JP2016087716A - Cutting tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cutting tool in which working ability is not reduced even when an operator performs a cutting work with an unstable posture.SOLUTION: A cutting tool comprises a circular saw 100 comprising: a main body 2 to which a saw blade 8 is attached; a motor 9 stored in the main body 2 and driving the saw blade 8; a battery pack 20 for supplying drive power to the motor 9; and a base 1 attached to the main body 2 and capable of sliding on a material to be cut, and the circular saw comprises an acceleration sensor 30 for detecting a posture of the main body 2, and a control part 23 for controlling so that the motor 9 rotates by predetermined rotation speed when a predetermined posture is detected by the acceleration sensor 30.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a cutting tool using a motor as a drive source.

  2. Description of the Related Art Conventionally, there are known cutting tools such as a circular saw in which a motor as a driving source rotates a saw blade to perform a cutting operation, and a jigsaw that performs a cutting operation by converting the rotational motion of the motor into a reciprocating motion of the blade. This type of cutting tool uses a cutting blade such as a saw blade or blade protruding from the bottom of the base while moving the main body while the base attached to the main body is in contact with the work material. Cutting. In particular, cordless cutting tools that use a battery pack as a power source are frequently used for cutting work with an unstable posture such as wall opening work and ceiling drilling work because of the ease of handling.

  Some cutting tools described above can be used by switching between two modes, a power mode for driving the cutting blade at a high speed and a silent mode for driving at a low speed. The operator operates the switch for mode switching attached to the main body, for example, if you want to work with reduced vibration and noise, select silent mode, if you want to work at high speed, select power mode. select. The cutting tool drives the cutting blade by rotating the motor at a rotation speed according to the selected mode.

  By the way, the silent mode with low vibration and low vibration is suitable for cutting work with an unstable posture. However, if the power mode has been selected in advance, the cutting tool will drive the cutting blade at high speed unless the operator operates the switch to select switching to the silent mode. As a result, there are problems such as loss of workability and distortion on the cut surface.

  Therefore, there has been a demand for a cutting tool that does not impair workability even when an operator performs a cutting operation with an unstable posture.

  In order to solve the above problems, a cutting tool according to the present invention includes a housing to which a cutting blade is attached, a motor housed in the housing and driving the cutting blade, supply means for supplying driving power to the motor, and a housing. A base that is mounted and slidable on the work material, a posture detection means that detects the posture of the housing, and controls the motor to a predetermined rotation speed when a predetermined posture is detected by the posture detection means. And a control means.

  According to such a configuration, the control of the motor can be changed in accordance with the attitude of the housing, so that it is possible to maintain good workability even when performing cutting work with an unstable posture.

  Further, load control means for detecting the load of the motor is further provided, and the control means controls the drive power so as to have a predetermined duty ratio when the load detected by the load detection means exceeds the first load. It is preferable.

  According to such a configuration, it becomes possible to change the driving power following the load of the motor. Therefore, the motor can be controlled according to the work situation, and the motor can be driven with high efficiency.

  Preferably, the control means controls the motor to have a predetermined rotational speed when the load detected by the load detection means becomes equal to or less than a second load that is smaller than the first load.

  According to this configuration, the motor can be controlled in accordance with the work situation, and the value of the second load is set to be smaller than the first load. It becomes possible to prevent the control from becoming unstable.

  Preferably, the control means can selectively switch between rotation speed control for controlling the motor to have a predetermined rotation speed and duty control for controlling drive power to have a predetermined duty ratio.

  According to such a configuration, the rotation speed control and the duty control can be switched according to the work situation, so that the workability can be improved.

  The control means preferably switches between the rotational speed control and the duty control based on the attitude detected at the time of activation.

  According to such a configuration, since control is selected according to the attitude of the housing at the time of startup, it is possible to ensure good workability.

  A setting means for setting the rotation speed; and when the set rotation speed is equal to or higher than a predetermined rotation speed, the attitude detection means detects the attitude, and based on the detected attitude, the rotation speed control and It is preferable to switch the duty control.

  According to such a configuration, since the posture is detected only when the cutting blade is driven at a high speed, efficient work can be performed.

  It is preferable that the control unit further includes a switching unit for switching to the duty control, and when the control unit is switched to the duty control by the switching unit, the duty control is continued even when the predetermined posture is detected by the posture detection unit.

  According to such a configuration, the operator can select desired control, so that convenience is further improved.

  The supply means preferably includes a battery.

  According to such a configuration, when the load is small, it is possible to suppress power consumption by keeping the rotation speed at a low speed, so that it is possible to increase the amount of work in one charge.

  The housing preferably includes a motor housing that houses the motor, and a handle, and the posture detection means is attached to the handle.

  According to such a configuration, since the attitude of the housing can be accurately detected, it is possible to switch to an appropriate control mode.

  The posture detection means is preferably an acceleration sensor.

  According to such a configuration, it is possible to accurately detect cutting work with an unstable posture such as wall opening work or ceiling drilling work, and to switch to an appropriate control mode, so that the distortion of the cut surface Etc. are suppressed and good workability is maintained.

  According to the cutting tool according to the present invention, good workability can be maintained even when an operator performs a cutting operation with an unstable posture.

1 is an external view of a circular saw according to an embodiment of the present invention. It is a side view of the circular saw which concerns on embodiment of this invention. It is a front view of the circular saw which concerns on embodiment of this invention. It is a top view of the circular saw which concerns on embodiment of this invention. It is a figure which shows the structure of the operation display part. It is a front view which shows the tilting state of the circular saw which concerns on embodiment. It is a side view which shows the minimum cutting state of the circular saw which concerns on embodiment. It is a circuit diagram which shows the electrical constitution of the circular saw which concerns on embodiment of this invention. It is a figure which shows the structure of the acceleration sensor in embodiment. It is explanatory drawing which shows an example of the output voltage value of an acceleration sensor. It is explanatory drawing which shows the gravity concerning the X-axis of an acceleration sensor in each cutting condition, and an output voltage value. It is a flowchart which shows operation | movement of the circular saw which concerns on 1st Embodiment. It is explanatory drawing which shows the characteristic of the rotational speed of the saw blade with respect to the drive current of a motor. It is a flowchart which shows operation | movement of the circular saw which concerns on 2nd Embodiment. It is a flowchart which shows the operation | movement of the circular saw concerning 3rd Embodiment. It is a partial cross section side view of the jigsaw which concerns on the 4th Embodiment of this invention. It is a flowchart which shows operation | movement of the jigsaw which concerns on 4th Embodiment. It is explanatory drawing which shows the correlation of a speed dial selection value and the setting rotational speed of a motor.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Here, the case where the present invention is applied to a circular saw and a jigsaw will be described as an example. In addition, the same code | symbol is attached | subjected to the same or equivalent component, member, etc. which are shown by each drawing, and the overlapping description is abbreviate | omitted suitably. Further, each embodiment is an example, not limiting the invention, and all features and combinations thereof described in each embodiment are not necessarily essential.

  First, the configuration of the circular saw according to the embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an external view of a circular saw 100 according to an embodiment of the present invention. 2, FIG. 3, and FIG. 4 are a side view, a front view, and a plan view of the circular saw 100, respectively. A circular saw 100 according to an embodiment of the present invention is a cordless electric circular saw, and includes a base 1 and a main body 2.

  The base 1 is a substantially rectangular plate made of metal such as aluminum. The longitudinal direction of the base 1 coincides with the cutting direction of the circular saw 1, that is, the front-rear direction shown in FIG. The bottom surface of the base 1 is a sliding surface with the work material. The main body 2 is connected to the base 1 at two front and rear positions, and can rotate with respect to the base 1 and can be tilted to the left and right.

  The main body 2 includes a motor housing 3, a handle portion 4, a gear cover 5, a saw cover 6, a protective cover 7, and a saw blade 8. The motor housing 3, the handle portion 4, the gear cover 5, the saw cover 6 and the protective cover 7 correspond to the housing of the present invention, and the handle portion 4 corresponds to the handle of the present invention.

  The motor housing 3 is made of resin, for example, and incorporates a motor 9 as shown in FIG. The motor 9 is a drive source that rotationally drives the saw blade 8, and is a brushless motor in the present embodiment. As shown in FIG. 4, the motor 9 has a rotation shaft 9 a and is arranged so that the axial direction of the rotation shaft 9 a coincides with the left-right direction.

  The saw blade 8 is formed in a disk shape and is supported so as to be rotatable coaxially with the rotating shaft 9a of the motor 9. The lower part of the saw blade 8 protrudes downward from the bottom surface of the base 1. The saw blade 8 corresponds to the cutting blade of the present invention.

  The handle portion 4 is made of the same material as the motor housing 3 and extends in the front-rear direction above the motor housing 3. The handle portion 4 is a portion that is held by an operator during cutting work, and is provided with a main trigger switch 18 for the operator to turn on / off the drive of the motor 9.

  A battery pack mounting portion 4 a and a control circuit board storage portion 4 b are integrally provided at the lower rear end of the handle portion 4. The battery pack 20 can be detachably attached to the lower part of the battery pack mounting portion 4a by sliding from the rear. The battery pack 20 supplies driving power to the motor 9 in a state where the battery pack 20 is mounted on the battery pack mounting portion 4a. The battery pack 20 corresponds to the supply means of the present invention. The control circuit board storage portion 4 b is provided on the right side of the battery pack 20 and stores and holds the control circuit board 21. The control circuit board 21 is arranged so that the board plane is substantially parallel to the rotation surface of the saw blade 8, that is, substantially perpendicular to the rotation axis 9 a of the motor 9 and the rotation axis of the saw blade 8. A control unit (described later) for controlling is mounted.

  An operation display unit 16 is provided below the handle unit 4 and on the upper surfaces of the battery pack mounting unit 4a and the control circuit board storage unit 4b. FIG. 5 shows the configuration of the operation display unit 16. The operation display unit 16 includes a mode switch 16a, a mode display LED 16b, and a battery remaining amount display LED 16c. The mode switch 16a is a switch for switching the control mode of the motor 9, and corresponds to the switching means of the present invention. The operator can instruct switching of the control mode by operating the mode switch 16a. The mode display LED 16 b is a display unit for notifying the control mode of the motor 9. When the control mode of the motor 9 is switched, the mode display LED 16b is turned on or off to notify the control mode switching. The battery remaining amount display LED 16c is a display unit for notifying the operator of the remaining battery capacity of the battery pack 20.

  The gear cover 5 is provided on the right side of the handle portion 4. The gear cover 5 is made of metal, for example, and incorporates a rotation transmission mechanism (not shown) for transmitting the rotation of the motor 9 to the saw blade 8. Here, the rotation transmission mechanism is constituted by a known speed reduction mechanism or the like. The saw cover 6 is attached to the gear cover 5 and covers the upper portion of the saw blade 8 together with the gear cover 5. The saw cover 6 may be formed of the same material as the gear cover 5 and integrally therewith. The front end portions of the gear cover 5 and the saw cover 6 are rotatably connected by a rotation support portion 14 described later.

  The protective cover 7 is made of resin, for example, and is provided on the rear side of the gear cover 5 so as to be rotatable along the outer edges of the gear cover 5 and the saw cover 6. A spring (not shown) exists between the gear cover 5 and the protective cover 7. This spring urges the protective cover 7 against the gear cover 5 in the circumferential direction of the gear cover 5 and the saw cover 6 and in the direction covering the lower side of the saw blade 8 (counterclockwise in FIG. 2). Thereby, in the state where cutting work is not performed, the protective cover 7 covers the lower part of the saw blade 8, that is, the part protruding downward from the bottom surface of the base 1, except for the front part.

  A bevel plate 12 is erected in front of the base 1. The bevel plate 12 stands upright in a short direction substantially orthogonal to the cutting direction. A long hole 13 is provided in the bevel plate 12. The long hole 13 is formed in an arc shape centering on the first tilting shaft portion 15a extending in the cutting direction and orthogonal to the first tilting shaft portion 15a. An inclination angle adjusting lever 11 is engaged with the long hole 13. The rotation support portion 14 is supported so as to be tiltable to the left and right with respect to the base 1 with the first tilt shaft portion 15a as a center. The tilting position of the rotation support portion 14 is adjusted with the tilt angle adjustment lever 11 loosened, and is fixed by tightening the tilt angle adjustment lever 11. The rotation support portion 14 is an axis parallel to the rotation axes of the motor 9 and the saw blade 8 and supports the front end portion of the saw cover 6 so as to be rotatable.

  In FIG. 3, the tilt angle adjusting lever 11 is fixed at the lowermost portion of the long hole 13, the saw blade 8 is at an angle of approximately 90 ° with respect to the bottom surface of the base 1, and the rotational axis of the saw blade 8 is the base 1 It is substantially parallel to the bottom surface of. The tilt angle of the circular saw 100 in this state is denoted as 90 °.

  FIG. 6 is a front view showing the tilted state of the circular saw 100. In FIG. 6, the tilt angle adjusting lever 11 is fixed at the uppermost portion of the long hole 13, and the saw blade 8 forms an angle of about 45 ° with respect to the base 1. The tilt angle of the circular saw 100 in this state is denoted as 45 °. The circular saw 100 can be tilted within a tilt angle range of 90 ° to 45 °.

  On the rear side of the base 1, a link 10 is provided along the left side surface of the gear cover 5 so as to be rotatable around a tilting shaft portion 15 b coaxial with the first tilting shaft portion 15 a. The link 10 is made of a metal such as aluminum. Further, a cutting depth adjusting lever 19 is provided behind the base 1. The link 10 and the gear cover 5 can slide relative to each other when the cutting depth adjusting lever 19 is loosened, and the rotational position of the saw cover 6 with respect to the base 1, that is, the cutting depth can be adjusted. And the rotation position of the gear cover 5 can be fixed by tightening the cutting depth adjusting lever 19. In FIG. 2, the saw cover 6 is not rotated, and the cutting depth is maximum.

  FIG. 7 is a side view showing a minimum cutting state of the circular saw 100 according to the embodiment. In FIG. 7, the saw cover 6 is rotated to the maximum, and the cutting depth is minimum. For example, at the time of windowing or drilling, the operator sets the cutting depth to the minimum, grasps the handle portion 4 and lifts the back of the circular saw 100, and abuts the tip of the base 1 against the work material. In this state, the cutting work is started. At this time, the bottom surface of the base 1 forms an angle with the surface of the work material. Here, an angle formed by the front-rear direction of the bottom surface of the base 1 and the surface of the work material is referred to as a cutting angle. When the cutting operation is performed with the entire bottom surface of the base 1 in contact with the work material, the cutting angle is 0 °.

  Next, the circuit configuration of the circular saw 100 will be described with reference to FIG. FIG. 8 is a circuit diagram showing an electrical configuration of the circular saw 100 according to the embodiment of the present invention. As shown in FIG. 6, the circular saw 100 includes a motor 9, a battery pack 20, an inverter circuit unit 22, and a control unit 23.

  In this embodiment, the motor 9 is composed of a three-phase brushless motor, and includes a rotor 9b having a rotating shaft 9a (FIG. 4) and a plurality of permanent magnets, and a plurality of coils arranged at positions facing the rotor 9b. And a stator 9c provided.

  Three magnetic sensors 24 are arranged in the vicinity of the rotor 9b. The magnetic sensor 24 is, for example, a Hall element, detects the rotational position of the rotor 9b, and outputs a detection signal.

  The inverter circuit unit 22 is configured by mounting six switching elements 22a connected in a three-phase bridge form on a substrate. Here, the switching element 22 a is, for example, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor). A voltage from the battery pack 20 is input to the inverter circuit unit 22. The inverter circuit unit 22 converts this input voltage into an AC voltage and supplies it to the motor 9.

  A detection resistor 25 is connected between the battery pack 20 and the inverter circuit unit 22 on the drive current path of the motor 9.

  The control unit 23 is mounted on the control circuit board 21 shown in FIG. 4 and performs various controls such as drive control of the inverter circuit unit 22 and lighting control of the mode display LED 16b and the battery remaining amount display LED 16c. As shown in FIG. 6, the control unit 23 includes a motor current detection circuit 26, a switch operation detection circuit 27, a rotor position detection circuit 29, a motor rotation number detection circuit 30, an acceleration sensor 31, a calculation unit 32, and a control signal output. A circuit 33 is included.

  The motor current detection circuit 26 detects the drive current of the motor 9 based on the terminal voltage of the detection resistor 25. The drive current of the motor 9 corresponds to the load of the motor 9, and the motor current detection circuit 26 corresponds to the load detection means of the present invention.

  The switch operation detection circuit 27 detects the operation of the main trigger switch 18 by the operator. The rotor position detection circuit 29 detects the rotational position of the motor 9 based on the detection signal from the magnetic sensor 24. The motor rotation speed detection circuit 30 detects the rotation speed of the motor 9 based on the detection signal from the rotor position detection circuit 29.

  The acceleration sensor 31 is mounted on the control circuit board 21 and detects the acceleration of the main body 2 of the circular saw 100. FIG. 9 is a diagram showing a configuration of the acceleration sensor 31 in the present embodiment. In the present embodiment, the acceleration sensor 31 is a three-axis acceleration sensor, detects accelerations in three axes, that is, the X-axis, Y-axis, and Z-axis directions, and outputs them as voltage values Vx, Vy, and Vz. The acceleration sensor 31 is arranged such that the X axis and the Y axis are parallel to the control circuit board 21 and the Z axis is perpendicular to the control circuit board 21. As described above, the control circuit board 21 is disposed substantially perpendicular to the rotation axis of the saw blade 8. In the present embodiment, the acceleration sensor 31 is arranged such that the Z axis is substantially parallel to the rotation axis of the saw blade 8 and the X axis and the Y axis are substantially perpendicular to the rotation axis of the saw blade 8. The acceleration sensor 31 corresponds to the posture detection means of the present invention that detects the posture of the main body 2 of the circular saw 100.

  Returning to FIG. 8, the calculation unit 32 switches the control mode based on the signal from the mode switch 16a. In the present embodiment, the circular saw 100 is set with two control modes, that is, a power mode and a silent mode.

  The power mode is a control mode in which constant duty control is performed by setting a duty ratio of driving power supplied to the motor 9 to a predetermined value. In the circular saw 100 of the present embodiment, in the power mode, the duty ratio of the driving power supplied to the motor 9 is set to 100%. That is, the power mode is a control mode in which the saw blade 8 is rotated at a high speed.

  In the silent mode, when the driving current of the motor 9 is less than or equal to a predetermined value, constant speed control is performed to set the rotational speed of the saw blade 8 to a predetermined value. When the driving current exceeds a predetermined value, the driving power supplied to the motor 9 This is a control mode for performing constant duty control in which the duty ratio is set to a predetermined value. In the circular saw 100 according to the present embodiment, when the drive current of the motor 9 is increasing, when the drive current is 17 A or less, the rotational speed of the saw blade 8 is set to 3000 rpm (rotations / minute), and the drive current is If it exceeds 17A, the duty ratio of the driving power supplied to the motor 9 is set to 100%. Further, when the drive current of the motor 9 is decreasing, if the drive current is 14A or more, the duty ratio of the drive power supplied to the motor 9 is set to 100%, and when the drive current becomes smaller than 14A, the saw blade 8 Set the rotation speed to 3000 rpm. That is, the silent mode is a control mode in which the saw blade 8 is rotated at a low speed. The drive current corresponds to the load of the motor 9, and 17A and 14A correspond to the first load and the second load, respectively.

  When switching the control mode, the operator turns on the mode switch 16a. Based on this ON operation, a signal indicating that the ON operation has been performed is input from the mode switch 16a. The calculation unit 32 sets the duty ratio and the rotation speed based on the signal from the mode switch 16a.

  The calculation unit 32 calculates and detects the rotation speed of the saw blade 8 based on the rotation number of the motor 9 detected by the motor rotation number detection circuit 30 and the reduction ratio of the motor 9 and the saw blade 8. . The calculation unit 32 determines the selected control mode, the rotation position of the motor 9 detected by the rotor position detection circuit 29, the rotation speed of the saw blade 8 detected based on the detection result of the motor rotation number detection circuit 30, and the like. Based on this, the control signal output circuit 33 is driven, and each switching element 22a of the inverter circuit unit 22 is subjected to switching control. The computing unit 32 further determines whether the posture of the main body 2 is stable or unstable based on the output from the acceleration sensor 31.

  The control unit 23 performs lighting control of the mode display LED 16b and the battery remaining amount display LED 16c. The control unit 23 turns on the mode display LED 16b when the silent mode is set, and turns off the mode display LED 16b when the power mode is set. Further, the control unit 23 turns on and off the battery remaining amount display LED 16c according to the remaining battery capacity of the battery pack 20.

  Further, the control unit 23 has a memory (not shown) for storing the set control mode, a threshold value (described later) used for posture determination by the calculation unit 32, and the like.

  A control circuit voltage supply circuit 34 is connected between the battery pack 20 and the control unit 23. The control circuit voltage supply circuit 34 converts the voltage of the battery pack 20 into a voltage suitable for the operation of the control unit 23 and supplies the voltage to the control unit 23.

  Next, the determination of the posture by the acceleration sensor 31 and the control unit 23 according to the present embodiment will be described in more detail.

  The output voltage value V of the acceleration sensor 31 is expressed as V = 1.65 + 0.66 g (V) in the present embodiment. Here, g takes a value of +1 when the axial direction coincides with the direction of gravity, that is, downward in the vertical direction, takes a value of -1 when coincides with the upward in the vertical direction, and coincides with the horizontal direction. This parameter is zero. Hereinafter, gravity applied downward in the vertical direction is denoted as 1 g, and gravity applied upward in the vertical direction is denoted as −1 g. Further, gravity applied in the horizontal direction is denoted as 0 g.

  FIG. 10 is an explanatory diagram illustrating an example of the output voltage value of the acceleration sensor 31. In each figure, the vertical direction of the paper surface corresponds to the vertical direction, and the lower side is the direction of the ground. Further, the left-right direction and the front-back direction on the paper surface correspond to the horizontal direction.

  Fig.10 (a) shows the output voltage value of the acceleration sensor 31 in the stationary attachment state. The value in parentheses represents the gravity applied to each axial direction. As shown in FIGS. 2 and 4, the steady state is that the tilt angle of the circular saw 100 is 0 °, the base 1 is horizontal, and the main body 2 is positioned above the base 1 in the vertical direction. It's time. This corresponds to, for example, a case where a horizontal surface such as a floor is cut in parallel at an inclination angle of 0 °. At this time, in the acceleration sensor 31, the X-axis direction coincides with the vertical direction downward, and the Y-axis direction and the Z-axis direction coincide with the horizontal direction. In this case, the output values Vx, Vy, and Vz of the acceleration sensor 31 are 2.31V, 1.65V, and 1.65V, respectively.

  FIG. 10B corresponds to the case where the Y-axis direction of the acceleration sensor 31 coincides downward in the vertical direction, and the Z-axis direction and the X-axis direction coincide with the horizontal direction. At this time, the output values Vx, Vy, and Vz of the acceleration sensor 31 are 1.65V, 2.31V, and 1.65V, respectively.

  FIG. 10C corresponds to the case where the Z axis direction of the acceleration sensor 31 coincides with the vertical direction upward, and the X axis direction and the Y axis direction coincide with the horizontal direction. At this time, the output values Vx, Vy, and Vz of the acceleration sensor 31 are 1.65V, 1.65V, and 0.99V, respectively.

  FIG. 10D corresponds to the case where the Y-axis direction of the acceleration sensor 31 matches the vertical direction upward, and the Z-axis direction and the X-axis direction match the horizontal direction. At this time, the output values Vx, Vy, and Vz of the acceleration sensor 31 are 1.65V, 0.99V, and 1.65V, respectively.

  FIG. 10E corresponds to the case where the X-axis direction of the acceleration sensor 31 matches the vertical direction upward, and the Y-axis direction and the Z-axis direction match the horizontal direction. At this time, the output values Vx, Vy, and Vz of the acceleration sensor 31 are 0.99V, 1.65V, and 1.65V, respectively.

  FIG. 10F corresponds to the case where the Z-axis direction of the acceleration sensor 31 coincides downward in the vertical direction, and the X-axis direction and Y-axis direction coincide with the horizontal direction. At this time, the output values Vx, Vy, and Vz of the acceleration sensor 31 are 1.65V, 1.65V, and 2.31V, respectively.

  The calculation unit 32 determines whether the posture of the main body 2 is stable or unstable based on the output from the acceleration sensor 31. In the present embodiment, the calculation unit 32 determines the posture based only on the output voltage value Vx in the X-axis direction among the three output voltage values Vx, Vy, and Vz from the acceleration sensor 31. The calculation unit 32 stores a preset threshold value Vth and compares the output voltage value Vx of the acceleration sensor 31 with the threshold value Vth. When the output voltage value Vx is equal to or less than the threshold value Vth, it is determined that the posture of the main body 2 is unstable. Further, when the output voltage value Vx is larger than the threshold value Vth, it is determined that the posture of the main body 2 is stable.

  FIG. 11 is an explanatory diagram showing the gravity applied to the X axis of the acceleration sensor 31 and the output voltage value Vx under each cutting condition. “Parallel cutting” is a cutting operation when cutting a horizontal surface such as a floor, and “wall cutting” corresponds to a cutting operation when cutting a vertical surface such as a wall. “Ceiling cutting” is a cutting operation in which a horizontal surface located above an operator such as a ceiling is cut by placing the base 1 on the upper side and the main body 2 on the lower side. For each cutting operation, the output voltage value Vx corresponding to the case where the cutting depth is maximum (FIG. 2) and the case where the cutting depth is minimum (FIG. 7) is shown.

  First, the case of parallel cutting will be described. In FIG. 11, “right angle cut” corresponds to the case where the tilt angle is 90 ° (FIG. 3), and “tilt cut” corresponds to the case where the tilt angle is 45 ° (FIG. 6). In the case of a right angle cut with a maximum cutting depth and a tilt angle of 90 °, the X axis of the acceleration sensor 31 coincides downward in the vertical direction, and the gravitational force in the X axis direction is 1 g. At this time, the output voltage value Vx is 2.31V. Further, when the cutting depth is the maximum and the tilting angle is 45 °, the main body 2 tilts, so that the X-axis direction of the acceleration sensor 31 is also shifted by 45 ° from the vertical direction. At this time, the gravity applied to the acceleration sensor 31 in the X-axis direction is 0.71 g, and the output voltage value Vx is 2.12V.

  On the other hand, when the cutting depth is minimum, the cutting operation is performed in a state where the rear of the circular saw 100 is lifted and the tip portion of the base 1 is in contact with the work material. FIG. 11 shows the output voltage value Vx when the angle between the front-rear direction of the bottom surface of the base 1 and the horizontal direction, that is, the cutting angle is 30 °. When the tilt angle is 90 °, the main body 2 is tilted only in the front-rear direction, and the gravity applied to the acceleration sensor 31 in the X-axis direction is 0.87 g. In this case, the output voltage value Vx of the acceleration sensor 31 is 2.22V. When the tilt angle is 45 °, the main body 2 is tilted in both the front-rear direction and the left-right direction, and the gravity applied to the acceleration sensor 31 in the X-axis direction is 0, 61 g. In this case, the output voltage value Vx of the acceleration sensor 31 is 2.05V.

  Next, the case of wall cutting will be described. In the case of right-angle cutting with a maximum cutting depth and a tilt angle of 90 °, the bottom surface of the base 1 of the circular saw 100 coincides with the vertical direction, and the X-axis direction of the acceleration sensor 31 coincides with the horizontal direction. At this time, gravity applied to the acceleration sensor 31 in the X-axis direction is 0 g, and the output voltage value Vx is 1.65V. On the other hand, when the cutting depth is the minimum, the cutting angle is 30 °, and the tilt angle is 90 °, the gravitational force applied to the acceleration sensor 31 in the X-axis direction varies depending on the cutting direction, from −0.5 g to +0. A value between 5 g will be taken. For example, when the cutting direction is upward in the vertical direction, the gravitational force in the X-axis direction is 0.5 g, and the output voltage value Vx is 1.98V. Further, when the cutting direction is downward in the vertical direction, the gravitational force in the X-axis direction is −0.5 g, and the output voltage value Vx is 1.32V.

  Next, the case of ceiling cutting will be described. In the case of right-angle cutting with a maximum cutting depth and a tilt angle of 90 °, the bottom surface of the base 1 of the circular saw 100 coincides with the horizontal direction, and the X-axis direction of the acceleration sensor 31 coincides upward in the vertical direction. At this time, the gravity applied to the acceleration sensor 31 in the X-axis direction is −1 g, and the output voltage value Vx is 0.99V. On the other hand, when the cutting depth is minimum, the cutting angle is 30 °, and the tilting angle is 90 °, the gravitational force in the X-axis direction of the acceleration sensor 31 is −0.87 g, and the output voltage value Vx is 1.08V. It is.

  In consideration of the output voltage value Vx under each cutting condition shown in FIG. 11, in the circular saw 100 of the present embodiment, the threshold value Vth used for determining the posture of the main body 2 is set to 2.00V. This makes it possible to determine that the posture is stable in the case of parallel cutting, and to determine that the posture is unstable in the case of wall cutting and ceiling cutting, regardless of the tilt angle or the cutting angle. .

  Next, the operation of the circular saw 100 according to the first embodiment will be described in detail based on FIG. FIG. 12 is a flowchart showing the operation of the circular saw 100 according to the first embodiment. In the present embodiment, the circular saw 100 performs posture detection and determination at the start of driving of the motor 9 and during operation in the power mode.

  Note that the flowchart shown in FIG. 12 is started when the main trigger switch 18 is turned on by the operator's operation, and ends when the main trigger switch 18 is turned off.

  When the main trigger switch 18 is turned on, the arithmetic unit 32 reads a control mode from a memory (not shown) (step S101). The memory stores the previously set control mode, and the calculation unit 32 reads the control mode.

  Moreover, the calculating part 32 determines whether the attitude | position of the main body 2 of the circular saw 100 is unstable based on the output voltage value Vx from the acceleration sensor 31 (step S102). In the case of parallel cutting, the output voltage value Vx from the acceleration sensor 31 is larger than the threshold value Vth = 2.00 V as shown in FIG. The computing unit 32 compares the output voltage value Vx with the threshold value Vth, and determines that the posture of the main body 2 is not unstable when the output voltage value Vx is larger than the threshold value Vth (step S102: No). Subsequently, the calculation unit 32 determines whether or not the control mode read from the memory is the power mode (step S103).

  In step S102, in the case of wall cutting or ceiling cutting, the output voltage value Vx from the acceleration sensor 31 is a value smaller than the threshold value Vth = 2.00V as shown in FIG. When the output voltage value Vx is less than the threshold value Vth, the calculation unit 32 determines that the posture of the main body 2 is unstable (Step S102: Yes). In this case, the calculation unit 32 sets the silent mode without determining whether the control mode read from the memory is the power mode or the silent mode. The computing unit 32 stores the silent mode in the memory.

  When the silent mode is set in the memory (step S103: No), or when it is determined that the posture of the main body 2 is unstable (step S102: Yes), the control unit 23 performs the control in the silent mode. Do. The computing unit 32 detects the rotational speed of the saw blade 8 based on the signal from the motor rotational speed detection circuit 30, and determines whether or not the detected rotational speed is less than 3500 rpm (step S104). Since the rotational speed of the saw blade 8 is 0 at the start of driving, it is determined that it is less than 3500 rpm (step S104: Yes). Subsequently, the control unit 23 turns on the mode display LED 16b in order to notify the operation in the silent mode (step S105). Then, the control unit 23 performs constant speed control so as to increase and maintain the rotational speed of the saw blade 8 up to 3000 rpm (step S106).

  In step S104, when the rotational speed of the saw blade 8 is 3500 rpm or more (step S104: No), the calculation unit 32 performs soft fall to lower the rotational speed to 3000 rpm by the soft start control (step S113). When the rotational speed reaches 3000 rpm, the control unit 23 turns on the mode display LED 16b (step S105), and performs constant speed control to maintain the rotational speed of the saw blade 8 at 3000 rpm (step S106).

  If the operation in the silent mode is continued without turning off the mode switch 16a (step S107: No), the control unit 23 continues the constant speed control. At this time, the load fluctuates according to the state of the cutting work, and the drive current flowing through the motor 9 fluctuates. The calculation unit 32 monitors the numerical value of the drive current detected by the motor current detection circuit 26, and when the drive current is 17A or less (No in Step S108), maintains the rotational speed of the saw blade 8 at 3000 rpm (Step S108). S106).

  When the load increases and the drive current exceeds 17 A (step S108: Yes), the control unit 23 performs the duty ratio of the drive power supplied to the motor 9 from the constant speed control that maintains the rotational speed of the saw blade 8 at 3000 rpm. The control shifts to constant duty control in which is set to 100%. The calculation unit 32 performs soft start-up that gradually increases the duty ratio toward 100% by soft start control (step S109). When the duty ratio reaches 100%, the operation of the motor 9 is continued by constant duty control (step S110). The calculating part 32 monitors the numerical value of drive current, and when drive current is 14 A or more (step S111: No), it continues constant duty control (step S110).

  When the load decreases and the drive current decreases to less than 14 A (step S111: Yes), the control unit 23 changes from constant duty control with a duty ratio of 100% to constant speed control that maintains the rotational speed of the saw blade 8 at 3000 rpm. Transition. The calculation unit 32 performs soft fall to lower the rotation speed to 3000 rpm by soft start control (step S112). When the rotational speed reaches 3000 rpm, the operation of the motor 9 is continued by constant speed control (step S106).

  When the constant speed control in the silent mode is continued (step S106), when the mode changeover switch 16a is turned on (step S107: Yes), the calculation unit 32 stores the power mode in the memory and performs soft start control. Software startup is performed to gradually increase the duty ratio toward 100% (step S114).

  Moreover, the calculating part 32 determines whether the attitude | position of the main body 2 is unstable based on the output voltage value Vx from the acceleration sensor 31 (step S102). If it determines with being unstable (step S102: Yes), the control part 23 will continue control in silent mode, without switching control mode from silent mode to power mode (step S104-S112).

  When it is determined that the posture of the main body 2 is not unstable after the mode switch 16a is turned on (step S108: Yes) (step S102: No), the calculation unit 32 is based on the power mode stored in the memory. The control is switched to the power mode (step S103: Yes).

  When the power mode is set in the memory at the start of startup or when the power mode is switched during the constant speed control (step S103: Yes), the control unit 23 turns off the mode display LED 16b (step S115). Then, constant duty control is performed to set the duty ratio of the driving power to 100% (step S116). The arithmetic unit 32 performs soft start-up that gradually increases the duty ratio toward 100% by soft start control, and when the duty ratio reaches 100%, the operation of the motor 9 is continued by constant duty control (step S32). S116).

  If the operation in the power mode is continued without turning on the mode switch (step S117: No), the calculation unit 32 always operates the posture of the main body 2 based on the output voltage value Vx from the acceleration sensor 31. It is determined whether or not is unstable (step S102). When the posture is not unstable (step S102: No), the control unit 23 continues the constant duty control in the power mode (steps S115 to S117).

  If it is determined that the posture of the main body 2 is unstable during the operation in the power mode (step S102: Yes), the calculation unit 32 stores the silent mode in the memory and changes the control mode from the power mode to silent. Enter mode. And the control part 23 performs control in silent mode (step S104-S112).

  When the mode switch 16a is turned on while the operation in the power mode is continued (step S117: Yes), the arithmetic unit 32 switches the control mode from the power mode to the silent mode based on the signal from the mode switch 16a. The silent mode is stored in the memory. Further, the control unit 23 turns on the mode display LED 16b (step S118). And the calculating part 32 performs the software fall which gradually reduces the rotational speed of the saw blade 8 to 3000 rpm by soft start control (step S119). When the rotational speed reaches 3000 rpm, the operation of the motor 9 is continued by constant speed control (step S106).

  As described above, when it is determined that the posture of the main body 2 is unstable at the start of driving of the motor 9, the silent mode is forcibly selected. Further, during the operation in the power mode, the posture is always determined, and when it is determined that the posture is unstable, the mode is immediately switched to the silent mode.

  FIG. 13 is an explanatory diagram showing the characteristics of the rotational speed of the saw blade 8 with respect to the drive current of the motor 9. In FIG. 13, the solid line indicates a characteristic curve when the silent mode is set, and the alternate long and short dash line indicates a characteristic curve when the power mode is set. The dotted line corresponds to the case where constant speed control is performed to keep the rotational speed of the saw blade 8 at 3000 rpm.

  In the circular saw 100, when the silent mode is set, when the drive current of the motor 9 is 17 A or less, constant speed control is performed, and the rotational speed of the saw blade 8 is maintained at 3000 rpm. When the drive current exceeds 17 A, a soft start-up is performed in which the duty ratio of the drive power of the motor 9 is gradually increased to 100% regardless of the rotation speed, and the duty ratio is maintained at 100%. By such control, the rotational speed of the saw blade 8 is increased from 3000 rpm at the time of constant speed control to about 3800 rpm. At this time, the rotational speed of the saw blade 8 and the drive current of the motor 9 are located on the power mode characteristic curve. Thereafter, as the drive current increases, the rotational speed of the saw blade 8 decreases.

  As described above, in the circular saw 100 according to the present embodiment, the silent mode is forcibly selected when it is determined that the posture of the main body 2 is unstable when the motor 9 starts to be driven. At the time of cutting work with an unstable posture such as cutting of the ceiling or the ceiling, the rotational speed of the saw blade 8 can be suppressed to 3000 rpm or less even when the load is small. Therefore, the occurrence of distortion of the cut surface is suppressed and good workability is ensured. In addition, the power consumption of the battery pack 20 can be suppressed, and the amount of work in a single charge can be increased.

  Furthermore, even if the posture is not unstable at the start of driving, the posture is always determined during operation in the power mode, and if it is determined to be unstable, the mode is immediately switched to the silent mode. Even when the operation continuously shifts from the parallel cutting to the wall cutting in the power mode, the control mode is switched and the rotation speed of the saw blade 8 is changed to a low speed without the operator operating the mode switch 16a. Therefore, good workability can be maintained.

  Even during operation in silent mode, if the drive current exceeds 17A, switching from constant speed control to constant duty control makes it possible to follow the load and increase drive power, further improving workability. Is realized. When the drive current is reduced to 14 A or less, the constant duty control is switched to the constant speed control, so that power consumption when the load is small can be suppressed. At this time, since different threshold values are used when the drive current is increasing and decreasing, it is possible to prevent frequent switching of the control mode, and it is possible to perform stable work.

  Next, a circular saw according to the second embodiment will be described. Since the configuration of the circular saw according to the present embodiment is the same as the configuration of the circular saw 100 according to the first embodiment, description thereof will be omitted. Here, the operation of the circular saw according to the second embodiment will be described with reference to FIG. FIG. 14 is a flowchart showing the operation of the circular saw according to the second embodiment. This embodiment is different from the first embodiment in that the posture of the main body 2 is determined only when the main trigger switch 18 is turned on.

  The flowchart shown in FIG. 14 starts when the main trigger switch 18 is turned on, and ends when the main trigger switch 18 is turned off. When the main trigger switch 18 is turned on, the calculation unit 32 reads out the control mode from the memory (step S101) and determines whether the posture of the main body 2 is unstable based on the output voltage value Vx from the acceleration sensor 31. Is determined (step S102).

  When it determines with the attitude | position of the main body 2 not being unstable (step S102: No), the calculating part 32 sets the control mode read from memory (step S103). If it is determined that the posture of the main body 2 is unstable (step S102: Yes), the calculation unit 32 sets the silent mode, and the control unit 23 lights the mode display LED 16b (step S105).

  When the silent mode is set, the control unit 23 performs constant speed control so as to increase and maintain the rotational speed of the saw blade 8 up to 300 rpm (step S106). Then, similarly to the circular saw 100 of the first embodiment, control based on the silent mode is performed (steps S107 to S112).

  It is determined that the posture of the main body 2 is not unstable at the time of startup (step S102: No), and the mode switch 16a is turned on when the power mode is set (step S103: Yes) and during the operation in the silent mode. In the case (step S107: Yes), the control unit 23 performs control based on the power mode (step S115 to step S119). After the power mode is set, the driving of the motor 9 is continued without determining the posture.

  As described above, in the circular saw according to the second embodiment, the posture of the main body 2 is determined only when the driving of the motor 9 is started, and the control mode is determined only by the operation of the mode switch 16a after the driving is started. Therefore, it is possible to prevent the start of cutting operation at high speed in an unstable posture, and the posture is misjudged due to vibration associated with the cutting operation after driving, and the control mode is unintentionally switched. It can be prevented from occurring. In addition, it is possible to prevent the control mode from being switched every time the posture is changed due to the cutting work after driving. Therefore, good workability is ensured and the cutting work can be continued in the operator's desired control mode, thereby improving convenience.

  Next, a circular saw according to the third embodiment will be described. Since the configuration of the circular saw according to the present embodiment is the same as the configuration of the circular saw 100 according to the first embodiment, description thereof will be omitted. Here, the operation of the circular saw according to the third embodiment will be described with reference to FIG. FIG. 15 is a flowchart showing the operation of the circular saw according to the third embodiment. In the present embodiment, the posture of the main body 2 is determined only when the main trigger switch 18 is turned on, which is the same as the circular saw according to the second embodiment, and when an unstable posture is detected. The second embodiment is different from the second embodiment in that only the constant speed control is performed by blinking the mode display LED 16b.

  The flowchart shown in FIG. 15 starts when the main trigger switch 18 is turned on, and ends when the main trigger switch 18 is turned off. When the main trigger switch 18 is turned on, the calculation unit 32 reads out the control mode from the memory (step S101) and determines whether the posture of the main body 2 is unstable based on the output voltage value Vx from the acceleration sensor 31. Is determined (step S102).

  When it is determined that the posture of the main body 2 is not unstable (step S102: No), the subsequent operation is the same as that of the second embodiment (steps S103 to S119).

  When it determines with the attitude | position of the main body 2 being unstable, the control part 23 blinks mode display LED16b (step S201). And the calculating part 32 performs constant speed control in order to maintain the rotational speed of the saw blade 8 at 3000 rpm (step S202).

  Note that the speed control indicated by the dotted line in FIG. 13 corresponds to the constant speed control (step S202 in FIG. 15) when the unstable posture of the main body 2 is detected in the circular saw of the present embodiment.

  As described above, in the circular saw according to the third embodiment, as in the second embodiment, the posture of the main body 2 is determined only when the driving of the motor 9 is started, and the mode is switched after the driving is started. Since switching of the control mode is performed only in accordance with the operation of the switch 16a, good workability is ensured, and the operator can continue cutting work in the desired control mode, thereby improving convenience. . In addition, when it is determined that the posture is unstable, only constant speed control is performed regardless of the magnitude of the load, so that good workability is maintained. In addition, since the mode display LED 16b blinks, it is possible to reliably notify the operator that the posture is unstable and the vehicle is operating under constant speed control, and convenience is improved.

  Next, a fourth embodiment will be described. In the present embodiment, the case where the present invention is applied to a jigsaw will be described as an example.

  FIG. 16 is a partial sectional side view of a jigsaw according to the fourth embodiment of the present invention. The jigsaw 200 includes a base 201 and a main body 202.

  The base 201 is a substantially rectangular plate made of metal such as aluminum. The longitudinal direction of the base 201 coincides with the cutting direction of the jigsaw 200, that is, the front-rear direction shown in FIG. The bottom surface of the base 201 is a sliding surface with the work material.

  The main body 202 includes a motor housing 203, a handle housing 204, a gear housing 205, and a blade 208. The motor housing 203, the handle housing 204, and the gear housing 205 correspond to the housing of the present invention, and the handle housing 204 and the gear housing 205 correspond to the cutting blade housing of the present invention.

  The motor housing 203 is made of, for example, resin, and as shown in FIG. 16, the motor 209 and the control unit 223 are incorporated, and a power cable 203a is provided. The power cable 203a extends rearward from the rear portion of the motor housing 203, and power is supplied to the jigsaw 200 by connecting to an external power source (not shown). In addition, although the jigsaw 200 of this Embodiment is connected and used for an external power supply, this invention is not limited to this. The present invention can also be applied to a cordless jigsaw that uses a battery pack as a power source. In this case, the battery pack corresponds to the supply means of the present invention.

  The motor 209 is a drive source that drives the blade 208, and is a brushless motor in the present embodiment. As shown in FIG. 16, the motor 209 has a rotating shaft 209a and is arranged so that the axial direction of the rotating shaft 209a coincides with the front-rear direction.

  The control unit 223 includes an acceleration sensor (not shown), detects the posture of the main body 202, and determines whether it is unstable. Further, the control unit 223 performs speed control of the motor 209.

  The handle housing 204 is made of the same material as the motor housing 203 and connects the rear portion of the motor housing 203 and the upper portion of the gear housing 205. The handle housing 204 is a portion that is held by an operator during a cutting operation, and includes a main trigger switch 218, a switch mechanism 217, and a setting mechanism 227. A long hole 204 a extending in the front-rear direction is formed in the upper front portion of the handle housing 204.

  The main trigger switch 218 is provided on the lower side of the front portion of the handle housing 204 and is configured to be operable while an operator holds the handle housing 204. The switch mechanism 217 is housed in the handle housing 204 and is connected to the main trigger switch 218 and the control unit 223. The switch mechanism 217 detects that the main trigger switch 218 is turned on and outputs a signal to the control unit 223.

  The setting mechanism 227 is a mechanism for setting the rotational speed of the motor 209, and is accommodated in front of the switch mechanism 217 inside the handle housing 204. The setting mechanism 227 includes a speed dial 216 that can be manually operated by an operator, and a position detection unit 228 that detects a rotational position of the speed dial 216. The setting mechanism 227 corresponds to the setting unit of the present invention.

  The speed dial 216 has a disk shape, and six numbers “1” to “6” are engraved on the side surface. These numbers are used when selecting the rotational speed of the motor 209. The number “1” is a number indicating that the selected rotation speed is the smallest, that is, the low speed, and the number “6” is a number indicating that the selected rotation speed is the highest, that is, the high speed. is there.

  The numbers stamped on the speed dial 216 are visible one by one from the elongated hole 204 a of the handle housing 204. The operator selects a desired rotation speed by rotating the speed dial 216 and changing the number visible from the long hole 204a. Hereinafter, a number that can be visually recognized from the long hole 204a is referred to as a selection value of the speed dial 216. For example, when the selection value of the speed dial 216 is “1”, the rotation speed of the selected motor 209 is the slowest, and when the selection value of the speed dial 216 is “6”, the rotation speed of the selected motor 209. Is the fastest. Hereinafter, the rotational speed of the motor 209 selected based on each selected value is described as a rotational speed “1” and a rotational speed “2”.

  For example, when the rotation speed “1” is selected, the operator rotates the speed dial 216 so that the number located in the long hole 204a becomes “1”. When the speed dial 216 rotates, the position detection unit 228 detects the rotation position and outputs a signal to the setting mechanism 227. The setting mechanism 227 detects the selection value “1” of the speed dial 216 based on the signal from the position detection unit 228, sets the rotation speed “1”, and outputs a signal to the control unit 223.

  The gear housing 205 is formed on the front side of the motor housing 203 so as to extend in the vertical direction, and includes a motion conversion mechanism 206 and a plunger 207 inside thereof. Further, an LED (not shown) for notifying the speed control at a low rotational speed equal to or lower than the rotational speed “3” is provided above the gear housing 205 and below the handle housing 204. Further, a base 201 is attached to the lower side of the gear housing 205.

  The motion conversion mechanism 206 includes a support shaft 261, a gear portion 262, and an engagement pin 263. The support shaft 261 is provided so as to extend in the front-rear direction substantially at the center in the vertical direction inside the gear housing 205. The gear portion 262 is rotatably supported on the gear housing 205 by a support shaft 261. The engagement pin 263 rotates around the support shaft 261 together with the gear portion 262. The engagement pin 263 protrudes forward in a state different from and parallel to the rotation shaft 209a of the motor 209.

  The plunger 207 has a substantially cylindrical shape, extends in a direction orthogonal to the rotation shaft 209a of the motor 209, that is, in the vertical direction, and is supported by the main body 2 so as to be able to reciprocate in the vertical direction. The plunger 207 includes a pin receiving portion 207A and a blade holding portion 207B.

  The pin receiving portion 207A is provided substantially at the center in the up-down direction of the plunger 207, is substantially U-shaped in a side view, and is arranged so that the U-shaped opening faces rearward. The pin receiving portion 207A extends in the left-right direction (the front and back direction in FIG. 16), and the engagement pin 263 is inserted therein. Since the engaging pin 263 is allowed to move in the left-right direction within the groove of the pin receiving portion 207A and is restricted from moving in the vertical direction, the pin receiving portion 207A can only move up and down in accordance with the movement of the engaging pin 263. I do. Thereby, the motion conversion mechanism 206 can convert the rotational motion of the rotating shaft 209a of the motor 9 into vertical motion.

  The blade holding portion 207B is provided at the lower end portion of the plunger 207, and holds the blade 208 in a detachable manner.

  The blade 208 is held by the blade holding portion 207 </ b> B and protrudes downward from the bottom surface of the base 201. A blade portion 208 </ b> A extending in the vertical direction is formed at the front portion of the blade 208. The blade 208 corresponds to the cutting blade of the present invention.

  Subsequently, the operation of the jigsaw 200 according to the present embodiment will be described with reference to FIG. FIG. 17 is a flowchart showing the operation of the jigsaw 200 according to the fourth embodiment.

  The flowchart shown in FIG. 17 starts when the main trigger switch 218 is turned on and ends when the main trigger switch 218 is turned off. When the main trigger switch 218 is turned on, the control unit 223 determines whether the selected value of the speed dial 216 is greater than “3” based on the signal from the setting mechanism 227 (step S301).

  When the selection value is any one of “1”, “2”, and “3” (step S301: No), the control unit 223 uses the rotation speed corresponding to the selection value as a set rotation speed to control the speed of the motor 209. Is performed (step S310).

  When the selected value is any one of “4”, “5”, and “6” (step S301: Yes), the control unit 223 determines whether the posture of the main body 202 is unstable based on the output from the acceleration sensor. Whether or not is determined (step S302).

  When it determines with the attitude | position of the main body 202 not being unstable (step S302: No), the control part 223 performs speed control of the motor 209 by setting the rotational speed corresponding to a selection value as a setting rotational speed (step S310).

  When it determines with the attitude | position of the main body 202 being unstable (step S302: Yes), the control part 223 lights up LED which is not shown in figure (step S303). In addition, the control unit 223 performs speed control of the motor 209 using the rotation speed corresponding to “3” as the set rotation speed (step S304).

  When the speed dial 216 is operated by the operator during the speed control of the motor 209 by turning on the LED and the selection value is changed (step S305: Yes), the control unit 223 turns off the LED (step S306). .

  Subsequently, the control unit 223 determines whether or not the difference between the rotation speed corresponding to the selected value and the rotation speed is larger than a preset threshold value (step S307).

  When it is determined that the value is larger than the threshold value (step S307: Yes), the control unit 223 performs software startup to gradually increase the rotation speed (step S308). When the selected rotational speed is reached, the speed of the motor 209 is controlled using the rotational speed as the set rotational speed (step S309).

  When it is determined in step S307 that it is equal to or less than the threshold value (step S307: No), the control unit 223 performs speed control of the motor 209 using the selected rotation speed as the set rotation speed without performing software startup. (Step S309).

  As described above, the posture of the main body 202 is determined only when the selected value of the speed dial 216 is 4 or more at the start of driving of the motor 209, and when the posture is determined to be unstable, Speed control is performed at a low rotational speed. When the selection value of the speed dial 216 is changed during driving, the speed control at the low rotation speed is canceled and the speed control according to the selection value of the speed dial 216 is switched.

  FIG. 18 is an explanatory diagram showing the correlation between the selected value of the speed dial 216 and the set rotational speed of the motor 209. When it is determined that the posture of the main body 202 is not unstable, the set rotation speed of the motor 209 increases as the selected value increases, that is, increases in speed, as indicated by a broken line. On the other hand, when it is determined that the posture of the main body 202 is unstable, as indicated by a solid line, the rotation speed corresponding to the selection value is set from “1” to “3”. When the selection value is “4” or more, the rotation speed corresponding to the selection value “3” is fixed.

  As described above, in the jigsaw according to the fourth embodiment, the posture of the main body 202 is determined only when the driving of the motor 209 is started. Therefore, even when the main body 202 vibrates as the blade 208 is driven, the posture is determined. It is possible to prevent unintentional switching to the rotational speed based on the erroneous determination. In addition, when it is determined that the posture is unstable, the rotation speed is set to “3”, so that it is possible to prevent the cutting operation from starting at a high speed in an unstable posture, and the distortion of the cut surface is reduced. Occurrence and the like can be prevented, and good workability can be ensured. Further, since the posture is determined only when the selected value of the speed dial 216 is “4” or more, an unnecessary determination operation is not performed when setting a low rotational speed that does not require the rotational speed to be changed. Smooth start of work is possible.

  Furthermore, since it is determined that the posture is unstable and the speed is controlled at a low rotational speed, the LED is lit, so that it is possible to notify the operator and the convenience is improved. If the selected value of the speed dial 216 is changed by the operator's operation during speed control at a low speed, the speed control at the low speed is canceled and the speed is set according to the selected value. Therefore, when the unstable posture is improved during the cutting operation, the rotation speed can be changed at high speed according to the work situation without turning off the driving of the motor 209. Is improved.

  While the present invention has been described based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  In the embodiment described above, when it is determined that the posture is unstable, the control mode and the rotation speed are automatically switched. However, the present invention is not limited to this. For example, when it is detected that the unstable posture is released based on the output from the acceleration sensor, the control may be changed to constant duty control or high rotation speed. In this case, it is desirable to switch the mode change only when the release of the unstable posture is detected continuously for a predetermined time so that the rotation speed of the motor does not repeat fluctuation.

  In the embodiment described above, constant speed control is performed at a low rotational speed in the case of an unstable posture, but the present invention is not limited to this. For example, the duty ratio of the driving power supplied to the motor may be set low when an unstable posture is detected, and the duty ratio may be changed high when not unstable.

1, 201 Base 2, 202 Main body 3, 203 Motor housing 8 Saw blade 9, 209 Motor 16a Mode change switch 20 Battery pack 23, 223 Control unit 31 Accelerometer 100 Circular saw 200 Jigsaw 208 Blade 216 Speed dial

Claims (10)

A housing to which a cutting blade is mounted;
A motor housed in the housing and driving the cutting blade;
Supply means for supplying drive power to the motor;
A base attached to the housing and slidable on a work material;
Posture detecting means for detecting the posture of the housing;
A cutting tool comprising: control means for controlling the motor to have a predetermined rotational speed when a predetermined attitude is detected by the attitude detecting means. Load detecting means for detecting the load of the motor;
2. The cutting tool according to claim 1, wherein when the load detected by the load detection unit exceeds a first load, the control unit controls the driving power to have a predetermined duty ratio. .   The control means controls the motor to be at the predetermined rotational speed when the load detected by the load detection means becomes equal to or less than a second load that is smaller than the first load. The cutting tool according to claim 2.   The control means can selectively switch between rotational speed control for controlling the motor to achieve the predetermined rotational speed and duty control for controlling the driving power to achieve the predetermined duty ratio. The cutting tool according to claim 2, wherein the cutting tool is provided.   The cutting tool according to claim 4, wherein the control means switches between the rotation speed control and the duty control based on the posture detected at the time of activation. Further comprising setting means for setting the rotational speed;
When the set rotation speed is equal to or higher than the predetermined rotation speed, the attitude is detected by the attitude detection means, and the rotation speed control and the duty control are switched based on the detected attitude. The cutting tool according to claim 4. It further has switching means for switching to the duty control,
5. The cutting according to claim 4, wherein when the control unit is switched to the duty control by the switching unit, the duty control is continued even when the predetermined posture is detected by the posture detection unit. tool.   The cutting tool according to any one of claims 1 to 7, wherein the supply means includes a battery. The housing includes a motor housing that houses the motor, and a handle.
The cutting tool according to any one of claims 1 to 8, wherein the posture detection means is attached to the handle. The cutting tool according to any one of claims 1 to 9, wherein the posture detection means is an acceleration sensor.

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