JPH04371757A - Capacity control system for freezer device - Google Patents

Abstract

PURPOSE:To determine an operation starting capacity in response to an increasing degree of suction pressure just before starting operation and to provide a stable operation even under a low load by shortening a cooling time at the time of starting of the operation. CONSTITUTION:Pressures at outlet ports of an evaporator 5a of a high load and another evaporator 5b of a low load are detected by a low pressure sensor 6. A suction pressure increasing speed of a compressor 1 just before starting operation is calculated by a controller 7, a value of the load is judged and then an inverter driving motor 1ab and a commercial power supply driving motor 1bb are controlled through a solenoid switch. With such an arrangement, the operation is started as a low pressure becomes a set value and an operation capacity is controlled in such a way as the low pressure converges into a specified range. Accordingly, a cooling time under a starting of operation is shortened and a stable operation can be carried out even under a low load.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention uses an inverter to control the rotational speed of the compressor and the number of compressors in order to maintain freshness by keeping the evaporation pressure of the refrigerant constant in the evaporator and keeping the internal temperature constant by the evaporator. The present invention relates to a refrigeration system that performs capacity control through control.

0002

[Prior Art] Although there is no detailed description of control in the prior art, the same system was developed in U.S. Pat.
There is a publication. A typical start-up in this system would begin with minimum capacity and then enter capacity increase control.

0003

[Problem to be solved by the invention] In the above conventional technology,
There was a problem in that startup was slow when a large amount of capacity was required (hereinafter referred to as "a large load case").

The object of the present invention is to increase the starting capacity when the load is large, and to reduce the starting capacity when the load is small.

[0005]

[Means for Solving the Problems] The above object is achieved by determining the operation start capacity by detecting an increase in load immediately before the start of operation.

[0006]

[Operation] In the case of a refrigeration system, an increase or decrease in load is due to an increase or decrease in low pressure. When this low pressure reaches the set value, operation starts,
The operating capacity is controlled so that the low pressure after operation converges within the specified range.

[0007] By detecting the rising speed of the low pressure immediately before the start of operation, the magnitude of the load after the start of operation can be determined.

[0008]

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1, 2, and 3.

Although this embodiment shows a twin type compressor having two compression mechanisms in one chamber, the same applies to a multiple type compressor consisting of separate compressors.

Generally, as shown in FIG. 2, when the low pressure reaches the operation start pressure value P1, the inverter drive side motor 1ab starts operating, and then speeds up depending on the degree of convergence of the low pressure. If the pressure does not converge to the specified pressure, operate the motor on the commercial power drive side.

This is not a problem if only the evaporator 5a on the small load side in FIG. 1 is used, but in the case of a large load side, it takes a long time for the low pressure to converge.

[0012] Therefore, when this load is large, as shown in FIG.
The convergence time can be shortened by starting the inverter drive side and the commercial power supply drive side almost simultaneously when the operation start pressure value P1 is reached as shown in FIG.

As shown in FIGS. 2 and 3, the capacity at the start of operation is expressed as the low pressure rise ΔP per unit time before the start of operation.
/Δt can be detected.

[0014]

[Effects of the Invention] According to the present invention, it is possible to shorten the conventional cooling time during start-up, and stable operation is possible even under a small load.

[Brief explanation of drawings]

FIG. 1 is a system diagram of an embodiment of a refrigeration cycle of the present invention.

FIG. 2 is an explanatory diagram of control according to the present invention.

[Explanation of symbols]

1... Compressor, 1aa, 1ba... Compression mechanism section, 1ab... Inverter drive side motor, 1bb... Commercial power supply drive side motor, 2... Condenser, 3a... Large load side liquid solenoid valve, 3b... Small load side liquid solenoid valve , 4a, 4b...expansion valve, 5a...large load side evaporator, 5b...small load side evaporator, 6...low pressure sensor, 7...
Controller, 8... Inverter, 9... Electromagnetic switch.

Claims (1)

[Claims] Claim 1: In a refrigeration system with capacity control in which the suction pressure during operation is controlled so as to converge to a preset suction pressure value, the operation start capacity is determined based on the degree of increase in suction pressure immediately before the start of operation. A capacity control method for a refrigeration system characterized by control.