,1998, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention:

The present invention relates to a pump equipment having plural rotary pumps and a method for assembling the pump equipment. In particular, the present invention is preferably applied to an internal gear pump such as a trochoid pump or the like for brake apparatus for vehicles.

2. Description of Related Art:

A rotary pump, for example, an internal gear pump, is comprised of a drive shaft to be driven by a motor, an inner rotor and an outer rotor to be rotated by the drive shaft and a casing for containing the drive shaft and the inner and outer rotors. The casing is provided with a pump room in which the inner and outer rotors are contained, an intake port and a discharge port for sucking and discharging oil and a shaft hole communicating to the pump room from the motor side. The drive shaft is fitted into the inner rotor through the shaft hole.

As an example of the pump in which two rotary pumps are rotated by a drive shaft, a tandem pump equipment is described in JP-A-H.9-126157. In the tandem pump equipment, the discharge ports of the two rotary pumps are provided, respectively, in the same direction from the drive shaft and the intake ports, respectively, in the same direction from the drive shaft, but in the opposite direction from the respective discharge ports. Each pressure at the respective discharge ports of the two rotary pumps is reacted in the same direction against the drive shaft and the drive shaft receives an unbalance force so that the pump operation may be adversely affected due to the bending of the shaft.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a pump equipment having a plural of rotary pumps capable of smoothly rotating the pumps because of a limited bending of their drive shafts. The pump equipment has a construction that the respective discharge ports of the rotary pumps are located at the points which are nearly symmetrical with respect to the center axis of the drive shaft. The respective reaction forces against the drive shaft to be produced by the high pressure at the respective discharge ports may be counterbalanced each other so that the possible bending of the drive shaft may be limited.

As an another aspect of the present invention for limiting the bending of the drive shaft for the pump equipment having two rotary pumps, the intake and discharge fluid conduits of one pump and the intake and discharge fluid conduits of the other pump are arranged at the locations which are, not between the pumps, but outside from the pumps, respectively. Preferably, these locations of the intake and discharge fluid conduits will serve to narrow the space between the two pumps so that the pump equipment may become compact.

As a further aspect of the present invention, two bearings for holding the drive shaft are arranged outside the two pumps, that is, at the respective positions between which the two pumps are inserted. The forces due to the high pressure at the discharge ports are reacted against the drive shaft inside the two bearings. Therefor, the bending of the drive shaft is more limited, compared with a case that the forces are reacted against the drive shaft outside the two bearings.

Furthermore, it is one of the objects to provide a method for assembling the pump equipment in such a way that a part of the peripheral border between respective cylindrical members piled up for constituting the casing is tentatively welded by laser beam at first and, then, all around the peripheral borders are finally welded. Such a method is effective for limiting a deformation or a position shift of the respective members, because the energy of the tentative spot welding by laser beam is less than that of the final welding and, therefor, the deformation force by laser beam is not so strongly influenced.

It is preferable to apply to the welding portions the laser beams from plural side positions at the same time so as to counterbalance each other the respective forces given by laser beams to the welding portions. This method may be used in the above tentative spot welding. Furthermore, such a method makes it possible to weld all around the peripheral borders without causing the deformation or the position shift of the respective cylindrical members, even if the tentative spot welding is eliminated and the relatively large energy of laser beams is applied at the same time to the welding portions.

It is a final object of the present invention to provide a brake apparatus having a hydraulic circuit in which the pump equipment described above is applied. The pump equipment is used for increasing fluid pressure to wheel cylinders in the hydraulic circuit. In particular, each of plural rotary pumps is operative in each of fluid conduits separately provided in the hydraulic circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will be appreciated, as well as methods of operation and the function of the related parts, from a study of the following detailed description, the appended claims, and the drawings, all of which form a part of this application. In the drawings:

FIG. 1

is an outline structure of a brake apparatus;

FIG. 2

is a schematic sectional view of a pump equipment;

FIG. 3A

is a sectional view taken along a line IIIA—IIIA of

FIG. 2

;

FIG. 3B

is a sectional view taken along a line IVA—IVA of

FIG. 3A

;

FIG. 4A

is a sectional view taken along a line IIIB—IIIB of

FIG. 2

;

FIG. 4B

is a sectional view taken along a line of

FIG. 4A

;

FIG. 5

is a sectional view of a welding equipment;

FIG. 6

is an outlook viewed from a line of VI—VI of FIG.

5

.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1

shows an outline structure of a brake apparatus to which a trochoid pump is applied as a rotary pump. The basic constitution of the brake apparatus will be described with reference to FIG.

1

. In this embodiment, a brake apparatus is applied to a vehicle provided with a hydraulic circuit of a diagonal conduit system having a first conduit connecting wheel cylinders of a front right wheel and a rear left wheel and a second conduit connecting wheel cylinders of a front left wheel and a rear right wheel. The vehicle is a four wheel vehicle of front wheel drive.

As shown in

FIG. 1

, a brake pedal

1

is connected to a booster

2

. Brake depression force (brake pedal stroke) is boosted by the booster

2

.

Further, the booster

2

is provided with a rod for transmitting boosted depression force to a master cylinder

3

. In detail, the master cylinder

3

generates master cylinder pressure when the rod pushes a master piston arranged in the master cylinder

3

. The brake pedal

1

, the booster

2

and the master cylinder

3

correspond to a brake fluid pressure generating device.

The master cylinder

3

is provided with a master reservoir

3

a

for supplying brake fluid into the master cylinder

3

or storing extra brake fluid of the master cylinder

3

.

Further, the master cylinder pressure is transmitted to a wheel cylinder

4

for a front right wheel (FR) and a wheel cylinder

5

for a rear left wheel (RL) via a brake assist system provided with a function of an antilock brake system (hereinafter, referred to as ABS). In the following explanation, the brake apparatus will be described with respect to the hydraulic circuit in the first conduit connecting the wheel cylinders of a front right wheel (FR) and a rear left wheel (RL). The explanation for the second conduit connecting the wheel cylinders of a front left wheel (FL) and a rear right wheel (RR) will be omitted since the hydraulic circuit in the second conduit is quite similar to that in the first conduit.

The brake apparatus is provided with a conduit (main conduit) A connected to the master cylinder

3

. A proportioning valve (PV)

22

is disposed in the main conduit A. The main conduit A is divided into two portions by the proportioning valve

22

. That is, the main conduit A is divided into a first conduit Al from the master cylinder

3

to the proportioning valve

22

and a second conduit A

2

from the proportioning valve

22

to the respective wheel cylinders

4

and

5

.

The proportioning valve

22

has a function of transmitting a reference pressure of a brake fluid to the downstream side with a predetermined attenuation rate when the braking fluid flows in the positive direction (in this embodiment, a direction from the side of the wheel cylinder to the side of the master cylinder is the positive direction). That is, by inversely connecting the proportioning valve

22

as shown in

FIG. 1

, pressure of the brake fluid on the side of the second conduit A

2

becomes the reference pressure.

Further, the second conduit A

2

branches out two conduits. A pressure increasing control valve

30

for controlling an increase of brake fluid pressure of the wheel cylinder

4

is installed to one of the branched conduits and a pressure increasing control valve

31

for controlling an increase of brake fluid pressure of the wheel cylinder

5

is installed to the other thereof.

The pressure increasing control valves

30

and

31

are two-position valves capable of controlling communicating and shut-off states by an electronic control unit (hereinafter, referred to as ECU). When the two-position valves are controlled to a communicating state, the master cylinder pressure or the brake fluid pressure produced by a pump

10

can be applied to the respective wheel cylinders

4

and

5

.

In the normal braking operation where ABS is not controlled by the ECU as in the case where pressure reduction of the wheel cylinder pressure is not carried out, the pressure increasing control valves

30

and

31

are always controlled in the communicating state. Safety valves

30

a

and

31

a

are installed in parallel with the pressure increasing control valves

30

and

31

, respectively. The safety valves

30

a

and

31

a

allows the brake fluid to swiftly return from the wheel cylinders

4

and

5

to the master cylinder

3

when ABS control has been finished by stopping depression of the brake pedal

1

.

Pressure reducing control valves

32

and

33

capable of controlling communicating and shut-off states by the ECU are respectively arranged at conduits B connecting the second conduits A

2

between the pressure increasing control valves

30

and

31

and the wheel cylinders

4

and

5

, and a reservoir port

20

a

of a reservoir

20

. In the normal braking operation, the pressure reducing control valves

32

and

33

are always brought into a cut-off state.

A rotary pump

10

is arranged at a conduit C connecting the reservoir hole

20

a

of the reservoir

20

and the second conduit A

2

between the proportioning valve

22

and the pressure increasing control valves

30

and

31

. Safety valves

10

a

and

10

b

are disposed in the conduit C on both sides of the rotary pump

10

. The safety valves

10

a

and

10

b

may be built in the rotary pump

10

. A motor

11

is connected to the rotary pump

10

to drive the rotary pump

10

. A detailed explanation of the rotary pump

10

will be given later.

A damper

12

is arranged on the discharge side of the rotary pump

10

in the conduit C to alleviate pulsation of the brake fluid delivered by the rotary pump

10

. An auxiliary conduit D is installed to connect the conduit C between the reservoir

20

and the rotary pump

10

, and the master cylinder

3

. The rotary pump

10

sucks the brake fluid of the first conduit A

1

via the auxiliary conduit D and discharges it to the second conduit A

2

, whereby the brake fluid pressures of the wheel cylinders

4

and

5

are made higher than the master cylinder pressure. As a result, wheel braking forces of the wheel cylinders

4

and

5

are increased. The proportioning valve

22

works to hold the pressure difference between the master cylinder pressure and the wheel cylinder pressure.

A control valve

34

is installed in the auxiliary conduit D. The control valve

34

is always brought into a cut-off state in the normal braking operation.

A check valve

21

is arranged between a connection point of the conduit C and the auxiliary conduit D and the reservoir

20

to prevent the brake fluid drawn via the auxiliary conduit D from flowing in a reverse direction to the reservoir

20

.

A control valve

40

is disposed between the proportioning valve

22

and the pressure increasing control valves

30

and

31

in the second conduit A

2

. The control valve

40

is normally controlled in a communicating state. However, the control valve

40

is switched to a differential pressure producing state to hold the pressure difference between the master cylinder pressure and the wheel cylinder pressure, in a case that the vehicle is rapidly braked, when the master cylinder pressure is too low to obtain the necessary wheel cylinder pressure by some reasons, for example, in a case where the boosting function of the booster

2

is lowered or lost and, at this time, the pump

10

is operated. Also, the control valve

40

is switched to the differential pressure producing state when traction control (TRC) is carried out. Though the control valve

40

and the proportioning valve

22

are employed in this embodiment, it is possible to have only a pressure difference control valve for holding the pressure difference between the master cylinder and the wheel cylinder.

The structure of the pump equipment

100

will be described with reference to FIG.

2

. As mentioned above, the brake apparatus is provided with the hydraulic circuit having first and second conduit lines. The pump equipment

100

is constituted by a casing

50

, a drive shaft

54

to be driven by the motor

11

shown in

FIG. 1

, the first rotary pump

10

for the first conduit line and a second rotary pump

13

for the second conduit line.

As described in

FIG. 2

, the casing

50

is constituted by first, second and third cylinders

71

a

,

71

b

and

71

c

and first and second cylindrical center plates

73

a

and

73

b

. After piling up in order the first cylinder

71

a

, the first cylindrical center plate

73

a

, the second cylinder

71

b

, the second cylindrical center plate

73

b

and the third cylinder

71

c

, the casing

50

of the pump equipment

100

is assembled by welding all of peripheral borders of the piled up cylinders

71

a

,

71

b

and

71

c

and cylindrical center plates

73

a

and

73

b

. A pump room

50

a

of the first rotary pump

10

is constructed by putting the first cylindrical center plate

73

a

between the first and second cylinders

71

a

and

71

b

. On the other hand, a pump room

50

b

of the second rotary pump

13

is constructed by putting the second cylindrical center plate

73

b

between the second and third cylinders

71

b

and

71

c.

The first, second and third cylinders are respectively provided with first, second and third center bores

72

a

,

72

b

and

72

c

. A roll type first bearing

91

is disposed at the internal periphery of the first center bore

72

a

and a roll type second bearing

92

at the internal periphery of the third center bore

72

c

. The drive shaft

54

inserted through the first, second and third center bores

72

a

,

72

b

and

72

c

is held between the first and second bearings

91

and

92

. Consequently, the two rotary pumps

10

and

13

may be put between the bearings

91

and

92

.

The third cylinder

71

c

has a hollow at the opposite side from the surface where the second cylindrical center plate is welded. The drive shaft

54

has a key

54

a

which is formed by being partly projected from its end portion and protruded into the hollow of the third cylinder

71

c

. The key

54

a

is used to couple the drive shaft

54

with a motor shaft of the motor

11

. An oil seal

93

is disposed in the hollow of the third cylinder

71

c

in such a way that the outside surface of the drive shaft may be wrapped up.

The outside surfaces of the first, second and third cylinders

71

a

,

71

b

and

71

c

are provided respectively with flange portions

74

a

,

74

b

and

74

c

, each of which is protruded further from the portions where the first, second and third cylinders

71

a

,

71

b

and

71

c

and the first and second cylindrical center plates

73

a

and

73

b

are welded. The flange portions

74

a

,

74

b

and

74

c

are so constructed that the respective outer diameter of the welded portions, even if expanded by welding, may not go beyond the respective outer diameter of the flange portions

74

a

,

74

b

and

74

c

. As the expanded outer diameter of the welded portions never exceeds the outer diameter of o rings(not shown)installed on the outer surface of the casing

50

as the flange portions

74

a

,

74

b

and

74

c

are formed, the pump

100

may be effectively assembled to the brake apparatus. Further, the outer surface of the third cylinder is provided with a flange

74

d

, the outer diameter of which is larger than that of the flange portion

74

c

. The flange

74

d

is used as a position setting reference for assembling and welding the casing

50

of the pump equipment

100

, as described later. Screws

94

and

95

are for the temporal fitting before the welding, as explained in detail later.

FIG. 3A

is a sectional view taken along a line IIIA—IIIA of FIG.

2

and

FIG. 3B

is a sectional view taken along a line IIIA—IIIA of FIG.

3

A.

FIG. 4A

is a sectional view taken along a line IVA—IVA of FIG.

2

and

FIG. 4B

is a sectional view taken along a line IVB—IVB of FIG.

4

A. First, the structure of the rotary pump

10

will be described with reference to

FIGS. 3A and 3B

.

An outer rotor

51

and an inner rotor

52

are contained in the pump room

50

a

of the casing

50

of the rotary pump

10

. The outer rotor

51

and the inner rotor

52

are assembled in the casing

50

in a state where respective central axes (point X and point Y in the drawing) are shifted from each other. The outer rotor

51

is provided with an inner teeth portion

51

a

at its inner periphery. The inner rotor

52

is provided with an outer teeth portion

52

a

at its outer periphery. The inner teeth portion

51

a

of the outer rotor

51

and the outer teeth portion

52

a

of the inner rotor

52

form a plurality of gap portions

53

and are in mesh with each other. As is apparent from

FIG. 3A

, the rotary pump

10

is a pump of a multiple teeth trochoid type having no partition plate (crescent) in which the gap portions

53

are formed by the inner teeth portion

51

a

of the outer rotor

51

and the outer teeth portion

52

a

of the inner rotor

52

. The inner rotor

52

and the outer rotor

51

share a plurality of contact points (that is, contact faces) at the mesh faces in order to transmit rotation torque of the inner rotor

52

to the outer rotor

51

.

The drive shaft

54

for driving the inner rotor

52

is provided with a key

54

b

, whereby drive force is transmitted from the drive shaft

54

to the inner rotor

52

via the key

54

a

. The outer rotor

51

and the inner rotor

52

are rotatably arranged in the center bore of the cylindrical center plate

73

a

. That is, a rotating unit constituted by the outer rotor

51

and the inner rotor

52

is rotatably incorporated in the pump room

50

a

of the casing

50

. The outer rotor

51

rotates with point X as a rotation axis and the inner rotor

52

rotates with point Y as a rotation axis.

A hole

201

is provided for inserting a pin

251

described in the

FIG. 2

for the position setting at the welding operation as explained later. In the first and second cylinders

71

a

and

71

b

, recesses are also provided at the position corresponding to the hole

201

for inserting the pin

251

, respectively.

When a line running on both point X and point Y respectively corresponding to the rotation axes of the outer rotor

51

and the inner rotor

52

is defined as a center line Z of the rotary pump

10

, an intake port

60

and a discharge port

61

both of which communicate with the pump room

50

a

are formed on the left and right sides of the center line Z in the first cylinder

71

a

. There are also provided with an intake conduit

60

a

extending from the intake port

60

to the intake conduit

19

and a discharge conduit

61

a

extending from the discharge port

61

to the discharge conduit

21

, as described in

FIGS. 2 and 3

. The intake port

60

and the discharge port

61

are arranged at positions communicating with a plurality of gap portions

53

constituted by intake chambers

53

a

and discharge chambers

53

b

. The brake fluid from outside can be sucked into the intake chambers

53

a

via the intake port

60

and the brake fluid in the discharge chambers

53

b

can be discharged to outside via the discharge port

61

.

The first cylinder

71

a

is provided with communicating paths

75

a

and

75

b

for communicating the outer periphery of the outer rotor

51

with the intake port

60

and a communicating path

76

for communicating the outer periphery of the outer rotor

51

with the discharge port

61

. The communicating paths

75

a

and

75

b

are arranged at positions advanced respectively in left and right directions from the center line Z to the intake port

60

by an angle of about 45 centering on point X constituting the rotation axis of the outer rotor

51

. The communicating path

76

is formed to communicate the gap portion

53

most adjacent to the first closed gap portion

53

c

in the plurality of gap portions

53

communicating with the discharge chamber

53

b

with the outer periphery of the outer rotor

51

. Specifically, the communicating path

76

is arranged at a position advanced in right direction from the center line Z to the discharge port

61

by an angle of about 22.5 centering on point X.

Recessed portions

77

a

and

77

b

are formed on a wall face of the first cylindrical center plate

73

a

forming the pump room

50

a

at a position advanced in the left direction from the center line Z to the intake chamber

53

a

by an angle of about 22.5 degrees and at a position advanced in right direction from the center line Z to the discharge chamber

53

b

by an angle of about 90 degrees centering on point X constituting the rotation axis of the outer rotor

51

. Seal members

80

and

81

are respectively installed in the recessed portions

77

a

and

77

b

to restrain the brake fluid from flowing in the outer periphery of the outer rotor

51

. Specifically, the seal members

80

and

81

are arranged respectively at an intermediate point between the communicating paths

75

a

and

76

and the communicating paths

76

and

75

b

. The seal members

80

and

81

serve to separate, in the clearance between the outer rotor

51

and the cylindrical center plate

73

a

, a portion in which pressure of the brake fluid is low from a portion in which pressure of the brake fluid is high. Further, a sealing member

89

is shown in

FIG. 2

disposed in the clearance between an inner surface of the second cylinder

71

b

and the outer surface of the drive shaft

54

for restricting fluid communication between the two rotary pumps

10

and

13

.

The seal members

80

and

81

are constituted by rubber members

80

a

and

81

a

substantially in a shape of a circular cylinder and resin members

80

b

and

81

b

made of Teflon in a shape of a cube. The resin members

80

b

and

81

b

are biased by the rubber members

80

a

and

81

a

to be brought into contact with the outer rotor

51

. That is, more or less error amount is caused in the size of the outer rotor

51

by fabrication error or the like. Accordingly, the error amount can be absorbed by the rubber members

80

a

and

81

a

having elastic force.

The rotary pump

10

has the construction as described above and, hereafter, the rotary pump

13

will be explained according to

FIGS. 4A and 4B

. As the construction of the rotary pump

13

is nearly same as that of the rotary pump

10

, only the different portions thereof will be described and the explanation of the portions having the same reference number as that of the rotary pump

10

will be omitted.

The outer and inner rotors of the rotary pump

13

is contained in a pump room

50

b

constituted by the second cylindrical center plate

73

b

and the second and third cylinders

71

b

and

71

c

. Respective parts and components of the rotary pump

13

are arranged at the positions where the respective parts and components of rotary pump

10

shown in the

FIGS. 3A and 3B

are rotated by an angle of 180 degrees with respect to the center axis of the drive shaft

54

. The third cylinder

71

c

is provided with intake and discharge conduits

62

a

and

63

a

extending respectively from intake and discharge ports

62

and

63

to the second conduit line of the brake apparatus. The positions of the intake and discharge conduits

60

a

and

61

a

in the first cylinder

71

a

and the positions of the intake and discharge conduits

62

a

and

63

a

in the third cylinder

71

c

are opposite each other, in another word, nearly symmetrical, with respect to the center axis of the drive shaft

54

, as illustrated in FIG.

2

.

A hole

202

shown in

FIG. 4A

is for inserting a pin

252

described in

FIG. 2

for the position setting at the welding operation as explained later. In the second and third cylinders

71

b

and

71

c

, recesses are also provided at the position corresponding to the hole

202

for inserting the pin

252

, respectively.

The rotary pumps

10

and

13

constituting the pump equipment

100

are constructed as described above.

Next, an explanation will be given of operation of the brake apparatus and the pump equipment

100

with reference to the rotary pump

10

. The control valve

34

provided in the brake apparatus is pertinently brought into a communicating state when high pressure brake fluid needs to be supplied to the wheel cylinders

4

and

5

, for example, when braking force in correspondence with depressing force of the brake pedal

1

cannot be obtained because of failure of the booster

2

, or when an amount of operating the braking pedal

1

is large. When the control valve

34

is switched in the communication state, the master cylinder pressure generated by depressing the brake pedal

1

is applied to the rotary pump

10

via the auxiliary conduit D.

In the rotary pump

10

, the inner rotor

52

is rotated in accordance with rotation of the drive shaft

54

by driving the motor

11

. In response to rotation of the inner rotor

52

, the outer rotor

51

is also rotated in the same direction by the mesh between the inner teeth portion

51

a

and the outer teeth portion

52

a

. At this time, the volume of each of the gap portions

53

is changed from large to small or vice versa during a time period in which the outer rotor

51

and the inner rotor

52

make one turn. Therefore, the brake fluid is sucked from the intake port

60

to the intake chambers

53

a

and is discharged from the discharge port

61

through the discharge chambers

53

b

to the second conduit A

2

. Pressures of the wheel cylinders can be increased using the discharged brake fluid.

In this way, the rotary pump

10

can carry out a basic pumping operation in which the brake fluid is sucked from the intake port

60

and is discharged from the discharge port