Fixing structure and fixing method

Abstract

To provide a fixing structure which can fix a shaft member more easily while inhibiting removal of the shaft member, and to provide a fixing method.SOLUTION: A fixing structure includes: a fixed object which is formed by using a metallic material and provided with an insertion hole; and a shaft member which is formed by using a metallic material, and has a body and an extension part, which extends from the body in an axial direction and is press-fitted in the insertion hole, in which the extension part has a protruding part protruding in a radial direction and is formed so as to elastically deform to the radial inner side more easily than the body and the protruding part is engaged with the fixed object so as to restrict movement of the extension part in a direction such that the extension part is removed from the insertion hole.SELECTED DRAWING: Figure 3A

Description

[Technical Field]

[0001] The present invention relates to a fixing structure and a fixing method. [Background technology]

[0002] BACKGROUND ART As an actuator applied to a brake booster of an automobile or the like, for example, a ball screw device in which a piston is fixed to the tip of a screw shaft is known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-014437 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above configuration, the screw shaft is fixed to the piston by press-fitting the tip of the screw shaft into an insertion hole provided in the piston. During press-fitting, it is necessary to manage the press-fit interference and press-fit length to prevent the screw shaft from coming out, which is difficult to control. Thus, when fixing a metal shaft member such as a screw shaft to a metal fixing object such as a piston, a configuration is needed that makes it easier to perform the work while preventing the shaft member from coming out.

[0005] The present invention has been made in view of the above, and has an object to provide a fixing structure and a fixing method that can fix a shaft member more easily while suppressing the shaft member from coming loose. [Means for solving the problem]

[0006] A fixing structure according to one aspect of the present invention comprises a fixing object formed using a metal material and having an insertion hole; and an axial member formed using a metal material and having a main body portion and an extension portion extending axially from the main body portion and pressed into the insertion hole, the extension portion having a protrusion that protrudes radially and is formed so as to be more easily elastically deformed radially inward than the main body portion, the protrusion being engaged with the fixing object so as to restrict movement of the extension portion in the direction of coming out of the insertion hole.

[0007] According to this configuration, the extension portion is formed to be more easily elastically deformed radially inward than the main body portion, so that it can be easily press-fitted into the insertion hole of the object to be fixed. The extension portion is also provided with a protrusion that protrudes radially outward, and this protrusion is engaged with the object to be fixed. Therefore, when the extension portion is press-fitted into the insertion hole, movement in the direction of removal from the insertion hole is restricted. Therefore, removal of the shaft member can be prevented without managing the press-fit interference, press-fit length, etc. This makes it possible to more easily fix the shaft member while preventing removal of the shaft member.

[0008] In a preferred embodiment of the fixing structure, at least a portion of the extension of the shaft member is formed in a cylindrical shape. With this configuration, the extension can be easily elastically deformed radially inward compared to the main body.

[0009] In a preferred embodiment of the fixing structure, the shaft member has a slit extending in the axial direction in at least a part of the extension portion. With this configuration, the provision of the slit makes it easier for the extension portion to elastically deform radially inward than the main body portion.

[0010] In a preferred embodiment of the above-described fixing structure, the fixing object and the shaft member have a rotation restriction mechanism that restricts relative rotational movement around the axis between the fixing object and the shaft member when the shaft member is press-fitted into the fixing object. With this configuration, by press-fitting the shaft member into the insertion hole, it is possible to restrict rotation while also preventing the shaft member from coming out.

[0011] In a preferred aspect of the above-described fixing structure, the rotation restricting mechanism has a slit provided in the shaft member and extending in the axial direction, and a fitting portion provided in the fixed object and fitted into the slit. With this configuration, the slit formed in the shaft member can be used to restrict relative rotational movement around the axis between the fixed object and the shaft member.

[0012] In a preferred embodiment of the above-described fixing structure, the rotation restricting mechanism has a key provided on one of the shaft member and the fixed object, and a key groove corresponding to the key provided on the other. With this configuration, the key and key groove provided on the shaft member and the fixed object can be used to restrict relative rotational movement around the axis between the fixed object and the shaft member.

[0013] In a preferred embodiment of the above-described fixing structure, the protrusion has a ring member disposed between the object to be fixed and the shaft member, and restricts relative axial movement between the object to be fixed and the shaft member. According to this configuration, by using the ring member as the protrusion, it is possible to more reliably restrict relative axial movement between the object to be fixed and the shaft member.

[0014] In a preferred embodiment of the above-described fixing structure, the object and the shaft member each have a receiving groove that receives a portion of the ring member. With this configuration, the ring member is received in the receiving groove, thereby forming a state in which it is locked to both the object and the shaft member. This makes it possible to prevent axial displacement of the object and the shaft member.

[0015] In a preferred embodiment of the above-described fixing structure, the ring member is disposed with a portion thereof exposed from the accommodation groove, and the exposed portion of the ring member is disposed with the portion axially protruding outside the accommodation groove. This configuration prevents the entire ring member from being buried in the accommodation groove. Therefore, the ring member can be maintained in a state where it is engaged with both the object to be fixed and the shaft member.

[0016] In a preferred aspect of the above-described fixing structure, the object to be fixed has an abutment surface that abuts against the main body portion of the shaft member in a press-fitted state, and a convex portion provided on a part of the abutment surface, the shaft member has a recess that is recessed radially inward at the end of the extension portion that faces the main body portion, and the object to be fixed is arranged in a state in which the abutment surface abuts against the main body portion by press-fitting, causing the convex portion to deform and be accommodated in the recess. With this configuration, the convex portion is accommodated in the recess by press-fitting, thereby restricting relative movement in the axial direction between the object to be fixed and the shaft member.

[0017] In a preferred embodiment of the fixing structure, the shaft member is a screw shaft that constitutes a ball screw device. With this configuration, when fixing the screw shaft to a fixing object, it is possible to fix the screw shaft more easily while preventing the screw shaft from coming off.

[0018] In a preferred aspect of the above-described fixing structure, the fixing object is a piston. With this configuration, when fixing the shaft member to the piston, it is possible to fix the shaft member more easily while preventing the shaft member from coming off.

[0019] In a preferred aspect of the above-described fixing structure, the object to be fixed is a gear. With this configuration, when fixing a shaft member to a gear, it is possible to fix the shaft member more easily while preventing the shaft member from coming off.

[0020] In a preferred embodiment of the fixing structure, the shaft member holds the object to be fixed and a bearing portion between the protrusion and the main body in the axial direction. This configuration allows for a wider range of options for the arrangement of the bearing portion.

[0021] A fixing structure according to one aspect of the present invention includes a press-fitting process in which the extension portion of an axial member formed using a metal material has a main body portion and an extension portion extending axially from the main body portion, the extension portion having a protrusion that protrudes radially and is formed so as to be more easily elastically deformed radially inward than the main body portion, into an insertion hole of a fixing object formed using a metal material and having an insertion hole; and a locking process in which the protrusion portion is locked to the fixing object so as to restrict movement of the extension portion in the direction of coming out of the insertion hole.

[0022] With this configuration, the extension is formed to be more easily elastically deformed radially inward than the main body, so it can be easily press-fitted into the insertion hole of the object to be fixed. Also, by engaging the protrusion with the object to be fixed, it is possible to easily restrict movement in the direction of removal from the insertion hole. [Effects of the Invention]

[0023] According to the aspects of the present invention, the shaft member can be more easily fixed while preventing the shaft member from coming loose. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a cross-sectional view taken along the axial direction of a linear motion actuator using a fixing structure according to this embodiment. [Figure 2] FIG. 2 is a diagram showing an example of a fixing structure according to this embodiment. [Figure 3A] FIG. 3A is a diagram showing the configuration along the cross section AA in FIG. [Figure 3B] FIG. 3B is a cross-sectional view showing another example of the fixing structure. [Figure 3C] FIG. 3C is a cross-sectional view showing another example of the fixing structure. [Figure 4] FIG. 4 is a perspective view showing an example of a fixing structure. [Figure 5] FIG. 5 is a perspective view showing an example of a screw shaft. [Figure 6] FIG. 6 is a perspective view showing an example of a piston. [Figure 7] FIG. 7 is a process diagram schematically illustrating an example of a fixing method according to this embodiment. [Figure 8] FIG. 8 is a process diagram schematically illustrating an example of a fixing method according to this embodiment. [Figure 9] FIG. 9 is a process diagram schematically illustrating an example of a fixing method according to this embodiment. [Figure 10] FIG. 10 is a perspective view showing another example of the fixing structure. [Figure 11] FIG. 11 is a perspective view showing another example of the fixing structure. [Figure 12] FIG. 12 is a cross-sectional view showing another example of the fixing structure. [Figure 13] FIG. 13 is a cross-sectional view showing another example of the fixing structure. [Figure 14] FIG. 14 is a cross-sectional view showing a modified example of the fixing structure shown in FIG. [Figure 15] FIG. 15 is a cross-sectional view showing another example of the fixing structure. [Figure 16] FIG. 16 is a cross-sectional view showing another example of the fixing structure. [Figure 17] FIG. 17 is a perspective view showing another example of the fixing structure. [Figure 18] FIG. 18 is an exploded perspective view of the fixing structure shown in FIG. [Figure 19] FIG. 19 is a perspective view showing another example of the fixing structure. [Figure 20] FIG. 20 is a side view showing an example of the fixing structure shown in FIG. [Figure 21] FIG. 21 is a diagram showing the configuration along the cross section BB in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, embodiments of a fixing structure and a fixing method according to the present invention will be described with reference to the drawings. Note that the present invention is not limited to these embodiments. Furthermore, the components in the following embodiments include those that are easily replaceable by those skilled in the art, or those that are substantially the same, or so-called equivalents. The components disclosed in the following embodiments can be combined as appropriate.

[0026] 1 is a cross-sectional view of a linear motion actuator using a fixing structure according to this embodiment, taken along the axial direction. The linear motion actuator 100 is a brake booster that is mounted on a vehicle and generates hydraulic pressure corresponding to the amount of depression of the brake pedal. As shown in FIG. 1, the linear motion actuator 100 includes a motor 101, a transmission device 102, a housing 103, a ball screw device 110, and a piston 120.

[0027] Hereinafter, the direction parallel to the axis O of the screw shaft 112 of the ball screw device 110 will be referred to as the axial direction. Furthermore, within the axial direction, the direction in which the piston 120 is disposed as viewed from the nut 111 of the ball screw device 110 will be referred to as the first direction X1, and the direction opposite to the first direction X1 will be referred to as the second direction X2.

[0028] The motor 101 includes a stator (not shown), a rotor (not shown), and an output shaft 101a. The motor 101 receives power from a power source (not shown), causing the rotor and output shaft 101a to rotate. The motor 101 is supported by a housing 103, and the output shaft 101a is parallel to the screw shaft 112.

[0029] The transmission device 102 includes a first gear 104 that fits onto the output shaft 101a of the motor 101, and a second gear 105 that fits onto the outer periphery of the nut 111. The second gear 105 has a larger diameter than the first gear 104. Therefore, the transmission device 102 reduces the speed of the rotational motion generated by the motor 101 and transmits it to the nut 111.

[0030] The ball screw device 110 includes a nut 111, a screw shaft 112, and a plurality of balls 113. The nut 111 is cylindrical and has an axis O as its center. An inner circumferential raceway 111a is provided on the inner circumferential surface of the nut 111. The nut 111 is supported by a bearing 106 that fits into the inner circumferential surface of the housing 103. This allows the nut 111 to rotate freely around the axis O of the screw shaft 112.

[0031] The screw shaft 112 is a solid shaft part that passes through the nut 111. The screw shaft 112 includes a main body 114 having an outer peripheral raceway surface 114a on its outer peripheral surface, and an extension portion 115 that extends in the first direction X1 from an end face of the main body 114 in the first direction X1. Although not particularly shown, the main body 114 is supported by the housing 103 so as to be movable in the axial direction and unrotatable around the axis O. The screw shaft 112 may be provided with a rotation prevention member (not shown).

[0032] A spiral track is formed between the inner circumferential raceway surface 111a and the outer circumferential raceway surface 114a. A plurality of balls 113 are arranged on this spiral track. When the nut 111 rotates, the inner circumferential raceway surface 111a presses the outer circumferential raceway surface 114a in the axial direction via the balls 113. This causes the screw shaft 112 to move in the axial direction. In this embodiment, when the nut 111 rotates in one rotation direction about the axis O, the screw shaft 112 moves in a first direction X1. On the other hand, when the nut 111 rotates in another rotation direction about the axis O, the screw shaft 112 moves in a second direction X2.

[0033] The extending portion 115 has a smaller diameter than the main body portion 114. Therefore, at the boundary between the extending portion 115 and the main body portion 114, an annular stepped surface 114b facing the first direction X1 is provided.

[0034] The piston 120 is a cylindrical component arranged coaxially with the axis O. The piston 120 is preferably manufactured by forging, but may be formed by a known processing method such as cutting. The piston 120 is arranged inside the cylinder 107 near an end in the second direction X2. Note that, although the cylinder 107 in this embodiment is integrally provided with the housing 103, in the present disclosure, the cylinder 107 and the housing 103 may be separate bodies. Brake fluid (not shown) is contained inside the cylinder 107. The piston 120 has a first end face 121 facing the first direction X1 and a second end face 122 facing the second direction X2.

[0035] The first end surface 121 is provided with a concave surface 121a recessed in the second direction X2. The concave surface 121a faces the bottom surface 107b of the cylinder 107. A coil spring (not shown) is disposed between the concave surface 121a and the bottom surface 107b. When the piston 120 is pressed in the first direction X1, the piston 120 moves against the coil spring (not shown). Note that the piston of the present disclosure may not be provided with the concave surface 121a.

[0036] An insertion hole 123 that opens in the second direction X2 is provided in the center of the second end face 122. The extension portion 115 is inserted into the insertion hole 123. The inner diameter of the insertion hole 123 is slightly smaller than the outer diameter of the extension portion 115, providing an interference. Therefore, the piston 120 moves in the axial direction integrally with the screw shaft 112 without separating from the screw shaft 112. The opening of the insertion hole 123 is chamfered in a tapered shape.

[0037] Hereinafter, the portion of the piston 120 that fits with the extension portion 115 (a cylindrical wall portion that surrounds the outer periphery of the insertion hole 123) will be referred to as the inner cylindrical portion 124. As shown in FIG. 1, an end surface 124a of the inner cylindrical portion 124 in the second direction X2 abuts against the annular stepped surface 114b of the screw shaft 112.

[0038] The outer peripheral surface of the piston 120 is in slidable contact with a seal member 108 on the inner peripheral side of the cylinder 107. This prevents brake fluid (not shown) from flowing toward the nut 111 and the screw shaft 112.

[0039] The outer diameter of the piston 120 is larger than the outer diameter of the nut 111. A ring-shaped outer cylinder portion 125 that protrudes in the second direction X2 and surrounds the outer periphery of the nut 111 is provided on a second end surface 122 of the piston 120. In other words, the outer periphery of the piston 120 is expanded in the second direction X2 by the outer cylinder portion 125. Therefore, even when the piston 120 moves in the first direction X1, the outer cylinder portion 125 and the seal member 108 are in sliding contact with each other, and sealing performance is maintained.

[0040] Next, the operation of the linear motion actuator 100 of the first embodiment will be described. When the motor 101 is driven, a rotational motion is transmitted to the nut 111 via the transmission device 102. This causes the nut 111 to rotate. Furthermore, when the rotation direction of the nut 111 is one direction about the axis O, the threaded shaft 112 moves in a first direction X1. Accordingly, the piston 120 also moves in the first direction X1, and the hydraulic pressure of the brake fluid increases. As a result, the hydraulic pressure of the brake fluid is transmitted to an external device through the through-hole 107a.

[0041] On the other hand, when the nut 111 rotates in the other direction around the axis O, the threaded shaft 112 moves in the second direction X2. Accordingly, the piston 120 moves in the second direction X2, and the hydraulic pressure of the brake fluid decreases.

[0042] Fig. 2 is a diagram showing an example of a fixing structure 150 according to this embodiment. Fig. 3A is a diagram showing a configuration along the cross section AA in Fig. 2. Fig. 4 is a perspective view showing an example of the fixing structure 150. Fig. 4 shows a state in which a part of the piston 120 is cut away.

[0043] 2 to 4, the fixing structure 150 includes a piston 120, which is an object to be fixed, and a threaded shaft 112, which is an axial member. The piston 120 is formed using a metal material such as an aluminum alloy. The material constituting the piston 120 may also be another metal material.

[0044] The piston 120 has an insertion hole 123. The insertion hole 123 has an expanded diameter portion 127 at its end in the first direction X1. The expanded diameter portion 127 has a hole diameter that is expanded compared to other parts of the insertion hole 123. By providing the expanded diameter portion 127, a step surface 128 is formed between the insertion hole 123 and the expanded diameter portion 127. The axial length of the expanded diameter portion 127 is longer than that of the protruding portion 116.

[0045] The screw shaft 112 is formed using a metal material such as chrome molybdenum steel. The screw shaft 112 may be made of other metal materials. The screw shaft 112, together with a nut 111 and balls 113 (see FIG. 6), constitutes a ball screw mechanism 110. As shown in FIG. 4, the nut 111 may be provided with a gear 160. The screw shaft 112 has a cylindrical extending portion 115 at its end in the first direction X1. The extending portion 115 has a protruding portion 116 at its tip. The protruding portion 116 protrudes radially outward from an outer circumferential surface 115a of the extending portion 115.

[0046] The extending portion 115 has a recess 117 formed from an end surface 115b in the first direction X1 toward the second direction X2. The recess 117 is circular when viewed in the second direction X2. By providing the recess 117, a part of the tip side of the extending portion 115 is formed into a cylindrical shape. With this configuration, the extending portion 115 is configured to be more easily elastically deformed radially inward than the main body portion 114. The tip of the extending portion 115 on the first direction X1 side is chamfered in a tapered shape.

[0047] The extension portion 115 is configured to be press-fitted into the insertion hole 123 of the piston 120. When the extension portion 115 is press-fitted into the insertion hole 123, it is tightly fastened by the inner cylindrical portion 124 of the piston 120 without any gaps. This suppresses rattle between the extension portion 115 and the inner cylindrical portion 124. When the extension portion 115 is press-fitted into the insertion hole 123, the protrusion 116 is housed in the enlarged diameter portion 127. When the protrusion 116 is housed in the enlarged diameter portion 127, the extension portion 115 is elastically deformed radially inward.

[0048] When the protruding portion 116 is housed in the expanded diameter portion 127, the protruding portion 116 is locked against the step surface 128 in the second direction X2. This configuration restricts movement of the extending portion 115 in the second direction X2. In other words, movement of the screw shaft 112 in the direction of coming out of the insertion hole 123 is restricted.

[0049] Fig. 3B is a cross-sectional view showing another example of the fixing structure. Fixing structure 150A shown in Fig. 3B has a configuration in which a step portion 115c is provided on extension portion 115 of screw shaft 112. Step portion 115c is connected to end face 114b on the first direction X1 side and to end face 114c on the second direction X2 side. In addition, piston 120 has step portion 123c corresponding to step portion 115c. Step portion 123c is connected to end face 124a on the first direction X1 side and to end face 124b on the second direction X2 side.

[0050] In the fixing structure 150A, the screw shaft 112 is in a state where the step portion 115c is press-fitted into the step portion 123c. The end face 114c on the screw shaft 112 side and the end face 124b on the piston 120 side are in contact with each other. A gap is formed between the end face 114b on the screw shaft 112 side and the end face 124a on the piston 120 side. A gap is also formed between the outer peripheral surface 115a on the screw shaft 112 side and the inner peripheral surface 123a surrounding the insertion hole 123 on the piston 120 side.

[0051] FIG. 3C is a cross-sectional view showing another example of the fixing structure. A fixing structure 150B shown in FIG. 3C has a configuration in which a protrusion 117A is provided on an end surface 115b of the extending portion 115. The protrusion 117A protrudes from the end surface 115b in the second direction X2. The protrusion 117A extends cylindrically from the end surface 115b toward the second direction X2 side, and has a curved tip on the second direction X2 side (a so-called bullet shape). The diameter of the protrusion 117A is set so that the protrusion 116 of the screw shaft 112 can be inserted therein. In the fixing structure 150B, the protrusion 117A is inserted into the inside of the extending portion 115 of the screw shaft 112. By inserting the protrusion 117A into the inside of the extending portion 115, the screw shaft 112 is less likely to come out.

[0052] Fig. 5 is a perspective view showing an example of the screw shaft 112. As shown in Fig. 5, the extending portion 115 is provided with a slit 115s extending in the axial direction. The slit 115s is formed linearly from the end face 115b of the extending portion 115 along the second direction X2. A plurality of slits 115s are formed at predetermined intervals in the axial direction. By providing the slits 115s, the extending portion 115 is configured to be more susceptible to elastic deformation radially inward.

[0053] FIG. 6 is a perspective view showing an example of the piston 120. As shown in FIG. 6, a fitting portion 129 is provided on the enlarged diameter portion 127 of the piston 120. The fitting portion 129 is fitted into the slit 115s when the protrusion 116 is housed in the enlarged diameter portion 127. The fitting portion 129 may be disposed at a position where it fits into all of the slits 115s, or at a position where it fits into at least one of the slits 115s. With this configuration, the piston 120 and the screw shaft 112 are locked in the axial direction, thereby restricting relative rotational movement between the piston 120 and the screw shaft 112 in the axial direction. In this manner, the slit 115s and the fitting portion 129 constitute a rotation restriction mechanism 151 that restricts relative rotational movement between the piston 120 and the screw shaft 112 in the axial direction when the screw shaft 112 is press-fitted into the piston 120. In a configuration in which a stopper is disposed on the piston 120, the provision of the rotation restriction mechanism 151 enables torque transmission between the piston 120 and the screw shaft 112. Furthermore, in a case in which an anti-rotation configuration is provided in which relative rotational movement around the axis between the cylinder 107 and the piston 120 is restricted, for example, by providing a groove extending in the axial direction in the cylinder 107 and providing a key on the outer circumferential surface of the piston 120 to be inserted into the groove, the provision of the rotation restriction mechanism 151 can restrict the piston 120 and the screw shaft 112 from rotating together with the rotation of the nut 111.

[0054] 7 to 9 are process diagrams schematically illustrating an example of a fixing method according to this embodiment. As shown in Fig. 7, when fixing the threaded shaft 112 to the piston 120, the extension portion 115 of the threaded shaft 112 is made to face the insertion hole 123 of the piston 120.

[0055] From this state, a force is applied to the screw shaft 112 in the first direction X1 to press-fit the extension portion 115 into the insertion hole 123 (press-fitting process). In the press-fitting process, as shown in FIG. 8, the extension portion 115 is press-fitted into the insertion hole 123 while being elastically deformed in the radial direction. In this embodiment, the tip of the extension portion 115 on the first direction X1 side is chamfered in a tapered shape, which makes it easier to insert into the insertion hole 123. Furthermore, the opening of the insertion hole 123 is chamfered in a tapered shape, which makes it easier to insert the extension portion 115. Furthermore, the extension portion 115 is configured to be more easily elastically deformed radially inward than the main body portion 114, which makes it easier to press-fit the extension portion 115.

[0056] By continuously applying a force to the screw shaft 112 in the first direction X1, as shown in FIG. 9 , the annular step surface 114b abuts against the end surface 124a of the inner cylindrical portion, and the protrusion 116 is accommodated in the expanded diameter portion 127. When the protrusion 116 is accommodated in the expanded diameter portion 127 from the insertion hole 123, the hole diameter expands, thereby reducing elastic deformation of the extending portion 115. By appropriately adjusting the hole diameter of the expanded diameter portion 127, the extending portion 115 can be restored from its elastically deformed state (to a state where it is not elastically deformed), or the extending portion 115 can remain elastically deformed. By accommodating the protrusion 116 in the expanded diameter portion 127, the protrusion 116 is engaged with the step surface 128 in the second direction X2. This prevents the screw shaft 112 from moving in the second direction X2 relative to the piston 120, i.e., prevents the screw shaft 112 from coming off the piston 120.

[0057] As described above, the fixing structure 150 of this embodiment comprises: a piston 120 formed using a metal material and provided with an insertion hole 123; and a screw shaft 112 formed using a metal material and having a main body 114 and an extension portion 115 extending axially from the main body 114 and pressed into the insertion hole 123, the extension portion 115 having a protrusion 116 that protrudes radially and is formed so as to be more easily elastically deformed radially inward than the main body 114, and the protrusion 116 is engaged with the piston 120 so as to restrict movement of the extension portion 115 in the second direction X2 through the insertion hole 123.

[0058] According to this configuration, the extending portion 115 is formed to be more easily elastically deformed radially inward than the main body portion 114, and therefore can be easily press-fitted into the insertion hole 123 of the piston 120. In addition, the extending portion 115 is provided with a protruding portion 116 that protrudes radially outward, and the protruding portion 116 is engaged with the piston 120. Therefore, when the extending portion 115 is press-fitted into the insertion hole 123, movement of the extending portion 115 in the direction of coming out of the insertion hole 123 is restricted. Therefore, it is possible to prevent the screw shaft 112 from coming out without managing the press-fit interference, press-fit length, and the like. This makes it possible to more easily fix the screw shaft 112 while preventing the screw shaft 112 from coming out.

[0059] In the fixing structure 150, the screw shaft 112 has at least a portion of the extending portion 115 formed in a cylindrical shape. According to this configuration, by making at least a portion of the extending portion 115 cylindrical, it is possible to make the extending portion 115 more easily elastically deform radially inward than the main body portion 114.

[0060] In the fixing structure 150, the screw shaft 112 has a slit 115s extending in the axial direction in at least a part of the extension portion 115. With this configuration, the provision of the slit 115s makes it easier for the extension portion 115 to elastically deform radially inward than the main body portion 114.

[0061] In the fixing structure 150, the piston 120 and the screw shaft 112 have a rotation restriction mechanism 151 that restricts relative rotational movement around the axis between the piston 120 and the screw shaft 112 when the screw shaft 112 is press-fitted into the piston 120. According to this configuration, by press-fitting the screw shaft 112 into the insertion hole, it is possible to restrict the screw shaft 112 from coming out and also to restrict its rotation.

[0062] In the fixing structure 150, the rotation restricting mechanism 151 has a slit 115s that is provided in the screw shaft 112 and extends in the axial direction, and a fitting portion 129 that is provided in the piston 120 and fits into the slit 115s. According to this configuration, the slit 115s formed in the screw shaft 112 can be used to restrict relative rotational movement between the piston 120 and the screw shaft 112 in the direction around the axis.

[0063] In the fixing structure 150, the shaft member is the screw shaft 112 that constitutes the ball screw device. In addition, in the fixing structure 150, the fixing object is the piston 120. According to this configuration, when fixing the screw shaft 112 to the piston 120, it is possible to fix the screw shaft 112 more easily while suppressing the screw shaft 112 from coming loose.

[0064] The fixing method according to this embodiment includes a press-fitting step of press-fitting the extension portion 115 of the screw shaft 112, which has a main body portion 114 formed using a metal material and an extension portion 115 extending axially from the main body portion 114, the extension portion 115 having a protrusion 116 protruding radially and formed so as to be more easily elastically deformed radially inward than the main body portion 114, into an insertion hole 123 of a piston 120, which is formed using a metal material and has an insertion hole 123; and a locking step of locking the protrusion 116 to the piston 120 so as to restrict movement of the extension portion 115 in the direction of coming out of the insertion hole 123.

[0065] According to this configuration, extension portion 115 is formed to be more easily elastically deformed radially inward than main body portion 114, and therefore can be easily press-fitted into insertion hole 123 of piston 120. Furthermore, by engaging protrusion 116 with piston 120, movement in the direction of removal from insertion hole 123 can be easily restricted.

[0066] 10 and 11 are perspective views showing other examples of the fixing structure. FIG. 10 shows another example of a screw shaft, and FIG. 11 shows another example of a piston. The screw shaft 212 shown in FIG. 10 has a main body 214, an extension 215, and a protrusion 216. The screw shaft 212 has a protrusion forming a key 215k on the outer circumferential surface 215a of the extension 215. In contrast, the piston 220 shown in FIG. 11 has a key groove 223k corresponding to the key 215k on the inner circumferential surface of the insertion hole 223. When the extension 215 of the screw shaft 212 is inserted into the insertion hole 223 of the piston 220, the key 215k is inserted into the key groove 223k. With this configuration, the key 215k and the key groove 223k are locked in the axial direction. This restricts relative rotational movement between the piston 220 and the screw shaft 212 in the axial direction.

[0067] In this way, the key 215k and the key groove 223k configure a rotation restriction mechanism 251 that restricts relative rotational movement around the axis between the piston 220 and the screw shaft 212 when the screw shaft 212 is press-fitted into the piston 220. According to this configuration, the key 215k provided on the screw shaft 212 and the key groove 223k provided on the piston 220 can be used to restrict relative rotational movement around the axis between the piston 220 and the screw shaft 212. The key 215k may be provided in the protruding portion 216. In this case, the key groove 223k may be provided in the expanded diameter portion 217.

[0068] Fig. 12 is a cross-sectional view showing another example of a fixing structure. As shown in Fig. 12, fixing structure 350 has a threaded shaft 312, a piston 320, and a ring member 351. In fixing structure 350, an accommodating groove 315b capable of accommodating ring member 351 is provided on outer peripheral surface 315a of extension portion 315 of threaded shaft 312. Ring member 351 is provided with a portion of its radial length accommodated in accommodating groove 315b. Ring member 351 elastically deforms in the radial direction so that its entirety can be accommodated in accommodating groove 315b. Ring member 351 includes a retaining ring.

[0069] An accommodation groove 323b that accommodates a portion of the outer circumferential side of the ring member 351 is provided on an inner circumferential surface 323a of the insertion hole 323. An accommodation groove 315b that accommodates a portion of the inner circumferential side of the ring member 351 is provided on an outer circumferential surface 315a of the extension portion 315. By being accommodated in the accommodation grooves 323b, 315b, the ring member 351 is prevented from shifting in the axial direction.

[0070] When forming the fixing structure 350, the ring member 351 is placed in the accommodating groove 315b, and the ring member 351 is elastically deformed to be accommodated in the accommodating groove 315b, and the extension portion 315 is press-fitted into the insertion hole 323 of the piston 320. When the ring member 351 moves in the first direction X1 by the press-fitting and reaches the accommodating groove 323b, the elastic deformation is restored and the outer circumferential portion is accommodated in the accommodating groove 323b on the piston 320 side, and the inner circumferential portion is accommodated in the accommodating groove 315b on the screw shaft 312 side. This restricts the axial movement of the screw shaft 312 and the piston 320 via the ring member 351.

[0071] As described above, the fixing structure 350 further includes a ring member 351 that is disposed between the piston 320 and the screw shaft 312 and restricts relative axial movement between the piston 320 and the screw shaft 312. According to this configuration, the use of the ring member 351 makes it possible to more reliably restrict relative axial movement between the piston 320 and the screw shaft 312.

[0072] Furthermore, in the fixing structure 350, the piston 320 and the screw shaft 312 have accommodation grooves 323b and 315b that accommodate a portion of the ring member 351. According to this configuration, by accommodating the ring member 351 in the accommodation grooves 323b and 315b, it is possible to suppress misalignment of the ring member 351 in the axial direction.

[0073] Fig. 13 is a cross-sectional view showing another example of the fixing structure. As shown in Fig. 13, fixing structure 450 has a configuration in which extension portion 415 of threaded shaft 412 axially passes through insertion hole 423 of piston 320, and protrusion portion 416 protrudes toward recessed surface 421a. An O-ring 452 is disposed between inner circumferential surface 423a of insertion hole 423 and outer circumferential surface 415a of extension portion 415. Providing O-ring 452 ensures sealing. At least one of inner circumferential surface 423a and outer circumferential surface 415a of insertion hole 423 may be provided with a groove portion for holding O-ring 452.

[0074] A ring member 451 is disposed between the protruding portion 416 and the recessed surface 421a. An accommodation groove 415b is provided on the outer peripheral surface 415a of the extending portion 415 to accommodate a part of the inner peripheral side of the ring member 451. The inner peripheral portion of the ring member 451 is accommodated in the accommodation groove 415b, and the outer peripheral portion abuts against the recessed surface 421a, thereby suppressing misalignment in the axial direction.

[0075] In this way, the extension portion 415 of the screw shaft 412 passes through the insertion hole 423 of the piston 420, and the ring member 451 is engaged between the concave surface 421a of the piston 420 and the accommodating groove 415b of the screw shaft 412. With this configuration, it is possible to more reliably prevent the screw shaft 412 from coming off.

[0076] Fig. 14 is a cross-sectional view showing a modified example of the fixing structure shown in Fig. 13. As shown in Fig. 14, ring member 451A is arranged with a part of its outer periphery exposed from accommodating groove 415b, and exposed portion 451s exposed from accommodating groove 415b is provided so as to protrude outside accommodating groove 415b in the axial direction. Ring member 451A has a configuration in which exposed portion 451s is so-called crimped.

[0077] In this way, in the fixing structure 450, the ring member 451A is arranged with a portion thereof exposed from the accommodating groove 415b, and the exposed portion 451s exposed from the accommodating groove 415b is provided in a state where it protrudes outside the accommodating groove 415b in the axial direction. This configuration can prevent the outer periphery of the ring member 451A from being accommodated in the accommodating groove 415b, so that the state where the ring member 451A is locked between the screw shaft 412 and the piston 420 can be more reliably maintained.

[0078] 15 and 16 are cross-sectional views showing another example of the fixing structure. The fixing structure 550 shown in Figs. 15 and 16 has a piston 520 and a screw shaft 512. The piston 520 has an insertion hole 523, an end face 524a, and a protrusion 525. The screw shaft 512 is press-fitted into the insertion hole 523. The end face 524a abuts against an annular step surface 514a of the screw shaft 512 when the screw shaft 512 is press-fitted. The protrusion 525 is provided on a part of the end face 524a.

[0079] The screw shaft 512 has a main body portion 514, an extending portion 515, and a recessed portion 517. The extending portion 515 extends from the main body portion 514 in the second direction X2. The extending portion 515 is press-fitted into the insertion hole 523 of the piston 520. The main body portion 514 has an annular stepped surface 514a at an end portion in the second direction X2. The annular stepped surface 514a abuts against an end face (abutment surface) 524a of the inner cylinder portion 524 of the piston 520 in a state in which the extending portion 515 of the screw shaft 512 is press-fitted into the insertion hole 523.

[0080] Recess 517 is provided at the end of extension 515 on the annular step surface 514a side, and has a shape recessed radially inward. As shown in Fig. 16 , extension 515 is press-fitted into insertion hole 523, whereby protrusion 525 on the piston 520 side is elastically deformed and accommodated in recess 517. As protrusion 525 is accommodated in recess 517, protrusion 525 is engaged with recess 517 in the axial direction.

[0081] Thus, in fixing structure 550, piston 520 has end surface 524a that abuts against main body portion 514 of threaded shaft 512 in a press-fitted state, and protrusion 525 provided on part of end surface 524a, threaded shaft 512 has recess 517 that is recessed radially inward at the end of extension portion 515 on the main body portion 514 side, and piston 520 is disposed in a state in which protrusion 525 is deformed and accommodated in recess 517 when end surface 524a abuts against main body portion 514 through press-fitting. According to this configuration, protrusion 525 elastically deforms and is accommodated in recess 517, thereby constituting a protrusion that protrudes radially inward. When protrusion 525 is accommodated in recess 517 through press-fitting, relative axial movement between piston 520 and threaded shaft 512 can be restricted.

[0082] FIG. 17 is a perspective view showing another example of the fixing structure. FIG. 18 is an exploded perspective view of the fixing structure shown in FIG. 17. The fixing structure 650 shown in FIGS. 17 and 18 has a gear 620 and a screw shaft 612. Unlike the above-described configurations, the fixing structure 650 has a configuration in which the screw shaft 612 rotates. In the fixing structure 650, the fixing object is the gear 620. The gear 620 is disk-shaped, has a circular insertion hole 621 in the center, and has a plurality of teeth 622 on the outer periphery. The insertion hole 621 penetrates the gear 620 in the axial direction. The gear 620 has an inner circumferential surface 623 surrounding the insertion hole 621. A key 623a is provided on the inner circumferential surface 623.

[0083] The screw shaft 612 has a configuration similar to that of the screw shaft 112 described above, and includes a main body 614, an extending portion 615, and a protruding portion 616. The extending portion 615 has a cylindrical shape at its tip end in the first direction X1, and a slit 615s is provided from an end surface 615b in the first direction X1 along the second direction X2. This configuration makes the extending portion 615 more easily elastically deformable radially inward than the main body 614. Furthermore, when the extending portion 615 is inserted into the insertion hole 621, a key 623a on the inner circumferential surface 623 of the gear 620 is inserted into the slit 615s. This restricts relative rotation between the screw shaft 612 and the gear 620 in the axial direction, forming a so-called rotation stop. The extending portion 615 is press-fitted into the insertion hole 621 and is disposed in a state where it penetrates the insertion hole 621. The protrusion 616 is disposed on the opposite side of the gear 620 with respect to the main body 614. The protrusion 616 is engaged with the first surface 620a of the gear 620. With this configuration, when the screw shaft 612 is fixed to the gear 620, the screw shaft 612 can be fixed more easily while preventing the screw shaft 612 from coming loose.

[0084] Thus, in the fixing structure 650, the object to be fixed is the gear 620. According to this configuration, when fixing the screw shaft 612 to the gear 620, it is possible to fix the screw shaft 612 more easily while preventing the screw shaft 612 from coming loose.

[0085] FIG. 19 is a perspective view showing another example of the fixing structure. FIG. 20 is a side view showing an example of the fixing structure shown in FIG. 19. FIG. 21 is a view showing a configuration along the cross section BB in FIG. 19. The fixing structure 750 shown in FIGS. 19 and 21 includes a gear 720, a screw shaft 712, and a bearing portion 730. The screw shaft 712, together with a nut 711 and a plurality of balls 713, constitutes a ball screw device 710. The fixing structure 750 is configured so that the screw shaft 712 rotates. The screw shaft 712 has a configuration similar to that of the screw shaft 112 described above and includes a main body portion 714, an extension portion 715, and a protrusion portion 716. The tip side of the extension portion 715 in the first direction X1 is cylindrical, and a slit 715s is provided from an end face 715b in the first direction X1 along the second direction X2. The gear 720 has an inner circumferential surface 723. A key 723a having the same configuration as the above-described key 623a is provided on the inner circumferential surface 723. Furthermore, when the extension portion 715 is inserted into an insertion hole surrounded by the inner circumferential surface 723, the key 723a on the inner circumferential surface 723 of the gear 720 is inserted into the slit 715s. This restricts relative rotation between the screw shaft 712 and the gear 720 in the axial direction, forming a so-called rotation stop.

[0086] The bearing portion 730 is sandwiched between the gear 720 and the main body portion 714 of the screw shaft 712. In other words, the gear 720 and the bearing portion 730 are sandwiched between the protrusion 716 of the screw shaft 712 and the main body portion 714 in the axial direction.

[0087] Thus, in the fixing structure 750, the threaded shaft 712 holds the gear 720 and the bearing portion 730 between the protrusion 716 and the main body portion 714 in the axial direction. This configuration allows for a wider range of options for the arrangement of the bearing portion 730.

[0088] The screw shaft 612, 712 may be configured such that a protrusion constituting a key is provided on the outer peripheral surface of the extension portion 615. In this case, the gear 620, 720 has a key groove corresponding to the key provided on the inner peripheral surface of the insertion hole 623, 723. When the extension portion 615, 715 of the screw shaft 612, 712 is inserted into the insertion hole 623, 723 of the gear 620, 720, the key is inserted into the key groove. With this configuration, the key and the key groove are locked in the axial direction, and relative rotational movement between the gear 620, 720 and the screw shaft 612, 712 in the axial direction is restricted.

[0089] The technical scope of the present invention is not limited to the above-described embodiments, and appropriate modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiments, a threaded shaft is used as an example of the shaft member, but the present invention is not limited to this. The shaft member may have a configuration other than a threaded shaft. Similarly, a piston and a gear are used as an example of the fixed object, but the present invention is not limited to this. The fixed object may have a configuration other than a piston and a gear. [Explanation of symbols]

[0090] O axis center X1 1st direction X2 2nd direction 100 Linear Actuator 101 Motor 101a Output shaft 102 Transmission Device 103 Housing 104 First Gear 105 2nd gear 106 Bearings 107 cylinders 107a Through hole 107b Bottom 108 Sealing material 110,710 Ball screw device 111,711 nuts 111a Inner raceway surface 111a,115b,124a,615b,715b End face 112,212,312,412,512,612,712 screw shaft 113,713,733 balls 114,514,614,714 Main body 114a Outer raceway surface 114b Annular step surface 115,215,315,415,515,615,715 Extension part 115a,215a,315a,415a Outer surface 115s, 615s, 715s Slit 116,316,416,616,716 Projection 117,517 recesses 120,220,320,420,520 Piston 121 1st end face 121a,421a concave 122 Second end face 123,223,323,423,523,621 Insertion holes 124 Inner cylinder 125 outer cylinder 126 Opposite Surface 127 Expanded diameter part 128,328,428 Step surface 129 Fitting part 150,350,450,550,650,750 Fixed structure 151,251 Rotation control mechanism 215k keys 223k keyway 315b, 323b, 415b Storage groove 323a,423a Inner surface 351, 451, 451A Ring member 451s Exposed part 452 O-ring 514a Annular step surface 516,524 Contact surface 525 convex part 620,720 gears 620a Page 1 622 teeth 730 Bearing section 731 Inner circumference 732 Outer periphery

Claims

1. a fixing object formed using a metal material and having an insertion hole; a shaft member formed using a metal material, having a main body and an extension portion that extends axially from the main body and is press-fitted into the insertion hole, the extension portion having a protrusion that protrudes radially and is formed so as to be more easily elastically deformed radially inward than the main body, and the protrusion is engaged with the fixed object so as to restrict movement of the extension portion in the direction of removal from the insertion hole; Equipped with the fixed object and the shaft member have a rotation restriction mechanism that restricts relative rotational movement between the fixed object and the shaft member in a direction around the axis when the shaft member is press-fitted into the fixed object, The rotation restriction mechanism has a slit provided in the shaft member and extending in the axial direction, and a fitting portion provided in the fixed object and fitted into the slit. Fixed structure.

2. At least a part of the extending portion of the shaft member is formed in a cylindrical shape. The fixing structure according to claim 1 .

3. The shaft member has a slit extending in the axial direction in at least a part of the extension portion. The fixing structure according to claim 2 .

4. The rotation restriction mechanism has a key provided on one of the shaft member and the fixed object, and a key groove provided on the other of the shaft member and the fixed object and corresponding to the key. The fixing structure according to claim 1 .

5. A fixed object formed using a metal material and having an insertion hole; a shaft member formed using a metal material, having a main body and an extension portion that extends axially from the main body and is press-fitted into the insertion hole, the extension portion having a protrusion that protrudes radially and is formed so as to be more easily elastically deformed radially inward than the main body, and the protrusion is engaged with the fixed object so as to restrict movement of the extension portion in the direction of removal from the insertion hole; Equipped with the fixed object has a contact surface that contacts the main body portion of the shaft member in a press-fitted state, and a protrusion provided on a part of the contact surface, the shaft member has a recessed portion recessed radially inward at an end of the extension portion on the main body side, The object to be fixed is arranged in a state in which the contact surface contacts the main body portion by press-fitting, whereby the convex portion is deformed and accommodated in the concave portion. Fixed structure.

6. The shaft member is a screw shaft that constitutes a ball screw device. The fixing structure according to claim 5.

7. The fixed object is a piston. The fixing structure according to claim 5 or 6.

8. The fixed object is a gear. The fixing structure according to claim 5 or 6.

9. The shaft member sandwiches the object to be fixed and a bearing portion between the protrusion and the main body in the axial direction. The fixing structure according to claim 8.

10. a press-fitting step of press-fitting the extension of a shaft member, the extension having a main body portion formed using a metal material and an extension portion extending axially from the main body portion, the extension portion having a protrusion protruding radially and formed so as to be more easily elastically deformed radially inward than the main body portion, into an insertion hole of a fixed object formed using a metal material and having an insertion hole provided therein; a locking step of locking the protruding portion to the fixed object so as to restrict movement of the extending portion in a direction of coming out of the insertion hole; Including, In the press-fitting step, when the extension portion is press-fitted into the insertion hole, a fitting portion provided on the object to be fixed is fitted into a slit provided on the shaft member and extending in the axial direction, thereby restricting relative rotational movement around the axis between the object to be fixed and the shaft member. Fixing method.

11. a press-fitting step of press-fitting the extension of a shaft member, the extension having a main body portion formed using a metal material and an extension portion extending axially from the main body portion, the extension portion having a protrusion protruding radially and formed so as to be more easily elastically deformed radially inward than the main body portion, into an insertion hole of a fixed object formed using a metal material and having an insertion hole provided therein; a locking step of locking the protruding portion to the fixed object so as to restrict movement of the extending portion in a direction of coming out of the insertion hole; Including, In the press-fitting step, the main body portion of the shaft member is brought into contact with an abutment surface provided on the object to be fixed, thereby deforming a convex portion provided on a part of the abutment surface, and the convex portion is accommodated in a concave portion that is provided on an end of the extension portion of the shaft member on the main body side and is recessed inward in the radial direction. Fixing method.

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