Method for reducing transmission noises of drive train of vehicle e.g. small size car, involves controlling torque in drive train such that drive oscillations are suppressed depending on tensile or axial load in transfer box

The invention relates to a method for starting an internal combustion engine for a vehicle, the crankshaft of the internal combustion engine being connected via at least one separable clutch to a drive train having a transmission in which at least one electrical machine is arranged, the crankshaft of the internal combustion engine preferably in a start preparation phase is brought into a predefined starting rotational position by the electrical machine, the angular speed and the angular position of the crankshaft being determined by a speed sensor during operation.

A start / drive unit for an internal combustion engine of a motor vehicle is known from DE 198 58 992 A1, the internal combustion engine being connectable to a drive train having an intermediate gear via a crankshaft and a clutch. The intermediate gear is connected to an electrical machine with which various starting methods can be carried out. Each starting method is preceded by a starting clarification phase in which the crankshaft is rotated by means of the electric machine and in which the starting conditions are recorded when the clutch is closed, a decision is made about the subsequent operating phases and their starting parameters are determined. The speed ratios and the speed curve on the input and output side of the clutch are recorded via two speed sensors on both sides of the clutch in an electrical start control device and a decision is made about the starting method to be used and the starting parameters for it are determined in a clarification phase.

Speed ​​sensors used as standard, for example for determining the crankshaft speed, are relatively inexpensive, but have the disadvantage that the position of the crankshaft can only be determined imprecisely and above a minimum speed. In particular, when the crankshaft is rotating slowly, speed sensors can no longer be used for positioning the crankshaft. Position encoder, which can also be used at low speed or Being able to provide angularly accurate information about the position of the crankshaft at a standstill, however, is relatively expensive.

DE 198 08 472 A1 describes a method for starting a motor vehicle internal combustion engine with injection. In the run-up to the ignition, the engine is brought into such a position by a drive at slow speed that the piston of a cylinder is at top dead center. With the ignition command, another small rotary movement is forced on the engine, injected and ignited. The position of the crankshaft is recorded by its own crankshaft position sensor.

WO 01/88370 A1 describes a starting method and a starting device for internal combustion engines, the crankshaft being rotated into a predetermined starting position by an electrical machine. The crankshaft position is recorded by a dedicated rotation and position sensor that interacts with the crankshaft. Such position sensors are relatively expensive.

DE 100 62 985 A1 describes a method and a control device for determining the crankshaft angle of an internal combustion engine, the internal combustion engine being coupled to an electrical machine in that its rotor is non-rotatably connected to the crankshaft. The electrical machine has a control device for controlling the same and a device for determining the angular position of the rotor in relation to the stator. To determine the crank angle, the current angular position of the rotor is recorded by the device for determining the angular position and forwarded to the control device. The corresponding current crankshaft angle is then determined in the control device on the basis of the angular position values ​​detected. The crankshaft angle determined in this way is forwarded by the control device to the control of the internal combustion engine.

EP 1 113 169 A1 describes a starter arrangement for an internal combustion engine and a method for controlling the starter arrangement during a start and stop process

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Internal combustion engine. The starter arrangement includes an electric drive system with an electric machine, which can be connected to the internal combustion engine via a clutch.

The object of the invention is to enable the crankshaft to be positioned for a starting process in the simplest possible manner.

According to the invention, this is achieved in that a means for precisely determining the rotational angle position of the electrical machine is provided, that when the clutch is closed and at a crankshaft speed above a predefined minimum speed, a synchronization between the speed sensor and the means for precisely determining the rotational angle position of the electrical machine is carried out , whereby the latter is adjusted to the speed sensor, and that the assumption of the starting rotational position by means of the means for determining the rotational angle position of the electrical machine is monitored and controlled after the synchronization process and that the means for determining the rotational angle position is formed by a method without an encoder.

Means for the precise determination of the rotational position are sometimes used as standard in electrical machines.

In the method according to the invention, the means for precisely determining the rotational position of the electrical machine is used to determine the exact rotational position of the crankshaft during the shutdown phase of the internal combustion engine and to monitor it during the start preparation phase. Another additional precision position encoder is therefore not required.

It can be provided that the crankshaft is driven by the electric machine to assume the starting position, or that the crankshaft is braked to assume the starting position, preferably by the electric machine.

The invention is explained in more detail with reference to the figure.

The figure shows an internal combustion engine 1 which is connected via a crankshaft 2 and a switchable clutch 3 to a drive train 4 in which a transmission 5 is arranged. An electrical machine 6, which is optionally operatively connected to the transmission input shaft 10 or the transmission output shaft 7, is operatively connected to the transmission 5. Such arrangements of internal combustion engine 1, clutch 3, transmission 5 and electric machine 6 are often used in hybrid vehicles.

To monitor the speed of the crankshaft 2, a speed sensor 8 is, for example, in

Area of ​​a flywheel is provided, which can detect the rotational position of the crankshaft 2 only from a predefined minimum speed of the crankshaft 2 of, for example, 100 revolutions per minute. A high-precision position encoder 9 or an encoderless method is provided for detecting and monitoring the exact rotational angle position of the electrical machine 6, whereby the rotational angle position can be determined with an accuracy of approximately 0.5 ° crank angle. Such position encoders or encoderless methods are used as standard in electrical machines designed as rotary field machines.

In order to enable a quick start after the internal combustion engine 1 has been switched off, the crankshaft 2 is brought into a predefined starting rotational position in a start preparation phase.

The fact that the crankshaft 2 is brought into a precisely predefined starting rotational position before the fuel is injected and ignited enables rapid synchronization of the engine electronics on the one hand and an optimal start-up of the internal combustion engine on the other hand in order to overcome the first compression phase as quickly as possible. In order to achieve this, the method according to the invention provides that the rotational angle position of the crankshaft 2 is controlled via the position encoder 9 of the electrical machine 6 or the encoderless method

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Determination of the angular position is monitored. The prerequisite for this, however, is that the position encoder 9 or the encoderless method is coordinated with the crankshaft position beforehand. This is carried out with the aid of the speed sensor 8 used as standard for measuring the crankshaft speed. To this end, in a first step it is checked whether the clutch 3 is closed. If not, this state is established and a rigid rotary connection is established between the crankshaft 2 and the drive train 4 and the electrical machine 6, with the drive train being separated from the drive wheels at the same time. It is also checked whether the speed of the crankshaft 2 is above a minimum speed at which the speed sensor 8 can be used to determine the position. If these two prerequisites are met - the closed clutch 3 and the speed of the crankshaft 2 above the minimum speed - the position encoder 9 or the encoderless method is adapted to the speed encoder 8 and synchronization is thus carried out. This process, which only takes a few fractions of a second to seconds, can take place after the internal combustion engine 1 has been switched off and while it is running down.

In the start preparation phase, which can be carried out after switching off or only immediately before the starting process, the crankshaft 2 is brought into the predefined starting rotational position with the aid of the electrical machine 6 and the position encoder 9. This can be done by actively driving the crankshaft 2 by the electrical machine 6, or - especially after the internal combustion engine 1 has been switched off - by braking the crankshaft 2, for example with the aid of the electrical machine 6, into the predefined starting position.

In this way, a very precise starting position of the crankshaft 2 and a very rapid starting process can be made possible without additional precision position sensors being required.