US20040101417A1 - Volume control apparatus of radial piston pump or motor and positioning apparatus - Google Patents
Volume control apparatus of radial piston pump or motor and positioning apparatus Download PDFInfo
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- US20040101417A1 US20040101417A1 US10/699,809 US69980903A US2004101417A1 US 20040101417 A1 US20040101417 A1 US 20040101417A1 US 69980903 A US69980903 A US 69980903A US 2004101417 A1 US2004101417 A1 US 2004101417A1
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- Prior art keywords
- piston
- pressure
- control valve
- servo piston
- cam ring
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B1/00—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders
- F04B1/04—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders having cylinders in star- or fan-arrangement
- F04B1/06—Control
- F04B1/07—Control by varying the relative eccentricity between two members, e.g. a cam and a drive shaft
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/12—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00 by varying the length of stroke of the working members
- F04B49/123—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00 by varying the length of stroke of the working members by changing the eccentricity of one element relative to another element
- F04B49/125—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00 by varying the length of stroke of the working members by changing the eccentricity of one element relative to another element by changing the eccentricity of the actuation means, e.g. cams or cranks, relative to the driving means, e.g. driving shafts
Definitions
- the present invention relates to a volume control apparatus of a radial piston pump or a motor in which each of pistons is arranged so as to slide in a radial direction with respect to a rotation axis, and a positioning apparatus for a cam ring of the radial piston pump or a swash plate of an axial piston pump.
- a hydraulic working machine such as a construction machine or the like
- a hydraulic pump and a hydraulic motor in order to drive an upper revolving body, a lower traveling body and the like.
- each of pistons is arranged so as to slide in a radial direction with respect to a rotation axis.
- a cam ring is pressed by an actuator for regulating a volume, and a center of the cam ring is positioned at a position which is eccentric with respect to a center of the rotation axis (or a main axis).
- a volume (cc/rev) is determined in correspondence to an eccentric amount of the cam ring.
- each of the pistons is arranged so as to slide in parallel to the rotation axis.
- a swash plate is oscillated by an actuator for regulating a volume, and the swash plate is positioned at a tilted position with respect to the rotation axis (or a main axis).
- a volume is determined in correspondence to a tilting amount of the swash plate.
- the present invention is made by taking the actual condition mentioned above into consideration, and a first achieving object of the present invention is to downsize a radial piston pump or a motor, reduce a weight and improve a freedom in arrangement.
- a second achieving object of the present invention is to reduce a weight by downsizing a positioning apparatus for positioning a cam ring of a radial piston pump or a motor, and a swash plate of an axial piston pump or a motor.
- Japanese Unexamined Patent Publication No. 11-50968 there is disclosed a positioning apparatus in which a position of a cam ring in a radial piston pump is detected by a distance sensor, a detection signal of the distance sensor is amplified by an amplifier, the amplified signal is incorporated as a feedback amount into a servo valve, and the cam ring is positioned at a target position by controlling so as to drive the piston by the servo valve.
- the positioning apparatus described in the publication is constituted by the distance sensor, the amplifier, the servo valve and the piston, there is a problem that a place product is increased in the case of being used as the actuator for regulating the volume of the radial piston pump.
- a volume control apparatus of a radial piston pump or a motor for regulating a volume by positioning a cam ring of the radial piston pump or the motor comprises a control valve positioned at a position in correspondence to a volume control pressure, and a servo piston having said control valve built-in, being operated following to the control valve and pressing the cam ring so as to position the cam ring.
- a servo piston 8 is operated following to a control valve (a spool) 9 , presses a cam ring 2 so as to position the cam ring 2 at a position in correspondence to a volume control pressure, and regulates a volume. Accordingly, the same servo mechanism as that of the prior art can be achieved. Further, since the volume control apparatus has the control valve 9 built in the servo piston 8 , the place product becomes small, and the weight becomes light. Therefore, the radial piston pump or the motor is downsized, the weight is reduced, and a freedom in arrangement is improved.
- a volume control apparatus of a radial piston pump or a motor as recited in the first aspect, wherein one set of the control valve and the servo piston and another set of the control valve and the servo piston are provided at opposing positions with respect to the cam ring.
- the control valve (a spool) 9 and the servo piston 8 , and a control valve (a spool) 19 and a servo piston 18 are provided at opposing positions with respect to the cam ring 2 , and the cam ring 2 can be made eccentric in both sides with respect to a center of a piston valve 5 .
- FIG. 5B in the case that the volume control apparatus is applied to an alternating type hydraulic pump 61 which can change a discharging direction to two directions, it is possible to regulate the volume in both discharging directions on the basis of a small place product.
- a positioning apparatus comprises a control valve positioned at a position in correspondence to a volume control pressure, and a servo piston being said control valve built-in, being operated following to the control valve and pressing a positioning member so as to position the positioning member.
- a positioning apparatus comprises a control valve carrying out a stroke in correspondence to a control pressure applied to a pressure receiving surface, and a servo piston having the control valve built-in and pressing a positioning member in correspondence to a driving pressure,
- a throttle is formed between the control valve and the servo piston, in such a manner that the driving pressure introduced to the servo piston is increased in accordance that the control valve carries out the stroke relatively close to the positioning member with respect to the servo piston, and the driving pressure introduced to the servo piston is reduced in accordance that the servo piston carries out the stroke relatively close to the positioning member with respect to the control valve, and
- a spring for generating a spring force opposing to the control pressure is applied to the control valve
- the control pressure is applied to the pressure receiving surface so as to carry out a stroke of the control valve
- the servo piston carries out a stroke following to the control valve on the basis of the driving pressure introduced via the throttle
- the control valve is positioned at a position where the spring force of the spring and the control pressure are balanced
- the servo piston is positioned in accordance the positioning of the control valve.
- the servo piston is operated following to the control valve (the spool) 9 , presses a positioning member (a cam ring or a swash plate) 2 or 50 , and positions the positioning member 2 or 50 at a position in correspondence to the control pressure. Since the positioning apparatus has the control valve 9 built in the servo piston 8 , the place product becomes small and the weight becomes light. Accordingly, the radial pump or the motor, and the axial piston pump or the motor are downsized, the weight thereof is reduced, and a freedom in arrangement is improved.
- FIG. 1 is a view showing an entire structure of a radial piston pump in accordance with an embodiment of the present invention
- FIG. 2 is a view showing a detailed structure of a volume control apparatus of the radial piston pump shown in FIG. 1;
- FIG. 3 is a view showing details of a volume control apparatus having a different structure from that shown in FIG. 2;
- FIG. 4 is a view showing details of a volume control apparatus having a different structure from those shown in FIGS. 2 and 3;
- FIGS. 5A and 5B are views showing a structure embodiment in which volumes in both discharging directions of a radial piston pump are changed.
- FIG. 6 is a view showing a structure embodiment in the case that a volume control apparatus in accordance with the present embodiment is applied to an axial piston pump.
- FIG. 1 shows an entire structure of a radial piston pump in accordance with the present embodiment.
- the radial piston pump in FIG. 1 is used as a driving pressure source for a hydraulic motor mounted on a construction machine and driving an upper revolving body, or a hydraulic motor driving a lower traveling body.
- FIG. 1 is a view of a radial piston pump 1 as seen along a vertical cross section to a rotation axis, and shows an eccentric type radial piston pump.
- the radial piston pump 1 is structured such as to receive a cylinder block 3 and the like in an inner portion of a case 14 .
- the cylinder block 3 is integrally formed with a rotation axis (not shown).
- a cylindrical piston valve 5 is fitted and fixed to the case 14 in accordance with an arrangement aspect that a rotation axis and a center axis are set identical.
- a pump port P is formed in the piston valve 5 over a predetermined circumferential length along a circumferential direction of the piston valve.
- the pump port P is open to an outer peripheral surface of the piston valve 5 .
- a suction port S is formed in the piston valve 5 over a predetermined circumferential length along a circumferential direction of the piston valve.
- the suction port S is open to the outer peripheral surface of the piston valve 5 .
- a plurality of bores are formed in the cylinder block 3 at an even pitch in a radial direction of a rotation axis.
- a piston 4 is slidably provided within each of the bores.
- a shoe 49 is slidably connected to each of the pistons 4 .
- a cam ring 2 is arranged in an outer side of the shoe 49 . The cam ring 2 is arranged such that an inner peripheral surface can slide against a sliding surface of each of the shoe 49 .
- the case 14 is provided with a servo piston 8 and an opposing piston 7 constituting a volume control apparatus, in such a manner as to hold a rotation axis therebetween.
- the servo piston 8 and the opposing piston 7 press the cam ring 2 so as to support in such a manner as to freely eccentrically move a center of the cam ring 2 with respect to a center of the rotation axis.
- a bearing 6 for slidably moving the cam ring 2 is arranged between the cam ring 2 and the case 14 .
- a cylinder side port 4 a communicating with each of the bores is formed in the cylinder block 3 .
- the cylinder side port 4 a is open to positions opposing to a pump port P and a suction port S in the side of the piston valve 5 .
- the servo piston 8 and the opposing piston 7 is operated, whereby the center of the cam ring 2 is made eccentric with respect to the center of the rotation axis at a predetermined eccentricity amount. Accordingly, when the piston 4 is positioned at a position where the piston valve 5 and the cam ring 2 are closest, the piston 4 is in a top dead center state. When the piston 4 is rotated further half along the circumferential direction of the piston valve 5 from the position, the piston 4 is in a bottom dead center state at a position where the piston valve 5 and the cam ring 2 are most apart from each other. When the piston is rotated further half, the piston 4 becomes in the top dead center state from the bottom dead center state.
- the piston 4 carries out one stroke (the top dead center-the bottom dead center-the top dead center) every one rotation along the circumferential direction of the piston valve 5 , and an amount of one stroke corresponds to twice an amount of eccentricity.
- a pressure oil at a volume (cc/rev) corresponding to the stroke amount is sucked and then discharged.
- the opposing piston 7 is slidably provided in the case 14 , an oil chamber 28 is formed in an inner side of the opposing piston 7 , and a spring 27 is attached.
- a thrust is generated in correspondence to a hydraulic pressure within the oil chamber 28 and a spring force of the spring 27 , and the cam ring 2 is pressed against the side of the servo piston 8 .
- the servo piston 8 is slidably provided in the case 14 , and an oil chamber 20 is formed in an inner side of the servo piston 8 .
- a thrust is generated in correspondence to a hydraulic pressure within the oil chamber 20 , and the cam ring 2 is pressed against the side of the opposing piston 7 .
- a fixed driving pressure is supplied to an inner side of the oil chamber 28 in the side of the opposing piston 7 , and a fixed thrust is generated in the opposing piston 7 .
- the driving pressure within the oil chamber 20 in the side of the servo piston 8 is changed in accordance with a volume control pressure supplied to the pilot port 12 , and the thrust of the servo piston 8 is changed in accordance with the volume control pressure.
- the cam ring 2 is made eccentric at the position in correspondence to the volume control pressure supplied to the pilot port 12 of the servo piston 8 . In accordance that the cam ring 2 is moved to the opposing piston 7 by the servo piston 8 , the volume is reduced from the maximum volume.
- FIG. 2 is an enlarged view of the servo piston 8 in FIG. 1, and shows a volume control apparatus in accordance with the present embodiment.
- a spool 9 corresponding to the control valve is built in the servo piston 8 in such a manner as to be slidable with respect to the servo piston 8 .
- the pilot port 12 to which the pilot pressure serving as the volume control pressure is supplied is formed on an outer peripheral surface of the servo piston 8 .
- a pilot pressure introducing oil passage 21 for introducing the pilot pressure supplied to the pilot port 12 to an inner side of the servo piston 8 .
- an original pressure port 13 to which the driving pressure for driving the servo piston 8 is supplied is formed on an outer peripheral surface of the servo piston 8 .
- a driving pressure introducing oil passage 22 for introducing the driving pressure supplied to the original pressure port 13 to an inner side of the servo piston 8 .
- a tank discharging oil passage 24 communicating a tank 26 with the inner side of the servo piston 8 .
- the spool 9 is provided with a small diameter portion having a diameter D 1 and a large diameter portion having a diameter D 2 , and is provided with a pressure receiving surface 9 a formed as a step between the small diameter portion and the large diameter portion.
- the pressure receiving surface 9 a has a pressure receiving area corresponding to a difference of pressure receiving areas ((D 2 ) ⁇ (D 1 )) ⁇ /4 between the small diameter portion and the large diameter portion.
- the pressure receiving surface 9 a of the spool 9 is formed at a position in correspondence to the pilot pressure introducing oil passage 21 . Accordingly, the pilot pressure is applied to the pressure receiving surface 9 a of the spool 9 from the pilot port 12 via the pilot pressure introducing oil passage 21 .
- the spool 9 carries out a stroke toward the cam ring 2 in accordance with the pilot pressure applied to the pressure receiving surface 9 a thereof.
- a spring 11 and a spring 10 which are expanded and contracted in the same direction as the stroke direction of the spool 9 are received in an inner side of the spool 9 .
- One end of the spring 11 is brought into contact with the servo piston 8 , and another end of the spring 11 is brought into contact with the spool 9 . Further, one end of the spring 10 is brought into contact with the spool 9 , and another end of the spring 10 is brought into contact with an adjusting screw 15 .
- the adjusting screw 15 is fixed to the case 14 via a lock nut 16 .
- a spring chamber in which the spring 11 is received is defined by the servo piston 8 and the spool 9 , and forms the oil chamber 20 .
- An oil passage 9 d for communicating the oil chamber 20 (the spring chamber of the spring 11 ) with a spring chamber in which the spring 10 is received is formed in an inner side of the spool 9 .
- An oil passage 9 c for communicating the inner oil chamber 20 with an outer side of the spool 9 is formed in the spool 9 .
- the oil passage 9 c is formed at a position corresponding to the tank discharging oil passage 24 .
- a throttle 25 is formed between the oil passage 9 c and the tank discharging oil passage 24 .
- An opening area of the throttle 25 is increased in accordance with a stroke of the spool 9 toward an opposite side to the cam ring 2 , and the pressure oil is discharged from the oil chamber 20 to the tank 26 via the oil passage 9 c , the throttle 25 and the tank discharging oil passage 24 . Accordingly, since the driving pressure within the oil chamber 20 is reduced and the thrust of the servo piston 8 is reduced, the cam ring 2 carries out a stroke toward an upper side on the basis of the thrust of the opposing piston 7 . Therefore, the servo piston 8 carries out a stroke toward an upper side.
- the opening area of the throttle 25 is reduced in accordance with a stroke of the servo piston 8 toward an upper side, and the reduction in the driving pressure within the oil chamber 20 is inhibited. Accordingly, the servo piston 8 carries out a stroke toward an upper side in the drawing at a moving amount of the spool 9 .
- An oil passage 9 b for communicating the spring chamber of the inner spring 10 with the outer side of the spring 9 is formed in the spool 9 .
- the oil passage 9 b is formed at a position corresponding to the driving pressure introducing oil passage 22 .
- a throttle 23 is formed between the oil passage 9 b and the driving pressure introducing oil passage 22 .
- the spool 9 When the pressure of the pilot port 12 is increased, the spool 9 carries out a stroke toward a lower side in the drawing, that is, toward the cam ring 2 .
- An opening area of the throttle 23 is increased in accordance with the stroke of the spool 9 toward the cam ring 2 , and the pressure oil supplied from the original pressure port 13 to the oil chamber 20 via the driving pressure introducing oil passage 22 , the throttle 23 , the oil passage 9 b , the spring chamber of the spring 10 and the oil passage 9 d is increased.
- a thrust in correspondence to the driving pressure within the oil chamber 20 is generated in the servo piston 8 , and presses the cam ring 2 . Since the pressure receiving area of the opposing piston 7 is smaller than the pressure receiving area of the servo piston 8 , the cam ring 2 carries out a stroke toward a lower side in the drawing on the basis of the thrust generated in the servo piston 8 , and the servo piston 8 also carries out a stroke toward a lower side. When the servo piston 8 carries out the stroke toward the lower side, the opening area of the throttle 23 is reduced, and the increase in the driving pressure within the oil chamber 20 is inhibited. Accordingly, the servo piston 8 carries out a stroke toward a lower side at a moving amount of the spool 9 .
- a seal member 27 is fixed to the servo piston 8 by a snap ring 28 , and seals in the inner side of the servo piston in such a manner that the pressure oil in the outer side of the spool 9 does not leak to the external portion.
- the spool 9 is at a standstill under a state in which a force downward in the drawing in correspondence to the pilot pressure applied to the pressure receiving surface 9 a and a spring force K (obtained by subtracting the spring force of the spring 10 from the spring force of the spring 11 ) upward in the drawing applied by the spring 11 and the spring 10 are balanced. Further, the opening areas of the throttle 23 and the throttle 25 are regulated, and the thrust generated in the servo piston 8 and the thrust obtained by adding the thrust of the opposing piston 7 to the thrust of the piston 4 applied via the cam ring 2 are balanced and at a standstill.
- the spool 9 stands still at a position where the downward force corresponding to the pilot pressure and the spring force K upward in the drawing applied by the spring 10 are balanced.
- the spring 10 is positioned at the lower position expanding from the state shown in FIG. 2.
- the servo piston 8 stands still at the position corresponding to the position at which the spool 9 is positioned in a standstill state, in a state in which the thrust generated in the servo piston 8 is balanced with the thrust obtained by adding the thrust of the opposing piston 7 to the thrust of the piston 4 applied via the cam ring 2 .
- the spool 9 stands still at a position where the downward force in correspondence to the reduced pilot pressure and the upward spring force K applied by the spring 11 and the spring 10 are balanced. In other words, the spool 9 is positioned at a further upper position where the spring 10 is contracted from the state in FIG. 2.
- the servo piston 8 stands still at a position corresponding to the position where the spool 9 is positioned at a standstill, in a state in which the thrust generated in the servo piston 8 is balanced with the thrust obtained by adding the thrust of the opposing piston 7 to the thrust of the piston 4 applied via the cam ring 2 .
- the servo piston 8 presses the cam ring 2 following to the spool 9 , and positions the cam ring 2 at the position corresponding to the pilot pressure so as to regulate the volume. Accordingly, the same servo mechanism as that in accordance with the prior art can be achieved. Further, since the volume control apparatus has the spool 9 built in the servo piston 8 , the place product becomes small, and the weight becomes light. Therefore, the radial piston pump 1 is downsized, the weight is reduced, and the freedom in arrangement is improved.
- FIG. 3 shows a volume control apparatus having a structure corresponding to FIG. 2, and a description will be given of different parts from those in FIG. 2.
- the original pressure port 13 is formed in the lower side of the servo piston 8 close to the cam ring 2
- the pilot port 12 is formed in the upper side apart from the cam ring 2 .
- the pilot port 12 is formed in the lower side of the servo piston 8 close to the cam ring 2
- the original pressure port 13 is formed in the upper side apart from the cam ring 2 .
- the pressure receiving surface 9 a of the spool 9 is formed in the lower side closer to the cam ring 2 in FIG. 3 than in FIG. 2.
- the seal member 27 is provided in the upper side of the servo piston 8 and the spool 9 in FIG. 2, however, is provided in the lower side of the servo piston 8 and the spool 9 in FIG. 3.
- FIG. 4 shows a structure of the volume control apparatus in correspondence to FIGS. 2 and 3, and shows an embodiment in which only one spring 10 is attached to the spool 9 .
- the spring 10 expanding and contracting in the same direction as the direction of stroke of the spool 9 is received in the inner side of the spool 9 .
- One end of the spring 10 is brought into contact with the spool 9
- another end of the spring 10 is brought into contact with the adjusting screw 15 .
- the spool 9 is at a standstill under a state in which a downward force in correspondence to the pilot pressure applied to the pressure receiving surface 9 a and an upward spring force K applied by the spring 10 are balanced. Further, the opening areas of the throttle 23 and the throttle 25 are regulated, and the thrust generated in the servo piston 8 and the thrust obtained by adding the thrust of the opposing piston 7 to the thrust of the piston applied via the cam ring 2 are balanced and at a standstill.
- the spool 9 stands still at a position where the downward force corresponding to the pilot pressure and the upward spring force K applied by the spring 10 are balanced.
- the spring 10 is positioned at the lower position contracting from the state shown in FIG. 4.
- the servo piston 8 stands still at the position corresponding to the position at which the spool 9 is positioned in a standstill state, in a state in which the thrust generated in the servo piston 8 is balanced with the thrust obtained by adding the thrust of the opposing piston 7 to the thrust of the piston 4 applied via the cam ring 2 .
- the spool 9 stands still at a position where the downward force in correspondence to the reduced pilot pressure and the upward spring force K applied by the spring 10 are balanced. In other words, the spool 9 is positioned at a further upper position where the spring 10 is expanded from the state in FIG. 4.
- the servo piston 8 stands still at a position corresponding to the position where the spool 9 is positioned at a standstill, in a state in which the thrust generated in the servo piston 8 is balanced with the thrust obtained by adding the thrust of the opposing piston 7 to the thrust of the piston 4 applied via the cam ring 2 .
- Either the embodiments mentioned above are based on the one-flow-way type radial piston pump in which the discharging direction is fixed.
- the present invention can be applied to an alternating type radial piston pump in which the discharging direction can be changed to two directions.
- FIG. 5A is a view corresponding to FIG. 1.
- the case 14 is provided with the servo piston 8 having the spool 9 built-in in the same manner as the structure shown in FIG. 2, and the opposing piston 7 , in such a manner as to oppose to each other so as to hold the rotation axis therebetween.
- the servo piston 18 having the spool 19 built-in and the opposing piston 17 are provided in such a manner as to oppose to each other so as to hold the rotation axis therebetween.
- the servo piston 8 having the spool 9 built-in, and the servo piston 18 having the spool 19 built-in are provided at opposing positions with holding the cam ring 2 therebetween. Accordingly, it is possible to make the cam ring 2 to be eccentric in both sides with respect to the center of the rotation axis, and the center of the piston valve 5 .
- the radial piston pump 1 capable of flowing in two direction shown in FIG. 5A is used as a constituting element of a hydraulic circuit shown in FIG. 5B.
- the hydraulic circuit in FIG. 5B is used in a hydro static transmission (HST) vehicle such as a bulldozer or the like.
- HST hydro static transmission
- right and left traveling bodies (wheels or crawler belts) of a vehicle body are independently driven by the HST provided respectively in right and left sides.
- the hydraulic motor 60 rotates forward and the vehicle moves forward.
- a switching valve 40 for changing between the forward movement and the backward movement, an electromagnetic proportional control valve 31 for controlling the volume at a time of forward moving, and an electromagnetic proportional control valve 32 for controlling the volume at a time of moving backward.
- hydraulic pressure sources of the pilot pressure and the driving pressure supplied to the servo pistons 8 and 18 there are provided respectively pilot hydraulic pressure sources 27 and 27 and a driving pressure source 29 .
- the driving pressure source 29 can employ the radial piston pump 1 itself.
- the electromagnetic proportional control valve 31 is opened at an opening degree in proportional to the forward movement command signal S 1 , and the pilot pressure of the pilot hydraulic pressure source 27 is reduced to the pilot pressure in correspondence to the opening degree of the electromagnetic proportional control valve 31 , and is supplied to the pilot port 12 of the servo piston 8 via the switching valve 40 and the oil passage 41 .
- the driving pressure of the driving pressure source 29 is supplied to the original pressure port 13 of the servo piston 8 via the switching valve 40 and the oil passage 42 . Further, the driving pressure of the driving pressure source 29 is supplied to the oil chamber 28 of the opposing piston 7 opposing to the servo piston 8 via the switching valve 40 and the oil passage 46 . In this case, the opposing piston 17 , the pilot port 12 of another servo piston 18 and the original pressure port 13 are respectively communicated with the tank 26 via an oil passage 43 , an oil passage 44 , an oil passage 45 and the switching valve 40 .
- the servo piston 8 and the spool 9 are operated as described in FIG. 2, and the cam ring 2 is made eccentric to the position corresponding to the pilot pressure supplied to the pilot port 12 of the servo piston 8 .
- the cam ring 2 is made eccentric to a left side in the drawing with respect to the rotation axis. Accordingly, the pressure oil at a volume corresponding to the forward movement command signal S 1 is discharged from one discharging direction of the radial piston pump 1 , and the vehicle travels forward at a speed corresponding to the forward movement command signal S 1 .
- the electromagnetic proportional control valve 32 is open at an opening degree in proportion to the backward movement command signal S 2 , and the pilot pressure of the pilot hydraulic pressure source 27 is reduced to a pilot pressure corresponding to the opening degree of the electromagnetic proportional control valve 32 and is supplied to the pilot port 12 of the servo piston 18 via the switching valve 40 and the oil passage 44 .
- the driving pressure of the driving pressure source 29 is supplied to the original pressure port 13 of the servo piston 18 via the switching valve 40 and the oil passage 45 . Further, the driving pressure of the driving pressure source 29 is supplied to an oil chamber 38 of the opposing piston 17 opposing to the servo piston 18 via the switching valve 40 and the oil passage 43 . In this case, the opposing piston 7 , the pilot port 12 of another servo piston 8 and the original pressure port 13 are communicated respectively with the tank 26 via the oil passage 46 , the oil passage 41 , the oil passage 42 and the switching valve 40 .
- the servo piston 18 and the spool 19 are operated as described in FIG. 2, and the cam ring 2 is made eccentric to a position corresponding to the pilot pressure supplied to the pilot port 12 of the servo piston 18 .
- the cam ring 2 is made eccentric to a right side in the drawing with respect to the rotation axis. Therefore, the pressure oil at the volume corresponding to the backward movement command signal S 2 is discharged from another discharging direction of the radial piston pump 1 , and the vehicle travels backward at a speed corresponding to the backward movement command signal S 2 .
- the structure in FIG. 5A is based on the volume control apparatus having the structure shown in FIG. 2, however, can employ the volume control apparatus having the structure shown in FIGS. 3 or 4 .
- volume control apparatus for the radial piston pump or motor, but can be applied to a volume control apparatus for a swash plate type axial piston pump or motor.
- FIG. 6 shows an embodiment employing the volume control apparatus shown in FIG. 2 as a volume control apparatus for regulating the volume by pressing a swash plate 50 of an axial piston pump 55 and oscillating the swash plate 50 .
- the servo piston 8 having the spool 9 built-in in the same manner as the structure shown in FIG. 2 is brought into contact with the swash plate 50 , and the servo piston 8 presses the swash plate 50 on the basis of a thrust corresponding to the pilot pressure so as to oscillate the swash plate 50 , and positions the swash plate 50 at a position tilted from a rotation axis 51 .
- a stroke amount of a piston 54 is determined in correspondence to a tilting amount of the swash plate 50 with respect to the rotation axis 51 , and a volume of the axial piston pump 55 is determined.
- the structure is made such that a position of a supporting point of a ball for supporting the tilting motion of the swash plate 50 is displaced to a left side in the drawing from a position of a working point of a resultant force applied to the swash plate 50 by the shoe of the piston 54 , thereby generating a force opposing to the thrust of the servo piston 8 existing in a right side in the drawing with respect to the ball, and achieving the same function as that of the opposing piston 7 in FIG. 1.
- the structure in FIG. 6 can be applied also to the axial piston motor as it is.
- FIG. 6 is based on the volume control apparatus having the structure shown in FIG. 2, however, may employ the volume control apparatus having the structure shown in FIGS. 3 or 4 .
- the apparatus having the structure shown in FIGS. 2, 3 and 4 is not limited to the apparatus for positioning the cam ring or the swash plate of the hydraulic pump or motor, and may be used as a positioning apparatus for positioning the other members to be positioned than the cam ring and the swash plate to a desired position.
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- General Engineering & Computer Science (AREA)
- Reciprocating Pumps (AREA)
- Hydraulic Motors (AREA)
- Control Of Positive-Displacement Pumps (AREA)
Abstract
The invention provides a volume control apparatus of a radial pump or motor which downsizes a hydraulic pump or motor, reduces a weight thereof and improves a freedom in arrangement, and a positioning apparatus. Accordingly, a servo piston (8) is operated following to a control valve (9), presses a cam ring (2) so as to position the cam ring at a position in correspondence to a volume control pressure, and regulates a volume.
Description
- The present invention relates to a volume control apparatus of a radial piston pump or a motor in which each of pistons is arranged so as to slide in a radial direction with respect to a rotation axis, and a positioning apparatus for a cam ring of the radial piston pump or a swash plate of an axial piston pump.
- In a hydraulic working machine such as a construction machine or the like, there is mounted a hydraulic pump and a hydraulic motor, in order to drive an upper revolving body, a lower traveling body and the like.
- As one kind of the hydraulic pump, there is a radial piston pump in which each of pistons is arranged so as to slide in a radial direction with respect to a rotation axis. In the radial piston pump, a cam ring is pressed by an actuator for regulating a volume, and a center of the cam ring is positioned at a position which is eccentric with respect to a center of the rotation axis (or a main axis). A volume (cc/rev) is determined in correspondence to an eccentric amount of the cam ring.
- Further, as one kind of the hydraulic pump, there is an axial piston pump in which each of the pistons is arranged so as to slide in parallel to the rotation axis. In the axial piston pump, a swash plate is oscillated by an actuator for regulating a volume, and the swash plate is positioned at a tilted position with respect to the rotation axis (or a main axis). A volume is determined in correspondence to a tilting amount of the swash plate.
- In this case, in recent years, in the case that the hydraulic pump or the like is mounted on the construction machine or the like, there is a request of making a weight of the hydraulic pump light by making a place product of the hydraulic pump itself small on the basis of a constraint of a mounting space, a demand from a market and the like, and improving a freedom for arranging the hydraulic pump. Accordingly, a downsizing and a weight reduction are required in the volume regulating actuator mounted to the hydraulic pump. The same matter is applied to the hydraulic motor.
- The present invention is made by taking the actual condition mentioned above into consideration, and a first achieving object of the present invention is to downsize a radial piston pump or a motor, reduce a weight and improve a freedom in arrangement.
- Further, a second achieving object of the present invention is to reduce a weight by downsizing a positioning apparatus for positioning a cam ring of a radial piston pump or a motor, and a swash plate of an axial piston pump or a motor.
- A general technical level in connection with the achieving object of the present invention is as follows.
- In a document listed up as one example of a prior art: Japanese Unexamined Patent Publication No. 11-50968, there is disclosed a positioning apparatus in which a position of a cam ring in a radial piston pump is detected by a distance sensor, a detection signal of the distance sensor is amplified by an amplifier, the amplified signal is incorporated as a feedback amount into a servo valve, and the cam ring is positioned at a target position by controlling so as to drive the piston by the servo valve.
- Since the positioning apparatus described in the publication is constituted by the distance sensor, the amplifier, the servo valve and the piston, there is a problem that a place product is increased in the case of being used as the actuator for regulating the volume of the radial piston pump.
- In order to achieve the first achieving object, in accordance with a first aspect of the present invention, there is provided a volume control apparatus of a radial piston pump or a motor for regulating a volume by positioning a cam ring of the radial piston pump or the motor, comprises a control valve positioned at a position in correspondence to a volume control pressure, and a servo piston having said control valve built-in, being operated following to the control valve and pressing the cam ring so as to position the cam ring.
- In the volume control apparatus in accordance with the first aspect, as shown in FIG. 1, a
servo piston 8 is operated following to a control valve (a spool) 9, presses acam ring 2 so as to position thecam ring 2 at a position in correspondence to a volume control pressure, and regulates a volume. Accordingly, the same servo mechanism as that of the prior art can be achieved. Further, since the volume control apparatus has thecontrol valve 9 built in theservo piston 8, the place product becomes small, and the weight becomes light. Therefore, the radial piston pump or the motor is downsized, the weight is reduced, and a freedom in arrangement is improved. - In accordance with a second aspect of the present invention, there is provided a volume control apparatus of a radial piston pump or a motor as recited in the first aspect, wherein one set of the control valve and the servo piston and another set of the control valve and the servo piston are provided at opposing positions with respect to the cam ring.
- In accordance with the second aspect, as shown in FIG. 5A, the control valve (a spool)9 and the
servo piston 8, and a control valve (a spool) 19 and aservo piston 18 are provided at opposing positions with respect to thecam ring 2, and thecam ring 2 can be made eccentric in both sides with respect to a center of apiston valve 5. Accordingly, as shown in FIG. 5B, in the case that the volume control apparatus is applied to an alternating typehydraulic pump 61 which can change a discharging direction to two directions, it is possible to regulate the volume in both discharging directions on the basis of a small place product. - In order to achieve the second achieving object, in accordance with a third invention, there is provided a positioning apparatus comprises a control valve positioned at a position in correspondence to a volume control pressure, and a servo piston being said control valve built-in, being operated following to the control valve and pressing a positioning member so as to position the positioning member.
- In order to achieve the second achieving object, in accordance with a fourth invention, there is provided a positioning apparatus comprises a control valve carrying out a stroke in correspondence to a control pressure applied to a pressure receiving surface, and a servo piston having the control valve built-in and pressing a positioning member in correspondence to a driving pressure,
- wherein a throttle is formed between the control valve and the servo piston, in such a manner that the driving pressure introduced to the servo piston is increased in accordance that the control valve carries out the stroke relatively close to the positioning member with respect to the servo piston, and the driving pressure introduced to the servo piston is reduced in accordance that the servo piston carries out the stroke relatively close to the positioning member with respect to the control valve, and
- wherein a spring for generating a spring force opposing to the control pressure is applied to the control valve, the control pressure is applied to the pressure receiving surface so as to carry out a stroke of the control valve, the servo piston carries out a stroke following to the control valve on the basis of the driving pressure introduced via the throttle, the control valve is positioned at a position where the spring force of the spring and the control pressure are balanced, and the servo piston is positioned in accordance the positioning of the control valve.
- In the positioning apparatuses in accordance with the third aspect and the fourth aspect, as exemplified in FIGS. 1 and 6, the servo piston is operated following to the control valve (the spool)9, presses a positioning member (a cam ring or a swash plate) 2 or 50, and positions the
positioning member control valve 9 built in theservo piston 8, the place product becomes small and the weight becomes light. Accordingly, the radial pump or the motor, and the axial piston pump or the motor are downsized, the weight thereof is reduced, and a freedom in arrangement is improved. - FIG. 1 is a view showing an entire structure of a radial piston pump in accordance with an embodiment of the present invention;
- FIG. 2 is a view showing a detailed structure of a volume control apparatus of the radial piston pump shown in FIG. 1;
- FIG. 3 is a view showing details of a volume control apparatus having a different structure from that shown in FIG. 2;
- FIG. 4 is a view showing details of a volume control apparatus having a different structure from those shown in FIGS. 2 and 3;
- FIGS. 5A and 5B are views showing a structure embodiment in which volumes in both discharging directions of a radial piston pump are changed; and
- FIG. 6 is a view showing a structure embodiment in the case that a volume control apparatus in accordance with the present embodiment is applied to an axial piston pump.
- A description will be given below of an embodiment of a volume control apparatus and a positioning apparatus in accordance with the present invention with reference to the accompanying drawings.
- FIG. 1 shows an entire structure of a radial piston pump in accordance with the present embodiment. The radial piston pump in FIG. 1 is used as a driving pressure source for a hydraulic motor mounted on a construction machine and driving an upper revolving body, or a hydraulic motor driving a lower traveling body.
- FIG. 1 is a view of a
radial piston pump 1 as seen along a vertical cross section to a rotation axis, and shows an eccentric type radial piston pump. Theradial piston pump 1 is structured such as to receive acylinder block 3 and the like in an inner portion of acase 14. - The
cylinder block 3 is integrally formed with a rotation axis (not shown). Acylindrical piston valve 5 is fitted and fixed to thecase 14 in accordance with an arrangement aspect that a rotation axis and a center axis are set identical. - A pump port P is formed in the
piston valve 5 over a predetermined circumferential length along a circumferential direction of the piston valve. The pump port P is open to an outer peripheral surface of thepiston valve 5. Further, a suction port S is formed in thepiston valve 5 over a predetermined circumferential length along a circumferential direction of the piston valve. The suction port S is open to the outer peripheral surface of thepiston valve 5. - A plurality of bores are formed in the
cylinder block 3 at an even pitch in a radial direction of a rotation axis. Apiston 4 is slidably provided within each of the bores. Ashoe 49 is slidably connected to each of thepistons 4. Acam ring 2 is arranged in an outer side of theshoe 49. Thecam ring 2 is arranged such that an inner peripheral surface can slide against a sliding surface of each of theshoe 49. - The
case 14 is provided with aservo piston 8 and anopposing piston 7 constituting a volume control apparatus, in such a manner as to hold a rotation axis therebetween. Theservo piston 8 and theopposing piston 7 press thecam ring 2 so as to support in such a manner as to freely eccentrically move a center of thecam ring 2 with respect to a center of the rotation axis. Abearing 6 for slidably moving thecam ring 2 is arranged between thecam ring 2 and thecase 14. - Further, a
cylinder side port 4 a communicating with each of the bores is formed in thecylinder block 3. Thecylinder side port 4 a is open to positions opposing to a pump port P and a suction port S in the side of thepiston valve 5. - When the rotation axis is driven so as to rotate by a driving source, for example, an engine, the
cylinder block 3 is relatively rotated with respect to thepiston valve 5. Accordingly, theshoe 49 slides along an inner periphery of thecam ring 2. - The
servo piston 8 and the opposingpiston 7 is operated, whereby the center of thecam ring 2 is made eccentric with respect to the center of the rotation axis at a predetermined eccentricity amount. Accordingly, when thepiston 4 is positioned at a position where thepiston valve 5 and thecam ring 2 are closest, thepiston 4 is in a top dead center state. When thepiston 4 is rotated further half along the circumferential direction of thepiston valve 5 from the position, thepiston 4 is in a bottom dead center state at a position where thepiston valve 5 and thecam ring 2 are most apart from each other. When the piston is rotated further half, thepiston 4 becomes in the top dead center state from the bottom dead center state. As mentioned above, thepiston 4 carries out one stroke (the top dead center-the bottom dead center-the top dead center) every one rotation along the circumferential direction of thepiston valve 5, and an amount of one stroke corresponds to twice an amount of eccentricity. In the course of one stroke of thepiston 4, a pressure oil at a volume (cc/rev) corresponding to the stroke amount is sucked and then discharged. - In other words, when the
piston 4 is positioned at the position where thecylinder side port 4 a is communicated with the suction port S, the pressure oil is sucked from a tank into the bore via the suction port S and thecylinder side port 4 a. Next, when thepiston 4 is positioned at the position where thecylinder side port 4 a is communicated with the pump port P, the pressure oil compressed by thepiston 4 is discharged from the bore via thecylinder side port 4 a and the pump port P, and is supplied to a hydraulic actuator in an outer portion. As mentioned above, the pressure oil at the volume corresponding to the amount of eccentricity of thecam ring 2 is supplied to the hydraulic actuator in the outer portion via the pump port P. - The opposing
piston 7 is slidably provided in thecase 14, anoil chamber 28 is formed in an inner side of the opposingpiston 7, and aspring 27 is attached. In the opposingpiston 7, a thrust is generated in correspondence to a hydraulic pressure within theoil chamber 28 and a spring force of thespring 27, and thecam ring 2 is pressed against the side of theservo piston 8. - The
servo piston 8 is slidably provided in thecase 14, and anoil chamber 20 is formed in an inner side of theservo piston 8. In theservo piston 8, a thrust is generated in correspondence to a hydraulic pressure within theoil chamber 20, and thecam ring 2 is pressed against the side of the opposingpiston 7. In this case, a fixed driving pressure is supplied to an inner side of theoil chamber 28 in the side of the opposingpiston 7, and a fixed thrust is generated in the opposingpiston 7. - On the contrary, the driving pressure within the
oil chamber 20 in the side of theservo piston 8 is changed in accordance with a volume control pressure supplied to thepilot port 12, and the thrust of theservo piston 8 is changed in accordance with the volume control pressure. Accordingly, thecam ring 2 is made eccentric at the position in correspondence to the volume control pressure supplied to thepilot port 12 of theservo piston 8. In accordance that thecam ring 2 is moved to the opposingpiston 7 by theservo piston 8, the volume is reduced from the maximum volume. - FIG. 2 is an enlarged view of the
servo piston 8 in FIG. 1, and shows a volume control apparatus in accordance with the present embodiment. - A
spool 9 corresponding to the control valve is built in theservo piston 8 in such a manner as to be slidable with respect to theservo piston 8. Thepilot port 12 to which the pilot pressure serving as the volume control pressure is supplied is formed on an outer peripheral surface of theservo piston 8. In theservo piston 8, there is formed a pilot pressure introducingoil passage 21 for introducing the pilot pressure supplied to thepilot port 12 to an inner side of theservo piston 8. - Further, an
original pressure port 13 to which the driving pressure for driving theservo piston 8 is supplied is formed on an outer peripheral surface of theservo piston 8. In theservo piston 8, there is formed a driving pressure introducingoil passage 22 for introducing the driving pressure supplied to theoriginal pressure port 13 to an inner side of theservo piston 8. Further, in theservo piston 8, there is formed a tank dischargingoil passage 24 communicating atank 26 with the inner side of theservo piston 8. - The
spool 9 is provided with a small diameter portion having a diameter D1 and a large diameter portion having a diameter D2, and is provided with apressure receiving surface 9 a formed as a step between the small diameter portion and the large diameter portion. Thepressure receiving surface 9 a has a pressure receiving area corresponding to a difference of pressure receiving areas ((D2)−(D1))π/4 between the small diameter portion and the large diameter portion. - The
pressure receiving surface 9 a of thespool 9 is formed at a position in correspondence to the pilot pressure introducingoil passage 21. Accordingly, the pilot pressure is applied to thepressure receiving surface 9 a of thespool 9 from thepilot port 12 via the pilot pressure introducingoil passage 21. Thespool 9 carries out a stroke toward thecam ring 2 in accordance with the pilot pressure applied to thepressure receiving surface 9 a thereof. - A
spring 11 and aspring 10 which are expanded and contracted in the same direction as the stroke direction of thespool 9 are received in an inner side of thespool 9. - One end of the
spring 11 is brought into contact with theservo piston 8, and another end of thespring 11 is brought into contact with thespool 9. Further, one end of thespring 10 is brought into contact with thespool 9, and another end of thespring 10 is brought into contact with an adjustingscrew 15. The adjustingscrew 15 is fixed to thecase 14 via alock nut 16. - A spring chamber in which the
spring 11 is received is defined by theservo piston 8 and thespool 9, and forms theoil chamber 20. Anoil passage 9 d for communicating the oil chamber 20 (the spring chamber of the spring 11) with a spring chamber in which thespring 10 is received is formed in an inner side of thespool 9. - An
oil passage 9 c for communicating theinner oil chamber 20 with an outer side of thespool 9 is formed in thespool 9. Theoil passage 9 c is formed at a position corresponding to the tank dischargingoil passage 24. Athrottle 25 is formed between theoil passage 9 c and the tank dischargingoil passage 24. When the pressure of thepilot port 12 is reduced, thespool 9 carries out a stroke toward an upper side in the drawing, that is, an opposite side to thecam ring 2. An opening area of thethrottle 25 is increased in accordance with a stroke of thespool 9 toward an opposite side to thecam ring 2, and the pressure oil is discharged from theoil chamber 20 to thetank 26 via theoil passage 9 c, thethrottle 25 and the tank dischargingoil passage 24. Accordingly, since the driving pressure within theoil chamber 20 is reduced and the thrust of theservo piston 8 is reduced, thecam ring 2 carries out a stroke toward an upper side on the basis of the thrust of the opposingpiston 7. Therefore, theservo piston 8 carries out a stroke toward an upper side. The opening area of thethrottle 25 is reduced in accordance with a stroke of theservo piston 8 toward an upper side, and the reduction in the driving pressure within theoil chamber 20 is inhibited. Accordingly, theservo piston 8 carries out a stroke toward an upper side in the drawing at a moving amount of thespool 9. - An
oil passage 9 b for communicating the spring chamber of theinner spring 10 with the outer side of thespring 9 is formed in thespool 9. Theoil passage 9 b is formed at a position corresponding to the driving pressure introducingoil passage 22. Athrottle 23 is formed between theoil passage 9 b and the driving pressure introducingoil passage 22. - When the pressure of the
pilot port 12 is increased, thespool 9 carries out a stroke toward a lower side in the drawing, that is, toward thecam ring 2. An opening area of thethrottle 23 is increased in accordance with the stroke of thespool 9 toward thecam ring 2, and the pressure oil supplied from theoriginal pressure port 13 to theoil chamber 20 via the driving pressure introducingoil passage 22, thethrottle 23, theoil passage 9 b, the spring chamber of thespring 10 and theoil passage 9 d is increased. - A thrust in correspondence to the driving pressure within the
oil chamber 20 is generated in theservo piston 8, and presses thecam ring 2. Since the pressure receiving area of the opposingpiston 7 is smaller than the pressure receiving area of theservo piston 8, thecam ring 2 carries out a stroke toward a lower side in the drawing on the basis of the thrust generated in theservo piston 8, and theservo piston 8 also carries out a stroke toward a lower side. When theservo piston 8 carries out the stroke toward the lower side, the opening area of thethrottle 23 is reduced, and the increase in the driving pressure within theoil chamber 20 is inhibited. Accordingly, theservo piston 8 carries out a stroke toward a lower side at a moving amount of thespool 9. - In this case, a
seal member 27 is fixed to theservo piston 8 by asnap ring 28, and seals in the inner side of the servo piston in such a manner that the pressure oil in the outer side of thespool 9 does not leak to the external portion. - A description will be given of an operation of the volume control apparatus in accordance with the present embodiment.
- In a steady state, as shown in FIG. 2, the
spool 9 is at a standstill under a state in which a force downward in the drawing in correspondence to the pilot pressure applied to thepressure receiving surface 9 a and a spring force K (obtained by subtracting the spring force of thespring 10 from the spring force of the spring 11) upward in the drawing applied by thespring 11 and thespring 10 are balanced. Further, the opening areas of thethrottle 23 and thethrottle 25 are regulated, and the thrust generated in theservo piston 8 and the thrust obtained by adding the thrust of the opposingpiston 7 to the thrust of thepiston 4 applied via thecam ring 2 are balanced and at a standstill. - In this case, when the pilot pressure supplied to the
pilot port 12 is increased, the force in correspondence to the pilot pressure applied to thepressure receiving surface 9 a becomes larger than the spring force K applied by thespring 11 and thespring 10, and thespool 9 carries out a stroke toward a lower side, that is, toward thecam ring 2. - When the
spool 9 relatively carries out a stroke toward thecam ring 2 with respect to theservo piston 8, the opening area of thethrottle 23 is increased, the pressure oil supplied from theoriginal pressure port 13 to theoil chamber 20 via the driving pressure introducingoil passage 22, thethrottle 23, theoil passage 9 b, the spring chamber of thespring 10 and theoil passage 9 d is increased, and the driving pressure is increased. Accordingly, the thrust generated in theservo piston 8 becomes larger than the thrust obtained by adding the thrust of the opposingpiston 7 to the thrust of thepiston 4 applied via thecam ring 2, and theservo piston 8 presses thecam ring 2 against the opposingpiston 7, and moves toward the opposingpiston 7. - Since the
spool 9 moves toward thecam ring 2 and theservo piston 8 moves toward thecam ring 2, thespring 10 is expanded while the length of thespring 11 is not changed, so that the spring force K (obtained by subtracting the spring force of thespring 10 from the spring force of the spring 11) upward in the drawing is increased. Accordingly, the movement of thespool 9 is inhibited. Therefore, the opening area of thethrottle 23 is reduced, and the increase of the driving pressure supplied to theoil chamber 20 from theoriginal pressure port 13 via the driving pressure introducingoil passage 22, thethrottle 23, theoil passage 9 b, the spring chamber of thespring 10 and theoil passage 9 d is inhibited. - As mentioned above, the
spool 9 stands still at a position where the downward force corresponding to the pilot pressure and the spring force K upward in the drawing applied by thespring 10 are balanced. In other words, thespring 10 is positioned at the lower position expanding from the state shown in FIG. 2. - The
servo piston 8 stands still at the position corresponding to the position at which thespool 9 is positioned in a standstill state, in a state in which the thrust generated in theservo piston 8 is balanced with the thrust obtained by adding the thrust of the opposingpiston 7 to the thrust of thepiston 4 applied via thecam ring 2. - As a result, the
cam ring 2 moves further closer to the opposingpiston 7 rather than the state in FIG. 2 by theservo piston 8, and the volume of theradial piston pump 1 is reduced. - On the other hand, when the pilot pressure supplied to the
pilot port 12 is reduced from the state in FIG. 2, the force in correspondence to the pilot pressure applied to thepressure receiving surface 9 a becomes smaller than the spring force K applied by thespring 11 and thespring 10, and thespool 9 carried out a stroke toward an upper side, that is, in a direction of moving apart from thecam ring 2. - When the
spool 9 carries out the stroke in the direction of relatively moving apart from thecam ring 2 with respect to theservo piston 8, the opening area of thethrottle 25 is increased, the pressure oil discharged from theoil chamber 20 to thetank 26 via theoil passage 9 c, thethrottle 25 and the tank dischargingoil passage 24 is increased, and the driving pressure is reduced. Accordingly, the thrust generated in theservo piston 8 becomes smaller than the thrust obtained by adding the thrust of the opposingpiston 7 to the thrust of thepiston 4 applied via thecam ring 2, and theservo piston 8 moves in the direction of moving apart from the opposingpiston 7 while being pressed by thecam ring 2. - Since the
spool 9 moved in the direction of moving apart from thecam ring 2, and theservo piston 8 moves in the direction of moving apart from the opposingpiston 7, thespring 10 is contracted while the length of thespring 11 is not changed, so that the upward spring force K applied by thespring 11 and thespring 10 is reduced. Accordingly, the movement of thespool 9 is inhibited. Accordingly, the opening area of thethrottle 25 is reduced, the pressure oil discharged from theoil chamber 20 to thetank 26 via theoil passage 9 c, thethrottle 25 and the tank dischargingoil passage 24 is reduced, and the reduction in the driving pressure is inhibited. - As mentioned above, the
spool 9 stands still at a position where the downward force in correspondence to the reduced pilot pressure and the upward spring force K applied by thespring 11 and thespring 10 are balanced. In other words, thespool 9 is positioned at a further upper position where thespring 10 is contracted from the state in FIG. 2. - Further, the
servo piston 8 stands still at a position corresponding to the position where thespool 9 is positioned at a standstill, in a state in which the thrust generated in theservo piston 8 is balanced with the thrust obtained by adding the thrust of the opposingpiston 7 to the thrust of thepiston 4 applied via thecam ring 2. - As a result, the
cam ring 2 moves toward the side of moving further apart from the opposingpiston 7 in comparison with the state in FIG. 2 by theservo piston 8, and the volume of theradial piston pump 1 is increased. - As mentioned above, in accordance with the present embodiment, the
servo piston 8 presses thecam ring 2 following to thespool 9, and positions thecam ring 2 at the position corresponding to the pilot pressure so as to regulate the volume. Accordingly, the same servo mechanism as that in accordance with the prior art can be achieved. Further, since the volume control apparatus has thespool 9 built in theservo piston 8, the place product becomes small, and the weight becomes light. Therefore, theradial piston pump 1 is downsized, the weight is reduced, and the freedom in arrangement is improved. - In this case, when rotating a head portion of the adjusting
screw 15 so as to regulate the screwing position with respect to thecase 14, it is possible to change the length of the spring regulated by the adjustingscrew 15. Accordingly, a corresponding relation between the pilot pressure (the volume control pressure) and the actual volume of theradial piston pump 1 can be set. When the corresponding relation between the pilot pressure and the volume is set to a desired relation in accordance with the adjustment of the adjustingscrew 15, the adjustingscrew 15 is fixed to thecase 14 by thelock nut 16. - Various modifications (applications) can be employed in the present embodiment mentioned above. A description will be given below of the various modifications by attaching the same reference numerals to the same constituting elements as those in FIGS. 1 and 2 and omitting overlapping portions.
- FIG. 3 shows a volume control apparatus having a structure corresponding to FIG. 2, and a description will be given of different parts from those in FIG. 2. In FIG. 2, the
original pressure port 13 is formed in the lower side of theservo piston 8 close to thecam ring 2, and thepilot port 12 is formed in the upper side apart from thecam ring 2. On the contrary, in FIG. 3, thepilot port 12 is formed in the lower side of theservo piston 8 close to thecam ring 2, and theoriginal pressure port 13 is formed in the upper side apart from thecam ring 2. In correspondence to this structure, thepressure receiving surface 9 a of thespool 9 is formed in the lower side closer to thecam ring 2 in FIG. 3 than in FIG. 2. Further, theseal member 27 is provided in the upper side of theservo piston 8 and thespool 9 in FIG. 2, however, is provided in the lower side of theservo piston 8 and thespool 9 in FIG. 3. - In this case, in FIGS. 2 and 3, two
springs spool 9, and the force corresponding to the pilot pressure is balanced with the spring force, however, one spring may be provided. - FIG. 4 shows a structure of the volume control apparatus in correspondence to FIGS. 2 and 3, and shows an embodiment in which only one
spring 10 is attached to thespool 9. In other words, thespring 10 expanding and contracting in the same direction as the direction of stroke of thespool 9 is received in the inner side of thespool 9. One end of thespring 10 is brought into contact with thespool 9, and another end of thespring 10 is brought into contact with the adjustingscrew 15. - In a steady state, as shown in FIG. 4, the
spool 9 is at a standstill under a state in which a downward force in correspondence to the pilot pressure applied to thepressure receiving surface 9 a and an upward spring force K applied by thespring 10 are balanced. Further, the opening areas of thethrottle 23 and thethrottle 25 are regulated, and the thrust generated in theservo piston 8 and the thrust obtained by adding the thrust of the opposingpiston 7 to the thrust of the piston applied via thecam ring 2 are balanced and at a standstill. - In this case, when the pilot pressure supplied to the
pilot port 12 is increased, the force in correspondence to the pilot pressure applied to thepressure receiving surface 9 a becomes larger than the spring force K applied by thespring 10, and thespool 9 carries out a stroke toward a lower side, that is, toward thecam ring 2. - When the
spool 9 relatively carries out a stroke toward the lower side, that is, toward thecam ring 2 with respect to theservo piston 8, the opening area of thethrottle 23 is increased, the pressure oil supplied from theoriginal pressure port 13 to theoil chamber 20 via the driving pressure introducingoil passage 22, thethrottle 23, theoil passage 9 b and theoil passage 9 d is increased, and the driving pressure is increased. Accordingly, the thrust generated in theservo piston 8 becomes larger than the thrust obtained by adding the thrust of the opposingpiston 7 to the thrust of thepiston 4 applied via thecam ring 2, and theservo piston 8 presses thecam ring 2 against the opposingpiston 7, and moves toward the opposingpiston 7. - Since the
servo piston 8 moves relatively downward, that is, toward thecam ring 2, with respect to thespool 9, whereby the opening area of thethrottle 23 is reduced, and the increase of the driving pressure supplied to theoil chamber 20 from theoriginal pressure port 13 via the driving pressure introducingoil passage 22, thethrottle 23, theoil passage 9 b and theoil passage 9 d is inhibited. - As mentioned above, the
spool 9 stands still at a position where the downward force corresponding to the pilot pressure and the upward spring force K applied by thespring 10 are balanced. In other words, thespring 10 is positioned at the lower position contracting from the state shown in FIG. 4. - The
servo piston 8 stands still at the position corresponding to the position at which thespool 9 is positioned in a standstill state, in a state in which the thrust generated in theservo piston 8 is balanced with the thrust obtained by adding the thrust of the opposingpiston 7 to the thrust of thepiston 4 applied via thecam ring 2. - As a result, the
cam ring 2 moves further closer to the opposingpiston 7 rather than the state in FIG. 4 by theservo piston 8, and the volume of theradial piston pump 1 is reduced. - On the other hand, when the pilot pressure supplied to the
pilot port 12 is reduced from the state in FIG. 4, the force in correspondence to the pilot pressure applied to thepressure receiving surface 9 a becomes smaller than the spring force K applied by thespring 10, and thespool 9 carried out a stroke toward an upper side, that is, in a direction of moving apart from thecam ring 2. - When the
spool 9 carries out the stroke relatively toward the upper side, that is, in the direction of relatively moving apart from thecam ring 2 with respect to theservo piston 8, the opening area of thethrottle 25 is increased, the pressure oil discharged from theoil chamber 20 to thetank 26 via theoil passage 9 c, thethrottle 25 and the tank dischargingoil passage 24 is increased, and the driving pressure is reduced. Accordingly, the thrust generated in theservo piston 8 becomes smaller than the thrust obtained by adding the thrust of the opposingpiston 7 to the thrust of thepiston 4 applied via thecam ring 2, and theservo piston 8 moves in the direction of moving apart from the opposingpiston 7 while being pressed by thecam ring 2. - Since the
servo piston 8 moves relatively upward, that is, in the direction of moving apart from thecam ring 2, with respect to thespool 9, the opening area of thethrottle 25 is reduced, the pressure oil discharged from theoil chamber 20 to thetank 26 via theoil passage 9 c, thethrottle 25 and the tank dischargingoil passage 24 is reduced, and the reduction in the driving pressure is inhibited. - As mentioned above, the
spool 9 stands still at a position where the downward force in correspondence to the reduced pilot pressure and the upward spring force K applied by thespring 10 are balanced. In other words, thespool 9 is positioned at a further upper position where thespring 10 is expanded from the state in FIG. 4. - The
servo piston 8 stands still at a position corresponding to the position where thespool 9 is positioned at a standstill, in a state in which the thrust generated in theservo piston 8 is balanced with the thrust obtained by adding the thrust of the opposingpiston 7 to the thrust of thepiston 4 applied via thecam ring 2. - As a result, the
cam ring 2 moves toward the side of moving further apart from the opposingpiston 7 in comparison with the state in FIG. 4 by theservo piston 8, and the volume of theradial piston pump 1 is increased. - Either the embodiments mentioned above are based on the one-flow-way type radial piston pump in which the discharging direction is fixed. However, the present invention can be applied to an alternating type radial piston pump in which the discharging direction can be changed to two directions.
- FIG. 5A is a view corresponding to FIG. 1. The
case 14 is provided with theservo piston 8 having thespool 9 built-in in the same manner as the structure shown in FIG. 2, and the opposingpiston 7, in such a manner as to oppose to each other so as to hold the rotation axis therebetween. In the same manner, theservo piston 18 having thespool 19 built-in and the opposingpiston 17 are provided in such a manner as to oppose to each other so as to hold the rotation axis therebetween. Further, theservo piston 8 having thespool 9 built-in, and theservo piston 18 having thespool 19 built-in are provided at opposing positions with holding thecam ring 2 therebetween. Accordingly, it is possible to make thecam ring 2 to be eccentric in both sides with respect to the center of the rotation axis, and the center of thepiston valve 5. - The
radial piston pump 1 capable of flowing in two direction shown in FIG. 5A is used as a constituting element of a hydraulic circuit shown in FIG. 5B. The hydraulic circuit in FIG. 5B is used in a hydro static transmission (HST) vehicle such as a bulldozer or the like. In the HST vehicle, right and left traveling bodies (wheels or crawler belts) of a vehicle body are independently driven by the HST provided respectively in right and left sides. In a hydraulic circuit of the HST, in the case that the pressure oil is discharged from one discharge port of ahydraulic pump 61 and the pressure oil is flowed into one port of ahydraulic motor 60, thehydraulic motor 60 rotates forward and the vehicle moves forward. Further, in the case that the pressure oil is discharged from another discharge port of thehydraulic pump 61 and the pressure oil is flowed into another port of thehydraulic motor 60, thehydraulic motor 60 rotates backward and the vehicle moves backward. A gear change is performed by changing the volume of thehydraulic pump 61 and thehydraulic motor 60. - As shown in FIG. 5A, in order to change the moving direction of the vehicle to the forward moving direction and the backward moving direction, and change the volume of the
radial piston pump 1 in each of the directions, there are provided a switchingvalve 40 for changing between the forward movement and the backward movement, an electromagneticproportional control valve 31 for controlling the volume at a time of forward moving, and an electromagneticproportional control valve 32 for controlling the volume at a time of moving backward. As hydraulic pressure sources of the pilot pressure and the driving pressure supplied to theservo pistons hydraulic pressure sources pressure source 29. In this case, the drivingpressure source 29 can employ theradial piston pump 1 itself. - When a forward movement command signal Si is applied to an electromagnetic solenoid of the electromagnetic
proportional control valve 31 by an operation lever (not shown) or the like, the electromagneticproportional control valve 31 is driven to an open side, and the pilot pressure is applied to apilot port 40 d of the switchingvalve 40 via the electromagneticproportional control valve 31 from the pilothydraulic pressure source 27. Accordingly, the switchingvalve 40 is changed to a forward moving position 40 a from a neutral position 40 c. Therefore, the electromagneticproportional control valve 31 is opened at an opening degree in proportional to the forward movement command signal S1, and the pilot pressure of the pilothydraulic pressure source 27 is reduced to the pilot pressure in correspondence to the opening degree of the electromagneticproportional control valve 31, and is supplied to thepilot port 12 of theservo piston 8 via the switchingvalve 40 and theoil passage 41. - The driving pressure of the driving
pressure source 29 is supplied to theoriginal pressure port 13 of theservo piston 8 via the switchingvalve 40 and the oil passage 42. Further, the driving pressure of the drivingpressure source 29 is supplied to theoil chamber 28 of the opposingpiston 7 opposing to theservo piston 8 via the switchingvalve 40 and theoil passage 46. In this case, the opposingpiston 17, thepilot port 12 of anotherservo piston 18 and theoriginal pressure port 13 are respectively communicated with thetank 26 via anoil passage 43, anoil passage 44, anoil passage 45 and the switchingvalve 40. - Accordingly, the
servo piston 8 and thespool 9 are operated as described in FIG. 2, and thecam ring 2 is made eccentric to the position corresponding to the pilot pressure supplied to thepilot port 12 of theservo piston 8. Thecam ring 2 is made eccentric to a left side in the drawing with respect to the rotation axis. Accordingly, the pressure oil at a volume corresponding to the forward movement command signal S1 is discharged from one discharging direction of theradial piston pump 1, and the vehicle travels forward at a speed corresponding to the forward movement command signal S1. - On the contrary, in the case that a backward movement command signal S2 is applied to an electromagnetic solenoid of the electromagnetic
proportional control valve 32 by the operation lever or the like, the electromagneticproportional control valve 32 is driven to an open side, and the pilot pressure is applied to apilot port 40 e of the switchingvalve 40 from the pilothydraulic pressure source 27 via the electromagneticproportional control valve 32. Accordingly, the switchingvalve 40 is changed to a backward movingposition 40 b from the neutral position 40 c. Therefore, the electromagneticproportional control valve 32 is open at an opening degree in proportion to the backward movement command signal S2, and the pilot pressure of the pilothydraulic pressure source 27 is reduced to a pilot pressure corresponding to the opening degree of the electromagneticproportional control valve 32 and is supplied to thepilot port 12 of theservo piston 18 via the switchingvalve 40 and theoil passage 44. - The driving pressure of the driving
pressure source 29 is supplied to theoriginal pressure port 13 of theservo piston 18 via the switchingvalve 40 and theoil passage 45. Further, the driving pressure of the drivingpressure source 29 is supplied to anoil chamber 38 of the opposingpiston 17 opposing to theservo piston 18 via the switchingvalve 40 and theoil passage 43. In this case, the opposingpiston 7, thepilot port 12 of anotherservo piston 8 and theoriginal pressure port 13 are communicated respectively with thetank 26 via theoil passage 46, theoil passage 41, the oil passage 42 and the switchingvalve 40. - Accordingly, the
servo piston 18 and thespool 19 are operated as described in FIG. 2, and thecam ring 2 is made eccentric to a position corresponding to the pilot pressure supplied to thepilot port 12 of theservo piston 18. Thecam ring 2 is made eccentric to a right side in the drawing with respect to the rotation axis. Therefore, the pressure oil at the volume corresponding to the backward movement command signal S2 is discharged from another discharging direction of theradial piston pump 1, and the vehicle travels backward at a speed corresponding to the backward movement command signal S2. - In this case, the structure in FIG. 5A is based on the volume control apparatus having the structure shown in FIG. 2, however, can employ the volume control apparatus having the structure shown in FIGS.3 or 4.
- The embodiment mentioned above is described on the basis of the radial piston pump, however, can be applied also to the radial piston motor as it is.
- Further, the embodiments mentioned above are not limited to the volume control apparatus for the radial piston pump or motor, but can be applied to a volume control apparatus for a swash plate type axial piston pump or motor.
- FIG. 6 shows an embodiment employing the volume control apparatus shown in FIG. 2 as a volume control apparatus for regulating the volume by pressing a
swash plate 50 of an axial piston pump 55 and oscillating theswash plate 50. - The
servo piston 8 having thespool 9 built-in in the same manner as the structure shown in FIG. 2 is brought into contact with theswash plate 50, and theservo piston 8 presses theswash plate 50 on the basis of a thrust corresponding to the pilot pressure so as to oscillate theswash plate 50, and positions theswash plate 50 at a position tilted from arotation axis 51. A stroke amount of apiston 54 is determined in correspondence to a tilting amount of theswash plate 50 with respect to therotation axis 51, and a volume of the axial piston pump 55 is determined. In FIG. 6, the structure is made such that a position of a supporting point of a ball for supporting the tilting motion of theswash plate 50 is displaced to a left side in the drawing from a position of a working point of a resultant force applied to theswash plate 50 by the shoe of thepiston 54, thereby generating a force opposing to the thrust of theservo piston 8 existing in a right side in the drawing with respect to the ball, and achieving the same function as that of the opposingpiston 7 in FIG. 1. - In this case, the structure in FIG. 6 can be applied also to the axial piston motor as it is.
- Further, the structure in FIG. 6 is based on the volume control apparatus having the structure shown in FIG. 2, however, may employ the volume control apparatus having the structure shown in FIGS.3 or 4.
- Further, the apparatus having the structure shown in FIGS. 2, 3 and4 is not limited to the apparatus for positioning the cam ring or the swash plate of the hydraulic pump or motor, and may be used as a positioning apparatus for positioning the other members to be positioned than the cam ring and the swash plate to a desired position.
Claims (4)
1. A volume control apparatus of a radial piston pump or a motor for regulating a volume by positioning a cam ring of the radial piston pump or the motor, comprising:
a control valve positioned at a position in correspondence to a volume control pressure; and
a servo piston having said control valve built-in, being operated following to the control valve and pressing said cam ring so as to position the cam ring.
2. A volume control apparatus of a radial piston pump or a motor as claimed in claim 1 , wherein one set of said control valve and said servo piston and another set of said control valve and said servo piston are provided at opposing positions with respect to said cam ring.
3. A positioning apparatus comprising:
a control valve positioned at a position in correspondence to a control pressure; and
a servo piston having said control valve built-in, being operated following to the control valve and pressing a positioning member so as to position the positioning member.
4. A positioning apparatus comprising:
a control valve carrying out a stroke in correspondence to a control pressure applied to a pressure receiving surface; and
a servo piston having said control valve built-in and pressing a positioning member in correspondence to a driving pressure,
wherein a throttle is formed between said control valve and said servo piston, in such a manner that the driving pressure introduced to said servo piston is increased in accordance that said control valve carries out the stroke relatively close to said positioning member with respect to said servo piston, and the driving pressure introduced to said servo piston is reduced in accordance that said servo piston carries out the stroke relatively close to said positioning member with respect to said control valve,
wherein a spring for generating a spring force opposing to said control pressure is applied to said control valve,
wherein said control pressure is applied to said pressure receiving surface so as to carry out a stroke of said control valve, said servo piston carries out a stroke following to said control valve on the basis of the driving pressure introduced via said throttle, and
wherein said control valve is positioned at a position where the spring force of said spring and said control pressure are balanced, and said servo piston is positioned in accordance the positioning of the control valve.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2002342560A JP2004176601A (en) | 2002-11-26 | 2002-11-26 | Capacity control device and positioning device for radial piston pump or motor |
JP2002-342560 | 2002-11-26 |
Publications (1)
Publication Number | Publication Date |
---|---|
US20040101417A1 true US20040101417A1 (en) | 2004-05-27 |
Family
ID=32321990
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US10/699,809 Abandoned US20040101417A1 (en) | 2002-11-26 | 2003-11-03 | Volume control apparatus of radial piston pump or motor and positioning apparatus |
Country Status (2)
Country | Link |
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US (1) | US20040101417A1 (en) |
JP (1) | JP2004176601A (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2014113152A1 (en) * | 2013-01-15 | 2014-07-24 | Husco International, Inc. | Hydraulic piston pump with throttle control |
US8926298B2 (en) | 2012-01-04 | 2015-01-06 | Husco International, Inc. | Hydraulic piston pump with a variable displacement throttle mechanism |
US20230042317A1 (en) * | 2021-08-03 | 2023-02-09 | Huaqiao University | Radial piston hydraulic device distributed by pilot operated check valves |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPWO2019215850A1 (en) * | 2018-05-09 | 2020-05-28 | 株式会社ラピート | Radial piston type hydraulic actuator |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4077745A (en) * | 1976-02-26 | 1978-03-07 | Robert Bosch Gmbh | Adjustment mechanism for radial-piston pump |
US4652215A (en) * | 1984-04-12 | 1987-03-24 | Nippondenso Co., Ltd. | Variable capacity radial piston pump |
-
2002
- 2002-11-26 JP JP2002342560A patent/JP2004176601A/en active Pending
-
2003
- 2003-11-03 US US10/699,809 patent/US20040101417A1/en not_active Abandoned
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4077745A (en) * | 1976-02-26 | 1978-03-07 | Robert Bosch Gmbh | Adjustment mechanism for radial-piston pump |
US4652215A (en) * | 1984-04-12 | 1987-03-24 | Nippondenso Co., Ltd. | Variable capacity radial piston pump |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8926298B2 (en) | 2012-01-04 | 2015-01-06 | Husco International, Inc. | Hydraulic piston pump with a variable displacement throttle mechanism |
WO2014113152A1 (en) * | 2013-01-15 | 2014-07-24 | Husco International, Inc. | Hydraulic piston pump with throttle control |
US9062665B2 (en) | 2013-01-15 | 2015-06-23 | Husco International, Inc. | Hydraulic piston pump with throttle control |
US20230042317A1 (en) * | 2021-08-03 | 2023-02-09 | Huaqiao University | Radial piston hydraulic device distributed by pilot operated check valves |
US11781537B2 (en) * | 2021-08-03 | 2023-10-10 | Huaqiao University | Radial piston hydraulic device distributed by pilot operated check valves |
Also Published As
Publication number | Publication date |
---|---|
JP2004176601A (en) | 2004-06-24 |
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