EP1073842B2 - Method and starter system for starting an internal combustion engine - Google Patents

Abstract

The invention relates to a method for starting an internal combustion engine and a corresponding starter system. The crankshaft (4) of the internal combustion engine (1) is accelerated at least until it reaches a starting speed that is required to start the internal combustion engine (1). Before the starting process actually begins, the crankshaft (2) is placed at a given angle using an electric machine (4), whereupon the starting process is initiated.

Description

The present invention relates to a method for starting an internal combustion engine as well Starter system for an internal combustion engine.

From practice it is known that internal combustion engines, e.g. in motor vehicles, not on their own Can start power. You must first go through one external power source, the so-called starter, fired and on the needed to start the engine Motor speed can be accelerated. Only they can continue on their own.

In motor vehicles is often a battery powered DC motor as electric starter used, which has the necessary starting torque over engaging in a ring gear on the flywheel Drive pinion on the crankshaft of the internal combustion engine transfers. From DE 44 06 481 A1 is Furthermore, a starter system with an electric starter motor known, whose rotor is directly on the crankshaft the internal combustion engine sits and rotatably connected to it is. With such an arrangement one uses the Mass of the rotor of the electric machine at the same time as a flywheel.

The starting torque of an internal combustion engine and the minimum starting speed depend, among other things of engine type, displacement, number of cylinders, bearing friction, Compression and mixture preparation and before everything from the temperature. Of importance to the Compression of an internal combustion engine and thus for his willingness to start is also in which section of the Working the cylinder or the engine when starting up. For example, this affects the Compression of a currently in the compression stroke Cylinder unfavorable for the star behavior because they are the starter right at the start of the start an excessive torque opposes.

So far, one has in the prior art Influence is not taken into account sufficiently. Well-known starters had to do so in terms of performance be designed that the internal combustion engine under all conditions can be started.

Although WO 91/16538 discloses a method as well a starter system for starting an internal combustion engine known. Thereafter, after switching off or dying of the internal combustion engine with the crank angle Help one of the crankshaft associated rotation angle sensor automatically detected; and an electric machine then provides a favorable starting angle for the next starting operation, e.g. a crank angle, at which has no or least piston before or in a compression stroke. The for the starter operation required electrical energy is either a Battery or a conventional vehicle battery, i.e. electrochemical energy stores, taken, which does not always have optimal starting, e.g. at low Temperatures, can guarantee.

In EP-A-0 569 347 is also before the actual Starting process on the crankshaft position Influence, before the start of the crankshaft turned back at a certain starting angle, in which an increased compression maximum pressure is reached becomes. The internal combustion engine then becomes out of this Starting angle out, where the electric Starter but fed from a conventional battery becomes.

Occupy the following citations with partial aspects of the invention: DE-A-3 117 144, FR-A-2 569 776 and DE-A-4 200 606.

Furthermore, it is well known that one an internal combustion engine with the help of capacitors can start.

Object of the present invention is a Method for easier starting of an internal combustion engine and a corresponding starter system provide.

This problem is solved by the invention procedurally by the An article according to claim 1 and apparatus by the Article according to claim 11. Preferred embodiments of The invention are described in the respective dependent claims.

Thereafter, in a method according to the invention for starting an internal combustion engine in a motor vehicle, the crankshaft of the internal combustion engine at least one for starting the internal combustion engine necessary speed (so-called start speed) accelerates, wherein for this purpose an electrical machine is used, whose Rotor directly or via an interposed translation acting on the crankshaft. Further, the crankshaft shortly before the start of the starting process, triggered by Opening the central locking of the motor vehicle, with the help of the electric machine for the starting process in a predetermined crank angle position or in a predetermined Crank angle (hereinafter called "start angle") brought and the engine out of this starting angle started, with the energy required to start at least partially one in a DC link of an inverter the electric machine arranged short-term memory is removed. The actual boot process of Internal combustion engine can then from a favorable starting angle Begin and will additionally - not as usual completely from a starter battery but - at least partially fed a short-term memory, the necessary electrical Takeoff performance much faster than a conventional one Battery can deliver. Incidentally, a short-term memory, such as a capacitor memory, much less temperature sensitive as an electrochemical battery, so too trouble-free starting possible at very low temperatures is.

The charging of the short-term memory can be different Done way. One possibility is that the short-term memory only before starting from a starter battery is charged. This is preferably the setting process the crankshaft start angle triggering command at the same time as a signal for charging the short-term memory is used from the starter battery. Starting the internal combustion engine can be done without any waiting time.

A corresponding inventive starter system for a Internal combustion engine in a motor vehicle comprises: an electric machine whose Rotor directly or via an interposed translation rotatably connected to the crankshaft of the engine is to at least one of the internal combustion engine for Accelerate necessary speed (start speed) to accelerate; Means for detecting and / or deriving the crank angle the internal combustion engine; a control device which the electric machine shortly before the start of the starting process, triggered by Opening the central locking of the motor vehicle, so controls that the crankshaft of the Internal combustion engine for the starting process in a predetermined Start angle brought and the whole or part of the Start required energy from a short term memory is taken in the intermediate circuit of an inverter the electric machine is arranged. The erfindugsgemäße Short term memory may also preferably be a combination from electrical capacitor elements and electrochemical Be battery elements.

In the invention it has been recognized that the position of the crankshaft at start up essential for the Starting behavior of an internal combustion engine is. Building on this The invention is based on the idea that by influencing on the crank angle before the actual starting process as well as on the type of starting energy supply essential Improvement of the starting behavior of an internal combustion engine can be achieved. With the help of the electric machine, e.g. a so-called crankshaft starter with a directly with the Crankshaft rotatably connected rotor, manages the to Setting a desired starting angle necessary moments in both directions of rotation of the crankshaft and with great accuracy applied. Avoid one in this way unfavorable crankshaft position at the beginning of the start, about if one or more cylinders of an internal combustion engine can condense at the beginning, so can with a reduced Starting power to be started. the apparatus, the starter system for this purpose has a control device on, which in knowledge of the current crank angle the rotor of the electric machine, if necessary under Attention to the translation ratio between Rotor and crankshaft, so controls that the crankshaft is brought into the desired starting angle.

The use of the invention is advantageous Starter system both in gasoline engines as well in diesel engines, e.g. Four-stroke engines with intake manifold injection or with direct injection, for the Designed for use in passenger vehicles are.

In a preferred invention Variant is chosen as the starting angle that crank angle, in which of the electric machine Starting torque to be applied at the beginning of the starting process less than in known starter systems. At a e.g. Four-stroke internal combustion engine takes the cylinder pressure and thus the Compression to be overcome by a starter Course of a compression stroke and reached Maximum approximately in the area of top dead center. Becomes now in a preferred method variant for a Four-stroke internal combustion engine, the crank angle for the next start at the end of the compression stroke, preferably in an area immediately after the upper one Dead center, set, the starter must start at the start only the relatively low-compression intake stroke overcome the internal combustion engine. Furthermore After the start, the starter will have almost two full ones Turns, to overcome the next Compaction clock enough to build up start performance. This is particularly favorable for a cold start.

In a further procedural variant is chosen as the starting angle that crank angle, in which the stardauer, i. the duration from the start until the engine starts, until is reduced to a minimum. In a four-stroke internal combustion engine with intake manifold injection is this preferably the crank angle position at the beginning of the intake stroke, especially preferred in the overlapping area between ejection and intake stroke; in a four-stroke internal combustion engine with direct injection, however, preferably the Crank angle position at the end of the intake stroke. Is the internal combustion engine also consisting of a conventional sensor from inductive sensor and gear with reference mark to the Equipped detection of the crank angle, the starting angle adjustment process thus shortening the start time be that the starting angle in the area immediately before the reference mark of the rotation angle sensor is selected. The Angle detection can then start immediately without delay of the startup process.

If starting can be done without any delay, so this also serves to improve traffic safety and increase ease of use e.g. of motor vehicles. Furthermore, it is about to start a total amount of energy required for an internal combustion engine less, which is advantageous a smaller dimensions of the starter energy storage allowed.

The previous description of the invention applies to single-cylinder and multi-cylinder engines alike, considering the choice of the crankshaft start angle on those cylinders of a Tuned multi-cylinder engine, which is ignited first. In The rule is the order in which the cylinders are consecutive Ignite, given. According to the inventive method but is also a variant conceivable in which at least in the selection of the first ignited cylinder of one specified firing order is deviated and a specific cylinder for the first ignition depending on the one to be set Starting angle of the crankshaft is selected.

According to the invention, the desired starting angle is only shortly before the start of Startup automatically set, e.g. by the electric Engine the crankshaft of the stationary internal combustion engine in the desired starting angle forward or turns backwards. This is an undesirable "Verstellens" once set start angle in the time between excluded from the adjustment process and the starting process. Especially it is favorable, if in conjunction with the latter Process variant required for starter operation Energy at least partially a capacitor memory is removed.

For the adjustment of the star angle of the crankshaft is the current crank angle determined in the control device with the value of the given crankshaft start angle compared and any change in the crank angle again is monitored. For this purpose, it is preferable to use an in the electric machine integrated angle detection. Especially Preferably, the rotor of the electric machine is a suitable rotation angle sensor, e.g. an inductive or optical Rotary encoder, assigned. The angle of rotation of the electric But machine can also from the magnetic reflux of the rotor detected in the stator of the electric machine become. Because the rotor of the electric machine either directly or via a translation with the crankshaft of Ver combustion engine is connected, results in the crank angle directly or by simple conversion under consideration the translation ratio.

For the starter system according to the invention is basically every kind of electrical machine, whether DC, AC, Three-phase asynchronous or three-phase synchronous machine, which is able to apply the necessary moments and perform desired crank angle adjustment precisely. Preferably, the electric machine of the invention Starter system acting as a starter / generator electrical Machine that prefers permanently with the internal combustion engine starts to rotate. Particular preference is given to the electric machine of the starter system according to the invention around an inverter-controlled induction machine.

Under "induction machine" is a machine understood, in which a magnetic rotating field occurs, which rotates 360 ° and thereby takes the runner. The inverter receives the signals from the Control device and provides alternating currents freely adjustable frequency, amplitude and phase ready. Such an arrangement is for applying high moments Excellent in both directions of rotation of the crankshaft suitable.

Embodiments and features above or subsequently in connection with the Procedures are described, of course also as related to the corresponding Starter system disclosed (and vice versa).

Fig. 1

eine schematische Darstellung eines Startersystems mit einem Verbrennungsmotor;

Fig. 2

ein schematisches Diagramm zur Darstellung des Motordrehzahlverlaufs in Abhängigkeit des Kurbelwinkels eines Viertaktverbrennungsmotors;

Fig. 3

ein Flußdiagramm einer ersten Verfahrensvariante zum Starten eines Verbrennungsmotors; und

Fig. 4

ein Flußdiagramm einer zweiten Verfahrensvariante zum Starten eines Verbrennungsmotors.

Further advantages, features and embodiments of the invention will be explained in more detail with reference to exemplary embodiments and the appended schematic drawings. In the drawing show:

Fig. 1

a schematic representation of a starter system with an internal combustion engine;

Fig. 2

a schematic diagram illustrating the engine speed curve as a function of the crank angle of a four-stroke combustion engine;

Fig. 3

a flowchart of a first method variant for starting an internal combustion engine; and

Fig. 4

a flowchart of a second method variant for starting an internal combustion engine.

The starter system according to Fig. 1 is e.g. for a Motor vehicle, intended as a passenger car. It has a working after the four-stroke process Four-cylinder internal combustion engine 1, the Torques via a crankshaft 2, a clutch 3 and further (not shown) parts of a drive train emits on the drive wheels of the motor vehicle. In the present embodiment is immediate on the crankshaft 2 serving as a starter / generator electric machine 4, here an asynchronous three-phase machine, arranged. She has a direct on the crankshaft 2 sitting and rotatably connected to her Rotor 5, as well as e.g. on the housing of the internal combustion engine 1 supported stator 6. Such electric machine has a high breakaway torque for starter operation.

In other embodiments (not shown) is the rotor of an electric machine, e.g. one DC series motor, via a transmission gear coupled with the crankshaft 2, if necessary over an interposed Einspurgetriebe.

In the embodiment of FIG. 1, the (not shown) winding of the stator 6 of the electrical Machine 4 by an inverter 7 with electrical alternating currents or voltages practically freely adjustable amplitude, phase and frequency fed. It is preferably a DC-link inverter, essentially from a machine-side DC-AC converter 7a, a DC link 7b and an on-board side DC-DC converter 7c is constructed. The latter is with a vehicle electrical system 8 and a vehicle electrical system long-term storage 9, e.g. a conventional one Lead-sulfuric acid battery, coupled. In the intermediate circuit 7b is a temporary memory, here a capacitor memory 10 switched.

The electric machine 4 and the inverter 7 are designed so that they can be used to set a desired crank angle position before starting the required torque in both directions of rotation Crankshaft 2 and also when starting the required Starting power for directly driving the crankshaft 2 apply to the required starting speed capital. A higher-level control device 11 controls the starting angle adjusting operation and the Startup process by the inverter 7, namely the inverter 7a and the converter 7c controls. Of a integrated in the electric machine 4, e.g. Inside installed on the housing and the rotor. 5 associated inductive rotation angle sensor 12 receives the control device 11 the current angle of rotation of the rotor 5. The measured rotor angle corresponds due to the direct coupling of the rotor 5 with the crankshaft 2 the crank angle of the crankshaft. 2

According to the invention, the starting process in particular Way prepared: after completion of the engine operation, e.g. at or shortly after shutdown the ignition of a motor vehicle, controls the control device 11, the electric machine 4 via the inverter 7 so that the crankshaft 2 in a favorable crank angle position for the next start is brought. Here, the electric machine transmits 4 optional braking or accelerating moments on the crankshaft 2 of the expiring engine 1 to set the desired crank angle. When the engine 1 is stopped, the electric machine 4 are also operated so that they the crankshaft 2 forward or backward in the desired Crank angle turns to e.g. on the path of the "least applied torque "the desired crank angle adjust. This does not necessarily have to also be the "shortest" way.

The "optimal" crank angle, ie the starting angle, to start an internal combustion engine depends i.a. from the engine type, number of cylinders and firing order, and besides of the desired starting behavior, whether e.g. for the next start a low starting torque at the beginning the startup process or a shortened startup duration it is asked for. For a as shown in Fig. 1 Four-cylinder four-stroke internal combustion engine 1 is a cheaper Starting angle with reduced starting torque in one Area immediately after the top dead center of the first ignited cylinder. As with a four-cylinder in-line engine usually the two outer cylinders in synchronism with each other, but in the opposite direction to operate the two inner cylinders is located Accordingly, the favorable starting angle immediately after the top dead center of the two outer cylinders of the Internal combustion engine 1.

The advantage of this set starting angle is that at the beginning of the subsequent boot process From the starter machine 4 applied breakaway torque is considerably lower than in known Starter systems. If the engine 1 off started out of this set crank angle position, so put at least the two outer cylinders the internal combustion engine 1 of the electric machine 4 a relatively low - mainly due to friction - Moment against. Until the next compression stroke (the two inner cylinders) can be the electrical Machine 4 gives the system enough (start) energy to overcome the compression.

The diagram in Fig. 2 is intended to illustrate how the "optimal" starting angle can be determined, for example, with reduced starting torque for any type of engine and drive arrangements. Fig. 2 shows schematically the dependence of the engine speed n of the crank angle φ at constant torque of the electric starter machine. The specific wavy course is due to the design, in particular depending on engine type, displacement, cylinder number, bearing friction, compression ratio, etc. The areas a with decreasing speed n followed by areas b with increasing speed n go along with the repetitive compression phases followed by combustion phases such as a four-stroke engine , In the areas of lowest speed are accordingly also the areas of greatest compression, which is followed by a low-compression phase of the internal combustion engine. If one chooses the values φ _i for the crank angle, this corresponds to an "optimal" crankshaft position with reduced starting torque. In the case of a four-cylinder four-stroke combustion engine, the starting angles φ _i are approximately 180 ° apart, since the two outer and the two inner cylinders each run synchronously. A corresponding characteristic map is stored, for example, in the control device 11 in FIG.

In the flowchart of FIG. 3 is a first method variant for starting with reduced Starting moment illustrated: In step S1 is a Command for setting the crankshaft start angle at or shortly after switching off the internal combustion engine 1 (for example, by switching off the ignition in the Motor vehicle). Then, in step S2, a direct Measurement of the crank angle or a measurement of the Rotor angle of the electric starter machine 4 and a Derivation of the crank angle. Furthermore, the Control device 11 the desired "optimal" Starting angle of the crankshaft 2 and possibly required Crank angle change to the desired Set start angle. Then in step S3 with Help the electric machine 4, the crankshaft 2 in the desired crank angle position for the next start by braking or accelerating the crankshaft in the phase out of the engine. The steps S2 and S3 can also be during engine shutdown be repeated continuously to ensure that no unwanted change of starting angle up to next start. On a starting line in the Step S4, which initiates the actual staring process, at step S5, the crankshaft 2 of the internal combustion engine 1 of the electric machine 4 on a driven starting speed. In the following Step S6 then jumps the internal combustion engine 1 (after the typical start time has elapsed). In a direct injection internal combustion engine you can also only between steps S5 and S6 let the starting time pass until the fuel is injected, i. the engine 4 is for a certain period of time without fuel added until reaching and possibly even further at the starting speed driven.

In the process variant according to FIG. 4 in step S1, the command for setting the desired Start angle just before the beginning of the next Startup given. This can be at a Motor vehicle e.g. by opening the central locking to be triggered. In this variant will also the capacitor memory 10 as an energy storage for the all or part of the needed for starter operation Energy used. Triggered by the setting command in step S1 is therefore especially at prolonged engine standstill of the capacitor memory 10th charged for the next boot from the battery 9 (Step S2). The one required for safe starting Charge level of the capacitor memory 10th can also be dependent on the engine and / or outside temperature to get voted. The following Steps S3 to S7 then correspond substantially Steps S2 to S6 of the method according to FIG. 3. The present method is merely to this end modified, that in step S6 the whole or a part required for the operation of the electric machine 4 Energy from the capacitor storage 10th comes.

Claims (18)

1. Method for starting a combustion engine (1) of a vehicle, comprising:

   a) shortly before the start of the starting operation, by opening the central locking of the vehicle, the crankshaft (2) being brought to a defined crank angle (starting angle) for a later starting operation by an electrical machine (4), the rotor (5) of which interacts directly or via intermediate gearing with the crankshaft (2),

   b) the crankshaft (2) of the combustion engine (1) being accelerated on a start command at least to a speed necessary for starting the combustion engine (1) (starting speed), and

   c) the whole or a part of the energy required for starting is taken from a short-term storage element (10) arranged in a link circuit (7b) of an inverter (7) of the electrical machine (4) and the combustion engine (1) is started from the set starting angle.
2. Method according to Claim 1, characterised in that, as a starting angle, that crank angle is chosen at which the starting torque is reduced.
3. Method according to Claim 2, characterised in that, in the case of a four-stroke combustion engine, the starting angle is chosen to be at the end of the compression stroke, preferably in an area immediately after the top dead centre.
4. Method according to Claim 1, characterised in that, as a starting angle, that crank angle is chosen at which the starting duration is reduced.
5. Method according to Claim 4, characterised in that, in the case of a four-stroke combustion engine with induction manifold injection, the starting angle is chosen to be at the beginning of the induction stroke.
6. Method according to Claim 4, characterised in that, in the case of a four-stroke combustion engine with direct injection, the starting angle is chosen to be at the end of the induction stroke.
7. Method according to one of the preceding claims, characterised in that, in the case of a multi-cylinder combustion engine, the starting angle is chosen taking into account which of the several cylinders is fired first.
8. Method according to one of the preceding claims, characterised in that, initiated by a command to set the starting angle, the short-term storage element (10) is charged from a battery (9) for the next starting operation.
9. Method according to Claim 8, characterised in that the charge level of the short-term storage element (10) required for reliable starting is chosen as a function of the engine and/or outside temperature.
10. Method according to one of the preceding claims, characterised in that the crank angle of the combustion engine (1) is derived from the angular position of the rotor (5) of the electrical machine (4).
11. Starter system for a combustion engine (1) of a vehicle, comprising:

    an electrical machine (4), the rotor (5) of which is connected to the crankshaft (2) of the combustion engine (1) directly or via intermediate gearing in order to accelerate the crankshaft (2) at least to a speed necessary for starting the combustion engine (1) (starting speed),

    means for detecting and/or deriving the crank angle of the combustion engine (1),

    a control device (11) which controls the electrical machine (4) shortly before the start of the starting operation, by opening the central locking of the vehicle, in such a way that the crankshaft (2) is brought to a defined crank angel (starting angle) for a later starting operation, and the whole or a part of the energy required for starting is taken from a short-term storage element (10), which is arrange in a link circuit (7b) of an inverter (7) of the electrical machine (4).
12. Starter system according to Claim 11, characterised in that the control device (11) uses the means for detecting the rotor angle of the electrical machine (4) to derive the crank angle of the combustion engine (1).
13. Starter system according to Claim 12, characterised in that an integrated rotation-angle sensor is assigned to the rotor (5) of the electrical machine (4).
14. Starter system according to one of Claims 11 to 13, characterised in that the combustion engine (1) is a fourt-stroke diesel or spark-ignition engine with induction manifold injection or with direct injection, which is designed for use in passenger-type motor vehicles.
15. Starter system according to Claim 14, characterised in that the control device (11) is configured in such a way that injection and ignition of the fuel in the combustion chamber of the combustion engine (1) takes place only after the starting speed has been reached.
16. Starter system according to one of Claims 11 to 15, characterised in that the electrical machine (4) is designed as a starter/generator.
17. Starter system according to one of Claims 11 to 16, characterised in that the electrical machine (4) is an inverter-controlled three-phase machine.
18. Starter system according to one of Claims 11 to 17, characterised in that the short-term storage element (10) is constructed from a combination of electrical capacitor elements and electrochemical battery elements.

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