JP7769377B2 - Frozen dessert manufacturing equipment - Google Patents

Description

The present invention relates to a frozen dessert manufacturing device.

As prior art, Patent Document 1 discloses a refrigeration system that uses carbon dioxide as a refrigerant.

Japanese Patent Application Laid-Open No. 2006-194569

However, compared with, for example, fluorocarbon-based refrigerants, refrigerants made of carbon dioxide tend to increase in pressure as their temperature increases. Therefore, in a frozen dessert manufacturing apparatus that uses a refrigerant made of carbon dioxide to cool frozen dessert ingredients, the temperature of the refrigerant may increase, causing an increase in the refrigerant pressure, for example, during a production stoppage when frozen desserts are not being manufactured. If the refrigerant pressure becomes excessively high, there is a risk that the refrigerant may be released outside the frozen dessert manufacturing apparatus.
The present invention aims to suppress an excessive increase in refrigerant pressure in a frozen dessert manufacturing apparatus that uses a refrigerant made of carbon dioxide.

The present invention, which was completed with this object in mind, is a frozen dessert manufacturing apparatus comprising: a compressor that compresses a refrigerant made of carbon dioxide; a condenser that condenses the refrigerant compressed by the compressor when chiller water is supplied to the refrigerant; an expansion valve that expands the refrigerant condensed by the condenser; an evaporator that performs heat exchange between the refrigerant expanded by the expansion valve and frozen dessert ingredients, cooling the ingredients and evaporating the refrigerant; a storage unit that stores the refrigerant that has been cooled and condensed by the chiller water in the condenser; and a control unit that compresses the refrigerant with the compressor and stores a portion of the refrigerant condensed in the condenser in the storage unit, and then stops compression of the refrigerant by the compressor and continues to supply chiller water to the condenser, and then, when the pressure of the refrigerant in the evaporator exceeds a predetermined upper limit pressure, resumes compression of the refrigerant by the compressor and stores the refrigerant condensed in the condenser in the storage unit .
Here, the control unit may stop the compression of the refrigerant by the compressor when the pressure of the refrigerant in the evaporator becomes equal to or lower than a predetermined lower limit pressure after the compressor resumes compressing the refrigerant .

According to the present invention, excessive increases in refrigerant pressure can be suppressed in frozen dessert manufacturing equipment that uses a refrigerant made of carbon dioxide.

1 is a diagram showing an example of a schematic configuration of a frozen dessert manufacturing apparatus to which the present embodiment is applied. 1A and 1B are diagrams showing an example of the configuration of a stirring device to which the present embodiment is applied. FIG. 2 is a diagram illustrating an example of a schematic configuration of a control device. 5 is a flowchart illustrating an example of a frequency change process performed by a compressor control unit. 10 is a flowchart showing an example of a process for changing the opening degree of a hot gas valve performed by a hot gas control unit.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a diagram showing an example of a schematic configuration of a frozen dessert manufacturing apparatus 1 to which the present embodiment is applied.
The frozen dessert production apparatus 1 is used to produce frozen desserts such as ice creams and frozen desserts. The frozen dessert production apparatus 1 of this embodiment is equipped with a mixing device 100 that mixes and cools an ingredient mix, which is a mixture of frozen dessert ingredients and air. The configuration of the mixing device 100 will be described in detail later.

1, the frozen dessert production apparatus 1 includes a compressor 2, a condenser 3, an expansion valve 4, an evaporator 5, an accumulator 6, a heat exchanger 7, and a receiver 8. The frozen dessert production apparatus 1 also includes a ring-shaped refrigerant circuit 51 that connects the compressor 2, the condenser 3, the expansion valve 4, the evaporator 5, the accumulator 6, the heat exchanger 7, the receiver 8, etc.
The frozen dessert production apparatus 1 uses carbon dioxide refrigerant (hereinafter, may be referred to as " _CO2 refrigerant") as a refrigerant. _CO2 refrigerant has a lower global warming potential than fluorocarbon refrigerants. By using _CO2 refrigerant, the frozen dessert production apparatus 1 aims to reduce the environmental impact compared to apparatuses that use other refrigerants.

Furthermore, the frozen dessert manufacturing device 1 has a branch path 52 that branches off from the piping between the compressor 2 and the condenser 3 in the refrigerant circuit 51 and has an end connected to the evaporator 5.
In addition, the frozen dessert manufacturing apparatus 1 is equipped with a hot gas valve 9 on the branch path 52, which adjusts the amount of high-temperature, high-pressure gaseous refrigerant (hereinafter sometimes referred to as "hot gas") compressed by the compressor 2 that flows into the evaporator 5.
The frozen dessert manufacturing apparatus 1 also includes a well-known separator 11 that separates oil for lubricating the compressor 2 from the refrigerant flowing out of the compressor 2, and a well-known return section 12 that returns the oil separated by the separator 11 to the compressor 2.
The frozen dessert manufacturing apparatus 1 also includes an oil supplying device 20 that supplies oil into the refrigerant flowing into the compressor 2 .

Furthermore, the frozen dessert manufacturing apparatus 1 is equipped with an evaporation pressure sensor 31 that detects the pressure of the gaseous refrigerant in the accumulator 6, a liquid level sensor 32 that detects the liquid level of the liquid refrigerant in the evaporator 5, and a receiver pressure sensor 33 that detects the pressure of the refrigerant in the receiver 8.
The frozen dessert manufacturing apparatus 1 also includes a low-pressure side safety valve 35 that releases the refrigerant to the outside of the frozen dessert manufacturing apparatus 1 when the pressure of the refrigerant in the accumulator 6 measured by the evaporation pressure sensor 31 exceeds a predetermined upper limit value, and a high-pressure side safety valve 36 that releases the refrigerant to the outside of the frozen dessert manufacturing apparatus 1 when the pressure of the refrigerant in the receiver 8 measured by the receiver pressure sensor 33 exceeds a predetermined upper limit value.
Furthermore, the frozen dessert production apparatus 1 is equipped with a control device 60 that controls each part of the frozen dessert production apparatus 1.
The elements constituting the frozen dessert manufacturing apparatus 1 will be described in more detail below.

The compressor 2 draws in refrigerant through the suction port 2a, compresses it, and discharges it from the discharge port 2b. This causes the compressor 2 to circulate the refrigerant within the refrigerant circuit 51. The compressor 2 has a motor 2c as its driving source, and the operating frequency is continuously adjusted by controlling the motor 2c using the control device 60. Examples of the compressor 2 include, but are not limited to, a rotary compressor that compresses the refrigerant by rotating a piston using the motor 2c, and a reciprocating compressor that compresses the refrigerant by reciprocating a piston using the motor 2c. The operating frequency of the compressor 2 refers to the number of times (number of rotations, number of reciprocations) that a moving body, such as a piston, driven by the motor 2c in the compressor 2 moves per unit time (e.g., one second).

The condenser 3 condenses and liquefies the refrigerant compressed by the compressor 2 by heat exchange with chiller water cooled to a predetermined temperature by a cooling device (not shown). In this embodiment, a _CO2 refrigerant is used, which has a higher pressure when in a gaseous state than fluorocarbon refrigerants, so chilled water is used as chiller water to further cool the refrigerant discharged from the compressor 2. The device for generating chilled water and the device for supplying chilled water to the condenser 3 may be located within the frozen dessert production apparatus 1 or may be provided separately from the frozen dessert production apparatus 1. FIG. 1 shows an example in which the device for generating chilled water and the device for supplying chilled water to the condenser 3 are provided separately from the frozen dessert production apparatus 1.

The expansion valve 4 reduces the pressure and expands the refrigerant condensed in the condenser 3. In this embodiment, the expansion valve 4 is a so-called motor valve, having a valve (not shown) that opens and closes the flow path through which the refrigerant flows, and a motor 4a that drives the valve to open and close. Based on control by the control device 60, the motor 4a is driven to rotate the valve, adjusting the valve's rotation angle (hereinafter sometimes referred to as "opening degree") and changing the flow path area through which the refrigerant can flow. When the valve opening degree is 0 degrees, the valve is fully closed and the flow path area is 0. When the valve opening degree is at its maximum opening degree, the valve is fully open and the flow path area is maximum. The valve opening degree is continuously adjusted between 0 degrees and the maximum opening degree. This continuously adjusts the amount of refrigerant passing through the expansion valve 4 and supplied to the evaporator 5.

The evaporator 5 is provided inside the above-mentioned mixing device 100. The evaporator 5 evaporates the refrigerant expanded by the expansion valve 4 by heat exchange with the raw material mix of the frozen dessert supplied to a cylinder inner tube 110 (described later) of the mixing device 100. In addition, in the mixing device 100, the raw material mix is cooled by the refrigerant in the evaporator 5 to produce the frozen dessert.
The accumulator 6 separates the gaseous refrigerant and the liquid refrigerant discharged from the evaporator 5. The accumulator 6 then returns the separated liquid refrigerant to the evaporator 5, thereby preventing the liquid refrigerant from flowing into the compressor 2.

The heat exchanger 7 exchanges heat between the refrigerant evaporated in the evaporator 5 and passed through the accumulator 6, and the refrigerant condensed in the condenser 3 and discharged from the receiver 8. In addition, the heat exchanger 7 heats the refrigerant that has passed through the accumulator 6 with the high-temperature refrigerant discharged from the receiver 8, and if any liquid refrigerant remains in the refrigerant that has passed through the accumulator 6, the heat exchanger 7 vaporizes the remaining liquid refrigerant and prevents the liquid refrigerant from flowing into the compressor 2.
The receiver 8 is an example of a storage section, and stores a portion of the liquid refrigerant condensed in the condenser 3 and supplies the stored refrigerant to the expansion valve 4 .

The hot gas valve 9 supplies hot gas discharged from the compressor 2 to the evaporator 5 via the branch line 52. The hot gas valve 9 has a motor 9a that drives the valve to open and close. The opening of the hot gas valve 9 is continuously adjusted based on the control of the motor 9a by the control device 60. This continuously adjusts the flow rate of hot gas supplied to the evaporator 5 by the hot gas valve 9.

The evaporation pressure sensor 31 detects the pressure inside the evaporator 5 and the accumulator 6 , thereby detecting the pressure of the gaseous refrigerant in the accumulator 6 .
The receiver pressure sensor 33 detects the pressure in the piping between the receiver 8 and the high-pressure side safety valve 36, thereby detecting the pressure of the gaseous refrigerant that has evaporated from the liquid refrigerant in the receiver 8.

The liquid level sensor 32 detects the liquid level of the refrigerant in a space S2 (see FIGS. 2(a) and 2(b)) between an inner cylinder 110 and an outer cylinder 120 (described later) of the agitator 100 as the liquid level of the refrigerant in the evaporator 5. The liquid level sensor 32 is not particularly limited as long as it can continuously detect the liquid level of the refrigerant, and for example, a capacitance type liquid level sensor can be used.
The detection result by the liquid level sensor 32 is output to the control device 60 .

Next, a description will be given of the behavior of the refrigerant in the frozen dessert production apparatus 1 of this embodiment. In the frozen dessert production apparatus 1 of this embodiment, a refrigeration cycle is formed in which the refrigerant flows in order through the compressor 2, the condenser 3, the receiver 8, a separation heat exchanger 22 (described later), the heat exchanger 7, the expansion valve 4, the evaporator 5, the accumulator 6, and the heat exchanger 7, before returning to the compressor 2.
Specifically, in the frozen dessert production apparatus 1, high-temperature, high-pressure gaseous refrigerant compressed by the compressor 2 and discharged from the discharge port 2b flows into the condenser 3. In the condenser 3, the refrigerant exchanges heat with chiller water cooled to a predetermined temperature, where it is condensed and liquefied, and then discharged from the condenser 3. The high-pressure liquid refrigerant discharged from the condenser 3 passes through the receiver 8, the separation heat exchanger 22, and the heat exchanger 7. The refrigerant flowing from the receiver 8 into the heat exchanger 7 is used to heat and vaporize the refrigerant flowing from the accumulator 6 to the compressor 2. The high-pressure liquid refrigerant discharged from the heat exchanger 7 is then decompressed by the expansion valve 4, becomes a two-phase gas-liquid state, and then flows into the evaporator 5. In the evaporator 5, the refrigerant exchanges heat with the raw material mix, where it is evaporated and vaporized, and then discharged from the evaporator 5. The low-pressure gaseous refrigerant discharged from the evaporator 5 passes through the accumulator 6 and the heat exchanger 7, and is then drawn into the compressor 2 through the suction port 2a, where it is compressed again.

In addition, in the frozen dessert production apparatus 1, high-temperature, high-pressure gaseous refrigerant (hot gas) compressed by the compressor 2 and discharged from the discharge portion 2b passes through the branch path 52 and is supplied to the hot gas valve 9. Then, when predetermined conditions are met, the hot gas is supplied directly to the evaporator 5 by the hot gas valve 9.

(Agitator 100)
Next, the configuration of the stirring device 100 will be described. Figures 2(a) and 2(b) are diagrams showing an example of the configuration of the stirring device 100 to which this embodiment is applied. Figure 2(a) is a diagram showing the stirring device 100 as seen from the side, and Figure 2(b) is a cross-sectional view taken along line IIB-IIB in Figure 2(a).
2(a) and 2(b), the agitation device 100 includes a cylindrical inner cylinder 110 to which an ingredient mix for a frozen dessert is supplied, and a cylindrical outer cylinder 120 that is provided outside the inner cylinder 110 and through which a refrigerant is supplied to a space formed between the inner cylinder 110 and the outer cylinder 120. The agitation device 100 also includes a stirring unit 130 that is provided in the internal space of the inner cylinder 110 and stirs the ingredient mix supplied to the internal space of the inner cylinder 110.

In the frozen dessert manufacturing apparatus 1 of this embodiment, the inner cylinder 110 and the outer cylinder 120 of the stirring device 100 constitute the evaporator 5 described above.
In addition, in the stirring device 100 of this embodiment, the inner cylinder 110 and the outer cylinder 120 are arranged so that their central axes are substantially horizontal.

As described above, the raw material mix is supplied to the internal space S1 of the cylinder inner tube 110. Then, in the cylinder inner tube 110, the raw material mix is stirred and cooled in the space S1 to produce a finished frozen dessert.
The cylinder inner tube 110 has an ingredient supply port 111 provided at one axial end thereof, through which the ingredient mix is supplied toward the space S1, and a frozen dessert discharge port 112 provided at the other axial end thereof, through which the produced frozen dessert is discharged from the space S1. The ingredient mix is stored in an ingredient tank (not shown), and is supplied to the space S1 via the ingredient supply port 111 by an ingredient supply pump. The frozen dessert produced in the space S1 is discharged from the space S1 into a frozen dessert tank (not shown) via the frozen dessert discharge port 112 by a discharge pump.

The cylinder inner tube 110 also has a raw material temperature sensor 114 that measures the temperature of the raw material mix supplied to the raw material supply port 111. The cylinder inner tube 110 also has a frozen dessert temperature sensor 115 that measures the temperature of the frozen dessert discharged from the frozen dessert discharge port 112. The temperature measurement results from the raw material temperature sensor 114 and the frozen dessert temperature sensor 115 are output to the control device 60 (see Figure 1).

As described above, the cylinder outer cylinder 120 is positioned outside the cylinder inner cylinder 110, and a low-temperature, low-pressure, gas-liquid two-phase refrigerant expanded by the expansion valve 4 (see Figure 1) is supplied to the space S2 formed between the cylinder outer cylinder 120 and the outer surface of the cylinder inner cylinder 110. The refrigerant is supplied to the cylinder outer cylinder 120 so that the liquid level is higher than the vertically upper part of the outer surface of the cylinder inner cylinder 110. Heat exchange then occurs in the cylinder outer cylinder 120 between this refrigerant and the raw material mix supplied to the space S1 of the cylinder inner cylinder 110, causing the refrigerant to evaporate.

Here, in the stirring device 100 of this embodiment, the central axis of the cylinder inner tube 110 and the central axis of the cylinder outer tube 120 are arranged so as to be offset from each other. Specifically, as shown in FIG. 2(b), the central axis of the cylinder inner tube 110 is arranged so as to be offset vertically downward from the central axis of the cylinder outer tube 120. This makes it possible to reduce the amount of refrigerant required to cool the cylinder inner tube 110, and to increase the evaporation area of the refrigerant, thereby enabling more efficient heat exchange, compared to when the central axes of the cylinder inner tube 110 and the cylinder outer tube 120 are aligned, for example.

The cylinder outer tube 120 has a refrigerant supply port 121 through which the gas-liquid two-phase refrigerant expanded by the expansion valve 4 is supplied toward the space S2, and a refrigerant discharge port 122 through which the gaseous refrigerant evaporated by heat exchange is discharged. The refrigerant discharged from the refrigerant discharge port 122 flows into the accumulator 6 (see Figure 1). Furthermore, the cylinder outer tube 120 has a hot gas supply port 123 through which high-temperature gaseous refrigerant (hot gas) is supplied toward the space S2 by the hot gas valve 9. Furthermore, the cylinder outer tube 120 has a refrigerant suction port 124 through which the liquid refrigerant is drawn into the oil supply device 20.

The refrigerant supply port 121, refrigerant discharge port 122, hot gas supply port 123, and refrigerant suction port 124 are provided on the outer peripheral surface of the cylinder outer tube 120. In this example, the refrigerant supply port 121 is provided vertically downward on the outer peripheral surface of the cylinder outer tube 120. Two refrigerant discharge ports 122 are provided vertically upward on the outer peripheral surface of the cylinder outer tube 120. The hot gas supply port 123 is provided in the center of the cylinder outer tube 120 on the outer peripheral surface of the cylinder outer tube 120. The refrigerant suction port 124 is provided vertically upward from the refrigerant supply port 121 and in the center of the cylinder outer tube 120.

As described above, the agitating unit 130 agitates the raw material mix supplied to the space S1 within the cylinder inner tube 110. The agitating unit 130 includes a cylindrical support portion 131 extending axially within the space S1 within the cylinder inner tube 110 and a plurality of blades 132 provided on the outer peripheral surface of the support portion 131. The agitating unit 130 also includes a rotating shaft 133 extending axially from one end and the other end of the support portion 131 and rotatably supported via bearings 139 at both ends of the cylinder inner tube 110. The agitating unit 130 also includes a motor 135 that drives the rotating shaft 133 to rotate at a predetermined rotation speed under the control of the control device 60, and an inverter 136 that detects the rotational load of the rotating shaft 133 applied by the motor 135.
Here, in the stirring device 100 of this embodiment, the stirring unit 130 is disposed so that the central axis thereof substantially coincides with the central axis of the cylinder inner tube 110. In addition, in the stirring device 100, the stirring unit 130 is disposed substantially in the center of the cylinder inner tube 110.

When the rotating shaft 133 of the agitator 130 is driven to rotate by the motor 135, the support 131 and blade 132 rotate and move within the space S1 inside the cylinder inner tube 110. In the space S1, the blade 132 scrapes off any deposits adhering to the inner wall surface of the cylinder inner tube 110 while agitating the raw material mix.

(Oil supply device 20)
The oil supplying device 20 supplies oil into the refrigerant flowing into the compressor 2. The refrigerant used in the frozen dessert production apparatus 1 is a _CO2 refrigerant, which has the characteristic that the oil completely dissolves in the refrigerant in the temperature range present in the space S2, making it difficult to separate the oil from the refrigerant. Furthermore, if the refrigerant in the space S2 contains a large amount of oil, heat exchange between the refrigerant containing a large amount of oil and the ingredient mix in the cylinder inner tube 110 may be hindered.
In consideration of the above, the oil supply device 20 is provided within the frozen dessert manufacturing device 1, and pulls the refrigerant in the space S2 mixed with oil out of the cylinder outer tube 120, separates the refrigerant and oil, and supplies the oil into the refrigerant flowing into the compressor 2.

The oil supply device 20 has an ejector 21 that draws refrigerant from space S2 and a separation heat exchanger 22 that separates the oil from the refrigerant (containing oil) drawn by the ejector 21. The oil supply device 20 has a secondary branch path 54 that branches off from the branch path 52 upstream of the hot gas valve 9 and terminates at the ejector 21. The oil supply device 20 also has a suction path 55 that connects space S2 to the ejector 21 and allows the refrigerant in space S2 to flow toward the ejector 21. The oil supply device 20 also has an inflow path 56 that connects the ejector 21 to the separation heat exchanger 22 and allows the refrigerant flowing out of the ejector 21 to flow into the separation heat exchanger 22. The oil supply device 20 also has an outflow path 58 that connects the separation heat exchanger 22 to a pipe 57 between the heat exchanger 7 and the compressor 2, and allows the refrigerant that flows out of the separation heat exchanger 22 to flow into the pipe 57.

The ejector 21 has a nozzle portion 21a through which the refrigerant pressurized by the compressor 2 passes, and a suction portion 21b that draws in the refrigerant inside the cylinder outer tube 120. In this ejector 21, the refrigerant pressurized by the compressor 2 flows in through the inlet of the nozzle portion 21a, then reduces its pressure and expands as the flow path area decreases, increasing its flow rate before flowing out. Meanwhile, the refrigerant inside the cylinder outer tube 120 is drawn in through the inlet of the suction portion 21b due to the pressure difference between the inlet of the suction portion 21b and the nozzle portion 21a, and is drawn into the refrigerant pressurized by the compressor 2. The two refrigerants mix and flow out of the ejector 21. The behavior of the refrigerant in the ejector 21 utilizes the Venturi effect.

The refrigerant flowing out of the ejector 21 exchanges heat with the high-temperature, high-pressure liquid refrigerant condensed in the condenser 3 in the separation heat exchanger 22, where it is vaporized. This separates the refrigerant from the oil, and the separated oil flows through the outlet path 58 into the pipe 57 located upstream of the compressor 2. In this way, the oil is extracted from the refrigerant in the space S2 and injected into the gaseous refrigerant upstream of the compressor 2.

(Control device 60)
FIG. 3 is a diagram showing an example of a schematic configuration of the control device 60.
The control device 60 includes a CPU (Central Processing Unit) (not shown), a ROM (Read Only Memory) (not shown), a RAM (Random Access Memory) (not shown), etc. The ROM stores a basic program (operating system) executed by the CPU, various settings, etc. The CPU uses the RAM as a working area and executes application programs read from the ROM or a storage unit (not shown) such as a semiconductor memory or an HDD (Hard Disk Drive). The functions of the control device 60, which will be described below, are realized by the CPU executing the programs.

The control device 60 receives output signals from the evaporation pressure sensor 31, the liquid level sensor 32, and the like.
The control device 60 includes a compressor control unit 61 as an example of a control unit that controls the frequency F, which is the operating frequency of the compressor 2, a hot gas control unit 62 as an example of a supply unit that controls the opening degree of the hot gas valve 9, and an expansion valve control unit 63 that controls the opening degree of the expansion valve 4.

The control device 60 starts the raw material supply pump to store the raw material mix in the cylinder inner tube 110 and starts the mixer 100. The compressor 2 is then started at a predetermined frequency, and the hot gas valve 9 is set to a predetermined opening. This causes the temperature of the raw material mix in the cylinder inner tube 110 to drop and hardening begins. When the motor load of the mixer 100 reaches a predetermined load setting (hereinafter sometimes referred to as "pump start"), the raw material supply pump and discharge pump start (hereinafter sometimes referred to as "storage and initial freezing").

In addition, in the control device 60, when frozen desserts are produced (hereinafter sometimes referred to as "during production"), the compressor control unit 61 controls the frequency F of the compressor 2, and the hot gas control unit 62 controls the opening of the hot gas valve 9, thereby adjusting the temperature of the frozen dessert produced by the mixing device 100. Also, during production, the expansion valve control unit 63 controls the opening of the expansion valve 4, thereby adjusting the liquid level of the liquid refrigerant in the evaporator 5.

In addition, the control device 60 controls each device while detecting the pressure of the refrigerant in the evaporator 5 and accumulator 6 and the liquid level of the liquid refrigerant in the evaporator 5. This is to close the expansion valve 4, drive the compressor 2, and recover the refrigerant liquefied in the condenser 3 into the receiver 8 so that no liquid refrigerant remains in the evaporator 5 at the end of production. Hereinafter, operation of the frozen dessert production device 1 under this control may be referred to as "refrigerant recovery operation at the end of production." This is because if liquid refrigerant is present in the evaporator 5 when production is stopped, the pressure in the evaporator 5 and accumulator 6 will increase, causing the refrigerant to be released from the low-pressure side safety valve 35, creating a dangerous situation.

In addition, when frozen desserts are not being produced, the control device 60 detects the pressure inside the evaporator 5 and accumulator 6 using the evaporation pressure sensor 31, and when the detected pressure reaches a predetermined upper limit pressure, starts the compressor 2 at a predetermined frequency, and when the detected pressure drops to a predetermined lower limit pressure, stops the compressor 2. Hereinafter, operation of the frozen dessert production device 1 under this control may be referred to as "pressure maintenance operation when production is stopped." If the evaporation pressure rises when production is stopped, the control device 60 repeatedly starts and stops the compressor 2 under the above control.

The control performed by the control device 60 during production, the control of the refrigerant recovery operation when production is completed, and the control of the pressure maintenance operation when production is stopped will be described in detail below.
(Manufacturing control)
In the frozen dessert production apparatus 1, when the operating frequency of the compressor 2 is increased, gaseous refrigerant flows from the evaporator 5 and the accumulator 6 into the compressor 2, causing a decrease in the pressure of the refrigerant in the evaporator 5. Furthermore, when the operating frequency of the compressor 2 is reduced, the flow of gaseous refrigerant from the evaporator 5 and the accumulator 6 into the compressor 2 is inhibited, causing a rise in the pressure of the refrigerant in the evaporator 5.
In the evaporator 5, the refrigerant has a property that the temperature increases as the pressure increases, and the temperature decreases as the pressure decreases.
In the frozen dessert manufacturing apparatus 1 of this embodiment, based on this relationship, the frequency of the compressor 2 is controlled based on the pressure of the refrigerant in the evaporator 5 and accumulator 6 detected by the evaporation pressure sensor 31, and the opening of the hot gas valve 9 is also controlled, thereby controlling the temperature of the refrigerant within a predetermined range.

The compressor control unit 61 controls the frequency F of the compressor 2 based on the pressure P of the gaseous refrigerant in the accumulator 6 detected by the evaporation pressure sensor 31. In other words, the compressor control unit 61 controls the frequency F of the compressor 2 based on the pressure of the gaseous refrigerant evaporated in the evaporator 5. More specifically, when the pressure P detected by the evaporation pressure sensor 31 becomes higher than a predetermined set evaporation pressure Px, the compressor control unit 61 increases the rotation speed of the motor 2c to increase the frequency F of the compressor 2. On the other hand, when the pressure P detected by the evaporation pressure sensor 31 becomes lower than the predetermined set evaporation pressure Px, the compressor control unit 61 decreases the rotation speed of the motor 2c to decrease the frequency F of the compressor 2.
However, the compressor control unit 61 operates the compressor 2 within a predetermined frequency range.

The hot gas control unit 62 reduces the opening of the hot gas valve 9 when the pressure P detected by the evaporation pressure sensor 31 is equal to or higher than the set evaporation pressure Px.
On the other hand, when the pressure P detected by the evaporation pressure sensor 31 is lower than the set evaporation pressure Px, the hot gas control unit 62 increases the opening of the hot gas valve 9. Thereafter, when the pressure P detected by the evaporation pressure sensor 31 becomes equal to the set evaporation pressure Px, the hot gas control unit 62 maintains the opening of the hot gas valve 9.

FIG. 4 is a flowchart showing an example of a frequency change process performed by the compressor control unit 61.
The compressor control unit 61 repeatedly executes the frequency change process at predetermined intervals (for example, every 1 millisecond).
The compressor control unit 61 determines whether the pressure P detected by the evaporation pressure sensor 31 is equal to the set evaporation pressure Px (S401). If the pressure P is not equal to the set evaporation pressure Px (No in S401), the compressor control unit 61 determines whether the pressure P detected by the evaporation pressure sensor 31 is greater than the set evaporation pressure Px (S402). If the pressure P is greater than the set evaporation pressure Px (Yes in S402), the compressor control unit 61 increases the frequency F of the compressor 2 (S403). Thereafter, the compressor control unit 61 performs the process of S401.

On the other hand, if the pressure P is not higher than the set evaporation pressure Px (No in S402), the compressor control unit 61 reduces the frequency F of the compressor 2 (S404). Thereafter, the compressor control unit 61 performs the process of S401.
If the pressure P is equal to the set evaporation pressure Px (Yes in S401), the compressor control unit 61 maintains the frequency F of the compressor 2 (S405).

FIG. 5 is a flowchart showing an example of a process for changing the opening degree of the hot gas valve 9 performed by the hot gas control unit 62.
The hot gas control unit 62 repeatedly executes the opening degree changing process at predetermined intervals (for example, every 1 millisecond).
The hot gas control unit 62 determines whether the pressure P detected by the evaporation pressure sensor 31 is equal to the set evaporation pressure Px (S501). If the pressure P is not equal to the set evaporation pressure Px (No in S501), the hot gas control unit 62 determines whether the pressure P detected by the evaporation pressure sensor 31 is greater than the set evaporation pressure Px (S502). If the pressure P is greater than the set evaporation pressure Px (Yes in S502), the hot gas control unit 62 reduces the opening of the hot gas valve 9 (S503). Thereafter, the hot gas control unit 62 performs the process of S501.

On the other hand, if the pressure P is not higher than the set evaporation pressure Px (No in S502), the hot gas control unit 62 increases the opening of the hot gas valve 9 (S504). Thereafter, the hot gas control unit 62 performs the process of S501.
If the pressure P is equal to the set evaporation pressure Px (Yes in S501), the hot gas control unit 62 maintains the opening degree of the hot gas valve 9 (S505).

In this way, in the control device 60, the compressor control unit 61 adjusts the frequency of the compressor 2, and the hot gas control unit 62 adjusts the opening of the hot gas valve 9, thereby controlling the pressure of the gaseous refrigerant evaporated in the evaporator 5 to the set evaporation pressure Px. Because the refrigerant has the characteristic that its temperature increases as the pressure increases in the evaporator 5 and decreases as the pressure decreases, the control device 60 controls the refrigerant temperature to a predetermined value by controlling the refrigerant pressure to a predetermined value. This controls the temperature of the frozen dessert produced by the mixing device 100 to a predetermined value.

The expansion valve control unit 63 controls the opening degree of the expansion valve 4 using the detection height h, which is the liquid level of the liquid refrigerant in the evaporator 5 detected by the liquid level sensor 32. When the detection height h is higher than a predetermined set height hx, the expansion valve control unit 63 reduces the opening degree of the expansion valve 4, thereby reducing the amount of liquid refrigerant supplied to the evaporator 5. On the other hand, when the detection height h is lower than the set height hx, the expansion valve control unit 63 increases the opening degree of the expansion valve 4, thereby increasing the amount of liquid refrigerant supplied to the evaporator 5.

In this way, the expansion valve control unit 63 controls the opening degree of the expansion valve 4 so that the liquid level of the liquid refrigerant becomes a predetermined set height hx. The lower limit height hn of the refrigerant liquid level is set to the height of the lowest surface of the evaporator 5. The upper limit height hm of the refrigerant liquid level is set to the upper limit height of the liquid refrigerant liquid level sensor.

In the frozen dessert production apparatus 1 configured as described above, when the liquid refrigerant in the evaporator 5 vaporizes and the liquid level of the liquid refrigerant drops, the expansion valve control unit 63 increases the opening of the expansion valve 4. The expansion valve 4 is a so-called motor valve, and as the opening of the valve gradually increases, the amount of refrigerant supplied to the evaporator 5 through the expansion valve 4 gradually increases.
Here, if there is a large amount of liquid refrigerant in the evaporator 5, the cooling of the frozen dessert is more easily accelerated, and if there is a small amount of liquid refrigerant in the evaporator 5, the cooling of the frozen dessert is less accelerated. Consider a case where the expansion valve 4 is a solenoid valve that fully closes the refrigerant flow path when it is off and fully opens the refrigerant flow path when it is on. If the expansion valve 4 is a solenoid valve, when the expansion valve 4 is turned on and the flow path is fully opened from a fully closed state when it is off, a large amount of liquid refrigerant flows into the evaporator 5 all at once. On the other hand, when the solenoid valve is turned off and the flow path is fully closed from a fully open state when it is on, liquid refrigerant no longer flows into the evaporator 5. As a result, the amount of liquid refrigerant flowing into the evaporator 5 fluctuates greatly when the solenoid valve is switched on and off, which tends to cause large fluctuations in the temperature of the frozen dessert.
In contrast, in the frozen dessert production apparatus 1 according to the present embodiment, the opening of the expansion valve 4 changes gradually, so that the amount of liquid refrigerant flowing into the evaporator 5 changes gradually. As a result, the temperature of the frozen dessert changes little.

(Refrigerant recovery operation at the end of production)
At the end of production, the refrigerant present in the evaporator 5 is collected in the receiver 8.
When a user performs a predetermined operation to end production during production (for example, when the stop button is pressed), the control device 60 closes the expansion valve 4 and stops the raw material supply pump and the discharge pump. The control device 60 also causes the compressor 2 to continue operating at a predetermined frequency. The control device 60 also causes the agitator 100 to continue operating at a predetermined constant frequency.
Then, the control device 60 closes the hot gas valve 9 when the detected height h detected by the liquid level sensor 32 drops to a predetermined height.
In addition, when the pressure of the refrigerant in the evaporator 5 and the accumulator 6 detected by the evaporation pressure sensor 31 drops to a predetermined pressure, the control device 60 stops the compressor 2 and the stirring device 100.

At the end of production, the evaporator 5 does not evaporate the refrigerant, and the heat of evaporation is not consumed. Therefore, if refrigerant remains in the evaporator 5, the temperature of the remaining refrigerant rises. If a large amount of refrigerant remains in the evaporator 5, the refrigerant pressure tends to increase as the temperature rises. In contrast, in the frozen dessert production apparatus 1 of this embodiment, the refrigerant remaining in the evaporator 5 is recovered in the receiver 8 at the end of production, which makes it less likely for the refrigerant pressure to rise.

Furthermore, when production is completed, the control device 60 does not stop the supply of chiller water to the condenser 3, but continues to supply the chiller water as it did during production. As a result, the refrigerant recovered in the receiver 8 is cooled by the condenser 3, and the temperature of the receiver 8 is maintained at a low temperature, so that the pressure of the refrigerant in the receiver 8 is unlikely to increase.
After the production of the frozen dessert is stopped, the hot gas control unit 62 may increase the opening of the hot gas valve 9 to a value greater than 0 to supply hot gas into the stirring device 100 until the raw material mix in the cylinder inner tube 110 melts.

(Pressure maintenance operation when production is stopped)
After the refrigerant recovery is complete, the compressor control unit 61 controls the compressor 2 based on the pressure P of the gaseous refrigerant in the accumulator 6 detected by the evaporation pressure sensor 31. More specifically, as described above, the compressor control unit 61 stops the rotation of the motor 2c after the refrigerant recovery is complete. Then, when the pressure P detected by the evaporation pressure sensor 31 becomes higher than a predetermined upper limit pressure Py, the compressor control unit 61 rotates the motor 2c. Then, when the pressure P detected by the evaporation pressure sensor 31 becomes equal to or lower than a predetermined lower limit pressure Pm, the compressor control unit 61 stops the rotation of the motor 2c.
The compressor control unit 61 continues to perform the above control during the period when the production of frozen desserts is stopped.

Incidentally, when production is stopped, the refrigerant present in the evaporator 5 and the accumulator 6 is recovered in the receiver 8 as described above, but it is difficult to recover all of the refrigerant, and some refrigerant may remain in the evaporator 5 and the accumulator 6. Because the refrigerant used in the frozen dessert production apparatus 1 is a _CO2 refrigerant, even if the refrigerant is recovered in the receiver 8, the pressure of the refrigerant is likely to increase due to the passage of time since production of the frozen dessert was stopped, an increase in the ambient temperature of the frozen dessert production apparatus 1, and the like.
Furthermore, when production is stopped, so-called CIP (Cleaning In Place) cleaning may be performed, in which sterilizing water heated to a predetermined temperature is supplied to the space S1 of the cylinder inner tube 110 to clean it. Because the temperature of the sterilizing water used in CIP cleaning is high, at approximately 85°C, if refrigerant remains in the evaporator 5, the pressure of the refrigerant may rise suddenly.
If the pressure of the refrigerant becomes excessively high, there is a risk that the refrigerant will be released to the outside of the frozen dessert manufacturing apparatus 1 through the low-pressure side safety valve 35.

In contrast, in this embodiment, when the pressure P detected by the evaporation pressure sensor 31 becomes higher than a predetermined upper limit pressure Py, the compressor 2 is operated to recover the refrigerant present in the evaporator 5 and the accumulator 6 into the receiver 8. This reduces the refrigerant pressure in the evaporator 5 and the accumulator 6, suppressing a rise in the refrigerant pressure. As a result, the refrigerant is prevented from being released to the outside of the frozen dessert production apparatus 1 via the low-pressure side safety valve 35.
Furthermore, when the pressure P detected by the evaporation pressure sensor 31 becomes lower than a predetermined lower limit pressure Pm, the operation of the compressor 2 is stopped, thereby reducing power consumption when production is stopped.

In the above-described embodiment, the frozen dessert production apparatus 1 includes both the mixing device 100 and a refrigeration cycle that cools the raw material mix, etc., mixed by the mixing device 100. However, part of the refrigeration cycle configuration may be provided in a device other than the frozen dessert production apparatus 1.

1...Frozen dessert manufacturing apparatus, 2...Compressor, 3...Condenser, 4...Expansion valve, 5...Evaporator, 6...Accumulator, 7...Heat exchanger, 8...Receiver, 9...Hot gas valve, 11...Separator, 12...Return section, 51...Refrigerant circuit, 52...Branch, 60...Control device, 61...Compressor control section, 62...Hot gas control section, 63...Expansion valve control section, 100...Agitator, 110...Cylinder inner tube, 120...Cylinder outer tube, 130...Agitator

Claims (2)

a compressor that compresses a refrigerant made of carbon dioxide;
a condenser that receives chiller water and condenses the refrigerant compressed by the compressor;
an expansion valve that expands the refrigerant condensed in the condenser;
an evaporator that performs heat exchange between the refrigerant expanded by the expansion valve and the frozen dessert ingredients, thereby cooling the ingredients and evaporating the refrigerant;
a storage section that stores the refrigerant cooled and condensed by the chiller water in the condenser;
a control unit that compresses the refrigerant with the compressor and stores a portion of the refrigerant condensed in the condenser in the storage unit, then stops compressing the refrigerant with the compressor and continues supplying chiller water to the condenser, and then, when the pressure of the refrigerant in the evaporator exceeds a predetermined upper limit pressure, resumes compressing the refrigerant with the compressor and stores the refrigerant condensed in the condenser in the storage unit . The frozen dessert manufacturing apparatus of claim 1, characterized in that the control unit stops the compression of the refrigerant by the compressor when the refrigerant pressure in the evaporator falls below a predetermined lower limit pressure after the compressor resumes compressing the refrigerant.