GRINDER AND ROBOT

Description

This Nonprovisional application claims priority under 35 U.S.C. § 119 on Patent Application No. 2024-092484 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 and a robot.

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 tool rotates around an output shaft via which rotation of the motor is transmitted.

CITATION LIST

Patent Literature

[Patent Literature 1]

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

SUMMARY OF INVENTION

Technical Problem

The disc tool becomes worn by use. The worn disc tool needs to be replaced. However, with the disc grinder disclosed in Patent Literature 1, there is no method for detecting a worn state of the disc tool, except for making determination based on the subject view of the operator.

It is an object of an aspect of the present invention to detect a worn state of a disc tool.

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 rotate around a rotation shaft; a force sensor configured to detect a moment around the rotation shaft, the moment acting on the disc tool; and a controller, the controller carrying out a detection process of detecting a worn state of the disc tool on the basis of the moment obtained from the force sensor.

Advantageous Effects of Invention

According to an aspect of the present invention, it is possible to detect a worn state of a disc tool.

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 view for explaining one example of a worn state of a disc tool.

FIG. 3 is a block diagram illustrating one example of an internal configuration of a grinder.

FIG. 4 is a flowchart illustrating one example of a process method 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. 3), 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. 3) may be provided on the negative direction side of 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 around 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 a moment around the spindle 32, the moment 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 around an x axis, a moment My around a y axis, and a moment Mz around 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 around the x axis, around the y axis, and around 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. 3, the following will describe an example of an internal configuration of the grinder 1. FIG. 3 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. 3. 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 a process method M1 (described later) in accordance with instructions included in the control program P loaded on the primary memory 82.

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, 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 and a selection button 62. The selection button 62 is a button for inputting tool information of the disc tool 20. An operation of the selection button 62 by the operator causes the tool information of a new disc tool 20 attached to the grinder 1 to be inputted. The tool information includes at least one of outer diameter information of an unworn disc tool 20 which has not been used, and type information of the disc tool 20.

The grinder 1 may further include the inverter 90. The inverter 90 controls a rotation speed of the driving motor 30. The inverter 90 is one example of a rotation speed controlling device. 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. 4, the following will describe one example of a process method M1 carried out by the controller 80. FIG. 4 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.

Subsequently, the processor 81 carries out a detection process S2. In the detection process S2, the processor 81 detects a worn state of the disc tool 20 on the basis of the moment Mz obtained from the force sensor 40. In the detection process S2, the processor 81 calculates an outer diameter of the disc tool 20 as the worn state of the disc tool 20. In the detection process S2, the processor 81 may calculate a thickness of the disc tool 20 as the worn state of the disc tool 20.

With reference to FIG. 2, the following will describe one example of detection of a worn state of the disc tool 20. FIG. 2 is a schematic view for explaining one example of a worn state of the disc tool 20. FIG. 2 is a view of the disc tool 20 as seen from an axial direction of the spindle 32. The outer diameter D1 of the disc tool 20 illustrated by the reference numeral 100 in FIG. 2 is greater than the outer diameter D2 of the disc tool 20 illustrated by the reference numeral 101 in FIG. 2. When the disc tool 20 is used, the disc tool 20 becomes worn. For example, when the disc tool 20 is used, the outer diameter of the disc tool 20 may be reduced.

The moment Mz acting on the disc tool 20 is proportional to the size of the outer diameter of the disc tool 20. A smaller outer diameter of the disc tool 20 leads to a smaller moment Mz acting on the disc tool 20. For example, the moment Mz acting on the disc tool 20 illustrated by the reference numeral 101 in FIG. 2 is smaller than the moment Mz acting on the disc tool 20 illustrated by the reference numeral 100 in FIG. 2. The processor 81 detects a worn state of the disc tool 20 by calculating an outer diameter of the disc tool 20 on the basis of the moment Mz.

Subsequently, the processor 81 carries out a rotation speed controlling process S3. In the rotation speed controlling process S3, the processor 81 controls the inverter 90 on the basis of the moment Mz obtained from the force sensor 40 so that the rotation speed of the driving motor 30 becomes a target value corresponding to the outer diameter of the disc tool 20.

In the rotation speed controlling process S3, the processor 81 may control the inverter 90 so as to make a circumferential velocity of the disc tool 20 constant. In the rotation speed controlling process S3, the processor 81 controls the inverter 90 so as to prevent the circumferential velocity of the disc tool 20 from exceeding a limit velocity (hereinafter, referred to as “maximum operational circumferential velocity”) within which the disc tool 20 can be safely used. The maximum operational circumferential velocity is set by, for example, Ordinance on Industrial Safety and Health.

Next, the processor 81 carries out a notification process S4. In the notification process S4, the processor 81 carries out notification to prompt the operator to replace the disc tool 20 in a case where the moment Mz obtained from the force sensor 40 becomes less than a threshold. In the notification process S4, the processor 81 carries out the notification to the operator by, for example, causing the display 70 to display a display screen that prompts replacement of the disc tool 20. In this case, the processor 81 generates a display screen to be displayed on the display 70. In the notification process S4, the processor 81 may be configured to carry out the notification to the operator by, for example, outputting an alert sound or a voice with use of an output device, such as a speaker.

The threshold used in the notification process S4 is a value determined in advance on the basis of a factor such as the type, the outer diameter, or a circumferential velocity of the disc tool 20. The threshold may be a value set in accordance with tool information of the disc tool 20 inputted via the selection button 62 of the input device 60. That is, the threshold may be set in accordance with the outer diameter information and/or the type information of the disc tool 20 inputted with use of the selection button 62 of the input device 60.

The notification that prompts replacement of the disc tool 20 is not limited to a configuration in which a display screen is displayed on the display 70. For example, in the notification process S4, the processor 81 may carry out the notification to the operator by ringing an alarm. In the notification process S4, the processor 81 only needs to be configured to carry out the notification to the operator in an acoustic and/or visual manner.

As described above, the fact that the grinder 1 includes the force sensor 40 enables detection of the moment Mz around a rotation shaft of the spindle 32 of the disc tool 20. This enables detection of a worn state of the disc tool 20.

Typically, a smaller outer diameter of the disc tool 20 leads to a lower circumferential velocity of the disc tool 20. The controller 80 carrying out the rotation speed controlling process S3 enables control of the rotation speed of the driving motor 30 in accordance with the worn state of the disc tool 20 detected with use of the moment Mz obtained from the force sensor 40. This makes it possible to make the circumferential velocity of the disc tool 20 constant. It is also possible to carry out control so as to prevent the circumferential velocity of the disc tool 20 from exceeding the maximum operational circumferential velocity.

The controller 80 carrying out the notification process S4 enables the operator to recognize a timing for replacing the disc tool 20. This also enables the operator to set the replacement timing corresponding to at least one of the outer diameter information and the type information of the disc tool 20 by inputting the tool information of the disc tool 20 through the operation of the selection button 62. This enables replacement of the disc tool 20 at the replacement timing corresponding to the outer diameter and/or the type of 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 around the x axis, around the y axis, and around the z axis. The grinder 1 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 notification process S4, the processor 81 may light the indicator in order to prompt the operator to replace the disc tool 20. A configuration is also possible in which an external display is connected to the grinder 1. In this case, in the notification process S4, the processor may output a visual signal indicating generated displaying image to the external display to cause the display to display the displaying image that prompts replacement of the disc tool 20.

In the embodiment above, the input device 60 is configured to include the selection button 62, but this configuration should not be construed as a limitation. The input device 60 may include an initialization button instead of the selection button 62. A configuration is possible in which when the disc tool 20 is replaced with a new one, the operator presses the initialization button, so that the rotation speed of the driving motor 30 is initialized. In this case, the threshold used in the notification process S4 may be a value obtained by decreasing, by a predetermined percentage, a value of the moment Mz detected in the first processing after pressing the initialization button.

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 employed as the rotation speed controlling device configured to control the rotation speed of the driving motor 30. In this case, the rotation speed controlling device is phase-controlled. The rotation speed controlling device may apply voltage generated on the basis of phase control to the driving motor 30.

In the embodiment above, the grinder 1 is described as a grinder gripped by an operator, but this configuration should not be construed as a limitation. The grinder 1 described above may be attached to a robot. In this case, the controller 80 functions as a device configured to control operation of a robot including the grinder 1. The controller 80 that controls the robot may carry out a replacement process of causing the robot to replace the disc tool 20, on the basis of the worn state of the disc tool 20 detected. More specifically, in a case where the controller 80 determines that the worn state of the disc tool 20 detected in the detection process S2 shows that the disc tool 20 is worn to a degree to which the disc tool 20 needs to be replaced, the controller 80 carries out the replacement process. In the replacement process, the controller 80 causes the robot to replace the disc tool 20. According to such a configuration, in a case where the controller 80 detects that the disc tool 20 has been worn to a degree to which the replacement is needed, control by the controller 80 causes the robot to automatically replace the disc tool 20. This enables reduction in the man-hour for the operator by an amount needed to replace the disc tool 20.

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 rotate around a rotation shaft; a force sensor configured to detect a moment around the rotation shaft, the moment acting on the disc tool; and a controller, the controller carrying out a detection process of detecting a worn state of the disc tool on the basis of the moment 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 around a rotation shaft of the disc tool. This enables detection of a worn state of the disc tool.

A grinder in accordance with Aspect 2 of the present invention may be configured, in Aspect 1 above, such that in a case where the moment obtained from the force sensor becomes less than a threshold, the controller carries out a notification process of carrying out notification to prompt an operator to replace the disc tool.

The configuration of Aspect 2 enables the operator to recognize a timing for replacing the disc tool.

A grinder in accordance with Aspect 3 of the present invention may be configured, in Aspect 2 above, to further include an input device that enables input of tool information including at least one of outer diameter information of the disc tool and type information of the disc tool, the threshold being a value set in accordance with the tool information inputted with use of the input device.

The configuration of Aspect 3 enables setting of a replacement timing corresponding to at least one of the outer diameter information and the type information of the disc tool. This enables replacement of the disc tool at a replacement timing corresponding to the outer diameter and/or the type of the disc tool.

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: a driving motor configured to drive the rotation shaft; and an inverter configured to control a rotation speed of the driving motor, the controller carrying out a rotation speed controlling process of controlling the inverter on the basis of the moment obtained from the force sensor so that the rotation speed of the driving motor becomes a target value corresponding to an outer diameter of the disc tool.

The configuration of Aspect 4 enables control of the rotation speed of the driving motor in accordance with a worn state of the disc tool which is detected with use of the moment obtained from the force sensor. This makes it possible to make the circumferential velocity of the disc tool constant.

A robot in accordance with Aspect 5 of the present invention is a robot including the grinder according to any one of Aspects 1 to 4, which may be configured such that the controller is a device configured to control operation of the robot, and the controller may carry out a replacement process of causing the robot to replace the disc tool, on the basis of the worn state of the disc tool detect.

According to the configuration of Aspect 5, in a case where the controller detects that the disc tool has been worn to a degree to which the replacement is needed, control by the controller causes the robot to automatically replace the disc tool. This enables reduction in the man-hour for the operator by an amount needed to replace 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.