DE19857513B4 - Method and device for determining the axle load of a vehicle - Google Patents

Abstract

method for determining the axle load of a vehicle, one being the axle load representing the vehicle measuring signal is converted into an axle load, wherein the measurement signal is stored as a static axle load value when the vehicle for a particular Time is unrestrained and unaccelerated, characterized that the vehicle to store the static axle load with a given minimum speed.

Description

State of the art

The The invention relates to a method and a device for controlling the axle load of a vehicle.

In particular, in the control of brake systems, measurements with respect to the axle load of a vehicle are of essential importance, since the control of the braking force on the individual wheel brakes is set as a function of the detected axle load. An example of such a brake system control is from the DE 44 38 222 A1 ( U.S. 5,261,931A ) known. A generic method and a generic device are from the DE 690 19 556 T2 known. There, an electronic brake control for semitrailer tractors is described, wherein the static axle loads are always detected when static, even conditions exist.

It Object of the invention, measures for Specify the detection of the static axle load of a vehicle, the the static axle load in reliable, capture accurate manner without the interference of the measurement signal to falsify the result.

Advantages of the invention

It becomes a procedure for determining the static axle load of a vehicle indicated by which reliable signal values determined become. Of particular advantage is that disturbances, for example while a braking operation or during an acceleration operation on the determined by an axle load measuring signal act in the determination of the static axle load off become. Advantageously, therefore, a reliable value for the provided static axle load of a vehicle.

From particular advantage is that safely with the help of this Achslastwertes It can be determined if a trailer is coupled to a towing vehicle is or not. It is particularly advantageous that the absence of the trailer can be reliably detected, because in addition to the axle load additionally the Speed of the vehicle in determining if the semitrailer is decoupled becomes.

Especially it is advantageous that signals of non-pressurized spring bellows after prolonged service life of the vehicle, which are faulty in determining whether the semitrailer decoupled as a result of the criteria introduced for the determination of the uncoupled semitrailer be excluded.

Further Benefits emerge from the following description of exemplary embodiments or from the dependent ones Claims.

drawing

The invention will be explained below with reference to the embodiments shown in the drawing. 1 shows an electropneumatic brake system of a towing vehicle of a wagon train. In the 2 and 3 is a preferred embodiment of a procedure for determining the static axle load of the vehicle as well as for determining whether a semi-trailer is coupled or disconnected, sketched by the example of flowcharts.

Description of exemplary embodiments

1 shows an overview block diagram of an electronically controlled brake system using the example of an electronically controlled air brake system for a two-axle towing vehicle with trailer connection.

1 shows a central control unit 10 which has at least one microcomputer. Furthermore, decentralized so-called pressure control modules 12 . 14 . 16 and 18 provided, each of a wheel brake 20 . 22 . 24 and 26 are assigned to the towing vehicle. The central control unit 10 is about a communication system 28 , z. B. CAN, with the pressure control modules 12 to 18 connected. For detecting the applied brake pressures and for detecting wheel speeds and at least on one axle of the axle load (eg by pressure sensors in the air spring bellows) and possibly other variables such as brake temperatures, etc., the pressure control modules 12 to 18 each lines 34 . 36 . 38 and 40 from corresponding measuring devices 42 . 44 . 46 and 48 fed. The central control unit 10 is also via a line 50 with a brake value transmitter 52 connected. Further, to control a trailer brake system is a trailer control module 70 which is provided via the communication system 28 with the central control unit 10 connected is. It is in the range of the trailer control module 70 at least one pressure sensor is provided which detects the pressure in the pneumatic control line to the trailer and in 1 not shown. Furthermore, leads from the central control unit 10 a line 56 to the electrical connector 58 to the trailer.

The pneumatic part of the brake system, which may have an in 1 Not shown, not shown for pneumatic actuation of the wheel brakes, in the preferred embodiment consists of three reservoirs 62 . 82 and 86 , The wheel brakes 20 and 22 the front axle associated pressure control modules 12 and 14 be over lines 60 with one from the reservoir 62 stam supplied supply pressure. The trailer control module 70 is over a line 80 with the reservoir pressure vessel 82 connected. From the trailer control module 70 leads a pneumatic control line 72 to a first coupling head 74 , a supply line 76 to a second coupling head 78 , The pressure control modules 16 and 18 that the wheel brakes 24 and 26 the rear axle of the towing vehicle are assigned via a line 88 from the reservoir 86 supplied with supply pressure.

In a preferred embodiment, the central control unit 10 from the brake value transmitter 52 a measure of the degree of actuation of the brake pedal supplied. In the central control unit, this signal is processed and, if necessary, taking into account further operating variables such as axle loads, vehicle deceleration, etc. Solldruck-, Sollbremsmoment-, Sollkraft- or setpoint slip values for the individual wheel brakes or for the trailer in accordance with predetermined characteristics or maps determined. These setpoints are sent via the communication system 28 supplied to the individual pressure control modules and the trailer control module, which adjust the pressure in the individual wheel brakes or the control line to the brake system of the trailer according to the setpoint specification.

The from the at least one axle load sensor detected measurement signal is so by the procedure described below evaluated that one Measure of the static Axle load of the vehicle results. This static axle load of Vehicle is in the control of the towing vehicle in some functions essential, for example when determining the wheel-individual target pressures with a view to a given brake force distribution between front and rear axle, in determining the tuning of the brake systems the sub-vehicles of a wagon train, which are based on the quotient between braking forces and axle loads work as well as in connection with the estimation of vehicle mass while an acceleration process, because of the static rear axle load of the towing vehicle roughly closed to the load of the trailer can be and thus determines a starting value for the mass estimate can be.

The Axle loads of a towing vehicle in a wagon train are z. B. at a vehicle with air suspension from the compression bellows of the rear axle via a simple characteristic interpolation won. Since the measured axle load signal is severely disturbed, For example, in road bumps, braking or during acceleration processes, This characteristic interpolation may take place only if at the wheels, especially the rear wheels, where the axle load sensor is usually mounted, no strong Attack braking or drive torque. If that were the case, a part would the support force over the Trailing arm abgelei tet and relieved the bellows or charged additionally. The measured Axle load signal would be disturbed and correspond not the actual one static axle load of the vehicle.

Therefore In order to improve the determination of the static axle load, the read signal of the Federbalgdrucksensors initially heavily filtered, in particular heavily low-pass filtered (Filter with large Time constant). Subsequently the characteristic interpolation is performed so as to obtain a To determine axle load value. The calculated axle load value is displayed in stored in a sample-and-hold memory. The memory contents become updated only if the vehicle is unrestrained for a certain period of time, i.e. brake pressures and retarder torques are zero, and unaccelerated, i. the Engine torque is less than z. B. 25% of the maximum torque, and with driving at a speed the bigger than is a predetermined minimum speed. Are all these criteria Fulfills, the memory is reset. The contents of this memory correspond with it exactly the static axle load of the towing vehicle.

In the preferred embodiment, the determination of the static axle load of the towing vehicle is designed as a computer program of a microcomputer of the central and / or decentralized control units of the brake systems. An example of such a computer program is shown as a flow chart in FIG 2 outlined. The program is run when the supply voltage of the microcomputer at predetermined time intervals. After starting the program part is in the first step 100 read in the measuring signal of the axle load sensor and in the following step 102 a filtering, preferably a low-pass filtering with a large time constant subjected. Then in step 104 determined from a predetermined characteristic of the axle load value. In the following step 106 It is checked whether the vehicle is unrestrained and unaccelerated for a predetermined time and at a speed which is greater than a predetermined minimum speed vmin moves. If these conditions are met, it will be in step 108 the axle load value is stored as a static axle load value; in the opposite case, the previously stored static axle load value is retained and not updated. After the steps 108 respectively. 106 in the case of a no answer, the program is ended and repeated at the next time interval.

In connection with some functions in connection with the brake control, it is essential to recognize the unhitching, ie the coupling or uncoupling, of a semitrailer. This can be in semi-trailers from the static axle load Determine the value of the rear axle of the towing vehicle. The information as to whether a trailer change has taken place is essential, in particular, for functions which deal with the tuning of the brake systems of two partial vehicles of the wagon train. For example, a function in which the application pressure of the semi-trailer is learned, after a detected trailer change back to a default value. In addition, in a different context, depending on the recognized trailer change from an accurate adjustment of the wheel brakes of the two sub-vehicles can be switched to a fast adjustment process.

Of the static axle load value, in the context of the above Procedure has been identified, serves to detect if a semi-trailer is coupled. For this purpose, the static axle load signal with a predetermined minimum value FAUFL compared. This comparison value typically is about 1 ton above the static axle load of the towing vehicle without semi-trailer. Exceeds the measured sta tic axle load this limit, is determined by an existing Semitrailer gone out.

One Absence of the trailer is detected when the static rear axle load below a second predetermined value, which is the value of the solo towing vehicle corresponds, lies. This value is usually for example 500 kg less than the value for detecting the existing one Trailer. Since when changing the vehicle usually not the required minimum speed achieved or frequently braked the static axle load signal can not be evaluated. This is because the memory for the static axle load is not is updated. However, it has been shown that in the slow forward and reverse while Umsattelns usually despite the braking no strong falsification the measured axle load signal is carried out. That's why a missing one Semi-trailer recognized when the low-pass filtered axle load signal whose Value does not have to match the stored value during a given time below the limit and the driving speed is zero is.

immediate After switching on the vehicle's travel switch, the axle load signal must not be evaluated. If the vehicle is parked for a long time, are the bellows depressurized. In that case, would always missing semitrailer recognized, even if the train fully loaded is. Therefore, the detection of the missing trailer is performed only when briefly a speed greater than zero was detected. In In this case, the supply pressure has risen at least so far that the parking brake solved could be. This is a sign that the bellows with Pressure are applied and the Achslastsensorsignal is reliable.

A another possibility Detecting the decoupling consists of the axle load sensor signal determine the pressure drop when lowering the vehicle. A unhitching is recognized, for example, if during a period of about 10 sec. when the vehicle is stationary, the signal from the axle load sensor signal, which when using a pressure sensor in the bellows the bellows pressure corresponds, calculated rear axle load decreases by at least one ton.

In 3 is a preferred embodiment for the detection of the existing or missing trailer as a computer program using the example of a flowchart outlined.

Also in 3 sketched program is run at predetermined time intervals. In the first step 200 the operating variables to be evaluated are read in. These are the static axle load Achslast_stat_ha stored in the memory, the low-pass filtered axle load Achslast_ha and the vehicle speed VFZ. In the following step 206 it is checked whether the vehicle speed is greater than zero. If this is the case, then a mark will be created according to step 208 set to 1. This mark indicates that the vehicle has briefly reached a speed greater than zero after switching on the driving switch of the vehicle. Turning off the power switch will reset that flag to zero. If the speed is not greater than zero, then step 208 skipped. In the following step 202 Checks whether the stored static axle load (Achslast_stat_ha) of the rear axle exceeds the limit value FAUFL. If this is the case according to step 204 from an existing trailer and set a corresponding brand or maintain the set brand. Thereafter, the program is terminated and run through again at the next time interval.

Has according to step 202 the stored static axle load does not exceed the limit value, in step 210 it checks if the speed mark is greater than zero (step 208 ) has the value 1. If this is not the case, the program is terminated and run through the next time. If the mark 1, that is, the vehicle has already reached a speed greater than zero for a short time in this driving cycle, then the following steps are used to check whether the trailer is missing. This is done in step 212 checks whether, for a certain time, the filtered axle load (axle load_ha) is less than a predetermined limit value FSOLO and whether the vehicle speed is zero. If these two conditions are met, the step will be taken 214 a missing semi-trailer detected and reset the brand for the trailer accordingly or the back maintain set mark. Is one of the conditions according to step 212 is not fulfilled, the program is terminated and repeated at the given time.

Claims (7)

Method for determining the axle load of a vehicle, wherein a measurement signal representing the axle load of the vehicle is converted into an axle load value, the measurement signal being stored as a static axle load value when the vehicle is running unrestrained and unaccelerated for a specific time, characterized in that the vehicle is for Storing the static axle load value at a given minimum speed. Method according to claim 1, characterized in that that the vehicle is unbraked when no brake pressures and Retarder moments occur that it is unaccelerated when that Engine torque less than a certain percentage of the maximum torque is. Method according to one of the preceding claims, characterized characterized in that the measuring signal is determined from a sensor signal by filtering. Method according to claim 3, characterized that the filtering is a strong low-pass filtering. Method according to claim 3, characterized that from the filtered signal in accordance with a characteristic curve an axle load value is formed. Method according to one of the preceding claims, characterized in that the sensor is a pressure sensor in the bellows of the Suspension of the vehicle is. Device for determining the axle load of a vehicle, with a control unit representing a vehicle axle load Receiving signal, wherein means are provided which convert this signal as statistical Save the axle load signal if the vehicle is unbraked for a certain time and unaccelerated, characterized in that the Means save the signal as a statistical axle load signal, if the vehicle for driven a certain time at a given minimum speed is.