Electric work machine

Abstract

To provide an electric work machine which can detect a user grips a side handle and drive a motor at a housing side to which the side handle is attached.SOLUTION: A side handle fitting part is arranged in a housing accommodating a motor. A plurality of load detection parts detecting loads applied from a grip part of the side handle are distributedly arranged around a fitting hole into which a shaft of the side handle is inserted in the side handle fitting part. A control part determines, based on the loads detected by the plurality of load detection parts, whether the side handle is gripped or not. When the side handle is not gripped, drive power of the motor is restricted.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to an electric work machine equipped with a side handle. [Background technology]

[0002] Patent Document 1 describes a grinder in which a side handle is attached to a housing that houses a motor, and the motor can be driven when the user grips the side handle.

[0003] With this grinder, when the motor is driven without the user holding the side handle, the grinder is prevented from being swung around by the reaction force that the driven object rotated by the motor receives from the work object, which is known as kickback. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2017 / 051892 Summary of the Invention [Problem to be solved by the invention]

[0005] In the grinder, a detector attached to the side handle detects whether the user is holding the side handle, and the detection signal from the detector must be input to a control unit inside the housing that controls the drive of the motor.

[0006] Therefore, in the grinder described in Patent Document 1, it was difficult to secure a transmission path for the detection signal from the detection unit in the side handle to the control unit in the housing, and the device configuration for securing the transmission path was complex.

[0007] One aspect of the present disclosure aims to enable an electric work machine equipped with a side handle to detect that a user is gripping the side handle on the housing side to which the side handle is attached, and to drive the motor. [Means for solving the problem]

[0008] An electric work machine according to one aspect of the present disclosure includes a motor, a housing, a side handle, an attachment portion, a plurality of load detectors, and a controller. The motor is configured to drive an object to be driven and is housed in the housing, and the side handle is configured to be gripped by a user and is attached to the housing.

[0009] That is, the side handle has a shaft that serves as the axis and a grip portion provided around the shaft. In contrast, the housing has an attachment portion configured so that the side handle can be attached to the housing by inserting the shaft of the side handle. Therefore, the side handle is attached to the attachment portion of the housing.

[0010] The load detection units are provided in the housing mounting portion at locations dispersed around the mounting hole into which the shaft of the side handle is inserted, and each detects the load applied from the grip of the side handle.The control unit then determines whether the side handle is being gripped based on the loads detected by the load detection units.

[0011] In other words, when the side handle is attached to the mounting part of the housing, the grip part around the shaft of the side handle abuts against the periphery of the mounting hole, so that the load from the grip part of the side handle is applied to the multiple load detection parts in a substantially uniform manner.

[0012] In contrast, when a user grips the side handle and lifts the electric work machine to perform work, the gripping force applied to the side handle and the weight of the electric work machine itself disrupt the balance of the loads applied to the multiple load detection units, causing the load to change for each load detection unit. Therefore, the control unit can use the changes in each load based on the loads detected by the multiple load detection units to determine whether the side handle is being gripped.

[0013] When the side handle is not gripped, the control unit limits the driving power of the motor to suppress the driving force of the driven object by the motor, thereby reducing the reaction force applied from the work object to the driven object and suppressing the occurrence of the kickback described above.

[0014] In this way, according to the electric operating machine of the present disclosure, it is possible to determine whether or not the side handle is being gripped by utilizing the detection results from the multiple load detection units provided at the mounting portion of the housing.

[0015] Therefore, there is no need to provide a detector for grip detection on the side handle and secure a signal path for transmitting a detection signal from the detector to the control unit inside the housing, as described in Patent Document 1. This simplifies the configuration of the electric work machine and makes it easy to implement. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a perspective view illustrating an appearance of a grinder according to an embodiment. [Figure 2] 2A and 2B are explanatory diagrams showing the attachment portion of a side handle in a grinder, in which FIG. 2A is a front view of the attachment portion seen from the tip side of the gear housing, and FIG. 2B is a side view of the attachment portion seen from the lateral direction of the gear housing. [Figure 3] 3A and 3B are explanatory views showing the configuration of a side handle, in which FIG. 3A is a perspective view of the side handle as seen from the shaft side, and FIG. 3B is a side view showing the state in which the grip part is attached to the shaft. [Figure 4]4A and 4B are explanatory diagrams showing the state in which the side handle is attached to the grinder, with FIG. 4A being an explanatory diagram showing the state in which the side handle is not gripped, and FIG. 4B being an explanatory diagram showing the state in which the side handle is gripped. [Figure 5] FIG. 2 is a block diagram showing the overall configuration of a driving device for a grinder. [Figure 6] 10 is a flowchart showing a connection / holding determination process executed by a control unit. [Figure 7] 4 is a flowchart showing a motor control process executed by a control unit. [Figure 8] 10 is a flowchart illustrating a connection / holding determination process of a modified example. [Figure 9] 10 is a flowchart illustrating a modified example of a motor control process. DETAILED DESCRIPTION OF THE INVENTION

[0017] [Summary of the embodiment] In one embodiment of the electric operating machine, the plurality of load detection units may each be a resistance-type pressure sensor whose resistance value changes depending on the load. Also, three or more load detection units may be distributed around the mounting hole of the housing at equal distances from the center of the mounting hole.

[0018] Additionally / alternatively, a first elastic body may be provided on the surface of each of the load detection units facing the grip of the side handle. In this way, the load applied to each load detection unit from the grip of the side handle can be adjusted by the first elastic body. This protects each load detection unit from excessive load and allows the load detection sensitivity of the load detection unit to be adjusted.

[0019] Additionally / alternatively, the surface of the grip of the side handle facing the multiple load detection units may be configured to be perpendicular to the central axis of the shaft and to have a ring shape with the shaft as the center. In this way, even if the amount of screwing changes when the side handle is screwed into the housing and the position of the grip of the side handle facing the multiple load detection units changes, the load applied from the grip to each load detection unit can be made the same, and changes in load when the user grips the side handle can be detected effectively.

[0020] Additionally / alternatively, a second elastic body may be provided in the side handle between the shaft and the grip. This allows the second elastic body to absorb vibrations applied to the grip of the side handle from the housing when the electric power tool is in use. This allows the side handle to function as a so-called vibration-damping handle, preventing vibrations from the electric power tool from being transmitted to the user's hands.

[0021] In addition, if a first elastic body is provided on the detection surface of each of the load detection units and a second elastic body is provided between the shaft and the grip of the side handle, the spring constant of the second elastic body may be greater than the spring constant of the first elastic body. This prevents the load applied from the grip of the side handle to the load detection units from changing due to vibrations during use of the electric work machine. Therefore, it becomes possible to accurately determine whether the side handle is being gripped.

[0022] Additionally / alternatively, the control unit may be configured to determine that the side handle is attached to the housing when at least one of the loads detected by the plurality of load detection units is equal to or greater than a predetermined first threshold. In this case, when the control unit determines that the side handle is attached to the housing, the control unit may be configured to determine whether the side handle is being gripped.

[0023] Furthermore, if all of the loads detected by the multiple load detection units do not reach the first threshold, it may be determined that the side handle is not attached to the housing, and the drive power of the motor may be limited. In this way, when the side handle is not attached to the housing, it is possible to limit the drive power of the motor and suppress the occurrence of kickback without determining whether the side handle is being gripped.

[0024] Furthermore, as described above, when the control unit determines that a side handle is attached and then determines the gripping state of the side handle, it may be configured to determine whether at least one of the detected loads is equal to or greater than a second threshold value that is greater than the first threshold value.

[0025] In other words, when the side handle is not gripped, the loads applied from the grip of the side handle to the multiple load detection units are approximately the same initial load.In contrast, when the side handle is gripped, the balance of the loads applied from the grip of the side handle to the multiple load detection units is lost, and the load applied to at least one of the multiple load detection units becomes larger than the initial load.

[0026] Therefore, in this case, when at least one of the loads detected by the multiple load detection units is equal to or greater than the second threshold, it is determined that the side handle is being gripped. When all of the loads detected by the multiple load detection units are less than the second threshold, it is determined that the side handle is not being gripped, and the drive power of the motor is limited.

[0027] Additionally / alternatively, when the control unit determines that all of the loads detected by the multiple load detection units have not reached the second threshold, the control unit may be configured to determine whether at least one of the loads detected by the multiple load detection units has changed within a predetermined time.

[0028] In other words, even if the side handle is being gripped, if the user's grip on the side handle is weak, the load applied from the grip of the side handle to the multiple load detection units may not reach the second threshold. However, when the side handle is being gripped and the electric operating machine is being lifted, the load applied to each load detection unit fluctuates.

[0029] Therefore, as described above, it may be possible to determine whether at least one of the loads detected by the multiple load detection units has changed within a predetermined time, and determine that the side handle is being gripped when at least one of the loads has changed within the predetermined time, thereby making it possible to more accurately determine that the side handle is being gripped.

[0030] Additionally / alternatively, the control unit may be configured to determine that the object to be driven is being pressed against an external work object when at least one of the loads detected by the multiple load detection units is equal to or greater than a third threshold value that is greater than the second threshold value when the motor starts to drive.

[0031] In this case, the control unit may be configured to limit the driving power of the motor when it determines that the driven object is being pressed against an external work object, thereby preventing kickback from occurring immediately after the motor starts to be driven.

[0032] In addition, when the control unit determines that the object to be driven is being pressed against an external work object and limits the driving power of the motor, the control unit may be configured to subsequently release the limit on the driving power of the motor when all of the loads detected by the multiple load detection units become less than a third threshold value.

[0033] In this way, when the motor's drive power is limited due to the pressing of the driven object and the motor's rotation speed does not increase, the user can release the limit on the motor's drive power and increase the motor's rotation speed by loosening the pressure of the driven object. Therefore, even if the motor's drive power is limited when the user starts driving the motor, the user can return the motor to its normal rotation state by performing a subsequent operation and perform the desired task.

[0034] Additionally / alternatively, the motor may be an AC motor that is driven to rotate by AC power supplied from an AC power source. In this case, the multiple load detectors and the controller may be insulated from a drive system that drives the AC motor with AC power.

[0035] Specific Exemplary Embodiments Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings. In the present embodiment, a grinder 2 will be described as an example of an electric work machine.

[0036] <Overall configuration of the grinder> As shown in FIG. 1, the grinder 2 of this embodiment includes a motor housing 4, a gear housing 6, and a rear housing 8 as housings for the grinder body.

[0037] The motor housing 4 is a generally cylindrical housing, and houses the motor 30 shown in FIG. 5 inside. The motor 30 is an AC motor. The motor 30 is disposed inside the motor housing 4 so that its rotation axis is parallel to and generally coincides with the central axis of the motor housing 4. The rotation axis of the motor 30 protrudes toward the gear housing 6 in the front.

[0038] The rear housing 8 has a generally cylindrical shape similar to the motor housing 4, and is provided behind the motor housing 4, that is, on the opposite side from the gear housing 6. The rear housing 8 accommodates a drive unit 10 shown in FIG. 5 that receives power from an external AC power source via a power cord 9 to drive the motor 30.

[0039] The rear housing 8 is configured so that the user can hold it with one hand. A trigger 34 is provided on the motor housing 4 side of the rear housing 8 so that the user can pull it with the hand holding the rear housing 8.

[0040] The gear housing 6 houses a gear mechanism that converts the rotation of the motor 30 into a rotational force about the axis of the spindle 22 shown in Figure 2. The spindle 22 is housed in the gear housing 6 via a gear so that its central axis is perpendicular to the rotation axis of the motor 30. The gear mechanism includes, for example, two bevel gears that transmit the rotation of the motor 30 to the spindle 22.

[0041] 2, the tip of the spindle 22 protrudes from the gear housing 6. A disk-shaped blade 20 shown in FIG. 1 is attached to the protruding portion as a driven object. The blade 20 is used to grind, cut, or polish a workpiece, and may be, for example, a grinding wheel, a cutting wheel, a wire brush, or the like.

[0042] A wheel cover 24 is attached to the gear housing 6. The wheel cover 24 is intended to protect the user from fragments of the workpiece or the blade 20 that may fly off during grinding, cutting, polishing, or other operations. For this reason, the wheel cover 24 is formed in a substantially semicircular shape so as to cover a portion (approximately half in this embodiment) of the blade 20 fixed to the spindle 22 from the gear housing 6 side.

[0043] The wheel cover 24 is fixed to a portion of the gear housing 6 from which the spindle 22 protrudes. That is, the attachment portion of the gear housing 6 for attaching the wheel cover 24 has a cylindrical shape that is coaxial with the central axis of the spindle 22 and surrounds the spindle 22.

[0044] Next, as shown in FIG. 2, the gear housing 6 has mounting portions 42L and 42R on the left and right side walls sandwiching the spindle 22 and the rotation shaft of the motor 30, for mounting the side handle 50 shown in FIG.

[0045] The left and right mounting portions 42L, 42R are circular bases that protrude from the wall surface of the gear housing 6 at a certain height, and their end surfaces are flat and parallel to the rotation shaft of the motor 30.

[0046] In addition, in the mounting portions 42L, 42R, mounting holes 40L, 40R are provided in the center of the circular base for fixing the side handle 50 by inserting and screwing in the screw portion 62 formed at the tip of the shaft 60 of the side handle 50.

[0047] 3, the side handle 50 comprises a shaft 60 serving as the axis, and a grip portion 52 provided around the shaft 60 with vibration-damping rubber 58 interposed therebetween. The shaft 60 protrudes from the grip portion 52, and a threaded portion 62 serving as a male screw is formed at the tip of the shaft 60. The vibration-damping rubber 58 corresponds to the second elastic body of the present disclosure.

[0048] Meanwhile, threads constituting female threads into which the threaded portion 62 of the side handle 50 can be screwed are formed on the inner circumferential surfaces of the mounting holes 40L, 40R on the gear housing 6 side. Therefore, the side handle 50 can be firmly fixed to the mounting portions 42L, 42R of the gear housing 6 by screwing the threaded portion 62 into the mounting holes 40L, 40R and tightening them.

[0049] In the side handle 50, the tip of the gripping part 52 on the side of the threaded part 62 forms a flange 54 that extends around the shaft 60. The end face of the flange 54 on the side of the threaded part 62 has a protruding contact part 56 that comes into contact with the mounting parts 42L, 42R of the gear housing 6 when the side handle 50 is fixed to the gear housing 6.

[0050] The contact portion 56 is configured so that the surface facing the attachment portions 42L, 42R is perpendicular to the central axis of the shaft 60 and has an annular shape with the shaft 60 as the center. Therefore, when the side handle 50 is attached to the gear housing 6, the opposing surfaces of the contact portion 56 of the side handle 50 and the attachment portions 42L, 42R of the gear housing 6 are parallel to each other, as shown in FIG. 4A.

[0051] As shown in Figures 2 and 4, the mounting portions 42L, 42R of the gear housing 6 are provided with a load detection portion 44 for detecting the load applied from the abutment portion 56 of the side handle 50 when the side handle 50 is attached.

[0052] The load detection unit 44 is configured as a resistance-type pressure sensor whose resistance value changes depending on the load applied from the contact portion 56 of the side handle 50. The mounting portions 42L, 42R of the gear housing 6 are provided with three load detection units 44 dispersed at 120-degree intervals on a circumference a certain distance away from the center of the mounting holes 40L, 40R, respectively.

[0053] In addition, in each load detection unit 44, when the side handle 50 is attached to the mounting portion 42L or 42R of the gear housing 6, rubber 46 is provided as a first elastic body on the surface facing the abutment portion 56 of the side handle 50.

[0054] Therefore, when the side handle 50 is attached to the gear housing 6, an initial load F1 is applied approximately uniformly to the three load detection parts 44 provided on the mounting part 42L or 42R from the abutment part 56 of the side handle 50, as shown in Figure 4A.

[0055] On the other hand, when the user grips the side handle 50, the grip portion 52 of the side handle 50 tilts relative to the shaft 60 due to the gripping force of the user and the weight of the grinder 2 itself, as shown in FIG. 4B.

[0056] Here, the spring constant of the vibration-isolating rubber 58 as the second elastic body is greater than the spring constant of the rubber 46 as the first elastic body, and the vibration-isolating rubber 58 is harder than the rubber 46 provided in the load detection unit 44.

[0057] For this reason, when the side handle 50 is gripped, the grip portion 52 is supported by the vibration-damping rubber 58, which has a spring constant greater than that of the rubber 46 of the load detection portion 44. Therefore, the inclination of the grip portion 52 when the side handle 50 is gripped can be set as desired by adjusting the spring constant of the vibration-damping rubber 58.

[0058] Furthermore, when the side handle 50 is gripped and the grip portion 52 is tilted relative to the shaft 60, the balance of the loads applied from the contact portion 56 of the side handle 50 to the three load detection portions 44 is lost.

[0059] As a result, the load F2 applied to one or two of the three load detection units 44 becomes larger than the initial load F1, and the load F3 applied to the other load detection units 44 becomes smaller than the initial load F1. Since each of the three load detection units 44 is provided with rubber 46, the spring constant of the rubber 46 can be used to adjust the load applied to each load detection unit 44.

[0060] <Driver circuit configuration> As shown in FIG. 5, the drive unit 10 housed in the rear housing 8 includes a drive system 12 that drives the motor 30 with AC power supplied from an external AC power source, and a control system 14 that controls the driving of the motor 30.

[0061] The drive system 12 of the motor 30 is provided with a motor driver 36 that drives the motor 30 with AC power input via a trigger switch (hereinafter referred to as trigger SW) 35 that is turned on when a trigger 34 is pulled. The motor driver 36 is provided with a bidirectional thyristor, and the drive power of the motor 30 can be controlled by turning the bidirectional thyristor on and off.

[0062] The control system 14 of the motor 30 is provided with a control circuit 80 configured mainly with a microcontroller (hereinafter referred to as "micon") including a CPU, ROM, RAM, etc. Detection signals are input to the control circuit 80 from three load detection units 44 provided on the mounting portions 42L, 42R of the gear housing 6. The control circuit 80 corresponds to the control unit in the present disclosure.

[0063] The control circuit 80 determines whether or not a side handle 50 is attached to either of the attachment parts 42L, 42R based on the detection signals input from each load detection part 44. Furthermore, if a side handle 50 is attached to either of the attachment parts 42L, 42R, the control circuit 80 determines whether or not the user is gripping the side handle 50.

[0064] When the user is holding the side handle 50 and the trigger 34 is pulled to turn on the trigger switch 35, the control circuit 80 causes the motor driver 36 to supply normal drive power to the motor 30.

[0065] Furthermore, when the side handle 50 is not attached to the attachment portions 42L, 42R, the control circuit 80 limits the drive power supplied from the motor driver 36 to the motor 30, thereby suppressing the rotation of the motor 30.

[0066] Furthermore, when a side handle 50 is attached to the attachment portion 42L or 42R, the control circuit 80 determines whether the side handle 50 is being gripped by the user. Even when the side handle 50 is not being gripped, the control circuit 80 limits the drive power supplied from the motor driver 36 to the motor 30 to suppress rotation of the motor 30.

[0067] This is to enable normal work to be performed by driving the motor 30 only when the user is holding the rear housing 8 and the side handle 50 with both hands. In other words, when the side handle 50 is not attached, or when the side handle 50 is attached but not being held by the user, the drive power of the motor 30 is limited to a level lower than normal, thereby suppressing the occurrence of kickback.

[0068] Next, the drive device 10 of the motor 30 is provided with an AC / DC converter 82 that receives AC power input to the drive system 12 from the power cord 9 and generates a DC power supply voltage Vdc for operating the control circuit 80. An insulating AC / DC converter is used for the AC / DC converter 82 to insulate the AC power supply line of the drive system 12 from the DC power supply line of the control system 14.

[0069] The power supply voltage Vdc generated by the AC / DC converter 82 is also used as the power supply voltage for the sensor circuits 70R, 70L, which drive the three load detection units 44 provided on the mounting portions 42L, 42R of the gear housing 6 to output load detection signals.

[0070] A trigger operation signal indicating the on / off state of the trigger SW 35 is input to the control circuit 80 from the power supply line of the trigger SW 35 on the motor driver 36 side. In order to control the driving of the motor 30, the control circuit 80 outputs to the motor driver 36 an enable signal that enables driving of the motor 30 and a command signal that commands the driving power of the motor 30.

[0071] The trigger operation signal, the enable signal, and the command signal are transmitted from the drive system 12 of the motor 30 to the control system 14 or from the control system 14 to the drive system 12 via photocouplers 84, 86, and 88, respectively.

[0072] Therefore, the drive system 12 and the control system 14 of the motor 30 are completely insulated from each other, and the AC power used by the drive system 12 to drive the motor 30 can prevent the control system 14 from malfunctioning.

[0073] In the control system 14 for the motor 30, three LEDs 72, 74, and 76 for displaying the control state of the motor 30 are connected to the control circuit 80. Of the three LEDs, the first LED 72 is illuminated when the control circuit 80 determines that the side handle 50 is attached to the gear housing 6. The second LED 74 is illuminated when the control circuit 80 determines that the side handle 50 is being gripped. The third LED 76 is illuminated, for example, when the trigger SW 35 is in the on state.

[0074] <Control circuit operation> Next, we will explain the connection / hold determination process executed in the control circuit 80 to determine whether the side handle 50 is being held, and the motor control process executed when the trigger SW 35 is turned on to drive the motor 30. These processes are repeatedly executed as part of the main routine in the control circuit 80 by the CPU executing a program stored in the ROM.

[0075] As shown in FIG. 6, in the connection / holding determination process, first, in S110 (S represents step), the load measurement results are obtained from the three load detection units 44 provided on the left and right mounting portions 42L, 42R of the gear housing 6, respectively.

[0076] Then, in the following S120, it is determined whether or not at least one of the loads measured by the three load detection units 44 acquired for each of the left and right mounting units 42L, 42R in S110 is equal to or greater than a first threshold value LT1 set in advance.

[0077] In S120, if at least one of the three measured loads is equal to or greater than the first threshold value LT1, it is determined that the side handle 50 is attached to the attachment portion 42L or 42R on which the three load detection units 44 are provided.

[0078] Furthermore, if the loads measured by the three load detection units 44 provided on the left and right mounting portions 42L and 42R, respectively, do not all reach the first threshold value LT1, it is determined that the side handle 50 is not attached to the gear housing 6.

[0079] Then, if it is determined in S120 that the side handle 50 is not attached, the first LED 72 is turned off in S130, the second LED 74 is turned off in S140, the motor power limit flag is set in S150, and the connection / hold determination process is terminated.

[0080] If it is determined in S120 that the side handle 50 is attached, the first LED 72 is turned on in S160 to notify the user that the side handle 50 is attached, and the process proceeds to S170.

[0081] In S170, it is determined whether or not at least one of the loads measured by the three load detection units 44 provided on the mounting unit 42L or 42R to which the side handle 50 is attached is equal to or greater than the second threshold value LT2.

[0082] The second threshold value LT2 is a threshold value for determining whether the side handle 50 attached to the attachment portion 42L or 42R is being gripped by the user, and is set to a value greater than the first threshold value LT1.

[0083] If it is determined in S170 that at least one of the three measured loads is equal to or greater than the second threshold value LT2, the process proceeds to S180, where the second LED 74 is turned on to notify the user that the side handle 50 is being gripped, and the process proceeds to S190. In S190, since the side handle 50 is being gripped, the motor power limit flag is cleared, and the connection / grip determination process ends.

[0084] Next, if it is determined in S170 that none of the three measurement loads has reached the second threshold value LT2, the process proceeds to S200, where it is determined whether at least one of the three measurement loads has changed within a predetermined time.

[0085] In S200, if at least one of the three measured loads changes within a predetermined time, it is determined that the user is gripping the side handle 50, and the process proceeds to S180. In S200, if none of the three measured loads changes within a predetermined time, it is determined that the user is not gripping the side handle 50, and the process proceeds to S140.

[0086] In this way, in the connection / holding determination process, when the side handle 50 is attached to the mounting portion 42L or 42R of the gear housing 6 and the side handle 50 is being held by the user, the motor power limit flag is cleared.

[0087] In addition, when the side handle 50 is not attached to the mounting parts 42L, 42R of the gear housing 6, or when the side handle 50 is attached but not gripped by the user, a motor power limit flag is set.

[0088] 7, in the motor control process, first, in S310, it is determined whether or not the trigger SW 35 is in the ON state. If the trigger SW 35 is not in the ON state, the process of S310 is executed again to wait for the trigger SW 35 to be in the ON state.

[0089] If it is determined in S310 that the trigger switch 35 is in the ON state, the process proceeds to S320, where it is determined whether the motor power limit flag is set. If it is determined in S320 that the motor power limit flag is set, the process proceeds to S340, where a limited power supply command signal is set so that the motor driver 36 drives the motor 30 with a drive power that is more limited than normal, and the process proceeds to S310.

[0090] If it is determined in S320 that the motor power limit flag is not set, the process proceeds to S330, where a command signal is set to remove the limit on the drive power so that the motor driver 36 drives the motor 30 with normal drive power, and then the process proceeds to S310. The command signal set in S330 or S340 is output to the motor driver 36.

[0091] <Effects> As described above, in the grinder 2 of this embodiment, the side handle 50 can be attached to the attachment portion 42L or 42R provided on the gear housing 6, which is the housing of the grinder 2. The attachment portions 42L and 42R are each provided with three load detection units 44.

[0092] The control circuit 80 determines whether or not the side handle 50 is attached to the attachment portion 42L or 42R based on the load detected by the three load detection portions 44. Furthermore, if the side handle 50 is attached, it determines whether or not the user is gripping the side handle 50.

[0093] When the trigger 34 is operated and the trigger switch 35 is turned on, the control circuit 80 determines whether the side handle 50 is being gripped, and if the side handle 50 is being gripped, the control circuit 80 drives the motor 30 with normal drive power. On the other hand, if the side handle 50 is not being gripped, the control circuit 80 drives the motor 30 with a drive power that is more limited than normal.

[0094] As described above, with the grinder 2 of this embodiment, it is possible to determine in the control circuit 80 whether the side handle 50 is being gripped, without providing a detector on the side handle 50 that detects whether the side handle 50 is being gripped by the user, as described in Patent Document 1. Therefore, the grinder 2 of this embodiment has a simpler device configuration and can be easily realized compared to the one described in Patent Document 1. [Other embodiments] Although one embodiment of the present disclosure has been described above, the present disclosure is not limited to the above-described embodiment and can be implemented in various modifications.

[0095] For example, in the above embodiment, the attachment state of the side handle 50 to the gear housing 6 and the state of grip of the side handle 50 by the user are determined from the detection results of the three load detection units 44, and the driving power of the motor 30 is controlled according to the determination results.

[0096] However, in the grinder 2, when the driving of the motor 30 is started, the blade 20, which is the driven object, may be pressed against the work object. If the driving of the motor 30 is started normally in this state, the grinder 2 may be swung around due to the reaction force that the blade 20 receives from the work object.

[0097] Therefore, in order to prevent such kickback from occurring, the connection / holding determination process may be configured to determine whether or not the blade 20 is pressed against the work object based on the detection results of the three load detection units 44.

[0098] <Modification> Below, we will explain, as a modified example of the above embodiment, the connection / holding determination process that makes it possible to determine whether the blade 20 is pressed against the work object, and the motor control process that limits the driving power of the motor 30 based on the determination result.

[0099] As shown in FIG. 8, in the connection / holding determination process of the modified example, the processes of S110 to S190 are executed in the same manner as in the above embodiment, and then the determination process of S210 is executed. In S210, it is determined whether at least one of the loads measured by the three load detection units 44 provided on the mounting unit 42L or 42R to which the side handle 50 is attached is equal to or greater than the third threshold value LT3.

[0100] The third threshold value LT3 is a threshold value for detecting that the blade 20 is pressed against the workpiece, and is therefore a value even greater than the second threshold value LT2. If it is determined in S210 that at least one of the three measured loads is equal to or greater than the third threshold value LT3, the process proceeds to S220, where the third LED 76 is turned on to notify the user that the blade 20 is being pressed against the workpiece. In the following S230, since the blade 20 is being pressed against the workpiece, a pressing flag is set, and the connection / holding determination process ends.

[0101] Next, if it is determined in S210 that none of the three measured loads has reached the third threshold value LT3, the process proceeds to S240, where the third LED 76 is turned off, and then the process proceeds to S250, where the pressing flag is cleared and the connection / holding determination process ends.

[0102] On the other hand, in the motor control process of the modified example, as shown in FIG. 9, if it is determined in S310 that the trigger SW 35 is not in the ON state, the motor 30 is not being driven, so the immediately after start flag is set in S312 and the process of S310 is executed again.

[0103] Next, if it is determined in S310 that the trigger switch 35 is in the ON state, the process proceeds to S314, where it is determined whether the pressing flag is set. If it is determined in S314 that the pressing flag is set, the process proceeds to S318.

[0104] On the other hand, if it is determined in S314 that the pressing flag is not set, the blade 20 was not pressed against the workpiece when the motor 30 started to drive, so in S316 the immediately after start flag is cleared and the process proceeds to S318.

[0105] In S318, it is determined whether the immediately after start flag is set. If it is determined in S318 that the immediately after start flag is set, the blade 20 is pressed against the workpiece when the motor 30 starts to drive, and the process proceeds to S340.

[0106] If it is determined in S318 that the immediately after start flag is not set, the flow proceeds to S320, where it is determined whether the motor power limit flag is set. Therefore, in the modified motor control processing, the processing of S320 is executed when the blade 20 is not pressed against the workpiece when the motor 30 starts to drive, or when the blade 20 is released from being pressed against the workpiece after the motor 30 starts to drive.

[0107] After the determination process in S320 is executed, the process proceeds to S340 or S330 depending on whether the motor power limit flag is set, and the motor 30 is driven, as in the above embodiment.

[0108] In this way, according to this modification, if the blade 20, which is the driven object, is pressed against the workpiece when the motor 30 starts to drive, the drive power of the motor 30 is limited. This makes it possible to prevent kickback from occurring immediately after the motor 30 starts to drive.

[0109] Furthermore, after the motor 30 starts to operate with the drive power limited, when the blade 20 is released from pressing against the workpiece, the drive power limit is released and the motor 30 is driven with normal drive power.

[0110] Therefore, when the driving power of the motor 30 is restricted by pressing the blade 20 and the rotation of the motor 30 does not increase, the user can release the restriction on the driving power of the motor 30 and increase the rotation of the motor by loosening the pressure of the blade 20.

[0111] <Other variations> Next, in the above embodiment, the mounting portions 42L, 42R of the gear housing 6 are described as having three load detection portions 44, each composed of a resistance type pressure sensor, disposed at intervals of 120 degrees.

[0112] However, the load detection unit 44 does not have to be a resistive pressure sensor, and may instead be, for example, a pressure-sensitive rubber or a strain gauge. In other words, the load detection unit 44 may be anything that can detect the load applied from the side handle 50 to the mounting portions 42L, 42R of the gear housing 6.

[0113] Furthermore, the number of load detection units 44 is not limited to three, and may be four or more, or may be two. However, the reason for providing multiple load detection units 44 is to detect when the grip portion 52 is tilted relative to the shaft 60 when the user grips the side handle 50. For this reason, it is desirable to disperse the multiple load detection units 44 around the mounting holes 40L, 40R.

[0114] Next, in the above embodiment, the grinder 2 has been described as an example of an electric work tool equipped with a side handle. However, the technology of the present disclosure can be applied in the same manner as in the above embodiment to any electric work tool that can be fitted with a side handle on the housing of the main body, such as a driver drill.

[0115] Furthermore, multiple functions possessed by one component in the above embodiments may be realized by multiple components, or one function possessed by one component may be realized by multiple components. Furthermore, multiple functions possessed by multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Furthermore, part of the configuration of the above embodiments may be omitted. Furthermore, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0116] Furthermore, the present disclosure can be realized in various forms, such as an electric work machine such as a grinder, a system that includes an electric work machine as a component, a program for causing a computer to function as a control circuit 80, a non-transient physical recording medium such as a semiconductor memory on which this program is recorded, and a method for determining whether a side handle is connected / held. [Explanation of symbols]

[0117] 2...Grinder, 4...Motor housing, 6...Gear housing, 8...Rear housing, 12...Drive system, 14...Control system, 30...Motor, 40L, 40R...Mounting holes, 42L, 42R...Mounting portions, 44...Load detection portion, 46...Rubber (first elastic body), 50...Side handle, 52...Grip portion, 58...Vibration-damping rubber (second elastic body), 60...Shaft, 80...Control circuit.

Claims

1. a motor configured to rotate an object to be driven; a main body housing that accommodates the motor and a mechanism that transmits the rotation of the motor to an external driven object; a side handle having a shaft serving as an axis and a grip portion provided around the shaft, the side handle being configured to be gripped by a user; an attachment portion provided on the housing, the attachment portion configured to receive the shaft of the side handle so that the side handle is attached to the housing; a plurality of load detection units provided in the mounting portion of the housing so as to be dispersed around a mounting hole into which the shaft of the side handle is inserted, the load detection units being configured to detect a load applied from the grip portion of the side handle; a control unit configured to determine whether the side handle is being gripped based on the loads detected by the plurality of load detection units, and to limit the driving power of the motor when the side handle is not being gripped; An electric work machine equipped with

2. The electric operating machine according to claim 1, The electric work machine, wherein the plurality of load detection units are each configured as a resistance type pressure sensor whose resistance value changes depending on the load.

3. The electric operating machine according to claim 1 or 2, The electric work machine, wherein three or more of the load detection units are distributed around the mounting hole of the housing at positions that are the same distance from the center of the mounting hole.

4. The electric operating machine according to any one of claims 1 to 3, The electric work machine, wherein a first elastic body is provided on a surface of each of the plurality of load detection units facing the grip portion of the side handle.

5. The electric operating machine according to any one of claims 1 to 4, An electric work machine, wherein the surface of the grip portion of the side handle facing the multiple load detection units is configured to be perpendicular to the central axis of the shaft and to have a circular ring shape centered on the shaft.

6. The electric operating machine according to any one of claims 1 to 5, The electric work machine, wherein a second elastic body is provided in the side handle between the shaft and the grip portion.

7. An electric operating machine according to claim 6 which relies on claim 4, An electric operating machine, wherein the spring constant of the second elastic body is greater than the spring constant of the first elastic body.

8. The electric operating machine according to any one of claims 1 to 7, The control unit is configured to determine that the side handle is attached to the housing when at least one of the loads detected by the plurality of load detection units is equal to or greater than a predetermined first threshold, and to determine whether the side handle is being gripped, and to determine that the side handle is not attached to the housing when all of the loads detected by the plurality of load detection units do not reach the first threshold, and to limit the driving power of the motor.

9. The electric operating machine according to claim 8, The control unit is configured to determine that the side handle is being gripped when at least one of the loads detected by the multiple load detection units is equal to or greater than a second threshold value that is greater than the first threshold value, and to determine that the side handle is not being gripped when all of the loads detected by the multiple load detection units do not reach the second threshold value.

10. The electric operating machine according to claim 9, The control unit is configured to, when all of the loads detected by the plurality of load detection units have not reached the second threshold, determine whether at least one of the loads detected by the plurality of load detection units has changed within a predetermined time, and, when at least one of the loads has changed within the predetermined time, determine that the side handle is being gripped.

11. The electric operating machine according to claim 9 or 10, The control unit is configured to determine that the object to be driven is being pressed against an external work object when at least one of the loads detected by the multiple load detection units is equal to or greater than a third threshold value that is greater than the second threshold value when the motor starts to drive, and to limit the drive power of the motor, and thereafter, when all of the loads detected by the multiple load detection units become less than the third threshold value, to release the limit on the drive power of the motor.

12. An electric operating machine according to any one of claims 1 to 11, the motor is an AC motor that is driven to rotate by AC power supplied from an AC power source, The electric work machine, wherein the plurality of load detection units and the control unit are insulated from a drive system that drives the AC motor with the AC power.

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