JPH06190742A - Sensing method for failure fastening of bolt and nut - Google Patents

Abstract

PURPOSE:To conduct precise judging, simplify the configuration, and make the device inexpensive by judging as failure fastening when the set value is attained by the torque within a certain angle loosening range in loosening a bolt and nut. CONSTITUTION:When judgement is such that the value of fastening torque has attained the preset value, a control circuit 3 gives a command for reverse rotation to a nut runner, and loosening of the bolt and nut is started. The control circuit 3 judges that it is failure fastening if the preset value is attained by the torque value of a torque sensor 1 in the condition that loosening is started and a rotational angle sensor 2 installed in the nut runner has attained the preset range of return rotation angle 30-40 deg. If the set value is not attained, a normal operation indicating means 5 is operated in accordance with the size of the output from the torque sensor 1 in case the set value is not attained, and if attained, a bite-in indicating means 6 or a seizure indicating member 7 is driven in compliance with the size, and thus the displays for respective cases are performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to tightening a nut on a fixed bolt, or tightening a bolt on a fixed nut, for example, when tightening a nut for mounting a tire wheel on a wheel hub of an automobile, foreign matter is attached to the thread. The present invention relates to a bolt / nut abnormal tightening detection method for automatically detecting seizure of a screw, which may occur when tightening in a state where a bolt is inserted, and biting due to oblique insertion or rising of a mountain.

[0002]

2. Description of the Related Art Conventionally, a tightening time method has been used as a method for detecting seizure or biting due to tightening of bolts and nuts as described above. This method
The time from the start of tightening until reaching a certain torque is set, and if the torque is increased within that time, it is determined that the initial torque is abnormal (bite). Further, it is a method of setting a time from a constant torque to a final torque, and determining a torque abnormality (seizure) when the torque increases within the time.

[0003]

The tightening time method described above is a method of managing the time from the start of tightening, so that the time varies depending on the change in the rotation speed and the tightening situation, and the accuracy is improved. There was a problem that the judgment was impossible.

The present invention is intended to solve the above-mentioned problems, and an object of the present invention is to detect abnormal tightening of bolts and nuts by a simple method. It is to provide a method for detecting abnormal tightening of bolts and nuts, which is highly expensive and can judge whether it is due to biting or seizure.

[0005]

The method for detecting abnormal tightening of bolts and nuts of the present invention is intended to achieve the above-mentioned object, and means for tightening bolts and nuts by a nut runner after reaching a certain torque. ,bolt·
This is a method of rotating the nut in a loosening direction and determining that the tightening is abnormal when the torque value within the loosening range of a certain angle at this loosening reaches a preset value.

Further, according to the present invention, the torque value within the loosening range of the constant angle at the time of loosening is set to two values, and when there is a torque value between a low value and a high value, it is determined that there is a bite. However, when the value is higher than the high value, it is determined that the image is burnt in.

[0007]

According to the method of the present invention as described above, when the tightening of the bolt / nut reaches the constant torque value, the loosening operation is performed, and the preset torque value is reached within the constant return angle range of the loosening operation. First, it is judged that the tightening is abnormal.

Further, the set value at the constant return angle is set to two values, and if there is a loosening torque value between the low set value and the high set value, it is determined that there is a bite, and the set value is high. If the loosening torque value exceeds 0, seizure is determined.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the bolt / nut abnormal tightening detection method according to the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a torque sensor incorporated in a nut runner capable of tightening and loosening, and outputs an output according to a torque applied to a rotating shaft when tightening a bolt or a nut. Reference numeral 2 denotes a rotation angle sensor that outputs an output according to the rotation angle of the output shaft of the nut runner.

Reference numeral 3 is a control circuit such as a CPU for performing the operation shown in the flowchart of FIG. 2, and 4 is a torque value for completion of tightening of the nut runner during tightening operation and a loosening angle of 30 ° to 40 ° during loosening operation. RAMs for setting and storing two reference torque values for comparison with the torque value of No. 5 and No. 5 to No. 7 are bolts and nuts that are normally tightened, bite, or seized according to the judgment of the control circuit 3. It is a display means for displaying or.

Next, based on the configuration shown in FIG.
The operation will be described with reference to the flowchart of FIG. 3 and the torque waveform diagram of FIG. First, the nut runner is driven to start tightening the bolts and nuts (step S1). When the tightening is started, the torque sensor 1 incorporated in the nut runner outputs an output according to the tightening torque, so the control circuit 3 determines whether the output from the torque sensor 1 has reached a preset torque value. Monitor (step S
2).

When the control circuit 3 determines that the output from the torque sensor 1 matches the preset torque value, the control circuit 3 outputs an output for stopping the driving in the tightening direction to the nut runner to stop the nut runner.

Here, as shown in FIG. 3, when the bolts and nuts are properly tightened and when seizure occurs, the torque value rises smoothly until the torque value reaches a preset torque value, and biting occurs. Is occurring,
It is known that the rise of the torque value is very unstable.

That is, in the tightening operation of the bolts and nuts, when the abnormality of tightening is detected, since the waveforms of normal tightening and biting are different, it is possible to judge from this waveform whether it is normal or bite. Since the waveform with the image sticking is very similar, it is difficult to detect this difference. Therefore, the present invention focuses on the difference in the waveform at the time of loosening.

When it is determined in step S2 that the tightening torque value has reached the preset value, the control circuit 3 issues a command to the nut runner to drive the nut runner in the reverse direction (to loosen the bolt / nut),
The loosening of the nut is started (step S3).

Then, the control circuit 3 monitors whether or not the loosening of the bolts and nuts has started and the rotation angle sensor 2 incorporated in the nut runner has reached a preset return rotation angle range of 30 ° to 40 °. Then (step S4), the next judgment is made in the state where the return rotation angle is reached.

That is, when the tightening of the bolts and nuts is normal, the loosening torque becomes almost zero when the loosening rotation angle is between 30 ° and 40 °, but the low torque is generated when biting occurs. The output is lower than that of the torque sensor 1 though it is a value, and in the case of seizure, the torque sensor 1
A considerably larger output of

Therefore, in the present invention, the above 30 °
When the return angle has reached the rotation angle of 40 °, two reference set values of the low level L1 and the high level L2 are provided, and the comparison with the output from the torque sensor 1 is performed.

The control circuit 3 compares whether or not the output from the torque sensor 1 is lower than the preset low level L1 (step S5). If the output is low, the normal display means 5 is driven to display a normal display. Perform (step S6).

When the level is higher than the level L1, it is compared with the level L2 which is higher than the level L1 to determine whether or not the output from the torque sensor 1 exists (step S7), and the levels L1 and L2 are compared.
If there is a bite, it is determined that there is a bite and the bite display means 6 is driven to display the bite (step S8).

Further, when it is judged that the output from the torque sensor 1 does not exist between the levels L1 and L2 in the step S7, it is determined that the image is burnt and the burn-in display means 7 is driven to display the burn-in. This is done (step S9).

[0022]

As described above, the present invention performs the loosening operation after the tightening of the bolts and nuts reaches the constant torque value, and reaches the preset torque value within the constant return angle range of the loosening operation. In this case, since it is determined that the tightening is abnormal, the determination can be performed accurately and the configuration can be simplified, so that it can be provided at low cost.

Further, the set value at the constant return angle is set to two values, and if there is a loosening torque value between the low set value and the high set value, it is determined that there is a bite, and a higher set value is set. In the case where the loosening torque value exceeds, seizure is determined, and therefore, there is an effect that it is possible to distinguish between biting and seizure.

[Brief description of drawings]

FIG. 1 is a block diagram for implementing a bolt / nut abnormal tightening detection method according to the present invention.

FIG. 2 is a flowchart showing the operation of the control circuit of the above.

FIG. 3 is a characteristic diagram showing torque values with respect to rotation angles when tightening and loosening bolts and nuts.

[Explanation of symbols]

 1 Torque Sensor 2 Rotation Angle Sensor 3 Control Circuit 4 RAM 5 Normal Display Means 6 Biting Display Means 7 Burn-in Display Means

Claims (2)

[Claims] 1. After a certain torque is reached after tightening the bolts and nuts by a nut runner, the bolts and nuts are rotated in a loosening direction, and the torque value within a loosening range of a certain angle at this loosening reaches a preset value. Abnormal tightening detection method for bolts and nuts that determines that the tightening is abnormal. 2. A torque value within a slackening range of a certain angle at the time of slackening is set to two values, and when it is between a low value and a high value, it is determined to be a bite, and a torque higher than a high value is set. If it is, it is determined that seizure has occurred, and the method for detecting abnormal tightening of bolts and nuts according to claim 1, wherein.