Grinder

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.

The present invention relates to a grinder.

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.

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.

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.

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

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

With reference to, the following will describe an overview of the grinder.is a schematic side view illustrating a configuration of the grinderin accordance with an embodiment of the present invention. The grinderincludes a disc tool, a force sensor, and a controller. The grindermay further include a main body, a driving motor, an inertial measurement unit (IMU), and an input device(see), and a display.

The main bodyconstitutes a main part of the grinder. For the main body, an x-axis direction (direction of an x axis) is regarded as a longitudinal direction. The main bodyhas a first end partand a second end partlocated opposite to the first end part. The first end partis an end part located on a negative direction side in the x-axis direction. The second end partis an end part located on a positive direction side in the x-axis direction.

A gripping partis provided on a side closer to the first end partof the main body. The gripping partis formed so as to have a small diameter that allows easier gripping by an operator. The gripping partmay accommodate therein the IMUand the controller. A power source buttonincluded in the input device(see) may be provided on the negative direction side in the z-axis direction of the gripping part.

The disc toolis attached to a side closer to the second end partof the main body. More specifically, the disc toolis attached to a negative direction side in a z-axis direction of a gear accommodation partprovided on the side closer to the second end partof the main body. The gear accommodation partmay accommodate therein the driving motorand the force sensor. To the gear accommodation part, a side handle to be gripped by an operator may be attached.

The disc toolis a tool for processing, such as polishing, on a workpiece. Examples of the disc toolinclude a grindstone. The disc toolis attached to a spindlewith use of, for example, nuts. The disc toolrotates about the spindle. The spindleserves as a rotation shaft of the disc tool.

The driving motoris a motor configured to rotate the spindle. The spindleis connected to an output shaftof the driving motor.

The force sensordetects moments acting on the disc tool. The force sensoroutputs, to the controller, an output signal indicating the moment detected. The force sensormay detect forces acting on the disc tool. In this case, the force sensoroutputs, to the controller, an output signal indicating the force detected.

The force sensormay be attached to a flange partprotruding from an outer peripheral part of the driving motor. In a center part of the force sensor, a through holethrough which the output shaftof the driving motorand the spindleare inserted is formed.

In the present embodiment, a six-axis force sensor is used as the force sensor. The force sensordetects 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. Here, the x-axis direction is a direction from the first end partto the second end partof the main body. The z-axis direction is a direction parallel to an axis direction of the spindleof the disc toolwhich 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.

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

The displaydisplays an image indicating a posture of the disc toolwith respect to the workpiece. Examples of the displayinclude a display panel. The displayis provided on the main body. In the present embodiment, the displayis provided on the gripping part. The displayis provided in a position visible to an operator gripping the gripping part.

The controllercontrols the parts of the grinder.

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

The controllerincludes a processor, a primary memory, a secondary memory, and an input/output IF, as illustrated in. The processor, the primary memory, the secondary memory, and the input/output IFare connected with each other via a bus. Examples of a device usable as the controllerinclude a workstation.

The secondary memorystores a control program P. The processorloads, on the primary memory, the control program P stored in the secondary memory. The processorthen carries out processes included in process methods Mand M(described later) in accordance with instructions included in the control program P loaded on the primary memory. The secondary memorymay store teaching data TD generated by the grinder. The teaching data TD is data for causing a robot including the disc toolto process the workpiece.

Examples of a device usable as the processorinclude a central processing unit (CPU). Examples of a device usable as the primary memoryinclude a semiconductor random access memory (RAM). Examples of a device usable as the secondary memoryinclude a hard disk drive (HDD).

The input/output IFis an interface for communicating with the force sensor, the IMU, the input device, the display, an output device, and an inverter. Examples of the input/output IFinclude a universal serial bus (USB), an advanced technology attachment (ATA), a small computer system interface (SCSI), serial communication, and the like.

The input deviceis a device that can receive an input from the operator. The input devicemay be constituted by, for example, a button, a switch, a touch panel, or the like. In the present embodiment, the input deviceincludes the power source button.

The grindermay include the output deviceconfigured to output an alerting sound or a voice. Examples of the output deviceinclude speakers and buzzers.

The grindermay further include the inverter. The invertercontrols a rotation speed of the driving motor. The controllercarries out pulse width modulation (PWM) control over the inverter. Specifically, the controllersets a duty ratio, and outputs, via the input/output IF, a PWM signal generated on the basis of the set duty ratio, to the inverter. The invertercontrols current supplied to the driving motorby applying voltage generated on the basis of the inputted PWM signal to the driving motor. The voltage applied by the inverteris controlled, thereby controlling the rotation speed of the driving motor.

Next, with reference to, the following will describe one example of a process method Mcarried out by the controller.is a flowchart illustrating one example of the process method Mcarried out by the controller.

First, the processorcarries out an obtaining process S. In the obtaining process S, the processorobtains, via the input/output IF, an output signal outputted from the force sensor. In the obtaining process S, the processormay obtain an output signal outputted from the IMU.

Subsequently, the processorcarries out a detection process S. In the detection process S, the processordetects a posture of the disc toolwith respect to the workpieceon the basis of the output signal obtained from the force sensorin the obtaining process S. In the detection process S, the processordetects an angle between the surfaceof the workpieceand the disc toolas the posture of the disc tool.

In the detection process S, the processormay detect an inclination of the disc toolwith respect to the workpiecein a plane including the x axis among the planes orthogonal to the surface of the workpiece, on the basis of the moment My obtained. For example, as illustrated in, when the moment My acts on the disc tool, the disc toolinclines about the y-axis direction with respect to the surfaceof the workpiece. The angle θillustrated inis an angle of the inclination of the disc toolwith respect to the workpiecein the plane including the x axis among the planes orthogonal to the surface of the workpiece. The angle θhas a magnitude differing in accordance with the value of the moment My acting on the disc tool. The processordetects a posture of the disc toolwith respect to the workpieceby detecting the magnitude of the angle θ.

In the detection process S, the processormay detect an inclination of the disc toolwith respect to the workpiecein a plane including the y axis among the planes orthogonal to the surfaceof the workpiece, on the basis of the moment Mx obtained. For example, as illustrated in, when the moment Mx acts on the disc tool, the disc toolinclines about the x-axis direction with respect to the surfaceof the workpiece. The angle θillustrated inis an angle of the inclination of the disc toolwith respect to the workpiecein a plane including the y axis among the planes orthogonal to the surfaceof the workpiece. The angle θhas a magnitude differing in accordance with the value of the moment Mx acting on the disc tool. The processordetects a posture of the disc toolwith respect to the workpieceby detecting the magnitude of the angle θ. In a case where the workpieceis processed with the disc toolinclined about the y-axis direction, the processormay detect a variation in a thrust force in the X-axis direction of the disc toolon the basis of the moment Mx obtained.

In the detection process S, the processormay detect an angle between the surfaceof the workpieceand the disc toolon 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 S. In the detection process S, the processormay detect an amount of radial runout of the disc toolin the y-axis direction on the basis of an output signal indicating the obtained force Fy in the y-axis direction. The processormay detect a thrust force of the disc tooltoward 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 S, the processormay detect a pressing force of the disc toolagainst the workpieceon the basis of an output signal indicating the force Fz in the z-axis direction which has been obtained in the obtaining process S.

In the detection process S, the processormay detect a posture of the disc toolwith respect to the workpieceon the basis of the output signal obtained from the IMUin the obtaining process Sand the output signal obtained from the force sensorin the obtaining process S. Specifically, in the detection process S, the processordetects a posture of the main bodyon the basis of an output signal indicating the angular velocity and an output signal indicating the acceleration which have been outputted from the IMU. The processormay detect an angle between the surfaceof the workpieceand the disc toolon the basis of the posture of the main bodydetected by the IMUand the moment My and/or moment Mx detected by the force sensor.

Subsequently, the processorcarries out a displaying process S. In the displaying process S, the processorcauses the displayto display an image indicating whether or not the detected posture of the disc toolis a proper posture determined in advance. The proper posture is a posture permissible as ensuring good processing accuracy by the disc tool. The proper posture may be set in accordance with the type or the outer diameter of the disc tool. The proper posture may be set in accordance with the type or the shape of the workpiece, or the type of processing (e.g., polishing, grinding, or the like) carried out on the workpiece.

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

In the displaying process S, the processormay change a displaying aspect of the displaybetween a case where a value of the moment derived on the basis of the output signal obtained in the obtaining process Shas 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 S, the processormay cause the displayto display an image for guiding the posture of the disc toolin 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 displayallows the operator to recognize that the posture of the disc toolwith respect to the workpiecehas been deviated from a proper posture. This makes it possible to keep a proper posture of the disc toolwith respect to the workpiece.

Next, the processorcarries out a notification process S. In the notification process S, the processorcarries out notification using the output devicein 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 S, the processoroutputs an alerting sound or a voice from the output device to notify the operator that the posture of the disc toolhas been deviated from a proper posture. In the notification process S, the processormay 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 toolis deviated from a proper posture. In the notification process S, the output devicemay output a voice to guide the posture of the disc toolin a direction for correcting the posture to a proper posture.

The controllercarrying out the notification process Sthe operator to recognize that the posture of the disc toolwith respect to the workpiecehas been deviated from the proper posture. This makes it possible to keep a proper posture of the disc toolwith respect to the workpiece.

With reference to, the following will describe one example of the image displayed on the displayin the displaying process S.is a schematic view for explaining one example of an image displayed on the display.

The reference numeralofillustrates one example of an image showing a posture of the disc toolwith respect to the workpiecewhich has been detected on the basis of the moment My. As illustrated by the reference numeralin, the displaydisplays a posture imageshowing the posture of the disc toolwith respect to the workpiecewhich has been detected on the basis of the moment My. The posture imageis displayed at an angle corresponding to the detected posture of the disc tool. The displaymay also display reference linesto.

The reference lineis a line indicating that the disc toolis parallel to the surfaceof the workpiece. The reference lineis a line indicating that the disc toolis inclined by a first angle with respect to the workpiece. The reference lineis a borderline indicating whether or not the inclination of the disc toolwith respect to the workpiecefalls within a permissible range. The reference lineis a line indicating that the disc toolis inclined by a second angle with respect to the workpiece. The reference lineis a borderline indicating whether or not the inclination of the disc toolwith respect to the workpiecefalls within an abnormal range.

When the posture imageis located between the reference lineand the reference line, the posture imagemay be displayed in a blueish color considering that the posture of the disc toolfalls within a permissible range. When the posture imageis located between the reference lineand the reference line, the posture imagemay be displayed in a yellowish color considering that the posture of the disc toolfalls outside a permissible range. When the posture imageis located above the reference line, the posture imagemay be displayed in a reddish color considering that the posture of the disc toolclearly falls outside a permissible range. This enables the operator to recognize an inclination state of the disc toolwith respect to the workpieceabout the y-axis direction.

The reference numeralofillustrates one example of an image showing a posture of the disc toolwith respect to the workpiecewhich has been detected on the basis of the moment Mx. As illustrated by the reference numeralin, the displaydisplays a posture imageshowing a posture of the disc toolwhich has been detected on the basis of the moment Mx and a reference line. The posture imageis displayed at an angle corresponding to the detected posture of the disc tool. The reference lineis a line indicating that the disc toolis parallel to the surfaceof the workpiece. This enables the operator to recognize an inclination state of the disc toolwith respect to the workpieceabout the x-axis direction.

The reference numeralofillustrates one example of an image showing a force acting on the disc toolon the basis of the force Fx, the force Fy, and the force Fz which have been detected by the force sensor. The displaydisplays a force displaying imageshowing the force Fx, a force displaying imageshowing the force Fy, and a force displaying imageshowing the force Fz. The displaymay display one of the force displaying imagesto.

The force displaying imageincludes a permission displaying partindicating that the force Fx falls within a permissible range and abnormality displaying partsandeach indicating that the force Fx falls outside the permissible range. The permission displaying partis located between the abnormality displaying partand the abnormality displaying part. In a case where the force Fx falls within the permissible range, the permission displaying partmay 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 partmay 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 partmay light up in a warm color.

The force displaying imagemay 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 imagemay 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.