JP7212738B1 - ball bearing - Google Patents

Abstract

An object of the present invention is to provide a ball bearing in which the strength of a retainer is less likely to decrease and which has excellent durability.
SOLUTION: When the diameter of a rivet shaft 12 is D ₁ , the diameter of a root portion 13 is D ₂ , and the diameter of a ball 3 is Da, α=D ₁ /Da and β=D ₂ /D ₁ are respectively satisfied. The rivet shaft 12 and the base portion 13 are formed so as to satisfy the following expressions (1) and (2),
0.30<α<0.70 (1)
1.35<β<1.70 (2)
The crimping head 14 is formed so as to satisfy the following equations (3) and (4), where D ₃ is the diameter of the crimping head 14 and H is the height of the crimping head 14 .

[Selection drawing] Fig. 11

Description

This invention relates to ball bearings.

Ball bearings are often used as bearings that support rotating shafts in automobiles, industrial machinery, and the like. A ball bearing comprises an inner ring, an outer ring coaxially provided radially outside the inner ring, a plurality of balls provided in an annular space between the inner ring and the outer ring, and a retainer for holding the plurality of balls. have.

As a retainer for ball bearings (especially deep groove ball bearings), generally, a wave retainer that is excellent in cost and productivity is used (for example, Patent Document 1). The corrugated retainer disclosed in Patent Document 1 has a steel plate-made first annular member and a second annular member arranged to face each other in the axial direction, and the first annular member and the second annular member are joined by a plurality of rivets. be. The first annular member has alternating circumferentially arcuate first pocket wall portions for receiving balls and first plate portions having first rivet holes extending axially therethrough. Similarly, the second annular member also has arcuate second pocket wall portions for receiving balls and second flat plate portions having second rivet holes extending axially therethrough alternately in the circumferential direction. The rivet has a rivet shank, a base head formed in advance on one end of the rivet shank, and a crimping head formed by crimping the other end of the rivet shank.

The rivet shaft is inserted through the first rivet hole and the second rivet hole in a state in which the first flat plate portion and the second flat plate portion are overlapped. The root portion and the crimping head are arranged so as to sandwich the first flat plate portion and the second flat plate portion in the axial direction, the root portion axially locks the first flat plate portion, and the crimping head is It locks the second flat plate portion in the axial direction.

From the viewpoint of cost and productivity, the first annular member and the second annular member that constitute the above-described wave cage are often formed by press forming a rolled steel plate such as a cold rolled steel plate (SPCC). .

However, since the rolled steel plate has relatively low hardness and wear resistance, if the first and second annular members are formed of rolled steel plate, depending on the operating conditions of the bearing, the contact between the balls may cause the first and second annular members to become loose. The second annular member wears, and in the worst case, the retainer may break.

Therefore, in order to improve the durability of the corrugated cage, a method of subjecting the corrugated cage to nitrocarburizing has been proposed (see Patent Document 1). Soft nitriding is a process for forming a nitrided layer (surface hardening layer) on the surface of a steel material. It is a process in which nitrogen is permeated into the surface of the steel material to form a nitrided layer by heating in the range of about 590°C. By subjecting the corrugated cage to this nitrocarburizing treatment, it is possible to improve the durability of the corrugated cage without substantially changing the dimensions of the corrugated cage.

Japanese Patent No. 6098720

Assembly of the wave retainer is generally performed as follows. That is, first, the rivet is press-fitted into the first rivet hole of the first annular member. Next, the first annular member and the second annular member are axially opposed to each other, and the first flat plate portion is overlaid on the second flat plate portion so that the rivet shaft protruding from the first rivet hole is the second annular member. 2 Insert it into the rivet hole. After that, the first annular member and the second annular member are joined by crimping the portion of the rivet shaft protruding from the second rivet hole.

Here, two methods are conceivable as a method of soft-nitriding the corrugated retainer. The first method is to apply a nitrocarburizing treatment before the rivet is pressed into the first rivet hole. That is, first, the first annular member and the second annular member are each subjected to nitrocarburizing treatment, and then a rivet that has not been nitrocarburized is press-fitted into the first rivet hole of the first annular member. Thereafter, the first annular member is superimposed on the second annular member, and the rivet shaft portion protruding from the second rivet hole of the second annular member is crimped to join the first annular member and the second annular member.

In this first method, when the rivet is press-fitted into the first rivet hole, the difference in surface hardness between the rivet shaft not subjected to nitrocarburizing treatment and the first annular member subjected to nitrocarburizing treatment is As a result, the outer periphery of the rivet shaft is shaved, and the shavings are caught between the root portion of the rivet and the first flat plate portion of the first annular member. (bad seating of the rivets), and the strength of the retainer may be reduced.

A second method of applying soft-nitriding to the corrugated retainer is to perform soft-nitriding after press-fitting the rivet into the first rivet hole. That is, first, the rivet not subjected to nitrocarburizing treatment is press-fitted into the first rivet hole of the first annular member not subjected to nitrocarburizing treatment, and the rivet and the first annular member integrated by the press-fitting are nitrocarburized. It is a method of processing. After that, the first annular member is superimposed on the soft-nitrided second annular member, and the rivet shaft portion protruding from the second rivet hole of the second annular member is crimped to form the first annular member. A second annular member is coupled.

In this second method, when the rivet is pressed into the first rivet hole, neither the rivet shank nor the first annular member is subjected to nitrocarburizing treatment, so the outer periphery of the rivet shank is less likely to be scraped. It is possible to prevent poor seating.

However, the inventors of the present application produced a number of samples of corrugated cages soft-nitrided by the above-mentioned second method in-house, and conducted an evaluation test. It was found that the strength of the cage may be lowered even when the nitrocarburizing treatment is performed.

The reason why the strength of the retainer is lowered is considered as follows. That is, when nitrocarburizing is performed by the second method, the rivet is press-fitted into the first rivet hole of the first annular member, and the first rivet is nitrocarburized in this state. The inner circumference of the hole (the mating surface with the rivet shaft) is masked by the rivet shaft, and no nitride layer is formed. Then, after that, when the first annular member is superimposed on the second annular member and the portion of the rivet shaft protruding from the second rivet hole of the second annular member is crimped, the rivet shaft is moved radially by the crimping. The inner periphery of the first rivet hole is in a state where tensile stress is generated due to the plastic deformation of the rivet shaft. In other words, when the nitrocarburizing treatment is performed by the second method, a non-nitrided surface on which a nitrided layer (hardened surface layer) is not formed is formed on the inner circumference of the first rivet hole, and the non-nitrided surface is formed on the rivet shaft. It has been found that the strength of the retainer may be reduced due to the action of tensile stress accompanying expansion.

Here, when the portion of the rivet shaft protruding from the second rivet hole of the second annular member is crimped to form the crimped head portion, if the crimping load is small, the first annular member and the second annular member will be separated. Insufficient adhesion may result in deterioration of the strength of the retainer. Therefore, in order to ensure the tight contact between the first annular member and the second annular member, a large crimping load is generally set. When the crimping load is increased, the diameter of the crimped head increases and the height of the crimped head decreases. On the other hand, the inventors of the present application have focused on the problem that the strength of the retainer is reduced due to the tensile stress acting on the inner periphery of the first rivet hole due to the expansion of the rivet shaft. In order to solve this problem, the crimping load is reduced (that is, the diameter of the crimping head is decreased and the height of the crimping head is increased), thereby reducing the strength of the cage due to tensile stress. The inventors have found that it is possible to prevent the occurrence of this, and have made the present invention.

The problem to be solved by the present invention is to provide a ball bearing in which the strength of the retainer is less likely to decrease and which has excellent durability.

In order to solve the above problems, the present invention provides a ball bearing having the following configuration.
inner ring;
an outer ring coaxially provided radially outside the inner ring;
a plurality of balls embedded between the inner ring and the outer ring at intervals in the circumferential direction;
a corrugated retainer that retains the plurality of balls;
The wave retainer includes a first annular member made of steel, a second annular member made of steel and facing the first annular member in the axial direction, and a plurality of rings connecting the first annular member and the second annular member. and having a rivet of
The first annular member has arc-shaped first pocket wall portions for accommodating the balls and first flat plate portions having first rivet holes penetrating in the axial direction alternately in the circumferential direction,
The second annular member has arcuate second pocket wall portions for accommodating the balls and second flat plate portions having second rivet holes axially penetrating alternately in the circumferential direction,
The rivet is formed in advance on a rivet shaft inserted through the first rivet hole and the second rivet hole in a state in which the first flat plate portion and the second flat plate portion are overlapped, and one end of the rivet shaft, It has a base head for axially locking the first flat plate portion, and a crimping head formed by crimping the other end of the rivet shaft for axially locking the second flat plate portion. In ball bearings,
When D ₁ is the diameter of the rivet shaft, D ₂ is the diameter of the base portion, and Da is the diameter of the ball, α = D ₁ /Da and β = D ₂ /D ₁ are expressed by the following equations (1 ) the tack shaft and the root portion are formed so as to satisfy (2);
0.30<α<0.70 (1)
1.35<β<1.70 (2)
The crimping head is formed so as to satisfy the following equations ( ₃ ) and (4), where D is the diameter of the crimping head and H is the height of the crimping head. A ball bearing characterized by

By doing so, it is possible to reduce the magnitude of the tensile stress acting on the inner circumference of the first rivet hole when the rivet is crimped while ensuring the tight contact between the first annular member and the second annular member. Therefore, it is possible to effectively prevent a decrease in the strength of the retainer. The above formulas ( ₁ ) and ( ₂ ) are formulas to be satisfied by the diameter D1 of the rivet shaft and the diameter D2 of the base of the rivet after forming the crimped head.

a nitride layer is formed on the surface of the first annular member and the surface of the second annular member;
The nitride layer is formed on the entire inner periphery of the second rivet hole,
The inner periphery of the first rivet hole may have a non-nitrided surface on which the nitrided layer is not formed.

The structure described above is obtained when soft-nitriding is performed by the following method. First, the rivet is press-fitted into the first rivet hole of the first annular member that is not nitrocarburized. Next, the rivet and the first annular member, which are integrated by the press-fitting, are subjected to nitrocarburizing. At this time, a nitrided layer is formed on the surface of the first annular member by nitrocarburizing, but the inner periphery of the first rivet hole (the mating surface with the rivet shaft) is masked by the rivet shaft. Therefore, it has a non-nitrided surface on which a nitrided layer is not formed. After that, the first annular member is superimposed on the soft-nitrided second annular member, and the rivet shaft portion protruding from the second rivet hole of the second annular member is crimped to form the first annular member. A second annular member is coupled.

The first annular member and the second annular member may be made of carbon steel for machine structural use, carbon steel for cold heading, or stainless steel.

Also, the rivet may be made of carbon steel for machine structural use, carbon steel for cold heading, or stainless steel.

A first recess having an R-shaped cross section is formed on the edge of the opening of the first rivet hole opposite to the second flat plate portion,
The inner peripheral surface of the first rivet hole is a sheared surface having a striped pattern extending in the axial direction,
A tapered first chamfered portion is formed on the inner circumference of the end of the first rivet hole on the second flat plate portion side,
A second recess having an R-shaped cross section is formed at the opening edge of the second rivet hole on the side opposite to the first flat plate portion,
The inner peripheral surface of the second rivet hole is a sheared surface having a striped pattern extending in the axial direction,
It is preferable to employ a configuration in which a tapered second chamfered portion is formed on the inner circumference of the end of the second rivet hole on the first flat plate portion side.

By doing so, it is possible to prevent deterioration of the strength of the retainer particularly effectively. That is, when the first rivet hole is formed by punching using a punch, the first rivet hole is formed by punching the first flat plate portion from the side opposite to the second flat plate portion toward the second flat plate portion. Then, at the edge of the opening of the first rivet hole on the side opposite to the second flat plate portion, a first recess having an R-shaped cross section is formed by pulling the surface of the material of the first flat plate portion with the punch, In the inner peripheral surface of the first rivet hole, a sheared surface and a fractured surface are formed in order from the side opposite to the second flat plate portion toward the second flat plate portion. The sheared surface is a smooth surface with a streak-like pattern extending in the axial direction, and the fractured surface is an irregular uneven surface caused by tearing off the material of the first flat plate portion. Here, when the first rivet hole is used as it is without additional processing, the rivet is press-fitted into the first rivet hole, and the rivet shaft is crimped, the fractured surface (irregularity) of the inner circumference of the first rivet hole Tensile stress acts on the uneven surface), which may reduce the strength of the cage. Similarly, if the second rivet hole is formed by punching and the second rivet hole is used as it is without additional processing, tensile stress acts on the fracture surface of the inner circumference of the second rivet hole. , the strength of the retainer may be lowered. Therefore, a tapered first chamfered portion is formed on the inner periphery of the end of the first rivet hole on the second flat plate portion side, and the inner periphery of the end of the second rivet hole on the first flat plate portion side is also tapered. When the second chamfered portion is formed, the fractured surfaces on the inner peripheries of the first and second rivet holes are removed, so that the tensile strength due to the fractured surfaces on the inner peripheries of the first and second rivet holes is reduced. As a result, it is possible to prevent deterioration of the strength of the retainer.

It is preferable to employ a configuration in which an annular protrusion is formed on the outer circumference of the rivet shaft and engages with the first chamfered portion and the second chamfered portion at the same time.

With this configuration, the relative movement of the rivet with respect to the first flat plate portion and the second flat plate portion is restricted not only by the base portion and the crimping head portion, but also by the annular protrusion, so that the first flat portion by the rivet is restricted. It is possible to improve the bonding strength between the annular member and the second annular member.

In the ball bearing of the present invention, the magnitude of tensile stress acting on the inner periphery of the first rivet hole is small when the rivet is crimped. Therefore, the strength of the retainer is less likely to decrease, and the durability is excellent.

BRIEF DESCRIPTION OF THE DRAWINGS Sectional drawing which shows the ball bearing of embodiment of this invention FIG. 2 is a perspective view showing the corrugated retainer of FIG. 1; FIG. 3 is a view showing the manufacturing process of the corrugated cage shown in FIG. 2 , in which the first pocket wall portion and the first flat plate portion of the first annular member are formed by press forming a steel plate, and the first flat plate portion is punched; A diagram showing a state in which the first rivet hole is formed by applying Enlarged view of the first rivet hole in FIG. The figure which shows the state which removed the fracture surface by processing the 1st chamfering part in the 1st rivet hole shown in FIG. A view showing a state in which a rivet is press-fitted into the first rivet hole of the first annular member and the second annular member is axially opposed to the first annular member. Enlarged view of the vicinity of the rivet in FIG. The figure which shows the state which overlap|superposed the 1st annular member and 2nd annular member which are shown in FIG. Enlarged view of the vicinity of the rivet in FIG. FIG. 9 is a diagram showing a state in which the first annular member and the second annular member are coupled by crimping the rivet shaft of the rivet shown in FIG. 8 ; Enlarged view of the vicinity of the rivet in FIG. (a) is a diagram showing another example of the rivet shown in FIG. 7, and (b) is a diagram showing still another example of the rivet shown in FIG.

FIG. 1 shows a ball bearing according to an embodiment of the invention. This ball bearing includes an inner ring 1, an outer ring 2 provided coaxially outside the inner ring 1 in the radial direction, a plurality of balls 3 installed between the inner ring 1 and the outer ring 2 at intervals in the circumferential direction, and a plurality of and a corrugated retainer 4 (hereinafter simply referred to as "retainer 4") that maintains the circumferential spacing of the balls 3. As shown in FIG.

The inner circumference of the outer ring 2 is formed with an outer ring raceway groove 5 with which the balls 3 roll and contact. The outer ring raceway groove 5 is an arcuate groove having a concave arcuate cross section, and is formed so as to extend in the axial direction center of the inner circumference of the outer ring 2 in the circumferential direction. The outer circumference of the inner ring 1 is also formed with an inner ring raceway groove 6 with which the balls 3 roll and contact. The inner ring raceway groove 6 is an arcuate groove having a concave arcuate cross section, and is formed so as to extend in the axial direction center of the outer circumference of the inner ring 1 in the circumferential direction.

The ball 3 is radially sandwiched between the outer ring raceway groove 5 and the inner ring raceway groove 6 . This ball bearing is a deep groove ball bearing. That is, the outer ring raceway groove 5 is an arcuate groove symmetrical about the axial center of the outer ring 2 , and the inner ring raceway groove 6 is also an arcuate groove symmetrical about the axial center of the inner ring 1 . The axial width dimension of the outer ring raceway groove 5 is larger than half the diameter Da of the balls 3 , and the axial width dimension of the inner ring raceway groove 6 is also larger than half the diameter Da of the balls 3 .

As shown in FIG. 2, the retainer 4 includes a first annular member 7a made of steel, a second annular member 7b made of steel and facing the first annular member 7a in the axial direction, the first annular member 7a and the second annular member 7b. It has a plurality of rivets 8 connecting the two annular members 7b. The first annular member 7a has, in the circumferential direction, arc-shaped first pocket wall portions 9a for accommodating the balls 3 (see FIG. 1) and flat plate-shaped first flat plate portions 10a orthogonal to the axial direction alternately. Similarly, in the second annular member 7b, arc-shaped second pocket wall portions 9b for accommodating balls 3 (see FIG. 1) and flat plate-shaped second flat plate portions 10b orthogonal to the axial direction are alternately arranged in the circumferential direction. have in

As shown in FIGS. 10 and 11, the first flat plate portion 10a of the first annular member 7a is formed with a first rivet hole 11a penetrating in the axial direction, and the second flat plate portion 10b of the second annular member 7b is formed with a first rivet hole 11a. A second rivet hole 11b is also formed to penetrate axially, and a common rivet 8 is inserted into the first rivet hole 11a and the second rivet hole 11b.

The first annular member 7a shown in FIG. 2 is formed by press-molding a plate material formed of any one of carbon steel for machine structural use (SC material, S45C, etc.), carbon steel for cold heading, and stainless steel. there is Similarly, the second annular member 7b is also formed by press forming a plate material formed of any one of carbon steel for machine structural use, carbon steel for cold heading, and stainless steel. The rivet 8 is formed of a wire rod made of any one of carbon steel for machine structural use, carbon steel for cold heading, and stainless steel.

A nitride layer is formed on the surface of the first annular member 7a by performing a nitrocarburizing treatment, and a nitride layer is also formed on the surface of the second annular member 7b by performing a nitrocarburizing treatment. The nitride layer is a surface-hardened layer having a hardness of 400 HV or more, and is an extremely thin compound layer (a compound layer composed of iron and nitrogen) having a thickness of 20 μm or less. However, the inner periphery of the second rivet hole 11b shown in FIG. 11 has a nitrided layer formed over its entirety, whereas the inner periphery of the first rivet hole 11a has a non-nitrided surface on which no nitrided layer is formed. have

As shown in FIGS. 9 and 11, the rivet 8 includes a rivet shaft 12, a root portion 13 formed in advance on one end of the rivet shaft 12 (upper end in the drawings), and the other end of the rivet shaft 12 (lower end in the drawings). ), and a crimped head 14 formed by crimping. As shown in FIG. 11, the rivet shaft 12 is inserted through the first rivet hole 11a and the second rivet hole 11b in a state in which the first flat plate portion 10a and the second flat plate portion 10b are overlapped. The base portion 13 and the crimping head portion 14 are arranged so as to sandwich the first flat plate portion 10a and the second flat plate portion 10b in the axial direction, and the base portion 13 axially locks the first flat plate portion 10a. , the crimping head 14 axially locks the second flat plate portion 10b.

The retainer 4 described above can be manufactured as follows.

First, as shown in FIG. 3, a first annular member 7a having a first pocket wall portion 9a and a first flat plate portion 10a is formed by press forming a steel plate. Next, a first rivet hole 11a is formed in the first flat plate portion 10a of the first annular member 7a by punching. At this time, the first flat plate portion 10a is punched from the side opposite to the second flat plate portion 10b (upper side in the drawing) toward the second flat plate portion 10b (lower side in the drawing) to form the first rivet hole 11a. do. As a result, as shown in FIG. 4, the material of the first flat plate portion 10a is applied to the opening edge of the first rivet hole 11a opposite to the side of the second flat plate portion 10b (see FIG. 9) (upper side in the figure). A first droop portion 15 having an R-shaped cross section is formed by pulling the surface with a punch. In addition, on the inner peripheral surface of the first rivet hole 11a, from the side opposite to the side of the second flat plate portion 10b (see FIG. 9) (upper side in the figure) to the side of the second flat plate portion 10b (lower side in the figure) A sheared surface 16 and a fractured surface 17 are formed in this order. The sheared surface 16 is a smooth surface with a streaky pattern extending in the axial direction. On the other hand, the fracture surface 17 is an irregular uneven surface that is generated by tearing off the material of the first flat plate portion 10a. The fractured surface 17 has a surface roughness greater than that of the sheared surface 16 . Thereafter, as shown in FIG. 5, the inner circumference of the end of the first rivet hole 11a on the second flat plate portion 10b side (lower side in the figure) is cut to form a tapered first chamfered portion 18a. The inner circumference of the first chamfered portion 18a is a smooth surface. Similarly to the above, the second rivet hole 11b, the second chamfered portion 18b, etc. are also formed in the second annular member 7b.

Next, as shown in FIGS. 6 and 7, the rivet 8 is press-fitted into the first rivet hole 11a of the first annular member 7a. As shown in FIG. 7, the rivet 8 has a rivet shaft 12 and a root portion 13 preformed at one end of the rivet shaft 12 . The rivet shaft 12 is formed in a cylindrical shape having a constant diameter along the axial direction. The root portion 13 is formed to have a diameter larger than that of the rivet shaft 12 and has a flat bearing surface 19 perpendicular to the axial direction. Here, when the diameter of the rivet shaft 12 is D ₁ , the diameter of the rivet shaft 13 is D ₂ , and the diameter of the ball 3 (see FIG. 1) is Da, α= D ₁ /Da and β=D ₂ /D ₁ are formed so as to satisfy the following equations (1) and (2), respectively.
0.30<α<0.70 (1)
1.35<β<1.70 (2)

In consideration of the ease of assembly of the first annular member 7a and the second annular member 7b, it is also possible to provide the rivet shaft 12 with a tapered shape. For example, the rivet shank 12 is composed of a cylindrical rivet shank neck portion that continues from the root portion 13 and a tapered rivet shank tip portion that decreases in diameter from the rivet shank neck portion toward the tip of the rivet shank 12 . may be configured. In this case, the diameter D1 of the rivet shank ₁₂ is not the diameter of the rivet shank tip portion but the diameter of the rivet shank neck portion. Further, as shown in FIG. 11, even in a state where the portion of the rivet shaft 12 protruding from the second rivet hole 11b of the second annular member 7b is crimped to form the crimped head portion 14 (details will be described later), The diameter D ₁ of the rivet shaft 12 (the diameter of the portion excluding the annular projection 20) and the diameter D ₂ of the root portion 13 satisfy the above formulas (1) and (2).

After that, as shown in FIG. 6, the rivet 8 and the first annular member 7a integrated by press-fitting are subjected to nitrocarburizing. Soft nitriding is a process for forming a nitrided layer (surface hardening layer) on the surface of a steel material. It is a process in which nitrogen is permeated into the surface of the steel material to form a nitrided layer by heating in the range of about 590°C. By subjecting the retainer 4 to this nitrocarburizing treatment, the durability of the retainer 4 can be improved without substantially changing the dimensions of the retainer 4 . Although a nitrided layer is formed on the surface of the first annular member 7a by this nitrocarburizing treatment, the inner periphery of the first rivet hole 11a shown in FIG. Since it is in a state where it is in a state where a nitrided layer is not formed, it has a non-nitrided surface.

Further, as shown in FIG. 6, the second annular member 7b before being joined to the first annular member 7a is also nitrocarburized. At this time, the rivet 8 is not inserted into the second rivet hole 11b of the second annular member 7b, and the entire inner circumference of the second rivet hole 11b is exposed. A nitride layer is formed over the entire surface.

Next, as shown in FIGS. 8 and 9, the first annular member 7a is overlaid on the second annular member 7b, and the portion of the rivet shaft 12 protruding from the first rivet hole 11a is inserted into the second rivet hole 11b. . At this time, the rivet shaft 12 passes through the second rivet hole 11b and protrudes from the second rivet hole 11b. At this time, a plurality of balls 3 are assembled between the inner ring 1 and the outer ring 2 shown in FIG. The first annular member 7a and the second annular member 7b are put together so as to be sandwiched from both sides in the axial direction by the wall portion 9b.

Thereafter, as shown in FIGS. 10 and 11, the portion of the rivet shaft 12 protruding from the second rivet hole 11b of the second annular member 7b is crimped in the axial direction by a crimping die (not shown) (plastic deformation). ) to connect the first annular member 7a and the second annular member 7b. At this time, as shown in FIG. 11, due to the plastic deformation of the rivet shaft 12, an annular projection 20 is formed on the outer periphery of the central portion of the rivet shaft 12 in the axial direction and simultaneously engages the first chamfered portion 18a and the second chamfered portion 18b. is formed. In the drawing, the size of the annular protrusion 20 is exaggerated in order to make the presence of the annular protrusion 20 easier to understand.

Here, when crimping the portion of the rivet shaft 12 protruding from the second rivet hole 11b of the second annular member 7b as shown in FIG. , the diameter D ₃ of the crimping head 14 and the height H of the crimping head 14 shown in FIG. do.

By the way, as shown in FIGS. 6 and 7, when the rivet 8 is press-fitted into the first rivet hole 11a of the first annular member 7a and the first annular member 7a is nitrocarburized in this state, the first rivet Since the inner periphery of the hole 11a (the mating surface with the rivet shaft 12) is masked by the rivet shaft 12, no nitride layer is formed. Then, as shown in FIG. 8, the first annular member 7a is superimposed on the second annular member 7b, and as shown in FIGS. When the portion of the rivet shaft 12 is crimped, the rivet shaft 12 is plastically deformed so as to expand in the radial direction due to the crimping, and the plastic deformation of the rivet shaft 12 applies a tensile stress to the inner periphery of the first rivet hole 11a. has occurred. That is, the tensile stress associated with the expansion of the rivet shaft 12 acts on the non-nitrided surface (hardened surface layer) of the inner periphery of the first rivet hole 11a, which may cause the strength of the retainer 4 to decrease. There is

Therefore, in the ball bearing of the above-described embodiment, when the portion of the rivet shaft 12 protruding from the second rivet hole 11b of the second annular member 7b is crimped to form the crimped head 14, the crimping load is reduced to is also reduced, the diameter of the crimping head 14 is reduced and the height of the crimping head 14 is increased within a range that satisfies the above equations (3) and (4). As a result, it is possible to reduce the magnitude of the tensile stress acting on the inner circumference of the first rivet hole 11a when the rivet 8 is crimped while ensuring the tight contact between the first annular member 7a and the second annular member 7b. It has become. Therefore, the strength of the retainer 4 is unlikely to be lowered, and the durability is excellent.

In addition, as shown in FIG. 11, in this ball bearing, a tapered first chamfered portion 18a is formed on the inner circumference of the end portion of the first rivet hole 11a on the second flat plate portion 10b side. Since the tapered second chamfered portion 18b is formed on the inner circumference of the end portion on the side of the first flat plate portion 10a, it is possible to prevent deterioration of the strength of the retainer 4 particularly effectively. That is, when the first rivet hole 11a shown in FIG. Tensile stress acts on the broken surface 17 (irregularly uneven surface) of the cage 4, and the strength of the retainer 4 may be lowered. The same applies to the fracture surface 17 on the inner circumference of the second rivet hole 11b. Therefore, as shown in FIGS. 5 and 11, a tapered first chamfered portion 18a is formed on the inner circumference of the end portion of the first rivet hole 11a on the second flat plate portion 10b side, and the second rivet hole 11b If the tapered second chamfered portion 18b is also formed on the inner periphery of the end portion on the side of the first flat plate portion 10a, the fractured surfaces 17 on the inner periphery of the first rivet hole 11a and the second rivet hole 11b are removed. A decrease in tensile strength due to the fractured surfaces 17 on the inner peripheries of the rivet hole 11a and the second rivet hole 11b is suppressed, and as a result, it is possible to prevent the strength of the retainer 4 from decreasing.

Further, in this ball bearing, as shown in FIG. 11, an annular projection 20 is formed on the outer periphery of the rivet shaft 12 to engage with the first chamfered portion 18a and the second chamfered portion 18b at the same time. Relative movement of the rivet 8 with respect to the flat plate portion 10a and the second flat plate portion 10b is restricted not only by the root portion 13 and the crimping head portion 14, but also by the annular protrusion 20. Therefore, the coupling strength between the first annular member 7a and the second annular member 7b by the rivet 8 is high, and the durability is excellent.

In the above embodiment, as shown in FIG. 7, the rivet 8 having a crown-shaped root portion 13 was described as an example. However, as shown in FIG. A rivet 8 having a shaft or, as shown in FIG.

It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the meaning and range of equivalents of the scope of the claims.

1 inner ring 2 outer ring 3 ball 4 corrugated retainer 7a first annular member 7b second annular member 8 rivet 9a first pocket wall portion 9b second pocket wall portion 10a first flat plate portion 10b second flat plate portion 11a first rivet hole 11b Second rivet hole 12 Rivet shaft 13 Base head 14 Crimp head 15 First droop 16 Sheared surface 18a First chamfered portion 18b Second chamfered portion 20 Annular projection Da Ball diameter D _First rivet shaft diameter D _Binary Head diameter D _3Crimped head diameter H Height of crimped head

Claims (6)

an inner ring (1);
an outer ring (2) provided coaxially on the radially outer side of the inner ring (1);
a plurality of balls (3) embedded in the inner ring (1) and the outer ring (2) at intervals in the circumferential direction;
a corrugated retainer (4) for retaining the plurality of balls (3);
The corrugated retainer (4) includes a first annular member (7a) made of steel, a second annular member (7b) made of steel and facing the first annular member (7a) in the axial direction, and the first annular member (7b). an annular member (7a) and a plurality of rivets (8) connecting said second annular member (7b);
The first annular member (7a) comprises an arc-shaped first pocket wall (9a) for accommodating the ball (3) and a first flat plate (10a) having a first rivet hole (11a) axially penetrating therethrough. ) alternately in the circumferential direction,
The second annular member (7b) comprises an arc-shaped second pocket wall portion (9b) for accommodating the ball (3) and a second flat plate portion (10b) having a second rivet hole (11b) axially penetrating therethrough. ) alternately in the circumferential direction,
The rivet (8) is inserted through the first rivet hole (11a) and the second rivet hole (11b) in a state in which the first flat plate portion (10a) and the second flat plate portion (10b) are overlapped. a rivet shaft (12), a root portion (13) which is formed in advance on one end of the rivet shaft (12) and axially engages the first flat plate portion (10a), and the rivet shaft (12). A ball bearing having a crimping head (14) formed by crimping the other end of and axially locking the second flat plate portion (10b),
When the diameter of the rivet _shaft (12) is D1, the diameter of the root portion (13) is D2, and the diameter of the ball ( ₃ ) is Da, α=D1 _/ Da and β ₌ D2. The rivet shaft (12) and the root portion (13) are formed such that /D ₁ satisfies the following equations (1) and (2), respectively;
0.30<α<0.70 (1)
1.35<β<1.70 (2)
When the diameter of the crimping head (14) is D3 and the height of the crimping head (14) is H, the crimping head (14) satisfies the following equations ( ₃ ) and (4), respectively. A ball bearing characterized in that (14) is formed.

A nitride layer is formed on the surface of the first annular member (7a) and the surface of the second annular member (7b),
The nitride layer is formed on the entire inner periphery of the second rivet hole (11b),
The ball bearing according to claim 1, wherein the inner periphery of said first rivet hole (11a) has a non-nitrided surface on which said nitrided layer is not formed. 3. The method according to claim 1 or 2, wherein the first annular member (7a) and the second annular member (7b) are made of one of carbon steel for machine structural use, carbon steel for cold heading, and stainless steel. ball bearings. 4. A ball bearing according to any one of claims 1 to 3, wherein said rivet (8) is made of one of carbon steel for machine structural use, carbon steel for cold heading, and stainless steel. A first recess (15) having an R-shaped cross section is formed at the opening edge of the first rivet hole (11a) opposite to the second flat plate portion (10b),
The inner peripheral surface of the first rivet hole (11a) is a sheared surface (16) having a striped pattern extending in the axial direction,
A tapered first chamfered portion (18a) is formed on the inner circumference of the end portion of the first rivet hole (11a) on the side of the second flat plate portion (10b),
A second sagging portion having an R-shaped cross section is formed at the opening edge of the second rivet hole (11b) on the side opposite to the first flat plate portion (10a),
The inner peripheral surface of the second rivet hole (11b) is a sheared surface having a striped pattern extending in the axial direction,
5. A tapered second chamfered portion (18b) is formed on the inner circumference of the end of the second rivet hole (11b) on the side of the first flat plate portion (10a) according to any one of claims 1 to 4. ball bearings. 6. The ball according to claim 5, wherein an annular projection (20) is formed on the outer periphery of the rivet shaft (12) to engage with the first chamfered portion (18a) and the second chamfered portion (18b) at the same time. bearing.

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