Patent Application
20100063702
The present invention relates to a system and a method for stabilising a vehicle combination comprising a towing motor vehicle and a towed vehicle. The towed vehicle comprises one trailer or a combination of trailers. A trailer can either be a drawbar trailer, also named full trailer, or a semi-trailer.
From EP 0 941 905 a system of such kind is known. In this system, a tractor vehicle is provided with a steering wheel sensor, a yaw rate sensor, a transverse acceleration sensor and/or an inflection angle sensor detecting the angle between the longitudinal axis of the tractor vehicle and the longitudinal axis of the trailer. At the tractor/trailer interface, braking pressure for braking the trailer wheels may be provided in response to the sensors in the event of the presence of a stability-critical driving status is detected.
In U.S. Pat. No. 6,450,019 B1 another apparatus and method for stabilising a vehicle combination is described, wherein the inflection angle between the longitudinal axis of the tractor vehicle and the longitudinal axis of the trailer is determined and a comparison is performed as a function of the inflection angle variable and a comparison variable. An actuator arrangement is associated with the trailer with which a brake pressure can be established at one or more of the wheels of the trailer to re-establish a stability of the tractor/trailer combination.
These known systems are automatically re-establishing a stability if the tractor/trailer combination has become unstable, so-called “stretch braking” Previously, a manually operated separate trailer brake was installed, allowing the driver to use auxiliary trailer braking on the vehicle combination when releasing the accelerator pedal or when driving on slippery road conditions. But this caused a considerable wear on the trailer brakes, as the trailer brake was often used to decelerate the entire road train. Therefore such systems were abandoned and made illegal due to the adverse effect on road safety as the result of the manual trailer braking was that many trailers were driving around with worn brakes. The automatic systems are considered inadequate as they are quite complicated and expensive. In particular, as the tractors and trailers grow bigger in size to transport an increasing payload, the problem of instability of the vehicle combination will increase and with the known systems, the wear of the trailer brakes will also increase.
On this background, it is desirable to provide a stabilising method and system for a vehicle combination providing an improved stability of the vehicle combination.
In an aspect of a method and a system for stabilising a vehicle combination of a towing vehicle, such as a tractor or a truck, and a towed vehicle, such as at least one trailer or semi-trailer, the system includes: a trailer brake system on the towed vehicle which may be operated together with a vehicle brake system on the towing vehicle as well as independent from said vehicle brake system; means for detecting at least one signal corresponding to at least one driving condition; means for computing the detected at least one signal corresponding to said at least one driving condition and comparing the at least one detected signal with a corresponding predetermined values representing a critical driving condition; activation means for allowing independent operation of the trailer brake system in response to a detected critical driving condition; and means for automatically operating the trailer brake system in response to the activation means by applying temporary braking actions on the towed vehicle.
By an aspect of the present invention, a proactive stabilising trailer brake system is provided. Rather than sensing the actual relative position of the towing vehicle and trailer in the vehicle combination, the driving conditions are detected, and if the conditions are considered to be critical, e.g. a steep downhill road inclination, risk of slippery road conditions due to the ambient temperature, the trailer brake system can be activated. Hereby, the system can be used as a proactive system. The stabilising action can be defined as ESP (Electronic Stability Programme) interventions that allow temporary trailer braking actions. These actions preferably comprise short repeated trailer brake actuations that are strong enough to significantly affect the vehicle combination but not strong enough to cause significant trailer brake wear, fading or glazing problems. The computing means decide if a critical driving condition is detected and if so, allows the operating means (ESP) to perform automatic trailer braking actions. Hereby, a proactive stretch braking system for stabilising is achieved that can be defined as ESP interventions that (legally) allows temporary trailer braking actions. This is in particular advantageous for larger vehicle combinations which may be less stabile in some driving conditions.
The driving condition detection preferably includes detecting one or more of the following driving conditions:
Ambient temperature. If a risk of ice or snow on the road is present due to the ambient temperature, the system is informed of this.
Road inclination. The computing could be adapted in such a manner that the operation means are only allowed activation if the inclination angle is a downhill inclination above a certain angle or percentage.
Steering wheel angle. In order to avoid the separate trailer braking action to influence the driving path, a limitation in the activation of the operating means may be defined which is dependent on the steering wheel position.
Vehicle combination weight. In order to apply a suitable amount of temporary trailer braking, it would be advantageous for the system to have information of the vehicle combination weight.
Auxiliary braking of the tractor vehicle with a braking torque above a predefined limit, such as auxiliary brake usage, such as engine brake and/or retarder. This braking torque limit could also be temperature dependent.
Vehicle combination speed. A limit to the minimum and maximum speed for the allowance of the trailer brake system could be defined to avoid adversely affecting the stability of the vehicle combination at high speed and to avoid constrains in parking manoeuvres at low or reverse speed.
Braking balance between towing vehicle and trailer. This information can be obtained from the CFC (Coupling Force Control) function of the towing vehicle. An underbraked trailer, i.e. a trailer that is braked less than required, can cause a “jack-knife” situation. This situation would give a signal asking for a more powerful brake actuation of the trailer brake. An overbraked trailer, i.e. a trailer that is braked more than required, can cause a “trailer swing-out” situation. This situation would give a signal asking for less or no brake actuation of the trailer brake.
The computing of the detected signals determines if a critical driving condition is present and alerts the activation means. The independent operation of the trailer brake system may be automatically activated in response to the detected critical driving condition. Hereby, the driver does not need to activate the auxiliary trailer brake system. Alternatively, the independent operation of the trailer brake system may be activated by a driver operated activation switch in response to an indicator triggered by the detected critical driving condition. This indicator may be a audio, visual or audiovisual indicator in the driver compartment of the vehicle. If the driver must allow the ESP of activating the auxiliary trailer brake system, the driver can actively also decide not to do so, e.g. if the vehicle combination is reversed e.g. for parking or loading or unloading. The indicator and the activation switch may be integrated in a multiple function panel or provided as separate indicator lamps and switches.
In the following, the invention is described in more detail with reference to the drawings, in which:
In
In
The system according to the invention is illustrated schematically in
The measurements that are detected and fed to the computing unit 5 may be one or more measurements relating to parameters which may influence the driving condition of the vehicle combination.
In the following are listed some relevant parameters influencing the driving conditions, partly due to road conditions subjected to the vehicle combination, and that may determine the activation of the operation means 4 for allowing auxiliary trailer braking to take place. The parameters may be:
Ambient Temperature.
If a risk of ice or snow on the road is present due to the ambient temperature, the system is informed of this and if the temperature is below a predetermined limit the system may be allowed activation. A temperature below this threshold limit could itself alone cause the ESP operation means 4 to be allowed, or such allowability could be made dependent on other measurements as well.
Road Inclination.
The computing could be adapted in such a manner that the operation means 4 are only allowed activation if the inclination angle is a downhill inclination above a certain angle or percentage.
Steering Wheel Angle.
In order to avoid the separate trailer braking action to influence the driving path, a limitation in the activation of the operating means may be defined which is dependent on the steering wheel position.
Vehicle Combination Weight.
In order to apply a suitable amount of temporary trailer braking, it would be advantageous for the system to have information of the vehicle combination weight.
Auxiliary Braking/Deceleration.
Auxiliary braking of the tractor vehicle with a braking torque above a predefined limit, such as auxiliary brake usage, such as engine brake and/or retarder, may be detected by measuring the acceleration and in particular the deceleration. This braking torque limit could also be temperature dependent or dependent on other parameters in order to allow for activation of the ESP operation means 4.
Vehicle Combination Speed.
A limit to the minimum and maximum speed for the allowance of the trailer brake system could be defined to avoid adversely affecting the stability of the vehicle combination at high speed and to avoid constrains in parking manoeuvres at low or reverse speed.
Braking Balance Between Towing Vehicle and Trailer.
This information can be obtained from the CFC (Coupling Force Control) function of the towing vehicle. If the ratio between the braking torque of the towing vehicle and the braking torque of the trailer is unbalanced, the vehicle combination may be unstable. The ratio of the brake torque should then preferably be adjusted. An underbraked trailer, i.e. a trailer that is braked less than required, can cause a “jack-knife” situation. This situation would create a signal asking for a more powerful brake actuation of the trailer brake. An overbraked trailer, i.e. a trailer that is braked more than required, can cause a “trailer swing-out” situation. This situation would create a signal asking for less or no brake actuation of the trailer brake.
Measurements of many of these relevant parameters are already made in most electronic systems installed in trucks and tractors. Therefore, the system according to the invention is easy to implement. The system may be implemented during the design and manufacture of tractors or mounted subsequently on tractors, trucks and the like.
In the diagram in
By the invention, it is realised that the system may be applied to braking system that are both pneumatically, hydraulically or electrically operated.
In a further embodiment, a vehicle combination with a towing vehicle and two trailers is stabilised by the inventive system. The vehicle combination may e.g. comprise a tractor with a semi-trailer and an extra trailer coupled to the semi-trailer. This combination is used to make up for different length requirements in different states or regions. Another possible combination is a truck with two short trailers. In this embodiment, the system is adapted to start the braking actuation on the rearmost trailer when a critical driving condition is detected, in order to stabilise the vehicle combination. In this embodiment, it is possible to let the rearmost trailer brake operate independently, and also to let the front trailer brake operate independently of the vehicle brake but only when the rearmost trailer brake is actuated. In this way, the vehicle combination is stabilised from the rear of the combination.
Above, the invention is described with reference to some preferred embodiments. However, it is realised that other embodiments may be performed without departing from the scope of protection as defined by the accompanying claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0501657-1 | Jul 2005 | SE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/SE06/00849 | 7/6/2006 | WO | 00 | 1/8/2008 |
