JPH07314342A - Rotary impact tool - Google Patents

Abstract

PURPOSE:To perform torque control based on the number of times of impact, and aim at small size and light weight. CONSTITUTION:Torque is applied onto an output shaft 4 by impact on the output shaft 4 by a hammer 2 driven to rotate by a motor 1, and a control means is provided to control the torque based on the number of times of impact. As a detection means for the number of times of impact, that counting change of a current value through the motor 1, or that counting output change of a frequency generator provided on the motor 1 is used. By adding an electric circuit only, the number of times of impact can be counted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impact rotary tool such as an impact wrench or an impact driver used for tightening and loosening screws such as bolts and nuts.

[0002]

2. Description of the Related Art In an impact rotary tool, an impact shock from a rotary driven hammer is applied to the output shaft to rotate the output shaft for tightening and loosening work. The output shaft is directly rotated by the deceleration output of the motor. Although it is possible to obtain a higher tightening force than what can be done, on the other hand, when tightening small diameter bolts and nuts, they are often overtightened and damaged.If you fear this, insufficient tightening may occur. Will occur.

Therefore, as disclosed in Japanese Patent Publication No. 3-25304 and Japanese Patent Application Laid-Open No. 56-157967, the number of times the hammer hits the output shaft is mechanically counted, and this number of hits is calculated. When the set value is reached, it is provided that the motor is stopped as if the tightening with a predetermined torque is performed.

[0004]

However, in the former, since the number of hits is mechanically counted by utilizing the reversing operation of the hammer when the output shaft is hit, many parts are used as means for detecting the number of hits. In addition to the above, the size of the main body is inevitably increased and the structure becomes complicated and heavy in order to secure the space for storing them.
In the latter, the backward movement of the hammer at the time of hitting is detected using a photo interrupter to count the number of hits, but in this thing, because the placement position of the photo interrupter is restricted, its placement is restricted. In addition to the difficulty, the size of the photointerrupter is increased due to the placement of the photointerrupter, and the photointerrupter, the counter, and the control means having different placement positions must be electrically interconnected. Becomes complicated.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an impact rotary tool capable of controlling torque based on the number of times of impact and being small and lightweight. There is.

[0006]

SUMMARY OF THE INVENTION The present invention, however, is a means for detecting the number of impacts of an output shaft by a hammer in an impact rotary tool which applies a rotational force to the output shaft by the impact of the output shaft by a hammer rotationally driven by a motor. And a control means for controlling the torque when tightening the screws on the basis of the detected number of hits, and the detection means counts the change in the current value flowing through the motor, or It is characterized in that it counts changes in the output of the frequency generator provided in.

[0007]

According to the present invention, since the number of hits is counted only by adding an electric circuit, the hit count detection means does not increase the size and weight of the main body.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the illustrated embodiments. Here, as the striking structure of the output shaft 4 by the hammer 2, the following is used. That is, as shown in FIG. 2, the rotation of the motor 1 is performed by the speed reduction unit 1 including a planetary speed reduction mechanism.
A cylindrical hammer 2 is rotatably arranged on the outer periphery of the drive shaft 11 which is decelerated by 0 and transmitted, and a V-shaped cam groove 31 formed on the outer periphery of the drive shaft 11 and the hammer 2 are formed. Cam groove 32 formed on the inner peripheral surface of the
The cam 3 including the ball 33 that engages with each other restricts the movement of the drive shaft 11 and the hammer 2 in the axial direction and the movement around the axis. The hammer 2 is urged toward the output shaft 4 by the spring 5, and the tip end surface of the hammer 2 is engaged with an anvil portion 40 projecting laterally from the rear end of the output shaft 4. A section 24 is provided.

When the load is hardly applied to the output shaft 4 to which the driver bit or socket is attached at the tip,
The rotation of the drive shaft 11 is transmitted to the hammer 2 via the cam 3, and the striking portion 24 and the anvil portion 4 of the hammer 2 are also transmitted.
It is transmitted to the output shaft 4 by engaging with 0. When the load applied to the output shaft 4 increases, relative rotation occurs between the hammer 2 and the drive shaft 11 within the range permitted by the cam 3, and at this time, the hammer 2 is guided by the cam 3 and the hammer 2 moves. When the striking portion 24 and the anvil portion 40 are disengaged from each other and the striking portion 24 gets over the anvil portion 40, the hammer 2 is guided by the cam 3 by the restoring force of the spring 5 and moves forward. Then, the striking portion 24 is shock-engaged with the anvil portion 40, and a rotational force is applied to the output shaft 4 by striking impact.

The motor 1 is, as shown in FIG.
It is connected in series to a switching element 6 made of T, and is rotated by turning on the switching element 6 by a control circuit 7 made of a microcomputer. A current detecting resistor R is connected to the motor 1. The current value detected here is amplified by the amplifier 70 and then compared with the reference voltage by the comparator 71. Then, the output pulse of the comparator 71 is counted in the control circuit 7, and as shown in FIG.
When the number N of pulses reaches a predetermined number No, the switching element 6 is turned off to stop the motor 1. The switch SW2 is for turning on and off the tightening torque control based on the number of hits.

That is, when the hammer 2 strikes the output shaft 4, the load on the motor 1 increases,
Since the current value increases as shown in FIG. 3 (a), if the change in the current value is pulsed in the comparator 71 as shown in FIG. Can be detected. The motor 1
Although a large current flows at the time of starting, the influence of this starting current can be eliminated by canceling the pulse for the time set in the timer provided in the control circuit 7.

5 and 6 show another embodiment. Here, the frequency generator (FG) 8 provided in the motor 1 is connected to the control circuit 7 via an amplifier 81, a sample hold (S / H) circuit 82, and a comparator 83.
The output signal of the frequency generator 8 is as shown in FIG. 6 because the rotation speed of the motor 1 decreases at the moment when the hammer 2 hits the output shaft 4, and this is converted into a voltage change in the sample hold circuit 82. Then, a pulse signal is obtained by comparing with the reference voltage in the comparator 83. The number of hits can be detected by counting the number of pulses with the control circuit 7.

In the present invention, the circuit components for counting the number of hits and controlling the motor 1 are housed in the rear end portion of the housing located behind the motor 1. There are various striking structures of the output shaft 4 by the hammer 2,
Of course, any of these may be used.

[0014]

As described above, in the present invention, in controlling the torque when tightening the screws on the basis of the number of times the hammer hits the output shaft, the detecting means is
Since the one that counts the change in the current value flowing in the motor or the one that counts the change in the output of the frequency generator installed in the motor is used, that is, the number of hits can be counted only by adding an electric circuit. Since it is possible to secure the installation space, it is not difficult to secure the arrangement space, and the means for detecting the number of hits does not increase the size or weight of the main body, and tightening torque Although it can be controlled, it can be made small and lightweight.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment.

FIG. 2 is a cutaway side view of the above.

FIG. 3 is an operation explanatory diagram of the above.

FIG. 4 is a flowchart showing the same operation.

FIG. 5 is a circuit diagram of another embodiment.

FIG. 6 is an operation explanatory diagram of the above.

[Explanation of symbols]

 1 Motor 2 Hammer 4 Output shaft R Current detection resistor

Claims (2)

[Claims] 1. An impact rotary tool that applies a rotational force to an output shaft by striking the output shaft with a hammer that is rotationally driven by a motor, and means for detecting the number of times the hammer strikes the output shaft, and a screw based on the detected number of hits. An impact rotary tool, comprising: a control unit that controls a torque when tightening the class, and the detection unit counts a change in a current value flowing through the motor. 2. An impact rotary tool that applies a rotational force to an output shaft by striking the output shaft with a hammer that is rotationally driven by a motor, and means for detecting the number of times the hammer strikes the output shaft, and a screw based on the detected number of hits. An impact rotary tool, comprising: a control unit for controlling a torque when tightening and tightening the components, and the detection unit counts an output change of a frequency generator provided in the motor.