Freeze prevention device

Abstract

To use radiation heat from a heater for the prevention of freeze while suppressing a thermal damage of a low heat-resistance component in the vicinity due to the contact of a freeze prevention device with the heater.SOLUTION: A heater 31 for generating heat by electrification is attached to the outside of a pipe by making its longitudinal direction along an axial direction of a pipe 22. Further, a heater guide 33 which surrounds an outer face parallel with the longitudinal direction of the heater via a prescribed interval is arranged except for a face of the heater which opposes the pipe. A skeleton part 33b for inhibiting an approach of the heater, and blocking an electromagnetic wave radiated from the heater, and a passage part 33c for making the electromagnetic wave radiated from the heater pass therethrough without blocking it are arranged at the heater guide. By this constitution, even if a low heat-resistance component such as wiring approaches the heater, the approach is blocked by the skeleton part. Therefore, the electromagnetic wave radiated from the heater passes through the passage part and transmits heat to a peripheral member while suppressing the thermal damage to the low heat-resistance component in the vicinity due to contact with the heater, thus making it possible to use the radiation heat from the heater for the prevention of freeze.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a freeze prevention device that prevents freezing in pipes through which hot and cold water flows inside a water heater. [Background technology]

[0002] Various pipes for carrying hot water are arranged inside a water heater that heats water and supplies hot water, and it is known that anti-freezing devices are attached to the outside of the pipes to prevent them from freezing in winter. The anti-freezing device is equipped with a heater that generates heat when electricity is passed through it, such as a ceramic heater, and can be used to prevent freezing not only by conduction, in which the heat of the heater is directly transmitted to the pipe in contact with the heater and is transmitted to the water in the pipe via the pipe, but also by conduction (convection), in which the air around the heater and the water in the pipe are heated and flow, and radiation (radiation), in which electromagnetic waves (infrared rays) emitted from the heater transmit heat to surrounding components without passing through a medium.

[0003] Such anti-freezing devices are installed in positions inside the water heater that are effective for preventing freezing, and may be located near the electrical unit that controls the entire water heater. As is well known, various wiring such as harnesses and cables are connected to the electrical unit, and these wirings are often covered with low heat-resistant resin such as polyvinyl chloride, so there is a risk that the covering will melt and be damaged if the wiring comes into contact with the high-temperature heater. Therefore, it has been proposed to attach a heater cover that covers the periphery of the heater (for example, Patent Document 1), and the heater cover prevents contact between the heater and low heat-resistant parts such as nearby wiring. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-284230 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the heater is covered with a heater cover as described above, although it is possible to protect nearby low heat-resistant parts from coming into contact with the heater, the electromagnetic waves emitted from the heater are blocked by the heater cover, so there is a problem that heat cannot be radiated from the heater to be transferred to surrounding parts and used to prevent freezing.

[0006] This invention has been made in response to the above-mentioned problems in the conventional technology, and aims to provide a freeze prevention device that can utilize radiant heat from a heater to prevent freezing while suppressing thermal damage to nearby low heat-resistant parts due to contact with the heater. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the freeze prevention device of the present invention adopts the following configuration. In a freeze prevention device for preventing freezing in the pipes through which hot and cold water flows inside a water heater, a heater that generates heat when electricity is applied and is attached to the outside of the pipe with its longitudinal direction aligned with the axial direction of the pipe; a heater guard that surrounds an outer surface of the heater parallel to the longitudinal direction, except for a surface of the heater facing the pipe, with a predetermined gap therebetween; Equipped with The heater guard is a framework that prevents access to the heater and blocks electromagnetic waves emitted from the heater; a passage portion that passes the electromagnetic waves emitted from the heater without blocking them; The present invention is characterized by having the following.

[0008] In the freeze prevention device of the present invention, even if low heat-resistant parts such as wiring are arranged nearby, the low heat-resistant parts are prevented from approaching the heater by the framework, so that thermal damage to the low heat-resistant parts due to contact with the heater can be suppressed. Although the electromagnetic waves emitted from the heater are blocked by the framework, they can pass through the passing part, and the electromagnetic waves hit the surrounding members and the heat is transmitted, so that the radiant heat from the heater can be used to prevent freeze. Moreover, since the heater guard has the passing part, the radiant heat received by the heater guard itself from the heater is reduced compared to when there is no passing part, and the temperature rise of the heater guard can be suppressed, so that it is possible to suppress the occurrence of a situation in which a low heat-resistant part that comes into contact with the heater guard is thermally damaged.

[0009] In the heater guard of the freeze prevention device of the present invention described above, the framework portions and the passage portions may be arranged alternately and repeatedly in the vertical and horizontal directions.

[0010] In a freeze prevention device configured in this manner, the passing sections in the heater guard are distributed evenly, which prevents low heat-resistant parts such as wiring from entering the inside of the heater guard through the passing sections and coming into contact with the heater, and also makes it possible to transmit radiant heat from the heater evenly to the surrounding area.

[0011] In addition, in the above-mentioned anti-freezing device of the present invention, the ratio of the total area of ​​the passing parts to the total area of ​​the heater guard's skeleton and passing parts may be set within the range of 40% to 60%.

[0012] If the proportion of passing parts in the heater guard is too high, the strength of the heater guard (skeletal part) will be insufficient, and if the proportion of passing parts is too low (the proportion of skeleton part is too high), the anti-freezing effect using the radiant heat from the heater will not be sufficient. Therefore, by limiting the proportion of passing parts to the range of 40% to 60%, it is possible to ensure both the strength of the heater guard and the anti-freezing effect using the radiant heat from the heater.

[0013] The heater guard of the freeze prevention device of the present invention may have a protruding piece that protrudes from the framework toward the heater and has a length corresponding to the gap between the heater and the heater guard.

[0014] In a freeze prevention device configured in this manner, the protruding piece is interposed between the heater and the heater guard (skeletal part), so that the heater guard will not get closer to the heater than the length of the protruding piece, making it possible to ensure a predetermined gap between the heater and the heater guard.

[0015] In the above-described anti-freezing device of the present invention, a plurality of protruding pieces may be provided, and the device may have two or more protruding pieces protruding in different directions.

[0016] In a freeze prevention device configured in this manner, a predetermined gap is secured between the heater and the heater guard (skeleton) in each direction of two or more protruding pieces that protrude in different directions, making it possible to position the heater guard relative to the heater.

[0017] In the freeze prevention device of the present invention described above, the tip of the protruding piece may be formed in a shape that makes a point contact or a line contact when it comes into contact with the heater.

[0018] In a freeze prevention device configured in this manner, even if the tip of the protruding piece comes into contact with the heater, the contact is point or line, so the heat from the heater is less likely to be transferred to the protruding piece than in the case of surface contact, and therefore the temperature rise of the heater guard due to heat transfer through the protruding piece can be suppressed. [Brief description of the drawings]

[0019] [Figure 1] 1 is an explanatory diagram illustrating an example of the overall configuration of a water heater 1 equipped with a freeze prevention device 30 of the present embodiment. [Diagram 2] 13 is a perspective view showing an installation environment of a fourth anti-freezing device 30d as an example of the anti-freezing device 30. FIG. [Diagram 3] 13 is a perspective view showing a disassembled state of a fourth freeze prevention device 30d of the present embodiment before being attached to a hot water supply pipe 22. FIG. [Figure 4] 13 is a perspective view showing a state in which a fourth freeze prevention device 30d of the present embodiment is attached to a hot water supply pipe 22. FIG. [Diagram 5] 2 is a development view of the heater guard 33 of the present embodiment spread out on a plane. FIG. [Figure 6] 13 is a cross-sectional view of a fourth freeze prevention device 30d attached to a hot water supply pipe 22, taken along a plane perpendicular to the axial direction of the hot water supply pipe 22. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] FIG. 1 is an explanatory diagram illustrating the overall configuration of a water heater 1 equipped with a freeze prevention device 30 of this embodiment. As shown in the figure, the water heater 1 is equipped with a plurality of burners 3 (12 in this embodiment) housed in a combustion chamber 2 and combusting fuel gas. A main valve 5 for opening and closing the gas pipe 4 and a proportional valve 6 for adjusting the flow rate of the fuel gas are provided in a gas pipe 4 for supplying the fuel gas. In addition, in the water heater 1 of this embodiment, the gas pipe 4 is branched into two on the downstream side of the proportional valve 6 in response to the plurality of burners 3 (12) being divided into two burner groups, and is equipped with a first switching valve 7a for opening and closing a branch pipe corresponding to the first burner group consisting of four burners 3, and a second switching valve 7b for opening and closing a branch pipe corresponding to the second burner group consisting of eight burners 3. It is possible to change the amount of heat generated (hot water supply capacity) by controlling the opening and closing of these two switching valves 7a and 7b to select a burner group to supply fuel gas and by controlling the opening degree of the proportional valve 6.

[0021] In addition, the water heater 1 is provided with a combustion fan 10 that sends combustion air from below toward the burner 3, an ignition plug 11 that creates a spark at the burner 3 by discharging a high voltage, and a flame rod 12 that detects the flame (ignition) of the burner 3. By controlling the rotation speed of the combustion fan 10 according to the opening degree of the proportional valve 6, it is possible to adjust the air-fuel ratio to a desired value.

[0022] A first heat exchanger 13 is provided above the burner 3, and a second heat exchanger 14 is provided above the first heat exchanger 13. The exhaust gas generated by combustion in the burner 3 is sent upward by the airflow of the combustion fan 10, and passes through the first heat exchanger 13 and the second heat exchanger 14. At this time, the first heat exchanger 13 recovers sensible heat from the exhaust gas, and the second heat exchanger 14 recovers latent heat from the exhaust gas. The exhaust gas that has passed through the first heat exchanger 13 and the second heat exchanger 14 is discharged to the outside from an exhaust port 15 at the top of the water heater 1.

[0023] A water supply pipe 20 that supplies clean water is connected to the upstream side of the second heat exchanger 14. The downstream side of the second heat exchanger 14 is connected to the upstream side of the first heat exchanger 13 via a connecting pipe 21, and a hot water supply pipe 22 is connected to the downstream side of the first heat exchanger 13. In the water heater 1 of this embodiment, the water supply pipe 20 and the hot water supply pipe 22 are connected by a bypass pipe 23.

[0024] A water flow sensor 24 that detects the flow rate of clean water (feedwater flow rate) supplied through feedwater pipe 20 is provided upstream of the connection position of feedwater pipe 20 with bypass pipe 23, and when the feedwater flow rate reaches or exceeds a predetermined ignition flow rate, combustion of fuel gas is started in burner 3, and combustion in burner 3 is controlled according to the feedwater flow rate. The clean water supplied to second heat exchanger 14 through feedwater pipe 20 is first preheated in second heat exchanger 14 and then heated in first heat exchanger 13 to become hot water and flow out into hot water pipe 22.

[0025] Also, a portion of the clean water supplied through the water supply pipe 20 can pass through the bypass pipe 23 without being supplied to the second heat exchanger 14. The hot water heated in the first heat exchanger 13 is mixed with the clean water that has passed through the bypass pipe 23 in the hot water supply pipe 22 and is supplied to a bathtub or a hot water tap (a so-called faucet) (not shown). The mixing ratio of the hot water heated in the first heat exchanger 13 and the clean water that has passed through the bypass pipe 23 can be changed by a bypass servo 25 provided at the connection point between the water supply pipe 20 and the bypass pipe 23.

[0026] The hot water supply pipe 22 is provided with a heat exchanger temperature sensor 27 that detects the temperature of the hot water immediately after it flows out of the first heat exchanger 13, and a hot water supply temperature sensor 28 that detects the temperature of the hot water (hot water supply temperature) supplied to the bathtub or hot water tap downstream of the connection position with the bypass pipe 23. If the burner 3 is burning, the temperature detected by the hot water supply temperature sensor 28 will naturally be lower than the temperature detected by the heat exchanger temperature sensor 27, and fluctuations in the hot water supply temperature can be suppressed by adjusting the mixture ratio with the bypass servo 25. Thermistors whose electrical resistance changes according to changes in temperature are used for the various temperature sensors 27 and 28 in this embodiment.

[0027] In such a water heater 1, water in various pipes (water supply pipe 20, connection pipe 21, hot water supply pipe 22, bypass pipe 23) arranged inside may freeze when the outside temperature is low in winter. Therefore, a freeze prevention device 30 is attached at a position effective for preventing freezing. Details of the freeze prevention device 30 will be described later using another drawing, but in the example shown in FIG. 1, it has a first freeze prevention device 30a attached to the water supply pipe 20 near the second heat exchanger 14, a second freeze prevention device 30b attached to the connection pipe 21, a third freeze prevention device 30c attached to the hot water supply pipe 22 near the first heat exchanger 13, and a fourth freeze prevention device 30d attached downstream of the connection position of the hot water supply pipe 22 with the bypass pipe 23.

[0028] In addition, the water heater 1 is equipped with an electrical unit 40 that controls the entire system, and the aforementioned main valve 5, proportional valve 6, switching valves 7a, 7b, combustion fan 10, spark plug 11, frame rod 12, water volume sensor 24, bypass servo 25, heat exchanger temperature sensor 27, hot water temperature sensor 28, and freeze prevention devices 30a-30d are connected to the electrical unit 40 via wiring such as harnesses (not shown).

[0029] Furthermore, a remote control 41 that can be operated by a user of the water heater 1 is connected to the electrical equipment unit 40 via a cable (not shown). The remote control 41 includes an operation section 41a on which are provided various switches that are operated to make various settings such as the temperature of the hot water to be supplied and to switch various functions on and off, and a display section 41b that can display the setting status and operating status of the water heater 1.

[0030] Fig. 2 is a perspective view showing an installation environment of a fourth anti-freezing device 30d as an example of the anti-freezing device 30. To avoid the illustration becoming complicated, Fig. 2 mainly shows the parts inside the water heater 1 that are affected by the fourth anti-freezing device 30d, and other parts are omitted. As described above, the fourth anti-freezing device 30d of this embodiment is installed downstream (lower in the figure) of the hot water supply pipe 22 from the connection position with the bypass pipe 23, and the heater 31 that generates heat when electricity is applied is attached to the outside of the hot water supply pipe 22 by a mounting bracket 32. The hot water supply pipe 22 of this embodiment corresponds to the "pipe" of the present invention.

[0031] In the case of a stopped water heater 1 where no combustion is performed by the burner 3 and where freezing inside is expected as the outside air temperature drops in winter (for example, when the temperature detected by an outside air temperature sensor, not shown, drops below a predetermined freezing prevention temperature), the heater 31 generates heat by being energized. A well-known ceramic heater is used for the heater 31 in this embodiment, and the heat of the heater 31 is directly transmitted to the hot water supply pipe 22 to which the heater 31 is in contact, and is also transmitted to the water in the hot water supply pipe 22 via the hot water supply pipe 22 (so-called conduction). In addition, the air around the heater 31 and the water in the hot water supply pipe 22 are heated and flow upward, thereby transmitting the heat (so-called transmission or convection). Furthermore, the heat is transmitted to the surrounding members by electromagnetic waves (mainly infrared rays) emitted from the heater 31 without passing through a medium (so-called radiation or emission). In this way, by considering not only conduction but also transmission and radiation, the heat of the heater 31 can be effectively used to prevent freezing.

[0032] In the example shown in Fig. 2, the position where the fourth anti-freezing device 30d is attached to the hot water supply pipe 22 is close to the positions where the water volume sensor 24 and the bypass servo 25 are disposed. In the hot water heater 1 of this embodiment, the water volume sensor 24 and the bypass servo 25 are integrally formed of a resin material as the inflow unit 26. This resin inflow unit 26 is more likely to absorb electromagnetic waves without reflecting them than the metal water supply pipe 20 and bypass pipe 23, and therefore has a high heat transfer effect due to radiation from the heater 31. By heating the inflow unit 26 in this way, it is expected that the effect of preventing freezing within the inflow unit 26 and freezing within the water supply pipe 20 and bypass pipe 23 connected to the inflow unit 26 can be prevented.

[0033] In the example of FIG. 2, the fourth anti-freezing device 30d is disposed near the electrical unit 40. As described above, the electrical unit 40 is connected to various electrical components (main valve 5, proportional valve 6, switching valves 7a, 7b, combustion fan 10, ignition plug 11, flame rod 12, water volume sensor 24, bypass servo 25, heat exchanger temperature sensor 27, hot water supply temperature sensor 28, and anti-freezing devices 30a to 30d) via harnesses, and the remote control 41 is connected via cables. Therefore, various wiring such as harnesses and cables (not shown) are laid around the fourth anti-freezing device 30d. These wirings are often covered with low heat-resistant resin such as polyvinyl chloride, so that if the wirings come into contact with the heater 31, which becomes hot (about 300 degrees) when energized, the covering may melt and be damaged.

[0034] In conventional water heaters 1, a heater cover may be attached to cover the heater 31 to prevent the wiring from contacting the heater 31. However, because the electromagnetic waves emitted from the heater 31 are blocked by the heater cover, the above-mentioned effect of preventing freezing by transferring heat to the inflow unit 26 by radiation from the heater 31 cannot be expected. Therefore, the fourth freeze prevention device 30d of the present embodiment employs the following configuration to enable the radiant heat from the heater 31 to be used for freezing prevention while suppressing thermal damage to the wiring due to contact with the heater 31.

[0035] 3 is a perspective view showing the fourth anti-freezing device 30d of this embodiment in a disassembled state before being attached to the hot water supply pipe 22. As described above, a ceramic heater is used for the heater 31 of this embodiment, and as is well known, a ceramic heater is formed by covering an electric heating wire such as a nichrome wire with ceramic. The heater 31 shown in the figure is formed in a substantially rectangular parallelepiped shape, and is attached to the outside of the hot water supply pipe 22 with its longitudinal direction aligned with the axial direction of the hot water supply pipe 22. In addition, a groove 31a is formed in the longitudinal direction on the surface of the heater 31 facing the hot water supply pipe 22 to stabilize contact with the outer circumferential surface of the cylindrical hot water supply pipe 22.

[0036] The mounting bracket 32 ​​is formed by sheet metal processing using a thin plate such as stainless steel, and is provided with a pair of heater clamping parts 32a for clamping the heater 31 and a pair of pipe clamping parts 32b for clamping the hot water supply pipe 22. If the heater 31 is positioned between the pair of heater clamping parts 32a by widening the gap between them, the heater 31 is clamped by the elastic force of the heater clamping parts 32a. Similarly, if the heater 22 is positioned between the pair of pipe clamping parts 32b by widening the gap between them, the hot water supply pipe 22 is clamped by the elastic force of the pipe clamping parts 32b, so that contact between the hot water supply pipe 22 and the heater 31 is maintained. The method of mounting the heater 31 to the hot water supply pipe 22 is not limited to using the mounting bracket 32, and the heater 31 may be fixed with a heat-resistant adhesive. However, by detachably mounting the heater 31 using the mounting bracket 32, the heater 31 can be easily replaced during repairs, etc.

[0037] Furthermore, the fourth anti-freezing device 30d of this embodiment includes a substantially rectangular parallelepiped heater guard 33 that surrounds, with a predetermined gap, the outer surfaces of the heater 31 that are parallel to the longitudinal direction, except for the surface of the heater 31 that faces the hot water supply pipe 22. The heater guard 33 of this embodiment is formed by sheet metal processing using a thin plate such as stainless steel, and two pairs of clamping portions 33a for clamping the hot water supply pipe 22 are provided spaced apart in the longitudinal direction of the heater 31.

[0038] When the gap between the pair of clamping parts 33a is widened to accommodate the heater 31 inside the heater guard 33, the hot water supply pipe 22 is positioned between the pair of clamping parts 33a, and the hot water supply pipe 22 is clamped by the elastic force of the clamping parts 33a. The method of attaching the heater guard 33 to the hot water supply pipe 22 is not limited to clamping by the clamping parts 33a, and the heater guard 33 may be directly joined to the hot water supply pipe 22 by welding or the like. However, if the hot water supply pipe 22 is detachably clamped by the clamping parts 33a, the heater guard 33 can be easily removed when replacing the heater 31, for example. If the heater guard 33 is integrated with the mounting bracket 32, the heat of the heater 31 will be transmitted via the mounting bracket 32. To avoid this, it is desirable to form the heater guard 33 separately from the mounting bracket 32.

[0039] 4 is a perspective view showing a state in which the fourth anti-freezing device 30d of this embodiment is attached to the hot water supply pipe 22. As shown in the figure, the heater guard 33 of this embodiment does not uniformly cover the outer surface parallel to the longitudinal direction of the heater 31, but has a skeleton part 33b that prevents access to the heater 31 and forms a skeleton that blocks electromagnetic waves emitted from the heater 31, and a passage part 33c that is opened to allow the electromagnetic waves emitted from the heater 31 to pass through without being blocked.

[0040] By providing such a heater guard 33, even if low heat-resistant wiring is laid around the fourth anti-freezing device 30d, the skeleton 33b prevents the wiring from approaching the heater 31, so that thermal damage to the wiring due to contact with the heater 31 can be suppressed. Although the electromagnetic waves emitted from the heater 31 are blocked by the skeleton 33b, they can pass through the passing portion 33c, and the electromagnetic waves hit the surrounding members such as the inflow unit 26 described above and the heat is transmitted, so that the radiant heat from the heater 31 can be used to prevent freezing. Moreover, the amount of radiant heat that the heater guard 33 itself receives from the heater 31 is reduced by the amount that the passing portion 33c is open in the heater guard 33 compared to when the passing portion 33c is not open, and the temperature rise of the heater guard 33 can be suppressed, so that it is possible to suppress the occurrence of a situation in which the wiring in contact with the heater guard 33 is thermally damaged.

[0041] 5 is a development view of the heater guard 33 of this embodiment spread out on a plane. In the figure, the skeleton 33b is hatched. As shown in the figure, the heater guard 33 of this embodiment has skeletons 33b and passing parts 33c arranged alternately vertically and horizontally, and the skeleton 33b is formed in a substantially lattice shape. By distributing the passing parts 33c opening in the heater guard 33 in this manner without bias, it is possible to prevent low heat-resistant wiring, etc. from entering the inside of the heater guard 33 through the passing parts 33c and coming into contact with the heater 31, and it is also possible to uniformly transmit radiant heat from the heater 31 to the surroundings.

[0042] In the heater guard 33 of this embodiment, the ratio of the total area of ​​the passing portion 33c to the total area of ​​the skeleton portion 33b and the passing portion 33c is set within a range of 40% to 60%, and in the illustrated example, it is set to about 50%. If the ratio of the passing portion 33c in the heater guard 33 is too high, the strength of the heater guard 33 (skeleton portion 33b) is insufficient, and if the ratio of the passing portion 33c is too low (the ratio of the skeleton portion 33b is too high), the anti-freezing effect using the radiant heat from the heater 31 cannot be obtained sufficiently. Therefore, by limiting the ratio of the passing portion 33c to a range of 40% to 60%, it is possible to ensure both the strength of the heater guard 33 and the anti-freezing effect using the radiant heat from the heater 31.

[0043] Furthermore, in the heater guard 33 of this embodiment which is formed by sheet metal processing, when the passing portion 33c is punched out, some of the protruding pieces 33d (six in the illustrated example) remain connected to the skeletal portion 33b as shown in FIG. 5, and as the heater guard 33 is formed into an approximately rectangular parallelepiped shape by bending processing, the protruding pieces 33d are bent toward the inside of the heater guard 33.

[0044] 6 is a cross-sectional view of fourth anti-freezing device 30d attached to hot water supply pipe 22, cut along a plane perpendicular to the axial direction of hot water supply pipe 22. The figure shows a cross section cut at the position of protruding piece 33d of heater guard 33. As shown in the figure, protruding piece 33d protrudes from skeleton 33b toward heater 31, and is provided with a length corresponding to a predetermined gap to be secured between heater 31 and heater guard 33 (skeleton 33b).

[0045] By interposing such a protruding piece 33d between the heater 31 and the heater guard 33 (skeletal portion 33b), the heater guard 33 will not come closer to the heater 31 than the length of the protruding piece 33d, making it possible to ensure a predetermined gap between the heater 31 and the heater guard 33.

[0046] In particular, the heater guard 33 of this embodiment has three protruding pieces 33d corresponding to three faces parallel to the longitudinal direction of the approximately rectangular heater 31 excluding the face facing the hot water supply pipe 22, and these three protruding pieces 33d protrude in different directions. As shown in Figures 4 and 5, the heater guard 33 of this embodiment has two sets of three protruding pieces 33d protruding in different directions, spaced apart in the longitudinal direction of the heater 31.

[0047] The heater guard 33, which is attached to the hot water pipe 22 by clamping with the clamping portion 33a, can rotate around the central axis of the hot water pipe 22, but by having three protruding pieces 33d that protrude in different directions, a predetermined gap is secured between each of the three surfaces parallel to the longitudinal direction of the heater 31 and the heater guard 33 (skeleton portion 33b), making it possible to position the heater guard 33 relative to the heater 31.

[0048] In addition, in the heater guard 33 of this embodiment, the length of each protruding piece 33d is set so as to ensure a gap between the three faces parallel to the longitudinal direction of the heater 31 and the tips of the three corresponding protruding pieces 33d. By thus ensuring a gap so that the tips of the protruding pieces 33d do not come into contact with the heater 31, the heat of the heater 31 is less likely to be transmitted via the protruding pieces 33d, so that the temperature rise of the heater guard 33 can be suppressed.

[0049] In the heater guard 33 of this embodiment, three protruding pieces 33d protruding in different directions are provided, but the number is not limited to three, and as long as the heater guard 33 has two or more protruding pieces 33d protruding in different directions, it is possible to position the heater guard 33 with respect to the heater 31. That is, in the example shown in Fig. 6, there may be only two protruding pieces 33d arranged on the left and right of the heater 31 in the figure, or there may be only two protruding pieces 33d, one protruding piece 33d arranged on the opposite side of the heater 31 from the hot water supply pipe 22, and one protruding piece 33d on either the left or right side of the heater 31.

[0050] Furthermore, in the heater guard 33 of this embodiment, the tip of the protruding piece 33d is formed in an arc shape (see FIG. 5). As a result, even if the tip of the protruding piece 33d comes into contact with the heater 31, the contact is linear with a length equal to the thickness of the protruding piece 33d, and heat from the heater 31 is less likely to be transferred to the protruding piece 33d than in surface contact, so that the temperature rise of the heater guard 33 due to heat transfer via the protruding piece 33d can be suppressed. Note that the tip of the protruding piece 33d may be formed in a so-called pin angle, rather than an arc shape, so that it will be in line contact when it comes into contact with the heater 31. Also, the tip of the protruding piece 33d may be formed in a pointed shape, and when it comes into contact with the heater 31, it will be in point contact, so that heat will be less likely to be transferred than in line contact, and it is possible to suppress the temperature rise of the heater guard 33.

[0051] The above describes the fourth anti-freezing device 30d as an example of the anti-freezing device 30 of this embodiment, but the present invention is not limited to the above embodiment and can be embodied in various forms without departing from the gist of the present invention.

[0052] For example, in the above-described embodiment, a ceramic heater is used as the heater 31. However, the heater 31 is not limited to a ceramic heater, and may be a well-known glass tube heater as long as it generates heat when electricity is applied.

[0053] In the above-described embodiment, the heater 31 is formed in a substantially rectangular parallelepiped shape. However, the shape of the heater 31 is not limited to a substantially rectangular parallelepiped shape, and may be substantially cylindrical. In this case, the shape of the heater guard 33 surrounding the heater 31 may also be substantially cylindrical in correspondence with the heater 31.

[0054] In addition, the heater guard 33 in the above-described embodiment has the skeletal portion 33b formed in a substantially lattice shape. However, the heater guard 33 is not limited to a substantially lattice shape as long as the skeletal portions 33b and the passage portions 33c are arranged alternately and repeatedly vertically and horizontally. For example, the heater guard 33 may be formed of a punched metal in which a thin metal plate is punched to have a plurality of holes, such as round holes, regularly arranged therein, or the heater guard 33 may be formed of a wire mesh made of woven wire. Furthermore, the heater guard 33 is not limited to being made of metal, and may be formed of a heat-resistant resin (for example, polyphenylene sulfide).

[0055] In the above embodiment, the fourth anti-freezing device 30d has been described as an example, but the first to third anti-freezing devices 30a to 30c may also be configured in the same manner as the fourth anti-freezing device 30d. However, if low heat-resistant parts such as wiring are not arranged near the first to third anti-freezing devices 30a to 30c and there is no risk of the low heat-resistant parts coming into contact with the heater 31, the heater guard 33 may be omitted. [Explanation of symbols]

[0056] 1...water heater, 2...combustion chamber, 3...burner, 4...Gas pipe, 5...Main valve, 6...Proportional valve, 7a...first switching valve, 7b...second switching valve, 10...combustion fan, 11... spark plug; 12... flame rod; 13... first heat exchanger; 14...second heat exchanger, 15...exhaust port, 20...water supply pipe, 21...connection pipe, 22...hot water pipe, 23...bypass pipe, 24...water volume sensor; 25...bypass servo; 26...inflow unit; 27... heat exchanger temperature sensor, 28... hot water supply temperature sensor, 30... anti-freeze device, 31... heater; 31a... groove; 32... mounting bracket; 32a... heater clamping portion, 32b... pipe clamping portion, 33... heater guard, 33a... holding part, 33b... skeleton part, 33c... passing part, 33d...protruding piece, 40...electrical unit, 41...remote control, 41a...operation section, 41b...display section.

Claims

1. In a freeze prevention device for preventing freezing in the pipes through which hot and cold water flows inside a water heater, a heater that generates heat when electricity is applied and is attached to the outside of the pipe with its longitudinal direction aligned with the axial direction of the pipe; a heater guard that surrounds an outer surface of the heater parallel to the longitudinal direction, except for a surface of the heater facing the pipe, with a predetermined gap therebetween; Equipped with The heater guard is a framework that prevents access to the heater and blocks electromagnetic waves emitted from the heater; a passage portion that passes the electromagnetic waves emitted from the heater without blocking them; A freeze prevention device comprising:

2. The freeze prevention device according to claim 1, The heater guard has the framework and the passages arranged alternately in a row and column. A freeze prevention device characterized by the above.

3. The freeze prevention device according to claim 2, The ratio of the total area of ​​the passing portion to the total area of ​​the skeleton portion and the passing portion of the heater guard is set within a range of 40% to 60%. A freeze prevention device characterized by the above.

4. The freeze prevention device according to any one of claims 1 to 3, The heater guard has a protruding piece that protrudes from the framework toward the heater and has a length corresponding to the gap. A freeze prevention device characterized by the above.

5. The freeze prevention device according to claim 4, A plurality of the protruding pieces are provided, The device has two or more protruding pieces that protrude in different directions. A freeze prevention device characterized by the above.

6. The freeze prevention device according to claim 4, The tip of the protruding piece is formed in a shape that makes a point contact or a line contact when it comes into contact with the heater. A freeze prevention device characterized by the above.

Images