US3664316A - Device for adjusting the idling in an internal combustion engine - Google Patents

Abstract

The regulation of the idle speed of an internal combustion engine under no-load conditions is effected by a compensating chamber which communicates with the intake ducts of the several cylinders of the engine. Manual adjustment means (such as a screw) is used to adjust the flow passage area in the small ducts until a satisfactory adjustment is achieved.

Description

United States Patent Garcea [54] DEVICE FOR ADJUSTING THE IDLING IN AN INTERNAL COMBUSTION ENGINE Inventor: Giampaolo Garcea, Milan, Italy Assignee: Alia Romero S.p.A., Milan, Italy Filed: July 8, 1970 Appl. No.: 53,217

Foreign Application Priority Data July 15, 1969 Italy ..19,672 N69 US. Cl. ..l23/l24 R, 123/52 M, 123/127, 123/199 D, 123/139 AW, 123/119 DB Int. Cl ..F02m 23/04, FOZm 13/04 Field ofSearch ..123/119 D, 119 DB, 124, 127, 123/52 B, 52 M, 139 AW 51 May 23,1972

Primary Examiner-Wendell E. Burns Attorney-Holman & Stern ABSIRACT The regulation of the idle speed of an internal combustion engine under no-load conditions is effected by a compensating chamber which communicates with the intake ducts of the several cylinders of the engine. Manual adjustment means (such as a screw) is used to adjust the flow passage area in the small ducts until a satisfactory adjustment is achieved 5 Clains, 4 Drawing Figures the engine idle operation is experienced. The remaining and less considerable fraction of the pressure drop aforesaid is experienced in correspondence with the adjustable restricted port. It is only this latter remaining fraction of the pressure drop which draws into the cavity through the other small ducts, the mixture (or air) contained in the sections of the ducts of the other cylinders which is provided between the closed throttles and the intake valves which, for the other cylinders, are temporarily closed. From these duct sections, which can be considered as closed spaces having a constant volume, the fluid emerges as drawn by the aforementioned fraction of the overall pressure drop and flows into the common cavity only until such time as the pressure in the duct section equals the pressure in the cavity.

If the volume of fluid which thus leaves the section of the intake duct of the other cylinders is less than the internal volume of the small duct, and if the latter is so shaped that the fluid emerging from the duct sections of the other cylinders pushed before it the fluid which was present in the small duct without being admixed therewith, one can realize, as has been obtained, that only the fluid contained in the small duct enters the common capacity, It is thus avoided that the fluid which was contained in the closed portion of the intake duct, a fluid which was polluted by the reflown gases during the preceding cycles of the other cylinders, may enter the common capacity thus giving rise to irregular operation. In the capacity, only that fluid enters, which was contained in the small duct, a fluid which is formed by a non polluted mixture (or air) entered at the end of the preceding induction stroke of the corresponding cyclinder.

Another feature of the present device consists in that the degree of closure of the throttles of the several cylinders is such that the rate of flow of the mixture (or air) which flows through the passageway as confined by the peripheral edge of the closed throttle and by the internal cylindrical wall of the duct is a fraction, of less than percent, of the overall feed rate of flow of the cylinder. The remaining fraction of the rate of flow obviously flows through the restricted ports having a fixed and variable calibration which are arranged serially with respect to one another and in parallel with respect to the throttle. With a rate of flow in correspondence with the throttle, thus limited as above set forth, possible, even'discrete, variations due to misalignments of the throttles or deposits on the throttles, (which are somewhat different according to the throttle) a difference in feeding to the several cylinders which is quite acceptable is experienced.

A further improvement over what has been described above can be introduced for the operation of the device, by replacing the restricted port with a fixed calibration in each of the in dividual ducts, by two or more serially arranged restricted ports. In the light of what has been described, during the induction stroke of a cylinder with an idling engine, the pressure ratio upstream-downstream of the restricted port can not only be higher than the critical ratio but even higher than the square power of the critical ratio. A single restricted port should thus be oversized (to obtain the rate of flow which is necessary to ensure feeding) since the speed would never exceed sonic speed. Such an oversizing is detrimental when, during the induction strokes of the other cylinders, the flow which may cause the pollution of the capacity flows in the reverse direction (with pressure ratios which are always considerably below the critical ratio). With two or three restricted ports in series, the ratio of the direct feeding flow to the reversed flow (susceptible of originating pollution) is thus more favorable.

The above and other objects and advantages of the invention will become more readily apparent to persons skilled in the art from the following detailed description and annexed drawings, and in which drawings:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view, partly in cross-section of a four cylinder engine having the cylinders in line,

FIG. 2 is a fragmentary front view, partly in cross-section of the engine shown in FIG. 1,

FIG. 3 is a fragmentary cross-sectional view showing the restricted fixed port at the opening of the small intake duct of a cylinder, and

FIG. 4 is a fragmentary cross-sectional view showing the fixed calibration being obtained with two serially arranged restricted ports.

DETAILED DESCRIPTION OF THE DRAWINGS Referring to FIG. 1, there is illustrated an internal combustion engine E provided with a block B having four cylinders l, 2, 3 and 4 arranged in line. The engine is provided with valve seats 5 and 6 for intake and exhaust valves 16 and 19 respectively. The valve seat 5 is in communication with a main intake duct 7 in which is mounted a throttle 8, with the throttle being illustrated in the closed position. The valves 16 and 19 are operated by cams 14a and 17a on intake cam shaft 14 and exhaust cam shaft 17 respectively, with the cams coacting with heads 15 and 18 respectively. In FIG. 2, the intake valve 16 is illustrated in the open position and the exhaust 19 in the closed position. A piston 20 provided with a connecting rod 21 is shown in an intermediate position of the induction stroke and the cylinder 1 in its induction phase.

Of course, it is to be understood that each of the cylinders 2, 3 and 4 is provided with the above-discussed components.

A distributing chamber or space 1] is located downstream of a restricted port 12 and the calibration of such port is adjustable by means of a screw 13 having a conical tip 13a. By the proper manipulation of the screw 13, the conical tip 13a can be caused to penetrate to a greater or lesser extent in the port 12 for adjusting the flow rate of the fluid to the chamber 1 1.

It will be noted that a plurality of small ducts 10, preferably of resilient material, extend from the chamber 11 to the main intake duct 7 in parallelism with respect to the throttle 8. It will be understood that there is one duct 10 for each cylinder of the engine. Each duct 10 is in communication with the interior of each main duct 7 via a restricted port 9. As shown in FIG. 3, the restricted port 9 is provided in a sleeve 9a threaded into an opening provided in the main duct 7. The end of the small duct 10 is affixed to the sleeve 9a by a suitable clamping means or the like 9b.

In FIG. 4, it will be noted that the fixed calibration is obtained by two serially arranged respective ports. More specifically, in this embodiment a sleeve is also threaded into a bore in the main duct 7 with the inner end of the sleeve having a restricted port 9d and the outer end of the sleeve a restricted port 92. The small duct 10 is attached to the sleeve by suitable clamping means 9 f The air drawn by the induction stroke of the piston 20 reaches the intake duct 7 of the cylinder 1 through the restricted port 9 having a fixed calibration, in correspondence with which it undergoes a considerable pressure drop. Through the small duct 10, the air is drawn into the chamber 1 1 and due to the effect of the negative pressure not only the mixture or the air is drawn through the port 12 having a variable calibration, but also the mixture or the air contained in the small ducts relative to the cylinders 2, 3 and 4. By proportioning the ports, in this phase through the small ducts of the cylinders 2, 3 and 4, the cavity is reached only by the mixture or the air which was contained in said ducts, rather than the fluid which was contained in the intake ducts 7 of the cylinders 2, 3 and 4. By so doing, the mixture (or the air) cannot reach the cavity which, in the intake ducts 7 of the cylinders 2, 3 and 4 was polluted by the preceding reflow of exhaust gases of the corresponding cylinders.

What is claimed is:

1. In an internal combustion engine having a plurality of cylinders, a piston in each cylinder, an intake opening for each cylinder, a main intake duct leading to each intake opening and a throttle valve in each main intake duct, a control device for the idle running of the engine during no-load conditions,

DEVICE FOR ADJUSTING THE IDLING IN AN INTERNAL COMBUSTION ENGINE BACKGROUND OF THE INVENTION This invention relates to a control device for adjusting the idling of an internal combustion engine during no-load conditions.

It is known that very often, in order to increase the specific power of an alternative internal combustion engine, dynamic phenomena connected with the pulsatory trend both of the mixture (or air)in the intake ducts, and of the gases in the exhaust ducts are resorted to. The length and the cross-sectional area of the ducts in to neighborhood of the valves of the individual cylinders of the engine are optimized to this purpose. It is also known that the best exploitation of such phenomena is obtained by a phase adjustment in the distribution assembly so that, in the vicinity of the end of stroke, that is, between the end of the exhaust stroke and the beginning of the induction stroke, the intake and exhaust valves are kept somewhat open simultaneously, in the sense that the intake valve has already begun to open and the exhaust valve is not yet completely closed. The phase adjustments which optimize the engine power under fiat-out conditions, however, give rise to irregular feed phenomena when the engine is throttled whenever throttling is obtained with a single throttle for two or more cylinders. These irregularities are especially experienced at full throttling, that is when the engine runs idly at its minimum R.P.M. and also on stoppage since the engine often continues to run even when the current feed to the spark plug has been discontinued. It is known that, in order to do away with these irregularities in engines having a high specific power, the intake ducts of the individual cylinders are each equipped with a corresponding throttle. Thus, there are as many throttles as there are cylinders in the engine. It is also known that usually in the internal combustion engine, when the throttle is closed, that is when throttling is at a maximum (that which corresponds in motor cars to the accelerator pedal being wholly released), the engine is fed with a mixture (or air in the injection engines) essentially through a small duct arranged in parallel with respect to the section of the main duct in which the throttle is located, so that this small duct shortcircuits the throttle when the latter is closed. In the interior of the small duct, a restricted port, whose cross-sectional area can be manually varied by the motorist, permits an adjustment of the rate of flow of the feeding mixture (or air) so as to obtain the desired rate of rotation of the engine when idling under no-load conditions. It is known that this adjustment is necessary, since even small differences, both initially and during the service life of the motor car, in the mechanical and thermal efficiency of mass-produced engines, can originate values of the idling R.P.M. which are sharply different from the desired values. Also, in the above outlined case of engines having as many throttles as there are cylinders, the engine feed with the closed throttles takes place essentially through the small ducts which are arranged in parallel with respect to the throttles. In the interior of the small ducts there is the manually adjustable restricted port above mentioned.

With such an arrangement, the adjustment operation can be carried out with difficulty since the desired R.P.M. rating can be obtained with rates of flow of a mixture (or air) which are radically different from one cylinder to another. Only if the motorist has suitable control means available, can these differences be reduced within an acceptable range. Such control means, however, to be satisfactory, must be rather intricate and expensive, so that the motorist cannot resort to such control means for adjustments during the service life of the car engine.

In spite of these difficulties, however, the above arrangement (as many manually adjustable ports as there are throttles) is generally adopted since, if the intake ducts of the several cylinders are fed, under closed throttle conditions, with small ducts place in parallel and fed by a single adjustable restricted port, all the irregularity phenomena desired to be overcome by adopting as many throttles as there are cylinders in the engine, are experienced again.

Theoretical investigations and experimental runs have been carried out by the applicant in recent years on the physical reasons for the irregularity phenomena above mentioned and thus also on the possibility of overcoming the phenomena. Already a few years ago one of the principal reasons for the irregular run and the difficult stoppage of the engine as above stated has been identified. A substantial deep modification of the chemical structure of the gasoline hydrocarbons takes place when, in the intake ducts, there is an excessive reflow of exhaust gases due to the simultaneous opening of the intake and exhaust valves during a partial throttling operation. This phenomenon, due to overheating of the hydrocarbons of the fresh mixture admixed with the exhaust gases, naturally takes a certain time to occur and is thus the more pronounced, the longer is the time available, that is at low rotation speeds and when idling. The same is true the greater is the amount of reflow gases. Having a throttle available for each cylinder, the volume which is internal to the duct section provided between the throttle and the intake valves is much smaller and the same is true of the reflow of exhaust gases which is sufficient to cancel the pressure differential which originates the reflow phenomenon as itself.

Another important reason for the irregular operation has been identified. However, if the reflow of the exhaust gases from a cylinder enters the induction manifold which is common to a plurality of cylinders, inasmuch as the short time available does not permit a perfect admixture of the exhaust gases with the feeding mixture (or the air) contained in the manifold, a fraction of the reflow gases can be immediately drawn into the cylinder, but other fractions are drawn by the other cylinders. The splitting of the several fractional reflow streams, of course, is wholly at random and is unpredictable so that the degree of pollution of the draw-in mixture (or air) is different from one cylinder to another cylinder but is also different, for the same cylinder, from one cycle to another. The result, obviously, is an irregular operation of the engine, and this irregularity is still more serious in the case of an injection engine since the amount of injected fuel is always the same for all of the cylinders and along the several sequential cycles of a certain cylinder, whereas this does not occur for the drawn-in air. These results of the theoretical and experimental trials on the reasons for the irregularity phenomena have permitted the identification of the possibility of preventing such irregular operation by means of a device for the manual adjustment of the idle running of engines having as many throttles as there are cylinders.

SUMMARY OF THE INVENTION More particularly, such device affords considerable advantages as to the simplicity of construction and especially as to the convenience in the manual adjustment operation aforementioned. The adjustment is carried out, in fact, in the present device, by acting on a single restricted port whose flow passage section is adjustable and through which the mixture (or air) stream is caused to flow for feeding several cylinders or also all of the cylinders of the engine when the throttles are closed. Obviously, downstream of the restricted port there is a cavity from which extend small ducts equal in number to the cylinders fed by the device, and the small ducts open into the intake ducts of the several cylinders. By so doing, through the small ducts and the cavity, the several cylinders are also in communication with each other so that the reflow of exhaust gases from a cylinder could irregularly and unpredictably pollute the other cylinders unless the device does not embody as an integral part thereof, further restricted ports having a fixed calibration and arranged in the individual small duets, with the ports being so proportioned that, during the induction stroke of a cylinder in correspondence with the respective fixed restricted port, a considerable fraction of the pressure drop (with respect to atmospheric pressure) which is required for said control device including a distributing chamber, a small duct for each cylinder, each small duct being in communication at one end with the distributing chamber, and the opposite end of each of said small ducts being in communication, through at least one restricted port having a fixed calibration, with a main intake duct downstream of the throttle an inlet opening upstream of the distributing chamber through which a fluid to be fed to the cylinders enters the distributing chamber, and a screw having a conical tip cooperable with the inlet opening for adjusting the flow rate of the fluid to the cylinders.

2. The device according to claim 1 characterized in that the length of each of the small ducts is at least times the inside diameter of the duct.

3. The device according to claim 1, characterized in that, when the throttle is closed, the remaining flow passageway in correspondence with the edges of the throttle has an area which is by 25 percent smaller than the flow passageway of the cross-section of the fixed restricted port.

4. The device according to claim 1, characterized in that said small ducts are in communication with the respective intake ducts through a plurality of restricted ports having a fixed calibration and serially arranged with respect to each other.

5. The device according to claim 1, characterized in that the restricted ports having a fixed calibration are mounted in correspondence of the points at which the small duct open into the intake ducts, or in correspondence with the points at which the small ducts open into the capacity, or in an intermediate portion of said small ducts.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,664,316 Dated 23 May 1972 Invnt6r(S) iampaolo GARCEA It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the Abstract page, Item [73] Assignee the Assignee's name is spelled wrong and should be ALFA ROMEO S. p. A.

Signed and sealed this 31st day of October- 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Commissioner of Patents Attesting Officer USCOMM-DC 60376-P69 fi us. GOVERNMENT PRINTING OFFICE: I969 o3ss-su FORM PO-lOSO (10-69)

Claims (5)

1. In an internal combustion engine having a plurality of cylinders, a piston in each cylinder, an intake opening for each cylinder, a main intake duct leading to each intake opening and a throttle valve in each main intake duct, a control device for the idle running of the engine during no-load conditions, said control device including a distributing chamber, a small duct for each cylinder, each small duct being in communication at one end with the distributing chamber, and the opposite end of each of said small ducts being in communication, through at least one restricted port having a fixed calibration, with a main intake duct downstream of the throttle an inlet opening upstream of the distributing chamber through which a fluid to be fed to the cylinders enters the distributing chamber, and a screw having a conical tip cooperable with the inlet opening for adjusting the flow rate of the fluid to the cylinders.

2. The device according to claim 1, characterized in that the length of each of the small ducts is at least 10 times the inside diameter of the duct.

3. The device according to claim 1, characterized in that, when the throttle is closed, the remaining flow passageway in correspondence with the edges of the throttle has an area which is by 25 percent smaller than the flow passageway of the cross-section of the fixed restricted port.

4. The device according to claim 1, characterized in that said small ducts are in communication with the respective intake ducts through a plurality of restricted ports having a fixed calibration and serially arranged with respect to each other.

5. The device according to claim 1, characterized in that the restricted ports having a fixed calibration are mounted in correspondence of the points at which the small duct open into the intake ducts, or in correspondence with the points at which the small ducts open into the capacity, or in an intermediate portion of said small ducts.

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