Patent Publication Number: US-10779924-B2

Title: Electric toothbrush device and method

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 15/735,414, filed Dec. 11, 2017, which claims priority under 35 U.S.C. § 371 to PCT/US2016/036611, filed Jun. 9, 2016, which claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2015-124172, filed Jun. 19, 2015, and Japanese Patent Application No. 2015-122896, filed Jun. 18, 2015, the disclosures of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     Electric toothbrushes are popular devices for cleaning teeth. Some electric toothbrushes attempt to estimate the sites that the toothbrush has brushed. This information can be useful in correcting bad brushing habits and encouraging a more thorough brushing of all teeth. But such toothbrushes have difficulty providing accurate information. What is needed is an electric toothbrush device that can accurately estimate brushing sites. 
     BRIEF SUMMARY 
     The present disclosure is directed to an apparatus, method, and medium for estimating brushing sites. In one aspect, an electric toothbrush comprises a trajectory detecting module configured to detect a trajectory of movement of a brush, the trajectory comprising a plurality of positions; an attitude detecting module configured to detect an attitude of the brush; a site estimating module configured to estimate a brushing site for each of the plurality of positions of the trajectory, each estimated brushing site being based on the trajectory detected by the trajectory detecting module; and a back most tooth detecting module configured to detect a back most tooth based on a change of the attitude detected by the attitude detecting module; wherein the site estimating module is further configured to correct the estimated brushing site for each of the plurality of positions of the trajectory based on the estimated site of the detected back most tooth. 
     In another aspect, a method includes detecting a trajectory of movement of a brush, the trajectory comprising a plurality of positions; detecting an attitude of the brush; estimating a brushing site for each of the plurality of positions of the trajectory, each estimated brushing site being based on the trajectory detected; detecting a back most tooth based on a change of the attitude detected by the attitude detecting module; and correcting the estimated brushing site for each of the plurality of positions of the trajectory based on an estimated site of the detected back most tooth. 
     In another aspect, a non-transitory computer-readable storage medium encoded with instructions which, when executed on a processor, performs a method of detecting a trajectory of movement of a brush, the trajectory comprising a plurality of positions; detecting an attitude of the brush; estimating a brushing site for each of the plurality of positions of the trajectory, each estimated brushing site being based on the trajectory detected; and detecting a back most tooth based on a change of the attitude detected by the attitude detecting module; and correcting the estimated brushing site for each of the plurality of positions of the trajectory based on an estimated site of the detected back most tooth. 
     In yet another aspect, an electric toothbrush includes a driving module configured to oscillate a brush unit; an acceleration sensor configured to generate an output signal; a signal extraction module configured to extract from the output signal (a) a first signal having a frequency at a first threshold or higher and (b) a second signal having a frequency at a second threshold or lower; a brushing site estimation module configured to estimate a brushing site of the brush unit based on the output signal of the acceleration sensor; and a correction module configured to correct the brushing site estimated by the brushing site estimation module based on an amplitude of the first signal and an amplitude of the second signal. 
     In another aspect, a brushing site estimation method for an electric toothbrush includes extracting a first signal from an output signal of an acceleration sensor of an electric toothbrush, the first signal having a frequency at a first threshold or higher; extracting a second signal from the output signal of the acceleration sensor, the second signal having a frequency at a second threshold or lower; estimating a brushing site of the brush unit based on the output signal of the acceleration sensor; and correcting the brushing site estimated by the brushing site estimation module based on an amplitude of the first signal and an amplitude of the second signal. 
     In another aspect, a non-transitory computer-readable storage medium encoded with instructions which, when executed on a processor, perform a method of extracting a first signal from an output signal of an acceleration sensor of an electric toothbrush, the first signal having a frequency at a first threshold or higher; extracting a second signal from the output signal of the acceleration sensor, the second signal having a frequency at a second threshold or lower; estimating a brushing site of the brush unit based on the output signal of the acceleration sensor; and correcting the brushing site estimated by the brushing site estimation module based on an amplitude of the first signal and an amplitude of the second signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a block diagram illustrating an example configuration of an electric toothbrush for describing an embodiment. 
         FIG. 2  is a perspective view illustrating an external appearance of the electric toothbrush device of  FIG. 1 . 
         FIG. 3  is a cross section view illustrating an internal configuration of the electric toothbrush of  FIG. 1 . 
         FIG. 4  is a diagram illustrating the division of brushing sites. 
         FIG. 5  is a flow chart illustrating an example of the brushing evaluating process. 
         FIG. 6  is a diagram illustrating an example of the estimating method of brushing sites based on the attitude of the brush. 
         FIG. 7  is a diagram illustrating an example of the detecting method of the back most tooth based on the attitude of the brush. 
         FIG. 8  is a diagram illustrating another example of the detecting method of the back most tooth based on the attitude of the brush. 
         FIG. 9  is a diagram illustrating an example of the detecting method of the back most tooth based on the trajectory of movement of the brush. 
         FIG. 10  is a diagram illustrating an example of the correcting process of brushing sites. 
         FIG. 11  is a diagram for describing the brush angle. 
         FIG. 12  is a diagram illustrating an example of outputting evaluation results of the brushing. 
         FIG. 13  is a diagram illustrating a variation of a configuration of the electric toothbrush device. 
         FIG. 14  is a schematic of a brushing support system according to an embodiment. 
         FIG. 15  is a schematic of an acceleration sensor and peripheral circuit according to an embodiment. 
         FIG. 16  is a flow chart for describing the brushing site estimation process according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention or inventions. The description of illustrative embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description of the exemplary embodiments disclosed herein, any reference to direction or orientation is merely intended for convenience of description and is not intended in any way to limit the scope of the present inventions. The discussion herein describes and illustrates some possible non-limiting combinations of features that may exist alone or in other combinations of features. Furthermore, as used herein, the term “or” is to be interpreted as a logical operator that results in true whenever one or more of its operands are true. 
     Features of the present inventions may be implemented in software, hardware, firmware, or combinations thereof. The computer programs described herein are not limited to any particular embodiment, and may be implemented in an operating system, application program, foreground or background processes, driver, or any combination thereof. The computer programs may be executed on a single computer or server processor or multiple computer or server processors. 
     Processors described herein may be any central processing unit (CPU), microprocessor, micro-controller, computational, or programmable device or circuit configured for executing computer program instructions (e.g., code). Various processors may be embodied in computer and/or server hardware of any suitable type (e.g., desktop, laptop, notebook, tablets, cellular phones, etc.) and may include all the usual ancillary components necessary to form a functional data processing device including without limitation a bus, software and data storage such as volatile and non-volatile memory, input/output devices, graphical user interfaces (GUIs), removable data storage, and wired and/or wireless communication interface devices including Wi-Fi, Bluetooth, LAN, etc. 
     Computer-executable instructions or programs (e.g., software or code) and data described herein may be programmed into and tangibly embodied in a non-transitory computer-readable medium that is accessible to and retrievable by a respective processor as described herein which configures and directs the processor to perform the desired functions and processes by executing the instructions encoded in the medium. A device embodying a programmable processor configured to such non-transitory computer-executable instructions or programs may be referred to as a “programmable device”, or “device”, and multiple programmable devices in mutual communication may be referred to as a “programmable system.” It should be noted that non-transitory “computer-readable medium” as described herein may include, without limitation, any suitable volatile or non-volatile memory including random access memory (RAM) and various types thereof, read-only memory (ROM) and various types thereof, USB flash memory, and magnetic or optical data storage devices (e.g., internal/external hard disks, floppy discs, magnetic tape CD-ROM, DVD-ROM, optical disk, ZIP™ drive, Blu-ray disk, and others), which may be written to and/or read by a processor operably connected to the medium. 
     In certain embodiments, the present inventions may be embodied in the form of computer-implemented processes and apparatuses such as processor-based data processing and communication systems or computer systems for practicing those processes. The present inventions may also be embodied in the form of software or computer program code embodied in a non-transitory computer-readable storage medium, which when loaded into and executed by the data processing and communications systems or computer systems, the computer program code segments configure the processor to create specific logic circuits configured for implementing the processes. 
     The disclosure is divided into two sections. Section I discusses a first electric toothbrush and method for estimating a brushing site. Section II discusses a second electric toothbrush and method for estimating a brushing site. To the extent a term, reference number, or symbol is used differently in different sections, context should be taken from the relevant section and not the other section. 
     Section I 
       FIG. 1  illustrates an example configuration of an electric toothbrush for describing an embodiment,  FIG. 2  illustrates an external appearance of the electric toothbrush device of  FIG. 1 , and  FIG. 3  illustrates an internal configuration of the electric toothbrush of  FIG. 1 . 
     The exemplified electric toothbrush device illustrated in  FIG. 1  and  FIG. 2  includes a main body  2  that has a brush  5  that oscillates by the drive of a built in motor  10 , wherein the motor  10  that is the drive source is placed in the main body  2 , a charger  100  for charging the main body  2 , and a display unit  110  for outputting the brushing result. 
     In this embodiment, the main body  2  is roughly a cylindrical shape, and also serves as a handle part for the user to grip by hand when brushing the teeth. In the main body  2 , a switch S is provided for carrying out switching of power on/off. Furthermore, a motor  10  that is the drive source, a drive circuit  12 , a rechargeable battery  13  that is the power source, and a coil  14  for recharging is provided in the interior of the main body  2 . When charging the rechargeable battery  13 , by simply placing the main body  2  on the charger  100 , it is possible to charge without contacting by electromagnetic induction. The drive circuit  12  has a central processing unit (CPU)  120  of executing various calculations and control, a memory  121  for storing programs and various setting values, a timer  122 , a data transmission module  123  and the like. The data transmission module  123  carries out wireless communication with the data receiving module  112  of the display unit  110 . The display unit  110  includes a display  111  for outputting data such as the brushing results received by the data receiving module  112 . 
     Furthermore, in the interior of the main body, for example, an acceleration sensor  15  of multiple axes (here, the three axes x, y, z), an angular velocity sensor  16  of multiple axes (here, the three axes x, y, z) and geomagnetic sensor  17  of multiple axes (here, the three axes x, y, z), are provided for sensing the trajectory of movement and the three-dimensional attitude of the brush  5 . 
     The acceleration sensor  15  is disposed so that the x-axis is parallel with respect to the brush surface, the y-axis coincides with the longitudinal direction of the main body  2 , and the z-axis is perpendicular to the brush surface. In other words, when the main body is placed in the charger  100 , the gravitational acceleration vector is parallel to the y-axis; when the brush surface is facing upwards, the gravitational acceleration vector is parallel to the z-axis; and when the brush surface is facing to the back, the gravitational acceleration vector is parallel to the x-axis. The output of each axis of the acceleration sensor  15  is input to the CPU  120 , and employed for detecting the trajectory of movement and the attitude of the brush  5 . A piezoresistive type, a capacitance type, or a MEMS sensor of a thermal sensing type is preferably employed as the acceleration sensor  15 . Since the MEMS sensor is very small, it can easily be incorporated into the interior of the body  2 . However, the format of the acceleration sensor  15  is not limited to this, but a sensor such as an electrodynamic type, strain gauge type, or piezoelectric may be employed. 
     The angular velocity sensor  16  is disposed so that it can detect the angular velocity around the x-axis, the angular velocity around the y-axis, and the angular velocity around the z-axis. The output of each axis out the angular velocity sensor  16  in input to the CPU  120 , and employed for detecting the trajectory of movement and the attitude of the brush  5 . Any type of sensor such as an oscillation type, optical type, and mechanical type may be used as the angular velocity sensor  16 , but a MEMS sensor can appropriately be used since it is small and can easily be incorporated in main body  2 . 
     The geomagnetic sensor  17  is disposed so that it can detect geomagnetism in the x-axis direction, the y-axis direction, and the z-axis direction. The output of each axis of the geomagnetic sensor  17  is input to the CPU  120 , and employed for detecting the trajectory of movement and the attitude of the brush  5 . A MEMS sensor such as a MR (Magneto-resistive) element type, MO (Magneto-Impedance) element type, and a hole element type is preferably employed as the geomagnetic sensor  17 . The sensors discussed above can be used to detect a trajectory or attitude. Accordingly, these sensors (together or alone, depending on the embodiment) may be referred to as a “trajectory detecting module” and/or an “attitude detecting module.” In other embodiments, other devices can be used to detect trajectory or attitude. 
     Furthermore, a load sensor  18  for sensing the brush pressure (load acting on the brush) is included in the interior of the main body  2 . Although any type such as a strain gauge, a load cell, or a pressure sensor can be used, a MEMS sensor can be appropriately used as the load sensor  18  since it is small and can be easily incorporated in the main body  2 . 
     The brush  5  includes a stem part  20  fixed to the main body  2  side, and a brush component  21  mounted on the stem part  20 . Brush bristles  210  are attached to the top portion of the brush component  21 . Since the brush component  21  has consumable parts, it is configured to be freely detachable with respect to the stem part  20  so that it can be replaced with a new one. 
     In this embodiment, the stem part  20  is made from a resin material, and attached to the main body  2  via an elastic member  202  made from an elastomer. The stem part  20  is a cylindrical member in which the tip (tip end of the brush side) is closed, and has a bearing  203  in the tip end of the interior of the tube. The tip of the eccentric shaft  30  connected to the rotary shaft  11  of the motor  10  is inserted into the bearing  203  of the stem part  20 . The eccentric shaft  30  has a weight  300  near the bearing  203 , and the center of gravity of the eccentric shaft  20  is shifted from the center of rotation. Note that a minute clearance is provided between the tip of the eccentric shaft  30  and the bearing  203 . 
     In this embodiment, the CPU  120  is provided in the motor  10 , and rotates the rotary shaft  11  of the motor  10 . Although the eccentric shaft  13  also rotates along the rotation of the rotary shaft  11 , the eccentric shaft  30  carries out the movement such as turning about the axis of rotation since the center of gravity is shifted. Thus, the tip of the eccentric shaft  30  repeatedly collides against the inner wall of the bearing  203 , and the stem part  20  and the brush component  21  mounted thereon oscillates (moves) at high speed. That is, the motor  10  plays a role of the drive module for oscillating (moving) the brush  5  and the eccentric shaft  30  plays a role of a movement transmission mechanism (movement conversion mechanism) for converting the output (rotation) of the motor  10  to oscillation of the brush  5 . 
     The user can carry out brushing by applying the hand of the main body  2 , that is, the brush bristles  210  for oscillating at high speed, to the teeth. Note that, the CPU  210  monitors the continuous operation time by using the timer  122 , and automatically stops the oscillation of the brush  5  after a predetermined amount of time (for example, 2 minutes) has elapsed. 
     The way food residue and plaque are attached is different at each site, therefore the effective brushing operation is different at each site. Thus, it is preferable to carry out an evaluation at each site of whether or not appropriate brushing is being carried out. Therefore, the electric toothbrush device  1  performs a brushing evaluation of each site by estimating the brushing site based on the trajectory of movement and the attitude of the brush  5 , by using an acceleration sensor  15 , angular velocity sensor  16 , and a geomagnetic sensor  17 . Various evaluation items are considered, but here an evaluation of three items, the brushing time, brush angle, and brush pressure, is carried out. 
     As illustrated in  FIG. 4 , the upper and lower teeth surfaces are divided into 16 sections of a “maxillary front buccal surface”, “maxillary front lingual surface”, “maxillary left buccal surface”, “maxillary left lingual surface”, “maxillary left occlusal surface”, “maxillary right buccal surface”, “maxillary right lingual surface”, “maxillary right occlusal surface”, “mandibular front buccal surface”, “mandibular front lingual surface”, “mandibular left buccal surface”, “mandibular left lingual surface”, “mandibular left occlusal surface”, “mandibular right buccal surface”, “mandibular right lingual surface”, and a “mandibular occlusal surface”. However, division of the teeth surface is not limited to this, and may be divided into a rougher division or a finer division. 
     The flow of the brushing evaluation will be described specifically with reference to  FIG. 5 . Note that, the process described hereafter is a process performed according to the program stored in the memory  121  of the CPU  120 , unless otherwise stated. 
     When the power supply of the main body is ON, the CPU  120  detects the trajectory of movement and the attitude of the brush  5  based on the output of the acceleration sensor  15 , the angular velocity sensor  16 , and the geomagnetic sensor  17  (Step S 10 ). Then, the CPU  120  estimates the brushing site by using the trajectory detected by at least step S 10  (Step S 20 ). Then, the CPU  120  carries out detection of the back most tooth when the brushing site estimated by step S 20  is the back side site of the teeth rows end (Step S 30 ). Then, the CPU  120  corrects the brushing site of each position in the trajectory of movement of the brush  5  based on the position of the back most tooth detected by step S 30  (Step S 40 ). Then, the CPU  120  carries out estimation of the brush angle and sensing of the brush pressure (Step S 50 ). The information of the brushing site, the brush angle and the brush pressure is recorded in the memory  121  associated with a position in the trajectory of the brush  5 . 
     The process of steps S 10  to S 50  are repeatedly performed, when the power supply is turned OFF or the continuous operation time reaches a predetermined time (for example 2 minutes), the brushing results at each site are evaluated based on brushing information (brushing site, brush angle, brush pressure) recorded in the memory  121 , and outputs the evaluation results to the display unit  110  (Step S 60 ). 
     Hereinafter, the process of step S 10  to S 60  will be described in detail. 
     The CPU  120  acquires outputs Ax, Ay and Az of the x-axis, y-axis and z-axis respectively, from the acceleration sensor  15 ; acquires outputs Bx, By and Bz of the x-axis, y-axis and z-axis respectively, from the angular velocity sensor  16 ; and acquires outputs Cx, Cy and Cz of the x-axis, y-axis and z-axis respectively, from the geomagnetic sensor  17 . Ax displays the acceleration component of the x-axis direction, Ay displays the acceleration component of the y-axis direction, and Az displays the acceleration component of the z-axis direction. Bx displays the angular velocity component about the x-axis, By displays the angular velocity component about the y-axis, Bz displays the angular velocity component about the z-axis. Cx displays the magnetic component of the x-axis direction, Cy displays the magnetic component of the y-axis direction, Cz displays the magnetic component of the z-axis direction. 
     When the size of the resultant vector A (Ax, Ay, Az) is smaller than a predetermined threshold value equivalent to the gravitational acceleration, the CPU  120  determines that the main body  2  is stationary, and the output Ax, Ay and Az of the acceleration sensor  15  is made to be the attitude vector D (Dx, Dy, Dz) for displaying a three dimensional attitude of the brush. 
     When the size of the resultant vector A (Ax, Ay, Az) is greater than the threshold value, the CPU  120  determines that the main body  120  is moving. The angular variation amount of the main body  2  is obtained about each axis of the x-axis, y-axis and z-axis from when the main body  2  was most recently determined to be stationary. Based on the outputs Bx, By and Bz of the angular velocity sensor, rotated at the angular variation amount for obtaining a resultant vector A (Ax, Ay, Az) of when the main body  2  was most recently determined to be stationary, the attitude vector D (Dx, Dy Dz) is obtained. 
     The attitude vector D (Dx, Dy, Dz) obtained as above, corresponds to the gravitational acceleration. Note that the angular velocity sensor  16  generally results in drift, and after the error in calculation of the angular velocity amount is accumulated, the CPU  120  carries out a zero calibration of the angular velocity sensor  16  from time to time by using output of the acceleration sensor  15  and the geomagnetic sensor  17 . 
     Furthermore, the CPU  120  obtains the variation amount of each axis direction of the x-axis, y-axis and z-axis, based on the acceleration component obtained by removing the gravitational component from the output Ax, Ay and Az of the acceleration sensor  15 . The gravitational acceleration included in the outputs Ax, Ay and Az can use the attitude vector D (Dx, Dy, Dz). Also, the CPU  120  obtains the trajectory of the movement of the brush  5  by taking into consideration the position of the brush  5  in the main body  2  that is determined from the three dimensional attitude of the brush  5 . 
     The CPU  120  estimates the brushing site at each position on the trajectory of movement of the brush  5  by carrying out matching of the trajectory of movement of the brush  5  and the teeth row surface. (In this regard, the CPU  120  is sometimes referred to as a “site estimating module,” though other processors can be used to estimate a site.) Although the estimation accuracy of the brushing sites increases as the trajectory is accumulated, if the starting site of brushing is reported to the user, it is possible to accurately carry out estimation of the brushing site from a relatively early stage. 
     Note that, by taking this into consideration together with the attitude of the brush  5 , it is possible to estimate the brushing site with a higher accuracy. For example, it is possible to determine whether it is the maxillary or the mandibular based on the z-axis direction component Dz of the attitude vector D. As illustrated in  FIG. 6 , it is noted that when brushing the maxillary teeth, the brushing surface faces considerably upwards, and when brushing the mandibular teeth, the brush surface faces considerably downwards, and it is possible to detect that when Dz&gt;0 it is the maxillary, and when Dz≤0 it is the mandibular. 
     When the estimated brushing site is the back side site of the teeth row ends, that is, the “maxillary left buccal surface”, “maxillary left lingual surface”, “maxillary left occlusal surface”, “maxillary right buccal surface”, “maxillary right lingual surface”, “maxillary right occlusal surface”, “mandibular left buccal surface”, “mandibular left lingual surface”, “mandibular left occlusal surface”, “mandibular right buccal surface”, “mandibular right lingual surface”, and a “mandibular occlusal surface”, the CPU  120  carries out detection of the back most tooth. (In this regard, the CPU  120  is sometimes referred to as a “back most tooth detecting module,” though other processors can be used in detecting a back most tooth.) 
       FIG. 7  illustrates and example of a detection method of the back most tooth when the estimated brushing site is the “mandibular left buccal surface” and the “mandibular left lingual surface”, and  FIG. 8  illustrates and example of a detection method of the back most tooth when the estimated brushing site is the “mandibular left occlusal surface”. 
     When brushing the side surface S 0  of the maxillary left back most tooth, typically, the brush  5  reaches the side surface S 0  of the back most tooth by moving to the back side along the mandibular left teeth row ends. 
     When the brush  5  is moved along the “mandibular left buccal surface” for example, the brush  5  rapidly rotates about the x-axis in a process leading to the side surface S 0  from the buccal surface S 1  of the back most tooth, as illustrated in  FIG. 7 . There, when the estimated brushing site is the “mandibular left buccal surface”, and when the variation amount θa of the attitude about the x-axis of the brush  5  is greater than a predetermined threshold value on the basis of the attitude of the brush  5  along the teeth row ends of the “mandibular left buccal surface”, it is possible to detect the back most tooth. The attitude of the brush  5  along the teeth row surface of the mandibular left buccal surface that serves as a reference, for example, can be an average of the attitude of the brush  5  at each position estimated as the “mandibular left buccal surface” in the trajectory of the brush  5 . 
     When the brush  5  moves along the “mandibular left lingual surface”, the brush  5  rapidly rotates about the x-axis in a process leading to the side surface S 0  from the back most tooth lingual surface S 2 . There, when the estimated brushing site is the “mandibular left lingual surface”, and when the variation amount θb of the attitude about the x-axis of the brush  5  is greater than a predetermined threshold value on the basis of the attitude of the brush  5  along the teeth row ends of the “mandibular left lingual surface” and on the basis of the attitude of the brush  5 , it is possible to detect the back most tooth. 
     Furthermore, when the brush  5  moves along the “mandibular left occlusal surface”, the brush  5  rapidly rotates about the x-axis in a process leading to the side surface S 0  from the back most tooth occlusal surface S 3 , as illustrated in  FIG. 8 . There, when the estimated brushing site is the “mandibular left occlusal surface”, and when the variation amount θc of the attitude about the x-axis of the brush  5  is greater than a predetermined threshold value on the basis of the attitude of the brush  5  along the teeth row ends of the “mandibular left occlusal surface”, it is possible to detect the back most tooth. 
     When the estimate brushing site is the “mandibular right buccal surface”, “mandibular right lingual surface”, “maxillary left buccal surface”, “maxillary left lingual surface”, “maxillary right buccal surface”, and the “maxillary right lingual surface”, in the same manner as the detection method in  FIG. 7 , and furthermore, when the brushing site is the “mandibular right occlusal surface”, “maxillary left occlusal surface”, and the “maxillary right occlusal surface”, in the same manner as the detection method illustrated in  FIG. 8 , it is possible to detect the back most tooth based on the variation of attitude of the brush  5 . 
     The detection of the back most tooth above focuses on the three dimensional attitude of a specific brush  5  in brushing of the back most tooth, but the detection method of the back most tooth illustrated in  FIG. 9  focuses on the movement of a specific brush  5  in brushing of the back most tooth. 
     Normally, it is difficult to move the brush  5  to the back most tooth along the teeth row ends due to interference of biological tissue in the mouth. Furthermore, after the brush  5  reaches the back most tooth by moving to the teeth side along the teeth row ends, the brush  5  is moved again to the front side. There, as illustrated in  FIG. 9 , in the trajectory portion of the back side portion of the teeth row ends of among the trajectory of movements of the brush  5 , and of among a return point RP 1 , RP 2 , and RP 3  of movement of the brush  5 , it is possible to detect the return point RP 3  of the movement of the brush  5  in the back most tooth as the back most tooth. Note that, the trajectory portion of the “mandibular left buccal surface” in  FIG. 9  is illustrated, but even for trajectory portions of another back side portion, a returning point of the movement of the brush  5  in the same back most tooth can be detected as the back most tooth. 
     The CPU  120  is configured so as to detect the back row teeth by independently carrying out detection of the back most tooth based on variation of the attitude of the brush  5  above, detection of the back most tooth based on the trajectory of the brush  5  respectively, and preferably is configured so as to detect the back most tooth based on variation of the attitude of the brush  5  at the returning point of the back most side of movement of the brush  5 . Thus, it is possible to further increases the detection accuracy of the back most tooth. 
       FIG. 10  illustrates an example of a correction process of the brushing sites at each position on the trajectory of movement of the brush  5 . 
     For each position P 1  to P 11  on the trajectory of movement of the brush  5 , the brushing sites of brush position P 1  to P 4  is estimated as the “mandibular right buccal surface”, the brushing sites P 5  to P 7  are estimated as the “mandibular front buccal surface”, and the brushing sites P 8  to P 11  are estimated as the “mandibular left buccal surface”. Also, for position P 12  of the brush  5  detected by the following step S 10 , the brushing site is estimated as the “mandibular left buccal surface, and the back most tooth is detected in the position P 12 . 
     The CPU  120  updates the position of the mandibular left back most tooth to position P 12  in the trajectory of movement of the brush  5  when the back most tooth are detected by position P 12 . Also, the CPU  120  corrects the brushing site of each position P 1  to P 11  estimated by the matching of the teeth row ends and the trajectory of movement of the brush  5 , based on the position of the updated back most tooth. In the example illustrated, due to the correction, P 1  to P 3  are corrected to the “mandibular right buccal surface”, P 4  to P 8  are corrected to the “mandibular front buccal surface”, and P 9  to P 11  are corrected to the “mandibular left buccal surface”. 
     Thus, when the back most tooth is detected, the position of the back most tooth in the trajectory of movement of the brush  5  accumulated to that point, can further increase the estimation accuracy of the brushing site by matching of the teeth row ends and the following trajectory, due to correcting the brushing site at each position in the trajectory based on the position of the updated back most tooth. 
     The CPU  120  estimates the brush angle based on the attitude of the brush  5  detected by step S 10 . The brush angle is the angle per brush against the tooth axis (axis along the head and root of the tooth). The upper part of  FIG. 11  illustrates a state in which the brush angle=15 degrees, the middle part illustrates a state in which the brush angle=45 degrees, and the lower part illustrates a state in which the brush angle=90 degrees. When effectively scraping out food residue and plaque from between the teeth and the periodontal pockets, the bristles of the brush may move the brush so as to enter between the teeth and the periodontal pockets. Therefore, a brush angle in the range of 35 degrees to 55 degrees is preferred. 
     The brush angle, for example, can be estimated from the z-axis direction component Dz of the attitude vector D; when the brush angle is about 90 degrees Dz will be about 0, and as the brush angle decreases the absolute value of Dz increases, which is because the value of Dz changes significantly corresponding to the brush angle. The brush angle may be calculated in a continuous quantity, or it may be a rough estimate such as “less than 35 degrees”, “35 to 55 degrees”, and “55 degrees or above”. 
     Furthermore, the CPU  120  calculates the brush pressure based on the output of the load sensor  18 . When the brush pressure is too mall the plaque removal power decreases, and conversely, when it is too large there is a possibility of problems such as a decrease in the brush life and an increased burden on the gums occurring. Since the brush pressure of an electric toothbrush may be less than a normal toothbrush, most people who started using an electric toothbrush said there was a tendency of excessive brush pressure. The optimum value of brush pressure is about 100 g. 
     The CPU  120  evaluates the brushing results of each site based on the brushing information (brushing site, brush angle, brush pressure) of each position in the trajectory of movement of the brush  5  recorded in the memory  121 , and outputs the evaluation results to the display unit  110  (Display  111 ). Here, an evaluation of the brushing time, brush angle, and brush pressure are carried out. 
     The brushing time of every site is counted by counting up every site of the brushing sites of each position in the trajectory of the brush  5 . For example, if the process of step S 10  to S 50  is performed once for 0.1 seconds, each time the brushing site is counted up, the brushing time of the site is counted up by +0.1 seconds. 
     The brush angle of every site is aggregated at every site of the brush angle of each position based on the brushing site of each position in the trajectory of movement of the brush  5 , and for example, is calculated as the average value. Likewise, the brush pressure of every site is aggregated at every site of the brush angle of each position based on the brushing site of each position in the trajectory of movement of the brush  5 , and for example, is calculated as the average value. 
     The evaluation of the brushing time, brush angle, and brush pressure of every site is not particularly limited. The brushing time can be evaluated in three stages for example, 7 seconds is “insufficient”, 7 seconds to 15 seconds is “good”, and greater than 15 seconds is “excessive”. Furthermore, the brush angle can be evaluated in three stages for example, “less than 35 degrees” is “insufficient”, “35 degrees to 55 degrees” is “good”, and “55 degrees or above” is “excessive”. Furthermore, the brush pressure can be evaluated in three stages for example, less than 80 g is “insufficient”, 80 g to 150 g is “good”, and greater than 150 g is “excessive”. These evaluation results are transmitted to the display unit  110 . 
     The output of the evaluation results in the display unit  110  are not particularly limited. For example, as illustrated in  FIG. 12 , the upper and lower teeth are displayed, and each site can be displayed by a color (“insufficient” is white, “good” is yellow, “excessive” is red, and the like) corresponding to the evaluation results of each site by seeing a display as such, the user can intuitively understand when the brushing of some site in a tooth row is insufficient or excessive. 
     Also, since the position of the back most tooth in the trajectory of movement of the brush  5  is detected, it is possible to evaluate the results of the brushing of the back most tooth as a detailed site of among the back side portion of the teeth row ends. The CPU  120  carries out an evaluation of whether or not the back most tooth was brushed based on the presence or absence of the detection of the back most tooth, and furthermore, an evaluation of the brushing time, brush angle, and brush pressure of the back most tooth based on the brush position that detected the back most tooth and the brushing information near that position. The back most tooth in which there is a tendency to leave un-brushed is detected, and by presenting the evaluation results regarding the brushing of the back most tooth to the user, it is possible to promote health of the teeth. 
     As described above, according to the electric toothbrush device  1 , since it is possible to detect the back most tooth with an acceleration sensor  15  and the like for detecting the trajectory of movement and the attitude of the brush  5 , the configuration of the electric toothbrush  1  can be made to be simple. Also, when the back most tooth is detected, the position of the back most tooth in the trajectory of movement of the brush  5  accumulated to that point are updated, and it is possible to accurately estimate the brushing site since the brushing site at each position in the trajectory is correct based on the position of the updated back most tooth. 
       FIG. 13  illustrates a configuration of a variation of the electric toothbrush  1 . 
     The example illustrated in  FIG. 13  provides a camera  19  in the end of the y-axis direction of the brush  5 . Any camera that can acquire image information in the mouth, such as a visible light camera or an infrared camera, can be employed as the camera  19 . The infrared camera monitors the emitted heat (also referred to as thermography). Since the mouth can be dark while brushing, an infrared camera is more preferable than a visible light camera. Since the contour of the uvula may be understood as described below, the resolution of the camera may be not very high. 
     The CPU  120  acquires an image from the camera  19  in addition to the output of the acceleration sensor  15 , angular velocity sensor  16 , and geomagnetic sensor  17  in step S 10  ( FIG. 5 ), the uvula can be detected from the image. The detection of the uvula is possible using a well-known image analysis technique. For example, contour detection of the uvula by edge extraction or Hough transform, or detection of the uvula by pattern matching and the like is considered. 
     When the brush  5  is on the lingual side, there is a high probability that the uvula will appear in order for the end of the brush  5  to face towards the throat. On the other hand, when the brush  5  on the buccal side, the uvula does not appear in the image. Therefore, CPU  120  determines it to be “lingual” when the uvula is not detected, and as “buccal” when the uvula is detected. 
     Note that, although the uvula is the detected object, the attitude and position of the brush may be determined by recognizing other sites in the mouth (for example, tongue, throat, teeth, gums and the like). For example, if the tongue and throat appear in the image, it can be determined that the brush is in the lingual side. 
     Thus, in addition to the trajectory of movement of the brush  5  detected based on the output of the acceleration sensor  15 , angular velocity sensor  16 , and geomagnetic sensor  17 , by complementarily using the image of the camera  19  in estimation of the brushing site, it is possible to further increase the estimation accuracy of the brushing site. 
     Note that, a light sensor provided in the brush portion is preferable to a camera. Since light is detected in the lingual side whereas the buccal side is completely dark, it is possible to determine both by analyzing the output of the light sensor. 
     The embodiments described herein are in all respects examples and are in no way considered to be limited thereto. The scope of the present invention is indicated by the scope of the patent claims and is intended to include all alternatives within equivalent meaning and scope to the patent claims. 
     As described above, the following matters are disclosed in the present specification. The disclosed electric toothbrush includes: a trajectory detecting module for detecting the trajectory of movement of a brush; an attitude detecting module for detecting the attitude of the brush; a site estimating module for estimating the brushing site at each position in the trajectory, using a trajectory detected by at least the trajectory detecting module; and a back most tooth detecting module for detecting the back most tooth based on change of attitude detected by the attitude detecting module, wherein the site estimating module updates the position of the back most tooth in the trajectory detected by the trajectory detecting module, when the back most tooth is detected by the back most tooth detecting module, and corrects the brushing sites at each position on the trajectory based on the position of the updated back most tooth. 
     Furthermore, in the disclosed electric toothbrush device, the back most tooth detecting module, in reference to the attitude of the brush along the teeth row surface of the back side site, detects the back most tooth based on a difference between the reference of attitude detected by the attitude detecting module. 
     Furthermore, in the disclosed electric toothbrush device, the back most tooth detecting module detects the returning point at the back most side of movement of the brush as the back most tooth, in the trajectory portion in which the brushing site estimated by the site estimation module of among the trajectory detected by the trajectory detecting module is the back side site of the teeth row end. 
     Furthermore, in the disclosed electric toothbrush device, the site estimation module further uses an attitude detected by the attitude detecting module, and estimates the brushing site at each site on the trajectory detected by the trajectory detecting module. 
     Furthermore, the disclosed electric toothbrush device further comprises an evaluation output module for evaluating and outputting brushing results of every site. 
     Section II 
     A brushing site can be estimated based on the detection signal of an acceleration sensor, but the accuracy of such a method can be insufficient. For example, when a user moves his face and the electric toothbrush together in the state of inserting a brush unit into his mouth, although the tooth that the brush unit is contacting does not change, a change occurs in the detection signal of the acceleration sensor. Because of this, there is a possibility that the brushing site can be estimated falsely. 
     Furthermore, when the user moves only his face in the state of inserting the brush unit into his mouth, although a change does not occur in the detection signal of the acceleration sensor, the tooth that the brush unit is contacting changes. Because of this, there is a possibility that the brushing site can be estimated falsely. Accordingly, there is need to address such issues to provide improved brushing site estimation accuracy. 
     The electric toothbrush of the present invention is provided with a driving module that oscillates the brush unit, an acceleration sensor, a first signal achieved from a frequency of a first threshold or more from the output signal of the acceleration sensor, a signal extraction module that extracts a second signal achieved from a frequency of a second threshold or less, a brushing site estimation module by the brush unit based on the output signal of the acceleration sensor, and a correction module that corrects the brushing site estimated by the brushing site estimation module based on the amplitude of the first signal and the amplitude of the second signal. 
     The brushing site estimation method of the present invention is a brushing site estimation method by the electric toothbrush having the driving module that oscillates the brush unit and the acceleration sensor and is provided with a signal extraction step that extracts the first signal achieved from the frequency of the first threshold or more and the second signal achieved from the frequency of the second threshold or less, a brushing site estimation step that estimates the brushing site by the brush unit based on the output signals of the acceleration sensor, and a correction step that corrects the brushing site estimated by the brushing site estimation step. 
       FIG. 14  is a diagram illustrating the schematic structure of the brushing support system for describing an embodiment of the present invention. This system is provided with an electric toothbrush  31 , a charging unit  3100 , and a display unit  3110 . 
     The electric toothbrush  31  is provided with a main body  32  having a motor  311  built in as a driving module that oscillates a brush unit  33 , and the brush unit  33  that oscillates by the driving of the motor  311 . 
     The main body mainly exhibits a cylindrical shape and also has a handle portion for the user to grasp with their hand when brushing teeth. The brush unit  3  has a brush portion arranged by a plurality of brush groups bundling several hairs, and has a detachable structure to a main body  32 . 
     A switch  312  for performing a power on/power off is provided on the main body  32  of the electric toothbrush  31 . 
     The motor  311  (for example, a direct current motor), a charging battery  313  that is the power source for supplying electricity to each portion, a CPU (Central Processing Unit)  314 , and the like are provided on the inner portion of the main body  32  of the electric toothbrush  31 . 
     The CPU  314  carries out each type of calculation and control. A memory  315 , a data sending module  316 , a display module  317 , and the like are connected to the CPU  314 . The memory  315  houses a program, each type of set value, and the like. The data sending module  316  performs wireless communication between a data receiving module  3111  of the display unit  3110 . The display unit  317  displays the brushing effect and the like. 
     A voltage monitor  318  for detecting the output voltage (the remaining battery) of the charging battery  313 , an acceleration sensor  319  for sensing the attitude of the electric toothbrush  31 , and a filter module  320  that filter processes the output signal of the acceleration sensor  319  are further provided on the inner portion of the main body  32  of the electric toothbrush  31 . 
     For example, a multi-axis (here the 3 axes of x, y, and z) acceleration sensor is used in the acceleration sensor  319 . The output of each axes of the acceleration sensor  319  is input into the CPU  314  and is used to detect the 3 dimensional attitude of the brush unit  33 . 
     A piezoresistive type, a capacitance type, or a micro electro mechanical systems (MEMS) heat sensing type can be preferably used for the acceleration sensor  319 . Building the MEMS sensor on the inner portion of the main body  32  is simple since is extremely small-sized. However, the form of the acceleration sensor  319  is not limited to this and a sensor of an electrodynamic formula, a strain gage formula, a voltage formula, and the like may also be used. 
     Furthermore, while not specifically shown, it is good to provide a corrective circuit to correct the balance of the sensitivity of the sensor of each axis, the sensitivity of the temperature characteristics, the temperature drift, and the like. Furthermore, a band pass filter (low pass filter) for removing a dynamic acceleration component and noise may be provided. Furthermore, noise may be reduced by smoothing the output waveform of the acceleration sensor. 
     The system of the present embodiment mounts the main body  32  and is provided with the charging unit  3100  for charging the electric toothbrush  31  and the display unit  3110  for outputting the brushing effect. When charging the charging battery  313 , it is possible to charge by non-contact electromagnetic induction just by mounting the main body  32  on the charging unit  3100 . 
     The display unit  3110  is provided with a data receiving module  3111  that performs wireless communication with the data sending module  316  provided on the inside of the main body  32  of the electric toothbrush  31 , and a display  3112  for outputting the data of the brushing result and the like received from the receiving module  3111 . 
       FIG. 15  is a diagram schematically illustrating the acceleration sensor  319  and a peripheral circuit thereof according to one embodiment. As illustrated in  FIG. 15 , the filter module  320  is connected to the acceleration sensor  319 . The CPU  314  is connected to the filter module  320 . Furthermore, the acceleration sensor  319  is connected directly to the CPU  314 . 
     The filter module  320  receives the output signal from the acceleration sensor  319  and has a Band Pass Filter (BPF)  3201  that passes through only the signal of the specified frequency zone a High Pass Filter (HPF)  3202  connected in parallel to the BPF  3201 , and a low pass filter (LPF)  3203 . 
     The HPF  3202  passes through only a first  3202 P signal of a frequency of a specified cut off frequency (for example, several hundred to several thousand Hz) or more that is a first threshold out of an input signal from the BPF  3201 , and outputs to a processor  3141 . The first threshold is the first signal  3202 P output from the HPF  3202  being set to a large value to an extent reflecting a moveable component of the electric toothbrush  31  occurring by the brush unit  3  being oscillated at high speed by the motor  311 . 
     The LPF  3203  passes through only a second  3203 P signal of a frequency of a specified cut off frequency (for example, several Hz) or less that is a second threshold out of an input signal from the BPF  3201 , and outputs to a processor  3142 . The second threshold is the second signal  3203 P output from the LPF  3203  being set to a small value to an extent reflecting when the electric toothbrush  31  moves much more slowly than the oscillation of the brush unit  33  and a moveable component. 
     The HPF  3202  and the LPF  3203  function as a signal extraction module that extract the first signal  3202 P and the second signal  3203 P from the output signal of the acceleration sensor  319 . The first signal  3202 P is a high frequency signal to the second signal  3203 P. In other embodiment, the signal extraction module can be any device for obtaining the first and second signals from the output of the acceleration sensor. 
     The CPU  314  is provided with the processor  3141 , the processor  3142 , a brushing site estimation module  3143 , and a correction module  3144 . Each of these modules is function block realized by carrying out the program that the CPU  314  housed in the memory  315 . 
     The processor  3141  seeks the amplitude of each waveform of the high-frequency first signal  3202 P output from the HPF  3202  and calculates the variation amount in the specified period on the sought amplitude. 
     The processor  3142  seeks the amplitude of each waveform of the low frequency second signal  3203 P output from the LPF  3203 . 
     The brushing site estimation module  3143  can use the algorithm described in Japanese Unexamined Patent Application Publication No. 2009-240760, or Japanese Unexamined Patent Application Publication No. 2011-156204, which are hereby incorporated by reference in their entireties. These algorithms are based on the output signal from the acceleration sensor  319  to estimate the site being contacted by the brush portion of the brush unit (the brushing site). 
     The correction module  3144  corrects the brushing site estimated by the brushing site estimation module  3143  based on the amplitude of the first signal  3202 P sought by the processor  3141  and the amplitude of the second signal  3203 P sought by the processor  3142 . 
       FIG. 16  is a flow chart for describing the estimation process of the brushing site in the electric toothbrush  31  according to an embodiment. When the switch  312  is operated and the power supply of the electric toothbrush  31  is ON, the CPU  314  performs a process that formats each portion, and the brushing site estimation module  3143  detects the attitude (slant) of the brush based on the output of the acceleration sensor  319  (step S 31 ). 
     Next, the brushing site estimation module  3143  estimates the brushing site based on the attitude detected by the step S 31  (step S 32 ). 
     Next, the correction module  3144  determines, based on the output signal of the processor  3141 , whether or not the amplitude of the first signal  3202 P has changed, that is to say, whether or not the variation amount of the amplitude of the first signal  3202 P is at the third threshold or above (step S 33 ). 
     During teeth brushing, the brush unit  33  will move along with the row of teeth while contacting the row of teeth. In a state in which the brush portion of the brush unit  33  is contacting one tooth contained in the row of teeth, the amplitude of the first signal  3202 P will change at a practically fixed value. That is to say, the variation amount of amplitude of the first signal  3202 P is small in a fixed time. 
     When the brush unit  33  moves along the row of teeth, the brush portion passes through the interdental space. When the brush portion passes through the interdental space, the amplitude of the first signal  3202 P gets smaller in this time because time occurs where the brush unit is not in contact with the tooth. 
     That is to say, from a state where the brush portion is in contact with an arbitrary tooth, when moving the brush portion from this tooth to a neighboring tooth, the amplitude of the first signal  3202 P returns to a first value after the amplitude changes to a second value smaller than the first value from the state of the first value. In this manner, the variation amount of amplitude of the first signal  3202 P gets larger in a fixed time. 
     Therefore, it can be distinguished by the size of the variation amount of amplitude of the first signal  3202 P whether the brush unit  33  is still regarding the tooth or whether the brush unit  33  is moving regarding the tooth. Because of this distinguishing, the step S 33  processing is performed. 
     If the determination of the step S 33  is YES, it can be determined that the brush unit  33  is moving with respect to the tooth, and if the determination of the step S 33  is NO, it can be determined that the brush unit  33  is still with respect to the tooth. 
     When the determination of the step S 33  is YES, the correction module  3144  determines whether or not the amplitude of the second signal  3203 P is large, that is to say, whether or not the amplitude of the second signal  3203 P exceeds a fourth threshold based on the output signal of the processor  3142  (step S 34 ). 
     The pattern in which the brush unit  33  moves with respect to the tooth has a first pattern in which only the electric toothbrush moves in a state where the face is still and a second pattern in which the only the face moves in a state where the electric toothbrush  31  is still. 
     The amplitude of the second signal  3203 P in the first pattern becomes larger because the electric toothbrush is moving. On the other hand, the amplitude of the second signal  3203 P in the second pattern becomes a sufficiently smaller value than the first pattern (a value of the fourth threshold or less) because the electric toothbrush  31  is still. 
     Therefore, it can be distinguished whether it is the first pattern or the second pattern by the determination in step S 34 . 
     When the determination of the step S 34  is YES (the amplitude of the second signal  3203 P exceeds the fourth threshold), the correction module  3144  distinguishes that “the face is still and the brush portion is moving” (step S 35 ). 
     When it is distinguished that “the face is still and the brush portion is moving,” the reliability of the brushing site estimated based on the output signal of the acceleration sensor  319  is high. Because of this, the correction module  3144  makes the brushing site estimated by the brushing site estimation module  3143  effective as it is after the step S 35  (step S 36 ). 
     When the determination of the step S 34  is NO (the amplitude of the signal  3203 P is the fourth threshold or less), the correction module  3144  distinguishes that “the face is moving and the brush portion is still” (step S 37 ). 
     When it is distinguished that “the face is moving and the brush portion is still,” the reliability of the brushing portion estimated based on the output signal of the acceleration sensor  319  gets low. Because of this, the correction module  3144  corrects (substitutes) the brushing site estimated by the brushing site estimation module  3143  to the site neighboring that site (a site estimated to not yet be brushed) after the step S 37  (step S 38 ). 
     When the determination of step S 33  is NO, the correction module  3144  determines whether or not the amplitude of the second signal  3203 P is small, that is to say, whether or not the amplitude of the second signal  3203 P is the fourth threshold or less based on the output of the processor  3142  (step S 39 ). 
     When the correction module  3144  determines that the amplitude of the second signal  3203 P to be small (step S 39 : YES), it distinguishes that “the face is still and the brush portion is also still” (step S 40 ). In this case, the reliability of the brushing site estimated based on the output of the acceleration sensor  319  is high. Because of this, the correction module  3144  makes the brushing site estimated by the brushing site estimation module  3143  effective as it is (step S 41 ). 
     When the correction module  3144  determines that the amplitude of the second signal  3203 P is not small (step S 39 : NO), it distinguishes that “the face and the brush are moving integrally” (step S 42 ). In this case, the reliability of the brushing site estimated based on the output of the acceleration sensor  319  is low. Because of this, the correction module  3144  corrects (substitutes) the brushing site estimated by the brushing site estimation module  3143  to the site estimated just before (step S 43 ). That is to say, the correction module  3144  does not perform a renewal of the brushing site, but performs a process maintaining the brushing site estimated just before. 
     The CPU  314  is estimated as above, and outputs the corrected brushing site to the display unit  3110  (the display  3112 ) via the data sending module  316  (step S 44 ). 
     As above, it is possible to improve the brushing site estimation accuracy based on the amplitude of a high frequency component and the amplitude of a low frequency component output from the acceleration sensor  319  provided on the electric toothbrush  31 . Therefore, it becomes possible to perform effective brushing support. 
     Each process performed by the CPU  314  in the present embodiment can also be presented as a program for carrying out on a computer. Furthermore, the process performed by the filter  320  can also be presented as a program for carrying out on a computer. This manner of program is recorded to a non-temporary (non-transitory) recording medium as a program that can be read by the computer. 
     This manner of “recording medium that can be read by a computer” is, for example, an optical medium such as a Compact Disc-ROM (CD-ROM), and includes magnetic recording mediums such as a memory card. Furthermore, this manner of program can also be presented by download via a network. 
     It should be thought that all of the points of the embodiment shown this time are examples and are not limited. The scope of the present invention is not the above description, but is illustrated in the scope of claims, and all of the changes having meaning equal to the scope of claims and within the scope are implied to be included. 
     As described above, the below matters are shown in the present specification. The electric toothbrush shown is comprised of a driving module that oscillates the brush unit, an acceleration sensor, a signal extraction module that extracts the first signal derived from the frequency being at the first threshold or more and the second signal derived from the frequency being at the second threshold or below from the output signal of the acceleration sensor, a brushing site estimation module that estimates the brushing site by the brush unit based on the output signal of the acceleration sensor, and a correction module that corrects the brushing site estimated by the brushing site estimation module based on the amplitude of the first signal and the amplitude of the second signal. 
     The electric toothbrush shown is something wherein the correction module performs corrections in the first case wherein the variation amount of the amplitude of the first signal is at the third threshold or more and when variation amount of the amplitude of the second signal is at the fourth threshold or less, or in the second case wherein the variation amount of the amplitude of the first signal is less than the third threshold and the amplitude of the second signal exceeds the fourth threshold. 
     The electric toothbrush shown is something wherein the correction module substitutes the brushing site estimated by the brushing site estimation module to the neighboring site in the first case. 
     The electric toothbrush shown is something wherein the correction module substitutes the brushing site estimated by the brushing site estimation module to the brushing site estimated by the brushing site estimation module in a state just before the variation amount of the amplitude of the first signal becomes less than the third threshold. 
     The brushing site estimation method shown is a brushing site estimation method by an electric toothbrush having a driving module that oscillates the brush unit and an acceleration sensor, and is provided with a signal extraction step that extracts the first signal achieved from the frequency of the first threshold or more and the second signal achieved from the frequency of the second threshold or less, a brushing site estimation step that estimates the brushing site by the brush unit based on the output signals of the acceleration sensor, and a correction step that corrects the brushing site estimated by the brushing site estimation step. 
     The present invention has especially high convenience applied as a household use electric toothbrush and is effective. 
     While the inventions have been described with respect to specific examples, those skilled in the art will appreciate that there are numerous variations and permutations of the above described inventions. It is to be understood that other embodiments may be utilized and structural and functional modifications may be made without departing from the scope of the present inventions. Thus, the spirit and scope should be construed broadly as set forth in the appended claims.