JP2011237095A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure that a protection function of a compressor operates before a compressor temperature (temperature of a sealed container) reaches an operation limit temperature, even in a negative pressure operation state where there is a little of or return inhaled refrigerant or no refrigerant returns, and to improve the reliability of the protection function.SOLUTION: When a container temperature Tc is a predetermined operation limit temperature Tmax or lower and the container temperature Tc is higher than a discharge gas temperature Tg even in either of a time point t1 when a predetermined time has passed after the compressor starts operation and a time point t2 after a predetermined time has passed from the time point t1, the operation of the compressor is stopped.

Description

  The present invention relates to an air conditioner, and more particularly to a protective function of a compressor that compresses a refrigerant.

  As shown in FIG. 4, many air conditioners are configured by connecting a compressor 11, a four-way valve 12, an indoor heat exchanger 13, an expansion valve 14, an outdoor heat exchanger 15, and an accumulator 16 through a refrigerant pipe. A refrigerant circulation system is provided as a basic configuration. The indoor heat exchanger 13 and the outdoor heat exchanger 15 are each provided with a blower fan, but the illustration thereof is omitted in FIG.

  In the case of the separator type (split type), the compressor 11, the four-way valve 12, the expansion valve 14, the outdoor heat exchanger 15 and the accumulator 16 are disposed in the outdoor unit 1, and the indoor heat exchanger 13 is disposed in the indoor unit 2. Placed in.

  The outdoor unit 1 and the indoor unit 2 are connected to each other through a gas side pipe 17 and a liquid side pipe 18. These pipes 17 and 18 are connected to the outdoor unit 1 and the indoor unit 2, respectively. After installation at a predetermined location, the gas side pipe 17 is connected via a two-way valve 17a, and the liquid side pipe 18 is connected via a three-way valve 18a having a refrigerant inlet.

  Although not shown in detail, the compressor 11 is usually a hermetic compressor in which a rotary or scroll type refrigerant compression unit and an electric motor that drives the refrigerant compression unit are housed in a hermetic container. It is done. This type of compressor is classified into a constant speed type with a constant rotational speed and a variable capacity type with a variable rotational speed (including an inverter type, hereinafter referred to as an “inverter type”).

  In a hermetic compressor, high-temperature and high-pressure gas refrigerant generated in the refrigerant compressor is ejected into a hermetic container and cooled down after the motor is discharged, and then discharged toward the refrigerant circuit. The compressor temperature is maintained within a safe temperature range.

  However, the compressor 11 is operated in a state where the two-way valve 17a and the three-way valve 18a for pipe connection are forgotten to be opened or the expansion valve 14 is fully closed after installation of the units 1 and 2, for example, due to an erroneous operation. Then, a negative pressure operation with a small amount of return suction refrigerant (or an empty operation without a return suction refrigerant) may occur, and the temperature of the compressor may rise abnormally, resulting in the worst failure.

  Therefore, most air conditioners are provided with a protection function for monitoring the temperature of the compressor (temperature of the sealed container) and stopping the operation of the compressor if the temperature rise is abnormal (for example, Patent Documents 1 and 2).

  The problem of the conventional protection function during negative pressure operation with a small amount of return suction refrigerant will be described with reference to FIG. Tc is the container temperature of the compressor hermetic container, and Tg is the discharge gas temperature of the compressor. Tmax is an operation limit temperature at which the protection function is operated, and is 108 ° C. in this example.

  When the indoor / outdoor air conditioning load is high, the compressor is operated at a high rotational speed for both the constant speed type and the inverter type, so that the container temperature Tg rapidly increases from the start of operation as indicated by a one-dot chain line. Thus, the operation limit temperature Tmax is reached in a relatively short time, and the protective function is activated.

  However, in the inverter type, when the indoor and outdoor air conditioning load is low, the compressor is operated at a low rotational speed, so that the container temperature Tg rises with a gentle gradient as shown by the two-dot chain line, and the operation limit is reached. It takes a relatively long time to reach the temperature Tmax and activate the protection function. Meanwhile, since the compressor is in a negative pressure operation state with a small amount of returned suction refrigerant, for example, the bearing portion of the drive shaft of the electric motor may abnormally generate heat and cause a seizure accident.

JP-A-62-2178 JP-A-9-79709

  Therefore, an object of the present invention is to provide a compressor protection function before the compressor temperature (the temperature of the sealed container) reaches the operating limit temperature even in a negative pressure operation state where there is little or almost no return suction refrigerant. It is to ensure the operation and increase the reliability of the compressor.

In order to solve the above problems, the present invention provides an air conditioner including a compressor including a refrigerant compression unit and an electric motor for driving the refrigerant compression unit in a hermetic container in a refrigeration cycle. A first temperature sensor for detecting Tg; a second temperature sensor for detecting a container temperature Tc of the closed container; a discharge gas temperature Tg and a container temperature Tc output from the first temperature sensor and the second temperature sensor; Control means for controlling the operation of the compressor on the basis of the above-mentioned control means, wherein the control means is a time point t1 after a lapse of a predetermined time from the start of operation of the compressor, and a time point t2 after a lapse of a predetermined time from the time point t1. At any time, if the container temperature Tc is equal to or lower than a predetermined operation limit temperature Tmax and the container temperature Tc> the discharge gas temperature Tg, the operation of the compressor is stopped. It is characterized in that.

  According to a preferred aspect of the present invention, the control means is configured such that the temperature difference α2 of the container temperature Tc> the discharge gas temperature Tg at the time t2 is greater than the container temperature Tc> the discharge gas temperature Tg at the time t1. When the temperature difference α1 is larger than the above, the operation of the compressor is stopped.

  When the compressor is stopped before reaching the time point t1 or the time point t2, the control means restarts the temperature monitoring control from the time when the operation of the compressor is resumed.

  According to the present invention, the container temperature Tc is equal to or lower than the predetermined operation limit temperature Tmax at the time t1 after the predetermined time has elapsed since the compressor started operation and at the time t2 after the predetermined time has elapsed from the time t1. However, when the container temperature Tc> the discharge gas temperature Tg, the compressor operation (sealed container temperature) does not reach the operation limit temperature because the operation of the compressor is stopped. Further, it is possible to prevent the negative pressure operation state with little or little return suction refrigerant from continuing for a long time, and the reliability of the compressor is improved.

The schematic diagram for demonstrating embodiment of this invention. The graph which shows the relationship between the container temperature at the time of starting operation | movement of a compressor from when the container temperature and discharge gas temperature are substantially the same temperature, and discharge gas temperature. The graph which shows the relationship between the container temperature and discharge gas temperature when a compressor restarts an operation | movement after a comparatively short stop time. The schematic diagram which shows the basic refrigerant circulation system with which an air conditioner is provided. The graph which shows the relationship between the container temperature and discharge gas temperature for demonstrating the problem of the conventional compressor protection function.

  Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 3, but the present invention is not limited to this.

  The air conditioner according to this embodiment also includes a refrigerant circulation system similar to that of the conventional example described with reference to FIG. 4, but only the compressor 11 is shown in FIG.

  The compressor 11 includes a metal hermetic container (shell) 110, and the refrigerant container 120 and an electric motor 130 that drives the refrigerant compressor 120 are accommodated in the airtight container 110.

  In the illustrated example, the refrigerant compressor 120 is a rotary type, but may be a scroll type. Refrigerating machine oil is stored in the lower part of the refrigerant compressor 120. As the electric motor 130, an inner rotor type induction motor or the like is used.

  A refrigerant discharge pipe 111 reaching the four-way valve 12 is connected to the upper part of the sealed container 110, and a refrigerant suction pipe 112 from the accumulator 16 is connected to the lower part of the sealed container 110.

  The return refrigerant supplied from the refrigerant suction pipe 112 is compressed by the refrigerant compressor 120 and becomes a high-temperature and high-pressure gas refrigerant, which is jetted into the sealed container 110, cools the stator winding of the electric motor 130, etc., and then discharges the refrigerant. It is discharged from the pipe 111 to the refrigerant circulation system.

  In the present invention, as the constituent elements of the protective function of the compressor 11, the first and second at least two temperature sensors 141 and 142, and the energization of the electric motor 130, for example, based on the detected temperatures of these temperature sensors 141 and 142. Control means 143 for opening and closing the switch SW.

  The first temperature sensor 141 is attached to the refrigerant discharge pipe 111 and detects the refrigerant discharge gas temperature Tg. The second temperature sensor 142 is attached to the sealed container 110 and detects the container temperature Tc of the sealed container.

  It is preferable that the 2nd temperature sensor 142 is attached to the bottom part side of the airtight container 110 in which refrigerator oil is stored. According to this, since the refrigerating machine oil has a relatively high thermal conductivity, the temperature in the sealed container 110 can be detected more accurately. In some cases, the second temperature sensor 142 may be disposed in the sealed container 110.

  Next, the operation of the control unit 143 will be described. When the compressor 11 is operating normally, the discharge gas temperature Tg is higher than the container temperature Tc as before ta and after tc in FIG.

  On the other hand, as described above, after installation of the units 1 and 2, for example, by mistaken operation, the pipe connection two-way valve 17 a or the three-way valve 18 a is forgotten to be opened, or the expansion valve 14 is fully closed. When the compressor 11 is operated, the negative pressure operation (or the idling operation without the return suction refrigerant) with little return suction refrigerant is performed, and the container temperature Tc is higher than the discharge gas temperature Tg.

  In the graph of FIG. 2, when the compressor 11 is stopped for a long time and the operation is started at a low rotation speed with a low indoor / outdoor air conditioning load, the discharge gas temperature Tg and the container temperature Tc are almost equal. It shows the transition from the same temperature.

  As described above, the container temperature Tc rises with a gentle gradient during the negative pressure operation at a low rotational speed and a small amount of the return suction refrigerant, so it easily reaches the operation limit temperature Tmax (108 ° C. in this example). Not reach.

  Therefore, in the control means 143, after the compressor 11 is started to operate, the time t1 after a predetermined time has elapsed (for example, 30 minutes), and the time t2 after the predetermined time has elapsed from the time t1 (for example, 60 The container temperature Tc and the discharge gas temperature Tg are compared at least twice (at the time when the minute has elapsed). In any of them, the container temperature Tc is equal to or lower than a predetermined operation limit temperature Tmax, and the container temperature Tc> the discharge gas temperature. If it is Tg, it is determined that the return suction refrigerant is in a negative pressure operation (idle operation) state, the energization switch SW is turned off, and the compressor operation is stopped. In this example, the temperature detection time interval is set to 30 minutes because of the empirical rule that neither the container temperature Tc nor the discharge gas temperature Tg changes rapidly in a short time, and is set to be shorter than 30 minutes. It may be long.

  Note that the first comparison time point is the time point t1 after the elapse of a predetermined time after the start of the compressor operation, as shown in FIG. 3, the stop time of the compressor 11 (between ta and tb) is short, In particular, when the outside air temperature is low, the container temperature Tc may be temporarily higher than the discharge gas temperature Tg due to the heat transfer time lag.

  Preferably, in order to further improve the reliability, when the temperature difference α2 of the container temperature Tc> the discharge gas temperature Tg at the time t2 is larger than the temperature difference α1 of the container temperature Tc> the discharge gas temperature Tg at the time t1, That is, when the temperature difference α increases with time, the power switch SW is turned off to stop the operation of the compressor.

  Further, when the compressor 11 is stopped before reaching the time t1 or the time t2, the control unit 143 restarts the temperature monitoring control from the time when the operation of the compressor 11 is resumed.

  Note that, for example, the operation of the compressor 11 may be started in a state where the expansion valve 14 is clogged with dust, and thereafter, the clogging of the expansion valve 14 may be eliminated and the refrigerant may start to circulate. In such a case, the return refrigerant amount of the compressor 11 increases, so that the temperature difference of the container temperature Tc> the discharge gas temperature Tg decreases with time.

  Therefore, the temperature difference of container temperature Tc> discharge gas temperature Tg at time t3 after a lapse of a predetermined time from time t2 is α3, and the temperature difference of container temperature Tc> discharge gas temperature Tg, such as α1> α2> α3. Is gradually reduced, it is preferable not to stop the compressor 11 even if the compressor 11 returns to normal operation.

DESCRIPTION OF SYMBOLS 11 Compressor 110 Airtight container 111 Refrigerant discharge pipe 112 Refrigerant suction pipe 120 Refrigerant compression part 130 Electric motor 141 1st temperature sensor 142 2nd temperature sensor 143 Control means

Claims (3)

In an air conditioner equipped with a compressor including a refrigerant compression unit and an electric motor driving the refrigerant compression unit in a closed container in a refrigeration cycle,
A first temperature sensor for detecting a discharge gas temperature Tg of the compressor; a second temperature sensor for detecting a container temperature Tc of the closed container; and a discharge gas output from the first temperature sensor and the second temperature sensor. Control means for controlling the operation of the compressor based on the temperature Tg and the container temperature Tc,
The control means is configured such that the container temperature Tc is equal to a predetermined operation limit temperature Tmax at a time point t1 after a predetermined time has elapsed since the start of operation of the compressor and a time point t2 after a predetermined time has elapsed from the time point t1. The air conditioner is characterized in that the compressor operation is stopped when the container temperature Tc is greater than the discharge gas temperature Tg.   When the temperature difference α2 of the container temperature Tc> the discharge gas temperature Tg at the time t2 is greater than the temperature difference α1 of the container temperature Tc> the discharge gas temperature Tg at the time t1 The air conditioner according to claim 1, wherein operation of the compressor is stopped.   3. The temperature monitoring control according to claim 1, wherein when the compressor is stopped before the time point t <b> 1 or the time point t <b> 2, the control unit restarts the temperature monitoring control from the time when the operation of the compressor is resumed. The air conditioner described.

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