JPS6325917B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention has two motors, a series-wound commutator motor for high-speed, low-torque use and a series-wound commutator motor for low-speed, high-torque use. This relates to a bolt tightening machine that tightens bolts and nuts.

(Background of the Invention) Normally, when tightening bolts of an assembled structure, temporary tightening is not performed, and the bolts and nuts rotate idly several times and hit the tightening member to reach a predetermined tightening torque or rotation angle. Once this is reached, complete tightening of bolts and nuts. That is, the tightening work is performed from the state where the bolts and nuts are freely rotating. Moreover, the time required to tighten each bolt is minimized,
Work efficiency must be improved.

Generally, when tightening bolts and nuts using a bolt tightening machine, when the tightening torque of the bolt or nut reaches the set tightening torque T ₀ and the power of the bolt tightening machine is cut off, the bolt tightening machine Let ω ₀ be the rotational speed of the output shaft of the bolt tightener, J be the inertia factor of the rotating part of the bolt tightening machine, k be the proportionality constant, and T be the final tightening torque acting on the bolt/nut, then T = √ ₀ ² + ₀ ² , the larger ω ₀ is, the greater the influence of inertia on the final tightening torque T is, and the smaller ω ₀ is, the smaller the influence of inertia on the final tightening torque T. The time required for tightening will be longer.
Therefore, in order to tighten bolts and nuts to the set tightening torque in a short time, it is necessary to rotate the bolts and nuts at high speed and low torque during free rotation (during light load).
When tightening (when the load exceeds a predetermined value), it is sufficient to rotate at low speed and high torque.

However, with conventional bolt tightening machines that connect a single prime mover to a reduction gear with a large reduction ratio and use it at low speed and high torque, even when bolts and nuts are freely rotating during bolt tightening work, Since the bolts and nuts are rotated at the same low speed and tightened with a set tightening torque or a set rotation angle, it takes a long time to tighten the bolts and nuts.

In addition, one prime mover is connected to a first-stage reduction gear, a friction clutch, a one-way clutch, and a second-stage reduction gear, and when the bolts and nuts are freely rotating, the first-stage reduction gear is used alone to reduce the speed and speed of the bolts and nuts. When rotated with torque, the bolt/nut comes into close contact with the tightening member, the tightening torque of the bolt/nut increases, and the torque reaches a predetermined value, causing the friction clutch to slip.
There is also a conventional bolt tightening machine that automatically switches to low speed and high torque using a one-way clutch and a second stage reduction gear, and tightens bolts and nuts at a set tightening torque or a set rotation angle. This bolt tightening machine had the disadvantage that the friction clutch had a short lifespan because it slipped during low-speed tightening. There is also a method of tightening bolts and nuts using two motors (Japanese Patent Laid-Open No. 52-80599), but in this case, current is constantly flowing through the two motors, which is uneconomical. Additionally, since the final tightening uses bevel gears, there are drawbacks such as the power wrench itself being large.

In addition, torque is detected based on the motor current value, and when the torque reaches about 1/3 of the regulated torque at high speed rotation, the motor voltage is lowered to slow down the rotation, and at the same time, the encoder counts pulses and rotates at the specified angle. There is also a screw tightening device (Special Publication No. 52-34795) that stops the rotation of the motor when a pulse equivalent to In order to switch to this, the motor voltage is lowered and the rotation is lowered, so in order to obtain the required large tightening torque, a very large capacity electric motor is required and it takes a long time to complete tightening.

Additionally, when tightening bolts and nuts,
The difference in tightening torque between the idling period until the bolt/nut is seated (temporary tightening) and the tightening period after seating (final tightening) is very large; for example, temporary tightening requires approximately 0.5 kg.
A tightening torque of f・m or less is sufficient, but final tightening requires a tightening torque of several tens of kgf・m to several hundred kgf・m, and the power required for final tightening is much greater than for temporary tightening. Power is required. When a very large amount of power is required for final tightening, tightening is performed with reduced power, which poses a major problem.Also, from the point of view of inertia, as mentioned above, reducing power during final tightening is a major problem. also requires a large-capacity electric motor that can provide a very large tightening torque.
Since this large-capacity electric motor is rotated at high speed during temporary tightening, the inertia force becomes extremely large, and even if the voltage is lowered and the speed is reduced during final tightening, it is not enough, and the inertia force described above causes excessive tightening. There are disadvantages such as the result.

(Objective of the Invention) In view of the above points, the present invention does not use a friction clutch or the like, can arbitrarily select two motors, automatically switches from high speed, low torque to low speed, high torque, and The purpose of the present invention is to provide a bolt tightening machine that improves work efficiency by minimizing the time required to tighten bolts and nuts according to the law.

(Structure of the Invention) According to the present invention, the object is to provide a high-speed, low-torque electric motor that tightens bolts and nuts at high speed and low torque up to temporary tightening torque when the load is light; a high-speed, low-torque motor current cutoff means for outputting a signal to cut off a gate of a thyristor circuit of the torque motor and operate the low-speed, high-torque motor; activated by a signal from the high-speed, low-torque motor current cutoff means; A low-speed, high-torque electric motor that tightens bolts and nuts to a set rotation angle at low speed and high torque via a one-way clutch; A rotation angle setting device that sets the tightening rotation angle of the bolts and nuts tightened by this low-speed, high-torque electric motor in advance. This is achieved by a bolt tightening machine characterized by comprising a low-speed, high-torque motor current cutoff means that cuts off a gate of a thyristor circuit of the low-speed, high-torque motor when the set rotation angle is reached. .

(Example) Fig. 1 is a schematic diagram of the mechanical structure of the bolt tightening machine of the present invention, and Figs. 2 to 4 are block lines showing embodiments of the control circuit of the bolt tightening machine of the present invention. In the figures, the high-speed, low-torque motor current cutoff means in FIGS. 2 and 3 compares the current of the high-speed, low-torque motor with the current value corresponding to the torque value set in the torque setting device, and a first comparator A that outputs a signal when they are equal; a gate cutoff circuit 23 that is energized by the signal from the first comparator A and outputs a stop signal; and a thyristor activated by the stop signal from the gate cutoff circuit 23. It is composed of a phase control circuit 31 that shuts off the gate of the circuit 15. The high-speed low-torque motor current cutoff means shown in FIG. 4 includes a zero rotation detector 32 that detects when the rotation of the high-speed low-torque electric motor reaches almost zero rotation and outputs a signal.
A gate cutoff circuit 23 that is energized by the signal from the zero rotation detector 32 and outputs a stop signal; and a phase control circuit 31 that cuts off the gate of the thyristor circuit 15 with the stop signal from the gate cutoff circuit 23. has been done.

In addition, the low speed and high torque motor current interrupting means is
A comparator that compares the set rotation angle set on the rotation angle setting device with the rotation angle of the bolt/nut tightened by the low-speed high-torque electric motor and outputs a signal when the two become equal; The thyristor circuit is composed of a gate cutoff circuit that is energized by a signal from the gate cutoff circuit and outputs a stop signal; and a phase control circuit that cuts off the gate of the thyristor circuit using the stop signal from the gate cutoff circuit.

In addition, in FIGS. 1 to 4, the same numbers represent the same members.

In FIG. 1, a bolt tightening machine 1 includes a high-speed, low-torque electric motor 3 (hereinafter abbreviated as electric motor 3),
A high-speed low-torque transmission section 5 consisting of a reduction mechanism 4, a gear 11 attached to the output shaft of the reduction mechanism 4 and meshing with a gear 12 fixed to a socket shaft 9, and a low-speed high-torque electric motor 6 (hereinafter referred to as electric motor 6). ) and a reduction mechanism 7, a socket shaft 9, a socket 10 detachably attached to the socket shaft 9, and the socket shaft 9.
A socket drive unit 13 consisting of a gear 12 fixed to the output shaft of the reduction mechanism 4 and meshing with a gear 11 attached to the output shaft of the reduction mechanism 4, a one-way clutch 14, a control device 2 and a bolt tightening machine 1 are connected to an external power source (not shown). The high-speed low-torque transmission section 5 is connected to the socket drive section via the gear 12 meshing with the gear 11, and the low-speed high-torque transmission section 8 is connected via the one-way clutch 14 to the socket drive section. It is connected to 13. FIG. 2 shows an embodiment of the control circuit for the bolt tightening machine of the present invention. and are connected in series to thyristor circuits 15 and 16, respectively, and to a plug 24 via a common switch 17. The control circuit of the electric motor 3 includes a speed setting device 18, a soft start circuit 19, a thyristor circuit 15, and a current detector 2.
0, a high-speed and low-torque motor current cutoff means consisting of an amplifier 21, a temporary tightening torque setter 22 (hereinafter abbreviated as torque setter 22), a first comparator A, a gate cutoff circuit 23, and a phase control circuit 31; The control circuit for the electric motor 6 includes a thyristor circuit 16, a rotation angle setting device 26, and a rotation angle detector 2.
7, and a low-speed, high-torque motor current cutoff means consisting of a second comparator B, a gate cutoff circuit 28, and a phase control circuit 25. Now, when the plug 24 is connected to an external power source, the socket 10 is fitted to the bolt/nut to be tightened, and the switch 17 is turned on, the soft start circuit 19 is energized, and the motor 3 is activated by the phase control circuit 31, A soft start is performed via the thyristor circuit 15, and the rotation speed gradually increases to the rotation speed set in the speed setting device 18, and the rotation is transferred from the high-speed low torque transmission section 5 to the socket drive via the gears 11 and 12. 13, causing the socket 10 to rotate at high speed. This rotation is blocked by the one-way clutch 14 and is not transmitted to the low speed high torque transmission section 8. Therefore, the bolt/nut rotates freely at high speed, and when the bolt/nut comes into close contact with a tightening member (not shown), the current in the motor 3 increases. This current of the motor 3 is detected by a current detector 20, taken out via an amplifier 21, and compared with a pre-tightening torque value set in advance in a torque setting device 22 by a first comparator A. When becomes equal to the current value corresponding to the temporary tightening torque value, a signal is sent to the gate cutoff circuit 2.
3, energizes the gate cutoff circuit 23, outputs a stop signal from the gate cutoff circuit 23 to the phase control circuit 31, gates off the thyristor circuit 15, and stops the motor 3. Also, the first comparator A
The signals are simultaneously sent to the phase control circuit 25 and rotation angle setting device 26 of the control circuit of the electric motor 6, and the phase control circuit 25 and rotation angle setting device 26 are energized. When the phase control circuit 25 is energized, the electric motor 6 rotates at full speed via the thyristor circuit 16. Further, when the rotation angle setting device 26 is energized, the set rotation angle set in the rotation angle setting device 26 and the rotation angle of the bolt/nut detected by the rotation angle detector 27 are matched by the second comparator B. When the detected rotation angle of the bolt/nut reaches the set rotation angle, the gate cutoff circuit 28 is energized by the signal from the second comparator B.
A stop signal is output to the phase control circuit 25, the thyristor circuit 16 is gated off, and the motor 6 is stopped. Therefore, the bolt/nut is temporarily tightened with the temporary tightening torque value set in the temporary tightening torque setting device 22, and the rotation angle setting device 2 starts from this point.
It can be tightened correctly at the position rotated by the rotation angle set at 6. Then, when switch 17 is turned off, all circuits are reset. By fitting the socket 10 of the bolt tightening machine 1 to the next bolt/nut and repeating the above operation, the bolt/nut will be continuously tightened.
Can perform nut tightening work. In addition,
In this case, the speed setter 18 may be removed.

FIG. 3 is a block diagram of another embodiment of the control circuit for the bolt tightening machine of the present invention, in which the electric motor 3 of FIG.
In the control circuit, the soft start circuit 19 is removed, a phase control circuit 31 and a speed setter 18 are provided between the thyristor circuit 15 and the gate cutoff circuit 23, and a dead zone is provided between the current detector 20 and the amplifier 21. A circuit 29 is provided, and the other configurations are completely the same as in FIG. 2. That is, when the switch 17 is turned on, the rotation speed of the motor 3 rapidly increases to the speed set in the speed setting device 18 via the thyristor circuit 15, but the starting current of the motor 3 at that time causes the gate cutoff circuit 23 to prevent it from operating.
For a certain period of time after the electric motor 3 starts, the current detector 2
A dead band circuit 29 is provided to prevent the current of the electric motor 3 detected by 0 from being matched with the set torque value of the high-speed/low-torque torque setting device 22.Other functions and effects are shown in Fig. 2. The same is true for . In this case, the speed setting device 18
may be removed.

FIG. 4 is a block diagram showing another embodiment of the control circuit for a bolt tightening machine according to the present invention.
The mechanical structure of the bolt tightening machine is exactly the same as the bolt tightening machine 1 shown in FIG. In FIG. 4, electric motors 3 and 6 have armatures 3A and 6A and series field windings 3F and 6F, respectively, and are connected in series to thyristor circuits 15 and 16, respectively, through a common switch 17. It is connected to the plug 24.
The control circuit of the electric motor 3 is a high-speed control circuit consisting of a thyristor circuit 15, a current detector 20, an amplifier 21, a first comparator A, a current limit setting device 30, a zero rotation detector 32, a gate cutoff circuit 23, and a phase control circuit 31. The configuration of the control circuit of the electric motor 6 is exactly the same as that of the electric motor 6 shown in FIG. 2. Now, when the plug 24 is connected to an external power source, the socket 10 is fitted to the bolt or nut to be tightened, and the switch 17 is turned on, the electric motor 3 is started via the thyristor circuit 15, and its rotation is at high speed and low speed. Gear 1 from torque transmission part 5
2 to the socket drive unit 13, causing the socket 10 to rotate at high speed. Therefore, the bolt/nut rapidly approaches the tightening member (not shown) while rotating freely at high speed, and when the bolt/nut tightly contacts the tightening member and attempts to rotate, the tightening force acting on the bolt/nut is reduced. As the applied torque increases, the current of the motor 3 increases, and the current of the motor 3 as the bolts and nuts are tightened is detected by the current detector 20, taken out via the amplifier 21, and set in advance by the current limit setting device. The first comparator A compares the current setting value set at 30, and the thyristor circuit 15 is controlled by the phase control circuit 31. As a result, the bolts and nuts are tightened, and when the current of the motor 3 reaches the current limit value, the phase is narrowed down by the phase control circuit 31, so that the rotation of the motor 3 gradually decreases. When the state is detected by the zero rotation detector 32 and the rotation of the motor 3 reaches almost zero rotation, a signal is sent to the gate cutoff circuit 23, the gate cutoff circuit 23 is energized, and the gate cutoff circuit 23 is activated. A stop signal is output to the phase control circuit 31, the gate of the thyristor circuit 15 is cut off, and the motor 3 is stopped. Further, the signal of the zero rotation detector 32 is simultaneously transmitted to the phase control circuit 25 of the control circuit of the electric motor 6 and the rotation angle setting device 26.
In exactly the same way as in the case shown in FIG. Tightened. Then, when switch 17 is turned off, all circuits are reset. By fitting the socket 10 of the bolt tightening machine 1 into the next bolt/nut and repeating the above-described operation, the bolt/nut tightening work can be performed continuously.

Note that an integrator is incorporated in the zero rotation detector 32 so that the zero rotation detector 32 does not operate at the moment the electric motor 3 is started. Further, it is obvious that a solid state relay or a contactor may be used in place of the thyristor circuit 16 and the phase control circuit 25.

(Effects of the Invention) As described above, when the bolt tightening machine of the present invention is used, when the load is light, the bolts and nuts are rotated at high speed and low torque by the high speed and low torque electric motor, and the bolts and nuts are tightened. , the tightening torque of the bolts and nuts increases, and when this reaches the temporary tightening torque value, the high speed and low torque motor current cutoff means automatically cuts off the current of the high speed and low torque motor, and at the same time, the A low-speed, high-torque electric motor is operated via a directional clutch to tighten bolts and nuts to the set rotation angle at low speed and high torque, which not only saves energy, but also correctly tightens bolts and nuts to the plastic range using the rotation angle method. be able to. In addition, since two electric motors, a high-speed, low-torque electric motor and a low-speed, high-torque electric motor, can be arbitrarily selected, the time required for tightening bolts and nuts can be minimized, and work efficiency is therefore improved. Further, since a friction clutch or the like is not used, there are no disadvantages caused by a friction clutch. Furthermore, since the output shaft of the low-speed, high-torque electric motor and the socket shaft are on the same axis, power transmission loss is reduced, so the electric motor can be made smaller than the conventional two-motor system, which has great effects.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the mechanical structure of the bolt tightening machine of the present invention, and FIGS. 2 to 4 are block diagrams showing embodiments of the control circuit of the bolt tightening machine of the present invention. DESCRIPTION OF SYMBOLS 1... Bolt tightening machine, 2... Control device, 3... Series commutator motor for high speed and low torque, 4, 7... Reduction mechanism,
5... High speed low torque transmission section, 6... Low speed high torque series commutator motor, 8... Low speed high torque transmission section, 9...
Socket shaft, 10... Socket, 11, 12... Gear, 13... Socket drive unit, 14... One-way clutch, 15, 16... Thyristor circuit, 18... Speed setting device, 19... Soft start circuit, 20... Current detector, 21...Amplifier, 22...Torque setter for high speed and low torque, 23, 28...Gate cutoff circuit, 26...
Rotation angle setter, 27...Rotation angle detector, 29...
Dead band circuit, 30...Current limit setting device, 25, 31
...Phase control circuit, 32...Zero rotation detector, A...First
Comparator, B...second comparator.

Claims (1)

[Claims] 1. A high-speed, low-torque electric motor that tightens bolts and nuts to a temporary tightening torque at high speed and low torque during light loads; High-speed, low-torque motor current cutoff means outputs a signal to shut off the gate and operate the low-speed, high-torque electric motor; A low-speed, high-torque electric motor that tightens bolts and nuts to a set rotation angle with high torque; The tightening rotation angle of the bolts and nuts tightened by this low-speed and high-torque electric motor is a set rotation angle that is preset in the rotation angle setting device. 1. A bolt tightening machine comprising: low-speed, high-torque motor current cutoff means for cutting off a gate of a thyristor circuit of the low-speed, high-torque motor when 2. The high-speed, low-torque motor current cutoff means compares the current of the high-speed, low-torque motor with the current value corresponding to the temporary tightening torque value set in the torque setting device, and when the two become equal, the low-speed, high-torque motor current is cut off. a comparator that outputs a signal to operate the motor; a gate cutoff circuit that is energized by the signal from this comparator and outputs a stop signal; and a phase that cuts off the gate of the thyristor circuit with the stop signal from this gate cutoff circuit. A bolt tightening machine according to claim 1, comprising a control circuit. 3. A zero rotation detector for detecting when the rotation of the high speed low torque electric motor reaches almost zero rotation and outputting a signal for operating the low speed high torque electric motor; Claim 1 comprising: a gate cutoff circuit that is energized by a signal from the zero rotation detector and outputs a stop signal; and a phase control circuit that cuts off the gate of the thyristor circuit with the stop signal from the gate cutoff circuit. Bolt tightening machine described in section. 4 The low-speed, high-torque motor current cutoff means compares the set rotation angle set in the rotation angle setting device with the rotation angle of the bolt/nut tightened by the low-speed, high-torque motor, and outputs a signal when the two become equal. A patent consisting of a comparator that outputs; a gate cutoff circuit that is energized by a signal from this comparator and outputs a stop signal; and a phase control circuit that cuts off the gate of a thyristor circuit with a stop signal from this gate cutoff circuit. A bolt tightening machine according to claim 1.