JPH01312358A - Air conditioner - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to control of an expansion valve of an air-cooled heat pump type air conditioner.

[Conventional technology]

- The conventional device is disclosed in Japanese Patent Application Laid-Open No. 62-213655. As described in the above issue, the expansion valve is controlled to open and close so that the difference between the discharge gas temperature of the compressor and the high-pressure side condensation temperature is constant, and the above temperature is maintained at the outlet of the evaporator so that a moist state can be maintained at all times. The difference was set, and the optimal value of the degree of superheating was determined for each condensation temperature. Further, in Japanese Patent Application Laid-Open No. 62-218655, the setting value of the degree of superheating is determined separately for the operating frequency, but no special consideration is given to a setting method that takes both factors into consideration at the same time.

[Problem to be solved by the invention]

In the above conventional technology, since the compressor frequency is variable, when comparing the speed at which the frequency changes and the speed at which the expansion valve is controlled to the target degree of superheating, the speed at which the frequency changes is large. It is difficult to stabilize the refrigeration cycle if the setting value is set for the high pressure side, and if the setting value is set for the condensing temperature on the high pressure side, the pressure on the low pressure side is high when the frequency is low. Even if the setting value is such that the refrigerant at the heat exchanger outlet is originally wet, it may overheat, and if the frequency is high, the refrigerant at the heat exchanger outlet may become excessively wet. There was a problem with that.

An object of the present invention is to provide a control device that can control an expansion valve so as to form a highly efficient and stable refrigeration cycle even when the temperature condition of a heat exchanger or the rotation speed of a compressor changes. be.

[Means to solve the problem]

The above purpose is to set the set superheat degree in relation to both the stable discharge side of the refrigeration cycle, the humidity temperature, the high efficiency compressor operating frequency on the refrigeration cycle, and to adjust the expansion valve to approach the set value. This is achieved by controlling the opening degree μs.

[Effect]

First, set the degree of superheat on the compressor discharge side relative to the condensing temperature,
A target degree of superheat is determined by correcting the set degree of superheat according to the compressor operating frequency at that time, and the expansion valve is operated so as to bring the detected degree of superheat closer to this. As a result, the degree of superheating is controlled under all conditions so that the heat exchanger exit is in a wet state, and the refrigeration cycle can be operated stably and efficiently.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 1 is a refrigeration cycle system diagram in which the present invention is implemented. The refrigeration cycle consists of compressor 1, condensation 62, and expansion valve 3.
, evaporators 4 are successively connected, and the refrigerant circulates through the above-mentioned route and undergoes repeated state changes. The opening/closing operation of the expansion valve 8 is performed by detecting the discharge gas temperature Td of the compressor 1 by the detector 7 and the condensation temperature Tc of the discharge gas by the detector 68.
The degree of opening is electrically controlled by a device, and the control device 6 controls the supply of power to drive the compressor 1 to determine the operating frequency. FIGS. 2, 3, and 3 are Mollier diagrams showing changes in the state of the refrigeration cycle, and the following description will be made with reference to these diagrams. The high-temperature gas refrigerant 0 compressed in the compression 41 is cooled and liquefied in the condenser 2, and then the pressure is reduced by the expansion valve 3 7'1. (g) The air flows into the evaporator 4, where it is evaporated while absorbing heat from the outside air, and then sucked into the compressor 1 again.Here, the operation of the expansion valve will be explained.

The discharge gas temperature Td and condensation temperature Tc of the compressor 1 are detected by respective temperature detectors 7.8 and input to the control device 6. The control device 6 includes a condensing section (Tc1.
Tc2...Tcn), the target value of superheat degree is (
SHl, SH2...5Hn) are set. Also, for the compressor frequency (Hx1+Hz...Hzn), the correction value (Δ8H1゜ΔS
H2...Δ5Hn) is set, and the control device 6 calculates the degree of superheat (Td - Tc) derived from the detected temperature.
ΔT is the target value of superheat degree (SH1) corresponding to the above condensation temperature.
The opening degree of the expansion valve 3 is increased by 1tjl to bring it closer to 1Δ5Hn).
J groan. The target value Vi of the degree of superheating is set so that the refrigerant at the outlet of the evaporator remains slightly wet even when operating conditions such as the temperature condition of the heat exchanger and the frequency of the compressor change. In other words, in Fig. 3, the Mollier diagram at the rated frequency is shown as a solid line, but here, at SHn set by the condensing temperature, the degree of superheating at the evaporator outlet is small, but
If the frequency becomes low, if the setting value is SHn, the suction pressure is high and the refrigerant at the evaporator outlet is overheated.
This means that the capacity of the evaporator is not fully utilized. On the other hand, if the frequency is high, the refrigerant becomes excessively wet at the evaporator outlet, resulting in damage to the bearings of the compressor 1. Therefore, a correction value ΔSHn is provided for the frequency, which lowers the target value of the degree of superheat when the frequency is low, and increases the target value of the degree of superheat when the frequency is high.

In a steady state of operation, if the evaporator 4 has a small amount of heat and the refrigeration cycle is operated as shown by the solid line in Figure 2, the degree of superheat ΔT on the discharge side of the compressor 1 in this case is It is smaller than the set value SH2 of the degree of superheating with respect to the temperature TC2. At this time, the temperature detected by the discharge gas temperature detector 7 and the condensing temperature 8 is input to the control device 6, and the control device 6 adds a correction ΔSH2 to the frequency until it reaches the target value (SH2+Δ8H2). Move the expansion valve in the throttle direction to bring it closer. Conversely, if the degree of superheat is greater than the target value, the expansion valve 3 is opened and control is performed to bring it closer to the target value.

〔Effect of the invention〕

According to the present invention, it is possible to finely control the degree of superheating on the discharge side of the compressor in response to changes in the load condition of the heat exchanger 3 and the rotational speed of the compressor, thereby efficiently increasing the capacity of the compressor and heat exchanger. Since it can be maintained at a high level, the performance of the air conditioner can be improved.

Furthermore, when the rotational speed of an inverter-driven compressor is increased, the temperature is likely to rise due to the high load. Therefore, in order to reduce the discharge gas temperature, the humidity on the suction side is increased, which has the effect of reducing the rise in motor coil temperature and improving the reliability of the compressor.

[Brief explanation of the drawing]

Fig. 1 is a refrigeration cycle diagram of an embodiment of the present invention, Fig. 2 is a refrigeration cycle diagram of an embodiment of the invention, and Fig. 8 is a refrigeration cycle diagram of an embodiment of the invention. ! ! FIG. 4 is a Mollier diagram corresponding to the rotation frequency. 1... Compressor 2... Condenser 3... Expansion valve... Evaporator 5... Control panel 7... Discharged gas detector 8... Condensing temperature regulator. enthalpy 1
Sita t and -3 Yanagi ff6 raw control method≠shi

Claims (1)

[Claims] Compressor with variable operating frequency, four-way valve, outdoor heat exchanger,
In an air conditioner that connects an expansion valve and an indoor heat exchanger via piping to form a refrigeration cycle, and is equipped with means for detecting the discharge gas temperature and condensation temperature of a compressor, the detection is performed based on the discharge gas temperature and condensation temperature. The degree of superheating of the discharged gas that corresponds to the condensation temperature of a plurality of discharged gases set in advance is set to be small when the frequency is low, and to be large when the frequency is high, with respect to the operating frequency of the compressor. An air conditioner characterized in that the degree of superheat is set by correcting the degree of superheat, and the opening degree of an expansion valve is controlled so as to maintain the set degree of superheat.