toothbrush

Abstract

To provide a toothbrush which has high versatility and allows a user to recognize a proper brushing pressure.SOLUTION: A toothbrush has: a head part provided on a tip side in a long axis direction and has an implantation surface; a grip part arranged on a rear end side of the head part; and a neck part arranged between the implantation surface and the grip part, wherein a sensing part which senses that external force in a first direction orthogonal to the implantation surface exceeds a threshold is provided on a rear end side than the implantation surface. The toothbrush comprises: an inversion part for connecting a first region on a tip side than the sensing part and a second region on the rear end side, and snap buckling and inverting, following to displacement of the head part to a back surface side caused by the external force greater than the threshold; and an elastic deformation part arranged at an interval from the inversion part, connecting the first region and the second region, and elastically deforming to at least a degree of the external force in which the inversion part snap buckles and inverts. The inversion part is positioned between an external shape contour on the implantation surface side in the elastic deformation part and an external shape contour on the back surface side, in side view from a direction which is orthogonal to a long axis direction and the first direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a toothbrush. This application claims priority based on Japanese Patent Application No. 2018-246145 filed in Japan on December 27, 2018, and incorporates its content herein.

Background Art

[0002] While the proportion of people having 20 teeth at the age of 80 is about 50%, the proportion of dental caries (root caries) in the elderly is increasing. Root caries is dental caries of dentin exposed due to gingival recession. However, since dentin has a higher proportion of organic components than enamel, the progress of dental caries is rapid. One of the causes of the above gingival recession is overbrushing, which is brushing with a brushing pressure greater than the appropriate value.

[0003] Since the brushing pressure is defined by load / implantation area, to reduce the brushing pressure, it can be achieved by at least one of reducing the load and increasing the implantation area. Regarding the reduction of the load, there are commercially available toothbrushes with specifications designed to brush with the force when the neck part is straightened after being tilted upward above the implantation surface in advance during brushing so that the neck part flexes during brushing, soft-specification toothbrushes using thinner filaments, and toothbrushes with specifications where it is difficult for force to be applied to the implantation part by arranging the center of gravity of the gripping part closer to the rear end of the handle. Regarding the increase of the implantation area, there are commercially available toothbrushes with a wide head width. However, in these specifications, although it is possible to reduce the brushing pressure, it is difficult to make all users recognize the appropriate brushing pressure at the same level and control the brushing pressure.

[0004] Also, regarding the appropriate brushing method, although receiving guidance at a dental clinic, it has been found that there are not a few users who are aware of overbrushing but have not been able to improve because it is difficult to handle on their own due to reasons such as not clearly understanding how to adjust the force.

[0005] Therefore, as a means of making the user aware of the appropriate brushing pressure, for example, the toothbrush disclosed in Patent Document 1 can be cited. The toothbrush disclosed in Patent Document 1 has a two-beam structure, with a rear beam positioned between the head portion and the gripping portion, to which compressive stress is applied during normal use, and a face-side beam to which tensile stress is applied.

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

[0007] [Patent Document 1] Special Publication No. 6-504937 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] However, the toothbrush disclosed in Patent Document 1 mentioned above has a limit to the amount of deformation of the rear beam, as the rear beam deforms in a direction that approaches the face-side beam when excessive brushing load is applied, and therefore cannot be said to be sufficiently versatile.

[0009] This invention was made with the above points in mind, and aims to provide a toothbrush that can recognize the appropriate brushing pressure with high versatility. [Means for solving the problem]

[0010] According to a first aspect of the present invention, the invention comprises a head portion having a bristle surface provided on the tip side in the longitudinal direction, a gripping portion disposed on the rear end side of the head portion, and a neck portion disposed between the bristle surface and the gripping portion, wherein a sensing portion is provided on the rear end side of the bristle surface to sense when an external force in a first direction perpendicular to the bristle surface exceeds a threshold, the sensing portion connects a first region on the tip side of the sensing portion to the sensing portion and a second region on the rear end side of the sensing portion, and the external force exceeding the threshold in the first direction A toothbrush is provided, comprising: a reversing portion that jumps, buckles, and reverses as the head portion is displaced toward the back side, which is the side opposite to the bristle surface; and an elastic deformation portion that is positioned with a gap from the reversing portion, connects the first region and the second region, and elastically deforms at least until the external force causes the reversing portion to jump, buckle, and reverse, wherein the reversing portion is located between the outer contour of the bristle surface side and the outer contour of the back side of the elastic deformation portion in a side view taken in a direction perpendicular to the long axis and the first direction.

[0011] Furthermore, in the toothbrush according to one aspect of the present invention described above, the elastic deformation portion and the reversal portion are arranged with a gap between them in a second direction perpendicular to the first direction and the long axis direction, respectively.

[0012] Furthermore, in the toothbrush according to one aspect of the present invention described above, the elastic deformation portion and the reversal portion are arranged with a gap between them in a second direction perpendicular to the first direction and the long axis direction, respectively.

[0013] Furthermore, in a toothbrush according to one aspect of the present invention described above, the reversal portion is characterized in that it is convex on the back side when the external force in the first direction is less than or equal to a threshold, and reverses to a convex shape on the bristle surface side when the external force in the first direction exceeds a threshold.

[0014] Furthermore, in a toothbrush according to one aspect of the present invention described above, the reversing portion is characterized in that, when the external force in the first direction is below a threshold, it inclins toward the bristle surface side from the apex of the convex shape toward the end in the longitudinal axis direction, and the angle at which the reversing portion inclins with respect to a plane parallel to the first direction and the longitudinal axis direction, respectively, is 5 degrees or more and 11 degrees or less.

[0015] Furthermore, in a toothbrush according to one aspect of the present invention described above, the reversing portion is characterized in that the region including the apex of the convex shape has grooves extending in the second direction on at least one of the bristle-planted surface side and the back side.

[0016] Furthermore, in a toothbrush according to one aspect of the present invention described above, the distance traveled by the apex of the convex shape in the first direction when the reversing portion jumps, buckles, and reverses is 0.2 mm or more and 5.0 mm or less.

[0017] Furthermore, in a toothbrush according to one aspect of the present invention described above, the reversing portion is provided in the center of the second direction, and the elastically deformable portion is provided on both sides of the reversing portion in the second direction.

[0018] Furthermore, in a toothbrush according to one aspect of the present invention described above, if the maximum thickness of the reversing portion in the first direction is T and the maximum thickness of the elastically deformable portion in the first direction is t, the value expressed as T / t is 0.05 or more and 0.35 or less.

[0019] Furthermore, in a toothbrush according to one aspect of the present invention described above, if the maximum width of the reversing portion in the second direction is L and the maximum width of the elastically deformable portion in the second direction is W, the value expressed as L / W is 0.05 or more and 0.35 or less.

[0020] Furthermore, in a toothbrush according to one aspect of the present invention described above, the reversible portion is formed of a hard resin, and a part of the elastically deformable portion is formed of a resin with a different hardness from the hard resin.

[0021] Further, in the toothbrush according to one aspect of the present invention, the flexural modulus of the hard resin is 1500 MPa or more and 3500 MPa or less.

[0022] Further, in the toothbrush according to one aspect of the present invention, a part of the elastic deformation portion is formed of a soft resin.

[0023] Further, in the toothbrush according to one aspect of the present invention, the gap is a through-hole extending in the first direction.

Advantages of the Invention

[0024] In the present invention, it is possible to provide a toothbrush that can recognize an appropriate brushing pressure with high versatility.

Brief Description of the Drawings

[0025] [Figure 1] It is a view showing an embodiment of the present invention and is a front view of the toothbrush 1. [Figure 2] It is a cross-sectional view of the toothbrush 1 cut along a plane including the center in the width direction. [Figure 3] It is a cross-sectional view of the sensing portion 70 cut along a plane parallel to the thickness direction and the width direction. [Figure 4] It is a cross-sectional view of the sensing portion 70 cut along a plane parallel to the thickness direction and the major axis direction. [Figure 5] It is a partial front view of the periphery of the sensing portion 70 in the hard portion 70H. [Figure 6] It is a partial side view of the periphery of the sensing portion 70 in the hard portion 70H. [Figure 7] It is a cross-sectional view of the sensing portion 70 cut along a plane parallel to the thickness direction and the major axis direction for explaining that the reversing portion has reversed.

Embodiments for Carrying Out the Invention

[0026] Hereinafter, embodiments of the toothbrush of the present invention will be described with reference to Figures 1 to 7. The following embodiments represent one aspect of the present invention and do not limit it; they can be modified at will within the scope of the technical idea of ​​the present invention. Furthermore, in the following drawings, the scale and number of components differ from the actual structure for clarity. In the following description, the direction perpendicular to the flocked surface in a side view is referred to as the up and down direction, the flocked surface side as the upper side, and the back side opposite the flocked surface as the lower side. Note that the terms "up and down direction," "upper side," and "lower side" are merely descriptive terms and do not limit the actual positional relationships or directions in the present invention.

[0027] Figure 1 is a front view of toothbrush 1. Figure 2 is a cross-sectional view of toothbrush 1 cut by a plane containing the center in the width direction (vertical direction in Figure 1).

[0028] The toothbrush 1 of this embodiment comprises a head portion 10 positioned on the front end side in the longitudinal direction (hereinafter simply referred to as the front end side) and having a bundle of bristles (not shown) implanted on it, a neck portion 20 extending from the rear end side in the longitudinal direction of the head portion 10 (hereinafter simply referred to as the rear end side), a sensing portion 70 extending from the rear end side of the neck portion 20, and a gripping portion 30 extending from the rear end side of the sensing portion 70 (hereinafter the head portion 10, neck portion 20, gripping portion 30 and sensing portion 70 together are referred to as the handle body 2).

[0029] 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 part H constitutes at least a portion of each of the head part 10, neck part 20, gripping part 30, and sensing part 70. The soft part E constitutes a portion of each of the gripping part 30 and sensing part 70 (details will be described later).

[0030] [Head section 10] The head portion 10 has a bristle surface 11 on one side in the thickness direction (the direction perpendicular to the plane of the paper in Figure 1). Hereafter, the side with the bristle surface 11 in the thickness direction will be referred to as the front side in the front direction, the side opposite the bristle surface will be referred to as the back side, and the direction perpendicular to the thickness direction and the long axis will be referred to as the width direction (or, as appropriate, the side direction). Multiple bristle holes 12 are formed in the bristle surface 11. Bundles of bristles (not shown) are implanted in the bristle holes 12.

[0031] The width of the head portion 10, that is, the length in the width direction parallel to the bristle surface 11 on the front side and perpendicular to the long axis direction (hereinafter simply referred to as width), is not particularly limited, but is preferably 7 mm or more and 13 mm or less. If it is above the lower limit, a sufficient area for implanting the bristle bundles can be secured, and if it is below the upper limit, the operability in the oral cavity can be further improved.

[0032] The length of the head portion 10 in the longitudinal direction (hereinafter simply referred to as length) is not particularly limited, but is preferably 10 mm or more and 33 mm or less. If the length of the head portion 10 is greater than or equal to the lower limit, sufficient area for implanting the hair bundle can be secured, and if it is less than or equal to the upper limit, the operability in the oral cavity can be further improved. In this embodiment, the boundary in the longitudinal direction between the neck portion 20 and the head portion 10 is the position where the width of the neck portion 20 is at its minimum, moving from the neck portion 20 towards the head portion 10.

[0033] The length of the head portion 10 in the thickness direction (hereinafter simply referred to as thickness) can be determined considering the material, etc., and is preferably 2.0 mm or more and 4.0 mm or less. If the thickness of the head portion 10 is greater than or equal to the lower limit above, 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 upper limit above, the ability to reach the back of the molars can be improved, and the maneuverability in the oral cavity can be further improved.

[0034] A hair bundle is made up of multiple hairs bundled together. The length from the hair implantation surface 11 to the tip of the hair bundle (hair length) can be determined considering the desired hair stiffness and other factors, and is, for example, 6 to 13 mm. All hair bundles may have the same hair length, or they may be different from one another.

[0035] The thickness of the hair bundle (hair bundle diameter) can be determined by considering the desired stiffness and other properties of the hair bundle, and is typically set at 1-3 mm. All hair bundles may have the same diameter, or they may differ from one another.

[0036] Examples of the hairs used to make up the hair bundle include tapered hairs, which gradually decrease in diameter towards the tip and have a sharpened tip, and straight hairs, which have a nearly constant diameter from the hair implantation surface 11 towards the tip. Examples of straight hairs include those with a tip that is a plane approximately parallel to the hair implantation surface 11, and those with a tip that is rounded into a hemispherical shape.

[0037] Examples of materials for the bristles include polyamides such as 6-12 nylon (6-12NY) and 6-10 nylon (6-10NY), polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), and polybutylene naphthalate (PBN), polyolefins such as polypropylene (PP), and elastomer resins such as polyolefin-based elastomers and styrene-based elastomers. These resin materials can be used individually or in combination of two or more. Furthermore, examples of bristles include polyester bristles having a multi-core structure with a core and at least one sheath layer provided on the outside of the core.

[0038] The cross-sectional shape of the bristles is not particularly limited and may be circular, elliptical, polygonal, star-shaped, three-leaf clover-shaped, four-leaf clover-shaped, etc. The cross-sectional shapes of all bristles may be the same or different.

[0039] The thickness of the bristles can be determined considering the material and other factors. For example, if the cross-section is circular, the thickness is typically 6-9 mil (1 mil = 1 / 1000 inch = 0.025 mm). Furthermore, multiple bristles of different thicknesses may be used in arbitrary combinations, taking into consideration factors such as feel, brushing sensation, cleaning effect, and durability.

[0040] [Neck section 20] The length of the neck portion 20 is preferably 40 mm or more and 70 mm or less for ease of operation. The width of the neck portion 20 is formed such that, for example, it gradually increases from the position where it is at its minimum value toward the rear end. In this embodiment, the neck portion 20 is formed such that its width gradually increases from the position where it is at its minimum value toward the rear end. Furthermore, the thickness of the neck portion 20 is formed such that it gradually increases from the position where it is at its minimum value toward the rear end.

[0041] The width and thickness of the neck portion 20 at its minimum position are preferably 3.0 mm or more and 4.5 mm or less. If the width and thickness of the neck portion 20 at its minimum position are greater than or equal to the lower limit, the strength of the neck portion 20 can be further increased, and if they are less than or equal to the upper limit, the lips can be closed more easily, the ability to reach the molars can be improved, and the maneuverability in the oral cavity can be further improved. The width and thickness of the neck portion 20, which is formed to gradually increase from the minimum position toward the posterior end, can be appropriately determined considering the material and other factors.

[0042] In a side view, the front side of the neck portion 20 is inclined toward the front as it approaches the rear end. In a side view, the rear side of the neck portion 20 is inclined toward the rear as it approaches the rear end. In a front view, the neck portion 20 is inclined in a direction in which the distance from the center in the width direction increases toward the rear end.

[0043] In this embodiment, the boundary between the neck portion 20 and the sensing portion 70 is the position of the tip of the neck portion 20 where the elastic deformation portion 90, described later, is provided. Here, the width expands in an arc shape from the neck portion 20 toward the gripping portion 30 in both front and side views, and the boundary between the neck portion 20 and the sensing portion 70 coincides with the position in the long axis direction where the position of the center of curvature of the arc changes. More specifically, in the front view shown in Figure 1, the boundary between the neck portion 20 and the sensing portion 70 coincides with the position in the long axis direction where the center of curvature changes from the outside of the arc shape toward the center in the width direction. Also, in the side view shown in Figure 2, the boundary between the neck portion 20 and the sensing portion 70 coincides with the position in the long axis direction where the center of curvature changes from the outside of the arc shape toward the center in the thickness direction.

[0044] [Gripping part 30] The gripping portion 30 is arranged along the long axis. As shown in Figure 1, the widthwise length of the gripping portion 30 gradually narrows from the boundary with the sensing portion 70 toward the rear end, and then extends for a substantially constant length. As shown in Figure 2, the thicknesswise length of the gripping portion 30 gradually narrows from the boundary with the sensing portion 70 toward the rear end, and then extends for a substantially constant length.

[0045] In this embodiment, the boundary between the sensing portion 70 and the gripping portion 30 is the position of the tip of the gripping portion side 30 where the elastic deformation portion 90, described later, is provided. Here, the width decreases in an arc-shaped contour from the sensing portion 70 toward the gripping portion side 30 in both front and side views, and the boundary between the sensing portion 70 and the gripping portion 30 coincides with the position in the long axis direction where the position of the center of curvature of the arc changes. More specifically, in the front view shown in Figure 1, the boundary between the sensing portion 70 and the gripping portion 30 coincides with the position in the long axis direction where the center of curvature changes from the center in the width direction to the outside of the arc-shaped contour. Also, in the side view shown in Figure 2, the boundary between the sensing portion 70 and the gripping portion 30 coincides with the position in the long axis direction where the center of curvature changes from the center in the thickness direction to the outside of the arc-shaped contour.

[0046] The position in the longitudinal axis direction where the length of the gripping portion 30 in the width direction gradually narrows as it moves from the boundary with the sensing portion 70 toward the rear end, and then becomes approximately constant in length, is the same as the position in the longitudinal axis direction where the length of the gripping portion 30 in the thickness direction gradually narrows as it moves from the boundary with the sensing portion 70 toward the rear end, and then becomes approximately constant in length.

[0047] The gripping portion 30 has a soft portion 31E in the center of its width direction on the front side. The soft portion 31E constitutes a part of the soft portion E. In a front view, the soft portion 31E gradually narrows from the boundary with the sensing portion 70 toward the rear end, and then extends for a substantially constant length. In a front view, the side edge of the soft portion 31E and the side edge of the gripping portion 30 on the width direction are formed at a substantially constant distance.

[0048] The gripping portion 30 has a hard portion 30H. The hard portion 30H constitutes a part of the hard portion H. The hard portion 30H has a recess 31H on its front side into which a part of the soft portion 31E is embedded. In a front view, the recess 31H gradually narrows from the boundary with the sensing portion 70 toward the rear end, and then extends for a substantially constant length.

[0049] A portion of the soft portion 31E protrudes beyond the hard portion 30H that is exposed on the front side. The rest of the soft portion 31E is approximately flush with the hard portion 30H that is exposed on the front side.

[0050] The gripping portion 30 has a soft portion 32E in the center of its width on the rear side (see Figures 1 and 2). The soft portion 32E constitutes a part of the soft portion E. In a front view, the soft portion 32E has an outer contour that is substantially the same as that of the soft portion 31E. That is, the soft portion 32E gradually narrows from the boundary with the sensing portion 70 toward the rear end, and then extends for a substantially constant length. In a rear view, the side edge of the soft portion 32E and the side edge of the gripping portion 30 on the width side are formed at a substantially constant distance.

[0051] The rigid portion 30H has a recess 32H (see Figure 2) on its rear side in which a portion of the flexible portion 32E is embedded. The recess 32H gradually narrows from the boundary with the sensing portion 70 toward the rear end when viewed from the rear, and then extends for a substantially constant length.

[0052] A portion of the soft part 32E protrudes beyond the hard part 30H exposed on the back side. The other soft parts 32E are nearly flush with the hard part 30H exposed on the front side.

[0053] Since a soft part 31E is provided on the front side of the gripping part 30 and a soft part 32E is provided on the back side, the gripping performance when gripping the gripping part 30 is improved.

[0054] [Sensing section 70] The sensing unit 70 detects when an external force in a first direction perpendicular to the bristled surface 11 exceeds a threshold. As shown in Figure 1, the sensing unit 70 has a reversing section 80 and an elastically deformable section 90 that connect the neck section 20 located towards the tip of the sensing unit 70 and the gripping section 30 located towards the rear end of the sensing unit 70.

[0055] Figure 3 is a cross-sectional view of the sensing unit 70 cut in a plane parallel to the thickness direction and width direction. Figure 4 is a cross-sectional view of the sensing unit 70 cut in a plane parallel to the thickness direction and long axis direction. As shown in Figure 3, the elastic deformation portion 90 is provided on both sides of the inversion portion 80 in the width direction, with a gap S between them. The gap S is formed by a through hole K that penetrates in the thickness direction. As shown in Figure 1, the through hole K is formed in a rectangular shape in plan view, extending in the longitudinal direction.

[0056] By providing a gap S, the reversing section 80 can be reversed without interfering with the surrounding structure (making it easier to reverse). Also, since the deformation of the reversing section 80 does not follow the deformation of the elastic deformation section (because there is no interference), the functional roles (described later) of the reversing section 80 and the elastic deformation section 90 can be made independent. This increases the degree of design freedom to obtain the following effects, for example. For example, it is possible to clearly generate vibrations and sounds when the reversing section 80 reverses, as described later. Also, for example, it becomes possible to increase the rebound force up to the threshold in proportion to the amount of displacement, and in particular, it is possible to maintain the proportional relationship even near the threshold (the rate of increase in rebound force does not slow down). As a result, in the region up to the amount of displacement that reaches the upper limit of pressure, the pressure expected by the user is directly reflected in the rebound force, so the brushing load can be appropriately controlled. If the rate of increase in rebound force is set to gradually slow down near the threshold, the user may unintentionally continue brushing at a pressure near the upper limit. Furthermore, if the gap S is also connected to both sides in the thickness direction of the reversing section 80, the above effects will be further improved. By widening the gap S in the thickness direction, the vector of the load applied to the brush part (bristles) during brushing, the direction in which the gap opens, and the direction in which the reversing part 80 and the elastically deformable part 90 deform become parallel (see Figure 7), making it easy to link the generation of vibration and sound due to reversal with the brushing load. Furthermore, if the gap S is extended through the front and back sides by a through hole K, for example, the range of motion of the elastically deformable part 90, which is responsible for the bending function of the toothbrush skeleton in response to the load during brushing, can be further expanded (the tensile behavior on the front and the compressive behavior on the back associated with bending are less likely to be hindered). If there is no through hole K between the elastically deformable part 90 and the reversing part 80, the range of motion of the elastically deformable part 90 becomes narrower. In this case, it is conceivable that the reversing part 80 may not be given an opportunity to reverse within an appropriate load range, and that the reversing part 80 may reverse before reaching an appropriate load range, or it may not reverse even within an appropriate load range. In contrast, by providing a through hole K between the elastic deformation section 90 and the reversal section 80, the "threshold" at which the reversal section 80 reverses (described later) can be controlled within a finer range.The gap S does not necessarily have to penetrate in the thickness direction; for example, it may be formed by a closed cavity extending in the longitudinal direction within the elastically deformable portion 90. Alternatively, it may be formed by a recess (described later) opening on the front or back side.

[0057] Each elastic deformation section 90 has a hard section 90H and a soft section 90E. As shown in Figure 1, the hard section 90H and the soft section 90E connect the rear end of the neck section 20 and the front end of the gripping section 30. As shown in Figures 3 and 4, a recess 71 opening to the front and a recess 72 opening to the back are provided between the pair of elastic deformation sections 90. The bottoms of both ends in the width direction of the recesses 71 and 72 are connected to through holes K. A reversal section 80 is exposed at the bottom of the center in the width direction of the recesses 71 and 72. By providing the recesses 71 and 72, for example, the range of motion of the elastic deformation section that is responsible for the bending function of the toothbrush skeleton in response to the load during brushing can be further expanded, and the anisotropy of bending in the thickness direction can be improved. Note that the recesses between the pair of elastic deformation sections 90 do not have to penetrate in the thickness direction, and may open only on one side 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 may be formed in the width direction with the cavity in the center.

[0058] The pair of elastically deformable portions 90 are connected in the width direction at the ends of the long axis direction of the soft portion 90E on both the front and back sides. The soft portion 90E of the pair of elastically deformable portions 90 is provided around the oval-shaped recesses 71 and 72 when viewed from the front. The rear end of the soft portion 90E is connected to the soft portion 31E of the gripping portion 30.

[0059] Because the soft portion 90E is connected in the width direction at both the front and rear ends of the elastic deformation portion 90, stress is less likely to concentrate at the end of the hinge structure even when it is repeatedly reversed, making it less likely to break. In addition, because the soft portion 90E is connected in the width direction at both the front and rear ends of the elastic deformation portion 90, the anisotropy in the sensing portion 70 is increased, so for example, the pair of elastic deformation portions 90 can bend in the thickness direction without twisting in response to brushing movements. Furthermore, because the soft portion 90E is connected in the width direction, the amount of heat contained in the soft resin (elastomer) during injection molding increases, which improves the adhesion between the neck portion 20 and the sensing portion 70 (neck portion 20 and elastic deformation portion 90).

[0060] Figure 5 is a partial front view of the area around the hard part 70H in the sensing unit 70. Figure 6 is a partial side view of the area around the hard part 70H in the sensing unit 70. As shown in Figure 5, the hard portion 70H is formed in a rectangular shape in plan view, connecting the hard portion 20H which is the neck portion 20 and the hard portion 30H of the gripping portion 30 in the longitudinal direction.

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

[0062] If the curved surfaces 73H to 76H are absent, stress may concentrate at the boundary between the leading edge of the hard section 70H and the hard section 20H, and at the boundary between the trailing edge of the hard section 70H and the hard section 30H. In contrast, the presence of the curved surfaces 73H to 76H alleviates the concentrated stress. Furthermore, the presence of the curved surfaces 73H to 76H allows both the leading edge and trailing edge of the elastic deformation section 90 and the reversal section 80 to deform flexibly (allowing for more precise sensing of the degree of deformation of the elastic deformation section 90 that triggers the reversal).

[0063] The rigid portion 70H has through holes 73 provided on both sides of the reversal portion 80 in the width direction. The through holes 73 extend in the longitudinal direction. The length of the through holes 73 in the longitudinal direction is such that the leading end of the through hole 73 is spaced apart from the rigid portion 20H, and the rear end of the through hole 73 is spaced apart from the rigid portion 30H. As shown in Figure 3, of the through holes 73, a soft portion 90E is provided closer to the rigid portion 90H in the width direction, and a through hole K is formed closer to the reversal portion 80 in the width direction.

[0064] In the rigid section 70H, the rigid section 90H is arranged on both sides in the width direction with the reversal section 80 at its center via through holes 73. Therefore, even if a load is applied and the elastic deformation section 90 deforms, the shape of the reversal section 80 can be maintained. When the rigid section H, which constitutes the entire length of the toothbrush 1, bends, the reversal section 80 of the sensing section 70 reverses in an attempt to release the accumulated strain energy. For example, if the rigid section 70H is connected to the neck section 20 and gripping section 30 by only the reversal section 80, it will not be able to accumulate energy and will reverse immediately. If the reversal section 80 is injection molded integrally with the first region A1, the second region A2, the neck section 20 and gripping section 30, and the rigid section 70H, the accumulated strain energy can be efficiently transmitted to the reversal section.

[0065] The hard portion 90H is formed on the widthwise side of the hard portion 70H, beyond the through hole 73. As shown in Figure 3, the hard portion 90H has a roughly rectangular cross-sectional shape. The hard portion 90H is embedded in the soft portion 90E. Because the hard portion 90H is embedded in the soft portion 90E, the stress applied to the hard portion 90H can be reduced from a strength standpoint. Furthermore, from the perspective of the degree of deflection of the toothbrush 1 under load, the elastic behavior of the elastic deformation portion 90 can be controlled. In addition, the deflection anisotropy in the sensing portion 70 is increased, making it possible to deflect the elastic deformation portion 90 without twisting in the thickness direction in response to brushing movements, for example.

[0066] As an example of the material for the rigid part H, a resin with a flexural modulus (JIS 7171) of 1500 MPa or more and 3500 MPa or less can be used, such as polyacetal resin (POM). A flexural modulus of 2000 MPa or more and 3500 MPa or less is more preferable for the rigid part H. By using a material with a high modulus of elasticity (e.g., POM), even if the shape is made thin or narrow, when an excessive load is applied, jump buckling occurs and vibration is generated. Furthermore, by using a material with a high modulus of elasticity, it is possible to quickly return to the initial state (the state in which the deflection of the elastically deformed part 90 is released) after jump buckling occurs.

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

[0068] As shown in Figure 5, the reversal section 80 extends in the longitudinal direction in a front view and connects a first region A1 on the tip side of the through hole 73 in the hard section 70H to a second region A2 on the rear end side of the through hole 73. In the first stable state shown in Figure 4 (hereinafter referred to as the first state), where no external force is applied to the head section 10 on the rear side (or an external force below a predetermined threshold, described later, is applied), the reversal section 80 is formed in a roughly V-shape in a side view, gradually sloping toward the rear side from both ends in the longitudinal direction toward the center. That is, in the first state, the reversal section 80 is formed in a convex shape toward the rear side with the center in the longitudinal direction being the apex.

[0069] For example, when an external force is applied to the head portion 10 on the back side while the gripping portion 30 is gripping, if the magnitude of the external force is below a predetermined threshold, the elastic deformation portion 90 and the reversal portion 80 will elastically deform according to the magnitude of the external force.

[0070] When the magnitude of the external force exceeds a predetermined threshold, the elastic deformation part 90 bends and undergoes elastic deformation in accordance with the magnitude of the external force exceeding the threshold. On the other hand, when the magnitude of the external force exceeds a predetermined threshold, the inversion part 80 jumps onto the neck part 20 when it deforms, as shown by the dashed line in Figure 7, buckles and inverts, and enters a second stable state (hereinafter referred to as the second state). In the second state, the inversion part 80 inverts in a direction that is gradually inclined toward the front side as it approaches the center, resulting in a roughly inverted V shape in side view. In the second state, the inversion part 80 is formed in a convex shape toward the front side, with the center in the direction of the long axis being the apex.

[0071] In other words, when the magnitude of the external force exceeds a predetermined threshold, the elastic deformation part 90 elastically deforms, ensuring the deflection strength in the sensing part 70, and the reversal part 80 jumps from the first state, buckles, and reverses to the second state. Furthermore, since a through hole K is provided between the reversal part 80 and the elastic deformation part 90, the reversal part 80 and the elastic deformation part 90 can deform independently of each other, making it easier to reverse the reversal part 80. That is, when a brushing load is applied, because a through hole K is provided, the deformation behavior of each part is not hindered, and first only the elastic member 90 bends, followed by the reversal part 80. Note that the space between the reversal part 80 and the elastic deformation part 90 does not necessarily have to be a through hole; a gap S is sufficient.

[0072] The vibrations caused when the reversing part 80 jumps, buckles, and reverses allow the user holding the gripping part 30 to sense that the external force applied to the back of the head part 10 has exceeded a threshold, resulting in an overbrushing condition.

[0073] The reversal section 80 has a groove 81 in the center of the long axis direction on the front side, i.e., in the region including the vertex of the convex shape. The reversal section 80 has a groove 82 in the center of the long axis direction on the back side, i.e., in the region including the vertex of the convex shape. The grooves 81 and 82 extend in the width direction. The groove 81 is formed in an arc shape in a side view with the arc center positioned on the front side. The groove 82 is formed in an arc shape in a side view with the arc center positioned on the back side. If the reversal section 80 is not provided with grooves 81 and 82, stress will be uniformly generated throughout the reversal section 80, making it less likely for jump buckling to occur. On the other hand, if the reversal section 80 is provided with grooves 81 and 82, stress will be concentrated in the grooves 81 and 82, making jump buckling more likely.

[0074] When viewed from the side, the radius of the arc-shaped grooves 81 and 82 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, the reversing section 80 may not reverse. If the radius of the grooves 81 and 82 exceeds 2 mm, the vibration of the reversing section 80 during reversal becomes small, making it difficult to detect that an overbrushing state is occurring.

[0075] Regarding the depth of the grooves 81 and 82, it is preferable that groove 81 is deeper than groove 82. When groove 82 is deeper than groove 81, the reversing section 80 becomes less likely to reverse even when the magnitude of the external force exceeds a predetermined threshold. Also, when groove 81 is deeper than groove 82, it becomes possible to guide the reversing section 80 to jump more to the front side and buckle more easily. Furthermore, the configuration does not have to include both grooves 81 and 82; it may also be a configuration in which groove 82 is not provided and only groove 81 is provided.

[0076] Since the inversion section 80 has grooves 81 and 82 in the region containing the vertex of the convex shape, the region containing the vertex of the convex shape is thinner than other regions. Therefore, the strain energy accumulated by the deformation of the inversion section 80 due to an external force exceeding a threshold can be instantaneously released starting from the grooves 81 and 82, causing the inversion section 80 to invert. Furthermore, by adjusting the position of the grooves 81 and 82 in the thickness direction, it is possible to adjust the position at which the inversion section 80 inverts from the first state to the second state.

[0077] Furthermore, since the grooves 81 and 82 are formed in an arc shape when viewed from the side, stress concentration at the apex can be mitigated even when the apex of the inverted portion 80, which includes the grooves 81 and 82, moves in the thickness direction, compared to, for example, a case where it is formed in a V shape by two intersecting planes.

[0078] The threshold value for external force applied to the back side of the head portion 10 is, for example, the upper limit of the appropriate brushing pressure.

[0079] As shown in Figure 4, the angle θ at which the reversal section 80 is inclined with respect to a plane parallel to the long axis and width direction is preferably 5 degrees or more and 11 degrees or less, and more preferably 7 degrees or more and 11 degrees or less. If the inclination angle θ is less than 5 degrees, the reversal section 80 may deform without jumping and buckling, making it difficult to detect the overbrushing condition. If the inclination angle θ exceeds 11 degrees, the overbrushing pressure may make it difficult for the reversal section 80 to jump and buckle and reverse, or the reversal section 80 may break when it jumps and buckles and reverses, resulting in a loss of reversibility.

[0080] The thickness of the reversal section 80 is preferably 1 mm or more and 2 mm or less, excluding the grooves 81 and 82. If the thickness of the reversal section 80 is less than 1 mm, it may deform but not buckle by jumping, making it difficult to detect that it is in an overbrushing state. If the thickness of the reversal section 80 exceeds 2 mm, it may become difficult for the reversal section 80 to buckle and reverse due to the overbrushing pressure, or it may break when it buckles and reverses, resulting in a loss of reversibility.

[0081] If the maximum thickness of the reversal section 80 is T (mm) and the maximum thickness of the sensing section 70 is t (mm), then by defining a value expressed as T / t, it becomes possible to control the ease with which the reversal section 80 reverses when an excessive brushing load is applied, and the timing (threshold). The value expressed as T / t is preferably 0.05 or more and 0.35 or less, and more preferably 0.10 or more and 0.35 or less. If the value expressed as T / t is less than 0.05, the reversal section 80 will deform in accordance with the bending of the sensing section 70 (elastic deformation section 90), but it will not jump and buckle, making it difficult to detect an overbrushing condition. If the value expressed as T / t exceeds 0.35, the overbrushing pressure may make it difficult for the reversal section 80 to jump and buckle and reverse, or it may break when it jumps and buckles and reverses, resulting in the loss of reversibility of the reversal section 80.

[0082] In other words, by setting T / t within the aforementioned range, the deflection strength of the reversing section 80 becomes flexible at a constant rate relative to the elastic deformation section 90, making it possible to operate the reversing section 80 with a slight delay in response to the deflection of the elastic deformation section 90 that forms the handle frame. This makes it possible to control how easily the reversing section 80 reverses, and the timing (threshold) at which the reversing section 80 reverses, even when an excessive brushing load is applied.

[0083] As shown in Figure 3, if the maximum width of the reversing section 80 is L (mm) and the maximum width of the sensing section 70 is W (mm), then by defining a value expressed as L / W, it becomes possible to control, for example, how easily the reversing section 80 reverses when an excessive brushing load is applied, and the timing (threshold). The value expressed as L / W is preferably 0.05 or more and 0.35 or less, and more preferably 0.10 or more and 0.35 or less. If the value expressed as L / W is less than 0.05, the reversing section 80 will deform in accordance with the bending of the sensing section 70 (elastic deformation section 90), but it will not buckle easily, and it may become difficult to detect that an over-brushing state is occurring. If the value expressed as L / W exceeds 0.35, the reversing section 80 will not deform or reverse easily with the bending of the handle body 2 that occurs within the range of normal brushing. Therefore, under excessive brushing pressure, the reversal section 80 may jump and buckle, making it difficult to reverse, or it may break when it jumps, buckles, and reverses, resulting in the loss of reversibility of the reversal section 80. In other words, by keeping L / W within the aforementioned range, the deflection strength of the reversal section 80 becomes flexible at a constant rate relative to the elastic deformation section 90, making it possible to operate the reversal section 80 with a slight delay in response to the deflection of the elastic deformation section 90 that forms the handle frame. Therefore, even when excessive brushing load is applied, it becomes possible to control how easily the reversal section 80 reverses, and the timing (threshold) at which the reversal section 80 triggers the reversal.

[0084] The length of the reversal section 80 in the longitudinal direction is 15 mm or more and 30 mm or less. Preferably, it is 15 mm or more and 25 mm or less, more preferably 15 mm or more and 20 mm or less. The position of the front end of the reversal section 80 is the position of the front end of the through hole 73. The position of the rear end of the reversal section 80 is the position of the rear end of the through hole 73. If the length of the reversal section 80 in the longitudinal direction is less than 15 mm, it becomes difficult for the reversal section 80 to jump and buckle and reverse under normal brushing pressure, and it may not be possible to generate the deformation necessary for jump buckling to occur. If the length of the reversal section 80 in the longitudinal direction exceeds 30 mm, the displacement required for jump buckling becomes very large, which greatly reduces usability, and the deformation behavior of the reversal section 80 may be similar to that of the elastic deformation section 90.

[0085] The reversal portion 80 is located between the outer contour of the bristle surface side 11 and the outer contour of the back side of the elastic deformation portion 90 in a side view. More specifically, the position of the reversal portion 80 in the thickness direction is such that the reversal portion 80 does not form the outermost outline of the toothbrush, and does not extend beyond the thickness of the elastic deformation portion 90 in a side view, thereby preventing the reversal portion from coming into contact with the user during use. Specifically, it is preferable that the position of the reversal portion 80 is on the back side of the position where the thickness of the elastic deformation portion 90 is halved. When the position of the reversal portion 80 in the thickness direction is on the back side of the position where the thickness of the sensing portion 70 is halved, the possibility that the apex of the reversal portion 80 will protrude from the front surface of the elastic deformation portion 90 and come into contact with the user's fingers when the reversal portion 80 reverses to the second state can be reduced. Furthermore, by positioning the inversion section 80 on the back side of the point where the thickness of the elastically deformable section 90 is halved, the back side is compressed more than the front side when the inversion section 80 bends. This makes it easier for energy that triggers inversion to accumulate, and allows strain energy to be efficiently transferred to the inversion section 80.

[0086] The flexural modulus of the rigid resin constituting the reversal section 80 is preferably 1500 MPa or more and 3500 MPa or less, and more preferably 2000 MPa or more and 3500 MPa or less. If the flexural modulus of the rigid resin is less than 1500 MPa, the reversal section 80 will deform but will not buckle by jumping, making it difficult to sense that an overbrushing condition has occurred. If the flexural modulus of the rigid resin exceeds 3500 MPa, the overbrushing pressure may make it difficult for the reversal section 80 to buckle by jumping and reverse, or it may break when it buckles by jumping and reverses, resulting in the loss of reversibility of the reversal section 80. Furthermore, by using a material with a specified flexural modulus, the vibrations associated with jumping buckling occur intensively in a short period of time and become sharp (large). As a result, it becomes easier for the user to sense that overbrushing has occurred.

[0087] When the reversal section 80 jumps and buckles, the distance traveled in the thickness direction at the apex of the convex shape is preferably 0.2 mm or more and 5.0 mm or less. If the distance traveled in the thickness direction at the apex is less than 0.2 mm, the vibration when it jumps and buckles will be small, and it may be difficult to sense that it is in an overbrushing state. If the distance traveled in the thickness direction at the apex exceeds 5.0 mm, it may become difficult for the reversal section 80 to jump and buckle and reverse due to the overbrushing pressure, or it may break when it jumps and buckles and reverses, resulting in the loss of reversibility of the reversal section 80. If the distance traveled by the reversal section 80 when it jumps and buckles is within the above range, the vibration generated by the jumping and buckling will occur intensively in a short time and will be sharp (large). As a result, it will be easier for the user to sense that it is overbrushing.

[0088] The thickness of the rigid portion 90H in the elastically deformable portion 90 is preferably 2.0 mm or less, and the width is preferably greater than the thickness. When the thickness of the rigid portion 90H is 2.0 mm or less, a plane stress state is achieved, making it difficult for the rigid portion 90H to generate internal stress. As a result, it becomes less likely to fracture even when deformed, and sufficient energy required for the reversal of the reversal portion 80 can be accumulated.

[0089] Furthermore, in the toothbrush 1 of this embodiment, since the reversal section 80 and the elastic deformation section 90 are arranged with a gap in the width direction, the sensing section 70 can be more easily deformed on the front and back sides, and a plane stress state can be achieved in which it hardly deforms in the longitudinal axis direction and width direction. In other words, in the toothbrush 1 of this embodiment, the direction in which the reversal section 80 and the elastic deformation section 90 deform is the thickness direction, spaced apart from each other in the width direction, and they are not configured to lie on the same plane. In other words, the path through which the elastic deformation section 90 deforms due to an external force in the thickness direction and the path through which the reversal section 80 deforms due to an external force in the thickness direction are provided to be non-interfering. Therefore, in the toothbrush 1 of this embodiment, the elastic deformation section 90 and the reversal section 80 are less constrained by each other and can deform, so it is possible to store even more energy required for the reversal of the reversal section 80, stress is concentrated in the reversal section 80 (especially the grooves 81 and 82), and sensitive jump-to-buckling occurs.

[0090] Furthermore, in the toothbrush 1 of this embodiment, since wobbling in the width direction is suppressed, the deflection in the thickness direction caused by brushing can be transmitted to the reversing section 80 without loss. In addition, by arranging the reversing section 80 and the elastic deformation section 90 in the width direction, it becomes possible to separate the deflection of the elastic deformation section 90 and the reversal of the reversing section 80 and stagger their timing. If the elastic deformation section 90 and the reversing section 80 were arranged in the thickness direction, the deflection of the elastic deformation section 90 and the reversal of the reversing section 80 might interfere with each other's roles.

[0091] As described above, in the toothbrush 1 of this embodiment, the elastic deformation part 90, which elastically deforms up to an external force that causes the reversal part 80 to jump over, buckle, and reverse, and the reversal part 80, which jumps over, buckles, and reverses due to an external force on the back side that exceeds a threshold, are arranged with a gap in the width direction. Therefore, when an external force exceeding a predetermined threshold is applied to the back side of the head part 10, the vibration caused when the reversal part 80 jumps over, buckles, and reverses allows the user holding the grip part 30 to sense that the external force applied to the back side of the head part 10 has exceeded a threshold and is in an over-brushing state.

[0092] [Examples] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples and can be implemented with appropriate modifications without departing from its essence.

[0093] (Examples 1-9, Comparative Examples 1-4) In accordance with the specifications shown in [Table 1], toothbrushes with different bending moduli and inclination angles θ of the reversal section 80 were used as samples for Examples 1 to 9 and Comparative Examples 1 to 4. For Comparative Example 1, a toothbrush without a sensing section (reversal section and elastic deformation section) (Lion Corporation, Clinica Advantage toothbrush) was used as a sample. For Comparative Example 2, a toothbrush in which the elastic deformation section and the reversal section are aligned in the thickness direction was used as a sample compared to the sample in Example 2. For Comparative Example 3, a toothbrush in which the elastic deformation section and the reversal section are joined together and there is no gap between the elastic deformation section and the reversal section was used as a sample compared to the sample in Example 2.

[0094] [Evaluation Method] (1) Occurrence of vibration in the reversal section [Test Method] A panel of five experts brushed each sample and evaluated whether they felt vibration when the reversing part reversed, using a 5-point scale in actual use. The average score was used for evaluation as follows. The average score was rounded to one decimal place by two decimal places. [Rating] 5 points: Very much feels, 4 points: feels, 3 points: feels somewhat, 2 points: doesn't feel much, 1 point: doesn't feel at all [Rating] ◎: 4.6-5 points, ○: 4.1-4.5 points, △: 3.1-4.0 points, ×: 3.0 points or less (2) Reversible inversion of the inversion section [Test Method] A panel of five experts used each sample for one week and evaluated whether or not inversion occurred after one week. [Evaluation] ○: Reversal present, ×: Reversal not present (× if even one line is not reversed) (3) Vibration occurs at approximately 200-250g [Test Method] For each sample, the gripping part 30 was fixed from the boundary between the sensing part 70 and the gripping part 30 so that the bristled surface of the head was horizontal. A test was performed in which a load was applied to the bristled surface of the head toward the back side in the thickness direction. The load was measured when the center of the bristled surface of the head was pressed with the indenter of a push-pull gauge (DS2-50N, manufactured by IMADA Corporation) and the reversing part was reversed. Measurements were taken three times, and the average value was used as the measured value. The average value was rounded to the first decimal place. [Rating] ◎: 200~250g, ○: 251~300g, △: 150~199g, ×: 149g or less, or 301g or more, -: No vibration For the evaluation results, ◎, ○, and △ were considered passing grades (OK), while × was considered a failing grade (NG). The evaluation of the measured load is based on the principle that by generating vibrations during reversal in the range of, for example, 230-250g, the load when a user actually brushes their teeth with toothbrush 1 will be the recommended value of 200g.

[0095] As shown in [Table 1], in the samples of Examples 1 to 9, in which the flexural modulus was 1500 MPa or more and 3500 MPa or less, and the inclination angle θ of the reversal section was 5 degrees or more and 11 degrees or less, it was confirmed that vibration associated with the reversal of the reversal section, reversible reversal of the reversal section, and vibration at a load of approximately 200 to 250 g were sufficiently exhibited.

[0096] On the other hand, even when the flexural modulus was in the range of 1500 MPa to 3500 MPa, the sample of Comparative Example 1, which did not have a sensing part (reversal part and elastic deformation part), did not reverse itself, and therefore, no vibration associated with the reversal of the reversal part and no vibration at a load of approximately 200-250 g occurred. Furthermore, even when the elastic modulus was in the range of 1500 MPa to 3500 MPa, the inclination angle θ of the reversal part was in the range of 5 degrees to 11 degrees, and the values ​​expressed as T / t and L / W were in the range of 0.05 to 0.35, neither the sample of Comparative Example 2, in which the elastic deformation part and the reversal part were aligned in the thickness direction, nor the sample of Comparative Example 3, which had a sensing part consisting only of a reversal part without an elastic deformation part, exhibited vibration associated with the reversal of the reversal part or vibration at a load of approximately 200-250 g.

[0097] Furthermore, even when the elastic modulus was in the range of 1500 MPa to 3500 MPa, the inclination angle θ of the reversal part was in the range of 5 degrees to 11 degrees, and the values ​​expressed as T / t and L / W were in the range of 0.05 to 0.35, in the case of the sample of Comparative Example 4, which had a sensing part in which the elastic deformation part and the reversal part were joined without any gap between them, vibration occurred due to the reversal of the reversal part, but no vibration occurred at a load of approximately 200 to 250 g.

[0098] [Table 1]

[0099] Preferred embodiments of the present invention have been described above with reference to the attached drawings, but it goes without saying that the present invention is not limited to these examples. The shapes and combinations of the constituent members shown in the above examples are merely examples, and can be modified in various ways based on design requirements, etc., without departing from the spirit of the present invention.

[0100] For example, in the above embodiment, a configuration in which the sensing unit 70 is provided between the neck unit 20 and the gripping unit 30 was illustrated, but the configuration is not limited to this. The sensing unit 70 may be provided on the neck unit 20 or on the gripping unit 30.

[0101] Furthermore, although the above embodiment illustrates a configuration in which one reversal unit 80 is provided in the sensing unit 70, the configuration is not limited to this, and a configuration in which multiple reversal units 80 are provided may also be used. For example, when two reversing sections 80 are provided, one is formed with a thickness, inclination angle θ, etc. that reverses at an appropriate upper limit of the brushing load, and the other is formed with a thickness, inclination angle θ, etc. that reverses at an appropriate lower limit of the brushing load. This configuration makes it easy to define both the upper and lower limits of the brushing load.

[0102] Furthermore, although the above embodiment illustrates a configuration in which the reversing unit 80 reverses in the thickness direction, it is not limited to this configuration. For example, it may reverse in the width direction or in an oblique direction that is perpendicular to the long axis direction and intersects with the width and thickness directions. By adopting a configuration in which the reversing unit 80 reverses in an oblique direction, it becomes possible to detect overbrushing when brushing using the rolling method. [Industrial applicability]

[0103] This invention can be applied to toothbrushes. [Explanation of Symbols]

[0104] 1...Toothbrush, 2...Handle, 10...Head, 11...Bristle surface, 20...Neck, 30...Gripping part, 70...Sensing part, 80...Reversing part, 81, 82...Groove part, E, 31E, 32E...Soft part, H...Hard part, K...Through hole, S...Gap

Claims

1. It has a head portion having a bristle surface provided on the tip side in the longitudinal direction, a gripping portion positioned at the rear end of the head portion, and a neck portion positioned between the bristle surface and the gripping portion. A sensing unit is provided at the rear end of the aforementioned bristled surface to detect when an external force in a first direction perpendicular to the bristled surface exceeds a threshold value. The sensing unit is A reversing section is provided that connects a first region on the tip side of the sensing section and a second region on the rear end side of the sensing section, and in response to the displacement of the head portion toward the back side, which is opposite to the flocked surface in the first direction, due to the external force exceeding the threshold, the reversing section jumps, buckles, and reverses, The reversal portion is positioned with a gap between it and the first region and the second region, and comprises an elastically deformable portion that elastically deforms at least until the external force causes the reversal portion to jump, buckle, and reverse, The inversion portion is located between the outer contour on the flocked surface side and the outer contour on the back side of the elastically deformable portion in a side view taken in a direction perpendicular to the long axis and the first direction, The reversing portion has grooves on the flocked surface side and the back side, respectively. A toothbrush characterized in that the groove on the bristle-planted surface is deeper than the groove on the back surface.

2. The toothbrush according to claim 1, characterized in that the path through which the elastic deformation portion deforms due to the external force in the first direction and the path through which the reversal portion deforms due to the external force in the first direction are provided in a non-interfering manner.

3. The elastic deformation portion and the reversal portion are arranged with a gap between them in a second direction that is perpendicular to the first direction and the long axis direction, respectively. The toothbrush according to claim 2.

4. The reversing portion is provided in the center of the second direction, The toothbrush according to claim 3, wherein the elastic deformation portion is provided on both sides of the reversal portion in the second direction.

5. The reversing portion is convex on the back side when the external force in the first direction is less than or equal to the threshold, and reverses to a convex shape on the flocked surface side when the external force in the first direction exceeds the threshold. The toothbrush according to any one of claims 1 to 4.

6. The inverting portion is inclined toward the flocked surface side as it moves from the apex of the convex shape toward the end in the longitudinal direction, when the external force in the first direction is less than or equal to the threshold, The angle at which the reversing portion is inclined with respect to a plane parallel to the first direction and the longitudinal axis is 5 degrees or more and 11 degrees or less. The toothbrush according to claim 5.

7. The inverted portion has the groove portion extending in a second direction perpendicular to the first direction and the long axis direction, respectively, in a region including the vertex of the convex shape. The toothbrush according to claim 5 or 6.

8. When the reversing portion jumps and buckles and reverses, the distance traveled by the vertex of the convex shape in the first direction is 0.2 mm or more and 5.0 mm or less. The toothbrush according to any one of claims 5 to 7.

9. The maximum thickness of the reversing portion in the first direction is T, If the maximum thickness of the elastically deformable portion in the first direction is t, The value expressed as T / t is between 0.05 and 0.

35. A toothbrush according to any one of claims 1 to 8.

10. The maximum width of the reversing portion in the second direction which is perpendicular to the first direction and the long axis direction, respectively, is L. If the maximum width of the elastically deformable portion in the second direction is W, The value expressed as L / W is between 0.05 and 0.

35. A toothbrush according to any one of claims 1 to 9.

11. The reversing portion is formed of a hard resin, A portion of the elastically deformable portion is formed of a resin with a different hardness than the hard resin. A toothbrush according to any one of claims 1 to 10.

12. The flexural modulus of the rigid resin is 1500 MPa or more and 3500 MPa or less. The toothbrush according to claim 11.

13. A portion of the elastically deformable portion is made of a soft resin. The toothbrush according to claim 11 or 12.

14. The gap is a through hole extending in the first direction. A toothbrush according to any one of claims 1 to 13.

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