JP2000205202A - Electro-hydraulic servomotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electro-hydraulic servo motor having a compact structure by devising the arrangement of a control valve. SOLUTION: This servomotor comprises a first helical gear 49 connected to an output shaft 34, second helical gears 52, 53 screw connected to a command rotary shaft of a pulse motor also meshed with the first helical gear 49 to be driven thereby, a spool valve energized by the second helical gear 52 so as to move therewith in accordance with changing of a rotational speed in one electric motor and the output shaft 34 to control a supply amount of operating oil to hydraulic drive means 37, 38, and another spool valve energized by the other second helical gear 53 so as to move therewith in accordance with changing of a rotational speed in a command rotary shaft of the other electric motor and the output shaft 34 to control a discharge amount of operating oil from the hydraulic drive means 37, 38.

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 Conventionally, in this type of electro-hydraulic servomotor, as shown in FIGS.
4 rotatably supports the casing 1. A valve plate 9 is fixed to the inner wall of the casing 1, and a cylinder block 7 is fixed to the periphery of the output shaft 2. A plurality of pressure chambers 7a are formed in the cylinder block 7, and pistons 8 are housed in these pressure chambers 7a, respectively. The pistons 8 are moved in the axial direction by hydraulic pressure of hydraulic oil introduced into the pressure chambers 7a. Is reciprocated.

[0003] A swash plate 6 inclined at a predetermined angle facing the valve plate 9 is fixed to the inner wall of the casing 1 on the tip side of the output shaft 2, and the tip of the piston 8 presses and slides the swash plate 6. At the same time, the cylinder block 7 slides on the valve plate 9 and the output shaft 2
And the cylinder block 7 rotate together.

The casing 1 is provided with a spool valve 11 which moves in the axial direction, and a screw member 12 and a gear 13 are fixed to a front end and a rear end of the spool valve 11, respectively. The casing 1 includes a pulse motor 14
The command rotary shaft 15 of the pulse motor 14 is rotatably supported by the casing 1. The torque of the command rotation shaft 15 is transmitted to the spool valve 11 via the gear 16 and the gear 13, and the torque of the output shaft 2 is
The power is transmitted to the spool valve 11 via the control valve 12. The rotation of the spool valve 11 allows the oil discharge passage 1a, the oil supply passage 1b, and the communication passages 1c, 1d to communicate with each other. In this electrohydraulic servomotor, the output shaft 2, the spool valve 11, and the pulse motor 14 are arranged on the same axis.

[0005]

In such a conventional electrohydraulic servomotor, since the output shaft 2, the spool valve 11, and the pulse motor 14 are arranged on the same axis, the overall length becomes longer, and other mechanical There is a problem that it does not fit well in such cases. Further, the screw member 10 and the screw member 12
Since the rotation ratio of the pulse motor 14 is 1: 1 in order to increase the speed of the output shaft 2, there is a problem that the capacity of the pulse motor 14 must be increased and the pulse motor 14 must be driven at high speed.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an electrohydraulic servomotor having a compact structure and capable of reducing the capacity of a pulse motor. Is to do.

[0007]

SUMMARY OF THE INVENTION The present invention provides an electric motor for rotating a command rotary shaft in response to an input signal, and a control valve for controlling supply and discharge of hydraulic oil in response to rotation of the command rotary shaft of the motor. And hydraulic drive means for rotating an output shaft by hydraulic pressure of hydraulic oil from the control valve, wherein the electric motor comprises a pair of electric motors in an electrohydraulic servomotor that rotates an output shaft in accordance with supply and discharge of the hydraulic oil. A first toothed shaft connected integrally to the output shaft in the rotation direction, and a first toothed shaft which is screw-coupled to a commanded rotary shaft of the pair of electric motors and meshes with the first toothed shaft, respectively. One and the other second toothed shafts that are rotationally driven by the toothed shaft, and the one second toothed shaft in the axial direction according to a change in the number of rotations of the command rotation shaft and the output shaft of the one motor. Attached to the one second toothed shaft so as to move. A supply-side control valve for controlling an amount of hydraulic oil supplied to the hydraulic drive means, and the other second toothed shaft according to a change in the number of rotations of a command rotation shaft and the output shaft of the other electric motor. A discharge-side control valve urged by the other second toothed shaft so as to move in the axial direction together with the hydraulic drive means to control a discharge amount of the hydraulic oil from the hydraulic drive means. Preferably, preferably, the first toothed shaft and the second toothed shaft are meshed so that their axes are orthogonal to each other.

According to the present invention, the length of the shaft of the electrohydraulic servomotor can be shortened by setting the control valve for controlling the supply and discharge of the hydraulic oil in a horizontal state crossing the output shaft.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view of an electrohydraulic servomotor according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line BB of FIG.

The electrohydraulic servomotor shown in FIGS.
It has a cup-shaped first casing 30 and a second casing 31 fastened and fixed to the first casing 30 by bolts 32. In the second casing 31, an oil supply passage 31a, an oil discharge passage 31b, and communication passages 31c and 31d are formed. The output shaft 34 is rotatably supported by the first casing 30 and the second casing 31 by bearings 41 and 48, and is urged by a spring 42 toward one end of the output shaft 34.

One end of an output shaft 34 protruding outside the first casing 30 is connected to driving units (not shown) of an external device, so that torque is transmitted to these driving units. I have. In the drawing, reference numeral 33 denotes a bolt hole into which the bolt is screwed when the first casing 30 is fastened and fixed to another member of the external device by a bolt (not shown).

The second casing 31 at the other end of the output shaft 34
A valve plate 40 is fixed to the side wall of the valve plate 40, and the output shaft 34 is connected to the valve plate 40.
It is inserted in the center of. The valve plate 40 is connected to the communication passage 31.
Arc holes 40a communicating with c and 31d, respectively, are formed concentrically, and supply and discharge of hydraulic oil to and from a pressure chamber 37a in the cylinder block 36 described later are performed through the arc holes 40a.

The cylinder block 36 is fixed to the periphery of the output shaft 34. The cylinder block 36 has a plurality of pressure chambers 37a having an axis parallel to the axis of the output shaft 34 at equal intervals in the circumferential direction. And a plurality of pistons 37 slidably housed in the pressure chamber 37a.
The piston 37 is reciprocated in the axial direction of the output shaft 34 by the hydraulic pressure of the hydraulic oil introduced into the section a.

The distal end 38 of the piston 37 is formed in a substantially spherical shape, and the first casing 3 extends from one end of the output shaft 34.
A swash plate 35, which is inclined at a predetermined angle and has an output shaft 34 inserted in the center, is fixed to the inner wall of the zero.

The tip portion 38 of the piston 37 is
9 and is rotatably engaged with the distal end portion 38 of the piston 37.
Presses the swash plate 35 through the shoe member 39, and the shoe member 39 slides on the slope 35 a of the swash plate 35 while the tip end portion 38 rolls on the shoe member 39. When the shoe member 39 slides on the swash plate 35, the cylinder block 36 slides on the valve plate 40, so that the output shaft 34 and the cylinder block 36 rotate together.

Reference numeral 49 denotes a first helical gear as a first toothed shaft, 52 and 53 denote second helical gears as one and the other second toothed shafts. Is output shaft 3
4 is fixed to the rear end. Second helical gear 52, 5
3 are arranged in parallel with each other with their rotation axes oriented in a direction orthogonal to the rotation axis of the first helical gear 49,
Each of the first helical gears 49 meshes. A pair of spool valves 63L, 63R are disposed adjacent to the outer end sides of the second helical gears 52, 53, and these spool valves 63L, 63R are inwardly mounted on the motor (second motors) by springs 64L, 64R. (The helical gears 52 and 53 side).

Further, on the outer wall of the second casing 31,
A pair of electric motors, for example, a pair of pulse motors 50L, 50L
R is mounted, and the command rotation shafts 51 of the pulse motors 50L, 50R are inserted into the second helical gears 52, 53 and screwed together. Therefore, when a difference occurs between the rotation speed of the command rotation shaft 51 of the pulse motors 50L and 50R and the rotation speed of the second helical gears 52 and 53 (that is, the rotation speed fed back from the output shaft 34), The second helical gears 52 and 53 can move in either one of the axial directions. The springs 64L and 64R are contracted between the spool valves 63L and 63R and the pulse motors 50L and 50R, respectively.

In the peripheral portions of the spool valves 63L and 63R, annular grooves 63a are respectively formed in the circumferential direction, and when the spool valves 63L and 63R move in the axial direction,
The annular groove 63a is provided in the oil drain passage 31a of the second casing 31,
The opening of the annular groove 63a is controlled by communicating with the oil supply passage 31b and the communication passages 31c and 31d. That is, in FIG. 2, a pair of second helical gears 52 and 53 are provided.
Is moved to the right, the oil supply passage 31b is connected to the communication passage 31c.
In addition, the communication passage 31d communicates with the oil drain passage 31a, and the hydraulic oil is supplied and discharged to the arc hole 40a of the valve plate 40. Conversely, when the second helical gears 52 and 53 move to the left, the oil supply passage 31b communicates with the communication passage 31d, and the communication passage 31c communicates with the oil discharge passage 31a, and the hydraulic oil is discharged. It is supplied to and discharged from the arc hole 40a of the valve plate 40. In the figure, reference numeral 46 denotes a cap cover which closes the opening of the second casing 31.

Next, the operation will be described below.

In the above-described electrohydraulic servomotor, the second helical gears 52 and 53 are displaced in the axial direction in accordance with the rotation of the command rotary shaft 51, and the rotational fluctuation of the output shaft 34 is changed by the second helical gear. The second helical gears 52 and 53 rotate according to the feedback amount by being mechanically fed back to the wheels 52 and 53. And the second helical gear 5
As the spool valves 63L and 63R move in the axial direction with respect to the command rotation shaft 51 together with the rotation shafts 2 and 53, the supply and discharge of the hydraulic oil are controlled, and the rotation speed of the output shaft 34 is reduced to the rotation speed of the pulse motors 50L and 50R. Control is performed so as to follow.

In this state, the operating oil is supplied to the pressure chamber 37.
a, and the tip 38 of the piston 37 is
The swash plate 35 is pressed through the
Rotates together with the cylinder block 36 to drive an external device. At this time, supply of hydraulic oil to the pressure chamber 37a
Switching of the discharge is performed by the rotating cylinder block 36 and the arc hole 40 a of the valve plate 40.

Here, for example, when a load is applied to the external device for some reason and the rotational speed of the output shaft 34 decreases, the rotational speeds of the second helical gears 52 and 53 decrease and the second helical gears 52 and 53 decrease.
A difference occurs between the rotation speeds of the helical gears 52 and 53 and the rotation speed of the command rotation shaft 51. At this time, the second helical gears 52, 5
3 makes a screw motion with respect to the command rotation shaft 51 and moves in the axial direction.

As the second helical gears 52, 53 move, the pair of spool valves 63L, 63R move in the axial direction, and the opening of the annular groove 63a increases. For this reason,
A large amount of hydraulic oil introduced from the oil supply passage 31a is supplied to the pressure chamber 37a of the piston 37 extending from the one arc hole 40a of the valve plate 40 through the annular groove 63a of one of the spool valves 63L and 63R and the communication passage 31d. Supplied, piston 37
Strongly presses the swash plate 35, and the hydraulic oil in the pressure chamber 37 a of the reduction-side piston 37 flows from the other arc hole 40 a of the valve plate 40 through the communication passage 31 c and the other spool valve 63.
A large amount of oil is discharged from the oil discharge passage 31b through the annular grooves 63a of L and 63R, and the rotation speed of the output shaft 34 increases.

As described above, by the movement of the spool valves 63L, 63R, the rotation speed of the output shaft 34 increases to a predetermined rotation speed, and the control of the rotation speed of the output shaft 34 follows the rotation speed of the pulse motors 50L, 50R. Is performed with high accuracy.

In this embodiment, the first toothed shaft and the second
By making the toothed shafts intersect each other, and especially perpendicular to each other, the output shaft, the spool valve and the pulse motor are not arranged coaxially as in the conventional device, and a compact electro-hydraulic servo motor with a short overall length is provided. can get. Therefore,
It is possible to improve the accommodation in other machines and the like.

Also, by making the spool valves 63L and 63R contact the second helical gears 52 and 53 so as to slide, the rotation of the spool valves 63L and 63R is eliminated, and the wear friction is prevented. it can. Further, by individually driving the pair of spool valves 63L and 63R,
Supply and discharge of hydraulic oil to and from the piston 37 can be controlled independently, and optimal motor rigidity can be obtained.

In this embodiment, the first toothed shaft and the second toothed shaft are helical gears, but the present invention is not limited to this. For example, it is also possible to set a predetermined speed ratio between the two toothed shafts by using another transmission gear, a worm screw, a worm wheel, or the like. In such a case, the rotation speed of the output shaft becomes the first toothed shaft and Since the speed is reduced by the second toothed shaft, the rotation speed of the second toothed shaft can be lower than the rotation speed of the output shaft, and the capacity of the electric motor can be reduced.

[0029]

According to the present invention, it is possible to provide a compact electro-hydraulic servomotor having a short overall length by intersecting the first toothed shaft and the second toothed shaft with each other, and in particular, at right angles. In addition, by individually driving the pair of spool valves, the supply and discharge of the hydraulic oil can be controlled independently, and the optimum motor rigidity can be obtained. Further, if the spool valve is prevented from rotating, its wear friction can be prevented.

[Brief description of the drawings]

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

FIG. 2 is a sectional view taken along line BB of FIG.

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

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

[Explanation of symbols]

 Reference Signs List 30 first casing 31 second casing 31a oil discharge path 31b oil supply path 31c, 31d communication path 34 output shaft 35 swash plate 36 cylinder block (hydraulic drive means) 37 piston (hydraulic drive means) 37a pressure chamber 38 tip 39 shoe member 40 Valve plate 40a Arc holes 41, 48 Bearing 42 Spring 49 First helical gear (first toothed shaft) 50L, 50R Pulse motor 51 Commanded rotary shaft 52 Second helical gear (one second toothed shaft) 53) second helical gear (the other second toothed shaft) 63L spool valve (supply-side control valve) 63R spool valve (discharge-side control valve) 63a annular groove

Claims (2)

[Claims] An electric motor for rotating a command rotary shaft in response to an input signal, a control valve for controlling supply and discharge of hydraulic oil in response to rotation of the command rotary shaft of the motor, and an operation from the control valve Hydraulic drive means for rotating the output shaft by oil pressure,
An electrohydraulic servomotor that rotates an output shaft in accordance with supply and discharge of the hydraulic oil, wherein a pair of the motors are provided, and a first toothed shaft integrally connected to the output shaft in a rotational direction; One and the other second toothed shafts which are screw-coupled to the command rotary shafts of the pair of electric motors, mesh with the first toothed shafts, and are rotationally driven by the first toothed shafts, respectively. The one second toothed shaft is urged to move in the axial direction together with the one second toothed shaft in response to a change in the number of rotations of the command rotation shaft and the output shaft, and A supply-side control valve for controlling a supply amount of hydraulic oil, and a supply-side control valve for moving in the axial direction together with the other second toothed shaft in accordance with a change in the number of rotations of a command rotation shaft and the output shaft of the other electric motor. The other second toothed shaft urges the hydraulic drive means Electro-hydraulic servomotor, characterized in that provided as the discharge-side control valve for controlling the discharge amount of hydraulic oil al, a. 2. The electro-hydraulic servo motor according to claim 1, wherein the first toothed shaft and the second toothed shaft are meshed so that their axes are orthogonal to each other.