JP2576309B2 - Screw refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a screw refrigeration system,
More specifically, the present invention relates to a screw refrigerating apparatus in which a check valve is interposed in an economizer pipe connected between a screw compressor and an intercooler.

[0002]

2. Description of the Related Art Conventionally, in this type of screw refrigeration system,
For example, as disclosed in JP-A-60-134166 and shown in FIG. 4, a condenser B, an economizer C, an expansion valve D and an evaporator E are provided on the discharge side of the screw compressor A.
To allow refrigeration operation by flowing the refrigerant as indicated by the solid line arrow, while connecting the port F opening to the compression chamber of the screw compressor A and the economizer C,
The screw compressor A and the economizer C are connected by a branch pipe J provided with a capillary I, while being connected by an economizer pipe H provided with a check valve G interposed therebetween. A part of the refrigerant is decompressed by the capillary I, and then supplied to the economizer C, as shown by a dotted arrow, and the refrigerant is decompressed by the capillary I in the economizer C;
Heat exchange is performed between the refrigerant flowing through the economizer C and the refrigerant flowing to the evaporator E, and the refrigerant flowing into the evaporator E is cooled through the port F by cooling the refrigerant flowing to the evaporator E to an intermediate pressure. There has been proposed a screw compressor A that can be injected into a compression chamber of the screw compressor A to improve the refrigerating capacity of the screw compressor A.

[0003] In the above configuration, the check valve G is interposed in the economizer pipe H for the following reason. That is, the port F is open to a compression chamber in which a screw rotor in the screw compressor A is housed, and the port F that opens to the compression chamber has a pressure fluctuation due to the closing and opening of the compression chamber, This is to prevent the pulsation of the economizer pipe H due to the pressure fluctuation and to prevent the pipe from vibrating. By providing the check valve G near the port F, the reverse flow from the port F to the economizer pipe H is prevented. This prevents the gas refrigerant from flowing backwards and is not affected by the pressure fluctuation.

[0004]

However, in the prior art, the check valve G is interposed in the economizer pipe H communicating with the port F. Therefore, when the outside air temperature is low or the cooling load is reduced. When the load is low, such as when
When the height differential pressure is reduced, there is a problem that the check valve G causes chattering to generate a sound or a pipe vibration. That is, when the pressure difference between the discharge pressure and the suction pressure of the screw compressor A decreases, the intermediate pressure in the economizer C, which is reduced by the capillary I, also decreases, and the primary pressure of the check valve G decreases. Become.

On the other hand, the pressure at the time of closing and closing the compression chamber is higher than the intermediate pressure, that is, the secondary pressure of the check valve G is higher than the intermediate pressure. And the pressure at the time of opening the compression chamber becomes lower than the intermediate pressure, that is, the secondary pressure of the check valve G is lower than the intermediate pressure. Therefore, the pushed-up check valve G is caused to return, and at a low load where the intermediate pressure acting on the primary side of the check valve G is low, the influence of pressure fluctuation due to closing and opening of the compression chamber is reduced. As a result, so-called chattering occurs.

Accordingly, even when the check valve G is provided at a low load with a small differential pressure, even if the check valve G is provided, noise is generated due to the chattering of the check valve G, piping vibration is generated, and
The pulsation causes a small power loss, and also causes a problem that the reliability of the check valve G is reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to prevent chattering of the check valve even at a low load with a small high-low differential pressure such that the check valve interposed in the economizer piping causes chattering, thereby generating noise and an economizer. An object of the present invention is to provide a screw refrigeration apparatus that can prevent vibration of piping, can improve the reliability of a check valve, and can prevent power loss.

[0008]

In order to achieve the above object, according to the present invention, an economizer pipe 7 is connected between the screw compressor 1 and the intercooler 3, and a check valve 8 is connected to the economizer pipe 7. In the screw refrigerating apparatus interposed, the differential pressure between the primary side pressure and the secondary side pressure of the check valve 8 is provided on the secondary side of the check valve 8 in the economizer passage including the economizer pipe 7. An on-off valve 9 that closes the economizer passage when a negative pressure differential is applied is provided.

The on-off valve 9 has a high pressure side pressure receiving surface 92 on which the high pressure side pressure acts and a low pressure side pressure receiving surface 94 on which the low pressure side pressure acts, and the primary side pressure and the secondary side pressure of the check valve 8. 9 that operates when the differential pressure between before and after is negative
Preferably, 0 is provided.

[0010]

In a low load operation with a small differential pressure, the check valve 8 is closed due to the pressure fluctuation on the secondary side of the check valve 8 caused by closing and opening of the compression chamber of the screw compressor 1. When the differential pressure between the primary side pressure and the secondary side pressure becomes a negative differential pressure, the secondary side of the check valve 8 can be closed by closing the on-off valve 9, The check valve 8 is not affected by pressure fluctuations on the secondary side of the check valve 8. Therefore, even when the check valve 8 causes chattering and a low differential pressure is small and the load is low, chattering of the check valve 8 can be prevented, and generation of noise and vibration of the economizer pipe 7 can also be prevented.
As a result, the reliability of the check valve 8 can be improved, and a slight power loss due to pulsation can be prevented.

The open / close valve 9 has a high pressure side pressure receiving surface 92 on which the high pressure side pressure acts and a low pressure side pressure receiving surface 9 on which the low pressure side pressure acts.
And a spool 90 which operates when the differential pressure between the primary pressure and the secondary pressure of the check valve 8 becomes negative, ie, a high / low differential pressure.
When the pressure difference between the primary side pressure and the secondary side pressure of the check valve 8 is negative, the spool 90 operates reliably, and the check valve 8 The next side can be closed. Therefore, chattering of the check valve 8 can be surely prevented.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A screw refrigerating apparatus shown in FIG. 1 has a motor housing 12 in which a motor 11 is mounted in a closed casing 10 and a screw rotor 13 driven by the motor 11.
And a compression element storage portion 14 that forms a compression chamber by using a screw compressor 1 provided with an oil separator 15 on the discharge side of the storage portion 14, and on the discharge side of the screw compressor 1. , The condenser 2, the intercooler 3, the expansion valve 4, and the evaporator 5 are connected via a refrigerant pipe 6, and the refrigerant compressed by the screw compressor 1 is passed through a path shown by a solid line arrow in FIG. It circulates and performs freezing operation.

On the outlet side of the condenser 2, there is provided a branch pipe 62 branched from the refrigerant pipe 6 and provided with an intermediate expansion valve 61 in the middle thereof. A check valve 8 is connected to the economizer pipe 7 which connects the intercooler 3 and the screw compressor 1 while being connected to the compressor 3.
To form an economizer passage from the outlet side of the condenser 2 to the compression element accommodating portion 14 of the screw compressor 1 through the intermediate expansion valve 61, the intercooler 3, and the economizer pipe 7. A part of the liquid refrigerant passing through the condenser 2 is decompressed by the intermediate expansion valve 61 as shown by a dotted arrow in FIG.
And heat exchange with the liquid refrigerant supplied to the evaporator 5 in the intercooler 3,
The intermediate cooling refrigerant in a liquid-gas mixed state by the heat exchange is injected into the compression element housing 14 through the economizer pipe 7 so that the refrigerating capacity of the screw compressor 1 can be improved. .

Reference numeral 63 denotes a temperature-sensitive cylinder of the intermediate expansion valve 61;
Numeral 64 denotes a pressure equalizing line for controlling the degree of superheat of the discharge gas. Reference numeral 65 denotes a check valve interposed on the discharge side of the oil separator 15.

Thus, in the screw refrigerating apparatus constructed as described above, the primary side pressure and the secondary side of the check valve 8 are placed on the secondary side of the check valve 8 in the economizer passage including the economizer pipe 7. The on-off valve 9 is provided to close the economizer passage when the pressure difference before and after the pressure is a negative pressure difference.

More specifically, as shown in FIG. 2, an intermediate suction passage 72 having an intermediate injection port 71 opening to the compression element housing 14 is formed in the wall 16 of the closed casing 10 of the screw compressor 1. The intermediate suction passage 7
2, a secondary side of the check valve 8 in the economizer pipe 7 is connected, and a valve chamber 91 in which a spool 90 described later is freely slidably provided is provided so as to intersect the intermediate suction passage 72, The on-off valve 9 is formed so that the intermediate suction passage 72 can be opened and closed by the movement of the spool 90.

The spool 90 has a high pressure side land 93 having a high pressure side pressure receiving surface 92 on which a high pressure side pressure acts, and a low pressure side land 95 having a low pressure side pressure receiving surface 94 on which a low pressure side pressure acts. An annular communication groove 96 formed between the lands 93 and 95 is provided, and both sides in the sliding direction of the spool 90 provided in the valve chamber 91 communicate with the low pressure side via a first passage 101. And a high-pressure chamber 104 communicating with the high-pressure side via the second passage 103. The low-pressure chamber 102 is provided with a spring 105 for urging the spool 90 in the direction of the high-pressure chamber 104. The adjusting body 1 for screwing the spring 105 to the low pressure chamber 102 side
06, the spring pressure can be adjusted.

The spool 90 receives the urging force of the spring 105, the low pressure side pressure introduced into the low pressure chamber 102 via the first passage 101 and acts on the low pressure side pressure receiving surface 94, and the second passage 103. The intermediate suction passage 72 is opened, closed and opened / closed by moving in balance with the high pressure side pressure which is introduced into the high pressure chamber 104 and acts on the high pressure side pressure receiving surface 92. When the pressure difference between the high-pressure side pressure acting on the low-pressure side pressure receiving surface 94 and the high-pressure side pressure falls below a predetermined pressure difference, the communication groove 96 becomes non-communicative with the intermediate suction passage 72. That is, the intermediate suction passage 72 is closed, that is, the secondary side of the check valve 8 in the economizer pipe 7 is closed. On the other hand, the high pressure side and the low pressure side pressure receiving surface 9
When the height differential pressure acting on the second and fourth pressures is equal to or greater than a predetermined differential pressure, the communication groove 96 is communicated with the intermediate suction passage 72, the intermediate suction passage 72 is opened, and the The intermediate cooling refrigerant can be injected into the compression element housing portion 14 through the intermediate injection port 71.

The high pressure side and the low pressure side pressure receiving surface 92,
The operating differential pressure acting on the spool 90 and acting on the spool 90 is determined by the pressure receiving areas of the pressure receiving surfaces 92 and 94 and the adjusting body 10.
6 and the spring pressure of the spring 105, which is adjusted by the pressure of the spring 105. Due to the influence of pressure fluctuation on the secondary side of the check valve 8 caused by closing and opening of the compression chamber of the screw compressor 1, The differential pressure between the primary pressure and the secondary pressure of the check valve 8 is negative, ie, the intermediate pressure of the intermediate cooling refrigerant, that is, the check valve 8
Primary pressure becomes lower than the pressure at the time of closing the compression chamber, that is, the secondary pressure of the check valve 8, the differential pressure across the check valve 8 becomes negative, and the check valve 8 Is set such that the intermediate suction passage 72 is closed when the pressure difference is slightly higher than the pressure difference. For example, using Freon R20 as a refrigerant, and adjusting the discharge pressure of the screw compressor 1 to 12 to 1
When operating at 4 kg / cm ² , the operating differential pressure is 5 kg
/ Cm ² .

The spool 90 closes when the differential pressure is smaller than the differential pressure set as described above, that is, 5 kg / cm ² , and the intermediate suction is performed. Since the passage 72 is closed, the check valve 8 is not affected by pressure fluctuation on the secondary side of the check valve 8 caused by closing and opening of the compression chamber of the screw compressor 1. There is no.

Next, the operation of the screw refrigerating apparatus having the above configuration will be described.

First, when operating under a normal load condition, the differential pressure between the discharge pressure and the suction pressure is equal to the operating differential pressure (5).
Kg / cm ² ), and when the pressure difference is high, the spool 90 opens as shown in FIG. 2 and the secondary side of the check valve 8 is opened. The intermediate cooling refrigerant can be injected from the intermediate injection port 71 into the compression element accommodating section 14, and the refrigerating capacity of the screw compressor 1 can be improved by using the economizer passage.

Next, the cooling load is reduced, for example, the outside air temperature is reduced, or the number of rooms for cooling is reduced, and the low pressure operation is performed, so that the differential pressure of the screw compressor 1 is reduced. When the pressure becomes lower than the operating differential pressure (5 kg / cm ² ), the spool 90 is moved from the position shown in FIG. 2 to the position shown in FIG. And the intermediate suction passage 72 is closed by the low-pressure side land 95, that is, the intermediate suction passage 72 cannot communicate with the intermediate suction passage 72 through the communication groove 96. The secondary side of the check valve 8 is closed.

That is, when the pressure difference during the low load operation decreases and the compression chamber in which the intermediate injection port 71 opens is closed, the difference between the primary pressure and the secondary pressure of the check valve 8 is determined. Even if the pressure becomes negative, the spool 9
Since the secondary side of the check valve 8 interposed in the economizer pipe 7 can be closed by the closing operation of 0, the check valve 8 is affected by the pressure fluctuation on the secondary side of the check valve 8. They do not receive it. Therefore, the check valve 8 can be prevented from chattering even at a low load with a small differential pressure so that the check valve 8 causes chattering, and the generation of noise can be prevented. This chattering causes the economizer pipe 7 to vibrate. Can also be prevented. As a result, the reliability of the check valve 8 can be improved, and a slight power loss due to pulsation in the economizer passage can be prevented.

Further, the spool 90 has a high pressure side pressure receiving surface 92 on which the high pressure side pressure acts and a low pressure side pressure receiving surface 94 on which the low pressure side pressure acts, and controls the primary pressure and the secondary pressure of the check valve 8. It operates when the differential pressure before and after is negative
The spool 90 operates when the differential pressure between the primary pressure and the secondary pressure of the check valve 8 is a negative differential pressure, and the spool 90 operates,
The secondary side of the check valve 8 can be closed. Therefore,
As a result, it is possible to reliably prevent generation of noise due to chattering of the check valve 8.

In the above embodiment, the on-off valve 9 is formed on the wall 16 of the closed casing 10. However, the economizer provided between the check valve 8 and the wall 16 of the closed casing 10 is provided. It may be interposed in the middle of the pipe 7.
Further, the on-off valve 9 is opened and closed by utilizing its own pressure. However, the on-off valve 9 may be electrically opened and closed by providing a differential pressure detector, or a type other than a spool type may be used. .

[0027]

As described above, according to the present invention, in the economizer passage including the economizer piping 7 connected between the screw compressor 1 and the intercooler 3, the secondary side of the check valve 8 is provided. The on-off valve 9 for closing the economizer passage is provided when the differential pressure between the primary pressure and the secondary pressure of the check valve 8 is negative and the pressure difference between the primary and secondary pressures becomes negative. Due to the effect of pressure fluctuations on the secondary side of the check valve 8 caused by closing and opening of the compression chamber of the screw compressor 1, the differential pressure between the primary pressure and the secondary pressure of the check valve 8 is reduced. When the pressure difference becomes negative, the secondary side of the check valve 8 can be closed by the closing operation of the on-off valve 9, and the check valve 8 is connected to the secondary side of the check valve 8. It is not affected by pressure fluctuations on the side. Therefore, even when the check valve 8 causes chattering and a low differential pressure is small and the load is low, chattering of the check valve 8 can be prevented, and generation of noise and vibration of the economizer pipe 7 can also be prevented. As a result, the reliability of the check valve 8 can be improved, and a slight power loss due to pulsation can be prevented.

The on-off valve 9 has a high pressure side pressure receiving surface 92 on which the high pressure side pressure acts and a low pressure side pressure receiving surface 94 on which the low pressure side pressure acts, and the primary side pressure and the secondary side pressure of the check valve 8. Spool 9 that operates when the differential pressure between before and after becomes negative
0, the spool 90 operates when the differential pressure between the primary side pressure and the secondary side pressure of the check valve 8 becomes negative, and the spool 90 operates, and the secondary Side can be closed. Therefore, since the self-pressure can be used, the structure can be simplified, and the operation can be performed with a good response without delay to the change of the high / low differential pressure, and the occurrence of the chattering of the check valve 8 can be surely prevented. It is.

[Brief description of the drawings]

FIG. 1 is a piping diagram of a screw refrigeration apparatus according to the present invention.

FIG. 2 is an enlarged sectional view showing a main part of FIG.

FIG. 3 is a sectional view showing an operation state of FIG. 1;

FIG. 4 is a piping diagram illustrating a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Screw compressor 3 Intercooler 7 Economizer piping 8 Check valve 9 On-off valve

Claims (2)

(57) [Claims] 1. A screw refrigerating apparatus in which an economizer pipe 7 is connected between a screw compressor 1 and an intercooler 3, and a check valve 8 is interposed in the economizer pipe 7.
In the economizer passage including the economizer pipe 7, on the secondary side of the check valve 8, when the differential pressure between the primary side pressure and the secondary side pressure of the check valve 8 is a high-low differential pressure where the differential pressure is negative. A screw refrigerating device comprising an on-off valve 9 for closing an economizer passage. 2. The on-off valve 9 has a high pressure side pressure receiving surface 92 on which the high pressure side pressure acts and a low pressure side pressure receiving surface 94 on which the low pressure side pressure acts.
2. The screw refrigeration system according to claim 1, further comprising a spool that operates when the pressure difference between the primary side pressure and the secondary side pressure of the check valve becomes negative.