JPS6220687A - Screw compressor - Google Patents

Abstract

PURPOSE:To relieve the pressure pulsation due to overcompression by providing the casing adjacent to the discharge port with grooves which communicate the enclosing space with the discharge port and further determining the cross-sectional area of each of these grooves so as to be enlarged gradually up to the start of discharge. CONSTITUTION:On the inner wall of the casing 3 adjacent to the discharge port 2 of a screw compressor, grooves 16, 16a which communicate the enclosing space 10 immediately before discharge with the discharge port 2 are formed. And, the total passage area of these V-grooves 16, 16a is determined so as to be enlarged gradually while the enclosing space 10 moves in the position where it communicates with the discharge port 2. Thus, the gas overcompressed in the enclosing space 10 is gradually discharged through V-grooves 16, 16a, and the pressure pulsation due to overcompression can be relieved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a screw compressor used in air-conditioning equipment, refrigeration, etc.

(Prior art) - As shown in Fig. 5, a screw compressor has suction port 1.
A pair of male and female screw rotors 4.5 rotatably interlocked with each other are housed in a casing 3 having a discharge port 2 and a discharge port 2.
In the space formed by the plurality of tooth grooves 6 and the casing 3,
Regas is sucked in through the suction port 1, compressed, and then discharged through the discharge port 2. As shown in FIGS. 6 and 7, the discharge port 2 includes an axial discharge port 7 that opens in the end face of the pair of male and female screw rotors 4, 5, that is, in the axial direction.
A radial discharge port 8 is continuously opened in the radial direction. This radial discharge port 8 is formed between the tips of the teeth of the female screw rotor 4 and the male screw rotor 5 that intersect with each other and the casing 3, and is connected to a substantially ■-shaped tip seal line 9 that forms the boundary between the adjacent confined space. Open to the matching shape.

For example, when the confined space 10 in the part filled with the middle temperature point in FIG. 7 moves from the suction side and the tip seal line 9 crosses the edge of the radial discharge port 8, the tip seal line 9 The belt-shaped discharge ports formed by the edges of the screw rotors 4 and 5 and the green of the 7th axis discharge port 7 are opened, and compressed gas is discharged. The opening area of this discharge port increases as the rotor rotates, reaches a maximum just before the other tip seal line 9 of the confined space 10 crosses the green of the radial discharge port 8, and then decreases.

In this way, at the start of discharge, the opening area of the discharge port 2 is small, creating flow resistance and discharging smoothly, so even during discharge, the gas is compressed and a so-called overload occurs. Compression will occur.

This overcompression will be further explained based on FIG. 8. In Fig. 8, the rotation angle φ of the rotor is plotted from the right side of the horizontal axis, with Oo being the point at which suction gas confinement is completed, and the pressure of the confined space, the force P1, the stroke volume V, and the discharge port area S are plotted on the vertical axis. 6 Ideally, the pressure P before and after discharge should change as shown by the dotted line in the figure. That is, as the rotor rotates, the stroke volume (2) decreases and compression is performed, and the pressure P increases as the suction pressure Ps increases. Then, when the pressure P reaches the pressure on the discharge side (discharge pressure) Pd (point A in the figure),
The discharge port opens and compressed gas is sent out.

However, as shown in the figure, the discharge port area S gradually changes according to the rotation of the rotor, and since the discharge port area S is particularly small at the start of discharge, the increase in the discharge port area S tends to follow the discharge stroke. Therefore, compression continues without sufficient discharge, and as shown in section B in the figure, the discharge pressure Pd is exceeded, resulting in an overcompression state. and,
As the rotor rotates further, the discharge port area S becomes larger, and when it comes to follow the amount of discharged gas, the normal discharge stroke returns.

According to the calculation results performed by the inventor, for example, the pressure 1
In a screw compressor that compresses from ata to 3 ata, overcompression of about 3.2 to 3.3 ata occurs.

This overcompression phenomenon is caused by a large capacity and a small number of teeth (
Combination of male screw rotor with 3 teeth and female screw rotor with 4 teeth, or male screw rotor with 2 teeth and 3 teeth
This is particularly noticeable in screw compressors (such as screw compressors consisting of a combination of female screw rotors).

(Problem to be solved by the invention) Due to this overcompression phenomenon, excessive power is required for the screw pressure Ia, which increases the load and causes power loss, and also causes pulsation, which causes vibration. Problems such as:

Therefore, as shown by the two-dot chain line in Fig. 8, the discharge port is enlarged, the opening timing of the discharge port is advanced from the rotor rotation angle φ1 position to the φ1゛ position, and the discharge port area at point A is increased. It is possible to do so. However, with the method of enlarging the discharge port, fine adjustment of the discharge port area is difficult, and since the discharge port opens before the discharge pressure Pd is reached, the gas on the discharge side flows backwards, only in the area shown by hatching in the figure. Work will increase and volumetric efficiency will decrease.

The present invention was made in view of such problems, and an object of the present invention is to provide a screw compressor that can suppress overcompression and has less power loss and vibration.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides tooth spaces of a pair of male and female screw rotors rotatably engaged with each other housed in a casing having a suction port and a discharge port, and a casing. In a squirting compression rock that sucks gas through a suction port into a confined space formed by a suction port, compresses it, and discharges it from a discharge port. A passage communicating with the port is provided, and the passage area is formed so as to gradually expand until the discharge starts.

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

In FIG. 1, 1 and 2 are a suction port and a discharge port provided in a casing 3, and the discharge port 2 consists of an axial discharge port 7 and a radial discharge port 8. 4
, 5 are a pair of male and female rotors housed in a rotor chamber 11 provided in the casing 3, and a radial bearing 12
The length of the sleeve is extended by a thrust bearing 13, and the shaft is sealed by a mechanical seal 14, thereby configuring a conventionally well-known screw compressor. A small hole 15.15a is provided in the casing 3 near the radial discharge port 8. These small holes 15.15a include three small holes 15 along the edge of the radial discharge port 8 and one small hole 1
5a is provided at an appropriate distance from the small hole 15 on the suction side to communicate the discharge port 2 and the rotor chamber 11. Then, the confined space 10 just before the discharge (the part filled with dots in FIGS. 1 and 2) first communicates with the discharge port 2 through one small hole 15a, and then communicates with the discharge port 2 through the three small holes 15a. The cross-sectional area of the small hole, which is formed to communicate with the discharge port 2 through the small hole 15 and through which the confined space 10 just before discharge communicates with the discharge port 2, gradually increases until the discharge starts. There is.

As described above, as a result of providing the small hole 15.15a that communicates the confined space 10 immediately before discharge with the discharge port 2, the discharge port 2- is at the discharge starting point A, that is, the rotor rotation angle, as shown in FIG. It opens through the small holes 15, 15a at the position φ2 before the position φ1.

At this time, the pressure inside the confined space 10 is still the discharge pressure Pd
Since the discharge gas has not reached 15.0, the discharged gas tries to flow backward from the discharge side, but the small hole 15. The cross-sectional area of ISa is small,
Since flow resistance occurs, the pressure does not rise instantly to Pd as shown by the two-dot chain line in Fig.
Compared to the conventional pressure curve shown by the dotted chain line, the rotor rotation angle φ
When the pressure is opened from 2 to φ, the pressure changes with a rather steep gradient.

Then, at the start of discharge, the cross-sectional area of these small holes 15, 15a is already open, and overcompression that occurs in the conventional case due to the small discharge port area S at the start of discharge is reduced.

Therefore, the pressure gradient of the pressure P in the confined space 10 changes rapidly from the time the small hole 15a opens, but the peak B of overcompression is 2. Katsu M! This decreases compared to the conventional overcompression peak B' shown by /a.

FIG. 4 shows a second large embodiment of the present invention, in which a groove 16.degree. 16a is provided in place of the small hole 15.1'5a of the first embodiment. In other words, this ■ groove 16.16a is
They are provided with different lengths on the inner surface of the rotor chamber 11, and are shaped so that the cross-sectional area expands toward the green of the radial discharge port 8 due to the confined space 10 immediately before discharge. Therefore, the passage area where the confined space 10 and the discharge port 2 communicate with each other immediately before discharge gradually expands until the discharge starts, and the same effect as in the first embodiment is achieved.

Incidentally, instead of the groove (2) in this second embodiment, a concave groove may be formed so that the depth or width thereof gradually increases.

Furthermore, the small hole 15.15a in the first embodiment is made into a screw hole, and a blind plug or aperture plug shown in FIGS. 28 and 2b is removably attached to the screw hole to adjust the opening area. It may be possible.

(Effects of the Invention) As is clear from the above description, according to the present invention, a passage is provided in the casing near the discharge port to communicate the discharge port with the confined space immediately before discharge, so that the area of the passage is equal to the area at which discharge starts. Since the discharge port area increases at the start of discharge and discharge is performed smoothly, overcompression is suppressed and power loss is reduced. Furthermore, the amplitude of pulsation caused by overcompression is reduced, making it possible to suppress vibrations of the screw compressor.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the screw compressor according to the present invention, Fig. 2 is a perspective view of the screw rotor seen from the radial discharge port, and Figs. 2a and 2b are the small holes 15 in Fig. 151.
Figure 3 is a sectional view showing a blind plug and a throttle plug, respectively, which are attached to = 15a, and Fig. 3 shows the screw pressure mt according to the present invention.
m rotor rotation angle and pressure. A diagram showing the relationship between stroke volume and discharge port area, FIG. 4 is a perspective view of a screw rotor of a screw compressor according to another embodiment of the present invention, and FIG. 5 is a cross-sectional view schematically showing a conventional screw compressor. Figure 6 is a sectional view taken along the line 1-1 in Figure 5, Figure 7 is a sectional view taken along the ■-■ line in Figure 5, and Figure 8 is the rotor rotation angle and pressure per stroke volume of a conventional screw compressor. , is a diagram showing the discharge port area. 1... Suction port, 2... Discharge port, 3... Casing, 4... Female screw rotor, 5... Male screw rotor, 10... Confined space immediately before discharge, 15.
15a...small hole, 16,16a...■groove. Patent applicant Kobe Steel Co., Ltd. agent Patent attorney 2 people
2nd g11g3 figure 114W! J Figure 5 Figure 6

Claims (1)

[Claims] (1) Gas is sucked through the suction port into the confined space formed by the casing and the tooth grooves of a pair of male and female screw rotors that rotatably mesh with each other, which are housed in a casing that has a suction port and a discharge port, and then compresses and discharges the gas. In a screw compressor that discharges from a port, a passage is provided in the casing near the discharge port to communicate the discharge port with the confined space immediately before discharge among the confined spaces, and the area of the passage is increased until the discharge starts. A screw compressor characterized by being formed so as to gradually expand.