Apparatus for the spring-mounted suspension of a wheel of a motor vehicle.

The invention relates to an apparatus for the spring-mounted suspension of a wheel of a motor-vehicle, in particular a motor-cycle, comprising an inner and outer leg which are telescopingly slidable in each other against the action of a spring means.

When such an apparatus is used for the front fork of a motor-cycle, a relatively long spring compression distance is commonly used. Especially at strongly braking the front fork of the motor-cycle will strongly be compressed, whereby the ball-head angle and the trailing distance change relatively much, which causes a substantial decrease of the steerability of the motor-cycle. Moreover, the braking power of the back wheel decreases. It is attempted to obviate this disadvantage by reducing the through-flow of the demper oil in the apparatus at braking. However, this known solution is relatively complicated and, in practice, does not show a satisfactory operation.

The invention aims to provide an apparatus of the above-mentioned kind wherein the above-mentioned disadvantages are obviated in a simple but nevertheless effective manner.

To this end, the apparatus according to the invention is characterized by means for increasing the spring bias force of the spring means at braking of the motor-vehicle.

In this manner the distance along which the inner leg can slide in the outer leg is reduced by the increased bias force of the spring means at braking, so that, for example at a motor-cycle, the ball-head angle and the trailing distance does not undergo a great change and the steerability of the motor-cycle hardly decreases. Further, the brake power of the back wheel of the motor-cycle is substantially maintained thereby.

According to a simple embodiment of the apparatus according to the invention said means comprises a cylinder piston assembly, the piston rod of which is operable by a movement occurring at braking.

When the spring means is at least partially formed by a gas mixture provided in a closed space at least under atmospheric pressure, said space lying within the inner and outer legs,said means can increase the pressure of the gas mixture in the closed space in accordance with an embodiment of the invention.

When the spring means at least partially consists of a helical spring mounted in the inner and outer legs the cylinder piston assembly can, according to the invention, operate a piston mounted in the inner leg or outer leg, respectively, which piston engages one end of the helical spring.

Preferably, the cylinder piston assembly is connected with the outer leg at one end and at the other end with a brake segment carrier of the wheel, which brake segment carrier is rotatably mounted around the wheel axis. Thereby, a movement occurring at braking is used in a favourable manner, wherein, moreover, the increase of the spring bias forceisdi- rectly related to the degree of braking.

The invention will hereinafter be further explained by reference to the drawings in which some embodiments of the apparatus according to the invention are schematically shown. <ul id="ul0001" list-style="none"><li>Fig. 1 shows a schematical side view of a front fork of a motor-cycle, wherein a first embodiment of the apparatus according to the invention is shown.</li><li>Fig. 2 shows a side view corresponding to fig. 1, wherein a second embodiment of the apparatus according to the invention is employed.</li><li>Fig. 3 shows a detail of a front fork of a motor-cycle wherein a third embodiment of the apparatus according to the invention is employed.</li></ul>

Referring to fig. 1 there is shown a front fork of a motor-cycle which consists of two spring legs 1, only one of which being shown in the drawings. Between these spring legs or apparatuses 1 for the spring-mounted suspension of a wheel, a front wheel 3 is mounted by means of an axis 2. Each apparatus 1 consists of an inner leg 4 and an outer leg 5, which can telescopingly slide in each other. In order to prevent that dirt and the like can penetrate into the interior of the apparatus 1, a rubber bush 6 is provided. The inner leg 4 and the outer leg 5 determine a closed space in which a gas under pressure is provided whereby the desired spring operation is obtained. This closed space is accessible through a nipple 7 mounted at the upper end of the inner legb 4. The gas may consist of a pure gas as for example C0₂ or of a mixture of a plurality of gasses. The gas pressure may be higher than or equal to the atmospheric pressure.

The wheel 3 is provided with a brake drum 8 and a back plate 9 in a normal way. This back plate 9 carries brake segments not shown in the drawings, the brake linings of which can be pressed against the brake drum 8 in a usual manner for braking of the motor-cycle.

The back plate 9 is provided with a support 10 rotatably connected with a piston rod 11 of a cylinder piston assembly 12. The end of the cylinder 13 opposite of the piston rod 11 is provided with a coupling piece 14 rotatably connected with a clamp 15 mounted on the outer leg 5. The cylinder space lying at the side of the piston (not shown) opposite of the piston rod 11, is connected with the nipples 7 of both apparatuses 1 by means of a tube 16. It is noted that the term cylinder piston assembly also indicates an assembly comprising a closed cylinder space the volume of which can be varied, such as a cylinder plunger assembly or a cylinder membrane assembly.

As the back plate 9, except of the coupling with the outer leg 5 by the cylinder piston assembly 12, is freely rotatable around the axis 2 of the wheel 3, the back plate 9 will rotate with the wheel 3 along a certain angular distance at braking of the motor-cycle, so that the support 10 will push in the piston rod 11 and the amount of gas in the closed space determined by the inner and outer legs 4, 5 is increased. Thereby, the pressure in this closed space increases and the distance along which the inner leg 4 can slide into the outer leg 5 will decrease so that ball-head angle and the trailing distance will not change much and the steerability of the motor-cycle is maintained.

If the motor-cycle is braked only lightly, the angular distance along which the back plate 9 is rotated will not be very great in view of the pressure of the gas, so that in this case the amount of gas in the closed space is hardly changed and the normal spring operation remains maintained. However, as the motor-cycle is braked stronger and the distance along which the inner leg 4 would slide into the outer leg 5 and thereby the change of the ball-head angle and the trailing distance would increase, the back plate 9 will rotate along a greater angular distance so that the amount of gas in the closed space is substantially increased and the so-called dipping of the motor-cycle is counteracted to a large extent.

Fig. 2 shows a side view of a front fork which mainly corresponds to the front fork of fig. 1 and wherein corresponding parts are indicated with the same reference numbers. At this embodiment a piston 18 is mounted in the end 17 of the inner leg 4 opposite of the outer leg 5, said piston 18 being operable by the cylinder piston assembly 12 made as a hydraulic cylinder piston assembly. The end face 19 of the piston 18 forms an end wall of the closed space 20 filled with the gas and determined by the inner and outer legs 4, 5.

At braking of the motor-cycle the support 10 will operate the piston rod 11, whereby the piston 18 is pressed further in the inner leg 4 so that the pressure of the gas in the closed space 20 increases and the dipping of the motor-cycle is counteracted.

_Fig. 3 shows a detail of a front fork of a motor-cycle equipped with helical springs 21. In this case a hydraulic cylinder piston assembly 12 is also used (not shown in fig. 3) which is connected to the nipples 7 of both apparatuses 1 through a tube also not shown. In the end 17 of the inner leg 4 opposite of the outer leg 5 a piston 22 is mounted, said piston 22 being slidable in a casing 23. An end face 24 of the piston 22 engages the adjacent end of the helical spring 21. In this manner the bias force of the helical spring 21 is increased at braking of the motor-cycle, so that the dipping of the motor-cycle is counteracted.

It.is noted that this embodiment can also be used in combination with a spring leg filled with a gas.

Further, it is noted that the hydraulic cylinder piston assembly at the embodiments of fig. 2 and 3 can be replaced by a cylinder piston assembly filled with gas which operates a piston mounted in the spring leg in a corresponding manner.

It is noted that the apparatus according to the invention is described by reference to a front fork of a motor-cycle by way of example only. The apparatus could for example also be used for the spring-mounted suspension of the front wheels of a motor-car.

Further, it is noted that the coupling between the cylinder 13 and the spring leg 1 shown in the drawings,is . only schematically shown and, of course, can be achieved in another way. For example, it is also possible to connect the cylinder 13 to the lower end of the spring leg 1, in which case at the embodiment according to fig. 2 and 3 the - piston 18 or 22, respectively, is mounted in the lower end of the spring leg 1.

The invention is therefore not restricted to the above-described embodiments which can be varied in a number of ways within the scope of the claims.

The invention can also be used at a spring leg of the type with an oil demping system, for example.

Further, the application of the invention is not restricted to a motor-cycle with a brake drum system. On the contrary, the invention can also be used at a motor-cycle with a brake disk system. In this case the cylinder piston assembly is operated by the brake claws carrying the brake pads.