JP2002114004A - Bearing device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing device for vehicle simplified in the structure of a caulking part when assembling a constant velocity joint into a hub unit. SOLUTION: A shaft part 4 of a constant velocity joint 3 is spline-fitted in an insertion hole 2 of a hub unit 1 supported by a double row rolling bearing 5 on the car body side, and a vehicle inner side end of the hub unit 1 is caulked to a vehicle inner side end surface of an inner ring 20 of the bearing 5 after enlarging the diameter of the vehicle inner side end part of the hub unit 1, and cross sectional shape of the caulking part along the shaft center 6 direction on the vehicle inner side is formed into a convex surface projected to the vehicle inner side. When connecting the shaft part 4 to the hub unit 1 while making the shaft part 4 relatively come close to the hub unit in the shaft center direction, a flat end surface of the constant velocity joint 3 opposite to the hub unit 1 is made to abut on the convex surface so as to push the convex surface toward the vehicle outer side, and the convex surface is finely and plastically deformed into a flat surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle bearing device to which a disk rotor and wheels of a disk brake device in a vehicle such as an automobile are attached.

[0002]

2. Description of the Related Art Conventionally, as a vehicle bearing device of this type, a hub unit for mounting a wheel rotatably supported on a double row rolling bearing supported on a vehicle body side around an axis, and a hub unit for the hub unit are provided. A constant-velocity joint, which is provided at one end with a shaft portion that is spline-fitted from the vehicle inner side into an insertion hole formed along the axis, and that is connected to the other end side such that the drive shaft can be tiltably linked to the hub unit. Are well known.

In the hub unit, a double row rolling bearing for rotatably supporting the hub unit on the vehicle side is disposed at a position on the vehicle inner side. In some cases, the inner ring of the double row rolling bearing is used separately from the hub unit.In this case, the inner ring and the hub unit are integrally fixed so that the inner ring does not come off from the hub unit in the fixed state. In order to do so, conventionally, the inner end of the cylindrical hub unit having a through hole and having a vehicle inner side is expanded in diameter, and the expanded portion is connected to the inner ring from the vehicle inner side. The thing which made it close is known. Furthermore, the position regulation of the constant velocity joint, in which the shaft portion was spline-fitted into the insertion hole of the hub unit, toward the vehicle outer side, was achieved by contacting the constant velocity joint with the caulked portion, which was the enlarged diameter portion where the caulking was performed. It is done by letting it. Then, in order to stabilize the posture of the constant velocity joint with the contact, the flat surface perpendicular to the axis of the caulked part is cut in accordance with the flat end face of the constant velocity joint to which the caulked part is applied in advance. Those formed by processing or the like are well known.

[0004]

However, it is troublesome to form the caulked portion on a flat surface by cutting or the like, and the end face of the constant velocity joint is brought into contact with the caulked portion in the state of the flat surface. As the contact area between the constant velocity joint and the caulked portion increases, the force acting on the inner ring of the bearing from the caulked portion increases even if the caulked portion receives a small surface pressure from the constant velocity joint. However, there is a risk that the rolling element such as a ball or a roller may strongly contact the outer ring side due to the acting force, and there is a problem that the rolling friction of the rolling element may increase.

The present invention provides a vehicle bearing device which can simplify the structure of a caulking portion when assembling a constant velocity joint to a hub unit, and can prevent the rolling friction of a rolling element of a bearing from becoming unduly large. The purpose is to do.

[0006]

According to a first aspect of the present invention, there is provided a vehicle bearing device comprising: a wheel mounting hub unit rotatably supported around an axis on a double-row rolling bearing supported on a vehicle body side; A shaft portion that is spline-fitted from the vehicle inner side is provided at one end in an insertion hole formed along the axis in the hub unit, and a drive shaft is tiltable with respect to the hub unit at the other end. In addition to being constituted by a constant velocity joint interlockingly connected, an inner ring in the double row rolling bearing is arranged near the constant velocity joint, and a vehicle inner side end of the hub unit is provided on a vehicle inner side end face of the inner ring. A vehicle bearing device in which the hub unit and the inner ring are integrated after being expanded in diameter, wherein the inner ring is swaged from the vehicle inner side in the vehicle inner side in the axial direction. The cross-sectional shape is formed on a convex curved surface protruding toward the vehicle inner side, and when the shaft portion is moved toward the vehicle outer side in the axial direction relative to the hub unit and connected to the hub unit, The flat end surface of the constant velocity joint facing the hub unit side is brought into contact with the convex curved surface of the caulked portion and pressed toward the vehicle outer side, so that the convex curved surface is slightly plastically deformed to be a flat surface. Is a characteristic configuration.

According to the configuration of the first aspect of the present invention, it is not necessary to previously form a flat surface for restricting the end face of the constant velocity joint in the caulking portion by cutting or the like.
The labor such as cutting work can be omitted. Also, when caulking, the force acting on the inner ring of the double row rolling bearing from the caulking point should be set to such an extent that it can simply adhere to the caulking part, or a slight pressing force acts on the inner ring side somewhat more than that. In other words, even if the contact point with the end face of the constant velocity joint in the caulked portion is formed to be somewhat flat by plastic deformation, an unreasonably large force does not act on the inner ring side, so the rolling friction of the rolling element in the bearing Is maintained satisfactorily without becoming unduly large. Furthermore, when fixing the shaft portion of the constant velocity joint to the hub unit, the end surface of the constant velocity joint on the hub unit side is pressed against the caulked portion, and the convex curved surface of the caulked portion is plastically deformed to a somewhat flat surface. By doing so, the contact state of the constant velocity joint to the hub unit can be brought into surface contact over the entire circumference around the axis, so when steering the vehicle, the moment generated by the force transmitted from the wheels, that is, the axis, The contact between the double row rolling bearing and the constant velocity joint is the surface contact between the constant velocity joint and the relative moment between the bearing and the constant velocity joint. A large rotational displacement can be prevented.

According to a second aspect of the present invention, in the vehicle bearing device according to the first aspect, the vehicle outer side end of the shaft portion, which is spline-fitted into an insertion hole of the hub unit, is inserted. Project from the vehicle outer end of the hole,
The shaft portion is fixed to the hub unit by screwing and fastening a nut to a male screw portion formed on the projecting portion.

According to the configuration of the second aspect of the present invention, the shaft can be easily fixed to the hub unit by screwing and fastening the nut to the male screw portion of the shaft, so that the manufacturing is inexpensive. be able to.

A vehicle bearing device according to a third aspect of the present invention is the vehicle bearing device according to the first aspect, wherein the shaft portion, which is spline-fitted into an insertion hole of the hub unit, is on the vehicle outer side. A screw hole is formed at an end portion, and a bolt is screwed into the screw hole from the vehicle outer side, whereby the shaft portion is fixed to the hub unit.

According to the configuration of the third aspect of the present invention, the shaft can be easily fixed to the hub unit by screwing the bolt into the screw hole of the shaft. Can be.

A vehicle bearing device according to a fourth aspect of the present invention is the vehicle bearing device according to the first aspect, wherein the shaft portion is spline-fitted into an insertion hole of the hub unit on a vehicle outer side. An end portion is caulked to an end portion of the hub unit on the vehicle outer side, and the shaft portion is fixed to the hub unit.

According to the fourth aspect of the present invention, the shaft is fixed to the hub unit by a simple process of caulking the vehicle outer end of the shaft to the vehicle outer end of the hub unit. Therefore, it can be manufactured at low cost.

According to a fifth aspect of the present invention, there is provided the vehicle bearing device according to the second aspect, wherein the male screw portion forming portion in the projecting portion of the shaft portion has the constant velocity. The nut screwed into the protrusion while the shaft portion is spline-fitted into the insertion hole such that the end surface of the joint comes into contact with the convex curved surface of the caulked portion is regulated by the end surface of the hub unit. In addition to the screw forming portion for fastening to the position where the screw is formed, at least the screw forming portion required for screwing and tightening the nut more than the regulation position and slightly deforming the convex curved surface of the caulking portion into a flat surface. It is provided with a characteristic configuration.

According to the fifth aspect of the present invention, the shaft portion is spline-fitted into the insertion hole of the hub unit, and the flat end surface of the constant velocity joint on the vehicle outer side contacts the convex curved surface of the caulked portion. In this state, the nut is screwed into the male screw portion of the protruding portion at the vehicle outer side end of the shaft portion, so that the nut is restricted to the position where the position of the nut is restricted to the vehicle outer side end surface of the hub unit. It is fastened to the male screw part of the protruding part, and furthermore, since the male screw part is provided with a screw forming part so that the nut can be screwed and fastened, the nut is fastened to the screw forming part As the shaft part is pulled toward the vehicle outer side, the caulked part is slightly deformed into a flat surface by the flat end surface of the constant velocity joint on the vehicle outer side, and it is swaged by a simple work of fastening the nut Place for department It is possible to form a flat surface.
In addition, as shown in FIG. 1, the length of the insertion hole 2 of the hub unit 1 in the vehicle inside and outside direction (the length from the rear end of the caulking portion 23 before fastening the nut to the end surface of the insertion hole 2 on the vehicle outer side). Also, by setting the length from the end surface 24 of the shaft portion of the constant velocity joint to the formation of the male screw portion 25 to be small, it is possible to use a small nut to tighten the caulked portion without using a special nut. Flattening can be achieved at low cost. That is, the length of the insertion hole 2 of the hub unit 1 in the vehicle inside and outside direction is the same as the length from the end face 24 of the shaft portion of the constant velocity joint to the formation of the male screw portion 25, or the former length. If the length is shorter than the latter length, a special nut such as a cap nut must be used, which leads to an increase in cost, but this point can be solved.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention.
And an example of an embodiment according to claim 2 is shown.

As shown in FIG. 1, a shaft portion 4 of a constant velocity joint 3 is spline-fitted into an insertion hole 2 of a hub unit 1 for mounting wheels, and the hub unit 1 is a multi-piece supported on the vehicle body side. A row rolling bearing 5 is rotatably supported around an axis 6.

A mounting flange 7 is formed on the outer peripheral surface of the hub unit 1 so as to protrude outward in the radial direction. A disk rotor of the disk brake device and the wheels (not shown) are provided at several places around the mounting flange 7. A mounting bolt 8 for fixing is penetrated.

The constant velocity joint 3 includes a hub unit 1
The drive shaft 9 is connected to the drive shaft 9 in such a manner that the drive shaft 9 can be tilted relative to the drive shaft 9. The specific configuration of the constant velocity joint 3 includes a ball 10 for tilting and guiding the hub unit 1 with respect to the drive shaft 9, an inner ring 11 and a retainer 1 for the ball 10.
Bowl-shaped guide part (hereinafter referred to as outer ring) 1 in which 2 and the like are stored
3 and the shaft portion 4 integrally connected to a small diameter side (outer vehicle side) of the outer ring 13. In FIG. 1, the small-diameter side end surface of the outer race 13 is in contact with the vehicle inner-side end surface of the hub unit 1.

Reference numeral 14 denotes a sealing boot for sealing the constant velocity joint 3. One end covers the open side of the outer ring 13 of the constant velocity joint 3, and the other end covers the middle of the drive shaft 9. Have been.

The double row rolling bearing 5 has a plurality of balls 15 and 16 as rolling elements arranged in two rows, and these balls 15 and 16.
And two inner races 17, an inner race and an outer race 18. The hub unit 1 and the annular inner race member 20 fitted to the vehicle inner side of the hub unit 1 are used as the raceways of the inner race. . That is, one ball 15
The outer peripheral surface of the hub unit 1 is used as the raceway surface of the row,
The outer peripheral surface of the annular inner race member 20 is used as the raceway surface of the other 16 rows of balls. The outer race 1 of the double row rolling bearing 5
A radially outward mounting flange 21 which is bolted to a vehicle body or the like is formed on an outer peripheral surface of the vehicle body 8.

The outer race 18 of the double row rolling bearing 5 is arranged such that the outer end surface of the outer race 18 is close to the mounting flange 7 of the hub unit 1.

Further, the vehicle outer side and the vehicle inner side of the double row rolling bearing 5 and the hub unit 1 (the annular inner ring member 2)
0) is sealed with a contact-type sealing material 22.

As shown in FIG. 2, the hub unit 1 is fixedly held to the hub unit 1 by the annular inner ring member 20 as the inner ring of the double row rolling bearing 5 on the vehicle inner side.
The inner end of the vehicle is plastically deformed to expand the diameter, and then the expanded portion is swaged toward the inner side of the annular inner race member 20 to form the caulking portion 23. This caulking portion 23
When caulking, when the caulking is performed, the force acting on the inner ring of the double row rolling bearing from the caulking point is such that it can simply adhere to the caulking part, or a slight pressing force acts on the inner ring side slightly more As shown in FIG. 2, the end face of the caulking portion 23 on the vehicle inner side has a curved shape in which the cross-sectional shape along the direction of the axis 6 is convex toward the vehicle inner side. Then, the constant velocity joint 3 is formed without any processing of the end face while being swaged.
Of the outer ring 13 of the constant velocity joint 3 is in contact with the caulking portion 23, and then the shaft portion 14 is inserted. A nut 26 is screwed and fastened to a male screw portion 25 screwed to a projecting shaft portion as a projecting portion projecting from the end of the hole 2 on the outer side of the vehicle. The caulking portion 23 is pressed against the outer side of the vehicle body to make contact therewith.
3 is plastically deformed, and as shown in FIG. 3, is deformed into a flat surface corresponding to the end surface 24. However, the flat surface is formed by a force such that the ball 16 does not improperly contact the annular inner ring member 20 and the outer ring 18 with the pressing force applied from the caulking portion 23 to the annular inner ring member 20. Will be concluded. As a result, the vehicle outer side end surface 2 of the swaged portion 23 and the outer ring 13 is formed.
4 can be brought into surface contact with a predetermined area, and contact so as to have a contact surface having substantially the same width in the radial direction over the entire circumference centered on the axis 6. Therefore, when the vehicle is running, Even if the steering is performed, the steering can sufficiently withstand the moment generated in the annular inner race member 20 by the steering. As shown in FIG. 1, the protruding shaft portion on which the male screw portion 25 is formed has a portion which is smaller in diameter than the portion where the spline is formed at the vehicle outer side end portion of the shaft portion 4 and protrudes toward the vehicle outer side. Say. In a state where the shaft portion 4 is spline-fitted into the insertion hole 2 and the end surface 14 of the constant velocity joint 3 is in contact with the caulking portion 23, the axial center range of the male screw portion 25 formed on the protruding shaft portion is set. Is further tightened by tightening the nut 26 at the portion of the hub unit 1 located in the insertion hole 2 from the end position of the insertion hole 2 on the vehicle outer side in addition to the portion projecting toward the vehicle outer side from the insertion hole 2. Is set so that a minute flat surface can be formed.
Therefore, even if the nut 26 is fastened to the male screw portion 25 and the nut 26 is in contact with the hub unit 1 and its position is regulated, if the nut 26 is further screwed and fastened, the nut 26 connects the shaft 4 to the vehicle. By pulling to the outer side, the end face 24
The convex curved surface of the caulking portion 23 in contact with the plastic deformation is slightly plastically deformed into a flat surface.

Next, the constant velocity joint 3 is attached to the hub unit 1.
The procedure for assembling is described. First, the vehicle outer side of the shaft portion 4 of the constant velocity joint 3 is aligned with the insertion hole 2 and pushed into the insertion hole 2. Then, the insertion hole 2
The shaft unit 4 is spline-fitted to the hub unit 1
And the shaft portion 4 are integrally mounted rotatably around the shaft center 6. Next, when the nut 26 is screwed and fastened to the male screw portion 25, the constant velocity joint 3 itself comes close to the hub unit 1, and the end surface 24 of the constant velocity joint 3 becomes the curved surface of the caulked portion 23. Therefore, the contact portion of the caulking portion 23 with the end face 24 is slightly plastically deformed and flattened to the end face 24, and the line contact state becomes the surface contact state.

(Another Embodiment) Next, an example of another embodiment will be described below. The description of the same structure as in the above embodiment is omitted, and the same reference numeral is given.

As shown in FIG. 4, a shaft portion 4 of a constant velocity joint 3 is spline-fitted along an axis 6 into an insertion hole 2 formed in the hub unit 1. Unlike the above-described embodiment, the shaft portion 4 is formed in a tubular shape having a bottom on the vehicle inner side. Then, in order to fix the annular inner ring member 20 of the double row rolling bearing 5 that rotatably supports the hub unit 1 around the shaft center 6 to the hub unit 1, similarly to the above embodiment, the vehicle inner of the hub unit 1 is mounted. The diameter of the side end is increased by a caulking jig, and the annular inner ring member 20 is formed at the enlarged diameter portion.
Caulk. The caulking portion 23 has a protruding curved surface cross-sectional shape in the axial direction of the vehicle inner end surface, similar to the caulking portion 23 shown in FIG. 2 in the above embodiment. Then, the shaft portion 4 is spline-fitted into the insertion hole 2,
When the caulking portion 23 and the end surface 24 of the constant velocity joint 3 are in contact with each other, the vehicle outer end of the insertion hole 2 slightly projects from the vehicle outer end of the insertion hole 2. . Then, in order to fix the shaft portion 4 to the hub unit 1, the outer end of the shaft portion 4 is enlarged by a caulking jig, and the enlarged diameter portion 27 is inserted into the vehicle outer through the insertion hole 2 of the hub unit 1. Swage to the side edge. By this caulking, the outer ring 13 of the constant velocity joint is also changed to the hub unit 1.
As a result, the caulking portion 23 is pressed against the hub unit 1 by the end surface 24 of the constant velocity joint 3. As a result, the shape of the protruding curved surface of the caulked portion 23 is slightly plastically deformed to become a somewhat flat surface, similar to the caulked portion 23 shown in FIG. 3 in the above embodiment. As a result, the end surface 24 and the caulked portion 23 come into surface contact over the entire circumference in the circumferential direction centering on the axis 6, and between the hub unit and the outer ring 13 of the constant velocity joint 3 as the vehicle is steered. It can withstand the acting moment sufficiently.

(Another Embodiment 2) As shown in FIG.
In the same structure as that of the above embodiment, the vehicle outer end surface 2 of the outer race 13 of the constant velocity joint 3 is spline-fitted to the hub unit 1 and the convex curved surface of the caulking portion 23.
In a state where the shaft portion 4 is in contact with the vehicle, the vehicle outer side end surface of the shaft portion 4 is located at a predetermined distance inside the vehicle outer side end of the insertion hole 2 of the hub unit. One screw hole 27 is formed around the axis. A bolt 28 is screwed into the screw hole 27, and the bolt 28 is fastened so that the head of the bolt 28 is brought into contact with the end surface 29 of the hub unit 1 on the vehicle outer side. The constant velocity joint 3 is fixed to the hub unit 1. In the fastening of the bolt 28, even before the fastening of the bolt 28, since the vehicle outer end of the shaft portion 4, which is abutted against the caulking portion 23, is located in the insertion hole 2, the head of the bolt 28 is positioned at the end surface 29. Is further tightened than in the state of just contacting the
The end surface 24 of the outer race 13 in contact with the outer ring 13 slightly plastically deforms the caulked portion 23 to make a state of some surface contact.

[0029]

As described above, according to the vehicle bearing device of the first aspect of the present invention, the caulked portion is formed in a curved state, and the end surface of the constant velocity joint is formed on the caulked portion. In the contact state, the constant velocity joint and the caulked portion are in line contact with each other, but when the constant velocity joint is fastened with a screw member or the like so as to approach the hub unit, the caulked portion becomes Plastic deformation is performed according to the end face of the speed joint, and the caulked portion and the end face of the constant velocity joint are in surface contact, and there is no unduly rattling or gap between the hub unit and the constant velocity joint It will be. In addition, since the curved end edge at the time when the caulking is completed can be made into a flat surface state without further performing a cutting process or the like, labor for the processing can be omitted. Also, when caulking, the force acting on the inner ring of the double row rolling bearing from the caulking point should be set to such an extent that it can simply adhere to the caulking part, or a slight pressing force acts on the inner ring side somewhat more than that. In other words, even if the contact point with the end face of the constant velocity joint in the caulked portion is formed to be somewhat flat by plastic deformation, an unreasonably large force does not act on the inner ring side, so the rolling friction of the rolling element in the bearing Is maintained satisfactorily without becoming unduly large. Furthermore, when fixing the shaft portion of the constant velocity joint to the hub unit, the end surface of the constant velocity joint on the hub unit side is pressed against the caulked portion, and the convex curved surface of the caulked portion is plastically deformed to a somewhat flat surface. By doing so, the contact state of the constant velocity joint to the hub unit can be brought into surface contact over the entire circumference around the axis, so when steering the vehicle, the moment generated by the force transmitted from the wheels, that is, the axis, The contact between the double row rolling bearing and the constant velocity joint is the surface contact between the constant velocity joint and the relative moment between the bearing and the constant velocity joint. A large rotational displacement can be prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional plan view showing a bearing device for a vehicle.

FIG. 2 is an enlarged cross-sectional plan view of a main part before a power joint is assembled.

FIG. 3 is an enlarged cross-sectional plan view of a main part to which a power joint is attached.

FIG. 4 is a cross-sectional plan view showing a vehicle bearing device according to another embodiment.

FIG. 5 is a cross-sectional plan view showing a vehicle bearing device according to still another embodiment.

[Explanation of symbols]

 Reference Signs List 1 hub unit 2 insertion hole 3 constant velocity joint 4 shaft part 5 double row rolling bearing 6 shaft center 9 drive shaft 20 annular inner ring member (inner ring) 23 caulking part 24 end face 25 male screw part 26 nut 27 screw hole 28 bolt

Continued on the front page (72) Inventor Yoshifumi Shige 3-5-8 Minamisenba, Chuo-ku, Osaka-shi Koyo Seiko Co., Ltd. F-term (reference) 3J017 AA02 BA10 DB08 3J101 AA02 AA32 AA43 AA54 AA62 AA72 FA60 GA03

Claims (5)

[Claims] 1. A hub unit for mounting a wheel rotatably supported on a double row rolling bearing supported on a vehicle body side around an axis, and an insertion hole formed in the hub unit along the axis. A shaft portion that is spline-fitted from the vehicle inner side is provided at one end, and a drive shaft is provided at the other end side with a constant velocity joint that is interlockably connected to the hub unit so as to be tiltable with respect to the hub unit. A vehicle in which an inner ring is arranged near the constant velocity joint, and the hub unit and the inner ring are integrated with each other by expanding a diameter of a vehicle inner side end portion of the hub unit on a vehicle inner side end surface of the inner ring. A bearing device, wherein the inner ring is swaged from the vehicle inner side, and the cross-sectional shape along the axial direction of the vehicle inner side of the caulking portion is formed as a convex curved surface protruding toward the vehicle inner side. When the shaft portion is moved relative to the hub unit in the axial direction toward the vehicle outer side and connected, the flat end face of the constant velocity joint facing the hub unit side is caulked. A bearing device for a vehicle, wherein the convex curved surface is flattened by being slightly plastically deformed by being brought into contact with the convex curved surface of the portion and pressed toward the vehicle outer side. 2. The vehicle bearing device according to claim 1, wherein a vehicle outer side end of the shaft portion, which is spline-fitted into the insertion hole of the hub unit, is a vehicle outer side end of the insertion hole. A bearing device for a vehicle, wherein the shaft portion is fixed to the hub unit by further projecting and screwing and fastening a nut to a male screw portion formed at the projecting portion. 3. The vehicle bearing device according to claim 1, wherein a screw hole is formed at a vehicle outer side end of the shaft portion spline-fitted into the insertion hole of the hub unit,
A vehicle bearing device, wherein the shaft portion is fixed to the hub unit by screwing a bolt to the screw hole from the vehicle outer side. 4. The vehicle bearing device according to claim 1, wherein a vehicle outer end of the shaft unit, which is spline-fitted into an insertion hole of the hub unit, is connected to a vehicle outer side end of the hub unit. A bearing device for a vehicle, wherein the shaft portion is fixed to the hub unit. 5. The vehicle bearing device according to claim 2, wherein the male screw portion forming portion in the projecting portion of the shaft portion has the end surface of the constant velocity joint formed on a convex curved surface of the caulking portion. In addition to the screw forming portion for fastening the nut screwed to the protruding portion to a position regulated to the end face of the hub unit in a state where the shaft portion is spline-fitted into the insertion hole so as to abut against the screw portion, A bearing device for a vehicle, comprising at least a screw forming portion required for screwing and fastening the nut further than the restricted position to slightly deform the convex curved surface of the caulked portion into a flat surface. .