WO2018146805A1

WO2018146805A1 - Refrigerating device

Info

Publication number: WO2018146805A1
Application number: PCT/JP2017/005109
Authority: WO
Inventors: 雅浩神田; 雅章上川
Original assignee: 三菱電機株式会社
Priority date: 2017-02-13
Filing date: 2017-02-13
Publication date: 2018-08-16

Abstract

Provided is a refrigerating device that can prevent compressor galling. A refrigerating device comprises: a refrigerant circuit (A) in which refrigerant is circulated and which comprises a compressor (101) that is provided internally with a compression chamber (6) to take in refrigerant and perform compression, a condenser (102), a pressure reducing device (103), and an evaporator (104); a pressure sensor (105) that measures a refrigerant pressure between the evaporator outlet and the refrigerant intake portion of the compression chamber; a predictive calculation device (106) that, from a history of pressures measured by the pressure sensor, calculates and predicts the pressure for a time point at which a preset time will have elapsed; and a low pressure protection device (107) that stops the compressor when the predicted value calculated and predicted by the predictive calculation device is lower than the set value.

Description

Refrigeration equipment

The present invention relates to a refrigeration apparatus including a compressor used for refrigerant compression, and more particularly to protection of the compressor.

General refrigeration equipment includes a refrigerant circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected in order. Then, the refrigerant is compressed into a high-temperature and high-pressure refrigerant gas by a compressor, and the refrigerant gas is heat-exchanged with outside air from the blower by a condenser to obtain a high-pressure refrigerant liquid. The refrigerant liquid is squeezed and expanded by the expansion valve to become a low-temperature and low-pressure gas-liquid two-phase refrigerant. The refrigerant in the gas-liquid two-phase state evaporates by exchanging heat with the room air in the evaporator and returns to the compressor as a refrigerant in a low-temperature and low-pressure gas state.

In this type of refrigeration system, if the low-pressure pressure that is the pressure from the outlet of the expansion valve to the suction part of the compressor is too low, the refrigerant circulation amount is insufficient and the compressor is seized. For this reason, conventionally, a technique is known that includes a low-pressure protection device that stops the compressor when the low-pressure pressure drops below a set value. As such a low-pressure protection measure, in Patent Document 1, at the time of operation mode switching that may cause the low-pressure pressure to fall below a set value, the frequency of the compressor is kept low so that the low-pressure protection device does not operate. The operation can be continued.

Japanese Utility Model Publication No. 4-14153

The low-pressure protection measures of Patent Document 1 are targeted at the time of operation mode switching. However, the decrease in the low pressure of the refrigerant circuit is not limited to the switching of the operation mode, but the amount of refrigerant enclosed in the refrigerant circuit is insufficient, the refrigerant amount is insufficient due to refrigerant leakage, and the opening of the expansion valve catches up with the environmental change. It occurs in the situation that there is no. However, Patent Document 1 cannot cope with such a situation and is insufficient as a measure for suppressing the seizure of the compressor.

The present invention has been made to solve the above-described problems, and an object thereof is to obtain a refrigeration apparatus capable of suppressing the seizure of a compressor.

A refrigeration apparatus according to the present invention includes a compressor, a condenser, a decompression device, and an evaporator provided with a compression chamber that sucks and compresses refrigerant, and includes a refrigerant circuit in which the refrigerant circulates and an outlet of the evaporator. A pressure sensor that measures the pressure of the refrigerant up to the refrigerant suction portion of the compression chamber, a prediction calculation device that predicts and calculates a pressure value after a preset time from the pressure history measured by the pressure sensor, and a prediction calculation The apparatus includes a low-pressure protection device that stops the compressor when the predicted value calculated by the apparatus becomes lower than the set value.

According to the present invention, the compressor is stopped when the predicted value calculated by the prediction calculation device is lower than the set value. For this reason, the compressor can be stopped in advance before the actual low pressure falls below the set value, and the seizure of the compressor can be suppressed.

FIG. 3 is a refrigerant circuit diagram of the refrigeration apparatus according to Embodiment 1 of the present invention. It is a figure which shows the compression principle of the compressor with which the freezing apparatus which concerns on Embodiment 1 of this invention was equipped. It is a figure which shows the flowchart of the low voltage | pressure protection control in the freezing apparatus which concerns on Embodiment 1 of this invention. It is a refrigerant circuit figure of the freezing apparatus which concerns on Embodiment 2 of this invention.

Hereinafter, a refrigeration apparatus according to an embodiment of the invention will be described with reference to the drawings. Here, in FIG. 1 and the following drawings, the same reference numerals denote the same or corresponding parts, and are common to the whole text of the embodiments described below. And the form of the component represented by the whole specification is an illustration to the last, Comprising: It does not limit to the form described in the specification. Further, the level of temperature, pressure, etc. is not particularly determined in relation to absolute values, but is relatively determined in terms of the state, operation, etc. of the system, apparatus, etc.

Embodiment 1 FIG.
FIG. 1 is a refrigerant circuit diagram of a refrigeration apparatus according to Embodiment 1 of the present invention.
The refrigeration apparatus 100 includes a refrigerant circuit A in which a compressor 101, a condenser 102, a decompression apparatus 103, and an evaporator 104 are sequentially connected by a refrigerant pipe, and the refrigerant circulates. In addition, the refrigeration apparatus 100 includes a pressure sensor 105, a prediction calculation device 106, and a low-pressure protection device 107.

Compressor 101 sucks refrigerant and compresses the refrigerant to a high temperature and high pressure state. The compressor 101 is driven by supplying electric power from a power supply source (not shown) to the motor 2 via the inverter 108.

The condenser 102 cools and condenses the refrigerant gas discharged from the compressor 101. The decompression device 103 decompresses and expands the refrigerant. The decompression device 103 includes an electronic expansion valve or a capillary tube that can variably adjust the opening of the throttle, and throttles and expands the refrigerant liquid from the condenser 102. The evaporator 104 evaporates the refrigerant flowing out from the decompression device 103. The evaporator 104 may be in any form of one provided in a refrigerator arranged indoors or one provided on the facility side arranged outdoors.

The pressure sensor 105 is installed between the outlet of the evaporator 104 and the suction portion of the compressor 101, and measures the pressure of the refrigerant at the installation location, that is, the low pressure of the refrigerant circuit A.

The prediction calculation device 106 predicts and calculates a low pressure value after a preset time from the history of low pressure measured by the pressure sensor 105. Although the prediction calculation method is arbitrary, for example, there are the following methods. For example, when pressure measurement in the pressure sensor 105 is performed every second, a pressure value after 1 second is predicted from a linear expression based on a measured value measured at a certain timing and a measured value measured 1 second before. To do. The predictive arithmetic unit 106 can be configured by hardware such as a circuit device that realizes the function, or can be configured by an arithmetic unit such as a microcomputer or a CPU and software executed on the arithmetic unit. .

The low-pressure protection device 107 is a device having a function of shutting down the compressor 101 by shutting off the power supply circuit to the motor 2 when the predicted value calculated by the prediction calculation device 106 becomes lower than a preset set value. For example, it is constituted by a microcomputer and a circuit for cutting off a power supply circuit to the motor 2.

Furthermore, the refrigeration apparatus 100 includes a control device 109 that can control the entire refrigeration apparatus 100, such as control of the decompression apparatus 103, control of the inverter frequency, and operation control of the low-pressure protection apparatus 107. The control device 109 can be configured by hardware such as a circuit device that realizes the function, or can be configured by an arithmetic device such as a microcomputer or a CPU and software executed thereon.

Hereinafter, the compressor 101 will be described with reference to FIG. FIG. 1 shows a single screw compressor of a type in which two gate rotors are engaged with one screw rotor.

The compressor 101 includes a cylindrical casing 1, a motor 2 accommodated in the casing 1, a screw shaft 3 fixed to the motor 2 and driven to rotate by the motor 2, and a screw rotor fixed to the screw shaft 3. 4 mag. The motor 2 includes a stator 2a that is inscribed and fixed to the casing 1, and a motor rotor 2b that is disposed inside the stator 2a. The motor rotor 2 b is arranged on the same axis as the screw rotor 4 and is fixed to the screw shaft 3.

The screw rotor 4 has a cylindrical shape, and a plurality of spiral screw grooves 4a are formed on the outer peripheral surface. The screw rotor 4 is rotationally driven by the motor rotor 2b.

A pair of gate rotors 5 are arranged on the side surfaces of the screw rotor 4 so as to be axially symmetric with respect to the screw shaft 3.

The gate rotor 5 has a disk shape, and a plurality of teeth 5a are radially provided on the outer peripheral surface along the circumferential direction. The teeth 5 a of the gate rotor are meshed with the screw grooves 4 a of the screw rotor 4, and the compression chamber 6 is formed in a space surrounded by the teeth 5 a of the gate rotor 5, the screw grooves 4 a and the inner cylindrical surface of the casing 1. ing. A strainer 7 is disposed in the refrigerant suction portion of the casing 1 in order to prevent dust from flowing into the compressor 101.

Further, the inside of the casing 1 is partitioned by a partition wall 110 into a low-pressure portion 111 where the low-pressure refrigerant is located and a compression chamber 6 and a high-pressure portion 112 where the high-pressure refrigerant is located. A discharge port 8 (see FIG. 2 described later) is formed.

Next, the operation of the compressor 101 will be described.
FIG. 2 is a diagram illustrating a compression principle of the compressor provided in the refrigeration apparatus according to Embodiment 1 of the present invention.
When the motor 2 is started in the compressor 101, the screw rotor 4 rotates in the direction of the solid arrow as the screw shaft 3 (see FIG. 1) rotates. Since the teeth 5a of the gate rotor 5 are engaged with the screw grooves 4a of the screw rotor 4, when the screw rotor 4 rotates, the teeth 5a of the gate rotor 5 relatively move in the screw grooves 4a. Thereby, the gate rotor 5 rotates in the direction of the thin white arrow. Thereby, in the compression chamber 6, the suction stroke, the compression stroke, and the discharge stroke are set as one cycle, and this cycle is repeated. Here, each stroke will be described focusing on the compression chamber 6 shaded with dots in FIG.

FIG. 2 (a) shows the state of the compression chamber 6 in the suction stroke. The screw rotor 4 is driven by the motor 2 and rotates in the direction of the solid arrow. In conjunction with this rotation, the teeth 5a of the gate rotor 5 are sequentially rotated toward the discharge port 8, whereby the volume of the compression chamber 6 is reduced as shown in FIG. 2B, and the refrigerant gas in the compression chamber 6 is reduced. Is compressed.

When the screw rotor 4 continues to rotate, the compression chamber 6 communicates with the discharge port 8 as shown in FIG. Thereby, the high-pressure refrigerant gas compressed in the compression chamber 6 is discharged from the discharge port 8 to the outside. Then, the same compression is performed again on the back surface of the screw rotor 4.

FIG. 3 is a diagram showing a flowchart of low-pressure protection control in the refrigeration apparatus according to Embodiment 1 of the present invention. The processing of the flowchart of FIG. 3 is performed at arbitrarily set control time intervals during operation of the refrigeration apparatus.
The low pressure protection device 107 compares the predicted value of the low pressure calculated by the prediction calculation device 106 with the set value (S1), and continues the operation of the compressor 101 if the predicted value is equal to or greater than the set value. On the other hand, if the predicted value is lower than the set value, the low-pressure protection device 107 stops the compressor 101 (S2).

As described above, in the first embodiment, when the predicted value of the low-pressure pressure predicted by the prediction calculation device 106 is lower than the set value, the low-pressure protection device 107 is activated and the compressor 101 is stopped. With this configuration, the compressor 101 can be stopped in advance before the actual low-pressure pressure falls below the set value. For this reason, the seizure of the compressor 101 during the operation of the refrigeration apparatus 100 can be suppressed. That is, according to the first embodiment, it is possible to obtain a highly reliable refrigeration apparatus that can suppress seizure of the compressor 101 even when the low-pressure pressure rapidly decreases due to, for example, a failure of the decompression device 103. In addition, when the evaporator 104 is a so-called chiller that is a cold / hot water generator and is configured to exchange heat between the water-side flow path and the refrigerant flow path, the low-pressure pressure is reduced due to clogging of the water-side flow path with dust and the like. In this case, a highly reliable refrigeration apparatus that can suppress seizure of the compressor 101 can be obtained.

The refrigerant circulating in the refrigerant circuit A is not particularly limited, and a low-pressure refrigerant with a low operating pressure such as R134a or R1234yf or a high-pressure refrigerant with a high operating pressure such as R410A can be used.

Incidentally, in the refrigeration apparatus 100, when the discharge temperature of the compressor 101 rises excessively, inconvenience such as burn-in of the compressor 101 occurs. For this reason, the discharge temperature is measured by the discharge temperature sensor 113 (see FIG. 1) so that the discharge temperature does not rise above the set upper limit temperature. When a low-pressure refrigerant is used as the refrigerant, the density of the low-pressure refrigerant is smaller than that of the high-pressure refrigerant. Therefore, the amount of refrigerant circulation when an event in which the low-pressure pressure is reduced occurs is smaller than when the high-pressure refrigerant is used. When the refrigerant circulation amount is reduced in this way, the discharge temperature sensor is less likely to detect an abnormality. Therefore, if the configuration of the present embodiment is not adopted, the compressor may be burned before the low-pressure protection device operates. is there.

However, in the first embodiment, even if the refrigerant circulation amount is reduced by using the low-pressure refrigerant, the low-pressure protection device 107 is activated in advance and the compressor 101 before the actual low-pressure pressure falls below the set value. Stop. For this reason, even when a low-pressure refrigerant is used, a highly reliable refrigeration apparatus that can suppress seizure of the compressor 101 can be obtained.

In the first embodiment, the single screw compressor is described as the compressor 101. However, the compressor applied to the refrigeration apparatus of the present invention is not limited to a single screw compressor. As a compressor applied to the refrigeration apparatus of the present invention, for example, a twin screw compressor, a reciprocating compressor, and a scroll compressor that include, for example, two screw rotors and meshes groove portions of these screw rotors to form a compression chamber. Further, a turbo compressor and a rotary compressor may be used.

In the first embodiment, the pressure sensor 105 is provided at the outlet of the evaporator 104. However, the pressure sensor 105 only needs to be able to detect the low pressure of the refrigerant circuit A. From the outlet of the evaporator 104 to the refrigerant suction portion of the compressor 101. It may be provided anywhere between them.

Embodiment 2. FIG.
In the first embodiment, the pressure between the outlet of the evaporator 104 and the refrigerant suction portion of the compressor 101 is detected as the low pressure of the refrigerant circuit A. In the second embodiment, the point of detecting the low pressure of the refrigerant circuit A is the same, but the detection position is different from that of the first embodiment.

FIG. 4 is a refrigerant circuit diagram of the refrigeration apparatus according to Embodiment 2 of the present invention.
In the second embodiment, the pressure measurement position of the pressure sensor 105 is set to the low pressure part 111 inside the compressor 101. The low pressure portion 111 is a region from the downstream side of the strainer 7 to the front of the refrigerant suction portion of the compression chamber 6, and is a region indicated by dots in FIG. The configuration of the second embodiment other than the pressure measurement position of the pressure sensor 105 is all the same as that of the first embodiment.

According to the above configuration, for example, even when the compressor 101 is operated while a stop valve (not shown) attached to the refrigerant suction portion of the compressor 101 is closed, the low pressure pressure is measured and predicted, The compressor 101 can be stopped. Further, even when the strainer 7 attached to the refrigerant suction portion of the compressor 101 is clogged, the compressor 101 can be stopped by detecting and predicting a decrease in low-pressure pressure. That is, the second embodiment can obtain the compressor 101 and the refrigeration apparatus 100 that are more reliable than the first embodiment.

1 casing, 2 motor, 2a stator, 2b motor rotor, 3 screw shaft, 4 screw rotor, 4a screw groove, 5 gate rotor, 5a teeth, 6 compression chamber, 7 strainer, 8 discharge port, 100 freezer, 101 compressor, 102 Condenser, 103 Depressurizer, 104 Evaporator, 105 Pressure sensor, 106 Prediction calculation device, 107 Low pressure protection device, 108 Inverter, 109 Control device, 110 Bulkhead, 111 Low pressure section, 112 High pressure section, 113 Discharge temperature sensor, A Refrigerant circuit.

Claims

A refrigerant circuit that includes a compressor, a condenser, a decompression device, and an evaporator, each having a compression chamber that sucks and compresses the refrigerant;
A pressure sensor for measuring the pressure of the refrigerant between the outlet of the evaporator and the refrigerant suction part of the compression chamber;
From a history of pressure measured by the pressure sensor, a prediction calculation device that predicts and calculates a pressure value after a preset time, and
A refrigeration apparatus comprising: a low-pressure protection device that stops the compressor when a predicted value calculated by the prediction calculation device is lower than a set value.
The refrigeration apparatus according to claim 1, wherein the compressor is partitioned into a low pressure section and a high pressure section having the compression chamber, and the pressure sensor measures the pressure of the low pressure section.