DE19946905B4 - Traction control system - Google Patents

Abstract

Traction slip control system, in which a traction control is provided which then reduces at least one drive wheel, the torque of the drive unit of the motor vehicle and / or builds braking force on spinning drive wheel, wherein the traction control has at least one variable parameter, the gear on when detected gear change in the presence of an inadmissible slip a value is changed, which results in a reduction in the sensitivity of the controller, characterized in that the insensitive switching of the traction control takes place only when no stability-critical operating condition is present.

Description

State of the art

The invention relates to a traction control system.

Such traction control systems are known from the prior art in many ways. In principle, the slip of the respective drive wheel is determined in such traction control systems on the basis of the wheel speeds, in particular by comparing the wheel speed of the respective driven wheel with a reference variable determined on the basis of the wheel speed of at least one non-driven wheel. This is compared with a maximum permissible slip, wherein when the maximum permissible slip limit is exceeded by the slip value at the respective drive wheel, a slip-reducing intervention in the torque of the drive unit of the vehicle and / or the wheel brake of the respective drive wheel takes place. The filter time with which the start of such a traction control system is filtered, the calculation of the slip limit value and / or the setpoint values transmitted for controlling the torque of the drive unit and / or the magnitude of the applied brake pressure in the spinning drive wheel are predetermined or are predefined as a function of operating variables. Such a traction control system is, for example, from DE 195 48 564 A1 (US Patent US 5,884,719 A ) known.

From the generic DE 38 44 121 A1 a traction control system for motor vehicles is known. In this, a lower limit is set for the throttle opening degree command with respect to each shift position of the transmission. When the manual transmission is upshifted, the throttle opening degree command is lowered to the lower limit of the throttle opening degree command, which corresponds to the shift position occupied by the upshift operation.

The DE 689 12 006 T2 shows a device for slip control, which is such that it can prevent slippage of the driven wheels with improved driving stability.

From the US 5 243 526 A Device is known which reduces the drive torque of a motor regardless of the driver's request.

The US 5,971,089 A further teaches a drive control system that controls drive power and braking force to prevent wheelspin during acceleration.

In some applications, these traction control systems show unsatisfactory behavior during a gearshift. This is because in the restoration of the frictional connection between the engine and drive train after a gear change, in particular in an upshift, the drive wheels have a phase with high slip. This can lead to an activation of the traction control, which is perceived as disturbing, as it is associated with short traction degradations. This effect was also observed at higher coefficients of friction between the road and the tire, where normally the engine torque is insufficient to build up excessive slippage. The excessive slip results in the special operating situation of the gear change from the additional energy through an engine speed excess, which must be reduced. Too high a slip occurs especially when there is too high compared to the Antriebsradgeschwindigkeit engine speed, which arises in particular in a too fast switching with a too slow drop in engine speed or by a revving of the engine before restoring the frictional connection. Lock control functions of an engine control system also contribute to this, because they support the slow drop in engine speed.

It is an object of the invention to provide a traction control system, which shows improved properties in a gear change.

This is achieved by the characterizing features of the independent claims.

From the DE 43 33 822 A1 (US Patent US 5 562 569 A ), a procedure is known with which a gear change is detected on the basis of the engine speed and the wheel speed.

Advantages of the invention

There is provided a traction control system which exhibits significantly improved gear changing characteristics. By measures that can be applied individually or in combination, the traction control is made insensitive to the normal operating state in this special operating condition, so that short-term traction dips are eliminated or at least mitigated. A significant improvement in traction during gear changes is the result.

The driving stability, which is likewise supported by a traction control system, is also maintained in a critical driving situation even during a gear change. This is because the measures that make the traction control system less sensitive are only performed if there is no stability-critical operating situation (such as cornering, etc.). If such a stability-critical operating situation exists, the at least one, the control system insensitive doing measure wholly or partially withdrawn.

It is particularly advantageous that the control system is infinitely less sensitive, so that a soft transition that is not felt by the driver, is achieved.

In a particularly advantageous manner, the procedure described below is applied to both automatic and manual transmissions.

Further advantages will become apparent from the following description of exemplary embodiments or from the dependent claims.

drawing

The invention will be explained in more detail below with reference to the embodiments shown in the drawing. 1 shows an overview diagram of a control device in which a traction control system is implemented. 2 shows on the basis of a time diagram a typical course of different speed values during the gear change. In 3 FIG. 12 is a flowchart representing a program illustrating an implementation of the influence of the traction control system on a gearshift. FIG.

Description of exemplary embodiments

1 shows a control unit 10 which at least one input circuit 12 , at least one microcomputer 14 and at least one output circuit 16 includes. These elements are through a communication system 18 connected to each other for mutual data exchange. The input circuit 12 Input lines are supplied, are fed via the signals that represent operating variables or from which operating variables of the vehicle, the wheel brakes, the drive unit, etc. are derivable. For clarity, in 1 only the input lines are represented, via which signals evaluated for carrying out the procedure described below are supplied. So be on input lines 20 to 24 Signals are supplied representing the wheel speeds. These are used in measuring equipment 26 to 30 determined on each wheel of the vehicle. Furthermore, in a preferred embodiment, an input line 40 provided by a control unit for controlling an automatic transmission 42 receives information about the presence of a gear change. However, this information can also be determined in other ways, in particular without additional information from a transmission control unit, for example from the behavior of engine speed and output speed. About the output circuit 16 and the output lines connected thereto are the control unit 10 Command values within the scope of the control unit 10 calculated traction control from. In the preferred embodiment, the at least one output line leads 32 to an electrically actuated actuator 34 which affects the torque or the power of the vehicle. This is in the preferred embodiment, an electronic engine control, which controls the torque of the drive unit of the vehicle by influencing the air supply, fuel supply and / or ignition angle. In a preferred embodiment, as part of the traction control via at least one further output line 36 Furthermore, an electrically controllable brake system 38 controlled by the vehicle, can be controlled by the braking force on the spinning drive wheels or the.

The mode of operation of a traction control system is familiar to the person skilled in the art. It is thus briefly outlined below. On the basis of the wheel speeds, the drive slip of each drive wheel of the vehicle is determined. This is compared with a possibly dependent on operating variables variable target slip value, wherein when the target value is exceeded by the wheel slip on at least one drive wheel a wheel slip reducing engagement takes place in the motor and / or brake of the respective drive wheel. Optionally, a filter time is provided before the use of the slip reducing measures, which allows short-term overshoot of the desired slip through the wheel slip, without intervening the reducing measures to make only short-term disturbances in the signal curves do not trigger the traction control. This filter time is much shorter in normal operation than the duration of a gear change. The magnitude of the reduction of the torque of the drive unit of the vehicle upon occurrence of a tendency to spin (an inadmissible slip) and / or the speed and / or the corresponding parameters in the braking force buildup on the spinning drive wheel is made or increased depending on the respective wheel slip until the unacceptable wheel slip has disappeared ,

Depending on the operating range, this traction control is designed for improved traction or improved stability. If an improved traction of the vehicle, in particular in the starting range, sought, the desired slip value is chosen to be larger in magnitude. at higher speeds and / or during cornering and / or similar, stability-endangering driving situations, value is placed on improved stability of the vehicle and the target slip is lowered accordingly.

In addition, other types of traction control are known in which, for example, on the basis of predetermined maps on the specifications of the wheel speeds and, if necessary, their change drive values for reducing the torque of the drive unit and / or to build up braking force are selected on the drive wheel. The procedure described below is also used accordingly in such traction controllers.

As described above, such a traction control shows in some cases when changing gears unsatisfactory behavior, especially when upshifting the gear, in which after completion of the gear change, the ratio of engine speed to output speed is smaller. When restoring the frictional connection between the engine and the drive train, in this operating state, the drive wheels often have a phase with excessive slip, which leads to the engagement of the traction control. The associated reduction of the torque and / or the build-up of braking force leads to a perceived annoying, short traction deterioration.

In 2 is based on a time chart a typical course of the relevant operating variables before, shown during and after a gear change. The dot-dashed line shows the time course of the engine speed NMOT, the dashed line the wheel speed of a driven wheel VRADAN and the solid line the time course of the wheel speed of a non-driven wheel VRADNA. Up to a time T0 the speed or speed signals are in a fixed ratio to each other, which is determined by the engaged gear ratio. At the time T0, a gear change, in the example shown an upshifting of the gear, is initiated. This initially leads to a rapid drop in engine speed and a slower decrease in the wheel speeds (because of the inertia of the vehicle) because of the separated frictional connection. Until a time T1, the frictional connection in the drive train is interrupted. Engine speed and wheel speeds thus change independently, with the engine speed being adjusted by the driver and / or by the transmission control. At time T1, the adhesion is restored in the new gear. At this time, the engine speed is increased. It may happen that as in 2 shown, the engine speed is raised far above the synchronous speed of the new gear out. This ultimately leads to an engine speed excess and thus an excess of drive torque when restoring the frictional connection. Accordingly, the speed of the driven wheel increases from time T1, thus indicating a deviation from the speed of the non-driven wheel. This deviation may be so great that the determined on the basis of this deviation slip of the drive wheel exceeds the allowable threshold and pulls a traction control engagement by itself. At time T2, the engine speed is lowered to the synchronous speed of the new gear. The gear change is over. The slip of the drive wheel decreases in accordance with the reduction of the engine speed again. From the time T2 there is again an operating condition with adhesion, in the engine speed and wheel speeds change in fixed proportion to each other.

In order to avoid or at least mitigate a brief drop in traction during the gear change, in particular when restoring the frictional connection between the engine and drive train, the measures described below are provided in conjunction with the traction control, which are used individually or in any combination. Common to these measures is that the traction control is made less sensitive, so that it does not respond or at least later to an inadmissible slip during the gear change. Thus, greater slip values are allowed on the drive wheels, causes later intervention of the traction control or reduces the extent of controller intervention on engine torque and / or braking force. The measures in detail are an increase in the filter time for the start of control of the traction control system over normal operation, an increase in the desired slip over the value provided in normal operation, a reduction in the size of the torque reduction and / or a reduction in the speed of reduction, d. H. an increase in the value of the transmitted setpoint value compared with a comparable slip situation during normal operation and / or a limitation of change and / or corresponding measures in connection with the braking force build-up.

These measures are preferably carried out at a recognized gear change for a predetermined period of time, which is normally such that the entire gear change is covered to restore the frictional connection and to settling the engine speed to the new synchronous speed.

When changing the at least one size for insensitive switching of the regulator, a filter function is used in the preferred embodiment, which continuously realizes the transition from the normal value to the gear change value. In other embodiments, a changeover is realized.

On the described measures) to reduce the sensitivity of the traction control in a gear change is omitted in a preferred embodiment or the measure (s) not in full, d. H. performed with smaller values when there is an operating condition that is critical to stability (for example, cornering). Thus, in one embodiment, the full effectiveness of the described measure (s) is given only with stability-uncritical straight ahead.

Preferably, the measure (s) is used both in conjunction with an automatic transmission and with a manual transmission.

The change of gear is detected, for example, by transmitting a corresponding signal from a transmission control, by the measures mentioned in the cited prior art or by comparing the relationship between engine speed and wheel speed, whereby a gear change is detected, if this ratio corresponds to the value assigned to a gear leaves.

In the preferred embodiment, the above-described procedure becomes a program of the microcomputer 14 realized. An example of realization represents this in 3 illustrated flowchart. This program is traversed at predetermined times.

After starting the program will be in the first step 100 based on the transmitted from the transmission control signal or on the basis of other variables such as engine speed and wheel speed determines whether a gear change is present. If this is not the case, in step 102 the at least one variable parameter of the traction controller is set in accordance with the manner provided for normal operation. The at least one parameter is the filter time for the ASR control start and / or the calculation of the allowable slip threshold and / or the magnitude of the setpoint and / or the rate of change over which reduces the torque of the internal combustion engine and / or the size or speed of the built-up braking force in the spinning drive wheel. After step 102 the program is terminated and run through at the next time.

Is a gear change in step 100 has been recognized, is in the step 104 a counter T is started whose count is in step 106 is compared to a maximum value. When the maximum value Tmax is reached, step follows 102 , the gear shift phase is considered over. If the time period determined by the maximum value has not yet elapsed since the gear change has been detected, then in step 108 the at least one variable parameter of the traction controller is set in accordance with the manner provided for the operating state gear change manner. The filter time is increased and / or increases the slip threshold and / or weighting the torque reduction causing value with a factor which leads to an increase of the setpoint and thus to a lower torque reduction, and / or the change of the desired value or the torque to a predetermined Value limited and / or treated the control signal for the braking force to be established according to the target value. After step 108 the counter T in step 110 incremented and the program with step 106 continued.

In the preferred embodiment, a step is also provided, which allows the special measures in the gear change only when a stability-critical operating state (for example, the straight-ahead driving) is present.

In the preferred embodiment, bills are considered only in which an upshift takes place, d. H. a shift operation in which the ratio of engine speed to wheel speed becomes smaller. In other embodiments, the illustrated approach is realized with gear changes in both directions.

The described measures to improve the gear change are performed individually or in any combination. This means that either only one of the above-mentioned variable parameters or any combination of these parameters assumes different values during the gear change.

The above approach is used in conjunction with gasoline or diesel internal combustion engines or alternative drive concepts such as electric motors or fuel cell drives as well as in conjunction with hydraulic, pneumatic, electro-hydraulic, electropneumatic or electromechanical wheel brakes.

Claims (8)

Traction slip control system, in which a traction control is provided which then reduces the torque of the drive unit of the motor vehicle in at least one drive wheel in the presence of an inadmissible slip and / or builds up braking force on the spinning drive wheel, wherein the traction control comprises at least one variable parameter, which is changed in a recognized gear change to a value which results in a reduction in the sensitivity of the controller, characterized in that the insensitive switching the traction control takes place only when no stability-critical operating condition exists. Traction control system according to one of the preceding claims, characterized in that the permissible slip value, beyond which a slip-reducing intervention takes place, is increased compared to the normal operation. Traction control system according to one of the preceding claims, characterized in that the control signals, in dependence of which the torque of the drive unit is reduced and / or the braking force is built up, are influenced with respect to the control signals in normal operation such that a smaller torque reduction or a lower braking force build-up takes place. Traction control system according to one of the preceding claims, characterized in that the changeover of the at least one parameter of the traction slip controller is made steplessly. Traction slip control system according to one of the preceding claims, characterized in that the insensitive switching of the traction slip controller takes place for a predetermined period of time after a recognized gear change. Traction control system according to claim 1, characterized in that after expiry of the predetermined period of time the traction control is switched back to the parameters used in normal operation. Traction control system according to one of the preceding claims, characterized in that the drive unit is a gasoline or diesel internal combustion engine or an electric motor or a fuel cell drive, the wheel brake is a hydraulic, pneumatic, electro-hydraulic, electropneumatic or electromechanical wheel brake. Traction slip control system according to claim 1, characterized in that it is the cornering of the stability-critical driving condition.

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