JP4429669B2 - 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 (for example, see Patent Document 1). Shell-type needle roller bearings using this shell-type outer ring have a wide variety of uses, including automobile parts, because of the economical advantage that the manufacturing cost is low.

  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.

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

  The shell-type outer ring formed by the press work described above has a rougher inner surface than the outer ring formed by the cutting process. Normally, the surface roughness of the inner diameter surface of the outer ring formed by shaving is about Ra 0.05 μm, whereas the surface roughness of the inner diameter surface of the shell type outer ring is about Ra 0.4 μm. For this reason, conventional shell-type needle roller bearings are less expensive than those in which the outer ring is formed by cutting, but the sound in use associated with rolling of the needle rollers on the inner diameter surface is more than that of the machined product. large.

  In recent years, high quality, high performance and low cost of automobiles have progressed, and along with this, parts such as bearings used in car air conditioners and transmissions are also required to be low cost and quiet. It has become.

  Accordingly, an object of the present invention is to reduce the sound level during use in a shell 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 pressing, and an inner diameter surface of the outer ring The surface roughness was made finer than the surface roughness of the outer diameter surface.

  That is, the surface roughness of the inner diameter surface of the shell type outer ring is made finer than that of the outer diameter surface, so that the sound level in use accompanying the rolling of the needle roller on the inner diameter surface can be reduced.

  The circumferential surface roughness of the inner surface of the outer ring is preferably Ra 0.05 to 0.3 μm. The lower limit of the circumferential surface roughness is set to Ra 0.05 μm. If the circumferential surface roughness becomes finer than this and the inner surface becomes too smooth, it is held in the elastic contact region of the needle roller that rolls. This is because the amount of lubricating oil is less and surface damage such as smearing is likely to occur. The reason why the upper limit of the circumferential surface roughness is set to Ra 0.3 μm is as follows.

  The present inventors conducted an acoustic measurement test using a rotary tester on a shell-type needle roller bearing in which the surface roughness of the inner surface of the shell type outer ring was changed, and the circumferential surface roughness of the inner surface was made fine. It has been found that the acoustic level of the bearing is effectively reduced, and as shown in FIG. 4 later, it has been confirmed that the acoustic level can be greatly reduced by setting this to Ra 0.3 μm or less.

  It is considered as follows that the circumferential surface roughness of the inner diameter surface is particularly effective in reducing the sound level. That is, when the irregularities (circumferential surface roughness) in the rotation direction of the rollers with respect to the roller diameter of the needle rollers become rougher than a certain level, the vertical vibrations of the needle rollers increase and a large sound is generated. Since the roller diameter of the needle roller is relatively small, it is considered that a large sound is generated when the circumferential surface roughness exceeds Ra 0.3 μm.

  The axial surface roughness of the inner surface of the outer ring is preferably Ra 0.3 μm or less. Needle rollers have a longer roller length than the roller diameter. Therefore, the unevenness (axial surface roughness) in the width direction of the inner surface of the outer ring also affects the vertical vibration of the needle rollers, and it seems that the sound increases when the axial surface roughness exceeds Ra 0.3 μm.

  As a means for making the surface roughness of the outer ring inner diameter surface finer than the outer diameter surface, a pressing process for forming the shell type outer ring is provided, and an outer diameter side serving as the outer diameter surface of the outer ring in the ironing process is provided. It is possible to adopt means for bringing the lubrication condition on the ironing surface into a substantially fluid lubrication state.

  The present inventors conducted a squeezing and ironing test of the SCM415 steel sheet using a press tester, and investigated the surface roughness of the inner and outer diameter surfaces of the cup molded product. As a result, when 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 surface roughness of the inner diameter surface of the cup molded product that becomes the inner diameter surface of the shell type outer ring is reduced. It was found to be finer than the outer diameter surface. An example is shown in FIG. 7, whereas the surface roughness of the blank material is about Ra 0.49 μm on both the front and back surfaces, whereas the surface roughness of the inner diameter surface of the cup molded product is very fine, Ra 0.15 μm. . The surface roughness of the outer diameter surface of the cup molded product is Ra 0.44 μm, which is not much different from the surface roughness of the blank material. In addition, although the surface roughness of the inner and outer diameter surfaces of the cup molded product shown in FIG. 7 is measured in the axial direction, the surface roughness measured in the circumferential direction is almost equivalent to these. This result is the opposite of what is observed with normal drawing and ironing, and with normal drawing and ironing, the outer diameter surface of the cup product that is squeezed with a die has a finer surface roughness, and the surface of the inner diameter surface. The roughness is not much different from the surface roughness of the blank material.

  The above test results are considered as follows. That is, the surface roughness of the outer diameter surface of the cup molded product was not much different from the surface roughness of the material. On the ironing surface on the outer diameter side of the cup molded product, the material to be processed and the die hardly contact each other. It is thought that it was in a state. 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. As shown in FIG. 8, the material is uniformly reduced in thickness in the thickness direction.

  FIG. 8 shows a plate thickness cross-sectional photograph of the upper end portion of the cup molding. As the above estimation is verified, the upper end portion of the cup molded product in which the press working oil having excellent lubricity is applied to the die side is uniformly extended in the axial direction in the plate thickness direction. In this way, when the material is uniformly reduced in thickness in the plate thickness direction and stretched in the axial direction, the inner diameter surface of the cup molded product that comes in contact with the punch moves relative to the punch surface in the axial direction. It is considered that the surface roughness of the inner diameter surface became fine by sliding with the punch surface. On the other hand, the outer diameter surface side of the upper end portion of the cup molded product obtained by normal drawing ironing process is remarkably extended in the axial direction. This is because the outer diameter surface side of the cup molded product is preferentially reduced in thickness by the shearing force resulting from friction with the die, and the inner diameter surface side is not significantly reduced in thickness. In this way, in the normal drawing and ironing process in which the inner diameter surface side is not so thinly deformed, the inner diameter surface of the cup molded product hardly moves relative to the punch surface, so the surface roughness is not much different from that of the material.

  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. In addition, it is expected that the inner ring roundness of the outer ring and the thickness deviation of the cylindrical portion can be improved by uniformly reducing and deforming the material between the punch and the die.

  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 squeezing, a reduction in the dimensional accuracy of the cup molded product due to a setting error 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 shrinkage flange and the wrinkle holding force at the flange part. 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 this invention, the surface roughness of the inner diameter surface of the shell type outer ring is made finer than the outer diameter surface, and preferably the circumferential surface roughness is Ra 0.05 to 0.3 μm. The sound level during use of the bearing can be reduced without causing surface damage such as smearing while being a low-cost shell type. Therefore, it can be suitably used for applications where generation of noise is hated.

  A means for making the surface roughness of the inner surface of the outer ring finer than that of the outer diameter surface is provided by a pressing process for forming a shell-type outer ring, and an outer diameter side ironing surface that becomes the outer diameter surface of the outer ring in the ironing process. By making the lubrication condition in the substantially fluid lubrication state, the upper end surface of the cup molded product becomes nearly uniform in the plate thickness direction, so the blank diameter is reduced and the yield is improved, and the press required for drawing The load can also be reduced. Further, since the material is uniformly reduced in thickness between the punch and the die, it is possible to improve the inner diameter roundness of the outer ring and the thickness deviation of the cylindrical portion.

  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. By reducing the number of apertures, 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, the shell type needle roller bearing is formed by arranging a plurality of needle rollers 3 along the inner diameter surface 2 of the 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.

  About the shell type outer ring 1 manufactured in the manufacturing process of FIG. 2, the surface roughness in the circumferential direction and the axial direction of the inner diameter surface 2 was measured. The measured dimensions of the outer ring 1 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. was used, and the outer ring 1 was divided into two semi-cylindrical shapes, and the surface roughness of the inner diameter surface 2 was measured. The circumferential surface roughness 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, and the axial surface roughness was measured at four locations with a 90 ° phase in the circumferential direction. As shown in FIG. 7, the surface roughness of the blank material is about Ra 0.49 μm on both the front and back surfaces, and the surface roughness of the outer diameter surface of the cup molded product that is the outer diameter surface of the outer ring 1 is the circumferential direction and the axial direction. Both are about Ra0.44 μm.

  3A and 3B show examples of the measurement results of the surface roughness. FIG. 3A shows the circumferential surface roughness measured at the center position in the length direction of the outer ring 1 and 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 finer than the surface roughness of the blank material and the outer diameter surface. FIG. 3B shows the axial surface roughness measured with one phase, which is Ra 0.15 μm. Although illustration is omitted, the axial surface roughness measured at other phases is also very fine with Ra of 0.3 μm or less.

[Example A]
As an example, a shell-type needle roller bearing having a circumferential surface roughness of Ra 0.05 to 0.3 μm was prepared. In these examples, the axial surface roughness is Ra 0.3 μm or less. As a comparative example, a shell-type needle roller bearing having an outer ring inner diameter surface with a circumferential surface roughness exceeding Ra 0.3 μm was also prepared. The dimensions of the shell-type needle roller bearing are 28 mm in outer diameter and 16 mm in length in both Examples and Comparative Examples.

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. 4 shows the measurement result of the acoustic level in the acoustic measurement test. From these measurement results, the examples in which the circumferential surface roughness of the inner diameter surface is Ra 0.05 to 0.3 μm all have an acoustic level of 60 dB or less, and the acoustic level is significantly reduced compared to the comparative example. You can see that.

[Example B]
Table 1 shows the inner diameter roundness and cylinder 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 result of having measured the partial thickness deviation is shown. 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, the same size as that of Example A. The measurement positions in the axial direction of the inner diameter roundness and the cylindrical part thickness deviation are the same three positions as the measurement positions of the circumferential surface roughness of the inner diameter surface. The measurement was performed at a total of 12 positions at 4 positions with a 90 ° phase in the circumferential direction. A roundness measuring machine (Talirond) manufactured by Taylor Hobson was used for measuring the inner diameter roundness, and a micrometer was used for measuring the thickness deviation of the cylindrical portion. 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.

Bearing life tests were conducted on the shell needle roller bearings of the examples and comparative examples shown in Table 1. The number of samples in each example and comparative example was eight, and the bearing life was evaluated based on the 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

  The results of the bearing life test are shown in FIGS. FIG. 5 shows the relationship between the inner diameter roundness and the L10 life, and FIG. 6 shows the relationship between the cylinder thickness deviation and the L10 life. Each of the examples in which the roundness of the inner diameter of the shell type outer ring is 10 μm or less and the thickness deviation of the cylindrical portion is less than 10 μm, the L10 life exceeds 200 hours, and the bearing life is greatly extended. 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 reduces the sound level but also significantly improves the bearing life.

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. 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 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 Graph showing the surface roughness of the inner and outer diameter surfaces of the cup molding and the surface roughness of the blank material 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 (4)

In 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 pressing, a pressing process is provided in the press-forming for forming the shell-type outer ring, and the pressing The squeezing step in the squeezing step is 3 times or less, and the squeezing step is a squeezing and squeezing step that is performed simultaneously with the final squeezing step. The outer ring material is reduced to a uniform thickness in the thickness direction by making the lubrication condition in the fluid lubrication state in which the shearing force on the outer diameter side ironing surface is almost eliminated, and the surface roughness of the inner diameter surface of the outer ring is reduced . Is made finer than the surface roughness of the outer diameter surface, and the circumferential surface roughness of the outer ring inner diameter surface is Ra 0.05 to 0.3 μm . The shell needle roller bearing according to claim 1 , wherein an axial surface roughness of the outer ring inner diameter surface is set to Ra 0.3 µm or less. 3. The shell needle roller bearing according to claim 1, wherein the number of times of drawing in the drawing step is one, and the ironing step is a drawing and ironing step that is performed simultaneously with the one drawing step. The shell-type needle roller bearing according to any one of claims 1 to 3 , wherein a material of the shell-type outer ring is a phosphate-coated steel plate.