JP2022147350A - Manufacturing method for corrugated holder - Google Patents

Abstract

To provide a high-quality corrugated holder with excellent durability and reliability.SOLUTION: A manufacturing method for a corrugated holder 7 comprising a pair of annular members 8 and a plurality of fastening members (rivets 9) in which the pair of annular members 8 is connected so as to be superimposed in an axial direction, includes a heat treatment step of performing heat treatment for an unquenched annular member 8 made of a press-molded product of a steel plate. In the heat treatment step, a primary heat treatment of performing soft nitriding treatment for the unquenched annular member 8 at a temperature of 400 to 590°C, and a secondary heat treatment of holding the annular member 8 subjected to the soft nitriding treatment at a temperature of 180 to 200°C are executed.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a method of manufacturing a corrugated retainer that is incorporated into a ball bearing and used.

In a ball bearing having an inner ring and an outer ring that rotate relative to each other via a plurality of balls, a retainer arranged between the inner and outer rings to hold the plurality of balls is usually provided with a retainer that is superimposed in the axial direction of the ball bearing. A pair of annular members are axially coupled using a plurality of fastening members (for example, rivets) spaced apart in the circumferential direction of the ball bearing. In this retainer, each annular member has a hemispherical bulging portion defining a pocket for cooperating with a mating member (a mating annular member) to hold the ball so that it can roll freely, and a fastening member. It is called a "wavy retainer" because it has a corrugated shape in which the flat portions coupled with the counterpart are alternately arranged in the circumferential direction.

For the annular member that constitutes the corrugated retainer, a steel plate (unquenched steel plate) with excellent workability such as SPCC is press-formed into the above-mentioned corrugated shape by press forming. A heat-treated product is preferably employed. As the above heat treatment, for example, as described in Patent Document 1 below, a nitriding treatment (concept including "soft nitriding treatment") for forming a nitrided layer as a surface hardened layer on the annular member is preferably adopted. be done. Compared to hardening such as carburizing and quenching, which requires the work to be heated to a temperature higher than the transformation point of steel, nitriding treats the work at a significantly lower heating temperature during the treatment, thereby suppressing or preventing thermal deformation of the work. , so there is an advantage that finishing work (shape correction work) after processing can be omitted. When a work made of SPCC is nitrocarburized, the surface hardness of the work becomes about 400 to 500 in terms of Vickers hardness (HV).

In Patent Document 1, one of the pair of annular members is nitrided while a rivet is press-fitted into the flat portion thereof, and the other of the pair of annular members is nitrided as a single unit. Then, a pair of annular members are joined by crimping a rivet previously press-fitted into one of the annular members (nitrided together with the one of the annular members). . According to such method,
・Exclusive nitriding process for rivets can be omitted.
・It is possible to improve the handleability of the one annular member in which the rivet is press-fitted in advance.
・There are advantages such as increased durability of the wave cage.

Japanese Patent No. 6098720

However, in the method described in Patent Document 1, a pair of annular members whose surface hardness is increased by nitriding are axially joined using rivets whose surface hardness is also increased by nitriding. At times, the tensile residual stress generated and accumulated in the retainer (annular member) becomes large. This may lead to a decrease in the strength of the cage when using a cage of

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to make it possible to manufacture a corrugated cage that has high surface hardness (wear resistance) and fatigue strength, as well as excellent durability and reliability.

The present invention, which has been devised to achieve the above object, comprises a pair of annular members and a plurality of fastening members which are joined in a state in which the pair of annular members are axially overlapped, each annular member being a mating member. A corrugated shape in which hemispherical protuberances that define pockets that cooperate with the side to hold the ball so that it can roll freely and flat portions that are overlapped in the axial direction with the other side are alternately arranged in the circumferential direction. A method for manufacturing a corrugated cage for a ball bearing comprising: a heat treatment step of heat-treating an unquenched annular member made of a press-formed steel plate; and a bonding step of axially bonding with, in the heat treatment step, a primary heat treatment in which the unquenched annular member is subjected to nitrocarburizing at a temperature of 400 to 590 ° C., and a nitrocarburized annular member. and a secondary heat treatment that holds at a temperature of 180 to 200°C.

As described above, in the heat treatment step of heat-treating an unquenched annular member made of a press-formed product, first, a primary heat treatment is performed in which the unquenched annular member is nitrocarburized at a temperature of 400 to 590 ° C. When executed, a nitrided layer having higher hardness than the base material is formed on the surface of the annular member while preventing thermal deformation of the annular member, so that a highly accurate annular member with improved surface hardness and wear resistance can be obtained. Obtainable. Subsequently, when a secondary heat treatment is performed to hold the soft-nitrided annular member at a temperature of 180 to 200° C., the shape accuracy and surface hardness of the soft-nitrided annular member are maintained, and the ring is The cross-sectional hardness of the base material of the member can be reduced to increase the toughness of the annular member. Therefore, in the joining step after the heat treatment step, it is possible to reduce the tensile residual stress generated in the annular members as the pair of annular members are axially coupled by the fastening member, and as a result, fatigue of the corrugated retainer can be reduced. Strength can be increased.

In this case, even if the pair of annular members are axially coupled using a high-hardness, high-strength fastening member that has undergone heat treatment such as nitriding or quenching, the corrugation is retained during use (during operation of the ball bearing). Early breakage of the wave retainer due to stress repeatedly applied to the container can be prevented as much as possible. Therefore, when connecting the pair of annular members in the axial direction, it is possible to use a heat-treated high-hardness and high-strength fastening member without any problem. Therefore, it is possible to manufacture a high-quality corrugated retainer that is highly reliable and durable.

The fastening member may be a rivet integrally having a shaft portion passing through the flat portions of one and the other of the pair of annular members and a head portion axially engaged with one of the pair of annular members. In this case, in the connecting step, a crimping process is performed to form a crimping portion that axially clamps one flat portion and the other flat portion between the free end of the shaft portion and the head portion.

As described above, according to the present invention, it is possible to manufacture a high-quality wave cage having high surface hardness (wear resistance), high fatigue strength, and high durability and reliability.

1 is a partial longitudinal sectional view of a ball bearing; FIG. 2 is a schematic perspective view of the corrugated cage for the ball bearing shown in FIG. 1; FIG. FIG. 2 is a cross-sectional view of the wave retainer taken along line AA of FIG. 1;

Embodiments of the present invention will be described below. The present invention relates to a method of manufacturing a retainer for a ball bearing (wavy retainer). An example of the wave retainer for 1 will be described with reference to FIGS. 2 and 3. FIG.

A ball bearing 1 shown in FIG. a plurality of balls 6 which are freely rollable between 4 and 5; and an annular wave cage 7 which is arranged between the inner ring 2 and the outer ring 3 and holds the plurality of balls 6 at intervals in the circumferential direction. , and a lubricant such as grease (not shown) interposed in the annular space between the inner ring 2 and the outer ring 3 . In order to prevent the lubricant from leaking to the outside and foreign matter from entering the annular space, seal members 20 are arranged at the ends of the annular space on one side and the other in the axial direction.

As shown in FIGS. 2 and 3, the corrugated retainer 7 is arranged with a pair of annular members 8, 8 which are axially overlapped (opposed to each other in the axial direction) and spaced apart in the circumferential direction, A rivet 9 is provided as a fastening member axially connecting the pair of annular members 8 , 8 .

Each annular member 8 has a hemispherical bulging portion 10 that defines a pocket 7a that cooperates with a mating member (a coupling mating annular member 8) to hold the ball 6 in a rollable manner, Each of the plurality of flat portions 11 arranged at intervals in the circumferential direction has an opening on both front and back surfaces of the annular member 8. A through hole 12 is formed.

The annular member 8 having the above configuration uses a press-formed product formed into a predetermined shape (the above-described wave shape) by press working a steel plate (unquenched steel plate) as a base material, and the press-formed product is heat-treated. The mechanical strength, surface hardness, etc., required for the corrugated retainer 7 are ensured. Although the details will be described later, here, after performing the primary heat treatment for soft-nitriding the press-formed product (unquenched annular member), the secondary heat treatment for annealing the soft-nitrided annular member By performing the heat treatment, the annular member 8 is obtained in which desired mechanical strength, surface hardness, etc. are ensured. Therefore, although detailed illustration is omitted, the surface of the annular member 8 is provided with a nitrided layer formed along with the nitrocarburizing treatment. Thereby, the surface hardness of the annular member 8 is higher than the hardness of the base material of the annular member 8 (the portion of the annular member 8 where the nitride layer is not formed). Specifically, the surface hardness of the annular member 8 is about 400 to 500 in Vickers hardness (HV), and the hardness of the base material of the annular member 8 is about 150 to 200 HV.

A rivet 9 as a fastening member is axially connected to a shaft portion 9a inserted through a through-hole 12 of a pair of axially overlapped annular members 8 and a flat portion 11 (outer surface thereof) of one of the annular members 8. The engaged head 9b is engaged with (the outer surface of) the flat portion 11 of the other annular member 8 in the axial direction, and the flat portions 11 of both annular members 8 are clamped between the head 9b and crimped. and a portion 9c are integrally provided. Although illustration is omitted, the rivet 9 before use (individual component) consists of only the shaft portion 9a and the head portion 9b, and does not have the crimping portion 9c.

The corrugated retainer 7 having the above configuration is mainly performed in a molding process for obtaining a press-formed product that is the base material of the annular member 8, and a heat treatment process for heat-treating the press-formed product (unquenched annular member 8). , and a joining step of joining a pair of heat-treated annular members 8 with a fastening member 9 . Each of the above steps will be described below.

[Molding process]
In this forming process, an unquenched steel plate is press-worked using a press die having a mold part corresponding to the shape of the annular member 8, thereby forming a base material (unquenched unquenched An annular member 8) is obtained. As the steel plate, for example, a cold-rolled steel plate typified by SPCC, a hot-rolled steel plate typified by SPHD, and the like, which are soft and highly workable, are preferably used.

[Heat treatment process]
In this heat treatment step, a primary heat treatment for soft-nitriding the unquenched annular member 8 and a secondary heat treatment for annealing the soft-nitrided annular member 8 are performed.

For the soft nitriding treatment as the primary heat treatment applied to the unquenched annular member 8, for example, a gas atmosphere filled with ammonia gas ( _NH3 gas) as a nitriding medium and an endothermic modified gas (RX gas) is applied. A so-called gas nitrocarburizing treatment is selected in which the placed annular member 8 is heated at a temperature of 400 to 590° C. (400° C. to 590° C.) for a predetermined time (for example, 1 to 3 hours). By subjecting the unquenched annular member 8 to this nitrocarburizing treatment, a high-hardness nitride layer (nitride film) made of a compound of iron and nitrogen is formed on the surface of the annular member 8 . The reason why the heating temperature of the unquenched annular member 8 is set to 400° C. or more and 590° C. or less during the nitrocarburizing treatment is that if the heating temperature is less than 400° C., a high-quality nitrided layer cannot be obtained. exceeds 590° C., the annular member 8 may be thermally deformed.

In addition to the above-mentioned nitriding media, the nitriding medium used in soft nitriding may be a mixed gas of ammonia gas and methanol decomposition gas, a decomposition gas of solid urea (CO(NH ₂ ) ₂ ), or a nitrogen base (N ₂ +NH ₃ +CO ₂ +H ₂ ) gas or the like may be used. Moreover, the nitrocarburizing treatment applied to the unquenched annular member 8 may be a salt bath nitrocarburizing treatment. However, since the salt bath contains cyanide, which is a kind of harmful substance, the salt bath nitrocarburizing treatment requires anti-pollution measures (anti-pollution measures).

Annealing treatment as a secondary heat treatment is applied to the annular member 8 that has been soft-nitrided. This annealing treatment is performed, for example, by holding the annular member 8 placed in an oxygen atmosphere at a temperature of 180 to 200° C. for a predetermined time (for example, 1 to 3 hours). As a result, the cross-sectional hardness of the region of the annular member 8 excluding the formation region of the nitride layer is softened. The reason why the heating temperature of the annular member 8 during the annealing treatment is set to 180° C. or more and 200° C. or less is that if the heating temperature is less than 180° C., the tensile residual stress generated and accumulated during crimping increases, and the desired temperature increases. This is because the mechanical strength cannot be obtained, and if the heating temperature exceeds 200° C., the surface hardness decreases.

[Binding step]
In this joining step, after the heat-treated annular members 8 subjected to the above heat treatment (nitrocarburizing treatment and annealing treatment) are superimposed in the axial direction, the pair of annular members 8 are joined together using rivets 9 as fastening members. Axial coupling operation is performed by Although illustration is omitted, this joining operation involves inserting the shaft portions 9a of the rivets 9 into the through holes 12 of the pair of annular members 8 that are axially overlapped, and then compressing the rivets 9 from both sides in the axial direction. The free end of the shaft portion 9a (the end opposite to the head portion 9b) is crushed to form a crimped portion 9c that axially clamps the flat portions 11 of both annular members 8 with the head portion 9b. It is done by As a result, the corrugated retainer 7 shown in FIG. 2 is obtained in which the pair of heat-treated annular members 8 are axially coupled.

As described above, in the present embodiment, in the heat treatment step of heat-treating the unquenched annular member 8 made of a press-formed steel plate (unquenched steel plate), first, the unquenched annular member 8 is A primary heat treatment for soft nitriding is performed at a temperature of 400 to 590°C. As a result, while preventing thermal deformation of the annular member 8, a nitrided layer having a hardness higher than that of the base material of the annular member 8 is formed on the surface of the annular member 8, so that surface hardness and wear resistance are enhanced. A highly accurate annular member 8 can be obtained.

In the present embodiment, following the primary heat treatment (soft-nitriding treatment), a secondary heat treatment (annealing treatment) is performed in which the ring member 8 subjected to the soft-nitriding treatment is held at a temperature of 180 to 200° C. for a predetermined time. be. As a result, while maintaining the shape accuracy and surface hardness of the annular member 8 , the cross-sectional hardness of the base material of the annular member 8 can be reduced to increase the toughness of the annular member 8 . Therefore, in the joining step after the heat treatment step (secondary heat treatment), it is possible to reduce the tensile residual stress generated in the annular members 8 when the pair of annular members 8 are joined in the axial direction using the rivets 9. As a result, the fatigue strength of the corrugated retainer 7 can be increased.

In this case, even if the pair of annular members 8 are joined in the axial direction using high-hardness and high-strength rivets 9 that have undergone heat treatment such as nitriding or quenching, the wave cage 7 will not move when the ball bearing 1 operates. Early breakage of the wave retainer 7 due to repeated stress can be prevented as much as possible. Therefore, when joining the pair of annular members 8 in the axial direction, it is possible to use the heat-treated high-hardness and high-strength rivets 9 without any problems.

Combined with the above effects, according to the present invention, it is possible to manufacture a high-quality wave cage 7 with high precision, high reliability and durability with improved wear resistance and fatigue strength. .

The inventors of the present invention have investigated whether the annular member 8 subjected to the nitrocarburizing treatment is subjected to the above-described annealing treatment or not, as the rivet 9 is fastened, the annular member 8 (the corrugated retainer) 7) It was confirmed how much difference occurred in the residual stress generated inside. Specifically, of the wave retainer 7, a portion (the flat portion 11 of one annular member 8) with which the head portion 9b of the rivet 9 is in contact, and a portion (the other annular member) with which the caulking portion 9c of the rivet 9 is in contact. The residual stress was measured at two points on the flat portion 11) of the member 8. Confirmation results (average value of N=8) are as follows.
(1) When annealing is performed Residual stress at the portion where the head 9b of the rivet 9 is in contact: 354 MPa
・Residual stress at the site where the crimped portion 9c of the rivet 9 is in contact: 341 MPa
(2) When no annealing treatment is performed Residual stress at the portion where the head 9b of the rivet 9 is in contact: 504 MPa
・Residual stress at the site where the crimped portion 9c of the rivet 9 is in contact: 481 MPa

As is clear from the above confirmation results, if the ring member 8 subjected to nitrocarburizing is annealed at a temperature of 180 to 200° C. for a predetermined period of time, compared to the case where this annealing is not performed. It is possible to reduce the residual stress by about 30%. Therefore, it can be said that the present invention is useful in manufacturing a corrugated cage 7 having excellent wear resistance and fatigue strength.

Although the method for manufacturing the wave retainer 7 according to one embodiment of the present invention has been described above, the embodiment of the present invention is not limited to this, and can be modified as appropriate without departing from the gist of the present invention. can be applied.

For example, in the above description, the rivet 9 is used as the fastening member for axially coupling the pair of annular members 8 after heat treatment. It may be a combination product of a nut member having a portion. However, if the rivets 9 are used, the pair of annular members 8 can be axially coupled more easily and quickly than when the pair of annular members 8 are axially coupled by so-called bolt-nut fixing. The production efficiency of the retainer 7 can be enhanced.

1 ball bearing 6 ball 7 corrugated retainer 7a pocket 8 annular member 9 rivet (fastening member)
10 hemispherical bulging portion 11 flat portion

Claims (2)

A pair of ring-shaped members and a plurality of fastening members are provided in which the pair of ring-shaped members are axially overlapped and connected, and each ring-shaped member cooperates with the other side to hold the ball rollably. For manufacturing a corrugated cage for a ball bearing, the corrugated retainer has a corrugated shape in which hemispherical bulges that define pockets that form a circle and flat portions that are axially overlapped with the mating side are alternately arranged in the circumferential direction. a method,
A heat treatment step of heat-treating the unquenched annular member made of a press-formed steel plate, and a joining step of axially joining the pair of heat-treated annular members with the fastening member,
In the heat treatment step, the unquenched annular member is subjected to a nitrocarburizing treatment at a temperature of 400 to 590° C. for a primary heat treatment, and the nitrocarburized annular member is held at a temperature of 180 to 200° C. A method for manufacturing a corrugated retainer, characterized by performing a secondary heat treatment. The fastening member is a rivet integrally having a shaft portion penetrating the flat portions of one and the other of the pair of annular members and a head portion axially engaged with one of the pair of annular members. ,
2. The method according to claim 1, wherein in the connecting step, a crimping process is performed to form a crimping portion that axially clamps the one flat portion and the other flat portion between the free end of the shaft portion and the head portion. A method of manufacturing the described corrugated retainer.

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