EP2326805A1

EP2326805A1 - Method for adjusting a crankshaft of an internal combustion engine, camshaft adjustment system, and internal combustion engine having an adjustable crankshaft

Info

Publication number: EP2326805A1
Application number: EP09780891A
Authority: EP
Inventors: Jens Schäfer; Mike Kohrs
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2008-08-21
Filing date: 2009-07-21
Publication date: 2011-06-01
Anticipated expiration: 2029-07-21
Also published as: US20110146603A1; DE102008039007A1; US8813703B2; EP2326805B1; WO2010020509A1

Abstract

The invention relates to a method for adjusting a crankshaft (03) of an internal combustion engine comprising a camshaft adjuster having a triple-shaft gear mechanism, comprising a setting shaft, a camshaft sprocket (01), and a camshaft, wherein the camshaft sprocket (01) is drivably connected to the crankshaft (03), characterized in that during the motor standstill or in a transition phase, in which at least one of the three shafts of the triple-shaft gear mechanism stands still, a driving of the setting shaft occurs. The invention also relates to a camshaft adjustment system comprising a triple-shaft gear mechanism, which comprises a control device that adjusts the crankshaft during the motor standstill or in a transition phase.

Description

Name of the invention

Method for adjusting a crankshaft of an internal combustion engine, camshaft adjusting system and engine with adjustable crankshaft

description

Field of the invention

The invention relates to a method for adjusting a crankshaft of an internal combustion engine by means of a camshaft adjuster with a three-shaft transmission. Generic methods are used in particular in so-called start-stop concepts for internal combustion engines. In addition, the invention relates to a camshaft adjuster and an internal combustion engine with an adjustable crankshaft at engine standstill.

To adjust a camshaft, among other things, electro-mechanical camshaft adjustment systems are known from the prior art. In electromechanical camshaft phasing systems, three-shaft transmissions are commonly used in which a first shaft of the transmission, usually the drive shaft, is connected to the camshaft sprocket of an internal combustion engine, a second shaft (output shaft) is operatively connected to the camshaft via the camshaft sprocket and a third shaft , the adjusting shaft, with the rotor shaft of an electric variable speed motor (electric motor) is connected. The adjusting shaft serves to adjust the relative angular position between the camshaft and crankshaft during operation of the internal combustion engine. Examples of such three-shaft transmissions are swashplate transmissions and internal eccentric transmissions, which are described in WO 2006/018080. These also include the shaft gears known from WO 2005/080757 and the transmissions contained in US 2007/0051332 A1 and US 2003/0226534 A1. As actuators in such three-shaft systems are often electric motors for adjusting the adjusting used. However, it is also possible to use electrical, mechanical or hydraulic brakes or rotary or linear electromagnets to enable the phase adjustment.

All known camshaft adjuster systems are designed due to their operating principle and / or their dimensions for the phase adjustment of the camshaft during engine operation. Joint use of actuator and actuator for pre-positioning of the crankshaft at engine standstill is not possible with such systems.

It is an object of the invention to provide strategies which make it possible to turn the crankshaft of an internal combustion engine out of the state by means of an electromechanical camshaft adjuster in order to pre-position the piston position and possibly the camshaft phase position for the subsequent starting process of the internal combustion engine.

The object is achieved by a method according to claim 1, by a camshaft adjusting system according to claim 10 and an internal combustion engine according to claim 16.

In a method according to the invention for adjusting a crankshaft of an internal combustion engine, which has an electromechanical camshaft adjuster with a three-shaft gear, an actuating shaft is driven during the engine standstill or in a transitional phase in which at least one of the three shafts of the three-shaft gear is stationary to complete a timing drive or partially to adjust the crankshaft and optionally one or more camshaft in its angular position.

The three-shaft gearbox serves as a power split. It is subject to the following physical relationships: Speeds. n _A -! ₀ _AC x π _c - (1 - io_Ac) xn _B = 0, where n _A, n _B, and n _c are the rotational speeds of the three shafts of the three-shaft transmission. In the present case, therefore, n _{A is} the speed of the camshaft, n _{B is} the speed of the control shaft and n _{c is} the speed of the camshaft sprocket; ι _o _Ac is the stand translation between shaft A and C at a stationary shaft B, so here between the drive and output shaft of Dreiwellengetπebes (The state translation is determined by the number of teeth ratios of the gear stages in the three-shaft gear, the ratio between NW and KW with ι = 0.5 results from the number of teeth ratio in the control drive.

The sum of the external torques is zero: T _A + T _B + T c = 0.

The power is calculated for each wave from P = 2 π x n x T.

To adjust or pre-position the shaft A (= camshaft) or C (= camshaft sprocket, crankshaft-fixed) via the actuator (electric motor, control shaft), the antifrictive power of the actuator must flow to the shaft to be positioned. If only one of the two shafts is to be adjusted via the control shaft, the power for the shaft that is not to be adjusted must be zero. In the simplest case, the wave must therefore be recorded (i.e., n = 0).

Accordingly, for the pre-positioning of the camshaft sprocket and crankshaft, the torque of the camshaft (T _NW ) must be greater than the moment of the crankshaft acting on the camshaft _sprocket , (T _{NW KRAD} = T _KW * 0.5), ie T _N W ⁵¹ TNW _KRAD - or T _A > T _C> so that part of the power of the actuator does not flow into the camshaft. Such a torque ratio is more likely for engines with few cylinders and high camshaft friction (eg when using tappets) conceivable. Therefore, in larger engines, if necessary, a device for blocking the camshaft must be provided.

The torque ratio on the shafts can also be changed by relieving the control and crank mechanism, for example by decompression or decompression of the chains of the timing gear. An inventive extended camshaft adjustment system with a three-shaft transmission comprises a control device which allows an adjustment of the control shaft when at least one of the other two shafts of the three-shaft transmission is stationary.

In a preferred embodiment, the camshaft phasing system includes an additional pre-gearbox which additionally pre-gears the drive connection between actuator (e.g., electric motor) and actuator stem (three-shaft gearbox). The Vorssetzungsgetriebe can be arranged between the control shaft and the Steliergehäuse or between the actuating shaft and the actuator housing (Nockenwellenkettenrad). Furthermore, the camshaft adjusting system in this embodiment comprises a control device for carrying out the method according to the invention.

The adjustability of the crankshaft angle in engine standstill by means of the camshaft adjusting system according to the invention allows the pre-positioning of the shaft and thus the gas piston for the realization of the direct start of the internal combustion engine, without further units such as starter or positioning niermotoren are required. To control compression, air flow, ignitability, catalyst heating u. a. The pre-positioning of the crankshaft can take place with or without superimposed change of the camshaft phase angle.

Preferably, activation of the camshaft phasing system is triggered by a switch or message, for example via a CAN bus, or by opening the driver's door of the vehicle or by seat occupancy or the like to adjust and maintain the desired crankshaft angle and / or camshaft angle.

The method according to the invention should also be effective in the transition areas between engine standstill and starting process, as well as between engine standstill and shutdown. Such a transitional area is, for example, se, if one of the three shafts of the camshaft adjuster already or still stands still or in motors with multiple adjustment individual shafts resting and still rotate the other waves.

A pre-positioning of the control drive, the crankshaft and / or the camshaft can be controlled or unregulated. In the case of uncontrolled pre-positioning, "blind" is adjusted in one direction With controlled adjustment, a continuous target / actual comparison is carried out, and regulated operation is generally preferred.

According to the invention three adjustment strategies are applicable:

1. The camshaft stops during the positioning of the crankshaft.

2. The camshaft rotates during the positioning of the crankshaft. 3. The camshaft stops first and is subsequently carried along.

Irrespective of the choice of one of the three possible adjustment strategies for engine standstill, the following conditions for the pre-positioning of the crankshaft must be taken into account:

In internal combustion engines with multiple camshaft adjustment systems (for example, for intake and exhaust camshaft) all actuators are to be used synchronously by a corresponding circuit to adjust the crankshaft. - The tow of the crankshaft should preferably be carried out against the normal drive direction of the control drive. The normal direction of drive is the normal direction of rotation of the motor (forward). The opposing rotation of the crankshaft has the advantage of tightening the draft margin for later launch. In another embodiment, however, the pre-positioning can take place in the direction with the lowest rotational resistance regardless of the chain tension of the actuator in order to save positioning time and energy. If needed then tightened the timing drive by turning in the opposite direction again.

In aggregate mode and in the connections to additional aggregates of

Camshaft or crankshaft are preferably provided freewheels in the respective hubs so that these components are not mitzuschleppen when pre-positioning in the opposite direction. Such freewheels are already partially available.

The crankshaft must be decoupled from the vehicle transmission during the pre-positioning process. This can be done by an automated clutch or by a freewheel. Here, a fuse that prevents unintentional rolling away of the vehicle when the gearbox is disengaged must be used.

Preferably, an apparatus for decompressing the cylinders is provided to reduce the drag torque of the crankshaft.

In a particularly preferred embodiment, the crankshaft and camshaft position are detected by a sensor system, and the adjustment selected such that the shorter adjustment is used to the direct start the optimal piston from 1 to 4 in a four-cylinder engine with the least time and energy to position.

In order to be able to carry out the method according to the invention in an internal combustion engine, certain conditions must be met both on the camshaft adjuster and on the internal combustion engine: The camshaft adjusting system requires a reinforced electric motor with an engine constant ke> 13 mVs / rad compared to a conventional camshaft adjuster, which is additionally provided in the case of passive camshaft adjusters is.

Between the control shaft and the output shaft, in this case the camshaft sprocket, a total reduction of more than 1: 50 or 1: -50 must be maintained.

In accordance with the increased requirements, the mechanics and electronics of the camshaft adjuster must be designed. The internal combustion engine must provide the required electrical energy of> 100 W via a generator (alternator).

The camshaft breakaway torque, the camshaft drag torque, the crankshaft breakaway torque, and the crankshaft drag torque must each be <30 Nm.

Preferably, an active camshaft and crankshaft sensor is used for the accurate determination of crankshaft and camshaft position.

The requirements mentioned above do not all have to be met in parallel. By appropriate design, the lack of one or more specific requirements can be compensated. Inventive adjustment strategies are explained below with reference to the figures. Show it:

Fig. 1: a partial view of a camshaft adjusting system;

Fig. 2: schematic views of three configuration variants of a control drive.

1 and 2, the structure of a camshaft adjuster and the various adjustment strategies according to the invention are explained below. A camshaft sprocket 01 is an actuator of a camshaft adjuster via a chain 02 in operative connection with a crankshaft 03. These components form the timing drive. During normal operation of a combustion engine, the crankshaft 03 drives the or the camshaft sprocket wheels 01 at half the crankshaft rotational speed in a direction of rotation 04.

The control drive can also be arranged further actuators or camshafts and camshaft adjuster (eg for separate camshafts for intake and exhaust valves). Further actuators and camshafts may be arranged in a separate secondary drive 05 (FIG. 2, FIGS. B and c). The secondary drive 05 can in a known manner as a chain drive (Fig b) or as Gear drive (Fig. C) be executed. The primary drive can also be designed as a spur gear drive.

A stop washer 06 is rotatably connected to a camshaft (not shown). The stop disk 06 has a cutout 07 which defines a boundary of the adjustment range. The cutout 07 has radially spaced from each other an early stop 08 and a late stop 09 on. A stop lug 11 on the camshaft sprocket 01 is provided such that camshaft sprocket 01 and stopper plate 06 between the stops 08, 09 can be rotated relative to each other.

In normal operation of the camshaft adjuster these stops 08, 09 determine the range of the phase adjustment of the camshaft relative to the crankshaft 03. As a result, the valve opening times are adapted to the variable load conditions on the internal combustion engine in a known manner in order to achieve an increase in efficiency. When the internal combustion engine is stopped, the relative position between camshaft sprocket 01 and stopper plate 06 is not determined without the use of so-called start-stop strategies, i. the stop lug in the sprocket is positioned within the cutout 07.

Adjustment strategy 1:

According to a first adjustment strategy are now control gear and crankshaft

03 within an adjustment range 12 via the Nockenwellenkettenrad 01 for the purpose of pre-positioning of the crankshaft 03 is rotated. The adjustment range 12 is determined by the distance or the angle between the stop lug 11 and one of the stops 08, 09. For this purpose, the control shaft is driven by the electric motor as a controller. During this time, the camshaft is stationary.

The advantage of this strategy is the fact that the camshaft sprocket 01 with a stationary camshaft has a similar high reduction to the control shaft, as in normal operation of the internal combustion engine, ie when the camshaft sprocket 01 is rotating as a reference system for the camshaft-side driven gear. Depending on the application can be dispensed with a separate reduction gear to further increase the translation (= pre-translation).

However, the angle range between the stops 08, 09 is limited to less than 180.degree. Crankshaft due to fail-safe concepts with current camshaft adjustments. Furthermore, the crankshaft positioning must be largely regardless of the camshaft phase angle, which could possibly adversely affect the start and exhaust behavior. Depending on the given friction conditions, the camshaft may need to be held in place by an auxiliary device (eg lock or brake device) during crankshaft positioning.

A position determination of the crankshaft 03 can take place with referencing of the stop lug 1 1 on one of the two end stops 08, 09 of the stop plate 06 and with knowledge of the camshaft angle and the Verstellwellenwinkels. Preferably, the crankshaft position is determined directly. Irrespective of this, so-called active crankshaft and / or camshaft sensors are required because parts of the internal combustion engine are stationary at the time of adjustment. Active sensors are voltage-fed sensors that can be sensed even at low speeds until the motor stops.

Adjustment strategy 2:

A second adjustment strategy is used when the camshaft adjuster has been turned off at one of the two stops 08, 09. When using a stop strategy, the corresponding stop can already be set active when the internal combustion engine is switched off. It depends on the towing direction and the type of the variable speed gear, which stop is to be approached in the stop strategy used. An adjustment in the direction of the late limit stop must be used for a negative gear ratio of the three-shaft gearbox, right-hand drive direction and right-hand drive motor direction, or if the three-shaft gearbox is positive, the direction of control is left and direction of rotation is left. An adjustment in the direction of the early limit stop must be used for a positive gear ratio of the three-shaft gearbox, right-hand drive direction and right-hand drive motor direction, or for negative gear ratio of the three-shaft gearbox, left direction control drive and left hand drive direction of rotation.

The camshaft is initially stationary (or may need to be held in addition). Upon reaching the other end stop the camshaft is entrained in the drive direction of the camshaft adjuster and thus the crankshaft. In the case of inverse towing operation, the opposite end stop must be used accordingly.

A particular advantage of this adjustment strategy is that any crankshaft angle can be adjusted.

However, the electric motor haul timing gear, crankshaft and camshaft in the ratio 1: 1, which is why a separate Vorversetzungsgetriebe to increase the effective ratio is required or the electric motor must be sized similarly large starter machine.

Optionally, after successful acceptance of the crankshaft start position, a subsequent pre-adjustment of the camshaft phase position is possible before the injection takes place and the internal combustion engine is ignited.

Adjustment strategy 3

In a third adjustment strategy, the control drive and the crankshaft are first to be towed out of the static friction with the aid of the high gear ratio of the three-shaft transmission during an adjustment of the camshaft sprocket within the adjustment range 12 (according to the first adjustment strategy). When the stop 08 or 09 Qe is reached after trailing direction) can be adjusted with a pre-translation in front of the control shaft, the crankshaft 03 on the adjustment 12 addition. Here, a lower pretranslation is required in comparison to the second adjustment strategy, since the breakaway torque of the crankshaft 03 has already been overcome.

This strategy requires that when the internal combustion engine of the camshaft adjuster takes a camshaft phasing outside of a tow stop so that can always be towed with the high translation. The tow stop is the stop, from which then the camshaft is towed with.

Bezugszeϊchenliste

01 Camshaft sprocket

02 chain 03 crankshaft

04 direction of rotation NORMAL

05 secondary drive

06 stop disc

07 Section 08 Stop EARLY

09 stop LATE

10 -

11 stop lug

12 adjustment range

Claims

claims

1. A method for adjusting a crankshaft (03) of an internal combustion engine with a camshaft adjuster with a three-shaft transmission, comprising an actuating shaft, a Nockenwellenkettenrad (01) and a

Camshaft, wherein the Nockenwellenkettenrad (01) is drivingly connected to the crankshaft (03), characterized in that during the engine standstill or in a transitional phase, in which at least one of the three shafts of the three-shaft gear is stationary, a drive of the control shaft.

2. The method according to claim 1, characterized in that the drive crankshaft by means of the actuating shaft opposite to the usual drive direction of the crankshaft (03).

3. The method according to claim 1, characterized in that the drive of the control shaft is in the direction of the least rotational resistance.

4. The method according to claim 3, characterized in that the direction of the lowest rotational resistance is determined as a function of the crankshaft position.

5. The method according to any one of claims 1 to 4, characterized marked, that the crankshaft (03) is decoupled from a vehicle transmission, before the actuating shaft is driven.

6. The method according to any one of claims 1 to 5, characterized in that the cylinders of the internal combustion engine are decompressed before the actuating shaft is driven.

7. The method according to any one of claims 1 to 6, characterized in that the camshaft during the adjustment of the crankshaft (03) stands still and the adjustment of the control shaft within an adjustment range (12) between two mechanical end stops (08, 09) of the camshaft adjuster takes place.

8. The method according to any one of claims 1 to 6, characterized in that the camshaft rotates during the adjustment of the crankshaft (03).

9. The method according to any one of claims 1 to 6, characterized marked, that during the adjustment of the crankshaft (03) the camshaft initially stands still and rotates in the further course of the crankshaft adjustment after reaching an end stop (08, 09) on the camshaft adjuster.

A camshaft phasing system for an internal combustion engine having a three-shaft transmission comprising an actuating shaft, a camshaft sprocket (01) and a camshaft, the camshaft sprocket (01) being operatively connected to the crankshaft (03), characterized in that it comprises a control device incorporating the Adjustment of the control shaft controls by the controller performs a method according to any one of claims 1 to 9, to effect about the control shaft, an adjustment of the crankshaft, while at least one of the shafts of the three-shaft transmission is stationary.

11. Camshaft adjusting system according to claim 10, characterized in that between the actuating shaft and an actuator housing or between the actuating shaft and the Nockenwellenkettenrad (01), a pre-gearbox is connected.

12. Camshaft adjusting system according to claim 11, characterized in that the three-shaft gear and the pre-gearbox provide a total reduction of more than 1: 50 or 1: -50.

13. Camshaft adjusting system according to one of claims 10 to 12, characterized in that it further comprises a sensor system for detecting a crankshaft position and / or a camshaft position.

14. Camshaft adjusting system according to one of claims 10 to 13, characterized in that it comprises an electric motor for driving the control shaft.

15. Camshaft adjusting system according to claim 14, characterized in that the electric motor has an engine constant ke of greater than 15 mVs / rad.

16. Internal combustion engine with a camshaft adjustment system according to one of claims 10 to 15, characterized in that it provides for the operation of the camshaft adjuster a power of more than 100 W.

17. Internal combustion engine according to claim 16, characterized in that it comprises a camshaft breakaway torque, a camshaft drag torque, a crankshaft breakaway torque and a crankshaft breakaway torque of less than 30 Nm each.

18. Internal combustion engine according to claim 16 or 17, characterized in that it comprises an active camshaft sensor for determining the position of the camshaft.

19. Internal combustion engine according to one of claims 16 to 18, characterized in that it comprises an active crankshaft sensor for determining the position of the crankshaft (03).

20. Internal combustion engine according to one of claims 16 to 19, characterized in that it comprises a lock for the crankshaft (03) and / or a lock for the camshaft.

21. Internal combustion engine according to claim 20, characterized in that the barrier is a mechanical brake or an electromagnetic or hydraulic latch pin.