JPS6344956B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a screw compressor, and particularly to its discharge axial port.

[Background of the invention]

The structure of the screw compressor will be explained with reference to FIGS. 1 and 2. As shown in FIG. 2, the compressor includes a casing 4 comprising a working space 1 consisting of two intersecting cylindrical holes 1a and 1b, a suction passage 2 communicating with this working space 1, and a discharge passage 3.
It is housed in the working space 1 of this casing 4 and has lobes 5a and 6a, grooves 5b and 6b,
A pair of male and female rotors 5 that mesh with each other and rotate
and 6. The discharge casing 7 is made separately from the casing 4, and is integrally connected to the casing 4 with bolts. The shaft portion of the male rotor 5 is extended, and the rotor 9 of the electric motor 8 is attached to the extended portion to drive the rotor of the compressor. Both ends of the male rotor 5 and female rotor 6 are supported by the casing via bearings. The discharge port of the compressor consists of a radial port 10 provided in the casing 4 and an axial port 11 provided in the discharge casing 7. Next, the axial port of a conventional compressor will be explained.

Figure 3 shows the axial port indicated by the arrow in Figure 1.
The view is shown in the direction of. The male rotor 5 and female rotor 6 are rotated in the directions of arrows 20 and 21, respectively. The axial port is formed by a continuous curve from point 12a to point 13a. Between points 12a and 12b and point 13
The part between a and 13b is made to match the edges of the grooves 5b and 6b at the position where discharge starts, and as the rotor rotates, the grooves 5b and 6 shown by two-dot chain lines are formed.
Immediately after b reaches this position, grooves 5b and 6b open to the discharge ports, and gas is discharged. Curves 12b-14 and curves 13b-15
are usually formed equal to the bottom circles of grooves 5b and 6b, respectively.

The details of the shape between points 14 and 15 are shown in the fourth section.
As shown in the figure. A closed curve 31, shown as a broken line in FIG.
32 and 33 are the loci of the theoretical contact points of both rotors projected onto this plane. This is usually called the seal line because it is also the locus of the point that seals the groove that confines high-pressure gas during the compression or discharge stroke and the groove that sucks low-pressure gas during the suction stroke. Several closed spaces are formed by the engagement of the rotor profiles at the discharge end face of the rotor, and the boundary points of the spaces are curved 31, as shown in FIGS. 5 and 6.
Come on 32, 33. Of these, the area between 31 and 32 is the locus of the contact point between the tooth profile near the tooth tip of the female rotor and the tooth profile of the male rotor, and the main part is the outer diameter line (tip circle) of the female rotor. It's inside.
Also, between 32 and 33 is the locus of the contact point between the tooth profile near the tip of the male rotor and the tooth profile of the female rotor, and the main part is inside the outer diameter line (tip circle) of the male rotor. It is in. A portion of the discharge port has conventionally been formed along this seal line. This will be explained in more detail below.

In FIG. 5, 34, 35, 36, 37 and 38 indicate spaces (working chambers) formed by engagement of the rotor profiles at the discharge end face. Among these, spaces 34 and 35 are in communication with each other, and are spaces that are shrinking and trapping high pressure gas. Reference numeral 36 denotes an expanding space that communicates with the suction side chamber along the twisted groove of the rotor. 37 is a space that is shrinking and traps high pressure gas. Reference numeral 38 denotes an expanding space which follows the twisted groove of the rotor and communicates with the suction side chamber. The rotor's theoretical contact points, shown at 39, 40, and 41, lie on the seal line shown in dashed lines.

FIG. 6 shows a state in which the rotor has rotated more than in FIG. 5, and the space 37 in FIG. 5 has disappeared, and the space 3 in FIG.
6 communicates with the space 38 to form a space 42 in FIG. As can be seen from both figures, the portion of the discharge end face surrounded by the seal line may be exposed to an expanding space, that is, a space communicating with the suction side chamber. Therefore, this part of the casing surface facing the discharge end face of the rotor must be closed. However, on the other hand, it is desirable to make the discharge port as large as possible in order to reduce discharge resistance. In the case of the space 37 in FIG. 5, a large portion of the opening at the discharge end face is within the area surrounded by the seal line, and other portions are also undesirably close to the seal line.

From the above viewpoint, the conventional discharge port was formed along the seal line as shown in FIG. 4. In FIG. 4, curves 16 to 18 and 17
-19 are each along a part of the seal line. However, in actual shields, the seal line is often approximated by an arc. Normally this part should be 16-18
It should be in the form of ~32~19~17, but 1
Short-circuit some parts like 8 to 19, 18, 32, 1
Usually, the part surrounded by 9 is opened to the discharge side chamber. The reason why this is done is that the crescent-shaped opening of the space 36 in Fig. 5, which communicates with the suction side chamber, is small near the point 32, and even if it is opened, leakage will not occur to the suction side chamber. This is because the amount of gas is very small and does not pose a problem in practice. 14~
Portions 16 and 15 to 17 are circular arcs that are smoothly continuous with the curves extending at both ends thereof. Incidentally, the above-mentioned conventional example is shown in Japanese Patent Laid-Open No. 48-21806.

In the above-mentioned conventional compressors, the main focus was on reducing the discharge resistance, and consideration was given to making the discharge port as large as possible, but insufficient consideration was given to gas leakage at the discharge end face of the rotor. The end face of the rotor has sharp edges that are dangerous, so they are chamfered. However, the chamfered part not only causes gas leakage, but due to cutting errors, etc., the actual seal line differs from the theoretical seal line. It is normal for it to shift. For this reason, the seventh
As shown in the figure, a portion 36b of the opening 36 at the discharge end of the space communicating with the suction side chamber may communicate with the discharge side chamber. At this time, the gas in the discharge side chamber leaks into the suction side chamber through the opening 36b. If the end of the rotor is chamfered, the leakage area at this portion is further enlarged. Among the internal leaks of the screw compressor, direct leakage from the discharge side chamber to the suction side chamber causes a large loss due to the large pressure difference, and must be kept as small as possible.

[Purpose of the invention]

An object of the present invention is to provide a screw compressor having an axial port shape that can maintain high compression efficiency by suppressing discharge gas from leaking to the suction side through a discharge port.

[Summary of the invention]

A feature of the present invention is that in the case where the seal line on the axis-perpendicular cross section formed by the meshing of both rotors exists inside the outer circumferential circle of the other rotor, the male rotor side of the chevron-shaped curve in the outline of the axial port is , the curve drawn on the outer circumference of the female rotor or on the outside of the outer circumference, and the female rotor side being a curve drawn on the outer circumference of the male rotor or on the outer circumference of the outer circumference.

With the above configuration, a wide seal area is formed between the seal line and the contour of the axial port, so the operation of the suction stroke exists inside the seal line on the axis-perpendicular cross section. The chamber and the discharge port are separated by a sealing area having a predetermined width, so that gas leakage from the discharge port to the suction side is almost eliminated.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 8 shows an embodiment of the present invention. In the figure, points 44 and 45 are the center points of the male and female rotors, respectively, and curves 46 and 47 indicate the outer circumferential circles of the male and female rotors, respectively. The curved line from points 51 to 52 is part of a circle whose center is point 45 and whose radius is larger than the radius of circle 47. The curved line from point 53 to point 54 is a part of a circle whose center is point 44 and whose radius is larger than the radius of circle 46 . The distance between points 52 and 53 is given by a straight line, and the distance between points 14 and 51 and between points 54 and 15 is given by a circular arc with a small radius.

FIG. 9 shows another embodiment of the invention. In the figure, the area between points 51 and 52 is the outer circumference 4 of the female rotor.
7 and points 53 to 54
The distance up to this point is defined by a straight line outside the outer circumferential circle 46 of the male rotor. This embodiment is simpler to manufacture than the embodiment of FIG. 8, and the straight sections are shorter, so the practical effect is almost the same.

As described above, according to the present invention, the protrusion in the shape of the axial port of the screw compressor is
By forming it as shown in Figure 9 or Figure 9, the edge of the protrusion that separates the discharge side chamber from the working chamber during the suction stroke is always on the outside of the rotor's outer periphery, so the sealing point can be theoretically positioned. Even if the pump deviates from the normal position, the discharge side chamber and the working chamber during the suction stroke will not communicate with each other. This is because the deviation of the seal line is limited to at most the range of the outer circumference of both rotors, and it is impossible for the seal point (meshing point) to be displaced outside the outer circumference. Therefore, it is possible to maintain high compressor efficiency at all times.

[Brief explanation of the drawing]

Figure 1 is a vertical sectional view showing the structure of a screw compressor, Figure 2 is a view taken in the direction of the - arrow in Figure 1, and Figure 3 is an explanatory diagram of a conventional axial port, which is shown in Figure 1.
4 is a partial enlarged view of FIG. 3, FIGS. 5 and 6 are explanatory diagrams of the action of the conventional axial port, and FIG. 7 is an explanation explaining the drawbacks of the conventional axial port. 8 are views showing one embodiment of the present invention, and FIG. 9 is a view showing another embodiment of the present invention (FIGS. 5 to 9 are all axial views). 5... Male rotor, 6... Female rotor, 11... Axial port, 36, 37... Working chamber, 44,
45...Rotation center.

Claims (1)

[Scope of Claims] 1. A casing having a working space formed by intersecting two circular holes whose end faces are closed with walls, a suction passage and a discharge passage formed in series with the working space, and an operation of this casing. A male rotor having a plurality of twisted convex lobes and a female rotor having a plurality of twisted concave grooves are rotatably housed in a space in a state of meshing with each other, and are formed by the meshing of the two rotors. Of the seal line, the part located on the discharge port side with respect to the straight line connecting the centers of both rotors is inside the outer circumferential circle of both rotors, and the part of the discharge port in the communication part between the working space and the discharge passage is located inside the outer circumferential circle of both rotors. The axial port formed on the discharge side end surface of the working space has a curve along the lobe of the male rotor, a curve along the locus of the valley bottom of the male rotor when the rotor rotates, a curve along the groove of the female rotor, and a curve along the valley bottom of the female rotor. The contour of the axial port is a combination of a curve along the locus of the rotor during rotation and a chevron-shaped curve formed in the intersection area of the circular hole and protruding in the direction of decreasing the port area. The chevron-shaped curve is a curve whose male rotor side is drawn on the outer circumferential circle of the female rotor or outside the outer circumferential circle,
The female rotor side is on the outer circumference of the male rotor, or
A screw compressor characterized in that the shape is a curved line drawn on the outside of the outer circumferential circle. 2. The screw compressor according to claim 1, wherein the male rotor side of the chevron-shaped curve is an arc along the outer circumference of the female rotor, and the female rotor side is an arc along the outer circumference of the male rotor. 3. The screw compressor according to claim 1, wherein the male and female rotor sides of the chevron-shaped curve are both straight lines.