Land vehicles – Wheeled – Occupant propelled type
Reexamination Certificate
1999-12-03
2002-01-08
Mai, Lanna (Department: 3619)
Land vehicles
Wheeled
Occupant propelled type
C180S219000, C280S277000
Reexamination Certificate
active
06336647
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a front suspension for a two-wheeled vehicle in which a cushioning effect of the suspension is improved.
2. Background Art
Telescopic type suspensions, or bottom link type suspensions, are conventional in two-wheeled vehicles. A telescopic type suspension is capable of expansion and contraction like a telescope, and is suitable for a two-wheeled vehicle having a relatively small caster angle (the angle between a vertical line and front forks). In two-wheeled motor vehicles of large caster angle, also known as “American” type motorbikes, it is difficult to absorb vertical movements of a front wheel using a telescopic type suspension because the front forks extend horizontally. A bottom link type suspension is not overly influenced by the caster angle, and is therefore suitable for a two-wheeled motor vehicle having a large caster angle.
A conventional bottom link type suspension is shown in Japanese Utility Model Publication No. Sho 60-15744, entitled “A Front Wheel Suspension in a Two-wheeled Vehicle.” According to this suspension, as shown in
FIGS. 1 and 2
of the publication, a front wheel W is suspended by parallel links (reference numerals
3
,
8
,
6
and F), a hydraulic damper (not shown) and a suspension coil spring
14
. The suspension shown in
FIG. 1
is a leading type suspension, because an axle
5
of the front wheel W is located ahead of the suspension, while the suspension shown in
FIG. 2
of the publication is a trailing type suspension, because the front wheel axle
5
is located behind the suspension.
In
FIG. 1
of the publication, when a brake is applied to the front wheel, the front wheel W rises relatively with respect to a vehicle body frame, and jumping results in a relative descent of the front wheel W. Thus, a large suspension stroke results. In the same figure, the angle between a leading arm
3
and a link
8
is approximately 90°. As the front wheel W descends relatively, the angle becomes larger than 90°, while with a relative ascent of the front wheel W, the angle becomes smaller than 90°. Also in the above
FIG. 2
, the angle between the leading arm
3
and the link
8
is approximately 90°, which angle increases and decreases above and below 90°. This angular change will be explained below with reference to
FIG. 7
of the present application.
FIG. 7
of the present application is a schematic diagram of
FIG. 2
of Japanese Utility Model Publication No. Sho 60-15744, showing the principle elements of a conventional bottom link type suspension. The leading arm as referred to in the publication is here denoted a front wheel supporting arm
103
, which is a trailing arm. One end of the front wheel supporting arm
103
is connected to a lower end of a front fork
101
and is swingable through a first pin
102
, an axle
105
of a front wheel
104
is secured to the opposite end of the front wheel supporting arm
103
. A lower end of a push rod
107
is connected to an intermediate position of the front wheel supporting arm
103
through a second pin
106
. An upper link
109
extends from an upper portion of the front fork
101
through a third pin
108
, and an upper end of the push rod
107
is connected to an intermediate position of the upper link
107
through a fourth pin
110
. An end of the upper link
109
opposite to the front fork side is connected to a lower end of a suspension spring
111
. Thus, the front wheel
104
is suspended by a parallel link structure.
An axis passing through both first and second pins
102
,
106
is a first axis
103
A, an axis passing through both second and fourth pins
106
,
110
is a second axis
107
A, and the angle on the front fork
101
side between the first axis
103
A and the second axis
107
A is the angle &psgr;, which increases and decreases with upward and downward movements of the front wheel
104
. That is, when the axle
105
moves from
1
to
2
, the angle &psgr; becomes large, while when the axle
105
moves from
1
to
3
, the angle &psgr; becomes small. In many cases &psgr; changes in the range of 70° to 110° on both sides of 90°.
Taking note of a vertically upward movement of the fourth pin
110
, it is seen that in the region where the angle &psgr; is smaller than 90°, the amount of upward displacement of the fourth pin increases as the angle approaches 90°, while in the region where the angle &psgr; exceeds 90°, the amount of upward displacement of the fourth pin
110
decreases as the angle &psgr; becomes larger than 90°. As a sine curve, with the angle of 90° as its peak angle, the amount of an upward displacement of the fourth pin
110
decreases before and after the peak angle of 90°.
FIG. 8
of the present application is an illustration of the axes shown in FIG.
7
. The distance from a horizontal axis Ha which passes through the first pin
102
up to the fourth pin
110
is “H”, and the distance from the horizontal axis Ha to the second pin
106
is “h”. The length of the first axis
103
A is “r” and the inclination angle thereof is “&psgr;
2
”, the length of the second axis
107
A is “R”, and the inclination angle thereof is “&psgr;
1
”, with &psgr; defined by &psgr;=&psgr;
1
+&psgr;
2
. The following expressions are therefore established:
&psgr;=&psgr;
1
+&psgr;
2
R
cos &psgr;
1
=
H+h
h=r
cos &psgr;
2
H=R
cos &psgr;
1
−
r
cos &psgr;
2
eqn. (4)
H′=−R
sin &psgr;
1
+
r
sin &psgr;
2
eqn. (5)
sin &psgr;
2
=sin(&psgr;−&psgr;
1
)=sin &psgr; cos &psgr;
1
−cos &psgr; sin &psgr;
1
eqn. (6)
If &psgr;=90°, sin &psgr;=1, cos &psgr;=0 sin &psgr;
2
=cos &psgr;
1
H′=−R sin &psgr;
1
+r cos &psgr;
1
eqn. (7)
As shown in the above equation (4), the distance H becomes a function of R, r, &psgr;
1
and &psgr;
2
.
A rate of change of H can be determined by differentiation. The result of the differentiation is as shown in the above equation (5). sin &psgr;
2
is defined according to equation (6).
As noted above, the angle &psgr; has heretofore been approximately 90°, so if the angle &psgr; is assumed equal to 90°, H′ can be approximated by equation (7), and it becomes a function of R, r and &psgr;
1
.
FIG. 9
of the present application is a graph showing R sin &psgr;
1
and r cos &psgr;
1
plotted with respect to &psgr;
1
along the axis of abscissa, according to a conventional suspension. The angle &psgr;
1
becomes (&psgr;-&psgr;
2
) and it is presumed that there is a change at around a half of &psgr;, i.e., 45°. The sine curve and the cosine curve intersect each other at an angle of between 0° and 90°. If this intersecting point is assumed to be M, R sin &psgr;
1
is larger than r cos &psgr;
1
on the 90°+side with respect to the intersecting point M, so that the above equation (7) becomes negative in sign (−). In the 0°-90° side with respect to the intersecting point M, R sin &psgr;
1
becomes smaller than r cos &psgr;, so that the above equation (7) becomes positive in sign (+).
Thus, if the angle &psgr; is near 90° and if H′ is positive, the fourth pin
110
rises while being accelerated, while if H is negative, the fourth pin rises while being decelerated. Thus, if a peak in the amount of displacement or a point of change between acceleration and deceleration is present intermediate to the vertically moving stroke of the front wheel, a cushion feeling having a sense of incongruity results.
According to the conventional art, such incongruity sense is absorbed by a suspension spring. To this end, however, a special spring whose spring coefficient varies according to the amount of compression (for example, a spring different in diameter depending position, or a multi-stage spring) must be used as the suspension spring, thus leading to an increase in cost of the suspension spring.
It is therefore an object of the present invention to provide a front wheel suspension in
Aika Takanori
Ito Shinji
Iwai Toshiyuki
Honda Giken Kogyo Kabushiki Kaisha
Mai Lanna
To Toan
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