WO2021043431A1

WO2021043431A1 - Internal combustion engine with eccentric tumble chamfer for a petrol engine with a four-valve/crossflow cylinder head

Info

Publication number: WO2021043431A1
Application number: PCT/EP2020/000141
Authority: WO
Inventors: Andreas Boemer; Marco Jung
Original assignee: Deutz Aktiengesellschaft
Priority date: 2019-09-04
Filing date: 2020-08-05
Publication date: 2021-03-11
Also published as: DE102019006238A1

Abstract

1. An internal combustion engine with eccentric tumble chamfer for a petrol engine with a four-valve/crossflow cylinder head 2. An internal combustion engine, in particular a petrol engine, is described, comprising at least one crankcase (2), at least one cylinder head (1), wherein the cylinder head has at least one inlet valve (3) and at least one outlet valve (4), wherein the inlet valve (3) and the outlet valve (4) have in each case one valve seat (8, 9), at least one inlet duct (5) and at least one outlet duct (6), and at least one piston with piston rings and the corresponding crankshaft, characterized in that an eccentric tumble chamfer (10) is arranged in the region of the inlet valve (3) and the associated valve seat (8).

Description

Internal combustion engine with eccentric tumble bevel for a gasoline engine with four-valve / cross-flow cylinder head

DESCRIPTION

The invention relates to a cylinder head of a gasoline engine with at least two inlet ducts which open out at a cylinder head base, and each with a valve seat for an inlet valve provided in the inlet duct, the valve seat having a central axis. The combustion process in an engine is particularly influenced by the flow in the cylinder. A distinction is made between macroscopic flow - that is swirl and tumble - and microscopic flow - that is turbulence. Swirl is a vortex flow whose axis of rotation is parallel to the cylinder axis. A tumble is a vortex flow whose axis of rotation is arranged at right angles to the cylinder axis.

A tumble combustion process is often used in gasoline engines. This combustion process generates a tumble flow generated on the inlet side, uses a roof-shaped combustion chamber and a piston bowl that supports the tumble flow. The tumble flow generated during the suction phase is crushed during the compression phase and converted into turbulence. The turbulence accelerates the combustion and enables good lean running properties and high exhaust gas recirculation rates.

Stationary gas engines that work with a combustion process, with swirl inlet ducts and omega piston bowls are known. Twist chamfers are used to increase the twist. These are eccentric chamfers on the cylinder head below the inlet valves, which direct the outflow from the inlet ports in a targeted manner in the direction of the swirl. The diesel swirl combustion process aims to achieve good mixture formation within the engine. A method for operating an internal combustion engine is known from EP 814245 B1, the gas exchange of which is controlled by periodically actuated inlet and outlet valves, the fresh gas flowing in via the inlet valve being impressed with a flow movement in such a way that the exhaust gas swirl flow and the fresh gas flow movement a charge stratification with increased fresh gas concentration in the vicinity of a spark plug sets in the combustion chamber and the swirl flow is impressed on the recirculated exhaust gas by a chamfer extending only partially around the flow cross-section, the directions of the two chamfers on the exhaust valves deviating from one another in such a way that form two swirl flows rotating in opposite directions around parallel cylinder axes, so that the flow movement impressed on the fresh gas is a tumble flow rotating transversely to the cylinder axis.

A cylinder head for a diesel or gasoline engine is known from DE 102008026728 A1. The cylinder head has at least one inlet channel with a valve seat and inlet valve for each individual working cylinder. In order to generate a swirl flow, the valve seat of the inlet valve is provided with a swirl chamfer, the swirl chamfers of two or all of the cylinders being designed differently. The bevel angle or the size of the bevel can be considered as the variable size of the bevel.

From EP 1493910 A1 a cylinder head of a diesel engine with Zylin derkopfboden and two inlet ports is known. Each inlet channel has a valve seat for an inlet valve and a chamfer in the area of the cylinder head base, which are designed and arranged in such a way that a swirling flow of the incoming gas is brought about.

DE 10065888 A1 discloses a method for optimizing the swirl values for inlet channels. EP 1215377 A1 describes a cylinder head of a diesel or gasoline engine with a cylinder head base and an inlet duct. The inlet channel comprises a valve seat for an inlet valve. A rib is arranged on the inner wall of the inlet channel in front of it.

The rib increases the vortex movement as it flows into the combustion chamber. The rib can be at least partially formed when the inlet channel is formed or by machining the inner wall of the channel.

A cylinder head of a gasoline engine is known from FR 2890119 A1. The cylinder head has a cylinder head base, two inlet channels and one valve seat for one inlet valve per inlet channel. In the area of the cylinder head base, the inlet ducts each include a bevel that extends in the direction of the outlet ducts. As a result, a tumble flow is generated in the direction of the exhaust ducts when it flows into the cylinder.

DE 19619782 A1 discloses a cylinder head of a diesel or gasoline engine. The cylinder head has a cylinder head base and an inlet channel with a valve seat for an inlet valve. A raised section is provided in the inlet channel which directs the intake air flow in the inlet channel in the direction of the cylinder wall closest to the inlet valve, so that a tumble flow is generated.

The invention is based on the object of designing and arranging a cylinder head of a gasoline engine in such a way that a tumble flow is generated in a targeted manner.

The object is achieved according to the invention by a cylinder head according to claims 1 and 8. Further advantageous embodiments are contained in the subclaims.

This is particularly advantageous in the case of stationary gasoline engines with a camshaft located at the bottom. Stationary gas engines usually have one Camshaft located at the bottom, so that the respective cylinder-related cylinder head can be easily dismantled for the purpose of maintenance and servicing. A common cylinder head for several or up to 20 or 24 cylinders with integrated camshafts would therefore not only be too expensive to manufacture, but would also be disadvantageous in terms of maintenance. However, this is accompanied by a limited variability with regard to the arrangement and alignment of the inlet and outlet valves. The latter in particular against the background that stationary gas / spark-ignition engines are diesel-based engines whose cylinder head architecture is oriented towards a swirl flow. The function of the tumble bevels can be described in more detail as follows. The tumble bevels are particularly effective when the valve lift is low, i.e. when the valve is opened and closed, when the flow through the valve is forcibly guided to the bevel or the chamfer. With a large valve lift, the outflow from the inlet channel runs primarily along the valve axis and is hardly influenced by the chamfer.

The chamfer leads to a significant increase in the tumble flow in the cylinder. The efficiency of this measure is good; H. the movement of the cargo is significantly increased without the use of air being impaired in an inadmissible manner. The chamfer can be introduced into series production without the cylinder head having to be redesigned in any other way. The eccentric chamfer can be implemented with no production costs.

Overall, the gas engine results in an improved combustion process with increased efficiency.

The maximum M is achieved in that the axis of symmetry of the bevel is arranged eccentrically and / or adjusted to the central axis of the valve seat. In contrast to the eccentric arrangement, the inclination of the axis of symmetry ensures that the inclination angle of the bevel surface varies over the circumference relative to the central axis. The eccentric arrangement and the employment can of course be provided alternatively or in combination.

The formation of the bevel can therefore be determined by their flan kenwinkel, d. H. the cone angle of an eccentrically attached milling tool and / or by their employment, d. H. the angle of incidence between the axis of the milling tool and the surface normal of the cylinder head base. The flank angle or cone angle is preferably between 100 ° and 140 °. The setting or the setting angle is preferably between 0 ° and 10 °. Both measures can be used to produce a bevel that is asymmetrical to the central axis and with the desired alignment. The cone angle of the eccentrically applied milling tool and / or the setting angle of the milling tool are selected in such a way that an efficient flow control is achieved.

Both currents thus converge in the area of the closest cylinder wall and are favorably deflected downwards so that a tumbling movement is initiated.

According to the invention, the alignment of the tumble bevels using one of the aforementioned angles is such that the flow deflection is aimed in the direction of the cylinder wall closest to the two inlet valves. Thus, on the one hand, a tumble flow is generated in interaction with the curvature of the cylinder wall and, on the other hand, a distance between the tumble bevel and the cylinder wall is ensured.

The eccentricity E of the countersinks or tumble bevel is selected so that a significant intensification of the tumble flow is achieved without the flow quality of the inlet channels being significantly impaired.

It is also advantageous to provide a spark plug in such a way that it is not blown out by the tumble. In passenger car gasoline engines, the maximum intensity of the tumble flow must be limited so that the flame core between the spark plug electrodes is not blocked by the strong flow. will blow. This limitation is eliminated by using a chamber candle. The chamber plug shields the ignition location or the flame core from the flow in the combustion chamber through the spark plug prechamber and creates its own, defined ignition conditions. A strong tumble flow and high turbulence therefore primarily affect the combustion in the main combustion chamber and not directly on the sensitive ignition phase in the spark plug prechamber. A maximum intensification of the tumble flow 13 is possible. It is advantageous if a spherically, toroidally or lenticularly shaped piston recess 14 is provided. The tumble flow 13 generated at the inlet channel 5 can only be fully used if the engine has a piston bowl 14 that supports the tumble flow. Compared to the deep bowl such as the omega bowl, such a piston bowl 14 also has the advantages that the flame paths from the spark plug 12 to the edge of the combustion chamber are particularly short and the surface area of the combustion chamber is small.

It is also advantageous that the combustion chamber is filled with the aid of a turbocharger or a compressor.

A method for producing a cylinder head of a stationary gas engine is advantageous in which a milling tool is used to produce the bevel 11, which has a cone angle and is set with the eccentricity to the central axis and / or at an angle of attack to the central axis.

In connection with the design and arrangement according to the invention, it can be advantageous if the gas engine is operated with a cylinder head as described above with a high scavenging pressure drop, the scavenging pressure drop being between 700 mbar and 1200 mbar.

In the case of a stationary, charged gas engine, there is a high purging pressure gradient between the inlet and outlet channels. This creates a strong flow when the inlet valves are opened until the pressure conditions have equalized. The Tumblefasen therefore have in this Period has a particularly strong effect. It can also be advantageous if the operation takes place using Miller control times with early closing of the inlet valves, the inlet valve closing at a crank angle CA of CA> = 20 ° before BDC, measured with a valve lift of 1 mm. I. E. with a crank angle KW of KW = 20 °, the inlet valve is just 1 mm open. These support the tumbling movement because the inlet valves are already closing while the piston is still moving towards bottom dead center. This creates a strong flow when the inlet valves are closed as well as when they are opened, which also explains the effect of the tumble bevels during the closing process. In four-stroke engines, the number and arrangement of the gas exchange organs in the cylinder depends on various boundary conditions. The main criteria are the valve arrangement and the valve train, the arrangement of the mixture generator, desired filling and charge movement, required limit speed, package, friction, maintenance, timing drive, which determine the effort and manufacturing costs. The basic characteristics of the charge movement are the swirl flow, the rotation of the cylinder charge around the cylinder axis and the tumble flow, the rotation around the axis perpendicular to the cylinder's vertical axis or around the longitudinal axis of the engine.

The requirements on the gas exchange with regard to charge, charge composition and charge movement, which mostly vary over the wide load and speed range, are often taken into account by variabilities that affect the opening profile of the valves as well as the geometry of the intake system and in some cases also the Extend exhaust system.

Charge movement flaps (twist and tumble)

The charge movement turns out to be one of the most important parameters for combustion, as its modification can have significant effects on the combustion process. By adapting the inlet ducts and / or the valve control times, it is possible to specifically influence the mixture formation and the combustion process. Attempts are made to increase the turbulence by means of a directed flow and to prepare the mixture better and, for example in the case of stratified charging, to guide the charge in a targeted manner. An effect on the wall heat transfer, the mass transport and the propagation speed of the combustion can also be achieved.

The swirl flow is already taken into account when designing the inlet ducts, with different configurations being implemented. One of the channels can be designed as a filling channel for this purpose. In this configuration, the filling channel can be provided with a swirl flap that can be closed depending on the operating point.

The other channel is often referred to as the tangential channel and is used to generate the twist. The air thus flows asymmetrically into the combustion chamber and induces a flow shape that rotates around the vertical axis of the cylinder, with the swirl level being able to increase as the swirl flap is adjusted more and more.

The opening of the filling channel is only expedient in areas of high speeds or towards full load. The swirl flow is supported by a suitable design of the piston shape, with the so-called omega-bowl pistons proving themselves here. In contrast to the tumble, the twist is also retained in the compression phase.

Tumble

The tumble represents a flow around an axis perpendicular to the cylinder's vertical axis. This flow direction is achieved in that certain measures at the inlet force the air to flow through the upper part of the intake duct. For this purpose, either the suction channel is provided with a shape that supports the flow in the upper part of the channel, or the lower part of the channel is closed by a flap arranged in it. The rotary flap closes the lower part of the suction duct and thus ensures a narrowing of the cross-section, which is accompanied by an increase in speed.

This leads to an increase in the kinetic energy. In comparison to the swirl, the tumble is not independent of the piston movement, which means that it breaks up into individual turbulence eddies at TDC. This behavior is desirable in gasoline engines because it creates a high level of turbulence. Here, a specially designed piston, for example with a nose or as a lens piston, supports the deflection of the tumble flow.

There are several different key figures for quantifying the swirl and tumble flow. A well-established characterization takes place via the twist or tumble number ZD, T. By definition, it is the ratio of the angular velocity of the charge movement WD or WT to the angular velocity of the crankshaft W «.

Phase adjusters for the intake and exhaust side as well as partially and fully variable valve lift systems offer further options for targeted influencing of the gas exchange process.

Further advantages and details of the invention are explained in the patent claims and in the description and shown in the figures. Show it:

Fig. 1 is a schematic diagram of the cylinder head in the view from below,

2 shows a schematic diagram of a sectional illustration of the cylinder head,

3 shows a schematic representation of swirl and tumble flow,

4 Tumble generation,

5 shows a section through an internal combustion engine with an eccentric tumble bevel.

In Fig. 1, a schematic diagram of the cylinder head 1 is shown in a view from below. The inlet valves 3, the outlet valves 4 and the spark plug 12 can be seen. Furthermore, the inlet channel 5 can be seen, to which the fresh air is closed brings the inlet valves 3. After the fresh air has flowed through the inlet channel, it has to pass the valves 3 and inevitably comes into the area of the eccentric tumble bevel 10 on the inlet valve. The eccentric tumble bevel 10 on the inlet valve 3 is arranged on the opposite side of the valve disk as the inlet channel 5.

The outlet channel 6, through which the exhaust gases flow after they have passed the opened outlet valves 4, leads away from the outlet valves.

FIG. 2 shows a schematic diagram of the illustration from FIG. 1 in a side view. The inlet valves 3, the outlet valves 4 and the spark plug 12 can be seen. The inlet channel 5, which brings the fresh air to the inlet valves 3, can also be seen. After the fresh air has flowed through the inlet duct, it has to pass the valves 3 and inevitably comes into the area of the eccentric tumble bevel 10 on the inlet valve. The eccentric tumble bevel 10 on the inlet valve 3 is arranged on the opposite side of the valve disk than the inlet channel 5. The outlet channel 6 leads away from the outlet valves, through which the exhaust gases flow after they have passed the open outlet valves 4.

A schematic representation of swirl and tumble flow can be seen in FIG. 3.

4 shows schematically how a tumble is generated.

In FIG. 5, a section through an internal combustion engine with an eccentric tumble bevel 11 is disclosed. The inlet valves 3, the outlet valves 4 and the spark plug 12 can be seen. The inlet channel 5, which brings the fresh air to the inlet valves 3, can also be seen. After the fresh air has flowed through the inlet channel, it has to pass the valves 3 and inevitably comes into the area of the eccentric tumble bevel 10 at the inlet valve. The eccentric tumble bevel 10 on the inlet valve 3 is arranged on the opposite side of the valve disk as the inlet channel 5. The outlet channel 6, through which the exhaust gases flow after they have passed the open outlet valves 4, leads away from the outlet valves.

In the case of a cross-flow cylinder head for a gasoline engine that is operated with a tumble-based combustion process, the flow from the two inlet valves is deflected in such a way that a tumble flow results in the cylinder. For this purpose, a shallow incline of the inlet channels would be desirable. For structural reasons, however, this cannot be done to the desired extent, e.g. B. because of existing cooling channels.

Instead of an extremely flat arrangement of the inlet channels, the fibers at the outlet of the inlet channels are designed eccentrically in the outlet direction. As a result, the fresh air or the gas / air mixture preferably flows into the combustion chamber in such a way that the tumble occurs.

List of reference symbols

1 cylinder head

2 crankcase 3 inlet valve

4 exhaust valve

5 inlet port

6 exhaust port

7 piston 8 valve seat inlet valve

9 Valve seat exhaust valve

10 Eccentric tumble bevel on the inlet valve

11 bevel angles

12 spark plug 13 tumble

14 Piston recess

Claims

EXPECTATIONS

1. Internal combustion engine, in particular Otto engine, comprising at least one crankcase (2), at least one cylinder head (1), the cylinder head having at least one inlet valve (3) and at least one outlet valve (4), the inlet valve (3) and the outlet valve ( 4) each have a valve seat (8, 9) and at least one inlet channel (5) and at least one outlet channel (6) and at least one piston with piston and the corresponding crankshaft, characterized in that in the area of the inlet valve (3) and the associated valve seat (8) an eccentric tumble bevel (10) is arranged.

2. Internal combustion engine according to claim 1, characterized in that the eccentric tumble bevel (10) is arranged in the flow direction of the incoming fresh air between the inlet and outlet valve.

3. Internal combustion engine according to claim 1 or 2, characterized in that the eccentric tumble bevel (10) is arranged towards the center of the combustion chamber in the region of the valve seat of the inlet valve (8).

4. Internal combustion engine according to one or more of the preceding claims, characterized in that the eccentric tumble bevel (10) forms an angle of about 20-25 degrees between the cylinder head (1) and the valve disk of the inlet valve (3) in the closed state. 5. Internal combustion engine according to one or more of the preceding claims, characterized in that the eccentric tumble bevel (10) has an angle of about 22,

5 degrees between the cylinder head (1) and the valve head of the inlet valve (3) when closed.

6. Internal combustion engine according to one or more of the aforementioned

Claims, characterized in that it has at least one spark plug.

7. Internal combustion engine according to one or more of the aforementioned

Claims, characterized in that it is a gas-powered internal combustion engine.

8. Internal combustion engine according to one or more of the aforementioned

Claims, characterized in that it has at least one turbocharger.

9. Internal combustion engine according to one or more of the aforementioned

Claims, characterized in that it has at least one compressor.

10. A method for operating an internal combustion engine, characterized in that an internal combustion engine according to one or more of the preceding claims is used.