Toothbrush

Abstract

Provided is a toothbrush capable of uniformly warming the entirety of a head part and efficiently heating gums without causing excessive heating of a heating element. The toothblush includes: a head part which has a brush part; a grip part which is positioned on the rear end side of the head part; a heat transfer body which is provided at least in the head part and which has a heat conductivity larger than that of the head part; and a heating element which is provided in contact with the heat transfer body and which generates heat by energization.

Description

toothbrush

[0001] This application claims priority from Japanese Patent Application No. 2023-123789, filed on July 28, 2023, the contents of which are incorporated herein by reference.

[0002] A technique for preventing periodontal disease by heating the gums is known. Patent Document 1 discloses a toothbrush with a heating element attached to the head. The toothbrush disclosed in Patent Document 1 describes how the head is heated to a desired temperature by the heat generated by the heating element, and when brushing teeth, the heated bristles or the tip of the head are brought into contact with the gums, transferring thermal energy to the gums and promoting blood circulation in the gums.

[0003] Japanese Patent Application Laid-Open No. 2001-137046

[0004] When heating the head of a toothbrush, it is necessary to heat it up to the desired temperature immediately after use, taking usability into consideration. Because the amount of power that can be installed in a toothbrush is limited, one possible measure to rapidly generate heat is to use a small heating element and concentrate the power there.

[0005] However, the resin used in the head has poor thermal conductivity, and when the head is heated with a small heating element, the heat generated by the heating element does not easily spread throughout the head, resulting in a localized heating range. As a result, the area heated to the target temperature is limited, resulting in the problem of not being able to heat the gums efficiently.

[0006] Furthermore, heating the entire head requires excessive heat from the heating element, which creates problems with power efficiency and safety. While it is conceivable to provide heating elements throughout the entire head, the amount of power that can be installed in a toothbrush is limited, which means that it takes time to heat up all of the heating elements installed throughout the head, resulting in usability issues.

[0007] The present invention has been made in consideration of the above points, and aims to provide a toothbrush that can heat the gums efficiently by evenly heating the entire head portion without causing the heating element to overheat.

[0008] The present invention has the following aspects. [1] A toothbrush comprising: a head portion having a brush part; a handle portion located at the rear end of the head portion; a heat transfer body provided at least in the head portion and having a higher thermal conductivity than the head portion; and a heating body provided in contact with the heat transfer body and generating heat when electricity is applied. [2] The toothbrush described in [1] above, in which the heat transfer body provided in the head portion is provided inside the head portion and is not exposed. [3] The toothbrush described in [1] above or [2] above, in which the toothbrush has a substrate on which the heating body is mounted, the brush part is provided on the bristle-implanted surface of the head portion, and the heat transfer body, the heating body, and the substrate are sequentially arranged in the head portion from the back side opposite the bristle-implanted surface toward the bristle-implanted surface in a first direction perpendicular to the bristle-implanted surface. [4] The toothbrush according to [3], wherein the brush section has bristle bundles planted in bristle planting holes formed in the bristle planting surface, and the distance between the surface of the heat transfer body closest to the bristle planting surface and the bottom of the bristle planting holes is longer than the distance between the rear surface of the heat transfer body and the rear surface of the head section. [5] The toothbrush according to [3], wherein the heating element is disposed in the head section, and in a front view from the side facing the bristle planting surface in the first direction, the area of ​​the heating element is 3% to 20% of the area of ​​the heat transfer body, and in the front view, the area of ​​the heat transfer body is 60% or more of the area of ​​the head section. [6] The toothbrush according to [4], wherein a plurality of bristle planting holes are provided in the bristle planting surface, and all of the bristle planting holes at least partially overlap with the heat transfer body in a front view from the side facing the bristle planting surface. [7] The toothbrush according to [4] or [6], wherein the minimum distance from the outermost periphery of the head to the heat transfer body in a front view from the side opposite the bristle surface is equal to or greater than the minimum distance from the outermost periphery of the head to the bristle holes. [8] The toothbrush according to any one of [3] to [7], wherein the heat transfer body contains any of copper, silver, and aluminum, and the dimension of the heat transfer body in the first direction is equal to or greater than 0.1 mm and equal to or less than 1.0 mm.[9] A toothbrush described in any one of [1] to [8], having a temperature detection unit that detects the temperature of the heating element, and a control unit that controls the amount of electricity supplied to the heating element based on the temperature detected by the temperature detection unit.

[0009] The present invention can provide a toothbrush that can heat the entire head portion uniformly and efficiently heat the gums without causing the heating element to generate excessive heat.

[0010] Fig. 2 is a diagram showing an embodiment of the present invention, and is a front view of a toothbrush. Fig. 3 is a front view of a head portion. Fig. 4 is a cross-sectional view taken along the line A-A in Fig. 2. Fig. 5 is a control block diagram relating to temperature control. Fig. 6 is a diagram showing the temperature distribution of a sample in Experimental Example 4. Fig. 7 is a diagram showing the temperature distribution of a sample in Experimental Example 7. Fig. 8 is a diagram showing a control method relating to temperature control.

[0011] An embodiment of the toothbrush of the present invention will be described below with reference to Figures 1 to 7. Note that the following embodiment shows one aspect of the present invention, does not limit the present invention, and can be modified as desired within the scope of the technical concept of the present invention. In addition, in the following drawings, the scale and number of each structure are different from the actual structure to make each component easier to understand.

[0012] 1 is a front view of a toothbrush 1. The toothbrush 1 includes a grip portion 2 that is held by a user and a brush body 3 that is detachably attached to the grip portion 2. The toothbrush 1 of this embodiment can be warmed by heating at least a portion of the brush body 3.

[0013] The grip portion 2 is, for example, cylindrical, and has a power switch 4 located on a portion of its outer periphery. A battery 5 serving as a power source is detachably housed inside the grip portion 2, making it replaceable. The detachable portion between the grip portion 2 and the brush body 3 is provided with a connector portion (not shown) for connecting a power supply line (not shown) inside the grip portion 2 to a circuit board 30 (described later) inside the brush body 3.

[0014] The brush body 3 has a connecting base 6, a neck 7, a head 10, a substrate 30, a heating element 40, and a heat transfer element 50. The connecting base 6, the neck 7, and the head 10 can be made of resin, such as polypropylene resin (PP), polyacetal resin (POM), polystyrene resin (PS), polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), acrylonitrile butadiene styrene resin (ABS), polyarylate resin, polycarbonate resin, and acrylonitrile styrene resin (AS).

[0015] The connecting base 6 is formed in a conical shape and is detachably attached to one end of the grip portion 2 in the longitudinal direction. The head portion 10 is formed in a substantially elliptical shape when viewed from the front from the side opposite the flocking surface 12 described below. The head portion 10 is disposed at the other end of the grip portion 2 in the longitudinal direction. The neck portion 7 is disposed between the connecting base 6 and the head portion 10. The neck portion 7 gradually becomes wider from the head portion 10 toward the connecting base 6 when viewed from the front. The boundary between the neck portion 7 and the head portion 10 in the longitudinal direction is the position where the width of the head portion 10 gradually narrows and then starts to widen when viewed from the front.

[0016] Fig. 2 is a front view of the head unit 10. Fig. 3 is a cross-sectional view taken along line A-A in Fig. 2. As shown in Fig. 3, the head unit 10 has a brush unit 11. The brush unit 11 is provided on a bristle-implanted surface 12 of the head unit 10.

[0017] In the following description, the longitudinal direction of the grip portion 2 will be simply referred to as the longitudinal direction, the direction perpendicular to the bristle-implanted surface 12 will be referred to as the thickness direction, and the direction parallel to the bristle-implanted surface 12 and perpendicular to the longitudinal direction of the grip portion 2 will be referred to as the width direction. The thickness direction corresponds to the first direction. In the thickness direction, the side of the bristle-implanted surface 12 will be referred to as the front side, and the side opposite the bristle-implanted surface 12 will be referred to as the back side, as appropriate. In the longitudinal direction, the side on which the brush body 3 is arranged will be referred to as the tip side, and the side on which the grip portion 2 is arranged will be referred to as the rear side.

[0018] The brush portion 11 has a plurality of bristle bundles 13. The bristle bundles 13 are implanted in bristle implantation holes 14 formed in the bristle implantation surface 12. A plurality of bristle implantation holes 14 are provided in the bristle implantation surface 12. The bristle implantation holes 14 are recesses recessed from the bristle implantation surface 12 toward the back side. The bristle bundles 13 are folded in half, with a flat wire sandwiched between them, and the flat wire is driven into the bristle implantation holes 14, thereby implanting the bristle bundles 13 in the bristle implantation surface 12. There are no particular limitations on the thickness of the head portion 10, but from the viewpoint of ease of insertion into the oral cavity, it is preferable that the thickness be, for example, 5 mm or less.

[0019] The substrate 30 is embedded inside the brush body 3 in a non-exposed state. As shown in FIG. 2, the substrate 30 is located at the center in the width direction and extends in the longitudinal direction. As shown in FIG. 3, the substrate 30 is arranged on the rear side of the tufting holes 14. FIG. 4 is a control block diagram related to temperature control. As shown in FIG. 4, the substrate 30 has a power supply line (not shown), a temperature detection unit 31, and a control unit 32. The control unit 32 may be provided inside the gripping unit 2 instead of the substrate 30.

[0020] The power supply line is connected to a connector provided on the grip portion 2 when the brush body 3 is attached to the grip portion 2. Power from the battery 5 can be supplied to the power supply line via the connector. Power may be supplied from the grip portion 2 to the brush body 3 wirelessly. The temperature detection unit 31 detects the temperature of the heating element 40. The temperature detection unit 31 outputs the detected temperature of the heating element 40 to the control unit 32. The control unit 32 controls the amount of power supplied to the heating element 40 in accordance with the temperature of the heating element 40 detected by the temperature detection unit 31 (details will be described later).

[0021] The heating element 40 is embedded inside the brush body 3 without being exposed. The heating element 40 is provided in contact with the heat transfer element 50. In this embodiment, the heating element 40 is provided in the head portion 10. The heating element 40 generates heat when electricity is applied. The heating element 40 is an electronic component that generates heat by itself due to electrical resistance. The heating element 40 includes a resistor that generates heat when current is applied, a protective film covering the resistor, and an electrode portion (all not shown). The heating element 40 can be a rigid chip resistor or a film heater. Among these, chip resistors are preferred because they offer a high degree of freedom in controlling resistance by changing the cross-sectional area and length. Chip resistors made of silver, silver / palladium, or ruthenium oxide are also preferred. The heating element 40 is mounted on the back side of the substrate 30. The heating element 40 mounted on the substrate 30 is connected to a power supply line and can be energized via the power supply line.

[0022] The heat transfer body 50 has a planar shape extending in a direction perpendicular to the thickness direction. The heat transfer body 50 is provided at least in the head portion 10. The heat transfer body 50 is embedded inside the brush body 3 in a non-exposed state. In this embodiment, the heat transfer body 50 is provided in the head portion 10. The heat transfer body 50 may be provided from the head portion 10 to the neck portion 7. If the heat transfer body 50 is also provided in the neck portion 7, the heating element 40 may be configured to be provided in the neck portion 7. The heat transfer body 50 is formed of a material having a higher thermal conductivity than the material forming the head portion 10. As an example, the heat transfer body 50 is formed of a metal. From the viewpoint of heat transfer, the metal forming the heat transfer body 50 preferably includes any of copper, silver, and aluminum.

[0023] When the metal constituting the heat transfer body 50 includes copper, silver, or aluminum, it not only has excellent thermal conductivity but also excellent processability, allowing it to be easily processed into a shape and size that matches the head portion 10. Furthermore, by processing the heat transfer body 50 thin, flexibility is maintained, so bending during use of the toothbrush is not hindered. Furthermore, copper, silver, and aluminum have excellent corrosion resistance and are less likely to corrode even in the oral cavity, which contains a lot of moisture. Of copper, silver, and aluminum, copper is preferred from the standpoint of high thermal conductivity and cost.

[0024] The heat transfer body 50 is provided in contact with the heating body 40. The heat transfer body 50 is heated by the heat generated by the heating body 40. The head unit 10 is heated via the heat transfer body 50 by the heat generated by the heating body 40. The heat transfer body 50 is arranged on the rear side of the substrate 30 and the heating body 40. In other words, the heat transfer body 50, the heating body 40, and the substrate 30 are arranged in this order on the head unit 10 from the rear side toward the tufting surface 12, at positions rearward of the tufting holes 14.

[0025] Although the drawings of this embodiment show an unexposed embodiment of the heat conductor, an exposed embodiment is also possible. The unexposed embodiment is preferable for the following reasons. When the heat conductor 50 is disposed on the head portion 10, considering the need to reduce heat loss and directly heat the target area, such as the gums, those skilled in the art (prior art) would consider exposing the heat conductor 50. To maintain a constant temperature in the head portion 10, the amount of current flowing through the heating element 40, which serves as the heat source, must be controlled according to the temperature of the head portion 10. Because the head portion 10 moves around the oral cavity during brushing, the temperature outside the head portion 10 changes discretely. Therefore, if the heat conductor 50 is exposed from the head portion 10 and immediately transfers heat to the outside of the head portion 10, the heating element 40 and the heat conductor 50 may instantaneously reach high temperatures as the heating element 40 responds to this temperature change. Furthermore, the heat conductor 50 has a higher thermal conductivity than the resin forming the head portion 10, making it easier to transfer heat to oral tissues, increasing the risk of burns in the oral cavity. Furthermore, the heat transfer body 50 becomes extremely hot in an instant, which increases the risk of deformation or deterioration of the resin that forms the head portion 10 .

[0026] In addition, the specific heat of the resin forming the head portion 10 is greater than that of the heat transfer body 50, making it difficult to heat up or cool down. For example, if the resin forming the head portion 10 is polypropylene, the specific heat is 1.93 J / (kg·K), and if the material of the heat transfer body 50 is copper, the specific heat is 0.385 J / (kg·K).

[0027] Therefore, in a more preferred embodiment, the heat transfer body 50 is embedded inside the brush body 3 in an unexposed state, thereby enhancing the heat retention effect, slowing down temperature changes in the head portion 10, and not only reducing the risk of deformation and deterioration of the resin that forms the head portion 10, but also making temperature control easier.

[0028] Furthermore, while the rear side of the head unit 10 is flat and the resin is uniformly distributed, the front side where the tufted surface 12 is located has a complex structure because the thickness varies depending on the presence or absence of the tufted holes 14. Therefore, by locating the heating element 40 and the heat transfer element 50 on the rear side of the substrate 30, the substrate 30 functions as a heat insulator, reducing the risk of the resin on the front side of the head unit 10 deforming due to heat.

[0029] Furthermore, because the gums have little sense of temperature, by arranging the heat transfer element 50, the heating element 40, and the substrate 30 in the head unit 10 in this order from the back side toward the implanted surface 12 as shown in Figure 3, the back side of the head unit 10 is heated preferentially, and when the head unit 10 is inserted into the oral cavity, the cheek side that comes into contact with the back side is also heated, thereby providing a sense of heat. Note that, in order to prevent the heat from the heat transfer element 50 and the heating element 40 from adversely affecting the implanted hole 14, it is preferable that the substrate 30 be a thick rigid substrate rather than a thin flexible substrate or film substrate.

[0030] As shown in FIG. 3 , the distance Ta between the surface of the heat transfer body 50 closest to the implanted surface 12 and the bottom surface 14a of the implanted holes 14 is preferably longer than the distance Tb between the rear surface of the heat transfer body 50 and the rear surface of the head portion 10. To minimize heat loss from the heat transfer body 50 to the oral cavity, it is preferable to position the heat transfer body 50 close to the implanted surface 12. However, as described above, positioning the heat transfer body 50 close to the implanted surface 12 increases the risk of thermal deformation of the resin on the front side due to changes in thickness depending on the presence or absence of implanted holes 14, and of cracks occurring in the head portion 10 due to a reduced thickness between the bottom surface 14a of the implanted holes 14 and the heat transfer body 50. Therefore, by making the distance Ta longer than the distance Tb, the above risks can be reduced and heat loss from the heat transfer body 50 to the oral cavity can be reduced. The distance Tb is preferably 1 mm or less.

[0031] When the heating element 40 is placed in the head portion 10, it is preferable that the area of ​​the heating element 40 is 3% or more and 20% or less of the area of ​​the heat transfer element 50 when viewed from the front, and it is preferable that the area of ​​the heat transfer element 50 is such that the lower limit is 60% or more and the upper limit is 100% or less of the area of ​​the head portion 10 when viewed from the front.

[0032] By placing the heating element 40 in the head portion 10, the head portion 10 can be heated to the desired temperature in a short time via the heat transfer element 50. Furthermore, the amount of heat transferred by conduction is proportional to the cross-sectional area perpendicular to the heat transfer direction. When the heating element 40 is placed in the neck portion 7, the neck portion 7 is narrower than the head portion 10, making it difficult for heat to be transferred from the neck portion 7 to the head portion 10. Additionally, heat dissipation occurs on the surface of the heat transfer element 50 while the heat is being transferred from the neck portion 7 to the head portion 10, increasing the temperature difference between the head portion 10 and the neck portion 7. Therefore, the neck portion 7 becomes too hot before the head portion 10 reaches the desired temperature, which can cause deformation or deterioration of the neck portion 7, as well as issues with safety for oral tissue and power efficiency.

[0033] For the above reasons, it is preferable that the heating element 40 be disposed in the head unit 10. The power applied to the heating element 40 is P (W), the specific heat is c (kJ), and the density is ρ (kg / m ３ ) and the volume is V (m ３ ), the temperature difference due to heating is ΔT (°C), the heating time is t (h), and the Joule coefficient is α, the following relationship holds: t = α × c × ρ × ΔT × V / P As is clear from the above equation, the heating time t and the volume V are proportional, and the larger the heating element 40 and the larger the volume V, the longer the heating time t.

[0034] [Relationship between size of heating element 40 and heating time t] For the samples of Experimental Examples 1-3, which used film heaters and chip resistors with the specifications shown in Table 1 as the heating element 40, experiments were conducted to confirm the time it took for the heating element 40 to heat up to 40°C. The film heaters had resistance values ​​of 5Ω and 10Ω, and the chip resistors had a resistance value of 15Ω. A current of 3.0 V was passed through the heating element 40, and the time it took for the heating element 40 to heat up to 40°C was measured.

[0035]

[0036] As shown in Table 1, when comparing the sample of Experimental Example 1 and the sample of Experimental Example 2, in which the difference in area of ​​the heating element 40 was small, it was confirmed that a difference of 5 Ω in the resistance value resulted in a difference of just under one minute in the time it took for the heating element 40 to heat up to 40°C. On the other hand, when comparing the sample of Experimental Example 2, in which the area of ​​the heating element 40 was large, with the sample of Experimental Example 3, in which the area of ​​the heating element 40 was small, the time it took for the sample of Experimental Example 3 to heat up to 40°C was more than one minute shorter, even though the resistance value was 5 Ω higher. From the above results, it was confirmed that the time to reach the target temperature can be significantly shortened by reducing the area of ​​the heating element 40.

[0037] [Relationship between the presence or absence of heat transfer body 50, distance Tb, heating time, and cooling time] Experiments were conducted using samples of experimental examples 4-7 with the specifications shown in Table 2 to confirm the time it takes for the head portion 10 to be heated to 40°C and the time it takes for the head portion 10, heated to 40°C, to cool down to 35°C, with respect to the presence or absence of heat transfer body 50 and the distance Tb in the head portion 10.

[0038] The sample of Experimental Example 4 has a head portion 10 made of polypropylene resin and a heat transfer body 50, and the distance Tb is 0.5 mm. The sample of Experimental Example 5 is a sample in which, compared to the sample of Experimental Example 4, a plate made of polypropylene resin and having a thickness of 0.8 mm is provided on the back side of the head portion 10, thereby setting the distance Tb to 1.3 mm. The sample of Experimental Example 6 is a sample in which, compared to the sample of Experimental Example 5, a plate made of polypropylene resin and having a thickness of 0.8 mm is provided on the back side of the head portion 10, thereby setting the distance Tb to 2.1 mm. The sample of Experimental Example 7 is a sample in which, compared to the sample of Experimental Example 4, the heat transfer body 50 is not provided.

[0039] The samples of Experimental Examples 4 to 7 had the following common configurations: When viewed from the front, the ratio of the area of ​​the heating element 40 to the area of ​​the heat transfer element 50 was 11%. When viewed from the front, the ratio of the area of ​​the heat transfer element 50 to the area of ​​the head portion 10 was 82%.

[0040] [Experimental Method] A voltage of 3.0 V and a current of 0.20 A were applied to the heating element 40, and the time taken for the center of the head portion 10 of each sample to reach 40°C and the time taken for the temperature to drop from 40°C to 35°C were measured.

[0041]

[0042] As shown in Table 2, it was confirmed that the longer it took for the sample in Experimental Example 4 to heat up and cool down, the thicker the resin on the back side became. It was also confirmed that an increase in resin thickness of 0.8 mm lengthened the heat-up time by 30 seconds or more and the heat-down time by 5 seconds or more. These results confirmed that even a difference of 1 mm or less in the thickness of the resin on the back side covering the heat transfer body 50 significantly affected the heat-up time and the heat-down time, thereby affecting the usability of the toothbrush 1.

[0043] [Relationship between heating time of outermost portion of head portion with and without heat transfer body 50] The relationship between heating time and cooling time of outermost portion of head portion with and without heat transfer body 50 was confirmed using the samples of Experimental Examples 4 and 7 above.

[0044] [Experimental Method] A voltage of 3.0 V and a current of 0.20 A were applied to the heating element 40, and the temperature and time when the outermost periphery of the head portion 10 of each sample in each experiment reached 40°C were measured. Thermography was used to measure the temperature. A copper plate was used as the heat transfer element 50. The temperature of each sample was measured from the side of the flocked surface 12.

[0045]

[0046] It was confirmed that when the outermost periphery of the head portion 10 was heated to 40°C, there was a difference of about 20°C in the temperature of the heating element 40 between when there was a heat transfer body 50 and when there was not. Furthermore, with regard to the time required to warm up to the outermost periphery of the head portion 10 under the above conditions, the sample of Experimental Example 4, which had a heat transfer body 50, warmed up to 40°C in 50 seconds or more shorter.

[0047] Fig. 5 is a diagram showing the temperature distribution of the sample of Experimental Example 4. Fig. 6 is a diagram showing the temperature distribution of the sample of Experimental Example 7. As shown in Fig. 5, in the sample of Experimental Example 4 having the heat transfer body 50, it was confirmed that the surface of the head unit 10 was uniformly heated up to the vicinity of the outermost periphery. In contrast, as shown in Fig. 6, in the sample of Experimental Example 7 not having the heat transfer body 50, it was confirmed that the temperature was high around the heating element 40 and low near the outermost periphery, and a temperature gradient was generated in the head unit 10.

[0048] From these results, it was confirmed that by adopting a configuration including the heat transfer body 50, it is possible to prevent the heating body 40 from becoming too hot, and to heat the head portion 10 evenly and quickly.

[0049] If the amount of power supplied to the heating element 40 has an upper limit and the power P is constant at the upper limit, when the area of ​​the heat transfer element 50 in the head unit 10 is taken as 100%, if the area of ​​the heating element 40 relative to the heat transfer element 50 exceeds 20%, the heating element 40 is too large and takes a long time to heat up. Furthermore, because power is supplied to the heating element 40 from the substrate 30 disposed through the neck portion 7, a larger heating element 40 requires a larger substrate 30 to secure the heating element 40, which increases production costs. If the area of ​​the heating element 40 relative to the heat transfer element 50 is less than 3%, the difference in time for heat to be transferred between the center of the head unit 10 and the edge of the head unit 10 when viewed from the front becomes large, resulting in a large temperature difference. By making the area of ​​the heating element 40 relative to the heat transfer element 50 3% or more and 20% or less, the heating element 40 can be heated in a short time, and the heat transfer element 50 functions effectively in the head portion 10, reducing the temperature difference between the center of the head portion 10 and the edge of the head portion 10, making it possible to heat evenly.

[0050] Furthermore, the thickness of the front side of the head 10 where the tufting surface 12 is located varies depending on whether or not there are tufting holes 14, so localized heating is undesirable in terms of shape changes such as enlargement of the tufting holes 14 and hair loss. By having at least a portion of the multiple tufting holes 14 overlap with the heat transfer body 50 when viewed from the front, it becomes possible to heat all of the tufting holes 14 evenly, preventing shape changes and reducing the risk of hair loss due to shape changes.

[0051] The thickness dimension of the heat transfer body 50 is preferably 0.1 mm or more and 1.0 mm or less, and more preferably 0.1 mm or more and 0.5 mm or less. Because the heat transfer body 50 must be placed within a limited space in the toothbrush 1, it is expected to be thin. If the thickness dimension of the heat transfer body 50 is less than 0.1 mm, the heat transfer body 50 is too thin, reducing the cross-sectional area perpendicular to the heat transfer direction of the heat source (heat generating element 40), making it difficult for heat to be transferred to the ends. As a result, heat is concentrated in the center, increasing the risk of deformation and cracking due to thermal expansion. If the thickness dimension of the heat transfer body 50 is too thick, exceeding 1.0 mm, the time difference in heat transfer between the center and ends of the head portion 10 becomes large, resulting in a large temperature difference.

[0052] When viewed from the front, the minimum distance Tc from the outermost periphery of the head portion 10 to the heat transfer body 50 is preferably equal to or greater than the minimum distance Td from the outermost periphery of the head portion 10 to the tufting holes 14. To reduce heat loss from the heat generated by the heating element 40 until it is transferred to the oral cavity, it is preferable that the minimum distance Tc from the outermost periphery of the head portion 10 to the heat transfer body 50 be short. However, if the minimum distance Tc is less than the minimum distance Td, the heat retention effect of the resin forming the head portion 10 is impaired, and the temperature of the head portion 10 may become unstable. The minimum distance Tc from the outermost periphery of the head portion 10 to the heat transfer body 50 is preferably at least 0.8 mm or more and 2.0 mm or less.

[0053] In the toothbrush 1, when controlling the temperature of the head unit 10, the control unit 32 controls the amount of electricity supplied to the heating element 40 based on the temperature of the heating element 40 detected by the temperature detection unit 31. Fig. 7 is a diagram showing a control method for temperature control, showing the relationship between the set temperature and voltage over time.

[0054] The control unit 32 applies a voltage selected from three preset voltages, a first voltage, a second voltage, and a third voltage, to the heating element 40. The first voltage is the highest voltage. The second voltage is a voltage lower than the first voltage. The third voltage is a voltage lower than the first and second voltages.

[0055] As shown in Figure 7, since it is necessary to quickly raise the temperature at startup, the control unit 32 applies a high-voltage first voltage to the heating element 40 to heat the head unit 10. When the temperature of the heating element 40 exceeds a reference value, the control unit 32 applies a low-voltage third voltage to the heating element 40 to reduce the heating of the head unit 10. When the temperature of the heating element 40 falls below the reference value, the control unit 32 applies a medium-voltage second voltage to the heating element 40 to increase the heating of the head unit 10. Thereafter, the control unit 32 alternates between applying the third voltage to lower the temperature and applying the second voltage to raise the temperature, depending on the detected temperature of the heating element 40.

[0056] For example, if ON / OFF control is performed using only the high first voltage, the temperature rises rapidly when the heater is on and drops slowly when the heater is off. With high voltage, it is difficult to control the temperature to within a few degrees, so the time the temperature of the head unit 10 remains at the target temperature is shortened. If ON / OFF control is performed using only medium or low voltage, it is possible to control the temperature to within a few degrees, but it takes time to reach the target temperature from startup, resulting in poor usability. By controlling the temperature of the head unit 10 using multiple voltages, the heater element 40 is energized at high voltage during startup, allowing the head unit 10 to quickly heat up to the target temperature and then maintain the target temperature constant.

[0057] As described above, the toothbrush 1 of this embodiment has a heat transfer body 50 that is provided in the head portion 10 and has a thermal conductivity greater than that of the head portion 10, and a heating element 40 that is provided in contact with the heat transfer body 50 and generates heat when electricity is passed through it.Therefore, even if the number of power sources that can be installed and the amount of power that can be output are limited, the heat generated by the heating element 40 can be transmitted over a wide area by thermal conduction through the heat transfer body 50, so that the entire head portion 10 can be heated evenly and the gums can be heated efficiently without causing the heating element 40 to generate excessive heat.

[0058] In the past, it was considered to install multiple or large heating elements because it is preferable for the entire head portion 10 to warm up quickly when operation begins. In this case, however, it takes time for the heating elements themselves to warm up, which in turn makes it take longer for the head portion 10 to warm up, making it less user-friendly. However, the toothbrush 1 of this embodiment has the above-mentioned configuration, which solves this problem.

[0059] Furthermore, if the heating element 40 is made smaller, the resin of the head portion 10 has poor thermal conductivity, making it difficult for heat to spread throughout the entire head portion 10, resulting in a localized heated area. When the heated area is localized, the area of ​​the head portion 10 that reaches the target temperature becomes smaller, making it less efficient to heat the desired area. Furthermore, when heating a head portion 10 whose thickness varies due to the presence of the tufting holes 14, the resin in the thinner parts of the head portion 10 is likely to soften at high temperatures, making it more likely to deform due to localized heating, resulting in bristle loss.

[0060] Furthermore, if the heating element 40 is made smaller, it must generate excessive heat to heat the entire head unit 10, but it is difficult to heat it uniformly, which increases the temperature gradient within the head unit 10 and increases the risk of deformation. In addition, excessive heat generated by the heating element 40 poses problems in terms of safety, power efficiency, and deterioration.

[0061] Therefore, in the toothbrush 1 of this embodiment, the heat generated by the heating element 40 is transferred over a wide area by the heat transfer element 50 through thermal conduction, thereby solving the above problem.

[0062] While the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to these examples. The shapes and combinations of the components shown in the above examples are merely examples, and various modifications can be made based on design requirements, etc., without departing from the spirit of the present invention.

[0063] For example, in the above embodiment, a configuration in which the heat transfer body 50 and the heating body 40 are disposed in the head portion 10 is exemplified, but the present invention is not limited to this configuration. As described above, the heat transfer body 50 may be disposed across the head portion 10 and the neck portion 7. In this case, the heating body 40 may be disposed in the neck portion 7. When the heating body 40 is disposed in the neck portion 7, the power supply line connected to the heating body 40 becomes shorter, which reduces power loss related to power supply, thereby extending the life of the battery 5.

[0064] The present invention is applicable to toothbrushes.

[0065] REFERENCE SIGNS LIST 1 toothbrush, 2 gripping portion, 10 head portion, 11 brush portion, 12 bristle implantation surface, 13 bristle bundle, 14 bristle implantation holes, 30 substrate, 31 temperature detection portion, 32 control portion, 40 heating element, 50 heat transfer portion

Claims

1. A toothbrush comprising: a head portion having a brush portion; a handle portion located at the rear end of the head portion; a heat transfer body provided at least in the head portion and having a higher thermal conductivity than the head portion; and a heating body provided in contact with the heat transfer body and which generates heat when electricity is passed through it.

2. The toothbrush according to claim 1, wherein the heat transfer body provided in the head portion is provided inside the head portion and is not exposed.

3. A toothbrush as described in claim 1 or 2, further comprising a substrate on which the heating element is mounted, the brush portion being provided on the bristle-implanted surface of the head portion, and the head portion having the heat transfer body, the heating element and the substrate sequentially arranged in a first direction perpendicular to the bristle-implanted surface from the rear side opposite the bristle-implanted surface towards the bristle-implanted surface.

4. The toothbrush according to claim 3, wherein the brush portion has bristles implanted in bristle implantation holes formed in the bristle implantation surface, and the distance between the surface of the heat transfer body closer to the bristle implantation surface and the bottom surface of the bristle implantation holes is longer than the distance between the rear surface of the heat transfer body and the rear surface of the head portion.

5. The toothbrush of claim 3, wherein the heating element is disposed in the head portion, and when viewed from the front from the side opposite the bristle surface in the first direction, the area of ​​the heating element is 3% or more and 20% or less of the area of ​​the heat transfer body, and when viewed from the front, the area of ​​the heat transfer body is 60% or more of the area of ​​the head portion.

6. The toothbrush according to claim 4, wherein a plurality of the bristle implantation holes are provided in the bristle implantation surface, and all of the bristle implantation holes at least partially overlap with the heat transfer body when viewed from the side opposite the bristle implantation surface.

7. The toothbrush according to claim 4, wherein the minimum distance from the outermost periphery of the head portion to the heat transfer body in a front view from the side opposite the bristle surface is equal to or greater than the minimum distance from the outermost periphery of the head portion to the bristle holes.

8. The toothbrush according to claim 3, wherein the heat conductor contains any one of copper, silver and aluminum, and the dimension of the heat conductor in the first direction is 0.1 mm or more and 1.0 mm or less.

9. The toothbrush according to claim 1 or 2, comprising: a temperature detection unit that detects the temperature of the heating element; and a control unit that controls the amount of electricity supplied to the heating element based on the temperature detected by the temperature detection unit.

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