JP2009192068A - Strut type fluid pressure shock absorber and method for manufacturing base shell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a strut type fluid pressure shock absorber that can make full use of a weight reduction effect of a double tube structure of a base shell. <P>SOLUTION: A bottom side of the bottomed base shell 1 containing a shock absorbing mechanism under the portion where a spring seat 11 is mounted has a double tube structure in which a partial shell 13 is closely fitted in a shell body 12 defining an overall shape of the base shell 1, and the double tube structure ensures such a strength as endures bending moment input into the base shell 1. The double tube structure can be advantageous in terms of strength to meet a reduced total wall thickness, and a single tube part over the portion where the spring seat 11 is mounted can meet a significantly reduced wall thickness. The reductions in wall thickness can provide a significantly reduced weight. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a strut type fluid pressure shock absorber used for a vehicle suspension and a method of manufacturing a base shell constituting the strut type fluid pressure shock absorber.

  In this type of strut type fluid pressure shock absorber, a knuckle bracket located on the bottom side and attached to a knuckle on the wheel side is suspended on a base shell having a bottom and containing a shock absorbing mechanism. Some spring seats that receive springs are fitted and fixed. In such a strut type fluid pressure shock absorber, a large bending moment is input to the base shell when the vehicle is traveling, and thus the base shell is required to have a high strength that can withstand the bending moment. In order to increase the strength of the base shell, it is necessary to increase its section modulus. Conventionally, this has been dealt with by increasing the wall thickness, and it has been inevitable that the weight of the entire shock absorber will increase. .

By the way, when comparing with the same wall thickness, when the same bending moment is input, it is known that the maximum stress is smaller in the double pipe structure than in the single pipe (from the stress balance calculation of the combined cylinder). Yes. Therefore, by making the base shell in the above-described strut type fluid pressure shock absorber a double tube structure, the total thickness can be reduced while ensuring the required strength, and the weight can be reduced accordingly. . Patent Document 1 describes a damper tube having a double tube structure in which an iron cylinder is inserted into an aluminum outer tube.
JP 2000-304082 A

  However, when the steel base shell has a simple double-pipe structure, the thickness of the steel base shell can be reduced to a small extent, and so much weight reduction cannot be expected. Note that the weight reduction of the damper tube described in Patent Document 1 is mainly due to the aluminumization of the outer tube.

  The present invention has been made in view of the above-described technical background, and the object of the present invention is to provide a strut type fluid capable of maximizing the lightening effect due to the double shell structure of the base shell. The object is to provide a pressure damper and to provide a manufacturing method capable of mass-producing a lightweight base shell.

  In order to solve the above-mentioned problems, a strut type fluid pressure shock absorber according to the present invention has a double-pipe structure in which the bottom side of the base shell is closer to the inner surface of the shell body than the spring seat mounting portion. It is characterized by becoming.

  Further, the method of manufacturing the base shell according to the present invention includes a tubular body insertion step of inserting a second tubular body having a shorter length into a long first tubular body until one end is aligned, It comprises a diameter reducing step for tightly fitting the inner surface of the tubular body to the second tubular body by a diameter reducing process, and a sealing step for sealing the tube ends of the first and second tubular bodies. And

  According to the strut type fluid pressure shock absorber according to the present invention, since the bottom portion side of the base shell to which the bending moment is input has a double tube structure, the lightening effect is maximized while ensuring a desired strength. be able to.

  Moreover, according to the manufacturing method of the base shell which concerns on this invention, a base shell can be mass-produced using a well-known plastic processing technique.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows the overall structure of a strut-type fluid pressure shock absorber according to one embodiment of the present invention. In the figure, 1 is a bottomed base shell, which will be described in detail later, 2 is a cylinder housed in the base shell 1, 3 is a piston slidably mounted in the cylinder 2, 4 is a piston 3 The piston rod is connected at one end, and the other end of the piston rod 4 is inserted through a rod guide 5 and an oil seal 6 fitted in common to the open ends of the base shell 1 and the cylinder 2 and extends to the outside. It is being done. A fluid (here, oil) is sealed in the cylinder 2, a damping force generating means 7 is disposed on the piston 3, and a base valve 8 is disposed on the bottom of the cylinder 2. The above-described configuration is generally seen as a twin tube type hydraulic shock absorber. The oil liquid circulates through the damping force generating means 7 and the base valve 8 in accordance with the extension and shortening of the piston rod 4, thereby extending the stroke. And the damping force of the contraction stroke is generated, and the oil liquid of the entry and exit of the piston rod 4 is compensated by the reservoir 9 between the base shell 1 and the cylinder 2. Accordingly, the components such as the cylinder 2, the piston 3, and the piston rod 4 housed in the base shell 1 constitute a buffer mechanism.

  The strut type fluid pressure shock absorber (here, the hydraulic shock absorber) having the above-described structure is configured to fit and fix a bracket (knuckle bracket) 10 attached to a knuckle on the wheel side to the bottom of the base shell 1 and also to the base shell. A spring seat 11 that receives a suspension spring interposed between the vehicle body and the vehicle body is fitted and fixed to the upper side of the body 3 and is used in practice.

  Here, as shown in FIG. 2, the base shell 1 has a partial shell 13 that is shorter than the attachment portion of the spring seat 11 on the inner surface of the shell body 12 that defines the overall shape of the base shell 1. It has a double-pipe structure in which are closely fitted. More specifically, both the shell body 12 and the partial shell 13 have a bottomed shape having bottom plate portions 12a and 13a, and both are joined in a state where the bottom plate portions 12a and 13a are in close contact with each other. Further, the shell main body 12 has a radial step 14 at the attachment site of the spring seat 11, and the partial shell 13 is fitted to the shell main body 12 with its open end in contact with the step 14. Yes. That is, the partial shell 13 is constrained in the axial direction by bringing the bottom plate portion 13a into close contact with the bottom plate portion 12a on the shell body 12 side and bringing the opening end into contact with the step 14 on the shell body 12 side. Here, the height of the step 14 is set to be approximately equal to the thickness of the partial shell 13, so that the inner surface of the base shell 1 is substantially flush over its entire length.

  In the present embodiment, as shown in FIG. 3, the knuckle bracket 10 has a base that is formed by an overhanging caulking portion 15 in which the tubular portion 10a is integrally and radially extended inwardly with the base shell 1. Coupled to shell 1. A processing method for forming the overhanging caulking portion 15 is known as mechanical clinching, and here, two pairs are formed opposite to the peripheral surface of the cylindrical portion 10a of the knuckle bracket 10. On the other hand, as shown well in FIG. 4, the spring seat 11 has the base shell 1 in a state in which the step portion 11 b formed on the cylindrical portion 11 a is seated on the step 14 formed in the middle of the shell body 12. Is held fitted.

  The strut type hydraulic shock absorber configured as described above is assembled into the suspension in an upright state with the bottom of the base shell 1 being the lower side and the upper end of the piston rod 4 being the upper side. Moment is input. In this case, it is known that the bending moment input to the base shell 1 is the largest between the attachment portion of the spring seat 11 and the attachment portion of the knuckle bracket 10. In the present hydraulic shock absorber, the bottom side of the base shell 1 with respect to the spring seat mounting portion has a double tube structure of the shell body 12 and the partial shell 13, so that it can sufficiently withstand the bending moment described above.

  By the way, when the same bending moment is input as described above, it is known that the maximum stress is smaller in the double pipe structure than in the single pipe, and the base shell 1 is changed to the double pipe structure as described above. If you do, follow this principle. In other words, if the required strength is the same, the total thickness of the double-pipe structure portion of the base shell 1 (the fitting portion between the shell body 12 and the partial shell 13) can be made smaller than that of the integral base shell. Accordingly, the base shell 1 can be reduced in weight. On the other hand, in this hydraulic shock absorber, the double-pipe structure portion of the base shell 1 is limited to the bottom side from the spring seat mounting portion (step 14), and the upper side portion from the step 14 is a single tube of the shell body. Therefore, in this single pipe portion, the wall thickness is greatly reduced as compared with the case where the whole is a double pipe structure, and the weight can be greatly reduced.

  In other words, in this hydraulic shock absorber, only the portion of the base shell 1 that requires strength has a double-pipe structure, and the other portions have a single-pipe structure. Not only the base shell but also the base shell with a double tube structure as a whole can be significantly reduced in weight. It should be noted that the thickness of the single pipe portion (shell body 12) of the base shell 1 is sufficient if the thickness matches the strength that allows the rod guide 5 and the oil seal 6 to be maintained.

  Particularly in the present embodiment, the spring seat 11 is fitted and fixed to the shell main body 12 using the step 14 formed in the middle of the shell main body 12 (FIG. 4), so that it is like a general hydraulic shock absorber. Troublesome processing such as fixing the spring seat by welding or forming a bulging portion for locking the spring seat on the base shell by bulge processing can be omitted.

  Hereinafter, a method for manufacturing the base shell 1 will be described with reference to FIGS.

  When manufacturing the base shell 1, first, as shown in the upper half of FIG. 5, a first tubular body 20 for the shell body is prepared, and a mandrel 21 is attached to the first tubular body 20 from one end thereof. Inserting to the depth, the cylindrical first die 22 is moved along the first mandrel 21, and swaging (parallel swaging) is performed. This swaging is performed so as to squeeze between the first mandrel 21 while the first tube 20 is being squeezed by the first die 22, and thereby a reduced diameter portion is formed on one end side of the first tube 20. 20a is formed. In addition, the 1st die | dye 22 used at this time has the taper-shaped introduction part 22a in the front end side of the advancing direction, and the smooth movement of the 1st die | dye 22 is ensured by this introduction part 22a. In addition, a taper-shaped stepped portion 23 is formed at the boundary between the first tubular body 20 and the reduced diameter portion 20a by the introduction portion 22a.

  Next, as shown in the lower half of FIG. 5, a second mandrel 24 is inserted into the first tubular body 20 from the side opposite to the insertion side of the first mandrel 21 to form a cylindrical second The die 25 is moved along the reduced diameter portion 20a of the first tubular body 20, and the stepped portion 23 is shaped (squared). A small diameter portion 24a having the same outer diameter as the inner diameter of the reduced diameter portion 20a is formed at a tip portion of the second mandrel 24 through a step 24b that rises at a right angle. The step 24 a is inserted to a position where the step 24 a is engaged with the step portion 23. At this time, the first mandrel 21 is slightly retracted while maintaining the state where the tip of the first mandrel 21 is abutted against the second mandrel 21. The second die 25 moves from the tube end side of the reduced diameter portion 20a, and presses the tapered step portion 23 against the step 24b of the second mandrel 24, thereby positioning the partial shell 13. A step 14 (FIG. 2) is formed.

  Next, as shown in the upper half of FIG. 6, the second tubular body 30 for the partial shell 13 is inserted into the unprocessed portion of the first tubular body 20 together with the third mandrel 31. The third mandrel 31 is formed with a step 31a for supporting the tube end of the second tube 30. The tip of the second tube 20 is a step 14 on the first tube 20 side. It is inserted until it abuts. The raw part of the first tubular body 20 has an inner diameter that is slightly larger than the inner diameter of the shell body 12, thereby forming a slight gap S between the two tubular bodies 20 and 30. Insertion of the second tubular body 30 into the first tubular body 20 becomes easy.

  Next, as shown in the lower half of FIG. 6, the cylindrical third die 32 is moved along the third mandrel 31 from the tube end side to perform swaging (parallel swaging). This swaging is performed so as to squeeze between the third mandrel 31 while the first tube 20 is being squeezed by the third die 32, thereby reducing the diameter of the unprocessed portion of the first tube 20. In close contact with the second tubular body 30. The third die 32 used at this time is substantially the same as the first die 22, and a tapered introduction portion 32a for facilitating movement is provided on the front end side in the traveling direction. .

  Each swage process (FIGS. 5 and 6) may be replaced with a rotating ironing process performed by turning a roll having a cross-sectional shape similar to that of each of the dies 22, 25, and 32.

  FIG. 7 shows the base shell base pipe 35 after the series of steps described above is finished, and thereafter, as shown in FIG. 8, the tube end portion of the base shell base pipe 35 is closed, The base plate 1 in which the bottom plate portions 12a and 13a are integrally formed and the partial shell 13 is closely fitted to the bottom portion side in the shell body 12 is thus completed. The closing process of the tube end can be performed by applying a method described in Japanese Patent Application Laid-Open No. 2006-342725, for example. In this case, since the inner second tube body 30 has its tip abutted against the step 14 of the first tube body 20 and is prevented from moving forward (FIG. 7), the base shell base tube 35 The end portions of the tube can be integrally squeezed and sealed, whereby the bottom plate portions 12a and 13a are formed seamlessly. Of course, the bottom plate portion may be formed by welding a separate base cap.

  Thereafter, as shown in FIG. 9, the knuckle bracket 20 is fitted and fixed to the bottom side of the base shell 1 using the mechanical clinch described above, and the spring seat 21 is fitted and fixed using the step 14. Mechanical clinch can be performed by applying a method described in Japanese Patent Application Laid-Open No. 2004-35318, for example. Of course, the knuckle bracket 20 may be fixed by other methods such as welding.

It is sectional drawing which shows the whole structure of the strut type fluid pressure buffer which is one embodiment of this invention. It is sectional drawing which shows the attachment structure of the base shell which comprises this fluid pressure buffer, the knuckle bracket, and a spring seat with respect to this. It is sectional drawing which follows the AA arrow line of FIG. It is an expanded sectional view of the B section of FIG. It is sectional drawing which shows typically the initial stage of the manufacturing process of the base shell which concerns on this invention. It is sectional drawing which shows typically the intermediate step of the manufacturing process of this base shell. It is sectional drawing which shows the structure of the base shell intermediate tube obtained by finishing the process shown in FIG. 5 and FIG. It is sectional drawing which shows the structure of the base shell after finishing the last step of the manufacturing process of this base shell. It is sectional drawing which shows the attachment structure of the knuckle bracket with respect to the base shell manufactured by this invention.

Explanation of symbols

1 Base shell 2 Cylinder (buffer mechanism)
3 Piston (buffer mechanism)
4 Piston rod (buffer mechanism)
DESCRIPTION OF SYMBOLS 10 Knuckle bracket 11 Spring seat 12 Shell main body 12a Bottom plate part of shell main body 13 Partial shell 13a Bottom plate part of partial shell 14 Step

Claims (5)

  In a strut type fluid pressure shock absorber in which a knuckle bracket is located on the bottom side and a spring seat is located on the top side of the bottomed base shell containing the cushioning mechanism, the base shell is A strut type fluid pressure shock absorber having a double pipe structure in which a partial shell is closely fitted to an inner surface of a shell body on a bottom side from a mounting portion of a spring seat.   The shell main body has a radial step at a mounting portion of the spring seat, and the partial shell is constrained in an axial direction with one end abutting the step. Item 2. The strut type fluid pressure buffer according to Item 1.   The strut type fluid pressure buffer according to claim 2, wherein the bottom portion of the base shell is formed by integrally closing an end portion of the shell main body and an end portion of the partial shell. vessel.   A tube insertion step of inserting a second tube shorter than the first tube into the long first tube until one end is aligned, and the inner surface of the first tube is reduced by reducing the diameter. A method for manufacturing a base shell, comprising: a diameter reducing step for tightly contacting a second tubular body; and a sealing step for sealing the tube ends of the first and second tubular bodies.   The base shell manufacturing method according to claim 4, wherein the sealing step includes a closing process in which the tube ends of the first and second tube bodies are integrally squeezed to seal the tube.

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