ELECTRIC TOOTHBRUSH, SYSTEM, BRUSH POINT DETECTION METHOD AND PROGRAM

Abstract

Electric toothbrush (90) comprising: a main body (1) having, along its longitudinal axis, a head section (4) having a brush side into which brush bristles (210) are inserted, a handle section (5) to be held by a human hand, and a neck section (3) configured to connect the head section (4) and the handle section (5); a gyroscope sensor (16) located within the main body (1) and configured to detect an angular velocity of the main body (1); a brush point detection unit configured to obtain a translational position of a brush point in a dentition based on an output from the gyroscope sensor (16); and a receiving unit capable of receiving a setting parameter from outside the main body (1), wherein the brush point detection unit provides an approximation curve curved according to the dentition as a curve,which is equivalent to a part of an ellipse expressed by a function y = b[{1 - (x / a)2}1 / 2- 1] using positive coefficients a and b, or is set as a parabola expressed by a function 4py = x2 using a negative coefficient p, in a data space where a rectangular xy coordinate system is defined, sets the coefficients a and b or the coefficient p variably according to the setting parameter received via the receiving unit, based on the output from the gyroscope sensor (16) obtains an angle formed by a longitudinal axis of the main body in a state where the brush bristles (210) of the head section (4) touch the brushing point of the teeth, with respect to the longitudinal axis of the main body (1) in a state where the brush bristles (210) of the head section (4) touch a reference position of the teeth, and based on the angle obtains a corresponding point,which corresponds to the brushing point on the approximation curve, in order to use the coordinates of the corresponding point as the translation position of the brushing point.

Description

Technical FieldThe present invention relates to an electric toothbrush, a system and a brush location detecting method capable of detecting a brush location in a denture.The present invention also relates to a program for causing a computer to execute the brush location detection method.Prior ArtConventionally, for example, an electric toothbrush disclosed in JP 2009-240 759 A has an acceleration sensor in a toothbrush main body, and a brushing site in a denture (which in this document represents a translation position in a plane defined by the denture) is obtained during dentifrice cleaning by calculating amounts of movement in an x-axis direction, a y-axis direction, and a z-axis direction by performing second-order integration on respective dynamic acceleration components in the x-axis direction, y-axis direction, and z-axis direction obtained from the output of the acceleration sensor.Further, this document discloses that, based on a gravity acceleration component obtained from an output of the acceleration sensor, a direction about a longitudinal axis (y-axis) of the toothbrush is obtained (which is referred to as a "brush angle" in this document). Alternatively, it is also disclosed that a toothbrush main body is further provided with a gyro sensor (gyroscope), and an output of the gyro sensor is cumulatively added (integrated) to obtain a brush angle. Based on the brush angle obtained in this manner, it can be recognized which of a front surface, a rear surface, and a chewing surface of the tooth is being brushed.CN 1 05 029 891 A discloses a method for correcting brush movement detection comprising the following steps:Step 1: Receiving an angular velocity of the user's brush movement and its change and / or an acceleration and its change;Step 2: identifying brush motion as a plurality of different regions according to the angular velocity of brush motion and its change and / or acceleration and its change; and determining the duration of brush motion, for each region, the angle formed from the toothbrush to the tooth surface of the inner tooth, and the uniformity of brush motion;Step 3: Grasp the effectiveness of brushing operation according to the duration of brushing operation in each area, the angle between the toothbrush and the tooth surface of the tooth in the area, and the uniformity of brushing operation.SUMMARY OF THE INVENTIONTechnical ProblemsHowever, in the electric toothbrush of JP 2009-240 759 A, a vibration component from a drive motor that vibrates the brush (brush bristles) is included as noise in the output of the acceleration sensor. Further, since the dynamic acceleration component obtained from the output of the acceleration sensor is integrated in the second order to obtain the translation position of the brush, it is considerably affected by noise in the calculation process. For this reason, there is a problem that the accuracy of the obtained translation position of the brush site is not good enough.Therefore, it is an object of the present invention to provide an electric toothbrush, a system, and a brush location detection method capable of accurately obtaining a translation position of the brush location in a denture.It is also an object of the present invention to provide a program for causing a computer to perform the brush location detection method.Solutions to the ProblemsIn order to solve the above problem, an electric toothbrush according to the present invention comprises:a main body having, along its longitudinal axis direction, a head portion having a brush side into which brush bristles are inserted, a grip portion to be held by a human hand, and a neck portion configured to connect the head portion and the grip portion;a gyro sensor mounted inside the main body and configured to detect an angular velocity of the main body;a brush location detecting unit configured to obtain a translation position of a brush location in a denture based on an output from the gyro sensor; anda receiving unit capable of receiving a setting parameter from outside the main body,wherein the brush spot detecting unitan approximation curve curved according to the denture as a curve equivalent to a part of an ellipse expressed by a function y = b[{1-(x / a) 2}1 / 2- 1] using positive coefficients a and b, or as a parabola expressed by a function 4py = x 2 using a negative coefficient p, in a data space in which an xy rectangular coordinate system is defined,variably adjusting the coefficients a and b or the coefficient p according to the adjustment parameter received via the receiving unit,based on the output from the gyro sensor, an angle formed by a longitudinal axis of the main body in a state in which the brush bristles of the head portion contact the brushing location of the denture with respect to the longitudinal axis of the main body in a state in which the brush bristles of the head portion contact a reference position of the denture, andbased on the angle, a corresponding point corresponding to the brush location on the approximate curve is obtained to use coordinates of the corresponding point as the translation position of the brush location.In the present specification, the "brushing site" refers to a site that is brushed with the brush bristles described above at multiple sites (that contact the brush bristles) defined by dividing surfaces of the denture in the oral cavity. The brushing site of the denture is specified by a combination of a translation position in the real space in which the denture exists and which of the front surface, the rear surface and the chewing surface of the denture is brushed.The "reference position" of the denture refers to a certain position as a reference for measuring the angle of the denture.In the electric toothbrush according to the present invention, the brush location detecting unit obtains the translation position of the brush location of the denture based on the output of the gyro sensor. In other words, the brush location acquisition unit sets an approximation curve curved according to the denture as a curve equivalent to a part of an ellipse expressed by a function y=b[{1-(x / a) 2}1 / 2- 1] using positive coefficients a and b or as a parabola expressed by a function 4py=x 2 using a negative coefficient p, in a data space in which an xy rectangular coordinate system is defined. In addition, the brush location acquisition unit variably sets the coefficients a and b or the coefficient p according to the setting parameter received via the reception unit. Thereafter, the brush location detection unit obtains an angle formed by a longitudinal axis of the main body in a state where the brush bristles of the head portion contact the brush location of the denture with respect to the longitudinal axis of the main body in a state where the brush bristles of the head portion contact the reference position of the denture, based on the output of the gyro sensor. Thereafter, the brush location acquisition unit obtains, based on the angle, a corresponding point corresponding to the brush location on an approximation curve, and coordinates of the corresponding point are used as the translation position of the brush location.With this configuration, since the output of the gyro sensor is an angular velocity, a vibration component from the drive motor that vibrates the brush (brush bristles) is hardly included as noise. Further, since the output of the gyro sensor is an angular velocity, the angle can be obtained by first-order integration and is not easily affected by noise in the calculation process. Therefore, the translation position of the brushing site of the denture can be obtained with high accuracy. In addition, the brush location acquisition unit variably sets the coefficients a and b or the coefficient p according to the setting parameter received via the reception unit. Therefore, the approximate curve can be set appropriately according to the sizes and shapes of the dental arches of various users. In such a case, the translation position of the brushing site of the denture can be obtained with higher accuracy.In the electric toothbrush of an embodiment, the brush position detecting unit sets a reference tangent that contacts a reference point corresponding to the reference position with respect to the approximate curve, sets a movable tangent that forms the angle with respect to the reference tangent and contacts the approximate curve, and obtains a point as the corresponding point where the movable tangent contacts the approximate curve.Here, the "movable tangent" represents a tangent that is variably set when the angle changes, or in other words, when the brushing location of the denture changes.In the electric toothbrush according to the embodiment, the brush position detection unit sets a reference tangent that contacts the approximate curve at a reference point corresponding to the reference position, and sets a movable tangent that forms the angle with respect to the reference tangent and contacts the approximate curve. A point where the movable tangent contacts the approximate curve is obtained as the corresponding point. Thereby, the corresponding point on the approximation curve can be obtained by a relatively simple process.In the electric toothbrush of an embodiment, the reference position of the denture is a center of a front surface of the denture.In the electric toothbrush according to the embodiment, since the reference position of the denture is the center of the front surface of the denture, the user can easily set the brush bristles of the head portion to the reference position where the user is to start brushing his teeth. Further, the brush location detection unit can easily obtain the translation position of the brush location by means of an analytical expression.In another aspect, an electric toothbrush of the present invention comprises:a main body having, along its longitudinal axis direction, a head portion having a brush side into which brush bristles are inserted, a grip portion to be held by a human hand, and a neck portion configured to connect the head portion and the grip portion;a gyro sensor configured to detect an angular velocity of the main body and an acceleration sensor mounted in the main body; anda brush location detecting unit that specifies the brush location of the denture based on the output of the gyro sensor and the output of the acceleration sensor, wherein the brush location detecting unitan angle formed by the longitudinal axis of the main body in a state in which the brush bristles of the head portion contact the brushing site of the denture with respect to the longitudinal axis of the main body in a state in which the brush bristles of the head portion contact a reference position of the denture,based on the angle, a corresponding point corresponding to the brushing spot is obtained on an approximate curve curved according to the denture to use the coordinates of the corresponding point as a translation position of the brushing spot,obtaining a direction in which the brush bristles of the head portion face about the longitudinal axis of the main body based on a direction of gravitational acceleration output from the acceleration sensor, and determines which of a front surface, a rear surface, and a chewing surface of the denture is brushed based on the direction in which the brush bristles of the head portion face; andthe brushing site of the denture specifies which of the front surface, the rear surface, and the chewing surface of the denture is brushed according to a combination of the translation position of the brushing site obtained based on the output from the gyro sensor and a determination result.In the electric toothbrush according to the present invention, the brush location detecting unit obtains an angle formed by the longitudinal axis of the main body in a state where the brush bristles of the head portion contact the brush location of the denture with respect to the longitudinal axis of the main body in a state where the brush bristles of the head portion contact a reference position of the denture, and further obtains, based on the angle, a corresponding point corresponding to the brush location on an approximate curve curved corresponding to the denture to use the coordinates of the corresponding point as a translation position of the brush location. In addition, the brush location detection unit obtains a direction in which the brush bristles of the head portion face about the longitudinal axis of the main body based on the direction of the gravitational acceleration output by the acceleration sensor, and determines which of the front surface, the rear surface, and the chewing surface of the denture is to be brushed according to the direction in which the brush bristles of the head portion face. Then, the brush location acquisition unit specifies the brush location of the denture according to a combination of the translation position of the brush location determined based on the output of the gyro sensor and the determination result which of the front surface, the rear surface, and the chewing surface of the denture is brushed. Thereby, the brushing site of the denture can be accurately specified.In the electric toothbrush of an embodiment, the brush location detection unit calculates a translation movement amount of the main body based on the acceleration of the main body output from the acceleration sensor in each predetermined summary time unit, and performs a first correction process to maintain the translation position of the brush location obtained based on the output from the gyro sensor during a certain summary time unit when the translation movement amount of the main body in the summary time unit is equal to or lower than a predetermined first threshold value.In the present specification, the "translation movement amount" of the main body and the "change amount" of the direction of the longitudinal axis of the main body in a predetermined summary time unit respectively represent a total translation movement and a total change amount during the summary time unit.In the electric toothbrush according to the embodiment, the brush detection unit calculates the translation movement amount of the main body based on the acceleration of the main body output from the acceleration sensor at every predetermined summary time unit. Then, when the translation movement amount of the main body in a summary time unit is equal to or less than a predetermined first threshold value, the brush location acquisition unit performs the first correction process of maintaining the translation position of the brush location obtained based on the output of the gyro sensor in a summary time unit. Therefore, for example, when a user brushing his teeth significantly changes the direction of the longitudinal axis of the main body with almost no translation movement of the main body (particularly, the head portion), the translation position of the brushing site obtained based on the output of the gyro sensor is maintained before and after the change. This allows the accuracy of the obtained translation position of the brushing site to be maintained.In the electric toothbrush of one embodiment, the brush detection unit calculates the translation movement amount of the main body based on the acceleration of the main body output from the acceleration sensor in each predetermined summary time unit, and performs a second correction process to obtain the corresponding point again based on the output from the gyro sensor by shifting to a part corresponding to a translation movement target of the main body in the approximate curve when the translation movement amount of the main body is equal to or greater than a predetermined second threshold value.In the electric toothbrush according to the embodiment, the brush detection unit calculates the translation movement amount of the main body based on the acceleration of the main body output from the acceleration sensor at every predetermined summary time unit. Then, when the translation movement amount of the main body is equal to or greater than a predetermined second threshold value, the brush point detection unit shifts to a portion corresponding to a translation movement target of the main body on the approximation curve, and performs a second correction process for again determining the corresponding point based on the output of the gyro sensor. Therefore, the translation position of the brushing site of the denture can be obtained with high accuracy when the user brushing his teeth performs a translation movement of the main body by sliding from the left cheek side site to the right cheek side site via the front lip site in the upper jaw denture with almost no change in the orientation of the longitudinal axis of the main body.Note that it is desirable to perform both the first correction process and the second correction process in each summary time unit.The electric toothbrush of an embodiment further comprises a transmitting unit configured to transmit data concerning brushing to the outside of the main body.In this specification, the "data concerning brushing" includes largely actual brushing time data for each place (data including a specified brushing place and an actual brushing time associated with the place) and other data concerning brushing.In the electric toothbrush according to the embodiment, the transmitting unit may transmit data concerning brushing to the outside of the main body. In this case, the data may be received by, for example, a computer device provided outside the main body and used for various processes and applications.In another aspect, a system according to the present invention comprises:the above-described electric toothbrush; anda computer device provided outside the main body of the electric toothbrush, wherein the electric toothbrush and the computer device are capable of communicating with each other.The "computer device" may be any device as long as the devices substantially function as a computer. For example, a smartphone, a tablet terminal, and the like may be used.In the system of one embodiment, a brush procedure for brushing each of a plurality of places of the denture is set in a predetermined order for a predetermined set brush time, and the system further includes a brush evaluation unit configured to calculate an evaluation value representing a degree of agreement regarding the brush procedure based on the brush place specified by the brush place acquisition unit.In the system according to the embodiment, the brushing procedure is defined such that a plurality of places of the denture are each brushed in a predetermined order for a predetermined predetermined brushing time. Here, the brush evaluation unit calculates an evaluation value representing a degree of matching with the brush procedure based on the brush location specified by the brush location acquisition unit. Therefore, the user can recognize the degree of matching (or difference) compared to the brushing procedure based on the evaluation value.In another aspect, a brush location detection method of the present invention is a brush location detection method for detecting a brush location brushed by an electric toothbrush in a denture, the electric toothbrush including a main body having, along its longitudinal axis direction, a head portion having a brush side in which brush bristles are inserted, a grip portion to be held by a human hand, and a neck portion configured to connect the head portion and the grip portion, a gyro sensor mounted inside the main body and configured to detect an angular velocity of the main body, and a receiving unit capable of receiving a setting parameter from outside the main body, and the brush location detection method includes:setting an approximation curve curved according to the denture as a curve equivalent to a part of an ellipse expressed by a function y = b[{1-(x / a) 2}1 / 2- 1] using positive coefficients a and b, or as a parabola expressed by a function 4py = x 2 using a negative coefficient p, in a data space in which an xy rectangular coordinate system is defined;adjusting the coefficients a and b or the coefficient p variably according to the adjustment parameter received via the receiving unit;obtaining a differential angle formed by a longitudinal axis of the main body in a state in which the brush bristles of the head portion contact the brushing location of the denture with respect to the longitudinal axis of the main body in a state in which the brush bristles of the head portion contact a reference position of the denture based on an output from the gyro sensor in a real space in which the denture is present; andObtaining, based on the difference angle in the real space, a corresponding point corresponding to the brushing location on the approximation curve set in the data space to use coordinates of the corresponding point as data representing a translation position of the brushing location.In the brush spot detecting method according to the present invention, first, an approximate curve curved according to the denture is set as a curve equivalent to a part of an ellipse expressed by a function y = b[{1-(x / a) 2}1 / 2- 1] using the positive coefficients a and b, or as a parabola expressed by a function 4py = x 2 using the negative coefficient p, in a data space in which an xy rectangular coordinate system is defined. In addition, the coefficients a and b or the coefficient p are variably set according to the setting parameter received from the outside of the electric toothbrush main body via the receiving unit. Thereafter, a differential angle formed by the longitudinal axis of the main body in a state where the brush bristles of the head portion contact the brushing site of the denture with respect to the longitudinal axis of the main body in a state where the brush bristles contact the reference position of the denture is obtained based on an output from the gyro sensor in the real space where the denture exists. Thereafter, based on the difference angle in the real space, a corresponding point corresponding to the brushing location is obtained on the approximate curve set in the data space, and the coordinates of the corresponding point are used as data indicating the translation position of the brushing location.With this configuration, since the output of the gyro sensor is an angular velocity, a vibration component from the drive motor that vibrates the brush (brush bristles) is hardly included as noise. In addition, since the output of the gyro sensor is an angular velocity, the differential angle can be obtained by first-order integration and is not easily affected by noise in the calculation process. Therefore, the translation position of the brushing site of the denture can be obtained with high accuracy. In addition, in this brush location detecting method, the coefficients a and b or the coefficient p are variably set according to the setting parameter received via the receiving unit. Therefore, the approximate curve can be set appropriately according to the sizes and shapes of the dental arches of various users. In such a case, the translation position of the brushing site of the denture can be obtained with higher accuracy.In another aspect, a program of the present invention is a program for causing a computer to execute the above-described brush location detection method.According to the program of the present invention, the above-described brush spot detecting method can be executed by a computer.In still another aspect, a brush location detection method of the present invention is a brush location detection method for detecting a brush location brushed by an electric toothbrush in a denture, the electric toothbrush including a main body having, along its longitudinal axis direction, a head portion having a brush side in which brush bristles are inserted, a grip portion to be held by a human hand, and a neck portion configured to connect the head portion and the grip portion, a gyro sensor configured to detect an angular velocity of the main body, and an acceleration sensor mounted in the main body, and the brush location detection method includes:obtaining an angle formed by the longitudinal axis of the main body in a state in which the brush bristles of the head portion contact the brushing location of the denture with respect to the longitudinal axis of the main body in a state in which the brush bristles of the head portion contact a reference position of the denture based on an output from the gyro sensor;obtaining, based on the angle of a corresponding point corresponding to the brushing site on an approximation curve curved corresponding to the denture, to use the coordinates of the corresponding point as a translation position of the brushing site;obtaining a direction in which the brush bristles of the head portion face about the longitudinal axis of the main body based on a gravitational acceleration output from the acceleration sensor to determine which of a front surface, a rear surface and a chewing surface of the denture is being brushd according to the direction in which the brush bristles of the head portion face; andspecifying the brushing position of the denture based on a combination of the translation position of the brushing position obtained based on the output from the gyro sensor and the determination result which of the front surface, the rear surface and the chewing surface of the denture is brushed.According to the brush location detecting method of the present invention, the brush location of the denture can be specified with high accuracy.In yet another aspect, a program of the present invention is a program that causes a computer to execute the brush location detection method.According to the program of the present invention, the above-described brush spot detecting method can be executed by a computer.Advantageous Effects of the InventionAs is apparent from the above, according to the electric toothbrush, the system and the brush location detecting method of the present invention, a translation position of a brush location of the denture can be obtained with high accuracy.Further, according to the program of the present invention, such a brush spot detecting method can be executed by a computer.Brief Description of the DrawingsFIGS. 1A and 1B are diagrams illustrating an appearance of an electric toothbrush according to an embodiment of the present invention, viewed obliquely from opposite sides. FIG. 2 is a diagram illustrating a longitudinal section when the electric toothbrush is cut along the longitudinal axis direction. FIG. 3 is a diagram illustrating a block configuration of a control system of the electric toothbrush. FIG. 4 is a diagram illustrating a schematic flow of a process for specifying a brush location in a denture executed by the electric toothbrush as a brush location detection method according to an embodiment of the present invention. FIG. 5 is a diagram illustrating a detailed flow of a process (step S 2) for obtaining a translation position of the brush spot described in FIG. 4. FIG. 6 is a diagram illustrating 16 locations of the denture in the oral cavity. FIG. 7A is a diagram illustrating a "standard" approximation curve that is part of an ellipse. FIG. 7B is a diagram illustrating a "long" approximation curve that is part of another ellipse. FIG. 7C is a diagram illustrating a "small" approximation curve that is part of another ellipse. FIG. 8 is a diagram for explaining a differential angle θ formed by a longitudinal axis (Y axis) of a main body in a state where the brush bristles of the head portion contact the brushing site in a denture with respect to the longitudinal axis (Y axis) of the main body in a state where the brush bristles of the head portion contact a reference position of the denture in a real space. FIG. 9 is a diagram for explaining a process of obtaining a corresponding point corresponding to a brushing spot on a "standard" approximation curve in a data space based on the difference angle θ. FIG. 10 is a diagram illustrating a direction of the gravitational acceleration G output from an acceleration sensor as viewed from the head portion side (+Y direction) in a state where the longitudinal axis (Y axis) of the main body is in a horizontal posture. FIG. 11 is a diagram illustrating a state in which the head portion (+Y direction) is arranged leftward with respect to the face of the user as viewed from the user. FIG. 12 is a diagram illustrating a state in which the head portion (+Y direction) is arranged rightward with respect to the face of the user as viewed from the user. FIGS. 13A to 13C are diagrams illustrating a classification for determining which of a front surface, a rear surface, and a chewing surface of a "left rear tooth" in a maxilla denture is being brushed. FIGS. 13D to 13F are diagrams illustrating a classification for determining which of a front surface, a rear surface, and a chewing surface of a "left rear tooth" in a lower jaw denture is being brushed. FIGS. 14A and 14B are diagrams illustrating a classification for determining which of a front surface and a rear surface of a "front tooth" in the upper jaw denture is being brushed. FIGS. 14C and 14D are diagrams illustrating a classification for determining which of a front surface and a rear surface of a "front tooth" in the lower jaw denture is being brushed. FIGS. 15A to 15C are diagrams illustrating a classification for determining which of a front surface, a rear surface, and a chewing surface of a "right rear tooth" in the upper jaw denture is being brushed. FIGS. 15D to 15F are diagrams illustrating a classification for determining which of a front surface, a rear surface, and a chewing surface of a "right rear tooth" in the lower jaw denture is being brushed. FIG. 16 is a diagram illustrating a mode in which a user brushing his teeth performs a substantial change in the direction of the longitudinal axis (Y axis) of the main body in a state in which the translation movement of the head portion is nearly stopped. FIG. 17 is a diagram illustrating a mode in which a user brushing his teeth switches the location to another location and performs a large translation movement of the main body without changing the orientation of the longitudinal axis (Y axis) of the main body. FIG. 18 is a diagram illustrating a flow of a correction process. FIG. 19 is a diagram illustrating a process of obtaining a corresponding point corresponding to a brushing location on a parabola as an approximation curve in a data space based on the difference angle θ. FIG. 20 is a diagram illustrating a configuration of a system including the electric toothbrush and a smartphone.DESCRIPTION OF THE EMBODIMENTHereinafter, embodiments of the present invention will be described in detail with reference to the drawings.(Configuration of Electric Toothbrush)Figs. 1A and 1B illustrate an external appearance of an electric toothbrush (generally indicated by reference numeral 90) of an embodiment according to the present invention as viewed obliquely from opposite sides. This electric toothbrush 90 has a head portion 4 with brush bristles 210 inserted, a grip portion 5 to be held by a human hand, and a neck portion 3 connecting the head portion 4 and the grip portion 5 in the longitudinal axis direction (Y-axis direction). The head portion 4 and the neck portion 3 are integrally configured as a brush member 2 which can be attached to and detached from the grip portion 5. The head portion 4, the neck portion 3 and the grip portion 5 are collectively referred to as a main body 1. The main body 1 has an elongated shape in the Y-axis direction for convenience of brushing the teeth. Note that a charger 100 is illustrated in FIG. 1A.FIG. 2 illustrates a longitudinal section of the electric toothbrush 90 cut along the longitudinal axis (Y axis). The grip portion 5 has a shaft 6 provided to protrude from the outer shell of the grip portion 5 toward the neck portion 3 side. The shaft 6 has a cylindrical shape with a closed tip. In this example, the neck portion 3 of the brush member 2 is engaged and fixed so as to cover the shaft 6. Since the brush member 2 is a consumable part, it is configured to be detachable from the grip portion 5 so that it can be replaced with a new one. On a surface (brush side) 4 aof the head portion 4 of the brush member 2, brush bristles (brushes) 210 in this example are inserted by flocking so as to protrude from the brush side 4 ain the range of about 10 mm to 12 mm. The brush bristles 210 may be welded or bonded instead of flocking.A power switch S for turning on and off the power is provided on an outer surface of the grip portion 5 of the main body 1. Inside the grip portion 5, a motor 10 as a drive source, a drive circuit 12, a rechargeable battery 13 as a power supply unit, a charging coil 14, an acceleration sensor 15, a gyro sensor 16, and the like are mounted. In charging the rechargeable battery 13, the rechargeable battery 13 can be charged in a non-contact manner only by electromagnetic induction by simply disposing the main body 1 on the charger 100 shown in FIG. 1.As shown in FIG. 2, a bearing 203 is provided inside the shaft 6. A tip of an eccentric shaft 30 connected to a rotation shaft 11 of the motor 10 is inserted into the bearing 203. The eccentric shaft 30 has a weight 300 in the vicinity of the bearing 203, and the center of gravity of the eccentric shaft 30 is deviated from the center of rotation. When the drive circuit 12 supplies a drive signal (for example, a pulse width modulation signal) to the motor 10 according to a mode of operation and rotates the rotation shaft 11 of the motor 10, the eccentric shaft 30 also rotates with the rotation of the rotation shaft 11. Therefore, the tip of the eccentric shaft 30 repeatedly collides with an inner wall of the bearing 203, and this vibrates (moves) the brush bristles 210 at high speed.In this example, the acceleration sensor 15 is a commercially available microelectromechanical system (MEMS) type product and outputs a signal representing accelerations of three axes, the X, Y, and Z axes. X, Y, and Z show orthogonal coordinate systems fixed to the main body 1. In this example, as illustrated in FIG. 1A, the X axis is parallel to the brush 4 aside, and the Y axis is oriented in the direction from the grip portion 5 to the head portion 4 in the longitudinal axis direction of the main body 1. In addition, the Z axis is set to coincide with the direction from the brush 4 aside toward the tips of the brush bristles 210. For example, when the main body 1 is disposed on the charger 100, the acceleration vector of gravity is in the -Y direction, and when the tips of the brush bristles 210 are directed downward, the acceleration vector of gravity is in the +Z direction. The output of the acceleration sensor 15 related to each axis is input to a control unit 110 described later and is used to specify the brushing place (the details will be described later).In this example, the gyro sensor 16 is made of a commercially available MEMS type product and outputs a signal indicative of the angular velocity of the X, Y, and Z axes, which are the angular velocity about the Z axis, the angular velocity about the X axis, and the angular velocity about the Y axis. The output of each axis of the gyro sensor 16 is input to the control unit 110 described later, and is used together with the output of the acceleration sensor 15 to specify the brushing site (the details will be described later).Whether the brush bristles 210 actually contact the brush location is detected by a load sensor (not shown, detecting a load acting on the brush bristles 210) provided in the main body 1.FIG. 3 illustrates a block configuration of a control system of the electric toothbrush 90. Within the grip portion 5 of the electric toothbrush 90, in addition to the above-described acceleration sensor 15 and gyro sensor 16, there are provided the control unit 110, a storage unit 115, an operation unit 130, and a notification unit 140, a communication unit 180, and a power supply unit 170 constituting the above drive circuit 12. Note that a drive unit 101 represents the above-described motor 10, the rotation shaft 11, the eccentric shaft 30, the bearing 203, and the weight 300.In this example, the control unit 110 includes a central processing unit (CPU) that is operated by software and performs, in addition to driving the motor 10, a process of specifying a brushing site of the denture and various other processes. Further, the control unit 110 has a built-in timer for time measurement.The operation unit 130 includes the above-described power switch S and operates so that a user can turn on or off the power of the electric toothbrush 90.In this example, the storage unit 115 includes an electrically rewritable nonvolatile memory (EEPROM) capable of storing data in a nonvolatile manner. The storage unit 115 stores a control program for controlling the control unit 110. Further, in this example, the storage unit 115 stores data concerning brushing, such as data indicating the actual brushing time for each location of the denture (referred to as "actual brushing time data") during brushing of the teeth, as a table (to be described later).In this example, the notification unit 140 includes a red light emitting diode (LED) lamp 140R and a green LED lamp 140G (see FIG. 1A ), and notifies progress of brushing compared to a predetermined brushing procedure by turning on and off the LED lamps 140R and 140G. Further, the notification unit 140 may include a buzzer (not shown), and may notify progress of brushing compared to the brushing procedure by sounding the buzzer.The communication unit 180 is controlled by the control unit 110 to transmit, as a transmission unit, various kinds of information (actual brushing time data and the like) to an external device via a network, or receives, as a reception unit, various kinds of information (a setting parameter described later or the like) from an external device via the network to transmit information to the control unit 110. In this example, communication over this network is wireless communication (for example, Bluetooth (BT (registered trademark)) communication, BLE (Bluetooth (registered trademark) low power) communication, or the like). The network is typically, but is not limited to, a home local area network (LAN) or a hospital LAN, and the Internet or the like may be used.The power supply unit 170 includes the above-described rechargeable battery 13, and supplies power (a DC voltage in this example) to each unit in the electric toothbrush 90.(Sites in the denture)In this example, as shown in FIG. 6, the upper and lower dentures 98U and 98L are divided into 16 places SQ 1, SQ 2..., and SQ 16 (the boundaries between adjacent places are indicated by broken lines). The upper jaw denture 98U includes a left cheek side site SQ 1, a left caudation surface site SQ 8 and a left SQ 7 in the left rear tooth region, a front lip site SQ 2 and a front lingual site SQ 6 in the front tooth region, and a right cheek side site SQ 3, a right caudation surface site SQ 4 and a right lingual site SQ 5 in the right rear tooth region. The lower jaw denture 98L includes a left cheek side site SQ 9, a left caudation surface site SQ 16, and a left lingual site SQ 15 in the left rear tooth region, a front lip site SQ 10 and a front lingual site SQ 14 in the front tooth region, and a right cheek side site SQ 11, a right caudation surface site SQ 12, and a right lingual site SQ 13 in the right rear tooth region.The upper jaw denture 98U has six "front teeth" in total, which have three teeth for left and right, respectively. Five are included as "left rear teeth" and "right rear teeth", respectively. These "left rear teeth", "front teeth", and "right rear teeth" divide a range of translation positions along the dental arch. In the upper jaw denture 98U, the range of the "front teeth" is divided into a range of 20 mm from the reference position BP 0, which is the center of the front surface, to the right and left (that is, a range of 40 mm width to the right and left). The "left rear tooth" is divided into a range of more than 20 mm to the left from the center BP 0 on the front surface. The "right rear tooth" is divided into a range of more than 20 mm to the right from the center BP 0 on the front surface. These divisions are corresponding in the lower jaw denture 98L.In summary, the upper jaw denture 98U and the lower jaw denture 98L are divided into the locations along with a range of translation positions along the dental arch and one of the anterior surface, the chewing surface and the posterior surface, as indicated by the following Table 1. Here, the table body of Table 1 indicates reference numerals SQ 1 to SQ 16 from each location determined by the combination of the translation position range ("left rear tooth", "front tooth", or "right rear tooth") listed in the upper part of the table and one of the "front surface", the "chewing surface", and the "rear surface" listed on the side of the table. Note that, for the "front teeth", a location (range) corresponding to the combination with "chewing surface" is not set (which is indicated by "-"). [Table 1] Sites in the dentures [Table 1] Sites in the denturesUpper jaw denturesFront surfaceSQ1SQ2SQ3Chewing surfaceSQ8-SQ4Rear surfaceSQ7SQ6SQ5Lower jaw denturesFront surfaceSQ9SQ10SQ11Chewing surfaceSQ16-SQ12Rear surfaceSQ15SQ14SQ13Note that the locations of the denture are not limited to this example, and smaller locations may be set. For example, locations may be defined by each tooth along the dental arch, or the locations may be defined by a right and left half of each tooth.(Brush Spot Detection Method)FIG. 4 illustrates a schematic flow of a process in which the control unit 110 of the electric toothbrush 90 specifies brushing locations in the dentures 98U and 98L as a brushing location detection method according to an embodiment. In this example, it is assumed that a brushing procedure is set in advance so that brushing is performed in ascending order with respect to the reference numerals from the locations SQ 1 to SQ 8 in the upper jaw denture 98U and then from the locations SQ 9 to SQ 16 in the lower jaw denture 98L in FIG. 6.In the flow of FIG. 4, when the user turns on the power switch S of the electric toothbrush 90, the control unit 110 rotates the motor 10 to oscillate the brush bristles 210. Here, according to the above brushing procedure, at the time (momentary) when the power switch S is turned on, the user applies the brush bristles 210 of the head portion 4 to the reference position BP 0 (see FIG. 8 ) which is the center of the front surface of the denture 98U. The user can easily align the brush bristles 210 of the head portion 4 with this reference position BP0. As described in step S 1 of FIG. 4, the control unit 110 starts measurement of the brushing time by a built-in timer.Thereafter, as described in step S 2, the control unit 110 serves as a brush location detection unit and obtains a translation position of the brush location (represented by the symbol "BP") of the denture 98U or 98L (which is initially limited to the upper jaw denture 98U) based on the output of the gyro sensor 16 (which will be described in detail later).Thereafter, as described in step S 3, the control unit 110 serves as a brush location detection unit, obtains a direction (+Z direction) in which the brush bristles 210 of the head portion 4 face about the longitudinal axis (Y axis) of the main body 1 based on the output of the acceleration sensor 15, and determines whether the brushing is performed on the front surface, the rear surface, or the chewing surface of the denture 98U or 98L based on the direction (+Z direction) in which the brush bristles 210 of the head portion 4 face (which will be described in detail later).Thereafter, as illustrated in step S 4, the control unit 110 serves as a brush location detection unit, and specifies the brush location BP of the denture 98U or 98L according to a combination of the translation position of the brush location BP determined based on the output of the gyro sensor 16 and the determination result whether one of the front surface, the rear surface, or the chewing surface of the denture 98U or 98L is being brushed.Thereafter, as described in step S 5, the control unit 110 determines whether the set brushing time has elapsed for the specified brushing place BP based on the time measurement result by the built-in timer. When the set brushing time for the location BP has not yet elapsed (No in step S 5), the processes of steps S 2 to S 5 are repeated. In this example, the control unit 110 repeats the processing of steps S 2 to S 5 every 0.1 second as a processing time unit.Thereafter, when the set brush time for the specified brush place BP has elapsed (Yes in step S 5), the control unit 110 temporarily displays the green LED lamp 140G included in the notification unit 140 for about 0.2 seconds, for example, to notify the user that the set brush time for the place BP has elapsed (step S 6). If the user continues brushing at the location BP, although the set brushing time is exceeded for example 1 second or more (No at step S7), for example, by temporarily turning on the red LED lamp 140R for about 0.2 second, a warning may be given to the user at step S6 to prevent over brushing, for example. Further, while the LED lamp 140G or 140R is temporarily lit, the progress of brushing regarding the brushing procedure may be notified by the sound of a buzzer included in the notification unit 140.Thereafter, when the user moves the head portion 4 to the "next place" of the specified brushing place BP of the denture 98U or 98L (Yes in step S 7), the control unit 110 associates the specified brushing place BP and the actual brushing time for the place BP, and records the associated data as actual brushing time data for each place in a table prepared in the storage unit 115 (step S 8). Note that the storage unit 115 may also record other information related to brushing.Returning to step S1, the control unit 110 then starts measurement of the brushing time by the built-in timer for the "next place".In this manner, the brushing location BP of the denture 98U or 98L is sequentially specified, and the actual brushing time data for each location is sequentially recorded. Then, when the above brushing procedure is completed or the power switch S is turned off (step S9), the process ends.(Process to Obtain the Translation Position of Brush)The process in step S 2 described in FIG. 4 (a process for obtaining a translation position of a brush point based on an output of the gyro sensor 16) will be described with reference to the detailed flow in FIG. 5. i) First, as illustrated in step S 21 of FIG. 5, the control unit 110 serves as a brush point detection unit and sets an approximation curve E 1 equivalent to a part of an ellipse E curved corresponding to the denture 98U or 98L as illustrated in FIG. 9 in the data space DS where the xy-rectangular coordinate system is defined.More specifically, as is known in the dental field, the dental arch can be approximated by a part of an ellipse (Tsutomu SAKA, "The studies on the factor analysis of the morphological variation of the palatal vault-In relation to the maxilo-fadai-cranial pattern-", Journal of Japanese Society of Oral and Maxillacial Surveys, B. 34, No. 3, pp. 451-469, March 1988). Therefore, in this example, as illustrated in FIG. 7A, a part having the depth D 1≈50 mm and the width W 1≈70 mm of the ellipse E having the minor axis 2 a=71.76 mm and the major axis 2 b=128.2 mm is used as the approximation curve E 1 to correspond to a "standard" denture.In this example, as illustrated in FIG. 9, the approximate curve E 1 running in a convex manner is set to contact the x-axis at an origin O (0, 0) as a reference point. The ellipse E touching the origin O(0,0) in a convex manner with respect to the x-axis can be expressed as: where a and b are positive coefficients (i.e., a>0 and b>0). Specifically, the approximate curve E 1 equivalent to the upwardly convex part of the ellipse E is expressed by an explicit function as:In this case, the approximation curve E 1 can be set by determining the coefficients a and b in a manner approximating the actual denture 98U or 98L. Consequently, the corresponding point P representing the translation position of the brush point can be accurately obtained on the approximation curve E1.Note that the process of step S 21 may be executed only once after the power is turned on, instead of being performed each time the process of step S 2 is performed. Also, in this example, the setting of the approximate curve E 1 in the data space DS represents that the coordinates (x i, y i) ( i=0, 1, 2,... ) of the point string constituting the approximate curve E 1 are stored in the storage unit 115. Further, the data of the approximate curve E 1 may be stored in the storage unit 115 in advance.ii) Thereafter, as illustrated in step S 22 of FIG. 5, the control unit 110 serves as a brush location detection unit, and obtains a differential angle θ formed by the longitudinal axis (Y axis) Y 1 of the main body 1 in a state in which the brush bristles 210 of the head portion 4 contact the brush location BP of the denture 98U or 98L (the denture 98U is illustrated in the example of FIG. 8 ) with respect to the longitudinal axis (Y axis) Y 0 of the main body 1 in a state in which the brush bristles 210 of the head portion 4 contact the reference position BP 0 of the denture 98U in a real space RS, where the denture 98U or 98L is present, as shown in FIG. 8, based on the output from the gyro sensor 16.Specifically, in this example, as described above, when the power switch S is turned on (currently), the user sets the brush bristles 210 of the head portion 4 to the reference position BP 0, which is the center of the front surface of the denture 98U. Thereafter, according to the brushing procedure, the user continues to set the brush bristles 210 of the head portion 4 to other locations (brushing locations) BP of the denture 98U or 98L. In this procedure, an angle (differential angle) θ is formed by the longitudinal axis (Y axis) Y 1 of the main body 1 in a state where brush bristles 210 of the head portion 4 contact the brushing location BP of the denture 98U or 98L with respect to the longitudinal axis (Y axis) Y 0 of the main body 1 in a state where the brush bristles 210 of the head portion 4 contact the reference position BP 0 of the denture 98U. Here, since the output of the gyro sensor 16 is an angular velocity, the differential angle θ can be obtained by first-order integration.Note that the control unit 110 may perform the process of step S 21 and the process of step S 22 in FIG. 5 in parallel, or may perform the process of step S 22 before the process of step S 21.iii) Thereafter, as described in steps S 23 and S 24 of FIG. 5, the control unit 110 serves as a brush location acquisition unit, sets a reference tangent (corresponding to the x-axis in this example) that touches the approximate curve E 1 at the origin O corresponding to the reference position BP 0 in the data space DS, and sets a movable tangent Q that forms the difference angle θ with respect to the reference tangent (x-axis) and touches the approximate curve E 1, as illustrated in FIG. 9. Here, the movable tangent Q is variably set as the differential angle θ changes, in other words, as the brushing location BP of the denture 98U or 98L changes. Then, the control unit 110 obtains a point where the movable tangent Q contacts the approximate curve E 1 as a corresponding point P (step S 25 in FIG. 5 ). Thereby, the corresponding point P on the approximation curve E 1 can be obtained by a relatively simple process.Specifically, as shown in FIG. 9, it is assumed that a certain moving tangent Q contacts the approximate curve E 1 at a point P (x 1, y 1). The equation of the movable tangent Q can be expressed by a mathematical formula:Further, since the point P (x 1, y 1) is a point on the ellipse E, the following equation is established.Here, when the slope of the movable tangent Q is m, based on the equation (Eq. 2) m is expressed as follows:Using equations (Eq. 3) and (Eq. In FIG. 4), the coordinates x 1, y 1 of a touch point P with respect to the approximation curve E 1 can be respectively expressed using the slope m as follows:Further, the angle formed by the movable tangent Q with respect to the x-axis is regarded as θ (assuming that the counterclockwise direction is positive, and -π / 2≤θ≤π / 2), and the slope is expressed as a slope m=tanθ. Then, the equation (Eq. 5) expressed as follows:According to this equation (Eq. In FIG. 6 ), based on the difference angle θ in the real space RS, the coordinates (x 1, y 1) of the corresponding point P corresponding to the brushing location BP are obtained on the approximation curve E 1 in the data space DS. The coordinates (x 1, y 1) of the corresponding point P are used as data representing the translation position of the brush location BP. In this way, the translation position of the brush BP can be easily determined by the analytical equation (Eq. 6). Specifically, the equation (eq. This is also simplified by setting the center of the front surface of the denture 98U as the reference position BP 0. Note that the center of the front surface of the denture 98L may be set as the reference position BP 0.In such a case, since the output of the gyro sensor 16 is an angular velocity, the vibration component from the drive unit 101 (motor 10) is hardly included as noise. Further, since the output of the gyro sensor 16 is an angular velocity, the differential angle θ can be obtained by first-order integration, and is hardly affected by noise in the calculation process. Therefore, the translation position of the brushing site BP of the denture 98U or 98L can be obtained with high accuracy.When the coordinates (x 1, y 1) of the corresponding point P are determined according to the above equation (Eq. As the position of translation of the brush position BP is determined as which of "left rear tooth", "front tooth", or "right rear tooth" in Table 1.For example, when the difference angle θ in the real space RS is 60 degrees and hence the coordinates (x 1, y 1) of the corresponding point P in the data space DS are almost equal to (-25.0, -18.1) (the unit is mm), the translation position of the brushing site BP is the site "left rear tooth". When the difference angle θ in the real space RS is 45 degrees and hence the coordinates (x 1, y 1) of the corresponding point P in the data space DS are almost equal to (-17.5, -8.2) (the unit is mm), the translation position of the brushing location BP is the location "front tooth". When the difference angle θ in the real space RS is -60 degrees and hence the coordinates (x 1, y 1) of the corresponding point P in the data space DS are almost equal to (25.0, -18.1) (the unit is mm), the translation position of the brushing site BP is the "right rear tooth" site. (Determination of which of the front surface, the rear surface, and the chewing surface is being brushed)Next, the process of step S 3 in FIG. 4 (processing to obtain the direction (+Z direction) in which the brush bristles 210 of the head portion 4 face about the longitudinal axis (Y axis) of the main body 1 based on the output of the acceleration sensor 15 and to determine which of the front surface, the rear surface, and the chewing surface of the denture 98U or 98L is brushed corresponding to the direction (+Z direction) in which the brush bristles 210 of the head portion 4 face) will be described in detail with reference to FIGS. 6 and 10 to 15.In the brushing procedure described with reference to FIG. 6, brushing is performed in ascending order with respect to the reference numerals from the locations SQ 1 to SQ 8 in the upper jaw denture 98U and then from the locations SQ 9 to SQ 16 in the lower jaw denture 98L. In addition, in the brushing procedure, each location SQ 1 to SQ 16 is, as indicated in brackets (HL) or (HR) in FIG. 6, provided that the head portion 4 (+Y direction) is set to face leftward or rightward with respect to the user's face while the longitudinal axis (Y axis) of the main body 1 is kept horizontal. The symbol HL represents that the head portion 4 (+Y direction) is arranged leftward with respect to the user's face as illustrated in FIG. 11. On the other hand, the symbol HR represents that the head portion 4 (+Y direction) is arranged rightward with respect to the user's face as illustrated in FIG. 12. As can be seen from FIG. 6, when brushing the locations SQ 1, SQ 7, SQ 8, SQ 9, SQ 15, and SQ 16 classified as "left rear teeth", the head portion 4 (+Y direction) is set to be located leftward HL. On the other hand, when brushing the locations SQ 3, SQ 4, SQ 5, SQ 11, SQ 12, and SQ 13 classified as "right rear teeth", the head portion 4 (+Y direction) is set to be located rightward HR. These adjustments are necessarily required when brushing the "left rear tooth" or the "right rear tooth". Further, in brushing the locations SQ 2, SQ 6, SQ 10, and SQ 14 classified as "front teeth", they are respectively set in the same direction as the direction of brushing the immediately preceding location in this example. In other words, when brushing the locations SQ 2 and SQ 10, the head portion 4 (+Y direction) is set to be arranged leftward in the direction HL. Further, when brushing the locations SQ 6 and SQ 14, the head portion 4 (+Y direction) is set to be arranged in the right direction HR.FIG. 10 illustrates the direction of the gravitational acceleration G output by the acceleration sensor 15 as viewed from the head portion 4 (+Y direction) in a state where the longitudinal axis (Y axis) of the main body 1 is in a horizontal posture. As can be seen from FIG. 10, based on the direction of the gravitational acceleration G output from the acceleration sensor 15, the direction in which the brush bristles 210 of the head portion 4 face about the longitudinal axis (Y axis) of the main body 1 (+Z direction) is expressed as a rotation angle φ about the longitudinal axis. In this example, it is assumed that the rotation angle φ about the longitudinal axis is 0 degrees in the downward vertical direction, and takes values within a range between 0 degrees and 359.99 degrees (up to two decimal places) in the counterclockwise direction as viewed from the head portion 4 (+Y direction) in a state where the longitudinal axis (Y axis) of the main body 1 is in a horizontal posture as illustrated in FIG. 10.FIGS. 13A to 13C illustrate the locations used in determining which of the front surface, the rear surface, and the chewing surface of the "left rear tooth" in the upper jaw denture 98U is being brushed. In the state where the longitudinal axis (Y axis) of the main body 1 takes a horizontal posture, the head portion 4 (+Y direction) is disposed leftward HL with respect to the user's face, and the rotation angle φ about the longitudinal axis is within the range of 90 to 135 degrees, as illustrated in FIG. 13A, it is determined that the front surface (i.e., the left cheek side location) SQ 1 is brushed. In the same state, when the rotation angle φ about the longitudinal axis is within the range of 135 to 225 degrees as illustrated in FIG. 13B, it is determined that the chewing surface (i.e., the left chewing surface location) SQ 8 is being brushed. In the same state, when the rotation angle φ about the longitudinal axis is within the range of 225 to 270 degrees as illustrated in FIG. 13C, it is determined that the back surface (i.e., the left lingual site) SQ 7 is brushed.In the same manner, FIGS. 13D to 13F illustrate classifications used in determining which of the front surface, the rear surface, and the chewing surface of the "left rear tooth" is being brushed in the lower jaw denture 98L. In the state where the longitudinal axis (Y axis) of the main body 1 takes a horizontal posture, the head portion 4 (+Y direction) is disposed leftward HL with respect to the user's face, and the rotation angle φ about the longitudinal axis is within the range of 45 to 90 degrees, as illustrated in FIG. 13D, it is determined that the front surface (i.e., the left cheek side location) SQ 9 is brushed. In the same state, when the rotation angle φ about the longitudinal axis is within the range of 0 to 45 degrees or 315 to 359.99 degrees as shown in FIG. 13E, it is determined that the chewing surface (i.e., the left chewing surface location) SQ 16 is brushed. In the same state, when the rotation angle φ about the longitudinal axis is within the range of 270 to 315 degrees as illustrated in FIG. 13F, it is determined that the back surface (i.e., the left lingual site) SQ 15 is brushed.FIGS. 14A and 14B illustrate the locations used in determining which of the front and rear surfaces of the "front tooth" of the upper jaw denture 98U is being brushed. In a state where the longitudinal axis (Y axis) of the main body 1 takes a horizontal posture, the head portion 4 (+Y direction) is disposed leftward HL with respect to the user's face, and the rotation angle φ about the longitudinal axis is within the range of 90 to 180 degrees as illustrated in FIG. 14A, it is determined that the front surface (i.e., the front lip location) SQ 2 is brushed. In the same state, when the rotation angle φ about the longitudinal axis is within the range of 180 to 270 degrees, which is outside the brushing procedure, it is determined that the back surface (and hence the front lingual site) SQ 6 is brushed. On the other hand, in a state where the longitudinal axis (Y axis) of the main body 1 takes a horizontal posture, the head portion 4 (+Y direction) is disposed rightward HR with respect to the user's face, and the rotation angle φ about the longitudinal axis is within the range of 90 to 180 degrees, as illustrated in FIG. 14B, it is determined that the rear surface (i.e., the front lingual location) SQ 6 is brushed. Here, in this state, when the rotational angle φ about the longitudinal axis is within the range of 180 to 270 degrees outside the brushing procedure, it is determined that the front surface (and thus the front lip position) SQ 2 is brushed.In the same manner, FIGS. 14C and 14D illustrate the locations used in determining which of the front and rear surfaces of the "front teeth" of the lower jaw denture 98L is being brushed. In a state where the longitudinal axis (Y axis) of the main body 1 takes a horizontal posture, the head portion 4 (+Y direction) is disposed leftward HL with respect to the user's face, and the rotation angle φ about the longitudinal axis is within the range of 0 to 90 degrees, as illustrated in FIG. 14C, it is determined that the front surface (i.e., the front lip location) SQ 10 is brushed. Here, in the same state, when the rotation angle φ about the longitudinal axis is within the range of 270 to 359.99 degrees, which is outside the brushing procedure, it is determined that the back surface (i.e., the front lingual site) SQ 14 is brushed. On the other hand, in a state where the longitudinal axis (Y axis) of the main body 1 takes a horizontal posture, the head portion 4 (+Y direction) is disposed rightward HR with respect to the user's face, the rotation angle φ about the longitudinal axis is within the range of 0 to 90 degrees, as illustrated in FIG. 14D, it is determined that the rear surface (i.e., the front lingual site) SQ 14 is brushed. Here, in the same state, when the rotation angle φ about the longitudinal axis is within the range of 270 to 359.99 degrees outside the brushing procedure, it is determined that the front surface (i.e., the front lip position) SQ 10 is brushed.FIGS. 15A to 15C illustrate locations used in determining which of the front surface, the rear surface, and the chewing surface of the "right rear tooth" in the upper jaw denture 98U is being brushed. In a state where the longitudinal axis (Y axis) of the main body 1 takes a horizontal posture, the head portion 4 (+Y direction) is disposed rightward HR with respect to the user's face, the rotation angle φ about the longitudinal axis is in the range of 90 to 135 degrees, as illustrated in FIG. 15A, it is determined that the back surface (i.e., the right lingual location) SQ 5 is brushed. In the same state, when the rotation angle φ about the longitudinal axis is within the range of 135 to 225 degrees as illustrated in FIG. 15B, it is determined that the chewing surface (i.e., the right chewing surface location) SQ 4 is being brushed. In the same state, when the rotation angle φ about the longitudinal axis is within the range of 225 to 270 degrees as illustrated in FIG. 15C, it is determined that the front surface (i.e., the right cheek side location) SQ 3 is brushed.In the same manner, FIGS. 15D to 15F illustrate locations used in determining which of the front surface, the rear surface, and the chewing surface of the "right rear tooth" is being brushed in the lower jaw denture 98L. In a state where the longitudinal axis (Y axis) of the main body 1 takes a horizontal posture, the head portion 4 (+Y direction) is disposed rightward HR with respect to the user's face, and the rotation angle φ about the longitudinal axis is within the range of 45 to 90 degrees, as illustrated in FIG. 15D, it is determined that the back surface (i.e., the right lingual location) SQ 13 is brushed. In the same state, when the rotation angle φ about the longitudinal axis is within the range of 0 to 45 degrees or 315 to 359.99 degrees as shown in FIG. 15E, it is determined that the chewing surface (i.e., the right chewing surface location) SQ 12 is brushed. In the same state, when the rotation angle φ about the longitudinal axis is within the range of 270 to 315 degrees as illustrated in FIG. 15F, the front surface (i.e., the right cheek side location) SQ 11 is brushed.In summary, the correspondence relationship between the rotation angle φ about the longitudinal axis and the front surface, the rear surface, and the chewing surface can be described as in the following Table 2. Here, the table body of Table 2 indicates the rotation angle φ about the longitudinal axis in a state where the head portion 4 (+Y direction) is disposed to the left HL or to the right HR. The page of Table 2 represents the front surface, the chewing surface, and the rear surface of the "left rear tooth", and the front and rear surfaces of the "front tooth", and the front surface, the chewing surface, and the rear surface of the "right rear tooth" of the upper jaw denture 98U or the lower jaw denture 98L corresponding to the rotational angle φ about the longitudinal axis. The symbol "-" in the body of Table 2 indicates that brushing cannot be performed. The angle of rotation φ in brackets ( ) indicates that brushing can take place but is outside the brushing procedure described above. [Table 2] Correspondence relationship between the rotation angle φ about the longitudinal axis and the front surface, the rear surface, and the chewing surface [Table 2] Correspondence relationship between the rotation angle φ about the longitudinal axis and the front surface, the rear surface, and the chewing surfaceUpper jaw denturesLeft Back ToothFront surface90 up to 135 degrees-Chewing surface135 up to 225 degrees-Rear surface225 up to 270 degrees-Front toothFront surface90 up to 180 degrees(180 up to 270 degrees)Rear surface(180 up to 270 degrees)90 up to 180 degreesRight Rear ToothFront surface-225 up to 270 degreesChewing surface-135 up to 225 degreesRear surface-90 up to 135 degreesLower jaw denturesLeft Back ToothFront surface45 up to 90 degrees-Chewing surface0 up to 45 degrees or 315 to 359.99 degrees-Rear surface270 up to 315 degrees-Front toothFront surface0 up to 90 degrees(270 up to 359.99 degrees)Rear surface(270 up to 359.99 degrees)0 up to 90 degreesRight Rear ToothFront surface-270 up to 315 degreesChewing surface-0 up to 45 degrees or 315 to 359.99 degreesRear surface-45 up to 90 degreesAs described in Table 2, according to the rotation angle φ about the longitudinal axis representing the direction in which the brush bristles 210 of the head portion 4 face (+Z direction), which of the front surface, the rear surface, and the chewing surface of the denture 98U or 98L is to be brushed can be determined.As described above, the control unit 110 may obtain the direction (+Z direction) in which the brush bristles 210 of the head portion 4 face about the longitudinal axis (Y axis) of the main body 1 as a rotation angle φ about the longitudinal axis based on the output of the acceleration sensor 15, and determine which of the front surface, the rear surface, and the chewing surface of the denture 98U or 98L is to be brushed according to the rotation angle φ about the longitudinal axis.Therefore, as described above, the control unit 110 can specify a brushing location BP of the denture 98U or 98L according to a combination of the translation position of the brushing location BP obtained based on the output of the gyro sensor 16 and the determination result which of the front surface, the rear surface, and the chewing surface of the denture 98U or 98L is brushed. Thereby, the brushing site BP of the denture 98U or 98L can be specified with high accuracy.Note that it is desirable for left-handed users to change right and left throughout the brushing procedure described above.(Correction Process)In the brushing procedure described with reference to FIG. 6, as indicated by arrows HCG 1, HCG 2, HCG 3, HCG 4 in the drawing, in the displacement from the location SQ 2 to the location SQ 3, the displacement from the location SQ 6 to the location SQ 7, the displacement from the location SQ 10 to the location SQ 11, the displacement from the location SQ 14 to the location SQ 15 of the denture 98U or 98L, the direction of the longitudinal axis (Y axis) of the main body 1 is changed significantly from the left HL to the right HR, and conversely from the right HR to the left HL, respectively, the translation movement of the head portion 4 is almost stopped. In addition, regardless of the brushing procedure described above, for example, the user brushing his teeth as illustrated in FIG. 16 can significantly change the orientation of the longitudinal axis (Y axis) of the main body 1 from Y 2 to Y 3 as indicated by the arrow MV 1 in a state where the translation movement of the head portion 4 is nearly stopped. When the orientation of the longitudinal axis (Y axis) of the main body 1 is significantly changed in this manner while the translation movement of the head portion 4 is nearly stopped, an error occurs in the process of step S 2 described in FIG. 4 (the process to obtain a translation position of a brushing site based on an output of the gyro sensor 16).Also, as illustrated in FIG. 17, there may be, for example, a case where the user brushing his teeth performs a large translation movement of the main body 1, for example, from the left cheek side location SQ 1 to the right lingual location SQ 5 via the locations in the upper jaw denture 98U as indicated by the arrow MV 2, with hardly any change in the direction of the longitudinal axis (Y axis) of the main body 1, regardless of the brushing procedure described above. In this manner, when a large translation movement of the main body 1 is performed across the locations with hardly any change in the orientation of the longitudinal axis (Y axis) of the main body 1, an error occurs in the process of step S 2 described in FIG. 4 (the process to obtain a translation position of a brushing location based on an output of the gyro sensor 16).Therefore, in this example, the control unit 110 performs a correction process described in the flow of FIG. 18 while repeating the processes in steps S 2 to S 5 in FIG. 4.In other words, as described in step S 41 of FIG. 18, the control unit 110 performs second-order integration based on the acceleration of the main body 1 output from the acceleration sensor 15 every 0.1 second, which is the processing time unit, and obtains a translation movement amount of the main body 1. note that the accelerations in the directions of the three axes of the main body 1 are represented by Acc_X, Acc_Y, and Acc_Z, respectively, the speeds in the directions of the three axes are represented by v_X, v_Y, and v_Z, respectively, and the translation movement amount of the main body 1 in the directions of the three axes is represented by D_X, D_Y, and D_Z, respectively. Then, the translation movement amount Di (where i=1, 2, 3,... ) of the main body 1 for each processing time unit is expressed by the following equations (Eq. 7), (eq. 8) and (Eq. 9).Thereafter, as described in step S 42, the control unit 110 summarizes the translation movement amount Di of the main body 1 every 0.5 seconds, which is a predetermined summary time unit. Here, assuming that the translation movement amount Di for each processing time unit is expressed as D 1, D 2, D 3, D 4, and D 5, respectively, the total translation movement amount D_total for a certain summary time unit is represented by the following equation (Eq. 10).Thereafter, as described in step S 43, the control unit 110 determines whether the total translation movement amount D_total for a certain summary time unit is equal to or less than a predetermined first threshold value α 1. In this example, α1=20 mm is set. Here, when D_total≤α1 (Yes in step S 43), the process proceeds to step S 44, and the control unit 110 maintains the translation position of the brush location BP obtained based on the output of the gyro sensor 16 during the summary time unit (a first correction process).In this case, when the user brushing his teeth significantly changes the orientation of the longitudinal axis (Y axis) of the main body 1 with hardly any translation movement of the main body 1 (particularly, the head portion 4), as illustrated in FIG. 16, for example, the translation position of the brushing site BP obtained based on the output of the gyro sensor 16 is maintained before and after the change. Thereby, the accuracy of the obtained translation position of the brush BP can be maintained.In addition, when the denture is divided into smaller locations than those in Table 1, that is, when it is divided into individual teeth along the dental arch, for example, or when each individual tooth is divided into right and left halves, it is desirable to set the value of the first threshold value α1 correspondingly smaller, for example, to 10 mm or 5 mm.On the other hand, when the total translation movement amount D_total exceeds the first threshold value α 1 in step S 43 in FIG. 18 (No in step S 43), the control unit 110 advances the process to step S 45, and the control unit 110 determines whether the translation movement amount D_total is equal to or greater than a predetermined second threshold value α 2 for the summary time unit. In this example, α2is larger than α1, and α2=30 mm is set. Here, when D_total≥α2 (Yes in step S 45), the control unit 110 advances the process to step S 46, and the control unit 110 shifts to a position on the approximation curve E 1 in the data space DS corresponding to the translation movement target of the main body 1, and recomputes the corresponding point P based on the output of the gyro sensor 16 (a second correction process).For example, when the main body 1 is moved significantly over the locations from the left cheek side location SQ 1 to the right lingual location SQ 5 in the upper jaw denture 98U with hardly any change in the orientation of the longitudinal axis (Y axis) of the main body 1, for example, as illustrated in FIG. 17, the control unit 110 shifts from a position where the x coordinate is close to -a to a position where the x coordinate is close to + a on the approximation curve E 1 in the data space DS illustrated in FIG. 9, and recalculates the corresponding point P based on the output (a difference angle θ) of the gyro sensor 16.In this case, the translation position of the brushing site BP of the denture 98U or 98L can be obtained with high accuracy.In this example, second-order integration is performed based on the output of the acceleration sensor 15, and the translation movement amount Di of the main body 1 for each processing time unit is calculated. For this reason, the calculated total translation movement amount D_total of the main body 1 may not be accurate due to the influence of noise. However, the calculated total translation movement amount D_total of the main body 1 may be sufficient to determine whether the translation movement amount of the main body 1 (specifically, the head portion 4) is small (step S 43 in FIG. 18 ) or extremely large (step 45 in FIG. 18 ).When α 1<D_total<α 2 (No in step S 43 in FIG. 18 and No in step S 45 in FIG. 18 ), the control unit 110 determines that there is no need for correction, and the process returns to the flow of FIG. 4 (steps S 2 to S 5).In the above example, in order to obtain the translation position of the brush location BP, the "standard" approximation curve E1 which is a part of the ellipse E shown in Fig. 7A is used. However, the present invention is not limited to this example. For example, for a user having a "long" denture that is longer and narrower than the "standard" denture, a part having a depth D2≈60 mm and a width W2≈60 mm in the ellipse E' having a minor axis 2a' =60.43 mm and a major axis 2b' =136.2 mm may be used as an approximate curve E 2, as illustrated in FIG. 7B. For a user having a "small" denture compared to the "standard" denture, a part having a depth D3≈50 mm and a width W3≈60 mm in the ellipse E" having a minor axis 2a" = 62.21 mm and a major axis 2b" = 135.9 mm may be used as an approximate curve E3, as illustrated in FIG. 7C. The selection of this "standard" approximate curve E1, "long" approximate curve E2 or "small" approximate curve E3 (including the setting of the minor axis and the major axis) is performed by a setting parameter from the outside of the main body 1 via the communication unit 180 serving as a receiving unit in this example. In such a case, the approximate curve can be set appropriately according to the sizes and shapes of dental arches of various users. Thereby, the translation position of the brush BP of the denture can be obtained with higher accuracy.Further, the actual brushing time data for each location acquired by the control unit 110 and other data related to brushing may be transmitted from the main body 1 to the outside via the communication unit 180 serving as a transmission unit. In this case, the data may be received by, for example, a computer device provided outside the main body 1 and used for various processes and applications.(Another approximation curve)In the above-described embodiment, the dental arch of the person in the real space RS is approximated by a curve (approximation curve E 1, E 2, or E 3) equivalent to a part of the ellipse E in the data space DS; however, the present invention is not limited to this example.As shown in FIG. 19, the person's dental arch in the real space RS can be approximated by a parabola U in the data space DS. For simplicity, the parabola U is assumed to contact the x-axis at the origin O(0,0) in a convex manner.The parabola U touching the x-axis at the origin O (0, 0) in a convex manner, where p is a negative coefficient (i.e., p<0), is expressed as:It is assumed that a certain moving tangent Q touches the parabola U at the point P (x 1, y 1). The equation of the movable tangent Q is expressed by the mathematical formula:Further, since the point P (x 1, y 1) is a point on the parabola U, the following equation is established.Here, when the slope of the movable tangent Q is m, it is calculated based on the equation (Eq. In this example, 12) is expressed as follows.When the coordinates x 1 and y 1 of the touch point P with respect to the parabola U are determined by the slope m using the equations (Eq. 13) and (Eq. In the case where the coordinates can be expressed as follows, respectively.Further, the angle formed by the movable tangent Q with respect to the x-axis is regarded as θ (assuming that the counterclockwise direction is positive, and -π / 2≤θ≤π / 2), and the slope is expressed as a slope m=tanθ. Then, the equation (Eq. 15) expressed as follows.According to this equation (Eq. In FIG. 16 ), the coordinates (x 1, y 1) of the corresponding point P corresponding to the brush location BP on the parabola U in the data space DS are obtained based on the difference angle θ in the real space RS.In this case, an approximation curve can be set by determining a coefficient p. Therefore, the process of obtaining the corresponding point P can be easily performed.(System)FIG. 20 illustrates a configuration of a system (the entire system is denoted by reference numeral 700) including the above-described electric toothbrush 90 and a smartphone 600. This system 700 includes the electric toothbrush 90 and the smartphone 600 as a computing device that are communicable with each other via a network 900.The smartphone 600 includes a main body 600M and a control unit 610, a storage unit 620, an operation unit 630, a display 640, a communication unit 680, and a power supply unit 690, which are attached to the main body 600M. The smartphone 600 is a commercially available smartphone in which application software described later has been installed.The control unit 610 includes a CPU and its auxiliary circuit, controls each unit of the smartphone 600, and performs processing according to programs and data stored in the storage unit 620. For example, the data input from the communication unit 680 is processed based on an instruction input via the operation unit 630, and the processed data is stored in the storage unit 620, displayed on the display 640, or output via the communication unit 680.The storage unit 620 includes a random access memory (RAM) used as a work area required for execution of the program by the control unit 610, and a read only memory (ROM) for storing a basic program to be executed by the control unit 610. Further, as a storage medium of an auxiliary storage device for supporting the storage area of the storage unit 620, a semiconductor memory (memory card), a solid state drive (SSD), or the like may be used.In this example, the operation unit 630 includes a touch panel provided on the display 640. Note that a keyboard or other hardware operation device may be included.In this example, the display 640 includes a display screen made of a liquid crystal display element (LCD) or an organic electroluminescence (EL) display. The display 640 displays various images on the display screen according to the control by the control unit 610.The communication unit 680 may perform wireless communication (for example, BT communication, BLE communication, and the like) with the electric toothbrush 90 via the network 900 under control of the control unit 610.The power supply unit 690 includes a rechargeable battery in this example, and supplies power to each unit of the smartphone 600.It is assumed that the user previously installs application software (referred to as an "electric toothbrush program") in the smartphone 600. This electric toothbrush program wirelessly communicates with the electric toothbrush 90, makes various settings concerning the brushing procedure and the like on the electric toothbrush 90, receives data specifying the brushing location BP, a translation position (coordinate value) of the brushing location, the direction in which the brush bristles 210 of the head portion 4 face, the output value of the gyro sensor or the acceleration sensor and the like from the electric toothbrush 90, and uses the received data in various processes.(Setting of Approximate Curve)For example, it is assumed that the user activates the electric toothbrush program and selects the "Set the electric toothbrush" mode via the operation unit 630. Then, a "setting approximate curve" screen is displayed on the display 640, and the "standard" approximate curve E 1 (a part having a depth D 1≈50 mm and a width W 1≈70 mm in the ellipse E with a minor axis 2 a=71.76 mm and a major axis 2 b=128.2 mm) and the "long" approximate curve E 2 (a part having a depth D 2≈60 mm and a width W 2≈60 mm in the ellipse E' with a minor axis 2 a' =60.43 mm and a major axis 2 b' =136.2 mm) and the "small" approximate curve E 3 (a part, are displayed as candidates for selection, The width of the ellipse E" is indicated by a depth D3≈50 mm and a width W3≈60 mm, with a minor axis 2a" =62.21 mm and a major axis 2b" =135.9 mm). When the user selects any one of these selection candidates via the operation unit 630, the selected approximate curve is set in the electric toothbrush 90.Note that the minor axis and the major axis of the selected ellipse and the dimensions (depth and width) of the part of the selected ellipse used as an approximation curve can be adjusted by changing continuous values on the screen of the display 640.Further, when the parabola U is used as the approximation curve, the coefficient p is preferably variably set.(Brush rating)In the brushing procedure described with reference to FIG. 6, brushing is performed in ascending order with respect to the reference numerals from the locations SQ 1 to SQ 8 in the upper jaw denture 98U and then from SQ 9 to SQ 16 in the lower jaw denture 98L. Further, in the brushing procedure, as described in the following Table 3, during brushing, each location SQ 1 to SQ 16 is set to brush for a predetermined set brushing time for each location SQ 1 to SQ 16. For example, in the upper jaw denture 98U, the set brushing time is set to 8 seconds for the site SQ 1, 4 seconds for the site SQ 2, 9 seconds for the site SQ 3, and so on. In the lower jaw denture 98L, the set brushing time is set to 5 seconds for the site SQ 9, 5 seconds for the site SQ 10, 7 seconds for the site SQ 11, and so on. [Table 3] [Table 3]Upper jaw denturesLeft Back ToothFront surfaceSQ1187,290%Chewing surfaceSQ8866100%Rear surfaceSQ77105,252%Front toothFront surfaceSQ2243,793%Rear surfaceSQ6676,187%Right Rear ToothFront surfaceSQ3396,977%Chewing surfaceSQ4476,796%Rear surfaceSQ55115,247%Lower jaw denturesLeft Back ToothFront surfaceSQ9955100%Chewing surfaceSQ161666100%Rear surfaceSQ151585,164%Front toothFront surfaceSQ101054,692%Rear surfaceSQ141485,366%Right Rear ToothFront surfaceSQ111176,694%Chewing surfaceSQ121254,182%Rear surfaceSQ131385,569%As described with respect to step S 8 in FIG. 4, the specified brush location BP and the actual brush time for the location BP are linked to each other and recorded in the table prepared in the storage unit 115 as the actual brush time data for each location. In this example, as described in Table 3, the actual brushing times are values of 7.2 seconds for the site SQ 1, 3.7 seconds for the site SQ 2, 6.9 seconds for the site SQ 3,... in the upper jaw denture 98U. In the lower jaw denture 98L, the values were 5 seconds for the site SQ9, 4.6 seconds for the site SQ10, 6.6 seconds for the site SQ11, and so on.In this example, the control unit 610 of the smartphone 600 receives data (including actual brushing time data for each place) recorded in the table in the storage unit 115 from the electric toothbrush 90 via the communication unit 680. The control unit 610 functions as a brush evaluation unit and calculates an evaluation value (brush evaluation value) representing a degree of matching with the brush procedure based on the actual brush time data for each location.Specifically, a brush evaluation value (unit: %) for the respective locations SQ 1 to SQ 16 is calculated by the following formula.In the example of the data in Table 3, the brush evaluation values are 90% for the site SQ1, 93% for the site SQ2, 77% for the site SQ3, and so on in the upper jaw denture 98U. In the lower jaw denture 98L, the values are 100% for the site SQ9, 92% for the site SQ10, 94% for the site SQ11, and so on.In this example, the controller 610 of the smartphone 600 displays these brush evaluation values on the display screen of the display 640. With this configuration, the user can recognize the degree of matching or difference of his brushing manner compared to the brushing procedure by looking at the display screen of the display 640. Specifically, the user can recognize the tendency of the difference of his brushing with respect to the brushing procedure described above, that is, for example, the tendency that brushing of the rear surface of the left rear tooth (location SQ 7) and the rear surface of the right rear tooth (location SQ 5) is particularly insufficient in the upper jaw denture 98U. Therefore, the user can improve his or her brushing manner.In the above-described embodiment, the control unit 110 of the electric toothbrush 90 performs the function of the brush part detection unit; however, this example does not put any limitation. During the execution of communication between the electric toothbrush 90 and the smartphone 600 during toothbrushing, the control unit 610 of the smartphone 600 may execute part or all of the function of the brush location acquisition unit. In such a case, the configuration of the control unit 110 of the electric toothbrush 90 can be simplified. As a result, the control unit 110 can be configured by, for example, a logic integrated circuit (IC) as a substitute for the CPU.For example, the control unit 610 of the smartphone 600 may perform the correction process (the flow in FIG. 18 ) while the control unit 110 of the electric toothbrush 90 performs basic specification of the brushing site BP among the functions of the brushing site detection unit (the flow in FIG. 4, specifically, steps S 2 and S 3). With this configuration, the processing load can be distributed between the electric toothbrush 90 and the smartphone 600.In order to configure the system combined with the electric toothbrush 90, a device serving substantially as a computer device such as a tablet terminal or a personal computer may be used as a substitute for the smartphone 600.The processing method executed by the control unit 110 of the electric toothbrush 90 or the control unit 610 of the smartphone 600 may be recorded in a recording medium that can store data in a nonvolatile manner, such as a compact disc (CD), a digital versatile disc (DVD), flash memory, and the like, as application software (computer program). When the application software recorded on such a recording medium is installed in a wide-area computing device such as a personal computer, a personal digital assistance (PDA), a smartphone, and the like, the above-described method can be executed on the computing device.When the dental arch of the user is inclined with respect to the horizontal plane, an xyz orthogonal coordinate system can be set in the data space, and an approximate curve inclined with respect to the xy horizontal plane can be set. Thereby, the dental arch of such a user can be approximated with an approximation curve with high accuracy. Therefore, the translation position of the brushing site of the denture can be obtained with high accuracy.The above embodiments are illustrative and are modifiable in a variety of ways without departing from the scope of this invention. Note that the above-described various embodiments can be individually understood in each embodiment, but the embodiments can be combined with each other. It should also be noted that the various features in different embodiments may be individually understood, but the features in different embodiments may be combined.List of reference characters1, 600M Main body 3 Neck portion 4 Head portion 5 Grip portion 15 Acceleration sensor 16 Gyro sensor 90 Electric toothbrush 110, 610 Control unit 210 Brush bristle 600 Smartphone 640 Display 700 System

Claims

An electric toothbrush (90) comprising: a main body (1) having, along its longitudinal axis direction, a head portion (4) having a brush side into which brush bristles (210) are inserted, a grip portion (5) to be held by a human hand, and a neck portion (3) configured to connect the head portion (4) and the grip portion (5); a gyro sensor (16) mounted inside the main body (1) and configured to detect an angular velocity of the main body (1); a brush location detection unit configured to obtain a translation position of a brush location in a denture based on an output from the gyro sensor (16); and a receiving unit capable of receiving a setting parameter from outside the main body (1), wherein the brush spot detecting unit sets an approximate curve curved according to the denture as a curve equivalent to a part of an ellipse expressed by a function y = b[{1-(x / a) 2}1 / 2- 1] using positive coefficients a and b, or as a parabola expressed by a function 4py = x 2 using a negative coefficient p, in a data space in which an xy rectangular coordinate system is defined, the coefficients a and b or the coefficient p variably set according to the setting parameter received via the receiving unit, based on the output from the gyro sensor (16), an angle obtained by a longitudinal axis of the main body in a state, in which the brush bristles (210) of the head portion (4) contact the brushing position of the denture is formed with respect to the longitudinal axis of the main body (1) in a state in which the brush bristles (210) of the head portion (4) contact a reference position of the denture, and based on the angle, obtains a corresponding point corresponding to the brushing position on the approximate curve to use coordinates of the corresponding point as the translation position of the brushing position.The electric toothbrush according to claim 1, wherein the brush position detecting unit sets a reference tangent that contacts a reference point corresponding to the reference position with respect to the approximation curve, sets a movable tangent that forms the angle with respect to the reference tangent and contacts the approximation curve, and obtains, as the corresponding point, a point where the movable tangent contacts the approximation curve.The electric toothbrush according to claim 1 or 2, wherein the reference position of the denture is a center of a front surface of the denture.An electric toothbrush (90) comprising: a main body (1) having, along its longitudinal axis direction, a head portion (4) having a brush side into which brush bristles (210) are inserted, a grip portion (5) to be held by a human hand, and a neck portion (3) configured to connect the head portion (4) and the grip portion (5); a gyro sensor (16) configured to detect an angular velocity of the main body (1) and an acceleration sensor (15) mounted in the main body (1); and a brush location detection unit specifying the brush location of the denture based on the output of the gyro sensor (16) and the output of the acceleration sensor (15), wherein the brush location detection unit obtains an angle, which is formed by the longitudinal axis of the main body (1) in a state in which the brush bristles (210) of the head portion (4) contact the brushing site of the denture with respect to the longitudinal axis of the main body (1) in a state in which the brush bristles (210) of the head portion (4) contact a reference position of the denture, obtains, based on the angle, a corresponding point corresponding to the brushing site on an approximation curve curved according to the denture to use coordinates of the corresponding point as a translation position of the brushing site, obtains a direction in which the brush bristles (210) of the head portion (4) face about the longitudinal axis of the main body (1) based on a direction of gravitational acceleration output from the acceleration sensor, and determines, which of a front surface, a rear surface and a chewing surface of the denture is brushed based on the direction in which the brush bristles (210) of the head portion (4) face, and specifies the brushing location of the denture according to a combination of the translation position of the brushing location obtained based on the output from the gyro sensor (16) and a determination result which of the front surface, the rear surface and the chewing surface of the denture is brushed.The electric toothbrush according to claim 4, wherein the brush location detecting unit calculates a translation movement amount of the main body (1) based on the acceleration of the main body output from the acceleration sensor (15) at each predetermined summary time unit, and performs a first correction process to maintain the translation position of the brush location obtained based on the output from the gyro sensor (16) at a certain summary time unit when the translation movement amount of the main body (1) at the summary time unit is equal to or lower than a predetermined first threshold value.The electric toothbrush according to claim 4, wherein the brush detection unit calculates the translation movement amount of the main body (1) based on the acceleration of the main body (1) output from the acceleration sensor (15) at each predetermined summary time unit, and performs a second correction process to obtain the corresponding point again based on the output from the gyro sensor (16) by shifting to a part corresponding to a translation movement target of the main body (1) in the approximate curve when the translation movement amount of the main body (1) is equal to or greater than a predetermined second threshold value.The electric toothbrush according to any one of claims 1 to 6, further comprising a transmitting unit configured to transmit data concerning brushing to the outside of the main body (1).A system (700) comprising: the electric toothbrush (90) according to claim 7; and a computing device provided outside the main body (1) of the electric toothbrush (90), wherein the electric toothbrush (90) and the computing device are capable of communicating with each other.The system according to claim 8, wherein a brush procedure for brushing a plurality of places of the denture in a predetermined order is set for a predetermined set brush time, and the system further comprises a brush evaluation unit configured to calculate an evaluation value representing a degree of agreement with respect to the brush procedure based on the brush place specified by the brush place acquisition unit.A brush location detecting method for detecting a brush location to be brushed by an electric toothbrush (90) in a denture, the electric toothbrush (90) comprising: a main body (1) having, along its longitudinal axis direction, a head portion (4) having a brush side in which brush bristles (210) are inserted, a grip portion (5) to be held by a human hand, and a neck portion (3) configured to connect the head portion (4) and the grip portion (5), a gyro sensor (16) mounted inside the main body (1) and configured to detect an angular velocity of the main body (1), and a receiving unit capable of receiving a setting parameter from outside the main body (1), and the brush location detecting method comprises: setting an approximate curve, which is curved according to the denture as a curve equivalent to a part of an ellipse expressed by a function y = b[{1-(x / a) 2}1 / 2- 1] using positive coefficients a and b, or as a parabola expressed by a function py = x 2 using a negative coefficient p, in a data space in which an xy rectangular coordinate system is defined; setting the coefficients a and b or the coefficient p variably according to the setting parameter received via the receiving unit; Obtaining a differential angle formed by a longitudinal axis of the main body (1) in a state in which the brush bristles (210) of the head portion (4) contact the brushing location of the denture with respect to the longitudinal axis of the main body (1) in a state in which the brush bristles (210) of the head portion (4) contact a reference position of the denture based on an output from the gyro sensor (16) in a real space in which the denture exists; and obtaining, based on the differential angle in the real space, a corresponding point corresponding to the brushing location on the approximation curve set in the data space to use coordinates of the corresponding point as data representing a translation position of the brushing location.A program for causing a computer to execute the brush location detection method according to claim 10.A brush location detecting method for detecting a brush location to be brushed by an electric toothbrush (90) in a denture, the electric toothbrush (90) comprising: a main body (1) having, along its longitudinal axis direction, a head portion (4) having a brush side in which brush bristles (210) are inserted; a grip portion (5) to be held by a human hand and a neck portion (3) configured to connect the head portion (4) and the grip portion (5); and a gyro sensor (16) configured to detect an angular velocity of the main body and an acceleration sensor (15) mounted in the main body, and the brush location detecting method comprising: obtaining an angle formed by the longitudinal axis of the main body (1) in a state, in which the brush bristles (210) of the head portion (4) contact the brushing site of the denture is formed with respect to the longitudinal axis of the main body (1) in a state in which the brush bristles (210) of the head portion (4) contact a reference position of the denture based on an output from the gyro sensor (16); obtaining, based on the angle of a corresponding point corresponding to the brushing site on an approximation curve curved corresponding to the denture, coordinates of the corresponding point as a translation position of the brushing site; obtaining a direction in which the brush bristles (210) of the head portion (4) face about the longitudinal axis of the main body (1) based on an acceleration of gravity output from the acceleration sensor (15) to determine which of a front surface, a rear surface and a chewing surface of the denture is brushed according to the direction in which the brush bristles (210) of the head portion (4) face; and specifying the brushing location of the denture based on a combination of the translation position of the brushing location obtained based on the output from the gyro sensor (16) and the determination result of which of the front surface, the rear surface and the chewing surface of the denture is brushed.A program for causing a computer to execute the brush location detection method according to claim 12.

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