Bearing track component and method for manufacturing bearing track component

Abstract

This bearing track component comprises a shaft member comprising a first portion and a second portion. The first portion is made of a first steel material containing a first alloy component, and the second portion is made of a second steel material containing a second alloy component. The first alloy component is different from the second alloy component. The first portion has a bearing part having a track, and the second portion has a power transmission part having teeth. The first portion has a first surface-hardened layer provided along the outer peripheral surface of the first portion, and a first inner part. The average hardness of the first surface-hardened layer is greater than the average hardness of the first inner part. The second portion has a second surface-hardened layer provided along the outer peripheral surface of the second portion, and a second inner part. The average hardness of the second surface-hardened layer is greater than the average hardness of the second inner part. The first surface-hardened layer and the second surface-hardened layer are both carburized layers or carbonitrided layers, and the first surface-hardened layer and the second surface-hardened layer are connected to each other.

Description

Bearing raceway component and method for manufacturing bearing raceway component

[0001] The present disclosure relates to a bearing race component having a power transmission portion with teeth and a method for manufacturing a bearing race component having a power transmission portion with teeth.

[0002] A bearing raceway component in which an inner ring of a bearing and a gear shaft are integrated is known. Patent Document 1 (JP-A-2005-102626) describes a transmission including a first shaft unit connected to a drive shaft of a drive unit, the first shaft unit including a first shaft connected to the drive shaft and having a first shaft raceway on its outer circumferential surface, a first output gear mounted on the first shaft and rotating integrally with the first shaft, a first outer ring attached to a first support part supporting the first shaft and surrounding the first shaft raceway, the first outer ring having a first outer ring raceway on its inner circumferential surface, and a plurality of first rolling elements disposed between the first shaft raceway surface and the first outer ring raceway surface. The first shaft of the transmission includes a raceway and an output gear on its outer circumferential surface.

[0003] JP 2023-020380 A

[0004] When a single shaft member is provided with a raceway of a bearing portion having a raceway and teeth of a power transmission portion having teeth, such as the teeth of a gear or a toothed pulley, it has been difficult to simultaneously satisfy the strength required for the raceway of the bearing portion having a raceway and the strength required for the teeth of the power transmission portion having teeth. In other words, when a single shaft member is provided with a raceway of a bearing portion having a raceway and teeth of a power transmission portion having teeth, a compromise has had to be made between the strength required for the raceway of the bearing portion having a raceway and the strength required for the teeth of the power transmission portion having teeth. Therefore, a shaft member is needed that can simultaneously satisfy the strength required for the raceway of the bearing portion having a raceway and the strength required for the teeth of the power transmission portion having teeth.

[0005] The bearing raceway component of the present disclosure is a bearing raceway component made of a columnar or cylindrical shaft member and provided with a power transmission portion having teeth, wherein the shaft member has a central axis, the shaft member has a first portion on a first axial side and a second portion on a second axial side of the first portion, the first portion being integrated with the second portion, the first portion being made from a first steel material, the first steel material containing a first alloy component, the second portion being made from a second steel material, the second steel material containing a second alloy component, the first alloy component being different from the second alloy component, the first portion having a bearing portion having a raceway, and the second portion having a power transmission portion having teeth, The first portion has a first surface-hardened layer and a first interior portion, the first surface-hardened layer being provided along the circumferential surface of the first portion, the first interior portion being provided on the opposite side of the first surface-hardened layer from the circumferential surface of the first portion, the average hardness of the first surface-hardened layer being harder than the average hardness of the first interior portion, the second portion has a second surface-hardened layer and a second interior portion, the second surface-hardened layer being provided along the circumferential surface of the second portion, the second interior portion being provided on the opposite side of the second surface-hardened layer from the circumferential surface of the second portion, the average hardness of the second surface-hardened layer being harder than the average hardness of the second interior portion, the first surface-hardened layer and the second surface-hardened layer both being carburized layers or both being carbonitrided layers, and the first surface-hardened layer and the second surface-hardened layer being connected.

[0006] One method for manufacturing a bearing raceway part according to the present disclosure is a method for manufacturing a bearing raceway part having a power transmission portion with teeth according to the present disclosure, comprising: friction welding or welding a first portion of a workpiece in a first state and a second portion of a workpiece in a first state to form an integrated first workpiece; performing one of the following steps first and second: forming a portion that will become the bearing portion with a raceway in the first portion of the first workpiece by first machining; and forming a portion that will become the power transmission portion with teeth in the second portion of the first workpiece by second machining, to form a second workpiece; and simultaneously carburizing or carbonitriding the portion of the second workpiece that will become the bearing portion with raceway and the portion that will become the power transmission portion with teeth, followed by quenching and tempering.

[0007] Another method for manufacturing a bearing raceway part according to the present disclosure is a method for manufacturing a bearing raceway part having a power transmission portion with teeth according to the present disclosure, comprising the steps of: forming a portion that will become the bearing portion with a raceway on a first portion of a workpiece in a first state by a first machining process; and forming a portion that will become the power transmission portion with teeth on a second portion of a workpiece in a first state by a second machining process; performing one of these steps first and the other step later to create the first portion of the workpiece in a second state and the second portion of the workpiece in a second state; combining the first portion of the workpiece in the second state and the second portion of the workpiece in the second state into an integrated second workpiece by friction welding or welding; simultaneously carburizing or carbonitriding the portion of the second workpiece that will become the bearing portion with raceway and the portion that will become the power transmission portion with teeth, followed by quenching and tempering.

[0008] The bearing raceway component of the present disclosure can achieve both strength suitable for the raceway of a bearing part having a raceway and strength suitable for the teeth of a power transmission part having teeth, in a single bearing raceway component. The manufacturing method of the bearing raceway component of the present disclosure is suitable for manufacturing the above-mentioned bearing raceway component.

[0009] Fig. 1 is a cross-sectional schematic view of a bearing raceway component according to a first embodiment. Fig. 2 is a cross-sectional schematic view of a bearing device having the bearing raceway component of Fig. 1. Fig. 3 is a partially enlarged view of Fig. 1. Fig. 4 is a diagram for explaining a first manufacturing method of a bearing raceway component. Fig. 5 is a diagram for explaining a second manufacturing method of a bearing raceway component. Fig. 6 is a diagram showing heat treatment conditions. Fig. 7 is a cross-sectional view of a bearing raceway component according to a third embodiment.

[0010] <Outline of Embodiments of the Invention of the Present Disclosure> The following will list and describe outlines of embodiments of the invention of the present disclosure. (1) A bearing raceway component of the present disclosure is a bearing raceway component made of a columnar or cylindrical shaft member and provided with a power transmission portion having teeth, wherein the shaft member has a central axis, the shaft member has a first portion on a first axial side and a second portion on a second axial side of the first portion, the first portion being integrated with the second portion, the first portion being made of a first steel material, and the first steel material containing a first alloy component, the second portion being made of a second steel material, and the second steel material containing a second alloy component, the first alloy component being different from the second alloy component, the first portion having a bearing portion having a raceway, and the second portion having a power transmission portion having teeth, The first portion has a first surface-hardened layer and a first interior portion, the first surface-hardened layer being provided along the circumferential surface of the first portion, the first interior portion being provided on the opposite side of the first surface-hardened layer from the circumferential surface of the first portion, the average hardness of the first surface-hardened layer being harder than the average hardness of the first interior portion, the second portion has a second surface-hardened layer and a second interior portion, the second surface-hardened layer being provided along the circumferential surface of the second portion, the second interior portion being provided on the opposite side of the second surface-hardened layer from the circumferential surface of the second portion, the average hardness of the second surface-hardened layer being harder than the average hardness of the second interior portion, the first surface-hardened layer and the second surface-hardened layer both being carburized layers or both being carbonitrided layers, and the first surface-hardened layer and the second surface-hardened layer being connected.

[0011] The bearing raceway component has a first portion having a raceway and a second portion having a power transmission portion with teeth, and the first portion and the second portion are made of different steel materials and are integrated together, thereby achieving both strength suitable for the raceway of the bearing portion having the raceway and strength suitable for the teeth of the power transmission portion with teeth.

[0012] (2) In the bearing raceway component of (1) above, the teeth of the power transmission part having teeth are preferably teeth of a gear, spline, or toothed pulley.

[0013] (3) In the bearing raceway part of (1) or (2) above, it is preferable that the first steel contains carbon as a first alloy component, the second steel contains carbon as a second alloy component, and the carbon content (mass %) of the first steel is greater than the carbon content (mass %) of the second steel.

[0014] (4) In the bearing raceway part of any one of (1) to (3) above, the first steel material contains at least one of manganese, nickel, chromium, and molybdenum as a first alloy component, the second steel material contains at least one of manganese, nickel, chromium, and molybdenum as a second alloy component, and it is preferable that the total content (mass%) of manganese, nickel, chromium, and molybdenum in the first steel material is more than 1.5 times the total content (mass%) of manganese, nickel, chromium, and molybdenum in the second steel material.

[0015] (5) In any of the bearing raceway parts (1) to (4) above, it is preferable that the depth from the surface of the raceway of the bearing part having the raceway of the first part, which has a hardness of 700 HV or more, is deeper than the depth from the surface of the tooth bottom of the teeth of the power transmission part having the teeth of the second part, which has a hardness of 700 HV or more.

[0016] (6) In the bearing raceway part of any one of (1) to (5) above, it is preferable that the first steel material contains silicon as a first alloy component, the second steel material contains silicon as a second alloy component, and the silicon content (mass %) of the first steel material is less than the silicon content (mass %) of the second steel material.

[0017] (7) In any of the bearing raceway parts (1) to (6) above, it is preferable that the carbon content (mass %) within a range of 50 μm deep from the surface of the raceway of the bearing part having the raceway of the first part is greater than the carbon content (mass %) within a range of 50 μm deep from the surface of the tooth bottom of the tooth of the power transmission part having the teeth of the second part.

[0018] (8) The manufacturing method of a bearing raceway part of the present disclosure is a manufacturing method of a bearing raceway part having a power transmission portion with teeth as described in any one of (1) to (7) above, comprising: friction welding or welding a first portion of a workpiece in a first state and a second portion of a workpiece in a first state to form an integrated first workpiece; performing one of the following steps first and second: forming a portion that will become the bearing portion with a raceway in the first portion of the first workpiece by first machining; and forming a portion that will become the power transmission portion with teeth in the second portion of the first workpiece by second machining, to form a second workpiece; and simultaneously carburizing or carbonitriding the portion of the second workpiece that will become the bearing portion with a raceway and the portion that will become the power transmission portion with teeth, followed by quenching and tempering.

[0019] (9) In the manufacturing method of the bearing raceway part of (8) above, it is preferable to use the tempered work as a third work, and to perform a third machining process on the part of the third work that will become the bearing part having the raceway, and a fourth machining process on the part of the third work that will become the power transmission part having the teeth, and to perform either one of these processes first and the other second.

[0020] (10) A manufacturing method for a bearing raceway part according to the present disclosure is a manufacturing method for a bearing raceway part having a power transmission portion with teeth as described in any one of (1) to (7) above, wherein one of the following steps is carried out first, forming a portion that will become the bearing portion with a raceway on a first portion of a workpiece in a first state by a first machining process, and forming a portion that will become the power transmission portion with teeth on a second portion of a workpiece in a first state by a second machining process, to create a first portion of a workpiece in a second state and a second portion of a workpiece in a second state; the first portion of a workpiece in the second state and the second portion of a workpiece in the second state are integrated into a second workpiece by friction welding or welding; and the portion of the second workpiece that will become the bearing portion with a raceway and the portion that will become the power transmission portion with teeth are simultaneously carburized or carbonitrided, followed by quenching and tempering.

[0021] (11) In the manufacturing method of the bearing raceway part of (10) above, it is preferable to use the tempered work as a third work, and to perform a third machining process on the part of the third work that will become the bearing part having the raceway, and a fourth machining process on the part of the third work that will become the power transmission part having the teeth, and to perform either one of these processes first and the other second.

[0022] The bearing raceway components of the present disclosure can be manufactured by the manufacturing method described in (8) above, the manufacturing method described in (9) above, the manufacturing method described in (10) above, and the manufacturing method described in (11) above.

[0023] <Details of the Embodiments of the Invention of the Present Disclosure> Hereinafter, embodiments of the present disclosure will be described. Note that in this disclosure, the embodiments of the invention are to be considered as illustrative in all respects and not restrictive. The scope of the rights of the present invention is defined by the claims, and it is intended to include all modifications within the meaning and scope equivalent to the claims.

[0024] [First embodiment] Fig. 1 is a cross-sectional schematic view of a bearing raceway component according to this embodiment. Fig. 2 is a cross-sectional schematic view of a bearing assembly having the bearing raceway component of Fig. 1. Fig. 3 is a partially enlarged view of Fig. 1. Fig. 3 shows a portion of area A in Fig. 1. First, a bearing assembly 1 having a bearing raceway component 2 according to this embodiment will be described. Then, the bearing raceway component 2 will be described in detail.

[0025] As shown in Figure 2, the bearing device 1 comprises a bearing raceway component 2, an outer ring 3, a cage 8, and a plurality of balls (rolling elements) 4. The bearing raceway component 2 has a central axis C. One axial side of the central axis C is defined as the first axial side, and the other axial side is defined as the second axial side. In the following description, the direction perpendicular to the central axis C is referred to as the radial direction. Furthermore, the direction circumferentially around the central axis C is referred to as the circumferential direction. Figures 1 and 2 show cross sections cut along an imaginary plane passing through the central axis C.

[0026] The outer ring 3 has an outer ring raceway 3c. The bearing raceway component 2 has an inner ring raceway 2c (raceway groove 11, described later). A plurality of balls 4 are held by a cage 8 and arranged between the outer ring raceway 3c and the inner ring raceway 2c.

[0027] As shown in Fig. 1, the bearing raceway component 2 is a cylindrical shaft member. The bearing raceway component 2 has a bearing portion 10 having a raceway and a power transmission portion 20 having teeth for transmitting power. The bearing portion 10 having the raceway is on a first axial side of the power transmission portion 20 having teeth. The power transmission portion 20 having teeth is on a second axial side of the bearing portion 10 having the raceway. The bearing portion 10 having the raceway and the power transmission portion 20 having teeth are joined at a joining surface 5 by friction welding or welding. The bearing raceway component 2 is a member in which two portions are integrated.

[0028] The bearing raceway component 2 is a component that has an inner ring raceway of a bearing and teeth of an external gear on the outer peripheral surface of an integrated shaft member. Therefore, by press-fitting the inner ring and / or external gear of the bearing onto the shaft, it is easier to achieve miniaturization compared to components that have the same function as the bearing raceway component 2.

[0029] In the bearing raceway component 2, the diameter of the outer peripheral surface 12 of the bearing portion 10 having the raceway is smaller than the root diameter of the power transmission portion 20 having teeth. In this case, it is easy to mesh the teeth 21 of the external gear with the teeth 7 of the gear that is paired with the external gear. The portion of the power transmission portion 20 having teeth whose diameter is equal to or smaller than the root diameter is the root cylindrical portion 26, and the portion of the power transmission portion 20 having teeth whose diameter is larger than the root diameter is the tooth 21.

[0030] The bearing portion 10 having a raceway has a raceway groove 11 that becomes the inner ring raceway 2c on part of its outer circumferential surface. As described above, the bearing portion 10 having a raceway is combined with the outer ring 3, the cage 8, and a plurality of balls 4 to form the rolling bearing 6. The material of the bearing portion 10 having a raceway is a first steel material. The preferred first steel material is a steel material suitable for raceway components of a rolling bearing.

[0031] The first steel material may, for example, contain carbon as an alloying component. The first steel material may, for example, contain at least one of manganese, nickel, chromium, and molybdenum as an alloying component. The first steel material may, for example, contain silicon as an alloying component. A preferred first steel material contains carbon, silicon, manganese, nickel, chromium, and molybdenum as alloying components.

[0032] Examples of the first steel material include alloy steel materials for machine structures such as chromium steel, chromium-molybdenum steel, nickel-chromium-molybdenum steel, etc. Specific examples of the first steel material include SCr420, SCM420, SNCM420, SCM440, SNCM439, etc.

[0033] The toothed power transmission portion 20 serves to transmit power between the bearing raceway component 2 and an element other than the bearing raceway component 2 by means of the teeth. The toothed power transmission portion 20 has gear teeth 21 for transmitting power on part of its outer circumferential surface. The teeth 21 are teeth of a helical gear. These teeth 21 mesh with the teeth 7, 7 of other gears (see FIG. 2 ), thereby receiving power from an element other than the bearing raceway component 2 and transmitting power to an element other than the bearing raceway component 2. The toothed power transmission portion 20 is made of a second steel material. The second steel material is preferably a steel material suitable for gears, splines, toothed pulleys, etc.

[0034] The second steel material may, for example, contain carbon as an alloying component. The second steel material may, for example, contain at least one of manganese, nickel, chromium, and molybdenum as an alloying component. The second steel material may, for example, contain silicon as an alloying component. A preferred second steel material contains carbon, silicon, manganese, nickel, chromium, and molybdenum as alloying components.

[0035] Examples of the second steel material include alloy steel materials for machine structures such as chromium steel, chromium-molybdenum steel, nickel-chromium-molybdenum steel, etc. Specific examples of the second steel material include SCr420, SCM420, SNCM420, etc.

[0036] The alloying elements contained in the first steel material are different from the alloying elements contained in the second steel material, so that the bearing raceway component 2 can have both strength suitable for the raceway in the bearing portion having a raceway and strength suitable for the teeth in the power transmission portion having teeth.

[0037] In the bearing raceway component 2, the bearing portion 10 having the raceway has a first surface-hardened layer 13 and a first interior portion 14. The first surface-hardened layer 13 is provided along the surface, including the outer peripheral surface 12, of the bearing portion 10 having the raceway. The first interior portion 14 is provided on the side of the first surface-hardened layer 13 opposite the surface, including the outer peripheral surface 12, of the bearing portion 10 having the raceway. The first surface-hardened layer 13 is a carburized layer or a carbonitrided layer. Therefore, the first surface-hardened layer 13 refers to a region having a higher carbon content than the first steel material before the carburizing or carbonitriding treatment. When the carbon content of the bearing portion 10 having the raceway is measured in the depth direction (direction perpendicular to the outer peripheral surface) from the outer peripheral surface, the carbon content gradually decreases and stops changing at a certain depth (referred to as a first depth D1 in this disclosure). The range from the surface, including the outer peripheral surface 12, of the bearing portion 10 having the raceway to the first depth D1 corresponds to the first surface-hardened layer 13. The average hardness of the first surface-hardened layer 13 is higher than the average hardness of the first inner portion 14. Therefore, the first surface-hardened layer 13 in the bearing portion 10 having the raceway contributes to extending the life of the bearing.

[0038] In the bearing raceway component 2, the toothed power transmission portion 20 has a second surface-hardened layer 23 and a second inner portion 24. The second surface-hardened layer 23 is provided along a surface, including the outer peripheral surface 22, of the toothed power transmission portion 20. The second inner portion 24 is provided on the side of the second surface-hardened layer 23 opposite the surface, including the outer peripheral surface 22, of the toothed power transmission portion 20. The second surface-hardened layer 23 is a carburized layer or a carbonitrided layer. Therefore, the second surface-hardened layer 23 refers to a region having a higher carbon content than the second steel material before the carburizing or carbonitriding treatment. When the carbon content of the toothed power transmission portion 20 is measured in the depth direction (direction perpendicular to the outer peripheral surface) from the outer peripheral surface, the carbon content gradually decreases and stops changing at a certain depth (referred to as the second depth D2 in this disclosure). The range from the surface, including the outer peripheral surface 22, of the toothed power transmission portion 20 to the second depth D2 corresponds to the second surface-hardened layer 23. The average hardness of the second surface-hardened layer 23 is greater than the average hardness of the second inner portion 24. Therefore, the second surface-hardened layer 23 in the toothed power transmission portion 20 contributes to extending the life of the toothed power transmission portion 20.

[0039] The first surface-hardened layer 13 and the second surface-hardened layer 23 are connected to each other. The entire surface of the bearing raceway part 2, including the outer peripheral surfaces 12, 22 of the cylindrical shaft member, is formed by the surface-hardened layers 13, 23. The first surface-hardened layer 13 and the second surface-hardened layer 23 are formed through a carburizing treatment or a carbonitriding treatment. The carburizing treatment and the carbonitriding treatment will be described in detail later.

[0040] The depth D10 from the surface of the inner ring raceway 2c (raceway groove 11) of the bearing portion 10 having a raceway of the bearing raceway component 2 in the range having a hardness of 700 HV or more is deeper than the depth D20 from the surface of the tooth bottoms 25 of the teeth 21 in the range having a hardness of 700 HV or more of the tooth bottoms 25 of the teeth 21 of the toothed power transmission portion 20. In this case, the bearing raceway component 2 is likely to have a good bearing life, and compressive stress is applied to the teeth, which tends to improve the pitting strength of the gear.

[0041] The depth from the surface of the inner ring raceway 2c in the bearing part 10 having a raceway is the depth in a direction perpendicular to the surface of the inner ring raceway 2c. The depth from the surface of the tooth 21 in the power transmission part 20 having teeth is the depth from the surface of the tooth bottom 25 of the tooth 21. Furthermore, the depth from the surface of the tooth bottom 25 is the depth in a direction perpendicular to the surface of the tooth bottom 25. The position at which the depth from the surface is measured to measure the hardness of the tooth 21 of the power transmission part 20 having teeth is the tooth bottom 25 of the tooth 21. This is because the tooth bottom cylindrical portion 26 is present in the depth direction perpendicular to the surface of the tooth bottom 25 of the tooth 21, and therefore a position deeper than the depth D10 from the surface in the range having a hardness of 700 HV or more will always remain.

[0042] The depth D10 from the surface of the inner ring raceway 2c of the bearing part 10 having a raceway and having a hardness of 700 HV or more is preferably 0.2 mm or more and 2.0 mm or less. The depth D20 from the surface of the tooth bottoms 25 of the teeth 21 of the power transmission part 20 having teeth and having a hardness of 700 HV or more is preferably 0.1 mm or more and 1.0 mm or less.

[0043] The concept required for the depth from the surface of the raceway of a bearing part having a raceway in a range of hardness of 700 HV (hard portion) or more is as follows: It is required to extend the rolling fatigue life of the raceway of a bearing part having a raceway until internally initiated flaking occurs, which is initiated by non-metallic inclusions inside the raceway. When the depth from the surface of the raceway of a bearing part having a raceway in a range of hardness of 700 HV (hard portion) or more is deep, the rolling fatigue life is longer compared to when this depth is shallow. It is also required to suppress the formation of Brinell indentations in the raceway of a bearing part having a raceway due to the rolling elements being statically pressed against the raceway. When the depth from the surface of the raceway of a bearing part having a raceway in a range of hardness of 700 HV (hard portion) or more is deep, the formation of Brinell indentations is suppressed compared to when this depth is shallow. For this reason, it is desirable that the range having a hardness of 700 HV (hard portion) or more exists deep from the surface of the raceway of a bearing part having a raceway.

[0044] On the other hand, the depth from the surface of the tooth root of a power transmission part having teeth in a range having a hardness of 700 HV or more (hard portion) is considered as follows: The difference between the depth of the tooth surface of the power transmission part having teeth 20 having a hardness of 700 HV or more and the depth of the range of the tooth root of the power transmission part having teeth 20 having a hardness of 700 HV or more is smaller than the difference between the depth of the range of the hardness of 700 HV or more in the inner ring raceway 2c of the bearing part having raceway 10 and the depth of the range of the hardness of 700 HV or more at the tooth root of the power transmission part having teeth 20. The depth of the tooth surface of the power transmission part having teeth 20 having a hardness of 700 HV or more can be substituted for the depth of the range of the tooth root of the power transmission part having teeth 20 having a hardness of 700 HV or more. It is required to suppress tooth surface pitting damage occurring on the outermost surface of the teeth of the power transmission part having teeth. For this reason, the teeth of the toothed power transmission part require a hardness of 700 HV (hard portion) or more on the tooth surface. Furthermore, the teeth of the toothed power transmission part have an uneven shape, and are required to have a core structure (non-carburized structure) inside the convex teeth of the toothed power transmission part, and a hard portion (carburized structure) on the tooth surface. If the inside of the teeth of the toothed power transmission part has a hard portion (carburized structure), the toughness of the teeth of the toothed power transmission part will decrease, making the teeth more susceptible to fracture. For this reason, it is desirable that the range having a hardness of 700 HV (hard portion) or more remain shallow from the surface of the teeth of the toothed power transmission part.

[0045] The depth D10 in the inner ring raceway 2c of the bearing portion 10 having a raceway is measured using the following method. First, the bearing raceway component 2 is cut along a plane including the central axis so as to pass through the inner ring raceway 2c. Next, a Vickers indenter is applied to the resulting cut surface from the surface (outer peripheral surface) toward the interior in the depth direction (a direction perpendicular to the tangent to the outer peripheral surface in the cross section) at a pitch of 50 μm to measure the Vickers hardness. The change in Vickers hardness is plotted, and the depth in the range having a hardness of 700 HV or more is calculated by interpolation. The depth D20 in the tooth 21 of the toothed power transmission portion 20 is measured in the same manner as the depth D10, except that the cutting location is changed. In measuring the depth D20, the bearing raceway component 2 is cut along a plane perpendicular to the central axis so as to pass through the tooth 21 of the toothed power transmission portion 20.

[0046] The first alloy component contained in the first steel material is different from the second alloy component contained in the second steel material. The preferable relationship between the first alloy component and the second alloy component is one of the following relationships (a) to (c):

[0047] (a) The carbon content (mass %) of the first steel material is greater than the carbon content (mass %) of the second steel material. In this case, the penetration depth of carbon into the steel material by carburizing or carbonitriding is likely to be deeper in the bearing portion 10 having the raceway than in the power transmission portion 20 having the teeth. Therefore, the depth of the range in the bearing portion 10 having the raceway where the hardness is 700 HV or more is likely to be deeper than the depth of the range in the power transmission portion 20 having the teeth where the hardness is 700 HV or more.

[0048] The carbon content of the first steel material is preferably 0.25% by mass or more and 1.10% by mass or less, and the carbon content of the second steel material is preferably 0.15% by mass or more and 0.25% by mass or less.

[0049] (b) The total content (mass %) of manganese, nickel, chromium, and molybdenum in the first steel is more than 1.5 times the total content (mass %) of manganese, nickel, chromium, and molybdenum in the second steel. In this case, when the bearing portion 10 having a raceway made of the first steel and the power transmission portion 20 having teeth made of the second steel are hardened, the hardenability of the bearing portion 10 having a raceway tends to be superior to the hardenability of the power transmission portion 20 having teeth. Therefore, the depth of the range having a hardness of 700 HV or more in the inner ring raceway 2c of the bearing portion 10 having a raceway is likely to be deeper than the depth of the range having a hardness of 700 HV or more at the tooth roots of the power transmission portion 20 having teeth.

[0050] In the first steel material, the total content of manganese, nickel, chromium, and molybdenum is preferably 2.5 mass% or more and 6.5 mass% or less.In the second steel material, the total content of manganese, nickel, chromium, and molybdenum is preferably 1.5 mass% or more and 2.5 mass% or less.

[0051] (c) The silicon content (mass %) of the first steel is less than the silicon content (mass %) of the second steel. In this case, when carburizing or carbonitriding is performed, the penetration of carbon into the first steel, which is the material of the bearing portion 10 having the raceway, is less inhibited than the penetration of carbon into the second steel, which is the material of the power transmission portion 20 having teeth.

[0052] In the first steel material, the silicon content is preferably 0.10 mass% or more and 0.34 mass% or less.In the second steel material, the silicon content is preferably 0.35 mass% or more and 1.00 mass% or less.

[0053] The number of non-metallic inclusions having a width of 30 μm or more contained in the first steel material is smaller than the number of non-metallic inclusions having a width of 30 μm or more contained in the second steel material. In this case, the inner ring raceway 2 c of the bearing portion 10 having a raceway in the bearing device 1 is likely to have an improved bearing life.

[0054] In a preferred bearing raceway component 2, the carbon content (mass %) within a range of 50 μm deep from the surface of the inner ring raceway 2c of the bearing portion 10 having a raceway is greater than the carbon content (mass %) within a range of 50 μm deep from the surface of the tooth root 25 of the tooth 21 of the toothed power transmission portion 20. In this case, the bearing raceway component 2 is likely to have a good bearing life, the amount of coarse carbides in the tooth 21 is likely to be small, and the gear tooth tip strength is likely to be good. The position at which the depth of the carbon content within the range from the surface of the tooth 21 of the toothed power transmission portion 20 is measured is the tooth root 25 of the tooth 21. This is because a tooth root cylindrical portion 26 is present in the depth direction perpendicular to the surface of the tooth root 25 of the tooth 21, and a position deeper than 50 μm deep from the surface will always remain.

[0055] The carbon content within a range of 50 μm deep from the surface of the inner ring raceway 2 c of the bearing part 10 having a raceway is preferably 0.75 mass % or more and 0.95 mass % or less. The carbon content within a range of 50 μm deep from the surface of the tooth root 25 of the tooth 21 of the power transmission part 20 having teeth is preferably 0.55 mass % or more and 0.75 mass % or less.

[0056] The considerations required for the surface carbon amount (carbon contained within a range of 50 μm deep from the surface) of the raceway of the bearing part 10 having a raceway are as follows: When the rolling elements repeatedly roll on the raceway of the bearing part 10 having a raceway, stress is repeatedly applied to the raceway of the bearing part 10 having a raceway, resulting in internally initiated flaking or surface initiated flaking in the raceway of the bearing part 10 having a raceway. It is required to extend the rolling fatigue life until internally initiated flaking or surface initiated flaking occurs. When the surface carbon amount is high, the rolling fatigue life is longer than when the surface carbon amount is low. For this reason, it is desirable for the surface carbon amount of the raceway of the bearing part 10 having a raceway to be high.

[0057] On the other hand, the consideration required for the surface carbon amount at the tooth bottom of the toothed power transmission part 20 is as follows: When the surface carbon amount is high, the bending fatigue strength of the tooth bottom of the toothed power transmission part 20 is lower than when the surface carbon amount is low. Also, when the surface carbon amount is high, coarse carbides are precipitated at the tooth tips of the teeth of the toothed power transmission part 20, reducing the toughness of the tooth tips compared to when the surface carbon amount is low. For this reason, it is desirable for the surface carbon amount of the teeth of the toothed power transmission part 20 to be low.

[0058] The carbon content within a range of 50 μm deep from the surface of the inner ring raceway 2 c of the bearing part 10 having a raceway is measured by cutting the bearing raceway component 2 along a plane including the central axis so as to pass through the inner ring raceway 2 c, and measuring the carbon content within a range of 50 μm deep from the outer circumferential surface of the obtained cut surface using an electron probe microanalyzer (EPMA). The carbon content within a range of 50 μm deep from the tooth bottoms 25 of the teeth 21 of the toothed power transmission part 20 is measured by cutting the bearing raceway component 2 along a plane perpendicular to the central axis so as to pass through the teeth 21, and measuring the carbon content within a range of 50 μm deep from the tooth bottoms 25 of the teeth 21 of the toothed power transmission part 20 of the obtained cut surface using an electron probe microanalyzer (EPMA).

[0059] The preferred steel materials and preferred qualities including the relationships (a) to (c) described above are suitable for ensuring a balance in performance between the raceway and the teeth when the outer diameter of the teeth is approximately 0.5 to 5 times the smallest outer diameter of the inner raceway or the largest inner diameter of the outer raceway in terms of the dimensional relationship between the raceway of a bearing part having a raceway (which may be an inner raceway or an outer raceway instead of an inner raceway) and the teeth of a power transmission part having teeth.

[0060] Next, a description will be given of a method for manufacturing the bearing raceway component 2. The bearing raceway component 2 can be manufactured by, for example, a first manufacturing method or a second manufacturing method.

[0061] (First Manufacturing Method) Figure 4 is a diagram illustrating a first manufacturing method for a bearing raceway component. (1) A cylindrical workpiece 51 made of a first steel material and a cylindrical workpiece 52 made of a second steel material are prepared, and these workpieces are joined to produce a cylindrical joined workpiece (first workpiece) 53 in which the two workpieces are integrated. The first steel material and the second steel material are different steel materials, and their types are as described above. The workpieces 51 and 52 are joined by friction welding or welding. The workpiece 51 is a workpiece prior to first machining, which will result in a bearing portion having a raceway after subsequent processing. The workpiece 52 is a workpiece prior to second machining, which will result in a power transmission portion having teeth after subsequent processing. Friction welding and welding are performed using known techniques, and the processing conditions are appropriately selected depending on the type and size of the steel material, etc.

[0062] (2) A portion 55 that will become the inner ring raceway 2c is formed in a part of a workpiece 51 made of a first steel material by cutting as a first machining process. Also, a portion 56 that will become the gear teeth 21 is formed in a part of a workpiece 52 made of a second steel material by cutting as a second machining process. Either the formation of the portion 55 that will become the inner ring raceway or the formation of the portion 56 that will become the gear teeth is performed first, and the other is performed later. In this process, a second workpiece 57 is obtained in which the portion 55 that will become the inner ring raceway and the portion 56 that will become the gear teeth are formed.

[0063] (3) The second workpiece 57 is subjected to heat treatment. Specifically, the second workpiece 57 is carburized or carbonitrided, followed by quenching, and then tempering. The entire second workpiece 57 is subjected to heat treatment. In other words, the portion 55 that will become the inner ring raceway and the portion 56 that will become the gear teeth are simultaneously heat-treated. The carburizing treatment is performed under conditions, for example, a carbon potential of 0.9 to 1.4, a carburizing atmosphere at a temperature of 900 to 1000°C, and a holding time of 1 to 15 hours. The carbonitriding treatment is performed under conditions, for example, a carbon potential of 0.9 to 1.4, an ammonia gas flow rate relative to the carburizing gas flow rate of 1 to 5 mass%, and a carbonitriding atmosphere at a temperature of 830 to 900°C, and a holding time of 1 to 15 hours. During the carburizing and carbonitriding treatments, the carbon potential, ammonia gas flow rate, and temperature may be changed during the process.

[0064] The conditions for the quenching treatment are, for example, that the workpiece after carburizing or carbonitriding is held at 820 to 870°C for 0.5 to 2 hours, followed by oil cooling.The conditions for the tempering treatment are, for example, that the workpiece after quenching is held at 150 to 200°C for 1 to 5 hours, followed by air cooling.

[0065] This step yields a third workpiece 58 having a carburized layer or a carbonitrided layer formed on its outer peripheral surface. Because the carburized layer or the carbonitrided layer formed on the third workpiece 58 is formed by the method described above, the carburized layer or the carbonitrided layer formed on the workpiece 51 made of the first steel material is connected to the carburized layer or the carbonitrided layer formed on the workpiece 52 made of the second steel material. Furthermore, the interior of the workpiece 51 made of the first steel material is connected to the interior of the workpiece 52 made of the second steel material. Furthermore, the carburized layer or the carbonitrided layer is a surface-hardened layer whose hardness has been increased through carburizing or carbonitriding, quenching, and tempering.

[0066] (4) The third workpiece 58 is subjected to polishing as the third machining process and polishing as the fourth machining process. The third workpiece 58 is finished to a predetermined precision by polishing as the third machining process to form the inner ring raceway 2c, and by polishing as the fourth machining process to form the gear teeth 21. At this time, one of the polishing as the third machining process performed on the portion that will become the inner ring raceway and the polishing as the fourth machining process performed on the portion that will become the gear teeth is performed first, and the other is performed later. The bearing raceway component 2 is manufactured by performing these steps (1) to (4).

[0067] (Second Manufacturing Method) Figure 5 is a diagram illustrating a second manufacturing method for a bearing raceway component. (1) A cylindrical workpiece 61 made of a first steel material is prepared. A portion 65 that will become the inner ring raceway 2c is formed in a portion of the workpiece 61 made of this first steel material by cutting as a first machining process. This results in a first portion of the workpiece 63 formed with the portion 65 that will become the inner ring raceway. A cylindrical workpiece 62 made of a second steel material is prepared. A portion 66 that will become the gear teeth 21 is formed in a portion of the workpiece 62 made of this second steel material by cutting as a second machining process. This results in a second portion of the workpiece 64 formed with the portion 66 that will become the gear teeth.

[0068] The first steel material and the second steel material are different steel materials, and their types are as described above. One of the first portion of the workpiece 63 and the second portion of the workpiece 64 is produced first, and the other is produced later. The workpiece 61 is an unmachined workpiece that will become a bearing part having a raceway after a subsequent process. The workpiece 63 is a workpiece that has been subjected to cutting as a first machining process and will become a bearing part having a raceway after a subsequent process. The workpiece 62 is an unmachined workpiece that will become a power transmission part having teeth after a subsequent process. The workpiece 64 is a workpiece that has been subjected to cutting as a second machining process and will become a power transmission part having teeth after a subsequent process.

[0069] (2) The first workpiece 63 and the second workpiece 64 are joined together to produce a cylindrical second workpiece 67, which is an integrated combination of the two workpieces. The first workpiece 63 and the second workpiece 64 are joined by friction welding or welding. Friction welding and welding are performed using known techniques, and processing conditions are appropriately selected depending on the type and size of the steel material, etc.

[0070] (3) The second workpiece 67 is subjected to heat treatment. Specifically, the second workpiece 67 is carburized or carbonitrided, then quenched, and then tempered. This step is performed in the same manner as step (3) in the first manufacturing method. In this case, the bearing portion 65 having the raceway that will become the inner ring raceway and the power transmission portion 66 having the teeth that will become the gear teeth are simultaneously subjected to heat treatment.

[0071] This step yields a third workpiece 68 having a carburized layer or a carbonitrided layer formed on its outer peripheral surface. Because the carburized layer or the carbonitrided layer formed on the third workpiece 68 is formed by the method described above, the carburized layer or the carbonitrided layer formed on the workpiece 61 made of the first steel material is connected to the carburized layer or the carbonitrided layer formed on the workpiece 62 made of the second steel material. Furthermore, the interior of the workpiece 61 made of the first steel material is connected to the interior of the workpiece 62 made of the second steel material. Furthermore, the carburized layer or the carbonitrided layer is a surface-hardened layer whose hardness has been increased through carburizing or carbonitriding, quenching, and tempering.

[0072] (4) The third workpiece is polished. This step is performed in the same manner as step (4) of the first manufacturing method. The bearing raceway component 2 can also be manufactured by the second manufacturing method, which includes steps (1) to (4).

[0073] [Second Embodiment] The bearing race component 2 according to the first embodiment is a cylindrical shaft member. On the other hand, the bearing race component 2 according to the present invention may be a columnar shaft member that does not have the hole of the bearing race component 2 according to the first embodiment. Furthermore, the bearing race component 2 according to the present invention may be a hollow shaft member having a sealed hollow hole, with a first axial position sealed from the joining surface 5 of the hole of the bearing race component 2 according to the first embodiment, and a second axial position sealed from the joining surface 5 of the hole of the bearing race component 2 according to the first embodiment. The bearing race component of this embodiment is manufactured by preparing a cylindrical workpiece made of a first steel material and a cylindrical workpiece made of a second steel material, and friction welding or welding these workpieces. The bearing race component of this embodiment was manufactured and its properties were evaluated below. The 700 HV depth and surface carbon content were measured as properties.

[0074] (Manufacturing and evaluation of bearing raceway components) A plurality of bearing raceway components A to G were manufactured by changing the combination of the first steel material and the second steel material. The properties of the resulting bearing raceway components A to G were evaluated. The bearing raceway components were manufactured by the first manufacturing method described above.

[0075] (1) Preparation of round bars Round bars of diameter φ: 40 mm x length L: 100 mm were prepared, consisting of steel materials A to D with the compositions shown in Table 1. Steel material A is SNCM420. Steel material B is SCM440. Steel materials C and D are SCM420. Carbon is represented by C, manganese by Mn, nickel by Ni, chromium by Cr, molybdenum by Mo, and silicon by Si.

[0076]

[0077]

[0078] (2) Joining of the first steel material and the second steel material Two round bars were friction-welded using the combination shown in Table 2 to obtain the first workpiece in which the two types of round bars were integrated.

[0079] (3) Cutting The first workpiece was cut to first align the outer diameter of the entire first workpiece and align the central axes of the two round bars. Next, the portion made of the first steel material was cut to create the portion that would become the inner raceway of the deep groove ball bearing, and then the portion made of the second steel material was cut to create the portion that would become the gear teeth. This resulted in the second workpiece.

[0080] (4) The second workpiece was subjected to heat treatment to become the third workpiece. The specific heat treatment conditions are shown in Figure 6. First, the second workpiece was held in a carburizing atmosphere with a carbon potential of 1.2 and a temperature of 930°C for 3 hours. Next, the carbon potential was changed to 1.0 and held for 2 hours. Subsequently, the second workpiece was held at 850°C for 30 minutes and then oil-cooled. Furthermore, as a tempering treatment, the second workpiece was held at 180°C for 2 hours and then air-cooled. By subjecting the second workpiece to this heat treatment, a carburized layer was formed on the outer surface of the second workpiece, and the second workpiece became the third workpiece.

[0081] (5) The third workpiece was subjected to polishing as the third machining process and polishing as the fourth machining process, and the inner ring raceway and gear teeth were finished to become a bearing raceway part.

[0082] (6) Property Evaluation (6-1) Depth Measurement of Portions with Vickers Hardness of 700 HV or More The bearing raceway component was cut, and the Vickers hardness of the inner raceway and the tooth roots of the resulting cross-section of the bearing raceway component was measured along the depth direction. The bearing raceway component was cut at two locations. One of the cut locations was the portion where the inner raceway was provided. The other cut location was the portion where the gear teeth were provided. First, the portion where the gear teeth were provided was cut on a plane perpendicular to the central axis, and then the portion where the inner raceway was provided was cut on a plane including the central axis. The depth of the portions with a Vickers hardness of 700 HV or more was determined by applying a Vickers indenter to the cross-section of the resulting bearing raceway component at 50 μm intervals from the surface (the surface of the inner raceway and the surface of the gear tooth root) in the depth direction. Measurements were performed at three locations on each cross-section, and the average of the measured values ​​was used as the result. The results are shown in Table 3.

[0083] (6-2) Measurement of Surface Carbon Content The bearing raceway component was cut, and the carbon content of the inner raceway and tooth roots in the cross section of the resulting bearing raceway component was measured within a range of 50 μm from the surface in the depth direction. The bearing raceway component was cut at two locations. One of the cut locations was the portion where the inner raceway was provided. The other cut location was the portion where the gear teeth were provided. First, the portion where the gear teeth were provided was cut on a plane perpendicular to the central axis, and then the portion where the inner raceway was provided was cut on a plane including the central axis. The carbon content was measured using an electron probe microanalyzer (EPMA). The results are shown in Table 3.

[0084]

[0085] As shown in Table 3, bearing raceway components A to G were obtained as embodiments of the present invention, with different properties for the bearing portion having a raceway and the power transmission portion having teeth. Among bearing raceway components A to G, when the dimensional relationship between the raceway of the bearing portion having a raceway and the teeth of the power transmission portion having teeth was such that the outer diameter of the teeth was approximately 0.5 to 5 times the smallest outer diameter of the inner ring raceway, bearing raceway components A, B, and G were bearing raceway components in which the bearing portion having a raceway had properties suitable for a bearing and the power transmission portion having teeth had properties suitable for gear teeth.

[0086] (Third Embodiment) A bearing raceway component according to an embodiment of the present invention may have a bearing portion having two or more raceways and a power transmission portion having one or more teeth, or may have a bearing portion having one or more raceways and a power transmission portion having two or more teeth. Figure 7 is a cross-sectional view of a bearing raceway component according to a third embodiment. As shown in Figure 7, a bearing raceway component 102 according to this embodiment is a cylindrical shaft member. The bearing raceway component 102 has two bearing portions 110A, 110B having raceways and two power transmission portions 120A, 120B having teeth.

[0087] As shown in Figure 7, the bearing raceway component 102 comprises, from the first side to the second side, a power transmission portion with teeth 120B, a bearing portion with raceway 110A, a power transmission portion with teeth 120A, and a bearing portion with raceway 110B. The power transmission portion with teeth 120B and the bearing portion with raceway 110A are joined at a joining surface 105B by friction welding or welding. The bearing portion with raceway 110A and the power transmission portion with teeth 120A are joined at a joining surface 105A by friction welding or welding. The power transmission portion with teeth 120A and the bearing portion with raceway 110B are joined at a joining surface 105C by friction welding or welding. The bearing raceway component 102 is a member formed by integrating four portions.

[0088] The structure of the bearing portion 110A with a raceway is similar to that of the bearing portion 10 with a raceway of the first embodiment. The bearing portion 110A is combined with an outer ring 3, a cage 8, and a plurality of balls to form a bearing. The structure of the toothed power transmission portion 120A is similar to that of the toothed power transmission portion 20 of the first embodiment. The toothed power transmission portion 120A has external gear teeth 121A on a portion of its outer circumferential surface as the toothed power transmission portion 120A. The toothed power transmission portion 120A has tooth roots 125A of the teeth 121A between the teeth 121A. The portion of the toothed power transmission portion 120A having a diameter equal to or smaller than the tooth root diameter is a tooth root cylindrical portion 126A, and the portion of the toothed power transmission portion 20A having a diameter larger than the tooth root diameter is the tooth 121A. The teeth 121A are helical gear teeth. The teeth 121A can mesh with the teeth of another gear to transmit power to elements other than the bearing raceway component 2. The first hardened surface layer 113A of the bearing portion 110A having the raceway is connected to the second hardened surface layer 123A of the power transmission portion 120A having the teeth. The first inner portion 114A of the bearing portion 110A having the raceway is connected to the second inner portion 124A of the power transmission portion 120A having the teeth.

[0089] The bearing part 110B with raceway has a raceway groove 111B that forms an inner ring raceway on part of its outer periphery. The bearing part 110B with raceway is combined with an outer ring, a cage, and a plurality of balls to form a bearing. The material of the bearing part 110B with raceway is the first steel material described above. The material of the bearing part 110B with raceway may be the same as or different from the material of the bearing part 110A with raceway.

[0090] Similar to the bearing portion with raceway 10, the bearing portion with raceway 110B has a first hardened surface layer 113B and a first inner portion 114B. The first hardened surface layer 113B is provided along a surface, including the outer peripheral surface 112B, of the bearing portion with raceway 110B. The first inner portion 114B is provided on the opposite side of the first hardened surface layer 113B from the surface, including the outer peripheral surface 112B, of the bearing portion with raceway 110B. The average hardness of the first hardened surface layer 113B is higher than the average hardness of the first inner portion 114B. The first hardened surface layer 113B is a carburized layer or a carbonitrided layer. The first hardened surface layer 113B connects to the second hardened surface layer 123A of the power transmission portion with teeth 120A adjacent to the bearing portion with raceway 110B. The first inner portion 114B of the bearing portion with raceway 110B connects to the second inner portion 124A of the power transmission portion with teeth 120A. The preferred configuration of the bearing portion 110B with raceway is similar to the bearing portion 10 with raceway.

[0091] The toothed power transmission portion 120B serves to transmit power between the bearing raceway component 102 and an element other than the bearing raceway component 102. The toothed power transmission portion 120B has spline teeth 121B on a portion of its outer periphery. These spline teeth 121B can be connected to a motor shaft, for example, to transmit power to and from the motor. The toothed power transmission portion 120B is made of the second steel material described above. The material of the toothed power transmission portion 120B may be the same as or different from the material of the power transmission portion 120A. The toothed power transmission portion 120B has tooth roots 125B between the teeth 121B. The portions of the toothed power transmission portion 120B having a diameter equal to or smaller than the tooth root diameter are tooth root cylindrical portions 126B, and the portions of the toothed power transmission portion 120B having a diameter larger than the tooth root diameter are teeth 121B.

[0092] Similar to the toothed power transmission portion 20, the toothed power transmission portion 120B has a second hardened surface 123B and a second inner portion 124B. The second hardened surface 123B is provided along a surface, including the outer peripheral surface 112B, of the power transmission portion 120B. The second inner portion 124B is provided on the opposite side of the second hardened surface 123B from the surface, including the outer peripheral surface 122B, of the toothed power transmission portion 120B. The average hardness of the second hardened surface 123B is higher than the average hardness of the second inner portion 124B. The second hardened surface layer 123B is a carburized layer or a carbonitrided layer. The second hardened surface layer 123B connects to the first hardened surface 113A of the bearing portion 110A having the adjacent raceway. The second inner portion 124B of the toothed power transmission portion 120B connects to the first inner portion 114A of the bearing portion 110A having the raceway. The preferred configuration of toothed power transmission portion 120B is similar to toothed power transmission portion 20.

[0093] In the bearing raceway component 102, the entire outer peripheral surfaces 112A, 112B, 122A, and 122B of the cylindrical shaft member are formed with surface-hardened layers 113A, 113B, 123A, and 123B. Both end surfaces and the inner peripheral surface of the bearing raceway component 102 are also formed with surface-hardened layers. The surface-hardened layers 123B and 113A, the surface-hardened layers 113A and 123A, and the surface-hardened layers 123A and 113B are all connected. The surface-hardened layers 113A, 113B, 123A, and 123B are either all carburized layers or all carbonitrided layers. Furthermore, the interiors 124B and 114A, the interiors 114A and 124A, and the interiors 124A and 114B are all connected.

[0094] In the bearing raceway part 102, as in the bearing raceway part 2, the bearing part having a raceway and the power transmission part having teeth have a preferred relationship with respect to the range of hardness of 700 HV or more, the relationship between the first alloy component and the second alloy component, and the carbon content contained in the range of 50 μm deep from the outer circumferential surface. The preferred relationship between the bearing part having a raceway and the power transmission part having teeth may be the same as that between a bearing part having a raceway and a power transmission part having teeth that are adjacent to each other.

[0095] The bearing raceway component 102 can be manufactured in the same manner as in the first embodiment, except for the number of workpieces to be joined by friction welding or welding.

[0096] Other Embodiments The bearing raceway component according to the embodiment of the present invention may have teeth of a gear, spline teeth, toothed pulley teeth, or the like as teeth of a power transmission part having teeth.

[0097] In the bearing raceway component according to the embodiment of the present invention, as long as the bearing portion having a raceway and the power transmission portion having teeth are joined together, the number of bearing portions having a raceway and the power transmission portion having teeth is not limited, and may be three in total, two bearing portions having a raceway and one power transmission portion having teeth, or three in total, one bearing portion having a raceway and two power transmission portions having teeth, or may be five or more in total. However, if the total number is too large, the central axis may be easily misaligned or distortion may occur in the bearing raceway component, so the total is preferably four or less.

[0098] In the bearing raceway component according to the embodiment of the present invention, the bearing portion having a raceway may have a plurality of raceways. In the bearing raceway component according to the embodiment of the present invention, the bearing portion having a raceway is not limited to a bearing portion having an inner ring raceway, but may be a bearing portion having an outer ring raceway. The raceway may be provided on the inner peripheral surface.

[0099] In the bearing raceway component according to the embodiment of the present invention, the power transmission part having teeth may have multiple types of teeth as the teeth that constitute the power transmission part. In the bearing raceway component according to the embodiment of the present invention, the power transmission part having teeth is not limited to a power transmission part having an external gear, but may also be a power transmission part having an internal gear. The gear may be provided on the inner peripheral surface.

[0100] In the bearing raceway component according to an embodiment of the present invention, in terms of the dimensional relationship between the raceway of the bearing portion having a raceway and the teeth of the power transmission portion having teeth, the preferred steel material and quality were shown when the outer diameter of the teeth was approximately 0.5 to 5 times the smallest outer diameter of the inner ring raceway, but the value of the outer diameter of the teeth relative to the outer diameter of the raceway outside this range is also acceptable.If the radius of the tooth root is less than 0.5 times the smallest radius of the inner ring raceway and the strength required of the raceway is less than the strength required of the tooth root, the values ​​of the steel material and quality of the teeth and the steel material and quality of the raceway may be reversed.

[0101] The use of the bearing raceway component according to the embodiment of the present invention is not particularly limited, and it can be used in various applications, specifically, for example, in a drive reducer for an automobile.

[0102] 1: Bearing device 2, 102: Bearing raceway component 2c: Inner ring raceway 3: Outer ring 3c: Outer ring raceway 4: Ball 5, 105A, 105B, 105C: Joint surface 6: Bearing 7: Teeth 10, 110A, 110B: Bearing portion having raceway 11, 111A, 111B: Raceway groove 12, 22, 112A, 112B, 122A, 122B: Outer peripheral surface 13, 23, 113A, 113B, 123A, 123B: Surface-hardened layer 14, 24, 114A, 114B, 124A, 124B: Interior 20, 120A, 120B: Power transmission portion having teeth 21, 121A, 121B: Teeth 25, 125A, 125B: Tooth root 26, 126A, 126B: Cylindrical portion of tooth root 51, 52, 57, 58, 61, 62, 63, 64, 67, 68: Workpiece 53: Joined workpiece 55, 65: Portion that becomes inner ring raceway 56, 66: Portion that becomes gear teeth

Claims

1. A bearing raceway component comprising a columnar or cylindrical shaft member and having a power transmission portion with teeth, the shaft member having a central axis, the shaft member having a first portion on a first axial side and a second portion on a second axial side of the first portion, the first portion being integrated with the second portion, the first portion being made of a first steel material, the first steel material containing a first alloy component, the second portion being made of a second steel material, the second steel material containing a second alloy component, the first alloy component being different from the second alloy component, the first portion having a bearing portion with a raceway, the second portion having a power transmission portion with teeth, the first portion having a first hardened surface layer and a first interior, the first hardened surface layer being provided along a circumferential surface of the first portion and the first interior being provided on the opposite side of the first hardened surface layer to the circumferential surface of the first portion, A bearing raceway component, wherein an average hardness of the first surface-hardened layer is harder than an average hardness of the first interior, the second portion has a second surface-hardened layer and a second interior, the second surface-hardened layer is provided along a circumferential surface of the second portion, and the second interior is provided on the opposite side of the second surface-hardened layer to the circumferential surface of the second portion, the average hardness of the second surface-hardened layer is harder than the average hardness of the second interior, the first surface-hardened layer and the second surface-hardened layer are both carburized layers or both carbonitrided layers, and the first surface-hardened layer and the second surface-hardened layer are connected.

2. The bearing raceway component according to claim 1, wherein the teeth of the power transmission part having teeth are teeth of a gear, teeth of a spline, or teeth of a toothed pulley.

3. A bearing raceway component as described in claim 1 or 2, wherein the first steel contains carbon as a first alloy component, the second steel contains carbon as a second alloy component, and the carbon content (mass %) of the first steel is greater than the carbon content (mass %) of the second steel.

4. A bearing raceway component as described in claim 1 or 2, wherein the first steel contains at least one of manganese, nickel, chromium, and molybdenum as a first alloy component, the second steel contains at least one of manganese, nickel, chromium, and molybdenum as a second alloy component, and the total content (mass %) of manganese, nickel, chromium, and molybdenum in the first steel is more than 1.5 times the total content (mass %) of manganese, nickel, chromium, and molybdenum in the second steel.

5. A bearing raceway component as described in claim 1 or 2, wherein the depth from the surface of the raceway of the bearing part having the raceway of the first portion, the raceway having a hardness in a range of 700 HV or more, is deeper than the depth from the surface of the bottom of the teeth of the power transmission part having the teeth of the second portion, the bottom of the teeth of the power transmission part having the teeth of the second portion, the bottom of the teeth of the power transmission part having the teeth in a range of 700 HV or more.

6. A bearing raceway component as described in claim 1 or 2, wherein the first steel contains silicon as a first alloy component, the second steel contains silicon as a second alloy component, and the silicon content (mass %) of the first steel is less than the silicon content (mass %) of the second steel.

7. A bearing raceway component as described in claim 1 or 2, wherein the carbon content (mass %) contained within a range of 50 μm deep from the surface of the raceway of the bearing part having the raceway of the first part is greater than the carbon content (mass %) contained within a range of 50 μm deep from the surface of the bottom of the teeth of the power transmission part having the teeth of the second part.

8. A method for manufacturing a bearing raceway component having a power transmission part having teeth as described in claim 1 or 2, comprising the steps of: friction welding or welding a first portion of a workpiece in a first state and a second portion of a workpiece in a first state to form an integrated first workpiece; forming a portion that will become the bearing part having a raceway in the first portion of the first workpiece by a first machining process; and forming a portion that will become the power transmission part having teeth in the second portion of the first workpiece by a second machining process, one of which is carried out first and the other is carried out later to form a second workpiece; and simultaneously carburizing or carbonitriding the portion of the second workpiece that will become the bearing part having a raceway and the portion that will become the power transmission part having teeth, followed by quenching and tempering.

9. A method for manufacturing a bearing raceway part as described in claim 8, wherein the tempered product is used as a third workpiece, a third machining process is performed on a portion of the third workpiece that will become a bearing portion having the raceway, and a fourth machining process is performed on a portion of the third workpiece that will become a power transmission portion having the teeth, and one of these processes is performed first and the other is performed later.

10. A method for manufacturing a bearing raceway component having a power transmission part having teeth as claimed in claim 1 or 2, comprising the steps of: forming a portion which will become the bearing part having a raceway on a first portion of a workpiece in a first state by a first machining process; and forming a portion which will become the power transmission part having teeth on a second portion of a workpiece in a first state by a second machining process; forming the first portion of the workpiece in a second state and the second portion of the workpiece in a second state into an integrated second workpiece by friction welding or welding; and simultaneously carburizing or carbonitriding the portion of the second workpiece which will become the bearing part having a raceway and the portion of the second workpiece which will become the power transmission part having teeth, followed by quenching and tempering.

11. A method for manufacturing a bearing raceway part as described in claim 10, wherein the tempered product is used as a third workpiece, and a third machining process is performed on a portion of the third workpiece that will become a bearing portion having the raceway, and a fourth machining process is performed on a portion of the third workpiece that will become a power transmission portion having the teeth, and one of these processes is performed first and the other is performed later.

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