Speed control for power tools
First Claim
1. A power tool, comprising:
- a driven element,an electric motor coupled to the driven element so as to drive the driven element,an electric power source electrically coupled to the motor so as to supply electric current to the motor and a control circuit arranged to control the supply of electric current to the motor from the power source, anda current sensor operable to output a current signal indicative of the current flowing through the motor;
in which the control circuit has a high speed mode and a low speed mode, the control circuit being arranged so that;
when it is in the high speed mode, the control circuit supplies electric current to the motor so as to attempt to drive the driven element at a first desired speed;
when it is in the low speed mode, the control circuit supplies electric current to the motor so as to attempt to drive the driven element at a second desired speed which is lower than the first desired speed; and
the control circuit switches between the high speed mode and the low speed mode dependent on the current signal, wherein the control circuit is configured to switch to the high speed mode when the current signal indicates increasing current and to switch to the low speed mode when the current signal indicates lessening current.
2 Assignments
0 Petitions
Accused Products
Abstract
A power tool, typically battery-operated, such as a lawnmower, comprising: a driven element (9), an electric motor (7) coupled to the driven element so as to drive the driven element, an electric power source (2) electrically coupled to the motor (7) so as to supply electric current to the motor (7) and a control circuit (3) arranged to control the supply of electric current to the motor (7) from the power source (2), and a current sensor (6) operable to output a current signal indicative of the current flowing through the motor (7); in which the control circuit (3) has a high speed mode (40) and a low speed mode (32), the control circuit (3) being arranged so that: when it is in the high speed mode (40), the control circuit supplies electric current to the motor (7) so as to attempt to drive the driven element (9) at a first desired speed (54); when it is in the low speed mode (32), the control circuit supplies electric current to the motor (7) so as to attempt to drive the driven element (9) at a second desired speed (52) which is lower than the first desired speed (54); and the control circuit (3) switches between the high speed mode (40) and the low speed mode (32) dependent on the current signal. As such, energy can be saved by efficient use of electrical power, by increasing the speed of the driven element when the load increases.
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Citations
13 Claims
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1. A power tool, comprising:
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a driven element, an electric motor coupled to the driven element so as to drive the driven element, an electric power source electrically coupled to the motor so as to supply electric current to the motor and a control circuit arranged to control the supply of electric current to the motor from the power source, and a current sensor operable to output a current signal indicative of the current flowing through the motor; in which the control circuit has a high speed mode and a low speed mode, the control circuit being arranged so that; when it is in the high speed mode, the control circuit supplies electric current to the motor so as to attempt to drive the driven element at a first desired speed; when it is in the low speed mode, the control circuit supplies electric current to the motor so as to attempt to drive the driven element at a second desired speed which is lower than the first desired speed; and the control circuit switches between the high speed mode and the low speed mode dependent on the current signal, wherein the control circuit is configured to switch to the high speed mode when the current signal indicates increasing current and to switch to the low speed mode when the current signal indicates lessening current. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of controlling a power tool, the power tool comprising a driven element, an electric motor coupled to the driven element so as to drive the driven element and a control circuit arranged to control the supply of electric current to the motor from the power source;
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the method comprising the control circuit driving the electric motor in a high speed mode so as to attempt to drive the driven element at a first desired speed; and
in the low speed mode so as to attempt to drive the driven element at a second desired speed which is lower than the first desired speed;in which the method comprises the control circuit switching between the high speed mode and the low speed mode dependent on the current flowing through the motor, wherein the control circuit switches to the high speed mode when the current increases and switches to the low speed mode when the current lessens. - View Dependent Claims (9, 10, 11, 12, 13)
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Specification