JP5834240B2 - Electric tool - Google Patents

Description

  The present invention relates to an electric power tool, and more particularly to an electric power tool performing feedback control of a motor rotation speed.

  Many electric tools that use a brushless DC motor as a power source make the motor rotation speed variable by, for example, PWM control and perform feedback control of the motor rotation speed.

  On the other hand, there are two types of work using electric tools: high speed and low torque rotation is desired, and low speed and high torque rotation is desired, and the motor must be rotated so that both types of work can be handled. What outputs to an output part via the reduction gear with a speed change function is provided.

  In such an electric tool with a speed change function, when the feedback control of the motor rotation speed is performed, the feedback control is performed in the same cycle regardless of the shift state.

  In this case, when the reducer is set in a state where low-speed and high-torque rotation can be obtained, and when the reducer is set in a state where high-speed and low-torque rotation can be obtained, the amplitude of the motor rotation speed relative to the target motor rotation speed is the same. It becomes.

Japanese Patent Laid-Open No. 11-090845

  Here, when low speed rotation is selected, it is often preferable that the rotational speed fluctuation associated with the feedback control be as small as possible. However, if the same feedback control is performed as when high speed rotation is selected, It is difficult to reduce the width.

  This invention is made | formed in view of such a point, and makes it a subject to provide the electric tool which can make the pulsation of motor rotation speed small at the time of the operation | work at low speed rotation.

The present invention is an electric tool including a motor as a drive source and a control circuit for feedback control of the rotation speed of the motor for driving control of the motor , through an acceleration / deceleration means having a speed change function. The rotation of the motor is transmitted to the output unit, and the control circuit is in a low speed mode in which the output unit is set to a low speed and a high speed mode in which the output unit is set to a high speed. It is characterized in that the control cycle of the motor rotation speed is slower than that . By changing the control cycle of the feedback control according to the shift setting, the fluctuation range of the rotational speed can be changed.

The control circuit includes: a rotation output mode that directly transmits the rotation of the motor to the output unit; and an impact mode that transmits the rotation of the motor to the output unit via an impact mechanism. than the motor rotational speed control cycle of the output mode, or may be faster motor rotational speed control cycle during the impact mode.

Further, the control circuit increases or decreases the motor rotation speed according to the operation amount of the operation means, and when the operation amount of the operation means is large, the control cycle of the motor rotation speed is accelerated and the operation amount is reduced. When it is small , the motor rotation speed control cycle may be delayed .

  In the present invention, the control cycle is changed in accordance with the setting of the motor rotation speed. When the rotation speed of the final output unit is reduced, the fluctuation width of the motor rotation speed is reduced by delaying the feedback control cycle. Thus, since a rotation with extremely small pulsation can be obtained, the accuracy at the time of working at a low speed can be improved, and it is possible to avoid the occurrence of trouble at the time of working at a high speed.

It is a flowchart which shows operation | movement of an example of embodiment of this invention. It is a schematic sectional drawing same as the above. It is a block circuit diagram same as the above. It is explanatory drawing of a high speed mode and a low speed mode same as the above. (a) is a time chart of the motor speed in the high speed mode, and (b) is a time chart of the motor speed in the low speed mode. It is a flowchart which shows operation | movement of another example. It is a flowchart which shows operation | movement of another example.

  The power tool shown in FIGS. 2 and 3 will be described in detail based on an embodiment of the present invention. The electric power tool shown in FIG. 2 and FIG. Is detachably mounted, and the motor 11 is driven by the current supplied from the battery pack 2. In the tool body 1, the rotational output of the motor 11 is decelerated and output to the output unit 13. A circuit board 39 on which the control circuit 3 for controlling the number of revolutions of the motor 11 and the power supply circuit 30 (see FIG. 3), etc. are mounted according to the pulling amount of the machine 12 and the trigger switch lever 14 is housed.

  When the trigger switch lever 14 is retracted, the control circuit 3 starts power supply to the motor 11 via the switching element 32 when the trigger switch 17 is turned on, and rotates the motor 11. When the trigger switch lever 14 is pulled to the maximum, for example, PWM control is performed so that the motor rotation speed increases as the pull-in amount increases. Fully rotate.

  The control circuit 3 also performs a feedback control (PID control) of the rotational speed using a frequency generator built in the motor 11 and the motor rotational speed target set according to the pulling amount of the trigger switch lever 14. Converge the motor speed to the value. In FIG. 3, 30 is a power supply circuit, 31 is a battery voltage detection circuit, and the control circuit 3 also performs motor control according to the battery voltage detected by the battery voltage detection circuit 31.

The speed reducer 12 in the electric tool has a speed change function for switching the speed reduction ratio to two steps in accordance with the operation of the mode switching lever 15, and the rotation speed of the output unit is as shown in FIG. In addition, a high-speed mode with high speed and low torque and a low-speed mode with low speed and high torque can be selected.

  Here, the control circuit 3 can detect whether the control circuit 3 is in the high speed mode or the low speed mode by the switch 16 which is turned on / off by the operation of the mode switching lever 15. The control circuit 3 performs the above-described feedback control when in the high speed mode. However, when it is detected that the control circuit 3 is in the low speed mode, the control circuit 3 sets the motor rotation speed feedback control cycle to be higher than the feedback control cycle in the high speed mode. Slow down.

  Specifically, as shown in FIG. 1, when in the high speed mode, PWM output to the motor drive circuit including the switching element 32, PWM presence / absence of fluctuation of the pull amount of the trigger switch lever 14, and rotation speed feedback It is determined whether the on-duty needs to be increased or decreased. When it is determined that the on-duty needs to be increased or decreased, the PWM on-duty is increased or decreased to perform the next PWM output. By inserting this step, the motor speed control cycle is made slower than in the high-speed mode.

Since the control gain according to the difference between the target value of the motor speed at the time of feedback control and the detected motor speed is not changed between the high speed mode and the low speed mode, FIG. As shown in a), the motor rotation speed approaches the target value quickly although the amplitude H is large, and in the low speed mode , the motor rotation speed reaches the target value as shown in FIG. The runout width H is reduced. That is, the pulsation of the motor speed is extremely small in the low speed mode.

  In the case where the power tool can be switched to the impact mode in which the impact in the rotational direction is applied, the control cycle may be accelerated in the impact mode, and the control cycle may be delayed in the drill driver mode. FIG. 6 shows a flowchart in this case.

  The impact mode is a mode in which a wooden screw or the like is tightened by repeatedly storing a force in the hammer spring and releasing and applying a rotational impact to the anvil with the hammer. During this time, the rotation of the motor 11 is applied to the spring. The speed is low while the power is stored, and the high speed is high while the shock is released, and the feedback to the motor rotation speed target value requires instantaneous response. Should be faster. On the other hand, in the drill driver mode, the motor rotational speed directly becomes the rotational speed of the output unit via the speed reducer 12, and therefore it is better not to increase the feedback speed compared to the impact mode when work accuracy is required. .

  Therefore, in a power tool that allows switching to the impact mode in addition to the high speed mode and the low speed mode (both drill driver modes) by operating the mode switching lever 15, the feedback control cycle in the impact mode is the most effective. It is better to set the control cycle to be faster or faster than the impact mode in the high-speed mode and the slowest control cycle in the low-speed mode. Note that it is effective to change the control cycle between the impact mode and the drill driver mode even in an electric tool that does not have a speed change function.

  When the motor rotation speed is changed according to the pull-in amount of the trigger switch lever 14, the pull-in amount of the trigger switch lever 14 is increased in order to increase the motor rotation speed as the pull-in amount of the trigger switch lever 14 increases. When the value exceeds a predetermined value, the control cycle may be accelerated, and when the pull-in amount does not reach the predetermined value, the control cycle may be delayed. FIG. 7 shows a flowchart in this case.

  Also in this case, it is effective to change the control cycle in accordance with the pulling amount of the trigger switch lever 14 in an electric tool that does not have a speed change function.

  In each of the above embodiments, the processing cycle for feedback control is changed by changing the control cycle by inserting the step “Wait for a predetermined time”, but the control cycle (time) is also changed by changing the operation clock of the control circuit 3. Target interval) may be changed.

DESCRIPTION OF SYMBOLS 1 Tool main body 2 Battery pack 3 Control circuit 10 Tool main body 11 Motor 12 Reducer 13 Output part

Claims (3)

An electric tool comprising a motor as a drive source and a control circuit for feedback control of the rotation speed of the motor for driving control of the motor,
The rotation of the motor is transmitted to the output unit via the speed increasing / decreasing means having a speed change function, and the control circuit is in a low speed mode in which the output part in the speed setting of the speed increasing / decreasing means is at a low speed. An electric tool characterized in that the motor rotation speed control cycle is made slower than in the high-speed mode in which the output section is at a high speed . A rotation output mode for directly transmitting the rotation of the motor to the output unit; and an impact mode for transmitting the rotation of the motor to the output unit via an impact mechanism. 2. The electric tool according to claim 1 , wherein the motor rotation speed control cycle in the impact mode is made earlier than the motor rotation speed control cycle . The control circuit increases or decreases the motor rotation speed according to the operation amount of the operation means. When the operation amount of the operation means is large, the control cycle of the motor rotation speed is shortened and the operation amount is small. 2. The electric power tool according to claim 1, wherein the control cycle of the motor rotation speed is slowed .

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