JP2001165102A - Electrohydraulic survomotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized electrohydraulic survomotor capable of controlling surely the spool position in the axial direction of a spool without being influenced by the temperature of a hydraulic oil. SOLUTION: This electrohydraulic survomotor 100 for rotating an output shaft 61 according to the difference between the numbers of revolution of a rotary shaft 41 and the output shaft 61 is equipped with a revolution detector 80 for detecting the numbers of revolution of a shaft to be detected 81, and for outputting a revolution signal corresponding to the numbers of revolution, and a CPU 90 for receiving an input predetermined signal predetermined to be inputted into a pulse motor 40 and the revolution signal, for processing the input predetermined signal based on the numbers of revolution of the rotary shaft 41 and the revolution signal so that the spool position in the axial direction of the spool 71 becomes in a prescribed range to generate an input signal, and for outputting the generated input signal to the pulse motor 40. The pool 71 is controlled so as not to collide with cap covers 36, 37 by the CPU 90.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrohydraulic servomotor used for a hydraulic excavator, a crane, an asphalt finisher, a machine tool, and the like (hereinafter, simply referred to as an external device).

[0002]

2. Description of the Related Art As a conventional electrohydraulic servomotor, there is an electrohydraulic servomotor 200 as shown in FIGS.

In the electrohydraulic servomotor 200,
The spool position in the axial direction of the spool 171 moves in accordance with the rotation of the rotation shaft 141 of the pulse motor 140, and the supply amount of the working oil in the hydraulic motor 160 changes, so that the output shaft 161 rotates.

The displacement sensor 180 is connected to the spool 17
1 and detects a spool position in the axial direction, and outputs a spool position signal corresponding to the detected spool position to the signal transmission path 1.
Output to the CPU 190 via 93. CPU190
In addition to the spool position signal, an input expected signal to be input to the pulse motor 140 is input via the signal transmission path 191 so that the spool position in the axial direction of the spool 171 is within a predetermined range. The input signal is processed to generate an input signal, and the generated input signal is output to the pulse motor 140 via the signal transmission path 192 to control the spool position.

That is, the conventional electrohydraulic servomotor 2
00, the spool 1 is detected by the displacement sensor 180.
By detecting the spool position in the axial direction of the spool 71, the spool 171 moves the cap covers 136 and 137
Was controlled so as not to collide.

[0006]

However, in the above-described conventional electro-hydraulic servomotor 200, the oil supply passage 131 is not provided.
a, the communication path 131b, the communication path 131c, or the oil discharge path 131
Since the spool 171 expands and contracts due to the temperature of the hydraulic oil flowing through the d and the like, the spool 17
There is a problem that the spool position in the axial direction becomes unstable, and control of the spool position in the axial direction of the spool 171 becomes uncertain.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a small-sized electro-hydraulic servomotor capable of reliably controlling the spool position in the axial direction of the spool without being affected by the temperature of the hydraulic oil.

[0008]

According to a first aspect of the present invention, there is provided an electro-hydraulic servomotor according to the first aspect of the present invention, wherein an electric motor for rotating a rotating shaft in response to an input signal and an output based on the pressure of hydraulic oil. Hydraulic drive means for rotating the shaft, a first shaft connected to the rotating shaft, a cylindrical second shaft screwed to the first shaft and having external teeth formed on the outer periphery, and external teeth formed on the outer periphery. The third shaft, which is formed and meshes with the external teeth of the second shaft, is connected at one end to the output shaft, and the spool is moved in the axial direction to supply and discharge hydraulic oil to the hydraulic drive means. A spool valve for controlling the amount, wherein the spool is interlocked with the second shaft, whereby the output shaft is rotated according to a difference in the number of rotations between the rotation shaft and the output shaft. A fourth shaft connected to the third shaft at the other end of the third shaft Detects the rotational speed of the fourth shaft,
A number-of-rotations detecting means for outputting a number-of-rotations signal corresponding to the number of rotations, an input scheduled signal to be input to the electric motor and the number-of-rotations signal being input, and the position of the spool in the axial direction being within a predetermined range; So that the input scheduled signal is
Input signal processing means for generating an input signal by processing based on the rotation speed of the rotating shaft and the rotation speed signal, and outputting the input signal to the motor, wherein the motor is controlled by the input signal processing means. It is characterized in that the rotating shaft is rotated according to the output input signal. According to the electrohydraulic servomotor of the first aspect, since the rotation speed of the fourth shaft is detected by the rotation speed detecting means, the spool is reliably prevented from being affected by the temperature of the hydraulic oil in the axial direction of the spool. The position can be controlled.

According to a second aspect of the present invention, in the electro-hydraulic servo motor, the extension of the axis of the rotary shaft and the extension of the axis of the output shaft are arranged so as to maintain a predetermined angle. Features. According to the electro-hydraulic servo motor of the second aspect, the overall length of the electro-hydraulic servo motor can be shortened, so that the electro-hydraulic servo motor can be downsized.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to FIGS.

First, the configuration of the electrohydraulic servomotor according to the present embodiment will be described.

1 and 2, the electrohydraulic servomotor 100 has a cup-shaped first casing 30 and a second casing 31 fastened and fixed to the first casing 30 by bolts 32. A bolt hole 33 into which a bolt is screwed when the electro-hydraulic servomotor 100 is fastened and fixed to an external device (not shown) is formed in the first casing 30, and an oil supply passage is formed in the second casing 31. A communication path 31a, a communication path 31b, a communication path 31c, and an oil discharge path 31d are formed.

A pulse motor 40 is mounted on the outer wall of the second casing 31 as a motor for rotating the rotating shaft 41 in response to an input signal. Pulse motor 4
A drive shaft 51 as a first shaft having a male screw 51a formed on the outer periphery is integrally connected to the 0 rotation shaft 41 in the rotation direction. In the present embodiment, the rotating shaft 41 and the driving shaft 51 are formed of one component, but in the present invention, the rotating shaft 41 and the driving shaft 51 may be formed of separate components. . Reference numeral 37 denotes a cap cover for preventing hydraulic oil from flowing out to the pulse motor main body 42.

The drive shaft 51 has a first helical gear 52 as a cylindrical second shaft having an internal thread 52a formed on the inner periphery and external teeth 52b formed on the outer periphery. 51a is connected by screwing into the female screw 52a of the first helical gear 52. The first helical gear 52 has a second helical gear 5 as a third shaft having external teeth 53a formed on the outer periphery.
3, when the external teeth 52b of the first helical gear 52 mesh with the external teeth 53a of the second helical gear 53, the axis of the first helical gear 52 and the second helical gear 53 Are connected so as to be orthogonal to each other.

One end of a second helical gear 53 is connected to one end of an output shaft 61 of a hydraulic motor 60 as hydraulic drive means, which will be described later, via a connecting member 54 so as to be integrally rotatable. In the present embodiment, the second helical gear 53 and the output shaft 61 are composed of separate components, but in the present invention, the second helical gear 53 and the output shaft 6 are different.
1 may be composed of one part.

The shapes of the male screw 51a, the female screw 52a, the external teeth 52b, and the external teeth 53a are different from each other when a difference occurs in the rotation speed between the drive shaft 51 and the second helical gear 53. It is determined that the first helical gear 52 moves in the axial direction while rotating about the axis according to the difference in the number of rotations from the second helical gear 53.

The hydraulic motor 60 is composed of a first casing 30 and a second casing 31 by a bearing 68 and a bearing 69.
And the output shaft 61 urged toward the other end by the urging force of the spring 67, and fixed to the side wall of the second casing 31 to form the communication passage 31 b and the communication passage 31.
The plurality of arc holes 62a respectively communicating with c are slidably engaged with the valve plate 62 formed at positions spaced at equal intervals in the circumferential direction by the biasing force of the spring 67,
A cylinder block in which a plurality of pressure chambers 63a, which are fixed to the peripheral portion of the output shaft 61 in the rotation direction integrally with the output shaft 61 and have an axis parallel to the axis of the output shaft 61, are formed at positions equidistantly spaced in the circumferential direction. 63 and a plurality of pistons 64 housed in the pressure chamber 63a of the cylinder block 63 so as to be slidable in the axial direction and having a substantially spherical tip 64a at the tip.
And a shoe member 65 with the tip end 64a of the piston 64 rollably engaged with the shoe member 65, the shoe member 65 slidably engaged with the slope member 66a inclined at a predetermined angle with respect to the output shaft 61.
And the swash plate 6 fixed to the inner wall of the first casing 30
6 is comprised.

A drive section of an external device (not shown) is connected to the output shaft 61 protruding outside the first casing 30 so that a rotational force is transmitted to the drive section.

The spool valve 70 has a spool 71
And a second casing 31.

The spool 71 is connected to the first helical gear 52 via bearings 55 and 56 composed of thrust bushes. Here, the spool 71 is slidably engaged with the cap cover 36 mounted on the second casing 31 via the key 35. Therefore,
The spool 71 does not rotate around an axis.

An annular groove 71a and an annular groove 71b are formed in the outer peripheral portion of the spool 71 to connect the oil supply passage 31a and the oil discharge passage 31d of the second casing 31 to the communication passage 31b or 31c, respectively.

The other end of the second helical gear 53 has
A detected shaft 81 as a fourth shaft is connected at one end of the detected shaft 81, and the detected shaft 81 is connected to the first and second detection units 84 and 85 of the detection unit mounted on the second casing 31. And is rotatably supported by the second housing 85 of the detection unit by a bearing 83. In the first housing 84 of the detecting section, the other end of the detected shaft 81 detects the number of rotations of the detected shaft 81 and outputs a number-of-rotations signal corresponding to the number of rotations. The container 80 is mounted. A seal 82 is disposed in a space formed between the first housing 84 of the detection unit and the shaft 81 to be detected so that the hydraulic oil in the second casing 31 does not enter the rotation speed detector 80. Has become.

Reference numeral 90 denotes an input scheduled signal and a rotation speed signal to be input to the pulse motor 40, and the input scheduled signal is set so that the spool position of the spool 71 in the axial direction is within a predetermined range. A central processing unit (hereinafter simply referred to as a CPU) as input signal processing means for generating an input signal by processing based on the rotation speed and the rotation speed signal of the rotation shaft 41 and outputting the generated input signal to the pulse motor 40. ). Incidentally, reference numerals 91, 92 and 93 are signal transmission paths.

Next, the operation of the electrohydraulic servomotor 100 will be described.

The electrohydraulic servomotor 100 has a rotating shaft 4
When there is a difference between the rotation speeds of the output shaft 61 and the output shaft 61, the rotation shaft 4
The output shaft 61 is rotated according to the difference between the rotation speeds of the output shaft 61 and the output shaft 61.

Hereinafter, when a difference occurs in the number of rotations between the rotating shaft 41 and the output shaft 61, the electrohydraulic servomotor 100 changes the output shaft 6 according to the difference in the number of rotations between the rotating shaft 41 and the output shaft 61.
The operation of rotating 1 will be described.

Since the drive shaft 51 is integrally connected to the rotation shaft 41 in the rotation direction, the rotation speed of the rotation shaft 41 is
1 and the output shaft 61 has a second helical gear 5
3 is connected integrally in the rotational direction via the connecting member 54, the rotation speed of the output shaft 61 becomes equal to the rotation speed of the second helical gear 53.

Therefore, when there is a difference between the rotation speeds of the rotation shaft 41 and the output shaft 61, the drive shaft 51 and the second helical gear 5
There is also a difference in the number of revolutions from 3.

When a difference occurs in the number of rotations between the drive shaft 51 and the second helical gear 53, as described above, according to the difference in the number of rotations between the drive shaft 51 and the second helical gear 53, The first helical gear 52 moves in the axial direction while rotating about the axis.

When the first helical gear 52 moves in the axial direction while rotating about the axis, the spool 71 is connected to the first helical gear 52 via the bearings 55 and 56, 71 also moves in the axial direction in conjunction with the first helical gear 52. Spool 71 is the first helical gear 5
When it moves in the axial direction in conjunction with 2, an annular groove 71 a and an annular groove 71 b connecting the oil supply passage 31 a and the oil discharge passage 31 d of the second casing 31 to the communication passage 31 b or 31 c respectively are formed on the outer peripheral portion of the spool 71. The oil supply passage 31a, the communication passage 31b, the communication passage 31c, and the oil discharge passage 3
The flow rate of the hydraulic oil flowing through 1d changes.

Oil supply passage 31a, communication passage 31b, communication passage 31
When the flow rate of the working oil flowing through the oil passage 31d and the oil passage 31d changes, the communication passage 31b and the communication passage 31c are connected to the cylinder block 6 through a plurality of arc holes 62a formed in the valve plate 62.
Since the plurality of pressure chambers 63a communicate with the plurality of pressure chambers 63a, the flow rates of the hydraulic oil flowing into the plurality of pressure chambers 63a change. When the flow rate of the hydraulic oil flowing into each of the plurality of pressure chambers 63a changes, the piston 64 flows out into the plurality of pressure chambers 63a because the piston 64 is slidably housed in the pressure chamber 63a of the cylinder block 63. Slides in the axial direction according to the pressure of the operating oil. When the piston 64 slides in the axial direction, the distal end 6 of the piston 64
4a is rollingly engaged with the shoe member 65, and the shoe member 65 is slidably engaged with the slope 66a of the swash plate 66. Is pressed. When the piston 64 presses the slope 66 a of the swash plate 66 via the shoe member 65,
The cylinder block 63 rotates about the axis by the reaction force of the force of the piston 64 pressing the slope 66 a of the swash plate 66.

When the cylinder block 63 rotates about the axis, the communication passage 31b and the communication passage 31c communicate with each other through a plurality of arc holes 62a formed in the valve plate 62. Changes. Cylinder block 6 in which communication passage 31b and communication passage 31c communicate with each other through a plurality of arc holes 62a formed in valve plate 62
When the pressure chamber 63a formed in 3 changes, the flow rate of the hydraulic oil flowing out to each of the plurality of pressure chambers 63a changes.
When the flow rate of the hydraulic oil flowing into each of the plurality of pressure chambers 63a changes, as described above, the cylinder block 63 rotates around the shaft again.

Therefore, the oil supply passage 31a and the communication passage 31
b, when the flow rate of the working oil flowing through the communication passage 31c and the oil discharge passage 31d changes, the cylinder block 63
1a, the communication path 31b, the communication path 31c, and the rotation in the rotation direction and the rotation speed according to the flow rate of the working oil flowing through the oil discharge path 31d around the shaft.

The cylinder block 63 is connected to the oil supply passage 31a,
When the cylinder block 63 is rotated around the shaft in a rotation direction and a rotation speed corresponding to the flow rate of the working oil flowing through the communication passage 31b, the communication passage 31c, and the oil discharge passage 31d, the cylinder block 63 Since the output shaft 61 is fixed integrally in the rotation direction, the output shaft 61 is also centered on the shaft in the rotation direction and the rotation speed according to the flow rate of the working oil flowing through the oil supply passage 31a, the communication passage 31b, the communication passage 31c, and the oil discharge passage 31d. Rotate.

Here, the drive shaft 51 and the second helical gear 53
When there is a difference in the number of rotations, the direction in which the first helical gear 52 moves in the axial direction while rotating about the axis is the direction of the male screw 51a, the female screw 52a, the external teeth 53a, and the external teeth 52b. It can be determined by the shape. That is, when a difference occurs in the rotation speed between the drive shaft 51 and the second helical gear 53 due to the shapes of the male screw 51a, the female screw 52a, the external teeth 53a and the external teeth 52b, the drive shaft 51 and the second helical gear 53 Helical gear 53
The rotation direction and the rotation speed at which the output shaft 61 rotates can be determined according to the difference between the rotation speed and the rotation speed.

Therefore, the male screw 51a and the female screw 52
a, when the shapes of the external teeth 53a and the external teeth 52b are determined, when a difference occurs in the rotation speed between the drive shaft 51 and the second helical gear 53, that is, when the rotation shaft 41 and the output shaft 61 When a difference occurs in the rotation speed, the output shaft 61 can be rotated so that the difference in rotation speed between the rotation shaft 41 and the output shaft 61 is reduced.

As described above, when there is a difference between the rotation speeds of the rotation shaft 41 and the output shaft 61, the electrohydraulic servomotor 100 responds to the difference between the rotation speeds of the rotation shaft 41 and the output shaft 61. The output shaft 61 is rotated.

Further, the spool 71 of the electrohydraulic servomotor 100 has the cap cover 36 or the cap cover 3.
7 can be prevented.

Hereinafter, the electro-hydraulic servomotor 100 will be described.
The operation of preventing the collision with No. 7 will be described.

When the spool 71 moves significantly in the axial direction in conjunction with the first helical gear 52 and approaches within a predetermined distance from the cap cover 36 or the cap cover 37, the axial direction of the first helical gear 52 Is determined from the rotational speeds of the drive shaft 51 and the second helical gear 53, so that the rotational speed of the drive shaft 51 or the second helical gear 53 changes.

The rotation speed of the drive shaft 51, that is, the rotation shaft 41
Is determined by the input signal generated by the CPU 90, the CPU 90 can always obtain the rotation speed of the drive shaft 51. The rotation speed of the second helical gear 53, that is, the rotation speed of the detected shaft 81, is
0 is used as a rotation speed signal by the CPU 9 via the signal transmission path 93.
Since the output is set to 0, the CPU 90 can always obtain the rotation speed of the second helical gear 53 from the rotation speed signal output by the rotation speed detector 80.

Therefore, when the rotation speed of the drive shaft 51 or the second helical gear 53 changes, the CPU 90 determines that the spool 71 has approached the cap cover 36 or the cap cover 37 within a predetermined distance.

When the CPU 90 determines that the spool 71 has approached the cap cover 36 or the cap cover 37 within a predetermined distance, the CPU 90 prevents the spool 71 from approaching the cap cover 36 or the cap cover 37 within a predetermined distance, ie, The signal transmission path 9 is set so that the spool position in the axial direction of the spool 71 is within a predetermined range.
The input signal to be input to the pulse motor 40 input from 1 is processed based on the rotation speed signal and the rotation speed of the rotary shaft 41 to generate an input signal, and the generated input signal is transmitted to a signal transmission path. Output to the pulse motor 40 via 92.

When the CPU 90 outputs an input signal to the pulse motor 40 via the signal transmission path 92, the pulse motor 4
A value of 0 causes the rotating shaft 41 to rotate in response to the input signal output from the CPU 90, and sets the spool position of the spool 71 in the axial direction within a predetermined range.

As described above, the electrohydraulic servomotor 100 prevents the spool 71 from colliding with the cap cover 36 or the cap cover 37.

It should be noted that the spool 71 is
Alternatively, as a case of approaching within a predetermined distance from the cap cover 37, for example, as a result of the CPU 90 outputting an input signal to the pulse motor 40 through the signal transmission path 92, the rotation speed of the rotation shaft 41 and the output shaft 61 is extremely low. A big difference,
When the spool 71 moves significantly in the axial direction in conjunction with the first helical gear 52 to approach the cap cover 36 or the cap cover 37 within a predetermined distance, or when the output shaft 61
Receives a load from an external device, a very large difference occurs in the number of rotations between the rotating shaft 41 and the output shaft 61, and the spool 71
However, there are cases where the first helical gear 52 moves significantly in the axial direction in conjunction with the helical gear 52 and approaches within a predetermined distance from the cap cover 36 or the cap cover 37.

In the present embodiment, the spool 71 is prevented from colliding with the cap cover 36 or the cap cover 37. However, in the present invention, any member that can collide with the spool 71 may be used as the cap cover 36 or the cap cover 36. The cap cover 37 may not be used.

Further, the rotation number detector 80 is not limited to the one shown in the present embodiment.
Any device that can detect the number of rotations may be used.

The key 35 prevents the spool 71 from rotating around the shaft. When the spool 71 rotates around the shaft and collides with the second helical gear 53, the key 71 Alternatively, the second helical gear 53 is prevented from being damaged.

In this embodiment, the second shaft and the third shaft are helical gears. However, in the present invention, the helical gears need not be helical gears. For example, a predetermined speed ratio can be set between the second shaft and the third shaft by using another transmission gear, a worm screw, a worm wheel, or the like. When a predetermined speed ratio is set between the second shaft and the third shaft, the rotation speed of the output shaft 61 is reduced by the second shaft and the third shaft. Can be made smaller than the number of rotations. Therefore, the capacity of the pulse motor 40 can be reduced, and the size of the electrohydraulic servomotor 100 can be reduced.

In this embodiment, the bearing 55 and the bearing 56 are constituted by thrust bushes.
In the present invention, when the first helical gear 52 moves in the axial direction, the spool 71 is moved in the axial direction, and when the first helical gear 52 rotates about the shaft, the spool 71 moves about the shaft. The thrust bush is not limited to the thrust bush, and any other member may be used as long as the member prevents rotation.

In the present embodiment, the spool 7
1 is a first helical gear 52 via a bearing 55 and a bearing 56
However, in the present invention, the spool 71
May be connected to the first helical gear 52 via a spring.

In this embodiment, since the axis of the first helical gear 52 and the axis of the second helical gear 53 are connected to be orthogonal to each other, the axis of the rotary shaft 41 and the output Although the axes of the shafts 61 are also connected so as to be orthogonal to each other, in the present invention, the extension of the axis of the rotation shaft 41 and the extension of the axis of the output shaft 61 are maintained at another predetermined angle. May be arranged.

[0054]

According to the electrohydraulic servomotor of the first aspect, the rotation speed of the fourth shaft is detected by the rotation speed detecting means, so that the rotation of the spool can be reliably performed without being affected by the temperature of the hydraulic oil. The spool position in the axial direction can be controlled.

Further, according to the electro-hydraulic servo motor of the second aspect, the overall length of the electro-hydraulic servo motor can be shortened, so that the electro-hydraulic servo motor can be downsized.

[Brief description of the drawings]

FIG. 1 is a side sectional view of an electrohydraulic servomotor according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a side sectional view of a conventional electrohydraulic servomotor.

FIG. 4 is a sectional view taken along the line BB of FIG. 3;

[Explanation of symbols]

 41 rotating shaft 40 pulse motor (electric motor) 61 output shaft 60 hydraulic motor (hydraulic driving means) 51 drive shaft (first shaft) 52b external teeth 52 first helical gear (second shaft) 53a external teeth 53 second Helical gear (third shaft) 71 Spool 70 Spool valve 100 Electro-hydraulic servo motor 81 Detected shaft (Fourth shaft) 80 Rotation speed detector (Rotation speed detection means) 90 CPU (Input signal processing means)

Claims (2)

[Claims] An electric motor for rotating a rotating shaft in response to an input signal; hydraulic drive means for rotating an output shaft by the pressure of hydraulic oil; a first shaft connected to the rotating shaft; A cylindrical second shaft screw-coupled to the shaft and having external teeth formed on the outer periphery; and external teeth formed on the outer periphery and meshed with the external teeth of the second shaft, and one end is connected to the output shaft. A third shaft, and a spool valve for moving a spool in the axial direction to control a supply amount and a discharge amount of hydraulic oil to the hydraulic drive means, and wherein the spool is interlocked with the second shaft, An electro-hydraulic servomotor that rotates the output shaft according to a difference in the number of rotations between the rotation shaft and the output shaft, wherein a fourth shaft connected to the third shaft at the other end of the third shaft; A rotation speed detector that detects the rotation speed of the fourth shaft and outputs a rotation speed signal corresponding to the rotation speed. Means, an input scheduled signal to be input to the electric motor and the rotation speed signal are input, and the input scheduled signal of the rotation shaft is set so that the position of the spool in the axial direction is within a predetermined range. Input signal processing means for generating an input signal by processing based on a rotation speed and the rotation speed signal, and outputting the input signal to the electric motor, wherein the input of the electric motor is output by the input signal processing means. An electro-hydraulic servo motor characterized by rotating a rotating shaft according to a signal. 2. An electro-hydraulic servo according to claim 1, wherein an extension of an axis of said rotary shaft and an extension of an axis of said output shaft are arranged so as to keep a predetermined angle. motor.