JPH0725564Y2 - Refrigerator oil return controller - Google Patents

Description

[Detailed Description of the Invention] (Industrial field of application) The present invention is directed to a refrigerator equipped with a variable capacity compressor such as a screw compressor, which prevents the oil from rising due to liquid suction at the time of start and is a stable refrigerator. The present invention relates to an oil return control device that can be operated.

(Prior Art) It is a well-known technology to dispose an accumulator in a suction line connected to a suction port of a compressor to prevent liquid refrigerant from being directly sucked into the compressor. Bulletin,
As disclosed in Japanese Utility Model Publication No. 53-92751 and Japanese Utility Model Publication No. 63-63660.

(Problems to be solved by the invention) When the accumulator is provided in this way, the liquid refrigerant is not sucked in as much as possible, but the lubricating oil accumulated in the accumulator must be returned to the compressor side. No. 52-169150 discloses that an oil return hole is provided at the bottom of the outlet pipe and is closed when the amount of oil pool is small.
A float valve that opens when there are many is provided in the oil return hole.

On the other hand, the description in Japanese Utility Model Publication No. 53-92751 discloses an oil return port (hole).
It has a structure in which an on-off valve that closes when the low-pressure gas becomes wet is provided.

In both of these examples, when the compressor is in operation, it is possible to suck up the lubricating oil that has accumulated in the accumulator while not sucking the liquid refrigerant, but when the compressor starts, the liquid in the accumulator can be Since the amount of refrigerant is large and each valve is open, the stored liquid refrigerant is sucked in at the same time when the compressor is started, and therefore the suction gas becomes moist and the oil separation function deteriorates due to the decrease in the discharge gas temperature. There is a problem that occurs and causes the oil rising phenomenon.

Moreover, in both of the above examples, the valve whose specifications were determined at the time of design is housed inside the accumulator, so it cannot be adjusted from the outside at all, and it is difficult to adapt it to the usage state and it is inconvenient to fully return oil. there were. Therefore, the actual exploitation 63-63660
According to the publication, a bypass circuit having an electromagnetic valve is provided between the accumulator and the compressor suction pipe, and the solenoid valve is opened / closed according to the temperature of the compressor suction pipe and is kept closed for a certain time when the compressor is started. Was proposed.

However, the valve is completely closed for a certain period of time after the start-up, and even after that, it can be said that the control is based on temperature, and the valve is open (100%) and closed (0%). The problem was that it was difficult to obtain quick and stable operation.

SUMMARY OF THE INVENTION In order to solve the conventional problems, the present invention intends to provide a device which can be easily adjusted especially from the outside and which can reliably return the lubricating oil while preventing the liquid from returning at the time of starting. The purpose of the present invention is to improve reliability by extending the life of the compressor.

(Means for Solving the Problems) The present invention, as shown in the embodiment of the accompanying drawings, firstly relates to the invention of claim 1, the variable displacement compressor (1), the bottom of the accumulator (5) and the suction. In a refrigerator provided with an oil return pipe (8) connecting to a pipe (7), a flow control mechanism (9) capable of increasing or decreasing the flow rate is provided in the middle of the oil return pipe (8). , The flow control mechanism (9) is capable of controlling the valve opening of the flow control valve in response to the increase of the compressor capacity immediately after the start of the compressor (1), or by increasing the valve opening. The present invention is characterized in that the control means (10) is provided to increase the minimum flow rate by increasing the number of valves (12) and (13) that have been opened.

Further, in the invention of claim 2, the flow rate control mechanism (9) is formed in a valve circuit in which two electromagnetic valves (12) and (13) having substantially the same function are connected in parallel, and the control means ( 10) Open one solenoid valve (12) when the operating capacity of the variable capacity compressor (1) is about 50% or less, and open two solenoid valves (12) when it exceeds about 50%. ) And (13) are formed in a two-step control system in which the valve is opened.

(Operation) When the compressor (1) is started with a low capacity, the flow rate control mechanism (9) throttles the flow rate, so that even if the liquid refrigerant accumulates in the accumulator (5), it is rapidly sucked into the compressor side. Being caught is prevented.

Then, when the operation of the compressor (1) is stable and a sudden change in suction pressure does not occur, the throttle of the oil return pipe (8) is released to increase the flow rate. Is done normally.

In the second aspect, the flow rate control mechanism (9) is composed of two solenoid valves (12) and (13), so that the structure is simple and the control means (10) is a two-step control of ON / OFF. Since it is a system, it may be simplified.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a circuit diagram of an apparatus according to an example of the present invention, which is known by a compressor (1), for example, a screw compressor, a condenser (2), an expansion valve (3), an evaporator (4) and an accumulator (5). Form a refrigeration cycle.

In the refrigeration cycle, an oil recovery unit (6) is provided in the middle of the discharge pipe connecting the compressor (1) and the condenser (2), and the oil separated by the recovery unit (6) (not shown). Are stored at the bottom and only the refrigerant gas is discharged to the condenser (2).

As is well known, the screw compressor (1) reduces or increases the compression capacity during operation by reducing and increasing the opening degree of a slide valve by a drive mechanism (14), for example, a mod roll motor (14), and increasing It is possible to control steplessly in the range of 100%.

On the other hand, the accumulator (5) is connected to the outlet side of the evaporator (4) via a low pressure gas pipe, and is connected to the suction port of the compressor (1) via a suction pipe (7) to connect the evaporator (4). The passed refrigerant is once diffused in the accumulator (5) to be divided into a liquid component and a gas component, the liquid component containing the lubricating oil is stored at the bottom of the container, and the gas component is fed into the suction pipe (7). The liquid refrigerant functions so as not to be directly sucked into the suction pipe (7).

The accumulator (5) has an oil return pipe (8) drawn out from the bottom and its end is branched and connected to a suction pipe (7). The accumulator (5) side is provided in the middle of the oil return pipe (8). From filter (11) and flow control mechanism (9)
Is installed.

The flow rate control mechanism (9) may be a flow rate control valve capable of controlling the valve opening steplessly such as an electric valve, but in the illustrated example, two solenoid valves (12) and (13) having substantially the same function are arranged in parallel. A connected valve circuit is used, which is an example of the invention according to claim 2, in which both solenoid valves (12) and (13) are fully opened by coil excitation.

Control means (1) for controlling the flow rate control mechanism (9)
0) outputs an output according to the operating capacity of the compressor (1), that is, the opening of the slide valve. In the illustrated example, the rotational displacement of the modtrol motor (14) is detected and the compression functional force is The same as the first limit switch (15) that detects the slide valve opening position corresponding to the minimum
In response to a signal from the second limit switch (16) that detects the slide valve opening position corresponding to about%, the solenoid valve (12), (13) outputs an on-off valve output. There is.

When the flow rate control mechanism (9) has a structure that has a control valve capable of continuously adjusting the valve opening degree, the control means (10) receives an electric signal proportional to the slide valve opening degree to change the slide valve opening degree. The structure may be such that an output is given to the control valve so that the valve opening corresponds to.

Next, the operation of the oil return device will be described. The solenoid valves (12) and (13) are both closed while the compressor (1) is stopped, and the control means (10) outputs Did not emit.

When a start command is issued to the compressor (1) to start the operation, the compressor (1) starts from the minimum capacity, so only one solenoid valve (12) is opened by the signal of the first limit switch (15). The output that causes it is emitted from the control means (10).

Thus, the oil return pipe (8) is throttled by the flow rate control mechanism (9), while the compressor (1) has an increased intake air amount with an increase in rotation and an intake pressure decrease with an increase in capacity. The oil-containing refrigerant in the accumulator (5) is sucked into the suction pipe (7) while gradually increasing its amount, so that the problem of wet compression does not occur.

When the start of the compressor (1) progresses and the capacity increase control is performed to reach about 50%, the second limit switch (1
The control means (10) outputs an output for fully opening the solenoid valve (13) by the detection operation of 6).

Thus, the oil return pipe (8) is fully opened with the restriction removed, and the return amount of the oil-containing refrigerant becomes the value as originally designed and the compressor (1) operating with a predetermined capacity is kept wet. Without this, the discharge gas temperature rises as stipulated, so the oil separation efficiency of the oil recovery unit (6) does not decrease, and the oil rising phenomenon is eliminated.

The relationship between the compression function force and the oil return amount at the time of starting the compressor described above is as shown in FIG. 2, and the relationship between the intake air amount (Q) to the compressor (1) and the oil return amount (q). Is ΔP∞
From Q ² It is clear that they are approximately proportional based on the relational expression of. In addition, ΔP represents a differential pressure between the internal pressure of the accumulator (5) and the internal pressure of the suction pipe (7).

(Effects of the Invention) As described above, the present invention uses the combination of the flow rate control mechanism (9) and the control means (10) during the capacity increasing operation at the time of starting the compressor (1) to improve the compressor (1). It is possible to increase the oil return amount almost in proportion to the intake air amount, and it is possible to solve the problem of wet compression by returning a large amount of the oil-containing refrigerant in the accumulator (5) at the time of starting. .

Thus, the oil rising phenomenon due to the low discharge gas temperature is also solved, and stable operation is performed.

Further, in claim 2, a general-purpose solenoid valve (12), (1
Control structure (10) with a simple structure using two 3)
Also, since the control circuit of the two-stage on / off system is sufficient, the device can be simplified while exhibiting the desired flow control mechanism.

[Brief description of drawings]

FIG. 1 is a device circuit diagram according to an embodiment of the present invention, and FIG. 2 is a characteristic diagram similarly illustrating a control mode. (1) …… Variable capacity compressor, (5) …… Accumulator, (7) …… Suction pipe, (8) …… Oil return pipe, (9)
...... Flow rate control mechanism, (10) …… Control means, (12), (1
3) ... Solenoid valve.

Claims (2)

[Scope of utility model registration request] 1. A refrigerator having a variable capacity compressor (1) and an oil return pipe (8) connecting a bottom portion of an accumulator (5) and a suction pipe (7), wherein the oil return pipe ( Flow rate control mechanism (9) that can increase or decrease the flow rate in the middle of 8)
And an increase in the valve opening degree by which the flow rate control mechanism (9) can control the valve opening degree of the flow rate control valve according to the increase in the compressor capacity immediately after the instruction of the compressor (1). Due to
Alternatively, a control means (10) provided with a plurality of valves (12) and (13) and increasing the minimum flow rate by increasing the number of valves that have been opened.
An oil return control device for a refrigerator, characterized by being provided with. 2. The flow control mechanism (9) is a valve circuit in which two solenoid valves (12) and (13) having substantially the same function are connected in parallel, and the control means (10) has a capacity. When the operating capacity of the variable compressor (1) is less than about 50%, one solenoid valve (12) is opened, and when it exceeds about 50%, two solenoid valves (12), (13) 3. The oil return control device for a refrigerator according to claim 1, wherein the oil return control device is formed in a two-step control system for opening the valve.