JP2527615B2 - Temperature control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a temperature control device which is applied to a constant temperature bath or the like and precisely controls the temperature of a control target to a set temperature by using a heater and a refrigerating device.

(B) Conventional technology Conventionally, for example, in a plant or a general-purpose incubator, the temperature inside the refrigerator is set to −10 by combining a heater and a refrigerating device.
It can be controlled by setting it in a wide range from ℃ to 50 ℃.
As a method of this control, there are a method in which the heater and the compressor of the refrigerating apparatus are heated or operated in a reverse cycle, and a method in which the compressor is continuously operated to adjust the amount of heat generated by the heater.

(C) Problems to be solved by the invention However, in the former method, the fluctuation of the internal temperature is large,
It is necessary to frequently operate and stop the compressor, there is a problem in durability and startability of the compressor, and there is a problem that the temperature greatly fluctuates.

In the latter method, the heater capacity corresponding to the refrigerating capacity of the compressor is additionally required, and the power consumption is wasted. In particular, since the temperature of the evaporator becomes low due to continuous operation, the amount of dehumidification increases, and there are problems such as drying inside the refrigerator and frost on the evaporator.

 The present invention aims to solve such a problem.

(D) Means for Solving the Problems The present invention is directed to a heater for heating a controlled object, a refrigerating apparatus including an evaporator and a compressor for cooling the controlled object, and an electric motor connected to a suction side of the compressor. The control valve controls the start and stop of the heater and compressor based on the temperature of the controlled object and the set temperature, and the change amount of the deviation between the set temperature and the detected temperature in the output value of the heater per unit time and the deviation. A temperature control device is configured by a control device that controls the opening degree of the electric control valve by adding the change speed of the change amount of the control amount, and controls the temperature of the control target by heating by the heater and cooling by the evaporator. Is.

In addition, the control device has a deviation between the temperature of the controlled object and the set temperature,
The compressor is stopped based on the heater output value and the opening degree of the electric control valve, and the compressor is started based on the deviation and the heater output value.

(E) Action According to the present invention, it is possible to adjust the refrigerating capacity of the refrigerating device by controlling the heater output to be small by the electric control valve regardless of whether the compressor is stopped.

Further, it is possible to reduce wasteful refrigeration capacity and prevent frequent compressor shutdowns.

(F) Embodiment Next, an embodiment will be described with reference to the drawings. FIG. 1 is a refrigerant circuit diagram to which the present invention is applied, and is used for a constant temperature chamber such as a plant or a general-purpose culture chamber. Reference numeral 1 denotes an electric compressor, and the refrigerant discharged from the compressor 1 flows into the condenser 2 to radiate heat, and then is decompressed by the capillary tube 3 and flows into the evaporator 4. The refrigerant evaporates in the evaporator 4 and removes latent heat from the surroundings, so that the evaporator 4 exhibits a refrigerating ability. The refrigerant that has exited from the evaporator 4 passes through the suction pipe 6 and returns to the compressor 1, and the suction pipe 6 is provided with an electric control valve 5.

The valve 5 is driven by, for example, a step motor to adjust its opening degree with high accuracy, thereby increasing or decreasing the flow rate of the refrigerant passing therethrough with high accuracy.
FIG. 2 shows the state of opening of the valve 5 and the evaporator 4 when the compressor 1 is operating.
The following shows the relationship of the refrigerating capacity ratio. Assuming that the refrigerating capacity when the valve 5 is fully opened is 1, the refrigerating capacity occurs along this curve as the opening degree decreases. Further, since the load on the compressor 1 is reduced due to the decrease in the refrigerating capacity, the power consumption is also reduced as a result. Since there is some leakage in the valve 5, the refrigerating capacity remains even in the fully closed state.

FIG. 3 shows a block diagram of an electric circuit of the temperature control device of the present invention. Reference numeral 7 is a general-purpose microcomputer, and a sensor 8 for detecting the temperature PV in a thermostat (not shown).
Then, the output of the setting device 9 for outputting the set temperature SV in the constant temperature chamber is used as an input, and outputs are generated to the compressor 1, the valve 5 and the heater 10 for heating the inside of the constant temperature chamber to control them.

FIG. 4 shows a block diagram of the control system and the control target. First, the control of the heater 10 will be described. The value of the deviation e calculated by the above-mentioned SV-PV is input to the heater control means 12, where the heater output H (%) is calculated by the PID calculation processing shown in the following equation.

Here, Kp, TD, and TI are a proportional constant, a differential constant, and an integral constant, respectively, and the sampling period is, for example, 3 seconds. The proportional term of the equation acts so as to eliminate it proportionally to the increase / decrease of the deviation e, the integral term acts to eliminate the steady deviation, and the differential term acts to suppress the abrupt change of the deviation e. By this control, the microcomputer 7 increases / decreases the heat generation amount of the heater 10 so as to bring the internal temperature PV close to the set temperature SV and adjusts it precisely.

Next, the operation of the valve 5 will be described. Reference numeral 13 is the above-mentioned valve control means, which similarly inputs the value of the deviation e, and further the heater means.
Input the heater output H from 12. The valve control means 13 calculates the change amount ED of the deviation e for each sampling cycle according to the following equation.
Further, the speed of change DED is calculated by the formula.

_{ED = e n -e n-1} ...... DED = (e n -e n-1) - (e n-1 -e n-2) ...... valve control means 13 adds these values to the heater output H Then, the control output Y of the valve 5 is calculated by the following formula.

Y = H + X ₁ ED + X ₂ DED ... X ₁ and X ₂ are coefficients for adapting to the output (%) of the heater 10, and X ₁ > 0 and X ₂ > 0.

FIG. 5 is a graph showing the relationship between the heater output H and the operation of the valve 5, and FIG. 6 is a flow chart showing the software for controlling the valve 5 of the microcomputer 7.

In step 14, the output Y is calculated, and in step 15, it is judged whether or not ED is 0 or more. If it is 0 or less, the process proceeds to step 16 to judge whether Y is X ₃ % or less.
And open valve 5 one step. On the other hand, when ED is greater than 0 in step 15, the process proceeds to step 18 and it is determined whether Y is X ₄ % or more, and if it is, valve 5 is closed by one step. Here, it is assumed that X ₄ > X ₃ .

These operations will be described with reference to FIG. The horizontal axis shows the heater output (%), and the vertical axis shows the above-mentioned ED. Upper valve opening operation region of the L ₁ shown by a solid line, the lower valve closing region of the L _2, L ₁ and L ₂
Each interval represents a dead zone. Therefore, L ₁ and L ₂ show the operation when the speed of change DED is 0, and when ED is 0 or less, the temperature PV is rising, and when ED is greater than 0, the temperature PV is It is a case where the vehicle is descending, and therefore, judgment is made by classifying (step 15).

When the heater output H is large while the inside temperature PV is decreasing, the valve 5 is closed to reduce the refrigerating capacity to suppress the decrease in the temperature PV and to reduce the heater output H.

At this time, if the right side of the above expression is only the H term, Y becomes H ₄
Only in the above cases, the valve 5 is closed (step 19). However, since the term X ₁ ED exists, the valve 5 is closed from a state where H is small to some extent when the temperature drop amount is large. . This is illustrated by the inclined portion of the L _2. Furthermore, since there is a term of X ₂ DED in the equation, when the value of this term is large in +, the process shifts to L ₃ shown by the broken line. That is, when the descending speed is high, the valve 5 is closed from the stage where H is lower, and the refrigerating capacity is reduced. Conversely, when the descending speed is low, the process proceeds to L ₄ indicated by broken lines, H is as close the valve 5 becomes larger state. This makes it possible to reduce fluctuations in the temperature PV and stably control to the set value SV.

When the heater output H is small while the inside temperature PV is increasing, the valve 5 is opened to increase the refrigerating capacity and suppress the increase in temperature PV.

At this time, similarly, if the right side of the equation is only the H term, then Y becomes H
The valve 5 is opened only when the temperature is X ₃ or less (processing of step 17), but since the term of X ₁ ED exists, the valve 5 should be opened from a state where H is large to some extent when the temperature rise amount is large. become. This is illustrated by the inclined portion of the L _1. Furthermore, the formula
Since there is a term of X ₂ DED, when the value of this term is large at −, it shifts to L ₅ indicated by a broken line. That is, when the ascending speed is high, the valve 5 is opened from the stage where H is larger, and the refrigerating capacity is increased. On the contrary, when the rising speed is small, the flow shifts to L ₆ shown by the broken line, and the valve 5 is opened after H becomes smaller. By these controls, it becomes possible to reduce the fluctuation of the temperature PV and precisely control the set value SV.

Next, the operation of the compressor 1 will be described. In FIG. 4, reference numeral 21 is a compressor control means, which is the above-mentioned deviation e, heater output H and valve 5
The output related to the opening degree is input to determine whether the compressor 1 is started or stopped.

FIG. 7 is a flowchart showing software for controlling the compressor 1 of the microcomputer 7. In step 22, it is determined whether PV is SV-X ₅ (° C.) or less, that is, whether the deviation e is X ₅ or more. If PV is SV-X ₅ or less, the process proceeds to step 23. X ₅ is the value of for example 0.3 ° C. and the like. In step 23, it is determined whether the heater output H is, for example, a value X ₆ such as 50% or more, and if it is above, it is determined in step 24 whether the valve 5 is currently fully closed,
If it is fully closed, the compressor 1 is stopped in step 25. If all of steps 22, 23, and 24 are denied, PV is SV + X _{5 in} step 26.
It is judged whether it is larger than (° C.), that is, whether the deviation e is smaller than −X ₅ or not, and if PV is larger than SV + X ₅ , the process proceeds to step 26, and the heater output H is, for example, 25% or less value X ₇ If it is below, the compressor 1 is started in step 28.

That is, the compressor 1 stops when the heater output H is X ₆ % or more and the valve 5 is fully closed when the inside temperature PV becomes lower than the set temperature SV by X ₅ ° C or more. When the valve 5 is fully closed, the refrigerating capacity cannot be further reduced by the valve 5, and when the heater output H is low, the output H can be increased even if the temperature PV is reduced, but it is high to some extent. This is because the heating effect is relatively low in the state and the power consumption of the heater 10 is reduced.

Further, the compressor 1 is started when the inside temperature PV is higher than the set temperature SV by X ₅ ° C. or more and the heater output H is X ₇ % or less. This is because when the heater output H is low and the temperature PV is rising, further temperature reduction cannot be expected, and it is necessary to exert the refrigerating capacity by the compressor 1.

As a result, the temperature PV does not deviate from around the set temperature SV,
In addition, the power consumption of the heater can be reduced.

In addition, although the present invention is applied to the temperature control of the incubator in the embodiments, the present invention is not limited to this and can be applied to other thermostatic devices such as a showcase. Further, although the opening degree of the electric control valve is changed one step at a time in each predetermined sampling period, the present invention is not limited to this, and a method in which the opening degree is directly changed to a target opening degree may be used.

(G) Effect of the Invention According to the invention of claim 1, the temperature of the controlled object can be controlled to a wide range of set temperatures by heating the heater and cooling the refrigerating device, and the set value and the detected temperature are set to the output value of the heater. The amount of change in the deviation per unit time and the change rate of the amount of change in the deviation are added to adjust the opening of the motor-operated control valve to enable precise temperature control with less temperature fluctuation and dehumidification amount.

Further, according to the invention of claim 2, proper starting of the compressor,
The temperature control performance of the controlled object is improved by stopping, and
Wasteful refrigerating capacity Heater output can be reduced and energy can be saved.

[Brief description of drawings]

Each figure shows an embodiment of the present invention, FIG. 1 is a refrigerant circuit diagram, FIG. 2 is a diagram showing a relationship between an electric control valve and a refrigerating capacity ratio, FIG. 3 is a block diagram of an electric circuit, and FIG. FIG. 5 is a diagram showing the relationship between the heater output and the operation of the electric control valve, FIG. 6 is a flowchart showing software for controlling the electric control valve of the microcomputer, FIG. FIG. 7 is a flowchart showing software for controlling the compressor of the microcomputer. 1 ... Compressor, 4 ... Evaporator, 5 ... Electric control valve, 7 ...
… Microcomputer, 8 …… Sensor, 10 …… Heater.

Claims (2)

(57) [Claims] 1. A heater for heating an object to be controlled, a refrigerating device including an evaporator and a compressor for cooling the object to be controlled, an electric control valve connected to a suction side of the compressor, and the control. While controlling the start and stop of the heater and the compressor based on the target temperature and the temperature, the change amount of the deviation between the set temperature and the detected temperature in the output value of the heater per unit time and the change amount of the deviation A temperature control device comprising: a control device that controls the opening degree of the electric control valve by adding the changing speed, and controls the temperature of the control target by heating by the heater and cooling by the evaporator. 2. The control device stops the compressor based on the deviation between the temperature to be controlled and the set temperature, the heater output value and the opening degree of the electric control valve, and starts the compressor based on the deviation and the heater output value. The temperature control device according to claim 1, wherein: