JP2019107716A - Electric tool - Google Patents

Abstract

To provide an electric tool by which an operator can recognize increase in a load.SOLUTION: The electric tool comprises: a motor (4); a drive part (8) which drives the motor; a control part (7) which controls the drive part; and a notification part (25, 27) which notifies a state of a load applied to the motor. The control part is so configured as to gradually or stepwisely change plural notification states of the notification part according to a magnitude of a load applied to the motor.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a power tool.

  2. Description of the Related Art Conventionally, an electric circular saw, which is a cutting machine for cutting wood or the like as an electric power tool, has been widely used. For example, Patent Document 1 describes an electric circular saw for protecting the switching element by stopping the motor when the current supplied to the switching element becomes excessive with an increase in load.

JP, 2015-27711, A

  The electric circular saw described in Patent Document 1 has a problem that the operator can not recognize that the load is increasing. For this reason, for example, even if the load applied to the motor is increased, the operator can not work to reduce the load, nor can it be prepared for stopping the motor. In other words, the stop of the motor due to the increase of the load becomes abrupt for the worker. In addition, even if the operation is resumed after the motor is stopped, the cut surface of the workpiece (the smoothness of the cut surface) may become uneven.

  In view of such a subject, an object of the present invention is to provide a power tool which can recognize that a worker is increasing a load.

  In order to achieve the above object, the present invention comprises a motor, a drive unit for driving the motor, a control unit for controlling the drive unit, and a notification unit for notifying a state of a load applied to the motor. The control unit may be configured to gradually or stepwise change a plurality of notification states of the notification unit according to the size of a load applied to the motor. There is. According to such an electric power tool, since the state of the notification unit is changed according to the load applied to the motor, it is possible to make the operator recognize the change of the load based on the state of the notification unit.

  It is preferable that the control unit changes a state notified by the notification unit according to a load applied to the motor before the load on the motor increases and the motor stops. Further, the control unit stops the motor when the load exceeds the allowable range, and the control unit is configured to shift to an overload state in which the load exceeds a predetermined magnitude within the allowable range. Preferably, the state notified by the notification unit is changed according to the load.

  According to such a power tool, it is possible to make the operator recognize a change in load before an overload is applied.

  It is preferable that the control unit maintain a constant state in which the notification unit notifies that the load has a predetermined magnitude after the motor starts rotating.

  The control unit can execute constant speed control for maintaining the rotational speed of the motor at a predetermined speed, and the control unit applies a load to the motor that can not maintain the constant speed control. It is preferable to change the state which the said alerting | reporting part alert | reports later according to the said load.

  According to such an electric power tool, it is possible to cause the operator to recognize that a load that can not maintain constant speed control is applied to the motor.

  The control unit further includes at least one of a rotation speed detection unit that detects the rotation speed of the motor and a current detection unit that detects a current value flowing to the motor, and the control unit determines that the rotation speed is less than a predetermined rotation speed or the current Preferably, the notification state of the notification unit is changed when the value becomes equal to or greater than a predetermined current value.

  According to such a power tool, it is possible to make the operator recognize the change in load by specifying the load by the rotational speed or the current value.

  The notification unit is a lighting device capable of emitting light, and the control unit preferably changes the amount of light emitted by the notification unit according to a load applied to the motor.

  According to such a power tool, it is possible to make the operator recognize the change in load by the change in the amount of light emitted by the notification unit.

  It is preferable that the control unit changes the amount of light emitted by the notification unit according to the load after the load applied to the motor exceeds a predetermined size.

  According to such an electric power tool, when the load applied to the motor exceeds a predetermined size, it is possible to make the operator recognize the change of the load by the change of the amount of light irradiated by the notification unit.

  Preferably, the notification unit is a lighting device capable of emitting light, and the control unit gradually or stepwise changes the amount of light emitted by the notification unit according to a load applied to the motor. It is preferable that the control unit gradually or stepwise reduce the amount of light emitted by the notification unit as the load increases.

  According to such a power tool, the reduction in the amount of light can allow the operator to recognize the degree of the load.

  Preferably, the control unit gradually or stepwise increases the amount of light emitted by the notification unit as the load increases.

  According to such a power tool, it is possible to make the operator recognize the degree of the load by increasing the amount of light.

  The control unit changes the state notified by the notification unit when the load is the first load after the load applied to the motor exceeds a predetermined magnitude, to the first state, and the load is the load. It is preferable to change the state notified by the notification unit to the second state when the second load is larger than the first load. It is preferable that the control unit continuously change the state of notification by the notification unit according to the load when the load applied to the motor exceeds a predetermined magnitude.

  The control unit may further include a switching unit that performs a switching operation to switch the notification unit between an on state and an off state, and the control unit gradually or stepwise changes the duty ratio of the switching operation according to a load applied to the motor. Is preferred. Preferably, the control unit gradually or stepwise reduces the duty ratio as the load increases. Preferably, the controller increases the duty ratio gradually or stepwise as the load increases.

  The present invention also includes a motor, a drive unit for driving the motor, a control unit for controlling the drive unit, and a notification unit, and the control unit increases the load on the motor to increase the load. According to the present invention, there is provided the electric power tool characterized in that the state notified by the notification unit is changed according to the magnitude of the load before the motor stops. According to such an electric power tool, since the state of the notification unit is changed according to the load applied to the motor, it is possible to make the operator recognize the change of the load based on the state of the notification unit.

  Furthermore, the present invention includes a motor, a drive unit that drives the motor, a control unit that controls the drive unit, and a notification unit, and the control unit sets the rotational speed of the motor to a predetermined speed. The constant speed control to be maintained can be executed, and the control unit changes the state notified by the notification unit according to the load when a load impossible to maintain the constant speed control is applied to the motor. An electric power tool characterized by According to such an electric power tool, it is possible to cause the operator to recognize that a load that can not maintain constant speed control is applied to the motor.

  In order to solve the above-mentioned subject, the present invention provides an electric tool which can recognize that a worker is increasing load.

BRIEF DESCRIPTION OF THE DRAWINGS It is an external view of the electric circular saw in the 1st Embodiment of this invention. It is a block diagram which shows the electric constitution of the electrically-driven circular saw of the 1st Embodiment of this invention. It is the graph which showed the relationship between the rotational speed of a motor and the 2nd duty ratio to the electric current in a 1st embodiment of the present invention. It is a flow chart explaining the main processing in a 1st embodiment of the present invention. It is a timing chart explaining the main processing in a 1st embodiment of the present invention. It is a flow chart explaining the main processing in a 2nd embodiment of the present invention. It is an external view of the bench-top circular saw in the modification of this invention.

  A cordless electric circular saw 1 which is an example of a cutting machine according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 5. The electric circular saw 1 is an electric cutting machine for cutting a workpiece such as wood.

  In the following description, “front” shown in the drawings is defined as a front direction, “rear” as a rear direction, and “upper” as an upper direction. When dimensions, numerical values, etc. are referred to in this specification, not only dimensions and numerical values that completely coincide with the dimensions, numerical values, etc., but also substantially identical dimensions, numerical values, etc. (for example, Shall be included. Similarly, “substantially the same”, “substantially orthogonal”, “substantially parallel”, “substantially identical”, “identical”, “orthogonal”, “parallel”, “coincidence”, “uniform”, “constant”, etc. It is assumed that “substantially flush”, “substantially constant” and the like are included.

  As shown in FIGS. 1 and 2, the electric circular saw 1 has a base 2, a housing 3 supporting a circular saw blade P 1, a motor 4, and a battery pack 5.

  The base 2 is made of metal such as aluminum, for example, and has a substantially rectangular shape in a bottom view. The base 2 is formed with an elongated hole extending in the front-rear direction that allows the circular saw blade P1 to enter. The bottom surface of the base 2 is a sliding surface that slides on the workpiece during the cutting operation.

  The housing 3 is provided on the top of the base 2 and accommodates the motor 4. The housing 3 has a gripping portion 31 which can be gripped by a worker. The grip portion 31 is provided with a trigger 32 interlocked with a manually operable trigger switch 32A (FIG. 2). The operator operates the trigger 32 to rotate the motor 4. When the motor 4 rotates, the power of the motor 4 is transmitted to the circular saw blade P1 by a power transmission mechanism (not shown), and the cutting operation of the workpiece by the circular saw blade P1 can be performed.

  An LED light 25 as an illumination device is provided in front of the grip portion 31. The LED light 25 can emit light to the workpiece placed under the base 2. The LED light 25 irradiates light to a place where the workpiece is cut by the circular saw blade P1.

  The battery pack 5 is removably attached to the rear of the housing 31 and accommodates a plurality of battery cells inside. The battery cell type is not particularly limited, and an arbitrary secondary battery is targeted, but in the present embodiment, an example using a lithium ion battery for the battery cell will be described.

  FIG. 2 is a block diagram showing the electrical configuration of the motorized circular saw 1. As shown in FIG. 2, the motorized circular saw 1 includes a motor 4, a control circuit 7, a switching circuit 8, a thermistor 9, a Hall IC 10, a shunt resistor 71, a power supply circuit 72, and a voltage detection circuit 73. , A battery connection terminal 11, a trigger switch 32A, an LED light 25, and a transistor 15. The control circuit 7 is an example of a control unit. The switching circuit 8 is an example of a drive unit. The shunt resistor 71 is an example of a current detection unit. The Hall IC 10 is an example of a rotational speed detection unit. The LED light 25 is an example of a notification unit.

  The battery connection terminal 11 is connectable to a terminal (not shown) of the battery pack 5 and has a plus terminal 11A, a minus terminal 11B, and a signal terminal 11C. The plus terminal 11A and the minus terminal 11B are respectively connected to the not-shown plus terminal and minus terminal of the battery pack 5, and receive DC power from the battery pack 5. The signal terminal 11C is connected to a signal terminal (not shown) of the battery pack 5 and receives a stop signal output from the battery pack 5. When the battery pack 5 is connected to the housing 3 and the current output from the battery pack 5 exceeds a predetermined current value, the battery pack 5 determines that it is in an overcurrent state, and outputs a stop signal to the signal terminal 11C. Do. In addition, when the voltage of the battery cell falls below a predetermined voltage value, the battery pack 5 determines that the battery is over-discharged, and outputs a stop signal to the signal terminal 11C.

  The motor 4 is a three-phase brushless DC motor. The motor 4 has a stator (not shown) and a rotor rotatable relative to the stator. The power of the rotor is transmitted to the circular saw blade P1 by a power transmission mechanism (not shown) to rotate the circular saw blade P1.

  The switching circuit 8 is connected to the terminals 11A and 11B and the motor 4. The switching circuit 8 includes a drive circuit (not shown) and a plurality of switching elements (for example, FETs), and receives power from the battery pack 5 via the terminals 11A and 11B and outputs the power to the motor 4 4 can be rotated. At this time, a drive circuit (not shown) drives an FET (not shown) with a first pulse width modulation signal (hereinafter referred to as a first PWM signal).

  The shunt resistor 71 is provided between the switching circuit 8 and the negative terminal 11B. The shunt resistor 71 is for detecting the current output from the battery pack 5, and the control circuit 7 detects the current supplied from the battery pack 5 based on the voltage drop due to the shunt resistor 71.

  The power supply circuit 72 is a circuit that converts the voltage of the battery pack 5 into a power supply voltage (for example, 5 V) of the control circuit 7. The voltage detection circuit 73 includes two resistors (not shown), and the control circuit 7 measures the voltage of the positive terminal 11A (battery pack 5) based on the voltage division of the two resistors.

  The thermistor 9 is provided in the vicinity of the switching circuit 8 and detects the temperature of the switching circuit 8 (for example, a FET which is a switching element). The thermistor 9 is connected to the control circuit 7 and transmits a temperature signal indicating the detected temperature to the control circuit 7.

  The Hall IC 10 is provided in the vicinity of the rotor (not shown) of the motor 4 and detects the rotational speed (the number of revolutions per unit time) of the rotor (not shown) of the motor 4. The Hall IC 10 is connected to the control circuit 7 and transmits a rotation speed signal indicating the detected rotation speed to the control circuit 7.

  The LED light 25 is connected to the control circuit 7 via the transistor 15. When the transistor 15 is in the on state, the LED light 25 emits light toward the workpiece (the point to be cut by the circular saw blade). In the present embodiment, the LED light 25 applies light to the area on the left side of the circular saw blade P1 in the workpiece. The transistor 15 constitutes a switching unit.

  The control circuit 7 is, for example, a microcomputer, and is connected to the power supply circuit 72, the voltage detection circuit 73, the shunt resistor 71, the switching circuit 8, the trigger switch 32A, and the like. The control circuit 7 receives the drive power generated by the power supply circuit 72 and operates. The control circuit 7 can receive the motor stop signal sent from the battery pack 5 via the terminal 11C. The control circuit 7 stops or restricts the rotation of the motor 4 via the switching circuit 8 when the motor stop signal is received.

  The control circuit 7 controls the switching operation of the switching circuit 8 based on the rotational speed signal received from the Hall IC 10. In the present embodiment, the control circuit 7 can perform constant speed control to rotate the motor 4 at a predetermined rotation speed RC (FIG. 3) by controlling the switching operation. At this time, the control circuit 7 sets the first duty ratio based on the rotational speed signal, and outputs the set first duty ratio to the switching circuit 8. The first duty ratio is a ratio of the on period to a predetermined period in the first PWM signal. The drive unit of the switching circuit 8 generates a first PWM signal having the received first duty ratio, and drives an FET (not shown) by the first PWM signal. Thereby, the motor 4 is rotated at a predetermined rotational speed RC. For example, the case where the load of the motor 4 is changed to multiple stages will be described. When the load of the motor 4 is set to the duty ratio A (less than 100%) as the first duty ratio in a state of a predetermined load (first load), the motor 4 has a second load that is larger than the first load. Since the rotational speed of 4 is lower than the predetermined rotational speed RC, the control circuit 7 sets the first duty ratio to the duty ratio B increased from the duty ratio A so as to maintain the motor 4 at the predetermined rotational speed RC. Set Further, when the third load is larger than the second load, the duty ratio C is set to be larger than the duty ratio B. Conversely, when the load of the motor 4 becomes a fourth load smaller than the first load, the rotational speed of the motor 4 increases more than the predetermined rotational speed RC. Therefore, the duty ratio D obtained by reducing the first duty ratio from the duty ratio A Set to That is, the first duty ratio is adjusted according to the increase or decrease of the load of the motor 4, and the first duty ratio is increased if the load is increased with respect to a predetermined load, and the first duty ratio is decreased if the load is reduced. Thus, constant speed control is performed while maintaining the rotational speed of the motor 4 at a predetermined rotational speed RC (area of current 0 to IC in FIG. 3 described later). Here, the first duty ratio is a duty ratio for maintaining the rotational speed of the motor 4 constant, and is not a fixed value because it changes according to the load. If the load is too large (for example, larger than the third load), even if the first duty ratio is 100%, the rotational speed of the motor 4 can not be maintained constant (constant speed control), which increases the load. Accordingly, the rotational speed of the motor 4 is reduced (a region exceeding the current IC of FIG. 3 described later).

  The trigger switch 32A is interlocked with the trigger 32 of FIG. When the trigger 32 is pulled by a worker, the trigger switch 32A outputs an ON signal to the control circuit 7. The control circuit 7 starts the switching operation of the switching circuit 8 when receiving the on signal from the trigger switch 32A. Thereby, the rotation of the motor 4 is started. When the trigger 32 is not pulled by the operator, the trigger switch 32A stops the output of the on signal. The control circuit 7 stops the switching operation of the switching circuit 8 when detecting that the output of the on signal is stopped. Thereby, the motor 4 is stopped.

  The control circuit 7 lights the LED light 25 by the second PWM control. Here, the second PWM control is control for switching on / off of the transistor 15 using a second pulse width modulation signal (second PWM signal). The control circuit 7 sets a second duty ratio, generates a second PWM signal based on the second duty ratio, and outputs the second PWM signal to the base of the transistor 15. The second duty ratio is a ratio of the on period to a predetermined period in the second PWM signal. In the present embodiment, control circuit 7 determines the second duty ratio based on the rotational speed of motor 4. Although the LED light 25 blinks strictly because the transistor 15 is switched on and off by the second PWM control, the period of the output signal in the second PWM control is sufficiently short. At the duty ratio, the LED light 25 appears to be always on. However, since the time average of the light amount decreases as the second duty ratio decreases, the light amount appears to the eye of the operator. In addition, when the second duty ratio is 0 or near, the LED light 25 appears to be off to the eyes of the worker. Hereinafter, the time average of the light amount is simply referred to as the light amount.

  Next, referring to FIG. 3, a method of setting the second duty ratio of the present embodiment will be described. FIG. 3 is a graph showing the relationship between the current flowing through the motor 4 (horizontal axis), the rotational speed (the number of revolutions per unit time of the motor 4), and the second duty ratio (both vertical axes). The solid line indicated by [1] in FIG. 3 represents the second duty ratio of the present embodiment. When constant speed control is performed, the rotational speed is constant at RC. In detail, even if the load of the motor 4 increases, the motor 4 can perform constant speed control up to the current value IC (third predetermined value). That is, the first duty ratio is adjusted according to the load of the motor 4 to control the motor 4 at a constant speed. Here, the load indicates a torque acting in the direction to stop the rotation of the motor 4. When the load further increases after the current reaches the IC, the current also increases, and even if the first duty ratio is set to 100%, the rotational speed of the motor 4 can not be maintained constant and the rotational speed increases the load. It decreases according to. When the load increases and the current reaches IE, the motor 4 is stopped by the load. As shown in FIG. 3, when the current is ID (second predetermined value) larger than IC, the rotation speed is RD, and when the current is IS (first predetermined value) larger than ID, the rotation speed Is RS. Thus, if the load increases after leaving the area where constant speed control is possible, the current increases and the rotational speed decreases. In other words, after shifting to constant speed control, if it deviates from the area where constant speed control is possible (current is 0 to IC) (if current is larger than IC), the current and rotation speed must be estimated load. Is a possible indicator. Although it has been described in FIG. 3 that the current increases to IE in order to explain the load applied to the motor 4, in the present embodiment, an overcurrent is prevented from being output from the battery cell in the battery pack 5. In order to stop the motor 4 at the current IS between the current IE and the IC, the over-current protection control is performed. Therefore, no current larger than the current value IS flows in the motor 4 in actual work.

  In the present embodiment, when the current reaches a current value ID between IC and IS, the motor 4 shifts to the overload state. In other words, when the rotational speed becomes RD between RC and RS, the motor 4 shifts to the overload state. That is, the control circuit 7 determines that the overload state has occurred based on the current value flowing to the motor 4 or the rotational speed of the motor 4. For example, the state of the rotational speed RD, which is the initial state of the overload state, may decrease the rotational speed of the motor 4 and the efficiency of the cutting operation may become unacceptable depending on the type of workpiece. It is not necessary to stop the motor 4 but it is necessary to stop the motor 4 when the load further increases. In addition, when the current is IS and the rotational speed is RS (when the overcurrent protection control is performed to stop the motor 4), an overload state may be set. Hereinafter, when the current is IS and the rotational speed is RS (when the overcurrent protection control is performed to stop the motor 4) is referred to as a second overload state.

  When a load that can not maintain constant speed control is applied (that is, when it is greater than current IC or falls below rotation speed RC), the rotation speed is R, the current value of motor 4 is I, and K1 is a positive constant Then, the relationship between R and I in FIG. 3 is as shown in the following equation (1).

(1)
R = RC−K1 × (I−IC) Formula (1)

  That is, after the constant speed control can not be maintained due to the load, the rotational speed R decreases as the current value I increases.

  In the present embodiment, the second duty ratio is 100% in constant speed control. When the load increases after leaving the constant speed control region (after the first duty ratio is set to 100%), the second duty ratio is continuously (slowly) reduced according to the load. In other words, when the rotational speed becomes less than RC (when the current becomes larger than IC) after leaving the constant speed control region, the second duty ratio is decreased according to the decrease in the rotational speed (the increase of the current). More specifically, assuming that the second duty ratio is D and K2 is a positive constant when a load that can not maintain constant speed control is applied, the relationship between D and R is given by the following equation (2): Become.

(2)
D = 100-K2 x (RC-R) Formula (2)

  Here, RC-R indicates an increment of load from the time when constant speed control is finished (out of the constant speed control area). Therefore, the second duty ratio D continuously (slowly) decreases as the load on the motor 4 increases. In other words, the second duty ratio is set to decrease as the rotational speed decreases (the current increases). The amount of light of the LED light 25 decreases as the load increases, so that the worker can estimate the increase in the load from the brightness of the LED light 25. In addition, since the material to be cut is difficult to see because the amount of light irradiated to the material to be processed is reduced, it is possible to prompt the operator to interrupt the work.

  Before the control circuit 7 determines that the motor 4 is in the second overload state (before determining that the motor 4 needs to be stopped in the overload state and before the rotational speed decreases to RS, the current reaches IS). Before the increase), the duty ratio is reduced according to the load. This makes it possible to notify the user of the increase in load at a timing sufficiently before the rotation of the motor 4 is stopped and before the transition to the second overload state.

  The second duty ratio D can also be expressed by the following equation (3) using a positive constant K3 (product of K1 and K2).

(Number 3)
D = 100-K3 x (I-IC) Formula (3)

  FIG. 4 is a flow chart for explaining the main processing for realizing the control of FIG. At S1, the control circuit 7 stands by until the trigger switch 32A is turned on. When the trigger switch 32A is turned on (S1: YES), in S3, the control circuit 7 causes the switching circuit 8 to execute a switching operation to start the motor 4. At this time, the control circuit 7 sets the second duty ratio to 100% to light the LED light 25. At S5, when the rotational speed of the motor 4 increases and reaches a predetermined rotational speed RC, the control circuit 7 performs constant speed control. In constant speed control, the first duty ratio in the switching operation of the motor 4 is adjusted to maintain the rotational speed of the motor 4 at a constant RC. The control circuit 7 keeps the second duty ratio at 100% and lights the LED light 25 until the rotational speed reaches the predetermined rotational speed RC.

  In S7, the control circuit 7 detects the value of the current supplied to the switching circuit 8 (motor 4) using the shunt resistor 71. Also in the battery pack 5, the value of the current and the voltage of the battery cell are detected.

  At S9, the control circuit 7 determines whether the rotational speed of the motor 4 is less than a predetermined rotational speed RC. As described above, in the state where constant speed control is performed in a state where the first duty ratio is set to 100%, when the load is further increased, the rotational speed can not be maintained constant, and the rotational speed of the motor 4 is descend. Therefore, it is possible to determine whether the load applied to the motor 4 is increasing by the determination of S9. In S9, it may be determined whether the current supplied to the motor 4 is larger than the IC, and it may be determined whether the load applied to the motor 4 is increasing. Alternatively, it may be determined that the load is increasing when the rotational speed is less than the predetermined rotational speed RC and the current is larger than the IC. If a negative determination is made in S9, the rotational speed RC can be maintained, so the control circuit 7 sets the second duty ratio to 100% in S11.

  On the other hand, when the positive determination is made in S9, the rotational speed RC can not be maintained even if the first duty ratio is set to 100%. Therefore, based on the rotational speed of the motor 4 in S13 2 Determine the duty ratio. Specifically, the second duty ratio is determined using equation (2). In the equation (2), since the rotational speed decreases as the load applied to the motor 4 is large, the second duty ratio is set to a value corresponding to the load applied to the motor 4.

  When S13 or S11 is executed, in S15, the control circuit 7 drives the transistor 15 with the set second duty ratio to cause the LED light 25 to emit light.

  At S17, the control circuit 7 determines whether the current value detected at S7 is larger than IS. When an affirmative determination is made in S17, the control circuit 7 stops the motor 4. That is, the operation of the switching circuit 8 is stopped. This can prevent the overcurrent from being output from the battery cells of the battery pack 5. The control circuit 7 also stops the motor 4 when a stop signal is input from the battery pack 5 via the signal terminal 11C.

  If a negative determination is made in S17, the control circuit 7 detects the temperature of the switching circuit 8 based on the temperature signal from the thermistor 9 in S19, and determines whether the detected temperature is equal to or higher than a predetermined heating protection temperature Do. When an affirmative determination is made in S19, the control circuit 7 stops the motor 4. Thereby, the switching circuit 8 can be prevented from being burnt out.

  If a negative determination is made in S19, it is determined in S21 whether the trigger switch 32A has been turned off. When an affirmative determination is made in S21, the control circuit 7 stops the motor 4.

  If a negative determination is made in S21, the control circuit 7 returns to S7.

  FIG. 5 is a timing chart showing the current and rotational speed of the motor 4 and the second duty ratio in the process of FIG.

  At time T1, when the trigger switch 32A is turned on, the current supplied to the motor 4 rapidly increases due to the transient current (starting current). Since this excessive current is generated instantaneously, the control circuit 7 ignores the excessive current and continues control of the motor 4 and the LED light 25. After activation of the motor 4, the control circuit 7 sets the second duty ratio to 100% and lights the LED light 25. The control circuit 7 maintains 100% until time T4 when constant speed control ends. In the period from time T2 to T3, the rotational speed of the motor 4 is increased, and the current of the motor 4 is decreased. At time T3, the rotational speed of the motor 4 reaches a predetermined rotational speed RC, and constant speed control is performed.

  The constant speed control is executed until time T4, and the current flowing to the motor 4 changes according to the load. Constant speed control is performed by adjusting the first duty ratio according to the load. That is, the first duty ratio is increased to 100% as the load increases. At time T4, when the load increases and the first duty ratio can not be increased, constant speed control can not be realized, and thereafter the rotational speed of the motor 4 gradually decreases. After time T4, the control circuit 7 changes the second duty ratio according to the rotational speed, and changes the light amount of the LED light 25. Thereby, after time T4, the light quantity of the LED light 25 decreases with the increase of the load. Although not shown in FIG. 5, according to the main processing shown in FIG. 4, if the load is reduced, the light amount of the LED light 25 increases.

  After time T5, the load further increases and the rotational speed sharply decreases. For this reason, the second duty ratio also decreases sharply. At time T6, the control circuit 7 stops the motor 4 because the value of the current flowing through the motor 4 becomes IS. At this time, the second duty ratio becomes 0 and the LED light 25 is turned off.

According to the control of the electric circular saw 1 described above, the second duty ratio of the second PWM signal is set according to the rotation speed of the motor 4. Since the second duty ratio also decreases as the rotational speed of the motor 4 decreases, the worker recognizes that the light amount decreases, and the load increases before the motor 4 stops due to an overload state. It can be judged. As a result, the operator can determine that the motor 4 may stop if the load further increases. Since the amount of light decreases with an increase in load, for example, when the motor 4 is stopped for over current protection (S17) or heating protection (S19), the worker feels that the motor 4 has suddenly stopped Can be suppressed. Alternatively, the worker can interrupt the operation or switch to an operation to reduce the load as the light amount decreases. In the case of a power tool that performs constant speed control, for example, a cutting tool such as an electric circular saw 1, when the constant speed control can not be performed during work, the work is performed in a state where the cut surface of the cut surface of the workpiece becomes worse May continue. Therefore, such a thing can be suppressed by alerting | reporting to an operator immediately, when it remove | deviates from a constant speed control area | region. Further, in the case of a tightening tool such as a driver, the possibility of unevenness in tightening torque can be suppressed.
Second Embodiment

  The configuration of the power tool 1 according to the second embodiment is the same as the power tool 1 according to the first embodiment except for the following points. Therefore, only the configuration different from the first embodiment will be described here, and the description of the other configurations will be omitted.

  As shown in FIG. 2, the electric circular saw 1 according to the second embodiment further includes an LED light 27 and a transistor 17. As shown in FIG. 1, the LED light 25 irradiates light to the work material on the left side of the worker (left side of the circular saw blade P1), but the LED light 27 is on the right side of the worker (circular saw blade P1) In the right side of the figure, light is irradiated to the work material (cutting point). With such a configuration, the workpiece can be irradiated with light in the left and right regions of the circular saw blade P1. Since light is irradiated from the left and right sides of the circular saw blade P1, it is possible to suppress that the shadow of the circular saw blade P1 can be formed on the workpiece. The other configurations of the LED light 27 and the transistor 17 are the same as the configurations of the LED light 25 and the transistor 15, and therefore the description thereof is omitted.

  FIG. 6 is a flowchart for explaining the main processing of the second embodiment. In the second embodiment, the control circuit 7 generates a second PWM signal and a third PWM signal for controlling the LED lights 25 and 27, respectively. The second PWM signal and the third PWM signal have a second duty ratio and a third duty ratio, respectively. The control circuit 7 sets the second duty ratio and the third duty ratio, and drives the transistors 15 and 17 by the second PWM signal and the third PWM control based on the second duty ratio and the third duty ratio. The second duty ratio and the third duty ratio are both 100% from the start of the main process to the process of S5.

  The determination of S30 is the same as S9 of FIG. If a negative determination is made in S30, the control circuit 7 sets both the second duty ratio and the third duty ratio to 100% in S31.

  On the other hand, if an affirmative determination is made in S30, the control circuit 7 sets the second duty ratio to 100% and determines the third duty ratio based on the rotational speed of the motor 4 in S33. Specifically, the third duty ratio is determined using equation (2). That is, in the second embodiment, the LED light 25 is always lit based on the second duty ratio of 100%, whereas the LED light 27 is set to the third duty set according to the load such as the rotational speed. Lights in ratio.

According to the main processing of the second embodiment, the LED light 25 is always lit at the second duty ratio of 100%, whereas the LED light 27 is lit at the third duty ratio according to the rotational speed. Do. Since the LED light 25 is always lighted with sufficient brightness to perform work, it is possible to suppress deterioration in workability. At the same time, the LED light 27 makes it possible for the worker to recognize that the load is increasing, so that the same effect as that of the first embodiment can be obtained.
(Modification)

  The power tool according to the present invention is not limited to the embodiment described above, and various modifications and improvements are possible within the scope of the claims.

  For example, although the electric circular saw 1 has been described as an example of the electric power tool, the main process shown in FIG. 4 may be performed in the control of the tabletop circular saw 101 shown in FIG. 7. The desktop circular saw 101 has a circular saw blade P2, an LED light 125 for irradiating light to a work material, and a transistor for driving the LED light 125. The desktop circular saw 101 performs the main processing shown in FIG. 4 to determine the duty ratio of the PWM signal output to the transistor for driving the LED light 125.

  The desktop circular saw 101 is operated by an AC power supply. Therefore, the motor 4 is stopped not to protect the battery cells of the battery pack 5 from outputting an overcurrent but to prevent the motor 4 and the switching circuit 8 from being burnt out by the overcurrent. The electric circular saw 1 may also operate with an AC power supply.

  Further, an LED light (not shown) may be added to the LED light 125 shown in FIG. 7 and the main processing of FIG. 6 may be performed. In this case, the left and right of the circular saw blade P2 are irradiated with light by the LED light 125 and the added LED light, and the worker is notified of an increase in load by reducing the light amount of any of the LED lights. it can. In this case, if the LED light to be added is provided on the left or right side or on both left and right sides of the circular saw blade P2 similarly to the LED light 25, it is possible to make the cut portion easy to see.

  The electric power tool may be, for example, an electric drill, an impact wrench, or the like in addition to the bench-top circular saw 101.

Further, the configuration for notifying the worker that the load is increasing is not limited to the LED light, and
It may be a configuration that can notify the worker that the load is increasing and that the motor 4 may stop, and can also notify the degree of the load. For example, a speaker or the like is provided on the motorized circular saw 1, and the speaker makes a beep at the stage when the load reaches a predetermined level (the stage when the rotational speed becomes less than RC or the stage when the current becomes larger than the IC). And the volume of the buzzer may be increased as the current increases.

  In the second embodiment, the second duty ratio for lighting the LED light 25 may be changed according to the rotation speed, and the third duty ratio for lighting the LED light 27 may be 100%. Alternatively, the second duty ratio and the third duty ratio may be set in accordance with the rotational speed of both the LED lights 25 and 27.

  In the above embodiment, the setting of the second duty ratio is determined according to the rotational speed based on the equation (2). However, the second duty ratio is not limited to the equation (2) as long as it is set according to the load. Equation (3) may be used to determine based on the current. In this case, the second duty ratio may be maintained at 100% immediately after the start of the motor 4 until the predetermined period ends, in consideration of the transient current at the start of the motor 4. Alternatively, the second duty ratio may be set based on the reciprocal of the current.

  The method of setting the second duty ratio in S13 may be changed. For example, the second duty ratio may be set as indicated by [2] to [4] in the dotted line in FIG.

  For example, in [2], the second duty ratio is set to about 60% when the rotational speed becomes less than RC (when the current becomes larger than IC). In this case, since the second duty ratio instantaneously decreases to about 60% from 100%, the light amount of the LED light 25 rapidly decreases. Such a sudden change in the light quantity causes the load on the operator to increase, making it easy to notice that the overcurrent protection stop is approaching. When the current value becomes larger than IC, the second duty ratio is set to be proportional to the change in rotational speed (RC-R).

  In the case of [3], the second duty ratio is set to a discontinuous value, that is, any of a plurality of discrete values. That is, the second duty ratio is set to a first value less than 100% for the rotational speed from RC to RD (current from IC to ID), and the second value for ID to IS is smaller than the first value Set to In such a case, as the load increases, the amount of light gradually decreases by gradually reducing the second duty ratio.

  As shown in the first embodiment and [1] to [3], the second duty ratio decreases monotonously (gradually or stepwise) when the current reaches the IC which is a predetermined value. The LED light 25 may be turned off when the rotational speed reaches RS (or the current reaches IS).

  In the case of [4], the LED light 25 is extinguished by maintaining the second duty ratio at 0 until constant speed control is finished (until the current becomes IC). The second duty ratio is set to a value larger than 0 when the current IC is achieved, and thereafter, the second duty ratio is set to increase in proportion to (I-IC) or (RC-R). . As described above, the second duty ratio may be monotonously (progressively) increased with an increase in load when the current reaches IC which is a predetermined value. Further, the second duty ratio may be increased stepwise as the load increases. For example, some power tools may have a mode in which the LED light is turned off by the operation of the worker, but also in this case when the control is performed as in [4] and the load increases. By automatically turning on the LED light 25, it is possible to notify an operator of an increase in load.

  In the above embodiment, the setting of the second duty ratio in the motorized circular saw 1 performing constant speed control has been described, but switching between the power tool not performing constant speed control and the mode performing constant speed control and the mode not performing The second duty ratio may be set according to the load of the motor 4 in a possible power tool or the like. As described above, when constant speed control is not performed, the second duty ratio is maintained at 100% until the target rotational speed is reached after the motor 4 is started, and the stage is reduced from the target rotational speed. Second, the duty ratio may be changed. The target rotational speed may be the rotational speed achievable at the maximum current allowed in the power tool.

  The LED light 25 may emit light of a plurality of colors such as white, green and red, and these colors may be changed according to the load. For example, in constant speed control, white light is irradiated, and when load increases and constant speed control can not be realized, switching to green light and switching to red light when load further increases It is also good. Furthermore, the duty ratio of the PWM signal at the time of lighting each light may be changed.

  Alternatively, the LED light 25 may blink as the load increases. The blinking here is blinking with a cycle that is recognizable by the operator. In this case, the control circuit 7 may perform control to turn on and off the transistor 15 in a cycle longer than the cycle of the second PWM signal. In addition, as the load increases, the blinking cycle may be shortened. Alternatively, the flashing cycle may be extended as the load increases.

  In S17 of FIG. 4, the control circuit 7 determines the overcurrent based on the current detection by the shunt resistor 71. For example, when the motor stop signal is received from the battery pack 5, it is determined that the overcurrent is generated. The motor 4 may be stopped.

  Further, in the above embodiment, the motor 4 is stopped when it is determined that the overcurrent is for the purpose of protecting the battery cells of the battery pack 5 in S17. However, the circuit elements such as the motor 4 and the switching circuit 8 The determination of overcurrent may be made for the purpose of protecting the The current value serving as a threshold value for determining the over current may be determined according to the protection target.

1 electric circular saw 3 casing 4 motor
Reference Signs List 7 control circuit 8 switching circuit 25 27 LED light 15 17 transistor 5 battery pack

Claims (14)

Motor,
A drive unit for driving the motor;
A control unit that controls the drive unit;
And a notification unit for notifying of a state of a load applied to the motor,
The power tool according to claim 1, wherein the control unit is configured to gradually or stepwise change the plurality of notification states of the notification unit according to the magnitude of a load applied to the motor.   The said control part changes the state which the said alerting | reporting part alert | reports according to the load concerning the said motor, before the load concerning the said motor increases and the said motor stops. Electric tool.   The said control part maintains the state which the said alerting | reporting part alert | reports uniformly until the said load becomes a predetermined magnitude | size, after the said motor starts rotation. Power tools. The control unit is capable of executing constant speed control for maintaining the rotational speed of the motor at a predetermined speed,
The control unit may change a state in which the notification unit notifies in accordance with the load after a load on which the constant speed control can not be maintained is applied to the motor. The power tool according to any one of 3. The apparatus further comprises at least one of a rotational speed detection unit that detects a rotational speed of the motor and a current detection unit that detects a current value flowing to the motor.
The control unit changes the notification state of the notification unit when the rotation speed is equal to or less than a predetermined rotation speed or the current value is equal to or more than a predetermined current value. The electric power tool described in the section. The notification unit is a lighting device capable of emitting light,
The electric control method according to any one of claims 1 to 5, wherein the control unit gradually or stepwise changes the amount of light emitted by the notification unit according to a load applied to the motor. tool.   The power tool according to claim 6, wherein the controller gradually or gradually reduces the amount of light as the load increases.   The power tool according to claim 6, wherein the control unit gradually or stepwise increases the amount of light as the load increases.   The control unit changes the state notified by the notification unit when the load is the first load after the load applied to the motor exceeds a predetermined magnitude, to the first state, and the load is the load. The power tool according to any one of claims 1 to 8, wherein the state notified by the notification unit when the second load is larger than the first load is changed to the second state. The switching unit has a switching operation that switches between the on state and the off state of the notification unit according to a signal from the control unit.
10. The electric motor according to any one of claims 1 to 9, wherein the control unit gradually or stepwise changes the duty ratio of the switching unit according to the size of a load applied to the motor. tool.   The power tool according to claim 10, wherein the control unit gradually or stepwise decreases the duty ratio as the load increases.   The power tool according to claim 10, wherein the control unit gradually or stepwise increases the duty ratio as the load increases. Motor,
A drive unit for driving the motor;
A control unit that controls the drive unit;
And a notification unit;
The power tool according to claim 1, wherein the control unit changes a state notified by the notification unit according to a size of the load before the load applied to the motor increases and the motor stops. Motor,
A drive unit for driving the motor;
A control unit that controls the drive unit;
And a notification unit;
The control unit is capable of executing constant speed control for maintaining the rotational speed of the motor at a predetermined speed,
The said control part changes the state which the said alerting | reporting part alert | reports according to the said load, when the load which can not maintain the said constant speed control acts on the said motor.

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