JPH021508Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial field of application] The present invention relates to a pair of screw rotors used in screw machines, and in particular uses synchronous gears to prevent tooth profile surfaces from coming into contact with each other. This invention relates to a screw rotor tooth profile used in a dry screw compressor that meshes and rotates.

[Conventional technology]

Female and male screw rotors rotate synchronously around two parallel axes while meshing with each other, and the inner diameter is approximately equal to the outer diameter of the rotor, and the cross-sectional space has a shape in which the respective circles partially overlap. A screwdriver is housed in a casing having a compressible fluid, and its both ends are closed with end plates, and one end plate has a suction port for the compressible fluid, and the other end plate has a discharge port for the compressible fluid.・The compressor was publicly known before the filing of this application. This type of compressor is used in fields where the presence of oil in the compressed gas is undesirable.
With this type of compressor, a small gap is always maintained between the casing and the rotor, and a synchronous gear at the end of the shaft keeps a constant narrow gap between the rotor's meshing tooth surfaces. Rotate it so that it does not touch. The gaps between each part should be approximately 1/1000 of the rotor diameter to prevent a drop in efficiency due to internal leakage. The size of this gap is greatly affected by the operating conditions, especially the gas temperature, but as mentioned earlier, since cooling and lubricant cannot be put inside the casing, the inside of the main body becomes extremely hot during operation. The casing or each of its constituent members, including its end plates, expands and deforms due to thermal expansion. Normally, a water jacket is installed around the casing or between the shafts of its end plates to cool the equipment body, so the temperature rise there is smaller than that of the rotor inside the casing. Since no lubricant can enter inside, even the slightest contact can cause galling or seizing of the rotor tooth profile. Also, in order to avoid this, it is possible to make each gap larger in advance, but if you simply create gaps only in areas where there is a risk of contact, sufficient compression will not be achieved under the optimal compression condition. No improvement in efficiency can be expected.

[The problem that the idea attempts to solve]

Therefore, in the screw rotor of the present invention, the screw rotor of the above-mentioned type is expanded and deformed between the shafts of the casing supported via bearings or the end plates thereof, and when the rotor is in steady operation. By giving the tooth profile in advance during machining to form a regular tooth profile curve, the casing, the space between the rotor and the female
There is no risk of failures such as galling or seizure occurring between the male rotor tooth profile, and high compression efficiency can be obtained over a long period of time during steady operation, and rotor meshing noise during the above operation is reduced. The present invention aims to provide a screw compressor which can also reduce the noise of the entire machine.

[Means to solve the problem]

In order to solve the above-mentioned problems, the screw rotor of the present invention has the following constituent requirements.

(1) A casing that pivotally supports a pair of female and male screw rotors that engage and rotate around two parallel axes within the casing, or the shafts of its end plates, is placed under steady operating conditions, and one When the rotor tooth profile of the above rotor is set as a theoretical tooth profile curve, the other rotor tooth profile is formed by a tooth profile curve that is modified by subtracting the optimum clearance from the meshing curve from the theoretical tooth profile created to mesh with the rotor without clearance. It is a screw rotor consisting of female and male rotors that are driven synchronously while meshing with an optimum clearance between them. When the temperature difference between the temperature of the rotor in the state and the temperature of the rotor during processing is △t, and the coefficient of linear expansion of the rotor constituent material is α, then The point Po (xo, yo) obtained from Y/(1+α)△t is found corresponding to each tooth profile curve during steady operation, and the forming process is performed using the tooth profile curve formed by connecting each of these points. A screw rotor characterized by a tooth-shaped curve.

(2) During molding, the size of the tooth profile of the rotor is adjusted to the extent that the temperature rises from the air suction side to the air discharge side along each axis of rotation.
The screw rotor according to item 1 above, which is formed by applying a slope in the direction of the rotor's rotational axis so that it is corrected and slightly smaller.

[Effect]

During rotation, the screw rotor of this invention sucks air into the working chamber defined by the meshing line between the rotor teeth, the sliding tangent line with the cylinder inner wall, and the end surface, and closes off the working chamber and the suction side. After cutting, the volume of the working chamber is sequentially reduced to adiabatically compress the air trapped inside the chamber, and the air that has reached the required compression ratio is released to the discharge side. By repeating this process, the compressor can be used as a compressor. ing. At that time, heat is generated due to the compressed action of the air, and the air and sliding friction heat between each member heat the casing that makes up the action chamber or each member such as its end plate, which eventually causes the cylinder and other components to heat up. This continues until the amount of heat radiated from the outside and the amount of heat generated by air compression are balanced.

Therefore, as mentioned above, cooling means are normally provided, such as installing a water jacket around the cylinder and passing cooling water through it, but this causes a large temperature rise not only in the vicinity of the working chamber but also in the rotor itself, especially in the rotor. It is difficult to completely prevent a temperature rise in members such as the casing or end plate on the compressed air discharge side.

For this reason, the rotor tooth profile expands and deforms, causing galling and galling on the meshing surface, cylinder sliding surface, etc.
Although there is a risk of accidents such as seizure, the screw rotor of the present invention allows for an increase in the distance between the axes of the casing or its end plates to an extent that corresponds to the above-mentioned normal temperature rise. Since machining is performed using a tooth profile and diameter that have been reduced in advance, when the screw compressor enters steady operation, the gap between the screw rotor tooth profiles, etc.
From the suction side to the discharge side, there is an appropriate gap as designed, and the specified performance can be achieved.

〔Example〕

Figure 1 shows the meshing of the female and male rotor teeth during steady operation of the screw rotor of the present invention. In this state, the distance between the axes of the casing or its end plate, indicated by Of and Om, is also the same. It is expanding by the amount commensurate with the rise in temperature. The rotor members are also heated to high temperatures and are deformed due to thermal expansion. In this state, the tooth profile curves of the female and male rotors are adjusted to form an optimal gap between the tooth profile surfaces of both rotors with respect to the theoretical tooth profile curve. A tooth profile curve that has been subjected to tooth profile correction in advance is processed during molding so that the tooth profile curve is a modified tooth profile curve.

That is, for example, with respect to the theoretical tooth profile curve of the male rotor, the normal tooth profile curve of the female rotor is the optimum tooth profile of the test rotor, which is created so that it meshes with the theoretical tooth profile curve of the male rotor without any clearance. This is the tooth profile curve reduced by the gap.

Figure 2 shows the tooth profile curves of each rotor shown in Figure 1.
Figure 2a shows the male rotor 1 .
Figure 2b shows the tooth profile curve of the female rotor 2 which rotates synchronously while meshing with the same rotor.

In Figure 2a, the shape drawn by solid line 3 is the operating state,
If we show the tooth profile during thermal expansion deformation, that is, the normal tooth profile curve, and use this as the theoretical tooth profile curve,
On the other hand, the tooth profile of the female rotor was modified by subtracting the optimum gap from the theoretical tooth profile curve created to mesh with the theoretical tooth profile of the male rotor, which is shown by the dashed line 4 in Figure 2b. The tooth profile is as shown by solid line 5. In addition, in order to correct the gap between the tooth surfaces from the theoretical tooth profile curve and obtain a regular tooth profile curve, it is possible to correct only the tooth profile of the female rotor as described above, or conversely, to correct the tooth profile of the male rotor Furthermore, both the female and male rotors may be modified together. In the figure, the tooth profile curve indicated by the dotted line 6 is a modified tooth profile curve at the time of machining, which is the regular tooth profile curve indicated by the previous solid line at room temperature, that is, in a state where thermal expansion deformation has not occurred.

The coordinates of an arbitrary point P on the tooth profile curve of the male rotor, indicated by the solid line 3 in FIG. 2a, are X, Y, and
Corresponding to this, the coordinates of a point Po on the modified tooth profile curve during machining indicated by the dotted line 6 are Xo, Yo, the coefficient of linear expansion of the material constituting the rotor is α, and the temperature difference between the temperature in the steady operating state and the room temperature. Let △t be the point Po(Xo,
Yo) is determined by Xo=X/(1+α)△t, Yo=Y/(1+α)△t (1). Since the material constituting the rotor, that is, the coefficient of linear expansion α in this case, has already been determined at the design stage, by actually measuring Δt and giving that value, the tooth shape at the time of machining relative to the regular tooth shape can be determined. A curve, ie a tooth profile curve indicated by the dotted line 6, can be determined. Machining is performed based on this tooth profile curve.

In this case, since the casing or end plate side is cooled by the water jacket, the rate of temperature rise there is different from that on the rotor side. Therefore, the amount of expansion between the shafts due to temperature rise does not necessarily have to be the same as that of the rotor.

The tooth profile curve of the female rotor 2 shown in Figure 2b can be processed in exactly the same way.

In addition, in this type of screw rotor, the volume of the working chamber formed by the meshing of the two rotors and the inner wall of the casing decreases as it advances toward the fluid discharge port, and as a result, the temperature of the fluid that is adiabatically compressed there increases. The heat generation part is fixed because it heats up the screw rotor, but the rotor is rotating at high speed, and the materials that make up the rotor and casing are generally made of materials with high thermal conductivity. and the rotor is housed in the casing,
Since its heat capacity is considered to be relatively large, it can be understood that when the screw rotor is in steady operation, the rotor is approximately heated evenly from its entire circumferential surface. Since heat generation due to fluid compression is particularly significant on the discharge side, even if we assume that the rotor has a nearly constant temperature gradient from the discharge side to the suction side in the direction of the rotation axis, the temperature difference will be significantly different from the actual case. It is thought that there is no such thing.

Figure 3 is a side view of the rotor, where the shape drawn by the solid line is the outer diameter of the rotor during steady operation, and the regular tooth profile curve over the entire longitudinal direction of the rotor's rotation axis under thermal expansion deformation. It is what forms the. At that time, the rotor moves from the discharge side H to the suction side L.
Assuming that there is a temperature gradient at a constant rate in the longitudinal direction of the rotating shaft, when the rotor returns to normal temperature,
That is, the outer shape of the rotor during processing is tapered toward the discharge side, as shown by the dotted line. Of course, the tooth profile itself is also thermally shrunk as described above. Therefore, in the case of machining the tooth profile curve of the rotor, the amount of modification of the tooth profile is gradually increased as the rotor approaches the discharge side H, and the tooth profile is formed into a relatively small diameter and small profile. The degree or numerical value can be derived from the above equation (1).
Of course, △t must be solved in advance, but this is due to the large compression ratio due to the screw rotor.
Related to small.

The above-mentioned shaping of the tooth profile can be done, for example, in the finishing process by: (1) changing the center and passing it through the cutter according to the change in △t related to the temperature gradient, and machining the screw rotor tooth profile curve to create a taper; give.

(2) When machining the tooth profile, change the lead of the cutter in relation to the change in Δt, and process the advancing side and trailing side curved surfaces of the tooth profile curve separately.

(3) In addition, when finishing the grinding of the tooth profile, the external shape of the complete grinding wheel is controlled and deformed by dressing in relation to the feed in the direction of the rotational axis of the rotor, so that the taper is adjusted in relation to the change in △t. Grind the shaped tooth profile.

It is possible to implement it by doing this.

[Effect of idea]

When using the screw rotor of the present invention, the distance between the axes of the casing supporting the rotor or its end plates, and further, when the rotor is in operation,
The tooth profiles of the male and female rotors have been modified in advance so that when heated to high temperatures, the tooth profiles of the male and female rotors will thermally expand and form regular tooth profiles.
In addition to preventing accidents such as galling and seizure, it also ensures an optimal clearance between the meshing tooth profiles during steady operation of the compressor, ensuring the highest efficiency of the tooth profiles, that is, the meshing between the female and male rotors. This minimizes leakage between the rotor and the cylinder sliding surface, improves volumetric efficiency and prevents an increase in power loss due to the leakage, and further reduces noise caused by meshing between rotor tooth profiles. The effects are significant, such as reducing the operating noise level of the entire machine, which can be maintained over a long period of time.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the meshing state of the female and male rotor teeth during steady operation of the screw rotor of the present invention, Fig. 2a is the male rotor tooth profile and the tooth profile curve at room temperature or during processing, and Fig. 2b is 2a is a similar view of the female rotor, and FIG. 3 is a schematic side view of the tooth profile curve of the rotor of the present invention during steady operation and at room temperature or during processing. 1 ...male rotor, 2 ...female rotor, L...intake side, H...discharge side.

Claims (1)

[Claims for Utility Model Registration] 1. A pair of female and male screw rotors that mesh with each other and rotate around two parallel axes within a casing, and a casing that supports these rotors, or between the axes of its end plates. Under steady-state operating conditions, when one rotor tooth profile is set to the theoretical tooth profile curve, the other rotor tooth profile is corrected by meshing with the theoretical tooth profile curve created to mesh with the rotor without any clearance and subtracting the optimum clearance. It is a screw rotor consisting of a female rotor and a male rotor, which are formed by a tooth profile curve and are driven synchronously while meshing with each other while maintaining an optimum clearance. For y), when the temperature difference between the temperature of the rotor in the state of steady operation and the temperature of the rotor during processing is △t, and the coefficient of linear expansion of the rotor constituent material is α, then Xo=X/ (1+α)△t, Yo=Y/(1+α)△t The point Po(Xo, Yo) obtained from each tooth profile curve during steady operation is found and formed by connecting each of these points. A screw rotor characterized in that the tooth profile curve used in forming the rotor is used as the tooth profile curve during molding. 2. During the forming process, along each axis of rotation, from the air suction side to the air discharge side, the size of the tooth profile of the rotor increases by an amount commensurate with the temperature rise.
A screw rotor according to claim 1, which is formed by forming a slope in the direction of the rotational axis of the rotor so as to be corrected and slightly smaller.