DE10330951A1 - Motor vehicle drive train operating method in which a slip is applied to the clutch mechanism for a limited time period when the driver presses the accelerator to increase the engine power output - Google Patents

Abstract

The method for operating the drive train of a motor vehicle that comprises a combustion engine (11) with a turbocharger (12), a clutch (16), a control arrangement (13, 17) and an accelerator pedal (14), whereby when a power increase is requested by the driver pressing the vehicle pedal, to increase the rotation speed of the engine and turbocharger a slip is applied to the clutch for a limited time period, i.e. so that it has different input and output speeds.

Description

The The invention relates to a method for operating a drive train of a motor vehicle with an internal combustion engine charged by an exhaust gas turbocharger and a power-operated clutch.

Internal combustion engines with turbocharging develop their torque at a power requirement, for example during an acceleration phase, uneven. The torque developed very quickly up to a full load torque of the subordinate Naturally aspirated engine. Subsequently delayed However, the further torque build-up, there is still a running gear, So a turbine wheel, a shaft and a compressor wheel in the exhaust gas turbocharger has to be accelerated. This delay is called so-called Called turbo lag. With the increased speed of the exhaust gas turbocharger increases a boost pressure of the internal combustion engine and the maximum torque, the so-called full load, can be achieved.

Around the dynamic behavior of internal combustion engines with exhaust gas turbochargers To positively influence, various approaches have been developed. For example Turbochargers are equipped with a variable turbine geometry or The exhaust gas turbocharger are at low engine speeds electrically supported.

In contrast, is It is the object of the invention to provide a cost effective method of operation to propose a powertrain, which has a spontaneous and comfortable operation of the motor vehicle allows. According to the invention Problem solved by a method according to claim 1.

Of the Drive train has at least one control device, by means of which the internal combustion engine and after the internal combustion engine arranged, power-operated Clutch are controllable. The coupling can for example as an automated startup clutch or a lockup clutch of a hydrodynamic torque converter accomplished be. The coupling may be by means of an electric actuator, For example, an electric motor, or a hydraulic or pneumatic actuator, such as a piston-cylinder unit, actuated and so open and getting closed. By means of the control device, a defined Slip on the clutch, so a defined differential speed be set between clutch input and clutch output.

One driver can by means of a power actuator, such as an accelerator pedal, a Performance target for set the engine. For this purpose, the power actuator For example, directly with a throttle valve of the engine be connected. In modern motor vehicles, this exists directly Coupling no longer. In this case, an operation degree of the power actuator becomes measured by said control device and therefrom a Performance target for derived the internal combustion engine. The control device controls then actuators of the internal combustion engine according to the power specification at. The power specification may, for example, as a target torque in [Nm] or a nominal power in [kW].

According to the invention is at an increase in Performance specification by the driver to increase Speeds of the internal combustion engine and the exhaust gas turbocharger in time limited slippage on the clutch set. If the clutch even before the increase The slip was operated with the output specification, then the slip elevated.

to Setting a slip, the clutch is at least partially open, with which the transferable Torque of the coupling drops. The internal combustion engine becomes so Relieves and their speed can rise quickly. With it rises the mass flow through the internal combustion engine, resulting in a fast Increase in the speed of the turbocharger leads. This leads to a rapid increase in the Boost pressure of the exhaust gas turbocharger. Since the output torque of the Internal combustion engine becomes larger with increasing boost pressure, the torque increases also fast. This allows the inventive method a very fast and spontaneous reaction of the internal combustion engine on a change the performance specification by the driver.

to Implementation of the method according to the invention are not additional Components or changes on the internal combustion engine or on the exhaust gas turbocharger necessary. The Procedure can thus very cost-effective and without installation space be implemented.

One further increase the dynamics of the motor vehicle is achieved in that during the increase of Engine speed kinetic energy in the internal combustion engine is stored, which helps reduce the slip back into the drive train is fed.

The inventive method is particularly advantageous when the maximum torque of the supercharged Brennkraftma machine is very small. Performance requirements that require torques that are below the maximum torque of the subordinate naturally aspirated engine are also implemented by a supercharged internal combustion engine without the support of the exhaust gas turbocharger, ie in so-called suction mode. If the maximum torque of the subordinate suction engine is very small, the range in which the internal combustion engine can implement a power requirement without the assistance of the exhaust gas turbocharger is also very small. Thus, the boost pressure of the exhaust gas turbocharger has to be increased almost every time the power requirement is increased, thus accelerating the power tool. Without the use of the method according to the invention, a turbocharger would always occur. When using the method according to the invention, the internal combustion engine reacts very quickly and spontaneously, ie without a turbo lag.

By the use of the method according to the invention can customer acceptance of motor vehicles with supercharged internal combustion engines clearly increased become. This allows internal combustion engines with small displacement and High charging as a substitute for large volume Suction motors realize (downsizing), which then accepted by customers and bought. These internal combustion engines have in comparison too large volume Naturally aspirated a very low consumption, making a cost-effective and environmentally friendly operation of the vehicles equipped therewith.

In Embodiment of the invention, the adjustment of the slip takes place depending on the coupling one of the increase the performance specification characterizing characteristic value. Characteristics are for example the degree of activity the power actuator, a position of a throttle valve of the internal combustion engine, the torque or the power of the internal combustion engine after the Increase or the height the change of the sizes mentioned the increase the performance target. Furthermore can be a characteristic value from a time derivative of the change derived from one of the mentioned sizes be. A characteristic can also be a combination of several formed the aforementioned sizes become.

In The control device, for example, different target curves for the slip stored on the clutch. Depending on one or more the parameters mentioned is a Target course selected and the slip is set according to the desired course.

The target curves are especially chosen that is a linear increase in the torque of the internal combustion engine results. This course of the torque is called by the driver especially comfortable.

In order to The structure of the slip can be linked to the actual increase of the Performance specifications are adjusted. For example, at a fast change the degree of actuation of the power actuator a higher Slip set as a slow change. This builds up the torque of the internal combustion engine in a rapid change faster than a slow change. This also corresponds the expectations of the driver. Next to the height the slip can also, for example, a course of the slip dependent on changed by a characteristic value become. This corresponds to the reaction of the powertrain to a increase the performance target especially the ideas of the driver, what leads to a particularly high level of acceptance by the driver.

In Embodiment of the invention is only a slip on the clutch set if the specified characteristic value is greater than a limit value. The bigger the Characteristic value is, the larger and / or more dynamic is the increase the performance specification by the driver. In a small or very slowly executed increase The performance requirement may be either without the support of the requirement Exhaust gas turbocharger or under taking in a retarding Construction of the torque done. This will only slip adjusted to the clutch, if necessary for the acceptance of the driver is. this leads to to a low wear the clutch and allows as well the driver the choice of whether a quick or slow torque build-up should.

In Embodiment of the invention is the slip on the clutch before Reaching a torque corresponding to the power specification of Internal combustion engine reduced. This allows a very accurate setting the corresponding torque, without any overshoot, so the setting too high torque occurs. This will certainly prevent that the internal combustion engine gives off a higher torque, as it does the driver pretends by means of the power actuator. This will be a safer Operation of the motor vehicle ensured.

Further Embodiments of the invention will be apparent from the description and the Drawing forth. embodiments The invention are shown in simplified form in the drawing and explained in more detail in the following description. In the drawing show:

1 a schematic diagram of a powertrain of a motor vehicle and

2a . 2 B . 2c Diagrams showing the time course of operating variables of the powertrain.

According to 1 has a powertrain 10 a motor vehicle, not shown, via an internal combustion engine 11 with an exhaust gas turbocharger 12 , The turbocharger 12 is from an exhaust stream of the internal combustion engine 11 driven and thus builds up a boost pressure according to its speed. The turbocharger 12 can thus the internal combustion engine 11 deliver a pre-compressed fresh gas charge.

The internal combustion engine 11 is from a controller 13 driven. The control device 13 stands with not shown actuators, such as a throttle plate actuator, and sensors, such as speed sensors, in signal communication. The control device 13 also features a power actuator designed as an accelerator pedal 14 in signal connection, by means of which a vehicle driver a performance target for the internal combustion engine 11 can adjust.

Between the internal combustion engine 11 and an automatic transmission 15 is a power-operated clutch 16 arranged. The executed in the form of an automatic transmission transmissions 15 and the clutch 16 are from a controller 17 driven. The control device 16 stands with not shown actuators, such as an electric clutch actuator, and sensors, such as speed sensors, in signal communication. Thus, the control device 17 the coupling 16 open, close and specifically set a slip. In addition, it can circuits in the transmission 15 To run.

The gear 15 is by means of a drive shaft 18 with a axle drive 19 connected, which in known manner the output torque of the internal combustion engine 11 about side waves 20 on powered vehicle wheels 21 transfers.

The control devices 13 and 17 are connected to each other via a serial bus connection, for example via a CAN bus, in signal connection. This can be detected variables, such as the speed of the internal combustion engine 11 , exchanged or requirements for a control device, for example, the requirement for setting a defined slip on the clutch 16 from the controller 13 the internal combustion engine 11 to the control device 17 the clutch 16 to be sent.

The For example, transmission can also be called a manual transmission, a Be executed planetary gear or a continuously variable transmission.

The Coupling can also be used, for example, as a bypass clutch of a hydrodynamic Torque converter or as one of two clutches of a dual clutch transmission accomplished be.

In the 2a . 2 B and 2c are on abscissa 30a . 30b and 30c each time and on an ordinate 31a an operation degree of the power actuator 14 and a speed, on an ordinate 31b a speed and on an ordinate 31c applied a torque.

In the 2a . 2 B and 2c are the time profiles of the speeds before (speed of the internal combustion engine 11 , solid line 32 ) and after (transmission input speed, dashed line 33 ) of the clutch 16 , the power requirement in the form of a degree of actuation of the power actuator 14 (dash-dotted line 34 ), a speed of the exhaust gas turbocharger 12 (Line 35 ) and the torque of the internal combustion engine 11 (solid line 36 ) With an increase in the power requirement, ie an increase in the degree of actuation of the power actuator 14 represented. In 2c is next to the curve of the torque (solid line 36 ) When setting a slip on the clutch for comparison purposes, a curve of the torque (dashed line 37 ) without setting a slip.

In the presentation, it is assumed that the gear of the transmission 15 and the speed of the motor vehicle does not change during the increase in the power demand. This keeps the transmission input speed constant.

Until one time 38 the driver provides a constantly low power requirement (activation level 39 ) to the internal combustion engine 11 , The coupling 16 is closed, so no slip on the clutch 16 occurs. This results in a constant speed of the internal combustion engine 11 , an equal transmission input speed, a constant speed of the exhaust gas turbocharger 12 and a constant torque of the internal combustion engine 11 ,

At the time 38 the driver abruptly increases the power requirement to an activation level 40 , The control device 13 notes that the degree of activity 40 greater than a stored limit 41 is. Based on this determination, the controller sends 13 a request to the controller 17 the clutch 16 , a slip according to one stored desired course of the coupling 16 adjust. The maximum slip value may for example be between 300 and 1500 [1 / min]. The speed of the internal combustion engine 11 rises immediately and becomes larger than the transmission input speed. Due to the increased mass flow rate through the internal combustion engine 11 increases the speed of the exhaust gas turbocharger 12 with a short time delay as well. The desired course of the slip is chosen so that there is a linear increase in the rotational speed of the exhaust gas turbocharger 12 results.

The slip on the clutch 16 is already before reaching the power requirement corresponding torque 42 at the time 43 again reduced, with the slip only after the time 43 completely degraded again. For example, the period of time in which slippage is set may be between 1 and 3 seconds.

In 2c is additionally the course of the torque (dashed line 37 ), which is without setting a slip on the clutch 16 would result. Compared to the torque (solid line 36 ) with slip on the clutch 16 the torque increases without slip directly after the time 38 faster and steeper. This is due to the fact that no torque for increasing the speed of the internal combustion engine 11 is needed. After the steep climb, however, there is a kink and the further increase is much slower compared to the torque with slip. The reason for this lies in a much lower speed of the exhaust gas turbocharger (not shown). The torque 42 is achieved without setting a slip until about 1 s later than setting a slip.

In addition to the faster achievement of the torque 42 is the course of the torque with setting a slip much smoother and more harmonious, which is perceived by the driver as comfortable.

Claims (4)

Method for operating a drive train of a motor vehicle with - one of an exhaust gas turbocharger ( 12 ) supercharged internal combustion engine ( 11 ), - one after the internal combustion engine ( 11 ), power-operated clutch ( 16 ), - at least one control device ( 13 . 17 ), by means of which the internal combustion engine ( 11 ) and the coupling ( 16 ) are controllable and - a power actuator ( 14 ), by means of which a vehicle driver sets a performance target for the internal combustion engine ( 11 ) can be set, wherein at an increase in the power setting by the driver to increase rotational speeds of the internal combustion engine ( 11 ) and the exhaust gas turbocharger ( 12 ) limited slip on the clutch ( 16 ) is set. A method according to claim 1, characterized in that the adjustment of the slip on the coupling ( 16 ) takes place as a function of a characteristic value characterizing the increase of the power specification. A method according to claim 2, characterized in that only one slip on the coupling ( 16 ) is set if said characteristic value is greater than a limit value. Method according to claim 1, 2 or 3, characterized in that the slip on the coupling ( 16 ) before reaching a torque corresponding to the power specification ( 42 ) of the internal combustion engine ( 11 ) is reduced.