JPH04222354A - Operation controller for refrigerating equipment - Google Patents

Abstract

PURPOSE:To prevent the shortage of oil in respective compressors by a method wherein two sets of compressors, connected in parallel, are connected by an oil equilibrating pipe and discharging refrigerant is bypassed into the oil equilibrating pipe when one of the compressor is operated with a low capacity while the other compressor is operated with a high capacity. CONSTITUTION:Domes of two sets of compressors 1A, 1B, connected in parallel to a refrigerant circuit 14, are connected through an oil equilibrating pipe 33. The amount of oil in the compressors 1A, 1B is retained uniformly through the oil equilibrating pipe 33 during normal operation. When one of the compressor 1A is operated with a high capacity and the other compressor 1B is operated with a low capacity, a pressure in the dome of the compressor 1A is reduced whereby lubricating oil tries to flow from the side of the compressor 1B through the oil equilibrating pipe 33. An opening and closing valve 36, provided on a bypass passage 35, is opened by an opening and closing control means 50 under such an operating condition and discharging refrigerant is introduced into the oil equilibrating pipe 33. Accordingly, the flow of oil in the oil equilibrating pipe 33 is precluded by the gas refrigerant and the shortage of oil in the compressor 1B due to the outflow of excessive oil into the compressor 1A can be prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation control device for a refrigeration system in which a plurality of compressors connected to each other via oil equalizing pipes are connected in parallel to a refrigerant circuit, and more particularly to a countermeasure against oil shortage.

0002

[Prior Art] Conventionally, for example, Japanese Patent Application Laid-Open No. 2-12604
As disclosed in Publication No. 4, two compressors are connected in parallel to a refrigerant circuit, and the operating capacity of each compressor is inverted.
The capacity of the compressor can be finely adjusted by variably adjusting the compressor and unloader mechanisms, and the lubricating oil of each compressor is evenly distributed by connecting the domes of each compressor with oil equalizing pipes. It is a known technique to distribute oil through oil pipes to make the amount of oil uniform in each compressor.

0003

[Problem to be Solved by the Invention] However, in the above-mentioned conventional system, if operation continues for a long time under conditions where the capacity difference between the compressors is large, the dome pressure of the higher capacity compressor will increase. This causes oil to flow from the low-capacity compressor to the high-capacity compressor via the oil-equalizing pipe, and this increased flow causes uneven hot water, causing a shortage of lubricating oil in the high-capacity compressor. However, there is a risk that failures such as burnout may occur and reliability may be impaired.

[0004] In order to prevent the above-mentioned unbalanced oil, the pressure loss in the suction pipe of one compressor is made larger than the pressure loss in the suction pipe of the other compressor. A so-called forced differential pressure system has also been adopted in which a large amount of oil sucked into the dome pressure side compressor is transferred to the low dome pressure side compressor via an oil equalization pipe to provide an oil equalization effect.

However, even when oil equalization is achieved using the forced differential pressure method, there is a risk that each compressor may run out of oil depending on operating conditions. In other words, if the high dome pressure side compressor has a low capacity and the low dome pressure side compressor has a high capacity and is operated for a long period of time, the dome differential pressure between each compressor becomes excessive and oil movement occurs. The amount becomes too large and the high dome pressure compressor becomes starved of oil. Conversely, if the compressor on the high dome pressure side is operated at high capacity and the compressor on the low dome pressure side is operated at low capacity for a long period of time, the differential pressure between each compressor will reverse, causing the low dome pressure side to There was a risk that the oil in the pressure side compressor would flow back into the high dome pressure side compressor, causing the low dome pressure side compressor to become starved of oil.

[0006] The present invention has been made in view of the above-mentioned problems, and its purpose is to reduce the amount of oil under operating conditions in which an insufficient amount of oil may occur due to uneven operating capacity among the compressors. The purpose of this invention is to prevent oil shortages in each compressor by taking measures to prevent the flow of oil in the oil equalizing pipes, thereby improving reliability.

[0007]

[Means for achieving the object] In order to achieve the above object, the solution of the present invention provides that under operating conditions with large capacity differences,
The purpose is to introduce the discharged refrigerant into the oil equalizing pipe.

Specifically, the means taken by the invention of claim 1 is as shown in FIG. A refrigeration system is assumed in which the domes of the compressors (1A) and (1B) are connected to each other by oil equalizing pipes (33).

[0009] As an operation control device for a refrigeration system,
The discharge side of the compressors (1A) and (1B) and the oil equalizing pipe (
33), an on-off valve (36) that opens and closes the bypass passage (35), and one of the two compressors (1A) and (1B).
1A) is operated at a low capacity and the other compressor (1B) is operated at a high capacity, an opening/closing control means (50) opens the opening/closing valve (36) to bypass the discharged refrigerant to the oil equalizing pipe (33); ). The means taken by the invention of claim 2 is that in the invention of claim 1, the pressure loss in the suction pipe of one of the two compressors (1A) and (1B) is lower than the pressure loss of the suction pipe of the other compressor (1A). Compressor (
1B) is configured to increase the pressure loss of the suction pipe,
The opening/closing control means (50) is configured such that the compressor (1B) on the side with a large pressure loss has a small capacity and the compressor (1B) on the side with a large pressure loss (
1A) is configured to control the on-off valve (36) to open when it is operated at high capacity.

0010

[Operation] With the above configuration, in the invention of claim 1, two compressors (
The domes of 1A) and (1B) are connected by an oil equalizing pipe (33), and during normal operation, the oil amount in each compressor (1A) and (1B) is maintained uniformly through the oil equalizing pipe (33). be done. on the other hand,
One of the two compressors (1A) and (1B) (
For example, one compressor (1A) is operated at high capacity and the other compressor (1B
) is operated at a low capacity, the pressure inside the dome on the one compressor (1A) side decreases, so lubricating oil flows in from the other compressor (1B) side via the oil equalizing pipe (33). However, under such operating conditions, the opening/closing control means (50)
Therefore, the on-off valve (36) provided in the bypass path (35)
) is opened and the discharged refrigerant is introduced into the oil equalizing pipe (33), so the flow of oil in the oil equalizing pipe (33) is blocked by the presence of this gas refrigerant, and excess oil is not transferred to one compressor (1A). This will prevent oil shortage in the other compressor (1B) due to oil leakage.

In the invention of claim 2, during normal operation, lubricating oil flows from one compressor (1A) with a large amount of oil to the low dome pressure side compressor (1B), so that the amount of oil in both is uniform. maintained. Then, when one compressor (1A) is operated at high capacity and the other compressor (1B) is operated at low capacity, the differential pressure is reversed and from the other compressor (1B) to one compressor (1A). )
However, under such operating conditions, the on-off valve (36) is opened by the on-off control means (50) and the discharged refrigerant flows back into the oil equalizing pipe (33). Since this is introduced, backflow of oil due to reversal of differential pressure is prevented, and oil equalization by forced differential pressure is more reliably performed.

(Example) An example of the present invention will be described below with reference to FIG. 2 and subsequent drawings.

FIG. 2 shows a refrigerant piping system of a multi-type air conditioner according to an embodiment of the present invention, in which (A) is an outdoor unit, and (B) to (D) are connected in parallel to the outdoor unit (A). This is an indoor unit. Inside the outdoor unit (A), a compressor (1) and an oil separator (4) that separates oil in the gas discharged from the compressor (1),
There is a four-way switching valve (5) that switches as shown in the solid line in the figure during cooling operation and as shown in the broken line in the figure during heating operation, and an outdoor heat exchanger (5) that functions as a condenser during cooling operation and as an evaporator during heating operation.
6) and two outdoor fans (6a), (6b) attached to the outdoor heat exchanger (6), and an outdoor electric expansion device that adjusts the refrigerant flow rate during cooling operation and throttles the refrigerant during heating operation. A valve (8), a receiver (9) for storing liquefied refrigerant, and an accumulator (10) for removing liquid refrigerant from the suction refrigerant are built-in as main equipment.
Each of the devices (1) to (10) is connected to a refrigerant connecting pipe (11).
) are connected to allow refrigerant flow. The indoor units (B) to (D) have the same configuration, and each has an indoor heat exchanger (12), which serves as an evaporator during cooling operation and a condenser during heating operation, and its fan (12a),... The liquid refrigerant branch pipes (11a), ... of the indoor heat exchangers (12), ... are equipped with indoor electric expansion valves (11a), which adjust the refrigerant flow rate during heating operation, and throttle the refrigerant during cooling operation.
13),... are respectively interposed, and after merging, a manual closing valve (1
7) and (17), and is connected to the outdoor unit (A) by a connecting pipe (11b). That is,
Each of the above devices is connected through refrigerant piping (11) so that refrigerant can flow, and a main refrigerant circuit (14) is configured to release heat obtained through heat exchange with outdoor air to indoor air. ing.

Here, the compressor (1) is a first compressor (1A) whose capacity is controlled by an unloader mechanism (1a).
and a second compressor (1B) whose operating frequency is variably adjusted by an inverter (1b).
1A) and (1B) in the main refrigerant circuit (14),
The first and second suction branch pipes (31A) of the suction pipe (31), (
31B) and the first and second discharge branch pipes (32) of the discharge pipe (32)
The domes of each compressor (1A) and (1B) are connected in parallel to each other via capillary tubes (33a).
) are connected. Here, although not shown, the second
The suction pipe (31B) is the first pipe to which the main thick pipe is connected.
The first suction pipe (31A) is smaller in diameter than the suction pipe (31A).
) is provided so as to protrude into the second suction pipe (3
1B) is set to be larger than the pressure loss in the first suction pipe (31A). In other words, by providing a forced differential pressure in this way, under normal operating conditions, that is, when the capacities of the compressors (1A) and (1B) do not have such an extreme difference in capacity, the compressor has the property of flowing along the wall surface. While allowing more oil to flow into the first compressor (1A) than the second compressor (1B), each compressor (1A
) and (1B) during operation, oil flows from the first compressor (1A) side to the second compressor (1B) side through the oil equalizing pipe (33), causing oil to flow between both ( 1A), (
1B) is used to equalize the oil.

Further, an oil return passage (34) for returning recovered oil from the oil recovery device (4) to the upstream side of the accumulator (10) of the main refrigerant circuit (14) is connected to the capillary tube (3).
4a), and furthermore, the downstream side of the capillary tube (34a) of the oil return passage (34) and the oil equalizing pipe (33) are connected by a branch passage (35), and this branch passage (35) is provided with an on-off valve (36) that opens and closes the branch path (35). This on-off valve (36) is normally closed, and a small amount of gas refrigerant mixed with oil is always returned to the suction side of the compressor (1) only through the oil return passage (34), while the on-off valve (36) is open. When this happens, a large amount of gas refrigerant mixed with oil is introduced into the oil equalizing pipe (33).

Note that (11e) is a heating overload control bypass path that connects the discharge pipe and the liquid pipe side so that the discharge gas (hot gas) can be bypassed;
1e) includes an auxiliary heat exchanger (22) installed in the air passage common with the outdoor heat exchanger (6), a capillary tube (28), and an electromagnetic on-off valve (2) that opens when the refrigerant is at high pressure.
4) are sequentially connected in series and in parallel with the outdoor heat exchanger (6), and the electromagnetic shut-off valve (24) is turned on or opened at all times during cooling operation and when high pressure rises excessively during heating operation. A part of the discharged gas is transferred to the main refrigerant circuit (14).
He is trying to bypass from there to the heating overload control bypass path (11e). At this time, part of the discharged gas is condensed in the auxiliary heat exchanger (22) to support the capacity of the outdoor heat exchanger (6), and is also transferred to the outdoor heat exchanger (6) side through the capillary tube (28). This is done to balance the pressure loss.

Furthermore, (11g) is connected to the liquid refrigerant side piping of the heating overload bypass path (11e) and the main refrigerant circuit (14).
) is a liquid injection bypass passage for adjusting the degree of superheating of suction gas during cooling/heating operation, and is connected to the suction line of the compressor (1). An injection solenoid valve (29a) that opens and closes in conjunction with a capillary tube (29a)
9b) is interposed. Note that (30) cools the suction refrigerant through heat exchange between the suction refrigerant in the suction pipe (11) and the liquid refrigerant in the liquid pipe (11), and
The suction pipe heat exchanger (GP) for compensating for the increase in superheat of the refrigerant in b) is a gauge port.

[0018] In addition, many sensors are arranged in the device, (TH1),... are room temperature thermostats that detect the indoor temperature, (TH2),... and (TH3),... are the room temperature thermostats that detect the indoor temperature, respectively. The indoor liquid temperature sensor and the indoor gas temperature sensor (TH5) detect the temperature of the refrigerant in the liquid side and gas side piping of the exchanger (12),... during heating operation, from the outlet temperature of the outdoor heat exchanger (6). The defrost sensor (TH6) that detects the frost condition is arranged in the suction pipe (11) on the downstream side of the suction pipe heat exchanger (31), and the suction pipe sensor (TH7) that detects the temperature of the suction pipe is the outdoor heat The outside temperature sensor (P1) is placed at the air suction port of the exchanger (6) and detects the intake air temperature.The outside temperature sensor (P1) detects the low pressure of the refrigerant, that is, the saturation temperature equivalent to the evaporation pressure during cooling operation, and the high pressure that corresponds to the condensing pressure during heating operation. The pressure sensor (HPS) that detects the saturation temperature is a high-pressure pressure switch for compressor protection.

Each of the solenoid valves and sensors described above is connected to an outdoor control unit (15) that controls the operation of the device along with each main device by a signal line, either directly or via an indoor control unit (not shown). Outdoor control unit (15)
, each device of the outdoor unit (A) is controlled.

In FIG. 2, during cooling operation of the air conditioner, the four-way switching valve (2) switches to the solid line side in the figure, and the electromagnetic on-off valve (24) of the auxiliary heat exchanger (22) is always open. The refrigerant compressed by the compressor (1) is condensed in the outdoor heat exchanger (6) and the auxiliary heat exchanger (22), and then transferred to the connecting pipe (11b).
It is then branched and sent to each indoor unit (B) to (D). In each of the indoor units (B) to (D), the pressure is reduced by each indoor electric expansion valve (13), . . . and evaporated in each indoor heat exchanger (12), .
) and circulated in a gaseous state to be sucked into the compressor (1).

On the other hand, during heating operation, the four-way switching valve (5)
switches to the dashed line side in the figure, and the flow of the refrigerant is reversed to that during the above-mentioned cooling operation, and the refrigerant compressed by the compressor (1) is condensed in each indoor heat exchanger (12), and then merges. The liquid flows into the outdoor unit (A), is depressurized by the outdoor electric expansion valve (8), is evaporated in the outdoor heat exchanger (6), and is then transferred to the compressor (1).
).

[0022] At that time, the outdoor control unit (15)
The details of the operation control of the air conditioner will be explained based on the state transition diagram of FIG. 3 and the flowchart of FIG. 4. FIG. 3 is a control state transition diagram showing switching of the biased oil flag HOLF, which will be described later, in which the capacity of the first compressor (1A) is at full load and the operating frequency of the second compressor (1B) is 48Hz.
When the condition is below, the state is switched from HOLF =0 to HOLF =1, and in other operating states, HOLF =0 is set.

Next, FIG. 4 shows the operation control contents of the air conditioner, in which it is determined in step ST1 whether or not the compressor (1) is on standby for 4 minutes, and in step ST2 it is determined whether or not the compressor (1) is on standby for 1 minute after starting the compressor (1). In step ST3, it is determined whether the defrost operation is in progress, and only when neither condition is met, the process proceeds to step ST4. And step ST
In step 4, it is determined whether the oil imbalance flag HOLF according to the settings shown in Fig. 3 above is "1" or not. If HLOF = 0, the differential pressure between each compressor (1A) and (1B) is appropriate. If it is determined that HOLF is maintained, the process proceeds to step ST5, where the on-off valve (36) of the branch passage (35) of the oil return passage (34) is kept closed. The first compressor (1A) is fully loaded and the second compressor (1B)
If the operating frequency of the on-off valve (36
) to introduce hot gas into the oil equalizing pipe (33).

In the above flow, by the control in step ST5, one of the two compressors (1A) and (1B) (the first compressor (1A)) has a low capacity, and the other compressor has a low capacity. When the second compressor (1B) is operated at high capacity, the on-off valve (36) is opened and the discharged refrigerant is transferred to the oil equalizing pipe (33).
) opening/closing control means (50) for controlling the bypass.
is configured.

Therefore, in the above embodiment, two compressors (1A
) and (1B) are connected by an oil equalizing pipe (33),
During normal operation, each compressor (1
The oil amounts in A) and (1B) are maintained uniformly. On the other hand, among the two compressors (1A) and (1B), one compressor (first compressor (1A) in the above embodiment) has a high capacity, and the other compressor (in the above embodiment, the second compressor If the compressor (1B)) continues to operate at low capacity for a long time, the first compressor (1B)
Since the pressure inside the dome on the A) side decreases, the oil equalizing pipe (33)
There is a risk that the lubricating oil may excessively flow from the second compressor (1B) side to the first compressor (1A) side via the lubricating oil, causing the second compressor (1B) to run out of lubricating oil. There is a risk that such a lack of lubricating oil may cause failures such as burnout of the second compressor (1B), but in the present invention, the opening/closing control means (50) controls one compressor (the first compressor). (1A)) is operated at high capacity and the other compressor (second compressor (1B)) is operated at low capacity, the on-off valve ( 36) to drain the discharged refrigerant into the oil equalizing pipe (
33), so the oil equalizing pipe (
33) is blocked by the presence of this gas refrigerant, thereby preventing oil shortage in the second compressor (1B).

In particular, as in the above embodiment, the first compressor (
1A) than the first suction pipe (31A) of the second compressor (1B).
), which increases the pressure loss in the second suction pipe (31B) and provides a forced differential pressure to lower the pressure inside the dome of the second compressor (1B), the oil volume is large during normal operation. Lubricating oil flows from the first compressor (1A) to the second compressor (1B), and the oil amount in both is maintained uniformly.
If A) is operated at a high capacity and the second compressor (1B) is operated at a low capacity for a long time, the differential pressure will reverse and the pressure will flow from the second compressor (1B) to the first compressor (1A). Oil equalizing pipe (33)
However, under such operating conditions, the on-off valve (36) is turned off by the on-off control means (50) as described above. is opened and the discharged refrigerant is introduced into the oil equalizing pipe (33), which prevents the oil from flowing backwards due to the reversal of the differential pressure.
Combined with the oil equalization effect due to forced differential pressure, it can be extremely effective.

In the above embodiment, the main refrigerant circuit (14
), two compressors (1A) and (1B) were connected in parallel, but the present invention is not limited to such an example.
Three or more compressors may be arranged. Even in that case, the above-described effects can be obtained by applying the present invention to each of the two compressors.

Furthermore, although the above embodiment has been described with respect to a system in which a forced differential pressure is provided, the present invention can also be applied to a system in which a forced differential pressure is not provided. In that case, all compressors are unloaded. The present invention can also be applied to a case where the capacity is controlled by a compressor mechanism, or a case where the operating frequency of each compressor is adjusted by an inverter.

Furthermore, in the forced differential pressure type air conditioner, in the above embodiment, corresponding to the invention of claim 2,
The first compressor (1A) has a high capacity and the second compressor (1B)
The backflow of oil was prevented by introducing the discharged refrigerant into the oil equalizing pipe (33) only when the capacity of the first compressor (1A) was low and the capacity of the second compressor (1B) was low. The on-off valve (36) may also be opened when operating at high capacity. In that case, it is possible to prevent an excessive amount of oil from flowing from the first compressor (1A) to the second compressor (1B) due to the forced pressure difference.

Furthermore, in the above embodiment, the oil return passage (34) is provided with a branch passage (35) as a bypass passage from the discharge side of the compressor (1) to the oil equalizing pipe (33). It goes without saying that if (34) is not provided, a bypass path may be provided directly from the discharge pipe (32) to the oil equalizing pipe (33). However, in the case of the above embodiment, the oil return passage (34)
The advantage of using this is that the configuration can be simplified.

[0031]

As explained above, according to the invention of claim 1, two compressors are connected in parallel to the refrigerant circuit, and the domes between the compressors are connected by an oil equalizing pipe. In the refrigeration system, the discharge side of the compressor and the oil equalizing pipe are connected by a bypass path via an on-off valve, and one of the two compressors has a high capacity and the other has a low capacity. When the compressor is operated, the on-off valve is opened to introduce the discharged refrigerant into the oil equalizing pipe, which prevents excess oil from leaking into one compressor and causing an oil shortage in the other compressor. , therefore,
Reliability can be improved.

According to the invention of claim 2, in the invention of claim 1, each compressor is configured to have a larger pressure loss in the suction pipe of one compressor than in the suction pipe of the other compressor. Since a forced differential pressure is provided for the dome pressure, during normal operation, oil flows from one compressor with a large amount of oil to the other compressor through an oil equalization pipe, making the oil amount uniform in both compressors. When one compressor is operated at a high capacity and the other at a low capacity, the backflow of oil can be prevented by introducing the discharge refrigerant gas into the oil equalizing pipe, thus reducing the forced differential. Combined with the oil equalization effect due to pressure, it can be extremely effective.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention.

FIG. 2 is a refrigerant piping system diagram of an air conditioner according to an embodiment of the present invention.

FIG. 3 is a control state transition diagram showing switching of the biased oil flag in the embodiment.

FIG. 4 is a flowchart showing control details of the outdoor control unit.

[Explanation of symbols]

1A 1st compressor 1B Second compressor 14 Main refrigerant circuit 33 Oil equalizing pipe 35 Branch road (bypass road) 36 On-off valve 50 Opening/closing control means

Claims (2)

[Claims] Claim 1: Two variable capacity compressors (1A), (1B) are connected in parallel to a refrigerant circuit (14), and a connection between the domes of each of the compressors (1A), (1B) is provided. a bypass path (35) connecting the discharge sides of the compressors (1A) and (1B) and the oil equalizing pipe (33) by bypass;
An on-off valve (36) that opens and closes the bypass passage (35), and one compressor (1A) of the two compressors (1A) and (1B) has a low capacity, and the other compressor (1B) Operation of a refrigeration system characterized by comprising an opening/closing control means (50) for controlling the opening/closing valve (36) to open the opening/closing valve (36) to bypass the discharged refrigerant to the oil equalizing pipe (33) when the refrigeration system is operated at a high capacity. Control device. 2. In the operation control device for a refrigeration system according to claim 1, the pressure loss in the suction pipe of one of the two compressors (1A) and (1B) is greater than the pressure loss in the suction pipe of the other compressor (1A). The opening/closing control means (50) is configured to increase the pressure loss of the suction pipe of the compressor (1B), and the opening/closing control means (50) is configured so that the compressor (1B) on the side with the large pressure loss has a small capacity and the compressor (1B) on the side with the large pressure loss An operation control device for a refrigeration system characterized by controlling an on-off valve (36) to open when a compressor (1A) is operated at high capacity.