JP3395449B2 - Air conditioner - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner. 2. Description of the Related Art A conventional air conditioner is disclosed in
As described in JP-A-56, the detection of the discharge pressure is performed by bypassing a part of the high-temperature and high-pressure gas discharged from the compressor and cooling it by a heat exchange unit provided in a low-pressure gas pipe, thereby forming a two-phase gas-liquid refrigerant. State, further, through a capillary to make a low-temperature low-pressure refrigerant gas, and then flow into the compressor high-pressure side,
A temperature sensor is provided between the heat exchange section and the capillary, and the sensor detects the saturation temperature. The pressure is estimated from the relationship between the saturation temperature and the pressure to control the operation of the heat pump device. In the prior art, no consideration has been given to the problem that the refrigeration cycle capacity is reduced by bypassing a part of the discharge gas of the compressor, and that the refrigeration cycle is complicated by the use of bypass piping. . On the other hand, another conventional air conditioner is disclosed in
As described in Japanese Patent No. 179754, when an auxiliary heater is provided to compensate for a decrease in the heating capacity when the outside temperature of the heating air is low, a sensor for detecting the compressor current detects an increase in the compressor current, and an increase in the compressor current is detected. In order to prevent the total current from exceeding the set value, the current flowing through the auxiliary heater is controlled so as to suppress the total current by performing phase control using a triac or amplitude control using a transistor. In this technique, no consideration has been given to controlling the discharge pressure to be suppressed by the compressor operating current until the discharge pressure rises when the outside air temperature rises in the heating operation and the protection device operates. In the above-mentioned prior art, since a part of the discharge gas is bypassed and the high-temperature and high-pressure gas is used as a gas refrigerant and a two-phase refrigerant, the absolute value of the pressure is detected accurately. However, there is a problem that a delay occurs in detecting a rapid pressure fluctuation. There is also a problem in accuracy in estimating pressure from temperature. An object of the present invention is to detect the absolute value of the discharge pressure by a pressure switch provided in a high-pressure gas pipe when the discharge pressure rises, and to provide the pressure rise width from the pressure switch operation set value to the heat exchanger outlet side. An object of the present invention is to prevent the rise of the discharge pressure by detecting the condensation temperature detecting thermistor provided. A second object of the present invention is to estimate a discharge pressure by operating a pressure switch and a thermistor for detecting a condensing temperature, and to stop the compressor before the discharge pressure reaches a set value of a protection device operation to protect the compressor. It is to prevent the operation of the device. A third object of the present invention is to estimate a discharge pressure by operating a pressure switch and a thermistor for detecting a condensing temperature, and as a pressure reducing device during a refrigeration cycle before the discharge pressure reaches a protection device operation set value. The opening of the provided electronic expansion valve is opened to give an opportunity to lower the discharge pressure to prevent the pressure from increasing.If the discharge pressure further increases, the compressor is stopped before the discharge pressure reaches the protection device operation set value. To prevent the operation of the protection device. In the above-mentioned prior art, the compressor operating current is detected, but it is used to control the current of the auxiliary heater so that the total current value does not exceed a predetermined value. For this reason, no consideration has been given to estimating the change in the discharge pressure from the change in the compressor operating current value and stabilizing the refrigeration cycle. A fourth object of the present invention is to utilize the fact that the input of the compressor increases and the operating current value of the compressor increases when the discharge pressure increases, and the absolute value of the discharge pressure is supplied to the high-pressure gas pipe. An object of the present invention is to prevent a rise in discharge pressure by checking the pressure switch provided and detecting a pressure rise from a pressure switch operation set value by a current change width detected by a compressor operation current detection sensor. A fifth object of the present invention is to estimate the discharge pressure by operating a pressure switch and a current sensor, stop the compressor before the discharge pressure reaches a protection device operation set value, and prevent the operation of the protection device. Is to do. A sixth object of the present invention is to estimate the discharge pressure by operating a pressure switch and a current sensor, and to provide an electronic expansion provided as a low-pressure device during a refrigeration cycle before the discharge pressure reaches a protection device operation set value. Open the valve to prevent the pressure from increasing by giving the opportunity to lower the discharge pressure.If the discharge pressure rises, stop the compressor before the discharge pressure reaches the protection device operation set value. To prevent the operation of [0014] In order to achieve the above object, a first air conditioner of the present invention comprises an outdoor unit and an indoor unit connected to the outdoor unit by a gas pipe and a liquid pipe. Constituting a cycle, the outdoor unit comprises a compressor for compressing the refrigerant gas, a four-way valve for switching the destination of the compressed refrigerant gas, and an outdoor heat exchanger for exchanging heat between the external heat source and the refrigerant, and the indoor unit comprises a refrigerant. In an air conditioner including an indoor heat exchanger that exchanges heat with indoor air and an expansion valve that is connected to the indoor heat exchanger and decompresses refrigerant, a control pressure switch provided on a compressor discharge gas pipe; Condensation temperature detection thermistors provided at the outlet of the indoor heat exchanger on the liquid pipe side and at the outlet of the outdoor heat exchanger on the liquid pipe side are used to operate the control pressure switch and the control pressure switch. From the condensation temperature detection thermistor temperature and its rise value, the pressure fluctuation of the discharge gas discharged from the compressor is captured,
Discharge pressure rise prevention control is provided. According to the second air conditioner of the present invention, in addition to the first invention, when the pressure increase width exceeds a predetermined value, the compressor is stopped to prevent the discharge pressure from rising, The compressor is restarted when the discharge pressure decreases to the following level, and control is provided to prevent the discharge pressure from rising. According to a third air conditioner of the present invention, in addition to the first aspect of the present invention, when the pressure rise width exceeds a predetermined value, the electronic expansion valve is opened to prevent the discharge pressure from rising. It is characterized by. A fourth air conditioner of the present invention includes a current sensor for detecting a compressor operating current instead of the condensing temperature detecting thermistor in the first aspect of the present invention. The present invention is characterized in that a discharge pressure rise prevention control is provided by detecting a pressure fluctuation of a discharge pressure discharged from the compressor from a compressor operating current value and a rise width thereof when the switch is operated. According to a fifth aspect of the present invention, in addition to the fourth aspect of the present invention, when the pressure increase width exceeds a predetermined value, the compressor is stopped to prevent the discharge pressure from increasing, and If the discharge pressure drops below, restart the compressor,
It is characterized by having a control for preventing the discharge pressure from rising. According to the sixth air conditioner of the present invention, in addition to the fourth aspect of the present invention, when the pressure rise width exceeds a predetermined value, the electronic expansion valve is opened to prevent the discharge pressure from rising. Features. The operating value of the control pressure switch installed in the discharge gas pipe of the compressor is 30 kg / cm ² for the normal protection (high pressure cut) pressure switch, so that the protection device does not operate. It is set to 25 kg / cm, which is about 5 kg / cm ² lower. When the discharge pressure rises sharply, a condensation temperature detector is installed on the liquid pipe connection side of the heat exchanger to monitor the discharge pressure value from the time the control pressure switch is activated until the protection pressure switch is activated. The discharge pressure is captured by the rise width from the time of operating the pressure switch for controlling the condensation temperature by the thermistor,
Before the discharge pressure reaches the protective pressure switch activation value,
By stopping the compressor or opening the electronic expansion valve, an increase in the discharge pressure can be prevented. That is, the absolute value of the discharge pressure can be detected by the operation of the control pressure switch, and the subsequent pressure rise can be detected by the variation width of the condensing temperature, and the pressure can be accurately estimated by a method less expensive than the pressure sensor. . When the discharge pressure increases by 25 kg / cm ² or more, the degree of supercooling cannot be obtained at the heat exchanger outlet, and the heat exchanger outlet temperature becomes a saturation temperature. It is not necessary to equip with a complicated refrigeration cycle piping such as cooling by cooling and two-phase refrigerant and converting the pressure from the saturation temperature, it is possible to measure the condensation temperature simply by installing a thermistor at the heat exchanger outlet It becomes possible. Also, when the discharge gas pressure rises, the operation of the control pressure switch and the control pressure switch of the compressor operating current detected by the sensor are utilized by utilizing the fact that the compressor input increases and the operating current also links and increases. The discharge pressure can be estimated from the rise width from the time of operation. That is, the compressor can be stopped before the protection pressure switch is operated, or the electronic expansion valve can be opened to prevent the discharge pressure from rising. When the compressor operating current is detected by the sensor, the response of the current value detected by the sensor to the pressure fluctuation is good, so that a rapid pressure fluctuation can be accurately detected. When the saturation temperature is detected by the temperature sensor, there is a problem that a delay due to the time constant of the temperature sensor accompanies, and it is difficult to catch a rapid pressure fluctuation. An embodiment of the present invention will be described below with reference to FIGS. The outdoor unit 1 comprises a compressor 2, a four-way valve 3 having a port connected to a discharge port of the compressor 2, and an outdoor heat exchanger 4 having one end of a refrigerant flow path connected to a port of the four-way valve 3.
A blocking valve 18 connected to the port of the four-way valve 3, an accumulator 5 connected to one end of the suction port of the compressor 2 and the other end connected to the port of the four-way valve 3, and the other end of the outdoor heat exchanger 4. Temperature sensor 15 for detecting the temperature of the outlet of the outdoor heat exchanger 4 (condensation temperature during cooling)
And a current sensor 17 for detecting a compressor operating current, a control pressure switch 18 for detecting a compressor discharge pressure, a protection pressure switch 19, and a temperature sensor and a pressure switch which are connected to the outdoor to take in signals from these. Control device 1
1 is included. The signals from these sensors are taken into the outdoor controller 11 by the electronic expansion valve 10 on the indoor side.
Is provided with control means for determining the degree of opening. The indoor unit 8 has an indoor heat exchanger 9 having one end of the refrigerant flow path communicating with the port of the four-way valve 3 via the gas pipe 7 and the blocking valve 18, and an indoor heat exchanger 9 having one end.
The electronic expansion valve 10 connected to the other end of the refrigerant flow path and the temperature sensor 16 for detecting the outlet temperature (condensing temperature during heating) of the indoor heat exchanger 9, a signal from the temperature sensor, and an operation command An indoor controller 12 connected to the outdoor controller 11 of the outdoor unit 1 via the circuit 13 and the operation information circuit 14 is included. The indoor control device 12 has control means for taking in signals from the temperature sensors 15, 16 and the current sensor 17 to stop and start the compressor. In the refrigeration cycle at the time of cooling, the four-way valve 3 is operated such that its ports are connected to each other. In this refrigeration cycle, the refrigerant is compressed to a high temperature and a high pressure by the compressor 2 of the outdoor unit 1, enters the outdoor heat exchanger 4 from the four-way valve 3, and is condensed to become a liquid refrigerant. However, when the outside air temperature is high and the discharge pressure is high,
Since the condensation performance of the outdoor heat exchanger 4 becomes smaller with respect to the outdoor air load, a supercooling degree cannot be obtained at the heat exchanger outlet, and the refrigerant becomes a two-phase refrigerant. The two-phase refrigerant flows through the liquid pipe 6 and the indoor unit 8
Flows into. The two-phase refrigerant flowing into the indoor unit 8 adiabatically expands through the electronic expansion valve 10, and then expands in the indoor heat exchanger 9.
And evaporates into low-temperature low-pressure gas, which flows through the gas pipe 7,
Return to indoor unit 1 again. The gas refrigerant returned to the outdoor unit 1 enters the accumulator 5 via the four-way valve 3, where the gas refrigerant is separated into gas and liquid, and then returns to the compressor 2. On the other hand, in the heating refrigeration cycle, the four-way valve 3
Are operated such that the ports and the ports are communicated with each other, and a refrigerant circuit circulating in a direction opposite to the refrigerant circuit at the time of cooling is formed. In this refrigeration cycle, the gas refrigerant compressed to a high temperature and a high pressure by the compressor 2 of the outdoor unit 1 enters the indoor unit 8 via the four-way valve 3 and the gas pipe 7. The gas refrigerant that has flowed into the indoor unit 8 is condensed in the indoor heat exchanger 9 and becomes a liquid refrigerant. However, when the discharge pressure rises and the control pressure switch operates, the refrigerant is not supercooled and becomes a two-phase refrigerant. The pressure of the two-phase refrigerant is reduced by the electronic expansion valve 10, passes through the liquid pipe 6, and returns to the outdoor unit 1. The two-phase refrigerant flows into the outdoor heat exchanger 4 and evaporates to become a low-temperature low-pressure gas, enters the accumulator 5 via the four-way valve 3, and returns to the compressor 2. FIG. 2 shows the operating state of the compressor, the discharge pressure of the electronic expansion valve opening, the condensing temperature, and the operating current of the compressor on the horizontal axis and the vertical axis on the vertical axis. [0030] During the cooling with the rise of the discharge pressure condensation temperature T _c of 4 outlets outdoor heat exchanger during heating condensation temperature T _c of the indoor heat exchanger 9 outlet is increased. That is, since the condensation temperature is linked to the discharge pressure and changes, the discharge pressure can be estimated from the condensation temperature. Further, as the discharge pressure increases, the input of the compressor 2 increases, and the operating current flowing through the compressor 2 increases. In the case of the current value, the response to the pressure fluctuation is better than the condensation temperature, and is suitable for detecting a sudden pressure fluctuation. In the first embodiment shown in FIG. 3, the discharge pressure rises, the control pressure switch 18 operates at 25 kg / cm ² , and the condensation temperature T _co at this time is stored in the outdoor controller 11. Keep it. Next, the control pressure switch 18 is used as it is.
When the condensing temperature rises and the absolute value of the condensing temperature is compared with a set value, and when the condensing temperature rises above the judgment value, the compressor 2 is stopped to prevent the pressure from rising. . When estimating the pressure based on the condensing temperature, since the detection error of the temperature thermistor is large, it is possible to estimate the pressure based on both the change width of the temperature sensors 15 and 16 and the absolute value thereof, thereby reducing the detection error. The second embodiment shown in FIG. 4 is a first embodiment in which the change width of the condensing temperature detected by the condensing temperature sensors 15 and 16 and the absolute value thereof are measured after the control pressure switch 18 is operated. If the condensing temperature rises after the determination, instead of immediately stopping the compressor 2, the electronic expansion valve 10 is once opened to the full open, giving an opportunity to reduce the discharge pressure, and the opening degree of the electronic expansion valve 10. If the discharge pressure further increases and the condensing temperature rises after the operation, the compressor is stopped to prevent the protection pressure switch 19 from operating. This control makes it possible to extend the continuous operation time of the unit and prevent frequent repetition of compressor on / off. In the third embodiment shown in FIG. 5, after the control pressure switch 18 is operated in the first and second embodiments, the current sensor 17 is used instead of the temperature thermistor to change the current variation width and The operation of opening the electronic expansion valve 10 and the ON / OFF control of the compressor are performed in order to determine a rise in pressure based on the absolute value and measure a decrease in pressure. By using a current sensor instead of a temperature sensor, the responsiveness to discharge fluctuations is good, so that a rapid pressure rise at startup can be detected, and the refrigeration cycle can be stabilized. Further, since the absolute value of the current value detected by the current sensor also has a large error, it is an appropriate method to capture the pressure fluctuation based on the variation width of the current value. Further, the present invention is to reduce the pressure before the protective pressure switch is activated by increasing the discharge pressure. In this region, the discharge pressure is reduced at the outlet of the heat exchanger on the condenser side in this region. Since the refrigerant is not two-phase refrigerant, the condensation temperature can be detected by a simple method. Also, by using a current sensor instead of a temperature sensor, the current changes responsively to a change in the discharge pressure, so that it effectively works against a sudden pressure change at the time of startup, and the discharge pressure is used for protection. The pressure can be reduced before reaching the pressure switch operation value. According to the present invention, the rise of the discharge pressure can be detected by the change width of the condensing temperature and its absolute value, and the pressure sensor and a part of the discharge gas are bypassed and cooled by the low-pressure pipe. The discharge pressure can be estimated by a relatively inexpensive method as compared with a method of detecting the saturation temperature of a two-phase refrigerant.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a system diagram of a refrigeration cycle of a pair type air conditioner according to first to third embodiments of the present invention. FIG. 2 is a time chart showing a compressor operating state, an electronic expansion valve opening, and a time change of each sensor according to the first to third embodiments of the present invention. FIG. 3 is a flowchart of the first embodiment of the present invention. FIG. 4 is a flowchart of a second embodiment of the present invention. FIG. 5 is a flowchart of a third embodiment of the present invention. [Description of Signs] 1 ... Outdoor unit, 2 ... Compressor, 4 ... Outdoor heat exchanger, 8
... indoor unit, 9 ... indoor heat exchanger, 10 ... electronic expansion valve, 15 ... temperature sensor, 17 ... current sensor.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takashi Mori 390 Muramatsu, Shimizu-shi, Shizuoka Prefecture Air Conditioning Systems Division, Hitachi, Ltd. (56) References JP-A-4-225771 (JP, A) JP-A-62- 196562 (JP, A) JP-A-6-82130 (JP, A) JP-A-1-277159 (JP, A) JP-A-63-143464 (JP, A) Japanese Utility Model Publication No. 58-131374 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) F25B 1/00 341

Claims (1)

(57) [Claims 1] In an air conditioner constituting a refrigeration cycle by sequentially connecting a compressor, an outdoor heat exchanger, an electronic expansion valve, an indoor heat exchanger and an accumulator, a high pressure control system is provided. A pressure switch and a thermistor for detecting a condensing temperature are provided in the room and at the outlet of the outdoor heat exchanger, and a rise in high pressure is determined based on an operation signal of a pressure switch for high pressure control and a condensing temperature when the pressure switch is operated. Detected by the amount of rise
An air conditioner comprising a control means for preventing an increase in high pressure.