EP2587043A1

EP2587043A1 - An intake assembly for an internal combustion engin

Info

Publication number: EP2587043A1
Application number: EP11186880.8A
Authority: EP
Inventors: Marco Cuniberti; Francesco Vattaneo; Caterina Venezia
Original assignee: Centro Ricerche Fiat SCpA
Current assignee: Centro Ricerche Fiat SCpA
Priority date: 2011-10-27
Filing date: 2011-10-27
Publication date: 2013-05-01

Abstract

An intake assembly (100) for an internal-combustion engine (2) comprising a plurality of cylinders (CY), wherein the intake assembly comprises an intake duct (104) for each cylinder (CY) of the internal-combustion engine and an airbox (106) defining a volume with which each intake duct (104) is in fluid communication.

In addition, in the intake assembly (100):
- the airbox (106) is in fluid communication with the external environment by means of an intake mouth (116);
- the airbox (106) comprises, inside it, a filter element (114) designed for filtering a flow of fluid taken in by the internal-combustion engine (2); and
- each of the intake ducts (104) is in fluid communication with the airbox (106) by means of a respective throttle body (108) including a throttle valve (110) operable for regulating a flow rate of fluid taken in by the internal-combustion engine (2).

Description

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).
Figure 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 Figure 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.

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.

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 having all the characteristics listed at the start of the present description and further characterized in that:

the airbox is in fluid communication with the external environment by means of an intake mouth;
the airbox comprises, inside it, a filter element designed for filtering a flow of fluid taken in by the internal-combustion engine; and
each of the intake ducts is 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.

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:

Figure 1, which has been described previously, is a schematic view of an intake assembly of a known type, coupled to an internal-combustion engine;
Figure 2 is a schematic view of an intake assembly according to the present invention and coupled to an internal-combustion engine;
Figure 3 is a perspective view of a preferred embodiment of the intake assembly of Figure 2;
Figure 4 is a cross-sectional view along the line of trace IV-IV of the intake assembly of Figure 3 coupled to an internal-combustion engine, which is also sectioned and with some components removed for reasons of clarity; and
Figure 5 is an enlarged schematic view corresponding to that of Figure 2 but illustrating a functional assembly according to an advantageous aspect of the present invention.

Detailed description of the invention

In Figure 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 Figures 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 Figures 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 Figure 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 Figures 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 Figure 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, a single monitoring channel 120 is provided.
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.
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.

Claims

An intake assembly (100) for an internal-combustion engine (2) comprising a plurality of cylinders (CY), wherein the intake assembly comprises an intake duct (104) for each cylinder (CY) of the internal-combustion engine and an airbox (106) defining a volume with which each intake duct (104) is in fluid communication, the intake assembly (100) being characterized in that:
- said airbox (106) is in fluid communication with the external environment by means of an intake mouth (116);

- said airbox (106) comprises, inside it, a filter element (114) designed for filtering a flow of fluid taken in by the internal-combustion engine (2); and

- each of said intake ducts (104) is in fluid communication with said airbox (106) by means of a respective throttle body (108) including a throttle valve (110) operable for regulating a flow rate of fluid taken in by the internal-combustion engine (2).
The intake assembly (100) according to Claim 1, characterized in that it comprises a monitoring channel (120) fluid-dynamically connecting a pair of adjacent intake ducts (104) on which pressure-sensor means (PS) and temperature-sensor means (TS) are installed.
The intake assembly (100) according to any one of the preceding claims, characterized in that the throttle valves (110) of each of the throttle bodies (108) are mechanically connected and operable by means of a common actuator device.
The intake assembly (100) according to any one of the preceding claims, characterized in that it comprises two independent intake manifolds, each comprising an intake duct (104) and the respective throttle body (108) thereof.
The intake assembly (100) according to any one of the preceding claims, characterized in that said airbox (106) is substantially L-shaped and comprises:
- a first volume (1060), which develops parallel to an array of intake ducts (104) and connected to which are said throttle bodies (108); and

- a second volume (1061), housed within which is said filter element (114), said second volume (1061) being substantially orthogonal to said first volume (1060).
The intake assembly (100) according to Claim 5, characterized in that said first volume (1060) is traversed by holes (118) designed to house elements for fixing said airbox (100) to said internal-combustion engine (2).