JP4508587B2 - Shell needle roller bearing - Google Patents

Description

  The present invention relates to a shell needle roller bearing.

  Some needle roller bearings in which a plurality of needle rollers are arranged along the inner diameter surface of the outer ring use a shell-type outer ring formed by press working including a drawing process. The applications of the shell type needle roller bearing using the shell type outer ring are diversified due to the economic advantage that the manufacturing cost is low, but in recent years, there are many applications that require a longer life.

  A schematic process for pressing a conventional shell-type outer ring is as follows. First, a circular blank is formed into a cup shape in the drawing step, and the cup bottom corner portion is determined and pushed to a predetermined corner radius in the decision pushing step. After that, the center portion of the cup bottom is punched out in the bottoming step to form one ridge of the outer ring, and the upper end portion of the cup is trimmed to a uniform height in the trimming step. An ironing process may be added after the drawing process or the final pressing process. Usually, these press processes are performed using a transfer press or a progressive press, and when a transfer press is used, a blank blank punching process is often incorporated together. The other collar of the outer ring is formed by bending the upper end of the cup inward in the assembly process after heat treatment.

  For the blank material of the shell type outer ring, a steel plate made of case-hardened steel such as SCM415 is used, and heat treatment such as carburizing and quenching and tempering is performed after press working in order to ensure a predetermined product strength. Case-hardened steel has a high carbon content compared to mild steel such as SPCC and has a low r value, which is a standard for drawability, so the number of draws in the drawing process can be divided into multiple draws. The ratio is set small.

  In this way, the shell type outer ring is formed through a number of press working processes, so the roundness of the cylindrical part, the amount of uneven thickness, etc., due to the accuracy error of the mold and the accumulation of non-uniform strain for each working process The dimensional accuracy of the bearing is inferior to that of the outer ring formed by cutting, and the life of the bearing is shortened.

  In order to improve the life of such a shell type needle roller bearing, heat treatment of the shell type outer ring is performed after the assembly of the bearing, and this heat treatment is further quenched and tempered after carbonitriding. There is a manufacturing method of a shell-type needle roller bearing in which the outer diameter roundness is increased and the strength of each bearing component is also increased (see, for example, Patent Document 1).

Japanese Patent No. 3073937 (page 1-2, Fig. 1-3)

  As described above, since a plurality of needle rollers are arranged on the inner diameter surface of the shell type outer ring and these rollers roll on the inner diameter surface, the inner diameter roundness is greater than the outer diameter roundness. It is thought that it will greatly contribute to the improvement. The manufacturing method of the shell type needle roller bearing described in Patent Document 1 can reduce the thermal strain of the shell type outer ring and increase its outer diameter roundness by performing heat treatment after the assembly of the bearing. However, the roundness of the inner diameter of the shell-type outer ring produced by this manufacturing method can be increased only by the margin for improving the roundness of the outer diameter. Incidentally, the roundness of the inner diameter of a conventional shell type outer ring is 15 to 40 μm when the inner diameter is about 25 mm, and is slightly over 10 μm when the manufacturing method described in Patent Document 1 is used.

  However, in recent years, automobiles have been improved in quality, performance and durability, and along with this, further longer life and lower costs for automobile parts have been demanded. In particular, bearing parts used for car air conditioners, transmissions, and the like have very severe use conditions including lubrication, and there is a great demand for longer life and lower costs.

  Therefore, an object of the present invention is to increase the roundness of the inner diameter of the shell type outer ring and to greatly extend the life of the shell type needle roller bearing.

  In order to solve the above-described problems, the present invention provides a shell-type needle roller bearing in which a plurality of needle rollers are arranged along an inner diameter surface of a shell-type outer ring formed by press working. A configuration with a circularity of 10 μm or less was adopted.

  The present inventors conducted a bearing life test on a shell needle roller bearing in which the inner diameter roundness of the shell type outer ring is changed, and as shown in FIG. 3 later, there is a good correlation between the inner diameter roundness and the bearing life. When the inner diameter roundness is 10 μm or less, it has been confirmed that a sufficiently long life can be achieved even under severe conditions required in the future.

  The roundness of the inner diameter of this shell-type outer ring is effective in extending the life of the bearing. The rolling of the needle roller on the inner diameter surface is smooth, and the inner diameter surface due to roller slip or rattling is the reason. It is thought that local wear and stress concentration are suppressed.

  As a means for setting the inner diameter roundness of the outer ring to 10 μm or less, a pressing process for forming the shell-type outer ring is provided, and an outer diameter side ironing surface that is an outer diameter surface of the outer ring in the ironing process is provided. A means for bringing the lubricating condition into a substantially fluid lubrication state can be employed.

  The present inventors conducted a squeezing and ironing test of the SCM415 steel sheet using a press tester, and investigated the roundness of the inner diameter of the cup molded product. As a result, when a high-viscosity press working oil with excellent lubricity is applied to the die side (the outer diameter side ironing surface of the cup molded product), the roundness of the inner diameter of the cup molded product is 10 μm as shown in Table 1 below. The following improvements were confirmed.

  FIG. 7 shows the observation results of the surface roughness of the blank material and the surface roughness of the outer diameter surface of the cup molded product when a lubricating oil having excellent lubricity is applied to the die side in the drawing ironing test. The surface roughness of the cup molded product outer diameter surface is Ra 0.44, which is not much different from the surface roughness Ra 0.49 of the blank material. Moreover, FIG. 8 shows a plate thickness cross-sectional photograph of the upper end portion of the cup molded product, but the outer diameter side of the upper end portion of the cup molded product formed by ordinary drawing and ironing is remarkably extended in the axial direction. On the other hand, the upper end portion of the cup molded product when a lubricating oil having excellent lubricity is applied to the die side extends uniformly in the axial direction in the plate thickness direction.

  These observation results are considered as follows. In other words, the surface roughness of the outer surface of the cup molded product did not differ much from the surface roughness of the material when a lubricating oil with excellent lubricity was applied to the die side. In terms of the surface, it is considered that the material to be processed and the die were in a substantially fluid lubrication state with little contact. In this way, when the lubrication condition on the die side is set to a substantially fluid lubrication state, there is almost no shearing force on the ironing surface on the outer diameter side caused by friction with the die, and the stress at the ironing part between the punch and the die is reduced by the plate thickness. It becomes a state of uniform compressive stress in the direction, and the material is uniformly reduced in thickness in the thickness direction. When the material is uniformly reduced and deformed in the thickness direction in this way, the thickness deviation of the cylindrical portion of the cup molded product is suppressed, and the inner diameter surface of the cup molded product in contact with the punch is axial along the punch surface. It is considered that the roundness of the inner diameter of the cup molded product is well maintained even after releasing from the punch.

  On the other hand, in the normal drawing and ironing process, the outer diameter surface side of the cup molding is preferentially reduced in thickness by the shearing force caused by the friction with the die, and as shown in FIG. Stretch to. Accordingly, the inner diameter side of the cup molded product is not so thinly deformed and hardly moves relative to the punch surface. Therefore, even if ironing is applied, the inner diameter roundness and uneven thickness of the cup molded product are not significantly improved.

  In the processing method in which the lubrication condition on the outer diameter side ironing surface is in a substantially fluid lubrication state, as shown in FIG. 8, the upper end surface of the cup molding is uniform in the plate thickness direction. Thus, the yield can be improved, and by reducing the blank diameter, the press load necessary for the drawing process is also reduced. Further, it is expected that the surface roughness of the inner surface of the outer ring can be finely improved by the relative movement of the inner surface of the cup molded product with the punch surface.

  By reducing the number of squeezing in the squeezing process of the press working to 3 times or less and making the squeezing process a squeezing and squeezing process that is performed simultaneously with the final squeezing process, the number of dies and processes for press working are reduced. The manufacturing cost can be reduced. Further, by reducing the number of times of throttling, a decrease in dimensional accuracy of the outer ring due to setting errors of each mold is suppressed.

  Incidentally, it is known that the drawing and ironing process can obtain a larger drawing ratio than a simple drawing process. That is, in the drawing process, the drawing limit is determined by the fracture at the punch shoulder due to the tensile stress caused by the deformation resistance of the shrink flange and the wrinkle holding force at the flange, but in the drawing ironing, the flange acting on the punch shoulder Since the tensile stress from the side is blocked by the ironing portion, the drawing limit becomes high and a large drawing ratio can be obtained.

  By reducing the number of times of drawing in the drawing process to one and making the ironing process a drawing and ironing process that is performed simultaneously with this one drawing process, it is possible to further promote the reduction of manufacturing costs and the improvement of the dimensional accuracy of the outer ring. it can.

  By making the shell type outer ring material a phosphate-coated steel plate, the holding ability of the pressing oil on the outer diameter side ironing surface in the ironing process is increased, and a lower pressing oil is used to The lubrication condition on the radial ironing surface can be set to a substantially fluid lubrication state.

  In the shell type needle roller bearing of the present invention, by setting the roundness of the inner diameter of the shell type outer ring to 10 μm or less, the bearing life is greatly extended, and both a long life and low cost are achieved. Therefore, even if it is used for a car air conditioner, a transmission or the like that is particularly severe, it is possible to achieve a sufficiently long life and low cost.

  The means for setting the inner ring roundness of the outer ring to 10 μm or less is provided with an ironing process in the press working for forming the shell-type outer ring, and the lubrication conditions on the outer diameter side ironing surface which becomes the outer diameter surface of the outer ring in the ironing process Since the upper end surface of the cup molded product becomes nearly uniform in the plate thickness direction by making the fluid lubrication state substantially fluid, the blank diameter is reduced to improve the yield and the press load required for drawing processing is also reduced. be able to. Moreover, since the surface roughness of the inner surface of the outer ring on which the roller rolls can be finely improved by the relative movement of the inner surface of the cup product with the punch surface, the sound level during use can be reduced.

  By reducing the number of drawing in the drawing process to 3 or less and making the ironing process a drawing ironing process that is performed at the same time as the final drawing process, the number of press dies and the number of processes are reduced, thereby reducing manufacturing costs. can do. Further, by reducing the number of times of throttling, it is possible to suppress a decrease in dimensional accuracy of the outer ring due to setting errors of each mold.

  By making the number of times of drawing in the drawing process one time and making the ironing process a drawing and ironing process that is performed simultaneously with this one drawing process, it is possible to further promote the reduction of the manufacturing cost and the improvement of the dimensional accuracy of the outer ring. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, this shell type needle roller bearing is formed by arranging a plurality of needle rollers 3 along an inner diameter surface 2 of a shell type outer ring 1 made of SCM415 formed by pressing. The needle roller 3 is held by a SPCC cage 4 that is also formed by press working. At both ends of the outer ring 1, flanges 1a and 1b are formed.

  FIG. 2 shows a schematic process for manufacturing the shell-type outer ring 1. First, by pressing, a circular blank of SCM415 phosphate-coated steel sheet is formed into a cup molding in one drawing and ironing process, and the cup bottom corner portion is determined and pressed into a predetermined corner radius in the final pressing process. . In the squeezing and ironing process, press working oil having excellent lubricity is applied to the die side, and the lubrication condition on the ironing surface on the outer diameter side is substantially fluid lubricated. Next, the center part of the cup bottom is punched in the bottoming process to form one flange 1a (see FIG. 1) of the outer ring 1, and the upper end part of the cup is trimmed to a uniform height in the trimming process. After that, the press-processed outer ring 1 is subjected to carburizing and quenching and tempering in a heat treatment process, and in the final assembly process, the other flange 1b (see FIG. 1) is formed by bending inward.

  In the embodiment described above, the drawing process in the outer ring pressing process is performed only once, and the ironing process is a drawing ironing process performed simultaneously with this one drawing process, but the drawing process is performed three or less times and the ironing process is performed. The process may be a drawing and ironing process that is performed simultaneously with the final drawing process, or the ironing process may be performed separately after the drawing process or the final pressing process. Moreover, you may heat-process after a bearing assembly like what was described in patent document 1. FIG.

[Example A]
Table 1 shows the roundness of the inner diameter of the shell type outer ring (Examples 1 to 6) manufactured in the manufacturing process of FIG. 2 and the shell type outer ring (Comparative Examples 1 to 6) manufactured in the conventional manufacturing process. The results are shown. The measured dimensions of the outer ring were an outer diameter of 28 mm, a length of 16 mm, and a wall thickness of 0.95 mm. The roundness of the inner diameter was measured at three locations, 2 mm each from the both ends of the outer ring 1 and the central position in the length direction, using a roundness measuring machine (Talirond) manufactured by Taylor Hobson. In addition, a micrometer was used for the measurement of the thickness deviation of the cylindrical portion, and a total of 12 locations were measured at 4 locations each in a 90 ° phase in the circumferential direction at the same axial position as the measurement position of the inner diameter roundness. In all of the examples, the roundness of the inner diameter is 10 μm or less and the thickness deviation of the cylindrical portion is less than 10 μm. In addition, the comparative example 1 is manufactured by the manufacturing method described in Patent Document 1.

A bearing life test was conducted on the shell needle roller bearings of the above examples and comparative examples. The number of samples in each example and comparative example was eight, and the bearing life was evaluated by L10 life (time in which 90% of the sample can be used without being damaged). The test conditions are as follows.
・ Axial load: 9.81kN
・ Rotation speed: 5000rpm
・ Lubricating oil: Spindle oil VG2

  FIG. 3 shows the relationship between the inner diameter roundness and the L10 life in the bearing life test. It can be seen that in each of the examples in which the roundness of the inner diameter of the shell type outer ring is 10 μm or less, the L10 life exceeds 200 hours, and the bearing life is significantly extended. In the comparative example having an inner diameter roundness exceeding 10 μm, even the most excellent comparative example 1 has an L10 life of less than 200 hours.

  FIG. 4 shows the relationship between the cylinder wall thickness deviation and the L10 life in the bearing life test. Regarding the cylindrical part thickness deviation, the L10 life of each of the examples of less than 10 μm exceeds 200 hours, and the bearing life is greatly extended.

[Example B]
5A and 5B show an example of the result of measuring the surface roughness of the inner diameter surface of the shell type outer ring manufactured in the manufacturing process of FIG. The measured dimensions of the outer ring are an outer diameter of 28 mm, a length of 16 mm, and a wall thickness of 0.95 mm. For this measurement, a surface roughness measuring machine (Surfcom) manufactured by Tokyo Seimitsu Co., Ltd. is used, and the circumferential surface roughness is measured at three positions in the same axial direction as the measurement positions of the inner diameter roundness and the cylindrical wall thickness deviation. The axial surface roughness was measured at four points with a 90 ° phase in the circumferential direction. FIG. 5A shows the circumferential surface roughness measured at the center position in the length direction of the outer ring, which is very fine as Ra 0.18 μm. Although illustration is omitted, the circumferential surface roughness measured at positions of 2 mm from both ends is also in the range of Ra 0.05 to 0.3 μm, which is more than the surface roughness of the blank material and the outer diameter surface shown in FIG. It is fine. FIG. 5B shows the axial surface roughness measured at one phase in the circumferential direction, which is Ra 0.15 μm. Although illustration is omitted, the surface roughness in the axial direction measured at other phases is also very fine with Ra 0.3 μm or less.

  As an example, a shell-type needle roller bearing having a circumferential surface roughness of Ra 0.05 to 0.3 μm was prepared. As a comparative example, a shell-type needle roller bearing having the same bearing dimensions and a circumferential surface roughness of the outer ring inner surface exceeding Ra 0.3 μm was also prepared.

The shell type needle roller bearings of the above examples and comparative examples were attached to a rotation tester, and an acoustic measurement test was performed. The test conditions are as follows.
・ Rotation speed: 4800 rpm
・ Radial load: 180N
・ Lubrication: Viscosity 2cSt oil application ・ Sound measurement position: Position at a distance of 100 mm in a 45 ° direction from the bearing

  FIG. 6 shows the measurement result of the sound level in the sound measurement test. In all of the examples in which the circumferential surface roughness of the inner diameter surface is Ra 0.05 to 0.3 μm, the sound level is 60 dB or less, and the sound level is significantly reduced as compared with the comparative example. Therefore, it can be seen that the shell type needle roller bearing having the shell type outer ring manufactured in the manufacturing process of FIG. 2 not only improves the life but also significantly reduces the sound level.

Longitudinal sectional view showing an embodiment of a shell needle roller bearing Process drawing which shows the outline manufacturing process of the shell type needle roller bearing of FIG. The graph which shows the relationship between the internal diameter roundness of a shell type outer ring | wheel and L10 life in the bearing life test of a shell type needle roller bearing The graph which shows the relationship between the cylindrical part thickness deviation of a shell type outer ring | wheel, and L10 life in the bearing life test of a shell type needle roller bearing a and b are graphs showing the surface roughness in the circumferential direction and the axial direction of the inner surface of the shell-type outer ring manufactured in the manufacturing process of FIG. Graph showing the relationship between the circumferential surface roughness of the inner surface of the outer ring and the sound level in the sound measurement test of the shell needle roller bearing Graph showing the surface roughness of the blank material and the surface roughness of the outer diameter surface of the cup molding in the drawing ironing test Thickness cross-sectional photograph of the upper end of the cup molding in the drawing ironing test

Explanation of symbols

1 Shell type outer ring 1a, 1b 鍔 2 Inner diameter surface 3 Needle roller 4 Cage

Claims (6)

In a shell-type needle roller bearing in which a plurality of needle rollers are arranged along the inner diameter surface of a shell-type outer ring formed by pressing, an ironing process is provided in the pressing process for forming the shell-type outer ring. The outer ring side ironing surface, which is the outer diameter surface of the outer ring, is made substantially fluid lubricated so that the inner ring roundness of the outer ring is 10 μm or less, and the acoustic level under the following test conditions is 60 dB. A shell needle roller bearing characterized by the following.
・ Rotation speed: 4800 rpm
・ Radial load: 180N
・ Lubrication: Viscosity 2cSt oil application ・ Sound measurement position: Position at a distance of 100mm in a 45 ° direction from the bearing   The shell type needle roller bearing according to claim 1, wherein the circumferential surface roughness of the inner diameter surface of the shell type outer ring is finer than the circumferential surface roughness of the outer diameter surface.   3. The shell-type needle roller bearing according to claim 1, wherein a circumferential surface roughness of an inner diameter surface of the shell-type outer ring is Ra 0.05 to 0.3 μm. Wherein the number diaphragm by pressing the drawing step and less than 3 times, the ironing process, the last round of the drawing step and shell type needle according to any one of claims 1 to 3 was drawn and ironed process carried out at the same time Roller bearing. The shell-type needle roller bearing according to claim 4 , wherein the number of times of drawing in the drawing step is one, and the ironing step is a drawing and ironing step performed simultaneously with the one drawing step. The shell-type needle roller bearing according to claim 4 or 5 , wherein a material of the shell-type outer ring is a phosphate-coated steel plate.