DE10148342A1 - Operating method for automobile drive unit, has required value for control of drive unit calculated from engine revs instead of vehicle velocity during starting off - Google Patents

Abstract

The operating method has a required value, used for control of the automobile drive unit, provided independently of the position of a driver control, e.g. the gas pedal and the velocity of the vehicle. The engine revs is used for calculation of the required value instead of the vehicle velocity during starting off. An Independent claim for a device for operation of an automobile drive unit is also included.

Description

State of the art

The invention relates to a method and a device for operating a drive unit of a vehicle.

In connection with electronic control systems that are used for Operating drive units of vehicles will serve the driver's request for the longitudinal movement of the vehicle is recorded. This driver request is primarily based on the extent of Actuation of a control element which can be actuated by the driver, for example, an accelerator pedal. Are in the stand various solutions have been proposed in technology. From the DE 196 19 324 A1, for example, discloses a setpoint for to determine the internal torque of an internal combustion engine, by a signal representing the accelerator pedal position between a variable maximum value and a variable minimum value is interpolated. The result is therefore a relative desired torque based on the inner moment, d. H. of the moment caused by combustion processes of the Internal combustion engine is generated. Depending on the moment request then the torque of the engine is particularly controlled a throttle valve.

Another solution is described in DE-A 196 44 881 (US patent 6068574). There the driver request is not considered internal moment of the internal combustion engine, but as Wheel torque. Depending on the position of an accelerator pedal representing the desired wheel torque is determined, by placing this signal between a maximum value of the Wheel torque and a minimum value of the wheel torque interpolated becomes. These values are dependent on company size. The result is a relative wheel torque request from the Driver. The driver decides directly using the accelerator pedal the vehicle movement regardless of the current one Engine speed, the gear selected and possibly coupled Consumers.

Furthermore, from DE-A 42 10 956 (US Pat. No. 5,325,740) known an output torque setpoint or Wheel torque setpoint depending on the accelerator pedal actuation representative signal and the output speed or Determine vehicle speed.

In the state of the art mentioned above, the driver's request formed via speed and accelerator pedal position. The data the map used is selected so that at constant accelerator pedal position the desired torque as the speed drops Speed increases. This progression in the map corresponds the behavior of a motor with a mechanically operated Throttle valve, since there with constant throttle valve position and Accelerator pedal position and falling speed fill and thus the engine torque increases (effect of self-stabilization). This automatic torque increase supports this Start to counteract engine stalling.

This effect of the increasing torque with decreasing speed and constant accelerator pedal position is omitted if the Driver request is determined as a wheel torque, especially in Dependency of the accelerator pedal position and the Vehicle speed. This is because when starting, i.e. H. when standing Vehicle, the vehicle speed regardless of the Engine speed is zero.

This means that when a load is coupled in, the sinking Speed active by the driver by pressing the Accelerator pedal must be compensated. He has to be very sensitive about that Adjust the accelerator pedal speed, not by the self-stabilization of the system described above is supported. Therefore, it can be especially when starting easily over- or under-compensation that in extreme cases, the engine stalling or starting with high wheel slip (cavalier start).

Advantages of the invention

By considering the engine speed during the Starting process also when creating a driver request as Wheel torque, output or transmission output torque becomes a Effect of self-stabilization achieved. When sinking Engine speed increases the required torque, so that the Starting process is supported and the engine stalls or avoiding starting with high wheel slip can, since the driver can't handle the increasing load of the engine must compensate sensitively by accelerator pedal actuation.

It is particularly advantageous if during the starting process instead of vehicle speed to determine the Driver request a calculated vehicle speed is used, which depends on the current engine speed and the given translation is determined. This is only slight changes in driver torque generation necessary. The calculated speed corresponds to the Speed, which at the current engine speed in engaged state without slip would result. This Speed decreases with decreasing engine speed, so that in advantageously achieved the self-stabilizing effect becomes.

The transition from the measured to the calculated speed by a Design of the transition, for example a taxation of the Difference between the two speeds and / or a transition with equal speeds comfortably designed. The transition takes place in another direction preferably depending on the vehicle speed, e.g. B. at stationary vehicle (vehicle speed zero) instead.

Overall, the driver is at the start supports and a more sensitive metering of the engine torque allows.

Further advantages result from the following Description of exemplary embodiments or from the dependent Claims.

drawing

The invention is explained below with reference to the embodiments shown in the drawing. Fig. 1 shows an overview diagram of a control device for controlling a drive unit of a vehicle, while in FIG. 2, the determination of the driver is illustrated by a flowchart.

Description of exemplary embodiments

Fig. 1 shows an electronic control unit 10, which has at least one microcomputer 12, and input 14 and output circuits 16. The input circuits 14 , the microcomputer 12 and the output circuits 16 are connected to a communication system 18 for mutual data exchange. The input circuit 14 is supplied with various input lines from various measuring devices, operating elements, etc. The output parameters of the drive unit are influenced via output lines connected to the output circuits 16 of the control unit 10 . In the preferred exemplary embodiment, the drive unit is an internal combustion engine. A first output line 20 therefore leads to an electrically actuable throttle valve 22 for influencing the air supply to the internal combustion engine. The control unit 10 influences the ignition timing and fuel metering via further output lines 24 and 26 . A first input line 28 connects the control unit 10 to a measuring device 30 for detecting the engine speed. An input line 32 leads from a measuring device 34 which, via a mechanical connection 36, to an operating element 38 , eg. B. an accelerator pedal is connected to the control unit 10 . Another input line 40 connects the control unit 10 to a measuring device 42 for detecting the vehicle speed or output speed of the drive train. To detect the transmission ratio in the drive train, an input line 44 is provided in an exemplary embodiment with an automatic transmission, which connects the control unit 10 to a control unit 46 for transmission control. Information about the current transmission ratio in the drive train is supplied to the control unit 10 via the connection. In other exemplary embodiments, this connection is absent, in particular in connection with manual transmissions, where the gear ratios are determined by comparing the engine speed and the vehicle speed or output speed. Additional input lines 56-58 connect the control unit 10 to measuring devices 60-62 , the further operating variables of the internal combustion engine and / or the vehicle, such as engine temperature, exhaust gas composition, battery voltage, engine load, status information about the current operating status of auxiliary consumers such as air conditioning, power steering, etc. to capture.

In the preferred embodiment, the following is described solution shown in an internal combustion engine. The described solution comes with the appropriate Advantages for Otto engines as well as for diesel engines or with alternative drive concepts, e.g. B. Electric drives applied.

In the preferred exemplary embodiment, the electronic control unit 10 , where the microcomputer 12 uses computer programs on the basis of the degree of actuation of the operating element 38 , forms what is known as a driver's desired torque, which serves as a setpoint for a torque to be output by the drive unit or the drive train and by controlling the performance parameters the drive unit is realized. In other exemplary embodiments, it is not a driver's desired torque, but a driver's desired output or another output variable of the drive unit that is specified as a target value, hereinafter referred to as the driver's request, as a function of the degree of actuation.

In order to form the driver's request, in the preferred exemplary embodiment a desired wheel torque, output torque of the drive train of the vehicle or a transmission output torque, a map is provided which determines the driver's request as a function of an accelerator pedal position signal and a vehicle speed signal. The map is determined in the context of the application of the control system. During the starting process, for example when the vehicle speed is zero or near zero, the addressing of this map is changed so that it is not the current measured speed that is used, but a speed variable that is dependent on the speed of the drive unit. This variable represents in particular a calculated speed, which is formed depending on the current engine speed and the given gear ratio between engine and wheel (VFZ _rech = N _mot .Ü). This speed corresponds to the speed that would be set if the vehicle were running without slip at the current engine speed in the engaged state. In an automatic transmission, the vehicle speed is determined from the pump speed and mechanical transmission. The gear ratios of a converter are not taken into account. In other versions, the latter are also included.

This measure results during the start-up process an effect of self-stabilization, as the Engine speed the calculated speed drops and than As a result, the driver's request (required target torque) increases. This is because the driver's request map regardless of the calculation of the vehicle speed has a negative gradient, d. H. that the Driver request (moment) with decreasing speed (and constant accelerator pedal position) increases. This will make one allows constant setting of defined working points.

Thus, the addressing of the Driver request map using a different size performed. The transition is preferred Embodiment depends on the speed, the Addressing the map at a vehicle speed below a minimum speed depending on the speed occurs, depending on the speed. in the In the simplest case, the transition is made by switching the corresponding signal when the threshold is exceeded. This Solution is provided by measures to smooth the transition improved. Then in a preferred embodiment from speed-dependent addressing to speed signal dependent addressing passed when the calculated and current speed within the given range Tolerances are the same. In another embodiment the difference between calculated and measured vehicle speed. This difference is then calculated by manipulating the Speed with a factor dependent on time to 0 reduced and then switched.

The transition between measured and calculated speed. at Reaching a transition point (e.g. falling below a Speed threshold) is calculated by a Speed correcting factor equality made between the two sizes. The factor is then reduced to zero by means of a time function.

The effects of the described procedure are as follows. Due to the vehicle speed-dependent Addressing of the desired wheel torque map is achieved at different vehicle speeds the set The engine torque only depends on the accelerator pedal position and is not from the current speed. I.e. at Different gears or external loads show no change in the Torque. During a start-up with the vehicle stationary However, vehicle and various external loads show up a speed dependency in the torque of the drive unit, if a constant accelerator pedal angle is specified.

Above was in the context of the preferred embodiment on switching the signals during a Starting process shown. A corresponding procedure leaves apply even when in other operating conditions self-stabilization of the system depends on the Engine speed proves to be advantageous. Likewise, the Advantages in specifying a different physical size than the desired wheel torque, for example a power or of a speed value.

In the preferred embodiment, the procedure shown is implemented as a program of the microcomputer 12 of the control unit 10 . An example of such a program, which is also the subject of the described invention, is outlined in the flowchart in FIG. 2.

The individual blocks of this flow chart represent Programs, program parts or program steps represent while the connecting lines outline the flow of information.

A driver's request map 100 is provided, in which values for a desired wheel torque MRad set depending on the accelerator pedal angle β and the vehicle speed VFZ are entered. These two variables are supplied to the map, the wheel torque being read out as a function of these two variables. This is then implemented in a correction stage 102 with the function of the current transmission ratios in the drive train, which are determined in 104 , into a target value for an output torque of the internal combustion engine (MKUP _soll ). The clutch torque setpoint is then linked in a further correction stage 106 to a minimum engine torque (M _min ), which is calculated in 107 , and the driver's request as the internal engine torque MI target _is determined in this way. The internal engine torque corresponds to the torque which is generated by combustion processes and takes into account both the output torque to be set and the torque which the internal combustion engine has to exert in order to overcome the internal losses and to drive auxiliary consumers. In a known manner, this inner desired engine torque is then converted into control signals in 108 for setting the air supply, the fuel metering and / or the ignition angle.

The formation of the minimum engine torque M _min is also known from the prior art. It essentially corresponds to the loss torque above a predetermined accelerator pedal angle, ie the torque which the internal combustion engine has to apply in order to overcome the internal losses and to operate auxiliary units which do not contribute to the drive. Below an accelerator pedal angle, the minimum engine torque corresponds to this loss torque, reduced by means of a scaling factor, in order to allow the fuel supply to be switched off at high engine speeds.

In order to improve the starting behavior, a switching means 110 is provided as described above, which switches between the measured vehicle speed VFZ and a calculated vehicle _speed VFZ. The switchover condition is formed in 112 as a function of the measured vehicle speed and / or the calculated vehicle speed. To calculate the vehicle speed, the engine speed N _mot and the gear ratios Ü determined in 104 in the drive train are evaluated in 114 . Corresponding calculations determine a calculated vehicle _speed VFZ in 114 which is dependent on the engine speed. If a starting situation is recognized, for example because the measured vehicle speed VFZ is below a minimum value, the switching means 110 is switched to the dashed position and the computed speed is supplied to the map 100 for determining the desired wheel torque. If the actual speed exceeds a predetermined threshold value, in the simplest exemplary embodiment the dummy element 110 is switched back to the solid position. In other exemplary embodiments, the difference between the calculated and measured vehicle speed is formed in 112 and only switched over when the predetermined tolerances of these two values match. If, in one exemplary embodiment, a control of this difference is provided as described above, this is also carried out in 112 , the computing speed then being manipulated accordingly (see dashed line).

Claims (10)

1. A method for operating a drive unit of a vehicle, a setpoint being formed as a function of the position of a control element which can be actuated by the driver and the speed of the vehicle, in dependence on which the drive unit is controlled, characterized in that the formation of the Desired value depending on a variable depending on the engine speed instead of the vehicle speed. 2. The method according to claim 1, characterized in that that the size depending on the engine speed is a calculated vehicle speed is. 3. The method according to any one of the preceding claims, characterized in that the at least one Operating state is a starting process of the vehicle. 4. The method according to any one of the preceding claims, characterized in that a map is provided is at what moment desired values that occur on the output side of the drive unit, depending the accelerator pedal angle and one Vehicle speed are stored. 5. The method according to claim 4, characterized in that this is the desired torque values, Required transmission output torques or Desired output moments are, taking into account the Gear ratios in the drive train to a target torque of Drive unit is converted into Dependency the performance parameters of the drive unit can be set. 6. The method according to any one of the preceding claims, characterized in that the arithmetic Vehicle speed depending on the engine speed and the transmission ratios in the drive train is calculated. 7. The method according to any one of the preceding claims, characterized in that the switchover from the measured vehicle speed to the calculated Vehicle speed is then made when the vehicle speed below one predetermined minimum value is located. 8. The method according to any one of the preceding claims, characterized in that the switchover from the calculated vehicle speed to the measured Vehicle speed occurs when the Vehicle speed exceeded a threshold or if the difference between the Vehicle speed and the calculated Vehicle speed is essentially the same. 9. The method according to claim 8, characterized in that the difference between calculated Vehicle speeds and measured Vehicle speed by manipulating the calculated Vehicle speed is steered to 0, the Control when leaving the start-up operating area takes place. 10. Device for operating a drive unit Vehicle, with a control unit that is one of the Position of an accelerator pedal representing size and determined a vehicle speed variable and the forms a setpoint depending on these variables, depending on which the drive unit is controlled is characterized in that the control unit Means comprises, which at least in one Operating status instead of the measured speed Determination of the setpoint a speed-dependent variable use.