WO2011012787A1

WO2011012787A1 - Method for monitoring the flow of intake fluid for an internal combustion engine, and engine for implementing said method

Info

Publication number: WO2011012787A1
Application number: PCT/FR2010/051199
Authority: WO
Inventors: Clément Dumand
Original assignee: Peugeot Citroën Automobiles SA
Priority date: 2009-07-31
Filing date: 2010-06-16
Publication date: 2011-02-03
Also published as: FR2948729B1; FR2948729A1

Abstract

The invention relates to a method for monitoring the flow of an intake fluid for an internal combustion engine comprising a combustion chamber (4) connected to at least one intake manifold (6) with a curved end portion (A) leading into the combustion chamber (4) through an intake opening (7), a bimetallic strip (13) that is deformable on the basis of the temperature thereof in order to divert the intake fluid and placed in the end portion (A) upstream from the intake opening (7), characterized in that the deformation of the bimetallic strip (13) is caused by the variation in the temperature thereof resulting from heat being supplied by burnt gases from the combustion chamber (4) and going back up into the intake manifold (6). The invention also relates to an engine for implementing said method.

Description

A method of controlling flow of an intake fluid for an internal combustion engine and engine for carrying out said method.

Technical field of the invention

The invention relates to internal combustion engines, and more particularly the control of the flow of air at the inlet.

Technological background

As the constraints on European and international standards on pollutant and greenhouse gas emissions become more and more severe, it is more important than ever to look for new ways to limit emissions at the source of internal combustion engines. . At the heart of this problem, the combustion system and its environment (aerodynamics, injection system ...) must meet new challenges in terms of efficiency and control.

In the case of internal combustion engines, this efficiency is strongly influenced by better control of the preparation of the mixture and the aerodynamic structures of the flow. Combustion, its tolerance to highly diluted or poor mixtures and the reduction of exhaust emissions are then directly related to the ability to control these processes.

To arrive at such results, it is known to generate a strong turbulence in the combustion chambers. In order to do this, a tumbling movement is created in the driving cylinder, the main axis of rotation of which is substantially perpendicular to that of the driving cylinder, or a so-called "swirl" swirling movement whose axis of rotation is substantially around the longitudinal axis of the engine cylinder.

Many devices have been proposed to create and / or intensify these swirling movements.

Among these devices, document JP59120718 discloses a "swirl" swirling motion control device for an internal combustion engine. The device comprises a bimetallic element or bimetallic disposed substantially flush along the end portion of an intake manifold, near an inlet opening into the combustion chamber of the engine. The control of the swirling motion is ensured by the deformation of the bimetallic element. In this device, the deformation is caused by passing an electric current through the bimetallic element in order to increase the temperature Joule effect and thus cause the expansion of the metal elements. However, such a device requires external control and causes additional energy expenditure for the electric heating of the bimetallic element.

The invention aims to overcome the disadvantages of the state of the prior art by providing a new admission fluid flow control process simpler to implement and more economical.

The subject of the present invention is a method for controlling the flow of an intake fluid for an internal combustion engine comprising a combustion chamber connected to at least one intake manifold with a curved end portion opening into the chamber of combustion. combustion by an inlet orifice, a bimetallic strip able to deform as a function of its temperature to deflect the intake fluid and disposed in the terminal portion upstream of the inlet orifice, characterized in that the deformation of the bimetal is caused by the variation of its temperature under the effect of a heat input provided by flue gases from the combustion chamber and up into the intake manifold. It has indeed appeared that the flue gases rising in the exhaust manifold, especially during the valve crossover phase, raised the temperature in the intake manifold and that this rise in temperature could be directly applied to the exhaust manifold. advantage to control the deformation of a bimetal in order to influence the intensity of the swirling basic movement printed by the geometric conformation of the intake manifold.

Preferably, for heavily loaded engine operating points, the bimetal is deformed so as to be substantially flush with the intake manifold to promote the filling of the combustion chamber. Indeed, it is necessary for heavily loaded points to maximize filling to achieve the target performance of the engine.

Preferably, for weakly loaded motor operating points, the bimetallic strip is deformed so as to mask part of the passage section of the tubing and cause a deviation of the intake fluid in said tubing. Indeed, it is necessary for weakly charged points to increase aerodynamics to accelerate combustion reduce consumption and emissions of pollutants. Moreover, the subject of the invention is also an internal combustion engine comprising at least one intake fluid intake manifold with a curved terminal portion opening into a combustion chamber through an intake orifice, the engine further comprising a bimetallic strip adapted to deform with respect to its temperature to deflect the intake fluid and disposed in the curved end portion and connected on the side of the bimetallic strip upstream of the flow of the intake fluid by means of fixing, characterized in that it comprises a thermal insulation disposed between the bimetallic strip and the intake manifold. In this way, by limiting heat exchange with the material of the tubing, the temperature of the bimetallic strip is essentially the result of the heat provided by the gases flowing in the intake manifold.

Furthermore, the engine according to the invention may comprise one or more of the following features: Preferably, the engine implements the method of the invention.

Preferably, the thermal insulation is maintained between the bimetallic strip and the tubing by the fixing means. Advantageously, the fastening means is in a thermally insulating material. In this way, a thermal bridge between the tubing and the bimetal is avoided.

Advantageously, the fastening means is a screw, for reasons of economy and technical simplicity.

Advantageously, the bimetal comprises an additional baffle disposed on the side of the bimetal placed downstream of the flow of the intake fluid. Indeed, this increases the deflection surface of the intake fluid and the effectiveness of the device.

Brief description of the drawings

Other features and advantages will appear on reading the following description of a particular embodiment, not limiting of the invention, with reference to the figures in which:

- Figure 1 is a schematic representation of an internal combustion engine with a bimetallic flow control device. FIG. 2 is a table presenting the average temperature in the intake manifold measured as a function of the engine speed and engine load conditions determined.

FIG. 3 is a table showing the average temperature in the intake manifold measured as a function of engine speed, engine load and EGR rate conditions.

- Figure 4 shows, in cross section, a bimetal implantation detail in the intake manifold, the bimetallic strip being straight for a mean temperature in the low intake manifold.

- Figure 5 shows, in cross section, a bimetal implantation detail in the intake manifold, the bimetal being bent for a mean temperature in the high intake manifold.

- Figure 6 is a table indicating an order of magnitude of the deflection of a bimetallic strip of 100 mm depending on the temperature of said bimetal, for two types of bimetallic strip.

- Figure 7 is a schematic representation of a bimetal variant which is joined at its free end an additional baffle.

FIG. 8 shows a first arrangement of a plurality of rectangular bimetallic strips

- Figure 9 shows a second arrangement of a plurality of substantially triangular bimetals.

detailed description

FIG. 1 shows an internal combustion engine comprising at least one cylinder 1 of longitudinal axis XX, closed at the top by a cylinder head 2. Inside this cylinder is housed a piston 3 which makes it possible to define a chamber 4 of combustion formed by the side wall of the cylinder 1, the portion of the yoke 2 facing the piston 3 and the upper part of said piston 3 and inside which is admitted a fluid to achieve the combustion of a mixture carbide. The engine also comprises intake means 5, generally carried by the cylinder head 2, which comprise at least one intake manifold 6 opening through an orifice 7 in the combustion chamber 4. At the orifice 7 is placed in in addition, inserted in the cylinder head 2, a valve seat 8 whose central bore corresponds to the orifice 7 and which is used with an intake valve of which only the general axis 9 is shown in FIG. 1 for reasons of clarity. The intake manifold 6 has a curved end portion A. This portion thus comprises a lower surface 10 close to the cylinder and an extrados 1 1 opposite the intrados. In addition, the engine is provided with exhaust means comprising at least one exhaust valve, of which only the general center line 12 is shown in FIG. 1 for reasons of clarity, which make it possible to evacuate the flue gases. contained in the combustion chamber 4.

The conformation curves the end portion A of the intake manifold 6 to introduce the intake fluid into the combustion chamber 4 in such a manner that the fluid has a circular motion about an axis of rotation YY which is substantially perpendicular to that XX of the engine cylinder. This swirling movement is better known by the term "tumble".

The fluid admitted into the combustion chamber 4 may as well be a supercharged or non-supercharged air introduced through the pipe 6 to be then mixed with a fuel that a fuel-based fuel mixture mixed with supercharged air or not, possibly added with recirculated flue gas.

In accordance with the invention, the intake manifold 6 carries, near its orifice 7, a bimetallic strip 13. The term "bimetallic strip" refers to an element consisting of two plates integrally bonded to one face. These two plates consist of materials having different thermal expansions. Thus, when the temperature of the bimetallic strip 13 increases, it bends on the side of the material having the smallest expansion. The bimetallic strip 13 is close to the orifice 7 in order to have a noticeable effect on the deflection of the flow. In the case of an internal combustion engine with gasoline and homogeneous combustion, this type of engine controls its intake air intake through a throttle arranged in the intake line, not shown here, upstream of the tubing 6 intake. This throttle creates a pressure drop that controls the amount of air admitted into the cylinder 1 at each engine cycle.

On low-load engine operating points, the throttle valve is closed to lower the pressure in the intake line and limit the amount of air in the engine. On the points of low load, the pressure in the intake line is lower than the atmospheric pressure and, a fortiori, lower than the pressure in the exhaust line. As an indication, the pressure in the intake line is then between 0.3 and 1 bar. On high-load engine operating points, the throttle is fully open and the pressures may even exceed atmospheric pressure if the engine is supercharged or acoustically adapted. Such a gasoline internal combustion engine is further characterized by a so-called valve crossing phase, that is to say that it is a few moments during an exhaust phase of the engine cycle during which the intake and exhaust valves are open simultaneously. This valve crossover phase promotes flue gas scavenging at the end of the exhaust for the busiest operating points. This crossing phase also induces a return flow (generally referred to by the English expression of "back flow") of the flue gases in the intake manifold 6 for the points of low load where the pressure at the intake is less than the pressure prevailing in the combustion chamber 4. These hot burnt gases return to the intake manifold as long as the valves cross, and are readmitted when the exhaust valve closes.

One-dimensional calculations calibrated on tests carried out on a single-cylinder gasoline engine have shown that this phenomenon of return of gases burns during the valve crossover phase induces a rise in the average temperature in the intake manifold 6 because there is has a coming and going of burnt gas before admission of fresh air.

FIG. 2 shows the average temperature measured in the intake manifold 6 as a function of the engine speed N, expressed in rpm, and the engine load C, conventionally represented by the PMI (mean indicated pressure) expressed in bar.

It appears that this rise in temperature is several tens of degrees on average on low load points. As an example taken from Figure 2, the temperature rise is 50 ⁰ C between a first engine operating point at 5 bar PMI and a second point 2.8 PMI bar, at 2000 rev / min. At higher load, the temperature rise is lower as shown in the figure where the temperature rise is only δ'O between a first operating point at 20 bar of PMI and a second point at 15 bar of PMI. , at 2000 rpm. In a variant not shown where the engine further comprises a burnt gas recirculation device or EGR (for the acronym for the Exhaust Gas Exhaust Gas Expression), a portion of exhaust gases exhausted exhaust being taken to be reinjected on admission, it is noted that, as shown in Figure 3, the addition of EGR gas tends to reduce the average temperature in the intake manifold. Indeed, the addition of EGR gas tends to limit the opening of the throttle and increases the intake pressure. This increase in intake pressure reduces the "backflow" of the flue gas during the crossing of the valves and thereby reduces the average temperature in the intake manifold 6. Thus, for example, an operating point at 2000 rpm and at a constant PMI of 2.8 bar is observed to reduce by 30 ^° C. for a change from a zero gas-to-gas ratio at a rate of 20%. Thus, a correlation is found between the average temperature in the intake manifold 6 and the engine load. Indeed, as the load increases, the inlet pressure increases, the return flow of hot burned gas decreases, and therefore, the average temperature in the intake manifold 6 decreases. In addition, there is a correlation between engine load and aerodynamic requirements: on low load points, there is a need to increase aerodynamics to accelerate combustion, while on high load points it is necessary to necessary to maximize filling to achieve engine performance. It then appeared that this correlation between the average temperature in the intake manifold 6, the engine load and the associated aerodynamic requirements is an opportunity to provide a judicious, simple and effective means adapted to automatically adapt the aerodynamics of the engine. flow of the intake fluid into the cylinder 1 at the engine operating point.

Figures 4 and 5 show schematically a detail of the implantation of the bimetallic strip 13 in the intake manifold 6 on the side of the intrados 10 of said manifold. The bimetal 13 is formed of a first plate 14 integrally bonded to a second plate 15. The two plates 14, 15 are made of materials having different thermal expansions, the material of the first plate 14 having a thermal expansion less than that of the material of the second plate 15. The intake fluid flowing in the direction of the arrow F to the combustion chamber 4, the bimetallic strip 13 is fixed to the intake pipe 6 by a fixing means 16, such that a screw as shown schematically in Figure 4 or Figure 5, the side placed upstream of the flow, its side placed downstream of the flow remaining free. Thus the deformation of the bimetal 13 is caused by the variation of its temperature under the effect of a heat input provided by flue gases from the combustion chamber 4 and up in the intake manifold 6. Advantageously, for weakly loaded operating points, that is to say when the average temperature in the intake manifold is high (FIG. 5), bimetallic strip 13 is deformed so as to mask part of the passage section. of the tubing and causing a deviation of the intake fluid in said tubing. More specifically, the bimetallic strip 13 is implanted so as to orient the intake fluid towards the extrados 1 1 of the tubing 6,

For heavily loaded engine operating points (Figure 4), ie when the average temperature in the intake manifold is lower, and so as not to impede the flow by creating a pressure drop, the bimetallic strip 13 must preferably respect the shape of the intake manifold 6 and is deformed so as to be substantially flush with said manifold. This promotes the filling of combustion chamber 4. For this purpose, it is expected that bimetallic 13 is disposed in a housing 23 provided in the intake manifold 6 (Figure 4). Furthermore, the inlet pipe 6 is generally part of the cylinder head 2 which is itself cooled by a circulation of coolant. However, the bimetallic strip 13 must be essentially sensitive to the average temperature of the intake fluid in the intake manifold 6. In order to thermally isolate the bimetallic strip 13 from conductive cooling from the wall of the intake manifold 6, preferably a thermal insulator 17 is provided between the inlet manifold 6 and the bimetallic strip 13.

The thermal insulation may be a thin element such as a flat plastic washer.

For reasons of simplicity of assembly, the thermal insulation 17 is preferably maintained between the bimetallic strip 13 and the tubing 6 by the fixing means 16. In the embodiment illustrated in FIGS. 4 and 5, the thermal insulator 17 is crossed by the fixing means 16.

Preferably the fixing means is a fixing screw. Other fastening means may also be envisaged such as a rivet, a glue, a weld spot, etc.). Advantageously, the fixing means 16 is in a thermally insulating material such as a plastic, polymer or composite resistant to temperatures of the order of 200 to 300 ^° C. The heat exchange between bimetal 13 and the intake manifold 6.

As regards the mounting and fixing of the bimetallic strip 13 on the intake manifold 6, provision may be made to drill into the intake manifold 6 or to leave a foundry hole to allow the passage and positioning of the bimetallic strip. 13 and its thermal insulation 17, as well as securing to the pipe by the fastening means 16, then to close this building hole after mounting the bimetal 13.

The main advantages of the invention is that the bimetal is a reliable and robust mechanical member that acts as both controller, actuator and functional element. There exists for the constitution of a bimetal a great diversity of materials such as metals or alloys with a wide choice in the thermal expansion characteristics.

By way of non-exhaustive example of embodiment, the material of the first plate 14 may be a 36% nickel iron alloy or a 42% nickel iron alloy of chemical composition FeNi ₃₆ or FeNi ₄₂ , known for have a low coefficient of expansion. The material of the second plate 15 may be an alloy of chemical composition MnCui ₈ Nii ₀ or FeNi ₂₀ Mn ₆ having a coefficient of thermal expansion greater than the material of the first plate 14.

In FIG. 6 is presented a first curve 18 indicating the deflection D of a bimetallic strip consisting of a pair FeNi ₃₆ / MnCUi ₈ Ni ₁₀ as a function of the temperature of the bimetal. A second curve 19 indicates the deflection A of a bimetallic strip made up of a FeNi ₃₆ / Fe Ni ₂₀ Mn ₆ pair. The deflection D is given here for an arbitrary length of bimetallic strip of 10 cm, unrealistic length in the case of an implantation in an intake manifold, but which nevertheless makes it possible to show through these two examples that the bimetallic strips have a range of linearity in a temperature range up to 300 'which is compatible, as shown in Figures 3 and 4 with the temperature range seen in an intake manifold.

In a variant not shown, the deflection of the bimetallic strip 13 can be limited by only partially covering the second plate 15 by the first plate 14. embodiment part of the free side of the bimetal 13 does not include a plate 14. The portion of the second plate not covered by the first plate 14 will not deform under the effect of temperature and then remains straight. In another embodiment illustrated in FIG. 7, an additional deflector 20 is advantageously disposed on the side of the bimetallic strip 13 placed downstream of the flow of the intake fluid, that is to say at the free end of the bimetallic strip 13 in order to improve the deflection efficiency of the intake fluid by increasing the deflection surface. The additional deflector 20 is provided curved so as to marry the shape of the intake manifold 6 when the bimetallic strip 13 is rectilinear.

In another embodiment, illustrated in FIG. 8, the deflection of the intake fluid is achieved by the cooperation of a plurality of bimetals. FIG. 8 shows a first arrangement of rectangular bimetallic strips 21. In a high load position, indicated by the reference PC, because of the low temperature in the intake manifold, the bimetallic strips 21 are substantially rectilinear and do not interfere with the passage of the intake fluid to allow optimized filling of the cylinder 1. In the low load position, indicated by the reference FC, due to the elevation of the temperature in the intake manifold, the bimetallic strips 21 bend and overlap to block a portion of the passage section of the intake manifold and thus divert the intake fluid in the direction of the upper surface 1 1 so as to contribute to intensify the swirling movement of "tumble" in the cylinder 1. This overlapping arrangement has the advantage of ensuring the deflection of the entire intake fluid to the unobstructed portion of the intake manifold 6.

FIG. 9 shows a second arrangement of substantially triangular bimetallic strips 22. This second arrangement differs from the previous arrangement in that in the low load position FC, because of the high temperature in the intake manifold, the bimetallic strips 21 are curved to allow to block a portion of the passage section of the intake manifold but do not overlap. This non-overlapping arrangement has the additional advantage over the previous arrangement of avoiding providing at the design a folding order of each of the bimetals.

In a variant not shown, the engine being designed with two intake manifolds shaped to generate a basic swirling movement of type

"Swirl", bimetallic strips are arranged in only one of the two pipes, so as to completely or partially obscure the passage of the intake fluid in said tubing during the backflow of the burnt gases to the inlet, so as to force the passage of the intake fluid preferentially to the unobstructed tubing and to promote the appearance of a "swirl" movement for the low load engine operating points. The invention is not limited either to the gasoline engine with homogeneous combustion, in fact, it can be applied to gasoline and diesel stratified engines (or the homogeneous diesel engine and other engines CNG, etc.).

Using this invention, the usual compromise on the choice of the intake manifold geometry between a geometry favoring low load aerodynamics and a geometry favoring high load filling is no longer necessary. Indeed the intake manifold 6 may be provided at the design with a geometry favoring the filling with high load and the invention will provide the required vortex level of motion at low load.

Claims

claims

1. A method of controlling flow of an intake fluid for an internal combustion engine having a combustion chamber (4) connected to at least one intake manifold (6) with a curved end portion (A) opening into the combustion chamber combustion chamber (4) by an inlet orifice (7), a bimetallic strip (13) able to deform as a function of its temperature to deflect the intake fluid and disposed in the terminal portion (A) upstream of the inlet orifice (7), characterized in that the deformation of the bimetallic strip (13) is caused by the variation of its temperature under the effect of an input of heat supplied by flue gases from the combustion chamber ( 4) and up into the intake manifold (6).

Flow control method according to claim 1, characterized in that for heavily loaded motor operating points, the bimetallic strip (13) is deformed so as to be substantially flush with the intake manifold (6) to favor filling the combustion chamber (4).

Flow control method according to Claim 1 or Claim 2, characterized in that for weakly loaded motor operating points, the bimetallic strip (13) is deformed so as to mask a portion of the passage section of the tubing (6) and cause a deviation of the intake fluid in said tubing.

4. Internal combustion engine comprising at least one inlet fluid admission pipe (6) with a curved end portion (A) opening into a combustion chamber (4) via an inlet orifice (7). , the motor further comprising a bimetallic strip (13) adapted to deform as a function of its temperature to deflect the intake fluid and disposed in the curved end portion (A) and connected on the side of the bimetallic strip (13) placed upstream of the flow of the intake fluid by a fixing means (16), characterized in that it comprises a thermal insulator (17) disposed between the bimetallic strip (13) and the inlet pipe (6).

5. Internal combustion engine according to claim 4, characterized in that it implements the method according to any one of claims 1 to 3.

6. Internal combustion engine according to claim 4 or claim 5, characterized in that the thermal insulation (17) is maintained between the bimetallic strip (13) and the tubing (6) by the fixing means (16).

7. Internal combustion engine according to any one of claims 4 to 6, characterized in that the fastening means (16) is in a thermally insulating material.

8. Internal combustion engine according to any one of claims 4 to 7, characterized in that the fastening means (16) is a screw.

9. Internal combustion engine according to any one of claims 4 to 8, characterized in that the bimetal (13) comprises an additional baffle (20) disposed on the side of the bimetallic strip (13) placed downstream of the fluid flow. intake.