JPS6117634B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nut runner that has little error in tightening force and can accommodate a wide range of tightening torques.

In nut runners, the tightening torque value is generally set in accordance with the amount of increase in the load current of the electric motor serving as the power source.

Therefore, when tightening with this type of nut runner, it is necessary to tighten the nut in advance to an extent that slightly increases the tightening torque, so-called temporary tightening. In the light load range where the torque is small, the motor as the power source rotates at high speed and has a large inertia, and this rotational inertia is used to determine the relationship between the load current and the tightening torque, which serves as an indicator for setting the tightening torque. Since the torque changes over a certain period, a nut set to a tightening torque value (low torque value) within this period will be overtightened by the inertial force of the electric motor or the like.

This negative effect is particularly noticeable when tightening at low torque values, and for this reason, when tightening at low torque, it is necessary to use a nut runner specifically designed for low speed rotation or low tightening torque, and the tightening work must be carried out separately. There were problems such as complication.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a nut runner configured such that the output torque gradually increases up to a set tightening torque value in accordance with the amount of increase in load due to nut tightening. There is.

The present invention will be explained below based on an illustrated embodiment.

In Fig. 1, AC power supply 1 is connected to start switch 2.
It is connected via a thyristor 3 to an electric motor 4 which is a power source that drives a nut tightening part (not shown), and the electric motor 4 is further connected to a load current detection circuit 5.
are connected in series.

The thyristor 3 and the trigger circuit 6 that controls the phase of this gate signal constitute a voltage adjustment circuit 9 that adjusts the voltage supplied to the motor 4. The detection circuit 5 receives its output signal via a feedback circuit 7. The circuit 6 is connected in such a way that it is fed back positively to the circuit 6.

The voltage adjustment circuit 9 is configured to adjust the average value of the voltage supplied to the motor 4 by conducting or cutting off the AC voltage of the AC power source 1 at an arbitrary phase every half cycle, and adjusts the average value of the voltage supplied to the motor 4. When the output signal of the detection circuit 5, which is fed back positively through the feedback circuit 7, is small, the conduction amount of the thyristor 3 is made small, and on the other hand, when the load current increases and the output signal increases as the load increases, the thyristor 3 is turned on. 3
increases the amount of conduction.

In addition, the stop circuit 8 has a function of setting the nut tightening torque value, and the nut runner tightens (=
When the output signal from the detection circuit 5 reaches this set value, the trigger circuit 6 is operated to break the conduction of the thyristor 3 and the AC voltage to the motor 4 is stopped. Stop supply.

Further, the voltage adjustment circuit 9 is configured to provide negative feedback to the voltage of the AC power source 1 via the feedback circuit 7 to compensate for the operation so as not to cause malfunctions due to voltage fluctuations in the AC power source 1. Therefore, even if a voltage drop occurs in the AC power supply 1 due to load fluctuations, the tightening torque can be accurately tightened to the set tightening torque value.

In this way, the feedback circuit 7 compares the output signal of the detection circuit 5 that receives positive feedback and the voltage fluctuation of the AC power supply 1 that receives negative feedback, and sends this output signal to the trigger circuit 6.
The trigger circuit 6 has a time constant circuit that is variably operated by the output signal of the feedback circuit 7 and is configured with a unidirectional transistor or the like, so that the phase of the gate signal of the thyristor 3 can be adjusted to increase the load. can be easily configured to respond to

Furthermore, in this case, since it is extremely easy to stop the oscillation of the unijunction transistor, the circuit configuration for turning on and off the thyristor 3 using the output signal of the stop circuit 8 can be simplified.

Furthermore, the detection circuit 5 may be any device that can simply obtain an output signal that is approximately proportional to the increase or decrease in load current, such as a transformer such as a current transformer, or
It can be constructed from an impedance element with a resistance value of about 0.1 ohm.

Fig. 2 shows the relationship between the load current of the motor 4 and the average value of the supply voltage, and line A indicates the light load section when the nut is free-down during temporary tightening, etc.
Line B shows an area where the tightening torque increases due to actual tightening.

When the start switch 2 of the nut runner is connected in such a configuration, the output signal of the detection circuit 5 is small because the motor 4 is under light load during idling with a low load or in a temporary tightening section of the nut. The amount of conduction of 3 is greatly limited.

Therefore, since the supplied voltage is low, the electric motor 4 rotates at a low speed, and the rotational inertia of the rotating portion becomes extremely small.

Next, when the temporary tightening of the nut is completed and the tightening torque starts to gradually increase, the output signal of the detection circuit 5 increases due to the corresponding increase in the load current, and this output signal is fed back to the voltage adjustment circuit. 9
gradually increases the voltage supplied to the electric motor 4.

Therefore, since the output of the electric motor 4 gradually increases, the tightening torque of the nut runner can be gradually increased in accordance with the load condition of the nut, and the nut runner can be tightened strongly.

In other words, as shown in Fig. 2, the voltage supplied to the motor 4 remains almost constant during the light load section due to the free-down of the nut, indicated by line A, and does not increase, and the tightening load increases due to the substantial start of tightening. Then, as shown by line B, it gradually rises.

When the nut is tightened to a predetermined tightening torque value set by the stop circuit 8, the stop circuit 8 operates the trigger circuit 6 using its output signal to cut off conduction of the thyristor 3.

According to the above configuration, the output torque of the nut runner gradually increases in response to the increase in the tightening load while the nut is being tightened, so the rotation speed does not increase abnormally even under light load. Since the load related to tightening the nut and the output torque of the electric motor gradually increase while always maintaining a balance, it is possible to tighten the nut almost constant and at a low speed, so there is no need to overtighten due to rotational inertia. It is possible to tighten accurately to the torque value set in step 8.

According to the present invention, it is possible to obtain a nut runner that can easily and accurately perform tightening operations over an extremely wide range from low tightening torque values to high tightening torque values.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a configuration example of the present invention, and FIG. 2 is a diagram showing the relationship between the load current and supply voltage of the motor. 3... Thyristor, 4... Electric motor, 5... Detection circuit, 6... Trigger circuit, 7... Feedback circuit, 8...
...stop circuit, 9...voltage adjustment circuit.

Claims (1)

[Claims] 1. A voltage adjustment circuit that adjusts the voltage supplied to the motor of the power source, and a detection circuit that detects the load current of the motor, and provides positive feedback of the output signal of the detection circuit to the voltage adjustment circuit to adjust the voltage of the load. When the supply voltage is configured to steplessly increase in proportion to the increase in current, and the output torque is increased in accordance with the amount of increase in load, and a certain tightening torque is reached by the output of the detection circuit. A nut runner characterized in that it is provided with an operative stop circuit and further provides negative feedback of fluctuations in power supply voltage to the voltage adjustment circuit.