JPH0642824A - Operation control device for freezer - Google Patents

Abstract

PURPOSE:To realize a specified capability without adjusting any disturbance in sensing performance of a pressure sensor as well as a thermistor for use in controlling an over-heating degree in an operation control device for a freezer in which an over-heating degree control of refrigerant gas sucked into a compressor is carried out under an adjustment of a degree of opening of an electrical expansion valve. CONSTITUTION:This operation control device is comprised of a degree of opening adjusting means for adjusting a degree of opening by changing a degree of opening of the electrical expansion valve 3 in a stepwise manner, a suction pressure sensor 7 for sensing a suction pressure Ps and a degree of opening setting means 8 for fixing a degree of opening of the electrical expansion valve 3 at the time when a degree of variation of the sucking pressure Ps under a condition in which a degree of opening of the electrical adjusting means is adjusted to be increased after receiving an output signal of the sensor 7 is lower than a predetermined value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating machine operation control device, and more particularly to measures for preventing variations in superheat degree in refrigerating machines.

[0002]

2. Description of the Related Art As a conventional operation control device for a refrigerator, for example, a device known from Japanese Patent Laid-Open No. 59-145450 discloses a compressor, a heat source side heat exchanger, an electronic expansion valve and a utilization side heat exchanger. Are connected in sequence, the suction temperature of the refrigerant gas sucked into the compressor is detected by a thermistor, and the suction temperature is preset in the refrigerator during superheat control operation. When it is larger than the superheat degree, the opening degree of the electronic expansion valve is increased to lower the suction temperature, while when it is smaller, the opening degree is decreased to raise the suction temperature.

[0003]

By the way, in the above-mentioned conventional device, the signal detected by the thermistor is received and regarded as the actual suction temperature, and the superheat control is performed based on this. However, commonly used thermistors have a variation in detection performance of about ± 2 ° C.
Therefore, in superheat control performed based on such a thermistor, variations in maximum actual superheat of about 4 ° C inevitably occur depending on the refrigerator, and the capacity of each refrigerator can be the same model. There is a problem that it does not always become a constant value.

Regarding this, it is conceivable to make adjustment so as to correct the temperature detected by the thermistor for each refrigerator, but there is a problem that it takes a lot of trouble because the degree of variation varies depending on the refrigerator. Then, a thermistor with high accuracy must be used, but this results in an increase in cost. It should be noted that even in the case where the suction pressure is detected by using the pressure sensor and the superheat control is performed based on the suction pressure, the detection performance of the pressure sensor varies, and the same problem as described above occurs.

The present invention has been made in view of the above points, and an object thereof is to make it possible to exert a certain capability for each refrigerator without adjusting the variation in the detection performance of the thermistor or the pressure sensor. To do.

[0006]

To achieve the above object, in the invention of claim 1, after the superheat control operation is once performed, the opening degree of the electronic expansion valve is gradually increased to increase the suction pressure. The opening is fixed when the degree of change of is sufficiently small.

That is, in the present invention, as shown in FIG. 1, a compressor (1), a heat source side heat exchanger (2), an electronic expansion valve (3) and a utilization side heat exchanger (4) are sequentially connected. A refrigerating machine operation control device is provided which is provided with a refrigerant circuit (5) and is configured to control the degree of superheat of the refrigerant gas sucked into the compressor (1) by adjusting the opening degree of the electronic expansion valve (3). Is.

After the superheat control operation, the opening of the electronic expansion valve (3) is gradually changed stepwise to adjust the opening, and the compressor (1). ), The suction pressure detection means (7) for detecting the suction pressure (Ps) of the refrigerant gas, and the output signal of the detection means (7) are received, and the opening adjustment means (6) controls the electronic expansion valve (7). Opening degree setting means for fixing the opening degree of the electronic expansion valve (3) when the degree of change of the suction pressure (Ps) when the opening degree of 3) is adjusted to be large becomes smaller than a predetermined value. (8) is provided.

According to the invention of claim 2, the above-mentioned claim 1
In the invention, after the superheat control operation, the stability determination means (9) that receives the output signal of the suction pressure detection means (7) and determines that the degree of variation of the suction pressure (Ps) is smaller than a predetermined value. ) And an opening holding means (10) which receives the output signal of the judging means (9) and delays the opening adjustment timing when the degree of variation of the suction pressure (Ps) is larger than a predetermined value. The configuration.

According to the third aspect of the invention, it is the same that the opening degree of the electronic expansion valve is increased stepwise after the superheat control operation is once performed, and the capacity of the utilization side heat exchanger is substantially maximized. The opening is fixed with. In other words, by maximizing the ability, we tried to stabilize it.

That is, according to the present invention, the compressor (1),
A heat source side heat exchanger (2), an electronic expansion valve (3) and a use side heat exchanger (4) are connected in sequence to a refrigerant circuit (5), and the refrigerant gas sucked into the compressor (1) is Superheat control is performed by adjusting the opening degree of the electronic expansion valve (3), and heat is exchanged between the refrigerant and the heat exchange medium in the medium circulation portion (4a) of the utilization side heat exchanger (4). The operation control device for the refrigerator thus configured is a prerequisite.

After the superheat control operation, the opening adjustment means (6) for adjusting the opening by sequentially changing the opening of the electronic expansion valve (3) step by step, and the heat exchange medium. Inlet temperature detecting means (11) for detecting the temperature (Twi) at the inlet of the medium circulating portion (4a), and outlet temperature detecting means (12) for detecting the temperature (Two) at the outlet of the medium circulating portion (4a). ,
The opening adjusting means (6) receives the output signals of the inlet temperature detecting means (11) and the outlet temperature detecting means (12).
Temperature (Twi) and outlet temperature (Two) when the opening degree of the electronic expansion valve (3) is adjusted to be large by
And a degree of opening setting means (8) for fixing the degree of opening of the electronic expansion valve (3) when the difference between and becomes larger than a predetermined value.

According to the invention of claim 4, the above-mentioned claim 3 is adopted.
In the invention, the opening degree setting means (8) controls the inlet temperature (Twi) and the outlet temperature (Two) after the present opening adjustment.
It is configured to determine that the difference between and is smaller than the previous time. Then, the opening adjustment means (6) receives the output signal of the opening setting means (8), and the difference between the inlet temperature (Twi) and the outlet temperature (Two) after the current opening adjustment is determined to be the previous value. When it becomes smaller than the above, the opening degree of the electronic expansion valve (3) is adjusted to be gradually reduced stepwise.

According to the invention of claim 5, the above-mentioned claim 3 is adopted.
Or the suction pressure detecting means (7) for detecting the suction pressure (Ps) of the refrigerant gas sucked into the compressor (1).
And a stability determination means (9) that receives the output signal of the suction pressure detection means (7) and determines that the degree of variation of the suction pressure (Ps) is smaller than a predetermined value after the superheat control operation. And an opening holding means (10) for receiving the output signal of the determination means (9) and delaying the opening adjustment timing when the degree of variation in the suction pressure (Ps) is larger than a predetermined value. And

Further, in the invention of claim 6, in the invention of claim 1, 2 or 5, the condition change judging means (13) for judging the change of the operating condition after the opening adjustment, and the judging means. A resetting means (1) for receiving the output signal of (13) and re-executing the superheat control operation when the operating conditions change.
4) and.

According to the invention of claim 7, the above-mentioned claim 6 is used.
In the invention, the condition change determination means (13) is configured to receive the output signal of the suction pressure detection means (7) and determine the change in the operating condition based on the stability of the suction pressure (Ps).

[0017]

In the invention of claim 1, first, the electronic expansion valve (3)
The conventional suction superheat control operation is performed by adjusting the opening degree. At this stage, although the actual degree of superheat still varies depending on the refrigerator, the suction gas is overheated to the extent that it does not become wet. Then, the opening adjustment means (6) adjusts the opening of the electronic expansion valve (3) so that the opening gradually increases in stages. In response to this, the suction pressure (Ps) of the refrigerant gas detected by the suction pressure detection means (7)
Changes in an increasing direction, and the degree of this change is judged by the opening degree setting means (8). Then, when the degree of the above-mentioned change becomes smaller than a predetermined value, the wetness of the suction gas is close to zero, and the predetermined capacity of the refrigerator is constant at the efficiency optimum for the use side heat exchanger (4). The opening of the electronic expansion valve (3) is fixed by considering it as a point to be exerted.

Further, in the invention of claim 2, after the superheat control operation, the degree of variation of the suction pressure (Ps) is determined by the stability determination means (9) which receives the output signal of the suction pressure detection means (7). Is determined. When the degree of variation is larger than a predetermined value, that is, the suction pressure (Ps) before opening adjustment is unstable, and the suction pressure (Ps) after opening adjustment is based on such suction pressure (Ps). When it is difficult to determine the degree of change, the opening degree holding means (10) delays the timing of opening degree adjustment. As a result, the suction pressure (Ps)
Is stabilized.

According to the third aspect of the present invention, after the superheat control operation is performed, the opening adjustment means (6) sequentially increases the opening of the electronic expansion valve (3) step by step, so that the superheat decreases. The efficiency of the heat exchanger (4) on the use side increases according to
The ability is rising. On the other hand, with respect to the heat exchange target medium whose heat is exchanged with the refrigerant in the medium flow section (4a) of the heat exchanger (4), the medium flow section (4a) detected by the inlet temperature detecting means (9). ) The change in the difference between the temperature (Twi) at the inlet and the temperature (Two) at the outlet of the medium circulation unit (4a) detected by the outlet temperature detecting means (10) is
It is determined by the opening degree setting means (8). Since this inlet / outlet temperature difference increases with the increase in the above capacity, the opening of the electronic expansion valve (3) is fixed at the stage when the temperature difference becomes maximum, assuming that the capacity of the refrigerator is maximum. .

Further, according to the invention of claim 4, at a certain stage of the opening adjustment of the electronic expansion valve (3), when the inlet / outlet temperature difference becomes smaller than the previous one, the opening setting means (8). Is determined to be too large,
In this case, the opening degree of the electronic expansion valve (3) is gradually reduced by the opening degree adjusting means (6).

Further, in the invention of claim 5, after the superheat control operation, the degree of variation of the suction pressure (Ps) is determined by the stability determining means (9) which receives the output signal of the suction pressure detecting means (7). Is determined. When the degree of variation is larger than a predetermined value, that is, the suction pressure (Ps) before the opening adjustment is unstable, and the suction pressure (Ps) after the opening adjustment is based on such suction pressure (Ps). When it is difficult to determine the degree of change of the opening degree, the opening degree holding means (10) delays the timing of the opening degree adjustment. As a result, the suction pressure (P
s) is stabilized.

Further, in the invention of claim 6, when the operating conditions such as the outside air temperature, the discharge pressure and the suction pressure are changed,
The superheat control operation is performed again by the resetting means (11) which has received the output signal of the condition change determining means (13). As a result, the capacity can be made constant according to the operating conditions.

Further, according to the invention of claim 7, the change of the suction pressure (Ps) becomes large by the condition change judging means (12) which receives the output signal of the suction pressure detecting means (7) after the opening adjustment. In this case, it is determined that the operating conditions have changed.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a cooling device and its control system according to this embodiment. The cooling device serves as a chilling unit (B) which is a utilization system for cooling a machine tool and a heat exchange medium of the unit (B). And a refrigerator (A) for cooling the cooling water.

The refrigerator (A) includes a compressor (1) for sucking and discharging a refrigerant gas, and a condenser as a heat source side heat exchanger for condensing and liquefying the refrigerant discharged from the compressor (1). (2), an electric expansion valve (3) (electronic expansion valve) for expanding the refrigerant liquefied in the condenser (2), and the expansion valve (3)
A refrigerant circuit (5) is formed by sequentially connecting, via a refrigerant pipe (15), an evaporator (4) as a utilization side heat exchanger that evaporates and gasifies the refrigerant expanded in (1). The compressor (1)
An unloader mechanism (16) for switching the capacity between full load and unload by opening and closing the pilot valve (16a) is arranged in the. (16b) is a backflow preventing capillary tube. Further, the electric expansion valve (3)
Has a pulse motor, and the valve opening degree is variable according to the number of pulses of a pulse signal given to the motor.

The evaporator (4) has a cooling water circulating portion (4a) as a medium circulating portion through which the cooling water circulating in the chiller circuit (17) of the chilling unit (B) flows, and the refrigerant circuit In (5), the refrigerant gives cold heat obtained in the condenser (2) to the cooling water by heat exchange in the evaporator (4),
The cooling water is cooled.

Further, sensors are arranged in the cooling device. (7) is a suction pressure sensor (suction pressure detection means) for detecting the suction pressure (Ps) of the refrigerant gas sucked into the compressor (1), and (18) is the refrigerant gas discharged from the compressor (1). A discharge pressure sensor that detects the discharge pressure (Pd), and (11) is an inlet water temperature that detects the water temperature (Twi) (inlet temperature) at the heat exchange inlet of the cooling water that is heat-exchanged with the evaporator (4). Sensors (inlet temperature detecting means), (12) are outlet water temperature sensors (outlet temperature detecting means) for detecting the water temperature (Two) (outlet temperature) at the outlet of the cooling water. The output signal of each sensor is input to the controller (C) for controlling the operation of the refrigerator (A), and in the controller (C), the electric expansion valve (3 The operation of the cooling device including the control of the degree of superheat of the refrigerant gas by adjusting the degree of opening is controlled.

Here, the control operation performed in the controller (C) to make the cooling capacity of the evaporator (4) of the refrigerator (A) constant will be described with reference to the flowcharts of FIGS. 3 and 4.

First, in step S1, the superheat degree (SH) of the refrigerant gas sucked into the compressor (1) is controlled, and then in step S2, the suction pressure (Ps) and the discharge pressure (Pd) are input. , In step S3, the input suction pressure (Ps)
And the discharge pressure (Pd) to the first suction pressure (Ps1) and the first discharge pressure (Pd1), and the already set first suction pressure (Ps1) and the first discharge pressure (Pd1) to the second suction pressure. (Ps2) and the second discharge pressure (Pd2), the second suction pressure (Ps2) and the second discharge pressure (Pd2) that have already been set are set to the third suction pressure (Ps3) and the third discharge pressure (P
d3) respectively. In steps S4 and S5, the degree of variation in the discharge pressure (Pd) after the superheat control is determined. That is, the absolute value of the difference between the first discharge pressure (Pd1) and the third discharge pressure (Pd3) is determined in step S4, and the first discharge pressure (Pd is determined in step S5.
It is determined whether or not the absolute value of the difference between 1) and the second discharge pressure (Pd2) is larger than a constant (α) (for example, 0.5 kgf / cm ² ). When these determinations are YES, it means that the discharge pressure (Pd) is not stable yet, and thus the process proceeds to step S6. On the other hand, step S
When NO in 4 and S5, respectively, the discharge pressure (P
Regarding d), it is considered to be sufficiently stable, and step S
7, the process proceeds to S8, and the stability of the suction pressure (Ps) is determined this time.

The above steps S7 and S8 constitute the stability determination means (9) in the present invention, and here, the degree of variation of the suction pressure (Ps) after the superheat control is determined, respectively. That is, the absolute value of the difference between the first suction pressure (Ps1) and the third suction pressure (Ps3) is calculated in step S7, and the first suction pressure (Ps3) is calculated in step S8.
The absolute value of the difference between 1) and the second suction pressure (Ps2) is smaller than the above constant (α) by a constant (β) (for example,
0.05kgf / cm ² ) It is judged whether it is large or not. When the determination is YES, the suction pressure (Ps) is not yet sufficiently stable, so the process proceeds to step S6.

The step S6 constitutes the opening holding means (10) in the present invention, and here, after waiting for a predetermined time (x) (for example, 3 minutes), the stability after the waiting is further stabilized. The process returns to step S2 to determine the degree. On the other hand, when NO is determined in each of steps S7 and S8, it is determined that the suction pressure (Ps) is also sufficiently stable, and the process proceeds to step S10 shown in FIG.

The step S10 constitutes the opening adjusting means (6) in the present invention, and here, the electric expansion valve (3) is opened by a predetermined pulse number (a) (for example, 2 pulses). The number of determinations (n) for the stability of the suction pressure (Ps) and the discharge pressure (Pd) for determining the change in the operating conditions is set to n = 20, and steps S11 and S12 are performed. Move to. Step S1
In 1, the suction pressure (Ps) and the discharge pressure (Pd) are input respectively, and in step S12, the input suction pressure (Ps) and discharge pressure (Pd) are the fourth suction pressure (Ps4) and the fourth discharge pressure (Pd4). And the already set fourth suction pressure (Ps4) and fourth discharge pressure (Pd4) to the fifth suction pressure (Ps4).
s5) and the fifth discharge pressure (Pd5), the fifth suction pressure (Ps5) and the fifth discharge pressure (Pd) that have already been set.
5) is the sixth suction pressure (Ps6) and the sixth discharge pressure (Pd6)
Set each to. In step S13, it is determined whether the sixth suction pressure (Ps6) and the sixth discharge pressure (Pd6) have already been set, and if the determination is NO, the process proceeds to step S14 and waits for a predetermined time (y). After performing, the process returns to step S11. On the other hand, if the determination is YES in step S13, the process proceeds to step S15, and the suction pressure (Ps) and the discharge pressure (Pd) are input again, and then the process proceeds to steps S16 and S17.

In steps S16 and S17, it is determined whether or not the stability of the suction pressure (Ps) and the discharge pressure (Pd) has collapsed due to changes in operating conditions. Step S16 is a condition change determining means (1
3), and here, the newly input suction pressure (Ps) and the fourth to sixth suction pressures (Ps4) to (Ps).
It is determined whether the absolute value of the difference from the average value of s6) is larger than a constant (b) (for example, 0.5 kgf / cm ² ) which is substantially the same as the above constant (α). Then, when the determination is YES, it is determined that the operating conditions have changed due to the deterioration of stability, and the process returns to step S1 and the superheat degree control is performed again. On the other hand, if the determination is NO, the process proceeds to step S17. In step S17, the newly input discharge pressure (Pd) and the fourth to sixth discharge pressures (Pd4) to (Pd).
Whether or not the absolute value of the difference from the average value of d6) is larger than the constant (c) (for example, 0.05 kgf / cm ² ) which is substantially the same as the above constant (β) is determined. When the determination is YES, it is determined that the operating conditions have changed due to the deterioration of stability, and the process returns to step S1 and the superheat control is restarted. On the other hand, when NO is determined in step S17, "1" is subtracted from the number of determinations (n) in step S18, and the process proceeds to step S19 to determine whether n = 0. If n ≠ 0 in this determination, the process returns to step S11, and the determination on the stability is repeated. On the other hand, if n = 0, it is determined that there is no change in the operating conditions and step S2.
Move to 0.

The step S20 constitutes the opening degree setting means (8) in the present invention, in which the suction pressure (Ps) by the present opening adjustment is the first suction before the present opening adjustment. It is determined whether or not the pressure (Ps1) is larger than a value obtained by adding a constant (d) smaller than the above constant (b) (for example, 0.01 kgf / cm ² ). If the determination is NO, it is determined that the degree of change in the suction pressure (Ps) has become sufficiently small, and the process ends. That is, the opening degree of the electric expansion valve (3) is fixed at the current stage. On the other hand, if the determination is YES, it is determined that the degree of change is still large, and step S21 is performed.
To the first suction pressure (Ps)
The suction pressure (Ps1) is set, the process returns to step S10, and the opening degree of the electric expansion valve (3) is further increased.

Next, the control operation for making the capacity constant by maximizing the cooling capacity of the evaporator (4) of the refrigerator (A) will be described with reference to the flow charts of FIGS. In this control, steps S'1 to S '
8 and steps S'10 to S'19 are the same as the above-mentioned control operation for making the cooling capacity constant, and only steps S'20 to S'24 and step S'9 thereafter are added. 3 are different from those shown in FIGS. 3 and 4 (steps S'1 to S'8 and steps S'10 to S'19).
The same step number is assigned to the same item and its description is omitted.

In step S'9 of FIG. 6, the inlet water temperature (Twi) and the outlet water temperature (Two) before opening adjustment are input,
After adjusting the opening and confirming that the operating conditions are not changed in steps S'10 to S'19, the process proceeds to step S'20 in FIG. In this step S'20, the inlet water temperature (Twi) and the outlet water temperature (Two) input before the current opening adjustment (step S'9) are used as the first inlet water temperature (Twi).
Wi1) and the first outlet water temperature (Two1) respectively, and after inputting the inlet water temperature (Twi) and the outlet water temperature (Two) by the present opening adjustment in step S'21, the steps S'22, S ' Move to 23.

The steps S'22 and S'23 constitute the opening degree setting means (8) of the present invention. In step S'22, the inlet water temperature (Twi) after the opening adjustment is changed to the outlet water temperature (Twi). The value obtained by subtracting (Two) is the first outlet water temperature (Twi1) from the first inlet water temperature (Twi1) before the opening adjustment.
Is greater than the value obtained by subtracting and adding a constant (d) (for example, 0.1 ° C.), that is, whether the current temperature difference is greater than the previous temperature difference plus the constant (d) (this time>
The previous time + d) is determined. If the determination is YES, it is determined that the temperature difference may still be large and step S'10.
Return to and adjust the opening again. On the other hand, if the determination is NO, the process proceeds to step S'23.

In step S'23, the value obtained by subtracting the outlet water temperature (Two) from the inlet water temperature (Twi) after the opening adjustment is the first inlet water temperature (Twi1) before the opening adjustment.
The first outlet water temperature (Two1) is subtracted from the above, and a constant (e) (for example, 0.1 ° C.) that is approximately the same as the above constant (d).
Is smaller than the value obtained by subtracting, that is, the current temperature difference is smaller than the value obtained by subtracting the constant (e) from the previous temperature difference (this time <previous-e). If the determination is YES, it is determined that the temperature difference is smaller than the previous time, and the process proceeds to step S'24.

The step S'24 constitutes the opening adjusting means (6) in the present invention. Here, the opening is reduced by the predetermined number of pulses (a) and the previous adjustment is performed. Return to stage. Then, after setting the number of times (n) of determination of change in operating conditions to n = 20, step S '
Return to 11. On the other hand, when the determination is NO, it is determined that the difference between the inlet water temperature (Twi) and the outlet water temperature (Two) has become substantially the maximum (previous −e ≦ this time ≦ previous + d), the processing is terminated, and the electric operation is performed. The opening of the expansion valve (3) is fixed at the current stage.

The operation of the cooling device and the controller (C) thereof configured as described above will be described.

The refrigerant gas discharged from the compressor (1) is
Flowing in the direction of the arrow shown in FIG. 2 and flowing into the condenser (2),
After being condensed and liquefied in this condenser (2) to obtain cold heat, it is expanded by the electric expansion valve (3) and flows into the evaporator (4). In the evaporator (4), the refrigerant evaporates and gasifies, and the cold heat is transferred to the chiller circuit (1) in the cooling water flow section (4a) of the evaporator (4).
After being applied to the cooling water in 7), it is sucked into the compressor (1).

In the constant capacity control of the refrigerator (A), first, the electric expansion valve (3) is controlled so that the suction temperature of the refrigerant gas sucked into the compressor (1) matches a predetermined superheat degree. A superheat control operation for controlling the opening is performed. At this stage, the refrigerator (A) has a variation in the degree of superheat and the capacity is not constant yet, but the degree of superheat that does not become wet can be obtained. After the superheat control, the controller (C) that receives the output signals of the suction pressure sensor (7) and the discharge pressure sensor (18) freezes it based on the stability of the suction pressure (Ps) and the discharge pressure (Pd). When it is determined that the operating state of the machine (A) is stable, the opening degree of the electric expansion valve (3) is gradually increased stepwise.

By adjusting the opening, the amount of refrigerant increases, the suction pressure (Ps) rises, the degree of superheat decreases, and the wetness of the suction refrigerant gas is substantially zero, that is, performance is improved for the evaporator (4). It approaches the most efficient and optimal point. Then, the stage where the degree of change in the suction pressure (Ps) becomes sufficiently small is determined to be the optimum point, and the opening degree of the electric expansion valve (3) is fixed at that stage. Also, if the operating conditions change during operation,
The superheat control operation is performed again based on the determination whether the stability of the suction pressure (Ps) and the discharge pressure (Pd) has collapsed, and the opening degree of the electric expansion valve (3) is reset based on the capacity constant control. Is set.

As a result, even if the superheat degree due to the superheat control operation varies depending on the refrigerator (A), the refrigerator (A) can be made to exhibit a certain capacity.

On the other hand, the refrigerator (A) is controlled by the capacity maximization control.
In order to make the capacity of the compressor constant, first, the degree of superheat that controls the opening degree of the electric expansion valve (3) so that the suction temperature of the refrigerant gas sucked into the compressor (1) matches a predetermined degree of superheat. After the control operation is performed, if it is determined that the operation state of the refrigerator (A) is stable based on the stability of the suction pressure (Ps) and the discharge pressure (Pd), the electric expansion valve (3) is opened. The degree is gradually increased step by step.

When the degree of superheat is lowered and the cooling capacity of the evaporator (4) is increased by the adjustment of the opening degree, the inlet water temperature (Tw) of the cooling water in the cooling water flow section (4a) is correspondingly increased.
The difference between i) and the outlet water temperature (Two) increases.
Then, when the inlet / outlet water temperature difference becomes substantially maximum, the opening degree of the electric expansion valve (3) is fixed. If the water temperature difference becomes lower than the previous stage of the opening adjustment by the opening adjustment, the water temperature difference becomes the maximum by reducing the opening.

As a result, even when the superheat degree due to the superheat control operation varies depending on the refrigerator (A), the refrigerator (A) can exhibit a maximum capacity which is a constant capacity. Note that this capacity maximization control is basically performed during full load operation and does not require maximum capacity during unload operation, and a capacity difference of ± several% is not a problem in practice. Although not denied, the COP can be improved by performing the above control when the unloading operation continues.

Although the chiller unit (B) is used as the utilization system in the above embodiment, the present invention is not limited to this embodiment, and the utilization side heat exchanger is used as a condenser to supply hot water. Alternatively, it can be applied to an air conditioner in which the heat exchange medium is air and the outlet temperature thereof is controlled.

Further, in the above-described embodiment, the control is performed directly based on the suction pressure, but it may be performed based on the suction temperature obtained from the suction pressure.

Further, in the above embodiment, the change of the operating condition is judged based on the change of the suction pressure, but it may be judged based on the change of the outside air temperature, the water temperature, the high pressure, the high pressure and the low pressure. Good.

[0051]

According to the invention of claim 1, after the suction superheat degree control, the opening degree of the electronic expansion valve is increased stepwise, and when the degree of change of the suction pressure becomes sufficiently small, the opening degree is increased. Since the above is fixed, even if the above superheat control is performed based on the detection value of the thermistor or pressure sensor with variations in detection performance, it is possible to optimize the efficiency of the use side heat exchanger in terms of performance. Therefore, the capacity of the refrigerator can be made constant.

Further, according to the invention of claim 2, it is possible to obtain a stable state of the suction pressure after the superheat control and before the adjustment of the opening degree. The degree of change in suction pressure can be properly determined.

According to the third aspect of the present invention, after the suction superheat control, the opening degree of the electronic expansion valve is gradually increased and the heat exchange medium for exchanging heat with the refrigerant in the heat exchanger on the use side. Since the opening is fixed at the stage where the inlet / outlet temperature difference becomes maximum, even if the above superheat control is performed based on the detection value of the thermistor or pressure sensor with variations in detection performance, Ability can be constant at maximum level.

Further, in the invention of claim 4, when the difference in inlet / outlet temperature of this time is smaller than that of the previous time, the opening is reduced to restore the maximum capacity. In, it is possible to avoid a decrease in capacity due to an excessively large opening.

According to the invention of claim 5, in the invention of claim 3 or 4, the same effect as that of the invention of claim 2 can be obtained.

Further, in the invention of claim 6, the opening is reset at the stage of adjusting the opening based on the change of the operating condition. Therefore, in the invention of claim 1, 2 or 5, the operation is performed. The capacity of the refrigerator can be made constant according to changes in conditions.

Further, according to the invention of claim 7, the change of the operating condition is judged based on the stability of the suction pressure. Therefore, in the invention of claim 6, the operating condition is changed without using a new detecting means. Can be determined.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of the present invention.

FIG. 2 is a block diagram of a cooling device and its controller according to an embodiment of the present invention.

FIG. 3 is a flowchart showing a first half of constant capacity control.

FIG. 4 is a flowchart showing the latter half of the capability constant control.

FIG. 5 is a flowchart showing a front stage part of capacity maximization control.

FIG. 6 is a flowchart showing a middle stage part of capacity maximization control.

FIG. 7 is a flowchart showing a latter part of the capacity maximization control.

[Explanation of symbols]

 (1) Compressor (2) Condenser (heat source side heat exchanger) (3) Electric expansion valve (electronic expansion valve) (4) Evaporator (use side heat exchanger) (4a) Cooling water flow section (medium flow) Part) (5) refrigerant circuit (6) opening adjustment means (7) suction pressure sensor (suction pressure detection means) (8) opening setting means (9) stability determination means (10) opening holding means (11) Inlet water temperature sensor (inlet temperature detection means) (12) Outlet water temperature sensor (outlet temperature detection means) (13) Condition change determination means (14) Resetting means (Ps) Suction pressure (Twi) Inlet water temperature (inlet temperature) (Two) ) Outlet water temperature (outlet temperature)

Claims (7)

[Claims] 1. A compressor (1), a heat source side heat exchanger (2),
The electronic expansion valve (3) and the usage-side heat exchanger (4) are connected in sequence to provide a refrigerant circuit (5) for controlling the degree of superheat of the refrigerant gas sucked into the compressor (1). The operation control device for a refrigerator configured to perform the opening degree adjustment of 3), wherein the opening degree of the electronic expansion valve (3) is sequentially changed stepwise after the superheat control operation. An opening adjustment means (6) for adjusting, and a suction pressure (P of the refrigerant gas sucked into the compressor (1).
s) is detected, and the output signals of the suction pressure detecting means (7) are received, so that the opening degree adjusting means (6) increases the opening degree of the electronic expansion valve (3). When the degree of change of the suction pressure (Ps) when adjusted to 0 becomes smaller than a predetermined value, the electronic expansion valve (3)
And an opening degree setting means (8) for fixing the opening degree of the refrigerator. 2. A stability determining means for receiving an output signal of the suction pressure detecting means (7) after the superheat control operation and determining that the degree of variation of the suction pressure (Ps) is smaller than a predetermined value. 9) and an opening holding means (10) for receiving the output signal of the stability judging means (9) and delaying the opening adjustment timing when the degree of variation of the suction pressure (Ps) is larger than a predetermined value. The operation control device for a refrigerator according to claim 1, further comprising: 3. A compressor (1), a heat source side heat exchanger (2),
The electronic expansion valve (3) and the usage-side heat exchanger (4) are connected in sequence to provide a refrigerant circuit (5) for controlling the degree of superheat of the refrigerant gas sucked into the compressor (1). Operation control of a refrigerator which is performed by adjusting the opening degree of 3) and is configured to perform heat exchange between the refrigerant and the heat exchange medium in the medium circulation portion (4a) of the utilization side heat exchanger (4). An apparatus for controlling the opening degree of the electronic expansion valve (3) by gradually changing the opening degree of the electronic expansion valve (3) after the superheat control operation, and the heat exchange medium. Temperature detecting means (11) for detecting the temperature (Twi) at the inlet of the medium circulating portion (4a) of the above, and an outlet temperature for detecting the temperature (Two) at the outlet of the medium circulating portion (4a) of the heat exchange target medium Detection means (12) and respective output signals of the inlet temperature detection means (11) and the outlet temperature detection means (12) In response to the above, the opening adjustment means (6)
Temperature (Twi) and outlet temperature (Two) when the opening degree of the electronic expansion valve (3) is adjusted to be large by
And an opening degree setting means (8) for fixing the opening degree of the electronic expansion valve (3) at a stage when the difference between the above and the predetermined value becomes larger than a predetermined value. 4. The opening degree setting means (8) determines that the difference between the inlet temperature (Twi) and the outlet temperature (Two) after the present opening adjustment is smaller than that of the previous time. The opening adjusting means (6) receives the output signal of the opening setting means (8) and receives the inlet temperature (Tw) after the current opening adjustment.
When the difference between i) and the outlet temperature (Two) becomes smaller than the previous time, the opening degree of the electronic expansion valve (3) is adjusted to be gradually reduced stepwise. The operation control device for a refrigerator according to claim 3, wherein. 5. A superheat degree is obtained by receiving a suction pressure detecting means (7) for detecting a suction pressure (Ps) of a refrigerant gas sucked into a compressor (1) and an output signal of the suction pressure detecting means (7). After the control operation, the stability determination means (9) for determining that the degree of variation in the suction pressure (Ps) is smaller than a predetermined value.
And an opening holding means (10) that receives the output signal of the stability determination means (9) and delays the opening adjustment timing when the degree of variation of the suction pressure (Ps) is larger than a predetermined value. The operation control device for a refrigerator according to claim 3 or 4, characterized in that. 6. After the opening adjustment, a condition change determination means (13) for determining a change in operating conditions and an output signal from the condition change determination means (13) are received, and when the operating conditions change, overheating occurs. The operation control device for a refrigerator according to claim 1, 2 or 5, further comprising a resetting means (14) for re-performing the temperature control operation. 7. The condition change determination means (13) is configured to receive the output signal of the suction pressure detection means (7) and determine a change in operating conditions based on the stability of the suction pressure (Ps). The operation control device for a refrigerator according to claim 6, wherein