JPS6230371B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tightening torque detection device for a power wrench.

Conventionally, in order to generate appropriate axial force in bolts, etc., wrenches that manage tightening torque include so-called constant torque wrenches with a mechanical clutch mechanism and power wrenches with a torque detector installed on the drive shaft. Are known.

These devices prevent the tightening torque from exceeding a certain value from being applied to the bolt, or control the tightening torque by reading the tightening torque signal from a torque detector. The tightening torque cannot be changed in response to changes in the condition of the fastened objects or bolts, such as misalignment between the fastened objects, rust on the fastened objects or bolts, or clogging with dirt, etc. Since the axial force of the bolt is not constant, there have been problems such as loosening of the bolt, breakage of the bolt, and loss of threads.

The object of the present invention is to provide a device that does not have such inconveniences.The wrench body supports the drive shaft in order to manage the tightening torque value after the seating point and obtain an appropriate bolt axial force. an accelerometer for detecting acceleration in the rotational direction of the drive shaft, and a torque detector for detecting torsion of the drive shaft for the drive shaft, and means for specifying the seating point based on the output of the accelerometer; The present invention is characterized by comprising means for calculating an increase in tightening torque after the seating point based on the output of the torque detector.

Embodiments of the present invention will be described below with reference to the drawings.

In FIGS. 1 to 3, reference numeral 1 denotes a wrench body, inside of which there is an air motor 2 that is activated by pulling a trigger 2a, for example, and an anvil 3 that is rotated by the air motor 2. and a hammer 4, which is a drive shaft part, which has a protrusion 4a formed at one end, a bolt tightening part 4b protruding outward from the wrench body 1 at the other end, and is rotatably supported by a bearing 5. A recess 3a is formed in the inner peripheral surface of the anvil 3, in which a striking pin 7 biased by a spring 6 and striking the protrusion 4a of the hammer 4 when the anvil 3 rotates is disposed. 8
is a torque detector made of a strain gauge, for example, which is fixed to the hammer 4, which is a drive shaft portion, and this lead wire 9 is connected to a slip ring 10 provided on the hammer 4, and a sliding A torque signal is taken out from the electric wire 12 connected to the child 11. 13 is an accelerometer fixed to the wrench body 1.

Next, to explain its operation, an operator grasps the gripping part 1a of the wrench body 1, and attaches the bolt tightening part 4b of the hammer 4 to the bolt 16 that is locked in the screw hole 15 of the two members 14a and 14b to be tightened.
When the wrench is engaged through the socket 17 and the trigger 2a is pulled, air is supplied to the air motor 2 connected to a drive source such as an air tank (not shown) provided separately from the wrench body 1, and the motor 2 is activated. Start rotating. The hammer 4 rotates as the protrusion 4a is intermittently struck by the striking pin 7 of the anvil 3 which rotates as the air motor 2 rotates, thereby rotating the bolt 16 in the tightening direction. The bolt 16 rotates and enters the members 14a and 14b a predetermined length,
When the seat surface of the bolt 16 reaches a position where it contacts the member 14a, the tightening torque begins to increase and the axial force of the bolt 16 begins to act on the members 14a, 14b. (Hereinafter, this point will be referred to as a seating point.) As the bolt 16 further enters the members 14a and 14b, the tightening torque increases and the axial force of the bolt 16 also increases. This situation is shown in FIG.
4B shows the tightening torque signal obtained from the torque detector 8 fixed to the hammer 4, and FIG. 4C shows the axial force of the bolt 16 over time. As mentioned above, when the bolt 16 reaches the seating point, the members 14a, 1
Since the axial force of the bolt 16 acts on the wrench 4b, a reaction force acts on the wrench body 1 at this point, so that a signal with a large amplitude appears on the accelerometer 13.
FIG. 4A shows the time course of the output signal of the accelerometer 13. FIG. 5 shows a schematic block diagram of the electrical circuit of a tightening torque control device using one embodiment of the present invention.

In the figure, 18 is an accumulator, which is connected to the torque detector 8 via an AD converter 19 and an amplifier 20. 21 is a seating point setting device;
22 is a comparator that compares the output signals of the seating point setter 21 and the accelerometer 13, and issues an output signal when the output signal of the accelerometer 13 exceeds the seating point setting level L; 23 is a tightening torque memory; 24 is a Seating point tightening torque memory, 25 is a calculator, 26 is a tightening torque memory that stores the results calculated by the calculator 25, 27 is a tightening torque setting device, and 28 is a tightening torque read out from the tightening torque memory 26. A comparator that compares the tightening torque with the appropriate tightening torque set by the tightening torque setting device 27, 29 a control device that cuts off the air motor 2 from the drive source based on the output of the comparator 28, and 30 a tightening state. This is a display device that indicates that the information is appropriate.

In the above configuration, the air motor 2 of the power wrench is driven to rotate the bolt 16, and when the bolt 16 reaches the seating point ts, the torque detector 8
The torque signal Ts outputted from the amplifier 20, amplified by the amplifier 20, and converted to a digital value by the A-D converter 19 is written to the accumulator 18 by the seating signal output from the comparator 22, and then read out and converted to a digital value by the A-D converter 19. It is transferred to the point tightening torque memory 24 and stored there. On the other hand, the tightening torque signal output from the AD converter 19 is intermittently written and stored in the tightening torque memory 23. Then, in the calculator 25, the difference value between the tightening torque and the seating point tightening torque read from the tightening torque memory 23 and the seating point tightening torque memory 24 is calculated, and the result is stored in the tightening torque memory 26. The tightening torque read from the tightening torque memory 26 is the preset appropriate tightening torque.
It is compared with Tf by a comparator 28. When the tightening torque reaches the proper tightening torque Tf, the control device 29 is operated by the output of the comparator 28, power to the air motor 2 is cut off, and the tightening is completed tf.

In FIG. 5, the electronic circuit surrounded by broken lines includes a controller which is not shown in the drawings and which operates in conjunction with the trigger 2a to issue commands to the AD converter, arithmetic unit, etc. when each memory and wrench is activated.

Further, the electronic circuit can also be configured with a microcomputer.

As described above, according to the present invention, an accelerometer for detecting acceleration in the rotating direction of the drive shaft is disposed on the wrench body that supports the drive shaft, and a torque detector for detecting twisting of the drive shaft is disposed on the drive shaft. and means for identifying a seating point based on the output of the accelerometer;
Since it is equipped with a means for calculating the increase in tightening torque after the seating point based on the output of the torque detector, even if the condition of the object to be tightened or the bolt changes before seating, the The axial force of the bolt can be detected, which has the effect of preventing loosening of tightening, bolt breakage, etc.

[Brief explanation of the drawing]

1 to 3 are partially cutaway side views of an example of the device of the present invention, a sectional view taken along the line of FIG. 1 and a sectional view taken along the line of FIG. FIG. 5 is a schematic block diagram of an electric circuit of a tightening torque control device using this device. 1...Wrench body, 2...Air motor, 3...Anvil, 4...Hammer, 5...Bearing, 6...Spring, 7
...Strike pin, 8...Torque detector, 13...Accelerometer.

Claims (1)

[Claims] 1. An accelerometer for detecting acceleration in the rotating direction of the drive shaft is disposed on the wrench body that supports the drive shaft, and a torque detector for detecting torsion of the drive shaft is disposed on the drive shaft, and the output of the accelerometer is used to detect the A tightening torque detection device for a power wrench, comprising means for specifying a seating point, and means for calculating an increase in tightening torque after the seating point based on the output of the torque detector.