JPS61153350A - 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 [Industrial Application Field] The present invention relates to air conditioners, and more particularly to an air conditioner in which the driving frequency of a compressor, etc. can be controlled in accordance with a refrigerant temperature signal of a refrigerant circuit.

[Prior Art] Fig. 9 is a refrigerant circuit diagram showing a conventional air conditioner disclosed in, for example, Japanese Unexamined Patent Publication No. 59-77268. The valve (3) is an outdoor heat exchanger, (4) is an electric expansion valve, and (5) is an indoor heat exchanger. These are connected by refrigerant piping (6) to form the refrigerant circuit (7) of the heat pump refrigeration cycle. ). (6
a) to (6f) show each part of the refrigerant piping. (8a)
(8b) is the refrigerant pipe (6c) on both sides of the expansion valve (4)
A capillary tube forming a bypass circuit from (6d) to the suction pipe (6f) of the compressor (1), and (9) a refrigerant temperature detector for detecting the suction refrigerant temperature provided in the suction pipe (6f).

(lO) is a refrigerant temperature detector for detecting the suction pressure saturation temperature, which is provided at the outlet (8c) of the capillary tube (8a) (8b).

Next, we will explain its operation. During cooling operation, the four-way valve (2) is in the position shown, and the high-temperature, high-pressure gas refrigerant discharged from the compressor 1 (1) passes through the pipe (6a), the four-way valve (2), and the pipe (6b) to the outside. It enters the heat exchanger (3), where it condenses to become a liquid refrigerant and reaches the pipe (6C).

Most of the liquid refrigerant is depressurized by the electric expansion valve (4) and transferred to the piping (
6d) into the indoor heat exchanger (5).

By removing heat from the room, it evaporates and becomes a low-temperature, low-pressure gas refrigerant.
f) and is sucked into the compressor (1). On the other hand, some of the liquid refrigerant passes through the bypass capillary (8a) from the refrigerant pipe (6c) and is discharged to the suction pipe (6f) in an unevaporated state to the compressor (
Return to 1). Here, the refrigerant temperature after evaporation in the suction pipe (6f) is detected by the refrigerant temperature detector (9), and the temperature of the refrigerant after evaporation in the suction pipe (6f) is detected, and
After passing through the refrigerant at its outlet (8C), a refrigerant temperature detector (10) detects the saturation temperature corresponding to the suction (evaporation) pressure, that is, the saturated evaporation temperature. The amount of superheat is detected from the difference in temperature signals from these refrigerant temperature detectors (9) and (10), and the control device controls the electric expansion valve (4) so that the amount of superheat falls within a predetermined range. do. During heating, the pressure on the refrigerant pipe (6d) is high, so the bypass refrigerant passes through the capillary tube (8b) to the compressor (1).
Return to

[Problems to be Solved by the Invention] In the conventional air conditioner described above, it is easy to detect the saturation temperature at the evaporation pressure, that is, the saturated evaporation temperature, but it is difficult to detect the saturation temperature at the condensation pressure, that is, the saturated condensation temperature. Therefore, it has the disadvantage that it is not suitable for more advanced control including compressor rotation speed control. In order to detect the saturated condensation temperature, it is necessary to detect the temperature of the internal and external heat exchangers or to attach a pressure sensor, both of which are expensive and complicated.

This invention was made in order to solve the above problems, and it is an object of the present invention to effectively utilize the oil recovery circuit of an oil separator to detect the saturated condensation temperature, and to provide an air conditioner capable of more advanced control. It is an object.

[Means for Solving the Problems] The air conditioner according to the present invention includes an inlet pipe and a capillary tube connected in series between an oil separator provided in the discharge pipe of the compressor and the suction pipe of the compressor. An oil recovery circuit consisting of an oil recovery circuit and an outlet pipe is provided, and the inlet pipe is provided with a heat exchange section for cooling the refrigerant therein to a two-phase region, and a refrigerant temperature detector is attached to the inlet side of the capillary tube, and this temperature detector The power supply frequency for energizing the compressor is controlled according to the refrigerant temperature signal from the compressor.

[Function] The air conditioner according to the present invention collects oil from the oil return port of the oil separator in the discharge pipe of the compressor, as well as a part of the gas refrigerant in the high-temperature, high-pressure superheated region through the oil recovery circuit. The refrigerant temperature is cooled down to a two-phase region while the pressure is kept almost constant through heat exchange in the inlet pipe, and the refrigerant temperature is measured at the discharge (condensing) pressure by the refrigerant temperature sensor in this state. Detect saturation temperature (saturated condensation temperature). The refrigerant in the two-phase region at the discharge pressure is reduced in pressure by the second capillary to a two-phase region corresponding to the suction pressure, that is, the evaporation pressure, and is returned to the suction pipe through the outlet pipe. Then, the control device optimally controls the energizing power frequency of the compressor in accordance with the suction refrigerant temperature signal from the temperature signal corresponding to the saturated condensation temperature from the refrigerant temperature detector.

[Example code] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a refrigerant circuit diagram showing one embodiment of the present invention.

In the figure, (1) to (7) and (9) indicate the same or corresponding parts as the same reference numerals in FIG. (11) is an oil separator installed in the discharge pipe (6a) of the compressor (1).

Compressor (1), four-way valve (2), outdoor heat exchanger (3), indoor heat exchanger (5), expansion valve (4) and refrigerant piping (6)
are connected to form a heat pump refrigerant circuit (7). The oil separator (11) captures the refrigerating machine oil discharged from the compressor (1) together with the refrigerant into the discharge pipe (6a) and returns it to the suction pipe (6f). (12) is the oil return port (lla) of this oil separator (11) and the suction pipe (6).
f) an intervening oil recovery circuit, the details of which are shown in FIG.

Figure 2 is a configuration diagram showing an example of the oil recovery circuit (!2) in Figure 1. In the figure, (13) indicates that its inlet (13a) is connected to the oil return port (lla) of the oil separator in Figure 1. A series of entrances, (1
4) is a capillary tube connected to the outlet (13b) of this inlet (13), and (15) is a capillary tube whose inlet (15b) is connected to the capillary tube (15).
4).

The outlet (15a) is an outlet pipe connected to the suction pipe (6f) in FIG. These inlet pipes (13) + outlet pipes (15)
The inner diameter of the capillary tube (14) is made larger than the inner diameter of the capillary tube (14), and the inlet tube (13) and the outlet tube (15) are placed in parallel contact with each other by a predetermined amount and are fixed by brazing to form a contact heat exchange section. (16). (17) is a capillary tube (14
) This is a refrigerant temperature detector installed near the inlet to detect the saturated condensation temperature.

Next, its operation will be explained 6. For example, in the case of cooling operation, most of the high temperature and high pressure gas refrigerant is discharged from the compressor (1) and the oil separator (11) separates the refrigerating machine oil from the discharge pipe (6a
), the four-way valve (2), and the outdoor heat exchanger (
3), where it condenses to become a liquid refrigerant and reaches the pipe (6c). Subsequently, the pressure is reduced by the expansion valve (4), and the refrigerant passes through the pipe (6d) and enters the indoor heat exchanger (5), where the refrigerant is evaporated to produce a cooling effect.
2), enters the suction pipe (6f), and returns to the compressor (1), forming a heat pump type refrigeration cycle. On the other hand, a part of the discharged refrigerant is sent to the oil return port (lla) of the oil separator (11).
A flow is formed in which the oil and the refrigerating machine oil separated from the oil pass through the oil recovery circuit (12) and enter the suction pipe (6f).
At this time, the high-temperature, high-pressure superheated gas refrigerant passes through the inlet pipe (13) and is cooled by heat exchange with the low-temperature refrigerant whose pressure is reduced in one capillary (14) in the contact heat exchange section (16). 13) becomes a high-pressure two-phase refrigerant at the outlet (13b). This high-pressure two-phase refrigerant becomes a low-pressure two-phase refrigerant through the capillary tube (14), enters the outlet pipe (15), and enters the outlet pipe (15).
5), it is heated by heat exchange in the contact heat exchange section (16), and becomes a low-pressure superheated gas refrigerant with almost the same enthalpy as the refrigerant at the inlet (13a) of this oil recovery circuit (12). Return to (6f).

Figure 4 is a Mollier diagram showing the above operation, where the horizontal axis represents enthalpy i and the vertical axis represents pressure P. The cycle (18) shown by the broken line is the flow of refrigerant flowing through the main refrigerant circuit (7). A cycle (19) indicated by a solid line is a cycle of the refrigerant bypass circuit (12), that is, a saturation temperature detection cycle.

In addition, (6a) to (6f), (13a) (13b) in the figure
) (15a) (15b) are the refrigerant i of each pipe and capillary in these cycles (18) and (19) during cooling.
- represents P.

A refrigerant temperature detector (
18) detects the saturated condensation temperature and controls the compressor energizing power frequency as described below.

Next, the operation frequency control of the compressor according to the refrigerant temperature detected by the refrigerant temperature detector (I7) described above will be explained.

Fig. 3 is a block diagram showing the control system of an air conditioner that is an embodiment of the present invention. In Fig. 1, (1) and (17) are the same compressors as in Figs. The refrigerant temperature detector (20) for temperature detection is this refrigerant temperature detector (1
(21) is a control device consisting of a microcomputer, etc.; and (22) is a variable frequency power supply consisting of an inverter that makes the rotation speed of the compression 4fi (1) variable.

The operation of the above control system will be explained with reference to FIGS. 5, 6, and 7. Figure 5 shows a control device (21) for control.
The flowchart of the program executed in FIG. 6 shows the relationship between the maximum allowable rotation speed of the compressor (1), that is, the maximum allowable power supply frequency Fwax, and the saturated condensation temperature CT detected by the refrigerant temperature detector (17). FIG. 7 is a control characteristic diagram showing the relationship between the indoor air temperature difference ΔT and the required frequency of the compressor (1). In general, the saturated condensing temperature CT increases with the increase in pressure of the refrigerant discharged from the compressor.
The figure shows that the permissible rotational speed of the compressor, F l1ax , decreases with an increase in discharge refrigerant pressure. This is C
When T is high, that is, when the discharge refrigerant pressure is high, the frequency is high;
That is, if the compressor is operated at high rotational speed, it may cause failures such as seizure of the bearings. Therefore, it is necessary to keep the relationship between CT and Fmax within the range shown in FIG.

Therefore, in step (23) in FIG. 5, the control device!
! (21) calculates and determines Fmax in the relationship shown in FIG. 6 using the saturated condensing temperature CT detected by the refrigerant temperature detector (17) and input through the temperature input circuit (21). Next, in step (24), depending on the difference ΔT between the intake air temperature of the indoor heat exchanger (5) and the set temperature, the energizing power frequency of the compressor (1) (hereinafter the required Fr (referred to as frequency) is determined. and step (25)
Then, compare the required frequency Fr with the maximum allowable frequency Fmax, and if Fr is larger than Fmax, set the output frequency Fo to Fmax in step (26), and if it is smaller, set the output frequency FO to Fmax in step (27). The required frequency Fr is set as the output frequency F in step (28).
o is output to a variable frequency power supply (22) which is an inverter to control the rotation speed of the compressor (1).6 Figure 8 is a refrigerant circuit diagram showing another embodiment of the present invention. ) of the heat exchange section (16) of the inlet pipe (13
) and the suction pipe (6f) of the compressor (1). That is, the high-temperature, high-pressure gas refrigerant in the inlet pipe (13) is cooled by exchanging heat with the suction pipe (6f).
Use as a phase refrigerant. The temperature of this two-phase refrigerant is measured by a refrigerant temperature detector (
17), it is possible to detect the saturated condensation temperature in the same manner as described above.

Although the explanation of the control of the expansion valve was omitted in the above embodiment, it is clear that the saturated evaporation temperature can be detected at the outlet of the capillary tube (14), so this temperature is detected and the control of the suction tube (6f) is performed. It goes without saying that the superheat amount can be calculated from the temperature difference between the temperature of the refrigerant and the refrigerant temperature, and the expansion valve can be controlled using this amount.

[Effects of the Invention] As described above, according to the present invention, the heat exchange section is installed in the oil recovery circuit of the oil separator, making it possible to detect the saturated condensation temperature. This has the effect of providing a highly reliable air conditioner that is capable of advanced control.

[Brief explanation of drawings]

Fig. 1 is a refrigerant circuit diagram showing one embodiment of this invention, Fig. 2 is a configuration diagram showing an example of an oil recovery circuit thereof, Fig. 3 is a block diagram showing its control system, and Fig. 4 is a block diagram showing an example of its oil recovery circuit. A Mollier diagram for explaining its operation, FIG. 5 is a flowchart for explaining its control operation, FIGS. 6 and 7 are its control characteristic diagrams, and FIG. 8 shows another embodiment of the present invention. Refrigerant Circuit Diagram, FIG. 9 is a block diagram showing a control system of a conventional air conditioner. In the figure, (1) is the compressor, (2) is the four-way valve, (3) is the outdoor heat exchanger, (4) is the expansion valve, (5) is the indoor heat exchanger, (6) is the refrigerant pipe, (6a ) is the discharge pipe, (6f)
is the suction pipe, (7) is the refrigerant circuit, (9) is the suction pipe refrigerant temperature detector, (11) is the oil separator, (lla) is its oil return port, (12) is the oil recovery circuit, (13) ) is the inlet pipe,
(13a) is its entrance, (13b) is its exit, (
14) is a capillary tube, (15) is an outlet pipe, (15a) is its outlet, (15b) is its inlet, (16) is a contact heat exchange section, (17) is a refrigerant temperature detector, (20) is A temperature input circuit, (21) a control device, and (22) a variable frequency power supply. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (3)

[Claims] (1) Compressor, oil separator powered by variable frequency power supply,
In an air conditioner equipped with a refrigerant circuit in which a four-way valve, an outdoor heat exchanger, an expansion valve, an indoor exchanger, etc. are connected by refrigerant piping, an oil separator provided in the discharge piping of the compressor and the compressor An inlet pipe having an inlet connected to the oil return port of the oil separator and a heat exchange section for cooling the refrigerant therein to a two-phase region, and an outlet connected to the suction pipe. an oil recovery circuit comprising an outlet pipe, and a capillary tube connecting the outlet of the inlet pipe and the inlet of the outlet pipe; a refrigerant temperature detector attached to the inlet side of the capillary of the oil recovery circuit; 1. An air conditioner comprising: a control device for controlling a power supply frequency for energizing the compressor according to a refrigerant temperature signal from the air conditioner. (2) exchanging heat between the oil recovery circuit inlet pipe and outlet pipe;
The air conditioner according to claim 1, wherein the inlet pipe is a heat exchange section. (3) The air conditioner according to claim 1, wherein the oil recovery circuit inlet pipe and the suction pipe of the compressor exchange heat, and the inlet pipe is used as a heat exchange part.