POWER TOOL

• US 20120234573A1
• Filed: 10/29/2010
• Published: 09/20/2012
• Est. Priority Date: 11/11/2009
• Status: Active Grant

• Current Assignee: Makita Corporation
• Original Assignee: Makita Corporation
• Inventors: Suda, Hidekazu, Kusakawa, Takuya
• Granted Patent: US 9,314,914 B2
• Time in Patent Office: Days
• US Class Current: 173/217
• CPC Class Codes: B25F 5/00 Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for
• CPC Class Codes: B25F 5/026 in the form of an auxiliary handle B25F5/024 takes precedence

Abstract

A power tool includes a motor, a rotating speed adjusting switch, a regulating member, and a control unit. The regulating member regulates an upper limit position when the switch is displaced by manipulation by a user into an upper limit of any one of stages by the manipulation by the user. The control unit controls an amount of a current flowing to the motor by a duty ratio based on a manipulation amount of the switch, thereby increasing the rotating speed of the motor in accordance with an increase of the manipulation amount. A predetermined set number of duty ratios are set for each of the stages. A proportion of the predetermined set number of duty ratios to a manipulable amount of the switch is higher in a first stage having the lowest upper limit position than in the stages other than the first stage.

Claims

1. A power tool comprising:

a motor which drives a tool;

a rotating speed adjusting switch which is displaced by manipulation by a user;

a regulating member which regulates an upper limit position when the rotating speed adjusting switch is displaced to an upper limit position of any one of a plurality of stages by the manipulation by the user; and

a control unit which controls an amount of a current flowing to the motor by a duty ratio based on a manipulation amount of the rotating speed adjusting switch, the control unit increasing the rotating speed of the motor in accordance with an increase in the manipulation amount, a predetermined set number of duty ratios being set for each of the plurality of stages, and a proportion of the set number of duty ratios to a manipulable amount of the rotating speed adjusting switch being higher in a first stage, where the upper limit position is the smallest, than in stages other than the first stage.

2. The power tool according to claim 1, wherein the regulating member regulates the upper limit position so that the manipulable amount in the first stage is larger than the manipulable amount in the stages other than the first stage.

3. The power tool according to claim 1, wherein

at least in the first stage of the plurality of stages, the control unit controls the duty ratio so that the rotating speed increases when the manipulation amount of the rotating speed adjusting switch increases to the upper limit position, and controls the duty ratio, when the manipulation amount is reduced from the upper limit position to a predetermined position, by a Hysteresis characteristic in which the rotating speed remains constant until the manipulation amount reaches the predetermined position.

4. The power tool according to claim 1, comprising a rotation direction changing switch which changes rotation of the motor to one of a positive rotation and a reverse rotation by manipulation by the user, wherein

when the reverse rotation of the motor is selected by the rotation direction changing switch, the control unit increases the rotating speed as the manipulation amount increases at least in the first stage, and holds the rotating speed constant regardless of the manipulation amount in the stages other than the first stage.

5. The power tool according to claim 2, wherein at least in the first stage of the plurality of stages, the control unit controls the duty ratio so that the rotating speed increases when the manipulation amount of the rotating speed adjusting switch increases to the upper limit position, and controls the duty ratio, when the manipulation amount is reduced from the upper limit position to a predetermined position, by a Hysteresis characteristic in which the rotating speed remains constant until the manipulation amount reaches the predetermined position.

6. The power tool according to claim 2 comprising a rotation direction changing switch which changes rotation of the motor to one of a positive rotation and a reverse rotation by manipulation by the user, wherein

when the reverse rotation of the motor is selected by the rotation direction changing switch, the control unit increases the rotating speed as the manipulation amount increases at least in the first stage, and holds the rotating speed constant regardless of the manipulation amount in the stages other than the first stage.

7. The power tool according to claim 3, comprising a rotation direction changing switch which changes rotation of the motor to one of a positive rotation and a reverse rotation by manipulation by the user, wherein

when the reverse rotation of the motor is selected by the rotation direction changing switch, the control unit increases the rotating speed as the manipulation amount increases at least in the first stage, and holds the rotating speed constant regardless of the manipulation amount in the stages other than the first stage.

8. The power tool according to claim 5 comprising a rotation direction changing switch which changes rotation of the motor to one of a positive rotation and a reverse rotation by manipulation by the user, wherein

when the reverse rotation of the motor is selected by the rotation direction changing switch, the control unit increases the rotating speed as the manipulation amount increases at least in the first stage, and holds the rotating speed constant regardless of the manipulation amount in the stages other than the first stage.