Portable cutting machine

Abstract

To provide a technique capable of detecting a predictive behavior of a kickback before the kickback occurs in a portable cutting machine.SOLUTION: The portable cutting machine according to the present invention is provided with a physical quantity detection unit configured to detect physical quantities related to the behavior of the portable cutting machine when it is used, and a predictive behavior detection unit configured to detect predictive behavior of kickback occurrence based on the detection results of the physical quantity detection unit.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a portable cutting machine.

Background Art

[0002] A cutting machine called a portable marnoko (hereinafter simply referred to as a marnoko) includes a base and a main body. The main body includes an electric motor and a substantially circular cutting tool that is rotationally driven by the electric motor. The main body is disposed on one side with respect to the base, but a part of the cutting tool protrudes to the other side beyond the base. When using such a marnoko, the user brings the lower surface of the base into contact with the material to be cut with the cutting tool rotating, and moves the cutting machine forward. As a result, the cutting tool protruding beyond the base cuts the material to be cut.

[0003] In such a marnoko, at the time of (or just before) completion of cutting, there is a risk that the cutting tool is sandwiched between the material to be cut from both sides thereof, and kickback occurs.

[0004] The following Patent Document 1 discloses a technique for detecting the occurrence of such kickback. Specifically, an acceleration sensor and an angular velocity sensor are used to detect a change in the posture of the marnoko, and based on the detection result, the occurrence of kickback is detected. When the occurrence of kickback is detected, the driving of the electric motor is stopped.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, Patent Document 1 described above cannot predict the occurrence of kickback. If the occurrence of kickback could be predicted, desired measures (for example, stopping the drive of the electric motor) could be taken earlier. Such problems are common not only to portable miter saws but also to various portable cutting machines in which kickback can occur when the cutting tool is pinched by the material to be cut. For this reason, it is expected to provide a technique capable of detecting the precursor behavior of kickback before the occurrence of kickback.

[0007] This specification discloses a portable cutting machine. The portable cutting machine may include a physical quantity detection unit configured to detect a physical quantity related to the behavior of the portable cutting machine during use, and a precursor behavior detection unit configured to detect a precursor behavior of the occurrence of kickback based on the detection result of the physical quantity detection unit.

[0008] According to this portable cutting machine, the precursor behavior of kickback can be detected. That is, it is possible to predict the occurrence of kickback before kickback occurs. Therefore, compared with a configuration that detects that kickback has already occurred, desired measures (for example, stopping the drive of the electric motor) can be taken earlier.

[0009] This specification further discloses a portable cutting machine. The portable cutting machine may include a rotatable cutting tool, an electric motor for providing a rotational driving force to the cutting tool, a physical quantity detection unit configured to detect a physical quantity related to the behavior of the portable cutting machine during use, and a controller configured to control the operation of the electric motor. The controller may be configured to execute any one of stopping the power supply to the electric motor, reducing the output of the electric motor, and braking the rotation of the electric motor or the cutting tool when the physical quantity satisfies a predetermined condition. The physical quantity may include at least one of the vibration of the portable cutting machine and the current value of the electric motor.

[0010] According to this portable cutting machine, compared with a configuration that detects that a kickback has already occurred, based on at least one of the vibration of the portable cutting machine and the current value of the electric motor, the power supply to the electric motor can be stopped, the output of the electric motor can be reduced, or the rotation of the electric motor or the cutting tool can be braked earlier.

Brief Description of the Drawings

[0011]

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Modes for Carrying Out the Invention

[0012] Hereinafter, representative and non-limiting specific examples of the present invention will be described in detail with reference to the drawings. This detailed description is merely intended to show those skilled in the art the details for implementing preferred examples of the present invention, and is not intended to limit the scope of the present invention. Further, the additional features and inventions disclosed hereinafter can be used separately or together with other features and inventions in order to provide further improved devices, methods for manufacturing the same, and methods for using the same.

[0013] Also, the combinations of features and steps disclosed in the following detailed description are not essential for implementing the present invention in the broadest sense, and are described only for the purpose of explaining representative specific examples of the present invention in particular. Further, the various features of the above and below representative specific examples, as well as the various features described in the independent and dependent claims, do not have to be combined as described in the specific examples herein or in the order listed when providing additional and useful embodiments of the present invention.

[0014] All features described in this specification and / or the claims are intended to be disclosed separately and independently of each other as limitations to the initial disclosure and the claimed specific matters, apart from the configurations of the features described in the embodiments and / or the claims. Further, all descriptions regarding numerical ranges and groups or populations are made with the intention of disclosing intermediate configurations as limitations to the initial disclosure and the claimed specific matters.

[0015] In one or more embodiments, the physical quantity detection unit may include a vibration sensor configured to detect the vibration of the portable cutting machine. The precursor behavior detection unit may be configured to detect the occurrence of precursor behavior based on the vibration value detected by the vibration sensor. Immediately before the occurrence of kickback, a state occurs in which the cutting tool of the cutting machine is intermittently clamped by the workpiece to be cut from both sides. In this state, vibrations smaller than those at the time of kickback (i.e., when the cutting tool is completely clamped) occur. According to this configuration, by detecting this small vibration, the precursor behavior of kickback can be detected.

[0016] In one or more embodiments, the vibration sensor may be configured to detect the vertical vibration in the posture of the portable cutting machine during use. The precursor behavior detection unit may be configured to detect the occurrence of precursor behavior based on the vertical vibration value. When the cutting tool is clamped by the workpiece to be cut from both sides, due to the rotation direction of the cutting tool, an upward reaction force from the workpiece acts on the rear part of the cutting tool (the part opposite to the side where cutting progresses), and a downward reaction force from the workpiece acts on the front part of the cutting tool (the part where cutting progresses). Therefore, the portable cutting machine behaves in such a way that its rear side is lifted. This means that in the precursor behavior of kickback, the vertical vibration becomes larger than the vibrations in other directions. According to this configuration, the precursor behavior of kickback can be accurately detected based on the relatively large vertical vibration.

[0017] In one or more embodiments, the vibration sensor may be in the form of an acceleration sensor. According to this configuration, vibrations can be easily detected using a general-purpose sensor.

[0018] In one or more embodiments, when the vibration sensor defines the direction in which cutting is advanced by the portable cutting machine as the front side and the side opposite to the front side as the rear side, it may be disposed behind the rotation axis of the cutting tool of the portable cutting machine. As described above, in the pre-kickback behavior, the portable cutting machine behaves such that its rear side is lifted. According to this configuration, since the vibration sensor is disposed in the region where the portable cutting machine is largely displaced in the pre-kickback behavior, vibrations corresponding to the pre-kickback behavior can be accurately detected.

[0019] In one or more embodiments, the portable cutting machine may include a base, an electric motor disposed on a first side with respect to the base, a cutting tool configured to rotate about a rotation axis by a driving force provided by the electric motor, and a cutting depth adjustment mechanism configured to displace the cutting tool relative to the base such that the amount of protrusion of the cutting tool from the first side of the base to a second side opposite to the first side can be changed. The vibration sensor may be directly or indirectly attached to the base. According to this configuration, since the vibration sensor is attached to the base where the position with respect to the material to be cut does not change even when the setting of the amount of protrusion of the cutting tool with respect to the base changes, the detection position of the vibration with respect to the material to be cut can be fixed. Therefore, vibrations corresponding to the pre-kickback behavior can be accurately detected regardless of the setting of the amount of protrusion of the cutting tool with respect to the base.

[0020] In one or more embodiments, the portable cutting machine may include a base and a main body. The main body may have an electric motor disposed on a first side with respect to the base, and a cutting tool configured to rotate about a rotation axis by a driving force provided by the electric motor. The portable cutting machine may further include a cutting depth adjustment mechanism configured to displace the main body relative to the base so that the protruding amount of the cutting tool to a second side opposite to the first side from the base can be changed. The vibration sensor may be attached to the main body adjacent to the electric motor behind the electric motor. According to this configuration, the vibration sensor pivots integrally with the main body according to the setting of the protruding amount of the cutting tool with respect to the base, and is disposed adjacent to the electric motor behind the electric motor, so that the electrical wiring related to the vibration sensor can be realized with a simple configuration, and the insulation structure can also be simplified. Moreover, since the vibration sensor is disposed behind the electric motor, it can accurately detect vibrations corresponding to the predictive behavior of kickback that causes the rear of the cutting machine to lift compared to the case where it is disposed in front of the electric motor.

[0021] In one or more embodiments, the portable cutting machine may include a rotatable cutting tool and an electric motor for providing a rotational driving force to the cutting tool. The physical quantity detection unit may include a current detector configured to detect the current value of the electric motor. The predictive behavior detection unit may be configured to detect the occurrence of predictive behavior based on the current value detected by the current detector. Immediately before the occurrence of kickback, a state occurs in which the cutting tool of the cutting machine is intermittently clamped by the material to be cut from both sides thereof. In this state, the load on the electric motor increases and the current value rises. The value or rising speed of the current value at this time is smaller than that at the time of occurrence of kickback (that is, the state where the cutting tool is completely clamped). According to this configuration, the predictive behavior of kickback can be detected by detecting such a value or rising speed of the current value.

[0022] In one or more embodiments, the current detector may include a shunt resistor. According to this configuration, the current can be easily detected using off-the-shelf components.

[0023] In one or more embodiments, the predictive behavior detection unit may be configured to detect the occurrence of a predictive behavior when the rate of increase in the current value is equal to or greater than a threshold value set to 350 (amperes / second) or less. With this configuration, it is possible to clearly distinguish between the occurrence of a kickback and a predictive behavior of a kickback, and to accurately detect the predictive behavior of a kickback.

[0024] In one or more embodiments, the portable cutting machine may include a rotatable cutting tool and an electric motor for providing a rotational drive force to the cutting tool. The physical quantity detection unit may include a rotation speed sensor configured to detect the rotation speed of the electric motor. The predictive behavior detection unit may be configured to detect the occurrence of the predictive behavior when the speed reduction rate of the electric motor's output is equal to or greater than a threshold set to 20 (rpm / millisecond) or less. Just before the occurrence of kickback, a state occurs in which the cutting tool of the cutting machine is intermittently pinched from both sides by the material to be cut. In this state, the load on the electric motor increases, and the rotation speed of the electric motor decreases. The speed reduction rate of the rotation speed at this time is smaller than that at the occurrence of kickback (i.e., when the cutting tool is completely pinched). According to this configuration, the predictive behavior of kickback can be detected by detecting such a speed reduction rate of the rotation speed.

[0025] In one or more embodiments, the portable cutting machine may include a rotatable cutting tool and an electric motor for providing a rotational driving force to the cutting tool. The physical quantity detection unit may include a vibration sensor configured to detect the vibration of the portable cutting machine and a current detector configured to detect the current value of the electric motor. The foreshadowing behavior detection unit may be configured to detect the occurrence of foreshadowing behavior based on the vibration value detected by the vibration sensor and the current value detected by the current detector. The occurrence of vibration or an increase in the current value may occur not only as a foreshadowing behavior of kickback. For example, vibrations of a predetermined magnitude or greater may also be caused by a collision of the portable cutting machine (e.g., a collision with the material to be cut), and the current value may also occur during high-load cutting. However, the simultaneous occurrence of the generation of vibration and an increase in the current value is unlikely to occur other than as a foreshadowing behavior of kickback. Therefore, according to this configuration, the foreshadowing behavior of kickback can be detected with higher accuracy. Further, in addition to vibration, the presence or absence of the occurrence of foreshadowing behavior of kickback is determined based on the current value as well. Therefore, compared with the case of determining the presence or absence of the occurrence of foreshadowing behavior of kickback based only on vibration, the threshold value related to vibration can be set to a smaller value. Therefore, the foreshadowing behavior of kickback can be detected earlier.

[0026] In one or more embodiments, the vibration sensor may be configured to detect at least the vertical vibration in the posture of the portable cutting machine during use. The foreshadowing behavior detection unit may be configured to detect the occurrence of foreshadowing behavior based on the vertical vibration value. As described above, in the foreshadowing behavior of kickback, the vertical vibration becomes relatively large. Therefore, according to this configuration, the foreshadowing behavior of kickback can be accurately detected.

[0027] Hereinafter, with reference to FIGS. 1 to 11, a portable saw (hereinafter simply referred to as a saw) 10 as an example of a portable cutting machine according to an exemplary first embodiment will be described in more detail. In the following description, when the user holds the saw 10 in hand and cuts a material to be cut (in other words, when the saw 10 is in the posture during use), the side where the saw 10 advances (the side where cutting is advanced by a cutting tool 35 described later) is defined as the front side of the saw 10, and the opposite direction is defined as the rear side of the saw 10. Also, at this time, the side located vertically upward is defined as the upper side of the saw 10, and the opposite side is defined as the lower side of the saw 10. Further, the direction orthogonal to the front-rear direction and the up-down direction is defined as the left-right direction. Among the left-right directions, the right side when viewed from the rear side to the front side is defined as the right side of the saw 10, and the opposite side is defined as the left side of the saw 10. The material to be cut is mainly wood.

[0028] As shown in FIGS. 1 and 2, the saw 10 includes a base 20, a handle support housing 13, a handle 14, and a main body 30. The base 20 has a substantially rectangular outer shape. The longitudinal direction of the base 20 is the front-rear direction. The base 20 has a flat lower surface for abutting against the material to be cut when cutting the material to be cut.

[0029] As shown in FIG. 1, the main body 30 is basically disposed above the base 20. As shown in FIGS. 1 to 3, the main body 30 includes a motor housing 11, a gear housing 12, an electric motor 31, a cutting tool 35, a fixed cover 33, and a movable cover 34.

[0030] As shown in FIG. 3, a part of the cutting tool 35 penetrates through the through-hole of the base 20 and protrudes below the base 20. The cutting tool 35 is a circular saw blade also called a tipped saw blade and has a substantially disk-shaped configuration. The cutting tool 35 has a disk-shaped base metal and a plurality of cutting edges located at its outer edge. In a tipped saw, the cutting edges are formed by welding a separate part called a chip to the base metal. The chip protrudes left and right from the base metal in the plate thickness direction. The cutting tool 35 is configured to rotate about a rotation axis AX1 (see FIG. 3) extending in the left-right direction by the rotational driving force provided by the electric motor 31. An arrow 36 indicating the rotation direction of the cutting tool 35 is attached to the right surface of the fixed cover 33. The fixed cover 33 covers the upper portion of the cutting tool 35 in an arc shape. The movable cover 34 covers the cutting tool 35 below the fixed cover 33. The movable cover 34 is configured to be retractable along the outer peripheral edge of the cutting tool 35 and is normally biased by a biasing member (not shown) toward the position shown in FIG. 3. When the marquetry 10 is in use, it is pressed against the material to be cut and retracts rearward, thereby exposing the portion of the cutting tool 35 located below the base 20.

[0031] As shown in FIGS. 1 and 2, the gear housing 12 is disposed on the left side of the fixed cover 33. Inside the gear housing 12, a mechanical mechanism (such as a spindle and reduction gears) for transmitting the rotational driving force of the electric motor 31 to the cutting tool 35 is accommodated. Further, a controller 38 for controlling the operation of the marquetry 10 is accommodated in the upper region of the gear housing 12. The motor housing 11 is disposed on the left side of the gear housing 12. The electric motor 31 is accommodated inside the motor housing 11.

[0032] As shown in FIG. 2, a handle support housing 13 is disposed behind the motor housing 11 and the gear housing 12. An arch-shaped handle 14 is disposed on the top of the handle support housing 13. In the present embodiment, the handle support housing 13 and the handle 14 are integrally formed. As shown in FIGS. 2 and 7, the handle support housing 13 is fixed to the base 20 at the rear side of the base 20 and substantially at the center in the left-right direction. Inside the handle 14, a switch 39 for driving the electric motor 31 is accommodated. A switch lever 32 for operating the start and stop of the electric motor 31 is attached to the handle 14 in the vicinity of the switch 39. By manually operating the switch lever 32, the state of the switch 39 can be switched between an on state for driving the electric motor 31 and an off state for stopping the electric motor 31.

[0033] As shown in FIG. 7, the handle support housing 13 is provided with a battery mounting portion 15 on its left surface. The battery mounting portion 15 includes an electrical terminal for establishing an electrical connection with the battery 16 and a guide groove extending in the front-rear direction for engaging with the battery 16. A battery 16 for supplying power to the electric motor 31 and the like is removably mounted on the battery mounting portion 15 (see FIG. 2). Instead of the battery 16, a commercial AC power supply may be used.

[0034] When using the marquetry 10, when the user presses the switch lever 32, the cutting tool 35 rotates by the driving force of the electric motor 31. In this state, the user brings the lower surface of the base 20 (the portion in front of the cutting tool 35) into contact with the material to be cut and moves the marquetry 10 forward. As a result, the cutting of the material to be cut proceeds in the moving direction of the marquetry 10 by the cutting tool 35 protruding downward beyond the lower surface of the base 20.

[0035] In such a marnoko 10, the cutting tool 35 is configured to be tiltable with respect to the base 20 about a tilting axis AX2 (see FIG. 7) extending in the front-rear direction. According to this configuration, the workpiece to be cut can be cut obliquely. Such a tilting operation is realized by using an angular plate 21 (see FIG. 1) fixed to the base 20. Since the structure for tilting using the angular plate 21 is well known, its description will be omitted.

[0036] Furthermore, the cutting tool 35 is configured to be able to change the amount of downward protrusion (i.e., cutting depth) with respect to the lower surface of the base 20. Specifically, the main body 30 is supported at the front side by a support shaft 25 (see FIGS. 3, 6, and 7) extending in the left-right direction. As shown in FIGS. 1, 2, and 7, a bracket 37 is attached to the front edge of the fixed cover 33 of the main body 30. As shown in FIGS. 3 and 6, the support shaft 25 is supported by a bracket 22 fixed to the angular plate 21 while passing through the bracket 37. The bracket 22 is fixed to the angular plate 21 so as to tilt together when the cutting tool 35 (main body 30) is tilted with respect to the base 20. Since the angular plate 21 is fixed to the base 20, the bracket 37 (and thus the main body 30 including the fixed cover 33 to which the bracket 37 is attached) is tiltable with respect to the base 20 about the support shaft 25 (swing axis AX3 shown in FIG. 7).

[0037] Also, the main body 30 is supported at the rear side by a depth guide 40. The depth guide 40 is a member for fixing the tilting position of the cutting tool 35 (in other words, the main body 30) with respect to the base 20. As shown in FIG. 5, the depth guide 40 is disposed between the fixed cover 33 and the handle support housing 13. The proximal end 41 of the depth guide 40 is fixed to the base 20.

[0038] As shown in Fig. 4, the depth guide 40 has a guide hole 42 penetrating in the left-right direction. As shown in Figs. 4 and 5, a bolt 43 passing through a through hole (not shown) formed in the left surface of the fixed cover 33 penetrates the guide hole 42 in a non-rotating state. On the left side of the depth guide 40, a nut 44 is attached to the tip of the bolt 43, and a fixing lever 45 is attached to the outer periphery of the nut 44. By tightening the nut 44 using the fixing lever 45, the fixed cover 33 and the depth guide 40 are tightened in a direction orthogonal to the side surface of the cutting tool 35. As a result, the main body 30 is fixed to the depth guide 40 and supported by the depth guide 40. Since the guide hole 42 is formed in an arc shape centered on the support shaft 25 (oscillation axis AX3), the position of the bolt 43 can be guided when the main body 30 oscillates.

[0039] According to such a configuration, the user can loosen the fixing lever 45, swing the main body 30 about the support shaft 25, and tighten the fixing lever 45 at a desired swing position, thereby fixing the main body 30 at the desired swing position. In this way, the user can adjust the cutting depth of the cutting tool 35.

[0040] As described above, the Marunoko 10 has a configuration for predicting kickback occurrence by detecting the precursor behavior of kickback occurrence. Hereinafter, the configuration therefor will be described. As shown in FIG. 9, the Marunoko 10 includes a controller 38, a vibration sensor 60, a current detector 70, and a switch 39. Further, the electric motor 31 includes a rotation speed sensor 80 for detecting its rotation speed. The vibration sensor 60, the current detector 70, the switch 39, and the above-described battery 16 and electric motor 31 are each electrically connected to the controller 38. The controller 38 controls the operation of the electric motor 31 by controlling the supply of power to the electric motor 31. The controller 38 also functions as a precursor behavior detection unit 38a, which will be described later. In the present embodiment, the controller 38 includes a CPU and a memory, and realizes its functions by executing a program stored in the memory. However, the functions of the controller 38 may be realized by a dedicated circuit specialized for specific functions. Alternatively, the controller 38 may include a CPU and a dedicated circuit. The switch 39 detects the operation of the switch lever 32 and inputs a command for driving or stopping the electric motor 31 to the controller 38.

[0041] As described above, the handle support housing 13 including the battery mounting portion 15 and the vibration sensor 60 are disposed on the base 20, and the handle 14 in which the switch 39 is housed is disposed on the handle support housing 13. On the other hand, the main body portion 30 including the gear housing 12 in which the controller 38 is housed is swingable and tiltable with respect to the base 20. Such various electrical components are electrically connected to each other by arranging the electrical wiring 91 along the path described below.

[0042] As shown in Fig. 7, the maruko 10 includes a first wiring case 92 and a second wiring case 94. The first wiring case 92 extends forward from the left edge of the handle support housing 13 and extends rightward near the front edge of the base 20 (immediately behind the angular plate 21). The first wiring case 92 is disposed on the base 20 and fixed to the base 20. One end (the rear end) of the first wiring case 92 is connected to the handle support housing 13, and the interior of the first wiring case 92 and the interior of the handle support housing 13 communicate with each other. An arc groove 93 is formed at the other end (the front and right end) of the first wiring case 92.

[0043] The second wiring case 94 is disposed above the portion of the first wiring case 92 that extends in the left-right direction near the front edge of the base 20. The second wiring case 94 is supported by a bracket 22 that can tilt together with the main body 30. The second wiring case 94 is provided with protruding portions 95 that extend in a columnar shape in the front-rear direction on the front and rear surfaces of one end (the lower and right end) (in Fig. 7, only the protruding portion 95 that protrudes rearward from the rear surface is visible). The two protruding portions 95 have a diameter that fits into the arc groove 93 of the first wiring case 92 and are rotatably accommodated in the arc groove 93. The central axis of the two protruding portions 95 coincides with the tilting axis AX2. Therefore, when the main body 30 is tilted with respect to the base 20, the second wiring case 94 can also tilt together with the main body 30. The interior of the first wiring case 92 and the interior of the first wiring case 92 communicate with each other through an opening at one end of the second wiring case 94 and an opening at the other end of the first wiring case 92 (both not shown).

[0044] The other end (the upper and left end) of the second wiring case 94 is provided with an engaging portion 96. The engaging portion 96 protrudes cylindrically toward the left. The central axis of the engaging portion 96 coincides with the rocking axis AX3. As shown in FIG. 8, the engaging portion 96 is rotatably fitted into a cylindrical portion 17 formed in a gear housing 12 which is a part of the main body portion 30. Therefore, when the main body portion 30 is rocked with respect to the base 20, the gear housing 12 can rock while maintaining the connection relationship between the cylindrical portion 17 and the second wiring case 94. The inside of the second wiring case 94 and the inside of the gear housing 12 communicate with each other via the engaging portion 96 and the cylindrical portion 17.

[0045] As shown in FIGS. 7 and 8, the electrical wiring 91 connecting the switch 39 and the controller 38 extends from the inside of the handle 14, through the inside of the handle support housing 13, and through the inside of the first wiring case 92 and the second wiring case 94 to extend into the gear housing 12 and reach the controller 38. Similarly, the electrical wiring 91 connecting the battery mounting portion 15 and the vibration sensor 60 and the controller 38 respectively extends from the inside of the handle support housing 13 through the inside of the first wiring case 92 and the second wiring case 94 to extend into the gear housing 12 and reach the controller 38. As described above, since the vibration sensor 60 is disposed adjacent to the handle support housing 13 (see FIGS. 3 and 5), the electrical wiring 91 extending from the vibration sensor 60 can reach into the handle support housing 13 through the opening of the handle support housing 13 without being exposed to the outside. In FIGS. 7 and 8, only one electrical wiring 91 is shown schematically.

[0046] According to the above-described configuration, the electrical parts in the handle 14 and the handle support housing 13 whose positions with respect to the base 20 are fixed and the controller 38 in the gear housing 12 whose position with respect to the base 20 can be changed can be electrically connected without exposing the electrical wiring 91 to the outside and while ensuring the necessary insulation structure.

[0047] The vibration sensor 60 detects the vibration of the maruko 10 and inputs the detection result to the controller 38 as a non-limiting example of a physical quantity related to the behavior of the maruko 10 during use. In the present embodiment, an acceleration sensor is used as the vibration sensor 60. Thereby, vibration can be easily detected using off-the-shelf components. However, any known type of vibration sensor can be adopted as the vibration sensor 60. In the present embodiment, it is configured to detect vibration in the vertical direction. As shown in FIGS. 3 and 5, in the present embodiment, the vibration sensor 60 is disposed behind the rotation axis AX1 (see FIG. 3) in the front-rear direction. In the present embodiment, the vibration sensor 60 is directly attached to the base 20 at approximately the center in the left-right direction and the rear edge of the base 20. The vibration sensor 60 is disposed adjacent to the base of the handle support housing 13. However, the vibration sensor 60 may be indirectly attached to the base 20 via other members such as brackets. The detection value of the vibration sensor 60 is input to the controller 38.

[0048] The current detector 70 detects the current value supplied from the battery 16 to the electric motor 31 as a non-limiting example of a physical quantity related to the behavior of the maruko 10 during use. In the present embodiment, a shunt resistor is used as the current detector 70. Thereby, the current value can be easily detected using off-the-shelf components. However, any known type of current detector can be adopted as the current detector 70. The detection value of the current detector 70 is input to the controller 38.

[0049] Next, a kickback prevention process for detecting a sign of kickback and preventing the occurrence of kickback in advance according to the above configuration will be described with reference to FIG. 10. This kickback prevention process is repeatedly executed by the controller 38 while the maruko 10 is being used for cutting work (in other words, while the electric motor 31 is being driven). Note that the detection cycles of vibration and current by the vibration sensor 60 and the current detector 70 described above are set to be shorter than the cycle of the kickback prevention process. Further, the cycle of the kickback prevention process is set to be sufficiently shorter than the time from the start point of the sign behavior of kickback, which will be described later, to the occurrence point of kickback (for example, a time of 1 / 10 or less).

[0050] When the kickback prevention process is started, the controller 38 first determines, as the process of the sign behavior detection unit 38a, whether or not the rising speed of the current value detected by the current detector 70 (the amount of increase per unit time, and the unit is amperes / second) is equal to or greater than the threshold value TH1 (step S110). As a result, if the rising speed of the current value is equal to or greater than the threshold value TH1 (step S110: YES), then the controller 38 next determines, as the process of the sign behavior detection unit 38a, whether or not the vibration value (in this embodiment, the vibration value in the vertical direction) detected by the vibration sensor 60 is equal to or greater than the threshold value TH3 (step S120).

[0051] Just before the occurrence of kickback, a state occurs where the cutting tool 35 of the miter saw 10 is intermittently clamped to the workpiece from both sides thereof. In this state, the load on the electric motor 31 increases and the current value rises. Further, in this state, due to the rotational direction of the cutting tool 35, a reaction force acts upward from the workpiece on the portion behind the rotational axis AX1 of the cutting tool 35, and a reaction force acts downward from the workpiece on the front portion of the cutting tool 35. For this reason, the miter saw 10 exhibits behavior in which its rear side is lifted with the front edge thereof as a fulcrum (hereinafter also referred to as floating behavior). When the cutting tool is a chip saw as in the present embodiment and the workpiece is wood, the chip cuts the wood with low resistance at the left and right protruding portions (called asari), so that vibrations are generated mainly by the sliding resistance between the base metal and the wood. Due to such behavior, vibrations occur in the miter saw 10.

[0052] The behavior of the vibration and the current value at this time will be described in detail with reference to FIG. 11. In the figure, "vibration X" means vibration in the X direction (left - right direction). "Vibration Y" means vibration in the Y direction (front - rear direction). "Vibration Z" means vibration in the Z direction (up - down direction). Also, here, the standard deviation per unit time of the acceleration in each of the X, Y, and Z directions detected by the vibration sensor 60 (acceleration sensor) is treated as vibration. As shown in FIG. 11, before the occurrence of the precursor behavior of kickback (that is, floating behavior), almost no vibration occurs in any of the X, Y, and Z directions. On the other hand, from just before the occurrence of the precursor behavior of kickback to the occurrence of kickback, the vibration gradually begins to increase in all of the X, Y, and Z directions. In this example, the time from the occurrence of the precursor behavior of kickback to the occurrence of kickback is less than 0.2 seconds. As is clear from FIG. 11, due to the large displacement of the miter saw 10 in the up - down direction in the floating behavior, the vibration in the up - down direction is larger than the vibrations in the front - rear direction and the left - right direction. And about 0.05 seconds after the occurrence of kickback, the vibration rapidly increases in all of the X, Y, and Z directions.

[0053] Also, regarding the current value, it starts to gradually increase approximately 0.05 seconds before the occurrence of the kickback's precursor behavior. And after the occurrence of the kickback's precursor behavior, the current value further increases. The rising speed (the slope of the graph) at this time is greater than that before the occurrence of the kickback's precursor behavior. Note that in the kickback's precursor behavior, since the tool 35 is intermittently clamped into the material to be cut, when the clamping state is released, the current value decreases. For this reason, the current value rises while repeating vertical movement. And immediately after the occurrence of the kickback, the slope of the current value suddenly becomes large, and accordingly, the current value also rises sharply.

[0054] By paying attention to such vibration and current behaviors, it is possible to detect the kickback's precursor behavior while clearly distinguishing it from the occurrence of the kickback. The above-mentioned processes of S110 and S120 are processes for detecting the kickback's precursor behavior, and the threshold value TH1 regarding the rising speed of the current and the threshold value TH3 regarding the vibration value are set in advance in consideration of the above-mentioned vibration and current behaviors. Specifically, the threshold value TH1 is set to a value that is greater than the rising speed before the occurrence of the kickback's precursor behavior and smaller than the rising speed after the occurrence of the kickback's precursor behavior. The threshold value TH1 may be set to 350 (ampere / second) or less. In this way, it is possible to clearly distinguish the kickback's precursor behavior from the occurrence of the kickback. The threshold value TH3 is set to a value that is greater than the vibration value before the occurrence of the kickback's precursor behavior and smaller than the vibration value after the occurrence of the kickback's precursor behavior.

[0055] Returning the explanation to FIG. 6 here. When the rising speed of the current value detected by the current detector 70 is equal to or higher than the threshold value TH1 (step S110: YES), and the vibration value detected by the vibration sensor 60 is equal to or higher than the threshold value TH3 (step S120: YES), the controller 38 determines that a sign behavior of kickback has occurred (detects a sign operation), brakes the rotation of the electric motor 31, and stops the rotation of the electric motor 31 (step S150). In the present embodiment, the electric motor 31 is in the form of a brake motor, and its braking function is used to brake the electric motor 31.

[0056] On the other hand, when the vibration value is less than the threshold value TH3 (step S120: NO), since no sign behavior of kickback has occurred, the controller 38 ends the kickback prevention process. Instead of ending the kickback prevention process, the controller 38 may determine whether the rising speed of the current is equal to or higher than the threshold value TH5. This threshold value TH5 is set to a value larger than the threshold value TH1. In that case, the controller 38 may proceed with the process to step S150 when the rising speed of the current is equal to or higher than the threshold value TH5, and may end the kickback prevention process when the rising speed of the current is less than the threshold value TH5. According to this configuration, even if no sign behavior of kickback has occurred, when an excessive high load has occurred, the rotation of the tool 35 can be stopped. In this case, the threshold value TH3 may be set to a value equal to or less than half of the threshold value TH5.

[0057] If the rising speed of the current value is less than the threshold value TH1 (step S110: NO), then the controller 38 determines whether the current value is equal to or higher than the threshold value TH2 as a process of the sign behavior detection unit 38a (step S130). This threshold value TH2 is set to a value larger than the current value before the occurrence of the sign behavior of kickback and smaller than the current value after the occurrence of the sign behavior of kickback.

[0058] As a result of the determination, if the current value is less than the threshold TH2 (step S130: NO), since the high-load state of the electric motor 31 does not occur (since the omen behavior of kickback does not occur), the controller 38 ends the kickback prevention process. On the other hand, if the current value is equal to or greater than the threshold TH2 (step S130: YES), the controller 38 determines whether or not the vibration value is equal to or greater than the threshold TH4 as the process of the omen behavior detection unit 38a (step S140). This threshold TH4 is set to a value greater than the vibration value before the occurrence of the omen behavior of kickback and less than the vibration value after the occurrence of the omen behavior of kickback.

[0059] As a result of the determination, if the vibration value is less than the threshold TH4 (step S140: NO), since the omen behavior of kickback does not occur, the controller 38 ends the kickback prevention process. On the other hand, if the vibration value is equal to or greater than the threshold TH4 (step S140: YES), it is determined that the omen behavior of kickback has occurred (the omen operation is detected), and the electric motor 31 is braked to stop the rotation of the electric motor 31 (step S150).

[0060] According to steps S130 and S140, in the omen behavior of kickback, even if the current value moves up and down as described above, the omen behavior of kickback can be accurately detected. A relatively high current value can also be caused by high-load disconnection, but by combining step S130 and step S140, the omen behavior of kickback and high-load disconnection can be accurately distinguished. In the present embodiment, the threshold TH3 used in step S120 is set to a value smaller than the threshold TH4 used in step S140. When high-load disconnection is started, the rising speed of the current increases and the current value increases, but the rising speed of the current is easy to distinguish between high-load disconnection and the omen behavior of kickback. Therefore, even with such a setting, the detection of the omen behavior based on the threshold TH3 can be accurately performed. Moreover, if the threshold TH3 is set to a smaller value, the omen behavior of kickback can be detected earlier, so the process of step S150 can be performed earlier.

[0061] The predictive behavior of kickback may be executed based on the rotational speed of the electric motor 31 detected by the rotational speed sensor 80, instead of the vibration value and / or current value described above. Specifically, the predictive behavior detection unit 38a may detect the occurrence of predictive behavior when the decreasing speed of the rotational speed at the output of the electric motor 31 is equal to or higher than a sixth threshold value TH. Immediately before the occurrence of kickback, a state occurs in which the cutting tool 35 of the turning tool 10 is intermittently clamped from both sides thereof to the workpiece to be cut. In this state, the load on the electric motor 31 increases, and the rotational speed of the electric motor 31 decreases. The decreasing speed of the rotational speed at this time is smaller than that at the time of the occurrence of kickback (that is, the state in which the cutting tool 35 is completely clamped). According to this configuration, the predictive behavior of kickback can be detected by detecting such a decreasing speed of the rotational speed. If the sixth threshold value TH is set to a value of 20 rpm / millisecond or less, the predictive behavior of kickback and the occurrence of kickback can be clearly distinguished. In the present embodiment, the sixth threshold value TH is 13.8 rpm / millisecond.

[0062] According to the turning tool 10 described above, the predictive behavior of kickback can be detected based on the vibration value and the current value. Therefore, compared with a configuration for detecting that kickback has already occurred, the electric motor 31 can be braked earlier to stop the rotation of the electric motor 31.

[0063] Furthermore, according to the turning tool 10, since the predictive behavior detection unit 38a detects the occurrence of predictive behavior based on the vibration value in the vertical direction where the vibration is the largest in the predictive behavior of kickback, compared with a configuration for detecting the occurrence of predictive behavior based on the vibration value in the front-rear direction or the left-right direction, the predictive behavior of kickback can be detected with higher accuracy. However, as illustrated in FIG. 7, in the predictive behavior of kickback, the vibration values in the front-rear direction and the left-right direction also increase. Therefore, the controller 38 may detect the occurrence of predictive behavior based on the vibration value in the front-rear direction or the left-right direction.

[0064] Furthermore, according to the woodpecker 10, the vibration sensor 60 is disposed on the rear side of the woodpecker 10. That is, the vibration sensor 60 is disposed in a region where the woodpecker 10 is more largely displaced in the above-described floating behavior (foreshadowing behavior of kickback). Therefore, vibrations corresponding to the foreshadowing behavior of kickback can be detected with higher accuracy.

[0065] Furthermore, according to the woodpecker 10, the vibration sensor 60 is attached to the base 20 such that the position with respect to the workpiece does not change even when the protrusion amount of the cutting tool 35 with respect to the base 20 is changed using the depth guide 40. Therefore, the detection position of the vibration with respect to the workpiece can be fixed. In other words, the detection position of the vibration associated with the foreshadowing behavior of kickback can be fixed in the vertical direction regardless of the setting of the protrusion amount of the cutting tool 35. Therefore, vibrations corresponding to the foreshadowing behavior of kickback can be detected with higher accuracy.

[0066] Furthermore, according to the woodpecker 10, the foreshadowing behavior of kickback is detected based on both vibration and current value. For this reason, compared with a configuration in which the foreshadowing behavior of kickback is detected based on only one of vibration and current value, the foreshadowing behavior of kickback, the occurrence of vibrations associated with a collision of the woodpecker 10 (for example, the collision of the movable cover 34 against the workpiece) (no increase in current value accompanies), and / or the increase in current value due to high-load cutting (usually, no large vibrations occur), and the foreshadowing behavior of kickback can be more accurately distinguished, and the detection accuracy of the foreshadowing behavior of kickback can be improved.

[0067] Hereinafter, the woodpecker 210 according to the second embodiment will be described with reference to FIG. 12. In FIG. 12, the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment. The woodpecker 210 is different from the first embodiment only in the arrangement of the vibration sensor 60. Hereinafter, the woodpecker 210 will be described only with respect to the differences from the first embodiment. In the second embodiment, the vibration sensor 60 is attached to the main body 30 behind the electric motor 31 and adjacent to the electric motor 31.

[0068] According to Marunoko 210, since the vibration sensor 60 is attached to the main body 30, the electrical wiring related to the vibration sensor 60 can be intensively arranged together with the wiring related to the electric motor 31. For this reason, the electrical wiring related to the vibration sensor 60 can be realized with a simple configuration, and the insulation structure can also be integrated with the insulation structure for the electric motor 31 and its power supply components, thus simplifying the insulation structure. Moreover, since the vibration sensor 60 is arranged behind the electric motor 31, it will be located more rearward compared to the case where it is arranged in front of the electric motor 31. Therefore, vibrations corresponding to the foreshadowing behavior of kickback, such as when the rear of Marunoko 10 is lifted, can be accurately detected.

[0069] As described above, several embodiments have been explained. However, the above-described embodiments are for facilitating the understanding of the present invention and do not limit the present invention. The present invention can be changed and improved without departing from its gist, and equivalents thereof are included in the present invention. Also, within the range where at least a part of the above-described problems can be solved, or at least a part of the effects can be achieved, any combination or omission of each form element described in the claims and the specification is possible.

[0070] For example, the vibration sensor 60 is not limited to the examples of the above-described embodiments and can be arranged at any location of Marunoko 10.

[0071] Alternatively, the foreshadowing behavior detection unit 38a may detect the foreshadowing behavior of kickback based on only one of the vibration value and the current value.

[0072] Alternatively, in order to brake the rotation of the electric motor 31 when the foreshadowing behavior of kickback is detected (see step S150 in FIG. 6), instead of the brake function of the electric motor 31, a mechanical brake may be used. As such a mechanical brake, for example, a configuration in which a brake shoe is pressed against the rotating member of the motor is known. Alternatively, instead of the configuration for braking the rotation of the electric motor 31, the rotation of the tool 35 may be braked (for example, a configuration for braking the rotation of the electric motor 31 may be adopted.

[0073] Alternatively, when a sign behavior of kickback is detected, instead of braking the rotation of the electric motor 31, other measures may be taken. In this case, for example, when the sign behavior of kickback is detected, the controller 38 may stop supplying power to the electric motor 31 regardless of the operation state of the switch lever 32. Alternatively, the controller 38 may perform control to reduce the output (rotation speed) of the electric motor 31. Alternatively, when the sign behavior of kickback is detected, the controller 38 may notify the user. Such notification may be performed, for example, in the form of lighting of an LED lamp.

[0074] Furthermore, the various forms described above are not limited to the marqueno, and are applicable to any portable cutting machine in which kickback can occur when a cutting tool, such as a cutter having a diamond wheel as the cutting tool, is sandwiched between the workpiece to be cut.

[0075] The correspondence between the components of the above embodiment and the components of the present invention is shown below. However, each component of the embodiment is merely an example and does not limit the components of the present invention. The marquenos 10 and 210 are examples of "portable marquenos". The vibration sensor 60, the current detector 70, and the rotation speed sensor 80 are examples of "physical quantity detection units". The sign behavior detection unit 38a is an example of a "sign behavior detection unit". The vibration sensor 60 is an example of a "vibration sensor". The current detector 70 is an example of a "current detector". The rotation speed sensor 80 is an example of a "rotation speed sensor". The base 20 is an example of a "base". The electric motor 31 is an example of an "electric motor". The cutting tool 35 is an example of a "cutting tool". The depth guide 40, the bolt 43, the nut 44, and the fixing lever 45 are examples of "cutting depth adjustment mechanisms". The support shaft 25 is an example of a "support shaft". The controller 38 is an example of a "controller".

Description of Reference Numerals

[0076] 10, 210... Portable marqueno 11... Motor housing 12... Gear housing 13... Handle support housing 14... Handle 15... Battery mounting part 16... Battery 17... Cylindrical part 20... Base 21... Angular plate 22... Bracket 25... Support shaft 30... Main body part 31... Electric motor 32... Switch lever 33... Fixed cover 34... Movable cover 35... Cutting tool 36... Arrow 37... Bracket 38... Controller 38a... Sign behavior detection part 39... Switch 40... Depth guide 41... Base end of depth guide 42... Guide hole 43... Bolt 44... Nut 45... Fixed lever 60... Vibration sensor 70... Current detector 80... Rotation speed sensor 91... Electrical wiring 92... First wiring case 93... Arc groove 94... Second wiring case 95... Protrusion 96... Engagement part

Claims

1. A portable cutting machine, a physical quantity detection unit configured to detect a physical quantity related to the behavior of the portable cutting machine during use; a sign behavior detection unit configured to detect a sign behavior of kickback occurrence based on the detection result of the physical quantity detection unit A portable cutting machine comprising.

2. The portable cutting machine according to Claim 1, wherein the physical quantity detection unit includes a vibration sensor configured to detect the vibration of the portable cutting machine; The sign behavior detection unit is configured to detect the occurrence of the sign behavior based on the vibration value detected by the vibration sensor A portable cutting machine.

3. The portable cutting machine according to Claim 2, wherein the vibration sensor is configured to detect the vertical vibration in the posture of the portable cutting machine during use; The sign behavior detection unit is configured to detect the occurrence of the sign behavior based on the vertical vibration value A portable cutting machine.

4. The portable cutting machine according to Claim 2 or Claim 3, wherein the vibration sensor is in the form of an acceleration sensor A portable cutting machine.

5. The portable cutting machine according to Claim 2 or Claim 3, wherein when the direction in which cutting is advanced by the portable cutting machine is defined as the front side and the side opposite to the front side is defined as the rear side, the vibration sensor is disposed behind the rotation axis of the cutting tool of the portable cutting machine A portable cutting machine.

6. The portable cutting machine according to Claim 5, a base; an electric motor disposed on a first side with respect to the base; a cutting tool configured to rotate about a rotation axis by a driving force provided by the electric motor; a cutting depth adjustment mechanism configured to displace the cutting tool relative to the base so that the protruding amount of the cutting tool from the base to a second side opposite to the first side can be changed comprising, wherein the vibration sensor is directly or indirectly attached to the base A portable cutting machine.

7. The portable cutting machine according to Claim 5, a base; a main body portion having an electric motor disposed on a first side with respect to the base and a cutting tool configured to rotate about a rotation axis by a driving force provided by the electric motor; a cutting depth adjustment mechanism configured to displace the main body portion relative to the base so that the protruding amount of the cutting tool from the base to a second side opposite to the first side can be changed comprising, The vibration sensor is attached to the main body adjacent to the electric motor behind the electric motor. Portable cutting machine. **Claim 8** The portable cutting machine according to claim 1, A rotatable cutting tool, An electric motor for providing a rotational driving force to the cutting tool, and Comprising, The physical quantity detection unit includes a current detector configured to detect a current value of the electric motor, The precursor behavior detection unit is configured to detect the occurrence of the precursor behavior based on the current value detected by the current detector. Portable cutting machine. **Claim 9** The portable cutting machine according to claim 8, The current detector includes a shunt resistor. Portable cutting machine. **Claim 10** The portable cutting machine according to claim 8 or claim 9, The precursor behavior detection unit is configured to detect the occurrence of the precursor behavior when the rising speed of the current value is equal to or higher than a threshold value set to 350 (ampere / second) or less. Portable cutting machine. **Claim 11** The portable cutting machine according to claim 1, A rotatable cutting tool, An electric motor for providing a rotational driving force to the cutting tool, and Comprising, The physical quantity detection unit includes a rotation speed sensor configured to detect the rotation speed of the electric motor, The precursor behavior detection unit is configured to detect the occurrence of the precursor behavior when the decreasing speed of the rotation speed at the output of the electric motor is equal to or higher than a threshold value set to 20 (rpm / millisecond) or less. Portable cutting machine. **Claim 12** The portable cutting machine according to claim 1, A rotatable cutting tool, An electric motor for providing a rotational driving force to the cutting tool, and Comprising, The physical quantity detection unit includes a vibration sensor configured to detect the vibration of the portable cutting machine and a current detector configured to detect the current value of the electric motor. The precursor behavior detection unit is configured to detect the occurrence of the precursor behavior based on the vibration value detected by the vibration sensor and the current value detected by the current detector. Portable cutting machine. **Claim 13** The portable cutting machine according to claim 12, The vibration sensor is configured to detect at least the vertical vibration in the posture during use of the portable cutting machine. The precursor behavior detection unit is configured to detect the occurrence of the precursor behavior based on the vertical vibration value. Portable cutting machine. **Claim 14** A portable cutting machine, A rotatable cutting tool, An electric motor for providing a rotational driving force to the cutting tool, and A physical quantity detection unit configured to detect a physical quantity related to the behavior of the portable cutting machine during use; A controller configured to control the operation of the electric motor; and; the controller is configured to execute any one of stopping power supply to the electric motor, reducing the output of the electric motor, and braking the rotation of the electric motor or the cutting tool when the physical quantity satisfies a predetermined condition; the physical quantity includes at least one of the vibration of the portable cutting machine and the current value of the electric motor; A portable cutting machine.

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