JPH0113977Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to an air conditioner equipped with a heat pump type refrigeration cycle having a variable capacity compressor.

[Technical background of the invention]

A conventional air conditioner of this type is shown in FIG. In FIG. 1, reference numeral 1 denotes a variable capacity compressor, which is a parallel body consisting of the compressor 1, a four-way valve 2, an outdoor heat exchanger 3, a thermoelectric expansion valve 4 and a check valve 5, and a thermoelectric expansion valve 6 and a check valve 5 in parallel. A parallel body with the stop valve 7, an indoor heat exchanger 8, etc. are sequentially connected to form a heat pump type refrigeration cycle. In this manner, during cooling operation, the refrigerant flows in the direction of the solid arrow shown in the drawing, and during heating operation, the four-way valve 2 is switched, so that the refrigerant flows in the direction of the broken arrow shown in the drawing. An outdoor fan 9 is disposed near the outdoor heat exchanger 3, and an indoor fan 10 is disposed near the indoor heat exchanger 8. The compressor 1 is a frequency-controlled variable capacity compressor, and the capacity changes according to the frequency of an alternating current voltage supplied from an inverter (not shown). In other words, as shown in Figure 2, the capacity is A (frequency 75Hz), B (frequency 65Hz), and C (frequency
55Hz), D (frequency 45Hz), E (frequency 35Hz), and F (frequency 25Hz). Also,
Corresponding to this change in capacity, the speed (airflow amount) of the fan motor 9M of the indoor fan 9 changes from H (high speed), M (medium speed), and L (low speed).

The thermoelectric expansion valves 4 and 6 each have a heat-sensitive cylinder (not shown) that senses the temperature of the refrigerant, converts the sensed heat into pressure, and mechanically changes the valve body according to the pressure. During cooling operation, the opening degree changes according to the degree of superheating of the indoor heat exchanger 8 that acts as an evaporator, and during heating operation, the opening degree changes according to the degree of superheating of the outdoor heat exchanger 3 that acts as an evaporator. I'm starting to do that. That is, refrigerant flow rate control is performed in response to load fluctuations.

[Problems with background technology]

By the way, in such an air conditioner, the thermoelectric expansion valve converts the heat sensed by the heat-sensitive cylinder into pressure as described above, and the valve body is mechanically varied by the pressure, so the response is There is a problem in that the refrigerant flow rate cannot be quickly and optimally controlled in response to changes in the capacity of the variable capacity compressor based on load fluctuations. In particular, since the gas balance is delayed at the start of operation, a very large load that is not commensurate with the torque is placed on the compressor.
Additionally, thermoelectric expansion valves can only handle refrigerant flow in one direction, so two are required, one for cooling and one for heating, and along with this, two check valves are also required. This results in complication of the refrigeration cycle and increase in cost.

[Purpose of invention]

This invention was made in view of the above circumstances, and its purpose is to perform quick and optimal refrigerant flow control that corresponds to the operation control of a variable capacity compressor based on load fluctuations. Furthermore, we provide an air conditioner that provides sufficient safety protection for the compressor, prevents frost from freezing on the indoor heat exchanger during cooling, and also simplifies the refrigeration cycle and reduces costs. It's about doing.

[Summary of the idea]

This idea is an air conditioner equipped with a heat pump type refrigeration cycle having a variable capacity compressor. means for controlling the capacity of the compressor according to the load for a certain period of time from the start of operation and maintaining the electric expansion valve in a fully open state; If the refrigerant temperature discharged from the compressor is within a set range, the capacity of the compressor is controlled according to the load,
and a means for keeping the opening degree of the electric expansion valve unchanged, and a means for keeping the capacity of the compressor unchanged if the discharge refrigerant temperature of the compressor is not within a set range after a certain period of time from the start of operation; means for controlling the opening degree of the electric expansion valve so that the discharge refrigerant temperature falls within a set range, and changing the set range according to the refrigerant temperature between the indoor heat exchanger and the four-way valve during cooling operation; It is provided with a means for causing the

[Example of idea]

An embodiment of this invention will be described below with reference to the drawings. In this case, the same parts as in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted.

As shown in FIG. 3, an electric expansion valve 20 is connected between the outdoor heat exchanger 3 and the indoor heat exchanger 8. As shown in FIG. 4, this electric expansion valve 20 includes a stator 21 that is excited by a drive pulse signal supplied from the outside, a rotor 22 that is rotated by a magnetic field generated in this stator 21, and a rotor 22 that is rotated by a magnetic field generated in this stator 21. A needle 24 is connected through a screw/shaft 23 to the refrigerant pipes 25 and 2, and the opening degree of the orifice changes depending on the vertical movement of the needle 24.
6, etc., and is a so-called dual flow type that can handle the flow of refrigerant in both directions, and the opening degree changes sequentially depending on the supplied drive pulse as shown in Figure 5. However, the refrigerant flow rate can be controlled linearly.

Therefore, a refrigerant temperature sensor (thermistor) 31 is attached to the discharge side refrigerant pipe of the variable capacity compressor 1, and a refrigerant temperature sensor (thermistor) is installed to the refrigerant pipe between the indoor heat exchanger 8 and the four-way valve 2. 32 is attached.

FIG. 6 shows the control circuit. First, X is a circuit on the indoor unit side, and Y is a circuit on the outdoor unit side. The indoor unit side circuit
The main control unit 41 is connected to the R and T phases of a three-phase AC power supply 46 via crossover wires 44, 45 and the outdoor unit side circuit Y, and the output of the power supply 46 is The relay contact 4 of the main control section 41 is consumed at the same time as the main control section 41.
Indoor fan motor 10M via 7, 48, 49
It is also supplied to A driving operation section 50 is connected to the main control section 41 .

On the other hand, the outdoor unit side circuit Y includes the control section 51,
The power supply 46 is connected to the electric expansion valve 20, the high pressure switch 52, and the relay contacts 53 and 54 of the control unit 51, to which drive pulses are supplied from the control unit 51, respectively.
The four-way valve 2 and the outdoor fan motor 9M connected to the R and T phases of , S, and T phases, an inverter drive circuit 57 that drives the inverter circuit 56 in accordance with commands from the control unit 51, and a compressor motor 1M to which the output of the inverter circuit 56 is supplied. The control section 51 is configured with a crossover wire 5.
8 to the main control section 41 of the indoor unit side circuit
connected to. Here, the inverter circuit 56
converts the frequency of AC power supplied from the power source 46 into a predetermined frequency by operating a switching element responsive to the output of an inverter drive circuit 57, and supplies the frequency to the compressor motor 1M. Thus, the rotation speed of the compressor motor 1M changes depending on the frequency of the supplied AC power, and the capacity of the variable capacity compressor 1 is thereby determined.

Next, in the above configuration, FIGS. 7 and 8
The operation will be explained with reference to FIG. 9 and FIG.

First, when the operation is stopped, the electric expansion valve 2
0 is fully opened by the drive pulse supplied in advance,
Continue in that fully open state.

Now, when the cooling operation is started, a compression function force setting command is supplied from the main control section 41 to the control section 51 according to the difference between the indoor temperature detected by the indoor temperature sensor 42 and the set temperature, and the control section By the actions of the inverter circuit 56 and the inverter drive circuit 57 based on the command 51, the capacity of the compressor 1 changes appropriately within the range of A to F as shown in FIG. Along with this, the amount of air blown by the indoor fan 10 is also changed to H, M, and L as appropriate under the control of the main control unit 41. This state continues for t ₁ hour from the start of operation.

Therefore, after t ₁ time has elapsed, the control unit 51 adjusts the discharge refrigerant temperature Ta°C of the compressor 1 detected by the refrigerant temperature sensor 31 and the outflow refrigerant temperature Tc of the indoor heat exchanger 8 detected by the refrigerant temperature sensor 32. The following controls are performed depending on the temperature. First, the discharge refrigerant temperature Ta
is set value Tm≦Ta≦set value To or Tm−10≦
If it is within the range of Ta≦To−10, the capacity of the compressor 1 is changed according to the indoor temperature, and if it is not within the range, the capacity of the compressor 1 is maintained in the previous state, and this control is Continue _{in 2} minute increments.
On the other hand, if the outflow refrigerant temperature Tc is equal to or higher than the set value Tc', a drive pulse is supplied to the electric expansion valve 20 in order to bring the discharge refrigerant temperature Ta into the range Tm≦Ta≦To, and the electric expansion valve 20 Change the opening degree. This is done every t ₂ minutes. However, in this case, if the discharge refrigerant temperature Ta is Ta≦Tm (Tm
−Ta)×Δn number of throttle direction driving pulses are generated to throttle the opening degree of the electric expansion valve 20. Discharge refrigerant temperature
If Ta is Ta≧To, an opening direction drive pulse of (Ta−To)×Δn is generated to increase the opening degree of the electric expansion valve 20. Note that Δn is the number of drive pulses required to raise or lower the discharge refrigerant temperature Ta by 1°C.

In addition, if the outflow refrigerant temperature Tc is below the set value Tc', the discharge refrigerant temperature Ta is increased to prevent frost from freezing in the indoor heat exchanger 8, which acts as an evaporator.
A drive pulse is supplied to the electric expansion valve 20 to change the opening degree of the electric expansion valve 20 in order to reach the range of Tm-10≦Ta≦To-10. This is also done every t ₂ minutes. However, in this case, if the discharge refrigerant temperature Ta is Ta≦Tm−10, the opening degree of the electric expansion valve 20 is throttled by emitting a number of throttle direction drive pulses equal to (Tm−10−current Ta)×Δn. Discharge refrigerant temperature
If Ta is Ta≧To−10 (currently Ta−To+
10) × Δn drive pulses are generated to increase the opening degree of the electric expansion valve 20.

Next, the case of heating operation will be described. For t ₁ minute from the start of operation, the capacity of the compressor 1 is changed according to the room temperature as in the case of cooling, and the electric expansion valve 20 is kept fully open.

When ₁ minute has elapsed, the control unit 51 performs the next control using only the discharge refrigerant temperature Ta detected by the refrigerant temperature sensor 31. First, the discharge refrigerant temperature Ta is
If it is within the range of Tm≦Ta≦To, the capacity of the compressor 1 is changed according to the indoor temperature, and if it is not within the range, the capacity of the compressor 1 is maintained in the previous state, and this control is changed to t. Continue for ₂ minutes every ₂ minutes. This is the same as when cooling. On the other hand, when t ₁ minute has passed since the start of operation, (Tm - current Ta) ×
The opening degree of the electric expansion valve 20 is reduced by emitting Δn number of aperture direction drive pulses. Thereafter, every t ₂ minutes, if the discharge refrigerant temperature Ta is Ta≦Tm, a number of throttling direction drive pulses (Tm - current Ta) x Δn are generated to throttle the opening of the electric expansion valve 20, and the discharge If the refrigerant temperature Ta is Ta≧To (current Ta−To) × Δn
The electric expansion valve 2
Increase the opening degree of 0.

In this way, the electric expansion valve 20 is of a dual flow type and has a quick response that changes its opening depending on the supplied drive pulse signal, and the opening of the electric expansion valve 20 is controlled by changing the opening of the compressor 1. Since the control is performed based on the discharge refrigerant temperature Ta, it is possible to quickly and optimally control the refrigerant flow rate in response to changes in the capacity of the variable capacity compressor 1 based on load fluctuations. In other words, it is possible to successfully balance variable capacity and stable cycles. In particular, since the electric expansion valve 20 is kept fully open for a certain period of time after the start of operation, the gas balance can be achieved quickly, thereby reducing the load on the compressor 1. Safety protection is possible. Furthermore, during cooling, the outflow refrigerant temperature Tc of the indoor heat exchanger 8 that acts as an evaporator is detected, and the setting range of the discharge refrigerant temperature control is changed according to the outflow refrigerant temperature Tc. When Tc is greater than the set value Tc′, the setting range is Tm≦Ta≦To, and the set value
Below Tc′, lower the setting range by 10°C and set Tm−10≦Ta.
Since ≦To−10 is set, freezing of frost in the indoor heat exchanger 8 can be reliably prevented. Also,
Since the electrically operated expansion valve 20 is a twin flow type, there is no need to use two unlike thermoelectric expansion valves, and accordingly, a check valve is also not required, thereby simplifying the refrigeration cycle and reducing costs.

It should be noted that this invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made without changing the gist.

[Effect of idea]

As described above, according to this invention, it is possible to perform quick and optimal refrigerant flow control that corresponds to the operation control of a variable capacity compressor based on load fluctuations.
Furthermore, we provide an air conditioner that provides sufficient safety protection for the compressor, prevents frost from freezing on the indoor heat exchanger during cooling, and also simplifies the refrigeration cycle and reduces costs. can.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a conventional heat pump type refrigeration cycle, Figure 2 is a diagram showing changes in capacity and air flow in Figure 1, and Figure 3 is a block diagram of a heat pump type refrigeration cycle in an embodiment of this invention. , FIG. 4 is a schematic configuration diagram of the electric expansion valve in the same embodiment, FIG. 5 is an operating characteristic diagram of FIG. 4, FIG. 6 is a configuration diagram of the control circuit in the same embodiment, and FIG.
The figure is a diagram showing changes in discharge refrigerant temperature for explaining the operation of the same embodiment, and FIGS. 8 and 9 are flowcharts for explaining the operation of the same embodiment, respectively. 1... Capacity variable compression, 2... Four-way valve, 3... Outdoor heat exchanger, 8... Indoor heat exchanger, 20... Electric expansion valve, 31, 32... Refrigerant temperature sensor, X...
...Indoor unit side control circuit, Y...Outdoor unit side control circuit, 41...Main control section, 51...Control section.

Claims (1)

[Scope of utility model registration request] A heat pump type consisting of a variable capacity compressor, a four-way valve, an outdoor heat exchanger, a dual-flow electric expansion valve whose opening degree changes according to the supplied drive pulse signal, an indoor heat exchanger, etc., all connected in sequence. In an air conditioner equipped with a refrigeration cycle, a means for detecting a discharge refrigerant temperature, and a means for detecting a refrigerant temperature between an indoor heat exchanger and a four-way valve, the electrically operated means for maintaining the expansion valve in a fully open state and controlling the capacity of the compressor according to the load; and a means for controlling the capacity of the compressor according to the load; Means for controlling the capacity of the compressor according to the load while keeping the opening degree of the valve unchanged; and a means for controlling the capacity of the compressor according to the load; means for controlling the opening degree of the electric expansion valve so that the refrigerant temperature falls within a set range and keeping the capacity of the compressor unchanged; and a refrigerant between the indoor heat exchanger and the four-way valve during cooling operation. An air conditioner comprising: a control device having means for lowering a set range of refrigerant temperature discharged from the compressor by a predetermined value when the temperature is below a set value.