JP2004176601A - Capacity control device and positioning device for radial piston pump or motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To promote downsizing, weight reduction and improvement of degrees of freedom in the arrangement of a radial piston pump or a motor, and to promote downsizing and weight reduction of a positioning device that determines positions of a cam ring of the radial piston pump or the motor, a swash plate of an axial piston pump or the motor and the like. <P>SOLUTION: A piston 8 operates by following a control valve (spool) 9, presses the cam ring 2, and determines the position of the cam ring 2 in accordance with capacity control pressure to adjust the capacity. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a device for controlling the capacity of a radial piston pump or a radial piston motor arranged such that each piston slides in a radial direction with respect to a rotation shaft, a cam ring of the radial piston pump, a swash plate of an axial piston pump, and the like. The present invention relates to a positioning device that performs positioning.
[0002]
2. Description of the Related Art
BACKGROUND ART A hydraulic working machine such as a construction machine is equipped with a hydraulic pump and a hydraulic motor for driving an upper swing body, a lower traveling body, and the like.
[0003]
One type of hydraulic pump is a radial piston pump in which each piston slides in a radial direction with respect to a rotation axis.
[0004]
In the radial piston pump, the cam ring is pressed by the displacement adjusting actuator, and the center of the cam ring is positioned at a position eccentric with respect to the center of the rotating shaft (main shaft). The capacity (cc / rev) is determined according to the amount of eccentricity of the cam ring.
[0005]
One type of hydraulic pump is an axial piston pump in which each piston slides parallel to a rotation axis.
[0006]
In an axial piston pump, a swash plate is swung by a displacement adjusting actuator, and the swash plate is positioned at a position inclined with respect to a rotation axis (main shaft). The capacity is determined according to the amount of tilt of the swash plate.
[0007]
By the way, when mounting hydraulic pumps on construction machines in recent years, due to restrictions on mounting space and demands from the market, it is desired to reduce the area of the hydraulic pump itself, reduce the weight, and improve the freedom of arrangement of the hydraulic pump. There is a request. For this reason, there is a demand for miniaturization and weight reduction of the capacity adjusting actuator attached to the hydraulic pump. The same applies to the hydraulic motor.
[0008]
SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and a first object of the present invention is to reduce the size, weight, and flexibility of a radial piston pump or motor.
[0009]
Another object of the present invention is to reduce the size and weight of a positioning device 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.
[0010]
The general technical levels related to the problem to be solved by the present invention are as follows.
[0011]
(Prior art 1)
In Patent Literature 1 listed below, the position of a cam ring of a radial piston pump is detected by a distance sensor, the detection signal of the distance sensor is amplified by an amplifier, and the amplified signal is taken into a servo valve as a feedback amount, and the servo valve receives the amplified signal. There is disclosed a positioning device that drives and controls a piston to position a cam ring at a target position.
[0012]
Since the positioning device described in Patent Literature 1 includes a distance sensor, an amplifier, a servo valve, and a piston, there is a problem that a field area is large when used as an actuator for adjusting the capacity of a radial piston pump.
[0013]
(Patent Document 1)
JP-A-11-50968 (particularly FIG. 1)
Means for Solving the Problems and Effects
The first invention is to achieve the first solution,
In a displacement control device for a radial piston pump or a motor for adjusting a displacement by positioning a cam ring (2) of the radial piston pump or a motor,
A control valve (9) positioned at a position corresponding to the displacement control pressure;
A piston (8) having the control valve (9) built therein, operating following the control valve (9), pressing the cam ring (2) and positioning the cam ring (2);
It is characterized by having.
[0014]
In the displacement control device of the first invention, as shown in FIG. 1, the piston 8 operates following the control valve (spool) 9 to press the cam ring 2 and position the cam ring 2 at a position corresponding to the displacement control pressure. And adjust the capacity. Therefore, a servo mechanism equivalent to that of the prior art 1 is realized. In addition, since the displacement control device has the control valve 9 built in the piston 8, the volume is reduced and the weight is reduced. For this reason, the radial piston pump or the motor is reduced in size, the weight is reduced, and the degree of freedom in arrangement is improved.
[0015]
The second invention is based on the first invention,
The control valves (9, 9 ') and the pistons (8, 8') are provided at positions facing each other across the cam ring (2).
It is characterized by.
[0016]
According to the second invention, as shown in FIG. 5 (a), the control valve 9, the piston 8 and the control valve 9 ', the piston 8' are provided at positions facing each other with the cam ring 2 interposed therebetween. 2 can be eccentric on both sides with respect to the center of the pintle valve 5. For this reason, as shown in FIG. 5B, when applied to a double swing hydraulic pump 1 capable of changing the discharge direction in two directions, it is possible to adjust the capacity in both discharge directions with a small space. Can be.
[0017]
The third invention is to achieve the second solution,
A control valve (9) positioned at a position corresponding to the control pressure;
A piston (8) which incorporates the control valve (9), operates following the control valve (9), presses the positioning member (2, 50), and positions the positioning member (2, 50);
It is a positioning device provided with.
[0018]
The fourth invention is to achieve the second solution,
A control valve (9) that strokes according to a control pressure applied to the pressure receiving surface (9a), and a piston (8) that includes the control valve (9) and presses the positioning member (2, 50) according to a driving pressure. ) Is provided,
As the control valve (9) strokes toward the positioning member (2, 50) relative to the piston (8) between the control valve (9) and the piston (8). As the driving pressure introduced to the piston (8) increases, the piston (8) strokes toward the positioning member (2, 50) relative to the control valve (9). Forming throttles (23, 25) for reducing the driving pressure introduced to the piston (8) side,
A spring (10, 11) for generating a spring force opposing the control pressure is applied to the control valve (9),
When the control pressure is applied to the pressure receiving surface (9a), the control valve (9) strokes, and the driving pressure introduced through the throttles (23, 25) causes the piston (8) to move the control valve (9). Stroke following 9),
The control valve (9) is positioned at a position where the spring force of the springs (10, 11) balances with the control pressure, and the piston (8) is positioned accordingly.
It is a positioning device.
[0019]
In the positioning device of the third and fourth inventions, as illustrated in FIGS. 1 and 6, the piston 8 operates following the control valve (spool) 9 to operate the positioning members (cam rings, swash plates) 2, 50. To position the positioning members 2 and 50 at positions corresponding to the control pressure. In this positioning device, since the control valve 9 is built in the piston 8, the field is reduced and the weight is reduced. For this reason, the radial piston pump or motor, the axial piston pump or motor, and the like are reduced in size, the weight is reduced, and the degree of freedom of arrangement is improved.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a capacity control device and a positioning device according to the present invention will be described with reference to the drawings.
[0021]
FIG. 1 shows the configuration of the radial piston pump of the embodiment. The radial piston pump shown in FIG. 1 is mounted on, for example, a construction machine and used as a drive pressure source for a hydraulic motor driving an upper revolving unit or a hydraulic motor driving a lower traveling unit.
[0022]
FIG. 1 is a view of the radial piston pump 1 as viewed in a section perpendicular to a rotation axis (main axis). FIG. 1 shows an eccentric radial piston pump.
[0023]
As shown in FIG. 1, the radial piston pump 1 is configured by housing a cylinder block 3 and the like inside a case 14.
[0024]
The cylinder block 3 is formed integrally with a rotating shaft (main shaft) not shown.
[0025]
The cylindrical pintle valve 5 is fixed to the case 14 by fitting in an arrangement mode in which the rotation axis and the central axis are the same.
[0026]
A pump port P is formed in the pintle valve 5 over a predetermined circumferential length along the circumferential direction. The pump port P is open on the outer peripheral surface of the pintle valve 5. Further, the pintle valve 5 is formed with a suction port S over a predetermined circumferential length along the circumferential direction. The suction port S is open on the outer peripheral surface of the pintle valve 5.
[0027]
A plurality of bores are formed in the cylinder block 3 at equal pitches in the radial direction of the rotation shaft (main shaft). A piston 4 is slidably provided in each bore. A shoe 49 is swingably connected to each piston 4.
[0028]
The cam ring 2 is arranged outside the shoe 49. The cam ring 2 has an inner peripheral surface slidably disposed on a sliding surface of each shoe 49.
[0029]
The case 14 is provided with a servo piston 8 and an opposing piston 7, which constitute a capacity control device, facing each other so as to sandwich the rotation shaft (main shaft). The servo piston 8 and the opposing piston 7 press and support the cam ring 2 so that the center of the cam ring 2 can move eccentrically with respect to the center of the rotating shaft (main shaft). A bearing 6 for sliding the cam ring 2 is disposed between the cam ring 2 and the case 14.
[0030]
The cylinder block 3 has a cylinder-side port 4a communicating with each bore. The cylinder-side port 4a is open at a position facing the pump port P and the suction port S on the pintle valve 5 side.
[0031]
When the rotating shaft (main shaft) is driven to rotate by a drive source, for example, an engine, the cylinder block 3 rotates relatively to the pintle valve 5. Thereby, the shoe 49 slides along the inner peripheral surface of the cam ring 2.
[0032]
By operating the servo piston 8 and the opposing piston 7, the center of the cam ring 2 is eccentric with respect to the center of the rotation shaft (main shaft) by a predetermined eccentric amount. Therefore, when the piston 4 is located at a position where the pintle valve 5 and the cam ring 2 are closest to each other, the piston 4 is in a top dead center state, The piston 4 is at a position where the pintle valve 5 and the cam ring 2 are most separated from each other, and the piston 4 is in a bottom dead center state. Further, when the piston 4 makes a half turn around the pintle valve 5, the piston 4 moves between the bottom dead center and the top dead center. Thus, the piston 4 makes one stroke (top dead center to bottom dead center to top dead center) each time it makes one rotation along the circumferential direction of the pintle valve 5, and the amount of one stroke corresponds to twice the amount of eccentricity. In the course of one stroke of the piston 4, pressure oil having a capacity (cc / rev) corresponding to the stroke amount is sucked and discharged.
[0033]
That is, when the piston 4 is located at a position where the cylinder side port 4a communicates with the suction port S, pressure oil is sucked from the tank into the bore via the suction port S and the cylinder side port 4a. Then, when the piston 4 is located at a position where the cylinder side port 4a communicates with the pump port P, the pressure oil compressed by the piston 4 is discharged from the bore through the cylinder side port 4a and the pump port P and the external oil pressure is applied. Supplied to the actuator. In this way, a pressure oil having a capacity corresponding to the amount of eccentricity of the cam ring 2 is supplied to the external hydraulic actuator via the pump port P.
[0034]
The opposed piston 7 is slidably provided in the case 14. An oil chamber 28 is formed inside the opposed piston 7, and a spring 27 is provided to the opposed piston 7. In the opposing piston 7, a thrust corresponding to the oil pressure in the oil chamber 28 and the spring force of the spring 27 is generated, and the cam ring 2 is pressed against the servo piston 8.
[0035]
The servo piston 8 is slidably provided on the case 14, and an oil chamber 20 is formed inside the servo piston 8. In the servo piston 8, a thrust corresponding to the oil pressure in the oil chamber 20 is generated, and the cam ring 2 is pressed against the opposing piston 7. Here, a constant driving pressure is supplied into the oil chamber 28 on the side of the opposed piston 7, and a constant thrust is generated in the opposed piston 7.
[0036]
On the other hand, the driving pressure in the oil chamber 20 on the servo piston 8 side changes according to the displacement control pressure supplied to the pilot port 12, and the thrust of the servo piston 8 changes according to the displacement control pressure. Therefore, the cam ring 2 is eccentric to a position corresponding to the displacement control pressure supplied to the pilot port 12 of the servo piston 8. As the cam ring 2 is moved toward the opposing piston 7 by the servo piston 8, the capacity decreases from the maximum capacity.
[0037]
FIG. 2 is an enlarged view of the servo piston 8 of FIG. 1 and shows a capacity control device of the embodiment.
[0038]
As shown in FIG. 2, a spool 9 as a control valve is slidably built in the servo piston 8 with respect to the servo piston 8.
[0039]
On the outer peripheral surface of the servo piston 8, a pilot port 12 to which a pilot pressure as a capacity control pressure is supplied is formed. The servo piston 8 is provided with a pilot pressure introducing oil passage 21 for guiding the pilot pressure supplied to the pilot port 12 to the inside of the servo piston 8.
[0040]
On the outer peripheral surface of the servo piston 8, a source pressure port 13 to which a driving pressure for driving the piston 8 is supplied is formed. The servo piston 8 has a drive pressure introducing oil passage 22 that guides the drive pressure supplied to the source pressure port 13 to the inside of the servo piston 8.
[0041]
The servo piston 8 is formed with a tank discharge oil passage 24 that communicates between the tank 26 and the inside of the servo piston 8.
[0042]
The spool 9 has a small-diameter portion having a diameter D1 and a large-diameter portion having a diameter D2, and has a pressure receiving surface 9a formed as a step between the small-diameter portion and the large-diameter portion. The pressure receiving surface 9a has a pressure receiving area corresponding to a pressure receiving area difference ((D2) 2- (D1) 2) π / 4 between the large diameter portion and the small diameter portion.
[0043]
The pressure receiving surface 9a of the spool 9 is formed at a position corresponding to the pilot pressure introducing oil passage 21. Therefore, pilot pressure is applied from the pilot port 12 to the pressure receiving surface 9 a of the spool 9 via the pilot pressure introduction oil passage 21.
[0044]
The spool 9 strokes toward the cam ring 2 when a pilot pressure is applied to the pressure receiving surface 9a.
[0045]
Inside the spool 9, springs 11 and 10, which expand and contract in the same direction as the stroke direction of the spool 9, are housed.
[0046]
One end of the spring 11 is in contact with the servo piston 8, and the other end of the spring 11 is in contact with the spool 9. One end of the spring 10 is in contact with the spool 9, and the other end of the spring 10 is in contact with the adjusting screw 15. The adjusting screw 15 is fixed to the case 14 via a lock nut 16.
[0047]
A spring chamber in which the spring 11 is housed is defined by the servo piston 8 and the spool 9, and forms an oil chamber 20.
[0048]
An oil passage 9 d is formed inside the spool 9 to communicate the oil chamber 20 (the spring chamber of the spring 11) with the spring chamber in which the spring 10 is housed.
[0049]
An oil passage 9c is formed in the spool 9 to communicate the inner oil chamber 20 (the spring chamber of the spring 11) with the outside of the spool 9. The oil passage 9c is formed at a position corresponding to the tank discharge oil passage 24. A throttle 25 is formed between the oil passage 9c and the tank discharge oil passage 24. When the pressure of the pilot port 12 decreases, the spool 9 strokes upward in the drawing, that is, on the side opposite to the cam ring 2. As the spool 9 strokes upward in the drawing, that is, on the side opposite to the cam ring 2, the opening area of the throttle 25 increases, and from the oil chamber 20 to the tank 26 via the oil passage 9 c, the throttle 25, and the tank discharge oil passage 24. Is discharged. As a result, the driving pressure in the oil chamber 20 is reduced and the thrust of the servo piston 8 is reduced, so that the cam ring 2 is stroked upward by the thrust of the opposing piston 7. Therefore, the servo piston 8 moves upward. As the servo piston 8 strokes upward, the opening area of the throttle 25 decreases, and a decrease in the driving pressure in the oil chamber 20 is suppressed. This causes the servo piston 8 to stroke upward in the drawing by the amount of movement of the spool 9.
[0050]
An oil passage 9 b is formed in the spool 9 to communicate the spring chamber of the inner spring 10 with the outside of the spool 9. The oil passage 9b is formed at a position corresponding to the drive pressure introducing oil passage 22. A throttle 23 is formed between the oil passage 9b and the drive pressure introducing oil passage 22. When the pressure of the pilot port 12 increases, the spool 9 strokes downward in the drawing, that is, toward the cam ring 2. As the spool 9 strokes downward in the drawing, that is, toward the cam ring 2, the opening area of the throttle 23 increases, and the drive pressure introducing oil passage 22, the throttle 23, the oil passage 9 b, and the spring chamber of the spring 10 extend from the original pressure port 13. The pressure oil supplied to the oil chamber 20 via the oil passage 9d increases.
[0051]
In the servo piston 8, a thrust corresponding to the driving pressure in the oil chamber 20 is generated, 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 strokes downward in the figure by the thrust generated by the servo piston 8, and the servo piston 8 strokes downward in the figure. When the servo piston 8 strokes downward in the figure, the opening area of the throttle 23 decreases, and an increase in the driving pressure in the hydraulic pressure 20 is suppressed. This causes the servo piston 8 to stroke downward in the figure by the amount of movement of the spool 9.
[0052]
Note that a seal member 27 is fixed to the servo piston 8 by a snap ring 28, and seals the inside of the servo piston 8 so that pressure oil outside the spool 9 does not leak outside.
[0053]
Hereinafter, the operation of the capacity control device of the present embodiment will be described.
[0054]
In a steady state, as shown in FIG. 2, the spool 9 applies a downward force in the figure according to the pilot pressure applied to the pressure receiving surface 9a, and an upward spring force K (the spring 11 (Spring force−spring force of spring 10) is balanced and stationary. Further, the opening areas of the throttles 23 and 25 are adjusted, and the thrust generated by the servo piston 8 and the total thrust of the thrust of the opposing piston 7 and the thrust of the piston 4 acting via the cam ring 2 are balanced. It is stationary.
[0055]
Here, when the pilot pressure supplied to the pilot port 12 increases, the force corresponding to the pilot pressure applied to the pressure receiving surface 9a becomes larger than the spring force K by the springs 11 and 10, and the spool 9 moves to the lower side in the figure. That is, the stroke is made to the cam ring 2 side.
[0056]
When the spool 9 strokes relatively downward with respect to the servo piston 8 in the figure, that is, toward the cam ring 2, the opening area of the throttle 23 increases, and the drive pressure introduction oil passage 22, the throttle 23, the oil passage 9b, the pressure oil supplied to the oil chamber 20 via the spring chamber of the spring 10 and the oil passage 9d increases, and the driving pressure increases. As a result, the thrust generated by the servo piston 8 becomes larger than the sum of the thrust of the opposing piston 7 and the thrust of the piston 4 acting via the cam ring 2, and the servo piston 8 moves the cam ring 2 toward the opposing piston 7. It is moved to the opposing piston 7 side by pressing.
[0057]
Since the spool 9 moves to the cam ring 2 side and the servo piston 8 moves to the cam ring 2 side, the length of the spring 11 does not change, but the spring 10 expands. 11-the spring force of the spring 10). Therefore, the movement of the spool 9 is suppressed. As a result, the opening area of the throttle 23 is reduced, and is supplied from the source pressure port 13 to the oil chamber 20 via the drive pressure introducing oil passage 22, the throttle 23, the oil passage 9b, the spring chamber of the spring 10, and the oil passage 9d. An increase in driving pressure is suppressed.
[0058]
Thus, the spool 9 stops at a position where the downward force according to the increased pilot pressure and the upward spring force K (the spring force of the spring 11-the spring force of the spring 10) by the spring 10 are balanced. That is, the spring 10 is positioned at a lower position in the figure, which is extended from the state of FIG.
[0059]
The servo piston 8 has a thrust generated by the servo piston 8 at a position corresponding to the positioning position where the spool 9 is stationary, a thrust obtained by summing the thrust of the opposing piston 7 and the thrust of the piston 4 acting via the cam ring 2. Balances and comes to rest.
[0060]
As a result, the cam ring 2 is further moved to the opposite piston 7 side by the servo piston 8 than in the state of FIG. 2, and the capacity of the radial piston pump 1 is reduced.
[0061]
On the other hand, when the pilot pressure supplied to the pilot port 12 decreases from the state of FIG. 2, the force corresponding to the pilot pressure applied to the pressure receiving surface 9a becomes smaller than the spring force K by the springs 11 and 10, and 9 strokes in the upper direction in the drawing, that is, in the direction away from the cam ring 2.
[0062]
When the spool 9 strokes relatively upward with respect to the servo piston 8 in the drawing, that is, in a direction away from the cam ring 2, the opening area of the throttle 25 increases, and the oil passage 9c, the throttle 25, and the oil passage for tank discharge extend from the oil chamber 20. The pressure oil discharged to the tank 26 via 24 increases, and the driving pressure decreases. As a result, the thrust generated by the servo piston 8 becomes smaller than the sum of the thrust of the opposing piston 7 and the thrust of the piston 4 acting via the cam ring 2. Move in the direction away from 7.
[0063]
Since the spool 9 moves in the direction away from the cam ring 2 and the servo piston 8 moves in the direction away from the opposing piston 7, the length of the spring 11 does not change, but the spring 10 contracts because the spring 10 is retracted. The spring force K (the spring force of the spring 11-the spring force of the spring 10) is reduced. Therefore, the movement of the spool 9 is suppressed. As a result, the opening area of the throttle 25 is reduced, and the pressure oil discharged from the oil chamber 20 to the tank 26 via the oil passage 9c, the throttle 25, and the tank discharge oil passage 24 is reduced, and a decrease in drive pressure is suppressed. You.
[0064]
Thus, the spool 9 stops at a position where the downward force according to the reduced pilot pressure and the upward spring force K (the spring force of the spring 11-the spring force of the spring 10) of the spring 10 are balanced. That is, the spring 10 is positioned at a more retracted position than in the state of FIG.
[0065]
The servo piston 8 has a thrust generated by the servo piston 8 at a position corresponding to the positioning position where the spool 9 is stationary, a thrust obtained by summing the thrust of the opposing piston 7 and the thrust of the piston 4 acting via the cam ring 2. Balances and comes to rest.
[0066]
As a result, the cam ring 2 is moved further away from the opposing piston 7 by the servo piston 8 than in the state of FIG. 2, and the capacity of the radial piston pump 1 is increased.
[0067]
As described above, according to the present embodiment, the servo piston 8 operates following the spool 9 to press the cam ring 2, position the cam ring 2 at a position corresponding to the pilot pressure, and adjust the capacity. I have. Therefore, a servo mechanism equivalent to that of the prior art 1 is realized. In addition, since the capacity control device has the spool 9 built in the piston 8, the volume is reduced and the weight is reduced. For this reason, the radial piston pump 1 is reduced in size, weight is reduced, and the degree of freedom in arrangement is improved.
[0068]
When the head of the adjusting screw 15 is rotated to adjust the screwing position with respect to the case 14, the length of the spring 10 regulated by the adjusting screw 15 can be changed. Thereby, the correspondence between the pilot pressure (capacity control pressure) and the actual capacity of the radial piston pump 1 is set. When the correspondence between the pilot pressure and the capacity is set to a desired relationship by adjusting the adjusting screw 15, the adjusting screw 15 is fixed to the case 14 by the lock nut 16.
[0069]
Various modifications can be made to the embodiment shown in FIGS. 1 and 2 described above. Hereinafter, the same components are denoted by the same reference numerals, and the description will not be repeated.
[0070]
FIG. 3 shows a configuration of the capacity control device corresponding to FIG.
[0071]
2 will be described. In FIG. 2, a source pressure port 13 is formed below the servo ring 8 near the cam ring 2 and a pilot port 12 is formed farther from the cam ring 2 in the figure. 3, a pilot port 12 is formed below the servo ring 8 near the cam ring 2 in the figure, and a source pressure port 13 is formed farther from the cam ring 2 in the figure. Correspondingly, the pressure receiving surface 9a of the spool 9 is formed in the lower part of FIG. 3 closer to the cam ring 2 in FIG. 2, the seal member 27 is provided at the upper part of the servo piston 8 and the spool 9 in FIG. 2, whereas in FIG. 3, the seal member 27 is provided at the upper part of the servo piston 8 and the spool 9 in the figure.
In FIGS. 2 and 3, two springs 10 and 11 are applied to the spool 9 to balance the force according to the pilot pressure with the spring force. However, an embodiment in which one spring is provided is also possible.
[0072]
FIG. 4 shows the configuration of the displacement control device corresponding to FIGS. 2 and 3, showing an embodiment in which only one spring 10 is provided to the spool 9.
[0073]
As shown in FIG. 4, a spring 10 that expands and contracts in the same direction as the stroke direction of the spool 9 is housed inside the spool 9.
[0074]
One end of the spring 10 is in contact with the spool 9 and the other end of the spring 10 is in contact with the adjusting screw 15.
[0075]
In the steady state, as shown in FIG. 4, the spool 9 is stationary because the downward force in the figure according to the pilot pressure applied to the pressure receiving surface 9a and the upward spring force K by the spring 10 are balanced. ing. Further, the opening areas of the throttles 23 and 25 are adjusted, and the thrust generated by the servo piston 8 and the total thrust of the thrust of the opposing piston 7 and the thrust of the piston 4 acting via the cam ring 2 are balanced. It is stationary.
[0076]
Here, when the pilot pressure supplied to the pilot port 12 increases, the force corresponding to the pilot pressure applied to the pressure receiving surface 9a becomes larger than the spring force K by the spring 10, and the spool 9 is moved to the lower side in FIG. Stroke to the side.
[0077]
When the spool 9 strokes relatively downward with respect to the servo piston 8 in the figure, that is, toward the cam ring 2, the opening area of the throttle 23 increases, and the drive pressure introduction oil passage 22, the throttle 23, the oil passage 9b, the pressure oil supplied to the oil chamber 20 via the oil passage 9d increases, and the driving pressure increases. As a result, the thrust generated by the servo piston 8 becomes larger than the sum of the thrust of the opposing piston 7 and the thrust of the piston 4 acting via the cam ring 2, and the servo piston 8 moves the cam ring 2 toward the opposing piston 7. It is moved to the opposing piston 7 side by pressing.
[0078]
The opening area of the throttle 23 is reduced by the servo piston 8 having moved relatively downward in the drawing, that is, toward the cam ring 2 with respect to the spool 9, and the drive pressure introducing oil passage 22, the throttle 23, An increase in driving pressure supplied to the oil chamber 20 via the passage 9b and the oil passage 9d is suppressed.
[0079]
Thus, the spool 9 stops at a position where the downward force according to the increased pilot pressure and the upward spring force K by the spring 10 are balanced. That is, the spring 10 is positioned at a lower position in the figure, which is retracted from the state of FIG.
[0080]
The servo piston 8 has a thrust generated by the servo piston 8 at a position corresponding to the positioning position where the spool 9 is stationary, a thrust obtained by summing the thrust of the opposing piston 7 and the thrust of the piston 4 acting via the cam ring 2. Balances and comes to rest.
[0081]
As a result, the cam ring 2 is further moved to the opposite piston 7 side by the servo piston 8 than in the state of FIG. 4, and the capacity of the radial piston pump 1 is reduced.
[0082]
On the other hand, when the pilot pressure supplied to the pilot port 12 decreases from the state of FIG. 4, the force corresponding to the pilot pressure applied to the pressure receiving surface 9a becomes smaller than the spring force K by the spring 10, and the spool 9 The stroke is made in the middle upper direction, that is, in the direction away from the cam ring 2.
[0083]
When the spool 9 strokes relatively upward with respect to the servo piston 8 in the drawing, that is, in a direction away from the cam ring 2, the opening area of the throttle 25 increases, and the oil passage 9c, the throttle 25, and the oil passage for tank discharge extend from the oil chamber 20. The pressure oil discharged to the tank 26 via 24 increases, and the driving pressure decreases. As a result, the thrust generated by the servo piston 8 becomes smaller than the sum of the thrust of the opposing piston 7 and the thrust of the piston 4 acting via the cam ring 2. Move in the direction away from 7.
[0084]
The opening area of the throttle 25 is reduced by moving the servo piston 8 relatively upward with respect to the spool 9 in the drawing, that is, in the direction away from the cam ring 2, and the oil passage 20 c, the oil passage 9 c, the throttle 25, The pressure oil discharged to the tank 26 via the passage 24 decreases, and the decrease in the driving pressure is suppressed.
[0085]
Thus, the spool 9 stops at a position where the downward force according to the reduced pilot pressure and the upward spring force K by the spring 10 are balanced. In other words, the spring 10 is positioned at a position higher in the drawing than in the state of FIG.
[0086]
The servo piston 8 has a thrust generated by the servo piston 8 at a position corresponding to the positioning position where the spool 9 is stationary, a thrust obtained by summing the thrust of the opposing piston 7 and the thrust of the piston 4 acting via the cam ring 2. Balances and comes to rest.
[0087]
As a result, the cam ring 2 is moved further away from the opposing piston 7 by the servo piston 8 than in the state shown in FIG. 4, and the capacity of the radial piston pump 1 is increased.
[0088]
In the above-described embodiment, a one-flow-way type radial piston pump having a fixed discharge direction is assumed. However, the present invention can be applied to a double swing type radial piston pump that can change the discharge direction in two directions.
[0089]
FIG. 5A is a view corresponding to FIG. 1. In the case 14, a servo piston 8 having a built-in spool 9 having the same configuration as that in FIG. 2 and an opposing piston 7 oppose each other so as to sandwich the rotation shaft (main shaft). It is provided. Similarly, a servo piston 8 'having a built-in spool 9' having the same configuration as that of FIG. 2 and an opposing piston 17 are provided so as to face each other so as to sandwich the rotation shaft (main shaft). A spool 9 and a servo piston 8 having the same configuration as in FIG. 2 and a spool 9 ′ and a servo piston 8 ′ having the same configuration are provided at positions facing each other with the cam ring 2 interposed therebetween. Therefore, the cam ring 2 can be eccentric on both sides with respect to the center of the rotation shaft (main shaft) and the center of the pintle valve 5.
[0090]
The radial piston pump 1 capable of two-way flow shown in FIG. 5A is used, for example, as a component of a hydraulic circuit shown in FIG. 5B. The hydraulic circuit of FIG. 5B is used for an HST (Hydro Static Transmission) vehicle such as a bulldozer. In an HST vehicle, left and right running bodies (wheels or crawler tracks) of the vehicle body are independently driven by HSTs provided on the left and right sides, respectively. In the hydraulic circuit of the HST, when pressure oil is discharged from one discharge port of the hydraulic pump 1 and pressure oil flows into one port of the hydraulic motor 60, the hydraulic motor 60 rotates forward and the vehicle moves forward. When the pressure oil is discharged from the other discharge port of the hydraulic pump 1 and the pressure oil flows into the other port of the hydraulic motor 60, the hydraulic motor 60 rotates in the reverse direction and the vehicle moves backward. The shift is performed by changing the capacity of the hydraulic pump 1 and the hydraulic motor 60.
[0091]
As shown in FIG. 5 (a), the vehicle is switched between the forward direction and the reverse direction, and in order to change the displacement of the radial piston pump 1 in each direction, a switching valve 40 for switching forward and backward, and a displacement control valve for forward displacement. An electromagnetic proportional control valve 31 and an electromagnetic proportional control valve 32 for controlling the displacement during reverse movement are provided. A pilot hydraulic pressure source 27 and a driving pressure source 29 are provided as hydraulic pressure sources for the pilot pressure and the driving pressure supplied to the servo pistons 8 and 8 ', respectively. Here, the driving pressure source 29 can use the radial piston pump 1 itself.
[0092]
When the forward command signal S1 is applied to the electromagnetic solenoid of the electromagnetic proportional control valve 31 by an operation lever or the like (not shown), the electromagnetic proportional control valve 31 operates to the open side, and the pilot pressure from the pilot hydraulic pressure source 27 causes the electromagnetic proportional control valve 31 to operate. It is added to the pilot port 40d of the switching valve 40 via the switching valve 40. As a result, the switching valve 40 is switched from the neutral position 40c to the forward position 40a. Therefore, the electromagnetic proportional control valve 31 is opened at an opening proportional to the forward command signal S1, the pilot pressure of the pilot hydraulic pressure source 27 is reduced to a pilot pressure corresponding to the opening of the electromagnetic proportional control valve 31, and the switching valve 40, The oil is supplied to the pilot port 12 of the servo piston 8 via the oil passage 41. The drive pressure of the drive pressure source 27 is supplied to the source pressure port 13 of the servo piston 8 via the switching valve 40 and the oil passage 42. The drive pressure of the drive pressure source 27 is supplied to the oil chamber 28 of the opposed piston 7 that faces the servo piston 8 via the switching valve 40 and the oil passage 46. The opposing piston 17 and the pilot port 12 and the source pressure port 13 of the other servo piston 8 'communicate with the tank 26 via an oil passage 43, an oil passage 44, an oil passage 45, and a switching valve 40, respectively.
[0093]
Therefore, the servo piston 8 and the spool 9 operate in the same manner as described with reference to FIG. 2, and the cam ring 2 is eccentric to a position corresponding to the pilot pressure supplied to the pilot port 12 of the servo piston 8. The cam ring 2 is eccentric to the left side in the figure with respect to the rotating shaft (main shaft). Therefore, a pressure oil having a capacity corresponding to the forward command signal S1 is discharged from one discharge direction of the radial piston pump 1, and the vehicle travels forward at a speed corresponding to the forward command signal S1.
[0094]
On the other hand, when the reverse command signal S2 is applied to the electromagnetic solenoid of the electromagnetic proportional control valve 32 by the operation lever or the like, the electromagnetic proportional control valve 32 operates to the open side, and the pilot pressure is supplied from the pilot hydraulic pressure source 27 to the electromagnetic proportional control valve. It is added to the pilot port 40e of the switching valve 40 through the port 32. As a result, the switching valve 40 is switched from the neutral position 40c to the reverse position 40b. For this reason, the electromagnetic proportional control valve 32 opens at an opening proportional to the reverse command signal S2, and the pilot pressure of the pilot hydraulic power source 27 is reduced to a pilot pressure corresponding to the opening of the electromagnetic proportional control valve 32, and the switching valve 40, The oil is supplied to the pilot port 12 of the servo piston 8 'via the oil passage 44. The drive pressure of the drive pressure source 27 is supplied to the source pressure port 13 of the servo piston 8 'via the switching valve 40 and the oil passage 45. The drive pressure of the drive pressure source 27 is supplied to the oil chamber 38 of the opposed piston 17 facing the servo piston 8 ′ via the switching valve 40 and the oil passage 43. The pilot port 12 and the source pressure port 13 of the opposing piston 7 and the other servo piston 8 communicate with the tank 26 via an oil passage 46, an oil passage 41, an oil passage 42, and a switching valve 40, respectively.
[0095]
Therefore, the servo piston 8 'and the spool 9' operate in the same manner as described with reference to FIG. 2, and the cam ring 2 is eccentric to a position corresponding to the pilot pressure supplied to the pilot port 12 of the servo piston 8 '. The cam ring 2 is eccentric to the right side in the figure with respect to the rotation shaft (main shaft). Therefore, a pressure oil having a capacity corresponding to the reverse command signal S2 is discharged from the other discharge direction of the radial piston pump 1, and the vehicle travels backward at a speed corresponding to the reverse command signal S2.
[0096]
Although FIG. 5A assumes the capacity control device having the configuration shown in FIG. 2, a capacity control device having the configuration shown in FIG. 3 or FIG. 4 may be used in FIG.
[0097]
In the embodiment described above, the radial piston pump has been described, but the present invention can be applied to a radial piston motor as it is.
[0098]
The embodiment described above is not limited to the displacement control device of the radial piston pump or the motor, and can be applied to the displacement control device of the oblique axis type axial piston pump or the motor.
[0099]
FIG. 6 illustrates a case in which the displacement control device shown in FIG. 2 is used as a displacement control device for adjusting the displacement by pressing the swash plate 50 of the axial piston pump 1 ′ and swinging the swash plate 50.
[0100]
As shown in FIG. 6, a servo piston 8 containing a spool 9 is in contact with the swash plate 50 as in the configuration shown in FIG. 2, and the servo piston 8 moves the swash plate 50 with a thrust corresponding to the pilot pressure. By pressing and swinging, the swash plate 50 is positioned at a position inclined with respect to the rotation shaft (main shaft) 51. The amount of stroke of the piston 4 'is determined according to the amount of tilt of the swash plate 50 with respect to the rotating shaft (main shaft) 51, and the capacity of the axial piston pump 1' is determined. 6, the fulcrum position of the ball that supports the tilting of the swash plate 50 is shifted to the left in the drawing from the position of the resultant point of the resultant force of the force of the shoe of the piston 4 'acting on the swash plate 50. A function equivalent to that of the opposing piston 7 in FIG. 1 is realized by generating a force opposing the thrust of the servo piston 8 existing on the right side in the figure with respect to the ball.
[0101]
The configuration shown in FIG. 6 can be applied to an axial piston motor as it is.
[0102]
In FIG. 6, the capacity control device having the configuration shown in FIG. 2 is assumed, but in FIG. 6, a capacity control device having the configuration shown in FIG. 3 or FIG. 4 may be used.
[0103]
Further, the apparatus having the configuration shown in FIGS. 2, 3 and 4 is not limited to a device for positioning a cam ring and a swash plate of a hydraulic pump or a motor. It can be used as a positioning device for positioning.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a radial piston pump according to an embodiment.
FIG. 2 is a diagram showing a capacity control device shown in FIG. 1;
FIG. 3 is a diagram illustrating a configuration of a capacity control device having a configuration different from that of FIG. 2;
FIG. 4 is a diagram showing a configuration of a capacity control device having a configuration different from those of FIGS. 2 and 3;
FIGS. 5A and 5B are diagrams showing a configuration example in which the displacement of the radial piston pump in both discharge directions is changed.
FIG. 6 is a diagram illustrating a case where the displacement control device of the embodiment is applied to an axial piston pump.
[Explanation of symbols]
2 cam ring
8 Servo piston
9 spool
10,11 spring
23, 25 aperture
50 Swash plate

Claims (4)

In a displacement control device for a radial piston pump or a motor for adjusting a displacement by positioning a cam ring (2) of the radial piston pump or a motor,
A control valve (9) positioned at a position corresponding to the displacement control pressure;
A piston (8) which has the control valve (9) built therein, operates following the control valve (9), presses the cam ring (2) and positions the cam ring (2). Radial piston pump or motor capacity control device. The radial piston pump according to claim 1, wherein the control valve (9, 9 ') and the piston (8, 8') are provided at positions facing each other across the cam ring (2). Motor capacity control device. A control valve (9) positioned at a position corresponding to the control pressure;
A piston (8) which incorporates the control valve (9) and operates following the control valve (9) to press the positioning member (2, 50) to position the positioning member (2, 50); A positioning device characterized by the above-mentioned. A control valve (9) that strokes according to the control pressure applied to the pressure receiving surface (9a);
A piston (8) for incorporating the control valve (9) therein and for pressing the positioning member (2, 50) in accordance with a driving pressure;
As the control valve (9) strokes toward the positioning member (2, 50) relative to the piston (8) between the control valve (9) and the piston (8). As the driving pressure introduced to the piston (8) increases, the piston (8) strokes toward the positioning member (2, 50) relative to the control valve (9). Forming throttles (23, 25) for reducing the driving pressure introduced to the piston (8) side,
A spring (10, 11) for generating a spring force opposing the control pressure is applied to the control valve (9),
When the control pressure is applied to the pressure receiving surface (9a), the control valve (9) strokes, and the driving pressure introduced through the throttles (23, 25) causes the piston (8) to move the control valve (9). Stroke following 9),
The positioning device, wherein the control valve (9) is positioned at a position where the spring force of the springs (10, 11) and the control pressure are balanced, and the piston (8) is positioned accordingly.

Images