WO2015176706A1

WO2015176706A1 - Method for synchronising uncoupled sub-engines of an internal combustion engine before starting up

Info

Publication number: WO2015176706A1
Application number: PCT/DE2015/000311
Authority: WO
Inventors: Sascha Steinbach
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2014-05-20
Filing date: 2015-05-19
Publication date: 2015-11-26
Also published as: DE112015002388A5; DE102015008073A1

Abstract

The invention relates to a method for synchronising an equidistant firing order of a split internal combustion engine operated according to the four-stroke principle, having a first sub-engine with a first crankshaft and two cylinders, each with a piston received by the first crankshaft and a gyrating mass associated with the first crankshaft, and a second sub-engine with a second, rotatable crankshaft and two cylinders, each with a piston shifting between a top dead centre and a bottom dead centre, and a system for detecting and determining the angle of rotation of the crankshafts at a predetermined, synchronised engagement position of the crankshafts by means of engagement elements each associated with a crankshaft. In order to be able to design a low-wear and low-noise connection between the crankshafts with small differential angular velocities, the crankshafts are synchronised at the engagement position, before the internal combustion engine is started, in that the second crankshaft is rotated while the first crankshaft remains stationary, the direction of rotation of the second crankshaft being dependent on a differential angle of the engagement elements relative to each other.

Description

Method for the pre-synchronization of decoupled partial motors of an internal combustion engine

The invention relates to a method for synchronizing an equidistant ignition sequence of a divided, operated according to the four-stroke principle internal combustion engine with a first engine with a first crankshaft and two cylinders each having a recorded on the first crankshaft piston and one of the first crankshaft associated flywheel and a second engine part with a second, rotatably drivable crankshaft and two cylinders, each with a piston displaced between a top dead center and a bottom dead center and a device for detecting and determining the rotational angle of the crankshafts at a predetermined, synchronizing the crankshaft locking position of the crankshaft, each associated with a crankshaft locking elements.

Generic internal combustion engines such as internal combustion engines are used for economical operation, in particular of motor vehicles. Here, the internal combustion engine is divided into two separate engine parts with separate crankshafts and camshafts, which can be decoupled in a partial load operation, a sub-engine and coupled again at full load. In order to produce a phase-selective connection of the crankshafts of the partial motors which ensures an equidistant firing sequence, a phase-selective connection by means of latching elements is provided at a predetermined latching position.

From DE 10 2011 101 161 A1 a generic internal combustion engine and a method for controlling a synchronization of the two partial motors during operation is known. DE 10 2012 206 476 A1 discloses a method for operating an internal combustion engine having two partial engines and their connection by means of a synchronizer clutch arranged between the crankshafts of the partial engines.

The object of the invention is to propose a method for synchronizing an internal combustion engine with a split crankshaft.

The object is solved by the features of the method of claim 1. The dependent of this claims give advantageous embodiments of the method of claim 1 again.

The proposed method is used to synchronize an equidistant ignition sequence of a divided, operated according to the four-stroke principle internal combustion engine before the start of this standing crankshafts. The internal combustion engine operates on the four-stroke principle in

confirmation copy Form of a petrol or diesel engine and has two phase-selectively coupled part motors. Here, a first partial engine has a first crankshaft with an associated flywheel as master with two cylinders and pistons received on the first crankshaft. The pistons are here on the same crank the

Crankshaft added. Furthermore, a single cylinder can be provided with a single piston. A second sub-motor operated as a slave contains a second crankshaft, which is rotatably driven, for example, by a starter, electric motor or the like, preferably without flywheel and two cylinders whose pistons each move between a top dead center and a bottom dead center, on the second crankshaft received piston. The pistons are in this case added to the same crank of the crankshaft. Furthermore, a single cylinder can be provided with a single piston. The ignition of the cylinders of the two engine parts can be offset by 360 °.

For detecting and determining the rotational angle of the crankshafts are corresponding encoders, such as incremental angle sensors or the like with associated

Evaluation devices provided so that the position of the crankshafts at standstill and during synchronization of the crankshafts before the start of the internal combustion engine are available in sufficient local and temporal resolution. The crankshafts are positively connected to one another by means of corresponding latching elements at a predetermined synchronous position such as latching position.

The two in the uncoupled state against each other rotatable crankshafts must be synchronized in a common operation on each other with respect to their individual function, for example, to a coordinated ignition angle. For this purpose, a detent position is provided, which synchronizes the crankshafts at a predetermined angle to each other and rotationally connected. For pre-synchronization of the crankshafts with stationary part motors with known rotation angle of the two locking elements, or their angular positions with stationary engine against each other, the synchronization of the crankshaft is provided at the locking position before the start of the internal combustion engine by rotational drive of the second crankshaft with stationary first crankshaft. Here is a selectable, from the rotary actuator as

Electric motor initiated direction of rotation of a rotation of the second crankshaft depending on a differential angle of the locking elements to each other. It has been shown that by influencing the compression forces acting on displacement of the pistons in the cylinders a desired relative speed of the two Crankshaft is difficult to control when approaching the locking position, especially when a rotary drive with the lowest possible power to be used.

In an advantageous embodiment of the method, the direction of rotation of the crankshaft is provided depending on a falling in the differential angle dead center of the cylinder of the second part of the engine. Here, at a differential angle of the angular positions without inclusion of a dead center, the second crankshaft can be rotated with its locking element directly in the direction of the locking element of the first crankshaft. At a differential angle of the angular positions including the bottom dead center, the second crankshaft can be rotated with its locking element over the bottom dead center in the direction of locking element of the first crankshaft. At a differential angle including the top dead center, the direction of rotation of the crankshaft can be specified depending on a predetermined angle of rotation threshold. This means that on reaching or exceeding the rotational angle threshold, the locking element of the first crankshaft can be approached via the bottom dead center and approached when falling below the rotational angle threshold above the top dead center.

Alternatively or additionally, it may be provided to set the direction of rotation of the second crankshaft as a function of a rotational angle of the angular positions of the locking elements relative to the top dead center. In this case, the direction of rotation of the second crankshaft can be determined as a function of a locking element located before or after top dead center.

In other words, the proposed method relates to the coupling and synchronization of split crankshaft internal combustion engines by engaging the two crankshafts prior to starting / starting. Here, internal combustion engines should enable a demand-based shutdown of sub-engines, for example, by physically or completely disconnected two or four cylinders and switched on again when needed. The connection takes place at a predetermined crankshaft angle position in order to obtain an equidistant ignition sequence after connection. For this purpose, a lock is considered at a certain relative angular position.

The lock is open, for example, when the two partial motors are at a standstill. Before starting / starting the internal combustion engine such as internal combustion engine as a whole engine, for example, at a predetermined condition of a common start such as cold starts of the overall engine, this lock is closed and locked again at the locking position. Here, the two sub-motors are mutually adjusted so that the latching position reached as quickly as possible and when latching the lowest possible relative speed of the crankshaft is present. The detection of the two crankshaft positions at standstill in a set rest position, the relative angle to be calculated therefrom and the relative speed in the case of a rotationally driven crankshaft takes place by means of a rotational angle detection which is known per se.

Prerequisite is a multi-cylinder internal combustion engine, such as a gasoline or diesel engine, in which a plurality of cylinders are physically separated and can be interconnected via a lock such as locking elements on the crankshaft of the engine part to form an overall engine. Both part motors are stopped according to the procedure. The relative speed of the two partial motors is low when locked to avoid noise and not wear the components. The synchronization such as locking at the locking position of the locking elements is very fast, that is, essentially without detectable for a driver deceleration at start.

The method, such as the control algorithm, serves for the rapid synchronization of the two partial motors to their latching position before starting the entire engine. For this purpose, a first of the two partial engines can be regarded as the main engine such as master, whose first crankshaft has a flywheel. The other, second, zuzuschaltende engine as a subordinate engine with a second crankshaft without flywheel serves as a slave. Due to the lower mass, the slave can be moved / accelerated faster by an electric starter. The rotary drive of the crankshaft of the slave by means of an electric motor such as starter either in both directions to adjust the locking position, while the master is preferably not moved / displaced.

The highest moments for adjusting the slave, which are to be applied by the rotary drive such as electric motor, caused by large volume change of the gas mass in the cylinder. In this case, the moments in a movement from bottom dead center (UT, maximum cylinder charge) in the direction of top dead center (TDC, maximum compression) are greater than vice versa. For a movement from UT near OT across high moments of the electric motor are needed. Exceeding the OT has a strong acceleration of the slave to be coupled due to the lack of inertia and the high gas torque in the cylinder. This acceleration can not be reliably prevented in all occurring operating states with an electric motor designed, if possible, with low power. Thus, a latching position after TDC and in close proximity to the OT in compliance with the requirement "low differential speed" is not feasible in any case, when the rest position / home position of the slave, for example, UT proximity.

The proposed method is preferably used for the interconnection of internal combustion engines with two partial engines with two cylinders on the four-stroke principle, since a latching within 360 ° relative angle are provided here and no phase selection needs to take place. For sub-engines with more than two cylinders per sub-engine, a corresponding phase selection is provided.

Neglecting the friction and blow-through effects (blow-by), the moment integral of a cylinder over the crankshaft angle is dead center symmetrical. This means that energy that must be applied to overcome the dead center, is available again after the dead center. This effect occurs at UT and in enhanced form at OT. At approximately symmetrical ratio, that is, a ratio of the starting angle of a locking element to a dead center and a target angle of the locking position to this dead center or a rest position of the crankshaft of the slave to a locking point on the master, this effect can be used. The necessary for exceeding the dead center, applied by the electric motor energy can be resumed by the electric motor after the dead center. Furthermore, a kinetic energy introduced by the electric motor must be dissipated again from this.

For example, the following approaches to the formation of the connection of the crankshafts are proposed:

With a strong mismatch of the angle, for example, starting from a rest position of the slave from UT proximity and a detent position shortly after TDC near the Einrastpunkt a high moment and so to expect a strong acceleration of the slave motor, the electric motor can not decelerate. A rotation of the crankshaft in this direction of rotation is therefore preferably excluded.

Exceeding the TDC is possible with symmetrical angle situation between rest position and locking position, but is provided due to the expected high torque only for small angles between the rest position of the locking element of the second crankshaft and TDC. For larger angles a UT passage is provided due to the lower pressure differences.

The delimitation and thus the formation of a rotational angle threshold with respect to the small and large angles listed depend inter alia on the properties of the entire engine and / or one of the sub-motors, in particular the second sub-motor (slave):

- Compression ratio: With a low compression ratio, the angle of rotation threshold can be shifted to larger angles of rotation, for example 20-30 °. At higher compression ratios, for example, angle of rotation thresholds smaller than or equal to 10 ° are proposed.

- Starter / electric motor: The synchronization time for a synchronized according to the proposed method internal combustion engine depends on the formation of the rotary drive such as electric motor. The angle of rotation threshold is to achieve preferred short Synchroni sationszeiten before the start of the internal combustion engine, for example, depending on the compression ratio of the second part of the engine and the power or the torque of the electric motor, a cold start behavior, the inertia of the second part motor and the like designed.

The invention will be explained in more detail with reference to the process sequences 1 to 11 of the proposed method illustrated in FIGS. 1 to 11. Here are the individual

Processes 1 to 11 on the crank circle KW of the crankshaft of an internal combustion engine with two partial engines, each with a crankshaft with top dead center and top dead center UT of the pistons of the second sub-engine, the crankshaft is rotationally driven, respectively the angular positions A1 to A11, B1 to B11 the locking elements of a first crankshaft of a first sub-motor master and a second crankshaft of a second sub-motor slave before the rotation of the second crankshaft by means of a rotary drive such as electric motor. Depending on the positioning of the angular positions A1 to A11, B1 to B11, the arrows C1 to C11, D respectively show the method-specific selection of the direction of rotation of the second crankshaft. In this case, the angular position B1 to B11 represent the latching position, to which by means of rotation of the second crankshaft the latching elements are displaced from the respective angular position A1 to A11, thus forming the positive connection between the two crankshaft positionally true and thus with respect to equidistant ignition sequences and phase-selective.

Figures 1 and 2 show the positions of the locking elements each on a divided by a vertical semicircle of the crank circle KW in a rotational angle α1, a2 spaced apart, so that when the angular position A1, A2 of the crankshaft of the sub-motor slave to the angular position B1, B2 of the sub-motor master can be carried out without inclusion of a dead center UT or OT. As a result, in a determination of such a method sequence 1, 2, the crankshaft of the sub-motor slave is rotated directly in the direction of the arrows C1, C2.

In the figure 3 with the process flow 3 are the angular position A3, B3 in the upper half of the crank circle KW. In this case, the shorter rotational angle a3 leads to the transfer of the angular position A3 to the angular position B3 via the top dead center OT. Furthermore, the angle of rotation a3 is above a predetermined angle of rotation threshold and the angle position B3 lies within a rotational angle threshold to the top dead center OT. The process sequence 3 therefore provides a direction of rotation of the second crankshaft in the direction of the arrow C3 over the bottom dead center UT. As a result, the rotary drive can use the build-up rotational acceleration for bottom dead center UT in order to reach the angular position B3 after the bottom dead center UT with reduced energy. In contrast to this, in FIG. 4, the angular position A4 for an almost compressed cylinder is within a rotational angle threshold to the top dead center OT at a rotational angle lying outside a rotational speed threshold between the angular positions A4, B4. Here, the force of the rotary drive for overcoming the top dead center OT is low, so that a rotation of the second crankshaft for displacement of the angular position A4 on the angular position B4 via the top dead center OT in the direction of arrow C4.

FIGS. 5 and 6 show the process sequences 5, 6, in which the angle of rotation of the angle of rotation α5, a6 between the angular positions A5, A6, B5, B6 is undershot, including the top dead center. Furthermore, the two rotational angle thresholds of the angular positions A5, A6, B5, B6 are undershot with respect to the top dead center OT, so that in each case in the direction of the arrows C5, C6, the angular positions A5, A6 are transferred to the angular positions B5, B6 via the top dead center OT.

In Figures 7 and 8 with the procedures 7, 8, the speed threshold of the rotation angle α7, a8 between the angular positions A7, A8 and B7, B8 is exceeded and the speed thresholds of the angular positions A7, A8 and B7, B8 respectively exceeded the top dead center OT , so that not the shorter rotation angle α7, a8 above the top dead center OT but the longer rotation angle over the bottom dead center UT along the arrows C7, C8 is selected by rotation of the second crankshaft of the sub-motor slave, the locking element at the angular position A7, A8 to connect positively with the locking element at the angular position B7, B8.

In FIG. 9, the rotational angle threshold of the rotational angle a9 is exceeded in the method sequence 9, but the angle of rotation of the angular position A9 with respect to the top dead center OT is undershot, so that in both directions of the arrows C9, D a low-energy displacement of the locking element from the angular position A9 to the Angular position B9 is possible. In this case, the selection of the direction of rotation can take place on the basis of other sequence conditions, for example the faster or the angular position B9 which can be achieved with a lower relative speed.

FIGS. 10 and 11 show the process sequences 10, 11 with a rotational angle a10 (FIG. 10) exceeding the rotational angle threshold between the angular positions A10, A11 and B10, B11 and a falling rotational angle a11 (FIG. 11), wherein the bottom dead center UT is in each case between the angular positions A10, A11 and B10, B11 included and the rotational angle thresholds of the angular positions A10, A11 and B10, B11 are exceeded with respect to the top dead center OT. In this case, the transfer of the angular positions A10, A11 in the angular positions B10, B11 respectively in the direction of arrows C10, C11 via the bottom dead center UT. LIST OF REFERENCES

1 procedure

2 procedure

3 procedure

4 procedure

5 Procedure

6 Procedure

7 Procedure

8 Procedure

9 Procedure

10 procedure

1 1 Procedure

A1 angular position

A2 angular position

A3 angular position

A4 angular position

A5 angular position

A6 angular position

A7 angular position

A8 angular position

A9 angular position

A10 angular position

A11 angular position

B1 angular position

B2 angular position

B3 angular position

B4 angular position

B5 angular position

B6 angular position

B7 angular position

B8 angular position

B9 angular position

B10 angular position B11 angular position

C1 arrow

C2 arrow

C3 arrow

C4 arrow

C5 arrow

C6 arrow

C7 arrow

C8 arrow

C9 arrow

C10 arrow

C11 arrow

D arrow

KW crank circle

OT top dead center

UT bottom dead center a1 rotation angle a2 rotation angle a3 rotation angle a4 rotation angle a5 rotation angle a6 rotation angle al rotation angle a8 rotation angle a9 rotation angle a10 rotation angle a11 rotation angle

Claims

claims

1. A method for synchronizing an equidistant firing order of a divided, operated according to the four-stroke principle internal combustion engine with a first partial engine (master) ter with a first crankshaft and two cylinders each having a recorded on the first crankshaft piston and one of the first crankshaft flywheel and a second partial engine (slave) with a second, rotatably drivable crankshaft and two cylinders, each with a displaced between a top dead center (TDC) and a bottom dead center (UT) piston and means for detecting and determining the rotational angle of the crankshafts at a predetermined the crankshafts synchronized to each other defining locking position of the

Crankshafts each having a crankshaft associated latching elements, characterized in that the synchronization of the crankshafts at the latching position before the start of the internal combustion engine by rotational drive of the second crankshaft with a stationary first crankshaft and a direction of rotation of the second crankshaft depending on a differential angle (α1, α2, α3, α4, a5, d6, al, α8, α9, α10, α11) of

Angular positions (A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, B1, B2, B3, B4, B5, B6, B7, B8, B9, B10, B11) of the locking elements to each other becomes.

2. The method according to claim 1, characterized in that the direction of rotation depending on a falling in the differential angle (α1, α2, α3, α4, A5, D6, α7, α8, α9, α10, a11) provided dead center of the cylinder of the second part of the engine becomes.

3. The method according to claim 1 or 2, characterized in that at a differential angle (α1, a2) without inclusion of a dead center, the second crankshaft is rotated with its locking element directly in the direction of the locking element of the first crankshaft.

4. The method according to claim 2 or 3, characterized in that at a differential angle (α9, α10, a11) including the bottom dead center, the second crankshaft is rotated with its locking element over the bottom dead center in the direction of locking element of the first crankshaft.

5. The method according to any one of claims 2 to 4, characterized in that at a differential angle (α3, α4, a5, d6, α7, a8) with the inclusion of top dead center the Direction of rotation of the crankshaft is specified depending on a predetermined angle of rotation threshold.

A method according to claim 5, characterized in that when reaching or exceeding the rotational angle threshold, the locking element of the first crankshaft approached via the bottom dead center and approached when falling below the rotational angle threshold above the top dead center.

Method according to one of claims 2 to 6, characterized in that the direction of rotation depends on a between the top dead center (TDC) and an angular position (A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11 ) of the second crankshaft is adjusted from top dead center.

8. The method according to any one of claims 2 to 7, characterized in that the rotational direction depends on a between the top dead center (TDC) and an angular position (B1, B2, B3, B4, B5, B6, B7, B8, B9, B10 , B11) of the first crankshaft relative to the top dead center.

9. The method according to claim 7 or 8, characterized in that the direction of rotation of the second crankshaft depends on a lying before or after top dead center Wnkelposition (A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, B1, B2, B3, B4, B5, B6, B7, B8, B9, B10, B11) of the locking elements is determined.