JP2015108458A - Fluid heating control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluid heating control device having a configuration where a heat exchanger is controlled by combining feed forward control and feedback control, and preventing outflow of high-temperature hot water even when the feedback control is not normally functioned due to malfunction of an outflow water temperature sensor.SOLUTION: The fluid heating control device includes: an operation part 11 receiving setting of hot water temperatures; and an electric heater 14 where an incurrent water temperature sensor 12 and an outflow water temperature sensor 13 are installed. The control value of feedback control is limited under an upper limit value determined by referring to the control value of feed forward control.

Description

  The present invention relates to a fluid heating control device that is incorporated in a toilet device with a hot water cleaning function and performs heating control of cleaning water.

  The following patent document 1 is mentioned as an example of the prior art which concerns on the above fluid heating control apparatuses. In the sanitary washing device, there are a water thermistor and a water thermistor installed in the heat exchanger, and if the difference between the predicted hot water temperature predicted from the incoming water temperature and the hot water temperature detected by the hot water thermistor is large, It is described that the power supply to the exchanger is cut off.

  The sanitary washing apparatus described in Patent Document 1 basically seems to control the heat exchanger by feedforward control with respect to the incoming water temperature. However, when the heat exchanger is controlled by feedforward control, an error between the set temperature and the tapping temperature may increase due to factors such as room temperature. Therefore, if the control method is improved and the heat exchanger is controlled by combining the feedforward control and the feedback control, the error between the set temperature and the tapping temperature can be further reduced.

JP 2012-046969

  When feedforward control and feedback control are combined, even if feedforward control is not performed normally due to failure of the incoming thermistor, etc., if the outgoing thermistor is normal, feedback control will prevent the low-temperature hot water or hot hot water to some extent. it can. However, when the water discharge thermistor breaks down and feedback control is not normally performed, it is difficult to prevent high temperature hot water caused by the feed forward control.

  Since such high temperature hot water can naturally occur, a mechanical fail-safe function should also be incorporated as a preventive measure. Specifically, the power supply is forcibly cut off using a thermosensitive element such as a thermostat. However, before activating such a mechanical fail-safe function, it is desirable to activate the fail-safe function by software processing to prevent high-temperature hot water discharge and keep the hot-water temperature within an appropriate range. The present invention aims to realize such a demand.

  A fluid heating control apparatus according to the present invention includes an operation unit that receives a hot water temperature setting and an electric heater provided with an incoming water temperature sensor and an outgoing water temperature sensor, and performs feedforward control for incoming water temperature and feedback control for outgoing water temperature. A fluid heating control device for controlling energization of an electric heater in combination, wherein a control value of the feedback control is limited to an upper limit value or less determined by referring to a control value of the feedforward control. To do.

  The total value of the control value of the feedforward control and the control value of the feedback control is compared with the fail-safe upper limit value calculated by a predetermined function of the incoming water temperature, and the electric heater is based on a smaller value among them May be energized.

  The predetermined function may be obtained by multiplying a temperature difference between the predetermined upper limit temperature and the incoming water temperature by a coefficient.

  The predetermined function may be obtained by multiplying a temperature difference between the predetermined upper limit temperature and the incoming water temperature by a coefficient and further adding a constant.

  The electric heater heats human body washing water, and the coefficient is obtained when the electric heater that exhibits the upper limit capability or the lower limit capability within a tolerance is controlled based on the fail-safe upper limit value. The water temperature may be selected so as to be within an allowable range of human body washing water.

  According to the present invention, the control value of the feedback control is limited to the upper limit value or less determined with reference to the control value (incoming water temperature) of the feedforward control. Therefore, even if feedback control is not normally performed due to a failure of the water temperature sensor, high temperature hot water can be prevented.

It is a principal part block diagram of the fluid heating control apparatus made into an example of embodiment of this invention. It is the graph which showed the time change of the water temperature when energization control of the electric heater was carried out only by feedforward control, and when the electric heater was energized and controlled by combining feedforward control and feedback control. It is the graph which showed the heating temperature in 2 examples of electricity supply control of an electric heater, and the water temperature as a function of water temperature. It is the graph which showed the heating temperature in the other example of electricity supply control of an electric heater, and the outgoing water temperature as a function of incoming water temperature. It is the graph which showed the heating temperature when the electric heater assumed that it was rated power, the upper limit capability in tolerance, and a lower limit capability as a function of incoming water temperature.

  The fluid heating control device according to the present invention is assumed to be incorporated in, for example, a toilet device with a hot water cleaning function, a bathroom hot water supply system, or the like. In such a fluid heating control device, the temperature of the tapping water is basically controlled by software processing using a computer or the like. However, since a computer may malfunction, it is desirable to incorporate a mechanical fail-safe function that prevents hot hot water in particular. Specifically, a thermosensitive element such as a thermostat is used to forcibly shut off the electric heater if the water temperature is abnormal.

  Of course, it is desirable to activate the fail-safe function by software processing before such a mechanical fail-safe function is activated. For example, when the outlet water temperature sensor of the fluid heating control device fails and the maximum electric heater continues to be driven at the maximum power, the mechanical fail-safe function only detects an abnormality in the outlet temperature and shuts off the power supply. For this reason, the hot water temperature that has risen too much will then be too low, which will cause discomfort to the user. The present invention has been devised with the intention of preventing such discomfort, and a fail-safe function by software processing that can keep the hot water temperature within an appropriate range even if the water temperature sensor fails. Propose. Hereinafter, the basic configuration and operation of the fail-safe function by such software processing will be specifically described with reference to drawings and mathematical expressions.

  As shown in FIG. 1, the fluid heating control apparatus according to the present invention includes an operation unit 11 that receives a hot water temperature setting, and an electric heater 14 provided with an incoming water temperature sensor 12 and an outgoing water temperature sensor 13.

  The operation unit 11 is provided with a dial, a slide switch, a selection button, a touch panel, or the like, and accepts operations for hot water temperature setting and flow rate setting by these operations.

  The electric heater 14 has a function of causing heat exchange between a fluid such as tap water passing therethrough and a heat source that generates heat when energized. There is no limit. The incoming water temperature sensor 12 and the outgoing water temperature sensor 13 are composed of, for example, a thermistor, and are provided at the inlet and outlet of the electric heater 14, respectively. A flow sensor 15 is further provided on the water inlet side of the electric heater 14.

  The fluid is preloaded by a pump or the like (not shown), and the flow rate thereof is variably controlled by an electromagnetic valve or the like (not shown) arranged upstream of the flow rate sensor.

  The power supply unit 16 supplies AC or DC power to the electric heater 14. A power supply path from the power supply unit 16 to the electric heater 14 is provided with a switch element 17 that connects and disconnects the power supply. The type of the switch element 17 is not particularly limited, and can be constituted by, for example, a thyristor, a bipolar transistor, a field effect transistor, or the like.

  The control unit 18 includes an arithmetic element such as a microcomputer and an output circuit that controls the switch element 17. The control unit 18 controls energization of the electric heater by combining feedforward control with respect to the incoming water temperature and feedback control with respect to the outgoing water temperature.

  Briefly describing the energization control, the electric heater 14 consumes predetermined power when the switch element 17 is connected, and does not consume power when the switch element 17 is cut off. Therefore, as the energization control, the average power consumption of the electric heater 14 can be freely controlled by adjusting the duty ratio of the drive signal of the switch element 17 by, for example, PWM control.

  In the energization control of the electric heater 14, the feed forward control and the feedback control are basically combined with the former mainly to control the electric heater 14 and to correct the water temperature error based on the environmental conditions such as the incoming water temperature and the room temperature. This is because it is intended to be corrected by the latter.

  More specifically, the feedforward control is based on a specific incoming water temperature and room temperature. As a result, if the incoming water temperature or the room temperature is lower than the prerequisite, the outlet water temperature is lower than the hot water temperature set value. Lower. And vice versa. On the other hand, in the feedback control, the outlet water temperature is controlled to increase when the outlet water temperature is lower than the hot water temperature set value, and is controlled to decrease the outlet water temperature when the outlet water temperature is higher than the hot water temperature set value. Therefore, the error in the water temperature due to the feedforward control can be corrected by the feedback control.

  In FIG. 2, the temporal change of the water temperature when the electric heater is energized and controlled only by the feedforward control is compared with the time change of the water temperature when the electric heater is energized and controlled by combining the feedforward control and the feedback control. doing. In any case, it is assumed that the hot water temperature set value is 40 ° C., and the incoming water temperature or room temperature is higher than the precondition.

  In that case, if the electric heater is energized and controlled only by feedforward control, the water temperature will naturally be higher than the hot water temperature set value. However, if this is combined with feedback control, the water temperature should be close to the hot water temperature set value. Whether the outlet water temperature tends to oscillate with the hot water temperature set value (shown) or asymptotically approaches the hot water temperature set value depends on the capacity of the electric heater, feedforward control and feedback control. Because it depends on various conditions such as how to combine with water, incoming water temperature, room temperature, etc., it cannot be said unconditionally.

  Further, when the feedforward control and the feedback control are combined, it is possible to prevent the temperature of the discharged water from deviating from the hot water temperature set value even when an abnormality occurs in the feedforward control. The feedforward control abnormality occurs, for example, when the incoming water temperature sensor detects 10 ° C. lower than a normal value due to a solder crack or the like. However, when an abnormality occurs in the feedback control due to a failure of the outlet water temperature sensor or the like, the abnormality in the outlet water temperature cannot be suppressed by the feedforward control.

  The present invention proposes to limit the control value of feedback control to a predetermined upper limit value or less as a countermeasure for such a problem. That is, the purpose is to prevent high-temperature hot water by preventing the control value of the feedback control from becoming abnormally high.

  The control value of the feedback control may be limited to a fixed constant as an upper limit value or less, but is preferably limited to an upper limit value or less determined with reference to the control value of the feedforward control.

  Thus, if the control value of the feedback control is limited to the upper limit value or less determined by referring to the control value (incoming water temperature) of the feedforward control, the fluid having a high incoming water temperature is further heated by the maximum power of the electric heater. Such a situation cannot occur and high temperature hot water can be prevented. Moreover, since there is room for sufficient feedback control, it does not adversely affect normal usability.

が成り立つ。これはフィードフォワード御のみの式である。この式に対して、所望の係数Ｋを乗じたフィードバック制御の項を加えることができる。

Hereinafter, the principle of the fail-safe function by software processing will be described in detail using mathematical formulas and the like. First, the basic formula for energization control of the electric heater is shown. Here, fluid flow rate F (grams / minute), set temperature Tset, incoming water temperature Tin, outgoing water temperature Tout, heater rated power consumption W (watts), energization rate control value r (duty ratio of drive pulse of switch element), Specific heat C (calories / gram). The energization control of the electric heater is performed by calculating an energization rate control value r and drivingly controlling the switch element based on the calculated value. Input power per unit time = specific heat x flow rate per unit time x rising temperature.

Holds. This is a formula for feedforward only. A feedback control term multiplied by a desired coefficient K can be added to this equation.

ここに、Ａ項は定数項であって、通電率は、流体の流量Ｆに比例し、ヒータの定格消費電力Ｗに反比例することを示している。Ｂ項はフィードフォワード制御の制御値であり、Ｃ項はフィードバック制御の制御値である。係数Ｋはフィードフォワード制御に対するフィードバック制御の割合を規定する正値であるが、その値は特に制限されず、以下では簡単のため値１を採用する。 The following three terms will be referred to as A term, B term, and C term, respectively.

Here, the term A is a constant term, and the energization rate is proportional to the flow rate F of the fluid and inversely proportional to the rated power consumption W of the heater. The term B is a control value for feedforward control, and the term C is a control value for feedback control. The coefficient K is a positive value that defines the ratio of the feedback control to the feedforward control. However, the value is not particularly limited, and the value 1 is adopted below for simplicity.

としてもよい。ここにＸは定数、Ｔｍａｘは上限温度であって、入水温Ｔｉｎがその上限温度Ｔｍａｘを超えたときには加熱を行わないという値である。これらの値は出水温Ｔｏｕｔの許容範囲等を考慮して決定すればよい。 In the present invention, an upper limit value Cmax determined with reference to the B term is set for the C term.
For example

It is good. Here, X is a constant, Tmax is an upper limit temperature, and when the incoming water temperature Tin exceeds the upper limit temperature Tmax, heating is not performed. These values may be determined in consideration of the allowable range of the water temperature Tout.

であるから、更に換言すれば、Ｂ項＋Ｃ項＞Ｘ・（Ｔｍａｘ−Ｔｉ）となった場合は、Ｂ項＋Ｃ項の代わりに、Ｘ・（Ｔｍａｘ−Ｔｉ）を採用するとしてもよい。 That is, when C term> Cmax, Cmax is adopted instead of C term, but when B term + C term> B term + Cmax, B term + C term is replaced by B In other words, the term + Cmax may be adopted.

Therefore, in other words, when B term + C term> X · (Tmax−Ti), X · (Tmax−Ti) may be adopted instead of the B term + C term.

  In short, the sum of the control value of the feedforward control and the control value of the feedback control is compared with the fail safe upper limit value calculated by a predetermined function of the incoming water temperature Tin, and the electric value is calculated based on the smaller value. That is, the heater is energized. At this time, the predetermined function is X · (Tmax−Tin). That is, the predetermined function is obtained by multiplying the temperature difference between the upper limit temperature Tmax and the incoming water temperature Tin by a coefficient. If such a linear function is used, the control value can be easily calculated.

を採用してもよい。この場合も前記と同様の考え方が成り立ち、入水温Ｔｉｎの所定関数は、Ｘ・（Ｔｍａｘ−Ｔｉ）^２となる。 The upper limit value of the C term is not limited. For example, as an upper limit Cmax determined with reference to the B term

May be adopted. In this case as well, the same concept as described above holds, and the predetermined function of the incoming water temperature Tin is X · (Tmax−Ti) ² .

FIG. 3 shows the heating temperature ΔT and the outlet water temperature Tout when the energization control of the electric heater is performed according to A term · X · (Tmax−Tin) and according to A term · X ′ · (Tmax−Tin) ^2. Is shown as a function of the incoming water temperature Tin. Here, the heating temperature ΔT is defined as the difference between the incoming water temperature Tin and the outgoing water temperature Tout. In the figure, the heating temperature ΔT is indicated by a solid line, and the outlet water temperature Tout is indicated by a broken line. Thus, in any case, if Tmax and X are set appropriately, it is understood that overheating of the outlet water temperature Tout can be suppressed even when the outlet water temperature sensor fails.

を採用してもよい。この場合、所定関数は、Ｘ・（Ｔｍａｘ−Ｔｉｎ）＋Ｔｍｉｎ、すなわち上限温度Ｔｍａｘと入水温Ｔｉｎとの温度差に係数を乗じ、更に定数Ｔｍｉｎを加えたものになる。ここにＴｍｉｎはフィードバック制御における最低限の加熱性能を確保するための定数である。例えばその値を３とすれば、フィードバック制御によって少なくとも３℃の加熱が可能になる。 Moreover, as an upper limit Cmax determined with reference to the B term,

May be adopted. In this case, the predetermined function is X · (Tmax−Tin) + Tmin, that is, a value obtained by multiplying the temperature difference between the upper limit temperature Tmax and the incoming water temperature Tin by a coefficient and further adding a constant Tmin. Here, Tmin is a constant for ensuring the minimum heating performance in the feedback control. For example, if the value is 3, heating at least 3 ° C. is possible by feedback control.

  FIG. 4 shows the heating temperature ΔT and the discharge water temperature Tout when the energization control of the electric heater is performed according to A term · X · (Tmax−Tin) and according to A term · X · (Tmax−Tin) + Tmin. It is shown as a function of the incoming water temperature Tin. Again, the heating temperature ΔT is indicated by a solid line, and the outlet water temperature Tout is indicated by a broken line.

  In the figure, when the energization control of the electric heater is performed according to A term · X · (Tmax−Tin), the heating temperature ΔT1 is very small if the incoming water temperature Tin is close to Tmax. On the other hand, when the energization control of the electric heater is performed according to A term · X · (Tmax−Tin) + Tmin, it can be seen that a heating temperature ΔT2 equal to or higher than Tmin is obtained.

  Finally, the control value limit of the feedback control when the tolerance is expected in the capacity of the electric heater will be considered. The electric heater has a plus or minus tolerance with respect to the rated power due to individual differences of components related thereto, such as a heating element, a fluid path, an incoming water temperature sensor, an outgoing water temperature sensor, and a flow rate sensor. Further, even in a commercial 100V power source that is a power source voltage, the specified range is 101 ± 6V.

  Considering individual differences of parts, a specified range of the power supply voltage, and the like, for example, when the rated power of the electric heater is 1200 W, the upper limit of the allowable range may be assumed to be 1500 W and the lower limit may be about 900 W.

  Here, because of the failure of the water temperature sensor, the water temperature Tout when the electric heater is controlled based on the term A · X · (Tmax−Tin) depends on the capacity of the electric heater when the water temperature Tin is 0 ° C. It becomes like this.

If the electric heater is rated power (1200W)

If the electric heater has an upper limit capacity (1500 W),

If the electric heater is the lower limit capacity (900 W),

On the other hand, when the incoming water temperature Tin is Tmax, regardless of the power consumption of the electric heater,

  What is required here is to keep the water temperature Tout according to Equation 8-11 within the allowable range of human body washing water. Among the equations 8-10, the water discharge temperature Tout according to the equation 9 is the highest. Therefore, if Tmax = 57 ° C. (burn limit) is adopted as the outlet water temperature Tout according to Equation 11, and if the value of X is determined based on the upper limit capability of tolerance, the outlet water temperature Tout according to Equation 9 is set to 57 ° C. The condition is X = 0.8. And if X = 0.8, the outlet water temperature Tout according to Equations 8 and 10 will be 45.6 ° C. and 34.2 ° C., respectively. If X <0.8, the water temperature Tout according to Equation 10 will be too low.

  FIG. 5 shows the heating temperature ΔT and the outlet water temperature Tout as a function of the incoming water temperature Tin when the electric heater is assumed to have the rated power, the upper limit capacity, and the lower limit capacity. The heating temperature ΔT is indicated by a solid line, and the outlet water temperature Tout is indicated by a broken line. As can be understood from the above description, Tmax and X may be selected so that the water discharge temperature Tout in the circles in the figure falls within the allowable range of human body washing water, where Tmax = 57 ° C. and X = 0.8 are An example of such a selection.

  According to the above, when the coefficient (X) is selected and set based on the upper limit capacity of the tolerance of the electric heater, it is possible to control high temperature hot water prevention. Moreover, when the coefficient is selected and set based on the lower limit capability of the tolerance of the electric heater, it is possible to control the low temperature hot water prevention. Therefore, for example, even when the water temperature sensor breaks down, the human body washing water does not become hot water or cold water and can be used safely without making the user uncomfortable.

11 Operation unit 12 Incoming water temperature sensor 13 Outlet water temperature sensor 14 Electric heater

Claims (5)

A fluid that includes an operation unit that receives a hot water temperature setting and an electric heater provided with an incoming water temperature sensor and an outgoing water temperature sensor, and that controls feed of the electric heater by combining feedforward control for incoming water temperature and feedback control for outgoing water temperature. A heating control device,
The fluid heating control device according to claim 1, wherein the control value of the feedback control is limited to an upper limit value or less determined with reference to the control value of the feedforward control. In claim 1,
The total value of the control value of the feedforward control and the control value of the feedback control is compared with the fail-safe upper limit value calculated by a predetermined function of the incoming water temperature, and the electric heater is based on a smaller value among them A fluid heating control device characterized in that energization is controlled. In claim 2,
The fluid heating control apparatus according to claim 1, wherein the predetermined function multiplies a temperature difference between a predetermined upper limit temperature and an incoming water temperature by a coefficient. In claim 3,
The fluid heating control device according to claim 1, wherein the predetermined function is obtained by multiplying a temperature difference between a predetermined upper limit temperature and an incoming water temperature by a coefficient and further adding a constant. In claim 3 or 4,
The electric heater heats human body washing water,
The coefficient is selected so that the water temperature obtained when the electric heater that exhibits the upper limit capacity or the lower limit capacity within the tolerance is controlled based on the fail safe upper limit value falls within the allowable range of human body washing water. A fluid heating control device.

Images