RU2116622C1 - Process of manufacture of hollow rotor of electrostatic gyro - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: process may find use in manufacture of electrostatic gyro with capacitive reading of information on position of vector of kinetic moment. Process consists in mechanical fitting of external surface of thin-walled sealed rotor with extended ellipsoid of inertia having variable thickness of wall and vacuum inside to sphere in atmosphere of excessive pressure. Rotor in the form of shell with spherical external surface consists of two symmetric hemispheres interjoined along split line in basic material in vacuum by method of diffusion welding. Internal surface of each hemisphere has variable radius r smoothly rising from pole to split plane. In this case thickness of wall grows smoothly from h on pole to h_w in equatorial split plane according to law of square of sine of angle h_e read from axis of poles of rotor. EFFECT: improved efficiency and reliability of process. 4 dwg

Description

 The invention relates to the field of precision instrumentation and can be used in the manufacture of an electrostatic gyroscope (ESG).

 Known ESG with capacitive information retrieval on the angular position of the rotor [1], p. 170, [2], p. 17-19, having an equatorial unbalance. The rotation of the rotor with an equatorial unbalance with a frequency exceeding the natural frequency of the suspension occurs around an axis passing through the center of gravity (around an axis offset from the geometric center of the rotor). In this case, in the measuring circuit of the rotor suspension system, a voltage modulated by the rotor speed arises along each coordinate. The phase shift of the stresses generated in two different coordinates of the system depends on the angular position of the axis of rotation of the rotor relative to these coordinates (relative to the gyroscope housing).

However, an ECG with such a rotor has several disadvantages:
the appearance in the servo suspension systems of additional high-voltage voltages from the radial unbalance of the rotor;
during acceleration, in resonance (when passing a speed equal to the natural frequency of the suspension), loads may occur that can lead to disruption of the gyroscope;
to increase the accuracy of angular removal, it is necessary to increase the radial unbalance, however, an increase in the unbalance requires considerable energy and time to spin the rotor to its rated speed, since the suspension rotates the rotor with its own field, the greater the greater the rotor unbalance;
the requirement to fulfill the shape of the rotor with an error not exceeding the unbalance values, since any rotor error with the exception of local distortions is perceived by the capacitive sensor as the radial unbalance of the rotor.

 However, under certain conditions, the shape of the rotor can, like radial unbalance, serve as a source for measuring its angular position.

 There is a method of reducing deformations of the outer surface of thin-walled spherical gyroscope rotors [3] p. 114-119, with which you can make an ellipsoidal, hollow, sealed rotor with a flattened inertia ellipsoid by mechanical grinding of its outer surface in an overpressure environment. The rotor made in this way has the shape of an ellipsoid with an axis of symmetry directed along the axis of rotation. With the introduction of the equatorial unbalance into it, it is possible to carry out, as in analogues, capacitive information retrieval about the angular position of the rotor with the inherent disadvantages of this method, and optical information retrieval, requiring additional optoelectronic communication channels, which complicates the ESG.

где
E - модуль упругости материала ротора;
δ - величина асферичности ротора;
R - радиус наружной поверхности;
ν - коэффициент Пуассона;

h_э - толщина оболочки в экваториальной плоскости симметрии;
h_о - толщина оболочки на полюсах;
при этом совмещают геометрический центр ротора с центром масс, в радиус внутреннего профиля ротора удовлетворяет уравнению:
r(Q) - (R-h_o) + (h_o-h_э)sin²Q,
где
r(Q) - радиус внутренней поверхности ротора;
Q - угол, отсчитываемый от оси полюсов ротора.The ESG rotor was adopted as a prototype [2], pp. 19-20. In order to realize capacitive information retrieval of the position of the rotor kinetic moment vector with the elimination of the disadvantages inherent in analogs, it is necessary to manufacture a rotor aspherical in the region perpendicular to the axis of rotation and not having a radial unbalance. In this case, the outer surface of the rotor in the form of a thin-walled hermetic shell with a vacuum inside it is mechanically rubbed to a sphere in an overpressure environment, which is determined by the formula:

Where
E is the modulus of elasticity of the rotor material;
δ is the asphericity of the rotor;
R is the radius of the outer surface;
ν is the Poisson's ratio;

h _e - shell thickness in the equatorial plane of symmetry;
h _about - shell thickness at the poles;
while combining the geometric center of the rotor with the center of mass, the radius of the internal profile of the rotor satisfies the equation:
r (Q) - (Rh _o ) + (h _o -h _e ) sin ² Q,
Where
r (Q) is the radius of the inner surface of the rotor;
Q is the angle measured from the axis of the poles of the rotor.

In FIG. 1 shows a sectional view of an ESG rotor. The rotor in the form of a shell with a spherical outer surface 1 consists of two symmetrical hemispheres 2 and 3, which are interconnected along the plane of the connector 4 along the main material in vacuum by diffusion welding (DSW). The inner surface 5 of each hemisphere is made of variable radius r, gradually increasing from the pole to the plane of the connector 4, while the wall thickness gradually decreases from h _о at the pole to h _e in the equatorial plane of the connector 4 according to the law of the square of the sine of the angle Q, counted from the axis of the poles of the rotor .

 This shape of the inner surface 5 is easily ensured by turning on software controlled machines (CNC) with high accuracy in the dimension of hemisphere profiles 2 and 3. It is known that one of the main factors affecting the accuracy of the ECG is unbalance due to the mismatch of the geometric center and the center of mass of the rotor [2], pp. 25-26.

 To improve the accuracy of the ECG, it is necessary to balance at various stages of the manufacture of the rotor. In practice, most often there are cases when the body is simultaneously unbalanced both statically and dynamically, which is explained by the inevitable inaccuracies in the dimensions of the parts, the uneven density of the material and the presence of local inclusions and porosities in it, as well as the asymmetry of the shape relative to the axis of rotation. In order to reduce the unbalance values in the early stages of manufacturing the rotor for hemispheres 2 and 3, blanks are used in the form of rods from isostatically pressed powder, while ensuring the isotropy of the physicomechanical properties of the material. Hemispheres are made in pairs from one rod with a common plane of their connector. Hemispheres made with high dimensional accuracy are controlled by weight before welding.

 After welding, mechanical lapping is carried out at normal pressure in a three-spindle installation to the exact sphere and balancing using an air suspension. Thus, before mechanical grinding in the high-pressure chamber, the main part of the unbalance is eliminated and the geometric center and the center of mass of the rotor are aligned with a certain accuracy. A rotor placed in an overpressure medium is deformed.

где
h - толщина стенки ротора.It is known [4], p. 204 that the radial deformation of W _g , the surface of a thin-walled rotor from excess pressure P, is determined by the expression:

Where
h is the wall thickness of the rotor.

на полюсе

На фиг. 2, 3, 4 изображен процесс последовательных изменений формы ротора: на фиг. 2 - под действием давления; на фиг. 3 - при притирке; на фиг. 4 - после притирки, в вакууме, сечение, проходящее через ось симметрии;
Величина давления, при котором притирается ротор для получения заданной асферизации δ = W_gэ-W_go , определяется по формуле

Числовой пример: расчет давления, необходимого для образования ротора с асферичностью δ = 1 мкм, R = 25 мм, h_о = 1,8 мм, h_э = 0,7 мм, E = 2,8•10⁶ кг/см², ν = 0,3.The amount of deformation of the rotor at the equator

at the pole

In FIG. 2, 3, 4 depict a process of successive changes in the shape of the rotor: in FIG. 2 - under the influence of pressure; in FIG. 3 - when grinding; in FIG. 4 - after lapping, in vacuum, the cross section passing through the axis of symmetry;
The pressure at which the rotor is rubbed to obtain a given aspherization δ = W _gе -W _go is determined by the formula

Numerical example: calculation of the pressure necessary for the formation of a rotor with an asphericity δ = 1 μm, R = 25 mm, h _о = 1.8 mm, h _e = 0.7 mm, E = 2.8 • 10 ⁶ kg / cm ² , ν = 0.3.

Процесс механической притирки в камере высокого давления осуществляют временными циклами с постепенным увеличением давления до заданного с промежуточными балансировками на воздушном подвесе и контролем эллипсоидальной формы. Корректировка неуравновешенности массы ротора осуществляется методами направленной доводки на ранних стадиях притирки и при финишной притирке на расчетном давлении с использованием точечных выжиганий материала лазерным лучом. Сочетание механической притирки при ступенчатом повышении давления с промежуточным контролем формы поверхности ротора и балансировками на воздушном подвесе обеспечивают с приемлемой точность совмещение геометрического центра ротора с центром масс.

The process of mechanical grinding in the high-pressure chamber is carried out in temporary cycles with a gradual increase in pressure to a predetermined level with intermediate balancing on the air suspension and control of an ellipsoidal shape. The rotor mass imbalance is corrected by directional refinement methods at the early stages of grinding and at finishing grinding at the design pressure using the point-by-point burning of material by a laser beam. The combination of mechanical grinding with a stepwise increase in pressure with intermediate control of the surface shape of the rotor and balancing on the air suspension provide with acceptable accuracy the combination of the geometric center of the rotor with the center of mass.

 The rotor manufactured by the proposed method has an elongated ellipsoid of inertia (axis of rotation perpendicular to the axis of symmetry of the hemispheres).

 The outer surface of the rotor has ellipses in sections perpendicular to the axis of rotation of the gyro rotor.

 This allows you to determine the direction of the vector of the kinetic moment of the rotor by the value of the instantaneous values of the signals of the electric suspension system, proportional to the gap between the electrodes and the rotor.

 The implementation of the capacitive readout of information on the angular position of the rotor relative to the gyroscope due to the shape of the rotor obtained by the proposed method of its manufacture with the combination of its geometric center with the center of mass and the center of the suspension system, eliminates the runout of the rotor surface relative to the electrode system during rotation. This eliminates the disadvantages inherent in the known method of capacitive information retrieval, which provides improved accuracy of the ESG.

 For the implementation of the invention, an apparatus is used, which is a high-pressure chamber in which a three-spindle lapping device is placed. The internal profile of the hemispheres of the rotor is formed according to the program on CNC machines. Hemispheric diffusion welding is carried out in a high vacuum welding installation. In the manufacture of the rotor, high-precision balancing and metrological equipment is used.

 The rotor made by the proposed method can be used in an ESG with capacitive readout of information about the position of the kinetic moment vector.

Sources of information
1. Martynenko Yu. G. The motion of a solid in electric and magnetic fields. M.:, Science, 1988, p. 170.

 2. Maleev P.I. New types of gyroscopes, L .: Shipbuilding, 1971, p. 17-19, 25-26.

 3. Anfinogenov A.S., Parfenov O.I. A method of reducing deformations of the outer surface of thin-walled spherical gyroscope rotors, L .: Shipbuilding, Marine Instrumentation N 1, p. 114-119.

 4. Reference machine engineer, t. 3, edited by S.V. Serensen, ed. 1956, p. 204.

Claims (1)

A method of manufacturing a hollow rotor of an electrostatic gyroscope, characterized in that the outer surface of the rotor in the form of a thin-walled sealed shell with a vacuum inside it is mechanically rubbed to a sphere in an overpressure environment, which is determined by the formula

where E is the modulus of elasticity of the rotor material;
R is the radius of the outer surface;
δ is the asphericity of the rotor;
ν is the Poisson's ratio;
h _t = h _e - h ₀ / h _e h _o ;
h _e - shell thickness in the equatorial plane of symmetry;
h _about - the thickness of the shell at the poles,
in this case, the geometric center of the rotor is combined with the center of mass, and the radius of the internal profile of the rotor satisfies the equation
r (Q) = (R - h _o ) + (h _o - h _e ) sin ² Q,
where r (Q) is the radius of the inner surface of the rotor;
Q is the angle measured from the axis of the poles of the rotor.

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