JP2014114879A - Rolling bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing device that is hard to cause seizure, even if used at high speed of rotation, and has a long life.SOLUTION: A motor compressor includes: a substantially cylindrical housing 1; a rotating shaft 2 inserted into the inside of the housing 1 and coaxially arranged; and a pair of roller bearings 10, 10 arranged between the housing 1 and the rotating shaft 2, and rotatably supporting the rotating shaft 2 with respect to the housing 1. An impeller 3 for compressing air is attached to the end part of the rotating shaft 2. A limit PV value of the roller bearing 10 is 1720 MPa m/s or more and 2400 MPa m/s or less. Axial pre-compression is given to one side among the pair of roller bearings 10, 10 by a spring 21 for pre-compression load. The pre-compression strength is set in such a strength that a PV value of the roller bearing 10 during rotation is 1720 MPa m/s or more and 2400 MPa m/s or less, and is the limit PV value or less.

Description

  The present invention relates to a rolling bearing device.

  A housing, a rotating shaft provided with an impeller at its end, a rolling bearing that rotatably supports the rotating shaft on the housing, a rotor provided on the outer peripheral surface of the rotating shaft, and an inner peripheral surface of the housing; A rolling bearing device including a stator, in which a rotor and a stator are arranged to face each other in a radial direction, is incorporated in, for example, an in-vehicle supercharger or a pneumatic feeder, and is used as an electric compressor or an electric blower (Patent Document) 1).

JP 2002-369474 A

For example, an electric compressor (rolling bearing device) used for an on-vehicle supercharger is generally used at a high rotational speed of tens of thousands to hundreds of thousands of rpm, so that slip occurs between the rolling elements and the raceway surface. As a result, seizure and bearing life may be shortened. Therefore, the rolling bearing device as described above is required to prevent seizure.
SUMMARY OF THE INVENTION The present invention solves the problems of the prior art as described above, and an object of the present invention is to provide a long-life rolling bearing device that is unlikely to cause seizure even when used at a high rotational speed.

In order to solve the above-described problems, an aspect of the present invention has the following configuration. That is, a rolling bearing device according to an aspect of the present invention includes a housing, a shaft inserted into the housing, and a plurality of rolling elements between an inner ring and an outer ring, the rolling bearing device, A rolling bearing device disposed between the shaft and supporting the shaft so as to be relatively rotatable with respect to the housing, wherein a limit PV value of the rolling bearing is 1720 MPa · m / s or more and 2400 MPa. Pre-load is applied to the rolling bearing so that the PV value of the rolling bearing during rotation is 1720 MPa · m / s to 2400 MPa · m / s and less than the limit PV value. It is characterized by being.
In this rolling bearing device, the rolling bearing may be a ball bearing, and the groove radius of the raceway groove provided in the inner ring may be 54% or more and 58% or less of the diameter of the ball that is the rolling element.

  The rolling bearing device of the present invention has a long life because seizure hardly occurs even when used at a high rotational speed.

It is sectional drawing which shows the structure of the electric compressor which is one Embodiment of the rolling bearing apparatus which concerns on this invention. It is the fragmentary sectional view which expanded and showed the rolling bearing with which the electric compressor of FIG. 1 is provided, and its peripheral part. It is sectional drawing which shows the structure of a test apparatus. It is a graph which shows the relationship between a preload and PV value. It is a graph which shows the relationship between PV value and durable time.

DESCRIPTION OF EMBODIMENTS Embodiments of a rolling bearing device according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing the structure of an electric compressor which is an embodiment of a rolling bearing device according to the present invention. FIG. 2 is an enlarged partial cross-sectional view showing the rolling bearing provided in the electric compressor of FIG. 1 and its peripheral portion.
The electric compressor of FIG. 1 includes a substantially cylindrical housing 1, a rotary shaft 2 inserted into the housing 1 and arranged coaxially, and a housing 1 and the rotary shaft 2. And a pair of rolling bearings 10 and 10 for rotatably supporting the rotating shaft 2.

As the rolling bearing 10, for example, as shown in FIGS. 1 and 2, an inner ring 11, an outer ring 12, and a plurality of rolling elements (balls) 13 that are arranged to freely roll between the inner ring 11 and the outer ring 12. , Angular ball bearings are used. The limit PV value of the rolling bearing 10 is 1720 MPa · m / s or more and 2400 MPa · m / s or less.
Note that grease (not shown) is sealed inside the rolling bearing 10 (internal space formed between the outer peripheral surface of the inner ring 11 and the inner peripheral surface of the outer ring 12). The grease lubricates the inner ring 11, the outer ring 12, and the rolling elements 13 of the rolling bearing 10, thereby reducing friction and suppressing seizure. Further, the rolling bearing 10 may be provided with a cage and a sealing device as shown in FIG. 2, but may not be provided.

  One end of the rotating shaft 2 (the right end in FIG. 1) protrudes from the opening 1 a of the housing 1 to the outside. An impeller 3 for compressing air is attached to an end portion of the rotating shaft 2 protruding outside the housing 1 by a nut 22, and the impeller 3 is arranged outside the housing 1. An air supply pipe 23 containing the impeller 3 is integrally formed at the axial end of the housing 1 on the side where the impeller 3 is located (the right end in FIG. 1). ing.

  The opening 1 a is provided with a sealing device (not shown) such as a labyrinth seal or a mechanical seal, and seals between the rotating shaft 2 and the housing 1. In the following, the axial end (the right end in FIG. 1) on the side where the impeller 3 is located among the axial ends of the housing 1 and the rotary shaft 2 is referred to as “impeller side end”. The opposite axial end (the left end in FIG. 1) may be referred to as the “anti-impeller side end”.

  For example, two rolling bearings 10 are used, and these two rolling bearings 10 and 10 are interposed between the housing 1 and the rotating shaft 2 in a front combination (DF) and are spaced apart in the axial direction. It is arranged. The two rolling bearings 10, 10 are arranged between the outer peripheral surface of the rotating shaft 2 and the inner peripheral surface of the housing 1, and the respective inner rings 11, 11 are fixed to the rotating shaft 2 by press fitting or the like. , 12 are fixed to the housing 1.

  An inner ring spacer 24 fitted to the outer peripheral surface of the rotary shaft 2 is interposed between the two rolling bearings 10 and 10. And each inner ring | wheel 11, 11 of these rolling bearings 10 and 10 has the inner side surface (side surface which mutually opposes) abuts against the inner ring spacer 24, and the outer side surface (side surface which is not facing the axial direction outer side). The abutting portion is abutted against the side wall 2a of the step portion formed in the vicinity of both end portions of the rotating shaft 2. Thereby, the axial displacement with respect to the rotating shaft 2 of the inner rings 11, 11 of the two rolling bearings 10, 10 is restricted.

  On the other hand, of the two rolling bearings 10, 10, the outer ring 12 of the anti-impeller side rolling bearing 10 (the outer ring 12 of the left side rolling bearing 10 in FIG. 1) is fitted to the housing 1 so as to be displaceable in the axial direction. The preload load spring 21 is abutted against the outer side surface (the side surface on the outer side in the axial direction which is not opposed), and the axial preload is applied by the preload load spring 21. ing. With such a configuration, a preload is applied to the rolling bearing 10 against which the preload load spring 21 is abutted, and the rotary shaft 2 is rotatably supported inside the housing 1 without rattling.

Of the two rolling bearings 10, 10, the outer ring 12 of the impeller-side rolling bearing 10 (the outer ring 12 of the right-side rolling bearing 10 in FIG. 1) is the outer surface (the axially outer side surface that is not opposed). ) Is press-fitted and fixed in contact with the side surface of the housing 1.
The strength of the preload applied to the rolling bearing 10 is set to such a strength that the PV value of the rolling bearing 10 during rotation is not less than 1720 MPa · m / s and not more than 2400 MPa · m / s and not more than the limit PV value. To do. That is, the strength of the preload applied to the rolling bearing 10 is set according to the rotational speed and temperature of the rolling bearing 10 during operation of the electric compressor, and the PV value of the rolling bearing 10 during rotation is 1720 MPa · m / s. Above 2400 MPa · m / s and below the limit PV value.

  In addition, when a ball bearing is used as the rolling bearing 10, the preload is applied to accurately position the rolling bearing 10 in the axial direction, suppress the runout of the rotating shaft 2, and suppress the sliding of the rolling element 13. Can do. As a preloading method, a constant pressure preloading method using a preloading spring 21 is preferable. As the preload spring 21, for example, a compression coil spring can be used.

  Furthermore, the electric compressor includes an electric motor including a rotor 5 and a stator 6. A rotor 5 having a field magnet is fixed by an interference fit at an intermediate portion in the axial direction of the outer peripheral surface of the rotary shaft 2 and between the two rolling bearings 10 and 10. A stator 6 is fixed to a portion of the inner peripheral surface of the housing 1 that faces the outer peripheral surface of the rotor 5. The rotor 5 may be a laminated core formed by laminating a plurality of thin magnetic metal plates in the axial direction, and may be configured without a magnet. The type of the stator 6 is not particularly limited. For example, as shown in FIG. 1, the armature coil 6b is wound around a laminated core 6a formed by laminating a plurality of magnetic metal thin plates in the axial direction. The thing comprised by is mentioned.

When the armature coil 6b is connected to the motor inverter 27 and energized, the rotary shaft 2 is rotationally driven by the electric motor, so that the impeller 3 fixed to the rotary shaft 2 rotates. The air is pumped through the air supply pipe 23 by the rotation of the impeller 3. In the electric compressor of this embodiment, since the rotor 5 and the rolling bearings 10 and 10 are fixed to the rotating shaft 2, the weight is reduced, the size is reduced, the efficiency is increased, and the system is simplified.
Such an electric compressor of the present embodiment can be used for various purposes for compressing gas, and can be suitably used for, for example, a vehicle-mounted supercharger (electric motor-driven supercharger). Electric compressors used in in-vehicle superchargers are generally used at high rotational speeds of tens of thousands to hundreds of thousands of rpm, so slippage occurs between the rolling elements and the raceway surface, and seizure is likely to occur. .

  However, in the electric compressor of the present embodiment, as described above, the limit PV value of the rolling bearing 10 is 1720 MPa · m / s or more and 2400 MPa · m / s or less (preferably 1720 MPa · m / s or more and 2000 MPa · m / s). And a PV value of the rolling bearing 10 during rotation is 1720 MPa · m / s or more and 2400 MPa · m / s by applying an appropriate preload according to the rotation speed and temperature to the rolling bearing 10. Below (preferably 1720 MPa · m / s or more and 2000 MPa · m / s or less) and below the limit PV value. With such a configuration, the rolling bearing 10 is less likely to slip between the rolling elements 13 and the raceway surface of the inner ring 11, and therefore seizure occurs even when used at a high rotational speed of tens of thousands to hundreds of thousands of rpm. It is difficult and has a long life. This point will be described in detail below.

  When an excessive axial load is applied to the rolling bearing 10, the surface pressure at the contact portion between the raceway surface of the inner ring 11 and the rolling element 13 may increase and the sliding speed may increase. At this time, if the PV value becomes excessive, the frictional heat in the contact portion increases, and seizure is likely to occur. As a result, the rolling bearing 10 is damaged and the grease is deteriorated at an early stage. It is difficult to continue to operate stably over a long period of time. If the PV value is too small, the rigidity of the rolling bearing 10 is lowered, the rolling bearing 10 is displaced in the axial direction, and the impeller 3 and the housing 1 may interfere with each other.

Therefore, by applying an appropriate preload load corresponding to the rotational speed and temperature to the rolling bearing 10 so that the sliding speed at the contact portion between the raceway surface of the inner ring 11 and the rolling element 13 does not increase, the rolling bearing 10 is sintered. The sticking is suppressed and the life is extended.
At this time, the seizure can be further suppressed by appropriately setting the groove radius of the raceway surface (the raceway groove) of the inner ring 11 where seizure is likely to occur. That is, the groove radius of the raceway groove provided in the inner ring 11 is preferably 54% or more and 58% or less, and more preferably 56% or more and 58% or less of the diameter of the ball that is the rolling element 13.

  Such a configuration is particularly preferably applied to the rolling bearing 10 (the left-side rolling bearing 10 in FIG. 1) disposed at the end portion on the side opposite to the impeller. The reason is as follows. When the impeller 3 rotates and pumps air, a force in the direction from the end portion on the anti-impeller side toward the end portion on the impeller side (force in the right direction in FIG. 1) acts on the rotary shaft 2. Therefore, in the rolling bearing 10 arranged at the end portion on the impeller side, the preload increases as the rotational speed of the impeller 3 increases, and the sliding speed of the sliding generated between the revolving rolling element 13 and the raceway surface of the inner ring 11 is increased. However, the force does not act on the rolling bearing 10 disposed at the end portion on the side opposite to the impeller, and the preload does not increase even if the rotational speed of the impeller 3 increases. As a result, since the sliding speed of the rolling bearing 10 disposed at the end portion on the side opposite to the impeller is relatively high, seizure occurs more easily than the rolling bearing 10 disposed on the end portion on the impeller side.

Further, the rolling bearing device having the same configuration as that of the electric compressor of the present embodiment can be used as an electric blower. The electric blower can be used for various applications for sending gas, and can be suitably used for, for example, a pneumatic feeder for a fuel cell and a water vapor pump.
In addition, this embodiment shows an example of this invention and this invention is not limited to this embodiment. For example, in the present embodiment, the two rolling bearings 10 and 10 are a front combination (DF), but may be a rear combination (DB).

  In this embodiment, an angular ball bearing has been described as an example of a rolling bearing. However, in the present invention, various types of ball bearings other than the angular ball bearing can be used. For example, radial ball bearings such as deep groove ball bearings, four-point contact ball bearings, and self-aligning ball bearings. However, it is also possible to use radial roller bearings such as cylindrical roller bearings, tapered roller bearings, needle roller bearings, and self-aligning roller bearings. It is also possible to use a thrust type rolling bearing such as a thrust ball bearing or a thrust roller bearing.

Further, when a plurality of rolling bearings are provided as in the present embodiment, one or more types of rolling bearings may be used. And when providing 2 or more types of rolling bearings, the combination of the kind is not specifically limited. Furthermore, the number of the rolling bearings 10 that support the rotating shaft 2 is not particularly limited, and may be one or two or more.
Furthermore, the material of the race rings (inner ring 11 and outer ring 12) of the rolling bearing 10 is not particularly limited, but a metal such as steel is preferable. Specific examples include heat-resistant steel such as M50 (when heat resistance and wear resistance are required), stainless steel such as SUS440C, bearing steel such as SUJ2, and carburized steel.

Further, the material of the rolling element 13 is not particularly limited, but a metal such as steel or ceramic is preferable, and when the rotating shaft 2 is used at a high speed rotation of several tens of thousands to several hundred thousand rpm, the ceramic is more suitable. preferable. Specific examples of the ceramic include silicon nitride (Si ₃ N ₄ ), alumina (Al ₂ O ₃ ), silicon carbide (SiC), zirconia (ZrO ₂ ), aluminum nitride (AlN), and the like.

  In the electric compressor of the present embodiment, since the electric motor is installed inside the housing 2, the temperature of the rolling bearing 10 rises due to the heat generated by the electric motor, and the raceway surface of the rolling bearing 10 and the rolling elements 13. There is a possibility that the oil film existing between the rolling surfaces becomes thin. If a ceramic having a lower density than the bearing steel used in general is used as the material of the rolling element 13, the centrifugal force acting on the rolling element 13 during rotation of the rotating shaft 2 is reduced, and the rolling bearing 10 is loaded. The increase in the calorific value can be suppressed by suppressing the load.

In addition, when the rolling element 13 is made of metal, there is a possibility that wear may occur and seizure may occur. However, if the rolling element 13 is made of ceramic, the wear is suppressed. Further, if the races 11 and 12 are made of steel such as heat-resistant steel and the rolling elements 13 are made of ceramic, the races 11 and 12 and the rolling elements 13 are made of different materials, so the oil film becomes insufficient. However, they are less likely to adhere to each other and have excellent wear resistance and seizure resistance. Therefore, the rolling bearing 10 has a long life, and as a result, the electric compressor has a long life.
In addition, when the gas to be compressed or pumped is high temperature, it is preferable that the races 11 and 12 are made of heat-resistant steel and the rolling element 13 is made of ceramic. There is a risk that a change in preload due to the difference between the two occurs. Therefore, in order to suppress a change in preload due to a difference in linear expansion coefficient, it is preferable to use a constant pressure preload.

〔Example〕
Using the test apparatus shown in FIG. 3, the seizure resistance of the rolling bearing device of the present invention was evaluated. The test apparatus shown in FIG. 3 includes a substantially cylindrical housing 101, a rotating shaft 102 coaxially disposed inside the housing 101, and a pair of rolling bearings 110 and 110 that rotatably support the rotating shaft 102 on the housing 101. It is equipped with. The pair of rolling bearings 110, 110 is a front combination.

  The pair of rolling bearings 110 and 110 are directly fitted to the inner peripheral surface of the housing 101. More specifically, the inner rings of the rolling bearings 110 and 110 are press-fitted and fixed to the rotating shaft 102, and axial displacement with respect to the rotating shaft 102 is restricted. Further, the outer ring of one of the rolling bearings 110 (the left bearing in FIG. 3) is fitted and fixed (gap fit) so as to be axially displaceable with respect to the housing 101 and is preloaded in the axial direction by a spring 104. Is granted. Furthermore, the outer ring of the other rolling bearing 110 (the right bearing in FIG. 3) is press-fitted and fixed in a state in which the outer surface (the axially outer side surface that is not opposed) abuts the side surface of the housing 101. The rolling bearings 110 and 110 have an outer diameter of 24 mm, an inner diameter of 8 mm, and an outer ring width of 11 mm.

  Under the environment of 100 ° C., the rotating shaft 102 was rotated at a rotational speed of 90000 rpm while applying a radial load 44N, and the time until seizure occurred on the rolling bearing 110 (the left bearing in FIG. 3) was measured. The outer ring temperature was measured, and it was determined that seizure occurred when the temperature increased by 10 ° C. from the temperature at the start of the test. And when it did not generate | occur | produce seizure even if it rotated for 100 hours, it was set as the pass, and when seizure occurred by rotation for less than 100 hours, it was set as the failure.

  Table 1 shows the preload applied to the rolling bearing 110, the groove radius of the raceway groove provided in the inner ring as the rotating wheel, the rotation time until seizure occurs, and the PV value. The groove radius is shown as a relative value when the diameter of the ball as the rolling element is 1.

  As can be seen from Table 1, the test No. with a PV value greater than 2400 MPa · m / s. 1 and test no. No. 2 rolling bearing was rejected, and the PV value was 2400 MPa · m / s or less. 3, test no. 4 and test no. The rolling bearing of 5 passed.

FIG. 4 is a graph showing the results of calculating the relationship between the preload and the PV value in each test bearing. In addition, Ri in FIG. 4 is a groove radius (relative value when the diameter of a ball as a rolling element is 1).
As shown in FIG. 4, when the groove radius of the raceway groove provided in the inner ring is small, the PV value becomes large, and seizure is likely to occur due to frictional heat between the rolling elements and the raceway surface of the inner ring. Also, if the preload is increased, the surface pressure between the rolling elements and the raceway surface of the inner ring will increase, leading to the generation of noise and the reduction of bearing life. It is not desirable to increase the preload (more than the amount).

FIG. 5 is a graph showing the relationship between the PV value and the durability time (rotation time until seizure occurs). From FIG. 5, it can be seen that if the PV value is 2400 MPa · m / s or less (preferably 2000 MPa · m / s or less), seizure does not occur even when rotated for 100 hours. On the other hand, if the PV value is too small, the bearing rigidity is lowered and the bearing is displaced, so that the impeller and the housing may interfere with each other. Therefore, the PV value is preferably 1720 MPa · m / s or more.
Therefore, the life of the rolling bearing can be extended by applying an appropriate preload at a limit PV value or less in each test bearing.

DESCRIPTION OF SYMBOLS 1 Housing 2 Rotating shaft 10 Rolling bearing 11 Inner ring 12 Outer ring 13 Rolling element

Claims (2)

A housing, a shaft inserted into the housing, and a plurality of rolling elements between an inner ring and an outer ring are rollable, and the shaft is disposed between the housing and the shaft so that the shaft is attached to the housing. A rolling bearing device that is rotatably supported relative to the rolling bearing device,
The rolling bearing has a limit PV value of 1720 MPa · m / s to 2400 MPa · m / s, and the rotation bearing has a PV value of 1720 MPa · m / s to 2400 MPa · m / s and the limit PV value. A rolling bearing device in which a preload is applied to the rolling bearing as described below.   2. The rolling bearing according to claim 1, wherein the rolling bearing is a ball bearing, and a groove radius of the raceway groove provided in the inner ring is 54% or more and 58% or less of a diameter of the ball that is the rolling element. apparatus.

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