Motor vehicles – Special wheel base – Having only three wheels
Reexamination Certificate
2000-03-16
2001-12-11
Dickson, Paul N. (Department: 3618)
Motor vehicles
Special wheel base
Having only three wheels
C280S124103, C280S093510
Reexamination Certificate
active
06328125
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a vehicle provided with
at least three wheels,
a frame comprising a first frame part and a second frame part, it being possible for the frame parts to tilt with respect to one another about a tilting axis which lies in the longitudinal direction,
at least one front wheel which is connected to the first frame part and can tilt about a front-wheel steering axle which lies essentially parallel to the plane of the front wheel,
a steering wheel which is rotatably connected to the first frame part,
tilting means which are connected to the first and second frame parts for executing a tilting movement between the first and second frame parts, and
a sensor which is coupled to the front wheel and to the tilting means for forming a control signal for driving the tilting means.
A vehicle of this kind is known from WO95/34459 in the name of the applicant. This document describes a self-balancing, preferably three-wheeled vehicle, in which the sensor, which in this case is formed by a hydraulic rotary valve, measures the force or the moment on the front wheel. In response to the signal from the sensor, the front frame part, which comprises the driver's cab and the steering wheel, is tilted until the moment on the front wheel is virtually equal to zero. In this way, a self-stabilizing tilting action is obtained, which causes the vehicle to corner in a stable manner at all speeds. Since narrow vehicles as described in WO95/34459 generally have insufficient lateral stability and manoeuvrability to be able to participate in normal (automotive) traffic, a tilting system of this nature increases the stability, in such a manner that a narrow vehicle of this nature can become a fully functioning means of transport. The tilting system described is fully automatic, with the result that the driver does not require any special skills to control the vehicle. The known system provides a vehicle which reacts safely and predictably in all conceivable driving conditions.
Although the known tilting vehicle is very effective, the force sensor for determining the force or the moment on the front wheel is relatively complex. Furthermore, the feel of the steering of the known device can be improved further.
SUMMARY OF THE INVENTION
Therefore, the object of the present invention is to provide a tilting vehicle which comprises a simple and robust control of the tilting action, combined with an optimum feel of the steering for the driver.
To this end, the vehicle according to the present invention is characterized in that the steering wheel is connected, via a steering axle, to the first frame part, which steering axle can rotate about its axis with respect to the front-wheel steering axle, the sensor determining the angle of rotation between the front-wheel steering axle and the steering axle.
The present invention is based on the insight that a vehicle, which may be a tilting vehicle, can be steered in two fundamentally different ways:
Firstly, the driver may have direct control over the position of the front wheel or the front wheels. The driver, by imparting a specific angular displacement to the front wheel, provides the vehicle with a turning radius.
Secondly, the driver may have direct or indirect control over the tilting position of the vehicle. In this case, the combination of the vehicle speed and the tilting position provides a specific turning radius. The front wheel assumes an appropriate position which is governed by the speed and the tilting position, which front-wheel position is not used to determine the direction of travel. A motorcycle works on this principle. By means of complex steering manoeuvres, the driver continuously adjusts the tilting position, resulting in the desired direction of travel. In practice, this has been found to provide a vehicle which is easy to control. In the case of the vehicle according to the invention, the driver can fix the tilting position directly by means of the tilting means, in contrast to the indirect fixing of the tilting position via the handlebars, as takes place in the case of a motorcycle. According to the invention, the optimum instrument allowing the driver to control and actuate the tilting system comprising the tilting means, and therefore to adjust the tilting position, is the steering wheel. According to the invention, the standard rigid connection between the steering wheel and the front wheel is replaced by a connection in which the steering axle can rotate about its axis with respect to the front-wheel steering axle. This flexible connection, in which the rotation-angle sensor is accommodated, provides a signal for the desired tilting position of the vehicle. The tilting of the vehicle can then be actuated The optimum position of the front wheel, which is appropriate for the combination of tilting angle and speed of travel, is automatically adopted in a manner which is imperceptible to the driver.
The tilting system according to the present invention allows the sensor to be of very simple design and also allows the tilting means to be actuated in a robust and operationally reliable manner.
The sensor, the control arrangement and the tilting means themselves may each separately use various technological principles, for example they may be of mechanical, hydraulic, pneumatic or electrical design. The present invention will provide a description of a (largely) hydraulic design of the components. In this case, the rotation-angle sensor may comprise a cylinder which is connected at a first end to the front wheel and at the second end to the steering column. The tilting means may comprise hydraulic or pneumatic cylinders which, via a valve, are connected to a pressure source. The cylinder of the angle-position sensor actuates the valve of the tilting means. This valve may be a simple on/off slide valve.
The vehicle according to the present invention may comprise a rear frame part provided with two wheels and a front frame part which has one wheel and can tilt with respect to the rear frame part. It is also possible to use a rear tiltable frame part provided with one wheel and an untiltable front frame part with two wheels. Finally, it is also possible to employ a tiltable frame structure as described in Dutch patent application number 1005894 in the name of the applicant.
EP-A-0,592,377 has disclosed a tilting vehicle in which the tilting of the front frame part with respect to the rear frame part, which supports the drive, is obtained by the angular displacement of the front wheel about the front-wheel steering axle with respect to the frame, the steering wheel and the front wheel being rigidly connected. A system of this nature has the drawback that the tilting is not dependent on the vehicle speed and is therefore not accurate. A stable ride is therefore not obtained.
EP-A-0,020,835 has disclosed a tilting vehicle in which the tilting position can be obtained by actuating foot pedals or by moving the steering column, transversely to its axis of rotation. The steering axle is again rigidly connected to the front wheel. In this known device, the tilting position is not dependent on the vehicle speed, so that a stable ride is not obtained.
The way in which the vehicle according to the present invention operates differs fundamentally from the way in which the vehicles which are known from the prior art and have been described above operate. When the driver of the vehicle according to the invention is driving straight on a flat road surface and wants to turn a corner, he rotates the steering wheel. Since the geometry and gyroscopic stability of the front wheel mean that the latter tends to remain directed straight on, the steering angle of the steering axle as dictated by the driver will lead to an angular displacement a between the front-wheel steering axle and the steering axle. On the basis of this angular displacement &agr;, the rotation-angle sensor forms a control signal which leads to the tilting means being driven and to a predetermined tilting angle &bgr; of the first frame part. As the t
Kroonen Hendrik Marinus
Van Den Brink Christopher Ralph
Brinks Westmaas B.V.
Dickson Paul N.
Young & Thompson
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