SE509073C2 - Method and apparatus for adjusting the braking force of a trailer vehicle to one of a towing vehicle and at least one trailer combination vehicle combination - Google Patents

Abstract

The method involves a tractor vehicle and at least one trailer. Initially, multiple actual values of variables characterising braking behaviour of the trailer are determined, these variables being for a multiple of braking requirements controlled at the tractor vehicle. A first braking curve is determined from the multiple of actual values of the variable characterising the braking behaviour of the trailer. A desired braking curve (Zsoll,Zsoll1,Zsoll2) is then determined. A correction value is determined for the braking requirement of the trailer, as the difference between the desired and the actual braking curve (Zist). The braking requirement of the tractor vehicle is thus altered according to the correction value, and the corrected braking requirement of the trailer is controlled.

Description

15 20 25 3Û_: 509 073 2 DE 41 30 848 Cl provides a method of brake pressure control for a trailer, without the need for a clutch force transducer. Only the wheel speed of the towing vehicle and of the trailer is determined there. The braking force division between towing vehicle and trailer is set so that the intermediate speed of the wheels on non-driven axles on both vehicle parts becomes equal. The brake pressure of the trailer is then set in the corresponding position based on a predetermined initial value.

EP 0 621 161 A1 provides a method for determining the pressure force from a trailer, whereby the forces acting between towing vehicles and trailers can be determined without the use of load sensors.

The older, unpublished German patent applications P 44 12 430 and P 44 46 358.8 finally describe a method for setting the brake disc division between a towing vehicle and a trailer, where the total energy of the vehicle combination at three different times is determined on the basis of measured and vehicle-specific quantities, stored values. In this way, the vehicle mass and the angle of inclination can be determined and the braking force distribution between towing vehicle and trailer adjusted. At the latter P 44 46 358.8, the measurements are carried out only when the vehicle is in a non-driven state and the brake is not activated.

In general, it can be stated that when braking a vehicle combination, the driver gives a brake demand signal via the brake pedal, on the basis of which a brake pressure is set for the towing vehicle and for the trailer. The braking pressure set in the towing vehicle differs from the braking pressure in the trailer, whereby it is a basic goal to keep the coupling forces between the towing vehicle and the trailer within predetermined limits, even at varying load conditions for the trailer.

In the prior art described above, however, it is nevertheless indirectly taken into account that different trailers have very sharply varying braking curves. Brake curve refers to the braking force as a function of the set brake pressure. If - as according to the known 10 15 20 30: 3 BÜ9 Û73 technology - the braking pressure in the trailer is regulated as a function of the coupling force between the trailer and the towing vehicle, this of course also indirectly takes into account the trailer's braking curve, but a certain specific time is needed before the control device has set the "correct" brake pressure in the trailer, whereby, depending on the type of regulator used, there may also be a turn-in process or overshoots.

The object of the present invention is to further develop the initially stated method and device in such a way that the braking pressure in the trailer is set as quickly as possible optimally as a function of the braking requirement for the entire vehicle combination.

This object is achieved for the method by the features stated in claim 1 and for the device by the features stated in claim 13.

Advantageous designs and further developments of the invention appear from the subclaims.

The basic idea of the invention lies in determining the brake curve, ie. the braking force as a function of the braking pressure, for the trailer through several measurements and to adjust the braking pressure of the trailer during subsequent braking so that, based on the established braking curve for the trailer, a freely predeterminable setpoint curve for the trailer is obtained. In other words, seen from the towing vehicle, the trailer is forced into an arbitrary, desired "should" brake curve. From the towing vehicle's point of view, this means that any trailer, regardless of its current braking properties, always has the same unambiguously determined braking curve. For each brake demand signal from the driver, a unambiguous braking pressure for the towing vehicle adapted to the towing vehicle's braking curve can thereby be determined in advance, which braking pressure can thereby be set immediately in the trailer without regulation. 10 15 20 509 073 4 The set-brake curve for the trailer can be determined according to a freely predeterminable function. According to a variant of the invention, the brake curve of the trailer is determined so that it is equal to the brake curve of the towing vehicle, whereby all axles in vehicle combinations are braked equally. This is done by the connection where Fh is the horizontal coupling force, FV the vertical coupling force, a the vehicle's acceleration and g the earth acceleration.

According to another variant of the invention, the curve of the trailer is determined so that it lies in the middle of a predetermined compatibility band.

For the determination of the is-brake curve, a straight line is formed on the basis of a large number of measured values, which in themselves can have an extreme spread, according to the smallest square method. This straight line is then considered as the actual curve and is adjusted according to the said freely predeterminable function according to the above criteria.

As the individual measured values for the trailer's actual brake line in practice spread sharply, which e.g. due to irregularities in the road surface, the braking curve assumed as a straight line in the individual case time can deviate sharply from the actual values. In order to avoid an overbraking of the trailer, according to a variant of the invention, certain limit conditions are taken into account for determining the set-brake curve on the basis of the straight-line curve present. These limit conditions âI fi the maximum braking pressure in the trailer is limited to a predetermined value (for example 7 bar); the maximum increase in the braking pressure of the trailer relative to the braking pressure of the towing vehicle is limited to a predetermined value (eg 2 bar). 10 15 20 2f. 5509 073 Measurement of the individual points on the 'is-curve can take place in any way, for example also by means of sensors such as clutch power sensors on the trailer coupling, load sensors for determining the mass of the trailer, etc.

In principle, the braking curve of a trailer is determined by the following relation: ma * a "fltüi" Fwm + mA * g * sí-na FA lx 'lco mA * g * -i-ï- * cost: lt where Zär is the value of braking action F AH braking force between the road surface and the wheels of the trailer; F A the axle load perpendicular to the road surface from the trailer; m A The mass of the trailer; a acceleration of the vehicle combination; FKH the horizontal coupling force at the trailer coupling; FWID summing force of rolling resistance and air resistance; g the earth acceleration; o: the angle of inclination between the road surface and the horizontal plane; IK the distance between the pivot pin in the trailer coupling and the rnit axle of the trailer; and the ICG distance between the center of gravity of the trailer and the axle axis of the trailer.

Features FWID; IK and ICG are vehicle-specific values, which are given by the manufacturer as immutable quantities. Likewise, the earth acceleration g is a constant, known quantity. The mass of the trailer m A is present in modern vehicles with air suspension in the form of a measured value. However, it can also be determined together with the angle of inclination according to the older, unpublished German patent applications P 44 12 430.9 or P 44 46 358.8 by the following steps: 10. 15, 509 073 - measurement of the vehicle speed (v), - measurement of a quantity (Md) connected to the drive energy of the towing vehicle and - measuring a quantity (p) connected to the braking energy at three different times 00 »n» a »- determining the total energy (EO, El, EQ) of the vehicle combination at these three mentioned times (to , ti, Lz) on the basis of the measured values corresponding to the measured quantities corresponding to vehicle-specific quantities, this being determined according to the following relationship: E = Em¿r + Egh + Epu_E ~ n-'E fl rw_EbrI whereby - E the total energy for the vehicle combination, - Emm, the driving energy as a function of the quantity associated with dxivenergy (Md), - Ek-m the kinetic energy of the vehicle combination as a function of mass (m) and velocity (m / 2 * vz), - Epot the potential energy as a function of mass (m), the the road traveled (s) and the angle of inclination (a) according to the relationship m * g * s * sin (a), - Emm the roll energy losses as a function of mass, ground acceleration and a constant, - EVW air resistance losses as a function of the air resistance coefficient and velocity, and - Ebr brake energy loss as a function of the vehicle speed (v) and the quantity associated with the braking energy (p), - Determination of the vehicle mass (m) and the angle of inclination (a) on the basis of the determined energy values (ED, El, Ez), for this purpose twice each of the the energy values (ED, El, EQ) determined at three different times (to, tl, Lz) are assumed to be equal (E0 = E1, E0 = E¿). 10 15 20 7 i 5 0 9 0 7 5 Preferably, the total energy (EO) at the first of the three mentioned measurement times (to) is set equal to the kinetic energy of the vehicle combination, while all other sub-energies are set to zero.

A further development lies in the fact that the three mentioned measurement times (to, t1, t2) are at equidistant time distances from each other, that the angle of inclination is assumed constant at all three measurement times, and that the energy (EO) at the First measurement purilct is set equal to the energy (E1) at the second measurement time and equal to the energy (Fa) at the third measurement time, whereby thereafter the vehicle mass (m) and the angle of inclination (a) are obtained.

The vehicle acceleration a (which assumes negative values during braking) is supplied by the anti-lock device arranged in the towing vehicle as a "measured value". The coupling force FKH can, on the basis of the method known from the prior art (EP 0 621 161 A1), also be derived from measured values already present in the vehicle combination, without the need for special coupling force sensors.

An important advantage of the invention also lies in the fact that forces which only affect the towing vehicle, such as e.g. air forces or a retarder have no effect on the determination of the braking curve of the trailer.

If, as described above, the is-brake curve for the trailer has been determined, then in a modification of the arrangement with the compatibility band, it is tested whether this is-brake curve is within this compatibility band. If this is the case, it is a question of a well-braked trailer; corrections are not required. In the case of a poorly braked trailer, the braking pressure set in the trailer is increased until it is within the compatibility band at the corresponding braking requirements, the limit conditions specified above being taken into account. 10 15 20 D ”. aug 509 (173 3 The invention makes it possible to couple even very poorly braked trailers with a very flat running brake curve to a well-braked towing vehicle and nevertheless be able to control the optimum braking force for the trailer as well.

In the following, the drawing is explained in detail on the basis of the drawing. The drawing shows: fi g. 1 is a schematic sketch of a vehicle combination in an incline, to explain the different concepts, fi g. 2 is a diagram of braking action as a function of braking pressure for two different trailers, fi g. 3 different diagrams showing the processes for pressure and braking effect according to the invention, and fi g. 4 is a block diagram of a device according to the invention.

First, reference is made to fi g. 1: In the case of a trailer such as e.g. the trailer of a saddle-type trailer is obtained at a load condition by means of the trailer control pressure P anh a braking force F AH and a axle load FA acting perpendicular to the road surface. The current braking effect Z for the semi-trailer thus constitutes For the i fi g. 1 consisting of a towing vehicle 1 and a semi-trailer 2 which are interconnected via a semi-trailer coupling 3 and where the distance between the pivot pin in the semi-trailer coupling 3 and the center axis of the semi-trailer 2 has the value lk and the distance between the center of gravity 4 of the semi-trailer 2 and the center axle 5 for the semi-trailer 2 has the value ICG, and where the pitch angle o: between the roadway 6 and a horizontal plane 7 is known and finally the mass of the semi-trailer amounts to m A, the current braking effect Zär is obtained as the following expression from the condition that there should be a balance between the forces: fg * sina Fm mA * a ~ Fm 'Fwm l' mA Z__ = = FA lg "lco. IK where the designations a and FKH constitute a function of the brake pressure.

In general, the braking properties of a trailer can be characterized by means of a diagram (cf. fi g. 2 and 3), which shows the above-defined braking effect Z as a function of the trailer brake pressure P ANH (also called trailer steering pressure). This here, referred to as the "braking curve" and in the professional literature also often referred to as the "braking ratio", is called the braking property in visas g. 2 for a well braked trailer with curve A1 and for a poorly braked trailer with curve A2. The curve Al starts at the origin, ie. even at a very low trailer steering pressure there is a braking effect. In relation to the curve A2, the curve A1 also runs relatively steep and linear. Curve A2 for the "poorly" braked trailer, on the other hand, runs clearly fl more accurately and shows a "dead" area where, despite an already existing trailer steering pressure, no braking effect can be determined.

The two dashed lines Bm and Bkz delimit a “compatibility band” BK, within which the braking curve of the trailer must lie in order for the towing vehicle and the trailer to be compatible with each other in terms of braking action, which is the same as the coupling forces between the towing vehicle and the trailer must remain within predetermined limits. This compatibility band is determined by the brake curve of the towing vehicle, the brake curve of the towing vehicle usually being in the middle of the compatibility band. According to the invention, however, it is also possible to determine the compatibility band on the basis of an aruian arbitrary function, which can be determined freely in advance. As a result, the trailer can be given an arbitrary braking curve. For example, it is also possible to determine the brake curve of the trailer so that the absolute value of the thrust forces on the trailer coupling deviates from the maximum possible absolute value of the traction forces in the trailer coupling. In this case, the compatibility band would thus be laid asymmetrically relative to the braking curve of the towing vehicle. The compatibility band also does not need, as shown in fi g. 2, they are connected with a straight line.

It is possible to use arbitrary functions, e.g. curved lines. It is also possible to change the "width" of the compatibility band as a function of the pressure, for example so that at low brake pressures the compatibility band is relatively wide and at large brake pressures, on the other hand, narrow. It is also possible to make the compatibility band dependent on additional parameters, for example on the vehicle speed, the vehicle deceleration or the mass of the vehicle combination. For example, the compatibility band may be wider at low speeds than at higher speeds.

Pig. 3a shows the braking pressure p A of the trailer as a function of the braking pressure pz of the towing vehicle in a vehicle without the present invention. The two pressures are identical, ie. as big; the corresponding curve therefore runs at an angle of 45 ° relative to the two main axis lines.

I fi g. 3b shows the braking action Z A of the trailer as a function of the braking pressure pz of the towing vehicle, which without equalization is equal to the pressure p A of the trailer, as shown by the solid line. A grid pattern indicates the "compatibility band" BK. As long as the brake curve is within this compatibility band BK, it can be assumed that the trailer curve of the trailer and the brake curve of the towing vehicle match each other with sufficient accuracy. For the one in fi g. 3b for a trailer, this occurs only in the lower, but not in the upper pressure range. At higher braking pressures for towing vehicles and trailers, the trailer would therefore be braked too weakly in relation to the towing vehicle, with known negative consequences, starting with excessive use of the towing vehicle brakes and instability for the entire vehicle combination and buckling of the towing vehicle relative to the longitudinal axis of the trailer.

With the method according to the invention (fi g. 3c and d), the brake curve Zär of the trailer is determined on the basis of a plurality of measured values. According to a variant of the invention, values determined by the plurality are formed according to the least squares method, a straight line, which is considered as the set-off curve Zär for braking action. Then, in the case of a specific brake requirement P1, it is tested whether the associated value Zär on this curve is within the compatibility band. If this is the case, the same brake pressure is set in the towing vehicle and in the trailer. If, on the other hand, this is not the case, ie. if Zâr is outside the compatibility band BK, then the braking pressure p A for the trailer will change relative to the braking pressure pZ for the towing vehicle, ie. in the example shown, the amount delta p2 (fi g. 3d) is increased, so that the braking ratio for the trailer is improved by the amount delta Z2 according to fi g. 3c, whereby the braking ratio for the trailer follows the curve Zbörz. In the case of a "better" braking trailer in relation to the towing vehicle (something which in practice is quite rare), on the other hand, the brake pressure of the trailer is reduced until it is within the compatibility band BK.

Av fi g. 3c shows that the setpoint curve Zbör for braking action from a certain braking pressure is divided into two curves Zbörl and Zbörz. The curve Zbörl runs substantially parallel to the upper limit BKI to the compatibility band BK, while the curve Zbörz runs parallel to the actual brake curve Zär. Depending on whether the trailer's brake curve is raised to the curve Zbörz or Zb 61.1, a corresponding increase in pressure of the trailer's control yoke over the towing vehicle's steering pressure is obtained, corresponding to the pressure increase delta P2 or delta P1 according to fi g. 3d, which corresponds to an increase in the brake curve with delta Z2 and delta Z1 in fi g, respectively. 3c. 10 15 20 509 073 12 According to a variant of the invention, the brake curve for the trailer is "lifted" only to the curve Zb 51.2, ie. the braking pressure increase of the trailer's steering pressure is limited to a fixed predetermined maximum value delta P2, which for example has the value 2 bar.

This is based on the following considerations: The measured values of which the linear function Zär according to fi g. 3c is formed, spreads very strongly in practice, something which is essentially caused by irregularities in the road surface, partly by measurement errors, partly by digitization or rounding errors when evaluating the measurement results, partly but also by fluctuations in the braking characteristics of the individual brakes. Determining the brake curve as a straight line Zâr is therefore a very useful practice in practice, but nevertheless not an approximate value corresponding to the real conditions. This can, for example, for an extreme case at the brake pressure pl i fi g. 3c the actual braking effect amounts to Zl and therefore lies within the compatibility band BK, while the linear curve Zär gives the much lower value Zärl. If in such a case one were to lift the brake curve with the amount delta 21 to get from Zärl to a value 24 on the setpoint curve Zbörl, one would actually from 21 reach the value 25, which is clearly above the compatibility band BKI. The trailer would thus be heavily braked. For this reason, the increase of the curve has been limited to the value delta P2, so that even when the value Z1 is the real existing braking effect, an increase with delta ZZ leads only to the value 23, which is within the compatibility band BK.

As a further measure of a similar type, it is so arranged that the maximum value of the brake pressure for the trailer is limited to a predetermined value of, for example, 7 bar. If the braking pressure of the towing vehicle in this example exceeds the value of 5 bar, then the braking pressure of the trailer is no longer increased by the maximum amount of delta p2 (2 bar), but only to the limited absolute value of 7 bar. Thereby, an overbraking of the trailer is prevented due to deviations between the actual braking action and the idealized braking curve -Zär 10 15 20 so; 13 bÛ9 073 Fig. 2 shows in a similar way as fi g. 3c the brake curves for a well-braked trailer A1 and a poorly braked trailer A2. The curve Al is, apart from a small lower pressure range, within the compatibility band. A correction is not necessary. Curve A2, on the other hand, is predominantly outside the compatibility band. At a braking pressure p6 a braking action 26 is obtained, which is below the compatibility band. In order to reach a value 27 of the braking action within the compatibility band BK, the braking pressure in the trailer must be increased by the amount of p to the value p7, whereby the braking action 27 is achieved. In this case, the pressure p6 is thus set in the towing vehicle, while the pressure p7 is set in the trailer, in order to achieve a braking compatible with the towing vehicle for the trailer.

Fig. 4 shows a block diagram of a device according to the invention.

The towing vehicle is shown with a block 11 and the trailer with a block 12. The towing vehicle has a brake valve 13 and at least one sensor 14, which here is a speed sensor which generates an electrical signal proportional to the speed of a monitored wheel. Depending on the design of the braking system in the towing vehicle, each wheel can have its own sensor; in many braking systems, however, it may also be sufficient if only each axle has a sensor.

Similarly, the trailer 12 has at least one brake valve 15 and at least one sensor 16. A braking process is started with a brake claim 17, for example by depressing a brake pedal in the towing vehicle. This brake requirement is converted into an electrical signal and applied to a control unit 18. The core of the control unit is a microprocessor 19, which in addition to the brake requirement is applied to additional electrical signals from an engine control device 20 (Electronic Diesel Control), an anti-lock device 21, a vehicle specific value for the air resistance 22 and a vehicle-specific, stored value 23 for the mass of the towing vehicle. 10 15 20 25 se: 509 073 14 On the basis of these added values, the microprocessor 19 provides a setpoint for the braking pressure of the towing vehicle, which is set via a regulator 24 in the brake valve 13.

Furthermore, on the basis of the brake caliper 17, the microprocessor 19 gives a setpoint for the trailer's brake pressure, which is set via a regulator 25 in the brake valve 15 in the trailer 12. This value for the trailer's brake setpoint is calculated according to the procedure described above. of this curve is stored in a memory 26 connected to the microprocessor 19. These parameters may, for example, be values for the compatibility band described above as well as limit values for the pressure increase or limit value for the maximum brake pressure that can be applied to the trailer.

By means of measuring means 27 and 28, respectively, the actual brake pressure is supplied to the towing vehicle and the trailer, respectively, and is fed into the microprocessor 19 or into the regulators 24 and 25, respectively. These measuring means 27 and 28 may be pressure measuring boxes; however, it is also advantageously possible to determine the pressures in other known ways, for example by measuring the opening and closing times of valves.

Of course, the vehicle-specific values in the building groups 22 and 23 can also be stored in the memory 26. Furthermore, the anti-lock function can be taken over by the microprocessor 19.

During each braking, on the basis of measured, derived and stored values, current values of the trailer's braking action Zâr will be determined and entered into the memory 26. On the basis of a number of such "measurement values" for braking action, the breaking curve Z A i fi g is then given by the microprocessor 19. 3b and Zär i ñg respectively. 3c, which preferably takes place according to the least squares method. The more "measured values" that exist, the more accurately the brake curve Zär is adapted to the actual braking ratio for the trailer. Therefore, this curve is calculated a 10 15 20 one »15 509 073 fl several times again, something that can happen according to different criteria. One criterion is that at the beginning of a journey the curve is determined again. The beginning of a journey can, for example, be detected as maneuvering of the ignition key. Furthermore, a new calculation of the curve can always be triggered by a dry-determined number of new "measured values" having been reached.

This number can be determined arbitrarily and even in the extreme case have the value 1. It is also possible to always carry out a new calculation of the curve in connection with a braking.

Once the curve has been determined, during subsequent braking, the brake pressure to be set in the trailer will be modified on the basis of the braking requirement and the brake curve so that the braking of the trailer takes place with a brake pressure required to be within the compatibility band. As a result, already at the beginning of a braking the brake pressure on the trailer will be set in advance to the "correct" value and does not need to be determined first during a control process during braking.

According to the invention, a "table" or curve can finally be stored in the memory 26 which indicates the trailer's brake pressure p A as a function of the towing vehicle's brake pressure pz, whereby each brake pressure for the towing vehicle has a unique brake pressure for the trailer.

Claims (13)

10 15 20 25 so; 509 075 m ten v A method of setting the braking force of a trailer at a vehicle combination consisting of a towing vehicle and at least one trailer with the following steps: - determining a plurality of setpoints for a quantity which characterizes the braking of the trailer, at a number of braking requirements controlled by the towing vehicle; - determination of an is-brake curve on the basis of said fl number setpoints for quantities which characterize the brake pressure of the trailer; calculation of a set-brake curve for the trailer; determining a correction value for the braking requirement of the trailer such as the difference between the set-brake curve and the actual-brake curve; change of the brake slave for the towing vehicle with the correction value; and - steering the conical brake requirement in the trailer. Method according to Claim 1, characterized in that the quantity which characterizes the braking of the trailer constitutes the ratio between the braking force of the trailer (F AH) and the axle load (FA) of the trailer. A method according to claim 2, characterized in that the ratio between braking force for the trailer and axle load for the trailer is determined by the following relationship: wherein - Zär is the value for braking action - FAH braking force between the road surface and the wheels of the trailer; FA the axle load of the trailer perpendicular to the road surface; - m A The mass of the trailer; 10 15 20 so: 11 5091073 - a acceleration of the vehicle combination; - FKH the horizontal coupling force in the trailer coupling; - FWID summing force of rolling resistance and air resistance; - g the earth acceleration; - the angle of inclination between the road surface and a horizontal plane; - IK the distance between the pivot pin of the trailer coupling and the rnit axis of the trailer; and - the ICG distance between the center of gravity of the trailer and the center axis of the trailer. Method according to one of Claims 1 to 3, characterized in that the is-brake curve is calculated with the least squares method from the is-values for the quantities which characterize the braking of the trailer. Method according to one of Claims 1 to 4, characterized in that the set-brake curve for the trailer according to a freely predeterminable function is formed from the actual brake curve of the trailer. Method according to one of Claims 1 to 5, characterized in that the set-brake curve lies within a compatibility band, the limits of which have a predetermined distance from the brake curve of the towing vehicle. Method according to one of Claims 1 to 6, characterized in that the correction value for the brake requirement of the trailer is limited to a fixed, predetermined maximum value. Method according to one of Claims 1 to 7, characterized in that the correction value of the trailer's braking requirement is so limited that the maximum value of the trailer's braking requirement does not exceed a fixed, dry-determined value. Method according to one of Claims 1 to 8, characterized in that the values of the trailer's braking required values of the mass of the trailer and the pitch between the road surface and a horizontal plane are determined by the following steps: of the vehicle speed (v), - measurement of a quantity (Md) connected to the drive energy of the towing vehicle and - measurement of a quantity (p) connected to the braking energy at three different times (tr “1- ä), - determination of the total energy (EO, El , Ez) for the vehicle combination at these three mentioned times (to, tl, Iz) on the basis of the measured values corresponding to measured and against specific vehicle quantities, these being determined according to the following relationship: E = Eanir + Ekin + E9 fl '-_ Ef ° u- Ew-Ebf 'wherein - E the total energy of the vehicle combination, - Emm, the driving energy as a function of the quantity (Md) associated with the driving energy, - the kinetic energy of the vehicle combination as a function of mass (m) and velocity (m / 2 * V2), - EPC , the paw ntial energy as a function of mass (m), distance traveled (s) and angle of inclination (a) according to the relationship m * g * s * sin (a), - Emu roll energy losses as a function of mass, ground acceleration and a constant, - Evw air resistance losses as a function of the coefficient of air resistance and speed, and - Ebr the braking energy losses as a function of the vehicle speed (v) and the quantity associated with the braking energy (p), and - determination of the vehicle mass (m) and the angle of inclination (a) based on the calculated energy values (EQ, El, EZ), whereby for this purpose twice each of the energy values calculated at three different times (to, tl, tg) (EQ, El, Ez) is assumed to be equal (E0 = E1, EO = E.2). Method according to claim 9, characterized in that the total energy (EQ) at the first of the three mentioned measurement times (to) is set equal to the lcinetic energy of the vehicle combination, while all other sub-energies are set to zero. Method according to claim 10, characterized in that the said measuring points (to, t1, t2) are at equidistant time distances from each other, that at all three measuring times the angle of inclination is considered to be constant and that the energy (EC) is assumed at the first measuring time be equal to the energy (EI) at the second and equal to the energy (ä) at the third measurement time, on the basis of which the vehicle mass (m) and the angle of inclination (a) are determined. Method according to one of Claims 1 to 8, characterized in that they determine the required values of the mass of the trailer and of the pitch between the road surface and a horizontal plane for determining the quantities which characterize the braking of the trailer and are determined by the following steps: al) measurement of the vehicle speed (v) , az) determination of a quantity corresponding to the current gear (Gü), ag) determination of a quantity corresponding to the current braking condition (Br '), a4) testing using the quantity corresponding to the current gear (Gü) and the to the current braking condition corresponding to the quantity (Br ') that the vehicle is not in driven condition and that the brake is not activated, for a period of time (TO-TZ), _ as) determination of the total energy of the vehicle combination (Bo, El, Ez) at three different times (T o, TI, Tz), which are within the said time space (T o-Tz) on the basis of the measured values and corresponding to vehicle specific quantities, a6) determination (1) of the angle of inclination (a) on the basis of the determined the energy values, '10 15 20 25 of 509 073 20 bl) measurement of a quantity (Md) associated with the traction of the towing vehicle, bz) measurement of the vehicle speed (v), b3) determination of a quantity corresponding to the current gear (Gü) , b 4) determination of a quantity corresponding to the current braking condition (Br '), b5) testing by means of the quantity corresponding to the current gear (Gü), and the quantity corresponding to the current braking condition (Br') that the vehicle is in a driven state and that no brake is activated, at a time (T 3), bó) determination (2) of the mass (m) of the vehicle combination by means of the force equilibrium on the basis of the measured and corresponding to vehicle-specific quantities corresponding to the stored values and the determined incline inclination angle (a), and c) automatic adjustment of the brake slip distribution between towing vehicle and trailer as a function of the mass (m) thus determined for the vehicle combination. Device for adjusting the braking force of a trailer in a vehicle combination consisting of a towing vehicle and at least one trailer, characterized by measuring and counting devices (14, 16, 17, 20, 21, 22, 23, 19), which on the basis of measured and stored quantities, a characteristic quantity (Zär) for the braking of the trailer for a plurality of braking requirements controlled in the towing vehicle (11) determines that the counting unit (19) on this basis determines an is-brake curve from the plurality of is-values quantities which characterize the braking of the trailer and input them into a memory (26), that the counting unit (19) determines a set-brake curve (Z-bearing) for the trailer (12); that the counting unit (19) determines correction values (ö p) for the braking requirements of the trailer (12) from a difference between the set-brake curve (Zbör) and the is-brake curve (Zär) and at a brake control valve (15) on the trailer (12) controls a signal for a brake requirement on the trailer which corresponds to the brake requirement for the towing vehicle changed by the correction value (1 l).