AU2017350238B2

AU2017350238B2 - Refrigeration device, refrigeration system

Info

Publication number: AU2017350238B2
Application number: AU2017350238A
Authority: AU
Inventors: Masaki Ikeda; Akio KAWANISHI; Kenichi Murakami; Minemasa Omura
Original assignee: Mitsubishi Heavy Industries Thermal Systems Ltd
Current assignee: Mitsubishi Heavy Industries Thermal Systems Ltd
Priority date: 2016-10-31
Filing date: 2017-10-10
Publication date: 2020-07-16
Anticipated expiration: 2037-10-10
Also published as: WO2018079242A1; EP3499148A1; JP2018071909A; AU2017350238A1; EP3499148A4

Abstract

A condensing unit (3) is provided with: a compressor (31) which compresses a refrigerant; a gas cooler (32) which condenses the refrigerant compressed in the compressor (31); an electronic expansion valve (33) which expands the refrigerant condensed in the gas cooler (32); and a controller (100) which adjusts the degree of opening of the electronic expansion valve (33) such that the pressure of the refrigerant compressed by the compressor (31) approaches a target high-pressure value set on the basis of the outside air temperature, and which corrects the target high-pressure value if the opening degree of the electronic expansion valve (33) exceeds a predetermined opening upper limit value or opening lower limit value.

Description

DESCRIPTION

Title of the Invention

REFRIGERATION DEVICE, REFRIGERATION SYSTEM

Technical Field

[0001]

The present invention relates to a refrigeration

device and a refrigeration system.

Priority is claimed on Japanese Patent Application No.

2016-213257, filed October 31, 2016, the content of which

is incorporated herein by reference.

Background Art

[0002]

A reference herein to a patent document or any other

matter identified as prior art, is not to be taken as an

admission that the document or other matter was known or

that the information it contains was part of the common

general knowledge as at the priority date of any of the

claims.

[0002a]

For example, in stores or the like, a plurality of

refrigerating and freezing devices, such as a refrigerator,

a freezer, and a showcase, which store or display goods,

such as food and a drink, in a refrigerated state or frozen state, are used. The plurality of refrigerating and freezing devices receive supply of a low-temperature low pressure liquid refrigerant from a separately provided condensing unit. Each refrigerating and freezing device cools goods by supplying the liquid refrigerant to an internal heat exchanger.

[0003]

- la -

The condensing unit is a so-called refrigeration

device. The condensing unit includes a compressor, a cooler

(gas cooler), an expansion valve, and a receiver (gas-liquid

separator). In the condensing unit, the refrigerant warmed

by the external refrigerating and freezing device is

compressed by the compressor. The compressed refrigerant

is expanded in the expansion valve and turned into a low

pressure low-temperature refrigerant after being cooled in

the cooler. The refrigerant brought into a gas-liquid two

phase state through the expansion valve is separated into a

gaseous phase (gas refrigerant) and a liquid phase (liquid

refrigerant) by the receiver. The separated liquid

refrigerant is supplied to the external refrigerating and

freezing device. On the other hand, the separated gas

refrigerant is sent into the compressor and compressed again.

[00041

In the refrigerating and freezing device to which the

liquid refrigerant is supplied from the condensing unit,

the control of adjusting a cooling temperature at which

goods are actually cooled is individually performed in

accordance with a set temperature. For this reason, the

refrigerating and freezing device includes an adjusting

valve that adjusts the amount of the refrigerant to be

supplied to each heat exchanger, and a controller that

controls an opening degree of the adjusting valve. In the refrigerating and freezing device, when the cooling temperature reaches the set temperature, the adjusting valve is closed by the controller to reduce the amount of supply of the refrigerant to the heat exchanger.

[00051

As such a condensing unit, PTL 1 discloses a

refrigeration device including a throttle mechanism

(expansion valve) on a heat source side (condensing unit

side) and a throttle mechanism (expansion valve) on a use

side (refrigerating and freezing device side) so as to

expand the refrigerant in two steps. The refrigeration

device sets a target value (hereinafter referred to as a

target high-pressure value) of a high-pressure refrigerant

pressure to be discharged from the compressor on the basis

of outside-air temperature and refrigerant temperature. In

the refrigeration device, the throttling amount of each

throttle mechanism (the opening degree of the expansion

valve) is adjusted such that the high-pressure refrigerant

pressure becomes the target high-pressure value.

Citation List

Patent Literature

[00061

[PTL 1] Japanese Unexamined Patent Application

Publication No. 2007-263383

Summary of Invention

[00071

Meanwhile, the target high-pressure value fluctuates

in accordance with the outside-air temperature.

Specifically, the target high-pressure value becomes low if

the outside-air temperature is low, and conversely, becomes

high if the outside-air temperature is high. If the

refrigeration capacity load from the refrigerating and

freezing device side is large in a case where the outside

air temperature is low, the high-pressure refrigerant

pressure may exceed target high pressure. As a result, the

opening degree of the expansion valve on the condensing unit

side becomes large, and the pressure on a downstream side

of the expansion valve becomes high. In a case where the

expansion valve is brought into a fully-opened state in this

way, pressure resistance design is required for a member

provided on the downstream side of the expansion valve, for

example, an injection circuit that sends a gas refrigerant

from the receiver into the compressor, a pipe that connects

refrigerating and freezing devices to each other, or the

like, and this leads to a cost rise.

[00081

Additionally, if the refrigeration capacity load from

the refrigerating and freezing device side is low in a case

where the outside-air temperature is high, the high-pressure

refrigerant pressure may fall below the target high-pressure.

As a result, the opening degree of the expansion valve on

the condensing unit becomes small, and the liquid

refrigerant to be supplied from the condensing unit to the

refrigerating and freezing device side decreases. In a case

where the expansion valve is brought into the fully-closed

state in this way, there is a possibility that the

refrigerant may be insufficient on the refrigerating and

freezing device side.

[00091

The invention provides a refrigeration device and a

refrigeration system capable of making it difficult for an

expansion valve to be brought into a fully-opened state or

a fully-closed state.

[0010]

A refrigeration device related to a first aspect of

the invention comprises a compressor that compresses a

refrigerant; a heat exchanger that condenses the refrigerant

compressed in the compressor; an expansion valve that

expands the refrigerant condensed in the heat exchanger;

and a controller that adjusts an opening degree of the

expansion valve such that a pressure of the refrigerant

compressed in the compressor approaches a target high

pressure value set on the basis of an outside-air temperature, and that corrects the target high-pressure value in a case where the opening degree of the expansion valve exceeds a preset opening degree upper limit value or opening degree lower limit value.

[0011]

According to such a configuration, by correcting the

target high-pressure value, the opening degree of the

expansion valve changes to an opening degree according to

the corrected target high-pressure value. Specifically, by

making a difference between the target high-pressure value

and the pressure of the refrigerant compressed in the

compressor small, the amount of adjustment of the opening

degree of the expansion valve changes. Hence, by correcting

the target high-pressure value, in a case where the opening

degree of the expansion valve exceeds the opening degree

upper limit value or the opening degree lower limit value,

it is possible to suppress that the opening degree of the

expansion valve changes greatly.

[00121

Additionally, in the refrigeration device related to

a second aspect of the invention based on the first aspect,

the controller may correct the target high-pressure value

to be increased in a case where the opening degree of the

expansion valve exceeds the opening degree upper limit value.

[00131

By adopting such a configuration, in a case where the

opening degree of the expansion valve is large, the target

high-pressure value can be increased and approach the

pressure of the refrigerant compressed in the compressor.

As a result, the difference between the target high-pressure

value and the pressure of the refrigerant compressed in the

compressor becomes relatively small, and the amount of

adjustment of the opening degree of the expansion valve

becomes small. Accordingly, the opening degree of the

expansion valve is not easily brought into the fully-opened

state after the opening degree thereof exceeds the opening

degree upper limit value.

[0014]

Additionally, in the refrigeration device related to

a third aspect of the invention based on the first aspect

or the second aspect, the controller may correct the target

high-pressure value to be decreased in a case where the

opening degree of the expansion valve exceeds the opening

degree lower limit value.

[00151

By adopting such a configuration, in a case where the

opening degree of the expansion valve is small, the target

high-pressure value can be decreased and approach the

pressure of the refrigerant compressed in the compressor.

As a result, the difference between the target high-pressure value and the pressure of the refrigerant compressed in the compressor becomes relatively small, and the amount of adjustment of the opening degree of the expansion valve becomes small. Accordingly, the opening degree of the expansion valve is not easily brought into the fully-closed state after the opening degree thereof falls below the opening degree lower limit value.

[00161

Additionally, in the refrigeration device related to

a fourth aspect of the invention based on any one of the

first aspect to the third aspect, the controller may

repeatedly correct the target high-pressure value multiple

times to be increased or decreased in a preset predetermined

percentage multiple times.

[0017]

By adopting such a configuration, by repeatedly

correcting the target high-pressure value to be increased

or decreased, the difference between the target high

pressure value and the pressure of the refrigerant

compressed in the compressor becomes gradually small. As a

result, the opening degree of the expansion valve is

gradually adjusted, and the amount of adjustment at a time

becomes small. This can prevent the opening degree of the

expansion valve from being brought into the fully-opened

state or the fully-closed state with high accuracy.

[00181

Additionally, in the refrigeration device related to

a fifth aspect of the invention based on any one of the

first aspect to the fourth aspect, the compressor may

include a first-stage compression section and a second-stage

compression section, a receiver that separates the

refrigerant condensed in the expansion valve into a gas

refrigerant and a liquid refrigerant, and an injection

circuit that sends the gas refrigerant separated in the

receiver into the second-stage compression section of the

compressor.

[0019]

In such a configuration, by making it difficult for

the opening degree of the expansion valve to be brought into

the fully-opened state, the pressure of a medium-pressure

gas refrigerant to be sent into the compressor through the

injection circuit can be suppressed. Accordingly, the

pressure resistance performance required for a member

through which the refrigerant flow is suppressed, and a cost

rise can be suppressed.

[00201

Additionally, in the refrigeration device related to

a sixth aspect of the invention based on any one of the

first aspect to the fifth aspect, the refrigerant may be

carbon dioxide.

[00211

Additionally, a refrigeration system related to a

seventh aspect of the invention includes the refrigeration

device of any one of the first aspect to the sixth aspect;

and a loading apparatus that is connected to the

refrigeration device and has a heat exchanger of the loading

apparatus that exchanges heat with the refrigerant to be

supplied from the refrigeration device.

[0022]

Additionally, in the refrigeration system related to

an eighth aspect of the invention based on the seventh

aspect, the loading apparatus may further include a

expansion valve of the loading apparatus that expands the

refrigerant to be supplied from the refrigeration device.

[00231

By adopting such a configuration, the expansion valve

on the refrigeration device side is not easily brought into

the fully-opened state or the fully-closed state, and an

expansion process is reliably performed even in the

expansion valve of the loading apparatus. For that reason,

it is possible to realize an efficient refrigeration cycle

by expanding the refrigerant in two steps in the expansion

valve on the refrigeration device side and the expansion

valve of the loading apparatus.

[00241

Additionally, in the refrigeration system related to

a ninth aspect of the invention based on the seventh aspect

or the eighth aspect, a plurality of the loading apparatuses

may be connected to the refrigeration device.

Advantageous Effects of Invention

[0025]

According to the invention, by making it difficult for

the expansion valve to be brought into the fully-opened

state or fully-closed state, a cost rise and shortage of

the amount of supply of the liquid refrigerant can be

suppressed, and it is possible to enhance refrigeration

cycle efficiency.

[0025a]

Where any or all of the terms "comprise",

"comprises", "comprised" or "comprising" are used in this

specification (including the claims) they are to be

interpreted as specifying the presence of the stated

features, integers, steps or components, but not precluding

the presence of one or more other features, integers, steps

or components.

Brief Description of Drawings

[0026]

Fig. 1 is a schematic view illustrating the

configuration of a refrigeration system and a refrigeration

device related to an embodiment of the invention.

Fig. 2 is a view illustrating a circuit configuration

of the above refrigeration device.

Fig. 3 is a flowchart illustrating a flow of target

high-pressure value correction control performed in

accordance with the opening degree of an expansion valve in

the above refrigeration device.

Fig. 4 is a view illustrating an example of changes in

the target high-pressure value and changes in the opening

- 11a - degree of an electronic expansion valve in a case where the target high-pressure value correction control is executed and in a case where the same correction control is not executed, in an actual condensing unit.

Description of Embodiments

[00271

Hereinafter, embodiments for carrying out a

refrigeration device and a refrigeration system according

to the invention will be described with reference to the

accompanying drawings. However, the invention is not

limited only to these embodiments.

[00281

As illustrated in Fig. 1, a refrigeration system 1 of

the present embodiment includes a plurality (three in the

present embodiment) loading apparatuses 2, and a condensing

unit (refrigeration device) 3. In the present embodiment,

the refrigeration system uses C02 (carbon dioxide) 1 as a

refrigerant.

[00291

Each loading apparatus 2 is a refrigerating and

freezing device, such as a refrigerator or a freezer, which

cools or refrigerates and store goods and a showcase that

cools or refrigerates and displays goods. The loading

apparatus 2 receives supply of a liquid refrigerant RL from

the condensing unit 3. The loading apparatus 2 includes a heat exchanger 21 of the loading apparatus, a control valve

(expansion valve of the loading apparatus) 22, a controller

of the loading apparatus 23, and a temperature sensor 24.

[00301

The heat exchanger 21 of the loading apparatus

exchanges heat with the liquid refrigerant RL supplied from

the condensing unit 3, thereby cooling goods. The heat

exchanger 21 of the loading apparatus returns the

refrigerant after the heat exchange to the condensing unit

3.

[00311

The control valve 22 adjusts the flow rate of the

liquid refrigerant RL supplied from the condensing unit 3,

thereby adjusting the cooling temperature of goods.

[00321

On the basis of a set temperature set from the outside

and a cooling temperature which is detected by the

temperature sensor 24 and at which goods are actually cooled,

the controller of the loading apparatus 23 adjusts the

opening degree of the control valve 22 such that the

internal cooling temperature approaches the set temperature.

[00331

As illustrated in Fig. 2, the condensing unit 3 mainly

includes a compressor 31, a gas cooler (heat exchanger) 32,

an electronic expansion valve (expansion valve) 33, a receiver 34, an injection circuit 38, an oil separator 39, a low-pressure sensor 40, a high-pressure sensor 41, an outside-air temperature sensor 43, and a controller 100.

The compressor 31, the gas cooler 32, the electronic

expansion valve 33, the receiver 34, and the oil separator

39 are coupled to each other by a refrigerant pipe 300.

[0034]

The compressor 31 compresses the refrigerant supplied

via an accumulator 35 by a suction pipe 302 from the loading

apparatus 2. The compressor 31 discharges a high-pressure

high-temperature refrigerant. In the present embodiment,

C02 having a larger compression ratio than fluorocarbon or

the like is used as the refrigerant. The compressor 31 is

a two-stage compressor having a first-stage compression

section 31a, and a second-stage compression section 31b.

The compressor 31 has a temperature sensor 37 that detects

the temperature of the refrigerant liquid and oil in the

first-stage compression section 31a of the compressor 31.

[00351

The high-pressure high-temperature refrigerant is

supplied to the gas cooler 32 via the oil separator 39 after

being discharged from the compressor 31. The gas cooler 32

exchanges heat with the supplied high-pressure high

temperature refrigerant and the air sent by a blower (not

illustrated), and condenses the refrigerant. In the present embodiment, a plurality of (two in the present embodiment) the gas coolers 32 are provided in parallel. The oil separator 39 recovered the lubricant oil included in the refrigerant, respectively, and returns the lubricant oil to the compressor 31.

[00361

The electronic expansion valve 33 expands the

refrigerant condensed in each gas cooler 32, and produces a

low-pressure low-temperature refrigerant. The refrigerant

expanded in the electronic expansion valve 33 is brought

into a gas-liquid two-phase state.

[0037]

The receiver 34 separates the refrigerant in the gas

liquid two-phase state expanded in the electronic expansion

valve 33 into a gas refrigerant RG that is a gaseous-phase

refrigerant, and a liquid refrigerant RL that is a liquid

phase refrigerant. In the present embodiment, a plurality

of (two in the present embodiment) the receivers 34 are

provided in parallel. Each receiver 34 has a tank 341 that

contains the refrigerant in the gas-liquid phase state. A

liquid sending pipe 301 and the injection circuit 38 are

connected to the tank 341. The liquid refrigerant RL

separated within the tank 341 is supplied to each external

loading apparatus 2 through the liquid sending pipe 301.

[00381

Additionally, the gas refrigerant RG separated within

the tank 341 of the receiver 34 is suctioned into the

compressor 31 via the injection circuit 38. In the present

embodiment, the injection circuit 38 is connected to the

second-stage compression section 31b of the compressor 31.

The injection circuit 38 supplies the gas refrigerant RG

within the tanks 341 to the second-stage compression section

31b.

[00391

The injection circuit 38 is provided with an

electromagnetic valve 36. The opening degree of the

electromagnetic valve 36 is adjusted in accordance with the

temperature of the refrigerant liquid and the oil detected

in the temperature sensor 37, by the control of the

controller 100. By opening and closing the electromagnetic

valve 36, the flow rate of the gas refrigerant RG from the

receiver 34 is adjusted.

[0040]

The low-pressure sensor 40 measures the value (low

pressure value) of the pressure of a low-pressure

refrigerant to be supplied to the compressor 31 via the

loading apparatus 2. The low-pressure sensor 40 outputs

the measurement result to the controller.

[0041]

The high-pressure sensor 41 measures the value (high pressure value) of the pressure of a high-pressure refrigerant discharged from the compressor 31. The high pressure sensor 41 outputs the measurement result to the controller.

[00421

The outside-air temperature sensor 43 measures an

outside-air temperature around the condensing unit 3. The

outside-air temperature sensor 43 outputs the measurement

result to the controller.

[00431

The controller 100 controls the operation ON/OFF and

the rotation speed of the compressor 31, and the opening

degree of the electronic expansion valve 33. The controller

100 of the present embodiment controls the opening degree

of the electronic expansion valve 33 on the basis of the

outside-air temperature, the low-pressure value, and the

high-pressure value.

[00441

Hereinafter, the control contents of the controller

100 will be described in detail. The controller 100 starts

the compressor 31 if the condensing unit 3 is started. The

controller 100 operates the compressor 31 between a

predetermined upper limit rotation speed and a predetermined

lower limit rotation speed.

[00451

Additionally, the controller 100 sets a target high

pressure value HP as a target value of the pressure of the

high-pressure refrigerant to be discharged from the

compressor 31, on the basis of the outside-air temperature

detected by the outside-air temperature sensor 43. The

controller 100 adjusts the opening degree of the electronic

expansion valve 33, on the basis of the set target high

pressure value HP, and a high-pressure refrigerant pressure

P that is an actual pressure value of the high-pressure

refrigerant detected by the high-pressure sensor 41. The

controller 100 adjusts and controls the opening degree of

the electronic expansion valve 33 such that the high

pressure refrigerant pressure P approaches the target high

pressure value HP. The controller 100 corrects the target

high-pressure value HP in a case where a preset opening

degree upper limit value or a preset opening degree lower

limit value is exceeded. The controller 100 repeatedly

corrects the target high-pressure value HP multiple times

while increasing or decreasing the target high-pressure

value HP in a preset predetermined percentage.

[00461

Here, the target high-pressure value HP is a value

determined depending on the outside-air temperature of the

condensing unit 3. The target high-pressure value HP

becomes larger the outside-air temperature becomes higher and becomes smaller as the outside-air temperature becomes lower. For example, in the condensing unit 3 of the present embodiment, the target high-pressure value HP falls within a range of 4 (Mpa-G) to 6 (Mpa-G) in a case where the outside air temperature is 00C or lower. Additionally, the target high-pressure value HP falls within a range of 6 (Mpa-G) to

8 (Mpa-G) in a case where the outside-air temperature is 0°C

or higher and 30°C or lower. Additionally, the target high

pressure value HP falls within a range of 8 (Mpa.G) to 12

(Mpa-G) in a case where the outside-air temperature is 300C

or higher.

[00471

The controller 100 of the present embodiment adjusts

the opening degree of the electronic expansion valve 33

through a PI control based on a deviation between the target

high-pressure value HP and the high-pressure refrigerant

pressure P.

[00481

In addition, it is preferable that the controller 100

performs the PI control via a primary delay for 3 seconds

in order to reduce the influence of noise on the input of

the high-pressure sensor 41.

[00491

Additionally, the opening degree range of the

electronic expansion valve 33 is set to be within a preset range. In the present embodiment, the opening degree range of the electronic expansion valve 33 is set, for example, as follows:

Maximum opening degree (fully-opened state): 470

pulses

Minimum opening degree (fully-closed state): 10 pulses.

[0050]

Moreover, the controller 100 performs the opening

degree adjustment control of the electronic expansion valves

33 as described above after a certain period of time has

elapsed since the operation of the compressor 31 is started

and the operation rotation speed of the compressor 31 has

reached a rated operation rotation speed. The controller

100 executes the correction control of the target high

pressure value HP in accordance with the opening degree of

the electronic expansion valve 33 as illustrated in Fig. 3

at predetermined time intervals.

[00511

In the correction control of this target high-pressure

value HP, the controller 100 controls the opening degree of

the electronic expansion valve 33 such that the opening

degree of the electronic expansion valve 33 so as not to be

full opened or full closed on the basis of the target high

pressure value HP, and the high-pressure refrigerant

pressure P of the refrigerant detected by the high-pressure sensor 41. For this reason, the opening degree upper limit value and the opening degree lower limit value of the electronic expansion valve 33 are set in advance by controller 100. In the present embodiment, the opening degree upper limit value of the electronic expansion valve

33 is set to 70% to 90% of the maximum opening degree. The

opening degree lower limit value of the electronic expansion

valve 33 is set to 5% to 20% of the maximum opening degree.

Specifically, the opening degree upper limit value of the

electronic expansion valve 33 of the present embodiment is

set to, for example, 400 pulses, and the opening degree

lower limit value is set to, for example, 80 pulses.

[00521

As illustrated in Fig. 3, in a case where the

correction control is performed, first, the controller 100

sets the target high-pressure value HP on the basis of the

outside-air temperature detected in the outside-air

temperature sensor 43 (Step S101).

[00531

After the setting of the target high-pressure value

HP, the controller 100 determines whether or not the opening

degree of the electronic expansion valve 33 is equal to or

more than the opening degree upper limit value (Step S102).

The controller 100 determines whether or not the opening

degree of the electronic expansion valve 33 is equal to or less than the opening degree lower limit value in a case where it is determined that the opening degree of the electronic expansion valve 33 is equal to or less than the opening degree upper limit value (Step S106). The controller 100 repeats the processing of Step S101, Step

S102, and Step S106 at predetermined time intervals in a

case where it is determined that the opening degree of the

electronic expansion valve 33 is not equal to or less than

the opening degree lower limit value.

[0054]

The controller 100 maintains the opening degree of the

electronic expansion valve 33 until a preset standby time

has elapsed in a case where it is determined that the opening

degree of the electronic expansion valve 33 is equal to or

more than the opening degree upper limit value in Step S102

(Step S103). Here, the standby time is the time that is

required until the value of the high-pressure refrigerant

pressure P is stabilized after the opening degree of the

electronic expansion valve 33 is maintained. Specifically,

the standby time may be about 1 minute to 10 minutes, and

preferably about 5 minutes.

[00551

After the standby time has elapsed, the controller 100

corrects the target high-pressure value HP set in Step S101

so as to increase the target high-pressure value HP (Step

S104). Specifically, a pressure addition value that is the

predetermined percentage is added to the target high

pressure value HP set in Step S101. In addition, the

pressure addition value is an increased percentage when a

correction determined in accordance with the target high

pressure value HP is performed. The pressure addition value

of the present embodiment is, for example, 0.1 (MPa-G). In

Step S104, the target high-pressure value HP is corrected

so as to increase by the pressure addition value.

[00561

The controller 100 corrects the target high-pressure

value HP in this way, and then, determines whether or not

the target high-pressure value HP before the correction

varies as the outside-air temperature detected in the

outside-air temperature sensor 43 varies. Specifically,

the controller 100 determines whether or not a measurement

value input from the outside-air temperature sensor 43

varies (Step S105)

[0057]

In a case where it is determined in Step S105 that the

outside-air temperature varies, the controller 100 ends a

series of correction processing. The controller 100

continues the opening degree control of an ordinary

electronic expansion valve 33 that brings the high-pressure

refrigerant pressure P close to the target high-pressure value HP.

[00581

Additionally, in a case where it is determined in Step

S105 that the outside-air temperature does not vary, the

controller 100 returned to Step S103 where the opening

degree of the electronic expansion valve 33 is maintained

until the preset standby time elapses. The controller 100

repeats Step S103 to Steps S105 multiple times, thereby

gradually increasing the target high-pressure value (HP)

multiple times by every pressure addition value.

[00591

The processing of increasing and correcting the target

high-pressure value HP as in Step S103 and Step S104 can be

repeated up to a predetermined number of times, for example,

times. In a case where the predetermined number of times

has been reached, the controller 100 ends the processing of

increasing and correcting the target high-pressure value HP

regardless of a change situation of the outside-air

temperature. Thereafter, the controller 100 continues the

opening degree control of the ordinary electronic expansion

valve 33 that brings the high-pressure refrigerant pressure

P close to the target high-pressure value HP.

[00601

Additionally, the controller 100 maintains the opening

degree of the electronic expansion valve 33 until the preset standby time has elapsed in a case where it is determined that the opening degree of the electronic expansion valve

33 is equal to or less than the opening degree lower limit

value in Step S106 (Step S107).

[00611

After the standby time has elapsed, the controller 100

corrects the target high-pressure value HP set in Step S101

so as to decrease the target high-pressure value HP (Step

S108). For this, a pressure subtraction value that is a

predetermined percentage is subtracted from the target high

pressure value HP set in Step S101. In addition, the

pressure subtraction value is a decreased percentage when a

correction determined in accordance with the target high

pressure value HP is performed. The pressure subtraction

value of the present embodiment is, for example, 0.1 (MPa.G)

Accordingly, the target high-pressure value HP is corrected .

so as to decrease by a pressure subtraction value.

[00621

The controller 100 corrects the target high-pressure

value HP in this way, and then, determines whether or not

the target high-pressure value HP before the correction

varies as the outside-air temperature detected in the

outside-air temperature sensor 43 varies. Specifically,

the controller 100 determines whether or not a measurement

value input from the outside-air temperature sensor 43 varies (Step S109)

[00631

In a case where it is determined in Step S109 that the

outside-air temperature varies, the controller 100 ends a

series of correction processing. The controller 100

continues the opening degree control of the ordinary

electronic expansion valve 33 that brings the high-pressure

refrigerant pressure P close to the target high-pressure

value HP.

[00641

Additionally, in a case where it is determined in Step

S109 that the outside-air temperature does not vary, the

controller 100 returned to Step S107 where the opening

degree of the electronic expansion valve 33 is maintained

until the preset standby time elapses. The controller 100

repeats Step S107 to Steps S109 multiple times, thereby

gradually decreasing the target high-pressure value (HP)

multiple times by every pressure subtraction value.

[00651

The processing in which the target high-pressure value

HP is corrected so as be decreased as in Step S107 and Step

S108 can be repeated up to a predetermined number of times,

for example, 5 times. In a case where the predetermined

number of times has been reached, the controller 100 ends

the processing of decreasing and correcting the target high pressure value HP regardless of a change situation of the outside-air temperature. Thereafter, the controller 100 continues the opening degree control of the ordinary electronic expansion valve 33 that brings the high-pressure refrigerant pressure P close to the target high-pressure value HP.

[00661

The following actions are obtained by repeatedly

executing the processing of Steps S101 to S109 as described

above at every predetermined time during the operation of

the compressor 31 in the controller 100. For example, in a

case where the outside-air temperature is low, the target

high-pressure value HP becomes low. On the other hand, if

the refrigeration capacity load on the loading apparatus 2

side is large, the high-pressure refrigerant pressure P that

is the pressure of the refrigerant discharged from the

compressor 31 becomes high. For that reason, in a case

where the outside-air temperature is low, the high-pressure

refrigerant pressure P may exceed the target high-pressure

value HP. In such a state, the opening degree of the

electronic expansion valve 33 may be brought into the fully

opened state beyond the opening degree upper limit value by

the opening degree of the electronic expansion valve 33

being adjusted by the controller 100. However, when the

opening degree of the electronic expansion valve 33 approaches the fully-opened state beyond the opening degree upper limit value by the correction processing of increasing the target high-pressure value HP as described above being executed by the controller 100, the target high-pressure value HP is increased. For that reason, the target high pressure value HP is corrected so as to approach the high pressure refrigerant pressure P. If the difference between the target high-pressure value HP and the high-pressure refrigerant pressure P becomes small by such correction, the percentage of the opening degree of the electronic expansion valve 33 enlarged by the controller 100 become small, and the electronic expansion valve 33 is not easily brought into the fully-opened state.

[0067]

Additionally, for example, in a case where the

outside-air temperature is high, the target high-pressure

value HP becomes high. On the other hand, if the

refrigeration capacity load on the loading apparatus 2 side

is small, the high-pressure refrigerant pressure P becomes

low. For that reason, in a case where the outside-air

temperature is high, the high-pressure refrigerant pressure

P may fall below the target high-pressure value HP. In such

the state, by the opening degree of the electronic expansion

valve 33 being adjusted by the controller 100, the opening

degree of the electronic expansion valve 33 may become equal to or less than the opening degree lower limit value and the electronic expansion valve 33 may be brought into the fully-closed state. However, when the opening degree of the electronic expansion valve 33 falls below the opening degree lower limit value and approaches the fully-closed state by the correction processing of decreasing the target high-pressure value HP as described above being executed by the controller 100, the target high-pressure value HP is decreased. For that reason, the target high-pressure value

HP is corrected so as to approach the high-pressure

refrigerant pressure P. By such correction, the opening

degree of the electronic expansion valve 33 becomes large.

Accordingly, if the difference between the target high

pressure value HP and the high-pressure refrigerant pressure

P becomes small, the percentage of the opening degree of

the electronic expansion valve 33 decreased by the

controller 100 become small, and the electronic expansion

valve 33 is not easily brought into the fully-closed state.

[00681

A specific example will be described with reference to

Fig. 4. Fig. 4 is a view illustrating an example of changes

in the target high-pressure value HP and changes in the

opening degree of the electronic expansion valve in a case

where the correction control of the target high-pressure

value HP by the controller 100 as described above is executed and in a case where the correction control is not executed, in the actual condensing unit 3. In addition,

Fig. 4 illustrates changes in a state where the high

pressure refrigerant pressure P exceeds the target high

pressure value HP because the outside-air temperature is

low and the refrigeration load capacity from the loading

apparatus 2 side is large. A two-dot chain line L2

represents the target high-pressure value HP in a case where

when no correction is performed. A solid line L12

represents the target high-pressure value HP in a case where

the correction of the present embodiment has been performed.

A two-dot chain line L3 represents the opening degree of

the electronic expansion valve 33 in a case where the

correction of the target high-pressure value HP is not

performed. A solid L13 represents the opening degree of

the electronic expansion valve 33 in a case where the

correction of the target high-pressure value HP has been

performed.

[00691

In a case where the correction control of the target

high-pressure value HP according to the opening degree of

the electronic expansion valve 33 is not performed, as

indicated by the two-dot chain line L2 in Fig. 4, the target

high-pressure value HP that is not corrected remains

constant as being set in accordance with the outside-air temperature at the beginning. Additionally, as indicated by the two-dot chain line L3 in Fig. 4, as a result of the electronic expansion valve 33 having performed the control of enlarging the opening degree such that the pressure of the refrigerant approaches the target high-pressure value

HP in a state where the refrigeration load capacity from

the loading apparatus 2 side is large, the opening degree

is brought into the fully-opened state.

[0070]

In contrast, in a case where the correction control of

the target high-pressure value HP according to the opening

degree of the electronic expansion valve 33 has been

performed, as indicated by the solid line L12 in Fig. 4,

the target high-pressure value HP is set in accordance with

the outside-air temperature at the beginning, and then,

increases stepwise as a result of the opening degree of the

electronic expansion valve 33 having reached the opening

degree upper limit value. Additionally, as indicated by

the solid line L13 in Fig. 4, the electronic expansion valve

33 is brought into a constant state before the opening

degree reaches the fully-opened state as a result of the

target high-pressure value's HP increasing stepwise in a

state where the refrigeration load capacity from the loading

apparatus 2 side is large.

[00711

According to the condensing unit 3 and the

refrigeration system 1 as described above, in a case where

the opening degree of the electronic expansion valve 33 has

exceeded the preset opening degree upper limit value or

opening degree lower limit value, the target high-pressure

value HP is corrected so as to approach the high-pressure

refrigerant pressure P. By correcting the target high

pressure value HP, the opening degree of the electronic

expansion valve 33 changes to an opening degree according

to the corrected target high-pressure value HP.

Specifically, by making the difference between the target

high-pressure value HP and the high-pressure refrigerant

pressure P small, the amount of adjustment of the opening

degree of the electronic expansion valve 33 becomes small.

Hence, by correcting the target high-pressure value HP, in

a case where the opening degree of the electronic expansion

valve 33 has exceeded then opening degree upper limit value

or the opening degree lower limit value, it is possible to

suppress that the opening degree changes greatly, and the

electronic expansion valve 33 is not easily brought into

the fully-opened state or the fully-closed state.

[0072]

Accordingly, it is possible to make it difficult for

the refrigerant with excessively high pressure to flow into

a portion where the high-pressure refrigerant discharged from the compressor 31 flows. The pressure resistance performance required for each part is suppressed is suppressed, and a cost rise can be suppressed.

[00731

Additionally, by making it difficult for the opening

degree of the electronic expansion valve 33 to be brought

into the fully-opened state, it is possible to prevent

formation of a one-stage throttle configuration in which

the electronic expansion valve 33 is brought into the fully

opened state, the refrigerant cannot be sufficiently

expanded, and the refrigerant is expanded only by the

control valve 22 that is an expansion valve on the loading

apparatus 2 side. As a result, it is possible to suppress

that the discharge temperature of the refrigerant rises and

the refrigeration cycle efficiency decreases. Similarly,

by making it difficult for the electronic expansion valve

33 to be brought into the fully-closed state, a throttle

region in the control valve 22 becomes large. For that

reason, it is possible to suppress that the discharge

temperature of the refrigerant rises and the refrigeration

cycle efficiency decreases. Accordingly, shortage of the

amount of supply of the liquid refrigerant RL can be

suppressed, and it is possible to enhance the refrigeration

cycle efficiency.

[00741

More specifically, in a case where the opening degree

of the electronic expansion valve 33 exceeds the opening

degree upper limit value, the controller 100 corrects the

target high-pressure value HP so as to increase the target

high-pressure value HP. For that reason, in a case where

the opening degree of the electronic expansion valve 33 is

large, the target high-pressure value HP can be increased

and approach the high-pressure refrigerant pressure P. As

a result, the difference between the target high-pressure

value HP and the high-pressure refrigerant pressure P

becomes relatively small, and the amount of adjustment of

the opening degree of the electronic expansion valve 33

becomes small. Accordingly, the electronic expansion valve

33 is not easily brought into the fully-opened state after

the opening degree thereof exceeds the opening degree upper

limit value.

[0075]

Additionally, in a case where the opening degree of

the electronic expansion valve 33 exceeds the opening degree

lower limit value, the controller 100 may correct the target

high-pressure value HP so as to decrease the target high

pressure value HP. For that reason, in a case where the

opening degree of the electronic expansion valve 33 is small,

the target high-pressure value HP can be decreased and

approach the high-pressure refrigerant pressure P. As a result, the difference between the target high-pressure value HP and the high-pressure refrigerant pressure P becomes relatively small, and the amount of adjustment of the opening degree of the electronic expansion valve 33 becomes small. Accordingly, the electronic expansion valve

33 is not easily brought into the fully-closed state after

the opening degree thereof falls below the opening degree

lower limit value.

[00761

Additionally, by repeatedly correcting the target

high-pressure value HP to increase or decrease the target

high-pressure value HP, the difference between the target

high-pressure value HP and the high-pressure refrigerant

pressure P becomes gradually small. As a result, the

opening degree of the electronic expansion valve 33 is

gradually adjusted, and the amount of adjustment at a time

becomes small. This can prevent the opening degree of the

electronic expansion valve 33 from being brought into the

fully-opened state or the fully-closed state with high

accuracy.

[00771

Additionally, by making it difficult for the opening

degree of the electronic expansion valve 33 to be brought

into the fully-opened state, the pressure of a medium

pressure gas refrigerant RG to be sent into the compressor

31 through the injection circuit 38 is suppressed. Hence,

the pressure resistance performance required for a member,

such as the injection circuit 38, through which the

refrigerant flows can be suppressed, and a cost rise can be

suppressed.

[00781

Additionally, by making it difficult for the

electronic expansion valve 33 on the condensing unit 3 side

to be brought into the fully-opened state or fully-closed

state, an expansion process is reliably performed in both

the electronic expansion valve 33 and the control valve 22.

For that reason, it is possible to realize an efficient

refrigeration cycle by expanding the refrigerant in two

steps in the electronic expansion valve 33 on the condensing

unit 3 side and the control valve 22.

[00791

(Modification Example of Embodiment)

Although the embodiment of the invention has been

described above in detail with reference to the drawings,

the respective components, combinations thereof, or the like

in the embodiment are exemplary. Additions, omissions,

substitutions, and other modifications of the components

can be made without departing from the spirit of the

invention. Additionally, the invention is not limited by

the embodiment, and is limited only by the scope of the

Claims

claims.

[00801

For example, in the above embodiment, the

refrigeration system 1 is one having a two-stage expansion

process including the electronic expansion valve 33 and the

expansion valve 22 of the loading apparatus. However, the

invention is also applicable to a configuration including

only one-stage expansion process.

[00811

Additionally, although the compressor 31 is configured

to include the first-stage compression section 31a and the

second-stage compression section 31b and compress the

refrigerant in two stages, a case where only one-stage

compression is performed may be adopted.

[00821

Generally, in the configuration of one-stage expansion

and one-stage compression, if the electronic expansion valve

33 is brought into the fully-opened state in a case where

the outside-air temperature becomes low and the high

pressure refrigerant pressure P becomes low, or in a case

where pipe length is long, the control by the electronic

expansion valve 33 does not function, and the liquid

refrigerant RL easily returns to the compressor 31.

Additionally, in the configuration of one-stage expansion

and one-stage compression, if the electronic expansion valve

33 is brought into the fully-closed state in a case where

the outside-air temperature is high and a pressure

difference between the high-pressure refrigerant pressure

and a load side is high, the amount of circulations of the

refrigerant decreases and the performance becomes deficient.

[00831

In contrast, in the configuration of one-stage

expansion and one-stage compression, it is possible to

suppress that an inflow of the liquid refrigerant RL into

the compressor 31 or a decrease in the amount of

circulations of the refrigerant occurs by applying the

correction control of the target high-pressure value HP in

accordance with the opening degree of the electronic

expansion valve 33 as shown in the above embodiment.

[00841

Additionally, the control by the controller 100 is not

limited to one exemplified above, and the processing order

may be changed or some kinds of processing may be omitted.

[00851

Additionally, in the above embodiment, the

refrigeration system 1 includes the plurality of loading

apparatuses 2 and the condensing unit 3. However, the

number of loading apparatuses 2 is not limited at all. It

is obvious that the plurality of loading apparatuses 2 may

not need to be of the same type, and a plurality of types of loading apparatuses 2 may be provided in a mixed manner.

[00861

Moreover, the refrigeration system 1 may be a unit

having the loading apparatuses 2 and the condensing unit 3

integrally. As such a unit, there are, for example, vending

machines for beverages or the like. Additionally, the

refrigeration system 1 may be applied to an air-conditioning

system.

Industrial Applicability

[0087]

According to the above refrigeration device and the

above refrigeration system, by making it difficult for the

expansion valve to be brought into the fully-opened state

or fully-closed state, a cost rise and shortage of the

amount of supply of the liquid refrigerant can be suppressed,

and it is possible to enhance the refrigeration cycle

efficiency.

Reference Signs List

[00881

1: REFRIGERATION SYSTEM

2: LOADING APPARATUS

3: CONDENSING UNIT (REFRIGERATION DEVICE)

21: HEAT EXCHANGER OF LOADING APPARATUS

22: EXPANSION VALVE OF LOADING APPARATUS

23: CONTROLLER OF LOADING APPARATUS

24: TEMPERATURE SENSOR

31: COMPRESSOR

31a: FIRST-STAGE COMPRESSION SECTION

31b: SECOND-STAGE COMPRESSION SECTION

32: GAS COOLER (HEAT EXCHANGER)

33: ELECTRONIC EXPANSION VALVE (EXPANSION VALVE)

34: RECEIVER

: ACCUMULATOR

36: ELECTROMAGNETIC VALVE

37: TEMPERATURE SENSOR

38: INJECTION CIRCUIT

39: OIL SEPARATOR

: LOW-PRESSURE SENSOR

41: HIGH-PRESSURE SENSOR

43: OUTSIDE-AIR TEMPERATURE SENSOR

100: CONTROLLER

300: REFRIGERANT PIPE

301: LIQUID SENDING PIPE

302: SUCTION PIPE

341: TANK

HP: TARGET HIGH-PRESSURE VALUE

P: HIGH-PRESSURE REFRIGERANT PRESSURE

RG: GAS REFRIGERANT

RL: LIQUID REFRIGERANT

The claims defining the invention are as follows:

[Claim 1]

A refrigeration device comprising:

a compressor that compresses a refrigerant;

a heat exchanger that condenses the refrigerant

compressed in the compressor;

an expansion valve that expands the refrigerant

condensed in the heat exchanger; and

a controller that adjusts an opening degree of the

expansion valve such that a pressure of the refrigerant

compressed in the compressor approaches a target high

pressure value set on the basis of an outside-air

temperature, and that corrects the target high-pressure

value in a case where the opening degree of the expansion

valve exceeds a preset opening degree upper limit value or

opening degree lower limit value.
[Claim 2]

The refrigeration device according to Claim 1,

wherein the controller corrects the target high

pressure value to be increased in a case where the opening

degree of the expansion valve exceeds the opening degree

upper limit value.
[Claim 3]

The refrigeration device according to Claim 1 or 2, wherein the controller corrects the target high pressure value to be decreased in a case where the opening degree of the expansion valve exceeds the opening degree lower limit value.
[Claim 4]

The refrigeration device according to any one of

Claims 1 to 3,

wherein the controller repeatedly corrects the target

high-pressure value to be increased or decreased in a preset

predetermined percentage multiple times.
[Claim 5]

The refrigeration device according to any one of

Claims 1 to 4,

wherein the compressor includes

a first-stage compression section and a second-stage

compression section,

a receiver that separates the refrigerant condensed in

the expansion valve into a gas refrigerant and a liquid

refrigerant, and

an injection circuit that sends the gas refrigerant

separated in the receiver into the second-stage compression

section of the compressor.
[Claim 6]

The refrigeration device according to any one of

Claims 1 to 5, wherein the refrigerant is carbon dioxide.
[Claim 7]

A refrigeration system comprising:

the refrigeration device according to any one of

Claims 1 to 6; and

a loading apparatus that is connected to the

refrigeration device and has a heat exchanger of the loading

apparatus that exchanges heat with the refrigerant to be

supplied from the refrigeration device.
[Claim 8]

The refrigeration system according to Claim 7,

wherein the loading apparatus further includes a

expansion valve of the loading apparatus that expands the

refrigerant to be supplied from the refrigeration device.
[Claim 9]

The refrigeration system according to Claim 7 or 8,

wherein a plurality of the loading apparatuses are

connected to the refrigeration device.