JPH0422901Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field The invention applies a predetermined stopping torque to the driver bit when screw tightening is completed to stop the rotation of the driver bit and to smoothly remove the driver bit from the screw. Regarding the configured automatic screw tightening machine.

Prior Art Recently, a screw tightening machine described in Japanese Patent Application No. 112646/1988 has been developed in order to eliminate the influence of inertia of a driver bit when screw tightening is completed. As shown in FIGS. 4 and 5, this screw tightening machine 1 has a driver mounting base 8 that is raised and lowered by the operation of a cylinder 7, and this driver mounting base 8 is provided with a third spring 9 at a predetermined interval. A desk 10 is arranged which is resiliently biased. Further, this driver mounting base 8 is configured to move together with the driver base 10 along a guide shaft 11 to a predetermined position. A driver main body 12 is fixed to the upper part of the driver mounting base 8, and the driver main body 12 is configured to rotate a driver bit 14 via a connecting mechanism 13, which will be described later. On the other hand, a chuck unit 15 is fixed to the chuck base 10, and the driver bit 14 passes through the chuck unit 15.
Screw held by chuck claw 15a (not shown)
is configured to be screwed into place.

The driver main body 12 has an inner cylinder part 17 having a fixture 16 fixed to the driver mounting base 8, and a housing 18 integrated with the bottom part 17a. Moreover, this driver main body 12 is connected to a rotary drive source motor 19 fixed to the housing 18.
The drive shaft 19a is connected to an input disk 21 of an operating planetary mechanism 20 constituting an automatic transmission. This input disk 21 has an annular portion 21a on its outer periphery.
The annular portion 21a is configured to frictionally engage with the transmission surface formed by the circumferential grooves 23a of the plurality of planetary cones 23. Also, this planetary cone 2
3 is held by a cone holder 22 with its axis tilted, and a flat surface 23b is formed on the back surface thereof. Furthermore, 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.

Around the planetary cone 23, there is a conical surface 2.
A speed change ring 25 is positioned so as to be in contact with 3c, and this speed change ring 25 is held by a plurality of linear springs 26, which will be described later. This linear spring 2
6 is bent in response to the torque applied to the speed change ring 25, and the frictional engagement position of the speed change ring 25 with the conical surface 23c changes, thereby causing the cam disc 2
4 is configured to decrease by continuously changing the reduction ratio. Further, the frictional engagement position of the speed change ring 25 is at the position shown in FIG. 6 (a:
The cam disk 24 is configured to make zero rotation when it reaches the position where b=c:d. At this time, the motor 19 continues to rotate, and the driver bit 14 is configured to be held at a predetermined stopping torque and stop rotating.

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 continuous 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. has been done. 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 driven clutch shaft 32a is connected to the lower end of the clutch shaft 29 via a dog clutch, and the connecting mechanism 13 is connected to the driven clutch shaft 32a. There is. The dog clutch is composed of a driving clutch part 30 having rectangular teeth, a driven clutch part 32, and a clutch spring 31 interposed between the two parts. Further, the connecting mechanism 1
3 has two universal joints 33 and a connecting member 35 that rotatably holds them together and is biased by a thrust spring 34 so as to be relatively movable, and connects the dog clutch and driver bit 14.
are configured to be integrally rotatable, and the dog clutch is configured to be movable relative to the driver bit 14.

Problems to be Solved by the Invention In the above automatic screw tightening machine, the screw is tightened by the driver bit 14, and as the tightening torque approaches the set torque, the rotational speed of the driver bit 14 is steplessly reduced, and the set tightening is performed. When the torque is reached, the driver bit 14 is held at a predetermined stopping torque and stops, and the screw is moved back to the driver bit 14.
It can be tightened to the set torque without being affected by inertia. However, when the screw tightening is completed, the linear spring 26, dog clutch and driver bit 14
A stalling torque corresponding to the set torque is generated in the member in a torsionally deflected state.

On the other hand, since the working planetary mechanism is at an infinite deceleration position (the rotational speed on the output shaft side is zero), the differential planetary mechanism does not rotate in reverse, and the torsion on the output side is not resolved. Therefore, driver bit 14
is maintained at an extremely large stall torque. When the motor is raised with the stall torque acting on the driver bit 14, there is no problem while the thrust spring 34 is extended, but as shown in FIG. When the dog clutch disengages, the dog clutch cannot be disengaged because a frictional force is exerted between the teeth 30b, 32b of the dog clutch due to the stall torque. Therefore, when the dog clutch is engaged, it rises together with the motor, and the driver bit 1
4 may rise. In this case, the tip of the driver bit 14 may pry off the head of the screw, causing damage to the screw or the driver bit 14. In addition, sometimes the driver bit 14 may rise while biting into the workpiece, and in this case, a workpiece holder is required to separate the workpiece from the driver bit 14, resulting in drawbacks such as an expensive device. ing.

Means for Solving the Problems The present invention aims to eliminate the above-mentioned drawbacks.
The rotation of the drive shaft of the rotary drive source is changed steplessly by an operating planetary mechanism and is transmitted to the driver bit via a dog clutch consisting of a drive clutch, a driven clutch, and a clutch spring. Furthermore, the dog clutch and the driver bit are arranged so as to be rotatable together, and the driver bit is elastically biased by a thrust spring so as to be movable relative to the dog clutch. On the other hand, the engagement surfaces of the teeth of the drive clutch portion and the driven clutch portion of the dog clutch are formed with inclined surfaces having a predetermined angle. The angle α of this inclined surface is determined by the resultant force of the component force Q in the clutch disengagement direction caused by the stall torque of the driver bit and the elastic force _T1 of the clutch spring when the clutch is engaged, when the driver bit comes out from the screw. The thrust force is set to be greater than the thrust force of the thrust spring.

Function In the automatic screw tightening machine described above, the driver bit rotates as the rotary drive source rotates, and the screw held at the tip of the driver bit is screwed into the workpiece. When the screw is screwed into the workpiece and the set tightening torque is reached, the differential planetary mechanism reaches an infinite deceleration position and the driver bit stops rotating. In this state, when the rotational drive source starts to rise, the thrust spring begins to expand, and the thrust spring is almost in an expanded state. At this time, the elastic force _T2 of the thrust spring is larger than that of the clutch spring, but due to the stalling torque of the driver bit, a component force Q is generated in the direction of disengaging the driven clutch portion of the dog clutch, and this component force Q and Since the resultant force with the elastic force _T1 of the clutch spring is greater than the thrust force applied to the driver bit when the driver bit cams out, the driven clutch part separates from the driving clutch part before the driver bit cams out from the screw. Therefore, no torque is applied to the driver bit, and the driver bit can be smoothly removed from the screw.

Embodiments Hereinafter, embodiments will be described with reference to the drawings. In Figures 1 to 3, 8 is a driver mounting base of an automatic screw tightening machine, and a driver main body 12 is fixed to the upper part of this driver mounting base 8. Fixed staff 1
It has an inner cylindrical portion 17 fixed via a cylindrical tube 6 and a housing 18 integrated with this bottom portion 17a. Moreover, this driver main body 12 is configured to transmit the rotation of a motor (not shown) to the connecting shaft 28 via the differential planetary mechanism 20.

A driving clutch portion 30 is connected to the connecting shaft 28 via a clutch shaft 29, and a driven clutch portion 32 is rotatably disposed below the driving clutch portion 30. Further, the clutch shaft 29 is inserted into the driven clutch portion 32,
Moreover, a clutch spring 31 is disposed between the drive clutch portion 30 and the clutch spring 31 . Further, the drive clutch portion 30 and the driven clutch portion 32 have tooth portions 30b and 32b that are screwed into each other.
The screwing surfaces of 0b and 32b are formed with inclined surfaces having a predetermined inclination angle. The angle of inclination of this inclined surface is determined by the resultant force of the component force in the clutch disengagement direction that occurs when a stall torque is applied to the driver bit (not shown) and the elastic force T1 of the clutch spring 31 when the meshing clutch is engaged. The elasticity T2 of the thrust spring 34 is set to be greater than the elasticity T2.

Here, the inclination angle α is determined by the resultant force p of the drag force N generated on the meshing surface due to the stall torque and the friction force μN, as shown in FIG. From the force F _t applied to the tooth portion 32b and the friction angle φ, it is expressed by the following equation.

F _t = P cos (π/2-φ-α) = P sin (φ+α), and the component force Q in the clutch release direction applied to the driven clutch portion 32 is Q=P sin (π/2-φ-α )=P cos(φ+α), From the above formula, Q=F _t cos(φ+α)/sin(φ+α)=F _t 1/tan(φ
+α) Q=F _t 1−tanφ・tanα/tanφ+tanα Here, since tanφ=μ, Q=F _t 1−μtanα/μ+tanα.

Into the above equation, substitute the actual values, that is, the stall torque T _r = 15 Kgcm at the time of completion of tightening, the effective radius R of the teeth 30b of the drive clutch portion 30 = 0.75 cm, and the coefficient of sliding friction between steel and steel μ = 0.1. Then, Q = 15/0.75 , Q and find the inclination angle α of the meshing surface.

On the other hand, the driven clutch portion 32 has a driven clutch shaft 32a, and two universal joints 33 are disposed on the driven clutch shaft 32a so that they can rotate together, and are relatively movable by a thrust spring 34. A linkage mechanism 13 consisting of a biased link 35 is connected and configured to transmit the rotation of the motor to the driver bit (not shown).

In the automatic screw tightening machine described above, the driver bit rotates as the motor rotates, and the screw held at the tip of the driver bit is screwed into the workpiece. When the screw is screwed into the workpiece and the set tightening torque is reached, the driver bit stops rotating due to the operation of the differential planetary mechanism 20. At this time, the member consisting of the linear spring 26, dog clutch, and driver bit has a stalling torque corresponding to the set torque in a torsionally flexed state, so the driver bit is not rotated regardless of whether or not the motor is rotating. Maintained with high stall torque. In this state, when the motor starts to rise as the driver mounting base 8 rises, the thrust spring 34 begins to expand, and the thrust spring 34 becomes almost in an expanded state. At this time, as shown in FIG. 3, the elastic force T ₂ of the thrust spring 34 is greater than the elastic force T ₁ of the clutch spring 31, but due to the stalling torque T _r of the driver bit, the engagement surface of the clutch is A component force Q in the direction of disengaging the driven clutch portion 32 is generated by the resultant force P of the drag force N generated in The resultant force with T ₁ becomes greater than the elastic force F ₂ of the thrust spring 34 before the driver bit cams out from the screw, and the driven clutch portion 32 separates from the drive clutch portion 30. Therefore, no torque is applied to the driver bit, and even if the motor rises further, the driver bit will smoothly separate from the screw.

Effects of the Invention As explained above, the present invention forms the engagement surface of the dog clutch with an inclined surface having a predetermined angle, and uses that angle to combine the component force in the disengagement direction generated by the stall torque acting on the driver bit with the clutch. The structure is such that the resultant force with the elastic force of the spring is greater than the thrust force of the spring when the driver bit comes out, so even if the driver bit is stopped with a high stall torque when the screw tightening is completed, , when the driver bit separates from the screw,
Since the dog clutch is disengaged first, the head of the screw is not pried by the tip of the driver bit and the screw or the tip of the driver bit is not damaged. Since the workpiece is not bitten by the workpiece and lifted up, extra parts such as a workpiece holder are not required, and there are advantages such as being able to provide an inexpensive device.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the main parts of the present invention, Figure 2 is an enlarged front view of the main parts of the dog clutch according to the invention, and Figure 3 is a cross-sectional view of the main parts of the invention.
The figure is an explanatory view of the main part of the dog clutch according to the present invention, Fig. 4 is an overall explanatory view of the conventional example, Fig. 5 is a sectional view of the main part of Fig. 4, and Fig. 6 is the differential of Fig. 5. FIG. 7 is an enlarged view of the main part of the clutch shown in FIG. 5, showing the operation of the main part of the planetary mechanism. 1... Automatic screw tightening machine, 7... Cylinder, 8...
...driver mounting base, 9...third spring, 10...chuck stand, 11...guide shaft, 12...driver body, 13...coupling mechanism, 14...driver bit, 15...chuck unit, 15a...
...Chuck claw, 16...Fixing tool, 17...Inner cylinder part, 17a...Bottom part, 18...Housing, 19
... Motor, 19a ... Drive shaft, 20 ... Differential planetary mechanism, 21 ... Input disk, 21a ... Annular part,
22... Cone holder, 23... Planetary cone, 2
3a... Circumferential groove, 23b... Flat part, 23c...
Conical surface, 24... Cam disk, 25... Speed change ring, 26... Linear spring, 27... Pressure regulating mechanism, 2
8... Connection shaft, 29... Clutch shaft, 30... Drive clutch portion, 30b... Teeth portion, 31... Clutch spring, 32... Driven clutch portion, 32a... Driven clutch shaft, 32b... Teeth portion , 33... Universal joint, 34... Thrust spring, 35...
Connector.

Claims (1)

[Claims for Utility Model Registration] A plurality of planetary cones 23 that transmit the rotation of a drive shaft 19a of a rotary drive source to an input disk 21 of a differential planetary mechanism and are held so as to rotate with their axes tilted. A transmission ring 25 is disposed so as to contact the outer periphery of the planetary cone 23 and regulate its rotational speed, while the rotation of the cam disc 24 is transmitted to the cam disc 24 through a meshing mechanism having a clutch spring 31. The force is transmitted to the driver bit 14 via the clutch, and a thrust spring 3 is provided between the dog clutch and the driver bit 14.
4, and when tightening the screw, the cam disc 24
The contact position between the speed change ring 25 and the planetary cone 23 is changed by the reaction force applied to the planetary cone 23.
In an automatic screw tightening machine configured to change the rotational speed of the screwdriver bit 14 and to hold the driver bit 14 at a predetermined stop torque and stop when screw tightening is completed, the driving clutch portion 30 and the driven clutch portion of the dog clutch are The meshing surfaces of the tooth portions 30b and 32b of 32 are sloped at a predetermined angle, and the slope angle α of the slope is determined by the component force Q in the clutch disengagement direction caused by the stall torque acting on the driver bit 14 and the meshing clutch. Elastic force of clutch spring 31 during engagement
An automatic screw tightening machine characterized in that the resultant force with _T1 is set to be greater than the thrust of the thrust spring 34 when the driver bit 14 comes out from the screw.