Tilting vehicle provided with steerable rear wheels

Description of the invention

The invention relates to a tilting vehicle.

From the international patent application No. WO 95/34459, a tilting vehicle is known, the front frame part of which is tilted relative to the rear frame part by means of two piston cylinders when driving in a curve. The front part of the frame has one wheel and the rear part of the frame has two wheels. The force sensor measures the moment of force of the front wheel about the steering axis of the front wheels. This torque produces a control signal which drives the tilt cylinders, resulting in a tilt capability while maintaining the natural tilt stability. The movement of the tilt cylinders ceases when the force or moment at the front wheel is zero, which is the moment when, depending on the radius of the turn, the speed of the vehicle and its weight, including the rider, the correct degree of bank roll is achieved. When the force or moment about the steering axis of the front wheels on the front wheel is zero, the tilt position of the front frame is kept constant.

It is also possible to use the sensor as a position indicator as described in WO 99/14099. With this structure, the driver can activate the tilting cylinders by rotating the steering element relative to the front steered wheels, the front wheel being steered automatically at the right angle and as a function of speed by the tilting mechanism described in this patent.

However, it has been found that at high speeds, i.e. above about 60 km / h, there is unstable zig-zag zigzagging of the entire prior art vehicle, both when driving straight ahead and when driving around a curve. As a result, undesirable oscillations occur in the tilted cab with the result that the operating conditions of the tilting vehicle are worsened.

A tilting vehicle according to the invention, having a frame with a front part having a longitudinal axis and a rear part having a tilting axis, the driver's seat and at least one front wheel being pivotally movable about the front wheel control axis situated to the front part of the frame. transversely to the longitudinal axis of the front part of the frame, while two rear wheels are attached to the rear part of the frame and the rear part of the frame is connected to the front part of the frame so that it is movable about a tilting axis parallel to the direction of the longitudinal axis of the front frame, characterized in that the rear wheels of the rear frame are movable in rotation about their driving rear wheel axes transverse to the longitudinal axis and the rear wheels tilt about the rear-wheel tilt axis, parallel to the direction of the longitudinal axis.

Each of the wheels of the rear part of the rear frame is connected to the rear part of the frame by a corresponding vertically oriented steering axle of the rear wheels.

Each of the rear wheels of the rear frame part has a control arm which is transverse to the steering axis of the rear wheels and is connected at its free end, via a suitable steering rod, to a crank arm which is pivotally connected about the longitudinal axis to the front part of the frame, and transversely to the longitudinal axis and is rotated about the longitudinal axis by the front frame portion when tilting the front frame portion about the tilt axis.

The other end of the control arm is attached, via a first pivot, to a cross arm which is parallel to the corresponding steering rod and connected via a second pivot to the rear part of the frame.

Each of the transverse arms of the rear wheels is connected by a pivot joint to a longitudinal guide which is parallel to the longitudinal axis.

The longitudinal guides of each of the parallel cross arms are interconnected by a torsion bar disposed transversely to the longitudinal direction.

The steering axles of the rear wheels are inclined with respect to the longitudinal axis, each of which is independently suspended from a portion of the rear frame, and each has a shock absorber.

The vehicle comprises an externally actuated tilting device connected on the one hand to the front part of the frame and on the other hand to the rear part of the frame for relative tilting of the frame part about the tilt axis, a steering sensor, which is a steering sensor, being connected to the tilting device. the tilting device as a function of the relative inclination of the front and rear parts.

An advantage of the solution according to the invention is that a tilting vehicle is obtained which avoids oscillation, even at relatively high speeds.

PL 205 331 B1

An advantage of the invention is that, with the tilt function of the present invention, also the rear wheels, each around a substantially vertically directed steering axis of said rear wheel, or by tilting the rear wheels, each around a substantially longitudinally extending tilting axis of said rear wheel. the rear wheels are capable of developing a sufficiently large lateral force quickly enough, and complete elimination of relatively high steering instability at high speed values, both when cornering and when driving straight, while maintaining favorable steering parameters and steering feel by the driver.

In case the tilting vehicle is not provided with active tilting means, the tilting of the front frame portion may be controlled by self-balancing on the part of the driver by orienting the front wheel and transferring the weight.

On tilting the front part of the frame about its longitudinal axis, the crank arm is rotated so that the control arms of the rear wheels are moved, and steering of the rear wheels dependent on the length of the crank arm is achieved. The degree of steering can be precisely adjusted by changing the geometry of the crank arm and the steering arm.

The subject matter of the invention is shown in an exemplary embodiment in which Fig. 1 shows a simplified perspective view of the frame of a tilting vehicle according to the present invention, and Figs. 2 and 3 show a preferred embodiment of a steering structure for the rear wheels of a tilting vehicle according to the present invention.

Fig. 1 shows schematically a chassis of a tilting vehicle 1 according to the present invention, comprising a front frame portion 2 and a rear frame portion 3 connected to a front frame portion 2 such that it can tilt. The front part 2 of the frame has a front wheel 4 which can be rotated about the simplified front steering axle 5 by means of a steering wheel 6. The front part 2 of the frame comprises a seat 7 for a driver, schematically indicated in this figure. The front part 2 of the frame can be tilted about a tilting axis 8 ', which in Fig. 1 coincides with the longitudinal axis 8. The tilting of the front part 2 of the frame takes place under the action of a drive from a tilting device 9 comprising two piston hydraulic cylinders 10, 11, with each of which is connected with one end to the rear portion 3 of the frame and the other end to the front portion 2 of the frame. The hydraulic cylinders 10, 11 are connected to a control unit, not shown in detail in the drawing.

When the driver turns the steering wheel 6, the steering force or steering moment is measured on the front wheel 4 by a sensor. The tilting device 9 is actuated by the sensor 12 by means of a conduit 13, which is shown in a simplified manner, causing the front part 2 of the frame to tilt in relation to it. the rear part 3 of the frame. The tilting continues until the force or torque detected by the sensor 12 is zero. When the force or torque registered by the sensor 2 is zero, the front part 2 of the frame is held in the tilted position reached, and in this position the piston hydraulic cylinders 10, 11 are immobilized. Instead of the force or torque sensor 12, it is also possible to use an angle sensor, known from the state of techniques.

It is also possible to control the tilt by computer based on the acceleration or angular position of the front part of the frame, or the speed and / or angular position of the front wheel 4 detected by sensors. The invention also applies to a tilting vehicle without a tilting device 9.

The position of the rear wheels 14, 15 is adjustable to prevent oscillation at relatively high speed, both in straight and in a curve. Each of the rear wheels 14, 15 can be steered about a steering axle 19, 20 of the rear wheel which is substantially perpendicular to the longitudinal axis 8. The rear wheels 14, 15 can also be connected to the rear axle 16 so that they are tiltable, in other words, the plane of each of the rear wheels can tilt about a tilt axis 17, 18 of the rear wheel which is oriented substantially in the direction of the axle. longitudinal 8, while it is possible to use the steering properties of the tilted rear wheels 14, 15. The drive for tilting about the tilt axis 17, 18 or the rotation about the steering axis 19, 20 of the rear wheel can depend on a large number of measurement signals, such as the tilt angle of the front part 2 of the frame, the tilt speed or the tilt acceleration of the front part 2 of the frame, the rolling angle, rolling speed or rolling acceleration of the non-tilting rear section 3 of the frame, forces acting on the tires of the rear wheels, or combinations thereof. It has been found that undesirable oscillations in driving can be counteracted by correct steering of the rear wheels 14, 15.

PL 205 331 B1

Fig. 2 shows a preferred embodiment of the invention with independent suspension of the rear wheels 14, 15, each of which is suspended such that it can pivot about its own steering axis of the rear wheel 14, 15. Each of the rear wheels 14, 15 is suspended via a separate shock absorber 22, 23 on the support 40 of the rear frame portion 3. Each of the rear wheels is provided with a control arm 24, the control arm 24 being connected via a steering rod 25, 26 to the end of the crank arm 27. The steering rods 25, 26 are connected via respective ball joints 28 to the respective control arm 24. The crank arm 27 is rigidly connected to the front part 2 of the frame and is rotated about the longitudinal axis 8 as the front part 2 of the frame is tilted. As a result, the ends of the control arms 24 are moved and the rear wheels 14, 15 rotate about the steering axes 19, 20 of the rear wheels, with the steering axles of the rear wheels passing through the upper attachment point of the shock absorbers 22, 23 and the ball joint 28.

The other end 28 'of each of the control arms 24 is connected to the rear part 3 of the frame via transverse levers 29, 30 and ball joints 31, 32 at the ends of the transverse levers 29, 30. Each of the transverse levers 29, 30 is connected via a rubber hanger. suspension 33 'with a longitudinal guide 33, the longitudinal guides being connected to each other by a torsion bar 36 which also serves as a rolling stabilizer for the rear part 3 of the frame.

As shown in Fig. 3, when the front part 2 of the frame is tilted to the right (viewed from the driver's side), the crank arm 27 will rotate to the left, causing the rear wheels 14, 15 to turn right about the steering axles 19, 20. rear wheels. As a result, the rear wheels 14, 15 can develop lateral force sufficiently quickly to achieve favorable cornering handling, which is important mainly at speeds above 60 km per hour. The steering degree of the rear wheels 14, 15 can be adjusted by changing the length of the crank arm 27, the length of the control arm 24 or the position of the mounting point 35 of the steering rods 25, 26 on the crank arm 27.

Although the invention has been described with reference to tilting a vehicle with one front wheel 4, it is also possible to apply the present invention to a tilting vehicle provided with two front wheels.