JPH03164591A - Casing structure for screw type compression/expansion machine - Google Patents

Abstract

PURPOSE: To greatly enhance efficiency by opening the boring of a casing at each end, providing at a high pressure end a hoop of an inner boring diameter much smaller than the diameter of the boring, and providing a low pressure end with a diameter equal to or greater than the diameter of a screw. CONSTITUTION: The boring of a casing 9 is opened at each end, and a hoop 16 of a single structure having an inner boring diameter substantially smaller than the diameter of the boring 17 is provided at the high-pressure end 38 of the casing 9. The low-pressure end of the casing boring 17 has a diameter equal to or greater than the diameter of a screw 1 in order to introduce the screw 1 into the casing boring 17 during assembly of the screw 1 and the casing 9. This constitution greatly improves efficiency since a clearance has a much greater influence at the high pressure side than at the low pressure side in terms of leakage. Since the hoop 16 supporting a high-pressure end bearing 4 is provided, the rigidity of the casing 9 at the high pressure side increases, reducing deformations caused by pressure and thermal deformation, and decreasing the clearance at the high pressure side.

Description

DETAILED DESCRIPTION OF THE INVENTION It is already known to produce compressors or expansion machines using a screw coupled with at least one gate rotor. . Darning machines have been described, for example, in U.S. Pat. No. 3,180,565. Such machines have been widely used for over 20 years and are manufactured by nearly a dozen different manufacturers.

The most common design involves a cylindrical screw in conjunction with one or two planar gate rotors. Although Figure 5 of U.S. Patent No. 3.18 (No. The machine had a casing such that the screw was introduced into the casing from the high pressure side.

The first reason for this latter approach to the screw/casing assembly is that the construction of FIG. 5 of the aforementioned patent, which shows a blind hole on the high pressure end of the casing, allows The problem lies in the fact that a bearing positioned in one direction cannot be on the high-pressure end, but will be on the opposite low-pressure end. However, although this has not yet been experienced in the art, it is recommended to position the screw as axially as close as possible to the high-pressure end of the screw groove in order to minimize the relative displacement of the high-pressure end of the screw groove due to thermal expansion. It is desirable to obtain such a bearing.

The second reason is that it is very convenient to have a bearing holder that can be moved on the high pressure end of the casing. In a near compressor, the above facilitates an inexpensive flow path for connecting both discharge ports between the holder and the casing. In refrigeration compressors, a bearing holder portion centered within the casing bore is used to prevent the volume side fit slider from vibrating as shown in U.S. Pat. No. 4,075,957 (reference number 22); It has been used for pressure equalization purposes. Such use of a centered bearing holder is unnecessary for a slider that is angularly positioned independently of the bearing holder, as shown in US Pat. No. 4,571.166.

[Problems to be Solved by the Invention] However, introducing the screw into the casing on the high-pressure side means that the bearing that supports the screw shaft on the high-pressure side is not directly positioned inside the casing, but is positioned indirectly by the bearing holder. It is extremely undesirable because it means that Since the bearing holder has some clearance with the casing to allow assembly and disassembly, the screw cannot be completely inserted into the casing on the high-pressure side without special precautions that are expensive to implement. cannot be centered.

As a result, the clearance between the screw thread crest and the casing increases, with an associated corresponding loss in machine operating efficiency.

[Means for Solving the Problems] The present invention includes a screw mounted to rotate about a single axis and having a plurality of threads, the top of the thread being concentric with the axis of the screw. for the compression or expansion of a fluid, such as for the compression or expansion of a fluid, such as a stationary casing having a cylindrical bore placed over a cylinder and partially surrounding the rotor and arranged to interlock in a substantially fluid-tight manner. Concerning machines. At least one binion gate rotor having teeth disposed in interlocking engagement with the threads of the screw is supported by the casing and adapted to rotate about an axis transverse to the axis of rotation of the screw. . At least one low pressure port is disposed within the casing on one end of the screw and one high pressure port is disposed within the casing on the opposite end proximate the pinion rake. The screw is held by a shaft that is supported by two sets of bearings, one at each end of the screw.

The cylindrical bore of the casing is open at both ends;
It includes an integral annular transverse wall for installing a reinforcing hoop on the high pressure end, and the bore is open on the low pressure end for the purpose of introducing a screw.

〔Effect of the invention] Several advantages result from the structure described above.

First of all, the conventional screw design was able to center perfectly within the casing on the low-pressure side, but not on the high-pressure side, so on the low-pressure side there was a minimum radial distance between the casing and the screw. Whereas this resulted in a larger gap on the high-pressure side even though there was only a gap, according to the present invention, the exact opposite is true, and the gap has a much greater effect as a leak on the high-pressure side than on the low-pressure side. This greatly improves efficiency.

Secondly, the provision of hoops to support the high-pressure end bearings increases the rigidity of the casing on the high-pressure side, and the deformation of the casing boring due to pressure and thermal deformation is greatly reduced, so that the boring It can remain more circular and less elliptical, thus reducing the radial screw casing clearance on the high pressure side. This is particularly true for refrigeration compressors that are equipped with a brinum chamber in the area immediately after the discharge port for noise reduction purposes. In immersion type compressors, which do not require lubricating oil, the Brinum chamber is at the condensing temperature while most of the casing is at the suction temperature, thus contributing to the deformation of the casing and the circular screw receiving the bore. It will make a big contribution. As a result of the annular flange-like hoop according to the invention, such deformations are significantly reduced.

Measurements on a refrigeration compressor G lump operating at R22 with suction temperatures in the range of 0° to -20°C and discharge at about 40°C showed ovalization of the casing. That is, the difference between the short axis and the long axis of the high pressure end of the boring had to be reduced by about 40%.

Third, when a slider is used to control the capacity of a compressor, as shown, for example, in U.S. Pat. The gutter created in it has to be machined from the casing end where the screw is introduced, i.e. from the high pressure end in the prior art. This means that a gutter with high pressure gas exists in the area where the screw terminates and the sealing ring described in U.S. Pat. No. 4,475,877 is installed. . This means that no space can be left between any part near the bore and the sealing ring, be it a bearing holder or a part constituting a hoop of the casing. If any space were left, high pressure gas could easily enter the seal ring and casing and leak all around the seal ring and casing, significantly reducing efficiency.

The sealing ring must be precisely positioned axially relative to the screw, and the screw itself must be precisely positioned axially within the casing with a shim, so the shim is a It must be installed between the holders or between the bearing holder and the screw. As a result, the screw must first be assembled within the casing, the proper positioning must be determined, and the desired shims must be determined.

The screw must then be disassembled and reassembled with the correct shims.

By introducing the screw from the low-pressure side, the gutter for the slider can be machined from the same side and stopped before reaching the area where the sealing ring will be installed.
It is thus possible to prevent high pressure from reaching the area between the sealing ring and the casing hoop lining it.

It is then possible to install a shim that positions the screw on the outside of the assembly, accessible without disassembling the screw. There are slots between the seal rings. Such a slot was created out of the need to allow some relative axial displacement of the screw and seal in relation to the casing, but without high pressure reaching it.

DESCRIPTION OF THE DRAWINGS In the accompanying drawings, like parts are designated with like reference numbers.

The invention can be more fully understood from the following description of a preferred embodiment of a compressor embodying the invention, which is illustrated in the drawings.

In FIG. 1, a screw 1 mounted on a shaft 2, which is rotatably supported by bearings 3 and 4, is threaded into engagement with teeth 6 of two symmetrical gate rotors 7 and 8. 5. The screw and gate rotor are rotatable within the casing 9. When used for operation in a refrigeration system, casing 9 typically includes one or more sliders 10, preferably constructed according to the teachings of US Pat. No. 4,571,166. The slider 10 is axially movable by a piston I2 which is itself actuated by fluid power means, such as hydraulic pressure or discharge pressure gas.

The casing 9 has a suction or low pressure port communicating with the suction pipe 14 . Discharge port 41
is located near the gate rotor near the high pressure end 38 of screw I.

The screw l is connected to the high pressure end 3 by the high pressure end seal 15.
8 and sealed in relation to the casing 9.

Details of the high pressure end seal 15 can be found in U.S. Pat. No. 4,475.
No. 877.

The casing 9 includes an annular wall portion or hoop 16 transverse to the upper opening L7 on the inside of the casing,
A screw 1 is rotatably positioned in such a hoop. Such wall I6 has an outer end face 37 against which end plate 18 is pressed by bolt 19. Additional bolts 20 extend from the end plate 18 to the shaft end seal 15 and draw the shaft end seal 15 against the bearing 4 and through the shim 21 against the end plate 18.

From such an assembly, it is seen that the axial positioning of the screw 1 is determined by the thickness of the shim 21 and that such a shim can be replaced at will by simply removing the end plate 18 without disassembling the screw from the casing 9. That's what I understand. It can likewise be seen that there is a gap 11 between the high pressure seal 15 and the wall 16 in order to facilitate such axial adjustment of the screw 1.

Similarly, the side groove 22 in which the slider 10 is accommodated is the seal 1.
5 and the internal surface of the end wall 16 of the casing 11
It can also be seen that it terminates at a single axial point spaced from . If the gutter had to be machined from the high pressure side or if the wall I6 is on the low pressure port side and the bearing holder (supporting the bearing 3) is located at the high pressure end of the bore I7 as in the prior art If it had been placed above, the above would not have been possible. The latter condition described above in conventional machines introduces high pressures into the gap 11 and causes leakage around the seal in the space 24 between the high pressure seal and the casing, impairing efficiency. Furthermore, the high pressure seal 15 will be subjected to high pressure over the entire surface of the gap 11 on one side, while the opposite side of the seal 150 will be exposed to the volume 25 between the end of the screw 1 and the seal 15.
is under suction pressure because it is connected to suction pressure by the hole or holes 26 in the screw according to conventional methods.

As shown in FIG. 3, the discharge report 41 communicates with a brinum chamber 50 formed in the casing 9 and discharging high pressure gas into a discharge tube 52 through a hole 51. Identical and symmetrical Brinnium chambers (not shown)
The presence of a plenum chamber immediately behind the discharge port, which is provided adjacent to the gate rotor 7 (FIG. 2) for discharging high pressure gas through the discharge tube 53, ensures that each pulsation is The addition of the brinum chamber 50 helps to reduce the noise due to the reduction of the pulsating energy of the high pressure gas exiting each groove in the screw 1 as a result of the transition to a larger volume, especially in refrigeration and air conditioning machines. is extremely important for noise reduction in On the other hand, in the case of an air conditioning compressor that operates by injection of liquid condensed gas rather than oil injection (this is a technology currently widely used), most of the casing 9 including area 54 in FIG. The chamber 50 is at the condensing temperature while it is at the suction temperature. As a result, the casing is subjected to extensive thermal deformation forces which tend to change the shape of the bore 17 at the high pressure end of the screw 1 from a circular to an elliptical shape.

The aforementioned thermal deformation forces are effectively resisted by the hoop 16 at the high pressure end of the casing 9. In this respect, the degree of resistance of the stiffness of the casing 9 at the high pressure end to the applied forces is determined by It is limited by the size of the through bore 45 required to access the high pressure end of the J knee I. However, the combination of the axial dimensions of the hoop needed to accommodate the bearing 4 and the required diameter of the boring 45 will result in a suitable tool 1 to achieve the required opening strength.
16 radial cross sections are possible. For example, 140
In machines with a screw diameter of millimeters,
The outer diameter of the bearing 4 is typically 80 mm, so as to provide a radial hoop dimension equal to 60% of the end face of the boring 17. To accommodate the combined thickness of the bearing 4 and shim 21, the hoop 16 extends approximately 40 millimeters in the axial direction, thus providing an appropriate internal cross-sectional area of the hoop 16 to achieve the intended stiffness.

Such an improvement in stiffness is achieved without increasing the overall length or overall volume of the machine, since in the prior art the bearing holder is identical to the bearing 4 and supports the bearing;
Therefore, rigidity at the high pressure end of the casing required the same axial dimension or thickness without using any material thickness.

From the foregoing, it can be seen that by assembling the screw (1) in the casing 9 from the suction end of the casing 9, there is no need for costly disassembly in order to position the screw axially.

Moreover, a tighter gap between the outer diameter of the screw 1 and the casing bore 17 and thus a higher efficiency are thus possible.

The bore 45 in the wall 16 in which the bearing 4 is set can be machined absolutely concentrically with the bore 17 in the casing 9. This is because the rain bore can be machined together without disassembly. On the other hand, the precise positioning of the bearing 3 in the center of the boring I7 means that such a bearing is supported by the bearing holder 23, which must not have some clearance with the boring 17 for assembly and disassembly. This is difficult because the gap is
When assembling the bearing holder 23 and the casing 9, the axis of rotation of the screw cannot be evenly distributed so that it is pushed towards one side of the boring. Therefore, a larger clearance must be provided between the screw and the casing on the suction side than on the high pressure side, for example by making the screw slightly conical.

In the prior art, the same situation occurred, but in this case the holder was on the high pressure side and therefore the screw 1 casing clearance was greatest at the discharge end, thus creating a much larger leakage.

Furthermore, having the hoop 16 at the high pressure end of the casing gives the casing greater stiffness and prevents its deformation in areas where clearance is more critical.

In the above example of a refrigeration compressor with a rotational speed of 360 rpm and a screw diameter of 140 mm, which compresses refrigerant R22 with a compression ratio of about 4 and is cooled by a jet of liquid refrigerant, the deformation of the casing under pressure and thermal deformation. is reduced by about 40% at the high pressure end, which translates into 75% to 7
It was found that this appears to be responsible for the increase in the assistance rate from 6% to approximately 78%.

[Brief explanation of the drawing]

1 is a sectional view taken along line I-1' in FIG. 2, FIG. 2 is a sectional view taken along line nn' in FIG. FIG. 2 is a partial cross-sectional view taken along the line ■-III' in FIG. 1; ■...Screw 3.4...Bearing,...
Screw thread, 6. 8... Gate rotor, 9 0... Slider, 1 2... Piston, 1 5... High pressure end seal, 1 7... Earth boring, 18 9... Bolt, 20 1 ...Shim, 22 3...Bearing holder, 38 1...Discharge port, 45 0...Brinham chamber, ■...Hole, 52...Teeth, ...Casing, 1. ...Gap, 4.Suction pipe, 6.Hoop, ...End plate, ...Additional bolt, ...Gutter, ...High pressure end, ...Through boring, ...Discharge pipe. Procedural amendment (method) % formula % Display of the case 1990 Patent Application No. 240173 2゜ Title of the invention Casing structure for screw type compression/expansion machine 3゜ Person making the amendment Relationship to the case

Claims (1)

[Claims] 1. A screw having opposing low-pressure and high-pressure ends, capable of being mounted to rotate about a single axis, and provided with a plurality of threads, which engage with such threads. at least one pinion rotatable about an axis transverse to the axis of rotation of the screw having teeth arranged to engage; at least one low pressure port positioned near the low pressure end of the screw; a high-pressure port located near the opposite high-pressure end of the screw in immediate vicinity of the pinion, the crest of the thread being located on a cylinder concentric with the axis of rotation of the screw; the screw is arranged in substantially fluid-tight communication with a stationary casing having a cylindrical bore surrounding it at least in part; In machines for the compression or expansion of fluids, such as those held by a shaft supported by a shaft, the bore of such a casing is open at both ends, and the high-pressure end of the casing has a diameter considerably larger than the diameter of said bore. a unibody hoop having a small internal boring diameter, and a low pressure end of the casing boring having a diameter of the screw for introducing the screw into the casing boring during assembly of the screw and casing; A machine characterized by having a diameter of 2. A screw having opposing low-pressure and high-pressure ends, capable of being mounted for rotation about a single axis, and provided with a plurality of threads, arranged for interlocking engagement with such threads; at least one pinion capable of rotating about an axis transverse to the axis of rotation of the screw; at least one low-pressure port located near the low-pressure end of the screw; a high pressure port located immediately adjacent to the opposite high pressure end of the screw, the crest of the thread being located on a cylinder concentric with the axis of rotation of the screw and at least partially disengaging the screw; arranged in substantially fluid-tight interlocking relation with a stationary casing having a surrounding cylindrical bore, said screw being supported by two sets of bearings each disposed at each end of the screw; In machines for the compression or expansion of fluids, such as those carried by a shaft, a bearing set placed on the high pressure port end of said screw is integral with the casing transverse to the casing bore. and the bearing set on the low pressure end of such screw rests on a bearing holder fixed to the casing at the low pressure end of such screw. A machine characterized by: