JPH0455738B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention generally relates to a temperature control device for a constant temperature device in physical and chemical equipment.

(b) Prior Art A conventional method for controlling the temperature of this type of constant temperature device is disclosed in, for example, Japanese Patent Laid-Open No. 35856/1983.
This type of constant temperature device is required to precisely control the temperature inside the refrigerator to a target value of, for example, 15℃ to 30℃, which requires a heater to heat the inside of the constant temperature device and a compressor to cool it. It is equipped with a cooling device with a machine.

In this case, when the target value is higher than the ambient temperature of the constant temperature device, it is necessary to drive the heater, but it is not necessary to drive the cooling device. On the other hand, when controlling from around the ambient temperature to below it, cooling with a cooling device is required in addition to the heater.Also, even if the target value is high, cooling is still required when high temperature samples are stored. becomes. Unlike the heater, the compressor of the cooling system cannot be stopped frequently due to its mechanism, so for this type of precise control, it is common to control the heater output while the compressor is running. However, this naturally consumes a lot of power, so when the target value is high, the user has to manually stop the compressor.

In order to save this effort, the above-mentioned publication adopts a method in which the heater and the compressor are driven alternately, this switching is performed automatically, and the heater is proportionally controlled to reduce power consumption.

(C) Problems to be Solved by the Invention In the above-mentioned publication, the heater was proportionally controlled, but PI or PID control may be considered for more precise control. Here, PI control is proportional-integral control, and PID control further includes differential control. The general formula for PID control is shown below.

y=Kpe+Kp/Ti∫edt+KpTdde/dt...(i) Here, y is the manipulated variable that is the output of the heater, Kp is the proportional sensitivity, Ti is the integral time, Td is the differential time, and e is the target value (hereinafter referred to as (SV)) ) and the temperature in the thermostat (hereinafter referred to as (C)), and is
Kpe indicates the proportional manipulated variable, Kp/Ti∫edt indicates the integral manipulated variable, and KpTdde/dt indicates the differential manipulated variable.

The proportional manipulated variable is proportional to the increase in the deviation e and acts to reduce it, the integral manipulated variable integrates the deviation and acts to eliminate steady deviations, and the differential manipulated variable acts to eliminate sudden temperature fluctuations. It acts in the direction of slowing down.

In Figure 5, the target value (SV) is set to +5℃, and upper and lower limits (DH) and lower limits (DL) are set at ±0.5℃ above and below the target value (SV), and when the temperature (C) drops to (DL), the compressor is turned off. The figure shows the change in temperature (C) over time when the compressor is stopped, raised to (DH) and driven, and the heater is made to generate heat under PID control while the compressor is stopped. In this case, the compressor is driven and the temperature (C) decreases, and when the compressor stops at point f in the figure, the temperature (C) is lower than the target value (SV) at that point, so proportional and integral operations are performed. The amount will increase the output of the heater, and even if the compressor stops, the temperature (C) will decrease due to undershoot, so the differential operation amount will also increase the output of the heater. Therefore, the entire manipulated variable y is 100%.
Therefore, the temperature (C) rises rapidly. At this time, formula (i)
The integral term in the diagram integrates the shaded range from point f to point g in the direction in which the output increases, and integrates the shaded range from point g to point h in the direction in which the output decreases. Therefore, the integral from point f to point g exceeds the integral from point g to point h, and even if the heater output is stopped at point h, the integral operation amount remains in the direction of increasing the heater output. This accumulates and the next time the heater starts heating, the heater output will be 100% again.
As a result, the result is the same as driving the compressor and heater alternately at 100% output, and temperature control becomes unstable with large undershoots and overshoots.

The present invention has been made to solve these problems.

(d) Means for Solving the Problems The present invention maintains the inside of the constant temperature device at a target temperature by respectively driving a heating means for heating the inside of the constant temperature device and a cooling means for cooling the inside of the constant temperature device in a temperature control device for a constant temperature device. a means for setting a target temperature, a means for detecting the temperature within the constant temperature device,
The control means has a calculation section for driving the heating means or the cooling means alternately based on the target temperature and the temperature in the constant temperature device and controlling the heating means by PI or PID, and the control means has a control means that stops the cooling means. The calculation unit is provided with means for setting a predetermined initial value of integration when performing the calculation.

(E) Effect According to the present invention, power consumption can be reduced because the heating means and the cooling means are not driven simultaneously. Furthermore, stable temperature control by the heating means is possible by PI or PID control of the heating means. In particular, the heater can be controlled appropriately after the cooling means has stopped, and control with less temperature fluctuation is possible.

(F) Embodiments Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a functional block diagram of a temperature control device 1 of the present invention. 2 is a well-known microcomputer as a control means, and the microcomputer 2 has a switching control section 3, a PID calculation section 4,
It has an integral initial value setting section 5 and a switch 6. 7
is a temperature setting unit that sets the target temperature SV inside a constant temperature device (not shown), such as an incubator;
The target temperature SV is output to the switching control section 3 and the PID calculation section 4. Reference numeral 8 denotes a temperature detection section that detects the internal temperature C of the incubator, and outputs the temperature C to the switching control section 3 and the PID calculation section 4 via the A/D converter 9. 11 is a commercial AC power source, and a changeover switch 12 is connected to its output. 13
is a compressor constituting a refrigerant circuit of a cooling device for cooling the inside of the refrigerator (not shown), and is connected to the a contact point of the switch 12. Reference numeral 14 denotes a heater for heating the interior of the refrigerator, and the amount of heat generated by the heater is controlled by the duty ratio of the energization time by a heater drive circuit 15 which is connected to the b contact of the switch 12 and is constituted by a switching element.

The switching control unit 3 changes the target value SV up and down by ±0.5, for example.
Set the upper limit temperature DH and lower limit temperature DL at the point of °C,
When temperature C is higher than DH, switch 12 is closed to a contact, and when it decreases from that state and reaches DL, b
The contact closes, and the temperature C rises further from that state.
When DH is reached, the a contact is closed again. Also, when the switch 12 is closed to the a contact, the calculation of the PID calculation section 4 is stopped, and when switching from the a contact to the b contact, the switch 6 is instantaneously closed and the predetermined integral is set by the integral initial value setting section 5. PID calculation 4 for initial value I ₀
, and replaces it with the integral manipulated variable stored in the PID calculation section 4. The PID calculation unit 4 calculates the temperature C and the target value while the switch 12 is closed to the b contact.
Perform PID calculation based on the above formula (i) from SV,
The resulting operation amount y is output to the heater drive circuit 15, and the switching element is controlled to control the amount of heat generated by the heater 14 based on the operation amount y.

Next, the operation will be explained based on the flowchart showing the software of the microcomputer 2 shown in FIG. 2, and with reference to the diagram showing the time course of the temperature C shown in FIG. Starting from power-on, the target temperature SV is read from the temperature setting part 7 in step 20, the internal temperature C is read from the temperature detection part 8 in step 21, the deviation e is calculated in step 22 based on it, and the deviation e is calculated in step 23. Based on that, by equation (i)
Execute PID calculation and determine the manipulated variable y. Next, in step 24, it is determined whether the temperature C is higher than the upper limit temperature DH.

Here, FIG. 3 shows temperature control when the ambient temperature is, for example, +20°C and the target temperature SV is +5°C. At point i in the figure, temperature C is higher than DH, so proceed to step 26 and switch 12 is turned on. Closed to A contact,
The compressor 13 is driven and the output of the heater 14 is stopped. Next, in steps 27 and 28, the target temperature is set in the same way.
Read SV and temperature C, and set temperature C in step 29.
Determine whether or not is less than DL. Since the answer at point i in FIG. 3 is negative, the process returns to step 26. Step 2 below
Repeat steps 6 to 29 to cool down the inside of the incubator, and when the temperature C reaches DL at point j in Figure 3, proceed to steps 29 to 30, close switch 6, and let PID calculation section 4 integrate. Input the initial value I ₀ . Changes in the integral operation amount in the PID calculation section 4 are shown in the bottom row of FIG. That is, when the temperature C reaches DL, the integral manipulated variable is set to a predetermined low value (for example, -50
%) is initialized to I ₀ . Next, return to step 20 and execute steps 21 to 23 below, and since step 24 is negative, step 25 is executed.
, the switch 12 is switched to the B contact, and the heater 14 is in a state where power is supplied based on the manipulated variable y,
The compressor 13 is stopped.

At this time, at point j in FIG. 3, the temperature C is decreasing due to undershoot, so step 2
In the PID calculation according to No. 3, the proportional term and the differential term in equation (i) increase in the direction of increasing the heat generation of the heater 14, that is, in the direction of increasing the manipulated variable y in FIG. However, the integral term is negative in step 30.
Since the initial value is set to _I0 , the manipulated variable y as a whole is not 100% as shown in FIG. 5, but is, for example, about 30%, so that the temperature C increases slowly thereafter. Thereafter, steps 20 to 25 are repeated to heat the inside of the refrigerator by PID control of the heater 14, but since the output of the heater 14 when it starts generating heat is low, the manipulated variable y, that is, near the upper limit temperature DH, is Since the output of the heater 14 is quite low, the rate of increase in temperature C is slow, so DH is reached at one point in FIG. By starting, the temperature C immediately begins to decrease, thereby minimizing the overshoot of the temperature C as shown after point l in FIG. Moreover, since the time to reach point l becomes longer, the burden when starting up the compressor 13 is reduced. After that, repeat this and change the temperature C to DH and DL.
Go within the control range. In particular, when the target temperature SV is lower than the ambient temperature, the temperature C will naturally rise even if the heater 14 does not generate heat if the compressor 13 stops, so if the initial integral value I ₀ is not set, As shown in FIG. 5, the temperature C becomes very unstable, but if the temperature C is controlled as shown in FIG. 5, control with little overshoot can be achieved as shown in FIG. It becomes effective.

FIG. 4 shows control when the ambient temperature is +20°C and the target temperature SV is, for example, +30°C. When the power is turned on, the temperature C is sufficiently lower than the target temperature SV, so the manipulated variable y in step 23 starts from 100%, and steps 20 to 25 are repeated until the temperature C is lowered by the heating of the heater 14. going up. The output of the heater 14 decreases as it approaches the target temperature SV, but when it reaches the temperature DH at point m in the figure, the process proceeds from steps 24 to 26, where the switch 12 is switched to the a contact and the compressor 13 is cooled. is started. Steps 26 to 29 are repeated until cooling progresses and when DL is reached at point n in the figure, step 2 is started.
Proceed from step 9 to step 30, set the initial integral value _I0 , return to step 20, and then proceed from step 20 to step 2 in the same manner.
By repeating step 5, the temperature inside the refrigerator is controlled by PID control of the heater 14. In this case as well, since the manipulated variable y is at a low value when the heater 14 starts generating heat, the rate of increase in temperature C becomes slow in the process of approaching the target temperature SV, so the target temperature
There is little overshoot from SV, and after that the temperature C is kept at the target temperature by PID control of the heater 14.
Stably controlled by SV. In addition, in the example
Although PID control has been described, PI control may also be used.

(G) Effects of the Invention According to the present invention, power consumption can be reduced because the heating means and the cooling means are not driven at the same time, and since the control device automatically switches between them, management by the user is facilitated. In particular, when cooling is not required, stable temperature control is possible by PI or PID control of the heating means, and when the cooling means is stopped in situations where cooling is required, the integral operation amount of PI or PID calculation is set to a predetermined value. Since it is set to the initial value of , overshoot due to excessive heating is reduced, and stable temperature control of the thermostat is possible.

[Brief explanation of drawings]

1 to 4 show an embodiment of the present invention, in which FIG. 1 is a functional block diagram of a temperature control device, FIG. 2 is a flowchart showing software of a microcomputer, and FIGS. The figure shows the time course of the temperature inside the thermostat;
FIG. 2 is a diagram showing a temperature change over time according to a conventional control device corresponding to the diagram. 1...Temperature control device, 2...Microcomputer, 3...Switching control section, 4...PID calculation section,
5... Integral initial value setting section, 7... Temperature setting section, 8
...Temperature detection unit, 13...Compressor, 14...Heater.

Claims (1)

[Claims] 1. In a device that maintains the inside of the constant temperature device at a target temperature by respectively driving a heating means for heating the inside of the constant temperature device and a cooling means for cooling the inside of the constant temperature device, a means for setting the target temperature and a means for setting the temperature inside the constant temperature device are provided. and a control means having a calculation unit for driving the heating means or the cooling means alternately based on the target temperature and the temperature in the constant temperature device and controlling the heating means by PI or PID. . A temperature control device for a constant temperature device, wherein the control means includes means for setting a predetermined integral initial value in the arithmetic unit when the cooling means is stopped.