JP2765934B2 - Operation control method of refrigeration system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an operation method for controlling a frequency within a set pressure (or temperature) range in a refrigeration apparatus that operates by controlling an inverter frequency.

[Conventional technology]

Conventional control is an operation that controls an inverter frequency to maintain a pressure between an upper limit and a lower limit within a set pressure (or temperature) range as employed in an inverter refrigerator mounted on a semi-hermetic compressor tower. Was the way.

FIG. 2 shows a conventional operation method, and shows a state of an operation change of a set suction pressure and an inverter frequency which are operation-controlled.
Set pressure Psb and set pressure range Δ depending on load conditions on low pressure side
P is set. The refrigerator controls the operation so as to maintain the set pressure range ΔP. The inverter operates at the same high frequency up to the set pressure Psb. When the operating pressure becomes lower than the set pressure Psb, the inverter frequency is reduced. When the operating pressure increases within the set pressure range ΔP at this frequency, the operation is controlled within the set pressure range ΔP at the same frequency. When the operation state at this frequency exceeds the upper limit Psb + ΔP of the set pressure range ΔP, the inverter frequency is increased and the operation control to return to within the set pressure range ΔP is performed. By repeating such operation control, the set pressure range Δ
It is controlled to maintain P.

Further, when the detected pressure is out of an allowable pressure range between a set upper limit pressure value and a lower limit pressure value, an inverter circuit is controlled so as to prohibit the rotation speed from decreasing and increasing continuously. It is described in the gazette.

[Problems to be solved by the invention]

According to the above-mentioned prior art, in the operation within the set pressure (or temperature) range, the operation of the inverter is only controlled so as to maintain the range between the upper limit and the lower limit of the range. In addition, it is necessary to operate for a long time at a high frequency, and there is a problem that the efficiency of energy saving operation is deteriorated because no consideration is given to ensuring high efficiency.

An object of the present invention is to operate the compressor at a frequency as low as possible so that the suction side pressure or the suction side temperature of the compressor is operated as close to the upper limit as possible within a set value range to prevent overcooling. Another object of the present invention is to provide a method for controlling the operation of a refrigeration system which can achieve a high energy saving effect.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a refrigerating apparatus that is operated by controlling the frequency by an inverter so that the suction side pressure or the suction side temperature of a compressor falls within a target set value range, and maintains the same frequency. When the operating state continues for a preset time, if the suction side pressure or the suction side temperature is within a target set value range, the set inverter frequency is lowered, and the operation with the reduced frequency is performed for a set time. After the continuation, if the suction side pressure or the suction side temperature is still within the target set value range, the set frequency is further reduced and the operation is continued for the set time, and thereafter, the suction side pressure or the suction side temperature becomes the upper limit of the set range. Until the above, the operation of decreasing the frequency step by step at every set time is continued, and when the suction side pressure or the suction side temperature exceeds the upper limit of the set range, the frequency is increased. Driving, when you return to an upper limit of the set range, in which again so as to continue the operation stepwise lowered every predetermined time frequency, and adapted to operate at the lowest possible frequency.

[Operation] The pressure (temperature) and the pressure (temperature) range are set according to the cooling load conditions, and the operation is controlled while maintaining the set values. According to the present invention, since the operation of decreasing the frequency stepwise at every set time is continued within the set value range, the suction side pressure or the suction side temperature of the compressor is set to the upper limit as much as possible within the set value range. Since the compressor can be operated in the vicinity, and thus the compressor can be operated at a frequency as low as possible, it is possible to prevent overcooling and obtain a high energy saving effect.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to FIG.

FIG. 1 shows an operation state diagram of the suction pressure and the inverter frequency in the operation control method according to one embodiment of the present invention.

In the figure, the vertical axis indicates the operating frequency and the suction pressure of the refrigeration system, and the horizontal axis indicates the operating time. Psb is the lower limit set value of the operating suction pressure, Psb + ΔP is the upper limit set value of the operating suction pressure, and ΔP is the set pressure range. A time is the set operation time within the set pressure range (ΔP), B time is the set frequency decrease time, CHz is the set decrease frequency, and after A or B time elapses, the frequency is set as long as the suction pressure is within the set pressure range ΔP. It acts in the direction of decreasing and acts in the direction of increasing when the suction pressure exceeds the upper limit value Psb + ΔP. The B time is set so as to be reduced step by step at small intervals.

When the operation state enters the upper limit Psb + ΔP of the set pressure range ΔP, and the state in the set pressure range ΔP continues for the set A time, the inverter frequency is reduced by CHz. After the frequency CHz decreases, after the lapse of the set B time, if the pressure is still within the set pressure range ΔP, the frequency is further reduced by CHz, and this frequency control is performed at the set pressure range ΔP.
Is repeated until the upper limit Psb + ΔP is reached. When the value exceeds the upper limit Psb + ΔP, the frequency is increased and returned to within the set pressure range ΔP. The above-described operation control is repeated on condition that the set time A continues once the set pressure range ΔP is entered again.

According to the present embodiment, if there is an operation state within the set pressure range (ΔP), the frequency is gradually reduced to reach the upper limit of the set pressure range, so that it is possible to operate at a low inverter frequency and to achieve high operation efficiency. It is possible to secure energy saving operation.

〔The invention's effect〕

According to the present invention, in the set pressure range, the operation is performed by gradually decreasing the inverter frequency until the upper limit of the range is reached. This has the effect of preventing operation and achieving high efficiency and high energy saving operation.

[Brief description of the drawings]

FIG. 1 is a change diagram showing the relationship between the operating frequency and the suction pressure according to one embodiment of the present invention, and FIG. 2 is a change diagram showing the relationship between the frequency and the suction pressure in the conventional operation. Psb: Set pressure, ΔP: Set pressure range, A: Operation set time within the set range, B: Frequency decrease set time, C: Decrease set frequency.

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Masahiro Yazaki 390 Muramatsu, Shimizu-shi, Shizuoka Prefecture Inside Shimizu Plant, Hitachi Ltd. (72) Inventor Osamu Hagiri 390 Muramatsu, Shimizu-shi, Shizuoka Pref. Hitachi Shimizu Engineering Co., Ltd. (56) References JP-A-62-19655 (JP, A) (58) Fields investigated (Int. . ^6, DB name) F25B 1/00 F04B 49/06 341

Claims (1)

(57) [Claims] In a refrigerating apparatus which is operated under frequency control by an inverter so that a suction side pressure or a suction side temperature of a compressor falls within a target set value range, an operation state in which the same frequency is maintained is determined in advance. At the point in time when the set time is continued, if the suction side pressure or the suction side temperature is within the target set value range, the set inverter frequency is reduced. If the side pressure or the suction side temperature is still within the target set value range, the set frequency is further reduced and the operation is continued for the set time, and thereafter, the operation is continued until the suction side pressure or the suction side temperature reaches the upper limit of the set range. If the suction side pressure or the suction side temperature exceeds the upper limit of the set range, the frequency is increased and the operation is continued. When returned to the upper limit of the range, the operation control method of the refrigeration system, characterized by continuing the operation stepwise lowered every again set the frequency time.