MOTOR-DRIVEN APPLIANCE AND BATTERY PACK

• US 20140217934A1
• Filed: 01/30/2014
• Published: 08/07/2014
• Est. Priority Date: 02/07/2013
• Status: Active Grant

• Current Assignee: Makita Corporation
• Original Assignee: Makita Corporation
• Inventors: SUZUKI, Hitoshi
• Granted Patent: US 9,325,265 B2
• Time in Patent Office: Days
• US Class Current: 318/139
• 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: H02P 7/285 controlling armature supply only

Abstract

A motor-driven appliance includes a battery; a motor including permanent magnets as field magnets; a momentary maximum current upper limit storage unit in which a predetermined momentary maximum current upper limit is stored; a current detection unit that detects a current flowing in the motor; a current threshold setting unit that generates a current threshold based on the momentary maximum current upper limit, and outputs the generated current threshold; a current exceedance determination unit that determines whether the current detected by the current detection unit has become equal to or greater than the current threshold, and outputs an interruption signal used to interrupt a current path from the battery to the motor when the detected current has become equal to or greater than the current threshold; and a current flow interruption unit that interrupts the current path when the interruption signal is outputted from the current exceedance determination unit.

Claims

1. A motor-driven appliance comprising:

a battery;

a motor that includes permanent magnets as field magnets and is operated by electric power from the battery;

a momentary maximum current upper limit storage unit in which a predetermined momentary maximum current upper limit is stored;

a current detection unit that detects a current flowing in the motor;

a current threshold setting unit that generates a current threshold based on the momentary maximum current upper limit stored in the momentary maximum current upper limit storage unit, and outputs the generated current threshold;

a current exceedance determination unit that determines whether the current detected by the current detection unit has become equal to or greater than the current threshold, and outputs an interruption signal used to interrupt a current path from the battery to the motor when the detected current has become equal to or greater than the current threshold; and

a current flow interruption unit that interrupts the current path when the interruption signal is outputted from the current exceedance determination unit.

2. The motor-driven appliance according to claim 1,

wherein the momentary maximum current upper limit is a value set in advance based on a current value that causes demagnetization of the permanent magnets when such a current is caused to flow to the motor.

3. The motor-driven appliance according to claim 2,

wherein the momentary maximum current upper limit is a maximum value of a current that has no risk of causing demagnetization of the permanent magnets when such a current is caused to flow to the motor, or a predetermined value less than the maximum value.

4. The motor-driven appliance according to claim 1,

wherein the current threshold setting unit is configured to generate, as the current threshold, a value lower than the momentary maximum current upper limit by a predetermined amount, the value being decided so that the current path is interrupted by the current flow interruption unit before the current flowing in the motor exceeds the momentary maximum current upper limit when the current exceedance determination unit determines that the detected current is equal to or greater than the current threshold based on the momentary maximum current upper limit stored in the momentary maximum current upper limit storage unit.

5. The motor-driven appliance according to claim 1,

wherein the current exceedance determination unit is configured to perform determination of whether the current detected by the current detection unit has become equal to or greater than the current threshold and output of the interruption signal, by a hardware circuit without going through a software process by a computer.

6. The motor-driven appliance according to claim 1, including:

a battery pack having at least the battery housed therein; and

a main body to which the battery pack is detachably attached and which has at least the motor and the momentary maximum current upper limit storage unit mounted therein.

7. The motor-driven appliance according to claim 6,

wherein the main body includes a first control unit that controls the motor;

wherein the first control unit is configured to accomplish, from among functions of the current threshold setting unit, at least an acquisition function for acquiring the momentary maximum current upper limit stored in the momentary maximum current upper limit storage unit; and

wherein the current threshold setting unit is configured to generate the current threshold based on the momentary maximum current upper limit acquired by the acquisition function.

8. The motor-driven appliance according to claim 7,

wherein the battery pack includes a second control unit that monitors a state of the battery,

wherein the first control unit is designed to accomplish the acquisition function from among the functions of the current threshold setting unit, and includes an upper limit information output unit that acquires the momentary maximum current upper limit stored in the momentary maximum current upper limit storage unit and outputs upper limit information indicating the momentary maximum current upper limit to the second control unit,

wherein the second control unit is configured to accomplish, from among the functions of the current threshold setting unit, at least a current threshold setting information generation function that acquires the upper limit information outputted from the upper limit information output unit in the main body and generates current threshold setting information indicating the current threshold based on the upper limit information, and

wherein the current threshold setting unit includes a threshold generation unit that is provided in the battery pack and generates the current threshold based on the current threshold setting information generated by the current threshold setting information generation function in the second control unit.

9. The motor-driven appliance according to claim 6,

wherein the battery pack includes:

the current exceedance determination unit; and

an interruption signal output unit that outputs the interruption signal to the main body when the current exceedance determination unit determines that the detected current has become equal to or greater than the current threshold, and

wherein the current flow interruption unit is mounted in the main body, and is configured to interrupt the current path when the interruption signal is inputted from the battery pack.

10. The motor-driven appliance according to claim 6,

wherein the current exceedance determination unit and the current flow interruption unit are mounted in the battery pack.

11. The motor-driven appliance according to claim 6,

wherein the current detection unit, the current threshold setting unit, the current exceedance determination unit, and the current flow interruption unit are mounted in the main body.

12. The motor-driven appliance according to claim 6,

wherein the main body includes;

an operation switch; and

an operation amount signal output unit that outputs an operation amount signal indicating an operation amount of the operation switch to the battery pack,

wherein the battery pack includes;

the current detection unit;

the current threshold setting unit;

the current exceedance determination unit;

the current flow interruption unit;

a switching element that conducts and interrupts the current path from the battery to the motor; and

a control unit that controls the current flowing from the battery to the motor by turning on and off the switching element based on the operation amount signal inputted from the main body, and

wherein the current flow interruption unit is configured to interrupt the current path by forcibly turning off the switching element when the interruption signal is outputted from the current exceedance determination unit.

13. The motor-driven appliance according to claim 1,

wherein the current threshold setting unit is configured to generate the current threshold of an analog form and outputs the generated current threshold to the current exceedance determination unit.

14. The motor-driven appliance according to claim 1, including a temperature detection unit that detects a temperature of the permanent magnets in the motor directly or indirectly,

wherein the current threshold setting unit is configured to generate the current threshold based on the momentary maximum current upper limit and the temperature detected by the temperature detection unit.

15. A battery pack used attached to a main body of a motor-driven appliance, the battery pack comprising:

a battery that supplies electric power to a motor that is mounted in the main body and includes permanent magnets as field magnets;

a current detection unit that detects a current flowing from the battery to the motor;

a current threshold setting unit that generates a current threshold based on a momentary maximum current upper limit stored in the main body, and outputs the generated current threshold; and

a current exceedance determination unit that determines whether the current detected by the current detection unit has become equal to or greater than the current threshold, and outputs an interruption signal used to interrupt a current path from the battery to the motor when the detected current has become equal to or greater than the current threshold.