JP2004101143A - Vapor compression type refrigerator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent reduction of the amount of refrigerating machine oil to be returned to a compressor. <P>SOLUTION: The state of a large refrigerant flow rate is forcibly switched from the state of a small refrigerant flow rate when a state that the refrigerant flow rate Gr is below a predetermined value G1 lasts for a predetermined time. Accordingly, even when the refrigerant flow rate Gr is below the predetermined value G1, and the refrigerant flow speed is reduced, the refrigerant flow rate is forcibly increased/decreased, and the refrigeration machine oil staying at outlets of evaporators 5a and 5b and in a low-pressure pipe or the like can be sufficiently circulated to a suction side of a compressor 1 by the refrigerant flow. Therefore, reduction of the amount of the refrigeration machine oil returned to the compressor 1 can be prevented in advance, occurrence of seizure or the like of the compressor 1 can be prevented, and the durability of the compressor 1 can be improved thereby. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor compression refrigerator having first and second evaporators, and more particularly, to a front seat air conditioning unit for air conditioning a front seat side area of a vehicle compartment, and air conditioning for a rear seat side area of a passenger compartment. The present invention is suitably applied to a vehicle air conditioner including a rear seat side air conditioning unit.
[0002]
[Prior art]
Conventionally, in a dual air conditioner having a front seat air conditioning unit and a rear seat air conditioning unit, when the continuous operation time of the compressor exceeds a predetermined time, the electromagnetic clutch is forcibly turned on and off to thereby control the suction side pressure of the compressor. Is forcedly changed so that the refrigerating machine oil retained in the evaporator or the low-pressure refrigerant pipe on the rear seat side is returned to the compressor (for example, see Patent Document 1).
[0003]
The refrigerating machine oil is a lubricating oil for lubricating a sliding portion in a compressor. In a vapor compression refrigerating machine, lubricating oil (refrigerating oil) is usually added to a sliding portion in a compressor by mixing lubricating oil in a refrigerant. Machine oil).
[0004]
[Patent Document 1]
JP 2000-283576 A
[Problems to be solved by the invention]
By the way, according to the experimental study of the present inventor, for example, in an air conditioner, when the flow rate of the refrigerant circulating in the refrigerator becomes less than a predetermined flow rate and the flow rate of the refrigerant decreases, the refrigerant oil stagnant at the evaporator outlet or the low-pressure pipe or the like is cooled. It was found that the flow could not sufficiently recirculate to the compressor suction side, and the amount of refrigerating machine oil that could be returned to the compressor was reduced.
[0006]
In view of the above points, the present invention firstly provides a new vapor compression type refrigerator different from the conventional one, and secondly, prevents a reduction in the amount of refrigerating machine oil returning to the compressor. With the goal.
[0007]
[Means for Solving the Problems]
To achieve the above object, according to the first aspect of the present invention, the first and second evaporators (5a, 5b), the radiator (2), the pressure reducing means (4a, 4b), and the compressor ( A vapor compression refrigerator including the above (1), wherein when a state in which the circulating refrigerant flow rate is less than a predetermined flow rate (G1) continues for a predetermined time, a large refrigerant flow state and a small refrigerant flow state are forcibly switched. A flow rate switching control means (S130) is provided, and the predetermined flow rate (G1) is determined when both the first and second evaporators (5a, 5b) generate heat absorption capability and when the first and second evaporators (5a, 5b) are used. It is characterized in that it is different from the case where only one of the evaporators generates the heat absorbing ability.
[0008]
As a result, even if the refrigerant flow rate becomes lower than the predetermined flow rate (G1) and the refrigerant flow rate decreases, the refrigerant flow rate is forcibly increased and decreased, and the refrigerating machine oil stagnated in the low-pressure pipe at the outlet of the evaporator (5a, 5b) is removed. Since the refrigerant can be sufficiently recirculated to the suction side of the compressor (1) by the refrigerant flow, it is possible to prevent the amount of refrigerating machine oil returning to the compressor (1) from decreasing. As a result, it is possible to prevent the occurrence of problems such as seizure of the compressor (1), so that the durability of the compressor (1) can be improved.
[0009]
According to the second aspect of the present invention, the compressor (1) is a variable displacement compressor capable of changing the discharge capacity, and the flow rate switching control means (S130) changes the discharge capacity to change the large refrigerant. It is characterized in that the flow state and the small refrigerant flow state are forcibly switched.
[0010]
According to the third aspect of the present invention, a large refrigerant flow state is set by maximizing the discharge capacity of the compressor (1), and a small refrigerant flow state is set by minimizing the discharge capacity of the compressor (1). It is characterized by the following.
[0011]
Incidentally, the reference numerals in parentheses of the respective means are examples showing the correspondence with specific means described in the embodiments described later.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
(1st Embodiment)
In the present embodiment, the vapor compression refrigerator according to the present invention is applied to an air conditioner for a vehicle, and FIG. 1 is a schematic diagram of the vapor compression refrigerator according to the embodiment.
[0013]
The compressor 1 receives power from a traveling engine to suck and compress refrigerant, and in the present embodiment, controls the pressure in a swash plate chamber (crank chamber) to continuously change the inclination angle of the swash plate. The compressor employs a variable displacement compressor that can continuously change the discharge capacity.
[0014]
More specifically, the discharge capacity of the compressor 1 is controlled by controlling the pressure in the swash plate chamber by a control valve. In the present embodiment, when the discharge capacity is increased, the current value or the current supplied to the control valve is controlled. When the duty ratio (hereinafter, referred to as a control current value) is increased, and the discharge capacity is reduced, the control current value is decreased.
[0015]
Incidentally, the discharge capacity means a theoretical (geometric) volume discharge flow rate discharged when the shaft of the compressor makes one rotation.
[0016]
The condenser 2 is a radiator for cooling the high-temperature and high-pressure refrigerant discharged from the compressor 1, and the receiver 3 separates the refrigerant flowing out of the condenser 2 into a gaseous refrigerant and a liquid-phase refrigerant and converts the surplus refrigerant into a liquid-phase refrigerant. The gas-liquid separator stores the refrigerant as a refrigerant. In the present embodiment, the liquid-phase refrigerant is supplied to the decompressors 4a and 4b described later.
[0017]
The first and second decompressors 4a and 4b are expansion valves for expanding the high-pressure refrigerant by isenthalpy, and the first and second evaporators 5a and 5b exchange heat between the depressurized refrigerant and air blown into the room to exchange heat. The first evaporator 5a is a heat exchanger that absorbs heat from the air that is blown out and evaporates the refrigerant. The first evaporator 5a cools the air that is housed in the front seat side air conditioning unit and mainly blows out to the front seat side, and the second evaporator 5b Cools air that is housed in the rear air conditioning unit and blows out mainly to the rear seat side.
[0018]
The first decompressor 4a is a well-known temperature-type expansion valve that variably controls a throttle opening so that a refrigerant superheat degree at a refrigerant outlet of the first evaporator 5a becomes a predetermined value. , Having a structure similar to that of the first decompressor 4a, and controls the throttle opening so that the refrigerant superheat degree at the refrigerant outlet of the second evaporator 5b becomes a predetermined value.
[0019]
The first blower 6a is a blower for a front seat air conditioning unit, and the second blower 6b is a blower for a rear seat air conditioning unit. In FIG. 1, the first and second blowers 6a and 6b are depicted as axial fans, but FIG. 1 is a schematic diagram and does not show the actual shape of the blower. Incidentally, in this embodiment, a centrifugal fan is used as a blower.
[0020]
An electronic control unit (ECU) 7 controls a discharge capacity of the compressor 1, that is, a valve (not shown) for controlling a pressure in the swash plate chamber. The pressure sensor 7a detects the pressure Pd, the air temperature immediately after passing through the first evaporator 6a, that is, the post-evaporation temperature sensor 7b for detecting the temperature of the first evaporator 6a, the outside air temperature sensor 7c for detecting the outdoor air temperature, and the room. The detected temperature of the inside air temperature sensor 7d for detecting the air temperature and the temperature setting device 7e for setting the room temperature desired by the occupant are input.
[0021]
The discharge capacity of the compressor 1 is controlled so that the temperature detected by the post-evaporation temperature sensor 7b becomes a predetermined value (for example, 3 ° C. to 4 ° C.).
[0022]
Next, the operation of the vehicle air conditioner according to the present embodiment will be described.
[0023]
1. Switching between single operation and dual operation Single operation, that is, when operating either the front air conditioning unit or the rear air conditioning unit, the refrigerant is circulated while the blower of the operating unit is operating. Let it. On the other hand, in the dual operation, that is, when both the front seat side air conditioning unit and the rear seat side air conditioning unit are operated, the refrigerant is circulated in a state where both the blowers 6a and 6b are operated. When both air conditioning units are stopped, the discharge capacity of the compressor 1 is set to the minimum (0%) capacity with both the blowers 6a and 6b stopped.
[0024]
2. Control of refrigerating machine oil amount returning to compressor 1 This control mode is a control mode for preventing the refrigerating machine oil amount returning to compressor 1 from excessively decreasing. It is executed in any operation of the dual operation. Hereinafter, the operation of this control mode will be described based on the flowchart shown in FIG.
[0025]
When a start switch (not shown) of the air conditioner is turned on, it is determined whether the circulating refrigerant flow rate Gr is less than a predetermined flow rate G1 (S100), and the refrigerant flow rate Gr is less than the predetermined flow rate G1. Is continued for a predetermined time, the large refrigerant flow state and the small refrigerant flow state are forcibly switched (S110 to S130). In the present embodiment, the coolant flow rate Gr and the predetermined flow rate G1 mean a mass flow rate.
[0026]
At this time, the predetermined flow rate G1, which is the threshold value, is determined during the dual operation in which both the first and second evaporators 5a and 5b generate the heat absorbing capability, and between one of the first and second evaporators 5a and 5b. In the present embodiment, the predetermined flow rate G1 in the dual operation is set to a value larger than the predetermined flow rate G1 in the single operation.
[0027]
Incidentally, although the predetermined flow rate G1 varies depending on the type of the evaporator and the required air conditioning capacity, in the present embodiment, the predetermined flow rate G1 in the dual operation is set to 40 to 80 kg / h, and the predetermined flow rate G1 in the single operation is set. It is 20 to 40 kg / h.
[0028]
In the “forceful switching between the large refrigerant flow state and the small refrigerant flow state”, in the present embodiment, as shown in FIG. 3, the maximum (100%) capacity operation and the minimum (0%) capacity operation are performed. Switching is performed three times every 10 seconds.
[0029]
In the present embodiment, the refrigerant flow rate Gr is obtained from the characteristic diagram shown in FIG. 4, that is, the control current (discharge capacity) and the discharge pressure pd, but the present invention is not limited to this.
[0030]
Next, the operation and effect of the present embodiment will be described.
[0031]
In the present embodiment, when the state in which the refrigerant flow rate Gr is less than the predetermined flow rate G1 continues for a predetermined time, the large refrigerant flow state and the small refrigerant flow state are forcibly switched, so that the refrigerant flow rate Gr becomes less than the predetermined flow rate G1. Even if the flow rate of the refrigerant is reduced, the flow rate of the refrigerant is forcibly increased and decreased, and the refrigerating machine oil stagnated at the outlets of the evaporators 5a and 5b and the low-pressure pipe and the like can be sufficiently returned to the suction side of the compressor 1 by the refrigerant flow. it can.
[0032]
Therefore, since it is possible to prevent the amount of the refrigerating machine oil returning to the compressor 1 from being reduced, it is possible to prevent a problem such as the seizure of the compressor 1 and to improve the durability of the compressor 1. be able to.
[0033]
FIG. 5 is a test result showing changes in the amount of refrigerant returning to the compressor 1 and the oil circulation rate (= refrigeration oil circulation amount / (refrigeration oil circulation amount + refrigeration circulation amount)). Thus, if the large refrigerant flow state and the small refrigerant flow state are forcibly switched after the continuation of the predetermined time Tx, it can be seen that the oil circulation rate increases, and the amount of refrigerating machine oil returning to the compressor 1 increases.
[0034]
Incidentally, in the present embodiment, the predetermined time Tx is selected based on the time when the oil circulation rate becomes 1.5% or less.
[0035]
Further, since the predetermined flow rate G1, which is the threshold value, is made different between the single operation and the dual operation, the oil return control suitable for the operation state can be performed.
[0036]
(2nd Embodiment)
In the first embodiment, whether or not the refrigerant flow rate Gr is less than the predetermined flow rate G1 is determined by directly measuring the refrigerant flow rate Gr. However, the correlation between the amount of air blown to the evaporator and the refrigerant flow rate Gr is determined. Accordingly, in the present embodiment, as shown in FIG. 6, in S100, it is determined in S100 whether the blowing amount is less than the predetermined blowing amount, and the refrigerant flow Gr is indirectly determined to be less than the predetermined flow G1. It is determined whether or not there is.
[0037]
(Other embodiments)
In the above-described embodiment, a variable displacement compressor is used. However, the present invention is not limited to this. For example, a fixed displacement compressor may be employed. In this case, since the discharge capacity cannot be changed, it is necessary to forcibly switch between the large refrigerant flow state and the small refrigerant flow state by stopping the compressor 1 or reducing the rotation speed. is there.
[0038]
Further, in the above-described embodiment, the maximum (100%) capacity operation and the minimum (0%) capacity operation are switched every 10 seconds. However, the present invention provides a “condition in which the refrigerant flow rate Gr is less than the predetermined flow rate G1. Since the flow rate is forcibly increased and decreased when the predetermined time is continued, the discharge capacity or the flow rate is not limited to the maximum and the minimum.
[0039]
Further, the coolant flow rate Gr is not limited to the mass flow rate, and may be determined as a volume flow rate.
[0040]
Further, the method of measuring the refrigerant flow rate Gr is not limited to the method described in the above embodiment.
[0041]
In the above-described embodiment, the single operation and the dual operation are switched by the blowers 6a and 6b. However, the present invention is not limited to this. For example, the refrigerant flow itself is controlled by a valve such as an electromagnetic valve. You may switch between single operation and dual operation.
[0042]
Further, in the above embodiment, the present invention is applied to the air conditioner, but the application of the present invention is not limited to this.
[Brief description of the drawings]
FIG. 1 is a schematic view of a vapor compression refrigerator according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing a control flow of the vapor compression refrigerator according to the first embodiment of the present invention.
FIG. 3 is a characteristic diagram showing characteristics of control according to the first embodiment of the present invention.
FIG. 4 is a characteristic diagram showing a relationship between a control current (discharge capacity), a discharge pressure pd, and a refrigerant flow rate Gr.
FIG. 5 is a diagram showing a relationship between a refrigerant oil amount and an oil circulation rate returned to a compressor and a refrigerant flow rate Gr. FIG. 6 is a control flow of a vapor compression refrigerator according to a second embodiment of the present invention. It is a flowchart which shows.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Compressor, 2 ... Condenser, 3 ... Receiver, 4a, 4b ... Decompressor (expansion valve),
5a, 5b: evaporator, 6a, 6b: blower.

Claims (3)

A vapor compression refrigerator including first and second evaporators (5a, 5b), a radiator (2), a pressure reducing means (4a, 4b), and a compressor (1),
A flow switching control means (S130) for forcibly switching between a large refrigerant flow state and a small refrigerant flow state when a state in which the circulating refrigerant flow rate is less than a predetermined flow rate (G1) continues for a predetermined time;
The predetermined flow rate (G1) is determined when the first and second evaporators (5a and 5b) generate heat absorption capacity and when the heat is absorbed by one of the first and second evaporators (5a and 5b). A vapor compression refrigerator characterized in that it differs only when it generates heat absorption capacity only by itself. The compressor (1) is a variable displacement compressor capable of changing a discharge capacity,
2. The vapor compression refrigerator according to claim 1, wherein the flow rate switching control means (S130) forcibly switches between a large refrigerant flow state and a small refrigerant flow state by changing a discharge capacity. The large refrigerant flow state is set by maximizing the discharge capacity of the compressor (1), and the small refrigerant flow state is set by minimizing the discharge capacity of the compressor (1). Item 3. A vapor compression refrigerator according to item 2.

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