1. An electric rotating tool comprising:
an operating part;
a power source part;
a motor having a rotor and a stator coil;
an inverter circuit part which has a semiconductor switching element inserted between the power source part and the stator coil;
a rotation number detection part configured to detect the rotational rate of the rotor relative to the stator coil and outputs a signal corresponding to a result of the detection; and
a control part which generates and outputs a pulse-width modulation (PWM) signal for driving the semiconductor switching element of the inverter circuit part, wherein
the control part includes a computer and the computer generates a first rotational speed threshold value that changes in accordance with a PWM duty of the PWM signal, the duty being varied in accordance with an operated degree of the operating part, the control part being used to control the operation of the electric rotating tool in response to the rotational rate of the rotor detected by the rotation number detection part dropping below the first rotational speed threshold.
2. The electric rotating tool according to claim 1, further comprising a current detection part that detects a drive current flowing through the stator coil and outputs a signal corresponding to a result of the detection, wherein
the computer determines a second current threshold value, and
the computer determines a locked state of the motor under conditions that a value of the drive current detected by the current detection part exceeds the second current threshold value and that the rotational rate of the rotor detected by the rotation number detection part is smaller than the first rotational speed threshold value.
3. The electric rotating tool according to claim 2, wherein the computer sets a predetermined time period and the control part generates a control signal to stop the motor when the set time period is elapsed after the locked state of the motor is detected.
4. The electric rotating tool according to claim 3, further comprising a temperature measurement part that measures the temperature of the motor or the inverter circuit part, wherein
the computer determines the time period based on the temperature measured by the temperature measurement part before the locked state of the motor is detected.
5. The electric rotating tool according to claim 4, wherein the computer determines the time period such that the temperature measured by the temperature measurement part does not reach a burnout temperature after the locked state is detected.
6. The electric rotating tool according to claim 3, wherein the control part generates a control signal to restrict the drive current to a predetermined value, which is smaller than the second current threshold value, within the time period set by the computer.
7. The electric rotating tool according to claim 6, wherein the control part controls the PWM duty of the PWM signal such that the drive current is smaller than the second current threshold value.
8. The electric rotating tool according to claim 2, wherein when the locked state of the motor is detected, the computer controls the motor to rotate in a reverse rotation direction for a predetermined time period, and then stops the motor.
9. The electric rotating tool according to claim 2, wherein when the locked state of the motor is detected, the computer controls the motor to rotate in a reverse rotation direction for a predetermined time period and then rotate in a forward rotation direction again, and controls the motor so that the motor can be activated in the forward rotation direction.
10. The electric rotating tool according to claim 2, further comprising an indicating part that is lit when the computer determines that the motor is in the locked state.
11. The electric rotating tool according to claim 2, wherein the electric rotating tool is a driver drill, a drill, an impact driver, a driver, or a disk grinder.
12. The electric rotating tool according to claim 1, wherein the computer determines the PWM duty of the PWM signal in accordance with the operated degree of the operating part.
13. The electric rotating tool according to claim 1, wherein the power source part is a battery pack, the battery pack comprising a secondary battery.
14. The electric rotating tool according to claim 1, wherein the power source part is a battery pack, the battery pack comprising a lithium ion secondary battery.
15. The electric rotating tool according to claim 1, wherein the motor is a brushless DC motor.
16. A power tool comprising:
a housing;
a brushless motor housed in the housing;
an inverter circuit part that drives the brushless motor;
a control circuit part that controls the inverter circuit part; and
a trigger operating part operated by an operator; wherein
the control circuit part outputs a pulse-width modulation (PWM) signal that has a duty rate corresponding to a pressed distance of the trigger operating part to the inverter circuit part, thereby adjusting power to the brushless motor,
when the trigger operating part is being operated and the motor is caused to be in a locked state when current I flowing to the brushless motor has exceeded a threshold value Ir, the control circuit part allows current to flow to the brushless motor even in the locked state but only for an allowable time, and
the allowable time becomes longer as the threshold value Ir becomes smaller.
17. The power tool according to claim 16, wherein when the pressed distance of the trigger operating part is large, the duty rate of the PWM signal becomes larger than when the pressed distance of the trigger operating part is smaller, and when the duty rate is larger, the threshold value Ir becomes larger, thereby shortening the allowable time.
18. The power tool according to claim 16, wherein when the duty rate of the pulse width modulation signal is large, the threshold value Ir becomes larger, thus shortening the allowable time.
19. The power tool according to claim 16, wherein when a temperature Tc of the brushless motor or the inverter circuit part is higher, the allowable time is shorter than when the temperature Tc is low.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. A passenger detection system comprising:
an antenna electrode which is provided to a portion of a vehicle in front of a seat of the vehicle so as to face a passenger seated on the seat;
an oscillation means for generating a high frequency low voltage oscillation signal in order to generate a weak alternating electric field around the antenna electrode;
a current detection means for detecting a transmission current which passes between the oscillation means and the antenna electrode depending on the weak alternating electric field which is generated around the antenna electrode; and
a judgment means for judging the distance between the passenger and the portion of the vehicle based on the transmission current which has been detected by the current detection means.
2. A passenger detection system as claimed in claim 1, wherein the passenger detection system is connected with an air bag unit which is capable of deploying an air bag in front of the passenger in case of collision so that data concerning the distance judged by the judgment means can be sent to the air bag unit, and the air bag unit is set at a deployment mode in which the air bag unit deploys the air bag on collision or a no deployment mode in which the air bag unit does not deploy the air bag on collision according to the data concerning the distance sent from the judgment means.
3. A passenger detection system as claimed in claim 2, wherein the judgment means executes judgment on whether the distance between the passenger and the portion of the vehicle is more than a minimum allowable distance or less than the minimum allowable distance by comparing the transmission current detected by the current detection means with a prestored threshold value concerning the transmission current corresponding to the minimum allowable distance, and the air bag unit is set at the no deployment mode if the distance is judged to be less than the minimum allowable distance.
4. A passenger detection system as claimed in claim 3, wherein the antenna electrode is provided to the dashboard of a car.
5. A passenger detection system as claimed in claim 4, wherein a control unit is made up by enclosing the oscillation means, the current detection means and the judgment means in a common housing, and the control unit is placed inside or near the dashboard.
6. A passenger detection system as claimed in claim 1, wherein the antenna electrode is provided so that the area of the antenna electrode facing part of the passenger will be as large as possible.
7. A passenger detection system as claimed in claim 1, further comprising an amplitude control means for controlling the voltage amplitude of the oscillation signal which is supplied by the oscillation means to the antenna electrode at an almost constant value.
8. A passenger detection system as claimed in claim 1, further comprising a power circuit for generating a single uniform DC voltage utilizing power derived from a battery, in which the single uniform DC voltage supplied by the power circuit is utilized as the system power source for circuits in the passenger detection system including the oscillation means, the current detection means and the judgment means.
9. A passenger detection system comprising:
an antenna electrode which is provided to a portion of a vehicle in front of a seat of the vehicle so as to face a passenger seated on the seat;
an oscillation means for generating a high frequency low voltage oscillation signal in order to generate a weak alternating electric field around the antenna electrode;
a current detection means for detecting a transmission current which passes between the oscillation means and the antenna electrode depending on the weak alternating electric field which is generated around the antenna electrode;
a phase difference detection means for detecting the phase difference between the oscillation signal supplied from the oscillation means and an output signal which is supplied to the antenna electrode; and
a judgment means for judging the presence or absence of a passenger seated on the seat based on the phase difference which has been detected by the phase difference detection means and judging the distance between the passenger and the portion of the vehicle based on the transmission current which has been detected by the current detection means.
10. A passenger detection system as claimed in claim 9, wherein the passenger detection system is connected with an air bag unit which is capable of deploying an air bag in front of the passenger in case of collision so that data concerning the judgment can be sent from the passenger detection system to the air bag unit, and the air bag unit is set at a deployment mode in which the air bag unit deploys the air bag on collision or a no deployment mode in which the air bag unit does not deploy the air bag on collision according to the data concerning the judgment sent from the judgment means.
11. A passenger detection system as claimed in claim 10, wherein the judgment means executes judgment on the presence or absence of a passenger seated on the seat by comparing the phase difference detected by the phase difference detection means with a prestored threshold value concerning the phase difference and executes judgment on whether the distance between the passenger and the portion of the vehicle is more than a minimum allowable distance or less than the minimum allowable distance by comparing the transmission current detected by the current detection means with another prestored threshold value concerning the transmission current corresponding to the minimum allowable distance, and the air bag unit is set at the no deployment mode if it is judged that no passenger is seated on the seat or the distance is less than the minimum allowable distance.
12. A passenger detection system as claimed in claim 11, wherein the antenna electrode is provided to the dashboard of a car.
13. A passenger detection system as claimed in claim 12, wherein a control unit is made up by enclosing the oscillation means, the current detection means, the phase difference detection means and the judgment means in a common housing, and the control unit is placed inside or near the dashboard.
14. A passenger detection system as claimed in claim 9, wherein the antenna electrode is provided so that the area of the antenna electrode facing part of the passenger will be as large as possible.
15. A passenger detection system as claimed in claim 9, further comprising an amplitude control means for controlling the voltage amplitude of the oscillation signal which is supplied by the oscillation means to the antenna electrode at an almost constant value.
16. A passenger detection system as claimed in claim 9, further comprising a power circuit for generating a single uniform DC voltage utilizing power derived from a battery, in which the single uniform DC voltage supplied by the power circuit is utilized as the system power source for circuits in the passenger detection system including the oscillation means, the current detection means, the phase difference detection means and the judgment means.
17. A passenger detection system as claimed in claim 9, wherein the phase difference detection means detects the phase difference between signals at both ends of the current detection means.
18. A passenger detection system as claimed in claim 9, wherein the phase difference detection means detects the phase difference between the oscillation signal and the output signal, by detecting the phase difference between a risingfalling edge of a square wave signal corresponding to the oscillation signal and a risingfalling edge of a square wave signal corresponding to the output signal.
19. A passenger detection system as claimed in claim 9, wherein the oscillation means generates the high frequency low voltage oscillation signal substantially in the form of a square wave.
20. A passenger detection system as claimed in claim 19, wherein an MPU (MicroProcessor Unit) is utilized as the oscillation means for generating the high frequency low voltage oscillation signal in the form of a square wave.
21. A passenger detection method comprising the steps of:
a field generation step in which a weak alternating electric field is generated by an oscillation means around an antenna electrode which is provided to a portion of a vehicle in front of a seat of the vehicle so as to face a passenger seated on the seat;
a transmission current detection step in which a transmission current which passes in the antenna electrode depending on the weak alternating electric field is detected; and
a judgment step in which the distance between the passenger and the portion of the vehicle is judged based on the transmission current which has been detected in the transmission current detection step.
22. A passenger detection method as claimed in claim 21, further comprising the steps of:
a data communication step in which data concerning the judgment on the distance is sent to an air bag unit; and
an air bag unit setting step in which the air bag unit is set at a deployment mode in which the air bag unit deploys the air bag on collision or a no deployment mode in which the air bag unit does not deploy the air bag on collision according to the data concerning the judgment on the distance.
23. A passenger detection method as claimed in claim 22, wherein in the judgment step, whether the distance between the passenger and the portion of the vehicle is more than a minimum allowable distance or less than the minimum allowable distance is judged by comparing the transmission current detected in the transmission current detection step with a threshold value concerning the transmission current corresponding to the minimum allowable distance, and in the air bag unit setting step, the air bag unit is set at the no deployment mode if the distance is judged to be less than the minimum allowable distance.
24. A passenger detection system as claimed in claim 23, wherein the antenna electrode is provided to the dashboard of a car.
25. A passenger detection method comprising the steps of:
a field generation step in which a weak alternating electric field is generated by an oscillation means around an antenna electrode which is provided to a portion of a vehicle in front of a seat of the vehicle so as to face a passenger seated on the seat;
a transmission current detection step in which a transmission current which passes in the antenna electrode depending on the weak alternating electric field is detected;
a phase difference detection step in which the phase difference between an oscillation signal which is supplied from the oscillation means and an output signal which is supplied to the antenna electrode is detected; and
a judgment step in which the presence or absence of a passenger seated on the seat is judged based on the phase difference which has been detected in the phase difference detection step and the distance between the passenger and the portion of the vehicle is judged based on the transmission current which has been detected in the transmission current detection step.
26. A passenger detection method as claimed in claim 25, further comprising the steps of:
a data communication step in which data concerning the judgment in the judgment step is sent to an air bag unit; and
an air bag unit setting step in which the air bag unit is set at a deployment mode in which the air bag unit deploys the air bag on collision or a no deployment mode in which the air bag unit does not deploy the air bag on collision according to the data concerning the judgment.
27. A passenger detection method as claimed in claim 26, wherein in the judgment step, the presence or absence of a passenger seated on the seat is judged by comparing the phase difference detected in the phase difference detection step with a prestored threshold value concerning the phase difference and whether the distance between the passenger and the portion of the vehicle is more than a minimum allowable distance or less than the minimum allowable distance is judged by comparing the transmission current detected in the transmission current detection step with another threshold value concerning the transmission current corresponding to the minimum allowable distance, and in the air bag unit setting step, the air bag unit is set at the no deployment mode if it is judged that no passenger is seated on the seat or the distance is less than the minimum allowable distance.
28. A passenger detection system as claimed in claim 27, wherein the antenna electrode is provided to the dashboard of a car.
29. A passenger detection system as claimed in claim 25, wherein in the phase difference detection step, the phase difference between the oscillation signal and the output signal is detected by detecting the phase difference between a risingfalling edge of a square wave signal corresponding to the oscillation signal and a risingfalling edge of a square wave signal corresponding to the output signal.
30. A passenger detection system as claimed in claim 25, wherein the oscillation means generates a high frequency low voltage square wave oscillation signal in order to generate the weak alternating electric field.
31. A passenger detection system as claimed in claim 30, wherein an MPU (MicroProcessor Unit) is utilized as the oscillation means for generating the high frequency low voltage square wave oscillation signal.