JP2000121177A - Chiller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a chiller which can operate while keeping the pressure of refrigerant below a specified level by controlling the frequency of AC power being fed to an AC motor for driving a compressor depending on the temperature in a refrigerator. SOLUTION: The chiller comprises a refrigerating machine for circulating refrigerant compressed by a compressor through a condenser and an evaporator, a refrigerator being cooled by the refrigerating machine, an AC motor for driving the compressor, and an inverter for outputting AC power of desired frequency to the AC motor. The chiller is provided with means for detecting the temperature in the refrigerator, and a control means. Based on the detected temperature in the refrigerator, the control means decreases the frequency of AC power being outputted from the inverter if the temperature in the refrigerator is high and increases the frequency of AC power being outputted from the inverter as the temperature in the refrigerator decreases.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating apparatus for circulating a refrigerant compressed by a compressor through a condenser and an evaporator, and more particularly to a refrigerating apparatus in which the compressor is driven by an AC motor.

[0002]

2. Description of the Related Art In recent years, refrigerating vehicles for transporting foodstuffs and the like in a frozen state have become widespread. In this type of refrigerating car,
Generally, a refrigerator for circulating a refrigerant compressed by a compressor through a condenser and an evaporator is mounted. As a method of driving a compressor of a refrigerator, a method of directly driving by an engine such as an internal combustion engine and a method of driving by an output of an AC generator driven by the engine or an AC motor driven by a commercial power supply are generally used. Have been.

The cooling capacity of a refrigerator is proportional to the rotation speed of the compressor. However, a refrigeration system in which the compressor of the refrigerator is directly driven by a traveling engine has a low engine rotation speed when the vehicle is running at a low speed or idling. Therefore, there is a problem that the cooling capacity of the refrigerator is reduced. On the other hand, a refrigeration system that drives a compressor of a refrigerator with an AC motor uses an inverter to control the frequency of AC power applied to the AC motor, thereby increasing the rotation speed of the compressor regardless of the engine speed. Therefore, it has been widely used and disclosed in, for example, Japanese Patent Publication No. 6-103137.

[0004]

[Problems to be Solved by the Invention]
The refrigeration apparatus disclosed in Japanese Patent No. 03137 discloses that as long as the output voltage of the AC generator driven by the engine has a margin, the AC power supplied to the AC motor driving the compressor has a rotation speed at which the efficiency of the compressor is maximized. The frequency is controlled so that it rises. However,
In a refrigeration apparatus that circulates a refrigerant compressed by a compressor through a condenser and an evaporator, when the pressure of the refrigerant becomes higher than a predetermined pressure, each member constituting the refrigeration apparatus may be damaged, and therefore, the pressure of the refrigerant becomes a predetermined value. A pressure switch for detecting the pressure (for example, 22.5 kg / cm ² ) or more is provided. When the pressure switch is turned on, the operation of the compressor is stopped and the refrigeration cycle is stopped. On the other hand, the pressure of the refrigerant compressed by the compressor changes depending on the temperature of the circulating refrigerant (the temperature of the refrigerant is proportional to the temperature in the freezer), and increases as the refrigerant temperature increases. Therefore, in the refrigeration apparatus disclosed in the above publication, as the frequency of the AC power supplied to the AC motor driving the compressor in a state where the temperature of the refrigerant is high, the pressure of the refrigerant is increased to a predetermined value (for example, 22.
5 kg / cm ² ) or more. At this point, the operation of the compressor is stopped. For this reason, there is a problem that the refrigeration system cannot exhibit its intended function.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and its main technical problem is to control the frequency of AC power supplied to an AC motor for driving a compressor in accordance with the temperature in the freezer. It is another object of the present invention to provide a refrigeration apparatus that can operate at a refrigerant pressure equal to or lower than a predetermined value.

[0006]

According to the present invention, in order to solve the above-mentioned main technical problems, a refrigerator that circulates a refrigerant compressed by a compressor through a condenser and an evaporator, and is cooled by the refrigerator. A refrigerator, an AC motor for driving the compressor, and a refrigerator having an inverter that outputs AC power of a desired frequency to the AC motor, a refrigerator temperature detecting unit that detects a temperature in the refrigerator, Based on the inside temperature detected by the inside temperature detection means, when the inside temperature is high, the frequency of the AC power output by the inverter is low, and as the inside temperature decreases, the AC power output by the inverter is lowered. Control means for controlling the frequency of the refrigeration to be high.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a refrigeration apparatus constructed according to the present invention will be described below in more detail with reference to the accompanying drawings.

FIG. 1 is a schematic block diagram of a refrigerator / refrigerated vehicle constructed according to the present invention. The illustrated refrigerating / refrigerated vehicle has an AC generator 3 (ACG) driven by a traveling engine 2 mounted on the vehicle and an AC motor 4 (ACG) driven by electric power generated by the AC generator 3 (ACG). M1). The AC generator 3 (ACG) is driven to rotate by an output shaft of the traveling engine 2 via, for example, a belt transmission mechanism. The AC output of the AC generator 3 (ACG) is supplied to the AC motor 4 (M1) via the power supply circuit 5. The power supply circuit 5 includes a power supply switch 51, a rectifier 52, an automatic voltage regulator 53, and an inverter 54.
(INV). The power supply switch 51 is connected to the AC generator 3 (ACG) and the commercial power supply. When the commercial power supply is connected, the commercial power supply is switched to the rectifier 5.
2 and an AC generator 3 (ACG) is connected to the rectifier 52 when the commercial power supply is not connected. The DC power, which is converted to DC by the rectifier 52 and adjusted to a predetermined voltage by the automatic voltage regulator 53, is further converted to AC by an inverter 54 (INV) and frequency-controlled by control means to be described later.
(M1). The refrigeration system 6 is operated by the AC motor 4 (M1). In the illustrated embodiment, the rectifier 52 converts the direct current into direct current.
The DC power adjusted to a predetermined voltage by the automatic voltage regulator 53 charges a battery 56 mounted on the vehicle via a DC power supply circuit 55.

The refrigerator 6 includes a compressor 61, a condenser 62, and an evaporator 63. The compressor 61 is connected to the AC motor 4 (M) via an electromagnetic clutch 611 (CLT1) and a belt transmission mechanism 612.
It is power-coupled to the output shaft of 1). When the electromagnetic clutch 611 (CLT1) is energized, the compressor 6
When the power is transmitted to the compressor 1 and deenergized, the power transmission to the compressor 61 is shut off, and the operation thereof is controlled by control means described later.

The compressor 61, condenser 62 and evaporator 63 are connected to pipes 641 and 64, respectively.
2, 643, and the refrigerant compressed by the compressor 61 is circulated as indicated by arrows in the figure. A pressure switch 65 (SW1) for detecting the pressure of the refrigerant discharged from the compressor 61 is provided on a pipe 641 connecting the compressor 61 and the condenser 62. The pressure switch 65 (SW1) is connected to the pressure of the refrigerant. Is a predetermined value (for example, 22.5
kg / cm ² ), an ON signal is sent to control means described later.

A pipe 641 for connecting the compressor 61 and the condenser 62 and a pipe 642 for connecting the condenser 62 and the evaporator 63 are connected by a bypass pipe 644 provided around the condenser 62. . The bypass pipe 644 and the pipe 641
An electromagnetic switching valve 66 (V1) is provided at the connection portion with. The electromagnetic switching valve 66 (V1) sends the refrigerant to the condenser 62 when deenergized, and sends the refrigerant to the evaporator 63 via the bypass pipe 644 and the pipe 642 by bypassing the condenser 62 when energized. The operation is controlled by control means described later. Therefore, when the electromagnetic switching valve 66 (V1) is deenergized, a refrigerant cycle compressed by the compressor 61 is circulated through the condenser 62 and the evaporator 63. On the other hand, when the electromagnetic switching valve 66 (V1) is energized, the refrigerant compressed by the compressor 61 bypasses the condenser 62 and is introduced into the evaporator 63.

The condenser 62 is disposed outside the freezer 7 mounted on the vehicle, and the evaporator 63 is connected to the freezer 7.
It is installed in the warehouse. The condenser 62 and the evaporator 63 include blowers 621 and 632, respectively. The blowers 621 and 632 are respectively driven by DC motors 622 (M2) and 632 (M3) driven by a power source of a battery 56 mounted on the vehicle. Activated. Note that a freezer temperature sensor 8 (SNS1) for detecting the freezer temperature is provided in the freezer 7, and the freezer temperature sensor 8 (SNS1) sends a detection signal to a control unit described later.

The illustrated refrigeration apparatus has a control means 1 shown in FIG.
00 is provided. The control means 100 is constituted by a microcomputer, and has a central processing unit (CPU) 101 for performing arithmetic processing according to a control program, and a read-only memory (ROM) for storing the control program.
102, a readable and writable random access memory (RAM) 103 for storing calculation results and the like, and a timer 104
(T), and an input interface 105 and an output interface 106. The detection signals of the pressure switch 65 (SW1) and the internal temperature sensor 8 (SNS1) are input to the input interface 105 of the control means 100 thus configured. The input interface 105 includes a refrigeration system operation switch 111 (SW2) disposed on a refrigerator control plate disposed in a cab (not shown) of the refrigeration car, and a refrigeration temperature setter 112.
(FTS) is input. On the other hand, from the output interface 106, the AC motor 4 (M
1), DC motors 622 (M2) and 632 (M
3), inverter 54 (INV), electromagnetic clutch 611
(CLT1), and outputs a control signal to the electromagnetic switching valve 66 (V1) and the like. Further, the output interface 106 outputs a control signal to a display means 113 (DISP) such as a liquid crystal display disposed on the refrigerator control panel.

The refrigeration apparatus in the illustrated embodiment constructed according to the present invention is constructed as described above, and its operation will be described below. Control means 10 described later
0 indicates that when the refrigeration system operation switch 111 (SW2) is turned on, the refrigerator temperature is set to the refrigeration temperature setter 112 based on the detection signal from the refrigerator temperature sensor 8 (SNS1).
When the temperature is equal to or higher than the first set temperature arbitrarily set by the (FTS), the electromagnetic clutch 611 (CLT1) is energized to drive the compressor 61, and the fan driving DC motors 622 (M2) and 632 are driven. (M
3) is driven to operate the refrigerator 6. The inverter 54 (INV) that outputs AC power to the AC motor 4 (M1) that drives the compressor 61 is controlled by the control device 100 based on the internal temperature detected by the internal temperature sensor 8 (SNS1). The frequency is controlled as follows. In this way, the operation of the refrigerating device 6 lowers the temperature in the refrigerator, and when the temperature in the refrigerator falls below the second set temperature lower than the first set temperature, the controller 1
00 deactivates the electromagnetic clutch 611 (CLT1) to stop driving of the compressor 61, and drives the DC motors 622 (M2) and 632 (M3) for driving the fan.
And the operation of the refrigeration system 6 is stopped. When the pressure of the refrigerant discharged from the compressor 61 becomes higher than a predetermined value (for example, 22.5 kg / cm ² ) during the operation of the refrigeration apparatus 6, the members constituting the refrigeration apparatus 6 may be damaged. The control means 100 controls the pressure switch 65 (SW1)
When the ON signal is sent from the electromagnetic clutch 6
11 (CLT1) is deenergized to stop the driving of the compressor 61, and the DC motor 62
2 (M2) and 632 (M3) are deenergized, and the operation of the refrigeration system 6 is stopped. When the operating time of the above-described refrigeration cycle reaches a predetermined refrigeration time (for example, 3 hours), the control unit 100 activates the electromagnetic switching valve 66 to execute a defrost cycle. As a result, the refrigerant discharged from the compressor 61 bypasses the condenser 62 and is directly introduced into the evaporator 63, and the frost attached to the evaporator 63 is removed. Then, when a predetermined defrosting time (for example, 10 minutes) is operated in the defrost cycle, the control means 100 deenergizes the electromagnetic switching valve 66 to return to the refrigeration cycle.

Next, the operation of the control means 100 during the refrigeration cycle will be described with reference to the flowchart shown in FIG. The control means 100 checks in step S1 whether the refrigeration apparatus operation switch 111 (SW2) is ON, that is, is turned on. If the refrigeration apparatus operation switch 111 (SW2) is ON, the process proceeds to step S2 and the storage is started. The internal temperature (TF) detected by the internal temperature sensor 8 (SNS1) is read and temporarily stored in a random access memory (RAM) 103. Next, the control means 100 proceeds to step S3, and checks whether or not the inside temperature (TF) is equal to or lower than the second set temperature (T2), that is, the temperature at which the refrigeration cycle is stopped. When the temperature in the refrigerator (TF) is equal to or lower than the second set temperature (T2), the temperature in the freezer 7 has sufficiently decreased and the refrigerator 6 does not need to be operated.
The control means 100 proceeds to step S4 to deactivate the electromagnetic clutch 611 (CLT1) to stop driving the compressor 61 and to control the fan driving DC motor 6
22 (M2) and 632 (M3) are stopped,
The operation of the refrigerator 6 is stopped. Then, the control means 100 proceeds to step S5, where the refrigeration system operation switch 111
It is checked whether (SW2) is ON. If the refrigeration apparatus operation switch 111 (SW2) has not been turned ON, the process returns to step S1, and the refrigeration apparatus operation switch 11
If 1 (SW2) is ON, the control means 100 proceeds to step S6, reads the inside temperature (TF) detected by the inside temperature sensor 8 (SNS1), and in step S2, executes the random access memory (RAM). ) 103
Is rewritten with the internal temperature (TF) temporarily stored in. next,
The control means 100 proceeds to step S7, where the inside temperature (T
It is checked whether or not F) is equal to or higher than the first set temperature (T1), that is, the temperature at which the refrigeration cycle is started (set at a temperature higher than the second set temperature (T2)). If (TF) is equal to or higher than the first set temperature (T1), the process returns to step S1. On the other hand, when the internal temperature (TF) is lower than the first set temperature (T1), the internal temperature (T
F) is the first set temperature (T1) and the second set temperature (T1).
Since it is within the range of 2), the control unit 100 returns to the step S4 and repeatedly executes the steps S4 to S7.

In step S3, the internal temperature (T
If F) is higher than the second set temperature (T2), the control means 100 proceeds to step S8, where the pressure switch 65
(SW1) is OFF, that is, the refrigerant pressure is equal to the operating pressure of the pressure switch 65 (SW1) (22.5 kg / c
Check if m ² ) has not been reached. When the pressure switch 65 (SW1) is OFF, the refrigerant pressure is equal to the operating pressure of the pressure switch 65 (SW1) (22.5 kg / c).
m ² ), the control means 100 proceeds to step S
In step 9, the electromagnetic clutch 611 (CLT1) is energized to drive the compressor 61 and the DC motors 622 (M2) and 632 (M3) for driving the fan.
To operate the refrigerator 6. And control means 10
In step S10, the process proceeds to step S10, where the inverter 54 (INV) that outputs AC power to the AC motor 4 (M1) performs frequency conversion. This frequency conversion is performed based on the inside temperature (TF) detected by the inside temperature sensor 8 (SNS1) in step S2. Hereinafter, the frequency control based on the inside temperature (TF) will be described.

[0017] FIG. 4 is a graph showing the relationship between the frequency of the alternating current supplied to the AC motor 4 (M1) for driving the compressor 61 (H _Z) and the refrigerant pressure (kg / cm ^2). 4, the horizontal axis is the frequency of the AC power supplied to the AC motor _{4 (M1) (H Z)} , the vertical axis pressure of the refrigerant in the refrigerating machine 6 (Kg / cm ^2). Incidentally, the compressor when in the illustrated embodiment, the rotational speed of the compressor 61 when the AC motor 4 (M1) is driven by the 50 H _Z is 1125Rpm, AC motor 4 (M1) is driven by the 60 H _Z 61 of the rotational speed 1350 rpm, the compressor 61 speed at the AC motor 4 (M1) is driven by the 70 H _Z is 1575Rpm, AC motor 4 (M
Rotational speed of the compressor 61 when the 1) is driven by the 80 H _Z is 1800 rpm. In FIG. 4, the solid line, the one-dot chain line and the two-dot chain line
Shows the relationship between the frequency (H _Z ) of the AC power supplied to the AC motor 4 (M1) that drives the motor and the pressure (kg / cm ² ) of the refrigerant, and the solid line indicates that the internal temperature (TF) is 0 ° C. The one-dot chain line indicates the inside temperature (TF) of -18 ° C, and the two-dot chain line indicates the inside temperature (T
F) at 10 ° C.

In FIG. 4, the internal temperature (T
When F) is 0 ° C., but the AC motor to drive the compressor 61 4 (M1) is driven at 50 H _Z pressure of the refrigerant is about 18.5 kg / cm ^2, the alternating current motor 4 to (M1) 80 the pressure of the refrigerant when driven by H _Z becomes 21 kg / cm ² approximately. In addition, the inside temperature (TF) indicated by the dashed line is -18 ° C.
In the case of, the pressure of the refrigerant is driven AC motor 4 (M1) in 50 H _Z is about 17 kg / cm ^2, pressure of the refrigerant is driven AC motor 4 (M1) in 80 H _Z 18.
It is about 5 kg / cm ² . Further, when the inside temperature indicated by the two-dot chain line (TF) of 10 ° C., although the AC motor 4 (M1) is driven at 50 H _Z pressure of the refrigerant is about 19 kg / cm ^2, the alternating current motor 4 the pressure of the refrigerant when driven (M1) in 80 H _Z becomes 22.5 kg / cm ² approximately.

In FIG. 4, the internal temperature (TF) indicated by a chain line.
There the case of -18 ° C., the pressure of the refrigerant be driven alternating current motor to drive the compressor 61 4 (M1) in 80 H _Z is about 18.5 kg / cm ^2, the pressure switch 65 (SW
It is considerably lower than the operating pressure of 1) of 22.5 kg / cm ² .
Therefore, when the inside temperature (TF) of -18 ° C., the alternating current motor 4 to (M1) can be raised by driving up 80 H _Z. When the internal temperature (TF) indicated by the solid line is 0 ° C., the AC motor 4 (M
Operating pressure of the pressure switch 65 (SW1) in Driving 1) in 80 H _Z pressure of the refrigerant is 21 kg / cm ² about (22.5
kg / cm ²⁾ less than, but considering the variation of the pressure switch 65 (SW1) and interior temperature sensor 8 (SNS1), involves a risk to drive AC motor 4 (M1) in 80 H _Z. On the other hand, the internal temperature (TF) indicated by the two-dot chain line is 1
In the case of 0 ° C., the compressor 61 is connected to the AC motor 4 (M
Since Driving 1) in 80 H _Z pressure of the refrigerant becomes 22.5 kg / cm ² as a working pressure of the pressure switch 65 (SW1), can not be driven by the AC motor 4 (M1) of 80 H _Z . Further, when the inside temperature indicated by the two-dot chain line (TF) of 10 ° C., since the pressure of the refrigerant be driven alternating current motor 4 to (M1) in 70 H _Z exceeds the 21 kg / cm ^2, the pressure switch 65 (SW1) and internal temperature sensor 8 (SNS
Considering the variation of 1), it involves the risk to drive AC motor 4 (M1) in 70 H _Z. From the above,
The refrigerant pressure is, for example, 20 kg / c at each internal temperature (TF).
By setting the frequency (H _Z) of the alternating current supplied to the AC motor 4 which can operate in m ² (M1),
The refrigerator 6 can be operated without operating the pressure switch 65 (SW1).

[0020] Figure 5 is shown an embodiment of a control map setting the frequency (H _Z) of the alternating current supplied to the AC motor 4 (M1) in each predetermined range of each of the internal temperature (TF) I have. This frequency (H _Z), when the AC motor 4 (M1) is driven at each frequency _{(H Z), 22.5kg / cm} 2 pressure of the refrigerant is operating pressure of the pressure switch 65 (SW1)
It is determined experimentally to be a lower value. The control map set in this way is stored in the read-only memory (R
OM) 102 in advance. Based on the internal temperature sensor 8 (SNS1) is detected inside temperature according to the control map (TF), the alternating current supplied to the AC motor 4 (M1) for driving the compressor 61 frequency (H _Z)
, The refrigerator 6 can be operated without operating the pressure switch 65 (SW1).

As described above, the AC motor 4 (M) that drives the compressor 61 based on the internal temperature (TF)
After the frequency conversion of the alternating current supplied to 1) is performed, the control unit 100 returns to step S1.

In step S8, if the pressure switch 65 (SW1) is ON, the refrigerant pressure abnormally rises for some reason and the operating pressure of the pressure switch 65 (SW1) becomes 22.5 kg / cm ² . Since it has reached, the control means 100 determines that there is a risk that each member constituting the refrigerator 6 may be damaged, and proceeds to step S11 to proceed to step S11.
11 (CLT1) is deenergized to stop driving of the compressor 61, and a DC motor 622 for driving the fan.
The drive of (M2) and 632 (M3) is stopped, and the operation of the refrigerator 6 is stopped. Then, the control unit 100 proceeds to step S12, and displays a message of an abnormality alarm on the display unit 113 (DISP).

As described above, the present invention has been described based on the illustrated embodiments. However, the present invention is not limited to only the embodiments, and various modifications are possible within the technical idea of the present invention. For example, in the illustrated embodiment, an example is shown in which the present invention is applied to a refrigeration system in which a driving engine drives an AC generator and a compressor is driven by an AC motor driven by the output of the AC generator. However, a method in which an AC generator is driven by an engine dedicated to a refrigerator, or an AC motor is driven by a commercial power supply,
The present invention may be applied to a refrigeration system in which a compressor is driven by this AC motor.

[0024]

The refrigerating apparatus according to the present invention is constructed as described above, and has the following effects.

That is, based on the inside temperature detected by the inside temperature detecting means, when the inside temperature is high, the frequency of the AC power supplied to the AC motor for driving the compressor is lowered, and the inside temperature is reduced. Is controlled so that the frequency of the AC power supplied to the AC motor increases as the pressure decreases, so that a refrigeration apparatus that can operate the refrigerant pressure at a predetermined value or less even when the internal temperature is high can be obtained. .
Therefore, the refrigerant pressure does not rise abnormally to the predetermined value due to the high internal temperature, but the refrigerator does not stop even though it is not abnormal.

[Brief description of the drawings]

FIG. 1 is a schematic configuration block diagram of a refrigerator / refrigerated vehicle configured according to the present invention.

FIG. 2 is a block diagram of control means provided in the refrigerator / freezer vehicle configured according to the present invention.

FIG. 3 is a flowchart showing an example of the operation of the control means shown in FIG. 2;

FIG. 4 is a graph showing a relationship between a frequency ( _HZ ) of an alternating current supplied to an AC motor driving a compressor and a pressure (kg / cm ² ) of a refrigerant.

FIG. 5 is a control map in which the frequency (H _Z ) of the AC current supplied to the AC motor with respect to the temperature inside the refrigerator is set.

[Explanation of symbols]

 2: Running engine 3: AC generator (ACG) 4: AC motor (M1) 5: Power supply circuit 51: Power supply switch 52: Automatic voltage regulator 53: Rectifier 54: Inverter (INV) 55: DC power supply circuit 56 : Battery 6: Refrigeration unit 61: Compressor 611: Electromagnetic clutch (CLT1) 612: Belt transmission mechanism 62: Condenser 622: DC motor (M2) 63: Evaporator 632: DC motor (M3) 641, 642, 643, 644: Piping 645: Bypass piping 65: Pressure switch (SW1) 66: Electromagnetic switching valve (V1) 7: Freezer / refrigerator 8: Internal temperature sensor (SNS1) 100: Control means 111: Refrigeration device operation switch (SW2) 112: Freezing temperature Setting device (FTS) 113: display means (DISP)

Claims (1)

[Claims] 1. A refrigerator for circulating a refrigerant compressed by a compressor through a condenser and an evaporator, and a refrigerator cooled by the refrigerator.
A refrigerator having an AC motor for driving the compressor and an inverter for outputting AC power of a desired frequency to the AC motor; a refrigerator internal temperature detecting means for detecting a temperature in the refrigerator; Based on the internal temperature detected by the temperature detection means, when the internal temperature is high, the frequency of the AC power output by the inverter is low, and as the internal temperature decreases, the frequency of the AC power output by the inverter is reduced. A refrigeration apparatus, comprising: control means for performing high control.