Patent Publication Number: US-6216666-B1

Title: Intake passage arrangement in an internal combustion engine

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to an intake passage arrangement in an internal combustion engine, including at least two intake ports or port sections per cylinder which are located in a cylinder head and are separated by a joint wall section, and which branch off from a common intake flow path, a control flap being positioned in a section of the intake passage in the area of the branch-off, which flap is rotatable about a rotation axis situated at one end of the control flap, the control flap opening both intake ports or port sections in one position and blocking one intake port in another position, and the part of the intake passage section carrying the control flap being configured as a separate intermediary part adjacent to the intake ports. 
     DESCRIPTION OF THE PRIOR ART 
     There are examples of cylinder heads where one of the intake valves is designed to impart a swirl to the cylinder charge. This is achieved by configuring at least one intake port as a swirl passage (spiral or tangential passage). In lean-mix, spark-ignition engines, in particular, the requirements concerning the intake flow will vary with the load or speed of the engine. Whereas no swirl motion but optimum filling will be required under conditions of full load and/or high RPM, a slight swirl is desirable at low load, which can reduce smoke emission considerably. Filling is of minor importance under low load conditions, however. 
     In EP 0 258 207 A2 a cylinder head for a two-valve internal combustion engine is described, where the intake passage has a partition along its length, such that two partial intake passages are formed which reunite in the valve region. In the area of the intake pipe, i.e., just before it connects to the intake passage, one of the two partial passages can be closed by means of a control flap positioned in a separate part of the intake pipe. If a swirl flow is desired for part-load operation or low RPM, the control flap is actuated to control the flow in this partial passage. The unsymmetrical flow through the uncontrolled partial passage will produce the swirl motion desired for this operating range. If, on the other hand, optimum cylinder filling is to be obtained at full load, the flap is opened completely to make available the entire passage cross-section. In this manner a low-swirl or swirl-free flow is induced. For fuel injection into the intake pipe an injector opens into the part of the intake pipe containing the control flap. This essentially cylindrical part of the intake pipe adds to the dimensions of the engine and requires further connecting elements, such as bolts or the like. 
     AT 402 326 B presents an intake passage arrangement with two intake ports opening side by side in the area of the intake pipe. One of these intake ports has a partition running along its length, thus forming two partial passages reuniting in the area of the intake valve. The other intake port and the partial passage of the first intake port next to it, are jointly controlled by a control flap located at the beginning of the intake pipe. In the closed position of the control flap one partial passage of the first intake port and the second intake port are closed, such that the open other partial passage will generate a swirl flow in the cylinder. In the open position of the control flap both intake ports are open. These provisions are intended to produce a similar performance as regards swirl generation and filling in multi-valve arrangements. 
     In DE 36 19 550 A1 a cylinder head is described in which the first intake port is configured as a swirl-generating passage and where the partitioning wall has an opening connecting the two partial passages upstream of the valve chamber. The passage which is separated from the helical intake passage by the partitioning wall, is activated to interfere with, and thus control, the generated swirl. Interference is controlled with the use of a throttle, which is located in the cylinder head in the second intake port. 
     A similar type of cylinder head with two intake valves and two comparatively short intake passages, one of which is configured as swirl-generating passage, is known from EP 0 173 014 A2. In that instance a bypass passage branches off from the passage that does not generate a swirl, which bypass opens into the valve chamber of the swirl-generating passage. By means of a control flap positioned in the cylinder head the flow of the non-swirl-generating passage and the bypass passage may be controlled. With this arrangement swirl control is effected by interference, in a manner similar to that described in the context of DE 36 19 550 A1 above. 
     Flaps that are located in the cylinder head or intake pipe require large design efforts, while maintenance in this area involves considerable efforts of assembly and disassembly. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to overcome these problems and to further develop an intake passage arrangement of the above type such that it will permit effective swirl control of the intake flow whilst offering a simple and compact design. 
     In the invention this object is achieved by essentially configuring the intermediary part carrying the control flap as a thin, flat frame, and preferably as a die-cast part made of aluminum. This will eliminate the need for complex design efforts concerning the structure of the cylinder head, thus allowing the frame to be retrofitted in conventional cylinder heads, if desired. The intermediary part is inserted between the intake pipe and a corresponding intake flange of the cylinder head. 
     In a variant of the invention featuring ease of manufacture and assembly the intermediary parts of several cylinders be connected to each other, and preferably are configured as an integral unit. In this way the number of required components may be minimized. 
     In order to ensure a most simple actuation of the control flaps the rotation axes of the control flaps of a plurality of cylinders are situated in one plane, and the control flaps are actuated via a lever mechanism and a vacuum capsule in dependence on the intake pressure. The system of actuating a control flap via a vacuum capsule using the intake pressure has been described in EP 0 173 014 A2, for example. 
     In a further variant of the invention the rotation axis of the control flap is situated in the longitudinal centre plane, and preferably just before the branch-off, such that in one extreme position of the control flap the one intake port or port section, which is preferably configured as a tangential passage, will be blocked, and in the other extreme position of the control flap the other intake port or port section, which is preferably configured as a spiral passage, will be blocked, whilst in an intermediate position of the control flap both intake ports or port sections will remain open to approximately the same degree. In this way the swirl motion in the combustion chamber may be controlled by a simple switchover between the two intake ports or port sections. 
     Special preference is given to a variant of the invention which proposes that the control flap have a flow profile flaring, at least partially, in flow direction, thus essentially assuming the shape of a wedge or drop, which is preferably symmetrical relative to a longitudinal plane through the flap, the flow-directing surfaces of the control flap forming a more or less continuous contour with the walls of the joint wall section when the flap is in its intermediate position. As a consequence, cylinder filling in this position will be largely loss-free. Further improvement is achieved by configuring the control flap and the section of the intake passage in which the control flap is positioned, as preferably essentially symmetrical flow dividers. The control flap of the intake passage arrangement proposed by the invention may assume any intermediate position desired, and thus effect a continuously variable switchover between tangential and spiral passage and produce suitable combinations of tangential and spiral flows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be further described with reference to the accompanying drawings, in which 
     FIG. 1 is a sectional view of an intake passage arrangement in accordance with the invention; 
     FIG. 2 is a sectional view of an intake passage arrangement for a plurality of cylinders along line II—II in FIG. 3; 
     FIG. 3 is a view of a section of the intake passage as shown in FIG. 2, along line III—III in FIG. 2; 
     FIG. 4 is a view of a section of the intake passage as shown in FIG. 2, along line IV—IV in FIG. 2; 
     FIG. 5 is a view of a section of the intake passage including the actuating mechanism for the control flap, along line V—V in FIG. 4; 
     FIG. 6 is an exploded view of the intermediary part; 
     FIG. 7 is an oblique view of an intake passage arrangement in accordance with the invention. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     An internal combustion engine has two intake valves  2 ,  3  per cylinder  1   b,  which are located in a cylinder head  1 . Each intake valve  2 ,  3  is provided with an intake port  4 ,  5 , one of which intake ports, i.e.,  4 , is configured as tangential passage, and the other one, i.e.,  5 , is configured as spiral passage. The two intake ports  4 ,  5  are divided by a joint wall section  6  and depart from a common intake flow path  7 . They are situated on different sides of the extended longitudinal centre plane  7   c  of the intake flow path  7 . At the end of the common intake flow path  7  there is provided an intake passage section  8  with a branch-off  9 . 
     In the area of the branch-off  9  a swirl control device configured as control flap  10  is provided, which is held in a part  13  of the intake passage section  8  so as to be rotatable about a rotation axis  12  situated at one end  11  of the control flap  10 . The part  13  is configured as a separate intermediary  14  connecting to the intake ports  4 ,  5 , which is inserted between a flange  7   a  of the intake flow path  7  constituted by an intake pipe, and a corresponding intake flange  1   a  of the cylinder head  1 . The intermediary part  14  is essentially configured as a thin, flat frame and may be supplied as a die-casting made of aluminum, for example. 
     In the variant shown in FIG. 2 a single intermediary  14  includes the parts  13  for a plurality of cylinders  1   b.  As is seen in FIGS. 1 and 2, the control flap  10  has a flow profile flaring in flow direction, thus assuming essentially the shape of a wedge or drop. The flow-directing surfaces  10   a,    10   b  of the control flap  10  form a more or less continuous contour with the walls  6   a,    6   b  of the joint wall section  6  of the intake ports  4 ,  5  and are symmetrical relative to a longitudinal plane  10   c  of the control flap  10 , which plane  10   c  contains the rotation axis  12 . As a consequence, the control flap  10  exhibits minimum flow resistance in its intermediate position shown in FIGS. 1 and 2. In the intermediate position the longitudinal plane  10   c  of the valve  10  is situated along the longitudinal centre plane  7   c  of the intake flow path  7 . 
     As is seen in FIGS. 3 to  6 , each control flap  10  is connected via a hinge pin  15  held in the intermediary part  14  and an intermediate disk  16  acting as a lever, to an actuating rod  17 , which is operated via an intermediate disk  18  by an operating pin  19  held in the intermediate part  14 . To the operating pin  19  is attached a lever  20 , which is actuated by a vacuum capsule  21  (FIG. 7) in dependence on the intake pressure in the intake flow path  7 . Reference number  22  refers to a sealing element of the hinge pin  15 , whilst  23  refers to sealing elements between the intake flow path  7  and the intermediary part  14 . Hinge pins  15  and operating pin  19  are borne by special projections  24 ,  25  provided on the intermediary part  14 . 
     In the embodiment of the invention shown in FIG. 7 the intake flow paths  7  are constituted by an intake manifold  26  for a multicylinder internal combustion engine. In this variant every four cylinders are provided with an intermediary part  14  configured as an integral unit, the four control flaps  10  of each intermediary part  14  being actuated by a vacuum capsule  21  in dependence on the intake pressure.