JPH01273779A - Front fork for motorbicycle - Google Patents

Abstract

PURPOSE:To enable shorting of a stroke without worsening a riding feeling, by a method wherein cushioning spring is formed with upper and lower springs disposed in series through a spring support seat, and an auxiliary spring disposed to the one of the springs and having both ends supported to the spring support seat. CONSTITUTION:An upper string 20 having a spring contact k1 and a lower spring 21 having a spring constant k2 are disposed through a spring support seat 22 between a flange part 19a of a spring stopper 19 and a flange part 7a of an impact absorbing cylinder 7. An auxiliary spring 23 having a spring constant k3 is supported on the upper spring 20 side to the inner hole of the spring support seat 22 through the spring support seats 22 and 24. The front fork of a motor bicycle is formed so as to have spring characteristics in which with the increase in a load, a spring constant is gradually increased in a way that a spring constant is increased in a multistage manner. Thereby, a spring change at each of points of inflection (d) and (e) can be decreased, and a stroke responding to a maximum load Fmax can be reduced from (b) to (c).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a front fork for a motorcycle, and in particular to a fork pipe in which an inner tube is inserted into an outer tube so as to be slidable relative to each other so that the fork pipe can be expanded and contracted. This invention relates to a front fork for a telescopic motorcycle, in which a buffer spring and a shock absorbing cylinder are housed.

[Prior art] - In normal conditions with relatively low loads, the front fork of a motorcycle has a small spring constant and a large load in order to fully demonstrate its cushioning ability and provide a comfortable ride. In order to suppress the increase in the total stroke amount and reduce the pitching motion of the vehicle body while ensuring the maximum load, it is required to have progressive spring characteristics such as increasing the spring constant.

For this reason, buffer springs with non-linear spring characteristics have been considered in which the spring constant increases continuously as the stroke increases. In order to obtain this non-linear spring characteristic, -a changes the diameter of the coil spring and the diameter of the wire used in the front fork, and changes the number of turns of the coil spring.

However, changing the spring wire diameter and number of turns in this way requires a large amount of wire and requires a special spring structure, which not only increases cost but also increases weight. Put it away.

Therefore, a front fork equipped with a buffer spring that uses a penetrating coil spring to ensure cushioning ability under low loads and suppresses the increase in stroke under high loads has been considered. As an example of such a front fork, conventionally, for example, Utility Model Publication No. 50-2172
The one shown in Publication No. 0 is known.

As is clear from FIG. 5, the front fork shown in this publication includes a buffer spring 02 housed in a fork pipe 01, and this spring 02 is divided into an upper spring 02a and a lower spring 02b. has been done. A spring receiving seat 03 is interposed between the two springs 02a and 02b. The compression amount of the upper spring 02a is the spring seat 03.
is regulated to a predetermined value or less by contacting the stopper 04.

In the front fork configured in this way, both the upper and lower springs 02a and 02b are compressed until the spring receiving seat 03 comes into contact with the stopper 04, so the spring constant is relatively small, and the spring receiving seat 03 comes into contact with the stopper 04. After contact, only the lower spring 02b is compressed, so the spring constant increases.

That is, the spring characteristic of the front fork is such that the spring constant increases by one step at the inflection point a as the stroke increases, as shown by the dashed line in FIG.

[Problems to be Solved by the Invention] However, in this publication, in order to shorten the stroke from b to C while ensuring the maximum loads F, IA, and I, the stroke shown by the broken line in FIG. If the spring constant after the inflection point a is made much larger than that before the inflection point a, as shown in the figure, the load will not rise smoothly at the inflection point a, causing a bottoming out problem and poor riding comfort. turn into. For this reason, the spring constant after the inflection point a cannot be made very large. Since there is a limit to how thick the spring constant can be, there is also a limit to how short the stroke can be.

Therefore, the front fork as shown in the above-mentioned publication cannot reliably and fully meet the above-mentioned requirements for spring characteristics.

The present invention was made in view of these circumstances, and its purpose is to provide a front fork that can shorten the stroke without deteriorating riding comfort and can be manufactured at low cost. .

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a fork vibro in which an inner tube 6a is inserted so as to be movable relative to an outer tube 6b so as to be extendable and retractable; It is equipped with a buffer spring 25 and a shock absorption cylinder 7 housed in the fork vibro, and when the front wheel 3 receives an impact force, the shock force is absorbed and alleviated by the buffer spring 25 and the shock absorption cylinder 7. In the front fork 2 of a two-wheeled motor vehicle, the buffer spring 25 is provided in the front fork 2. 1 dj spring 25 is an upper spring 20 and a lower spring 21 that are arranged in series via a spring receiving seat 22 between the fork pole 10 fixed to the upper end of the fork vibro and the shock absorbing cylinder 7. and an auxiliary spring 23 disposed on at least one side of the upper spring 20 and the lower spring 21, with one end supported by the spring receiving seat 22 and the other end supported by the other spring receiving seat 24. , said side spring receiver U seat 22.24
One end is fixed to the fork pole 10, the other end is slidably fitted to the piston rod 11 connected to the piston 13 in the shock absorbing cylinder 7, and the fork bolt 10 is fixed to the both spring receiving seats. It is characterized in that a spring stopper 19 is provided opposite either one of 22 and 24.

C action] In the front fork of the motorcycle according to the present invention having such a configuration, the spring constant of the buffer spring at high loads is relatively thick compared to the spring constant at low loads (even if set, these springs Since a spring constant is set between the constants, the spring constant becomes thicker (does not change) at each inflection point.

Therefore, the load rises smoothly at the inflection point, and the front fork does not bottom out.

Since the spring constant under high loads is set to a large value, the total stroke of the front fork becomes shorter.

Further, when the front fork strokes, the spring receiving seat supporting the winter spring moves while being guided by the piston rod of the piston of the shock absorbing cylinder. Therefore, the spring receiver does not move sideways (moves smoothly), so the spring receiver and the auxiliary spring do not interfere with the upper spring or the lower spring.

E. Embodiment Embodiments of the front fork of a motorcycle according to the present invention will be described below with reference to the drawings. 1 and 2 show an embodiment of the present invention, FIG. 1 is a side view of a motorcycle to which an embodiment of the front fork of the present invention is applied, and FIG. 2 is a side view of a motorcycle to which an embodiment of the front fork of the present invention is applied. FIG. 1 is a cross-sectional view taken along the line ■-■ in FIG.

As shown in FIG. 1, the motorcycle includes a main frame 1, a front fork 2 is supported at the front end of the main frame 1, and a front wheel 3 is supported by the front fork 2. A rear arm 4 is supported near the rear end of the main frame 1 so as to be slidable in the vertical direction, and a rear wheel 5 is supported on this rear arm 4.

As shown in FIG. 2, the front fork 2 includes a fork vibro in which an inner tube 6a is slidably inserted into an outer tube 6b so that the front fork 2 is extendable and retractable. A shock absorbing cylinder 7 is housed across the inner tube 6a and the outer tube 6b, and its lower end is fixed to the bottom of the outer tube 6b with a bolt 9. And, the inner tube 6a is capable of relative sliding along the fJi shock absorbing cylinder 7 by means of a bearing 8 provided at its lower end.

The upper end of a piston rod 11 is supported and fixed to a fork bolt 10 fixed to the upper end of the inner tube 6a, and the lower end of this piston rod 11 extends into the shock absorbing cylinder 7. The midway portion of the piston rod 11 is connected to a bearing 12 provided at the upper end of the shock absorbing cylinder 7.
is slidably supported in the axial direction. Further, a piston 13 is fixed to the lower end of the piston rod 11.

In the shock absorbing cylinder 7, a first chamber 14 and a second chamber 5 filled with oil are formed below the piston 13. Both chambers I4 and I5 are connected to the piston rod 11.
and the chamber 15 communicates with a reservoir tank with a known gas chamber, not shown.

The piston 13 is provided with a passage 17 that communicates between the first chamber 14 and the second chamber 15.
A check valve 18 is provided which allows fluid to flow from the second chamber 15 towards the first chamber 14, but prevents fluid from flowing in the opposite direction. Therefore, when the front fork 2 is retracted, the oil flows from the second chamber 15 to the first chamber 14 through the passages 16 and 17, so that the flow rate of oil increases. For this reason, the front fork 2 is designed to contract relatively quickly.

Furthermore, when the front fork 2 is extended, the check valve 18 closes the passage 17, so oil flows from the first chamber 14 to the second chamber 15 through the passage 16 only. For this reason, the flow rate of oil becomes small, and the front fork 2 extends relatively slowly.

A cylindrical spring stopper 19 is fitted into the protrusion lOa of the fork bolt 10, and an upper spring 20 with a spring constant of 1 is connected between the flange portion 19a of the spring stopper 19 and the flange portion 7a of the shock absorbing cylinder 7. , and a lower spring 21 with a spring constant of 2 are arranged in series with a cylindrical spring receiving seat 22 interposed therebetween. The initial loads of the upper spring 20 and lower spring 21 are set to predetermined values depending on the weight of the driver, driving conditions, and the like.

An auxiliary spring 23 with a spring constant is disposed in the inner hole of the spring receiving seat 22 on the upper spring 20 side, and this auxiliary spring 2
3 is supported at one end by the spring receiving seat 22, and at the other end by another spring receiving seat 24 which is relatively slidably disposed within the inner hole of the spring receiving seat 22. The spring receiving seat 22 and the other spring receiving seats 24 are fitted onto the piston rod 11 and are guided by the piston loft 11 so that they can slide in the axial direction. In addition, under normal conditions, the auxiliary spring 23 has a free length, and the spring 1
A predetermined length d is set between the lower end of the buckle 19 and the other spring receiving ridge 24. The upper spring 20, the lower spring 21, and the auxiliary spring 23 constitute a buffer spring 25 of the front fork 2 of the present invention.

Next, we will discuss the operation of this embodiment configured as described above.
explain. However, it is assumed that the initial loads of the upper spring 20 and the lower spring 21 are set to Fo as shown in FIG.

When the front wheel 3 receives an impact force Uj due to unevenness of the beard, etc., the upper spring 20 and the lower spring 21 are compressed to relieve the impact force, and the sortie absorption cylinder 7 contracts to absorb the vibration at that time. . In that case, the spring receiving seat 22 moves guided by the piston Ron Fil, so the upper spring 2
0 and the lower spring 21 are smoothly compressed without wobbling laterally.

At this time, the composite spring characteristic I of the front fork 2 is expressed as k''k+kg/(k+''kl). Therefore, the composite spring characteristic of the front fork 2 is the characteristic directly along X in Fig. 3. Become.

When the upper spring 20 is compressed by a predetermined amount and the stroke of the front fork 2 reaches d, the other spring receiving seat 24 comes into contact with the lower end of the spring stopper 19. Furthermore, when the front fork 2 contracts, the auxiliary spring 23 also comes to be compressed. At this time, the spring receiving seat 22 and the other spring receiving seats 24 are
Since each spring 20, 21, 23 moves while being guided by the piston mouth/throat 11, each spring 20, 21, 23 is smoothly compressed. The composite spring constant at this time is k= (k, □10 kg kg)/(k+ +
kg + ks). That is, the spring constant at this stage is larger than the spring constant at the previous stage. Therefore, in FIG. 3, the composite spring characteristics of the front fork 2 will be along the line MY which has a larger slope than the slope of the direct X, and the point of the stroke d will be the first inflection point of the spring constant. .

When the auxiliary spring 23 is completely compressed and the sui-loaf of the front fork 2 reaches e, the upper spring 20 is no longer compressed. Therefore, the front fork 2
When contracted, only the lower spring 21 continues to be compressed. The spring constant at this time is 2, which is the spring constant of the lower spring 21, and is even larger. That is, the spring characteristics of the front fork 2 are along the straight line Z, which has a larger slope than the straight line Y, and the point of the stroke e becomes the second inflection point. .

In this manner, the spring characteristic of the buffer spring 25 of the front fork 2 is such that the spring constant increases in three stages as the stroke increases. In this case, the increase in the spring constant at each inflection point d and e is not so large, but the spring constant at high loads represented by the straight line Z is considerably larger than the spring constant at low loads represented by the straight line X. Become something.

Therefore, in the conventional front fork having the spring constant shown by the dashed line in FIG. 3, when the spring constant represented by L'lZ is applied, a feeling of bottoming out occurs at the inflection point a, but the present invention With the front fork 2 according to the above, such a feeling of bottoming out does not occur at each of the inflection points d and e. By setting the spring constant of the front fork 2 at a high load to a large value, the maximum load F is increased. , the stroke for X becomes shorter from b to C.

In addition, in the above-mentioned embodiment, the auxiliary spring 23 is provided on the upper spring 20 side, but the present invention is not limited to this, and as shown in FIG.
The auxiliary spring 23 is placed on the lower spring 21 side, and the spring receiving seat 2
It can also be fixed at 2. In this case, the second and third
It goes without saying that the spring constants of the stages are different from the spring constants of the previous embodiments. Furthermore, the auxiliary spring 23 is connected to the upper spring 2.
It can also be provided on both sides of the 0 side and the lower spring 21 side.

In this case, the spring characteristic is such that the spring constant increases in four steps.

[Effects of the Invention] As is clear from the above description, the front fork of the motorcycle according to the present invention has a spring characteristic in which the spring constant increases gradually in response to an increase in load by increasing the spring constant in multiple steps. Therefore, even if the spring constant at high r: 1 load is set larger than the spring constant at low load, the change in the spring constant at each inflection point is small, allowing the load to rise smoothly. I am now able to do this. Therefore, it is possible to exhibit extremely good notion ability without bottoming out.

Furthermore, by increasing the spring constant under high loads, the stroke of the front fork can be shortened. Therefore, it is possible to reduce the pitching motion of the vehicle body.

Furthermore, since the spring bearing seats supporting the buffer springs are slidably supported on the piston rod of the shock absorbing cylinder, each spring is reliably compressed without wobbling laterally. Therefore, the buffer spring can reliably perform its cushioning function.

Furthermore, since the buffer spring can be constructed of, for example, an ordinary coil spring, the front fork can be manufactured at low cost by using such a coil spring.

[Brief explanation of the drawing]

FIG. 1 is a side view of a motorcycle to which an embodiment of the present invention is applied, FIG. 2 is a sectional view of the front fork of this motorcycle, taken along the line ■-■ in FIG. 1, and FIG. An explanatory diagram illustrating the spring characteristics of this front fork and the spring constant of a conventional front fork, FIG. 4 is a sectional view corresponding to FIG. 2 showing a modification of the front fork according to the present invention, and FIG. FIG. 3 is a sectional view corresponding to FIG. 2 showing the fork. 2...Front fork, 3...Front wheel, 6...Fork pipe, 6a...Inner tube, 6b...
Outer tube, 7... Shock absorption cylinder, 10...
・Fork bolt, 11...Piston rod, 19・
...Spring stopper, 20...Upper spring, 21...Lower spring, 22...Spring receiver, 23...Auxiliary spring,
24...Other spring receiving seat, 25...Buffer spring. Patent applicant: Yamaha Motor Co., Ltd. Representative Patent Attorney Hiroki Shirai (4 others) Figure 1 Figure 5

Claims (1)

[Claims] (1) Equipped with a fork pipe in which the inner tube is slidably inserted into the outer tube so as to be extendable and retractable, and a buffer spring and a shock absorbing cylinder housed in the fork pipe, the front wheel receives the impact force. In the front fork of a motorcycle, the shock force is absorbed and alleviated by a shock absorbing cylinder and a shock absorbing spring. An upper spring and a lower spring arranged in series through a spring receiving seat, and an upper spring and a lower spring disposed on at least one side of the upper spring and the lower spring, one end supported by the spring receiving seat and the other end supporting the other spring. and an auxiliary spring supported by a receiving seat, the spring receiving seats having one end fixed to the fork bolt and the other end slidably fitting into a piston rod connected to a piston in the shock absorbing cylinder. A front fork for a motorcycle, characterized in that the fork bolt is further provided with a spring stopper facing either one of the spring receiving seats.