JPH05231362A - Screw fluid machinery - Google Patents

Abstract

(57) [Abstract] [Purpose] In screw fluid machinery, compensates for increase in internal clearance during operation due to thermal deformation of casing and deflection of rotor, reduces leakage loss and lowers discharge temperature, and improves energy efficiency. .. [Structure] In an oil-free screw fluid machine in which cooling jackets 35 and 36 are placed between the high pressure port and the high pressure side bearing, the high pressure side intersection line of both bores in the plane perpendicular to the rotor axis when stationary at normal temperature When the bore wall surfaces 33, 34 are traced in the direction of the low-pressure side intersection line, the clearance between the male and female bore wall surfaces 17, 18 and the outer circumferences of the rotors 1, 2 gradually decreases at first and then increases again after reaching the minimum value. To configure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw fluid machine for handling air, refrigerant and other gases, and more particularly to a casing structure suitable for high performance and high reliability.

[0002]

2. Description of the Related Art The basic structure of a screw fluid machine is described in detail in Japanese Patent Publication No. 56-17559. In this type of fluid machine, the clearance between the rotors and the clearance between the rotor casings dominates the performance. The smaller these clearances, the less internal leakage and the better the performance of the fluid machine.On the other hand, if the clearance is too small, contact between moving parts may occur and the machine may burn out. It is necessary to secure a large gap.

The operating clearance of the screw fluid machine is considerably different from that when it is stationary at room temperature. The cause is mainly due to thermal deformation of the casing and the rotor.

The effect of thermal deformation is remarkable especially in the case of oilless type. For example, in the case of an oil-free screw compressor that compresses air at a compression ratio of 8, the high temperature side air temperature is 300 when operating.
In some cases, the temperature may exceed ℃, and the temperature of the rotor and casing partially rises to a temperature close to this. Therefore, these parts are thermally deformed, which affects the internal clearance.

Regarding the clearance between the rotors, Japanese Patent Publication No. 61-
As can be seen in Japanese Patent No. 47992, a clearance design that compensates for thermal expansion of the female and male rotors in advance is performed to ensure an appropriate clearance during operation.

Similarly, the casing also undergoes thermal deformation and affects the clearance between the outer peripheral portion of the rotor and the bore wall surface of the casing (hereinafter referred to as the rotor outer peripheral clearance). It is known that the radial expansion amount of the bore wall surface is not uniform in the circumferential direction unlike the outer circumference of the rotor, the deformation amount is large near the high pressure port and small near the low pressure port. Japanese Patent Laid-Open No. 63-106301 discloses an invention which compensates for thermal deformation and keeps the rotor outer peripheral clearance small during operation.

[0007]

In the above-mentioned known example, it is disclosed that the circumferential distribution of the rotor outer peripheral clearance at the time of stationary at normal temperature is made smaller nearer the high pressure port.

However, when calculating the amount of thermal deformation during operation of casings of various structures, the amount of radial expansion of the bore wall surface with respect to the rotor center does not necessarily become larger near the high pressure port. , It was found that, depending on the structure, it may be maximum at a distance from the intersection of the bores. In particular, the casing near the high-pressure side bearing is sufficiently cooled by a cooling water jacket,
This occurs when the center distance between the female and male rotors does not change much during operation.

That is, the wall surface of the bore is deformed by the heating of the gas so that the center distance is separated. On the other hand, when the center distance of the rotor changes little, the center distance of the center distance near the intersection of the female and male bores is small. The rotor outer circumference relatively approaches the bore wall surface by the amount of deviation. The thermal clearance is added to this relative displacement to form the actual clearance. Calculating the change in the rotor outer peripheral clearance during operation compared to when stationary at this time, the displacement does not necessarily become maximum near the high pressure port as described above. , There is a possibility that contact may occur between the outer circumference of the rotor and the wall surface of the bore.

On the other hand, the structure in which the casing near the high-pressure side bearing is cooled by a cooling water jacket or the like can suppress the expansion of the center distance between the rotors and prevent an increase in the clearance between the rotors. Has been done.

An object of the present invention is to provide a highly efficient and highly reliable screw fluid machine which maintains a proper clearance between rotors and a rotor outer peripheral clearance during operation of the screw fluid machine.

[0012]

In order to achieve the above object, the present invention provides an oil-free screw fluid machine having a cooling jacket between a high-pressure port and a high-pressure side bearing. When the bore wall surface is traced in the direction from the high pressure side intersection line of both bores to the low pressure side intersection line in a right-angled plane, the rotor outer peripheral clearance is gradually reduced at the beginning and then increased again after reaching the minimum value.

Further, in order to obtain the above structure, the center of the rotor is eccentric to the center of the bore in the direction of the high pressure port when stationary at room temperature.

Further, in order to obtain the above-mentioned structure, a coating layer having a thickness varying in the circumferential direction is formed on the wall surface of the bore.

[0015]

The structure in which the casing near the high pressure side bearing is cooled by a cooling water jacket or the like is effective for improving the performance because the increase in the center distance between the rotors can be suppressed and the clearance between the rotors can be prevented from increasing. On the other hand, in the compressor of this structure, during operation, as described above, there is a gap between the center of the bore and the center of the rotor, and the outer circumference of the rotor and the wall surface of the rotor come close to each other near the intersection of the female and male bores. Although the substantial radial extension of the bore wall surface seen from above is smaller than that of the portion far from the bore intersection line, according to the present invention, the thermal deformation of the bore wall surface in consideration of such relative center deviation. Since compensation is performed, a more uniform and appropriate clearance distribution can be obtained, and a high-performance screw fluid machine can be obtained.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The oil-free screw compressor shown in FIGS. 1 and 2 will be described below as an embodiment of the present invention.

In FIG. 1, 1 is a male rotor, 3 is a casing, 4 is a suction casing in contact with the suction side of the rotor, 5
Is a discharge side cover that covers the discharge side end of the rotor shaft.
In the compressor, the suction port and the discharge port are the low pressure port and the high pressure port, respectively. The rotor has a shaft 6 on each of the suction side and the discharge side.
And the shaft 7 are attached, and the shaft 6 on the suction side is a cylindrical roller bearing 8
Further, the discharge side shaft 7 is supported by a cylindrical roller bearing 9 and a combination angular contact ball bearing 10, respectively. Also,
In order to maintain the confidentiality of the compression space with respect to the outside, shafts 11 and 12 are provided on the suction side shaft 6 and the discharge side shaft 7, respectively, and further, lubricating oil of the bearing leaks from the shaft sealing portion to the compression space. Oil drainers 13 and 14 are attached respectively to prevent entry.

Between the shaft seal 11 and the oil drainer 13 and between the shaft seal 1
A hole 15 and a hole 16 are provided between the oil drainer 2 and the oil drainer 14 to prevent the oil from entering the shaft seal portion even if oil leaks from the oil drainer. Although not shown for the female rotor, the rotor elements and mechanisms described for the male rotor are similarly equipped for the female rotor.

FIG. 2 shows a cross section taken along the cutting line I-I in FIG. In the figure, the male rotor 1 meshes with the female rotor 2 and rotates as shown by arrows 19 and 20 in the male-side bore 17 and the female-side bore 18 which intersect in a spectacle shape. Reference numeral 21 is a contour line of the discharge port opened at the discharge side end of the bore. As shown in FIG. 1, a timing gear 22 is provided at the shaft end of the male rotor 1 and meshes with a timing gear on the female rotor side (not shown). By these timing gears, the rotation angles of the rotors 1 and 2 are synchronized with each other, and a narrow clearance is always maintained between the tooth flanks so that the rotors 1 and 2 rotate without contact.

The male rotor 1 is driven from an external drive source such as an electric motor via a pinion 23 attached to the shaft end.

Bearing 8 on the suction side, bearings 9 and 10 on the discharge side
In addition, the timing gear 23 has oil filling holes 24,
Lubricating oil is supplied from 25 and 26, and after lubricating the bearing or the gear, it is discharged from the oil drain holes 27 and 28. Gas flows from the suction chamber 29 through the suction port 30 to both rotors 1 and 2
Is discharged into the discharge chamber 32 through the discharge port 31 after being taken into the groove, that is, the compression space and compressed.

Around the wall surface 33 of the male bore and the wall surface 34 of the female bore in FIG. 2 are surrounded by water jackets 35 and 36, and both wall surfaces are cooled. Water jacket 35
1 and 36 are connected in series and further extend to the casing portion that houses the shaft and the bearing on the discharge side, and form water jacket portions indicated by 37 and 38 in FIG.

When this compressor is cut along the cutting line II-II in FIG. 1, the jackets 37 and 38 are connected as shown in FIG. 3, and further, including the female side portion 39,
It surrounds the shaft of the casing and the bearing housing portion 40.

Cooling water is supplied from the inlet 41 of FIG.
After passing through each part of the water jacket, the water is discharged from the outlet 42 to the outside of the machine.

In this embodiment, the center 43 of the male rotor and the center 44 of the female rotor are eccentric with respect to the centers 45 and 46 of the male and female bores, respectively, when stationary at room temperature. The eccentric direction is
The direction is closer to the discharge chamber 32 in the direction perpendicular to the line segment 47 connecting the centers 43 and 44 of both rotors. For convenience of later description, in FIG. 2, the intersection of the straight line passing through the two points 43 and 45 and the bore wall surface 33 is 48.

In the present embodiment, for example, on the male side, the clearance between the outer circumferential circle 49 of the rotor and the bore wall surface 33 is changed from the discharge side intersection line 50 of the female and male bore wall surfaces toward the suction side intersection line 51. When going up, the clearance gradually narrows from 50 to 48 and, conversely, gradually increases after passing 48. This feature is the same for the female side. The point 48 where the clearance should be the minimum is not always 2
It is not always on the straight line passing through the points 43 and 45, and may be slightly deviated from this depending on the driving specifications.

When the compressor enters the operating state, the temperature of the gas rises and the rotor and casing are gradually heated. As mentioned above, if air is compressed from atmospheric pressure to 8 kg / cm ² (abs) in a single stage, the temperature of the discharged air will be close to 300 ° C, and the temperature of the rotor and casing will also be at some locations. The temperature is close to the temperature. The temperature of the casing is highest near the discharge port, but decreases axially toward the suction end face. Also, when viewed in the cross section perpendicular to the axis, the area near the intersection of the discharge side bores is highest, and in the cross section perpendicular to the axis where the discharge port is open and there is no bore intersection, the temperature is highest on the boundary edge of the discharge port. The temperature becomes lower as it goes toward the suction side bore intersection line along the surface.

Due to such temperature distribution, the radius of the bore wall surface expands, and the centers of both bores move away from each other. On the other hand, the rotor also expands due to the heating of the gas, but since it rotates at a high speed, the amount of increase in the radius of the rotor outer circle is substantially uniform in the cross section perpendicular to the same axis.

Since the casing of the rotor bearing portion is surrounded by the water jacket and is well cooled, the extension of the center distance is small. Therefore, since the bore wall surface near the discharge end surface is relatively close to the rotor, the radial expansion due to thermal deformation is partially canceled out, and the substantial amount of radial expansion seen from the center of the rotor is It is smaller than around 48.

In the present embodiment, in consideration of these, the rotor outer peripheral clearance at the point 50 is made larger than that at the point 48 at the time of stationary at room temperature, so that the radial displacement of the bore wall is compensated, and during operation, A uniform and appropriate rotor outer clearance can be obtained.

If such compensation is not performed, the rotor outer peripheral clearance during operation will not be uniform, and an excessively large clearance will be generated in some parts to increase the leakage loss of the compressor, or the rotor and casing May cause contact with.

As described above, according to this embodiment, a proper clearance distribution can be maintained during operation, and a highly efficient compressor can be obtained.

4 and 5 show another embodiment of the present invention.

In this embodiment, as shown in FIG. 4, a coating layer 52 made of a material different from that of the casing is provided on the bore wall surface 17 near the discharge port 31. The thickness of the coating layer gradually increases from the side with the suction port 30 toward the side with the discharge port 31 as shown in the figure.

FIG. 5 is a sectional view taken along the section line III-III of the compressor of FIG. 4, showing only the outer circumference circles 49 and 53 of the rotor and omitting the tooth shape. In this example,
Centers 43 and 44 of the male and female rotors when stationary at room temperature
On the other hand, the centers of the bores 17 and 18 formed in the casing are coincident with each other. However, due to the coating layer 52 on the male side and the coating layer 54 on the female side, the substantial rotor outer peripheral clearance has a distribution similar to that shown in FIG. That is, for example, when tracing the bore wall surface from the bore crossing line 50 on the discharge side to the bore crossing line 51 on the suction side on the male side, the rotor outer peripheral clearance gradually decreases at the beginning and reaches a minimum value on the way. , Gradually increase.

According to this embodiment, since the thermal deformation compensation can be finely matched with the thermal deformation distribution of the bore wall surface, the advantages of the present invention can be obtained more effectively.

In the above embodiment, the method of compensating the thermal deformation of the bore wall surface with a smooth curve is described. However, even if it is not always a smooth curve, the wall surface shape can be changed stepwise for the convenience of processing. However, thermal deformation compensation can be performed approximately, and the effect of the present invention can be obtained.

[0038]

According to the present invention, a screw fluid machine,
The increase in the clearance between the rotor casings caused by the thermal deformation of the bore during operation can be compensated and kept small by simple means. Therefore, leakage loss is reduced and energy efficiency is improved.

Further, by reducing the leakage loss, the temperature rise of the gas due to the loss can be suppressed and a highly reliable screw fluid machine can be obtained.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an oil-free screw compressor according to an embodiment of the present invention.

2 is a cross-sectional view taken along the section line I-I of the compressor shown in FIG.

3 is a cross-sectional view taken along the section line II-II of the compressor shown in FIG.

FIG. 4 is a vertical sectional view of an oil-free screw compressor according to another embodiment.

5 is a transverse cross-sectional view taken along the section line III-III of the compressor shown in FIG.

[Explanation of symbols]

1 ... Male rotor, 2 ... Female rotor, 17 ... Male side bore wall surface, 1
8 ... Female side bore, 33, 34 ... Bore wall surface, 35, 36 ... Water jacket.

Claims (1)

[Claims] 1. A low-pressure rotor having a male rotor and a female rotor, each of which rotates about two parallel axes, meshes with teeth twisted in opposite directions, and has at least a rotary shaft connected to a high-pressure side supported by bearings. A bearing for supporting a shaft connected to the high-pressure side, and the high-pressure port, which have two bores that respectively have the male rotor and the female rotor In a screw fluid machine including a casing thermally insulated from at least a jacket through which a cooling medium flows, a wall surface of the male rotor side bore and the female rotor in a plane perpendicular to the rotor axis when stationary at room temperature. When the clearance between the wall surface of the side bore and the outer peripheral surface of each rotor is traced from the line of intersection of the high pressure side of the two bores to the line of intersection of the low pressure side, the The screw fluid machine is characterized in that it gradually or stepwise decreases as the distance from the point increases, reaches a maximum value, and then gradually or stepwise increases toward the intersection line on the low pressure side.