Abstract:
A simplified variable intake manifold is disclosed for use with an internal combustion engine. The manifold utilizes a single valve actuator to vary the resonant frequency of a pair of plenums. The two plenums are joined by first and second communication passages of differing lengths connected to provide cross flow between two plenums. Each plenum has an inlet for receiving intake air from a throttle body and a group of runners adapted for connection with a like group of engine cylinders to direct inlet air from the plenums to combustion chambers of the cylinders. A control valve having an elongated shaft extends through the first and second communication passages and includes separate blades rotatable with the shaft to open or close the passages to provide at least three modes of tuning of the plenums. A stepper motor or other suitable device acts upon the shaft to rotate the blades within the communication passages.

Description:
TECHNICAL FIELD 
     This invention relates to engine air intake manifolds and, more particularly, to air intake manifolds having dual plenums valved to provide three modes of resonance tuning of engine cylinder air charges. 
     BACKGROUND OF THE INVENTION 
     A majority of engine air intake manifolds have a fixed volume plenum with fixed length runners tuned for a particular application, such as low rpm torque, midrange torque, or high rpm torque. 
     Variable geometry intake manifolds provide more than one tuned frequency to optimize engine performance over a wider range of engine rpm. One such variable geometry intake manifold utilizes a pair of plenums connected together by differing length communication passages to vary the tuning and effective volume of the plenums. The communication passages are controlled by separate valves, which selectively open or close their respective communication passages to vary flow between the plenums and thereby alter the effective volume of the plenums. By varying the effective volumes, the resonant frequencies of the manifold can be extended to optimize airflow through the plenums and obtain desired volumetric efficiencies at various engine rpm. 
     Another type of variable geometry intake manifold uses a fixed volume plenum connected to short and long runners. This manifold also uses multiple valves to vary the geometry of the manifold by switching between two runner lengths. When switched to the longer runner length, the resonant frequency of the intake manifold decreases. This provides additional engine torque at lower engine speeds. When switched to the shorter runner length, the resonant frequency of the intake manifold increases thereby increasing the engine speed where maximum volumetric efficiency occurs. This provides additional engine horsepower at higher engine speeds. 
     SUMMARY OF THE INVENTION 
     The present invention provides a simplified variable intake manifold utilizing only one valve actuator for tuning a pair of plenums. The manifold may be used in conjunction with inline or V-type internal combustion engines, having two groups of cylinders. For example, in a V-type engine the cylinders may be grouped by cylinder banks and in an inline engine, the single cylinder bank may be grouped into front and rear halves. 
     In an exemplary embodiment, an intake manifold designed for a V-type engine includes a pair of plenums joined together by first and second communication passages. These may be alternately opened to provide cross flow between the two plenums or may both be closed to separate the plenum volumes. 
     The first communication passage, tuned to improve high rpm torque, provides a short, high flow volume connection between the plenums that connects the two plenums into a single large volume plenum connecting with all the engine cylinders. The second communication passage, tuned to improve midrange torque, provides a longer, lower flow volume passage connecting ends of the plenums for tuning the resonance of the connected volumes. With both passages closed, the separate plenums are tuned to improve low speed torque. Each plenum has an inlet for receiving intake air from a throttle body and a series of runners connecting the plenum with a respective group of cylinders to direct inlet air from the plenum to the combustion chambers of its respective cylinder group. 
     A control valve having an elongated shaft with first and second ends extends into the first and second communication passages. A single stepper motor or other suitable device acts upon the shaft to rotate the shaft within the communication passages. Within the first communication passage, a rotatable valve or blade is mounted on the shaft and is operative to control airflow through the first communication passage. Within the second communication passage, a second rotatable valve or blade is mounted on the shaft and is operative to control airflow through the second communication passage. 
     If desired, the blades may be angularly offset from one another or the communication passages may be angularly offset so that when the shaft is rotated to a first mode position, the first blade closes the first communication passage and the second blade closes the second communication passage for engine operation in a first mode with enhanced low speed torque. When the shaft is rotated to a second mode position, the first blade closes the first communication passage and the second blade opens the second communication passage for engine operation in a second mode with enhanced mid speed torque. When the shaft is rotated to a third mode position within the communication passages, the first blade opens the first communication passage and the second blade closes the second communication passage for operation of the engine in a third mode with enhanced high speed torque. 
     If desired, sealing disks or other suitable sealing devices may be installed on the shaft adjacent the blades and the ends of the shaft to prevent air leakage around the shaft and the ends of the blades. 
     These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded pictorial view of an exemplary intake manifold according to the invention for use with a V-type internal combustion engine; 
         FIG. 2  is a top view of the intake manifold of  FIG. 1  cut away to show communication passages between the plenums; 
         FIG. 3  is a pictorial view of a control valve for use in either  FIG. 1  or  2  showing one possible blade configuration; 
         FIG. 4  is a diagram illustrating a control valve in a first mode position, the control valve having angularly offset blades and parallel communication chambers; 
         FIG. 5  is a diagram illustrating the control valve of  FIG. 5  in a second mode position; 
         FIG. 6  is a diagram illustrating a the control valve of  FIG. 5  in a third mode position; 
         FIG. 7  is a diagrammatic view of an alternative embodiment of an intake manifold adapted for an inline engine according to the present invention; and 
         FIG. 8  is a diagram illustrating three mode positions of an alternative control valve wherein the communication passages are angularly offset and the blades are parallel. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to  FIGS. 1 and 2  of the drawings in detail, numeral  10  generally indicates a simplified variable intake manifold for use with a V-type internal combustion engine, not shown, having two groups of cylinders, each comprising a cylinder bank. The intake manifold  10  includes a pair of longitudinally extending plenums  12 ,  13  spaced laterally from one another and each connected with multiple runners  14  for connection with associated cylinders of the engine. The plenums are joined by a tubular valve body  15  having a longitudinal axis  16  and first and second communication passages  17 ,  18 , each extending laterally between the two plenums. 
     The first communication passage  17  extends between adjacent plenums  12 ,  13  and provides a short, high flow volume connection between the plenums  12 ,  13  which effectively forms one larger plenum feeding all the runners  14 . The second communication passage  18  extends from the ends  20 ,  22  of the plenums  12 ,  13  and laterally through the valve body  15  to provide a longer, lower flow volume tuning passage connecting the plenums. The plenums  12 ,  13  have inlets  23 ,  24  connected to receive intake air from a throttle body  26 . The runners  14  direct the intake air from the plenums  12 ,  13  to intake ports, not shown, connecting with the cylinders of an associated engine. 
     Communication between the plenums is controlled by a single control valve  38  shown in  FIGS. 1–6 . Valve  38  has an elongated shaft  40  with first and second ends  42 ,  44 . The elongated shaft  40  extends into the valve body  15  along its longitudinal axis  16  and across the first and second communication passages  17 ,  18 . An actuator  45  is connected to one end of the elongated shaft and is operable to rotate the valve  38  within the first and second communication passages  17 ,  18 . The actuator  45  may be of any suitable type, for example an electric stepper motor with mechanical gearing, not shown. Within the first communication passage  17 , a first blade  46  is carried on the shaft  40  and is operative to control airflow through the first communication passage. Within the second communication passage  18 , a second blade  48  is carried on the shaft  40  and is operative to control airflow through the second communication passage. As shown, the first and second communication passages  17 ,  18  intersect the valve body axis  16  at the axially spaced locations of the valve blades  46 ,  48  along the shaft  40 . 
     Preferably, in an exemplary embodiment the blades  46 ,  48  are angularly offset from one another and the communication passages  17 ,  18  are parallel to one another as shown in  FIGS. 1–6 . It should be understood that various blade angle offset combinations and communication passage angle offset combinations are possible for achieving the goal of the claimed invention. In the exemplary embodiment, the blades  46 ,  48  are angularly offset by 60 degrees so that three modes of operation can be obtained by rotating the control valve 120 degrees. Examples of these operating modes are illustrated in  FIGS. 4–6 . 
       FIG. 4  shows the control valve  38  positioned in a first mode position within the communication passages  17 ,  18  in which the first blade  46  closes the first communication passage  17  and the second blade closes the second communication passage  18 .  FIG. 5  shows the control valve  38  rotated clockwise 60 degrees to a second mode position in which the first blade  46  still closes the first communication passage  17  but the second blade  48  opens the second communication passage  18  to communicate the plenums through the longer passage  18 .  FIG. 6  shows valve  38  rotated an additional 60 degrees to a third mode position in which the first blade  46  opens the first communication passage  17  and the second blade  48  closes the second communication passage  18  to communicate the plenums through the short passage  17 . 
     In operation of intake manifold  10  as illustrated in  FIGS. 1–3 , the engine, not shown, continuously draws inlet air through the intake manifold. As engine speed increases, the volume of air drawn through the intake manifold increases as well as the resonant frequency of the air pulsations. In order to improve volumetric efficiency and increase engine torque output, the resonant frequency of the intake manifold  10  is varied to match that of the engine. More particularly, the resonant frequency in the manifold is determined by plenum volume and wave length which are varied by selectively opening and closing the communication passages  17 ,  18  between the plenums  12 ,  13 . 
     During low speed operation, the control valve  38  is disposed in a first mode position, shown in  FIG. 4 , for low engine speed tuning. In this mode position, the first blade  46  closes the first communication passage  17  while the second blade  48  closes the second communication passage  18 . This causes air to flow directly from the inlets  23 ,  24  of the plenums  13 ,  14  to the runners  14  of the separate plenums. As a result, the plenums operate independently to improve volumetric efficiency and increase engine torque at lower engine speeds. 
     As the engine speed increases, the control valve  38  is rotated to the second mode position, as shown in  FIG. 5 , to alter the tuning of the intake manifold  10 . In the second mode position, the first blade  46  closes the first communication passage  17  while the second blade  48  opens the second communication passage  18 . This allows pressure waves to travel between the plenums through the longer, end connected, second communication passage, which is tuned for midrange engine rpm. As a result, this tuning of the intake manifold  10  improves the volumetric efficiency and increases engine torque at intermediate speeds. 
     As the engine speed is further increased, the control valve  38  is further rotated to the third mode position, shown in  FIG. 6 , to again alter the tuning of the intake manifold  10 . In this mode position, the first blade  46  opens the first communication passage  17  while the second blade  48  closes the second communication passage  18 . Thus, the two plenums  12 ,  13  are connected through the shorter communication passage  17 , which effectively forms a single larger plenum volume tuned for high engine rpm. As a result, the tuning of the intake manifold  10  improves volumetric efficiency and increases engine torque at higher engine speeds. 
       FIG. 7  illustrates schematically an inline four cylinder engine  49  connected with an alternative embodiment of intake manifold  50  according to the invention. The manifold  50  includes a pair of longitudinally extending, laterally spaced plenums  52 ,  54  that are joined together by first and second communication passages  56 ,  58 . The first communication passage  56  provides a short, large area passage connecting adjacent ends  60 ,  62  of the plenums. The second communication passage  58  extends from the ends  60 ,  62  of the plenums and laterally through the valve body to provide a longer, lower flow volume, tuning passage connecting the plenums, as in the first described embodiment. 
     The plenums  52 ,  54  have inlets  64 ,  66 , respectively, connected to receive intake air from a throttle body  68 . Four runners  70  direct intake air from the plenums  52 ,  54  to associated first and second groups  78 ,  80  of cylinders  74  within a single cylinder bank  76 . The first and second groups  78 ,  80  of cylinders  74  comprise alternately firing cylinder groups. However, it should be understood that the runners  70  and the cylinders  74  may rearranged depending upon the firing order of the cylinders. 
     The manifold includes a control valve  38  functionally similar to control valve  38  of  FIGS. 1–6 . Control valve  38  also has an elongated shaft  40  with first and second ends  42 ,  44  and spaced blades  46 ,  48 . The shaft  40  extends on a longitudinal axis  81  through the first and second axially spaced communication passages  56 ,  58 , which are controlled by blades  46 ,  48  carried on the shaft at the axially spaced locations of the communication passages  56 ,  58 . An actuator  45  is connected to one end of the shaft  40  to rotate the valve  38  to control communication through the first and second communication passages  56 ,  58 . 
     The remaining features and operation of the valve are as described previously with respect to the embodiment of  FIGS. 1–6 . 
     Thus, intake manifold  50  when installed with an inline engine operates in a manner similar to intake manifold  10  in that the control valve  38  alters air tuning of the manifold  50  to improve volumetric efficiency over a wide range of engine rpm. 
     It should be understood that seals may be provided to limit air leakage in either of the intake manifolds  10 ,  50 .  FIGS. 1–3  illustrate possible seal configurations where radially extending sealing disks  82  extend from the shaft  40  to limit air leakage around blades  46 ,  48  and around the circumferential surface  84  of the shaft. 
       FIG. 8  illustrates an alternative embodiment of the invention wherein the communication passages are angularly offset and the blades of the control valve are aligned along the length of the shaft. The figure shows a cross-sectional view similar to those of  FIGS. 4–6  but wherein the single figure shows all three mode positions of the control valve. Like numerals are use to indicate components similar to those of the embodiment of  FIGS. 4–6 . 
     Referring to  FIG. 8 , numeral  90  indicates a fragmentary portion of a modified intake manifold  90  which is similar to the embodiment of  FIGS. 1–3 . The cross-sectional view extends normal to the rotational axis  16  of the valve  38  and to the shaft  40  extending along the axis. The embodiment differs from  FIGS. 1–3  in that the longitudinally spaced communication passages  17 ,  18  in the tubular valve body  15  are not parallel, but angularly offset. Also, the longitudinally spaced control valve blades  46 ,  48  are longitudinally aligned. 
     In particular, the first communication passage  17  extends (horizontally in  FIG. 8 ) across the cylindrical center of the valve body  15 , while the second communication passage  18  is angularly offset at an angle of 60 degrees clockwise from passage  17 . The cross section is taken through the second passage  18 , so that this passage is shown by solid lines and the first passage  17 , located behind, is shown by hidden (dashed) lines. Additionally, since the first and second blades are axially aligned, the angular positions are the same so that the second blade  48  is seen in the second passage  18  and the first blade  46  is hidden behind the second blade  48 . Thus blade  46  is not seen in the figure but its position in the hidden first passage  17  is the same as that of blade  18  which is seen. 
     The three modes of operation of an engine with the manifold arrangement of  FIG. 8  is essentially the same as for manifolds  10  and  50 . At low engine speeds the control valve blades  46 ,  48  (shown in phantom lines with long dashes) are disposed in a first mode position  92  (60 degrees clockwise from horizontal in  FIG. 8 ) in which both the first communication passage  17  and the second passage  18  are blocked. The separate plenums  12 ,  13 , shown in  FIGS. 1 and 2 , thus remain separated and are tuned to increase engine torque at lower engine speeds. 
     At medium engine speeds, the valve  38  is rotated 60 degrees counterclockwise to a second mode position  94  in which the second valve blade  48  is shown in solid lines. In this mode position, both valve blades lie parallel with the second communication passage  18  so that the first blade  46  continues to close the first communication passage  17  while the second blade  48  opens the second communication passage  18 . The separate plenums are thus communicated through the longer passage  18 , which tunes the manifold to enhance engine torque at medium engine speeds. 
     At higher engine speeds, the valve is again rotated another 60 degrees counterclockwise to a third mode position  96  in which both blades lie horizontal, as shown in  FIG. 8 , and the first valve blade  46  is shown in hidden lines (with short dashes). In this mode position, both valve blades lie parallel with the first communication passage  17 , so that the first blade  46  opens the first communication passage  17  while the second blade  48  again closes the second communication passage  18 . The separate plenums are thus communicated through the shorter passage  18  which tunes the manifold to enhance engine torque at higher engine speeds. 
     While the previously discussed embodiments were directed to a V6 engine and an inline four cylinder engine, it should be understood that the intake manifold may be modified so that the two plenums are associated to other engine arrangements wherein the two plenums are connected to alternately firing cylinder groups as in the previously discussed embodiments. 
     While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.