JPH0772565B2 - Vehicle alternator - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle alternator.

Conventional technology and its problems Conventional high-carbon chromium bearing steel (SUJ2) is standard-quenched and tempered material is used for the inner and outer rings of the bearings of conventional vehicle alternators (alternators).

In recent years, in response to needs for improving fuel efficiency of vehicles and increasing various electric loads, alternators have been required to be compact, lightweight, and have high output. To meet this requirement, the pulley ratio has been increased and the alternator has been used at high speeds, and the maximum speed has exceeded 12000 rpm.

As a problem for high-speed rotation, there is belt slip outside the alternator, but this problem was solved by increasing the number of belts and increasing belt tension. On the other hand, as a problem inside the alternator, it is necessary to make the bearing capable of withstanding such high speed rotation and high tension accompanied therewith. In other words, a bearing that can solve the problem of shortening the grease life due to the increase in stirring heat due to high-speed rotation and friction heat due to high tension, and can prevent large vibrations that occur during high-speed rotation due to deformation of the raceway surface due to high tension Has become necessary. Generally, in order to satisfy only high speed rotation, reducing the bearing size is an effective means for reducing the amount of heat generation. However, in the case of bearing a high tensile load such as an alternator bearing, reducing the size reduces the load capacity and shortens the fatigue life.
The thing of about mm is used.

As described above, in order to reduce the size and weight of the alternator, and to increase the speed and tension required for higher output, it is necessary to simultaneously solve the contradictory problems of heat generation suppression and high load countermeasures and the problem of vibration reduction. However, this is difficult with the conventional alternator as described above.

The object of the present invention is to solve the above problems, to reduce the size and weight,
It is an object of the present invention to provide an automotive alternator capable of increasing the speed required for higher output and accompanying higher tension.

Means for Solving the Problems In a vehicle AC generator according to the present invention, a rotating shaft of a rotor is rotatably supported by a frame provided with a stator via a pair of bearings, and protrudes outside the frame. In the vehicular AC generator in which a drive pulley is provided at the end of the rotating shaft, at least the outer ring of the bearing on the pulley side of the inner ring and the outer ring of the pair of bearings has a residual austenite amount of 0.05.
% Or more and less than 10% of steel to prevent plastic deformation of the raceway surface due to decomposition of retained austenite under the raceway surface.

When the amount of retained austenite is 10% or more, plastic deformation of the raceway surface is likely to occur, and vibration generated at high speed becomes large. If the amount of retained austenite is less than 0.05%, sufficient hardness required for the bearing ring of the bearing rotating at high speed cannot be obtained. That is, when quenching and tempering steel, the higher the tempering temperature, the less retained austenite and the more martensite. However, if the tempering temperature becomes too high, the structure of martensite becomes relatively soft, and the amount of retained austenite increases.
If the tempering temperature is less than 0.05%, a relatively large amount of martensite is relatively soft and sufficient hardness cannot be obtained.

Embodiment FIG. 1 shows an alternator for a vehicle.

A pair of frames that form the outer shell of an alternator (10) (11)
Has a bowl shape and is fixed to each other by a plurality of sets of bolts and nuts. A stator (12) is fixed to the inner circumference of the frame (10) (11) by an appropriate method such as press fitting. The stator (12) is connected to the stator core (12
It is a known one composed of a) and a stator coil (12b) wound around it.

Cylindrical bearing boxes (10a) (11a) projecting inward are formed at the center of each frame (10) (11). Radial ball bearings (13) and (14) are attached to the bearing boxes (10a) and (11a), respectively, and a rotary shaft (15) is rotatably supported by these bearings (13) and (14). A pair of claw pole cores (16a) (16b) are mechanically fixed to the shaft (15) so as to be located inside the stator (12), and a rotor coil (17) is held between them. ing. Then, the shaft (15), pole core (16a) (16
A known rotor (rotor) (18) is constituted by b) and the rotor coil (17).

Pole core (16a) of the first bearing (13) and rotor (18)
A collar (19) is fitted around the axis (15) between
A pulley (20) located outside the frame (10) (11) is fixed by a nut (21) to the end of the shaft (15) protruding from the bearing (13) of the frame to the outside of the frame (10). . Then, the shaft (15) is rotated by an engine (not shown) via the pulley (20).

Of the inner ring and outer ring of the pair of bearings (13) (14), at least the outer ring of the bearing (13) on the pulley (20) side is made of steel having a residual austenite content of less than 10%.

In normal quenching and tempering, austenite remains on average 11 to 14%, but as a method of reducing this to 10% or less, there is a method of applying a Zabu zero treatment between quenching and tempering. Further, as another method, the amount of retained austenite can be reduced by raising the tempering temperature to 250 to 380 ° C. as compared with the normal temperature of 150 to 200 ° C.

FIG. 2 shows the relationship between the amount of retained austenite and the rolling frictional force. The rolling friction force ratio in FIG. 2 is shown as 1 when the contact surface pressure is 250 kgf / mm ² and the residual austenite amount is 10%. The relationship between the amount of retained austenite and the yield strength is shown in FIG. The proof stress shown in FIG. 3 is shown for a strain of 5 × 10 ⁶ strain. Since austenite has a lower yield strength than martensite, the raceway surface that receives a load when the ball passes through has a large amount of austenite, which deforms and the ball rolls in the recess. , The frictional force becomes large. Therefore, conversely, by reducing the amount of austenite, it is possible to suppress an increase in the amount of heat generated inside the bearing due to the speeding up and increasing the tension of the alternator, and to improve the durability life against grease seizure. Also, if the amount of retained austenite is large,
Due to the increase in load due to the high tension, plastic deformation is likely to occur in the track, and vibration is generated every time the ball passes through this uneven recessed portion during rotation. Especially when used in high-speed rotation, this vibration becomes even larger, and in the worst case, the rotor and the stator may interfere with each other, causing locking. It is effective to reduce the amount of retained austenite against such plastic deformation.

In order to demonstrate the above effect by reducing the amount of retained austenite, an example evaluated using a radial ball bearing will be shown.

First, as the pulley side bearing of the alternator, four kinds of samples using the materials shown in Table 1 for the inner ring and the outer ring, that is, Comparative Examples and Examples 1 to 3 were prepared. Further, as the bearing on the opposite side (rear side), a sample was prepared in which the same material as in the comparative example was used for the inner ring and the outer ring.

Comparative Example A current bearing was used as a reference for effect comparison. the material is,
SUJ2 is a commonly used bearing material. The quenching heating temperature was 845 ° C, and after oil quenching, tempering treatment was performed at 180 ° C.

Example 1 The material is SUJ2 as in the comparative example. After quenching and heating at 845 ° C and oil cooling, tempering treatment was performed at 350 ° C.

Example 2 The material is SUJ2 as in the comparative example. After quenching heating at 845 ℃ and oil cooling, subzero treatment at -60 ℃
A tempering treatment was performed at 0 ° C.

Example 3 The material is SUJ2 as in the comparative example. After quenching and heating at 845 ° C and oil cooling, sub-zero treatment was performed at -196 ° C, then 2
A tempering treatment was performed at 00 ° C.

The amount of retained austenite was measured by the X-ray diffraction method in the radial direction on the raceway surface of the bearing up to a depth of 0.2 mm. For the bearing size, the pulley side bearing is model number 6302 (outer diameter 42 mm) and the rear side bearing is model number 6002 (outer diameter 32 mm).
mm).

The above sample was incorporated into an alternator and a high speed, high tension test was performed. The test conditions are as follows.

Belt tension: 100 kgf Inner ring speed: 12000 rpm Atmosphere temperature: 70 ° C Table 2 shows the test results.

The breakage occurred only in the comparative example, the form of which was the baking life, the grease was carbonized, the inner and outer rings and the balls were greatly discolored, and the retainer was broken, which caused rotation lock. Moreover, this breakage occurred only in the bearing on the pulley side. This is because the pulley side bearing is
Since it is close to the pulley, the moment load it bears is large,
Therefore, the temperature rise is also high.

Although none of Examples 1 to 3 was destroyed, an infrared spectroscopic analysis was performed on grease deterioration to investigate the difference in oxidative deterioration degree. As a result, in Examples 1 and 3, almost no deterioration was observed, and only Example 2 was deteriorated.

Further, in the comparative example, when the temperatures of the inner ring and the outer ring were measured under the test conditions, it was confirmed that the temperature of the outer ring was higher than that of the inner ring by 8 to 12 ° C. This is because the inner ring is connected to the rotor, and this rotor is used at a higher speed than before, so the effect of the fan is sufficient for self-cooling and the temperature of the inner ring is kept below that of the conventional one. On the other hand, since the outer ring is assembled to the frame to which the stator whose heat generation amount is increased due to the high output is attached, it is shown that the temperature is higher than before due to the increase in heat transfer amount from this stator. .

FIG. 4 shows an example of the result of investigation on a change in vibration with the lapse of test time by mounting a vibration acceleration sensor on the frame. In this test, no fracture mode was observed in which the rotor and the stator interfered with each other and locked, but it was confirmed that the vibration level of the comparative example was high, so that the one with a large amount of retained austenite had a large plastic deformation. It is estimated that

As described above, by using the bearings of Examples 1 to 3 in which the amount of retained austenite is reduced in the alternator, it is possible to increase the speed and tension of the alternator.

Conventionally, some bearings used in precision measuring instruments and the like have been subjected to sub-zero treatment for the purpose of suppressing dimensional change due to decomposition of austenite. On the other hand, in the present invention, rather than focusing on such dimensional stability, focusing on the characteristics of the retained austenite itself, by combining a bearing with a reduced retained austenite amount with an alternator, it is possible to reduce the size and weight, It was possible to create a completely new effect of output.

A carburizing material such as SAE5120 may be used as the material of the bearing, and the Zabu zero treatment may be performed after the carburizing and quenching. In this case, since compressive residual stress is added compared to the case of SUJ2,
It is also effective for fatigue life. Therefore, it is possible to deal with the case where the tension is increased in order to rotate at a higher speed.

Effects of the Invention According to the vehicle alternator of the present invention, as described above,
By reducing the amount of retained austenite, it is possible to prevent plastic deformation of the raceway surface. And thereby, it is possible to prevent the occurrence of uneven recesses on the raceway surface, to reduce the vibration, and to reduce the rolling friction force,
It is possible to suppress heat generation. Therefore, it is possible to increase the speed and increase the tension, and thus to reduce the size and weight and the output.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention, FIG. 2 is a graph showing a relationship between residual austenite amount and rolling friction force, FIG. 3 is a graph showing a relationship between residual austenite amount and proof stress, and FIG. Is a graph showing changes in vibration level with the lapse of test time. (10) (11) ... frame, (12) ... stator, (13) (1
4) ... Bearing, (15) ... Rotary shaft, (18) ... Rotor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Tozozo Aichi Prefecture, Kariya City, 1-1, 1-1 Showa-cho, Nihon Denso Co., Ltd. (72) Inventor Shiga, Aichi Prefecture, Kariya City, 1-1, Showa-cho Co., Ltd. (72) Inventor Masayuki Kitamura, 2 Nishinomachi Nishinomachi, Minami-ku, Osaka City, Osaka Prefecture Koyo Seiko Co., Ltd. (72) Yoshiki Fujita 2, Nishinocho-cho, Minami-ku, Osaka City, Osaka Koyo Seiko Co., Ltd. In-house (56) References JP-A-56-34615 (JP, A)

Claims (5)

[Claims] 1. A rotary shaft of a rotor is rotatably supported by a frame provided with a stator via a pair of bearings, and a drive pulley is provided at an end of the rotary shaft protruding outside the frame. In the vehicle alternator, at least the outer ring of the bearing on the pulley side of the inner ring and the outer ring of the pair of bearings has a residual austenite amount of 0.05.
% Of less than 10% of steel, which prevents plastic deformation of the raceway surface due to decomposition of retained austenite under the raceway surface. 2. The amount of retained austenite is 0.05% or more 6
% Or less, The vehicle alternator according to claim 1. 3. The vehicle alternator according to claim 1 or 2, wherein the amount of retained austenite is reduced by subzero treatment. 4. The vehicular AC generator according to claim 1 or 2, wherein the retained austenite amount is reduced by performing a tempering treatment at a temperature of 250 to 380 ° C. 5. The vehicle alternator according to any one of claims 1 to 4, wherein the steel is a carburized and quenched material.