JPH0512626B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to the study of what characteristics various products and materials have in a certain temperature environment, and how they are affected by the environment. The present invention relates to a method of obtaining a target low temperature using a refrigeration device in an environmental test device such as a thermostat, etc., and a refrigeration device for carrying out the method.

[Prior art and its problems] Direct temperature control is an old method for controlling a constant temperature at a certain target point in an environmental test device, etc. According to this method, a heater and a refrigerator are used for temperature control, and the target temperature is maintained at a constant temperature. If it is lower, heat it with a heater,
If the temperature is higher than the target temperature, cool it by flowing refrigerant into the evaporator of the refrigerator. However, according to this method, since the heater and the refrigerator operate alternately, the articles placed in the temperature-controlled space are exposed alternately to hot air and cold air, which is not preferable because they receive thermal shock.

As a way to solve this problem,
There is a method disclosed in No. 29265. In this method,
A constant amount of refrigerant is always allowed to flow through the refrigerator evaporator to obtain the lowest temperature within the control temperature range, and the heater is controlled and operated according to the target temperature to harmonize the refrigerator function and heater output. to obtain the desired temperature.

According to the latter method, there is less thermal shock during temperature control and it is possible to perform smooth temperature control as a whole, but even when trying to obtain a constant low temperature,
As in the case of high temperature control, the temperature must be controlled by increasing or decreasing the output of the heater, and the problem remains that energy is wasted accordingly.

By the way, the slope of the temperature drop due to the refrigerator is the fourth
As shown in the figure, it is clear that the opening of the evaporator expansion mechanism is large immediately after it is set to a certain opening degree, and becomes smaller as time passes.

Therefore, the present invention attempts to solve the conventional problems by utilizing this phenomenon.In order to obtain a constant target low temperature, it is possible to smoothly control the temperature with less thermal shock, and at the same time, it is possible to save energy compared to the conventional method. The object is to provide a method and a refrigeration apparatus for carrying out the method.

[Means for solving problems]

The object of the present invention is to provide a method for obtaining a target low temperature at a target location using a refrigeration system, which comprises: using a variable opening type expansion mechanism as an expansion mechanism for an evaporator in a refrigeration circuit; The expansion mechanism is throttled in stages from an opening larger than the opening to obtain a low temperature, and the expansion mechanism throttle operation is as follows:
When the temperature drop gradient at the target location at the current expansion mechanism opening reaches a predetermined gentleness, the expansion mechanism is moved to a next smaller opening. It is determined whether the temperature has reached a predetermined proportional band for proportional control, and while the temperature at the target location has not reached the proportional band, the expansion mechanism is throttled and the proportional band is reached. 2. A method characterized in that the temperature of the target location is thereafter proportionally controlled toward the target low temperature when the temperature of the target location reaches the proportional band by repeatedly determining whether or not the temperature has been lowered. A refrigeration system whose configuration is shown in , namely: a refrigeration circuit using a variable opening expansion mechanism as an expansion mechanism for an evaporator; an expansion mechanism drive means for adjusting the opening of the expansion mechanism; and a goal. Temperature detection means for detecting the temperature of the target location to be lowered; target low temperature setting means; initial opening degree setting means for the expansion mechanism; a reference value setting means for determining the temperature drop gradient at the initial stage of the temperature drop at the expansion mechanism opening degree as a reference value; and after the temperature drop gradient at the initial temperature drop is determined by the reference value setting means, the temperature detection temperature drop gradient detection means for determining the temperature drop gradient of the location to be set to the target low temperature based on the temperature detected by the means; When the latter value reaches a predetermined ratio with respect to the former reference value, a drive signal is issued to the expansion mechanism driving means to throttle the expansion mechanism by a predetermined amount, and the ratio is reached. a first comparing means that issues a detection instruction signal to the temperature drop gradient detecting means when the temperature drop gradient is not detected; Temperature difference detection means for determining the difference between the detected temperature and the target low temperature; means for setting a proportional band for proportional control; and means for determining the temperature difference determined by the temperature difference detection means and the width of the proportional band. By comparison, it is determined whether the temperature of the part to be set to the target low temperature has reached the proportional band, and if it has reached the proportional band, outputs a proportional control instruction signal;
a second comparison means for outputting a reference value setting instruction signal to the reference value setting means if the reference value has not been reached; and a proportional drive signal for outputting a proportional drive signal to the expansion mechanism drive means upon receiving the proportional control instruction signal from the second comparison means. This is achieved by a refrigeration system characterized by comprising: a proportional control means that performs the following steps.

In the method of the present invention, the predetermined gentleness of the temperature drop gradient at the target location may be a predetermined ratio of the reference value, for example, based on the temperature drop gradient at the initial stage of temperature drop at the valve opening at that time. can.

Further, in the proportional control in the present invention, in order to avoid extreme undershoot and overshoot and to achieve control as quickly as possible, for example, the temperature at the target location first reaches the proportional band. Measure the temperature of the target location at predetermined time intervals from the point in time, calculate the average value of the measured values every predetermined number of measurements, and calculate the difference between the average value and the target temperature each time the average value is calculated. Depending on the situation, one reference adjustment amount can be selected from a plurality of pre-prepared reference adjustment amounts for proportional control. In this case, the reference adjustment amount includes a reference adjustment amount for fine proportional control and a reference adjustment amount for rougher and faster control, and when the average value is in the proportional band, the most fine adjustment amount is prepared. A controllable reference adjustment amount is adopted.

The reference adjustment amount for the proportional control can be determined, for example, as a function of the target temperature based on experiments.

The expansion mechanism according to the present invention includes, for example, a variable opening type expansion valve, several types of capillary reach tubes connected in parallel, and an on-off valve connected to each, so that any one of the capillary reach tubes can be selectively used. I can list some things that I did.

The means for setting the initial opening degree of the expansion mechanism in the refrigeration system of the present invention, which is larger than the opening degree for obtaining the target low temperature, includes, for example, an initial opening degree input device and the above-mentioned opening degree based on the value inputted by the input device. one that includes means for outputting a drive signal to the expansion mechanism drive means; a memory means that stores one or more initial opening degrees suitable for a target temperature determined in advance through experiments; and means for selecting a corresponding initial opening degree from among them and outputting a drive signal to the expansion mechanism drive means based on the selected initial opening degree.

Further, as the proportional band setting means, for example,
The device includes a proportional band input device and a storage means for storing the values inputted by the input device, and a proportional band suitable for the target temperature, which has been determined in advance by experiment, is set as 1.
Or one that includes a storage means for storing two or more and a means for selecting a proportional band suitable for the target temperature from the storage means, which selects a proportional band from an appropriate proportional band width determined in advance by experiment and the target temperature. Examples include those that include means for determining.

[Effect]

According to the method and apparatus of the present invention, after the target low temperature and the initial opening degree of the expansion mechanism are set, the expansion mechanism of the refrigeration circuit is gradually throttled toward the target low temperature, and the temperature at the target location is adjusted proportionally for proportional control. Once the temperature reaches the temperature range, the opening degree of the expansion mechanism is then adjusted by proportional control to obtain the target low temperature.

〔Example〕

Examples of the present invention will be described below regarding temperature control in a low-temperature incubator for investigating the low-temperature characteristics of various samples.

The illustrated thermostatic chamber 10 has a test area 102 in which a sample is housed in a thermostatic chamber 101, and has an evaporator 11 and an air circulation fan 12 behind the area.

The evaporator 11 and fan 12 are constituent members of a refrigeration system to be described later. The refrigeration circuit 1 is known per se, and includes the evaporator 11 as well as the compressor 1.
3. A variable opening expansion valve 15 for the condenser 14 and the evaporator 11 is provided.

The valve 15 is of a type in which when a shaft (not shown) is rotated, the valve body moves and the valve opening degree changes.

An example method for obtaining a constant desired low temperature T1 in this thermostat is as shown in the flowchart of FIG. That is, first, test area 10
A constant target low temperature T1 within 2 is determined, and the initial opening degree of the valve 15 is set to be larger than the valve opening degree required to obtain the target low temperature (step). The valve opening degree is fully open in this embodiment. Next, immediately after the initial setting of the valve opening, the temperature drop gradient S1 at the initial stage of temperature drop is determined.
The S1 is set as a reference value (step). The S1 is
The current temperature T2 in the test area 102 is measured and detected n times (six times in this example) at fixed time intervals (10 seconds in this example), and the temperature decreases s1 for each fixed time.
= -dT/dt (dt: unit time, dT: temperature drop within unit time) and average them.

After the step, the temperature drop gradient S2 is determined again (step). The S2 is also determined using the same procedure as that for determining the S1.

Next, it is determined whether the slope S2 of the temperature drop has reached a certain rate of gradualness of the reference value S1.S1×α<S2
Judgment is made based on whether the following conditions are satisfied (step). Here, α is a constant that is arbitrarily determined in advance in consideration of the temperature drop rate, and in the case of this embodiment, it is determined based on experiments.

If the condition is not satisfied, return to the step again, and if the condition is satisfied, the expansion valve 1 is closed.
5 by a predetermined amount (step).

After the throttle operation, the temperature T2 in the test area 102 is measured (step), and it is determined whether the temperature has reached the preset proportional band for proportional control by |T1−T2|≦Ta( Judgment is made based on whether or not the condition Ta: 1/2 of the proportional band width is satisfied (step). If not, return to step; if satisfied, from then on, set the expansion valve opening to the desired degree. Enter proportional control to obtain low temperature T1 (step).

The proportional control measures the temperature T2 inside the test area 102 at predetermined time intervals (10 seconds in this example) from the time when |T1−T2|≦Ta is satisfied for the first time, and repeats the measurement a predetermined number of times. The average value Tm of the measured values is determined every n (six times in this example), and the average value
Find the difference |T1−Tm| between Tm and target temperature T1, and |
Determine whether T1−Tm｜≦Ta (Step 8)
1). If so, adopt the valve opening standard adjustment amount Kp=F(T1) for proportional control (step 82),
Based on this, the opening degree of the expansion valve 15 is adjusted (step 83). Otherwise, Ta＜|T1−Tm
Determine whether ｜≦Tb (step 84), and Ta<
If |T1−Tm|≦Tb, the valve opening standard adjustment amount Kp=G(T1) for proportional control is adopted (step 85), and the opening of the expansion valve 15 is adjusted based on this (step 85). Step 86). Otherwise, the valve opening reference adjustment amount for proportional control Kp = H (T1)
is adopted (step 87), and the opening degree of the expansion valve 15 is adjusted based on this (step 88). Thereafter, steps 81 to 88 are selectively repeated.

The above F(T1), G(T1), and H(T1) are the target temperature T1
is a function of F(T1)<G(T1)<H(T1), which is determined based on experiments in this example
There is a relationship between

Therefore, when the average value Tm is outside the proportional band, in other words, Ta<|T1−Tm|≦Tb or
When Tb<|T1−Tm|, H (T1) or G
(T1) is adopted to perform proportional control quickly with a large amount of operation, but when the average value Tm is in the proportional band, in other words, when 〓T1−Tm〓≦Ta, F(T1) is adopted. Carefully perform proportional control to eliminate or minimize so-called overshoot and undershoot.

The above Tb should be G(T1) or H(T1)
This is the criterion value for determining whether to adopt the temperature range, and is determined based on experiments, and in this example, it is 5°C.

Next, a refrigeration apparatus for carrying out the above method will be explained.

The general structure of the refrigeration system is shown in FIG. 3.

The refrigeration system includes, in addition to the refrigeration circuit 1, an expansion valve 15.
a step motor 21 attached to the motor 21; a pulse output generator 22 that outputs pulses to the motor 21;
It includes a temperature detector 3 that detects the temperature in the test area, a target low temperature input device 4, and a generator 2.
2. The temperature detector 3 and the target low temperature input device 4 are connected to an input/output port of a microcomputer (hereinafter referred to as "microcomputer") 5. Note that 31 is an A/D converter.

The motor 21 and the pulse output generator 22 correspond to an expansion valve driving device.

The target low temperature input device 4 corresponds to a part of the target low temperature setting means and is of a keyboard type.

The microcomputer 5 has a function corresponding to a part of the target low temperature setting means, and further includes an expansion valve initial opening setting means, a means for setting a proportional band for proportional control,
Reference value S1 setting means, temperature drop gradient S2 detecting means, determining whether S1×α<S2, and if so, driving the pulse output generator 22 of the expansion valve drive device 2 to throttle the expansion valve 15 by a predetermined amount. first comparison means for outputting a signal and, if not, issuing a detection instruction signal to the temperature drop gradient S2 detection means;
Temperature difference detection means for determining the difference between the temperature T2 detected by the temperature detector 3 and the target low temperature T1 after the expansion valve 15 is throttled based on the drive signal; |
It is determined whether or not the condition T1−T2｜≦Ta (Ta: 1/2 of the proportional band width) is satisfied. If it is satisfied, a proportional control instruction signal is output, and if it is not, it is set to the reference value. A second comparing means outputs a reference value setting instruction signal to the S1 setting means, and a proportional control means receives a proportional control instruction signal from the second comparing means and outputs a proportional drive signal to the expansion valve drive device 2. The system operates according to the procedure shown in the flowchart of FIG.

The expansion valve initial opening degree setting means consists of a storage means in the microcomputer that stores the initial opening degree fully open, and a means in the microcomputer that outputs a drive signal to the pulse output generator 22 in accordance with the stored opening degree. .

In addition, the proportional band setting means consists of means within the microcomputer that determines the proportional band (T1-Ta) to (T1+Ta) from the proportional band width (Ta x 2) determined in advance by experiment and the target temperature T1. ing.

Therefore, when the target low temperature is set by the target low temperature input device 4 as an initial setting, and the initial opening degree and proportional band of the expansion valve 15 are set by the microcomputer 5, the process is automatically performed step by step toward the target low temperature. When the opening degree of the expansion valve 15 is narrowed and the temperature inside the test area 102 reaches the proportional band for proportional control, the expansion valve opening degree is thereafter adjusted by proportional control to obtain the target low temperature T1.

Initially, the expansion valve 15 has a large opening degree and therefore a large cooling capacity, and is gradually narrowed down in stages.
The target low temperature is approached extremely quickly, and once the target low temperature is reached, the opening is adjusted by proportional control, achieving smooth temperature control, and the proportional control is performed with virtually no overshoot or undershoot. Therefore, even smoother temperature control is achieved.

〔Effect of the invention〕

According to the present invention, there is almost no thermal shock compared to conventional constant temperature control, and yet the target temperature can be quickly approached and the target low temperature can be achieved with smooth temperature control. The invention is therefore also particularly advantageously applicable to environmental test equipment.

[Brief explanation of the drawing]

Fig. 1 is a flowchart showing one embodiment of the method of the present invention, Fig. 2 is a block diagram showing the configuration of the apparatus of the present invention, and Fig. 3 is an overall state in which an example of the apparatus of the present invention is applied to a low-temperature incubator. The schematic diagram, FIG. 4, is a diagram showing a temperature drop curve. DESCRIPTION OF SYMBOLS 1... Refrigeration circuit, 12... Fan, 15... Variable opening type expansion valve, 2... Valve drive device, 21... Step motor, 22... Pulse output generator, 3... Temperature detector, 4... Target low temperature input device, 5 ...microcomputer.

Claims (1)

[Scope of Claims] 1. A method for obtaining a target low temperature at a target location using a refrigeration system, which uses a variable opening type expansion mechanism as an expansion mechanism for an evaporator in a refrigeration circuit, and sets the opening degree of the expansion mechanism to the target temperature. The expansion mechanism is throttled in stages from an opening larger than the opening for obtaining a low temperature, and the expansion mechanism throttle operation is performed when the temperature drop gradient at the target location reaches a predetermined gentleness at the expansion mechanism opening at that time. After each expansion mechanism throttle operation, it is determined whether the temperature at the target location has reached a predetermined proportional band for proportional control. While the temperature at the target location has not reached the proportional band, the expansion mechanism throttle operation and the judgment as to whether or not the proportional band has been reached are repeated, and when the temperature at the target location reaches the proportional band, from then on, A method characterized in that the temperature at the target location is proportionally controlled toward the target low temperature. 2. The predetermined gentleness of the temperature drop gradient at the target location is a predetermined ratio of the reference value based on the temperature drop gradient at the initial stage of temperature drop at the expansion mechanism opening at that time. The method described in Section 1. 3 The proportional control is performed by measuring the temperature of the target location at predetermined time intervals from the time when the temperature of the target location first reaches the proportional band, and calculating the average value of the measured values every predetermined number of measurements. A patent for determining the average value, and selecting one standard adjustment amount from a plurality of pre-prepared standard adjustment amounts for proportional control according to the difference between the average value and the target temperature each time the average value is calculated. A method according to claim 1 or 2. 4. A refrigeration circuit using a variable-opening expansion mechanism as an expansion mechanism for an evaporator, an expansion mechanism drive means for adjusting the opening of the expansion mechanism, and a temperature sensor for detecting the temperature of a target location to be set to a target low temperature. a detection means; a target low temperature setting means; an initial opening degree setting means for the expansion mechanism; and an initial temperature drop at the target location at the expansion mechanism opening degree at that time based on the temperature detected by the temperature detection means. a reference value setting means for determining a gradient of descent as a reference value; and after the gradient of temperature drop at the initial stage of the temperature drop is determined by the reference value setting means, the target low temperature is further determined based on the temperature detected by the temperature detection means. temperature drop gradient detection means for determining the temperature drop gradient at a location where the temperature should be lowered; and a temperature drop gradient detection means that compares the reference value obtained by the reference value setting means with the value obtained by the temperature drop gradient detection means, and determines whether the latter value is If the former standard value has reached a predetermined ratio, a drive signal is issued to the expansion mechanism driving means to throttle the expansion mechanism by a predetermined amount, and if the ratio has not been reached, a detection instruction is given to the temperature drop gradient detection means. a first comparison means for emitting a signal; and a first comparison means for detecting a difference between the temperature detected by the temperature detection means and the target low temperature after the expansion mechanism is throttled by a predetermined amount by the expansion mechanism drive means based on the drive signal. A means for detecting a temperature difference to be determined; a means for setting a proportional band for proportional control; and a means for determining the temperature difference at a location where the target temperature is to be achieved by comparing the temperature difference obtained by the temperature difference detecting means with the width of the proportional band. Determines whether the temperature has reached the proportional band, and outputs a proportional control instruction signal if the temperature has reached the proportional band.
a second comparison means for outputting a reference value setting instruction signal to the reference value setting means if the reference value has not been reached; and a proportional drive signal for outputting a proportional drive signal to the expansion mechanism drive means upon receiving the proportional control instruction signal from the second comparison means. A refrigeration device characterized by comprising: proportional control means for controlling. 5. The proportional control means measures the temperature of the target location at predetermined time intervals based on the temperature detected by the temperature detection means from the time when the proportional control instruction signal is received from the second comparison means. means for calculating the average value of the measured values for each predetermined number of measurements, and each time the average value is input from the means for calculating the average value, from a reference adjustment amount for a plurality of types of proportional control prepared in advance, A patent claim comprising means for selecting one reference adjustment amount according to the difference between the average value and the target temperature and outputting a proportional drive signal to the expansion mechanism drive means based on the reference adjustment amount. The refrigeration device according to item 4.