JP3683446B2 - Electrohydraulic servo motor - Google Patents

Description

[0001]
BACKGROUND 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]
[Prior art]
In the conventional electrohydraulic servo motor, as shown in FIGS. 5 and 6, the output shaft 2 is rotatably supported on the casing 1 by bearings 3 and 4. A valve plate 9 is fixed to the inner wall of the casing 1, and a cylinder block 7 is fixed to the peripheral portion of the output shaft 2. A plurality of pressure chambers 7a are formed in the cylinder block 7, and pistons 8 are respectively stored in the pressure chambers 7a. The pistons 8 reciprocate in the axial direction by the hydraulic pressure of the hydraulic oil introduced into the pressure chambers 7a. It has become.
[0003]
A swash plate 6 inclined at a predetermined angle is fixed to the inner wall of the casing 1 on the tip end side of the output shaft 2, and the tip end portion of the piston 8 presses and slides on the swash plate 6, while The block 7 slides on the valve plate 9 so that the output shaft 2 and the cylinder block 7 rotate together.
[0004]
The casing 1 is provided with a spool valve 11 that moves in the axial direction, and a screw member 12 and a gear 13 are fixed to a front end portion and a rear end portion of the spool valve 11, respectively. In addition, a pulse motor 14 is attached to the casing 1, and a rotating shaft 15 of the pulse motor 14 is rotatably supported by the casing 1. The rotational force of the rotary shaft 15 is transmitted to the spool valve 11 via the gear 16 and the gear 13, and the rotational force of the output shaft 2 is transmitted to the spool valve 11 via the screw member 10 and the screw member 12. Yes. The spool valve 11 communicates with the oil discharge passage 1a, the oil supply passage 1b, and the communication passages 1c and 1d by rotation.
[0005]
In the conventional electrohydraulic servomotor, the output shaft 2, the spool valve 11 and the pulse motor 14 are arranged on the same axis.
[0006]
[Problems to be solved by the invention]
However, in the above conventional electrohydraulic servomotor, the output shaft 2, the spool valve 11 and the pulse motor 14 are arranged on the same axis, so that the total length becomes long, and the fitting to other machines or the like is bad. was there.
[0007]
Therefore, an object of the present invention is to provide a small electrohydraulic servomotor.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, an electrohydraulic servo motor according to claim 1 is an electric motor that rotates a rotating shaft in accordance with an input signal, a hydraulic drive unit that rotates an output shaft by the pressure of hydraulic oil, A first shaft connected to the rotating shaft, a cylindrical second shaft screwed to the first shaft and having external teeth on the outer periphery, and external teeth on the outer periphery to form an outer side of the second shaft. A third shaft connected to the output and connected to the output shaft, and a spool valve that controls the supply amount and discharge amount of hydraulic oil to the hydraulic drive means by moving the spool in the axial direction, In the electrohydraulic servomotor that rotates the output shaft in accordance with the difference in the number of rotations between the rotating shaft and the output shaft by interlocking with the second shaft, the axial direction of the spool is coupled to the spool Detect the spool position at A spool position detecting means for outputting a spool position signal corresponding to the position, a signal inputted to the electric motor and the spool position signal are inputted, and inputted to the electric motor so that the spool position falls within a predetermined range. Input signal processing means for processing a signal and outputting it to the electric motor, wherein the electric motor rotates a rotating shaft in accordance with a signal output by the input signal processing means, and the electric motor is on one end side of the spool. Arranged, the spool position detecting means is arranged on the other end side of the spool, the second shaft is arranged between the electric motor and the spool position detecting means, and an extension line of the axis of the rotating shaft and the output shaft The extension lines of the axis are arranged so as to be orthogonal to each other . According to the electrohydraulic servomotor of the first aspect, the axis of the rotary shaft and the output shaft need not be on the same line, so the electrohydraulic servomotor can be reduced in size. In addition, since it is not necessary to cause the spool to collide with other members and stop, the electrohydraulic servomotor can be manufactured with small and low-strength parts, and the electrohydraulic servomotor can be miniaturized.
[0009]
Further , since a new space provided for arranging the spool position detecting means can be reduced, the electrohydraulic servo motor can be reduced in size.
[0010]
Moreover , since the total length of the electrohydraulic servomotor can be shortened, the electrohydraulic servomotor can be reduced in size.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[0012]
First, the configuration of the electrohydraulic servomotor according to the present embodiment will be described.
[0013]
1 to 4, the electrohydraulic servomotor 100 includes a cup-shaped first casing 30 and a second casing 31 fastened and fixed to the first casing 30 by bolts 32. Further, the first casing 30 is formed with a bolt hole 33 into which a bolt is screwed when the electrohydraulic servo motor 100 is fastened and fixed to an external device (not shown). 31a, a communication path 31b, a communication path 31c, and an oil discharge path 31d are formed.
[0014]
A pulse motor 40 is mounted on the outer wall of the second casing 31 as an electric motor that rotates the rotating shaft 41 in accordance with an input signal. A driving shaft 51 serving as a first shaft having a male screw 51a formed on the outer periphery thereof is coupled to the rotating shaft 41 of the pulse motor 40 so as to be integrated in the rotating direction. In the present embodiment, the rotary shaft 41 and the drive shaft 51 are composed of one component. However, in the present invention, the rotary shaft 41 and the drive shaft 51 may be composed of separate components. . Reference numeral 37 denotes a cap cover that prevents hydraulic oil from flowing into the pulse motor main body 42.
[0015]
The drive shaft 51 has a first helical gear 52 as a cylindrical second shaft formed with a female screw 52a on the inner periphery and outer teeth 52b on the outer periphery, and a male screw 51a on the drive shaft 51. The first is coupled by being screwed to the female screw 52 a of the helical gear 52. The first helical gear 52 includes a second helical gear 53 as a third shaft having external teeth 53a formed on the outer periphery, and an external tooth 52b of the first helical gear 52 is a second helical gear. The first helical gear 52 and the second helical gear 53 are coupled so that the axis of the first helical gear 52 and the axis of the second helical gear 53 are orthogonal to each other.
[0016]
One end of an output shaft 61 of a hydraulic motor 60 serving as a hydraulic drive unit, which will be described later, is connected to one end of the second helical gear 53 via a connecting member 54 so as to be integrated in the rotational direction. The other end of the second helical gear 53 is rotatably supported by a cap cover 34 attached to the second casing 31. In the present embodiment, the second helical gear 53 and the output shaft 61 are composed of separate parts. However, in the present invention, the second helical gear 53 and the output shaft 61 are identical. You may be comprised from components.
[0017]
The shapes of the male screw 51a, the female screw 52a, the external teeth 52b, and the external teeth 53a are such that when there is a difference in the rotational speed between the drive shaft 51 and the second helical gear 53, The first helical gear 52 is determined so as to move in the axial direction while rotating about the shaft in accordance with the difference in rotational speed with the helical gear 53.
[0018]
The hydraulic motor 60 is rotatably supported by the first casing 30 and the second casing 31 by a bearing 68 and a bearing 69, and an output shaft 61 urged to the other end side by the urging force of a spring 67. The valve plate 62, which is fixed to the side wall of the second casing 31 and communicates with the communication passage 31b and the communication passage 31c, respectively, is formed at spool positions that are equidistant from each other in the circumferential direction. A plurality of pressure chambers 63 a that are slidably engaged with the valve plate 62 by the urging force, are fixed to the periphery of the output shaft 61 integrally with the output shaft 61 in the rotational direction, and have an axis parallel to the axis of the output shaft 61. A cylinder block 63 formed at spool positions that are equidistant from each other in the circumferential direction, and is housed in a pressure chamber 63a of the cylinder block 63 so as to be slidable in the axial direction. A plurality of pistons 64 formed with 64 a, a shoe member 65 in which the tip end portion 64 a of the piston 64 is slidably engaged, and the shoe member 65 slidably engages with each other with respect to the output shaft 61. And a swash plate 66 fixed to the inner wall of the first casing 30.
[0019]
The output shaft 61 protruding outside the first casing 30 is connected to a drive unit of an external device (not shown) so that a rotational force is transmitted to the drive unit.
[0020]
The spool valve 70 includes a spool 71 and a second casing 31.
[0021]
The spool 71 is connected to the first helical gear 52 via a bearing 55 and a bearing 56. Here, the spool 71 is slidably engaged with the cap cover 36 attached to the second casing 31 via the key 35. Therefore, the spool 71 does not rotate around the shaft.
[0022]
The bearing 55 and the bearing 56 are constituted by a thrust bush.
[0023]
In addition, an annular groove 71a and an annular groove 71b that respectively connect the oil supply passage 31a and the oil discharge passage 31d of the second casing 31 to the communication passage 31b or 31c are formed on the outer periphery of the spool 71, respectively.
[0024]
Reference numeral 80 denotes a displacement sensor as spool position detecting means for detecting a spool position in the axial direction of the spool 71 and outputting a spool position signal corresponding to the spool position. The displacement sensor 80 has a sensor shaft 81 and is fixed to the cap cover 36. Since a male screw is formed at the tip 81a of the sensor shaft 81 and a female screw is formed at the sensor shaft coupling portion 71c of the spool 71, the male screw formed at the tip 81a and the sensor shaft coupling portion 71c are connected to each other. The sensor shaft 81 is coupled to the spool 71 by screwing the formed female screw.
[0025]
Reference numeral 90 denotes a pulse obtained by processing a signal input to the pulse motor 40 and a spool position signal so that the spool position in the axial direction of the spool 71 is within a predetermined range. A central processing unit (hereinafter simply referred to as a CPU) serving as an input signal processing means for outputting to the motor 40.
[0026]
Reference numerals 91, 92 and 93 are signal transmission paths.
[0027]
The pulse motor 40 is disposed on one end side of the spool 71, and the displacement sensor 80 is disposed on the other end side of the spool 71.
[0028]
Next, the operation of the electrohydraulic servomotor 100 will be described.
[0029]
The electro-hydraulic servo motor 100 rotates the output shaft 61 according to the difference in the rotational speed between the rotary shaft 41 and the output shaft 61 when a rotational speed difference between the rotary shaft 41 and the output shaft 61 occurs.
[0030]
Hereinafter, the electrohydraulic servomotor 100 rotates the output shaft 61 according to the difference in the rotational speed between the rotary shaft 41 and the output shaft 61 when a difference occurs in the rotational speed between the rotary shaft 41 and the output shaft 61. Will be described.
[0031]
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 equal to the rotation speed of the drive shaft 51, and the second helical gear 53 is connected to the output shaft 61. Since the rotation direction is integrally connected via 54, the rotation speed of the output shaft 61 is equal to the rotation speed of the second helical gear 53.
[0032]
Therefore, when a difference occurs in the rotation speed between the rotation shaft 41 and the output shaft 61, a difference also occurs in the rotation speed between the drive shaft 51 and the second helical gear 53.
[0033]
When a difference occurs in the rotational speed between the drive shaft 51 and the second helical gear 53, as described above, according to the difference in rotational speed between the drive shaft 51 and the second helical gear 53, the first The helical gear 52 moves in the axial direction while rotating around the shaft.
[0034]
When the first helical gear 52 rotates about the shaft and moves in the axial direction, the spool 71 is connected to the first helical gear 52 via the bearing 55 and the bearing 56. One moves in the axial direction in conjunction with the helical gear 52. When the spool 71 moves in the axial direction in conjunction with the first helical gear 52, the oil supply passage 31a and the oil discharge passage 31d of the second casing 31 communicate with the communication passage 31b or 31c, respectively, on the outer periphery of the spool 71. Since the annular groove 71a and the annular groove 71b are formed, 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 changes.
[0035]
When the flow rate of the hydraulic fluid flowing through the oil supply passage 31a, the communication passage 31b, the communication passage 31c, and the oil discharge passage 31d changes, the communication passage 31b and the communication passage 31c are connected via a plurality of arc holes 62a formed in the valve plate 62. Since the plurality of pressure chambers 63a formed in the cylinder block 63 communicate with each other, the flow rate of the hydraulic oil flowing out to the plurality of pressure chambers 63a changes. When the flow rate of the hydraulic oil flowing out to the plurality of pressure chambers 63a changes, the piston 64 is slidably accommodated in the pressure chamber 63a of the cylinder block 63, so that the piston 64 flows out to the plurality of pressure chambers 63a. It slides in the axial direction according to the pressure of the operating oil. When the piston 64 slides in the axial direction, the tip end portion 64a of the piston 64 is slidably engaged with the shoe member 65, and the shoe member 65 is slidably engaged with the inclined surface 66a of the swash plate 66. Therefore, the piston 64 presses the slope 66 a of the swash plate 66 through the shoe member 65. When the piston 64 presses the inclined surface 66a of the swash plate 66 through the shoe member 65, the cylinder block 63 rotates about the axis by the reaction force of the force by which the piston 64 presses the inclined surface 66a of the swash plate 66.
[0036]
When the cylinder block 63 rotates about the shaft, the pressure chamber 63a formed in the cylinder block 63 in which the communication path 31b and the communication path 31c communicate with each other through a plurality of arc holes 62a formed in the valve plate 62 changes. . When the pressure chamber 63a formed in the cylinder block 63 in which 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, the hydraulic oil flows out to the plurality of pressure chambers 63a, respectively. The flow rate of changes. When the flow rate of the hydraulic oil flowing out to the plurality of pressure chambers 63a changes, the cylinder block 63 rotates again about the shaft as described above.
[0037]
Therefore, when 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 changes, the cylinder block 63 is connected to the oil supply passage 31a, the communication passage 31b, the communication passage 31c, and the oil discharge passage 31d. Rotate around the shaft at a rotation direction and a rotation speed according to the flow rate of the hydraulic oil flowing through.
[0038]
When the cylinder block 63 rotates about the shaft at a rotational direction and a rotational speed according to the flow rate of the hydraulic oil flowing through the oil supply passage 31a, the communication passage 31b, the communication passage 31c, and the oil discharge passage 31d, the cylinder block 63 outputs the output shaft. Since the output shaft 61 and the rotation direction are integrally fixed to the periphery of 61, the output shaft 61 also rotates 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 around an axis with direction and rotational speed.
[0039]
Here, when there is a difference in the rotational speed between the drive shaft 51 and the second helical gear 53, the direction in which the first helical gear 52 moves in the axial direction while rotating about the shaft is the male screw. 51a, female screw 52a, external teeth 53a and external teeth 52b can be determined. That is, when there is a difference in the rotational speed between the drive shaft 51 and the second helical gear 53 due to the shape 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 The rotational direction and rotational speed at which the output shaft 61 rotates can be determined according to the difference in rotational speed with the helical gear 53.
[0040]
Accordingly, by determining the shapes of the male screw 51a, the female screw 52a, the external teeth 53a, and the external teeth 52b, when a difference occurs in the rotational speed between the drive shaft 51 and the second helical gear 53, that is, rotation When a difference occurs in the rotation speed between the shaft 41 and the output shaft 61, the output shaft 61 can be rotated so that the difference in rotation speed between the rotation shaft 41 and the output shaft 61 decreases.
[0041]
As described above, the electro-hydraulic servo motor 100 has the output shaft 61 in accordance with the difference in the rotation speed between the rotation shaft 41 and the output shaft 61 when a difference occurs in the rotation speed between the rotation shaft 41 and the output shaft 61. Rotate.
[0042]
Further, the electrohydraulic servomotor 100 can prevent the spool 71 from colliding with the cap cover 36 or the cap cover 37 by the displacement sensor 80.
[0043]
First, the operation of the displacement sensor 80 will be described.
[0044]
As described above, since the sensor shaft 81 is coupled to the spool 71, when the spool 71 moves in the axial direction, the sensor shaft 81 also moves in the axial direction. Therefore, the displacement sensor 80 can detect the spool position in the axial direction of the spool valve 70 by detecting the movement distance of the sensor shaft 81 from the initial position.
[0045]
Further, the displacement sensor 80 outputs a spool position signal corresponding to the detected spool position in the axial direction of the spool valve 70 to the CPU 90.
[0046]
Next, the action of the electrohydraulic servomotor 100 for preventing the spool 71 from colliding with the cap cover 36 or the cap cover 37 by the displacement sensor 80 will be described.
[0047]
First, the spool 71 moves greatly in the axial direction in conjunction with the first helical gear 52 due to a very large difference in the rotational speed between the rotary shaft 41 and the output shaft 61, and the cap cover. 36 or the cap cover 37 within a predetermined distance.
[0048]
Next, when the spool 71 approaches within a predetermined distance from the cap cover 36 or the cap cover 37, the CPU 90 determines whether the spool 71 is in the cap cover 36 or from the spool position signal output from the displacement sensor 80 via the signal transmission path 93. It is determined that the cap cover 37 has been approached within a predetermined distance.
[0049]
Next, when the CPU 90 determines that the spool 71 has approached within a predetermined distance from the cap cover 36 or the cap cover 37, the CPU 71 prevents the spool 71 from approaching within the predetermined distance from the cap cover 36 or the cap cover 37, that is, the spool. The signal input to the pulse motor 40 input from the signal transmission path 91 is processed so that the spool position in the axial direction of 71 falls within a predetermined range, and is output to the pulse motor 40 via the signal transmission path 92. To do.
[0050]
Finally, the pulse motor 40 having a signal output from the CPU 90 via the signal transmission path 92 rotates the rotary shaft 41 in accordance with the signal output from the CPU 90 via the signal transmission path 92.
[0051]
For example, a signal input to the pulse motor 40 is externally input to the CPU 90 via the signal transmission path 91, and the CPU 90 transmits a signal input to the pulse motor 40 input from the outside via the signal transmission path 91. As a result of the output to the pulse motor 40 via the path 92, a very large difference occurs in the rotational speed between the rotating shaft 41 and the output shaft 61, and the spool 71 is greatly linked to the first helical gear 52 in the axial direction. And the cap cover 36 or the cap cover 37 is approached within a predetermined distance.
[0052]
First, the CPU 90 determines from the spool position signal output from the displacement sensor 80 via the signal transmission path 93 that the spool 71 has approached the cap cover 36 or the cap cover 37 within a predetermined distance.
[0053]
Next, the CPU 90 detects that the spool 71 does not approach within a predetermined distance from the cap cover 36 or the cap cover 37, and the rotation shaft 41 receives a signal input to the pulse motor 40 input from the outside via the signal transmission path 91. Accordingly, the signal input to the pulse motor 40 input from the outside via the signal transmission path 91 is processed so as to rotate at the rotation speed closest to the rotation speed at the time of rotation. Output to the pulse motor 40.
[0054]
Further, as a result of the output shaft 61 receiving a load from the external device, a very large difference occurs in the rotational speed between the rotary shaft 41 and the output shaft 61, and the spool 71 is linked to the first helical gear 52 in the axial direction. And the cap cover 36 or the cap cover 37 is approached within a predetermined distance.
[0055]
First, the CPU 90 determines from the spool position signal output from the displacement sensor 80 via the signal transmission path 93 that the spool 71 has approached the cap cover 36 or the cap cover 37 within a predetermined distance.
[0056]
Next, the CPU 90 detects that the spool 71 does not approach within a predetermined distance from the cap cover 36 or the cap cover 37, and the rotation shaft 41 receives a signal input to the pulse motor 40 input from the outside via the signal transmission path 91. Accordingly, the signal input to the pulse motor 40 input from the outside via the signal transmission path 91 is processed so as to rotate at the rotation speed closest to the rotation speed at the time of rotation. Output to the pulse motor 40.
[0057]
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 may collide with the spool 71 may be used. The cover 37 may not be used.
[0058]
Further, the displacement sensor 80 is not limited to the one shown in the present embodiment, and in the present invention, any sensor that can detect the spool position in the axial direction of the spool valve 70 may be used.
[0059]
Further, the key 35 prevents the spool 71 from rotating around the shaft, and the spool 71 rotates around the shaft and collides with the second helical gear 53, so that the spool 71 or the second The helical gear 53 is prevented from being damaged.
[0060]
In the present embodiment, the second shaft and the third shaft are helical gears. However, in the present invention, they may not be helical gears. For example, a predetermined speed ratio can be set between the second shaft and the third shaft 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 rotational speed of the output shaft 61 is decelerated by the second shaft and the third shaft, so the rotational speed of the second shaft is the output shaft 61. The number of rotations can be smaller. Therefore, the capacity of the pulse motor 40 can be reduced, and the electrohydraulic servomotor 100 can be reduced in size.
[0061]
In the present embodiment, the bearing 55 and the bearing 56 are constituted by thrust bushes. However, in the present invention, when the first helical gear 52 moves in the axial direction, the spool 71 is moved in the axial direction. The first helical gear 52 is not limited to the thrust bushing and may be composed of other members as long as it prevents rotation around the axis of the spool 71 when the helical gear 52 rotates around the axis.
[0062]
In this embodiment, the spool 71 is connected to the first helical gear 52 via the bearing 55 and the bearing 56. However, in the present invention, the spool 71 is connected to the first helical gear via a spring. It may be connected to the gear 52.
[0063]
In the present embodiment, the axis of the first helical gear 52 and the axis of the second helical gear 53 are coupled so as to be orthogonal to each other, so that the axis of the rotary shaft 41 and the output shaft 61 Although the axes are also coupled so as to be orthogonal to each other, the extension of the axis of the rotating shaft 41 and the extension of the axis of the output shaft 61 may be arranged so as to maintain another predetermined angle.
[0064]
【The invention's effect】
According to the first aspect of the invention, the axis of the rotary shaft and the output shaft do not need to be on the same line, so that the electrohydraulic servomotor can be reduced in size. In addition, since it is not necessary to cause the spool to collide with other members and stop, the electrohydraulic servomotor can be manufactured with small and low-strength parts, and the electrohydraulic servomotor can be miniaturized.
[0065]
Further , since a new space provided for arranging the spool position detecting means can be reduced, the electrohydraulic servo motor can be reduced in size.
[0066]
Further , since the total length of the electrohydraulic servomotor can be shortened, the electrohydraulic servomotor can be reduced in size.
[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 cross-sectional view taken along the line BB of FIG.
3 is a side sectional view of the periphery of the spool position detecting means shown in FIG. 1. FIG.
4 is a side view of the spool position detecting means shown in FIG. 1. FIG.
FIG. 5 is a side sectional view of a conventional electrohydraulic servomotor.
6 is a cross-sectional view taken along arrow AA in FIG. 5;
[Explanation of symbols]
41 Rotating shaft 40 Pulse motor (electric motor)
61 Output shaft 60 Hydraulic motor (hydraulic drive means)
51 Drive shaft (first shaft)
52b External tooth 52 First helical gear (second shaft)
53a External tooth 53 Second helical gear (third shaft)
71 Spool 70 Spool valve 100 Electrohydraulic servo motor 80 Displacement sensor (spool position detecting means)
90 CPU (input signal processing means)

Claims (1)

An electric motor that rotates a rotating shaft in accordance with an input signal;
Hydraulic drive means for rotating the output shaft by the pressure of hydraulic oil;
A first shaft coupled to the rotating shaft;
A cylindrical second shaft screwed to the first shaft and having external teeth on the outer periphery;
Forming external teeth on the outer periphery and meshing with the external teeth of the second shaft; and a third shaft connected to the output shaft;
A spool valve that moves the spool in the axial direction to control the amount of hydraulic oil supplied and discharged to the hydraulic drive means;
With
In the electrohydraulic servomotor that rotates the output shaft in accordance with the difference in the number of rotations between the rotating shaft and the output shaft by interlocking the spool with the second shaft,
Spool position detecting means coupled to the spool for detecting a spool position in the axial direction of the spool and outputting a spool position signal corresponding to the spool position;
An input signal processing means for inputting the signal input to the electric motor and the spool position signal, processing the signal input to the electric motor so that the spool position is within a predetermined range, and outputting the processed signal to the electric motor;
With
The electric motor rotates a rotating shaft according to a signal output by the input signal processing means ,
The electric motor is disposed at one end of the spool;
The spool position detecting means is disposed on the other end side of the spool;
The second shaft is disposed between the electric motor and the spool position detecting means;
An electro-hydraulic servo motor characterized in that an extension line of the axis of the rotation shaft and an extension line of the axis of the output shaft are arranged to be orthogonal to each other .

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