CN203731704U - Dry-burning-prevention device and electric water heater - Google Patents

Abstract

The utility model discloses a dry-burning-prevention device and an electric water heater. The dry-burning-prevention device is applied to dry-burning-prevention protection of the electric heater. The dry-burning-prevention device comprises a PTC heating pipe, a detection circuit and a control circuit, wherein a power supply circuit of the PTC heating pipe is electrically connected with the detection circuit, the detection circuit is electrically connected with the control circuit, the detection circuit is used for detecting current signals of the power supply circuit of the PTC heating pipe, and the control circuit controls the power supply circuit of the electric heater to be on and off according to the current signals. The electric water heater is further disclosed. Thus, the dry-burning-prevention device is simple in structure and capable of accurately conducting dry-burning prevention protection in time, and ensures that electricity utilization is safe and reliable.

Description

Anti-dry device and electric water heater

technical field

The utility model relates to the technical field of electric water heaters, in particular to an anti-dry heating device and an electric water heater.

Background technique

With the improvement of people's living standards, electric water heaters are widely used in ordinary families. At the same time, the safety of electric water heaters has gradually attracted everyone's attention. Among them, the anti-dry performance of electric water heaters has become the choice of electric water heaters for consumers. an important indicator of . In the prior art, the commonly used anti-dry control methods for electric water heaters are temperature control type and water level detection type.

For the temperature-controlled anti-dry control method, a thermal protector (thermostat) is installed outside the end of the inner tank where the heater is installed or outside the flange of the heater. When the thermal protector senses the inner tank When the shell or the flange of the heater reaches the preset temperature, the thermal protector acts and cuts off the power supply circuit of the heater. Since the shell of the liner and the flange of the heater are far away from the effective heating section of the heater, the thermal protector has a certain hysteresis in detecting the temperature of the effective heating section of the heater, and heating may occur before the thermal protector does not operate normally. The device is damaged due to long-term dry burning, and the anti-dry burning effect is not good.

For the anti-dry heating control mode of the water level detection type, two anti-dry electrodes that are insulated and installed on the heater flange of the electric water heater and extend into the inner tank are arranged. When the two anti-dry electrodes are turned on, the controller circuit conducts the power supply circuit of the heater; when the water level in the inner tank is lower than one of the anti-dry electrodes, the electrical connection between the two anti-dry electrodes is broken. On, the control circuit disconnects the power supply circuit of the heater to form an anti-dry protection. This anti-dry heating device judges whether the water heater is short of water and dry by detecting whether the two anti-dry electrodes form a circuit. The installation structure is complicated and increases the risk of water leakage due to poor sealing; 2. The shell of the anti-dry electrode is made of metal. When soaked in hot water for a long time, scale will be formed on the surface. When the scale reaches a certain thickness, it will It prevents the two anti-dry electrodes from forming a circuit through the water body, thereby affecting the normal operation of the water heater.

The above content is only used to assist in understanding the technical solution of the present utility model, and does not mean to admit that the above content is the prior art.

Utility model content

The main purpose of the utility model is to provide an anti-dry heating device and an electric water heater, so as to enable timely and accurate anti-dry heating protection to ensure safe and reliable electricity use.

In order to achieve the above purpose, the utility model provides an anti-dry heating device, which is suitable for the anti-dry heating protection of electric heaters. The anti-dry heating device includes a PTC heating tube, a detection circuit and a control circuit, wherein: the PTC heating tube The power supply circuit of the PTC heating tube is electrically connected to the detection circuit, and the detection circuit is electrically connected to the control circuit; the detection circuit is used to detect the current signal of the power supply circuit of the PTC heating tube, and the control circuit according to the current The signal controls the on-off of the power supply circuit of the electric heater.

Preferably, the PTC heating tube includes a metal outer tube with one end closed, an insulating end cap, a first lead rod, a second lead rod, a PTC heating element, and an insulating and heat-conducting medium; the insulating and heat-conducting medium is filled in the metal outer tube wherein, the PTC heating element is buried in the insulating and heat-conducting medium, the insulating end cap is sealed and connected to the open end of the metal outer tube, and the first lead rod and the second lead rod pass through the insulating end The cover partially extends into the metal outer tube, and the first lead rod is electrically connected to the second lead rod through the PTC heating element.

Preferably, the PTC heating element is a PTC metal heating wire, one end of the PTC metal heating wire is electrically connected to the first lead rod, and the other end is electrically connected to the second lead rod.

Preferably, the PTC heating element is a rod-shaped PTC ceramic, and the PTC ceramic is sandwiched between the first lead rod and the second lead rod.

Preferably, the first lead rod, the second lead rod and the PTC ceramics are arranged in parallel and extend to a position close to the end of the metal outer tube.

Preferably, the insulating and heat-conducting medium is magnesium oxide powder.

The utility model further provides an electric water heater, which includes an inner tank and an electric heater, and the electric heater is installed on the inner tank through a flange. In addition, the electric water heater also includes the anti-dry heating device of any of the above-mentioned embodiments. device, the anti-dry device includes a PTC heating tube, a detection circuit and a control circuit, wherein: the power supply circuit of the PTC heating tube is electrically connected to the detection circuit, and the detection circuit is electrically connected to the control circuit; The detection circuit is used to detect the current signal of the power supply circuit of the PTC heating tube, and the control circuit controls the on-off of the power supply circuit of the electric heater according to the current signal.

Preferably, the PTC heating pipe is installed on the flange and located above the electric heater.

Preferably, the electric water heater further includes a temperature measuring tube, the temperature measuring tube is installed on the flange and located between the PTC heating tube and the electric heater.

Preferably, the electric water heater also includes an electric control board and a warning module, and the warning module is electrically connected to the electric control board.

The anti-dry heating device and electric water heater provided by the utility model adopt the PTC heating tube with PTC (positive temperature coefficient) characteristics as the dry heating detection element of the electric heater. When the PTC heating tube is immersed in water, The PTC heating tube is normally heated, and its resistance value is small. The detection circuit detects a normal current signal. At this time, the control circuit conducts the power supply circuit of the electric heater according to the normal current signal provided by the detection circuit, and the electric heater heats normally; when the water level When it drops below the position where the PTC heating tube is located, the PTC heating tube burns dry, and its temperature rises sharply. According to the characteristics of PTC, its resistance value also increases sharply. The detection circuit detects an abnormal current signal. The abnormal current signal provided by the circuit disconnects the power supply circuit of the electric heater, and the electric heater stops heating, thereby realizing the protection against dry heating. It can be seen that the anti-dry heating device of the present utility model is not only simple in structure, but also can timely and accurately perform anti-dry heating protection to ensure safe and reliable electricity consumption.

Description of drawings

Fig. 1 is the structural representation of the preferred embodiment of the utility model electric water heater;

Fig. 2 is a schematic structural view of a preferred embodiment of the utility model anti-dry burning device;

Fig. 3 is the structural representation of an embodiment of the PTC heating tube shown in Fig. 2;

Fig. 4 is the structural representation of another embodiment of the PTC heating tube shown in Fig. 2;

Fig. 5 is the control schematic diagram of the anti-dry burning device of the utility model;

Fig. 6 is a curve diagram of temperature and resistivity of PTC metal heating wire;

Figure 7 is a graph showing the temperature and resistance characteristics of PTC ceramics.

The realization of the purpose of the utility model, functional characteristics and advantages will be further described in conjunction with the embodiments and with reference to the accompanying drawings.

Detailed ways

It should be understood that the specific embodiments described here are only used to explain the utility model, and are not intended to limit the utility model.

The utility model provides an electric water heater, referring to Fig. 1, in one embodiment, the electric water heater includes an inner tank 11, an electric heater 13 and an electric control board 12, and the inner tank 11 is provided with a water inlet 111 and a water outlet 112 And the sewage outlet 113, the inner tank 11 is a cylindrical structure extending longitudinally, and is arranged horizontally, the electric heater 13 is installed on the axial end of the inner tank 11 through the flange 16 (see Figure 2), and the electric heater 13 It is electrically connected with the electric control board 12, and under the control of the electric control board 12, electric heating is realized. In addition, the electric water heater also includes an outer shell 10 for accommodating an inner tank 111, and an insulating layer (not shown) is provided between the outer shell 10 and the inner tank 11 for heat insulation. It should be noted that the electric water heater also includes other relevant components known to those skilled in the art, so as to constitute a complete electric water heater that can be used normally, which will not be repeated here.

In order to improve the safety of the electric water heater and avoid the electric heater 13 from burning dry due to the low water level of the inner tank 11, the electric water heater in this embodiment also includes a dry heating prevention device. 2 and 5, specifically, the anti-dry device includes a PTC heating tube 15, a detection circuit 30 and a control circuit 20, wherein: the power supply circuit of the PTC heating tube 15 is electrically connected to the detection circuit 30, and the detection circuit 30 is connected to the control circuit 30. The circuit 20 is electrically connected; the detection circuit 30 is used to detect the current signal of the power supply circuit of the PTC heating tube 15 , and the control circuit 20 controls the on-off of the power supply circuit of the electric heater 13 according to the current signal detected by the detection circuit 30 . In this embodiment, the PTC heating tube 15 is a heating element with PTC (positive temperature coefficient) characteristics. In a preferred embodiment, the PTC heating tube 15 is installed on the flange 16 and is located above the electric heater 13. During the normal operation of the electric water heater, the PTC heating tube 15 can assist the electric heater 13 to heat the water body in the inner tank 11, and simultaneously serve as a dry-burning detection element of the electric heater 13 to avoid dry-burning of the electric heater 13. The working principle of the anti-dry burning device is as follows:

When the PTC heating tube 15 is immersed in water, the PTC heating tube 15 is normally heated, and its resistance value is small, so the current of the power supply circuit of the PTC heating tube 15 is relatively large, and the detection circuit 30 detects a normal current signal. At this time, the control circuit 20 According to the normal current signal provided by the detection circuit 30, the power supply circuit of the electric heater 13 is turned on, and the electric heater 13 is heated normally; when the hot water of the electric water heater is used, the water level in the inner tank 11 will gradually drop. When it is lower than the position where the PTC heating tube 15 is located, the PTC heating tube 15 is exposed to the water surface, and the PTC heating tube 15 is dry-burned, and its temperature rises sharply. rapid increase), the resistance of the PTC heating tube 15 also increases sharply, so the current of the power supply circuit of the PTC heating tube 15 decreases sharply, and the detection circuit 30 detects an abnormal current signal. The abnormal current signal provided cuts off the power supply circuit of the electric heater 13, and the electric heater 13 stops heating, thereby realizing the protection against dry heating. It can be seen that the anti-dry heating device of the present utility model is not only simple in structure, but also can timely and accurately perform anti-dry heating protection to ensure safe and reliable electricity consumption.

Further, the electric water heater also includes a temperature measuring tube 14, which is used to detect the temperature of the hot water in the inner tank 11, and feed back the temperature information to the electric control board 12, when the temperature of the hot water in the inner tank 11 When the preset value is reached, the electric control board 12 cuts off the power supply circuit of the electric heater 13, and the electric heater 13 stops heating; The power supply circuit of device 13, electric heater 13 starts heating. Specifically, the temperature measuring tube 15 is installed on the flange 16, and is located between the PTC heating tube 15 and the electric heater 13, that is, the electric heater 13, the temperature measuring tube 14 and the PTC are arranged in sequence from bottom to top in the vertical direction. The heating pipe 15 can better monitor the water temperature, and cut off the power supply circuit of the electric heater 13 in time when the water temperature rises abnormally, so as to further prevent the electric heater 13 from dry-burning.

In addition, the electric water heater also includes a warning module (not shown), and the warning module is electrically connected with the electric control board 12 . In this embodiment, the warning module may be a voice module or an indicator light module, which is used to warn the user of the heating state of the electric water heater. When the current signal detected by the detection circuit 30 is abnormal, the electric control board 12 sends corresponding warning information to the warning module. The user is reminded that the water level of the electric water heater is too low, and the electric heater 13 may be in danger of dry burning, which further improves the safety of the electric water heater.

It is worth mentioning that, in the above embodiments, the control circuit 20 is preferably a relay control circuit, the control loop of the relay control circuit is connected in series with the current signal output terminal of the detection circuit 30, and the main circuit of the relay control circuit is connected to the electric heater 13 The power supply loop of the electric heater 13 is connected in series, so the closing and opening of the main circuit of the relay control circuit can be controlled according to the output current of the detection circuit 30, so as to realize the on-off control of the power supply loop of the electric heater 13. When using the hot water of the electric water heater, the water level in the inner tank 11 will gradually drop. When the water level drops below the position where the PTC heating tube 15 is located, the PTC heating tube 15 will be exposed to the water surface, and the PTC heating tube 15 will be dry. The resistance value of the PTC heating tube 15 also increases sharply, so the current of the power supply circuit of the PTC heating tube 15 decreases sharply, and the output current of the detection circuit 30 decreases accordingly. At this time, the main circuit of the relay control circuit is disconnected. , thereby cutting off the power supply circuit of the electric heater 13, the electric heater 13 stops heating, and realizes anti-dry heating protection. It can be seen that the control circuit 20 of the present invention has the characteristics of simple structure, low cost, stability and reliability. It should be noted that, in other embodiments of the utility model, the control circuit 20 may also be in any other applicable structural form, which will not be repeated here.

The specific structural form of the PTC heating tube 15 of the anti-dry burning device of the present utility model is described in detail below:

Specifically, referring to FIG. 3 and FIG. 4 , the PTC heating tube 15 includes a metal outer tube 151 with one end closed, an insulating end cap 152 , a first lead rod 154 , a second lead rod 155 , a PTC heating element 156 and an insulating and heat-conducting medium 153 . Wherein, the insulating and heat-conducting medium 153 is a powdery material, which has good insulation and heat-conducting capabilities. The insulating and heat-conducting medium 153 is filled in the metal outer tube 151, so that the metal outer tube 151 forms a solid body, which is beneficial to heat the inside of the PTC heating tube 15. The heat is transferred to the water body in the inner tank 11. In a preferred embodiment, the insulating and heat-conducting medium 153 is magnesium oxide powder, and of course it can also be any other suitable insulating and heat-conducting material; the PTC heating element 156 is embedded in the insulating and heat-conducting medium 153 , and arranged along the length direction of the metal outer tube 151; the insulating end cap 152 is made of a material with high temperature resistance and good insulation performance, and the insulating end cap 152 is sealed and connected with the open end of the metal outer tube 151. In a preferred embodiment , the insulating end cap 152 is provided with an external thread, and the metal outer tube 151 is provided with an external thread of the insulating end cap 152 to be screwed with a suitable internal thread, and the insulating end cap 152 and the metal outer tube 151 are sealed and fixed by threaded connection; the first lead rod 154 And the second lead rod 155 is made of a material with better electrical conductivity, such as copper, the first lead rod 154 and the second lead rod 155 pass through the insulating end cover 152 and partly extend into the metal outer tube 151, and the PTC heating element 156 are respectively electrically connected with the first lead rod 154 and the second lead rod 155 located in the metal outer tube 151, the first lead rod 154 and the second lead rod 155 are located in the outer part of the metal outer tube 151 and the PTC heating tube 15 The power supply circuit is connected, that is, the first lead rod 154 is electrically connected to the second lead rod 155 via the PTC heating element 156 .

Referring again to FIG. 3 , in one embodiment, the PTC heating element 156 is a PTC metal heating wire, one end of the PTC metal heating wire is electrically connected to the first lead rod 154 , and the other end is electrically connected to the second lead rod 155 . The PTC metal heating wire in this embodiment is preferably a spring type, so the total length of the PTC metal heating wire can be extended, the heating efficiency can be improved, and at the same time, the anti-dry heating device can be guaranteed to work more reliably. Referring to Figure 6, it can be seen from the graph of the relationship between the temperature and the resistivity of the PTC metal heating wire that as the temperature of the PTC metal heating wire increases, its resistance value also increases incrementally. It can be seen that when the water level drops below When the PTC heating tube 15 is at the position, the PTC heating tube 15 is dry-burned, and its temperature rises sharply. According to the characteristics of the PTC, its resistance value also increases sharply. The detection circuit 30 detects an abnormal current signal. The abnormal current signal provided by the circuit 30 cuts off the power supply circuit of the electric heater 13, and the electric heater 13 stops heating, thereby realizing the protection against dry heating. Therefore, the anti-dry heating device of the present utility model is not only simple in structure, but also can perform anti-dry heating protection in time and accurately, so as to ensure safe and reliable electricity consumption.

Referring to FIG. 4 again, in another embodiment, the PTC heating element 156 is a rod-shaped PTC ceramic, and the PTC ceramic is sandwiched between the first lead rod 154 and the second lead rod 155 . It should be noted that, in order to make the PTC ceramic conduct electricity and generate heat sufficiently, the PTC ceramic is in full electrical contact with the first lead rod 154 and the second lead rod 155 respectively in the longitudinal direction of the PTC ceramic. Referring to Figure 7, it can be seen from the temperature and resistance characteristic curve of PTC ceramics that as the temperature of PTC ceramics increases, especially after the temperature exceeds the Curie point, its resistance value increases stepwise. It can be seen that when When the water level drops below the position where the PTC heating tube 15 is located, the PTC heating tube 15 is dry-burned, and its temperature rises sharply. According to the characteristics of the PTC, its resistance value also increases sharply. The detection circuit 30 detects an abnormal current signal. The control circuit 20 cuts off the power supply circuit of the electric heater 13 according to the abnormal current signal provided by the detection circuit 30, and the electric heater 13 stops heating, thereby realizing the protection against dry heating. Therefore, the anti-dry heating device of the present utility model is not only simple in structure, but also can perform anti-dry heating protection in time and accurately, so as to ensure safe and reliable electricity consumption.

Further, the first lead rods 154 , the second lead rods 155 and the PTC ceramics are arranged in parallel and extend to a position close to the end of the metal outer tube 151 . The PTC heating tube 15 with this structure has a better heating effect, which is beneficial to save electric energy, and at the same time ensures the reliable operation of the PTC heating tube 15 and avoids the phenomenon of dry burning of the electric heater 13 .

It should be understood that the above are only preferred embodiments of the present utility model, and cannot therefore limit the patent scope of the present utility model. Any equivalent structure or equivalent flow conversion made by using the utility model specification and accompanying drawings, or directly or Indirect applications in other related technical fields are all included in the scope of patent protection of the utility model in the same way.

Claims (10)

1. An anti-dry device, which is suitable for the anti-dry protection of electric heaters, is characterized in that the anti-dry device comprises a PTC heating tube, a detection circuit and a control circuit, wherein: The power supply circuit of the PTC heating tube is electrically connected to the detection circuit, and the detection circuit is electrically connected to the control circuit; The detection circuit is used to detect the current signal of the power supply circuit of the PTC heating tube, and the control circuit controls the on-off of the power supply circuit of the electric heater according to the current signal. 2. The anti-dry device according to claim 1, wherein the PTC heating tube comprises a metal outer tube with one end closed, an insulating end cap, a first lead rod, a second lead rod, a PTC heating element, and an insulating Heat-conducting medium: the insulating and heat-conducting medium is filled in the metal outer tube, the PTC heating element is buried in the insulating and heat-conducting medium, the insulating end cap is sealed and connected with the open end of the metal outer tube, the The first lead rod and the second lead rod pass through the insulating end cap and partially extend into the metal outer tube, and the first lead rod is electrically connected to the second lead rod through the PTC heating element. 3. anti-dry device as claimed in claim 2, is characterized in that, described PTC heating element is PTC metal heating wire, and one end of described PTC metal heating wire is electrically connected with described first lead rod, and the other end is with The second lead rod is electrically connected. 4. The anti-dry burning device according to claim 2, characterized in that, the PTC heating element is a rod-shaped PTC ceramic, and the PTC ceramic is sandwiched between the first lead rod and the second lead rod. 5. The anti-dry burning device according to claim 4, characterized in that, the first lead rod, the second lead rod and the PTC ceramics are arranged in parallel and extend to a position close to the end of the metal outer tube. 6. The anti-dry burning device according to claim 2, wherein the insulating and heat-conducting medium is magnesium oxide powder. 7. An electric water heater, comprising an inner container and an electric heater, the electric heater is installed on the inner container through a flange, characterized in that the electric water heater also includes the electric heater according to any one of claims 1 to 6. The anti-dry heating device described above includes a PTC heating tube, a detection circuit and a control circuit, wherein: The power supply circuit of the PTC heating tube is electrically connected to the detection circuit, and the detection circuit is electrically connected to the control circuit; The detection circuit is used to detect the current signal of the power supply circuit of the PTC heating tube, and the control circuit controls the on-off of the power supply circuit of the electric heater according to the current signal. 8. The electric water heater according to claim 7, wherein the PTC heating pipe is installed on the flange and is located above the electric heater. 9. The electric water heater according to claim 7, characterized in that, the electric water heater also includes a temperature measuring tube, the temperature measuring tube is installed on the flange, and is located between the PTC heating tube and the electric heating tube. between devices. 10. The electric water heater according to any one of claims 7 to 9, characterized in that the electric water heater further comprises an electric control board and a warning module, and the warning module is electrically connected to the electric control board.