JPH0811027A - Screw tightening device - Google Patents

Abstract

PURPOSE:To judge the presence or absence of the biting between a socket and a screw without lifting a work after the screw is tightened by the.socket in the work. CONSTITUTION:A screw tightening device 4 tightens a screw into a work W by fitting a socket 5 to the screw and rotating it by a rotary shaft 18a of an electric motor 18. The device 4 is provided with a first cylinder 12 to integratedly move the socket 5 and the rotary shaft 18a to the position approaching to the work W arranged therebelow and the position away upward from the work W. The socket 5 is connected to the rotary shaft 18a in an integratedly rotatable and relatively movable manner through a spindle 22. The socket 5 and the spindle 22 are relatively movable to the rotary shaft 18a by a second cylinder 17. The value of the moving force to be given to the socket 5 and the spindle 22 by the second cylinder 17 is set to be smaller than the gravity value of the work W.

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 used for tightening screws such as bolts and nuts on a work.

[0002]

2. Description of the Related Art Conventionally, for example, in an automobile engine assembly line, various assembly processes have been set with the engine body as a work. Among them, a screw tightening device called a "nut runner" is used in place of manpower for tightening screws such as bolts and nuts. The nut runner is used in various processes such as tightening of the cylinder head to the cylinder block, tightening of the crank cap to the cylinder block, tightening of the bearing cap to the cylinder head, etc., to automate screw tightening.

This type of nutrunner has a socket,
The screw is tightened by being rotated by the drive source while the socket is fitted in the screw.
Some nutrunners are provided so as to be vertically movable with respect to the work. In this type of nut runner, the nut runner is lowered toward the work when the screw is tightened, and after tightening is completed, the nut runner is lifted away from the work in order to deal with the next work.

In the nut runner as described above, excessive torque is transmitted from the socket to the screw when the screw is tightened. Therefore, for example, when one socket is used for a long time, there is a possibility that a phenomenon called "bite" in which the socket is coupled to the screw occurs. In this case, the socket cannot be removed from the screw when the screw is completely tightened, and the work and the nut runner are integrated. Therefore, as the nut runner rises, the work may be completely lifted from the mounting surface.

To solve the above problem, a nut runner capable of detecting bite between a socket and a screw is proposed in Japanese Utility Model Laid-Open No. 4-51370.

As shown in FIG. 12, this nut runner includes a tool shaft 62 supported by a support plate 61, and a socket 63 is fixed to the lower end of the tool shaft 62. A drive source 64 for the tool shaft 62 is provided on the upper surface of the support plate 61. The support plate 61 is provided so as to be vertically movable. For this up-and-down movement, it is possible to use a motor or a hydraulic cylinder. The nut runner main body 65 is configured by the above-mentioned members 61 to 64, and the support plate 61 is moved up and down, thereby
5 is moved up and down.

In this nut runner, a fluid pressure cylinder device 66 is mounted on the lower surface of the support plate 61 in parallel with the tool shaft 62. The cylinder device 66 is a cylinder 67.
And the piston rod 6 that can advance from the cylinder 67
8 and. The tip of this rod 68 is the socket 6
It is possible to advance to a position slightly lower than the tip of No. 3. A contact piece 69 capable of contacting the work W is fixed to the tip of the rod 68. Inside the cylinder 67, a magnet 70 is attached to the upper end of the rod 68. Corresponding to the magnet 70, the cylinder 67
A magnet switch 71 is fixed to the lower end of the outer peripheral wall of the. In this switch 71, the rod 68 is the cylinder 67.
It is possible to operate close to the magnet 70 when it is most advanced.

After tightening the bolts 72, the rod 68 is advanced from the cylinder 67 when the nut runner is raised. At this time, when the bite does not occur between the socket 63 and the bolt 72, the relative movement of the nut runner and the work W is allowed, and the advance of the rod 68 is allowed up to its maximum stroke, so that the switch 71 is moved.
Works. Therefore, based on the operation of the switch 71, it is possible to detect that no bite has occurred. On the other hand, when biting between the socket 63 and the bolt 72 occurs, relative movement between the nut runner and the work W is hindered, the rod 68 is not allowed to advance to its maximum stroke, and the switch 71 does not operate. Therefore, based on the non-operation of the switch 71, it is possible to detect that no bite has occurred.

[0009]

However, in the above-mentioned conventional nut runner, in order to detect the presence or absence of bite between the socket 63 and the bolt 72, it is necessary to once raise the nut runner. Therefore, when the driving force for raising the nut runner is set to be larger than the total weight of the work W and the nut runner in advance, the work W and the nut runner are slightly moved by the bite between the socket 63 and the bolt 72. May be lifted. In this case, the work W is once lowered and then the socket 6
It is necessary to release the bite between 3 and the bolt 72. Alternatively, when the work W is slightly lifted, unreasonable stress may be generated between the socket 63 and the bolt 72, and both members 63 and 72 may be damaged.

The present invention has been made in view of the above circumstances, and an object thereof is to bite between the socket and the screw without lifting the work after the screw is tightened by the socket in the work. It is to provide a screw tightening device capable of determining the presence or absence of a screw.

[0011]

In order to achieve the above object, the first invention according to claim 1 is to fit a socket to a screw and rotate the shaft by a rotary shaft, so that the screw is attached to a work. A screw tightening device configured to be tightened against each other, comprising a first moving means for moving the socket to a position approaching a workpiece arranged below the socket and a position separating upward from the workpiece, It is intended that the value of the moving force applied to the socket by the first moving means to separate the socket from the screw after the screw is tightened by the socket is set to be smaller than the gravity value of the work.

In order to achieve the above-mentioned object, the second aspect of the present invention is that the socket is fitted on the screw and rotated by the rotary shaft, so that the screw is tightened to the work. A configured screw tightening device, comprising: second moving means for integrally moving the socket and the rotating shaft to a position closer to a work arranged below them and a position separated upward from the work; A connecting means for connecting the socket to the rotating shaft so as to rotate integrally therewith, and a connecting means for connecting the socket so that the socket can move relative to the rotating shaft; and a third moving means for moving the socket relative to the rotating shaft. And the value of the moving force applied to the socket by the third moving means is set to be smaller than the gravity value of the work.

In order to achieve the above-mentioned object, the third invention according to claim 3 is the structure of the first invention or the second invention, in which the first moving means is for separating the socket from the screw. Alternatively, it is intended to provide detection means for detecting the presence or absence of movement of the socket when the third movement means operates.

[0014]

According to the structure of the first aspect of the invention, the socket is brought closer to the work by activating the first moving means to move the socket downward. At this time, by fitting the socket to the screw and operating the rotating shaft, the socket is rotated and the screw is tightened in the work.

If there is no bite between the socket and the screw during this tightening, the first moving means is actuated to separate the socket from the screw after the screw is tightened by the socket. By doing so, the socket is separated upward from the screw and the work. Therefore, the movement of the socket indicates that there is no bite between the socket and the screw.

On the other hand, when biting occurs between the socket and the screw when tightening the screw, the biting causes the socket and the workpiece to be integrated, and the screw tightens the screw. When the first moving means is actuated in order to separate the socket from the screw after the above, the moving force is transmitted from the socket to the work through the screw. However, since the value of the moving force applied to the socket is smaller than the gravity value of the work here, the moving force does not raise the socket, the screw, and the work together, and the socket is not separated from the screw. Absent. Thus, the immobility of the socket indicates that there is a bite between the socket and the screw.

According to the second aspect of the invention, the second moving means is operated to move the socket and the rotary shaft together downward, thereby bringing them closer to the work. At this time, by fitting the socket to the screw and operating the rotary shaft, the socket is rotated through the connecting means, and the screw is tightened in the work.

When there is no bite between the socket and the screw at the time of this tightening, the third moving means is operated to move the socket with respect to the rotary shaft and to move the screw and the work. Away from. Therefore,
The movement of the socket indicates that there is no bite between the socket and the screw.

In this case, the second moving means is further actuated to move the socket and the rotary shaft upward together, whereby the socket and the rotary shaft are moved to a position away from the work.
On the other hand, when biting occurs between the socket and the screw during tightening, the biting causes the socket and the work to be integrated, and when the third moving means is operated. The moving force is transmitted from the socket to the work through the screw. However, since the value of the moving force applied to the socket is smaller than the gravity value of the work here, the moving force does not raise the socket, the screw, and the work together, and the socket is not separated from the screw. Absent. Thus, the immobility of the socket indicates that there is a bite between the socket and the screw.

According to the structure of the third aspect, when the socket is separated from the screw, the presence or absence of the movement of the socket is detected by the detecting means. Therefore, the presence or absence of bite between the socket and the screw is indicated by the detection result of the detection means.

[0021]

【Example】

(First Embodiment) A first embodiment of the screw tightening device according to the first to third inventions will be described below in detail with reference to FIGS.

In this embodiment, the screw tightening device is arranged and embodied in an automobile engine assembly line. In this assembly line, for example, a screw tightening device is used in a process such as tightening a cylinder head to a cylinder block, tightening a crank cap to a cylinder block, or tightening a bearing cap to a cylinder head. Tightening is done automatically.

As shown in FIGS. 1 and 3, the assembly line is provided with a conveyor 1 for carrying the work W. This conveyor 1 is formed by connecting a plurality of conveyors 2,
A cylinder block, a cylinder head, and the like are mounted on each table 2 as a set of works W. The conveyor 1 is moved at a predetermined low speed based on the operation of the drive motor 3, so that the works W are sequentially transported along the assembly line.

At a predetermined position on the assembly line, the screw tightening device 4 in this embodiment is arranged above the conveyor 1. The device 4 has a pair of sockets 5 for tightening screws at its lower end. Then, in this device 4, as shown in FIG. 2, the sockets 5 are fitted into the heads 6a of the bolts 6 and rotated, whereby the bolts 6 are rotated.
Are fastened to the work W.

The device 4 is supported by rails 7 installed above the conveyor 1. The device 4 is provided with a carriage 8, which can be moved along a rail 7 by a pulley 9. Below the carriage 8,
The first support plate 10 is arranged horizontally, and the support plate 10 is fixed to the lower ends of a plurality of support rods 11 extending downward from the carriage 8. A first air cylinder 12 as the first and second moving means of the present invention is mounted on the support plate 10, and an operating rod 12a thereof penetrates through the support plate 10 and projects downward. . Similarly, on the support plate 10, a plurality of linear bushes 13 are attached. A guide bar 13a is attached to each of the bushes 13 so as to be vertically slidable. Each guide bar 13a extends below the support plate 10. A second support plate 14 that is horizontally arranged is fixed to the lower end of each guide bar 13a. Working rod 12
The lower end of a is connected to the second support plate 14.

When the operating rod 12a of the first air cylinder 12 expands and contracts, the second support plate 14 moves up and down while being guided by the cooperation of the linear bushes 13 and the guide bars 13a.

A plurality of support rods 15 extending downward are fixed to the lower side of the second support plate 14. At the lower end of each support rod 15, a third support plate 16 is arranged horizontally.
Has been fixed. A second air cylinder 17 as the first and third moving means of the present invention is mounted on the support plate 16, and an operating rod 17a thereof penetrates the support plate 16 and projects downward. . Similarly, a pair of electric motors 18 having a rotary shaft 18a according to the present invention is mounted on the support plate 16, and the rotary shafts 18a extend downward through the support plate 16. A linear bush 19 is attached to the lower side of the support plate 16. A guide bar 19a is attached to the bush 19 so as to be vertically slidable. At the lower end of the guide bar 19a, a horizontally arranged fourth support plate 20 is provided.
Has been fixed. The lower end of the operating rod 17a is connected to the fourth support plate 20. In this embodiment, the stroke amount of the operating rod 17a of the second air cylinder 17 is smaller than the stroke amount of the operating rod 12a of the first air cylinder 12.

A pair of bushing bushes 21 are attached to the fourth support plate 20 so as to correspond to the respective rotary shafts 18a. A spindle 22 is rotatably attached to each bush 21 so as not to fall off. Revolving shafts 18a are connected to the respective spindles 22 so as to be integrally rotatable and relatively movable in the vertical direction.

That is, as shown in FIG.
A flange 22a that can be engaged with the bush 21 is provided on the upper part of 2
Are formed. The flange 22a prevents the spindle 22 from falling off. A hole 22b that opens upward is formed at the center of each spindle 22. On the other hand, the tip of each rotary shaft 18a is formed thinner than the other to form a spline shaft 18b, and these shafts 18a are inserted into the corresponding holes 22b of the respective spindles 22. Then, this spline shaft 18b and the hole 22 of the spindle 22
By the engagement with b, the rotational force is transmitted from the rotary shaft 18a to the spindle 22, while the relative movement in the vertical direction is allowed between the two 22 and 18a. A spring 23 is attached to the outer circumference of each rotary shaft 18a.
Is interposed between the spindle 22 and the rotary shaft 18a. Each spindle 22 is biased downward by a spring 23, and is vertically movable against the biasing force. The socket 5 described above is attached to the lower end of each spindle 22 so as to be removable and integrally rotatable. At the lower end of each socket 5, a recess 5a that can be fitted into the head 6a of the bolt 6 is formed. The recess 5a has a shape matching the head 6a of the bolt 6.

The rotary shaft 18a of each electric motor 18
Is rotated, each socket 5 is rotated together with each spindle 22. Therefore, by rotating the socket 5 with the recess 5a of the socket 5 fitted to the head 6a of the bolt 6, the bolt 6 is tightened to the work W.

On the other hand, by expanding and contracting the operating rod 17a of the second air cylinder 17, each linear bush 1
The fourth support plate 20 is moved up and down by the cooperation of 9 and each guide bar 19a and the cooperation of each rotating shaft 18a and each spindle 22. By this operation, each socket 5 is moved in the vertical direction relative to each rotary shaft 18a.

That is, in this embodiment, the spline shaft 1
The connecting means in the present invention is constituted by 8b and the spindle 22. And by both 18b and 22,
The socket 5 is connected to the rotary shaft 18a so as to be integrally rotatable, and the socket 5 is vertically movable relative to the rotary shaft 18a within a range smaller than the range of movement by the operation of the first air cylinder 12. It is connected.

In the following description, the second support plate 1
4 and each member 5, 15 to 23 supported on the lower side thereof
Are collectively referred to as a nut runner portion 24. As shown in FIG. 3, in this embodiment, each air cylinder 1
First and second control valves 25 and 26, which are three-way valves, are provided to switch the supply of air to the valves 2 and 17, respectively.

The first control valve 25 operates to selectively supply the air supplied from an air source (not shown) with a predetermined pressure to the first air cylinder 12 through the two paths 27a and 27b. The control valve 25 includes first and second solenoids 28 and 29 for switching the air paths 27a and 27b. Then, when the first solenoid 28 is turned on, air is supplied to the first air cylinder 12 through one path 27a, and the operating rod 12a is extended. On the other hand, the second solenoid 2
9 is turned on, air is supplied to the first air cylinder 12 through another path 27b, and the operating rod 1
2a is shortened. The first air cylinder 12 has a first
And the second limit switches 30 and 31 are attached. The first limit switch 30 is the operating rod 12
When a is extended and reaches the longest position (longest position), it is detected and turned on. When the operating rod 12a is contracted and reaches the shortest position (shortest position), the second limit switch 31 detects that fact and is turned on.

The second control valve 26 operates to selectively supply the air supplied from the same air source as described above to the second air cylinder 17 through the two paths 32a and 32b. The control valve 26 includes third and fourth solenoids 33 and 34 for switching the air passages 32a and 32b. Then, when the third solenoid 33 is turned on, one path 3 is provided to the second air cylinder 17.
Air is supplied through 2a, and the operating rod 17a is extended. On the other hand, when the fourth solenoid 34 is turned on, air is supplied to the second air cylinder 17 through another path 32b, and the operating rod 17a is contracted.

A pressure reducing valve 35 with a relief is provided in the middle of the path 32b. The pressure reducing valve 35 adjusts the outlet side pressure value to a set pressure value lower than the inlet side pressure value regardless of the inlet side pressure value. In this embodiment, the pressure reducing valve 35 constitutes a moving force setting means for setting the value of the moving force of each socket 5. Then, based on the set pressure value in the pressure reducing valve 35, the value of the moving force applied to each socket 5 by the operation of the second air cylinder 17 is set to be smaller than the gravity value of the work W. The set value of this moving force is sufficient to separate the socket 5 from the bolt 6.

Third and fourth limit switches 36 and 37 are attached to the second air cylinder 17. The third limit switch 36 detects that when the operating rod 17 is extended and reaches its longest position, and is turned on. When the operating rod 17a is contracted and reaches the shortest position, the fourth limit switch 37 detects that fact and is turned on. In this embodiment, the limit switches 36 and 37 constitute the detecting means of the present invention. Then, the limit switches 36 and 37 detect whether or not each socket 5 has moved when the second air cylinder 17 is activated.

As shown in FIG. 3, a control panel 38 for controlling the screw tightening device 4, the conveyor 1 and the like is arranged beside the assembly line. This control panel 38 has
First and second operation switches 39 and 4 for manually operating the screw tightening device 4 and the operation of the conveyor 1 and the like, respectively.
0 is provided. The control panel 38 is provided with an alarm 41 that lights and sounds when a malfunction of the screw tightening device 4 is detected.

FIG. 4 is a block diagram showing the electrical construction of the screw tightening device 4 as described above. The limit switches 30, 31, 36, 37 and the operation switches 39, 40 described above are connected to the input side of a computer 51 built in the control panel 38. On the output side of the computer 51, each drive circuit 5 also incorporated in the control panel 38
2 to 58 through the solenoids 28, 29, 3 described above.
3, 34, each electric motor 18, the drive motor 3, and the alarm 41 are connected. The computer includes an input / output interface, a central processing unit (CPU), a memory, and the like, and the memory stores a control program for controlling the screw tightening device 4 and the conveyor 1.
The CPU also has a timer function. Then, the computer operates the switches 30, 31, 36, 37, 39, 4
Based on the input signal from 0, each member 28, 29, 3
The operation of 3, 34, 18, 3, 41 is suitably controlled.

Next, the contents of the control program in the computer 51 and the movement of the screw tightening device 4 and the like obtained based on the program will be described with reference to FIGS.

FIG. 5 is a flow chart showing the contents of the control program in the computer 51. 6 to 9
FIG. 6 is a diagram showing a series of movements of the screw tightening device 4 and the like,
FIG. 6 shows the initial state. In this initial state, the operating rod 12a of the first air cylinder 12 is arranged at its shortest position, the second support plate 14 is arranged close to the first support plate 10, and the nut runner portion 24 is the work piece. It is arranged at a position away from W. Conveyor 1
Is controlled based on a separate control routine.

When the processing of this routine is started by the computer 51, first, at step 110, the first solenoid 28 is turned on for a predetermined period from the initial state to operate the first air cylinder 12. here,
When the operating rod 12a of the air cylinder 12 is extended and its longest position is detected by the first limit switch 30, the first solenoid 28 is turned off.

By this process, the nut runner portion 24 is lowered from the position shown in FIG. 6 to the position shown in FIG. Then, each socket 5 is lowered until it contacts the work W,
Each socket 5 is fitted on the head 6 a of the bolt 6.

Next, at step 120, each electric motor 18 is operated for a predetermined period to rotate each socket 5. By this process, the bolt 6 is fastened to the work W.

After that, when the tightening of the bolt 6 by each socket 5 is completed, the fourth solenoid 34 is turned on to operate the second air cylinder 17 in step 130.

Further, in step 140, in order to measure the time after the fourth solenoid 34 is turned on,
The value of the timer (timer value) T is incremented. Then, in step 150, the second air cylinder 17
In order to detect whether or not the operating rod 17a has reached the shortest position, it is determined whether or not the fourth limit switch 37 is turned on. Based on this determination, it is determined whether or not each socket 5 is separated from the work W.

Here, if the fourth limit switch 37 is not turned on, the process proceeds to step 160. Then, in step 160, it is determined whether the timer value T is larger than the predetermined value α. The predetermined value α is a time set for determining whether or not the socket 5 and the bolt 6 bite each other, and is set in consideration of the time required for the socket 5 to be separated from the bolt 6. . If the timer value T is not larger than the predetermined value α, the process proceeds to step 130 and steps 130 to 1 are performed.
The processing of 60 is repeated.

While repeating the processing of steps 130 to 160, if the fourth limit switch 37 is turned on in step 150 before the timer value T exceeds the predetermined value .alpha. Assuming that the bolt 6 is separated, the process proceeds to step 170.

Then, in step 170, the fourth solenoid 34 is turned off to stop the operation of the second air cylinder 17. Here, the operating rod 17a of the air cylinder 17 is stopped at its shortest position. By this processing, each socket 5 is moved from the state shown in FIG. 7 to a position separated upward from the work W as shown in FIG.

Subsequently, at step 180, the second solenoid 29 is turned on for a predetermined period to operate the first air cylinder 12. Here, the air cylinder 12
When the operating rod 12a is contracted and its shortest position is detected by the second limit switch 31, the second solenoid 29 is turned off.

By this process, the nut runner portion 24 is raised from the state shown in FIG. 8 to the position shown in FIG. 9, and each socket 5 is moved to a position further away from the work W. Then, in step 190, the third solenoid 33
Is turned on for a predetermined period to operate the second air cylinder 17. Here, the operating rod 1 of the air cylinder 17
7a is extended, and when the longest position thereof is detected by the third limit switch 36, the third solenoid 33
Is turned off.

By this process, the nut runner portion 24 is lowered from the state shown in FIG. 9 to the position shown in FIG. 6, and the screw tightening device 4 is returned to the initial state. And step 20
At 0, after resetting the timer value T to "0", the subsequent processing is temporarily ended until the next screw tightening process is started.

On the other hand, before the fourth limit switch 37 is turned on in step 150, if the timer value T exceeds the predetermined value α in step 160, each socket 5 does not separate from the work W and the socket 5 Bolt 6
Assuming that a bite with
Move to 0.

In this embodiment, the second air cylinder 17
Since the value of the moving force applied to the socket 5 by the operation of is set to be smaller than the gravity value of the work W,
Even if the socket 5 tries to move upward, the work W is not lifted from the carrier table 2 due to the bite between the socket 5 and the bolt 6.

Then, in step 210, the fourth
The solenoid 34 of the second air cylinder 17 is turned off.
Immediately stop the operation of. At the same time, in step 220, the drive motor 3 is stopped and the conveyor 1 is immediately stopped.

Further, in step 230, the alarm 41 is turned on and sounds. By the operation of this alarm 41, the operator is warned that a bite has occurred between the socket 5 and the bolt 6.

Then, in step 200, the timer value T is reset to "0" and the subsequent processing is terminated. The tightening device 4 and the like are controlled as described above. In this embodiment, the computer 51 that executes the processing of the control routine corresponds to the control means for controlling the operation of the screw tightening device 4. The computer 51 that executes the processing of steps 130 to 160 in this control routine corresponds to the bite determining means for determining whether or not there is a bite between the socket 5 and the bolt 6. Further, in this control routine, steps 210 and 220 are performed.
The computer 51 that executes the process of 1 corresponds to a stop control unit that stops the second air cylinder 17 and the conveyor 1 when it is determined that a bite has occurred between the socket 5 and the bolt 6. are doing. In addition, the computer 51 that executes the process of step 230 in this control routine corresponds to a warning control means for activating the alarm 41 when it is determined that the socket 5 and the bolt 6 bite. are doing.

In this embodiment, the restoration work of the screw tightening device 4 after the bite of the socket 5 has occurred is performed as follows. FIG. 10 shows a flowchart of steps involved in the recovery work after the occurrence of bite. First, in step 310, the operator confirms the bite of the socket 5. Next, in step 320, the operator releases the bite between the socket 5 and the bolt 6 by using a jig or the like.

After that, in step 330, the operator operates the first operation switch 39 to return the screw tightening device 4 to the initial state in step 340. That is, in this embodiment, by operating the switch 39, the respective solenoids 28, 29, 33, 34 are
Are sequentially controlled, the cylinders 12 and 17 are sequentially controlled, and the device 4 is returned to the initial state shown in FIG.

Then, in step 350, the operator operates the second operation switch 40 to restart the control of the screw tightening device 4 and the conveyor 1 by the computer 51 in step 360.

As described above, according to the screw tightening device 4 of this embodiment, when the bolts 6 are tightened to the work W by the sockets 5, the bite between the sockets 5 and the bolts 6 is prevented. A confirmation operation is performed. And
When the bite does not actually occur between the both 5, 6, by operating the second air cylinder 17,
Each socket 5 is pulled upward from the bolt 6 and the work W while moving relative to each rotary shaft 18a. Therefore, it is shown that the movement of the socket 5 does not cause a bite between the socket 5 and the bolt 6.

On the other hand, when there is actually a bite between the two 5, 6, the socket 5 and the bolt 6 are integrated, and each of them is operated based on the operation of the second air cylinder 17. The moving force applied to the socket 5 is transmitted to the work W via the bolt 6. However, in this example,
Since the value of the moving force applied to each socket 5 by the second air cylinder 17 is smaller than the gravity value of the work W, the socket 5 does not rise integrally with the bolt 6 and the work W, and the socket 5 does not rise. The bolt 5 will not be separated from the bolt 6. Therefore, the fact that the socket 5 does not move indicates that there is a bite between the socket 5 and the bolt 6.

As a result, when the worker is monitoring, after the bolt 6 is tightened by the socket 5 in the work W, the worker visually confirms whether or not each socket 5 has moved. , It is possible to determine whether or not there is a bite between the both 5 and 6 without lifting the work W. Here, when the bite between the two 5 and 6 is slight, the operator who is monitoring can assist the movement of the socket 5 to release the bite between the both 5 and 6. It is possible.

In addition, in this embodiment, when the second air cylinder 17 is operated, the presence or absence of movement of each socket 5 is detected by each limit switch 36, 37.
Therefore, the detection result indicates whether or not there is a bite between the socket 5 and the bolt 6. In this embodiment, the presence or absence of bite between the limit switches 36 and 37 can be automatically determined by the computer 51 based on the detection results of the limit switches 36 and 37. Further, when it is determined that the bite has occurred, the second air cylinder 1
7 and the operation of conveyor 1 are immediately stopped, and alarm 4
1 works.

As a result, after the bolt 6 is tightened by the socket 5 on the work W, it is possible to automatically determine whether or not there is a bite between the two 5 and 6 without lifting the work W. Here, since the work W is not lifted even if a significant bite between the two 5 and 6 occurs, the lifted work W is released to release the bite between the both 5 and 6. No work is required, and the work of restoring the screw tightening device 4 can be simplified. Furthermore, unlike the case where the work W is lifted, undue stress is not generated between the two,
It is possible to prevent the both 5 and 6 from being damaged.

Further, even if biting occurs, the operation of the second air cylinder 17 and the conveyor 1 is stopped, so that an unreasonable stress acts between the two 5, 6 or the screw tightening device 4 itself. Can be prevented. In that sense, it is possible to prevent the screw tightening device 4 and the conveyor 1 from being damaged.

In addition, in this embodiment, even if the presence or absence of bite is not monitored by the operator, the occurrence of the bite is immediately notified to the operator by the operation of the alarm 4. As a result, the operator can quickly start the work of restoring the screw tightening device 4, and in that sense, the downtime of the assembly line can be minimized.

(Second Embodiment) Next, a second embodiment embodying the screw tightening device of the first and second inventions will be described with reference to FIG.
Follow the instructions below. In the structure of this embodiment, the same members as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted. Hereinafter, the points different from the first embodiment will be mainly described.

FIG. 11 shows a screw tightening device 46 in this embodiment. In this embodiment, the second air cylinder 17, the linear bush 19, the guide bar 19a, the fourth support plate 20, the bush 21 and the spring 23 in the first embodiment are omitted, and the rotary shaft 1 of each electric motor 18 is omitted.
A socket 5 is attached to 8a via a spindle 23. In this embodiment, the second support plate 14 and the members 5, 15, 18, 22 supported below the second support plate 14 are collectively referred to as a nut runner portion 47.

Then, by operating the first air cylinder 12, the nut runner portion 47 is moved up and down with respect to the work W. Further, the nut runner portion 47 is lowered onto the work W, the sockets 5 are fitted into the bolts 6 and the electric motor 18 is operated, whereby the bolts 6
Are fastened to the work W.

In this embodiment, the first air cylinder 12
This constitutes the first moving means in the present invention. The first and second limit switches 30 and 31 constitute the detecting means of the present invention. Furthermore,
A pressure reducing valve 35 with a relief is provided in the middle of one path 17b for sending air to the first air cylinder 12. In this embodiment, the pressure reducing valve 35 constitutes a moving force setting means for setting the value of the moving force of each socket 5. In this embodiment, the pressure reducing valve 35
After the bolts 6 are tightened by the sockets 5 based on the level of the set pressure in, the value of the moving force applied to each socket 5 by the operation of the air cylinder 12 to separate each socket 5 from the bolt 6 is , Work W
It is set to be smaller than the gravity value of. The set value of this moving force is sufficient to separate the socket 5 from the bolt 6.

Therefore, according to the screw tightening device 46 of this embodiment, when the bolts 6 are tightened by the sockets 5 and biting does not actually occur between the two 5, 5, the nut runner is used. First to raise part 47
When the air cylinder 12 of is operated, each socket 5
Is pulled upward from the bolt 6 and the work W. Therefore, it is shown that the movement of the socket 5 does not cause a bite between the socket 5 and the bolt 6.

On the other hand, when biting actually occurs between the both 5, 6, the socket 5 and the bolt 6 will be integrated, and the first air for raising the nut runner portion 47 will be generated. When the cylinder 12 is operated, the moving force of the operating rod 12a is transmitted to the work W via the bolt 6. However, in this embodiment, since the value of the moving force applied to each socket 5 by the first air cylinder 12 is smaller than the gravity value of the work W, the socket 5 is integrated with the bolt 6 and the work W. It does not rise and the socket 5 does not separate from the bolt 6. Therefore, since the socket 5 does not move, the socket 5
It is shown that there is a bite between the bolt and the bolt 6.

As a result, after the bolts 6 are tightened by the sockets 5 on the work W, the worker visually confirms whether or not each socket 5 has moved, and
It is possible to determine whether or not there is a bite between the two 5 and 6 without lifting. The effects associated with this decision are:
It is basically the same as that of the first embodiment.

In addition, in this embodiment as well, the detection results of the limit switches 30 and 31 indicate the presence or absence of bite between the socket 5 and the bolt 6, respectively. Based on
The presence or absence of bite between 6 can be automatically judged by the computer 51. Further, when it is determined that the bite has occurred, the first air cylinder 12
And the operation of the conveyor 1 is immediately stopped, and the alarm 41
Can also be activated.

As a result, it is possible to automatically determine whether or not there is a bite between the workpieces 5 and 6 without lifting the work W. The effect associated with the judgment by the computer 51 is basically the same as that of the first embodiment.

The present invention can be embodied in the following other embodiments. Also in the following other embodiments, it is possible to obtain the same actions and effects as those of the respective embodiments. (1) In each of the above embodiments, the first to third moving means in the present invention are constituted by the first and second air cylinders 12 and 17, but they may be constituted by hydraulic cylinders, electric motors or the like. Good.

(2) In each of the above embodiments, the pair of sockets 5 and the pair of rotary shafts 18a are provided, but the number of sockets and rotary shafts may be appropriately changed according to the number of bolts. (3) In each of the above-described embodiments, the bolt 6 is used as a screw for tightening with the socket 5, but the nut or other screws may be used for tightening with the socket.

(4) In the first embodiment, the connecting means in the present invention is constituted by the spline shaft 18b of the rotary shaft 18a and the spindle 22, but the connecting means is a key provided between the rotary shaft and the socket. It can also be configured with a keyway. That is, the socket can be integrally rotatable with respect to the rotating shaft and can be relatively moved by the engagement relationship between the key and the key groove.

(5) In each of the above embodiments, the rotary shaft 18a is the output shaft of the electric motor 18 itself, but the rotary shaft may be provided separately from the output shaft of the motor. (6) In each of the above-described embodiments, the screw tightening devices 4 and 46 are combined with the conveyor 1 and embodied in an engine assembly line. However, the screw tightening devices are embodied in an assembly site without a conveyor. You can also do it.

Although the respective embodiments of the present invention have been described above, it is noted that the respective embodiments include the following various embodiments relating to the technical idea described in the scope of claims. It describes with the effect.

(A) In the third aspect of the present invention, there is provided biting determination means for determining whether or not there is biting between the socket and the screw based on the detection result of the detection means. The screw tightening device provided.

According to this structure, it is possible to automatically determine the occurrence of bite between the socket and the screw without a person, and it is not necessary for a person to monitor the presence or absence of the bite.

(B) In the third invention according to claim 3, when it is determined that a bite has occurred between the socket and the screw based on the detection result of the detection means, A screw tightening device provided with stop control means for stopping the operation of the first moving means or the third moving means.

According to this structure, even if there is a bite between the socket and the screw, it is possible to prevent unreasonable stress from acting on the screw and the screw tightening device itself. (C) In the third invention according to claim 3, an alarm is activated when it is determined that a bite has occurred between the socket and the screw based on the detection result of the detection means. Screw tightening device with warning control means for.

According to this structure, even if the presence or absence of bite between the socket and the screw is not monitored by a person, the occurrence of the bite can be notified to the person. In this specification, means, members and the like relating to the constitution of the invention are defined as follows.

(A) A screw means a member such as a bolt and a nut, which is screwed to a work by being rotated. (B) The alarm means an alarm device, and includes an alarm light that is turned on and blinks, a horn that sounds, or a device that performs both lighting and blinking.

[0088]

According to the first invention described in claim 1,
After the screw is tightened by the socket, the value of the moving force applied to the socket by the first moving unit to separate the socket from the screw is set to be smaller than the gravity value of the work.

Therefore, after the screw is tightened by the socket in the work, the socket does not move, which indicates that the biting occurs between the socket and the screw. As a result, it is possible to determine whether or not there is a bite between the socket and the screw without lifting the work.

According to the second aspect of the present invention, with respect to the socket and the rotary shaft that are integrally moved in the vertical direction by the second moving means, the socket and the rotary shaft can be integrally rotated by the connecting means. In addition to the connection, the socket is connected so as to be relatively movable upward with respect to the rotation shaft. And
The value of the moving force applied to the socket by the third moving means for moving the socket relative to the rotation axis is set smaller than the gravity value of the work.

Therefore, after the screw is tightened by the socket in the work, the socket does not move, which indicates that the biting occurs between the socket and the screw. As a result, it is possible to determine whether or not there is a bite between the socket and the screw without lifting the work.

According to the third aspect of the present invention, the presence or absence of movement of the socket is detected by the detecting means when the socket is pulled away from the screw. Therefore,
After the screw is tightened by the socket in the work, the presence or absence of bite between the socket and the screw is indicated by the detection result of the detection means. As a result, it is possible to determine whether or not there is a bite between the socket and the screw without lifting the work, and it is possible to achieve the effect of automating the determination.

[Brief description of drawings]

FIG. 1 is a front view showing a screw tightening device according to a first embodiment that embodies first to third inventions.

FIG. 2 is a side view showing the main part of the screw tightening device in a partially broken manner in the first embodiment.

FIG. 3 is a front view showing a screw tightening device, a conveyor and the like in the first embodiment.

FIG. 4 is a block diagram showing an electrical configuration of a screw tightening device in the first embodiment.

FIG. 5 is a flowchart showing a control routine executed by a computer in the first embodiment.

FIG. 6 is a front view showing the movement of the screw tightening device in the first embodiment.

FIG. 7 is a front view showing the movement of the screw tightening device in the first embodiment.

FIG. 8 is a front view showing the movement of the screw tightening device in the first embodiment.

FIG. 9 is a front view showing the movement of the screw tightening device in the first embodiment.

FIG. 10 is a flowchart showing a process related to a recovery work after the occurrence of bite in the first embodiment.

FIG. 11 is a front view showing a screw tightening device according to a second embodiment of the first and third aspects of the invention.

FIG. 12 is a front view showing a nut runner of the related art.

[Explanation of symbols]

4 ... Screw tightening device, 5 ... Socket, 6 ... Screw bolt, 12 ... First air cylinder as first and second moving means, 17 ... Second as third and third moving means Air cylinder, 18a ... Rotating shaft, 18b ... Spline shaft, 22 ... Spindle (connecting means is constituted by 18b and 22), 30 ... First limit switch,
31 ... Second limit switch (30, 31 constitutes a detecting means), 36 ... Third limit switch, 37 ... Fourth limit switch (36, 37 constitutes a detecting means).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryosuke Mise 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (72) Inventor Seizo Fukumoto 1-9-15 Mizuhashi, Higashi Osaka City, Osaka Prefecture Within the corporation

Claims (3)

[Claims] 1. A screw tightening device configured to tighten a screw onto a workpiece by fitting the socket into a screw and rotating the socket by a rotating shaft, wherein the socket is arranged below the socket. A first moving means for moving the work to a position approaching the work and a position moving upward from the work, and after the screw is tightened by the socket, the socket is moved to separate the socket from the screw. A screw tightening device characterized in that the value of the moving force applied to the socket by the first moving means is set to be smaller than the gravity value of the work. 2. A screw tightening device configured to tighten a screw to a work by fitting the socket into a screw and rotating the screw by a rotating shaft, wherein the socket and the rotating shaft are Second moving means for moving integrally to a position that is arranged below the work and a position that is separated upward from the work, and the socket is integrally rotatably connected to the rotary shaft and And a third moving means for relatively moving the socket with respect to the rotary shaft. The third moving means is provided with A screw tightening device, wherein the value of the moving force applied to the socket is set to be smaller than the gravity value of the work. 3. The screw tightening device according to claim 1, wherein the socket is moved when the first moving means or the third moving means is operated in order to separate the socket from the screw. A screw tightening device comprising a detection means for detecting the presence or absence of movement of the screw.