Motorcycle

A motorcycle in which the forward nose-diving during braking is to be prevented. For that purpose, the motorcycle includes a spring-damping system which acts upon a pressure gas space; the pressure gas space is supplied during the braking operation with compressed gas from a pressure reservoir, by way of a control valve. The pressure which builds up in the gas pressure space thereby acts opposite the nose-diving of the motorcycle.

The present invention relates to a motorcycle, in which the front wheel is 
arranged at the motorcycle frame by way of a spring-damping system and in 
which the spring-damping system acts upon a gas pressure space which is 
connected with a pressure reservoir by way of a closure device during the 
braking of the motorcycle. 
During the braking, a motorcycle nose-dives forwardly, conditioned by the 
dynamic axle load change, if the front wheel is arranged at the motorcycle 
frame by way of a spring-damping system. A motorcycle is disclosed in the 
DE-OS 32 02 740, in which this is to be prevented. During the braking 
operation, a customary directional control valve connects in that case the 
gas pressure space of the spring-damping system with a pressure reservoir. 
The pressure building up in the gas pressure space acts opposite the 
nose-diving of the motorcycle. The disadvantage of this solution resides 
in that the entire pressure of the pressure reservoir exists always in the 
gas pressure space, independently of the brake force and therewith of the 
deceleration of the motorcycle. As a result thereof, with a light braking, 
exactly the opposite may occur; namely, an erecting or raising of the 
motorcycle. 
It is the object of the present invention to so further develop a 
motorcycle of the type described above that without excessive additional 
structural expenditures, the pressure in the gas pressure space builds up 
as a function of the brake force, respectively, of the deceleration of the 
motorcycle. 
The underlying problems are solved according to the present invention in 
that the closure device is constructed as control valve having a vent 
channel for the gas pressure space and a slide valve member displaceable 
by the deceleration of the motorcycle and in pressure-connection with the 
gas pressure space, which, in its normal position, closes off the feed 
line from the pressure reservoir to the gas pressure space and opens up 
the venting of the gas pressure space. 
In the motorcycle according to the present invention, always exactly so 
much pressure is produced in the gas pressure space during the braking as 
is necessary in order to prevent a forward nose-diving of the motorcycle. 
Responsible therefor is essentially the closure slide valve member. It 
opens and closes during the braking operation in alternate sequence the 
vent channel of the gas pressure space. It is caused to operate in this 
manner by the opposite forces which act on the same. This involves, on the 
one hand, the force which is produced by the pressure of the gas pressure 
space and the effective area of the closure slide valve member, and on the 
other, the oppositely directed force from the mass of the closure slide 
valve member and its acceleration. With these forces, an equilibrium will 
always establish itself whereby the absolute amount of the forces follows 
the deceleration of the motorcycle and therewith the brake force. 
The control valve with the closure slide valve member can be constructed as 
compact structural part. It is thereby advantageous if, on the one hand, 
the valve housing includes a reduced through-bore and, on the other hand, 
the closure slide valve member is constructed as stem part having an outer 
annular collar. The closure slide valve member can then be guided both 
with it stem part as also with the annular collar within the through-bore. 
The through-bore may thereby serve as abutment for the closure slide valve 
member within the area of its diameter change. 
If the closure slide valve member controls the pressure feed of the gas 
pressure space by means of its annular collar, then it is appropriate to 
provide two annular collars arranged at a distance from one another. The 
feed connections for the pressure supply of the gas pressure space then 
terminate intermediate these annular collars. As a result thereof, the 
closure slide valve member itself is not acted upon by the pressure within 
this area. 
The necessary mass of the closure slide valve member can be calculated 
readily on the basis of the data specific of the motorcycle. 
Appropriately, the normal condition of the motorcycle, i.e., with one 
driver of average weight is used as base for its design. Since, however, 
most of the motorcycles also provide a space for a passenger, the 
conditions change when driving with two persons. In other words, the mass 
of the closure slide valve member is too small in this case. For that 
purpose, the present invention provides in an advantageous construction an 
additional inertia mass which acts on the closure slide valve member. If 
only one person drives the motorcycle, this inertia mass can be stopped 
and thus can be rendered inoperable.

Referring now to the drawing wherein like reference numerals are used 
throughout the various views to designate like parts, and more 
particularly to FIG. 1, a motorcycle generally designated by reference 
numeral 1 is shown in this figure on which is seated a driver M. The 
motorcycle includes a front wheel 2 and a frame 3. A spring-damping 
system, generally designated by reference numeral 4, connects the front 
wheel 2 with the frame 3. In its rear section, the motorcycle includes a 
control valve 5 and a pressure reservoir 6. A feed line 7 connects these 
two elements. The pressure reservoir 6 is preferably supply by way of a 
pump (not shown) so that always the maximum pressure exists within the 
same. For the sake of completion, it should be mentioned that the 
motorcycle 1 additionally includes a rear wheel 9 which is pivotally 
connected at the motorcycle frame 3 by way of a swinging arm 10. 
FIG. 3 illustrates the spring-damping system 4 in front elevation. It is 
constructed as so-called telefork with two identically constructed fork 
members generally designated by reference numerals 11 and 12 which are 
connected with each other by fork bridges 13 and 14. The fork member 12 
and the fork bridge 14 are shown only in part for the sake of simplicity. 
The fork bridges 13 and 14 carry a steering head 15, by way of which the 
damping-spring system 4 together with the front wheel 2 is pivotally 
connected at the motorcycle frame 3. The fork member 11 is composed of a 
tubular slide member 16 and of a vertical tubular member 17 telescopically 
displaceable therein. The tubular slide member 16 receives the bearing 
axle of the front wheel 2 (not shown) whereas the fork bridges 13 and 14 
are secured at the tubular member 17. An interior tubular member 18 is 
rigidly connected with the tubular slide member 16. The tubular member 17 
includes at its immersed lower end a piston 19 which slides between the 
tubular slide member 16 and the inner tubular member 18. A compression 
spring 20 is supported, on the one hand, at a ring 21 secured at the 
tubular member 17 and, on the other, at a collar-like shoulder of the 
inner tubular member 18. The fork member is filled with damping fluid up 
to the ring 21. The structure described so far corresponds to the 
customary constructions as generally known. 
Located opposite the compression spring 20, a piston 22 rests on the ring 
21 which can additionally be pressed against its seat by a spring (not 
shown). A gas pressure space 23 extends above the piston 22. The pressure 
line 8 according to FIG. 1 terminates in this gas pressure space 23. 
The control valve 5 is illustrated in detail in FIG. 2. It includes a valve 
housing 24 with a control slide valve member 25. Additionally, the valve 
housing receives an inertia mass 26 arranged coaxially to the closure 
slide valve member 25, which is adapted to be stopped in the valve housing 
24 by a symbolically indicated screw 27. The valve housing 24 includes a 
bore offset in its diameter for receiving the closure slide valve member 
25 and the inertia mass 26. This bore passes over from a section 28a with 
large diameter into a section 28b with smaller diameter. A shoulder 28c is 
formed at the transition of the two bore sections. A flow channel 29 
terminates in the bore section 28a, to which is connected the feed line 7 
of the pressure reservoir 6 (FIG. 1). A further flow channel 30, disposed 
approximately opposite thereto, leads out of the bore section 28a and 
passes over into a pressure line 31. This pressure line 31 communicates 
with a flow channel 32 in the valve housing 24 which again terminates in 
the bore section 28b. A vent line 33 connects downstream of the flow 
channel 32, as viewed in the direction of the bore section 28a, the bore 
section 28b with the atmospheric air. 
The closure slide valve member 25 is constructed as elongated piston and 
projects with its stem portion 25a into the bore section 28b and is also 
guided therein. Furthermore, the closure slide valve member 25 includes 
within the area of the bore section 28a two adjacent annular collars 25b 
and 25c arranged at a distance from one another. The closure slide valve 
member 25 is guided within the bore section 28a by means of these annular 
collars 25b and 25c. 
The closure slide valve member 25 is in its normal rest position in FIG. 2. 
It thereby abuts with its annular collar 25c at an abutment 34 inserted 
into the valve housing 24. A compression spring 35 between the shoulder 
28c and the annular collar 25b additionally presses the closure slide 
valve member 25 against this abutment 34. In its normal position, the 
closure slide valve member 25 closes with it annular collar 25b the flow 
channel 29 whereas the flow channel 30 remains open between the two 
annular collars 25b and 25c. The stem portion 25a terminates in this 
position shortly behind the vent channel 33 and thus opens up the latter. 
Furthermore, it should be noted that the valve housing 24 includes vent 
bores 36. These vent bores 36 may be complemented or replaced by vent 
bores 37 in the inertia mass 26. 
During a normal inward spring movement of the front wheel, for example, 
when driving over a road unevenness, the tubular member 17 (FIG. 3) slides 
into the tubular slide member 16. As a result thereof, damping fluid is 
displaced which escapes in the direction of the piston 22. The piston 22 
is displaced upwardly since the gas present in the pressure space 23 can 
escape by way of the pressure line 8 and the vent channel 33 (FIG. 3). The 
spring system is therefore not impaired. 
If, however, the driver M brakes the motorcycle, the closure slide valve 
member 25 experiences an acceleration against the force of the compression 
spring 35 by reason of its inertia mass. The closure slide valve member 25 
valves with its stem portion 25a the vent channel 33 and closes the same 
(illustrated in FIG. 2 in dash lines). Simultaneously with the closing of 
the vent channel 33, the closure slide valve member 25 opens the flow 
channel 29 with its annular collar 25b. Compressed gas can now flow from 
the pressure reservoir by way of the flow channel 29 into the bore section 
28a. From there, it is conducted by way of the flow channel 30, the 
pressure line 31, and the flow channel 32 into the pressure line 8 and 
into the gas pressure space 23 (FIG. 3). A pressure builds up within the 
latter which presses the piston 22 against its seat. On the other hand, 
owing to the dynamic axle load change, the motorcycle 1 experiences a 
force pointing downwardly in the axial direction of the fork member 11 
which seeks to slide the tubular member 17 into the tubular member 16. 
Since, however, the damping fluid can no longer escape by displacement of 
the piston 22, the fork 11 as a whole does not nose-dive. 
The pressure of the pressure gas space, however, is also present at the end 
area of the stem portion 25a of the closure slide valve member 25. The 
larger this pressure now becomes, the more it acts opposite the 
acceleration force of the closure slide valve member 25. This condition is 
symbolically indicated in FIG. 2 by two force arrows 38 and 39. If the 
force produced by the pressure increase now exceeds the counterforce 
resulting from the acceleration 39, then the closure slide valve member 25 
is again pressed back into its normal position. It partially opens up the 
vent channel 33 with the consequence that the pressure in the pressure gas 
space 23 decreases. As a result thereof, the acceleration force 39 again 
once more predominates and the closure slide valve member 25 again closes 
the flow channel 33. This alternating cycle continues during the entire 
braking operation. It can be readily seen that the larger the deceleration 
of the motorcycle 1, i.e., the more strongly the motorcycle is being 
braked, the greater becomes the acceleration and therewith the 
acceleration force 39 of the closure slide valve member 25 and the higher 
must become the pressure increase in the gas pressure space 23 in order to 
be able to push back the closure slide valve member 25 in the manner 
described above. 
On the other hand, the force in the downward direction which acts in the 
telefork is the larger the greater the deceleration of the motorcycle. In 
order to prevent a nose-diving of the fork member 11, however, also the 
pressure in the gas pressure space 23 must be correspondingly large. With 
a proper design and dimensioning of the structural parts, the pressure 
necessary with a predetermined deceleration of the motorcycle 1 will 
always establish itself in the gas pressure space 23 by reason of the 
described relationships. The conditions and the design of the structural 
parts can be readily determined mathematically by a person skilled in the 
art. 
In the illustrated embodiment, a front wheel fork of customary type of 
construction is illustrated. However, it is also apparent that the present 
invention can be utilized with differently constructed front wheel 
suspensions. Especially, it is also possible that the pressure gas space 
is not integrated in the fork member but is accommodated in a separate 
structural part. 
Thus, while I have shown and described only one embodiment in accordance 
with the present invention, it is understood that the same is not limited 
thereto but is susceptible of numerous changes and modifications as known 
to those skilled in the art, and I therefore do not wish to be limited to 
the details shown and described herein but intend to cover all such 
changes and modifications as are encompassed by the scope of the appended 
claims.