GB2282424A - Method of braking a tractor and trailer or semitrailer - Google Patents

Method of braking a tractor and trailer or semitrailer Download PDF

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Publication number
GB2282424A
GB2282424A GB9424088A GB9424088A GB2282424A GB 2282424 A GB2282424 A GB 2282424A GB 9424088 A GB9424088 A GB 9424088A GB 9424088 A GB9424088 A GB 9424088A GB 2282424 A GB2282424 A GB 2282424A
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GB
United Kingdom
Prior art keywords
tractor
brake pressure
trailer
semitrailer
value
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB9424088A
Other versions
GB2282424B (en
GB9424088D0 (en
Inventor
Bernhard Topfer
Bodo Klein
Wolfgang Muller
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Daimler Benz AG
Original Assignee
Daimler Benz AG
Mercedes Benz AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from DE4136571A external-priority patent/DE4136571C1/de
Application filed by Daimler Benz AG, Mercedes Benz AG filed Critical Daimler Benz AG
Priority to GB9424088A priority Critical patent/GB2282424B/en
Publication of GB9424088D0 publication Critical patent/GB9424088D0/en
Publication of GB2282424A publication Critical patent/GB2282424A/en
Application granted granted Critical
Publication of GB2282424B publication Critical patent/GB2282424B/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
    • B60T13/10—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release
    • B60T13/66—Electrical control in fluid-pressure brake systems
    • B60T13/662—Electrical control in fluid-pressure brake systems characterised by specified functions of the control system components
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T7/00—Brake-action initiating means
    • B60T7/12—Brake-action initiating means for automatic initiation; for initiation not subject to will of driver or passenger
    • B60T7/20—Brake-action initiating means for automatic initiation; for initiation not subject to will of driver or passenger specially for trailers, e.g. in case of uncoupling of or overrunning by trailer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
    • B60T8/18—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to vehicle weight or load, e.g. load distribution
    • B60T8/1887—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to vehicle weight or load, e.g. load distribution especially adapted for tractor-trailer combinations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
    • B60T8/26—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force characterised by producing differential braking between front and rear wheels
    • B60T8/266—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force characterised by producing differential braking between front and rear wheels using valves or actuators with external control means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
    • B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
    • B60T8/321—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration deceleration
    • B60T8/323—Systems specially adapted for tractor-trailer combinations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
    • B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
    • B60T8/321—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration deceleration
    • B60T8/3255—Systems in which the braking action is dependent on brake pedal data
    • B60T8/3275—Systems with a braking assistant function, i.e. automatic full braking initiation in dependence of brake pedal velocity

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  • Engineering & Computer Science (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Regulating Braking Force (AREA)

Abstract

In a method of braking a tractor and trailer (or semitrailer) the ratios of deceleration to the brake pressure, at various load states, of a tractor alone are stored, and, for a tractor and trailer, the trailer brake pressure is controlled such that the actual value of the deceleration which is then set at the prevailing tractor brake pressure, giving due regard to the tractor load state, corresponds to the value, derived from the stored ratios corresponding to the same load state, of the deceleration achieved without a trailer at the same brake pressure of the tractor. A method is also disclosed, in which, when the deceleration derived from the position or actuation speed of a brake pedal is below a set value, the brake pressure supplied to the trailer for a particular duration at the beginning of a braking operation is increased in relation to the brake pressure resulting from the position of the brake pedal.

Description

A method of determinins an optimised value of the brake pressure ratio between a tractor and a trailer or semitrailer The invention relates to a method of determining an optimised value of the brake pressure ratio between a tractor and a trailer or semitrailer.
A method of determining a value of the brake pressure ratio between a tractor and a trailer or semitrailer has already been disclosed by the document P 40 35 805.4 which was not previously published, according to which method the allocations of the brake pressures of the tractor and of the trailer or semitrailer are recorded during steady-state braking operations and stored as reference values for future braking operations. In this case, intermediate values between these stored allocations are gained by interpolation from the stored allocations.
After the reference values of the brake pressures have been set, an adjustment takes place in such a way that the measured coupling force between the tractor and the trailer or semitrailer is adjusted to its set value. If, in turn, a steady-state braking operation is achieved by this adjustment, the allocation of the brake pressures of the tractor and the trailer or semitrailer which have then been set is, in turn, recorded and stored. Furthermore, it is known from this document to carry out a pressure boost at the beginning of a braking operation by giving the trailer or semitrailer a constant value of the brake pressure which is increased in relation to steady-state values for a particular duration at the beginning of a braking operation.
The present invention seeks a method to determine a brake pressure ratio between a tractor and a trailer or semitrailer in such a way as to give the greatest possible driving comfort, the least possible wear of the components and the greatest possible degree of driving safety with the least possible constructional expenditure at the same time.
According to the present invention there is provided a method of determining an optimised value of the brake pressure ratio between a tractor and a trailer or semitrailer in braking operations when the tractor is travelling with a trailer or semitrailer, a brake pressure PAnh being targeted for the trailer, which brake pressure is allocated to the brake pressure Pzug of the tractor, wherein, in braking operations when a tractor is travelling without a trailer or semitrailer, an allocation of the achieved deceleration Zist to the brake pressure Pzug of the tractor is stored as a function of the load state of the tractor, it being possible for this allocation to consist, in particular, in the fact that the ratio 6 of the achieved deceleration Zist to the brake pressure Pzug is formed, that in subsequent braking operations when the tractor is travelling with a trailer or semitrailer, a brake pressure PAnh is supplied for the trailer or semitrailer, which brake pressure is allocated to the brake pressure Pzug of the tractor in such a way that, in the braking operations, the actual value of the deceleration Zist at a prevailing brake pressure Pzug of the tractor, giving due regard to the current load state of the tractor, corresponds to the value, derived from the stored allocation, of the deceleration achieved without a trailer or semitrailer at the same brake pressure Pzug and with the same load state of the tractor.
It has proved to be advantageous in the invention that the sensing of the coupling force can be dispensed with.
To simplify the illustration, only the term "trailer" is used in the following text; the ratios for a semitrailer result analogously.
To compensate for or at least reduce the "run-up impact of the trailer at the beginning of a braking operation, firstly a relative increase of the trailer brake pressure takes place in relation to the trailer brake pressure usually resulting from the brake pressure of the tractor in order thus to compensate for the longer response time of the brake system of the trailer. In a braking operation with a large deceleration requirement, no relative increase of the trailer brake pressure takes place at the beginning of the braking operation in order to guarantee the shortest possible braking path and to ensure that no overbraking of the trailer takes place.In braking operations with a low deceleration requirement, no problems arise in respect of driving stability (lateral guiding, traction) due to a certain overbraking of the trailer at the beginning of a braking operation. On the contrary, clear improvements result in respect of comfort and economy.
Furthermore, in braking operations, control of the brake pressure of the trailer can be implemented so as to give an optimised coordination of the brake force distribution between the tractor and the trailer. This can take place in a manner according to the invention in that the deceleration of the tractor resulting from a particular brake pressure is stored as a function of the respective load state (loading) when the tractor travels without a trailer. When travelling with a trailer, a brake pressure is then supplied for the trailer such that, under the prevailing load state of the tractor corresponding to the prevailing brake pressure, a deceleration is set which corresponds to the stored value of the deceleration of the tractor without a trailer under the same load state and the same brake pressure.It is thus guaranteed that, on the one hand, the brakes of the tractor do not have to perform braking work which arises due to the additional load of the trailer (avoiding overbraking of the tractor) and that, on the other hand, the brakes of the trailer do not have to perform braking work which arises due to the load of the tractor (avoiding overbraking of the trailer). On the contrary, only that braking work is then performed by each part of the vehicle (tractor and trailer) which has to be applied due to the respective load of the individual parts of the vehicle.
Exemplary embodiments of the invention are illustrated diagrammatically and described in greater detail below, with reference to the drawings, in which: Figure 1 shows a flow chart which indicates the relative increase of the trailer brake pressure in relation to the trailer brake pressure usually resulting from the brake pressure of the tractor at the beginning of a braking operation, Figure 2 shows an illustration of the increase of the brake pressure of the trailer as a function of time, Figure 3 shows an illustration of the dependence of the increase of the brake pressure of the trailer as a function of the temporal change of the set value of the deceleration of the tractor-trailer unit and as a function of the speed of the tractor-trailer unit at the beginning of the braking operation, Figure 4 shows a flow chart of the method according to the invention, according to which the ratio r of the brake pressure Pzug of the tractor to the brake pressure PAnh of the trailer during the steady-state phase of a braking operation is stipulated, and Figure 5 shows a possibility of standardising the ratio 6(L) of the deceleration Zist to the brake pressure Pzug of the tractor.
As can be seen in Figure 1, a check is firstly made in the box 101 as to whether the prevailing braking operation has a low or a large deceleration requirement.
This can take place, for example, using the deceleration set value z5011 of the tractor-trailer unit derived from the position of the brake pedal or using the temporal change dzSoll/dt of the deceleration set value of the tractortrailer unit derived from the actuation speed of the brake pedal. In this case, a braking operation with a large deceleration requirement can be derived if the deceleration set value z5011 is greater than 0.3 g, g also describing the acceleration due to gravity in the following text. A braking operation with a large deceleration requirement can likewise be derived if the temporal change of the deceleration set value dzsoll/dt exceeds a value of 1.5*g/s. If it has been derived - as just explained, for example - that there is a large deceleration requirement, the procedure illustrated in Figure 1 is ended (arrow 102), otherwise there is a move to step 104 in accordance with the arrow 103.
Correspondingly, the brake pressure PAnh is then determined in accordance with step 104. This brake pressure PAnh corresponds to the brake pressure of the trailer which usually results from the brake pressure of the tractor during a braking operation.
In this case, the increase of the brake pressure of the trailer can take place by the brake pressure of the trailer PAnh, which is normally set on the basis of the position of the brake pedal and the brake pressure of the tractor resulting from this position, being established and suitably increased. Instead of PAnhr according to the invention a brake pressure can now be targeted on the trailer which is proportional to said brake pressure PAnh' the proportionality constant fÜ being greater than 1 and still being dependent in an advantageous manner on the speed of the tractor-trailer unit at the beginning of the braking operation and on the temporal change of the deceleration set value dzsoll/dt, as is shown, for example, in Figure 3.In step 105, the brake pressure PAnh is multiplied by this proportionality constant fÜ in order to maintain the brake pressure PBAnh to be targeted at the beginning of the braking operation.
In accordance with step 106, a check is made as to whether this brake pressure PBAnh, to be targeted at the beginning of a braking operation, lies below a particular threshold value PBmaX which can be in the order of magnitude of 2-3 bar. If the brake pressure PBAnh to be targeted at the beginning of a braking operation exceeds the particular threshold value PBmaxr it may happen that excessive wheel slip occurs on the trailer. For this reason, a check takes place in step 108 as to whether there is an antiblocking system (ABS) on the trailer. If there is an ABS, there is a move to step 107 since it is then ensured, even in the case of a larger brake pressure on the trailer, that the braking operation cannot lead to the trailer wheels blocking.
Otherwise, a limitation to the particular threshold value PBmax takes place for the brake pressure to be targeted at the beginning of the braking operation in accordance with step 109. If the brake pressure is below the value PBmaxr the brake pressure PBAnh is supplied at the beginning of a braking operation in accordance with step 107.
In accordance with step 110, the brake pressure PB is then targeted for the trailer at the beginning of a braking operation, which brake pressure corresponds either to the brake pressure PBAnh or, if appropriate, its limit value, the brake pressure PBma > . A check is made in step 111 as to whether any ABS present on the trailer has been activated. If this Is the case, it is concluded that the trailer should no longer be braked excessively. For this reason, there is a direct move to step 113, i.e. the point in time t1 is considered to be reached.
A check is made in step 112 as to whether the beginning of the braking operation with the increased trailer brake pressure has ended. For this purpose, the actual value of the deceleration Zist is determined using the measured wheel speeds of the tractor. If this actual value of the deceleration Zist reaches a particular fraction x, which can for example be 0.2 to 0.5, of the set value of the deceleration z,,ll, i.e. if the condition Zist > = x * ZsO,l is met, there is a move to step 113 in which there is a move to the actual braking operation in which both the tractor and the trailer are decelerated. This point in time is then denoted by t1. In addition to this condition, a further condition is also monitored.In order not to decelerate the use of the tractor brake too greatly, the time span tR, which elapses from the point in time to to the point in time t1, is limited, specifically in such a way that with tt dropping, tR can also decrease down to 0. In this case, the calculation can be performed according to the following equation: tR = tR,max * (fÜ 1).
In this case, t,max can be 0.1 to 0.3 s. If neither of the two conditions has yet been met, there is a return to step 101.
In an advantageous manner, there is a continuous, especially linear, transition from the brake pressures at the beginning of the actual braking operation, i.e. from. t1 to the brake pressures on the tractor and the trailer which result on the basis of the position of the brake pedal and in accordance with a brake pressure distribution PHIA which is stipulated for the steady-state braking operation, PHIA being the ratio of the brake pressure of the tractor to the brake pressure cf the trailer.In this case, a time tp is established in step 113, after which time the brake pressures should have been set which result on the basis of the position of the brake pedal, it also being possible for this time tp to be varied in an advantageous manner as a function of the temporal change of the set value of the deceleration dzsOll/dt in that it is calculated, just like tR, using the actual size of füX This calculation is done according to the following equation: tp =tp,max * (fü 1).
In this case, just like tR,maxs tp,max can lie in the order of magnitude of 0.1 to 0.3 s.
In accordance with step 114, a pressure change of (PAnh - PB)/tp is then targeted per unit of time for the trailer and a pressure change of pzug/tp for the tractor.
A check is then made in step 115 as to whether the time tp has elapsed from the point in time t1. If this is the case, the phase of the pressure change is ended since the brake pressures PAnh of the trailer and PZug of the tractor corresponding to the position of the brake pedai have then been reached. From this point in time onwards, the brake pressure PAnh in the trailer is no longer increased during the current braking operation, that is to say in step 117 a ratio r between the brake pressure pug of fle tractor and the brake pressure PAnh of the trailer correspcnding to a steady-state braking operation is supplied.
Otherwise, the loop from 101 again takes place in the next calculation cycle.
Figure 2 shows an illustration of the increase of the brake pressure of the trailer PAnh as a function of time, in which illustration it can also be seen how the brake pressure of the tractor Pzug rises with time and how the deceleration of the tractor-trailer unit Zist increases with time and reaches the set value Zsoll The brake pressure of the trailer PAnh firstly rises until it has reached its set value fü*pAnhs This value of the pressure is then held until the point in time t1, until the actual value of the deceleration Zist has reached a particular fraction x of the set value of the deceleration Zsollt or the time has elapsed since the beginning of the braking operation.
From the point in time t1, up to the point in time t1 + tp, the brake pressure PAnh is then decreased to its end value and the brake pressure Pzug is increased to its end value.
In this case, both the decrease and the increase of the brake pressure take place continuously.
According to Figure 3, there is a variation in the size of the brake pressure PB at the beginning of a braking operation. The parameter u is the factor with which the brake pressure of the trailer P nh resulting from the position of the brake pedal is multiplied in order to maintain the brake pressure PB to be targeted at the beginning of the braking operation. In principle, it can thus be seen in Figure 3 that, with an increasing rate of change of the set value of the deceleration dzsoll/dt, the factor u decreases, i.e. that the relative increase of the brake pressure of the trailer becomes less. The relative change of the set acceleration is thus plotted relative to the acceleration due to gravity g per second s.In this case, the curve 301 shows the ratios at set values of the deceleration zSOll < =0.15g; the curve 302 shows the ratios at set values of the deceleration z5011 > =0 .3g. With an increasing set value of the deceleration Zsollt the curves located further down in Figure 3 thus apply. The uninterrupted parts of the curves at values of dzsoll/dt greater than 50 (304) apply to a speed range of less than 40 km/h, the dot/dashed parts of the curves at values of dzsoll/dt greater than 50 (303) apply to a speed range of greater than 80 km/h.
The factor fÜ is accordingly established as follows: In the range dzsoll/dt < =0.5g/s the value corresponding to the curve 301 is taken if Zsoll or Zist is smaller than 0.15g. The value fÜ2 corresponding to the curve 302 is taken if Zsoll is greater than 0.3 g. If zsoll lies between 0.15 g and 0.3 g, an interpolation is carried out.
If a linear interpolation takes place between the two curves 301 and 302, this is done according to the following equation (1): ffj = fü2 + (fÜ1-fÜ2)*(0.3g-Zsoll)/(0.3g-0.15g) (1).
In the range dz5011/dt > 0.5g/s, 2 intermediate values are calculated, if appropriate, as a function of the speed.
If the speed v is below 40 km/h, the final calculation of the factor fÜ is carried out according to the equation (1), the value corresponding to the speed 40 km/h and the current value of dzSoll/dt being used for fÜl If the speed v is above 80 km/h, the final calculation of the factor fÜ is carried out according to the equation (1), the value corresponding to the speed 80 km/h being used for fÜl If the speed v lies between 40 km/h and 80 km/h, an interpolation is carried out between two intermediate values.In this case, the first intermediate value fÜzl is calculated according to equation (1) by using the value corresponding to the speed 40 km/h for fÜl In this case, the second intermediate value is likewise calculated according to equation (1) by using the value corresponding to the speed 80 km/h for fÜl The final factor fÜ is calculated in the latter case according to the following equation (2): = füz2 + (fuz1-fu.z2)*(v-40km/h)/(80km/h-40km/h) (2) The maximum value fümax of the factor fÜ can be about 2.5 for a twin-axle tractor and about 2.0 for a triple-axle tractor.
Figure 4 shows a flow chart of the method according to the invention, according to which a current value for the ratio r of the brake pressure Pzug of the tractor to the brake pressure PAnh of the trailer during the steady-state phase of a braking operation is stipulated. The ratio r is stipulated as a function of the deviation of the actual deceleration from the set deceleration at a particular brake pressure taking the load state of the tractor into consideration.
In this case, measured values are firstly read in in a step 401. These measured values include the brake pressure PZug,akt of the tractor, the speed Qakt of at least one wheel of the tractor and/or of the trailer as well as the loading stage Lakt. The brake pressure PZug,akt can be measured directly or the value of the brake pressure of the tractor Pzug targeted on the basis of the position of the brake pedal can be used as measured value.In this case, the speed Sakt is measured airecti and the momentary deceleration Zist is then derived in a manner known per se from the measured speed n Sakz Methods of establishing the deceleration from the speed ?akt are described In sufficient numbers in conjunction with antiblocking systems 'ABS,. In this case, the loading stage L akt can be recorded by sensing the pressure of the bellows in air suspension tractors and the spring path in tractors with steel suspension. In order thereby to be able to rule out erroneous measured values as a result of shifts in the axle loading, the load state is advantageously recorded at a constant travelling speed.In this case, the signal representing the load state is advantageously additionally filtered at a low limit frequency.
Additionally, the load state can be recorded by evaluating the wheel speed differences between the front and the rear wheels. In this case, differences in the tyre radius result as a function of the rear axle load and lead to the said wheel speed differences. Measured values read in are firstly processed in step 401 in such a way that the ratio #(Lakt)akt of the actual value of the deceleration Zist to the brake pressure Pakt is formed.
A check is made in step 402 as to whether there is a trailer on the tractor during the braking operation. This can be recognized in a known manner via the trailer plug connection. If there is no trailer on the tractor, there is a move to step 403 in which the stored values of the ratio #(L)store are updated. Otherwise, a brake pressure PAnh of the trailer is targeted in accordance with step 404 in such a way that the ratio r between the brake pressure Pzug of the tractor and the brake pressure PAnh cf the trailer is implemented. In this case, an initial value for the ratio r can be given, for example, by the deceleration band.
In step 403, the stored ratio 6(L)store is pdated by the value 6(Lakt3akt established in step 401. In this case, the values (5(L)store can be deposited in such a way that a plurality of support values are stored over the range of all the possible load states. In this case, the ratio 6(Lakt)store corresponding to the momentary load state Lakt is updated. In this case, tis updating expediently takes place in the form of a sliding mean value procedure, that is to say that the new value is calculated with the previously stored value with a lower weighting. In this case, this weighting can be a few per cent, in particular 5%.
In step 404, the brake pressure corresponding to the ratio r is then targeted on the trailer.
A check is then made in step 405 as to whether the value of the current ratio 6(Lakt) kt (tractor and trailer) is greater than the stored value of the ratio 6(Lakt)Store (tractor without trailer). If this is the case, a deceleration Zist of the tractor-trailer unit has been set which is greater than one corresponding to the momentary level of the brake pressure Pzug of the tractor. There is then obviously overbraking of the trailer.
In step 406, a reduction of the brake pressure PAnh of the trailer is then undertaken. In this case, this reduction can take place in such a way that the order of magnitude of this reduction takes place as a function of the difference between the ratio 6(Lakt)akt and the stored ratio 6(Lakt)store In this case, this dependence can, in particular, be proportional. The sequence of the procedure is then again continued with step 405.
If it was established in step 405 that the ratio 6(Lakt)akt is not greater than the ratio 6 6(Lakt)storel a check is made in step 407 as to whether the ratio 6(Lakt)akt is smaller than the ratio 6(Lakt)store. If this is the case, a deceleration Zist of the tractor-trailer unit has been set which is smaller than one corresponding to the momentary level of the brake pressure Pzug of the tractor. The braking of the trailer is then obviously too weak.
In step 408, an increase in the brake pressure PAnh of the trailer is then undertaken. In this case, this increase can take place in such a way that the order of magnitude of this increase takes place as a function of the amount of the difference between the ratio 6(Lakt)akt and the stored ratio 6(Lakt)store In this case, this dependence can, in particular, be proportional. The sequence of the procedure is then again continued with step 405.
If it was established in step 407 that the ratio 6(Lakt)akt is not smaller than the ratio 6(Lakt)storel the ratio r is updated in step 409. In this case, this updating expediently takes place in the form of a sliding mean value procedure, that is to say that the new Value of the ratio r is calculated with the value of the ratio r previously stored for the journey with a lower weighting. In this case, this weighting can be a few per cent, in particular 5% to 20%.
The sequence of the procedure then begins again with step 401.
In the two checks 405 and 407, it is expediently not merely checked whether the ratio 6(LaRt)akt is greater or smaller than the ratio 6(Laktstorel but whether the difference between 6(Lakt)akt and 6(Lakt)store does not exceed (405) or fall below (407) a certain value. Within a certain range around the value 6CLakt)store which corresponds to this certain value, it can be assumed that, within a permissible tolerance, only that braking work is performed by each part of the vehicle (tractor and trailer) which has to be applied by them on the basis of the respective load of the individual parts of the vehicle.
As a default value at the beginning of the method according to the invention, a brake pressure PAnh is targeted on the trailer which will correspond to a ratio of r=1. The tractor and the trailer are then within the tolerance of the EC braking band and unsafe handling characteristics of the tractor-trailer unit due to an inadequate distribution of the braking force between the tractor and trailer are thus not possible even under these conditions.
A possibility of standardising the parameter 6(L) can be seen in Figure 5 and Figure 6. Since the deceleration Zist achievable at a particular brake pressure Pzug depends on the travelling speed, it is advantageous to undertake standardisation for a comparison of the parameter 6(L) with a parameter 6(L) determined later for a tractor-trailer unit using the same tractor. In this case, Figures 5 and 6 show as an example the ratios with standardisation to a particular travelling speed Vref In this case, the 6 values are recorded in a range from vinin to vinax in a step 501.In a step 502, a straight line is then drawn through these measuring points, for example by means of the method of the smallest fault squares, which then has the following from: 6 = 6 - v.
These two steps 501 and 502 in Figure 5 can be carried out in preliminary experiments as representative of entire vehicle construction series. The value cv is then stored permanently in the electronic system.
Figure 6 then shows the performance of the standardisation of individual values of the ratio 6. In this case, a particular speed vref is stipulated, to which standardisation takes place. The standardised ratio 6norm at a current travelling speed Vakt and a determined current ratio 6akt is then calculated in a step 601 according to the following equation: 6norm 6#akt + Cv ( Vakt - Vref ) In principle, the standardisation can also take place to other parameters, such as, for example, the product of the travelling speed v and the deceleration z.
Reference is nereby made to our co-pending application 9221896.5 dated 19th October 1992 which also claims priority from German Patent Application P 4136571.2 dated 7th November 1991.

Claims (6)

Claims
1. A method of determining an optimised value of the brake pressure ratio between a tractor and a trailer or semitrailer in braking operations when the tractor is travelling with a trailer or semitrailer, a brake pressure PAnh being targeted for the trailer, which brake pressure is allocated to the brake pressure Pzug of the tractor, wherein, in braking operations when a tractor is travelling without a trailer or semitrailer, an allocation of the achieved deceleration ist to the brake pressure Pzug of the tractor is stored as a function of the load state of the tractor, it being possible for this allocation to consist, in particular, in the fact that the ratio 6 of the achieved deceleration Zist to the brake pressure Pzug is formed, that in subsequent braking operations when the tractor is travelling with a trailer or semitrailer, a brake pressure PAnh is supplied for the trailer or semitrailer, which brake pressure is allocated to the brake pressure Pzug of the tractor in such a way that, in the braking operations, the actual value of the deceleration Zist at a prevailing brake pressure PZug of the tractor, giving due regard to the current load state of the tractor, corresponds to the value, derived from the stored allocation, of the deceleration achieved without a trailer or semitrailer at the same brake pressure Pzug and with the same load state of the tractor.
2. A method according to Claim 1, wherein, when a tractor is travelling with a trailer or semitrailer, the ratio r of the value of the brake pressure Pzug of the tractor to the value of the targeted brake pressure PAnh of the trailer or semitrailer is stored and, in future braking operations on the same journey, a brake pressure P nh allocated to the brake pressure Pzug of the tractor on the basis of this stored ratio r is targeted for the trailer or semitrailer.
3. A method according to Claim , or 2, wherein the achieved deceleration 2ist is updated to the brake pressure Pzug of the tractor and, if appropriate, the ratio r is updated by means of a sliding mean value procedure.
4. A method according to any one of Claims 1 to 3, wherein the allocation of the achieved deceleration Zist to the brake pressure PZug of the tractor is standardised to particular influencing parameters.
5. A method according to claim 4 wherein the influencing parameter comprises the initial travelling speed v.
6. A method of determining an optimised value of the brake pressure ratio between a tractor and a trailer or semitrailer, substantially as described herein with reference to and as illustrated in the accompanying drawings.
GB9424088A 1991-11-07 1992-10-19 A method of determining a brake pressure ratio between a tractor and a trailer or semitrailer Expired - Fee Related GB2282424B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9424088A GB2282424B (en) 1991-11-07 1992-10-19 A method of determining a brake pressure ratio between a tractor and a trailer or semitrailer

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE4136571A DE4136571C1 (en) 1991-11-07 1991-11-07
GB9221896A GB2261269B (en) 1991-11-07 1992-10-19 A method of determining the brake pressure ratio between a tractor and a trailer or semitrailer
GB9424088A GB2282424B (en) 1991-11-07 1992-10-19 A method of determining a brake pressure ratio between a tractor and a trailer or semitrailer

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GB9424088D0 GB9424088D0 (en) 1995-01-18
GB2282424A true GB2282424A (en) 1995-04-05
GB2282424B GB2282424B (en) 1995-09-20

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ITTO20110587A1 (en) * 2011-07-04 2013-01-05 Cnh Italia Spa METHOD AND APPARATUS FOR BRAKING A TRACTOR EQUIPPED WITH A TRAILER
US10076326B2 (en) 2015-09-23 2018-09-18 Ethicon Llc Surgical stapler having current mirror-based motor control
US11385651B2 (en) 2018-06-26 2022-07-12 Ford Global Technologies, Llc System and methods for detection and response to interference between trailer coupler and hitch ball

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10479334B2 (en) 2017-05-24 2019-11-19 Ford Global Technologies, Llc Method to automatically adjust a trailer brake controller

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ITTO20110587A1 (en) * 2011-07-04 2013-01-05 Cnh Italia Spa METHOD AND APPARATUS FOR BRAKING A TRACTOR EQUIPPED WITH A TRAILER
WO2013004315A1 (en) * 2011-07-04 2013-01-10 Cnh Italia S.P.A. Method of and apparatus for braking a tractor-trailer combination
US9481346B2 (en) 2011-07-04 2016-11-01 Cnh Industrial America Llc Method of and apparatus for braking a tractor-trailer combination
US10076326B2 (en) 2015-09-23 2018-09-18 Ethicon Llc Surgical stapler having current mirror-based motor control
US11385651B2 (en) 2018-06-26 2022-07-12 Ford Global Technologies, Llc System and methods for detection and response to interference between trailer coupler and hitch ball

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GB2282424B (en) 1995-09-20
GB9424088D0 (en) 1995-01-18

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