A steering detection device for articulated vehicles

Abstract: The steering detection device is for articulated vehicles consisting of a tractor truck and a semitrailer, connected by means of a thrust bearing (5) present on the tractor truck and having a hole designed to house a corresponding pin (1) on the semitrailer, creating an axis of relative rotation (X) between the tractor truck and the semitrailer; the device consisting of a shaft (4), attached to the pin (1) in such a way that it may rotate freely, to which a sensor (3) may be fitted, designed to interact with the thrust bearing (5) when the tractor truck is attached to the semitrailer, and of a transducer (2) fitted between the pin (1) and the shaft (4), designed to transform into electric signals the angular movements relative to the rotation between the shaft (4) which is attached to the thrust bearing (5) by means of the said sensor (3), and the pin (1), in order to obtain signals relative to the rotation of the tractor truck with respect to the semitrailer (FIG. 1).

Description: The present invention relates to a steering detection device for articulated vehicles which consists of drive means, or a tractor truck, which tows a semitrailer. To allow medium and large articulated vehicles greater manoeuvrability, self-steering axles are currently widely used, that is to say, a pair of wheels with the relative supporting axle attached to the rear wheels, and which are self-steering when the lorry moves forwards. Problems arise with these particular types of axles when the articulated vehicle must effect reversing manoeuvres during which, on the free axle at the rear of the vehicle, understeering may arise, blocking the vehicle during the manoeuvre. Two different solutions were examined in order to eliminate this fault on the self-steering axle: the first simply locks the axle in a set position, whilst the second, more technologically advanced, causes a controlled movement of the axle wheels even as the articulated vehicle or lorry reverses. The first solution envisages that the self-steering axle be equipped with a locking device (mechanical - hydraulic), activated at the moment in which the reverse gear is engaged on the tractor truck, or more often by the driver (a pin is inserted in a corresponding hole made in the axle); this locking must be effected with the wheels in the normal forward position. However, this solution does not satisfy the manoeuvrability requirements of articulated vehicles, since not only is wear on the tyres of the self-steering axle increased, but there are always parts which create friction on the blocked wheels, giving rise to errors in the steering direction of the articulated vehicle or lorry. In contrast, the second solution, designed by the Applicant named herein (see patent specification IT-A-1 258 555 ), envisages that the self-steering axle be equipped with a hydraulic drive unit (a twin action piston) which acts upon the axle wheels; the unit is controlled by an electrical-hydraulic control unit, connected to the reverse control of the articulated vehicle or lorry so that it is activated only when the vehicle is put into reverse (that is to say, the axle remains passive during forward movement, and becomes active during reversing), and acts upon the piston chambers, allowing the self-steering axle wheels to move in the same way as the front wheels of the tractor truck. The synchronization of the tractor truck front wheels and those of the self-steering axle is controlled by a pair of detectors (linear transducers) which are connected to both steering axles and act upon the control unit which drives the self-steering axle. The use of transducers able to detect the steering angle of the controlled axle allows an exact reading of the effective angle (rather than the estimated angle): thus, if the desired steering angle is not reached, for example due to obstacles to the wheels, upon removal of the impediment it does not prevent the wheels from positioning themselves at the said desired angle, since it is the transducer which reads " the effective position and controls the hydraulic control unit. This solution has proven to be technically reliable, although it has been noticed that whilst it is not difficult to fit linear transducers on normal lorries (on which they are attached to the axles of the directional wheels), on articulated vehicles of the tractor truck-semitrailer type the linear transducer which reads the tractor truck angle must be fitted between the tractor truck and the semitrailer. The most suitable control point is the rotating restraint between the tractor truck and semitrailer (which replaces the lorry's front steering axle), which consists or a thrust bearing which acts as a joint between the tractor truck and semitrailer during manoeuvres. However, technical difficulties prevent the fitting of the said linear transducer at this point, due both to its size (the transducer must be fitted in the extremely limited space between the thrust bearing and semitrailer), and to the fact that the angle of movement available to the tractor truck is, theoretically, much greater than that of the semitrailer and cannot be controlled by normal linear transducers. German Patent Application DE-A-1 957 662, on which is based the preamble of claim 1, discloses an hydraulic steering system, electronic controlled, which comprises a potentiometer fixed to the pin of the semitrailer in such a way that is rotated with the relative steering angle between the tractor truck and the semitrailer. The objective problem compared to this prior art document is the structural fitting of the potentiometer to the pin of the semitrailer and the way by which the potentiometer is rotated by the tractor truck in respect to the semitrailer. In fact, being the potentiometer fitted on the pin of the semitrailer, the connection the potentiometer with the tractor truck should be made in a way that permits the separation of the two vehicles (tractor truck and semitrailer) without disassembling the potentiometer. The solution is to provide the steering detection device rotatably fitted to the pin of the semitrailer with a mechanical sensor having means for coupling the sensor with the thrust bearing of the tractor truck when the tractor truck is attached to the semitrailer. The solution is achieved by the characterising features of claim 1. With a shaft rotatably mounted to the pin of the semitrailer, a mechanical sensor coupled to the shaft, means for coupling the sensor with the thrust bearing of the tractor truck, the steering detection device of the present invention detects the angular movements relative to the rotation between the shaft and the pin and transforms them into electric signals. Further features and advantages of the invention will be appreciated from the dependent claims. The technical features and advantages of the present invention, in accordance with the aforementioned objects, will now be described in detail with reference to the accompanying drawings which illustrate an embodiment by way of example only and in which: figure 1 is a schematic side view with some parts cut away to better view others of an embodiment of the present invention; figure 2 is a partial schematic plan view of the embodiment shown in figure 1; figure 3 is a schematic side view with some parts cut away to better view others, of another embodiment of the present invention; figure 4 is a partial schematic plan view of the embodiment shown in figure 3. In accordance with the accompanying drawings, a steering detection device is for articulated vehicles consisting of a tractor truck and a semitrailer with at least one self-steering axle. The accompanying drawings show only a lower portion of the front end of a semitrailer 7 connected in this way. The tractor truck and the semitrailer 7 are attached by means of a thrust bearing 5 present on the tractor truck and having a hole designed to house a corresponding pin 1 on the semitrailer. The pin 1 may be fitted to the semitrailer in several ways (flanged, bolted, etc.), although the shape of the pin's lower portion, to be connected to the thrust bearing, is always the same, allowing absolute compatibility between the tractor truck and different semitrailers, respecting established standard sizes. The pin 1 defines an X-axis of relative rotation between the tractor truck and the semitrailer. The device consists of a shaft 4, attached to the pin 1 in such a way that it may rotate freely, to which a sensor 3 may be fitted, designed to interact with the thrust bearing 5 when the tractor truck is attached to the semitrailer, and of a transducer 2 fitted between the pin 1 and the shaft 4, designed to transform into electric signals the angular movements relative to the rotation between the shaft 4 which is attached to the thrust bearing 5 by means of the said sensor 3, and the pin 1, in order to obtain signals relative to the rotation between the tractor truck and semitrailer which can be used to check the steering of at least the self-steering axle of the semitrailer. In the illustrated embodiments, the shaft 4 is positioned inside and coaxial to the pin 1, and corresponds to the axis of rotation X. For the connection of the pin to the thrust bearing 5, the presence of a guide zone 51, defined by two tabs or extensions which substantially form a V " shape is envisaged. The height HT of the sensor 3 should not exceed that of the corresponding height HP of the pin 1, so that it does not extend above or below the thrust bearing-pin assembly. The sensor 3 may consist of a connecting bar 32 having separable means for connection to the shaft 4 (at the shaft's lower end 42) and, at the other end, supporting a fitting 31 which can be inserted in the guide zone 51 to interact with the thrust bearing 5. The fitting may consist of a sealed part 31, as shown in figures 1 and 2, or, as illustrated in figures 3 and 4, may be an open plate 31a. The plate 31a is substantially semi-circular in shape and is fixed at its centre to the connecting bar 32, the concave side facing outwards. The plate is substantially "C"-shaped and is made of a flexible material, preloaded, its respective ends 33 making contact with the two "V"-shaped sections of the guide zone 51, so that it interacts with the latter, reducing the force with which it acts upon the connecting bar 32. The connection between the thrust bearing 5 and pin 1 is made by means of a hook or jaw 52 on the thrust bearing 5, designed to grip the pin 1 on a plane P perpendicular to the X-axis (the hook or jaw is not illustrated in figures 3 and 4 for greater clarity). In both embodiments illustrated, the connecting bar 32 can be attached to the shaft below the said plane P (corresponding to the lower end 42 of the shaft 4, with fixing means 43) and extends for a length L not less than the length of the hook 52 from the said X-axis in the direction of the aforementioned guide zone 51, so that the said fitting 31 does not interfere with the hook. The transducer 2 is, preferably, a rotating sensor fitted in a central seat 11 on the pin 1 and attached to the shaft 4 at the top end 41, and equipped with control means designed to determine an angle read by the said rotating sensor, constituting an input variable, which is a function of the rotation between the pin 1 and shaft 4, producing a linear output signal which may be used for the said steering. The transducer 2 may be a potentiometer, an encoder, or similar sensors. Moreover, figures 3 and 4 show a covering plate 10, designed to cover the top of the transducer 2 and the relative seat 11.

Claims: A steering detection device for articulated vehicles, the vehicles consisting of a tractor truck which tows a semitrailer, the semitrailer having at least one self-steering axle, the tractor truck and the semitrailer being joined by a thrust bearing (5) on the said tractor truck, the thrust bearing (5) having a hole designed to house a corresponding pin (1) on the semitrailer, creating an axis (X) of relative rotation between the tractor truck and the semitrailer, the steering detection device comprising a transducer connected to the tractor truck and the semitrailer, so that it detects the angle between the tractor truck and the semitrailer and provides electric signals proportional to the said angle, characterised in that the steering detection device comprises a shaft (4) rotatably mounted to the pin (1), a mechanical sensor (3) coupled to the shaft (4), means (31, 31a, 33) for coupling the sensor (3) with the thrust bearing (5) when the tractor truck is attached to the semitrailer; and in that the transducer (2) is coupled between the shaft (4) and the pin (1) in such a way that the angular movements relative to the rotation between the shaft (4) and the pin (1) are transformed into electric signals. The steering detection device for articulated vehicles as described in claim 1, characterized in that the said shaft (4) is positioned at least partially inside and coaxial to the said pin (1), corresponding to the said axis of rotation (X). The steering detection device for articulated vehicles as described in claim 1, on which, for the connection of the said pin (1) and thrust bearing (5), the presence of a guide zone (51) is envisaged, defined by two tabs or extensions which substantially form a V " shape, characterized in that the height (HT) of the said sensor (3) does not exceed the corresponding height (HP) of the pin (1), the sensor consisting of a connecting bar (32) having separable means for connection to the shaft (4) at one end and, at the other end, supporting a fitting (31) which can be inserted in the guide zone (51) to interact with the thrust bearing (5). The steering detection device for articulated vehicles as described in claim 3, on which the said connection between the thrust bearing (5) and the pin (1) is made by means of a hook or jaw (52) on the thrust bearing (5), designed to grip the pin (1) on a plane (P) perpendicular to the said axis (X) , characterized in that the said shaft (4) is positioned at least partially inside and coaxial to the said pin (1), corresponding to the said axis of rotation (X) and that the said connecting bar (32) is attached to the shaft below the said plane (P) and extends for a length (L) not less than the length of the said hook (52) from the axis (X) in the direction of the guide zone (51), so that the fitting (31) does not interfere with the hook or jaw (52). The steering detection device for articulated vehicles as described in claim 1, characterized in that the transducer (2) is a rotating sensor positioned in a central seat (11) envisaged on the said pin (1) and attached to the shaft (4) and equipped with control means designed to determine an angle read by the said rotating sensor, constituting an input variable, which is a function of the rotation between the pin (1) and shaft (4), producing a linear output signal which may be used for the said steering. The steering detection device for articulated vehicles as described in claim 1, in which for the connection of the pin to the thrust bearing, a guide zone (51) is envisaged on the thrust bearing (5) for connection of the pin (1), the guide zone being defined by two tabs or extensions which substantially for a "V" shape, characterized in that the sensor (3) consists of a connecting bar (32), having at one end separable means (43) for connection to the said shaft (4) and, at the other end, supporting a fitting (31a) , consisting of a substantially semi-circular plate, attached at its centre to the connecting bar (32) and flexible so that when preloaded and inserted in the guide zone (51), its ends (33) interact with the "V"-shaped tabs or extensions.

Inventors: BETTINI MARCO, BETTINI, MARCO
Applicants: BETTINI MARCO, BETTINI, MARCO
Application year: 1995
Main classification: B62D13
IPC codes: B62D13