JPH11301562A - Steering device of motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering device of motorcycle that can easily change the caster corner and the wheelbase and can support bearings with high accuracy and rigidity for supporting front folk without increasing the cost of the part. SOLUTION: A steering device 10 of motorcycle comprises a head tube 3 which is installed at the front head of a vehicle body frame 2, a bearing housing 16 which is formed in a direct tube shape with a dimension of external diameter tightly fittable with a bore diameter of the head tube 3 and fixed detachably relative to the head tube 3, and a pair of upper and lower bearings 21, 22 which are fitted to an internal periphery of the upper and lower end portions of the bearing housing 16 and axially supports a steering column 45 of a front folk 8 rotatably. In this case, prepared are bearing housings 16, one with the shaft center Ca of the bearings 21, 22 are identical relative to the central axis of the bearing housing, and one displaced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering device for a motorcycle in which a front fork supporting a front wheel is rotatably supported on the front head of a body frame so as to be rotatable left and right, and more particularly, a caster angle and a wheel of the front fork. The present invention relates to a motorcycle steering device having a base changeable.

[0002]

2. Description of the Related Art A front fork supporting a front wheel of a motorcycle is provided with a caster angle in order to improve the straight running stability. The caster angle is determined by the angle of the head pipe, and cannot be easily changed by a general motorcycle. Further, the distance between the front wheel and the rear wheel, that is, the wheelbase cannot be changed.

[0003] In view of the above, a large number of steering devices capable of changing the caster angle and the wheel base have been developed. For example, Japanese Patent Publication No. Sho 51-22264, Japanese Utility Model Publication No. Sho 56-354
Such is the case described in Japanese Patent Publication No. 92 and Patent Publication No. 2690863.

In each of these steering devices, separate bearing housings are detachably provided at the upper end and the lower end of a head pipe of a body frame, and bearings are mounted (press-fitted) into these bearing housings, respectively, and the upper and lower bearings are provided. The front fork is configured to be pivotally supported.

[0005] Each bearing housing is prepared in such a manner that the axis of the bearing is displaced with respect to its central axis. By changing the direction of such a bearing housing or replacing it with a bearing housing having a different displacement, casters are provided. It allows changing corners and wheelbase.

[0006]

However, in such a conventional steering device, since the bearing housing into which the upper and lower bearings are press-fitted is separate from the upper and lower parts as described above, the machining accuracy of the bearing housing is sufficiently improved. Unless otherwise, it is impossible to align the axes of the upper and lower bearings coaxially. If the machining accuracy is improved, the price of the parts of the bearing housing increases, and if the machining accuracy is decreased, the rotation of the front fork becomes poor and the straight running stability deteriorates.

In addition, since the upper and lower bearings are mounted on the head pipe via bearing housings each having a short axial length, not only the bearing rigidity is low, but also between the bearings (between the bearing housings) during traveling. There is a possibility that the distance of the front fork may be shortened, and there is a concern that rattling may occur at the shaft support portion of the front fork.

In addition, since the number of parts is increased by the upper and lower separate bearing housings and the bearing housing is press-fitted into the head pipe, disassembly and assembly workability is extremely poor. Especially when press-fitting the bearing housing, if the mounting direction is not checked carefully, the mounting of the front fork may not be possible. It may lead to damage and may require replacement.

[0009] In addition, if the bearing housings that are not used are not always stored in an up-and-down set, there are also inconveniences in spare part management that several types of caster angles and types of wheel bases become unknown.

The present invention has been made in order to solve such a problem, and can easily change a caster angle and a wheel base, and also support the front fork without increasing the price of parts. It is an object of the present invention to provide a motorcycle steering device that can support a bearing with high accuracy and rigidity, has a small number of parts, is easy to disassemble and assemble, and easily manages spare parts.

[0011]

According to a first aspect of the present invention, there is provided a motorcycle steering apparatus according to the present invention, comprising: a head pipe provided on a front head of a vehicle body frame; A bearing housing which is formed in a straight tube having an outer diameter dimension that can be closely fitted to the inner diameter portion of the head pipe, and is detachably fixed to the head pipe; and inner peripheral portions at upper and lower ends of the bearing housing. And a pair of upper and lower bearings that rotatably support the steering column of the front fork. The bearing housing separates the bearings whose center axis coincides with the center axis of the bearing and those that are displaced. Prepared.

According to a second aspect of the present invention, in the motorcycle steering system, the entire length of the bearing housing is formed to be longer than the head pipe, and a lower end of the bearing housing is provided on a lower surface of the head pipe. Forming a male screw on the outer peripheral surface of the upper end of the bearing housing while forming the stopper flange to abut, inserting the bearing housing into the inner diameter part of the head pipe from below, and fastening the lock nut to the male screw protruding from the upper end of the head pipe The bearing housing is fixed to the head pipe.

Further, in the motorcycle steering apparatus according to the present invention, the contact surface between the head pipe and the lock nut is formed as a tapered surface centered on the center axis of the head pipe. did.

In the motorcycle steering apparatus according to the present invention, an outer upper fitting surface and an outer lower fitting surface are formed at upper and lower ends of an inner peripheral portion of the head pipe, respectively. And forming an inner upper fitting surface and an inner lower fitting surface at upper and lower ends of an outer peripheral portion of the bearing housing, thereby forming a reduced diameter portion therebetween. The inner upper fitting surface is tightly fitted to the fitting surface, while the inner lower fitting surface is tightly fitted to the outer lower fitting surface. The fitting diameter of the surfaces was set smaller than the fitting diameter of the outer lower fitting surface and the inner lower fitting surface.

Further, the motorcycle steering apparatus according to the present invention is provided with positioning means for defining a position of the bearing housing around the axis with respect to the head pipe.

Further, in the motorcycle steering apparatus according to the present invention, as described in claim 6, the element on the bearing housing side of the positioning means is provided at two positions at 180 ° intervals in the circumferential direction of the bearing housing. Provided.

According to the first aspect of the present invention, the center position of the bearing with respect to the center axis of the head pipe is displaced by replacing the bearing housing, so that the caster angle and the wheel base are changed. In this configuration, the upper and lower bearings are mounted on the upper and lower ends of one straight tubular bearing housing,
Since the bearing mounting portion of the bearing housing can be machined up and down simultaneously, the axes of the upper and lower bearings are aligned coaxially with extremely high accuracy, and each bearing is supported with high rigidity.

Further, when the steering apparatus for a motorcycle is constructed as in claim 2, the entire bearing housing can be attached to and detached from the head pipe simply by attaching and detaching the lock nut. improves.

Further, according to the third aspect of the present invention, when the lock nut is tightened, the lock nut and the bearing housing are centered with respect to the head pipe, and the bearing housing is connected to the head pipe. Can be assembled with high accuracy.

According to the fourth aspect of the present invention, when the bearing housing is attached to and detached from the inner diameter portion of the head pipe from below,
The fitting between the head pipe and the bearing housing except where the inner upper fitting surface and the inner lower fitting surface of the bearing housing are fitted to the outer upper fitting surface and the outer lower fitting surface of the head pipe, respectively. Since the connection is loosened, it is possible to easily and quickly insert and remove the bearing housing, and the detachability of the bearing housing is improved.

According to the fifth aspect of the present invention, the position of the bearing housing around the axis with respect to the head pipe is quickly and accurately determined, thereby improving the assemblability of the steering device.

Further, by constructing the steering apparatus for a motorcycle according to claim 6, the bearing housing can be used from two directions by rotating the bearing housing by 180 ° with respect to the head pipe, thereby displacing the axis of the bearing. In the bearing housing, the amount of displacement can be properly used in two ways, and the number of bearing housings as spare parts can be reduced.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a left side view showing a vehicle body configuration of a motorcycle to which a steering device according to the present invention is applied.

In the body frame 2 of the motorcycle 1, a pair of left and right thick main pipes 4 extend diagonally downward and rearward from a head pipe 3 provided on the frontal head, and are connected to a pair of left and right frame bodies 5. The rear frame 6 extends rearward from the upper part of the vehicle. The left and right main pipes 4 and the frame body 5 are connected by a bridge member (not shown) extending in the vehicle width direction.

The head pipe 3 is provided so that its upper end is inclined rearward. A front fork 8 is pivotally supported on the head pipe 3 so as to be able to turn left and right, and a front wheel 9 is pivotally supported at the tip. The head pipe 3 is a component of a steering device 10 described later, and its inclination angle is set to, for example, 24 ° with respect to a vertical line. Note that a steering handlebar 11 is integrally provided above the front fork 8.

On the other hand, a pivot shaft 12 extending in the vehicle width direction is provided between the left and right frame bodies 5, and a swing arm 13 is rotatably supported on the pivot shaft 12, and a rear wheel is provided at a rear end thereof. 14 is supported. Swing arm 13
A cushion unit 15 is provided at the base of the swing arm 13, whereby the rotational shock of the swing arm 13 is attenuated, and the swing arm 13 is restored to the home position. An engine (not shown) is mounted so as to straddle the main pipe 4 and the frame body 5, and its output is transmitted to the rear wheels 14 by a chain or the like.

FIG. 2 shows a steering device 10 according to the present invention.
It is a longitudinal section showing one embodiment. This steering device 10 is configured as follows.

First, a bearing housing formed in a straight tubular shape is provided on the inner diameter portion of the head pipe 3 of the body frame 2.
16 is detachably fixed. 3 and 4 are longitudinal sectional views each showing the head pipe 3 and the bearing housing 16 alone. FIGS. 5 and 6 are a view taken in the direction of arrows V and VI in FIG. 2, respectively.

The overall length of the bearing housing 16 is set to be longer than the head pipe 3, and a stopper flange 17 is formed at the lower end thereof, while a male screw is formed on the outer peripheral surface at the upper end.
18 are formed. Bearing mounting portions 19 and 20 whose inner diameters are increased by one step are formed in the inner peripheral portions of the upper and lower ends of the bearing housing 16.
22 is attached by press fitting or the like.

On the other hand, an outer upper fitting surface 24 is formed at the upper end of the inner peripheral surface of the head pipe 3, and an outer lower fitting surface 25 is formed at the lower end. The inner diameter therebetween is expanded to form an enlarged diameter portion 26.

The outer diameter of the bearing housing 16 is set to a size that can be closely fitted to the inner diameter of the head pipe 3. That is, an inner upper fitting surface 27 that is closely fitted to the outer upper fitting surface 24 of the head pipe 3 is formed on the outer peripheral portion of the upper end of the bearing housing 16, and the outer lower fitting portion of the head pipe 3 is formed on the outer peripheral portion of the lower end. An inner lower fitting surface 28 that is closely fitted to the mating surface 25 is formed. This inner upper mating surface 27
The outer diameter between the inner surface and the inner lower fitting surface 28 is reduced to form a reduced diameter portion 29.

Here, the fitting diameter D1 of the outer upper fitting surface 24 and the inner upper fitting surface 27 is slightly smaller than the fitting diameter D2 of the outer lower fitting surface 25 and the inner lower fitting surface 28 ( For example
0.5 mm to 1.0 mm). The male screw 18 is formed on the outer peripheral surface above the inner upper fitting surface 27.

The bearing housing 16 is a head pipe 3
Is inserted from below into the inside diameter of the stopper flange.
17 is pushed until it comes into contact with the lower surface of the head pipe 3. And a male screw projecting from the upper end of the head pipe 3
A lock nut 31 is fastened to the portion 18, whereby the bearing housing 16 is firmly fixed to the inner diameter of the head pipe 3. 7 and 8 are a side view and a bottom view, respectively, showing a lock nut 31 alone in a vertical section.

The contact surfaces 32 and 33 (see FIGS. 3 and 7) where the head pipe 3 and the lock nut 31 are in close contact with each other are formed in a tapered surface centering on the center axis C of the head pipe 3. For this reason, even if there is a gap between the outer upper fitting surface 24 and the inner upper fitting surface 27, as the lock nut 31 is tightened, the lock nut 31 and the bearing housing 16 move with respect to the head pipe 3. The bearing housing 16 is aligned with the head pipe 3 with high accuracy. The same centering action can be obtained even if the upper surface of the stopper flange 17 and the lower surface of the head pipe 3 are formed as tapered surfaces.

As shown in FIGS. 2 and 5, the lock nut 31 is provided with a detent 34. This detent 34
As shown in FIGS. 9 and 10, for example, the component is made of a sheet metal press, and is fixed to the rear portion of the head pipe 3 by two screws 35. A plurality of claws 36 adjacent to the outer periphery of the lock nut 31 are formed on the rotation stopper 34.
Are fitted into grooves 37 (grooves into which the claws of the fastening tool are engaged) formed on the outer periphery of the lock nut 31 to prevent the lock nut 31 from loosening.

Further, as positioning means for defining the position of the bearing housing 16 about the axis with respect to the head pipe 3, for example, as shown in FIGS. The above-mentioned knock pin is attached to 16 stopper flanges 17
A U-shaped notch 40 that fits into 39 is formed. By fitting the notch 40 to the dowel pin 39, the bearing housing 16 is accurately positioned with respect to the head pipe 3, and the co-rotation of the bearing housing 16 when the lock nut 31 is fastened is restricted, so that the assembling property is improved. Greatly improved.

In the front fork 8, the left and right fork pipes 42 (see FIG. 1) are fixed in parallel by two upper and lower upper brackets 43 and a lower bracket 44, and a steering wheel is provided between the upper bracket 43 and the lower bracket 44. The column 45 has a fixed structure.

Then, the steering column 45 is inserted into the inner diameter of the bearing housing 16, and the bearings 21, 22 provided at the upper and lower ends of the bearing housing 16 are provided.
Supported by Thereby, the entire front fork 8 is pivotally attached to the head pipe 3 of the body frame 2. Note that a dust cap 46 is attached to the upper part of the lock nut 31.

The bearing housing shown in FIG. 2 (FIG. 4)
Reference numeral 16 indicates that the center axes Ca of the upper and lower bearings 21 and 22 with respect to the center axis C coincide. For this reason, the caster angle α of the front fork 8 is set to the same angle as the inclination angle of the head pipe 3, that is, 24 ° in the present embodiment.

In the bearing housings 16A and 16B shown in FIGS. 11 and 12, the axis Ca of the bearings 21 and 22 with respect to the center axis C is displaced.

In the bearing housing 16A shown in FIG. 11, the axis Ca of the bearings 21, 22 is inclined forward by θ ° with respect to the center axis C. The reference point for this slope is
For example, it is the center point P at the lower end of the bearing housing 16A. If the angle of θ is 1 °,
The caster angle α of the front fork 8 is set to 23 ° which is obtained by subtracting 1 ° from 24 ° which is the inclination angle of the head pipe 3.

In this bearing housing 16A, U-shaped cutouts 40, which are elements of the positioning means, are formed at two positions in the circumferential direction of the stopper flange 17 at an angular interval of 180 °. Therefore, the bearing housing 16A can be rotated from the head pipe 3 by 180 ° and used from two directions.

When the bearing housing 16A is turned by 180 ° from the state shown in FIG. 11, the axis Ca of the bearing is inclined backward by θ ° with respect to the center axis C. If the value of θ is, for example, 1 °, For example, the caster angle α of the front fork 8 is set to 25 ° by adding 1 ° from the normal 24 °.

On the other hand, the bearing housing 16 shown in FIG.
In B, the axis Ca of the bearing is displaced forward by a dimension x in parallel with the center axis C thereof. If the value of x is, for example, 5 mm, the wheel base of the motorcycle 1 is extended by 5 / cos 24 ゜ = 5.5 mm as compared with the case of the bearing housing 16 shown in FIG. 2 (FIG. 4).

In the case of the bearing housing 16B,
The U-shaped notch 40 extends in the circumferential direction of the stopper flange 17 1
The bearing housing 16B is attached to the head pipe 3 by 180
゜ By rotating, the axis Ca of the bearing can also be displaced rearward parallel to the center axis C by the dimension x. In this case, if the value of x is 5 mm, the wheelbase of the motorcycle 1 is reduced by 5.5 mm.

The steering apparatus configured as described above
10, the bearing housing 16 (16A and 16B)
By changing the position, the position of the axis Ca of the bearings 21 and 22 with respect to the center axis C of the head pipe 3 is changed, so that the caster angle α of the front fork 8 and the wheel base can be easily changed.

The steering device 10 has a straight tubular bearing housing 16 in which the upper and lower bearings 21 and 22 are one.
(16A, 16B) are mounted on both upper and lower ends, and bearing mounting parts where each bearing 21, 22 is held
Since 19 and 20 can be processed simultaneously by turning or the like, the axis Ca of each of the bearings 21 and 22 can be coaxially aligned with extremely high machining accuracy, and the bearing housing
No price increase of 16

Moreover, since the bearings 21, 22 are held at both ends of the bearing housing 16 (16A, 16B) having a long overall length, the support rigidity of the bearings 21, 22 is remarkably increased. The bearing housing 16 (16A,
Since 16B) is a single part, the number of components of the steering device 10 is small, disassembly and assembly workability is good, and
It is also easy to manage unused bearing housings 16 (16A, 16B) as spare parts.

The bearing housing 16 (16A, 16A)
B) is fixed to the head pipe 3 by a lock nut 31 and is not fixed by press fitting or the like as in the related art.
This greatly contributes to the improvement of assembly workability.

As described above, the enlarged diameter portion 26 is formed between the outer upper fitting surface 24 and the outer lower fitting surface 25 of the head pipe 3, and the bearing housing 16 (16A, 16A) is formed.
A reduced diameter portion 29 is formed between the inner upper fitting surface 27 and the inner lower fitting surface 28 of 16B). Also, the outer upper mating surface 24
And the fitting diameter D1 of the inner upper fitting surface 27 is the outer lower fitting surface.
It is set smaller than the fitting diameter D2 of the inner lower fitting surface 28 and the inner lower fitting surface 28.

For this reason, the bearing housing 16 (16
A, 16B) when attaching and detaching the inner diameter of the head pipe 3 from below, the bearing housing 16 (16A, 16B)
The inner upper mating surface 27 is the outer lower mating surface of the head pipe 3.
25 and the inside of the enlarged diameter portion 26, and the outer lower fitting surface 25 of the head pipe 3 is also
(16A, 16B) easily passes through the inside upper fitting surface 27 and the outside of the reduced diameter portion 29.

Therefore, while the fitting between the head pipe 3 and the bearing housing 16 (16A, 16B) is set densely, the mounting of the bearing housing 16 (16A, 16B) on the head pipe 3 can be prevented from galling. Prevent,
The bearing housing 16 (16A, 16B) can be easily and quickly attached to and detached from the head pipe 3.

Further, bearing housings 16A, 16B
As described above, the U-shaped notches 40 are provided at two positions in the front and rear direction at an angular interval of 180 ° in the circumferential direction of the stopper flange 17 as described above, and the bearing housings 16A and 16B are provided.
By rotating the shaft 180 ° with respect to the head pipe 3, the displacement amount of the bearing axis Ca can be used in two ways, so that two settings can be made with one bearing housing 16A or 16B, and as a spare part The cost can be reduced by reducing the number of bearing housings 16A and 16B, and spare parts management can be facilitated.

[0054]

As described above, the steering head device for a motorcycle according to the present invention comprises a head pipe of a body frame, a bearing housing which is closely fitted to the head pipe and is detachably fixed. A pair of upper and lower bearings mounted on the upper and lower ends of the bearing housing to rotatably support a steering column of a front fork, wherein the bearing housing has the center axis of the bearing aligned with its central axis. By displacing the bearing housing separately, the center axis position of the bearing with respect to the center axis of the head pipe can be displaced by replacing the bearing housing, making it possible to easily change the caster angle and wheelbase, and to reduce the cost of parts. Bear that supports the front fork without raising It can be supported with high accuracy and rigidity ring.

Further, in the motorcycle steering head device according to the present invention, the entire length of the bearing housing is formed longer than the head pipe, and a stopper flange is formed at the lower end of the bearing housing, while the outer peripheral surface of the upper end of the bearing housing is formed. Since the bearing housing is fixed to the head pipe by inserting a bearing housing from below into the inner diameter part of the head pipe and fastening the lock nut to the male screw, it is only necessary to attach and detach the lock nut. The whole bearing housing can be attached to and detached from the head pipe,
Thereby, the disassembly and assemblability of the steering device can be improved.

Further, in the steering head device for a motorcycle according to the present invention, the contact surface between the head pipe and the lock nut is formed as a tapered surface centered on the center axis of the head pipe. The bearing housing can be accurately assembled to the head pipe by performing the centering action.

In the steering head device for a motorcycle according to the present invention, an outer upper fitting surface and an outer lower fitting surface are formed at upper and lower ends of an inner peripheral portion of the head pipe, respectively, and an enlarged diameter portion is formed therebetween. On the other hand, an inner upper fitting surface and an inner lower fitting surface are respectively formed at upper and lower ends of an outer peripheral portion of the bearing housing to form a reduced diameter portion therebetween, and the inner upper fitting surface is formed on the outer upper fitting surface. While the mating surfaces are tightly fitted, the inner lower fitting surface is tightly fitted to the outer lower fitting surface, and the outer upper fitting surface and the inner upper fitting surface have a fitting diameter of the outer lower fitting surface. Since the fitting diameter is set smaller than the fitting diameter of the fitting surface and the inner lower fitting surface, the detachability when the bearing housing is attached to and detached from the inner diameter portion of the head pipe from below is improved, so that the disassembling and assembling of the steering head device is further improved. To improve Can.

Further, in the steering head device for a motorcycle according to the present invention, since the positioning means for defining the position of the bearing housing around the axis with respect to the head pipe is provided, the position of the bearing housing around the axis with respect to the head pipe is determined. Positioning can be performed quickly and accurately, which can further contribute to improvement in assembly.

Further, in the steering head device for a motorcycle according to the present invention, since the elements of the positioning means on the bearing housing side are provided at two positions at 180 ° intervals in the circumferential direction of the bearing housing, the axial center of the bearing is provided. Can be used in two different ways, thereby reducing the number of bearing housings as spare parts, thereby reducing costs and facilitating the management of spare parts.

[Brief description of the drawings]

FIG. 1 is a left side view showing a vehicle body configuration of a motorcycle to which a steering device according to the present invention is applied.

FIG. 2 is a longitudinal sectional view of a steering device showing one embodiment of the present invention.

FIG. 3 is a longitudinal sectional view showing the head pipe alone.

FIG. 4 is a longitudinal sectional view showing the bearing housing alone.

FIG. 5 is a view taken in the direction of the arrow V in FIG. 2;

FIG. 6 is a view taken in the direction of arrow VI in FIG. 2;

FIG. 7 is a side view partially showing a lock nut alone in a longitudinal section.

FIG. 8 is a bottom view of the lock nut alone.

FIG. 9 is a plan view of a detent.

FIG. 10 is a longitudinal sectional view taken along the line XX of FIG. 9;

FIG. 11 is a longitudinal sectional view showing an example of use of a bearing housing incorporated in a steering device.

FIG. 12 is a longitudinal sectional view showing a modified use example of a bearing housing incorporated in a steering device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Motorcycle 2 Body frame 3 Head pipe 8 Front fork 10 Steering device 16 Bearing housing 17 Stopper flange 18 Male screw 21, 22 Bearing 24 Outer upper fitting surface 25 Outer lower fitting surface 26 Large diameter portion 27 Inner upper fitting surface 28 Inner lower fitting surface 29 Reduced diameter portion 31 Lock nut 32, 33 Adhesion surface between head pipe and lock nut 39 Dowel pin constituting positioning means 40 Notch constituting positioning means 45 Steering column C Center axis of head pipe and bearing housing Ca Shaft core of bearing D1 Fitting diameter of upper fitting surface and inner upper fitting surface D2 Fitting diameter of lower fitting surface and inner lower fitting surface

Claims (6)

[Claims] 1. A head pipe 3 provided on the front head of a vehicle body frame 2 and a straight pipe having an outer diameter dimension capable of being closely fitted to an inner diameter portion of the head pipe 3. A bearing housing 16 detachably fixed to the bearing housing; and a pair of upper and lower bearings 21 mounted on inner peripheral portions of upper and lower ends of the bearing housing 16 to rotatably support a steering column 45 of the front fork 8.
22. The steering device for a motorcycle, wherein the bearing housing 16 is provided with a shaft housing Ca whose center axis C coincides with the center axis C thereof and a shaft housing Ca displaced. 2. The bearing housing 16 has a total length longer than that of the head pipe 3, and a lower end of the bearing housing 16 is provided with a stopper flange 17 which is in contact with a lower surface of the head pipe 3.
An external thread 18 is formed on the outer peripheral surface of the upper end of the head pipe 3, the bearing housing 16 is inserted into the inner diameter portion of the head pipe 3 from below, and a lock nut 31 is fastened to the external thread 18 protruding from the upper end of the head pipe 3. The steering device for a motorcycle according to claim 1, wherein the steering wheel is fixed to the head pipe 3. 3. The head pipe 3 and the lock nut.
The motorcycle steering apparatus according to claim 2, wherein the contact surfaces (32, 33) of the (31) are tapered around the center axis (C) of the head pipe (3). 4. An outer upper fitting surface 24 and an outer lower fitting surface 25 are respectively formed at upper and lower ends of an inner peripheral portion of the head pipe 3 to form an enlarged diameter portion 26 therebetween, while the bearing housing 16 is formed. An inner upper fitting surface 27 and an inner lower fitting surface 28 are formed at upper and lower ends of the outer peripheral portion, respectively, to form a reduced diameter portion 29 therebetween, and the inner upper fitting surface 27 is formed on the outer upper fitting surface 24. While the inner lower fitting surface 28 is closely fitted to the outer lower fitting surface 25, and the fitting diameter D1 of the outer upper fitting surface 24 and the inner upper fitting surface 27 is adjusted. The motorcycle steering device according to any one of claims 1 to 3, wherein the diameter of the outer lower fitting surface (25) and the inner lower fitting surface (28) is set to be smaller than D2. 5. The motorcycle steering apparatus according to claim 1, further comprising positioning means for defining a position of the bearing housing 16 around the axis with respect to the head pipe 3. 6. The motorcycle steering apparatus according to claim 5, wherein the positioning means includes two elements (40) on the bearing housing 16 side at intervals of 180 ° in the circumferential direction of the bearing housing 16.