ITRM940383A1 - EXACT STEERING MECHANISM AND MECHANISM FOR CONNECTING THE CAR BODY TO THE WHEELS - Google Patents

Description

DESCRIPTION

accompanying a patent application for an industrial invention entitled: "Exact steering mechanism and mechanism for connecting the car body to the wheels"

The present invention relates to the exact steering mechanism and finds its main application in vehicles.

The purpose of the exact steering mechanism is to obtain, for each position assumed by the front steering wheels, the coincidence of the respective axes with that of the rear non-steering wheels at a point (which is the instantaneous center of rotation of the vehicle) located on the axis of the latter.

The purpose of the mechanism for connecting the car body to the wheels (object of the present invention) is to obtain greater grip conditions when cornering and to make the movement of the car body with respect to the wheels not influencing the steering.

Currently, Ackermann's and Jeantaud's steering wishbones are used to steer the wheels of a motor vehicle.

the main drawback of this mechanism consists in the fact that it is possible to obtain the coincidence of the axes of all the wheels only for a value of the steering angle.

In reality there are mechanisms capable of obtaining for each position of the wheels the coincidence of their axes in the center of instant rotation (Davis steering, Bernardi biquadrilateral, etc.) but they are rather complex and for this reason unused.

This drawback is intended to be overcome by means of the exact steering mechanism. In order to give a complete description of the present invention, it is appropriate to retrace from the beginning the phases which allowed its conception.

First of all, it should be noted that, in order for all the wheels of a vehicle to move on circumferences having the same center, (coinciding with the center of the curve traveled), it is necessary that the steering angles of the front steering wheels are such as to allow their axles meet for each steering position at a point on the axis of the rear non-steer wheels.

This result can be achieved by constraining the axles of the front steering wheels to a curved guide (see figure 1).

The equation of the curve according to which said guide must be conformed is obtained thanks to the analytical procedure described below.

The steering shaft (A) through the gearbox (B) controls the rotation of the telescopic arm (C).

THE TELESCOPIC ARM (C) (see figure 2):

1) in relation to the position assumed by sliding along the curved guide (E) through the profile (D), it must assume different lengths;

2) rotates around the axis (i);

3) acts on the profile (D).

THE PROFILE (D) (see figure 2 and figure 4 -representing enlargement of the details-):

1) in its lower part, is made in such a way that it can slide along the guide (E). This guide (E) is anchored to the car body and is shaped according to a curved line, graphic expression of the equation reached thanks to the analytical procedure reported above;

2) in its upper part, is made in such a way as to allow, at one end of the overlying prismatic rod (G) and element (1S <I>), the rotation around the axis (i <IV>) axis which is constantly orthogonal to the plane on which the curved guide (E) rests and passes through the curved line on which the latter has been shaped.

The ELEMENT (1 S <I>) (see figure 2) in the opposite end to the one in which it is connected to the upper end of the underlying profile (D), is made in such a way as to allow the rotation of the telescopic arm (F ), (to which it is also connected) around the (i <V>) axis.

This axis (i <V>):

a) passes through the connection point of the element (1S <I>) and the telescopic arm (F), b) is orthogonal to the plane passing through the axis of symmetry of the telescopic arm (F) and the axis ( i <IV>);

THE TELESCOPIC ARM (F) (see figure 2):

1) in relation to the position occupied, it must assume different lengths;

2) rotates around the vertical axis (i <I>) passing through the geometric center of the wheel (1).

THE PRISMATIC ROD (G) (see figure 2):

1) is co-linked, with the opposite end and the one in which it is connected to the profile (D), to the underlying profile (N);

2) constitutes a guide to the element (L).

ELEMENT (L) (see figure 2):

1) in its upper component it is free to rotate around the vertical axis (i <II>), which is perpendicular to the prismatic rod (G) and is contained in the longitudinal vertical plane of symmetry of the same prismatic rod;

2) is also free to translate along the prismatic guide (M) which is anchored to the car body and whose longitudinal symmetry axis is contained in the vertical plane (π) passing through the geometric centers of wheels 1 and 2.

Thanks to the constraint created by the element (L), the prismatic rod (G), when it passes through its neutral position - steering wheels in straight running position - can only continue to rotate around its center of instantaneous rotation, passing through for the axis (i <II>).

THE PROFILE (N) (see figure 2):

1) in its lower part, is made in such a way as to be able to slide along the underlying guide (P) which is anchored to the car body and is shaped according to an arc of circumference having the center on a tip of the vertical axis (i <I >) passing through the geometric center of the wheel (2) and a radius equal to W (see figure 1);

2) in its upper part, is made in such a way as to allow, at one end of the overlying element (2S <I>) and prismatic rod (G), a rotation around the axis (r <VI>) which in any configuration it remains orthogonal to the plane on which the curved guide (P) rests and passes through the curved line on which the latter was generated.

The ELEMENT (2 S <I>) (see figure 2) in the opposite end to that in which it is connected to the profile (N), is made in such a way as to allow the rotation of the telescopic arm (H), to which it is also connected, around the axis (i <VII>).

This axis (i <VII>):

a) passes through the connection point of the telescopic arm (H) with the element (2s <I>),

b) is orthogonal to the plane passing through the axis of symmetry of the telescopic arm (H) and through the axis (i <I>);

THE TELESCOPIC ARM (H) (see figure 2).

1) rotates around the axis (i <I>);

2) must be able to assume different lengths corresponding to the different positions occupied by the wheel (2) with respect to the car body.

The movements of the wheel 2, with respect to the car body, can be determined: a) by the rolling phenomenon to which the car body is subjected and therefore by the exact steering mechanism anchored to it;

b) from the disconnections of the road surface.

The structure carrying the wheel (1) is rigidly connected to the element (1S <I>). The ELEMENT (1 S <I>), in the opposite end to that in which it is connected to the structure carrying the wheel (1), is made in such a way as to allow the rotation of the telescopic arm (F), which is also connected, around the axis (i <VII>).

This axis (i <VII>):

a) passes through the connection point of the telescopic arm (H) with the element (1S <I>);

b) is parallel to the (i <V>) axis.

The structure supporting the wheel (2) is rigidly connected to the element (2S <I>). The ELEMENT (2S <I>), in the opposite end to that in which it is connected to the structure carrying the wheel (2), is made in such a way as to allow the rotation of the telescopic arm (H), to which it is also connected , around the axis (i <IX>).

This axis (i <IX>):

a) passes through the connection point of the telescopic arm (H) with the element (2S <I>),

b) is parallel to the (i <VII>) axis.

In order to make the position of each wheel not influential from the car body and the exact steering mechanism, anchored to it, both from the vertical motion to which each wheel can be subjected with respect to the car body, and to the rolling motion, it is necessary to resort to the design solution described below.

Figures 6a and 6b show the two configurations assumed by the mechanical members in the rectilinear running position (Figure 6a) and in the heterogeneous folding position (Figure 6b) assumed by the car body as a consequence of the rolling motion.

ELEMENT (5) (see figure 2) consists of an upper part (5A), a lower part (5B) and a telescopic arm (5C) interposed between them and is made in such a way that the two components ( 5A) and (58) can approach each other and can never assume a greater distance than that existing between them in correspondence with the configuration assumed in straight running conditions.

The cylindrical guides constituted by the structures carrying the wheels (1) and (2) can transfer through the cylindrical seats made in proximity to the ends of the element (5B).

The shock absorber (8) is connected with its upper part to the right end of the element (5A) and with its lower part to the structure supporting the wheel (1). Similarly, the shock absorber (9) is connected with its upper part to the left end of the element (5A) and with its lower part to the bearing structure of the wheel (2).

The element (7) (see figure 3) is identical to the element (5) and is located in correspondence with the rear wheels.

At the upper right ends of the elements (5A) and (7 A) (see figure 3) there are cylinders (5A <I>) and (7A <I>) rotating around the axis passing through their centers (i <X>).

At the upper left ends of the elements (5A) and (7 A) (see figure 3) there are cylinders (5A <I>) and (7A <I>) rotating around the axis passing through their centers (i <XII>).

THE CAR BODY (6) (see figure 5):

1) is connected to elements (5) and (7) by means of two hinges in correspondence with the axis (i <X>). These hinges (see Figure 3) are located at the center, respectively, of the element (5B) and (7B). The axis (i <X>) (see figure 2) is the longitudinal symmetry axis of the vehicle lying in the plane that contains the axis of the prismatic rod (G) in straight running conditions;

2) in straight running conditions it rests (see figure 6) at the front end, above the cylinders (5A <I>) and (5A <I>), at the rear, above the cylinders (7A <I> ) and (7A <II>) making a guide for each cylinder.

In this way :

A) the only relative movement allowed to the car body with respect to elements (5) and (7) (see figure 6a and 6b) is that of oscillation around the axis of the hinges (i <X>) referred to in point 1 above );

B) the wheels (1) and (2) are released from the oscillations with respect to the axis (i <X>) of the car body and of the steering mechanism;

C) when the vehicle goes through a curve, the car body undergoes an inclination acting accordingly, depending on whether it is a left-hand or right-hand curve, above the cylinders (5A <I>) and (7A <I>) or above the cylinders (5A <I>) and (7A <I>); the latter, in turn, cause the lowering of the elements (5A) and (7A) which <*> l thus approach respectively the elements (5B) and (7B) causing, consequently, an equal compression of the springs, parts components of the shock absorbers of the wheels (1) and (2) (in relation to the front end) and of the wheels (3) and (4) (in relation to the rear end), both in the case of right-hand and left-hand curves; D) all the wheels remain in any configuration orthogonal to the ground; E) when cornering, due to the greater and uniform compression of all the springs making up the wheel shock absorbers;

a) the highest adhesion conditions necessary to counteract the additional forces acting due to these particular maraa conditions occur;

b) there is a limited transverse lying down of the car (roll) which excludes the need to resort to systems such as the stabilizer bar or others. Indeed, these systems limit the transverse lying down of the car but do nothing to reduce the pressure exerted by the tires on the road surface (in correspondence with the wheels closest to the center of instant rotation) and to prevent all four wheels from tilting with respect the aforementioned road surface (change in structure); age with evident impairment of adherence. Moreover, these systems involve the presence of additional organs. The use of the proposed design solution entails the following advantages: 1) in all driving conditions, there are optimal conditions:

a) for tire wear which is uniform;

b) for the stresses due to the weight force since it is uniformly distributed on the tire support surface;

c) for the grip which is always maintained at the maximum level and of equal entity on all four wheels,

2) it is not necessary to resort to the artifice of convergence which, as is known, consists in arranging, in the straight running position, the steering wheels not parallel but converging towards the front in order to take into account the failures that occur during the gear and wheel movements during springing. The elimination of the convergence excludes the following drawbacks typical of this artifice;

a) greater passive resistances;

b) uneven tire wear,

c) accurate and frequent adjustments, especially if the vehicle during (while running) comes into contact with marked bumps in the road surface.

The present invention has been described in a schematic embodiment in order to make it as clear as possible, consequently constructional variations may be made without prejudice to the operating principles.

Claims (5)

CLAIMS 1) Steering mechanisms in which steering of the steering wheels is obtained by constraining the extremity of the axis of the steering wheels to move along a curved guide of analytically determined equation. 2) Steering mechanisms, according to the previous claim, in which the movement of its members is not influenced by that of the wheels with respect to translations in a direction perpendicular to the ground by means of hinges of the type made in correspondence with the axes indicated below (see figure 2): a) (i <V>) and (i <VI>) in relation to the telescopic arm (F), b) (i <VI>) and (i <IX>) in relation to the telescopic arm (H). 3) Mechanisms, according to the preceding claims, which allow the rotation of the steering wheels around an axis orthogonal to the ground passing through the geometric center of each steering wheel. 4) Mechanisms, according to the preceding claims, which allow the vehicle to roll by making the vehicle body rotate around a longitudinal axis of symmetry of the vehicle itself with the exclusion of any inclination of the wheels with respect to the road surface (attitude variation). 5) Mechanisms, according to the preceding claims, which, during the travel of any curve, allow the rotation of the car body around a longitudinal axis of symmetry of the vehicle causing a simultaneous and identical compression of the springs making up the shock absorbers located in correspondence with all ie wheels.