JPH11114851A - Stabilizing method for screw fastening torque to rotating speed - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep screw fastening torque of a screw fastening body constant regardless of a rotating speed by correcting an electric current according to a rotating speed of a motor. SOLUTION: When a screw is fastened by a screw fastening body 2 of a screw fastener 4, preset torque and a preset speed are read in a first step 10 and a second step 11 by an operation part 5 composed of a CPU and the like, and next, optimal correction data 21 is read in from a memory 20 according to the preset speed in a third step 12. A target electric current value is calculated by performing operation processing on (preset torque x correction data x an electric current conversion value) in a fourth step 13, and a motor 1 is rotate according to this target electric current value. In this way, since a motor driving current of the motor 1 of the screw fastener is corrected by the correction data 21, torque can be kept constant in a rotating speed of a wide range, and a speed of screw fastening work can be changed by freely changing a rotating speed at screw fastening time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for stabilizing a screw tightening torque with respect to a rotational speed, and more particularly to a novel improvement for obtaining a constant screw tightening torque regardless of a rotational speed.

[0002]

2. Description of the Related Art In a conventional screw tightening apparatus which does not use a known torque sensor, a torque is freely controlled by a current flowing through a motor, and the screw is tightened by a screw tightening torque according to a purpose of use. Had gone.

[0003]

Since the conventional screw fastening device is configured as described above, there are the following problems. In other words, since the torque is controlled by the current flowing through the motor, changing the rotation speed of the motor changes the torque even if the current is constant, changing the rotation speed depending on the screw tightening target product, and reducing the working time. Therefore, it was impossible to increase the rotation speed of the motor.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and in particular, a method of stabilizing a screw tightening torque with respect to a rotation speed so as to obtain a constant screw tightening torque regardless of the rotation speed. The purpose is to provide.

[0005]

According to the present invention, there is provided a method of stabilizing a screw tightening torque with respect to a rotation speed, in a screw tightening apparatus which rotates a screw tightener by a motor without using a torque sensor to tighten a screw. In this method, the current is corrected according to the rotation speed of the motor so that the screw tightening torque of the screw tightening body is kept constant regardless of the rotation speed.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a method for stabilizing a screw tightening torque with respect to a rotation speed according to the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart showing the operation of the method for stabilizing the screw tightening torque with respect to the rotation speed according to the present invention. A motor 1 not using a well-known torque sensor (not shown) shown in FIG. First, when the screws of the screw tightening body 2 of the screw tightening device 4 are to be tightened, the set torque is read (the first step 10) and the set speed is read (the second step 11) by the calculation unit 5 including the CPU and the like in FIG. ), Each correction data 2 previously stored in the memory 20 corresponding to the set speed.
1 is read out (third step 12), and in the fourth step 13, the target torque is calculated by calculating the aforementioned set torque × correction data (21) × current conversion value (predetermined constant). Calculate the value.

Next, a current limit for screw tightening, that is, a target current value 22 is set (sixth step 1).
4) and rotate the motor 1 (sixth step 1)
5). Accordingly, by correcting the rotation speed of the motor 1 of the screw tightening device with the correction data 21 for the motor drive current, the torque can be kept constant over a wide range of rotation speeds, and the rotation speed during screw tightening can be freely changed. Then, the speed of the screw tightening operation can be changed.

[0008]

The method for stabilizing the screw tightening torque with respect to the rotation speed according to the present invention is configured as described above, and therefore the following effects can be obtained. In other words, since the drive current is corrected according to the rotation speed, the screw tightening torque can be kept constant over a wide range of rotation speeds, and the productivity is improved by moving the speed up and down according to the screw tightening target product. can do.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a method for stabilizing a screw tightening torque with respect to a rotation speed according to the present invention.

[Explanation of symbols]

 1 motor 2 screw tightening body 3 screw

Claims (1)

[Claims] 1. A motor without using a torque sensor.
In the screw tightening device that rotates the screw tightening body (2) by (1) to tighten the screw (3), by correcting the current according to the rotation speed of the motor (1), the rotation speed is reduced. A method for stabilizing a screw tightening torque with respect to a rotation speed, characterized in that a screw tightening torque of the screw tightening body (2) is kept constant regardless of the rotation speed.