Method for controlling brakes

Abstract

Disclosed is a method for automatically controlling brakes in a trailer vehicle having antilock control, wherein wheel rotational speeds are continuously monitored and evaluated at wheels having antilock control. According to the method, lateral acceleration and longitudinal acceleration of the trailer vehicle are determined. If a predefined, critical lateral acceleration is exceeded, an automatic braking process occurs. A control unit and trailer vehicle are also disclosed in connection with the inventive method.

Claims

1. A method for the automatic actuation of brakes in a trailer vehicle with antilock control, wherein wheel revolution rates on wheels with antilock control are continuously monitored and analyzed by the trailer vehicle, said method comprising: a) determining a lateral acceleration a.sub.Q and a longitudinal acceleration a.sub.L of the trailer vehicle, b) on exceeding a predefined, critical lateral acceleration a.sub.Qkrit, carrying out an automatic braking process comprising: b1) increasing a brake pressure on a side of the trailer vehicle on an inside of a turn incrementally over a plurality of pressure steps, b2) checking in each of the plurality of pressure steps whether a longitudinal acceleration limit a.sub.Lkipp is reached, and b3) checking in each of the plurality of pressure steps whether wheels on the inside of the turn lock or the antilock control engages for wheels on the inside of the turn, wherein b31)if wheels on the inside of the turn lock or the antilock control engages for wheels on the inside of the turn before a.sub.Lkipp is reached, the method further comprises starting deceleration braking at least on a side of the trailer vehicle on an outside of the turn, and b32)if a.sub.Lkipp is reached without wheels on the inside of the turn locking or the antilock control engaging for wheels on the inside of the turn, the method further comprises terminating the braking process.

2. The method as claimed in claim 1, wherein deceleration braking according to step b31 is terminated once the lateral acceleration a.sub.Q is less than a critical lateral acceleration a.sub.QKRIT.

3. The method as claimed in claim 1, wherein after terminating the braking process according to step b32, the automatic braking process is only initiated again according to b, if the lateral acceleration a.sub.Q has continued to increase and exceeds the critical lateral acceleration a.sub.QKRIT by a defined magnitude, or if the trailer vehicle has travelled a defined distance since the last braking process according to b and the lateral acceleration a.sub.Q is still greater than the critical lateral acceleration a.sub.QKRIT.

4. The method as claimed in claim 1, wherein increasing the brake pressure on the side of the trailer vehicle on the inside of the turn is carried out in small steps.

5. The method as claimed in claim 4, wherein the small steps are from 0.1 to 0.2 bar.

6. A trailer vehicle with a brake system for carrying out the method as claimed in claim 1.

7. A control unit for carrying out the method as claimed in claim 1.

8. A trailer vehicle comprising the control unit of claim 7.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The invention is described in greater detail below with reference to the accompanying figures, in which:

(2) FIG. 1 shows the schematic representation of a pneumatic brake system of a trailer vehicle (trailer) with three axles,

(3) FIG. 2 shows the trailer vehicle in rear view with a representation of the forces in a left turn, and

(4) FIG. 3 shows a schematic top view of the trailer vehicle with a towing vehicle while traversing a left turn.

DETAILED DESCRIPTION

(5) With reference to the specific embodiments of the Figures, wherein like numerals generally indicate like parts throughout the several views, a trailer vehicle is generally shown at 10. A trailer vehicle 10 of the trailer type comprises a pneumatic brake system with an anti-lock function. On four of six wheels 11 (two of three axles), wheel revolution rate sensors 12 are provided. The operation of brake cylinders 13 is controllable by a control unit 14. An electrical line P, a pneumatic pressure line AS and a pneumatic control line AC are connected to the control unit 14.

(6) In the case of fast cornering and/or a relatively high center of gravity S of the trailer vehicle 10, there is a risk of tipping over. Assuming a height h or a position of the center of gravity S, a centrifugal force F.sub.Z and a load-dependent, vertically oriented gravitational force F.sub.V, there is a resulting force F.sub.R, see FIG. 2. Corresponding forces occur in the region of contact surfaces 15, 16 between the wheels 11 and the road 17, see arrows 18 (left contact force), 19 (right contact force) and 20 (cornering force). It can be seen that for increasing centrifugal force F.sub.Z, the resultant force F.sub.R deviates ever more from the vertical force F.sub.V and is smaller according to the left contact force (arrow 18). In the extreme case, the left contact force changes sign and the trailer vehicle 10 tips over.

(7) In order to avoid tipping over when traversing a turn, a longitudinal acceleration a.sub.L and a lateral acceleration a.sub.Q are continuously detected, in particular by sensors 21, 22 disposed in the control unit 14. Alternatively or additionally, the lateral acceleration a.sub.Q can be determined from the different revolution rates of the wheels 11 on the inside of the turn and on the outside of the turn. Similarly, the longitudinal acceleration a.sub.L can be alternatively or additionally determined from the change of the wheel revolution rates.

(8) A vehicle combination consisting of a towing vehicle 23 and a trailer vehicle 10 is driving for example at a speed of v=60 km/h in a turn. The lateral acceleration of the vehicle a.sub.Q is monitored continuously, as is the longitudinal acceleration of the vehicle a.sub.L. A tipping-over-critical lateral acceleration a.sub.QKRIT is determined from the design of the vehicle and/or from empirical values. Similarly, a limit value a.sub.LKIPP for a longitudinal acceleration is determined from empirical values or from the design of the vehicle. The following shall apply here: a.sub.QKRIT=3 m/s.sup.2 a.sub.LKIPP=0.24 m/s.sup.2 (or 0.16 m/s.sup.2 for a trailer with two axles, as in North America).

(9) On exceeding the tipping-over-critical lateral acceleration a.sub.QKRIT, an automatic braking process is triggered. This consists of test brakings with brake pressure increasing in stages. The brake pressure is introduced in pulses into the brake cylinder. For each pulse, a period of time of about five to ten milliseconds is used in specific embodiments. Other values can result from the design of the vehicle and the reaction times of the components participating in the braking process. Depending on the steering angle and center of gravity for a given speed v of 60 km/h, the following processes result:

(10) Process 1

(11) The control unit 14 determines a lateral acceleration a.sub.Q of more than 3 m/s.sup.2. The tipping-over-critical lateral acceleration a.sub.QKRIT is thus exceeded. The automatic braking process is triggered and the brake pressure on the side on the inside of the turn (contact surface 15 and arrow 18 in FIG. 2) is increased in defined steps, in particular in about 0.1 bar-steps. In the usual anti-lock controllers, increasing the brake pressure can be controlled via actuation times of inlet magnets on control valves. At the same time, the longitudinal acceleration a.sub.L is monitored. In this case, a negative longitudinal acceleration a.sub.L is determined, the magnitude of which is greater than the predetermined longitudinal acceleration limit a.sub.LKIPP. This means that owing to the automatic braking process of the wheels on the inside of the turn, the trailer vehicle decelerates more than specified by the longitudinal acceleration limit a.sub.LKIPP. The wheels on the inside of the turn do not lock. Thus, the decelerated wheels on the side on the inside of the turn still have sufficient contact force. There is no risk of tipping over. The automatic braking process is terminated. The last measured or calculated lateral acceleration a.sub.Q is stored until further notice, however.

(12) Should the lateral acceleration a.sub.Q increase further, for example by a defined difference or by 5% to 10%, an automatic braking process takes place again.

(13) Process 2

(14) As in process 1, the measured or calculated lateral acceleration a.sub.Q is greater than the critical lateral acceleration a.sub.QKRIT. Brake pressure is increased in pulses, in specific embodiments in 0.1 bar steps, on the side on the inside of the turn. In contrast to process 1, a significantly lower negative longitudinal acceleration a.sub.L is now measured or calculated during the automatic braking process. The magnitude of the longitudinal acceleration a.sub.L is thus smaller than the limit value a.sub.LKIPP of 0.24 m/s.sup.2. This case can for example occur if the vehicle has a center of gravity lying higher than in process 1. The adhesion to the road surface of the wheels on the inside of the turn is still only low. The wheels on the inside of the turn do not have sufficient contact force and lock, or antilock control engages for the wheels on the inside of the turn. As a result, deceleration braking is initiated for the trailer vehicle 10, at least for the wheels on the outside of the turn, in particular for all wheels. Owing to the deceleration braking, the lateral acceleration a.sub.Q reduces to below the critical lateral acceleration a.sub.QKRIT. The braking process is then terminated, because the vehicle is stable again. The process can start from the beginning again, depending on the determined lateral acceleration a.sub.Q.

(15) Process 3

(16) The measured/calculated lateral acceleration a.sub.Q of the vehicle lies below the critical lateral acceleration a.sub.QKRIT of 3 m/s.sup.2. This case can occur in turns with a larger radius or in the case of a very low center of gravity of the vehicle. No automatic braking process takes place.

(17) The terms comprising or comprise are used herein in their broadest sense to mean and encompass the notions of including, include, consist(ing) essentially of, and consist(ing) of. The use of for example, e.g., such as, and including to list illustrative examples does not limit to only the listed examples. Thus, for example or such as means for example, but not limited to or such as, but not limited to and encompasses other similar or equivalent examples. The term about as used herein serves to reasonably encompass or describe minor variations in numerical values measured by instrumental analysis or as a result of sample handling. Such minor variations may be in the order of 0-25, 0-10, 0-5, or 0-2.5, % of the numerical values. Further, The term about applies to both numerical values when associated with a range of values. Moreover, the term about may apply to numerical values even when not explicitly stated.

(18) Generally, as used herein a hyphen - or dash in a range of values is to or through; a > is above or greater-than; a is at least or greater-than or equal to; a < is below or less-than; and a is at most or less-than or equal to. On an individual basis, each of the aforementioned applications for patent, patents, and/or patent application publications, is expressly incorporated herein by reference in its entirety in one or more non-limiting embodiments.

(19) It is to be understood that the appended claims are not limited to express and particular compounds, compositions, or methods described in the detailed description, which may vary between particular embodiments which fall within the scope of the appended claims. With respect to any Markush groups relied upon herein for describing particular features or aspects of various embodiments, it is to be appreciated that different, special, and/or unexpected results may be obtained from each member of the respective Markush group independent from all other Markush members. Each member of a Markush group may be relied upon individually and or in combination and provides adequate support for specific embodiments within the scope of the appended claims.

(20) The present invention has been described herein in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. The present invention may be practiced otherwise than as specifically described within the scope of the appended claims. The subject matter of all combinations of independent and dependent claims, both single and multiple dependent, is herein expressly contemplated.