JPS63189745A - Refrigerator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a refrigeration system, and particularly to a refrigeration system that ensures the freshness of objects to be cooled and that effectively removes oil mixed in a refrigerant into a compressor. The present invention relates to a refrigeration device that is designed to revert back to its original state.

[Conventional technology]

Conventionally, there was a device of this type as shown in Fig. 2. In Fig. 2, (1) is a parallel compression type refrigeration device, (2)
) has multiple showcases (2a), (2b), (2C
) This is a cooling device composed of a combination of The parallel compression refrigeration system (1) has a compressor with a rated capacity ratio of approximately 2 to 1 on a liquid receiver connected downstream of a water-cooled condenser (1a) or an air-cooled condenser (not shown). Two large-capacity compressors (1b) and small-capacity compressors (1c) selected as 1 are installed in parallel, and each compressor (1b) and (IC
) A refrigerant discharge pipe (1d) and a suction pipe (1e) are connected in parallel to each other. In addition, (1f) is for each compressor (1b
This is a pressure equalizing oil pipe that connects the crank chambers of ) and (IC) with each other.

In addition, (5) is the refrigerant pressure set by the pressure setting unit (4) that sets the refrigerant pressure on the low pressure side to be converged with the output signal of the pressure detection unit (3) that detects the refrigerant pressure on the low pressure side. This is a control unit that individually controls operation and shutdown of the compressors (1b) and (1c) according to the pressure difference between the compressors (1b) and (1c).

(7) is a compressor independent operation time integration unit that integrates the time during which only one of the compressors (1b) and (IC) is operating. In addition, (6) means that when the compressor independent operation time integration unit (7) reaches a predetermined time of 1, the compressor (1b)
), (1c) are both stopped for a certain period of time, and the cumulative time of the compression independent operation integration section (7) is set to 0, and the two compressors (1b), (1c) with different rated capacities are 2
This is the compressor capacity setting unit that starts operation from the unit operation.

(9) is a forced intermittent operation control unit that generates a signal to stop the two compressors (1b) and (1c) for a certain period of time at certain intervals.

In addition, as shown in FIG. 8, the continuous pressure region is determined by the three pressure values set by the pressure setting section (4): the capacity up pressure value, the capacity down pressure value, and the low pressure cut value. Area (d) above the capacity up pressure value that sends out a capacity up signal in (1), and parallel compression refrigeration system (1)
Region (c) above the capacity down pressure value where neither a capacity down signal nor a capacity up signal is issued and less than the capacity up pressure value (c), and a region below the capacity down pressure value where a capacity down signal is issued to the parallel compression refrigeration system (1). It can be divided into four regions: (b) a region where the pressure is below the low pressure cut value that sends a stop signal to the parallel compression refrigeration system (1) (b).

Next, the operation will be explained. For example, cooling device (2)
When the required power to obtain the required refrigerating capacity for the refrigerating load is 15)P, the rated capacity of one compressor (1b) is toH:', and the rated capacity of the other compressor (1c) is 5W. has been selected.

On the other hand, multiple showcases (2a), (2b),
In the cooling device (2) consisting of (2c), the cooling load varies greatly from 0 to 100% depending on the usage status of each showcase.

Here, when the refrigeration load decreases, the refrigerant pressure on the low pressure side of the refrigeration cycle decreases, and the pressure detection section (3)
The level of the pressure detection signal outputted to the control unit (5) also decreases.

The control unit (5) has a comparison circuit that compares the pressure detection signal with a reference value (capacity up pressure value or capacity down pressure value), so if the pressure detection signal is lower than the capacity down pressure value, In other words, in the case of area (b),
The control unit (5) controls the capacity of the parallel compression type refrigeration device (1) to decrease, thereby lowering the cooling capacity. When the cooling capacity is lowered in this way, the refrigerant pressure on the low-pressure side of the refrigeration cycle increases rapidly, converges in region (c), and the operation becomes stable.

Additionally, when the cooling load is high, the refrigerant pressure on the low pressure side of the refrigeration cycle increases, and the level of the pressure detection signal output from the pressure detection section (3) to the control section (5) increases accordingly. . As a result, when the pressure detection signal is higher than the capacity increase pressure value, that is, in the case of region (d), the control unit (5) controls the parallel compression refrigeration system (1) to increase its capacity. , increasing cooling capacity. When the cooling capacity increases in this way, the refrigerant pressure on the low pressure side of the refrigeration cycle decreases and converges to region (c), and the operation becomes stable.

Note that the time from when the pressure detection unit (3) detects the pressure in area (d) or area (b) until the capacity up signal or capacity down signal is generated from the control unit (5) is the same. It is.

In addition, if the refrigerant pressure on the low pressure side of the refrigeration cycle is below the low pressure cut value, that is, in the region (a), the compressor (lb)
, (lc) is designed to stop immediately.

Therefore, for the above refrigeration load fluctuation, the refrigeration load is 3
At partial loads of 3% or less, a compressor with a rated capacity of 5) P (1
c) is operated independently. In addition, the refrigeration load is 33 to 6
In the range of 6%, only the compressor (1b) with a rated capacity of 101P is operated independently.

Furthermore, when the refrigeration load reaches 66 to 100%, the compressor (1
b) and (1c) are operated in parallel at the same time. The transition of this capacity control operation is shown in FIG. 4.

That is, as shown in FIG. 4, by selectively controlling the operation and stopping of large and small compressors whose rated capacity ratio is approximately 2:1,
% capacity control operation can be performed.

Moreover, the compressors (lb) and (lc) are stopped for a fixed period of time (for a fixed period of time) at fixed intervals, regardless of the capacity control operation described above, due to the function of the forced intermittent operation control section (9).

Furthermore, in a compressor that compresses a refrigerant to high temperature and high pressure, lubricating oil of the compressor is mixed in the refrigerant at a weight ratio of 0.5 to 1%. This mixed lubricating oil mixes well with the refrigerant when the refrigerant is in a liquid state, but when the refrigerant is vaporized, it does not mix with the refrigerant and separates. Therefore, in conventional refrigeration systems, the lubricating oil mixed in the refrigerant does not return to the compressor, as will be explained next, and the lubricating oil in the compressor sometimes decreases.

In a conventional refrigeration system, for example, a cooler (2a) is installed in each of a plurality of parts to be cooled, such as a showcase.

In a refrigeration system equipped with (2b) and (2c),
In order to control the temperature of each showcase, each showcase was equipped with a temperature regulator and a liquid line solenoid valve that controlled the flow of refrigerant. In this case, for example, in a refrigeration system that has eight showcases and controls three showcases individually, only one cooler (2a) may be operated for a long time due to load reduction at night.

At this time, the load has been reduced, so the refrigeration system operates with the evaporation temperature of the cooler (2a) lowered, and the refrigerant gas flow rate in the suction pipes of the compressors (lb) and (lc) increases. Decrease. When the refrigerant gas flow rate decreases, the lubricating oil separated from the refrigerant gas has a poor return to the compressor (lb), (lc), and the lubricating oil in the compressor (lb), (lc) decreases, causing the compressor to There was a risk that sliding parts such as bearings would burn out. Furthermore, in anticipation of a reduction in the load of operating one of the coolers (2a), the suction pipe diameters of the compressors (lb) and (lc) are made smaller to ensure the refrigerant gas flow rate.
When eight coolers (2a), (2b), and (2c) are operated under heavy load, the refrigerant gas flow rate becomes extremely high, and the pressure loss in the suction pipes of the compressors (lb) and (IC) becomes extremely large. Become. For this reason, the compressor (lb),
There was a drawback that the compression capacity of (lc) was reduced, and the refrigeration capacity of the refrigeration system was reduced.

In order to eliminate these drawbacks, we have adopted so-called capacity control operation, which changes the capacity of the refrigeration system according to the refrigerant pressure on the low-pressure side of the refrigeration cycle and keeps the evaporation temperature on the suction side constant, as described above. compressor (lb) due to a decrease in suction side pressure as the load is reduced.

(lc), the time during which only one compressor operates is accumulated by the compressor independent operation time accumulating section (7), and when the value reaches a predetermined time, the compressor capacity setting section (6) (
After stopping both the compressors (lb) and (lc) for a certain period of time, the two compressors (lb) and (lc) with different rated capacities are
lc) is set to start operating. That is,
By stopping the compressors (lb) and (lc) for a certain period of time, the liquid refrigerant on the high-pressure side switches to the low-pressure side, increasing the refrigerant pressure on the low-pressure side and restarting the compressors (lb) and (lc). The flow rate of refrigerant gas in the suction pipe increases, and the lubricating oil accumulated in the suction pipe during low-load operation is transferred to the compressor (lb), (
lc) - by returning the air to the compressor (lb)
, (lc) Decrease in internal temperature lubricant is prevented.

[Problem that the invention seeks to solve]

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

This invention was made to solve the above-mentioned conventional problems, and it reduces the time during which the compressor is stopped as much as possible to maintain the freshness of the cooled material, and also to reduce the amount of water that accumulates 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 to solve the problem]

In this invention, the refrigerant pressure on the low pressure side of the refrigeration cycle is detected by the pressure detection section to generate a pressure detection signal, the refrigerant pressure to be converged is set by the pressure setting section, and the pressure detection signal is a control unit that determines whether the refrigerant pressure is above or below the desired refrigerant pressure and generates a capacity control output signal to control the capacity of the refrigerator; and a control unit that stops the compressor for a certain period of time at certain intervals. a forced intermittent operation control section that generates a signal to cause the compressor to run; a compressor independent operation time accumulation section that accumulates the time during which only one compressor is in operation; a compression capacity setting section that stops both of the compressors for a certain period of time, sets the cumulative time of the compressor independent operation time cumulative section to 0, and starts the operation of the two compressors; A compressor that releases a compressor stop function by the compressor capacity setting unit when the time for stopping the compressor by the forced intermittent operation control unit exceeds the time for stopping the compressor by the compressor capacity setting unit. The above object is achieved by configuring a refrigeration system by providing an independent operation time correction section.

[Effect]

In the refrigeration system of the present invention, the compressor capacity setting section i? - If the above-mentioned compressor stop time is exceeded, the function of the compressor independent operation time correction section cancels the compressor stop function of the above-mentioned compressor capacity setting section, so there is more time to stop the compressor. Therefore, the freshness of the object to be cooled can be maintained, and the lubricating oil accumulated in the suction pipe can be effectively returned to the compressor.

[Embodiment 1] FIG. 1 is a block diagram showing an embodiment of a refrigeration system according to the present invention, and the same parts as 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 force for stopping the compressors (1b) and (lc) by the forced intermittent operation control unit (9);
The compressor (tb) is set by the compressor capacity setting section (6).
, (tc) has a function of canceling the compressor stop function by the compressor capacity setting section (6).

Next, the operation will be explained. The compressor independent operation time accumulating unit (7) calculates the operating time of only one of the compressors (lb) and (lc), and calculates, for example, 48
When the minute reaches, the compressor capacity setting unit (6) sets both the compressors (lb) and (lc) for a certain period of time, e.g.
By stopping the compressor for 8 minutes and setting the accumulated time (48 minutes) of the compressor independent operation time accumulating section (7) to 0, and operating two compressors (lb) and (lc) with different rated capacities. It is now ready to start driving. By the way, in the intermittent operation control section (9), the compressor (lb), (
The time for stopping lc) can be arbitrarily changed using a variable resistor or the like. The above forced intermittent operation control section (9
), the time for stopping the compressors (lb), (lc) becomes 8 minutes, and the compressor capacity setting section (6) sets the time for stopping the compressors (lb), (lc) to be longer than 8 minutes. In this case, the compressor capacity setting unit (6) cancels the compressor stop function by the compressor capacity setting unit (6) by the function of the compressor independent operation time correction unit (8).
), the compressors (lb) and (lc) will not stop.

Therefore, the time during which the compressor is stopped is kept as short as possible to maintain the freshness of the object to be cooled.

By stopping (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 compressor (1
b) By restarting operation in (1c), the flow rate of 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 (lb) and (lc).
.

By doing so, it is possible to prevent the lubricating oil in the compressors (lb) and (lc) from decreasing.

In addition, although capacity control is performed using two compressors in the example described, even when controlling the capacity of the compressor by changing the output frequency of the inverter, it is possible to effectively remove the mixed oil in the refrigerant. In order to return the output frequency to the compressor, the time during which the output frequency of the compressor is operated at a predetermined value, e.g., 40 Hz or less, is accumulated, and when that value reaches a predetermined value, e.g., 48 minutes, the compressor is operated for a predetermined period of time. For example, when the compressor is stopped for 3 minutes, the time for the forced intermittent operation control section to stop the compressor is, for example, 3 minutes, the time for the compressor capacity setting section to stop the compressor or more, A similar effect can be obtained by the compressor low frequency vi and operation time correction section canceling the compressor stop function of the compressor capacity setting section.

〔Effect of the invention〕

As explained above, in the refrigeration system of the present invention, the pressure detection section detects the refrigerant pressure on the low pressure side of the refrigeration cycle, generates a pressure detection signal, and sets the refrigerant pressure to be converged using the pressure setting section. In addition, 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 controlling the capacity of the refrigerator; a forced intermittent operation control section that generates a signal to stop the compressor over time; 1. When the compressor independent operation time accumulating unit accumulates the time during which only one compressor is operating, and the compressor independent operating time accumulating unit reaches a predetermined time, the compressor is
The compressor capacity setting unit stops both compressors for a certain period of time, sets the cumulative time of the compressor independent operation time cumulative unit to 0, and starts operating the two compressors, and the forced intermittent operation control unit controls the compressor a compressor independent operation time correction unit that cancels a compressor stop function by the compressor capacity setting unit when the time for stopping the compressor exceeds the time for stopping the compressor by the compressor capacity setting unit; As a result, the time during which the compressor is stopped can be kept as short as possible, the freshness of the cooled material can be maintained, and the lubricating oil accumulated in the suction pipe can be effectively returned to the compressor. Lol

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a refrigeration system according to the present invention, FIG. 2 is a block diagram showing a conventional refrigeration system, FIG. 3 is a diagram showing a region of refrigerant pressure on the low pressure side, and FIG. FIG. 3 is an explanatory diagram of capacity control operation of the refrigeration system in FIG. 2; In the figure, (1a) is a condenser, (ic) is a compressor, (2a) to (2c) are coolers, (3) is a pressure detection section, (4) is a pressure setting section, (5) is a control section, (6) is a compressor capacity setting section, (7) is a compressor independent operation time integration section, (8) is a compressor independent operation time correction section, and (9) is a forced intermittent operation control section. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 2, each having a suction pipe and a discharge pipe connected in parallel;
A refrigeration system in which a single compressor, a condenser that condenses and liquefies the refrigerant discharged from these compressors, and a cooler that evaporates and vaporizes the refrigerant sent out from this condenser are connected by piping in order to form a closed circuit. circuit, a pressure detection unit that detects the refrigerant pressure on the low pressure side of this refrigeration circuit and generates a pressure detection signal according to this refrigerant pressure, and a pressure that sets the convergence pressure value of the refrigerant pressure on the low pressure side that is to be converged. a setting unit, a control unit that determines whether the pressure detection signal is greater than or equal to the convergence pressure value and generates a capacity control output signal for controlling the capacity of the refrigerator based on the determination result; a forced intermittent operation control section that generates a signal to stop the compressor for a certain period of time; a compressor independent operation time accumulation section that accumulates the time during which only one compressor is in operation; and a compressor independent operation time When the integration time of the integration section reaches a predetermined time,
A compressor capacity setting section that stops both of the compressors for a certain period of time, sets the accumulated time of the compressor independent operation accumulation section to 0, and starts operation of the two compressors; and the forced intermittent operation control section. a compressor independent operation time correction unit that cancels a compressor stop function by the compressor capacity setting unit when the time for stopping the compressor exceeds the time for stopping the compressor by the compressor capacity setting unit; A refrigeration device characterized by comprising: