A control device and method for starting an electric heater in a low temperature environment and an electric heater

Abstract

The present invention provides a control device, method and electric heater for starting an electric heater in a low temperature environment, the control device includes a heating module; a motor detection module, the motor detection module is used to detect the load condition of the motor and obtain the current value of the motor in real time; a control module, the control module is electrically connected to the motor detection module, and can receive the current value obtained by the motor detection module and compare it with a preset current threshold and judge the load condition of the motor according to the comparison result; the control module is configured to control the operation mode of the heating module according to the load condition of the motor to control the heating amount of the heating module. Based on the technical solution of the present invention, according to the comparison result between the current value and the current threshold when the motor is started, when the motor load is too large and the air volume is reduced, the heating amount of the heating module is reduced to avoid the problem of triggering the overheating protection of the temperature limiter due to the inability to transfer the heat in time due to the reduction of the motor air volume.

Description

Technical Field

[0001] The present invention relates to the technical field of electric heaters, and in particular to a control device and method for starting an electric heater in a low-temperature environment, and an electric heater. Background Art

[0002] At present, the winter temperature in some parts of China is low and heating is not provided, so users mainly use electric heaters for heating. Many users have reported that after the electric heater is left in a low temperature environment for a long time, the overheat protection of the internal temperature limiter will be triggered after the whole machine starts running for a period of time, causing the electric heater to fail to operate normally.

[0003] After analysis, it was found that the reason why the overheat protection of the temperature limiter was triggered and the electric heater could not operate normally was that the motor of the electric heater was in a low temperature environment for a long time, and its lubricating oil became thicker and its fluidity decreased, and the lubrication effect was weakened, causing the motor speed to drop and the air volume to decrease. The reduced air volume of the motor made it impossible for the heat generated by the electric heater of the whole machine to dissipate in time, causing the heat to accumulate inside the electric heater, thereby triggering the overheat protection of the temperature limiter of the whole machine, causing the electric heater to be unusable, affecting the user experience.

[0004] To solve this problem, it is necessary to design a control device and a control method to meet the startup requirements of the electric heater in a low temperature environment. Summary of the invention

[0005] In response to the problems in the above-mentioned prior art, the present application proposes a control device, method and electric heater for starting an electric heater in a low-temperature environment. According to the comparison result of the current value when the motor starts and the current threshold, the heat generation of the heating module is reduced when the motor load is too large and the air volume is reduced, so as to avoid the problem of triggering the overheating protection of the temperature limiter due to the inability to transfer heat in time due to the reduction of the motor air volume.

[0006] In a first aspect, the present invention provides a control device for starting an electric heater in a low temperature environment, comprising:

[0007] Heating module;

[0008] A motor detection module, which is used to detect the load condition of the motor and obtain the current value of the motor in real time;

[0009] A control module, wherein the control module is capable of receiving the current value acquired by the motor detection module and comparing it with a preset current threshold value, and determining the load condition of the motor according to the comparison result;

[0010] The control module is configured to control the operation mode of the heating module according to the load condition of the motor so as to control the heat generation of the heating module.

[0011] In one embodiment, the control module is configured to: control the heating module to operate in a normal mode when the current value is less than the current threshold, and control the heating module to operate in a duty cycle mode when the current value is greater than the current threshold;

[0012] The heating module generates less heat in the duty cycle mode than in the normal mode.

[0013] In one embodiment, the control module includes a power supply control unit, which is connected to the power supply circuit of the heating module and is used to control the normal power supply to the heating module or the power supply according to a preset duty cycle.

[0014] In one embodiment, the heating module is a PTC electric heater. According to this embodiment, the PTC electric heater is a heating device commonly used in electric heaters, and is suitable for electric heater products corresponding to the actual control device.

[0015] In a second aspect, the present invention proposes a control method for starting an electric heater in a low temperature environment, which is applied to the above-mentioned control device and includes:

[0016] Real-time acquisition of the motor current value after the electric heater is started;

[0017] comparing the current value with a current threshold;

[0018] The operation mode of the heating module of the electric heater is controlled according to the comparison result to control the heating value thereof.

[0019] In one embodiment, controlling the operation mode of the heating module of the electric heater according to the comparison result includes:

[0020] When the current value is less than the current threshold, it is determined that the motor load is normal, and the heating module of the electric heater is powered normally;

[0021] When the current value is greater than the current threshold, it is determined that the motor load is too large, and the heating module of the electric heater is powered according to a preset duty cycle to reduce the heat generated.

[0022] In one embodiment, before obtaining the current value of the motor after the electric heater is started in real time, the control method further includes: determining the current threshold. According to this embodiment, the current threshold is determined first, so that the working condition of the motor can be accurately judged according to the current value.

[0023] In one embodiment, determining the current threshold comprises:

[0024] In a low temperature environment, a relationship between the current value change during the motor startup operation and whether the overheat protection of the temperature limiter is triggered is established to determine the current threshold. Through this embodiment, the relationship between the current value change and whether the overheat protection of the temperature limiter is triggered is established through experiments, so that the current threshold can be determined more accurately.

[0025] In one embodiment, before the heating module of the electric heater is powered at a preset duty cycle, the control method further includes: determining the preset duty cycle corresponding to the acquired current value. Through this embodiment, the preset duty cycle is determined first, and then the heating module can be powered accordingly, meeting the requirement of not triggering overheat protection.

[0026] In one embodiment, determining the preset duty cycle corresponding to the acquired current value includes:

[0027] In a low temperature environment, the premise of not triggering the overheat protection of the temperature limiter is met, the relationship between the current value x and the duty cycle Y during the motor startup operation is established and a functional relationship f(x) is established to determine the preset duty cycle.

[0028] In one embodiment, the duty cycle Y corresponding to the current value x in the functional relationship f(x) satisfies the shortest time required for the motor to recover from the current state to the normal state. Through this embodiment, the heating module is powered according to the duty cycle Y corresponding to the functional relationship f(x), and the entire process of starting and recovering the motor takes the shortest time, so that normal heating can be provided to the user more quickly, improving the user experience.

[0029] In a third aspect, the present invention provides an electric heater, which includes the above-mentioned control device.

[0030] The above technical features can be combined in various suitable ways or replaced by equivalent technical features as long as the purpose of the present invention can be achieved.

[0031] The control device, method and electric heater for starting an electric heater in a low temperature environment provided by the present invention have at least the following beneficial effects compared with the prior art:

[0032] The present invention provides a control device, method and electric heater for starting an electric heater in a low temperature environment. When the electric heater is started in a low temperature environment, the load condition of the motor when starting is determined by comparing the current value of the motor inside the electric heater with the current threshold, and the heating value of the heating module can be controlled according to the load condition of the motor. Thus, when the motor load is too large and the air volume is reduced, the heating value of the heating module is reduced to avoid the heat being unable to be transferred out in time due to the reduction of the motor air volume, thereby avoiding triggering the overheating protection of the temperature limiter and causing the electric heater to shut down, thereby ensuring the normal use of the electric heater. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be described in more detail below based on embodiments and with reference to the accompanying drawings, wherein:

[0034] Figure 1 A schematic diagram showing the structure of the control device of the present invention is shown;

[0035] Figure 2 A control flow chart of the control method of the present invention is shown.

[0036] In the drawings, like reference numerals are used for like parts. The drawings are not necessarily to scale.

[0037] Reference numerals:

[0038] 10-heating module, 20-motor detection module, 30-control module. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the accompanying drawings.

[0040] The present invention provides a control device for starting an electric heater in a low temperature environment, comprising:

[0041] Heating module 10;

[0042] The motor detection module 20 is used to detect the load condition of the motor and obtain the current value of the motor in real time;

[0043] The control module 30 can receive the current value obtained by the motor detection module 20 and compare it with a preset current threshold value, and judge the load condition of the motor according to the comparison result;

[0044] The control module 30 is configured to control the operation mode of the heating module 10 according to the load condition of the motor so as to control the heat generation of the heating module 10 .

[0045] Specifically, as shown in the attached figure Figure 1 As shown, the control device mainly includes a heating module 10, a motor detection module 20 and a control module 30. The heating module 10 is a heating component inside the electric heater, which generates heat according to the heating needs of the user; the motor detection module 20 and the motor monitoring module are used to detect the current value of the motor in real time and reflect the load condition of the motor; the control module 30 is used to control the operation of the motor monitoring module and the heating module 10, and at the same time control the operation mode of the heating module 10 according to the motor current value obtained by the motor monitoring module.

[0046] The electric heater of the present invention generates heat through a heating module 10, and then transfers the heat in the form of hot air through the operation of the motor to achieve heating for the user. When the electric heater is placed in a low-temperature environment for a long time and started, the lubrication effect of the motor decreases, the motor speed decreases, and the air volume decreases due to the low ambient temperature, and the heat generated by the heating module 10 cannot be transferred out in the form of hot air in time. Heat continues to accumulate inside the electric heater and causes the temperature to rise, and eventually the overheating protection of the temperature limiter is triggered due to the high temperature, and finally the electric heater is shut down due to overheating.

[0047] When the motor is started in a low temperature environment, the motor load is large, and the current value at this time is larger than the current value under normal operation. Therefore, by detecting the current value during the motor startup process and comparing it with the preset current threshold, the operation and load conditions of the motor at this time can be judged. According to the comparison result of the motor current value and the current threshold, the control module 30 controls the operation mode of the heating module 10 to obtain different amounts of heat. Ensure that if the motor air volume is reduced, excessive heat generation is avoided to trigger the overheating protection of the temperature limiter.

[0048] It should be noted that the current threshold should be determined according to the ambient temperature, because the ambient temperature directly determines the load and the current value of the motor during the starting process.

[0049] Preferably, the heating module 10 is a PTC electric heater.

[0050] In one embodiment, the control module 30 is configured to: control the heating module 10 to operate in normal mode when the current value is less than the current threshold, and control the heating module 10 to operate in duty cycle mode when the current value is greater than the current threshold; the heat generated by the heating module 10 in the duty cycle mode is less than the heat generated in the normal mode.

[0051] Specifically, when the current value of the motor is less than the current threshold, it indicates that the load of the motor is normal at this time, and the air volume during its startup operation can meet the requirements of timely heat transfer. At this time, the heating module 10 is controlled to operate in normal mode, that is, the heating module 10 is fully loaded and its heat generation is the rated value. When the current value of the motor is greater than the current threshold, it indicates that the load of the motor is beyond the normal range and the load is large. The air volume during its startup operation cannot meet the requirements of timely heat transfer, so the heat generation of the heating module 10 needs to be reduced at this time, and the heating module 10 is controlled in duty cycle mode. The heating module 10 in duty cycle mode is not fully loaded, and the heat generation is less than its rated value. At this time, the heat generation will not trigger the overheating protection of the temperature limiter.

[0052] It should be noted that for the case where the current value is equal to the current threshold, it can be set according to the actual situation, and can be classified as a situation where the motor load is normal or a situation where the motor load is normal.

[0053] In one embodiment, the control module 30 includes a power supply control unit, which is connected to the power supply circuit of the heating module 10 and is used to control the normal power supply to the heating module 10 or the power supply according to a preset duty cycle.

[0054] Specifically, the control module 30 controls the operation mode of the heating module 10 by controlling the power supply. In the normal mode, the heating module 10 is supplied with the rated power, and in the duty cycle mode, the heating module 10 is supplied with the power less than the rated power demand.

[0055] The present invention provides a control method for starting an electric heater in a low temperature environment, which is applied to the aforementioned control device and includes:

[0056] Step S100: determining a current threshold;

[0057] The ambient temperature directly affects the operation and load conditions of the motor when it starts, so the current value when the motor starts is directly related to the ambient temperature, and thus the determination of the current threshold has a certain relationship with the temperature. The current threshold is further determined through step S101.

[0058] Step S101: In a low temperature environment, a relationship between a change in current value during the motor startup operation and whether the overheat protection of the temperature limiter is triggered is established to determine a current threshold.

[0059] For the electric heater, multiple groups of startup and operation experiments were conducted after long-term storage in low-temperature environments. The ambient temperature of each group of experiments was different. By monitoring the motor current throughout the process, the relationship between the motor current value and whether the temperature limiter was triggered for overheating protection at different ambient temperatures was established, and a current value obtained in the experiment was determined as the current threshold.

[0060] For example, when the electric heater is started in a low-temperature environment, due to the heating of the electric heater and the motor itself, the lubrication performance of the motor gradually recovers, the load of the motor gradually returns to normal from excessive, and the current value of the motor gradually decreases. When the current value of the motor decreases to a certain value x1, the overheating protection of the temperature limiter may be triggered because the heat is not transferred out in time and accumulates. At this time, the current value x1 can be used as the current threshold, so that the heat accumulated by the heating module during the process from the start of the motor to the current value being reduced to x1 can be reduced, avoiding triggering the overheating protection of the temperature limiter. Of course, in the above example, the set current threshold can also be adjusted according to the actual situation. As long as the heating module can be controlled with reference to the current threshold, the heat generated during the process from the start of the motor to the current value being reduced to x1 can be reduced.

[0061] Under different ambient temperatures, the current value when the motor starts will be different, that is, the lower the ambient temperature, the greater the load when the motor starts and the larger the current value; therefore, we first obtain the relationship between the overheating protection of the temperature limiter and the current value at different ambient temperatures based on experiments, and then combine the possible temperature range of the actual application environment of the electric heater with reference to the current value data of multiple groups of experiments to set a current threshold that covers the possible ambient temperature range of its application environment as much as possible.

[0062] Step S110: obtaining in real time the current value of the motor after the electric heater is started;

[0063] After the electric heater is started, a command is synchronously issued to obtain the current value of the motor. The current value of the motor obtained is the current value data during its startup process, that is, the process from startup to normal operation.

[0064] Step S120: comparing the current value with the current threshold;

[0065] After the current value of the motor is obtained, the current value is compared with the current threshold. The comparison result between the current value and the preset current threshold reflects the operation and load status of the motor during the starting process.

[0066] Step S130: controlling the operation mode of the heating module of the electric heater according to the comparison result to control the heating amount thereof;

[0067] Step S131: when the current value is less than the current threshold, it is determined that the motor load is normal, and the heating module of the electric heater is powered normally;

[0068] When the motor load is normal, the motor speed can meet the heat dissipation requirements of the heating module when it is heating normally. At this time, the heating module is powered normally and the whole machine operates normally. This state indicates that the electric heater may not be in a low temperature environment;

[0069] Step S132: when the current value is greater than the current threshold, it is determined that the motor load is too large, a preset duty cycle corresponding to the acquired current value is determined, and the heating module of the electric heater is powered according to the preset duty cycle to reduce the heat generation;

[0070] In step S132, the preset duty cycle is determined as follows:

[0071] In a low temperature environment, the premise of not triggering the overheat protection of the temperature limiter is met, and the relationship between the current value x and the duty cycle Y during the motor startup process is established and a functional relationship f(x) is established to determine the preset duty cycle; the duty cycle Y corresponding to the current value x in the functional relationship f(x) satisfies the shortest time required for the motor to recover from the current state to the normal state.

[0072] The heating module will heat the motor while generating heat, which helps to restore the motor's own lubrication performance. Therefore, under the premise that the heat generated by the heating module is not too large to trigger the overheating protection of the temperature limiter, theoretically, the greater the heat generated by the heating module, that is, the larger the duty cycle Y, the shorter the time T taken for the motor to recover to normal state. The shorter the time T, the more it meets the user's usage needs.

[0073] The whole electric heater was subjected to multiple groups of startup and operation experiments after being placed in a low-temperature environment for a long time. On the premise that the temperature limiter does not trigger the overheat protection after the whole machine is started, the relationship between different duty cycles Y and the time T and current value x taken for the motor to recover to the normal state was established. That is, based on a certain current value x, multiple groups of experiments were conducted to determine the time T taken for the motor to recover to the normal state when the heating module was running at different duty cycles Y; for a certain current value x, the duty cycle Y with the minimum time T taken for the motor to recover to the normal state is the best choice. The functional relationship f(x) between the duty cycle Y and the current value x of the motor that was finally determined reflects the optimal duty cycle Y that can minimize the time T taken for the motor to recover to the normal state corresponding to the current value x when the motor is started.

[0074] Therefore, the preset duty cycle in step S132 is the optimal duty cycle Y that minimizes the time T required for the motor to return to a normal state.

[0075] It should be noted that, based on the example in step S101, the current threshold value needs to be further determined based on the relationship between the current value x1 when the overheat protection of the temperature limiter is triggered and the current value x′ of the motor in a normal state and in combination with the specific value of the duty cycle Y:

[0076] If the current value x1 when the temperature limiter overheat protection is triggered is exactly equal to the current value x′ when the motor is in a normal state, that is, the temperature limiter overheat protection is triggered when the motor starts and just recovers to normal, then under the condition that other conditions remain unchanged, theoretically the current threshold value can be set to be larger than x1 and smaller than the current value when the motor starts. In this way, no matter what the duty cycle Y is (as long as it is less than 100%), the total heat accumulated in the process from motor starting to the current value decreasing to x1 (x′) can be reduced, and the temperature limiter overheat protection will not be triggered.

[0077] If the current value x1 when the overheat protection of the temperature limiter is triggered is greater than the current value x' when the motor is in a normal state, it means that the total heat accumulated during the process from when the motor starts to when the current value is reduced to x1 has triggered the overheat protection of the limiter. By controlling the heating module to reduce the accumulated heat in this process, it can only be ensured that the overheat protection of the limiter is not triggered when the current value is x1. There is also a process of heat accumulation between the current value x1 and the current value x' when the motor returns to a normal state, and it must be ensured that the heat accumulated in the latter section is not greater than the heat reduced in the former section. This requires the specific value of the duty cycle Y corresponding to the former section to be controlled. Taking the current value x1 when the overheat protection of the limiter is triggered as the boundary, it is necessary to control the specific value of the duty cycle Y to ensure that the heat reduced by the heating module in the former section when the heating module operates according to the duty cycle Y is greater than the heat accumulated again inside the electric heater when the heating module operates normally in the latter section. The specific value of the duty cycle Y is set based on the process of determining the preset duty cycle in the above step S132.

[0078] Reference Figure 2 The flow chart of the control method of the present invention is shown:

[0079] a. The electric heater starts as a whole, the motor starts synchronously, and the current value x0 when the motor starts is detected and obtained;

[0080] b. Determine the magnitude of the current value x0 obtained when the motor starts and the preset current threshold value A;

[0081] If the current value x0 is less than the current threshold A, it is determined that the motor load and the air volume are normal, and the heating module of the electric heater is powered normally;

[0082] If the current value x0 is greater than the current threshold A, it is judged that the motor load is too large and the air volume is reduced, and the heating module of the electric heater is powered according to the preset duty cycle;

[0083] c. When the heating module of the electric heater is powered according to the preset duty cycle, the current value of the motor gradually decreases, and the real-time current value x of the motor is continuously obtained. i And make a size judgment with the preset current threshold A;

[0084] At the current value x i Before the current is less than the current threshold A, it is determined that the motor state has not returned to normal, and the heating module is continuously powered according to the preset duty cycle;

[0085] At the current value x i When the current is less than the current threshold A, it is determined that the motor is restored to normal and the air volume is normal, and the power supply to the heating module of the electric heater is switched to normal power supply;

[0086] d. Control is completed and the electric heater operates normally.

[0087] The case where the current value x is equal to the current threshold value A has been explained in the foregoing content, that is, it can be classified as a case where the motor load is normal or a case where the motor load is excessive according to actual needs.

[0088] The present invention provides an electric heater, which includes the aforementioned control device and thus has all the technical effects possessed by the control device.

[0089] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "bottom", "top", "front", "back", "inside", "outside", "left", "right", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0090] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in other described embodiments.

Claims

1. A control device for starting an electric heater in a low temperature environment, characterized in that: include: Heating module; A motor detection module, which is used to detect the load condition of the motor and obtain the current value of the motor in real time; A control module, wherein the control module is capable of receiving the current value acquired by the motor detection module and comparing it with a preset current threshold value, and determining the load condition of the motor according to the comparison result; The control module is configured to control the operation mode of the heating module according to the load condition of the motor so as to control the heat generation of the heating module; The control module is further configured to: control the heating module to operate in a normal mode when the current value is less than the current threshold, and control the heating module to operate in a duty cycle mode when the current value is greater than the current threshold; The heating module generates less heat in the duty cycle mode than in the normal mode.

2. The control device for starting an electric heater in a low temperature environment according to claim 1, characterized in that: The control module comprises a power supply control unit, which is connected to the power supply circuit of the heating module and is used to control the normal power supply to the heating module or the power supply according to a preset duty cycle.

3. The control device for starting an electric heater in a low temperature environment according to claim 1, characterized in that: The heating module is a PTC electric heater.

4. A control method for starting an electric heater in a low temperature environment, applied to the control device according to any one of claims 1 to 3, characterized in that: include: Real-time acquisition of the motor current value after the electric heater is started; comparing the current value with a current threshold; The operation mode of the heating module of the electric heater is controlled according to the comparison result to control the heating value thereof.

5. The control method for starting an electric heater in a low temperature environment according to claim 4, characterized in that: The operation mode of the heating module of the electric heater is controlled according to the comparison result, including: When the current value is less than the current threshold, it is determined that the motor load is normal, and the heating module of the electric heater is powered normally; When the current value is greater than the current threshold, it is determined that the motor load is too large, and the heating module of the electric heater is powered according to a preset duty cycle to reduce the heat generated.

6. The control method for starting an electric heater in a low temperature environment according to claim 4 or 5, characterized in that: Before obtaining the current value of the motor after the electric heater is started in real time, the control method further includes: The current threshold is determined.

7. The control method for starting an electric heater in a low temperature environment according to claim 6, characterized in that: Determining the current threshold comprises: In a low temperature environment, a relationship between a change in the current value during the motor startup operation and whether the overheat protection of the temperature limiter is triggered is established to determine the current threshold.

8. The control method for starting an electric heater in a low temperature environment according to claim 5, characterized in that: Before supplying power to the heating module of the electric heater according to a preset duty cycle, the control method further includes: The preset duty cycle corresponding to the acquired current value is determined.

9. The control method for starting an electric heater in a low temperature environment according to claim 8, characterized in that: Determining the preset duty cycle corresponding to the acquired current value includes: In a low temperature environment, the premise of not triggering the overheat protection of the temperature limiter is met, the relationship between the current value x and the duty cycle Y during the motor startup operation is established and a functional relationship f(x) is established to determine the preset duty cycle.

10. The control method for starting an electric heater in a low temperature environment according to claim 9, characterized in that: The duty cycle Y corresponding to the current value x in the functional relationship f(x) satisfies the requirement that the time taken for the motor to recover from the current state to the normal state is the shortest.

11. An electric heater, characterized in that: It comprises the control device according to any one of claims 1 to 3.

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