JPH07123631A - Electric actuator - Google Patents

Abstract

PURPOSE:To provide a compact electric actuator with accurate movement. CONSTITUTION:An output of revolutions at high speed from a rotor 15 of an electric rotation part is transmitted through a rotor shaft 21 to an input member in deceleration units 31 and 41. In the deceleration units 31 and 41, the high- speed revolution is, as an example, reduced to one several tenths or one several hundredths. Then, the output of low-speed revolution is transmitted to a rotation/linear movement conversion unit (screw mechanisms 57 and 65) so that a linear movement member 61 is drawn out or drawn back. These members can be all put in a casing of an electric actuator. In a design step, the rotor shaft and the input member of the deceleration unit may be formed in a body or a screw mechanism may be put in an axle part of the deceleration unit. Consequently, a compact electric actuator is realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric actuator which is used for positioning and clamping a machine tool and which performs a linear motion. In particular, the present invention relates to an electric actuator in which an electric rotating unit, a speed reducing unit, and a rotation / linear motion converting unit are housed in a set of casings to be compact.

[0002]

2. Description of the Related Art A speed reducer having a high speed reduction ratio, which has a speed reduction ratio of one stage and is several tenths to several hundredths, has been conventionally known.
For example, the one using a planetary gear mechanism, the one using an eccentric spline, the one using an elastic gear (trade name: harmonic drive, etc.) and the like can be mentioned. By combining these with a servomotor, a screw mechanism, and the like, it is possible to configure a device that performs precise linear movement.

[0003]

However, in the actuator relating to a simple combination of a plurality of devices as described above, there is a limit in making the whole compact. For example, in terms of length, the size of the entire actuator is the size of the shaft of each device and the size of the coupling connecting the shafts. On the other hand, in the case of a hydraulic actuator such as a hydraulic cylinder, it is necessary to install an oil supply system, and there is a problem that oil leakage occurs. It is an object of the present invention to provide an electric actuator that is compact and can be operated accurately.

[0004]

In order to solve the above problems, an electric actuator according to the present invention has a high reduction gear ratio including an electric rotating portion including a stator and a rotor, and an input member connected to a shaft of the rotor. And a linear motion member driven by the rotation / linear motion conversion unit, and a linear motion member driven by the rotation / linear motion conversion unit; It is characterized by being housed in a casing.

[0005]

The high speed rotation of the rotor of the electric rotating section is transmitted from the rotor shaft to the input member of the speed reducing section. In the reducer,
This high-speed rotation is decelerated from, for example, several tenths to several hundredths. This low-speed rotation is transmitted to the rotation / linear conversion unit (for example, a screw mechanism), and the linear motion member is extended / retracted. Since the electric actuator of the present invention has these parts housed in a set of casings, for example,
The electric actuator of the present invention can be made compact by designing the rotor shaft and the input member of the speed reducing unit as a single body or by designing such that the screw mechanism is housed in the shaft core of the speed reducing unit. In addition, "a set of casings" does not necessarily mean "a casing of one body". One casing may be configured in the assembled state.

In one mode of the electric actuator of the present invention, the speed reducing portion has an internal tooth spline and an external tooth spline having slightly different numbers of teeth, and the meshing positions of the teeth of both splines are the same as those of the input member. Along with the high-speed rotation, the splines move around the circumference to generate a phase difference between the splines, and the phase difference causes the output member to rotate at a low speed; the rotation / linear motion conversion unit is rotationally driven by the output member. As a push rod which is driven by the male screw and which engages with the casing in a non-rotatable and slidable manner. It is configured.

The deceleration portion of such an electric actuator can have a high reduction ratio even though it has a relatively simple structure. As a preferable example of the mechanism of the reduction gear unit of this aspect, a reduction mechanism (the same mechanism as the trade name Harmonic Drive reduction gear) in which the internal tooth spline is an elastic gear (flex spline) can be mentioned. This mechanism has a small number of parts, and since it is easy to incorporate a screw mechanism as a rotation / linear motion conversion unit in its hollow portion, the entire electric actuator can be made extremely compact.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will be given below with reference to the accompanying drawings. Figure 1
FIG. 3 is a schematic cross-sectional view of the internal structure of an electric actuator according to an embodiment of the present invention. FIG. 2 is a schematic diagram for explaining the deceleration mechanism of the deceleration unit of the electric actuator of FIG. The electric actuator 1 of FIG. 1 includes casings 3 and 7, an electric rotating portion (stator coil 11, rotor 15 and the like), a speed reducing portion (wave generator 25 which is an input member, a flex spline 31 and the like), a rotary / linear motion converting portion ( Female screw cylinder 51, male screw 65, etc., and
The push rod 61 is a linear motion member.

The front cover 3 is merely a cover for removing dust, and covers the deceleration portion and the rotation / linear motion conversion portion on the left side of the electric actuator 1 of this embodiment. The casing 7 is bolted to the front cover 3 at the center of the electric actuator 1. The casing 7 is fixed to the circular spline 41 with a bolt or the like, covers the electric rotating portion on the right side of the electric actuator 1, and extends to the left inside the electric actuator 1 so as to surround the outside of the push rod 61 (fixed inside). Tube 8), and further inner tube extension 9
Has reached. The fixed inner cylinder 8 may be connected to the casing 7 as a separate body.

The electric rotating portion of the electric actuator 1 of this embodiment is a DC motor, and is composed of a stator coil 11, a stator core 13, a rotor magnet 15, and a rotor shaft 21. For the electric rotating part of the electric actuator of the present invention, various types of motors can be used, regardless of DC or AC, as long as the motor can control the speed. It may be a so-called pulse motor, servo motor, or the like.

The rotor shaft 21 is rotated by the rotational force applied to the rotor magnet 15. The rotation speed is usually
It is 0 to 4,000 rpm. The right end 23 of the rotor shaft 21 is supported by the fixed inner cylinder 8 via a bearing 71, and the left end of the shaft is supported by a bearing 73. The left end of the rotor shaft 21 is a portion called a wave generator 25 having an inner diameter of a circle and an outer diameter of an ellipse. This portion serves as an input member of the speed reduction unit. That is, in the present embodiment, the rotor shaft 21 and the input member of the speed reducer are integrated.

Here, the speed reducing mechanism of the speed reducing portion of the electric actuator 1 of this embodiment will be described with reference to FIG.
The wave generator 25 is a rigid shaft having an elliptical outer shape. An elliptical bearing 29 is fitted on the outside of the wave generator 25. A flex spline 31 is fitted on the outside of the elliptical bearing 29. Here, the outer race of the elliptical bearing 29 and the flex spline 31 are thin-walled bodies made of a flexible material having high strength (for example, alloy steel). Repeat business trips and indentations.

A rigid circular spline 41 is fitted on the outside of the flex spline 31. Both splines have a dimensional relationship such that when the flex spline 31 travels outside due to being pushed by the thick portion 25a of the wave generator, the teeth of the spline (the flex outer teeth 33 and the inner teeth 43 of the circular spline 41) engage with each other. Has become. Thin portion 25b of wave generator
When the flex spline 31 is dented inward on the outside, the meshing of the teeth of both splines is completely displaced. The upper half of the cross section of the electric actuator 1 shown in FIG. 1 shows a state around the wave generator thick portion 25a, and the lower half thereof shows the wave generator thin portion 25b.
It shows the surroundings.

In this way, the flex spline 3
The outer tooth 33 of 1 is the inner tooth 4 of the circular spline 41.
The wave generator 25 rotates once so that the wave generator 25 is partially pressed against the position 3. Here, the number of external teeth 33 of the flex spline 31 is two or more smaller than the number of internal teeth 43 of the circular spline 41.
Therefore, when the wave generator 25 makes one clockwise rotation, the flex spline 31 rotates counterclockwise with respect to the circular spline 41 by the difference in the number of teeth. When the wave generator 25 continues to rotate, the flex spline 31 also rotates little by little. The reduction ratio at this time is a value obtained by dividing the number of external teeth 33 of the flex spline 31 by the difference in the number of teeth.

Next, the rotation / linear motion conversion portion of the electric actuator of this embodiment will be described. This rotation / linear motion conversion unit uses a screw mechanism, and includes a female screw cylinder 51,
And a push rod 61 having a male screw 65. Since the flange portion 53 of the female screw cylinder 51 is bolted to the hub 39 of the flex spline 31, the female screw cylinder 51 has the same rotational speed (low speed) as the flex spline 31.
To rotate. Naturally, the female screw 57 cut on the inner surface of the cylindrical portion 55 of the female screw cylinder 51 also rotates. The flex spline 31 and the female screw cylinder may be integrated.

On the other hand, the push rod 61 cannot be rotated with respect to the fixed inner cylinder 8 fixed to the casing 7 by the rotation stop pin 10 and the rotation stop groove 67. At the same time, the push rod 61 is provided with respect to the female screw cylinder 51 and the fixed inner cylinder 8.
It is slidable in the axial direction. Therefore, the female screw cylinder 5
When 1 rotates, the female screw 57 pushes the male screw 65 back and forth. Therefore, the push rod 61 moves leftward or rightward. Note that a gun metal bush or the like may be inserted in the sliding portion between the push rod 61 and the fixed inner cylinder 8 or the like.

A seal 8 is provided on the outer peripheral surface near both ends of the push rod 61.
1, 83 are attached to block the inside of the casing from the outside. Gear oil for lubricating the spline portion is put in the casing. A seal for sealing the gear oil so as not to enter the electric rotating portion may be added between the electric rotating portion and the speed reducing portion. Further, depending on the purpose of use, the spline portion may be lubricated with grease or the like.

Next, the position detecting device for the electric actuator will be described. A rotary encoder scale board 93 is attached to the hub 39 of the flex spline 31. The rotation angle of the graduation plate is read by the rotary encoder detection unit 91 attached to the outer surface of the inner cylinder extension 9 of the fixed inner cylinder 8. The moving position of the push rod 61 is detected from this rotation angle. Further, when it is not necessary to detect as highly accurately as the rotary encoder, a magnet sensor 95 is attached to the end of the stator coil 11 to detect a rough rotation angle. If the detection is rough, the limit switches 97 and 98 are used to push the push rod ends 63 and 69.
The position of may be detected.

In this embodiment, the electric actuator incorporating the electric rotating part has been described. However, even if only the speed reducing part and the rotary / linear motion converting part are integrated and a commercially available motor is connected to this, the size is compact. The conversion effect can be obtained. Further, the mechanism of the rotation / linear motion conversion unit may be a ball screw or the like in addition to the trapezoidal screw. Further, when the push rod 61 is pressed against something, the electric rotating portion may be continuously energized and torque may be applied. Alternatively, it is possible to continue energizing the electric rotating portion in order to prevent the push rod 61 from being displaced due to an external force.

[0020]

As is apparent from the above description, the electric actuator of the present invention exhibits the following effects. Since the electric rotating unit, the high reduction ratio reducing unit, and the rotary / linear motion converting unit are housed in a set of casings, the size can be made compact. When a screw mechanism is used for the rotation / linear motion conversion unit, it is possible to receive a large reaction force and to have a jack function. Since it is possible to detect the rotation angle of the high-speed rotating portion, it is possible to improve the positioning accuracy of the push rod in and out.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an internal structure of an electric actuator according to an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining a deceleration mechanism of a deceleration portion of the electric actuator of FIG.

[Explanation of symbols]

1 Electric Actuator 3 Front Cover 7 Casing 8 Fixed Inner Cylinder 9 Inner Cylinder Extension 10 Rotation Stop Pin 11 Stator Coil 13 Stator Core 15 Rotor Magnet 21 Rotor Shaft 23 Right End 24 Central Part 25 Wave Generator 29 Elliptical Bearing 31 Flex Spline 33 Flex external tooth 35 Flex tube 39 Hub 41 Circular spline 43 Internal tooth 51 Female thread tube 53 Flange section 55 Cylindrical section 57 Female thread 61 Push rod 63 Left end 65 Male thread 67 Non-rotating groove 69 Right side end 71, 73, 75, 77 Bearing 81, 83 Sticker 91 Rotary encoder detection unit 93 Rotary encoder scale 95 Magnet sensor 96 Signal line

Claims (2)

[Claims] 1. An electric rotating unit including a stator and a rotor, a high reduction ratio reduction unit including an input member connected to a shaft of the rotor, and a rotation unit driven by an output member of the high reduction ratio reduction unit. An electric actuator comprising: a linear motion conversion unit; and a linear motion member driven by the rotation / linear motion conversion unit; each of the above units being housed in a set of casings. 2. The high reduction ratio deceleration portion has an internal tooth spline and an external tooth spline having slightly different numbers of teeth, and the meshing position of the teeth of both splines is a spline according to the high speed rotation of the input member. A phase difference is generated between the splines by moving on the circumference, and the output member is rotated at a low speed by the phase difference; the rotation / linear motion converting portion is a female screw cylinder driven to rotate by the output member; A male screw threaded with a female thread of the female thread cylinder; the linear motion member is configured as a push rod which is driven by the male thread and is non-rotatably and slidably engaged with the casing. 1. The electric actuator according to 1.