JPH0735425A - Refrigerating device - Google Patents

Abstract

PURPOSE:To permit the equal retention of oil in respective compressors by a method wherein suction pipelines for a plurality of constant-speed compressors are provided respectively with a resistance which surely reduces the internal pressure of a compressor at a side, in which a compressor is readily stopped upon light load under the condition that all of the compressors are operated. CONSTITUTION:A suction pipe is provided with a resistance 10b so that a point, whereat the internal pressure of a variable speed compressor coincides with the internal pressure of a constantspeed compressor 1b, becomes the amount of suction oil while a resistance 10c, which reduces the internal pressure of the constant-speed compressor 1c so as to be lower than the same of the constant-speed compressor 1b, is provided. As a result, the direction of discharging oil amount suction oil amount becomes the low side of the internal pressure and oil is moved from a high-pressure side compressor, in which the discharging amount of oil becomes smaller than the amount of suction oil. The constant speed compressor 1c is provided with the resistance 10c so that the internal pressure becomes lower than the same of the constant-speed compressor 1b whereby oil is moved from the constant-speed compressor 1b. Accordingly, oil is retained in respective compressors equally whereby trouble accompanied by the shortage of amount of oil can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration system.

[0002]

2. Description of the Related Art FIG. 1 is a circuit diagram of a conventional refrigeration system using a plurality of compressors. In the figure, 1a is a variable speed compressor, 1b and 1c are constant speed compressors, 2a, 2b and 2c are oil separators provided in the discharge pipes of the compressors, and 3 is a connecting point of the discharge pipes. Four-way valve, 4 is an outdoor heat exchanger connected to the same four-way valve, 5 is a check valve connected to the same heat exchanger, 6 is an outdoor throttle provided in parallel with the check valve, 7a, 7b, 7c,
7d is a variable throttle connected to the check valve 5 and the outdoor throttle 6;
Reference numerals a, 8b, 8c, 8d are indoor heat exchangers connected to the variable throttles and the four-way valve 3, and 9 is connected to the four-way valve 3 and on each suction side of the compressors 1a, 1b, 1c. A continuous accumulator, 11 is an oil equalizing pipe that communicates with each compressor.

In this apparatus, the compressors 1a, 1b, 1c
The high-temperature, high-pressure refrigerant gas discharged from each of them enters the oil separators 2a, 2b, 2c, separates the oil components contained in the refrigerant gas, and then gathers to reach the four-way valve 3. In the cooling operation, the four-way valve 3 reaches the outdoor heat exchanger 4, where heat is radiated and condensed / liquefied. The liquefied refrigerant reaches the indoor unit through the check valve 5. Each indoor unit has a variable aperture 7a, 7b,
7c, 7d are provided, and the pressure is reduced here to reach the indoor heat exchangers 8a, 8b, 8c, 8d. In the indoor heat exchangers 8a, 8b, 8c, 8d, heat is exchanged with the indoor air, and the refrigerant evaporates and vaporizes. The vaporized refrigerant reaches the accumulator 9 via the four-way valve 3. The refrigerant discharged from the accumulator merges with the oil components separated in the oil separators 2a, 2b, 2c, and the compressors 1a, 1b, 1
Returning to step c, the refrigeration cycle is completed.

Even in the heating operation, the compressor portion is the same, and the high temperature / high pressure gas passing through the four-way valve 3 reaches each indoor heat exchanger 8a, 8b, 8c, 8d, where heat is exchanged with the indoor air. Dissipates heat and condenses and liquefies. The liquefied refrigerant is slightly decompressed in the variable throttles 7a, 7b, 7c, 7d and reaches the outdoor throttle 6. Here, the pressure is reduced again, reaches the outdoor heat exchanger 4, absorbs heat, evaporates and vaporizes, and returns to the compressor 1 via the four-way valve 3 and the accumulator 9. The number of operating compressors is changed according to the number of indoor units used. An oil equalizing pipe 11 is provided to make the oil level of each compressor uniform.

[0005]

In the circuit of FIG. 8, most of the oil contained in the refrigerant discharged from the compressors 1a, 1b, 1c is separated by the respective oil separators 2a, 2b, 2c, Although it returns to each compressor through the suction pipe connected to the compressor, a part of the refrigerant also goes out to the refrigeration cycle side together with the refrigerant gas. The oil content discharged during the refrigeration cycle circulates in the refrigeration cycle together with the refrigerant, and the accumulator 9
Leading to. After leaving the accumulator, it is distributed to each compressor. At this time, the variable speed compressor has a different discharge oil amount depending on the operating frequency, and the oil components discharged from each compressor are mixed and averaged by the refrigerant circuit and the accumulator 9,
The oil content returned to each compressor does not necessarily match the oil content output.

Therefore, the compressor has a large amount of oil discharged into the refrigeration cycle, and the amount of oil held in the compressor gradually decreases.
1 is used to move excess oil from the compressor side where the amount of retained oil increases. The movement of oil is performed from the high pressure side to the low pressure side by the internal pressure of the compressor connected by the oil equalizing pipe 11. Depending on the operating frequency of the variable speed compressor, the shape of the suction pipe connected to each compressor, and the like, the amount of oil in the compressor does not necessarily increase on the high-pressure side and the amount of oil decrease decreases on the low-pressure side.
If the amount of oil that decreases decreases to the high pressure side, the oil equalizing pipe 1
No oil is supplied from the compressor connected at 1, and the oil continues to decrease, and the oil content disappears, causing a compressor failure.

The oil component sucked into the compressor flows along the inner wall of the compressor, and while the oil flows down, the oil equalizing pipe provided on the inner wall of the compressor is connected to move directly from the high pressure side to the low pressure side. Therefore, if the amount of oil falls below the appropriate value, it will cause a compressor failure.

Further, from the accumulator 9 to the compressor 1a,
It is not possible to branch the oil at the ratio of the refrigerant circulation amount of each compressor at the branch portion of the suction pipe reaching 1b and 1c, and the amount of oil returned to either compressor is small, and the oil amount is below the appropriate value. In that case, it causes a compressor failure.

The present invention aims to solve the above-mentioned drawbacks of the prior art and to provide a refrigerating apparatus in which oil is uniformly held in each compressor.

[0010]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is one variable speed compressor, and one or more constant speed compressors connected in parallel to the variable speed compressor. A refrigerating apparatus provided with an oil equalizing pipe that connects a compressor, a condenser, a throttle, and an evaporator and sequentially connects two adjacent compressors each has the following features.

(1) When operating a plurality of compressors, the operating frequency of the variable speed compressor is such that the amount of discharge oil and the amount of intake oil of the variable speed compressor and the constant speed compressor connected thereto are equal. In this case, a resistance that equalizes the internal pressure of the variable speed compressor with the internal pressure of the constant speed compressor connected to the variable speed compressor by an oil equalizing pipe is provided in the suction pipe line, and the constant pressure connected to multiple units is fixed. The suction line of the high-speed compressor is equipped with a resistor that reduces the internal pressure of the compressor on the side that tends to stop when the load is light during full-compressor operation. Each compressor was connected with an oil equalizing pipe in an array in which the constant-speed compressors connected with the oil equalizing pipe were sequentially lowered.

(2) In the refrigerating apparatus according to the item (1), the oil equalizing pipe is attached so as to project inward from the inner wall of the compressor by a predetermined length or more.

(3) In the refrigerating apparatus according to the item (1), after a plurality of compressors have been operated for a certain period of time, the compressors on the operation stop side are sequentially stopped at light load, and then at light load. An oil-equalizing operation control means that sequentially operates for a fixed time from the compressor on the operation continuation side is provided.

[0014]

According to the invention of the above item (1), when a plurality of variable speed compressors and a constant speed compressor connected to the variable speed compressor by an oil equalizing pipe are in operation, the discharge oil amount> the intake oil amount side compressor. It is possible to prevent the oil from continuing to decrease by lowering the internal pressure and moving the oil from the compressor on the high internal pressure side where discharge oil amount <intake oil amount. At a frequency lower than the operating frequency of the variable speed compressor where the amount of discharged oil = the amount of intake oil, the regular compressor side discharges the amount of oil> the amount of intake oil, the internal pressure of the compressor becomes lower than that of the variable speed compressor, and the oil moves. Is variable speed → constant speed. When the operating frequency is high, the oil movement is from constant speed to variable speed.

When a plurality of constant speed compressors are connected and operated, the internal pressure of the constant speed compressor, which gradually stops at a light load, is increased compared to the constant speed compressor connected to the variable speed compressor by an oil equalizing pipe. By lowering it, the variable speed compressor and oil are moved. The oil level of each compressor can be secured by sequentially moving the oil from the constant speed compressor connected to the constant speed compressor by an oil equalizing pipe.

Regarding the invention of the above item (2), the refrigerant and the oil enter the inside of the compressor through the suction pipe and are sucked into the cylinder, but the oil component flows down along the inner wall of the compressor. By thrusting the oil equalizing pipe into the compressor by a certain amount or more, it is possible to prevent the oil falling along the inner wall of the compressor from being directly sucked into the oil equalizing pipe.
After the oil has accumulated in the compressor for a certain amount or more, the oil moves so that the oil level in the compressor can be secured.

With respect to the invention of the above item (3), since the internal pressure of the compressor becomes higher than that of the operating compressor by stopping the compressor, oil above the oil equalizing pipe level moves from the stop side to the operating side. Become. By controlling the operation of each compressor, it is possible to average the amount of oil.

[0018]

1 is a circuit diagram of a refrigerating apparatus having a plurality of compressors according to a first embodiment of the present invention. In the figure, 1a is a variable speed compressor, and 1b and 1c are constant speed compressors connected in parallel to the variable speed compressor. Generally, one or more constant speed compressors are connected. 10b and 10
c is a throttle connected to the accumulator 9 and branched on the way to the constant speed compressors 1b and 1c, 11a,
Reference numeral 11b is an oil equalizing pipe that sequentially connects two adjacent compressors. Since the configuration other than the above is the same as that of the conventional technique (FIG. 8), description thereof will be omitted.

The high-temperature, high-pressure refrigerant gas discharged from the compressors 1a, 1b, 1c gathers and reaches the four-way valve 3. After that, up to the accumulator 9, both the cooling operation and the heating operation are the same as in the case of FIG. 8 shown in the related art. Here, the amount of oil in the refrigerant discharged from each compressor is as shown in FIG. 2 with respect to the operating frequency of the variable speed compressor 1a. That is, in the variable speed compressor, the amount of discharged oil is large when the operating frequency is high, and the amount of discharged oil is small when the operating frequency is low. On the other hand, the constant frequency compressor has a constant operating frequency and a constant discharge oil amount. When operating a plurality of compressors, different oil refrigerants are mixed in the refrigerant circuit, and the averaged oil refrigerant returns from the accumulator 9 to the compressors 1a, 1b, 1c, and the relationship between the discharge oil amount and the intake oil amount is shown in FIG. It becomes the street. When the operating frequency of the variable speed compressor is low and the amount of discharged oil is low, the variable speed side has a discharge amount <suction amount, and the constant speed side has a discharge amount> a suction amount. When the operating frequency is high, the variable speed side is the discharge amount> the suction amount, and the constant speed side is the discharge amount <the suction amount, and the discharge oil amount and the suction oil amount of the compressors 1a and 1b match at a certain point.

On the other hand, the movement of oil between the compressors is carried out through the oil equalizing pipe due to the pressure difference inside the compressor, and the internal pressure of the compressor is as shown in FIG. 4 on the basis of the variable speed compressor.
Here, a resistance 10b is provided in the suction pipe so that the point where the internal pressures of the variable speed compressor 1a and the constant speed compressor 1b coincide with each other becomes the point (X _HZ ) where the suction oil amount = the discharge oil amount, and the constant speed is set. Compressor 1
A resistor 10c is provided so that the internal pressure of c becomes lower than that of the constant speed compressor 1b. As a result, between the variable speed compressor 1a and the constant speed compressor 1b, the internal pressure becomes lower when the discharge oil amount> the intake oil amount, regardless of the operating frequency of the variable speed compressor, and the discharge oil amount <the intake oil amount. Oil moves from the high pressure side compressor.
Since the constant speed compressor 1c is provided with a resistor 10c so that the internal pressure is lower than that of the constant speed compressor 1b, the constant speed compressor 1b is provided.
Move more. As shown in FIG. 5, when the oil equalizing pipes 11a and 11b are inserted into the compressor over a certain value, the oil moves to another compressor only when the oil equalizing pipe level position is reached. Disappears.

From the accumulator 9 to the compressors 1a, 1a
When the oil is not properly branched at the branch portion of the suction pipe reaching b and 1c and the oil amount of each compressor becomes uneven as shown in case A of FIG. 6, the following operation is performed. To make the oil surface uniform. The variable speed compressor 1a is operated at a high frequency to reduce the internal pressure of the compressor, and the constant speed compressor 1c is stopped to collect oil in the compressors 1a and 1b. Next, the variable speed compressor 1
A is operated at a low frequency to increase the internal pressure of the compressor to move the oil above the oil equalizing pipe of the variable speed compressor 1a to the constant speed compressor 1b. Next, by stopping the constant speed compressor 1b and operating the constant speed compressor 1c, the oil above the oil equalizing pipe of the constant speed compressor 1b is moved to the constant speed compressor 1c. Even when the amount of oil in each compressor is the case B in FIG. 6, the same amount of oil in each compressor can be averaged by performing the same operation. Further, the same result can be obtained by sequentially controlling the operation of the compressors on the stop side at light load, regardless of how many constant speed compressors are connected.

FIG. 7 is a circuit diagram of a refrigerating apparatus having a plurality of compressors according to the second embodiment of the present invention. In this device 1
Reference numeral a is a variable speed compressor, 2 is an oil separator provided on the discharge side of the variable speed compressor 1a, and the separated oil component is returned to the suction side. The structure and operation of the parts other than the above are the same as those of the first embodiment (FIG. 1).

In the present embodiment, most of the oil discharged from the compressor is separated in the oil separator 2 and is distributed to each compressor as described above, so that the oil separator 2 cannot be completely separated and the system is circulated. Even if the distribution of the oil content to each compressor is not necessarily appropriate, each compressor can hold an appropriate amount of oil. Further, as for the oil separator, it is not necessary to individually provide each compressor as in the prior art (FIG. 8), so that the system is economical.

In common with each of the above-mentioned embodiments, the throttle for adjusting the internal pressure of each compressor is designed so that the resistance of the compressor on the continuous operation side at the time of low load becomes smaller, so that the load becomes smaller. Efficient operation can be performed even when the size becomes small.

[0025]

In the refrigerating apparatus of the present invention, when operating a plurality of compressors, the discharge oil amount and the intake oil amount of the variable speed compressor and the constant speed compressor connected thereto become equal. At the operating frequency of the variable speed compressor, a resistance such that the internal pressure of the variable speed compressor is equal to the internal pressure of the constant speed compressor connected to the variable speed compressor by an oil equalizing pipe is provided in the suction pipeline, and , The suction pipes of multiple constant-speed compressors are equipped with resistances so that the internal pressure of the compressor on the side that tends to be stopped during light load during operation of all compressors will always be low. The pressure is gradually lowered from the constant speed compressor connected to the variable speed compressor with the oil equalizing pipe, and each compressor is connected with the oil equalizing pipe, or the oil equalizing pipe further protrudes inward from the inner wall of the compressor for a certain length or more. And installed, and moreover, the operation of multiple compressors is After the time has elapsed, the compressors on the light load operation stop side are sequentially stopped, and then the compressors on the light load operation continuation side are sequentially operated for a certain period of time. In this case, the oil is held evenly, and it is possible to prevent a failure due to a shortage of the oil amount when the conventional oil amount unevenness occurs.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a refrigerating apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a compressor operating frequency and a discharge oil amount according to the above embodiment.

FIG. 3 is a diagram showing the relationship between the amount of discharged oil and the amount of sucked oil in the above embodiment.

FIG. 4 is a diagram showing a relationship between a compressor operating frequency and a compressor internal differential pressure according to the above embodiment.

FIG. 5 is a view of a compressor cross section and an oil level pipe fixing position according to the above embodiment.

FIG. 6 is a diagram of an oil leveling operation control method and the amount of each compressor oil according to the above embodiment.

FIG. 7 is a circuit diagram of a refrigerating apparatus according to a second embodiment of the present invention.

FIG. 8 is a circuit diagram of a conventional refrigeration system.

[Explanation of symbols]

 1a Variable speed compressor 1b, 1c Constant speed compressor 2 Oil separator 3 Four-way switching valve 4 Outdoor heat exchanger 5 Check valve 6 Heating throttle 7a, 7b, 7c, 7d Cooling and heating variable throttle 8a, 8b, 8c, 8d Indoor heat exchanger 9 Accumulator 10b, 10c Fixed throttle 11a, 11b Oil level pipe

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsutoshi Kitagawa 3-chome, Asahimachi, Nishibiwajima-cho, Nishikasugai-gun, Aichi Prefecture Mitsubishi Heavy Industries, Ltd. Air Conditioning Factory

Claims (3)

[Claims] 1. A variable speed compressor, one or more constant speed compressors connected in parallel to the variable speed compressor, a condenser, a throttle, and an evaporator are connected to each other and adjacent to each other. In a refrigeration system provided with an oil equalizing pipe that sequentially connects the compressors one by one,
When operating multiple compressors, the variable speed compressor and the constant speed compressor connected to the variable speed compressor are operated at the operating frequency of the variable speed compressor at which the discharge oil amount and the intake oil amount are equal. The suction pipe of a constant-speed compressor in which a plurality of units are connected is provided with a resistance so that the internal pressure of the equalizer becomes equal to the internal pressure of the constant-speed compressor connected to the variable-speed compressor by an oil equalizing pipe. Each road is equipped with a resistance that reduces the internal pressure of the compressor on the side that is easy to stop when the load is light during full-compressor operation.
A refrigeration system in which each compressor is connected by an oil equalizing pipe in an array in which the internal pressure of the compressor is gradually lowered from a constant speed compressor connected by a variable speed compressor with an oil equalizing pipe. 2. The refrigerating apparatus according to claim 1, wherein the oil equalizing pipe is attached so as to project inward from the inner wall of the compressor by a predetermined length or more. 3. The refrigerating apparatus according to claim 1, wherein after a plurality of compressors have been operated for a certain period of time, the compressors on the light load operation stop side are sequentially stopped, and then the light load operation continuation side. Refrigerating apparatus comprising: an oil-equalizing operation control unit that sequentially operates for a predetermined time from the compressor.