JPH0621717B2 - Refrigeration equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a refrigerating device, and in particular, ensures the freshness of an object to be cooled and effectively uses oil mixed in a refrigerant to a compressor. The present invention relates to a refrigerating device that is returned.

[Conventional technology]

Conventionally, this type of device has been shown in FIG.
In FIG. 2, (1) is a parallel compression refrigeration system, and (2) is a refrigeration system composed of a combination of a plurality of showcases (2a), (2b), (2c). The parallel compression refrigeration system (1) consists of a water-cooled condenser (1a) or a receiver connected downstream of an air-cooled condenser (not shown) with a rated capacity ratio of about 2 Two large capacity compressors (1b) and small capacity compressors (1c) selected in No. 1 are installed in parallel, and each compressor (1b)
The refrigerant discharge function (1d) and the suction function (1e) of (b) and (1c) are connected in parallel with each other. Note that (1f) is a pressure equalizing and equalizing pipe that connects the crank chambers of the compressors (1b) and (1c) to each other.

Further, (5) is an output detection unit (3) for detecting the refrigerant pressure on the low pressure side.
The compressor (1b) and (1c) are operated individually according to the pressure difference with the refrigerant pressure set by the pressure setting unit (4) that sets the refrigerant pressure of the low pressure law that tries to converge with the output signal of -A control unit that controls the stop.

(7) is a compressor independent operation time integration unit that integrates the time when only one of the compressors (1b) and (1c) is operating. Further, (6) is such that when the compressor independent operation time integration unit (7) reaches a predetermined time, both of the compressors (1b) and (1c) are stopped for a certain period of time and the compressor independent operation integration unit. (7)
Is a compressor capacity setting unit which starts the operation from the operation of the two compressors (1b) and (1c) having different cumulative capacities and having different rated capacities.

(9) is a forced intermittent operation control unit that generates a signal to stop the two compressors (1b) and (1c) for a predetermined time that can be set and changed at regular time intervals.

Further, as shown in FIG. 3, the normal pressure region has three parallel compression refrigeration units (volume up pressure value, volume down pressure value, and low pressure cut value set by the pressure setting unit (4). Area (d) above the capacity increase pressure value that outputs the capacity increase signal to (1) and above the capacity down pressure value that does not output the capacity down signal or the capacity up signal to the parallel compression refrigeration system (1), and the capacity up pressure Area (c) below the value, volume down pressure signal to the parallel compression type refrigeration system (1), and area below the capacity down pressure value (b) and low pressure cut to issue a stop signal to the parallel compression type refrigeration system (1) It is divided into four areas (a) below the value.

Next, the operation will be described. For example, if the required power to obtain the required refrigerating capacity for the refrigeration load of the refrigeration system (2) is 15, the rated capacity of one compressor (1b) is 10, and the rated capacity of the other compressor (1c) is The capacity is set to 5.

On the other hand, in the refrigeration system (2) including a plurality of showcases (2a), (2b), and (2c), the cooling load greatly changes from 0 to 100% depending on the usage status of each showcase.

Here, when the refrigeration load decreases, the refrigerant pressure according to the low pressure law of the refrigeration cycle decreases, and the level of the pressure detection signal output from the pressure detection unit (3) to the control unit (5) also decreases accordingly.

In the control section (5). Since it has a comparison circuit that compares the pressure detection signal with a reference value (capacity up pressure value or capacity down pressure value), if the pressure detection signal is lower than the capacity down pressure value, that is, In this case, the control unit (5) controls so that the capacity of the parallel compression refrigeration system (1) is decreased, and the cooling capacity is decreased. When the cooling capacity is reduced in this way, the refrigerant pressure according to the low pressure law of the refrigeration cycle rises and converges to the region (c), and the operation becomes stable.

Further, when the cooling load is high, the refrigerant pressure of the low-pressure law of the refrigeration cycle increases, and the level of the pressure detection signal output from the pressure detection unit (3) to the control unit (5) accordingly increases. . As a result, when the pressure detection signal is higher than the capacity increase pressure value, that is, in the case of the region (d), the control unit (5) controls so that the capacity of the parallel compression refrigeration system (1) increases. , Increase the cooling capacity. When the cooling capacity is increased in this way, the refrigerant pressure on the low pressure side of the refrigeration cycle decreases, converges to the region (c), and the operation becomes stable. After the pressure detector (3) detects the pressure in the area (d) or the area (b), the time until the capacity up signal or the capacity down signal output from the controller (5) is the same. Is.

When the refrigerant pressure on the low-pressure side of the refrigeration cycle falls below the low-pressure cut value, that is, in region (a), the compressors (1b), (1c)
Is supposed to stop immediately.

Therefore, the refrigeration load is 3 when the above refrigeration load changes.
At a partial load of 3% or less, only the compressor (1c) with a rated capacity of 5 operates independently. Further, when the refrigeration load is in the range of 33 to 66%, only the compressor (1b) having a rated capacity of 10 operates independently.

Furthermore, if the refrigeration load reaches 66 to 100%, the compressor (1b) and (1
c) are operated in parallel at the same time. The transition of this capacity control operation is shown in FIG.

In other words, as shown in Fig. 4, by controlling the start and stop of large and small compressors whose rated capacity ratio is selected to be approximately 2 to 1, four stages of 0,33,100% are provided. The capacity control operation can be performed.

Further, the compressors (1b) and (1c) are the forced intermittent operation control unit (9).
By the function of irrespective of the above-mentioned capacity control operation, by stopping for a predetermined time at regular intervals,
The compressor operating time is shortened to save energy. The stop time at this time can be arbitrarily set according to a predetermined minimum temperature of the refrigeration load. That is, when the required minimum temperature is low, it is set short, and when it is high, it is set long.

Further, generally, in a compressor that compresses a refrigerant to a high temperature and high pressure, the lubricating oil of the compressor is mixed in the refrigerant in an amount of 0.5 to 1% by weight. The mixed lubricating oil mixes well with the refrigerant if the refrigerant is liquid, but separates without mixing with the refrigerant when the refrigerant is vaporized. Therefore, in the conventional refrigeration system, the lubricating oil mixed in the refrigerant does not return to the compressor as described below,
The lubricating oil in the compressor sometimes decreased.

In a conventional refrigeration system, for example, in a refrigeration system having coolers (2a), (2b), (2c) in each of a plurality of parts to be cooled, for example, a showcase, in order to control the temperature of each showcase, A temperature controller and a liquid line solenoid valve for controlling the flow of the refrigerant are provided in each showcase to control the temperature of each showcase. In this case, for example, there are three showcases, and in a refrigerating apparatus that individually controls the three showcases, one cooler (2a) may be operated for a long time by reducing the load at night. At this time, since the load is reduced, the refrigeration system operates with the evaporation temperature of the cooler (2a) lowered, and the compressor (1a
The refrigerant gas flow velocity in the suction pipe of b) and (1c) decreases. When the flow velocity of the refrigerant gas decreases, the lubricating oil separated from the refrigerant gas returns to the compressors (1b) and (1c) poorly, and the lubricating oil in the compressors (1b) and (1c) decreases to reduce the compressor. There was a risk that the sliding parts such as bearings would be burnt out. In addition, if the suction pipes of the compressors (1b) and (1c) are made smaller in order to reduce the load of operating one of the coolers (2a) to ensure the refrigerant gas flow velocity, the cooler ( 2
At the time of heavy load operating three units (a), (2b), (2c), the refrigerant gas flow velocity becomes very high, and the pressure loss in the suction pipes of the compressors (1b), (1c) becomes extremely large. Therefore, the compressor (1b),
There is a drawback that the compression capacity of (1c) is reduced and the refrigeration capacity of the refrigeration system is reduced.

In order to eliminate such a defect, the capacity of the refrigeration system is changed in accordance with the refrigerant pressure on the low pressure side of the refrigeration cycle as described above, and the so-called capacity control operation is performed to keep the evaporation temperature on the suction side constant. , The time when only one of the compressors (1b) and (1c) operates due to the decrease in the suction side pressure due to the reduction of the load is integrated by the compressor independent operation time integration part (7), and the value is calculated. When a predetermined time is reached, the compressor capacity setting unit (6) stops both of the compressors (1b) and (1c) for a predetermined time, and then the two compressors (1b) having different rated capacities ), (1c) start operation. That is, the compressor (1
By stopping b) and (1c) for a certain period of time, the liquid refrigerant on the high pressure side returns to the low pressure side, increasing the refrigerant pressure on the low pressure side, and the compressor (1
By restarting the operation of b) and (1c), the flow velocity of the refrigerant gas in the suction pipe increases, and the lubricating oil accumulated in the suction pipe during low load operation is returned to the compressors (1b) and (1c) all at once. , The above compressor
(1b), (1c) The reduction of lubricating oil can be prevented.

[Problems to be solved by the invention]

Since the conventional refrigeration system is configured as described above, 2
When only one of the two compressors is in operation for a predetermined time, the two compressors stop, and the freshness of the object to be cooled cannot be maintained.

The present invention has been made in order to solve the above-mentioned conventional problems, and shortens the time for stopping the compressor as much as possible to maintain the freshness of the object to be cooled and collect it in the suction pipe. It is an object of the present invention to provide a refrigeration system that effectively returns lubricating oil to a compressor.

[Means for solving problems]

In the present invention, the refrigerant pressure on the low pressure side of the refrigeration cycle is detected by the pressure detection unit to generate a pressure detection signal, and the refrigerant pressure to be converged is set by the pressure setting unit, and the pressure detection signal is converged. It is determined whether the refrigerant pressure is equal to or higher than the intended pressure, or less, and a control unit that generates a capacity control output signal for performing capacity control of the refrigerator, and the compressor over a predetermined time that can be set at regular intervals. A forced intermittent operation control unit that generates a signal to stop, a compressor independent operation time stacking unit that integrates the time during which only one compressor is operating, and an integration time of the compressor independent operation time integration unit that is a predetermined time Is reached, the plurality of compressors are stopped for a certain period of time, the integrated time of the compressor independent operation time integration unit is set to 0, and the compression capacity setting for starting the operation of the plurality of compressors is started. Section, if the time to stop the compressor by the forced intermittent operation control unit is set to be equal to or longer than the time to stop the compressor by the compressor capacity setting unit, the compressor stop function by the compressor capacity setting unit, The above object is achieved by constructing a refrigeration system by providing a compressor independent operation time correction unit that is released.

[Action]

In the refrigerating apparatus according to the present invention, when the time for stopping the compressor by the forced intermittent operation control unit is set to be equal to or longer than the time for stopping the compressor by the compressor capacity setting unit, the compressor single operation time correction unit Function cancels the compressor stop function by the compressor capacity setting unit, the time for stopping the compressor can be shortened as much as possible, the freshness of the object to be cooled is retained, and the water is accumulated in the suction pipe. The lubricating oil can be effectively returned to the compressor.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of a refrigerating apparatus according to the present invention, and the same portions as those in FIG. 2 are designated by the same reference numerals. In the figure, (8) is a compressor independent operation time correction unit, and the time to stop the compressors (1b), (1c) by the forced intermittent operation control unit (9) is the compressor capacity setting unit (6). ) Has a function of canceling the compressor stop function by the compressor capacity setting unit (6) when the time for stopping the compressors (1b) and (1c) is exceeded.

Next, the operation will be described. In the compressor independent operation time integration unit (7), the time during which only one of the compressors (1b) and (1c) is operating is integrated, and, for example, at 48 minutes, the compressor capacity setting unit ( According to 6), both of the compressors (1b) and (1c) are stopped for a certain period of time, for example, 3 minutes, and the integrated time (48 minutes) of the compressor independent operation time integration unit (7) is set to 0, In addition, the two compressors (1b) and (1c) with different rated capacities start operation. by the way,
As described above, the time for stopping the compressors (1b) and (1c) in the forced intermittent operation control unit (9) is arbitrarily changed by a variable resistor or the like according to the minimum temperature required for the refrigeration load, as described above. Can be set. By the forced intermittent operation control unit (9),
The time for stopping the compressors (1b), (1c) is set to, for example, 3 minutes, and the compressor capacity setting unit (6) controls the compressor
(1b), when it is more than the time to stop (1c), the function of the compressor independent operation time correction unit (8) to cancel the compressor stop function by the compressor capacity setting unit (6), The compressor capacity setting unit (6) does not stop the compressors (1b) and (1c).

Therefore, the time for stopping the compressor is shortened as much as possible to maintain the freshness of the object to be cooled, and the forced intermittent operation control unit (9) stops the compressors (1b) and (1c) for a predetermined time. The high-pressure liquid refrigerant returns to the low-pressure side, increases the low-pressure side refrigerant pressure, and restarts the operation of the compressors (1b) and (1c) to increase the flow rate of the refrigerant gas in the suction pipe. By returning the lubricating oil accumulated in the suction pipe to the compressors (1b) and (1c) at once, it is possible to prevent the lubricating oil in the compressors (1b) and (1c) from decreasing.

However, because the predetermined minimum temperature of the refrigeration load is good, if the stop time by the forced intermittent operation control unit (9) is set to be less than the stop time by the compressor capacity setting unit (6), the compressor alone The operating time correction unit (8) does not release the compressor stop function of the compressor capacity setting unit (6).

Further, in the above embodiment, the capacity control is performed by the two compressors. However, even when the output frequency of the inverter is changed to control the capacity of the compressor, the oil mixed in the refrigerant is effectively compressed. In order to return it to the machine, the output frequency of the compressor is accumulated for a predetermined value, for example 40 Hz or less, and when the value reaches a predetermined value, for example 48 minutes, the compressor is operated for a certain period of time, for example When stopped for 3 minutes, the time for stopping the compressor by the forced intermittent operation control unit is, for example, for 3 minutes, longer than the time for stopping the compressor by the compressor capacity setting unit, and The same effect can be obtained by the low frequency operation time correction unit of the machine canceling the compressor stop function of the compressor capacity setting unit.

〔The invention's effect〕

As described above, the refrigerating apparatus according to the present invention detects the refrigerant pressure on the low pressure side of the refrigeration cycle by the pressure detecting unit to generate a pressure detection signal, and sets the refrigerant pressure to be converged by the pressure setting unit. At the same time, a control unit that determines whether the pressure detection signal is above or below the refrigerant pressure to be converged and generates a capacity control output signal for performing capacity control of the refrigerant machine, and a setting variable at fixed time intervals Of the forced intermittent operation control unit that generates a signal to stop the compressor for a predetermined time, a compressor independent operation time integration unit that integrates the time during which only one compressor is operating, and the compressor independent operation When the time integration unit reaches a predetermined time, all the plurality of compressors are stopped for a certain period of time, the integration time of the compressor independent operation integration unit is set to 0, and the operation of the plurality of compressors is started. If the time to stop the compressor by the compressor capacity setting unit and the forced intermittent operation control unit is set to be longer than the time to stop the compressor by the compressor capacity setting unit, by the compression capacity setting unit Since it has a compressor independent operation time correction unit that releases the compression stop function, the time to stop the compressor can be shortened as much as possible, the freshness of the object to be cooled can be maintained, and the suction pipe The lubricating oil accumulated in the can be effectively returned to the compressor.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a refrigerating apparatus according to the present invention, FIG. 2 is a block diagram showing a conventional refrigerating apparatus, FIG. 3 is a diagram showing a refrigerant pressure region on a low pressure side, and FIG. It is explanatory drawing of the capacity control operation | movement of the refrigeration apparatus of FIG. In the figure, (1a) is a condenser, (1b) and (1c) are compressors, and (2a)
~ (2c) is a cooler, (3) is a pressure detection part, (4) is a pressure setting part,
(5) is a control unit, (6) is a compressor capacity setting unit, (7) is a compressor independent operation time integration unit, (8) is a compressor independent operation time correction unit,
(9) is a forced intermittent operation control unit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A plurality of compressors each having a suction pipe and a discharge pipe connected in parallel, a condenser for condensing and liquefying the refrigerant discharged from these compressors, and a refrigerant discharged from this condenser. A refrigerating circuit in which a cooler that evaporates and vaporizes forms a closed circuit in sequence, a refrigerating circuit that detects a refrigerant pressure on the low-pressure side of the refrigerating circuit, and a pressure detecting unit that generates a pressure detection signal corresponding to the refrigerant pressure, A pressure setting unit that sets a convergent pressure value of the low-pressure side refrigerant pressure to be converged,
A control unit that determines whether the pressure detection signal is equal to or greater than or equal to the convergent pressure value, and based on the determination result, generates a capacity control output signal for performing capacity control of the refrigerator, and sets at constant time intervals. Forced intermittent operation control unit that generates a signal to stop the compressor over a variable predetermined time, compressor independent operation time integration unit that integrates the time during which only one compressor is operating, compressor independent operation time When the integration time of the integration unit reaches a predetermined time, all the plurality of compressors are stopped for a certain time, the integration time of the compressor independent operation integration unit is set to 0, and the operation of the plurality of compressors is started. When the time to stop the compressor by the compressor capacity setting unit, the forced intermittent operation control unit is set to be equal to or longer than the time to stop the compressor by the compressor capacity setting unit,
A refrigeration apparatus comprising: a compressor independent operation time correction unit that releases the compressor stop function of the compressor capacity setting unit.