JPH0315437Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a seal structure for a ball bearing portion of a gear crankshaft of a bicycle.

The bearing part of the conventional bicycle gear crankshaft is
As shown in FIG. 1, it consists of a bracket 1 of a hanger portion of a frame, with bearing outer ring members 2, 3, bearing balls 4, and a gear crankshaft (hanger shaft or hanger core) 5 assembled. The bearing outer ring members 2 and 3 have the following features: one member 2 has a flange portion 10 for assembly and adjustment, and the other member 3 is screwed with a nut 11 in place of the flange portion 10; There is a difference in that the male threads on the outer periphery are opposite threads on the left and right sides, but both are screwed in from the outside of the bracket 1, and have a guide groove 12 on the inner peripheral surface for guiding the bearing ball 4. It's the same. A guide groove 13 is formed on the outer periphery of the gear crankshaft 5 opposite to the guide groove 12, and the ball 4 is held between the guide grooves 12 and 13. A gear (sprocket) 14 and a crank arm (an arm with a pedal) are attached to the right end of the gear crankshaft 5 in the figure, and only the crank arm is attached to the left end. In addition, in the figure, 15 is a frame lower pipe, and 16 is a chain stay. Since the bearing portion of the conventional gear crankshaft 5 is not sealed, mud and water easily enter the bearing portion, and the ball 4 and the guide grooves 12 and 13 are easily worn out. In response to this, a structure in which a sealing material 17 made of rubber is provided has been proposed, as shown in FIG. However, as shown in the figure, the structure was such that a sealing material holding groove 18 was provided on the inner circumferential surface of the outer end of the outer ring member 2a.
In order to secure the necessary groove width of the groove 18, the dimension el of the outer ring member 2a protruding from the outer end of the bracket 1 must be changed to be larger than the dimension e of a conventional bicycle, which is undesirable. In other words, when the dimension e becomes large, when the conventional gear crankshaft 5 is used and assembled, the first
The assembly width w shown in the figure is wider than before, and in relation to the assembly width of the rear gear, chain line 1
9 cannot be used because it is slanted, and a specially made gear crankshaft and gear are actually required.

The object of this invention is to provide a seal structure for a gear crankshaft bearing, which allows the conventional gear crankshaft and gear to be used as they are, and which can seal the bearing portion.

In order to achieve the above object, this invention forms an annular groove whose cross-sectional shape is enlarged at the inner part on the outer end surface of the bearing outer ring member of the gear crankshaft, and an annular groove is formed with a rubber-like material and the inner periphery is formed around the crankshaft. A sealing material having an annular engagement part that is in close contact with the surface and has an enlarged cross-sectional shape that fits into the annular groove is installed, and the outer ring member of the bearing on the side where the gear of the gear crankshaft is attached is attached to the outer end of the bracket. The protrusion dimension from the bearing outer ring member is made smaller than the original protrusion dimension by the dimension by which the sealing material protrudes from the bearing outer ring member.

An annular groove that engages with the annular engaging part of the sealing material is formed on the outer end surface, and the engagement relationship between the annular groove and the annular engaging part of the sealing material is pushed in using the elasticity of the rubber-like sealing material. Since the structure is such that the annular groove and the annular engaging portion are made relatively thin, there is no risk of disengagement, and there is no need to increase the dimension e. be.

Examples of this invention will be described below with reference to the drawings.
FIG. 4 shows one bearing outer ring member 20. FIG. Bearing outer ring member 2 without a conventional seal shown in Fig. 2
Compared to the bearing outer ring member 20, the bearing outer ring member 20 has an annular groove 21, the width of the flange portion 10b is made smaller, and the annular engagement portion 22 is fitted into the annular groove 21 and a sealing material 23 is attached. , the shape and dimensions of other parts are the same.

The annular groove 21 is formed on the outer end surface of the bearing outer ring member 20, that is, on the outer surface when it is assembled into the bracket 1, and has an annular shape concentric with the hole 24 through which the crankshaft passes, narrowing at the entrance and widening at the inner part. It is formed to have a cross-sectional shape.

The sealing material 23 includes an annular portion that has an inner hole that tightly fits on the outer periphery of the crankshaft and is relatively thin in the central axis direction, and a short cylindrical portion that protrudes from the large diameter to one side and further radially inward. It has an annular engaging portion 22 having a shape corresponding to the protruding annular groove. The inwardly protruding portion of the annular engagement portion 22 has a slightly rounded cross-sectional shape, which is designed to facilitate installation.

Note that the bearing outer ring member 20 described above corresponds to the outer ring member 2 on the right side in FIG.
The one corresponding to the left outer ring member 3 is also provided with an annular groove 21 and has a sealing material 23 installed therein, and is the same, so a description thereof will be omitted.

Right bearing outer ring member 2 fitted with sealing material 23
0 and left bearing outer ring members are conventional ones 2 and 3, respectively.
Since it has the same dimensions as the conventional gear crankshaft 5, it can be assembled into the bracket 1 together with the conventional gear crankshaft 5. The inner periphery of the sealing material 23 is in close contact with the outer periphery of the bearing ball guide groove 13 of the gear crankshaft 5 to perform a sealing action.

Therefore, according to this bearing seal structure for a bicycle gear crankshaft, the gear can be installed by simply replacing the outer ring member for the bearing equipped with the sealing material with the conventional one, without using a gear crankshaft of special dimensions. The bearing of the crankshaft can be in a sealed state.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway plan view showing the configuration of a hanger section of a conventional bicycle, Fig. 2 is a partially cutaway enlarged view of the right bearing outer ring member in Fig. 1, and Fig. 3 is a second view showing a conventional seal structure. FIG. 4 is a partially cutaway enlarged view showing a right side bearing outer ring member and a sealing material that are different from those shown in FIG. 1...Bracket, 2...Right side bearing outer ring member, 3...
Left bearing outer ring member, 4...Bearing ball, 5...
Gear crankshaft (hanger shaft), 20... Right side bearing outer ring member, 21... Annular groove, 23... Sealing material.

Claims (1)

[Scope of utility model registration request] A gear crankshaft for a bicycle that has a male thread on the outer periphery so as to be screwed in from the outside of the bracket, a bearing ball guide groove on the inner periphery, and an end wall with a hole drilled at the outer end for the gear crankshaft to pass through. In the outer ring member of the bearing, an annular groove whose cross-sectional shape is enlarged at the inner part is formed on the outer surface of the end wall, and the annular groove is formed in an annular shape with a rubber-like material and the inner periphery is in close contact with the circumferential surface of the crankshaft. A sealing material having an annular engagement part with a cross-sectional shape that is inserted into the groove and enlarged inside is installed, and the outer ring member of the bearing on the side where the gear of the gear crankshaft is attached has a protruding dimension from the outer end of the blanket. A seal structure for a bearing of a gear crankshaft of a bicycle, wherein the sealing material is formed to be smaller than its original protrusion dimension by the dimension that the seal material protrudes from the end of the bearing outer ring member.