FR2830216A1 - METHOD AND DEVICE FOR IMPLEMENTING A VEHICLE DRIVE UNIT - Google Patents

Abstract

Method for operating a drive unit of a vehicle according to which, depending on the position ß of an operating element actuated by the driver and the speed of the vehicle (VFZ), a set value is formed (Mradcons ) to control the drive unit. In at least one predetermined operating state, the setpoint is formed (114) as a function of a quantity (VFZcal) depending on the engine speed, instead of the speed (VFZ ) movement of the vehicle.

Description

s The present invention relates to a method and means

  for operating a drive unit of a vehicle.

  STATE OF THE ART The invention relates to a process for implementing a drive unit of a vehicle according to which, depending on the position of a

  operating element actuated by the driver and the vehicle speed

  runs, a set value is formed to control the drive unit. It also relates to a device for putting into operation a drive unit of a vehicle comprising a drive unit.

  command which determines a quantity representing the position of the

  accelerator plate and a quantity of the vehicle speed, and which forms a set value as a function of these quantities, the unit

  drive being controlled by this setpoint.

  In the context of electronic control systems for the implementation of vehicle drive units, the

  driver request for longitudinal movement of the vehicle.

  This request from the driver is thus deduced mainly from the actuation bias of an operating element actuated by the driver, for example the accelerator pedal. For this, different solutions are

  proposed in the state of the art.

  Thus, according to document DE 196 19 324 A1, it is for example known to determine a reference value of the internal torque of an internal combustion engine by making an interpolation for the if

  gnal representing the accelerator pedal between a maximum value

  reliable and variable minimum value. The result is thus a request

  relative torque based on the internal torque, i.e. the general torque

  generated by the combustion operations of the internal combustion engine.

  Depending on the torque demand, the engine torque is then adjusted,

  especially by ordering its throttle flap.

  DE-A-196 44 881 describes another solution.

  According to this document, the driver's request is not transformed into the internal torque of the internal combustion engine but into the drive torque of the wheels. A reference wheel drive torque is formed from a signal representing the position of the accelerator pedal by interpolation of this signal between a maximum value and

  a minimum value of the wheel drive torque. These values

  during each of the operating variables. The result is a relative demand for wheel drive torque by the driver. The driver directly determines the movement of the vehicle by the accelerator pedal, regardless of the instantaneous engine speed,

  gear ratio used and any accessories connected.

  s In addition, according to document DE-A-42 10 956, it is known to determine a set value of the output torque or a set value of the wheel drive torque as a function of a signal representing the actuation of the accelerator pedal as well as the speed

  output rotation or vehicle travel speed.

  o In the first state of the art mentioned above, the driver's request is formed as a function of the speed of rotation and the position of the accelerator pedal. The data of the characteristics field thus used are chosen so that for a constant position of the accelerator pedal, the requested torque increases as a function of the speed of rotation. This progression in the field of characteristics corresponds to the behavior of an engine with a throttle flap actuated mechanically because then, for a constant position of the throttle flap and a position of the accelerator pedal, the supply and so the engine torque increases (automatic stabilization effect o) while the speed decreases. This automatic increase in torque supports the start by opposing the ca

engine age.

  This effect of the increasing torque as an inverse function of the speed of rotation and for a constant position of the accelerator pedal disappears when the driver's demand corresponds to the wheel drive torque, in particular as a function of the position of the accelerator pedal and vehicle travel speed. This results from the fact that at start-up, that is to say when the vehicle is stopped, the speed of movement of the vehicle is zero, independently

engine speed.

  This means that when engaging a load, the reduction in speed must be actively compensated by the driver by actuating the accelerator pedal. It must regulate in a very fine way the speed by the accelerator pedal and the

  3s system is not assisted by the own stabilization described above.

  This is why, in particular during the start-up phase, this can easily result in an excess of compensation upwards or downwards, which in one extreme case results in stalling of the engine or, in the other

  case, by starting with wheel slip.

  Advantages of the invention The aim of the present invention is to remedy these disadvantages and to this end relates to a process of the type defined above,

  characterized in that in at least one predetermined operating state

  mined, the setpoint is formed as a function of a dependent quantity

  the engine speed instead of the vehicle speed. o Advantageously, the variable depending on the engine speed is a calculated speed and the operating state is the phase of

starting the vehicle.

  Taking into account the engine speed during the start-up phase and in forming the driver's demand as t5 wheel drive torque, as engine output torque or

  as transmission output torque, there is a stabilizing effect

  own tion. When the engine speed decreases, the torque

  demand increases, which supports the start-up phase, avoiding the

  engine run or starting with a strong slip because the driver o does not have to compensate for the increase in the load applied to the engine by

  fine actuation of the accelerator pedal.

  Preferably, a field of characteristics is provided containing the requested values of the torque, which are obtained at the output of the drive unit, these values being recorded as a function of the angle s of the accelerator pedal and of the vehicle travel speed. In addition, according to the invention, the requested torque values are the requested wheel drive torque, the requested transmission output torque, or the requested engine output torque, which is converted by taking account transmission conditions in a setpoint torque so of the drive unit and as a function of this, the parameters are adjusted

  power of the drive unit.

  It is particularly advantageous if during the

  starting, instead of vehicle speed to determine the de-

  driver's request, a calculated vehicle speed is used which

  : 5 determines according to the current engine speed and the damage ratio

  given multiplication. Thus, only slight variations in the torque demanded by the driver are sufficient. The calculated speed corresponds to the speed that there would have been for the current engine speed with a closed clutch without slip effect. This speed decreases with the decrease in the speed s of rotation of the motor, resulting advantageously in

self-stabilizing effect.

  In a particularly advantageous manner, the measured speed of the vehicle is switched to the calculated speed of the vehicle if the speed of the vehicle is less than a predetermined minimum value. The transition from the measured speed to the calculated speed takes place in a comfortable manner by the design of the transition, for example by the regulation of the difference between the two speeds and / or a transition when the speeds are identical. The passage in the other direction is preferably made as a function of the speed of the vehicle, for example when the vehicle is stopped (the vehicle speed is then zero). For example, the difference between the calculated speed of the vehicle and its measured speed is regulated to the value O by manipulation of the calculated speed, the com

  is a command that occurs when exiting start-up training mode.

  Overall, the driver is thus assisted in the starting phase and the invention allows a fine metering of the engine torque. In the device provided according to the invention, the control unit comprises means using to determine the set value at least in an operating state a quantity dependent

  of the regime instead of the measured speed.

  Drawings The present invention will be described below in more detail with the aid of embodiments represented in the ss of appended drawings in which: - Figure 1 is an overview of a control installation of a drive unit of a vehicle, - Figure 2 shows a flow chart to determine the driver's request.

  Description of the exemplary embodiments

  FIG. 1 shows an electronic control unit 10 comprising at least one microcomputer 12 as well as input 14 and output circuits 16. The input circuits 14, the microcomputer 12 s and the output circuits 16 are connected by a communication system 18 for the exchange of data. The input circuit 14 receives different input lines coming from different measurement installations, actuating elements, etc. The output lines connected to the control unit by the output circuits 16 influence the power settings of

the drive unit.

  In an exemplary prerential embodiment, the unit

  drive is an internal combustion engine.

  s A first outlet line 20 is connected to an electrically controlled throttle valve 22 to influence the air supply to the internal combustion engine. By other output lines 24 and 26, the control unit 10 influences the instant of ignition and the metering

fuel.

  o A first input line 28 connects the control unit 10 to a measuring installation 30 to capture the speed of rotation of the engine (engine speed). An input line 32 connects a measuring installation 34 to the control unit 1. This measuring installation is connected by a mechanical link 36 to a maneuvering element 38 actuated by the driver, for example an accelerator pedal. Another input line 40 connects the control unit 10 to a measuring installation 42 for entering the vehicle speed or the output rotation speed of the transmission line. To enter the transmission ratio in the transmission line, in the example of an automatic gearbox, an input line 44 has been provided, connecting the control unit 10 to a control unit 46 for controlling the gearbox. speeds. A link provides the control unit 10 with information giving the demulti

  current application of the transmission line.

  In other embodiments, there is not this link but a link with the manual gearbox; the de-multiplication ratio is then determined by comparing the engine speed to the speed of movement of the vehicle or the speed of rotation of the gearbox output. Other input lines 56-58 connect the control unit 10 to measuring installations 60-62 providing other operating parameters of the internal combustion engine and / or of the vehicle such as the engine temperature , the composition of the exhaust gases, the battery voltage, the engine charge, status information concerning the instant operating state of accessory consumers such as the air conditioning system, power steering, etc. According to a preferred embodiment, the solution presented below is applied to an internal combustion engine. However, the solution described applies with advantages corresponding to both petrol and diesel engines or in alternative drive concepts, for example drive by electric motors. According to the preferred embodiment, the electronic control unit 10, constituted by the microcomputer 12, with the

  programs according to the operating schedule of the element of man_u-

  vre 38, forms a torque requested by the driver which serves as a setpoint for the torque that must be provided by the drive unit or the transmission line and this torque is obtained by controlling the parameters of

  o power of the drive unit. In other examples of realizations

  There is no torque requested by the driver, but a power requested by the driver or another output quantity of the drive unit as a reference value called in the following "driver request" in function of the actuation dogré of

way of maneuver.

  To form the driver's request, in the preferred embodiment, with regard to the torque requested at the wheels, the vehicle transmission output torque or the gearbox output torque, a field of predefined has been defined. characteristics; o based on a signal representing the position of the accelerator pedal and a vehicle speed signal, the driver's request is determined. The field of characteristics is fixed as part of the application of the control system. During the start-up phase, when the vehicle speed is for example zero or close to a speed

  zero size, the addressing of this characteristic field is continuously modified

  so as not to use the instantaneous speed, measure, but a quantity of the speed depending on the speed of rotation of the unit

  drive. This quantity represents in particular a calculated speed

  formée according to the current engine speed and the reduction

  between the motor and the wheel (VFZrech = Nmot * U.

  This speed thus corresponds to the speed that we would have if

  the vehicle was traveling with instantaneous engine speed and the clutch

  fully engaged without skating. In the case of a gearbox

  speed, the speed of the vehicle is determined from the speed of rotation of the pump and the mechanical reduction. We don't hold

  counts in this case gear ratios of a converter.

  In other embodiments, this reduction ratio is also taken into account. Thanks to this means, during the start-up phase, there is a specific stabilization effect because when the speed of rotation of the motor decreases, the calculated speed decreases and consequently the demand of the driver (requested torque) increases. This results from the fact that the field of characteristics of the demands of the driver presents, independently of the calculation of the speed of the vehicle, always a negative gradient, that is to say that the demand of the driver (torque) increases when the speed decreases (for a constant position of the accelerator pedal). This makes it possible to constantly adjust a determined operating point. Thus, during the start-up phase, the addressing of the field of characteristics of the driver's requests is done using another quantity. The passage is done according to the preferred embodiment according to the speed; the addressing of the characteristics field for a vehicle speed is done according to the speed of rotation below a minimum speed and above it is done according to the speed of movement. In the simplest case, the passage is made by switching the signal corresponding to the exceeding of a threshold. This solution is improved by means of smoothing the transition. In an example of a pre-preferential embodiment, one then goes from addressing depending on the speed of rotation to addressing depending on the speed of movement, if the calculated speed and the instantaneous speed are identical within the given tolerance limits. In another exemplary embodiment, the difference between the calculated speed and the measured second speed of the vehicle is formed to smooth the transition. This difference is then reduced to zero by manipulation of the speed calculated with a coefficient.

  time dependent then we switch.

  The transition between the measured speed and the calculated speed is designed accordingly. When a transition point o is reached (for example when a speed threshold is exceeded below), the equality between the two quantities is achieved by a coefficient correcting the calculated speed. The coeffcient is then reduced to zero by a function of time. The effects of the procedure described above are as follows: by addressing the field of characteristics of the driver's requests as a function of the speed of the vehicle, it is obtained that for different speeds of the vehicle the set torque of the engine does not depend only from the position of the accelerator pedal and not from the current speed. This means that for different gear ratios or external loads, there is no change in torque. During the starting phase, the vehicle being stationary and the external loads being different, the torque of the drive unit however depends on the speed of rotation if a constant angle is predetermined for the accelerator pedal.

  In the context of the pre-preferential embodiment,

  sensed above a switching of the signals during the phase of

  startup. You can also apply a corresponding procedure if

  o in other operating states, it is advantageous to have a sta-

  proper system utilization according to the speed of rotation of the motor

  tor. Likewise, we have the advantages of predefining another physical quantity than the wheel drive torque requested, for example

  a power or a speed of rotation (speed).

  s In the preferred embodiment, the procedure is carried out in the form of a program for the microcomputer 12 of the control unit 10. An example of such a program, object of

  the invention is sketched by the flowchart of Figure 2.

  The different blocks of this flowchart represent o programs, parts of programs or stages of programs;

  the connecting lines represent the flow of information.

  I1 is provided a field of characteristics of the requests of the driver 100 containing the values of a wheel drive torque, requested MradcOns according to the angle of the accelerator pedal and the speed VFZ of the vehicle. These two quantities are applied to the field of

  characteristics and depending on these two quantities we extract the cost

  ple asked. This is then applied to a correction stage 102 which transforms it into a set value of the output torque of the internal combustion engine into a torque supplied by the internal combustion engine (MKUPcons) according to the current gear ratios. the transmission line; this ratio was obtained in step 104. The set value of the clutch torque is combined in a first correction stage 106 with a minimum engine torque (MmiIl) calculated in step 107; the driver's demand is determined in this way under the

  form of internal MIcons motor torque. The internal motor torque corresponds to

  pond the torque supplied by combustion, taking into account the output torque to be set as well as the torque required from the engine to overcome internal losses and drive the accessories. In a known manner, in step 108, this internal setpoint engine torque is converted into actuation signals to regulate the air supply, the fuel metering

and / or the ignition angle.

  It is also known according to the state of the art to form the minimum motor torque Mmn. This essentially corresponds, above a predetermined angle of the accelerator pedal, to the loss torque, that is to say the torque that the internal combustion engine must pass for internal losses and for training of accessories which do not participate in propulsion. Below an angle of the accelerator pedal 10, the minimum engine torque corresponds to this loss torque, reduced according to a scale coefficient, to allow cutting of

  the fuel supply at high speeds.

  To improve the start-up behavior it is planned

  as described above, a switching means 110 which com

  i5 switches between the travel speed of the VFZ vehicle and a calculated vehicle speed VFZc. The switching condition is formed in point 112 as a function of the measured vehicle speed and / or of the calculated speed. To calculate the vehicle speed, in step 114, the engine speed Nmot is used as well as the transmission ratio o of the transmission line obtained in step 104. By appropriate calculations, step 114 is determined, a calculated speed of the vehicle VFZc which depends on the engine speed. When a starting situation is detected, for example if the measured speed of the vehicle VFZ is less than a minimum value, the switching means 110 are switched to the position shown in dotted lines and the speed calculated in the characteristics field is used. 100 to determine the required wheel drive torque. If the actual speed exceeds a predetermined threshold, in the simplest example we switch back

  the switching element 110 in the position shown in solid lines.

  In other exemplary embodiments, in step 112 the difference between the measured speed and the calculated speed of the vehicle is formed and it is only in the event of agreement within the limits of the tolerances that these two values. If in an exemplary embodiment there is provision for an end of control of this difference as indicated above, this operation is also carried out as in step 112 and we

  correspondingly injects the calculated speed (dotted line).

Claims (5)

R E V E N D I C A T I O N S   1) Method for implementing a drive unit of a vehicle according to which, depending on the position of an operating element actuated by the driver and the speed of the vehicle, a setpoint s is formed to control the drive unit, characterized in that in at least one predetermined operating state, the target value is formed as a function of a quantity dependent on the engine speed   instead of the vehicle's travel speed.   2) Method according to claim 1, characterized in that   the quantity depending on the engine speed is a calculated speed.   S 3) Method according to claim 1, characterized in that   the operating state is the starting phase of the vehicle.   4) Method according to claim 1, characterized by a field of characteristics containing the requested values of the couple,   that are obtained at the output of the drive unit, these values being recorded   gistrces according to the angle of the accelerator pedal and the speed movement of the vehicle.   2s) Method according to claim 4, characterized in that the requested torque values are the wheel drive torque, requested, the transmission output torque, requested, or the engine output torque, requested, that l '' Converting taking into account the transmission conditions into a setpoint torque of the unit   drive and depending on it we set the power parameters drive unit.   3s 6) Method according to claim 1, characterized in that the speed of movement of the vehicle is calculated according to the speed   engine and transmission line transmission ratio.   7Q) Method according to claim 1, characterized in that the measured speed of the vehicle is switched to the calculated speed of the vehicle if the vehicle speed is less than a minimum pre value. s determined.   8) Method according to claim 1, characterized in that the calculated speed of the vehicle is switched to its measured speed if the speed of the vehicle exceeds a threshold or if the difference between the speed of the   vehicle and its calculated speed is practically zero.   9) Method according to claim 8, characterized in that is the difference between the calculated speed of the vehicle and its measured speed is   regulated to the value O by manipulation of the calculated speed, the com-   command occurring upon exiting start-up drive mode.    ) Device for implementing a drive unit of a vehicle comprising a control unit which determines a quantity representing the position of the accelerator pedal and a quantity of the speed of the vehicle, and which forms a setpoint as a function of these quantities, the drive unit being controlled by this setpoint, 2s characterized in that the control unit comprises means using to determine the   setpoint at least in an operating state a large   regime dependent instead of measured speed.