JPH0466655B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention provides an automatic screwdriver configured to eliminate the influence of inertia of a driver bit when screw tightening is completed and to reliably tighten screws with a desired screw tightening torque. Regarding tightening machines.

Conventional technology Conventionally, in order to eliminate the influence of the inertia of the driver bit when screw tightening is completed, devices generally tighten the screw at high speed and low torque until the screw is seated on the workpiece, and then tighten the screw at low speed and high torque after seating. It is true. An example of this type of device is a power screw tightening machine with an automatic transmission described in Japanese Utility Model Publication No. 51-14556. In this screw tightening machine, as shown in FIGS. 8 and 9, the drive shaft of the motor 19 is connected to a planetary gear mechanism 41.
This drive gear 4 constitutes a drive gear 42.
2 meshes with a ring gear 43 via a planetary gear 44. The planetary gear 44
The rotation is transmitted to the output shaft 45 via the carrier pin 49. Further, the ring gear 43 is connected to the output shaft 45 via a slip clutch 46, and when a torque of a predetermined torque or more is applied to the ring gear 43 due to the load torque of the output shaft 45, the output shaft 45 and the ring gear 4
3 is disengaged, and from now on planetary gear 4
4 rotates independently along a ring gear 43 to rotate an output shaft 45.

In this screw tightening machine, until the screw is seated on the workpiece, the rotation speed of the motor 19 is transmitted to a driver bit (not shown) at the tip of the output shaft 45 via the planetary gear 44, and the screw is driven at high speed and low torque. It can be tightened with. After that, when the screw comes into contact with the workpiece and the tightening torque approaches the predetermined torque,
With the slip clutch 46 disengaged, the ring gear 43, which had been rotating together with the output shaft 45, receives the rotation of the planetary gear 44 and receives a rotational force in the opposite direction, but at that position, the ring gear 43 is rotated by the rotation of the planetary gear 44 and receives a rotational force in the opposite direction. 48, the planetary gear 44 rotates along the ring gear 43. Therefore, the rotation speed of the motor 19 is reduced according to the gear ratio of the planetary gear 44 and the ring gear 43, so that the screw is tightened at low speed and high torque.

Problems to be Solved by the Invention In the screw tightening machine described above, the rotational speed of the driver bit is reduced immediately before screw tightening is completed, but the reduction ratio is determined by the gear ratio between the planetary gear 44 and the ring gear 43. However, there are limitations to the size of the device, and there is also a limit to the deceleration of the driver bit, and the number of rotations of the motor 19 must be set low in advance, resulting in the disadvantages that it takes a long time to tighten the screws. is occurring. Moreover, since the driver bit continues to rotate, although it is decelerated, not only is there a need for a means to stop it at a predetermined position, but it is also necessary to completely eliminate the influence of the inertia of the driver bit when it stops. However, there are drawbacks such as the fact that the screws are tightened to a torque exceeding a predetermined torque, making it impossible to perform accurate tightening work.

Means for Solving the Problems The present invention aims to eliminate the above-mentioned drawbacks.
The rotation of the drive shaft of the rotational drive source is configured to be transmitted to the input disk of the differential planetary mechanism. A plurality of planetary cones each having a transmission surface made of a circumferential groove that frictionally engages with the input disk are disposed on the input disk.
Moreover, a cam disk is arranged so as to frictionally engage with the transmission surface formed by the flat back surface of the planetary cone 23, so that the planetary cone rolls and the rotation of the input disk is extracted as rotation of the cam disk. It is configured as follows.

A speed change ring is disposed so as to be in common frictional engagement with the conical surface of the planetary cone, and this speed change ring is held by an elastic body, and when the load torque related to the driver bit is applied to the speed change ring, the speed change ring is The elastic body is bent so that the speed change ring slides along the conical surface and changes its frictional engagement position.

Further, a dog clutch is connected to the cam disc, and the rotation of the cam disc is configured to be transmitted to the driver bit via the dog clutch.

Effect: Therefore, when the rotary drive source rotates, the input disk of the differential planetary gear mechanism rotates. Along with this, the planetary cone that is frictionally engaged with the input disk rotates at that position, and the rotation of the planetary cone is transmitted to the cam disk. This cam disk rotates while reducing the rotational speed of the input disk at a reduction ratio determined by the position where the speed change ring frictionally engages with the conical surface of the planetary cone, and its rotation rotates integrally with the input disk through the meshing clutch. transmitted to the driver bit. At this time, the driver bit tightens the screw, the torque applied to the driver bit increases, and the rotational speed of the driver bit decreases. Along with this, the torque applied to the speed change ring also increases, the elastic body is deflected in accordance with this torque, and the frictional engagement position of the speed change ring moves toward the larger diameter side of the conical surface of the planetary cone. The speed change ring moves to a position where its torque and the elastic force of the elastic body are balanced, and stops at that position. Therefore, the driver bit gradually tightens the screw at low speed and high torque, but as the rotational speed of the driver bit decreases, the reduction ratio also increases continuously, and eventually the output shaft is rotated by the input disc. Despite this, the screw reaches zero rotation while being held at high torque, completing screw tightening.

When the screw tightening is completed and the driver bit rises, the dog clutch is disengaged, the high torque retention of the driver bit is released, and the driver bit is detached from the screw without any problem.

Embodiments Hereinafter, embodiments will be described with reference to the drawings. In FIGS. 1 to 3, reference numeral 1 denotes an automatic screw tightening machine, which has a support 3 implanted in a base 2. As shown in FIG. A fixed plate 4 is fixed to this support column 3, and upper brackets 5 are attached to this fixed plate 4 above and below.
and the lower bracket 6 are fixed. A cylinder 7 is fixed to the upper bracket 5, and a driver mounting base 8 is fixed to its rod (not shown). A chuck stand 10 elastically biased by a first spring 9 is arranged at a predetermined interval on the driver mounting stand 8,
This driver mounting base 8 is configured to move together with the driver base 10 along a guide shaft 11 to a predetermined position. Further, a driver main body 12 is fixed to the upper part of the driver mounting base 8, and this driver main body 12 is configured to rotate a driver bit 14 via a connecting mechanism 13. On the other hand, the desk 10
A chuck unit 15 is fixed to the chuck unit 1, and the driver bit 14 is connected to the chuck unit 1.
5, and a screw (not shown) held by the chuck claw 15a is screwed into a predetermined position.

The driver main body 12 has an inner cylinder part 17 fixed to the driver mounting base 8 via a fixture 16, and a housing 18 integrated with this bottom part 17a. Moreover, this driver main body 12 has a motor 19 as a rotational drive source fixed to the housing 18, and a drive shaft 19a of the motor 19 is located in a space formed by the housing 18 and the inner cylindrical portion 17 to form an automatic transmission. The input disk 21 of the differential planetary mechanism 20 is connected. This input disk 21 has an annular portion 21a on its outer periphery, and this annular portion 21a is a transmission surface formed by circumferential grooves 23a of a plurality of planetary cones 23 held with their axes inclined by a cone holder 22. It is configured to frictionally engage with. Moreover, this planetary cone 23 has a flat surface 23b on the back surface,
A cam disk 24 is frictionally engaged with this flat surface 23b, and holds this planetary cone 23 between it and the input disk 21. Further, a speed change ring 25 is positioned around the planet cone 23 so as to be in contact with its conical surface 23c, and this speed change ring 25 has a piano wire 26, which will be described later, which has one end fixed to the inner cylindrical portion 17 side. are connected to each other, and this speed change ring 25 is located at a predetermined distance from the bottom of the inner cylindrical portion 17, and the speed change ring 25 is configured to be rotatable and slidable along the conical surface 23c. . This piano wire 26 is bent in accordance with the torque applied to the speed change ring 25, and the position of frictional engagement of the speed change ring 25 with the conical surface 23c changes, whereby the rotational speed of the cam disk 24 is changed to the continuous speed reduction ratio. It is configured to decrease by change. Further, when the frictional engagement position of the speed change ring 25 reaches the position shown in FIG. 4 (a position satisfying a:b=c:d), the cam disc 24 is configured to make zero rotation. .

A pressure regulating mechanism 27 is connected to the cam disc 24, and the cam disc 24 is connected to the planetary cone 23.
It is configured to press. Further, the pressure regulating mechanism 27 has a connecting shaft 28, which passes through the cam disk 24 and is rotatably held via a bearing fixed to the upper part of the inner cylindrical portion 17. ing. An oil seal mechanism is disposed around the connecting shaft 28 and is configured to fill oil between the housing 18 and the inner cylindrical portion 17 to prevent wear of the differential planetary mechanism 20.

Furthermore, a clutch shaft 29 is connected to the connecting shaft 28, and a drive clutch portion 3 is connected to the lower end of the clutch shaft 29.
0 is inserted into the clutch shaft 29 so that the distal end of the clutch shaft 29 protrudes, and the distal end of the clutch shaft 29 is connected to a driven clutch portion 32 which will be described later.
It is configured to be located in the hollow part of. The drive clutch portion 30 and the clutch shaft 29 are connected by a second spring 31, and the second spring 31 absorbs the inertia that the connecting mechanism 13 and the driver bit 14 have when they rotate. . A driven clutch portion 32 is rotatably disposed below the driving clutch portion 30, and the clutch shaft 29 is inserted into the driven clutch portion 32. A spring 33 is arranged. Also,
The driven clutch portion 32 has a hollow portion, and a locking pin 34 is attached to protrude into the hollow portion as shown in FIG. 6. This locking pin 34 has a hemispherical portion at its tip, and this locking pin 34 engages with a pin 35 implanted in the clutch shaft 29, so that the rotation of the clutch shaft 29 is constantly transmitted to the driven clutch portion 32. It is configured to Further, the driven clutch portion 32 has a driven clutch shaft 32a, and the connecting mechanism 13 is connected to the driven clutch shaft 32a, so that the rotation of the motor 19 is transmitted to the driver bit 14. There is.

On the other hand, as shown in FIG. 5, a torque adjustment sleeve 36 is slidably disposed on the outer periphery of the inner cylindrical portion 17, and the bottom 17a of the inner cylindrical portion 17 integrated with the housing 18 and the A plurality of piano wires 26, which are linear elastic bodies, are fixed between the speed change ring 25 and the speed change ring 25. The torque adjustment sleeve 36 has notched grooves 36a at equal intervals on its outer periphery, and the piano wire 26 fits into the notched grooves 36a.
is configured to pass through. Further, the torque adjustment sleeve 36 has a flange portion, and an adjustment bolt 37 rotatably held in the bottom portion 17a of the inner cylindrical portion 17 at that position is screwed into the flange portion, and the torque adjustment sleeve 36 has a flange portion. By changing the height position of the adjustment sleeve 36, the spring constant of the piano wire 26 is changed, so that an elastic force corresponding to the tightening torque can be obtained.

In the above automatic screw tightening machine, when the motor 19 rotates, the rotation is transmitted from the input disk 21 to the cam disk 24 via the planetary cone 23, and the speed change ring 25 frictionally engages with the conical surface 23c of the planetary cone 23. It is decelerated by a reduction ratio determined by the position. This rotation of the cam disk 24 is transmitted to the drive clutch section 30. At this time, the drive clutch portion 3
0 and the driven clutch part 32 are not fitted, but the pin 35 of the clutch shaft 29 and the locking pin 34 of the driven clutch part 32 are engaged, and the cam disc 2
4 rotation is transmitted to the driver bit 14.

In this state, when the driver body 12 is lowered by the operation of the cylinder 7, the driver bit 14 is fitted into the screw in the chuck pawl 15, and the screw is seated on the workpiece, and the relative relationship between the connecting mechanism 13 and the driver bit 14 is Due to this upward movement, the driven clutch portion 32 also rises relatively against the third spring 33. Therefore, the engagement between the pin 35 on the clutch shaft 29 and the locking pin 34 of the driven clutch section 32 is released, and then the driving clutch section 30 and the driven clutch section 32 are brought into mesh with each other. Along with this, the driver bit 14 is rotated by the output torque of the cam disk, and the screw is screwed into a predetermined position.

As the tightening torque of the screw increases, the rotation speed of the driver bit 14 decreases. Depending on the load torque of the driver bit 14, the speed change ring 25 receives torque, and the piano wire 26 bends as shown in FIG. Therefore, the speed change ring 25 is
The shift ring 25 slides along the conical surface 23c of No. 3, its friction engagement position changes, and the movement of the shift ring 25 stops at the friction engagement position where the torque applied to the shift ring 25 and the elastic force of the piano wire 26 are balanced. .

Further, as the tightening torque increases, the shift ring 25 continues to move, and its reduction ratio increases, until the input disc 21
Despite the rotation, the cam disk 24 makes zero rotation, and the driver bit 14 stops while being held at a predetermined torque, completing the screw tightening.

When the screw tightening is completed and the driver bit 14 is raised, the dog clutch is disengaged, the high torque of the driver bit 14 is released, and the driver bit 14 can be detached from the screw without any trouble.

Effects of the Invention As explained above, the present invention is configured to transmit the rotation of the motor to the driver bit via an automatic transmission consisting of a differential planetary mechanism having a planetary cone. The reduction ratio of the motor can be continuously increased according to the decrease in rotation speed, and when the desired tightening torque is reached, the driver bit can be set to zero rotation regardless of the rotation of the motor, and screw tightening is completed. It has the advantage that it is not affected by the inertia of the driver bit and can perform tightening with extremely high precision. Furthermore, in the present invention, when the screw tightening is completed and the driver bit rises, the dog clutch is first disengaged and the high torque of the driver bit is released, so that the output shaft of the differential planetary mechanism, that is, the output torque of the driver bit becomes zero. After this, the driver bit can be separated from the screw, and there is an advantage that there is no possibility of damaging the tip of the driver bit or the head of the screw.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of the main part of the present invention, FIG. 2 is an overall explanatory diagram of the present invention, FIG. 3 is a partially cutaway sectional view of the driver main body according to the present invention, and FIG. 4 is a difference according to the present invention. A sectional view of the main parts showing the operating state of the moving planetary mechanism,
FIG. 5 is a perspective view of the main part of the torque adjustment ring according to the present invention, FIG. 6 is an enlarged perspective view of the main part seen from line A-A in FIG. 1, and FIG. 7 is a main part showing the operating state of the present invention. 8 is a sectional view of a main part of a conventional example, and FIG. 9 is a vertical sectional view taken along line B--B in FIG. 8. 1... Automatic screw tightening machine, 2... Base, 3... Support, 4... Fixed plate, 5... Upper bracket,
6... Lower bracket, 7... Cylinder, 8... Driver mounting base, 9... First spring, 10... Chunk stand, 11... Guide shaft, 12... Driver body, 13... Connection mechanism, 14 ...Driver bit, 15...Chuck unit, 15a...Chuck claw, 16...Fixing tool, 17...Inner cylinder part, 1
7a...bottom, 18...housing, 19...motor, 19a...drive shaft, 20...differential planetary mechanism, 21...input disk, 21a...annular part, 22
... Cone holder, 23 ... Planetary cone, 23a
... Circumferential groove, 23b ... Flat part, 23c ... Conical surface, 24 ... Cam disc, 25 ... Speed change ring, 26 ... Piano wire, 37 ... Pressure regulating mechanism, 28
...Connection shaft, 29...Clutch shaft, 30...Drive clutch section, 31...Second spring, 32...Driven clutch section, 32a...Driven clutch shaft, 33...
Third spring, 34... Locking pin, 35... Pin, 3
6... Torque adjustment sleeve, 36a... Notch groove,
37...adjustment bolt, 41...planetary gear, mechanism,
42... Drive gear, 43... Ring gear, 44
...Planetary gear, 45...Output shaft, 46...
...slip clutch, 47...stopper plate,
48...One-way stopper, 49...Carrier pin.

Claims (1)

[Scope of Claims] 1. The rotation of the drive shaft 19a of the rotary drive source is transmitted to the input disk 21 of the differential planetary mechanism 20, and the input disk 21 has a plurality of transmission surfaces each having a circumferential groove 23a. The planetary cone 23 is frictionally engaged, and the cam disk is frictionally engaged with the transmission surface formed by the flat surface 23b on the back surface of the planetary cone 23, so that the planetary cone is held so as to roll, and the input circle A speed change ring 25 is disposed at a position where the rotation of the plate is transmitted to the cam disc 24 and is commonly frictionally engaged with the conical surface 23c of the planetary cone 23, and this speed change ring is held by an elastic body and attached to the driver bit 14. When such a load torque is applied to the speed change ring 25, the elastic body is bent, causing the speed change ring 25 to slide along the conical surface 23c and change its frictional engagement position. An automatic screw tightening machine characterized in that the rotation is transmitted to a driver bit 14 via a meshing clutch. 2. The automatic screw tightening machine according to claim 1, wherein the elastic body is made of piano wire 26. 3. The dog clutch includes a drive clutch part 30 which is rotated by a clutch shaft 30 which is held in an inner cylinder part and rotates in response to the rotation of the cam disc 24, and a driven clutch part which is arranged to be able to mesh with the drive clutch part 30. 32, the driven clutch portion 32 is provided with a hollow portion in which the clutch shaft 29 is located, and the driven clutch portion 32 is provided with a locking pin 34 that protrudes into the hollow portion.
2. The automatic screw tightening machine according to claim 1, further comprising a pin 35 implanted in the clutch shaft 29 to engage with the locking pin 34.