Discussion on the principle of the direction of the steel body frame of the internal air-biting particle air compressor
The analysis shows that it is not appropriate to apply a moment to the external rotor to overcome the revolving trend. Instead, a force, ie the supporting force, should be applied to overcome the trend of the revolution. The position of the force on the outer rotor is the force of the rotor without the cylinder. The "support point" mentioned in the rotor of the rotor without the cylinder. If the whole machine is regarded as an isolated body, the supporting force is also in the category of internal force, which is generated by the action of gas force (of course, due to the particularity of the internal meshing rotor mechanism, its size and gas force are not equal), so Will be transmitted outside the machine. That is to say, after the outer rotor is subjected to the supporting force, the inner rotor also applies an equal and opposite supporting force to the main shaft, but the essence is similar to that of the outer rotor. As long as the situation on the outer rotor is studied, Basically reveal its characteristics.
Influence of assembly clearance on support points Under ideal conditions, the clearance between the inner and outer rotors, the outer rotor and the cylinder, the inner rotor shaft hole and the main shaft, and the main shaft and the bearing are neglected. The method used at the time, because most of the gaps in the compressor do not have an excessive effect on the force.
However, the supporting force between the outer rotor and the cylinder of the internal meshing cycloidal compressor is generated by the action of the outer bore of the outer rotor of the cylinder bore, and according to the analysis in the previous section, it is only necessary to provide a support to the outer rotor. The force can ensure that the outer rotor revolution tendency is suppressed.
The size of the assembly gap obviously changes the direction of the supporting force, and the difference in the direction causes a large change in the contact force between the teeth.
Due to the large number of mating surfaces, if all the gaps are introduced at one time, the problem becomes extremely complicated. Generally, the inter-tooth gap does not affect the position of the supporting force, and the influence of the clearance between the main shaft and the inner rotor shaft hole is similar to that caused by the outer rotor and the cylinder clearance. Therefore, the following assumptions are made: (1) Ignore the tooth (2) The force of all contact faces is directed to the normal direction; (3) The deformation caused by the force of the contact faces is negligible.
When there is a gap between the outer rotor and the cylinder, when there is a gap between the outer rotor and the cylinder, the outer rotor will be in tangent contact with the cylinder at a point in the second or third quadrant, defined before the contact, ie The gap when the cylinder rotor hole and the outer rotor axis coincide with each other is the radius gap Î”rc=(Dc-Do)/2(4) where: Dc is the bore diameter in the cylinder; and Do is the outer cylinder outer cylinder diameter.
According to the basic geometric theory <7>, the distance between the center of the inner and outer rotors, that is, the eccentricity is completely determined by the profile. If there is no gap between the inner and outer rotor profiles, the eccentricity is e, that is, the outer rotor center can only be in the Oi It is a circle C with a radius of e.
In addition, in order to make the outer rotor operate normally, taking the second quadrant of the example as an example, the outer rotor must be in contact with the cylinder body at the support point Od, that is, the cylinder rotor hole center Oc and the outer rotor center Oo fall on the common normal line N, The coordinates of the hole Oc in the cylinder are (e, 0).
The relationship between the outer circular surface of the outer rotor and the hole in the cylinder is tangent to the point Od, and |OcOo|=Î”rc=(Dc-Do)/2(5), the angle of deflection of the outer rotor is Î±o, c=2arcsin(6) The center coordinates of the outer rotor are Oo=ecosÎ±o, cesinÎ±o, c(7). When the outer rotor is deflected, its central coordinate moves accordingly. Because the instantaneous center is located on the line connecting the center of the outer rotor and the center of the inner rotor, the rotor is studied. When the force is applied, the position of the instantaneous center plays an important role. Therefore, it is considered that the connection between the center of the new outer rotor and the center of the inner rotor is the x' axis, so that the direction of the supporting force is the normal N and x' The angle of the axis Î²d,o=(Ï€-Î±o,c)/2=Ï€/2-arcsin(8) The coordinates of the support point are Od=Dccos(Î²d,o+Î±o,c)/2Dcsin(Î²d,o+ Î‘o, c) / 2 (9) As the gap increases, the angle of the supporting force becomes smaller.
In fact, it is impossible to use an excessive gap between the cylinder and the outer rotor, otherwise the oil film surface cannot be formed. Generally, the gap here is between several tens of Î¼m and several hundred Î¼m, so in this case, the deflection angle of the outer rotor is small, and the supporting force is about 90Â°, that is, substantially parallel to the y-axis. The relationship between the support angle of the lower support point and the gap change when there is a gap between the outer rotor and the cylinder 2.
The position of the supporting force when there is a gap between the outer rotor and the cylinder and the inner rotor and the main shaft assumes that the main shaft holes on the main shaft and the inner rotor are both circular, that is, regardless of how the main shaft transmits torque to the inner rotor. Similarly, when the axis of the main shaft and the inner rotor main shaft coincide, the radius gap between them is Î”rs, and the radius gap between the outer rotor and the cylinder is Î”rc.
In the steady state, the outer cylindrical surface of the outer rotor and the inner cylinder bore are always in tangential contact. Similarly, the inner rotor main bore and the main shaft must also be in tangent contact, that is, the inner rotor center Oi is always on the circle Ci, and the outer rotor The center Oo is always on the circle Co.
The center of the outer rotor hole has manufacturing tolerances, and the position of the supporting force when the outer rotor and the cylinder body have a gap. Because the cylinder body adopts an eccentric hole to place the outer rotor, the distance between the center of the cylinder hole and the center of the cylinder should be equal to the eccentricity e, but Due to manufacturing errors, it is impossible to ensure that the distance is strictly equal to the eccentricity.
The main shaft passes through the main shaft hole on the upper and lower end plates. Assuming that the main shaft hole and the cylinder hole are concentric, and the main shaft and the inner rotor are completely concentric, and the actual eccentricity of the cylinder hole is considered to be e', the coordinates of the center Oc of the cylinder hole are ( e', 0), that is, the tolerance is Î”e=e'-e(18). Similarly, the radius gap between the cylinder bore and the outer circular surface of the outer rotor is Î”rc=OcOo=(Dc-Do)/2(19). As shown, the inner and outer rotor deflection angles are Î±o, c=arccose2+(e+Î”e)2-Î”r2c2e(e+Î”e)(20) support point angle Î²d,o=Ï€-arccosÎ”r2c+(e+Î”e)2-e2Î”rc(e+ Î”e)-arccose2+(e+Î”e)2-Î”r2c2e(e+Î”e)(21)(a)Î”e>0(b)Î”e<0 Support force direction calculation diagram Support point coordinates Od=Dccos(Î²d,o+Î±o, c) / 2+e 'Dcsin (Î²d, o + Î±o, c) / 2 (22) It can be seen that when Î”e is small, even if the change of Î”rc is small, the support point will change greatly.
In the discussion of Section 3, considering only two gaps has complicated the analysis of the problem. It is conceivable that if the gaps of all components are considered, the problem will become very complicated, and in the actual machine, the gap may not be uniform. The position of the support points is also not unique. The support points are also in different positions when the rotor is running at different angles.
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