JPS6017668B2 - Natsutranna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nutrunner with improved reliability by providing a torque transducer with a bridge circuit of two sets of strain gauges.

Generally, a nut runner used for automatically tightening bolts is equipped with a torque transducer for detecting the tightening torque and determining when to stop tightening.

An example of this is shown in FIG. 1 is a motor that generates vertical force, 2 is a reducer that decelerates the motor rotation and generates a large torque, and 3 is a strain gauge attached to the side of the main body, which is fixed to the case of reducer 2. A torque transducer with four strips on its side as shown in Figure 2.
The engagements 4a, 4b, 4c, and 4d are pasted in sets of two on opposite sides.

Reference numeral 5 denotes a vertical bolt attachment fixed to the tip of the main shaft of the reducer 2.

In this structure, when the vertical bolt attachment 5 is fitted to the head of the bolt 6 to be vertically attached and the motor 1 is rotated, the attachment 5 fixed to the main shaft of the reducer 2 rotates, and the bolt is rotated. 6 continues, the torque transducer 3 receives a reaction force, and the torque transducer 3 is distorted by a force corresponding to the torque force. As shown in FIG. 3, this tightening torque T increases as time t passes and the vertical attachment progresses. Then, when the vertical mounting torque T reaches the set vertical mounting torque T', the vertical mounting is stopped. Therefore, the brazing torque T is detected by a strain gauge 4a attached to the torque transducer 3.
, 4b, 4c, and 4d are formed as striped lines on the bridge circuit 4 as shown in FIG. That is, if a constant AC or DC voltage is applied to the input side 4' of this bridge circuit 4,
A voltage corresponding to the vertical mounting torque is generated on the output side 4''.
The vertical torque is monitored using this voltage, and when it reaches the voltage set in accordance with the set vertical torque, the motor 1
to stop. In this way, vertical mounting can always be performed with a constant vertical mounting torque. There is no problem with this type of control system as long as the relationship between the brazing torque and the output box pressure V of the torque transducer always maintains a constant relationship, as shown by the solid line A in Figure 5. During use, if the characteristics of the strain gauge change as shown by the dotted line in Figure 5 due to poor attachment of the strain gauge or fatigue of the torque transducer body, the output voltage for the vertical torque will become low. If you control the torque transducer, the torque will increase and you will end up over-tightening.Furthermore, the output voltage of this torque transducer is usually not only used as a signal to control the movement of the nut. It is also used as a signal to display the vertical mounting torque when the bolt is actually installed.

In other words, the maximum value of the vertical mounting torque signal is memorized (peak hold) and displayed as the vertical mounting torque value. It is monitored by a comparison circuit.In other words, conventionally, four strain gauges (tortoise a), turtle (b), turtle (c), and one bridge circuit (a) are used to monitor the output signal only from one set of bridge circuits.
Nutrunner stop control and tightening torque value monitoring are shared. Therefore, if the relationship between the output voltage of the torque trass reducer and the tightening torque changes for some reason, the user can determine this from the outside. It is impossible to do this and everything will go wrong with this nut runner.

For example, if a nutrunner is installed in a horizontal position and used for a long period of time, permanent distortion may occur due to the bending moment due to the weight of the nutrunner itself acting on the torque transducer. There was a problem in which abnormalities due to permanent distortion could not be detected in the bridge circuit of the set.The nutrunner using this torque transducer is especially used for tightening important maintenance parts (in automobiles, the undercarriage part) that require high precision and high quality. However, the present invention has been made in view of the above-mentioned shortcomings and provides a nutrunner that can solve these problems and meet the above-mentioned requirements.

The present invention utilizes a torque transducer 3 as shown in FIG.
Two sets of strain gauge bridges are attached to the carp, and the output of the bridge circuit of one of the carp strain gauges is used for motor control. The output of the other set of bridge circuits is ~ the general value of its vertical torque value. It is used for holding and displaying and for monitoring to determine whether the r-lux value is appropriate.

That is, eight strain gauges 4b...torque h are attached to the circumferential surface of the torque transducer 900 as shown in Fig. 7.
Attach two sheets at intervals of . Comparing this with the installation condition of the subordinate torque transducer, one set of two
4 square gauges at 80o intervals Tsuru-e, Kame〇
Crane c? Mounting turtle a is the way to attach the follower, but in the present invention, four strain gauges turtle e, turtle f, turtle g, and 4h are attached at 180o intervals in sets of two with the pupils further shifted by 90o. It is being As shown in the diagram, two sets of bridges are connected to the input terminals of the fins, and AC or DC power supply voltage E is connected to each bridge circuit. organized. The input terminals of each bridge circuit are supplied with AC or DC power supply voltage, and the outputs of each bridge circuit are taken out separately. The comparator T82, which compares the amplified output signal voltage of one of the bridge circuits with the set vertical torque, outputs when the motor torque reaches the set value. This is a motor stop circuit that stops the motor in response to a stop signal.It is also a motor stop circuit that stops the motor in response to a stop signal.Furthermore, the other bridge circuit shaft of the Tomigani is used to receive the input of the amplified signal voltage and perform one vertical There is also a maximum value memory circuit that peak-holds the maximum attaching torque until the end of attaching.It is an indicator that displays the maximum vertical attaching torque output by the maximum value memory circuit. Even if the lower limit comparison circuit is a 1y'ma judgment indicator, the maximum vertical torque output from the maximum value memory circuit 3 is compared with the comparison value, and if it is within the set range, the judgment indicator quantity 71 is displayed. OK is displayed, and NG is displayed when the setting range is exceeded.The operator can also monitor the bolt tightening by looking at the display on the torque indicator 12 along with this OK or NG display. According to the above-mentioned results, if there is an abnormality in the bridge circuit 7 used for motor control, "the striping due to the outside of the proper competition torque will not be performed, but the bridge circuit 8 used for monitoring will Since the display is being performed, you can use the judgment display turtle 7 to discuss whether the display is NG or the torque display device 4 to discuss the vertical mounting torque at this time.

And you can know about abnormalities. In addition, if there is an abnormality in the monitoring bridge circuit 8, the judgment display 17 will indicate NG, even if the bolts are tightened with the appropriate vertical tightening torque.
Furthermore, since a torque value different from the shell fixed tightening torque is displayed on the torque indicator 14, abnormalities can be read in the same way. In this way, abnormalities in the torque transducer 3 can be detected by the monitoring bridge circuit, and the system can be used with confidence even in tightening parts where absolute reliability is required. In addition, the torque transducer 3 of the bridge circuit 7, 8- of the strain gauge
In addition to the structure shown in Fig. 7, the mounting method can also be as shown in Fig. 8.

The mechanism shown in Figure 8 consists of a bridge circuit consisting of four strain gauges, and two torque transducers that are connected to each other in the main direction of the nut runner. Even with this rough mounting, each torque transducer 3r, 3'' receives the same reaction force when the torque is vertically mounted, so each strain gauge 4a, 4b...4h produces the same strain as in the structure shown in Fig. 7. Therefore, if the outputs of the two sets of bridge circuits 7 and 8 are processed by a detection circuit as shown in FIG. 6, the same effect as described above can be obtained.As explained above, the present invention In a nutrunner with a torque transducer attached,
Place a strain gauge on the circumference of the torque transducer.
Two sets of bridge circuits pasted with a phase shift of 0000, a motor control circuit that amplifies the output of one set of bridge circuits and compares it with a predetermined set torque, and stops the motor when they match, and another set of bridge circuits. It amplifies the output of the bridge circuit and displays the maximum torque value via the maximum value memory circuit, and also monitors whether the maximum torque value is within the allowable range.If it is outside the allowable range, it is Since it is equipped with a monitoring circuit that displays the judgment, if an abnormality occurs in the torque transducer, the abnormality can be immediately detected by the monitoring circuit.For example, if the nut runner is installed in a horizontal position and used for a long period of time, When a bending moment due to the weight of the nutrunner itself acts on the torque transducer, and a certain value difference occurs between the two bridge circuits, it can be determined that permanent strain has occurred in the torque transducer, and a device abnormality is detected. can be discovered.

In other words, in the case of one set of conventional bridge turning wax, permanent distortion occurs due to the bending moment, and even if an error occurs in the traversing torque due to this, the abnormality cannot be discovered. As in this invention, two sets of bridge circuit strain gauges are pasted on the surface of the torque transducer with a phase shift of 900 degrees, one for motor control and the other for monitoring to display the maximum torque value and within the allowable range. By displaying an OK or NC judgment as soon as the condition is detected, abnormalities can be detected and reliability can be greatly improved.

[Brief explanation of the drawing]

Fig. 1 is a side view showing the schematic structure of the nut runner, Fig. 2 is a perspective view showing the conventional structure of the torque transducer, and Fig. 3 shows the relationship between the vertical installation time t and the vertical installation torque T during cotton attachment. Figure 4 is a diagram showing the strain gauge connection method, Figure 5 is a diagram showing the bridge circuit output voltage characteristics when an abnormality occurs in the strain gauge compared to a normal case, and Figure 6 is a diagram showing the strain gauge connection method. FIG. 7 is a sectional view of a torque transducer according to one embodiment of the invention, and FIG. 8 is a partially sectional side view showing a structural example of a torque transducer according to another embodiment. 1...Motor, 2...Reducer, 3, 3', 3''...
Torque transducer, 4a, 4b... Tortoise h... Strain gauge "5... Bolt tightening attachment, 6...
...Volt, 7, 8...Bridge circuit, 9, 10...
...Amplifier, 11...Comparator 2...Motor stop circuit, 13...Maximum value memory circuit, 14...
Torque indicator, 15... Upper limit comparison circuit "16...
・...lower limit comparison circuit, 17...judgment display. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] 1. In a nut runner that has a torque transducer with a strain gauge attached, there are two sets of bridge circuits with strain gauges attached to the surface of the torque transducer with a phase difference of 90 degrees, and one set of bridge circuit output. a motor control circuit that amplifies and compares the torque with a predetermined set torque and stops the motor when they match; and a motor control circuit that amplifies the output of another pair of bridge circuits and displays the maximum torque value via a maximum value memory circuit. A nut runner comprising: a monitoring circuit that monitors whether the maximum torque value is within a permissible range, and if it is outside the permissible range, determines and displays a defect or failure.