DE102014205770A1 - Method for adjusting control times of an internal combustion engine - Google Patents

Abstract

A method for operating a mechanism for adjusting the timing of at least one intake valve of a dual-mass flywheel internal combustion engine, wherein a resonance range of the dual-mass flywheel is in a speed range below the idling speed of the internal combustion engine, provides that when starting the internal combustion engine before passing through the resonance range, an intake valve closing time such is set by the mechanism that the timing of closing the intake valve corresponds to a crankshaft angle of the internal combustion engine, which is at least 10 ° away from a lower charge cycle dead center.

Description

Field of the invention

The invention relates to a method for valve control of a two-mass flywheel having internal combustion engine during the start of the internal combustion engine. The valve train of the internal combustion engine can in this case have continuous or discrete possibilities of adjusting control times.

Background of the invention

With the help of a dual-mass flywheel torsional vibrations of a motor vehicle engine can be damped. A bow spring system for a dual-mass flywheel, which is designed in particular for the given when starting an internal combustion engine conditions, for example, from DE 10 2012 211 093 A1 known. This bow spring system includes a start bow spring and two additional bow springs.

From the DE 10 2008 015 152 A1 a method for adjusting a camshaft by means of an electromechanical camshaft adjuster is known. In the context of this known method is provided to adjust the camshaft adjuster during the shutdown of the internal combustion engine to its end position "early". This has the advantage that when the internal combustion engine is restarted, the camshaft adjuster can be adjusted in the "late" direction with little expenditure of energy due to given friction torques. In this way, a desired target setting of the camshaft adjuster can be reached quickly.

Other methods for operating a camshaft adjuster are from DE 10 2008 039 007 A1 as well as from the DE 10 2008 039 008 A1 known. In the cited documents, particular attention is given to the starting process of the internal combustion engine. When starting the internal combustion engine, the timing drive is pre-positioned, which can be regulated or unregulated. While "blind" is adjusted in one direction in the case of unregulated pre-positioning, there is a continuous setpoint-actual comparison during controlled adjustment.

On special operating method of a camshaft adjuster when starting an internal combustion engine is also in the EP 2 591 215 B1 received.

Object of the invention

The invention has for its object to further develop a mechanism for adjusting control times, in particular closing times, at least one intake valve of an internal combustion engine of a vehicle with dual mass flywheel with respect to the cited prior art, in particular with regard to the suitability for start-stop systems.

Description of the invention

This object is achieved by an operating method with the features of claim 1. The method is applicable to motor vehicles having an internal combustion engine drive - in particular by a camshaft adjuster - variable control times, wherein in the drive train of the vehicle a dual mass flywheel, which by itself known type may be located.

Instead of a camshaft adjuster, for example, a sliding cam system or a valve train with switchable cam followers, for example switching cups or switchable cam followers, may be provided. In the latter variable valve trains, which typically provide only discrete switching possibilities between two valve lift curves, each of two possible adjustment positions of the mechanism for adjusting the control times is associated with a particular valve lift curve and thus with a characteristic selection of the control times.

By contrast, in the case of a space cam system, for example, there may be a continuum of possible setting positions between two extreme settings of the control times. Likewise, given a system for adjusting the phase position of a camshaft of the internal combustion engine in relation to the crankshaft, in particular in the case of an electric camshaft adjuster, there is no fundamental limitation on the number of setting positions.

The invention is based on the consideration that both early closing of the intake valves during start-up and late closing of the intake valves during start-up brings with it specific advantages and disadvantages. At very low speeds of the internal combustion engine, as they are given during the starting process, a better cylinder filling tends to be achieved by closing times of the intake valves, which correspond approximately to the bottom dead center of the internal combustion engine. The good filling of the cylinder leads to a rapid increase in the speed during startup.

The disadvantage here, however, is the fact that associated with the rapid increase in speed strong speed fluctuations, which as vibrations or as shaking in the vehicle are perceptible. In addition, vibrations in the drive train can lead to unwanted resonances of the dual mass flywheel, which on the one hand represent a significant mechanical load on components of the drive train, in particular the dual mass flywheel itself, and on the other hand reduce perceived comfort in the vehicle.

To reduce this effect, setting the timing of the intake valves, particularly the closing timing of the intake valves, to "late", that is, significantly lower than the lower dead center, may cause lower torque peaks to act on the crankshaft, which is perceived as a smoother engine start becomes. The disadvantage here, however, is the slower increase in speed, that is, the longer duration of the engine start. A comparable effect is given when the intake valve closing time is set to "early" so that the cylinder filling is significantly reduced compared to the maximum possible cylinder filling.

In order to efficiently counteract the described conflict of objectives, according to the invention, the mechanism for adjusting the timing at the start of the internal combustion engine during passage through the resonance range of the dual-mass flywheel is set such that the timing of closing the intake valve corresponds to a crankshaft angle of the internal combustion engine, which is at least 10 ° from the lower Charge change dead point deviates. For example, a late control time can be set, that is, a valve closing time of the intake valve, which corresponds to a crankshaft angle of at least 10 ° after bottom dead center. Due to the late intake valve closing time, part of the air sucked into the cylinder is expelled again. Thus, an adjustment of the control times is made during the passage through the resonance range, with which not the maximum possible torque in this speed range is generated.

According to a possible embodiment, before the resonance range is reached, an adjustment of the control times from "early" to "late" takes place. As a result, advantages with regard to a high initial filling of the combustion chamber can be combined with a low-vibration further startup of the internal combustion engine.

Particularly suitable for the realization of the method according to the invention are electromechanical camshaft adjuster. In particular, this may be camshaft adjuster with three-shaft transmission, as in principle, for example, from WO 2006/074734 A1 known. The adjustment of the timing of the internal combustion engine is not necessarily carried out at a constant adjustment speed. Rather, the adjustment can be done, for example, with varying speed or intermittently. Hydraulically operated camshaft adjusters are also suitable for less complex adjustment processes. The use of such adjuster with adjusting operations in the starting phase of the internal combustion engine requires that sufficient hydraulic pressure can be generated in this phase.

In all cases, at the time of closing the intake valves, if this happens within the resonance range of the dual mass flywheel, the crankshaft of the internal combustion engine in an angular position of at least 10 °, preferably at least 25 °, for example at least 45 °, before or after the lower charge cycle dead center. Preferably, the resonance range of the dual-mass flywheel is traversed in a period between the first and third ignition of the internal combustion engine.

Regardless of the mechanical configuration of the adjusting mechanism and the adjusting mode realized during the starting phase of the internal combustion engine is a throttle valve of the internal combustion engine during startup, before reaching the idle speed, especially during operation of the internal combustion engine in the resonance range of the dual mass flywheel, preferably to an opening angle of at least 3 ° , in particular to an opening angle of at least 10 °.

The setting of the phase angle of the intake camshaft to "late", provided that the resonance range of the dual-mass flywheel is traversed with this setting, can be done before the engine start or only after cranking the crankshaft. In both cases, the adjustment is completed in the direction "late" before reaching the resonance range of the dual mass flywheel. The late control time, in particular intake valve closing time, is preferably maintained at least up to a rotational speed of the internal combustion engine of 400 revolutions per minute. The same applies if during the passage through the resonance range of the dual-mass flywheel, the phase angle of the intake camshaft, mirrored at about the bottom dead center, is set to "early", that the intake valve at a crankshaft position of at least 10 °, 25 ° or 45 ° before the lower Charge change deadpoint closes. The phase angle of the intake camshaft does not necessarily remain the same throughout the passage of the resonance range. This also applies accordingly in mechanisms of valve control, in which the timing is not varied by camshaft adjustment.

However, in particular during the passage through the resonance range of the dual-mass flywheel, the phase angle of the intake camshaft can be regulated to a constant value. This also applies in cases in which the resonance range of the dual-mass flywheel is traversed with an adjustment of the intake valve closing time to at least 10 ° before the lower charge change dead point, that is, with pronounced "early" setting. In these cases, before reaching the resonance range of the dual mass flywheel, an adjustment of the timing in the direction of "early" take place, and this adjustment can either begin before the engine starts or only after the cranking of the crankshaft.

The object underlying the invention is also achieved by a control unit of an internal combustion engine, which is designed to carry out the method according to claim 1.

Several embodiments of the invention will be explained in more detail with reference to a drawing. Hereby shows:

Short description of the drawing

1 the course of the crankshaft speed and control timing settings of an internal combustion engine during engine start.

Detailed description of the drawing

In the single figure, as a function of the time t, the rotational speed n of the crankshaft of an internal combustion engine installed in a vehicle, namely a four-cylinder reciprocating engine, and the phase angle φ of an intake camshaft of the same engine in relation to the crankshaft are shown. The internal combustion engine is a diesel engine. Alternatively, it could also be a gasoline engine. In any case, the vehicle is equipped with a dual-mass flywheel. With regard to the basic structure and the function of a dual mass flywheel, reference is made to the cited prior art.

Individual combustion processes at the start of the engine are expressed in the course of the speed n, as in 1 seen, in local maxima. The first combustion process at the start of the engine - more precisely, the time during the engine start, at which the first local torque maximum occurs through the first combustion process - is in 1 marked with V.

Within the starting process, a distinction is made between an initial phase IP, which lasts from the time t ₀ , that is, the time of starting the rotation of the crankshaft of the internal combustion engine, until the time t ₁ , and a resonance range RB, which from the time t ₁ to the time t _{2 is} traversed and in which it can come to design due to significant resonant vibrations of the dual mass flywheel. The time t ₁ is before the triggered by the first ignition in a cylinder of the engine pressure and thus torque increase.

The resonance range RB is left before the idling speed of the internal combustion engine is reached. In addition, other components in the powertrain or elsewhere of the vehicle within the resonance range RB may be excited to vibrations perceivable in the vehicle. In particular, these may be vibrations, which are transmitted to components of the steering of the vehicle and are noticeable in the steering wheel.

Already at the beginning of the engine start, before reaching the resonance range RB, a camshaft adjuster on the inlet side of the internal combustion engine of the in 1 Adjusted with F setting "Early" in the setting designated "S late" adjusted. When set to S, the intake valve of the internal combustion engine closes at an angle of the crankshaft of the internal combustion engine of at least 10 °, in particular at least 25 °, for example at least 45 °, after the lower charge cycle dead center. Alternatively, settings of the control times could be selected in the resonance range RB, in which the intake valve closes well before the bottom dead center, namely at least 10 °, 25 ° or 45 ° before the lower charge cycle dead center.

With this setting of the control time, the entire resonance range RB is passed through. Subsequently, before or after reaching the idle speed, not shown further changes in the control time are possible.

Within the initial phase IP is in 1 Dashed an alternative course of the adjustment of the camshaft and thus outlines the timing of the internal combustion engine. In comparison to the operating method explained above, in this case the camshaft is already adjusted from the "early" setting F to the "late" setting S in an earlier period which can already start before the time t ₀ .

The explained with reference to the figure using the example of a four-cylinder engine method is also applicable to internal combustion engines with lower or higher number of cylinders. In particular, the method can be used for automatic starting in the context of a start-stop system.

LIST OF REFERENCE NUMBERS

• φ phase angle
• F "Early" setting
• IP initial phase
• n speed
• RB resonance range
• S "Late" setting
• t time
• t ₀ time
• t ₁ time
• t ₂ time
• V combustion process

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102012211093 A1 [0002]
• DE 102008015152 A1 [0003]
• DE 102008039007 A1 [0004]
• DE 102008039008 A1 [0004]
• EP 2591215 B1 [0005]
• WO 2006/074734 A1 [0015]

Claims (10)

A method of operating a mechanism for adjusting timing of at least one intake valve of a dual mass flywheel internal combustion engine, wherein a resonance range of the dual mass flywheel is in a speed range below the idle speed of the internal combustion engine, and wherein upon starting the engine before passing through the resonance range, an intake valve closing time is determined by the mechanism is set, that the timing of closing the intake valve corresponds to a crankshaft angle of the internal combustion engine, which is at least 10 ° from the lower charge cycle dead center. A method according to claim 1, characterized in that the mechanism is set prior to passing through the resonance range of the dual mass flywheel such that the timing of closing of the intake valve corresponds to a crankshaft angle of the internal combustion engine, which is at least 25 ° from the lower charge cycle dead center. A method according to claim 2, characterized in that the mechanism is set prior to passing through the resonance range such that the timing of closing of the intake valve corresponds to a crankshaft angle of the internal combustion engine which is at least 45 ° from the lower charge cycle dead center. Method according to one of claims 1 to 3, characterized in that the resonance range of the dual mass flywheel is traversed in a period between the first and third ignition. Method according to one of claim 4, characterized in that a throttle valve of the internal combustion engine during passage through the resonance range of the dual mass flywheel has an opening angle of at least 3 °. Method according to one of claims 1 to 5, characterized in that the mechanism is already set before starting the internal combustion engine to the late control time, which is held when passing through the resonance range of the dual mass flywheel. Method according to one of claims 1 to 5, characterized in that the mechanism is set only after the starting of the internal combustion engine to the late control time, which is held when passing through the resonance range. Method according to one of claims 1 to 7, characterized in that the control time, which is given when passing through the resonance range of the dual mass flywheel, is maintained up to a speed of the internal combustion engine of at least 400 / min. Method according to one of claims 1 to 8, characterized in that the control time is readjusted during passage through the resonance range of the dual mass flywheel. Control unit of an internal combustion engine, designed to carry out the method according to claim 1.

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