JPH0466656B2 - - 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.

Prior Art Conventionally, when tightening a screw to a workpiece with a desired tightening torque, the load current flowing through the armature winding of the motor that transmits rotation to the driver bit is statically proportional to the tightening torque. A screw tightening method is used in which the load current is detected, and when this load current reaches a preset value, the voltage supply to the motor is stopped and the screw tightening is completed.

Problems to be Solved by the Invention In this screw tightening method, even if the voltage supply to the motor is stopped when the screw is seated on the workpiece and the load current reaches the set value, the electrical As the armature undergoes rapid deceleration, the inertial force of the armature applies an output torque unrelated to the load current in the tightening direction, and the actual tightening value becomes lower than the torque value determined by the load current, as shown in Figure 9. becomes larger, and since its size is due to inertial force, it is not constant and becomes extremely inaccurate.
There are drawbacks such as the inability to accurately control the tightening torque. Furthermore, this tightening method has the disadvantage that if the circuit that compares the load current and the set value breaks down, the tightening operation cannot be performed reliably.

Means for Solving the Problems The present invention aims to eliminate the above-mentioned drawbacks.
A differential planetary mechanism whose reduction ratio changes continuously according to the load on the output side is used, and when the reduction ratio reaches infinity, constant transmission occurs due to the boundary lubrication effect on the frictional engagement surface of the differential planetary mechanism. This method uses force to tighten screws. A rotary drive source is fixed to one end of the driver body, and the rotation of the drive shaft is configured to be transmitted to the input disk of the differential planetary mechanism. A plurality of planetary cones are arranged on this input disk so as to be frictionally engaged with it, and a cam disk is also frictionally engaged with this planetary cone and can roll under the rotation of the cam disk. It is located in Further, a driver bit is connected to the cam disk so as to rotate together with the cam disk, and the rotation of the input disk is taken out as rotation of the cam disk through a planetary cone and transmitted to the driver bit. ing.

A speed change ring is arranged to frictionally engage with the conical surface of the planetary cone, and the amount of movement of this speed change ring on the high speed side is limited by an elastic holding member disposed within the driver body. Furthermore, the speed change ring is configured to be rotatable by the load torque of the driver bit and slidable in the axial direction along the conical surface. Further, the speed change ring is configured to be movable toward the larger diameter side of the conical surface against the elastic force of the elastic holding member until the driver bit stops. Furthermore, even though the rotary drive source is rotating, when the driver bit stops, a constant torque is output, and the screw is finally tightened with this torque.

Function In this automatic screw tightening machine, when the rotary drive source rotates, the input disk of the differential planetary mechanism rotates. Along with this, the planetary cone that is frictionally engaged with the input disk revolves while rotating 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 the rotation is transmitted to the driver bit. Thereafter, the driver bit tightens the screw, the load torque applied to the driver bit increases, and along with this load torque, reaction torque is applied to the speed change ring, causing the speed change ring to rotate. Along with this, the elastic holding member is tilted, and the speed change ring moves toward the larger diameter side of the conical surface of the planetary cone against the elastic force of the elastic holding member. The speed change ring moves to a position where the axial pressing force generated by the reaction torque and the elastic force of the elastic holding member are balanced, and stops at that position. Therefore, the position of frictional engagement between the speed change ring and the conical surface of the planetary cone changes, allowing the driver bit to gradually tighten the screw at low speed and high torque. As the load torque applied to the driver bit increases, the reduction ratio also increases continuously, and eventually the driver bit stops rotating even though the input disk is rotating, and the differential planetary A constant torque obtained by the boundary lubrication effect of the mechanism is output, and screw tightening is completed using this torque.

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. Furthermore, this driver body 12 has a motor 19 as a rotational drive source fixed to the housing 18, and an input disk 21 of a differential planetary mechanism 20 forming an automatic transmission is connected to the drive shaft 19a. . 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, and a cam disk 24 is frictionally engaged with this flat surface 23b, and this planetary cone 23 is connected to the input disk 21.
It is held between Further, the planetary cone 2
A speed change ring 25 is located around 3 so as to be in contact with the conical surface 23c, and the amount of movement of this speed change ring 25 on the high speed side is determined by the distance between the speed change ring 25 and the inner cylindrical portion 17 within the driver body 12. It is restricted by an elastic retaining member provided in the. The elastic holding member is made up of a plurality of piano wires 26, which will be described later, and the piano wires 26 bend while tilting in response to the reaction torque applied to the speed change ring 25, and the speed change ring 25 slides in its axial direction. It is configured as follows. The speed change ring 25 is configured to change the position of frictional engagement with the conical surface 23c by moving in its axial direction, so that the rotational speed of the cam disk 24 is reduced by a continuously changing reduction ratio. Further, when the frictional engagement position of the speed change ring 25 almost reaches the position shown in FIG. It is configured to output a constant torque due to the boundary lubrication effect at.

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.

Further, a clutch shaft 29 is connected to the connecting shaft 28, and a driving clutch portion 30 is rotatably fitted into the lower end of the clutch shaft 29. This drive clutch part 3
0 and the clutch shaft 29 are connected by a second spring 31, which is configured to alleviate the sudden impact that the driver bit 14 receives when the head of the screw is seated. 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.
Further, the driven clutch portion 32 has a hollow portion,
A locking pin 34 is inserted into the sixth hole so as to protrude into this hollow part.
Installed as shown. 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 is connected to the driven clutch shaft 3.
2a, the connecting mechanism 13 is connected to the driven clutch shaft 32a, and the rotation of the motor 19 is transmitted to the driver bit 14.

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 and serve as elastic holding members, are fixed between the shift ring 25 and the shift ring 25.
The piano wire 26 holds the speed change ring 25 rotatably and slidably in its axial direction. Further, the piano wire 26 is configured to hold the speed change ring 25 on the high speed side, and to generate a reaction force that returns the speed change ring 25 to the high speed side when the speed change ring 25 begins to rotate. On the other hand, the torque adjustment sleeve 36 has notched grooves 36a at equal intervals on its outer periphery, and the piano wire 26 has notched grooves 36a at equal intervals.
is configured to pass through. Further, the torque adjustment sleeve 36 has a flange portion into which an adjustment bolt 37 rotatably held at the bottom 17a of the inner cylinder portion 17 is screwed. Moreover, the torque adjustment sleeve 3
6 is the piano wire 2 by changing its height position.
The spring constant of 6 is changed so that an elastic force corresponding to the tightening torque can be obtained.

In the automatic screw tightening machine described above, when the motor 19 rotates, its rotation is transmitted to the cam disk 24 at a speed reduction ratio determined by the position where the speed change ring 25 and the conical surface 23c of the planetary cone 23 are frictionally engaged. This rotation of the cam disk 24 is transmitted to the drive clutch section 30. At this time, the drive clutch section 30 and the driven clutch section 32 are not fitted, but the pin 35 of the clutch shaft 29 and the locking pin 34 of the driven clutch section 32 are engaged, and the rotation of the cam disk 24 is prevented. The signal 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.

When the tightening torque of the screw increases, the speed change ring 25 rotates in response to the reaction torque in accordance with the load torque applied to the driver bit 14.
As shown in the figure, the piano wire 26 bends while being inclined.
Therefore, the speed change ring 25 moves in its axial direction against the elastic force of the piano wire 26 and slides along the conical surface 23c of the planetary cone 23, changing its frictional engagement position. The speed change ring 25 stops at a frictional engagement position where the axial pressing force generated from the reaction torque and the elastic force of the piano wire 26 are balanced.

Furthermore, when the screw is seated on the workpiece, the tightening torque increases and the reaction torque increases rapidly. Along with this, the speed change ring 25 moves close to the edge of the large diameter side of the conical surface, and its reduction ratio becomes larger and larger until finally, even though the input disk 21 rotates, the cam disk 24
becomes zero rotation. At this time, the driver bit 14 outputs a constant torque generated by the boundary lubrication effect of the differential planetary mechanism, and with this torque the driver bit 14 can finally tighten the screw.

Moreover, when the screw is seated on the workpiece, the size increases rapidly and reaches the set value, but since the rotation speed at this time is zero, the screw tightening is completed without being affected by the inertia of the rotation drive unit including the motor 19. be able to.

Effects of the Invention As explained above, the present invention is configured to transmit the rotation of the rotary drive source to the driver bit via an automatic transmission consisting of a differential planetary mechanism having a planetary cone, so As the reaction torque applied to the bit increases, not only can the rotation of the driver bit, which rotates due to rotation from the rotary drive source, be continuously decelerated, but when the desired tightening torque is reached, the rotation of the rotary drive source increases. Regardless of the rotation, the driver bit can be set to zero rotation, and when the screw tightening is completed, it is not affected by the inertia of the driver bit, which has the advantage that extremely high precision tightening is possible. Further, according to the present invention, the final tightening can be performed with a constant torque generated by the boundary lubrication effect of the differential planetary mechanism, and the torque is also stable at its maximum value as shown in the torque characteristic curve of FIG. This not only makes it possible to monitor torque extremely easily and accurately, but also has advantages such as being able to reliably tighten screws with a predetermined torque even if the torque monitoring device is out of order.

[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. FIG. 8 is a diagram showing a torque characteristic curve of a driver bit of an automatic screw tightening machine of the present invention, and FIG. 9 is a diagram of a torque characteristic curve of a driver bit of a conventional screw tightening machine. 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, 27 ... 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.

Claims (1)

[Claims] 1. A rotational drive source is fixed to one end of the driver body 12, and the rotation of the drive shaft 19a is controlled by the differential planetary mechanism 20.
A plurality of planetary cones 23 are arranged so as to be frictionally engaged with the input disk 21, and a cam disk 24 is frictionally engaged with the planetary cones 23. The input disk 21 is arranged so as to roll in response to the rotation of the cone 23, and the driver bit 14 is connected to the cam disk 24 so as to rotate integrally therewith, so that the rotation of the input disk 21 is extracted as the rotation of the cam disk 24. The speed change ring 25 is arranged so as to be frictionally engaged with the conical surface 23c of the planetary cone 23, and the amount of movement of the speed change ring 25 toward the high speed side is transmitted to the driver body 12.
The speed change ring 25 is configured to be rotatable by the load torque applied to the driver bit 14 and slidable in the axial direction along the conical surface 23c. This shift ring 2 until it stops rotating.
5 is configured to be movable toward the large diameter side of the conical surface 23c, and is configured to tighten the screw with a constant output torque generated when the driver bit 14 stops rotating.