Patent Publication Number: US-9845775-B2

Title: Intake assembly for an internal combustion engine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to European Patent Application No. 11186880.8 filed on Oct. 27, 2011 and European Patent Application No. 12180110.4 filed on Aug. 10, 2012, the entire disclosures of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present description relates to an intake assembly for an internal-combustion engine with controlled ignition comprising a plurality of cylinders, wherein the intake assembly comprises an intake duct for each cylinder of the internal-combustion engine and an airbox defining a volume with which each intake duct is in fluid communication. 
     GENERAL TECHNICAL PROBLEM 
     In internal-combustion engines in which air is supplied by natural induction, i.e., without the aid of a supercharging assembly, it is common practice to resort to “tuning” of the intake ducts in order to maximize the volumetric efficiency of the engine in a particular r.p.m. range, chosen according to the use for which the engine has been designed. 
     As is known to the person skilled in the branch, the term “tuning” is meant to indicate the choice of the geometry, in particular of the length and of the section of the ducts of the intake system in such a way that the pressure waves generated by the intake of fluid into the cylinders of the internal-combustion engine propagate within the intake assembly, enabling an increase of filling of the cylinders themselves (there is substantially obtained a sort of “natural supercharging”). 
     In other words, the frequency of the pulses of the pressure waves that are generated in the intake system, which depends—among other things—upon the r.p.m. of the internal-combustion engine, is exploited as reference for the choice of the length of the ducts so as to have, at the moment of intake, a pressure wave that travels towards the cylinder, compressing the fluid at inlet to the cylinder itself. In this way, the mass of air that enters the cylinder is greater, a condition similar to what arises (of course for different reasons) with the action of a supercharging assembly on supercharged engines. 
     Usually, in the case where it is desired to increase the volumetric efficiency of the engine (hence the torque supplied) at high r.p.m., intake ducts of reduced length are used, whereas, in the case where it is desired to have a higher torque at low r.p.m., longer intake ducts are used. 
     The latter choice is preferred on cars that, owing to their characteristics and their purposes of use, envisage an operation of the engine in the medium-to-low r.p.m. range (i.e., a fair share of the cars with natural-induction engine in circulation, with the exception, for example, of higher-performance models of cars). 
       FIG. 1  is a schematic illustration of an intake assembly  1  of a known type coupled to an internal-combustion engine  2 , comprising a plurality of cylinders CY. It should be noted that in this embodiment the internal-combustion engine  2  comprises two cylinders CY (here represented by way of example with cylinder head having four valves per cylinder), but it remains understood that the present description applies to any engine, regardless of the number of cylinders and the number of intake and exhaust valves. 
     The intake assembly  1  comprises, for each cylinder CY of the internal-combustion engine  2 , an intake duct  4  in fluid communication with (and connected to) an airbox  6 . Moreover installed on the airbox  6  is a throttle body  8  including a throttle valve  10 . The throttle body  8  is in fluid communication with the external environment by means of an intake line  12  on which a filter element  14  is installed, which is in turn connected to an intake mouth  16  of the internal-combustion engine  2 . As is known to the person skilled in the branch, the intake assembly  1  is coupled to the internal-combustion engine  2  in such a way that each intake duct  4  is in fluid communication with the corresponding cylinder CY. The airbox  6  and the filter element  14  introduce two localized capacities within the intake assembly  1 . 
     During operation of the internal-combustion engine  2 , the air is taken in through the intake mouth  16 , traverses the filter element  14 , the intake line  12 , and the throttle body  8 , to reach the airbox  6 , from which it can be sent on towards the ducts  4 . By regulating the position of the throttle valve  10  it is possible, as is known, to regulate the amount of air taken in by the engine  2 . 
     The position of the airbox  6  downstream of the throttle body  8  varies tuning of the intake assembly  1 . 
     In fact, to obtain a good tuning effect it is necessary for one end of the intake duct (in this case the duct  4 ) to present an expansion (in this case the airbox  6 ) that is sufficiently large to determine a decoupling with the circuit upstream of the duct, with the consequent reflection of the resonant waves in the duct itself. 
     In a traditional system like the one represented in  FIG. 1 , the volume of the airbox  6  cannot be increased sufficiently to enable a satisfactory decoupling in so far as by so doing the volume of fluid “under throttle” (i.e., the volume of fluid comprised between the throttle body and the intake valves) would be too large, with the consequent unacceptable slowness in the dynamics of control of the air at inlet to the engine. 
     It follows that the system has a weak tuning for the frequency corresponding to the resonance frequency of the ducts  4 , on account of the contained volume of the airbox  6 , but at the same time also has a weak tuning at the resonance frequency of the entire system up to expansion of the filter element  14  in so far as the volume of the airbox  6  has acted as decoupling element. 
     This is an evidently undesirable effect since the design effort for the development of intake ducts is in part nullified by a reduction of the volumetric efficiency of the internal-combustion engine  2 , and hence of the torque supplied. 
     Any one of the documents Nos. U.S. Pat. No. 5,181,491 A and EP 1 808 595 A2 shows an intake assembly according to the preamble of Claim  1 , i.e., in which said airbox is in fluid communication with the external environment by means of an intake mouth and includes, inside it, a filtering element designed for filtering a flow of fluid taken in by the internal-combustion engine, each of said intake ducts being in fluid communication with said airbox by means of a respective throttle body including a throttle valve, operable for adjusting a flow of fluid taken in by the internal-combustion engine. 
     OBJECT OF THE INVENTION 
     The object of the invention is to overcome the technical problems described previously. 
     In particular, the object of the invention is to provide an intake assembly for an internal-combustion engine that will enhance tuning of the intake ducts, by increasing the volumetric efficiency, and that at the same time will enable a simple and efficient control of the engine operating conditions. 
     SUMMARY OF THE INVENTION 
     The object of the invention is achieved by an intake assembly for an internal-combustion engine having the characteristics forming the subject of the ensuing claims, which form an integral part of the technical teaching provided herein in relation to the invention. 
     In particular, the object of the invention is achieved by an intake assembly of the type indicated above, in which the intake assembly comprises one intake duct for each cylinder of the internal-combustion engine, and an airbox defining a volume with which each intake duct is in fluid communication, said airbox being in fluid communication with the external environment by means of an intake mouth, and comprising, inside it, a filter element designed for filtering a flow of fluid taken in by the internal-combustion engine, each of the intake ducts being in fluid communication with the airbox by means of a respective throttle body including a throttle valve operable for regulating a flow rate of fluid taken in by the internal-combustion engine, 
     said intake assembly being characterized in that it includes: 
     a monitoring channel that connects said intake ducts together, configured for perturbing in a negligible way the dynamics of the fluid inside the intake ducts, and 
     pressure and temperature sensor means associated to said monitoring duct for monitoring the pressure and temperature inside said monitoring duct and consequently designed to send signals indicating the values of pressure and temperature of the fluid taken in by the engine to an electronic control unit. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The invention will now be described with reference to the annexed figures, which are provided purely by way of non-limiting example and in which: 
         FIG. 1 , which has been described previously, is a schematic view of an intake assembly of a known type, coupled to an internal-combustion engine; 
         FIG. 2  is a schematic view of an embodiment not forming part of the present invention, but the description of which is in any case useful for an understanding of the invention; 
         FIG. 3  is a perspective view of a further embodiment of the intake assembly of  FIG. 2 , which does not form part of the invention either; 
         FIG. 4  is a cross-sectional view along the line of trace IV-IV of the intake assembly of  FIG. 3  coupled to an internal-combustion engine, which is also sectioned and with some components removed for reasons of clarity; 
         FIG. 5  is an enlarged schematic view corresponding to that of  FIG. 2  but illustrating a functional assembly according to an advantageous aspect of the present invention; and 
         FIGS. 6 and 7  are a perspective view and a partially sectioned perspective view of a further embodiment according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In  FIG. 2 , the reference number  100  designates an intake assembly according to various embodiments of the invention. Any components that may have already been identified in the foregoing description will be designated by the same reference numbers. 
     The intake assembly  100  can be coupled to the internal-combustion engine  2  and comprises, for each cylinder CY, an intake duct  104  in fluid communication with an airbox  106  by means of a throttle body  108 . Each throttle body  108  comprises inside it a throttle valve  110 . 
     Housed within the airbox  106  is a filter element  114 , and an intake mouth  116  provided on the airbox  106  is directly in view of the aforesaid filter element  114  and is set upstream thereof and in fluid communication therewith. The intake mouth  116  may possibly be provided by means of a short stretch of duct coming under the airbox  106 . 
     With reference to  FIGS. 3, 4 , in a preferred embodiment of the intake assembly  1 , the airbox  106  develops with a substantially L-shaped geometry that bestows on it a substantially two-volume structure. More precisely, the airbox  106  comprises:
         a first volume  1060 , coming under which are the intake ducts  104  by means of the throttle bodies  108 , and which develops substantially in a direction parallel to the array of the intake ducts  104 ; and   a second volume  1061 , which has an orientation substantially transverse with respect to the first volume  1060  and a smaller extension, and housed within which is the filter element  114 ; the intake mouth  106  is in fluid communication with the second volume  1061 .       

     In any case, the solution presented in  FIGS. 3, 4  is to be assumed as one of the possible examples. Generalizing, the airbox  106  (which, as has been said, according to the present invention, has also function of box for housing the filter element), can assume various shapes according to the overall dimensions available and must be in any case characterized in that the two volumes (one upstream and one downstream of the filter element) behave fluid-dynamically as a single large volume. 
     Giving out on the airbox  106 , as described, are the two throttle bodies, which can be actuated by a single command synchronously and from which there branch off the two—in this embodiment—mutually independent intake ducts  104 . It should moreover be noted that, functionally, each ensemble comprising an intake duct  104  and the respective throttle body  108  in turn defines an independent intake manifold so that, in the embodiment illustrated by way of example herein, two independent intake manifolds are present. 
     With reference to  FIG. 4 , in this embodiment, the intake ducts  104  are substantially “C”-shaped and are fixed—at a first end—to a cylinder head  200  of the internal-combustion engine  2  so as to connect up with further stretches of intake duct provided in the cylinder head of the internal-combustion engine, as is known to the person skilled in the branch. 
     The curved shape of the intake ducts  104  is such that they substantially embrace part of the cylinder head  200  of the internal-combustion engine  2 . A second end of each intake duct  104  is fixed to a corresponding throttle body  108 , which is in turn fixed to the airbox  108  and is in fluid communication therewith. Each throttle body is here configured as a stretch of cylindrical duct, set within which is the throttle valve  110  and which is designed to set up a fluid communication between the ducts  104  and the airbox  106 . The latter is designed to be fixed on the top of the cylinder head  200  of the internal-combustion engine  2  by means of screws entering holes  118  that traverse the airbox  106  and engaging in the cylinder head  200 . 
     It should be noted, in any case, that the arrangement of the airbox  106  illustrated in  FIGS. 3 and 4 , where the filter element  114  is set above the engine, is not in any case a binding element in so far as the teaching of the present invention can be applied also to the case where the filter box is arranged on board the body. 
     Operation of the intake assembly  100  is described in what follows. 
     During operation of the internal-combustion engine  2  a flow of air is taken in through the intake mouth  116 , is filtered by the filter element  114 , and enters the airbox  106 . 
     From the airbox  106  the air is sent on towards the intake ducts  104  through the throttle valves  110  of each throttle body  108 , and then proceeds towards the cylinders CY of the internal-combustion engine  2 . 
     Regulation of the flow rate taken in occurs, given the arrangement of the throttle bodies  108  (and hence of the throttle valves  110 ), downstream of the airbox  106 . 
     Arrangement of the throttle valves  110  fluid-dynamically downstream of the airbox  106  enables amplification of the effect of the pressure waves that are set up within the intake assembly  100 , enhancing tuning of the ducts  104  and improving the volumetric efficiency of the internal-combustion engine. 
     This occurs since the section of the intake assembly  100  within which reflection of the pressure waves takes place is the one basically comprised between the facing section between the duct  104  and the filter box  106  in the area of the throttle valve  110  and the one or more intake valves associated to each cylinder CY, downstream of the corresponding intake duct  104 . It should be noted that the ends are the same also in the case of the intake assembly  1 , but in the intake assembly  100  the path no longer comprises the airbox. 
     This means that the reflection of the pressure waves is not conditioned by the presence of the localized capacity represented by the volume of the airbox, as instead occurs in the intake assembly  1  and moreover the desired amplitude of the pressure waves is greater thanks to the large volume of expansion guaranteed by the filter box. 
     The result is an increase of the volumetric efficiency and of the torque supplied by the internal-combustion engine. The inventors have found experimentally that said increase is in the region of 3-8% as compared to the same engine equipped with a traditional intake assembly, for example the assembly  1 . 
     According to an advantageous aspect of the present invention, the throttle valves  110  of the throttle bodies  108  can be connected mechanically and actuated by means of a common actuator device, for example a single electric motor, in order to reduce the costs of production of the intake assembly  100 . 
     Of course, in the case where the requirements were different, it is possible to actuate independently each throttle valve  110 . 
     Moreover, with reference to  FIG. 5 , according to a further advantageous aspect of the invention, the intake assembly  100  is provided with monitoring channels  120  that connect adjacent pairs of intake ducts  104 . In this embodiment, where the number of cylinders CY is equal to two, the two ducts  104  are connected by a single monitoring channel  120 . 
     In the field of management of the internal-combustion engine  2 , there is the need to know the values of pressure and temperature of the fluid entering the engine. In the perspective of reduction of the costs, it is conveniently possible to install a pressure sensor PS and a temperature sensor TS on the monitoring channel  120 . In this way, by saving on the set of sensors provided on board the internal-combustion engine  2  and perturbing in a way altogether negligible the dynamics of the fluid within the intake ducts  104 , it is possible to know the values of pressure and temperature P, T of the fluid taken in and send them on to an electronic control unit of the engine  2 . Alternatively, the pressure sensor can be located in the monitoring duct  120 , whereas the temperature sensor can be located in the airbox  106 , in an area adjacent to the intake ducts  104 . 
       FIGS. 6 and 7  show a further embodiment of the assembly according to the invention, illustrated only schematically in  FIG. 5 . In said figures, the parts that are in common or correspond to those of  FIG. 5  are designated by the same reference numbers. 
     Also the intake assembly  100  of  FIGS. 6 and 7  is pre-arranged for a two-cylinder four-stroke engine. Also in this case, a monitoring duct  120  is provided, which in the specific case is obtained with a flexible pipe (not illustrated) having its ends inserted in a fluid-tight way within corresponding holes  104   a  (just one of which is visible, sectioned, in  FIG. 7 ) made in the walls of the ducts  104 . 
     As described above, the duct  120  is configured for perturbing in an altogether negligible way the dynamics of the fluid inside the intake ducts  104 , so that the pressure sensor PS (not visible in  FIGS. 6, 7 ) and possibly the temperature sensor TS (not visible in  FIGS. 6, 7  either) that are associated to the monitoring duct  120 , in a way similar to what is illustrated in  FIG. 5 , are able to monitor the pressure and temperature within said monitoring duct and consequently to send signals indicating the values of pressure and temperature P, T of the fluid taken in by the engine to an electronic control unit. Since, as has been said, the monitoring duct  120  perturbs only in a negligible way the flows within the intake ducts  104 , within the monitoring duct  120  there is a substantially zero flowrate of fluid. Consequently, the value of pressure within said duct is practically identical to the value of pressure within the intake ducts. As indicated, in the monitoring duct  120  there may be provided also a temperature sensor TS, but alternatively it is envisaged to position the sensor TS within the airbox  106 , in an area adjacent to the intake ducts  104 . The temperature and pressure sensors necessary for monitoring the engine operating conditions can thus be associated to the duct  120  and/or to the airbox  106  instead of being set inside the engine or inside the intake ducts  104 , with consequent simplification of the structure of the engine and of the assembly operations. 
     In the case of the concrete embodiment that is illustrated in  FIGS. 6 and 7 , it has been found that to obtain said condition it is necessary for the diameter of the monitoring duct  120  not to be greater than 1/10 of the diameter of each intake duct  104 . 
     With reference once again to  FIGS. 6, 7 , in this case the airbox  100  has a hollow body, with a major plane surface  100   a  and a minor plane surface  100   b . The filtering element  114  has an independent casing  114   a  received in a seat of said hollow body of the airbox  100  and having a major surface and a minor surface, both of which are plane and are set substantially flush with the major and minor surfaces  100   a ,  100   b  of the body of the airbox  100 . 
     Once again with reference to  FIGS. 6 and 7 , the two intake ducts have stretches  104  set downstream of the respective throttle bodies  108 , which form part of a single body of plastic material  1104  and have curved conformations identical to one another that extend for an arc of approximately 90°. The two ducts  104  are parallel and set at a distance apart and have their walls rigidly connected together at the ends. 
     The throttle bodies  108  form part of a single assembly  1108 , made of metal or plastic material, set between the aforesaid downstream stretches  104  of the two intake ducts and upstream stretches  104 ′ that come out of the bottom wall  100   b  of the airbox  100 . As is clearly visible in  FIG. 7 , the aforesaid stretches  104 ′ of the intake ducts that are set upstream of the throttle bodies  108  project within the airbox. In the example illustrated, also the upstream stretches  104 ′ of the intake ducts have identical curved conformations that extend for an arc of approximately 90°, in such a way that one end of said ducts comes out vertically from the bottom wall of the airbox  100 , whereas the opposite end extends horizontally within the airbox  100 . Also said upstream stretches  104 ′ of the intake ducts form part of a single body  1104 ′ of plastic material. 
       FIGS. 6, 7  also show the fuel injectors I associated to the two ducts  104  and the corresponding supply rail R. 
     Of course, the details of construction and the embodiments may vary widely with respect to what has been described and illustrated herein, without thereby departing from the sphere of protection of the present invention, as defined by the annexed claims.