JP2014018870A - Electric tool and brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric tool and a brushless motor.SOLUTION: An electric tool 1 includes: a brushless motor 2 having a rotor 5, and plural coils 601-612 disposed circumferentially around the rotor 5; and a control unit 3 that changes a coil to be excited among the plural coils 601-612. The control unit 3 can change the number of coils to be simultaneously excited.

Description

  The present invention relates to an electric tool and a brushless motor.

  Conventionally, a brushless motor that includes a rotor having a plurality of poles and a plurality of coils arranged around the rotor, and rotates the rotor by sequentially switching coils to be excited is known.

  There has also been proposed an electric tool capable of changing the magnitude of torque of a brushless motor by switching a coil connection method between Y connection and delta connection (for example, see Patent Document 1).

JP 2004-343856 A

  However, in the electric power tool described in Patent Document 1, as a result of switching the coil connection method between Y connection and delta connection, not only the magnitude of torque but also the rotational speed of the rotor changes.

  Then, an object of this invention is to provide the electric tool and brushless motor which can change the magnitude | size of a torque, without changing the rotational speed of a rotor.

  In order to solve the above problems, the present invention includes a rotor having X pairs of N poles and S poles, and Y (Y is an integer greater than X) coils arranged circumferentially around the rotor, , And a control unit that switches a coil to be excited among the Y coils, the control unit being capable of changing the number of coils to be excited simultaneously. The electric tool characterized by this is provided.

  According to such a configuration, the magnitude of the torque of the brushless motor can be changed.

  Moreover, it is preferable that the control unit switches the coils to be excited at a constant timing even when the number of coils to be simultaneously excited is changed.

  According to such a configuration, even when the magnitude of the torque of the brushless motor is reduced, the rotation speed of the brushless motor can be kept constant.

  Moreover, the electric tool of the present invention includes a plurality of first switching elements respectively connected to a plurality of first coils among the Y coils, and a first switching for switching connected to the plurality of first switching elements. An element, a plurality of second switching elements respectively connected to a plurality of second coils among the Y coils, and a second switching element connected to the plurality of second switching elements. The control unit preferably changes the number of coils to be excited simultaneously by turning off one of the first switching element and the second switching element.

  According to such a configuration, the number of coils to be simultaneously excited, that is, the magnitude of torque is changed by simple control of turning off one of the first switching element and the second switching element. It becomes possible.

  Moreover, it is preferable that the electric tool of the present invention further includes a change-over switch that can be operated by a user, and the control unit changes the number of coils that are simultaneously excited when the change-over switch is operated.

  According to such a configuration, it is possible to change the number of coils that are excited simultaneously, that is, the magnitude of torque according to the user's intention.

  The power tool of the present invention further includes a current detection unit that detects a current flowing through the coil, and the control unit changes the number of coils that are excited simultaneously based on the current detected by the current detection unit. It is preferable.

  According to such a configuration, it is possible to work with a large torque when the load is large, and to save power when the load is small.

  According to another aspect of the present invention, a rotor having X pairs of N poles and S poles, and Y (Y is an integer greater than X) coils arranged circumferentially around the rotor, , A plurality of first switching elements respectively connected to a plurality of first coils among the Y coils, a first switching element connected to the plurality of first switching elements, and the Y coils A brushless motor, further comprising: a plurality of second switching elements respectively connected to the plurality of second coils; and a second switching element connected to the plurality of second switching elements. Is provided.

  According to such a configuration, the electric tool connected to the brushless motor of the present invention is excited simultaneously by simple control of turning off one of the first switching element and the second switching element. It becomes possible to change the number of coils, that is, the magnitude of the torque.

  According to the electric tool and the brushless motor of the present invention, the magnitude of torque can be changed.

The block diagram of the electric tool by embodiment of this invention. Operation | movement explanatory drawing of the brushless motor at the time of performing normal control. 1 is a circuit diagram of a brushless motor according to an embodiment of the present invention. Explanatory drawing of FET control by embodiment of this invention. Operation | movement explanatory drawing of the brushless motor at the time of performing control by embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  As shown in FIG. 1, the electric tool 1 includes a brushless motor 2, a control unit 3 that controls the brushless motor 2, and a changeover switch 4.

  As shown in FIGS. 2 and 3, the brushless motor 2 is arranged around the rotor 5, which is an electromagnet having four poles (in this embodiment, two pairs of N poles and S poles). 12 coils 601-612, 12 FETs 701-712, two switching FETs 713 and 714, a positive terminal 8A, and a negative terminal 8B.

  In this embodiment, the coils 601-612, the FETs 701-712, the switching FETs 813 and 814, the first coils 601, 603, 605, 607, 609, 611, the first FETs 701-706, A first coil set composed of a switching FET 713, a second coil composed of a second coil 602, 604, 606, 608, 610, 612, a second FET 707-712, and a second switching FET 714. It is classified as a coil set.

  Since the first coil set and the second coil set have the same configuration, the first coil set will be described below as an example.

  As shown in FIG. 3, the first coils 601, 603, 605 and the first coils 607, 609, 611 are each Y-connected.

  The first FET 701 and the first FET 704 are connected in series, and are connected between the plus terminal 8A and the minus terminal 8B via the first switching FET 713. Similarly, the first FET 702 and the first FET 705, and the first FET 703 and the first FET 706 are also connected in series via the first switching FET 713 between the plus terminal 8A and the minus terminal 8B. . It is assumed that a predetermined DC voltage is applied between the plus terminal 8A and the minus terminal 8B.

  The first coil 601 and the first coil 607 are connected to the contacts of the first FET 701 and the first FET 704, the first coil 603 and the first coil 609 are connected to the contacts of the first FET 702 and the first FET 705, and the contacts of the first FET 703 and the first FET 706 are connected. The first coil 605 and the first coil 611 are connected to each other.

  With such a configuration, for example, when the first FETs 701 and 706 are also turned on while the first switching FET 713 is turned on, current is supplied to the first coils 601 and 605 and the first coils 607 and 611. As shown in FIG. 4, the first coils 601, 605, 607 and 611 are excited.

  As shown in FIG. 2, the first coil 601 and the first coil 605 (the first coil 607 and the first coil 611) are arranged so that currents flow in opposite directions. Therefore, the first coil 601 and the first coil 605 (the first coil 607 and the first coil 611) are excited to have opposite polarities.

  On the other hand, the first coil 601 and the first coil 607 (the first coil 605 and the first coil 611) are arranged so that current flows in the same direction. Therefore, the first coil 601 and the first coil 607 (the first coil 605 and the first coil 611) are excited with the same polarity.

  On / off of the first FET 701-706 is controlled by the control unit 3. Specifically, as shown in FIG. 4, the control unit 3 controls the on / off of the FETs 701-706 at regular timings, thereby exciting the first coils 601, 603, 605, 607, 609, 611 is switched, and accordingly, the rotor 5 that is an electromagnet rotates.

  Further, the second coils 602, 604, 606, 608, 610, 612 of the second coil set are arranged between the first coils 601, 603, 605, 607, 609, 611 of the first coil set, respectively. . And the control part 3 controls so that the 1st coil 601 of the adjacent 1st coil set and the 2nd coil 602 of a 2nd coil set may excite simultaneously, for example. As a result, the rotor 5 is rotated with twice the torque as compared with the case where the rotor 5 is rotated only with one coil set.

  Here, the electric power tool 1 according to the present embodiment further includes a changeover switch 4, and the changeover switch 4 can switch the magnitude of the torque of the brushless motor 2 (rotor 5). .

  Specifically, when the change-over switch 4 is turned on by the user, the control unit 3 turns on the first torque switching FET 713 and the second torque switching FET 714 alternately as shown in FIG. As a result, as shown in FIG. 5, when the changeover switch 4 is turned off, one of the first coil and the second coil (for example, the first coil 601 and the second coil 602) that are energized at the same time. As a result, only the torque of the brushless motor 2 is halved.

  As described above, in the electric power tool 1 according to the present embodiment, the number of coils that are simultaneously excited can be changed. As a result, the magnitude of the torque of the brushless motor 2 can be changed. For example, when using a power tool 1 that is a disc grinder to grind a material that easily causes grinding burn such as stainless steel. By halving the magnitude of the torque of the brushless motor 2 (rotor 5), it is possible to prevent grinding burns and the like from occurring.

  Moreover, in the electric power tool 1 according to the present embodiment, the coils to be excited are switched at a constant timing even when the number of coils to be simultaneously excited is changed. As a result, even when the magnitude of the torque of the brushless motor 2 (rotor 5) is halved, the rotational speed of the brushless motor 2 (rotor 5) does not change. Is possible.

  Moreover, in the electric tool 1 according to the present embodiment, since the switching FETs 713 and 714 are provided in the brushless motor 2, the electric tool 1 (control unit 3) simply turns off one of the switching FETs 713 and 714. With this control, the number of coils that are excited simultaneously, that is, the magnitude of torque can be changed.

  In addition, since the electric power tool 1 according to the present embodiment includes the changeover switch 4, the number of coils that are simultaneously excited, that is, the magnitude of the torque can be changed according to the user's intention.

  The power tool according to the present invention is not limited to the above-described embodiment, and various improvements and modifications can be made within the scope described in the claims.

  For example, in the above embodiment, the number of coils that are excited simultaneously is changed according to whether the change-over switch 4 is turned on or off. However, the change-over switch 4 may not be provided and may be changed according to the load applied to the brushless motor 2. . Specifically, a current detection unit that detects a current flowing through the brushless motor 2 (coils 601-612) may be further provided, and the number of coils that are excited simultaneously may be changed based on the current detected by the current detection unit.

  According to such a configuration, for example, work can be performed with a large torque when the load is large, and power can be saved when the load is small.

  In the above-described embodiment, the brushless motor 2 having 4 poles and 12 coils is used. However, the brushless motor 2 is configured by a rotor having X pairs of N poles and S poles and Y (Y is an integer larger than X) coils. If so, a brushless motor having another configuration may be used.

  In addition, when using a brushless motor having three or more coil sets, the magnitude of the torque of the brushless motor 2 can be changed in stages by providing switching FETs according to the number of coil sets. It becomes possible.

  In the above embodiment, FETs are used as the first and second switching elements and the first and second switching elements of the present invention. However, other switching elements may be used.

  In the above embodiment, the switching FETs 713 and 714 are provided inside the brushless motor 2, but may be provided outside the brushless motor 2.

  Moreover, in the said embodiment, although the coil was Y-connected, for example, you may connect by other connection methods like a delta connection.

  In addition to the disc grinder, the power tool of the present invention can be applied to other power tools having convenience in switching the magnitude of torque.

DESCRIPTION OF SYMBOLS 1 Electric tool 2 Brushless motor 3 Control part 4 Changeover switch 5 Rotor 601-612 Coil 701-712 FET
713, 714 switching FET

Claims (6)

A brushless motor having a rotor having X pairs of N poles and S poles, and Y (Y is an integer larger than X) coils arranged circumferentially around the rotor;
A control unit that switches a coil to be excited among the Y coils;
An electric tool comprising
The said control part can change the number of the coils excited simultaneously, The electric tool characterized by the above-mentioned.   2. The electric tool according to claim 1, wherein the control unit switches the coils to be excited at a constant timing even when the number of coils to be simultaneously excited is changed. A plurality of first switching elements respectively connected to a plurality of first coils among the Y coils;
A first switching element connected to the plurality of first switching elements;
A plurality of second switching elements respectively connected to a plurality of second coils among the Y coils;
A second switching element connected to the plurality of second switching elements;
Further comprising
The said control part changes the number of the coils excited simultaneously by turning off either one of the said 1st switching element and the said 2nd switching element. Power tools. Further provided with a changeover switch operable by the user,
The electric power tool according to any one of claims 1 to 3, wherein the control unit changes the number of coils to be excited simultaneously when the changeover switch is operated. A current detection unit for detecting a current flowing in the coil;
The electric power tool according to any one of claims 1 to 4, wherein the control unit changes the number of coils to be simultaneously excited based on the current detected by the current detection unit. A rotor having X pairs of N and S poles;
Y (Y is an integer larger than X) coils arranged circumferentially around the rotor;
A plurality of first switching elements respectively connected to a plurality of first coils among the Y coils;
A first switching element connected to the plurality of first switching elements;
A plurality of second switching elements respectively connected to a plurality of second coils among the Y coils;
A second switching element connected to the plurality of second switching elements;
A brushless motor, further comprising:

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