Bolt fastening structure

Abstract

The utility model provides a bolt fastening structure. In the bolt fastening structure, an iron joint bolt is provided with a cylindrical part with a male thread formed on the outer peripheral surface and a female thread formed on the inner peripheral surface, and the male thread on the iron joint bolt is screwed with the female thread formed on the vehicle framework member. An iron bolt is inserted into a through-hole formed in a member to be assembled and into the interior of the cylindrical portion of the joint bolt, and a male thread formed on the iron bolt is screwed with a female thread on the inner peripheral surface of the cylindrical portion of the joint bolt. On the basis of the structure, an assembled component can be fastened on a vehicle framework component made of an aluminum die casting with larger axial force by using an iron bolt.

Description

Technical Field

[0001] The utility model relates to a bolt fastening structure. Background Art

[0002] In the past, in the assembly of assembled components such as suspension members to vehicle frame components, a bolt fastening method was often used. On the other hand, in recent years, in order to achieve the light weight of vehicles, aluminum die-castings are used to manufacture vehicle frame components. Aluminum die-castings are generally manufactured by a casting method in which molten aluminum alloy is poured into a mold while being pressurized.

[0003] Figure 4 FIG. is a cross-sectional view showing a prior art bolt fastening structure in which a suspension member b is bolted to a vehicle frame member a made of an aluminum die-casting. As Figure 4 described, in the prior art bolt fastening structure, an iron bolt c is inserted into a bolt insertion hole having an internal thread a1 formed in the vehicle frame member a and a through hole b1 formed in the suspension member b, and an external thread c1 of the bolt c is screwed with the internal thread a1 of the vehicle frame member a.

[0004] However, compared with iron, aluminum alloy has lower strength. Therefore, when the external thread c1 of the iron bolt c is screwed onto the internal thread a1 of the vehicle frame member a made of an aluminum die-casting, if the bolt c is tightened with a large fastening torque to obtain a large axial force so that the bolt c is not easily loosened, the pressing force applied by the external thread c1 of the bolt c in the acting direction of the axial force may cause the internal thread a1 of the vehicle frame member a to be deformed (the thread of the internal thread a1 is skewed). Therefore, there is a technical problem that it is difficult to tighten with a large axial force. This technical problem exists not only in the case where the suspension member b is bolted to the vehicle frame member a made of an aluminum die-casting, but also in the case where other assembled components are bolted to the vehicle frame member a. Summary of the Utility Model

[0005] In view of the above situation, the purpose of the present utility model is to provide a bolt fastening structure in which the thread is not easily deformed when an assembled component is fastened to a vehicle frame member made of an aluminum die-casting with an iron bolt with a large axial force.

[0006] As a technical solution to solve the above technical problems, the present utility model provides a bolt fastening structure. This bolt fastening structure is a bolt fastening structure in which an iron bolt fastens an assembled member to a vehicle frame member made of an aluminum die-casting. It is characterized in that: the iron joint bolt has a cylindrical portion with an external thread formed on its outer peripheral surface and an internal thread formed on its inner peripheral surface. The external thread on this joint bolt is screwed with the internal thread of a bolt socket formed on the vehicle frame member; the iron bolt is inserted into a through hole formed on the assembled member and the inside of the cylindrical portion of the joint bolt, and the external thread formed on this bolt is screwed with the internal thread on the inner peripheral surface of the cylindrical portion of the joint bolt.

[0007] The advantages of the above bolt fastening structure of the present utility model are as follows. Since the external thread on the joint bolt is screwed with the internal thread of the bolt socket formed on the vehicle frame member; the iron bolt is inserted into the through hole formed on the assembled member and the inside of the cylindrical portion of the joint bolt, and its external thread is screwed with the internal thread on the inner peripheral surface of the cylindrical portion of the joint bolt, that is, the iron bolt inserted into the cylindrical portion of the joint bolt fastens and connects the vehicle frame member made of an aluminum die-casting and the assembled member via the joint bolt, which is also made of iron and has an outer diameter larger than that of the iron bolt. Therefore, even when fastening with a relatively large axial force, the threads are not easily deformed.

[0008] Specifically, since both the bolt and the joint bolt are made of iron, when the external thread of the bolt is screwed onto the internal thread of the cylindrical portion of the joint bolt with a relatively large fastening torque, even if a relatively large axial force is generated between the external thread of the bolt and the internal thread of the joint bolt, the threads of both sides are not easily deformed.

[0009] On the other hand, since the outer diameter size of the cylindrical portion of the joint bolt is larger than the outer diameter size of the bolt, compared with the structure of the prior art ( Figure 4 shown) in which the internal thread of the vehicle frame member is directly screwed with the external thread of the bolt as a fastener, a larger amount of latching (the contact area between the threads of the internal thread and the threads of the external thread) can be obtained between the internal thread of the vehicle frame member and the external thread of the joint bolt as one of the fasteners. Therefore, during fastening, even when a relatively large axial force is generated between the internal thread of the vehicle frame member made of an aluminum die-casting and the external thread of the iron joint bolt, the internal thread of the vehicle frame member can withstand this axial force and is not easily deformed. Therefore, the assembled member can be fastened to the vehicle frame member with a relatively large axial force.

[0010] In addition, in the above bolt fastening structure of the present utility model, preferably, the thread depth dimension of the external thread formed on the outer peripheral surface of the cylindrical portion of the joint bolt is set to be greater than the thread depth dimension of the external thread formed on the iron bolt.

[0011] Based on this structure, it is possible to ensure a larger amount of engagement between the internal thread of the vehicle frame member and the external thread of the joint bolt. As a result, the internal thread and the external thread can withstand a greater axial force, and thus the assembled member can be fastened to the vehicle frame member with a greater axial force.

[0012] In addition, preferably, on the joint bolt, a flange portion is provided which is disposed between the vehicle frame member and the assembled member.

[0013] Based on this structure, as long as there are a variety of joint bolts with different thickness dimensions of the flange portion, by using different types of joint bolts, the relative position of the assembled member with respect to the vehicle frame member (the relative position in the thickness direction of the flange portion) can be varied. Therefore, when it is necessary to change the relative position of the assembled member with respect to the vehicle frame member, it is only necessary to replace the type of joint bolt used, without changing the shape of the vehicle frame member or the shape of the assembled member. Thus, it is possible to cope with the fastening between the vehicle frame members and the assembled members of different vehicle models. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a cross-sectional view showing a bolt fastening structure according to an embodiment of the present invention.

[0015] Figure 2 It is a view for explaining an operation of fastening a suspension member to a vehicle frame member with bolts.

[0016] Figure 3 It is a cross-sectional view showing a bolt fastening structure according to a modified example.

[0017] Figure 4 It is a cross-sectional view showing a bolt fastening structure according to the prior art. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a case where the bolt fastening structure of the present invention is applied to assembling a suspension member as an assembled member on a vehicle frame member will be described.

[0019] Figure 1 It is a cross-sectional view showing the bolt fastening structure of this embodiment. Figure 1 In this figure, the direction of the arrow OUT represents the outside in the vehicle width direction, and the direction of the arrow UP represents the upper side.

[0020] As Figure 1 shown, the bolt fastening structure of this embodiment is a structure in which a vehicle frame member 1 and a suspension member 2 are fastened together with a joint bolt 3 and a bolt 4. Hereinafter, each member will be described.

[0021] The vehicle frame member 1 is a member made of an aluminum die-cast, and has a portion for assembling the suspension member 2, that is, an assembling portion 11. The bottom surface of the assembling portion 11 is a flat assembling surface 12. On the assembling portion 11, a joint bolt insertion hole 13 penetrating it in the vertical direction is formed. The inner diameter dimension of the joint bolt insertion hole (the bolt insertion hole referred to in the present invention) 13 is substantially the same as the outer diameter dimension of the upper cylindrical portion (the cylindrical portion referred to in the present invention) 31 of the joint bolt 3 described later. The structure of the upper cylindrical portion 31 will be described later. Here, an internal thread 13a is formed on the entire surface (inner circumferential surface) inside the joint bolt insertion hole 13. The thread dimension (depth and pitch) of the internal thread 13a is larger than the thread dimension (depth and pitch) of the external thread 42a formed on the thread portion 42 of the bolt 4 described later.

[0022] The suspension member 2 is a member for supporting a suspension device (not shown). The inner portion of the suspension member 2 in the vehicle width direction is an assembling portion 21 assembled to the vehicle frame member 1. The assembling portion 21 has a top surface 22 and a bottom surface 23, and the top surface 22 and the bottom surface 23 are each configured as a flat surface. On the assembling portion 21, a through hole 24 penetrating it in the vertical direction is formed. The inner diameter dimension of the through hole 24 is substantially the same as the outer diameter dimension of the lower cylindrical portion 33 of the joint bolt 3 described later. The structure of the lower cylindrical portion 33 will be described later.

[0023] The joint bolt 3 is a member made of iron, and includes an upper cylindrical portion 31, a flange portion 32, and a lower cylindrical portion 33.

[0024] The upper cylindrical portion 31 is configured as a cylindrical shape closed at the upper side. As described above, the outer diameter dimension of the upper cylindrical portion 31 is substantially the same as the inner diameter dimension of the joint bolt insertion hole 13 of the vehicle frame member 1. And, on the entire outer circumferential surface of the upper cylindrical portion 31, an external thread 31a is formed. The thread dimension (depth and pitch) of the external thread 31a is the same as the thread dimension (depth and pitch) of the internal thread 13a formed on the inner circumferential surface of the joint bolt insertion hole 13 formed on the vehicle frame member 1, and the external thread 31a is screwed with the internal thread 13a.

[0025] As described above, the thread dimension (depth and pitch) of the internal thread 13a of the joint bolt insertion hole 13 is set to be larger than the thread dimension (depth and pitch) of the external thread 42a of the bolt 4, and thus, the thread dimension (depth and pitch) of the external thread 31a of the upper cylindrical portion 31 is also set to be larger than the thread dimension (depth and pitch) of the external thread 42a of the bolt 4.

[0026] The flange portion 32 is connected to the lower side of the upper cylindrical portion 31 and extends outward from the outer peripheral surface of the upper cylindrical portion 31. The shape of the flange portion 32 is, for example, a disc shape. When the upper cylindrical portion 31 of the joint bolt 3 is screwed into the joint bolt insertion hole 13 of the vehicle frame member 1, the position where the joint bolt 3 is tightened is the position where the top surface of the flange portion 32 abuts against the fitting surface 12 of the vehicle frame member 1.

[0027] The lower cylindrical portion 33 is configured in a cylindrical shape that is open at both the upper and lower sides, and its upper side is connected to the lower side of the flange portion 32. As described above, the outer diameter dimension of the lower cylindrical portion 33 is substantially the same as the inner diameter dimension of the through hole 24 of the suspension member 2. In addition, the inner diameter dimension of the lower cylindrical portion 33 is the same as the inner diameter dimension of the upper cylindrical portion 31. The inner diameter dimensions of the upper cylindrical portion 31 and the lower cylindrical portion 33 are substantially the same as the outer diameter dimension of the threaded portion 42 of the bolt 4. In addition, the depth dimension (dimension in the vertical direction) of the lower cylindrical portion 33 is set to be smaller than the depth dimension (dimension in the vertical direction) of the through hole 24 of the suspension member 2.

[0028] Among them, internal threads 34 are formed on the entire inner peripheral surface of the upper cylindrical portion 31 and the entire inner peripheral surface of the lower cylindrical portion 33. The thread dimensions (depth and pitch) of the internal threads 34 are the same as the thread dimensions (depth and pitch) of the external threads 42a formed on the threaded portion 42 of the bolt 4 described later.

[0029] The bolt 4 is made of iron and includes a bolt head 41 and a threaded portion 42. As described above, the outer diameter dimension of the threaded portion 42 is substantially the same as the inner diameter dimensions of the upper cylindrical portion 31 and the lower cylindrical portion 33. And, external threads 42a are formed on the outer peripheral surface of the threaded portion 42. The thread dimensions (depth and pitch) of the external threads 42a are the same as the thread dimensions (depth and pitch) of the internal threads 34 formed on the inner peripheral surfaces of the respective cylindrical portions (31, 33) of the joint bolt 3, and the external threads 42a are screwed with the internal threads 34.

[0030] Next, an operation of fastening the suspension member 2 to the vehicle frame member 1 with bolts will be described. Figure 2 This is a diagram for explaining this operation. This operation is performed in the order of joint bolt tightening operation, suspension member fitting operation, and bolt tightening operation.

[0031] First, in the joint bolt tightening operation, the external threads 31a formed on the outer peripheral surface of the upper cylindrical portion 31 of the joint bolt 3 are screwed onto the internal threads 13a formed on the inner peripheral surface of the joint bolt insertion hole 13 of the vehicle frame member 1, and the screwing operation of the joint bolt 3 is continuously performed until the top surface of the flange portion 32 abuts against the fitting surface 12 of the vehicle frame member 1. At this time, the lower cylindrical portion 33 of the joint bolt 3 is in a state of protruding from the lower side of the vehicle frame member 1.

[0032] During the suspension member assembly operation, the suspension member 2 is disposed below the vehicle frame member 1 so that the lower cylindrical portion 33 is inserted into the through hole 24 formed in the suspension member 2 and the top surface 22 of the suspension member 2 abuts against the bottom surface of the flange portion 32 .

[0033] In the bolt tightening operation, the washer 5 is brought into contact with the lower side of the through hole 24 of the suspension member 2, and then the bolt 4 is inserted into the washer 5, the through hole 24 of the suspension member 2, and the joint bolt 3 in sequence, and the external thread 42a formed on the outer peripheral surface of the threaded portion 42 of the bolt 4 is screwed onto the internal thread 34 formed on the inner peripheral surface of the lower cylindrical portion 33 and the inner peripheral surface of the upper cylindrical portion 31 of the joint bolt 3, respectively, until the bolt head 41 of the bolt 4 is brought into contact with the bottom surface 23 of the suspension member 2 through the washer 5 and a predetermined axial force is obtained, and the bolt 4 is tightened. In this way, the bolt 4 is tightened with a predetermined tightening torque.

[0034] In this way, the suspension member 2 is fastened to the vehicle frame member 1 by bolts. Figure 1 As described above, the external thread 31a formed on the outer peripheral surface of the upper cylindrical portion 31 of the joint bolt 3 having a larger outer diameter than the bolt 4 is screwed into the internal thread 13a of the vehicle frame member 1. Figure 4 Compared with the prior art structure in which the internal thread a1 of the vehicle frame member b shown is directly screwed with the external thread c1 of the bolt c as a fastener, the engagement amount (contact area between the internal thread 13a and the external thread 31a) between the internal thread 13a of the vehicle frame member 1 and the external thread 31a of the joint bolt 3 as one of the fasteners is increased.

[0035] On the other hand, when the external thread 42a of the bolt 4 is threadedly engaged with the internal thread 34 formed on the inner circumferential surface of the upper cylindrical portion 31 and the lower cylindrical portion 33 of the joint bolt 3, since both the bolt 4 and the joint bolt 3 are made of iron, although the amount of engagement between the external thread 42a of the bolt 4 and the internal thread 34 of the joint bolt 3 is small, they can also withstand a large axial force.

[0036] Similarly, an axial force is generated by screwing between the external thread 31a of the joint bolt 3 and the internal thread 13a formed on the inner peripheral surface of the joint bolt insertion hole 13 of the vehicle frame member 1. This axial force will further increase when the bolt 4 is tightened, and the strength of the internal thread 13a of the vehicle frame member 1 made of an aluminum die-cast is lower than that of the external thread 31a of the iron joint bolt 3. However, as described above, since a large amount of engagement is ensured between the internal thread 13a of the vehicle frame member 1 and the external thread 31a of the joint bolt 3, the internal thread 13a can withstand a large axial force. Therefore, even if the bolt 4 is tightened with a large tightening torque to generate a large axial force, deformation of the internal thread 13a of the vehicle frame member 1 in the direction of the axial force can be prevented.

[0037] In this way, since the iron bolt 4 tightly connects the vehicle frame member 1 made of an aluminum die-cast and the suspension member 2 via the iron joint bolt 3 with an outer diameter larger than that of the bolt 4, even when tightened with a large axial force, the threads (13a, 31a, 34, 42a) are not easily deformed. Thus, the suspension member 2 can be tightly fastened to the vehicle frame member 1 with a large axial force.

[0038] Next, an application example of the present utility model will be described. This application example is an example of various joint bolts 3 having different thickness dimensions of the flange portion 32.

[0039] Here, vehicle models as application objects include, for example, sedan-type vehicles and SUV (Sports Utility Vehicle)-type vehicles. Generally, sedan-type vehicles have a lower vehicle height, while SUV-type vehicles have a higher vehicle height. That is, the height positions of the vehicle frame members 1 of different vehicle models are different relative to the height positions of the tires or suspension devices.

[0040] In this example, for sedan-type vehicles, in the fastening structure between the vehicle frame member 1 and the suspension member 2, a joint bolt 3 with a smaller thickness dimension of the flange portion 32 is used (as shown in Figure 1 ); for SUVs, in the fastening structure between the vehicle frame member 1 and the suspension member 2, a joint bolt 3 with a larger thickness dimension of the flange portion 32 is used (as shown in Figure 3 ).

[0041] In this way, by using joint bolts 3 with different thickness dimensions of the flange portion 32, the height position of the vehicle frame member 1 relative to the tires or suspension devices can be changed, thereby being able to cope with vehicles of different models. Here, only the case of having two types of joint bolts 3 is taken as an example for description. The more types of joint bolts 3 available, the more vehicle models can be coped with.

[0042] Thus, based on this application example, as long as a variety of joint bolts 3 with different thickness dimensions of the flange portion 33 are prepared in advance and a suitable joint bolt 3 is selected, the relative position of the suspension member 2 with respect to the vehicle frame member 1 (the relative position in the thickness direction of the flange portion 33) can reach the desired position. In other words, by simply changing the type of the joint bolt 3 used, without changing the shape of the vehicle frame member 1 or the shape of the suspension member 2, the relative position of the suspension member 2 with respect to the vehicle frame member 1 can be changed.

[0043] The present utility model is not limited to the foregoing embodiments and application examples and can be appropriately changed. For example, in the foregoing embodiments and application examples, the case where the bolt fastening structure of the present utility model is applied to assembling the suspension member 2 on the vehicle frame member 1 has been described. However, it is not limited thereto, and the bolt fastening structure of the present utility model is also applicable to the case of assembling other members on the vehicle frame member 1.

[0044] In addition, in the foregoing embodiments and application examples, the bolt fastening structure for tightening the bolt 4 from the lower side has been described. However, it is not limited thereto, and the present utility model is also applicable to the bolt fastening structure for tightening the bolt 4 from the upper side and the bolt fastening structure for tightening the bolt 4 from the horizontal direction.

Claims

1. A bolt fastening structure, which is a bolt fastening structure for fastening an assembled component to a vehicle frame component made of aluminum die casting using iron bolts, characterized in that: The iron joint bolt has a cylindrical portion with an external thread formed on the outer circumference and an internal thread formed on the inner circumference, and the external thread on the joint bolt is screwed with the internal thread of the bolt insertion hole formed on the vehicle frame member; The iron bolt is inserted into a through hole formed in the assembled member and into the cylindrical portion of the joint bolt, and an external thread formed on the bolt is threadedly engaged with an internal thread on the inner circumferential surface of the cylindrical portion of the joint bolt.

2. The bolt fastening structure according to claim 1, characterized in that: The thread depth dimension of the external thread formed on the outer peripheral surface of the cylindrical portion of the joint bolt is set to be larger than the thread depth dimension of the external thread formed on the iron bolt.

3. The bolt fastening structure according to claim 1 or 2, characterized in that: The joint bolt is provided with a flange portion disposed between the vehicle frame member and the assembled member.

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