RU2345466C1 - Motor - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention relates to electrical engineering, and particularly to electric motors, which may be sued in drive systems operating in vacuum under conditions of limited heat-exchange with temperature gradient -100°C to +110°C. The motor includes housing where stator and rotor are installed. They are positioned in bearings and on the shaft. The bearings are installed in the centering lids at housing end sides. The lids are manufactured from polymer composite material with elasticity modulus E and specific weight p selected from the ratios 2 GPa≤E≤4 GPa, 1 g/cm³ <p<1.5 g/cm³. The outer bearing rings are installed in the centering lids with radial tightness δ selected from the range 0.004 D≤δ≤0.006 D, where D - outer bearing diameter. There are grooves made on the outer ring of one or two bearings, which interact with the projection on the reciprocal surface of the centering lid. Grooves are also available on the internal surface of in the inner bearing ring or reciprocal surface of the shaft. The resilient elements are installed in the grooves with preliminary tightness. They are made of the same material as lids material.

EFFECT: exclusion of jamming and avoiding large radial clearances in bearing units and improving reliable motor operation in vacuum under conditions of the limited heat-exchange with temperature gradient from -100°C to +110°C.

3 cl, 4 dwg

Description

The invention relates to electrical engineering, in particular to electric motors that can be used in drive systems operating in vacuum under conditions of limited heat exchange with a temperature gradient of -100 ° C to + 110 ° C.

A known electric motor in which there is a hollow metal housing with a stator, centering covers and a rotor installed in the bearing assemblies of the covers [1].

When reducing the weight of the engine due to the implementation of its covers made of light metals, in the case of large temperature gradients due to the difference in the coefficients of linear expansion in the bearing assembly or between bodies and raceways, large tightnesses appear, which leads to a loss of efficiency and, in some cases their jamming, or between the bearing rings and the counter surfaces of the housing or rotor shaft, respectively, increased radial clearances occur, which reduces the accuracy of the positioning of the rotor axis. In addition, even when using light metals to make covers, the weight of the engine remains large.

The closest technical solution, selected as a prototype, is an electric motor, including a hollow body, in which a stator and rotor are installed, located on the shaft in bearings mounted in centering steel covers on the side of the ends of the motor housing [2].

In this technical solution, bearings are placed between the respective landing surfaces of the cover and the rotor shaft, while pairing with one of these surfaces is carried out on a sliding (for example, with a cover), on the other - transitional - landing (for example, with a shaft).

A significant drawback of the engine is that when its covers are made of light metals to reduce weight under conditions of changes in engine temperature from -100 ° C to + 110 ° C during its operation due to differences in the linear expansion coefficients of the steel bearing and the cover of aluminum alloys either a large interference occurs between the bodies and raceways in the bearing assembly, resulting in a sharp increase in friction losses and, in some cases, the bearing wedges, or between the bearing surfaces of the bearing, housing and shaft a rotor having increased radial clearance, whereby substantially more complicated bearing mount and decreases the accuracy of positioning the rotor axis. Moreover, the use of light metals for the manufacture of caps does not allow to radically solve the problem of reducing the weight of the engine.

As a result of this, the use of this engine is not possible in drive systems moving from earth to outer space and working in it with limited heat transfer and a temperature gradient of -100 ° C to + 110 ° C.

The objective of the invention is the elimination of jamming and increased radial clearance in the bearing units and increase, due to this, the reliability of the electric motor when operating in vacuum under conditions of limited heat transfer with a temperature gradient from -100 ° C to + 110 ° C.

The solution to this problem is achieved by the fact that in the electric motor containing the housing, in which the stator and rotor are mounted, located on the shaft in bearings mounted in centering covers on the side of the ends of the housing, according to the technical solution, the covers are made of a polymer composite material having an elastic modulus E and specific gravity p, selected from the relations

2 GPa≤E≤4 GPa,

1 g / cm ³ <p <1.5 g / cm ³ ,

and the outer rings of the bearings are mounted in centering caps with a radial tension δ, selected from the range

0.004 D≤δ≤0.006 D,

where D is the outer diameter of the bearing.

At least one groove is made on the outer ring of one or two bearings, interacting with a protrusion made on the counter surface of the centering cover, and at least one groove is made on the inner surface of the inner ring of the bearing or the shaft surface responding to it, in which installed with preload an elastic-flexible element made of a polymer composite material having an elastic modulus E and specific gravity p, selected from the ratios

2 GPa≤E≤4 GPa,

1 g / cm ³ <p <1.5 g / cm ³ .

The exclusion of jamming of the bearing and increased radial clearance in the bearing units when operating in vacuum under conditions of limited heat exchange with a temperature gradient from -100 ° C to + 110 ° C with an increase, due to this, the reliability of the electric motor is achieved as a result of the following.

The use of a polymer composite material with an elastic modulus of 2 GPa≤E≤4 GPa ensures such compliance of the bearing mates with the covers and the shaft, on which, on the one hand, the occurrence of interference in the bearing mates with the cover and (or) the shaft, leading to a decrease in their efficiency or jamming, on the other hand, ensures the accuracy of centering of the axis of the rotor when it is loaded. The installation of the outer bearing rings in the centering caps with a radial tightness δ allows avoiding the occurrence of gaps during thermal expansion, leading to a loss of centering accuracy. Moreover, the use of a polymer composition with a specific gravity of 1 g / cm ³ <p <1.5 g / cm ³ provides a significant (18 ... 25%) reduction in engine weight.

The range of elastic moduli of the material is selected based on the following:

- with an elastic modulus of less than 2 GPa, the radial compliance of the housing becomes excessively high, as a result of which, when the rotor is radially loaded, the reliability of centering the bearing axis in the radial direction is reduced;

- when the elastic modulus is greater than 4 GPa, the radial stiffness of the bearing in combination with the initial interference leads to the appearance of small, but leading to a decrease in efficiency, interference between the bodies and the raceways of the bearing, this complicates the assembly of the bearing assembly and the strength characteristics of the polymer housing under conditions thermal cycling in an extended temperature range.

The range of variation of the specific gravity of the polymer material is selected based on the following:

- with a specific gravity greater than 1.5 g / cm ³ , it is less appropriate to use a polymer material due to a slight decrease in the weight of the engine;

- with a specific gravity of less than 1 g / cm, the required modulus of elasticity and strength characteristics of the polymer material are not provided under thermal cycling in an extended temperature range.

The range of variation of the radial interference of the bearings is selected based on the following:

- with a radial tightness greater than 0.006 D, it affects the efficiency of the bearing, which decreases, while there are certain problems with the strength characteristics of covers under thermal cycling in an extended temperature range;

- when the radial tightness is less than 0.004 D, under conditions of thermal cycling in an extended temperature range, the reliability of centering the bearing axis in the radial direction decreases.

Installation between the inner race of the bearing and the counter surface of the rotor shaft with a preload of an elastic-flexible element made of a material having an elastic modulus E and specific gravity p, selected from the ratios 2 GPa≤E≤4 GPa and 1 g / cm ³ <p <1.5 g / cm ³ , for example from polysulfone, which retains elastic properties in the temperature range from -100 ° C to + 110 ° C, also contributes to the solution of the problem. In this case, this element is placed in a groove on the inner surface of the inner ring of the bearing or on the counter surface of the shaft.

The invention is illustrated by figures.

Figure 1 shows the design of the engine.

In Fig.2, Fig.3 and Fig.4 shows options for the execution of the grooves on the outer and inner rings and the shaft of the bearing.

The electric motor (see Fig. 1) consists of a housing 1, a stator 2 located in the housing 1, and a rotor 3. In the stator 2, the excitation windings 4 are made. The rotor 3 of the motor is mounted on the shaft 5 and is permanently connected to it. Permanent magnets 6 are placed in the rotor 3. The centering caps 7 are made of a polymer material, for example polysulfone, having an elastic modulus E = 3.2 GPa and a specific gravity p = 1.3 g / cm ³ . Bearings 8 are installed in the centering caps, the shaft 5 is located in the seating surface of the inner rings of the bearings 5. Bearings 8 are installed in the centering caps 7 with a radial interference value δ, selected from the range 0.004 D≤δ≤0.006 D. The diameter D of the bearing is determined based on the purpose of the engine and modes of operation.

If necessary, a more reliable axial fastening on the outer surface of the outer ring 11 of the bearing 8 is a groove 10. In this case, a protrusion is made on the counter surface of the cover 7, having a reciprocal groove 10 in the form and placed in the groove 10 without gap.

On the inner surface of the inner ring 11 of one or two bearings 8, a groove 12 is made in which a gapless elastically resilient element 13 is installed (FIGS. 2, 3). In this case, the inner diameter of the resilient element 13 when it is placed in the groove 12 on the inner ring 11 of the bearing 8 is smaller by 0.05 ... 0.2 mm, respectively, of the diameter of the inner ring 11 of the bearing 8.

On the surface of the shaft 5, mating with the inner ring of the bearing 8, a groove 14 is made in which a gapless elastically resilient element 15 is placed (Fig. 4). The outer diameter of the resilient element 15 when it is placed in the groove 14 on the shaft 5 is large by 0.05 ... 0.2 mm of the diameter of the inner ring 11 of the bearing 8.

The grooves 12, 14 may be circular or in the form of rectangular or segmented keyways (see FIGS. 2, 3 and 4). In accordance with this, resilient elements 13, 15 will be made with a similar shape.

The elastic elements 13 and 15 when the bearings 8 are mounted on the shaft 5 are elastically compressed, creating a preload in the connection.

During operation of the electric motor in open space, when it is heated to 90 ... 110 ° C or more, the diameters of the outer 9 and inner 11 rings of the bearing 8 increase due to an internal heat source or solar radiation. In this case, the cover 7 is elastically deformed, creating an additional interference fit with the outer ring 9 of the bearing 8, however, due to the high flexibility of the material of the cover 7, the magnitude of this interference does not lead to a decrease in efficiency or seizure of the bearing. At the same time, with an increase in the inner ring of the bearing 8, the elastically flexible element 13 in the compressed state increases in size in diameter, as a result of which there is no gap in the connection of the inner ring 11 of the bearing 8 with the shaft 3.

When the bearing is cooled to -80 ... -100 ° C, the diameter of its outer 9 and inner 11 rings decreases. In this case, the pre-compressed cover 7 partially returns to its original (before the engine was assembled) state, as a result of which its internal landing diameter decreases. As a result of this, in the interface of the cover 7 with the outer ring 9 of the bearing 8, there is no gap leading to a loss of centering accuracy of the shaft axis 5. At the same time, the diameter of the inner ring 11 of the bearing 8 decreases. The elastic elements 13 and 15 are additionally compressed, however, due to their high compliance, this does not lead to the occurrence of significant interference between the bodies and raceways of the bearing 8, reducing its efficiency or jamming.

When axial movements of the outer 9 and inner 11 rings of the bearing 8 occur due to thermal deformations of the engine elements located in the grooves 10 and 12, respectively, the protrusion of the cover 7 and the elastically flexible element 13 are elastically deformed, reliably fixing the shaft 5 and the rotor rigidly connected to it in the axial direction 3 relative to the stator 2.

The use of the proposed technical solution in engines operating in a vacuum in the temperature range of -100 ° C to + 110 ° C allows not only to significantly reduce their weight, but also to increase reliability and improve vibro-acoustic characteristics.

Information sources

1. Patent GB 2172754 A, H02K 11/00, publ. 1986 year

2. Patent RU 2285996, Н02K 11/00, publ. 2005 year

Claims (3)

1. An electric motor containing a housing in which a stator and a rotor are installed, located on the shaft in bearings mounted in centering covers on the side of the ends of the housing, characterized in that the covers are made of a polymer composite material having an elastic modulus E and specific gravity p, selectable from the relations
2 GPa≤E≤4 GPa,
1 g / cm ³ <p <1.5 g / cm ³ ,
where GPa - gigapascal (according to the international SI system - 1 GPa = 10 ⁹ Pa = 10 ⁹ N / m ² ),
and the outer rings of the bearings are mounted in centering caps with a radial tension δ, selected from the range
0.004 D≤δ≤0.006 D,
where D is the outer diameter of the bearing. 2. The electric motor according to claim 1, characterized in that at least one groove is made on the outer ring of one or two bearings, interacting with a protrusion made on the counter surface of the centering cover. 3. The electric motor according to claim 1 or 2, characterized in that at least one groove is made on the inner surface of the inner ring of the bearing or the reciprocal of the shaft surface in which a resilient element made of a polymer composite material having a module is preloaded elasticity E and specific gravity p, selected from the relations
2 GPa≤E≤4 GPa,
1 g / cm ³ <p <1.5 g / cm ³ ,
where GPa - gigapascal (according to the international SI system - 1 GPa = 10 ⁹ Pa = 10 ⁹ N / m ² ).

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