JP5607128B2 - Manufacturing method of outer tube and manufacturing method of outer tube with bearing - Google Patents

Description

  The present invention relates to a method for manufacturing an outer tube formed in a cylindrical shape as a member constituting a shock absorber.

A cylindrical outer tube and a cylindrical inner tube are provided, and the inner tube is inserted into the inner side of the outer tube from one end opening side of the cylindrical tube through the one end opening of the outer tube. Each is configured to be movable in the direction along the central axis of the cylinder, and is provided with elasticity such as oil and coil spring provided inside the inner tube and outer tube, and a coil provided outside the inner tube and outer tube. 2. Description of the Related Art A front fork is known as a shock absorber that absorbs an impact by using elasticity such as a spring.
The outer tube is formed by casting (see Patent Document 1).
In addition, the bearing is fixed to the inner peripheral surface of the outer tube, and the inner tube is inserted into the outer tube from the one end opening side of the tube through the one end opening and the bearing hole of the outer tube, and the inner tube and the outer tube are inserted. There is known a shock absorber configured such that a tube can be moved in a direction along a central axis of a cylinder via a bearing (see Patent Document 2, etc.).
When the outer tube is formed by casting, generally, a core is installed inside the main mold, and a molten aluminum, for example, is poured between the main mold and the core to form the outer tube. In this case, in order to die-cut the core, as the core, the outer peripheral surface was formed in the inner peripheral surface molding portion for molding the inner peripheral surface of the outer tube into an inner peripheral surface having a casting gradient. Use things. For example, the core is formed of a truncated cone-shaped rod, and the inner peripheral surface forming portion is formed of the outer peripheral surface of the truncated cone. And when fixing a bearing to the inner peripheral surface of an outer tube, it cuts in order to make the inner peripheral surface of the part which fixes a bearing into a bearing press-fit diameter.

JP 2001-18049 A Utility Model Registration Publication No. 2541848

However, when the inner peripheral surface of the outer tube after molding is cut, not only the man-hour is increased, but also a cast hole generated inside the molded product by casting comes out on the inner peripheral surface (surface) of the outer tube. This may cause a cause of pressure leakage of the outer tube.
The present invention provides an outer tube manufacturing method and the like that can suppress the cause of pressure leakage of the outer tube, reduce the number of steps, and manufacture the outer tube at low cost.

In the outer tube manufacturing method according to the present invention, an outer tube which is a constituent member of a shock absorber is formed by high pressure die casting in which a core is installed inside a main mold and a molten metal is pushed between the main mold and the core. In the outer tube manufacturing method, as the core, an inner peripheral surface forming portion for forming the inner peripheral surface of the outer tube into an inner peripheral surface having a casting gradient, and a part of the inner peripheral surface of the outer tube The core with a bearing press-fitting surface molding part for molding a bearing press-fitting surface that is parallel to the central axis of the outer tube is used to suppress the cause of pressure leakage of the outer tube and reduce the man-hours. The outer tube can be manufactured at low cost.
The outer tube with bearing according to the present invention is manufactured by press-fitting a bearing into the bearing press-fitting surface formed on the inner peripheral surface of the outer tube formed by the outer tube manufacturing method. Since the attached outer tube with a bearing is manufactured, the bearing can be easily attached simply by fixing it to the bearing press-fitting surface, and the outer tube with a bearing with the bearing attached to the inner peripheral surface can be easily produced.

Process drawing which shows the manufacturing method of an outer tube. The perspective view which shows the core used for the manufacturing method of an outer tube. The principal part expanded sectional view of an outer tube. Sectional drawing of the front fork using an outer tube.

  Hereinafter, the present invention will be described in detail through embodiments of the invention. However, the following embodiments do not limit the invention according to the claims, and all combinations of features described in the embodiments are included in the invention. It is not necessarily essential to the solution, but includes a configuration that is selectively adopted.

  As shown in FIGS. 1 to 3, a manufacturing method of an outer tube constituting a shock absorber such as a front fork and a rear suspension of a motorcycle according to the embodiment is configured by installing a core 2 inside a main mold 1. When the molten tube 10 is poured between the mold 1 and the core 2 and the outer tube 3 is formed, the inner peripheral surface 4 of the outer tube 3 is formed into the inner peripheral surface 4 having a cast gradient as the core 2. And a bearing press-fitting surface molding part 22 for molding a bearing press-fitting surface 7 which is a surface parallel to the central axis 6 of the outer tube 3 on a part of the inner peripheral surface 4 of the outer tube 3. And a core 2 provided with

As shown in FIG. 2, the core 2 is constituted by a substantially rod-shaped metal rod similar to a cylinder, for example. A part of the outer peripheral surface 23 of the substantially truncated cone-shaped rod body is formed by an outer peripheral surface of a regular cylinder centering on the central axis 24 of the rod body, and the outer circumferential surface of the regular cylinder is formed by the bearing press-fitting surface molding portion 22. The outer peripheral surface that functions as the bearing press-fitting surface molding surface 25 and forms the side surface of the truncated cone other than the bearing press-fitting surface molding portion 22 of the rod body is formed so as to be inclined from one end side to the other end side of the rod body. It functions as the formed inner peripheral surface molding portion 21. The bearing press-fitting surface molding surface 25 is formed by the outer peripheral surface of a regular cylinder having a true circular cross section centering on the central axis of the rod body formed so as to protrude from the outer peripheral surface 23 of the truncated cone-shaped rod body. .
That is, the bearing press-fitting surface molding portion 22 includes a bearing press-fitting surface molding surface 25 and a bearing press-fitting bottom molding surface 26, and the bearing press-fitting bottom molding surface 26 is centered on the rod body from the outer peripheral surface 23 of the truncated cone-shaped rod body. A cylindrical end surface extending so as to intersect (for example, substantially orthogonal or orthogonal) with the axis 24 is formed, and the bearing press-fitting surface forming surface 25 extends in parallel with the central axis 24 of the rod body from the circle edge of the cylindrical end surface. It is formed by the outer peripheral surface of a regular cylinder whose central axis is the central axis 24 of the rod that reaches the outer peripheral surface (side surface) of the truncated cone of the body.

When the core 2 is installed inside the main mold 1 and the molten metal 10 is poured into the molding space between the main mold 1 and the core 2 and solidifies, the outer shape as shown in FIG. Tube 3 is formed. At this time, the inner peripheral surface 4 of the cylinder of the outer tube 3 is formed in a shape obtained by inverting the outer peripheral surface 23 of the substantially frustoconical rod body of the core 2. That is, the molten metal 10 in contact with the outer peripheral surface 23 of the core 2 is solidified to form the inner peripheral surface 4 of the cylinder of the outer tube 3, that is, the inner peripheral surface 4 having a casting gradient. At this time, the molten metal 10 in contact with the bearing press-fitting surface molding portion 22 of the core 2 is solidified, so that a bearing that is recessed from the inner peripheral surface 4 in a part of the inner peripheral surface 4 having the cast gradient of the outer tube 3. The press-fit portion 72 is formed. That is, the bearing press-fitting surface 7 formed by solidification of the molten metal 10 in contact with the bearing press-fitting surface molding surface 25 of the core 2 is the inner peripheral surface 4 formed on a part of the inner peripheral surface 4 of the outer tube 3. The bearing press-fit bottom surface 71 formed by the solidification of the molten metal 10 that contacts the bearing press-fit bottom surface forming surface 26 of the core 2 is constituted by a cylindrical inner peripheral surface that is more depressed. It is formed by an annular surface extending from one end circle edge so as to intersect (for example, substantially orthogonal or orthogonal) with the central axis 6 of the outer tube 3.
As the draft, it is preferable to provide a gradient of about 1/10 to 1/50. In addition, the length of the bearing press-fitting surface 7 in the direction along the central axis 6 of the outer tube 3 is set to a length (for example, about 5 mm) that does not affect when the core 2 is pulled out.

As shown in FIG. 1A, the main mold 1 is constituted by, for example, a mold, and has an outer surface molding surface 11 formed in a shape that forms the outer surface of the outer tube 3.
As shown in FIG. 1 (a), a core 2 is installed inside the main mold 1, a molten metal 10 such as aluminum is poured between the main mold 1 and the core 2, and the molten metal 10 is solidified. By doing so, the outer tube 3 in which the bearing press-fit portion 72 is formed on the inner peripheral surface 4 as shown in FIG. 1B; FIG. 3 is formed.
The outer tube 3 is formed by, for example, high pressure die casting. In this case, as shown in FIG. 1A, the molten metal 10 poured into the sleeve 13 communicating with the molten metal inlet 12 of the main mold 1 through the molten metal inlet 10A. Is pushed by the plunger 15 driven by the hydraulic mechanism 14 and pushed between the main mold 1 and the core 2.

  Then, as shown in FIGS. 1C and 1D, the bearing 8 is inserted from one end opening of the molded outer tube 3 and molded by the outer peripheral surface of the bearing 8 and the bearing press-fitting surface molding surface 25 of the core 2. By fitting the bearing 8 into the bearing press-fitting surface 7 so that the bearing press-fitting surface 7 is in contact with the fitted state, the bearing 8 is press-fitted into the bearing press-fitting surface 7 and is fixed. The outer tube 3 with a bearing in which the bearing 8 is attached and fixed to the surface 4 can be manufactured.

In the embodiment, the inner peripheral surface 4 of the outer tube 3 formed by the core 2 is not machined by a machine, and the bearing is fitted on the bearing press-fitting surface 7 formed on the inner peripheral surface 4 of the outer tube 3 by the core 2. Since 8 is press-fitted and attached in a fixed state, it is possible to reduce the labor of cutting the bearing press-fitted surface for press-fitting the bearing into the inner peripheral surface of the outer tube and attaching it in a fixed state as in the prior art. Moreover, since the chill layer is left on the inner peripheral surface without cutting the inner peripheral surface of the outer tube, it is possible to suppress the exposure of the cast hole on the inner peripheral surface, and to obtain the outer tube 3 having an excellent pressure leakage preventing effect. be able to. That is, the cause of pressure leakage of the outer tube 3 can be suppressed, and the number of steps can be reduced, so that the outer tube 3 can be manufactured at low cost.
Then, the bearing 8 is inserted from one end opening of the outer tube 3 and the bearing 8 is fitted into the bearing press-fitting surface 7 so that the outer peripheral surface of the bearing 8 and the bearing press-fitting surface 7 come into contact with each other. The outer tube 3 with a bearing in which the bearing 8 is attached to the inner peripheral surface 4 can be easily manufactured.

Next, a motorcycle front fork 50 as an example of a shock absorber configured using the outer tube 3 will be described with reference to FIG.
The front fork 50 includes an outer tube 3 formed of a cylinder and an inner tube 51 formed of a cylinder. The inner tube 51 is connected to the one end opening 32 of the cylinder of the outer tube 3 and the bearings 8A and 8B from the one end opening 52 side of the cylinder. The inner tube 51 and the outer tube 3 are each configured to be movable in a direction along the central axis 3A of the cylinder.
A bearing press-fit portion 72A is formed on the inner peripheral surface 4 near the one end opening 32 of the outer tube 3, and the inner space between the bearing press-fit portion 72A and the bottom surface 39 of the cylindrical hole located on the other end side of the outer tube 3 is formed. The peripheral surface 4 is also provided with a bearing press-fit portion 72B different from the bearing press-fit portion 72A, and the bearings 8A and 8B are inserted into the outer tube 3 from the one end opening 32 side of the outer tube 3 to press-fit each bearing. The parts 72A and 72B are press-fitted and fixed.
A bottomed tool insertion hole 36 extending from the other end outer surface 35 toward the one end opening 32 side is formed at the other end of the outer tube 3, and a screw hole 37 is connected to the bottom surface 38 of the tool insertion hole 36 and the outer tube. 3 is formed so as to communicate with the bottom surface 39 of the cylindrical hole located on the other end side. Each hole is formed so that the center axis 3A of the cylindrical hole of the outer tube 3, the center axis 3A of the tool insertion hole 36, and the center axis 3A of the screw hole 37 coincide. An axle through hole 40 is formed at the other end of the outer tube 3. The axle through hole 40 is formed by a through hole whose center axis is perpendicular to the center axis 3A of the cylindrical hole of the outer tube 3 and penetrates the tool insertion hole 36 and whose both ends are opened on the outer peripheral surface of the other end of the outer tube 3. Is done.

A seat pipe 41 is installed in the cylinder of the outer tube 3. The other end of the seat pipe 41 is connected to a fixing bolt 42 fixed to the screw hole 37 and fixed to the bottom surface 39 of the outer tube 3, and one end side of the inner pipe 51 passes through one end opening 52 of the inner tube 51. It is formed by the cylinder inserted inside. One end of the seat pipe 41 is formed in the piston portion 43.
A coil spring 45 is installed in the cylindrical hole of the inner tube 51 so that the central axis 3A of the cylindrical hole and the central axis of the coil of the coil spring 45 coincide.
A screw portion 54 is formed on the inner surface of the other end opening 53 of the inner tube 51, and a top cap 55, which is a screw lid, is attached to the screw portion 54 to close the other end opening 53 of the inner tube 51. The other end surface of the top cap 55 is used for inserting a tool for fastening a threaded portion formed on the outer peripheral surface of the top cap 55 to the threaded portion 54 of the inner tube 51 or for attaching the body to a vehicle body not shown. A hole 56 is formed. A cylindrical spring collar 57 is installed on the bottom surface of the other end of the tube hole of the inner tube 51 closed by the top cap 55 in the tube hole of the inner tube 51. The spring collar 57 has the other end surface of the cylinder in contact with the top cap 55, and a washer 58 is installed on one end surface of the spring collar 57. The other end of the coil spring 45 is seated on the seating surface formed by the washer 58, and one end of the coil spring 45 is positioned so as to seat on the seating surface formed by the piston portion 43 at one end of the seat pipe 41. The piston portion 43 of the seat pipe 41 is formed by, for example, an enlarged diameter portion 46 in which one end of the seat pipe 41 is enlarged. The outer peripheral surface of the enlarged diameter portion 46 and the inner peripheral surface of the inner tube 51 are configured to be slidable.
Fork oil 48 is accommodated in the cylinder of the outer tube 3, and the cylinder of the inner tube 51 inserted into the outer tube 3 serves as a reservoir chamber 64 which is an oil reservoir. 48A is an oil surface.
A cylindrical lock collar 49 is provided inside the one end opening 52 of the inner tube 51.
An oil circulation hole 59 for allowing the fork oil 48 to flow inside and outside the cylinder is formed in the cylinder wall on the one end opening 52 side of the inner tube 51 and the cylinder wall of the seat pipe 41.
An oil seal 60 is attached to the inner surface of the outer tube 3 on the one end opening 32 side, and a dust seal 61 is provided for preventing dust and the like from entering the cylinder of the outer tube 3 from the outside.
A lower oil chamber 62 is formed between one end opening 52 of the inner tube 51 and a bottom surface 39 of a cylindrical hole located on the other end side of the outer tube 3, and an upper oil chamber 63 is formed between the lock collar 49 and the piston portion 43. Is formed.
Therefore, when the inner tube 51 and the outer tube 3 each move in the direction along the central axis 3A of the cylinder (when the front fork 50 is extended and contracted), the resistance when the fork oil 48 flows through the oil circulation hole 59 A damping force is obtained.

A front suspension of a motorcycle is constructed by attaching the front fork 50 to the left and right of the axle of the motorcycle and to the vehicle body.
A front fork having a damping function configuration in which the coil spring 45 and the spring collar 57 are removed from the front fork 50 described above is used as the left or right front fork 50, and the fork oil 48 and the seat pipe 41 are used as the other front fork. The front suspension of the motorcycle may be configured by using a front fork having a spring suspension function from which the above is removed.

  According to the manufacturing method of the outer tube according to the present invention, the high-quality outer tube 3 having a bearing press-fit portion used for the upright front fork 50 or the inverted front fork as described above, and The outer tube 3 with a bearing can be manufactured inexpensively and easily.

According to the present invention, a plurality of bearing press-fit portions 72A; 72B are formed at two or more locations on the inner peripheral surface 4 of the outer tube 3 as in the outer tube 3 of the front fork 50 shown in FIG. You may shape | mold the outer tube 3 using the comprised core 2. FIG.
Further, the outer tube 3 is molded using the core 2 configured to mold the plurality of bearing press-fit portions 72A; 72B and the seal press-fit portion 60A for press-fitting and fixing the oil seal 60 shown in FIG. Also good.
Further, only the other bearing press-fit portion 72B of the outer tube 3 shown in FIG. 4 is formed using the core 2 according to the present invention, and one bearing press-fit portion near the one end opening 32 of the outer tube 3 shown in FIG. 72A and the seal press-fit portion 60A may be formed by cutting with a machine.
That is, when the outer tube 3 having a plurality of bearing press-fit portions at two or more locations on the inner peripheral surface is formed, at least one bearing press-fit portion may be formed using the core according to the present invention. In this case, in particular, it is preferable to form the other bearing press-fit portion 72B at a position close to the bottom surface side of the cylindrical hole of the outer tube 3 that is difficult to cut by a machine, using the core 2 according to the present invention.
In short, in the present invention, the bearing press-fitting portion or the like that has been conventionally cut is formed at the casting stage to reduce the labor of cutting the bearing press-fitting portion or the like, and the inner peripheral surface and outer periphery of the outer tube 3 are reduced. The object is to suppress the occurrence of cast holes by leaving a chill layer on the surface.

In the embodiment, the case of forming a cylindrical outer tube has been described, but a rectangular tube-shaped outer tube may be formed.
Moreover, the outer tube manufactured by this invention can be used for the outer tube of the rear suspension of a motorcycle, and the outer tube of other shock absorbers.

1 main mold, 2 core, 3 outer tube, 4 inner peripheral surface of the outer tube,
6 Center axis of outer tube, 7 Bearing press-fit surface, 8; 8A; 8B Bearing,
10 molten metal, 21 inner peripheral surface molding part, 22 bearing press-fitting surface molding part,
72A; 72B Bearing press-fit portion.

Claims (2)

In the outer tube manufacturing method of forming an outer tube which is a constituent member of a shock absorber by high pressure die casting in which a core is installed inside the main mold and a molten metal is pushed between the main mold and the core,
As the core, an inner peripheral surface forming portion for forming the inner peripheral surface of the outer tube into an inner peripheral surface having a casting gradient, and a part of the inner peripheral surface of the outer tube are parallel to the central axis of the outer tube An outer tube manufacturing method using a core including a bearing press-fitting surface forming portion for forming a bearing press-fitting surface which is a smooth surface.   An outer tube with a bearing in which a bearing is attached to the inner peripheral surface by press-fitting the bearing into the bearing press-fitting surface formed on the inner peripheral surface of the outer tube formed by the outer tube manufacturing method according to claim 1. A method for producing an outer tube with a bearing, characterized by comprising:

Images