JP3298724B2 - Screw tightening device and screw loosening device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw tightening device and a screw loosening device, and more particularly to a device suitable for being incorporated in an automated assembly line or the like.

[0002]

2. Description of the Related Art Conventionally, in automatic assembly and the like, screw tightening is performed using a dedicated automatic screw tightening device or an automatic screw tightening robot. In the dedicated automatic screw tightening device, first, the main body of the automatic screw tightening device on the vertical lifting device is lowered to a predetermined position by a large air cylinder. Next, at the start of screw tightening, the bit is strongly pressed against the screw by a small air cylinder, and after the screw tightening is started, the bit is pressed with a small force by a mechanical spring. This dedicated automatic screw tightening device employs a pressing mechanism for pressing the bit in the thrust direction of the screw using an air cylinder, a mechanical spring, or the like.

In a screw tightening robot, there is no pressing mechanism in the hand portion of the robot, and a pressing mechanism for the screw is provided on the arm side which is the base portion of the robot. The pressing mechanism of the base portion is roughly classified into a servo type and a mechanism using an air cylinder or a mechanical spring. The servo type applies a feedback to the thrust direction of the screw to make the pressing force equal to the servo gain, and has a special control device. Those using an air cylinder or a mechanical spring apply a pressing force using these air cylinders or compression or extension springs.

[0004] In order to cope with diversification of the screw size and the length under the neck in the automatic assembly, various kinds of dedicated screw tightening devices have been produced.

[0005]

However, in such a conventional dedicated automatic screw tightening device or robot, if a sufficient stroke corresponding to various screw members is to be provided, a pressing mechanism or a hand is required. There was a problem of being larger. In addition, when the servo system is adopted, an original control device is required, and it is difficult to incorporate the control device into a robot control device, so that the cost is increased.

Further, when a hydraulic cylinder such as an air cylinder is employed as the pressing mechanism, the fluid pressure tends to fluctuate, so that it is difficult to keep the pressing force of the bit constant, and the bit often breaks. Therefore, when assembling various types of products in automatic assembly, a single automatic screw tightening device or robot cannot cope with screw members having various screw dimensions and lengths under the neck, and many dedicated machines must be manufactured. I didn't get it.

Therefore, the present invention provides a screw tightening device main body or a robot hand corresponding thereto provided with a sensor for generating a rotation signal of a motor. The screw is tightened or loosened by moving the screw forward or backward by one lead length of the screw to provide a small-sized and low-cost screw tightening device and a screw loosening device capable of coping with various screw members. .

[0008]

In order to achieve the above-mentioned object, according to the first aspect of the present invention, there is provided a tool shaft which can be integrally engaged with a screw member in a rotational direction, and a motor for rotating the tool shaft in a screw tightening direction. And a moving mechanism for moving at least the tool axis in the axial direction so as to follow the axial movement of the screw member when the screw member is rotated by the tool shaft. A rotation detecting means for generating a one-pulse signal, and a movement control for moving the tool axis in the axial direction by one lead length of the screw member for each one-pulse signal based on the detection information of the rotation detecting means. Means is provided, and the invention according to claim 2 includes a tool shaft that can be integrally engaged with the screw member in the rotation direction and a motor that rotationally drives the tool shaft in the screw tightening direction. Screw tightening A robot arm having a thrust axis for moving the hand at least in the axial direction of the tool axis, and a controller for controlling the operation of the screw hand and the robot arm. Rotation detecting means for generating a one-pulse signal during rotation is provided, and the controller moves the tool axis in the axial direction by the lead length of the screw member for each one-pulse signal based on the detection information of the rotation detecting means. The operation of the thrust shaft is controlled so as to perform the operation.

According to a third aspect of the present invention, there is provided a tool shaft which can be integrally engaged with a screw member in a rotational direction, a motor for rotating the tool shaft in a screw loosening direction, and when the screw member is rotated by the tool shaft, A movement mechanism for moving at least the tool axis in the axial direction so as to follow the axial movement of the screw member, and a screw loosening device including:
Movement control means for providing rotation detection means for generating a one-pulse signal, and for moving the tool axis in the axial direction by one lead length of the screw member for each one-pulse signal based on detection information of the rotation detection means; The invention according to claim 4 is characterized in that the screw loosening includes a tool shaft that can be integrally engaged with the screw member in the rotation direction and a motor that rotationally drives the tool shaft in the screw loosening direction. A screw loosening device comprising a hand, a robot arm having a thrust axis for moving the hand at least in the axial direction of the tool axis, and a controller for controlling the operation of the screw loosening hand and the robot arm; Rotation detecting means for generating a one-pulse signal during rotation is provided, and the controller controls the screw member for each one-pulse signal based on detection information of the rotation detecting means. It is characterized in that so as to control the operation of the thrust to move the tool axis by the lead length fraction in the axial direction.

According to a fifth aspect of the present invention, there is provided a tool shaft which can be integrally engaged with a screw member in a rotational direction, a motor for driving the tool shaft to rotate in a screw tightening direction, and the screw member being rotated by the tool shaft. And a moving mechanism for moving at least the tool shaft in the axial direction so as to follow the axial movement of the screw member, wherein a two-pulse signal is generated during one rotation of the tool shaft. Two rotation detecting means are provided at intervals of approximately 180 degrees on a circle centered on the tool axis. Based on the detection information of the rotation detecting means, the tool axis is rotated by one lead length of the screw member for every two pulse signals. And a movement control means for moving the tool shaft in the rotation direction integrally with the screw member and the tool shaft in the screw tightening direction. Motor that rotates A screw tightening hand, a robot arm having a thrust axis for moving the hand at least in the axial direction of the tool axis, and a controller controlling operation of the screw tightening hand and the robot arm. Two rotation detecting means for generating a two-pulse signal during one rotation of the shaft are provided at intervals of approximately 180 degrees on a circle centered on the tool axis, and the controller generates two pulses based on information detected by the rotation detecting means. The operation of the thrust shaft is controlled so that the tool shaft is moved in the axial direction by one lead length of the screw member for each of the following signals.

Further, according to the present invention, a tool shaft which can be integrally engaged with the screw member in the rotation direction, a motor for rotating the tool shaft in the screw loosening direction, and the screw member being rotated by the tool shaft. And a movement mechanism for moving at least the tool axis in the axial direction so as to follow the axial movement of the screw member, wherein a two-pulse signal is generated during one rotation of the tool axis. Two rotation detecting means are provided at intervals of approximately 180 degrees on a circle centered on the tool axis. Based on the detection information of the rotation detecting means, the tool axis is rotated by one lead length of the screw member for every two pulse signals. And a movement control means for moving the tool shaft in a rotating direction integrally with the screw member and the tool shaft in the screw tightening direction. Motor that rotates A screw tightening device comprising: a screw tightening hand, a robot arm having a thrust axis for moving the hand at least in the axial direction of the tool axis, and a controller for controlling operation of the screw loosening hand and the robot arm. Two rotation detecting means for generating a two-pulse signal during one rotation of the shaft are provided at intervals of approximately 180 degrees on a circle centered on the tool axis, and the controller generates two pulses based on information detected by the rotation detecting means. The operation of the thrust shaft is controlled so that the tool shaft is moved in the axial direction by one lead length of the screw member for each of the following signals.

[0012]

According to the first aspect of the present invention, the rotation detecting means outputs a signal of one pulse every one rotation of the tool shaft, and the movement control means performs one rotation in the screw tightening direction of the tool shaft based on this signal. The moving means is controlled so that the tool axis is advanced by one lead length of the screw each time. Therefore, without using a large and complicated pressing mechanism or an expensive control device, the error in the feed of the tool shaft can be suppressed to a maximum of ± 1 lead length of the screw, and the pressing force at the time of screw tightening is kept within a certain range. be able to.

According to the second aspect of the present invention, the rotation detecting means outputs a one-pulse signal for each rotation of the tool shaft, and the controller for controlling the operation of the arm and the robot hand operates on the basis of this signal to control the screw of the tool shaft. The operation of the thrust shaft is controlled so that the tool shaft is advanced by one lead length of the screw for each rotation in the tightening direction. Therefore, a small and highly versatile screw fastening device can be realized by using the existing Z-axis elevating robot. In addition, since the error in the feed of the tool shaft is suppressed to a maximum of ± 1 lead length of the screw, the pressing force at the time of screw tightening can be kept within a certain range.

According to the third aspect of the present invention, the rotation detecting means outputs a signal of one pulse every one rotation of the tool shaft, and the movement control means outputs one pulse in the tool loosening direction based on the signal. The moving means is controlled so that the tool shaft is retracted by one lead length of the screw every rotation. Therefore, without using a large and complicated pressing mechanism or an expensive control device, the error of the feed of the tool axis can be suppressed to a maximum of ± 1 lead length of the screw,
The pressing force when the screw is loosened can be kept within a certain range.

According to the present invention, the rotation detecting means outputs a signal of one pulse for each rotation of the tool shaft, and the controller for controlling the operation of the arm and the robot hand controls the screw of the tool shaft based on this signal. The operation of the thrust shaft is controlled so that the tool shaft is retracted by one lead length of the screw for each rotation in the loosening direction. Therefore, a small and highly versatile screw loosening device is realized by using the existing Z-axis elevating robot. In addition, since the error in the feed of the tool shaft can be suppressed to a maximum of ± 1 lead length of the screw, the pressing force when the screw is loosened can be kept within a certain range.

According to the fifth and seventh aspects of the present invention, in addition to the same operation as the first or third aspect of the present invention, two chattering operations can be performed even if the rest position of the dog is applied to the sensor of the rotation detecting means and causes chattering. Since the tool axis is moved by one lead length when both signals of the sensor section are input, no malfunction occurs. According to the sixth and eighth aspects of the invention, in addition to the same operation as the second or fourth aspect of the invention, even if chattering occurs due to the dog's rest position being applied to the sensor of the rotation detecting means, the two sensor portions are not affected. By inputting both signals, the tool axis is moved by one lead length.
There is no malfunction.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. FIGS. 1 and 2 show one embodiment of the screw tightening device and the screw loosening device according to the first and third aspects of the present invention. First, the configuration will be described.

In FIG. 1, reference numeral 1 denotes a screw member which penetrates the first work 2 and is screwed to the screw hole 3a of the second work 3, and the screw member 1 tightens the first work 2 into the second work 3. Can be fastened and fixed. The screw member 1 is held by a holding means or guide means (not shown) as shown in FIG.
Is maintained in the position shown in Fig. Reference numeral 11 denotes a tool shaft driven by a tool shaft driving motor 12. The tool shaft 11 integrally engages with the screw member 1 in the rotation direction to rotate the screw member 1. The tool shaft drive motor 12 can be rotated forward and backward, and its rotation direction can be switched by a controller 15 described later depending on whether the screw is tightened or loosened. 4
Is a base, on which a frame 5 including a thrust shaft 16 and a linear guide (not shown) is provided. Reference numeral 6 denotes an automatic screw tightening machine as a screw tightening device and a screw loosening device, which is supported by a lifting bracket 17 guided by the linear guide so as to be able to move up and down. The main body 6 of the automatic screwing machine is moved up and down with the rotation of a motor 19 for driving the thrust shaft 16.
7 to go up and down. The elevating motor 19 is controlled by a controller 15 (movement control means) based on a pulse signal from a sensor 13 for detecting rotation of the tool axis driving motor 12. More specifically, the sensor 13 is, for example, an optical sensor that is shielded from light by a rotation detecting projection 14 a of a dog 14 attached to a rotation shaft of the tool axis driving motor 12. To output a one-pulse signal. The controller 15 includes a CPU, a ROM, a RAM, an I / O circuit, and a motor drive circuit. According to a control program stored in the ROM, various kinds of sensor information including the sensor 13 and various information corresponding to the screw member 1 are provided. The elevating motor 19 is controlled based on the setting information. The frame 5, the thrust shaft 16, the lifting bracket 17 and the lifting motor 19 constitute a moving mechanism 7 for moving the automatic screw tightening machine body 6 in the axial direction of the tool shaft 11, and the sensor 13 and the dog 14 A rotation detecting means for generating a signal of one pulse during one rotation of the tool shaft 11 is constituted.

FIG. 2 is a diagram showing the detailed structure of the main body 6 of the automatic screwing machine. In the figure, reference numeral 18 denotes a main body case, which is connected to the lifting bracket 17 by bolts or the like. Reference numeral 21 denotes a mounting base to which the tool shaft driving motor 12 is mounted, and is supported by the main body case 18 so as to be vertically displaceable by a stopper / guide shaft 21a. Further, a plurality of tension springs 22 are provided between the motor mount 21 and the main body case 18, and the motor mount 21 is constantly urged downward. These motor mount 21 and tension spring 2
2 constitutes a pre-pressing mechanism. Reference numeral 23 denotes a torque clutch interposed between the tool shaft 11 and the motor 12 for driving the tool shaft. At the end of the screw tightening in which the load torque of the tool shaft 11 suddenly increases, from the time when the load torque reaches a predetermined value, 1
1 and the tool shaft drive motor 12 are allowed to rotate relative to each other. Next, the operation will be described.

First, in the case of screw tightening, the first work 2
Is placed on the second work 3 and the screw member 1 is inserted up to the entrance of the screw hole 3a. Alternatively, the screw member 1 is supplied from an external supply device and is attracted to the tip of the tool shaft 11 magnetized in advance. Next, the thrust shaft 16 is moved by the elevating motor 19.
Is rotated to lower the automatic screw tightening machine main body 6 and bring the tool shaft 11 into contact with the screw member 1. At this time, the tension spring 22 expands, and a pressing force is applied to the screw member 1. Next, when the screw for rotation is given by the tool driving motor 12, the screw member 1 is screwed into the screw hole 3a while rotating. At this time, the screw member 1 descends by one lead length of the screw member 1 per rotation. At this time, the sensor 13 generates a signal of one pulse per one rotation of the motor 12 for driving the tool axis, and this signal is sent to the controller 15. The controller 15 rotates the thrust shaft 16 by the elevating motor 19 so as to lower the elevating bracket 17 by one lead length of the screw member 1 in response to one pulse signal input,
The tool shaft 11 is made to follow the advance of the screw member 1. When the screw is tightened and the tightening torque (load torque) reaches a predetermined value, the tightening torque of the screw member 1 does not increase any more, and the torque clutch 23 rotates the tool shaft driving motor 12 to the tool shaft 11. Is canceled. Next, the tool screw driving motor 12 is stopped by detecting this state or by detecting that a certain time has elapsed after the start of screw tightening, and then the automatic screw tightening machine body 6 is raised to a predetermined position. Then, a series of screw tightening work is completed.

Next, in the case of loosening the screw, the first work 2
Screw member 1 and tool shaft 11 for fastening
The automatic screwing machine body 6 is lowered to a position where is engaged with. At this time, the tension spring 22 slightly extends, and a pressing force is applied to the screw member 1. Next, when the tool shaft driving motor 12 is rotated in the screw loosening direction, the screw member 1 is retracted while rotating in that direction and comes out of the screw hole 3a. At this time, a signal from the sensor 13 that generates one pulse per one rotation of the tool shaft driving motor 12 is sent to the controller 15 while the screw member 1 rises by one lead length of the screw member 1 per rotation. The controller 15 rotates the thrust shaft 16 by the elevating motor 19 so as to raise the elevating bracket 17 by one lead length of the screw member 1 in response to one pulse signal input, and the tool shaft 11 follows the retraction of the screw member 1. Let it. Next, after the screw loosening is started, the tool shaft driving motor 12 is stopped by detecting that a certain time has elapsed, and then the automatic screw tightening machine main body 6 is raised to a predetermined position to perform a series of screw loosening operations. finish.

As described above, in this embodiment, the rotation of the tool shaft 11 is detected by the sensor 13 and the motor 12
The controller 15 controls the movement of the moving mechanism 7 in response to the one-pulse signal input. Therefore, the feed error when the tool shaft 11 is lowered and raised with the advance or retreat of the screw is a maximum of ± 1 lead length of the screw. In this range, the tension force of the tension spring does not change so much. The pressing force of the shaft 11 against the screw member 1 can be kept constant. As a result, there is no need for the conventional servo control and a large pressing mechanism having a large pressing stroke, and a small-sized and low-cost apparatus can be realized. In addition, the moving amount for each pulse is set according to the type of screw, and the controller 1
If it is stored in No. 5, it can correspond to a screw of each nominal size.

FIG. 3 is a view showing one embodiment of the screw tightening device and the screw loosening device according to the second and fourth aspects of the present invention. The same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted. In this embodiment, the main body 6 of the automatic screw tightener shown in FIG.
It is configured as an automatic screw tightening robot. That is, the Z-axis elevating robot 40
Has a rotatable first arm 43 and a second arm 44 which are robot arms, and a Z-axis 41 (thrust axis) supported by the second arm 44 so as to be able to move up and down. The main body case 18 of the main body 6 of the automatic screw tightening machine is connected to a lifting bracket 42 fixed to a lower end portion by a bolt or the like.

Reference numeral 45 denotes a Z-axis 4 of the Z-axis elevating robot 40.
1, a controller (movement control means) for controlling the operations of the first arm 43 and the second arm 44 and the main body 6 of the automatic screw tightening machine. The controller 45 controls the movement of the Z-axis 41 on the X and Y planes by the first and second arms 43 and 44 and the elevation by the Z-axis 41 itself to position the automatic screwing machine main body 6 at a predetermined position. And a function of controlling the screw tightening and loosening work by the automatic screw tightening machine main body 6 in accordance with the type of the screw member 1. Although not shown, the means for detecting the elevation position of the Z-axis 41 includes rotation of the elevation drive motor or Z-axis 4
An encoder or the like for detecting the displacement of No. 1 is used. Based on the information on the detection of the elevating position and the pulse from the sensor 13 for detecting the rotation of the tool shaft 11, the controller 45 responds to one signal from the sensor 13 by Z
When the shaft 41 is lowered by one lead length of the screw member 1, and when the screw is loosened, the elevation drive motor is rotated so that the Z-axis 41 is raised by one lead length of the screw member 1. Control lifting.

In this embodiment, the sensor 13 (rotation detecting means) outputs a signal of one pulse for each rotation of the tool shaft 11, and the operation of the first and second arms 43 and 44 and the main body 6 of the automatic screw tightener. The controller 45 controls the tool shaft 11 by one lead length of the screw member 1 for each rotation of the tool shaft 11 in the screw tightening or loosening direction based on this signal.
Of the Z axis 41 is controlled so as to move forward or backward. Therefore, a small and highly versatile screw tightening or loosening device can be realized by using the existing Z-axis elevating robot. In addition, since the error in the feed of the tool shaft is suppressed to a maximum of ± 1 lead length of the screw, the pressing force at the time of tightening or loosening the screw can be kept within a certain range.

In the above-described two embodiments, the sensor 13 as the rotation detecting means is connected to one of the motors 12 for driving the tool shaft.
Although one pulse signal is output for each rotation, the rotation detecting means is not limited to this, and outputs a plurality of pulse signals for one rotation of a tool driving motor or a tool shaft. Is also good. That is, as shown in FIG. 4, two sensors 31, 32 (rotation detecting means) for detecting the protrusion 14a at the tip of the dog 14 are provided as rotation detecting means, and a predetermined phase difference from these sensors 31, 32 is provided. The rotation detection signal is sent to the controller 15 or the controller 45.
(Moving control means) so that the tool shaft 11 is moved in the axial direction by one lead length of the screw member 1 every two pulse signals, so that the screw can be tightened or loosened.

In this manner, when the screw 13 is tightened or loosened, the two sensors 31 and 32 may be chattered even if the rotation detecting projection 14a hits the sensor 13 at the rest position of the dog 13. Both dog 1
By detecting the rotation detecting projection 14a of No. 4 and sending the signal to the controller 45, the tool shaft 11 is moved forward or backward by one lead length, so that malfunction does not occur.

Although the embodiment shown in FIG. 3 is constructed as a Z-axis elevating type robot, it is needless to say that the embodiment can be applied to other types of robot hands, and the robot is replaced with a robot having an AHC (automatic hand changer). A screw tightening hand and a screw loosening hand can be added as a part of a plurality of possible hands, or a corresponding control unit can be connected to the robot controller.

Further, in each of the above embodiments, the apparatus is capable of performing both screw tightening and screw loosening, but it is needless to say that the apparatus may perform only screw tightening or only screw loosening.

[0030]

According to the first aspect of the present invention, the error of the feed of the tool shaft is suppressed to a maximum of ± 1 lead length of the screw without using a large and complicated pressing mechanism or an expensive control device.
Since the pressing force at the time of screw tightening is kept within a certain range, it is possible to provide a small-sized and low-cost screw tightening device that can cope with various screw members.

According to the second aspect of the present invention, by controlling the operation of the thrust shaft provided on the robot arm, the error of the feed of the tool shaft is suppressed to a maximum of ± 1 lead length of the screw.
Since the pressing force at the time of screw tightening is kept within a certain range, a small and highly versatile screw tightening device can be realized using an existing Z-axis elevating robot. According to the third aspect of the present invention, the error in the feed of the tool shaft is suppressed to a maximum of ± 1 lead length of the screw without using a large and complicated pressing mechanism or an expensive control device. Since the pressure is kept within a certain range, it is possible to provide a small-sized and low-cost screw loosening device that can cope with various screw members.

According to the fourth aspect of the present invention, by controlling the operation of the thrust shaft provided on the robot arm, the error in the feed of the tool shaft is suppressed to a maximum of ± 1 lead length of the screw,
Since the pressing force at the time of screw loosening is kept within a certain range, a small and versatile screw loosening device can be realized using an existing Z-axis elevating robot.

According to the fifth and seventh aspects of the present invention, in addition to the same effect as the first or third aspect of the invention, even if chattering occurs due to the dog stationary position being applied to the sensor of the rotation detecting means, Since the tool axis is moved by one lead length by inputting both signals of the two sensor units, malfunction can be prevented. According to the sixth and eighth aspects of the invention, in addition to the same effects as those of the second or fourth aspect, even if chattering occurs due to the dog stationary position being applied to the sensor of the rotation detecting means, two sensors are provided. Since the tool axis is moved by one lead length when both signals of the section are input, malfunction can be prevented.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an embodiment of a screw tightening device and a screw loosening device according to the first and third aspects of the present invention.

FIG. 2 is a sectional view of a main part thereof.

FIG. 3 is an overall configuration diagram of one embodiment of a screw tightening device and a screw loosening device according to the second and fourth aspects of the present invention.

FIG. 4 is a plan view of a rotation detecting means of a screw tightening device and a screw loosening device according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Screw member 6 Automatic screw tightener main body 7 Moving mechanism 11 Tool axis 12 Tool axis drive motor 13 Sensor (rotation detecting means) 14 Dog (rotation detecting means) 15 Controller (movement control means) 16 Thrust axis 19 Lifting motor 21 Motor mounting base 22 Tension spring 23 Torque clutch 31, 32 Sensor (rotation detecting means) 40 Z-axis elevating robot 41 Z-axis (thrust axis) 43 First arm (robot arm) 44 Second arm (robot arm) 45 Controller ( Movement control means)

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-4-115834 (JP, A) JP-A-5-23928 (JP, A) JP-A-4-261723 (JP, A) JP-A-5-261 8134 (JP, A) JP-A-2-311231 (JP, A) JP-A-4-372199 (JP, A) JP-A-63-235818 (JP, A) JP-A-3-277200 (JP, A) JP-A-2-83846 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23P 19/06

Claims (8)

(57) [Claims] 1. A tool shaft that can be integrally engaged with a screw member in a rotational direction, a motor that drives the tool shaft to rotate in a screw tightening direction, and an axial movement of the screw member when the screw member is rotated by the tool shaft. And a movement mechanism for moving at least the tool axis in the axial direction so as to follow the rotation of the tool shaft. A rotation detecting means for generating a signal of one pulse during one rotation of the tool shaft is provided, A screw tightening device, comprising: movement control means for moving the tool axis in the axial direction by one lead length of the screw member for each pulse signal based on detection information of the detection means. 2. A screwing hand having a tool shaft which can be integrally engaged with a screw member in a rotational direction and a motor for rotating the tool shaft in a screw tightening direction, and moving the hand at least in the axial direction of the tool shaft. A screw tightening device comprising: a robot arm having a thrust axis; and a controller for controlling the operation of the screw tightening hand and the robot arm. A rotation detecting means for generating a signal of one pulse during one rotation of the tool shaft. The controller controls the operation of the thrust shaft so as to move the tool shaft in the axial direction by one lead length of the screw member for each pulse signal based on the detection information of the rotation detecting means. A screw tightening device characterized by the above-mentioned. 3. A tool shaft that can be integrally engaged with a screw member in a rotational direction, a motor that rotates the tool shaft in a loosening direction, and an axial movement of the screw member when the screw member is rotated by the tool shaft. And a moving mechanism for moving at least the tool axis in the axial direction so as to follow the rotation of the tool axis. A rotation detecting means for generating a signal of one pulse during one rotation of the tool axis, A screw loosening device comprising: movement control means for moving a tool axis in the axial direction by one lead length of the screw member for each pulse signal based on detection information of the detection means. 4. A screw loosening hand having a tool shaft which can be integrally engaged with a screw member in the rotation direction, and a motor for rotating the tool shaft in the screw loosening direction, and moving the hand at least in the axial direction of the tool shaft. A screw loosening device comprising: a robot arm having a thrust shaft; and a controller for controlling the operation of the screw loosening hand and the robot arm, wherein a rotation detecting means for generating one pulse signal during one rotation of the tool shaft. The controller controls the operation of the thrust shaft so as to move the tool shaft in the axial direction by one lead length of the screw member for each pulse signal based on the detection information of the rotation detecting means. A screw loosening device characterized by the above-mentioned. 5. A tool shaft that can be integrally engaged with a screw member in a rotational direction, a motor that rotates the tool shaft in a screw tightening direction, and an axial movement of the screw member when the screw member is rotated by the tool shaft. And a moving mechanism for moving at least the tool axis in the axial direction so as to follow the rotation of the tool axis. A rotation detecting means for generating a signal of two pulses during one rotation of the tool axis is provided. A screw tightening device, comprising: movement control means for moving the tool axis in the axial direction by one lead length of the screw member for every two pulse signals based on detection information of the detection means. 6. A screw-clamping hand having a tool shaft which can be integrally engaged with a screw member in a rotational direction, and a motor for rotating the tool shaft in a screw-clamping direction, and moving the hand at least in the axial direction of the tool shaft. A screw tightening device comprising: a robot arm having a thrust shaft; and a controller for controlling the operation of the screw tightening hand and the robot arm. A rotation detecting means for generating a signal of two pulses during one rotation of the tool shaft. The controller controls the operation of the thrust shaft so as to move the tool shaft in the axial direction by one lead length of the screw member for every two pulse signals based on the detection information of the rotation detecting means. A screw tightening device characterized by the above-mentioned. 7. A tool shaft that can be integrally engaged with a screw member in a rotational direction, a motor that drives the tool shaft to rotate in a screw loosening direction, and an axial movement of the screw member when the screw member is rotated by the tool shaft. A moving mechanism for moving at least the tool axis in the axial direction so as to follow the rotation of the tool axis. A rotation detecting means for generating a signal of two pulses during one rotation of the tool axis, Movement control means for moving a tool axis in the axial direction by one lead length of the screw member for every two pulse signals based on detection information of the detection means. 8. A screw loosening hand having a tool shaft engageable with a screw member integrally in a rotational direction, a motor for rotating the tool shaft in a screw loosening direction, and moving the hand at least in the axial direction of the tool shaft. A screw loosening device comprising: a robot arm having a thrust shaft; and a controller for controlling the operation of the screw loosening hand and the robot arm. The rotation detecting means for generating a signal of two pulses during one rotation of the tool shaft. And the controller controls the operation of the thrust shaft so as to move the tool shaft in the axial direction by one lead length of the screw member every two pulse signals based on the detection information of the rotation detecting means. A screw loosening device characterized by the above-mentioned.