Cutting device

Abstract

To provide a cutting device which can properly control an operation of cutting blades based on a current position of the cutting blades.SOLUTION: A cutting device 10 includes: a pair of cutting blades 111 which sandwiches and cuts a cut object; an electric motor 400 which generates drive force needed for operation of the cutting blades 111; a control unit 510 which controls the operation of the electric motor 400; blade members 110 provided with the cutting blades 111; contact parts 112 each of which contacts with the blade member 110 to restrict a range in which the pair of cutting blades 111 may operate; and a contact detection part 530 which detects the blade members 110 contacting with the contact part 112.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an electric cutting device. [Background Art]

[0002] As electric cutting devices, for example, electric pruning shears as described in Patent Document 1 below are known. In an electric cutting device, instead of a user's gripping force, a cutting blade is operated by the driving force of an electric motor, and an object to be cut is cut by being sandwiched between a pair of cutting blades. Although the above-mentioned electric pruning shears use objects to be cut such as tree branches, cutting devices that cut metals such as reinforcing bars are also known. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2021-40594 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] In an electric cutting device, in order to appropriately control the operation of the cutting blade, it is preferable to accurately grasp the current position of the cutting blade at each time point during operation. As a configuration for grasping the current position of the cutting blade, for example, as described in the above Patent Document 1, a configuration in which a proximity sensor such as a Hall sensor is provided in an internal drive mechanism is conceivable. Specifically, for example, a configuration in which a magnet is provided on a nut of a ball screw and a Hall sensor is provided at a specific position within the movement range of the nut is conceivable.

[0005] However, there is a possibility that a part of the cut object may enter the internal space including the movement range of the nut as a foreign matter. If the foreign matter adheres to the Hall sensor, it becomes impossible to accurately grasp the position of the nut and the corresponding current position of the cutting blade. As a result, it becomes difficult to appropriately control the operation of the cutting blade.

[0006] The present invention aims to provide a cutting device that can appropriately control the movement of a cutting blade based on the current position of the cutting blade. [Means for solving the problem]

[0007] The cutting device according to the present invention is an electric cutting device comprising: a pair of cutting blades that grip and cut an object to be cut; an electric motor that generates the driving force necessary for the operation of the cutting blades; a control unit that controls the operation of the electric motor; a first member on which one of the cutting blades is provided; a second member on which the other cutting blade is provided; a restricting unit that restricts the range in which the pair of cutting blades can operate by contacting at least one of the first member and the second member; and a contact detection unit that detects when at least one of the first member and the second member has come into contact with the restricting unit.

[0008] In the cutting device with the above configuration, the movement of the first member, which is equipped with a cutting blade, is physically restricted by contact with a restricting unit. The contact of the first member with the restricting unit can be detected by a contact detection unit. The position of the cutting blade at the time of contact is known. Therefore, by operating the first and second members until contact is detected by the contact detection unit, the pair of cutting blades can be moved to a preset initial position. After that, the current position of the cutting blade can be determined by calculating the amount of movement from the initial position of the first member, for example, based on the rotation amount of an electric motor. This makes it possible to appropriately control the movement of the cutting blade, such as stopping the cutting blade at a predetermined target position. [Effects of the Invention]

[0009] According to the present invention, a cutting device is provided that can appropriately control the movement of a cutting blade based on the current position of the cutting blade. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 shows the configuration of the cutting device according to the first embodiment. [Figure 2] Figure 2 shows the configuration of the guide plate included in the cutting device according to the first embodiment. [Figure 3] Figure 3 shows the configuration of the blade member included in the cutting device according to the first embodiment. [Figure 4] Figure 4 shows the configuration of the control board included in the cutting device according to the first embodiment. [Figure 5] Figure 5 is a flowchart showing the processing flow performed by the control board. [Figure 6] Figure 6 is a flowchart showing the processing flow performed by the control board. [Figure 7] Figure 7 is a flowchart showing the processing flow performed by the control board. [Figure 8] Figure 8 shows the configuration of a cutting device according to a modified example of the first embodiment. [Figure 9] Figure 9 shows the configuration of the blade member included in the cutting device according to the second embodiment. [Figure 10] Figure 10 shows the configuration of the blade member included in the cutting device according to the second embodiment. [Figure 11] Figure 11 shows an example of the time variation of the current supplied to an electric motor. [Figure 12] Figure 12 is a flowchart showing the processing flow performed by the control board. [Figure 13] Figure 13 is a flowchart showing the processing flow performed by the control board. [Figure 14] Figure 14 shows the configuration of a cutting device according to a modified example of the second embodiment. [Modes for carrying out the invention]

[0011] This embodiment will now be described with reference to the attached drawings. To facilitate understanding of the explanation, the same reference numerals are used for identical components in each drawing whenever possible, and redundant explanations are omitted.

[0012] A first embodiment will be described. The cutting device 10 according to the present embodiment is an electric cutting device configured as a device for cutting reinforcing bars at construction sites and the like. The configuration of the cutting device 10 will be described with main reference to Fig. 1. The cutting device 10 includes a housing 11, a trigger switch 12, a cutting mechanism 100, a ball screw 200, a speed reducer 300, an electric motor 400, a control board 500, and a storage battery 600.

[0013] The housing 11 is a container that defines the outer shape of the cutting device 10, and is formed of, for example, resin. The ball screw 200, the speed reducer 300 and the like which will be described later are accommodated inside the housing 11. In Fig. 1, a portion of the housing 11 on the near side of the drawing is removed, and the internal configuration of the cutting device 10 is shown as a cross-sectional view.

[0014] The trigger switch 12 is a switch operated by a user's finger. The user can turn the trigger switch 12 on by placing a finger on the trigger switch 12 and performing an operation of pulling it toward the user. When the user relaxes the force of the finger, the trigger switch 12 returns to the original position by the force of a spring and enters an off state. When the trigger switch 12 is switched between an on state and an off state, a corresponding signal is transmitted to the control board 500 which will be described later. As will be described later, when the trigger switch 12 is turned on by a user's operation, an operation for cutting the reinforcing bar is started.

[0015] The cutting mechanism 100 is a portion that cuts a reinforcing bar which is an object to be cut. The cutting mechanism 100 includes a pair of blade members 110 and a pair of link members 120.

[0016] Each blade member 110 has a cutting blade 111 formed on it that grips and cuts the material to be cut. The blade members 110 are held in a rotatable state around an axis 101 fixed to the housing 11. In this embodiment, the blade members 110 are arranged opposite each other so that the edges of the cutting edges 111 move along a trajectory that passes through approximately the same plane. This makes it possible to switch between an open state in which the cutting edges 111 are spaced apart from each other and a closed state in which the cutting edges 111 are in contact with (or close to) each other. In the example in Figure 1, the pair of cutting edges 111 are in the closed state. One blade member 110 corresponds to the "first member" in this embodiment, and the other blade member 110 corresponds to the "second member" in this embodiment.

[0017] The link member 120 is a rod-shaped member, with one end connected to the blade member 110 via a shaft 102, and the other end connected to the connecting member 230 (described later) via a shaft 231. The link member 120 and the blade member 110 are connected in a manner that allows them to rotate freely with respect to each other around the shaft 102. Similarly, the link member 120 and the connecting member 230 are connected in a manner that allows them to rotate freely with respect to each other around the shaft 231. As will be explained later, the connecting member 230 moves in the left-right direction in Figure 1 by the driving force of the electric motor 400.

[0018] When the connecting member 230 moves to the left from the state shown in Figure 1, the upper blade member 110 rotates counterclockwise, and the lower blade member 110 rotates clockwise. As a result, the pair of cutting blades 111 move from a closed state to an open state. On the other hand, when the pair of cutting blades 111 are in the open state, when the connecting member 230 moves to the right in Figure 1, the upper blade member 110 rotates clockwise, and the lower blade member 110 rotates counterclockwise. As a result, the pair of cutting blades 111 return to a closed state. In this way, the pair of blade members 110, the pair of link members 120, and the connecting member 230 as a whole constitute a so-called "toggle link mechanism".

[0019] For the sake of explanation, the right side of Figure 1 will be referred to as the "tip side" below, and the left side of the same figure will be referred to as the "rear end side" below. Figure 3 shows the state in which the pair of cutting blades 111 are widest apart, i.e., fully open. A contact portion 112 is formed on the part of each blade member 110 that is on the rear end side of the cutting blade 111. As the cutting blades 111 move away from each other, the respective contact portions 112 move closer to each other. Eventually, as shown in Figure 3, the respective contact portions 112 come into contact with each other, so the cutting blades 111 can no longer be opened any further. In other words, the cutting blades 111 are fully open.

[0020] The contact portion 112 of one blade member 110 contacts the contact portion 112 of the other blade member 110, thereby restricting the range in which the other blade member 110 can operate. Each contact portion 112 corresponds to a "restricting portion" in this embodiment. The restricting portion in this embodiment restricts the position of each cutting blade 111 when the distance between the cutting blades 111 is at its greatest.

[0021] In this embodiment, a pair of guide plates 700 are provided near the blade member 110. The guide plates 700 are plate-shaped members made of metal and are positioned to sandwich the blade member 110 from both the front and back sides of the paper in Figure 1. The shape of the pair of guide plates 700 is identical to that of the other. As shown in Figures 2 and 3, each guide plate 700 has a recess 710 formed therein.

[0022] The recesses 710 are formed to recede from the front end to the rear end of the guide plate 700. When the cutting device 10 is viewed from the side, as shown in Figures 1 and 2, each recess 710 is formed in a position that includes the cutting blade 111 in the closed state. As shown in Figure 3, in the standby state with the cutting blades 111 fully open, each cutting blade 111 is retracted to the outside of the recess 710, and the entire blade member 110 is hidden by the guide plate 700. The guide plate 700 has both the function of covering and protecting the cutting blades 111 in the standby state, and the function of guiding the reinforcing bar, which is the object to be cut, along the recess 710 to between the pair of cutting blades 111. The guide plate 700 also has the function of stabilizing the posture of the cutting device 10 before and after cutting by sandwiching the reinforcing bar in the recess 710.

[0023] The ball screw 200 is a device that converts the rotational motion of the electric motor 400 into the linear motion of the connecting member 230, thereby operating the cutting mechanism 100. The ball screw 200 has a screw shaft 210, a nut 220, and a connecting member 230.

[0024] The screw shaft 210 is a rod-shaped member that extends linearly from the rear end to the front end. A male screw is formed on the outer surface of the screw shaft 210. When the electric motor 400 is driven, the screw shaft 210 rotates around its central axis.

[0025] The nut 220 is a substantially cylindrical member positioned to surround the screw shaft 210 from the outer circumference. A female thread is formed on the inner surface of the nut 220, which screws onto a male thread formed on the outer surface of the screw shaft 210. The nut 220 is allowed to move along the longitudinal direction of the screw shaft 210, but its rotation around the central axis of the screw shaft 210 is restricted. Therefore, when the screw shaft 210 rotates around its central axis, the nut 220 moves along that central axis in the left-right direction as shown in Figure 1.

[0026] The connecting member 230 is a member attached to the nut 220 and moves along the screw shaft 210 together with the nut 220. The connecting member 230 is attached so as to protrude toward the tip side from the nut 220. A pair of link members 120 are connected to the portion of the connecting member 230 near the tip end via the shaft 231 mentioned earlier.

[0027] The reduction gear 300 is a device that reduces the rotation of the output shaft 410 of the electric motor 400 and then transmits it to the screw shaft 210 of the ball screw 200.

[0028] The electric motor 400 is a rotating electric machine that generates the driving force necessary for the operation of the cutting blade 111, and is, for example, a brushless DC motor. The electric motor 400 has an output shaft 410. The output shaft 410 is a substantially cylindrical member, and its central axis coincides with the central axis of the screw shaft 210. A portion of the output shaft 410 protrudes toward the reduction gear 300 and is connected to the reduction gear 300.

[0029] When current is supplied to the coil of the electric motor 400, the output shaft 410 rotates around its central axis. The rotation of the output shaft 410 is transmitted to the screw shaft 210 via the reduction gear 300, moving the nut 220 toward the front or rear end. This causes the cutting blade 111 of the cutting mechanism 100 to open and close, as described earlier.

[0030] A rotation sensor 420 is provided inside the electric motor 400. The rotation sensor 420 is a sensor that emits a pulse signal each time the output shaft 410 rotates by a predetermined angle, and is mounted on a circuit board 430 of the electric motor 400. The pulse signals from the rotation sensor 420 are transmitted to the control board 500. The control board 500 can determine the rotation angle of the output shaft 410 after a specific timing by counting the number of pulse signals. The control board 500 can also determine the rotation speed of the output shaft 410 based on the number of pulse signals input per unit time. The rotation sensor 420 may be a different type of sensor than in this embodiment, or it may be a sensor provided separately at a different location from the electric motor 400, as long as it can measure the rotation angle of the output shaft 410.

[0031] The control board 500 is a circuit board provided for controlling the overall operation of the cutting device 10, including the electric motor 400. The control board 500 includes an inverter circuit for adjusting the current supplied to the electric motor 400, and a microcontroller for controlling switching operations in the inverter circuit, etc.

[0032] The battery 600 stores the power necessary for the operation of the electric motor 400 and the control board 500, and is, for example, a lithium-ion battery. The part of the cutting device 10 that houses the battery 600 can be detached from the housing 11 as a battery pack and can be charged by connecting it to an external charger. Alternatively, the device may be configured to allow charging of the battery 600 while it remains attached to the housing 11.

[0033] The configuration of the control board 500 will be explained with reference to Figure 4. The control board 500, which includes a microcontroller, comprises the following elements that represent its function: a control unit 510, a movement amount acquisition unit 520, a contact detection unit 530, and a maximum current changing unit 540.

[0034] The control unit 510 controls the operation of the electric motor 400. The control unit 510 controls the opening and closing operation of the cutting blade 111 by adjusting the magnitude of the current supplied to the electric motor 400, for example, by PWM control. The control unit 510 also controls the braking operation of the cutting blade 111 by performing a so-called "short brake" by periodically or continuously short-circuiting some of the coils of the electric motor 400.

[0035] The movement amount acquisition unit 520 is the part that performs the process of acquiring the amount of movement of each blade member 110 from a state in which the contact portions 112 of the pair of blade members 110 are in contact with each other. In this embodiment, the count value of the pulse signal transmitted from the rotation sensor 420 is used as the "amount of movement". The method for acquiring the count value as the amount of movement will be explained later. The "amount of movement" acquired by the movement amount acquisition unit 520 can be any index that directly or indirectly indicates the amount of movement of the blade members 110, and may be a value other than the count value of the pulse signal. For example, when the angle between the pair of cutting blades 111 is θ, the amount of change in θ may be used as the "amount of movement".

[0036] The contact detection unit 530 is the part that performs the process of detecting when the contact portions 112 of a pair of blade members 110 come into contact with each other. When the electric motor 400 is driven to move the cutting blade 111 in the opening direction, if the contact portions 112 come into contact with each other and can no longer move, the current supplied to the electric motor 400 increases from that point onward as the load increases. Therefore, the contact detection unit 530 detects the contact between the contact portions 112 based on the current supplied to the electric motor 400. Specifically, the contact detection unit 530 compares the current value supplied to the electric motor 400 with a predetermined reference value, and detects that the contact portions 112 have come into contact with each other when the current value exceeds the reference value. The current value supplied to the electric motor 400 can be measured, for example, by a current sensor (not shown) built into the electric motor 400. The current sensor may also be provided on the outside of the electric motor 400.

[0037] The switching circuit (not shown) on the control board 500 is configured to control the electric motor 400 while keeping the current supplied to it below a predetermined current limit value. The current limit value can be described as the maximum current that can be supplied to the electric motor, and it is a variable parameter that the control board 500 can freely change. The maximum current changing unit 540 is the part that performs the process of changing this current limit value. The specific processing performed by the maximum current changing unit 540 will be explained later.

[0038] The specific flow of processing performed by the control board 500 will now be explained. The series of processes shown in the flowchart of Figure 5 are automatically started when the main power is turned on and the cutting device 10 is activated. Even if the main power is turned on, the processes in Figure 5 may not start automatically, but may start when the trigger switch 12 is first turned on by the user.

[0039] In the first step S01, the control unit 510 drives the electric motor 400 to start moving each cutting blade 111 in the opening direction. From thereafter, each cutting blade 111 opens at a roughly constant speed.

[0040] In step S02, following step S01, the contact detection unit 530 determines whether or not contact between the contact parts 112 has been detected. As mentioned earlier, this determination is made based on whether or not the current value supplied to the electric motor 400 exceeds a predetermined reference value.

[0041] If contact between the contact parts 112 is not yet detected, that is, if the current supplied to the electric motor 400 is below the reference value, the process in step S02 is executed again while the electric motor 400 continues to run. If contact between the contact parts 112 is detected, that is, if the current supplied to the electric motor 400 exceeds the reference value, the process proceeds to step S03.

[0042] In step S03, the electric motor 400 is stopped. As a result, each cutting blade 111 stops in its fully open position.

[0043] In step S04, following step S03, the count value of the pulse signal transmitted from the rotation sensor 420 is reset to 0. From this point onward, the movement amount acquisition unit 520 changes the count value in accordance with the operation of the cutting blade 111, but this value always represents the amount of movement of the cutting blade 111 relative to the fully open position. In other words, the count value can be used as a value representing the absolute position of each cutting blade 111. The process in Figure 5 is an initialization process to associate the count value with the absolute position of the cutting blade 111. Once this process is completed, the cutting device 10 enters a standby state with the cutting blade 111 in the fully open position.

[0044] When the user operates the trigger switch 12 to turn it ON while in standby mode, the process shown in Figure 6 begins.

[0045] In the first step S11 of the process, the control unit 510 drives the electric motor 400 to start moving each cutting blade 111 in the closing direction. This starts the cutting of the reinforcing bar, which is the object to be cut. Immediately after the cutting blades 111 begin to move, each cutting blade 111 comes into contact with a reinforcing bar (not shown), and as it continues to move, it causes plastic deformation of the reinforcing bar. In most cases, the reinforcing bar breaks while the cutting blades 111 are moving.

[0046] In step S12, following step S11, it is determined whether the amount of movement acquired by the movement amount acquisition unit 520, i.e., the count value, is greater than or equal to a predetermined value. This "predetermined value" is a value that has been set in advance as the position in which braking of the cutting blade 111 moving in the closing direction should begin. For example, the above-mentioned predetermined value can be set as the value corresponding to a position that is a braking distance in front of the position in which the cutting blade 111 is fully closed. Considering that the braking distance changes according to the operating speed of the cutting blade 111, the above-mentioned predetermined value may be changed each time according to the operating speed of the cutting blade 111.

[0047] If the count value is less than a predetermined value, the operation of the cutting blade 111 continues, and the process in step S12 is executed again. If the count value becomes equal to or greater than the predetermined value, the process proceeds to step S13. In step S13, the control unit 510 starts braking the cutting blade 111. After that, the cutting blade 111 stops at the target position. The target position may be the position where the cutting blade 111 is fully closed, or it may be a position slightly in front of the fully closed position, that is, a position where a small gap is formed between the cutting blades 111. In this way, the control unit 510 determines the timing to start braking the cutting blade 111 based on the amount of movement (i.e., the count value) acquired by the amount of movement acquisition unit 520.

[0048] After the rebar cutting is complete, the process shown in the flowchart of Figure 7 is executed, and the cutting blade 111 is returned to its original fully open position. This process may be started automatically after the cutting is complete, but it may also be started after, for example, the user returns the trigger switch 12 to its original position (i.e., the off state).

[0049] In the first step S21 of Figure 7, the control unit 510 drives the electric motor 400 to start moving each cutting blade 111 in the opening direction. From this point onward, each cutting blade 111 opens at a roughly constant speed. As the cutting blades 111 move in the opening direction, the amount of movement acquired by the movement amount acquisition unit 520, i.e., the count value, gradually decreases.

[0050] In step S22, following step S21, it is determined whether the above count value is below a predetermined threshold. This "threshold" is a value that has been set in advance as corresponding to the timing at which the current limit value should be changed to a smaller value than before. If the count value exceeds the threshold, the process in step S22 is executed again while the operation of the cutting blade 111 continues. When the count value becomes below the threshold, the process proceeds to step S23.

[0051] In step S23, the maximum current change unit 540 changes the current limit value to a smaller value than before. Since the upper limit of the force that can be generated by the cutting blade 111 is reduced, a situation in which the contact parts 112 collide violently when they reach the fully open position is prevented. As a result, it is no longer necessary to ensure the durability of the blade member 110 and nearby members more than necessary, making it possible to miniaturize and lighten the members.

[0052] Thus, the maximum current changing unit 540 determines the timing for changing the current limit value based on the amount of movement acquired by the amount of movement acquisition unit 520. Preferably, the timing for changing the current limit value to a smaller value is when the pair of cutting blades 111 are operating, and before the contact portions 112 of the blade members 110 come into contact with each other. In other words, as in this embodiment, it is preferable that the threshold used in the determination in step S22 of Figure 7 is set so that the contact portions 112 come into contact with each other after the current limit value has been changed.

[0053] In step S24, following step S23, the contact detection unit 530 determines whether or not contact between the contact parts 112 has been detected. If contact between the contact parts 112 has not yet been detected, that is, if the current supplied to the electric motor 400 is below the reference value, the process in step S24 is executed again while the electric motor 400 continues to run. If contact between the contact parts 112 has been detected, that is, if the current supplied to the electric motor 400 exceeds the reference value, the process proceeds to step S25.

[0054] In step S25, the electric motor 400 is stopped. As a result, each cutting blade 111 stops in its fully open position. After that, a process to reset the pulse signal count value to 0 may be performed, similar to step S04 in Figure 5. From this point onward, the cutting device 10 returns to the standby state.

[0055] When returning the cutting blade 111 to the fully open position, the electric motor 400 may be driven until the contact portions 112 come into contact with each other, as described above. Alternatively, braking similar to step S13 in Figure 6 may be performed at a predetermined timing before contact.

[0056] As described above, in the cutting device 10 according to this embodiment, the movement of the blade member 110, which is provided with the cutting blade 111, is physically restricted by contact with a restricting part (contact part 112). Contact with the restricting part is detected by a contact detection unit 530, and the position of the cutting blade 111 thereafter is acquired by a movement amount acquisition unit 520. This makes it possible to appropriately control the operation of the cutting blade 111, such as stopping the cutting blade 111 at a predetermined target position.

[0057] There is no need to install magnets or Hall sensors around the nut to obtain the position of the cutting blade 111. Therefore, a situation will not occur where the position of the cutting blade 111 cannot be obtained due to foreign matter adhering to the Hall sensor.

[0058] The contact detection unit 530 detects that at least one of the pair of blade members 110 has come into contact with the regulating portion based on the current supplied to the electric motor 400, as described above. Alternatively, the contact may be detected based on the voltage applied to the electric motor 400.

[0059] When the electric motor 400 is driven to move the cutting blade 111 in the opening direction, if the contact parts 112 come into contact with each other and can no longer move, the voltage applied to the electric motor 400 decreases as the current increases. Therefore, the contact detection unit 530 can compare the voltage value applied to the electric motor 400 with a predetermined reference value and detect that the contact parts 112 have come into contact with each other when the voltage value falls below the reference value.

[0060] Furthermore, the contact detection unit 530 may perform detection based on the rotational speed of the electric motor 400 per unit time, that is, the amount of change in the count value per unit time.

[0061] When the electric motor 400 is driven to move the cutting blade 111 in the opening direction, if the contact parts 112 come into contact with each other and can no longer move, the rotational speed of the electric motor 400 per unit time decreases sharply to approximately 0. Therefore, the contact detection unit 530 compares the amount of change in the count value per unit time with a predetermined reference value, and can detect that the contact parts 112 have come into contact with each other when the amount of change in the count value falls below the reference value.

[0062] A modified version of the first embodiment will now be described. Figure 8 shows a schematic cross-sectional view of the configuration of the modified blade member 110 and the guide plates 700 on both sides thereof. The cross-section shown in Figure 8 is the cross-section when the blade member 110, etc., is cut perpendicular to the central axis of the screw shaft 210.

[0063] In this modified example, the blade members 110 do not have contact portions 112 that abut each other in the fully open position. As shown in Figure 8, in this modified example, each blade member 110 is provided with a projection 113 that protrudes toward the guide plate 700. The guide plate 700 is also provided with a restricting surface 720 that abuts the projection 113 from the outside in the opening and closing direction of the blade members 110. As the blade members 110 move in the opening direction, eventually the projection 113 abuts against the restricting surface 720, preventing the blade members 110 from moving any further. The restricting surface 720 that abuts against the blade members 110 and restricts their movement corresponds to the "restricting portion" in this modified example.

[0064] In this modified example, the movement amount acquisition unit 520 acquires the amount of movement of each blade member 110 from the state in which the regulating surface 720 is in contact with the projection 113 of the blade member 110. The contact detection unit 530 also detects when the regulating surface 720 is in contact with the projection 113 of the blade member 110. This configuration also produces the same effects as described in the first embodiment.

[0065] Furthermore, the restricting surface 720, which functions as a restricting part, may, as in this modified example, contact each of the pair of blade members 110 to restrict the operating range of the cutting blade 111, or it may contact only one of the pair of blade members 110 to restrict it.

[0066] In this case, the contact detection unit 530 will also detect that only one of the pair of blade members 110 has come into contact with the restricting section. Furthermore, the amount of movement acquired by the movement amount acquisition unit 520 will be the amount of movement of the blade member 110 from the state in which one of the pair of blade members 110 has come into contact with the restricting section. Similarly, the maximum current change unit 540 will reduce the current limit value to a value lower than the previous value at a timing before one of the pair of blade members 110 comes into contact with the restricting section.

[0067] Thus, in the first embodiment and the above modified example, the distance between the cutting blades 111 is maximized when at least one of the pair of blade members 110 is in contact with the regulating portion.

[0068] A second embodiment will now be described. In the following, the differences from the first embodiment will be mainly described, and the points that are common to the first embodiment will be omitted as appropriate. In this embodiment, the distance between the cutting blades 111 is minimized when at least one of the pair of blade members 110 is in contact with the regulating portion, and this is where it differs from the first embodiment.

[0069] As shown in Figures 9 and 10, each blade member 110 according to this embodiment is provided with a contact portion 114. The contact portions 114 are located adjacent to the cutting blade 111 on the tip side and are positioned to protrude slightly toward the other cutting blade 111. Therefore, when the cutting blades 111 are moved toward the closing direction, as shown in Figure 9, the contact portions 114 come into contact with each other before the cutting blades 111 come into contact with each other, preventing the blade member 110 from moving any further.

[0070] The contact portion 114 of one blade member 110 contacts the contact portion 114 of the other blade member 110, thereby restricting the range in which the other blade member 110 can operate. Each contact portion 114 corresponds to a "restricting portion" in this embodiment.

[0071] Furthermore, in this embodiment, even when the blades are in the fully closed position, a small gap is formed between the cutting blades 111. Therefore, a situation in which the cutting blades 111 collide with each other is reliably prevented.

[0072] Alternatively, the amount of protrusion of the contact portion 114 relative to the cutting blade 111 may be set to 0. In this case, the pair of cutting blades 111 will come into contact with each other, and at the same time, the contact portions 114 will also come into contact with each other.

[0073] Figure 11 shows an example of the time variation of the current supplied to the electric motor 400 when cutting reinforcing bars. t0 is the start time of operation, at which point the cutting blade 111 is fully open.

[0074] Immediately after the cutting of the rebar begins, the current in the electric motor 400 increases as the cutting blade 111 closes. Once the acceleration of the cutting blade 111 is complete, the current gradually decreases and becomes roughly constant.

[0075] In Figure 11, t1 represents the time when the cutting blade 111 made contact with the reinforcing bar. After t1, the load on the electric motor 400 increases, so the current of the electric motor 400 gradually increases. However, the current remains below the current limit value shown by the dashed line.

[0076] In Figure 11, t2 represents the time when the reinforcing bar fractured. When the reinforcing bar fractures, the load on the electric motor 400 decreases rapidly, and the current also decreases rapidly. After that, the current becomes roughly constant.

[0077] In Figure 11, t4 represents the time when the contact portions 114 come into contact with each other and are fully closed. From this point onward, the load on the electric motor 400 increases rapidly, and the current also increases rapidly. The contact detection unit 530 in this embodiment can detect that the cutting blade 111 has reached the fully closed position by comparing the current of the electric motor 400 with a predetermined threshold SI.

[0078] In the example shown in Figure 11, at time t3, which is after time t2 but before time t4, the maximum current change unit 540 changes the current limit value to a smaller value than before. The current limit value from time t3 onward is set to a value slightly larger than the threshold value SI. Therefore, at time t5, immediately after the current of the electric motor 400 exceeds the threshold value SI, the current reaches the current limit value and stops increasing further. As a result, the force pressing the contact parts 114 against each other does not become too large. Note that the current limit value from time t3 onward may also be set to the same value as the threshold value SI.

[0079] The specific flow of processing performed by the control board 500 will now be explained. In this embodiment as well, when the main power is turned on and the cutting device 10 is started, the same initialization process as in the first embodiment (Figure 5) is performed. The series of processes shown in Figure 12 are performed by the control board 500 in this embodiment, instead of the series of processes shown in Figure 5.

[0080] In the first step S31, the control unit 510 drives the electric motor 400 to start moving each cutting blade 111 in the closing direction. From thereafter, each cutting blade 111 closes at a generally constant speed.

[0081] In step S32, following step S31, the contact detection unit 530 determines whether or not contact between the contact portions 114 has been detected. Similar to the first embodiment, this determination is made based on whether or not the current value supplied to the electric motor 400 exceeds a predetermined reference value.

[0082] If contact between the contact parts 114 is not yet detected, that is, if the current supplied to the electric motor 400 is below the reference value, the process in step S32 is executed again while the electric motor 400 continues to run. If contact between the contact parts 114 is detected, that is, if the current supplied to the electric motor 400 exceeds the reference value, the process proceeds to step S33.

[0083] In step S33, the electric motor 400 is stopped. As a result, each cutting blade 111 stops in the fully closed position.

[0084] In step S34, following step S33, the count value of the pulse signal transmitted from the rotation sensor 420 is reset to 0. From this point onward, the count value can be used to represent the absolute position of each cutting blade 111.

[0085] In step S35, following step S34, the control unit 510 drives the electric motor 400 to start moving each cutting blade 111 in the opening direction. From this point onward, each cutting blade 111 opens at a generally constant speed.

[0086] In step S36, following step S35, it is determined whether the amount of movement acquired by the movement amount acquisition unit 520, i.e., the count value, is less than or equal to a predetermined value. This "predetermined value" is a value that has been set in advance as the position in which braking of the cutting blade 111 moving in the opening direction should begin. For example, the above-mentioned predetermined value can be set as the value corresponding to a position that is a braking distance in front of the position in which the cutting blade 111 is fully open. Considering that the braking distance changes according to the operating speed of the cutting blade 111, the above-mentioned predetermined value may be changed each time according to the operating speed of the cutting blade 111.

[0087] If the count value exceeds a predetermined value, the operation of the cutting blade 111 continues, and the process in step S36 is executed again. If the count value falls below the predetermined value, the process proceeds to step S37. In step S37, the control unit 510 starts braking the cutting blade 111. After that, the cutting blade 111 stops at the target position, the fully open position. The cutting device 10 enters a standby state with the cutting blade 111 in the fully open position.

[0088] In the standby state, when the user operates the trigger switch 12 to the ON state, the process shown in Figure 13 is started in this embodiment.

[0089] In the first step S41 of this process, the control unit 510 drives the electric motor 400 to start moving each cutting blade 111 in the closing direction. This process is the same as the process performed in step S11 of Figure 6.

[0090] In step S42, following step S41, it is determined whether the amount of movement acquired by the movement amount acquisition unit 520, i.e., the count value, is greater than or equal to a predetermined threshold. This "threshold" is a value that is pre-set as corresponding to the timing at which the current limit value should be changed to a smaller value than before. This timing is time t3 in the example in Figure 11. If the count value exceeds the threshold, the operation of the cutting blade 111 continues and the process of step S42 is executed again. When the count value falls below the threshold, the process proceeds to step S43.

[0091] In step S43, the maximum current changing unit 540 changes the current limit value to a smaller value than before. Since the upper limit of the force that can be generated by the cutting blade 111 is reduced, a situation in which the contact parts 114 collide violently when they reach the fully open position is prevented. As a result, it is no longer necessary to ensure the durability of the blade member 110 and nearby members more than necessary, making it possible to miniaturize and lighten the members.

[0092] Thus, the maximum current changing unit 540 determines the timing for changing the current limit value based on the amount of movement (i.e., the count value) acquired by the amount of movement acquisition unit 520. Preferably, the timing for changing the current limit value to a smaller value is when the pair of cutting blades 111 are operating, and before the contact portions 114 of the blade members 110 come into contact with each other. In other words, as in this embodiment, it is preferable that the threshold used in the determination in step S42 of Figure 13 is set so that the contact portions 114 come into contact with each other after the current limit value has been changed.

[0093] In step S44, following step S43, the contact detection unit 530 determines whether or not contact between the contact parts 114 has been detected. If contact between the contact parts 114 has not yet been detected, that is, if the current supplied to the electric motor 400 is below the reference value, the process in step S44 is executed again while the electric motor 400 continues to run. If contact between the contact parts 114 has been detected, that is, if the current supplied to the electric motor 400 exceeds the reference value, the process proceeds to step S45.

[0094] In step S45, the electric motor 400 is stopped. As a result, each cutting blade 111 stops in the fully closed position. Subsequently, a process to reset the pulse signal count value to 0 may be performed, similar to step S34 in Figure 12.

[0095] When moving the cutting blade 111 to the fully closed position, the electric motor 400 may be driven until the contact portions 114 come into contact with each other, as described above. Alternatively, braking similar to step S37 in Figure 12 may be performed at a predetermined timing before contact.

[0096] After the rebar cutting is complete, the cutting blade 111 is returned to the fully open position and the cutting device 10 is put back into standby mode. This process is achieved, for example, by repeating steps S35 to S37 in Figure 12. The process of returning the cutting blade 111 to the fully open position may be started automatically following step S45 in Figure 13, but it may also be started after the user returns the trigger switch 12 to its original position (i.e., the off state).

[0097] A modified example of the second embodiment will now be described. Figure 14 shows a schematic cross-sectional view of the configuration of the modified blade member 110 and the guide plates 700 on both sides thereof. The cross-section shown in Figure 14 is the cross-section when the blade member 110, etc., is cut perpendicular to the central axis of the screw shaft 210.

[0098] In this modified example, there is no contact portion 114 that abuts against each other in the fully closed position. As shown in Figure 14, in this modified example, each blade member 110 is provided with a projection 113 that protrudes toward the guide plate 700. The guide plate 700 is also provided with a regulating surface 730 that abuts against the projection 113 from the inside in the opening and closing direction of the blade member 110. As the blade member 110 moves in the closing direction, eventually the projection 113 abuts against the regulating surface 730, preventing the blade member 110 from moving any further. The regulating surface 730 that abuts against the blade member 110 and restricts its movement corresponds to the "regulating portion" in this modified example. In the fully closed state when the projection 113 abuts against the regulating surface 730, in this modified example, the cutting blades 111 do not abut each other, and a small gap is left between them. It is also possible to configure the cutting blades 111 to abut each other at the same time that the projection 113 abuts against the regulating surface 730.

[0099] In this modified example, the movement amount acquisition unit 520 acquires the amount of movement of each blade member 110 from a state in which the regulating surface 730 is in contact with the projection 113 of the blade member 110, using that state as a reference. The contact detection unit 530 also detects when the regulating surface 730 is in contact with the projection 113 of the blade member 110. This configuration also produces the same effects as described in the second embodiment.

[0100] Furthermore, the restricting surface 730, which functions as a restricting part, may, as in this modified example, contact each of the pair of blade members 110 to restrict the operating range of the cutting blade 111, or it may contact only one of the pair of blade members 110 to restrict it.

[0101] In this case, the contact detection unit 530 will also detect that only one of the pair of blade members 110 has come into contact with the restricting section. Furthermore, the amount of movement acquired by the movement amount acquisition unit 520 will be the amount of movement of the blade member 110 from the state in which one of the pair of blade members 110 has come into contact with the restricting section. Similarly, the maximum current change unit 540 will reduce the current limit value to a value lower than the previous value at a timing before one of the pair of blade members 110 comes into contact with the restricting section.

[0102] Thus, in the second embodiment and the above modified example, the distance between the cutting blades 111 is minimized when at least one of the pair of blade members 110 is in contact with the restricting portion. The restricting portion only needs to contact at least one of the pair of blade members 110 at the same time as, or before, the pair of cutting blades 111 come into contact with each other, thereby restricting their movement.

[0103] The embodiments have been described above with reference to specific examples. However, this disclosure is not limited to these specific examples. Modifications made to these specific examples by those skilled in the art are also included within the scope of this disclosure, as long as they retain the features of this disclosure. The elements, their arrangement, conditions, shapes, etc., of each of the aforementioned specific examples are not limited to those illustrated and can be modified as appropriate. The elements of each of the aforementioned specific examples can be combined in different ways as appropriate, as long as no technical inconsistencies arise. [Explanation of Symbols]

[0104] 10: Cutting device 110: Blade component 111: Cutting blade 112: Contact part 400: Electric motor 510: Control Unit 520: Movement amount acquisition part 530: Contact detection unit 540: Maximum current change section

Claims

1. An electric cutting device, A pair of cutting blades that grip and cut the object to be cut, An electric motor that generates the driving force necessary for the operation of the cutting blade, A control unit that controls the operation of the electric motor, One of the first members provided with the cutting blade, The other side is the second member on which the cutting blade is provided, A restricting portion that contacts at least one of the first member and the second member to restrict the range in which the pair of cutting blades can operate, A contact detection unit that detects when at least one of the first member and the second member comes into contact with the restricting portion, A movement amount acquisition unit that acquires the amount of movement of the first member and the second member from a state in which at least one of the first member and the second member is in contact with the restricting portion, A maximum current changing unit that changes the maximum value of the current that can be supplied to the electric motor, Equipped with, The state in which at least one of the first member and the second member is in contact with the restricting portion is either the state in which the distance between the pair of cutting blades is the farthest, or the state in which the distance between the pair of cutting blades is the shortest. The aforementioned maximum current changing unit is A cutting device that determines the timing for changing the maximum value based on the amount of movement acquired by the amount of movement acquisition unit.

2. The control unit, The cutting device according to claim 1, wherein the timing for starting the braking of the cutting blade is determined based on the amount of movement acquired by the amount of movement acquisition unit.

3. When the pair of cutting blades are in operation, The cutting device according to claim 1, wherein the maximum current changing unit reduces the maximum value to a value prior to the current value at a timing prior to the first member and the second member coming into contact with the restricting unit.

4. The cutting device according to claim 1, wherein, when the pair of cutting blades move in the closing direction, at least one of the first member and the second member comes into contact with the regulating portion at the same time as, or before, the pair of cutting blades come into contact with each other.

5. The cutting device according to any one of claims 1 to 4, wherein the contact detection unit performs detection based on the current supplied to the electric motor.

6. The cutting device according to any one of claims 1 to 4, wherein the contact detection unit performs detection based on the voltage applied to the electric motor.

7. The cutting device according to any one of claims 1 to 4, wherein the contact detection unit performs detection based on the rotation speed of the electric motor.

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