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Variable displacement vane pump

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Variable displacement vane pump


A variable displacement vane pump has an inner peripheral face of a cam ring formed so that in a maximum eccentric state, a radius vector gradually shortens according to the rotation of a rotor in an area from a starting point of a first seal interval to an intermediate point of the first seal interval and an area from an intermediate point of a second seal interval to an end point of the second seal interval. The inner peripheral face of the cam ring is formed so that in a minimum eccentric state, the radius vector is substantially fixed or gradually lengthens according to the rotation of the rotor in other areas.


Browse recent Hitachi Automotive Systems, Ltd. patents - Hitachinaka-shi, JP
USPTO Applicaton #: #20130034460 - Class: 418 24 (USPTO) - 02/07/13 - Class 418 
Rotary Expansible Chamber Devices > With Changeable Working Chamber Magnitude >Spring Or Fluid Biased Movable Member

Inventors: Yoko Tsukada, Shinji Seto, Yukio Uchida

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The Patent Description & Claims data below is from USPTO Patent Application 20130034460, Variable displacement vane pump.

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BACKGROUND

1. Technical Field

The present invention relates to a variable displacement vane pump used for working fluid application equipment such as a power steering for reducing a steering wheel operating force of an automobile for example.

2. Related Art

For the well-known technology related to this type of variable displacement vane pump, a variable displacement pump (JP-A No. 2002-115673) can be given for an example, the variable displacement pump having structure that an inside diameter in an intermediate interval between a suction interval and a discharge interval in a pump room of a cam ring forms a negative sloping curve with an end of a suction port as a starting point so as to prevent a pulsation phenomenon of working fluid in a large eccentric area of the cam ring and further, the negative sloping curve and a complete round curve are connected by a higher order curve.

Generally, in a variable displacement vane pump, in a fixed displacement area equivalent to a low-speed area of the pump in which discharge per one rotation is fixed, when a situation in which a vane is separated from an inner peripheral face of a cam ring occurs, pressure pulsation is caused or in a variable displacement area equivalent to a high-speed area of the pump in which discharge per one rotation decreases as the rotation speed of the pump increases, vibration is apt to grow by the unbalance of pressure, compared with a case of a fixed displacement vane pump, and as noise is made by the pressure pulsation and the vibration, it has been a technical objective to reduce such noise.

In the variable displacement vane pump disclosed in JP-A No. 2002-115673, to reduce noise by the separation of a vane, in a maximum eccentric state in which the eccentricity to a rotor of the cam ring is maximum, a distance to the rotational center of the rotor is made to gradually shorten according to the rotation of the rotor in an area from a termination of a suction port to a starting end of a discharge port and an area from a termination of the discharge port to a starting end of the suction port on an inner peripheral face of the cam ring, hereby, the separation of the vane is prevented and the occurrence of noise is restrained.

However, as the compressibility of the volume of the pump room increases in a variable displacement area and peak pressure grows when the inner peripheral face of the cam ring has such a shape, the variable displacement vane pump has a problem that noise by vibration is apt to be made.

In short, the variable displacement vane pump disclosed in JP-A No. 2002-115673 has structure that even if the separation of the vane in a fixed displacement area is restrained and the occurrence of noise caused by pressure pulsation can be prevented, a peak of pressure in the pump room in the variable displacement area is not restrained and it is difficult to prevent the occurrence of noise by vibration.

SUMMARY

The present invention is made in view of such a problem and a technical object of the present invention is to provide a variable displacement vane pump having structure that the separation of a vane in a fixed displacement area and a peak of pressure in a pump room in a variable displacement area are restrained and the occurrence of noise caused by pressure pulsation and vibration can be fully prevented.

To achieve the technical object, in accordance with a first feature of the present invention, there is provided a variable displacement vane pump for transmitting steering operation on a steering wheel to a steered wheel and supplying working fluid to a steering gear for a vehicle that generates steering assist force by hydraulic pressure of the working fluid. The variable displacement vane pump includes a pump housing equipped with a pump element storage part, a driving shaft journaled to the pump housing, a rotor provided in the pump housing, rotatively driven by the driving shaft and having plural slots in a circumferential direction, plural vanes provided in a freely projecting/retreating manner in the plural slots, a cam ring annularly formed movably on/over the pump element storage part and forming plural pump rooms together with the rotor and the plural vanes on an inner peripheral side and a cam ring control mechanism that is provided to the pump housing and controls eccentricity to the rotor of the cam ring. The pump housing is provided with a suction port open to an area in which volume of the plural pump rooms increases according to the rotation of the rotor and a discharge port open to an area in which the volume of the plural pump rooms decreases. An inner peripheral face of the cam ring is formed so that in a maximum eccentric state in which eccentricity to the rotor of the cam ring is maximum, a distance to the rotational center of the rotor gradually shortens according to the rotation of the rotor in at least one of an area from a termination of the suction port to an intermediate point of the termination of the suction port and a starting end of the discharge port and an area from an intermediate point of a termination of the discharge port and a starting end of the suction port to the starting end of the suction port in a rotational direction of the rotor, and the inner peripheral face of the cam ring is formed so that in a minimum eccentric state in which the eccentricity to the rotor of the cam ring is minimum, the distance to the rotational center of the rotor is substantially fixed or gradually lengthens according to the rotation of the rotor in at least one of at least a part of an area from the intermediate point of the termination of the suction port and the starting end of the discharge port to the starting end of the discharge port and at least a part of an area from the termination of the discharge port to the intermediate point of the termination of the discharge port and the starting end of the suction port.

In accordance with a second feature, in addition to the first feature, the driving shaft is rotatively driven by an engine of the vehicle and the inner peripheral face of the cam ring is formed so that when the vehicle is run, the distance to the rotational center of the rotor is substantially fixed or gradually lengthens according to the rotation of the rotor in at least one of at least a part of the area from the intermediate point of the termination of the suction port and the starting end of the discharge port to the starting end of the discharge port and at least a part of the area from the termination of the discharge port to the intermediate point of the termination of the discharge port and the starting end of the suction port.

In accordance with a third feature, in addition to the first feature, the driving shaft is rotatively driven by the engine of the vehicle and the inner peripheral face of the cam ring is formed so that when engine speed is 1500 rpm or more every minute, the distance to the rotational center of the rotor is substantially fixed or gradually lengthens according to the rotation of the rotor in at least one of at least a part of the area from the intermediate point of the termination of the suction port and the starting end of the discharge port to the starting end of the discharge port and at least a part of the area from the termination of the discharge port to the intermediate point of the termination of the discharge port and the starting end of the suction port.

In accordance with a fourth feature, in addition to the first feature, the inner peripheral face of the cam ring is formed so that in the maximum eccentric state, at least one of the area from the termination of the suction port to the intermediate point of the termination of the suction port and the starting end of the discharge port and the area from the intermediate point of the termination of the discharge port and the starting end of the suction port to the starting end of the suction port and areas before and after at least the one that connect with at least the one are connected by a higher order curve and the inner peripheral face of the cam ring is formed so that in the minimum eccentric state, at least one of the area from the intermediate point of the termination of the suction port and the starting end of the discharge port to the starting end of the discharge port and the area from the termination of the discharge port to the intermediate point of the termination of the discharge port and the starting end of the suction port and areas before and after at least the one that connect with at least the one are connected by a higher order curve.

In accordance with a fifth feature, in addition to the first feature, the inner peripheral face of the cam ring is formed so that in the minimum eccentric state, the distance to the rotational center of the rotor gradually lengthens according to the rotation of the rotor in at least one of at least a part of the area from the intermediate point of the termination of the suction port and the starting end of the discharge port to the starting end of the discharge port and at least a part of the area from the termination of the discharge port to the intermediate point of the termination of the discharge port and the starting end of the suction port.

In accordance with a sixth feature, in addition to the first feature, the eccentricity to the rotor of the cam ring is controlled by swinging or rolling the cam ring in a state in which the cam ring is supported by a supporting face provided on a side of the discharge port of an inner peripheral face of the pump element storage part.

In accordance with a seventh feature, in addition to the sixth feature, the center of an inside diameter of the cam ring is located on the side of the suction port apart from the center of the rotor in an unloaded condition in which differential pressure between pressure on the side of the suction port and pressure on the side of the discharge port does not act on the driving shaft, the rotor and the cam ring, and in a state in which the driving shaft is elastically deformed on the side of the suction port by the action of the differential pressure, a relative position based upon a port reference line is located on the side of the discharge port apart from the relative position in the unloaded condition the cam ring is rollably supported by the supporting face provided on the side of the discharge port of the inner peripheral face of the pump element storage part and the supporting face is formed so that the center of the inside diameter of the cam ring gradually separates on the side of the discharge port from the port reference line as the cam ring is rolled in a direction from the maximum eccentric state to the minimum eccentric state.

In accordance with an eighth feature, in addition to the first feature, the inner peripheral face of the cam ring is formed so that in the maximum eccentric state, the distance to the rotational center of the rotor gradually shortens according to the rotation of the rotor in the area from the termination of the suction port to the intermediate point of the termination of the suction port and the starting end of the discharge port in the rotational direction of the rotor and the inner peripheral face of the cam ring is formed so that in the minimum eccentric state, the distance to the rotational center of the rotor is substantially fixed or gradually lengthens according to the rotation of the rotor in at least a part of the area from the intermediate point of the termination of the suction port and the starting end of the discharge port to the starting end of the discharge port.

In accordance with a ninth feature, in addition to the eighth feature, the inner peripheral face of the cam ring is formed so that in the maximum eccentric state, the distance to the rotational center of the rotor gradually shortens according to the rotation of the rotor in the area from the termination of the suction port to the intermediate point of the termination of suction port and the starting end of the discharge port and the area from the intermediate point of the termination of the discharge port and the starting end of the suction port in the rotational direction of the rotor and the inner peripheral face of the cam ring is formed so that in the minimum eccentric state, the distance to the rotational center of the rotor is substantially fixed or gradually lengthens according to the rotation of the rotor in at least a part of the area from the intermediate point of the termination of the suction port and the starting end of the discharge port to the starting end of the discharge port and at least a part of the area from the termination of the discharge port to the intermediate point of the termination of the discharge port and the starting end of the suction port.

In accordance with a tenth feature, in addition to the first feature, the plural odd slots and the plural odd vanes are provided to the rotor.

In accordance with an eleventh feature of the present invention, there is provided a variable displacement vane pump for transmitting steering operation on a steering wheel to a steered wheel and supplying working fluid to a steering gear for a vehicle that generates steering assist force by the hydraulic pressure of the working fluid. The variable displacement vane pump includes a pump housing equipped with a pump element storage part, a driving shaft journaled to the pump housing, a rotor provided in the pump housing, rotatively driven by the driving shaft and having plural slots in a circumferential direction, plural vanes provided in a freely projecting/retreating manner in the plural slots, a cam ring annularly formed movably on/over the pump element storage part and forming plural pump rooms together with the rotor and the plural vanes on an inner peripheral side and a cam ring control mechanism that is provided to the pump housing and controls eccentricity to the rotor of the cam ring. The pump housing is provided with a suction port open to an area in which volume of the plural pump rooms increases according to rotation of the rotor and a discharge port open to an area in which the volume of the plural pump rooms decreases, and an inner peripheral face of the cam ring is formed so that in a maximum eccentric state in which the eccentricity to the rotor of the cam ring is maximum, a distance to the rotational center of the rotor gradually shortens according to the rotation of the rotor in at least one of an area from a termination of the suction port to a starting end of the discharge port in a rotational direction of the rotor and an area from a termination of the discharge port to a starting end of the suction port and the inner peripheral face of the cam ring is formed so that in a minimum eccentric state in which the eccentricity to the rotor of the cam ring is minimum, distance to the rotational center of the rotor is substantially fixed or gradually lengthens according to the rotation of the rotor in at least one of at least a part of the area from the termination of the suction port to the starting end of the discharge port and at least a part of the area from the termination of the discharge port to the starting end of the suction port.

In accordance with a twelfth feature, in addition to the eleventh feature, the driving shaft is rotatively driven by an engine of the vehicle and the inner peripheral face of the cam ring is formed so that when the vehicle is run, the distance to the rotational center of the rotor is substantially fixed or gradually lengthens according to the rotation of the rotor in at least one of at least a part of the area from the termination of the suction port to the starting end of the discharge port and at least a part of the area from the termination of the discharge port to the starting end of the suction port.

In accordance with a thirteenth feature, in addition to the eleventh feature, the driving shaft is rotatively driven by the engine of the vehicle and the inner peripheral face of the cam ring is formed so that when engine speed is 1500 rpm or more every minute, the distance to the rotational center of the rotor is substantially fixed or gradually lengthens according to the rotation of the rotor in at least one of at least a part of the area from the termination of the suction port to the starting end of the discharge port and at least a part of the area from the termination of the discharge port to the starting end of the suction port.

In accordance with a fourteenth feature, in addition to the eleventh feature, the eccentricity to the rotor is controlled by swinging or rolling the cam ring in a state in which the cam ring is supported by a supporting face provided on a side of the discharge port of an inner peripheral face of the pump element storage part.

In accordance with a fifteenth feature, in addition to the fourteenth feature, the center of an inside diameter of the cam ring is located on the side of the suction port based upon a port reference line that joins the intermediate point of the termination of the suction port and the starting end of the discharge port and the center of the rotor in an unloaded condition in which differential pressure between pressure on the side of the suction port and pressure on the side of the discharge port does not act on the driving shaft, the rotor and the cam ring, a relative position based upon the port reference line in the unloaded condition in a state in which the driving shaft is elastically deformed on the side of the suction port by the action of the differential pressure is located on the side of the discharge port apart from the relative position the cam ring is rollably supported by the supporting face provided on the side of the discharge port of the inner peripheral face of the pump element storage part and the supporting face is formed so that the center of the inside diameter of the cam ring gradually separates from the port reference line as the cam ring is rolled in a direction from the maximum eccentric state to the minimum eccentric state.

In accordance with a sixteenth feature of the present invention, there is provided a variable displacement vane pump for transmitting steering operation on a steering wheel to a steered wheel and supplying working fluid to a steering gear for a vehicle that generates steering assist force by the hydraulic pressure of the working fluid. The variable displacement vane pump includes a pump housing equipped with a pump element storage part, a driving shaft journaled to the pump housing, a rotor provided in the pump housing, rotatively driven by the driving shaft and having plural slots in a circumferential direction, plural vanes movably provided in the plural slots, a cam ring annularly formed movably on/over the pump element storage part and forming plural pump rooms together with the rotor and the plural vanes on an inner peripheral side and a cam ring control mechanism that is provided to the pump housing and controls eccentricity to the rotor of the cam ring. The pump housing is provided with a suction port open to an area in which volume of the plural pump rooms increases according to rotation of the rotor and a discharge port open to an area in which the volume of the plural pump rooms decreases, an inner peripheral face of the cam ring is formed so that in a maximum eccentric state in which the eccentricity to the rotor of the cam ring is maximum in a state in which the cam ring is relatively moved from the side of the suction port to the side of the discharge port by the action on the driving shaft, the rotor and the cam ring of differential pressure between pressure on the side of the suction port and pressure on the side of the discharge port, compared with an unloaded condition in which no differential pressure acts, a distance to the rotational center of the rotor gradually shortens according to the rotation of the rotor in at least one of an area from a termination of the suction port to a starting end of the discharge port in a rotational direction of the rotor and an area from a termination of the discharge port to a starting end of the suction port and the inner peripheral face of the cam ring is formed so that in a minimum eccentric state in which the eccentricity to the rotor of the cam ring is minimum, the distance to the rotational center of the rotor is substantially fixed or gradually lengthens according to the rotation of the rotor in at least one of at least a part of the area from the termination of the suction port to the starting end of the discharge port and at least a part of the area from the termination of the discharge port to the starting end of the suction port.

In accordance with a seventeenth feature, in addition to the sixteenth feature, the driving shaft is rotatively driven by an engine of the vehicle and the inner peripheral face of the cam ring is formed so that when the vehicle is run, the distance to the rotational center of the rotor is substantially fixed or gradually lengthens according to the rotation of the rotor in at least one of at least a part of the area from the termination of the suction port to the starting end of the discharge port and at least a part of the area from the termination of the discharge port to the starting end of the suction port.



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stats Patent Info
Application #
US 20130034460 A1
Publish Date
02/07/2013
Document #
13564186
File Date
08/01/2012
USPTO Class
418 24
Other USPTO Classes
International Class
/
Drawings
10




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