Patent Publication Number: US-2002005185-A1

Title: Method and a supplemental valve assembly for controlling combustion air-supply in an internal combustion engine

Description:
FIELD OF THE INVENTION  
       [0001] The present invention relates to a method of controlling supply of combustion air in an internal combustion engine and a supplemental valve assembly for performing such method.  
       BACKGROUND OF THE INVENTION  
       [0002] German Patent DE 37 37 824 C2 discloses a method of controlling supply of combustion air in an internal combustion engine comprising at least one combustion chamber, a piston slidable in said combustion chamber and adapted to perform suction strokes an inlet passage for feeding combustion air to said combustion chamber, an inlet valve for controlling flow of combustion air into said combustion chamber and adapted to be opened during opening periods, and a supplemental valve assembly disposed in said inlet passage and movable between opening and closing positions, in which method combustion air supply is selectively controlled by said supplemental valve assembly during said opening periods of said inlet valve such that combustion air supply to the combustion chamber during said suction strokes of the piston is interrupted prior to the end of the respective suction stroke or enabled only towards the end of the respective suction stroke or is enabled in two phases such that combustion air flows into the combustion chamber in a first phase during a first half of said opening periods of said inlet valve and in a second phase during a last quarter of said opening periods of said inlet valve. This German patent discloses also a supplemental valve assembly for performing such method.  
       [0003] German patent DE 37 37 828 C2 discloses a supplemental valve assembly including a valve member which is designed as a pivotal flap. A pivotal valve flap which is mounted for pivotal movements about an eccentric axis is shown in German printed patent specification DE 196 00 501 A1.  
       [0004] In so-called sequential air supply methods, supply of combustion air into the combustion chamber of an internal combustion chamber is briefly interrupted by a supplemental valve when an associated piston is close to its bottom dead center. Since duration of free movement of the valve member of the supplemental valve must be very short, acceleration, braking forces and energy consumption of the supplemental valve are substantial, and therefore cost, weight and volume of the electrical drive of the supplemental valve are also substantial. It is in particular the space requirement of the drive that may cause substantial difficulties and problems in using such a method. Furthermore, substantial energy consumption will result in undesired heating of the components, and a complex control system may be required. In supercharging and heat loading methods using controlled check valves less expenditure is required; however, the range of different uses is greatly reduced as compared to the so-called sequential air supply.  
       SUMMARY OF THE INVENTION  
       [0005] It is an object of the present invention to provide a method and a supplemental valve assembly for controlling supply of combustion air in an internal combustion engine which allow for sequential air supply.  
       [0006] It is a further object of the invention to provide for reduced weight and volume of the drive of such a supplemental valve assembly and to substantially reduce energy consumption of the drive.  
       [0007] It is a further object of the invention to provide such a method and supplemental valve assembly that allow to reduce the duration of free movement of the valve member of the supplemental valve assembly in order to improve efficiency of such method and to enable use of such method also at high engine speeds.  
       [0008] The present invention controls the supplemental valve assembly such that movements of the valve member thereof will be assisted by combustion air flow prevailing at that time in the inlet passage.  
       [0009] The inventor has recognized that pressure differences prevailing in the inlet passage in the area of the supplemental valve and changing during each cycle of operation can be used for acceleration of the opening and closing movements of the valve member of the supplemental valve assembly. The additional energy resulting from such pressure differences is used to increase the velocity of the valve member and to reduce the energy to be provided by the drive of the supplemental valve assembly. As a result thereof the volume, weight and cost of the supplemental valve drive will be reduced, and the velocity of the valve member of the supplemental valve assembly can be increased. Such pressure differences may become effective in different directions depending on the mode of operation and/or the respective phase of the cycle of operation. If the valve member of the supplemental valve assembly is formed as a pivotal flap which can be moved to its open position only in one direction as known in the prior art, the gas flow resulting from such pressure differences can not always be used to assist the movements of the valve member.  
       [0010] Therefore, a first version of a supplemental valve assembly comprises a pivotal flap mounted so as to be rotatable about an eccentric axis to a closing positions for closing the inlet passage, with the closing position being a central position of the pivotal flap which is movable from the closing position in a first direction of rotation to a first opening position and in an opposite direction of rotation to a second opening position for opening the inlet passage. This supplemental valve assembly can be opened and closed by movements in two opposite directions, with the respective movements of the valve member being assisted by the gas flow prevailing at this time in the inlet passage. Such assisting action can be used in a great number of applications.  
       [0011] The use of a pivotal flap movable from a central closing position in opposite directions of rotation to a pair of opening positions may cause flow losses due to sealing problems.  
       [0012] A second version of a supplemental valve assembly comprises a first pivotal flap mounted in a first branch conduit of the inlet passage for pivotal movements between opening and closing positions, and a second pivotal flap mounted in a second branch conduit of the inlet passage for pivotal movements between opening and closing positions. The first and second pivotal flaps each are arranged such that they engage respective abutment surfaces for closing their respective branch conduits when they are in their closing positions, and are adapted to be temporarily retained in their closing positions by controllable retaining means. The first and second pivotal flaps are arranged to be rotated in opposite directions for being moved from their respective closing positions towards their respective opening positions. Preferably the two branch conduits are disposed in a common housing.  
       [0013] If there are provided at least two inlet passages and at least two inlet valves for feeding combustion air to a combustion chamber, it is preferred that each of the inlet passages has associated therewith one of said branch conduits. However, it would be possible to provide each of the inlet passages with a pair of branch conduits. In this connection the respective intended use of the combustion engine and the applied charging methods should be taken into consideration.  
       [0014] A supplemental valve assembly in a modified second version comprises a first pivotal flap and a second pivotal flap which are arranged to be rotated in opposite directions for being moved from their respective closing positions towards their respective opening positions, with said pivotal flaps being positioned in the inlet passage such that one pivotal flap is downstream of the other pivotal flap.  
       [0015] Preferably, the pivotal flaps can be retained both in their closing and opening positions by controllable retaining means.  
       [0016] Furthermore, the pivotal flaps are arranged to be rotated through not more than an acute angle in order to reduce the “switching times” of the supplemental valve assembly.  
       [0017] As a safety feature, the flow cross-sectional area of the inlet passage should be closable by selected actuation of at least one valve flap under any operational condition in order to allow to shut off the combustion engine at any time.  
       [0018] The supplemental valve assembly of the present invention can be used to increase or reduce the amount of combustion air or for changing the temperature of the combustion air. Increase of the amount of combustion air can be used in suction-type combustion engines or charger-type combustion engines having oscillatory intake passages for dynamic charging of the engine, wherein the inlet passage may be opened once or twice per cycle. Furthermore, it can be used in Otto-type charged engines and Diesel-type charged engines for after-charging thereof and control of fresh air supply and charger air supply. Furthermore, it can be used in all combustion engine to reduce the amount of combustion air in connection with stratified gas operation, expansion operation and switch-off of selected cylinders as well as in Otto-type suction and charging engines for expansion of gas flow by early closing the inlet thereof. Finally, it is suited for changing the temperature of the combustion air in Otto- and Diesel-type charging engines by cold air charging and expansion of cooled charging air, as well as in all engines for heat charging by late opening of the inlet valve.  
       [0019] Other advantages and objects of the present invention will become apparent to those skilled in the art from the subsequent detailed description, appended claims and drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0020] In the drawings which illustrate the best modc presently contemplated for carrying out the present invention:  
     [0021]FIG. 1 a  is schematic cross-sectional view of a first embodiment of a supplemental valve assembly which is positioned in an inlet passage of an internal combustion engine upstream of an inlet valve and which is in a first opening position;  
     [0022]FIG. 1 b  a cross-sectional view similar to FIG. 1 a , with the supplemental valve assembly being in its closing position;  
     [0023]FIG. 1 c  a cross-sectional view similar to FIG. 1 a , with the supplemental valve assembly being in its second opening position;  
     [0024]FIG. 2 a  a cross-sectional view similar to FIG. 1 a  of a modified embodiment of the supplemental valve assembly;  
     [0025]FIG. 2 b  a cross-sectional view similar to FIG. 2 a  of the modified supplemental valve assembly;  
     [0026]FIG. 2 c  a cross-sectional view similar to FIG. 1 c  of the modified supplemental valve assembly;  
     [0027]FIG. 3 a cross-sectional view of a second embodiment of a supplemental valve assembly;  
     [0028]FIG. 4 a cross-sectional view of a modified version of the second embodiment of the supplemental valve assembly shown in FIG. 3. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0029]FIGS. 1 a  and  c  show a supplemental valve assembly  10  in positions wherein the gas to be fed to a combustion chamber (not shown) via an inlet valve (not shown) flows through the supplemental valve assembly from the right side to the left side (in the drawing).  
     [0030] The supplemental valve assembly  10  shown in FIGS. 1 a  to  1   c  includes a housing  12  which encloses a portion of an inlet passage  14  wherein a valve member comprising a pivotal flap  16  is fixed to a pivot shaft  18  so as to be rotatable about the axis of the pivot shaft  18 . In the embodiment of FIGS. 1 a  to I c the pivotal flap  16  has one end fixed to the pivot shaft  18  which is disposed at one side of the inlet passage  14 . A first opening position A, a closing position B and a second opening position C of the pivotal flap  16  are characterized by the positions which the edge of the pivotal flap  16  remote from the pivot shaft  18  will be positioned at. When the pivotal flap  16  is in any of opening positions A and C, it engages the side of the inlet passage  14  to which the pivot shaft  18  is mounted. The pivotal flap  16  rotates through an angle of 180° for moving from one opening position to the other opening position. The closing position B is arranged centrally between the two opening positions A and C.  
     [0031] The radial length of the pivotal flap  16  exceeds the spacing between the pivot shaft  18  and the opposite side of the inlet passage  14  such that the inlet passage is provided with an arcuate encircling surface  20  concentric with the pivot shaft  18  and extending between a pair of control edges  22  and  24  which are spaced from the closing position B by the same angle of rotation and which limit a closing range α. When the pivotal flap  16  is within said closing range a its free edge engages the encircling surface  20  such that the pivotal flap  16  closes the inlet passage  14 , and the pivotal flap  16  opens the inlet passage  14  only after having passed any of the control edges  22  and  24  when moving towards any of the closing positions A and C. The angle of the closing range is dependent on the respective mode of operation and may be selected to be substantially less than shown. A greater angle can be selected to increase the breaking or acceleration energy available after closing and respectively, opening the valve.  
     [0032] The housing  12  may be provided with a much deeper pocket-like recess between the positions designated by A and C in FIGS. 1 a  to  1   c  so that e.g. movements of the pivot flap  16  are to be decelerated only when the pivotal flap has reached the opening position A or C without risk of collision.  
     [0033] The embodiment shown in FIG. 2 a  to  2   c  differs from the first embodiment only in that the pivotal flap  17 , by the pivot shaft  18 , is divided into a portion  17 ′ of greater radial length, and a portion  17 ″ of smaller radial length, so that the pivot shaft  18  is radially spaced from the side walls of the inlet passage  14  which are opposite to each other in a direction transverse to the pivot shaft  18 . Each of said side walls includes an encircling surface  20 ′ and, respectively,  20 ″ which cooperate with the respective edge of the pivotal flap portions  17 ′ and, respectively,  17 ′ in order to close the inlet passage  14  when the pivotal flap  17  rotates through the closing range α. The encircling surface  20 ′ is limited by control edges  22 ′ and  24 ′, and the encircling surface  20 ″ is limited by control edges  22 ″ and  24 ″.  
     [0034] The pivot shaft  18  is driven by a drive (not shown), for example an electrical drive. The pivotal flap  17  is controllable so that it can be held stationary in the positions A, B and C, at least however in the positions A and B. If desired, at least a part of the breaking energy resulting from deceleration of pivotal flap  16  or  17  may be stored and may be used for accelerating the pivotal flap thereafter. This may be obtained for example by resilient means and/or by switching the drive from motor operation to generator operation.  
     [0035] The supplemental valve assembly can be used for a great number of applications of which the following three load charging methods are of particular importance:  
     [0036] early termination of inlet opening as a measure for restriction free charge control in Otto-type engines,  
     [0037] very late inlet opening as a measure for heat loading during cold start,  
     [0038] sequential air supply and, respectively, charge exchange comprising a pair of subsequent inlet flow phases for dynamically charging the engine at low engine speeds.  
     [0039] The last mode of operation is a combination of the two first mentioned modes of operation and will be explained in more detail below, this allows to describe all types of valve movements and gas flow assisting such valve movements.  
     [0040] Prior to the beginning of the suction stroke the inlet valve of the combustion chamber and the supplemental valve assembly  10  are closed, and the pivotal flap  16  or  17  is in the position B. The space between the inlet valve (not shown) and the supplemental valve assembly will be called “valve space” in the following. This valve space contains, prior to the beginning of the suction stroke, air compressed in the preceding work cycle as will be explained in more detail below.  
     [0041] Immediately before the inlet valve adjacent the combustion chamber begins to move (inlet opening), the locking of the supplemental valve assembly  10  in the closing position B (FIGS. 1 b ,  2   b ) is released. The drive moves the pivotal flap  16  or  17  from the closing position B towards the opening position A. The compressed air in the valve space assists or enforces such movement of the valve flap until it passes the control edge  22  so as to abruptly open the inlet passage  14  and to release the air mass m 1 . Now the piston (not shown) which moves meanwhile towards its bottom dead center draws air (gas) into the combustion chamber. When the piston has moved to a position corresponding about 120° crank angle after its top dead center the drive begins to move the supplemental valve assembly  10  from the opening position A towards the closing position (FIG. 1 a ,  2   a ). The air mass m 1  flowing towards the combustion chamber at high velocity hits upon the pivotal flap  16  or  17  so as to accelerate its movement until it passes the control edge  22 . The ram pressure upstream of the pivotal flap  16  or  17  will be still active at that time. The air (gas) enclosed in the combustion chamber will expand due to further movement of the piston, and the air (gas) pressure acting upon the pivotal flap  16  or  17  will be further increased. On the other hand when the pivotal flap  16  or  17  approaches the closing position B the pivotal flap will be slowed down by the drive and will be retained in the closing position B, with the braking energy being regained to a certain extent.  
     [0042] The subpressure within the combustion chamber will increase until the pivotal flap  16  or  17  will be released by the locking means and will be moved by the drive towards the opening position  10 . with the drive being assisted by the subpressure in the combustion chamber. As soon as the pivotal flap passes the control edge  24 , the inlet passage  14  will be opened abruptly. The air mass m 2  flows into the inlet passage at high velocity and also assists in rotating the pivotal flap.  
     [0043] When the pivotal flap  16  or  17  approaches the opening position C, it will be slowed down by the drive, and the inflowing air (gas) initially is slowed down in the combustion chamber resulting in a pressure increase. Eventually the air will tend to flow in the opposite direction so as to enforce or accelerate respective rotational movement of the pivotal flap  16  or  17  which again is moved by the drive to the closing position B where it will be retained (locked). Shortly thereafter the inlet valve of the combustion chamber will be closed so that the compressed air will be enclosed and retained in the valve space; such compressed air will assist in rotating the pivotal flap from position B to position A at the beginning of the next work cycle.  
     [0044]FIG. 3 shows a supplemental valve assembly  110  for a pair of branch conduits  114   a  and  114   b  which are combined in a common housing  12  so as to form a structural unit. Direction of gas flow to the inlet valve (not shown) of the combustion chamber (not shown) is from left to right in the drawing. A pivotal flap  116   a  is mounted in the branch conduit  114   a  so as to be rotatable about a pivot shaft  118   a . The pivotal flap  116   a  when in its opening position is disposed within a pocket  119   a  of the housing  112  in order not to restrict fluid flow through the branch conduit  114   a . The pivotal flap  116   a  can be rotated by an actuator (not shown) such as an electrical actuator outside of the housing  112  for about 45° clockwise from the open position to the closing position wherein it engages an abutment surface  121   a . The above mentioned drive is also used to rotate the pivotal flap anticlockwise in the opening direction. Return spring means can be used to enforce closing movement of the pivotal flap. Furthermore, the pivotal flap  116   a  is retained in its opening position by retaining means such as a solenoid and, if desired, by a further retaining means such as a further solenoid; the retaining means can be made ineffective at any time by interrupting current supply to the respective solenoid. Instead of solenoid-type retaining means which may comprise magnetic locking means within a solenoid-type rotary drive, mechanical devices could be used.  
     [0045] The branch conduit  114   b  contains a similar arrangement, with similar or corresponding parts being designated by the same reference numerals as in the branch conduit  114   a  except that the letter a has been replaced by the letter b. The only difference between pivotal flaps  116   a  and  116   b  is that pivotal flap  116   b  moves clockwise to the opening position and anti-clockwise to the closing position.  
     [0046] Similar to the embodiments in FIGS. 1 a  to  2   c  the positions of the pivotal flap  116   a  are designated by the letters A and B 1 , and the positions of the pivotal flap  116   b  are designated by the letters B 2  and C; this should make clear that the supplemental valve assembly of the second version as shown in FIG. 3 can be moved to the same positions as the supplemental valve assembly of the first version, and movements of the pivotal flaps  116   a  and  116   b  will be enforced or accelerated by the pressure and/or flow conditions prevailing at that time in the inlet passage in the same manner as in the embodiments of the first version.  
     [0047] When the pivotal flaps  116   a  and  116   b  are at rest, they are in the closed position. In the space between these pivotal flaps and the inlet valve (not shown) adjacent the combustion chamber there prevails a slightly super atmospheric pressure. This super atmospheric pressure assists in rotating the pivotal flap  116  from position B 1  to position A after it has been released; this enables charging air to flow into the combustion chamber. This airflow will enforce or accelerate movement of the pivotal flap  116   a  from position A to position B 1 . The pivotal flap  116   a  will then be retained by the abutment surface  121   a , and the pivotal flap  116   b  will be retained by retaining means associated with abutment surface  121   b . A sub-atmospheric pressure will prevail in the space between the supplemental valve assembly  110  and the inlet valve adjacent the combustion chamber. Eventually, the retaining means will be made inoperative, the pivotal flap  116   b  will move from the closing position B 2  to the opening position C, there will be pulse or vibrational charging of the piston, and before the gas charge can flow back, the retained pivotal flap  116   b  will be released so that it can return from opening position C to closing position B 2 .  
     [0048] In the embodiment of FIG. 4 pivotal flaps  216   a  and  216   b  similar to pivotal flaps  116   a  and  116   b  described with reference to FIG. 3 arc positioned in a common inlet passage within passage portions  214   a  and  214   b  following each other in the flow direction. Also in this arrangement it is to be assumed that the combustion chamber (not shown) is positioned towards the right from the supplemental valve assembly as shown. Gas flow towards the combustion chamber is suited to assist in closing pivotal flap  216   a  and in opening pivotal flap  216   b , while gas flow from the combustion chamber or super-atmospheric pressure in the passage between the supplemental valve assembly and the combustion chamber is suited to assist in closing pivotal flap  216   b  and in opening pivotal flap  216   a  provided that the respective pivotal flap is released to perform such movements.  
     [0049] In the valve arrangements of FIGS. 1 and 2 the combustion engine can be brought to an emergency stop by moving the respective pivotal flap to closing position B. In the embodiment of FIG. 4 it could also be sufficient to move a pivotal flap, preferably pivotal flap  216   a , to the closing position B 1  to provide for an emergency stop. In the embodiment of FIG. 3. both pivotal flaps  116   a  and  116   b  must be moved to their closing positions B 1  and B 2  in order to stop air supply of the combustion engine.  
     [0050] When this description uses the term “air”, this term is not meant to be restrictive but rather, should encompass any gas a mixture of air, fuel and/or recirculated exhaust gas.