JP5520177B2 - Battery powered power tool - Google Patents

Description

  The present invention relates to a battery-powered tool that uses a battery as a power source.

  In a battery-type electric tool, for example, a battery-type electric tool that uses a brushless motor as a drive source and a lithium-ion battery as a battery as a power source, as shown in Patent Document 1, a motor control circuit is mounted. If the motor is driven or stopped in response to switch operation, the battery voltage falls below a predetermined value, the motor current value exceeds a predetermined value, or the battery or motor temperature exceeds a predetermined value, Therefore, the motor control circuit stops the motor.

  By the way, since an electronic component (microcomputer) that requires a stable power supply is used for the motor control circuit, if the power supply fluctuates, an error occurs in the measured value of the detection means such as the motor current or the motor control circuit (microcomputer). ) Will not work properly and the motor will not operate correctly, and in recent years, the use of batteries and motors that can supply large currents has increased the opportunity to use them for high-load work. For this reason, the fluctuation of the battery voltage becomes large, and the possibility that the above-mentioned defect appears tends to increase.

JP 2003-164066 A

  This invention is made | formed in view of such a point, and makes it a subject to provide the battery-type electric tool which can perform a motor drive more correctly.

  The present invention uses a battery as a power source and a motor as a drive source, a switch mechanism for instructing to drive and stop the motor, voltage detection means for detecting a voltage value of the battery, and an output of the switch mechanism. An electric tool comprising: motor control means for setting a motor speed based on the output of the voltage detection means; and motor drive means for driving the motor based on the speed setting of the motor control means. Is characterized in that when starting the motor from the stop, the acceleration at the start of rotation at the time of starting the motor is changed according to the battery voltage value before starting the motor detected by the voltage detecting means. doing.

  In this case, when starting the motor based on the output of the switch mechanism, the motor control means starts the motor at a rapid acceleration when the battery voltage value before starting the motor is high, and starts the motor when the battery voltage value is low. Is preferably started at a slow acceleration.

  Further, the motor control means may change acceleration of rising of the rotation of the motor in accordance with a difference value between battery voltage values before and after starting the motor.

  In the present invention, the rising acceleration of the motor rotation at the start of the motor is changed according to the battery voltage value before starting the motor. If the battery voltage value is low, the rapid acceleration that causes a large voltage drop is suppressed and slowed down. By starting with acceleration, it is possible to avoid a situation where the battery voltage falls below the lower limit value that would cause a malfunction due to a voltage drop due to the starting current, and for this reason, the motor can be driven more accurately. it can.

It is a flowchart in an example of an embodiment of the invention. It is operation | movement explanatory drawing same as the above. It is a flowchart of another example. It is the schematic which shows a basic composition. It is a block circuit diagram same as the above. (a) is an operation explanatory diagram at the time of no load, (b) is an operation explanatory diagram at the time of a drill driver, and (c) is an operation explanatory diagram at the time of an impact driver. (a) is explanatory drawing of operation | movement by a drill driver, (c) is explanatory drawing of operation | movement by an impact driver. (a) is an operation explanatory diagram when the battery voltage is high, and (b) is an operation explanatory diagram when the battery voltage is low.

  First, the basic configuration of the battery-type electric tool will be described. In FIGS. 4 and 5, reference numeral 1 denotes a tool body including a motor M as a drive source, a trigger switch S, and a control circuit 2, and 3 denotes a battery as a power source. B is a battery pack that includes B and is detachable from the tool body 1. When the trigger switch S is operated, the motor control circuit 4 supplies a current to the motor M via the FET 5 which is a motor driving means.

  The trigger switch S changes the resistance value of the variable resistor VR according to the pulling operation amount, and turns on the contact S1 when the pulling operation is performed. The motor control circuit 4 that performs PWM control of the FET 5 The motor M is rotated at the number of rotations corresponding to the pulling operation amount of S. That is, when the trigger switch S is pulled in and the contact S1 is turned on, the motor M is rotated at a rotation speed corresponding to the resistance value of the variable resistor VR by PWM control until the pulling operation amount becomes maximum, If retracted, the FET 5 is fully turned on and the motor M is fully rotated.

  The motor control circuit 4 to which a control power supply (for example, 5V) is supplied through the power supply circuit 6 includes a battery voltage measuring unit that measures the battery voltage by a divided value by the voltage dividing resistors R1 and R2. When the partial pressure value is lower than a predetermined value set in advance, the motor M is stopped regardless of the operation of the trigger switch S. In addition, when the battery temperature or the body temperature (motor temperature) becomes too high, the motor control circuit 4 stops the motor M or limits the number of rotations.

  Here, the predetermined value set in advance and the measured value of the battery voltage are stable when the power supplied to the motor control circuit 4 or the AD conversion reference value supplied to the motor control circuit 4 based on the power is stable. It is assumed that For this reason, if the power supply fluctuates, the above assumption will be lost, the voltage value will not be converted accurately, and it will be judged whether rotation is possible with an unexpected voltage value, and the protective function may malfunction, If the motor control circuit 4 composed of a microcomputer is reset or restarted as described above, the program stops, or the motor control is not performed correctly and a problem in use occurs.

  In order to avoid the above problems, the power supply circuit 6 shown in FIG. 2 is equipped with voltage stabilizing components such as a capacitor. However, in recent years, due to the torque increase of the motor M and the development of a battery pack capable of supplying a large current, Since the voltage fluctuation tends to be further increased, the possibility of the above-mentioned problem is high.

  By the way, the behavior of voltage and current when working with an electric tool, particularly the behavior when the trigger switch S is pulled in at a stroke to start the motor M at full rotation, is as follows. That is, when the motor control circuit 4 determines that the battery voltage is sufficient and turns on the FET 5, as shown in FIG. 6, since the motor M starts from 0, the starting current flows greatly. Once the battery voltage suddenly drops. When the motor starts to rotate, as shown in FIG. 6 (a) when there is no load, the motor M only consumes a current of about several A, and the battery voltage drop during rotation is small, but as a drill driver, FIG. When the drilling shown in a) is performed, the load increases as the drill D enters the mating member 9, so that the motor consumption current gradually increases and the voltage decreases until the drill D penetrates the mating material 9. When the screw driver shown in FIG. 7 (b) is used as an impact driver, as shown in FIG. 6 (c), the current value and battery voltage value are almost constant while the screw is hit and screwed. Since the load increases at the time of seating when the head of the screw 8 contacts the counterpart member 9, the current consumed by the motor M increases momentarily and the voltage decreases. In the time charts of FIGS. 6 (a), 6 (b), and 6 (c), the left side shows the case where the battery capacity is full, and the right side shows the case where the battery capacity is low and is nearly empty.

  Here, V2 in the figure is a voltage threshold value at which the motor M is stopped by the low voltage protection when the battery voltage decreases due to the battery capacity approaching empty. In order to prevent the low voltage protection from operating when the voltage drops below the threshold V2 due to an instantaneous voltage sudden drop at the start of the motor, the low voltage protection is performed when the threshold V2 is continuously lowered for a predetermined time. .

  In addition, V1 in FIG. 6 is a lower limit of the battery voltage at which the motor control circuit 4 operates stably, and if it falls below this, the voltage value cannot be accurately converted or reset. Therefore, unlike the threshold V2, regardless of the battery capacity, the instantaneous voltage drop of the starting current should not be less than V1, but in the case where the battery capacity is sufficient, as shown in FIG. As shown in FIG. 8, even when the voltage is not lower than the lower limit value V1, the power supply circuit 6 outputs the voltage lower than the lower limit value V1 as shown in FIG. There is a risk that the voltage value of the control power supply will drop.

  For this reason, in the present invention, when the motor M is started by operating the trigger switch S, the following control is performed. That is, as shown in FIG. 1, if the battery voltage when detecting that the trigger switch S is turned on is equal to or lower than the threshold value V2, the motor control circuit 4 keeps the FET 5 off for low voltage protection, Do not drive.

  Next, the pull-in amount of the trigger switch S is detected. If the pull-in amount is small, the FET is turned on under PWM control as a normal start-up, and the start-up is performed with the rotation speed limited. Since the amount of current supplied to the motor M is originally small, the battery voltage does not become lower than the lower limit value V1.

  And when the pull-in amount of the trigger switch S is large, the control is changed according to the battery voltage value. That is, if the battery voltage is higher than the set value, the FET is turned on as usual, assuming that the battery voltage does not fall below the lower limit value Vl even if the motor M requires a large starting current. However, if the battery voltage is lower than the set value, if the motor M requires a large start-up current, the battery voltage may drop to the lower limit value V1 or less and normal operation may not be ensured. The motor M is started by a slow-up start-up in which the duty ratio is gradually increased by PWM control and finally turned on by 100%. By suppressing the acceleration of the rotation of the motor M and suppressing a rapid current supply / voltage drop, the battery voltage is prevented from dropping below the lower limit value V1.

  It may be set in multiple steps such that the lower the battery voltage when the trigger switch S is operated, the slower the rotational acceleration of the motor M (so that the time required for slow-up activation becomes longer). Of course.

  In this way, even when the trigger switch S is fully retracted and originally started up at full acceleration, depending on the battery voltage, rotation can be started by gradually accelerating through PWM duty control. The situation where the voltage drop causes trouble can be avoided.

  When the processing speed of the motor control circuit 4 is sufficiently high, the slow-up activation may be performed in consideration of the battery voltage immediately after starting to supply current to the motor M. As shown in FIG. 3, the battery voltage value Vd immediately after the FET 5 is turned on by PWM control to start supplying current to the motor M and the trigger switch S before starting the motor M are operated for the slow-up activation. The difference between the battery voltage value V and the battery voltage value V is calculated in the motor control circuit 4, and the difference value (battery voltage drop amount) is large, and the voltage drop is more sudden than expected. If the motor control circuit 4 determines that there is a battery voltage, if the rapid current supply and voltage drop are suppressed by further slowing down the slow-up start-up speed that is 100% on from the PWM control, the battery voltage becomes the lower limit value. Since the possibility of becoming V1 or less can be further reduced, a more reliable motor control operation can be provided.

1 Tool body 2 Control circuit 3 Battery pack 4 Motor control circuit B Battery S Trigger switch M Motor

Claims (3)

  A battery mechanism as a power source, a motor as a drive source, a switch mechanism for instructing to drive and stop the motor, a voltage detection means for detecting the voltage value of the battery, an output of the switch mechanism, and the voltage detection means And a motor driving means for driving the motor based on the speed setting of the motor control means, wherein the motor control means includes the motor control means for setting the motor speed based on the output of the motor control means. When starting a motor from a stop, the battery-type power tool is characterized in that the acceleration at the start of rotation at the time of starting the motor is changed according to the battery voltage value before starting the motor detected by the voltage detecting means. .   When starting the motor based on the output of the switch mechanism, the motor control means starts the motor at a rapid acceleration when the battery voltage value before starting the motor is high, and slowly accelerates the motor when the battery voltage value is low. The battery-powered electric tool according to claim 1, wherein   The battery-powered electric tool according to claim 1 or 2, wherein the motor control means changes acceleration of rising of the rotation of the motor according to a difference value between battery voltage values before and after starting the motor.

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