JPH02262927A - Automatic screw tightening machine - Google Patents

Abstract

PURPOSE:To correct the reduction of the max. output torque due to the reduction of the traction coefficient due to the rise of the oil temperature by making an arm and a speed change ring from steel and making a driver body fro Invar having the less expansion coefficient than that of the arm and the ring. CONSTITUTION:When screw tightening work is repeated, and the temperature of the oil charge into a driver body 4 rises, the traction coefficient of the oil reduces, and the output torque reduces. Meanwhile, a speed change ring 14 and an arm 16 linearly expand over the driver body 4, accompanied with the rise of the oil temperature. Therefore, the speed change ring 14 shifts upwardly for an input disc 7, and the contact position with a planetary cone shifts to the high speed side. Through this shift, the tilt angle of the arm 16 increases. Further, the revolution torque generated on the speed ring at the time when the speed change ring 14 reaches the zero revolution position increases. Therefore, the output torque of the driver bit increases by the reduction portion of the max. output torque.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention eliminates the influence of inertia of the driver bit when screw tightening is completed, and ensures that the desired screw tightening is performed using torque. This invention relates to improvements to the automatic screw tightening machine constructed.

[Prior art] Recently, tightening torque has become strictly required in screw tightening and bolt tightening work, and tightening has been carried out in such a way as to eliminate the influence of inertia of the driver bit upon completion. Automatic screwdrivers have been developed that are configured to stop the driver bit upon completion. As shown in FIGS. 3 and 4, this automatic screw tightening machine 1 has a driver main body 4 fixed to a driver stand 3 that is raised and lowered by the operation of an elevating drive source 2, and a rotary drive source attached to one end of the driver main body 4. motor 5
is fixed. Further, the input disk 1 of the differential planetary mechanism 6 is held in the driver body 4 so as to rotate in response to the rotation of the drive shaft 5a of the motor 5.

A cone holder 8 is provided on the circumference surrounding the axis of the input disk 7.
A plurality of planetary cones 9 are arranged at predetermined intervals, and the planetary cones 9 are formed with a conical surface 9a, a flat surface 9b located on the back surface thereof, and a circumferential groove 9C. . The input disk 7 is in the circumferential groove 90, and the flat surface 9b
A cam disk 10 rotating concentrically with the input disk 7 is arranged so as to frictionally engage with the input disk 7. The cam disc 10 also has an inner cylindrical portion 11 that forms the bottom of the driver body 4.
A connecting shaft 10a rotatably held is connected to the connecting shaft 10a, and a driver bit 13 is connected to this connecting shaft 10a via a connecting mechanism 12 so as to rotate together with the connecting shaft 10a. moreover,
A speed change ring 14 is arranged on the outer periphery of the planetary cone 9 so as to move along the conical surface 9a, and together with the input disk 7, the planetary cone 9, and the cam disk 1G, a differential planetary mechanism 6 is formed. . Further, the speed change ring 14 is supported by a spring 15 held by a torque adjustment ring 17.
While being urged to be positioned on the high speed side, the high speed side position is regulated by being held by an arm 16 disposed between the inner cylindrical portion 11 and the bottom side. This speed change ring 14 is connected to the driver bit 1 depending on its position on the high speed side.
In addition to determining the speed reduction ratio during no-load conditions of No. 3, the speed change ring 14 is rotated in accordance with the load torque of the driver bit 13 to move the position of the speed change ring 14 on the conical surface 9a of the planetary cone 9, thereby making the speed reduction ratio stepless. It is designed to be large.

The driver body 4 is filled with oil for lubricating each component of the differential planetary mechanism 6, and the driver bit 13 is rotated by the traction coefficient of this oil and the elastic force of the spring 15. The output torque at the time of stopping is determined.

[Problems to be Solved by the Invention] In the automatic screw tightening machine described above, the speed change ring 14 rotates as the torque increases during tightening, and the contact position with the planetary cone 9 shifts to the larger diameter side of the planetary cone 9. The speed reduction ratio increases steplessly. When the speed change ring 14 moves roughly and reaches the position shown in FIG. 5 (a position that almost satisfies a:b=c:d), the cam disk 10 reaches zero rotation,
As shown in FIG. 6, the driver bit 13 can output the maximum output torque of the differential planetary mechanism 6 to complete tightening, and the influence of inertia of the driver bit 13 at the time of completion of tightening is eliminated. be able to.

In this case, the maximum output torque determined by the differential@star mechanism 6 is determined by the traction coefficient of the oil filled in the driver body 4 and the elastic force of the spring 15 that biases the speed change ring 14. If the work is repeated, frictional heat will be generated between each component of the differential planetary mechanism 6, the temperature of the oil will rise, and the traction coefficient will decrease. Therefore, the maximum output torque of the differential planetary mechanism 6 varies depending on the temperature of the oil, resulting in drawbacks such as the inability to perform screw tightening work with the desired torque value.

The present invention aims to eliminate the above-mentioned drawbacks, and seeks to provide an automatic screw tightening machine configured to compensate for a decrease in the maximum output torque of a differential planetary mechanism due to a decrease in traction coefficient due to a rise in oil temperature. It is something to do.

[Means for solving the problem] In order to solve the above problem, the gear ring and arm of the differential planetary mechanism of the automatic screw tightening machine are made of steel, and the driver body that holds the input disk is made of steel. In order to compensate for the decrease in the maximum output torque of the differential planetary mechanism due to the decrease in the traction coefficient due to the increase in oil temperature, the material has a coefficient of linear expansion smaller than that of the gear change ring and arm.
For example, it is composed of inba.

[Function] In the above automatic screw tightening machine, when a load torque is applied to the driver bit as the driver bit tightens the screw, a counter-cutting force corresponding to the load is applied to the speed change ring, causing the speed change in the opposite direction to the driver bit. The ring rotates.

In response to the rotation of the speed change ring, the arm tilts, the speed change ring moves in its axial direction, and its frictional engagement position moves toward the larger diameter side of the conical surface of the planetary cone. Along with this, the driver bit gradually tightens the screw at low speed and high torque, but when the head of the screw is seated and the load torque of the driver bit increases suddenly, the speed change ring suddenly tightens to near the edge of the conical surface. Despite the rotation of the input disk, the driver bit rotates at zero while outputting the maximum output torque of the differential planetary mechanism. Therefore, screw tightening can be performed with the maximum output torque of the differential planetary mechanism without being affected by the inertia of the rotation drive unit.

As this screw tightening process is repeated, frictional heat is generated between each part of the differential planetary mechanism, and the temperature of the oil filled in the driver body rises, causing the oil that determines the maximum output torque at zero rotation of the driver bit. The traction coefficient of the engine decreases, and the output torque decreases. On the other hand, as the oil temperature rises, the gear ring, arm, and driver body also expand linearly with the linear expansion coefficients of their respective materials. Since the coefficient of linear expansion is smaller than that of the linear expansion coefficient, the speed change ring and the arm linearly expand more than the driver main body. Therefore, the speed change ring moves upward with respect to the input disk held on the driver main body side, and the contact position with the planetary cone held in contact with the input disk moves toward the high speed side as the temperature rises.

By moving the speed change ring toward the high speed side, the distance traveled to the zero rotation position becomes longer, the speed change ring rotates that much more, and the angle of inclination of the arm that holds it increases. Moreover, when the speed change ring reaches the zero rotation position, the speed change ring receives a certain elastic force from the spring, so the rotational torque generated in the speed change ring when the speed change ring reaches the zero rotation position increases. Therefore, the output torque of the driver bit can be increased by the amount of the decrease in the maximum output torque of the differential planetary mechanism due to the decrease in the traction coefficient of the oil due to a change in temperature, and the maximum output torque when the driver bit is stopped can be changed to the temperature of the oil. Regardless of the situation, screw tightening work can be performed while holding the screw at a constant level.

[Example] Hereinafter, an example will be described with reference to the drawings. In FIG. 1, 4 is a driver body of a screw tightening machine having the same structure as the automatic screw tightening machine 1 shown in FIGS. 3 and 4. Invar, a material with a small coefficient of expansion (coefficient of linear expansion 2X)
10' or less). A motor 5 serving as a rotational drive source is fixed to one end of the driver body 4, and an inner cylindrical portion 11, which is fixed to the driver stand 3 and forms the bottom of the driver body 4, is fixed to the other end. Drive shaft 5 of the motor 5
Input disk 7 of the differential vJ play mechanism 6 that forms the automatic transmission is shown in a.
are connected. A plurality of planetary cones 9 are arranged on the circumference surrounding the axis of the input disk 7 at predetermined intervals by a cone holder 8, and each of the planetary cones 9 has a conical surface 9a as a transmission surface. A flat surface 9b on the back surface thereof and a circumferential groove 90 having a concave cross section located adjacent thereto are formed. Further, the input disk 7 is placed in the circumferential groove 90.
A cam disk 10 that rotates concentrically with the input disk 7 is arranged on the flat surface 9b so as to frictionally engage with the input disk 7.

This cam disc 10 has a joint 11id that rotates integrally with the cam disc 10.
llOa is connected, and this connecting shaft 10a is rotatably held by the inner cylinder BBt. Furthermore, a driver bit (not shown) is connected to the connecting shaft 10a via a buffer mechanism (not shown) and the connecting mechanism (not shown).

Further, a speed change ring 14 is provided on the outer periphery of the planetary cone 9 so as to be frictionally engaged with the conical surface 9a of the planetary cone 9 so as to be rotatable according to the load of the driver bit 13 and to move along the same.
is located. This speed change ring 14 is urged to be located on the high speed side by a spring 15 placed on a torque adjustment ring 17, which will be described later. Moreover, this speed change ring 14 is rotatably held via a plurality of arms 16 disposed between it and the bottom side of the inner cylindrical portion 11.
This arm 16 is configured to restrict the position of the speed change ring 14 on the high speed side.

Furthermore, each component constituting the differential planetary mechanism 6 is made of steel (linear expansion coefficient 11.7 x 10'), and as the temperature of the oil filled in the driver body 4 increases, these components become linear. configured to inflate.

On the other hand, a torque adjustment ring 17 is provided on the outer periphery of the inner cylinder portion 11.
is slidably arranged, and this torque adjustment ring 1
An adjustment bolt 18 that penetrates the bottom of the inner cylindrical portion 11 and is rotatably held at that position is screwed into 7 . These adjustment poles 1 to 18 are rotated by the torque adjustment ring 1.
7, the elastic force of the spring 15 is changed, and the maximum output torque of the differential planetary mechanism 6 determined by the traction coefficient of the oil and the elastic force of the spring 15, which will be described later, is changed. .

In general, the drive shaft 5a and the connecting shaft 10a of the motor 5
An oil seal mechanism is arranged around the driver body 4 and the inner cylindrical portion 11 to fill oil with a predetermined traction coefficient to prevent wear of the differential planetary mechanism 6. ing.

In the above automatic screw tightening machine, when the motor 5 rotates,
The rotation is transmitted from the input disk 7 to the cam disk 10 via the planet cone 9, and the speed change ring 14
The speed is reduced at a speed reduction ratio determined by the position of frictional engagement with the conical surface 9a of the drive bit 13, and the speed is transmitted to the driver bit 13.

When a load torque is applied to the driver bit 13 as the driver bit 13 tightens a screw (not shown) held by the chuck unit 19 to a workpiece (not shown), a reaction force corresponding to the load is generated from 1 to 1 ruq. is applied to the speed change ring 14, and the speed change ring 14 rotates in a direction opposite to the direction of rotation of the driver bit 13, as shown in FIG. When the speed change ring 14 rotates, the arm 16 tilts. This inclination of the arm 16 causes the speed change ring 14 to move toward the larger diameter side along the conical surface 9a of the planetary cone 9, so that its reduction ratio becomes larger and larger. As the screw is seated on the workpiece, the tightening torque increases rapidly, and the speed change ring 14 rapidly moves and reaches the edge of the conical surface 9a. Therefore, even though the input disk 7 rotates, the cam disk 10 rotates at zero, and the driver bit 13 integrated with it stops outputting the maximum output torque of the differential VT planet @ structure 6, and the screw is tightened. complete. The maximum output torque at this time is a value determined by the traction coefficient of the oil located between each component of the differential planetary mechanism 6 and the elastic force of the spring 15 urging the speed change ring 14.

When this screw tightening operation is repeated, friction heat is generated between each component of the differential planetary mechanism 6, and the temperature of the oil filled in the driver body 4 increases. Therefore, the traction coefficient of the oil that determines the maximum output torque at zero rotation of the driver bit decreases, and the maximum output torque tends to decrease accordingly. On the other hand, as the temperature of the oil rises, as shown in FIG. 2, the speed change ring 14, arm 16, and driver body 4 also undergo linear expansion based on the linear expansion coefficients of their respective materials. Moreover, the speed change ring 14
Since the arm 16 is made of steel and has a linear expansion coefficient larger than that of Invar forming the driver body 4, the speed change ring 14 and the arm 16 linearly expand more than the driver body 4. Therefore, the input disk 7 held in the driver body 4 moves in the -L direction, and the contact position with the planetary cone 9 held in contact with the input disk 7 moves toward the high speed side as the temperature rises. do.

This movement of the speed change ring 14 to the high speed side increases the distance it moves to the zero rotation position, and the speed change ring 14 rotates that much more, causing the arm 16 that holds it to tilt as shown in FIG. The angle θ becomes larger.

Moreover, when the speed change ring 14 reaches the zero rotation position,
The maximum output 1~luke (CB) of the differential planetary mechanism 6 increases for each component such as the speed change ring 14, the spring 15, and the arm 16. Therefore, the maximum output torque of the driver bit 13 can be increased by the amount of the decrease in the maximum output torque of the differential planetary mechanism 6 due to a decrease in the traction coefficient due to temperature rise, and ultimately the driver bit 13 will remain at the specified level regardless of temperature changes. It is possible to tighten screws by outputting the maximum output of .

[Effects of the Invention] As explained above, the present invention transmits the rotation of a rotary drive source to the driver bit via a differential planetary mechanism having a planetary cone, and when tightening is completed, the driver bit is stopped and the differential Because the driver body, which holds the input disk of the planetary mechanism, is made of a material with a coefficient of linear expansion smaller than that of the gear ring and arm, such as Invar, the traction coefficient of the oil for lubrication between each part of the differential planetary mechanism is Even if the maximum output torque of the differential 81BN structure, which is determined by the traction coefficient and the elastic force of the spring that biases the gear ring, decreases due to the rise in temperature, the gear ring and arm will decrease due to the rise in oil temperature. linearly expands more than the driver body and moves the speed change ring along the planetary cone to the high speed side, and the inclination angle of the arm increases when it reaches zero rotation, so the rotating torque, that is, the maximum output torque of the differential planetary mechanism, increases. This has the advantage that the decrease in the maximum output torque can be corrected according to the temperature, and screw tightening can always be performed with a constant maximum output torque regardless of the oil temperature.

Furthermore, as is clear from the experimental results shown in Figure 7, if an aluminum material with a coefficient of linear expansion larger than that of steel is used, the temperature-output torque characteristics will deteriorate further, and a material with a coefficient of linear expansion smaller than that of steel will worsen. In the example, the material of the driver body is Invar because the temperature-output torque characteristics are improved by using steel, but almost the same effect can be obtained by using a material with a coefficient of linear expansion smaller than that of steel. be able to

[Brief explanation of drawings]

Fig. 1 is a sectional view of the main part of the present invention, Fig. 2 is a sectional view of the main part showing the operating state of the invention, Fig. 3 is an overall explanatory diagram of the conventional example, and Fig. 4 is an enlarged view of the main part of Fig. 3. 5 is a sectional view of a main part showing the operating state of a conventional differential planetary mechanism, FIG. 6 is a torque-rotational speed characteristic curve diagram of an output shaft of a differential planetary mechanism according to the present invention, and FIG. The figure is a humidity-output torque characteristic curve obtained depending on the material of the driver body, and Figure 8 is the force generated in each part of the speed change ring, arm, and spring when the differential planetary mechanism according to the present invention outputs the maximum output torque. It is a vector diagram showing an equilibrium state of. 1 automatic screw tightening machine, 2 3 driver stand, 4 5 motor, 5a 6 differential planetary mechanism, 7 8 cone holder, 9 9a circular pincer surface, 9b 9C circumferential groove, 10 10a connecting shaft, 11 12 connecting mechanism, 13 14 Speed change ring, 15 16 Arm, 17 18 Adjustment bolt, 19 Lifting drive source, driver body, drive shaft, input disc, planetary cone, flat part, cam disc, inner cylinder part, driver bit, spring, torque adjustment ring , chuck unit, Fig. 1

Claims (1)

[Claims] 1) A rotary drive source is fixed to one end of the driver body, and an input disk is held so as to rotate in response to rotation of the drive shaft;
A plurality of planetary cones are arranged at predetermined intervals on a circumference surrounding the axis of the input disk, and a conical surface, a flat surface located on the back surface of the planetary cone, and a circumferential groove are formed on the planetary cone, An input disk is placed in the circumferential groove, a cam disk that rotates concentrically with the input disk is placed on the flat surface so as to be frictionally engaged with the input disk, and a driver bit is connected to the cam disk so as to rotate together with the input disk. Furthermore, a speed change ring is arranged so as to be rotatable and move along the conical surface by the load torque of this driver bit, and this speed change ring is biased by a spring to be located on the high speed side, while the high speed In an automatic screw tightening machine, an arm that limits the amount of lateral movement is provided between a speed change ring and an inner cylindrical portion forming the bottom of the driver body, and the driver body is further filled with oil having a predetermined traction coefficient. and an automatic screw tightening machine, characterized in that the speed change ring is made of steel, and the driver body is made of a material with a coefficient of linear expansion smaller than that of the arm and the ring. 2) The automatic screw tightening machine according to claim 1, wherein the material of the driver body is Invar.