JP7041460B2 - Screw tightening machine - Google Patents

Description

The present invention relates to a screw tightening machine provided with a planetary gear mechanism that increases an input rotational force.

As shown in Patent Document 1, the conventional screw tightening machine includes a speed reducer which is an example of a so-called planetary gear mechanism, and is described later. A sun gear that rotates integrally with a motor shaft and a plurality of sun gears around the shaft of the sun gear. It is provided with a planetary gear that is individually arranged and engages with a sun gear, an output shaft that rotatably supports each of these planetary gears, and an internal gear that is inserted into the sun gear and engages with the planetary gear. Further, these planetary gears, output shafts, and internal gears are each equipped with bearings for reducing rotational resistance.

The conventional screw tightening machine described above includes a motor provided with a motor shaft connected to the sun gear and driven to rotate, and a torque sensor fixed to the motor and capable of detecting torque by receiving the rotational force of the internal gear. It is configured so that the reaction force torque applied to the internal gear can be detected as the output torque applied to the output shaft. Further, a conventional screw tightening machine is configured by connecting a bit that can be fitted to a screw, which is an example of a fastening component to be fastened to the work, to the output shaft. As a result, the conventional screw tightening machine can input the rotation of the motor to the speed reducer and fasten the screw fitted to the bit to the work.

Further, the torque sensor is composed of a pipe-shaped strain generating body through which the sun gear can be inserted and a strain gauge attached to a thin portion of the strain generating body. One end of the strain-causing body is fixed to the motor, while the other end is connected to the internal gear.

As a result, in the conventional screw tightening machine, the reaction force torque corresponding to the rotational load of the output shaft is transmitted to the internal gear, and the strain-causing body connected to the internal gear is elastically deformed in the twisting direction. , A signal corresponding to the elastic deformation is emitted from the strain gauge to the outside, and the output torque is detected.

Japanese Unexamined Patent Publication No. 2016-97460

However, although the conventional screw tightening machine has bearings attached to each gear as described above, for example, the sun gear does not have the bearing, and the internal gear has one on one side of the motor. Only one bearing is placed. Therefore, the sun gear and the internal gear tend to tilt with respect to the axis of the reducer, and the contact with the planetary gear engaged with the sun gear and the internal gear becomes partially strong, so that the tooth portion of the sun gear, the internal gear, and the planetary gear becomes stronger. However, there was a problem that they were easily worn locally. Further, although two bearings attached to the output shaft are arranged, the attachment positions thereof are arranged so as to be continuous near the middle in the total length direction of the output shaft. Therefore, since the output shaft is not supported at both ends and is in a cantilevered state, it is easily tilted with respect to the axis of the screw tightening machine . Therefore, since the above-mentioned planetary gears are more easily tilted, there is also a problem that the above-mentioned wear is more likely to be locally worn than the above-mentioned wear.

Similarly, in the conventional screw tightening machine, since the internal tooth gear and the like are rotatably supported in a so-called cantilever state, the strain-causing tube integrated with the internal gear is also easily tilted. Therefore, there is also a problem that the accuracy error of the detection torque is large, such that the detection torque when tilted is poor and the detection torque when not tilted is good.

Further, in the conventional screw tightening machine, since the internal gear or the sun gear is easily tilted as described above, the torque transmission efficiency to the output shaft is reduced. As a result, when selecting the motor, it is necessary to select a motor having a capacity that is expected to reduce the torque transmission efficiency and exert a high rotational force, and there is also a problem that the cost of the motor increases.

The screw tightening machine according to the present invention was created in view of the above problems, and is arranged around an upper frame that fixedly supports the motor, a sun gear connected to the motor, and the axis of the sun gear. A planetary gear, an internal gear that meshes with the planet gear and is contained in an upper frame and is rotatably arranged, an output shaft that rotatably supports the sun gear and the planetary gear, and the internal tooth. In a screw tightening machine provided with a lower frame that regulates the rotation of the gear and rotatably supports the output shaft, the internal gear is supported by a plurality of bearings that are spaced apart from each other in the axial direction. The output shaft is supported by a bearing arranged at a position longer than the support interval of the bearing that supports the internal gear, and the lower frame engages with the internal gear. It is characterized in that the strain-causing body is included, and the strain-causing body is formed by externally outputting the reaction force of the internal gear. It is desirable that the output shaft is supported by bearings arranged on the upper frame and the lower frame, respectively. Further, it is desirable that the sun gear is supported by a plurality of bearings arranged apart from each other in the axial direction. Further, it is desirable that the planetary gear is provided with bearings at both ends thereof.

Since the screw tightening machine of the present invention includes an output shaft that is pivotally supported by a plurality of bearings while holding the sun gear, planetary gear, and internal gear, the output shaft is provided even if the sun gear or the like is tilted. Is hard to tilt. Therefore, there is an advantage that the output loss of rotation can be reduced and the transmission efficiency can be improved.

Further, in the screw tightening machine of the present invention, bearings are arranged on both sides of the gear portion of the sun gear and the internal gear, and these sun gear and the internal gear are both held by the bearing. As a result, the sun gear and the internal gear are also less likely to tilt like the output shaft described above, so that there is an advantage that the output loss of rotation is further reduced. Further, since the screw tightening machine of the present invention has a structure in which at least the sun gear and the internal gear are difficult to tilt, there is an advantage that local wear can be reduced as compared with the conventional case, and the input motor shaft is used. There is also an advantage that the rotation of the head can be transmitted to the output shaft with high efficiency.

Further, since the screw tightening machine of the present invention is provided with a strain-causing body that regulates the rotation of the internal gear, and a strain gauge is attached to the strain-causing body, the reaction torque of the internal gear is output. It can be detected as the torque received by the shaft. Therefore, since the strain-causing body is purely elastically deformed in the twisting direction without causing inclination with respect to the axis of the rotation axis, there is an advantage that the torque accuracy to be detected can be improved as compared with the conventional case.

It is a partial notch sectional view which shows one Embodiment which concerns on this invention. It is a perspective view which shows the whole of FIG.

Hereinafter, the screw tightening machine 50 of the present invention will be described with reference to FIGS. 1 and 2. The screw tightening machine 50 of the present invention has a motor M in which a motor shaft M1 protruding from one end is rotatably supported by a bearing B, and a motor shaft M1 extending downward of the motor M1 and being connected to the motor shaft M1. It is composed of a speed reducer 1 that increases the rotational force.

The speed reducer 1 includes a sun gear 2 that rotates together with the motor shaft M1, a planetary gear 3 that meshes with the sun gear 2, and a plurality of shafts of the planet gear 3 that mesh with each other around the axis of the sun gear 2. It is composed of an output shaft 4 and an internal gear 5 that forms an inner peripheral surface that meshes with the planetary gear 3 and constantly includes the planetary gear 3 in a meshed state.

The sun gear 2 is formed by inserting the motor shaft M1 into the upper portion thereof and fixing the sun gear 2 so as to rotate integrally with the motor shaft M1. Further, a gear portion matching the gear shape formed in the planetary gear 3 is formed in the lower portion of the sun gear 2, and a rotary shaft can be rotatably supported at both ends of the gear portion of the sun gear 2. Bearings 20a and 20b are arranged respectively. The bearing 20a is attached to the upper part of the output shaft 4, while the bearing 20b is attached to the vicinity of the middle of the output shaft 4.

The planetary gears 3 are arranged in three equal parts around the axis of the sun gear 2 and are configured to rotate in a direction opposite to the rotation direction of the sun gear 2. Further, these planetary gears 3 are provided with bearings 20c and 20d arranged at the upper and lower portions thereof, respectively, and are pivotally supported by pins 4a inserted into the inner diameters of these bearings 20c and 20d and attached to the output shaft 4. Consists of.

The output shaft 4 is rotatably supported by a bearing 20e attached to an upper frame F1 to which the motor M is fixed and a bearing 20f attached to the lower portion of a lower frame F2 arranged on the lower end side of the upper frame F1. Has been done. Further, the output shaft 4 is arranged with the bearings 20a and 20b that support both ends of the gear portion of the sun gear 2, and supports the sun gear 2 so as to rotate smoothly. Further, the output shaft 4 includes pins 4a that can be inserted into the bearings 20c and 20d of the planetary gear 3, and these pins 4a are such that the planetary gear 3 meshes with the gear portion of the sun gear 2. It is arranged so as to be located around the axis of. Further, the output shaft 4 is formed by rotatably arranging bearings 20g and 20h on the upper and lower portions of the planetary gear 3, and collars 11 and 12 are arranged on the outer rings of these bearings 20g and 20h. Further, the output shaft 4 is configured so that a bit (not shown) engaged with a screw, which is an example of a fastening component to be fastened to a work (not shown), can be connected.

In the internal gear 5, the internal teeth 5a that mesh with the planetary gear 3 are formed over the inner peripheral surface thereof, and the upper frame is such that the collars 11 and 12 are located at both ends of the internal teeth 5a. It is built in F1 and is configured to be rotatable in the upper frame F1. Further, a strain-causing body fitting member 5c fixed integrally with the internal gear 5 is arranged below the internal gear 5.

The strain-generating body fitting member 5c and the lower frame F2 are provided with spline holes 5cs and F2s, respectively. It is connected by 6. In this way, since the strain-causing body 6 is fitted into the strain-causing body fitting member 5c and the spline holes 5cs and F2s of the lower frame F2, the sun gear 2 rotates in the internal gear 5. Is also regulated so that it does not rotate. As a result, the planetary gear 3 revolves around the axis of the rotating sun gear 2, so that the output shaft 4 provided with the planetary gear 3 is decelerated to a predetermined rotation speed and rotates.

Further, the strain-causing body 6 has a strain gauge (not shown) attached to the outer peripheral portion 6a thereof, and is configured to be able to output a force in the twisting direction generated on the outer peripheral portion 6a of the strain-causing body 6 as a voltage. The voltage detected by this strain gauge is transmitted to the amplifier board 7a built in the box 7 arranged so as to project from the upper frame F1 and the lower frame F2, and further as torque applied to the output shaft 4 to the outside. It is being output.

Further, the total length of the output shaft 4 is set longer than that of the sun gear 2 and the internal gear 5, and the bearings 20e and 20f that support the output shaft 4 in a state of holding both of them are the bearings 20a. , 20b, the bearings 20c, 20d, or the bearings 20g, 20h are held together so that the support spacing is longer than the support spacing of each component. As a result, the output shaft 4 that receives an external force from a direction orthogonal to the axial direction can hardly tilt with respect to the axis of the reducer 1 and can always maintain a posture that matches the axis of the reducer. Therefore, the planetary gear 3 and the sun gear 2 that are pivotally supported by the planetary gear 3 are not tilted, and the axis of the internal gear 5 rotatably supported by the non-tilting output shaft 4 can be kept aligned with the axis of the reducer. can. Therefore, the screw tightening machine 50 can output rotation without tilting the output shaft 4 so as to coincide with the axis of the motor shaft M1. As a result, the screw tightening machine 50 does not tilt by itself due to gravity even if it is mounted in an oblique direction, so that it has an advantage of having high transmission efficiency even when it is used in various mounting directions.

In the present embodiment, the strain gauge is attached to the strain generator 6, but the present invention is not limited to this, and if it is not necessary to detect the torque of the output shaft 4, the strain generator is strained. The pipe 6 may be simply used as the rotation stop member of the internal gear 5, and the internal tooth 5a that meshes directly with the planetary gear 3 may be formed on the inner peripheral surface of the upper frame F1.

1 Reducer 2 Sun gear 3 Planetary gear 4 Output shaft 5 Internal gear 5c Distortion body fitting member 6 Distortion body 20g Bearing 20f Bearing 50 Screw tightener F1 Upper frame F2 Lower frame M Motor M1 Motor shaft

Claims (4)

An upper frame that fixedly supports the motor, a sun gear connected to the motor, a planetary gear arranged around the axis of the sun gear, and meshed with the planetary gear, are included in the upper frame and rotatably arranged. The internal gear, the output shaft that rotatably supports the sun gear and the planetary gear, and the lower frame that rotatably supports the output shaft while restricting the rotation of the internal gear. In the prepared screw tightening machine
The internal gear is supported by a plurality of bearings spaced apart from each other in the axial direction.
The output shaft is supported by a bearing arranged at a position longer than the support interval of the bearing that supports the internal gear by both sides .
The lower frame contains a strain-causing body that engages with the internal gear.
The strain-causing body is a screw tightening machine characterized in that the reaction force of an internal gear is output to the outside. The screw tightening machine according to claim 1, wherein the output shaft is supported by bearings arranged on the upper frame and the lower frame, respectively. The screw tightening machine according to claim 1 or 2, wherein the sun gear is supported by a plurality of bearings arranged apart from each other in the axial direction. The screw tightening machine according to any one of claims 1 to 3, wherein the planetary gear is provided with bearings at both ends thereof.

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