JP7208063B2 - transportation refrigeration machinery - Google Patents

Description

The present invention relates to transport refrigeration machines.

As an example of a refrigerating device, one described in Patent Document 1 below is known. The refrigeration system described in Patent Document 1 includes a compressor that compresses refrigerant, a condenser that exchanges heat between the compressed refrigerant and the air outside the freezer compartment, and the refrigerant supplied from the condenser that expands. It has an expansion valve that gasifies, and an evaporator that exchanges heat between the gasified refrigerant and the air in the freezer compartment. Furthermore, in this refrigeration system, a bypass passage that bypasses the evaporator and the expansion valve and a bypass passage that bypasses the evaporator and the expansion valve and a It also has a bypass valve. By opening the bypass passage, part of the refrigerant is returned to the compressor through the condenser. As a result, a larger amount of low-temperature refrigerant is supplied to the compressor than when the refrigerant passes through the evaporator and the expansion valve, and as a result, the temperature of the refrigerant discharged from the compressor can be lowered.

By the way, a transportation refrigeration machine mounted on a transportation machine such as a truck is operated by electric power extracted from the engine by an alternator while the engine is in operation. On the other hand, when the engine is stopped, the refrigeration system is operated by power supplied from the battery (secondary battery). As a result, the inside of the freezer compartment can be cooled regardless of the operating state of the engine.

JP-A-4-251163

However, applying the bypass passage as disclosed in Patent Document 1 increases the load on the compressor. As a result, in a configuration in which the refrigeration system is driven by a battery, the provision of the bypass passage increases the power consumption of the compressor and shortens the usable time of the battery. In addition, the depth of discharge of the battery increases, and there is a possibility that deterioration of the battery will be accelerated.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a transport refrigeration machine with improved performance.

A refrigeration machine for transport according to one aspect of the present invention is a refrigeration machine for transport that cools a freezer compartment provided in the transport machine, and is rotationally driven by a rechargeable battery and electric power supplied from the battery. a compressor for compressing a refrigerant; a condenser provided downstream of the compressor outside the freezer compartment for heat exchange between the refrigerant supplied from the compressor and external air; an expansion valve provided downstream of the condenser inside the freezing chamber; an evaporator that exchanges heat between them; a bypass passage that takes out a part of the refrigerant supplied from the condenser and guides it to the downstream side of the evaporator and the upstream side of the compressor; A bypass valve that opens and closes the bypass flow path, an indoor temperature measurement unit that measures the temperature in the freezer compartment, and a current measurement unit that measures the current value supplied from the battery or the current value supplied to the compressor. a discharge temperature measuring unit that measures a discharge temperature, which is the temperature of the refrigerant discharged from the compressor; and a battery charging amount calculated from the current value and the opening/closing state of the bypass valve based on the temperature. It is connected to a switching valve opening and closing unit, and the battery and the compressor, and based on the difference between the temperature in the freezer compartment and a predetermined set temperature, the operation mode of the compressor is switched at a relatively high rotation speed. an operation control unit having an operation mode switching unit that switches between a high rotation speed mode for operation and a low rotation speed mode for operation at a relatively low rotation speed;
and when the discharge temperature exceeds a predetermined threshold, the battery charge is greater than or equal to a predetermined threshold, and the compressor is in the high speed mode, the valve The opening/closing unit opens the bypass valve, and closes the bypass valve when the battery charge is less than the threshold value or when the compressor is in the low rotation speed mode. , the operation control unit lowers the rotation speed of the compressor to a rotation speed lower than the rotation speed in the low rotation speed mode.

According to the above configuration, when the current supplied from the battery or the current supplied to the compressor is equal to or greater than a predetermined threshold value, that is, when the battery has sufficient charge, the compressor When operating in the high speed mode, a portion of the refrigerant is returned to the compressor via the condenser by opening the bypass valve. As a result, more low-temperature refrigerant is supplied to the compressor than when the refrigerant passes through the evaporator and the expansion valve, and as a result, the temperature of the refrigerant discharged from the compressor can be lowered. Therefore, it becomes possible to rapidly lower the temperature in the freezer compartment.
On the other hand, if the current supplied by the battery is less than the above threshold (i.e., if the battery has insufficient charge) or if the compressor is in low speed mode, the bypass valve is closed. At the same time, the operation control unit further reduces the rotation speed of the compressor. That is, the temperature of the refrigerant discharged from the compressor can be lowered by lowering the rotation speed of the compressor with lower power consumption than when the bypass valve is open. Therefore, even when there is no margin in the charge amount of the battery, it is possible to efficiently lower the temperature in the freezer compartment.

The transport refrigeration machine further includes a condenser fan that blows air to the condenser, the operation control unit further includes an air volume adjustment unit that adjusts the rotation speed of the condenser fan, and the battery charge amount is equal to or higher than the threshold value. In some cases, the valve opening/closing unit may close the bypass valve, and the air volume control unit may increase the rotational speed of the condenser fan.

According to the above configuration, by increasing the number of revolutions of the condenser fan, the amount of air blown to the condenser is increased, and the amount of heat exchange (the amount of heat dissipation) in the condenser can be increased. As a result, the temperature of the refrigerant discharged from the compressor is further lowered, so the temperature in the freezer compartment can be efficiently lowered.

In the transport refrigeration machine, the operation control unit further has a map storage unit that stores a map showing the relationship between the rotation speed of the compressor and the operation efficiency of the compressor. When the compressor is operated at a rotation speed that maximizes operating efficiency and the discharge temperature of the refrigerant is higher than a predetermined limit value, the air volume adjustment unit increases the rotation speed of the condenser fan. may

According to the above configuration, based on the map, the compressor is operated at the rotation speed that maximizes the operating efficiency, and when the temperature of the refrigerant discharged from the compressor is still higher than the limit value, the rotation of the condenser fan the numbers go up. As a result, the amount of heat exchanged (the amount of heat released) in the condenser is further increased, and the temperature of the refrigerant discharged from the compressor can be further lowered.

In the transportation refrigeration machine, the bypass valve is an opening variable valve whose opening can be varied continuously, and the operation control unit controls the bypass so as to maintain the discharge temperature constant. You may adjust the opening degree of a valve.

According to the above configuration, it is possible to suppress a rapid change in the discharge temperature that occurs when the bypass valve opens and closes. As a result, the transportation refrigeration machine can be operated more stably.

According to the present invention, it is possible to provide a transportation refrigeration machine with improved performance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing the configuration of a transportation machine equipped with a transportation refrigeration machine according to a first embodiment of the present invention; It is a figure which shows the structure of the refrigerator unit which concerns on 1st embodiment of this invention. It is a figure which shows the electric power system of the refrigerating machine for transportation which concerns on 1st embodiment of this invention. It is a functional block diagram of a control part concerning a first embodiment of the present invention. It is a functional block diagram of a control part concerning a second embodiment of the present invention. It is an example of the graph (map) which shows the relationship between the rotation speed of the compressor and operating efficiency which concern on 2nd embodiment of this invention.

[First embodiment]
An embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG. A transportation refrigeration machine 2 according to the present embodiment is mounted on a refrigeration transportation vehicle 100 as shown in FIG. 1 as an example. A refrigerated transport vehicle 100 includes a vehicle body 1 (transport machine) and a transport refrigeration machine 2 .

The vehicle body 1 has a cab 11 including a cab and an engine 15, a loading platform 12 installed behind the cab 11, and a chassis 13 supporting the cab 11 and loading platform 12 from below. The inside of the loading platform 12 is a freezer compartment 14 for keeping cargo to be transported at a low temperature. The transport refrigeration machine 2 is provided to lower (cool) the temperature inside the freezer compartment 14 below the outside air temperature.

The transportation refrigeration machine 2 includes a refrigerator unit 21 provided outside the loading platform 12 (for example, above the cab 11 as shown in FIG. 1), and an indoor temperature measurement unit 22 for measuring the temperature inside the freezer compartment 14. , and a battery 3 capable of driving the refrigerator unit 21 . The battery 3 is a rechargeable secondary battery, and a lithium ion battery is preferably used as an example. While the engine 15 of the refrigerated transport vehicle 100 is in operation, the refrigerator unit 21 is driven by electric power generated by the alternator 16 provided with the engine 15 . On the other hand, when the engine 15 is stopped, the electric power from the alternator 16 cannot be used, so the refrigerator unit 21 is driven by electric power supplied from the battery 3 .

Next, a detailed configuration of the refrigerator unit 21 will be described with reference to FIG. As shown in the figure, the refrigerator unit 21 includes a refrigerant pipe P filled with refrigerant, a compressor 41 provided on the refrigerant pipe P, a condenser 42, a receiver 43, an expansion valve 44, an accumulator 45, and a It has an evaporator 46, a condenser fan 51, an evaporator fan 52, a discharge temperature measuring section 23, and a power system Sp (see FIG. 3).

The refrigerant pipe P is a pipe member for circulating a refrigerant, and the refrigerant is filled inside. Specifically, a refrigerant with a lower GWP (global warming potential) than conventional refrigerants (low GWP refrigerant) is used as the refrigerant. Low GWP refrigerants include, by way of example, materials designated 404A, 448A, and 449A. It is also possible to apply a refrigerant other than the low-GWP refrigerant to the refrigerator unit 21 according to this embodiment.

The refrigerant pipes P include a first pipe P1, a second pipe P2, a third pipe P3, a fourth pipe P4, a fifth pipe P5, a sixth pipe P6, and a bypass pipe Pb (bypass flow path). ,have. The first pipe P1 connects the discharge side of the compressor 41 and the condenser 42 . The second pipe P2 connects the downstream side of the condenser 42 and the receiver 43 . The third pipe P3 connects the downstream side of the receiver 43 and the expansion valve 44 . The fourth pipe P4 connects the downstream side of the expansion valve 44 and the upstream side of the evaporator 46 . A fifth pipe P<b>5 connects the downstream side of the evaporator 46 and the accumulator 45 . The sixth pipe P6 connects the downstream side of the accumulator 45 and the suction side of the compressor 41 . The bypass pipe Pb connects the third pipe P3 and the fifth pipe P5.

The compressor 41 compresses the high-temperature, low-pressure vapor-phase refrigerant sucked from the sixth pipe P6 side to generate a high-temperature, high-pressure vapor-phase refrigerant. This high-temperature, high-pressure vapor-phase refrigerant flows into the condenser 42 through the first pipe P1. A discharge temperature measurement unit 23 for measuring the temperature of the gas-phase refrigerant discharged from the compressor 41 is provided on the first pipe P1. Condenser 42 is provided outside freezer compartment 14 described above. The condenser 42 exchanges heat between the outside air and the refrigerant. A condenser fan 51 is provided to blow outside air toward the condenser 42 . As a result, the gas-phase refrigerant is condensed in the condenser 42 to generate a low-temperature, high-pressure liquid-phase refrigerant.

The low-temperature, high-pressure liquid-phase refrigerant flows into the receiver 43 through the second pipe P2. The receiver 43 is used to remove moisture contained in the refrigerant and to separate the refrigerant into liquid phase components and gas phase components. Of the refrigerant separated in the receiver 43, only the liquid phase component is sent to the expansion valve 44 through the third pipe P3. The low-temperature, high-pressure liquid-phase refrigerant that has flowed from the receiver 43 through the third pipe P3 is reduced in pressure by passing through the expansion valve 44, and becomes a low-temperature, low-pressure liquid-phase refrigerant.

The liquid-phase refrigerant that has passed through the expansion valve 44 and has become low temperature and low pressure flows into the evaporator 46 through the fourth pipe P4. The evaporator 46 is provided inside the freezer compartment 14 . In the evaporator 46, heat is exchanged between the air in the freezer compartment 14 and the refrigerant. An evaporator fan 52 is provided to send the air in the freezer compartment 14 to the evaporator 46 . The heat in the freezer compartment 14 is absorbed by the low-temperature liquid-phase refrigerant, so that the temperature in the freezer compartment 14 decreases. Along with this, the temperature of the liquid-phase refrigerant rises and changes from the liquid phase to the gas phase, becoming a high-temperature, low-pressure gas-phase refrigerant.

The gas-phase refrigerant, which has passed through the evaporator 46 and has become high temperature and low pressure, flows into the accumulator 45 through the fifth pipe P5. The accumulator 45 is provided to temporarily store refrigerant and stably supply a fixed amount of refrigerant to the compressor 41 . The high-temperature, low-pressure gas-phase refrigerant that has passed through the accumulator 45 is sucked into the compressor 41 again through the sixth pipe P6. By continuously performing such a cycle, the temperature in the freezer compartment 14 is adjusted to a desired value.

Further, the third pipe P3 and the fifth pipe P5 are connected by a bypass pipe Pb. That is, the bypass pipe Pb connects the downstream side of the receiver 43 and the downstream side of the evaporator 46 . As a result, part of the refrigerant that has flowed out of the receiver 43 can be taken out by the bypass pipe Pb, bypassed (detoured) through the expansion valve 44 and the evaporator 46 , and guided to the accumulator 45 . A bypass valve Vb is provided on the bypass pipe Pb as a valve device for switching the open/closed state of the bypass pipe Pb. This bypass valve Vb is an opening variable valve whose opening can be varied continuously.

Here, it is known that the temperature of the gas-phase refrigerant discharged from the compressor 41 tends to increase when the low GWP refrigerant as described above is used. As a result, the efficiency of the refrigeration system as a whole may decrease. Therefore, by opening the bypass valve Vb, the low-temperature, high-pressure liquid-phase refrigerant that has passed through the receiver 43 through the bypass pipe Pb is directly supplied to the accumulator 45 . As a result, since the temperature of the refrigerant sucked into the compressor 41 is relatively lowered, the temperature of the refrigerant to be discharged can also be relatively lowered.

On the other hand, when the discharge temperature of the refrigerant from the compressor 41 is lowered by opening the bypass flow path as described above, the load on the compressor 41 increases, so power consumption tends to increase. In particular, when the engine 15 is stopped (that is, when the transport refrigeration machine 2 is driven by the battery 3), the operable time of the transport refrigeration machine 2 is limited by the amount of charge in the battery 3. end up Moreover, the depth of discharge of the battery 3 increases, and deterioration of the battery 3 may be accelerated.

Therefore, in this embodiment, a configuration is adopted in which the opening/closing of the bypass valve Vb and the rotation speed of the compressor 41 are adjusted based on the amount of charge in the battery 3 and the difference between the temperature in the freezer compartment 14 and the set temperature. . As shown in FIG. 3, the electric power system Sp for driving the refrigerator unit 21 according to the present embodiment compresses electric power supplied from the battery 3, the alternator 16 (generator), and the commercial power supply Pw. It has a control device 6 that distributes to the compressor motor Mc that drives the compressor 41 , the first fan motor M1 that drives the condenser fan 51 , and the second fan motor M2 that drives the evaporator fan 52 .

The control device 6 includes a first DC converter 61 (AC converter), an inverter 62, an AC/DC converter 63 (AC/DC converter), a second DC converter 64 (AC converter), a current measuring unit 71, It has a power measurement unit 72 and an operation control unit 8 .

A first DC converter 61 is provided to increase the voltage of the DC current supplied from the battery 3 or the alternator 16 . As an example, when the voltage supplied from the battery 3 or the alternator 16 is 27V, the voltage becomes 270V DC through the first DC converter 61 . An inverter 62 is provided between the first DC converter 61 and the compressor motor Mc. Inverter 62 adjusts power for rotationally driving compressor motor Mc. In addition, the inverter 62 changes the electric power to be output based on an electric signal output from the operation control unit 8 which will be described later. Between the inverter 62 and the compressor motor Mc, there is provided a power measuring section 72 that measures the power consumed by the compressor motor Mc. A part of the electric power of the battery 3 (or the alternator 16 ) is also supplied to the operation control section 8 .

The AC/DC converter 63 converts the AC current into the DC current when the transportation refrigeration machine 2 is connected to the commercial power supply Pw (AC 200 V) at a service center (maintenance facility) or the like when the engine 15 is stopped. is provided to do so. As an example, the AC/DC converter 63 converts AC 200V to DC 270V. A part of this direct current is supplied to the compressor motor Mc via the inverter 62 . Another part of this DC current is stepped down by the second DC converter 64 to become DC 27V and then supplied to the operation control section 8 . The operation control unit 8 is connected to the above-described first fan motor M1, second fan motor M2, and other DC loads (auxiliaries) that are connected as necessary.

Next, the configuration of the operation control section 8 will be described with reference to FIG. As shown in the figure, the operation control unit 8 has a charge amount calculation unit 81 , an operation mode determination unit 82 and an output unit 83 .

The charge amount calculation unit 81 calculates the charge amount of the battery 3 based on the current value (current amount of the current supplied from the battery 3) input from the current measurement unit 71 described above. The calculated charge amount is sent to the output section 83 as an electric signal.

The operation mode determination unit 82 determines each value (the temperature of the refrigerant discharged from the compressor 41, the temperature in the freezer compartment 14 , and power consumption of the compressor motor Mc), the operation mode of the compressor 41 is determined. The operation modes of the compressor 41 include a high rotation speed mode and a low rotation speed mode. For example, when the temperature inside the freezer compartment 14 is higher than a predetermined set temperature, it is necessary to lower the temperature inside the freezer compartment 14 by accelerating the compression of the refrigerant by driving the compressor 41 at a high rotational speed. . In this case, the operation mode determination unit 82 sends an electric signal to the output unit 83 (an operation mode switching unit 92 described later) to the effect that the compressor 41 is to be operated in the high rotation speed mode.

On the other hand, when the temperature in the freezer compartment 14 is equivalent to the set temperature, it is desirable to operate the compressor 41 at a lower rotational speed than in the high rotational speed mode. In this case, the operation mode determination unit 82 sends an electric signal indicating that the compressor 41 is to be operated in the low rotation speed mode to the output unit 83 (an operation mode switching unit 92 described later).

The output unit 83 outputs the bypass valve Vb, the inverter 62, and the capacitor based on the charge amount of the battery 3 calculated by the charge amount calculation unit 81 and the electrical signal regarding the operation mode determined by the operation mode determination unit 82. It controls the driving state of the fan 51 (first fan motor M1). The output unit 83 has a valve opening/closing unit 91 , an operation mode switching unit 92 , and an air volume control unit 93 .

When the discharge temperature of the compressor 41 exceeds a predetermined threshold, the charge amount of the battery 3 is equal to or greater than a predetermined threshold, and the operation mode of the compressor 41 is the high rotation speed mode, The valve opening/closing unit 91 opens the bypass valve Vb. As a result, the bypass pipe Pb is opened. On the other hand, when the charge amount of the battery 3 is less than the above threshold, or when the operation mode of the compressor 41 is the low rotation speed mode, the valve opening/closing unit 91 switches the bypass valve Vb to the closed state. The valve opening/closing unit 91 keeps the discharge temperature of the compressor 41 constant by continuously changing the degree of opening of the bypass valve Vb. At the same time, the operation mode switching unit 92 reduces the rotation speed of the compressor 41 to a lower rotation speed than the rotation speed in the low rotation speed mode.

Furthermore, when the charge amount of the battery 3 is equal to or greater than the threshold value, the valve opening/closing unit 91 closes the bypass valve Vb. At the same time, the air volume control unit 93 increases the rotation speed of the condenser fan 51 (the rotation speed of the first fan motor M1).

According to the above configuration, when the charge amount of the battery 3 is equal to or higher than the predetermined threshold, that is, when the charge amount of the battery 3 has a margin, the compressor 41 is operated in the high rotation speed mode. At this time, part of the refrigerant is returned to the compressor 41 via the condenser 42 by opening the bypass valve Vb. As a result, more low-temperature refrigerant is supplied to the compressor 41 than when the refrigerant passes through the evaporator 46 and the expansion valve 44, and as a result, the temperature of the refrigerant discharged from the compressor 41 can be lowered. Therefore, it becomes possible to rapidly lower the temperature in the freezer compartment 14 .

On the other hand, if the charge amount of the battery 3 is less than the above threshold (that is, if the charge amount of the battery 3 has no margin), or if the compressor 41 is in the low rotation speed mode, the bypass valve Vb is closed. In addition to the closed state, the operation control unit 8 further reduces the rotation speed of the compressor 41 . That is, the temperature of the refrigerant discharged from the compressor 41 can be lowered by lowering the rotational speed of the compressor 41 with lower power consumption than when the bypass valve Vb is open. Therefore, even when the charge amount of the battery 3 is insufficient, the temperature in the freezer compartment 14 can be efficiently lowered.

Furthermore, when the charge amount of the battery 3 is equal to or higher than the threshold value, the valve opening/closing unit 91 closes the bypass valve Vb, and the air volume control unit 93 increases the rotational speed of the condenser fan 51 . As a result, the condenser fan 51 further actively blows the air to the condenser 42 , thereby increasing the amount of heat exchange (heat dissipation) in the condenser 42 . As a result, the temperature of the refrigerant discharged from the compressor 41 is further lowered, so that the temperature inside the freezer compartment 14 can be efficiently lowered.

The first embodiment of the present invention has been described above. Various changes and modifications can be made to the above configuration without departing from the gist of the present invention.

[Second embodiment]
Next, a second embodiment of the invention will be described with reference to FIGS. 5 and 6. FIG. In addition, the same code|symbol is attached|subjected about the structure similar to said 1st embodiment, and detailed description is abbreviate|omitted. As shown in FIG. 5, in the operation control unit 208 according to this embodiment, the output unit 83 further has a map storage unit 94 in addition to the configuration described in the first embodiment.

The map storage unit 94 stores a map showing the relationship between the rotation speed of the compressor 41 and the operational efficiency of the compressor 41 . A curve as shown in FIG. 6 is used as an example of such a map (graph). In the example shown in the figure, when the number of revolutions is a certain value R, the operating efficiency is maximized (maximum value η _max ). Based on such a map, when the operation mode switching unit 92 operates the compressor 41 at the rotation speed R and the discharge temperature of the refrigerant is higher than a predetermined limit value, the air volume adjustment unit 93 The rotation speed of the condenser fan 51 is adjusted to increase.

According to this configuration, based on the map, the compressor 41 is operated at the rotation speed that maximizes the operating efficiency, and when the temperature of the refrigerant discharged from the compressor 41 is still higher than the limit value, the condenser fan 51's revs go up even more. As a result, the heat exchange amount (heat release amount) in the condenser 42 is further increased, and the temperature of the refrigerant discharged from the compressor 41 can be further lowered. As a result, the performance of the transportation refrigeration machine 2 can be further improved.

The second embodiment of the present invention has been described above. Various changes and modifications can be made to the above configuration without departing from the gist of the present invention. For example, in each of the above-described embodiments, the configuration in which the current measurement unit 71 measures the current value supplied from the battery 3 has been described. However, the current measurement unit 71 can also adopt a configuration that measures the current value supplied to the compressor 41 . That is, the charge amount of the battery 3 may be calculated from the current value supplied to the compressor 41 and used.

DESCRIPTION OF SYMBOLS 1... Vehicle main body 2... Refrigeration machine for transportation 3... Battery 6... Control device 8, 208... Operation control part 11... Cab 12... Cargo bed 13... Chassis 14... Freezer compartment 15... Engine 16... Alternator 21... Refrigerator unit 22... Indoor temperature measurement unit 23 Discharge temperature measurement unit 41 Compressor 42 Condenser 43 Receiver 44 Expansion valve 45 Accumulator 46 Evaporator 51 Condenser fan 52 Evaporator fan 61 First DC converter 62 Inverter 63 AC/DC converter 64 Second DC converter 71 Current measurement unit 72 Power measurement unit 81 Charge amount calculation unit 82 Operation mode determination unit 83 Output unit 91 Valve opening/closing unit 92 Operation mode switching unit 93 Air volume adjustment Part 94...Map storage part 100...Vehicle for refrigeration transportation M1...First fan motor M2...Second fan motor Mc...Compressor motor P...Refrigerant pipe P1...First pipe P2...Second pipe P3...Third pipe P4... Fourth pipe P5 Fifth pipe P6 Sixth pipe Pb Bypass pipe Pw Commercial power supply Sp Power system Vb Bypass valve

Claims (4)

A transport refrigeration machine that cools a freezer compartment provided in the transport machine,
a rechargeable battery and
a compressor that is rotationally driven by power supplied from the battery and compresses a refrigerant;
a condenser provided downstream of the compressor outside the freezer compartment for heat exchange between the refrigerant supplied from the compressor and outside air;
an expansion valve provided downstream of the condenser inside the freezer compartment;
an evaporator provided downstream of the expansion valve inside the freezer compartment for exchanging heat between the refrigerant that has passed through the expansion valve and air in the freezer compartment;
a bypass flow path that extracts part of the refrigerant supplied from the condenser and guides it to the downstream side of the evaporator and the upstream side of the compressor;
a bypass valve provided on the bypass flow channel for opening and closing the bypass flow channel;
an indoor temperature measurement unit that measures the temperature in the freezer compartment;
a current measuring unit that measures the current value supplied from the battery or the current value supplied to the compressor;
a discharge temperature measurement unit that measures a discharge temperature, which is the temperature of the refrigerant discharged from the compressor;
A valve opening/closing unit that switches the opening/closing state of the bypass valve based on the battery charge amount calculated from the current value and the temperature, and is connected to the battery and the compressor, and is predetermined as the temperature in the freezer compartment. Based on the difference from the set temperature, the operation mode of the compressor is switched between a high rotation speed mode that operates at a relatively high rotation speed and a low rotation speed mode that operates at a relatively low rotation speed. an operation control unit having an operation mode switching unit;
with
When the discharge temperature exceeds a predetermined threshold, the battery charge is equal to or greater than a predetermined threshold, and the compressor is in the high rotation speed mode, the valve opening and closing unit Open the bypass valve,
When the battery charge is less than the threshold value, or when the compressor is in the low rotation speed mode, the valve opening/closing unit closes the bypass valve, and the operation control unit rotates the compressor. transport refrigeration machine that reduces the number of revolutions to a lower rpm than in said low rpm mode. further comprising a condenser fan for blowing air to the condenser;
The operation control unit further has an air volume adjustment unit that adjusts the rotation speed of the condenser fan,
2. The refrigeration machine for transportation according to claim 1, wherein the valve opening/closing unit closes the bypass valve and the air volume control unit increases the rotational speed of the condenser fan when the battery charge amount is equal to or greater than the threshold value. The operation control unit further has a map storage unit that stores a map showing the relationship between the rotation speed of the compressor and the operation efficiency of the compressor,
Based on the map, when the compressor is operated at the rotational speed at which the operating efficiency is maximized and the discharge temperature of the refrigerant is higher than a predetermined limit value, the air volume adjustment unit adjusts the 3. The transportation refrigeration machine according to claim 2, wherein the rotation speed of the condenser fan is increased. The bypass valve is an opening variable valve capable of continuously changing the opening,
4. The transportation refrigeration machine according to claim 1, wherein the operation control unit adjusts the degree of opening of the bypass valve so as to keep the discharge temperature constant.

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