Plastic fastening method and plastic fastening structure

Abstract

To surely prevent pulling-out of a fitting part in the axial direction while securing a holding force in a rotation direction in fit-fixing by plastic fastening between a rotation member and a shaft member.SOLUTION: This plastic fastening method press-inserts a hollow or solid shaft member into a hole formed in a rotation member, and causes a part of a material constituting the other of the outer peripheral surface of the shaft member and the inner peripheral surface of the hole to flow into a tooth part formed in one of the outer peripheral surface of the shaft member and the inner peripheral surface of the hole, thereby fixing the shaft member and the rotation member to each other in a rotation direction. This method integrally forms a lock part for fixing the shaft member and the rotation member to each other in the axial direction of the shaft member by causing a part of the material constituting the other of the outer peripheral surface of the shaft member and the inner peripheral surface of the hole to flow into a recess formed in one of the outer peripheral surface of the shaft member and the inner peripheral surface of the hole at a position different from that of the tooth part in the axial direction of the shaft member through the press-inserting.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a plastic fastening method and a plastic fastening structure. [Background Art]

[0002] For example, when fitting and fixing a shaft member such as a hollow or solid shaft into a hole formed in a rotating member such as a gear, a pulley or a pipe, it is known to provide uneven portions such as splines on the fitting surface of either the rotating member or the shaft member, and then fit the shaft member to the other. According to this method, when the shaft member is fitted into the hole formed in the rotating member, the material on the other side, which is not provided with the uneven portions, undergoes plastic flow and fills the uneven portions, whereby the rotating member and the shaft member are firmly fixed. Such fastening is referred to as "plastic fastening" or "plastic bonding", etc.

[0003] For example, Patent Document 1 (Japanese Unexamined Patent Publication No. 11-320274) discloses that a second metal pipe having serration-shaped coupling grooves formed on its outer peripheral surface is press-fitted into the interior of a first metal pipe, so that the material of the first metal pipe pressed on the fitting surface is caused to plastically flow toward the coupling grooves, thereby plastically bonding the two. According to this document, it is possible to bond metal pipes to each other or a metal pipe and a metal rod with high coaxial accuracy.

[0004] In addition, Patent Document 2 (Japanese Unexamined Patent Publication No. 2007-301627) discloses a first gear having a diameter-reducing cylindrical surface and a diameter-expanding cylindrical surface continuously formed on a fitting surface, and a second gear having a cylindrical surface in sliding contact with the diameter-expanding cylindrical surface and spline teeth biting into the diameter-reducing cylindrical surface continuously formed on a fitting surface. The diameter-expanding cylindrical surface and the cylindrical surface are used as guide surfaces during press-fitting, and the first gear and the second gear are press-fitted and fitted together while the spline teeth bite into the diameter-reducing cylindrical surface. According to this document, it is possible to obtain a plastic fastened component having sufficient bonding strength and excellent coaxiality.

[0005] Furthermore, Patent Document 3 (Japanese Patent Publication No. 2008-157273) discloses a plastic fastening method in which, when press-fitting a pulley shaft constituting a belt-type continuously variable transmission (CVT) into a fixed sheave, a restricting portion (protrusion) provided on the inner circumferential surface of the internal space (central hole) of the fixed sheave plastically deforms a plastically deformable portion (protrusion adjacent to the space) provided on the outer circumferential surface of the pulley shaft. According to this method, torque transmission between the pulley shaft and the fixed sheave can be improved without increasing the contact area between the two.

[0006] As described above, plastic fastening, which utilizes plastic flow, is frequently used in the fitting and fixing of rotating members to each other and / or between rotating members and shaft members. However, in these conventional techniques, although the holding force in the rotational direction is high, no consideration is given to preventing the fitting from coming loose in the axial direction, so under certain conditions, there is a concern that the fitting may come loose in the axial direction. As a measure to prevent the fitting from coming loose in the axial direction, one example is to fix the rotating members to each other and / or between rotating members and shaft members by fastening members such as welding or bolts. However, such measures not only lead to an increase in man-hours and / or the number of parts, but also result in an uneven mass distribution around the axis, making them unsuitable for applications involving rotating bodies.

[0007] Furthermore, the fixed sheave fitted and fixed to the pulley shaft by the plastic fastening method disclosed in Patent Document 3 (Japanese Patent Application Publication No. 2008-157273) prevents it from coming out in the insertion direction (direction of arrow E in Figure 1 of Patent Document 3) due to the contact between the restricting portion and the plastically deformed portion, and the contact between the tapered portions of each other. However, no consideration has been given to preventing it from coming out in the direction opposite to the insertion direction.

[0008] As described above, in this technical field, there is a need for a technology that can ensure holding force in the rotational direction while reliably preventing the fitting portion from coming loose in the axial direction when fitting and fixing rotating members together and / or rotating members together by plastic fastening. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 11-320274 [Patent Document 2] Japanese Patent Publication No. 2007-301627 [Patent Document 3] Japanese Patent Publication No. 2008-157273 [Overview of the project] [Problems that the invention aims to solve]

[0010] As mentioned above, in this technical field, there is a need for a technology that can ensure holding force in the rotational direction while reliably preventing the fitting portion from coming loose in the axial direction when fitting and fixing rotating members together and / or between rotating members and shaft members by plastic fastening. In the following description, unless otherwise specified, even when plastically fastening rotating members together, the other rotating member that is press-fitted into a hole formed in one rotating member will also be referred to as a "shaft member". [Means for solving the problem]

[0011] In view of the above problems, the present inventors have diligently researched and found that in a plastic fastening method for fixing a rotating member and a shaft member to each other by press-fitting into a fitting portion in which teeth are formed, the rotating member and the shaft member can be fixed to each other not only in the rotational direction but also in the axial direction by allowing the material constituting either the rotating member or the shaft member to flow into a recess formed in the other.

[0012] Specifically, the plastic fastening method according to the present invention (hereinafter sometimes referred to as "the present invention method") is a plastic fastening method that fixes a rotating member and a shaft member to each other in the rotational direction by press-fitting a hollow or solid shaft member into a hole formed in a rotating member, and allowing a portion of the material constituting the other of the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member to flow into teeth formed on one of the inner circumferential surfaces of the hole in the rotating member or the outer circumferential surface of the shaft member.

[0013] Furthermore, in the method of the present invention, the press-fitting process causes a portion of the material constituting the other of the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member to flow into a recess formed on either the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member, at a position different from the teeth in the axial direction of the shaft member. This integrally forms a locking portion, which is the part that fixes the rotating member and the shaft member to each other in the axial direction of the shaft member.

[0014] Furthermore, the plastic fastening structure according to the present invention (hereinafter sometimes referred to as "the present invention structure") is a plastic fastening structure between a rotating member and a shaft member formed by the present invention method described above. Specifically, the present invention structure is a plastic fastening structure in which a hollow or solid shaft member is press-fitted into a hole formed in the rotating member, and a portion of the material constituting the other of the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member flows into teeth formed on either the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member, thereby fixing the rotating member and the shaft member to each other in the direction of rotation.

[0015] Furthermore, in the structure of the present invention, at a position different from the teeth in the axial direction of the shaft member, a portion of the material constituting the other of the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member fills a recess formed on the one of the above. As a result, a locking portion, which is the part that fixes the rotating member and the shaft member to each other in the axial direction of the shaft member, is integrally formed. [Effects of the Invention]

[0016] In the present invention, as described above, when performing plastic fastening by press-fitting a hollow or solid shaft member into a hole formed in a rotating member, a portion of the material constituting the other of the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member is allowed to flow into a recess formed on one of the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member. This makes it possible to integrally form a locking portion, which is the part that fixes the rotating member and the shaft member to each other in the axial direction of the shaft member.

[0017] Accordingly, according to the present invention, in fitting and fixing a rotating member and a shaft member by plastic fastening, it is possible to reliably prevent the fitting portion from coming off in the axial direction while securing the holding force in the rotational direction.

[0018] Other objects, other features and attendant advantages of the present invention will be readily understood from the description of each embodiment of the present invention described below with reference to the following drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] [Figure 1] It is a schematic cross-sectional view showing an example of a process in which a locking portion is formed as the shaft member is press-fitted into a hole formed in the rotating member in the plastic fastening method (second method) according to the second embodiment of the present invention. [Figure 2] It is a schematic perspective view, cut by a plane including the axis of the shaft member, showing an example of a process in which a locking portion is formed as the shaft member is press-fitted into a hole formed in the rotating member in the second method. [Figure 3] It is a schematic perspective view showing an example of the configuration of the shaft member used in the second method. [Figure 4] It is a schematic perspective view showing an example of the configuration of the rotating member used in the second method. [Figure 5] It is a schematic cross-sectional view showing an example of a process in which a locking portion is formed as the shaft member is press-fitted into a hole formed in the rotating member in the plastic fastening method (fourth method) according to the fourth embodiment of the present invention. [Figure 6] It is a schematic perspective view, cut by a plane including the axis of the shaft member, showing an example of a process in which a locking portion is formed as the shaft member is press-fitted into a hole formed in the rotating member in the fourth method. [Figure 7] It is a schematic perspective view showing an example of the configuration of the rotating member used in the fourth method. [Figure 8] It is a schematic perspective view showing an example of the configuration of the shaft member used in the fourth method. [Figure 9]This is a schematic perspective view of the vicinity of the tip of the shaft member when it has been pressed into the bottomed hole formed in the rotating member in the fourth method, observed from different angles. [Modes for carrying out the invention]

[0020] 《First Embodiment》 The following describes a plastic fastening method according to the first embodiment of the present invention (hereinafter sometimes referred to as the "first method").

[0021] <composition> The first method is a plastic fastening method in which a rotating member and a shaft member are fixed to each other in the rotational direction by press-fitting a hollow or solid shaft member into a hole formed in a rotating member, and allowing a portion of the material constituting the other of the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member to flow into teeth formed on one of the inner circumferential surfaces of the hole in the rotating member or the outer circumferential surface of the shaft member.

[0022] As stated at the beginning of this specification, specific examples of rotating members include gears, pulleys, pipes, etc. Specific examples of shaft members include hollow or solid shafts, etc. As is well known to those skilled in the art, when fixing such rotating members and shaft members together by plastic fastening, a protrusion or recess, such as a spline, is formed as a tooth on either the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member. Then, by press-fitting the shaft member into the hole formed in the rotating member, a portion of the material forming the side of the rotating member or shaft member where the tooth is not formed (the other side) flows into the tooth. Therefore, the hardness of the side of the rotating member or shaft member where the tooth is formed (the other side) must be higher than the hardness of the side of the rotating member or shaft member where the tooth is not formed (the other side). This allows the rotating member and shaft member to be fixed together in the rotational direction.

[0023] Furthermore, in the first method, the press-fitting causes a portion of the material constituting the other side of the rotating member's inner circumferential surface or the rotating member's outer circumferential surface to flow into a recess formed on either side of the rotating member's inner circumferential surface or the rotating member's outer circumferential surface, at a position different from the teeth in the axial direction of the shaft member. That is, during the process of press-fitting the shaft member into the hole formed in the rotating member, a portion of the material constituting the side of the rotating member or shaft member where teeth are not formed (the other side) undergoes plastic flow to fill a recess formed on the side of the rotating member or shaft member where teeth are formed (the one side).

[0024] As described above, a portion of the rotating member or shaft member on the side without teeth (the other side) protrudes and fits into a recess formed on the side of the rotating member or shaft member on the side with teeth (the other side), forming a locking portion. Therefore, once the shaft member has been pressed into the hole formed in the rotating member, it becomes impossible to remove the shaft member from the rotating member. In other words, a locking portion, which fixes the rotating member and the shaft member together in the axial direction of the shaft member, is integrally formed.

[0025] The specific aspects of the first method will be described in detail later in the description of other embodiments of the present invention.

[0026] <effect> In the first method, as described above, when plastic fastening is performed by press-fitting a hollow or solid shaft member into a hole formed in the rotating member, a portion of the material constituting the other of the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member is allowed to flow into a recess formed on one of the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member. This makes it possible to integrally form a locking portion, which is the part that fixes the rotating member and the shaft member to each other in the axial direction of the shaft member.

[0027] Therefore, according to the first method, in fitting and fixing a rotating member and a shaft member by plastic fastening, it is possible to ensure holding force in the rotational direction while reliably preventing the fitting portion from coming loose in the axial direction.

[0028] 《Second Embodiment》 The plastic fastening method according to the second embodiment of the present invention (hereinafter sometimes referred to as the "second method") will be described below with reference to the drawings.

[0029] <composition> The second method is the first method described above, characterized in that the hardness of the shaft member is higher than the hardness of the rotating member. The measures for making the hardness of the shaft member higher than that of the rotating member are not particularly limited. For example, a shaft member made of a material having relatively high hardness as a material may be combined with a rotating member made of a material having relatively low hardness as a material. Alternatively, even if the materials are the same or different materials with no significant difference in hardness as materials, differences in hardness may be created by the presence or degree of hardening treatment such as work hardening and / or quenching. In this case, a shaft member made of the material having relatively high hardness can be combined with a rotating member made of the material having relatively low hardness.

[0030] Furthermore, the shaft member has a small diameter section, a large diameter section, and a constricted section. The small diameter section is formed at the tip of the shaft member and has a first outer diameter which is a predetermined outer diameter. The large diameter section is formed at the base end of the shaft member and has a second outer diameter which is a predetermined outer diameter which is larger than the first outer diameter. The constricted section is formed between the small diameter section and the large diameter section and has a third outer diameter which is a predetermined outer diameter which is less than or equal to the first outer diameter, and is a section in which a first void, which is a gap that widens inward in the radial direction of the shaft member, is formed as the aforementioned recess. In addition, the aforementioned teeth are formed on the outer circumferential surface of the small diameter section of the shaft member.

[0031] The specific shapes and sizes of the small-diameter section, large-diameter section, constricted section, teeth, and first gap of the shaft member are determined appropriately according to the mechanical strength and / or dimensions required for the application of the structure, for example, the combination of the shaft member and the rotating member. Furthermore, the third outer diameter, which is the outer diameter of the constricted section, is a predetermined outer diameter that is less than or equal to the first outer diameter, which is the outer diameter of the small-diameter section, as described above.

[0032] When the third outer diameter is equal to the first outer diameter, the first void is formed as a hole that opens onto the outer circumferential surface of the constricted portion and has a predetermined depth (length in the radial direction). The specific configuration of the first void thus formed is not particularly limited, as long as a portion of the material constituting the inner circumferential surface of the hole in the rotating member plastically flows into the first void to form the aforementioned locking portion, thereby enabling the rotating member and the shaft member to be fixed to each other in the axial direction of the shaft member.

[0033] For example, the first void may be configured as one or more holes opening onto the outer circumferential surface of the constricted portion and having a predetermined depth. However, considering its use as a rotating body, it is preferable to configure the first void such that the mass distribution around the axis is rotationally symmetric with respect to the axis. Furthermore, from the viewpoint of more firmly fixing the rotating member and the shaft member to each other in the axial direction of the shaft member, it is preferable to configure the first void as an annular hole opening onto the outer circumferential surface of the constricted portion, having a predetermined depth, and extending around the entire circumference of the outer circumferential surface of the constricted portion.

[0034] On the other hand, if the third outer diameter is smaller than the first outer diameter, the first gap can be an annular groove with the outer circumferential surface of the constricted portion as the bottom surface and the end face on the base end of the small diameter portion and the end face on the tip end of the large diameter portion as the side surfaces. Furthermore, one or more holes may be provided that open to the outer circumferential surface of the constricted portion, which is the bottom surface of the annular groove, and have a predetermined depth. In this case as well, considering its use as a rotating body, it is preferable to configure the holes so that the mass distribution around the axis is rotationally symmetric with respect to the axis. Moreover, from the viewpoint of more firmly fixing the rotating member and the shaft member to each other in the axial direction of the shaft member, it is preferable to configure the holes as annular holes that open to the outer circumferential surface of the constricted portion, which is the bottom surface of the annular groove, have a predetermined depth, and extend around the entire circumference of the outer circumferential surface of the constricted portion.

[0035] In addition, during the press-fitting process described above, the peripheral edge of the hole in the rotating member is pressed by the end face on the tip side of the large-diameter portion of the shaft member, causing a portion of the material constituting the inner circumferential surface of the hole in the rotating member to plastically flow into the first void, thereby forming the aforementioned locking portion.

[0036] As described above, in order for the peripheral edge of the hole in the rotating member to be pressed by the tip end face of the large-diameter portion of the shaft member during the process of press-fitting the shaft member into the hole formed in the rotating member, the shaft member must be able to move in the press-fitting direction even after the tip end face of the large-diameter portion of the shaft member comes into contact with the peripheral edge of the hole in the rotating member. One way to satisfy this requirement is to make the axial length (depth) of the hole formed in the rotating member greater than the axial length of the portion of the shaft member consisting of the small-diameter portion and the constricted portion.

[0037] As described above, when the peripheral edge of the hole in the rotating member is pressed by the end face on the tip side of the large diameter portion of the shaft member, plastic flow occurs in the material constituting the peripheral edge of the hole in the rotating member, and it flows into the first void, which is the portion formed as a recess. As a result, a locking portion, which is a fitting structure between the convex portion formed by the material filling the first void and the recess in the first void, is integrally formed, and the rotating member and the shaft member are fixed to each other in the axial direction of the shaft member by this locking portion. In other words, the detachment of the fitting portion in the axial direction is prevented.

[0038] Figures 1 and 2 are schematic cross-sectional and perspective views, respectively, illustrating an example of the process by which a locking portion is formed when a shaft member is press-fitted into a hole formed in a rotating member in the second method. Figures 1 and 2(a) illustrate the state before press-fitting of the shaft member 20 into the hole 11 formed in the rotating member 10 begins. Figures 1 and 2(b) illustrate the state when press-fitting of the shaft member 20 into the hole 11 formed in the rotating member 10 has begun, and the end face of the tip side (downward side in the drawing) of the large diameter portion 20L of the shaft member 20 is in contact with the peripheral edge of the hole 11. Figures 1 and 2(c) illustrate the state after press-fitting of the shaft member 20 into the hole 11 formed in the rotating member 10 is completed in the second method.

[0039] As illustrated in Figures 1 and 2, the second method is a plastic fastening method that fixes the rotating member 10 and the shaft member 20 to each other in the rotational direction by press-fitting the shaft member 20 into a hole 11 formed in the rotating member 10 and allowing a portion of the material constituting the inner surface of the hole 11 to flow into the teeth 21 formed on the outer surface of the shaft member 20. Furthermore, by the above press-fitting, a portion of the material constituting the inner surface of the hole 11 flows into a recess 22 formed on the outer surface of the shaft member 20 at a position different from the teeth 21 in the direction parallel to the axis AX of the shaft member 20, thereby integrally forming a locking portion which is a part that fixes the rotating member 10 and the shaft member 20 to each other in the axial direction of the shaft member 20.

[0040] Figure 3 is a schematic perspective view showing an example of the configuration of the shaft member used in the second method. In Figure 3, the shaft member is depicted as being cut by a plane containing the shaft, for the purpose of clearly showing the configuration of the shaft member. As illustrated in Figures 1 and 2(a) and Figure 3, the shaft member 20 has a small diameter portion 20S, a large diameter portion 20L, and a constricted portion 20N.

[0041] The small-diameter portion 20S is formed at the tip of the shaft member 20 and has a predetermined outer diameter DO1. The large-diameter portion 20L is formed on the base end side of the shaft member 20 and has a predetermined outer diameter DO2 that is larger than the first outer diameter DO1 (DO2 > DO1). The constricted portion 20N is formed between the small-diameter portion 20S and the large-diameter portion 20L and has a predetermined outer diameter DO3 that is less than or equal to the first outer diameter D01. The first void 22, which is an annular void that widens inward in the radial direction of the shaft member 20, is formed as the aforementioned recess. Furthermore, the aforementioned teeth 21 are formed on the outer circumferential surface of the small-diameter portion 20S of the shaft member 20.

[0042] Figures 1 and 2(b) are schematic diagrams illustrating the state in which the press-fitting of the shaft member 20 into the hole 11 formed in the rotating member 10 has begun, and the end face of the tip side (downward side in the drawing) of the large-diameter portion 20L of the shaft member 20 is in contact with the peripheral edge of the hole 11. As described above, in the second method, the hardness of the shaft member 20 is higher than that of the rotating member 10. Therefore, as the shaft member 20 is press-fitted into the hole 11, a portion of the material constituting the inner circumferential surface of the hole 11 flows into the teeth 21 formed on the outer circumferential surface of the small-diameter portion 20S of the shaft member 20, thereby fixing the rotating member 10 and the shaft member 20 to each other in the rotational direction.

[0043] Furthermore, as illustrated in Figures 1 and 2(b), at this point, the tip of the small-diameter portion 20S of the shaft member 20 and the bottom surface of the hole 11 are not in contact, and there is a gap between them. That is, the length (depth) of the hole 11 in the direction parallel to the axis AX is greater than the length of the portion of the shaft member 20 consisting of the small-diameter portion 20S and the constricted portion 20N in the direction parallel to the axis AX. Therefore, even after the point illustrated in Figure 1(b), it is possible to move the shaft member 20 in the press-fitting direction using a drive device (not shown) to complete the press-fitting of the shaft member 20 into the hole 11 formed in the rotating member 10.

[0044] Figures 1 and 2(c) are schematic diagrams illustrating the state in which the press-fitting of the shaft member 20 into the hole 11 formed in the rotating member 10 has been completed in the second method, as described above. This state is the result of continuing to move the shaft member 20 in the press-fitting direction even after the tip end face of the large-diameter portion 20L of the shaft member 20 has come into contact with the peripheral edge of the hole 11 formed in the rotating member 10, so that the tip of the small-diameter portion 20S of the shaft member 20 comes into contact with the bottom surface of the hole 11.

[0045] Figure 4 is a schematic perspective view showing an example of the configuration of the rotating member used in the second method, where (a) illustrates the shape of the rotating member before the press-fitting of the shaft member begins, and (b) illustrates the shape of the rotating member after the press-fitting of the shaft member is completed. During the period from the point illustrated in Figures 1 and 2(b) to the point illustrated in Figures 1 and 2(c), the peripheral edge of the hole 11 is pressed by the end face on the tip side of the large diameter portion 20L of the shaft member 20. As a result, as illustrated in Figures 1 and 2(c), a portion of the material constituting the inner circumferential surface of the hole 11 of the rotating member 10 plastically flows into the first void 22, and the first void 22 is filled with this material (see the thick solid arrow drawn in Figure 1(c)).

[0046] As a result of the above, a locking portion is integrally formed as a fitting structure between the annular protrusion 12 (see Figure 4(b)) formed by the material filling the first void 22 and the annular recess of the first void 22 (see the portion enclosed by the thick dashed line in Figures 1 and 2(c)), and the rotating member 10 and the shaft member 20 are fixed to each other in a direction parallel to the axis AX of the shaft member. In other words, the fitting portion is prevented from coming loose in the axial direction.

[0047] In the examples shown in Figures 1 to 3, the outer diameter of the small-diameter portion 20S of the shaft member 20 and the outer diameter of the teeth 21 formed on the outer circumferential surface of the small-diameter portion 20S increase as they approach the tip. However, the shape of the small-diameter portion 20S and the teeth 21 of the shaft member 20 is not limited to the above, as long as the processing load during press-fitting of the shaft member 20 into the hole 11 formed in the rotating member 10 is not excessive. For example, the outer diameter of the small-diameter portion 20S and the teeth 21 of the shaft member 20 may be constant along the entire length in the axial direction, or it may decrease as it approaches the tip.

[0048] <effect> In the second method, as described above, when the shaft member is press-fitted into a hole formed in the rotating member to perform plastic fastening, a portion of the material constituting the inner circumferential surface of the hole in the rotating member is allowed to flow into the first void, which is a recess formed in the constricted portion of the shaft member. This makes it possible to integrally form a locking portion, which is the part that fixes the rotating member and the shaft member to each other in the axial direction of the shaft member. Therefore, according to the second method, it is possible to ensure holding force in the rotational direction while reliably preventing the fitting portion from coming loose in the axial direction during fitting and fixing by plastic fastening between the rotating member and the shaft member.

[0049] 《Third Embodiment》 The plastic fastening method according to the third embodiment of the present invention (hereinafter sometimes referred to as the "third method") will be described below with reference to the drawings.

[0050] In the examples shown in Figures 1 to 3, the region opposite the peripheral edge of the hole 11 formed in the rotating member 10 on the tip side (downward side in the drawing) of the large-diameter portion 20L of the shaft member 20 is recessed so that it becomes deeper as it approaches the axis AX of the shaft member 20. In other words, this region has a concave shape toward the small-diameter portion 20S of the shaft member 20. To put it another way, the normal vector of this region has a component that approaches the straight line containing the axis AX of the shaft member 20.

[0051] Therefore, when the peripheral edge of the hole 11 is pressed by the end face on the tip side of the large diameter portion 20L of the shaft member 20, the material constituting the peripheral edge of the hole 11 is pressed more strongly toward the axis AX of the shaft member 20 compared to the case where the entire end face on the tip side of the large diameter portion 20L of the shaft member 20 is a plane perpendicular to the axis AX of the shaft member 20. As a result, the material constituting the inner circumferential surface of the hole 11 is more actively drawn into the recess 22 formed in the constricted portion 20N of the shaft member 20, thereby more reliably forming the locking portion that fixes the rotating member 10 and the shaft member 20 to each other in a direction parallel to the axis AX of the shaft member 20.

[0052] <composition> Therefore, the third method is the second method described above, characterized in that the normal vector of at least a portion of the end face on the tip side of the large-diameter portion of the shaft member has a component that approaches a straight line including the axis of the shaft member.

[0053] Furthermore, the specific shape of the "part in which the normal vector has a component that approaches the straight line containing the axis of the shaft member" is not particularly limited, as long as it is possible to press the material constituting the periphery of the hole formed in the rotating member more strongly toward the axis of the shaft member compared to the case where the entire end face on the tip side of the large diameter part of the shaft member is a plane perpendicular to the axis of the shaft member. For example, in a cross-section of a plane containing the axis of the shaft member, the part may be a curve (for example, part of a circular arc or parabola) that faces each other across the straight line containing the axis of the shaft member, or it may be a straight line that faces each other across the straight line containing the axis of the shaft member. In the latter case, the part has a shape like the side surface of a frustum of a cone with the straight line containing the axis of the shaft member as its central axis, as illustrated in Figures 1 to 3.

[0054] <effect> As described above, in the third method, the normal vector of at least a portion of the end face on the tip side of the large-diameter portion of the shaft member has a component that approaches a straight line including the axis of the shaft member. Therefore, in the third method, the material constituting the peripheral edge of the hole formed in the rotating member can be pressed more strongly toward the axis of the shaft member compared to the case where the entire end face on the tip side of the large-diameter portion of the shaft member is a plane perpendicular to the axis of the shaft member. As a result, according to the third method, a portion of the material constituting the inner circumferential surface of the hole formed in the rotating member can be more actively allowed to flow into the first void, which is a recess formed in the constricted portion of the shaft member, thereby more reliably forming a locking portion that fixes the rotating member and the shaft member to each other in the axial direction of the shaft member.

[0055] 《Fourth Embodiment》 The following describes a plastic fastening method according to the fourth embodiment of the present invention (hereinafter sometimes referred to as the "fourth method") with reference to the drawings.

[0056] In the plastic fastening method according to the second and third embodiments of the present invention described above, the hardness of the shaft member is higher than that of the rotating member, teeth and recesses are formed in the shaft member, and the material constituting the rotating member flows into these teeth and recesses, thereby fixing the shaft member and the rotating member to each other. However, the effects of the present invention can be achieved even if the hardness levels and the arrangement of the teeth and recesses are reversed from the above.

[0057] <composition> In other words, the fourth method is the first method described above, characterized in that the hardness of the rotating member is higher than the hardness of the shaft member. The measures for making the hardness of the rotating member higher than the hardness of the shaft member are also not particularly limited. For example, a rotating member made of a material having relatively high hardness as a material may be combined with a shaft member made of a material having relatively low hardness as a material. Alternatively, even if the materials are the same or different materials with no significant difference in hardness as materials, differences in hardness may be created by the presence or degree of hardening treatment such as work hardening and / or quenching. In this case, a rotating member made of the material having relatively high hardness can be combined with a shaft member made of the material having relatively low hardness.

[0058] The hole in the rotating member is not a through hole but is formed as a closed hole with a bottom surface. Furthermore, the aforementioned teeth are formed on the inner circumferential surface of the closed hole in the rotating member. In addition, a second void, which is a gap that extends outward in the radial direction of the shaft member, is formed as the aforementioned recess on the inner circumferential surface adjacent to the bottom surface of the closed hole in the rotating member.

[0059] The specific shape and size of the bottomed hole, teeth, and second void of the rotating member are determined appropriately according to the mechanical strength and / or dimensions required for the application of the structure, for example, the combination of the shaft member and the rotating member. Furthermore, the specific configuration of the second void is not particularly limited, as long as the material constituting the tip of the shaft member undergoes plastic flow into the second void to form the aforementioned locking portion, thereby enabling the rotating member and the shaft member to be fixed to each other in the axial direction of the shaft member.

[0060] For example, the second void may be configured as one or more holes that open to the inner circumferential surface adjacent to the bottom surface of the closed hole of the rotating member and have a predetermined depth. However, considering its use as a rotating body, it is preferable to configure the second void such that the mass distribution around the axis is rotationally symmetric with respect to the axis. Furthermore, from the viewpoint of more firmly fixing the rotating member and the shaft member to each other in the axial direction of the shaft member, it is preferable to configure the second void as an annular hole that opens to the inner circumferential surface adjacent to the bottom surface of the closed hole of the rotating member, has a predetermined depth, and extends around the entire circumference of the inner circumferential surface adjacent to the bottom surface of the closed hole of the rotating member.

[0061] On the other hand, if the third outer diameter is smaller than the first outer diameter, the first gap can be an annular groove with the outer circumferential surface of the constricted portion as the bottom surface and the end face on the base end of the small diameter portion and the end face on the tip end of the large diameter portion as the side surfaces. Furthermore, one or more holes may be provided that open to the outer circumferential surface of the constricted portion, which is the bottom surface of the annular groove, and have a predetermined depth. In this case as well, considering its use as a rotating body, it is preferable to configure the holes so that the mass distribution around the axis is rotationally symmetric with respect to the axis. Moreover, from the viewpoint of more firmly fixing the rotating member and the shaft member to each other in the axial direction of the shaft member, it is preferable to configure the holes as annular holes that open to the outer circumferential surface of the constricted portion, which is the bottom surface of the annular groove, have a predetermined depth, and extend around the entire circumference of the outer circumferential surface of the constricted portion.

[0062] In addition, during the press-fitting process described above, the tip of the shaft member comes into contact with the bottom surface of the blind hole and is pressed against the bottom surface of the blind hole, causing the material constituting the tip of the shaft member to plastically flow into the second void and form a locking portion.

[0063] As described above, in order for the tip of the shaft member to be pressed against the bottom surface of the blind hole during the press-fitting process and for plastic flow to occur in the material constituting the tip of the shaft member, it is necessary that the shaft member can move in the press-fitting direction even after the tip of the shaft member comes into contact with the bottom surface of the blind hole. As a measure to satisfy this requirement, for example, the axial length of the tip of the shaft member, which has a size and shape that allows it to be press-fitted into a hole formed in the rotating member, can be made larger than the axial length (depth) of the hole formed in the rotating member.

[0064] As described above, when the tip of the shaft member comes into contact with the bottom surface of the blind hole and is pressed against the bottom surface of the blind hole, plastic flow occurs in the material constituting the tip of the shaft member, and it flows into the second void, which is the recessed portion. As a result, a locking portion is integrally formed as a fitting structure between the convex portion formed by the material filling the second void and the recessed portion of the second void, and the rotating member and the shaft member are fixed to each other in the axial direction of the shaft member by this locking portion. In other words, the detachment of the fitting portion in the axial direction is prevented.

[0065] Figures 5 and 6 are schematic cross-sectional and perspective views, respectively, illustrating an example of the process by which a locking portion is formed when a shaft member is press-fitted into a hole formed in the rotating member in the fourth method. Figures 5 and 6(a) illustrate the state before the press-fitting of the shaft member 20 into the hole 11 (hereinafter sometimes referred to as "bottomed hole 11"), which is a bottomed hole formed in the rotating member 10, begins. Figures 5 and 6(b) illustrate the state when the press-fitting of the shaft member 20 into the bottomed hole 11 formed in the rotating member 10 has begun, and the tip of the shaft member 20 (the lower end in the drawing) is in contact with the bottom surface of the bottomed hole 11. Figures 5 and 6(c) illustrate the state after the press-fitting of the shaft member 20 into the bottomed hole 11 formed in the rotating member 10 in the fourth method is completed.

[0066] As illustrated in Figures 5 and 6, the fourth method is a plastic fastening method that fixes the rotating member 10 and the shaft member 20 to each other in the rotational direction by press-fitting the shaft member 20 into a bottomed hole 11 formed in the rotating member 10 and allowing a portion of the material constituting the outer surface of the shaft member 20 to flow into the teeth 13 formed on the inner surface of the bottomed hole 11. Furthermore, by press-fitting, the material constituting the tip of the shaft member 20 is allowed to flow into a recess 14 formed on the inner surface adjacent to the bottom of the bottomed hole 11 of the rotating member 10, thereby integrally forming a locking portion which is the part that fixes the rotating member 10 and the shaft member 20 to each other in the axial direction of the shaft member 20.

[0067] Figure 7 is a schematic perspective view showing an example of the configuration of the rotating member used in the fourth method. In Figure 7, the rotating member is depicted as being cut by a plane including the axis, for the purpose of clearly illustrating the configuration of the rotating member. As illustrated in Figures 5 and 6(a) and Figure 7, the hole 11 formed in the rotating member 10 is not a through hole but a closed hole with a bottom surface. In addition, the teeth 13 described above are formed on the inner circumferential surface of the closed hole 11 of the rotating member 10. Furthermore, a second void 14, which is an annular void that extends outward in the radial direction of the shaft member 20, is formed as the recess described above on the inner circumferential surface adjacent to the bottom surface of the closed hole 11 of the rotating member 10.

[0068] Figures 5 and 6(b) are schematic diagrams illustrating the state in which the press-fitting of the shaft member 20 into the blind hole 11 formed in the rotating member 10 has begun, and the tip of the shaft member 20 is in contact with the bottom surface of the blind hole 11, as described above. As described above, in the fourth method, the hardness of the shaft member 20 is higher than that of the rotating member 10. Therefore, as the shaft member 20 is press-fitted into the blind hole 11, a portion of the material constituting the outer surface of the shaft member 20 flows into the teeth 13 formed on the inner surface of the blind hole 11 of the rotating member 10, thereby fixing the rotating member 10 and the shaft member 20 to each other in the rotational direction.

[0069] However, as illustrated in Figures 5 and 6(b), at this point, although the tip of the shaft member 20 is in contact with the bottom surface of the blind hole 11, the material constituting the tip of the shaft member 20 has not yet begun to flow into the recess 14 formed on the inner circumferential surface adjacent to the bottom surface of the blind hole 11 of the rotating member 10. On the other hand, as will be described later with reference to Figure 8(a), since the shaft member 20 is a member having a simple cylindrical shape, it is possible to move the shaft member 20 in the press-fit direction by a drive device (not shown) even after the tip of the shaft member 20 has come into contact with the bottom surface of the blind hole 11, thereby completing the press-fitting of the shaft member 20 into the blind hole 11 formed in the rotating member 10.

[0070] Figures 5 and 6(c) are schematic diagrams illustrating the state in which the press-fitting of the shaft member 20 into the bottomed hole 11 formed in the rotating member 10 has been completed, as described above. This state is the result of continuing to move the shaft member 20 in the press-fitting direction even after the tip of the shaft member 20 has come into contact with the bottom surface of the bottomed hole 11, thereby completing the press-fitting of the shaft member 20 into the bottomed hole 11 formed in the rotating member 10.

[0071] Figures 8 and 9 are schematic perspective views showing examples of the configuration of the shaft member used in the fourth method. In Figure 8, the shaft member is depicted as being cut by a plane containing the shaft, for the purpose of clearly illustrating the configuration of the shaft member. Figure 8(a) illustrates the shape of the shaft member before press-fitting into the blind hole formed in the rotating member begins, and Figure 8(b) illustrates the shape of the shaft member after press-fitting into the blind hole formed in the rotating member is completed. Figures 9(a) and 9(b) are perspective views of the vicinity of the tip of the shaft member observed from different angles after press-fitting into the blind hole formed in the rotating member is completed.

[0072] During the period from the point illustrated in Figures 5 and 6(b) to the point illustrated in Figures 5 and 6(c), the tip of the shaft member 20 is pressed against the bottom surface of the bottomed hole 11. As a result, as illustrated in Figures 5 and 6(c), the material constituting the tip of the shaft member 20 plastically flows into the second void 14, and the second void 14 is filled with this material (see the thick solid arrow drawn in Figure 5(c)). Consequently, as illustrated in Figures 6(c), 8(b), and 9(a) and 9(b), an annular protrusion 23 is formed by the material filling the second void 14. In this way, a locking portion is integrally formed as a fitting structure between the convex portion 23 and the concave portion, which is the second gap 14 (see the portion enclosed by the thick dashed line in Figures 5 and 6(c)), and the rotating member 10 and the shaft member 20 are fixed to each other in a direction parallel to the axis AX of the shaft member. That is, the fitting portion is prevented from coming loose in the axial direction.

[0073] <effect> In the fourth method, as described above, when the shaft member is press-fitted into a hole formed in the rotating member to perform plastic fastening, the material constituting the tip of the shaft member is allowed to flow into the second void, which is a recess formed on the inner circumferential surface adjacent to the bottom surface of the bottomed hole in the rotating member. This makes it possible to integrally form a locking portion, which is the part that fixes the rotating member and the shaft member to each other in the axial direction of the shaft member. Therefore, according to the fourth method, it is possible to ensure holding force in the rotational direction while reliably preventing the fitting portion from coming loose in the axial direction during fitting and fixing by plastic fastening between the rotating member and the shaft member.

[0074] 《Fifth Embodiment》 The plastic fastening method according to the fifth embodiment of the present invention (hereinafter sometimes referred to as "the fifth method") will be described below with reference to the drawings.

[0075] In the examples shown in Figures 5 to 7, the bottom surface of the blind hole 11 formed in the rotating member 10 bulges outwards towards the upstream side (upwards in the drawing) in the press-fit direction as it approaches the axis AX of the shaft member 20. In other words, the bottom surface of the blind hole 11 formed in the rotating member 10 has a convex shape toward the opening of the blind hole 11. To put it another way, the normal vector of the bottom surface of the blind hole 11 has a component that moves away from the line containing the axis AX of the shaft member 20.

[0076] Therefore, when the tip of the shaft member 20 abuts against the bottom surface of the bottomed hole 11 and is pressed against the bottom surface of the bottomed hole 11, the material constituting the tip of the shaft member 20 is pressed more strongly outward in the radial direction of the shaft member 20 compared to when the entire bottom surface of the bottomed hole 11 is a plane perpendicular to the axis AX of the shaft member 20. As a result, the material constituting the tip of the shaft member 20 is more actively allowed to flow into the second void 14, which is a recess formed on the inner circumferential surface adjacent to the bottom surface of the bottomed hole 11, thereby more reliably forming a locking portion that fixes the rotating member 10 and the shaft member 20 to each other in a direction parallel to the axis AX of the shaft member 20.

[0077] <composition> Therefore, the fifth method is the fourth method described above, characterized in that the normal vector of at least a portion of the bottom surface of the bottom hole of the rotating member has a component that moves away from the straight line containing the axis of the shaft member.

[0078] Furthermore, the specific shape of the "part of the normal vector having a component that moves away from the line containing the axis of the shaft member" is not particularly limited, as long as it is possible to press the material constituting the tip of the shaft member more strongly in a direction away from the line containing the axis of the shaft member compared to the case where the entire bottom surface of the bottom hole is a plane perpendicular to the axis of the shaft member. For example, in a cross-section of the plane containing the axis of the shaft member, the bottom surface of the bottom hole may be a curve (for example, part of a circular arc or parabola) that has a convex shape toward the opening of the bottom hole. Alternatively, in a cross-section of the plane containing the axis of the shaft member, the bottom surface of the bottom hole may be composed of a pair of straight lines that face each other across a line containing the axis of the shaft member and are inclined so that they approach the opening of the bottom hole as they approach the line containing the axis. In the latter case, the bottom surface of the bottom hole is a part that has a shape like the side surface of a cone with the line containing the axis of the shaft member as its central axis, as illustrated in Figures 5 to 7.

[0079] <effect> As described above, in the fifth method, the normal vector of at least a portion of the bottom surface of the bottomed hole of the rotating member has a component that moves away from the line containing the axis of the shaft member. Therefore, in the fifth method, the material constituting the tip of the shaft member can be pressed more strongly in a direction away from the line containing the axis of the shaft member compared to the case where the entire bottom surface of the bottomed hole is a plane perpendicular to the axis of the shaft member. As a result, according to the fifth method, the material constituting the tip of the shaft member can be more actively drawn into the second void, which is a recess formed on the inner circumferential surface adjacent to the bottom surface of the bottomed hole, thereby more reliably forming the locking portion, which is the part that fixes the rotating member and the shaft member to each other in the axial direction of the shaft member.

[0080] 《Sixth Embodiment》 As stated at the beginning of this specification, the present invention relates not only to plastic fastening methods but also to plastic fastening structures. Hereinafter, a plastic fastening structure according to the sixth embodiment of the present invention (hereinafter sometimes referred to as the "sixth structure") will be described.

[0081] <composition> The sixth structure is a plastic fastening structure in which a hollow or solid shaft member is press-fitted into a hole formed in a rotating member, and a portion of the material constituting the other of the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member flows into teeth formed on either the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member, thereby fixing the rotating member and the shaft member to each other in the direction of rotation.

[0082] Furthermore, in the sixth structure, at a position different from the teeth in the axial direction of the shaft member, a recess formed on either the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member is filled with a portion of the material constituting the other of the other of the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member. As a result, a locking portion, which is the part that fixes the rotating member and the shaft member to each other in the axial direction of the shaft member, is integrally formed.

[0083] The sixth structure having the above configuration can be formed, for example, by the plastic fastening method (first method) according to the first embodiment of the present invention described above. Since each component constituting the sixth structure has already been described in the description of the first method, its description here is omitted. Furthermore, specific aspects of the sixth structure will be described in detail in the description of other embodiments of the present invention.

[0084] <effect> In the sixth structure, as described above, a hollow or solid shaft member is press-fitted into a hole formed in the rotating member, and a recess formed on one of the inner or outer circumferential surfaces of the rotating member or the shaft member is filled with a portion of the material that constitutes the other of the inner or outer circumferential surfaces of the shaft member. As a result, a locking portion is integrally formed, which is the part that fixes the rotating member and the shaft member to each other in the axial direction of the shaft member.

[0085] Therefore, according to the sixth structure, a plastic fastening structure between a rotating member and a shaft member can be achieved, which ensures holding force in the rotational direction while reliably preventing the fitting portion from coming loose in the axial direction by press-fitting a hollow or solid shaft member into a hole formed in the rotating member.

[0086] 《Seventh Embodiment》 The following describes a plastic fastening structure according to the seventh embodiment of the present invention (hereinafter sometimes referred to as the "seventh structure") with reference to the drawings.

[0087] <composition> The seventh structure is a plastic fastening structure, which is the sixth structure described above, characterized in that the hardness of the shaft member is higher than the hardness of the rotating member. The shaft member also has a small diameter portion, a large diameter portion, and a constricted portion. The small diameter portion is formed at the tip and has a first outer diameter which is a predetermined outer diameter. The large diameter portion is formed on the base end side and has a second outer diameter which is a predetermined outer diameter which is larger than the first outer diameter. The constricted portion is formed between the small diameter portion and the large diameter portion and has a third outer diameter which is a predetermined outer diameter which is less than or equal to the first outer diameter, and is a portion in which a first void, which is a gap that widens inward in the radial direction of the shaft member, is formed as the aforementioned recess. Furthermore, teeth are formed on the outer circumferential surface of the small diameter portion of the shaft member. In addition, the locking portion described above is formed by filling the first void with a part of the material that constitutes the inner circumferential surface of the hole in the rotating member.

[0088] The seventh structure having the above configuration can be formed, for example, by the plastic fastening method (second method) according to the second embodiment of the present invention described above. The specific configuration of the seventh structure was described in detail with reference to Figures 1 to 4 in the description of the second method, so the description is omitted here.

[0089] <effect> In the seventh structure, as described above, the first void is filled with a portion of the material constituting the inner circumferential surface of the hole in the rotating member, thereby integrally forming a locking portion that fixes the rotating member and the shaft member to each other in the axial direction of the shaft member. Therefore, according to the seventh structure, a plastic fastening structure between a rotating member and a shaft member can be achieved that ensures holding force in the rotational direction while reliably preventing the fitting portion from coming loose in the axial direction by press-fitting a hollow or solid shaft member into the hole formed in the rotating member.

[0090] 《Eighth Embodiment》 The following describes the plastic fastening method according to the eighth embodiment of the present invention (hereinafter sometimes referred to as the "eighth structure") with reference to the drawings.

[0091] As described in the explanation of the third method above, in the example shown in Figures 1 to 3, the normal vector of the region facing the peripheral edge of the hole 11 formed in the rotating member 10 on the tip side (downward side in the drawing) end face of the large diameter portion 20L of the shaft member 20 has a component that approaches a straight line including the axis AX of the shaft member 20. Therefore, when the peripheral edge of the hole 11 is pressed by the tip side end face of the large diameter portion 20L of the shaft member 20 during the process of press-fitting the shaft member into the hole formed in the rotating member, the material constituting the peripheral edge of the hole 11 is pressed more strongly toward the axis AX of the shaft member 20 compared to the case where the entire tip side end face of the large diameter portion 20L of the shaft member 20 is a plane perpendicular to the axis AX of the shaft member 20. As a result, the material constituting the inner circumferential surface of the hole 11 is more actively allowed to flow into the recess 22 formed in the constricted portion 20N of the shaft member 20, and the locking portion, which is the part that fixes the rotating member 10 and the shaft member 20 to each other in a direction parallel to the axis AX of the shaft member 20, can be formed more reliably.

[0092] <composition> Therefore, the eighth structure is a plastic fastening structure that is the seventh structure described above, characterized in that the normal vector of at least a portion of the end face on the tip side of the large-diameter portion of the shaft member has a component that approaches a straight line including the axis of the shaft member.

[0093] The eighth structure having the above configuration can be formed, for example, by the plastic fastening method according to the third embodiment of the present invention (third method) described above. The specific shape of the "part having a component in which the normal vector approaches a straight line including the axis of the shaft member" has already been described in the explanation of the third method, so the explanation is omitted here.

[0094] <effect> As described above, in the eighth structure, the normal vector of at least a portion of the end face on the tip side of the large-diameter portion of the shaft member has a component that approaches a straight line including the axis of the shaft member. Therefore, in the eighth structure, during the process of press-fitting the shaft member into the hole formed in the rotating member, the material constituting the peripheral edge of the hole formed in the rotating member can be pressed more strongly toward the axis of the shaft member compared to the case where the entire end face on the tip side of the large-diameter portion of the shaft member is a plane perpendicular to the axis of the shaft member. As a result, the eighth structure allows a portion of the material constituting the inner circumferential surface of the hole formed in the rotating member to flow more actively into the first void, which is a recess formed in the constricted portion of the shaft member, thereby more reliably forming a locking portion that fixes the rotating member and the shaft member to each other in the axial direction of the shaft member. In other words, the eighth structure makes it possible to more reliably achieve a plastic fastening structure between a rotating member and a shaft member that can reliably prevent the fitting portion from coming loose in the axial direction while ensuring holding force in the rotational direction by press-fitting a hollow or solid shaft member into the hole formed in the rotating member.

[0095] 《Ninth Embodiment》 The following describes a plastic fastening method according to the ninth embodiment of the present invention (hereinafter sometimes referred to as the "ninth structure") with reference to the drawings.

[0096] In the plastic fastening structures according to the seventh and eighth embodiments of the present invention described above, the hardness of the shaft member is higher than that of the rotating member, teeth and recesses are formed in the shaft member, and the material constituting the rotating member flows into these teeth and recesses, thereby fixing the shaft member and the rotating member to each other. However, the effects of the present invention can be achieved even if the hardness levels and the arrangement of the teeth and recesses are reversed from the above.

[0097] <composition> In other words, the ninth structure is the sixth structure described above, characterized in that the hardness of the rotating member is higher than the hardness of the shaft member, and is a plastic fastening structure. Furthermore, the hole in the rotating member is formed as a closed hole that is not through but has a bottom surface, and teeth are formed on the inner circumferential surface of the closed hole in the rotating member. In addition, a second void, which is a gap that extends outward in the radial direction of the shaft member, is formed as the recess described above on the inner circumferential surface adjacent to the bottom surface of the closed hole in the rotating member. Moreover, the locking portion described above is formed by filling the second void with the material that constitutes the tip of the shaft member.

[0098] The ninth structure having the above configuration can be formed, for example, by the plastic fastening method (fourth method) according to the fourth embodiment of the present invention described above. The specific configuration of the ninth structure was described in detail with reference to Figures 5 to 9 in the description of the fourth method, so the explanation is omitted here.

[0099] <effect> In the ninth structure, as described above, the second void, which is a recess formed on the inner circumferential surface adjacent to the bottom surface of the bottomed hole of the rotating member, is filled with the material constituting the tip of the shaft member, thereby integrally forming a locking portion that fixes the rotating member and the shaft member to each other in the axial direction of the shaft member. Therefore, according to the ninth structure, a plastic fastening structure between a rotating member and a shaft member can be achieved that ensures holding force in the rotational direction while reliably preventing the fitting portion from coming loose in the axial direction by press-fitting a hollow or solid shaft member into the hole formed in the rotating member.

[0100] 《Tenth Embodiment》 The following describes a plastic fastening structure according to the 10th embodiment of the present invention (hereinafter sometimes referred to as the "10th structure") with reference to the drawings.

[0101] As described in the explanation of the fifth method above, in the examples shown in Figures 5 to 7, the normal vector of the bottom surface of the blind hole 11 formed in the rotating member 10 has a component that moves away from the straight line containing the axis AX of the shaft member 20. Therefore, when the tip of the shaft member 20 abuts against the bottom surface of the blind hole 11 and is pressed against the bottom surface of the blind hole 11, the material constituting the tip of the shaft member 20 is pressed more strongly outward in the radial direction of the shaft member 20 compared to the case where the entire bottom surface of the blind hole 11 is a plane perpendicular to the axis AX of the shaft member 20. As a result, the material constituting the tip of the shaft member 20 is more actively allowed to flow into the second void 14, which is a recess formed on the inner circumferential surface adjacent to the bottom surface of the blind hole 11, thereby more reliably forming a locking portion that fixes the rotating member 10 and the shaft member 20 to each other in a direction parallel to the axis AX of the shaft member 20.

[0102] <composition> Therefore, the tenth structure is the ninth structure described above, wherein the normal vector of at least a portion of the bottom surface of the bottomed hole of the rotating member has a component that moves away from the straight line containing the axis of the shaft member. A plastic fastening structure characterized by the following features.

[0103] The tenth structure having the above configuration can be formed, for example, by the plastic fastening method (fourth method) according to the fifth embodiment of the present invention described above. The specific shape of the "part having a component in which the normal vector moves away from the straight line containing the axis of the shaft member" has already been described in the description of the fifth method, so the description is omitted here.

[0104] <effect> As described above, in the tenth structure, the normal vector of at least a portion of the bottom surface of the blind hole in the rotating member has a component that moves away from the line containing the axis of the shaft member. Therefore, in the tenth structure, during the process of press-fitting the shaft member into the hole formed in the rotating member, the material constituting the tip of the shaft member can be pressed more strongly in a direction away from the line containing the axis of the shaft member compared to the case where the entire bottom surface of the blind hole is a plane perpendicular to the axis of the shaft member. As a result, the tenth structure allows the material constituting the tip of the shaft member to flow more actively into the second void, which is a recess formed on the inner circumferential surface adjacent to the bottom surface of the blind hole, thereby more reliably forming the locking portion, which is the part that fixes the rotating member and the shaft member to each other in the axial direction of the shaft member. In other words, the tenth structure makes it possible to more reliably achieve a plastic fastening structure between a rotating member and a shaft member that can reliably prevent the fitting portion from coming loose in the axial direction while ensuring holding force in the rotational direction by press-fitting a hollow or solid shaft member into the hole formed in the rotating member.

[0105] In order to explain the present invention, several embodiments having specific configurations have been described, sometimes with reference to the accompanying drawings. However, the scope of the present invention should not be construed as being limited to these exemplary embodiments, and it goes without saying that modifications can be made as appropriate within the scope of the claims and the specification. [Explanation of Symbols]

[0106] 10…Rotating member 11… Holes (including bottomed pores) 12…Convex part 13… Teeth 14…Recess (second void) 20...Shaft member 20S…Small diameter part DO1…1st outer diameter 20L…Large diameter section DO2…2nd outer diameter 20N...constricted area DO3…3rd outer diameter 21… Teeth 22... Recess (first void) 23…Convex part AX… axis

Claims

1. A plastic fastening method for fixing a rotating member and a shaft member to each other in the rotational direction by press-fitting a hollow or solid shaft member into a hole formed in a rotating member, and allowing a portion of the material constituting the other of the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member to flow into teeth formed on one of the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member, By press-fitting, a portion of the material constituting the inner circumferential surface of the hole in the rotating member or the other of the outer circumferential surface of the shaft member flows into a recess formed on one of the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member at a position different from the teeth in the axial direction of the shaft member, thereby integrally forming a locking portion which is a part that fixes the rotating member and the shaft member to each other in the axial direction of the shaft member. The hardness of the shaft member is higher than that of the rotating member. The shaft member has a small diameter portion formed at the tip and having a first outer diameter which is a predetermined outer diameter; a large diameter portion formed at the base end and having a second outer diameter which is a predetermined outer diameter which is larger than the first outer diameter; and a constricted portion formed between the small diameter portion and the large diameter portion and having a third outer diameter which is a predetermined outer diameter which is less than or equal to the first outer diameter, and a first void which is a gap that widens inward in the radial direction of the shaft member is formed as the recess. The teeth are formed on the outer circumferential surface of the small diameter portion of the shaft member, During the press-fitting process, the peripheral edge of the hole in the rotating member is pressed by the end face on the tip side of the large diameter portion of the shaft member, causing a portion of the material constituting the inner circumferential surface of the hole in the rotating member to plastically flow into the first void, thereby forming the locking portion. The normal vector of at least a portion of the end face on the tip side of the large diameter portion of the shaft member has a component that approaches a straight line including the axis of the shaft member. A plastic fastening method characterized by the following:

2. A plastic fastening method for fixing a rotating member and a shaft member to each other in the rotational direction by press-fitting a hollow or solid shaft member into a hole formed in a rotating member, and allowing a portion of the material constituting the other of the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member to flow into teeth formed on one of the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member, By press-fitting, a portion of the material constituting the inner circumferential surface of the hole in the rotating member or the other of the outer circumferential surface of the shaft member flows into a recess formed on one of the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member at a position different from the teeth in the axial direction of the shaft member, thereby integrally forming a locking portion which is a part that fixes the rotating member and the shaft member to each other in the axial direction of the shaft member. The hardness of the rotating member is higher than that of the shaft member. The hole in the rotating member is formed as a closed hole that does not go all the way through but has a bottom surface. The teeth are formed on the inner circumferential surface of the bottomed hole of the rotating member. A second void, which is a void that extends outward in the radial direction of the shaft member, is formed as the recess on the inner circumferential surface adjacent to the bottom surface of the bottomed hole of the rotating member. During the press-fitting process, the tip of the shaft member comes into contact with the bottom surface of the bottomed hole and is pressed against the bottom surface of the bottomed hole, causing the material constituting the tip of the shaft member to plastically flow into the second void and form the locking portion. In a cross-section of the shaft member with respect to the axis, the bottom surface of the bottomed hole of the rotating member is a curved shape that is convex toward the opening of the bottomed hole. A plastic fastening method characterized by the following:

3. A plastic fastening structure in which a hollow or solid shaft member is press-fitted into a hole formed in a rotating member, and a portion of the material constituting the other of the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member flows into teeth formed on one of the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member, thereby fixing the rotating member and the shaft member to each other in the direction of rotation, A locking portion is integrally formed in the shaft member at a position different from the teeth in the axial direction of the shaft member, by filling a recess formed on either the inner surface of the hole in the rotating member or the outer surface of the shaft member with a portion of the material constituting the other of the inner surface of the hole in the rotating member or the outer surface of the shaft member, thereby fixing the rotating member and the shaft member to each other in the axial direction of the shaft member. The hardness of the shaft member is higher than that of the rotating member. The shaft member has a small diameter portion formed at the tip and having a first outer diameter which is a predetermined outer diameter; a large diameter portion formed at the base end and having a second outer diameter which is a predetermined outer diameter which is larger than the first outer diameter; and a constricted portion formed between the small diameter portion and the large diameter portion and having a third outer diameter which is a predetermined outer diameter which is less than or equal to the first outer diameter, and a first void which is a gap that widens inward in the radial direction of the shaft member is formed as the recess. The teeth are formed on the outer circumferential surface of the small diameter portion of the shaft member, The locking portion is formed by a part of the material that constitutes the inner circumferential surface of the hole in the rotating member that is filled in the first void, The normal vector of at least a portion of the end face on the tip side of the large diameter portion of the shaft member has a component that approaches a straight line including the axis of the shaft member. A plastic fastening structure characterized by the following features.

4. A plastic fastening structure in which a hollow or solid shaft member is press-fitted into a hole formed in a rotating member, and a portion of the material constituting the other of the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member flows into teeth formed on one of the inner circumferential surface of the hole in the rotating member or the outer circumferential surface of the shaft member, thereby fixing the rotating member and the shaft member to each other in the direction of rotation, A locking portion is integrally formed in the shaft member at a position different from the teeth in the axial direction of the shaft member, by filling a recess formed on either the inner surface of the hole in the rotating member or the outer surface of the shaft member with a portion of the material constituting the other of the inner surface of the hole in the rotating member or the outer surface of the shaft member, thereby fixing the rotating member and the shaft member to each other in the axial direction of the shaft member. The hardness of the rotating member is higher than that of the shaft member. The hole in the rotating member is formed as a closed hole that does not go all the way through but has a bottom surface. The teeth are formed on the inner circumferential surface of the bottomed hole of the rotating member. A second void, which is a void that extends outward in the radial direction of the shaft member, is formed as the recess on the inner circumferential surface adjacent to the bottom surface of the bottomed hole of the rotating member. The locking portion is formed by filling the second void with the material that constitutes the tip of the shaft member. In a cross-section of the shaft member with respect to the axis, the bottom surface of the bottomed hole of the rotating member is a curved shape that is convex toward the opening of the bottomed hole. A plastic fastening structure characterized by the following features.

Images