TWI455458B - Linear actuator - Google Patents

Description

Linear actuator

The present invention relates to a linear actuator that converts a rotational motion of a drive motor into a linear motion for output.

The present application claims priority to Japanese Patent Application No. 2007-243918, filed on Sep.

For example, a linear actuator that converts a rotational motion of a drive motor into a linear motion and outputs it is known, for example, as disclosed in Patent Document 1. The linear actuator includes a drive motor, a planetary reducer provided on an output shaft of the drive motor, and a driven member screwed to an output member of the planetary reducer.

The rotation of the drive motor is transmitted to the output member after being decelerated by the planetary reducer, and is converted into a thrust force that linearly moves the driven member screwed to the outer peripheral surface of the output member in the axial direction of the rotary shaft of the drive motor.

When the rotation of the output member is transmitted to the driven member, in order to prevent the output member and the driven member from rotating synchronously around the rotating shaft, it is necessary to provide the rotation preventing member.

Therefore, in Patent Document 1, a flat motor having a flat surface is used in the outer periphery of the drive motor, and the flat surface of the drive motor is slid in contact with the rotation stop portion provided on the driven member to perform the above-described rotation stop.

Further, in the linear actuator disclosed in Patent Documents 2 and 3, the stator of the drive motor is fixed to the frame of the linear actuator body, and the nut member is provided by the rotary sub-connection on the inner peripheral side of the stator. Female threaded portion and The male thread portion of the output shaft provided on the inner circumference side of the rotor is screwed to convert the rotation of the drive motor into a linear motion of the output shaft.

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2003-250246

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2001-231241

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2000-220715

However, in the linear actuator disclosed in Patent Document 1, since the driven member is prevented from rotating by the flat surface on the outer circumference of the drive motor having a low dimensional accuracy, the driven member is shaken around the rotary shaft of the drive motor. The problem of reduced positional accuracy. Further, the linear motion stroke of the linear actuator can ensure the length in the axial direction of the aforementioned rotating shaft of the flat surface of the drive motor, so that the use thereof is limited, and it is difficult to meet various expectations.

Further, in the linear actuator of Patent Document 1, since the thrust load received from the axial direction is received by the rotating shaft of the drive motor or the planetary reducer, the use of the device is further limited in consideration of the durability of the device.

Further, in the linear actuator disclosed in Patent Documents 2 and 3, it is necessary to arrange the output shaft whose output linear motion is transmitted through the inside of the drive motor. However, the drive motor configured as described above is not a general member, and therefore is manufactured. The increase in the cost of dedicated motors cannot be avoided. Further, since the output shaft is formed to have a small diameter, if the guide mechanism or the like is provided on the output shaft to secure the strength, the apparatus as a whole will increase.

The present invention has been made in view of the foregoing circumstances, and an object thereof is to provide a linear actuator that can drive a driven member around a rotating shaft without shaking The high-precision positioning and transmission ensure that the stroke of the linear motion is relatively long, ensuring the strength with respect to the thrust load, and the device can be constructed with low cost and compactness.

To achieve the foregoing objects, the present invention provides the following means. That is, the linear actuator of the present invention includes: a drive motor; a shaft portion that accommodates the drive motor; a rotation shaft rotatably coupled to the drive motor; and an output member having a male screw portion on an outer peripheral surface thereof; and an output member and the shaft The outer circumference of the portion, and the inner peripheral surface thereof has a driven member that receives the female thread portion of the rotation of the male thread portion; a rotation regulating portion that regulates the relative rotation of the shaft portion and the driven member; and a thrust load that receives the axial direction of the rotating shaft Bearing part.

According to the linear actuator of the present invention, there is provided a rotation regulating portion that regulates relative rotation of the shaft portion and the driven member, and the rotation regulating portion can have a relative position of the shaft portion and the driven member around the axis Precision positioning. Therefore, as before, the wobble caused by the regulation of the relative rotation of the shaft portion and the driven member, such as the flat surface of the outer circumference of the drive motor, which is low in dimensional accuracy, will not occur. That is, since the shaking around the aforementioned axis of the shaft portion and the driven member can be satisfactorily prevented, and the linear motion of the axial direction of the shaft portion and the driven member is guided with high precision, the positioning and transmission can be performed with high precision. .

In addition, the linear motion is performed on the flat surface of the outer circumference of the drive motor having a shorter length in the axial direction than in the prior art, and is performed along the rotation regulation portion provided on the axial portion and the driven member. The length of the aforementioned axial direction of the rotation regulating portion is set to be long to ensure the straightness of the linear actuator The stroke of the line motion is relatively long.

Further, since it is not necessary to prepare a special shape as the drive motor, a general small motor can be used, so that the cost of the drive motor can be reduced and the cost can be reduced.

Further, the shaft portion houses the protective drive motor and has a relatively large diameter with respect to the diameter of the entire device, and the strength can be favorably ensured, so that the durability is high.

Therefore, the guide mechanism or the like for ensuring the strength of the shaft portion as before is not necessary, and the device can be made compact.

Further, since the bearing portion that receives the thrust load in the axial direction is provided, there is no possibility that the rotating shaft of the driving motor or the speed reducer receives the thrust load due to malfunction or damage, so that the durability of the device can be further improved.

Further, in the linear actuator according to the present invention, the rotation regulating portion may include: a rotation regulating groove extending in the axial direction on the outer circumferential surface of the shaft portion; and the driven member being coupled to the rotation member A rotating gauge member that regulates the groove.

According to the linear actuator of the present invention, the outer peripheral surface of the shaft portion is provided with a rotation regulating groove extending, for example, by a spline groove extending in the axial direction of the rotary shaft of the drive motor, and the inner peripheral surface of the driven member is provided with, for example, A rotation regulating member composed of a projecting sliding material, and the rotation regulating grooves are engaged with the rotation regulating member to constitute a rotation regulating portion. Further, the rotation regulating portion regulates the relative rotation around the axis of the shaft portion and the driven member to prevent the driven member from being shaken, and guides the linear motion in the axial direction with high precision, so that the rotation can be performed with high precision Positioning, transmission.

Further, in the linear actuator of the present invention, the shaft portion further includes a speed reducer that decelerates the rotation of the drive motor, and the output member may be provided on an output shaft of the speed reducer. Further, as the speed reducer, if a singular planetary gear mechanism is used, for example, the reduction ratio is set to be extremely high, and the thrust of the linear motion can be sufficiently ensured even with a relatively small drive motor. Therefore, the drive motor can be further miniaturized, and the device can be made compact.

Further, the linear actuator of the present invention may further include a position detecting mechanism that detects a relative position of the shaft portion and the driven member. Further, by using, for example, a linear potentiometer as the position detecting means, the relative position of the axial direction of the shaft portion and the driven member is detected, and based on this, the rotation, the stop, the positive rotation, and the reverse rotation of the drive motor are controlled. Complex control can be used for a variety of expectations and uses.

[Effects of the Invention]

According to the linear actuator of the present invention, the driven member around the rotating shaft of the driving motor can be positioned and transmitted with high precision without shaking, and the stroke of the linear motion can be ensured to be relatively long, and the strength with respect to the thrust load can be ensured. Low cost and compact composition.

[Embodiment]

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 and 2 are side cross-sectional views showing a schematic configuration of a linear actuator according to an embodiment of the present invention, and Figs. 3 and 4 are linear representations of an embodiment of the present invention. A perspective view of the appearance of the actuator. 1 and 3 are linear actuators in a contracted state, and FIGS. 2 and 4 are linear actuators in an extended state.

As shown in FIG. 1 and FIG. 2, the linear actuator 1 of the present embodiment includes a small drive motor 2 and a substantially cylindrical shaft portion 4 that houses the speed reducer 3, and is formed to be slightly the same as the shaft portion 4. A substantially cylindrical output member 5 having an outer diameter of the diameter; a substantially cylindrical driven member 6 accommodating the shaft portion 4 and the output member 5; and a position detecting member 7 disposed on the outer circumference of the driven member 6.

As the drive motor 2, for example, a general-purpose small DC motor can be used. The drive motor 2 of the present embodiment has a substantially columnar shape, and its distal end (the right side in FIGS. 1 and 2) includes a rotating shaft 2a which is formed to rotate around the axis C. Further, the rear end of the drive motor 2 (the left side in FIGS. 1 and 2) is provided with a terminal 2b for supplying electric power to the drive motor 2.

Further, on the front end side of the drive motor 2, a speed reducer 3 having a diameter which is slightly the same as the outer diameter of the drive motor 2 is disposed. The speed reducer 3 has a so-called singular planetary gear mechanism, and includes a sun gear 3a that is coupled to a rotating shaft 2a of the drive motor 2 and that is rotatable about a rotation axis C, and a toothed shape that is engaged with a peripheral surface of the sun gear 3a. A plurality of planetary gears 3b are provided.

The fixed internal gear 3c and the movable internal gear 3d which are meshed with the planetary gear 3b are provided on the inner peripheral surface of the planetary gear 3b, and are disposed so as to overlap in the direction of the axis C. Further, the fixed internal gear 3c and the movable internal gear 3d are arranged such that the planetary gear 3b is slightly engaged with each other in the direction of the axis C. The fixed internal gear 3c is coaxially fixed to the front end side of the drive motor 2 so that the axis C is coaxially fixed to the center thereof, and the movable internal gear 3d is also coaxially coaxial with the axis C near the center thereof, and is rotatable around the axis C. Rotatingly Furnished. Further, the number of teeth of the movable internally toothed gear 3d is set differently from the minimum number of teeth of the fixed internally toothed gear 3c, and the reduction gearbox 3 can be configured to obtain a high reduction ratio.

Further, the front end portion of the movable internal gear 3d is a slightly cylindrical output shaft 3e which is smaller in diameter than the main portion thereof. A first bearing portion 11 composed of a radial ball bearing and a shaft output shaft 3e are disposed on a peripheral surface of the base end of the body portion close to the output shaft 3e. Further, the inner peripheral surface 3f of the hole portion opened at the front end of the output shaft 3e is subjected to female thread processing.

Further, a shaft portion 4 is disposed so as to cover the first bearing portion 11 and the drive motor 2 and the reduction gear 3 described above, and the inner circumferential surface of the shaft portion 4 is fixed to the outer peripheral surface of the first bearing portion 11 and the drive motor 2 outside the perimeter. The rear end of the shaft portion 4 is sealed by a shaft cap 4a composed of an insulator, and the terminal 2b of the drive motor 2 protrudes from the rear end of the shaft portion 4 through the shaft cap 4a.

The outer peripheral surface of the shaft portion 4 is provided with three bolt grooves (rotation regulating grooves) 4b extending in the direction of the axis C at equal intervals (120° intervals) in the circumferential direction. Further, the end surface of the front end of the shaft portion 4, the second bearing portion (bearing portion) 12 composed of the thrust ball bearing is inserted into the output shaft 3e of the reduction gear 3, and the front end surface of the second bearing portion 12 is disposed. The output member 5 having the male screw portion 5a on the outer circumference. The output member 5 is configured such that the bottom surface portion of the cylindrical hole opening toward the rear end abuts the front end surface of the second bearing portion 12 to receive the second bearing portion 12, and is fixed by the bolt 13 screwed to the inner circumferential surface 3f. On the output shaft 3e.

The driven member 6 is disposed on the outer circumference of the output member 5. The inner peripheral surface of the driven member 6 is engaged with the male screw portion 5a of the output member 5 to receive the female thread portion 6a of the rotation of the male screw portion 5a, and is slightly extended in the direction of the axis C thereof. Long distances are set continuously. Further, at the end portion of the rear end of the driven member 6, the projection-shaped rotation regulating member 6b which is slidably protruded in the three bolt grooves 4b of the shaft portion 4, and the three bolts which are equally spaced in the circumferential direction are also provided. The groove 4b is engaged, and the rotation regulating member 10 is constituted by the rotation regulating member 6b and the bolt groove 4b. The rotation regulating member 6b is formed of a sliding material made of, for example, a resin, and is fixed to the driven member 6.

Further, a linear potentiometer (position detecting member) 7 extending in the direction of the axis C is disposed on the outer circumference of the driven member 6. The linear potentiometer 7 has a rear end portion fixed to the shaft cap 4a of the shaft portion 4, and a detecting end 7a sliding in the direction of the axis C thereof is attached to the driven member 6, the axis of the driven member 6 and the shaft portion 4 The relative positional relationship in the C direction can be configured based on voltage change detection. Further, the linear potentiometer 7 is electrically connected to a control unit (not shown), and the control unit is electrically connected to the terminal 2b of the drive motor 2.

In addition, in Fig. 3 and Fig. 4, the outer peripheral surface of the driven member 6 (the right side in Figs. 3 and 4) has two bottomed cylindrical projections 6c arranged in the opposite direction, and the other shaft portion 4 The outer peripheral surface of the rear end of the shaft cap 4a (the left side in FIGS. 3 and 4) also has two bottomed cylindrical projections 4c arranged in the opposing direction. Therefore, for example, the protrusions 6c and 4c can be connected to the two members constituting the joint at the knuckle portion of the robot arm, thereby converting the reciprocating linear motion of the linear actuator 1 into the gripping operation of the robot arm. Use it.

Next, the operation of the linear actuator 1 of the present embodiment will be described.

In Fig. 1, the linear actuator 1 is in a state in which its full length is contracted to the shortest.

First, the control unit supplies electric power to the drive motor 2 to rotate the rotary shaft 2a, and the speed reducer 3 connected thereto transmits the rotation deceleration to the output shaft 3e. The output shaft 3e is rotated about the axis C.

The output member 5 connected to the output shaft 3e rotates around the axis C along the inside of the driven member 6 as the output shaft 3e rotates. The male screw portion 5a of the output member 5 is screwed to the female screw portion 6a of the driven member 6, and the shaft portion 4 and the driven member 6 are slid by the bolt groove 4b of the rotation regulating portion 10 and the rotation regulating member 6b. In combination, the gauges are made to move relative to each other about the axis C without relative rotation. Therefore, if the output member 5 rotates around the axis C, the equiaxed portion 4 and the driven member 6 slide in the direction of the axis C, and the linear actuator 1 is stretched.

Next, as shown in FIG. 2, the linear actuator 1 is extended to the longest state, and receives a control portion from the detection signal of the linear potentiometer 7, so that the rotation of the drive motor 2 is stopped, and the linear actuator 1 is caused. The stretch stops.

On the other hand, when the linear actuator 1 is contracted, electric power can be supplied from the control unit to the drive motor 2 so as to be rotated in the opposite direction to the rotation direction. Further, as shown in FIG. 1, the linear actuator 1 is contracted to the shortest state, and the control unit that receives the detection signal from the linear potentiometer 7 stops the rotation of the drive motor 2.

Further, since the detection signal from the linear potentiometer 7 is always transmitted to the control unit, the entire length of the linear actuator 1 is not limited to the shortest and longest state, and the rotation and stop of the drive motor 2 can be controlled at an arbitrary length. , positive rotation, reverse rotation.

As described above, according to the linear actuator 1 of the present embodiment, the outer peripheral surface of the shaft portion 4 is provided with a bolt groove (rotation regulating groove) 4b extending in the direction of the axis C of the rotary shaft 2a of the drive motor 2, and is driven. The inner peripheral surface of the member 6 is provided with a rotation regulating member 6b composed of a projecting sliding material, and the bolt groove 4b and the rotation regulation The members 6b are slidably engaged to constitute the rotation regulating portion 10, and are prevented from being shaken around the rotation axis C, and the linear movement of the shaft portion 4 and the driven member 6 in the direction of the axis C is guided with high precision. Therefore, it is possible to position and transmit with high precision.

In addition, the linear motion of the linear actuator 1 is performed along the peripheral flat surface of the drive motor as before, and is performed along the bolt groove 4b provided on the outer peripheral surface of the shaft portion 4, so that the shaft portion 4 is The length of the pinch groove 4b and the driven member 6 in the direction of the axis C is set to be long, respectively, and the stroke of the linear motion can be ensured to be relatively long.

Further, since the first bearing portion 11 that receives the radial load in the radial direction around the axis C and the second bearing portion 12 that receives the thrust load in the direction of the axis C, the two bearings can effectively withstand the load from each direction. Therefore, the durability of the device is high. In particular, since the second bearing portion 12 is provided, there is a possibility that the thrust load in the direction of the axis C does not cause malfunction or breakage due to the rotation shaft of the drive motor or the speed reducer. Further, according to this configuration, the linear actuator 1 can ensure sufficient strength with respect to the load even if it is linearly moved to reach the maximum extension state.

Further, since the motor 2 is driven by a so-called general-purpose small motor, it is not necessary to prepare a special specification for the drive motor 2, and the cost can be reduced.

Further, since the singular planetary gear mechanism is used as the speed reducer 3, the reduction ratio can be set to be very high, and the thrust of the linear motion can be sufficiently ensured even with the relatively small drive motor 2. Therefore, the device can be compact.

Further, the shaft portion 4 accommodates the drive motor 2 and the speed reducer 3 and protects the same, and the diameter thereof is formed to have a relatively large diameter with respect to the entire diameter of the device, so that the strength can be favorably secured and the durability is high.

Further, according to the above configuration, for example, the linear actuator 1 can be compactly controlled to have a diameter of about 15 mm, a full length (short) of about 50 mm, and a linear motion stroke of about 30 mm, and the thrust can be increased to About 500N. Therefore, it can cope with various expectations and uses that have not been completed before.

Further, since the linear actuator 7 as the position detecting mechanism is used in the linear actuator 1, the relative position of the shaft portion 4 and the driven member 6 is detected, and based on this, the rotation, the stop, the positive rotation, and the reverse rotation of the drive motor 2 are controlled. Therefore, more complex control can be performed, and more diverse kinds of expectations and uses can be handled.

The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit and scope of the invention. For example, in the present embodiment, as the rotation regulating portion 10, three outer peripheral surfaces of the shaft portion 4 are provided with three bolt grooves (rotation regulating grooves) 4b, and the other driven member 6 is provided with three rotations that are engaged with the bolt grooves 4b. The regulating member 6b is configured such that the pin grooves 4b and the rotation regulating member 6b are arranged at equal intervals in the circumferential direction. However, the present invention is not limited thereto, and the number of the pin grooves 4b and the number of the rotation regulating members 6b can be increased or decreased. It can also be configured by changing the interval between the circumferential directions.

In the present embodiment, the male screw portion 5a of the output member 5 is meshed with the female screw portion 6a of the driven member 6, and the male screw portion 5a and the female screw portion 6a are screwed together with the rotation of the output member 5 to cause the output member 5 and The driven member 6 is configured to move relative to each other along the axis C. However, the relative movement of the output member 5 and the driven member 6 is not limited to the movement by the sliding contact, and the movement by the rolling contact is also included. For example, the output member 5 and the driven member 6 may be stored between the male screw portion 5a and the female screw portion 6a by using a so-called ball screw. The plurality of balls move the output member 5 and the driven member 6 relatively.

In the present embodiment, the rotation regulating member 6b that is fastened to the plug groove 4b is described as a projecting sliding material. However, the present invention is not limited thereto, and the rotating regulation member 6b may be formed by a rotating body such as a ball or a roll. According to this, the sliding of the shaft portion 4 and the driven member 6 can be performed more smoothly, and the strength with respect to the radial load from the periphery of the axis C can be lifted, and positioning and transmission can be performed with higher precision.

In addition, although the rotation regulating groove is described using the pin groove 4b, the rotation regulating groove is not limited to this as long as it is a groove extending in the direction of the axis C, and can be engaged with the rotation regulating member 6b of the driven member 6. Yes, it can be other shapes.

Further, the rotation regulating groove may be formed in a curved shape or a spiral shape in the direction of the axis C in the outer peripheral surface of the shaft portion 4. Accordingly, for example, when the linear actuator 1 is extended and contracted, the relative positional relationship around the axis C of the shaft portion 4 and the driven member 6 can be rotated by 90°, respectively, and the use thereof can be realized. Further expansion.

In the present embodiment, the singular planetary gear mechanism is used as the speed reducer 3. However, the present invention is not limited thereto, and for example, a planetary gear mechanism, a spur gear mechanism, a planetary roller mechanism, or the like may be used. The speed reduction mechanism. However, if the singular planetary gear mechanism is used as in the present embodiment, it is preferable to obtain a high reduction ratio and ensure a high thrust, and it is possible to compact the speed reducer 3.

In the present embodiment, the drive motor 2 is described using a general-purpose small DC motor. However, the present invention is not limited thereto, and a stepping motor or a stepping motor may be used. DC brushless motor. Further, although the position detecting means is described using a linear potentiometer, the present invention is not limited thereto, and a sensor or a limit switch or a detecting end may be used to constitute a position detecting mechanism.

In the present embodiment, the first bearing portion 11 and the second bearing portion 12 are each illustrated as a ball bearing. However, the present invention is not limited thereto, and a roller bearing or a sliding bearing or a bearing other than the above may be used. . In addition, instead of the two bearing portions, a cross roller bearing that is subjected to a thrust load and a radial load together may be used to integrally form a bearing portion.

[Industry use possibility]

According to the present invention, it is possible to provide a linear actuator which can accurately position and transmit the driven member around the rotating shaft of the driving motor without shaking, and can ensure a relatively long stroke of the linear motion, ensuring a relative load with respect to the thrust. The strength makes the device low-cost and compact.

1‧‧‧linear actuator

2‧‧‧Drive motor

2a‧‧‧Rotary axis

3‧‧‧Reducer

3e‧‧‧ Output shaft

4‧‧‧Axis

4b‧‧‧Tie groove (rotation regulation groove)

5‧‧‧ Output components

5a‧‧‧ Male thread

6‧‧‧ driven components

6a‧‧‧Mask thread

6b‧‧‧Rotary regulatory components

7‧‧‧Linear potentiometer (position detection component)

10‧‧‧Rotation Regulation Department

12‧‧‧Second bearing part (bearing part)

C‧‧‧Rotation axis of the drive motor

Fig. 1 is a side cross-sectional view showing a schematic configuration of a linear actuator according to an embodiment of the present invention at the time of contraction.

Fig. 2 is a side cross-sectional view showing a schematic configuration of a linear actuator according to an embodiment of the present invention.

Fig. 3 is a perspective view showing the appearance of a linear actuator according to an embodiment of the present invention at the time of contraction.

Fig. 4 is a perspective view showing the appearance of the linear actuator according to an embodiment of the present invention when it is stretched.

1‧‧‧linear actuator

2‧‧‧Drive motor

2a‧‧‧Rotary axis

3‧‧‧Reducer

3e‧‧‧ Output shaft

4‧‧‧Axis

4b‧‧‧Tie groove (rotation regulation groove)

5‧‧‧ Output components

5a‧‧‧ Male thread

6‧‧‧ driven components

6a‧‧‧Mask thread

6b‧‧‧Rotary regulatory components

7‧‧‧Linear potentiometer (position detection component)

10‧‧‧Rotation Regulation Department

12‧‧‧Second bearing part (bearing part)

C‧‧‧Rotation axis of the drive motor

Claims (5)

A linear actuator comprising: a drive motor; a shaft portion accommodating the drive motor; a front end side of the rotation shaft of the drive motor and rotatably coupled to the rotation shaft, and an outer peripheral surface having a male thread portion The output member is disposed on the outer circumference of the output member and the shaft portion, and has an inner peripheral surface having a driven member that receives the female screw portion of the male screw portion; and the relative rotation of the shaft portion and the driven member is regulated a rotation regulating portion; and a bearing portion that receives the thrust load in the axial direction of the rotating shaft; and the rotation regulating portion includes: a rotation regulating groove formed by a bolt groove extending in the axial direction on the outer circumferential surface of the shaft portion; and a rotation regulating member provided on the driven member and engaged with the rotation regulating groove. The linear actuator of claim 1, wherein the rotation regulating groove is formed in a gentle curve or a spiral shape with respect to the axial direction. The linear actuator according to claim 1 or 2, wherein the shaft portion further accommodates a speed reducer that decelerates rotation of the drive motor, and the output member is provided on an output shaft of the speed reducer. The linear actuator of claim 1 or 2 further comprising a position detecting mechanism that detects a relative position of the shaft portion and the driven member. A linear actuator according to claim 3, further comprising: a position detecting mechanism that detects a relative position of the shaft portion and the driven member.