JP2003139144A - Multipoint contact ball bearing and pulley for automobile accessory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multipoint contact ball bearing which securely supports a moment load without causing abnormal heat and lubricant deterioration in use under high temperature conditions. SOLUTION: In the multipoint contact ball bearing 11 having four-point or three-point contacts, the curvature of radius of a first groove 12a providing a first contact point is made different from the curvature of radius of a second groove 12b for providing a second contact point, each groove formed in at least one of an inner ring 12 or an outer ring 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multipoint contact ball bearing suitable for supporting a pulley for an automobile accessory such as an electromagnetic clutch for a car air conditioner compressor driven by a belt.

[0002]

2. Description of the Related Art When a pulley as described above is supported by a bearing, the center position in the width direction of the belt wound around the pulley and the center position in the axial direction of the bearing may deviate from each other. In this case, the tension of the belt gives a radial load to the bearing and, at the same time, gives a moment load proportional to the amount of the offset. The moment load acts to incline the pulley with respect to the support shaft. Here, if the pulley is largely tilted, the belt is unevenly worn, which causes early damage of the belt. Further, in the case of the electromagnetic clutch, if the displacement or inclination of the pulley becomes large, a certain gap between the clutch members required for the clutch OFF state cannot be secured. If the gap between the clutch members becomes large, malfunction of the electromagnetic clutch occurs. Conversely, if the gap becomes small, problems such as collision of the members, wear, and abnormal noise occur. Therefore, a double row angular contact ball bearing with high rigidity has been conventionally used for such applications.

However, in recent years, in order to cope with the downsizing and cost reduction of automobiles, there is a tendency to use a single row of pulley supporting bearings. Since the double-row angular contact ball bearing has a larger width dimension than the single-row ball bearing, it is not suitable for the space-saving required in recent automobiles. Further, the double-row angular contact ball bearing is more expensive than the single-row ball bearing due to its structure and size.

As a single-row bearing for supporting a pulley, there is a movement to use a four-point contact ball bearing or a three-point contact ball bearing having high moment rigidity in order to suppress the displacement and inclination of the pulley as described above (for example, , JP-A-11-336795, JP-A-11-210766, JP-A-2000
-120668 gazette etc.).

There is also a tendency to use a four-point contact ball bearing or a three-point contact ball bearing from the viewpoint of suppressing abnormal noise generated when a double-row angular contact ball bearing is used (for example, Japanese Patent Laid-Open No. 9-119510). JP-A-9-126303, JP-A-2000-170752, etc.).

[0006]

However, in the above-mentioned four-point contact ball bearing and three-point contact ball bearing, Japanese Unexamined Patent Publication (Kokai) No. 11-21076.
As pointed out in Japanese Patent No. 6, gazette and 2 which are rolling elements
On a raceway ring that is in point contact, slippage is large due to the spin motion between the ball and the raceway, and problems such as excessive heat generation, seizure, and wear are likely to occur. Since the pulley supporting bearing is used in the vicinity of the engine of an automobile, the temperature around the bearing becomes a considerably high temperature depending on the usage conditions. When the surroundings are high in temperature and the heat inside the bearing is high, it can be assumed that the temperature inside the bearing, especially within the contact ellipse between the balls and the inner ring raceway, locally becomes extremely high. It is conceivable that the lubricating grease inside the bearing deteriorates due to the exposure to this local high temperature, and the bearing eventually locks due to poor lubrication. In a pulley supporting multi-point contact ball bearing used under high temperature, there is a high possibility that the operating performance of the bearing will be impaired due to poor lubrication due to deterioration of grease before reaching the rolling fatigue life.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a multi-point contact ball bearing which can firmly support a moment load and does not cause abnormal heat generation and lubricant deterioration even when used at high temperatures. And to provide a pulley for an automobile accessory.

[0008]

The object of the present invention is achieved by the following constitution. (1) In a four-point contact or three-point contact multi-point contact ball bearing, the groove curvature radius of the first groove and the second contact point, which are formed on at least one of the inner ring and the outer ring, and which provide the first contact point The multi-point contact ball bearing is characterized in that the radius of curvature of the second groove providing the above is set to a different value. (2) The multipoint contact ball bearing according to (1), wherein the difference between the radius of curvature of the first groove and the radius of curvature of the second groove is 0.5% or more of the ball diameter of the rolling element. . (3) A pulley for an automobile accessory, which uses the multipoint contact ball bearing according to (1) or (2).

According to the above structure, by increasing the radius of curvature of one of the first groove and the second groove in at least one of the inner ring and the outer ring, the contact ellipse within the contact ellipse formed between the groove and the ball is formed. Since the slip is small, it is possible to suppress the local heat generation within the contact ellipse. Therefore, the lubricant is less deteriorated and can be used under high temperature.
Further, the displacement and inclination of the pulley can be suppressed smaller than when the radius of curvature of both the two grooves is increased (when the two grooves are symmetrical).

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an enlarged cross-sectional view of a main part showing the configuration of an automobile accessory pulley. This automobile accessory pulley 1 relates to an electromagnetic clutch for a car air conditioner compressor. This electromagnetic clutch transmits or interrupts the rotational power generated in the vehicle running engine to the compressor of the refrigeration cycle. As shown in FIG. 1, a rotary disk 4 is provided at the tip of a drive shaft 3 that rotatably projects from the center of the compressor housing 2, and an armature 6 is provided on the outer peripheral side of the rotary disk 4 via a flexible member 5. It is installed. A cylindrical shaft 2a is provided so as to be integrated with the compressor housing 2 so as to surround the periphery of the drive shaft 3, and an inner ring 12 of a four-point contact ball bearing 11, which is an example of a multi-point contact ball bearing, is provided on the outer peripheral surface thereof. It is fixed.

A rotor 7 is fitted on the outer ring 13 of the four-point contact ball bearing 11. A pulley 7a is integrally provided on the outer peripheral surface of the rotor 7. A belt 8 is wound around the outer peripheral surface of the pulley 7a as shown by an imaginary line. On the side surface of the rotor 7 opposite to the compressor housing 2 side, a friction surface 7b that contacts the armature 6 and transmits the rotational force by the friction force is formed. A recess 7d is provided on the side surface of the rotor 7 on the compressor housing 2 side. The electromagnetic coil 9 is housed in the recess 7d so as not to contact the rotor 7. The electromagnetic coil 9 is fixed to the compressor housing 2.

When the electromagnetic coil 9 is not excited, the friction surface 7b
There is a gap G between the armature 6 and the armature 6. When a current is applied to the electromagnetic coil 9, a magnetic field is generated, the armature 6 is attracted toward the electromagnetic coil 9 side against the elasticity of the flexible member 5, and comes into pressure contact with the friction surface 7b. As a result, the pulley 7a
Is transmitted via the armature 6, the rotating disk 4, and the drive shaft 3 so as to drive the compressor. The widthwise center position α of the belt 8 and the axial direction center position β of the bearing 11
Are offset by an offset amount δ, and a moment load acts on the bearing 11.

As shown in FIG. 2, the four-point contact ball bearing 11 has a plurality of balls 14 rotatably arranged between an inner ring 12 and an outer ring 13. Ball 1 on the outer surface of inner ring 12
A first groove 12a which provides a first contact point with 4 and a ball 14
And a second groove 12b which provides a second contact point with the inner ring raceway. Outer ring 1
The inner diameter surface of 3 is also provided with a first groove 13a that provides a first contact point with the ball 14 and a second groove 13b that provides a second contact point with the ball 14, by which the outer ring raceway is formed. Are formed. The cross-sectional shape of the outer ring raceway is a Gothic arch shape that contacts the ball 14 at a rest angle θ, and is symmetrical with respect to the axial centerline β of the bearing. The radius of curvature R _O1 of the first groove 13a of the outer ring 13 and the radius of curvature R _O2 of the second groove 13b are equal. The radius of curvature center P _{o1 of} the first groove 13a,
The curvature radius center P _{o2 of} the second groove 13b is at the same position in the radial direction,
Moreover, they are arranged at symmetrical positions that are separated from the center P of the balls 14 in the axial direction by the same distance. Center P of curvature radius of the first groove 13a
_o1 is arranged on the line La indicating the rest angle, and the second groove 13
The center of curvature P _o2 of b is arranged on the line Lb indicating the rest angle. The symbol Dp attached to the left side of FIG. 2 represents the pitch circle diameter, Do represents the diameter of the ball 14 (ball diameter),
P represents the center of the ball 14.

The radius of curvature R _i1 of the first groove 12a forming the inner ring raceway is larger than the radius of curvature R _i2 of the second groove 12b. The center of curvature P _{i1 of} the first groove 12a and the second groove 1
The center P _{i2 of the} radius of curvature of 2b is arranged at a position different in the radial direction and at a position different in distance from the center P of the ball 14 on the opposite side in the axial direction. The connection point (the apex of the inner ring raceway) 12c between the first groove 12a and the second groove 12b is displaced from the bearing axial center position β. The bearing 11 is assembled to the automobile accessory pulley 1 so that the connection point 12c is located on the widthwise center position α side of the belt 8 shown in FIG. Here, the curvature radius center P _i1 of the first groove 12a is arranged on the line Lb indicating the rest angle, and the curvature radius center P _i of the second groove 12b.
_i2 is arranged on the line La indicating the rest angle. However, the present invention is not limited to this, and for example, the rest angle of the inner ring 12 is
The rest angle of the outer ring 13 may be different. For example, inner ring 1
The rest angle of 2 may be smaller than that of the outer ring 13.

The balls 14 are rotatably held by a cage 18. Sealing members 15 and 15 are provided on both sides of the ball 14 in the axial direction. The outer peripheral portion of the seal member 15 is fixed to a locking groove 17 provided on the inner diameter surface of the outer ring 13, and the inner peripheral portion (lip portion) of the seal member 15 is a seal groove 16 provided on the outer diameter surface of the inner ring. Touches the side of. Grease lubrication can be adopted as the lubrication method.

By using the four-point contact ball bearing 11 as described above in the automobile accessory pulley 1, the first groove 12 of the inner ring 12 is formed.
The slip in the contact ellipse formed between a and the ball 14 becomes small, and local heat generation in the contact ellipse can be suppressed. Therefore, the lubricant is less deteriorated and can be used for a long time at high temperature.

FIG. 3 shows another example of the multi-point contact ball bearing.
A three-point contact ball bearing 11 'is shown. As shown in FIG. 3, a first groove 12a and a second groove 12b are provided on the outer diameter surface of the inner ring 12, and these form an inner ring raceway. On the other hand, the inner ring surface of the outer ring 13 is formed with an outer ring track 13d that contacts the ball 14 at a single contact point. Other configurations can be the same as the ball bearing 11 shown in FIG.

Operation when a radial load is applied to a conventional four-point contact ball bearing having a Gothic arch shape in which both the inner ring raceway and the outer ring raceway are symmetrical with respect to the axial centerline β as shown in FIG. The state was simulated by computer analysis. Table 1 shows the conditions used for the analysis. The radial load was applied at a position (α in FIG. 1) axially displaced (offset) by 4.35 mm from the bearing center (β in FIGS. 1 to 3).

[0019]

[Table 1]

The method described in "Performance analysis of four-point contact ball bearing" (Taniguchi, Aramaki, Masada; Tribology Society of Japan, Tribology Conference Spring Tokyo 1996 Proceedings) was adopted as the analysis method. It is reported that the friction torque of the bearing calculated by this analysis agrees with the experimental torque measurement result. Here, attention is paid to the maximum PV value obtained by calculation. The PV value is a parameter often used as an index of heat generation and wear at the contact point between the ball and the inner and outer ring raceways (for example, JP-A-11-
No. 210766, etc.). The contact point between the ball and the orbit actually becomes a surface having an area represented by an ellipse in the Hertzian contact theory due to elastic deformation of the surface. The PV value is the product of the surface pressure P in the contact surface and the sliding speed V. In the analysis, the PV value is calculated within the contact surface between each ball and each orbit. A value μPV obtained by multiplying a PV value by a sliding friction coefficient μ between surfaces is a friction loss (= heat generation) due to a slip per unit area / unit time.

FIG. 5 shows the result of computer analysis of the maximum PV value at each contact point of the ball 54 when a radial load of 1000 N was applied to the four-point contact ball bearing 51 of FIG. As shown in FIG. 5, the PV value on the inner ring raceway (first groove) on the side closer to the position of the radial load applied to the outer ring 53 was larger than at other contact points.

Regarding the grease deterioration under high temperature which deteriorates the durability of the bearing, it is considered that local heat generation such as one ball or one contact ellipse and temperature rise influence. Therefore, by suppressing the sliding heat generation represented by the PV value as small as possible, it is possible to extend the life of the pulley bearing used under high temperature.

In order to suppress the PV value, it is effective to reduce the slip velocity V in the contact ellipse. By increasing the radius of curvature of the groove of the track and decreasing the size of the contact ellipse, the slip velocity V can be suppressed to a small value.
Therefore, the calculation was performed by changing only the radius of curvature of the first groove of the inner ring 52. The result of this calculation is shown in FIG. The groove curvature radii of the first groove and the second groove of the outer ring 53 and the second groove of the inner ring 52 are the same as the conditions in Table 1. Radial load is 1000
Regardless of N and 2000 N, when the radius of curvature of the inner ring first groove was increased, the maximum PV value at the contact point decreased. Therefore, local heat generation is reduced, and the effect of extending the durability time can be expected.

Although there are various theories regarding the limit of the PV value, the inventors' research shows that the calculated PV value is 1.5 to 2.0 GPam.
If it exceeds / s, it is known that the wear of the raceway surface becomes a problem (JP-A-11-210766). From the calculation results for the radial load of 2000 N, the groove curvature radius of the inner ring first groove is 52% or more of the ball diameter, that is, the groove curvature of the inner ring first groove and the inner ring second groove (groove curvature radius = 51.5% of the ball diameter). If the difference in radius is 0.5% or more of the ball diameter, the PV value is 2.
Below 0 GPam / s, problems such as abrasion are less likely to occur. Further, the radius of curvature of the first groove of the inner ring is set to 5 of the ball diameter.
If the difference in the radius of curvature between the inner ring first groove and the inner ring second groove is 3% or more of the ball diameter, the PV value is 1.5% or more.
It will be GPam / s or less, and it can be expected that problems due to track wear will not occur.

In an actual bearing, if the radius of curvature of the groove is excessively increased, the pressure at the contact point increases, which may shorten the rolling fatigue life. It is considered that the groove radius of curvature taken up in the present invention has an upper limit determined from the viewpoint of rolling fatigue life. From this viewpoint, the upper limit of the radius of curvature of the groove is preferably 60% of the ball diameter. Also,
Considering the mounting on pulleys and automobile accessories, bearings with different groove curvature radii in the first groove and the second groove should be installed in the correct direction with respect to the offset load direction. It is preferable to display an identification mark indicating.

If only the PV value at the contact point and heat generation are to be suppressed, the radius of curvature of the groove can be increased in the four-point contact ball bearing having the cross section in which the first groove and the second groove are symmetrical as shown in FIG. It is valid. That is, for example, in the inner ring, a method of increasing both the radiuses of curvature of the first groove and the second groove can be considered. This method is compared with the method of the present invention using an asymmetric groove.

FIG. 7 shows a radial load when only the radius of curvature of the inner ring first groove is changed and when the radius of curvature of both the inner ring first groove and the second groove is changed while being matched. It shows the result of analyzing the maximum PV value at the contact point of the ball at the position by a computer (radial load 100
0N). It is understood that when the radius of curvature of the groove is increased, the maximum PV value similarly decreases in both cases, heat generation is suppressed, and grease deterioration is prevented. However, the maximum PV value is larger when only the radius of curvature of the inner ring first groove is changed than when it is changed while keeping the radius of curvature of both the inner ring first groove and the second groove matched. Therefore, it can be said that the method of the present invention is advantageous.

FIG. 8 shows the axial displacement of the pulley outer diameter portion (φ110 mm) when the radius of curvature of the groove is changed in the same manner as described above (radial load 1000 N). When only the radius of curvature of the inner ring first groove is changed, the movement amount of the pulley outer diameter portion does not change much. On the other hand, the inner ring first groove,
It can be seen that when the radius of curvature of the second groove is changed together to form an inner ring having a symmetrical cross section, the displacement of the pulley outer diameter portion also increases when the radius of curvature of the groove is increased. The large displacement of the outer diameter portion of the pulley on which the belt is applied is not preferable because it causes uneven wear of the belt and malfunction of the clutch in the case of an electromagnetic clutch. Increasing the radius of curvature of one of the two grooves of the inner ring of the four-point contact ball bearing, which generates a large amount of slip heat, compared to the other groove allows the rigidity of the pulley bearing to be maintained while maintaining the local contact ellipse. It suppresses slip heat generation and has a great effect on extending the bearing durability time.

The function and effect of the present invention has been described above for the inner ring of the single-row four-point contact ball bearing. Similarly, for the two grooves on the outer ring, by making the groove curvature radius of the groove with the larger slippage larger than the groove curvature radius of the other groove, local heat generation is suppressed and grease deterioration is reduced. Has the effect of Also in the three-point contact ball bearing shown in FIG. 3, it is possible to reduce the spin slip by reducing the radius of curvature of the two grooves on the bearing ring that come into contact with the ball at two points. It has the effect of suppressing heat generation. Therefore, the present invention is also effective when applied to a three-point contact ball bearing.

[0030]

As described above, according to the multi-point contact ball bearing according to the present invention, it is possible to suppress the local heat generation on the raceway and prevent the deterioration of grease and the shortening of the service life due to wear.
In addition, an automobile accessory pulley to which this multi-point contact ball bearing is applied has a configuration in which the multi-point contact ball bearing enables local suppression of heat generation and extension of durability time while maintaining a predetermined rigidity. Therefore, it is possible to improve not only the reliability of the automobile accessory pulley itself, but also the reliability of the automobile.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a main part showing a configuration of an automobile accessory pulley that is an embodiment of the present invention.

FIG. 2 is a sectional view showing a first example of a multi-point contact ball bearing.

FIG. 3 is a sectional view showing a second example of a multi-point contact ball bearing.

FIG. 4 is a schematic sectional view showing positions of contact points between a ball and a track in a conventional product.

FIG. 5 is a characteristic diagram showing a relationship between a position of a contact point between a ball and a track and a maximum PV value.

FIG. 6 is a characteristic diagram showing a relationship between a groove curvature radius and a maximum PV value.

FIG. 7 is a characteristic diagram showing a relationship between a groove curvature radius and a maximum PV value.

FIG. 8 is a characteristic diagram showing a relationship between a groove curvature radius and an axial movement amount of a pulley outer diameter portion.

[Explanation of symbols]

1 Automobile accessory pulley 7a Pulley 8 Belt 11 Four-point contact ball bearing (multi-point contact ball bearing) 12 Inner ring 12a First groove 12b Second groove 14 Ball

Claims (3)

[Claims] 1. In a multi-point contact ball bearing of four-point contact or three-point contact, a groove radius of curvature of a first groove formed in at least one of an inner ring and an outer ring and providing a first contact point, and a second groove. A multi-point contact ball bearing, characterized in that the radius of curvature of the second groove that provides the contact point has a different value. 2. The multipoint contact ball according to claim 1, wherein the difference between the radius of curvature of the first groove and the radius of curvature of the second groove is 0.5% or more of the ball diameter of the rolling element. bearing. 3. A pulley for an automobile accessory, which uses the multi-point contact ball bearing according to claim 1 or 2.