JP2009113786A - Wheel disk for passenger car having excellent fatigue strength, forming die, working method and fitting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high fatigue strength type wheel disk having excellent fatigue strength, a forming die, a working method and a fitting method. <P>SOLUTION: The wheel disk 1 for a passenger car having excellent fatigue strength has a plurality of contact surfaces 3 with a vehicle hub 4 in the circumferential direction. The wheel disk is formed of a steel plate of the tensile strength of ≥590 MPa, and at least one recess 2 having deapth less than 50 μm, the minor diameter of a planar shape of 2-10 mm, and the major diameter of 3-20 mm with the ratio of the major diameter to the minor diameter being 1-8 at the center of each contact surfaces 3. The wheel disk has at least one projection of the height of ≤100 μm, the minor diameter in plan view of 2-10 mm, and the major diameter of 3-20 mm with the ratio of the major diameter to the minor diameter being 1-8 on the surface having the contact surfaces 3 with the vehicle hub 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wheel disc for a passenger car, a molding die thereof, a processing method, and a mounting method.

  In general, a wheel disc for an automobile has a hole in the disk portion, and a bolt attached to a vehicle hub of the automobile is passed through the hole, and is attached by tightening a nut from the outside. At this time, a portion that contacts the vehicle hub is generated on the wheel disc, and when a force is applied to the wheel during traveling, the contact portion with the vehicle hub tends to cause a fatigue failure under low stress called fretting fatigue. In the case of a wheel disc for a passenger car, the position 12 at which fretting fatigue cracks occur is a vehicle hub existing on both sides of the bolt hole 10 on the outer peripheral side (rim side) from the bolt hole 10 as shown in FIGS. 4 is a contact surface 3. Moreover, although it depends on the type of wheel, as shown in FIG. Improving the fretting fatigue strength of this part is necessary for reducing the weight of the wheel disc, and a method for improving the fretting fatigue life is desired.

  Several countermeasures have been studied for the fretting fatigue problem of the wheel disc. For example, Patent Document 1 discloses a method of forming irregularities having a size of 50 to 500 μm on the contact surface between the wheel disc and the vehicle hub. In addition, an automobile wheel having an annular groove that straddles the outer peripheral edge of the hub is formed in a portion of the wheel disc that contacts the outer peripheral edge of the vehicle hub, and a hardened layer is formed by quenching in the vicinity of the groove. Patent Document 2 discloses a wheel that forms a recess that opens only radially outward around a bolt hole in an annular flat surface outside the disk.

  Further, Patent Document 4 discloses a bus / truck wheel in which at least one recess having a depth of 0.5 mm or less is provided in a contact portion of a mounting surface with a vehicle hub in order to determine wear due to fretting of a wheel disk. It is disclosed.

JP-A-1-156101 JP 2001-260602 A JP 2006-256525 A Japanese Patent Laid-Open No. 8-91001

  Among the disclosed technologies, Patent Document 1 does not describe the depth of the recess formed in the contact surface between the disc and the vehicle hub, and the fretting fatigue strength of the wheel disc for a passenger car is too small because the size is too small. There is a problem that it cannot be improved sufficiently. Furthermore, since the contact surface is formed of fine irregularities rather than concave portions or linear grooves, there is a problem that the fretting fatigue strength of a passenger car wheel disk cannot be sufficiently improved.

  Further, in Patent Document 2, since a substantially elliptical recess is not formed at the center of the contact surface of the wheel disc with the vehicle hub, the fretting fatigue strength of the passenger wheel disc can be sufficiently improved in the same manner. There is no problem.

  Further, in Patent Document 3, since the concave portion or the linear groove is not formed in the center of the contact surface with the vehicle hub, the fretting fatigue strength of the passenger car wheel disk cannot be sufficiently improved. There's a problem.

  In patent document 4, since the substantially elliptical recessed part or linear groove | channel is not formed in the center of each contact surface with a vehicle hub, the fretting fatigue strength of a wheel disk for passenger cars cannot fully be improved. There is a problem. Furthermore, for the purpose of identifying wear, the recess does not come into contact with the vehicle hub surface until the wheel disc is worn and reduced in thickness during use, so that the fretting fatigue strength of the wheel disc for passenger cars can be sufficiently improved. There is a problem that it cannot be done.

  An object of the present invention is to provide a passenger car wheel disk, a molding die, a processing method, and a processing method thereof that are excellent in fretting fatigue strength.

  In order to solve the above problems, the present invention provides a wheel disc for a passenger car having a plurality of circumferential contact surfaces with a vehicle hub, comprising a steel plate having a tensile strength of 590 MPa or more, and a center of each contact surface. It has excellent fatigue strength characterized by having at least one recess having a depth of less than 50 μm, a short axis of 2-10 mm in a planar shape, a long axis of 3-20 mm, and a ratio of long axis / short axis of 1-8. Provide wheel discs for passenger cars.

  According to the present invention, there is also provided a press-molding die for a passenger car wheel disk according to claim 1, wherein the plane that forms a contact surface with the vehicle hub has a height of 100 μm or less and a planar short diameter. A die for press molding of a wheel disc for passenger cars having excellent fatigue strength, characterized in that it has at least one convex part having a major axis / minor axis ratio of 1 to 8 and a major axis of 2 to 10 mm, a major axis of 3 to 20 mm. Provided.

  Further, according to the present invention, there is provided a wheel disc for a passenger car having a plurality of circumferential contact surfaces with a vehicle hub, comprising a steel plate having a tensile strength of 590 MPa or more, and each contact surface having a depth of 50 to There is provided a wheel disc for a passenger car having excellent fatigue strength, characterized by having at least one groove having a width of 500 μm and a width of 1 mm or less.

  Furthermore, according to the present invention, there is provided a press-molding die for a passenger car wheel disk according to claim 3, wherein the surface forming the contact surface with the vehicle hub has a height of 100 to 500 μm and a width of 1 mm or less. There is provided a die for press molding of a wheel disc for a passenger car having excellent fatigue strength, characterized by having at least one linear protrusion.

  Furthermore, according to the present invention, a wheel for a passenger car having excellent fatigue strength, characterized in that a steel plate having a tensile strength of 590 MPa or more is press-formed using the press-molding die according to claim 2 or 4. A method for processing a disk is provided.

  Furthermore, according to the present invention, there is provided a method for mounting a passenger wheel disc according to claim 1 to a vehicle hub, wherein the recess is pushed and the entire inner surface of the recess comes into contact with the vehicle hub. There is provided a method for mounting a wheel disc for a passenger car having excellent fatigue strength, characterized by being bolted to a vehicle.

  According to the present invention, the surface pressure of the contact surface with the vehicle hub, which is the starting point of fretting fatigue cracks, can be reduced at the time of attachment to the vehicle hub. It is possible to obtain strength, and its industrial significance is great.

  Hereinafter, the present invention will be described in detail with reference to the drawings. In the present specification and drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

  1A and 1B are external views of the entire wheel disk according to the present invention. FIG. 1A is a side view, and FIG. 1B is a front view. FIG. 2 is an enlarged view of a part where the wheel disc 1 is attached to the vehicle hub 4 and a part thereof. As shown in FIG. 2, the wheel disc 1 is attached by passing the bolt 7 attached to the vehicle hub 4 through the bolt hole 10 of the wheel disc 1 and tightening the hub nut 6 from the outside. 1 and the vehicle hub 4 come into contact with each other at the contact surface 3. As shown in FIG. 1, a plurality of contact surfaces 3 are circumferentially provided on both sides of the bolt hole 10.

  In order to cope with the problem that fretting fatigue cracks are likely to occur on the contact surface with the vehicle hub due to the repeated load that the passenger car wheel disc receives during use, the present inventor first of the contact surface with the vehicle hub at the time of tightening The situation was examined in detail. As a result, the contact surface of the vehicle wheel disc with the vehicle hub is press-formed with the goal of flattening, but as shown in FIG. 13, it is actually slightly convex due to the springback of the steel plate. The center of the contact surface 3 is in the vicinity of the convex apex, and when the vehicle hub 4 is tightened with a nut, the contact surface pressure 5 is greatest at the center of the contact surface 3, as shown in FIG. Thus, it was found that the center of the contact surface 3 is the fretting fatigue crack generation position 12. It was also found that when the tightening force increases or the contact area decreases, the contact surface pressure increases and fretting fatigue cracks are likely to occur. Furthermore, it has also been found that fretting fatigue cracks are likely to occur frequently in wheel disks using steel plates of 590 MPa class or higher.

  As a result of examining the means for improving the fretting fatigue strength of the wheel disc, the surface pressure of the central portion of the contact surface 3 with the vehicle hub 4 where the fretting fatigue crack is generated can be reduced. The inventors have invented the formation of a recess 2 having a substantially elliptical planar shape at the center of 3. 3 and 4 show the shape of the recess 2 as seen from the side and front of the wheel disc 1, respectively. When the concave portion 2 having a substantially elliptical planar shape is formed at the center of the contact surface 3 with the vehicle hub 4, the concave portion 2 is formed when the wheel disk 1 is tightened by the hub nut 6 (FIG. 2) as shown in FIG. It has been found that the contact surface pressure 5 can be reduced as compared with a contact surface in which the recess 2 is not formed because it contacts the vehicle hub 4 while being spread. By reducing the contact surface pressure, the occurrence of fretting fatigue cracks can be suppressed, and the fretting fatigue strength can be greatly improved.

  Further, since the concave portion 2 comes into contact with the vehicle hub 4 while being expanded, the degree of adhesion with the vehicle hub 4 is increased, and even when a bending moment is applied, it is difficult to be displaced, and also from this point, the occurrence of fretting fatigue cracks is suppressed. It became clear that it was effective. The recess 2 is the center of the contact surface 3, the depth D is less than 50 μm, the elliptical minor axis d 1 is 2 to 10 mm, the major axis d 2 is 3 to 20 mm, and the major axis d 2 / minor axis d 1 is 1 to 8; It has been found that the surface pressure can be made sufficiently small. When the depth D of the concave portion 2 is 50 μm or more, the portion of the inner surface of the concave portion 2 that does not come into contact with the vehicle hub 4 at the time of attachment increases, and the surface area that is substantially in contact is reduced. As a result, the fretting fatigue strength is reduced. Although the lower limit of the depth D of the concave portion 2 is not particularly defined, it has been found that if the depth is too shallow, the effect of the concave portion 2 is lost, and therefore 20 μm or more is preferable. Further, if the minor axis d1 and the major axis d2 of the planar shape of the recess 2 are smaller than 2 mm and 3 mm, respectively, the surface pressure at the center of the contact surface 3 becomes considerably large, and the fretting fatigue strength is almost the same as that without the recess 2. The strength cannot be improved.

  Furthermore, when the short diameter d1 and the long diameter d2 of the concave portion 2 are larger than 10 mm and 20 mm, respectively, when the hub nut 6 is tightened, the portion of the inner surface of the concave portion 2 that does not come into contact with the vehicle hub 4 increases, and the contact area decreases. 3 increases the fretting fatigue strength. If the ratio of the major axis / minor axis is 1 or more, the contact surface pressure can be reduced. However, if the ratio exceeds 8, the recess 2 becomes extremely elongated, and the stress concentration at the tip of the recess 2 increases, increasing the fretting fatigue strength. Since the ratio is lowered, the ratio of major axis / minor axis is specified in the range of 1-8.

  In the case of a polygonal shape such as a triangle or a quadrangle, the planar shape of the concave portion 2 needs to be a smooth shape in order to increase the surface pressure of the contact surface near the corner portion and reduce the fretting fatigue strength. Moreover, when the planar shape of the concave portion 2 has a concave portion toward the outside, the contact surface pressure of the concave portion increases, so that an elliptical shape that is convex outward is effective.

  Furthermore, in the conventional wheel disc, the surface pressure at the center of the contact surface with the vehicle hub is high, and a fretting fatigue crack is generated from the center as shown in FIG. It needs to be formed to include. It has been found that the fretting fatigue strength can be improved if there is at least one recess 2 at the center of each of the contact surfaces 3 on the wheel disk 1. The center of the contact surface 3 referred to in the present invention is the center C of the portion having the maximum width dimension W in the radial direction of the wheel disk 1 of the contact surface 3 as shown in FIG.

  Thus, it consists of a steel plate with a tensile strength of 590 MPa or more, and has a depth of less than 50 μm in the center of the contact surface 3, a planar shape having a minor axis of 2 to 10 mm, a major axis of 3 to 20 mm and a major axis / minor axis ratio of 1 to 8. It has been found that a wheel disc for a passenger car having at least one recess has excellent fatigue strength.

  Next, a press molding die for molding a wheel disk having a recess according to the present invention will be described.

  The present inventor has studied a press molding die for a wheel disc for a passenger car having a recess for improving fatigue strength. As described above, a wheel disc for a passenger car having excellent fretting fatigue strength has a depth of less than 50 μm, a planar shape having a minor axis of 2 to 10 mm, a major axis of 3 to 20 mm and a major axis / long diameter at the center of the contact surface 3 with the vehicle hub 4. Although it is effective to have at least one recess having a minor axis ratio of 1 to 8, when a press mold for forming the recess 2 is studied, the contact surface 3 with the vehicle hub 4 is determined. A mold having at least one convex part having a height of 100 μm or less, a short shape of 2 to 10 mm, a major axis of 3 to 20 mm and a major axis / minor axis ratio of 1 to 8 is effective on the surface to be formed. I found.

  When the height of the substantially elliptical convex portion on the mold surface forming the contact surface 3 with the vehicle hub 4 exceeds 100 μm, the depth of the concave portion 2 formed on the contact surface 3 with the vehicle hub 4 Was 50 μm or more, and it was found that 100 μm or less was effective. The lower limit of the height of the convex portion is not particularly defined, but it has also been found that 50 μm or more is preferable because the concave portion 2 cannot be formed if it is too low. Further, if the short axis and the long axis of the planar shape of the convex part are smaller than 2 mm and 3 mm, respectively, the concave part 2 formed on the contact surface 3 with the vehicle hub 4 becomes smaller than 2 mm and 3 mm, thereby improving the fretting fatigue strength. I can not. Similarly, if the short diameter and long diameter of the convex portion are larger than 10 mm and 20 mm, respectively, the planar shape of the concave portion 2 formed on the contact surface 3 with the vehicle hub 4 becomes larger than 10 mm and 20 mm. It turns out that it cannot be improved. If the ratio of major axis / minor axis is 1 or more, the contact surface pressure can be reduced, but if the ratio exceeds 8, the recess 2 formed on the contact surface 3 with the vehicle hub 4 becomes extremely elongated, and the recess 2 Since the stress concentration at the elongate tip portion increases and the fretting fatigue strength decreases, the ratio of the major axis / minor axis of the convex portion is specified in the range of 1-8.

  Further, when the planar shape of the convex portion is a polygon such as a triangle or a quadrangle, the planar shape of the concave portion 2 formed on the contact surface 3 with the vehicle hub 4 is also a polygon, and the surface pressure of the contact portion close to the corner portion. Increases, and the fretting fatigue strength is lowered, so that the shape needs to be smooth. If the convex portion has a concave portion toward the outside, the contact pressure of the contact surface 3 at the concave portion is increased, and therefore, an elliptical shape that is all convex is effective. When the convex portion is not at the center of the contact surface 3 with the vehicle hub 4, the surface pressure at the center of the contact surface 3 with the vehicle hub 4 is high, and fretting fatigue cracks are generated from the center.

  Therefore, the surface forming the contact surface 3 with the vehicle hub 4 has a height of 100 μm or less, a planar shape having a minor axis of 2 to 10 mm, a major axis of 3 to 20 mm, and a major axis / minor axis ratio of 1 to 8. It has been found that a press molding die having at least one convex portion is effective for molding a wheel disc for a passenger car having excellent fatigue strength.

  Furthermore, as a result of studying another means for reducing the surface pressure at the central portion of the contact area with the vehicle hub, the present inventor has invented the formation of the groove 17 in the contact surface 3. That is, when the groove 17 is formed on the contact surface 3 with the vehicle hub 4, the linear groove 17 does not contact the vehicle hub 4 when the wheel disc 1 is tightened by the hub nut 6 as shown in FIG. The surface 3 is divided by the groove 17, so that the contact surface pressure 5 can be reduced, and the shear stress 20 generated in both the wheel disc 1 and the vehicle hub 4 can be reduced, greatly improving fretting fatigue strength. I found out that I can make it happen.

  It has been found that the groove 17 can reduce the contact surface pressure and increase the fretting fatigue strength when the depth a is 50 to 500 μm and the width b is 1 mm or less. When the depth a of the groove 17 is more than 500 μm, the thickness of the groove portion of the wheel disk 1 is reduced, and the bottom of the groove 17 is notched and fatigue cracks are likely to occur. If the depth a of the groove 17 is smaller than 50 μm, the bottom of the groove may come into contact during tightening, and the effect of reducing the shear stress is lost. Further, when the width b of the groove 17 exceeds 1 mm, the opening area by the groove 17 increases, the area of the non-contact portion increases, the surface pressure of the contact surface 3 increases, and the fretting fatigue strength cannot be improved. . The lower limit of the width b is not particularly defined, but if it is too narrow, the effect as a groove is lost, and therefore it is preferably 50 μm or more.

  The planar shape of the groove 17 is not limited to a straight line as long as it is a smooth line, and may be a curved line as shown in FIG. Further, fretting fatigue can be improved even if one groove 17 is provided on one contact surface 3 or a plurality of grooves 17 are arranged as shown in FIG. Further, although the position of the groove 17 is not particularly defined, it is preferably arranged in the vicinity of the center C of the contact surface 3 as shown in FIG. The center C of the contact surface 3 is the center C of the portion having the maximum width dimension W of the contact surface 3 in the radial direction of the wheel disc 1 as described above. Further, although the arrangement direction of the groove 17 is not particularly defined, it is preferable that the longitudinal direction of the groove 17 is arranged in the radial direction of the wheel disk 1 as shown in FIG.

  As described above, it has been found that a wheel disc for a passenger car, which is made of a steel plate having a tensile strength of 590 MPa or more and has at least one groove having a depth of 50 to 100 μm and a width of 1 mm or less on the contact surface, has excellent fatigue strength.

  Next, a press molding die for molding a wheel disk having grooves according to the present invention will be described.

  In order to obtain a wheel disc for a passenger car having excellent fretting fatigue strength, it is effective to have at least one groove 17 having a depth of 50 to 500 μm and a width of 1 mm or less on the contact surface 3 with the vehicle hub 4 as described above. However, when a press mold for forming the groove 17 was examined, a linear convex portion having a height of 100 to 500 μm and a width of 1 mm or less was formed on the surface forming the contact surface 3 with the vehicle hub 4. It has been found that a mold having at least one is effective.

  When the height of the linear convex portion on the mold surface forming the contact surface 3 with the vehicle hub 4 exceeds 500 μm, the depth of the groove 17 formed on the contact surface 3 with the vehicle hub 4 is 500 μm. Therefore, it was found that 500 μm or less is effective. It has also been found that when the height of the linear convex portion is smaller than 100 μm, a groove having a depth of 50 μm or more cannot be formed. In addition, when the width of the linear protrusion exceeds 1 mm, the width of the groove 17 formed on the contact surface 3 with the vehicle hub 4 becomes larger than 1 mm, and thus it is found that the fretting fatigue strength cannot be improved. did. The lower limit of the width of the linear convex portion is not particularly defined, but it has been found that if it is too narrow, a groove cannot be formed.

  Further, the shape of the linear convex portion is effective regardless of whether it is a straight line or a curved line as long as it is a smooth linear shape. Further, fretting fatigue can be improved even if one or a plurality of the contact surfaces 3 of the mold are arranged. Further, the position of the linear convex portion is not particularly defined, but it is preferably arranged in the vicinity of the center C of the contact surface 3. Moreover, although it does not prescribe | regulate especially about the direction of a linear convex part, it is preferable to arrange | position in the radial direction of the wheel disc 2. FIG.

  From the above, the press-molding die having at least one linear protrusion having a height of 100 to 500 μm and a width of 1 mm or less on the surface forming the contact surface 3 with the vehicle hub 4 has excellent fatigue strength. It has been found that it is effective for forming wheel discs for passenger cars.

  Next, the wheel disk processing method of the present invention will be described.

  As a method of forming the concave portion 2 or the groove 17 on the contact surface 3 of the steel wheel disc 1 with the vehicle hub 4, the present inventor press-molded a steel plate having a tensile strength of 590 MPa or more using the above mold. I found it effective. That is, the steel wheel disc is usually formed by a press molding process, but the recess 2 in the contact surface 3 of the vehicle hub 4 is incorporated by incorporating a step of forming the recess 2 or the groove 17 in the press molding process. Alternatively, the boundary of the groove 17 becomes smooth, and when the hub nut 6 is tightened, the contact can be started continuously from the outer contact surface 3 to the recess 2 or the groove 17 with respect to the wheel center, and the distribution of the contact surface pressure is smooth. And fretting fatigue strength can be improved.

  Since fretting fatigue is remarkable in a steel sheet having a tensile strength of 590 MPa or more, the tensile strength of the steel sheet is specified in a range of 590 MPa or more.

  Although the fretting fatigue strength is improved even when the recess 2 or the groove 17 is formed by a method other than press molding, for example, machining using a drill or a bite, the contact surface 3 and the recess of the vehicle hub 4 are improved. When the boundary between the groove 2 and the groove 17 becomes sharp, discontinuous contact occurs at the boundary between the recess 2 or the groove 17 when tightening with the hub nut 6, and the contact surface 3 close to the boundary between the recess 2 or the groove 17 increases the surface pressure. As a result, the fretting fatigue strength cannot be sufficiently improved, which is not preferable.

  Thus, it has been found that press forming a steel plate having a tensile strength of 590 MPa or more using the above die is effective as a method for processing a wheel disc for a passenger car having excellent fatigue strength.

  Next, a method for attaching the wheel disk of the present invention will be described.

  The present inventor has studied a method of attaching a passenger car wheel disc to a vehicle hub. As a result, when the wheel disk 1 having the above-described recess 2 on the contact surface 3 with the vehicle hub 4 is attached to the vehicle hub 4, bolting is performed so that the recess 2 is in contact with the vehicle hub 4 as shown in FIG. 3. It has been found that (fastening the hub nut 6) is particularly effective in improving the fatigue strength of the wheel disc 1 for passenger cars. That is, since all of the expanded inner surface of the recessed portion 2 comes into contact with the vehicle hub 4, the contact area can be increased and the surface pressure 5 of the contacted portion can be reduced, and the fretting fatigue strength can be improved. . FIG. 6 shows examples of different shapes of the recess 2, and thus the fretting fatigue strength is improved even if the recess 2 formed on the contact surface 3 with the vehicle hub 4 does not contact the vehicle hub 4. However, if the area of the non-contact portion becomes too large, the average value of the surface pressure becomes large and the fretting fatigue strength cannot be sufficiently improved.

  As described above, when the wheel disc 1 is fastened to the vehicle hub 4 with the bolts 7 and the hub nut 6 so that the recesses 2 on the contact surface 3 of the wheel disc 1 with the vehicle hub 4 are all in contact with the vehicle hub 4, the passenger car It was found that the fatigue strength of the wheel disc for use was improved.

  As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to this example. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims. It is understood that it belongs to.

  As test steels, 400 mm, 440 MPa, 590 MPa, and 780 MPa grade 3.2 mm thick hot-rolled steel sheets were used, and by press molding, a wheel disc for passenger cars having an outer diameter of 14 inches in the shape shown in FIG. 5 bolts 10 for mounting to the vehicle hub) were manufactured. At that time, wheel discs were formed in which the recesses 2 or grooves 17 of various dimensions were formed on the contact surface 3 with the vehicle hub 4. As a method for forming the recess 2 or the groove 17, machining and press molding were used. For comparison, a wheel disk without recesses and grooves was also produced. As shown in FIG. 12, a rim 16 (type J) having a width of 5 inches was attached to these wheel disks by welding, and a wheel life fatigue test was performed. In this test, a bending moment is applied through the vehicle hub 4 by rotating the weight 15 attached to the tip of the arm 14 of the wheel life tester. Here, the bending moment was 150 kgf · m. During the test, it was stopped every 1000 times and removed from the vehicle hub 4, and the presence or absence of fretting fatigue cracks on the contact surface 3 of the wheel disc 1 with the vehicle hub 4 was examined. When fretting fatigue cracks penetrated the plate thickness, the fretting fatigue life was defined and compared.

  First, the wheel life fatigue test result of the wheel disc which provided the recessed part in the contact surface with a vehicle hub is shown to Tables 1-4.

  First, the test results shown in Table 1 will be described. No. 1-3 are wheel discs whose test steel materials are 400 MPa class steel plate and 440 MPa class steel plate, fretting fatigue cracks do not occur on the contact surface with the vehicle hub, and fatigue cracks from other parts become large and breakage It came to.

  No. Nos. 12 to 16 are wheel disks using a 590 MPa grade steel plate, and show examples of wheel disks in which concave portions are formed on the contact surface with the vehicle hub by machining. These are inventions according to claim 1 of the present invention, and No. which does not process a recess with the same steel plate. No. 4 and No. 4 which is a comparative example in which a recess having a depth, minor axis, major axis, major axis / minor axis, and position outside the scope of the present invention is formed. The fretting fatigue life is dramatically improved as compared with 5-11. Specifically, no. 3 times that of No. 4, No. 4 Compared with 5-11, the lifetime improvement of 2 times or more was confirmed. No. Nos. 12, 13, and 15 are inventions according to claim 6 of the present invention and are examples in which the concave portions during tightening do not come into full contact with each other. 14 and no. A life improvement of 100,000 times or more was recognized compared to 16. In Table 1, numerical values or conditions indicated by underlining indicate that they are outside the scope of the present invention.

  Thus, from the results shown in Table 1, it was found that the wheel disk having a recess and the method for attaching the wheel disk of the present invention is effective in improving fretting fatigue strength.

  Next, the test results shown in Table 2 will be described. No. Nos. 24-28 are wheel discs using 590 MPa grade steel plates, and show examples of wheel discs in which concave portions are formed on the contact surface with the vehicle hub by press molding. These are inventions according to Claims 2 and 5 of the present invention, and No. which does not process recesses with the same steel plate. 4 (Table 1) and a comparative example in which a concave portion formed by a mold having convex portions of height, short diameter, long diameter, long diameter / short diameter, and position outside the scope of the present invention was formed by the same press molding. No. The fretting fatigue life is dramatically improved as compared with 17-23. Specifically, no. 4 times more than 4; Compared with 17-23, the lifetime improvement of 3 times or more was confirmed. The depth, minor axis, major axis, major axis / minor axis, and position of the recess are within the scope of the present invention. Compared with 12 to 16 (Table 1), at least 50,000 times or more life improvement was observed. Furthermore, no. Nos. 24, 25 and 27 are inventions according to claim 6 of the present invention, and are No. 4 which are other examples in which the concave portions do not come into full contact with each other during tightening. 26 and no. A life improvement of at least 100,000 times or more was observed compared to 28. In Table 2, numerical values or conditions indicated by underlining indicate that they are outside the scope of the present invention.

  Thus, from the results shown in Table 2, the wheel disk having a recess, the wheel disk processing method, the press molding die, and the wheel disk mounting method of the present invention are effective in improving fretting fatigue strength. It has been found.

  Furthermore, the test results shown in Table 3 will be described. No. Reference numerals 37 to 41 are wheel disks using a 780 MPa class steel plate, and show examples of wheel disks in which concave portions are formed on the contact surface with the vehicle hub by machining. These are inventions according to claim 1 of the present invention, and No. which does not process a recess with the same steel plate. No. 29, and a comparative example in which a recess having a depth, minor axis, major axis, major axis / minor axis, and position outside the scope of the present invention was formed. The fretting fatigue life is dramatically improved from 30 to 36. Specifically, no. 3.3 times that of No. 29, No. 29 Compared with 30-36, the lifetime improvement of 2.6 times or more was confirmed. No. Nos. 37, 38, and 40 are examples according to claim 6 of the present invention. 39 and no. Compared to 41, a life improvement of 100,000 times or more was recognized. In Table 3, numerical values or conditions displayed underlined indicate that they are outside the scope of the present invention.

  Thus, from the results shown in Table 3, it was found that the wheel disk having a recess and the method for attaching the wheel disk of the present invention is effective in improving fretting fatigue strength.

  Next, the test results shown in Table 4 will be described. No. Nos. 49 to 53 are wheel disks using 780 MPa class steel plates, and show examples of wheel disks in which concave portions are formed in contact portions with a vehicle hub by press molding. These are inventions according to Claims 2 and 5 of the present invention, and No. which does not process recesses with the same steel plate. 29 (Table 3) and a comparative example in which a concave portion formed by a mold having convex portions of height, short diameter, long diameter, long diameter / short diameter, and position outside the range of the present invention was formed by the same press molding. No. The fretting fatigue life is dramatically improved compared to 42-48. Specifically, no. 5.5 times more than No. 29, No. 29 Compared to 42-48, a life improvement of 4.2 times or more was confirmed. The depth, minor axis, major axis, major axis / minor axis, and position of the recess are within the scope of the present invention. Compared with 37-41 (Table 3), at least 120,000 times of life improvement was recognized. Furthermore, no. Nos. 49, 50, and 52 are examples according to claim 6 of the present invention. 51 and no. Compared to 53, at least 140,000 or more lifetime improvements were observed. In Table 4, numerical values or conditions displayed underlined indicate that they are outside the scope of the present invention.

  Thus, from the results shown in Table 4, the wheel disk having a recess, the wheel disk processing method, the press molding die, and the wheel disk mounting method of the present invention are effective in improving fretting fatigue strength. It has been found.

  Next, Tables 5 to 8 show the wheel life fatigue test results of wheel discs provided with grooves on the contact surface with the vehicle hub.

  First, the test results shown in Table 5 will be described. No. No. 54 to 56 are wheel discs whose test steel materials are 400 MPa class steel plate and 440 MPa class steel plate, fretting fatigue cracks do not occur on the contact surface with the vehicle hub, and fatigue cracks from other parts become large and break. It came to.

  Next, no. Reference numerals 62 to 66 denote wheel disks using a 590 MPa class steel plate, and show examples of wheel disks in which grooves are formed in contact portions with a vehicle hub by machining. These are the inventions according to claim 3 of the present invention, and No. which does not process grooves with the same steel plate. 57, and a comparative example in which grooves having a depth and width outside the scope of the present invention were formed. The fretting fatigue life is dramatically improved compared to 58-61. Specifically, no. 3.1 times that of No. 57, No. 57 Compared with 58-61, the lifetime improvement of 2.7 times or more was confirmed. In Table 5, numerical values or conditions displayed underlined indicate that they are outside the scope of the present invention.

  Thus, from the results shown in Table 5, it was found that the wheel disk having grooves according to the present invention is effective in improving fretting fatigue strength.

  Next, the test results shown in Table 6 will be described. No. 70 to 74 are wheel disks using a 590 MPa grade steel plate, and show examples of wheel disks in which a groove is formed in a contact portion with a vehicle hub by press molding. These are the inventions according to Claims 3 and 5 of the present invention, and No. which does not process grooves with the same steel plate. No. 57 (Table 5), and Comparative Example No. 1 which is a comparative example in which a groove formed by a mold having linear convex portions having a height / width outside the range of the present invention is formed by the same press molding. The fretting fatigue life is dramatically improved over 67-69. Specifically, no. 5.1 times more than 57, No. The lifetime improvement of 3.6 times or more was confirmed compared with 67-69. The depth and width of the groove are within the scope of the present invention. Compared with 62-66 (Table 5), at least 60,000 times or more life improvement was recognized. In Table 6, numerical values or conditions displayed underlined indicate that they are outside the scope of the present invention.

  Thus, from the results shown in Table 6, it was found that the wheel disk having a groove of the present invention, the wheel disk processing method, and the press-molding die are effective in improving fretting fatigue strength.

  Further, the test results shown in Table 7 will be described. No. Reference numerals 79 to 83 denote wheel disks using 780 MPa class steel plates, and examples of wheel disks in which grooves are formed in contact portions with a vehicle hub by machining. These are the inventions according to claim 3 of the present invention, and No. which does not process grooves with the same steel plate. 75 and No. 75, which is a comparative example in which grooves having a depth and width outside the scope of the present invention are formed. The fretting fatigue life is dramatically improved from 76 to 78. Specifically, no. Compared to 75, it is 3.2 times. Lifetime improvement of 2.7 times or more was confirmed compared with 76-78. In Table 7, numerical values or conditions indicated by underlining indicate that they are outside the scope of the present invention.

  Thus, from the results shown in Table 7, it was found that the wheel disk having grooves according to the present invention is effective in improving fretting fatigue strength.

  Next, the test results shown in Table 8 will be described. No. Reference numerals 87 to 91 are wheel disks using 780 MPa class steel plates, and show examples of wheel disks in which grooves are formed in a contact portion with a vehicle hub by press molding. These are the inventions according to Claims 3 and 5 of the present invention, and No. which does not process grooves with the same steel plate. No. 75 (Table 7) and No. 1 which is a comparative example in which a groove formed by a mold having linear convex portions with height and width outside the range of the present invention is formed by the same press molding. The fretting fatigue life is dramatically improved compared to 84-86. Specifically, no. 7.8 times higher than 75, No. Compared with 84-86, the lifetime improvement of 6.8 times or more was confirmed. The depth and width of the groove are within the scope of the present invention. Compared with 79-83 (Table 7), at least 200,000 times or more life improvement was recognized. In Table 8, numerical values or conditions displayed underlined indicate that they are outside the scope of the present invention.

  Thus, from the results shown in Table 8, it was found that the wheel disk having a groove of the present invention, the wheel disk processing method, and the press-molding die were effective in improving fretting fatigue strength.

  As described above, it was found that the wheel disk having a recess or groove, the wheel disk processing method, the press molding die, and the wheel disk mounting method of the present invention are extremely effective in improving fretting fatigue strength. .

  The present invention can be applied to various vehicle wheel discs, molding dies, processing methods, and attachment methods.

It is a figure which shows the external appearance and contact surface of a wheel disc for passenger cars. It is a side view which shows the contact condition with the vehicle hub of a wheel disc for passenger cars, and a fretting fatigue crack occurrence position. It is a figure which shows the surface pressure distribution at the time of contact with the recessed part and vehicle hub of a contact surface in the wheel disc of this invention. It is a top view which shows the recessed part shape of the contact surface in the wheel disc of this invention. It is a top view explaining the center of the contact surface in a wheel disc. It is a side view which shows the example from which the recessed part of the contact surface in the wheel disc of this invention differs, and the surface pressure distribution at the time of contact with a vehicle hub. It is a side view which shows the surface pressure distribution and the shear stress at the time of contact with the groove | channel of the contact surface and vehicle hub in the wheel disc of this invention. It is a top view which shows the example of the planar shape of the groove | channel of the contact surface in the wheel disk of this invention. It is a top view which shows the example from which the groove | channel of the contact surface in the wheel disc of this invention differs. It is a top view which shows the example of the arrangement position of the groove | channel of the contact surface in the wheel disc of this invention. It is a top view which shows the example of the arrangement direction of the groove | channel of the contact surface in the wheel disk of this invention. It is a figure which shows the wheel life test condition in the Example of this invention. It is a side view which shows the surface pressure distribution and the shear stress at the time of contact with the recessed part of a contact surface in a conventional wheel disc, and a vehicle hub.

Explanation of symbols

1 Wheel disc 2 Recess 3 Contact surface 4 Vehicle hub 5 Contact surface pressure distribution 6 Nut
7 Bolt 10 Bolt hole 12 Fretting fatigue crack occurrence position 14 Arm 15 Weight 16 Rim 17 Groove 20 Shear stress a Groove depth b Groove width
C Center of contact surface D Depth of recess d1 Short diameter of recess d2 Long diameter of recess

Claims (6)

  A wheel disc for a passenger car having a plurality of circumferential contact surfaces with a vehicle hub, comprising a steel plate having a tensile strength of 590 MPa or more, and having a depth of less than 50 μm and a short planar shape at the center of each contact surface. A wheel disc for a passenger car having excellent fatigue strength, characterized by having at least one recess having a diameter of 2 to 10 mm, a major axis of 3 to 20 mm, and a major axis / minor axis ratio of 1 to 8.   2. A press-molding die for a passenger car wheel disk according to claim 1, wherein a surface forming a contact surface with the vehicle hub has a height of 100 [mu] m or less, a short axis of a planar shape of 2 to 10 mm, and a long axis of A die for press molding of a wheel disc for a passenger car having excellent fatigue strength, characterized by having at least one convex part having a major axis / minor axis ratio of 1 to 8 at 3 to 20 mm.   A wheel disc for a passenger car having a plurality of circumferential contact surfaces with a vehicle hub, comprising a steel plate having a tensile strength of 590 MPa or more, and a groove having a depth of 50 to 500 μm and a width of 1 mm or less on each contact surface. A wheel disc for a passenger car having excellent fatigue strength, comprising at least one.   4. A press-molding die for a passenger car wheel disk according to claim 3, wherein at least one linear convex portion having a height of 100 to 500 [mu] m and a width of 1 mm or less is formed on a surface forming a contact surface with the vehicle hub. A die for press molding of a wheel disc for a passenger car having excellent fatigue strength.   A processing method for a wheel disc for a passenger car having excellent fatigue strength, comprising pressing a steel plate having a tensile strength of 590 MPa or more using the press molding die according to claim 2 or 4.   2. The method for attaching a wheel disc for a passenger car to a vehicle hub according to claim 1, wherein the recess is pushed and widened so that the entire inner surface of the recess comes into contact with the vehicle hub. A method of attaching a wheel disc for passenger cars with excellent fatigue strength.

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