JPH0455739B2 - - 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. Because this compressor cannot be stopped frequently due to its mechanism, for this kind of precise control it is common to control the heater output while the compressor is running, but the target value is If the temperature is higher than , cooling is required even though it is not necessary, and the output of the heater increases accordingly, necessitating a large amount of power consumption. It is also possible to change the cooling capacity of the cooling system in stages by changing the resistance value of the pressure reducer in the refrigerant circuit of the cooling system, changing the number of poles of the compressor, or changing the frequency using an inverter. In any case, the current situation is that when the target value is high, the user has to manually stop the compressor or reduce the cooling capacity.

In order to save this effort, the above publication uses proportional control of the heater, and automatically starts the compressor by driving the compressor when the output of the heater, that is, the amount of operation in the proportional control calculation decreases, and stopping it when the output increases. A method of controlling is adopted.

(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 proportional sensitivity, Ti is integral time, Td is differential time,
e is the target temperature (SV) and the temperature inside the constant temperature device (PV)
Kep in equation (i) is the proportional operation amount,
Kp/Ti∫edt indicates the integral operation amount, and KpTdde/dt indicates the differential operation amount. 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.

Figure 6 shows the target temperature (SV) in the constant temperature device +30.
℃ and the proportional band is set in the range of +31℃ (PH) and +29℃ (PL), and as in the above publication, the manipulated variable (y), which is the output of the heater, is, for example, 20% ( Change in temperature (PV) over time when the control device starts control from ambient temperature +20°C, which drives the compressor when the temperature drops to y _L ) and stops when it rises to 80% (y _H ). shows.

In Figure 6, at the start of control, the temperature (PV) is lower than the proportional band, so the manipulated variable (y) becomes 100%, the heater generates heat, and the temperature (PV) rapidly rises. When the proportional band lower limit (PL) is reached at point f in the figure, the temperature (PV) is rapidly increasing, so the proportional and differential operation amount in equation (i) rapidly decreases the heater output from 100%. output in the direction of
As a result, the manipulated variable (y) rapidly decreases to below (y _L ) at point g in FIG. 6, and the compressor is started.
Thereafter, the temperature (PV) slightly overshoots, but since the heater output is below (y _L ) and the cooling device is also cooling, the temperature (PV) begins to drop rapidly. In order to suppress this change, the amount of operation (y)
y increases rapidly, and at point h in FIG. 6, it again exceeds (y _H ) and the compressor stops. This situation will be repeated thereafter.

When the driving state of the compressor is controlled by the value of the manipulated variable (y) in this way, after the start of operation, the cooling capacity of the compressor is increased even though the target temperature (SV) is such that cooling is not required. In this case, the compressor was started), which caused the control condition to become unstable. This is because the manipulated variable (y) fluctuates drastically due to the proportional and differential manipulated variables that sensitively respond to changes in temperature (PV).

The present invention aims to solve these problems.

(d) Means for Solving the Problems The present invention provides a temperature control device for a constant temperature device that includes heating means for heating the inside of the constant temperature device, cooling means for cooling the inside of the constant temperature device, and a target temperature in the constant temperature device and a constant temperature device. control means that has a calculation unit that executes PI or PID calculation based on the temperature in the interior, drives the heating means with the manipulated variable obtained thereby, and increases the cooling capacity of the cooling means as necessary; The control means is configured to control the cooling means based on the integral operation amount in the calculation section.

(E) Effect The integral manipulated variable is determined by the integral value of the deviation,
This corrects steady deviations caused by ambient temperature and load conditions. Therefore, the temperature does not fluctuate rapidly due to temporary fluctuations in the internal temperature of the constant temperature device, so that the cooling means will not malfunction.

(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. Reference numeral 2 designates a well-known microcomputer as a control means, and the microcomputer 2 has as its functions a PID calculation section 3, an integral operation amount storage section 4, integral initial value setting sections 5, 6, a comparison section 7, and a switch 8. . Reference numeral 9 denotes a temperature setting unit for setting a target temperature (SV) inside a constant temperature device (not shown), such as an incubator.
Output to PID calculation section 3. Reference numeral 10 denotes a temperature detection unit that outputs the internal temperature (PV) of the incubator to the PID calculation unit 3 via the A/D converter 11. 1
A heater 3 serves as a heating means for heating the inside of the refrigerator, and is connected to a heater drive circuit 14. or,
Reference numeral 15 denotes a compressor constituting a refrigerant circuit of a cooling device for cooling the inside of the refrigerator (not shown). The compressor 15 is connected to an AC power source 17 via a switch 16, and the heater drive circuit 14 is directly connected to an AC power source 17.

PID calculation unit 3 calculates temperature (PV) and target temperature (SV)
PID calculation is performed based on the above formula (i), and in particular, the integral manipulated variable (hereinafter referred to as (I)) is read into the storage unit 4 each time the calculation is completed, and a new integral manipulated variable (I) is remembered again. The manipulated variable (y) is calculated by adding the integral manipulated variable (I) stored in the storage section 4 to the other manipulated variables (proportional and differential), and outputs it to the heater drive circuit 14. The heater drive circuit 14 controls the amount of heat generated by the heater 13 by adjusting the duty ratio of the energization time based on the operation amount (y).

The integral initial value setting units 5 and 6 each have predetermined integral initial values (I _OH ) (for example, +25%) and (I _OL ) (for example, −25%) stored in advance, and output these values. Each output is connected to the a contact and the b contact of the switch 8, and the common terminal of the switch 8 is connected to the storage section 4.

Based on the integral operation amount (I) stored in the storage section 4, the comparison section 7 switches the switch 1 when the operation amount (I) decreases to a predetermined value (I _L ) (for example, -45%) or less.
6 to start the compressor 15, while switch 8
Operate to close contact a momentarily and set the initial integral value (I _OH )
is input into the storage unit 4, its contents are erased (I _OH )
Replace with Also, when the manipulated variable (I) increases to a predetermined value (I _H ) (for example, +45%) or more, switch 16 is opened to stop the compressor 15, while switch 8 is momentarily closed to contact b to restart the next operation. inputs the initial integral value (I _OL ) into the storage unit 4, erases its contents, and replaces it with (I _OL ). It is assumed that the switch 8 is not always closed at any of its contacts.

Next, FIG. 2 is a flowchart showing the software of the microcomputer 2. The process starts at the same time as the power is turned on, and in step 20 the target temperature (SV) and temperature inside the refrigerator (PV) are read from the temperature setting section 9 and temperature detection section 10, and in step 21 it is determined whether (PV) is higher than (SV). Judge, if high, step
Proceed to step 28, and if below, proceed to step 22. In step 22, the comparator 7 keeps the switch 16 open and the compressor 15 stopped. In step 23, the temperature (PV) is read, and in step 24, the P(I)D calculation unit 3 calculates the (I) Execute D operation. Then, in step 25, the result (y) is output and the heater drive circuit 14 causes the heater 13 to generate heat. Next, in step 26, it is determined whether the integral operation amount (I) in the storage section 4 is less than or equal to (I _L ), and if not, the process returns to step 23, and if it is less than or equal to step 27
Then, the comparator 7 closes the switch 8 to contact a and writes the initial integral value (I) _OH into the memory 4. Next, in step 28, the switch 16 is closed to drive the compressor 15, the temperature (PV) is read in step 29, and the P(I)D calculation is executed again in step 30, and the resultant operation amount (y) is Accordingly, the output of the heater 13 is controlled by the heater drive circuit 31. Next, in step 32, it is determined whether the integral operation amount (I) in the storage section 4 is greater than or equal to (I _H ), and if not, step 29 is executed.
If the value is above, the process proceeds to step 33, closes the switch 8 to the b contact, writes the initial integral value (I _OL ) in the storage section 4, and returns to step 22.

Next, the operation of the temperature control device 1 of the present invention will be explained with reference to FIGS. 3 to 5, which show the time course of temperature (PV) in an actual control state. In Fig. 3, the target temperature (SV) is set to, for example, +30°C, and the proportional bands in the PID calculation unit 3 are set to the ranges of +31°C (PH) and +29°C (PL), respectively.
This shows the change in temperature (PV) over time when the power is turned on and control is started from an ambient temperature of +20°C. At this point, the temperature (PV) is lower than (SV), so step
Proceeding from step 21 to step 22, the compressor 15 does not start, and since the temperature (PV) is below the proportional band, the output of the heater 13 at step 25 is 100%, and the integral operation amount (I) is also calculated. From step 23 below
26 is repeated to make the heater 13 generate heat and rapidly raise the temperature (PV). Eventually, the proportional band is entered at point j in FIG. 3, calculation based on equation (i) is started at step 24, and the integral operation amount (I) also increases. On the other hand, at point j, the temperature (PV) is rapidly increasing, so the proportional and differential manipulated variables in equation (i) are increasing in the direction of decreasing the manipulated variable (y), and as a result, the output of the heater 13 is rapidly increasing. (This is faster than the rate at which the integral manipulated variable (I) increases), and at point k in Figure 3, the manipulated variable (y) decreases from, for example, 20% (y _L ). ((y _H ) is 80%), temperature (PV) is target temperature (SV)
Since the integral operation amount (I) is gradually increasing since it is still lower than (I _{L ), it never becomes less than (I L} ), and therefore the compressor 15 is not driven in steps 26 to 27 and 28. After that, the target temperature (SV) is set at point l in the diagram.
After reaching , the integral manipulated variable (I) begins to decrease due to some overshoot, but the proportional and differential manipulated variables increase again, and eventually the temperature (PV) becomes stable as it matches (SV), and the manipulated variable (y) and the integral operation amount (I) also converge to appropriate values. On the other hand, when the compressor 15 is driven when the manipulated variable (y) reaches (y _L ), the compressor 15 is started at point k in FIG. Although cooling is not necessary, the control state becomes unstable because it is cooled, but such a problem does not occur in the temperature control circuit 1. This is because the integral manipulated variable (I) is determined by the integral value of the deviation, and therefore outputs the most stable value against temporary temperature (PV) changes. In other words, the integral manipulated variable (I) changes with changes in the ambient temperature and internal load conditions, and is output to eliminate steady-state deviations. It is possible to determine the true necessity of cooling.

Next, in Figure 4, the temperature (PV) is the target temperature (SV).
This shows the control state when the ambient temperature rises from a stable state. At this time, the manipulated variable (y), which is the output of the heater 13, changes the temperature (PV) to the target temperature (SV).
The integral manipulated variable (I) gradually decreases in an attempt to adjust to When I) reaches (I _L ), the process proceeds from step 26 to step 27, where the initial integral value (I _OH ) is set, the manipulated variable (y) is forcibly raised, and the compressor 15 is started at step 28. When the compressor 15 starts at point m and cooling starts, the temperature (PV) tries to decrease rapidly, but
Since the output of the heater 13 is increased by setting the initial integral value (I _OH ), a sudden drop in temperature (PV) can be suppressed. Thereafter, the output and integral operation amount (I) of the heater 13 rise slightly due to the temporary drop in temperature (PV), but eventually shift to a new stable state due to heating by the heater 13 and cooling of the compressor 15.

If the integral operation amount (I _OH ) is not set here, the output of the heater 13 will have also decreased by the time the compressor 15 starts, and the temperature (PV) will drop rapidly, so the operation amount (y), ( I) increases and the compressor 15 is stopped even though cooling is required, which makes the control unstable, but the present invention does not have such a problem.

Next, FIG. 5 shows a control state when the ambient temperature drops from a state where the compressor 15 is being driven and the temperature (PV) is stable at the target temperature (SV). At this time, the manipulated variable (y) and the integral manipulated variable (I) rise in the opposite direction to the above, and eventually, when cooling is no longer necessary, the integral manipulated variable (I) reaches (I _H ) at point n in the figure. ,
The program proceeds from step 32 to step 33 to set the initial integral value (I _OL ), and in step 22 the compressor 15 is stopped. When the compressor 15 stops at point n, the temperature (PV) tries to rise rapidly, but the output of the heater 13 is forced to decrease because the integral operation amount (I) has been lowered to (I _OL ). As a result, a rapid rise in temperature (PV) is suppressed, and thereafter a stable state is reached by P(I)D control of only the heater 13.

If the initial integral value ( _IOL ) is not set here, the output of the heater 13 will have also increased when the compressor 15 stops, and the temperature (PV) will rise rapidly, so the manipulated variable (y), (I) decreases and the compressor 15 is started even though cooling is not necessary, making control unstable. However, the present invention solves this problem.

It is assumed that the absolute values of the initial integral values (I _OH ) and (I _OL ) are smaller than the absolute values of (I _H ) and ( _IL ), respectively. In addition, in the embodiment, the compressor 15 was controlled by starting and stopping, but in addition, the cooling capacity of the cooling means may be increased in stages by, for example, changing the resistance value of the pressure reducer in the refrigerant circuit in stages. The present application is valid even if it is lowered or lowered.

(G) Effect of the invention According to the present invention, the cooling capacity is increased only when cooling by the cooling means is required, and the P(I) of the heating means is increased.
Alternatively, power consumption can be reduced by stably controlling the temperature using P(I)D control. In particular, since the cooling means does not malfunction due to temporary temperature fluctuations within the constant temperature apparatus, unstable temperature conditions caused by such fluctuations are eliminated, and stable temperature control of the constant temperature apparatus is made possible.

[Brief explanation of the drawing]

1 to 5 show embodiments of the present invention, in which FIG. 1 is a functional block diagram of the temperature control device, FIG. 2 is a flowchart showing the software of the microcomputer, and FIGS. Figure 6 and Figure 5 are diagrams showing the time course of the temperature inside the thermostat;
This figure is a diagram showing the time course of temperature by a conventional control device corresponding to FIG. 3. DESCRIPTION OF SYMBOLS 1...Temperature control device, 2...Microcomputer, 3...P(I)D calculation part, 4...Storage part, 5, 6
... Integral initial value setting section, 7... Comparison section, 13... Heater, 15... Compressor.

Claims (1)

[Claims] 1 A heating means for heating the inside of the constant temperature apparatus, a cooling means for cooling the inside of the constant temperature apparatus, and a PI based on the target temperature in the constant temperature apparatus and the temperature in the constant temperature apparatus.
Alternatively, the controller comprises a control means that has a calculation section that performs PID calculation, drives the heating means with the manipulated variable obtained thereby, and increases the cooling capacity of the cooling means as necessary, and the control means A temperature control device for a constant temperature device, wherein the means controls the cooling means based on an integral operation amount in the calculation section.