JP3412020B2 - Fluid temperature controller - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a device for controlling the temperature of a fluid.

[0002]

2. Description of the Related Art Conventionally, temperature control of a large volume of fluid has been
It is performed by on / off control, continuous control, or a combination of these controls.

Here, the on / off control is a control for turning on / off the supply of heat generated by a heat source having a predetermined heat capacity to a fluid in accordance with the polarity of the deviation between the target temperature of the fluid and the current temperature. The control is control in which the heat generated by the heat source having the predetermined heat capacity is continuously supplied to the fluid based on the deviation.

In the temperature control device in which the temperature is controlled by the combination of the control device for performing the on / off control and the control device for performing the continuous control, the on / off control device controls a certain amount until reaching the target temperature and the rest is continuously operated. The temperature is controlled with high accuracy by controlling the temperature with the control device.

Further, the flow rate of the fluid and the temperature difference between the fluid inlet and the fluid outlet may be switched. In this case, since the temperature control capability is changed, the changeover switch installed on the operation panel, etc. is operated to selectively change the use / non-use of the on / off control device to switch the control capability. ing.

[0006]

As described above, in the conventional method in which the temperature control capability is switched alternatively, it is difficult to arbitrarily set the flow rate of the fluid and the target temperature. Furthermore, when the flow rate of the fluid changes significantly during temperature control due to external factors, the heat capacity of the fluid is
This causes a problem that the heat capacity of the heat source set by the changeover switch cannot be matched and the control accuracy cannot be ensured. The present invention has been made in view of the above circumstances, and it is a first object of the present invention to provide a temperature control device capable of performing optimum temperature control according to switching of a flow rate of a fluid and a temperature difference. Even if the flow rate of the fluid changes due to disturbance, etc.
A second object is to provide a temperature control device capable of performing optimum temperature control according to this change.

[0007]

Therefore, the first aspect of the present invention
In the invention, the control means for supplying the heat generated by the heat source to the fluid in accordance with the deviation between the target temperature of the fluid and the current temperature of the fluid is provided for each of the plurality of heat sources, and each of the plurality of control means is selected. In a fluid temperature control device that appropriately selects a combination of control means to control the fluid to a target temperature, control for turning on / off heat supply to the fluid in accordance with the polarity of the deviation is applied to all of the plurality of control means. Of the control means for controlling the heat source of the heat capacity corresponding to the estimated heat capacity by calculating the ratio of the ON time to one cycle of ON / OFF, estimating the heat capacity of the fluid based on the calculated ratio. A combination is selected from the plurality of control means, the control means of the selected combination is caused to perform temperature control, and the temperature of the fluid is controlled to the target temperature.

Further, in the main invention of the second aspect of the present invention, the control means is composed of two or more continuous control means and an on / off control means, and during the combination of each control means selected,
The continuous control means is always included, and when the operation amount of the continuous control means becomes the minimum value during the temperature control of the fluid, the on / off control means for performing the temperature control is decreased and the operation amount of the continuous control means is increased to the maximum. When the value is reached, the number of on / off control means for controlling the temperature is increased.

[0009]

According to the structure of the first aspect of the invention, a plurality of control means are provided, and all the control means perform on / off control before temperature control. Then, the ratio of the ON time to one ON / OFF cycle when the ON / OFF control is performed by all the control means in this way is calculated. Then, the heat capacity of the fluid to be controlled is estimated based on the calculated ratio, and the combination of the respective control means for controlling the heat source of the heat capacity corresponding to the estimated heat capacity is selected from the plurality of control means. To be done.

By causing the control means in the combination of the control means thus selected to perform the temperature control, the temperature control adapted to the heat capacity of the fluid can be accurately performed.

Further, according to the configuration of the second invention, the continuous control means is always included in the combination of the selected control means, and the operation amount of the continuous control means becomes the minimum value during the temperature control of the fluid. If the ON / OFF control means is decreased, the ON / OFF control means is increased / decreased so that the ON / OFF control means is increased when the operation amount of the continuous control means reaches the maximum value. The temperature control adapted to the above is accurately performed.

[0012]

Embodiments of the fluid temperature control apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a temperature control device according to an embodiment. As shown in FIG. 1, this temperature control device is roughly classified into a target value SV of fluid temperature and a current fluid temperature. PV_OUT is input to each temperature control unit 16
CPU 18 for outputting manipulated variables to 18, a memory 2 in which necessary data such as a combination of heat sources used for temperature control is stored as will be described later, ON / OFF control units 16 and 17 for ON / OFF control, and continuous control. A continuous control unit 18 to perform, a load 14 to which a fluid to be controlled is input and output,
The outlet temperature PV_OUT of the load 14 is detected, and the CPU
It is composed of an outlet temperature detector 15 which feeds back to 1. The temperature of the load 14 is controlled by supplying the heat generated by the heat source 11 having the heat capacity of 25% of the total, the heat source 12 of the same 25%, and the heat source 13 of the same 50%.

The mode changeover switch SW of the CPU 1 is a switch for switching the load heat capacity estimation mode or the temperature control mode, and when switched to the first contact 6, the load heat capacity estimation mode is set and the target value (fluid set temperature) S is reached.
The deviation er between V and the feedback amount (fluid outlet temperature) PV_OUT is added to the load heat capacity estimation unit 4 via the on / off control calculation unit 3, and the estimation calculation described below is executed. Further, when starting the temperature control, the switch SW has the second contact 7
Is switched to the temperature control mode, the deviation er is added to the manipulated variable calculation unit 5, and the manipulated variable M is output from the manipulated variable calculation unit 5.
V is supplied to the continuous control unit 18, and the load heat capacity estimating unit 4 selects the ON / OFF control unit 1 selected in the load heat capacity estimating mode.
A power supply command (ON command) is given to 6 and 17, and temperature control is executed.

The contactor 8 of the on / off control unit 16 includes:
The load heat capacity estimation unit 4 applies a signal at two positions of ON and OFF, that is, a manipulated variable of 100% (ON) or 0% (OFF), to apply electric power to the heat source 11 as required, and heat generated by the heat source 11 is generated. Supply to the load 14 is turned on and off. Similarly, the contactor 9 of the on / off control unit 17 receives a signal of two positions of ON and OFF from the load heat capacity estimation unit 4,
Electric power is applied to the heat source 12 as needed to turn on / off the supply of heat generated by the heat source 12 to the load 14.

In the temperature control mode, the manipulated variable calculator 5
The deviation er is multiplied by a predetermined gain or the like to calculate a manipulated variable MV, which is added to the phase control unit 10 of the continuous control unit 18. The phase control unit 10 of the continuous controller 18 controls the heat source 13 according to the manipulated variable MV applied from the manipulated variable calculator 5.
Load 1 of the heat generated by the heat source 13
The feed to 4 is continuously controlled. Further, in the phase heat control unit 10, in the load heat capacity estimation mode, the load heat capacity estimating unit 4 outputs a signal of two positions, that is, ON and OFF, that is, 100%.
By adding a manipulated variable of (on) or 0% (off),
Electric power is applied to the heat source 13 as needed to turn on / off the supply of heat generated by the heat source 13 to the load 14. The continuous control unit 18 performs PID control.

In the load heat capacity estimation mode, the on / off control calculation unit 3 adds an operation amount of 100% to all the control units 16, 17 and 18 when the deviation er is positive, and when the deviation er is negative. 0% operation amount is added and each control unit 1
6. Turn on / off control for 6, 17, and 18.

The load heat capacity estimating unit 4 has an on / off cycle time Tcy when the control units 16, 17 and 18 perform an on / off control operation in the load heat capacity estimating mode.
And the on time (heating time Tht) is measured, and these ratios,
That is, a process of estimating the heat capacity Q of the load 14 from the heating ratio Tht / Tcy and determining the combination of the heat sources 11 to 13 to be used is performed. Hereinafter, the control for turning on / off all the control units 16 to 18 will be referred to as a flow rate estimation operation.

Now, let the flow rate of the fluid of the load 14 be q [l / mi
n] and the temperature difference between the set temperature SV and the inlet temperature of the load 14 is ΔT [° c], the heat capacity Q required by the load 14
Is calculated by the following equation (1).

Q = C · q · ΔT [kW] (1) Here, C is a constant determined by the specific gravity and specific heat of the fluid.

As far as the equation (1) is concerned, the load 1
In order to obtain the heat capacity Q of No. 4, it is necessary to measure the fluid flow rate q and the like, but to measure the flow rate q and the like by performing the flow rate estimation operation as described above and calculating the following equation (2). Without, the heat capacity Q of the load 14 can be estimated.

That is, the total heat capacity H of the heat sources 11 to 13
And the above heating ratio Tht / Tcy and the heat capacity Q of the load 14 satisfy the following relationship: Q = H · Tht / Tcy (2), and if the heating ratio Tht / Tcy is calculated, this From the known value H, the heat capacity Q of the load 14 can be obtained.

Therefore, assuming that the heat capacity per module of the on / off control unit is hon [kW] and the heat capacity per module of the continuous control unit is hph [kW], non.hon <Q <non.hon + nph.hph ... ( Stable control can be expected by selecting the number of modules non of the on / off control unit and the number of modules nph of the continuous control unit so that the relational expression 3) holds.

Therefore, the combination of the continuous control unit and the on / off control unit for controlling the heat source of the heat capacity corresponding to the heat capacity Q is shown in FIG.
If it is determined in advance and stored in the memory 2 as shown in, the temperature control can be stably performed.

FIG. 5 shows various control modes M1, M2, and M3 set according to the heating ratio Tht / Tcy, and shows combinations of a continuous control unit and an on / off control unit according to the various control modes. The proportional gain Kp, the integration time TI, and the derivative time TD, which are the control constants of the continuous control unit 10, are also changed according to the control mode. For example, heating ratio Tht / T
When cy is in the range of less than 0.75 and 0.5 or more, the control mode is M2, and the on / off control unit 16 controls the heat source 11 of 25% and the continuous control unit 18 controls the heat source 13 of 50%.
Is selected, and the proportional gain Kp2, the integration time TI2, and the differentiation time TD2 are selected as the control constants of the phase control unit 10.

FIG. 2 is a block diagram showing the control system of the continuous control section 18 in more detail. As shown in FIG.
The manipulated variable MV of 0 to 100% calculated in 1 is added to the D / A converter 19 as a digital signal. In the D / A converter 19, the input digital signal is converted into an analog signal MVO such as current or voltage, which is added to the power controller 20 as a command value. Power controller 20
Then, the command value MVO of voltage or current is converted into electric power PW, and this is applied to the halogen lamp 13 which is a heat source. The halogen lamp emits light according to the input power PW and transmits the heat quantity HEAT to the pure water 14 as a load.

Here, the power P of the current or voltage MVO
There is non-linearity in the conversion into W and the conversion of the electric power PW into the heat quantity HEAT. However, if this correction is performed by calculation, the calculation load on the CPU 1 becomes too large. Therefore, if the relation between the manipulated variable MV and the heat amount HEAT is obtained in advance by experiments or calculations and is stored as a table in the memory 2, the calculation time and the program size can be shortened. it can.

The operation of the temperature control device shown in FIG. 1 at the time of startup will be described below with reference to the flow chart shown in FIG. As shown in FIG. 3, after the power source of the temperature control device is turned on (step 101), the mode changeover switch SW is changed over to the load heat capacity estimation mode (step 102), and a heating start switch (not shown) is turned on. First, the outlet temperature PV_INIT of the load 14 at that time is stored as an initial temperature (step 103), and the temperature difference ΔT
Let (= SV-PV_INIT) be the deviation er (step 105), and start heating according to this deviation er (FIG. 4).
See; step 106).

Next, the on / off operation as the load estimation operation, that is, the temperature PV_OUT of the fluid 14 is the target temperature S
When V or less, 100% operation amount is output and conversely temperature PV
When _OUT is larger than the target temperature SV, the on / off control calculation unit 3 performs a process of outputting a 0% manipulated variable to each of the control units 16, 17 and 18. Note that FIG. 4 shows the manipulated variable MV applied to the continuous control unit 18 (see FIG. 4;
Step 107).

During the on / off operation, the on time Tht and one cycle Tcy of the on / off cycle are measured, and the heating ratio Tht /
Tcy (see FIG. 4) is calculated by the load heat capacity estimation unit 4 (step 108). FIG. 5 is applied to the calculated heating ratio Tht / Tcy, and the combination of heat sources suitable for the heat capacity of the fluid 14, that is, the combination of the control means 16 to 18 for controlling the heat sources, that is, the control modes M1, M2, and M3. Either is selected and decided. The determined control mode is stored in the memory (step 109).

Thereafter, the mode selector switch SW is switched to the temperature control mode, and the deviation er is added to the manipulated variable calculating section 5.

The load heat capacity estimating unit 4 reads the control mode M1 ... Determined from the memory and fixes the on / off control units 16 and 17 selected in the load heat capacity estimating mode to the ON state. On the other hand, the manipulated variable calculator 5 calculates the manipulated variable MV based on the deviation er, and adds the calculated manipulated variable MV to the phase control unit 10 of the continuous controller 18. Thereby, the continuous control unit 18 controls the temperature by continuous control. In this embodiment, the continuous controller 18 is included in the combinations that are always selected (see FIG. 5).

As shown in FIG. 5, when the heating ratio Tht / Tcy is less than 0.5, the control mode is M1.
Only the continuous control unit 18 for controlling the 50% heat source 13 is selected, and the proportional gain Kp1, the integration time TI1, and the differential time TD1 are selected as the control constants of the phase control unit 10, and only the continuous control unit 18 is controlled as described above. Temperature control is performed by operating with a constant.

When the heating ratio Tht / Tcy is in the range of less than 0.75 and 0.5 or more, the control mode is M2,
ON / OFF control units 16 and 50 for controlling the heat source 11 of 25%
%, The continuous control unit 18 for controlling the heat source 13 is selected, and the proportional gain Kp2, the integral time TI2, and the differential time TD2 are selected as the control constants of the phase control unit 10, and the ON / OFF control unit 16 is operated and continuous control is performed. Part 18
Is controlled by the above-mentioned control constant to control the temperature.

When the heating ratio Tht / Tcy is in the range of 0.75 or more, the control mode is M3, all control units are selected, and the proportional gain Kp3, which is the control constant of the phase control unit 10, The integration time TI3 and the differential time TD3 are selected, and the on / off control units 16 and 17 are operated, and the continuous control unit 18 is operated with the above-mentioned control constant, whereby temperature control is performed.

As a result, the optimum temperature control suitable for the current heat capacity of the fluid 14 can be stably and accurately performed.

Although the case where the control constants Kp1 ... Stored in the memory according to the control mode M1 ... Is used as it is has been described above, the control constants Kp, TI, TD may be used as necessary.
May be readjusted by the limit cycle method described later. Such readjustment is performed in the so-called auto-tuning mode or when the control accuracy falls below a certain value.

Next, a description will be given of control in the case where a disturbance or the like is generated during the temperature control and the fluid flow rate or the like changes accordingly.

If the flow rate of the fluid 14 changes while the controller is operating, the control mode currently selected cannot be dealt with, and the output of the manipulated variable MV to the phase control unit 10 becomes the minimum (= 0%), and the capacity is reduced. Excessive, or maximum (= 100%) and insufficient capacity.

Therefore, in this embodiment, the on / off control section is appropriately operated or not operated depending on whether the capacity is excessive or insufficient.

FIG. 6A shows how the manipulated variable MV changes in such a case. In the temperature control mode, the manipulated variable MV has a minimum value (0%) equal to or longer than a preset time T1.
In the case of indicating that the capacity is excessive, one of the on / off control units currently selected, for example, the control unit 17 is made inoperative to reduce the heat supply amount (FIG. 6 (b)). )reference). Similarly, when the manipulated variable MV shows the maximum value (100%) for a preset time T2 or more in the temperature control mode, it means that the capacity is insufficient.
One of the currently selected on / off control units, for example, the control unit 17 is operated to increase the amount of heat supplied (see FIG. 6B).

In this embodiment, the control unit does not operate, that is, the heat source is increased or decreased one by one, but it is also possible to increase or decrease the heat source by two or more at a time.

Although the heat source is increased or decreased according to the set time, the inclination A when the manipulated variable MV shifts to the minimum value as shown in FIG. In this case, or when the slope B when the manipulated variable MV shifts to the maximum value becomes a certain value or more, the heat source may be reduced or increased, respectively. It is also possible to increase or decrease the heat source according to the change of the target value SV.

As described above, when the heat capacity and the heating capacity of the load 14 are balanced according to the increase or decrease of the heat source, the operation amount changes.

Therefore, Kp and T stored in the memory which are set for each mode according to the change of the control mode are stored.
It may be possible to switch to a control constant such as I or TD,
Alternatively, the control constant of the continuous controller 18 may be adjusted. 7 to 11 are diagrams for explaining this adjustment processing.

FIG. 7 shows the control system of the continuous controller 18 as a digital PID control block. In the figure, w corresponds to the target value SV, e corresponds to the deviation er,
u corresponds to the manipulated variable MV, and y corresponds to the controlled variable PV_OUT. T is a sampling time.

The continuous time control law of the PID compensator is generally defined by the following transfer function.

Gc = Kp (1 + 1 / TI · s + TD · s) (4) Here, Kp is a proportional gain, TI is an integration time, and TD is a differential time.

Since the PID compensator 22 of FIG. 7 is a digital compensator, the above equation (4) can be made into a discrete time velocity type PID control law by backward difference approximation, and the manipulated variable u (k) is u (k) = u (k-1) + (Kp + KI + KD) * e (k)-(Kp + 2KD) * e (k-1) + Kp * e (k-2) (5) and the sampling frequency k Can be represented.

Here, KI (= KpT / TI) is an integral gain, KD (= KpTD / T) is a differential gain, and the transfer function Gc is shown in FIG.

Kp, TI, T included in the above equation (5)
Each constant of D needs to be adjusted to an optimum value that is unique to the control system.

However, the adjustment of Kp, TI, and TD is delicate depending on the environment in which the system is placed and the controlled object, and conventionally, the experience of an on-site engineer has been the main factor.

Therefore, in this embodiment, the so-called closed loop type limit cycle tuning method is adopted in the temperature control mode so that even a beginner of PID tuning can easily adjust the PID.

That is, as shown in FIG. 8, at the time of PID tuning, the PID compensator 22 performs on / off control of two positions in which the manipulated variables become M and -M according to the positive / negative of the deviation. A limit cycle is generated as shown in (a). The horizontal axis t in FIG. 9 is time.

The amplitude X0 can be measured from the waveform of the limit cycle shown in FIG. 9 (a). Further, the period T0 and the on time Th can be measured from the waveform of the on / off cycle of the manipulated variable u in FIG. 9 (b).

The proportional gain Kp and the like can be determined from the amplitude X0 and the like thus measured as shown in the following table. It should be noted that the values are made different between the constant value control and the additional value control.

[0057] In the above table, A = 8M / πX0, and α is a correction coefficient. Normally, the value of the proportional gain Kp is calculated with α = 1, but the correction coefficient α can be determined according to the control system in order to bring it closer to the optimum constant. There is no particular method for determining α, and the value is determined by the experience of a veteran operator.
Although it is possible to adopt the I method, in this embodiment, the correction coefficient α is calculated by the following equation (6) from the description function of the nonlinear element.
It should be calculated from such an operation.

Α = √ ((1-cos (2Th / T0π)) / 2) (6) As shown in FIG. 10, hysteresis may be given to the on / off operation performed by the PID compensator 22. It should be noted that Δ in FIG. The reason why the hysteresis is given in this way is that the heating time Th or the cooling time T0-Th depends on the controlled object and the sampling time T
If it becomes smaller than, α = 0 and the proportional gain K
This is to prevent p = 0.

FIG. 11 shows the waveform of the controlled variable y and the waveform of the manipulated variable u when the on / off control with hysteresis is performed by the control system of FIG. 10, as in FIG.
The method of determining the control constant Kp of the PID compensator 22 from the amplitude X0 of these waveforms is the same as in the case of FIG.

When the hysteresis is applied in this way, the amplitude X0 of the controlled variable y may be increased more than in the case where it is not. However, even if X0 including this increase is directly used, as a result, Since the gain of the compensator 22 tends to decrease, it is considered that the influence thereof does not lead to unstable control.

As described above, even if the flow rate of the fluid changes due to disturbance or the like in the temperature control mode, the optimum control constant Kp etc. is determined by performing the PID tuning as described above, and stable accuracy is obtained. Good control can be continued.

Although the embodiment has shown the case where the continuous control unit performs the PID control, the present invention can be applied to other control such as fuzzy control. In this case, the same processing as the processing performed in the embodiment for the proportional gain, the integration time, and the differential time, which are control constants in PID control, may be performed for the membership function, which is a control constant in fuzzy control.

In the embodiment, the control section is composed of the on / off control section and the continuous control section, but it may be constituted by only the on / off control section or only the continuous control section. Further, in the embodiment, the total number of control units, that is, the total number of heat sources is set to 3, but the total number may be set to more than this.
Further, in some cases, the total number may be two.

[0064]

As described above, according to the present invention, the temperature control is performed by the combination of the control means for controlling the heat source adapted to the heat capacity of the fluid, so that the temperature control can be stably and accurately performed. . Further, even if a disturbance or the like occurs during the temperature control and the fluid flow rate or the like changes, the optimum combination is selected again according to the change and the temperature control is performed, so that accurate control can be performed regardless of the disturbance. It can be continued.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a fluid temperature control apparatus according to the present invention.

FIG. 2 is a block diagram showing the configuration of a control system of the continuous control unit shown in FIG.

3 is a flowchart showing a processing procedure executed by the CPU of FIG. 1, and is a diagram showing only processing at the time of activation of the apparatus shown in FIG.

FIG. 4 is a graph used to explain the process shown in FIG. 3, showing how the temperature of the fluid changes when on / off control is performed and how the control amount applied to the continuous control unit changes. It is a graph which shows.

5 is a diagram used for explaining the process shown in FIG. 3, and is a diagram showing a combination of control units corresponding to the calculated heating ratio.

FIG. 6 is a graph showing how the on / off control unit is instructed to operate or not when the control capability becomes excessive or insufficient during temperature control by the continuous control unit.

FIG. 7 is a block diagram showing the control system of the continuous control unit shown in FIG. 1 as a digital PID control block.

8 is a block diagram of a control system when the PID compensator shown in FIG. 7 performs on / off control.

9 is a graph showing how the control amount and the manipulated variable change when on / off control is performed by the control system shown in FIG. 8.

10 is a block diagram of a control system when hysteresis is given to the on / off operation performed in the PID compensator of FIG. 9.

11 is a graph showing how the control amount and the manipulated variable change when ON / OFF control is performed by the control system shown in FIG. 10.

[Explanation of symbols]

3 ON / OFF control calculation unit 4 Load heat capacity estimation unit 5 manipulated variable calculator 11 heat source 12 heat sources 13 heat source 14 load 16 ON / OFF control section 17 ON / OFF control unit 18 Continuous control unit

Claims (5)

(57) [Claims] 1. A control means for supplying heat generated by a heat source to the fluid according to a deviation between a target temperature of the fluid and a current temperature of the fluid is provided for each of the plurality of heat sources. In the fluid temperature control device for controlling the fluid to the target temperature by appropriately selecting a combination of the respective control means from among, the control for turning on / off the heat supply to the fluid according to the polarity of the deviation is performed by the plurality of control means. Controls that are performed by all, calculate the ratio of ON time to one cycle of ON / OFF, estimate the heat capacity of the fluid based on the calculated ratio, and control the heat source of the heat capacity corresponding to the estimated heat capacity A fluid temperature control device in which a combination of means is selected from the plurality of control means, the control means of the selected combination is caused to perform temperature control, and the temperature of the fluid is controlled to a target temperature. 2. An on / off control means for performing on / off control for turning on / off the supply of heat generated by the heat source to the fluid in accordance with the polarity of the deviation between the target temperature of the fluid and the current temperature of the fluid, or the heat source based on the deviation. A continuous control means is provided for each of a plurality of heat sources to continuously control the heat generated in the fluid to the fluid, and a combination of the control means is appropriately selected from the plurality of control means to target the fluid. In a fluid temperature control device for controlling the temperature, all on / off control means perform on / off control and all continuous control means perform on / off control,
A combination of control means for calculating a ratio of ON time to one cycle of ON / OFF, estimating the heat capacity of the fluid based on the calculated ratio, and controlling a heat source of a heat capacity corresponding to the estimated heat capacity is used. Selecting from the plurality of on / off control means and continuous control means, causing the on / off control means in the combination of the selected control means to perform on / off control, and continuously to the continuous control means in the selected combination. A fluid temperature control device for controlling the temperature of the fluid to a target temperature. 3. The continuous control means is always included in the combination of the selected control means, and the continuous control means is a control means for performing a predetermined control based on a predetermined control constant, The fluid temperature control device according to claim 2, wherein each value of the predetermined control constant used for controlling the continuous control means is predetermined for each combination of the selected control means. 4. The total number of the on / off control means and the continuous control means is 2 or more, and the continuous control means is always included in the combination of the selected control means, During the temperature control, when the operation amount of the continuous control means becomes the minimum value, the ON / OFF control means for performing the temperature control is decreased, and when the operation amount of the continuous control means becomes the maximum value, the temperature 3. The fluid temperature control device according to claim 2, wherein the number of on / off control means for performing control is increased. 5. The continuous means is a control means for performing PID control, and causes the continuous control means to perform on / off control during temperature control of the fluid to generate a limit cycle, and the amplitude and on / off of the limit cycle waveform. 3. The fluid temperature control device according to claim 2, wherein each of the proportional gain, the integral time, and the derivative time used for the control of the continuous control means is changed based on one cycle and the ON time.