Metal working cutter

Abstract

To provide a metal working cutter with which sparks produced in cutting are reduced.SOLUTION: A metal working cutter comprises: an electric motor; a chip saw capable of rotating according to rotational drive power provided from the electric motor, and having a substantially discoidal shape; and a controller for controlling operation of the electric motor. The controller controls the electric motor so that circumferential speed of the cutting edges of the chip saw during no-load driving of the electric motor is 15 m / s or lower.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to a metalworking cutting machine. [Background technology]

[0002] Stationary metalworking cut-off machines for cutting materials such as steel pipes and thin-walled lightweight steel frames have been known for some time. A stationary metalworking cut-off machine includes a base and a cutting machine body that rotatably supports a cutting tool. The material is fixed on the base, and the cutting machine body (the rotating cutting tool) is displaced from above toward the material to cut the material. The cutting tool has a generally disk shape and is typically a grinding wheel or a tipped saw blade. With such stationary metalworking cut-off machines, frictional heat generated between the cutting tool and the material during cutting operations causes chips to burn, generating sparks.

[0003] The following Patent Document 1 discloses such a stationary metalworking cut-off machine. The stationary metalworking cut-off machine of Patent Document 1 uses a chip saw as a cutting tool. When a chip saw is used as a cutting tool, the generation of sparks can be reduced compared to when a grinding wheel is used. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-307232 Summary of the Invention [Problem to be solved by the invention]

[0005] However, even when a tip saw is used as a cutting tool, some sparks are still generated. For this reason, it is desirable to further reduce the sparks generated during cutting. This problem is not limited to stationary metalworking cut-off machines, but is also common to portable metalworking cut-off machines that use tip saws as cutting tools. [Means for solving the problem]

[0006] This specification discloses a metalworking cutting machine. This metalworking cutting machine may include an electric motor, a generally disk-shaped tipped saw that can be rotated by a rotational driving force provided by the electric motor, and a controller configured to control the operation of the electric motor. The controller may be configured to control the electric motor so that the peripheral speed of the cutting edge of the tipped saw is 15 m / s or less when the electric motor is driven without load.

[0007] With this metalworking cut-off machine, the electric motor is controlled so that the peripheral speed of the tip of the saw blade is 15 m / s or less when driven without load. In other words, compared to conventional metalworking cut-off machines, the peripheral speed of the tip of the saw blade is controlled to a low speed at the moment when cutting of the workpiece begins (in other words, the moment when the saw blade and the workpiece begin to come into contact). This reduces the frictional heat generated between the tip of the saw blade and the workpiece at the start of cutting, resulting in fewer sparks.

[0008] This specification further discloses a stationary metalworking cut-off machine. This stationary metalworking cut-off machine may include an electric motor, a generally disk-shaped tipped saw that is rotatable by a rotational driving force provided by the electric motor, and a controller configured to control the operation of the electric motor. The diameter of the tipped saw may be equal to or greater than 300 mm and equal to or less than 360 mm. The controller may be configured to control the electric motor so that the rotation speed of the tipped saw is 900 rpm or less when the electric motor is driven under no load.

[0009] With this stationary metalworking cut-off machine, the electric motor is controlled so that the rotation speed of the tipped saw, which has a diameter of 300 mm or more and 360 mm or less, is 900 rpm or less. In other words, compared to conventional stationary metalworking cut-off machines, the rotation speed of the tipped saw is controlled to be lower at the moment when cutting begins. This reduces the frictional heat generated between the cutting edge of the tipped saw and the workpiece at the start of cutting, resulting in fewer sparks. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view of a saw blade according to one embodiment, with the blade body at top dead center. FIG. [Figure 2] FIG. 1 is a perspective view of a chip saw cutting machine, with the cutting machine body at the top dead center. [Figure 3] FIG. 1 is a perspective view of a chip saw cutting machine, with the cutting machine body at the bottom dead center. [Figure 4] This is a left side view of the chip saw cutter, with the cutter body at the bottom dead center. [Figure 5] 5 is a cross-sectional view of the saw blade taken along line AA in FIG. 4. [Figure 6] This is a left side view of the chip saw cutting machine, showing the time when cutting of the workpiece begins. [Figure 7] FIG. 2 is a block diagram showing the electrical connections of the components of the saw-tipped cutting machine. [Figure 8] FIG. 2 is a schematic circuit diagram for controlling the rotation speed of a motor. [Figure 9] 10 is a diagram showing the relationship between current and rotation speed of the chip saw when cutting is performed in a normal cutting mode and a spark reduction mode. FIG. [Figure 10] 10A and 10B are diagrams showing an example of the change in the rotation speed of the chip saw and the current value supplied to the electric motor when cutting is performed in normal cutting mode. [Figure 11] 10 is a diagram showing an example of the change in the rotation speed of the chip saw and the current value supplied to the electric motor when cutting is performed in the spark reduction mode. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Representative, non-limiting embodiments of the present invention will now be described in detail with reference to the accompanying drawings. This detailed description is intended simply to provide those skilled in the art with details for implementing preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Additionally, additional features and inventions disclosed below may be used separately or in conjunction with other features and inventions to provide further improved devices, methods of making and using the same.

[0012] Furthermore, the combinations of features and steps disclosed in the following detailed description are not essential to practicing the invention in its broadest sense, but are described solely to illustrate specific exemplary embodiments of the invention. Furthermore, the various features of the exemplary embodiments described above and below, and those described in the independent and dependent claims, do not necessarily have to be combined in the exact embodiments described herein, or in the exact order listed, to provide additional and useful embodiments of the invention.

[0013] All features described in this specification and / or claims are intended to be disclosed individually and independently of one another as limitations on the original disclosure and claimed particulars, apart from any configuration of the features described in the embodiments and / or claims. Furthermore, all numerical ranges and group or aggregation descriptions are intended to disclose intermediate configurations thereof as limitations on the original disclosure and claimed particulars.

[0014] In one or more embodiments, the controller may be configured to control the electric motor so that the peripheral speed of the cutting edge of the tipped saw blade is 10 m / s or less when driven without load. With this configuration, the peripheral speed of the cutting edge of the tipped saw blade is controlled to an even slower speed at the moment when cutting of the workpiece begins. This further reduces frictional heat generated between the cutting edge of the tipped saw blade and the workpiece at the start of cutting, thereby further reducing the generation of sparks.

[0015] In one or more embodiments, the controller may be configured to control the electric motor so that the peripheral speed of the cutting edge of the saw blade is 4 m / s or less when driven without load. This configuration further reduces frictional heat generated between the cutting edge of the saw blade and the workpiece at the start of cutting, thereby further reducing the generation of sparks.

[0016] In one or more embodiments, the controller may be configured to control the electric motor to increase the rotation speed of the electric motor after detecting a cutting state. The "cutting state" refers to a state in which the rotating tipped saw is cutting the workpiece (in other words, a load state of the electric motor). With this configuration, after increasing the rotation speed of the electric motor, cutting can be performed with the tipped saw rotating at high speed. Therefore, the workpiece can be cut efficiently in a short time. Since sparks are more likely to occur at the start of cutting when the contact area between the tipped saw and the workpiece is relatively large, increasing the rotation speed of the electric motor once cutting has progressed to the point where spark generation has decreased can both reduce spark generation at the start of cutting and achieve efficient cutting.

[0017] In one or more embodiments, the controller may be configured to control the electric motor to increase the rotation speed of the electric motor when a predetermined time has elapsed since the cutting state was detected. With this configuration, by setting the predetermined time in accordance with the period during which the amount of sparks generated at the start of cutting is relatively large, it is possible to achieve both reduced sparks at the start of cutting and efficient cutting with simple control.

[0018] In one or more embodiments, the predetermined time may be set to any time between 1 and 5 seconds, which optimizes both efficient cutting and reduced spark generation at the start of cutting.

[0019] In one or more embodiments, the controller may be configured to perform low rotation speed control, which controls the electric motor so that the electric motor rotates at a rotation speed lower than the rotation speed corresponding to the rated torque from when the electric motor is driven without load to when the electric motor is driven under a predetermined load. This configuration also reduces frictional heat generated between the cutting edge of the saw blade and the workpiece at the start of cutting, thereby reducing the occurrence of sparks.

[0020] In one or more embodiments, the electric motor may be a brushless DC motor. The controller may be configured to perform both low rotation speed control and PWM control of the electric motor on the same board. With this configuration, low rotation speed control is performed at the start of cutting, and normal control (i.e., control to rotate the electric motor at a rotation speed corresponding to the rated torque) is performed once cutting has progressed to the point where spark generation is reduced, thereby achieving both reduced spark generation at the start of cutting and efficient cutting. Moreover, because the controller can perform both low rotation speed control and PWM control on the same board, the device configuration can be simplified and made more compact.

[0021] In one or more embodiments, the controller may be configured to detect the disconnected state based on an increase in the current value of the power supplied to the electric motor, which allows for accurate detection of the disconnected state with a simple configuration.

[0022] In one or more embodiments, the controller may be configured to control the electric motor so that the rotation speed of the tipped saw is 500 rpm or less when the electric motor is operating without load. This configuration allows the rotation speed of the tipped saw to be controlled to a lower value at the moment when cutting of the workpiece begins. This further reduces frictional heat generated between the cutting edge of the tipped saw and the workpiece at the start of cutting, thereby further reducing the occurrence of sparks.

[0023] In one or more embodiments, the controller may be configured to control the electric motor so that the rotation speed of the saw blade is 200 rpm or less when the electric motor is driven without load. This configuration further reduces frictional heat generated between the cutting edge of the saw blade and the workpiece at the start of cutting, thereby further reducing the occurrence of sparks.

[0024] In one or more embodiments, the controller may be configured to selectively execute a first control that controls the electric motor so that the rotation speed of the chip saw is 900 rpm or less from the time of no-load operation to the time of operation under a predetermined load, and a second control that controls the electric motor so that the rotation speed of the chip saw is higher than that of the first control. This configuration allows an appropriate cutting method to be selected according to the user's preference (i.e., whether to prioritize reducing spark generation or cutting speed).

[0025] A more detailed description of a tipped saw cutting machine 10 (hereinafter also simply referred to as cutting machine 10) as an example of a stationary cutting machine for metalwork according to an exemplary embodiment will be given below with reference to the drawings. In the following description, the front side of the cutting machine 10 when a user faces the cutting machine 10 during use is defined as the front side of the cutting machine 10, and the opposite side (the rear side) is defined as the rear side of the cutting machine 10. Furthermore, the upper side as viewed from the user during use of the cutting machine 10 is defined as the upper side of the cutting machine 10, and the lower side is defined as the lower side of the cutting machine 10. Furthermore, the right side as viewed from the user during use of the cutting machine 10 is defined as the right side of the cutting machine 10, and the left side is defined as the left side of the cutting machine 10.

[0026] As shown in FIGS. 1 and 2, the cutting machine 10 includes a base 20 and a cutting machine main body 40. The base 20 has a substantially rectangular parallelepiped shape. When the cutting machine 10 is in use, the base 20 is mainly placed on the floor. The base 20 has a flat table surface 21 on which a steel material to be cut (e.g., a pipe with a circular cross section, a pipe with a rectangular cross section, a channel steel, etc.) is placed. The table surface 21 is the upper surface of the base 20.

[0027] A fence 22 in the form of a plate bent at a substantially right angle is fixed to the table surface 21 of the base 20. The fence 22 has a substantially rectangular abutment surface 23 extending upward. A vise device 30 is disposed in front of the fence 22. The vise device 30 includes a vise base 31, a feed screw 32, a knob 33, a vise plate 34, and a support column 35. The vise base 31 is fixed to the table surface 21 near the front edge of the base 20. The feed screw 32 has a male thread on its outer periphery and extends in the front-rear direction so as to penetrate the vise base 31. The feed screw 32 is threadedly engaged with the vise base 31 and moves forward and backward relative to the base 20 by rotating in the circumferential direction about the axis of the feed screw 32. A knob 33 is fixed to the front end of the feed screw 32. A user can rotate the feed screw 32 by gripping and rotating the knob 33.

[0028] The rear end of the feed screw 32 is connected to a vise plate 34. Specifically, the vise plate 34 is a generally flat member extending in the up-down and left-right directions, and includes two connecting portions 36 that face each other vertically. Each of the connecting portions 36 protrudes forward from the flat portion of the vise plate 34. A support pillar 35 extending in the up-down direction is provided between the two connecting portions 36, and the support pillar 35 is fixed to the two connecting portions 36. The feed screw 32 is rotatably connected to the support pillar 35, penetrating approximately the center of the support pillar 35. With this configuration, when the feed screw 32 moves forward and backward, the support pillar 35 and, therefore, the vise plate 34 also move forward and backward. As shown in Figure 6, the workpiece 90 is placed between the abutment surface 23 of the fence 22 and the vise plate 34, and the knob 33 is rotated to move the vise plate 34 rearward, thereby sandwiching the workpiece 90 between the abutment surface 23 and the vise plate 34, thereby fixing the workpiece 90 on the table surface 21 of the base 20.

[0029] As shown in Figures 1 and 2, the cutting machine body 40 includes a motor housing 41, a gear housing 42, a handle housing 43, a fixed cover 45, a movable cover 46, a body base 47, and a battery mounting section 48. The motor housing 41 is located on the left side of the cutting machine body 40. As shown in Figure 5, an electric motor 51 is housed inside the motor housing 41. In this embodiment, the electric motor 51 is a brushless DC motor. However, the electric motor 51 may also be a brushed motor or an AC motor. The gear housing 42 is located on the right side of the electric motor 51.

[0030] As shown in FIG. 5 , the motor shaft 52 of the electric motor 51 is rotatably supported by two bearings spaced apart in the left-right direction and extends from within the motor housing 41 to within the gear housing 42. The motor shaft 52 is provided with a drive gear 53 around the right end thereof. A driven gear 54 that meshes with the drive gear 53 is disposed below the drive gear 53. The drive gear 53 and the driven gear 54 are housed within the gear housing 42. The driven gear 54 is fixed around an output shaft 55. The rotational drive force of the motor shaft 52 is reduced in speed according to the gear ratio of the drive gear 53 and the driven gear 54 and transmitted to the output shaft 55. The output shaft 55 is rotatably supported by two bearings spaced apart in the left-right direction and extends from within the gear housing 42 through the left surface of the fixed cover 45 to the interior of the fixed cover 45.

[0031] A tip saw 56 is fixed to the right end of the output shaft 55. In this embodiment, the diameter of the tip saw 56 is 305 mm. Specifically, the tip saw 56 is sandwiched laterally between an inner flange 57 and an outer flange 58 and fixed to the output shaft 55 with bolts. The tip saw 56 has a generally disk shape. More specifically, the tip saw 56 has a disk-shaped base metal and multiple teeth located on its outer periphery. The teeth are formed by welding separate parts called tips to the base metal. With this configuration, the tip saw 56 is rotatable by a rotational driving force provided by the electric motor 51 via the motor shaft 52, drive gear 53, driven gear 54, and output shaft 55.

[0032] 1, the handle housing 43 extends in the front-rear direction at the same position as the gear housing 42 in the left-right direction. The handle housing 43 has a loop-shaped grip portion 44 at its front edge for a user to grip when performing cutting work with the cutting machine 10. A trigger 49 for starting and stopping the electric motor 51 is disposed on the grip portion 44.

[0033] As shown in FIGS. 1 and 2, the fixed cover 45 is located to the right of the gear housing 42 and the handle housing 43. The fixed cover 45 covers the upper portion of the chip saw 56. The movable cover 46 is located at the front edge of the fixed cover 45. The movable cover 46 is attached to the fixed cover 45 so as to be rotatable by a predetermined angle along the arc-shaped outer periphery of the fixed cover 45. As shown in FIG. 2, the movable cover 46 covers the front portion of the chip saw 56. As will be described later, when the cutting machine body 40 is displaced downward to perform cutting work, a stopper 46a located at the front and lower edge of the movable cover 46 abuts against the table surface 21 of the base 20 (see FIG. 3) or the workpiece 90 and is pressed upward, displacing the movable cover 46 in a direction exposing the chip saw 56.

[0034] As shown in FIG. 1 , the main body base 47 is located below and at the rear of the cutting machine main body 40. A support part 24 that supports the cutting machine main body 40 is fixed to the base 20 near the rear edge of the base 20. The support part 24 extends upward from the table surface 21 of the base 20. A support shaft 25 is attached near the upper edge of the support part 24. The support shaft 25 is fixed to the support part 24 while penetrating the support part 24 and the main body base 47 in the left-right direction. As a result, the cutting machine main body 40 is supported by the support part 24 so as to be swingable up and down around the support shaft 25.

[0035] The cutting machine body 40 can swing from the top dead center shown in FIG. 1 to the bottom dead center shown in FIG. 3. The bottom dead center is determined when the stopper 46a of the movable cover 46 abuts against and presses against the table surface 21 of the base 20, causing the movable cover 46 to displace to its limit position relative to the fixed cover 45. When the tip saw 56 is displaced below the table surface 21 of the base 20, it is inserted into the elongated hole 26 (see FIG. 2) of the base 20. As shown in FIG. 1, a torsion spring 50 is disposed around the support shaft 25. One end of the torsion spring 50 is engaged with the support portion 24, and the other end is engaged with the body base 47. When no external force is applied, the cutting machine body 40 is maintained at the top dead center by the biasing force of the torsion spring 50.

[0036] As shown in FIGS. 1 and 4, the battery mounting section 48 is located behind the handle housing 43 and above the main body base 47. The battery mounting section 48 has terminals that can be electrically connected to each of the two batteries 60. Two batteries 60 are removably mounted in the battery mounting section 48 as power sources for the cutting machine 10. The number of batteries 60 is not particularly limited. A commercial AC power source may be used instead of the batteries 60.

[0037] As shown in FIG. 5, a controller 70 that controls the operation of the electric motor 51 is housed within the upper portion of the motor housing 41. As shown in FIGS. 7 and 8, the controller 70 is electrically connected to the battery 60, main switch 61, mode selector switch 62, rotation speed detector 63, and electric motor 51. The main switch 61 detects the displacement of the trigger 49 and outputs a signal to the controller 70 to activate the electric motor 51. The mode selector switch 62 detects the user's operation of a mode selector (not shown) and outputs a signal to the controller 70 to switch the operation mode of the electric motor 51 between a normal cutting mode and a spark-reduced cutting mode. The normal cutting mode and the spark-reduced cutting mode will be described later. The rotation speed detector 63 is in the form of a rotation speed sensor and detects the rotation speed of the electric motor 51 and outputs the detected rotation speed to the controller 70. In this embodiment, a Hall sensor that detects the rotation angle position of the rotor to control the electric motor 51 is used as the rotation speed detector 63.

[0038] The controller 70 includes a calculation unit 71, a motor drive unit 72, and a cutting state detection unit 73, and variably controls the rotation speed of the electric motor 51 (i.e., the rotation speed of the tip saw 56). The calculation unit 71 includes a CPU and a memory, and executes predetermined functions by executing programs stored in the memory. For example, the calculation unit 71 outputs a drive signal to the motor drive unit 72 based on the difference between the rotation speed of the electric motor 51 input from the rotation speed detection unit 63 and a control target value for the rotation speed, so that the rotation speed of the electric motor 51 approaches the control target value. The motor drive unit 72 includes a switching circuit (inverter circuit) having switching elements such as transistors and FETs. The motor drive unit 72 supplies power from the battery 60 to the electric motor 51 by PWM control based on the drive signal input from the calculation unit 71. The cutting state detection unit 73 is configured to detect the state in which the rotating tip saw 56 is cutting the workpiece (i.e., the load state of the electric motor 51). In this embodiment, the disconnected state detection unit 73 is in the form of a current sensor. As the load on the electric motor 51 increases, the value of the current supplied to the electric motor 51 increases, so it is possible to detect that the electric motor 51 is in a predetermined load state based on the increase in the current value. The calculation unit 71, motor drive unit 72, and disconnected state detection unit 73 are mounted on the same board 70a.

[0039] The cutting machine 10 described above can perform a cutting operation as follows. First, the user secures the workpiece 90 on the table surface 21 of the base 20 using the method described above (see FIG. 6). Next, the user pulls the trigger 49 with the cutting machine body 40 positioned at the top dead center (see FIG. 1), rotating the electric motor 51 and the chip saw 56. Next, the user grips the grip 44 and moves the cutting machine body 40 (chip saw 56) downward. FIG. 6 shows a state in which the cutting machine body 40 has been moved until the rotating chip saw 56 contacts the workpiece 90 (in other words, the start of cutting). Then, the user moves the cutting machine body 40 further downward, causing the cutting to proceed. When the cutting machine body 40 reaches the bottom dead center (see FIG. 1), the cutting is completed. When the user releases the trigger 49 and releases the grip 44, the cutting machine body 40 returns to the top dead center due to the biasing force of the torsion spring 50. During such cutting work, sparks may fly mainly from the point of contact between the saw blade 56 and the workpiece 90 toward the rear in the rotation direction of the saw blade 56, as shown by arrow 91 in Figure 6.

[0040] Control of the rotation speed of the electric motor 51 by the controller 70 will now be described. In this embodiment, a normal cutting mode and a spark-reduced cutting mode are prepared as operating modes for the electric motor 51. When the controller 70 receives a signal to start the electric motor 51 from the main switch 61, the controller 70 determines whether the set operating mode is the normal cutting mode or the spark-reduced cutting mode based on an input from the mode selector switch 62, and controls the electric motor 51 according to the set operating mode. In this embodiment, the controller 70 is configured to selectively execute the normal cutting mode or the spark-reduced cutting mode (i.e., a single controller 70 is used for both the normal cutting mode and the spark-reduced cutting mode), which allows for a simpler and more compact device configuration than when separate controllers are provided for the normal cutting mode and the spark-reduced cutting mode.

[0041] In the normal cutting mode, the calculation unit 71 outputs a command for PWM control to the motor drive unit 72 to drive the electric motor 51 so that the electric motor 51 rotates at a rotation speed corresponding to the rated torque, as in conventional cutting machines. As shown by reference numeral 85 in FIG. 9 , in the normal cutting mode, the rotation speed of the tip saw 56 decreases as the current value of the electric motor 51 increases (in other words, as the load increases). In this case, the rotation speed of the tip saw 56 is 3000 to 4000 rpm in a low-speed cutting machine and 1000 to 1500 rpm in a low-speed cutting machine. In the normal cutting mode, the workpiece 90 can be cut efficiently (at high speed) from the start of cutting to the end of cutting.

[0042] As illustrated in FIG. 10 , in normal cutting mode, when the controller 70 receives a signal from the main switch 61 to start the electric motor 51 at time T0, the controller 70 quickly increases the rotation speed 82 of the tip saw 56 to a second rotation speed R2 corresponding to the rated torque of the electric motor 51. In FIG. 10 , the electric motor 51 is in an unloaded state from time T0 to time T1. Then, when cutting of the workpiece 90 begins at time T1, which is the start of cutting, the electric motor 51 is placed under load, and the rotation speed 82 gradually decreases and eventually becomes constant. As the cutting progresses and approaches the end of the cutting, the load gradually decreases, causing the rotation speed to begin to increase. At time T4, which is the end of cutting, the rotation speed 82 returns to the second rotation speed R2. As illustrated in FIG. 10 , the current value 81 of the power supplied to the electric motor 51 (i.e., the value detected by the cutting state detection unit 73) begins to increase from time T1, which is the start of cutting, as the load increases due to the start of cutting, and eventually becomes constant. Then, when the current value 81 reaches time T4, which is the end of disconnection, it returns to the current value corresponding to the no-load state.

[0043] In the spark reduction cutting mode, the controller 70 controls the electric motor 51 so that the electric motor 51 rotates at a speed lower than the speed corresponding to the rated torque from the time the electric motor 51 is driven without load (i.e., before cutting begins) until the time the electric motor 51 is driven with a predetermined load. This control method is sometimes referred to as a "soft no-load" control. As illustrated by reference numeral 86 in FIG. 9 , in the spark reduction cutting mode, the calculation unit 71 outputs a command for PWM control to the motor drive unit 72 to drive the electric motor 51 so that the rotational speed of the saw blade 56 remains constant at a value lower than the rotational speed corresponding to the rated torque (indicated by reference numeral 85) until the cutting state detection unit 73 detects a predetermined load state (a load state corresponding to current A1 in the figure). After the predetermined load state is detected, the calculation unit 71 outputs a command for PWM control to the motor drive unit 72 so that the same control as in the normal cutting mode is performed.

[0044] More specifically, when the controller 70 receives a signal from the main switch 61 to start the electric motor 51, it controls the electric motor 51 so that the rotation speed of the tip saw 56 is a first rotation speed R1, which is lower than the second rotation speed R2, as illustrated in FIG. 11 . In this embodiment, the second rotation speed R2 is 900 rpm. In this embodiment, the diameter of the tip saw 56 is 305 mm, and therefore the peripheral speed of the cutting edge of the tip saw 56 at this time is 14.4 m / s. This peripheral speed is maintained at least while the electric motor 51 is driven without load (the period from time T0 to time T1 shown in FIG. 11 ). If cutting of the workpiece 90 is started while maintaining a rotation speed lower than that in the normal cutting mode, the peripheral speed of the cutting edge of the tip saw 56 is controlled to a low speed at the moment when cutting of the workpiece 90 begins (i.e., the moment when the tip saw 56 and the workpiece 90 begin to come into contact with each other as shown in FIG. 6 ). Therefore, the frictional heat generated between the cutting edge of the tipped saw 56 and the workpiece 90 at the start of cutting is reduced, and as a result, the generation of sparks can be reduced.

[0045] This effect can be achieved by setting the peripheral speed of the cutting edge of the saw blade 56 to 15 m / s or less when the electric motor 51 is driven without load, assuming that the saw blade 56 has a given diameter. The peripheral speed of the cutting edge of the saw blade 56 when driven without load may be 10 m / s or less, or even 4 m / s or less. This further reduces the occurrence of sparks. Alternatively, this effect can be achieved by setting the rotation speed of the saw blade 56 when driven without load to 900 rpm or less when the saw blade 56 has a diameter of 300 mm or more and 360 mm or less. The rotation speed of the saw blade 56 when driven without load may be 500 rpm or less, or even 200 rpm or less. This further reduces the occurrence of sparks.

[0046] In this embodiment, the rotation of the tip saw 56 at the first rotation speed R1 is maintained for a predetermined period of time after cutting is initiated at time T0. Specifically, after the electric motor 51 is activated, the controller 70 monitors whether the current value detected by the cutting state detection unit 73 is equal to or greater than a threshold value TH. This threshold value TH is set in advance so that it can be determined that cutting has been initiated and the load on the electric motor 51 has increased (in other words, the cutting state). To prevent erroneous detection due to current fluctuations, the controller 70 may determine that the cutting state has been reached when it detects that the current value is equal to or greater than the threshold value TH multiple times. Then, as shown in FIG. 11 , when it is detected that the current value 83 is equal to or greater than the threshold value TH at time T2, the controller 70 increases the rotation speed of the electric motor 51 (and therefore the rotation speed 84 of the tip saw 56) after a predetermined time has elapsed (when time T3 in FIG. 11 is reached). In this embodiment, the controller 70 increases the rotation speed of the electric motor 51 to a rotation speed corresponding to the rated torque. This control is maintained until the cutting is completed (that is, until the trigger 49 is released).

[0047] The workpiece 90 shown in FIG. 6 is a pipe with a circular cross-section. At the beginning of the cut, the workpiece 90 and the cutting edge of the tipped saw 56 come into contact over a wide area along the periphery of the workpiece 90 (i.e., over a relatively wide contact area). This results in a relatively large amount of sparks. However, as the cut progresses, the only areas of contact between the workpiece 90 and the cutting edge of the tipped saw 56 are the front and rear edges of the workpiece 90, reducing the contact area between the workpiece 90 and the cutting edge of the tipped saw 56. In this state, the amount of sparks generated decreases. This reduction also occurs when the workpiece 90 is a pipe with a rectangular cross-section or a channel steel (the channel steel is fixed on the table surface 21 with the center of its approximate U-shape facing upward). Taking this into consideration, the predetermined time is set in advance to correspond to the period during which the amount of sparks generated increases relatively at the beginning of the cut. The predetermined time can be set to any value between 1 and 5 seconds, for example. Such a setting prevents excessive cutting when the rotation speed of the tip saw 56 is low.

[0048] According to this control, during the period from time T1 to time T3 when the amount of sparks generated is relatively large, the peripheral speed of the cutting edge of the tipped saw 56 is controlled to be relatively slow, thereby reducing the amount of sparks generated. After the amount of sparks generated becomes relatively small (after time T3), the peripheral speed of the cutting edge of the tipped saw 56 is controlled to be relatively fast, thereby allowing the workpiece 90 to be cut efficiently in a short time. In other words, it is possible to achieve both a reduction in sparks generated at the start of cutting and efficient cutting.

[0049] Furthermore, according to the cutting machine 10, the controller 70 can selectively execute a normal cutting mode and a spark reduction cutting mode, allowing the user to select an appropriate cutting method according to their preference (i.e., whether prioritizing spark reduction or cutting speed).

[0050] Furthermore, according to the cutting machine 10, the controller 70 is configured so that the function of executing PWM control of the electric motor 51 in the normal cutting mode and the function of executing rotation speed control in the spark reduction cutting mode are executed on the same board 70a, thereby simplifying the device configuration and making it more compact.

[0051] The correspondence between each component of the above embodiment and each component of the present invention is shown below. However, each component of the embodiment is merely an example and does not limit each component of the present invention. The chip saw cutting machine 10 is an example of a "metalworking cutting machine" and a "stationary metalworking cutting machine." The electric motor 51 is an example of an "electric motor." The chip saw 56 is an example of a "chip saw." The controller 70 is an example of a "controller." The normal cutting mode is an example of "second control." The spark reduction cutting mode is an example of "low rotation speed control" and "first control."

[0052] Although several embodiments have been described above, the above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit thereof, and the present invention includes equivalents thereof. Furthermore, any combination or omission of the elements described in the claims and specification is possible within the scope of solving at least part of the above-described problems or achieving at least part of the effects.

[0053] The above-described embodiment is not limited to the stationary tipped saw cutting machine 10, but can be applied to any metalworking cutting machine equipped with a tipped saw, such as a portable tipped saw cutter. [Explanation of symbols]

[0054] 10...Tip saw cutting machine 20...Base 21...Table surface 22...Fence 23...Abutment surface 24...Support part 25...Spindle 26...long hole 30...Vise device 31...Vise base 32...Feed screw 33...Knob 34...Vise plate 35...support column 36...Connection part 40...Cutting machine body 41...Motor housing 42...Gear housing 43...Handle housing 44...Gripping part 45...Fixed cover 46... Movable cover 46a...Stopper 47...Main body base 48...Battery compartment 49...Trigger 50...torsion spring 51...Electric motor 52...Motor shaft 53...Drive gear 54...Driven gear 55...Output shaft 56...Tip saw 57...Inner flange 58...Outer flange 60...Battery 61...Main switch 62...Mode switch 63...Rotation speed detector 70...Controller 70a...substrate 71... Arithmetic section 72...Motor drive unit 73...Disconnection status detection unit 81, 83...Current value 82,84...rpm 85...Relationship between current and rotation speed in normal cutting mode 86...Relationship between current and rotation speed in reduced spark cutting mode 90...Material to be cut 91...Arrow indicating the direction of sparks

Claims

1. A metalwork cutting machine, An electric motor; a substantially disk-shaped tip saw that can be rotated by a rotational driving force provided by the electric motor; a controller configured to control operation of the electric motor; Equipped with The controller is configured to control the electric motor so that the peripheral speed of the cutting edge of the chip saw is 15 m / s or less when the electric motor is driven without load. Cutting machine for metalworking.

2. The metalworking cutting machine according to claim 1, The controller is configured to control the electric motor so that the peripheral speed of the cutting edge of the tip saw is 10 m / s or less during the no-load driving. Cutting machine for metalworking.

3. The metalworking cutting machine according to claim 2, The controller is configured to control the electric motor so that the peripheral speed of the cutting edge of the tip saw is 4 m / s or less during the no-load driving. Cutting machine for metalworking.

4. The metalworking cutting machine according to any one of claims 1 to 3, The controller is configured to control the electric motor to increase the rotational speed of the electric motor after detecting a disconnection condition. Cutting machine for metalworking.

5. The metalworking cutting machine according to claim 4, The controller is configured to control the electric motor so as to increase the rotation speed of the electric motor when a predetermined time has elapsed since the disconnected state was detected. Cutting machine for metalworking.

6. The metalworking cutting machine according to claim 5, The predetermined time is set to any time between 1 and 5 seconds. Cutting machine for metalworking.

7. A metalworking cutting machine according to any one of claims 1 to 6, The controller is configured to perform low rotation speed control to control the electric motor so that the electric motor rotates at a rotation speed lower than the rotation speed corresponding to a rated torque from the time of no-load driving to the time of driving under a predetermined load. Cutting machine for metalworking.

8. The metalworking cutting machine according to claim 7, the electric motor is a brushless DC motor, The controller is configured to execute the function of performing the low rotation speed control and the function of performing PWM control of the electric motor on the same board. Cutting machine for metalworking.

9. A metalworking cutting machine according to claim 4, claim 5, and any one of claims 6 to 8 which depend on claim 4, The controller is configured to detect the disconnected state based on an increase in the current value of the power supplied to the electric motor. Cutting machine for metalworking.

10. A stationary cutting machine for metalwork, An electric motor; a substantially disk-shaped tip saw that can be rotated by a rotational driving force provided by the electric motor; a controller configured to control operation of the electric motor; Equipped with The diameter of the tip saw is 300 mm or more and 360 mm or less, The controller is configured to control the electric motor so that the rotation speed of the tip saw is 900 rpm or less when the electric motor is driven without load. Stationary cutting machine for metalwork.

11. 11. The stationary metalworking cutting machine according to claim 10, The controller is configured to control the electric motor so that the rotation speed of the tip saw is 500 rpm or less when the electric motor is driven without load. Stationary cutting machine for metalwork.

12. 12. The stationary metalworking cutting machine according to claim 11, The controller is configured to control the electric motor so that the rotation speed of the tip saw is 200 rpm or less when the electric motor is driven without load. Stationary cutting machine for metalwork.

13. A stationary metalworking cutting machine according to any one of claims 10 to 12, The controller is configured to selectively execute a first control for controlling the electric motor so that the rotation speed of the chip saw is 900 rpm or less from the time of the no-load driving to the time of driving under a predetermined load, and a second control for controlling the electric motor so that the rotation speed of the chip saw is higher than that of the first control. Stationary cutting machine for metalwork.

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