US20110165010A1 - Vane pump - Google Patents

Vane pump Download PDF

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Publication number
US20110165010A1
US20110165010A1 US12/763,697 US76369710A US2011165010A1 US 20110165010 A1 US20110165010 A1 US 20110165010A1 US 76369710 A US76369710 A US 76369710A US 2011165010 A1 US2011165010 A1 US 2011165010A1
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United States
Prior art keywords
rotor
vane
back pressure
end portion
discharge
Prior art date
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Abandoned
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US12/763,697
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English (en)
Inventor
Masaaki Iijima
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Hitachi Astemo Ltd
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Hitachi Automotive Systems Ltd
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Publication date
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Assigned to HITACHI AUTOMOTIVE SYSTEMS, LTD. reassignment HITACHI AUTOMOTIVE SYSTEMS, LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: IIJIMA, MASAAKI
Publication of US20110165010A1 publication Critical patent/US20110165010A1/en
Abandoned legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2/00—Rotary-piston machines or pumps
    • F04C2/30—Rotary-piston machines or pumps having the characteristics covered by two or more groups F04C2/02, F04C2/08, F04C2/22, F04C2/24 or having the characteristics covered by one of these groups together with some other type of movement between co-operating members
    • F04C2/34—Rotary-piston machines or pumps having the characteristics covered by two or more groups F04C2/02, F04C2/08, F04C2/22, F04C2/24 or having the characteristics covered by one of these groups together with some other type of movement between co-operating members having the movement defined in groups F04C2/08 or F04C2/22 and relative reciprocation between the co-operating members
    • F04C2/344—Rotary-piston machines or pumps having the characteristics covered by two or more groups F04C2/02, F04C2/08, F04C2/22, F04C2/24 or having the characteristics covered by one of these groups together with some other type of movement between co-operating members having the movement defined in groups F04C2/08 or F04C2/22 and relative reciprocation between the co-operating members with vanes reciprocating with respect to the inner member
    • F04C2/3441—Rotary-piston machines or pumps having the characteristics covered by two or more groups F04C2/02, F04C2/08, F04C2/22, F04C2/24 or having the characteristics covered by one of these groups together with some other type of movement between co-operating members having the movement defined in groups F04C2/08 or F04C2/22 and relative reciprocation between the co-operating members with vanes reciprocating with respect to the inner member the inner and outer member being in contact along one line or continuous surface substantially parallel to the axis of rotation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01C—ROTARY-PISTON OR OSCILLATING-PISTON MACHINES OR ENGINES
    • F01C21/00—Component parts, details or accessories not provided for in groups F01C1/00 - F01C20/00
    • F01C21/08—Rotary pistons
    • F01C21/0809—Construction of vanes or vane holders
    • F01C21/0818—Vane tracking; control therefor
    • F01C21/0854—Vane tracking; control therefor by fluid means
    • F01C21/0863—Vane tracking; control therefor by fluid means the fluid being the working fluid
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01C—ROTARY-PISTON OR OSCILLATING-PISTON MACHINES OR ENGINES
    • F01C21/00—Component parts, details or accessories not provided for in groups F01C1/00 - F01C20/00
    • F01C21/08—Rotary pistons
    • F01C21/0809—Construction of vanes or vane holders
    • F01C21/089—Construction of vanes or vane holders for synchronised movement of the vanes
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01C—ROTARY-PISTON OR OSCILLATING-PISTON MACHINES OR ENGINES
    • F01C21/00—Component parts, details or accessories not provided for in groups F01C1/00 - F01C20/00
    • F01C21/10—Outer members for co-operation with rotary pistons; Casings
    • F01C21/104—Stators; Members defining the outer boundaries of the working chamber
    • F01C21/108—Stators; Members defining the outer boundaries of the working chamber with an axial surface, e.g. side plates
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C14/00—Control of, monitoring of, or safety arrangements for, machines, pumps or pumping installations
    • F04C14/18—Control of, monitoring of, or safety arrangements for, machines, pumps or pumping installations characterised by varying the volume of the working chamber
    • F04C14/22—Control of, monitoring of, or safety arrangements for, machines, pumps or pumping installations characterised by varying the volume of the working chamber by changing the eccentricity between cooperating members
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2240/00—Components
    • F04C2240/80—Other components

Definitions

  • the present invention relates to vane pumps.
  • Japanese Patent Application Publication No. 7-259754 discloses a variable displacement vane pump which includes: a rotor including a plurality of slots at its outside periphery; a plurality of vanes mounted in corresponding ones of the slots, and adapted to project from, and travel inwards and outwards of the corresponding slots; a cam ring adapted to be eccentric with respect to the rotor, the cam ring surrounding the rotor; and a plurality of pump chambers defined by the vanes, an inside peripheral surface of the cam ring, and an outside peripheral surface of the rotor, wherein the displacement of the pump changes with a change in the eccentricity of the cam ring with respect to the rotor.
  • the vane pump is arranged so that when the distal end portion of a vane is positioned in a suction region or a discharge region, the proximal end portion of the vane is applied with a back pressure that is substantially identical to a pressure applied to the distal end portion, in order to reduce the resistance to the distal end portion of the vane when the vane slides on the inside peripheral surface of the cam ring, and thereby reduce a loss in power for driving the vane pump.
  • the proximal end portion of the vane starts to be applied with a discharge-side fluid pressure (high pressure), when the vane is positioned in the suction region before entering the discharge region. This is intended for ensuring that even when the vane pump is operating at low temperature where the viscosity of working fluid is relatively high, the vane projects from the slot, so as to seal the pump chambers well, and thereby make the pump operate normally.
  • Such vane pumps as disclosed in Japanese Patent Application Publication No. 7-259754 can encounter a problem that noise is generated due to factors such as contact between components. Accordingly, it is desirable to provide a vane pump in which noise is suppressed.
  • a vane pump comprises: a rotor adapted to be rotated by a drive shaft, the rotor including a plurality of slots at an outside periphery of the rotor; a plurality of vanes mounted in corresponding ones of the slots, and adapted to project from, and travel inwards and outwards of the corresponding slots; a cam ring adapted to be eccentric with respect to the rotor, the cam ring surrounding the rotor; and a plate arranged to face an axial end of the rotor, and define a plurality of pump chambers in cooperation with the rotor, the vanes, and the cam ring, wherein the plate includes at a side facing the rotor: a suction port opened in a suction region in which each pump chamber gradually expands while moving along with rotation of the rotor; a discharge port opened in a discharge region in which each pump chamber gradually contracts while moving along with rotation of the rotor; a first back pressure port arranged to receive a
  • FIG. 1 is a block diagram showing a continuously variable transmission (CVT) system to which a vane pump according to each embodiment of the present invention is adapted.
  • CVT continuously variable transmission
  • FIG. 2 is a partial sectional view of a vane pump according to a first embodiment of the present invention in an axial direction of a rotor under a condition that a side plate is removed.
  • FIG. 3 is a plan view of a first plate of the vane pump.
  • FIG. 4 is a sectional view of the first plate taken along the line IV-IV in FIG. 3 .
  • FIG. 5 is a sectional view of the first plate taken along the line V-V in FIG. 3 .
  • FIG. 6 is a sectional view of a portion of the vane pump, including a sectional view of the first plate taken along the line VI-VI in FIG. 3 .
  • FIG. 7 is an enlarged view of a portion indicated by VII in FIG. 6 , showing a sectional shape of a beginning end portion of a discharge-side back pressure port.
  • FIG. 8 is a sectional view of the vane pump taken along the line VIII-VIII in FIG. 6 .
  • FIG. 9 is a graphic diagram showing a relationship among the cross-sectional flow area and circumferential length of the beginning end portion of the discharge-side back pressure port, and noise level.
  • FIG. 10 is a sectional view of a vane pump according to a first comparative example, which corresponds to the sectional view of FIG. 8 .
  • FIG. 11 is a sectional view of a vane pump according to a second comparative example, which corresponds to the sectional view of FIG. 8 .
  • FIGS. 12A to 12D are plan views of beginning end portions of discharge-side back pressure ports according to variations of a second embodiment of the present invention.
  • FIGS. 13A and 13B are side sectional views of beginning end portions of discharge-side back pressure ports according to variations of the second embodiment.
  • FIGS. 14A to 14D are plan views of beginning end portions of discharge-side back pressure ports according to variations of a third embodiment of the present invention.
  • FIG. 15 is a side sectional view of a beginning end portion of a discharge-side back pressure port according to a variation of the third embodiment.
  • Pump 1 is adapted to be used to supply hydraulic pressure to a hydraulic actuator in a motor vehicle.
  • pump 1 is adapted to be used to supply hydraulic pressure to a belt-type continuously variable transmission (CVT 100 ).
  • CVT 100 continuously variable transmission
  • Pump 1 is not so limited, but may be used to supply hydraulic pressure to another hydraulic actuator such as a hydraulic actuator in a power steering system.
  • Pump 1 is driven by a crankshaft of an internal combustion engine, to suck and discharge working fluid.
  • working fluid is working oil such as ATF (automatic transmission fluid).
  • FIG. 1 shows a system of CVT 100 to which pump 1 is adapted.
  • CVT 100 includes a control valve unit 200 that is provided with various valves such as a shift control valve 201 , a secondary valve 202 , a secondary pressure solenoid valve 203 , a line pressure solenoid valve 204 , a pressure regulator valve 205 , a manual valve 206 , a lockup/select switch solenoid valve 207 , a clutch regulator valve 208 , a select control valve 209 , a lockup solenoid valve 210 , a torque converter regulator valve 211 , a lockup control valve 212 , and a select switch valve 213 .
  • various valves such as a shift control valve 201 , a secondary valve 202 , a secondary pressure solenoid valve 203 , a line pressure solenoid valve 204 , a pressure regulator valve 205 , a manual valve 206 , a lockup/select switch solenoid valve
  • Pump 1 discharges and supplies working fluid through control valve unit 200 to various parts of CVT 100 such as a primary pulley 101 , a secondary pulley 102 , a forward clutch 103 , a reverse brake 104 , a torque converter 105 , and a lubricating and cooling system 106 .
  • FIG. 2 is a partial sectional view of pump 1 in an axial direction of a rotor 6 under a condition that a side plate is removed.
  • a three dimensional normal coordinate system is assumed in which an x axis is defined to extend in a radial direction of pump 1 , a y axis is defined to extend in another radial direction of pump 1 , and a z axis is defined to extend in the axial direction of rotor 6 .
  • the x axis is defined to extend in a direction where a central axis “P” of a cam ring 8 moves or swings with respect to an axis of rotation “O” of rotor 6 .
  • the y axis is defined to extend in a direction perpendicular to both of the x axis and z axis.
  • FIG. 2 shows a view in the negative z-axis direction from the positive z side.
  • the positive x-axis direction is a direction where the central axis P of cam ring 8 deviates from the axis of rotation O (or in a direction from a second closing region RE 4 to a first closing region RE 3 as detailed below and shown in FIG. 3 ).
  • the positive y-axis direction is a direction from a suction region toward a discharge region.
  • Pump 1 is a variable displacement type capable of varying its displacement or discharge capacity or pump capacity, i.e. amount of fluid discharged per one rotation.
  • Pump 1 includes a pumping section 2 for sucking and discharging working fluid, and a control section 3 for controlling the discharge capacity, which are integrated as a unit.
  • Pumping section 2 is accommodated in a housing 4 , including a drive shaft 5 , a rotor 6 , vanes 7 , and a cam ring 8 .
  • Housing 4 includes a housing body 40 , a first plate 41 , and a second plate 42 , which are fixed together, for example, by bolting.
  • Housing body 40 is formed with a substantially cylindrical through hole 400 which extends in the z-axis direction, and in which an annular adapter ring 9 is mounted.
  • Adapter ring 9 includes a substantially cylindrical accommodation hole 90 that extends in the z-axis direction.
  • Accommodation hole 90 is formed with a first flat portion 91 which is located on the positive x side, and substantially parallel to the y-z plane.
  • Accommodation hole 90 is formed also with a second flat portion 92 which is located on the negative x side, and substantially parallel to the y-z plane.
  • Second flat portion 92 is formed with a recess 920 which is located substantially at a central position of second flat portion 92 in the z-axis direction, and extends in the negative x-axis direction.
  • Accommodation hole 90 is formed also with a third flat portion 93 which is located at the positive y side and slightly on the positive x side with respect to the axis of rotation O, and substantially parallel to the z-x plane.
  • Third flat portion 93 is formed with a groove or recess 930 having a semicircular section as viewed in the z-axis direction.
  • Third flat portion 93 is formed also with first and second communication passages 931 and 932 on both sides of recess 930 . Specifically, first communication passage 931 opens in a portion of third flat portion 93 on the positive x side of recess 930 , whereas second communication passage 932 opens in a portion of third flat portion 93 on the negative x side of recess 930 .
  • Accommodation hole 90 is formed also with a fourth flat portion 94 which is located at the negative y side, and substantially parallel to the z-x plane.
  • Fourth flat portion 94 is formed with a groove or recess 940 having a rectangular section as viewed in the z-axis direction.
  • Cam ring 8 is mounted in accommodation hole 90 of adapter ring 9 , and adapted to move or swing freely, wherein cam ring 8 has an annular shape.
  • Adapter ring 9 is thus arranged to surround cam ring 8 .
  • cam ring 8 has a substantially circular inside peripheral surface 80 , and a substantially circular outside peripheral surface 81 , where cam ring 8 has a substantially uniform radial thickness.
  • the outside peripheral surface 81 of cam ring 8 is formed with a groove or recess 810 having a semicircular section as viewed in the z-axis direction, where recess 810 is located at the positive y side of outside peripheral surface 81 .
  • the outside peripheral surface 81 of cam ring 8 is formed also with a substantially cylindrical recess 811 having a central longitudinal axis extending in the x-axis direction, where recess 811 is located at the negative x side of outside peripheral surface 81 .
  • a pin 10 which extends in the z-axis direction, and is fitted in the space defined between recesses 930 and 810 .
  • a seal 11 In the recess 940 in the periphery of adapter ring 9 is mounted a seal 11 . Seal 11 is in contact with the negative y side of outside peripheral surface 81 of cam ring 8 .
  • An elastic member such as a spring 12 is provided, which has a longitudinal end mounted in recess 920 in the inside periphery of adapter ring 9 .
  • Spring 12 is a coil spring.
  • the other longitudinal end of spring 12 is mounted in recess 811 of cam ring 8 .
  • Spring 12 is mounted in a compressed state so as to constantly urge the cam ring 8 in the positive x-axis direction with respect to adapter ring 9 or housing 4 .
  • the size of accommodation hole 90 in the x-axis direction i.e. the distance between the first flat portion 91 and second flat portion 92 , is set larger than the diameter of outside peripheral surface 81 of cam ring 8 .
  • Cam ring 8 is supported by adapter ring 9 or housing 4 on third flat portion 93 , for moving or swinging in the x-y plane about third flat portion 93 as a fulcrum.
  • Pin 10 serves to restrict deviation or relative rotation of cam ring 8 with respect to adapter ring 9 .
  • cam ring 8 The swinging motion of cam ring 8 is restricted on the positive x side by contact between the outside peripheral surface 81 and the first flat portion 91 of adapter ring 9 , and restricted on the negative x side by contact between the outside peripheral surface 81 and the second flat portion 92 of adapter ring 9 .
  • the eccentricity or distance of the central axis P of cam ring 8 with respect to the axis of rotation O is represented by O.
  • the central axis P of cam ring 8 is located substantially at the axis of rotation O so that the eccentricity ⁇ is equal to about zero. This position is called minimum eccentric position.
  • first plate 41 and second plate 42 are sealed by first plate 41 and second plate 42 , respectively, and divided fluid-tightly or liquid-tightly by third flat portion 93 and seal 11 into first and second control chambers R 1 and R 2 .
  • First control chamber R 1 is located on the positive x side, whereas second control chamber R 2 is located on the negative x side.
  • First control chamber R 1 hydraulically communicates with first communication passage 931
  • second control chamber R 2 hydraulically communicates with second communication passage 932 .
  • Drive shaft 5 is rotatably supported by first and second plates 41 and 42 of housing 4 .
  • Drive shaft 5 is linked with the crankshaft of the internal combustion engine through a timing chain so that drive shaft 5 rotates in synchronization with the crankshaft.
  • Rotor 6 is coaxially arranged with drive shaft 5 , and coupled by spline coupling to the outside periphery of drive shaft 5 .
  • Rotor 6 has a substantially cylindrical shape, and is mounted inside the cam ring 8 .
  • Cam ring 8 is thus arranged to surround the rotor 6 .
  • an annular chamber R 3 is defined between the inside peripheral surface 80 of cam ring 8 and an outside peripheral surface 60 of rotor 6 , and between first and second plates 41 and 42 .
  • Rotor 6 rotates about the axis of rotation O in a clockwise direction as viewed in FIG. 2 , along with drive shaft 5 .
  • Rotor 6 is formed with a plurality of slots 61 which extend radially of rotor 6 .
  • Each slot 61 extends straight in a radial direction of rotor 6 from the outside peripheral surface 60 toward the axis of rotation O by a predetermined depth as viewed in the z-axis direction, and extends over the entire length of rotor 6 in the z-axis direction.
  • Eleven slots 61 are arranged in the circumferential direction, and evenly spaced.
  • Eleven vanes 7 are provided, each of which is a substantially rectangular plate, and is mounted in a corresponding one of slots 61 , and adapted to project from, and travel inwards and outwards of slot 61 .
  • a distal end portion 70 of vane 7 which is outward in the radial direction of rotor 6 , or one of end portions farther from the axis of rotation O, is curved to be fitted with the inside peripheral surface 80 of cam ring 8 , as viewed in the z-axis direction.
  • the number of slots 61 or vanes 7 is not limited to eleven.
  • a proximal end portion 610 of slot 61 which is inward in the radial direction of rotor 6 , or one of longitudinal end portions closer to the axis of rotation O, is formed in a substantially cylindrical shape as viewed in the z-axis direction, where the cylindrical shape has a diameter larger than the size of a main portion 611 of slot 61 in the circumferential direction of rotor 6 .
  • the shape of proximal end portion 610 is not limited to a cylindrical shape, but may be formed in a rectangular shape like the main portion 611 .
  • the outside peripheral surface 60 of rotor 6 is formed with a plurality of projections 62 each of which is located at a corresponding one of vanes 7 , and has a substantially trapezoidal section as viewed in the z-axis direction.
  • Projection 62 extends over the entire length of rotor 6 in the z-axis direction, and extends from the outside peripheral surface 60 by a predetermined height in the radial direction of rotor 6 .
  • Slot 61 opens substantially at the center of projection 62 as viewed in the z-axis direction.
  • the length of slot 61 in the radial direction of rotor 6 i.e. the total length including the proximal end portion 610 and projection 62 , is set substantially equal to the length of vane 7 in the radial direction of rotor 6 .
  • the provision of projection 62 serves to constantly hold vane 7 in slot 61 even when vane 7 maximally projects from slot 61 , for example, in the first closing region RE 3 .
  • this structure serves to remove unnecessary portions from the outside peripheral surface 60 of rotor 6 except the projections 62 , while ensuring that slot 61 constantly holds vane 7 . This results in increase in the volumetric capacity of pump chambers “r”, increase in the pump efficiency, reduction in the weight of rotor 6 , and reduction in the power loss.
  • the annular chamber R 3 between rotor 6 and cam ring 8 is divided by eleven vanes 7 into eleven pump chambers r.
  • the distance between two adjacent vanes 7 in the rotational direction of rotor 6 (the clockwise direction in FIG. 2 , represented by RD 1 ) is defined as a unit pitch.
  • the length of pump chamber r in the rotor rotation direction RD 1 is equal to one pitch and unchanged.
  • the volumetric capacity of pump chamber r gradually increases while moving along with rotation of rotor 6 in the rotor rotation direction RD 1 (in the clockwise direction in FIG. 2 ) from the negative x side to the positive x side.
  • the volumetric capacity of pump chamber r gradually decreases while moving along with rotation of rotor 6 in the rotor rotation direction RD 1 (in the clockwise direction in FIG. 2 ) from the positive x side to the negative x side.
  • First and second plates 41 and 42 are a pair of disc-shaped plates (pressure plates or side plates). First and second plates 41 and 42 are arranged to face both axial ends of rotor 6 (and vanes 7 ) and cam ring 8 in the z-axis direction, where rotor 6 (and vanes 7 ) and cam ring 8 are sandwiched therebetween. First plate 41 is arranged to face the negative z side of rotor 6 and others.
  • FIG. 3 shows a plan view of first plate 41 from the positive z side. The outline of first plate 41 is schematically expressed with a circular shape, and bolt holes and the like are omitted.
  • FIG. 4 is a sectional view of first plate 41 taken along the line IV-IV in FIG. 3 .
  • FIG. 5 is a sectional view of first plate 41 taken along the line V-V in FIG. 3 .
  • a pump cover 49 On the negative z side of first plate 41 is arranged a pump cover 49 .
  • FIG. 5 shows a sectional view of pump cover 49 .
  • Pump cover 49 is formed with a through hole 490 , a first communication passage 491 , and a second communication passage 492 .
  • Drive shaft 5 is inserted and rotatably supported in through hole 490 .
  • First communication passage 491 is in the form of a groove for suction-side communication which is formed in a positive z side surface of pump cover 49 , and positioned to overlap with negative z side openings of a communication hole 451 and a communication hole 432 of first plate 41 which are described in detail below.
  • the positive z side surface of pump cover 49 is formed also with a seal groove 494 which surrounds the second communication passage 492 .
  • An O-ring 496 is mounted in seal groove 494 for sealing. Under a condition that the negative z side surface of first plate 41 is placed to face the positive z side surface of pump cover 49 , the O-ring 496 is compressed in the z-axis direction into tight contact with the negative z side surface of first plate 41 , to improve the liquid tightness of second communication passage 492 that is subject to high pressure.
  • First plate 41 is formed with a suction port 43 , a discharge port 44 , a suction-side back pressure port 45 , a discharge-side back pressure port 46 , a pin hole 47 , and a through hole 48 .
  • Pin 10 is inserted and fixed in pin hole 47 .
  • Drive shaft 5 is inserted and rotatably supported in through hole 48 .
  • Second plate 42 is formed with similar ports and holes in similar positions. However, the ports of second plate 42 may be omitted.
  • first and second plates 41 and 42 are formed with such similar ports, is effective for bringing into balance hydraulic forces which are applied from discharge port 44 and the like to rotor 6 and vanes 7 in the z-axis direction, and thereby suppressing the tear and resistance resulting from unbalanced contact.
  • suction port 43 and the like may be distributed to first and second plates 41 and 42 as appropriate.
  • Suction port 43 is arranged in a suction region or section RE 1 on the negative y side of first plate 41 where pump chamber r gradually expands while moving along with rotation of rotor 6 .
  • Working fluid is supplied through suction port 43 from the outside to pump chambers r located in the suction region RE 1 .
  • Suction port 43 includes a suction-side arc groove 430 , a suction hole 431 , and a communication hole 432 .
  • Suction-side arc groove 430 is formed in a positive z side surface 410 of first plate 41 , and arranged to receive a suction-side fluid pressure.
  • the suction-side arc groove 430 has the form of an arc about the axis of rotation O, extending in a circumferential direction of first plate 41 through a portion in which pump chambers r are arranged in suction region RE 1 .
  • the suction region RE 1 of pump 1 is defined by an angular range of suction-side arc groove 430 , i.e.
  • an angle ⁇ defined by a straight line connecting the axis of rotation O to a beginning end point “A” of suction-side arc groove 430 on the negative x side of first plate 41 and a straight line connecting the axis of rotation O to a terminal end point “B” of suction-side arc groove 430 on the positive x side of first plate 41 .
  • the angle ⁇ is equivalent to about 4.5 pitches in this example.
  • Each of the beginning end point A and terminal end point B of suction-side arc groove 430 is positioned away from the x axis by an angle f 3 in the negative y-axis direction, where the angle ⁇ is equivalent to about 0.5 pitch in this example.
  • Suction-side arc groove 430 is provided with a semicircular terminal end portion 436 that projects in the rotor rotation direction RD 1 .
  • Suction-side arc groove 430 is provided with a beginning end portion 435 that includes a main section beginning end portion 433 having a semicircular shape projecting in a direction opposite to the rotor rotation direction RD 1 (referred to as rotor reverse rotation direction), and a notch 434 formed continuous with main section beginning end portion 433 .
  • Notch 434 extends in the rotor reverse rotation direction from main section beginning end portion 433 by about 0.5 pitch to the beginning end point A.
  • suction-side arc groove 430 in the rotor radial direction is substantially uniform over the entire length in the circumferential direction, and substantially equal to the width of annular chamber R 3 in the rotor radial direction when cam ring 8 is in the minimum eccentric position, as shown in FIG. 2 .
  • Suction-side arc groove 430 has an inside radial edge 437 which is positioned somewhat outside of the outside peripheral surface 60 (except projections 62 ) of rotor 6 in the rotor radial direction.
  • Suction-side arc groove 430 has an outside radial edge 438 which is positioned somewhat outside of the inside peripheral surface 80 of cam ring 8 in the rotor radial direction when cam ring 8 is in the minimum eccentric position, and positioned slightly outside of the inside peripheral surface 80 of cam ring 8 in the rotor radial direction when cam ring 8 is in the maximum eccentric position.
  • pump chambers r in the suction region overlap with suction-side arc groove 430 as viewed in the z-axis direction and hydraulically communicate with suction-side arc groove 430 .
  • Suction hole 431 is opened substantially at the center of suction-side arc groove 430 in the circumferential direction.
  • Suction hole 431 has a substantially elliptic shape as viewed in the z-axis direction, and has a width in the rotor radial direction which is substantially equal to the width of suction-side arc groove 430 , and a length in the circumferential direction which is equal to about one pitch. Suction hole 431 is located to overlap with the y axis as viewed in the z-axis direction, extending through first plate 41 in the z-axis direction. Communication hole 432 is opened in suction-side arc groove 430 , and arranged adjacent to suction hole 431 and in the rotor reverse rotation direction from suction hole 431 (closer to the beginning end point A than suction hole 431 ).
  • Communication hole 432 has a similar shape as suction hole 431 , extending through first plate 41 in the z-axis direction.
  • the depth of the main section beginning end portion 433 , the portion between communication hole 432 and suction hole 431 , and the terminal end portion 436 in the z-axis direction is smaller than or equal to 20% of the thickness of first plate 41 in the z-axis direction.
  • the portion between main section beginning end portion 433 and communication hole 432 is inclined so that the depth gradually increases as followed in the rotor rotation direction RD 1 , and becomes equal to the thickness of first plate 41 at communication hole 432 .
  • the portion between suction hole 431 and terminal end portion 436 is inclined so that the depth gradually decreases as followed in the rotor rotation direction RD 1 , becomes equal to the depth of main section beginning end portion 433 at terminal end portion 436 .
  • the notch 434 is in the form of an acute angle triangle whose width in the rotor radial direction gradually increases as followed in the rotor rotation direction RD 1 , as viewed in the z-axis direction.
  • the maximum width of notch 434 in the rotor radial direction is set smaller than that of suction-side arc groove 430 .
  • the depth of notch 434 in the z-axis direction is set to increase from zero to several % of the thickness of first plate 41 as followed in the rotor rotation direction RD 1 .
  • Discharge port 44 is arranged in a discharge region or section RE 2 on the positive y side of first plate 41 where pump chamber r gradually contracts while moving along with rotation of rotor 6 .
  • Working fluid is discharged through discharge port 44 to the outside from pump chambers r located in the discharge region RE 2 .
  • Discharge port 44 includes a discharge-side arc groove 440 , a communication hole 441 , and a discharge hole 442 .
  • Discharge-side arc groove 440 is formed in the positive z side surface 410 of first plate 41 , and arranged to receive a discharge-side fluid pressure. As viewed in the z-axis direction, the discharge-side arc groove 440 has the form of an arc about the axis of rotation O, extending in the circumferential direction of first plate 41 through a portion in which pump chambers r are arranged in the discharge region RE 2 .
  • the discharge region RE 2 of pump 1 is defined by an angular range of discharge-side arc groove 440 , i.e.
  • Discharge-side arc groove 440 is provided with a rectangular beginning end portion 443 .
  • discharge-side arc groove 440 in the rotor radial direction is substantially uniform over the entire length in the circumferential direction, and slightly smaller than that of suction-side arc groove 430 .
  • Discharge-side arc groove 440 has an inside radial edge 446 which is positioned somewhat outside of the outside peripheral surface 60 (except projections 62 ) of rotor 6 in the rotor radial direction.
  • Discharge-side arc groove 440 has an outside radial edge 447 which is positioned substantially identical to the inside peripheral surface 80 of cam ring 8 in the rotor radial direction when cam ring 8 is in the minimum eccentric position.
  • Discharge hole 442 is opened in a terminal end portion 444 of discharge-side arc groove 440 which is located on the side of rotor rotation direction RD 1 of discharge-side arc groove 440 .
  • Discharge hole 442 has a substantially elliptic shape as viewed in the z-axis direction, and has a width in the rotor radial direction which is substantially equal to the width of discharge-side arc groove 440 , and a length in the circumferential direction which is somewhat larger than one pitch.
  • Discharge hole 442 is formed to extend through first plate 41 in the z-axis direction.
  • Discharge hole 442 has a semicircular edge that projects in the rotor rotation direction RD 1 , and substantially identical to the semicircular edge of terminal end portion 444 as viewed in the z-axis direction.
  • Communication hole 441 is opened on the side of rotor reverse rotation direction of discharge-side arc groove 440 , which is located in a position opposite to the position of communication hole 432 with respect to the axis of rotation O as viewed in the z-axis direction.
  • Communication hole 441 has a similar shape as discharge hole 442 and a length of about one pitch in the circumferential direction, extending through first plate 41 in the z-axis direction.
  • the beginning end portion 443 of discharge-side arc groove 440 extends from the beginning end point C to a rotor reverse rotation direction side edge 445 of communication hole 441 .
  • the rotor reverse rotation direction side edge 445 is in the form of a semicircle projecting in the rotor reverse rotation direction as viewed in the z-axis direction, and has a leading end point “E” which is located about one pitch from the beginning end point C in the rotor rotation direction RD 1 .
  • the leading edge of beginning end portion 443 facing the terminal end point B of suction-side arc groove 430 in the rotor reverse rotation direction is formed straight, extending in the rotor radial direction, as viewed in the z-axis direction.
  • the depth (in the z-axis direction) of a main section 448 between communication hole 441 and discharge hole 442 is equal to about 25% of the thickness of first plate 41 in the z-axis direction.
  • the depth of beginning end portion 443 in the z-axis direction is smaller than that of main section 448 , and changes as followed from the beginning end point C to the rotor reverse rotation direction side edge 445 of communication hole 441 .
  • the depth of beginning end portion 443 at the beginning end point C is equal to zero, and set to gradually increase as followed toward the rotor reverse rotation direction side edge 445 , and become smaller than or equal to about 10% of the thickness of first plate 41 at the rotor reverse rotation direction side edge 445 .
  • the cross-sectional flow area of beginning end portion 443 is set smaller than that of main section 448 , and set to gradually increase as followed in the rotor rotation direction RD 1 , thus forming a throttling portion.
  • first closing region RE 3 which is defined by an angle of 2 ⁇ made by a straight line connecting the axis of rotation O to the terminal end point B of suction-side arc groove 430 and a straight line connecting the axis of rotation O to the beginning end point C of discharge-side arc groove 440 .
  • the angle 2 ⁇ is equivalent to about one pitch.
  • second closing region RE 4 which is defined by an angle of 2 ⁇ made by a straight line connecting the axis of rotation O to the terminal end point D of discharge-side arc groove 440 and a straight line connecting the axis of rotation O to the beginning end point A of suction-side arc groove 430 .
  • the angle 2 ⁇ is equivalent to about one pitch.
  • first closing region RE 3 and second closing region RE 4 extends across the x axis.
  • First plate 41 is formed with a suction-side back pressure port 45 and a discharge-side back pressure port 46 which are provided independently of each other, and arranged to hydraulically communicate with the root of each vane 7 (back pressure chamber br formed in the proximal end portion 610 of slot 61 ).
  • Suction-side back pressure port 45 is arranged to hydraulically connect the suction port 43 to back pressure chambers br corresponding to most of vanes 7 located in the suction region RE 1 , specifically, back pressure chambers br corresponding to vanes 7 whose distal end portions 70 overlap with suction port 43 (suction-side arc groove 430 ).
  • Suction-side back pressure port 45 includes a suction-side back pressure arc groove 450 , and a communication hole 451 .
  • Suction-side back pressure arc groove 450 is formed in the positive z side surface 410 of first plate 41 , and arranged to receive a suction-side fluid pressure. As viewed in the z-axis direction, suction-side back pressure arc groove 450 has the form of an arc about the axis of rotation O, extending in the circumferential direction of first plate 41 through a portion in which back pressure chambers br (proximal end portion 610 of rotor 6 ) for vanes 7 are arranged. Suction-side back pressure arc groove 450 extends over an angular range of about three pitches, which is smaller than that of suction-side arc groove 430 .
  • Suction-side back pressure arc groove 450 has a beginning end point “a” that is located slightly ahead of the beginning end point A of notch 434 or suction-side arc groove 430 , and adjacent to main section beginning end portion 433 , in the rotor rotation direction RD 1 .
  • Suction-side back pressure arc groove 450 has a terminal end point “b” that is located about 1.5 pitches behind the terminal end point B of suction-side arc groove 430 in the rotor rotation direction RD 1 .
  • suction-side back pressure arc groove 450 in the rotor radial direction is substantially uniform over the entire length in the circumferential direction, and substantially equal to that of suction-side arc groove 430 , and substantially equal to that of proximal end portion 610 of slot 61 .
  • Suction-side back pressure arc groove 450 has an inside radial edge 454 that is located somewhat inside the inside radial edge of proximal end portion 610 of slot 61 in the rotor radial direction.
  • Suction-side back pressure arc groove 450 has an outside radial edge 455 that is located slightly inside the outside radial edge of proximal end portion 610 of slot 61 in the rotor radial direction.
  • suction-side back pressure arc groove 450 overlaps with most of back pressure chambers br (proximal end portions 610 of slots 61 ) as viewed in the z-axis direction so as to hydraulically communicate with the same.
  • Communication hole 451 is located on the rotor reverse rotation direction side of suction-side back pressure port 45 , closer to the beginning end point a than to the terminal end point b, and overlaps with communication hole 432 of suction-side arc groove 430 in the circumferential direction.
  • Communication hole 451 has a substantially elliptic shape as viewed in the z-axis direction, and has a width in the rotor radial direction which is substantially equal to the width of suction-side back pressure arc groove 450 , and a length in the circumferential direction which is equal to about one pitch. Communication hole 451 extends through first plate 41 in the z-axis direction, and hydraulically communicates with communication hole 432 of suction-side arc groove 430 through first communication passage 491 . In suction-side back pressure arc groove 450 , a beginning end portion 452 is formed between the beginning end point a and suction hole 431 .
  • beginning end portion 452 has a semicircular end which projects in the rotor reverse rotation direction.
  • Suction-side back pressure arc groove 450 has a semicircular terminal end portion 453 which projects in the rotor rotation direction RD 1 .
  • the depth of beginning end portion 452 in the z-axis direction is equal to about 40% or smaller of the thickness of first plate 41
  • the depth of terminal end portion 453 in the z-axis direction is equal to about 20% or smaller of the thickness of first plate 41 .
  • the portion between terminal end portion 453 and communication hole 451 is inclined so that the depth gradually increases as followed toward communication hole 451 , and becomes equal to the thickness of first plate 41 at communication hole 451 .
  • Discharge-side back pressure port 46 is arranged to hydraulically connect the discharge port 44 to back pressure chambers br corresponding to vanes 7 which are located in the discharge region RE 2 , the first closing region RE 3 , a major part of the second closing region RE 4 , and a part of the suction region RE 1 , specifically, back pressure chambers br corresponding to vanes 7 whose distal end portion 70 overlaps with discharge port 44 , the part of suction-side back pressure port 45 , the first closing region RE 3 , or the major part of the second closing region RE 4 .
  • Discharge-side back pressure port 46 includes a discharge-side back pressure arc groove 460 , and a communication hole 461 .
  • Discharge-side back pressure arc groove 460 is formed in the positive z side surface 410 of first plate 41 , and arranged to receive a discharge-side fluid pressure. As viewed in the z-axis direction, discharge-side back pressure arc groove 460 has the form of an arc about the axis of rotation O, extending in the circumferential direction of first plate 41 through a portion in which back pressure chambers br (proximal end portion 610 of rotor 6 ) for vanes 7 are arranged. Discharge-side back pressure arc groove 460 extends over an angular range of about seven pitches, which is larger than that of discharge-side arc groove 440 .
  • Discharge-side back pressure arc groove 460 extends through the first closing region RE 3 , and extends in the suction region RE 1 , having a beginning end point “c” that is located behind the beginning end point C of discharge-side arc groove 440 , and further behind the terminal end point B of suction-side arc groove 430 , in the rotor rotation direction RD 1 .
  • the beginning end point c of discharge-side back pressure arc groove 460 is located about one pitch (equivalent to the angle of 2 ⁇ behind the terminal end point B of suction-side arc groove 430 in the rotor rotation direction RD 1 .
  • a terminal end point “d” of discharge-side back pressure arc groove 460 is located about one pitch or smaller ahead of the terminal end point D of discharge-side arc groove 440 , and thus located closer to the terminal end point of the second closing region RE 4 , in the rotor rotation direction RD 1 .
  • the size of discharge-side back pressure arc groove 460 in the rotor radial direction is substantially uniform over the entire length in the circumferential direction, and slightly smaller than that of discharge-side arc groove 440 , and somewhat smaller than that of proximal end portion 610 of slot 61 .
  • Discharge-side back pressure arc groove 460 has an inside radial edge 464 that is located somewhat outside of the inside edge of proximal end portion 610 in the rotor radial direction. Discharge-side back pressure arc groove 460 has an outside radial edge 465 that is located slightly inside the outside edge of proximal end portion 610 in the rotor radial direction. Wherever cam ring 8 is positioned, discharge-side back pressure arc groove 460 overlaps with most of back pressure chambers br (proximal end portions 610 of slots 61 ) as viewed in the z-axis direction so as to hydraulically communicate with the same.
  • Communication hole 461 is located closer to the beginning end point c than to the terminal end point d, and in an angular position between the terminal end point B of suction-side arc groove 430 and the x axis (midpoint in the first closing region RE 3 ) on the beginning end side of the first closing region RE 3 .
  • the diameter of communication hole 461 is substantially equal to the width of discharge-side back pressure arc groove 460 in the rotor radial direction.
  • Communication hole 461 is formed to extend through first plate 41 with such an inclination relative to the z axis that the cross-section of communication hole 461 as viewed in the z-axis direction moves outwards in the rotor radial direction as followed in the negative z-axis direction.
  • Communication hole 461 is opened in the negative z side surface of first plate 41 , and arranged to hydraulically communicate with communication hole 441 of discharge port 44 (discharge-side arc groove 440 ) through second communication passage 492 .
  • Discharge-side back pressure arc groove 460 includes a beginning end portion 462 , and a back pressure port main section 468 .
  • FIG. 6 is a sectional view of pumping section 2 of pump 1 , including a sectional view of first plate 41 taken along the line VI-VI in FIG. 3 .
  • Back pressure port main section 468 is a main section of discharge-side back pressure arc groove 460 , extending from a beginning end point “e” to the terminal end point d.
  • the beginning end point e is located about 0.4 pitch or smaller behind the terminal end point B of suction port 43 in the rotor rotation direction RD 1 .
  • the depth of back pressure port main section 468 in the z-axis direction is substantially uniform.
  • the beginning end edge 467 of back pressure port main section 468 is substantially in the form of a semicircle projecting in the rotor reverse rotation direction.
  • the terminal end edge 463 of back pressure port main section 468 or discharge-side back pressure arc groove 460 is substantially in the form of a semicircle projecting in the rotor rotation direction RD 1 .
  • Beginning end portion 462 which is located on the rotor reverse rotation direction side of discharge-side back pressure arc groove 460 or behind back pressure port main section 468 in the rotor rotation direction RD 1 , extending in the suction region RE 1 from the beginning end point c toward the edge 467 (beginning end point e) by 0.5 pitch or more in the rotor rotation direction RD 1 .
  • the leading end of beginning end portion 462 facing the terminal end point b of suction-side back pressure arc groove 450 is substantially rectangular with a straight edge extending in the rotor radial direction.
  • FIG. 7 is an enlarged view of a portion of pumping section 2 indicated by VII in FIG. 6 , showing a sectional shape of beginning end portion 462 .
  • beginning end portion 462 is substantially flat. As viewed in the rotor rotation direction RD 1 , beginning end portion 462 has a rectangular section that is substantially constant as followed in the rotor rotation direction RD 1 . The depth (length in the z-axis direction) of beginning end portion 462 is substantially uniform. Beginning end portion 462 serves as a throttling portion which has a smaller cross-sectional flow area than back pressure port main section 468 . In the first embodiment, the cross section of beginning end portion 462 as viewed in the rotor rotation direction RD 1 is not limited to rectangular shapes, but may have any shape if the cross-sectional flow area is substantially uniform as followed in the rotor rotation direction RD 1 .
  • beginning end portion 462 may have a cross-section with a moderately projected portion at the center of the bottom.
  • the ratio of the depth of beginning end portion 462 with respect to that of back pressure port main section 468 may be selected arbitrarily.
  • Second plate 42 includes a discharge-side back pressure arc groove 460 , similar to first plate 41 .
  • the discharge-side back pressure arc groove 460 of second plate 42 includes a back pressure port main section 468 that extends from the beginning end point e, similar to the back pressure port main section 468 of first plate 41 , but includes no beginning end portion 462 in contrast to first plate 41 .
  • a portion of the negative z side surface of second plate 42 that faces the beginning end portion 462 of first plate 41 is formed with no recess.
  • second plate 42 may be provided with beginning end portion 462 in discharge-side back pressure arc groove 460 , similar to first plate 41 .
  • the clearance between rotor 6 and first or second plate 41 or 42 in the z-axis direction is set small enough to prevent flow of working fluid in places (first closing region RE 3 , etc.) where discharge-side back pressure arc groove 460 does not extend.
  • working fluid flows through discharge-side back pressure arc groove 460 between rotor 6 and first or second plate 41 or 42 .
  • Communication hole 461 is provided with an orifice 466 in a passage leading to discharge-side back pressure port 46 (discharge-side back pressure arc groove 460 ).
  • Orifice 466 serves to restrict the flow passage of working fluid from discharge-side back pressure port 46 to discharge port 44 , and thereby maintain the internal pressure of discharge-side back pressure port 46 to be high, promote the projection of vane 7 , and enhance the startability of pump 1 .
  • control section 3 is mounted in housing 4 , including a control valve 30 , first and second fluid passages 31 and 32 , and first and second control chambers R 1 and R 2 .
  • Control valve 30 is a hydraulically-controlled valve, such as a spool valve, which includes a spool 302 mounted in an accommodation hole 401 formed in housing body 40 , and a solenoid 301 mounted in housing 4 for actuating the spool 302 , so as to switch the supply of working fluid between first fluid passage 31 and second fluid passage 32 formed in housing body 40 .
  • First fluid passage 31 and first communication passage 931 constitute a first control fluid passage.
  • each pump chamber r expands and contracts periodically while revolving about the axis of rotation O.
  • Working fluid is sucked through suction port 43 to each pump chamber r in the suction region RE 1 on the negative y side where pump chamber r expands while moving along with rotation of rotor 6 , and working fluid is discharged through discharge port 44 from each pump chamber r in the discharge region RE 2 on the negative y side where pump chamber r contracts while moving along with rotation of rotor 6 .
  • each pump chamber r continues to expand until the rotor reverse rotation direction side vane 7 (rear-side vane 7 ) of pump chamber r passes through the terminal end point B of suction-side arc groove 430 , namely, until the rotor rotation direction side vane 7 (front-side vane 7 ) of pump chamber r passes through the beginning end point C of discharge-side arc groove 440 .
  • pump chamber r is maintained hydraulically connected to suction-side arc groove 430 , sucking working fluid through suction port 43 .
  • pump chamber r is hydraulically separated from both of suction-side arc groove 430 and discharge-side arc groove 440 , and thereby liquid-tightly closed.
  • pump chamber r contracts while moving along with rotation of rotor 6 , and gets hydraulically connected to discharge-side arc groove 440 , so as to discharge working fluid through discharge port 44 .
  • each pump chamber r is positioned in the second closing region RE 4 , i.e.
  • each of the first closing region RE 3 and second closing region RE 4 has a range of one pitch (i.e. the width of pump chamber r in the circumferential direction).
  • each of the first closing region RE 3 and second closing region RE 4 (the spacing between suction port 43 and discharge port 44 ) is not limited to one pitch, but may have an angular range of more than one pitch. Namely, the range of each of the first closing region RE 3 and second closing region RE 4 may be arbitrarily set if fluid communication can be prevented between the suction region RE 1 and the discharge region RE 2 .
  • the throttling function of the beginning end portion 443 of discharge-side arc groove 440 serves to prevent rapid fluid communication between pump chamber r and discharge-side arc groove 440 , and thereby suppress fluctuations in the internal pressures of discharge port 44 and pump chamber r.
  • beginning end portion 443 of discharge-side arc groove 440 may be omitted or modified arbitrarily.
  • the throttling function of the notch 434 of suction port 43 serves to prevent rapid fluid communication between pump chamber r and suction-side arc groove 430 , and thereby suppress fluctuations in the internal pressures of suction port 43 and pump chamber r. This prevents working fluid from rapidly flowing from pump chamber r having a higher pressure to suction port 43 having a lower pressure, and thereby prevents occurrence of bubbles (cavitation).
  • the notch 434 may be omitted or modified arbitrarily.
  • first control chamber R 1 is supplied with working fluid from control valve 30 through the first control fluid passage.
  • the supplied fluid pressure serves to produce a first hydraulic force for pressing the cam ring 8 in the negative x-axis direction against the biasing force of spring 12 .
  • second control chamber R 2 is supplied with working fluid from control valve 30 through the second control fluid passage. The supplied fluid pressure serves to produce a second hydraulic force for pressing the cam ring 8 in the positive x-axis direction in addition to the biasing force of spring 12 .
  • CVT control unit 300 controls operation of control valve 30 , and thereby changes the first and second hydraulic forces by suitable supply and drain of working fluid to and from first and second control chambers R 1 and R 2 . This operation causes movement of cam ring 8 , so that the eccentricity b changes. In this way, CVT control unit 300 controls the pump capacity. More specifically, when the hydraulic pressure in first control chamber R 1 is increased, the first hydraulic force is increased. On the other hand, when the hydraulic pressure in second control chamber R 2 is increased, the second hydraulic force is increased.
  • Second control chamber R 2 may be omitted so that only first control chamber R 1 serves to move cam ring 8 .
  • the device for constantly biasing the cam ring 8 is not limited to coil springs, but may be implemented differently.
  • back pressure chamber br is contracteding, it is possible that the distal end portion 70 of vane 7 undergoes a high frictional resistance in contact with the inside peripheral surface 80 of cam ring 8 , if working fluid is not smoothly discharged from back pressure chamber br so as to allow inward movement or retraction of vane 7 into slot 61 .
  • back pressure chamber br is supplied with working fluid from suction-side back pressure port 45 . This serves to improve the outward movement of vane 7 .
  • suction-side back pressure port 45 is hydraulically connected to suction port 43 through first communication passage 491 , the internal pressure of suction port 43 is substantially equal to that of suction-side back pressure port 45 .
  • the distal end portion 70 of vane 7 is prevented from being unnecessarily strongly pressed on the inside peripheral surface 80 of cam ring 8 , as compared to cases where back pressure chamber br is adapted to receive a high hydraulic pressure from a discharge port.
  • This results in reduction in the loss torque due to friction between the distal end portion 70 of vane 7 and the inside peripheral surface 80 of cam ring 8 .
  • this feature serves to reduce the frictional resistance to the sliding movement of the distal end portion 70 of vane 7 on the inside peripheral surface 80 of cam ring 8 , and thereby reduce the power loss, as compared to cases where all of the proximal end portions 71 of vane 7 positioned in the suction region RE 1 are applied with a discharge-side pressure.
  • the distal end portion 70 of vane 7 is subject to pressure from discharge port 44
  • the proximal end portion 71 of vane 7 is subject to pressure from discharge-side back pressure port 46 . Since discharge-side back pressure port 46 is hydraulically connected to discharge port 44 through second communication passage 492 , the distal end portion 70 and proximal end portion 71 of vane 7 are subject to substantially the same pressure. Accordingly, the distal end portion 70 of vane 7 is prevented from being unnecessarily strongly pressed on the inside peripheral surface 80 of cam ring 8 . This serves to reduce the loss torque due to friction between the distal end portion 70 of vane 7 and the inside peripheral surface 80 of cam ring 8 .
  • suction-side back pressure port 45 and discharge-side back pressure port 46 are separately provided for back pressure chambers br, so that both in the suction region RE 1 and in the discharge region RE 2 , the distal end portion 70 and proximal end portion 71 of vane 7 are subject to substantially the same pressure.
  • This feature serves to suitably press the vane 7 on cam ring 8 by the centrifugal force, while suppressing the frictional resistance between vane 7 and cam ring 8 .
  • This serves to reduce wear between vane 7 and the inside peripheral surface 80 of cam ring 8 , and reduce the power loss, because the required driving torque for rotating the rotor 6 is reduced.
  • pump 1 is formed as an efficient low-torque type pump where: the required driving torque is smaller with respect to rotational speed; the fuel efficiency is enhanced by reduction in the power loss; and the discharge rate is larger even if the exterior size is identical (i.e. pump 1 can be formed compact), as compared to typical variable displacement pumps.
  • the projection of vane 7 from slot 61 to the inside peripheral surface 80 of cam ring 8 is implemented mainly by the centrifugal force. Accordingly, when the internal combustion engine is operating in a low speed region, for example, when the engine is at start or at idle, rotor 6 is rotating slowly so that the centrifugal force is small, and the distal end portion 70 of vane 7 may be out of contact with the inside peripheral surface 80 of cam ring 8 because the pressing force for distal end portion 70 is insufficient. This is based on the fact that the amount of projection of vane 7 depends on the force acting on vane 7 outwards in the rotor radial direction.
  • the force depends mainly on the centrifugal force, the viscosity of working fluid, and the friction between vane 7 and slot 61 . Among those, the contribution of the centrifugal force is highest.
  • pump chamber r shifts between the suction region RE 1 and the discharge region RE 2 along with rotation of rotor 6 . If vane 7 moves into the first closing region RE 3 or second closing region RE 4 under a condition that vane 7 is out of contact with the inside peripheral surface 80 of cam ring 8 due to insufficient projection of vane 7 , pump 1 may encounter the following problem.
  • the front-side vane 7 of the first pump chamber r When the rear-side vane 7 of a first pump chamber r is positioned in the first closing region RE 3 , the front-side vane 7 of the first pump chamber r is positioned in the discharge region RE 2 so that the first pump chamber r is hydraulically connected to discharge port 44 , and thereby the internal pressure of the first pump chamber r is high, because the length of the first closing region RE 3 in the circumferential direction is equal to one pitch.
  • the pressure in discharge port 44 falls periodically while moving along with rotation of rotor 6 , and thereby causes pulsation of the discharge pressure. This causes a decrease in the amount of discharged working fluid, and a fall in the discharge-side pressure, and thereby causes a fall in the pump efficiency, and a fall in the startability of the system (CVT 100 ) that uses the pump discharge pressure.
  • pump 1 is configured so that the back pressure chamber br for each vane 7 is applied with high pressure, before the vane 7 enters the first closing region RE 3 . This ensures that vane 7 is pressed outwards in the rotor radial direction, and brought into contact with the inside peripheral surface 80 of cam ring 8 , so that the vane 7 liquid-tightly divides and seals the two adjacent pump chambers r from one another.
  • FIG. 8 is a sectional view of pump 1 taken along the line VIII-VIII in FIG. 6 . In FIG. 8 , the outside periphery of rotor 6 , the inside periphery of cam ring 8 , the shape of suction-side arc groove 430 , etc.
  • discharge-side back pressure port 46 (discharge-side back pressure arc groove 460 ) extends also in the suction region RE 1 , and the beginning end point c of discharge-side back pressure port 46 is located a distance L 0 (one pitch) behind the terminal end point B of suction port 43 (suction-side arc groove 430 ) in the rotor rotation direction RD 1 .
  • the distance L 0 may be larger than or smaller than one pitch.
  • the back pressure chamber br for the vane 7 is hydraulically connected to discharge-side back pressure port 46 .
  • the discharge-side pressure is supplied and applied from discharge-side back pressure port 46 to the proximal end portion 71 of vane 7 , so that the vane 7 moves outwards in the rotor radial direction, into pressing contact with cam ring 8 .
  • the back pressure chamber br for the vane 7 that defines the pump chamber r positioned in the first closing region RE 3 between the suction region RE 1 and the discharge region RE 2 is applied with high pressure, so that the distal end portion 70 of vane 7 is pressed on the inside peripheral surface 80 of cam ring 8 by the differential pressure between the distal end portion 70 and proximal end portion 71 of vane 7 .
  • This serves to maintain the liquid tightness of the pump chamber r that is positioned immediately behind the discharge region RE 2 in the rotor rotation direction RD 1 , and provide sealing between the low pressure suction side and the high pressure discharge side.
  • This feature serves to allow vane 7 to move out of slot 61 , and thereby allow pump 1 to perform the suction and discharge function normally, even when the viscosity of working fluid is high, for example, during cold start, so that the pressing force for vane 7 based on the centrifugal force is insufficient.
  • the startability of pump 1 at low temperature is thus enhanced.
  • the efficiency of a typical variable displacement pump is lower than a typical fixed displacement pump, namely, the required driving torque of the variable displacement pump is larger than that of the fixed displacement pump if the rotational speed is the same.
  • the efficiency of pump 1 is improved as described above, there is a region where the efficiency is lower than that of the fixed displacement type, and the effect of reduction in the power loss is insufficient. Accordingly, it is desirable to further reduce the power loss in a variable displacement pump.
  • pump 1 is configured so that the shape of discharge-side back pressure port 46 (the cross-sectional flow area and the position of the beginning end point c) is adjusted so as to optimize the angular range where the back pressure chamber br for vane 7 is supplied with high pressure before entering the first closing region RE 3 . This serves to prevent the flow through vane 7 between pump chambers r, and reduce the power loss even in a low speed region where the efficiency is relatively low.
  • the shape of discharge-side back pressure port 46 is set so that supply of the amount of working fluid corresponding to the clearance is completed when the rotor rotation direction side surface of the first vane 7 has reached a position as close to the terminal end point B of suction port 43 as possible.
  • A represents the cross-sectional flow area of a fluid passage from discharge-side back pressure port 46 to the back pressure chamber br for vane 7 , i.e. the cross-sectional flow area of discharge-side back pressure port 46 as viewed in the rotor rotation direction RD 1
  • Q represents an amount per unit time (volumetric flow rate) of working fluid flowing from discharge-side back pressure port 46 into the back pressure chamber br
  • C represents a flow rate coefficient
  • ⁇ represent the density of working fluid
  • ⁇ P represents the differential pressure through the fluid passage (the difference in pressure between discharge-side back pressure port 46 and back pressure chamber br ⁇ discharge pressure):
  • a quantity ⁇ Q (time integral of Q), which is a total amount of working fluid supplied to back pressure chamber br for vane 7 , is proportional to a product of a time period T when back pressure chamber br for vane 7 is hydraulically connected to discharge-side back pressure port 46 , and the cross-sectional flow area A.
  • the time period T depends on the rotational speed of rotor 6 (or the travel speed of vane 7 ), and a travel distance L* of vane 7 in the rotor rotation direction RD 1 in discharge-side back pressure port 46 (i.e. the angular range of travel of back pressure chamber br from the beginning end point c of discharge-side back pressure port 46 ).
  • the time period T is determined by the travel distance L*.
  • the quantity ⁇ Q is determined by the cross-sectional flow area A of discharge-side back pressure port 46 and the travel distance L* (or the position of the beginning end point c).
  • the distance (angular range) from the beginning end point c of beginning end portion 462 to the beginning end point e of back pressure port main section 468 , L, and the cross-sectional flow area of the beginning end portion 462 of discharge-side back pressure port 46 , A, are set so that the fluid quantity ⁇ Q conforms to the amount of working fluid corresponding to the clearance between vane 7 and cam ring 8 .
  • the distance L and cross-sectional flow area A are set so that while vane 7 moves from the beginning end point c of beginning end portion 462 to the beginning end point e of back pressure port main section 468 , the fluid quantity ⁇ Q which is identical to the total quantity supplied to back pressure chamber br so as to bring the distal end portion 70 of vane 7 into contact with the inside peripheral surface 80 of cam ring 8 .
  • discharge-side back pressure port 46 is arranged so that vane 7 is brought into contact with the inside peripheral surface 80 of cam ring 8 at the beginning end point e close to the terminal end point B, so as to prevent the flow through vane 7 between pump chambers r, and suppress the loss torque due to useless pressing contact.
  • FIG. 9 shows, in the lower part, combinations of the cross-sectional flow area A of the beginning end portion 462 of discharge-side back pressure port 46 and the distance L with which it is possible to reduce the loss torque while preventing the vane through flow, thus bringing the power loss into an allowable region.
  • Pump 1 is configured so that the point defined by the cross-sectional flow area A and the distance L is positioned in a region indicated by hatching pattern in FIG. 9 .
  • the allowable region may be defined so that the total loss torque is comparable to or smaller than the loss torque of a typical fixed displacement pump, when in a predetermined low speed region including a fixed displacement region or when in a mode where such a low speed region is frequently used.
  • the power loss of pump 1 can be thus reduced to a level comparable to or lower than that of a typical fixed displacement pump, even when the CVT to which pump 1 is adapted is operating in a mode where a low speed region where the efficiency is relatively low is frequently used. Also, the power loss of pump 1 can be reduced to a level comparable to or lower than that of a typical fixed displacement pump, even when pump 1 is used as a fluid pressure supply source for a power steering system which constantly uses a low speed region in which the efficiency is relatively low.
  • the cross-sectional flow area A and the distance L are set in such a desirable region (indicated by hatching pattern in FIG. 9 ) that even if vane 7 starts to contact the cam ring 8 at a point behind the beginning end point e of back pressure port main section 468 in the rotor rotation direction RD 1 under the influence of rotational speed, fluid temperature, and others, the loss torque due to pressing contact of vane 7 (vane loss torque) is below an upper limit of an allowable range. If vane 7 is maintained in contact with cam ring 8 in the suction region RE 1 , vane 7 continues to be in pressing contact with cam ring 8 after passing through the beginning end point c of the beginning end portion 462 , so that the loss torque becomes equal to the upper limit of the desirable region.
  • the maximum allowable value of the distance L is set to a value Lmax that is on the boundary of the allowable range of the vane loss torque, as shown in FIG. 9 .
  • the back pressure chamber br is supplied with working fluid at a larger flow rate after vane 7 passes through the beginning end point e than before, because the cross-sectional flow area of back pressure port main section 468 is set larger than that of beginning end portion 462 in discharge-side back pressure port 46 .
  • This feature serves to ensure the prevention of vane through flow, because supply of the amount of working fluid corresponding to the clearance between vane 7 and cam ring 8 is completed before the rotor rotation direction side surface of vane 7 passes through the beginning end point e of back pressure port main section 468 and then reaches the terminal end point B of suction port 43 .
  • Pump 1 may be modified so that when the rotor rotation direction side surface of vane 7 reaches the terminal end point B of suction port 43 , supply of the required amount of working fluid is completed.
  • the beginning end point e of back pressure port main section 468 may be moved to be identical to the terminal end point B of suction port 43 so that the beginning end portion 462 extends from the beginning end point c to the terminal end point B.
  • the range where vane 7 is in sliding contact is further reduced to reduce the loss torque more effectively.
  • the desirable position of the beginning end point c (or the desirable range of the distance L) for such cases may be defined with reference to the position of the terminal end point B of suction port 43 .
  • discharge-side back pressure port 46 is provided with beginning end portion 462 that has a reduced cross-sectional flow area A, and thus forms a throttling portion.
  • back pressure chamber br proximal end portion 610 of slot 61
  • working fluid flows from back pressure port main section 468 through beginning end portion 462 to back pressure chamber br. Since the cross-sectional flow area of beginning end portion 462 is set smaller than that of back pressure port main section 468 , the flow rate of working fluid supplied to back pressure chamber br (flow rate Q) is restricted.
  • the cross-sectional flow area A of beginning end portion 462 is adjusted so that the travel speed of vane 7 outwards in the rotor radial direction, V, when distal end portion 70 is contacting the inside peripheral surface 80 of cam ring 8 , is optimized, and thereby noise due to contact of vane 7 is within an allowable region.
  • speed V is set so as to permit a some level of noise during cold start, and suppress the occurrence of noise while pump 1 is at idle.
  • H C/V ⁇ (2 ⁇ P/ ⁇ ), where H represents an area ratio S/A.
  • the speed V is optimized by adjusting the area ratio H.
  • the cross-sectional flow area A of beginning end portion 462 is adjusted with reference to the cross-sectional area S, to achieve the optimized speed V.
  • the cross-sectional flow area A of beginning end portion 462 is set within a range from a predetermined minimum value Amin to a predetermined maximum value Amax.
  • the maximum value Amax is determined depending on an allowable noise level.
  • the minimum value Amin is determined depending on the distance L.
  • FIG. 9 shows, in the upper part, a relationship between the cross-sectional flow area A of discharge-side back pressure port 46 , and the noise level.
  • the relationship may be experimentally found or estimated on the basis of design values.
  • Pump 1 is configured so that the cross-sectional flow area A of the beginning end portion 462 of discharge-side back pressure port 46 is set within the desirable range from Amin to Amax, and thereby the noise level is below an upper limit of the allowable range.
  • allowable combinations of the cross-sectional flow area A and distance L are positioned within the region indicated by hatching pattern in FIG. 9 .
  • the beginning end portion 462 has a substantially rectangular section as viewed in the z-axis direction, where the depth in the z-axis direction is constant as followed in the rotor rotation direction. Namely, the size of beginning end portion 462 in the rotor radial direction is substantially constant as followed in the rotor rotation direction RD 1 , and the depth of beginning end portion 462 is also substantially constant. Accordingly, the cross-sectional flow area A of beginning end portion 462 is substantially constant as followed in the rotor rotation direction RD 1 , so that the flow rate Q of working fluid supplied to back pressure chamber br for vane 7 that is positioned at beginning end portion 462 is substantially constant. This makes it possible to easily set the speed V of vane 7 that moves into contact with cam ring 8 .
  • FIG. 10 is a sectional view of a vane pump according to a first comparative example, which corresponds to the sectional view of FIG. 8 .
  • FIG. 11 is a sectional view of a vane pump according to a second comparative example, which corresponds to the sectional view of FIG. 8 . As shown in FIG.
  • discharge-side back pressure port 46 (discharge-side back pressure arc groove 460 ) is formed to extend also in the suction region RE 1 , but discharge-side back pressure port 46 has a beginning end point c 1 closer to the terminal end point B of suction port 43 , where the distance L 1 between the beginning end point c 1 and the terminal end point B is equal to a value that is much smaller than the lower limit value Lmin of the desirable range (L 1 ⁇ Lmin).
  • cross-sectional flow area A of discharge-side back pressure port 46 is the same as that of back pressure port main section 468 according to the first embodiment, and equal to a value A 0 that is much larger than the upper limit Amax of the desirable range (A 0 >>Amax).
  • the amount of working fluid supplied to back pressure chamber br for vane 7 that is entering the first closing region RE 3 is to insufficient so that the projection of vane 7 is delayed to allow the vane through flow.
  • the combination of the cross-sectional flow area A 0 and the distance L 1 is positioned out of the desirable region in FIG. 9 , so that the occurrence of vane through flow vane is possible.
  • the fluid quantity ⁇ Q of working fluid supplied to back pressure chamber br during the period when the rotor rotation direction side surface of vane 7 moves from the beginning end point c 1 to the terminal end point B is below the amount corresponding to the clearance between vane 7 and cam ring 8 (the amount for eliminating the clearance).
  • the vane through flow occurs, because the distal end portion 70 of vane 7 is out of contact with the inside peripheral surface 80 of cam ring 8 when the rotor rotation direction side surface of vane 7 has reached the terminal end point B.
  • the travel speed of vane 7 when vane 7 collapses with cam ring 8 is high, because the cross-sectional flow area A is excessive.
  • the cross-sectional flow area A 0 of the first comparative example is larger than the upper limit Amax of the region where noise level is in the allowable range. Since the discharge-side back pressure port 46 of the first comparative example is provided with no such throttling portion (beginning end portion 462 according to the first embodiment), working fluid flows rapidly into back pressure chamber br. Accordingly, when vane 7 contacts the inside peripheral surface 80 of cam ring 8 after passing through the terminal end point B, the speed V of vane 7 is high. As a result, the noise due to contact or collapse of vane 7 is out of the allowable range.
  • discharge-side back pressure port 46 has a beginning end point c 2 that is substantially identical to the beginning end point c according to the first embodiment, where the distance L 2 between the beginning end point c 2 of discharge-side back pressure port 46 and the terminal end point B of suction port 43 is substantially equal to the distance L 0 according to the first embodiment, and smaller than upper limit value Lmax of the desirable range (L 2 ⁇ L 0 ⁇ Lmax).
  • cross-sectional flow area A of discharge-side back pressure port 46 in the suction region RE 1 is the same as that of back pressure port main section 468 according to the first embodiment, and equal to a value A 0 that is much larger than the upper limit Amax of the desirable range (A 0 >>Amax).
  • the amount of working fluid supplied to back pressure chamber br for vane 7 that is entering the first closing region RE 3 is sufficient to prevent the vane through flow.
  • vane 7 moves into sliding contact with cam ring 8 in earlier timing than in the first embodiment.
  • cross-sectional flow area A of discharge-side back pressure port 46 of the second comparative example is larger than that of the first embodiment, so that the fluid quantity ⁇ Q of working fluid supplied to back pressure chamber br exceeds the amount corresponding to the clearance between vane 7 and cam ring 8 (the amount for eliminating the clearance), when the rotor rotation direction side surface of vane 7 has traveled from the beginning end point c 2 to a point F which is behind the point for the first embodiment that is a distance L** ahead of the beginning end point c 2 .
  • the region where the distal end portion 70 of vane 7 is unnecessarily pressed on the inside peripheral surface 80 of cam ring 8 before passing through the terminal end point B, is larger than in the first embodiment, so that the loss torque is larger, but within the desirable range indicated by hatching pattern in FIG. 9 .
  • the speed of vane 7 when vane 7 collapses with cam ring 8 is high, because the discharge-side back pressure port 46 of the first comparative example is provided with no such throttling portion (beginning end portion 462 according to the first embodiment) so that the cross-sectional flow area A is excessive.
  • the cross-sectional flow area A 0 of the first comparative example is larger than the upper limit Amax of the region where noise level is in the allowable range. Accordingly, as in the first comparative example, when vane 7 contacts the inside peripheral surface 80 of cam ring 8 after passing through the terminal end point B, the speed V of vane 7 is high. As a result, the noise due to collapse of vane 7 is out of the allowable range.
  • the cross-sectional flow area A of the beginning end portion 462 of discharge-side back pressure port 46 in the suction region RE 1 and the distance L are set in the region indicated by hatching pattern in FIG. 9 , so as to simultaneously optimize the sealing effect, the loss torque, and the noise level, in consideration of the relationship shown in FIG. 9 between those parameters. Accordingly, it is possible to prevent the vane through flow, suppress the pulsation and noise, and suppress adverse effects on the pump efficiency and startability. Moreover, it is possible to reduce the region where vane 7 is unnecessarily pressed on cam ring 8 , and thereby reduce the power loss.
  • a vane pump ( 1 ) comprises: a rotor ( 6 ) adapted to be rotated by a drive shaft ( 5 ), the rotor ( 6 ) including a plurality of slots ( 61 ) at an outside periphery ( 60 ) of the rotor ( 6 ); a plurality of vanes ( 7 ) mounted in corresponding ones of the slots ( 61 ), and adapted to project from, and travel inwards and outwards of the corresponding slots ( 61 ); a cam ring ( 8 ) adapted to be eccentric with respect to the rotor ( 6 ), the cam ring ( 8 ) surrounding the rotor ( 6 ); and a plate (first or second plate 41 or 42 ) arranged to face an axial end of the rotor ( 6 ), and define a plurality of pump chambers (r) in cooperation with the rotor ( 6 ), the vanes ( 7 ), and the cam ring ( 8 ), wherein the plate (first plate 41 ) includes at a
  • the throttling portion (beginning end portion 462 ) has a cross-sectional flow area (A) that is substantially constant as followed in a direction of rotation of the rotor ( 6 ). This feature makes it possible to easily set the speed V of vane 7 when vane 7 moves into contact with cam ring 8 , by adjusting the depth of the throttling portion (beginning end portion 462 ).
  • the second vane ( 7 ) is behind in a direction of rotation of the rotor ( 6 ) and adjacent to a third one of the vanes ( 7 ) whose distal end portion ( 70 ) is positioned between a terminal end (terminal end point B) of the suction port ( 43 ) and a beginning end (beginning end point C) of the discharge port ( 44 ); and the second back pressure port (discharge-side back pressure port 46 ) is arranged to supply the proximal end portion ( 610 , or back pressure chamber br) of the second slot ( 61 ) at least with an amount of working fluid, during a period before the second vane ( 7 ) passes through the terminal end (B) of the suction port ( 43 ) after the proximal end portion ( 610 , br) of the second slot ( 61 ) starts to hydraulically communicate with the second back pressure port ( 46 ), wherein the amount of working fluid is sufficient to bring
  • the throttling portion (beginning end portion 462 ) has a rectangular cross-section with a substantially constant depth and a substantially constant width as viewed and followed in the rotor rotation direction RD 1 , so that the cross-sectional flow area A is substantially constant as followed in the rotor rotation direction RD 1 .
  • the shape of the throttling portion may be modified so that the cross-sectional flow area A changes as followed in the rotor rotation direction RD 1 , in consideration of the viscosity of working fluid, the density of working fluid, and other factors, as shown in FIGS. 12A to 15 .
  • the edge 467 of back pressure port main section 468 is rectangular, not semicircular as in the first embodiment.
  • the other parts are the same as in the first embodiment, and accordingly, description of the other parts is omitted.
  • the fluid quantity ⁇ Q is set by combination of the cross-sectional flow area A and distance L of the throttling portion (beginning end portion 462 ), so as to prevent the vane through flow, and the unnecessary pressing of vane 7 , as in the first embodiment. Since the cross-sectional flow area of beginning end portion 462 is not constant as followed in the rotor rotation direction RD 1 as in the first embodiment, the average of the cross-sectional flow area of beginning end portion 462 , which is averaged in the rotor rotation direction RD 1 , may be used as the cross-sectional flow area A to set the fluid quantity ⁇ Q.
  • beginning end portion 462 is formed so that the cross-sectional flow area of beginning end portion 462 increases as followed in the rotor rotation direction RD 1 .
  • This feature makes it possible to set the ejecting speed of vane 7 that is passing through the beginning end portion 462 as follows.
  • FIGS. 12A to 12D are plan views of beginning end portions 462 according to variations of the second embodiment in the z-axis direction. In the examples shown in FIGS.
  • the width of beginning end portion 462 in the rotor radial direction is set to increase as followed in the rotor rotation direction RD 1 , whereas the bottom (negative z side surface) of beginning end portion 462 is substantially flat, and the depth of beginning end portion 462 is substantially constant, as in the first embodiment.
  • the width (average width) of beginning end portion 462 is smaller than that in the first embodiment
  • the depth of beginning end portion 462 is set larger than that in the first embodiment, so that the cross-sectional flow area is not reduced.
  • the shape of the bottom may be modified arbitrarily.
  • the shape of beginning end portion 462 as viewed in the z-axis direction is substantially in the form of an acute angle triangle whose width gradually increases as followed in the rotor rotation direction RD 1 at a predetermined substantially constant rate to a predetermined value that is smaller than the width of back pressure port main section 468 . Accordingly, while vane 7 passes through beginning end portion 462 , the cross-sectional flow area of a passage to back pressure chamber br gradually increases from zero to a predetermined value at a substantially constant rate. As a result, the flow rate Q of working fluid supplied to back pressure chamber br gradually increases from zero, so that the ejecting speed of vane 7 is low at first, and gradually increases at a substantially constant rate.
  • the shape of FIG. 12A is desirable, when such characteristics are desired.
  • beginning end portion 462 is substantially in the form of a trapezoid whose width gradually increases as followed in the rotor rotation direction RD 1 at a predetermined substantially constant rate from a predetermined smaller value to a predetermined larger value that is smaller than the width of back pressure port main section 468 . Accordingly, while vane 7 passes through beginning end portion 462 , the cross-sectional flow area of a passage to back pressure chamber br gradually increases from a predetermined smaller value to a predetermined larger value at a substantially constant rate.
  • the flow rate Q of working fluid supplied to back pressure chamber br is above zero, at first, and then gradually increases, so that the ejecting speed of vane 7 is moderate at first, and then gradually increases at a substantially constant rate.
  • This feature serves to shorten the period in which vane 7 moves into contact with the inside peripheral surface 80 of cam ring 8 , as compared to the shape of FIG. 12A .
  • the shape of FIG. 12B is desirable, when such characteristics are desired.
  • beginning end portion 462 as viewed in the z-axis direction is substantially in the form of a semi-ellipse whose width gradually increases as followed in the rotor rotation direction RD 1 from zero to a predetermined value that is smaller than the width of back pressure port main section 468 .
  • the rate of increase is large at first, and then decreases.
  • the cross-sectional flow area of a passage to back pressure chamber br gradually increases from zero to a predetermined value at the rate that is large at first, and then decreases.
  • the shape of beginning end portion 462 as viewed in the z-axis direction is a combination of the rectangular shape according to the first embodiment and the trapezoidal shape of FIG. 12B , whose width is constant at first, and then gradually increases as followed in the rotor rotation direction RD 1 at a predetermined substantially constant rate to a predetermined value that is smaller than the width of back pressure port main section 468 . Accordingly, while vane 7 passes through beginning end portion 462 , the cross-sectional flow area of a passage to back pressure chamber br is constant at first, and then gradually increases at a substantially constant rate.
  • the flow rate Q of working fluid supplied to back pressure chamber br is constant, at first, and then gradually increases, so that the ejecting speed of vane 7 is constant at first, and then gradually increases at a substantially constant rate.
  • the ejecting speed of vane 7 does not change significantly as in the examples shown in FIGS. 12A to 12C .
  • the pressing of vane 7 to cam ring 8 is ensured.
  • the shape of FIG. 12D is desirable, when such characteristics are desired.
  • FIGS. 13A and 13B are side sectional views of the beginning end portions 462 according to other variations of the second embodiment.
  • the bottom of beginning end portion 462 is inclined as followed in the rotor rotation direction RD 1 so that the depth of beginning end portion 462 in the z-axis direction gradually increases as followed in the rotor rotation direction RD 1 .
  • the width of beginning end portion 462 in the rotor radial direction is substantially constant as followed in the rotor rotation direction RD 1 .
  • the bottom of beginning end portion 462 is composed of inclined surfaces and a level surface, specifically, composed of a first inclined surface where the depth of beginning end portion 462 gradually increases at a substantially constant rate from zero to a predetermined value as followed in the rotor rotation direction RD 1 , an intermediate level surface where the depth of beginning end portion 462 is constant as viewed in the rotor rotation direction RD 1 , and a second inclined surface where the depth of beginning end portion 462 gradually increases at a substantially constant rate from the first value to a second predetermined value, wherein the second inclined surface is connected to the back pressure port main section 468 .
  • the inclination of the first inclined surface is larger than that of the second inclined surface.
  • the cross-sectional flow area of a passage to back pressure chamber br gradually increases from zero to a predetermined value at a constant rate, and then becomes constant, and then gradually increases at a substantially constant and slower rate.
  • the flow rate Q of working fluid supplied to back pressure chamber br changes similarly, so that the ejecting speed of vane 7 relatively rapidly increases, and then becomes constant, and then relatively slowly increases. This is effective for reducing the acceleration of vane 7 temporarily, while ensuring that vane 7 is pressed on the inside peripheral surface 80 of cam ring 8 .
  • the shape of FIG. 13A is desirable, when such characteristics are desired.
  • the shape of beginning end portion 462 may be modified so that the inclination of the first inclined surface is smaller than that of the second inclined surface.
  • the bottom of beginning end portion 462 is composed of an inclined surface, so that the depth of beginning end portion 462 gradually increases at a substantially constant rate from zero to a predetermined value that is smaller than the depth of back pressure port main section 468 . Accordingly, while vane 7 passes through beginning end portion 462 , the cross-sectional flow area of a passage to back pressure chamber br gradually increases from zero to a predetermined value at a constant rate. As a result, the flow rate Q of working fluid supplied to back pressure chamber br changes similarly, so that the ejecting speed of vane 7 is low at first, and gradually accelerated to increase at a substantially constant rate.
  • the shape of FIG. 13B is desirable, when such characteristics are desired.
  • the shapes of FIGS. 12A to 12E and the shapes of FIGS. 13A and 13B may be combined so as to achieve a desirable set of characteristics.
  • beginning end portion 462 is formed so that the cross-sectional flow area of beginning end portion 462 gradually increases as followed in the rotor rotation direction RD 1 , is effective for reliably pressing the vane 7 on the inside peripheral surface 80 of cam ring 8 .
  • the beginning end portion 462 according to the second embodiment serves as a part (from the beginning end point e to the terminal end point B) of back pressure port main section 468 according to the first embodiment, i.e. serves to supply a large amount of working fluid to reliably prevent the vane through flow, because beginning end portion 462 according to the second embodiment has a larger cross-sectional flow area than the beginning end portion 462 according to the first embodiment.
  • the angular position of the beginning end point e of back pressure port main section 468 may be modified to be identical to the angular position of the terminal end point B of suction port 43 , and the distance from the beginning end point c of beginning end portion 462 to the beginning end point e of back pressure port main section 468 may be set equal to about one pitch (L 0 ).
  • the throttling portion (beginning end portion 462 ) has a cross-sectional flow area (A) that increases as followed in a direction of rotation of the rotor ( 6 ). This produces an advantageous effect of further preventing the vane through flow, in addition to the effects according to the first embodiment.
  • beginning end portion 462 is formed so that the cross-sectional flow area of beginning end portion 462 gradually decreases as followed in the rotor rotation direction RD 1 .
  • This feature makes it possible to set the ejecting speed of vane 7 when vane 7 is passing through the beginning end portion 462 .
  • FIGS. 14A to 14D are plan views of beginning end portions 462 according to variations of the third embodiment. In these examples, the width of beginning end portion 462 in the rotor radial direction is set to decrease in the rotor rotation direction RD 1 .
  • the bottom shape and depth of beginning end portion 462 are the same as in the second embodiment shown in FIGS. 12A to 12E .
  • the shape of beginning end portion 462 as viewed in the z-axis direction is a combination of a substantially circular end portion and a substantially rectangular portion, where the width of beginning end portion 462 in the rotor radial direction (cross-sectional flow area of passage to back pressure chamber br) rapidly increases and decreases in the circular end portion, and then becomes constant in the rectangular portion, as followed in the rotor rotation direction RD 1 . Accordingly, while vane 7 passes through beginning end portion 462 , the flow rate Q of working fluid supplied to back pressure chamber br changes similarly as the width of beginning end portion 462 , so that the ejecting speed of vane 7 increases and decreases rapidly at first, and then becomes substantially constant.
  • the shape of FIG. 14A is desirable, when such characteristics are desired.
  • beginning end portion 462 as viewed in the z-axis direction is substantially in the form of a triangle that is directed opposite to the triangle of FIG. 12A , where the width of beginning end portion 462 in the rotor radial direction (cross-sectional flow area of passage to back pressure chamber br) gradually decreases from a predetermined value, which is smaller than that of back pressure port main section 468 , to zero at a substantially constant rate as followed in the rotor rotation direction RD 1 .
  • the flow rate Q of working fluid supplied to back pressure chamber br changes similarly as the width of beginning end portion 462 , so that the ejecting speed of vane 7 is relatively fast at first, and then decreases at a substantially constant rate to a value close to zero.
  • the shape of FIG. 14B is desirable, when such characteristics are desired.
  • beginning end portion 462 as viewed in the z-axis direction is substantially in the form of a semi-ellipse that is directed opposite to the shape of FIG. 12C , where the width of beginning end portion 462 in the rotor radial direction (cross-sectional flow area of passage to back pressure chamber br) gradually decreases from a predetermined value, which is smaller than that of back pressure port main section 468 , to zero as followed in the rotor rotation is direction RD 1 .
  • the rate of decrease is relatively small at first, and is relatively large at last.
  • the flow rate Q of working fluid supplied to back pressure chamber br changes similarly as the width of beginning end portion 462 , so that the ejecting speed of vane 7 is relatively fast at first, and decreases slowly at first, and then decreases rapidly.
  • the shape of FIG. 14C is desirable, when such characteristics are desired.
  • beginning end portion 462 as viewed in the z-axis direction is substantially in the form of a combination of a trapezoid and a rectangular that is directed opposite to the shape of FIG. 12D , where the width of beginning end portion 462 in the rotor radial direction (cross-sectional flow area of passage to back pressure chamber br) gradually decreases from a predetermined value, which is smaller than that of back pressure port main section 468 , to zero at a substantially constant rate, and then becomes substantially constant, as followed in the rotor rotation direction RD 1 .
  • the flow rate Q of working fluid supplied to back pressure chamber br changes similarly as the width of beginning end portion 462 , so that the ejecting speed of vane 7 is relatively fast at first, and then decreases at a substantially constant rate, and then becomes constant.
  • the shape of FIG. 14D is desirable, when such characteristics are desired.
  • FIG. 15 shows another variation of the third embodiment, where the bottom of beginning end portion 462 is inclined so that the depth of beginning end portion 462 in the z-axis direction gradually decreases as followed in the rotor rotation direction RD 1 .
  • the width of beginning end portion 462 in the rotor radial direction is substantially constant as followed in the rotor rotation direction RD 1 .
  • the depth of beginning end portion 462 gradually decreases at a substantially constant rate from a predetermined value (somewhat smaller than the depth of back pressure port main section 468 ) to a value close to zero, as followed in the rotor rotation direction RD 1 .
  • the cross-sectional flow area of passage to back pressure chamber br gradually decreases from a predetermined value to a value close to zero, so that the flow rate Q of working fluid supplied to back pressure chamber br changes similarly, and so that the ejecting speed of vane 7 is relatively fast at first, and then decreases at a substantially constant rate to a value close to zero.
  • the shape of FIG. 15 is desirable, when such characteristics are desired.
  • the shape of beginning end portion 462 may be modified similarly as in the second embodiment shown in FIG. 13A , so that the inclined surface is formed with an intermediate level surface, so as to reduce the deceleration of vane 7 temporarily.
  • the shapes of FIGS. 14A to 14E and the shape of FIG. 15 may be combined to achieve a desirable set of characteristics.
  • Beginning end portion 462 is formed so that the cross-sectional flow area of beginning end portion 462 gradually decreases as followed in the rotor rotation direction RD 1 , and thereby fluid communication between the beginning end portion 462 and back pressure port main section 468 is restricted, as compared to the first and second embodiments. Accordingly, even if supply of working fluid from beginning end portion 462 to back pressure chamber br for vane 7 is started so that the pressure in beginning end portion 462 rapidly falls, the pressure in back pressure port main section 468 is prevented form rapidly changing (decreasing), because the flow rate of working fluid leaking from back pressure port main section 468 to beginning end portion 462 for replenishing the amount supplied to back pressure chamber br is restricted.
  • beginning end portion 462 also serves to prevent the pressure in back pressure port main section 468 from fluctuating or pulsating, and thereby stabilize the pressure applied to vane 7 from back pressure chamber br that is hydraulically connected to back pressure port main section 468 .
  • the throttling portion (beginning end portion 462 ) has a cross-sectional flow area (A) that decreases as followed in a direction of rotation of the rotor ( 6 ).
  • Pump 1 may use fluid other than oils (ATF) as working fluid.
  • ATF oils
  • the vane 7 (or slot 61 ) is formed to extend in the rotor radial direction, the vane 7 (or slot 61 ) may be formed to extend with inclination with respect to the rotor radial direction.
  • discharge-side back pressure port 46 may be implemented by: a first port arranged to receive a discharge-side fluid pressure, and hydraulically communicate with a proximal end portion ( 610 , back pressure chamber br) of at least a first one of slots ( 61 ) corresponding to a first one of vanes ( 7 ) positioned in a discharge region (RE 2 ); and a second port arranged to receive a discharge-side fluid pressure, and hydraulically communicate with a proximal end portion ( 610 , back pressure chamber br) of at least a second one of slots ( 61 ) corresponding to a second one of vanes ( 7 ) whose distal end portion ( 70 ) is positioned at a terminal end portion (B) of a suction port ( 43 ).

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  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
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US9181803B2 (en) 2004-12-22 2015-11-10 Magna Powertrain Inc. Vane pump with multiple control chambers
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