CROSS REFERENCE TO THE RELATED APPLICATIONS

This application is based upon and claims priority to Chinese Patent Application No. 202010786408.1, filed on Aug. 7, 2020, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to the technical field of electric tool switches, and in particular to a rotation speed regulation system for an electric tool switch.

BACKGROUND

A rotation speed regulating mechanism is typically arranged in an electric tool switch to control the speed of the motor. The rotation speed regulating mechanism is controlled by a speed regulating switch to control a speed regulating reed to slide on the speed regulating copper foil, thereby changing a speed regulating signal received by an electric tool controller. According to the speed regulating signal, the controller changes the duty cycle of the output pulse signal to adjust the motor speed of the electric tool.

Commonly used speed regulating mechanisms, however, have an unreasonable design. In the whole speed regulating stroke of the speed regulating switch, the speed regulating signal curve received by the controller is not uniform, which leads to non-uniform speed output of the whole machine. As shown inFIG. 1, the non-uniform speed regulating signal curve causes the controller to output a non-uniform duty cycle curve, resulting in obvious fluctuations when the motor speed changes.

SUMMARY

The technical problem to be solved by the present invention is to provide a rotation speed regulation system for an electric tool switch, whereby fluctuations caused by a change in the motor speed can be reduced or even eliminated.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical solution. A rotation speed regulation system for an electric tool switch includes a controller, a resistance regulating copper foil which is electrically connected to the controller, and a resistance regulating reed matched with the resistance regulating copper foil. The resistance regulating copper foil includes a first foil and a second foil separated from each other. The first foil is an intact long strip foil. The second foil includes a plurality of short-circuit gold fingers arranged at equal intervals in the middle part of the second foil and a full-resistance foil and a zero-resistance foil at both ends of the second foil. The short-circuit gold fingers in the middle part are arranged in sequence from one end of the full-resistance foil to one end of the zero-resistance foil. The short-circuit gold fingers, the zero-resistance foil and the full-resistance foil are sequentially connected in series through a resistor. The zero-resistance foil is electrically connected to the controller. The resistance regulating reed is bridged between the first foil and the second foil. One end of the resistance regulating reed contacting the first foil is a constant contact end, and the other end of the resistance regulating reed contacting the second foil is a resistance regulating contact end. A straight contact strip is formed between the resistance regulating contact end and the second foil. The contact strip is perpendicular to a sliding direction of the resistance regulating contact end on the second foil. The width of the short-circuit gold finger is 0.27 mm, and the distance between two adjacent short-circuit gold fingers is 0.2 mm. An inclination angle α is formed between the short-circuit gold finger and the sliding direction of the resistance regulating contact end. α is 107°-110° and the length L of the contact strip is 2.3-2.9 mm.

Preferably, the zero-resistance foil, the short-circuit gold fingers and the full-resistance foil are equidistantly spaced.

Preferably, the length direction of the first foil coincides with the length direction of the second foil.

Preferably, the inclination angle α is 108.5° and the length of the contact strip is 2.6 mm.

The advantages of the present invention are as follows. By optimizing the inclination angle of the short-circuit gold fingers relative to the sliding direction of the resistance regulating contact end and the length of the contact strip formed by the resistance regulating contact end on the second foil, the speed regulating signal received by the controller changes uniformly when the resistance regulating reed moves in the resistance regulating stroke, so as to obtain uniform speed output of the whole machine. In this way, fluctuations caused by a change in the motor speed are reduced or even eliminated.

