GB2484747A

GB2484747A - I.c engine inlet port with a tangential pipe and a helical pipe leading to a common cylinder inlet

Info

Publication number: GB2484747A
Application number: GB1017951.3A
Authority: GB
Inventors: Hartmut Herrmann; Domenico Maccarrone
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2010-10-18
Filing date: 2010-10-18
Publication date: 2012-04-25
Also published as: GB201017951D0

Abstract

An intake port 70 of an internal combustion engine comprises a first pipe 71 of tangential kind and a second pipe 72 of helical kind which lead to the same inlet (30, fig.2) of the cylinder. The tangential pipe 71 and helical pipe 72 may lead into opposite portions of the cylinder inlet 30. The helical portion 721 of the helical pipe 72 may extend around the axis x of the valve guide 53 through about 180o before passing beneath the tangential pipe 71. Alternatively (figs. 9-11), the helical portion 721 of the helical pipe 72 may extend around the axis x of the valve guide 53 through about 270o above the tangential pipe 71. The tangential and helical pipes 71, 72 may be joined laterally over their whole length or may be laterally separated.

Description

INT?JKE PCRT FOR AN Itfl'ERNAL CCI'IBUSTION ENGINE TECHNICAL flEll) The present invention relates to an intake port of an internal com- bustion engine, such as for exarrile a spark ignition engine or a Di-esel engine. an

An internal cortustion engine generally comprises one or more cylind-ers, each of which is provided with at least one inlet for inducting an air flow into the cylinder, which can eventually be mixed with a certain amount of fuel and/or with a certain amount of recirculated exhaust gas.

Each cylinder inlet is cyclically opened and closed by means of a dedicated intake valve, typically a poppet valve having an head and a stem, which is positioned so that the axis of the stern, usually con-sidered as the axis of the intake valve, almost coincides with the central axis of the cylinder inlet.

The valve stem is inserted into a valve guide that guides the intake valve to reciprocate along the above mentioned axis, between a cbs-ing position, in which the valve head rests against a valve seat,

I

thereby closing the cylinder inlet, and an opening position, in which the valve head is slightly moved inside the cylinder, thereby opening the cylinder inlet.

As a matter of fact, when the intake valve is in the opening posi-tion, it defines a cylindrical passage for the air flow, whose open area can be estimated as the perimeter of the valve head (or the cor-responding perimeter of the cylinder inlet) multiplied for the intake valve displacement.

Each cylinder inlet is further associated to a dedicated intake port, which directs the air flow into the cylinder and which is generally defined by a single pipe connecting the cylinder inlet to an intake manifold of the engine.

This intake port (i.e. the pipe defining the intake port) can be of a straight kind, so as to minimize the friction pressure loss of the air flow, but on occasion it can be of a particular shaped kind, so as to direct the air flow in a defined direction into the cylinder, which is favourable for supporting and improving the combustion process, specially when the engine operates under partial loading conditions.

As a drawback, the cross section of a shaped intake port is generally restricted compared to the cross section of a straight intake port, thereby reducing the volumetric efficiency and consequently the per-formance of the engine.

For good compromises, many engines are thus designed with two inlets per cylinder, one of which is associated to a straight intake port while the other one is associated to a shaped intake port, thereby achieving both a favourable guidance of the air flow and a good volu-metric efficiency of the engine.

At present, the above mentioned shaped intake port (i.e. the pipe de-S fining the intake port) can generally be of a tangent kind or of an helical kind.

A tangent intake port is basically designed to direct the air flow tangentially along the lateral surface of the cylinder, so as to create a swirl motion therein.

In order to create this effect, the tangent intake port extends along a longitudinal axis which is inclined with respect to the central axis of the respective cylinder inlet.

As a consequence, when the intake valve is in the opening position, most of the air flow enters into the cylinder through a reduced por-tion of the available cylindrical passage defined by the valve head, namely through a front side of this cylindrical passage which direct- ly faces the incoming direction of the tangent pipe, while the oppo-site rear side of the cylindrical passage is not used effectively, thereby limiting the volumetric efficiency of the engine.

An helical intake port is basically designed to direct the air flow radially in all directions into the cylinder.

In order to create this effect, the helical intake port extends along a longitudinal axis which winds helically around the central axis of cylinder inlet, so as to force the air flow in a spiral-kind rotating motion before entering into the cylinder.

In this case, when the intake valve is in the opening position, the available cylindrical passage defined by the valve head is better used, but the air flow is directed less precisely into the cylinder, and the volumetric efficiency is anyway reduced by the major friction pressure loss to which the air flow is subjected along the helical intake port.

In view of the above, it is an object of an embodin'ent of the present invention to provide an improved intake port capable to solve, or at least to positively reduce, the above mentioned drawbacks of the known intake ports.

DISCLOSURE

This and/or other objects are attained by the characteristics of the embodiments of the invention as reported in independent claims. The dependent claims recite preferred and/or especially advantageous fea-tures of the embodiments of the invention.

An embodiment of the invention provides an intake port of an internal combustion engine, wherein the internal combustion engine comprises a cylinder provided with at least an inlet, and wherein the intake port comprises a first pipe of a tangent kind and a second pipe of an hel-ical kind, both of which lead to the same inlet of the cylinder.

In this way, a portion of the inducted air flow is guided by the tan-gent pipe while the remaining portion is guided by the helical pipe, thereby combining the effect of a tangent intake port to the effect of an helical intake port and also achieving a synergistic effect which improves both of them.

The ratio between this two portions of the air flow depends on the final dimensioning of the proposed intake port, which can be designed according to predetenuined targets.

Mother advantage of the proposed intake port is that, where the cross section of the first pipe should be reduced in order to create an effective tangent design, the cross section of the second intake pipe of helical kind can be increased and vice versa. In this way, the global cross section of the proposed intake port, along the whole extension, can be bigger than the cross section of a conventional tangent intake port or of a conventional helical intake port, thereby achieving a better volumetric efficiency of the engine.

According to an aspect of the invention, the second pipe of helical kind leads in a rear portion of the cylinder inlet with respect to an incoming direction of the first pipe of tangent kind.

As a matter of fact, the incoming direction of the first pipe is de-fined by the longitudinal axis of the first pipe, so that the rear portion of the cylinder inlet can be defined starting from a first reference plane which contains both the axis of the cylinder inlet and the longitudinal axis of the first pipe.

Indeed, considering this first reference plane, it is possible to de-fine a second reference plane which contains the axis of the cylinder inlet and which is perpendicular to the first reference plane.

This second reference plane ideally separates two half spaces, one of which should necessarily contain the bigger portion of the first pipe of tangent kind.

The rear portion of the cylinder inlet is the portion which is con-tained in this one half space.

As explained in the preamble, due to the inclination of the first pipe of tangent kind, this rear portion of the inlet is not eff i-ciently used for the related portion of the air flow to enter into the cylinder.

The above rrentioned aspect of the invention has thus the advantage to direct the remaining portion of the air flow just into this rear por-tion of the cylinder inlet, thereby achieving a better use of the available cylindrical passage defined by the valve head, when the in- take valve is in the opening position, and therefore a better volume-tric efficiency of the engine.

According to another aspect of the invention, the second pipe of hel-ical kind comprises an helical portion which extends helically around the central axis of the cylinder inlet for an angle comprised between 160° and 200°, approximately for an angle of 180°.

This solution has the advantage that the cylinder inlet could be fed better with the air flow, thereby further improving the volumetric efficiency of the engine.

According to an alternative aspect of the invention, the helical por-tion of the second pipe extends helically around the central axis of the cylinder inlet for an angle comprised between 250° and 290°, ap-proximately for an angle of 270°.

This solution has the advantage to increase the spiral-kind rotating motion of the portion of the air flow corning from the second pipe, which can be helpful for increasing the swirl notion of the air flow inside the cylinder.

According to still another aspect of the invention, the first pipe of tangent kind and the second pipe of helical kind are laterally joined together, along their whole longitudinal development, so that the proposed intake port generally shows a single cross section having two lobes.

In this way, the intake port is defined by one compact volume which is easier to be manufactured.

According to an alternative aspect of the invention, the helical por-tion of the second pipe can be laterally separated by the first pipe of tangent kind.

This aspect has the advantage of further improving the spiral-kind rotating motion of the portion of the air flow coming from the second pipe of helical kind.

Another embodiment of the invention provides an internal combustion engine comprising a cylinder provided with an inlet, and the intake port described above associated to this cylinder inlet.

According to an aspect of this embodiment, the cylinder is provided with exactly one inlet only.

In this case, the design of the proposed intake port allows to reduce the diameter of this inlet compared to a conventional intake port, so that it is advantageously possible to locate the spark plug (in case of spark ignition engine) or the fuel injector (in case of Diesel en-gine) closer to the center of the cylinder.

BRIEF DESCRIPPION OF THE DRAWINGS

The present invention will now be described, by way of exarrvle, with reference to the acccxranying drawings.

Figure 1 is a schematic top view of an internal combustion engine.

Figure 2 is a detail of the section 11-Il of figure 1, showing a cy-under head of the internal combustion engine.

Figure 3 is a prospective view of an intake port according to a first embodiment of the invention.

Figure 4 is a lateral view of the intake port of figure 3.

Figure 5 is a frontal view of the intake port of figure 3.

Figure 6 is an opposite lateral view of the intake port of figure 3.

Figure 7 is a back view of the intake port of figure 3.

Figure 8 is a prospective view of a different version of the intake pipe of figure 3.

Figure 9 is a frontal view of an intake port according to a second embodiment of the invention.

Figure 10 is a lateral view of the intake port of figure 9 Figure 11 is a top view of the intake port of figure 9.

Figure 12 is a prospective view of the intake port of figure 9.

DETAILED DESCRIPTION

The internal combustion engine 10, in this case a Diesel engine, corn-prises a plurality of cylinders 20, each of which is provided with only one inlet 30 for inducting an air flow inside the cylinder 20, eventually mixed with a certain amount of recirculated exhaust gas, and with only one outlet 40 for discharging the exhaust gas from the cylinder 20.

As shown in figure 2, the inlet 30 is realized in a cylinder head 100 of the internal combustion engine 10, and it is cyclically opened and closed by means of a dedicated intake valve 50.

Notwithstanding it is not visible in figure 2, also the outlet 40 is realized in the cylinder head 100 and it is cyclically opened and closed by means of a dedicated exhaust valve.

The intake valve 50 and the exhaust valve (not shown) are of the same kind and they are actuated by a conventional cain/tappet apparatus (not shown) driven by the internal combustion engine 10.

In greater details, the intake valve 50 is a poppet valve having an head 51 and a stem 52.

The intake valve 50 is positioned so that the axis of the valve stem 52, also considered as the axis of the intake valve 50, coincides with the central axis X of the inlet 30.

The valve stem 52 is inserted into a valve guide 53 that guides the intake valve 50 to reciprocate along the central axis X between a closing position, in which the valve head 51 rests against a valve seat 54, thereby closing the inlet 30, and an opening position, in which the valve head 51 is slightly moved inside the cylinder 20, thereby opening the inlet 30.

More particularly, when the intake valve 50 is in the opening posi-tion, it defines a cylindrical passage for the air flow, whose open area can be estimated as the perimeter of the valve head 51 (or the corresponding peritreter of the inlet 30) multiplied for the displace-ment of the intake valve 50.

The inlet 30 is further associated to an intake port, globally inca- S cated with 70, which is realized in the cylinder head 100 of the in- ternal ccrnbustion engine 10, and which is generally provided for di-recting the air flow from an intake manifold 80 (see fig.1) into the cylinder 20.

As shown in the figures from 3 to 7, the intake port 70 comprises two pipes leading to the inlet 30 of the cylinder 20, wherein a first pipe 71 is of a tangent kind and a second pipe 72 is of an helical kind.

The first pipe 71 is basically designed to direct a portion of the air flow tangentially along the lateral surface of the cylinder 20, so as to create a swirl motion therein, which is favourable for sup- porting and improving the combustion process, specially when the in- ternal combustion engine 10 operates under partial loading condi-tions.

In order to create this effect, the first pipe 71 extends along a longitudinal axis Y which is considerably inclined with respect to the central axis X of the inlet 30.

As a consequence, when the intake valve 50 is in the opening posi-tion, the most of the air flow caning from the first pipe 71 enters into the cylinder 20 through a front portion 31 of the inlet 30, while the opposite rear portion 32 of the inlet 30 is not effectively used.

More particularly, the rear portion 32 of the inlet 30 can be defined considering a first reference plane P1 containing both the central axis X of the inlet 30 and the longitudinal axis Y of the first pipe 71, so that it is possible to define a second reference plane P2, which is perpendicular to this first reference plane P1 and which contains the central axis X of the inlet 30.

As shown in figure 4 and 6, this second reference plane P2 ideally separates two half spaces, one of which contains the bigger portion of the first pipe 71.

The rear portion 32 of the inlet 30 is the portion which is contained in this one half space.

The second pipe 72 is basically designed to direct a remaining por-tion of the air flow radially in all directions into the cylinder 20 via the inlet 30, so that, when the intake valve 50 is in the opening position, the available cylindrical passage defined by the valve head 51 is better used, irrroving the swirl motion caused by the first pipe 71 and achieving also an high volumetric efficiency of the in-ternal canbustion engine 10.

In order to create this effect, the second pipe 72 extends along a longitudinal axis Z which, in a region nearby the inlet 30, winds helically around the central axis X of the inlet 30, so as to force the air flow in a spiral-kind rotating motion before entering into the cylinder 20.

In greater detail, the second pipe 72 comprises a straight portion 720 extending substantially parallel to the first pipe 71; an helical portion 721 extending helically around the valve guide 53 (and thus around the axis X of the inlet 30), above the first pipe 71; and a final portion 722 leading down directly in the rear portion 32 of the inlet 30.

According to the embodiment of the invention shown in figures fran 3 to 7, the helical pcrtion 721 of the second pipe 72 extends helically around the valve guide 53 for an angle of approximately 180°.

This solution is referred as "under-passing design" since the second pipe 72 makes approximately an half loop around the axis X and then extends underneath the tangent pipe 71, directly into the rear por-tion 32 of the inlet 30.

This "under-passing design" has the advantage to cause low frictional pressure lost, so that the inlet 30 could be fed better with the air flow, thereby further improving the volumetric efficiency of the in-ternal combustion engine.

According to an alternative embodiment of the invention shown in fig- ures from 9 to 12, the helical portion 721 of the second pipe 72 ex- tends helically around the valve guide 53 for an angle of approx-imately 270°.

This solution is referred as "over-passing design" since the second pipe 72 makes a loop around the axis X, so as to pass over the first pipe 71, before extending down into the rear portion 32 of the inlet 30.

This "over-passing design" has the advantage to increase the spiral-kind rotating motion of the portion of the air flow coming from the second pipe 72, which can be helpful for increasing the swirl motion of the air flow inside the cylinder 20.

As clearly shown in figure 7, the first pipe 71 of tangent kind and the second pipe 72 of helical kind are laterally joined together, so that the intake port 70 generally shows a single cross section having two lobes.

This lateral joining is present along the whole longitudinal develop-ment of the first and the second pipes 71 and 72, so that the intake port 70 is globally defined by one compact volurre which is easier to be manufactured in the cylinder head 100.

According to an alternative embodiment shown in figure 6, the first pipe 71 and the second pipe 72 are laterally joined along their whole longitudinal development, except at the helical portion 721 of the second pipe 72 which is laterally separated by the first pipe 71 of tangent kind.

This aspect has the advantage of further improving the spiral-kind rotating motion of the portion of the air flow coming from the second pipe 72 of helical kind.

While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only exam- ples, and are not intended to limit the scope, applicability, or con- figuration in any way. Rather, the forgoing surramary and detailed de-scription will provide those skilled in the art with a convenient road map for irnplerri.enting at least one exemplary embodiment, it being understood that various changes may be made in the function and ar-rangement of elements described in an exemplary ernbodirrent without departing from the scope as set forth in the appended claims and in their legal equivalents.

REFERENCES

Internal combustion engine Cylinder Inlet 31 Front portion of the inlet 32 Rear portion of the inlet Outlet Intake valve 51 Valve head 52 Valve stern 53 Valve guide 54 Valve seat Intake port 71 First pipe 72 Second pipe Cylinder head 720 Straight portion of the second pipe 721 Helical portion of the second pipe 722 Final portion of the second pipe X Axis of the inlet Y Longitudinal axis of the first pipe Z Longitudinal axis of the second pipe P1 First reference plane P2 Second reference plane

Claims

claiMs 1. Intake port (70) of an internal cortustion engine (10) comprising a cylinder (20) provided with an inlet (30), wherein the intake port (70) comprises a first pipe (71) of a tangent kind and a second pipe (72) of an helical kind, which lead to the same inlet (30) of the cylinder (20).
2. Intake port (70) according to claim 1, wherein the second pipe (72) of helical kind leads in a rear portion (32) of the cylinder inlet (30), with respect to an incaning direction of the first pipe (71) of tangent kind.
3. Intake port (70) according to claim 1 or 2, wherein the second pipe (72) of helical kind comprises an helical portion (721) which extends helically around a central axis (X) of the cylinder inlet (30) for an angle coriprised between 160° and 200°.
4. Intake port (70) according to claim 1 or 2, wherein the second pipe (72) of helical kind comprises an helical portion (721) which extends helically around a central axis (X) of the cylinder inlet (30) for an angle corrprised between 250° and 290°.
5. Intake port (70) according to any claim from 1 to 4, wherein the first pipe (71) of tangent kind and the second pipe (72) of heli- cal kind are laterally joined together, along their whole longi-tudinal development.
6. Intake port (70) according to any claim from 1 to 4, wherein the second pipe (72) of helical kind comprises an helical portion (721) which is laterally separated by the first pipe (71) of tan-gent kind.
7. Internal combustion engine (10) comprising a cylinder (20) pro-vided with an inlet (30), and an intake port (70) according to any of the preceding claims associated to this cylinder inlet (30).
8. Internal combustion engine (10) according to claim 7, wherein the cylinder (20) is provided with exactly one inlet (30).