JP5824421B2 - Variable displacement vane pump - Google Patents

Description

  The present invention relates to a variable displacement vane pump used as a hydraulic power source of, for example, a hydraulic power steering device of an automobile.

  As a conventional variable displacement vane pump applied to a hydraulic power steering device of an automobile, for example, one described in Patent Document 1 below is known.

  Briefly, this variable displacement vane pump is provided with a drive shaft that is rotatably supported in a pump housing, a rotor that is driven to rotate by the drive shaft, and an outer peripheral portion of the rotor that can be moved in and out. A plurality of vanes and a cam ring that is accommodated on the outer peripheral side of the rotor so as to be eccentrically movable with respect to the axis of the drive shaft, and that defines a plurality of pump chambers in the circumferential direction together with the rotor and the plurality of vanes. The discharge flow rate is made variable by changing the volume of each pump chamber based on the amount of eccentricity.

  In such a variable displacement vane pump, in the vicinity of the boundary between the suction region where the volume of the pump chamber gradually increases and the discharge region where the volume of the pump chamber gradually decreases, it can be in any of the suction / discharge ports. Since the cam profile of the cam ring has a negative slope curve in the entire region (containment region) that defines the pump chamber that does not open, a slight compression is performed in advance in the pump chamber related to the confinement region. (Hereinafter referred to as “pre-compression”). As a result, the pressure difference when shifting from the confinement region to the discharge region is reduced, and vibration (noise) associated with the pulse pressure generated based on the pressure difference is suppressed.

JP 2002-115673 A

  However, the amount of pre-compression based on the cam profile varies depending on the amount of eccentricity of the cam ring. For this reason, for example, when the cam profile is set to have a negative slope curve in the entire confinement region when the cam ring eccentricity is maximum, the pre-compression is performed when the cam ring eccentricity is minimized. The amount will be too large. As a result, in the minimum eccentric state, a large pressure fluctuation occurs in the pump chamber when entering the confined region, and a surge pressure is generated based on the pressure fluctuation, resulting in an increase in pump vibration. There was a problem that.

  The present invention was devised in view of the technical problem of the conventional variable displacement vane pump, and is a variable displacement type that can suppress the surge pressure in the pump chamber while reducing the pulse pressure when the discharge port is opened. The aim is to provide a vane pump.

  The present invention relates to a variable displacement vane pump that supplies hydraulic oil to a vehicle steering device, wherein a point closest to the rotation center of a drive shaft in the circumferential direction on the inner circumferential surface of the cam ring is defined as 0 degrees in the rotation direction of the rotor. When the angle at each circumferential position on the inner circumferential surface of the cam ring is defined so that the angle increases toward the direction of the rotor, the slot of the rotor is opposite to the traveling direction when one of the plurality of vanes is located at the discharge port start end. The vanes adjacent to each other on the side are positioned at a first angular position that is an angular position between the suction port end portion and the cam ring circumferential direction 180 degree position, and the cam ring inner circumferential surface has an eccentric amount of the cam ring. In the maximum eccentric state in which the maximum is, the predetermined angle located between the first angular position and the cam ring circumferential direction position of the cam ring circumferential direction is the second angle. A positive profile in which the vane pop-out amount gradually increases in the radial direction between the rotor outer peripheral surface and the cam ring inner peripheral surface in the rotational direction of the rotor in the entire region from the inlet end portion to the second angular position. And having a negative profile in which the vane pop-out amount gradually decreases in the rotational direction of the rotor in the entire region from the second angular position to the discharge port start end, while the cam ring eccentricity is minimized. In the minimum eccentric state, the vane pop-out amount gradually decreases in the rotational direction of the rotor in the entire region from the suction port end portion to the discharge port start end portion.

  According to the present invention, in a state where the eccentric amount of the cam ring is maximized, a positive profile is formed in the entire region from the start end portion of the suction port to the second angular position, and the discharge port starts from the second angular position. By constructing a negative profile over the entire area up to the start end of the nozzle, the amount of vane popping out gradually decreases over the entire area from the end of the suction port to the start end of the discharge port when the cam ring eccentricity is minimized. However, it is possible to reduce the amount of pre-compression in the cam ring minimum eccentric state as compared with the conventional case, while being configured to have a negative profile. As a result, the pressure fluctuation with respect to the pump chamber at the time of entering the confined region in the minimum eccentric state is suppressed, and the generation of surge pressure due to the pressure fluctuation is suppressed. As a result, the pump vibration is reduced.

It is a cross-sectional view of the variable displacement vane pump according to the present invention. FIG. 2 is an enlarged view of a main part of FIG. 1 showing a cam profile constituting a confinement region at the time of cam ring maximum eccentricity. FIG. 2 is an enlarged view of a main part of FIG. 1 showing a cam profile constituting a confinement region at the time of cam ring minimum eccentricity. It is the diagram which compared the gradient of this invention and the conventional cam profile in the minimum / maximum eccentric state of a cam ring.

  Hereinafter, embodiments of a variable displacement vane pump according to the present invention will be described in detail with reference to the drawings. In the following embodiment, the variable displacement vane pump is applied to a power steering device for a vehicle as in the prior art.

  FIG. 1 is a diagram showing an outline of a variable displacement pump according to the present invention.

  That is, this variable displacement vane pump (hereinafter simply referred to as “pump”) is supported by a substantially cylindrical pump housing 11 having a pump element accommodating portion 11a therein, and is rotatably supported by the pump housing 11. A drive shaft 12 that is rotationally driven with a driving force from the engine, a substantially annular adapter ring 13 fitted to the peripheral wall of the pump element housing portion 11a, and a drive shaft 12 on the inner peripheral side of the adapter ring 13. And an annular cam ring 14 accommodated eccentrically with respect to the center (Q of the rotor 21 to be described later) Q, and accommodated and arranged on the inner peripheral side of the cam ring 14, and counterclockwise in the drawing ( The pump element 20 that performs the pump action described later by being rotationally driven by an arrow), and the discharge flow rate of hydraulic oil that is discharged by one rotation of the pump element 20 ( A control valve 30 for controlling the so-called specific discharge amount) (corresponding to the cam ring control mechanism of the present invention), and a.

  The adapter ring 13 is provided with a substantially semicircular cross-sectional holding groove continuously in the axial direction at a predetermined position in the inner circumferential portion of the adapter ring 13, and the cam ring 14 is swung in the holding groove. A rod-like rocking fulcrum pin 15 serving as a moving fulcrum is held. Further, on the inner peripheral surface of the adapter ring 13, a seal member is disposed along the axial direction at a position substantially opposite to the swing fulcrum pin 15 in the radial direction. 15, a first fluid pressure chamber P <b> 1 and a second fluid pressure chamber P <b> 2 used for swing control of the cam ring 14 are separated between the adapter ring 13 and the cam ring 14 in the radial direction.

  The cam ring 17 is made of a so-called sintered material obtained by sintering an iron-based metal material, and is supported by a swing fulcrum pin 15 through a support groove having a substantially semicircular cross section formed in a cutout in the outer peripheral portion. With the swing fulcrum pin 15 as a fulcrum, it can swing freely toward the first fluid pressure chamber P1 or the second fluid pressure chamber P2.

  The pump element 20 is fixed to the outer periphery of the drive shaft 12 so as to be integrally rotatable. The rotor 21 is rotatably accommodated on the inner peripheral side of the cam ring 14, and the outer periphery of the rotor 21 is radial along the radial direction. And 11 rectangular plate-like vanes 22 that are accommodated and held in the slots 21a that are formed in the notches. In a space formed between the cam ring 14 and the rotor 21, a total of 11 pump chambers 23 are defined by two adjacent vanes 22, 22, and the cam ring 14 is connected to the swing fulcrum pin 15. By swinging as a fulcrum, the volume of each pump chamber 23 can be increased or decreased.

  Here, a coil spring 24 supported by a retainer screwed to the side portion of the pump housing 11 is disposed in the second fluid pressure chamber P2, and a coil spring to which preload is applied by the retainer. 24, the cam ring 14 is constantly urged in the direction in which the amount of eccentricity (hereinafter simply referred to as “the amount of eccentricity”) with respect to the first fluid pressure chamber P1, that is, the center Q of the rotor 21, is maximized. It has become.

  Further, on the inner side surface of the axial end portion of the pump housing 11, a region where the volume of each pump chamber 23 gradually increases as the rotor 21 rotates (hereinafter referred to as “suction region X”) is illustrated. A substantially arc-shaped suction port 25 indicated by an imaginary line is cut out in the circumferential direction. Then, hydraulic oil is introduced from the outside (reservoir tank) to each pump chamber 23 located in the suction region X via a suction passage (not shown) connected to the suction port 25.

  On the other hand, the inner surface of the other end of the pump housing 11 is a position that is substantially axially symmetric with respect to the suction port 25, and a region in which the volume of each pump chamber 23 gradually decreases as the rotor 21 rotates (hereinafter, “ In the drawing, a substantially arc-shaped discharge port 26 indicated by an imaginary line is cut out in the circumferential direction. Then, hydraulic oil discharged from the pump chamber 23 located in the discharge region Y is led out to the outside through a discharge passage (not shown) connected to the discharge port 26.

  The discharge passage is bifurcated and formed on the downstream side, and a part of the discharge oil is guided to the high pressure chamber 34 described later related to the control valve 30 by one of the first discharge passages, and the other Part of the discharged oil is guided to the outside (power steering device) by the second discharge passage.

  With this configuration, in the pump chamber 23 opened to the suction region X, the hydraulic oil supplied from the suction port 25 with the negative pressure generated by the increase in the internal volume of the pump chamber 23 with the rotation of the rotor 21 is applied to the region. X is sucked into the pump chamber 23 related to X, and thereafter, each pump chamber 23 is sequentially discharged to the discharge region through a closed region Z that is in communication with neither the suction region X nor the discharge region Y and has the maximum internal volume. Open to Y. In the pump chamber 23 that opens to the discharge region Y, the hydraulic oil compressed by the positive pressure generated when the internal volume of the pump chamber 23 decreases with the rotation of the rotor 21 passes through the discharge port 26 to the outside. Will be discharged.

  The control valve 30 is arranged along the direction orthogonal to the drive shaft 15 inside the upper end side of the pump housing 11 and is slidably accommodated in a valve hole 11b drilled at the position. 31, a valve spring 33 that urges the valve body 31 to the left in the drawing so as to abut against a plug 32 screwed into one end opening of the valve hole 11 b, and the valve body 31 and the plug 32. A high pressure chamber 34 into which a part of discharge oil is introduced through one of the branched discharge passages, a valve spring 33 is accommodated therein, and the branch formation An intermediate pressure chamber 35 into which a part of the externally supplied oil decompressed by a metering orifice (not shown) disposed in the middle of the other discharge passage is introduced. The pressure difference with the pressure chamber 35 becomes a predetermined value or more. The valve body 31 is adapted to move to the right direction in FIG against the spring force of the valve spring 33.

  Here, when the valve body 31 is located on the left side in the figure, the first fluid pressure chamber P1 is located on the outer periphery of the valve body 41 via the communication oil passage 37 that communicates the first fluid pressure chamber P1 and the valve hole 11b. It will be connected to the low pressure chamber 36 defined on the side. The low pressure chamber 36 is connected to a low pressure passage (not shown) branched from the suction passage, and low pressure hydraulic oil from the suction passage is passed through the low pressure passage to the first fluid pressure chamber P1. be introduced.

  On the other hand, when the valve element 31 slides to the right in the figure due to the differential pressure between the high pressure chamber 34 and the intermediate pressure chamber 35, the first fluid pressure chamber P1 is disconnected from the low pressure chamber 36. Thus, the high pressure chamber 34 is communicated, and high pressure hydraulic oil is introduced into the first fluid pressure chamber P1. With this configuration, the first fluid pressure chamber P1 is selectively supplied with the oil pressure in the low pressure chamber 36 and the oil pressure (discharge pressure) on the upstream side of the metering orifice.

  The control valve 30 is provided with a relief valve 38 inside the valve body 31. When the pressure in the intermediate pressure chamber 35 reaches a predetermined value or more, that is, on the load side (on the power steering device side). ) Is released when the pressure reaches a predetermined value or higher, and a part of the externally supplied oil is recirculated to the suction passage through a low-pressure passage (not shown).

  On the other hand, the second fluid pressure chamber P2 is configured to communicate with the suction port 25 through a substantially arc-shaped suction pressure introduction portion 13b formed in a predetermined range on the inner peripheral surface of the adapter ring 13, and the suction port 25 The hydraulic pressure (low pressure) on the side is always introduced. As a result, the cam ring 17 is always pressed against the first fluid pressure chamber P1 by the suction side hydraulic pressure and the biasing force of the coil spring 24.

  FIGS. 2 and 3 are diagrams showing the cam profile related to the confinement region. FIG. 2 shows the cam profile at the maximum eccentricity of the cam ring, and FIG. 3 shows the cam profile at the minimum eccentricity of the cam ring. It appears. In each figure, the solid line indicates the shape of the cam profile according to the present embodiment, and the broken line indicates the shape when the cam profile is a perfect circle.

  That is, when the cam ring 14 is in the maximum eccentric state, as shown in FIG. 2, on the first half side (Z1 in the drawing) of the confinement region Z, a positive diameter formed so as to be smaller than a perfect circle. It is comprised so that it may become a profile, and it is comprised so that it may become a negative profile whose diameter is smaller than a perfect circle in the second half side (Z2 in a figure).

  On the other hand, when the cam ring 14 is in the minimum eccentric state, as shown in FIG. 3, the cam ring 14 is configured to have a negative profile smaller in diameter than the perfect circle in almost the entire confinement region Z. In the minimum eccentric state, the degree of the negative gradient related to the negative profile is also increased from the maximum eccentric state.

  FIG. 4 is a diagram comparing the gradients of the present invention and the conventional cam profile in the minimum and maximum eccentric state of the cam ring. In the figure, the solid line indicates the cam profile according to the present embodiment, the broken line indicates the conventional cam profile, the bold line indicates the cam profile in the cam ring maximum eccentric state, and the thin line indicates the cam ring in the minimum cam ring eccentric state. Shows the profile.

  First, a reference for the circumferential position of the inner peripheral surface of the cam ring will be described in comparing the cam profile according to the present embodiment with the conventional cam profile. That is, in FIG. 4, the cam ring inner peripheral surface closest to the rotation center of the drive shaft 12 in FIG. 1 is set to 0 degree, and the rotation direction of the rotor 21 (refer to the thick line arrows in FIGS. 1 and 4). The angle at each circumferential position of the cam ring inner circumferential surface 14a is defined so that the angle increases.

  And based on such a reference | standard, in this embodiment, when the 1st vane 22a which is one of the said some vane 22 is located in the start end part 26a of the discharge port 26, it adjoins in the advancing direction opposite side. The vane interval S is set so that the second vane 22b is positioned at the first angular position D1, which is the angular position between the terminal end 25a of the suction port 25 and the cam ring 180 degree position H, and the maximum of the cam ring 14 is set. In the eccentric state, when the predetermined angle located between the first angular position D1 and the cam ring 180 degree position H on the cam ring inner peripheral surface 14a is defined as the second angle D2, the second angular position from the terminal portion 25a of the suction port 25 is obtained. In the entire section up to D2, the vane pop-out amount W determined by the radial distance between the cam ring inner peripheral surface 14a and the rotor outer peripheral surface 21a is the rotor rotation direction. And a negative profile in which the vane pop-out amount W gradually decreases in the rotor rotation direction over the entire section from the second angular position D2 to the start end portion 26a of the discharge port 26. It is configured. Further, in the present embodiment, in the minimum eccentric state of the cam ring 14, the vane pop-out amount W is rotated by the rotor rotation over the entire confinement region Z from the terminal end portion 25b of the suction port 25 to the start end portion 26a of the discharge port 26. The negative profile gradually decreases in the direction.

  On the other hand, as a conventional cam profile, as shown by a broken line in FIG. 4, regardless of the eccentric amount of the cam ring 14, that is, whether the cam ring 14 is in the maximum or minimum eccentric state, It is configured to have a negative profile.

  As described above, in the present embodiment, the first vane 22a and the second vane 22b are configured so as to have the predetermined positional relationship, and at least when the eccentric amount of the cam ring 14 is maximum, the closing is performed. The eccentric amount of the cam ring 14 is configured such that a predetermined cam half region Z1 has a positive cam profile and a negative cam profile only in a predetermined rear half region Z2. Therefore, the negative gradient in the confinement region Z in the state with the smallest value can be suppressed sufficiently smaller than the conventional negative gradient in the same state, and the amount of precompression in the confinement region Z is reduced. .

  In other words, in the prior art, since the negative gradient in the confinement region Z is particularly large when the cam ring 14 is at the minimum eccentricity, as shown in FIG. 1, for example, the first vane 22a and the second When attention is paid to the pump chamber 23x defined between the second vane 22b and the vane 22b, the pre-compression of the pump chamber 23x becomes too large based on the negative gradient, and the second vane 22b enters the confinement region Z. In other words, that is, when the entire pump chamber 23x enters the closed region Z, the pressure fluctuation in the pump chamber 23x becomes large, resulting in surge pressure.

  On the other hand, according to the configuration according to the present embodiment, the unique configuration can reduce the precompression in the confinement region Z in the cam ring minimum eccentric state. The pressure fluctuation when the whole enters the confinement region Z is also suppressed. Thereby, generation | occurrence | production of the said surge pressure based on the said pressure fluctuation is also suppressed, and reduction of the vibration of a pump can be aimed at.

  In this embodiment as well, the pressure is changed when the pump chamber 23x communicates with the discharge port 26 because the pre-compression is performed in the closed region Z regardless of the amount of eccentricity of the cam ring 14. The generation of the pulse pressure based on the pressure change is also suppressed.

  The present invention is not limited to the configuration described in the above-described embodiment. For example, the intake port 25 and the discharge port 26 may be provided as long as they have a predetermined vane 22 arrangement and cam profile in the confined region Z. Other specific configurations of the pump, such as shape and size, can be freely changed according to the specifications of the pump.

DESCRIPTION OF SYMBOLS 11 ... Pump housing 11a ... Pump element accommodating part 12 ... Drive shaft 14 ... Cam ring 14a ... Inner peripheral surface 21 of a cam ring ... Rotor 21a ... Slot 22 ... Vane 23 ... Pump chamber 25 ... Suction port (suction port)
25a: End portion of the suction port (end portion of the suction port)
26 ... Discharge port (discharge port)
26a: Start end of discharge port (start end of discharge port)
30 ... Control valve (cam ring control mechanism)
D1 ... 1st angle D2 ... 2nd angle W ... Vane pop-out amount

Claims (1)

A variable displacement vane pump that transmits hydraulic oil to a vehicle steering device that transmits a steering operation of a steering wheel to a steered wheel and generates a steering assist force by hydraulic pressure of the hydraulic fluid,
A pump housing having a pump element housing therein;
A drive shaft rotatably supported by the pump housing;
A rotor housed in the pump element housing portion and driven to rotate by the drive shaft;
A plurality of vanes respectively housed in a plurality of slots formed in the rotor in a cutout manner;
An annular cam ring disposed in the pump element accommodating portion so as to be eccentrically movable with respect to the axis of the drive shaft, and forming a plurality of pump chambers together with the rotor and the plurality of vanes;
An inlet formed in the pump housing and formed in an area where the internal volume of each pump chamber increases with rotation of the rotor;
A discharge port formed in the pump housing and having an opening formed in a region where the internal volume of each pump chamber decreases with rotation of the rotor;
A cam ring control mechanism that is provided in the pump housing and controls the amount of eccentricity of the cam ring with respect to the rotation center of the rotor,
Of the inner circumferential surface of the cam ring, each point of the inner circumferential surface of the cam ring is set so that the point closest to the rotation center of the drive shaft in the circumferential direction is 0 degree and the angle increases toward the rotation direction of the rotor. When the angle at the circumferential position is defined,
The slot of the rotor is such that when one of the plurality of vanes is located at the start end of the discharge port, the adjacent vane on the opposite side of the advancing direction is located between the end of the suction port and the 180 ° cam ring circumferential position. Configured to be located at a first angular position that is an angular position between,
The inner peripheral surface of the cam ring is
In a maximum eccentric state where the amount of eccentricity of the cam ring with respect to the rotor is maximized, a predetermined angle between the first angular position and the cam ring circumferential direction 180 degree position among the circumferential positions of the cam ring is defined as a second angle. The vane popping amount determined by the radial distance between the outer peripheral surface of the rotor and the inner peripheral surface of the cam ring in the rotational direction of the rotor in the entire region from the terminal end of the suction port to the second angular position. While having a positive profile that gradually increases and a negative profile in which the vane pop-out amount gradually decreases in the rotational direction of the rotor in the entire region from the second angular position to the start end of the discharge port,
In the minimum eccentric state in which the eccentric amount of the cam ring with respect to the rotor is minimized, the vane pop-out amount gradually decreases in the rotational direction of the rotor in the entire region from the terminal end of the suction port to the start end of the discharge port. A variable displacement vane pump configured to have a negative profile.

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