JP3633220B2 - Rotational speed control device and electric tool - Google Patents

Rotational speed control device and electric tool Download PDF

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Publication number
JP3633220B2
JP3633220B2 JP19413697A JP19413697A JP3633220B2 JP 3633220 B2 JP3633220 B2 JP 3633220B2 JP 19413697 A JP19413697 A JP 19413697A JP 19413697 A JP19413697 A JP 19413697A JP 3633220 B2 JP3633220 B2 JP 3633220B2
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Prior art keywords
voltage
motor
rotation
detection
rotation speed
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JP19413697A
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JPH1141965A (en
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茂 篠原
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Koki Holdings Co Ltd
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Hitachi Koki Co Ltd
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Description

【０００１】
【発明の属する技術分野】
本発明はモータの回転を検出する回転検出部の異常を判別してモータ回転数の上昇を抑制するようにした回転数制御装置及び該回転数制御装置を備えた電動工具に関するものである。
【０００２】
【従来の技術】
モータの回転数を一定に制御するための回転数制御は、モータの回転を検出し、検出結果をフィードバックすることにより行っている。
【０００３】
【発明が解決しようとする課題】
回転数制御装置の回転検出手段としては、周知の如く、発電機式、電磁式、光電式等がある。発電機式、電磁式におけるコイルの断線、磁石の破損、光電式における発光ダイオード、ホトダイオード、ホトトランジスタ等の光半導体の故障により実際の回転数の検出ができなくなり、モータをフル回転させてしまう恐れがある。この回転数の上昇により、電動工具においては、ベアリング、ギヤ等を含めた機構部の破損を招く。特に電気ハンマのハンマ機構部、ジグソーの揺動機構部、振動ドリルの振動機構部等は顕著である。また、ディスクグラインダの砥石のように許容回転数が規定されている場合、回転数の上昇により許容回転数を超え砥石の破損を招くという安全上の問題が生じる。
本発明の目的は、回転検出部の故障に起因するモータ回転数の上昇を抑制することである。
【０００４】
【課題を解決するための手段】
上記目的は、モータ回転数を検出する回転検出手段からの検出信号によりモータ回転数に比例した直流電圧を出力するＦＶ変換手段の出力電圧が所定値より小さい時回転検出部が故障したと判別し、位相制御手段を介して半導体制御手段の導通角を小さくなる回転検出異常判別手段を設けることにより達成される。
【０００５】
更に、モータ回転数を徐々に設定回転数まで上昇させるソフトスタート信号を発生するソフトスタート信号発生手段のソフトスタート信号電圧が所定電圧に達するまでは前記回転検出異常判別手段の回転検出異常判別動作を休止させることにより、回転検出異常判別手段の誤検出を避けることが可能となる。また、モータに流れる電流を検出する電流検出手段の検出出力を受け、検出出力が所定値以上の時過負荷と判断し、前記ソフトスタート信号発生手段のソフトスタート信号電圧を所定値以下とする過負荷制限手段を設け、過負荷時での回転検出異常判別手段の誤検出を避けることが可能である。
【０００６】
【発明の実施の形態】
以下図面を参照して本発明の実施形態を説明する。図１において、１は交流電源、２はトリガスイッチ、３はモータ、４はトライアック等からなる半導体制御手段、５はモータ３に流れる電流を検出する電流検出手段、６はモータ３の回転数を検出する回転検出手段、７は回転検出手段６で検出したモータ３の回転数に比例した周波数信号を直流電圧に変換するＦＶ変換手段、８はモータ３の回転数を設定する回転数設定手段、９はＦＶ変換手段７の出力電圧と回転数設定手段８の設定電圧を比較し、位相制御電圧を発生する差動増幅手段、１０は差動増幅手段９の出力位相制御電圧に応じて半導体制御手段４の導通角を制御する位相制御手段である。
【０００７】
差動増幅手段９の出力位相制御電圧が小さい時は、半導体制御手段４の導通角を小さくしてモータ３への印加電圧を小さくする。差動増幅手段９の出力位相制御電圧が大きい時は、半導体制御手段４の導通角を大きくしてモータ３への印加電圧を大きくする。１１は起動の際モータ３の回転数を徐々に設定回転数まで上昇させるための信号を発生するソフトスタート信号発生手段で、電流源１１ａ、ソフトスタート用コンデンサ１１ｂ、ボルテージフォロワ１１ｃ、トランジスタ１１ｄ等から構成される。モータ３の加速度合いは電流源１１ａとソフトスタート用コンデンサ１１ｂで決まる。１２はモータ３が過負荷になった時モータ３への印加電圧を小さくし、モータ３の焼損を防止する過負荷制限手段、１３は回転検出手段６及びＦＶ変換手段７等の回転検出部に故障が生じたのを検出する回転検出異常判別手段で、比較手段１３ａ、１３ｂ、ＮＡＮＤゲート１３ｃ、トランジスタ１３ｄ等から構成される。前記トランジスタ１１ｄ、１３ｄはエミッタフォロワとして動作する。このトランジスタ１１ｄ、１３ｄのエミッタ−コレクタ間電圧と差動増幅手段９の出力位相制御電圧のうち一番小さい電圧が、位相制御手段１０の入力信号となる。すなわち、起動時はトランジスタ１１ｄのエミッタ−コレクタ間電圧、通常動作時は差動増幅手段９の出力位相制御電圧、回転検出部の故障時はトランジスタ１３ｄのエミッタ−コレクタ間電圧により、位相制御手段１０は制御される。
【０００８】
次に図２を参照して本発明実施形態の動作を説明する。トリガスイッチ２を投入すると、電流源１１ａからの充電電流によりソフトスタート用コンデンサ１１ｂの電圧Ｖ11が零から徐々に上昇する。このソフトスタート信号電圧Ｖ11をボルテージフォロワ１１ｃ、トランジスタ１１ｄを介して位相制御手段１０に入力し、半導体制御手段４の導通角を徐々に増やし、モータ３への印加電圧を大きくし、回転数を徐々に設定回転数まで上昇させる。このソフトスタート信号電圧Ｖ11が比較電圧Ｖref2に達するまでは、比較手段１３ｂの出力Ｖ13bがローレベルなので比較手段１３ａの出力Ｖ13aがどのような状態であろうと、ＮＡＮＤゲート１３ｃの出力Ｖ13cはハイレベルでトランジスタ１３ｄはオフ状態なので、位相制御手段１０の制御に影響を与えない。すなわち、起動時においてモータ３が回転し始め、回転数設定手段８から回転信号が発生し、ＦＶ変換手段７の出力電圧Ｖ7が比較電圧Ｖref1に達するまで時間遅れｔｄが生じることによる回転検出異常判別動作を禁止している。ソフトスタート信号電圧Ｖ11が比較電圧Ｖref2に達すると、比較手段１３ｂの出力Ｖ13bがハイレベルとなり、ＮＡＮＤゲート１３ｃの出力Ｖ13cは比較手段１３ａの出力Ｖ13aの状態に依存する。すなわち、回転検出部が正常な場合は比較手段１３ａの出力Ｖ13aはローレベルなので、ＮＡＮＤゲート１３ｃの出力Ｖ13cはハイレベルでトランジスタ１３ｄはオフ状態なので、位相制御手段１０に影響を与えない。しかし、回転検出部が故障の場合は比較手段１３ａの出力Ｖ13aはハイレベルになるので、ＮＡＮＤゲート１３ｃの出力Ｖ13cはローレベルになり、トランジスタ１３ｄのエミッタ−コレクタ間電圧もローレベルになり、位相制御手段１０は半導体制御手段４の導通角を小さくし、モータ３への印加電圧を小さくし、モータ３の回転数を抑制する。
【０００９】
モータ３の回転を一定に制御するための回転数制御は、モータ３の回転数を回転検出手段６で検出し、ＦＶ変換手段７でモータ３の回転数に比例した直流電圧と回転数設定手段８の設定電圧を差動増幅手段９で比較し、差動増幅手段９から出力する位相制御電圧で位相制御手段１０を制御し、モータ３の回転を一定に制御する。すなわち、モータ３への負荷が増加しモータ回転数が低下すると、ＦＶ変換手段７の出力電圧が減少し、回転数設定手段８の設定電圧との差電圧を増加し、差動増幅手段９の位相制御電圧が増加する。これにより位相制御手段１０は半導体制御手段４の導通角を大きくしてモータ３への印加電圧を大きくし、モータ回転数を上昇させる。逆に負荷が減少しモータ回転数が上昇すると、ＦＶ変換手段７の出力電圧が増加し、回転数設定手段８の設定電圧との差電圧が減少し、差動増幅手段９の位相制御電圧が減少する。これにより位相制御手段１０は半導体制御手段４の導通角を小さくしてモータ３への印加電圧を小さくし、モータ回転数を減少させる。この結果、モータ３の回転は一定になる。
【００１０】
モータ３の過負荷によるモータ焼損を避けるために設けた過負荷制限回路１２は、モータ３が過負荷になり電流検出手段５からの電圧が所定値より大きくなった時、ソフトスタート用コンデンサ１１ｂを急速に放電させ、位相制御手段１０の入力電圧を小さくし、半導体制御手段４の導通角を小さくし、モータ３への印加電圧を小さくする。過負荷制限回路１２が動作中はソフトスタート用コンデンサ１１ｂを放電させた状態にしているため、Ｖref2＞Ｖ11となり、比較手段１３ｂの出力Ｖ13bがローレベルなので比較手段１３ａの出力Ｖ13aがどのような状態であろうと、ＮＡＮＤゲート１３ｃの出力Ｖ13cはハイレベルでトランジスタ１３ｄはオフ状態となり、回転検出異常判別動作を禁止する。
【００１１】
【発明の効果】
以上説明したように本発明によれば、回転検出部の故障に起因するモータ回転数の上昇を抑制することが可能となる。この結果本発明を電動工具に採用した場合、回転検出部の故障に起因する電動工具の機構部品や砥石等の破損を未然に防止できるようになる。
【図面の簡単な説明】
【図１】本発明回転数制御装置の一実施形態を示すブロック回路図。
【図２】本発明の動作説明用タイミングチャート。
【符号の説明】
３はモータ、４は半導体制御手段、５は電流検出手段、６は回転検出手段、７はＦＶ変換手段、８は回転数設定手段、９は差動増幅手段、１０は位相制御手段、１１はソフトスタート信号発生手段、１２は過負荷制限手段、１３は回転検出異常判別手段である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rotation speed control device that discriminates an abnormality in a rotation detection unit that detects rotation of a motor and suppresses an increase in motor rotation speed, and an electric tool including the rotation speed control device .
[0002]
[Prior art]
The rotation speed control for controlling the rotation speed of the motor to be constant is performed by detecting the rotation of the motor and feeding back the detection result.
[0003]
[Problems to be solved by the invention]
As well known, there are a generator type, an electromagnetic type, a photoelectric type and the like as the rotation detecting means of the rotation speed control device. There is a risk that the actual number of revolutions cannot be detected and the motor can be rotated at full speed due to breakage of the coil in the generator type or electromagnetic type, breakage of the magnet, or failure of the optical semiconductor such as the light emitting diode, photodiode, or phototransistor in the photoelectric type. There is. Due to the increase in the rotational speed, in the electric power tool, the mechanism portion including the bearing, the gear and the like is damaged. In particular, the hammer mechanism part of an electric hammer, the swing mechanism part of a jigsaw, the vibration mechanism part of a vibration drill, etc. are remarkable. Further, when an allowable rotational speed is defined as in a grinder of a disk grinder, there is a safety problem in that the increase of the rotational speed exceeds the allowable rotational speed and causes the wheel to be damaged.
An object of the present invention is to suppress an increase in the number of rotations of the motor due to a failure of the rotation detection unit.
[0004]
[Means for Solving the Problems]
The purpose is to determine that the rotation detection unit has failed when the output voltage of the FV conversion means for outputting a DC voltage proportional to the motor rotation speed is smaller than a predetermined value based on the detection signal from the rotation detection means for detecting the motor rotation speed. This is achieved by providing rotation detection abnormality determining means for reducing the conduction angle of the semiconductor control means via the phase control means.
[0005]
Further, the rotation detection abnormality determining operation of the rotation detection abnormality determining means is performed until the soft start signal voltage of the soft start signal generating means for generating a soft start signal for gradually increasing the motor rotational speed to the set rotational speed reaches a predetermined voltage. By stopping the operation, it is possible to avoid erroneous detection of the rotation detection abnormality determining means. Further, the detection output of the current detection means for detecting the current flowing through the motor is received, and when the detection output is greater than or equal to a predetermined value, it is determined that there is an overload, and the soft start signal voltage of the soft start signal generation means is less than the predetermined value. Load limiting means can be provided to avoid erroneous detection of the rotation detection abnormality determining means during overload.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is an AC power source, 2 is a trigger switch, 3 is a motor, 4 is a semiconductor control means such as a triac, 5 is a current detection means for detecting a current flowing through the motor 3, and 6 is a rotation speed of the motor 3. Rotation detecting means for detecting, 7 is an FV converting means for converting a frequency signal proportional to the rotational speed of the motor 3 detected by the rotational detecting means 6 into a DC voltage, and 8 is a rotational speed setting means for setting the rotational speed of the motor 3. 9 is a comparison between the output voltage of the FV conversion means 7 and the setting voltage of the rotation speed setting means 8 to generate a phase control voltage, and 10 is a semiconductor control according to the output phase control voltage of the differential amplification means 9. Phase control means for controlling the conduction angle of the means 4.
[0007]
When the output phase control voltage of the differential amplification means 9 is small, the conduction angle of the semiconductor control means 4 is reduced to reduce the voltage applied to the motor 3. When the output phase control voltage of the differential amplification means 9 is large, the conduction angle of the semiconductor control means 4 is increased to increase the voltage applied to the motor 3. Reference numeral 11 denotes a soft start signal generating means for generating a signal for gradually increasing the rotational speed of the motor 3 to a set rotational speed at the time of starting, from a current source 11a, a soft start capacitor 11b, a voltage follower 11c, a transistor 11d, and the like. Composed. The acceleration of the motor 3 is determined by the current source 11a and the soft start capacitor 11b. Reference numeral 12 denotes an overload limiting means for reducing the voltage applied to the motor 3 when the motor 3 is overloaded to prevent the motor 3 from being burned out. Reference numeral 13 denotes a rotation detecting section such as the rotation detecting means 6 and the FV converting means 7. Rotation detection abnormality determining means for detecting that a failure has occurred, and comprises comparison means 13a and 13b, a NAND gate 13c, a transistor 13d, and the like. The transistors 11d and 13d operate as an emitter follower. The smallest voltage among the emitter-collector voltages of the transistors 11 d and 13 d and the output phase control voltage of the differential amplifying means 9 is the input signal of the phase control means 10. That is, the phase control means 10 is based on the voltage between the emitter and collector of the transistor 11d at the time of start-up, the output phase control voltage of the differential amplifying means 9 during normal operation, and the voltage between the emitter and collector of the transistor 13d when the rotation detector is faulty. Is controlled.
[0008]
Next, the operation of the embodiment of the present invention will be described with reference to FIG. When the trigger switch 2 is turned on, the voltage V11 of the soft start capacitor 11b gradually increases from zero due to the charging current from the current source 11a. This soft start signal voltage V11 is inputted to the phase control means 10 through the voltage follower 11c and the transistor 11d, the conduction angle of the semiconductor control means 4 is gradually increased, the applied voltage to the motor 3 is increased, and the rotational speed is gradually increased. Increase to the set speed. Until the soft start signal voltage V11 reaches the comparison voltage Vref2, since the output V13b of the comparison means 13b is at the low level, the output V13c of the NAND gate 13c is at the high level regardless of the state of the output V13a of the comparison means 13a. Since the transistor 13d is in an off state, the control of the phase control means 10 is not affected. That is, when the motor 3 starts rotating at the time of startup, a rotation signal is generated from the rotation speed setting means 8, and a rotation detection abnormality determination is caused by a time delay td until the output voltage V7 of the FV conversion means 7 reaches the comparison voltage Vref1. Operation is prohibited. When the soft start signal voltage V11 reaches the comparison voltage Vref2, the output V13b of the comparison means 13b becomes high level, and the output V13c of the NAND gate 13c depends on the state of the output V13a of the comparison means 13a. That is, when the rotation detection unit is normal, the output V13a of the comparison means 13a is at a low level, so the output V13c of the NAND gate 13c is at a high level and the transistor 13d is in an off state, so that the phase control means 10 is not affected. However, when the rotation detector is out of order, the output V13a of the comparison means 13a is at a high level, so the output V13c of the NAND gate 13c is at a low level, and the emitter-collector voltage of the transistor 13d is also at a low level. The control means 10 reduces the conduction angle of the semiconductor control means 4, reduces the voltage applied to the motor 3, and suppresses the rotation speed of the motor 3.
[0009]
The rotation speed control for controlling the rotation of the motor 3 at a constant level is performed by detecting the rotation speed of the motor 3 by the rotation detection means 6 and the FV conversion means 7 by the direct current voltage proportional to the rotation speed of the motor 3 and the rotation speed setting means. 8 is compared by the differential amplifying means 9, the phase control means 10 is controlled by the phase control voltage output from the differential amplifying means 9, and the rotation of the motor 3 is controlled to be constant. That is, when the load on the motor 3 increases and the motor rotation speed decreases, the output voltage of the FV conversion means 7 decreases, the voltage difference from the set voltage of the rotation speed setting means 8 increases, and the differential amplification means 9 The phase control voltage increases. As a result, the phase control means 10 increases the conduction angle of the semiconductor control means 4 to increase the voltage applied to the motor 3 and increase the motor speed. Conversely, when the load decreases and the motor rotation speed increases, the output voltage of the FV conversion means 7 increases, the voltage difference from the setting voltage of the rotation speed setting means 8 decreases, and the phase control voltage of the differential amplification means 9 decreases. Decrease. As a result, the phase control means 10 reduces the conduction angle of the semiconductor control means 4 to reduce the voltage applied to the motor 3, thereby reducing the motor speed. As a result, the rotation of the motor 3 is constant.
[0010]
An overload limiting circuit 12 provided to avoid motor burnout due to overloading of the motor 3 causes the soft start capacitor 11b to be activated when the motor 3 is overloaded and the voltage from the current detection means 5 exceeds a predetermined value. The voltage is rapidly discharged, the input voltage of the phase control means 10 is reduced, the conduction angle of the semiconductor control means 4 is reduced, and the voltage applied to the motor 3 is reduced. Since the soft start capacitor 11b is discharged while the overload limiting circuit 12 is in operation, Vref2> V11 and the output V13b of the comparison means 13b is at a low level, so what is the output V13a of the comparison means 13a? However, the output V13c of the NAND gate 13c is at a high level and the transistor 13d is turned off, thereby prohibiting the rotation detection abnormality determination operation.
[0011]
【The invention's effect】
As described above, according to the present invention, it is possible to suppress an increase in the number of rotations of the motor due to a failure of the rotation detection unit. As a result, when the present invention is employed in an electric power tool, it is possible to prevent damage to mechanical parts, grindstones, and the like of the electric power tool due to a failure of the rotation detection unit.
[Brief description of the drawings]
FIG. 1 is a block circuit diagram showing an embodiment of a rotation speed control device of the present invention.
FIG. 2 is a timing chart for explaining the operation of the present invention.
[Explanation of symbols]
3 is a motor, 4 is semiconductor control means, 5 is current detection means, 6 is rotation detection means, 7 is FV conversion means, 8 is rotation speed setting means, 9 is differential amplification means, 10 is phase control means, 11 is A soft start signal generating means, 12 is an overload limiting means, and 13 is a rotation detection abnormality determining means.

Claims (2)

モータへの印加電圧を制御する半導体制御手段と、モータの回転数を検出する回転数検出手段と、回転数検出手段からの信号によりモータの回転数に比例した直流電圧を出力するＦＶ変換手段と、モータの回転数を設定する回転数設定手段と、ＦＶ変換手段の出力電圧と回転数設定手段の設定電圧との差電圧を増幅する差動増幅手段と、差動増幅手段の出力に応じて半導体制御手段の導通角を制御する位相制御手段と、ＦＶ変換手段の出力電圧が所定値より小さい時回転検出部が故障したと判別し、位相制御手段を介して半導体制御手段の導通角を小さくする回転検出異常判別手段と、モータの回転数を徐々に設定回転数まで上昇させるための信号を発生するソフトスタート信号発生手段と、モータに流れる電流を検出する電流検出手段と、電流検出手段の検出出力を受け、検出出力が所定以上の時過負荷と判断し、前記ソフトスタート信号発生手段のソフトスタート信号電圧を所定値以下とする過負荷制限手段とを備え、前記回転異常検出手段の回転異常検出判別動作を、ソフトスタート信号発生手段のソフトスタート信号電圧が所定電圧に達するまで休止するようにしたことを特徴とする回転数制御装置。Semiconductor control means for controlling the voltage applied to the motor, rotational speed detection means for detecting the rotational speed of the motor, and FV conversion means for outputting a DC voltage proportional to the rotational speed of the motor by a signal from the rotational speed detection means A rotation speed setting means for setting the rotation speed of the motor, a differential amplification means for amplifying a differential voltage between the output voltage of the FV conversion means and the setting voltage of the rotation speed setting means, and the output of the differential amplification means When the output voltage of the phase control means for controlling the conduction angle of the semiconductor control means and the FV conversion means is smaller than a predetermined value, it is determined that the rotation detector has failed, and the conduction angle of the semiconductor control means is reduced via the phase control means. a rotation detecting abnormality judgment means for a soft-start signal generating means for generating a signal for increasing the rotational speed of the motor gradually set rotational speed, a current detecting means for detecting a current flowing through the motor, An overload limiting means for receiving a detection output of the flow detection means, determining that an overload is detected when the detection output is greater than or equal to a predetermined value, and setting a soft start signal voltage of the soft start signal generation means to be a predetermined value or less; A rotation speed control device characterized in that the rotation abnormality detection discrimination operation of the detecting means is suspended until the soft start signal voltage of the soft start signal generating means reaches a predetermined voltage . モータと、モータへの印加電圧を制御する半導体制御手段と、モータの回転数を検出する回転数検出手段と、回転数検出手段からの信号によりモータの回転数に比例した直流電圧を出力するＦＶ変換手段と、モータの回転数を設定する回転数設定手段と、ＦＶ変換手段の出力電圧と回転数設定手段の設定電圧との差電圧を増幅する差動増幅手段と、差動増幅手段の出力に応じて半導体制御手段の導通角を制御する位相制御手段と、ＦＶ変換手段の出力電圧が所定値より小さい時回転検出部が故障したと判別し、位相制御手段を介して半導体制御手段の導通角を小さくする回転検出異常判別手段と、モータの回転数を徐々に設定回転数まで上昇させるための信号を発生するソフトスタート信号発生手段と、モータに流れる電流を検出する電流検出手段と、電流検出手段の検出出力を受け、検出出力が所定以上の時過負荷と判断し、前記ソフトスタート信号発生手段のソフトスタート信号電圧を所定値以下とする過負荷制限手段とを備え、前記回転異常検出手段の回転異常検出判別動作を、ソフトスタート信号発生手段のソフトスタート信号電圧が所定電圧に達するまで休止するようにしたことを特徴とする電動工具。Motor, semiconductor control means for controlling applied voltage to the motor, rotation speed detection means for detecting the rotation speed of the motor, and FV that outputs a DC voltage proportional to the rotation speed of the motor by a signal from the rotation speed detection means Conversion means, rotation speed setting means for setting the rotation speed of the motor, differential amplification means for amplifying a differential voltage between the output voltage of the FV conversion means and the setting voltage of the rotation speed setting means, and the output of the differential amplification means When the output voltage of the FV conversion means is smaller than a predetermined value, it is determined that the rotation detector has failed, and the conduction of the semiconductor control means is made via the phase control means. Rotation detection abnormality determination means for reducing the angle, soft start signal generation means for generating a signal for gradually increasing the motor speed to the set speed, and current detection for detecting the current flowing through the motor And overload limiting means for receiving a detection output of the current detection means, determining that the detection output is overload when the detection output is equal to or greater than a predetermined value, and setting a soft start signal voltage of the soft start signal generation means to be a predetermined value or less, An electric power tool characterized in that the rotation abnormality detection determining operation of the rotation abnormality detecting means is suspended until the soft start signal voltage of the soft start signal generating means reaches a predetermined voltage.
JP19413697A 1997-07-18 1997-07-18 Rotational speed control device and electric tool Expired - Fee Related JP3633220B2 (en)

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JP19413697A JP3633220B2 (en) 1997-07-18 1997-07-18 Rotational speed control device and electric tool

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Application Number Priority Date Filing Date Title
JP19413697A JP3633220B2 (en) 1997-07-18 1997-07-18 Rotational speed control device and electric tool

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JP3633220B2 true JP3633220B2 (en) 2005-03-30

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JP2010012547A (en) * 2008-07-03 2010-01-21 Hitachi Koki Co Ltd Power tool
JP2010082761A (en) * 2008-09-30 2010-04-15 Hitachi Koki Co Ltd Electric tool
JP5534327B2 (en) * 2010-05-19 2014-06-25 日立工機株式会社 Electric tool
JP5771369B2 (en) * 2010-07-16 2015-08-26 セミコンダクター・コンポーネンツ・インダストリーズ・リミテッド・ライアビリティ・カンパニー Motor drive circuit

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