JP2024034788A - Shell type needle roller bearing - Google Patents

Abstract

To provide a shell type needle roller bearing having an outer ring that is difficult to cause seizure and is easy to manufacture, using a material with excellent corrosion resistance.SOLUTION: A material of a shell type outer ring 1 is an austenitic stainless material. On at least one of axial outer ring width faces 1b, a shell type needle roller bearing 10 having larger roughness on an outside diameter side face 7a than on an inside diameter side face 7b is used.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD This invention relates primarily to shell-type needle roller bearings for automobiles.

Automobiles are equipped with an electronically controlled throttle body (ETB) that adjusts the amount of air intake into the engine. The ETB is equipped with a throttle valve that opens and closes a flow path, and an outer ring made of iron such as case-hardened steel is used as a bearing that supports the rotation of this throttle valve.

A shell-shaped needle roller bearing used in such applications is listed in, for example, Patent Document 1. This shell type needle roller bearing is as follows. First, a steel strip made of chromium molybdenum steel (SCM415, etc.), which will be the material for the outer ring, is prepared. This steel band is deep drawn into the shape of an outer ring. At this time, only one edge of the outer ring is bent. A cage and needle rollers are assembled into this outer ring. After assembly, bend the other edge of the outer ring to prevent the cage and needle rollers from coming apart. After assembling as described above, a heat treatment step of carbonitriding followed by quenching and tempering is performed. The surface of the chromium molybdenum steel is hardened by heat treatment to become case hardened steel. There was a problem that when the edge of the outer ring was bent after heat treatment, the hardness at the end changed and the hardness was not uniform, but by heat treating after assembly, the hardness of the entire outer ring including both ends was made uniform. be able to. Furthermore, a nitrogen-enriched layer is formed on the surface layer of the outer ring by carbonitriding. A large amount of residual austenite exists in the nitrogen-enriched layer, and this plastic deformation alleviates stress concentration and extends life.

Patent No. 3212880

In recent years, exhaust gas recirculation systems (EGR) have been adopted in gasoline engines to improve fuel efficiency. As a result, the throttle valve bearing of the ETB is now exposed to components contained in the exhaust gas circulated by EGR. In an outer ring made of case hardened chromium molybdenum steel that is heat-treated, as used in the shelled needle roller bearing described in Patent Document 1, corrosion due to components contained in exhaust gas becomes a problem. In shell-shaped needle roller bearings used in such environments that are prone to corrosion, it is necessary to use a material with better corrosion resistance for the outer ring. Examples of such materials with excellent corrosion resistance include austenitic stainless steel materials.

However, austenitic stainless steel materials have a higher work hardening coefficient than conventional iron bearing materials and are characterized by being easier to work harden. For this reason, when attempting to manufacture the outer ring of a drawn cup needle roller bearing using austenitic stainless steel material by deep drawing, the austenitic stainless steel material adheres to the mold due to the effect of work hardening, resulting in problems such as seizure. There was a problem in that it was easy for this to occur.

In view of the above-mentioned background, an object of the present invention is to provide a shell-shaped needle roller bearing that uses a material with excellent corrosion resistance and has an outer ring that is resistant to seizure and easy to manufacture.

In order to solve the above problems, this invention
A first configuration of a shell-shaped needle roller bearing in which the material of the shell-shaped outer ring is an austenitic stainless steel material, and the outer diameter side surface of the shell-shaped outer ring is rougher than the inner diameter side surface on at least one width surface in the axial direction. It was adopted.

When forming the outer ring of a drawn cup needle roller bearing from a steel band, the width of the outer ring, which is the bottom of the cylinder when it is deformed into a cylinder, has a relatively small degree of processing compared to the entire outer ring, and the original state of the material is preserved. This is an easy part. In order for the outer diameter side surface to be rougher than the inner diameter side surface in this region, the surface of the original material that will be located on the outer diameter side surface is rougher than the surface that will be located on the inner diameter side surface. If the surface located on the outer diameter side surface is thus rough, an oil pool is suitably formed in the roughened recess during deep drawing. As a result, even if the austenitic stainless steel material is prone to seizure, it can be molded while suppressing seizure.

Further, in addition to the first configuration, the shell-shaped needle roller bearing according to the present invention has a second configuration in which the arithmetic mean roughness Ra of the outer diameter side surface of the outer ring width surface is 0.2 μm or more and 1.5 μm or less. The following configuration can be adopted.

Further, in the shell-shaped needle roller bearing according to the present invention, in the first or second configuration, a third configuration, which is an embodiment used for an electronic throttle body for an automobile or an exhaust gas recirculation device, can be adopted. .

The outer ring constituting the drawn cup needle roller bearing of this invention is not processed after the outer ring is formed by deep drawing, but is processed to have its outer diameter surface roughened in the form of a steel band prior to deep drawing. By doing so, processing defects such as burn-in can be suppressed and manufacturing can be carried out suitably. Since the heat treatment process and surface treatment after forming the outer ring can be omitted, the overall process is as low-cost as the outer ring of conventional products, making it possible to create drawn cup needle roller bearings with excellent corrosion resistance. Can be manufactured.

A sectional view showing one embodiment of a shell-shaped needle roller bearing according to the present invention (a) A flow diagram showing a series of steps for manufacturing the steel strip used in the drawn cup needle roller bearing according to the present invention, (b) A flow diagram showing an example of the manufacturing procedure for the drawn cup needle roller bearing according to the present invention. (a) Cross-sectional view of the deep-drawn outer ring used in the drawn cup needle roller bearing shown in Figure 1, (b) Enlarged cross-sectional view of the bottom surface of (a) with through holes provided, (c) (b) ) is an enlarged cross-sectional view of the state in which the needle roller and cage are assembled, (d) An enlarged cross-sectional view of the state in which the flange is formed after (c) A sectional view showing an example of the vicinity of a valve of an exhaust gas recirculation device incorporating an example of the drawn cup needle roller bearing according to the present invention. A sectional view showing an example of a throttle body incorporating an example of the drawn cup needle roller bearing according to the present invention.

The present invention is a shell-shaped needle roller bearing 10 having a feature in a shell-shaped outer ring 1. FIG. 1 is a schematic cross-sectional view showing an embodiment of a shell-shaped needle roller bearing according to the present invention. The illustrated embodiment is an example, and the present invention is not limited to the illustrated embodiment. The shell-shaped outer ring 1 has a substantially cylindrical outer diameter surface 1a. Both ends of the outer diameter surface in the axial direction are bent radially inward to form width surfaces 1b and 1c.

A plurality of needle rollers 2 are arranged on the inner diameter side of the shell-shaped outer ring 1 in contact with the shell-shaped outer ring 1. Each needle roller 2 is rotatably supported by a cage 3. The cage 3 has a substantially cylindrical shape with a smaller diameter than the shell-shaped outer ring 1, and has a plurality of window holes 4 oriented in the axial direction according to the shape of the needle rollers 2 at equal intervals in the circumferential direction. It is being The needle rollers 2 housed in the window holes 4 rotate while maintaining equal intervals from each other. In the shell-shaped needle roller bearing 10, a large number of needle rollers 2 support a load between the shell-shaped outer ring 1 and an axis passing through the center.

In the drawn cup needle roller bearing 10 according to the present invention, the roughness of the outer diameter side surface and the inner diameter side surface of at least one of the width surfaces 1b and 1c of the shell shaped outer ring 1 is greater than that of the inner diameter surface. is rougher. Here, an example will be described in which the width surface 1b has a cylindrical bottom in the manufacturing procedure described later. A surface located on the axially outer side of this width surface 1b is an outer diameter side surface 7a, and a surface located on the axial inner side of this width surface is called an inner diameter side surface 7b. Note that not only the width surface 1b but also the width surface 1c may similarly satisfy the roughness condition.

The roughness will be explained. In the shelled needle roller bearing 10 according to the present invention, it is preferable that the arithmetic mean roughness Ra of the outer diameter side surface 7a of either width surface 1b of the shelled outer ring 1 is 0.2 μm or more and 1.5 μm or less. . If it is less than 0.2 μm, there will be insufficient portions to serve as oil reservoirs during deep drawing, resulting in insufficient lubricity and a tendency to seize. On the other hand, if it exceeds 1.5 μm, the unevenness will be too strong, making deep drawing even more difficult. However, as a bearing after manufacture, there is no particular disadvantage due to the rough outer diameter side surface 7a. On the other hand, the arithmetic mean roughness Ra of the inner diameter side surface 7b, which is the back side of the width surface 1b, needs to be smaller than the arithmetic mean roughness Ra of the outer diameter side surface 7a, and is 0.3 μm or less. It is preferable to have one.

In the shelled needle roller bearing 10 according to the present invention, the maximum height Rz of the outer diameter side surface 7a of either width surface 1b of the shelled outer ring 1 is preferably 1.5 μm or more and 10.3 μm or less. On the other hand, the maximum height Rz of the corresponding inner diameter side surface 7b needs to be smaller than the maximum height Rz of the outer diameter side surface 7a, and is preferably 2.0 μm or less.

In the shelled needle roller bearing 10 according to the present invention, the maximum valley depth Rv of the outer diameter side surface 7a of either width surface 1b of the shelled outer ring 1 is preferably 1.0 μm or more and 4.0 μm or less. On the other hand, the maximum valley depth Rv of the corresponding inner diameter side surface 7b needs to be smaller than the maximum valley depth Rv of the outer diameter side surface 7a, and is preferably 1.0 μm or less.

In the shelled needle roller bearing 10 according to the present invention, it is preferable that the unevenness Rsk of the peaks and troughs of the outer diameter side surface 7a of either width surface 1b of the shelled outer ring 1 is −1.9 μm or more and 1.6 μm or less. . On the other hand, the deviation Rsk of the peaks and valleys of the corresponding inner diameter side surface 7b is preferably -0.5 μm or more and 0.8 μm or less.

In the shelled needle roller bearing 10 according to the present invention, it is preferable that the sharpness Rku of the outer diameter side surface 7a of one of the width surfaces 1b of the shelled outer ring 1 is 1.2 μm or more and 4.6 μm or less. On the other hand, the sharpness Rku of the corresponding inner diameter side surface 7b is preferably 2.2 μm or more and 5.4 μm or less.

The roughness of the surface in contact with the needle rollers on the inner diameter side of the shell-shaped outer ring 1 is close to the roughness of the inner diameter side surface 7b unless the inner diameter side is additionally machined after the end portion is formed. For this reason, if the inner diameter side surface 7b is too rough, it tends to hinder the rolling of the needle roller as the outer ring, so it is preferable that the roughness is as small as possible.

The shell-shaped outer ring 1 of the shell-shaped needle roller bearing 10 according to the present invention is made of austenitic stainless steel material. Austenitic stainless steel is a stainless steel that has an austenite structure as its main structure at room temperature. Contains chromium, which contributes to corrosion resistance, and nickel, which contributes to an austenitic structure. For example, SUS304 is a typical austenitic stainless steel material, and can be suitably employed in the present invention.

The components of the austenitic stainless steel material used for the shell-shaped outer ring 1 include, for example, Ni (6.0% by mass or more and 17.0% by mass or less), Cr (16.0% by mass or more and 26.0% by mass or less), and the remainder It is possible to select one in which the trace components are Fe. Here, as trace components, for example, C is 0.08% by mass or less, Si is 1.0% by mass or less, Mn is 2.0% by mass or less, P is 0.045% by mass or less, S is 0.030% by mass or less. It is preferable that it is less than % by mass. In addition to these, Mo, Cu, and N may be added within a range that does not impede the effect of the shell-shaped needle roller bearing.

The manufacturing procedure of the shelled needle roller bearing 10 will be explained using FIGS. 2(a) and 2(b). First, an austenitic stainless steel material prepared to have a predetermined mixing ratio is prepared (S11). Components of the material include stainless steel containing Cr and Ni shown in the above example. The hardness of the prepared material at the material stage is preferably 200 HV or less.

The prepared material is first hot rolled (S12) and roughly rolled into a sheet while maintaining the structure of the austenitic stainless steel material. After cooling this sheet-shaped material, it is further cold-rolled (S13) to obtain a steel strip with a smooth surface. This steel strip is subjected to dull finishing (S14) on at least one surface to make the surface rough. Here, one surface is a surface that becomes the outer diameter side surface 7a by deep drawing, which will be described later.

The arithmetic mean roughness Ra of the above one surface at the stage of dull finishing is preferably 1.1 μm or more and 3.6 μm or less. The maximum height Rz is preferably 6.0 μm or more and 14.8 μm or less. The maximum valley depth Rv is preferably 3.1 μm or more and 8.1 μm or less. It is preferable that the deviation degree Rsk of the peaks and valleys is −1.4 μm or more and 0.9 μm or less. The sharpness Rku is preferably 1.5 μm or more and 2.7 μm or less. By making the surface which becomes the outer diameter side surface rough in this way, it is possible to secure a sufficient portion that becomes an oil pool during deep drawing, thereby ensuring lubricity and making it easier to prevent seizure. In addition, it is preferable that the surface is not too rough, since if it is too rough, the unevenness will be too strong and it will become difficult to perform deep drawing.

On the other hand, it is preferable that the other surface, which is the inner diameter side surface, is not subjected to a dull finish and has a roughness of a level normally found in cold rolled steel. For example, the arithmetic mean roughness Ra is preferably 0.04 μm or more and 0.10 μm or less, and the maximum height Rz is preferably 1.50 μm or less. If smoothness to that extent can be ensured, it will be easy to ensure that the roughness of the raceway surface 1d after being processed into the shell-shaped outer ring 1 has enough precision to be usable as a bearing raceway surface.

The steel strip (S21) whose roughness is different between one surface and the other surface is deformed into a cylindrical shape as shown in FIG. 3(a) by deep drawing in multiple stages (S22). In order to ensure accuracy as a bearing, it is preferable to perform the process five times or more in multiple stages. During deep drawing, the process of reducing the thickness of the outer ring to ensure final bearing accuracy, so-called ironing, is generally performed one to three times during bearing processing. However, in the ironing process, the outer diameter of the outer ring and the inner diameter of the mold are strongly rubbed, so that the roughness of the outer diameter surface 1a of the outer ring 1 is smoothed, resulting in insufficient oil film during processing, which tends to cause processing defects. This phenomenon is noticeable in austenitic stainless steel materials, which are prone to localized increases in contact surface pressure due to work hardening. Therefore, it is preferable that the number of times of ironing is small. By performing deep drawing in stages in this manner, it becomes possible to form austenitic stainless steel material, which is a difficult-to-process material. In this case, it is preferable to process the finished product so that the outer ring raceway surface plate thickness is 0.6 tmm or more and 0.9 tmm or less with respect to the material plate thickness tmm of the outer ring, from the viewpoint of ensuring bearing accuracy.

After forming into a cylindrical shape by multistage deep drawing, a through hole 6 is provided in the center of the bottom surface 5 and opened (S23). A partial cross-sectional view of the vicinity of the shell-shaped outer ring 1 in this state is shown in FIG. 3(b). This configuration produces an open-ended embodiment. However, the shell-shaped needle roller bearing 10 according to the present invention is not limited to an open-end type, but may be a closed-end type. One end, which is the perforated side, leaves a width surface 1b that is a portion bent inward from the outer diameter surface 1a. In the drawn cup needle roller bearing 10 according to the present invention, the outer diameter side surface 7a is required to be rougher than the inner diameter side surface 7b in the width surface 1b of the outer ring, which is the bent portion, and the above-mentioned conditions are satisfied. It is good if it has a rough texture.

The needle roller 2 is held by the retainer 3 so that this end portion is caught on the bent width surface 1b, and is incorporated into the shell-shaped outer ring 1 (S24). A partial sectional view of this assembled state is shown in FIG. 3(c).

After the needle rollers 2 and cage 3 are assembled inside the shell-shaped outer ring 1, the other end of the shell-shaped outer ring 1 is bent to form a flange so that the needle rollers 2 and cage 3 do not come off. In this way, assembly is completed (S25). FIG. 3(d) shows a partial cross-sectional view of this end portion bent to form the other width surface 1c. Although the figure shows an embodiment in which there is one cage 3, an embodiment in which a plurality of cages 3 are arranged in the axial direction may be used.

Since the drawn cup needle roller bearing 10 according to the present invention is made of a hardened austenitic stainless steel material used for the shell shaped outer ring 1, the required hardness can be achieved without heat treatment after the above assembly is completed. . However, heat treatment may be performed if necessary. Further, surface finishing processing may be performed for the purpose of removing burrs generated during deep drawing of the outer ring or through hole processing.

Further, the thickness of the shell-shaped outer ring 1 is desirably 0.4 mm or more and 1.0 mm or less in terms of strength and ease of processing.

Further, the shell-shaped needle roller bearing 10 according to the present invention may have a seal in addition to the above-mentioned parts, and may be filled with grease.

The hardness of the raceway surface 1d of the shell-shaped outer ring 1 is preferably HV300 or higher, and more preferably HV400 or higher. If the hardness is too low, the life of the bearing will be too short. The surface hardness of conventional steel outer rings is around HV750, but for applications that support the sliding of valves that open and close, rather than for high-speed rotation, that degree of hardness is not required because the rotational speed is low and the radial load is low. . Examples of valves supported using the drawn cup needle roller bearing 10 according to the present invention include valves for electronic throttle bodies (ETBs) for automobiles and exhaust gas recirculation systems (EGR). Since the shell-shaped needle roller bearing according to the present invention is made of austenitic stainless steel material with excellent corrosion resistance, it can be suitably used even in ETB and EGR valves exposed to automobile exhaust gas.

FIG. 4 shows an example of a configuration in which an EGR valve is supported by a shell-shaped needle roller bearing 10. The housing 20 is provided with an exhaust gas flow path 21, a valve 13 is provided within the exhaust gas flow path 21, and the exhaust gas flow path 21 is opened and closed in response to rotation of the valve 13. The valve 13 is connected and fixed to the rotating shaft 11. This rotating shaft is supported by a shell-shaped needle roller bearing 10 together with a ball bearing 15. The shell-shaped needle roller bearing 10 according to the present invention is not easily deformed when assembled into the housing 20, and exhibits corrosion resistance even when exposed to exhaust gas flowing from the exhaust gas flow path 21.

Further, FIG. 5 shows an example of a configuration in which an ETB valve is supported by a shell-shaped needle roller bearing 10. The throttle valve device 31 has a throttle body 32 in which an intake passage is formed. Two shell-shaped needle roller bearings 10 are press-fitted into the housing, which is the throttle body 32. A drawn cup needle roller bearing 10 supports the shaft 33 and supports the rotation of a valve 34 fixed to the shaft. Even if it comes into contact with exhaust gas components introduced into the intake passage, the shelled needle roller bearing 10 exhibits corrosion resistance.

1 Shell-shaped outer ring 1a Outer diameter surface 1b, 1c Width surface 1d Raceway surface 2 Needle roller 3 Cage 4 Window hole 5 Bottom surface 6 Through hole 7a Outer diameter side surface 7b Inner diameter side surface 10 Shell-shaped needle roller bearing 11 Rotating shaft 13 Valve 15 Ball bearing 20 Housing 21 Exhaust gas passage 31 Throttle valve device 32 Throttle body 33 Shaft 34 Valve

Claims (3)

A shell-shaped needle roller bearing in which the material of the shell-shaped outer ring is an austenitic stainless steel material, and the outer diameter side surface of the shell-shaped outer ring is rougher than the inner diameter side surface in at least one width surface in the axial direction. The shell-shaped needle roller bearing according to claim 1, wherein the arithmetic mean roughness Ra of the outer diameter side surface of the width surface is 0.2 μm or more and 1.5 μm or less. The drawn cup needle roller bearing according to claim 1 or 2, which is used in an electronic throttle body for an automobile or an exhaust gas recirculation device.

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