JP2000134860A - Electric rotating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric rotating machine, such as an AC motor or the like in which the thickness of an oil film due to grease at a bearing is made constant over a wide temperature range, in which the generation of stray current corrosion can be suppressed sufficiently, even when the machine is driven by an inverter device and in which there is no possibility that the useful period of a rolling bearing is shortened. SOLUTION: An angular contact-type bearing 3 is used as a rolling bearing. A preload spring 4, which uses a temperature deformation material such as a shape memory alloy, a bimetal or the like, is interposed between a bearing bracket 23 and the rolling bearing 3. When it is at low temperature, a spring pressure which gives a preload to the rolling bearing is increased by the preload spring.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotating electric machine using a rolling bearing as a bearing, and more particularly to a rotating electric machine such as an AC motor suitable for an induction motor driven by an inverter.

[0002]

2. Description of the Related Art Capacitance exists between an armature winding and a rotor of an AC motor. As a result, a voltage from a power source is induced on the rotor from the armature winding and appears as an axial voltage. As a result, a current flows through the bearing due to the shaft voltage, and electric erosion occurs in the bearing. And
When this electrolytic corrosion occurs, the rolling surface of the rolling bearing, that is, the surface of the ball or roller, the outer peripheral surface of the inner race (the inner ring member), the outer race (the outer ring member)
The inner peripheral surface becomes rough, and the life is shortened.

When an inverter is used to drive a motor, the output of the motor generally contains many harmonics, so that a large shaft voltage is generated. As a result, a remarkable short circuit occurs in the life of the motor. Is especially problematic.

FIG. 4 is a diagram showing a configuration of a conventional induction motor disclosed in, for example, JP-A-10-28350. This is because, in an AC motor in which a rotor shaft is supported by a rolling bearing lubricated with grease and the rotor is rotatably held inside a stator, the grease lubricating the rolling bearing has a dielectric breakdown voltage of 25 g / m. By using a roller bearing having a temperature of 1 V or less at 1 ° C., the shaft voltage appearing between the rotating part and the fixed part of the rolling bearing is suppressed to 1 V or less. By suppressing the shaft voltage that appears between the rotating part and the fixed part of the rolling bearing to 1 V or less, the magnitude of the discharge energy is reduced to a value or less that causes electrolytic corrosion, so that electrolytic corrosion can be prevented. is there.

In the figure, reference numeral 20 denotes the whole induction motor, 21
Is a frame, 22 and 23 are bearing brackets which hold bearings 24 and 25 made of ball bearings.
1 are attached to both ends by fitting each spigot. Reference numeral 26 denotes a stator core. The stator core 26 has a stator winding 27 wound around its slot. 2
Reference numeral 8 denotes a rotor having a rotating shaft 29. The rotating shaft 29 is rotatably held by bearings 24, 25 of bearing brackets 22, 23 so that the rotating shaft 29 is fixed at a predetermined position in the stator core 26. It is configured to be able to rotate freely at a position facing the stator core 26.

[0006] When three-phase AC power is supplied to the stator winding 27 from an AC power source such as an inverter device (not shown), a rotating magnetic field is generated in a gap between the stator and the rotor. The rotor 28 generates a torque and rotates, so that power can be taken out from the rotating shaft 29. At this time, due to the capacitance existing between the stator winding 27 and the rotor 28, the rotating shaft 29 A certain value of potential is generated.

At this time, grease is sealed in the bearings 24 and 25, and a grease oil film is formed on the rolling surfaces thereof, so that the outer race and the inner race are electrically insulated. As a result, a shaft voltage is generated on the rotating shaft 29. However, the bearing 2 is controlled so that the value of the shaft voltage generated on the rotating shaft 29 is suppressed to 1 V or less.
The material of the grease enclosed in the bearings 4 and 25 is selected, and the occurrence of electrolytic corrosion in the bearings 24 and 25 can be sufficiently suppressed.

FIG. 5 is a diagram showing the effect of a physical quantity on the thickness of an oil film formed by grease disclosed in, for example, JP-A-10-28350. The dielectric breakdown voltage of grease in the bearing is mainly determined by the thickness of the oil film. As the oil film becomes thicker, the dielectric strength due to the oil film increases.
The effects on oil film formation include: a. Base oil viscosity: Specific to grease. Impact: Large. b. Change in film thickness due to axial load: Oil film thickness is 0.
It is inversely proportional to the 74th power. Impact: Medium. c. Influence of temperature: Appears very remarkably, and the film pressure is halved with a temperature rise of 20 ° C. Impact: Large. d. Influence of rotation speed: The film pressure increases as the rotation speed increases, and is proportional to the rotation speed to the 0.74th power. Impact: Medium. There is.

[0009] It is understood that the thickness of the oil film formed by grease is largely affected by the temperature, and the thickness of the oil film decreases as the temperature rises. It is necessary to limit the lower limit of the temperature, and a material that can form a sufficiently thin oil film even at the lower limit of the operating temperature is selected.

[0010]

In the conventional AC motor as described above, when the temperature decreases, the viscosity of the grease sealed in the bearing increases, and the thickness of the oil film increases. However, by selecting a grease that can form a sufficiently thin oil film, the occurrence of electrolytic corrosion in the bearing is suppressed, and the thickness of the oil film that decreases as the temperature rises depends on the viscosity of the base oil, which is unique to grease. There was a problem that it would be decided by.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a constant oil film thickness of grease in a bearing in a wide temperature range. It is an object of the present invention to provide a rotating electric machine such as an AC motor or the like that can suppress the occurrence of electrolytic corrosion in a bearing and does not have a risk of shortening the service life of the rolling bearing.

[0012]

Means for Solving the Problems A stator having a coil wound thereon, a frame for fixing the stator, a rotor opposed to the stator via a small gap, and the rotor are fixed. A rotating shaft rotatably supported via a rolling bearing, and a bearing bracket for supporting the rolling bearing, wherein an angular contact type bearing is used as the rolling bearing, and the bearing bracket Between the rolling bearing, a preload spring using a temperature deformable material such as a shape memory alloy or bimetal is interposed, and at a low temperature, the spring pressure for applying a preload to the rolling bearing at a low temperature is increased. The minimum oil film thickness of the grease in the bearing is made constant.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a diagram showing a structure of an electric motor according to one embodiment of the present invention. In the figure, 21, 22, 23, 26, 27, 28, and 29 are the same as those in the conventional device described above, and the description thereof is omitted.

1 is a whole induction motor, 2 and 3 are angular contact type bearings, 4 is a preload spring using a temperature deformable material such as a shape memory alloy or bimetal as a constituent material.

FIG. 2 is a view showing the structure of an angular contact type bearing used in an electric motor according to an embodiment of the present invention, which is shown as 2 and 3 in FIG. In the figure, 11 is an outer ring, 12 is an inner ring, 13 is a rolling element, 14 is a retainer, and 15 is a seal plate. This angular contact type bearing has a structure that can withstand a pressure from the lateral direction.

FIG. 3 is a view showing a mounting structure of an angular contact type bearing used for an electric motor according to an embodiment of the present invention. The angular contact type bearing 3 is provided between the rotating shaft 29 and the bearing bracket 23, and a lateral pressure is applied by a preload spring 4 using a temperature deformable material such as a shape memory alloy or a bimetal as a constituent material. It was done. The preload spring 4 is configured so that the spring pressure increases at low temperatures.

The thickness of the oil film is 0.74 of the bearing pressure.
Since it is inversely proportional to the power and doubles when the temperature drops by 20 ° C., the pressure from the side by the preload spring 4 becomes larger when converted to the pressure of this bearing. When the ratio is set so as to be as follows, the film thickness can be made constant.

According to the present invention, the bearing bracket and the bearing are provided with a preload spring using an angular contact type bearing which is strong against a lateral load, and further using a temperature-deformable material such as a shape memory alloy or a bimetal as a constituent material. And at a low temperature, the spring pressure is increased, so that the influence of the increase in the film thickness due to the decrease in temperature is reduced.

[0019]

Since the present invention is configured as described above, it has the following effects.

An angular contact type bearing is used as a rolling bearing, and a preload spring using a temperature deformable material such as a shape memory alloy or a bimetal is interposed between the bearing bracket and the rolling bearing. At times, the minimum oil film thickness of the grease in the bearing is made constant by increasing the spring pressure that applies a preload to the rolling bearing.Thus, even when driven by the inverter device in a wide temperature range, the bearing can be fully used. Can reduce the occurrence of electrolytic corrosion,
It is possible to provide a rotating electric machine that does not have a risk of shortening the service life of the rolling bearing.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure of an electric motor according to an embodiment of the present invention.

FIG. 2 is a view showing a structure of an angular contact type bearing used in the electric motor according to one embodiment of the present invention.

FIG. 3 is a diagram showing a mounting structure of an angular contact type bearing used for an electric motor according to an embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a conventional induction motor disclosed in, for example, Japanese Patent Application Laid-Open No. 10-28350.

FIG. 5 is a diagram showing the effect of a physical quantity on the thickness of an oil film due to grease disclosed in, for example, JP-A-10-28350.

[Explanation of symbols]

1 whole induction motor, 2, 3 angular contact type bearing, 4 preload spring using temperature deformable material such as shape memory alloy or bimetal as constituent material, 11 outer ring, 12 inner ring, 13 rolling element, 14 cage, 15 seal plate, 20 whole induction motor, 21 frame, 22, 23 bearing bracket, 24, 25 ball bearing bearing, 26 stator core, 27 stator winding, 28
Rotor, 29 rotation axis.

Claims (1)

[Claims] 1. A stator having a coil wound thereon, a frame for fixing the stator, a rotor facing the stator with a small gap therebetween, and the rotor being fixed,
In a rotating electrical machine having a rotating shaft rotatably supported via a rolling bearing and a bearing bracket supporting the rolling bearing, an angular contact type bearing is used as the rolling bearing, and the bearing bracket and the bearing bracket are used. A preload spring using a temperature deformable material such as a shape memory alloy or a bimetal is interposed between the rolling bearing and the preload spring increases the spring pressure for applying a preload to the rolling bearing at a low temperature, so that the inside of the bearing is increased. A rotating electric machine wherein the minimum oil film thickness of grease is made constant.