JP2014092344A - Refrigeration unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigeration unit capable of easily maintaining appropriate concentration or viscosity of lubrication oil in a compressor and reducing standby power.SOLUTION: A solenoid valve 48 is open when a compressor 40 is stopped, and refrigerant is bypassed from a discharge pipe 42 to a suction pipe 43 of the compressor 40 through a by-pass pipe 47. Pressure in the compressor 40 is equalized by the by-pass pipe 47. In this state, a crank case heater 46 is turned off and stops heating the compressor 40.

Description

  The present invention relates to a refrigeration apparatus that compresses refrigerant with a compressor.

  2. Description of the Related Art Conventionally, as an air conditioner that transfers heat between indoors and outdoors, there is an air conditioner that includes a use-side heat exchanger disposed indoors and a heat source-side heat exchanger disposed outdoor. In this air conditioner, in order to transfer heat, one of the use side heat exchanger and the heat source side heat exchanger becomes a radiator, and the other becomes an evaporator. For example, in such an air conditioner, since the refrigerant is circulated between the use side heat exchanger and the heat source side heat exchanger to transfer heat, the compressor that compresses the refrigerant, the use side heat exchanger, and the heat source Generally, a refrigeration apparatus is configured using a side heat exchanger (a radiator and an evaporator).

  In this type of refrigeration system, if the temperature of the lubricating oil (hereinafter referred to as the oil temperature) is low under a constant pressure in the crankcase when the compressor is stopped, the ratio of the refrigerant dissolved in the lubricating oil in the crankcase growing. When conditions such as long-term shutdown of the compressor and changes in the refrigerant temperature (outside air temperature) overlap, a phenomenon called so-called stagnation occurs, and a large amount of refrigerant dissolves in the lubricating oil in the compressor. When the refrigerant stagnates in the lubricating oil, for example, the viscosity of the lubricating oil decreases and the performance of the lubricating oil decreases.

  Therefore, conventionally, in order to prevent the stagnation of the refrigerant in the compressor, even when a heater is attached to the crankcase and the compressor is stopped, measures are taken to warm the compressor so that the refrigerant does not stagnate. ing. Moreover, the lubricating oil in a compressor may be warmed by the motor winding heating method by phase loss energization.

  However, when the heater is energized to warm the compressor, a certain amount of electric power (standby power) is consumed, resulting in an increase in the amount of power consumed by the refrigeration apparatus.

  In order to reduce the standby power of such a compressor, for example, in Patent Document 1 (Japanese Patent Laid-Open No. 2001-73952) and Patent Document 2 (Japanese Patent No. 4111246), compression is performed based on the refrigerant temperature and the outside air temperature. A technique is described in which a heater is not required to be heated and the standby power is reduced by controlling the heater.

  Although the techniques of Patent Document 1 and Patent Document 2 can reduce standby power, the period of unnecessary heating by the heater is not actively created, and thus reduction of standby power is limited.

  An object of the present invention is to provide a refrigeration apparatus that can easily maintain an appropriate oil concentration or oil viscosity for lubricating oil in a compressor and can reduce standby power.

  A refrigeration apparatus according to a first aspect of the present invention includes a compressor that circulates a refrigerant in a refrigeration circuit, a radiator that is installed in a subsequent stage of the compressor of the refrigeration circuit, and a radiator and a compressor that are disposed in the refrigeration circuit An installed evaporator, a high-pressure pipe connected to the discharge side of the compressor, a low-pressure pipe connected to the suction side of the compressor, a bypass pipe that bypasses the refrigerant from the high-pressure pipe to the low-pressure pipe, An opening / closing mechanism provided in the bypass pipe, and a compressor heating heater for heating the compressor, wherein the opening / closing mechanism includes a first state in which the bypass pipe is opened when the compressor is stopped and a first state in which the bypass pipe is closed. The compressor heating heater is configured to stop the heating of the compressor when the opening / closing mechanism is in the first state.

  According to the refrigeration apparatus of the first aspect, since the compressor can be equalized by the bypass pipe when the compressor is stopped with the opening / closing mechanism in the first state, the heater for heating the compressor when the opening / closing mechanism is in the first state Since the state where the pressure in the compressor is reduced and the oil temperature is high continues for a longer time than when the bypass pipe is not provided, evaporation of the refrigerant is promoted and the oil concentration can be increased.

  The refrigeration apparatus according to the second aspect of the present invention is the refrigeration apparatus according to the first aspect, and further includes a check valve downstream of the connection position of the bypass pipe of the high-pressure pipe and before the radiator.

  According to the refrigeration apparatus of the second aspect, the check valve provided downstream of the bypass pipe can prevent backflow from the radiator to the bypass pipe when pressure equalizing the compressor.

  A refrigeration apparatus according to a third aspect of the present invention is the refrigeration apparatus according to the first aspect or the second aspect, wherein the heater for heating the compressor is configured such that, in the first state, the pressure in the dome of the compressor and the suction side pressure are When the pressure difference becomes smaller than the first predetermined pressure difference, heating of the compressor is resumed.

  According to the refrigeration apparatus of the third aspect, it is possible to determine the heating restart timing of the compressor heating heater based on the pressure difference between the compressor dome internal pressure and the suction side pressure, and easily determine the heating restart timing. it can.

  A refrigeration apparatus according to a fourth aspect of the present invention is the refrigeration apparatus according to the first aspect or the second aspect, wherein the heater for the compressor heating has a saturation temperature obtained by converting the internal pressure of the dome and the outside in the first state. When the difference between the air temperature and the room temperature is lower than the predetermined temperature difference, heating of the compressor is resumed.

  According to the refrigeration apparatus of the fourth aspect, the OFF state can be continued until the pressure in the dome reaches a saturation pressure corresponding to a lower temperature of the outside air temperature or the room temperature after pressure equalization.

  The refrigeration apparatus according to a fifth aspect of the present invention is the refrigeration apparatus according to the fourth aspect, wherein the compressor heater is a saturation temperature, an outside air temperature, and an indoor temperature obtained by converting the dome internal pressure in the first state. The heating of the compressor is resumed when the difference from the lower temperature is less than the predetermined temperature difference and the state continues for the first predetermined time or longer.

  According to the refrigeration apparatus of the fifth aspect, heating can be resumed at an appropriate time even when the above-described saturation pressure is temporarily lowered before pressure equalization.

  A refrigeration apparatus according to a sixth aspect of the present invention is the refrigeration apparatus according to the first aspect or the second aspect, and the heater for the compressor heating has passed the second predetermined time after the compressor stopped in the first state. Sometimes resume heating of the compressor.

  According to the refrigeration apparatus of the sixth aspect, it is possible to determine the timing of resuming the heating of the compressor heating heater over time, and thus it is possible to reliably resume heating.

  A refrigeration apparatus according to a seventh aspect of the present invention is the refrigeration apparatus according to the first aspect or the second aspect, wherein the compressor heating heater has an oil temperature offset value larger than the first target offset value in the first state. When it is time, restart the compressor.

  According to the refrigeration apparatus of the seventh aspect, when the opening / closing mechanism is in the first state, the restart of heating of the compressor heating heater is determined including information related to the temperature, so the restart determination is accurate.

  A refrigerating apparatus according to an eighth aspect of the present invention is the refrigerating apparatus according to any one of the first aspect to the seventh aspect, wherein the compressor heating heater in the first state is the pressure inside the dome of the compressor and the suction. Stops heating of the compressor when the pressure difference with the side pressure becomes smaller than the second predetermined pressure difference or when the pressure difference between the compressor dome pressure and the discharge side pressure becomes larger than the third predetermined pressure difference. To do.

  According to the refrigeration apparatus of the eighth aspect, the second predetermined pressure difference that is smaller than the pressure difference generated in the section where the oil concentration or the oil viscosity decreases is used, and the pressure difference between the pressure in the dome and the suction side pressure is the second predetermined pressure. When the pressure difference between the pressure in the dome of the compressor and the discharge side pressure becomes smaller than the third predetermined pressure difference when the pressure becomes smaller than the difference, the oil concentration or oil viscosity decreases by stopping the heating of the compressor. It is possible to avoid stopping the heating of the heater for the compressor heating in the section to be performed.

  A refrigeration apparatus according to a ninth aspect of the present invention is the refrigeration apparatus according to any one of the first to seventh aspects, wherein the compressor heating heater is a third predetermined time after the compressor is stopped in the first state. When the time has elapsed, the heating of the compressor is stopped.

  According to the refrigeration apparatus of the ninth aspect, since the heating of the compressor is stopped when the third predetermined time has elapsed after the compressor is stopped, this third predetermined time is set from the period during which the oil concentration or the oil viscosity decreases. By setting it long, the heater for compressor heating can be turned off while avoiding the section where the oil concentration or the oil viscosity decreases.

  A refrigeration apparatus according to a tenth aspect of the present invention is the refrigeration apparatus according to any one of the first to seventh aspects, wherein the compressor heating heater has an oil temperature offset value of a second target offset in the first state. Stop compressor heating when greater than value.

  According to the refrigeration apparatus of the tenth aspect, by setting the second target offset value that is smaller than the oil temperature offset value in the section in which the oil concentration or oil viscosity decreases, avoid the section in which the oil concentration or oil viscosity decreases. The heater for heating the compressor can be turned off.

  In the refrigeration apparatus according to the first aspect of the present invention, the compressor heating heater can be turned off when the compressor is stopped and the opening / closing mechanism is in the first state, thereby reducing the power consumption of the compressor heating heater. It is possible to provide a refrigeration apparatus that can easily maintain an appropriate oil concentration or oil viscosity for the lubricating oil in the compressor and can reduce standby power.

  In the refrigeration apparatus according to the second aspect of the present invention, the reverse flow of the refrigerant during pressure equalization by the bypass pipe can be prevented, so that the state in which the pressure in the compressor is reduced and the oil temperature is high can be continued for a long time.

  In the refrigeration apparatus according to the third aspect of the present invention, it is possible to easily determine the timing for restarting the heating of the compressor heating heater.

  In the refrigeration apparatus according to the fourth aspect of the present invention, when the pressure in the dome reaches a saturation pressure corresponding to a lower temperature of the outside air temperature or the room temperature after the pressure equalization, the effect of reducing standby power is increased. .

  In the refrigeration apparatus according to the fifth aspect of the present invention, it is possible to improve the reliability of the operation when determining the resumption timing of the compressor heating heater using the saturation pressure.

  In the refrigeration apparatus according to the sixth aspect of the present invention, heating can be reliably restarted over time, and standby power can be reduced while maintaining high reliability.

  In the refrigeration apparatus according to the seventh aspect of the present invention, since the oil temperature is high for a while after reaching the equilibrium pressure from the pressure equalization, the judgment based on both the pressure and the oil temperature is compared to the judgment based only on the pressure. A long heating stop period can be secured.

  In the refrigeration apparatus according to the eighth aspect of the present invention, the interval in which the oil concentration or the oil viscosity decreases using the pressure difference between the dome internal pressure and the suction side pressure or the pressure difference between the compressor dome internal pressure and the discharge side pressure. Thus, the compressor heating heater can be turned off, and problems caused by turning off the compressor heating heater in such a section can be prevented.

  In the refrigeration apparatus according to the ninth aspect of the present invention, the heater for heating the compressor can be turned off while avoiding the section where the oil concentration or the oil viscosity decreases using the passage of the third predetermined time after the compressor is stopped. Or the malfunction by turning off the heater for compressor heating in the area where oil viscosity falls can be prevented.

  In the refrigeration apparatus according to the tenth aspect of the present invention, the heater for the compressor heating can be turned off by using the oil temperature offset value to avoid the section where the oil concentration or the oil viscosity is lowered, and the oil concentration or the oil viscosity is lowered. Problems caused by turning off the heater for heating the compressor can be prevented.

The circuit diagram of the refrigerating circuit of the air conditioner which concerns on 1st Embodiment of this invention. The partially broken perspective view for demonstrating the structure of a compressor. The flowchart explaining control of the crankcase heater of a control apparatus. (A) Conceptual diagram for explaining the state of pressure before the solenoid valve is opened after the compressor is stopped, (b) For explaining the state of pressure after the solenoid valve is opened after the compressor is stopped Conceptual diagram. The graph which shows the time change of the pressure of the refrigerant | coolant of each part of an air conditioner, and oil concentration. The flowchart explaining control of the crankcase heater of the modification 4-1. The flowchart explaining control of the crankcase heater of the modification 4-2. The flowchart explaining control of the crankcase heater of the modification 4-3. The graph which shows the other example of the time change of the pressure of the refrigerant | coolant of each part of an air conditioner, and oil concentration. The graph for demonstrating the difference of the saturation temperature converted from the pressure in a dome, and temperature. The flowchart for demonstrating control of the crankcase heater which concerns on 2nd Embodiment. The flowchart explaining control of the crankcase heater of the modification 7-1. The flowchart explaining control of the crankcase heater of modification 7-2. The flowchart explaining control of the crankcase heater of the modification 4-2 and 7-2. The graph which shows the relationship between saturation temperature and oil temperature offset value. The graph which shows the relationship between the pressure of a refrigerant | coolant, solubility, and the temperature of a liquid mixture. The schematic diagram for description about the setting of an oil temperature offset value. The graph for demonstrating the effect of the freezing apparatus which concerns on one Embodiment.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In addition, embodiment of the freezing apparatus which concerns on this invention is not restricted to 1st Embodiment demonstrated below, It can change in the range which does not deviate from the summary of invention.

(1) Configuration of refrigeration apparatus (1-1) Refrigeration circuit FIG. 1 is a circuit diagram of a refrigeration circuit provided in an air conditioner in which the refrigeration apparatus according to the first embodiment of the present invention is employed. The air conditioner 10 includes a use side unit 20 installed indoors and a heat source side unit 30 installed outdoors. In the use side unit 20, an indoor heat exchanger 21 and an indoor fan 22 are arranged. In the heat source side unit 30, an outdoor heat exchanger 31, an outdoor fan 32, an electric valve 33, an accumulator 34, a four-way switching valve 35, and a compressor 40 are arranged. Thus, the compressor 40, the four-way switching valve 35, the indoor heat exchanger 21, the outdoor heat exchanger 31, the electric valve 33, and the accumulator 34 are connected by the refrigerant pipe, and the refrigeration circuit 12 in which the refrigerant circulates is formed. Yes.

  The air conditioner 10 of FIG. 1 includes a four-way switching valve 35, and the four-way switching valve 35 can switch between a cooling operation for cooling the room and a heating operation for heating the room. In the cooling operation, the indoor heat exchanger 21 functions as an evaporator, and the outdoor heat exchanger 31 functions as a radiator. In the case of heating operation, conversely, the indoor heat exchanger 21 functions as a radiator and the outdoor heat exchanger 31 functions as an evaporator.

  The four-way switching valve 35 has four ports from the first port to the fourth port. A discharge pipe 42 of the compressor 40 is connected to the first port of the four-way switching valve 35 via a check valve 36, one end of the outdoor heat exchanger 31 is connected to the second port, and the third port is connected to the third port. One end of the indoor heat exchanger 21 is connected, and the suction pipe 34a of the accumulator 34 is connected to the fourth port. The four-way switching valve 35 is connected to the first port and the second port at the time of cooling and is connected to the third port and the fourth port, and is connected to the first port and the third port at the time of heating and the second port. The fourth port is connected.

  The connection of each part of the utilization side unit 20 and the heat source side unit 30 other than the four-way switching valve 35 in the air conditioner 10 is as follows. That is, one end of the electric valve 33 is connected to the other end of the outdoor heat exchanger 31, the other end of the indoor heat exchanger 21 is connected to the other end of the electric valve 33, and the discharge pipe of the accumulator 34 is connected to the suction of the compressor 40. It is connected to the tube 43. A bypass pipe 47 is connected between the discharge pipe 42 of the compressor 40 and the suction pipe 34 a of the accumulator 34, and an electromagnetic valve 48 that opens and closes the bypass pipe 47 is connected to the bypass pipe 47.

(1-2) Configuration of Compressor FIG. 2 is a partially broken perspective view of the compressor 40. In the compressor 40, a discharge pipe 42 is attached to a side portion of a cylindrical casing 41, and a suction pipe 43 is attached to an upper portion. A scroll 44 is provided below the suction pipe 43, and a motor 45 that drives the scroll 44 is provided below the scroll 44. The lubricating oil 70 is configured to accumulate on the bottom 41 a of the cylindrical casing 41, and the crankcase heater 46 is attached so as to be wound around the bottom 41 a of the casing 41. An oil temperature detector 62 is attached to the bottom 41a where the lubricating oil 70 is accumulated.

(1-3) Control Device and Measuring Device The air conditioner 10 also includes a control device 50 for controlling the operation of the air conditioner 10 and various measuring devices, as shown in FIG. Yes. Here, the measurement equipment related to the control of the crankcase heater 46 of the compressor 40 is shown, and the description of many other measurement equipment is omitted. The control device 50 is constituted by a microcomputer including, for example, a CPU (Central Processing Unit) 50a and a memory 50b.

  The control device 50 is connected to the fan motor 22 a of the indoor fan 22, the fan motor 32 a of the outdoor fan 32, the electric valve 33, the four-way switching valve 35, the motor 45 of the compressor 40, and the crankcase heater 46. Further, the control device 50 includes a refrigerant pressure detector 61 that measures the pressure of the suction pipe 43 of the compressor 40, an oil temperature detector 62 that detects the temperature of the lubricating oil 70 in the compressor 40, and an outside air temperature. An outside air temperature detector 63, a refrigerant pressure detector 64 that measures the pressure of the discharge pipe 42 of the compressor 40, a heat exchanger temperature detector 65 that detects the temperature of the indoor heat exchanger 21, and an indoor temperature detector that detects the indoor temperature. 66 is connected.

(2) Control of Crank Heater FIG. 3 is a flowchart showing an outline of control of the crankcase heater according to the first embodiment. FIG. 3 shows an outline of control related to the crankcase heater 46 after the compressor 40 is stopped. First, the compressor 40 is stopped by the control device 50 (step S1). At this time, the crankcase heater 46 is in an on state. Since the stop of the compressor 40 is performed according to an instruction from the control device 50, the control device 50 can detect the stop of the compressor 40. Therefore, in order to equalize the compressor 40 using the bypass pipe 47, the control device 50 opens the solenoid valve 48 (step S3). When the electromagnetic valve 48 is opened, the pressures in the discharge pipe 42 of the compressor 40 and the suction pipe 34a of the accumulator 34 are equalized, and the pressure in the compressor 40 is equalized. FIG. 4A shows a state of pressure before the electromagnetic valve 48 is opened after the compressor 40 is stopped, and FIG. 4B shows a state after the electromagnetic valve 48 is opened. The state of pressure is shown. As can be seen by comparing FIG. 4 (a) and FIG. 4 (b), before and after the electromagnetic valve 48 is opened, from the check valve 36 to the electric valve 33 through the outdoor heat exchanger 31. The pressure of the refrigerant in the pipe is kept high. On the other hand, the pressure in the piping from the compressor 40 to the check valve 36 changes from high pressure to low pressure when the electromagnetic valve 48 is opened.

  Thus, after the solenoid valve 48 is opened, the power supply of the crankcase heater 46 is turned off by the control device 50. Then, the control device 50 monitors whether or not the pressure difference ΔP between the dome pressure and the suction side pressure is smaller than the first predetermined pressure difference Y. The pressure difference between the pressure inside the dome and the suction side pressure is the measured value of the refrigerant pressure detector 61 attached to the suction pipe 43 from the measured value of the refrigerant pressure detector 64 attached to the discharge pipe 42 of the compressor 40. Is calculated by subtracting. If the control device 50 determines that the pressure difference ΔP is smaller than the first predetermined pressure difference Y (step S4), the crankcase heater 46 is turned on again (step S5). If it is determined that the pressure difference ΔP is not smaller than the first predetermined pressure difference Y (step S4), the crankcase heater 46 is kept off and the pressure difference ΔP is continuously monitored.

  The solenoid valve 48 is closed when the operation of the compressor 40 is resumed.

(3) Features (3-1)
As described above, in the refrigeration circuit 12 according to the first embodiment, the refrigerant is prevented from being dissolved in the lubricating oil due to the lower outside air temperature when the heating operation is performed. The indoor heat exchanger 21 installed in the subsequent stage of 40 functions as a radiator, and the outdoor heat exchanger 31 installed between the indoor heat exchanger 21 and the compressor 40 functions as an evaporator. Is the time. When the compressor 40 is stopped in such a refrigeration circuit 12, if the solenoid valve 48 (an example of an opening / closing mechanism) is opened (an example of a first state), the discharge pipe 42 of the compressor 40 is bypassed by a bypass pipe 47. The compressor 40 can be pressure-equalized through (an example of a high-pressure pipe) and the suction pipe 43 (an example of a low-pressure pipe).

  Since the solenoid valve 48 can be opened and the compressor 40 can be equalized by the bypass pipe 47 when the compressor 40 is stopped, the crankcase heater 46 (an example of a compressor heating heater) can be used when the solenoid valve 48 is opened. Even if the operation is stopped, the pressure in the compressor 40 is reduced, the evaporation of the refrigerant is promoted to increase the oil concentration, and the appropriate oil concentration or oil viscosity can be maintained for the lubricating oil in the compressor 40.

  This point will be described with reference to FIG. In FIG. 5, the curve φ1 indicates the refrigerant pressure in the suction pipe 43 of the compressor 40, the curve φ2 indicates the refrigerant pressure in the discharge pipe 42 of the compressor 40, and the curve φ3 indicates the check valve. The pipe pressure after 36 is shown, and the curve φ4 shows the oil concentration.

  The compressor 40 stops at the elapsed time tm0 in FIG. Looking at the curve φ1, it can be seen that the pressure in the suction pipe 43 is somewhat stable but is stable at a low pressure as the compressor 40 is stopped. On the other hand, when looking at the curve φ3, as the compressor 40 stops, the refrigerant pressure after the check valve 36 gradually decreases. For example, when a relatively long time such as 2 hours or 3 hours elapses, the pressure becomes constant. Convergence to pressure. This is because the entire refrigeration circuit 12 converges to a constant pressure after a sufficient time has elapsed since the compressor 40 was stopped.

  When the curve φ2 is compared with the curves φ1 and φ3, it can be seen that the pressure is higher than the pressure in the suction pipe 43 at the elapsed time tm0, but approaches the curve φ1 more rapidly than the curve φ3. This is because when the compressor 40 is stopped, the solenoid valve 48 is opened (step S2), and pressure equalization of the compressor 40 is started by the bypass pipe 47.

  With such operation of the air conditioner 10, the oil concentration decreases for a short period from the elapsed time tm0 and starts to increase from the elapsed time tm1, as shown by the curve φ4. Then, as the pressure equalization of the compressor 40 proceeds, the oil concentration also continues to increase, and converges to a constant value as a sufficient time elapses after the compressor 40 is stopped. The curve φ4 shown in FIG. 5 is measured with the crankcase heater 46 turned off.

  As shown by the curve φ4, the oil concentration in the compressor 40 rapidly increases with the pressure equalization by the bypass pipe 47, so that the necessary oil concentration is ensured even when the crankcase heater 46 is turned off. be able to. When the bypass pipe 47 is provided in this way, the pressure in the compressor 40 is reduced and the oil temperature can be kept longer than the case where the bypass pipe 47 is not provided, so that the evaporation of the refrigerant is promoted. Thus, the oil concentration can be increased, the appropriate oil concentration or oil viscosity can be easily maintained for the lubricating oil in the compressor 40, and standby power can be reduced.

(3-2)
As described above, the check valve 36 provided downstream of the bypass pipe 47 can prevent backflow from the outdoor heat exchanger 31 to the bypass pipe 47 when the compressor 40 is pressure-equalized. As a result, as shown in FIG. 5, the pressure in the compressor 40 can be suddenly lowered when the compressor 40 is stopped, so that the pressure in the compressor is reduced and the oil temperature is further increased. Can last long.

(3-3)
If the crankcase heater 46 is kept off after the crankcase heater 46 is turned off (step S3), the stagnation occurs again after a long time, and a lot of refrigerant is dissolved in the lubricating oil. In order to prevent such a situation, it is preferable to turn on the crankcase heater 46 again at an appropriate time. In the first embodiment, the crankcase heater 46 is configured such that the pressure difference ΔP between the pressure inside the dome of the compressor 40 and the suction side pressure is the first predetermined pressure when the electromagnetic valve 48 is open when the compressor 40 is stopped. When it becomes smaller than the difference Y, the heating of the compressor 40 is resumed. As described above, when the heating restart timing of the crankcase heater 46 is determined from the pressure difference ΔP between the dome pressure and the suction side pressure, the heating restart timing can be easily determined.

(4) Modification (4-1)
In the first embodiment, the air conditioner 10 turns off the crankcase heater 46 after the compressor 40 stops and turns on the crankcase heater 46 again by the pressure difference ΔP between the dome pressure and the suction side pressure. Judgment is made (step S4). However, the timing at which the crankcase heater 46 is turned on again can be determined by, for example, the passage of time of a timer instead of the pressure difference ΔP between the dome pressure and the suction side pressure.

  FIG. 6 is a flowchart in which step S4A is performed in place of step S4 in FIG. 3 to determine timing for turning on the crankcase heater 46 again by a timer. Therefore, since the operation performed by the air conditioner 10 in steps S1, S2, S3, and S5 in FIG. 6 is the same as the operation performed in the steps having the same reference numerals in FIG. 3, here, steps S1, S2, and S2 in FIG. Description of S3 and S5 is omitted.

  In step S4A of FIG. 6, the control device 50 determines whether or not to turn on the crankcase heater 46 again from the measured value of the timer that starts simultaneously with the stop of the compressor 40 (step S1). That is, when the measured value of the timer started when the compressor 40 is stopped exceeds the second predetermined time td2 set in the control device 50 in advance, the crankcase heater 46 is turned on again (step S6). The crankcase heater 46 is kept off until the second predetermined time td2 exceeds the measured value of the timer started when the compressor 40 is stopped. Thus, if the timing of restarting the heating of the crankcase heater 46 can be determined over time, heating can be reliably restarted over time, and standby power can be reduced while maintaining high reliability. it can.

(4-2)
In the first embodiment, the air conditioner 10 turns off the crankcase heater 46 after the compressor 40 stops and turns on the crankcase heater 46 again by the pressure difference ΔP between the dome pressure and the suction side pressure. Judgment is made (step S4). However, the timing at which the crankcase heater 46 is turned on again can be determined by, for example, an oil temperature offset value (oil temperature Toil−saturated gas temperature Tcg) instead of the pressure difference ΔP between the dome pressure and the suction side pressure. it can.

  FIG. 7 is a flowchart in which step S4B is performed in place of step S4 in FIG. 3 to determine the timing for turning on the crankcase heater 46 again based on the oil temperature offset value. Therefore, since the operation performed by the air conditioner 10 in steps S1, S2, S3, and S5 in FIG. 6 is the same as the operation performed in the steps having the same reference numerals in FIG. 3, here, steps S1, S2, and S2 in FIG. Description of S3 and S5 is omitted.

  In step S4B of FIG. 7, the control device 50 determines whether or not to turn on the crankcase heater 46 again from the oil temperature offset value. That is, after the compressor 40 is stopped, the crankcase heater 46 is turned on again when the oil temperature offset value falls below the first target offset value SH1 preset in the control device 50 (step S6). Until the oil temperature offset value falls below the first target offset value SH1, the crankcase heater 46 remains off. The oil temperature offset value will be described in detail later.

  When the solenoid valve 48 is open when the compressor 40 is stopped, the control device 50 determines whether or not to turn on the crankcase heater 46 again from the oil temperature offset value (oil temperature Toil−saturated gas temperature Tcg). For this reason, it is determined that the heating of the crankcase heater 46 is resumed including information on the temperature, and the determination of the restart is accurate. Since the oil temperature is high for a while after reaching the equilibrium pressure from the pressure equalization, the heating stop period can be ensured longer when judged by both the pressure and the oil temperature than when judging only by the pressure.

(4-3)
In addition, when the crankcase heater 46 is turned on again, instead of the pressure difference ΔP between the pressure inside the dome and the suction side pressure, for example, the lower one of the pressure inside the dome and the outside temperature or the room temperature (Tx) In other words, the pressure inside the dome is converted to the saturation temperature (Tref) and compared with the lower one of the outside air temperature and the indoor temperature (Tx) (Tref-Tx). It can also be judged by.

  FIG. 8 shows the timing for turning on the crankcase heater 46 again by comparing the saturation temperature (Tref) converted from the pressure in the dome with the above-described temperature (Tx) instead of step S4 in FIG. It is a flowchart which performs step S4C. Accordingly, since the operation performed by the air conditioner 10 in steps S1, S2, S3, and S5 in FIG. 8 is the same as the operation performed in steps with the same reference numerals in FIG. 3, here steps S1, S2, and S2 in FIG. Description of S3 and S5 is omitted.

  In step S4C of FIG. 8, the control device 50 determines whether or not to turn on the crankcase heater 46 again from the value of | Tref−Tx |. That is, after the compressor 40 is stopped, the difference between the saturation temperature (Tref) converted from the pressure inside the dome and the above-described temperature (Tx) falls below the temperature difference Td set in the control device 50 in advance. If the state continues for td1 or more, the crankcase heater 46 is turned on again (step S5). Until the oil temperature offset value falls below the first target offset value SH1, the crankcase heater 46 remains off.

  For example, depending on the control method at the time of stopping, the behavior as shown in FIG. 9 may be exhibited. As shown in FIG. 9, when the suction side pressure of the compressor 40 is greatly reduced, the pressure at the equalized elapsed time tm2 is still sufficiently low, and the curve indicating the pressure of the suction pipe 43 thereafter. The curve φ2 indicating φ1 and the pressure in the discharge pipe 43 rises and finally settles to a pressure corresponding to the outside air temperature (elapsed time tm3). By performing the determination in step S4C, the crankcase heater 46 can be kept off from the elapsed time tm2 to the elapsed time tm3, and the standby power reduction effect is improved.

  As a curve indicated by the value of (Tref−Tx), the curves φ5 and φ6 shown in FIG. 10 are typical examples. In the curve φ5, one temperature (Tref) gradually approaches the other temperature (Tx), so that one temperature is reversed from a state higher than the other temperature and one temperature is lower than the other temperature. There is no such thing. Therefore, even if the crankcase heater 46 is turned on when | Tref−Tx | falls below the temperature difference Td, the effect of reducing standby power is sufficiently improved. However, as shown by the curve φ6, the saturation temperature (Tref) is once lower than the temperature Tx before the pressure is equalized (elapsed time tm4). Therefore, it is necessary to avoid turning on the crankcase heater 46 at this time. In such a case, since | Tref−Tx | <Td is short in the vicinity of the elapsed time tm4, | Tref−Tx | <Td which is longer than the first predetermined time td1 longer than that time. If the state continues, the crankcase heater 46 may be turned on.

Second Embodiment
(5) Configuration of Air Conditioner and Control of Crank Heater In the first embodiment, as shown in the flowchart of FIG. 3, in the control device 50, the solenoid valve 48 is only on condition that the compressor 40 is stopped. The compressor 40 is configured to perform a pressure equalizing operation.

  However, when the curve φ4 in FIG. 5 is seen, the oil concentration tends to decrease from the elapsed time tm0 when the compressor 40 is stopped to the elapsed time tm1. If the oil concentration does not tend to decrease, or if there is a tendency to decrease, there is no problem even if the control device 50 performs the control as in the first embodiment.

  When such a tendency is remarkable, it is preferable to apply control of the control apparatus 50 by 2nd Embodiment demonstrated below. Since the configuration is the same as that of the air conditioner 10 of the first embodiment except for the control in the control device 50, the description of the configuration of the air conditioner 10 according to the second embodiment is omitted.

  FIG. 11 is a flowchart showing an outline of control related to the crankcase heater according to the second embodiment. First, the compressor 40 is stopped by the control device 50 (step S11). When the compressor 40 is stopped, the crankcase heater 46 is instructed to be kept on (step S12). Since the stop of the compressor 40 is performed according to an instruction from the control device 50, the control device 50 can detect the stop of the compressor 40. Therefore, in order to equalize the compressor 40 using the bypass pipe 47, the control device 50 opens the solenoid valve 48 (step S13). When the electromagnetic valve 48 is opened, the pressures in the discharge pipe 42 of the compressor 40 and the suction pipe 34a of the accumulator 34 are equalized, and the pressure in the compressor 40 is equalized.

  Immediately after the pressure equalization of the compressor 40 is performed, it is determined whether or not to turn off the crankcase heater 46 of the air conditioner 10 in which the decrease in the oil concentration of the curve φ4 in FIG. 5 becomes large (step S14). Specifically, in step S14, the control device 50 determines whether or not the pressure difference ΔP between the dome pressure and the suction side pressure is smaller than the second predetermined pressure difference X. The method for obtaining the pressure difference ΔP is the same as in step S4 of the first embodiment.

  Under the condition that the compressor 40 is stopped and the solenoid valve 48 is opened, monitoring is performed by the control device 50 until the pressure difference ΔP between the pressure in the dome and the suction side pressure becomes smaller than the second predetermined pressure difference X. Is done. When the pressure difference ΔP between the dome pressure and the suction side pressure becomes smaller than the second predetermined pressure difference X, the control device 50 turns off the power to the crankcase heater 46 (step S15).

  When the power supply of the crankcase heater 46 is turned off by the control device 50 after the solenoid valve 48 is opened (step S15), it is next determined whether or not the crankcase heater is turned on again (step S16). . When the pressure difference ΔP becomes smaller than the first predetermined pressure difference Y (step S16), the crankcase heater 46 is turned on again (step S17). If it is determined that the pressure difference ΔP is not smaller than the first predetermined pressure difference Y (step S16), the crankcase heater 46 continues to be off and the pressure difference ΔP is continuously monitored. The operations in step S16 and step S17 in the second embodiment are the same as the operations in step S4 and step S5 in the first embodiment. The solenoid valve 48 is closed when the operation of the compressor 40 is resumed.

(6) Features (6-1)
As described above, the crankcase heater 46 (an example of a heater for compressor heating) is a dome of the compressor 40 when the compressor 40 is stopped and the electromagnetic valve 48 is open (an example of the first state). When the pressure difference ΔP between the internal pressure and the suction side pressure becomes smaller than the second predetermined pressure difference X, the heating of the compressor 40 is stopped. For example, the crankcase heater 46 is turned off when the elapsed time tm1 in FIG. 5 elapses and the pressure difference ΔP between the dome pressure and the suction side pressure becomes smaller than the pressure difference ΔP of the elapsed time tm1. Can do. In FIG. 5, the oil concentration decreases from the elapsed time tm0 when the compressor 40 stops to the elapsed time tm1, but the second predetermined value smaller than the pressure difference generated in the section where the oil concentration or the oil viscosity decreases. By using the pressure difference X, it is possible to avoid stopping the heating of the crankcase heater 46 in a section where the oil concentration or the oil viscosity decreases. The crankcase heater 46 can be turned off while avoiding the section where the oil concentration or the oil viscosity decreases (for example, the section from the elapsed time tm0 to the elapsed time tm1 in FIG. 5), and the trouble caused by turning off the crankcase heater 46 in such a section Can be prevented in advance.

(7) Modification (7-1)
In the second embodiment, the timing at which the air conditioner 10 turns off the crankcase heater 46 after the compressor 40 is stopped is determined by the pressure difference ΔP between the dome pressure and the suction side pressure (step S14). This determination may be made based on the pressure difference between the pressure inside the dome of the compressor 40 and the discharge side pressure. In the air conditioner 10 shown in FIG. 1, since the check valve 36 is attached, the discharge side pressure becomes a pressure on the downstream side of the check valve 36. In this case, the crankcase heater 46 is turned on until the pressure in the dome of the compressor 40 and the discharge side pressure become larger than the third predetermined pressure difference. As described above, when the determination is made based on the pressure difference between the pressure in the dome and the discharge side pressure, for example, a pressure gauge is further provided on the downstream side of the check valve 36 or a fine differential pressure gauge is provided at both ends of the check valve 36. Can be attached.

(7-2)
In the second embodiment, the timing at which the air conditioner 10 turns off the crankcase heater 46 after the compressor 40 is stopped is determined based on the pressure difference ΔP between the dome pressure and the suction side pressure (step S14), and the crankcase again. The timing for turning on the heater 46 is also determined by the pressure difference ΔP between the pressure inside the dome and the suction side pressure (step S16). However, the timing at which the crankcase heater 46 is turned off and the timing at which the crankcase heater 46 is turned on again after the compressor 40 is stopped is changed to, for example, the time elapse of a timer instead of the pressure difference ΔP between the dome pressure and the suction side pressure. It can also be judged by.

  FIG. 12 shows step S14A for determining the timing for turning off the crankcase heater 46 by a timer instead of step S14 in FIG. 11, and timing for turning on the crankcase heater 46 again by a timer in place of step S16 in FIG. It is the flowchart which performs step S16A which judges. Accordingly, since the operation performed by the air conditioner 10 in steps S11, S12, S13, S15, and S17 in FIG. 12 is the same as the operation performed in the steps having the same reference numerals in FIG. 11, step S11 in FIG. Description of S12, S13, S15, and S17 is omitted.

  In step S14A of FIG. 12, the control device 50 determines whether or not to turn off the crankcase heater 46 from the measured value of the timer that starts simultaneously with the stop of the compressor 40 (step S11). That is, the crankcase heater 46 is turned off when the measured value of the timer started when the compressor 40 is stopped exceeds the third predetermined time td3 set in the control device 50 in advance (step S15). The crankcase heater 46 is kept on until the third predetermined time td3 exceeds the measured value of the timer started when the compressor 40 is stopped. Thus, if the crankcase heater 46 can be turned off over time, if the heating of the compressor 40 is stopped when the third predetermined time td3 has elapsed after the compressor 40 is stopped, the oil concentration or Since it is set longer than the period (tm0 to tm1) during which the oil viscosity decreases, the crankcase heater 46 can be turned on during the period in which the oil concentration or oil viscosity decreases. The crankcase heater 46 can be turned off while avoiding the section (tm0 to tm1) in which the oil concentration or the viscosity decreases, and the occurrence of problems can be prevented by turning off the crankcase heater 46 in such a section. Can do.

  In step S16A of FIG. 12, the control device 50 determines whether or not to turn on the crankcase heater 46 again from the measured value of the timer that starts simultaneously with the stop of the compressor 40 (step S11). That is, when the measured value of the timer started when the compressor 40 is stopped exceeds the second predetermined time td2 set in the control device 50 in advance, the crankcase heater 46 is turned on again (step S17). Until the second predetermined time td2 exceeds the measured value of the timer started when the compressor 40 is stopped, the crankcase heater 46 is kept off (step S16A). The value of the second predetermined time td2 is determined based on a test performed in advance. Since the timing of restarting the heating of the crankcase heater 46 can be determined from the passage of time, the heating can be reliably restarted.

(7-3)
In the second embodiment, the timing at which the air conditioner 10 turns off the crankcase heater 46 after the compressor 40 is stopped is determined based on the pressure difference ΔP between the dome pressure and the suction side pressure (step S14), and the crankcase again. The timing for turning on the heater 46 is also determined by the pressure difference ΔP between the pressure inside the dome and the suction side pressure (step S16). However, the timing at which the crankcase heater 46 is turned off after the compressor 40 is stopped and the timing at which the crankcase heater 46 is turned on again are, for example, the oil temperature offset value instead of the pressure difference ΔP between the pressure inside the dome and the suction side pressure. It can also be determined by (oil temperature Toil−saturated gas temperature Tcg).

  FIG. 13 is a flowchart in which step S14B is performed in place of step S14 in FIG. 11 to determine the timing for turning on the crankcase heater 46 again based on the oil temperature offset value. Accordingly, since the operation performed by the air conditioner 10 in steps S11, S12, S13, S15, and S17 in FIG. 13 is the same as the operation performed in the steps having the same reference numerals in FIG. 11, step S11 in FIG. Description of S12, S13, S15, and S17 is omitted.

  In step S14B of FIG. 13, the controller 50 determines whether or not to turn off the crankcase heater 46 from the oil temperature offset value after the compressor 40 is stopped (step S11). That is, after the compressor 40 is stopped, the crankcase heater 46 is turned off when the oil temperature offset value exceeds the second target offset value SH2 preset in the control device 50 (step S15). Until the oil temperature offset value falls below the second target offset value SH2, the crankcase heater 46 is kept on.

  When the compressor 40 is stopped, the control device 50 determines that when the solenoid valve 48 is open, the heater for the compressor heats the crankcase heater 46 when the oil temperature offset value becomes larger than the second target offset value SH2. Is turned off and heating of the compressor 40 is stopped.

  By setting the second target offset value SH2 that is smaller than the oil temperature offset value in the section in which the oil concentration or oil viscosity decreases, the crankcase heater 46 avoids the section in which the oil concentration or oil viscosity decreases (from tm0 to tm1). Can be turned off. By using the oil temperature offset value, the crankcase heater 46 can be turned off while avoiding the section where the oil concentration or the oil viscosity is lowered, and it is possible to prevent problems from occurring by turning off the crankcase heater 46 in such a section. can do.

  In step S <b> 16 </ b> B of FIG. 13, the control device 50 determines whether or not the crankcase heater 46 is turned on again from the oil temperature offset value. That is, after the compressor 40 is stopped, the crankcase heater 46 is turned on again when the oil temperature offset value falls below the first target offset value SH1 preset in the control device 50 (step S17). Until the oil temperature offset value falls below the first target offset value SH1, the crankcase heater 46 remains off (step S16B).

  When the compressor 40 is stopped, when the solenoid valve 48 is open, the control device 50 determines whether or not the crankcase heater 46 is to be turned on again from the oil temperature offset value. It is determined that the heating of the heater 46 is restarted, and the period until the heating of the compressor 40 is restarted after the pressure equalization by the bypass pipe 47 can be finely determined. Since it is possible to finely determine the period until the heating of the compressor is resumed after pressure equalization by the bypass pipe 47, the effect of reducing standby power can be sufficiently obtained. The oil temperature offset value will be described in detail later.

(8) General Control Using Oil Temperature Offset Value For example, general control of the crankcase heater 46 by the control device 50 using the oil temperature offset value will be described along the flowchart of FIG. Here, the general control of the crankcase heater 46 is a control at a time other than the control immediately after the compressor 40 is stopped as in the above-described modified examples 4-2 and 5-2. Since the control device 50 controls the motor 45 of the compressor 40, the control device 50 has information on the operation and stop state of the compressor 40. In the state where the compressor 40 is stopped, the control device 50 first receives the detection result of the refrigerant pressure detector 61 and calculates the saturated gas temperature Tcg in the compressor 40 (step S20). If the refrigerant pressure LP is known, the refrigerant saturated gas temperature Tcg can be easily calculated from the relationship between the refrigerant pressure and the saturation temperature using a well-known method. For example, the control device 50 stores a relational expression fa indicating the relationship between the refrigerant pressure LP and the saturated gas temperature Tcg, and calculates the saturated gas temperature Tcg using the relational expression fa.

Next, the control device 50 calculates the oil temperature target value T _so by adding a predetermined temperature (hereinafter referred to as an oil temperature offset value) to the saturated gas temperature Tcg obtained in step S20. The oil temperature offset value is determined based on data stored in the memory 50b of the control device 50 (step S21).

FIG. 15 is a graph showing the relationship between the saturated gas temperature Tcg and the oil temperature offset value. The graph shown in FIG. 15 varies depending on the oil concentration _Cso . FIG. 15 shows two graphs when the oil concentration C _so is 60% (refrigerant concentration is 40%) and when the oil concentration C _so is 70% (refrigerant concentration is 30%). For example, when the oil concentration _Cso of the refrigeration apparatus of the air conditioner 10 is determined to be 60%, the data on the lower side of FIG. 15 is used, and the other data is not used. If the saturated gas temperature Tcg obtained in step S20 is 5 ° C, the oil temperature offset value is determined as Tos1 ° C from the point P1. Therefore, the oil temperature target value T _so is determined as 5 ° C. + Tos 1 ° C. (saturated gas temperature Tcg + oil temperature offset value). The graph shown in FIG. 15 is approximated by, for example, a simple quadratic expression fb, and the control device 50 calculates the oil temperature target value T _so from the values of the oil concentration C _so and the saturated gas temperature Tcg. Formula fb (Tcg) is its formula is prepared for each oil concentration C _so. Then, an equation is selected according to the value of the oil concentration C _so , and the oil temperature target value T _so is calculated from the value of the saturated gas temperature Tcg using the selected equation fb (T _r ).

The control device 50 detects the oil temperature of the lubricating oil 70 in the compressor 40 using the oil temperature detector 62 (step S22). The oil temperature detector 62 may be installed so as to directly detect the oil temperature of the lubricating oil 70, but here is attached to the bottom 41 a of the casing 41. The oil temperature detector 62 may be installed at the side of the compressor 40 as long as it is around the oil reservoir. Therefore, the control unit 50 substitutes the detection results of the oil temperature detector 62 a simple correction formula fc detects the oil temperature T _o. This correction formula fc can be determined, for example, from actual measurements performed on the detection result of the oil temperature detector 62 and the value detected by inserting a temperature sensor directly into the lubricating oil 70.

In step S23, the control unit 50 compares the oil temperature target value T _so and the oil temperature T _o, the process proceeds to step S24 if the oil temperature T _o is reached the oil temperature target value T _so, the crank case heater 46 is turned on and the process returns to step S20. If, in step S23, is compared with the oil temperature target value T _so and the oil temperature T _o, if the oil temperature T _o is reached the oil temperature target value T _so, the controller 50 proceeds to step S25, The crankcase heater 46 is turned off and the process returns to step S20.

Controller 50, by performing such control, at the time of stopping the compressor 40, may be the oil temperature T _o to control the crank case heater 46 so as to satisfy the oil temperature target value T _so.

(9) the oil temperature offset value thus refrigeration system of the air conditioner 10 is under the control of the control unit 50, the oil temperature T _o of the lubricating oil 70 reaches the oil temperature target value T _so during the stop of the compressor 40 It is comprised so that a state can be maintained. The oil temperature target value T _so is determined by the saturated gas temperature Tcg + the oil temperature offset value.

The oil temperature offset value is set to the temperature of the mixed liquid of the lubricating oil 70 and the refrigerant _so that the oil temperature target value _Tso is the oil concentration at the time of dissolution equilibrium at the refrigerant pressure LP.

  This point will be described with reference to FIG. FIG. 16 is a graph showing the relationship between the refrigerant pressure LP in the equilibrium state, the temperature of the mixed liquid of the lubricating oil 70 and the refrigerant (hereinafter referred to as the liquid temperature), and the solubility of the refrigerant. The points Ps1, Ps2, Ps3, and Ps4 shown in FIG. 16 correspond to the points P1, P2, P3, and P4 in FIG. 15, respectively.

In the graph of FIG. 16, a point Ps1 is a point at which the oil concentration is 60% (the solubility of the refrigerant is 40%) in a state where the pressure is α1 and the liquid temperature is β1 during the dissolution equilibrium. Then, as shown in FIG. 17, if the crankcase heater 46 is left without being turned on in the state ST1 at the point Ps1, the liquid temperature of the refrigerant that maintains the equilibrium state ST2 at the pressure α1 from the current liquid temperature β1. changes to the saturation gas temperature Tcgα _1. At this time, the refrigerant further dissolves in the lubricating oil, and the oil concentration decreases from 60%. That is, in order to keep the oil concentration at 60%, the liquid temperature may be kept at β1.

Accordingly, the oil temperature offset value (oil concentration in pressure upon dissolution equilibrium [alpha] 1 is the liquid temperature to 60%) - is given by (saturation temperature of the refrigerant pressure [alpha] 1), i.e. β1-T _r α _1.

A method of determining the oil temperature offset value for each refrigerant saturation temperature will be described with reference to FIGS. 15 and 16. About oil concentration, the desired setting value is determined for every refrigeration apparatus from a viewpoint of reliability and standby power reduction. Therefore, in the case of a refrigeration apparatus in which the oil concentration is set to 60%, for example, a straight line parallel to the vertical axis (hereinafter referred to as the 40% line) at which the solubility is 40% and the curves L1, L2, L3, L4. Look at the relationship. Then, the solubility curve where the 40% line intersects at the point Ps2 of the pressure α2 is L2, the curve where the 40% line intersects at the point Ps3 of the pressure α3 is L3, and the curve where the 40% line intersects at the point Ps4 of the pressure α4 is L4. On the other hand, the temperature of the solubility curve of the virtual indicated by the two-dot chain line passing through the point P _th2 saturation temperature and the oil temperature is equal in pressure α2 becomes T _r alpha _2. Similarly, the temperature of the solubility curve of the virtual through the points P _th3 pressure α3 becomes T _r alpha _3, the temperature of the solubility curve of the virtual through the points P _th4 pressure α4 becomes T _r alpha _4. Accordingly, the oil temperature offset value when the pressure α2 is a value obtained by subtracting the temperature T _r alpha ₂ from the temperature β2 indicated by curve L2. Similarly, the oil temperature offset value is a value obtained by subtracting the temperature T _r α ₃ from the temperature β 3 indicated by the curve L 3 when the pressure is α ₃ , and the temperature T _r α ₄ indicated by the curve L 4 when the pressure is α _4. The value minus.

  As described above, the oil temperature offset value is a value determined as one when the pressure of the refrigerant in the compressor 40 is determined. The oil temperature offset value is also a value that can be obtained in advance if the graph of FIG. 16 is known.

  Plots of the oil temperature offset values of the four saturation temperatures obtained from the graph of FIG. 16 in this way are points P1, P2, P3, and P4 of the graph shown in FIG. For example, a graph showing the relationship between the saturation temperature and the oil temperature offset value is completed by applying a least square method or the like to the obtained points P1, P2, P3, P4. . An approximate expression indicating the curve of the graph shown in FIG. 15 is stored as data in the memory 50 b of the control device 50.

(10) Characteristics of general control using oil temperature offset value (10-1)
As described above, the refrigeration apparatus of the air conditioner 10 includes the indoor heat exchanger 21 (radiator or evaporator), the outdoor heat exchanger 31 (evaporator or radiator), the compressor 40, and the crankcase heater 46. A control device 50, a refrigerant pressure detector 61, and an oil temperature detector 62 are provided. Then, the control unit 50, the oil of the lubricating oil in the compressor 40 oil temperature offset value (predetermined temperature) of the oil temperature target value T _so obtained was added to the saturated gas temperature Tcg of the refrigerant in the compressor 40 temperature T _o to control the heater to reach.

  In the conventional technique, for example, as shown in FIG. 18, the crankcase heater may be turned on even in a high oil concentration section. In other words, when the outside air temperature increases from a low state where the crankcase heater must be turned on, the outside air temperature is turned off even if the oil concentration is high enough not to turn on the crankcase heater. In some cases, the ON state may be maintained regardless of the oil concentration in order to maintain the situation until the condition becomes.

On the other hand, in the control device 50 using the oil temperature offset value, the oil temperature target value _Tso is set to a predetermined oil concentration at the time of dissolution equilibrium at the refrigerant pressure in the compressor 40 by the oil temperature offset value (predetermined temperature). It is set to the temperature (for example, β1 to β4) of the mixed liquid of the lubricating oil 70 and the refrigerant having a value (for example, 60%). Therefore, the heater 50 is not affected by the temperature of the outside air, and the control device 50 can control the crankcase heater 46 with the oil concentration, and the standby power is not turned on without turning on the crankcase heater 46 in the high oil concentration section. Can be reduced. And the control apparatus 50 can control the crankcase heater 46 so that it may become the oil temperature which maintains a fixed oil concentration.

In the refrigeration apparatus that controls the crankcase heater 46 using the oil temperature offset value, as shown in FIG. 15, even if the temperature of the lubricating oil 70 and the refrigerant pressure change due to the crankcase heater 46 being turned on and off. Then, the oil temperature offset value is obtained from the saturated gas temperature Tcg obtained therefrom using the same simple formula representing the curve of FIG. That is, the control device 50 does not need to have information on the solubility curve, and can simplify the calculation associated with the heater control. Further, even if the types of the lubricating oil and the refrigerant are changed and it is necessary to obtain data as shown in FIG. 15 for newly holding in the control device 50, a predetermined set value (for example, oil concentration) (for example, 60%), it is only necessary to know the saturation temperature and the oil temperature offset value, so that it is not necessary to convert the solubility curve into data, and the design man-hour is shortened. In the embodiment described above, the case where the on / off control is performed has been described. However, in the air conditioner 10 according to the present embodiment, the control device 50 controls only the temperature for the crankcase heater 46. It is also easy to adopt a configuration that shortens the time required to reach the oil temperature target value _Tso using.

(10-2)
Further, there is little data stored in the memory 50b of the control device 50, and if the oil temperature offset value (predetermined temperature) is held as data for each saturation temperature shown in FIG. Necessary storage capacity and calculation load can be saved. Thereby, the control of the crankcase heater 46 in the control device 50 can be performed at a high speed, and the response to the change in the condition of the compressor 40 is accelerated.

(11) Modification of general control using oil temperature offset value (11-1)
The relationship between the saturation temperature and the oil temperature offset value held by the control device 50 described in the modification examples 4-2 and 5-2 does not indicate a curve in which the oil concentration becomes 60%, but a predetermined setting range, for example, It may be indicated by a curve or straight line that falls between 60 and 65%. For example, the straight line LN in FIG. 15 is a straight line that falls within the oil concentration setting range of 60 to 65%. The straight line LN is close to a curve indicating the relationship between the saturation temperature at which the oil concentration set value is 65% and the oil temperature offset value on the side where the saturation temperature is relatively low, and the oil concentration set value is on the side where the saturation temperature is relatively high. It is set to be close to a curve showing the relationship between the saturation temperature of 60% and the oil temperature offset value.

  When the control device 50 performs control using such a straight line LN, a certain range (for example, 60 to 65%) is formed in the control range of the oil concentration. For this reason, it is possible to set so that the set value of the oil concentration changes within a predetermined setting range. When the straight line LN is used, the oil temperature offset value is obtained by proportional calculation from the saturation temperature, and the control becomes simple.

(11-2)
In the air conditioner 10 described in the modification examples 4-2 and 5-2, the oil concentration is set as a set value, and the oil concentration is set to a predetermined setting range or a predetermined set value as shown in FIG. The relationship between the saturation temperature and the oil temperature offset value is obtained, and the control device 50 controls the crankcase heater 46 using the relationship.

  However, instead of the oil concentration value, the oil viscosity value may be used for the predetermined setting range or the predetermined setting value when obtaining the relationship between the saturation temperature and the oil temperature offset value. Originally, the control of the crankcase heater 46 in order to make the oil concentration within a predetermined set range or a predetermined set value has the purpose of preventing the oil viscosity from decreasing, so that the purpose can be achieved directly. Heater control that can be performed may be performed. Therefore, even when the oil viscosity is used, the oil temperature offset value can be determined as in the case of the oil concentration.

(11-3)
In the air conditioner 10 described in the modification examples 4-2 and 5-2, the case where the oil temperature of the lubricating oil 70 in the compressor 40 is detected by the oil temperature detector 62 has been described. The oil temperature of the lubricating oil 70 may be estimated from the detection result. For example, the detection result of the oil temperature detector 62 may be corrected by using the outside air temperature around the compressor 40, the temperature of the indoor heat exchanger 21, or the like, so as to further improve the accuracy. . Alternatively, without using the oil temperature detector 62, the oil temperature of the lubricating oil 70 in the compressor 40 is estimated from the measurement result of another measuring device that performs the measurement related to the parameter for estimating the oil temperature of the lubricating oil 70. You may do it.

(11-4)
In the air conditioner 10 described in the modified examples 4-2 and 5-2, the control device 50 performs on / off control of the crankcase heater 46, but changes the heating amount according to the value of the oil temperature offset value. Such control may be performed. For example, when the pressure change in the compressor 40 is steep, the value of the oil temperature offset value may become a negative value. In such a case, a change may be made to increase the heating amount as compared with the case where the oil temperature offset value takes a positive value.

(11-5)
In the air conditioner 10 described in the modification examples 4-2 and 5-2, the refrigerant pressure detector 61 is attached to the suction pipe 43, and the pressure of the refrigerant in the compressor 40 is measured on the suction pipe 43 side. Yes. However, when the pressure of the refrigerant in the compressor 40 can be measured better on the discharge pipe 42 side than on the suction pipe 43 side, a refrigerant pressure detector 61 is attached to the discharge pipe 42 on the suction pipe 43. The pressure may be detected.

(11-6)
In the air conditioner 10 described in the modification examples 4-2 and 5-2, the saturated gas temperature is used as the saturation temperature, but the saturated liquid temperature may be used as the saturation temperature.

(11-7)
In the air conditioner 10 described in the modification examples 4-2 and 5-2, the crankcase heater 46 is used to warm the lubricating oil 70. However, the heater for warming the lubricating oil 70 is limited to the crankcase heater 46. I can't. For example, a motor winding heating method by phase loss energization can be used as a method for warming the lubricating oil 70. In this case, a motor winding is used as a heater for warming the lubricating oil 70. In this case, the control device 50 performs on / off control of the motor winding heating by phase loss energization as the heater control.

DESCRIPTION OF SYMBOLS 10 Air conditioner 21 Indoor heat exchanger 31 Outdoor heat exchanger 36 Check valve 40 Compressor 42 Discharge pipe 43 Intake pipe 46 Crankcase heater 47 Bypass pipe 48 Solenoid valve 50 Control apparatus 61 Refrigerant pressure detector 62 Oil temperature detector 64 Refrigerant pressure detector

Japanese Patent Laid-Open No. 2001-73952 Japanese Patent No. 4111246

Claims (10)

A compressor (40) for circulating refrigerant in the refrigeration circuit;
A radiator (21) installed downstream of the compressor of the refrigeration circuit;
An evaporator (31) installed between the radiator of the refrigeration circuit and the compressor;
A high-pressure pipe (42) connected to the discharge side of the compressor;
A low-pressure pipe (43) connected to the suction side of the compressor;
A bypass pipe (47) for bypassing the refrigerant from the high pressure pipe to the low pressure pipe;
An opening / closing mechanism (48) provided in the bypass pipe;
A compressor heater (46) for heating the compressor;
With
The opening / closing mechanism is configured to be able to switch between a first state for opening the bypass pipe and a second state for closing the bypass pipe when the compressor is stopped,
The compressor heating heater stops the heating of the compressor when the opening / closing mechanism is in the first state. A check valve (36) is further provided downstream of the connection position of the bypass pipe of the high-pressure pipe and before the radiator.
The refrigeration apparatus according to claim 1. The heater for heating the compressor resumes heating of the compressor in the first state when a pressure difference between the pressure in the dome of the compressor and a suction side pressure becomes smaller than a first predetermined pressure difference;
The refrigeration apparatus according to claim 1 or 2. In the first state, the heater for heating the compressor is compressed when a difference between a saturation temperature obtained by converting the pressure inside the dome and a lower temperature of the outside air temperature and the room temperature is lower than a predetermined temperature difference. Resume heating the machine,
The refrigeration apparatus according to claim 1 or 2. The heater for heating the compressor is configured to heat the compressor when a difference between the saturation temperature and a lower temperature of the outside air temperature and the room temperature is less than the predetermined temperature difference and the state continues for a first predetermined time or more. Resume,
The refrigeration apparatus according to claim 4. The heater for heating the compressor resumes heating of the compressor in the first state when a second predetermined time elapses after the compressor is stopped;
The refrigeration apparatus according to claim 1 or 2. The compressor heating heater resumes heating of the compressor when the oil temperature offset value becomes smaller than the first target offset value in the first state.
The refrigeration apparatus according to claim 1 or 2. In the first state, the heater for heating the compressor is discharged when the pressure difference between the pressure inside the dome of the compressor and the pressure on the suction side becomes smaller than a second predetermined pressure difference or when the pressure inside the dome of the compressor is discharged. The heating of the compressor is stopped when the pressure difference with the side pressure becomes larger than a third predetermined pressure difference,
The refrigeration apparatus according to any one of claims 1 to 7. The heater for heating the compressor stops heating the compressor when a third predetermined time has elapsed after stopping the compressor in the first state.
The refrigeration apparatus according to any one of claims 1 to 7. The heater for heating the compressor stops heating the compressor when the oil temperature offset value becomes larger than the second target offset value in the first state;
The refrigeration apparatus according to any one of claims 1 to 7.

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