JPH0234048B2 - EKITAIYOKINOONDOSEIGYOSOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an analyzer for chemically analyzing a large number of samples, such as blood samples, in hospitals and various chemical analysis institutions. This invention relates to a temperature control device.

For example, when using a flow cell for colorimetric measurements, the samples that have undergone reaction are transferred one after another from the reaction container to the flow cell, and each sample is retained in the flow cell and colorimetrically measured at least once. ing. In this way, a sample in an amount that at least fills the flow cell is separated by a certain amount of air and is sent to the flow cell, and while it is stopped in the flow cell, it is rapidly heated or cooled to maintain a predetermined temperature for a predetermined period of time. need to be kept. The processing efficiency of recent chemical analyzers is high, and they are now able to process an extremely large number of specimens in a short period of time. Therefore, it is necessary to heat or cool the sample to a predetermined temperature within the flow cell in a short time. Furthermore, the recent trend in chemical analyzers is to reduce the amount of sample and reagent used as much as possible, and the flow cells are also becoming smaller, so the temperature control device for the sample in the flow cell is also becoming smaller. , it is necessary to make the entire analyzer compact.

Conventionally, methods using a constant temperature liquid bath and methods in which the flow cell is provided with direct heating and cooling means are known as methods for controlling the test liquid in the flow cell. In those that use a constant temperature liquid bath, a heating medium such as water or ethylene glycol is used, and a container is housed in this, and the temperature of the heating medium is controlled to maintain the temperature of the specimen at the desired set temperature. . However, in this case, the volume of the heat medium is required to be hundreds to thousands of times larger than the volume of the flow cell, resulting in a drawback that the entire device becomes extremely large. Moreover, a large-sized device is required to control the temperature of such a large-volume heat medium, which is expensive. Furthermore, since the heat capacity of the thermostatic liquid bath is very large, there is also the drawback that when changing the set temperature, it takes a very long time to reach the specified temperature. This means that when there is a temperature fluctuation, it takes a long time to reach an equilibrium state, resulting in poor reaction characteristics and, therefore, poor control accuracy.

In order to eliminate such defects, a pair of thermomodules 2a and 2b made of, for example, Peltier elements are attached to the opposing upper and lower surfaces or side surfaces of the flow cell 1, as shown in FIGS. 1A and B, and these surfaces are A pair of temperature sensors 3 on a plane orthogonal to
A model with a and 3b attached has been proposed. A test solution is introduced into this flow cell 1 through the introduction tube 4,
While the thermomodules 2a and 2b are heated or cooled by the outputs of the temperature sensors 3a and 3b to maintain the test liquid at a predetermined temperature, light from the light source 5 is transmitted through the flow cell 1 via the collimator lens 6. The sample is made incident on the light receiving element 7 for colorimetric measurement, and after the measurement, the sample is discharged to the outside of the flow cell 1 through the discharge pipe 8. When the thermomodules 2a and 2b are constructed using Bertier elements, cooling or heating can be performed selectively by changing the polarity of the voltage applied to them. It is complicated and expensive. Furthermore, there is always a dead zone at the time of switching from cooling to heating or vice versa, and there is a drawback that temperature stability deteriorates when disturbances occur at this point. Furthermore, the thermal response is poor, making it difficult to perform highly accurate control. Furthermore, as the process of sequentially introducing samples into the flow cell according to the time sequence is repeated dozens or even hundreds of times, the heat capacity increases and the difference between the temperature inside the flow cell and the set temperature gradually increases. There is also the drawback that offset occurs.

In this way, it is extremely difficult to bring the liquids sequentially introduced into the flow cell to a predetermined set temperature in a short period of time and maintain this state for a predetermined period of time, and it is necessary to solve several difficult problems. For example, considering each specimen, under adverse conditions such as two disturbances occurring within a short period of time, the environmental temperature fluctuating in the range of 18 to 28 degrees Celsius, and the power supply fluctuating by 10%, for example, the set temperature may be changed to 10%. It is necessary to meet extremely strict requirements such as maintaining the temperature within a range of 37° ± 0.2° for 2 seconds.
Moreover, it is necessary to make the entire device small and inexpensive.

Furthermore, in order to perform temperature control as described above, it is necessary to detect the temperature inside the flow cell, and for this purpose it is sufficient to place a temperature sensor inside the flow cell. This causes contamination, and it is necessary to take measures such as cleaning, and since it is immersed in liquid, there are problems with durability. In order to eliminate this drawback, it is necessary to place the temperature sensor outside the flow cell, but it is very difficult to accurately detect the temperature of the liquid inside the flow cell, especially when placed near a heating source. Then, the influence of heat received from this becomes large and accuracy deteriorates. In order to eliminate such drawbacks, it may be possible to arrange the device far away from the heating source, but this has the disadvantage of making the device large.

SUMMARY OF THE INVENTION An object of the present invention is to provide a temperature control device for a liquid container that can eliminate the above-mentioned conventional drawbacks and also satisfy the various conditions mentioned above.

A temperature control device for a liquid container according to the present invention includes a container body containing a liquid used for chemical analysis, a temperature sensor disposed in close contact with a part of the outer peripheral surface of the container body containing this liquid, and A heat delay member disposed outside the temperature sensor so as to cover the temperature sensor, a heat disposed so as to entirely surround the container body, the temperature sensor, and the heat delay member, and heat detected by the temperature sensor. a control circuit that controls power supply to the heater according to a temperature set and a set temperature, and a container body containing the liquid in which the heat delay member has a thermal time constant determined by its heat capacity and thermal resistance. It is characterized by being configured so that the thermal time constant is equal to the thermal time constant of

Furthermore, the temperature control device of the liquid container of the present invention includes:
A container body containing a liquid used for chemical analysis, a temperature sensor disposed in close contact with a part of the outer peripheral surface of the container body containing this liquid, and a temperature sensor placed on the outside of the temperature sensor to cover the temperature sensor. a heat delay member disposed in the container body, a heater disposed so as to entirely surround the container body, the temperature sensor, and the heat delay member; and a heater arranged in accordance with the temperature detected by the temperature sensor and the set temperature. a control circuit for controlling power supply to the heater, a constant temperature frame arranged to surround the heater, and a constant temperature frame connected to the constant temperature frame to maintain the constant temperature frame at a constant temperature lower than the set temperature. a cooling heat source, and the heat delay member is configured to accommodate the liquid with a thermal time constant determined by its heat capacity and thermal resistance so that the temperature sensor can detect the temperature of the liquid contained in the container body. The thermal time constant of the container body is set to be equal to the thermal time constant of the container body.

In a preferred embodiment of the invention, a cooling source is used in addition to the heating source, both of which are used to quickly and accurately maintain the liquid within the container at the desired set point temperature.

The present invention will be described in detail below with reference to the drawings.

FIG. 2 is a sectional view showing the configuration of an example of the temperature control device of the present invention. A flow cell 12 to which a test liquid is supplied and discharged via a pair of conduits 11 (only one is shown) is surrounded by a thermostatic frame 13 that constitutes a heat sink.
This flow cell 12 constitutes a container body. A plurality of depressions 14 are formed in the bottom 13A of the thermostatic frame 13, and filled with a substance having low thermal conductivity or air. In this example, it is filled with air. A Peltier element 15 functioning as a cooling heat source is arranged below the constant temperature frame bottom 13A, and the high temperature side of this Peltier element is connected to a heat sink 16. This heat sink 16 also serves as a support for the entire container, and the constant temperature frame 1
3 is fixed to the heat sink 16 with screws 17. This screw 17 is made of a thermally insulating material, for example Delrin.
A flat temperature sensor 20 is disposed in close contact with a part of the outer peripheral surface of the flow cell 12, and a similarly flat heat delay plate 19 is disposed so as to cover this temperature sensor. Furthermore, a heater 18 functioning as a heating source is arranged so as to almost entirely surround these flow cells 12, temperature sensors 20, and heat delay plates 19. These members are attached to the bottom 13 of the constant temperature frame 13.
placed in a space defined by A and side wall 13B,
The upper opening of this space is closed by a lid 21.
Further, an auxiliary temperature sensor 22 is provided on the outer surface of the side wall 13B of the constant temperature frame 13 for detecting the temperature of the constant temperature frame.
will be established.

As described above, since the Peltier element 15 is in contact with the bottom 13A of the constant temperature frame 13, there is a delay in heat conduction between the top and bottom of the constant temperature frame, and a temperature difference is likely to occur. Therefore, in this example, a recess 14 is formed in the bottom portion 13A, and a material with low conductivity is filled in the recess 14 to provide thermal resistance, thereby controlling the flow of cooling heat and making the entire thermostatic frame 13 uniform in temperature. It's on.
The heat capacity of the lid 21 located far from the Peltier element 15 is increased so that it also acts as an auxiliary cooling heat source. In this way, the constant temperature frame 13 and the lid 21 surrounding the flow cell 12 are cooled almost evenly by the Peltier element 15, but the temperature of these parts is kept at a desired set temperature, for example, 37°C.
The power supply to the Peltier element 15 is controlled by the detection output of the auxiliary temperature sensor 22 so that the temperature is maintained sufficiently lower than the temperature.

The temperature sensor 20 detects the temperature of the liquid contained in the flow cell 12. Although this temperature can be accurately measured by placing the sensor in the liquid, contamination between the liquids and durability Considering the performance, it is better not to place it inside the flow cell. However, when placed outside the flow cell, it becomes a problem how to accurately detect the temperature of the liquid inside the flow cell. Therefore, in this example, the sensor 20 is disposed immediately outside the flow cell 12, and a heat delay plate 19, which constitutes a heat resistance member, is disposed between the sensor 20 and the heater 18. By determining the thermal time constant determined by the thermal resistance and heat capacity of the heat delay plate 19 to be approximately equal to the thermal time constant of the flow cell 12, the flow cell
The temperature inside the flow cell can be accurately detected by the temperature sensor 20 located outside of the flow cell. As will be described later, the operating characteristics of the control system can be changed by making the thermal time constant of the heat delay plate 19 larger or smaller than that of the flow cell 12.

Furthermore, the temperature sensor 20 is constructed by trimming a foil made of carefully selected pure metal (Ni, Pt), etc., and then binding it with epoxy or the like. The electrical resistance value of such a foil temperature sensor 20 is several hundred Ω.
Since the thermal resistance and heat capacity are small, the response is extremely fast. Further, the heater 18 is constituted by a wire-wound heater in which a resistance wire is wound around an insulating plate. In this example, the heat delay plate 19 is connected to the constant temperature frame 13 or the heater 18.
The heat transfer time constant is determined so that the time delay between taking in the heat flow from the sample and transmitting it to the temperature sensor 20 is slightly longer than the time delay until the same heat flow is transmitted to the flow cell 12 containing the sample. . That is, the thermal time constant of the heat delay plate 19 is equal to that of the flow cell 1.
The thermal time constant is set to be slightly larger than the thermal time constant of 2. The heat delay plate 19 is made of a heat-resistant material such as glass epoxy resin, and has a transfer time constant determined by the product of its heat capacity and thermal resistance as described above. By appropriately selecting the material and thickness of this heat delay plate, the overall size of the container can be reduced.

In the temperature control device of this example, as described above, the flow cell 12 is surrounded by the heater 18, the heater is further surrounded by the constant temperature frame 13, the Peltier element cooling heat source 15 is brought into contact with this constant temperature frame 13, and the constant temperature frame 13 is set to a desired setting. The temperature is constantly maintained at a temperature lower than 37°C, for example 20°C. That is, the cooling heat source 15
acts as a kind of thermal bias that biases the temperature of the liquid in the flow cell toward the lower temperature side. By biasing to the low temperature side in this way, comparing the temperature detected by the temperature sensor 20 with the set temperature, and controlling the energization to the heater 18 according to the difference, the liquid in the flow cell can be quickly and accurately heated. A desired set temperature can be maintained. That is, by heating at the same time as cooling, control characteristics can be significantly improved.

FIG. 3 shows a thermal equivalent circuit of the entire container temperature control device shown in FIG. 2, and the correspondence between each element of this circuit and each part of the container is as follows.

R _K1 , R _K2 ... Thermal resistance of constant temperature frame 13 C _K ... Heat capacity of constant temperature frame 13 R _H1 , R _H2 ... Thermal resistance of heater 18 V _H ... Calorific value of heater 18 R _O1 ... Thermal resistance of heat delay plate 19 C _O ... Heat capacity of the heat delay plate 19 R _F ... Thermal resistance of the wall of the flow cell 12 C _F ... Heat capacity of the wall of the flow cell 12 R _X ... Thermal resistance of the liquid C _X ... Heat capacity of the liquid -I _P ... Cooling heat flow by the Peltier element 15 +I _H1 to +I _H4 ... Heating heat flow by heater 18 SW... Switch representing supply and discharge of liquid to and from flow cell 12 Points a to e of the thermal equivalent circuit correspond to points a to e shown in FIG. 2, respectively. Furthermore, in this thermal equivalent circuit, the thermal resistance and heat capacity of the temperature sensor 20 are ignored because they are small. This temperature sensor is at point C
It is located at the position of When comparing the left side and the right side of this point C, since the right side contains a flow cell and a liquid, the heat delay plate 19 having a thermal resistance and heat capacity that is approximately equal to the thermal resistance and heat capacity of these flow cells and the liquid is heated. By inserting the temperature sensor 20 between the temperature sensor 18 and the temperature sensor 20, the temperature sensor 20 is equivalently located approximately at the center of the entire system. temperature can be detected accurately.

FIG. 4 shows that after the liquid maintained at a predetermined temperature in the flow cell 12 is discharged, the next liquid is transferred to the conduit 1.
1 is a graph showing changes in the temperature at point e in the flow cell and the temperature at point c detected by the temperature sensor 20 when the liquid is supplied into the flow cell through the temperature sensor 20. When the liquid in the flow cell 12 is at a predetermined set temperature, point e
Point c is also at approximately the same desired set temperature. instantaneous
When the liquid in the flow cell starts to be discharged at T ₀ , the temperature at point e drops rapidly. On the other hand, the temperature at point c changes relatively slowly. When this temperature drop at point c is detected, the heater control circuit operates, supplies power to the heater 18, and raises the temperature. Therefore, from the instant _T1 , the temperature at point e in the flow cell begins to rise. . On the other hand, since there is a heat delay plate 19 between the heater 18 and the temperature sensor 20, the temperature rise at point c is delayed until the instant T ₂ ', and the temperature rise from instant T ₂ ' to point c
temperature will rise. New liquid is supplied at instant _T3 , but since the temperature of the new liquid is generally lower than the set temperature, point e
temperature drops sharply again. This liquid supply takes place up to the moment T ₄ . During this time, current continues to be supplied to the heater 18, and after a sufficient period of time has elapsed, the temperatures at points e and c are maintained at the desired set temperature of 37°C. Such a cycle is repeated for successive liquids to quickly and precisely maintain the successive liquids at a predetermined set point temperature. In addition, in FIG. 4, the ambient temperature is 24°C.

In this example, as described above, the thermal time constant of the heat delay plate 19 is set to be slightly larger than that of the flow cell 12, but with this configuration, the following effects can be obtained. FIG. 5 shows the state of temperature overshoot at points b, c and e, respectively. Assuming that the current set temperature is T _S , the heater 18 is energized and the temperature rises. In this case, the temperature at point b near the heater 18 rises most rapidly, as shown by curve b, and at point c, shown by curve c.
Although the temperature at point e is more gradual, it rises more rapidly than the temperature at point e shown by curve e. At instant _tS , when the temperature at point c reaches the set temperature, the temperature at point b has greatly overshot, but the temperature at point e has not yet reached the set temperature. point c
When the temperature exceeds T _S , the power supply to the heater 18 is cut off or reduced, and the temperature begins to drop. Therefore, the temperature at point e reaches the lower limit of the allowable error range ±ΔT _S centered on the set temperature T _S at the instant t _A , and further increases gradually, but does not exceed the upper limit of the allowable error range. In this way, overshoot can be suppressed within an allowable error range, and heating can be performed accurately to a desired set temperature within a short period of time.

Further, according to the present invention, the thermal time constant of the heat delay plate 19 can be made smaller than that of the flow cell 12, and the operating characteristics in this case are shown in FIG.
In this case, the rate of temperature rise at point e will be higher than at point c, and the temperature at point e in the flow cell will rise quickly and reach the set temperature T _S at instant t _A. In this way, the temperature of the liquid can be rapidly raised to the desired temperature. After that, when the temperature at point c reaches the set temperature T _S at an instant t _S , the energization to the heater ₁₈ is reduced and the temperature at point _e begins to drop. By configuring each part so that the temperature at point e at t _S is within the allowable error range T _S ±ΔT _S , the influence of overshoot can be eliminated and the rise characteristics can be improved.

FIG. 7 is a circuit diagram showing the configuration of an example of a control circuit that receives the output of the temperature sensor 20 and controls power supply to the heater 18. In FIG. 2, the output of the auxiliary temperature sensor 22 attached to the constant temperature frame 13 is supplied to the Peltier element control circuit 31, and the output voltage of the power supply 32 connected to the Peltier element 15 is controlled by the output, so that the constant temperature frame 13 is always Ensure that the temperature reaches the specified temperature. In the present invention, since the Peltier element 15 is used only as a cooling heat source, the power source 32 may be a unipolar DC power source. A temperature sensor 20 provided within the constant temperature frame 13 is connected to one side of a DC bridge 33, and the output signal of this bridge is supplied to a proportional control circuit 34. This proportional control circuit 34 controls the amount of heating from the heater 18 in proportion to the deviation between the set temperature and the flow cell temperature. The output signal of this proportional control circuit 34 is supplied to a differential control circuit 35. This differential control circuit does not work when the temperature of the flow cell does not change, but when the temperature of the flow cell changes rapidly due to liquid being supplied to and discharged from the flow cell 12, the heater is activated depending on the speed of the change. This is to control the amount of heating by 18. This differential control circuit 3
5 is further supplied to an integral control circuit 36.
This integral control circuit is for eliminating an offset, which is a steady deviation between the set temperature and the temperature of the flow cell. In this way, the proportional control circuit 34,
The output through the differential control circuit 35 and the integral control circuit 36 is supplied to the heater drive circuit 37. The heater drive circuit 37 includes a sawtooth wave generator 38, a differential amplifier 39 that calculates the difference between the output of the sawtooth wave generator 38 and the output of the integral control circuit 36, a pulse generation circuit 40 that generates switching pulses from this differential output, and Conduction and disconnection are controlled by switching pulses.
It is equipped with a switch 41 like an SCR. The switch 41 is, for example, a bidirectional switch in which two SCRs are connected in antiparallel, and is connected between the commercial power source 42 and the heater 18.

The operation of the heater drive circuit 37 of this example will be explained with reference to FIGS. 8A and 8B. FIG. 8A shows the output control voltage e of the integral control circuit 36 and the sawtooth wave generator 3.
A sawtooth voltage S from 8 is shown. The two voltages are compared by the differential amplifier 39, and the switching pulse generator 40 generates a switching pulse having a pulse width corresponding to the level difference between the two voltages, as shown in FIG. 8B. During the connection time of this switching pulse, the switch 41 is conductive, and the heater 18 is energized for only that period. In this way, the supply of electricity to the heater 18 can be controlled according to the difference between the temperature detected by the temperature sensor 20 and the set temperature, and the liquid in the flow cell can be maintained at a predetermined value.

If the output of the differential amplifier 39 is not synchronized with the voltage of the AC power supply 42, the power supply voltage will not necessarily be zero when the switch 41 is turned on and off, resulting in so-called switching bounce, which becomes noise and is transmitted to computers, etc. There is a risk that the signal may be transmitted and malfunction may occur. In order to eliminate such drawbacks, the ninth
As shown in the figure, the switching pulse generator 40 is provided with a power supply voltage zero-crossing detection circuit 40A shown in FIG. 10A, which generates a pulse at the zero-crossing point as shown in FIG. 40B. Pulses as shown in FIG. 10C are supplied from the differential amplifier 39 to the input side of the pulse shaping circuit 40B, and switching pulses synchronized with the zero-cross pulse are supplied from the output side as shown in FIG. 10D. is output. By controlling the SCR of the switch 41 with this pulse, conduction and disconnection are always performed at the instant when the power supply voltage becomes zero, so that the above-mentioned noise does not appear.

As mentioned above, the power supply to the heater 18 is controlled by turning on and off the commercial power supply using the switch 41, but the duty cycle of the switch pulse that triggers the switch 41 depends on the output voltage e of the integral control circuit 36. It will change almost proportionally.
For example, if the output voltage e changes over ±2V around OV depending on the difference between the detected temperature and the set temperature, a switch pulse with a duty cycle of 50% is obtained when the output voltage e is OV. is,
In this case, the temperature inside the flow cell is maintained at approximately the set temperature. Now, assuming that the period of the sawtooth voltage S is 0.1 seconds, the switch 41 is turned on and off every 0.05 seconds, and the commercial power supply is cut off every five half cycles. As the output voltage e approaches -2V, the duty cycle increases and heater 1
8 is supplied with power over 5 half cycles of the power supply, e=
At -2V, switch 41 is always ON,
The full power supply voltage will be applied. When the heater drive control circuit 37 is configured in this way, the set temperature can be easily changed by changing the temperature at which the output voltage e becomes OV.

The present invention is not limited to the embodiments described above, but can be modified in many ways. For example, the first
As shown in FIG. 1, the outer wall 13B of the constant temperature frame 13 can be gradually thickened as it moves away from the Peltier element 15 to increase the heat capacity. The temperature of the frame 13 can be made even more uniform.

Further, in the above-described embodiment, a Peltier element was used as the cooling heat source, but it is of course possible to use other cooling means and also to use a heater other than the wire-wound heater as the heating source. Further, if the temperature of the ambient atmosphere around the container does not change much, the cooling heat source 15 does not need to be controlled and the auxiliary temperature sensor 22 can be omitted. As described above, according to the present invention, since the temperature sensor is provided outside the container body, the problem of contamination between test liquids is eliminated and the durability of the temperature sensor is also improved. Further, since a heat delay member having heat delay characteristics approximately equal to that of the container body is inserted between the temperature sensor and the heater, the temperature of the liquid in the container body can be accurately determined. Moreover, by appropriately setting the characteristics of this heat delay member, the operating characteristics of the control system can be changed, and desired operating characteristics can be set depending on the purpose of use.

[Brief explanation of drawings]

1A and 1B are perspective views showing a conventional flow cell using a Peltier element as a heating source and a cooling heat source, and FIG. 2 is a sectional view showing the configuration of an example of a liquid container incorporating the temperature control device of the present invention. , Figure 3 is the same thermal equivalent circuit diagram, Figure 4 is a graph showing the temperature change in the flow cell and the temperature change of the temperature sensor, and Figures 5 and 6 are the thermal time constants of the heat delay plate in the flow cell. A graph showing the temperature overshoot when the temperature is set larger and smaller than the thermal time constant of , Fig. 7 is a circuit diagram showing the configuration of an example of the heater control circuit, and Fig. 8 A and B similarly explain its operation. FIG. 9 is a block diagram showing the configuration of an example of a switching pulse generation circuit, FIGS. 10A to 10D are waveform diagrams for explaining its operation, and FIG. 11 is a temperature diagram of the present invention. FIG. 7 is a cross-sectional view showing the configuration of another example of a liquid container incorporating a control device. DESCRIPTION OF SYMBOLS 11...Liquid conduit, 12...Flow cell, 13...Thermostatic frame, 15...Peltier element (cooling heat source), 16...
Heat sink, 18... Heater (heat source), 19... Heat delay plate, 20... Temperature sensor, 21... Lid, 22... Auxiliary temperature sensor, 33... Bridge, 34... Proportional control circuit, 35... Differential control circuit, 36... integral control circuit,
37... Heater drive circuit, 38... Sawtooth wave generator, 3
9...Differential amplifier, 40...Pulse generation circuit, 41...
Switch, 42...Commercial power supply, 40A...Zero cross detection circuit, 40B...Pulse shaping circuit.

Claims (1)

[Claims] 1. A container body containing a liquid used for chemical analysis, a temperature sensor disposed in close contact with a part of the outer peripheral surface of the container body containing this liquid, and an outer surface of the temperature sensor. a heat delay member disposed to cover the temperature sensor; a heater disposed to entirely surround the container body, the temperature sensor, and the heat delay member; and a temperature and setting detected by the temperature sensor. and a control circuit that controls power supply to the heater according to the temperature, and the heat delay member:
A temperature control device for a liquid container, characterized in that a thermal time constant determined by its heat capacity and thermal resistance is equal to a thermal time constant of a container body containing the liquid. 2. The heat delay member is configured in a plate shape, and the temperature sensor is configured as a flat temperature sensor whose surface receives heat flow between the plate-shaped heat delay member and the container body. A temperature control device for a liquid container according to claim 1. 3. The temperature control device for a liquid container according to claim 1, wherein the thermal time constant of the heat delay member is made larger than the thermal time constant of the container body containing the liquid. . 4. The temperature control device for a liquid container according to claim 1, wherein the thermal time constant of the heat delay member is smaller than the thermal time constant of the container body containing the liquid. 5. The control circuit includes a proportional control circuit that controls power supply to the heater in proportion to the deviation between the set temperature and the temperature detected by the temperature sensor, and a proportional control circuit that controls power supply to the heater in proportion to the deviation between the set temperature and the temperature detected by the temperature sensor, and when the temperature detected by the temperature sensor suddenly changes. , a differential control circuit that controls the power supply to the heater according to the speed of change; and a differential control circuit that controls the power supply to the heater so as to eliminate a steady deviation between the set temperature and the temperature detected by the temperature sensor. 2. The temperature control device for a liquid container according to claim 1, further comprising an integral control circuit for controlling the temperature of a liquid container. 6. A container body containing a liquid used for chemical analysis, a temperature sensor placed closely on a part of the outer peripheral surface of the container body containing this liquid, and a temperature sensor covering the outside of the temperature sensor. a heater arranged so as to entirely surround the container body, the temperature sensor, and the heat delay member; A control circuit that controls power supply to the heater, a constant temperature frame arranged to surround the heater, and a constant temperature frame connected to the constant temperature frame to maintain the constant temperature frame at a constant temperature lower than the set temperature. and a cooling heat source that accommodates the liquid, the heat delay member having a thermal time constant determined by its heat capacity and thermal resistance, so that the temperature sensor can detect the temperature of the liquid contained in the container body. 1. A temperature control device for a liquid container, characterized in that the temperature control device is configured to have a thermal time constant equal to the thermal time constant of the container body.