JP3977100B2 - Linear actuator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a linear actuator, and is incorporated in a small robot such as entertainment, medical forceps, and a transfer hand, and is driven by a small, lightweight and high thrust force to drive a joint portion constituting a part of the small robot, In addition, the present invention relates to a linear motion actuator that requires highly accurate positioning.
[0002]
[Prior art]
For example, conventional examples of linear motion actuators are disclosed in Japanese Patent Application Laid-Open Nos. 9-182407, 2000-341905, and 2001-86698.
[0003]
A linear actuator disclosed in Japanese Patent Laid-Open No. 9-182407 is provided on a stator that houses a stator coil, a rotor that axially supports a permanent magnet by a bearing, and an inner periphery of the rotor. A stepping motor comprising a threaded spindle that is engageable with a female screw and whose rotation is locked by a shaft support member. In this linear actuator, rotation of the rotor is converted into linear movement along the axial direction of the spindle.
[0004]
Further, a linear motion actuator disclosed in Japanese Patent Laid-Open No. 2000-341905 includes a rotor portion that rotates by energizing a coil, a screw shaft that is partially formed with a screw portion, and a rotational force of the rotor portion that is a screw shaft. A rotation transmission mechanism that transmits to the shaft, a motion conversion mechanism such as a fixing nut that converts the rotational force of the screw shaft into its axial propulsive force, and a bearing that holds the screw shaft rotatably and slidably in the axial direction. A linear drive motor is provided. In this linear actuator, the rotational force of the rotor portion is converted into a linear movement along the axial direction of the screw shaft.
[0005]
Further, the linear motion actuator disclosed in Japanese Patent Laid-Open No. 2001-86698 is arranged so as to face a rotor having a permanent magnet with magnetic poles divided and magnetized on the circumference, a winding for generating a magnetic field, and the magnetic poles. And a stator having a stator magnetic pole portion that generates a magnetic pole when a current flows through the winding, and a drive that is fixed to the rotor in a state of penetrating on the rotating shaft of the rotor and supported by a support member provided on the stator And a shaft. In this linear motion actuator, the rotor rotates about the rotation axis in accordance with the change of the magnetic pole in the stator magnetic pole portion, so that the drive shaft moves linearly along the rotation axis while rotating together with the rotor.
[0006]
[Problems to be solved by the invention]
By the way, none of the linear motion actuators disclosed in the above-mentioned JP-A-9-182407, JP-A-2000-341905, and JP-A-2001-86698 has a speed reduction mechanism, so that the thrust of the linear motion actuator is generated by the rotor. Linear actuators that are used to drive joint sites that form part of small robots such as entertainment, medical forceps, and transport hands, That is, it has been difficult to use in a linear actuator that requires positioning with a small size, light weight, high thrust, and high accuracy.
[0007]
Even if the speed reducing mechanism is provided in the linear motion actuator having the above-described structure, the weight of the whole of the linear motion actuator including the speed reduction mechanism is increased, resulting in a problem that the size is increased.
[0008]
Therefore, the present invention has been proposed in view of the above-mentioned problems, and the object of the present invention is to obtain a desired reduction ratio with a simple structure, and to achieve positioning with a small size, light weight, high thrust, and high accuracy. It is an object of the present invention to provide a linear actuator that can be easily realized.
[0009]
[Means for Solving the Problems]
As a technical means for achieving the above object, the present invention provides a planetary speed reducer on the output shaft of a drive motor, reduces the rotation of the drive motor via the planetary speed reducer, and then slides. A linear actuator that converts a linear reciprocating motion of the planetary reduction gear, wherein a screw portion is formed on the outer periphery of the output member of the planetary reduction gear to be screwed with the sliding member, and is at least one of the outer diameters of the driving motor. The portion has a flat surface, and the flat surface is used as a contact surface of the sliding member .
[0010]
In this linear actuator, the rotation of the drive motor is decelerated with a desired reduction ratio by a planetary reduction gear, and the reduced rotation is converted into a linear reciprocating motion of a sliding member, thereby achieving high thrust and high accuracy. However, at this time, the screw part that is screwed with the sliding member is formed on the outer periphery of the output member of the planetary reduction gear, thereby reducing the number of parts and making the linear motion actuator lightweight and compact. Realize. Further, at least a part of the outer diameter of the driving motor has a flat surface, and the flat surface serves as a contact surface of the sliding member, so that the flat surface of the driving motor functions as a detent for the sliding member. Therefore, it is not necessary to prepare a rotation preventing structure as a separate component other than the drive motor, and the number of components and the manufacturing cost can be reduced.
[0011]
The planetary speed reducer includes a sun gear coaxially provided on the output shaft of the drive motor, a rotary internal gear that is an output member screwed with the sliding member that is prevented from rotating, and the sun gear. A planetary gear mechanism comprising a plurality of planetary gears interposed between a gear and a rotating internal gear so as to mesh with both of them, and a carrier that rotatably holds these planetary gears at equal circumferential intervals. In particular, a sun gear coaxially provided on the output shaft of the drive motor, a rotary internal gear that is an output member screwed to the sliding member that is prevented from rotating, and the drive motor A fixed fixed internal gear, a plurality of planetary gears interposed between the sun gear, the rotating internal gear and the fixed internal gear so as to mesh with both, and the planetary gears at equal intervals in the circumferential direction; Consists of a carrier that can be freely rotated If paradox planetary gear mechanism, even more preferred in that a high reduction ratio is obtained.
[0012]
In the configuration of the invention, the sliding member constituting the output portion of the linear actuator has a hollow portion, and the driving motor and the planetary reduction gear are accommodated in the hollow portion. As a result, the space in the sliding member can be used effectively, the entire linear actuator can be made compact, and the linear reciprocating stroke of the sliding member can be easily increased.
[0014]
The said structure of this invention WHEREIN: Each component which comprises the said planetary reduction gear, and the component parts containing a sliding member were made from resin, It is characterized by the above-mentioned. As a result, the weight of the entire linear actuator can be reduced, and the manufacturing cost can be easily reduced. The resin is preferably an engineering plastic containing polyacetal, polyimide, or polyphenylene sulfide. If engineering plastics are used, the strength of the component parts can be secured and the wear resistance can be improved.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 and FIG. 2 show an embodiment of the present invention, which is a linear motion actuator equipped with a planetary reduction gear composed of a planetary gear mechanism. The linear actuator is a small drive motor 1, a planetary speed reducer 3 provided on the output shaft 2 of the drive motor 1, and an output member (a rotating internal gear described later) of the planetary speed reducer 3. The main part is constituted by the sliding member (nut) 4 screwed together. The linear actuator is a small unit having a diameter of about 10 mm and an axial length of about 20 mm, for example.
[0016]
The drive motor 1 and the planetary speed reducer 3 are accommodated in a sliding member 4 having a cylindrical shape. Since the drive motor 1 and the planetary speed reducer 3 are accommodated in the hollow portion 5 of the sliding member 4 in this way, the space in the sliding member 4 can be used effectively, and the entire linear motion actuator can be used. Compactness can be achieved, and the linear reciprocating stroke of the sliding member 4 can be easily increased.
[0017]
The planetary reduction gear 3 is a sun gear 6 coaxially provided on the output shaft 2 of the drive motor 1 and an output member that is rotatably supported by a shaft end of the sun gear 6 via a rolling bearing 7. A rotating internal gear 8, a plurality of planetary gears 9 interposed between the sun gear 6 and the rotating internal gear 8 so as to mesh with both, and the planetary gears 9 are freely rotatable at equal intervals in the circumferential direction. It is a planetary gear mechanism comprised with the carrier 10 hold | maintained to. The rolling bearing 7 for supporting the rotating internal gear 8 on the sun gear 6 is not necessarily required. The rolling bearing 7 is omitted, and the rotating internal gear 8 is directly supported on the sun gear 6 only by sliding. It may be.
[0018]
The rotating internal gear 8 has a cylindrical shape, and a tooth portion 12 that meshes with the planetary gear 9 is formed in the inner diameter of the hollow portion 11, and the planetary gear 9, the sun gear 6, and the carrier 10 are accommodated in the hollow portion 11. ing. Each planetary gear 9 has a shaft 13 protruding from both ends in the axial direction, and the shaft 13 of the planetary gear 9 is constituted by one carrier 10 fixed to the drive motor 1 and the other carrier 10 positioned on the rolling bearing 7 side. It is made the structure which supports so that it can rotate freely.
[0019]
A screw groove 14 that is a screw portion that is screwed into the sliding member 4 is formed on the outer periphery of the rotating internal gear 8 that is an output member of the planetary reduction gear 3. Thus, by forming the screw groove 14 directly on the outer periphery of the rotating internal gear 8, the number of parts can be reduced and the linear actuator can be reduced in weight and size.
[0020]
The sliding member 4 is formed with a screw thread 15 that is screwed to the rotary internal gear 8 on its inner diameter, and a rotation stopper 16 is integrally fixed to an end of the driving motor. Further, a protrusion 20 for preventing the slipping is formed at the tip end (stroke end) of the sliding member 4. By using a flat motor called a flat type for the drive motor 1, a flat surface 17 positioned above and below a contact surface on which a non-rotating 16 integrated with a sliding member 4 that linearly reciprocates slides. By doing so, the axial center rotation of the sliding member 4 is restricted.
[0021]
Considering the efficiency of converting the rotation of the rotating internal gear 8 into the linear reciprocating motion of the sliding member 4, the lead of the thread groove 14 of the rotating internal gear 8 and the thread 15 of the sliding member 4 is preferably large. If too much, the engagement between the thread groove 14 and the thread 15 is reduced. Considering the meshing of the thread groove 14 and the thread 15, the thread groove 14 and the thread 15 need to be at least two pitches.
[0022]
When the linear actuator is incorporated in a small robot, the base end of the driving motor 1 is fixedly supported, and a driving mechanism such as a joint part constituting a part of the small robot is provided on the outer diameter of the sliding member 4. It should be attached. In this way, it is possible to reduce the weight of the movable side by setting the driving motor 1 as the fixed side and the sliding member 4 as the movable side. It is also possible to make the motor 1 movable.
[0023]
In this linear actuator, the rotation of the drive motor 1 is reduced by the planetary reduction gear 3 with a desired reduction ratio, and the reduced rotation is converted into a linear reciprocating motion of the sliding member 4, thereby achieving high thrust. Realize high-precision positioning. Specifically, the sun gear 6 of the planetary reduction gear 3 is rotated by the rotation of the output shaft 2 of the drive motor 1, and the planetary gear 9 that is rotatably supported by the carrier 10 by the rotation of the sun gear 6 is By rotating around the sun gear 6, the rotation of the driving motor 1 is transmitted to the rotating internal gear 8 with a predetermined reduction ratio.
[0024]
Due to the reduced rotation of the rotary internal gear 8 with respect to the drive motor 1, the sliding member 4 screwed through the screw groove 14 and the screw thread 15 tries to rotate. Since it is in contact with the flat surface 17 of the drive motor 1, the axial center rotation of the sliding member 4 is restricted. In this way, the rotation stopper 16 of the sliding member 4 slides on the flat surface 17 of the driving motor 1, whereby the rotation of the rotating internal gear 8 is converted into the linear reciprocating motion of the sliding member 4 (FIG. 3). reference). The linear reciprocation of the sliding member 4 can drive a joint portion or the like constituting a part of the small robot with a small, light, high thrust and high-accuracy positioning.
[0025]
As described above, the flat surface 17 of the driving motor 1 is used as the contact surface of the detent 16 where the sliding member 4 linearly reciprocates, so that the flat surface 17 of the driving motor 1 functions as a detent of the sliding member 4. Therefore, it is not necessary to prepare a rotation preventing structure for the sliding member 4 as a separate part other than the driving motor 1, and the number of parts can be reduced and the manufacturing cost can be reduced. Note that the above-described detent 16 can be manufactured by integral molding with the sliding member 4.
[0026]
When this linear motion actuator is used by being incorporated in a small robot, it is necessary to detect the expansion / contraction position in order to control the operation of the linear motion actuator by the linear reciprocation of the sliding member 4. It is possible to monitor the expansion / contraction speed of the linear motion actuator from the time change of the expansion / contraction position of the linear motion actuator. The position detector for detecting the expansion / contraction position of the linear motion actuator can be incorporated into the linear motion actuator itself to be modularized, and this modularization can realize cost reduction and compactness.
[0027]
For example, the position detector is provided with a resistor that extends parallel to the movement direction (axial direction) of the rotation stopper 16 via an insulator such as a printed circuit board on the flat surface 17 of the drive motor 1. A structure in which a contact member (spring steel, gold plating) that slidably contacts the resistor is attached to a part of the resistor 16 can be easily realized. In this structure, the resistance value between the one end of the resistor and the contact member is a potentiometer that changes according to the expansion / contraction position of the linear motion actuator. That is, when a constant voltage is applied to both ends of the resistor, the voltage between one end of the resistor on the drive motor 1 side and the contact member extending from the detent 16 changes according to the amount of expansion / contraction of the linear actuator, The expansion / contraction position of the linear actuator can be detected based on the changing voltage value.
[0028]
In addition, each part which comprises a linear motion actuator, ie, the sun gear 6, the planetary gear 9, the rotation internal gear 8, the sliding member 4, and the rotation stopper 16 which comprise the planetary reduction gear 3, is made into a resin molded product. As a result, the entire linear actuator can be reduced in weight, and the manufacturing cost can be easily reduced. Usable resins include engineering plastics including polyacetal, polyimide, and polyphenylene sulfide. If engineering plastics are used, the strength of the component parts can be secured and the wear resistance can be improved. Further, since the thread groove 14 of the rotating internal gear 8 and the thread 15 of the sliding member 4 have good surface lubricity, the rotating internal gear 8 and the sliding member 4 are impregnated with a solid lubricant. It is preferable to use a resin.
[0029]
Next, FIG. 4 shows another embodiment of the present invention, which shows a linear motion actuator provided with a planetary reduction gear 3 ′ composed of a mysterious planetary gear mechanism. The same parts as those of the linear motion actuator of the embodiment of FIG. The linear actuator shown in FIG. 4 is different from the embodiment shown in FIG. 1 in that a mysterious planetary gear mechanism is used as the planetary reduction gear 3 ′. In this linear motion actuator, the rotation of the drive motor 1 is decelerated with a desired reduction ratio by the planetary reduction gear 3 ′, and the decelerated rotation is converted into a linear reciprocating motion of the sliding member 4 (FIG. 5). reference).
[0030]
The planetary reduction gear 3 ′ includes a sun gear 6 coaxially provided on the output shaft 2 of the drive motor 1, and a rotating inner shaft rotatably supported by a shaft end of the sun gear 6 via a rolling bearing 7. A gear 8, a fixed internal gear 18 fixed to the drive motor 1, and a plurality of planetary gears interposed between the sun gear 6, the rotary internal gear 8 and the fixed internal gear 18 so as to mesh with both of them. 9 is a mysterious planetary gear mechanism composed of 9 and two carriers 10 that rotatably hold the planetary gears 9 at equal intervals in the circumferential direction. The fixed internal gear 18 has a cylindrical shape, and a tooth portion 19 that meshes with the planetary gear 9 is formed on the inner diameter thereof. The planetary gear 11 is formed in the hollow portion 11 formed by the fixed internal gear 18 and the rotary internal gear 8. The gear 9, the sun gear 6, and the carrier 10 are accommodated.
[0031]
In this linear motion actuator, in the planetary reduction gear 3 ′ having a mysterious planetary gear mechanism, a difference in the number of teeth is required between the fixed internal gear 18 and the rotary internal gear 8, and the reduction ratio decreases as the difference in the number of teeth decreases. Becomes larger. Here, when the number of teeth of the sun gear 6 is A, the number of teeth of the rotating internal gear 8 is B, and the number of teeth of the fixed internal gear 18 is C, the reduction ratio in the planetary reduction gear 3 ′ is (1 + C / A) / (1-C / B). In the linear motion actuator of this embodiment, a higher reduction gear ratio can be obtained than in the embodiment (see FIG. 1) using a planetary reduction device comprising a planetary gear mechanism.
[0032]
In the two embodiments described above, the case where a planetary gear mechanism or a strange planetary gear mechanism is used as the planetary reduction gear has been described. However, the present invention is not limited to this, and a planetary roller using a planetary roller is used. A type speed reducer is also possible.
[0033]
【The invention's effect】
According to the present invention, the linear actuator is provided with a planetary reduction gear on the output shaft of the drive motor, and converts the rotation of the drive motor into a linear reciprocation of the sliding member after decelerating the rotation of the drive motor through the planetary reduction gear. In addition, by forming a threaded portion that engages with the sliding member on the outer periphery of the output member of the planetary reduction gear, a lightweight and compact linear motion actuator capable of positioning with high thrust and high accuracy can be achieved. realizable. In addition, by having a flat surface on at least a part of the outer diameter of the drive motor and making the flat surface a contact surface of the sliding member, the driving motor can also serve as a detent for the sliding member. There is no need to prepare a non-rotating structure as a separate part other than the drive motor, and the number of parts can be reduced and the manufacturing cost can be reduced.
[0034]
The sliding member constituting the output portion of the linear motion actuator has a hollow portion, and if the drive motor and the planetary reducer are accommodated in the hollow portion, the entire linear motion actuator can be made compact, and the sliding motion can be reduced. It is also easy to increase the linear reciprocating stroke of the moving member.
[0036]
If the components constituting the planetary reduction gear and the components including the sliding member are made of resin, the entire linear actuator can be reduced in weight, and the manufacturing cost can be easily reduced. If an engineering plastic containing polyacetal, polyimide, or polyphenylene sulfide is used as the resin, the strength of the component parts can be secured and the wear resistance can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a linear motion actuator including a planetary reduction gear composed of a planetary gear mechanism in an embodiment of the present invention.
FIG. 2 is a right side view showing the linear motion actuator of FIG. 1;
3 is a cross-sectional view showing a state in which the linear motion actuator of FIG. 1 is operated to linearly move the sliding member.
FIG. 4 is a cross-sectional view showing a linear motion actuator including a planetary reduction gear composed of a mysterious planetary gear mechanism according to another embodiment of the present invention.
5 is a cross-sectional view showing a state in which the linear motion actuator of FIG. 4 is operated to linearly move the sliding member.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Drive motor 2 Output shaft 3 Planetary reduction gear 4 Sliding member 5 Hollow part 6 Sun gear 8 Output member (rotating internal gear)
9 Planetary gear 10 Carrier 14 Threaded part (thread groove)
17 Flat surface 18 Fixed internal gear

Claims (6)

A planetary speed reducer provided on the output shaft of the drive motor, wherein the planetary speed reducer converts the rotation of the drive motor into a linear reciprocating motion of the sliding member after decelerating the speed through the planetary speed reducer. the outer periphery of the output member of the formula reducer, forming a threaded portion of the slide member and screwed, has a flat surface on at least a portion of the outer diameter of the driving motor, the sliding member and the flat surface A linear actuator characterized by a contact surface .   The planetary reducer includes a sun gear coaxially provided on an output shaft of a drive motor, a rotating internal gear that is an output member screwed with the sliding member that is prevented from rotating, and a rotation with the sun gear. It is a planetary gear mechanism composed of a plurality of planetary gears interposed between the internal gears so as to mesh with both of them and a carrier that rotatably holds these planetary gears at equal intervals in the circumferential direction. The linear motion actuator according to claim 1.   The planetary reduction device includes a sun gear coaxially provided on an output shaft of a drive motor, a rotary internal gear that is an output member screwed with the sliding member that is prevented from rotating, and a drive motor. A fixed fixed internal gear, a plurality of planetary gears interposed between the sun gear, the rotating internal gear and the fixed internal gear so as to mesh with both, and the planetary gears at equal intervals in the circumferential direction; The linear motion actuator according to claim 1, wherein the linear motion actuator is a mysterious planetary gear mechanism composed of a carrier that is rotatably held.   The linear actuator according to any one of claims 1 to 3, wherein the sliding member has a hollow portion, and the driving motor and the planetary speed reducer are accommodated in the hollow portion. Linear actuator according to any one of claims 1 to 4, characterized in that the components including the components and the sliding member constituting the planetary reduction gear was made of resin. 6. The linear actuator according to claim 5 , wherein the resin component is formed of an engineering plastic containing polyacetal, polyimide, and polyphenylene sulfide.

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