Abstract:
A system and method for controlling the flow of air to an intake port of an engine is described that includes a flexible intake manifold runner comprised of helically wound braids. In one example, the length and cross-sectional area are mechanically interlinked. In this way, the flexible intake manifold runner can be tuned over a wider operating band while maintaining a lower cost design.

Description:
FIELD 
     The present description relates to a system and method for controlling a flow of air to intake ports of an engine. 
     BACKGROUND AND SUMMARY 
     Intake manifold runners include pipes designed to deliver a flow of air to combustion chambers within an engine. However, during certain parts of the engine drive cycle, intake valves are closed and prevent the air from flowing. When one or more intake valves open, a pressure wave develops within the runner and may increase the amount of air entering the open cylinder chamber. Therefore, under some operating conditions (e.g. at certain RPMs), the time when the propagating pressure wave encroaches upon the intake valve may align with intake valve opening, which causes a significant improvement in the volumetric efficiency and thereby the performance of the engine. For this reason, the airflow may depend on the geometry of a runner. For instance, the time for a pressure wave to propagate through a long manifold runner and back to an intake valve is longer compared to the length of time in a short manifold runner. As such, an engine with longer runners may have a torque peak at a lower RPM range than an engine with short intake runners, which may instead have a power peak at a higher RPM. 
     In an attempt to accommodate a range of engine conditions, intake manifolds with variable length runners spread out the torque curve into a broad, more manageable profile. Previous variable runner length designs may include continuously variable and discretely variable lengths. Continuously variable intake manifold runners vary the length of a runner with no substantial change to the runner shape or cross-sectional area. Because of the constant cross-sectional area, under some engine conditions, the variable length runner may degrade torque output and thereby decrease fuel efficiency. On the other hand, discretely variable runners typically have preset long and short runner configurations and so often have a pronounced valley of low torque output. An example intake manifold system with continuously variable runners that couple a change in length to a change in cross-sectional area is shown in U.S. Pat. No. 5,687,684 and U.S. Pat. No. 5,762,036. However, the manifold assembly described therein includes parts with intricate groove-like features and non-symmetrical shapes that may be fabricated by a time consuming injection mold process. 
     The inventor has recognized the disadvantages of the approaches described above and herein discloses a manifold assembly encased in a plenum chamber that includes flexible intake manifold runners coupled to an actuator shaft on one end and to an intake port of an engine on the other end. The flexible manifold runner may be comprised of a helically braided tube. This design allows for a continuously variable runner length, cross-sectional area and tube shape with reduced artificial obstructions to the flow of air to an intake port. 
     The present description may provide several advantages. In particular, extension of a biaxially braided tube causes a decrease in the cross-sectional area, with the reverse occurring as the tube is compressed. Therefore, an intake manifold runner can be tuned over a wide operating band from low RPM torque to high RPM power in a manner that depends on the operating conditions of the engine. As such, the method allows a cost-effective measure to control the flow of air to the engine based on engine speed and load. Furthermore, because the change of runner length can be calibrated to the change in cross-sectional area, the method may be implemented in various engine systems for optimal engine performance based on the speed and load on the engine, which thereby increases fuel efficiency. 
     The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings. It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The advantages described herein will be more fully understood by reading an example of an embodiment, referred to herein as the Detailed Description, when taken alone or with reference to the drawings, where: 
         FIG. 1  shows a schematic vertical cross-section through an example plenum with a flexible intake runner in the long configuration; 
         FIG. 2  shows a schematic vertical cross-section through an example plenum with a flexible intake runner in the short configuration; 
         FIG. 3  is a side view of an example engine block with flexible intake runners in the long configuration; 
         FIG. 4  is a side view of an example engine block with flexible intake runners in the short configuration; 
         FIG. 5  is a flow chart illustrating a method for controlling the flow of air to intake ports of an engine; 
         FIG. 6   a  is a schematic diagram of an example flexible intake runner with a cylindrical tube shape; 
         FIG. 6   b  is a schematic diagram of an example flexible intake runner with a conical tube shape. 
     
    
    
     DETAILED DESCRIPTION 
     The present description relates to a system and method for controlling the flow of air to intake ports of an engine. The method involves adjusting the length of flexible intake manifold runners comprised of helically wound braids in a manner that also changes the cross-sectional area. In  FIGS. 1 and 2 , exemplary long and short curved runners are shown to illustrate how air flows through the plenum assembly of the engine in each configuration. Then,  FIGS. 3 and 4  show side view schematic diagrams of an example I4 engine block with multiple braided runners in the long and short configurations, respectively, to illustrate how linkage arms connected to the braided runners operate as a unit when adjusting the length of the runners. Because runner length is continuously variable, the flow chart of  FIG. 5  describes a method for adjusting the runner length based on the engine operating conditions in a manner that also changes the cross-sectional area, which allow for the flow of air delivered to the engine to be adjusted. With respect to the runner shape,  FIGS. 6   a  and  6   b  illustrate how the runner tube shape may be adjusting by changing structural elements of the helical braids, which thereby allows a flow of air through each runner to be calibrated in the manner described herein. 
     Referring now to  FIGS. 1 and 2 , engine system  100  contains cylinder block  132 . The cylinder block and cylinder head  130  form a unit comprising at least one cylinder, including cylinder walls, combustion chambers, piston heads connected to a crankshaft, and poppet valves connected to a camshaft. It will be appreciated that the configurations and methods disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above technology can be applied to V-6, V-8, V-12, I-6, opposed 4, and other engine types. 
       FIGS. 1 and 2  show schematic diagrams of example vertical cross-sections through plenum  104  of engine  100  to illustrate how actuator linkage arm  116  couples rotatable actuator shaft  118  to a flexible intake manifold runner  106 . Because each flexible runner tube is comprised of interwoven helical braids, the manifold assembly system allows for the length and cross-sectional areas of the tube to coupled, wherein extension of the biaxially braided tube causes a decrease in the cross-sectional area, and compression of the braided tube causes an increase in the cross-sectional area. This design allows for a continuously variable runner length, cross-sectional area and tube shape with no artificial obstructions to the airflow. 
     In  FIG. 1 , intake manifold runner  106  is shown in the long configuration, wherein the runner may be at its longest length. Within plenum  104 , which is an enclosed, sealed space to contain air before delivering it to a combustion chamber within the engine block, manifold runner  106  is shown coupled to intake manifold  108  through a solid stationary ring  110 . Therein, one end of the flexible intake runner is fixed at an outlet of a manifold plenum (e.g. via a manifold flange), and an opposite end of the flexible intake runner is moveable within the plenum while being spaced away from all inlets and outlets of the plenum. In the example figure, the second end of manifold runner  106 , which is uncoupled from intake manifold  108  and an intake manifold opening is shown coupled to actuator linkage arm  116  through a hard adjustable ring  112 . As such, the second end is moveable within the plenum cavity. In one embodiment, the hard adjustable ring  112  may further have an airhorn shape to minimize flow loss. Combustion chambers within cylinder head  130  and cylinder block  132  can receive intake air via intake manifold  108 . Furthermore, each intake runner may selectively communicate with a corresponding cylinder via one or more intake valves of that cylinder. In some embodiments, one or more of the intake passages may include a boosting device such as a turbocharger or a supercharger. 
     Generally, air enters plenum  104  through air intake passage  102  and fills the chamber. In some embodiments, a throttle  134  including a throttle valve  136  may be provided along an intake passage of the engine for varying the flow rate and/or pressure of intake air provided to the engine cylinders. When manifold runner  106  is in the long configuration, as air fills plenum  104 , at least some of the air flow may be directed into flexible intake manifold runner. For this reason, a first air flow  128  is shown in the figure. Conversely, a second air flow path  126  is also shown but is not directed toward the long flexible runner. Rather, this secondary air flow fills the plenum chamber first, and then enters the runner second, for instance, if an intake valve is held open for a length of time that allows substantially all of the air in plenum  104  to be delivered to the cylinder. 
     To demonstrate the difference in air flow when the intake manifold runner  106  is in the short configuration,  FIG. 2  shows actuator linkage arm  116  rotated by angle  230  (e.g. 90°). Therein, the curved path followed by actuator linkage arm  116 , and therefore adjustable ring  112 , is also represented by angle  230 . Furthermore, because the cross-sectional area increases as flexible intake manifold runner  106  is compressed, the diameter of the tube near adjustable ring  112  is shown larger compared to the same element shown in  FIG. 1 . That is, diameter Y 2 -Y 2  is greater than diameter Y 1 -Y 1  from  FIG. 1 . When the flexible manifold runners are in the short configuration, as air enters the plenum chamber, it fills the plenum in a similar manner as described with respect to  FIG. 1 . However, the first air flow  128  and the second air flow  126  may both be directed into the intake manifold runner, which thereby allows the power generated to be increased when the load on the engine is high, for example, when engine RPMs are greater than 5000. 
     Turning now to the structure of intake manifold runner  106 , the flexible runners are comprised of helically wound braids  114  that are shown schematically in  FIGS. 1-4 , but described in more detail below. Inclusion of the interwoven braids allows the diameter, or cross-sectional area of the tube, to be changed when the length of the tube is changed, which is adjustable via movement of the linkage arm. Therefore, the two parameters are coupled such that a change in the tube length causes a change in the cross-sectional area. This design is commonly known as a finger-trap. The helically wound braids  114  may be comprised of strands of a composite spring material, such as a carbon fiber film, fiberglass, wicker fibers or fabric. Furthermore, changing various elements of the composite spring strands allows the overall shape of the tube to be adjusted, which further enables tuning of an intake manifold runner based on the engine speed and load. For example, a cylindrical braided runner may have composite spring strands with a substantially constant width that allows uniform adjustment of the tube cross-section along the entire length of the tube. Conversely, a conical braided runner may include composite spring strands with a variable width that allows a variable taper from one end to the other and a varying cross-section of the tube along its length. Because stationary ring  110  and adjustable ring  112  are shown having different diameters, or sizes, in the example configurations shown, the braided runner has a conical shape. Therefore, the cross-section on one side of the tube (e.g. near stationary ring  110 ) is larger than the cross-section on the other side (e.g. near adjustable ring  112 ). For example, in  FIG. 1 , the distance X-X, which represents the diameter of the tube near stationary ring  110  is larger than the distance Y 1 -Y 1  that represents the diameter of the tube near adjustable ring  112 . When the diameters of the tube are different at each end, the shape of the tube is conical. To substantially eliminate any air from leaking between the individual woven strands, the braided flexible tubes may be further encased in a flexible polymer membrane such as a balloon. In some instances, the flexible polymer membrane may be applied in a liquid form to the woven structure and then allowed to solidify, but in other instances, a pre-formed membrane may be applied to the either the outer or inner diameter of the woven flexible tubes during the manufacturing process. 
     In some embodiments, actuation of a curved runner may use a rotary actuator. Therefore, actuator linkage arm  116  is shown coupled to a hard adjustable ring  112  on a first end, and to actuator shaft  118  on a second end. Therefore, engine  100  may also include control system  12  coupled to actuator shaft  118 , which may adjust the length of the braided runner by rotating actuator shaft  118  around a longitudinal axis based on the engine operating conditions. Because the braided runner is coupled to a rotary actuator, the motion of actuator linkage arm  116  may scribe an arc or curved path along which the curved, braided runner is designed to follow. In some embodiments, the path scribed by a linkage arm may not be curved but instead may be substantially linear. When this is the case, actuation may be provided by a linear actuator instead of a rotary actuator. In other embodiments, the path may be a combination of straight and curved based on different types of actuators and linkages having various motion ratios and paths of motion. 
     Although a long and a short configuration are shown in  FIGS. 1 and 2 , control system  12  may continuously adjust the position of adjustable ring  112  simply by rotating actuation shaft  118  around an axis with the linkage arm coupled thereto. As such, adjustable ring  112  may be stopped at any point along its path in a manner that allows continuous position adjustment. Then, based on the geometric characteristics of tube, the air delivered to intake ports of the engine can be calibrated for optimal delivery based on the speed and load on the engine. 
     With regard to modulation of runner length when multiple runners are present,  FIGS. 3 and 4  show schematic side view diagrams of an example I4 engine block that includes actuator shaft  118  coupled to shorter actuator linkage arms  116  and a longer central actuator linkage arm  117 . Because all three linkage arms are coupled to actuator shaft  118 , control system  12  may change the runner length simply by rotating actuator shaft  118  around an axis. Therefore, in some embodiments, the actuator shaft and linkage arms coupled to flexible runner tubes form a structure that operates as a unit. While adjustment of runner length is described in terms of a structural unit in this example embodiment, in some embodiments, the length of each runner may not be adjusted synchronously but may instead be adjusted independently in a manner that depends on the engine operating conditions. For instance, the movement of individual runners may be designed for optimal engine tuning based on the packing space available in the engine compartment, or on a set of desired engine torque curve characteristics. In still other embodiments, the movement of the arms may be non-uniform but still be adjusted in a manner that depends on the operating conditions of the engine. 
     In  FIGS. 3 and 4 , air flows into plenum  104  through air intake passage  102  as described with respect to  FIGS. 1 and 2 . However, in this example, as the flow of air enters the chamber, it may branch into multiple air paths  302  and begin to fill the chamber. As described above, each of these air paths may be comprised of a first and second air flow path as shown in  FIG. 1 . Although the pathways are represented by substantially straight arrows in the figures, in some instances, the air paths may form eddies or swirl as they fill the plenum chamber and so not flow directly into the runners. For example, when the intake ports are closed, air entering plenum  104  may fill the chamber but not flow to the intake ports until the pressure differential corresponding to intake valve opening occurs. With the runners in the long configuration, as air flows into the plenum at least some air may enter the flexible runners through adjustable rings  112 . For example, as air flows into the chamber, an airflow path may develop that is directed downward through plenum  104  toward adjustable ring  112  in a manner similar to the first air flow  128  shown in  FIG. 1 . This airflow may enter manifold runner  106  as it continues on toward intake manifold  108 . Arrows  304  shown therein represent the direction of flow through the braided runners. 
     In  FIG. 3 , actuator shaft  118  is shown connected to three linkage arms. However, in some embodiments, a different number of linkage arms may be present. Because the two outside intake manifold runners are shorter than the two central runners, two different types of linkage arms are present. In the example shown, the short linkage arms  116  are coupled to adjustable rings  112  as indicated in  FIG. 1 . For example, in some embodiments, coupling of linkage arms  116  to adjustable rings  112  may comprise a simple hook and eye closure while in other embodiments, the two metal parts may be attached in a more permanent bonded manner, for example, by adhering the linkage arms directly to the adjustable rings. Generally, a single or multi-bar linkage may be used independently or in combination with other linkages depending on the desired movement path of a runner, which may be a straight line, a circular or curved arc, or a combination of straight and curved paths. With regard to the central linkage arm  117 , which changes the length of the two longer braided runners by rotating actuator shaft  118 , the linkage arm is shown coupled to connecting part  306  that connects the linkage arm to the adjustable rings of the longer braided runners. In some embodiments, connector part  306  may be a rod that connects the two central adjustable rings while central linkage arm  117  is comprised of a hook on one end to couple the linkage arm to the rod. Therefore, when actuator shaft  118  rotates, a rotational force is transferred to the central linkage arm  117 , which is rigidly attached to actuator shaft  118  on one end. This rotational force is further transferred to connecting part  306  and thereby adjusts the length of the flexible manifold runners. 
     In contrast,  FIG. 4  shows a schematic side view diagram of the example I4 engine with braided runners in the short configuration. As such, actuation shaft  118  has been rotated about a longitudinal axis and actuator linkage arms  116  and central linkage arm  117  extend laterally away from actuator shaft  118  as shown in  FIG. 2 . In this view, because the linkage arms extend laterally away from the actuator shaft, all three arms are shown as small ovals to represent the view looking down the longitudinal axis of the linkage arms. Furthermore, connecting part  306  is shown bisecting actuator shaft  118  to indicate its position has also changed in response to the rotation of the shaft. Therefore, the structure has been rotated as a unit to adjust the length of the braided intake manifold runners. 
     As described in more detail in  FIG. 2 , air flow paths through plenum  104  and flexible braided runners in the short configuration are shown in  FIG. 4 . Advantages of the method include introducing more air into the intake manifold runners for higher power during operating conditions where the engine load and RPMs are high (e.g. greater than 5000 rpms). Therefore, as the air introduced through air intake passage  102  fills plenum  104 , at least some of the air is directed to intake manifold runners  106 , which flows to intake manifold  108 . As indicated above, arrows  304  depict the direction of flow through the intake manifold runners. 
     Engine  100  includes controller  12 , which may adjust the position of actuation shaft  118  based on the speed and load on the engine. Therefore, engine speed signal, RPM, may be generated by engine controller  12  from signal PIP. Manifold pressure signal MAP from a manifold pressure sensor may be used to provide an indication of vacuum, or pressure, in the intake manifold. Note that various combinations of the above sensors may be used, such as a MAF sensor without a MAP sensor, or vice versa. During stoichiometric operation, the MAP sensor can give an indication of engine torque. Further, this sensor, along with the detected engine speed, can provide an estimate of charge (including air) inducted into the cylinder. For example, in some embodiments, the control system may be comprised of a map that relates the speed of the vehicle or RPMs to the volume of air delivered to the intake ports of a combustion chamber. Then, in response to a detected speed and load, controller  12  may direct actuator shaft  118  to rotate its position based on the detected operating conditions. Because the shaft is continuously adjustable within an operating range, modulation of runner length is also continuously variable. Therefore, the tube shape can be designed and calibrated to adjust the length and cross-sectional area such that a known amount of air can be delivered to the engine based on the operating conditions. In this way, the intake manifold runners of an engine can be tuned to deliver air to the intake ports of an engine based on the speed and load on the engine. 
     The system described includes a method for controlling the volume of air delivered to intake ports of an engine based on the operating conditions therein. Therefore,  FIG. 5  shows a flow chart of method  500  that allows the position of the actuator shaft to be adjusted in order to control the flow of air through the variable intake manifold runners. 
     At box  502 , method  500  includes monitoring the engine operating conditions. For example, controller  12  may be a conventional microcomputer including: a microprocessor unit, input/output ports, read-only memory, random access memory, keep alive memory, and a conventional data bus. Although sensors within engine  100  are not shown, controller  12  may receive various signals from sensors coupled to engine  100 , including: engine coolant temperature (ECT) from a temperature sensor; a position sensor coupled to an accelerator pedal for sensing force applied by a foot; a measurement of engine manifold pressure (MAP) from a pressure sensor coupled to intake manifold  108 ; an engine position sensor from a Hall effect sensor sensing crankshaft position; a measurement of air mass entering the engine; and a measurement of throttle position. Barometric pressure may also be sensed for processing by controller  12 . In one aspect of the present description, an engine position sensor produces a predetermined number of equally spaced pulses per revolution of the crankshaft from which engine speed (RPM) can be determined. 
     At box  504 , method  500  may determine whether to adjust the length of the intake manifold runners based on the operating conditions of the engine. For example, if a load on an engine is increased in response to a vehicle driving uphill, controller  12  may detect the increased RPMs to determine that the length of the flexible manifold runner tube is to be shortened in order to increase the cross-sectional area and thereby increase the air to fuel ratio and deliver high power RPMs. In response, the volume of air may be adjusted when controller  12 , which includes memory with instructions to adjust the flexible intake runner based on the operating conditions, sends a signal to rotate actuator shaft  118 , which is indicated at box  506 . Therefore, the method includes rotating the shaft based on the engine load to adjust the length and cross-sectional area of the braided runners. However, if controller  12  determines that no adjustment is to be made based on the engine operating conditions, controller  12  may determine that the runner lengths are sufficient for the current operating conditions. In this case, the controller may not make an adjustment but instead continue to operate the vehicle using the current conditions while it monitors sensors within the engine system. 
     Turning to the shape of the flexible manifold runners,  FIGS. 6   a  and  6   b  show schematic diagrams of cylindrical and conical braided runners to illustrate the various elements of example helically wound braids. 
     In  FIG. 6   a , tube diameter  602  is indicated at one end of the figure. However, because the tube shape is cylindrical, the diameter of the tube shown is substantially constant over the entire length of the tube. Therefore, the diameter near the bottom of the tube is substantially equal to tube diameter  602  and the shape is cylindrical. Although a tube length  604  is also shown, it can be adjusted in the manner already described. In response to an extension of tube length  604 , tube diameter  602 , and therefore the cross-sectional area decreases. Conversely, a compression of tube length  604  is coupled to an increase in tube diameter  602 , and therefore the cross-sectional area. For a cylindrical tube, changes to tube diameter  602  are substantially equal as a function of tube length  604 . 
     In one embodiment, an intake manifold runner may be comprised of two helically wound braids. A first composite spring strand  606  and a second composite spring strand  608  are identified in  FIG. 6   a . By altering the widths of first composite spring strand  606  and second composite spring strand  608 , the length to diameter relationship of the tube can be changed. However, for a cylindrical tube, the width of the composite spring strands along the length of the runner is substantially constant.  FIG. 6   a  includes an inset showing an expanded view of the interwoven surface, wherein first composite spring strand  606  has strands that run in a first direction  610 , and second composite spring strand  608  has strands that run in a second direction  612  as the two strands interweave along the longitudinal axis of the cylindrical runner. The relationship between the change of tube length  604  and a change in the cross-sectional area, or tube diameter  602 , can be further defined by weave angle  614  of the multi-axial braid. 
     As illustrated in  FIG. 6   a , the interwoven braids include the strands positioned at an angle with respect to one another (90 degrees in this example), with the angle varying with the length of the tube. The interwoven braids repeatedly overlap with one another, with one strand laying on top and adjacent to, another strand. This woven structure, on a macro scale, enables the variable length as described herein in that the strands are not affixed or bonded to one another at the face-sharing contact areas. 
       FIG. 6   b  shows a schematic diagram of a conical runner whose shape may be defined by including a braid with a variable taper from one end to the other, which results in a variable cross-section along the length of the tube. For example, the width of first composite spring strand  606  and second composite spring strand  608  may vary over the length of the tube to create the conical structure. One possible configuration is shown in  FIG. 6   b  wherein the tube diameter  602  at a first end is different from smaller second diameter  603  at the other end of the tube. Because the tube diameters are different at each end, the tube has a conical shape that is different from the cylindrical shape shown in  FIG. 6   a . As described above with respect to  FIG. 6   a , an extension of tube length  604  results in a decrease in second diameter  603  and therefore the cross-sectional area of the tube. Conversely, a compression of tube length  604  is coupled to an increase in second diameter  603  and the cross-sectional area. For a conical tube, changes to second diameter  603  at the bottom of the tube may differ from changes to tube diameter  602  as a function of the tube length  604 . Furthermore, the relationship between the change of tube length  604  and a change in the cross-sectional area, or second diameter  603 , can be defined by weave angle  614  of the multi-axial braid. By varying the angular relationship of the strands in the braided runner, the change in cross-sectional area relative to the change in runner length can be varied. In addition, by altering the width of the individual braid strands and varying the angle of the braid over the length of the runner, the relative changes in cross-sectional area can be made non-uniform relative to changes in runner length, which allows for tuning of the runner shape and length for various operating conditions. Finally, to allow for packaging constraints, the braided runner can be woven over a form of requisite shape using individual strands with varying widths, which allows a tapered runner over a curved length. In this way, the volume of air delivered to the intake ports of an engine can be calibrated based on the speed and load of an engine. 
     This concludes the description. The reading of it by those skilled in the art would bring to mind many alterations and modifications without departing from the spirit and the scope of the description. For example, I3, I5, V6, V8, V10, and V12 engines operating in natural gas, gasoline, diesel, or alternative fuel configurations could use the present description to advantage.