JPS6054571B2 - heat source device - Google Patents

Description

Detailed Description of the Invention The present invention provides a refrigeration cycle heat source device using a compressor for compressing refrigerant, in which a motor for driving the compressor is driven at variable speed by an inverter capable of outputting a frequency higher than the commercial power frequency. The present invention relates to a heat source device that changes the refrigerating capacity by controlling the refrigerating capacity, and in particular, controls the refrigerating capacity while preventing the operating torque of the compressor from becoming excessive.

The purpose of the present invention is (a) to improve controllability and comfort, and to improve efficiency and save energy by proportionally controlling the capacity according to the load.

(b) By driving the compressor and its drive motor at high speed, the compressed yarn can be made smaller and lighter for the same refrigerating capacity, thereby saving resources.

(c) Stabilize operation, improve lifespan, and improve operability by controlling start/stop and operating conditions of the compressor using methods suitable for the compression system.

etc. Conventionally, there have been some compressor motors that perform stepwise control by changing the number of poles (for example, changing between two and four poles), but this has the disadvantage that proportional control of capacity according to load is not possible.

In addition, the compressor motor is driven at variable speed by an inverter, etc.
Although there is an idea to proportionally control the refrigerating capacity, there are various problems with simply proportionally controlling the capacity for compression systems that exhibit unique behavior. In particular, there were difficulties in the operating method (start-up/stop control), which caused problems with stable operation of equipment, lifespan of equipment such as compressors, vibration/noise, and comfort. The present invention will be explained below with reference to the drawings showing one embodiment thereof.

FIG. 1 shows a heat source device, such as a heat pump type, which heats and cools by a refrigeration cycle, and the figure is particularly applied to a separate type air conditioner. 1 is an outdoor unit of a separate air conditioner, 2 is an indoor unit, and the outdoor unit 1 has a compressor 3, a four-way valve 5 with a motor for driving the compressor 3, an outdoor heat exchanger 6, and an outdoor fan 7. .

In addition, the indoor unit 2 is composed of a capillary tube 8, an indoor heat exchanger 9, and an indoor fan 10.
0 allows the air in the air conditioned room to circulate, allowing heating, cooling, etc. The four-way valve 5 in the indoor unit 1 switches the refrigerant circulation direction to switch between heating and cooling, or heating operation,
This is used to switch the defrosting operation. Reference numeral 11 is a commercial power supply, particularly a three-phase 200V power supply.

Reference numeral 12 denotes a forward conversion section, which includes a diode stack 13, a choke coil, and a capacitor 15, and rectifies and smoothes the commercial power source 1 to convert it into a DC voltage.

16 is a chopper section, and a chopper transistor 17
, a choke coil 18, a capacitor 19, a flywheel diode 20, a transistor drive circuit 21, and a chopper control circuit 22.

The chopper transistor 17 chops the signal from the chopper control circuit 22 via the transistor drive circuit 21 and performs pulse width control (method of controlling on-time within one cycle) at a predetermined frequency, and chops the chopped voltage. is smoothed by a choke coil 18, a capacitor 19, and a flywheel diode 20. As will be described later, due to the operation of the chopper section 16, the forward conversion section 12
The rectified and smoothed DC voltage is converted into a DC voltage according to the input signal of the chopper control circuit 22. 23 is an inverse conversion section, and transistors 24 to 29 and flywheel diodes 30 to 35 form a three-phase bridge. A transistor drive circuit 36 and an inverse conversion control circuit 37 are connected to each other and correspond to the transistors 24 to 29.

The transistors 24 to 29 are turned on and off at predetermined intervals to generate a three-phase AC voltage, which is supplied to the motor 4. 38 is a torque limiting circuit, which consists of a current detector 39 and a signal processing circuit 40, which indirectly detects the current flowing to the motor 4 by the current detector 39, and outputs the current to the chopper control circuit 22 and the inverse conversion control circuit 37. A signal is issued to suppress the rotational speed of the motor 4, and the compressor 3
The function is to limit the operating torque so that it does not exceed a predetermined value.

41 is a speed command circuit.

This speed command circuit 41 inputs a temperature signal from a thermistor 42 that detects the room temperature of the air-conditioned room and a setting signal from a variable resistor 43 that sets the room temperature, and inputs a temperature signal from a thermistor 42 that detects the room temperature of the air conditioned room, and a setting signal from a variable resistor 43 that sets the room temperature, so that the rotation speed of the compressor 3 is within a predetermined range or It emits a speed command signal that becomes zero. Next, the operation will be explained.

First, the compressor 3 compresses refrigerant and discharges high-pressure refrigerant, but since the amount of refrigerant compressed in one revolution of the compressor 3 is constant, the unit The amount of refrigerant compressed per hour changes.

Therefore, if the rotational speed of the compressor 3 is changed, the amount of refrigerant circulating through the refrigerant cycle changes, which changes the amount of heating and heat absorption in the indoor heat exchanger 9, and changes the heating capacity and cooling capacity. I will do it. Therefore, by variable-speed driving the moke 4 that drives the compressor 3, the heating and cooling capacity of this air conditioner can be varied and capacity control according to the load can be achieved. Here, as the compressor 3, a rolling piston type or sliding vane type rotary compressor capable of high speed rotation and high efficiency is used, and the operating torque characteristics with respect to rotational speed when this is used are shown in FIG.

In FIG. 2, the operating torque Tc indicates the average torque with respect to the rotational speed N, and characteristic J is an example thereof. The rotational speeds NL and NH are the limits at which the safe operation of the compressor 3 is maintained, the upper limit rotational speed N8 indicates the maximum allowable rotational speed, and the lower limit rotational speed NL is the limit except when the compressor 3 is started.
Indicates the minimum rotational speed regulated from the viewpoint of oil lubrication of the compression system. Characteristic K is an example of a case where the speed is relatively quickly decelerated from the maximum allowable rotational speed and maximum operating torque. In addition, in an air conditioner, the state of the refrigerant changes depending on the indoor and outdoor air conditions, and there are cases where the operating torque Tc becomes extremely small. This is the area indicated by diagonal lines in Figure 2. Next, as the motor 4 that drives the compressor 3, a three-phase induction motor is used, which is capable of variable speed and high-speed drive, has excellent startability and maintainability, and does not require rotational position detection, etc. By adopting a three-phase variable voltage/variable frequency type in which the output frequency is approximately proportional, the compressor 3 can be adjusted within the range of possible operating torque characteristics of the compressor 3 shown in Fig. 2.
configured to drive.

The operation of the inverter will be explained below.

The speed command circuit 41 includes a thermistor 4 that detects room temperature.
2 is the detection signal and the setting signal from the variable resistor 43 for setting the room temperature, and the error signal ΔE of the two input signals is
is obtained, and a speed command signal Vs is output as shown in FIG.

That is, hysteresis characteristics are provided to regulate the maximum and minimum rotational speeds of the compressor 3 and to prevent frequent on/off operations of the compressor 3 when the air conditioning load is small (light load). In addition, in order to prevent rapid acceleration and deceleration of the compressor 3, a time constant circuit is provided to provide a speed command signal ■S that changes slowly even during operation with hysteresis characteristics.
is configured to emit.

Next, in FIG. 1, the chopper control circuit 22 inputs the speed command signal Vs and obtains a pulse width or time width such that the chopper transistor 17 is turned on within a certain period.

This signal turns on/off the chopper transistor 17 via the transistor drive circuit 21. That is, the pulse width of the chopper transistor 17 is controlled by the speed command signal Vs. As a result, the DC output voltage VA of the forward converter 12 (voltage at point A with respect to point G in FIG. 1)
is chopped and its chopped voltage VB
(Voltage at point B) is choke coil 18, capacitor 18
Due to the smoothing circuit including the curved wheel diode 20, the output voltage becomes approximately direct current. This DC output voltage VO (voltage at point C) is fed back to the chopper control circuit 22 at a certain ratio and compared with the speed command signal S, and the aforementioned pulse width is corrected according to the difference. This operation is repeated, and eventually the DC output voltage V output from the chopper section 16
c has a value proportional to the speed command signal Vs. Commercial power supply 1
1, the DC output voltage V of the forward converter 12
When A changes, the pulse width also changes and becomes a stable value. Note that the DC output voltage ■c is the average value of the chopped DC output voltage ■B. FIG. 4 shows the voltages at points A1, B1, and C in the chopper section 16.
The waveform of O is shown. Next, the inverse conversion control circuit 37 detects the DC output voltage VO of the chopper section 16, and as shown in FIG.
pulse train P.

to occur. This pulse train PO is converted by a logic circuit or the like into six-phase pulse signals P1 to P6 of frequency FO=W, as shown in FIG. 6, and output. The six-phase pulse signals P1 to P6 correspond to six transistors 24 to 29 connected in a three-phase bridge, and turn on and off the respective transistors 24 to 29 through six transistor drive circuits 36. Here, in FIG. 6, the high level period of each of the pulse signals P1 to P6 is a little less than 112 per period, that is, a value smaller than three periods of the pulse train PO by the rest time TR. This is for example to prevent transistors 24 and 25 from being turned on at the same time. Here, the pause time TR is constant regardless of the frequency F, and is selected to be sufficiently larger than the storage time and turn-off time of the transistor 24 and the like. As a result of the above, the six transistors 24 to 29 of the inverse conversion section 23 have the DC output voltage V of the chopper section 16.

is turned on and off at a frequency approximately proportional to , thereby generating a rectangular-wave three-phase AC voltage at points U, V, and W shown in FIG. 1, and this voltage is applied to the motor 4. Points U, V
, W exhibits a waveform as shown in FIG. 7 when power is being supplied to the motor 4. In the inverse converter 23, six diodes 30 to 35 connected in antiparallel to the transistors 24 to 29 are for the flywheel, and when the back electromotive force of the motor 4 is generated by the switching operation of the transistors 24 to 29, the transistors 24 to 29 are connected in antiparallel. ~29 functions to protect. Next, the torque limiting circuit 38 limits the operating torque of the compressor 3 driven by the motor 4 supplied with power from points U, ■, and W of the inverse converter 23 to within the range shown by diagonal lines in FIG. .

Here, if there is no torque limiting circuit 38 and the motor 4 is driven with the voltage and frequency relationship shown in FIG.
The output shaft torque Tm is as shown by the solid line in FIG. In FIG. 8, FCl, fC2, and fO3 are the frequencies of three-phase alternating current supplied to the motor 4. Here frequency Fc=F
cl, and if the operating torque Tc of the compressor 3 is TCl, the rotational speed N of the compressor 3 and motor 4 at that time is N1, and they are stably operated.

Then, when the refrigeration cycle conditions change and the operating torque Tc gradually increases, the operating state of the motor 4 changes to the frequency F.
It changes on the curve of Cl. For example, when the operating torque of the compressor 3 is Tc=TC2, the rotational speed N=N2. However, when the operating torque Tc continues to increase and finally reaches TC3,
When the limit for continued operation is reached (rotational speed N=N3 at this time) and the operating torque Tc becomes even slightly larger than this, the motor 4 and compressor 3 stop rotating at high speed, and the motor 4 becomes locked. I get used to it. Separately from this, the operating torque Tc of the compressor 3 is in a state of TC2 (Fc
=FOl, N=N2), the frequency F is set to lower the refrigeration capacity.

F from FOL. 2, at this time the state of the refrigerant in the refrigeration cycle changes only very slowly, so the characteristics of the operating torque Tc of the compressor 3 with respect to the rotational speed N are as shown in TC4 in Fig. 8. Therefore, the shaft torque Tm that the motor 4 can produce is smaller than the operating torque TC4 required for the compressor 3, so the frequency is F.

While the amount of FCl is decreasing from FCl to FO2, the compressor 3 and motor 4 immediately stop rotating at high speed, and the motor 4 becomes locked. When the above situation occurs, compressor 3,
This will lead to damage to the motor 4 and inverter.

Therefore, as shown in FIG. 1, the torque limiting circuit 38 detects the output voltage c and output current of the chopper section 16 and indirectly determines the operating torque Tc of the compressor 3.
A signal is issued to the chopper control circuit 22 and the inverse conversion control circuit 37, and when the operating torque Tc exceeds a predetermined value, the DC output voltage becomes the voltage (2) shown in FIG.

By correcting the relationship between and frequency F, the inverter output voltage,
It works to change the relationship between output frequencies and to decrease the frequency itself in response to an increase in operating torque Tc. FIG. 9 shows the shaft torque characteristics of the motor 4 obtained in this manner.

In FIG. 9, ■SH, VSM, and ■SL are three different values of the speed command signal Va, of which ■SH is the maximum value and VSL is the minimum value. In Fig. 9, the speed command signal ■S is VSH
When the operating torque Tc=Tcl of the compressor 3, the rotation speed N=N1'', and as the operating torque Tc increases, the frequency FO is lowered and the rotation is increased even though the speed command signal VS=VSH is constant. The direction is to decrease the speed N, and T
When c=Tc2, N=N2''.

When the operating torque Tc further increases and reaches the characteristic TC3, the frequency Fc is further reduced to continue stable operation at N=N3''. However, as a result, the operating torque Tc of the compressor 3 becomes The operating torque Tc of the compressor 3 is limited to an almost constant value due to a decrease in , for example VS=
When setting Vs=■9 from VSH, the operating torque Tc changes with the characteristic of TC4'', and the rotational speed becomes N4'',
Thereafter, as the state of the refrigerant stabilizes, the operating torque Tm of the motor 3 moves on a curve indicated by VSM, and reaches stable operation. Therefore, due to the operation of the torque limiting circuit 38, the range of possible operating torque Tc of the compressor 3 becomes the shaded area in FIG. 9, which is the range of possible operating torque Tc of the compressor 3 shown in FIG. Almost all of the above are met.

In addition, the compressor 3 and motor 4 do not have to momentarily stop from high-speed rotation, or the motor 4 does not have to remain in a locked state, and at the same time, the inverter can be protected from overcurrent, thereby improving the operation of the equipment. Stability, equipment protection, and lifespan can be improved. Further, the starting torque of the motor 4 exhibits a large value, and the compressor 3 can be restarted relatively easily and quickly after being stopped, and has excellent characteristics in terms of operability. FIG. 10 shows the refrigerating capacity Q (Kcal/
This is an example of the characteristic h). N is the rotational speed of the compressor 3, which indicates that the refrigerating capacity Q can be varied by driving the motor 4 at variable speed using an inverter to change the rotational speed N of the compressor 3. As described above, the heat source device according to the present invention is capable of varying or controlling the refrigeration capacity Q by changing the rotational speed N of the compressor 3. Since the refrigeration capacity can be controlled or adjusted not only by capacity control but also by automatic control or manual adjustment of other controlled objects, it is natural that it can be applied to control means for equipment having any refrigeration cycle.

In addition, in the embodiment shown in FIG.
As the input signal of 8, the DC output voltage of the chopper section 16 is
c and output current are input, but a rotation speed detector is provided to detect the output voltage and output frequency of the inverter, or the rotation speed of the compressor 3, and this is used to detect the operating torque of the compressor 3. etc. can be selected as appropriate.

In addition, as a power source for the inverter, a three-phase AC commercial power source 11
However, it is also possible to use a single-phase commercial power source, and in this case, the diode stack 13 of the forward conversion section 12 may be replaced with a single-phase bridge.

Furthermore, if a DC power source already exists, it is obvious that the forward converter 12 is unnecessary. In addition, the chopper transistor 17 and transistors 24 to 29 used in the inverter are of the NPN type in the embodiment, but are PNP.
Alternatively, field effect transistors FET or gate turn-off thyristors GT may be used.
It is also possible to use semiconductor switching elements such as O.

As is clear from the above embodiments, the heat source device of the present invention includes:
A refrigerant circuit is formed by sequentially connecting a compressor for refrigerant compression, a heat source side heat exchanger, a pressure reducing device, a user side heat exchanger, etc., and rectifies commercial power as a power source for a motor that drives the compressor. Forward conversion section, chopper section that controls DC voltage,
The compressor is equipped with an inverter including an inverse converter that converts the DC voltage into a three-phase AC voltage, a speed command circuit that sets the rotational speed of the motor, and a torque limiting circuit that limits the operating torque of the compressor. By controlling the rotation speed of the machine, the refrigeration capacity can be varied.By using an inverter to drive the motor and compressor at variable speeds and varying or controlling the refrigeration capacity, the refrigeration capacity can be adjusted according to the load. This improves controllability, comfort, and saves energy.Also, by driving the motor and compressor at high speed, the compression system can be made smaller and lighter, making it more economical and conserving resources. In addition, the rotational speed and torque of the motor and compressor can be controlled within a predetermined range by the operation of the speed command circuit and torque limiting circuit.
Able to measure equipment safety.

That is, it is possible to prevent overload operation, avoid wear and seizure of bearings due to extremely high-speed or low-speed operation, prevent frequent on/off operations, and limit overcurrent in the inverter.

[Brief explanation of the drawing]

Fig. 1 is an electric circuit diagram of a heat source device showing an embodiment of the present invention, Fig. 2 is a diagram explaining the torque characteristics of the compressor of the same device, Fig. 3 is a characteristic diagram of the speed specifying circuit of the same device, and Fig. 4 is a diagram of the torque characteristics of the compressor of the same device. The figure is a waveform explanatory diagram showing the operation of the chopper section of the same device, Figures 5 and 6 are explanatory diagrams of the inverse conversion control circuit of the same device, and Figure 7 is a three-phase AC output from the inverse conversion section of the same device. FIGS. 8 and 9 are characteristic diagrams of the shaft torque of the motor in explaining the operation of the torque limiting circuit of the same apparatus, and FIG. 10 is a characteristic diagram of the refrigerating capacity of the same apparatus. 1...Outdoor unit, 2...Indoor unit, 3...Compressor, 4...Motor, 5...
... Four-way valve, 6 ... Outdoor heat exchanger (heat source side heat exchanger), 8 ... Gear pillar tube (pressure reducing device), 9 ... Indoor heat Exchanger (utilization side heat exchanger), 12... forward conversion section, 16... chopper section, 17... transistor for chopper, 18...
... Choke coil (smoothing circuit), 19 ... Capacitor (smoothing circuit), 21 ... Transistor drive circuit, 22 ... Chopper control circuit, 23 ...
...inverse conversion section, 24, 25, 26, 27, 28, 2
9...Transistor, 30, 31, 32, 33
, 34, 35... flywheel diode,
37... Reverse conversion control circuit, 38... Torque limit circuit, 41... Speed command circuit.

Claims (1)

[Claims] 1. A compressor for compressing refrigerant, a heat source side heat exchanger, a pressure reducing device,
A refrigerant circuit is formed by sequentially connecting heat exchangers on the user side, and a speed command circuit that outputs a speed command signal for setting the rotational speed of the motor as a power source for the motor that drives the compressor, and a commercial power supply. a forward conversion section that rectifies, a chopper section that converts the DC voltage output from the forward conversion section into a DC output voltage corresponding to the speed command signal, and a DC output voltage generated by the chopper section that engages the voltage value thereof. The operating torque of the motor is detected by an inverse conversion unit that converts the frequency into a three-phase AC voltage and outputs it to the motor, and a current detector that detects the output current of the chopper unit. and a torque limiting circuit that reduces the output frequency of the inverse converter by emitting an output signal to at least one of the chopper section and the inverse converter. 2. The chopper section is driven by a chopper transistor that chops the DC voltage from the forward conversion section, a smoothing circuit that smoothes the pulsed voltage output from the chopper transistor and generates a DC output voltage, and drives the chopper transistor. A patent consisting of a transistor drive circuit, a chopper control circuit that inputs a speed command signal from a speed command circuit and a voltage proportional to the DC output voltage, and outputs a signal with a pulse width corresponding to the difference to the transistor drive circuit. A heat source device according to claim 1. 3. The inverse conversion section includes six transistors and six flywheel diodes connected in a three-phase bridge to the DC output voltage output from the chopper section, a transistor drive circuit corresponding to each of the six transistors, and the DC output voltage output from the chopper section. and an inverse conversion control circuit that generates a six-phase pulse signal with a frequency that matches the output voltage and outputs it to each of the six transistor drive circuits, and a three-phase AC voltage is generated from each connection point of the three-phase bridge. A heat source device according to claim 1 which outputs. 4. Input the detection signal from the temperature detection means for detecting the temperature of the controlled object and the setting signal from the temperature setting means for setting the temperature of the controlled object into the speed index cooling circuit, and calculate the error signal of the two input signals. 2. The heat source device according to claim 1, further comprising means for converting the rotational speed of the motor into a speed command signal that is within a predetermined range or zero.