JPH07314344A - Rotary impact tool - Google Patents

Abstract

PURPOSE:To improve tightening torque control precision by controlling tightening torque considering not only impact quantity but the sort of a screw or the like and a rotation number. CONSTITUTION:A motor 1 is connected serially through a switching element 6, and the switching element 6 is connected to a control circuit 7 through a speed control circuit 60. The motor 1 is put on/off by the control circuit 7 and the speed control circuit 60. In addition, an impact quantity detection circuit 71 to detect the number of times of impact on an output shaft by a hammer, a torque setting part 75, a load setting part 76 to set the sort of a screw or the like, and a memory 8 are connected to the control circuit 7, and the motor 1 is put on/off at a tightening torque in accordance with the number of times of impact and the sort of the screw or the like. In the memory 8, relation with the diameter, rotation number, impact quantity, and tightening torque which can be set by the load setting part 76 is memorized.

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.

For this reason, as disclosed in JP-A-56-157967 and JP-A-63-74576, the number of hits of the output shaft by a hammer is mechanically counted or the hit time is set. There is provided a device that counts and stops the motor when the number of hits and the hit time reach a set value, assuming that tightening is performed with a predetermined torque.

[0004]

However, the actual tightening torque cannot be controlled only by such an impact amount. As shown in FIG. 6, the same impact amount (number of impacts)
However, if the diameters of the screws tightened by this impact rotary tool (M6, M8, and M10 in FIG. 6 are nominal diameters) are different, the actual tightening torque will be different, and the number of rotations of the motor will be different. If they are different, as shown in FIG. 5, the actual tightening torque will be different even if the diameters of the screws are the same.

As disclosed in Japanese Patent Application Laid-Open No. 62-251086, a screw type setting unit is provided, and the torque and the number of impacts are set according to the screw type set by this setting unit. Although there are those that change the correspondence, it is difficult to say that an accurate tightening torque can be obtained because the tightening torque changes when the rotational speed changes. The present invention has been made in view of such a point, and an object thereof is to provide an impact rotary tool capable of accurately controlling a tightening torque.

[0006]

SUMMARY OF THE INVENTION The present invention, therefore, applies a rotational force to the output shaft by striking the output shaft with a hammer that is rotationally driven by a motor, and detects the amount of impact of the output shaft with the hammer. In an impact rotary tool equipped with a control means for controlling the torque when tightening and tightening the screws based on the hitting amount and the rotational speed, a speed control circuit for controlling the rotational speed of the motor and a torque for setting the torque A setting unit and a load setting unit that sets the type of screws are provided, and the control means sets the rotation speed and the impact amount of the motor according to the torque and the type of screws set by these setting units. It is characterized by being controlled.

[0007]

According to the present invention, in controlling the tightening torque,
Since not only the amount of impact but also the type of screw and the number of rotations are taken into consideration, there is no uncertain factor that causes the tightening torque to be different from the set value.

[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.

As shown in FIG. 1, the motor 1 is connected to a switching element 6 in series, and the switching element 6 is connected via a speed control circuit 60 to a control circuit 7 composed of a microcomputer. The control circuit 7 and the speed control circuit 60 control not only the on / off state of the motor 1 but also the rotation speed of the motor 1. A striking amount detection circuit 71 for detecting the number of striking of the output shaft 4 by the hammer 2 is connected to the control circuit 7, a torque setting section 75 for setting a tightening torque, and a type of screw type. The memory 8 is connected to the load setting unit 76 for setting the. Memory 8
Indicates the relationship among the diameters of screws, the number of revolutions, the amount of impact, and the tightening torque, which can be set by the load setting unit 76.

The hitting amount detecting circuit 71 is a device for mechanically detecting the hitting frequency, a device for optically detecting the hitting frequency,
It may be any one that is electrically detected from the motor current or the like, and may be one that detects not the number of hits but the time of hitting (hit time). Furthermore,
As the torque setting unit 75 and the load setting unit 76, as shown in FIG. 3, the volume setting switch and the changeover switch installed on the rear end surface of the housing are shown. It is not limited.

In this impact rotary tool, however, when the screws are tightened, the diameter of the screws to be tightened is set by the load setting section 76 and the tightening torque is set by the torque setting section 75. As shown in FIG. 4, the control circuit 7 obtains the number of revolutions Np and the amount of impact (the number of impacts) Kp when the two conditions are met from the information stored in the memory 8, and determines the rotation of the motor 1 based on this information. When the impact amount detected by the impact amount detection circuit 71 reaches the impact amount Kp, the motor 1 is stopped.

There may be a plurality of combinations of the number of rotations and the amount of impact when tightening screws of a certain diameter with a certain tightening torque, but the combination that minimizes the time required for tightening (usually the maximum number of rotations is set. It is a good idea to choose a combination of time). Further, if a feedback control circuit for controlling the constant speed of the rotation speed of the motor 1 is provided, a more accurate tightening torque can be obtained. Further, if the speed control circuit 70 is used to change the motor rotation speed in accordance with the pull-in amount of the trigger switch SW1, the operability at the time of rotation without hitting in the initial tightening work is improved, In this case, when it is detected that the impact has started, the trigger switch SW1
The rotation speed Np is set for the tightening torque control regardless of the pull-in amount.

In the present invention, the circuit components for counting the number of hits and controlling the motor 1 are housed in the rear end 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. In the examples, the number of hits is taken as the hit amount, but the hit time may be used.

[0015]

As described above, in the present invention, the speed control circuit for controlling the rotation speed of the motor, the torque setting section for setting the torque, and the load setting section for setting the type of screws are provided. In order for the control means to control the rotation speed and the impact amount of the motor according to the torque and the type of screw set in these setting units, that is, in controlling the tightening torque, not only the impact amount, Since the type of screw and the number of rotations are also taken into consideration, there are no uncertainties that cause the tightening torque to differ from the set one, and the tightening work can be performed with an accurate tightening torque.

[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 a front view of a setting unit of the above.

FIG. 4 is a flowchart showing the same operation.

FIG. 5 is an explanatory diagram of the correlation between the rotation speed, the number of hits, and the torque.

FIG. 6 is an explanatory diagram of a correlation among types of screws, the number of impacts, and torque.

[Explanation of symbols]

 1 Motor 2 Hammer 4 Output Shaft 7 Control Circuit 60 Speed Control Circuit 71 Impact Rate Detection Circuit 75 Torque Setting Section 76 Load Setting Section

Claims (1)

[Claims] 1. A hammer is driven by a motor to apply a rotational force to the output shaft by striking the output shaft, and based on the detected striking amount and rotation speed of the output shaft by the hammer. In an impact rotary tool equipped with a control means for controlling torque when tightening screws, a speed control circuit for controlling the rotation speed of a motor, a torque setting unit for setting torque, and a type of screws are set. And a load setting unit for controlling the number of revolutions of the motor and the impact amount according to the torque and the type of screws set by these setting units. Impact rotary tool.