JP7433310B2 - toothbrush - Google Patents

Description

The present invention relates to a toothbrush.
This application claims priority based on Japanese Patent Application No. 2019-121254 filed in Japan on June 28, 2019, the contents of which are incorporated herein.

While the proportion of people aged 80 with 20 teeth has reached approximately 50%, the proportion of elderly people suffering from caries (root caries) is increasing. Root caries is caries in dentin exposed due to gingival recession, but since dentin has a higher composition ratio of organic components than enamel, caries progresses faster. One of the causes of the above-mentioned gingival recession is overbrushing, in which brushing is performed with a brushing pressure (sweeping pressure) greater than the appropriate value.

Conventionally, as a toothbrush for reducing excessive brushing pressure, for example, a toothbrush described in Patent Document 1 has been disclosed. The toothbrush described in Patent Document 1 has a U-shape in which when the toothbrush is gripped with a palm grip and brushed, the part formed of thermoplastic resin of the part gripped by the thumb and forefinger of the handle part opens on the bristle side. The periphery of the portion made of thermoplastic resin is coated with a soft resin such as an elastomer material.

Regarding the toothbrush with the above structure in Patent Document 1, the load of the head part is applied not only to the neck part but also to the above-mentioned part of the handle part, so that the toothbrush is gentle and comfortable to touch the teeth and gums without damaging the gums. It is described that excessive brushing pressure is reduced while providing operability.

Japanese Patent Application Publication No. 2000-004944

However, since the toothbrush disclosed in Patent Document 1 has flexibility in all directions, it is difficult to stably apply the brush portion to a target area during brushing.

The present invention has been made in consideration of the above points, and an object of the present invention is to provide a toothbrush that has good operability and can thoroughly brush the target area while maintaining an appropriate brushing pressure.

According to the first aspect of the present invention, there is provided a head portion provided on the distal end side in the longitudinal direction and having a flocked surface, a gripping portion disposed on the rear end side of the head portion, the flocking surface and the gripping portion. and a neck portion disposed between the head portion and the neck portion, at least a portion of which is formed of hard resin, which is disposed in the grip portion, and which is disposed in a first direction perpendicular to the flocking surface. a deformable portion that deforms due to an external force; a first region that is disposed on the distal end side of the deformable portion and is not deformed by the external force in the first direction; and a first region that is disposed on the rear end side of the deformable portion and that is not deformed in the first direction. and a second region that is not deformed by an external force, and the gripping portion extends from at least the tip of the gripping portion to the second region in the longitudinal direction, and at least one region in a cross section perpendicular to the longitudinal direction. The deformable part includes a hard part made of the hard resin that connects the first region and the second region, and a hard part made of the hard resin that connects the first region and the second region, and a hard part made of the hard resin that connects the first region and the second region. occupancy of the cross-sectional area of the hard part with respect to the cross-sectional area of a closed space surrounded by the external contour of the deformable part or an extension of the external contour in a cross section perpendicular to the long axis direction; the bending strength in the first direction is greater than the bending strength in the second direction perpendicular to the long axis direction and the first direction. The soft portion has a concavo-convex structure in which concave portions and convex portions extending in a direction intersecting the major axis direction are arranged adjacent to each other in the major axis direction, and the concavo-convex structure portion includes: There is provided a toothbrush characterized in that the toothbrush is provided so as to be exposed on the bristle-planting surface side in the first direction and on the back side opposite to the bristle-planting surface side in the first direction.

Further, in the toothbrush according to the aspect of the present invention, the depth of the recessed portion relative to the convex portion is 2% or more and 20% or less of the maximum thickness of the deformed portion in the first direction. Features.

Further, in the toothbrush according to the aspect of the present invention, the deformed portion has a polygonal cross section perpendicular to the long axis direction, and the uneven structure portion is provided on both sides of the deformed portion in the second direction. It is characterized by

Further, in the toothbrush according to the aspect of the present invention, the outermost edge of the deformed portion in the second direction is located closer to the back side than the center position of the deformed portion in the first direction. .

Further, in the toothbrush according to one aspect of the present invention, the deformable portion branches in the second direction via a through hole penetrating in the first direction and extending in the longitudinal direction, and Each includes a core portion in which the hard portion is branched through the through hole and connects the first region and the second region, and a core portion in which the soft portion is branched through the through hole and covers the periphery of the core portion. It is characterized in that it has a covering part.

In the toothbrush according to the aspect of the present invention, the hard portion may include an inverted portion that is spaced apart from the core portion, penetrates the through hole in the longitudinal direction, and connects the first region and the second region. The reversing portion is characterized in that it jumps, buckles, and reverses when the external force in the first direction exceeds a threshold value.

Further, in the toothbrush according to one aspect of the present invention, the hard part has a flat plate shape, and the length of the hard part in the second direction is larger than the length of the hard part in the first direction. It is characterized by

Further, in the toothbrush according to one aspect of the present invention, the center of the hard part in the first direction is located closer to the back side than the center position of the deformable part in the first direction.

Further, in the toothbrush according to one aspect of the present invention, the length of the deformable portion in the long axis direction is 15 mm or more and 30 mm.

Further, in the toothbrush according to one aspect of the present invention, the length of the deformed portion in the second direction is 5 mm or more and 20 mm or less.

The present invention can provide a toothbrush that can accurately brush the dentition one tooth at a time while maintaining appropriate brushing pressure.

1 is a diagram showing an embodiment of the present invention, and is a front view of a toothbrush 1 according to a first embodiment. It is a cross-sectional view of the same toothbrush 1 cut along a plane including the center in the width direction. FIG. 7 is a cross-sectional view of the deformed portion 70 in the vicinity of an end in the longitudinal direction and perpendicular to the longitudinal direction. FIG. 7 is a cross-sectional view of the deformed portion 70 taken along a plane including the center in the width direction. FIG. 7 is a partial front view of the vicinity of the deformed portion 70 in the hard portion 70H. FIG. 7 is a partial side view of the vicinity of the deformed portion 70 in the hard portion 70H. FIG. 2 is a front view of a toothbrush 1 according to a second embodiment. It is a cross-sectional view of the same toothbrush 1 cut along a plane including the center in the width direction. FIG. 7 is a cross-sectional view of the deformed portion 70 at the center in the longitudinal direction and perpendicular to the longitudinal direction. FIG. 7 is a cross-sectional view of the deformed portion 70 taken along a plane including the center in the width direction. 7 is a partial front view of the vicinity of a hard portion 70H in the deformable portion 70. FIG. FIG. 7 is a cross-sectional view of the deformed portion 70 taken along a plane parallel to the thickness direction and the longitudinal direction, for explaining that the inverted portion has been inverted.

[First embodiment]
EMBODIMENT OF THE INVENTION Hereinafter, 1st Embodiment of the toothbrush of this invention is described with reference to FIG. 1 thru|or 6.
Note that the following embodiments illustrate one aspect of the present invention, and do not limit the present invention, and can be arbitrarily modified within the scope of the technical idea of the present invention. In addition, in the following drawings, in order to make each structure easier to understand, the scale, number, etc. of each structure are different from the actual structure. Further, in the following description, the direction perpendicular to the flocked surface in side view is referred to as the thickness direction, the flocked surface side in the thickness direction is the front side, and the side opposite to the flocked surface is the rear side.

FIG. 1 is a front view of the toothbrush 1. FIG. 2 is a cross-sectional view of the toothbrush 1 taken along a plane including the center in the width direction (vertical direction in FIG. 1).

The toothbrush 1 of the present embodiment includes a head portion 10 arranged on the distal end side in the longitudinal direction (hereinafter simply referred to as the distal end side) and in which a bundle of bristles (not shown) is implanted, and a head portion 10 having a long length. The neck portion 20 extends toward the rear end side in the axial direction (hereinafter simply referred to as the rear end side), and the grip portion 30 (hereinafter referred to as the head portion 10 , the neck portion 20 and the grip portion 30 are collectively referred to as a handle body 2).

The toothbrush 1 of this embodiment is a molded body in which a hard part H made of hard resin and a soft part E made of soft resin are integrally molded. The hard portion H constitutes at least a portion of each of the grip portions 30 including the head portion 10, the neck portion 20, and the deformable portion 70. The soft portion E constitutes a part of the grip portion 30 including the deformable portion 70. More specifically, the head portion 10 and the neck portion 20 of this embodiment are each formed of a hard resin, but a portion of the head portion 10 and the neck portion 20 of the present embodiment are made of the soft resin, for example, a part of the surface is covered with the soft resin. It may be made of resin. The grip part 30 including the deformable part 70 of this embodiment is partially formed of both hard resin and soft resin (details will be described later).

[Head part 10]
The head portion 10 has a flocked surface 11 on one side in the thickness direction (direction perpendicular to the paper surface in FIG. 1). Note that hereinafter, the direction perpendicular to the thickness direction and the long axis direction will be referred to as the width direction (or side surface direction, as appropriate). A plurality of tuft holes 12 are formed in the tuft surface 11. A tuft of hair (not shown) is implanted in the tufting hole 12 .

The width of the head portion 10, that is, the length in the width direction parallel to the flocking surface 11 on the front side and perpendicular to the long axis direction (hereinafter simply referred to as width) is not particularly limited, and is, for example, 7 mm or more and 13 mm or less. is preferred. If it is above the above-mentioned lower limit, a sufficient area for implanting the hair bundle can be secured, and if it is below the above-mentioned upper limit, operability in the oral cavity can be further improved.

The length of the head portion 10 in the longitudinal direction (hereinafter simply referred to as 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 lower limit, a sufficient area for implanting the hair bundle can be ensured, and if the length is equal to or less than the above upper limit, operability in the oral cavity can be further improved. Note that the boundary in the longitudinal direction between the neck portion 20 and the head portion 10 in this embodiment is the position where the width of the neck portion 20 becomes the minimum value from the neck portion 20 toward the head portion 10. If the area where the width of the neck portion 20 is the minimum value exists with a certain length (when the width of the neck portion 20 is not at one location), the length of the neck portion 20 and the head portion 10 The axial boundary is defined as the position closest to the tip of the head where the width of the neck portion 20 is at its minimum value.

The length of the head portion 10 in the thickness direction (hereinafter simply referred to as thickness) can be determined by considering the material and the like, 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 greater than the above lower limit, the strength of the head portion 10 can be further increased. If the thickness of the head portion 10 is less than or equal to the above upper limit value, it is possible to improve the ability to reach the back of the molar teeth, and to further improve the operability in the oral cavity.

A hair bundle is a bundle of hair. The length (hair length) from the flocking surface 11 to the tip of the hair bundle can be determined by taking into account the stiffness of the hair bundle, and is, for example, 6 to 13 mm. All the hair bundles may have the same hair length or may be different from each other.

The thickness of the hair bundle (hair bundle diameter) can be determined by taking into consideration the desired hair stiffness of the hair bundle, and is, for example, 1 to 3 mm. All the hair bundles may have the same hair bundle diameter or may be different from each other.

Examples of the bristles constituting the hair bundle include bristles whose diameter gradually decreases toward the tip of the bristles and whose bristles are sharpened (tapered bristles), and bristles whose diameter gradually decreases toward the tip of the hair (tapered bristles); Examples include straight hair that is the same. Examples of straight hair include those whose tips are flattened substantially parallel to the flocking surface 11, and those whose tips are rounded into a hemispherical shape.

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

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

The thickness of the bristles can be determined by 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). Further, a plurality of bristles of different thicknesses may be used in any combination in consideration of the usability, brushing feeling, cleaning effect, durability, etc.

[Neck part 20]
The length of the neck portion 20 is preferably 40 mm or more and 70 mm or less in terms of operability.
For example, the width of the neck portion 20 is formed to gradually increase from a minimum value toward the rear end side. The neck portion 20 in this embodiment is formed so that the width gradually increases from the position where the width is the minimum value toward the rear end side. Further, the neck portion 20 is formed so that the thickness thereof gradually increases from the minimum position toward the rear end side.

The width and thickness of the neck portion 20 at the minimum position are both preferably 3.0 mm or more and 4.5 mm or less. If the width and thickness of the neck part 20 at the minimum position are at least the above lower limit value, the strength of the neck part 20 can be further increased, and if it is below the above upper limit value, it will be easier to close the lips and it will be easier to reach the back teeth. In addition to improving the functionality, it also improves the operability in the oral cavity. The width and thickness of the neck portion 20, which is formed to gradually increase from the minimum value toward the rear end side, can be appropriately determined by taking into consideration the material and the like.

The front side of the neck portion 20 when viewed in the side direction is inclined toward the front side as it goes toward the rear end side. The back side of the neck portion 20 when viewed in the side direction is inclined in the direction toward the back side as it goes toward the rear end side. When viewed from the front, the neck portion 20 is inclined in such a direction that the distance from the center in the width direction increases toward the rear end side.

The boundary between the neck part 20 and the grip part 30 in this embodiment is the position of the tip of the neck side 20 where a deformable part 70, which will be described later, is provided. Here, the width expands from the neck part 20 toward the grip part 30 in an arc-shaped outline in both front and side views, and the position of the center of curvature of the arc coincides with the changed position in the longitudinal direction. There is. More specifically, in the front view shown in FIG. 1, the boundary between the neck portion 20 and the grip portion 30 (deformed portion 70) is a long axis where the center of curvature changes from the outside of the arcuate profile to the center in the width direction. Consistent with the position of the direction. In addition, in the side view shown in FIG. 2, the boundary between the neck portion 20 and the gripping portion 30 (deformed portion 70) is located in the longitudinal direction where the center of curvature changes from the outside of the arcuate profile to the center in the thickness direction. consistent with the location.

[Gripping part 30]
The grip portion 30 is arranged along the longitudinal direction. The grip portion 30 has a deformed portion 70 on the distal end side that forms a boundary with the neck portion 20 . As shown in FIG. 1, the width of the gripping part 30 on the rear end side of the deformed part 70 gradually narrows from the boundary with the deformed part 70 toward the rear end, and then extends to a substantially constant length. There is. As shown in FIG. 2, the thickness of the gripping part 30 on the rear end side of the deformed part 70 gradually becomes narrower from the boundary with the deformed part 70 toward the rear end, and then extends to a substantially constant length. ing. The width of the gripping portion 30 gradually narrows from the boundary with the deformed portion 70 toward the rear end side, and then becomes approximately constant in length, and the thickness of the gripping portion 30 differs from that of the deformed portion 70. The position in the long axis direction at which the length gradually becomes narrower from the boundary toward the rear end side and then reaches a substantially constant length is the same. The position of the rear end of the deformable portion 70 in this embodiment is the boundary between the soft portion 70E and the hard portion 30H.

The grip part 30 has a soft part 31E at the center in the width direction on the front side, on the rear end side of the rear end side end part of the deformable part 70. The soft portion 31E constitutes a part of the soft portion E. The soft portion 31E gradually narrows from the rear end of the deformable portion 70 toward the rear end when viewed from the front, and then extends for a substantially constant length. In front view, the side edge of the soft portion 31E and the widthwise outer side edge of the grip portion 30 are formed at a substantially constant distance.

The gripping portion 30 includes a hard portion 70H provided in the deformable portion 70 (see FIGS. 2 to 4) and a hard portion 30H provided on the rear end side of the deformable portion 70. Hard parts 30H and 70H constitute a part of hard part H. The hard part 30H has a depression 31H on the front side in which the soft part 31E is buried. The depression 31H gradually narrows from the rear end of the deformable portion 70 toward the rear end side when viewed from the front, and then extends in the longitudinal direction with a substantially constant length. A portion of the soft portion 31E buried in the depression 31H protrudes beyond the hard portion 30H exposed on the front side. The other soft portion 31E is substantially flush with the hard portion 30H exposed on the front side.

The grip part 30 has a soft part 32E at the center in the width direction on the back side (see FIGS. 1 and 2). The soft portion 32E constitutes a part of the soft portion E. The soft portion 32E has an outer contour that is substantially the same as the outer contour of the soft portion 31E when viewed from the front. That is, the soft portion 32E gradually becomes narrower from the rear end of the deformable portion 70 toward the rear end side, and then extends for a substantially constant length. In rear view, the side edge of the soft portion 32E and the widthwise outer side edge of the grip portion 30 are formed at a substantially constant distance.

The hard part 30H has a recess 32H (see FIG. 2) on the back side in which a part of the soft part 32E is buried. The depression 32H gradually narrows from the rear end of the deformable portion 70 toward the rear end side when viewed from the rear, and then extends for a substantially constant length. A portion of the soft portion 32E protrudes beyond the hard portion 30H exposed on the back side. The other soft portion 32E is substantially flush with the hard portion 30H exposed on the front side.

Since 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, grip performance when the grip portion 30 is gripped is improved.

[Deformation part 70]
The deformable portion 70 is deformed by an external force in the thickness direction perpendicular to the flocked surface 11 . The deformable portion 70 connects the neck portion (first region) 20 on the distal end side and the grip portion (second region) 30 on the rear end side. The deformable portion 70 has a hard portion 70H and a soft portion 70E. As shown in FIGS. 1 and 2, the deformable portion 70 has knurling portions (uneven structure portions) 101 to 104.

FIG. 3 is a cross-sectional view of the deformed portion 70 perpendicular to the long axis direction, and is a cross-sectional view taken along the line AA in FIG. FIG. 4 is a cross-sectional view of the deformable portion 70 taken along a plane including the center in the width direction.

As shown in FIG. 3, in this embodiment, the hard part 70H is surrounded by a soft part 70E. The maximum length of the deformable portion 70 in the major axis direction is preferably 15 mm or more and 30 mm or less. By setting the maximum length of the deformable portion 70 in the long axis direction to 15 mm or more, the user can sufficiently feel the deformation of the deformable portion 70 when the user grips the grip portion 30. Further, by setting the maximum length of the deformable portion 70 in the major axis direction to 30 mm or less, it is possible to prevent the deformable portion 70 from being easily bent too much. Moreover, the deformation area in the gripped portion is limited, and a decrease in operability is suppressed.

The deformed portion 70 is a polygon whose outline in a cross section perpendicular to the long axis direction is eccentric toward the back side in the thickness direction. The cross-sectional contour of the deformed portion 70 is a substantially hexagonal outer contour of a soft portion 70E in which a hard portion 70H is embedded. Among the six vertices of the external contour, the two vertices located halfway in the thickness direction (both ends in the width direction) are located on the back side of the deformed portion 70 (soft portion 70E) from the center in the thickness direction. There is. By arranging the two vertices closer to the back side than the center of the deformable portion 70 in the thickness direction, the back side becomes thinner than the front side, making it easier to bend the deformable portion 70 toward the back side.
In addition, since two vertices at the same position in the thickness direction are arranged at both ends in the width direction, the wall thickness at the apex positions is large, so that the bending resistance in the width direction is large. Therefore, the deformable portion 70 is difficult to bend in the width direction.

As shown in FIG. 3, the cross-sectional shape of the hard portion 70H is formed into a rectangular shape extending in the width direction, and the width is larger than the thickness. Since the width of the hard portion 70H is larger than the thickness, the hard portion 70H has a bending behavior (anisotropy regarding bending) in which it is easy to bend in the thickness direction and difficult to bend in the width direction. In other words, the deformable portion 70 has the hard portion 70H formed in a rectangular cross section extending in the width direction, the width of which is greater than the thickness, so that the bending strength in the thickness direction is regulated to be smaller than the bending strength in the width direction. has been done.

The center position of the hard part 70H in the thickness direction is located closer to the back side than the center position of the deformable part 70 in the thickness direction. That is, the hard portion 70H is arranged eccentrically toward the back side with respect to the thickness direction.

The occupancy rate of the cross-sectional area of the hard part 70H with respect to the cross-sectional area of the closed space surrounded by the external contour of the deformable part 70 or an extension of the external contour in the cross section perpendicular to the long axis direction is 35% in the long axis direction. It is as follows. When the outer contour of the deformable portion 70 forms a closed space as shown in FIG. 3, the area of the closed space is the cross-sectional area of the deformed portion 70. By setting the occupancy of the cross-sectional area of the hard portion 70H to 35% or less of the cross-sectional area of the deformable portion 70 in the major axis direction, the bending strength of the deformed portion 70 toward the back side can be reduced. The early stage occupancy rate is preferably 25% or less, more preferably 15% or less. Further, the occupancy rate is preferably 3% or more.

The knurling portions 101 to 104 are provided to be exposed on the front side, the back side, and both side edges in the width direction of the deformable portion 70, respectively. More specifically, the knurled portion 101 is provided to be exposed on the front side soft portion 70E of the deformed portion 70. The knurled portion 102 is provided to be exposed on the soft portion 70E on the back side of the deformed portion 70.

As shown in FIG. 1, the knurling parts 101 and 102 each have a plurality of concave parts 111 and convex parts 112 that extend in a direction intersecting the longitudinal direction and are arranged adjacent to each other in the longitudinal direction. The concave portion 111 and the convex portion 112 in this embodiment extend in the width direction. That is, the recess 111 has a groove shape extending in the width direction. The protrusion 112 is a protrusion extending in the width direction. As shown in FIG. 4, the cross section of the recess 111 cut along a plane including the center in the width direction has an arcuate shape recessed toward the center in the thickness direction. A cross section of the convex portion 112 cut along a plane including the center in the width direction has an arcuate shape that protrudes outward in the thickness direction.

By providing a plurality of recesses 111 in the long axis direction that form thin-walled portions extending in the width direction on the front and rear sides of the deformable portion 70, the deformable portion 70 can easily bend toward the rear and front sides around the recesses 111. . Therefore, the positions of the recesses 111 in the longitudinal direction are preferably the same in the knurling parts 101 and 102.

The depth of the concave portion 111 relative to the convex portion 112 (the distance in the thickness direction from the apex position of the convex portion 112 to the most depressed position of the concave portion 111) is 2% or more and 20% of the maximum thickness of the deformable portion 70. It is preferable that it is below. If the depth of the recess 111 is less than 2% of the maximum thickness of the deformed portion 70, the deformed portion 70 may not be effectively deflected in the thickness direction. If the depth of the recessed portion 111 exceeds 20% of the maximum thickness of the deformable portion 70, the grip portion 30 may be easily bent, and operability may be impaired. Therefore, by setting the depth of the recess 111 to 2% or more and 20% or less of the maximum thickness of the deformable portion 70, the deformable portion 70 can be easily bent toward the back side and the front side while maintaining operability. Become.

The depth of the recess 111 in the knurling part 101 and the depth of the recess 111 in the knurling part 102 may be different, but from the viewpoint of making the operability and the deflection characteristics in the thickness direction the same on the front side and the back side. Therefore, it is preferable that the depths of the recesses 111 be the same.

The maximum width of the knurling parts 101 and 102, that is, the maximum width of the deformed part 70, is preferably 8 mm or more and 20 mm or less. If the maximum width of the deformable portion 70 is less than 8 mm, the grip portion 30 may easily bend and the operability may be impaired. Further, if the maximum width of the deformable portion 70 exceeds 20 mm, the deformable portion 70 may not be effectively deflected in the thickness direction. Therefore, by setting the maximum width of the knurling parts 101 and 102 to 8 mm or more and 20 mm or less, the deformable part 70 can be easily bent toward the back side and the front side while maintaining operability.

The arrangement pitch RP of the concave portions 111 and convex portions 112 in the longitudinal direction of the knurling portions 101 and 102 is preferably 9% or more and 26% or less of the length of the deformable portion 70 in the longitudinal direction. If the arrangement pitch RP is less than 9%, there is a possibility that the deformable portion 70 will not be sufficiently bent. If the array pitch RP exceeds 26%, the deformable portion 70 may be bent too much, which may impair operability. Therefore, by setting the arrangement pitch RP of the concave portions 111 and convex portions 112 in the longitudinal direction of the knurling portions 101 and 102 to 9% or more and 26% or less of the length of the deformable portion 70 in the longitudinal direction, operability is ensured. In this state, the deformable portion 70 can be easily bent toward the back side and the front side.

The knurled portion 103 is provided to be exposed in the soft portion 70E of the side edge of the deformed portion 70 on one side in the width direction (the upper side in FIG. 1). The knurled portion 104 is provided so as to be exposed on the soft portion 70E of the other widthwise (lower side in FIG. 1) side edge of the deformed portion 70.

As shown in FIG. 4, the knurling portions 103 and 104 each have a plurality of concave portions 113 and convex portions 114 that extend in a direction intersecting the longitudinal direction and are arranged adjacent to each other in the longitudinal direction (Fig. 4, only the knurling portion 103 is shown). The concave portion 113 and the convex portion 114 in this embodiment extend in the thickness direction. That is, the recess 113 has a groove shape extending in the thickness direction. The protrusion 114 is a protrusion extending in the thickness direction. As shown in FIG. 1, when viewed from the front, the recess 113 has an arcuate shape recessed toward the center in the width direction. When viewed from the front, the convex portion 114 has an arc shape that protrudes outward in the width direction.

By providing a plurality of recesses 113 in the long axis direction on both sides of the deformable portion 70 in the width direction, which form thin wall portions extending in the thickness direction, the resistance when the deformable portion 70 bends in the thickness direction is reduced, and the deformed portion 70 can be easily bent toward the back side and the front side. Therefore, it is preferable that the positions of the recesses 113 in the long axis direction are the same in the knurling parts 103 and 104.

The depth of the concave portion 111 relative to the convex portion 114 (the distance in the thickness direction from the apex position of the convex portion 114 to the most depressed position of the concave portion 113) is 2% or more and 20% or less of the maximum width of the deformable portion 70. It is preferable that When the depth of the recess 113 is less than 2% of the maximum width of the deformed portion 70, the decrease in resistance when the deformed portion 70 is bent in the thickness direction is small, and the deformation of the deformed portion 70 in the thickness direction is reduced. It may not be expressed effectively. If the depth of the recessed portion 113 exceeds 20% of the maximum width of the deformable portion 70, the grip portion 30 may easily bend and the operability may be impaired. Therefore, by setting the depth of the recess 113 to 2% or more and 20% or less of the maximum width of the deformable portion 70, the deformable portion 70 can be easily bent toward the back side and the front side while maintaining operability. .

The depth of the recess 113 in the knurling part 103 and the depth of the recess 113 in the knurling part 104 may be different, but the operability and the deflection characteristics in the width direction should be the same on one side and the other side in the width direction. From this point of view, it is preferable that the depths of the recesses 113 be the same.

The depth of the recesses 111 in the knurling parts 101 and 102 arranged in the thickness direction and the depth of the recesses 113 in the knurling parts 103 and 104 arranged in the width direction may be the same, but from the viewpoint of making it easier to bend in the thickness direction. Therefore, it is preferable that the recess 111 is deeper than the recess 113.

Since the convex portions 112 and 114 are provided around the deformed portion 70 at intervals (recessed portions 111 and 113) in the longitudinal direction, grip performance when gripping the deformed portion 70 is improved.

The knurling parts 101 and 102 are not limited to a flat knurling structure in which the direction in which the recessed part 111 and the convex part 112 extend is perpendicular to the longitudinal direction in which the recessed part 111 and the convex part 112 are lined up. If the intersecting angle between the direction in which the concave portion 111 and the convex portion 112 extend and the direction in which they are lined up is other than 90 degrees, the direction in which the concave portion 111 and the convex portion 112 extend and the major axis direction intersect at a first angle and the long axis The first knurling group arranged in the axial direction, the direction in which the concave portion 111 and the convex portion 112 extend, and the major axis direction intersect at a second angle that is line symmetrical to the first angle with the major axis direction as the center, and the major axis is formed. A cross-grain knurl structure may be adopted in which a second knurl group is arranged in the direction. When adopting a cross-cut knurling structure in which the first angle and the second angle are symmetrical about the long axis direction, when the deformable portion 70 bends toward the back side and the front side around the recessed portion 111, the first angle The resistance of the knurling group and the second knurling group becomes the same, and it is possible to suppress the deformation portion 70 from being bent in a direction intersecting the thickness direction. The knurling portions 103 and 104 may similarly have a cross-grain knurling structure.

Furthermore, the cross-sectional shapes of the recesses 111 and 113 and the convex portions 112 and 114 are not limited to arc shapes, but may be rectangular, V-shaped, etc., for example. When the cross-sectional shapes of the recesses 111 and 113 include corners, there is a possibility of stress concentration at the corners, so the cross-sectional shapes of the recesses 111 and 113 are preferably arcuate.

FIG. 5 is a partial front view of the vicinity of the hard part 70H in the deformable part 70. FIG. 6 is a partial side view of the vicinity of the hard part 70H in the deformable part 70.
As shown in FIG. 5, the hard part 70H is formed into a rectangular shape in plan view that connects the hard part 20H which is the neck part 20 in the longitudinal direction and the hard part 30H on the rear end side of the deformed part 70 in the grip part 30. has been done. The width of the hard part 70H is smaller than the width of the hard part 20H and the width of the hard part 30H.

The hard part 20H connected to the hard part 70H constitutes a first region P1 which is rigid and has a width, thickness, and bending strength in the thickness direction greater than that of the hard part 70H. The hard part 30H connected to the hard part 70H constitutes a second region P2 that is rigid and has greater width, thickness, and bending strength in the thickness direction than the hard part 70H. In each of the first region P1 and the second region P2, the ratio of the hard resin to the soft resin is larger in the cross section perpendicular to the long axis direction. In the toothbrush 1, when an external force is applied to the head portion 10 toward the back side while gripping the gripping portion 30, the first region P1 on the tip side and the second region P2 on the rear end side of the deformable portion 70 bend. Since the strength is greater than that of the hard part 70H and it is rigid, it does not deform, and the deformable part 70 disposed between the first region P1 and the second region P2 deforms toward the back side.

As shown in FIG. 6, the front end side of the hard part 70H is connected to the hard part 20H (first region P1) by an arcuate curved surface 73H when viewed from the side. The rear end side of the front side of the hard part 70H is connected to the hard part 30H (second region P2) by an arcuate curved surface 74H when viewed from the side. The arc centers of the curved surfaces 73H and 74H are located closer to the front than the hard portion 70H when viewed from the side. The tip end side of the back side of the hard part 70H is connected to the hard part 20H by a curved surface 75H having an arc shape when viewed from the side. The rear end side of the hard part 70H on the back side is connected to the hard part 30H by an arcuate curved surface 76H when viewed from the side. The arc centers of the curved surfaces 75H and 76H are located on the back side of the hard portion 70H in side view. If curved surfaces 73H to 76H do not exist, stress may concentrate on the boundary between the tip side of hard part 70H and hard part 20H, and on the boundary between the rear end side of hard part 70H and hard part 30H. On the other hand, the presence of the curved surfaces 73H to 76H relieves the concentrated stress.

The thickness (minimum thickness) of the hard portion 70H is preferably 0.5 mm or more and 2.0 mm or less. If the thickness of the hard part 70H is less than 0.5 mm, the deformation of the deformable part 70 when an external force is applied to the back side of the head part 10 becomes large, and the operability during brushing may deteriorate. When the thickness of the hard portion 70H exceeds 2.0 mm, it becomes difficult to bend when an external force is applied to the head portion 10 toward the back side. Further, when an external force is applied, it becomes difficult to bring the hard portion 70H into a state of plane stress, which may reduce durability. Therefore, by setting the thickness of the hard part 70H to 0.5 mm or more and 2.0 mm or less, the hard part 70H can be brought into a plane stress state while maintaining operability during brushing.

Examples of the material of the hard part H include hard resins having a bending elastic modulus (JIS7171) of 1500 MPa or more and 3500 MPa or less, such as polyacetal resin (POM). The bending elastic modulus of the hard part H is more preferably 2000 MPa or more and 3500 MPa or less.

As a material for the soft part E, a material with a Shore hardness A of 50 or more and 90 or less is preferable, as an example, in that even if the brushing load increases, the load on the teeth etc. is within an appropriate range. More preferably, it is 60 or more and 80 or less. If the Shore hardness A is less than 50, there is a possibility that it will be easily bent in the width direction. Examples of the soft resin include elastomers (for example, olefin elastomers, styrene elastomers, polyester elastomers, polyurethane thermoplastic elastomers, etc.) and silicones. Styrenic elastomers are preferred because they have excellent miscibility with polyacetal resins.

As a countermeasure against over-brushing in the toothbrush 1, it is effective to ensure flexible deflection behavior and alleviate the brushing load. Therefore, regarding the deflection behavior of the toothbrush 1 in the thickness direction, it is required that the load be applied to the teeth and the like with as constant a pressure as possible even when the brushing pressure increases rapidly. However, if flexibility is applied not only in the thickness direction but also in the width direction during brushing, the pressure that should be applied to the teeth will be dispersed, leading to a reduction in cleaning power. Furthermore, when the head is deflected in various directions, it becomes difficult to apply the head portion 10 to the targeted area, which may lead to a decrease in operability.

On the other hand, the toothbrush 1 of the present embodiment is provided with the deformed portion 70 that has anisotropy in bending strength and is easily deformed in the thickness direction and difficult to deform in the width direction. It is possible to suppress the decline in performance and operability. In addition, in the deformable portion 70 of the toothbrush 1 of the present embodiment, the hard portion 70H is embedded in the soft portion 70E, and moderate elasticity acts as compared to the case where the deformable portion 70 is formed only of the hard portion. Even when the brushing pressure increases rapidly, the load on the teeth etc. is suppressed. Moreover, compared to the case where the deformable portion 70 is formed only of a soft portion, it immediately returns to its original shape when the load is released, and can accommodate various movements of the head portion 10.

As explained above, in the toothbrush 1 of the present embodiment, the occupancy rate of the cross-sectional area of the hard part 70H with respect to the cross-sectional area of the closed space surrounded by the external contour or an extension of the external contour is 35 in the long axis direction. % or less and whose bending strength in the thickness direction is regulated to be smaller than the bending strength in the width direction. It is possible to maintain good operability in that the target area can be thoroughly brushed while maintaining a suitable brushing pressure. Furthermore, in the toothbrush 1 of the present embodiment, the knurling parts 103 and 104 exposed on both sides of the deformable part 70 in the width direction are provided, so that the resistance when the deformable part 70 is bent in the thickness direction can be reduced. This makes it easier to bend the deformable portion 70 in the thickness direction.

[Second embodiment]
Next, a second embodiment of the toothbrush 1 will be described with reference to FIGS. 7 to 12.
In these figures, the same elements as those of the first embodiment shown in FIGS. 1 to 6 are denoted by the same reference numerals, and the explanation thereof will be omitted.

FIG. 7 is a front view of the toothbrush 1 according to the second embodiment. FIG. 8 is a cross-sectional view of the toothbrush 1 taken along a plane including the center in the width direction (vertical direction in FIG. 7).

As shown in FIGS. 7 and 8, the deformable portion 70 of the toothbrush 1 in this embodiment includes an inverted portion 80 and an elastic deformable portion 90. FIG. 9 is a cross-sectional view of the deformed portion 70 at the center in the long-axis direction, which is perpendicular to the long-axis direction, and is a cross-sectional view taken along the line BB in FIG. FIG. 10 is a cross-sectional view of the deformable portion 70 taken along a plane including the center in the width direction.

The inversion part 80 and the elastic deformation part 90 each connect the neck part (first region) 20 on the distal side of the deformation part 70 and the grip part (second region) 30 on the rear end side of the deformation part 70. As shown in FIG. 9, the elastic deformation parts 90 are provided on both sides of the reversing part 80 in the width direction with a gap S between them. The gap S is formed by a through hole K penetrating in the thickness direction. As shown in FIG. 7, the through hole K is formed in a rectangular shape in plan view extending in the longitudinal direction. That is, the deformable portion 90 is branched in the width direction via the through hole K, and each of the branched deformable portions 70 forms an elastically deformable portion 90.

By providing the gap S, the reversing section 80 can be reversed (easier to reverse) without interfering with surrounding structures. Furthermore, since the elastic deformation section 90 and the reversing section 80 do not interfere with each other, the deformation of the reversing section 80 does not follow the deformation of the elastic deforming section, so that the functional roles (described later) of the reversing section 80 and the elastic deforming section 90 are made independent. be able to.
Thereby, for example, the degree of freedom in design for obtaining the following effects can be increased. For example, it is possible to clearly generate vibrations and sounds when the reversing section 80, which will be described later, is inverted. Furthermore, for example, it is possible to increase the repulsive force of the reversing portion 80 in proportion to the amount of displacement until the magnitude of the external force reaches the threshold value, and it is possible to maintain the proportional relationship particularly in the vicinity of the threshold value. (The degree of increase in the repulsive force of the reversing portion 80 does not become slower). As a result, in the area up to the amount of displacement that reaches the upper limit pressure (brushing pressure), the pressure assumed by the user is directly reflected in the repulsive force of the reversing part 80, so the brushing load can be appropriately controlled. . If the setting is such that the degree of increase in the repulsion force gradually slows down when the magnitude of the external force reaches a threshold value, the user may unintentionally continue brushing with a pressure near the upper limit. Moreover, if the gap S is made to communicate with both sides of the reversing portion 80 in the thickness direction, the above-mentioned effect will be further improved.
Furthermore, by widening the gap S in the thickness direction, the vector of the load applied to the brush part (bristle) during brushing, the direction in which the gap opens, and the direction in which the reversing part 80 and the elastic deformation part 90 deform are parallel to each other. (see FIG. 9), making it easy to link the generation of vibration and sound due to reversal with the brushing load.

Furthermore, if the front side and the back side are penetrated through the gap S by the through hole K, it is possible to further expand the movable range of the elastic deformation part 90, which is responsible for the function of deflecting the toothbrush skeleton against the load during brushing, for example. (The tensile behavior on the front surface and the compressive behavior on the back surface are less likely to be inhibited due to deflection.) If the through hole K does not exist between the elastically deformable portion 90 and the reversible portion 80, the movable region of the elastically deformable portion 90 becomes narrow. In this case, there is a possibility that the reversing section 80 is not given an opportunity to reverse in an appropriate load range, and the reversing section 80 is reversed before reaching the appropriate load range, or it is not reversed even in an appropriate load range. is assumed. On the other hand, by providing the through hole K between the elastic deformation part 90 and the reversing part 80, the threshold value at which the reversing part 80 is reversed, which will be described later, can be controlled in a finer range.
Note that the gap S does not have to penetrate in the thickness direction, and may be formed, for example, as a closed cavity extending in the longitudinal direction inside the elastically deformable portion 90. Alternatively, it may be formed by a depression (described later) that opens on the front side or the back side.

Each elastically deformable portion 90 has a hard portion (core portion) 90H and a soft portion (covering portion) 90E. As shown in FIG. 7, the soft part 90E connects the rear end of the neck part 20 and the grip part 30 on the rear end side of the deformed part 70. As shown in FIGS. 9 and 10, a depression (recess) 71 that opens to the front side and a depression (recess) 72 that opens to the back side are provided between the pair of elastic deformation parts 90. The bottoms of the recesses 71 and 72 at both ends in the width direction are connected to the through holes K, respectively. An inverted portion 80 is provided to be exposed at the bottom of the recess 71 and the recess 72 at the center in the width direction. By providing the depressions 71 and 72, for example, it is possible to further expand the movable range of the elastic deformation part 90, which is responsible for the deflection function of the toothbrush skeleton against the load during brushing, and improve the deflection anisotropy in the thickness direction. can. Note that the depression between the pair of elastic deformation parts 90 does not need to penetrate in the thickness direction, and may be open only in one direction in the thickness direction. Alternatively, for example, a closed cavity extending in the longitudinal direction may be formed inside the elastically deformable portion 90, and a pair of elastically deformable portions 90 may be formed in the width direction with the cavity sandwiched in the center.

In the pair of elastic deformation parts 90, the ends of the soft part 90E in the longitudinal direction are connected in the width direction on both the front side and the back side. The soft portions 90E of the pair of elastically deformable portions 90 are provided around the depressions 71 and 72, which are oval in shape when viewed from the front. The rear end side of the soft portion 90E is connected to the soft portion 31E of the grip portion 30. Since the soft portions 90E are connected in the width direction on both the front end and rear end sides of the elastic deformation portion 90, stress is less likely to be concentrated at the end of the hinge structure even if the hinge structure is repeatedly reversed, making it less likely to break. In addition, the anisotropy in the deformable portion 70 is increased by connecting the soft portions 90E in the width direction on both the front end side and the rear end side of the elastic deformable portion 90, and the pair of elastic deformable portions 90 are resistant to movement during brushing. , it becomes possible to bend without twisting in the thickness direction. Furthermore, by connecting the soft portions 90E in the width direction, the amount of heat that the soft resin (elastomer) has during injection molding increases, so that the adhesiveness between the neck portion 20 and the deformable portion 70 (the adhesiveness between the neck portion 20 and the elastically deformable portion 90 ) increases.

If the external contour of the deformable portion 70 does not form a closed space as shown in FIG. The cross-sectional area of the deformable portion 70 is the area of the closed space surrounded by the outer contour.

FIG. 11 is a partial front view of the vicinity of the hard part 70H in the deformable part 70.
As shown in FIG. 11, the hard part 70H has through holes 73 provided on both sides of the inverted part 80 in the width direction. The through holes 73 each extend in the longitudinal direction. The length of the through hole 73 in the longitudinal direction is the length that separates it from the ends of the hard parts 20H and 30H, respectively. As shown in FIG. 9, in the through hole 73, a soft portion 90E is provided 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. In the hard part 70H, the hard part 90H is arranged on both sides in the width direction with the inverted part 80 at the center through the through holes 73, so even if the elastic deformation part 90 is deformed by a load, the inverted part 80 can maintain its shape. When the hard part H that constitutes the entire length of the toothbrush 1 is bent, the inverted part 80 of the deformed part 70 is inverted in an attempt to release the accumulated strain energy. For example, if the neck portion 20 and the grip portion 30 of the hard portion 70H are connected only by the reversing portion 80, the energy cannot be stored and the hard portion 70H will be reversed immediately. When the above-mentioned inversion part 80 is integrally injection molded with a first part A1 and a second part A2, which will be described later, as well as the neck part 20, grip part 30, and hard part 70H, the accumulated strain energy is transferred to the inversion part 80. can be transmitted efficiently.

The hard portion 90H is formed outside the through hole 73 in the width direction of the hard portion 70H. As shown in FIG. 9, the hard portion 90H has a substantially rectangular cross-sectional shape with long sides extending in the width direction. The hard part 90H is buried and covered by the soft part 90E. Since the hard part 90H is embedded in the soft part 90E, the stress applied to the hard part 90H can be alleviated from the viewpoint of strength. Furthermore, the elastic behavior of the elastically deformable portion 90 can be controlled in terms of the degree of deflection of the toothbrush 1 with respect to the load. In addition, by embedding the hard part 90H in the soft part 90E, the bending anisotropy in the deformable part 70 is increased, and for example, the elastic deformable part 90 can be moved without twisting in the thickness direction during brushing. It becomes possible to bend it.

The pair of hard parts 90H are arranged at the same position in the thickness direction. By arranging the pair of hard parts 90H at the same position in the thickness direction, the anisotropy in the deformation part 70 is increased, and the pair of elastic deformation parts 90 are resistant to movement in the thickness direction during brushing. It becomes possible to flex without twisting. Further, the position of the hard part 90H in the thickness direction is preferably on the back side of the position where the thickness of the elastically deformable part 90 becomes half. By locating the elastically deformable portion 90 on the back side of the position where the thickness is half, it is possible to ensure the behavior of immediately returning to the original shape when the load is released, while ensuring ease of bending in the thickness direction. . The width of the hard portion 90H is preferably 2.0 mm or more. By setting the width of the hard portion 90H to 2.0 mm or more, deflection in the width direction can be suppressed. The thickness of the hard portion 90H is preferably 2.0 mm or less. By setting the thickness of the hard part 90H to 2.0 mm or less, it becomes easy to bend repeatedly in the thickness direction. The width of the hard portion 90H is preferably larger than the thickness of the hard portion 90H in order to make the elastically deformable portion 90 more difficult to bend in the width direction than in the thickness direction.

Furthermore, the presence of the curved surfaces 73H to 76H in the hard part 90H allows both the elastic deformation part 90 and the front end and rear end sides of the inversion part 80 to deform with flexibility (this is the trigger for inversion). (The degree of deformation of the elastic deformation section 90 can be sensed more precisely.)

The minimum distance between the hard part 90H and the outer contour in the width direction of the deformable part 70, that is, the minimum thickness (thickness) of the soft part 90E on the outside in the width direction than the hard part 90H, should be 1.0 mm or less. preferable. By setting the minimum thickness of the soft portion 90E to 1.0 mm or less, deflection in the width direction can be suppressed.

By using a material with a high modulus of elasticity (for example, POM) as the material of the hard part H, even if the shape is made thin or thin, buckling occurs when an excessive load is applied, and vibration occurs. Moreover, by using a material with a high elastic modulus, it is possible to quickly return to the initial state (the state in which the elastic deformation portion 90 is released from deflection) after jump buckling occurs.

As for the material of the soft part E, the load on the teeth, etc. is within an appropriate range even if the brushing load increases until jumping buckling occurs, and as an example, Shore hardness A is 50 or more and 90 or less. It is preferable to have a Shore hardness A of 60 or more and 80 or less.

The deformable portion 70 in the toothbrush 1 of the present embodiment has an elastically deformable portion 90 in which the hard portion 90H is embedded in the soft portion 90E, and the elastically deformable portion 70 is moderately deformable compared to the case where the elastically deformable portion 90 is formed only of the hard portion. Because of this elasticity, the load on teeth etc. is suppressed even when the brushing pressure increases rapidly. Furthermore, compared to the case where the elastically deformable portion 90 is formed only of a soft portion, it immediately returns to its original shape when the load is released, and can accommodate various movements of the head portion 10. Furthermore, in this embodiment, since the pair of elastic deformation parts 90 are arranged side by side in the width direction, deflection in the width direction is suppressed in response to a load in the thickness direction, and deflection due to twisting can also be suppressed. As a result, the above-mentioned decrease in cleaning power and operability can be suppressed.

Furthermore, in this embodiment, since the pair of elastic deformation parts 90 are arranged side by side in the width direction, deflection in the width direction is suppressed in response to a load in the thickness direction, and deflection due to twisting can also be suppressed. As a result, the above-mentioned decrease in cleaning power and operability can be suppressed.

As shown in FIG. 7, the reversing portion 80 extends in the longitudinal direction when viewed from the front, and includes a first portion A1 on the distal end side of the through hole 73 in the hard portion 70H, and a second portion A1 on the rear end side of the through hole 73 in the hard portion 70H. This is a second hard part that connects with part A2. The reversing unit 80 is in a first stable state (hereinafter referred to as a first state) shown in FIG. ) is formed into a substantially V-shape in side view, gradually sloping toward the back side from both ends in the longitudinal direction toward the center. That is, in the first state, the reversing portion 80 is formed in a convex shape on the back side with the apex at the center in the longitudinal direction.

As shown in FIG. 9, a portion of the reversible portion 80 overlaps the hard portion 90H in the width direction in the first state. Further, as shown in FIG. 12, a portion of the reversible portion 80 overlaps the hard portion 90H in the width direction also in a second state described below. Since a portion of the inverted portion 80 overlaps the hard portion 90H in the width direction in both the first state and the second state, the anisotropy in the deformed portion 70 is increased, and the pair of elastic deformed portions 90 are prevented from moving during brushing. However, it becomes possible to bend without twisting in the thickness direction.

In the above-mentioned toothbrush 1, when an external force is applied to the head part 10 toward the back side while gripping the gripping part 30, the first area P1 on the front end side and the second area P2 on the rear end side of the deforming part 70 Since the bending strength is greater than that of the hard part 70H and it is rigid, it does not deform, and the deformable part 70 disposed between the first region P1 and the second region P2 deforms toward the back side.

At this time, if the magnitude of the external force is less than or equal to a predetermined threshold, the elastic deformation section 90 and the reversing section 80 elastically deform according to the magnitude of the external force. Further, at this time, the knurling portion 101 is bent toward the back side while being expanded in the longitudinal direction. The knurled portion 102 is compressed in the longitudinal direction and bent toward the back side. The knurling parts 101 and 102 are thin in the thickness direction due to the presence of the recess 111, and the unevenness is formed at the same pitch in the width direction on the front and back sides (front side and back side) of both branch parts. , it can be easily bent toward the back side without twisting in the thickness direction. Furthermore, since the knurling parts 103 and 104 are thinner in the width direction due to the presence of the recesses 111, the resistance when the deformed part 70 is bent in the thickness direction is reduced, and the deformed part 70 is further bent toward the back side. It becomes easier to Furthermore, by extending and connecting the unevenness (recessed part 111 and protruding part 112) on the front and back sides (front side and back side) to the unevenness (recessed part 113 and protruding part 114) on the side surface, it is possible to improve twisting in the thickness direction. It can be bent without any bending.

When the magnitude of the external force exceeds a predetermined threshold, the elastically deformable portion 90 bends and elastically deforms in accordance with the magnitude of the external force that exceeds the threshold. On the other hand, when the magnitude of the external force exceeds a predetermined threshold value, the reversing portion 80 jumps and buckles when the neck portion 20 is deformed and reverses, as shown by the two-dot chain line in FIG. 2 stable state (hereinafter referred to as the second state). In the second state, the reversing portion 80 is inverted in a direction that gradually inclines toward the front side toward the center and has a substantially inverted V shape when viewed from the side. In the second state, the reversing portion 80 is formed in a convex shape on the front side with the apex at the center in the longitudinal direction.

That is, when the magnitude of the external force exceeds a predetermined threshold, the elastically deformable portion 90 is elastically deformed, and the reversible portion 80 jumps from the first state while the bending strength in the deformable portion 70 is ensured. It moves, buckles, and reverses to the second state. Furthermore, since the through hole K is provided between the reversing section 80 and the elastically deforming section 90, the reversing section 80 and the elastically deforming section 90 can be deformed independently of each other, making it easy to reverse the reversing section 80. Become. That is, when a brushing load is applied, since the through hole K is provided, first only the elastic member 90 is deflected, and then the reversible portion 80 is deflected, without interfering with each other's deformation behavior. Note that it is not necessary that the reversing portion 80 and the elastically deforming portion 90 penetrate through each other, and it is sufficient that a gap S is formed therebetween.
Furthermore, since the elastically deformable portion 90 is suppressed from deflecting in the width direction in response to a load in the thickness direction on the head portion 10, it is also possible to suppress deflection due to twisting. This can contribute to accurate functioning. Furthermore, although it is necessary to accumulate strain energy to invert the inversion part 80, as described above, by suppressing the deflection in the width direction against the load in the thickness direction, the deflection due to twisting is also suppressed. Therefore, the load during brushing can be efficiently converted into strain energy. Therefore, in this embodiment, it is possible to clearly and repeatedly buckle the reversing portion 80 at appropriate timing.

Due to the vibrations caused when the reversing section 80 jumps, buckles, and reverses, the user who grips the gripping section 30 is in an overbrushing state in which the external force applied to the head section 10 toward the back side exceeds a threshold value. can be detected.

The reversing portion 80 has a groove portion 81 at the center in the longitudinal direction on the front side, that is, in a region including the apex of the convex shape. The reversing part 80 has a groove part 82 at the center in the longitudinal direction on the back side, that is, in a region including the apex of the convex shape. The grooves 81 and 82 extend in the width direction. The groove portion 81 is formed in an arc shape when viewed from the side with the center of the arc located on the front side. The groove portion 82 is formed in an arc shape when viewed from the side with the center of the arc located on the back side. If the grooves 81 and 82 are not provided in the reversible portion 80, stress is uniformly generated throughout the reversible portion 80, making it difficult to cause buckling. On the other hand, by providing the grooves 81 and 82 in the reversing portion 80, stress is generated intensively in the groove portions 81 and 82, and buckling is likely to occur.

The radius of the grooves 81 and 82, which are arcuate in side view, is preferably 1 mm or more and 2 mm or less. If the radius of the grooves 81 and 82 is less than 1 mm, there is a possibility that the reversal section 80 will not be reversed. If the radius of the grooves 81 and 82 exceeds 2 mm, the vibration of the reversing section 80 during reversing becomes small, and it may become difficult to detect overbrushing.

As for the depth of the grooves 81 and 82, it is preferable that the groove 81 is deeper than the groove 82. If the groove portion 82 is deeper than the groove portion 81, the reversing portion 80 will be difficult to reverse even if the magnitude of the external force exceeds a predetermined threshold. Moreover, when the groove part 81 is deeper than the groove part 82, it becomes possible to guide the reversible part 80 so that it jumps and buckles more easily on the front side. Note that instead of a configuration in which both grooves 81 and 82 are provided, a configuration in which groove 82 is not provided and only groove 81 is provided may be used.

In the reversing portion 80, the groove portions 81 and 82 are provided in the region including the apex of the convex shape, so the region including the apex of the convex shape is thinner than other regions. Therefore, the strain energy accumulated due to the deformation of the reversing section 80 due to the external force exceeding the threshold value can be instantly released starting from the grooves 81 and 82, and the reversing section 80 can be reversed. In addition, as described above, since the deformable part 70 has high anisotropy and deforms easily in the thickness direction of the reversed part 80, the strain energy accumulated due to the deformation of the reversed part 80 causes the reversed part 80 to be deformed in the thickness direction. This can contribute to functions such as efficient inversion. 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 reversing section 80 is reversed from the first state to the second state.

Furthermore, since the grooves 81 and 82 are formed in an arc shape in a side view, the inverted portion 80 including the grooves 81 and 82 is Even when the apex moves in the thickness direction, stress concentration at the apex can be alleviated.

The threshold value of the external force applied to the head portion 10 toward the back side is, for example, the upper limit of the appropriate brushing pressure.

As shown in FIG. 10, the angle θ at which the reversing portion 80 is inclined with respect to a plane parallel to the long axis direction and the width direction is preferably 5 degrees or more and 11 degrees or less, and preferably 7 degrees or more and 11 degrees. It is more preferable that the temperature is less than 30%. If the inclination angle θ is less than 5 degrees, the reversing portion 80 may jump and deform without buckling, making it difficult to detect the overbrushing state. If the above-mentioned inclination angle θ exceeds 11 degrees, the reversing portion 80 may jump and buckle due to overbrushing pressure, making it difficult to reverse, or the reversing portion 80 may jump and buckle when reversed. It may break and become non-reversible.

The thickness of the inverted portion 80 is preferably 1 mm or more and 2 mm or less, excluding the groove portions 81 and 82. If the thickness of the reversible portion 80 is less than 1 mm, it may deform but not buckle, making it difficult to detect overbrushing. If the thickness of the reversible part 80 exceeds 2 mm, the reversible part 80 will jump and buckle due to overbrushing pressure, making it difficult to reverse, or the reversible part 80 will jump and buckle and break when it is reversed. reversibility may be lost.

The width of the reversing portion 80 is preferably 1.5 mm or more. If the width of the reversing portion 80 is less than 1.5 mm, it may easily bend in the width direction.
If the maximum thickness of the inverted part 80 is T (mm) and the maximum thickness of the deformed part 70 is t (mm), by specifying the value expressed as T/t, it is possible to prevent excessive brushing load from being applied. In this case, it becomes possible to control the ease with which the inverting section 80 inverts and its timing (threshold value). The value expressed by T/t is preferably 0.05 or more and 0.35 or less, more preferably 0.10 or more and 0.35 or less. If the value expressed by T/t is less than 0.05, the inversion part 80 also deforms following the bending of the deformation part 70 (elastic deformation part 90), but does not jump and buckle, so overbrushing occurs. The condition may be difficult to detect. If the value expressed by T/t exceeds 0.35, the reversing part 80 will jump and buckle due to overbrushing pressure, making it difficult to reverse, or it will jump and buckle and break when it is reversed. Therefore, there is a possibility that the reversibility of the reversing section 80 is lost.

As shown in FIG. 9, if the maximum width of the inversion part 80 is L (mm) and the maximum width of the deformation part 70 is W (mm), by defining the value expressed by L/W, for example, It becomes possible to control the ease with which the reversing section 80 reverses and its timing (threshold value) when an excessive brushing load is applied. The value expressed by L/W is preferably 0.05 or more and 0.35 or less, more preferably 0.10 or more and 0.35 or less. If the value expressed by L/W is less than 0.05, the inversion part 80 also deforms following the bending of the deformation part 70 (elastic deformation part 90), but it is difficult to jump and buckle, resulting in an overbrushing state. It may be difficult to detect that When the value expressed by L/W exceeds 0.35, the reversing portion 80 becomes difficult to deform and reverse due to the bending of the handle body 2 that occurs during normal brushing. Therefore, the reversible part 80 may jump and buckle due to overbrushing pressure, making it difficult to reverse, or the reversible part 80 may jump and buckle and break when it is reversed, and the reversibility of the reversible part 80 may be lost. . That is, by setting T/t and L/W within the above ranges, the bending strength of the reversing part 80 becomes flexible at a constant rate with respect to the elastically deforming part 90, and the bending of the elastically deforming part 90, which is responsible for the handle skeleton, becomes flexible. In contrast, it becomes possible to operate the reversing unit 80 with a slight delay. Therefore, even when an excessive brushing load is applied, it is possible to control the ease with which the reversing section 80 is reversed and the timing (threshold value) that triggers the reversing section 80 to reverse.

The length of the reversing portion 80 in the major axis direction 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 distal end of the reversing portion 80 is the position of the distal end of the through hole 73. The position of the rear end of the reversing portion 80 is the position of the rear end of the through hole 73. If the length of the reversible part 80 in the long axis direction is less than 15 mm, the reversible part 80 will jump and buckle under normal brushing pressure, making it difficult to reverse, and the length necessary for the jump buckling to occur. Deformation may not occur. If the length of the reversible section 80 in the long axis direction exceeds 30 mm, the displacement required to jump and buckle becomes very large, resulting in a significant decrease in usability, and the deformation behavior of the reversible section 80 is elastic deformation. There is a possibility that the behavior will be similar to that of section 90.

The reversing portion 80 is located between the outer contour of the flocked surface side 11 and the outer contour of the back side of the elastically deformable portion 90 when viewed from the side. More specifically, the position of the inverted part 80 in the thickness direction is set at a position that does not protrude from the thickness of the elastically deformable part 90 in a side view so that the inverted part 80 does not form the outermost part of the toothbrush. For example, it is possible to prevent the reversing section 80 from coming into contact with the user during use. Specifically, it is preferable that the elastically deformable portion 90 be located closer to the back side than the position where the thickness of the elastically deformable portion 90 becomes half. If the position in the thickness direction of the inverted part 80 is on the back side of the position where the thickness of the deformed part 70 is half, when the inverted part 80 is inverted and enters the second state, the apex of the inverted part 80 It is possible to reduce the possibility that the elastically deformable portion 90 protrudes from the front surface of the elastically deformable portion 90 and comes into contact with the user's fingers. In addition, by arranging the inverted part 80 on the back side of the position where the thickness of the elastic deformation part 90 is half, the back side is compressed more than the front side when the inverted part 80 is bent, so for example , the energy that triggers the reversal is likely to accumulate, and the strain energy can be efficiently transferred to the reversing section 80.

The bending elastic modulus of the hard resin constituting the inverted portion 80 is preferably 1500 MPa or more and 3500 MPa or less, more preferably 2000 MPa or more and 3500 MPa or less. If the bending elastic modulus of the hard resin is less than 1500 MPa, the inverted portion 80 will deform but will not jump and buckle, and it may be difficult to detect the overbrushing state. If the bending elastic modulus of the hard resin exceeds 3500 MPa, the reversing part 80 will jump and buckle due to overbrushing pressure, making it difficult to reverse, or the reversing part 80 will jump and buckle and break when it is reversed. There is a possibility that the reversibility of the portion 80 may be lost. Furthermore, by using a material with a specified bending elastic modulus, vibrations associated with jump buckling occur intensively in a short period of time and become sharp and large. As a result, the user is more likely to sense overbrushing.

The movement distance of the apex of the convex shape in the thickness direction when the reversing portion 80 jumps and buckles is preferably 0.2 mm or more and 5.0 mm or less. If the moving distance of the apex in the thickness direction is less than 0.2 mm, the vibration when jumping and buckling becomes small, and it may be difficult to detect the overbrushing state. If the moving distance of the apex in the thickness direction exceeds 5.0 mm, the reversing part 80 may jump and buckle due to overbrushing pressure, making it difficult to reverse, or when the reversing part 80 jumps and buckles and is reversed. There is a possibility that it will break and the reversibility of the reversing section 80 will be lost. If the movement distance of the reversing portion 80 is within the above range when jump buckling occurs, the vibrations generated by jump buckling occur intensively in a short period of time and become sharp and large. As a result, the user is more likely to sense that he or she is overbrushing.

The thickness of the hard part 90H in the elastically deformable part 90 is preferably 2.0 mm or less, and the width is preferably larger than the thickness. If the thickness of the hard portion 90H is 2.0 mm or less, the hard portion 90H will be in a plane stress state, and therefore the hard portion 90H will be less likely to generate internal stress. As a result, it becomes difficult to break even when deformed, and it becomes possible to sufficiently store the energy required for reversing the reversing portion 80. Moreover, as a result, the anisotropy of the deflection behavior of the elastically deformable portion 90 can be made clear, and the elastic deformation portion 90 can be made less likely to twist.

In addition, in the toothbrush 1 of this embodiment, since the inversion part 80 and the elastic deformation part 90 are arranged with a gap in the width direction, it is easier to deform the deformation part 70 toward the front side and the back side, and the deformation part 70 can be made longer. A state of plane stress can be achieved with almost no deformation in the axial and width directions. That is, in the toothbrush 1 of this embodiment, the directions in which the reversing portion 80 and the elastically deforming portion 90 deform are in the thickness direction spaced apart from each other in the width direction, and are not located on the same plane. In other words, the path through which the elastic deformation portion 90 deforms due to an external force in the thickness direction and the path through which the inversion portion 80 deforms due to an external force in the thickness direction are provided so as not to interfere with each other. Therefore, in the toothbrush 1 of the present embodiment, the elastic deformation part 90 and the reversing part 80 are less subject to restrictions on each other and can be deformed, so that the energy required for reversing the reversing part 80 can be stored more sufficiently. , stress is generated intensively in the reversal portion 80 (particularly in the groove portions 81 and 82), and sharp jump buckling occurs.

In particular, in the toothbrush 1 of this embodiment, the pair of hard parts 90 in the elastically deformable part 90 are arranged at the same position in the thickness direction, and a part of the inverted part 80 with respect to the hard part 90H is in the first state. Since they overlap in the width direction, for example, even when an external force in the width direction is applied to the head portion 10, twisting around the axis extending in the longitudinal direction is difficult to occur. Therefore, in the toothbrush 1 of this embodiment, the deformable portion 70 becomes difficult to deform in the width direction, and the bending strength can be increased.

As shown in FIG. 9, in a cross section perpendicular to the long axis direction, the cross-sectional area of the space of the depressions 71 and 72 is calculated from the maximum cross-sectional area of the deformable portion 70 (from the maximum cross-sectional area of the deformable portion 70 to the pair of elastically deformable portions 90). The space occupancy rate of the recesses 71 and 72, expressed as the ratio of the cross-sectional area of the recess 71 and the cross-sectional area excluding the cross-sectional area of the reversing part 80, is preferably 35% or more and 60% or less. Here, the maximum cross-sectional area of the deformable portion 70 is defined as the maximum cross-sectional area of the deformable portion 70 that virtually connects the outermost front side of the pair of elastic deformable portions 90 in a cross section perpendicular to the long axis direction of the deformable portion 70 shown in FIG. This is the area of a figure formed by virtually connecting the outermost contours of the elastically deformable portion 90 on the back side.

If the occupancy is less than 35%, the occupancy of the elastically deformable portions 90 and the inversion portions 80 becomes large, and the bending strength toward the back side in the thickness direction increases during brushing. In this case, it may be difficult to maintain an appropriate brushing pressure, and it may be difficult to suppress overbrushing. If the above-mentioned occupancy exceeds 60%, the occupancy of the elastic deformation portion 90 and the reversal portion 80 becomes small, and the bending strength in the width direction during brushing becomes small. In this case, when brushing, the deflection becomes large in response to an external force in the width direction, and it may become difficult to accurately brush the tooth row one tooth at a time.

[Example]
Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples, and can be implemented with appropriate changes without departing from the gist thereof.

(Examples 1 to 4, Comparative Examples 1 to 4)
Samples of Examples 1 to 4 and Comparative Examples 1 to 4 were produced according to the specifications shown in Table 1 below.
In Examples 1 and 2 and Comparative Examples 1 and 2, toothbrushes (corresponding to the toothbrush shown in the first embodiment) that do not have a through hole in a deformed part and an inverted part were used as samples. In Examples 3 to 4 and Comparative Example 3, toothbrushes (corresponding to the toothbrush shown in the second embodiment) having a through hole in a deformed part and an inverted part were used as samples. In Comparative Example 4, a sample was a "Clinica Advantage 3-row Normal" toothbrush manufactured by Lion Corporation that did not have a deformed part.

Furthermore, in Examples 1 to 3 and Comparative Example 2, toothbrushes with knurling provided on the front side and back side (front and back) of the deformed portion were used as samples. For Example 4, a toothbrush was used as a sample in which knurling was provided on both sides (left and right) in the width direction in addition to the front and back sides (front and back) of the deformed portion.

[Evaluation method]
For Examples 1 to 4 and Comparative Examples 1 to 4, ``I feel that excessive brushing load is alleviated,'' ``I feel that I can thoroughly brush the target area (anisotropy),'' and ``I feel that the inverted part jumps and buckles.'' Each item was evaluated for its ease of use.

[Test method]
A panel of experts (5 people) brushed with each sample and found results such as ``I feel that the excessive brushing load is alleviated by bending (I feel like I can maintain an appropriate brushing load)'' and ``I feel that I can thoroughly brush the target area.'''' and ``easiness of buckling of the reversible part when excessive brushing load is applied'' were evaluated in 5 grades in actual use, and evaluated using the average score. The average value of the scores was rounded off to the second decimal place and expressed to the first decimal place.
[Rating]
5 points: I feel it very much, 4 points: I feel it a little, 3 points: I don't know, 2 points: I don't feel it much, 1 point: I don't feel it at all [Evaluation] ◎+ (Extremely Good): 4.7 to 5.0 , ◎(Very Good): 4.3 to less than 4.7, ○(Good): 4.0 to less than 4.3, △(Not Bad): 3.0 to less than 4.0, △-(Not Good ): 2.5 to less than 3.0, × (Bad): less than 2.5 points

As shown in [Table 1], an uneven structure part (knurling part) is provided on the front side and the back side of the deformed part, and the occupancy rate of the cross-sectional area of the hard part in the deformed part is 35% or less. In Sample 4, there was a feeling of ``relieving excessive brushing load'' and ``a feeling of being able to thoroughly brush the target area,'' and in Examples 3 and 4, which had an inverted part, ``the inverted part jumps and buckles easily.'' Good evaluations were obtained for all items.

On the other hand, the sample of Comparative Example 2, which has an uneven structure on the front side and back side of the deformed part, but in which the cross-sectional area occupancy of the hard part in the deformed part exceeds 35%, is subject to "excessive brushing". Neither "feeling that the load is being relieved" nor "feeling that the target area can be thoroughly polished" received favorable evaluations. In addition, although the cross-sectional area occupancy of the hard part in the deformed part is 35% or less, the sample of Comparative Example 1, which does not have an uneven structure on the front and back sides of the deformed part, was also found to be subject to "excessive brushing load." Neither ``feeling that the skin is being relieved'' and ``feeling that the target area can be thoroughly polished'' received favorable evaluations. In addition, the sample of Comparative Example 4, which does not have deformed parts or uneven structure parts, also received good evaluations for both ``feeling that excessive brushing load is being alleviated'' and ``feeling that the target area can be thoroughly polished.'' There wasn't. Furthermore, compared to the sample of Example 3, the sample of Comparative Example 3, which does not have an uneven structure in the deformed part, did not receive a good evaluation for "the feeling of being able to thoroughly polish the target area."

In addition, as shown in [Table 1], Examples 2 to 4 in which the ratio of the depth of the recess to the convex part in the knurling part to the maximum thickness of the deformed part is in the range of 2% or more and 20% or less. The sample obtained a better evaluation in terms of ``feeling that the target area can be thoroughly polished'' than Example 1, in which the ratio was outside the range of 2% or more and 20% or less. In addition, the sample of Example 4, which has an uneven structure on both sides in the width direction in addition to the front and back sides of the deformed part, was found to be able to "relieve excessive brushing load" compared to the samples of Examples 1 to 3. The feeling of being able to do something has improved.

Although 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 such examples. The various shapes and combinations of the constituent members shown in the above example are merely examples, and can be variously changed based on design requirements and the like without departing from the gist of the present invention.

For example, in the above embodiment, the deformable portion 70 is provided with the knurling portions 101 to 104, but the structure is not limited to this. For example, the knurling portions 103 and 104 on both sides in the width direction are not provided, and A configuration may be adopted in which only the knurling portions 101 and 102 are provided on the back side.

Further, in the above embodiment, the deforming section 70 has the elastic deforming section 90 and the reversing section 80, but the present invention is not limited to this configuration, and a configuration in which the elastic deforming section 90 and the reversing section 80 are not provided is also possible. There may be.

Further, in the above embodiment, a configuration in which a portion of the depressions 71 and 72 penetrate in the thickness direction by the through hole K is illustrated, but the configuration is not limited to this configuration, and a configuration in which only one of the front side or the back side is open. It may be.

The present invention can be applied to toothbrushes.

DESCRIPTION OF SYMBOLS 1... Toothbrush, 2... Handle body, 10... Head part, 11... Flocked surface, 20... Neck part (first area), 30... Grip part (second area), 70... Deformed part, 71, 72... Hollow ( 80... Reversed part, 81, 82... Groove part, 90... Elastic deformation part, 90H... Hard part (core part), H... Hard part, 90E... Covering part 101 to 104... Knurling part (uneven structure part), 111, 113...Concave portion, 112, 114...Convex portion, P1...First region, P2...Second region, E, 31E, 32E...Soft portion, S...Gap

Claims (10)

A head portion provided on the distal end side in the longitudinal direction and having a flocked surface, a gripping portion disposed on the rear end side of the head portion, and a neck portion disposed between the flocking surface and the gripping portion. have,
The head portion and the neck portion are at least partially formed of hard resin,
a deformable part disposed in the grip part and deformed by an external force in a first direction perpendicular to the flocking surface;
a first region that is disposed on the distal end side of the deformable portion and is not deformed by an external force in the first direction;
a second region that is disposed on the rear end side of the deformable portion and is not deformed by an external force in the first direction;
The grip part is formed of the hard resin at least in part in a cross section perpendicular to the long axis direction from the tip of the grip part to the second region in the long axis direction,
The deformable part has a hard part made of the hard resin that connects the first region and the second region, and a soft part made of a soft resin and covers at least a part of the hard part,
The occupancy rate of the cross-sectional area of the hard portion with respect to the cross-sectional area of the closed space surrounded by the outer contour of the deformable portion or the extension of the outer contour in the cross section perpendicular to the long axis direction is determined in the long axis direction. is less than 35%,
The hard part has a flat plate shape whose length in the long axis direction and a second direction perpendicular to the first direction is larger than the length in the first direction, and the hard part The hard part is easily deformed on the back side opposite to the face and is in a plane stress state with almost no deformation in the width direction,
The length of the deformed portion in the major axis direction is 15 mm or more and 30 mm or less,
The bending strength of the deformable portion in the first direction is regulated to be smaller than the bending strength in the second direction ,
The soft portion has an uneven structure portion in which a concave portion and a convex portion extending in a direction intersecting the long axis direction are arranged adjacent to each other in the long axis direction,
The toothbrush is characterized in that the uneven structure portion is provided so as to be exposed on the flocked surface side in the first direction and on the back side opposite to the flocked surface side in the first direction. The depth of the concave portion relative to the convex portion is 2% or more and 20% or less of the maximum thickness of the deformed portion in the first direction.
The toothbrush according to claim 1. The deformed portion has a polygonal cross section perpendicular to the long axis direction,
The uneven structure portions are provided on both sides of the deformable portion in the second direction, respectively.
The toothbrush according to claim 1 or 2. The outermost edge of the deformable portion in the second direction is located closer to the back side than the center position of the deformable portion in the first direction.
The toothbrush according to claim 3. The deformable portion branches in the second direction via a through hole that penetrates in the first direction and extends in the longitudinal direction,
Each of the branched deformable parts includes a core part in which the hard part is branched through the through hole and connects the first region and the second region, and a core part in which the soft part is branched through the through hole and connects the first region and the second region. and a covering part that covers the periphery of the core part,
The toothbrush according to any one of claims 1 to 4. The hard part has an inverted part that is spaced apart from the core part, penetrates the through hole in the longitudinal direction, and connects the first region and the second region,
The reversing portion jumps, buckles, and reverses when the external force in the first direction exceeds a threshold value.
The toothbrush according to claim 5. The thickness of the hard part is 0.5 mm or more and 2.0 mm or less,
The toothbrush according to any one of claims 1 to 6. The center of the hard part in the first direction is located closer to the back side than the center position of the deformable part in the first direction.
The toothbrush according to claim 7. The length of the deformable portion in the second direction is 8 mm or more and 20 mm or less,
A toothbrush according to any one of claims 1 to 8 . The occupancy rate of the cross-sectional area of the hard portion with respect to the cross-sectional area of the closed space surrounded by the outer contour of the deformable portion or the extension of the outer contour in the cross section perpendicular to the long axis direction is determined in the long axis direction. is 3% or more and 32% or less,
A toothbrush according to any one of claims 1 to 9.

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