JP2000334625A - Screw head damage preventing type power screwdriver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent damage of a screw head by rotation of a screwdriver by providing a stopping device for automatically stopping a motor when a state that pushing pressure on the screw head of the screwdriver can not be secured for a preliminarily fixed stipulated value or more according to the size of driving torque of the motor is made. SOLUTION: A control part 1 has a speed deciding part for calculating rotational speed of an electric motor 3 from a detected value of a Hall element 8, a torque deciding part for estimating driving torque of the electric motor 3 from a detected value of a Hall element 7, a deciding part for deciding whether a stipulated value or more of pushing pressure on a screw of a present screwdriver is applied to driving torque of the screwdriver or not and a motor control part for stopping rotation of the screwdriver. A feedback control rotating the electric motor 3 at designated rotational speed of a trigger 5 as much as possible is performed through a drive circuit 4. As a result, damage of a screw head can be reduced by rotation of the screwdriver.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electric screwdriver,
The present invention relates to an electric tool such as an electric drill.

[0002]

2. Description of the Related Art Conventionally, electric screwdrivers have been widely used for screw tightening work because of their high efficiency.
In addition, some electric drivers are built into an automatic robot at a factory or the like, and others are portable for human manual work. In particular, regarding the former, there is a technique disclosed in Japanese Patent Application Laid-Open No. H6-170663 as a technique which focuses on the relationship between the pressing pressure for joining the screwdriver and the screw and the driving torque of the motor.

Here, FIG. 3 shows a schematic diagram thereof. The purpose of this is to provide a screw tightening method capable of always performing appropriate screw tightening even if the shape and dimensions of the screw and the hardness of the screw tightening work material vary. A driver bit 1a for screwing a screw into the work, moving / pressing means 4-10 for moving the driver bit 1a toward / back to the work and applying a pressing force for screwing the screw into the driver bit 1a; In a screw tightening device having a control means 11 for controlling the pressure means 4 to 10, the control means 11 stores an appropriate pressing force corresponding to each tightening torque of various screws, from the start of screwing of the screw to the end of screwing. The tightening torque of the driver bit 1a is measured, and the appropriate pressing force corresponding to the measured tightening torque is determined by the driver. In addition to bit 1a.

[0004]

However, in the screw tightening method having the above-described structure, when the screw is screwed in, if the driver does not press the screw sufficiently, the load torque may increase. In addition, a problem arises in that the screwdriver is lifted up from the screw hole and the screw hole is damaged by the rotation of the screwdriver. In addition, when the screw is screwed in at a high speed, if the screw head is further damaged, the screwdriver may not be able to pull out or screw in, which may significantly deteriorate the work efficiency.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an electric screwdriver with an excellent screw head damage prevention method for preventing screw head damage due to rotation of the screwdriver.

[0006]

According to the first aspect of the present invention, in an electric screwdriver which tightens a screw with a driving torque of a motor, the screwdriver is disengaged from the screw during rotation of the screwdriver, and the screwdriver is rotated. In order to prevent the screw head from being damaged due to rotation, if the pressing pressure on the screw head of the driver cannot be maintained at a value higher than a predetermined value according to the magnitude of the driving torque of the motor, A stop device for automatically stopping the motor is provided.

According to the second aspect of the present invention, when the pressing pressure on the screw head of the driver approaches a predetermined value corresponding to the magnitude of the driving torque of the motor by a certain value or more, the driver is pressed more strongly. In this way, the apparatus is provided with an alarm generating device that alerts the worker.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing an electric screwdriver according to an embodiment of the present invention.
This will be described in detail with reference to FIGS. FIG. 1 is a system diagram of a drill driver according to the present invention, and FIG.
FIG. 4 is a flowchart of a motor control algorithm according to the present invention.

In this embodiment, an electric motor 3, a tightening torque generating mechanism 2 driven by the electric motor 3,
A Hall element 8 for detecting a current flowing through the electric motor 3, a Hall element 7 for detecting a change in the magnetic field of the electric motor 3, a piezoelectric element 9 for measuring a pressing pressure of a driver against a screw, A drive circuit 4 for starting the motor 3 and controlling the rotation of the electric motor 3 by specifying the rotation speed, a trigger 5 for specifying the rotation speed, a control unit (microcomputer) 1, and an alarm for urging the operator to press harder. And a buzzer section 6 that emits light.

A control unit (microcomputer) 1 estimates a rotation speed of the electric motor 3 from a detected value of the Hall element 8 and a drive torque of the electric motor 3 from a detected value of the Hall element 7. A torque determination unit for determining, and a determination unit that determines whether the current pressing pressure on the screw of the driver is greater than a specified value with respect to the driving torque of the driver,
A motor control unit for stopping the rotation of the driver; and performing feedback control such that the electric motor 3 is rotated at the designated rotation speed of the trigger 5 as much as possible through the drive circuit 4.

A 12 V power supply (rechargeable battery) 10 for supplying power to the electric motor 3 and the drive circuit 4 and a 5 V power supply (not shown) for driving the hall elements 7 and 8 and the control unit (microcomputer) 1 are provided. I have.

Next, the operation will be described with reference to FIG. In the steady processing, first, when the worker pulls the trigger from the stop state in step 300, the amount of pull-in is transmitted to the motor control unit (control unit 1), and the motor control unit (control unit 1) executes step 500. The motor is rotated at a specified speed according to the amount of pull-in. Next, when the electric motor 3 rotates, a driving torque is generated in the electric motor 3 and step 60 is performed.
At 0, the torque determining unit (control unit 1) calculates the driving torque from the detected value of the current detecting Hall element 8, and the speed determining unit (control unit 1) calculates the driving torque from the detected value of the magnetic field detecting Hall element 7. Calculate the rotation speed.

Further, at step 600, the pressure applied to the driver by the piezoelectric element 9 is detected and transmitted to the motor control unit (control unit 1). When this pressure approaches a specified value corresponding to the driving torque by a certain amount or more in step 1000, the motor control unit (control unit 1)
Instructs the alarm unit to give an alarm at, and if the value falls below a specified value according to the driving torque at step 800,
In step 900, the motor is stopped.

In the interrupt processing, first, at step 90
At 0, the magnetic field change reading speed is determined, the trigger input is read at step 900, the feedback calculation is performed at step 900, and the motor rotation speed is instructed at step 900. In this way, as described above, feedback control is performed through the drive circuit 4 so that the electric motor 3 rotates at the designated rotational speed of the trigger 5 as much as possible.

Although the present embodiment has been described on the assumption that the present invention is used for an electric driver or an electric drill, an example in which a bit of a driver or a drill is rotated by a DC motor, the technical idea of the present invention is to use a DC motor. It is applicable to other devices used.

[0016]

According to the first aspect of the present invention, it is possible to reduce the possibility that the screw between the driver and the screw is disconnected during the rotation of the driver and the screw head is damaged by the rotation of the driver.

According to the second aspect of the present invention, in addition to the effect of the first aspect of the present invention, when the driver's pressing pressure changes while the driver is rotating, an alarm prompting the operator to press harder. Therefore, the motor can be prevented from frequently stopping.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of a screw head damage prevention type electric screwdriver according to the present invention.

FIG. 2 is a flowchart of a motor control algorithm of the electric screwdriver for preventing screw head damage.

FIG. 3 is a configuration diagram of an embodiment of a conventional electric screwdriver.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Control part (microcomputer) 2 Tightening torque generation mechanism 3 Electric motor 4 Drive circuit 5 Trigger 6 Buzzer part 7 Hall element 8 Hall element 9 Piezoelectric element

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] October 28, 1999 (1999.10.
28)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006]

Means for Solving the Problems] According to a first aspect of the invention, the electric screwdriver to perform screw tightening by the drive torque of the motor, the driver out bonding between the driver and screw during the rotation, the rotation of the driver In order to prevent the screw head from being damaged by the motor, if the driver's pressing pressure on the screw head cannot be maintained at a value higher than the predetermined value determined in advance according to the magnitude of the driving torque of the motor, Is provided with a stopping device for stopping automatically.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

Although the present embodiment has been described on the assumption that the present invention is used for an electric driver or an electric drill, an example in which a bit of a driver or a drill is rotated by a DC motor, the technical idea of the present invention is to use a DC motor. Jigsaw used
And so on.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Minoru Yoshida 1048 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Co., Ltd. F-term (reference) 3C038 AA02 BC04 CA01 CB02 EA03

Claims (2)

[Claims] 1. An electric screwdriver for tightening a screw by a driving torque of a motor, wherein the screw between the screwdriver and the screwdriver is screwed to prevent the screwdriver from being disengaged from the screw while the driver is rotating and the screwhead being damaged by the rotation of the driver. A stop device is provided for automatically stopping the motor when the pressure applied to the head cannot be maintained at a value exceeding a predetermined value according to the magnitude of the driving torque of the motor. Screw head damage prevention type electric screwdriver. 2. When the pressing pressure of the screwdriver on the screw head approaches a predetermined value or more that is predetermined according to the magnitude of the driving torque of the motor, the operator is warned to press harder. 2. An electric screwdriver according to claim 1, further comprising an alarm generating device for prompting the driver.