Method of braking a vehicle and vehicle employing the method TECHNICAL FIELD

The invention relates to a method of braking a vehicle and a vehicle employing the method, particularly a towing vehicle and/or a towed vehicle of a truck.

BACKGROUND OF THE INVENTION

US 2003/0226727 A1 discloses a parking brake device for a vehicle equipped with steer by wire where at least two wheels on the same axle are steered wheels whose steering angle is imposed selectively on each steered wheel by a dedicated electric actuator. A parking brake control unit delivers a parking brake locking command to the control unit, such that, upon receipt of a parking brake locking command, the control unit transmits antagonistic steering angle commands to the two wheels on the same axle. The antagonistic steering angle results in a displacement incompatibility of the vehicle. A parking brake is obtained without fitting mechanical components dedicated to the function on the wheels or connected to the brake discs or brake shoes.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a method for braking a vehicle which is used for heavy vehicles, particularly trucks. Another object is to provide such a vehicle. The objects are achieved by the features of the independent claims. The other claims, the drawing and the description disclose advantageous embodiments df the invention. According to a first aspect of the invention, a method is proposed of braking a vehicle having at least three axles, particularly a towing vehicle and/or a towed vehicle of a truck, wherein each axle has at least one left wheel and one right wheel, wherein at least two selected axles and/or left and right wheels connected to at least two selected axles are steerable, and wherein, for exerting a brake force, the left and right wheels of at least one of two selected axles are turned compared to a straight direction to counteract cornering of the vehicle, and the left and right wheels associated with the same one of the two selected axles are turned in the same direction.

The expression "vehicle" is to be understood to include a tractor vehicle as well as a full trailer or a semitrailer. The method can be employed by only the tractor vehicle or only the trailer or semitrailer or by both the tractor vehicle and the trailer or semitrailer.

Advantageously, a steering angle of the left wheel of the selected axle is the same as the steering angle of the right wheel. It is to be understood that either the selected axle is a steered axle or the individual wheels of the selected axle can be individually steered, e.g. by an electrical or hydraulic wheel motor. Expediently, at least two selected axles are included to provide the braking force by turning the left and right wheels in an appropriate direction. However, more axles may be present.

A parking brake control unit may deliver a wheel turning command to e.g. a steering control unit. Upon receipt of the turning command, the control unit may transmit steering angle commands to the left and right wheels on the respective selected axles. Depending on the location of the selected steerable axles with respect to one or more non-steered (i.e. fixed) axles, the left and right wheels of the first one of the two selected axles can be oriented parallel to the left and right wheels of the second one of the selected axles or in an opposing direction compared to the left and right wheels of the second one of the selected axles. An undesired motion of the vehicle along the ground surface is blocked even without using a conventional parking brake. An additional brake force can be provided which adds to the brake force of the conventional parking brake. The parking brake force can be improved without additional components, particularly for a vehicle with tag or pusher axles. On the other hand, the conventional parking brake can be made lighter and cheaper with - in combination with said turning the left and right wheels - the same overall parking brake force. Favourably, at least at one axle a conventional parking brake can be omitted.

The invention is particularly useful in vehicles with active axle steering, for instance with active front and/or rear axle steering. The method can be included in the steering control procedure by appropriately adapting the steering control unit's control software. Active axle steering means that a control system can under certain conditions provide a steering angle and/or a steering force to the wheels on the steered axle or axles automatically with or without input from the steering wheel. According to an advantageous embodiment of the invention, the two selected axles may be arranged at different sides of a non-steered axle and the left and right wheels of one of the selected axles are turned in one direction and the left and right wheels of the other one of the selected axles are turned in the same direction. Due to the orientation of the left and right wheels of the selected axles the vehicle is prevented from undesired motion at standstill. The required orientation of the wheels for providing a braking force can easily be adapted to the actual configuration of steered and non-steered (fixed) axles on the vehicle.

According to an advantageous embodiment of the invention, the two selected axles may be arranged at the same side of a non-steered axle and the left and right wheels of one of the selected axles are turned in one direction and the left and right wheels of the other one of the selected axles are turned in opposing directions. Due to the orientation of the left and right wheels of the selected axles the vehicle is prevented from undesired motion at standstill. The required orientation of the wheels for providing a braking force can easily be adapted to the actual configuration of steered and non-steered (fixed) axles on the vehicle.

According to an advantageous embodiment of the invention, the left and right wheels of a selected front axle may be turned by not more than 45 degrees, preferably not more than 43 degrees. By limiting the steering angle of the left and right wheels, the wheels can be turned as much as possible while an unwanted contact of turned wheels with the frame can be avoided. According to an advantageous embodiment of the invention, the left and right wheels of a selected tag axle or a selected pusher axle may be turned by not more than 20 degrees, preferably by not more than 15 degrees. By limiting the steering angle of the left and right wheels, the wheels can be turned as much as possible while an unwanted contact of turned wheels with the frame can be avoided.

According to an advantageous embodiment of the invention, a steering linkage length between two left and right wheels of a selected axle may remain unchanged between the left and right wheels in a straight orientation and with the left and right wheels of the selected axle turned for braking. A simple standard solution of steering geometry and design is possible.

According to an advantageous embodiment of the invention, the orientation of the left and right wheels associated with a selected axle may deviate from being perpendicular to an Ackermann radius. In an idealized form, the wheels are oriented perpendicular to the Ackerman radius within usual tolerances when cornering. Wheels deviating from this orientation (taking into account usual tolerances) do not allow for cornering but rather block the movement of the vehicle. According to an advantageous embodiment of the invention, the left and right wheels of the selected axles may be turned at or close to standstill of the vehicle. Favourably, the moment for turning the left and right wheels can be initiated by the driver when parking of the vehicle is intended. Alternatively, the turning of the left and right wheels can be initiated automatically dependent on the speed of the vehicle when the intention to park the vehicle is recognized by a steering control, for instance in order to reduce the wear of the ordinary wheel brakes at normal service braking. In principle, the wheels can be turned for braking the vehicle when the vehicle is still driving. Advantageously wear on the ordinary service brakes can be reduced or alternatively, the brakes can be made smaller or even may be replaced by using turning of the wheels for braking.

According to an advantageous embodiment of the invention, the left and right wheels may be turned at or close to standstill of the vehicle and one or more wheels are recognized to slide on a road, and the left and right wheels are turned in a direction towards an edge of the road. Advantageously, the risk of sliding of the vehicle in an undesired direction such as a lane with oncoming traffic can be reduced.

According to another aspect of the invention, a vehicle is proposed, particularly a towing vehicle and/or towed vehicle of a truck, having at least three axles, wherein each axle has at least one left wheel and one right wheel, wherein at least two selected axles and/or left and right wheels connected to the at least two selected axles are steerable, and wherein, for exerting a brake force, the left and right wheels of at least one of two selected axles are turnable compared to a straight direction to counteract cornering of the vehicle, wherein a braking force is achieved by the method according to the first aspect of the invention, wherein the vehicle is adapted to turn left and right wheels associated with the same one of the two selected axles in the same direction.

Expediently, a control device can be provided to initiating the turning of left and right wheels associated with the same one of the two selected axles in the same direction for exerting a braking force by the turned wheel which can be added to the braking force of a conventional parking brake or which can be used as the only parking brake force of the vehicle.

According to an advantageous embodiment of the invention, at least one axle may be electrically or hydraulically steerable. The invention is particularly useful for vehicles with an active front or rear axle steering. Advantageously, with active steering it is possible to steer the axles to achieve the desired parking forces. According to an advantageous embodiment of the invention, one of the at least three axles may be a non-steered axle. The steered axles can be used for braking the vehicle (by applying a steering angle to the wheels), wherein the orientation of the steering angle of the wheels depends on the relative position to the non- steered axle compared to the non-steered axle.

According to an advantageous embodiment of the invention, the two selected axles may constitute a parking brake. A conventional parking brake may be supported by the braking force provided by the turned wheels or even be replaced. The safety of the vehicle can be improved. Particularly under slippery road conditions, the vehicle can be stabilized at standstill or close to standstill.

Advantageously, the steered wheels can be automatically turned in such a direction that the vehicle at sliding will move toward the pavement side stone that will obstruct further sliding.

According to another aspect of the invention, a computer program is proposed comprising a computer program code adapted to perform a method or for use in a method according to the first aspect of the invention, when said program is run on a programmable microcomputer. Preferably the computer program may be adapted to be downloadable to a control unit or one of its components when run on a computer which is connected to the internet.

According to another aspect of the invention, a computer program product stored on a computer readable medium is proposed, comprising a program code for use in a method according to the first aspect of the invention on a computer.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention together with the above-mentioned and other objects and advantages may best be understood from the following detailed description of the embodiment(s), but not restricted to the embodiments, wherein is shown

schematically: Figure 1 a, 1 b, 1 c an example embodiment of a vehicle with three axles with a non-steered axle in the middle of two steered axles with the left and right wheels of the steered axles turned for cornering (Figure 1 a) and the left and right wheels turned for braking (Figures 1 b, 1 c);

Figure 2a, 2b, 2c an example embodiment of a vehicle with three axles with a non-steered axle as the rear axle with two steered axles in front of it with the left and right wheels of the steered axles turned for cornering (Figure 2a) and the left and right wheels turned for braking (Figures 2b, 2c);

Figure 3a, 3b, 3c an example embodiment of a vehicle with three axles with a non-steered axle in the front of two steered axles with the left and right wheels of the steered axles turned for cornering (Figure 3a) and the left and right wheels turned for braking (Figures 3b, 3c);

Figure 4a, 4b, 4c an example embodiment of a vehicle with four axles with two non-steered axles in the middle between two steered axles with the left and right wheels of the steered axles turned for cornering (Figure 4a) and the left and right wheels turned for braking (Figures 4b, 4c);

Figure 5a, 5b, 5c an example embodiment of a vehicle with four axles with two non-steered axle at the rear and two steered axles in front with the left and right wheels of the steered axles turned for cornering (Figure 5a) and the left and right wheels turned for braking (Figures 5b, 5c);

Figure 6a, 6b, 6c an example embodiment of a vehicle with four axles with a non-steered axle in the middle of two steered axles and a third steered axle as front axle with the left and right wheels of the steered axles turned for cornering (Figure 6a) and the left and right wheels turned for braking (Figures 6b, 6c);

Figure 7 a vehicle on a slippery road with left and right wheels turned for hindering sliding according to the invention; and

Figure 8 a sketch of a theoretical Ackermann steering geometry. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE

INVENTION In the drawings, equal or similar elements are referred to by equal reference numerals. The drawings are merely schematic representations, not intended to portray specific parameters of the invention. Moreover, the drawings are intended to depict only typical embodiments of the invention and therefore should not be considered as limiting the scope of the invention.

Fig. 1 depicts schematically an example embodiment of a vehicle 100 with three axles 10, 20, 30 with a non-steered axle 10 having left wheels 101 and right wheels 10r oriented in a straight direction 80 in the middle of two steered axles 30, 50 with the left and right wheels 30I, 30r on the steered axle 30 in front and 50I, 50r on steered axle 50 at the rear of the vehicle 100.

Figure 1 a depicts the left and right wheels 30I, 30r and 50I, 50r of the steered axles 30, 50 turned with a steering angle for cornering of the vehicle 100, i.e. the left and right wheels 30I, 30r of the steered front axle 30 are turned in a left direction 80I and the left and right wheels 50I, 50r of the steered rear axle 50 are turned in a left direction 80I for cornering the vehicle 100 counterclockwise. A clockwise turn (not shown) can be performed with the left and right wheels 30I, 30r of the steered front axle 30 turned in the left direction 80I and the left and right wheels 50I, 50r of the steered rear axle 50 turned in the right direction 80r. The straight direction 80 is to be understood as a direction relative to the longitudinal axis of the vehicle 100, as the directions 80, 80I, 80r turn simultaneously with cornering of the vehicle 100.

Figures 1 b and 1 c depict the left and right wheels 30I, 30r, 50I, 50r of the steered axles 30 and 50 turned for braking. As the two selected axles 30, 40 are arranged at different sides of the non-steered axle 10 the left and right wheels 30I, 30r, 50I; 50r of the selected axles 30, 50 are all turned in the same direction 80I or 80r. In Figure 1 b, the wheels 30I, 30r, 50I, 50r of both steered axles are turned to the left direction 80I, which effectively prevents the vehicle 100 from cornering and instead blocks a movement of the vehicle 100. Figure 1 c shows a symmetric arrangement where the wheels 30I, 30r, 50I, 50r of both steered axles 30, 50 are turned to the right direction 80r, which effectively prevents the vehicle 100 from cornering and instead blocks a movement of the vehicle 100.

Figures 2a-2c depict an example embodiment of a vehicle 100 with three axles 10, 30, 40 with a non-steered axle 10 as the rear axle and two steered axles 30, 40 in front, with axle 30 as foremost axle. The left and right wheels 301, 30r, 401, 40r of the steered axles 30, 40 are turned for cornering in Figure 2a and turned for braking in Figures 2b, 2c. The axle 30 can be a driven axle and axle 40 a tag axle, or axle 40 can be driven and axle 30 can be a pusher axle. As seen in Figure 2a, the left and right wheels 301, 30r, 401, 40r have to be turned in the same direction 801 for cornering the vehicle 100 counterclockwise or 80r for cornering clockwise. In principle, all axles or only one or more can be driven.

As the two selected steered axles 30, 40 are arranged at the same side (e.g. in front) of the non-steered axle 10, the left and right wheels 30I, 30r, 40I, 40r of the selected axles 30, 40 are turned in different, opposing directions 80I, 80r for prohibiting cornering of the vehicle 100. In Figure 2b, the wheels 40I, 40r of the second steered axle 40 are turned to the right direction 80r and the wheels 30I, 30r of the front axle 30 are turned to the left direction 80I. Figure 2c shows a

symmetric arrangement where the left and right wheels 40I, 40r of the second steered axle 40 are turned to the left direction 80I and the left and right wheels 30I, 30r of the front axle 30 are turned to the right direction 80r.

Figures 3a-3c illustrates an example embodiment of a vehicle 100 with three axles 10, 60, 70 with a non-steered axle 10 in the front of two steered axles 60, 70 with the left and right wheels 60I, 60r, 70I, 70r of the steered axles 60, 70 turned for cornering in Figure 3a and the left and right wheels 60I, 60r, 70I, 70r turned for braking in Figures 3b, 3c. In Figure 3b, the wheels 701, 70r of the rear steered axle 70 are turned to the right direction 80r and the wheels 601, 60r of the steered axle 60 in front of it are turned to the left direction 801. Figure 2c shows a symmetric arrangement where the left and right wheels 701, 70r of the rear steered axle 70 are turned to the left direction 801 and the left and right wheels 601, 60r of the steered axle 60 in front of it are turned to the right direction 80r.

The axle 60 can be a driven axle and axle 70 a tag axle, or axle 70 can be driven and axle 60 can be a pusher axle. Axle 10 can be driven or undriven, but it is technically advantageous to have a driven axle 10.

Figures 4a-4c depict an example embodiment of a vehicle 100 with four axles 10, 20, 30, 50 with two non-steered axles 10, 20 in the middle between two steered axles 30 (front axle) and 50 (rear axle) with the left and right wheels 30I, 30r, 50I, 50r of the steered axles 30, 50 turned for cornering in Figure 4a and the left and right wheels 301, 30r, 501, 50r turned for braking in Figures 4b, 4c.

For cornering, as in Figure 1 a, i.e. the left and right wheels 30I, 30r of the steered front axle 30 are turned in a left direction 80I and the left and right wheels 50I, 50r of the steered rear axle 50 are turned in a left direction 80I for cornering the vehicle 100 counterclockwise. A clockwise turn (not shown) can be performed with the left and right wheels 30I, 30r of the steered front axle 30 turned in the left direction 80I and the left and right wheels 50I, 50r of the steered rear axle 50 turned in the right direction 80r, while the left and right wheels 101, 10r, 20I, 20r if the non-steered axles 10, 20 remain oriented in the straight direction 80.

Figures 4b and 4c depict the left and right wheels 30I, 30r, 50I, 50r of the steered axles 30 and 50 turned for braking. As the two selected axles 30, 40 are arranged at different sides of the non-steered axle 10 the left and right wheels 30I, 30r, 50I; 50r of the selected axles 30, 50 are all turned in the same direction 80I or 80r.

In Figure 4b, the wheels 30I, 30r, 50I, 50r of both steered axles 30, 50 are turned to the left direction 80I, which effectively prevents the vehicle 100 from cornering and instead blocks a movement of the vehicle 100. Figure 4c shows a symmetric arrangement where the wheels 301, 30r, 501, 50r of both steered axles 30, 50 are turned to the right direction 80r, which effectively prevents the vehicle 100 from cornering and instead blocks a movement of the vehicle 100. The non-steered axles 10, 20 stay oriented in the straight direction 80.

Figures 5a-5c show an example embodiment of a vehicle 100 with four axles 10, 20, 30, 40 with two non-steered axle 10, 20 at the rear and two steered axles 30, 40 in front where axle 30 is the foremost of the two steered axles 30, 40. The left and right wheels 30I, 30r, 40I, 40r of the steered axles 30, 40 turned for cornering in Figure 5a and turned for braking in Figures 5b, 5c.

As seen in Figure 5a, the left and right wheels 301, 30r, 401, 40r have to be turned in the same direction 801 for cornering the vehicle 100 counterclockwise or 80r for cornering clockwise. All axles can be driven but at least one, i.e. advantageously axle 10 is driven.

As the two selected steered axles 30, 40 are arranged at the same side (e.g. in front) of the non-steered axles 10, 20, the left and right wheels 30I, 30r, 40I, 40r of the selected axles 30, 40 are turned in different, opposing directions 80I, 80r for prohibiting cornering of the vehicle 100. In Figure 5b, the wheels 40I, 40r of the second steered axle 40 are turned to the right direction 80r and the wheels 30I, 30r of the front axle 30 are turned to the left direction 80I. Figure 5c shows a

symmetric arrangement where the left and right wheels 40I, 40r of the second steered axle 40 are turned to the left direction 80I and the left and right wheels 30I, 30r of the front axle 30 are turned to the right direction 80r.

Figures 6a-6c illustrate an example embodiment of a vehicle 100 with four axles 10, 30, 40, 50 with a non-steered axle 10 in the middle of two steered axles 40, 50 and a third steered axle 30 as front axle with the left and right wheels 30I, 30r, 40I, 40r, 50I, 50r of the steered axles 30, 40, 50 turned for cornering in Figure 6a and turned for braking in Figures 6b, 6c.

The left and right wheels 30I, 30r, 40I, 40r of the two steered axles 30, 40 at the same side of the non-steered axle 0 are turned in opposing directions, i.e. in Figure 6b left and right wheels 301, 30r of axle 30 to the left direction 801 and left and right wheels 401, 40r of axle 40 to the right direction 80r. The left and right wheels 501, 50r of the steered rear axle 50 are turned to the left direction 801.

However, left and right wheels 501, 50r of the steered rear axle 50 could also be turned to the right direction 80r or even stay straight in direction 80. It is expedient, however, to turn the wheels 501, 50r of the steered rear axle 50 as they can increase the braking force of the arrangement.

Figure 6c shows a symmetric arrangement where the wheels 301, 30r are turned in the right direction 80r and the wheels 401, 40r turned to the left direction 801 which effectively prevents the vehicle 100 from cornering and instead blocks a

movement of the vehicle 100. The non-steered axle 10 is oriented in the straight direction 80. The left and right wheels 50I, 50r of the steered rear axle 50 are turned to the left direction 80I but may be turned to the right direction 80r or even stay straight in direction 80. It is expedient, however, to turn the wheels 501, 50r of the steered rear axle 50 as they can increase the braking force of the

arrangement.

Figure 7 illustrates a vehicle 100 according to Figures 1 a-1 c on a road 200 with slippery ground conditions, e.g. when covered with snow. In case the vehicle 100 at standstill or close to standstill starts to slide, the left and right wheels 30I, 30r of the steered front axle 30 and the left and right wheels 50I, 50r of the steered rear axle 50 are turned to contravene cornering and turned in a way that, when sliding, the vehicle 100 slides to the edge of the road 200 instead to the lane of the oncoming traffic. This is indicated by an arrow pointing to the edge of the road 200.

The invention can take the form of a hardware embodiment, a software

embodiment or an embodiment containing both hardware and software elements. In a preferred embodiment, the invention is implemented in software, which includes but is not limited to firmware, resident software, microcode, etc.

Furthermore, the invention can take the form of a computer program product accessible from a computer-usable or computer readable medium providing program code for use by or in connection with a computer or any instruction execution system. For the purposes of this description, a computer-usable or computer readable medium can be any apparatus that can contain, store, communicate, propagate, or transport the program for use by on in connection with the instruction execution system, apparatus, or device. Particularly, the invention can be implemented in a steering control device.

The medium can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device) or a propagation medium.

Examples of a computer-readable medium include a semiconductor or solid state memory, magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disk and an optical disk. Current examples of optical disks include compact disk-read-only memory (CD-ROM), compact disk-read/write (CD-R/W) and DVD.

A software for performing the inventive method can be implemented in a control unit 1 10 on the vehicle 100. The control unit 10 can be coupled to a steering control unit or can be the steering control unit. Expediently, the left and right wheels of a selected steerable front axle are turned by not more than 45 degrees, preferably not more than 43 degrees, whereas the left and right wheels of a selected steerable tag axle or of a selected steerable pusher axle are turned by not more than 20 degrees, preferably by not more than 15 degrees.

The steered axles are usually non-driven axles, while the non-steered axles are driven axles. However, the steered axles can also be embodied as driven axles.

According to the invention, the turning of left and right wheels associated with selected steered axles can be used to brake the vehicle in a parking position when the turned vehicles do not fulfil a steering geometry, particularly if the steering angel of the wheels are not perpendicular to an Ackermann radius. Figure 8 depicts a known ideal Ackermann steering geometry where the wheels of two axles 200, 202 fulfil the steering geometry. The left and right wheels 2021, 202r of the steered axle 202 are perpendicular to an Ackerman radius A_202l and A_202r, respectively, as well as the wheels of the non-steered axle 200 which are oriented perpendicular to the Ackerman radius A_200. The wheels 2021, 202r on the axles 200, 202 then move (in an ideal theoretical case) on circle segments with a common midpoint 210. It is to be understood that these considerations represent an ideal case while in reality there are necessarily deviations from the

perpendicular orientations due to the real devices and linkages used. Wheels which do not fulfil the steering geometry will perform cornering but the wheels will have extensive slip towards the ground which will give rise to tyre wear.