JPS6344594B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a front fork for a two-wheeled vehicle.

For general motorcycle front forks, the friction of sliding surfaces such as bearings and pistons is
It has a great influence on the quality of its operation.

FIG. 1A shows a schematic diagram of a conventional telescopic front fork, and the sliding friction force is calculated as follows.

First, in the figure, 1 is an inner tube, 2 is an outer tube, 3 is a piston part, 4 is a bearing part, and 5 is an axle support part. Make sliding contact.

As is well known, this front fork is attached to the vehicle body at a predetermined inclination angle (caster angle) θ, so the load reaction force W from the ground contact surface is
produces an axial force F and a perpendicular force P.

The axial component force F compresses the internal suspension spring and increases the overlap between the inner tube 1 and the outer tube 2.

On the other hand, the lateral component P acts as a bending force on the outer tube 2, and the piston part 3 and the bearing part 4
Reaction forces Q and R are generated respectively.

FIG. 1B schematically shows these. Analyzing the relationship between the acting forces based on this figure shows that since the component force P of the axle support part 5 attempts to deflect the outer tube 2, the direction of the reaction force Q of the piston part 3 is reversed. On the other hand, since the piston part 3 serves as a fulcrum, the reaction force of the bearing part 4 becomes a reaction force R in the opposite direction to the reaction force Q, that is, in the same direction as the component force P.

Since the total values of these reaction forces in different directions are equal, P+R=Q (1-1) Now, consider the moment balance around point R and find Q and R.

First, the distance from the bearing part 4 to the axle support part 5 is L, the distance from the bearing part 4 to the piston part 3 is S,
When the distance from the piston part 3 to the axle support part 5 is l, the moment due to the component force P and the moment due to Q are balanced, so Q(L-l)=PL...(1-2) Therefore, Q=PL /L-l...(1-3) Now, from equation (1-1) above, R=Q-P...(1-1') Substituting equation (1-3) into this, R=PL/ L-l-P=Pl/L-l...(1-4) The frictional force _f1 between the piston part 3 and the bearing part 4
If f ₂ is the friction coefficient μ ₁ and μ ₂ respectively, then f ₁ = μ ₁ Q … (1-5) f ₂ = μ ₂ R Substantially μ ₁ ≒ μ ₂ , so μ ₁ = Letting μ ₂ = μ, and finding the total frictional force f _T , f _T = f ₁ + f ₂ …(1-6) In addition to this, equations (1-3), (1-4), and (1-5) are used. Substituting and organizing, f _T =μ(Q+R)=μ(PL/L-l+Pl/L-l) =L+l/L-lμ・P=(1+2l/L-l)μ・P=(1+2l/ S)μ・P...(1-7) Therefore, the operability of the front fork is
The smaller f _T is, the better it is, but in conventional front forks, S and l constantly change reciprocally, and especially when operating on the rebound side, S becomes smaller while l becomes larger. , f _T becomes very large, and the actuation is significantly inhibited.

The present invention solves this problem by ensuring that the sliding friction is always constant regardless of the expansion and contraction of the front fork.
Moreover, it is an object of the present invention to provide a front fork for a two-wheeled vehicle in which the frictional force itself can be relatively reduced.

For this purpose, in the present invention, two inner tubes are provided in the outer tube and are spaced apart from each other in the axial direction.
A state in which the outer tube is inserted into the two bearing parts and supported so as to be able to slide freely relative to each other, while an axle support part is provided on the outer tube so as to be located between the two bearing parts, and it is attached to the vehicle body at a predetermined caster angle. The line of action of the load reaction force from the ground contact surface acting on the axle is made to pass between two bearings provided axially apart on the outer tube, and the inner tube and outer tube are They were connected by a hydraulic damper installed in the

First, regarding the operating principle of the present invention, Fig. 2 A and B
I will explain based on this.

In the figure, 10 indicates an inner tube, 11 indicates an outer tube, and the outer tube 11
The inner tube 10 is slidably supported by bearings 12 and 13 at both ends.

The inner tube 10 is connected to the vehicle body at its upper end, while the axle support portion 14 of the outer tube 11 is set to be located between the bearing portions 12 and 13.

In other words, the line of action of the load reaction force from the ground contact surface acting on the axle is located between the two bearing portions 1 of the outer tube 11.
Set it so that it passes between 2 and 13. In this structure, if we calculate the sliding friction force f _T ′ of the front fork in the same way as in the previous case, we get:
It will look like this:

However, from the axle support part 14 to one bearing part 12
(upper part) is L, and the distance to the other bearing part 13 (lower part) is l, respectively.
It is the same as in FIG. 1B, such as setting the reaction forces of 13 to R and Q.

In this case, the points of action of the lateral component P are R and Q
Since the reaction forces R and Q are located between the two sides, the directions of these reaction forces R and Q are both equal and opposite to the component force P.

Analyze in the same manner as above using these conditions.

Q+R=P...(2-1) From the moment balance around point R, Q(L+l)=PL...(2-2) ∴Q=PL/L+l...(2-3) From equation (2-1), calculate R. Ask for this (2-3)
Substituting the formula and rearranging it, R=P-Q=P(L+l)/L+l-PL/L+l=Pl/
L+l...(2-4) Here, if the frictional forces at the bearings 12 and 13 are f ₁ and f ₂ , respectively, and the total frictional force f _T ′ is calculated in the same manner as in equation (1-6) above, f _T ′ = f ₁ + f ₂ = μ (Q + R) … (2-6) Organizing this, f _T ′ = μ (Q + R) = μ (PL/L + l + Pl/L + l) =
μ·P (2-7) As a result, f _T ′ becomes μ·P, which always takes a constant value regardless of the stroke of the front fork.

Comparing it with the above equation (1-7), we find that f _T = (1+2l/S) μ・P … (1-7) f _T ′= μ・P … (2-7), and here Since (1+2l/S)>1, f _T > f _T ' always holds true.

In other words, the sliding friction force f _T ' of the present invention is always smaller than that of the conventional front fork, and therefore the operability is improved accordingly.

Also, from f _T ′=μ・P, its value always takes the same value regardless of the expansion and contraction of the front fork, so
Operability does not deteriorate depending on the extended or contracted position.

Next, specific embodiments of the present invention will be described based on FIGS. 3 and 4.

In the figure, 10 is an inner tube whose upper end is attached to the vehicle body via a bracket 16, and 11 is an outer tube connected to the axle side. In this embodiment, the axle support is located at a position offset from the tube axis. 14 is formed.

Of course, this axle support part 14 is located between the bearing parts 12 and 13 of the outer tube 11.

The bearing parts 12 and 13 are provided at both ends of the outer tube 11, and are each secured to the outside by a snap ring 18 via a seal 17.

Further, a stopper sleeve 21 having a flange portion 20 is screwed onto the protruding lower end of the inner tube 10, and the inner tube 10 and the outer tube 1
We are doing the 1st stop.

A slider 22 is housed inside the inner tube 10 so as to be able to slide freely.
is connected to the outer tube 11 via a bolt 23.

Therefore, a pair of guide grooves 24 extending in the axial direction are formed on the side surface of the inner tube 10, and the bolts 23 are inserted into the guide grooves 24.

Note that a ring-shaped collar 25 and a rubber bush 26 are fitted around the bolt 23 in this order.

Suspension springs 27 and 28 are interposed between both surfaces of the slider 22 and the inner tube 10, acting on the compression side and the expansion side, respectively.

The upper spring 27 is interposed between the collar 29 fitted to the upper stepped portion of the inner tube 10, and the lower spring 28 is interposed between the stopper sleeve 2
1.

Next, a hydraulic damper 32 is attached via a pin 33 between a bracket 30 protruding from one side of the outer tube 11 and a bracket 31 protruding from the same side of the inner tube 10.

This hydraulic damper 32 damps vibrations of the inner tube 10 relative to the outer tube 11.

In the above configuration, the figure shows inner tube 1.
0 indicates the state of moving to the maximum extension side,
When a load is actually applied, the compression side spring 2
The inner tube 10 moves relatively downward while deflecting it until it is in equilibrium with the inner tube 7.

When receiving thrust from the road surface from its equilibrium position and operating on the compression side, the outer tube 1
1 moves upward while further compressing the spring 27 relatively, and the hydraulic damper 32 also contracts accordingly.

In the next extension stroke, the hydraulic damper 32 produces a predetermined damping effect and quickly damps free vibrations caused by the restoration of the compressed spring 27.

Regarding these damping operations, there is no difference from a normal front fork. As for its operability, as mentioned above, since the sliding friction force can be significantly reduced, extremely good and stable characteristics can be obtained.

By the way, in the present invention, as shown in FIG. 5A, the inner tube 10 and the outer tube 11 are
The backlash x of the axle in the longitudinal direction based on the sliding clearance δ between the axle and the axle is as follows, and it can be seen that it is much smaller than that of the conventional type shown in FIG. 5B. First, in the present invention, δ/L+l=x/L...(3-1) ∴x=L/L+lδ...(3-2) Here, since L/L+l<1, x<δ...(3-3) On the other hand, in the conventional example, δ/S=x'/S+l=x'/L...(4-1) ∴x'=L/Sδ...(4-2) Here, L in the entire operating range >S, so L/S>1, and x'>δ...(4-3) Therefore, from equations (3-3) and (4-3), x<x', and at the axle position The backlash is also reduced accordingly, and smooth operating characteristics can be obtained.

By the way, in the embodiments shown in FIGS. 3 and 4, the axle support portion 14 is offset from the fork axis;
The friction that affects its actuation is the same as in the case of the axis as follows.

This will be explained with reference to FIG.

Assuming that the amount of eccentricity from the axis of the axle support portion 14 is H, f _T is determined using the same method as described above.

First, from the moment balance around point R, PL=Q(L+l)+FH...(5-2) Q=PL-FH/L+l...(5-3) R=P-Q=P(L+l)/L+l-PL −FH/L+l=
Pl+FH/L+l...(5-4) Therefore, f _T = δ(Q+R)=μ(PL-FH/L+l+Pl+FH/L+
l) = μ・P (5-7) In this way, even if the axle support portion 14 is made eccentric, the operability will not deteriorate at all, and therefore the axle support portion 14 can be freely eccentric from the axis depending on the usage conditions. be able to.

As described above, according to the present invention, the operability of the front fork is greatly improved, and stable and smooth extension/contraction operation can always be obtained in the entire operating range.

In addition, separate hydraulic dampers are installed externally to the inner and outer tubes, so compared to installing them internally, there are fewer problems with malfunctions or damage due to mud and dust entering from the lower opening of the outer tube. The structure is simple and the damping characteristics can be freely selected.Furthermore, since the suspension spring is placed inside the inner tube, there is no interference with other parts and good operability can be maintained at all times.

[Brief explanation of the drawing]

Figures 1A and B are a schematic diagram and load distribution diagram of a conventional front fork, Figures 2A and B are a schematic diagram and load distribution diagram of the present invention, and Figure 3 is a cross-section of an embodiment of the present invention. Figure 4 is a sectional view taken along the - line,
5A and 5B are explanatory views showing the backlash of the present invention and the conventional front fork, and FIG. 6 is an explanatory view of the effect of load distribution. 10... Inner tube, 11... Outer tube, 12, 13... Bearing section, 14... Axle support section, 21... Stopper sleeve, 22... Slider, 23... Bolt, 24... Guide groove,
27, 28...Spring, 32...Hydraulic damper.

Claims (1)

[Claims] 1. The inner tube is inserted into two bearing parts provided in the outer tube separated from each other in the axial direction and supported so as to freely slide relative to each other, while the axle is supported in the outer tube so as to be located between the two bearing parts. The inner tube and the outer tube A front fork for a two-wheeled vehicle, characterized in that the tubes are connected to the tubes by a hydraulic damper disposed on the outside of the tubes.