JPH0338433B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a slide valve type screw compressor equipped with a fixed valve that regulates the axial movement range of the slide valve.

(Prior Art) Conventionally, a slide valve type screw compressor shown in FIG. 5 is known as this type of compressor.

This compressor is configured to be able to adjust its capacity, and rotates a pair of male and female screw rotors (hereinafter referred to as rotors) 5 that mesh with each other in a rotor chamber 4 of a casing 3 having an inlet 1 and an outlet 2. A slide valve 21 is provided so as to be able to be accommodated, and to be able to move forward and backward in parallel to the rotor shaft 7 while substantially in contact with both rotors, and a fixed valve 22 restricts the range of movement thereof. Furthermore, a through hole 23 is formed in the lower part of the fixed valve 22 to communicate the slide valve 21 side of the fixed valve 22 with the suction port 1 side.

A compression chamber is formed in the rotor chamber 4 by the rotor 5, the casing 3, and the slide valve 21, and the gas sucked in from the suction port 1 is compressed here and discharged to the discharge port 2, while the slide valve 21 is It is moved to the right in the figure to form a bypass flow path 24 from the compression chamber to the suction port 1, so that a part of the gas once sucked can be returned to the suction port 1 side through the bypass flow path 24. .

That is, during full-load operation when the fixed valve 22 and the slide valve 21 are in contact with each other as shown in FIG. 6, the bypass passage 24 is not formed and gas compression starts from the left end of the rotor 5. On the other hand, during capacity adjustment operation when the slide valve 21 moves to the right as shown in FIG. Since the process volume has decreased, capacity adjustment is performed. In FIGS. 6 and 7, P represents the pressure in the confined space, and L represents the distance from the end surface of the rotor chamber 4 on the suction port side.

(Problems to be Solved by the Invention) As mentioned above, this slide valve 21 is for capacity adjustment, and by moving it, the internal compression ratio πi (pressure immediately before discharge P ₂ with respect to suction pressure P ₁ Although the ratio P ₂ /P ₁ ) can be changed, since the slide valve 21 is not provided for this purpose, the capacity also changes. On the other hand, the adiabatic efficiency of the compressor is determined when the pressure immediately before discharge P ₂ is equal to the discharge pressure P ₃ , that is, when the internal compression ratio πi is equal to the external compression ratio πo
( _{The ratio P 3 /} P ₁ of the discharge pressure P ₃ to the suction pressure P 1 ) is the maximum.

By the way, compressors used in city gas supply equipment, for example, are sometimes used for two purposes: holder filling and pressure feeding. The difference between these two uses is that the discharge pressure is high for holder filling and low for pressure feeding, and there are two external compression ratios: high and low.

However, the slide valve type screw compressor described above has a problem in that the capacity changes as described above even if the internal compression ratio is adjusted to maximize the adiabatic effect (i.e., πi=π ₀ ). The same thing can also be said about vacuum pumps (discharge pressure is constant and suction pressure varies).

Therefore, a slide valve type screw compressor (Japanese Patent Laid-Open No. 58
-101289) has been proposed. Furthermore, it has been proposed to slidably provide an additional valve member between the operating fixed valve and the slide valve in order to obtain the best adiabatic efficiency in at least two different part-load operating conditions ( (Japanese Patent Application Laid-Open No. 126589/1989).

However, these compressors with variable internal compression ratios have a more complex structure than conventional capacity-adjustable compressors, so a simpler structure has been desired.

Therefore, the applicant of the present application has already proposed a slide valve type screw compressor suitable for applications in which the external compression ratio fluctuates as described above (Japanese Patent Application Laid-Open No. 121884/1984).

However, as described below, this compressor uses a slide valve in a high temperature region, so there is a problem that malfunction may occur due to thermal expansion.

In addition, when the slide valve is placed on the discharge port side and the fixed valve on the suction port side as in this compressor, the internal compression ratio is determined by whether or not the slide valve and fixed valve are in contact with each other. There was a problem that only two types could be changed depending on whether or not a discharge port was formed between them.

(Means for Solving the Problems) In order to solve the above-mentioned conventional problems, the present invention provides a pair of male and female rotors that mesh with each other, a casing having a rotor chamber housing the rotors, and a casing having an uneven wall surface of the rotor chamber. A slide valve is formed so that it can move forward and backward in parallel with the axis of the rotor, and a slide valve that similarly forms a part of the above-mentioned wall surface and that restricts the axial movement range of the slide valve. In a slide valve type screw compressor equipped with a fixed valve that forms the wall surface without creating a gap between the slide valve and the slide valve by knotting, the slide valve is on the suction port side and the fixed valve is on the discharge port side. In addition, when the slide valve is separated from the fixed valve, a bypass passage is provided to communicate the space between the two valves with the discharge port.

(Example) Next, an example of the present invention will be described with reference to the drawings.

1 and 2 show a slide valve type screw compressor according to the present invention, and the slide valve type screw compressor shown in FIG. 5 consists of a slide valve 21 and a fixed valve 2.
With the exception of 2, the other parts are substantially the same, and corresponding parts are given the same numbers and their explanation will be omitted.

As shown in the figure, in the compressor according to the present invention, the fifth
Contrary to the case of the compressor shown in the figure, a slide valve 11 is provided on the suction port side and a fixed valve 12 is provided on the discharge port side, and when the slide valve 11 is separated from the fixed valve 12, the A bypass flow path 13 is provided to communicate the space with the discharge port.

Therefore, when the fixed valve 12 is brought into contact with the slide valve 11 as shown in FIG. length (l ₁ + l ₂ )
It is formed in the part on the leaf outlet 2 side of the part, and the internal compression ratio becomes large. On the other hand, as shown in FIG. 2, when the slide valve 11 is moved toward the discharge port 2 side, the discharge port 14 is formed in the portion of the fixed valve 12 on the discharge port 2 side, and the internal compression ratio becomes smaller. That is, since the compressed gas flows from the space between the fixed valve 12 and the slide valve 11 through the bypass passage 12, the exposed port 14 becomes the portion _l3 . Therefore,
The lengths l ₁ and l ₂ of the fixed valve 12 and the slide valve 11 are determined during high pressure operation with a large internal compression ratio as described above (Fig. 1).
During low pressure operation with a small internal compression ratio (Fig. 2),
Each is determined to be equal to the external compression ratio.

By the way, as shown in Fig. 3, in the process in which the confined space in the rotor chamber moves from the suction port 1 side to the discharge port 2 side, the relationship between distance L and temperature is such that it moves toward the discharge port 2 side due to adiabatic compression. For example, a temperature of 40°C on the suction port 1 side will rise to 350°C just before flowering. On the other hand, even if the positions of the slide valve 11 and fixed valve 12 in FIGS. 1 and 2 are reversed, and the slide valve 11 is provided on the discharge port 2 side and the fixed valve 12 is provided on the suction port 1 side, the internal compression ratio It is possible to make it variable. However, in this case, the slide valve 11, which is a movable part, is located at the part shown by part B in FIG. 3 and is exposed to high temperatures, so there is a risk that it will not be able to move as a result of thermal expansion.

Therefore, in this compressor, the slide valve is located at the part A in FIG. 3 where the temperature rise is small, so that it can move smoothly forward and backward without being affected much by thermal expansion.

In addition, in the above embodiment, the bypass flow path 13 is provided between the fixed valve 12 and the outer wall of the casing 3, that is, in the casing 3, but the present invention is not limited to this. A bypass channel 13a shown in FIG. 4 may be provided. That is, this bypass flow path 13a is formed by piping outside the casing 3 so as to communicate the suction port side portion of the fixed valve 12a with the discharge port 2, and the other parts shown in FIG. 4, FIG. Parts common to those in FIG. 2 are given the same numbers.

Further, the fixed valves 12, 12a are connected to the casing 3.
It may be integrated with the casing 3, or a separate member may be attached to the casing 3.
Fixed valves may be formed by being fixed inside, or they may be made hollow and have cooling water passed through them, which tends to become hot.1
2 and 12a may be cooled.

(Effects of the Invention) As is clear from the above description, according to the present invention, the slide valve is provided on the suction port side and the fixed valve is provided on the discharge port side, and when the slide valve is separated from the fixed valve, both A bypass flow path is provided to communicate the space between the valves with the discharge port.

Therefore, even when the external compression ratio changes, it is possible to operate with optimal adiabatic efficiency without complicating the structure.

Furthermore, as mentioned above, since the slide valve operates in a low temperature area, accidents such as inoperability due to thermal expansion can be avoided.

Furthermore, by arranging the slide valve and the fixed valve as in the present invention, that is, by arranging the former on the suction port side and the latter on the leaf outlet side, the internal compression ratio can be adjusted continuously according to the amount of movement of the slide valve. It has the effect of being able to change the information.

[Brief explanation of the drawing]

FIGS. 1 and 2 are cross-sectional views showing the slide valve type screw compressor according to the present invention during high-pressure operation and low-pressure operation, and FIG. 3 shows the relationship between distance L and temperature in a confined space. Fig. 4 is a sectional view showing another embodiment of the present invention, Fig. 5 is a sectional view of a conventional slide valve type screw compressor, and Figs. 6 and 7 show a fixed valve and a slide valve in close contact with each other. FIG. 6 is a diagram showing the relationship between the distance from the end surface of the rotor chamber on the suction port side and the pressure in the confined space when the rotor chamber is closed and when the rotor chamber is separated from the rotor chamber. 3... Casing, 4... Rotor chamber, 5... Rotor (screw rotor), 11... Slide valve,
12, 12a... Fixed valve, 13, 13a... Bypass flow path.

Claims (1)

[Claims] 1 A pair of male and female screw rotors that mesh with each other, a casing having a rotor chamber housing the screw rotors, a slide valve that forms part of the wall of the rotor chamber and is provided so as to be movable in parallel with the axis of the rotor, and this slide valve. Similarly, it forms a part of the wall surface and regulates the axial movement range of the slide valve,
In a slide valve type screw compressor equipped with a fixed valve that forms the wall surface without creating a gap between the slide valve and the slide valve by bringing the slide valve into contact with the slide valve, the slide valve is placed on the suction port side, and the fixed valve is 1. A slide valve type screw compressor, characterized in that a slide valve is provided on a discharge port side, and a bypass flow path is provided that connects a space between both valves to the discharge port when the slide valve is separated from the fixed valve.