DE102015220807A1 - Method for controlling a motor vehicle drive train - Google Patents

Abstract

The drive control apparatus for an automotive powertrain according to the present invention is composed of a drive motor having an electronic engine controller in which an engine start-stop automatic function is implemented, and an automatic transmission having an electronic transmission control apparatus in which a creep reduction function is implemented. Creep reduction is activated at or near standstill of the vehicle by slipping or disengaging a clutch or brake in the automatic transmission such that traction in the powertrain of the vehicle is reduced or eliminated. According to the invention, a function module in the transmission control unit is configured or programmed in such a way that the creep reduction function is deactivated in the stalled vehicle, - if at standstill the brake pressure triggered by the driver is greater than a first predetermined brake pressure threshold value and / or if the engine control unit does not stop the engine announced by the engine start-stop automatic function.

Description

The invention relates to a method for controlling a motor vehicle drive train according to the preamble of patent claim 1.

Such a method is for example from the DE 44 46077 C2 known. This method relates in particular to automatic transmissions which are connected via a torque converter to the internal combustion engine of the motor vehicle. The torque converter has an engine-side pump and a transmission-side turbine. The pump is coupled to the internal combustion engine such that its speed corresponds to the speed of the internal combustion engine. When the motor vehicle is at standstill, the pump thus drives the transmission-side turbine at a speed corresponding to the idling speed of the internal combustion engine in such a way that a so-called creep of the motor vehicle would occur without a creep reduction function. In this case, when the vehicle brake system is actuated, a value proportional to the brake pressure is detected and the creep reduction is controlled as a function of this detected value. In the method known from the creep reduction is not only determined to determine whether, but also how much the vehicle brake system is operated to control. Thus, a swinging on and off creep reduction can be prevented if the vehicle brake system is operated intermittently only with low pressure, from which it can be concluded that just a creep of the vehicle, z. B. in traffic jams, is desired. However, if a significant brake pressure, preferably within a predetermined time window, detected, the desire of the driver to the actual standstill of the motor vehicle is detected and accommodated to this desire by turning on the creep.

The creep reduction or creep prevention is realized, for example, by upshifts starting from a currently preselected gear or by reducing the pressure in the responsible for the currently preselected gear clutch (starting gear).

Also from the DE 10 2009 030 605 A1 is a creep prevention known as stand-off. The DE 10 2009 030 605 A1 deals in particular with the transition from the state decoupling in the re-driving. In this case, the controlled closing of the creep prevention or Standabkoppelung partially or fully open starting clutch in response to the dynamics of the driver's request is in the foreground, which is also associated with a corresponding adjustment of the engine torque control.

It is an object of the invention to improve a method of the type mentioned in such a way that when switching off the state decoupling or creep reduction as uncomfortable perceived vibrations are avoided.

This object is solved by the features of patent claim 1. Advantageous developments of the invention are the subject matters of the dependent claims.

The drive control apparatus for an automotive powertrain according to the present invention is composed of a drive motor having an electronic engine control apparatus implementing an engine start-stop automatic function, and an automatic transmission having an electronic transmission control apparatus implementing a creep reduction function. Creep reduction is activated at or near standstill of the vehicle by slipping or disengaging a clutch or brake in the automatic transmission such that traction in the powertrain of the vehicle is reduced or eliminated.

• – wenn bei oder nach einem Übergang von einem Schubmoment in ein Kriechmoment der vom Fahrer ausgelöste Bremsdruck grösser als ein erster vorgegebener Bremsdruckschwellwert ist und/oder
• – wenn bei oder nach einem Übergang von einem Schubmoment in ein Kriechmoment das Motorsteuergerät einen Motor-Stopp durch die Motor-Start-Stopp-Automatikfunktion ankündigt, auch wenn dann der Bremsdruck unter einen zweiten Bremsdruckschwellwert sinkt, der kleiner oder gleich dem ersten Bremsdruckschwellwert ist.

According to the invention, a function module in the transmission control unit is configured or programmed in such a way that the creep reduction function is always activated first,

• If, during or after a transition from a thrust torque to a creep torque, the brake pressure triggered by the driver is greater than a first predetermined brake pressure threshold value and / or
• If, during or after a transition from a thrust torque to a creep torque, the engine control unit announces an engine stop by the engine start-stop automatic function, even if the brake pressure then drops below a second brake pressure threshold that is less than or equal to the first brake pressure threshold.

• – wenn im Stillstand der vom Fahrer ausgelöste Bremsdruck grösser als ein erster vorgegebener Bremsdruckschwellwert ist und/oder
• – wenn das Motorsteuergerät keinen Motor-Stopp durch die Motor-Start-Stopp-Automatikfunktion ankündigt.

Alternatively or additionally, according to the invention, a function module in the transmission control unit is configured or programmed in such a way that the creep reduction function is deactivated in the stalled vehicle,

• - When at standstill, the brake pressure triggered by the driver is greater than a first predetermined brake pressure threshold and / or
• - if the engine control unit does not announce an engine stop by the engine start-stop automatic function.

• – wenn der vom Fahrer ausgelöste Bremsdruck unter den zweiten vorgegebenen Bremsdruckschwellwert sinkt und das Motorsteuergerät bis dahin keinen Motor-Stopp durch die Motor-Start-Stopp-Automatikfunktion angekündigt hat und/oder
• – wenn der Motor-Stopp durch die Motor-Start-Stopp-Automatikfunktion abgeschlossen ist.

Preferably, by appropriate design of the function module, the creep reduction function is deactivated,

• - When the brake pressure triggered by the driver drops below the second predetermined Bremsdruckschwellwert and the engine control unit until then has announced no engine stop by the engine start-stop automatic function and / or
• - when the engine stop is completed by the engine start-stop automatic function.

In a further development of the invention, by appropriate design of the function module, the function for creep reduction deviating from the above conditions can also be activated if the engine control unit does not announce an engine stop by the engine start-stop automatic function and / or if triggered by the driver Brake pressure is not greater than the first predetermined brake pressure threshold, but if the transmission temperature is less than a predetermined temperature threshold.

By this inventive control of creep reduction is a driver-oriented responsive, yet comfortable start possible.

The invention is based on the following findings:
Empirical it was found that by tolerances in automatic transmissions, especially in an unrestrained vehicle and at comparatively low loads (especially at zero load) and at higher transmission temperatures during the exit from a creep (ie when closing the open clutch) so-called "Shuddern" uncomfortable swinging or jerking occurs.

By the invention, a creep prevention should only remain on when this Shudder either does not occur, so for example at low transmission temperatures, and / or insufficient braking force. If an engine restart is performed by an engine start-stop system, an excitation by the engine start is present anyway, which compensates the Shuddern. In the case of an engine start-stop automatic system start (engine start without releasing the brake and accelerator pedal activation), the traction is still established, so that a subsequent Ankriechen without Shudder is possible.

In the drawing, an embodiment of the invention is shown. It shows the essential components of the device according to the invention and the operation of the functional module according to the invention in the transmission control unit.

In the drawing is a drive motor, such as an internal combustion engine 1 , with an automatic transmission 2 via a torque converter 3 connected. The pump P of the torque converter 3 is by the internal combustion engine 1 driven. When the internal combustion engine is switched on 1 is through the pump P oil flow through the stator L of the torque converter 3 promoted on the blades of the turbine T. The turbine T of the torque converter 3 is with the input train of the transmission 2 rotatably connected. With block 4 are schematically supplementing other clutches and wheelsets of the transmission 2 indicated.

The internal combustion engine 1 is basically an electronic engine control unit 6 controlled. The automatic transmission 2 is basically an electronic transmission control unit 7 controlled. The engine control unit 6 and the transmission control unit 7 For example, they are interconnected via a CAN data bus. The engine control unit 6 terminates, for example via this data link the transmission control unit 7 by means of a signal MS an engine stop the engine start-stop system. The transmission control unit 7 additionally receives as input signals, for example, the vehicle speed v, the engine speed n_M, the brake pressure p of the vehicle brake triggered by the driver and the position of the accelerator pedal FP as a sensor signal corresponding to the engine load or the engine torque.

To insert a currently preselected gear is from the transmission control unit 7 a gear assigned to this gear, here for example the clutch 5 a starting gear, closed to the torque acting on the input line to the output line of the transmission 2 transferred to. When the motor vehicle is at a standstill, the rotational speed of the output rod n_A is 0. However, when the motor vehicle is at a standstill, the internal combustion engine with idling speed (n_M = n_LL) takes place via the pump P of the torque converter 3 a torque transmission to the turbine T, but with the vehicle braked and clutch closed 5 can not be exploited for the drive of the motor vehicle. This power loss of the internal combustion engine 1 leads to unnecessary fuel consumption. In known methods to solve this problem during standstill of the motor vehicle, ie n_A = 0, the clutch 5 completely or almost completely open, so that on the output train of the transmission 2 no or only a minimal moment is transmitted (creep prevention or creep reduction). In particular, a complete opening of the clutch 5 Although the creep reduction or creep prevention leads to the optimization of the fuel consumption reduction, but worsens the comfort when switching off the creep reduction and the transition to the starting process.

In principle, the creep reduction is switched on, for example, if the vehicle speed v is zero or even if the brake pressure p triggered by the driver is greater than a first predetermined threshold. The creep reduction is preferably switched off when the detected brake by p is less than a second predetermined threshold. The second predetermined threshold may also be equal to the first predetermined threshold. As a result, the deactivation of creep reduction is already carried out during stalling, so that the creep reduction is already switched off until the actuation of the accelerator pedal and thus a comfortable but responsive startup is made possible. For automatic parking brake functions, the creep reduction can be switched off when the accelerator pedal is actuated.

To optimize consumption reduction, complete opening of the clutch responsible for the currently preselected gear is advantageous since, in this case, there is no torque transmission to the gearbox output and thus no additional load for the engine (creep prevention). However, if the clutch is fully opened, the clutch clearance must be overcome at the beginning of the closing process when switching off the creep, then only to bring the clutch plates to the concern. During the clutch closing occurs in the slip phase of the clutch a noticeable, comfort-deteriorating rotational swinging (Shudder).

By the functional module according to the invention in the transmission control unit 7 In the exemplary embodiment illustrated here, the function for creep reduction is basically activated in the first instance when the brake pressure p triggered by the driver is at least greater than a predefined brake pressure threshold value SB at the transition from a thrust torque to a creep torque (ie during the so-called zero torque transition). The brake pressure threshold value SB is determined empirically and is preferably designed in such a way that with this minimum value certainly no advancement of the vehicle occurs (eg -100 Nm).

The creep reduction is then deactivated again when the brake pressure p triggered by the driver drops below the predetermined brake pressure threshold value SB or when the brake pressure p triggered by the driver threatens to fall below the predetermined brake pressure threshold value SB. But if the engine control unit 6 indicates and executes an engine stop MS by the engine start-stop automatic function (line A or alternatively line B of the engine return n_M), the creep reduction, even if then the brake pressure p drops below the brake pressure threshold SB, after the stoppage of Vehicle with engine off, here at the times t2 according to line A or t4 according to line B, disabled.

With the line A and the line B for the course of the engine speed n_M two possible situations of an engine start-stop automatic function are shown:
A first engine start-stop automatic function according to line A can already announce an engine stop MS during coasting (ie v = 0 at time t2) before the standstill (ie at time t1) and conclude at time t2. In this case, the creep prevention function can be deactivated from the time t2.

A second engine start-stop automatic function according to line B can only announce an engine stop MS after rolling out at standstill at time t2 (here at time t3) and conclude at time t4. In this case, the creep prevention function can be deactivated from the time t2.

However, the creep reduction function may also be activated and / or deactivated without the above conditions even if the transmission temperature T is less than a predetermined temperature threshold ST (eg, 55 ° C). This threshold value should also be determined empirically in such a way that basically no shuddering occurs.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4446077 C2 [0002]
• DE 102009030605 A1 [0004, 0004]

Claims (4)

Drive control device for a motor vehicle drive train consisting of a drive motor ( 1 ) with an electronic engine control unit ( 6 ), in which an engine start-stop automatic function is implemented, and from an automatic transmission ( 2 ) with an electronic transmission control unit ( 7 ), in which a creep reduction function is implemented, wherein the creep reduction is activated at or near a stop of the vehicle by a clutch or brake in the automatic transmission ( 2 ) is brought into sliding engagement or in the open position, that a frictional connection in the drive train of the vehicle is reduced or eliminated, wherein a functional module in the transmission control unit is designed such that the function for creep reduction is basically activated, - when or after a transition from a thrust moment in a creep torque of the brake pressure (p) triggered by the driver is at least greater than a first predetermined brake pressure threshold and / or - if at or after a transition from a thrust torque to a creep torque, the engine control unit ( 6 ) signals an engine stop (MS) by the engine start-stop automatic function even if the brake pressure (p) then drops below a second brake pressure threshold (SB) that is less than or equal to the first brake pressure threshold. Drive control device for a motor vehicle drive train consisting of a drive motor ( 1 ) with an electronic engine control unit ( 6 ), in which an engine start-stop automatic function is implemented, and from an automatic transmission ( 2 ) with an electronic transmission control unit ( 7 ), in which a creep reduction function is implemented, wherein the creep reduction is activated at or near a stop of the vehicle by a clutch or brake in the automatic transmission ( 2 ) is brought into sliding engagement or in the open position that a frictional connection in the drive train of the vehicle is reduced or eliminated, wherein a function module in the transmission control unit is configured such that the function for creep reduction is disabled in the stalled vehicle - when at standstill triggered by the driver Brake pressure is greater than a first predetermined brake pressure threshold and / or - if the engine control unit does not announce an engine stop by the engine start-stop automatic function. Drive control device according to claim 1 or 2, characterized in that by appropriate design of the function module, the creep reduction function is deactivated when the brake pressure (p) triggered by the driver is above the second predetermined from the transmission oil temperature dependent Bremsdruckschwellwert (SB) and the engine control unit ( 6 ) until then announced no engine stop (MS) by the engine start-stop automatic function. Drive control device according to one of the preceding claims, characterized in that by appropriate design of the function module, the function for creep reduction is also deactivated when the engine control unit ( 6 ) does not announce an engine stop (MS) by the engine start-stop automatic function and / or if the driver-initiated brake pressure (p) is not greater than the first predetermined brake pressure threshold, but the transmission temperature (T) is less than a predetermined one Temperature threshold (ST) is.

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