JPH0249983A - Capacity control device for compressor - Google Patents

Abstract

PURPOSE:To aim at saving energy and at miniaturizing a capacity control device by providing a variable frequency power source for determining a drive frequency in accordance with an output from a capacity adjusting means and a current limiting means adapted to deliver a signal for lowering the drive frequency to the power source. CONSTITUTION:A compressor motor 32 rotates a rotary type compressor 33. A capacity adjusting means 41 has an adjusting knob and delivers a signal in accordance with a difference from a detected temperature detected by a room temperature detecting element. A current detecting means 44 detects a current running through the motor 32. When a current detected by a current detecting means 44 exceeds a set current value, a signal for lowering the drive frequency to a chopper controller 42. Thus, if the detected current increases, the drive frequency is lowered. Accordingly, it is possible to aim at saving energy and at miniaturizing the capacity control device.

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a compressor capacity control device. BACKGROUND OF THE INVENTION Conventionally, as a means of efficiently controlling capacity, motor speed and
That is, means have been used to control the refrigerating capacity by changing the rotational speed of the compressor to increase or decrease the amount of refrigerant circulated. This method is effective for reciprocating compressors, but when applied to rotary compressors, at 4 poles (low speed), the oil seal becomes incomplete and the compressed refrigerant leaks from the rotor, reducing the volumetric efficiency and causing problems in terms of compression efficiency. there were. The conventional state is shown in Figures 1 and 2.
This will be explained according to the diagram. FIG. 1 is a cross-sectional view of a rotary compressor, showing a housing 1. Rotor 2° eccentric shaft 3. Partition vane 4. Spring 5. Refrigerant gas suction and entry pipe 6. Discharge pipe 7. Consists of valve 8. The second figure shows the compression efficiency obtained by varying the rotational speed of this rotary compressor. Problems to be Solved by the Invention In FIG. 2, the compression efficiency during two-pole operation at a commercial frequency of 60 Hz is p+ point, and is 22 points during four-pole operation. Also,
If the rotation speed is lowered to 1200 rpm, which is 1/3 of the rated speed, by another means, the compression efficiency will drop to 23 points. The reason for this is that the gap between the housing 1 and the rotor 2 in Figure 1 is several microns even when machined with high precision, and the oil in the refrigerant provides a sufficient seal at high speeds, but at low speeds, the oil viscosity is more compressible than the oil viscosity. The problem is that the pressure of the refrigerant gas overcomes it and the gas leaks while being compressed. Therefore, capacity control by changing the rotation speed of a rotary compressor is
There was a problem in that high efficiency could not be obtained simply by changing the rotation speed. In addition, when controlling the capacity of a rotary compressor by changing its rotational speed, overcurrent may occur, especially in overload conditions, and it is necessary to use larger power transistors than necessary. There was a problem in that the capacity control device became large. Therefore, the present invention aims to save energy and downsize compressors and their capacity control devices by increasing the compression efficiency when performing capacity control based on changes in rotational speed and preventing overcurrents caused by overload conditions. The purpose is to Means for Solving Problems In order to achieve the above object, the present invention provides a capacity adjustment means having an adjustment knob, and a variable frequency power supply that inputs commercial power and determines the driving frequency according to the output of the capacity adjustment means. a compressor motor driven based on the output from the variable frequency power supply device, a rotary compressor driven by the compressor motor, and a current detection means for detecting a current flowing through the compressor motor. and current limiting means for outputting a signal for lowering the driving frequency to the variable frequency power supply device when the current detected by the current detecting means exceeds the set current. Operation As described above, the present invention lowers the drive frequency when the detected current increases in an overload state, etc., so that the capacity control device can be downsized and energy-saving. Embodiment The performance and operation of an embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 3 is a control system diagram of a rotary compressor capacity control device using a variable frequency power source, which is an embodiment of the present invention. In the figure, 9 is a three-phase power supply, and 10 is a rectifier circuit, which is composed of a diode bridge 11, a choke coil 12, and a capacitor 13, and obtains a DC voltage. Reference numeral 14 denotes a chopper circuit, which uses a choke coil 17 and a capacitor 18 to smooth the on/off state of the chopper transistor 15. Diode 16 is for the flywheel. By changing the on/off duty of the transistor 15, the output voltage VDC can be varied. 19 is a bridge type inverter consisting of transistors 20°2], , 22.23, 24.25 and diodes 26, 27, 28, 29, 30.31. A compressor motor 32 rotates a rotary compressor 33. 34 is an outdoor unit that includes an outdoor heat exchanger 35 and a fan motor 36. 37 is an indoor unit, and an indoor heat exchanger 38. Capillary tube 39. It includes a fan motor 40 for indoor air circulation. Reference numeral 41 denotes a capacity adjustment means, which has an adjustment knob and outputs a signal based on the difference between the temperature and the temperature detected by the thermostat for detecting room temperature. 42 is a chopper controller, 43 is a current detection means for detecting the current flowing through the motor 32, and 44 is an inverter controller. Here, FIG. 6 shows a block diagram in which the compressor capacity control device of the present invention is implemented as a function realizing means. In the figure, the variable frequency power supply device includes, for example, a rectifier circuit 10. Chopper circuit 14, bridge type inverter 19. It consists of an inverter controller 44, which receives the three-phase power supply 9, which is a commercial power supply, as an input, and determines the driving frequency according to the output of the capacity adjustment means 41. In addition, the current control means in the same figure corresponds to a part of the chopper controller 42 in FIG. 3, and when the current detected by the current detection means 43 exceeds a preset setting current, the drive frequency is lowered to the variable frequency power supply device. It gives a signal. Next, the operation will be explained. First, the chopper controller 42 compares the set output 45 determined by the capacity adjustment means 41 and the input 46 of the output voltage V[)C of the chopper circuit 14, and the transistor 15 is turned on and off by this deviation output 47, and the set output 45 and the output voltage V[)C input 46 of the chopper circuit 14 are compared. Automatically controls the output voltage VDC input to have the same value. Therefore, the output voltage VDC is maintained at a predetermined voltage according to the set output 45. Next, in response to the input 46 of the output voltage VDC of the chopper circuit 14, a frequency output that maintains an approximately proportional relationship is generated from the deviation 47. Then, the inverter controller 44 receives the frequency output, and the inverter 1
9 transistors 20, 21, 22, 23.24.25
sequentially performs a phase shift operation with a 120 degree delay, and sends three-phase rectangular wave output to terminals R, S, and T. This three-phase rectangular wave output causes the compressor motor 32 to rotate, thereby rotating the rotary compressor 33. Note that the compression ratio of the rotary compressor 33 is almost constant whether it rotates at low speed or high speed, and the volume of the compression chamber (compression capacity) is constant, so it exhibits constant torque characteristics regardless of the rotation speed. be. Therefore, the compressor motor 32 is required to be driven with constant torque, and as shown in FIG. 4, it is necessary to maintain the voltage (VDC chopper output voltage) C of the compressor motor 32 and the driving frequency F (inverter frequency) in a substantially proportional relationship. . In FIG. 3, the deviation output 47 of the chopper controller 42 is the output of a V/F converter that is proportional to the output voltage VDC. As described above, when the output of the capacity adjustment means 41 is set low, the output voltage VDC of the chopper circuit 14
becomes low, and as a result, the frequency of the deviation output 47 of the chopper controller 42 also decreases, causing the inverter 19 to switch at a low frequency. Therefore, the compressor motor 32 is under constant torque control with a constant magnetic flux density. Furthermore, when the output of the capacity adjustment means 41 is increased, the frequency increases to high speed rotation and constant torque control. Therefore, the rotation speed of the rotary compressor 33 also changes, the amount of refrigerant circulation changes, and the refrigerating capacity can be varied. FIG. 2 shows the change in compression efficiency when capacity control is performed by raising the frequency of the inverter 19 higher than the commercial frequency. The maximum compression efficiency is 4,000 to 5,000 to 5,000, although it varies depending on the product type depending on the processing accuracy and clearance accuracy of the rotary compressor.
It is at 000 rpm. Therefore, the maximum rotation speed is set to 7,500 rotations as shown in Figure 2, and the rotation speed is lowered to 1/3 of that (general air conditioners use continuous rotation control at 1/3 capacity for comfort reasons). 2,500 rotations is the minimum, and therefore efficient capacity control including the maximum point of compression efficiency is possible in the 7,500 to 2,500 rotation range. As a result, it is possible to achieve specifications with significantly higher efficiency than the conventional system shown in FIG. 2 in which capacity is controlled simply by changing the number of poles. In addition, in Fig. 2, the compression efficiency decreases in the high-speed rotation range because the high-speed response of the partition vane 4 shown in Fig. 1 is poor (
and due to the vibration phenomenon of the spring 5, the discharge pipe 7
As a result of the delay in response between the opening and closing of the valve 8, the compression efficiency decreases. FIG. 5 shows torque characteristics when the capacity control device of FIG. 3 having the characteristics of FIG. 4 is used. The characteristics of the motor alone are T
Indicated by 1. Characteristic T2 indicates a characteristic in which the current flowing through the compressor motor 32 is detected by the current detecting means 43 of FIG. 3, and the flowing current is limited to add torque limitation. This operating principle is
The voltage VDC and frequency F are lowered in accordance with the characteristics shown in FIG. 4 so that the current flowing through the current detection means 43 does not exceed the set current. Ll is a standard load torque characteristic when the rotary compressor 33 operates in a standard state, and when the capacity adjustment means 41 is set to the maximum, it rotates at point Si. Further, when the ability adjustment means 41 is lowered, it rotates at 82 points, for example. When the rotary compressor 33 is operated with overload, the overload torque characteristic becomes L2, and if no torque limit is applied, it becomes 8.
It is operated at 3 points, resulting in inefficient operation with a lot of slip, but by adding a torque limit and lowering the voltage VDC and frequency F, it is operated at 84 points with less slip, which prevents a drop in efficiency and also increases the efficiency of the compressor motor. Since the current also decreases, it is possible to reduce the transistor capacitance and thereby reduce heat loss. Note that the frequency F may be lowered by the current control means not only gradually as described above, but also by lowering the frequency F all at once to a predetermined frequency. Additionally, the required mechanical torque for the compressor motor 32 and the rotary compressor 33 is also reduced;
Even if the mechanical strength is small, it will be difficult to withstand. Effects of the Invention According to the present invention, when using a rotary compressor to control its capacity by changing the number of rotations, the current flowing through the compressor motor is detected and the rotation of the motor is controlled, thereby preventing overload. At the same time, the rotation speed decreases, improving efficiency, and since overload conditions are avoided, the flowing current also decreases, reducing the size of the power transistor and improving the mechanical strength of the compressor motor and compressor.
Therefore, it has excellent effects such as being able to be made smaller and lighter.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a rotary compressor, Fig. 2 is a characteristic diagram of compression efficiency, Fig. 3 is a system diagram of a capacity control device in an embodiment of the present invention, and Fig. 4 is a chopper output voltage and driving frequency. Figure 5 is the rotation speed vs. motor torque characteristic diagram.
FIG. 6 is a block diagram in which the compressor capacity control device of the present invention is implemented as a function realizing means. 9... Three-phase power supply, 10... Rectifier circuit,
14... Chopper circuit, 19... Inverter, 41... Capacity adjustment means, 42...
...Chopper controller, 44...Inverter controller. Name of agent Patent attorney Toshio Nakao 1 person Figure 1 Tomb 2 Illustrations〉 times-3 (rfrn) Pannoil Ute ['-' Name of the invention in the amendment to the civil procedure Amending the capacity control device of a compressor Address related to the case: Address Name: Representative Patent Applicant: 1006 Kadoma, Kadoma City, Osaka Prefecture (582) Akio Tanii, Matsushita Electric Industrial Co., Ltd. 4 Agent Address: 1006 Kadoma, Kadoma City, Osaka Prefecture 571 Address: Matsushita Electric Industrial Co., Ltd. 6 Contents of amendment (1) The entire statement will be amended as shown in the attached document. (2) Amend Figures 2 and 3 of the drawings as shown in the attached document. Description 1, Name of the invention Compressor capacity control device 2, Claims Capacity adjustment means having an adjustment knob, and commercial power supply a variable frequency power supply device that receives as an input and determines a drive frequency according to the output of the capacity adjustment means; a compressor motor that is driven based on the output from the variable frequency power supply device; and a compressor motor that is driven by the compressor motor. a rotary compressor; the pressure;
a direct current detection means for detecting r current flowing through the compressor motor or the variable frequency generating device, and lowering the driving frequency to the variable frequency power supply device when the current produced by the current detection means exceeds a set current. A capacity control unit device for a compressor, comprising a direct current limiting means for outputting one word. 3. Detailed Description of the Invention Field of Industrial Application The present invention relates to a capacity control device for a compressor. Conventional V technology Traditionally, as a means to operate air conditioners comfortably and efficiently, a motor with variable number of poles to drive the compressor 1 has been used to drive a 2-pole,
There was one that controlled the capacity by switching four poles,
Because it was a two-stage switch, it was not possible to significantly improve comfort or efficiency. Another method is to drive the compressor motor at variable speeds, examples of which are shown in, for example, Japanese Patent Laid-Open No. 49-1043o7 and Japanese Patent Laid-Open No. 51-128142. Further, as an operation control system for the motor itself, for example, Japanese Patent Laid-Open No. 101815/1983 describes an acceleration pattern of the operating frequency when starting the motor using an inverter (variable frequency power supply). Problems to be Solved by the Invention In these conventional technologies, there is no specific configuration that takes into account the comfort and efficiency of the compressor in an air conditioner, small size, light weight, and safety. No consideration had been given to how to deal with the case where the machine load changes drastically depending on the operating conditions ◇ For example, in an air conditioner, when the air conditioning load conditions change and you try to increase the cooling and heating capacity, The compressor is rotated at high speed, but at this time, the compressor load becomes excessive because the difference in refrigerant pressure increases. As a result, the current of the compressor motor becomes excessive9, and in order to cope with this, the variable frequency power supply itself needs to have an extremely large capacity, and components such as power transistors are made larger than necessary. However, the problem is that the entire device becomes large in size. Therefore, the present invention improves compression efficiency when performing capacity control based on changes in rotational speed, and prevents excessive current from flowing to the compressor motor in overload conditions. The purpose is to save energy and downsize the device. Means for Solving the Problems In order to achieve the above objects, the present invention provides a capacity adjustment means having an adjustment knob, and a variable frequency power supply device which inputs commercial power and determines the driving frequency according to the output of the capacity adjustment means. a compression motor driven based on the output from the variable frequency power supply; a rotary compressor driven by the compressor motor; and a compressor motor driven by the output from the variable frequency power supply; a direct current detection means for detecting current; and a current limiting means for outputting a signal to the variable frequency power supply device to lower the operating frequency when the CE current detected by the direct current detection means exceeds the set current. It was established. Operation As described above, the present invention' allows the performance control device to be downsized and energy-saving in order to lower the driving and intercostal wave number when the production current increases in an overload state or the like. Embodiment Below, the configuration and operation of an embodiment of the present invention will be explained with reference to the accompanying drawings. FIG. 1 is a sectional view of an embodiment of a rotary compressor used in the compressor capacity control device of the present invention. In the figure, 1 is the housing, 2 is the opening, 3 is the eccentric shaft, 4 is the partition vane, and 6
6 is a refrigerant gas suction pipe, 7 is a discharge pipe, and 8 is a discharge valve. This rotary compressor compresses the refrigerant by rotating the eccentric shaft 3 with a compressor motor. ) is also suitable. FIG. 2 is a control system diagram of a rotary compressor capacity control device using a variable frequency power source, which is an embodiment of the present invention, and specifically shows the case where the device is used in an air conditioner. In the figure, 9 is a three-phase power supply, 10 is a rectifier circuit, and a diode bridge 11, a choke coil 12, and a capacitor 13 obtain a direct current voltage. 14 is a chopper circuit, and a transistor 15 for the chopper
The on/off state is smoothed by a choke coil 17 and a capacitor 18. Diode 16 is for the flywheel. By changing the on/off duty of the transistor 15, the output voltage VDC can be varied. 19 is a bridge type inverter with transistors 20, 21, 22, 23, 24, 25
and diodes 26, 2γ, 28, 29, 30, and 31. A compressor motor 32 rotates a rotary compressor 33. 34 is an outdoor unit that includes an outdoor heat exchanger 35 and a fan motor 36. 37 is an indoor unit,
Indoor heat exchanger 38. Capillary tube 39. It includes a fan motor 40 for indoor air circulation. Reference numeral 41 denotes a capacity adjustment means which has an adjustment knob and outputs a signal based on the difference between the temperature and the temperature detected by the room temperature detection element. 42 is a Hachiyonopa controller, 43 is an inverter controller, 44 is a current detection means for detecting the flow flowing through the motor 32, and 45 is a flow limiting means. Here, FIG. 3 shows a block diagram in which the compressor capacity control device of the present invention is implemented as a function realizing means. In the figure, the variable frequency power supply device includes, for example, a rectifier circuit 10. Chopper circuit 14° bridge type inverter 19. It consists of an inverter controller 244, which receives the three-phase power supply 9, which is a commercial power supply, as an input, and determines the driving frequency according to the output of the capacity adjustment means 41. Further, when the electric current detected by the current detecting means 44 exceeds a preset current set by me, the hawk flow rate suppressing means 45 controls the chopper controller 43 of the variable frequency power supply device.
This outputs a signal to lower the drive frequency. Next VC
@Explain the work. First, the setting output e1 determined by the capacity adjustment means 41
The chopper controller 42 compares the input signal e2 of the output of the chopper circuit 14 with the direct voltage Dc, and the deviation output e3 turns the transistor 16 on and off, and the input signal from the set output e1 and the output voltage vDc. Automatically control so that e2 has the same value. Therefore, the output voltage v
Dc is maintained at a predetermined voltage depending on the setting. Next, in response to the input signal e2 from the output voltage ■Dc of the chopper circuit 14, a frequency setting output θ4 that maintains a nearly proportional relationship is generated.
is generated from the chopper controller 42. The frequency setting output e4 is received by the inverter controller 44, and the transistors 20 and 20 of the bridge type inverter 19,
21, 22, 23, 24, and 26 sequentially perform a phase shift operation with a delay of 120 degrees, and send three-phase rectangular wave outputs to terminals R, S, and T. This three-phase rectangular wave output causes the compressor motor 32 to rotate, thereby rotating the rotary compressor 33. Here, the bridge type inverter 19 can generate a driving frequency higher than the source frequency of the commercial power source 9, and the rotary compressor 33 can be driven at high speed at a rotation speed higher than that obtained by the commercial power source 9. . Note that the compression ratio of the rotary compressor 33 is almost constant whether it rotates at low speed or high speed, and the volume of the compression chamber (compression capacity) is constant, so if the air conditioning load conditions are the same, regardless of the rotation speed. This shows almost constant torque characteristics. Therefore, the compressor motor 32 is required to be driven with constant torque, and as shown in FIG. 4, it is necessary to maintain the direct pressure vDc (chopper output direct pressure) of the compressor motor 32 and the drive frequency F (inverter frequency) in a substantially proportional relationship. There is. In FIG. 2, the chopper controller 420 frequency setting output e4, 7. is a V/F converter proportional to the output voltage ■Dc, 1 (1) The output voltage vDc becomes low, and as a result, the frequency of the frequency setting output e4 of the chopper controller 42 also decreases, and the bridge type inverter 19 switches at a low frequency. The pressure aa motor 32 rotates at a low speed and performs constant torque control with constant magnetic flux density. Also, as the set output e1 of the capacity adjustment means 41 increases, the frequency increases and becomes high speed rotation and constant torque control. Therefore, rotational compression The rotational speed of the machine 33 also changes, and the refrigerant circulation amount changes, so that the refrigerating capacity can be varied. Fig. 5 shows the torque characteristics when the capacity control device of Fig. 2 having the characteristics of Fig. 4 is used. The characteristics of the motor alone are T
Indicated by 1. The characteristic T2 is obtained by detecting the current flowing through the compressor motor 32 with the DC detection means 44 shown in FIG.
5 shows a characteristic in which the flowing 1d flow is restricted. The principle of operation is to lower the voltage Dc and the frequency F in accordance with the characteristics shown in FIG. 4 so that the current flowing through the current detection means 44 does not exceed the set current. Ll is the standard load torque characteristic when the rotary compressor 33 operates under standard conditions, and when the capacity adjustment means 41 is set to the maximum, 81
Rotate at a point. Further, when the ability adjustment means 41 is lowered, it rotates at 82 points, for example. When the rotary compressor 33 is operated with overload, it becomes overload torque characteristic L2, and unless DC restriction is applied, it will be operated at 83 times, but in this state, it will only result in inefficient operation with a lot of slip. However, by adding a current limit and lowering the voltage Dc and frequency F, it is operated at 84 points with less slip, which prevents a drop in efficiency and reduces the amount of current flowing to the compressor motor. Since the direct current also decreases, it is possible to reduce transistor capacity and thereby reduce heat loss. Additionally, the required mechanical torque for the compressor motor 32 and the rotary compressor 33 is also reduced;
Even small substitutes with low mechanical strength will be durable. Note that during overload, by lowering the frequency and the rotation speed of the rotary compressor, the heating and cooling capacity may not be as desired, but stable and safe operation for the equipment can be achieved. This will allow you to continue doing this. In other words, if you do not take measures to lower this same wave number, and try to operate at 83 points, for example, the overcurrent cutoff function, which was designed to protect the power transistor from overcurrent, will actually work, and the variable frequency power supply itself will The operation will stop, and as a result, there will be no heating or cooling operation at all. On the other hand, at a current level lower than that at which the overcurrent cutoff function operates during overload, etc.? [The flow restricting means 45 issues a command to lower the current, so that the air conditioning/heating operation can be performed in accordance with a standard. One embodiment of the compressor capacity control device of the present invention has been described above with reference to the accompanying drawings, but if explained in more detail, similar effects can be obtained with the following configuration. First, the method of lowering the frequency F by the current limiting means 46 is other than the method of lowering the frequency F gradually so as not to trap the set current as described above.
It may be possible to lower the frequency by -degrees (absolute value) or by a predetermined frequency/sound with respect to the current frequency. In these stepwise lowering methods, when the set current is exceeded again, lowering it by one more step is possible in all wave number ranges, and when the current drops by a predetermined value below the set current. controllability is ensured by returning to the original frequency in stages. Further, even if the current detection means 44 is configured to detect the current flowing to the compressor motor 32, the operation will be the same as in the actual example. Furthermore, the same effect can be expected even if the configuration is configured to detect the power supply current from the three-phase power supply 9 to the υ rectifier circuit 10. In addition, three-phase power supply 9
Of course, a single-phase power supply may also be used. Effects of the Invention According to the present invention, when controlling the capacity by changing the rotation speed using a rotary compressor, the current flowing through the compressor motor is detected and the rotation of the motor is controlled. As the rotation speed decreases, efficiency is improved, and overload conditions are avoided, allowing stable operation to continue.Furthermore, the current flowing to the pressure AA motor is reduced, allowing the power transistor to be made smaller and the compressor motor and The mechanical strength of pressure MJa can also be reduced, resulting in excellent effects such as miniaturization and weight reduction.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the rotary pressure aa, Fig. 2 is a system diagram of a capacity control device in an embodiment of the present invention, Fig. 3 is a characteristic diagram of the relationship between the chopper output voltage and drive frequency, and Fig. 4 is the main FIG. 6 is a block diagram illustrating the compressor capacity control device of the invention as a function realizing means, and FIG. 6 is a rotation speed vs. motor torque characteristic diagram. 9... Three-phase power supply, 1o... Rectifier circuit, 1
4... Chopper circuit, 19... Bridge type inverter, 32... Compressor motor, 33
... Rotary compressor, 41 ... Capacity adjustment means, 42 ... Chopper controller, 43 ...
...Inverter controller-y, 44...Current detection means, 46...Current limiting means. Name of agent: Patent attorney Toshio Nakao and one other figure procedure amendment (method) ■Indication of the case 1988 Patent Application No. 294436 2 Name of the invention Person who makes amendments to compressor capacity control device

Claims (1)

[Claims] capacity adjustment means having an adjustment knob; a variable frequency power supply device that receives commercial power as input and determines a driving frequency according to the output of the capacity adjustment means; and a compressor that is driven based on the output from the variable frequency power supply device. a motor, a rotary compressor driven by the compressor motor, a current detecting means for detecting a current flowing through the compressor motor, and a current detecting means for detecting a current flowing through the compressor motor; A capacity control device for a compressor, comprising current limiting means for outputting a signal to lower a driving frequency to a frequency power supply device.