JP2015024486A - Electric tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect loaded situation of an electric motor with high accuracy.SOLUTION: In a control device 23 which controls the rotation number of an electric motor 14, a triac 57 controls AC voltage applied to the electric motor by a conduction angle based on a control signal. A rotation number detection circuit 53 detects the rotation number of the electric motor. A control part 54 creates the control signal on the basis of the rotation number of the electric motor 14 detected by the rotation number detection circuit 53, and outputs it to the triac 57. And, the control part 54 determines that the electric motor 14 is under a loaded situation and controls the electric motor 14 to become a first rotation number set by a setting signal when the conduction angle of the triac 57 is larger than a load determination reference value, and determines that the electric motor 14 is under no loaded situation and controls the electric motor 14 to become a second rotation number less than the first rotation number set by the setting signal when the conduction angle of the triac 57 becomes less than a no-load determination reference value.

Description

  The present invention relates to an electric tool, and more particularly, to a technique effective for an electric tool that performs work by vibrating a tip tool with an electric motor.

  As an electric tool for cutting wood, gypsum board, plastic, metal or the like, a tool that converts a rotary motion of a motor into a reciprocating motion of a blade is widely known.

  In this electric power tool, one that controls the number of rotations by changing a conduction angle for energizing a motor by a triac or the like is known. During no load, noise, vibration, power consumption, and the like during no load are reduced by lowering the rotation speed of the motor than the rotation speed in the loaded state. For the determination of no load / load, for example, a current flowing through the motor is detected, and when the detected current exceeds a threshold value, it is determined that the load is in the load state.

  In addition, as a motor control technique in this kind of electric tool, there exists what determines an overcurrent state, for example based on the limit conduction angle corresponding to the set rotation speed (for example, refer patent document 1).

JP 2010-162672 A

  The value of the current flowing through the motor varies greatly depending on, for example, the type of the tip tool that can be taken by the electric tool, the material to be worked on, the voltage fluctuation of the power source, or the variation in motor characteristics.

  However, since the threshold value for determining whether or not the load state is constant, the load / no load of the motor is erroneously determined, resulting in insufficient cutting power and the efficiency of the work. There is a problem that it falls.

  An object of the present invention is to provide a technique capable of detecting a load state of an electric motor with high accuracy.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  An electric power tool according to an embodiment has a control device that controls the rotation speed of an electric motor. The control device includes a switching element, a rotation speed detection unit, and a control unit. The switching element controls the AC voltage applied to the electric motor based on the control signal based on the conduction angle. The rotation speed detection unit detects the rotation speed of the electric motor. A control part produces | generates a control signal based on the rotation speed of the electric motor which the rotation speed detection part detected, and outputs it to a switching element.

  When the conduction angle of the switching element is larger than the load determination reference value, the control unit determines that the electric motor is in a load state. Then, the control signal is generated so that the rotation speed of the electric motor becomes the first rotation speed set by the setting signal.

  The control unit determines that the electric motor is in the no-load state when the conduction angle of the switching element becomes smaller than the no-load determination reference value, and the rotation speed of the electric motor is set to the first rotation speed set by the setting signal. The control signal is generated so as to be the second rotational speed which is a lower rotational speed.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  It is possible to improve the working efficiency of the electric tool.

1 is an external view illustrating an example of an electric tool according to Embodiment 1. FIG. It is sectional drawing of the electric tool of FIG. It is a block diagram which shows an example of a structure of the control apparatus provided in the electric tool of FIG. It is explanatory drawing which shows an example of a structure of the no-load / load determination criteria table stored in the control part of FIG. It is a timing chart which shows an example of the rotation speed of the electric motor in the no-load / load rotation speed automatic switching process by the conduction angle detection, and the conduction angle of the triac. It is a flowchart which shows an example of a no-load / load rotation speed automatic switching process by conduction angle detection. FIG. 10 is an explanatory diagram illustrating an example of a configuration of a no-load / load determination reference table based on a no-load / load rotation number automatic switching process based on current detection according to the second embodiment. It is a timing chart which shows an example of the rotation speed of the electric motor in the no load / load rotation number automatic change processing by current detection, and the current value which flows into the electric motor. It is a flowchart which shows an example of a no-load / load rotation speed automatic switching process by electric current detection. FIG. 10 is an explanatory diagram illustrating an example of a configuration of an automatic switching load rotation speed table used for load rotation speed automatic switching processing based on conduction angle detection according to the third embodiment. It is explanatory drawing which shows an example of a structure of the no-load determination criteria table used for the load rotation speed automatic switching process by conduction angle detection. It is a timing chart which shows an example of the rotation speed of the electric motor in the load rotation speed automatic switching process by the conduction angle detection of this Embodiment 3, and the conduction angle of a triac. It is a flowchart which shows an example of the load rotation speed automatic switching process by a conduction angle detection. FIG. 16 is an explanatory diagram illustrating an example of a configuration of an automatic switching load rotation speed table used for load rotation speed automatic switching processing by current detection according to the fourth embodiment. It is explanatory drawing which shows an example of a structure of the no-load determination criteria table used for the load rotation speed automatic switching process by electric current detection. It is a timing chart which shows an example of the rotation speed of the electric motor in the load rotation speed automatic change processing by current detection, and the current value which flows into the electric motor. It is a flowchart which shows an example of the load rotation speed automatic switching process by electric current detection. It is explanatory drawing which shows the structural example of the inverter circuit which controls the brushless motor by other embodiment.

  In the following embodiments, when it is necessary for the sake of convenience, the description will be divided into a plurality of sections or embodiments. However, unless otherwise specified, they are not irrelevant to each other. There are some or all of the modifications, details, supplementary explanations, and the like.

  Further, in the following embodiments, when referring to the number of elements (including the number, numerical value, quantity, range, etc.), especially when clearly indicated and when clearly limited to a specific number in principle, etc. Except, it is not limited to the specific number, and may be more or less than the specific number.

  Further, in the following embodiments, the constituent elements (including element steps and the like) are not necessarily indispensable unless otherwise specified and apparently essential in principle. Needless to say.

  Similarly, in the following embodiments, when referring to the shape, positional relationship, etc. of components, etc., the shape of the component is substantially the case unless it is clearly specified and the case where it is clearly not apparent in principle. And the like are included. The same applies to the above numerical values and ranges.

  In all the drawings for explaining the embodiments, the same members are denoted by the same reference symbols in principle, and the repeated explanation thereof is omitted. In order to make the drawings easy to understand, even a plan view may be hatched.

(Embodiment 1)
Hereinafter, embodiments will be described in detail.

<Example of power tool configuration>
FIG. 1 is an external view showing an example of an electric tool according to the first embodiment. FIG. 2 is a cross-sectional view of the power tool of FIG.

  As shown in FIG. 1, the electric tool 10 is a power tool using the electric motor 14 shown in FIG. 2 as a power source. The electric tool 10 can perform a plurality of different types of work by changing the tip tool to be attached.

  For example, when a tip tool having a sawtooth is attached to the power tool 10, the power tool 10 can perform an operation of cutting an object with the tip tool. Further, when a tip tool having a diamond tip or a carbide tip fixed thereto is attached to the power tool 10, the power tool 10 can perform an operation of grinding or polishing an object with the tip tool. Furthermore, when a scraper-shaped tip tool or the like is attached to the electric power tool 10, an operation of peeling an object from an object with the tip tool can be performed.

  Here, the electric tool 10 shown in FIGS. 1 and 2 is an example in which a scraper-shaped tip tool 13 is attached.

  The electric power tool 10 includes a grip housing 11 that is gripped by an operator, and a front housing 12 that is slidably fitted to the tip of the grip housing 11. The grip portion housing 11 houses an electric motor 14 as a drive source. The electric motor 14 is fixed to the partition wall portion 15 of the grip portion housing 11 by mounting screws 25. Further, the grip portion housing 11 has a display portion 47. The display unit 47 is composed of a liquid crystal display, for example, and displays a target rotational speed, an actual rotational speed, and the like.

  A spindle 18 having an eccentric shaft 17 at the tip is fixed to the motor shaft 16 of the electric motor 14. An inner ring of a bearing 19 is fitted and fixed to the eccentric shaft 17 of the spindle 18.

  The drive unit 20 of the electric tool 10 is configured by the electric motor 14 including the spindle 18 and the grip housing 11 that supports the electric motor 14. The grip housing 11 includes a main switch 21 that is operated by an operator when starting the electric tool 10, a rotation speed setting dial 22 that is operated by an operator when adjusting the motor rotation speed, and an electric motor 14. A control device 23 for controlling the rotation of the motor is provided.

  In addition, a power cord 24 is connected to one end of the grip portion housing 11 in the longitudinal direction, and power from an AC power source is supplied to the electric motor 14 via the power cord 24. Further, in the grip housing 11, an automatic transmission control changeover switch 26 is provided below the power cord 24. The automatic transmission control changeover switch 26 is a switch for setting whether to automatically switch between the load mode and the no-load mode according to the load of the electric motor 14. In the load mode, the electric motor 14 has the maximum rotation speed set by the rotation speed setting dial 22, and in the no-load mode, the rotation speed is about 80% of the maximum rotation speed. By reducing the rotation speed when there is no load, the tip tool can be easily matched to the mating material.

  An inner case 30 is accommodated in the front housing 12, and a vibration shaft 31 is supported on the inner case 30 by a pair of bearings 32 and 33. In addition, a tool attachment portion 36 to which the tip tool 13 is attached using a fixing screw 34 is formed at the tip of the vibration shaft 31 protruding from the front housing 12 and the inner case 30.

  A swing arm 37 extending to the spindle 18 side is fixed to the base end portion of the vibration shaft 31. The swing arm 37 includes a fitting portion 38 fixed to the vibration shaft 31 and a pair of arm pieces 39 extending from the fitting portion 38 toward the spindle 18 in a bifurcated manner.

  Inside the arm piece 39, an outer ring of the bearing 19 fixed to the eccentric shaft 17 is slidably accommodated. That is, the pair of arm pieces 39 provided on the swing arm 37 functions as a housing portion that houses the eccentric shaft 17.

  As described above, the arm piece 39 is provided on one end side of the swing arm 37, and the fitting portion 38 is provided on the other end side of the swing arm 37. The vibration shaft 31 and the spindle 18 are connected through such a swing arm 37.

  Then, the rotational motion of the spindle 18, that is, the revolving motion of the eccentric shaft 17, is converted into a vibration motion that reciprocally rotates the vibration shaft 31 and the tip tool 13 at a predetermined angle via the swing arm 37. Such a vibration shaft 31, swing arm 37, inner case 30 and front housing 12 constitute a vibration unit 40 of the electric power tool 10. The inner case 30 is provided with a bearing 41 that supports the spindle 18. The spindle 18 is movable in the axial direction with respect to the bearing 41.

  A flange portion 42 is formed on the inner case 30 of the vibration unit 40, and a coil spring 43 is mounted between the flange portion 42 and the partition wall portion 15 of the grip portion housing 11. The coil spring 43 urges the flange portion 42 and the partition wall portion 15 in a separating direction, that is, a direction in which the driving unit 20 and the vibration unit 40 are separated.

  When the drive unit 20 and the vibration unit 40 are separated from each other, the bearing 19 that is in sliding contact with the arm piece 39 of the swing arm 37 moves in a direction away from the vibration shaft 31. When the drive unit 20 and the vibration unit 40 approach each other, the bearing 19 that comes into sliding contact with the arm piece 39 of the swing arm 37 moves in a direction approaching the vibration shaft 31.

  Here, since the amplitude of the eccentric shaft 17 is constant, when the distance between the center axis of the vibration shaft 31 and the contact point of the bearing 19 with respect to the arm piece 39 is increased, the vibration shaft 31 and the tip tool 13 are narrow with a small amplitude. Vibrate.

  On the other hand, when the distance between the center axis of the vibration shaft 31 and the contact point of the bearing 19 with respect to the arm piece 39 approaches, the vibration shaft 31 and the tip tool 13 vibrate with an amplitude wider than the above-described amplitude. Thus, by changing the positional relationship between the swing arm 37 and the eccentric shaft 17, the amplitudes of the vibration shaft 31 and the tip tool 13 are continuously changed.

<Example of control device configuration>
FIG. 3 is a block diagram showing an example of the configuration of the control device 23 provided in the electric tool 10 of FIG.

  As shown in FIG. 3, the control device 23 includes a power supply circuit 50, a zero cross detection circuit 51, a rotation speed pickup sensor 52, a rotation speed detection circuit 53, a control unit 54, a current detection circuit 55, a shunt resistor 56, a triac 57, and the like. Have

  The control device 23 is supplied with AC power when the main switch 21 is turned on, that is, in a conductive state. The power supply circuit 50 generates a DC power supply voltage VCC from the AC power supplied via the power cord 24 of FIG. The zero cross detection circuit 51 detects a zero point of the AC power supply, a so-called zero cross point.

  The rotational speed pickup sensor 52 is a sensor that detects the rotational speed of the electric motor 14 of FIG. The rotational speed pickup sensor 52 is a sensor that uses the Hall effect, and detects the presence or absence of a magnet attached to the rotating portion of the electric motor 14.

  A rotation speed detection circuit 53 that is a rotation speed detection unit calculates the rotation speed of the electric motor 14 from the detection result of the rotation speed pickup sensor 52.

  The shunt resistor 56 is a resistor that detects a current value flowing through the electric motor 14. The current detection circuit 55 serving as a current detection unit detects the value of the current flowing through the electric motor 14 based on the voltage generated in the shunt resistor 56 and outputs the detection result to the control unit 54.

  The triac 57 that is a switching element controls the conduction angle of the AC power supply by performing an on / off operation based on a control signal output from the control unit 54. Thereby, the electric power supplied to the electric motor 14 is controlled, and the rotation speed increases or decreases.

  The control part 54 consists of a microcomputer etc., for example. A setting signal set by the rotation speed setting dial 22 and a shift control signal set by the automatic shift control changeover switch 26 are input to the control unit 54.

  The controller 54 sets the maximum number of rotations of the electric motor 14 according to the input setting signal. The automatic transmission control changeover switch 26 is a switch for setting whether or not to automatically switch between the minimum rotation speed and the maximum rotation speed in accordance with the load of the electric motor 14. For example, when the operator turns on the automatic transmission control changeover switch 26, the control unit 54 performs control to automatically switch between the minimum rotation speed and the maximum rotation speed according to the load of the electric motor 14. Specifically, on / off of the triac 57 is controlled by a control signal output to the triac 57 so as to vary the conduction angle.

  When the operator turns off the automatic transmission control changeover switch 26, the control unit 54 controls on / off of the triac 57 so that the maximum number of revolutions is achieved regardless of the load of the electric motor 14.

  Further, the rotation speed of the electric motor 14 detected by the rotation speed detection circuit 53 and the detection result of the zero cross point detected by the zero cross detection circuit 51 are input to the control unit 54. The control unit 54 controls the rotation speed of the electric motor 14 to be substantially constant based on the rotation speed of the electric motor 14 detected by the rotation speed detection circuit 53.

  In the rotation speed control of the electric motor 14, the control unit 54 controls the conduction angle of the triac 57 by the control signal as described above. For example, when the rotation speed of the electric motor 14 is larger than the rotation speed set by the rotation speed setting dial 22, the triac 57 is controlled so as to reduce the conduction angle. As a result, the voltage supplied to the electric motor 14 decreases, and the rotational speed of the electric motor 14 decreases. When the rotational speed is smaller than the rotational speed set by the rotational speed setting dial 22, the triac 57 is controlled to increase the conduction angle. As a result, the voltage supplied to the electric motor 14 increases and the rotational speed of the electric motor 14 increases.

  Further, the control unit 54 controls the energization timing of the triac 57 at the zero cross point detected by the zero cross detection circuit 51. For example, when the conduction angle is 90 °, the remaining 90 ° is energized from the point where 90 ° has elapsed from the zero cross point detected by the zero cross detection circuit 51 at the phase angle of the sine wave.

  The control unit 54 has a memory unit (not shown). The memory unit includes a nonvolatile memory exemplified by a flash memory. The memory unit stores a no-load / load determination reference table for determining whether the electric motor 14 is in a no-load state or a load state.

<Configuration example of no-load / load judgment criteria table>
FIG. 4 is an explanatory diagram showing an example of the configuration of the no-load / load determination criterion table TB stored in the control unit of FIG.

  The no-load / load determination reference table TB in FIG. 4 has items of a rotational speed setting value, a load determination reference value, and a no-load determination reference value from left to right. The rotation speed setting value is a rotation speed setting value of the electric motor 14 set by the rotation speed setting dial 22.

  In the case of FIG. 4, the rotational speed setting value by the rotational speed setting dial 22 has five stages “1” to “5”, and the rotational speed of the electric motor 14 increases as the number increases.

  The load determination reference value is a reference value for a conduction angle for determining that the electric motor 14 is in a load state, and a value obtained by adding a preset load determination conduction angle to the initial conduction angle is set. The no-load determination criterion is a reference value for a conduction angle for determining that the electric motor 14 is in a no-load state, and a value obtained by adding a preset no-load determination conduction angle to the initial conduction angle is set. .

  The control unit 54 determines whether the electric motor 14 is in a load state or a no-load state from the detected conduction angle of the triac 57 with reference to the no-load / load determination reference table TB in FIG. And based on the determination result, the no load / load rotation number automatic switching process by the conduction angle detection which switches the electric motor 14 to the load mode or the no load mode is executed.

<Example of timing for automatic switching of no load / load speed>
Next, an outline of the no-load / load rotation number automatic switching process based on the conduction angle detection will be described with reference to FIG. FIG. 5 is a timing chart showing an example of the rotation speed of the electric motor 14 and the conduction angle of the triac 57 in the no-load / load rotation speed automatic switching process based on the conduction angle detection.

  First, when the main switch 21 is turned on, the electric motor 14 is operated in the no-load mode, and when the electric motor 14 becomes stable, the initial conduction angle of the triac 57 is stored. The no-load mode is a mode in which the electric motor 14 rotates at about 80% of the maximum rotation speed set by the rotation speed setting dial 22.

  Subsequently, when the load on the electric motor 14 increases during operation, the control unit 54 increases the conduction angle of the triac 57 in order to maintain the rotation speed of the electric motor 14. As the conduction angle increases, the control unit 54 performs control to drive the electric motor 14 in the load mode. The load mode is a mode in which the electric motor 14 rotates at the maximum rotation speed set by the rotation speed setting dial 22.

  When the work is finished and the electric motor 14 is in a no-load state, the load on the electric motor 14 is reduced. Therefore, the control unit 54 reduces the conduction angle of the triac 57 in order to maintain the rotation speed of the electric motor 14. .

  If it determines with the conduction angle of the triac 57 becoming small and the electric motor 14 will be in a no-load state, the control part 54 will perform control which drives the electric motor 14 in a no-load mode again.

  As described above, since the electric angle of the electric motor 14 is detected based on the conduction angle of the triac 57, it is detected whether the electric tool 14 is in a loaded state or a no-load state. Can be reduced.

<No load / Load rotation speed automatic switching processing example>
Next, the no-load / load rotation number automatic switching process based on the conduction angle detection will be described.

  FIG. 6 is a flowchart illustrating an example of a no-load / load rotation number automatic switching process based on conduction angle detection.

  First, the control unit 54 determines whether or not the automatic transmission control changeover switch 26 is turned on while the main switch 21 is turned on (step S101). When the automatic transmission control changeover switch 26 is turned off, the control unit 54 sets the rotation speed setting of the electric motor 14 to the load mode (step S102). The load mode is a mode in which the electric motor 14 rotates at the maximum rotation speed set by the rotation speed setting dial 22 as described above.

  Subsequently, the control unit 54 detects the rotation speed setting value of the electric motor 14 set by the rotation speed setting dial 22 (step S103), and the triac 57 is set to the maximum rotation speed of the detected rotation speed setting value. And the electric motor 14 is driven and controlled at a constant rotational speed (step S104).

  In the process of step S101, when the automatic transmission control changeover switch 26 is turned on, the control unit 54 sets the rotation speed setting of the electric motor 14 to the no-load mode (step S105). The no-load mode is a mode in which the electric motor 14 rotates at about 80% of the maximum rotation speed set by the rotation speed setting dial 22 as described above.

  And the control part 54 detects the rotation speed setting value of the electric motor 14 set by the rotation speed setting dial 22 (step S106). Subsequently, the conduction angle of the triac 57 is controlled so that the rotation speed of the electric motor 14 is 80% of the detected rotation speed setting value, and the electric motor 14 is driven and controlled at a constant rotation speed (step S107). ).

  The control unit 54 determines whether or not about 2 seconds have elapsed since the electric motor 14 started rotating to stabilize the rotation of the electric motor 14 (step S108). When about 2 seconds have elapsed from the start of the rotation operation and the rotation of the electric motor 14 is stabilized, the current conduction angle of the triac 57 that is energized is stored as an initial conduction angle in a memory unit or the like (step S109).

  Subsequently, the control unit 54 refers to the no-load / load determination reference table TB of FIG. 4 stored in the memory unit, and a load determination reference value corresponding to the rotation speed setting value detected by the process of step S106, and Each of the no-load determination reference values is read, and the initial conduction angle stored in the memory unit is read (step S110).

  The no-load / load determination reference table TB includes a load determination value that is an increased conduction angle corresponding to the rotation speed setting value in the load determination reference value item, and a rotation speed setting value in the no-load determination reference value item. A no-load determination value that is a corresponding increase conduction angle is set in advance.

  The control unit 54 adds the load determination value and the no-load determination value to the initial conduction angle detected in the process of step S109, and sets the addition results in the load determination reference value item and the no-load determination reference value item, respectively. To do.

  Then, the control unit 54 determines whether or not the electric motor 14 is operating in the no-load mode (step S111). Here, the first determination in step S111 is set to the no-load mode in the process of step S105. Therefore, the process of step S112 is performed.

  When the no-load mode is set, the control unit 54 determines whether or not the conduction angle of the energized triac 57 satisfies the load determination reference value read in the process of step S110 (step S112).

  For example, when the load determination reference value of the rotation speed setting value “1” is read in the process of step S110, the conduction angle of the energized triac 57 is greater than “initial conduction angle + 0.10 ms” from FIG. Determine whether it is larger.

  When the conduction angle of the triac 57 is larger than “initial conduction angle + 0.10 ms”, it is determined that the rotational load of the electric motor 14 has increased, and the conduction of the triac 57 is driven so as to drive the electric motor 14 in the load mode. The angle is increased (step S113), and the constant rotational speed according to the load mode is maintained (step S114).

  If the conduction angle of the triac 57 is smaller than “initial conduction angle + 0.10 ms” in the process of step S112, it is determined that the rotational load of the electric motor 14 has not increased, and the operation in the no-load mode is continued. (Step S114).

  When the process of step S114 ends, the process returns to step S111 again. When the load mode is set in step S113, it is determined in step S111 that the load mode is not set.

  When not in the no-load mode, the control unit 54 determines whether or not the conduction angle of the energized triac 57 is larger than the no-load determination reference value read in the process of step S110 (step S115).

  For example, when the no-load determination reference value of the rotation speed setting value “1” is read in the process of step S110, the current conduction angle of the triac 57 is greater than “initial conduction angle + 0.20 ms” from FIG. Determine whether it is larger.

  When the conduction angle of the triac 57 is larger than “initial conduction angle + 0.20 ms”, it is determined that the electric motor 14 is in the load state, and the operation in the load mode is continued (step S114).

  If the conduction angle of the triac 57 is smaller than “initial conduction angle + 0.20 ms”, it is determined that the electric motor 14 is in the no-load state, and the electric motor 14 is switched to the operation in the no-load mode (step S116). ), Maintaining the constant rotational speed in the no-load mode (step S114). As described above, when the electric motor 14 is in a no-load state, the vibration, noise, power consumption, and the like of the electric tool 10 can be reduced by reducing the rotation speed of the electric motor 14.

  Thereafter, the processes of steps S111 to S116 are repeatedly executed until the main switch 21 is turned off.

  As described above, it is possible to detect with high accuracy whether the electric motor 14 is in a loaded state or in an unloaded state.

(Embodiment 2)
<Overview>
In the first embodiment, the load state of the electric motor 14 is detected from the conduction angle of the triac 57. However, in the second embodiment, the current flowing through the electric motor 14 is not the conduction angle of the triac 57. A technique for detecting the load state of the electric motor 14 based on the value will be described.

  Here, it is determined from the detected current value flowing through the electric motor 14 whether the electric motor 14 is in a load state or a no-load state, and the electric motor 14 is set in a no-load mode or a load depending on the result. A no-load / load rotation speed automatic switching process is executed by detecting the current for switching to the mode.

  The electric power tool 10 is the same as the configuration shown in FIGS. 1 and 2 of the first embodiment, and a description thereof will be omitted. The configuration of the control device 23 provided in the electric tool 10 is also the same as that in FIG. 3 of the first embodiment.

  The difference from FIG. 3 of the first embodiment is the information of the current no load / current load determination reference table TB1 stored in the memory unit included in the control unit 54.

<Configuration example of current no load / current load criteria table>
FIG. 7 is an explanatory diagram showing an example of the configuration of the current no-load / current load determination reference table TB1 by the no-load / load rotation speed automatic switching processing based on current detection according to the second embodiment.

  The current no-load / current load determination reference table TB1 in FIG. 7 includes items of a rotational speed setting value, a current load determination reference value, and a current no-load determination reference value from left to right. The rotation speed setting value is a rotation speed setting value of the electric motor 14 set by the rotation speed setting dial 22.

  Also in FIG. 7, as in the case of FIG. 4, the rotational speed setting value by the rotational speed setting dial 22 has five stages of “1” to “5”. The rotation speed increases.

  The current load determination reference value is a current reference value for determining that the electric motor 14 is in a load state, and a value obtained by adding a preset load determination current value to the initial current value is set. The current no-load determination reference value is a current reference value for determining that the electric motor 14 is in the no-load state, and a value obtained by adding a preset no-load determination current value to the initial current value is set. Yes.

  The control unit 54 refers to the current no load / current load determination reference table TB1 in FIG. 7 and determines whether the electric motor 14 is in a loaded state or a no load state from the detected current value flowing through the electric motor 14. And the no-load / load rotation speed automatic switching process based on the current detection for switching the electric motor 14 to the no-load mode or the load mode is executed.

<Outline of no-load / load speed automatic switching process>
Next, an outline of the no-load / load rotation number automatic switching process based on current detection will be described with reference to FIGS. 3 and 8. FIG. 8 is a timing chart showing an example of the rotation speed of the electric motor 14 and the value of the current flowing through the motor 14 in the no-load / load rotation speed automatic switching processing based on current detection.

  First, when the main switch 21 is turned on, the electric motor 14 is operated in the no-load mode. The no-load mode is a mode in which the electric motor 14 rotates at about 80% of the maximum rotation speed set by the rotation speed setting dial 22. The temporary increase in the motor current at no load shown in FIG. 8 is the starting current. It is necessary to store the initial current value so as not to consider this starting current. According to this embodiment, as will be described later, the initial current value is stored after 2 seconds from the start of the motor.

  When the electric motor 14 is in a stable state, the initial current value flowing through the electric motor 14 is acquired and stored. When the load on the electric motor 14 increases during work, the value of the current flowing through the electric motor 14 increases. When detecting the increase in the current value, the control unit 54 performs control to drive the electric motor 14 in the load mode. The load mode is a mode in which the electric motor 14 rotates at the maximum rotation speed set by the rotation speed setting dial 22.

  When the work is completed and the electric motor 14 is in a no-load state, the load on the electric motor 14 is reduced, so that the current value flowing through the electric motor 14 is also reduced.

  As a result, it is determined that the electric motor 14 is in a no-load state, and the control unit 54 performs control to drive the electric motor 14 again in the no-load mode.

  As described above, it is possible to detect whether or not the electric motor 14 is in a load state also by the value of the current flowing through the electric motor 14. In this case, since the load / no load of the electric motor 14 is detected by increasing / decreasing the current with respect to the initial current value flowing through the electric motor 14, the detection error can be reduced regardless of variations in motor characteristics. .

<Example of no load / load rotation speed automatic switching>
Next, the no-load / load rotation number automatic switching process based on current detection will be described.

  FIG. 9 is a flowchart illustrating an example of a no-load / load rotation number automatic switching process based on current detection.

  First, the control unit 54 determines whether or not the automatic transmission control changeover switch 26 is turned on while the main switch 21 is turned on (step S201). When the automatic transmission control changeover switch 26 is turned off, the control unit 54 sets the rotation speed setting of the electric motor 14 to the load mode (step S202).

  Subsequently, the control unit 54 detects the rotation speed setting value of the electric motor 14 set by the rotation speed setting dial 22 (step S203), and the triac 57 is set to the maximum rotation speed of the detected rotation speed setting value. The electric motor 14 is driven and controlled at a constant rotational speed by controlling the conduction angle (step S204).

  If the automatic transmission control changeover switch 26 is turned on in step S201, the control unit 54 sets the rotation speed setting of the electric motor 14 to the no-load mode (step S205).

  Then, the control unit 54 detects the rotation speed setting value of the electric motor 14 set by the rotation speed setting dial 22 (step S206), and then the rotation speed of the electric motor 14 is 80% of the detected rotation speed setting value. The conduction angle of the triac 57 is controlled so as to be the rotational speed, and the electric motor 14 is driven and controlled so as to be the constant rotational speed (step S207).

  Subsequently, the control unit 54 determines whether or not about 2 seconds have elapsed since the electric motor 14 started rotating (step S208). When the rotation of the electric motor 14 is stabilized after about 2 seconds from the start of the rotation operation, the current value flowing through the operating electric motor 14 detected by the current detection circuit 55 is used as the initial current value and the memory of the control unit 54. (Step S209).

  The control unit 54 refers to the current no load / current load determination reference table TB1 stored in the memory unit, and determines the current load determination reference value corresponding to the rotation speed setting value detected by the process of step S206, and the current no load. Each determination reference value is read out, and the initial current value stored in the memory unit is read out (step S210).

  The current no load / current load determination reference table TB1 includes a load determination current value that is an increased current value corresponding to the rotation speed setting value in the current load determination reference value item, and a current no load determination reference value item. A no-load determination current value that is a current value of an increase corresponding to the rotation speed setting value is set in advance.

  The control unit 54 adds the load determination current value and the no-load determination current value to the detected initial current value, and sets the addition results in the current load determination reference value item and the current no-load determination reference value item, respectively. .

  Then, the control unit 54 determines whether or not the electric motor 14 is operating in the no-load mode (step S211). Here, the first determination in the process of step S211 is set to the no-load mode in the process of step S205. Therefore, the process of step S212 is executed.

  When the no-load mode is set, the control unit 54 determines whether or not the value of the current flowing through the electric motor 14 during operation satisfies the current load determination reference value read in the process of step S210 (step S212). ).

  For example, when the current load determination reference value of the rotation speed setting value “1” is read in the process of step S210, the current value flowing through the electric motor 14 during operation is “initial current value + 0.5 A” from FIG. It is judged whether it is larger than.

  When the value of the current flowing through the electric motor 14 is larger than the “initial current value + 0.5 A”, it is determined that the rotational load of the electric motor 14 has increased, and the triac 57 is driven to drive the electric motor 14 in the load mode. The conduction angle is increased (step S213), and the constant rotational speed according to the load mode is maintained (step S214).

  On the other hand, when the value of the current flowing through the electric motor 14 is smaller than the “initial current value + 0.5 A” in the process of step S212, it is determined that the rotational load of the electric motor 14 has not increased and the no-load mode is performed. The operation is continued (step S214).

  When the process of step S214 ends, the process returns to step S211 again. When the load mode is set in step S213, it is determined in step S211 that the load mode is not set.

  When not in the no-load mode, the control unit 54 determines whether or not the value of the current flowing through the electric motor 14 during operation is larger than the current no-load determination reference value read in the process of step S210 (step S215).

  For example, when the current no-load determination reference value of the rotation speed setting value “1” is read in the process of step S210, the current value flowing through the electric motor 14 during operation is “initial current value + 1. It is determined whether or not it is larger than “0A”.

  When the value of the current flowing through the electric motor 14 is larger than the “initial current value + 1.0 A”, it is determined that the electric motor 14 is in a load state, and the operation in the load mode is continued (step S214).

  If the value of the current flowing through the electric motor 14 is smaller than the “initial current value +1.0 A”, it is determined that the electric motor 14 is in a no-load state, and the electric motor 14 is switched to the operation in the no-load mode. (Step S216), the constant rotation speed in the no-load mode is maintained (Step S214).

  Thereafter, the processes of steps S211 to S216 are repeatedly executed until the main switch 21 is turned off.

  As described above, when the electric motor 14 is in a no-load state, the vibration, noise, power consumption, and the like of the electric tool 10 can be reduced by reducing the rotation speed of the electric motor 14.

  As described above, it is possible to detect with high accuracy whether the electric motor 14 is in a loaded state or in an unloaded state.

(Embodiment 3)
<Overview>
In the first and second embodiments, the rotation number of the electric motor 14 is determined by the operator using the rotation number setting dial 22. However, in the third embodiment, according to the load of the electric motor 14, A technique of automatic load rotation speed switching processing based on conduction angle detection that automatically selects the rotation speed of the electric motor 14 based on the conduction angle of the triac 57 will be described.

  The power tool 10 according to the third embodiment is different in that the rotation speed setting dial 22 and the automatic transmission control changeover switch 26 shown in FIGS. 1 and 2 of the first embodiment are not provided. Other configurations are the same as the configurations shown in FIGS. 1 and 2 of the first embodiment, and a description thereof will be omitted.

  The configuration of the control device 23 provided in the electric tool 10 is also the same as that in FIG. 3 of the first embodiment. In the control device 23 of FIG. 3, the memory unit included in the control unit 54 stores an automatic switching load rotation number table TB2 and a no-load determination reference table TB3, which are load rotation number tables.

<Example of automatic switching load rotation speed table configuration>
FIG. 10 is an explanatory diagram showing an example of the configuration of the automatic switching load rotation speed table TB2 used for the load rotation speed automatic switching process based on the conduction angle detection according to the third embodiment, and FIG. 11 shows the load based on the conduction angle detection. It is explanatory drawing which shows an example of a structure of the no-load determination reference | standard table TB3 used for a rotation speed automatic switching process.

  The automatic switching load rotation speed table TB2 is information for determining the rotation speed of the electric motor 14 in accordance with the load state of the electric motor 14 in the load mode. As shown in FIG. The relationship between the angle increase amount and the rotation speed of the electric motor 14 is shown.

  In the automatic switching load rotation speed table TB2, the initial conduction angle is divided into, for example, five ranges, and the rotation speed of the electric motor 14 increases as the initial conduction angle increases. The conduction angle increase amount is divided into, for example, four ranges, and the rotation speed of the electric motor 14 increases as the conduction angle increase amount increases.

  Therefore, in the automatic switching load rotation speed table TB2, when the initial conduction angle and the conduction angle increase amount are the largest, the electric motor 14 becomes the maximum rotation speed, and when the initial conduction angle and the conduction angle increase amount is the smallest, The electric motor 14 becomes the minimum rotation speed.

  The control unit 54 refers to the automatic switching load rotation speed table TB2 and sets an optimal rotation speed according to the load state of the electric motor 14 in the load mode.

  As shown in FIG. 11, the no-load determination reference table TB3 has a load rotation speed and a no-load determination reference value. The no-load determination reference value is a conduction angle reference value for determining that the electric motor 14 is in a no-load state according to the number of revolutions of the electric motor 14, and is a no-load that is set in advance to the initial conduction angle. A value obtained by adding the determination conduction angle is set. The control unit 54 determines whether or not the electric motor 14 is in a no-load state with reference to the no-load determination criterion table TB3.

<Overview of automatic load rotation speed switching>
Next, an outline of the load rotation number automatic switching process based on the conduction angle detection will be described with reference to FIGS. 3 and 12. FIG. 12 is a timing chart showing an example of the rotation speed of the electric motor 14 and the conduction angle of the triac 57 in the load rotation speed automatic switching process based on the conduction angle detection according to the third embodiment.

  First, when the main switch 21 is turned on, the electric motor 14 is operated in the no-load mode. When the electric motor 14 becomes stable, the initial conduction angle of the triac 57 is stored.

  Subsequently, when the load on the electric motor 14 increases during operation, the control unit 54 increases the conduction angle of the triac 57 in order to maintain the rotation speed of the electric motor 14. When the conduction angle increases from the initial conduction angle, the control unit 54 performs control to drive the electric motor 14 in the load mode.

  In the operation in the load mode, the rotation speed that is optimally selected according to the initial conduction angle of the electric motor 14 and the load state is set based on the automatic switching load rotation speed table TB2 shown in FIG.

  When it is determined that the electric motor 14 is in the no-load state based on the no-load determination reference table TB3 in FIG. 11, the conduction angle of the triac 57 is reduced and the electric motor 14 is operated in the no-load mode. And the rotational speed of the electric motor 14 is maintained.

  Thus, by controlling the rotation speed of the electric motor 14 in detail by the conduction angle of the triac 57, vibration, noise, power consumption, and the like of the electric tool 10 can be reduced.

  In addition, since the optimum number of rotations is set according to the load state of the electric motor 14, the load on the electric motor 14 is extremely reduced when cutting soft materials such as polystyrene foam. Accordingly, the rotational speed of the electric motor 14 is reduced. This can prevent the member from being melted by friction during cutting.

  On the other hand, when cutting a hard material such as metal, the load applied to the electric motor 14 becomes very large. Therefore, the rotation speed of the electric motor 14 is increased, and the cutting efficiency of a hard material such as metal can be improved.

<Example of automatic load rotation speed switching>
Subsequently, the load rotation speed automatic switching process based on the conduction angle detection will be described.

  FIG. 13 is a flowchart illustrating an example of load rotation speed automatic switching processing based on conduction angle detection.

  When the main switch 21 is turned on, the control unit 54 rotates the electric motor 14 in the no-load mode (step S301). The rotational speed of the electric motor 14 in the no-load mode is, for example, about 20% lower than 4000 rpm, which is the lowest rotational speed in the load mode shown in FIG.

  The control unit 54 determines whether or not about 2 seconds have elapsed since the electric motor 14 started rotating (step S302). When about 2 seconds have elapsed from the start of the rotation operation and the rotation of the electric motor 14 is stabilized, the conduction angle of the current triac 57 that is energized is stored as an initial conduction angle in the memory unit of the control unit 54 (step S303). ).

  Thereafter, the control unit 54 determines whether or not the conduction angle of the triac 57 has increased from the initial conduction angle (step S304), and when the conduction angle of the triac 57 becomes larger than the initial conduction angle, the control unit 54 stores it in the memory unit. On the basis of the automatic switching load rotation speed table TB2, the rotation speed of the electric motor 14 is selected from the initial conduction angle and the conduction angle increase amount increased from the initial conduction angle (step S305).

  The control unit 54 performs drive control of the electric motor 14 so as to maintain the rotation speed selected in the process of step S305 (step S306). Thereby, the rotation speed according to the load condition of the electric motor 14 is set.

  In an operation of cutting a metal such as iron, a load applied to the electric motor 14 is larger than that of an operation such as polishing. Moreover, in the electric tool 10, the weight of the tip tool attached as the load increases tends to increase. For example, in the work of cutting a hard metal such as iron, the material of the tip tool is also made of metal in accordance with that, and becomes heavy.

  Therefore, the inertia when the tip tool is driven increases as the weight of the tip tool increases. If the inertia increases, the initial conduction angle increases in order to maintain the rotation speed of the electric motor 14 in the no-load mode. From this, it can be predicted that the load applied to the electric motor 14 increases as the inertia of the tip tool attached to the electric tool 10 increases.

  Therefore, it is predicted that the larger the initial conduction angle is, the larger the load applied to the electric motor 14 is. Therefore, even if the increase amount of the conduction angle is the same value, the initial conduction angle in the no-load mode is Control is performed so as to increase the rotational speed of the electric motor 14 in the load mode as the value increases.

  Here, consider the case where the inertia of the tip tool is small and the initial conduction angle is, for example, 1.0 ms, and the case where the inertia of the tip tool is large and the initial conduction angle is, for example, 8.0 ms.

  When the initial conduction angle is 1.0 ms and the increase amount of the conduction angle is, for example, 0.3 ms, the rotation speed of the electric motor 14 in the load mode is determined from the automatic switching load rotation speed table TB2 in FIG. 6000 rpm. Therefore, the control unit 54 controls the conduction angle of the triac 57 so that the electric motor 14 is kept rotating at a rotation speed of 6000 rpm.

  On the other hand, when the initial conduction angle is 8.0 ms and the increase amount of the conduction angle is, for example, 0.3 ms as described above, in this case, from the automatic switching load rotation speed table TB2 in FIG. The rotational speed of the electric motor 14 at that time is 14000 rpm. Therefore, the control unit 54 controls the conduction angle of the triac 57 so that the electric motor 14 is kept rotating at the rotation speed of 14000 rpm.

  In this way, control for changing the rotation speed of the electric motor 14 in the load mode is performed according to the inertia of the attached tip tool. As a result, the optimum rotational speed is obtained in accordance with the load during work, so that power shortage during work or excessive application of power to the work member can be prevented.

  Subsequently, the control unit 54 determines whether or not it is larger than the no-load determination reference value corresponding to the rotation speed of the electric motor 14 during operation based on the no-load determination reference table TB3 in FIG. 11 (step S307). ).

  For example, in the process of step S305, when 6000 rpm is selected as the rotation speed of the electric motor 14 as described above, the no-load determination reference value is “initial conduction angle + 0.40 ms” from FIG. Therefore, in the process of step S307, it is determined whether or not the conduction angle of the triac 57 being energized is larger than “initial conduction angle + 0.40 ms”.

  In the process of step S307, when the conduction angle is larger than the no-load determination reference value, it is determined that the electric motor 14 is in a loaded state, and the process returns to step S306.

  If the conduction angle is smaller than the no-load determination reference value in the process of step S307, it is determined that no load is applied to the electric motor 14, and the process returns to step S301.

  As described above, since the optimum rotation speed can be controlled according to the load of the electric motor 14 by the conduction angle of the triac 57, vibration, noise, power consumption, and the like of the electric tool 10 can be reduced. Furthermore, in the power tool 10 that can attach various tip tools according to work applications such as cutting, peeling, polishing, etc. by vibrating the tip tool in the left-right direction, the optimum rotation speed is controlled according to the inertia of the tip tool can do.

(Embodiment 4)
<Overview>
In the third embodiment, the technique for selecting and setting the optimum rotational speed corresponding to the load state of the electric motor 14 from the conduction angle of the triac 57 has been described. However, in the fourth embodiment, the electric motor 14 is selected. A technique for selecting and setting the optimum number of rotations corresponding to the load state of the electric motor 14 from the value of the current flowing through the motor will be described.

  In the fourth embodiment, load rotation number automatic switching processing by current detection for automatically selecting the rotation number of the electric motor 14 according to the load of the electric motor 14 is executed. The difference is that the rotational speed of the electric motor 14 in the load mode is set not by the conduction angle of the triac 57 but by the value of the current flowing through the electric motor 14.

  The electric power tool 10 of the fourth embodiment is the same as that of the third embodiment shown in FIGS. 1 and 2, and the configuration of the control device 23 is the same as that of the third embodiment shown in FIG. Omitted.

  In the control device 23 of FIG. 3, the memory unit included in the control unit 54 includes an automatic switching load rotation speed table TB4 that is a current load rotation speed table and a current no-load determination reference table TB5 that is a current no-load determination reference table. Each is stored.

<Example of automatic switching load rotation speed table configuration>
FIG. 14 is an explanatory diagram showing an example of a configuration of an automatic switching load rotation speed table TB4 used for load rotation speed automatic switching processing by current detection according to the fourth embodiment, and FIG. 15 shows load rotation speed by current detection. It is explanatory drawing which shows an example of a structure of the no-current determination criterion table TB5 used for an automatic switching process.

  The automatic switching load rotational speed table TB4 is information for determining the rotational speed of the electric motor 14 in accordance with the load state of the electric motor 14 in the load mode. As shown in FIG. The relationship between the value increase amount and the rotation speed of the electric motor 14 is shown.

  The initial current value is a current value that flows through the electric motor 14 during operation in the no-load mode, and the current value increase amount is a current value increased from the current initial value.

  In the automatic switching load rotation speed table TB4, the initial current value is divided into, for example, five ranges, and the rotation speed of the electric motor 14 increases as the initial current value increases. Further, the amount of increase in current value is divided into, for example, four ranges, and the number of rotations of the electric motor 14 increases as the amount of increase in current value increases.

  Therefore, in the automatic switching load rotation speed table TB4, when the initial current value and the current value increase amount are the largest, the electric motor 14 becomes the maximum rotation speed, and when the initial conduction angle and the conduction angle increase amount are the smallest, The electric motor 14 becomes the minimum rotation speed.

  The control unit 54 refers to the automatic switching load rotation speed table TB4 and sets an optimal rotation speed according to the load state of the electric motor 14 from the current initial value and the current increase value in the load mode. .

  As shown in FIG. 15, the current no-load determination criterion table TB5 has a load rotation speed and a current no-load determination criterion value. The current no-load determination reference value is a reference value of a current value for determining that the electric motor 14 is in a no-load state according to the number of revolutions of the electric motor 14, and is set to an initial current value. A value obtained by adding the load judgment current value is set. The controller 54 determines whether or not the electric motor 14 is in a no-load state with reference to the current no-load determination reference table TB5.

<Overview of automatic load rotation speed switching>
Next, an outline of the load rotation speed automatic switching process based on current detection will be described with reference to FIGS. 3 and 16. FIG. 16 is a timing chart showing an example of the rotation speed of the electric motor 14 and the value of the current flowing through the electric motor 14 in the load rotation speed automatic switching process based on current detection.

  First, when the main switch 21 is turned on, the electric motor 14 is operated in the no-load mode. The rotational speed of the electric motor 14 in the no-load mode is, for example, about 20% lower than 4000 rpm, which is the lowest rotational speed in the load mode shown in FIG.

  When the electric motor 14 is in a stable state, the current value flowing through the electric motor 14 is detected and stored as an initial current value. Subsequently, when the work is started and the load of the electric motor 14 is increased, the control unit 54 increases the conduction angle of the triac 57 in order to maintain the rotation speed of the electric motor 14. As a result, the value of the current flowing through the electric motor 14 increases from the initial current value, and the electric motor 14 is driven in the load mode.

  In the operation in the load mode, the rotation speed that is optimally selected according to the initial current value flowing through the electric motor 14 and the load state is set based on the automatic switching load rotation speed table TB4 shown in FIG. .

  When it is determined that the electric motor 14 is in the no-load state based on the current no-load determination reference table TB5 in FIG. 15, the conduction angle of the triac 57 is reduced and the electric motor 14 is in the no-load mode. The motor is operated and the rotation speed of the electric motor 14 is maintained.

  Thus, by controlling the rotation speed of the electric motor 14 in detail by the value of the current flowing through the electric motor 14, vibration, noise, power consumption, and the like of the electric tool 10 can be reduced.

  Moreover, since the rotation speed selected optimally according to the load state of the electric motor 14 is set, it is possible to prevent the member from being melted when cutting a soft material. Furthermore, when cutting a hard material such as metal, the number of rotations of the electric motor 14 increases, so that it is possible to prevent power shortage during cutting. Work efficiency can be improved.

<Example of automatic load rotation speed switching>
Subsequently, the load rotation speed automatic switching processing based on the current value detection will be described with reference to FIGS. 3 and 17.

  FIG. 17 is a flowchart illustrating an example of load rotation speed automatic switching processing based on current detection.

  When the main switch 21 is turned on, the control unit 54 rotates the electric motor 14 in the no-load mode (step S401). As described above, the rotational speed of the electric motor 14 in the no-load mode is, for example, about 80% of 4000 rpm that is the lowest rotational speed in the load mode.

  The controller 54 determines whether or not about 2 seconds have elapsed since the electric motor 14 started rotating (step S402). When about 2 seconds have elapsed from the start of the rotation operation and the rotation of the electric motor 14 is stabilized, the current value flowing through the electric motor 14 detected by the current detection circuit 55 is stored as an initial current value in a memory unit or the like of the control unit 54. (Step S403).

  Thereafter, the control unit 54 determines whether or not the value of the current flowing through the electric motor 14 has increased from the initial current value (step S404). When the current value flowing through the electric motor 14 increases from the initial current value, the control unit 54 increases from the initial current value and the initial current value based on the automatic switching load rotation speed table TB4 stored in the memory unit. The rotational speed of the electric motor 14 is selected from the amount of increase in the current value (step S405), and drive control of the electric motor 14 is performed so as to maintain the rotational speed selected in the process of step S405 (step S406). Thereby, the rotation speed according to the load condition of the electric motor 14 is set.

  For example, when the initial current value is 1.5 A and the increase amount of the conduction angle is 1 A, the rotational speed of the electric motor 14 is set to 6000 rpm from FIG. Therefore, the control unit 54 controls the conduction angle of the triac 57 so that the electric motor 14 is kept rotating at a rotational speed of 5000 rpm.

  If the inertia of the tip tool attached to the electric power tool 10 increases, the initial current value flowing through the electric power tool 10 increases in order to maintain the rotation speed of the electric motor 14 in the no-load mode. Therefore, it is predicted that the load on the electric motor 14 increases as the inertia of the tip tool attached to the electric tool 10 increases.

  Therefore, it is predicted that the larger the initial current value is, the larger the load applied to the electric motor 14 is, and even if the increase amount of the current value in the load mode is the same value, Control is performed so that the rotation speed of the electric motor 14 in the load mode increases as the initial conduction angle increases.

  Here, consider the case where the inertia of the tip tool is small and the current value is 0.5 A, for example, and the case where the inertia of the tip tool is large and the current value is 4.5 A, for example.

  In the case where the current value is 0.5 A, if the increase amount of the current value is, for example, 0.5 A, the rotation speed of the electric motor 14 in the load mode is calculated from the automatic switching load rotation speed table TB4 of FIG. 4000 rpm. Therefore, the control unit 54 controls the conduction angle of the triac 57 so that the electric motor 14 is kept rotating at a rotational speed of 4000 rpm.

  On the other hand, when the initial current value is 4.5 A, if the amount of increase in the current value is 0.5 A similar to the above, in this case, from the automatic switching load rotation speed table TB4 in FIG. The rotation speed of the electric motor 14 is 12000 rpm. Therefore, the control unit 54 controls the conduction angle of the triac 57 so that the electric motor 14 is kept rotating at the rotation speed of 12000 rpm.

  In this way, control for changing the rotation speed of the electric motor 14 in the load mode is performed according to the inertia of the attached tip tool. As a result, the optimum rotational speed is obtained in accordance with the load during work, so that power shortage during work or excessive application of power to the work member can be prevented.

  Subsequently, based on the current no-load determination reference table TB5 in FIG. 15, the control unit 54 determines that the current value flowing through the electric motor 14 corresponds to the rotational speed of the electric motor 14 set in the process of step S405. It is determined whether it is larger than the load determination reference value (step S407).

  For example, in the process of step S405, when 4000 rpm is selected as the rotation speed of the electric motor 14 as described above, the current no-load determination reference value is “initial current value + 0.5 A” from FIG. .

  Therefore, in the process of step S407, it is determined whether or not the value of the current flowing through the electric motor 14 is greater than the “initial current value + 0.5 A”.

  In the process of step S407, if the value of the current flowing through the electric motor 14 is larger than the current no-load determination reference value, it is determined that the electric motor 14 is in a loaded state, and the process returns to step S406.

  In the process of step S407, if the value of the current flowing through the electric motor 14 is smaller than the current no-load determination reference value, it is determined that the electric motor 14 is not loaded, and the process of step S401 is performed. Return.

  In this way, since the rotation speed of the electric motor 14 is adjusted by increasing or decreasing the current with respect to the initial current value flowing through the electric motor 14, the rotation speed in the load mode can be set with high accuracy regardless of variations in motor characteristics. can do.

  As described above, since the optimum rotational speed can be controlled according to the load of the electric motor 14 by the value of the current flowing through the electric motor 14, vibration, noise, power consumption, and the like of the electric tool 10 can be reduced.

  Moreover, the working efficiency can be improved by setting the rotation speed that is optimally selected according to the load state of the electric motor 14. Furthermore, in the power tool 10 that can attach various tip tools according to work applications such as cutting, peeling, polishing, etc. by vibrating the tip tool in the left-right direction, the optimum rotation speed is controlled according to the inertia of the tip tool can do.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  In addition, this invention is not limited to above-described embodiment, Various modifications are included. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described.

  Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. . In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  For example, in the above-described embodiment, the conduction angle of the triac is controlled. However, as shown in FIG. 18, it may be configured by a brushless motor and an inverter circuit that controls the brushless motor. In this case, the inverter circuit 60 drives the brushless motor 61 by performing switching control of the switching elements Q1 to Q6 including six FETs as is well known. The brushless motor 61 includes a stator, a coil 61c (U to W phase) wound around the stator, and a rotor 61a disposed on the inner peripheral side of the stator. The inverter circuit is switching-controlled by a control device such as the microcomputer 62, and a control signal from the microcomputer 62 is input to each switching element via the control signal output circuit 63. Position information of the rotor 61 a of the brushless motor 61 is detected by position detectors 64 to 66 including three Hall elements, and is input to the microcomputer 62 via the rotor position detection circuit 67. A signal from the hall element is also input to the motor rotation number detection circuit 68 to detect the rotation number of the brushless motor 61. The current flowing through the brushless motor 61 is detected by detecting a voltage drop generated in the shunt resistor by the motor current detection circuit 69. A battery pack 70 is detachably attached to the electric tool as a drive source for the brushless motor 61. A drive power supply necessary for the microcomputer 62 and the like is generated from the battery pack 70 by the control circuit voltage supply circuit 71. Moreover, the microcomputer 62 controls the switching element by inputting the signal of the rotation speed setting dial 22 to the microcomputer 62. In such a configuration, the duty ratio of the switching element at the time of no load is stored as an initial duty ratio in the storage element in the microcomputer 62, and the rotation speed is controlled to the optimum according to the amount of increase in duty from the initial duty ratio. It may be. Note that the duty ratio is the ratio of the on time and the off time in a certain section, and is the on time in the section in which the conduction angle of the above-described embodiment is also, so these have equivalent meanings. Further, instead of the duty ratio, control may be performed according to the value of the current flowing through the brushless motor. In this case, the control may be performed in the same manner as in the above-described embodiment. Here, the conduction angle, the duty ratio, and the current value correspond to control values. In FIG. 18, a battery pack that can be attached to and detached from the electric power tool 10 is used as a drive source, but an AC power supply may be used.

DESCRIPTION OF SYMBOLS 10 Electric tool 11 Grip part housing 12 Front housing 13 Tip tool 14 Electric motor 15 Bulkhead part 16 Motor shaft 17 Eccentric shaft 18 Spindle 19 Bearing 20 Drive unit 21 Main switch 22 Rotation speed setting dial 23 Controller 24 Power cord 25 Mounting screw 26 Automatic shift control changeover switch 30 Inner case 31 Vibration shaft 32 Bearing 33 Bearing 34 Fixing screw 36 Tool attachment portion 37 Swing arm 38 Fitting portion 39 Arm piece 40 Vibration unit 41 Bearing 42 Flange portion 43 Coil spring 47 Display portion 50 Power supply circuit 51 Zero cross detection circuit 52 Rotational speed pickup sensor 53 Rotational speed detection circuit 54 Control unit 55 Current detection circuit 56 Shunt resistor 57 Triac TB No load / load judgment reference table TB1 No current load / electricity Load determination reference table TB2 Automatic switching load rotation speed table TB3 No load determination reference table TB4 Automatic switching load rotation speed table TB5 Current no load determination reference table 60 Inverter circuits Q1 to Q6 Switching element 61 Brushless motor 61a Rotor 61c Coil 62 Microcomputer 63 Control signal output circuits 64 to 66 Position detection unit 67 Rotor position detection circuit 68 Motor rotation speed detection circuit 69 Motor current detection circuit 70 Battery pack 71 Control circuit voltage supply circuit

Claims (33)

A plurality of accessory tools can be selectively attached and detached,
A control device for controlling the rotation speed of the electric motor is provided.
The controller is
A switching element for controlling a voltage applied to the electric motor based on the control signal;
A rotational speed detector for detecting the rotational speed of the electric motor;
A control unit that generates the control signal based on the rotation number of the electric motor detected by the rotation number detection unit and outputs the control signal to the switching element;
Have
The said control part is an electric tool which changes the control value of the said switching element according to the said tip tool. The electric tool according to claim 1,
The plurality of tip tools have different inertias;
The said control part is an electric tool which changes the said control value according to the said inertia. A plurality of accessory tools can be selectively attached and detached,
A control device for controlling the rotation speed of the electric motor is provided.
The controller is
A switching element for controlling a voltage applied to the electric motor based on the control signal;
A rotational speed detector for detecting the rotational speed of the electric motor;
A control unit that generates the control signal based on the rotation number of the electric motor detected by the rotation number detection unit and outputs the control signal to the switching element;
Have
The said control part is an electric tool which changes the rotation speed of the said electric motor according to the said tip tool. In the electric tool according to claim 3,
The said control part is an electric tool which changes the maximum rotation speed of the said electric motor according to the said tip tool. The electric tool according to claim 3 or 4,
The plurality of tip tools have different inertias;
The said control part is an electric tool which changes at least one of the said rotation speed and the said maximum rotation speed according to the said inertia. In the electric tool according to any one of claims 1 to 5,
When the control value of the switching element increases from an initial control value, the electric tool sets the number of rotations of the electric motor based on the initial control value and the increased control value. A control device for controlling the rotation speed of the electric motor is provided.
The controller is
A switching element for controlling the electric motor based on the control signal;
A rotational speed detector for detecting the rotational speed of the electric motor;
A control unit that generates the control signal based on the rotation number of the electric motor detected by the rotation number detection unit and outputs the control signal to the switching element;
Have
The control unit generates the control signal such that when the control value of the switching element is larger than a load determination reference value, the rotation speed of the electric motor becomes a first rotation speed set by a setting signal, When the control value of the switching element is smaller than the no-load determination reference value, the rotation speed of the electric motor becomes a second rotation speed that is lower than the first rotation speed set by the setting signal. A power tool for generating the control signal. In the electric tool according to any one of claims 1 to 7,
The electric power tool, wherein the control value is either a conduction angle or a duty ratio of the switching element or a current value of the electric motor. In the electric tool according to any one of claims 1 to 8,
The plurality of tip tools include a first tool for cutting an object, a second tool for grinding or polishing the object, and a second tool for peeling the object from an object,
The said control part is an electric tool which changes the said control value or the said rotation speed according to the said tip tool attached. A plurality of accessory tools can be selectively attached and detached,
A control device for controlling the rotation speed of the electric motor is provided.
The controller is
A switching element for controlling a voltage applied to the electric motor based on the control signal;
A rotational speed detector for detecting the rotational speed of the electric motor;
A control unit that generates the control signal based on the rotation number of the electric motor detected by the rotation number detection unit and outputs the control signal to the switching element;
Have
The said control part is an electric tool which discriminate | determines the said tip tool in the state where the said tip tool is unloaded, and changes control of the subsequent switching element based on the discrimination | determination result. A plurality of accessory tools can be selectively attached and detached,
A control device for controlling the rotation speed of the electric motor is provided.
The controller is
A switching element for controlling a voltage applied to the electric motor based on the control signal;
A rotational speed detector for detecting the rotational speed of the electric motor;
A control unit that generates the control signal based on the rotation number of the electric motor detected by the rotation number detection unit and outputs the control signal to the switching element;
Have
The said control part is an electric tool which controls the said switching element so that the rotation speed of the said electric motor becomes large, so that the control value of the said switching element in the state where the said front tool is unloaded is large. A control device for controlling the rotation speed of the electric motor is provided.
The controller is
A switching element for controlling the AC voltage applied to the electric motor by a conduction angle based on the control signal;
A rotational speed detector for detecting the rotational speed of the electric motor;
A control unit that generates the control signal based on the rotation number of the electric motor detected by the rotation number detection unit and outputs the control signal to the switching element;
Have
The control unit determines that the electric motor is in a load state when a conduction angle of the switching element is greater than a load determination reference value, and a first rotation number in which the rotation number of the electric motor is set by a setting signal When the conduction angle of the switching element becomes smaller than the no-load determination reference value, it is determined that the electric motor is in the no-load state, and the rotation speed of the electric motor is set to the setting signal. The electric power tool that generates the control signal so that the second rotation speed is lower than the first rotation speed set by the step (1). The power tool according to claim 12,
The control unit detects a conduction angle of the switching element after starting the electric motor as an initial conduction angle, sets a value obtained by adding a load determination conduction angle to the initial conduction angle as the load determination reference value, A power tool that sets a value obtained by adding a no-load determination conduction angle to an initial conduction angle as the no-load determination reference value. The power tool according to claim 13,
The control unit is an electric tool that controls the rotation speed of the electric motor to be the second rotation speed when detecting the initial conduction angle of the switching element. The power tool according to claim 12,
The control unit includes a memory unit that stores the set load determination reference value and the no-load determination reference value as a no-load / load determination reference table, and the number of rotations of the electric motor set by the setting signal is When having a plurality of rotation speeds, the load determination reference value and the no-load determination reference value are set for each rotation speed of the electric motor set by the setting signal, and the no-load / load determination reference table is set. Power tool to store. A control device for controlling the rotation speed of the electric motor is provided.
The controller is
A switching element for controlling a voltage applied to the electric motor based on the control signal;
A control unit that generates the control signal and outputs the control signal to the switching element;
A current detection unit that detects a current value flowing through the electric motor and outputs the current value to the control unit;
Have
The control unit determines that the electric motor is in a load state when a value of a current flowing through the electric motor is greater than a current load determination reference value, and the number of rotations of the electric motor is set by a setting signal. The control signal is generated so as to be the rotational speed, and when the current value flowing through the electric motor becomes smaller than the current no-load determination reference value, it is determined that the electric motor is in the no-load state, and the rotational speed of the electric motor An electric power tool that generates the control signal so that the second rotation speed is lower than the first rotation speed set by the setting signal. The electric tool according to claim 16,
The control unit detects an initial current value flowing through the electric motor, sets a value obtained by adding a load determination current value to the initial current value as the current load determination reference value, and sets the initial current value as a no-load determination current. The electric tool which sets the value which added the value as said electric current no load determination reference value. The electric tool according to claim 17,
The said control part is an electric tool which controls so that the rotation speed of the said electric motor becomes the said 2nd rotation speed, when detecting the initial current value which flows into the said electric motor. The electric tool according to claim 16,
The control unit includes a memory unit that stores the set current load determination reference value and the current no-load determination reference value as a current no-load / current load determination reference table, and the electric motor set by the setting signal The current load determination reference value and the current no-load determination reference value are set for each of the rotation speeds of the electric motor set by the setting signal when the rotation number has a plurality of rotation speeds. A power tool stored in a load / load judgment reference table. A control device for controlling the rotation speed of the electric motor is provided.
The controller is
A switching element that controls the voltage applied to the electric motor by a conduction angle based on the control signal;
A rotational speed detector for detecting the rotational speed of the electric motor;
A control unit that generates the control signal based on the rotation number of the electric motor detected by the rotation number detection unit and outputs the control signal to the switching element;
Have
The control unit detects an initial conduction angle of the switching element, and determines that the electric motor is in a load state when the conduction angle of the switching element increases more than the initial conduction angle, and increases with the initial conduction angle. The electric tool which sets the rotation speed of the said electric motor based on the said conduction angle. The power tool according to claim 20,
The control unit has a load rotation speed table that sets the rotation speed of the electric motor based on the initial conduction angle and the increased conduction angle, and when determining that the electric motor is in a load state, An electric tool that sets a rotation speed of the electric motor with reference to the load rotation speed table. The electric tool according to claim 21,
The load rotational speed table is an electric tool that is set such that the rotational speed of the electric motor increases as both the initial conduction angle and the increased conduction angle increase. The electric tool according to claim 21,
The control unit is an electric tool that controls the rotational speed of the electric motor to be lower than the rotational speed set in the load rotational speed table when detecting the initial conduction angle. The electric tool according to claim 23,
When the conduction angle of the switching element becomes smaller than a no-load determination reference value, the control unit determines that the electric motor is in a no-load state, and detects the initial conduction angle of the rotation speed of the electric motor. A power tool that controls the rotation speed to be set. The electric tool according to claim 24,
The control unit further includes a no-load determination reference table that stores the no-load determination reference value corresponding to the rotation speed of the electric motor, and the electric motor is unloaded with reference to the no-load determination reference table. A power tool that is determined to be in a state. The electric tool according to claim 24,
The said control part is an electric tool which sets the value which added the no-load determination conduction angle to the detected said initial conduction angle as the said no-load determination reference value in the said no-load determination reference table. A control device for controlling the rotation speed of the electric motor is provided.
The controller is
A switching element for controlling a voltage applied to the electric motor based on the control signal;
A rotational speed detector for detecting the rotational speed of the electric motor;
A current detector for detecting a current value flowing through the electric motor;
A control unit that generates the control signal based on the rotation number of the electric motor detected by the rotation number detection unit and outputs the control signal to the switching element;
Have
The control unit detects an initial current value flowing through the electric motor, and determines that the electric motor is in a load state when the current value flowing through the electric motor is greater than the initial current value. An electric tool that sets the number of rotations of the electric motor based on the increased current value. The electric tool according to claim 27,
The control unit has a current load rotation speed table that sets the rotation speed of the electric motor based on the initial current value and the increased current value, and determines that the electric motor is in a load state. An electric tool that sets the rotation speed of the electric motor with reference to the current load rotation speed table. The power tool according to claim 28,
The electric power tool, wherein the current load rotation speed table is set such that the rotation speed of the electric motor increases as both the initial current value and the increased current value increase. The power tool according to claim 28,
The control unit is an electric tool that controls the rotational speed of the electric motor to be lower than the rotational speed set in the current load rotational speed table when detecting the initial current value. The power tool according to claim 30, wherein
The control unit determines that the electric motor is in a no-load state when a current value flowing through the electric motor becomes smaller than a current no-load determination reference value, and detects the rotation speed of the electric motor based on the initial current value. A power tool that controls the rotational speed to be set at the time. The electric tool according to claim 31,
The control unit further includes a current no-load determination reference table that stores the current no-load determination reference value corresponding to the rotation speed of the electric motor, and the electric motor is referred to the current no-load determination reference table. Is determined to be in an unloaded state. The electric tool according to claim 32,
The said control part is an electric tool which sets the value which added the no-load determination electric current value to the detected said initial electric current value to the said electric current no-load determination reference table as the said electric current no-load determination reference value.

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