JPS6013796B2 - Electric tightening device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an electric tightening device configured to tighten vertically attached objects such as bolts and nuts using the rotational force of an electric motor, and to automatically stop when the tightening torque reaches a set torque. In particular, the present invention relates to an electric fastening device that can accurately tighten bolts, nuts, etc. by eliminating errors caused by inertia of a motor rotor, reduction gear, etc. as necessary.

BACKGROUND ART Conventionally, so-called bolt tightening machines have been used that tighten vertically attached bodies such as bolts and nuts using the rotational force of an electric motor.

Additionally, the tightening torque when tightening bolts and nuts is detected, and when the tightening torque reaches a set torque, the current supplied to the electric motor is cut off to regulate the tightening torque to a predetermined value. There is.

The torque control circuit in such a vertical bolt mounting machine, for example, as shown in FIG. The current in this circuit is detected by the current detector 5, and when this value reaches the value preset by the torque setting device 6, a cutoff signal is issued from the gate cutoff circuit 7, and the thyristor 4 is turned off.
The configuration is such that the electric motor is stopped when the condition is reached.

At this point, when starting the electric motor, that is, turn on the trigger switch 8.
A soft start circuit 9 is separately provided in order to prevent the influence of the starting current of the motor when the motor is overloaded.

In FIG. 1, the torque control section 1 is configured to be electrically connected to and disconnected from the electric motor section 0 through a detachable connector 10.

201 is a forward/reverse changeover switch.

By the way, in conventional bolt tightening machines, the reaction force when tightening bolts and nuts is received by moving the claw of the reaction force receiver against a nearby fixed pond, but the reaction force is absorbed after starting the electric motor. The motor reaches its maximum rotation before the catch claws apply support to other fixed objects nearby, and due to the inertia of the rotor, reduction gear, etc., the reaction force catch claws hit nearby bolts and nuts. In particular, when the set torque is small, the tightening force due to inertia becomes larger and may exceed the target set torque, and furthermore, the tightening force due to inertia cannot be controlled. However, there was a drawback that the cotton attachment torque varied greatly.

In addition, as a simple method for inspecting the tightening condition of bolts and nuts, mark the edge positions of the bolts and nuts when the bolts and nuts have been tightened, then tighten the bolts again to the set torque using a bolt tightening machine. A test method is also conducted to confirm that the edge of the nut does not shift from the position of the mark, but in such cases, the motor does not reach its maximum rotation until the reaction force receiver applies support to another fixed object nearby. When the claw of the reaction force receiver comes into contact with a nearby bolt or nut, a torque exceeding the set torque is applied to the bolt or nut to be tested due to the inertia of the rotor, reduction gear, etc., causing the inspection result to be incorrect. There is a risk that it will be inaccurate.

The inertia factor converted to the output shaft of the bolt tightening machine is J (k9・
), the rotation angle of the bolt after it begins to tighten is 8
(rad), the spring constant including the bolt tightened body is E(
If the time after turning off the electric motor's power is t (sec), and the output torque of the bolt cotton machine, which does not include torque for inertia, is T (N/rad), then J. et al. 8 nod
t2=T-E・0......tl) is established.

And since the output torque T of the bolt cotton machine becomes zero after the power is cut off, the above formula '11 becomes J・d20/dt2=−E・8……{21] after the current is cut off. Become.

This {2) formula is t=0, 8=8o, d8/dt=o
If you solve it as 8 = ノ.

8/8218.

・sin(8t10)..."...{31.

however, 82 ni E/J, 0 ni n-1.008/.

It is. On the other hand, the final tightening torque Tmax of the bolt is
At the maximum value of rotation angle 8, 8max, Tmax=E
・8・・・・・・・・・・・・・・・・・・'4} is given.

And 8max is from the above (3' formula) ○maX=ノwyo/82 18.

2 =ノJ/E・の.

18th evening...{51.

Therefore, from equations (1) and [5} above, the final tightening torque TmaX of the bolt when the electric motor has completely stopped is TmaX=noE・J・.

20E28 Evening...---It is expressed as (6).

Here, E28 is a torque corresponding to the current value at which the current is cut off, and EJW is a torque determined by the angular velocity of the motor at the time of cutting off the electric current of the motor, and is a component added as an electric current.

Therefore, when the tightening torque is low, the breaking current value is naturally low and the E28 term is small.

At this time, if the rotation of the motor reaches a high speed when the current is interrupted due to the condition of receiving the reaction force, EJ will occur. The term 2 becomes large,
This amount greatly influences the final vertical mounting torque Tmax.

To explain this with Fig. 4, when the electric current is cut off at a current value of lo in the cotton application torque curve T, the torque produced by the motor is E28.2 is To, and the torque due to inertia while the rotation decreases to 0 thereafter. E.J.'s.

2 is added, and the final tightening torque Tmax becomes T.

The energy of inertia is the area of the triangle F, T,, To, and when the spring constant E is small, the final longitudinal torque Tmax becomes L. The energy of inertia is the area of the triangle To, L, T. Note that triangles L, T. , To, and the triangles To, T2, and To2 have the same area. By the way, in order to prevent the influence of such inertia, Japanese Patent Application Laid-Open No. 50-14317 discloses a control method for a power tool that is equipped with a speed control circuit section that keeps the tightening rotational speed constant even if the load current changes. An apparatus is disclosed.

However, when the speed control circuit is integrally incorporated in this way, there are disadvantages in that the price is relatively high and the operability is reduced for applications that do not require constant speed control. The present invention was made in order to eliminate such conventional drawbacks, and it is possible to arbitrarily set =d8/dt in the formula '1}, and by tightening with extremely small peaks as necessary, It is an object of the present invention to provide an electric tightening device that is less affected by the above-mentioned inertia.

More specifically, the present invention provides a military tightening device having a constant speed control circuit that can be easily attached to a conventional tightening device as shown in FIG. When using a large amount of torque, a constant speed control circuit m, which will be described later, can be easily connected to the conventional torque control section 1 without any modification, thereby reducing the influence of inertia and making it possible to use the conventional torque control section 1. 1
This makes it possible to perform high-precision cotton-tapping at low cotton-tapping torques, which would have been impossible with just one bolt, and thereby make it possible to obtain a wide range of tightening torques.

The details of the present invention will be explained below with reference to embodiments shown in FIGS. 2 and 3. In FIG. 2, reference numeral 1 indicates a conventional torque control section, an electric motor section, and m a constant speed control section.

The electric motor section 0 and the constant speed control section, and the constant speed control circuit section m and the torque control section 1 are connected via detachable connectors. 11 is a speed setting device, 12 is a reaction force receiver, and 13 is a socket.

FIG. 3 shows a wiring diagram of each part of FIG. 2.

In the following explanation, the wiring diagram of the torque control section 1 and the electric motor section 0 is the same as that shown in FIG. 1, so the explanation of the operation will be omitted. A constant speed control section m is inserted between the torque control section 1 and the electric motor section B, and this constant speed control section m is connected using the same connector as the one that electrically connects the two in FIG. It is connected to the torque control section 1 and the electric motor section 0.

When the trigger switch 8 is turned on, the thyristor 14 is immediately turned on, and when the motor starts rotating and the rotation reaches a preset value of the rotation speed setting device 11, the constant speed control section m switches the phase controller. 15, the rotation of the electric motor is controlled to be constant. Note that the diode 16,
17 and resistors 18 and 19 are added to prevent backflow and stabilize operation.

In short, in the electric cotton applicator equipped with the constant speed control section m, when the trigger switch 8 is turned on, the rotational speed of the electric motor increases and reaches the set speed, and then the rotational speed is maintained by the constant speed control circuit. Therefore, the maximum rotation does not occur until the reaction force receiver applies support to the nearby fixed pond, and therefore the tightening torque does not exceed the target tightening torque due to inertia.

Further, for the same reason, in the method of inspecting the attachment condition of bolts and nuts, there is no possibility that the inspection results will be inaccurate due to the influence of inertia. Since the inertia section is limited by the constant speed control section m, it is possible to apply a low torque that could not be achieved by the torque control section 1 alone, and accurate tightening torque can be obtained over a wider range. This is clear from FIG.

FIG. 5 shows the rotation speed n in FIG. 4 by the constant speed control section m.
This figure shows the changes in torque (T), rotational speed (n), and current (i) when is set to approximately 1'2. In the figure, the solid line is the characteristic curve of the conventional bolt tightening machine, and the chain line is the characteristic curve of the bolt tightening machine of the present invention.

Now, if the power is cut off by current, the tightening torque at that time is theoretically To, but the tightening torque including inertia becomes L.

As is clear from the figure, T3 is significantly smaller than T in the conventional bolt tightening machine, and the influence of inertia in the conventional bolt tightening machine can be eliminated. In summary, in the haze tightening device of the present invention, by attaching the constant speed control section in a detachable manner, errors due to inertia can be reduced without changing the basic configuration of the conventional device, and bolts and nuts can be accurately tightened. It can be tightened over a wide range with a tightening torque of 3-), and has good operability, and its effects are extremely large.

[Brief explanation of drawings]

Figure 1 is a wiring diagram showing the control circuit of a conventional bolt tightening machine.
Fig. 2 is a configuration diagram of an embodiment of the present invention, Fig. 3 is a wiring diagram showing a control circuit of the embodiment, and Fig. 4 shows the current value and rotation speed over time of a conventional bolt tightening machine. Graph showing changes in torque. FIG. 5 is a graph showing changes in current value, rotation speed, and torque over time for the bolt tightening machine of the present invention and the conventional bolt tightening machine. 1......Torque control section, 0......
...Electric motor section, m...Constant speed control section. Figure 1 Figure 2 Figure 5 Figure 3 Figure 4

Claims (1)

[Claims] 1 an electric motor section, a torque control section that tightens an object to be tightened by the electric motor section, detects the tightening torque, and cuts off the supply of current to the electric motor section when the tightening torque reaches a set torque; The constant speed control section maintains the rotation when the rotation reaches a set speed, and the constant speed control section is housed in a separate casing from the electric motor section and the torque control section, and these are connected by detachable connectors. An electric tightening device characterized in that it is connected.