toothbrush

Abstract

The present invention aims to provide a toothbrush that is highly versatile, comfortable to use, and allows users to recognize appropriate brushing pressure. A sensor is provided rearward of the bristle surface, detecting when an external force in a first direction perpendicular to the bristle surface exceeds a predetermined value. The sensor measures the relationship between the amount of head displacement when a load is applied to the head in the first direction toward the back side (opposite the bristle surface) and the repulsive force generated in response to the amount of displacement. The sensor changes the repulsive force from increasing to decreasing at a first threshold value as the amount of displacement increases, and stops the decrease in the repulsive force at a second threshold value greater than the first threshold value. If the repulsive force when the amount of displacement is the first threshold value is A and the repulsive force when the amount of displacement is the second threshold value is B, the ratio B / A is 0.3 to 0.9.

Description

[Technical Field]

[0001] The present invention relates to a toothbrush. This application claims priority based on Japanese Patent Application No. 2018-246150, filed on December 27, 2018, the contents of which are incorporated herein by reference. [Background technology]

[0002] While the percentage of people who have 20 teeth at age 80 is now about 50%, the rate of elderly caries (root caries) is increasing. Root caries occurs in the dentin exposed by gingival recession, and because dentin has a higher proportion of organic components than enamel, caries progresses more quickly. One of the causes of gingival recession is overbrushing, which involves brushing with more pressure than is appropriate.

[0003] Since brushing pressure is defined as the ratio of load to bristle area, reducing brushing pressure can be achieved by at least one of reducing the load and increasing the bristle area. Regarding reducing the load, toothbrushes available on the market include those designed to tilt the neck portion above the bristle surface in advance, so that the neck portion bends during brushing and straightens out during brushing, those with softer bristles using narrower diameter bristles, and those designed to reduce the force applied to the bristle portion by positioning the center of gravity of the grip closer to the rear end of the handle. Regarding increasing the bristle area, toothbrushes with wider heads are also available. However, while these designs can reduce brushing pressure, it is difficult to ensure that all users recognize the appropriate brushing pressure at the same level and control the brushing pressure.

[0004] Furthermore, although people receive instruction at dental clinics on proper brushing techniques, it has been found that many users are aware that they are over-brushing but are unable to improve their brushing habits because they find it difficult to do so on their own due to reasons such as not being clear about how much pressure to use.

[0005] Therefore, one example of a means for making a user aware of the appropriate brushing pressure is the toothbrush disclosed in Patent Document 1. The toothbrush disclosed in Patent Document 1 is disposed between the head and the grip, and has a two-beam structure consisting of a rear beam to which compressive stress is applied during normal use, and a face-side beam to which tensile stress is applied.

[0006] In this toothbrush, when a user holds the grip and a compressive force exceeding a predetermined force is applied, the rear beam elastically buckles and reverses from an upwardly convex arc to a downwardly convex arc. In this way, the toothbrush disclosed in Patent Document 1 allows the user to recognize that the appropriate brushing pressure has been exceeded by the rear beam reversing. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 6-504937 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the toothbrush disclosed in Patent Document 1, when excessive brushing load is applied, the rear beam deforms in a direction approaching the face beam, which limits the amount of deformation of the rear beam and makes the toothbrush less versatile.Furthermore, when excessive brushing load is applied, the rear beam comes into contact with the face beam, which results in a poor user experience.

[0009] The present invention has been made in consideration of the above points, and has an object to provide a toothbrush that is highly versatile, has a good usability, and allows the user to recognize the appropriate brushing pressure. [Means for solving the problem]

[0010] According to a first aspect of the present invention, there is provided a toothbrush having a head portion having a bristle-implanted surface located at the tip end in the longitudinal direction, a handle portion located rearward of the head portion, and a neck portion located between the bristle-implanted surface and the handle portion, and a sensor portion located rearward of the bristle-implanted surface for detecting when an external force in a first direction perpendicular to the bristle-implanted surface exceeds a predetermined value, the sensor portion being configured to detect when an external force in a first direction perpendicular to the bristle-implanted surface exceeds a predetermined value, the sensor portion detecting a relationship between the amount of displacement of the head portion when a load is applied to the back side of the head portion in the first direction, which is the opposite side to the bristle-implanted surface, and the repulsive force generated in response to the amount of displacement, the repulsive force changing from increasing to decreasing at a first threshold value as the amount of displacement increases, and stopping the decrease in the repulsive force when the amount of displacement reaches a second threshold value greater than the first threshold value, where A is the repulsive force when the amount of displacement is the first threshold value, and B is the repulsive force when the amount of displacement is the second threshold value, and the value B / A is greater than or equal to 0.3 and less than 0.9.

[0011] In addition, in the toothbrush according to one aspect of the present invention, the repulsive force A is 1.0 N or more and 5.0 N or less.

[0012] Furthermore, in the toothbrush according to one aspect of the present invention, when the displacement amount at the first threshold is C and the displacement amount at the second threshold is D, the value represented by DC is greater than or equal to 0 mm and less than or equal to 1.5 mm.

[0013] In the toothbrush according to one aspect of the present invention, the displacement C is 28 mm or less.

[0014] In addition, in the toothbrush according to one aspect of the present invention, the sensing unit is characterized in that when the displacement amount exceeds the second threshold value, the sensing unit increases the repulsive force in accordance with an increase in the displacement amount.

[0015] Furthermore, in the toothbrush according to one aspect of the present invention, the rate of increase in the repulsive force from the displacement at the second threshold value as a starting point until the displacement of the head portion reaches 4 mm is 0.015 or more.

[0016] Furthermore, in the toothbrush according to one aspect of the present invention, the sensing unit is characterized in that when a load is applied to the rear side, and the reduction in the repulsive force is stopped at least, and then the load is released, the relationship between the displacement and the repulsive force after the release maintains the same relationship as before the load was applied.

[0017] In addition, in the toothbrush according to one aspect of the present invention, the sensing portion connects a first region closer to the tip end than the sensing portion and a second region closer to the rear end than the sensing portion, and is equipped with an inverted portion that snaps through and inverts when the head portion is displaced toward the back side, which is the opposite side from the bristle-implanted surface in the first direction, due to the external force exceeding the threshold value, and an elastic deformation portion that is arranged with a gap from the inverted portion, connects the first region and the second region, and elastically deforms at least up to the external force at which the inverted portion snaps through and inverts, and is characterized in that the inverted portion is located between the outer contour of the bristle-implanted surface side and the outer contour of the back side of the elastic deformation portion when viewed from the side in a direction perpendicular to the longitudinal axis and the first direction. Furthermore, in the toothbrush according to one aspect of the present invention, the path along which the elastic deformation portion is deformed by an external force in the first direction and the path along which the inverted portion is deformed by an external force in the first direction are arranged so as not to interfere with each other.

[0018] Furthermore, in the toothbrush according to one aspect of the present invention, the elastic deformation portion and the inverted portion are arranged with a gap in a second direction perpendicular to the first direction and the longitudinal axis direction, respectively.

[0019] Furthermore, in the toothbrush according to one aspect of the present invention described above, the inverted portion is convex toward the back side when the external force in the first direction is equal to or less than the predetermined value, and is inverted to a convex shape toward the bristle implantation surface when the external force in the first direction exceeds the predetermined value.

[0020] Furthermore, in the toothbrush according to one aspect of the present invention, the inverted portion has a groove portion extending in the second direction on at least one of the bristle implantation surface side and the back side in an area including the vertex of the convex shape.

[0021] Furthermore, in the toothbrush according to one aspect of the present invention, the inverted portion is formed of a hard resin, and a portion of the elastically deforming portion is formed of a resin having a different hardness from the hard resin.

[0022] In the toothbrush according to the above aspect of the present invention, the gap is a through hole extending in the first direction. [Effects of the Invention]

[0023] The present invention can provide a toothbrush that is highly versatile, has a good usability, and allows the user to recognize the appropriate brushing pressure. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a diagram showing an embodiment of the present invention, and is a front view of a toothbrush 1. FIG. [Figure 2] FIG. 2 is a cross-sectional view of the toothbrush 1 taken along a plane including the center in the width direction. [Figure 3] 1 is a cross-sectional view of the sensing unit 70 cut along a plane parallel to the thickness direction and width direction. [Figure 4] 1 is a cross-sectional view of the sensing unit 70 cut along a plane parallel to the thickness direction and the long axis direction. [Figure 5] FIG. 10 is a partial front view of the sensing unit 70 and its surroundings in the hard portion 70H. [Figure 6] FIG. 10 is a partial side view of the sensing unit 70 and its surroundings in the hard portion 70H. [Figure 7] FIG. 10 is a cross-sectional view of the sensing unit 70 cut along a plane parallel to the thickness direction and the long axis direction, for explaining that the inverted portion has been inverted. [Figure 8] FIG. 1 is a graph showing the relationship between the indentation amount (mm) and the deflection repulsive force (N) measured using an autograph testing machine. [Figure 9] FIG. 2 is a perspective view showing a sensing unit 70 of the toothbrush 1. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, an embodiment of the toothbrush of the present invention will be described with reference to FIGS. The following embodiment shows one aspect of the present invention, does not limit the present invention, and can be modified as desired within the scope of the technical concept of the present invention. In the following drawings, the scale and number of each structure are different from the actual structure to make each component easier to understand. In the following description, the direction perpendicular to the implanted surface in a side view is referred to as the up-down direction, with the implanted surface side being referred to as the upper side and the back side opposite the implanted surface being referred to as the lower side. The terms up-down direction, upper side, and lower side are merely used for the purpose of explanation and do not limit the actual positional relationship or direction in the present invention.

[0026] Fig. 1 is a front view of toothbrush 1. Fig. 2 is a cross-sectional view of toothbrush 1 cut along a plane including the center in the width direction (the vertical direction in Fig. 1).

[0027] The toothbrush 1 of this embodiment comprises a head portion 10 arranged at the tip end side in the longitudinal direction (hereinafter simply referred to as the tip end side) and having tufts of bristles (not shown) implanted therein, a neck portion 20 extending to the rear end side in the longitudinal direction of the head portion 10 (hereinafter simply referred to as the rear end side), a sensing portion 70 extending to the rear end side of the neck portion 20, and a grip portion 30 extending to the rear end side of the sensing portion 70 (hereinafter the head portion 10, neck portion 20, grip portion 30 and sensing portion 70 will be collectively referred to as the handle body 2).

[0028] The toothbrush 1 of this embodiment is a molded body in which a hard portion H made of hard resin and a soft portion E made of soft resin are integrally molded. The hard portion H constitutes at least a portion of each of the head portion 10, neck portion 20, grip portion 30, and sensing portion 70. The soft portion E constitutes a portion of each of the grip portion 30 and sensing portion 70 (details will be described later).

[0029] [Head part 10] The head unit 10 has a bristle implantation surface 11 on one side in the thickness direction (the direction perpendicular to the paper surface in FIG. 1). Hereinafter, the side of the bristle implantation surface 11 in the thickness direction will be referred to as the front side in the front direction, the side opposite the bristle implantation surface will be referred to as the back side, and the direction perpendicular to the thickness direction and the longitudinal direction will be referred to as the width direction (or side direction, as appropriate). A plurality of bristle implantation holes 12 are formed in the bristle implantation holes 12. Bundles of bristles (not shown) are implanted in the bristle implantation holes 12.

[0030] The width of the head portion 10, i.e., the length in the width direction parallel to the bristle implantation surface 11 on the front side and perpendicular to the longitudinal direction (hereinafter simply referred to as width), is not particularly limited, and is preferably 7 mm or more and 13 mm or less, for example. If it is equal to or greater than the above lower limit, a sufficient area for implanting tufts can be secured, and if it is equal to or less than the above upper limit, operability in the oral cavity can be further improved.

[0031] The length of the head portion 10 in the longitudinal direction (hereinafter simply referred to as the length) is not particularly limited, and is preferably, for example, 10 mm or more and 33 mm or less. If the length of the head portion 10 is equal to or greater than the above-mentioned lower limit, a sufficient area for implanting tufts of hair can be secured, and if it is equal to or less than the above-mentioned upper limit, operability in the oral cavity can be further improved. In this embodiment, the boundary between the neck portion 20 and the head portion 10 in the longitudinal direction is the position where the width of the neck portion 20 is minimum from the neck portion 20 toward the head portion 10.

[0032] The length in the thickness direction of the head portion 10 (hereinafter simply referred to as thickness) can be determined taking into consideration the material, etc., and is preferably 2.0 mm or more and 4.0 mm or less. If the thickness of the head portion 10 is equal to or more than the above-mentioned lower limit, the strength of the head portion 10 can be further increased. If the thickness of the head portion 10 is equal to or less than the above-mentioned upper limit, the reachability to the back of the molars can be improved and the operability within the oral cavity can be further improved.

[0033] The bristle bundle is a bundle of multiple hairs. The length from the implantation surface 11 to the tip of the bristle bundle (hair length) can be determined taking into consideration the desired hair stiffness of the bristle bundle, and is, for example, 6 to 13 mm. All the bristle bundles may have the same hair length, or may have different hair lengths.

[0034] The thickness of the tuft (tuft diameter) can be determined taking into consideration the desired tuft stiffness, etc., and is set to, for example, 1 to 3 mm. All tufts may have the same tuft diameter, or may have different tuft diameters.

[0035] The bristles constituting the bristle bundle include, for example, bristles whose diameter gradually decreases toward the tip and whose tip is sharpened (tapered bristles), bristles whose diameter is almost constant from the implantation surface 11 toward the tip (straight bristles), etc. Examples of straight bristles include bristles whose tip is a flat surface approximately parallel to the implantation surface 11 and bristles whose tip is rounded into a hemispherical shape.

[0036] Examples of materials for the bristles include polyamides such as 6-12 nylon (6-12NY) and 6-10 nylon (6-10NY), polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), and polybutylene naphthalate (PBN), polyolefins such as polypropylene (PP), polyolefin elastomers, and elastomer resins such as styrene elastomers. These resin materials can be used alone or in combination of two or more. Examples of bristles include polyester bristles with a multi-core structure having a core and at least one sheath layer provided on the outside of the core.

[0037] The cross-sectional shape of the bristles is not particularly limited, and may be a circle such as a perfect circle or an oval, a polygon, a star, a three-leaf clover, a four-leaf clover, etc. The cross-sectional shapes of all the bristles may be the same or different.

[0038] The thickness of the bristles can be determined taking into consideration the material, etc., and when the cross section is circular, it is, for example, 6 to 9 mils (1 mil = 1 / 1000 inch = 0.025 mm). In addition, multiple bristles of different thicknesses may be used in any combination taking into consideration the feel of use, brushing feel, cleaning effect, durability, etc.

[0039] [Neck part 20] The length of the neck portion 20 is preferably 40 mm or more and 70 mm or less from the viewpoint of operability. As an example, the width of the neck portion 20 is gradually increased from the minimum position toward the rear end. In this embodiment, the neck portion 20 is formed so that the width gradually increases from the minimum position toward the rear end. Also, the neck portion 20 is formed so that the thickness gradually increases from the minimum position toward the rear end.

[0040] The width and thickness of the neck portion 20 at its minimum position are preferably 3.0 mm or more and 4.5 mm or less. If the width and thickness of the neck portion 20 at its minimum position are equal to or greater than the above-mentioned lower limit, the strength of the neck portion 20 can be increased, and if they are equal to or less than the above-mentioned upper limit, the lips can be easily closed, the reach to the back teeth can be improved, and operability in the oral cavity can be increased. The width and thickness of the neck portion 20, which are formed so as to gradually increase from the minimum position toward the rear end, can be determined appropriately taking into account the material, etc.

[0041] The front side of the neck portion 20 in a side view is inclined toward the front side as it approaches the rear end. The back side of the neck portion 20 in a side view is inclined toward the rear end. The neck portion 20 in a front view is inclined in a direction such that the distance from the widthwise center increases toward the rear end.

[0042] In this embodiment, the boundary between the neck portion 20 and the sensing unit 70 is the position of the tip of the neck side 20 where the elastic deformation unit 90 (described later) is provided. Here, the width from the neck portion 20 toward the grip portion 30 expands along an arc-shaped outline in both front and side views, and the position of the center of curvature of the arc coincides with the position in the long axis direction where the arc changes. More specifically, in the front view shown in FIG. 1, the boundary between the neck portion 20 and the sensing unit 70 coincides with the position in the long axis direction where the center of curvature changes from the outside of the arc-shaped outline toward the center in the width direction. Furthermore, in the side view shown in FIG. 2, the boundary between the neck portion 20 and the sensing unit 70 coincides with the position in the long axis direction where the center of curvature changes from the outside of the arc-shaped outline toward the center in the thickness direction.

[0043] [Gripping part 30] The gripping portion 30 is disposed along the longitudinal axis. As shown in Fig. 1, the width of the gripping portion 30 gradually narrows from the boundary with the sensing portion 70 toward the rear end, and then extends at a substantially constant length. As shown in Fig. 2, the thickness of the gripping portion 30 gradually narrows from the boundary with the sensing portion 70 toward the rear end, and then extends at a substantially constant length.

[0044] In this embodiment, the boundary between the sensing unit 70 and the gripping unit 30 is the position of the tip of the gripping unit 30 where the elastic deformation unit 90 (described later) is provided. Here, the width from the sensing unit 70 to the gripping unit 30 decreases along an arc-shaped contour in both front and side views, and the position of the center of curvature of the arc coincides with the position in the long axis direction where the center of curvature changes from the center in the width direction to the outside of the arc-shaped contour in the front view shown in FIG. 1 . Furthermore, the boundary between the sensing unit 70 and the gripping unit 30 coincides with the position in the long axis direction where the center of curvature changes from the center in the thickness direction to the outside of the arc-shaped contour in the side view shown in FIG. 2 .

[0045] The position in the longitudinal direction where the widthwise length of the gripping portion 30 gradually narrows from the boundary with the sensing portion 70 toward the rear end and then becomes approximately constant is the same as the position in the longitudinal direction where the thicknesswise length of the gripping portion 30 gradually narrows from the boundary with the sensing portion 70 toward the rear end and then becomes approximately constant.

[0046] The gripping portion 30 has a soft portion 31E in the center in the width direction on the front side. The soft portion 31E constitutes a part of the soft portion E. In a front view, the soft portion 31E gradually narrows from the boundary with the sensing portion 70 toward the rear end, and then extends a substantially constant length. In a front view, the side edges of the soft portion 31E and the outer side edges of the gripping portion 30 in the width direction are formed at a substantially constant distance.

[0047] The grip portion 30 has a hard portion 30H. The hard portion 30H constitutes a part of the hard portion H. The hard portion 30H has a recess 31H on the front side in which a part of the soft portion 31E is embedded. The recess 31H gradually narrows from the boundary with the sensing portion 70 toward the rear end in a front view, and then extends a substantially constant length.

[0048] A part of the soft portion 31E protrudes further than the hard portion 30H exposed on the front side, while the other soft portion 31E is substantially flush with the hard portion 30H exposed on the front side.

[0049] The gripping portion 30 has a soft portion 32E in the center in the width direction on the rear side (see FIGS. 1 and 2). The soft portion 32E constitutes a part of the soft portion E. In front view, the soft portion 32E has an outer contour that is substantially the same as the outer contour of the soft portion 31E. That is, the soft portion 32E gradually narrows from the boundary with the sensing portion 70 toward the rear end, and then extends a substantially constant length. In rear view, the side edges of the soft portion 32E and the outer side edges of the gripping portion 30 in the width direction are formed at a substantially constant distance.

[0050] The hard portion 30H has a recess 32H (see FIG. 2) on the rear side in which a part of the soft portion 32E is embedded. The recess 32H gradually narrows from the boundary with the sensing portion 70 toward the rear end side in rear view, and then extends a substantially constant length.

[0051] A part of the soft portion 32E protrudes further than the hard portion 30H exposed on the rear side, while the other part of the soft portion 32E is substantially flush with the hard portion 30H exposed on the front side.

[0052] The soft portion 31E is provided on the front side of the grip portion 30, and the soft portion 32E is provided on the back side, so that the gripping ability when gripping the grip portion 30 is improved.

[0053] [Sensing section 70] The sensing unit 70 senses that an external force in a first direction perpendicular to the flocking surface 11 has exceeded a predetermined value (hereinafter referred to as the external force threshold value). The sensing unit 70 determines the relationship between the amount of displacement of the head unit 10 when a load is applied to the back side of the head unit 10 in the thickness direction and the repulsive force generated in response to the amount of displacement by changing the repulsive force from increasing to decreasing at a first threshold value as the amount of displacement increases, and by stopping the decrease in the repulsive force at a second threshold value at which the amount of displacement is greater than the first threshold value (details will be described later).

[0054] As shown in FIG. 1, the sensing portion 70 has a neck portion 20 on the tip side of the sensing portion 70 and an inverted portion 80 and an elastically deformable portion 90 that connect the grip portion 30 on the rear side of the sensing portion 70.

[0055] Fig. 3 is a cross-sectional view of the sensing unit 70 taken along a plane parallel to the thickness and width directions. Fig. 4 is a cross-sectional view of the sensing unit 70 taken along a plane parallel to the thickness and long axis directions. As shown in Fig. 3, the elastic deformation portions 90 are provided on both sides of the inverted portion 80 in the width direction with a gap S therebetween. The gap S is formed by a through hole K that penetrates in the thickness direction. As shown in Fig. 1, the through hole K is formed in a rectangular shape in a plan view that extends in the long axis direction.

[0056] By providing the gap S, the reversing portion 80 can be inverted (easier to be inverted) without interfering with the surrounding structure. Furthermore, because the deformation of the reversing portion 80 does not follow the deformation of the elastically deforming portion (due to the lack of interference), the functional roles of the reversing portion 80 and the elastically deforming portion 90 (described later) can be independent. This allows for greater design freedom to achieve the following effects, for example. For example, the vibrations and sounds generated when the reversing portion 80 inverts (described later) can be clearly generated. Furthermore, by extending the gap S to both sides of the reversing portion 80 in the thickness direction so as not to interfere with the reversing behavior of the reversing portion 80, the above effects can be further enhanced. By widening the gap S in the thickness direction, the vector of the load applied to the brush portion (bristles) during brushing becomes parallel to the direction in which the gap opens, and further the direction in which the reversing portion 80 and the elastically deforming portion 90 deform (see Figure 7). This makes it easier to link the generation of vibrations and sounds due to reversal with the brushing load, for example. Furthermore, by extending the gap S from the front side to the back side via the through-hole K, the movable range of the elastically deformable portion 90, which is responsible for the flexing function of the toothbrush skeleton in response to the load during brushing, can be further expanded (the tensile behavior on the front side and the compressive behavior on the back side associated with flexing are less likely to be hindered). If there is no through-hole K between the elastically deformable portion 90 and the inverted portion 80, the movable range of the elastically deformable portion 90 will be narrowed. In this case, it is possible that the inverted portion 80 will not be triggered to invert within the appropriate load range, and will invert before reaching the appropriate load range, or will not invert even when the load is within the appropriate load range. In contrast, by providing a through-hole K between the elastically deformable portion 90 and the inverted portion 80, the "external force threshold" at which the inverted portion 80 inverts (described below) can be more precisely controlled. The gap S does not have to penetrate the thickness direction; for example, it may be formed by a closed cavity extending in the longitudinal direction within the elastically deformable portion 90. It may also be formed by a recess (described below) opening to the front or back side.

[0057] Each elastically deforming portion 90 has a hard portion 90H and a soft portion 90E. As shown in FIG. 1, the hard portion 90H and the soft portion 90E connect the rear end of the neck portion 20 and the front end of the grip portion 30. As shown in FIGS. 3 and 4, a recess (recess) 71 opening to the front side and a recess (recess) 72 opening to the rear side are provided between a pair of elastically deforming portions 90. The bottoms of both widthwise ends of the recesses 71 and 72 are connected to through-holes K. An inverted portion 80 is exposed at the bottom of the widthwise center of the recesses 71 and 72. The provision of the recesses 71 and 72 can, for example, further expand the movable range of the elastically deforming portion responsible for the deflection function of the toothbrush skeleton in response to the load during brushing, thereby improving the deflection anisotropy in the thickness direction. Note that the recess between a pair of elastically deforming portions 90 does not have to penetrate through the thickness direction, and may be open only in one direction in the thickness direction. Also, for example, a closed cavity extending in the long axis direction may be formed inside the elastically deforming portion 90, and a pair of elastically deforming portions may be formed in the width direction with the cavity sandwiched in the middle.

[0058] The pair of elastic deformation parts 90 have longitudinal ends of the soft parts 90E connected in the width direction on both the front and rear sides. The soft parts 90E of the pair of elastic deformation parts 90 are provided around the oval recesses 71, 72 in a front view. The rear ends of the soft parts 90E are connected to the soft part 31E of the grip part 30.

[0059] Because the soft portions 90E are connected in the width direction at both the tip and rear end sides of the elastically deforming portion 90, stress is less likely to concentrate at the end of the inverted portion 80 even when the inverted portion 80 is repeatedly inverted, making the inverted portion less likely to break. Also, because the soft portions 90E are connected in the width direction, the amount of heat possessed by the soft resin (elastomer) during injection molding increases, thereby improving the adhesion between the neck portion 20 and the sensing portion 70 (between the neck portion 20 and the elastically deforming portion 90). Furthermore, because the soft portions 90E are connected in the width direction at both the tip and rear end sides of the elastically deforming portion 90, the anisotropy of the sensing portion 70 is increased, and, for example, the pair of elastically deforming portions 90 can bend in the thickness direction without twisting in response to the movement during brushing.

[0060] Fig. 5 is a partial front view of the periphery of the hard part 70H of the sensing unit 70. Fig. 6 is a partial side view of the periphery of the hard part 70H of the sensing unit 70. As shown in FIG. 5, the hard portion 70H is formed in a rectangular shape in a plan view, connecting the hard portion 20H of the neck portion 20 and the hard portion 30H of the grip portion 30 in the long axis direction.

[0061] As shown in FIG. 6, the front end side of the hard portion 70H is connected to the hard portion 20H by a curved surface 73H that is arc-shaped in a side view. The rear end side of the hard portion 70H is connected to the hard portion 30H by a curved surface 74H that is arc-shaped in a side view. The centers of the arcs of the curved surfaces 73H and 74H are located closer to the front side than the hard portion 70H in a side view. The front end side of the hard portion 70H is connected to the hard portion 20H by a curved surface 75H that is arc-shaped in a side view. The rear end side of the hard portion 70H is connected to the hard portion 30H by a curved surface 76H that is arc-shaped in a side view. The centers of the arcs of the curved surfaces 75H and 76H are located closer to the rear side than the hard portion 70H in a side view.

[0062] If the curved surfaces 73H-76H were not present, stress would likely concentrate at the boundary between the leading end of the hard portion 70H and the hard portion 20H, and at the boundary between the rear end of the hard portion 70H and the hard portion 30H. In contrast, the presence of the curved surfaces 73H-76H alleviates this concentrated stress. Furthermore, the presence of the curved surfaces 73H-76H allows both the leading end and rear end of the elastically deforming portion 90 and the inverted portion 80 to deform flexibly (the degree of deformation of the elastically deforming portion 90, which triggers inversion, can be sensed more precisely).

[0063] The hard portion 70H has through holes 73 provided on both sides of the inverted portion 80 in the width direction. The through holes 73 each extend in the long axis direction. The length of the through hole 73 in the long axis direction is the length at which the tip end of the through hole 73 is separated from the hard portion 20H and the rear end of the through hole 73 is separated from the hard portion 30H. As shown in FIG. 3 , a soft portion 90E is provided in the through hole 73 closer to the hard portion 90H in the width direction, and a through hole K is formed closer to the inverted portion 80 in the width direction.

[0064] In the hard portion 70H, the inverted portion 80 is centered on both sides of the inverted portion 80 in the width direction via the through-holes 73, so that the shape of the inverted portion 80 can be maintained even when a load is applied and the elastically deforming portion 90 is deformed. When the hard portion H, which constitutes the entire length of the toothbrush 1, is bent, the inverted portion 80 of the sensing unit 70 inverts in an attempt to release the accumulated strain energy. For example, if the hard portion 70H were to connect the neck portion 20 and the grip portion 30 only by the inverted portion 80, the energy would not be stored and the inverted portion would immediately invert. If the inverted portion 80 is injection molded integrally with the first region A1 and second region A2, which will be described later, as well as the neck portion 20, the grip portion 30, and the hard portion 70H, the accumulated strain energy can be efficiently transmitted to the inverted portion.

[0065] The hard portion 90H is formed on the outer side of the through-hole 73 in the width direction of the hard portion 70H. As shown in FIG. 3, the hard portion 90H has a substantially rectangular cross-sectional shape. The hard portion 90H is embedded in the soft portion 90E. Because the hard portion 90H is embedded in the soft portion 90E, the stress applied to the hard portion 90H can be alleviated in terms of strength. Furthermore, in terms of the degree of deflection of the toothbrush 1 in response to a load, the elastic behavior of the elastically deforming portion 90 can be controlled. Furthermore, the deflection anisotropy of the sensing portion 70 is enhanced, and it becomes possible to deflect the elastically deforming portion 90 in response to, for example, brushing movements without twisting in the thickness direction.

[0066] An example of a material for the hard portion H is a resin having a flexural modulus (JIS 7171) of 1500 MPa or more and 3500 MPa or less, such as polyacetal resin (POM). The flexural modulus of the hard portion H is more preferably 2000 MPa or more and 3500 MPa or less. By using a material with a high elastic modulus (e.g., POM), snap-through buckling occurs when an excessive load is applied, even if the shape is made thin or slim, resulting in vibration. Furthermore, by using a material with a high elastic modulus, snap-through buckling can be quickly restored to its initial state (a state in which the deflection of the elastically deformable portion 90 is released) after snap-through buckling occurs.

[0067] As a material for the soft portion E, a material having a Shore hardness of 90 or less A is preferred, and a Shore hardness of 50 to 80 A is more preferred, since the load at which snap-through buckling occurs is closer to the recommended brushing load value. Examples of soft resins include elastomers (e.g., olefin-based elastomers, styrene-based elastomers, polyester-based elastomers, polyurethane-based thermoplastic elastomers, etc.) and silicones. Styrene-based elastomers are preferred because of their excellent miscibility with polyacetal resins.

[0068] As shown in Fig. 5, the inverted portion 80 extends in the longitudinal direction in a front view and connects a first region A1 on the tip side of the through-hole 73 in the hard portion 70H with a second region A2 on the rear side of the through-hole 73. In a first stable state (hereinafter referred to as the first state) shown in Fig. 4 in which no external force is applied to the head portion 10 toward the rear side (or an external force equal to or less than a predetermined external force threshold described below is applied), the inverted portion 80 is formed in a substantially V-shape in a side view that gradually slopes toward the rear side from both ends in the longitudinal direction toward the center. That is, in the first state, the inverted portion 80 is formed in a convex shape toward the rear side with the center in the longitudinal direction as its apex.

[0069] For example, when an external force is applied to the back side of the head unit 10 while the gripping unit 30 is being gripped, if the magnitude of the external force is in a first state below a predetermined external force threshold, the elastic deformation unit 90 and the inversion unit 80 in the sensing unit 70 elastically deform according to the magnitude of the external force.

[0070] In other words, when an external force is applied to the back side of the head unit 10, the sensing unit 70 changes the relationship between the amount of displacement of the head unit 10 corresponding to the magnitude of the external force and the repulsive force (flexural repulsive force) generated according to that amount of displacement by changing the repulsive force from increasing to decreasing at a first threshold value as the amount of displacement of the head unit 10 increases, and stops the decrease in the repulsive force at a second threshold value at which the amount of displacement of the head unit 10 is greater than the first threshold value.

[0071] When the magnitude of the external force exceeds a predetermined external force threshold and the displacement of the head portion 10 exceeds a first threshold, the elastic deformation portion 90 bends and elastically deforms in accordance with the magnitude of the external force that exceeds the external force threshold. On the other hand, when the magnitude of the external force exceeds a predetermined external force threshold and the displacement of the head portion 10 exceeds the first threshold, the inverted portion 80 undergoes snap-through buckling and inverts when the neck portion 20 is deformed, as shown by the two-dot chain line in FIG. 7, and enters a second stable state (hereinafter referred to as the second state). In the second state, the inverted portion 80 inverts in a direction that gradually slopes toward the front side as it approaches the center, forming a roughly inverted V shape in side view. In the second state, the inverted portion 80 is formed in a convex shape toward the front side, with the center in the longitudinal direction being the apex.

[0072] When the inverting portion 80 transitions from the first state to the second state, the energy accumulated in the inverting portion 80 until it reaches the second state is released, so the displacement of the head portion 10 increases but the repulsive force decreases. Furthermore, since the inverting portion 80 is in a stable state when it reaches the second state, the decrease in the repulsive force stops.

[0073] That is, when the magnitude of an external force exceeds a predetermined external force threshold, the elastic deformation portion 90 elastically deforms, causing the inverted portion 80 to snap-through, buckle, and invert from the first state to the second state while the flexural strength of the sensing portion 70 is ensured. Furthermore, because a through hole K is provided between the inverted portion 80 and the elastic deformation portion 90, the inverted portion 80 and the elastic deformation portion 90 can deform independently of each other, making it easier to invert the inverted portion 80. That is, because the through hole K is provided, when a brushing load is applied, the elastic member 90 flexes first, followed by the inverted portion 80, without interfering with each other's deformation behavior. It is not necessary for the inverted portion 80 and the elastic deformation portion 90 to be penetrated; it is sufficient if a gap S is formed.

[0074] The above-mentioned reversal portion 80 snaps, buckles, and reverses, and the vibration and reduction in repulsive force that occur when it transitions from the first state to the second state allow the user holding the grip portion 30 to sense that the external force acting on the back side of the head portion 10 has exceeded the external force threshold, resulting in an overbrushing state.

[0075] Even after the inverted portion 80 snaps and buckles from the first state to the second state, if an external force is applied to the head portion 10 and the increased displacement of the head portion 10 exceeds a second threshold value greater than the first threshold value, the repulsive force stops decreasing at the second threshold value, and the inverted portion 80 is formed in a convex shape on the front side in the second state, and the repulsive force increases. Because the repulsive force increases when the inverted portion 80 is formed in a convex shape on the front side in the second state, even if the external force applied to the head portion 10 decreases, the brushing pressure behavior quickly returns to normal, thereby preventing operational problems. Therefore, a user holding the handle 30 perceives a two-stage change in the repulsive force: the repulsive force decreases as the displacement of the head portion 10 exceeds the first threshold value, and then the repulsive force stops decreasing as the displacement of the head portion 10 reaches the second threshold value. This allows the user to more accurately sense an overbrushing state. When an external force (load) is applied to the rear side, the sensing unit 70 at least stops the reduction in the repulsive force, and then when the load is released, the relationship between the displacement of the head unit 10 after the release and the repulsive force maintains the same relationship as before the load was applied.

[0076] Here, if the repulsive force when the displacement of the head unit 10 is a first threshold is A (N), and the repulsive force when the displacement is a second threshold is B (N), the value represented by B / A is preferably 0.3 or more and 0.9, and more preferably 0.65 or more and 0.85 or less. If the value represented by B / A is less than 0.3, the decay from repulsive force A to repulsive force B is large, which may impair the user's experience of use. Furthermore, when the displacement of the head unit 10 increases beyond the second threshold, the increase in repulsive force is large, which may impair the user's experience of use. If the value represented by B / A exceeds 0.9, the decay from repulsive force A to repulsive force B is small, which may make it difficult to recognize that an overbrushing state has occurred. Therefore, by setting the value represented by B / A to 0.3 or more and 0.9 or less, the user can fully recognize the increase in repulsive force when the displacement of the head unit 10 exceeds the second threshold and sense that an overbrushing state has occurred without impairing the user's experience of use.

[0077] The repulsive force A is preferably 1.0 N or more and 5.0 N or less, more preferably 1.5 N or more and 4.0 N or less, and even more preferably 1.5 N or more and 3.0 N or less. If the repulsive force A is less than 1.0 N, sufficient cleaning power may not be obtained. If the repulsive force A exceeds 5.0 N (approximately 500 g), harm to the gums may occur. Therefore, by setting the repulsive force A to 1.0 N or more and 5.0 N or less, sufficient cleaning power can be ensured while harm to the gums can be suppressed. Furthermore, the value of the repulsive force A is set within the above-mentioned preferred range so as not to exceed the recommended brushing pressure described below.

[0078] If the displacement of the first threshold is C (mm) and the displacement of the second threshold is D (mm), the value represented by DC is preferably 0 mm or more and 1.5 mm or less, more preferably 0 mm or more and 1.0 mm or less, and even more preferably 0 mm or more and 0.5 mm or less. If the value represented by DC exceeds 1.5 mm, the displacement of the head unit 10 exceeds the first threshold and the repulsive force decreases, and then the displacement of the head unit 10 exceeds the second threshold and the repulsive force increases. This may weaken the synergistic effect of recognizing the two-stage change in repulsive force. In other words, the sharp change in repulsive force when the first threshold is exceeded may be perceived as dull. Therefore, by setting the value represented by DC to 0 mm or more and 1.5 mm or less, a two-stage change in repulsive force can be generated over a short distance without compromising the user experience, allowing the user to accurately sense overbrushing.

[0079] The first threshold displacement C is preferably 28 mm or less. If the displacement C exceeds 28 mm, the amount of deflection during brushing increases, making oral hygiene difficult for the user. Therefore, by setting the displacement C to 28 mm or less, oral hygiene can be ensured. The first threshold displacement C is more preferably 24 mm or less. Furthermore, the lower limit of the displacement C is more preferably 10 mm or more. By setting the lower limit of the displacement C to 10 mm or more, the brushing load on the gums can be reduced. Furthermore, it is preferable that the repulsive force increases in proportion to the displacement, and it is particularly preferable that this proportional relationship does not change (the rate of increase in the repulsive force does not become slower) even as the displacement C is approached. Specifically, the rate of increase in the repulsive force per 1 mm of displacement until the displacement C is reached is preferably 0.05 or more, more preferably 0.08 or more, and even more preferably 0.09 or more. This allows for appropriate control of brushing load, as the pressure expected by the user is more likely to be reflected directly in the repulsive force in the range up to displacement C, which reaches the upper limit of pressure. If the repulsive force were set to gradually slow down as the displacement C approached, the user may unintentionally continue brushing with pressure near the upper limit.

[0080] Starting from the second threshold displacement D, the rate of increase in repulsive force until the displacement of the head portion 10 reaches 4 mm is preferably 0.015 or more. If the rate of increase in repulsive force from the second threshold displacement D until the displacement of the head portion 10 reaches 4 mm is less than 0.015, the increase in repulsive force after the inverted portion 80 is insufficient, which may impair the feel of use. Therefore, by setting the rate of increase in repulsive force from the second threshold displacement D until the displacement of the head portion 10 reaches 4 mm to 0.015 or more, it becomes possible to continue brushing without impairing the feel of use even after the inverted portion 80 is inverted.

[0081] The inverted portion 80 has a groove 81 at the center of the long axis direction on the front side, i.e., in a region including the apex of the convex shape. The inverted portion 80 has a groove 82 at the center of the long axis direction on the back side, i.e., in a region including the apex of the convex shape. The grooves 81, 82 extend in the width direction. The groove 81 is formed in an arc shape in side view with the arc center located on the front side. The groove 82 is formed in an arc shape in side view with the arc center located on the back side. If the inverted portion 80 does not have grooves 81, 82, stress is generated uniformly throughout the inverted portion 80, making snap-through buckling less likely to occur. On the other hand, if the inverted portion 80 has grooves 81, 82, stress is generated concentratedly in the grooves 81, 82, making snap-through buckling more likely to occur.

[0082] The radius of the arc-shaped grooves 81, 82 in side view is preferably 1 mm or more and 2 mm or less. If the radius of the grooves 81, 82 is less than 1 mm, the reversing portion 80 may not be reversed. If the radius of the grooves 81, 82 is more than 2 mm, the vibration of the reversing portion 80 when it is reversed may be small, making it difficult to detect over-brushing.

[0083] Regarding the depths of grooves 81 and 82, it is preferable that groove 81 is deeper than groove 82. When groove 82 is deeper than groove 81, inversion portion 80 is less likely to invert even when the magnitude of an external force exceeds a predetermined external force threshold. Furthermore, when groove 81 is deeper than groove 82, it is possible to guide inversion portion 80 so that it is more likely to snap-through buckling toward the front side. It should be noted that instead of a configuration in which both grooves 81 and 82 are provided, a configuration in which only groove 81 is provided without groove 82 may also be used.

[0084] Because the grooves 81 and 82 are provided in the region including the apex of the convex shape of the inverted portion 80, the region including the apex of the convex shape is thinner than other regions. Therefore, the strain energy accumulated due to deformation of the inverted portion 80 caused by an external force exceeding the external force threshold can be instantly released from the grooves 81 and 82 as a starting point, thereby inverting the inverted portion 80. Furthermore, by adjusting the positions of the grooves 81 and 82 in the thickness direction, it is possible to adjust the position at which the inverted portion 80 inverts from the first state to the second state.

[0085] Furthermore, since the grooves 81 and 82 are formed in an arc shape when viewed from the side, stress concentration at the vertex of the inversion portion 80 including the grooves 81 and 82 can be alleviated even when the vertex moves in the thickness direction, compared to when the grooves are formed in a V shape by two intersecting planes, for example.

[0086] The external force threshold value of the external force applied to the back side of the head unit 10 is, for example, the upper limit of an appropriate brushing pressure. This external force threshold value corresponds to the first threshold value of the displacement amount of the head unit 10 described above.

[0087] As shown in Figure 4, the angle θ at which the inverted portion 80 is inclined relative to a plane parallel to the longitudinal direction and width direction is preferably 5 degrees or more and 11 degrees or less, and more preferably 7 degrees or more and 11 degrees or less. If the inclination angle θ is less than 5 degrees, the inverted portion 80 may deform without snap-through buckling, making it difficult to detect an over-brushing state. If the inclination angle θ exceeds 11 degrees, the inverted portion 80 may snap-through buckle due to over-brushing pressure, making it difficult to invert, or the inverted portion 80 may break when snap-through buckling occurs and invert, resulting in loss of reversibility.

[0088] The thickness of the inverted portion 80, excluding the grooves 81 and 82, is preferably 1 mm or more and 2 mm or less. If the thickness of the inverted portion 80 is less than 1 mm, it may deform but not snap-through buckle, making it difficult to detect the over-brushing state. If the thickness of the inverted portion 80 exceeds 2 mm, the inverted portion 80 may snap-through buckle under over-brushing pressure, making it difficult to invert, or it may break when it snaps through and inverts, resulting in loss of reversibility.

[0089] Assuming that the maximum thickness of the inverted portion 80 is T (mm) and the maximum thickness of the sensing portion 70 is t (mm), specifying the value expressed by T / t makes it possible to control the ease with which the inverted portion 80 will invert when an excessive brushing load is applied, as well as the timing (external force threshold). The value expressed by T / t is preferably 0.05 or more and 0.35 or less, and more preferably 0.10 or more and 0.35 or less. If the value expressed by T / t is less than 0.05, the inverted portion 80 will deform in response to the bending of the sensing portion 70 (elastic deformation portion 90), but will not snap-through buckle, which may make it difficult to detect overbrushing. If the value expressed by T / t exceeds 0.35, the inverted portion 80 may snap-through buckle under overbrushing pressure, making it difficult to invert, or it may snap-through buckle and break when it inverts, resulting in a loss of reversibility of the inverted portion 80.

[0090] That is, by setting T / t within the above range, the bending strength of the inverting part 80 becomes flexible at a certain rate relative to the elastic deformation part 90, and it becomes possible to operate the inverting part 80 with a slight delay relative to the bending of the elastic deformation part 90 that supports the handle skeleton. This makes it possible to control the ease with which the inverting part 80 turns over and the timing (external force threshold) that triggers the inversion of the inverting part 80 even when an excessive brushing load is applied.

[0091] As shown in FIG. 3 , if the maximum width of the reversible portion 80 is L (mm) and the maximum width of the sensing portion 70 is W (mm), specifying the value expressed as L / W makes it possible to control, for example, the ease with which the reversible portion 80 will reversal when an excessive brushing load is applied, and the timing of this reversal (external force threshold). The value expressed as L / W is preferably 0.05 or more and 0.35 or less, and more preferably 0.10 or more and 0.35 or less. If the value expressed as L / W is less than 0.05, the reversible portion 80 will deform in response to the bending of the sensing portion 70 (elastic deformation portion 90), but it will be difficult to snap-through buckling, which may make it difficult to detect overbrushing. If the value expressed as L / W exceeds 0.35, the reversible portion 80 will be less likely to deform and reversal due to the bending of the handle body 2 that occurs during normal brushing. As a result, excessive brushing pressure may cause the inverting portion 80 to snap-through buckle, making it difficult to invert, or it may snap-through buckle and break when inverted, resulting in a loss of reversibility of the inverting portion 80. In other words, by setting L / W within the above range, the bending strength of the inverting portion 80 becomes flexible at a constant rate relative to the elastic deformation portion 90, making it possible to operate the inverting portion 80 with a slight delay relative to the bending of the elastic deformation portion 90 that supports the handle skeleton. Therefore, even when excessive brushing load is applied, it is possible to control the ease with which the inverting portion 80 inverts and the timing (external force threshold) that triggers the inverting of the inverting portion 80.

[0092] The longitudinal length of the inverted portion 80 is preferably 15 mm or more and 30 mm or less, more preferably 15 mm or more and 25 mm or less, and even more preferably 15 mm or more and 20 mm or less. The position of the leading end of the inverted portion 80 is the position of the leading end of the through-hole 73. The position of the rear end of the inverted portion 80 is the position of the rear end of the through-hole 73. If the longitudinal length of the inverted portion 80 is less than 15 mm, it may be difficult for the inverted portion 80 to snap-through buckle and invert with normal brushing pressure, and the deformation required for snap-through buckling may not occur. If the longitudinal length of the inverted portion 80 exceeds 30 mm, the displacement required for snap-through buckling becomes very large, significantly reducing usability, and the deformation behavior of the inverted portion 80 may be similar to that of the elastically deforming portion 90.

[0093] In a side view, the inverted portion 80 is located between the outer contour of the bristle-implanted side 11 of the elastically deformable portion 90 and the outer contour of the back side. More specifically, the thickness direction of the inverted portion 80 is determined so that the inverted portion 80 does not protrude beyond the thickness of the elastically deformable portion 90 in a side view, so that the inverted portion 80 does not form the outermost periphery of the toothbrush. This can prevent the inverted portion from coming into contact with the user during use, for example. Specifically, the inverted portion 80 is preferably located rearward of the position where the thickness of the elastically deformable portion 90 is halfway. If the inverted portion 80 is located rearward of the position where the thickness of the sensing portion 70 is halfway, the possibility that the apex of the inverted portion 80 will protrude from the front surface of the elastically deformable portion 90 and come into contact with the user's finger when the inverted portion 80 is inverted to the second state can be reduced. Furthermore, by positioning the inversion section 80 on the rear side of the position where the thickness of the elastic deformation section 90 is half, when the inversion section 80 bends, the rear side is compressed more than the front side, so that, for example, energy that triggers inversion is more likely to accumulate, and the strain energy can be efficiently transferred to the inversion section 80.

[0094] The inverted portion 80, which constitutes part of the rigid portion H, can be made to have a flexural modulus of 1500 MPa or more, thereby enabling the user to sense over-brushing due to snap-through buckling. Furthermore, by making the flexural modulus of the inverted portion 80 3500 MPa or less, it is possible to prevent the inverted portion 80 from breaking when snap-through buckling occurs and the reversibility of the inverted portion 80 is lost. Furthermore, by using a material with a specified flexural modulus, the vibrations associated with snap-through buckling occur intensively over a short period of time, making them sharp (large). As a result, the user can more easily sense over-brushing.

[0095] When the inverted portion 80 snaps, the thicknesswise movement distance of the apex of the convex shape is preferably 0.2 mm or more and 5.0 mm or less. If the thicknesswise movement distance of the apex is less than 0.2 mm, the vibration generated by snap-through buckling will be small, potentially making it difficult to detect overbrushing. If the thicknesswise movement distance of the apex exceeds 5.0 mm, the inverted portion 80 may snap-through buckle under overbrushing pressure, making it difficult to invert, or may break when snap-through buckling occurs, resulting in loss of reversibility of the inverted portion 80. If the movement distance of the inverted portion 80 when snap-through buckling is within the above range, the vibration generated by snap-through buckling will be concentrated in a short period of time and will be sharp (large). As a result, the user will be more likely to detect overbrushing.

[0096] The thickness of the hard portion 90H in the elastic deformation portion 90 is preferably 2.0 mm or less, and the width is preferably greater than the thickness. When the thickness of the hard portion 90H is 2.0 mm or less, the hard portion 90H is in a plane stress state, making it less likely to generate internal stress. As a result, the hard portion 90H is less likely to break even when deformed, and it is possible to sufficiently store the energy required to invert the inverted portion 80.

[0097] Furthermore, in the toothbrush 1 of this embodiment, the inverted portion 80 and the elastically deforming portion 90 are arranged with a gap in the width direction, which allows the sensing unit 70 to be more easily deformed toward the front and back sides and to be in a plane stress state with almost no deformation in the longitudinal axis direction or width direction. That is, in the toothbrush 1 of this embodiment, the inverted portion 80 and the elastically deforming portion 90 deform in the thickness direction, spaced apart from each other in the width direction, and are not on the same plane. In other words, the path along which the elastically deforming portion 90 deforms due to an external force in the thickness direction and the path along which the inverted portion 80 deforms due to an external force in the thickness direction are not interfering with each other. Therefore, in the toothbrush 1 of this embodiment, the elastically deforming portion 90 and the inverted portion 80 are less constrained by each other and are therefore deformable. This allows for more sufficient accumulation of the energy required to invert the inverted portion 80, which generates concentrated stress in the inverted portion 80 (particularly the grooves 81 and 82), resulting in sensitive snap-through buckling.

[0098] Furthermore, in the toothbrush 1 of this embodiment, because wobbling in the width direction is suppressed, bending in the thickness direction caused by brushing can be transmitted to the inverted portion 80 without loss. Furthermore, by arranging the inverted portion 80 and the elastically deforming portion 90 in the width direction, it is possible to separate the bending of the elastically deforming portion 90 and the inversion of the inverted portion 80, thereby shifting the timing. If the elastically deforming portion 90 and the inverted portion 80 were arranged in the thickness direction, there is a possibility that the bending of the elastically deforming portion 90 and the inversion of the inverted portion 80 would interfere with each other's roles.

[0099] As described above, in the toothbrush 1 of this embodiment, a sensing unit 70 is provided that measures the relationship between the amount of displacement of the head unit 10 when a load is applied to the back side of the head unit 10 in the thickness direction and the repulsive force generated in response to that amount of displacement. If the amount of displacement is equal to or less than a first threshold value, the repulsive force increases in response to an increase in the amount of displacement, and if the amount of displacement is equal to or less than a second threshold value that is greater than the first threshold value, the repulsive force decreases in response to an increase in the amount of displacement.The value expressed by B / A is greater than or equal to 0.3 and less than or equal to 0.9, making it highly versatile and providing a good usability, allowing the user to fully recognize the repulsive force and sense overbrushing.

[0100] [Modification of the sensing unit 70] In the above embodiment, a configuration in which the sensing unit 70 has an elastic deformation unit 90 and an inversion unit 80 is exemplified, but this configuration is not limited to this, and for example, the sensing unit 70 may have both the function of elastically deforming due to an external force in the thickness direction and the function of snap-through buckling.

[0101] Fig. 9(a) is a front view showing a modified example of the sensing unit 70. Fig. 9(b) is a side view showing a modified example of the sensing unit 70. Fig. 9(c) is a right side view of Fig. 9(a). In Figs. 9(a) to 9(c), the neck portion 20 and the grip portion 30 are not shown. As shown in FIG. 9(a), the sensing unit 70 of the modified example is rectangular in front view. The sensing unit 70 has a recess 70a that opens to the front side. As shown in FIG. 9(b), the sensing unit 70 has an arc-shaped curved surface 70b that is convex toward the back side in side view. In side view, the center of curvature of the curved surface 70b is located further toward the front side in the thickness direction than the long axis direction end of the curved surface 70b. In side view, the center of curvature of the curved surface 70b is located at the center of the sensing unit 70 in the long axis direction. In side view, the intersection angle (small value intersection angle) between the tangent to the curved surface 70b and a line parallel to the long axis direction is 0° (i.e., parallel) at the center in the long axis direction. In side view, the intersection angle between the tangent to the curved surface 70b and a line parallel to the long axis direction gradually increases from the center in the long axis direction toward the end. In side view, the center of curvature of curved surface 70b is located closer to the front surface in the thickness direction than the long axis direction end of curved surface 70b, and therefore the angle of intersection between the tangent to curved surface 70b and a line parallel to the long axis direction in side view is an acute angle or 0°. In side view, the bottom surface of recess 70a is curved surface 70d, which is located on the front side and has a certain width from curved surface 70b.

[0102] As shown in FIG. 9( c), the sensing unit 70 has an arc-shaped curved surface 70c that is convex toward the rear side in a right side view. In a right side view, the center of curvature of the curved surface 70c is located closer to the front in the thickness direction than the widthwise ends of the curved surface 70c. In a right side view, the center of curvature of the curved surface 70c is located at the center of the sensing unit 70 in the width direction. In a right side view, the intersection angle (small value intersection angle) between a tangent to the curved surface 70c and a line parallel to the width direction is 0° (i.e., parallel) at the center in the width direction. In a right side view, the intersection angle between a tangent to the curved surface 70c and a line parallel to the width direction gradually increases from the center in the width direction toward the end. Because the center of curvature of the curved surface 70c is located closer to the front in the thickness direction than the widthwise ends of the curved surface 70c in a right side view, the intersection angle between a tangent to the curved surface 70c and a line parallel to the width direction in a right side view is an acute angle or 0°. When viewed from the right side, the bottom surface of the recess 70a is a curved surface 70e that is disposed on the front side with a constant width from the curved surface 70c. The sensing unit 70 of the modified example can be made of the aforementioned hard resin, soft resin, metal, or the like. The sensing unit 70 has no restrictions on its length or width in the major axis direction, but its maximum thickness is 5 mm or less. To facilitate snap-through buckling, it is preferable to provide a through-groove 70f (shown by the two-dot chain line) at the widthwise center of the sensing unit 70, extending in the major axis direction and penetrating through in the thickness direction.

[0103] In the sensing unit 70 configured as described above, when an external force is transmitted through the neck portion 20 and the sensing unit 70 is deformed toward the rear side, the curved surface 70b has a convex shape toward the rear side in a side view and the curved surface 70c has a convex shape toward the rear side in a right side view, and thus has a high bending strength toward the rear side in the thickness direction, so that the sensing unit 70 elastically deforms as an elastic deformation portion when an external force below the external force threshold is applied. Meanwhile, because the sensing unit 70 is thin, with a maximum thickness of 5 mm or less, when an external force exceeding the external force threshold is transmitted, the sensing unit 70 snaps through as an inverted portion and inverts into a convex arc shape on the front side. In this way, the sensing unit 70 of the modified example can have both the function of elastic deformation due to an external force in the thickness direction and the function of snap-through buckling, without having to provide an elastic deformation portion and an inverted portion separately.

[0104] [Example] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the following examples and can be practiced with appropriate modifications within the scope of the present invention.

[0105] (Examples 1 to 9, Comparative Examples 1 to 4) Samples of Examples 1 to 9 and Comparative Examples 1 to 4 were prepared according to the specifications shown in Table 1. Example 4 is a toothbrush sample that, unlike Example 1, does not have a soft portion in the sensing unit. Example 6 is a toothbrush sample that, unlike Example 1, does not have an inverted portion, but has a first engagement portion whose base end is located in a second region more rearward than the sensing unit and extends in the longitudinal direction toward a first region more distal than the sensing unit, and a second engagement portion whose base end is located in the first region and extends in the longitudinal direction toward the second region. When an external force in the first direction is equal to or less than a threshold, the toothbrush separates in the first direction, engages with the head portion when the external force exceeds the threshold and displaces the head portion toward the rear side, which is the opposite side from the bristle-implanted surface, in the first direction, and the relative positional relationship in the first direction is reversed. Example 7 is a toothbrush sample in which the radius of grooves 81 and 82 in the inverted portion is changed from 1.5 mm to 2 mm. Example 9 is a toothbrush sample having a modified sensing unit shown in FIG. 9 compared to the sample of Example 1. Comparative Example 1 was a "Tekiatsu-kun" toothbrush manufactured by Wada Precision Dental Laboratory Co., Ltd. Comparative Example 3 was a toothbrush sample in which the gaps S of the sample of Example 1 were filled with soft resin. The bristles of the samples other than Comparative Example 1 had the same specifications as those of the Clinica Advantage toothbrush manufactured by Lion Corporation.

[0106] [Test method] For each sample, the boundary between the sensing unit 70 and the gripping unit 30 was fixed toward the gripping unit 30 so that the bristle surface of the head was horizontal. A test was conducted in which a load was applied to the back side of the bristle surface of the head in the thickness direction. An autograph testing machine (AGS-H, manufactured by Shimadzu Corporation) was used as the evaluation device for each test. In the test, the finger contact part at the most distal end of the gripping unit of the toothbrush was chucked, and the center of the bristle surface of the head as viewed from the front was pressed with a presser at a test speed of 100 mm / min, and the amount of pressing (displacement of the head) and the load (repulsion force) when the reversing part was reversed were measured. The test was conducted three times for each sample, and the average value was used.

[0107] [Evaluation method] A questionnaire was administered to each sample after one week of use. The survey was conducted by 10 panelists. The questionnaire consisted of five items: "notice of vibration," "feeling of use immediately after vibration," "harm to gums," "feeling of plaque being removed from the mouth," and "operability in the mouth," each of which was rated on a seven-point scale. The average scores obtained for each sample were used as the evaluation results, and are shown in Table 1. For each evaluation, an average score of over 4.0 was considered a pass (OK), and an average score of 4.0 or less was considered a fail (NG). Details of each evaluation item are provided below.

[0108] ·Vibration awareness The evaluation criteria are whether the user notices the vibration of the sensing part that occurs when repulsive force A decays to repulsive force B. The vibration referred to here refers to a short-duration, sharp, large vibration that occurs due to snap-through buckling. The vibration was rated on a seven-point scale: very difficult to understand (1 point), very difficult to understand (2 points), somewhat difficult to understand (3 points), neither difficult nor difficult (4 points), somewhat easy to understand (5 points), very easy to understand (6 points), and extremely easy to understand (7 points).

[0109] Immediate feeling of use after vibration This is the evaluation axis for the usability immediately after the vibration generated by the sensor occurs. If the decay from repulsive force A to repulsive force B does not interfere with the sequence of brushing actions, the usability is considered good, but if it interferes significantly, the usability is considered bad. The user experience was rated on a seven-point scale: very bad (1 point), very bad (2 points), somewhat bad (3 points), neutral (4 points), somewhat good (5 points), very good (6 points), and extremely good (7 points).

[0110] Harmful to gums This is an evaluation axis for determining whether or not the toothbrushing action just before the vibration generated by the sensing part occurs and during the process up to that point (up to the first threshold) is harmful to the gums. For this reason, the harmfulness was rated on a seven-point scale: very harmful (1 point), harmful (2 points), somewhat harmful (3 points), neutral (4 points), almost harmful (5 points), harmful (6 points), and completely harmful (7 points).

[0111] Feeling like plaque is falling off your mouth This is an evaluation axis for whether or not plaque in the mouth has been removed by brushing immediately before vibrations are generated from the sensing part and during the process up to that point (up to the first threshold). The feeling of plaque being removed was rated on a 7-point scale: very little (1 point), very little (2 points), somewhat little (3 points), neutral (4 points), somewhat noticeable (5 points), very noticeable (6 points), and very noticeable (7 points).

[0112] ·Easy to use in the mouth This is an evaluation axis for the quality of operability in the mouth during toothbrushing just before vibrations are generated from the sensing part and during the process up to that point (up to the first threshold). The operability was evaluated on a seven-point scale: very bad (1 point), very bad (2 points), somewhat bad (3 points), neutral (4 points), somewhat good (5 points), very good (6 points), and very good (7 points).

[0113] 8 is a diagram showing the relationship between the indentation amount (mm) and the deflection repulsive force (N) measured using an autograph testing machine for the samples of Examples 1, 4, and 6, and Comparative Example 1. Table 1 also shows the repulsive force A (N) at the first threshold indentation amount, the repulsive force B (N) at the second threshold indentation amount, the first threshold indentation amount (displacement) C (mm), the second threshold indentation amount (displacement) D (mm), B / A, and DC (mm) for the samples of Examples 1 to 9 and Comparative Examples 1 to 4.

[0114] [Table 1]

[0115] As shown in Table 1, it was confirmed that the values ​​represented by B / A for the samples of Examples 1 to 9 were within the range of 0.3 or more and 0.9 or less, while the values ​​represented by B / A for the samples of Comparative Examples 1 to 4 were outside the range of 0.3 or more and 0.9 or less. As the value represented by B / A increases, it becomes difficult to notice the vibration generated from the sensing part. On the other hand, as the value represented by B / A decreases, it becomes easier to notice the vibration, but the damping of the repulsive force becomes very large, resulting in a poor usability. Therefore, Comparative Examples 1 to 2 and Comparative Examples 3 to 4, in which the value represented by B / A was less than 0.3, 4 The sample of Comparative Example 3, in which the value represented by B / A was greater than 0.9, failed the evaluation of "noticeability of vibration." In contrast, the samples of Examples 1 to 9, in which the value represented by B / A was in the range of 0.3 or more and 0.9 or less, passed the evaluations of both "noticeability of vibration" and "noticeability of vibration."

[0116] Therefore, with the toothbrushes of Examples 1 to 9, the user can sense the overbrushing state by fully recognizing the decrease in repulsive force when the displacement of the head portion 10 exceeds the first threshold value, and the cessation of the decrease in repulsive force when the displacement of the head portion 10 reaches the second threshold value, without compromising the usability.

[0117] It was also confirmed that the values ​​of the repulsive force A of the samples of Examples 1 to 9 were within the range of 1.0 N or more and 5.0 N or less, while the value of the repulsive force A of the sample of Comparative Example 3 was outside the range of 1.0 N or more and 5.0 N or less. As the value of the repulsive force A increases, the harm to the gums increases. As the value of the repulsive force A decreases, the irritation to the gums disappears, but the plaque removal power decreases. Comparative Example in which the value of the repulsive force A exceeds 5.0 N 3 The sample failed the assessment of its risk to gums.

[0118] In contrast, the samples of Examples 1 to 9, which had a repulsive force A value in the range of 1.0 N or more and 5.0 N or less, passed the evaluations of both "feeling of plaque being removed from the mouth" and "harm to the gums." Therefore, the toothbrushes of Examples 1 to 9 can exert sufficient plaque removal power while minimizing irritation to the gums.

[0119] It was also confirmed that the DC values ​​of the samples of Examples 1 to 9 were within the range of 0 mm or more and 1.5 mm or less, while the DC values ​​of the samples of Comparative Examples 1 and 4 were outside the range of 0 mm or more and 1.5 mm or less. The smaller the DC value, the steeper the slope of the decrease in the repulsive forces A and B, making it easier to feel vibration. Conversely, the larger the DC value, the more gradual the decrease in the repulsive forces, making it harder to feel vibration. Therefore, the sample of Comparative Example 4, which had a DC value of more than 1.5 mm, failed the evaluation of "vibration awareness."

[0120] In contrast, the samples of Examples 1 to 9, in which the DC value was within the range of 0 mm or more and 1.5 mm or less, were evaluated as passing the "vibration awareness" rating. Therefore, with the toothbrushes of Examples 1 to 9, it is possible to sense that the toothbrush is overbrushing by fully recognizing the repulsive force decreasing when the displacement of the head portion 10 exceeds the first threshold value, and the stopping of the decrease in the repulsive force when the displacement of the head portion 10 reaches the second threshold value.

[0121] It was also confirmed that the samples of Examples 1 to 9 had values ​​of C within a range of 28 mm or less, while the sample of Comparative Example 1 had a value of C outside the range of 28 mm or less. The larger the value of C, the greater the deflection required before vibration occurs, resulting in a worsening usability. Therefore, the sample of Comparative Example 1, which had a value of C exceeding 28 mm, failed the evaluation of "operability in the mouth."

[0122] In contrast, the samples of Examples 1 to 9, whose C values ​​were within the range of 28 mm or less, passed the evaluation of "operability in the mouth." Therefore, the toothbrushes of Examples 1 to 9 ensure good operability in the mouth until vibration occurs.

[0123] While the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to these examples. The shapes and combinations of the components shown in the above examples are merely examples, and various modifications can be made based on design requirements, etc., without departing from the spirit of the present invention.

[0124] For example, in the above embodiment, the sensing unit 70 is provided between the neck portion 20 and the grip portion 30, but the present invention is not limited to this configuration. The sensing unit 70 may be provided in the neck portion 20 or in the grip portion 30.

[0125] Furthermore, in the above embodiment, a configuration in which one reversing section 80 is provided in the sensing section 70 has been exemplified, but the present invention is not limited to this configuration, and a configuration in which a plurality of reversing sections 80 are provided may also be used. For example, when two reversing portions 80 are provided, one can be formed with a thickness and inclination angle θ, etc. that reverses at the upper limit of the appropriate brushing load, and the other can be formed with a thickness and inclination angle θ, etc. that reverses at the lower limit of the appropriate brushing load, thereby making it possible to easily specify both the upper and lower limits of the brushing load.

[0126] In addition, in the above embodiment, the reversing portion 80 is configured to reversal in the thickness direction, but this is not limited to this configuration, and may be configured to reversal in the width direction or in a diagonal direction that is perpendicular to the longitudinal axis and intersects with the width direction and thickness direction. By adopting a configuration in which the reversing portion 80 is reversal in a diagonal direction, it becomes possible to detect over-brushing when brushing using the rolling method. [Industrial Applicability]

[0127] The present invention is applicable to toothbrushes. [Explanation of symbols]

[0128] REFERENCE SIGNS LIST 1...toothbrush, 2...handle body, 10...head portion, 11...bristle surface, 20...neck portion, 30...gripping portion, 70...sensing portion, 80...reversed portion, 81, 82...groove portion, E, 31E, 32E...soft portion, H...hard portion, K...through hole, S...gap

Claims

1. a head portion provided at the tip end in the longitudinal direction and having a bristle-implanted surface; a grip portion disposed at the rear end side of the head portion; and a neck portion disposed between the bristle-implanted surface and the grip portion, a sensor that senses when an external force in a first direction perpendicular to the implanted surface exceeds a predetermined value, the sensor being located rearward of the implanted surface; The sensing unit an inverted portion that connects a first region on the tip side of the sensing portion and a second region on the rear end side of the sensing portion, and that snaps through buckling and inverts in response to displacement of the head portion in the first direction toward a back side that is the opposite side to the flocked surface due to the external force exceeding the threshold value, wherein, where T is the maximum thickness of the inverted portion in the first direction and t is the maximum thickness of the sensing portion in the first direction, a value expressed as T / t is 0.05 or more and 0.35 or less, and where L is the maximum width of the inverted portion in a second direction that is orthogonal to the first direction and the major axis direction, respectively, and W is the maximum width of the sensing portion in the second direction, a value expressed as L / W is 0.05 or more and 0.35 or less; an elastic deformation portion that is disposed with a gap from the inverted portion, connects the first region and the second region, and elastically deforms at least up to the external force at which the inverted portion snaps through and inverts, the inverted portion is located between an outer contour of the flocking surface side and an outer contour of the back surface side of the elastically deforming portion in a side view seen in a direction perpendicular to the long axis direction and the first direction, and generates a sound without contacting the elastically deforming portion when the inverted portion snaps through and inverts, a path along which the elastic deformation portion is deformed by the external force in the first direction and a path along which the inverted portion is deformed by the external force in the first direction are provided so as not to interfere with each other, the elastic deformation portions are arranged on both sides of the inverted portion in the second direction with a gap therebetween, The sensing unit The relationship between the displacement of the head portion when a load is applied to the back side of the head portion, which is the opposite side to the flocked surface, in the first direction and the repulsive force generated in response to the displacement is The repulsive force is changed from increasing to decreasing at a first threshold value in response to an increase in the displacement amount, The reduction of the repulsive force is stopped at a second threshold value at which the displacement amount is greater than the first threshold value; When the displacement amount is a first threshold value, the repulsive force is A, and when the displacement amount is a second threshold value, the repulsive force is B. The value represented by B / A is 0.3 or more and 0.9 or less, Let C be the displacement amount at the first threshold value and D be the displacement amount at the second threshold value. A toothbrush characterized in that the value represented by DC is 0 mm or more and 1.5 mm or less.

2. The repulsive force A is 1.0 N or more and 5.0 N or less. The toothbrush of claim 1.

3. Let C be the displacement amount at the first threshold value and D be the displacement amount at the second threshold value. The value represented by DC is 0 mm or more and 1.0 mm or less. The toothbrush according to claim 1 or 2.

4. The displacement amount C is 28 mm or less. The toothbrush of claim 3.

5. When the displacement amount exceeds the second threshold value, the sensing unit increases the repulsive force in accordance with an increase in the displacement amount.

5. The toothbrush according to any one of claims 1 to 4.

6. an increasing rate of the repulsive force from the displacement amount at the second threshold value as a starting point until the displacement amount of the head portion reaches 4 mm is 0.015 or more; The toothbrush of claim 5.

7. The sensing unit When a load is applied to the rear surface side, and the reduction in the repulsive force is stopped at least, and then the load is released, the relationship between the displacement amount and the repulsive force after the release is maintained to be the same as that before the load was applied.

7. The toothbrush according to any one of claims 1 to 6.

8. The gap is a through hole extending in the first direction.

8. The toothbrush according to any one of claims 1 to 7.

9. the inverted portion has a convex shape toward the back surface when the external force in the first direction is equal to or less than the predetermined value, and is inverted to a convex shape toward the implanted surface when the external force in the first direction exceeds the predetermined value.

9. The toothbrush of any one of claims 1 to 8.

10. the inverted portion has a groove portion extending in the second direction on at least one of the implanted surface side and the back surface side in a region including the apex of the convex shape, 10. The toothbrush of claim 9.

11. The inverted portion is formed of a hard resin, A part of the elastic deformation portion is formed of a resin having a hardness different from that of the hard resin.

11. The toothbrush of any one of claims 1 to 10.

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