GRINDER

Description

This Nonprovisional application claims priority under 35 U.S.C. § 119 on Patent Application No. 2024-092483 filed in Japan on Jun. 6, 2024, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a grinder.

BACKGROUND ART

Patent Literature 1 discloses a disc grinder including a circular grindstone (hereinafter, also referred to as “disc tool”) driven to rotate by a motor. The disc grinder includes a housing accommodating therein the motor and a gear case located closer to a front side than the housing. The housing constitutes a gripping part to be gripped by an operator.

CITATION LIST

Patent Literature

[Patent Literature 1]

• • Japanese Patent Application Publication Tokukai No. 2010-269396

SUMMARY OF INVENTION

Technical Problem

The posture of the disc tool with respect to a workpiece has a relationship with processing accuracy. Therefore, when carrying out processing using the disc grinder, an operator carries out the processing while keeping the disc tool in a proper posture with respect to the workpiece. However, with the disc grinder disclosed in Patent Literature 1, there is no method for recognizing the posture of the disc tool with respect to the workpiece, except for making evaluation based on the subject view of the operator.

It is an object of an aspect of the present invention to detect a posture of a disc tool with respect to a workpiece.

Solution to Problem

In order to solve the foregoing problem, a grinder in accordance with an aspect of the present invention includes: a disc tool configured to process a workpiece; a force sensor configured to detect a moment acting on the disc tool; and a controller, the controller carrying out a detection process of detecting a posture of the disc tool with respect to the workpiece on the basis of an output signal obtained from the force sensor.

Advantageous Effects of Invention

According to an aspect of the present invention, it is possible to detect a posture of a disc tool with respect to a workpiece.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic side view illustrating a configuration of a grinder in accordance with an embodiment of the present invention.

FIG. 2 is a schematic side view for explaining an inclination of a disc tool with respect to a workpiece.

FIG. 3 is a schematic side view for explaining an inclination of a disc tool with respect to a workpiece.

FIG. 4 is a schematic view for explaining one example of an image displayed on a display.

FIG. 5 is a block diagram illustrating one example of an internal configuration of a grinder.

FIG. 6 is a flowchart illustrating one example of a flow of a process carried out by a controller.

FIG. 7 is a flowchart illustrating one example of a flow of a process carried out by a controller.

DESCRIPTION OF EMBODIMENTS

Embodiments

The following description will discuss a grinder 1 in accordance with an embodiment of the present invention in detail.

(Overview of Grinder)

With reference to FIG. 1, the following will describe an overview of the grinder 1. FIG. 1 is a schematic side view illustrating a configuration of the grinder 1 in accordance with an embodiment of the present invention. The grinder 1 includes a disc tool 20, a force sensor 40, and a controller 80. The grinder 1 may further include a main body 10, a driving motor 30, an inertial measurement unit (IMU) 50, and an input device 60 (see FIG. 5), and a display 70.

The main body 10 constitutes a main part of the grinder 1. For the main body 10, an x-axis direction (direction of an x axis) is regarded as a longitudinal direction. The main body 10 has a first end part 11 and a second end part 12 located opposite to the first end part 11. The first end part 11 is an end part located on a negative direction side in the x-axis direction. The second end part 12 is an end part located on a positive direction side in the x-axis direction.

A gripping part 13 is provided on a side closer to the first end part 11 of the main body 10. The gripping part 13 is formed so as to have a small diameter that allows easier gripping by an operator. The gripping part 13 may accommodate therein the IMU 50 and the controller 80. A power source button 61 included in the input device 60 (see FIG. 5) may be provided on the negative direction side in the z-axis direction of the gripping part 13.

The disc tool 20 is attached to a side closer to the second end part 12 of the main body 10. More specifically, the disc tool 20 is attached to a negative direction side in a z-axis direction of a gear accommodation part 14 provided on the side closer to the second end part 12 of the main body 10. The gear accommodation part 14 may accommodate therein the driving motor 30 and the force sensor 40. To the gear accommodation part 14, a side handle to be gripped by an operator may be attached.

The disc tool 20 is a tool for processing, such as polishing, on a workpiece 2. Examples of the disc tool 20 include a grindstone. The disc tool 20 is attached to a spindle 32 with use of, for example, nuts. The disc tool 20 rotates about the spindle 32. The spindle 32 serves as a rotation shaft of the disc tool 20.

The driving motor 30 is a motor configured to rotate the spindle 32. The spindle 32 is connected to an output shaft 31 of the driving motor 30.

The force sensor 40 detects moments acting on the disc tool 20. The force sensor 40 outputs, to the controller 80, an output signal indicating the moment detected. The force sensor 40 may detect forces acting on the disc tool 20. In this case, the force sensor 40 outputs, to the controller 80, an output signal indicating the force detected.

The force sensor 40 may be attached to a flange part 35 protruding from an outer peripheral part of the driving motor 30. In a center part of the force sensor 40, a through hole 41 through which the output shaft 31 of the driving motor 30 and the spindle 32 are inserted is formed.

In the present embodiment, a six-axis force sensor is used as the force sensor 40. The force sensor 40 detects a force Fx in an x-axis direction, a force Fy in a y-axis direction (direction of a y axis), a force Fz in a z-axis direction (direction of a z axis), a moment Mx about an x axis, a moment My about a y axis, and a moment Mz about a z axis which act on the disc tool 20. Here, the x-axis direction is a direction from the first end part 11 to the second end part 12 of the main body 10. The z-axis direction is a direction parallel to an axis direction of the spindle 32 of the disc tool 20 which direction is orthogonal to the x axis. The y-axis direction is a direction orthogonal to the x axis and the z axis. The x-axis direction and the y-axis direction are directions parallel to a radial direction of the disc tool 20.

The IMU 50 is an inertial measurement device configured to detect angular velocities and accelerations of the main body 10. More specifically, the IMU 50 can detect angular velocities about the x axis, about the y axis, and about the z axis of the main body 10. The IMU 50 can detect accelerations in the x-axis direction, in the y-axis direction, and in the z-axis direction of the main body 10. The posture of the main body 10 can be detected with use of the IMU 50. The IMU 50 outputs, to the controller 80, an output signal indicating the detected angular velocity and an output signal indicating the detected acceleration.

The display 70 displays an image indicating a posture of the disc tool 20 with respect to the workpiece 2. Examples of the display 70 include a display panel. The display 70 is provided on the main body 10. In the present embodiment, the display 70 is provided on the gripping part 13. The display 70 is provided in a position visible to an operator gripping the gripping part 13.

The controller 80 controls the parts of the grinder 1.

(Internal Configuration of Grinder)

With reference to FIG. 5, the following will describe an example of an internal configuration of the grinder 1. FIG. 5 is a block diagram illustrating one example of an internal configuration of the grinder 1.

The controller 80 includes a processor 81, a primary memory 82, a secondary memory 83, and an input/output IF 84, as illustrated in FIG. 5. The processor 81, the primary memory 82, the secondary memory 83, and the input/output IF 84 are connected with each other via a bus. Examples of a device usable as the controller 80 include a workstation.

The secondary memory 83 stores a control program P. The processor 81 loads, on the primary memory 82, the control program P stored in the secondary memory 83. The processor 81 then carries out processes included in process methods M1 and M2 (described later) in accordance with instructions included in the control program P loaded on the primary memory 82. The secondary memory 83 may store teaching data TD generated by the grinder 1. The teaching data TD is data for causing a robot including the disc tool 20 to process the workpiece 2.

Examples of a device usable as the processor 81 include a central processing unit (CPU). Examples of a device usable as the primary memory 82 include a semiconductor random access memory (RAM). Examples of a device usable as the secondary memory 83 include a hard disk drive (HDD).

The input/output IF 84 is an interface for communicating with the force sensor 40, the IMU 50, the input device 60, the display 70, an output device 75, and an inverter 90. Examples of the input/output IF 84 include a universal serial bus (USB), an advanced technology attachment (ATA), a small computer system interface (SCSI), serial communication, and the like.

The input device 60 is a device that can receive an input from the operator. The input device 60 may be constituted by, for example, a button, a switch, a touch panel, or the like. In the present embodiment, the input device 60 includes the power source button 61.

The grinder 1 may include the output device 75 configured to output an alerting sound or a voice. Examples of the output device 75 include speakers and buzzers.

The grinder 1 may further include the inverter 90. The inverter 90 controls a rotation speed of the driving motor 30. The controller 80 carries out pulse width modulation (PWM) control over the inverter 90. Specifically, the controller 80 sets a duty ratio, and outputs, via the input/output IF 84, a PWM signal generated on the basis of the set duty ratio, to the inverter 90. The inverter 90 controls current supplied to the driving motor 30 by applying voltage generated on the basis of the inputted PWM signal to the driving motor 30. The voltage applied by the inverter 90 is controlled, thereby controlling the rotation speed of the driving motor 30.

(Flow of Process by Controller)

Next, with reference to FIG. 6, the following will describe one example of a process method M1 carried out by the controller 80. FIG. 6 is a flowchart illustrating one example of the process method M1 carried out by the controller 80.

First, the processor 81 carries out an obtaining process S1. In the obtaining process S1, the processor 81 obtains, via the input/output IF 84, an output signal outputted from the force sensor 40. In the obtaining process S1, the processor 81 may obtain an output signal outputted from the IMU 50.

Subsequently, the processor 81 carries out a detection process S2. In the detection process S2, the processor 81 detects a posture of the disc tool 20 with respect to the workpiece 2 on the basis of the output signal obtained from the force sensor 40 in the obtaining process S1. In the detection process S2, the processor 81 detects an angle between the surface 3 of the workpiece 2 and the disc tool 20 as the posture of the disc tool 20.

In the detection process S2, the processor 81 may detect an inclination of the disc tool 20 with respect to the workpiece 2 in a plane including the x axis among the planes orthogonal to the surface of the workpiece 2, on the basis of the moment My obtained. For example, as illustrated in FIG. 2, when the moment My acts on the disc tool 20, the disc tool 20 inclines about the y-axis direction with respect to the surface 3 of the workpiece 2. The angle θ1 illustrated in FIG. 2 is an angle of the inclination of the disc tool 20 with respect to the workpiece 2 in the plane including the x axis among the planes orthogonal to the surface of the workpiece 2. The angle θ1 has a magnitude differing in accordance with the value of the moment My acting on the disc tool 20. The processor 81 detects a posture of the disc tool 20 with respect to the workpiece 2 by detecting the magnitude of the angle θ1.

In the detection process S2, the processor 81 may detect an inclination of the disc tool 20 with respect to the workpiece 2 in a plane including the y axis among the planes orthogonal to the surface 3 of the workpiece 2, on the basis of the moment Mx obtained. For example, as illustrated in FIG. 3, when the moment Mx acts on the disc tool 20, the disc tool 20 inclines about the x-axis direction with respect to the surface 3 of the workpiece 2. The angle θ2 illustrated in FIG. 3 is an angle of the inclination of the disc tool 20 with respect to the workpiece 2 in a plane including the y axis among the planes orthogonal to the surface 3 of the workpiece 2. The angle θ2 has a magnitude differing in accordance with the value of the moment Mx acting on the disc tool 20. The processor 81 detects a posture of the disc tool 20 with respect to the workpiece 2 by detecting the magnitude of the angle θ2. In a case where the workpiece 2 is processed with the disc tool 20 inclined about the y-axis direction, the processor 81 may detect a variation in a thrust force in the X-axis direction of the disc tool 20 on the basis of the moment Mx obtained.

In the detection process S2, the processor 81 may detect an angle between the surface 3 of the workpiece 2 and the disc tool 20 on the basis of an output signal indicating at least one of the force Fx in the x-axis direction and the force Fy in the y-axis direction that have been obtained in the obtaining process S1. In the detection process S2, the processor 81 may detect an amount of radial runout of the disc tool 20 in the y-axis direction on the basis of an output signal indicating the obtained force Fy in the y-axis direction. The processor 81 may detect a thrust force of the disc tool 20 toward the x-axis direction on the basis of an output signal indicating the obtained force Fx in the x-axis direction. In the detection process S2, the processor 81 may detect a pressing force of the disc tool 20 against the workpiece 2 on the basis of an output signal indicating the force Fz in the z-axis direction which has been obtained in the obtaining process S1.

In the detection process S2, the processor 81 may detect a posture of the disc tool 20 with respect to the workpiece 2 on the basis of the output signal obtained from the IMU 50 in the obtaining process S1 and the output signal obtained from the force sensor 40 in the obtaining process S1. Specifically, in the detection process S2, the processor 81 detects a posture of the main body 10 on the basis of an output signal indicating the angular velocity and an output signal indicating the acceleration which have been outputted from the IMU 50. The processor 81 may detect an angle between the surface 3 of the workpiece 2 and the disc tool 20 on the basis of the posture of the main body 10 detected by the IMU 50 and the moment My and/or moment Mx detected by the force sensor 40.

Subsequently, the processor 81 carries out a displaying process S3. In the displaying process S3, the processor 81 causes the display 70 to display an image indicating whether or not the detected posture of the disc tool 20 is a proper posture determined in advance. The proper posture is a posture permissible as ensuring good processing accuracy by the disc tool 20. The proper posture may be set in accordance with the type or the outer diameter of the disc tool 20. The proper posture may be set in accordance with the type or the shape of the workpiece 2, or the type of processing (e.g., polishing, grinding, or the like) carried out on the workpiece 2.

The configuration of causing the display 70 to display an image indicating whether or not the posture of the disc tool 20 is a proper posture allows the operator to view the image displayed on the display 70. This enables recognition of the posture of the disc tool with respect to the workpiece 2 in the processing. Thus, it is possible to keep a proper posture of the disc tool with respect to the workpiece.

In the displaying process S3, the processor 81 may change a displaying aspect of the display 70 between a case where a value of the moment derived on the basis of the output signal obtained in the obtaining process S1 has not exceeded a threshold and a case where the value of the moment has exceeded the threshold. Examples of the change in the displaying aspect include change in color, change in displaying position, and change in a displaying method by blinking or the like. Note that in the displaying process S3, the processor 81 may cause the display 70 to display an image for guiding the posture of the disc tool 20 in a direction for correcting the posture to a proper posture with use of, for example, characters or an arrow.

The change in the displaying aspect of the display 70 allows the operator to recognize that the posture of the disc tool 20 with respect to the workpiece 2 has been deviated from a proper posture. This makes it possible to keep a proper posture of the disc tool 20 with respect to the workpiece 2.

Next, the processor 81 carries out a notification process S4. In the notification process S4, the processor 81 carries out notification using the output device 75 in a case where the value of the moment derived on the basis of the output signal obtained from the force sensor has exceeded a threshold. In the notification process S4, the processor 81 outputs an alerting sound or a voice from the output device to notify the operator that the posture of the disc tool 20 has been deviated from a proper posture. In the notification process S4, the processor 81 may change, for example, a scale, a tone, or a ringing period of the outputted alerting sound in accordance with a degree to which the posture of the disc tool 20 is deviated from a proper posture. In the notification process S4, the output device 75 may output a voice to guide the posture of the disc tool 20 in a direction for correcting the posture to a proper posture.

The controller 80 carrying out the notification process S4 the operator to recognize that the posture of the disc tool 20 with respect to the workpiece 2 has been deviated from the proper posture. This makes it possible to keep a proper posture of the disc tool 20 with respect to the workpiece 2.

With reference to FIG. 4, the following will describe one example of the image displayed on the display 70 in the displaying process S3. FIG. 4 is a schematic view for explaining one example of an image displayed on the display 70.

The reference numeral 100 of FIG. 4 illustrates one example of an image showing a posture of the disc tool 20 with respect to the workpiece 2 which has been detected on the basis of the moment My. As illustrated by the reference numeral 100 in FIG. 4, the display 70 displays a posture image 700 showing the posture of the disc tool 20 with respect to the workpiece 2 which has been detected on the basis of the moment My. The posture image 700 is displayed at an angle corresponding to the detected posture of the disc tool 20. The display 70 may also display reference lines 701 to 703.

The reference line 701 is a line indicating that the disc tool 20 is parallel to the surface 3 of the workpiece 2. The reference line 702 is a line indicating that the disc tool 20 is inclined by a first angle with respect to the workpiece 2. The reference line 702 is a borderline indicating whether or not the inclination of the disc tool 20 with respect to the workpiece 2 falls within a permissible range. The reference line 703 is a line indicating that the disc tool 20 is inclined by a second angle with respect to the workpiece 2. The reference line 703 is a borderline indicating whether or not the inclination of the disc tool 20 with respect to the workpiece 2 falls within an abnormal range.

When the posture image 700 is located between the reference line 701 and the reference line 702, the posture image 700 may be displayed in a blueish color considering that the posture of the disc tool 20 falls within a permissible range. When the posture image 700 is located between the reference line 702 and the reference line 703, the posture image 700 may be displayed in a yellowish color considering that the posture of the disc tool 20 falls outside a permissible range. When the posture image 700 is located above the reference line 703, the posture image 700 may be displayed in a reddish color considering that the posture of the disc tool 20 clearly falls outside a permissible range. This enables the operator to recognize an inclination state of the disc tool 20 with respect to the workpiece 2 about the y-axis direction.

The reference numeral 101 of FIG. 4 illustrates one example of an image showing a posture of the disc tool 20 with respect to the workpiece 2 which has been detected on the basis of the moment Mx. As illustrated by the reference numeral 101 in FIG. 4, the display 70 displays a posture image 710 showing a posture of the disc tool 20 which has been detected on the basis of the moment Mx and a reference line 711. The posture image 710 is displayed at an angle corresponding to the detected posture of the disc tool 20. The reference line 711 is a line indicating that the disc tool 20 is parallel to the surface 3 of the workpiece 2. This enables the operator to recognize an inclination state of the disc tool 20 with respect to the workpiece 2 about the x-axis direction.

The reference numeral 102 of FIG. 4 illustrates one example of an image showing a force acting on the disc tool 20 on the basis of the force Fx, the force Fy, and the force Fz which have been detected by the force sensor 40. The display 70 displays a force displaying image 720 showing the force Fx, a force displaying image 730 showing the force Fy, and a force displaying image 740 showing the force Fz. The display 70 may display one of the force displaying images 720 to 740.

The force displaying image 720 includes a permission displaying part 721 indicating that the force Fx falls within a permissible range and abnormality displaying parts 722 and 723 each indicating that the force Fx falls outside the permissible range. The permission displaying part 721 is located between the abnormality displaying part 722 and the abnormality displaying part 723. In a case where the force Fx falls within the permissible range, the permission displaying part 721 may light up in a cold color. For example, in a case where the force Fx in the positive x-axis direction falls outside the permissible range, the abnormality displaying part 722 may light up in a warm color. In a case where the force Fx in the negative x-axis direction falls outside the permissible range, the abnormality displaying part 723 may light up in a warm color.

The force displaying image 730 may light up in a cold color in a case where the force Fy falls within a permissible range and may light up in a warm color in a case where the force Fy falls outside the permissible range. The force displaying image 740 may light up in a cold color in a case where the force Fz falls within a permissible range and may light up in a warm color in a case where the force Fz falls outside the permissible range.

According to the grinder 1, the fact that the grinder 1 includes the force sensor 40 enables detection of a moment acting on the workpiece 2. This makes it possible to detect a posture of the disc tool 20 with respect to the workpiece 2.

The detection of the moment My by the force sensor 40 enables detection of a y-axis-direction inclination of the disc tool 20 with respect to the workpiece 2. This makes it possible to detect a y-axis-direction posture of the disc tool 20 with respect to the workpiece 2.

The detection of the moment Mx by the force sensor 40 enables detection of an x-axis-direction inclination of the disc tool 20 with respect to the workpiece 2. This makes it possible to detect an x-axis-direction posture of the disc tool 20 with respect to the workpiece 2.

Further, it is possible to detect a movement of the disc tool 20 in the y-axis direction from the force Fy in the y-axis direction acting on the workpiece 2. This makes it possible to detect an amount of radial runout of the disc tool 20 in the y-axis direction. Further, it is possible to detect a movement of the disc tool 20 in the x-axis direction from the force Fx in the x-axis direction acting on the workpiece 2. This makes it possible to detect a thrust force of the disc tool 20 toward the x-axis direction. Further, it is possible to detect a pressing force of the disc tool 20 against the workpiece 2 from the force Fz in the z-axis direction acting on the workpiece 2. This makes it possible to improve processing accuracy for the workpiece 2 by the disc tool 20.

It is also possible to detect a posture and a position of the main body 10 with respect to the workpiece 2 from an angular velocity and an acceleration of the main body 10 that have been obtained from the IMU 50. This enables more accurate detection of a posture of the disc tool 20 with respect to the workpiece 2.

(Generation of Teaching Data)

The controller 80 may generate teaching data TD for causing a robot including the disc tool 20 to process the workpiece 2. With reference to FIG. 7, the following will describe one example of a process method M2 carried out by the controller 80. FIG. 7 is a flowchart illustrating one example of a flow of a process carried out by the controller 80.

First, the processor 81 carries out a generation process S11 of generating the teaching data TD. In the generation process S11, the processor 81 generates the teaching data TD on the basis of the output signal obtained from the force sensor 40 and the output signal obtained from the IMU 50. In the generation process S11, the processor 81 stores, in advance, a force and a moment that are indicated by the output signal outputted from the force sensor 40, in chronological order to generate the teaching data TD. In the generation process S11, the processor 81 stores, in advance, an angular velocity and an acceleration that are indicated by the output signal outputted from the IMU 50, in chronological order to generate teaching data TD.

As data used for generating the teaching data TD, data indicating, in chronological order, each of data on a force acting on the disc tool 20, data on an angle of the main body 10, data on a position of the main body 10, and data on a moving speed of the disc tool 20 with respect to the workpiece 2 is used, except for the information on the posture of the disc tool 20 with respect to the workpiece 2.

Subsequently, the processor 81 carries out an output process S12 of outputting the teaching data TD to an external device. In the output process S12, the processor 81 outputs the teaching data TD to an external device connected to the grinder 1. Examples of the external device include data loggers. The teaching data TD is supplied from the external device to the robot.

The processor 81 carrying out the output process S12 enables the robot to use the teaching data TD to carry out processing while keeping a proper posture of the disc tool 20 with respect to the workpiece 2. This makes it possible to improve accuracy of processing by the robot including the disc tool 20.

Other Embodiments

In the embodiment described above, the output shaft 31 of the driving motor 30 and the spindle 32, which serves as a rotation shaft of the disc tool 20, are configured to be parallel shafts, but this configuration should not be construed as a limitation. The output shaft 31 and the spindle 32 may be intersecting shafts. In this case, the force sensor 40 may be attached to a retaining member that retains the spindle 32. Further, the driving motor 30 may be disposed inside the gripping part 13.

In the embodiment above, the grinder 1 is configured to include the IMU 50, but this configuration should not be construed as a limitation. The grinder 1 may include an angular velocity sensor that can detect at least one of angular velocities about the x axis, about the y axis, and about the z axis. The grinder 1 also may include an acceleration sensor that can detect at least one of accelerations in the x-axis direction, in the y-axis direction, and in the z-axis direction.

In the embodiment above, the grinder 1 is configured to include the display 70, but this configuration should not be construed as a limitation. The main body 10 of the grinder 1 may be provided with an indicator, e.g., an LED lump or the like. In this case, in the displaying process S3, the processor 81 may turn on or off the indicator in order to indicate whether or not the detected posture of the disc tool 20 is a proper posture determined in advance. A configuration is also possible in which an external display is connected to the grinder 1. In this case, in the displaying process S3, the processor 81 may output an image signal indicating generated image data to the external display to cause the display to display an image showing a posture of the disc tool 20.

In the embodiment above, a configuration is employed in which the inverter 90 is used to control the rotation speed of the driving motor 30, but this configuration should not be construed as a limitation. A device including a triac element may be used to control the rotation speed of the driving motor 30. In this case, the device is phase-controlled. The device may apply voltage generated on the basis of phase control to the driving motor 30.

Aspects of the present invention can also be expressed as follows:

A grinder in accordance with Aspect 1 of the present invention includes: a disc tool configured to process a workpiece; a force sensor configured to detect a moment acting on the disc tool; and a controller, the controller carrying out a detection process of detecting a posture of the disc tool with respect to the workpiece on the basis of an output signal obtained from the force sensor.

According to the configuration of Aspect 1, the fact that the grinder includes the force sensor enables detection of a moment acting on the workpiece. This makes it possible to detect a posture of the disc tool with respect to the workpiece.

A grinder in accordance with Aspect 2 of the present invention may be configured, in Aspect 1 above, further include a main body provided with a gripping part located on a side closer to a first end part thereof and the disc tool attached to a side closer to a second end part thereof which side is located opposite to the side closer to the first end part, a direction from the first end part of the main body to the second end part of the main body being defined as a direction of an x axis, a direction parallel to a rotation shaft of the disc tool which shaft is orthogonal to the x axis being defined as a direction of a z axis, a direction orthogonal to the x axis and the z axis being defined as a direction of a y axis, the force sensor detecting a moment My about the y axis which acts on the disc tool, in the detection process, the controller detecting, as the posture of the disc tool, an angle between a surface of the workpiece and the disc tool.

According to the configuration of Aspect 2, detection of the moment My by the force sensor enables detection of a y-axis-direction inclination of the disc tool with respect to the workpiece. This makes it possible to detect a y-axis-direction posture of the disc tool with respect to the workpiece.

A grinder in accordance with Aspect 3 of the present invention may be configured, in Aspect 1 or 2 above, further include a main body provided with a gripping part located on a side closer to a first end part thereof and the disc tool attached to a side closer to a second end part thereof which side is located opposite to the side closer to the first end part, a direction from the first end part of the main body to the second end part of the main body being defined as a direction of an x axis, a direction parallel to a rotation shaft of the disc tool which shaft is orthogonal to the x axis being defined as a direction of a z axis, a direction orthogonal to the x axis and the z axis being defined as a direction of a y axis, the force sensor detecting a moment Mx about the x axis which acts on the disc tool, in the detection process, the controller detecting, as the posture of the disc tool, an angle between a surface of the workpiece and the disc tool.

According to the configuration of Aspect 3, detection of the moment Mx by the force sensor enables detection of an x-axis-direction inclination of the disc tool with respect to the workpiece. This makes it possible to detect an x-axis-direction posture of the disc tool with respect to the workpiece.

A grinder in accordance with Aspect 4 of the present invention may be configured, in any one of Aspects 1 to 3 above, to further include one or both of an angular velocity sensor configured to detect an angular velocity and an acceleration sensor configured to detect an acceleration, the controller detecting, in the detection process, the posture of the disc tool with respect to the workpiece on the basis of: one or both of an output signal obtained from the angular velocity sensor and an output signal obtained from the acceleration sensor; and the output signal obtained from the force sensor.

According to the configuration of Aspect 4, it is possible to detect a posture and a position of the main body with respect to the workpiece from one or both of the angular velocity and the acceleration of the main body. This enables more accurate detection of a posture of the disc tool with respect to the workpiece.

A grinder in accordance with Aspect 5 of the present invention may be configured, in any one of Aspects 1 to 4 above, to further include a display, the controller further carrying out a displaying process of causing the display to display an image indicating whether or not the posture of the disc tool detected is a proper posture determined in advance.

The configuration of Aspect 5 enables an operator to recognize the posture of the disc tool with respect to the workpiece in processing by viewing the image displayed on the display. Thus, it is possible to keep a proper posture of the disc tool with respect to the workpiece.

A grinder in accordance with Aspect 6 of the present invention may be configured, in Aspect 5 above, such that the controller changes, in the displaying process, a displaying aspect of the image between a case where a value of the moment derived on the basis of the output signal obtained from the force sensor has not exceeded a threshold and a case where the value of the moment has exceeded the threshold.

According to the configuration of Aspect 6, the change in the displaying aspect of the display enables an operator to recognize that the posture of the disc tool with respect to the workpiece has been deviated from the proper posture. Thus, it is possible to keep a proper posture of the disc tool with respect to the workpiece.

A grinder in accordance with Aspect 7 of the present invention may be configured, in any one of Aspects 1 to 6 above, to further include an output device configured to output an alerting sound or a voice, the controller further carrying out a notification process of using the output device to notify that a value of the moment derived on the basis of the output signal obtained from the force sensor has exceeded a threshold.

According to the configuration of Aspect 7, the controller carries out the notification process, thereby enabling the operator to recognize that the posture of the disc tool with respect to the workpiece has been deviated from the proper posture. Thus, it is possible to keep a proper posture of the disc tool with respect to the workpiece.

A grinder in accordance with Aspect 8 of the present invention may be configured, in Aspect 4 above, such that the controller further carries out a generation process of generating teaching data for causing a robot including the disc tool to process the workpiece, on the basis of: one or both of the output signal obtained from the angular velocity sensor and the output signal obtained from the acceleration sensor; and the output signal obtained from the force sensor.

According to the configuration of Aspect 8, use of the teaching data enables the robot to carry out processing while keeping a proper posture of the disc tool with respect to the workpiece. This makes it possible to improve accuracy of processing by the robot including the disc tool.

The present invention is not limited to the embodiments, but can be altered by a skilled person in the art within the scope of the claims. The present invention also encompasses, in its technical scope, any embodiment derived by combining technical means disclosed in differing embodiments.