JPH047900Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a tightening control device for an impact wrench.

An impact wrench is a tool that is relatively frequently used as a tool for tightening bolts and nuts because it produces little reaction during tightening work. When performing tightening work using this impact wrench, for example, if the tightening work is stopped while the tightening torque acting on the bolt or nut is small, sufficient tightening force may not be obtained, or If the tightening work is performed until a high torque is reached, the bolt may be damaged. In order to obtain stable tightening force,
It is necessary to stop the tightening operation when the tightening torque acting on the bolt or nut reaches a predetermined value, but currently, the timing to stop this tightening operation is determined by the sound or response during tightening. The reality is that the tightening process relies on the intuition of the operator based on the above, and therefore the accuracy of the tightening work cannot be said to be very high. On the other hand, various devices that stop the operation of impact wrenches when a predetermined tightening torque is reached have been developed and put into practical use, but these devices lack accuracy, cost, ease of handling, etc. It's not always satisfying.

This idea was created in view of the above, and its purpose was to accurately control the tightening torque of bolts and nuts.
To provide a tightening control device for an impact wrench that can be automatically controlled, is inexpensive, and is easy to handle.

The impact wrench tightening control device of this invention, which meets the above purpose, includes a reaction rotation amount detection mechanism that detects the reaction rotation angle amount of reaction rotation that occurs after the output shaft of an air motor is hit, and and a counter that sequentially integrates the amount of reaction rotation angle and issues a command signal when the integrated value reaches a set value, and an air supply cutoff mechanism that closes the air supply passage in response to the command signal from the counter. It is something.

Hereinafter, specific embodiments of this invention will be described in detail with reference to the drawings.

First, as shown in FIGS. 1 and 2, this impact wrench A has a grip part 1 and a main body casing 2 that is connected to the grip part 1 and extends in the front-rear direction. The main body casing 2 includes a central casing 3 integrally connected to the upper end of the grip part 1.
a front casing 4 extending further forward from the front end of the central casing 3;
It has a rear casing 5 that covers the rear part of the
An air motor 6 is housed in the central casing 3, a tightening torque generating mechanism 7 is housed in the front casing 4, and a reaction rotation amount detecting mechanism 8 is housed in the rear casing 5. Tightening torque generation mechanism 7
A cam 11 connected to the tip of the output shaft 9 of the air motor 6 by a spline, a hammer 12 rotationally driven by the cam 11, and a hammer 12 that supports the hammer 12 and rotates together with the hammer 12. The frame 13, the ampilling 14 that receives the blow from the hammer 12, and the ampilling 14 are fixed to the ampilling,
It consists of a main shaft 15 that is rotated together with the ampilling 14 by the impact of a hammer 12. (not shown) can be removably attached. The air that operates the air motor 6 passes through an air supply passage 18 in the grip part 1 from an air supply pipe connection port 17 attached to the lower end of the grip part 1, and passes through an air supply valve mechanism 19 for forward/reverse switching and flow rate adjustment. The air is supplied to the air motor 6 via the valve mechanism 21, and the exhaust gas from the air motor 6 is discharged to the outside through an appropriate route. The air supply valve mechanism 19 has an operation knob 22 protruding in front of the grip part 1 , a valve rod 23 that is directly connected to the operation knob 22 , and a valve element 24 formed at the inner tip thereof, which is fitted into the grip part 1 . The valve body 25 is a sleeve-shaped valve body with a valve seat 26 at the inner end hole edge, and by pushing in the operation knob 22, the valve element part 24 is pulled away from the valve seat 26, and the valve body 24 is formed in this part. Air can be supplied in the direction of the air motor 6 through the gap and the inside of the valve body 25, through a through hole 27 formed in the valve body 25. Also, operation knob 2
A magnet 28 is attached to the back side of the handle 2, and a reed switch 29 is attached to the front part of the grip part 1.
When the operation knob 22 is pushed in to start supplying air to the air motor 6, the reed switch 29 detects the proximity of the magnet 28 and can activate a tightening control device to be described later. Therefore, the connections 31, 31 of this reed switch 29 are led out via the connector 32. Note that 33 is a forward/reverse switching lever, and 34 is a flow rate adjustment knob.

Next, the reaction rotation amount detection mechanism 8 disposed inside the rear casing 5 will be explained. It is of a rotary encoder type and consists of a pair of photo interrupters 36 and 37 arranged with a phase difference between them. The rotary disk 35 has a large number of slits 38 bored along its circumferential direction, and a washer 41 is attached to the free end of a lead-out shaft 39 fixed to the rear end of the output shaft 9 of the air motor 6.
It is fixed by a bolt 42 via the .
Each photointerrupter 36, 37 is composed of a pair of light emitting diodes and a phototransistor that are arranged opposite to each other with a rotating disk 35 in between.
, that is, a number of signals corresponding to the rotation angles of the rotary disk 35 and the output shaft 9 are generated. Since both photo interrupters 36 and 37 are arranged with a phase shift, the signal from one photo interrupter 36 and the signal from the other photo interrupter 37 have a phase difference, so that the pulse edge of one signal has a phase difference. By determining the level of the other signal, it is possible to detect the direction of rotation of the rotary disk 35. Therefore, by using the rotary encoder described above, only the reaction rotation angle when the output shaft 9 of the air motor 6 returns in the opposite direction due to the reaction of the collision after the hammer 12 collides with the ampillar 14 can be detected. can do.

A control device that controls the tightening torque using the reaction rotation amount detection mechanism 8 will be explained based on FIG. 3. In the figure, the rotary disk 35 and the photo interrupters 36, 37 are as described above, but the photo interrupters 36, 37
The output from is first sent to Schmitt circuit 51 and waveform shaped. The count pulse output from the Schmitt circuit 51 is sent to the gate 52, and the direction pulse is sent to the gate 52 via the rotation direction switch 53. This is the part that determines which direction is the reaction rotation direction. As mentioned above, the air motor 6
The direction of rotation is determined by the forward/reverse switching valve mechanism 21 by operating the forward/reverse switching lever 33;
3, the switching lever 33 or the forward/reverse switching valve mechanism 21 may be interlocked. As a result of the above, only the count pulse in the reaction rotation direction is output from the gate 51, but this output is sent to the addition/subtraction counter 55 through the multiplier circuit 54 in order to improve the resolution. The addition/subtraction counter 55 integrates and counts these count pulses, and when this count reaches a preset count number set in the Samir switch 56, it issues a command signal to activate the relay 57, which activates the solenoid valve. The air supply cutoff mechanism 58 is operated to close the air supply passage, and the operation of the air motor 6 is stopped to complete the tightening work. Note that 59 is a digital display device, which is connected to the addition/subtraction counter 55 via a decoder 60, and can visually display the difference between the set count number of the Samir switch 56 and the detected cumulative count number. It's been like that. Also, 61 is a test switch, 6
Reference numeral 2 indicates a reset switch for testing, and reference numeral 29 indicates the above-mentioned lever interlocking switch.

In the above device, a tightening test for setting the set count number in the Samir switch 56 will be explained. First, test switch 6
1 to the test position and tighten the object in the same way as before. In this case, by switching the test switch 61 to the test position, the addition/subtraction counter 55 becomes up-counting, and performs up-counting when a count pulse is input. Therefore, when the tightening is completed, the digital display device 59
, the cumulative count of count pulses in the reaction rotation direction from the start of tightening to the end of tightening is displayed. Next, the actual tightening torque of the fastened object tightened as described above is measured, and this is done by measuring the loosening torque of the fastened object with a torque wrench or the like. This loosening torque is
Although it varies depending on the fastener, in most cases the value is about 80% of the tightening torque, so in practice it is possible to estimate the tightening torque from the measurement results of the loosening torque. If the measured torque value is appropriate, the test ends, but if the tightening torque is insufficient or excessive, operate the test reset switch 62 and perform the test again.
Repeat this test until the proper tightening torque is achieved. Then, as a result of the above test, the numerical value on the digital display device 59 when the tightening torque value is appropriate is read, and this numerical value is set in the Samir switch 56 by turning the setting dial to complete the test work and perform the test. release the switch 61.
As a result, the Samir switch 56 is set to the optimum value of the cumulative count number in the reaction rotation direction when the tightening torque reaches its optimum value. When performing tightening work using the impact wrench A as described above, first operate the operation knob 22 to activate the air motor 6 and start tightening, and at the same time the air motor 6 starts tightening based on the signal from the reed switch 29. Therefore, the control device is also activated. The reaction rotation angle of the output shaft 9 of the air motor 6 during tightening is detected as a cust pulse, and the detected count pulse is integrated in the addition/subtraction counter 55. The digital display device 59 displays the count number set in the Samir switch 56 at the start of tightening, but after the start of tightening, this display number changes according to the number of count pulses accumulated as described above. It is subtracted. When the number displayed on the digital display device 59 becomes zero, that is, when the cumulative number of count pulses reaches the set count number, a command signal is issued from the addition/subtraction counter 55 to operate the air supply cutoff mechanism 58 such as a solenoid valve. to shut off the air, stop the impact wrench, and complete the tightening work. Then, when the tightening work is completed, the trigger is returned, and at the same time, the set count number is automatically set again, and preparation for the next tightening work similar to the above is completed. In this manner, the impact wrench described above makes it possible to control the tightening torque with extremely high precision.

The main body and control device of the impact wrench A mentioned above may be installed separately and connected by an air supply hose and a lead wire running along this hose, or the control device may be built into the main body. You can also do it.

In addition to the above-mentioned hammer and unpillar type tightening torque generating mechanism 7, the tightening torque generating mechanism 7 generates an intermittent pressure increase in the fluid confinement area, and this pressure increase applies an impulsive force to the output shaft. Sometimes a form of giving is used.

The impact wrench tightening control device of the present invention is configured as described above, and therefore, according to the present invention, the tightening torque of bolts and nuts can be automatically controlled with high precision. Furthermore, it is possible to provide an impact wrench that is inexpensive and easy to handle. In other words, when adopting a configuration in which the impact wrench stops operating when the number of strikes after the object to be fastened, such as a bolt or nut, has been seated on the seat surface reaches a predetermined number of times, the The tightening torque applied to the fastened body varies depending on, for example, fluctuations in air supply pressure and variations in the rigidity of the fastened bodies, so the final tightening torque when stopped after a predetermined number of blows may vary depending on the above. The influence of the variable factors appears as is, and therefore the tightening torque cannot be managed accurately. In contrast, in the present invention, there is a high correlation between the tightening torque applied to the fastened object at the time of impact and the amount of reaction rotation angle at that time, and furthermore, by repeating the impact, The cumulative torque of the tightening torque applied to the object to be fastened,
Based on the high correlation with the integrated value of the recoil rotation angle amount for each impact, the amount of recoil rotation angle for each impact is accumulated sequentially, and when the cumulative value reaches the set value, the impact wrench is Automatically stop operation. Therefore, for example, when the air supply pressure is low and the tightening torque applied at each impact is small, the amount of each reaction rotation angle at this time is also small, and the air supply pressure will increase until the cumulative value reaches the set value. Since the pitch is low, an operation that performs an extra blow is performed. Such control reduces the influence of the above-mentioned fluctuation factors, thereby making it possible to improve tightening accuracy.

[Brief explanation of the drawing]

The figures show one embodiment of the present invention, in which Fig. 1 is a vertical front view, Fig. 2 is a cross-sectional view taken from the side of Fig. 1, and Fig. 3 is a block diagram of a control device.A...Impact wrench, 6 ... Air motor, 7 ... Tightening torque generation mechanism, 8 ... Reaction rotation amount detection mechanism, 9 ... Output shaft, 55 ... Counter,
58...Air supply cutoff mechanism.

Claims (1)

[Scope of utility model registration request] In an impact wrench that has an air motor and a tightening torque generation mechanism driven by the air motor, a reaction rotation amount detection mechanism that detects the amount of reaction rotation angle of reaction rotation that occurs after the output shaft of the air motor hits. a counter that sequentially integrates the amount of reaction rotation angle detected by the mechanism and issues a command signal when the integrated value reaches a set value; and an air supply cutoff that closes the air supply passage in response to the command signal from the counter. A tightening control device for an impact wrench, characterized by having a mechanism.