JPH0755413B2 - Screwed state determination device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a screwing device for tightening a male screw and a female screw to screw two machine elements together, when the screwing operation is performed. The present invention relates to a screwing state determination device that determines whether or not a predetermined screwing state has been obtained by wearing work.

[Prior Art] With the widespread use of screwing devices, a screwing state determination device that automatically determines a screwing state is widely used.

Conventional screwing state determination devices are roughly classified into the following three types according to the screwing state determination method.

The first is to judge whether or not the output torque of the screwing device has reached a predetermined value, and if the force for tightening the male screw or the female screw has reached a predetermined tightening completion torque, the desired screwing state Is determined to have been obtained.

Secondly, after the male screw or the female screw is tightened, the distance between the reference surface and the screw head is measured, and when the distance is a predetermined value, it is determined that the desired screwing state is established.

The third is to detect the adhesive force between the screwed portions of the male screw and the female screw.For example, when the adhesive force is detected to be a predetermined value or more by using ultrasonic waves, a desired screwed state is obtained. It is determined that it has been done.

[Problems to be Solved by the Invention] The following problems have not been solved in various conventional screwing state determination devices, and it has not been possible to accurately determine the screwing state.

The screwing state determination device that determines the screwing state based on whether or not the output torque of the screwing device reaches a predetermined value is a screwing failure in which the output torque of the screwing device becomes high, such as scratches or burrs on screw threads. It is impossible to discriminate a defective screw itself, a male screw and a female screw obliquely meshing with each other, so-called diagonal tightening, or the like.

Further, the screwing state determination device that determines the quality of the screwed state by measuring the distance between the reference surface and the screw head has an error such as a variation in the reference surface used as a reference during measurement or a tolerance of the screw head. The factor is large, for example, it is impossible to confirm the floating of the screw of 0.1 [mm] or less, and the screwing state cannot be determined with high accuracy.

The screwing state determination device that measures the adhesion force by ultrasonic waves does not have the above-mentioned problems, but a large measuring device such as an ultrasonic wave generating device and an ultrasonic wave receiving device is required, and furthermore, the male screw that is the object of measurement. If the internal thread is small, the measurement itself becomes difficult, and the applicable range is limited.

The present invention has been made in order to solve the above-mentioned problems that have not yet been solved by the conventional screwing state determination device, and easily and accurately determines the quality of the screwed state of any male screw and female screw. It is an object of the present invention to provide a screwing state determination device that can be used.

[Means for Solving the Problems] The means configured according to the present invention for solving the above problems is, as shown in the basic configuration diagram of FIG. 1, screwing two machine elements by tightening a male screw and a female screw. When the screwing work is performed by the screwing device, the screwing state determining device determines whether or not a predetermined screwing state is obtained by the screwing work, wherein the screwing device includes the male screw and the female screw. Torque value detecting means C1 for detecting the torque value output for tightening with, and within the time from the start of the screwing work until the male screw and the female screw are seated, and a predetermined torque after the seating Area value calculation means C2 for calculating the history of the torque value by the torque value detection means C1 within the time until reaching the value as an area value based on the time and the torque value for each time, and The area value calculation means C2 compares both area values with a predetermined standard value, and a quality determination means C3 for executing the quality determination of the screwing state performed by the screwing device is provided. The gist is a screwing state determination device.

[Operation] According to the screwing state determination device of the present invention, the torque value detection means
C1 detects the torque value of tightening the male screw and the female screw by the screwing device, the area value calculating means C2, within the time from the start of the screwing work until the male screw and the female screw are seated, and
The history of the torque value by the torque value detecting means C1 within a time period from the sitting to the time when the predetermined torque value is reached is calculated for each time as an area value based on the time and the torque value. Then, the quality determination means C3 compares both area values of the area value calculation means C2 with a predetermined standard value, and executes the quality determination of the screwing state performed by the screwing device.

Hereinafter, in order to more specifically describe the screwing state determination device of the present invention, examples thereof will be described in detail.

[Embodiment] FIG. 2 is a configuration block diagram of a screwing state determination device according to an embodiment.

As shown in the figure, the screwing state determination device of the embodiment has four torque transducers 10a to 10d that detect the tightening shaft torque of the screw tightening driver, and is configured to be capable of simultaneously determining four screw tightening states.

In addition, in the present embodiment, a configuration using four torque transducers 10a to 10d has been described for the sake of simplicity. However, up to the number of input channel switches (for example, 32) of the A / D converter 16 to be described later are connected in parallel. Can be configured to.

These torque transducers 10a to 10d convert the screw tightening torque value into an analog voltage value, and the waveform shaping circuits 12a to 12d in the next stage remove the high frequency component and amplify the waveform. Then, each waveform shaping circuit 12a-1
The output of 2d is sequentially switched through the analog multiplexer 14 and input to the A / D converter 16, where it is A / D converted at constant time intervals and transmitted to the processing circuit 18.

Here, the processing circuit 18 is a logic circuit mainly composed of a microcomputer and executes a logical operation.
A CPU 18a, a ROM 18b that non-volatilely stores a control program described later, a RAM 18c that temporarily stores information, and an input / output port (hereinafter referred to as an I / O port) 18d that exchanges information with an external device. It consists of

In addition, the screwing state determination device of the embodiment includes the output device 20 in order to visually notify the operator of the quality determination result of the four screw tightening states.

In the screwing state determination device configured as described above, the ROM 18b of the processing circuit 18 pre-stores a control program as shown in the flowchart of FIG. 3, and the CPU 18a executes the following processing according to this program. To do.

When the screwing state determination device is activated, the CPU 18a starts the process of successively extracting the control program from the ROM 18b, and first stores the screw tightening torque data (step 100).
This is a process of cyclically storing the outputs of the waveform shaping circuits 12a to 12d sequentially transmitted from the A / D converter 16 in the four storage areas of the RAM 18c. As a result, the torque information detected by the torque transducers 10a to 10d is accumulated in each of the four storage areas of the RAM 18c in the order according to the passage of time.

When the detection output from the torque transducers 10a to 10d reaches the maximum output torque Tmax of the screw tightening driver and the torque data accumulation (step 100) is completed, next 4 in RAM18c.
Based on the data of the one storage area, the thread quality determination process is executed.

It should be noted that this determination processing is similarly executed for each of the data in the four storage areas, and the CPU 18a time-divisionally connects the storage areas in parallel or independently in accordance with a predetermined order. It is the target of the judgment process.
Therefore, in the following, in order to avoid duplication of description, a determination process of data accumulated in any one storage area will be described.

In the pass / fail judgment process, first, the screw tightening torque data accumulated in the storage area of the RAM 18c is sequentially read (step 110), and the torque T shown in the torque data is set to a predetermined torque up level Tup. It is sequentially determined whether or not the above (step 120).

Here, the torque-up level Tup is a torque value of such a high value that it is estimated that the screw tightening work to be detected is completed. For example, if an example of the screw tightening torque data accumulated in the storage area of the RAM 18c is illustrated, it is as shown in the output torque characteristic diagram of FIG. 4 (A). As shown in the figure, when the screw tightening work is started at time t1, the low-level torque state necessary for screwing continues for a period depending on the screw pitch and the screwing depth. Then, from the time t2 when the male screw and the female screw are seated, the screw tightening torque sharply increases substantially linearly until the required screw tightening state is obtained, and reaches the maximum output torque Tmax of the screw tightening driver and a certain period of time elapses. Complete one screw tightening operation. The torque increase level is the maximum output torque Tmax
It is set to a slightly smaller value, and is a value at which sufficient screw tightening is completed.

When the sequentially read screw tightening torque data value becomes equal to or higher than the torque-up level Tup, the time A described later is calculated backward from the time t3, which is the time point at which the torque-up level is reached, and the male and female screws are seated and the torque increases rapidly The time t2 at which the rise is started is calculated, and the area A of the output torque characteristic diagram from this time t2 to the time t3 is calculated (step 13).
0).

Here, the time A is the time from when the male screw and the female screw are seated until the screw tightening torque reaches the torque-up level Tup, which is theoretically or experimentally simple depending on the rotation speed of the screw tightening driver and the screw pitch. Is a value that can be determined in advance, and that value is stored in the ROM 18b in advance.
Further, the area of the output torque characteristic diagram from the time t2 to the time t3 can be easily obtained by a pseudo integral calculation for adding all the screw tightening torque data obtained within the time A.

When the calculation of the area A is completed, the time B to be described later is calculated backward from the time t2 as a starting point, and the time when the screw tightening work is started.
The t1 is specified, and the area B of the output torque characteristic diagram during the so-called screwing time B from the time t1 to the time t2 at which the male screw and the female screw are seated is calculated (step 140).

The time B is the time from the start of screwing the male screw and the female screw to the seating, and can be easily determined theoretically or experimentally from the rotation speed of the screw tightening driver, the screw pitch, the screwing depth, and the like. It is a value, and the value is stored in the ROM 18b in advance. Also, from time t1 to time t2
The area of the output torque characteristic diagram up to is easily obtained by a pseudo integral calculation of adding all the screw tightening torque data obtained within this time B.

When the calculation of the area A and the area B is completed in this way, the calculation result is stored in the ROM 18b in advance as the standard value As.
Judgment processing is performed to determine whether the value is smaller than t or Bst (step 150, step 160), and when both calculated values are below the standard values Ast and Bst, work is completed as planned and the desired screw tightening is completed. An output device that outputs an output signal notifying that the state has been obtained
It is output to 20 (step 170) and the data processing stored in one storage area of the RAM 18c is completed.

On the other hand, when it is determined in step 150 or step 160 that the calculated value of the area A or the area B is larger than the standard values Ast and Bst stored in the ROM 18b, the CPU 18a determines that the output device An output signal for notifying that a problem has occurred in screw tightening is output to 20 (step 180), and the control program ends.

That is, as described below, the quality of the screw tightening can be accurately determined by simply comparing the areas A and B with the standard values Ast and Bst.

When the screw tightening work is executed well, the output torque characteristic diagram becomes the characteristic shown in FIG. 4 (A). During the time B from the start of screwing at time t1 to the seating of the male and female screws at time t2, the low-level torque state required for screwing continues in a stable state. And
The time A from the time of seating at time t2 until the screw tightening torque at time t3 reaches the torque-up level Tup is extremely short and exhibits a rapid torque increase characteristic.

Therefore, the area A and area B when good screw tightening is performed
Becomes a small value, and the standard values Ast and Bst are determined in advance in consideration of measurement errors and product variations.

On the other hand, as a defect that occurs in the screw tightening work process, there is so-called diagonal tightening in which a male screw and a female screw mesh with each other at an angle. Further, as a defect caused by a defect in the screw itself such as a scratch on a screw thread or a flash, there is a so-called biting or galling which hinders a screwing operation. Output torque characteristic diagrams when such a screw tightening operation failure occurs are the characteristics shown in FIGS. 4 (B) and 4 (C).

FIG. 4 (B) is an output torque characteristic diagram of diagonal tightening. In the case of such a failure, since a smooth screwing operation is impossible from time t1, a relatively large torque state continues, and The output torque increases as the screwing progresses. Therefore, both the area A and the area B are extremely large values, and the standard value Ast, which is determined as described above,
Greatly exceeds Bst.

Further, FIG. 4 (C) is an output torque characteristic diagram when a bite occurs, but in this case, a large output torque for resisting the bite during the time B when the bite occurs. Is observed, and the area B becomes larger than that in the normal state.

As described above, if any abnormality occurs, the area
Either A or area B, or both of them, are obviously larger than normal, and their measured values and standard values Ast, Bst
By a simple process of comparing the size with
The quality of the screw tightening work can be reliably determined.

Moreover, the screwing state determination device according to the present embodiment provides a simple history of the area A and the area B of the torque history determined from the output torque characteristic diagram.
Since the pass / fail judgment is made by substituting the addition calculation of, the purpose can be achieved by a simple control program as shown in FIG. 3, and the processing circuit 18 can be made compact and economical.

In addition, by checking the history of torque as area A and area B for each of the two characteristic works, it is possible to detect not only the screw tightening work failure but also whether the failure is due to diagonal tightening. It is also possible to judge whether it is due to a jam, and it is possible to classify even the occurrence status of defects.

The configuration of the screwing state determination device of the present invention is not limited to the above-described embodiment, and is embodied in various modes without departing from the gist thereof.

[Effect of the Invention] The screwing state determination device of the present invention has an area value based on the time from the start of screwing work to the time of sitting and the torque value within that time, and a predetermined torque value after sitting. The area value is calculated based on the time required to reach and the torque value within that time and compared with a predetermined standard value. Therefore, it is not necessary to compare the torque value with the predetermined value each time it is detected, the screwed state can be determined with a simple configuration, and both area values can be determined depending on an abnormal state such as diagonal tightening or biting. Since it is different, it is possible to take a configuration in which the cause of the tightening abnormality is specifically specified.

Therefore, regardless of the size of the screw, and without requiring a large device such as an ultrasonic generator, it is possible to easily and accurately determine the quality of the screwed state of all male and female screws. You can

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of the present invention, FIG. 2 is a configuration block diagram of a screwing state determination device according to an embodiment, and FIG. 3 is a flow chart of a control program executed by a processing circuit of the embodiment. FIGS. 4 (A), (B), and (C) are explanatory diagrams of the output torque characteristic diagram. 10a ~ 10d ...... Torque transducer 12a ~ 12d ...... Waveform shaping circuit 14 ...... Analog multiplexer 16 ...... A / D converter, 18 ...... Processing circuit 18a ...... CPU, 18b ...... ROM 18c ...... RAM, 18d ... … I / O port 20 …… Output device

Claims (1)

[Claims] 1. When the screwing operation is performed by a screwing device for screwing two machine elements by tightening a male screw and a female screw, whether or not a predetermined screwing state is obtained by the screwing work. In the screwing state determination device for determining whether or not, the screwing device detects a torque value output by the screwing device for tightening the male screw and the female screw, and the male screw from the start of the screwing work. The area based on the time and the torque value is the history of the torque value by the torque value detecting means within the time until the female screw is seated and within the time after the seating until the predetermined torque value is reached. Area value calculation means for calculating each time as a value and both area values of the area value calculation means and a predetermined standard value are compared, and the quality of the screwing state executed by the screwing device is determined. To Threaded state determination apparatus characterized by comprising: a quality determining means for lines.