Portable power tools

Abstract

[Problem] To provide a portable power tool that automatically gives a notification pertaining to the timing of replacement of a tip tool. [Solution] A portable power tool according to the present invention is a belt type grinding tool that performs grinding work by driving an endless grinding belt B. The belt type grinding tool calculates a cumulative drive time by summing the drive time of an air motor in a state in which the grinding work is being performed by the endless grinding belt, and compares the cumulative drive time with a replacement recommendation time stored in a memory (S112). Then, a notification signal is transmitted when the cumulative drive time becomes not less than the replacement recommendation time (S114). Further, when breakage of the endless grinding belt is detected (S116), a new replacement recommendation time is set (S118). When the new replacement recommendation time is less than the existing replacement recommendation time (S120), the replacement recommendation time is updated (S122).

Description

Technical Field

[0001] The present invention relates to a portable power tool, and more particularly to a portable power tool configured to perform machining operations by driving a tip tool.

Background Art

[0002] Portable power tools are known that perform various machining operations by driving various interchangeable tip tools such as endless grinding belts, drills, and polishing brushes with a drive unit such as an air motor or an electric motor. Portable power tools are widely known as hand-held types that are used by operators holding them by hand, but types configured to be mounted on automatic machines such as robots for use have also been developed. (Patent Documents 1 to 3)

[0003] The tip tool gradually wears out as machining operations are performed. Therefore, the tip tool needs to be replaced with a new tip tool when it has worn to a certain degree.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] Normally, the replacement of the tip tool is performed by the operator checking the state of the tip tool and performing the replacement as needed, or periodically at certain fixed intervals. However, the judgment of the replacement timing based on the operator's check requires a certain level of experience, and the variation in judgment between different people also becomes large. In addition, with the method of replacing at fixed intervals, there is a risk that replacement cannot be performed at an appropriate timing if there are fluctuations in the amount of machining operations.

[0006] Therefore, the present invention aims to provide a portable power tool that automatically notifies the user of the timing for replacing the tip tool. [Means for solving the problem]

[0007] In other words, the present invention is A portable power tool that drives a cutting tool to perform machining operations, A drive unit for driving the cutting tool, A memory unit that stores the recommended replacement time, A calculation unit is configured to calculate the total drive time by accumulating the drive time of the drive unit in a predetermined state, compare the total drive time with the recommended replacement time stored in the storage unit, and transmit a predetermined notification signal when the total drive time becomes equal to or greater than the recommended replacement time. To provide a portable power tool equipped with [a specific feature / feature].

[0008] In this portable power tool, the cumulative operating time of the drive unit under predetermined conditions is calculated, and a notification signal is sent when this cumulative operating time exceeds the recommended replacement time. Therefore, this notification signal makes it possible to know the appropriate timing for replacing the tip tool.

[0009] Furthermore, the calculation unit is configured to detect when machining work is being performed with the tip tool driven by the drive unit, so that the predetermined state is the state in which the machining work is being performed.

[0010] Since the cutting tool wears down during machining, accumulating only the driving time during machining as the total driving time makes it possible to more accurately determine and notify the timing of cutting tool replacement.

[0011] in particular, The drive unit is a rotary motor, and further comprises a rotational speed measuring means for measuring the rotational speed of the rotary motor. The calculation unit can be configured to determine that machining work is being performed with the tip tool driven by the rotary motor when the rotational speed measured by the rotational speed measuring means falls below a predetermined threshold.

[0012] Or, The drive unit is an electric motor, and further comprises a current detection unit for measuring the current flowing through the electric motor. The calculation unit can be configured to determine that machining work is being performed by the tip tool driven by the electric motor when the current measured by the current detection unit exceeds a predetermined threshold.

[0013] Also, The tool body on which the drive unit is located, A drive pulley rotated by the aforementioned drive unit, An idler pulley is rotatably attached to the tool body, Equipped with, The aforementioned tip tool is an endless grinding belt wrapped between the drive pulley and the idler pulley. The system further comprises a belt break detection means configured to detect the breakage of the endless grinding belt, The calculation unit can be configured to set a new replacement recommendation time based on the accumulated driving time at the time the belt break detection means detects the breakage of the endless grinding belt.

[0014] Furthermore, the calculation unit may update the recommended replacement time stored in the storage unit to the new recommended replacement time only if the new recommended replacement time is shorter than the recommended replacement time stored in the storage unit.

[0015] Hereinafter, embodiments of the portable power tool according to the present invention will be described with reference to the attached drawings. [Brief explanation of the drawing]

[0016] [Figure 1]FIG. 1 is a cross-sectional view of a belt-type grinding tool (portable power tool) according to one embodiment of the present invention. [Figure 2] FIG. 2 is a functional block diagram of the belt-type grinding tool of FIG. 1. [Figure 3] FIG. 3 is a view showing a state where an endless grinding belt is mounted on the belt-type grinding tool of FIG. 1. [Figure 4] FIG. 4 is an enlarged view of portion A in FIG. 3. [Figure 5] FIG. 5 is a view showing a state where the endless grinding belt of the belt-type grinding tool of FIG. 3 is broken. [Figure 6] FIG. 6 is an enlarged view of portion B in FIG. 5. [Figure 7] FIG. 7 is a flowchart illustrating the operation of the belt-type grinding tool of FIG. 1. [Figure 8] FIG. 8 is a functional block diagram of a belt-type grinding tool according to another embodiment of the present invention. [Figure 9] FIG. 9 is a flowchart illustrating the operation of the belt-type grinding tool of FIG. 8. DETAILED DESCRIPTION OF EMBODIMENTS FOR CARRYING OUT THE INVENTION

[0017] A portable power tool according to one embodiment of the present invention is a belt-type grinding tool 100 configured to perform grinding work by rotationally driving an endless grinding belt (end tool) B. As shown in FIG. 1, the belt-type grinding tool 100 includes a tool main body 110 having a base portion 112 and a tension bar 114, an air motor (drive unit, rotary motor) 116 disposed on the base portion 112 of the tool main body 110, a drive pulley 120 attached to a rotary shaft 118 of the air motor 116, and an idle pulley 122 rotatably attached to the tension bar 114 of the tool main body 110. The base portion 112 consists of a first section 124 that holds the tension bar 114, and a second section 126 that holds the air motor 116. The belt-type grinding tool 100 according to the present embodiment is configured to be used by being attached to an automated machine such as a robot.

[0018] The air motor 116 comprises a motor case 128, a rotor 130 rotatably mounted within the motor case 128, and a plurality of vanes 132 arranged to be radially displaceable relative to the rotor 130. The air motor 116 is rotationally driven by compressed air supplied via a tube (not shown) connected to a tube connecting joint 134 attached to the base portion 112. More specifically, the compressed air strikes the vanes 132 that protrude radially outward from the rotor 130, generating a rotational force on the rotor 130, thereby driving the rotor 130 to rotate. The rotating shaft 118 is formed integrally with the rotor 130 and rotates together with the rotor 130.

[0019] The tension bar 114 is held so as to be displaceable in the front-rear direction (up and down direction in the diagram) between a rearward position (Figure 1) and a forward position (Figure 5) relative to the base portion 112. The tool body 110 further has a spring 136 set between the tension bar 114 and the base portion 112, and the tension bar 114 is biased toward the forward position by this spring 136. The tool body 110 further has a locking member 138 that is displaceable in the lateral direction (left and right direction in the diagram). The tension bar 114 is locked in the rearward position by the engagement of a locking projection 142 of the locking member 138 with a locking recess 140 formed on its side surface 114a.

[0020] The belt-type grinding tool 100 further includes a plunger switch (belt break detection means) 144 attached to the base portion 112 of the tool body 110. The plunger switch 144 has a housing 146 fixed to the base portion 112 and a spherical contact 148 positioned at its tip, and is configured to be ON when the contact 148 is pushed into the housing 146. When the tension bar 114 is in the rear position shown in Figure 1, the contact 148 of the plunger switch 144 is in a groove 150 formed on the side surface 114a of the tension bar 114 and is not pushed into the housing 146. At this time, the plunger switch 144 is OFF. Wiring 152 extending from the rear end of the housing 146 of the plunger switch 144 is connected to a circuit housing 154 fixed to the base portion 112. Wiring 156 for power supply from an external power supply 155 (Figure 2) and signal output to external equipment is also connected to the circuit housing 154.

[0021] As shown in Figure 2, the circuit board 158, located within the circuit housing section 154, houses a microcomputer (arithmetic unit) 160, a microcomputer power supply generation circuit 162, and a Hall IC (rotation speed measuring means) 164. The microcomputer power supply generation circuit 162 converts the voltage supplied from the external power supply 155 to a voltage suitable for the microcomputer 160 (for example, 3.3V). The Hall IC 164 is positioned to detect the magnetic field of a magnet 166 attached to the rear end of the air motor 116. Since the magnet 166 rotates together with the rotor 130 of the air motor 116, the magnetic field detected by the Hall IC 164 changes periodically when the air motor 116 is rotating. The microcomputer 160 can determine the rotation speed of the air motor 116 from the periodic change in the magnetic field detected by the Hall IC 164.

[0022] When installing the endless grinding belt B, the tension bar 114 is in the rear position, the endless grinding belt B is positioned around the drive pulley 120 and idler pulley 122, and the locking member 138 is pushed in. When the locking member 138 is pushed in, the locking projection 142 of the locking member 138 disengages from the locking recess 140 of the tension bar 114, and the tension bar 114 is displaced forward by the biasing force of the spring 136. As a result, the endless grinding belt B is installed around the drive pulley 120 and idler pulley 122, as shown in Figure 3. At this time, the tension bar 114 has not been displaced to the forward position (Figure 5), but is in an intermediate position between the forward and rear positions. When compressed air is supplied from the tube connection fitting 134, the air motor 116 rotates, and consequently the drive pulley 120 rotates, and the endless grinding belt B is rotationally driven. Grinding can be performed by pressing the rotating endless grinding belt B against the workpiece.

[0023] The air motor 116 rotates when compressed air strikes vanes 132 that protrude radially outward from the rotor 130. However, if the vanes 132 are retracted into the rotor 130, insufficient rotational force is generated in the rotor 130, resulting in the rotor 130 not rotating or rotating at a slow speed, which can cause the air motor 116 to fail to start. In this belt-type grinding tool 100, the Hall IC 164 detects the rotational speed of the air motor 116, and if the air motor 116 is not rotating at a sufficient speed despite being supplied with compressed air, it sends a signal indicating a startup failure to the outside. Specifically, the microcomputer 160 determines the rotational speed of the air motor 116 based on the output from the Hall IC 164, and if the rotational speed is below a predetermined threshold (for example, 500 rpm), it sends a predetermined signal to the outside from the external output terminal 168. External equipment, such as an automated machine to which the belt-type grinding tool 100 is attached, can be configured to perform a reset operation of the air motor 116 when it receives a signal indicating a startup failure. The reset operation is an operation that causes the vanes 132 to pop out from the rotor 130 and allows the air motor 116 to rotate normally. Possible reset operations include repeatedly starting and stopping the supply of compressed air to the air motor 116, changing the posture of the belt-type grinding tool 100, shaking the belt-type grinding tool 100, forcibly rotating the rotor 130 together with the drive pulley 120 by rubbing the endless grinding belt B against the workpiece, or a combination of these operations. The means for detecting the rotational speed of the air motor 116 may be implemented by other arbitrary detection elements such as an optical encoder. Furthermore, the belt-type grinding tool 100 may be equipped with a light-emitting element or a speaker so that, when a startup failure is detected, instead of or in addition to transmitting a signal to the outside, the flashing of the light-emitting element or a buzzer sound from the speaker can be used to notify those nearby of the occurrence of the startup failure.

[0024] When the endless grinding belt B is properly installed, the tension bar 114 is in an intermediate position between the rear position (Figure 1) and the front position (Figure 5). At this time, as can be clearly seen in Figure 4, the contact 148 of the plunger switch 144 is located within the groove 150 of the tension bar 114 and is not pushed into the housing 146. If the installed endless grinding belt B breaks for any reason, as shown in Figure 5, the tension bar 114 is pushed by the spring 136 and displaced to the front position. As a result, the contact 148 of the plunger switch 144 is out of the groove 150 and is pushed into the housing 146 by the side surface 114a of the tension bar 114, as shown in Figure 6. This switches the plunger switch 144 from the OFF state to the ON state. When the microcomputer 160 detects that the plunger switch 144 has been turned ON, it transmits a predetermined break signal from the external output terminal 168 to the outside to notify that a break has been detected in the endless grinding belt B.

[0025] The microcomputer 160 also has a memory (storage unit) that stores various setting data related to control. The memory stores the cumulative drive time and the recommended replacement time to date. In this embodiment, the cumulative drive time is the cumulative drive time of the air motor 116 while grinding work is being performed with the endless grinding belt B. When the supply pressure of the supplied compressed air is constant, the rotational speed of the air motor 116 depends on the magnitude of the resistance force acting on the endless grinding belt B. That is, when grinding work is being performed by pressing the endless grinding belt B against the workpiece, a large resistance force acts on the endless grinding belt B, so the rotational speed of the air motor 116 decreases. The microcomputer 160 is configured to determine that grinding work is being performed when the rotational speed of the air motor 116, measured by the Hall IC 164, drops below a predetermined threshold (for example, 14,000 rpm). The recommended replacement time can be determined in advance based on previous experiments and experience, and stored in memory when the endless grinding belt B will need to be replaced.

[0026] The operation for replacing the endless grinding belt B of the belt-type grinding tool 100 will be explained with reference to Figure 7. When compressed air is supplied to the air motor 116, the air motor 116 is started to run (S100). The microcomputer 160 reads the accumulated drive time and the recommended replacement time from memory (S102). Note that the reading of the accumulated drive time and the recommended replacement time may be performed before the air motor 116 is started to run. Next, the microcomputer 160 determines the rotational speed of the air motor 116 based on the output of the Hall IC 164 and compares the measured rotational speed with a predetermined threshold (S104). If the rotational speed of the air motor 116 has not decreased to below the threshold (for example, 14000 rpm), it is determined that grinding work is not being performed and the drive time counter is turned OFF to stop counting the drive time (S106). If the rotational speed of the air motor 116 drops below a threshold, it is determined that grinding is in progress, and the drive time counter is turned ON to count the drive time (S108). The elapsed time is added to the accumulated drive time and the accumulated drive time is updated (S110). The elapsed time is the time elapsed since the control in S108 (effectively zero) if the drive time counter was turned ON for the first time in S108, or if it was switched from OFF to ON in S108. On the other hand, if the drive time counter was ON before S108 was performed, it is the time elapsed since the last control in S110 (the time required to execute one control loop). Next, the microcomputer 160 compares the accumulated drive time with the recommended replacement time (S112). If the accumulated drive time is greater than or equal to the recommended replacement time, a notification signal recommending the replacement of the endless grinding belt B is sent (S114). This notification signal is transmitted from the external output terminal 168 to an external device such as an automated machine. An external device that receives a notification signal can display a message prompting the replacement of the endless grinding belt B, or it can stop the supply of compressed air to the air motor 116 to stop the air motor 116 from operating. Alternatively, the belt-type grinding tool 100 may be equipped with a display device that prompts the replacement of the endless grinding belt B when a notification signal is sent from the microcomputer 160.If the cumulative drive time in S112 is not equal to or greater than the recommended replacement time, a notification signal recommending the replacement of the endless grinding belt B will not be issued.

[0027] Next, the microcomputer 160 detects the breakage of the endless grinding belt B (S116). Specifically, the microcomputer 160 detects the breakage of the endless grinding belt B based on the ON / OFF state of the plunger switch 144. If the plunger switch 144 is in the ON state and the breakage of the endless grinding belt B is detected, the microcomputer 160 sends a breakage signal (S118). The microcomputer 160 also sets a new recommended replacement time based on the accumulated drive time at the time the breakage of the endless grinding belt B is detected (S118). Specifically, it sets a time shorter than the accumulated drive time at that time (for example, 90% of the accumulated drive time) as the new recommended replacement time. If the new recommended replacement time is less than the existing recommended replacement time (S120), the recommended replacement time is updated to the new recommended replacement time and saved in memory (S122). If the new recommended replacement time is equal to or greater than the existing recommended replacement time, the existing recommended replacement time is used. If a break in the endless grinding belt B is not detected in S116, the control in S118 to S122 is not performed. Next, the microcomputer 160 checks for the presence of a motor stop command (S124). A motor stop command is determined to exist when the operator stops the air motor 116, when the microcomputer 160 determines that the motor should stop, or when a motor stop command is transmitted from an external device. For example, the microcomputer 160 can be configured to send a motor stop command when it sends a notification signal indicating the timing for replacing the endless grinding belt B or a break signal indicating the break of the endless grinding belt B. Also, an external device can be configured to send a motor stop command to the belt-type grinding tool 100 when it receives a notification signal or break signal transmitted from the microcomputer 160. If a motor stop command exists, the drive time counter is turned OFF and the current accumulated drive time is saved to memory (S126). Then, the drive of the air motor 116 is stopped (S128). If no motor stop command is issued, the process returns to S104, and the control steps S104 to S124 described above are repeated.In this embodiment, the air motor 116 is stopped by sending a motor stop signal from the microcomputer 160 to an external device, which then stops supplying compressed air. Alternatively, a valve can be provided in front of the air supply port of the air motor 116 of the belt-type grinding tool 100, and the microcomputer 160 can control the opening and closing of the valve to control the supply of compressed air to the air motor 116, thereby controlling the operation of the air motor 116.

[0028] The cumulative drive time can be reset at any time, such as when the endless grinding belt B is replaced. Furthermore, the recommended replacement time, updated due to the breakage of the endless grinding belt B, can be reverted to the original recommended replacement time, or a custom time can be manually set.

[0029] Another embodiment of the present invention, a belt-type grinding tool (portable power tool) 200, as shown in Figure 8, includes a microcomputer 260, a microcomputer power generation circuit 262, and an external output terminal 268, similar to the belt-type grinding tool 100. In this belt-type grinding tool 200, the drive unit is composed of an electric motor 216, and a motor drive circuit 270 is provided for driving the electric motor 216. A start switch 272 is also provided for starting and stopping the operation of the electric motor 216. The microcomputer 260 of the belt-type grinding tool 200 measures the current flowing to the electric motor 216 using a current detection unit 274. When the endless grinding belt B is attached, the electric motor 216 is subjected to the load necessary to rotate the endless grinding belt B. In particular, when grinding work is performed with the endless grinding belt B, resistance is generated in the endless grinding belt B, so an even greater load is placed on the electric motor 216. Therefore, when the endless grinding belt B is installed (especially when grinding is being performed), a larger current flows to the electric motor 216 during rotation compared to when there is no load. On the other hand, if the endless grinding belt B breaks while the electric motor 216 is rotating, the load that was on the electric motor 216 is released, and it effectively becomes an unloaded state, so the current flowing to the electric motor 216 decreases. The microcomputer 260 is configured to detect the breakage of the endless grinding belt B from the change in the magnitude of the current flowing to the electric motor 216. Specifically, the microcomputer 260 determines that the endless grinding belt B has broken when the current in the current detection unit 274 that flows to the electric motor 216 during operation drops below a predetermined threshold. In other words, in this belt-type grinding tool 200, the microcomputer 260, which measures the current flowing to the electric motor 216, also functions as a belt breakage detection means. When the microcomputer 260 detects a break in the endless grinding belt B from the current of the electric motor 216, it transmits a predetermined break signal to the outside from the external output terminal 268 to notify that a break in the endless grinding belt B has been detected.

[0030] The operation for replacing the endless grinding belt B of the belt-type grinding tool 200 will be explained with reference to Figure 9. When the start switch 272 is operated or a motor drive start command is received from an external device, the electric motor 216 is started to drive (S200). The microcomputer 260 reads the accumulated drive time and the recommended replacement time from memory (S202). Next, the microcomputer 260 measures the current flowing through the electric motor 216 in the current detection unit 274 and compares the measured current value with a predetermined threshold (S204). If the current flowing through the electric motor 216 is not above the predetermined threshold, it is determined that grinding work is not being performed, and the drive time counter is turned OFF to stop counting the drive time (S206). If the current flowing through the electric motor 216 is above the threshold, it is determined that grinding work is being performed, and the drive time counter is turned ON to start counting the drive time (S208). The elapsed time is also added to the accumulated drive time to update the accumulated drive time (S210). Next, the microcomputer 260 compares the cumulative drive time with the recommended replacement time (S212). If the cumulative drive time is equal to or greater than the recommended replacement time, it sends a notification signal recommending the replacement of the endless grinding belt B (S214). This notification signal is transmitted from the external output terminal 268 to an external device such as an automated machine. The external device that receives the notification signal can display a message prompting the replacement of the endless grinding belt B or send a signal indicating that the electric motor 216 has stopped. Alternatively, the belt-type grinding tool 200 may be equipped with a display device, which can display a message prompting the replacement of the endless grinding belt B when the microcomputer 260 sends a notification signal. If the cumulative drive time in S212 is not equal to or greater than the recommended replacement time, the notification signal recommending the replacement of the endless grinding belt B is not sent.

[0031] Next, the microcomputer 260 detects the breakage of the endless grinding belt B (S216). Specifically, as described above, the microcomputer 260 detects the breakage of the endless grinding belt B based on whether the current flowing to the electric motor 216 falls below a predetermined threshold. If the breakage of the endless grinding belt B is detected, the microcomputer 260 transmits a breakage signal (S218). The microcomputer 260 also sets a new recommended replacement time based on the accumulated drive time at the time the breakage of the endless grinding belt B is detected (S218). Specifically, it sets a time shorter than the accumulated drive time at that time (for example, 90% of the accumulated drive time) as the new recommended replacement time. If the new recommended replacement time is less than the existing recommended replacement time (S220), the recommended replacement time is updated to the new recommended replacement time and saved in memory (S222). If the new recommended replacement time is greater than or equal to the existing recommended replacement time, the recommended replacement time is not updated, and the existing recommended replacement time continues to be used. If a break in the endless grinding belt B is not detected in S216, the control in S218 to S222 is not performed. Next, the microcomputer 260 checks for the presence of a motor stop command (S224). A motor stop command is determined to exist when the operator stops the electric motor 216, when the microcomputer 260 determines that the motor should stop, or when a motor stop command is transmitted from an external device. For example, the microcomputer 260 can be configured to send a motor stop command when it sends a notification signal indicating the timing for replacing the endless grinding belt B or a break signal indicating the break of the endless grinding belt B. Also, an external device can be configured to send a motor stop command to the belt-type grinding tool 200 when it receives a notification signal or break signal transmitted from the microcomputer 260. If a motor stop command exists, the drive time counter is turned OFF and the accumulated drive time is saved to memory (S226). Then, the drive of the electric motor 216 is stopped (S228). If no motor stop command is issued, the process returns to S204, and the control steps S204 to S224 described above are repeated.

[0032] In the belt-type grinding tools 100 and 200 according to the above embodiment, a notification signal recommending the replacement of the endless grinding belt B is automatically sent by comparing the cumulative drive time with the recommended replacement time, making it possible to appropriately determine the timing for replacing the endless grinding belt B. Furthermore, if the endless grinding belt B breaks before the notification signal is sent, the system updates the recommended replacement time to a shorter time based on the cumulative drive time at that time. This makes it less likely for the endless grinding belt B to break before the notification signal is sent.

[0033] Although embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, in the above embodiments, the condition for accumulating the driving time is the state in which grinding work is being performed with an endless grinding belt, but the condition may be simply the state in which the drive unit is driven, regardless of whether grinding work is being performed or not. In particular, when attached to an automated machine such as a robot and the same operation is repeated, each operation will be almost the same, so even if the time in which the drive unit is driven is simply accumulated as the accumulated driving time and used to determine the timing for replacing the endless grinding belt, an appropriate replacement timing can be notified. Furthermore, although a belt-type grinding tool in which the tip tool is an endless grinding belt is shown as one embodiment of the portable power tool according to the present invention, other portable power tools can also be used. Such other portable power tools include, for example, a drilling tool that performs drilling work with a drill, and a polishing tool that performs polishing work with a polishing brush. The present invention is applicable to any other form of portable power tool that performs various processing operations with various tip tools. It may also be a handheld power tool used directly by the operator. Furthermore, the drive unit may be any other form, such as a piston that reciprocates in a straight line.

[0034] If the belt break detection means is composed of a detector such as a plunger switch that detects when the tension bar has been displaced to a forward position, the signals from these detectors may be output directly from an external output terminal without going through a microprocessor. The signal output unit for transmitting signals to the outside may be a wireless device for transmitting signals wirelessly instead of an external output terminal for outputting signals via a wire. Furthermore, the configurations shown in the above embodiment can be interchanged or combined with each other. For example, if the drive unit is an electric motor, a plunger switch may be used as the belt break detection means, or a configuration may be provided that includes both electric motor current detection and tension bar position detection by a plunger switch. The plunger switch for detecting the position of the tension bar may also be another mechanical switch such as a microswitch, or another non-contact type switch such as a proximity switch or optical sensor. [Explanation of Symbols]

[0035] 100 Belt-type grinding tools (portable power tools) 110 Tool body 112 Base section 114 Tension Bar 114a side 116 Air motor (drive unit, rotary motor) 118 Rotation axis 120 Drive Pulley 122 Idler Pulley 124 Part 1 126 Part 2 128 Motor Case 130 rotor 132 Bane 134 Tube connection fittings 136 Spring 138 Locking member 140 Locking recess 142 Locking projection 144 Plunger switch (belt break detection means) 146 cabinets 148 Contactor 150 groove 152 Wiring 154 Circuit housing 155 External power supply 156 Wiring 158 Circuit board 160 Microcomputer (Arithmetic Unit) 162 Microcontroller Power Generation Circuit 164 Hall IC (Rotational Speed ​​Measurement Means) 166 Magnets 168 External output terminals 200 Belt-type grinding tools (portable power tools) 216 Electric motor (drive unit, rotary motor) 260 Microcomputer (Arithmetic Unit) 262 Microcontroller Power Generation Circuit 268 External output terminals 270 Motor drive circuit 272 Start switch 274 Current detection unit B Endless grinding belt (cutting tool)

Claims

1. A portable power tool that drives a cutting tool to perform machining work, A drive unit for driving the cutting tool, A memory unit that stores the recommended replacement time, A calculation unit is configured to distinguish and detect when the tip tool is being driven by the drive unit from a state in which machining work is not being performed with the tip tool, to calculate the cumulative drive time by accumulating the drive time of the drive unit in the state in which machining work is being performed, to compare the cumulative drive time with the replacement recommendation time stored in the storage unit, and to transmit a predetermined notification signal when the cumulative drive time becomes equal to or greater than the replacement recommendation time. Equipped with, The drive unit is a rotary motor, and further comprises a rotational speed measuring means for measuring the rotational speed of the rotary motor. A portable power tool in which the calculation unit determines that a machining operation is being performed with the tip tool driven by the rotary motor when the rotational speed measured by the rotational speed measuring means falls below a predetermined threshold.

2. A portable power tool that drives a cutting tool to perform machining work, A drive unit for driving the cutting tool, A memory unit that stores the recommended replacement time, A calculation unit is configured to distinguish and detect when the tip tool is being driven by the drive unit from a state in which machining work is not being performed with the tip tool, to calculate the cumulative drive time by accumulating the drive time of the drive unit in the state in which machining work is being performed, to compare the cumulative drive time with the replacement recommendation time stored in the storage unit, and to transmit a predetermined notification signal when the cumulative drive time becomes equal to or greater than the replacement recommendation time. Equipped with, The drive unit is an electric motor, and further comprises a current detection unit for measuring the current flowing through the electric motor. A portable power tool, wherein the calculation unit determines that the machining operation is not being performed if the current measured by the current detection unit is not above a predetermined threshold, and determines that the machining operation is being performed by the tip tool driven by the electric motor when the current is above the predetermined threshold.

3. A portable power tool that drives a cutting tool to perform machining work, A drive unit for driving the cutting tool, A memory unit that stores the recommended replacement time, A calculation unit is configured to distinguish and detect when the tip tool is being driven by the drive unit from a state in which machining work is not being performed with the tip tool, to calculate the cumulative drive time by accumulating the drive time of the drive unit in the state in which machining work is being performed, to compare the cumulative drive time with the replacement recommendation time stored in the storage unit, and to transmit a predetermined notification signal when the cumulative drive time becomes equal to or greater than the replacement recommendation time. The tool body on which the drive unit is located, A drive pulley rotated by the aforementioned drive unit, An idler pulley is rotatably attached to the tool body, Equipped with, The aforementioned tip tool is an endless grinding belt wrapped between the drive pulley and the idler pulley. The system further comprises a belt break detection means configured to detect the breakage of the endless grinding belt, A portable power tool wherein the calculation unit sets a new recommended replacement time based on the accumulated driving time when the breakage of the endless grinding belt is detected by the belt breakage detection means.

4. A portable power tool that drives an endless grinding belt to perform machining operations, The tool body and The drive unit is arranged on the tool body, A drive pulley rotated by the aforementioned drive unit, An idler pulley rotatably attached to the tool body, wherein the endless grinding belt is wrapped between the drive pulley and the idler pulley, A memory unit that stores the recommended replacement time, A calculation unit is configured to calculate the total drive time by accumulating the drive time of the drive unit in a predetermined state, compare the total drive time with the recommended replacement time stored in the storage unit, and transmit a predetermined notification signal when the total drive time becomes equal to or greater than the recommended replacement time. A belt break detection means configured to detect the breakage of the endless grinding belt, Equipped with, A portable power tool wherein the calculation unit sets a new recommended replacement time based on the accumulated driving time when the breakage of the endless grinding belt is detected by the belt breakage detection means.

5. The portable power tool according to claim 3 or 4, wherein the calculation unit updates the recommended replacement time stored in the storage unit to the new recommended replacement time only if the new recommended replacement time is shorter than the recommended replacement time stored in the storage unit.

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