JP2004297981A - Compressor controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control a compressor 4 correctly even if a motor current is detected using an inexpensive current sensor 48. <P>SOLUTION: A compressor controller 24 comprises a low voltage sensor 22 for detecting the suction refrigerant pressure of the compressor 4, an inverter circuit 42 for controlling the driving frequency of the motor of the compressor 4, a current detecting circuit 43 having the current sensor 48 for detecting the motor current, and a control section 44 for delivering the driving frequency of the motor operated based on a signal from the low voltage sensor 22 to the inverter circuit 42, operating the motor current from a previously provided data base 51 indicative of the relation between a signal being detected by the current detecting circuit 43 in correspondence with each driving frequency and the motor current being fed actually, making a decision whether the motor is overloaded or not based on the decision results and stopping power supply to the motor if the motor is overloaded. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a compressor control device that controls the operation of a compressor used in a refrigeration system.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a refrigeration apparatus includes a compressor for compressing a refrigerant, a radiator for releasing the refrigerant, a receiver tank for storing the liquefied refrigerant that releases heat, and the like, so that the refrigerant is circulated in the refrigeration circuit.
[0003]
For example, a showcase or the like includes an indoor unit that is disposed indoors to cool and display products and the like, and an outdoor unit that is installed outside and connected to the indoor unit by a refrigerant pipe. Is provided with an accumulator, a compressor, an oil separator, a radiator, a receiver tank, and the like, and an indoor unit is provided with an expansion valve, an evaporator, and the like.
[0004]
Then, the refrigerant compressed by the compressor radiates heat by the radiator to be liquefied. At this time, lubricating oil is used to lubricate the sliding parts of the compressor, but this lubricating oil is discharged from the compressor together with the refrigerant. I'm back.
[0005]
The liquefied refrigerant radiated by the radiator is stored in the receiver tank, and supplied from the receiver tank to the indoor unit.
[0006]
In the indoor unit, the refrigerant is expanded by an expansion valve and is evaporated by an evaporator to generate cold heat, thereby cooling a product or the like.
[0007]
Thereafter, the refrigerant returns to the outdoor unit, is separated into gas and liquid by the accumulator, and only the gas refrigerant returns to the compressor.
[0008]
At this time, when the heat load fluctuates, the refrigeration capacity is increased or decreased by controlling the operating frequency of the compressor.
[0009]
FIG. 6 is a block diagram of a control device 101 that controls the operation of the compressor, and includes a rectifier circuit 102, an inverter circuit 103, a current detection circuit 104, a low-pressure sensor 105, a control unit 106, and the like (Patent Document 1). reference).
[0010]
Then, the power from the power supply is rectified by the diode module 107 by the rectifier circuit 102, smoothed by the inductance coil 108 and the capacitor 109, frequency-controlled by the inverter circuit 103, and the motor of the compressor 110 is driven.
[0011]
At this time, the frequency is controlled by the inverter circuit 103. This frequency is a frequency determined by detecting the refrigerant suction pressure of the compressor 110 with the low-pressure sensor 105 and calculating the optimum frequency by the control unit 106 based on the result. .
[0012]
Thus, the compressor 110 is operated at an optimum frequency with respect to the heat load fluctuation, and can cope with such heat fluctuation.
[0013]
On the other hand, it is assumed that an overcurrent flows through the motor of the compressor 110 for some reason. In such a case, if the power is continuously supplied as it is, the motor will be burned out. Therefore, when the motor current is detected by the current detection circuit 104 composed of a Hall element or the like, and the detected value exceeds a specified value, Controls the operation such as stopping the operation.
[0014]
[Patent Document 1]
JP-A-2002-101691
[Problems to be solved by the invention]
However, since the Hall element is expensive, a configuration using an inexpensive current sensor (CT) is desired. In this case, the current value supplied to the motor of the compressor 110 is reduced for the following reason. There was a problem in that the compressor 110 could not be detected accurately and the compressor 110 could not be properly controlled.
[0016]
That is, as described above, the control unit 106 calculates the drive frequency of the compressor 110 in order to cope with the fluctuation of the heat load, and the inverter circuit 103 performs the frequency control at this frequency. Therefore, the frequency of the current supplied to the motor changes according to the situation.
[0017]
FIG. 7 is a diagram showing a configuration of a current sensor. The current sensor 111 has a configuration in which an inductance coil 112 and a resistor 113 are connected in series. When an AC current flows through a power supply line 114, an AC magnetic field generated at that time is generated. By using the fact that an induced voltage is generated in the inductance coil 112, a current value is detected from the voltage value.
[0018]
When the current detection is performed by such a current sensor 111, as shown in FIG. 8, its output has a frequency dependency, and an accurate current cannot be detected.
[0019]
8, a solid line indicates a voltage waveform (current waveform) output from the current sensor 111 when the same current value flows at a frequency of 20, 40, and 60 Hz, and a dotted line indicates an actual voltage waveform (current waveform). I have.
[0020]
Therefore, an object of the present invention is to provide a compressor control device capable of controlling a compressor accurately even when a current value is detected by such an inexpensive current sensor.
[0021]
[Means for Solving the Problems]
In order to solve the above problems, the invention according to claim 1 includes a low pressure sensor for detecting a pressure of a refrigerant sucked into a compressor, an inverter circuit for controlling a driving frequency of a motor that drives a compression element of the compressor, and a motor. And a current detection circuit that detects a motor current supplied to the inverter, calculates a motor drive frequency based on a signal from the low-voltage sensor, outputs the calculated motor drive frequency to an inverter circuit, and outputs a signal from the current detection circuit corresponding to each drive frequency. A database indicating the relationship with the actually supplied motor current is provided in advance, and the motor current is calculated and calculated by the database based on the drive frequency output to the inverter circuit and the signal from the current detection circuit, and the motor is calculated based on the result. A control unit that determines whether or not the motor is overloaded and, in the event of an overload, stops power supply to the motor. , Characterized in that the signal from the current detection circuit for detecting a motor current and to allow control of exactly the compressor and correction.
[0022]
The invention according to claim 2 is characterized in that the current detection circuit includes a current sensor that generates an induced voltage by a motor current supplied to the motor.
[0023]
According to a third aspect of the present invention, the current detection circuit smoothes an output signal from the current sensor, and divides the signal smoothed by the smoothing circuit into a signal within an input signal range in the control unit. And a circuit.
[0024]
According to a fourth aspect of the present invention, the database is a numerical table indicating the relationship between the signal from the current detection circuit corresponding to each drive frequency and the actually supplied motor current, or the current table corresponding to each drive frequency. It is characterized by being formed by a relational expression showing the relation between the signal from the detection circuit and the actually supplied motor current.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a refrigerating apparatus applied to the present invention. The refrigerating apparatus 1 includes a compressor 4, a radiator 5, and the like. And an indoor unit 3 which is provided on the side of the heat utilization space and includes an evaporator 7 and the like.
[0026]
In the present embodiment, a case where cold heat is used by the refrigeration apparatus 1 will be described, but it goes without saying that a case where warm heat is used is also applicable. In addition, a description will be given of an example of a conventionally used HFC refrigerant or the like as a refrigerant, but a carbon dioxide refrigerant may be used.
[0027]
Then, the refrigerant compressed by the compressor 4 in the outdoor unit 2 releases heat in the radiator 5 and liquefies. The liquefied refrigerant is sent to the indoor unit 3 through the refrigerant pipe, expanded by the expansion valve 6 and evaporated by the evaporator 7 to generate cold heat. Thereafter, the refrigerant returns to the outdoor unit 2 through the refrigerant pipe and is compressed by the compressor 4.
[0028]
FIG. 2 is a diagram showing the configuration of such an outdoor unit 2 in detail. The outdoor unit 2 includes a radiator 5, a strainer 11, an accumulator 12, a compressor 4, an oil separator 13, a receiver tank 14, a filter dryer 15, a refrigerant injection device 20, and the like.
[0029]
Then, the refrigerant returned from the indoor unit 3 flows to the strainer 11, the accumulator 12, the compressor 4, and the oil separator 13 and flows into the radiator 5, and then passes through the receiver tank 14, the filter dryer 15, and the like. 3 is supplied.
[0030]
The strainer 11 removes impurities (dust such as abrasion powder) contained in the refrigerant returned from the indoor unit 3 to the outdoor unit 2. The accumulator 12 separates the refrigerant from the strainer 11 into gas and liquid so that only gaseous refrigerant can be supplied to the compressor 4 so that liquid compression does not occur in the compressor 4.
[0031]
The compressor 4 includes a compression chamber and a motor (not shown), and expands the space volume of the compression chamber by the power of the motor to draw in the gaseous refrigerant supplied from the accumulator 12, and then reduces the space volume of the compression chamber. It compresses the refrigerant by reducing the size.
[0032]
Various types of compressors 4 such as a compressor 4, a scroll compressor, a rotary compressor, and a piston compressor, which are applied to such a refrigeration apparatus, can be applied. It is also applicable to the compressor 4.
[0033]
The compressor 4 is provided with a high-pressure sensor 21, a low-pressure sensor 22, and a high-pressure manometer 23 for detecting the pressure in the case, and a compressor control device 24 is connected to the high-pressure sensor 21 and the low-pressure sensor 22.
[0034]
Then, the compressor control device 24 controls the operation stop of the compressor 4 based on the signal from the low pressure sensor 22, and forcibly stops the compressor 4 when the signal from the high pressure sensor 21 exceeds a predetermined level. So that the pressure does not exceed the preset abnormal pressure. The pressure at this time can be visually recognized by the high pressure manometer 23.
[0035]
FIG. 3 is a diagram showing a main configuration of such a compressor control device 24. The compressor control device 24 includes a rectifier circuit 41, an inverter circuit 42, a current detection circuit 43, a control unit 44, and the like. ing.
[0036]
The electric power from the power supply is rectified by the diode module 45 by the rectifier circuit 41, smoothed by the inductance coil 46 and the capacitor 47, and the inverter circuit 42 controls the frequency to drive the motor of the compressor 4.
[0037]
At this time, the frequency is controlled by the inverter circuit 42, and this frequency is a frequency determined by detecting the refrigerant suction pressure of the compressor 4 by the low pressure sensor 22 and calculating the optimum frequency by the control unit 44 based on the result. .
[0038]
Thus, the compressor 4 is operated at an optimum frequency with respect to the heat load fluctuation, and can cope with such heat fluctuation.
[0039]
On the other hand, the motor current (Mi) of the compressor 4 is detected by the current detection circuit 43. The current detection circuit 43 includes a current sensor 48 as shown in FIG. 7, a smoothing circuit 49 for smoothing an output from the current sensor 48, and a voltage dividing circuit 50 for dividing the smoothed voltage.
[0040]
Then, a voltage corresponding to the motor current (Mi) detected by the current sensor 48 is smoothed by the smoothing circuit 49 and divided by the voltage dividing circuit 50.
[0041]
In the control unit 44, various control processes are digitally processed, and a predetermined time (sampling time) is required to capture a signal. However, as shown in FIG. 8, the signal detected by the current sensor 48 changes rapidly when the signal exceeds the peak value. Therefore, the smoothing circuit 49 including a capacitor or the like is used to capture the peak value. To mitigate sudden changes in
[0042]
The signal input of the control unit 44 has an input signal range, and the signal from the current sensor 48 smoothed by the smoothing circuit 49 is divided by a voltage dividing circuit 50 so that a signal having a level larger than the input signal range is not input. The resistance is divided.
[0043]
In this way, the detection value (Mv) from the current detection circuit 43 is input to the control unit 44, and based on the detection value (Mv), the motor current (Mv) actually flowing from the motor current-detection value database 51 Mi) is required.
[0044]
In the motor current-detection value database 51, as shown in FIG. 4, the relationship between the detection value (Mv) and the motor current (Mi) flowing at that time is tabulated for each drive frequency and stored in advance. ing. Of course, it is also possible to store in a function format instead of a numerical table.
[0045]
As a result, when the motor current (Mi) is larger than the specified value (It) (Mi> It), the control unit 44 determines that the motor is in the overload state for some reason and stops the operation of the compressor 4 or the like. Perform control.
[0046]
FIG. 5 is a diagram showing such a control procedure. When the control of the compressor 4 is started, the control unit 44 sets the operating frequency of the motor based on a signal from the low pressure sensor 22 under a preset condition. (Step S1).
[0047]
Then, the calculation result is output to the inverter circuit 42, and the inverter circuit 42 drives the motor at the frequency (step S2).
[0048]
Next, the control unit 44 takes in the detection value (Mv) from the current detection circuit 43 (step S3), and based on the detection value (Mv), the motor current actually flowing from the motor current-detection value database 51. (Mi) is obtained (step S4).
[0049]
It is determined whether or not the obtained motor current (Mi) is equal to or greater than a specified value (It) (step S5). If the obtained motor current (Mi) is equal to or smaller than the specified value (It), the process returns to step S1 to repeat the above-described procedure. If the value is equal to or more than the value (It), it is determined that an overload has occurred, and the operation of the compressor 4 is stopped (step S6).
[0050]
For example, in FIG. 4, it is assumed that the specified value (It) at which the motor is overloaded is set to 55 A, and the operation frequency calculated by the control unit 44 based on the signal from the low-pressure sensor 22 is 20 Hz.
[0051]
At this time, if the detection value (Mv) from the current detection circuit 43 is 2V, the motor is not overloaded because the motor current (Mi) is 45A. However, when the detected value (Mv) is 2.5 V, the motor is overloaded because the motor current (Mi) is 62 A.
[0052]
As described above, by accurately calculating the motor current (Mi) based on the detection value (Mv) from the current detection circuit 43, the operation control of the compressor 4 can be appropriately performed even when the inexpensive current sensor 48 is used. As a result, cost can be reduced and reliability is improved.
[0053]
The oil separator 13 is a lubricating oil that has been discharged together with the refrigerant among the lubricating oil that has lubricated various sliding portions in the compressor 4 (for example, a contact portion between a plurality of members forming a rotating shaft of a motor and a compression chamber). The separated lubricating oil returns to the compressor 4 via the lubricating oil return pipe 25.
[0054]
The radiator 5 exchanges heat between the compressed high-temperature and high-pressure refrigerant and the outside air to radiate the refrigerant, and the outside air is blown by the blower 26.
[0055]
When an HFC refrigerant or the like is used as the refrigerant, the refrigerant is condensed and liquefied by radiating heat in the radiator 5, but in the case of carbon dioxide, a mixed state of a liquid phase and a gas phase ( (Supercritical state).
[0056]
However, as described above, in the present invention, not only the HFC refrigerant and the like but also carbon dioxide can be used as the refrigerant. "".
[0057]
The receiver tank 14 stores the refrigerant liquefied by the radiator 5 so that the refrigerant can be supplied without excess or deficiency with respect to the fluctuation of the heat load on the indoor unit 3 side.
[0058]
The receiver tank 14 is provided with a fusible plug 27 to prevent the refrigerant in the refrigeration apparatus 1 from being heated and ruptured by the heat when, for example, a house housing the outdoor unit 2 causes a fire. Meanwhile, when the temperature reaches a predetermined temperature (the melting point of the fusible plug 27), the refrigerant is melted and the refrigerant in the refrigeration apparatus 1 is released to the atmosphere, thereby preventing rupture.
[0059]
The filter dryer 15 removes the water so that when the refrigerant contains moisture, when the evaporator 7 in the indoor unit 3 evaporates, the moisture freezes and does not clog the refrigerant circuit. The moisture indicator 28 is used for visually recognizing the circulating refrigerant and determining the amount of the refrigerant and the time for replacing the filter used in the filter dryer 15.
[0060]
Further, the refrigerant injection device 20 includes an extraction pipe 29, a strainer 30, a thermo valve 31, a capillary tube 32, a temperature sensing cylinder 34, an injection control valve 37, and the like, and is stored in the receiver tank 14 as described above. A part of the liquefied refrigerant is injected into the compressor 4.
[0061]
The extraction pipe 29 is connected to the receiver tank 14 to extract the liquefied refrigerant stored in the receiver tank 14, and the strainer 30 removes dust contained in the extracted refrigerant.
[0062]
Since the extraction pipe 29 is for extracting a part of the liquefied refrigerant and allowing it to be injected into the compressor 4, the extraction pipe 29 is connected not only to the receiver tank 14 but also from the radiator 5 to the indoor unit 3 side. May be connected to the refrigerant pipe.
[0063]
As described above, if the radiator 5 is connected to the refrigerant pipe on the indoor unit 3 side, the present invention can be applied to a refrigeration apparatus having no receiver tank 14, and there is an advantage that the use range is widened.
[0064]
The temperature-sensitive cylinder 34 is mounted in close contact with the discharge pipe 38 of the compressor 4, and the thermovalve 31 controls the amount of refrigerant to be injected into the compressor 4 by adjusting the opening of the valve according to the temperature detected by the temperature-sensitive cylinder 34. It is for doing.
[0065]
The capillary tube 32 is connected in parallel with the thermovalve 31 for the purpose of compensating for a delay in the control of the thermovalve 31 by the thermosensitive cylinder 34, such as when the compressor 4 is started.
[0066]
【The invention's effect】
As described above, according to the present invention, a low-pressure sensor that detects a refrigerant pressure sucked into a compressor, an inverter circuit that controls a drive frequency of a motor that drives a compression element of the compressor, and a motor that is supplied to the motor A current detection circuit that detects the motor current, and calculates the motor drive frequency based on the signal from the low-voltage sensor and outputs it to the inverter circuit. The motor current is calculated based on the driving frequency output to the inverter circuit and the signal from the current detection circuit, and the motor is overloaded based on the result. And a control unit for stopping the power supply by the motor in the case of overload. The signal from the current detection circuit for detecting a current is corrected such should be able to control exactly compressor reliability is improved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a refrigeration apparatus applied to an embodiment of the present invention.
FIG. 2 is a diagram showing a detailed configuration of an outdoor unit.
FIG. 3 is a block diagram of a compressor control device.
FIG. 4 is a diagram illustrating a database including a relationship between a motor current and an output of a current detection circuit.
FIG. 5 is a diagram showing a control procedure of the compressor control device.
FIG. 6 is a diagram illustrating a configuration of a current sensor.
FIG. 7 is a block diagram of a compressor control device applied to the description of the related art.
FIG. 8 is a diagram showing the diameter of the output of the current sensor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Refrigeration apparatus 2 Outdoor unit 3 Indoor unit 4 Compressor 24 Compressor control device 41 Rectifier circuit 42 Inverter circuit 43 Current detection circuit 44 Control part 48 Current sensor 49 Smoothing circuit 50 Voltage dividing circuit 51 Database

Claims (4)

A low-pressure sensor for detecting a refrigerant pressure sucked into the compressor;
An inverter circuit that controls a driving frequency of a motor that drives a compression element of the compressor;
A current detection circuit for detecting a motor current supplied to the motor,
The drive frequency of the motor is calculated based on the signal from the low-pressure sensor and output to the inverter circuit, and the motor current that is actually supplied and the signal from the current detection circuit corresponding to each drive frequency. Is provided in advance, and the motor current is calculated by the database based on the drive frequency output to the inverter circuit and the signal from the current detection circuit, and the motor is overloaded based on the result. A controller for determining whether or not the motor is overloaded and stopping the power supply by the motor in the case of overload. The compressor control device according to claim 1, wherein the current detection circuit includes a current sensor that generates an induced voltage by a motor current supplied to the motor. The current detection circuit includes: a smoothing circuit that smoothes an output signal from the current sensor; and a voltage dividing circuit that divides a signal smoothed by the smoothing circuit into a signal in an input signal range in the control unit. 3. The compressor control device according to claim 2, wherein: The database is a numerical table indicating the relationship between the signal from the current detection circuit corresponding to each drive frequency and the actually supplied motor current, or from the current detection circuit corresponding to each drive frequency. The compressor control device according to any one of claims 1 to 3, wherein the compressor control device is formed by a relational expression indicating a relation between a signal and the actually supplied motor current.

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