JPH11351134A - Variable displacement swash plate type hydraulic pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To save energy by effectively using limited horsepower characteristics of a prime mover as curved characteristics in relationship between the discharge pressure and the discharge amount of a pump. SOLUTION: A link member 50 for a feedback mechanism 48 is integrally formed with a spherical portion 53 at the end of a feedback pin 52 and the side face of a swash plate 10 is provided with a cam plate 54 to be put in slide contact with the spherical portion 53. By operating a tilting actuator with tilting control pressure from a regulator 42 in response to a pump discharge pressure P, the swash plate 10 is tiltingly driven to change a tilting angle. The tilting motion of the swash plate 10 is transmitted from the cam face of the cam plate 54 through the spherical portion 53 of the feedback pin 52 to the link member 50 to rotationally displace the link member 50 in the directions indicated by arrowmarks E, F with a supporting pin 49 as a center and change the rotational displacement amount at this time corresponding to the cam shape of the cam plate 54.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable displacement swash plate type hydraulic pump suitably used as a hydraulic source for hydraulic equipment mounted on construction machines such as hydraulic excavators.

[0002]

2. Description of the Related Art In general, a construction machine such as a hydraulic shovel is provided with a hydraulic pump which constitutes a hydraulic source together with a tank, and the hydraulic pump is driven to rotate by a prime mover such as a diesel engine. In addition, pressure oil is supplied and discharged to each hydraulic actuator such as a traveling hydraulic motor.

A variable displacement type swash plate type hydraulic pump will be described as this type of conventional hydraulic pump with reference to FIGS. 7 to 10. FIG.

In FIG. 1, reference numeral 1 denotes a cylindrical casing. The casing 1 includes a bottomed cylindrical casing main body 1A and a front casing 1B in which the opening end side (front side) of the casing main body 1A is closed. ing. On the bottom side of the casing body 1A, a suction passage 1C for sucking hydraulic oil in the tank 32 described later and a discharge passage 1D for discharging pressure oil described later to the outside are provided.

The discharge passage 1D is connected to various hydraulic actuators (all not shown) such as a hydraulic cylinder and a hydraulic motor via a discharge pipe, a directional control valve, and the like. This is supplied to the hydraulic actuator. An opening 1E communicating with a valve housing 18 of a regulator 17 described later is formed on an outer peripheral side of the casing main body 1A, and a link member 26 described later is rotatably mounted in the opening 1E. I have.

Reference numeral 2 denotes a rotating shaft rotatably provided in the casing 1, and 3 denotes a cylinder block which is located in the casing main body 1A and rotates together with the rotating shaft 2. Cylinder 4 is bored. A piston 5 is slidably provided in each of the cylinders 4, and a shoe 6 is attached to each of the pistons 5 so as to swing.

Reference numeral 7 denotes an annular shoe retainer holding each shoe 6, and the shoe retainer 7 is a sliding surface 10 of a swash plate 10 described later.
A, each shoe 6 is pressed toward the sliding surface 10 of the swash plate 10.
This compensates for the sliding displacement of each shoe 6 so as to draw an annular locus on A.

Reference numeral 8 denotes a valve plate provided between the bottom of the casing body 1A and the cylinder block 3. The valve plate 8 slides on the end face of the cylinder block 3, and the cylinder block 3 rotates integrally with the rotary shaft 2. To compensate you. A pair of supply / discharge ports (not shown) having an eyebrow shape are formed in the valve plate 8, and one of the supply / discharge ports is always in communication with the suction passage 1C, and the other port is connected to the discharge passage. 1D
Is always in communication with

Each supply / discharge port of the valve plate 8 intermittently communicates with each cylinder 4 when the cylinder block 3 rotates, and the hydraulic oil sucked into each cylinder 4 from the suction passage 1C side by the piston 5. It has a function to pressurize and to discharge the high pressure oil (pump discharge pressure P) in each cylinder 4 from the discharge passage 1D to the outside in the direction indicated by the arrow in FIG.

Reference numeral 9 denotes a swash plate support provided around the rotating shaft 2 and provided on the front casing 1B. The swash plate support 9 is located on the back side of the swash plate 10, and tilts the swash plate 10. It has a tilt support portion 9A for supporting it as much as possible. And
The tilt support portion 9A has a concave curved surface shape as shown in FIG. 8, and has a configuration in which a tilt guide surface 10B of a swash plate 10 described later is slidably fitted.

Reference numeral 10 denotes a swash plate provided in the casing 1 so as to be tiltable via a swash plate support 9. The swash plate 10 has a front surface serving as a sliding surface 10A for each shoe 6 and a rear surface having a swash plate. It is a convex curved tilt guide surface 10B fitted to the tilt support portion 9A of the plate support 9. The swash plate 10 is disposed in a state of being inclined with respect to the rotating shaft 2 and the cylinder block 3 by the tilt angle θ as shown in FIG. 8, and the capacity of the hydraulic pump (pressure oil discharge amount Q) is tilted. Is variably controlled according to the magnitude of the angle θ.

Numerals 11A and 11B denote a pair of tilt actuators for driving the swash plate 10 to tilt.
1A and 11B are cylinder blocks 3 as shown in FIG.
And cylinder holes 12A and 12B formed in the casing body 1A at a position radially outward of the cylinder holes 12A and 12B.
12B is slidably inserted into the cylinder hole 12A, 1B.
2B, the tilt control pistons 14A, 14B defining hydraulic chambers 13A, 13B, and the tilt control pistons 14A, 14B are disposed in the hydraulic chambers 13A, 13B.
The springs 15A and 15B are constantly biased toward the zero side.

Here, the tilt actuator 11A is disposed at a position corresponding to the bottom dead center side of each piston 5 inserted into each cylinder 4 of the cylinder block 3, and the tilt actuator 11B is It is arranged at the position corresponding to the top dead center side of. And the tilt control piston 14
A is formed to have a smaller diameter than the tilt control piston 14B, and the pressure receiving area for the hydraulic chambers 13A, 13B in the cylinder holes 12A, 12B is smaller for the tilt control piston 14A than for the tilt control piston 14B. I have.

16A and 16B are tilt actuators 11
The control pressure passages 16A and 16B are formed in the casing main body 1A as shown in FIG.
A, 11B hydraulic pressure chambers 13A, 13B
Are connected to the supply / discharge ports 18A, 18B. Further, the control pressure passage 16A is connected to a pilot pump
The tilt control piston 1 which is connected via a small diameter and has a small diameter.
The pressure from the pilot pump 31 always acts on 4A.

The tilt actuators 11A, 11A
The tilt control pistons 14A and 14B of B move forward and backward from the cylinder holes 12A and 12B toward the swash plate 10 in accordance with the tilt control pressure supplied and discharged from the control pressure passages 16A and 16B via the regulator 17. . As a result, the swash plate 10 is tilted and driven in the directions indicated by arrows A and B in FIG. 8, and when the swash plate 10 is tilted in the direction indicated by arrows A, the tilt angle θ decreases, and the swash plate 10 decreases in the direction indicated by arrows B. When tilted, the tilt angle θ is controlled so as to increase.

Reference numeral 17 denotes tilt actuators 11A and 11B.
The regulator 17 is provided with a valve housing 18 provided on the casing body 1A outside the casing 1 (upper side of the casing 1 in FIG. 7) and a valve housing 18 which will be described later. Control sleeve 19, spool 20, valve springs 21, 22 and hydraulic pilot section 2
3 and the like, and constitutes a displacement control valve for a hydraulic pump as shown in FIG.

Here, the valve housing 18 of the regulator 17 has a supply / discharge port 1 for tilt control pressure as shown in FIG.
8A, 18B, a discharge port 18C, and the like are formed in the radial direction, and the supply / discharge port 18A is always in communication with the hydraulic chamber 13A of the tilt actuator 11A via the control pressure passage 16A. The supply / discharge port 18B is connected to the control pressure passage 16.
B, and always communicates with the hydraulic chamber 13B through the discharge port 18
C is always in communication with the tank 32 through the casing 1.

Reference numeral 19 denotes a cylindrical control sleeve which is slidably inserted into the valve housing 18. The control sleeve 19 has one end connected to a link member 26 to be described later via an output pin 27. , The valve housing 18 is slidably displaced in the axial direction in accordance with the movement.

Reference numeral 20 denotes a spool slidably inserted into the control sleeve 19, and the spool 20 is
By slidingly displacing the inside of the valve housing 18 in the axial direction via 9, the communication between the supply / discharge port 18 </ b> B and the supply / discharge port 18 </ b> A and the discharge port 18 </ b> C is selectively performed and blocked.

Numerals 21 and 22 denote valve springs disposed between one end of the spool 20 and the valve housing 18. Of the valve springs 21 and 22, the valve spring 21 having the larger coil diameter is used.
, Always urges the spool 20 in one direction toward the hydraulic pilot portion 23 side. The valve spring 22 having the smaller coil diameter keeps a free length state until the valve spring 21 is flexed and deformed by the specified dimension by the spool 20, and is deformed together with the valve spring 21 when the valve spring 21 exceeds the specified dimension. Accordingly, the spool 20 is biased toward the hydraulic pilot portion 23.

Reference numeral 23 denotes a hydraulic pilot portion located at the other end of the valve housing 18 and provided between the valve housing 18 and the spool 20. The hydraulic pilot portion 23 moves the spool 20 in the axial direction against the valve springs 21 and 22. Plunger 2 for driving
3A, and a pump discharge pressure P is introduced through a branch pipe 34 described later. The plunger 23A of the hydraulic pilot section 23 receives the pump discharge pressure P from the branch pipe line 34 as the pilot pressure, thereby sliding the spool 20 in the valve housing 18 in the axial direction in accordance with the pilot pressure. It is to let.

Reference numeral 24 denotes a feedback mechanism for performing feedback control of the regulator 17 by following the tilting operation of the swash plate 10. The feedback mechanism 24 is provided between the valve housing 18 of the regulator 17 and the casing body 1A as shown in FIG. It comprises a link member 26 rotatably mounted via a support pin 25 therebetween, and connection protruding portions 30 described later. The link member 26 forms a feedback link together with a feedback pin 28 and a spherical portion 29 described later.

Here, the link member 26 is swingably disposed in the opening 1E of the casing 1 by the support pin 25, and one end of the link member 26 extending from the position of the support pin 25 into the valve housing 18 is controlled by the regulator 17. Sleeve 19
Are rotatably connected to each other via an output pin 27. The other end of the link member 26 projects toward the inside of the casing body 1A.
8 are integrally fixed at the base end side. The feedback pin 28 extends substantially parallel to the side surface of the swash plate 10 toward the connection protrusion 30, and has a spherical portion 29 that is pivotally connected to the connection protrusion 30 at the tip end.

Reference numeral 30 denotes a connecting protrusion fixed to the side surface of the swash plate 10. The connecting protrusion 30 protrudes from the side surface of the swash plate 10 toward the spherical portion 29 of the feedback pin 28. It is a joint part 30A in the shape of a letter. And
A feedback pin 2 is provided at the joint 30A of the connecting projection 30.
Eight spherical portions 29 are swingably connected, whereby the connecting protrusions 30 are configured to rotate and displace the link member 26 following the tilting operation of the swash plate 10.

That is, when the swash plate 10 is tilted in the directions indicated by arrows A and B in FIG. 8, the feedback pin 28 (spherical portion 29) swings with respect to the connecting projection 30 in accordance with the tilting operation of the swash plate 10. The link member 26 is rotated about the support pin 25 by the dynamic displacement. And the support pin 25
The rotation displacement of the link member 26 centered on the arrow is taken out as a translational movement of the output pin 27 shown in the directions of arrows C and D in FIG. 8 and transmitted to the control sleeve 19 of the regulator 17 through the output pin 27. Thus, the feedback control of the regulator 17 is performed.

Reference numeral 31 denotes a pilot pump for generating a tilt control pressure. The pilot pump 31 sucks hydraulic oil from a tank 32, and moves a hydraulic oil for tilt control into a pipe line 33, as shown in FIG. Is discharged. in this case,
The pressure of the pressure oil discharged from the pilot pump 31 is maintained at a pressure sufficiently lower than the pump discharge pressure P by a low-pressure leaf valve (not shown) or the like.

Numeral 34 denotes a branch line directed to the bottom of the casing body 1A. The branch line 34 branches from a middle part of the discharge passage 1D as shown in FIG.
As shown in FIG.
It is connected to the. The branch pipe line 34 uses the pump discharge pressure P as a pilot pressure for controlling the capacity, and the regulator 1
7 is supplied to and discharged from the hydraulic pilot unit 23.

The variable displacement type swash plate type hydraulic pump according to the prior art has the above-described configuration, and its operation will be described below.

First, when the rotary shaft 2 is driven to rotate by the prime mover, the cylinder block 3 rotates integrally with the rotary shaft 2, so that each piston 5 repeats reciprocating motion in each cylinder 4 of the cylinder block 3. . During this time, each shoe 6 slides on the sliding surface 10A of the swash plate 10 so as to describe an annular trajectory, and compensates for smooth reciprocation of each piston 5 in each cylinder 4.

In this case, when each piston 5 retreats (extends) from the top dead center side to the bottom dead center side in the cylinder 4,
The hydraulic oil in the tank 32 is supplied to the cylinder 4 from the suction passage 1C side.
It becomes the suction stroke to suck in. Further, when the piston 5 enters (reduces) from the bottom dead center side to the top dead center side in the cylinder 4, the hydraulic oil in the cylinder 4 is pressurized, and the pressure is increased from the discharge passage 1D on the high pressure side to the outside. This is a discharge stroke for discharging oil (pump discharge pressure P).

Then, the pump discharge pressure P at this time is supplied as a pilot pressure for capacity control to the hydraulic pilot section 23 of the regulator 17 via the branch pipe line 34, and the regulator 17 uses the characteristic lines 35A, 35B shown in FIG. , The discharge amount Q of the pressure oil by the hydraulic pump is variably controlled according to the pump discharge pressure P.

That is, the regulator 17 is held at the neutral position (a) when the pump discharge pressure P is constant as shown in FIG. When the pump discharge pressure P increases in this state, the pilot pressure acting on the hydraulic pilot portion 23 of the regulator 17 increases, so that the spool 2
0 switches from the neutral position (A) to the switching position (B) against the valve spring 21.

As a result, the supply / discharge ports 18A and 18B of the valve housing 18 communicate with each other, and the tilt control pressure from the pilot pump 31 is supplied to the hydraulic chambers 13A and 13B of the tilt actuators 11A and 11B, respectively. The rotation control pistons 14A and 14B are driven in the direction of arrow A in FIG. 9 by the pressure receiving area difference. Then, the swash plate 10 of the hydraulic pump is driven by the tilt control piston 14B in the direction in which the tilt angle θ decreases (small tilt side), and the discharge amount Q of the pressure oil decreases.

At this time, the tilting operation of the swash plate 10 in the direction of arrow A is transmitted from the connecting projection 30 to the feedback pin 28 via the spherical portion 29 by the feedback mechanism 24.
The link member 26 is rotated about the support pin 25 in the direction of arrow C in FIG. Then, the rotational displacement of the link member 26 is transmitted to the control sleeve 19 of the regulator 17 as the displacement of the output pin 27 in the direction of arrow B, causing the control sleeve 19 to slide in the same direction as the spool 20. Thus, the feedback control of the regulator 17 is performed.

When the tilt angle θ (pressure oil discharge amount Q) of the swash plate 10 corresponds to the pump discharge pressure P, the regulator 17 returns to the neutral position (A) shown in FIG. Thus, the discharge amount Q of the pressure oil by the hydraulic pump is controlled so as to satisfy the relationship between the pump discharge pressure P and the characteristic lines 35A and 35B shown in FIG.

In this case, a characteristic line 36 indicated by a virtual line in FIG. 10 is a constant horsepower curve of the prime mover, and the pump discharge pressure P
When the relationship between the engine speed and the discharge amount Q becomes larger than the characteristic line 36, an overload acts on the prime mover, so that the prime mover causes engine stall (so-called engine stall).

Therefore, the conventional regulator 17
Adopts two valve springs 21 and 22 and provides a pump discharge pressure P
When the pressure is equal to or lower than the pressure P1, the relationship between the discharge amount Q and the discharge pressure P is controlled along the characteristic line 35A by urging the spool 20 with only the valve spring 21. When the pump discharge pressure P is in a high pressure state exceeding the pressure P1, the spool 20 is urged by using two valve springs 21 and 22 so that the relationship between the discharge amount Q and the discharge pressure P is represented by a characteristic line. Control is performed along 35B.

That is, when the spool 20 is urged only by the valve spring 21, the displacement of the spool 20 is relatively large with respect to the rate of change of the pump discharge pressure P, whereby the discharge amount Q is reduced. It changes relatively largely along the characteristic line 35A. On the other hand, when the spool 20 is biased by using the two valve springs 21 and 22, the displacement of the spool 20 is relatively small with respect to the rate of change of the pump discharge pressure P. Is controlled so that the rate of change becomes smaller along the characteristic line 35B in an area equal to or less than the discharge amount Q1.

[0039]

In the prior art described above, the regulator 17 is provided with two valve springs 21 and
2, the pump discharge pressure P exceeds the pressure P1 and the step below the pressure P1 so as to change the relationship between the pump discharge pressure P and the discharge amount Q along the characteristic lines 35A and 35B in FIG. In each of the stages, control is performed with linear characteristics (characteristic lines 35A and 35B) different from each other.

However, the constant horsepower curve of the prime mover is shown in FIG.
It has a curved characteristic like a characteristic line 36 indicated by an imaginary line, and as long as the relationship between the pump discharge pressure P and the discharge amount Q is controlled along the characteristic lines 35A and 35B, for example, the pump discharge pressure In a region where P is close to the pressure P1, the discharge amount Q of the hydraulic pump is suppressed to the level of the discharge amount Q1 lower than the characteristic line 36, and the limited horsepower characteristics of the prime mover are necessarily used effectively. There is a problem that can not be.

In the prior art, since two valve springs 21 and 22 are used for the regulator 17,
Not only does the number of parts increase and the workability during assembly deteriorates, but also the spring force of the valve springs 21 and 22 tends to vary, and the relationship between the pump discharge pressure P and the discharge amount Q is adjusted for each product. There is a problem that it is difficult to equalize.

The present invention has been made in view of the above-mentioned problems of the prior art, and the present invention makes it possible to effectively utilize the limited horsepower characteristics of the prime mover by making the relationship between the pump discharge pressure and the discharge amount into a curve-like characteristic. It is an object of the present invention to provide a variable displacement swash plate type hydraulic pump capable of increasing energy, improving workability during assembly, and improving productivity.

[0043]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a cylindrical casing, a rotating shaft rotatably provided in the casing, and a rotating shaft that rotates together with the rotating shaft. A cylinder block provided in a casing and having a plurality of cylinders drilled in an axial direction, a plurality of pistons reciprocally inserted into each cylinder of the cylinder block, and attached to an end of each piston. A swash plate that has a sliding surface on which the shoe slides and is tiltably provided in the casing; and a tilt actuator that tilts and drives the swash plate by supplying and discharging tilt control pressure. A regulator provided on the casing for controlling the tilt control pressure supplied to and discharged from the tilt actuator, the spool having a spool and a control sleeve; and a regulator of the regulator following the tilt operation of the swash plate. It is applied to a variable capacity swash plate type hydraulic pump comprising a feedback mechanism for readback control.

A feature of the structure adopted by the invention of claim 1 is that the feedback mechanism is rotatably provided between the regulator and a casing, one end of which is connected to a control sleeve of the regulator. A feedback link having a cam sliding contact portion whose end side projects toward the swash plate, and a feedback link provided on the swash plate, wherein the cam sliding contact portion of the feedback link slides to connect the feedback link to the swash plate. And a cam body that rotates and displaces in accordance with the tilting operation and changes the amount of the rotational displacement in accordance with the cam shape.

With this configuration, when the tilt control pressure is supplied to and discharged from the regulator to the tilt actuator to drive the tilting of the swash plate, the cam sliding portion of the feedback link continues to slide on the cam body. Therefore, the feedback link can be rotated and displaced with the tilting operation of the swash plate,
The amount of rotation displacement can be variably set according to the cam shape. The rotation displacement of the feedback link can be transmitted to the control sleeve of the regulator, the regulator can be feedback-controlled according to the cam shape of the cam body, and the tilt angle (pump capacity) of the swash plate can be curved with respect to the pump discharge pressure. Can be controlled with the characteristics described above.

According to the second aspect of the present invention, the cam body has a configuration in which the surface of the feedback link that the cam sliding portion slides on is formed as an inclined surface.

According to the third aspect of the present invention, the cam sliding portion of the feedback link is formed in a spherical shape. Thus, the spherical cam sliding contact portion of the feedback link can smoothly slide on the cam surface of the cam body.

According to the fourth aspect of the present invention, the regulator has the supply / discharge port for supplying / discharging the tilt control pressure to / from the tilt actuator, the spool being slidably fitted on the inner peripheral side together with the control sleeve. A valve spring disposed between the valve housing and the spool, the valve spring always biasing the spool in one direction, and a valve located on the opposite side of the valve spring with respect to the spool. Provided in the housing,
And a hydraulic pilot unit that receives the pump discharge pressure as a pilot pressure and causes the spool to slide and displace against the valve spring.

Accordingly, when the hydraulic pilot portion of the regulator receives the pump discharge pressure as the pilot pressure,
In accordance with the pilot pressure at this time, the spool slides in the valve housing against the valve spring. Then, since each supply / discharge port of the valve housing is communicated or disconnected via the spool and the control sleeve, it is possible to supply / discharge the displacement control pressure corresponding to the pump discharge pressure from the regulator to the displacement actuator.

On the other hand, according to the fifth aspect of the present invention, an urging means is provided between the casing and the feedback link to always urge the cam sliding portion toward the cam body. Thereby, the cam sliding contact portion can be kept in a state of being always in contact with the cam body, and the rotational displacement of the food back link can be stabilized.

According to the sixth aspect of the present invention, the cam body has a cam groove, and the cam slide contact portion of the feedback link is provided with an engagement projection which is slidably engaged with the cam groove. And Thus, the cam sliding contact portion (engaging projection) of the feedback link can be held in a state of being engaged with the cam groove of the cam body, and the rotational displacement of the feedback link can be stabilized.

[0052]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a variable displacement swash plate type hydraulic pump according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the embodiment, the same components as those of the above-described conventional technology are denoted by the same reference numerals, and description thereof will be omitted.

Here, FIGS. 1 to 3 show a first embodiment of the present invention. In the figure, reference numeral 41 denotes a casing of the swash plate type hydraulic pump according to the present embodiment.
Reference numeral 1 denotes a casing body 41A and a front casing 41B, which are almost the same as the casing 1 described in the related art, and a suction passage 41C, a discharge passage 41D, an opening 41E and the like are provided on the casing body 41A side.

The casing main body 41A is provided with a branch pipe 34 branched from an intermediate portion of the discharge passage 41D. The branch pipe 34 supplies a pump pressure P to a hydraulic pilot portion 47 of a regulator 42, which will be described later. It is supplied as. On the other hand, the front casing 41
B is provided with a swash plate support 9 that tiltably supports the swash plate 10.

Reference numeral 42 denotes the tilt actuators 11A and 11B.
The regulator 42 is a valve housing having supply / discharge ports 43A, 43B and a discharge port 43C for displacement control pressure, in substantially the same manner as the regulator 17 described in the related art. 43, a control sleeve 44, a spool 45, a valve spring 46, a hydraulic pilot portion 47 having a plunger 47A, and the like.

However, the regulator 42 according to the present embodiment is different from the conventional regulator 17 in that the spool 45 is constantly biased toward the hydraulic pilot portion 47 by a single valve spring 46. Are different.

Reference numeral 48 denotes a feedback mechanism for performing feedback control of the regulator 42 by following the tilting operation of the swash plate 10. The feedback mechanism 48 is substantially the same as the feedback mechanism 24 described in the prior art, and is provided on the casing body 1A side. And a link member 50 for feedback, which is rotatably mounted via a support pin 49, and the link member 50 constitutes a feedback link together with a feedback pin 52 and a spherical portion 53 described later.

However, in the feedback mechanism 48 according to the present embodiment, the support pin 49 is disposed in a direction substantially perpendicular to the rotation shaft 2 and the link member 50 is connected to the support pin 4.
It is configured to rotate in the directions indicated by arrows E and F around the center 9. An output pin 51 is provided at one end of a link member 50 extending into the valve housing 43, and the output pin 51 rotatably connects the link member 50 to the control sleeve 44 of the regulator 42.

A feedback pin 52 is integrally provided at the other end of the link member 50 extending into the casing body 41A. The feedback pin 52 is connected to a side surface of the swash plate 10 toward a cam plate 54 described later. They extend almost parallel. The distal end of the feedback pin 52 forms a spherical portion 53 as a cam sliding portion, and the spherical portion 53 slides on the cam plate 54 as shown in FIG.

Reference numeral 54 denotes a cam plate as a cam body fixed to the side surface of the swash plate 10. The cam plate 54 projects from the side surface of the swash plate 10 toward the spherical portion 53 of the feedback pin 52, and the spherical portion 53 A cam surface 54A as shown in FIG. The cam surface 54A of the cam plate 54 is formed by a slightly curved inclined surface or the like with a predetermined curvature.

Here, the cam surface 54A of the cam plate 54 is always in contact with the spherical portion 53 formed on the tip side of the feedback pin 52, and the swash plate 10 is moved in the direction of arrow A in FIG. When the cam surface 54A is tilted to
Is pressed in the retreating direction (arrow E direction) to rotate the link member 50 in the arrow E direction about the support pin 49 and to change the amount of rotation displacement at this time by the cam surface 54A.
Is changed according to the cam shape.

When the swash plate 10 is tilted in the direction of arrow B (large tilt side) in FIG.
When the second spherical portion 53 follows the cam surface 54A and advances in the direction of arrow F, the link member 50
Is rotated in the direction of arrow F, and the amount of rotational displacement at this time is also changed according to the cam shape of the cam surface 54A.

The variable displacement type swash plate type hydraulic pump according to the present embodiment has the above-described configuration, and its basic operation is not particularly different from that of the prior art.

According to this embodiment, however, the link member 50 of the feedback mechanism 48 is formed integrally with the spherical portion 53 serving as the cam sliding contact portion at the tip end of the feedback pin 52, and is formed on the side surface of the swash plate 10. Since the cam plate 54 is provided so as to be in sliding contact with the spherical portion 53, the following operational effects can be obtained.

That is, when the pump discharge pressure P of the hydraulic pump changes and the tilt control pressure is supplied and discharged from the regulator 42 to the tilt actuators 11A and 11B,
The tilt control pistons 14A, 14A are controlled according to the tilt control pressure.
By moving B toward the swash plate 10, the swash plate 10
Is tilted in the directions of the arrows A and B to change the tilt angle θ appropriately.

The tilting operation of the swash plate 10 is performed by the cam plate 54.
Of the feedback pin 52 from the cam surface 54A
3, the link member 50 is pivotally displaced around the support pin 49 in the directions indicated by arrows E and F, and the amount of the rotational displacement at this time is determined by the cam shape of the cam surface 54A. Can be changed according to

Thus, the link member 50 is connected to the swash plate 1
In response to the tilting operation of zero and the cam shape of the cam plate 54, the cam plate 54 is rotated in the directions indicated by the arrows E and F, and the rotational displacement at this time makes it possible to feedback-control the control sleeve 44 of the regulator 42. The tilt control pressure supplied and discharged from the regulator 42 to the tilt actuators 11A and 11B is controlled by the tilt angle θ of the swash plate 10 and the cam surface 54A of the cam plate 54.
(Cam shape).

As a result, the movement of the tilt actuators 11A and 11B can be changed in accordance with the cam shape of the cam plate 54, and the tilting operation of the swash plate 10 by the tilt actuators 11A and 11B (tilt angle θ). Can be variably controlled in accordance with the cam shape of the cam plate 54. As a result, the relationship between the pump discharge pressure P and the discharge amount Q can be approximated to a constant horsepower curve (characteristic line 36 indicated by a virtual line) of the prime mover, as indicated by a characteristic line 55 shown in FIG. The used horsepower can be used effectively.

The regulator 42 has a single valve spring 4.
6, the sliding displacement of the spool 45 can be controlled, so that it is not necessary to use two valve springs 21 and 22 unlike the regulator 17 (see FIG. 8) described in the related art, and the number of parts is reduced to assemble. Workability at the time can be improved. By employing a single valve spring 46, the influence of variations in spring force and the like can be reduced to a small extent, and the relationship between the pump discharge pressure P and the discharge amount Q can be easily reduced for each product. Can be resolved.

Therefore, according to the present embodiment, the relationship between the pump discharge pressure P and the discharge amount Q is set as a curved characteristic as shown by a characteristic line 55 in FIG. 3 to effectively use the limited horsepower characteristic of the prime mover. It can be utilized and energy can be saved. And the workability at the time of assembling the hydraulic pump can be improved, and the productivity can be improved.

In the above embodiment, a tension spring is provided in the valve housing 43 of the regulator 42 on the hydraulic pilot portion 47 side, and the tension spring is applied to the control sleeve 44 by the tension spring toward the hydraulic pilot portion 47 side. To give the link member 50 a turning power in the direction of arrow F. Thus, the spherical portion 53 of the feedback pin 52 can always be pressed against the cam surface 54A of the cam plate 54.

Next, FIG. 4 shows a second embodiment of the present invention. In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. It shall be. However, a feature of the present embodiment is that a spring 61 is provided as urging means for constantly urging the spherical portion 53 of the feedback pin 52 toward the cam surface 54A of the cam plate 54.

Here, a spring receiver 62 for a spring 61 is formed at an end of the link member 50 extending into the casing main body 41A, and the spring main body is located at a position facing the spring receiver 62 on the casing main body 41A. A receiver 63 is formed. The spring 61 is disposed between the spring supports 62 and 63 in a preset (compressive deformation) state, and the link member 50 is provided.
Is continuously applied to the cam plate 54 side (for example, the direction of arrow F).

Thus, in the present embodiment configured as described above, substantially the same operation and effect as those in the first embodiment can be obtained. In particular, in the present embodiment,
Since the link member 50 is always pressed against the cam surface 54A of the cam plate 54 together with the spherical portion 53 by the spring 61, the link member 50 is caused by external vibration or the like.
Thus, the problem that the spherical portion 53 separates from the cam plate 54 due to the vibration in the direction can be solved, and the feedback operation by the feedback mechanism 48 can be always maintained in a stable state.

Next, FIGS. 5 and 6 show a third embodiment of the present invention. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals. The description is omitted. However, a feature of the present embodiment is that a substantially L-shaped bent portion 71A is formed at the distal end of the feedback pin 71 provided at the end of the link member 50, and a cam slide is formed at the distal end of the bent portion 71A. A spherical portion 72 is formed as an engaging projection that forms a contact portion, and a cam plate 73 is formed on a side surface of the swash plate 10 as a cam. The spherical portion 72 is slidably engaged with the cam plate 73. U-shaped cam groove 7 to fit
3A is formed.

Here, the feedback pin 71 has substantially the same configuration as the feedback pin 52 described in the first embodiment, except for the bent portion 71A, and the spherical portion 72 extends from the bent portion 71A to the cam plate 73 of the cam plate 73. It protrudes into the groove 73A. The base end of the feedback pin 71 is integrated with the end of the link member 50,
Numeral 0 forms a feedback link together with the feedback pin 71 and the spherical portion 72.

The cam groove 73A of the cam plate 73 has a groove width corresponding to the outer diameter of the spherical portion 72, and the peripheral wall of the cam groove 73A is substantially the same as the cam surface 54A described in the first embodiment. Similarly, it is formed by a slightly curved inclined surface or the like with a predetermined curvature. When the swash plate 10 is tilted and driven in the directions indicated by arrows A and B, the spherical portion 72 serving as the cam sliding portion of the feedback pin 71 always contacts the cam groove 73A of each cam plate 73. It is rotated in the directions of the arrows E and F following the tilting operation, and the amount of rotation displacement at this time is variably adjusted according to the cam shape of the cam groove 73A.

Thus, in the present embodiment configured as described above, substantially the same operation and effect as those in the first embodiment can be obtained. In particular, in the present embodiment,
Since the spherical portion 72 provided on the distal end side of the feedback pin 71 is slidably engaged with the cam groove 73A of the cam plate 73, the link member 50 moves in the directions indicated by arrows E and F due to external vibration or the like. Problems such as separation from the cam plate 73 due to vibration can be solved, and the feedback operation by the feedback mechanism 48 can be stabilized.

In each of the above embodiments, the feedback pin 52 is provided at the end of the link member 50 to form a feedback link. However, the present invention is not limited to this. The link may be formed in advance as an L-shaped single member, and a spherical portion or the like may be provided as a cam sliding contact portion at the tip thereof.

[0080]

As described above in detail, according to the first aspect of the present invention, when the swash plate is tilted by supplying and discharging the tilt control pressure from the regulator to the tilt actuator, the feedback of the feedback mechanism is performed. The cam slide contact portion provided on the link is brought into sliding contact with the cam body on the swash plate side, the feedback link is rotated and displaced following the tilting operation of the swash plate, and the amount of this rotational displacement is determined by the cam shape of the cam body. The feedback control can be performed by making the control sleeve of the regulator follow the tilting operation of the swash plate and the cam shape of the cam body, and the tilt angle (pump capacity) of the swash plate is adjusted to the pump discharge pressure. On the other hand, it can be controlled with a curved characteristic. Accordingly, the relationship between the pump discharge pressure and the discharge amount is a curved characteristic, so that the limited horsepower characteristics of the prime mover can be effectively utilized, and energy saving can be achieved.

According to the second aspect of the present invention, since the cam body is formed such that the surface on which the cam sliding portion of the feedback link slides is formed as an inclined surface, the control sleeve of the regulator can be used for the tilting operation of the swash plate. By performing feedback control by following the cam shape of the cam body, the tilt angle (pump capacity) of the swash plate can be given a curved characteristic with respect to the pump discharge pressure, and the limited horsepower characteristic of the prime mover can be obtained. Can be used effectively.

According to the third aspect of the present invention, since the cam sliding portion of the feedback link is formed in a spherical shape, the spherical cam sliding portion contacts the cam surface of the cam body smoothly. And the amount of rotational displacement of the feedback link can be variably set according to the cam shape of the cam body.

According to the fourth aspect of the present invention, the regulator is disposed between the valve housing and the spool, the valve housing having the spool inserted slidably with the control sleeve on the inner peripheral side. When the hydraulic pilot portion of the regulator receives the pump discharge pressure as pilot pressure, the spool is opposed to the valve spring according to the pilot pressure in the valve housing. To slide and disengage each supply / discharge port of the valve housing via a spool and a control sleeve, thereby supplying / discharging a displacement control pressure corresponding to the pump discharge pressure from the regulator to the displacement mechanism. be able to. Then, only a single valve spring needs to be used for the regulator, so that the operation of adjusting the spring force and the like can be simplified, the workability during assembly can be improved, and the productivity can be improved.

According to the fifth aspect of the present invention, there is provided between the casing and the feedback link an urging means for constantly urging the cam sliding portion of the feedback link toward the cam body. In addition, problems such as the feedback link vibrating due to external vibration and the like and being separated from the cam body can be eliminated, the feedback operation by the feedback mechanism and the like can be stabilized, and the reliability and life can be improved.

Further, in the invention according to the sixth aspect, since the engaging projection slidably engaging with the cam groove of the cam body is provided on the cam sliding contact portion of the feedback link, the cam of the feedback link is provided. The sliding contact portion (engaging protrusion) can be held in a state of being engaged with the cam groove of the cam body, thereby preventing the feedback link from being inadvertently displaced by external vibration, and a feedback operation by the feedback mechanism. And improve reliability and life.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a variable displacement swash plate type hydraulic pump according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing the tilt actuator of the swash plate, a feedback mechanism, a cam plate, and the like, as viewed from the direction of arrows II-II in FIG. 1;

FIG. 3 is a characteristic diagram showing displacement characteristics of the variable displacement swash plate type hydraulic pump according to the first embodiment.

FIG. 4 is an enlarged longitudinal sectional view showing a main part of a variable displacement swash plate type hydraulic pump according to a second embodiment.

FIG. 5 is a front view showing a main part of a variable displacement swash plate type hydraulic pump according to a third embodiment.

FIG. 6 is an enlarged sectional view showing a feedback mechanism, a swash plate, a cam plate, and the like, as viewed from the direction indicated by arrows VI-VI in FIG. 5;

FIG. 7 is a longitudinal sectional view showing a conventional variable displacement swash plate type hydraulic pump.

FIG. 8 is an enlarged sectional view of the swash plate tilting actuator, feedback mechanism, cam plate, regulator, and the like, as viewed from arrows VIII-VIII in FIG. 7;

FIG. 9 is a hydraulic circuit diagram of the variable displacement swash plate type hydraulic pump shown in FIG. 7;

FIG. 10 is a characteristic diagram showing displacement characteristics of a conventional variable displacement swash plate type hydraulic pump.

[Explanation of symbols]

 2 Rotating shaft 3 Cylinder block 4 Cylinder 5 Piston 6 Shoe 8 Valve plate 9 Swash plate support 10 Swash plate 10A Sliding surface 11A, 11B Tilt actuator 31 Pilot pump 32 Tank 41 Casing 41E Opening 42 Regulator 43 Valve housing 43A, 43B Supply / discharge port 44 Control sleeve 45 Spool 46 Valve spring 47 Hydraulic pilot unit 48 Feedback mechanism 49 Support pin 50 Link member (feedback link) 51 Output pin 52, 71 Feedback pin 53 Spherical part 54, 73 Cam plate (cam body) 61 Spring (biasing means) 72 Spherical part (engaging projection) 73A Cam groove

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Tetsuya Sakairi 650, Kandamachi, Tsuchiura-shi, Ibaraki Pref.Hitachi Construction Machinery Co., Ltd. Tsuchiura factory

Claims (6)

[Claims] 1. A cylindrical casing, a rotating shaft rotatably provided in the casing, and a plurality of cylinders provided in the casing so as to rotate with the rotating shaft. A cylinder block, a plurality of pistons reciprocally inserted into respective cylinders of the cylinder block, and a sliding surface on which a shoe mounted on an end of each piston slides. A swash plate provided to be tiltable, a tilt actuator that tilts the swash plate by supplying and discharging a tilt control pressure, and a tilt control pressure that is supplied to and discharged from the tilt actuator. And a feedback mechanism provided in the casing and having a spool and a control sleeve, and performing a feedback control of the regulator following the tilting operation of the swash plate. In the variable displacement swash plate type hydraulic pump, the feedback mechanism is rotatably provided between the regulator and the casing, one end is connected to a control sleeve of the regulator, and the other end is directed toward the swash plate. A feedback link serving as a protruding cam sliding contact portion; and a cam link contact portion of the feedback link provided on the swash plate, whereby the feedback link is pivotally displaced by the tilting operation of the swash plate. A variable displacement swash plate type hydraulic pump characterized in that the swash plate type hydraulic pump includes a cam body that changes the amount of rotation according to the cam shape. 2. The variable displacement type swash plate type hydraulic pump according to claim 1, wherein the cam body is formed such that a surface on which the cam sliding portion of the feedback link slides is formed as an inclined surface. 3. The variable displacement swash plate type hydraulic pump according to claim 1, wherein the cam sliding contact portion of the feedback link is formed in a spherical shape. And a valve housing having a supply / discharge port for supplying / discharging a tilt control pressure to / from the tilt actuator. A valve spring that is disposed between the valve housing and the spool and constantly biases the spool in one direction; and a valve spring that is located on the opposite side to the valve spring with the spool interposed therebetween. 4. A variable displacement swash plate type hydraulic system according to claim 1, further comprising: a hydraulic pilot portion for receiving the pump discharge pressure as a pilot pressure to slide and displace said spool against a valve spring. pump. 5. The device according to claim 1, further comprising an urging means provided between the casing and the feedback link, for urging the cam sliding portion toward the cam body at all times. Variable displacement swash plate type hydraulic pump. 6. The cam body has a cam groove, and a cam sliding contact portion of the feedback link is provided with an engaging projection slidably engaged with the cam groove. 5. The variable displacement swash plate type hydraulic pump according to 3 or 4.