WO1999045267A1

WO1999045267A1 - Method for starting an engine of a motor vehicle

Info

Publication number: WO1999045267A1
Application number: PCT/EP1999/001333
Authority: WO
Inventors: Heinz Leiber
Original assignee: Lsp Innovative Automotive Systems Gmbh; MAGNETI MARELLI S.p.A.
Priority date: 1998-03-02
Filing date: 1999-03-02
Publication date: 1999-09-10
Also published as: DE19808472A1; EP1060333A1

Abstract

The invention relates to a method for starting an internal combustion engine of a motor vehicle with electromagnetic valve actuation. The intake and outlet valves and the ignition device are affected in such a way as to reduce the power required during the starting procedure.

Description

Method for starting a motor vehicle engine

The invention relates to a method for starting a motor vehicle engine with the features of the preamble of claim 1.

Motors with the devices as enumerated in the preamble of claim 1 are known. The use of electromagnetically operated intake and exhaust valves is on the rise.

The invention is based on the object of facilitating the starting process of a motor vehicle internal combustion engine in order to be able to reduce the size of the large and heavy starter customary today and to reduce the power requirement for starting the engine and thus to be able to reduce the size of the battery.

This object is solved by the features of claim 1.

To start, according to the state of the art, very high currents are required, for gasoline engines in the area around 500A, for diesel engines almost twice. This means that appropriate low-resistance cell structures and corresponding technologies must be used in the battery. During the journey, the battery is loaded with considerably lower currents, which are essentially determined only by the charging current of the generator; this moves in the Area less than 100A. In the event of a generator failure, the battery current in the area is around 50A for emergency operation. This means that the battery must be dimensioned 10 times stronger for the starting situation with regard to the current. Also not to be neglected is the start cable, i.e. the electrical connection between the battery and the starter, which usually weighs 1 kg. The performance of the starter is essentially determined by two factors, namely firstly the overcoming of the friction and the cylinder compression, and also in previous intake manifold injection systems by a certain intake speed and angle of rotation, so that the injected fuel can mix well with air.

The invention makes use of the property of electromagnetically actuated valves which do not have to be actuated in a defined sequence, but which can also be actuated in a different way from the actual engine operation and are controlled accordingly by an electrical control unit. The invention can be used both in engines with intake manifold injection and in engines with direct injection (GDI).

The mentioned changes in the valve control can, for. B. can be used to start the engine with an increased firing order with correspondingly changed valve control, the engine e.g. to operate in the start-up phase in two-stroke mode. At least in the case of direct injection, the engine is preferably moved in advance with a slow and low-power drive to a position in which at least one cylinder is in a position between 90 ° and 45 ° before TDC. In a 4-cylinder engine, two cylinders are in this position.

A further possibility to make starting easier is to ignite them simultaneously in the first cycle for an engine with two cylinders running in parallel (i.e. simultaneously arriving in TDC and LDC), which of course requires appropriate control of the valves.

Finally, it is also possible to avoid the compression process in cylinders at the start of the start by means of appropriate valve control or several other cylinders would counteract the start. This method can also be used in addition to the other methods mentioned above.

With the methods mentioned above, at least in the case of direct injection, at least one piston can additionally be pre-positioned in TDC or close to it. This prepositioning, which is explained in more detail below, can also be used without the starting facilitations explained above

When prepositioning, it is possible to rotate the crankshaft into this preposition at a relatively low speed and thereby compress air in the first cylinder. With the ignition command there is another small twist and it is injected and ignited. To reduce the drive power, it is advantageous to start the first cylinder only with partial filling, that is to say a lower pressure of compaction. It is also advisable to do this in the following cylinders until a sufficiently high starting speed is reached. This partial filling is particularly easy to achieve with electromagnetic valve control. To reduce the drive power offers itself, already when approaching the vehicle, for. B. by activating the remote control or opening the door to turn the crankshaft to bring a cylinder into the preposition. The rotation takes place e.g. B. to top dead center. If the ignition switch is then actuated, the injection into the cylinder and the ignition take place after a further small rotation, which results in the engine starting. If the engine is switched off briefly, a cylinder can already be held under compression.

When using an electromagnetic valve control, in which the compression phase is initiated after any closing of the valves, a cylinder can also be brought ready to start at an angle before TDC when the engine is switched off or when the door is opened, which is just sufficient to prevent the crankshaft from rotating further the ignition to create sufficient compression pressure.

With electromagnetic valve control, it is also a good idea to use the engine's swing energy after the engine has been switched off by switching the solenoid valves. So there is no compression work to be done. The generator can fully use the swing energy to charge the battery.

Exemplary embodiments of the invention are explained with the aid of the drawing.

1 shows a schematic diagram of an engine equipped according to the invention

2a to 2e diagrams of cylinder movements to explain starting processes

Fig. 3 shows a motor in principle to explain the

Default

Fig. 4 to 7 different usable drives

8 and 9 diagrams for the explanation of function

In Fig. 1, an engine 1 is shown in principle, of which a piston 2 of a cylinder, the crankshaft 3 and a connecting rod 4 are visible. With 5 and 6 electromagnetic actuators are designated which operate an inlet valve 7 and an outlet valve 8. 9 with a spark plug is designated. 10 is a crankshaft position transmitter, 11 a starter drive, which acts via an electromagnetic clutch 12, 13 on a belt drive 14, via which the crankshaft gear 3a and the crankshaft 3 can be driven. The generator of the motor can be connected to the shaft of the wheel 14a driven by the starter drive 11. By means of a second wheel 14b connected to the belt drive 14, a further unit, e.g. B. an air conditioning compressor or a supercharged engine. 15 is an injection valve. The actuators 5 and 6 for the valves 7 and 8, the spark plug 9, the injection valve 15, the starter drive 11 together with the clutch 12/13 are controlled by an electrical control unit 16. For this purpose, the control unit evaluates the signals from the crankshaft position transmitter 10. Before starting, the piston 2 can be placed in a position favorable for starting via the drive 11, the clutch 12/13 and the belt drive 14. This will be discussed in detail later. When starting itself, the drive 11, which starts up first, is activated first. The clutch 12/13 is then actuated and then fuel is injected via the injection nozzle 15 at the right time and ignited by means of the spark plug 9. The valves 7 and 8 are placed in corresponding positions. At the start, the belt drive can be tightened by means of a tensioner 17.

In FIG. 2, start sequences over time are compared for different engine types according to the prior art and according to the invention, in all cases 4-cylinder engines are assumed.

Fig. 2a shows the start of the 4-cylinder I to IV for an intake manifold injection according to the prior art. The cylinder I begins at t, with the compression K, followed by the combustion phase V, followed by phase A, during which the cylinder is connected to the exhaust via the exhaust valve 8. Finally, there is the air intake phase S. After 720 °, compression takes place again. At least 360 ° rotation is required here until a full suction phase S, specifically for cylinder III, has taken place at t ₂ and can be ignited shortly after TDC, which is indicated by a corresponding symbol. After 180 ° the ignition follows in cylinder IV, after another 180 ° that for cylinder I and finally after another 180 ° that for cylinder II.

In Fig. 2b an engine with direct injection (ie effective injection valve 15) and a start according to the prior art is assumed. Here the cylinder I can be ignited by at least 90 ° after the rotation. The other cylinders II, III and IV follow each after 180 °. Here, too, the process is repeated after 720 °, i.e. two turns.

Fig. 2c shows a start course for an engine with direct injection, according to an embodiment of the invention and here the valves 7 and 8 and the injection valves 15 of the four cylinders are controlled so that before t ₃ in the cylinders I and III compressed and ignited simultaneously in both cylinders after t ₃ . Cylinder III cannot be ignited again after 360 °, but cylinder II and cylinder IV are ignited as a result. The joint ignition after t ₃ gives a strong initial drive torque.

In Fig. 2d the course of a direct injection engine is shown again, in which the engine is driven in the start phase by correspondingly controlling the valves 7, 8 and 15 and the spark plugs 9 in two-stroke mode, i.e. each cylinder is fired at 360 ° intervals. This operating mode is maintained until the motor reaches a certain speed, e.g. Has reached 600rpm. Here, before the starting process, the pistons 2 of cylinders I and III are additionally set to a position x between 90 ° and 45 ° before TDC by a slow drive in order to facilitate the actual starting process. The rotation necessary until TDC is sufficient to achieve sufficient compression of the air in the cylinder.

2e shows the courses when starting an engine with intake manifold injection and a control of the valves and the ignition according to the invention. Here, too, the engine is started in two-stroke mode. It takes at least one turn through 360 ° until the first ignition in the 2nd and 4th cylinders. The valves are controlled so that no compression takes place in cylinders I and III until ignition in cylinders II and IV. By switching off the decelerating and thus disruptive compression, less torque is required. It can therefore be started with less power. The electromagnetic valves can also be used to only suction over about 90 °, as shown for the cylinders II and IV in the figure. , For this purpose, valves 7 and 8 are closed and only opened shortly before UT. Due to the resulting negative pressure in the cylinder, a large air speed is generated in the intake pipe after opening the intake valve, which causes the fuel to swirl. This suction over 90 ° is effected in the first and second cycle. The injection quantity must be measured accordingly. In the case of intake manifold injection, the prepositioning explained with reference to FIG. 2d can also be used. 3 shows the essential components and effective distances for the above-mentioned prepositioning of at least one piston close to or in the TDC. The engine 33 has injection valves 34, a battery 31, a generator 32, electromagnetic actuators 35 for the electromagnetic valve control, spark plugs 36, a clutch 37 and an electrical control unit 38. Input signals from a door switch of a remote control 40 and from an ignition start switch 41 are fed to the control unit. When approaching the driving. The remote control 40 is activated. The corresponding wireless signal is sent to the electronic control unit or, in the case of a networked vehicle, to the engine control unit via the corresponding bus node and the data bus. The door switch 39 for pilot control of the drive acts redundantly to this or without remote control. Here, the drive in the form of the generator 32, which can also be switched as a motor, is started, which rotates the crankshaft until a piston has reached a position close to TDC or "top dead center" TDC ready to start Injection and ignition via the ignition start switch 41, after which a small rotation from the initial position had previously taken place. After reaching the preset before TDC, the drive holds the cylinder in the position reached until the actual start command is given. Should, which is unusual, a longer one If there is a pause between opening the door and activating the ignition switch, the drive may have to bring the following cylinder into the compression phase, because the compression has meanwhile been reduced But it can also become a cylin after a certain time which are brought into the appropriate standby position by slow rotation. In vehicles with manual transmission, the engine must be disengaged via an electrical actuator when starting and when driving by means of clutch 37. Since many vehicles are already equipped with an electric clutch for reasons of comfort, this is not an obstacle to the introduction of the system. In addition to comfort advantages, the electric clutch also has safety advantages, because it ensures that the engine is always disengaged during the starting process and the vehicle cannot move. With Au- this is not necessary for the automatic transmission. The position of the crankshaft or the pistons is detected by a crankshaft position sensor 42.

The crankshaft position sensor 42 provides the electrical control unit with the information about the piston position so that the starting process relates to the correct piston. For this it is necessary that the position of the pistons, that is the firing order, is stored in the control unit when the engine is switched off.

As an alternative to this or as a supplement, at least one piston position transmitter 43 can be used. This is preferably attached to the crank mechanism.

3 is based on the fact that the generator 32 can also act as a starter with relatively low power. The drive power will be approximately 1/10 of the normal starter power; This means that the drive motor can be designed to be relatively small with a power of 100 to 200W.

4, the drive in the form of an electric motor 51 is switched on via a clutch 50. A flying clutch or preferably an electric clutch can be used. A powerful reduction gear 52 is connected downstream of the electric motor that drives the generator 53.

5 shows a so-called crankshaft starter generator 60, the rotor of which is simultaneously combined with the clutch 61. The desired reduced drive power can also be solved inexpensively by the crankshaft starter generator 60. With conventional starters, a very large ratio from the flywheel to the starter pinion and a reduction gear in the starter reduce the torque required for starting. Despite this transformation ratio, as mentioned above, the currents are very high. Due to the missing gear ratio, this is not a problem with the crankshaft starter, with the drive power reduced according to the proposal. Fig. 6 shows a stepping mechanism, the toothed disk 71 is connected to the flywheel. This solution combined with the clutch, but can also be combined with a crankshaft generator according to FIG. 5. The separation of the drive from the generator makes the design solution easier and the generator can be fully optimized for voltage generation.

Fig. 7 shows the stepping mechanism. At the beginning of the armature stroke movement, an unlocking magnet 80 is activated so that the pawl 81 comes into engagement. Subsequently, a pull magnet 82 is excited, which moves the armature lever 83 so far that one step is shifted further. This solution is particularly simple since the large lever arm of the flywheel is used as a toothed disk 84 and the magnetic forces can therefore be relatively low.

8 shows a compression process in a temporal pressure curve representation. The dashed curve shows the compression curve with full filling, which is not absolutely necessary. In particular when using the electromagnetic valve control, only a partial charge can be used to reduce the drive torque (solid curve). If the piston is slightly past the top dead center, the engine control is used to inject and ignite and thus start the engine, which is shown by a sharp increase in pressure. As already described, the piston is normally stopped at point 90a before TDC or at top dead center 90 until the start is then initiated via the ignition switch. Here, after 90a or 90, the crankshaft is rotated further by the drive and, at 91 after OT, the injection and ignition. Only a partial charge is preferably also used in the following cylinder, so that the speed fluctuations when starting are less (curve 93).

9 shows a recording of the pressure and speed curve over time when the engine is switched off. The restart, which may have taken place shortly thereafter, is prepared here by using control algorithms and in particular using the electromagnetic valve control to control the engine outlet so that a cylinder is already in compression at the end of the outlet. If necessary, the imprecise motor stopping in the position close to TDC or in the TDC position (point 100) can be corrected by switching on the drive. If a restart is to take place shortly afterwards, for example at traffic lights, the engine is ready to start immediately. The injection and ignition then take place at time 101 with the subsequent pressure increase and speed change (lower curve).

If the vehicle z. B. stands longer in traffic jam with the engine switched off, the compression built up by the Ausauf will decrease again and not sufficient to start the engine. If the engine start command is unsuccessful, the drive must continue to turn the engine until compression is built up in the next cylinder and the engine can start. This applies in general: If a start attempt is unsuccessful, the drive must move the engine to a position in which another cylinder has compression so that it can be started. However, after a certain time of parking, a cylinder can be brought back to the described starting position as a precaution.

As already mentioned, the flywheel energy can be used when the engine is switched off by the fact that the electromagnetic actuators of the valve control release them, so that there is no longer any need for compression work. This drives the generator and returns the energy to the battery via the electricity generated. The use of the swing energy does not rule out the aforementioned control, because the preparation of the next starting process is only effected in the final phase of the engine stopping.

Instead of the ignition start switch mentioned, another command, for example via the remote control, can trigger the engine start. Here there is a continuous pilot control without a stop beyond the top dead center position until the subsequent ignition. In the case of diesel engines, the pre-heating takes place in the pre-control phase and then the injection and thus the engine start at a small angle after TDC.

Claims

claims

1) Method for starting a motor vehicle internal combustion engine, comprising an ignition device (9) per cylinder (2) and at least one inlet (2) and one outlet valve (8), which valves are controlled by an electrical control unit (10) by means of electromagnetic actuating devices ^ , 6) are actuated and for all cylinders (2) a starting device (11 to 13), a battery, an electrical generator and a crankshaft position sensor (IO), characterized in that during the starting process the electrical control unit ^ 0) via the electromagnetic Actuators ^, 6) the inlet (7) and / or outlet valves (8) and possibly the ignition device (5) in the sense of reducing the required power.

2) Method according to claim 1, characterized in that the engine is ignited in the starting phase at shorter ignition intervals (Fig. 2d and 2e).

3) Method according to claim 2, characterized in that the engine is operated in two-stroke mode (Fig. 2d and 2e).

4) Method according to claim 1, characterized in that at least two cylinders are ignited simultaneously at least during the first ignition process (Fig. 2c).

5) Method according to one of claims 1 to 4, characterized in that during the starting process by appropriate control of the valves of at least one cylinder, compression in this is prevented. (Fig. 2Θ)

6) Method according to one of claims 1 to 5, characterized in that the starting device (11 to 13) acts on the crankshaft ^).

7) Method according to claim 6, characterized in that the starting device (11 to 13) acts on the crankshaft ^) via a belt drive (14). 8) Method according to claim 7, characterized in that an increased belt tension is generated during the starting process.

9) Method according to claim 7 or 8, characterized in that during the starting process the starter (11) with the belt drive (14) is connected via a clutch (12, 13).

10) Method according to claim 9, characterized in that the starter (11) starts first and then its coupling takes place (clutch 12, 13).

1 1) Method according to one of claims 1 to 10, characterized in that at least one cylinder is brought into a position between 90 ° and 45 ° before top dead center (TDC) before the actual start (Fig. 2).

12) Method according to one of claims 1 to 10, characterized in that in engines with direct injection to a command given before the ignition command (of 40) the engine (33) is rotated into a position by a drive (32) at low speed, where the piston of a cylinder is a little before or at top dead center (TDC position), that with the firing command from 41 the engine (33) continues to rotate in the correct direction of rotation and that the injection (valve 34) and ignition (spark plugs 36) the compressed mixture the actual start is triggered.

13) Method according to one of claims 1 to 10, characterized in that in engines with direct injection at a command the engine is rotated by a drive at low speed into a position in which the piston of a cylinder a position shortly after the TDC position reached and that then the injection and the ignition takes place.

14) Method according to claim 12 or 13, characterized in that the engine is a gasoline engine. 15) Method according to claim 12 or 13, characterized in that the engine is a diesel engine.

16) Method according to one of claims 12 to 15, characterized in that the drive is carried out by the generator (32).

17) Method according to one of claims 12 to 15, characterized in that the drive is carried out by an electric motor (51) which is coupled for driving via a releasable coupling (52).

18) Method according to one of claims 12 to 15, characterized in that the drive is carried out by a stepping mechanism, which preferably acts on the crankshaft flywheel (Fig. 5).

19) Method according to one of claims 12 to 18, characterized in that the rotation of the motor in the desired position of a cylinder when the door is opened (switch 39) or by remote control (40) of the door lock is triggered.

20) Method according to one of claims 12 to 17, characterized in that, controlled by the electromagnetic valve control, the engine outlet when the engine is switched off is used to set the piston of a cylinder into the desired position.

21) Method according to one of claims 12 to 20, characterized in that the cylinder, the piston of which is brought into the desired position, is only partially filled and thus has a lower compression pressure.

22) Method according to claim 21, characterized in that even in subsequent cylinders is only partially filled.

23) Method according to one of claims 12 to 22, characterized in that the clutch is actuated in switching vehicles during the starting process. 24) Method according to one of claims 12 to 23, characterized in that during the engine stopping by means of the electromagnetic valve control, the cylinders of the engine are at least partially switched without compression and that the engine's vibration energy is used via the generator to charge the battery.

25) Method according to one of claims 12 to 24, characterized in that when an ignition command is given without the engine being started, the drive rotates the engine into a position in which another cylinder has sufficient compression and that injection and ignition is then carried out.

26) Method according to one of claims 21 to 25, characterized in that the electric engine control unit has a memory which stores the crankshaft position, or firing order and thus position of the pistons after the engine has been switched off.

27) Method according to one of claims 12 to 26, characterized in that in addition to a crankshaft position transmitter, at least one piston position transmitter is used.