Abstract:
An exhaust valve actuation system utilizes pressurized air provided by an air compressor and controlled by signals from a controller, such as an engine control module. The pressurized air is directed by a pressure valve that operates under the control of the controller and the exhaust valve is thus moved as a function of a preselected parameter monitored by the engine control module. The pressure valve can operate in a two position manner or a multi position manner, depending on the particular embodiment of the present invention utilized.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is generally related to an exhaust valve actuator and, more particularly, to an exhaust valve actuator that incorporates an air compressor to provide air pressure that is used to actuate an exhaust valve under the control of an engine control module. 
     2. Description of the Prior Art 
     Exhaust valves used in conjunction with two cycle engines are well known to those skilled in the art. 
     U.S. Pat. No. 4,539,813, which issued to Tomita et al on Sep. 10, 1985, describes an exhaust system control apparatus in an internal combustion engine. The exhaust system includes a subsidiary chamber connected to the normal exhaust passage with a valve for opening and closing communication between the chamber and exhaust passage to change the pressure wave at the engine cylinder exhaust port to provide optimum performance at high and low speeds. The chamber valve is operated rapidly by a pneumatic actuator supplied with compressed air from one or more of the sources disclosed, namely, a belt driven or electric air compressor and piston and a cylinder device extending between or forming the suspension components of a two wheeled vehicle. A pneumatic valve is operated by engine speed sensing means to supply or release the pressurized air to the actuator at a predetermined engine speed. 
     U.S. Pat. No. 5,873,334, which issued to Heinrich on Feb. 23, 1999, describes an exhaust valve system for a two cycle engine. The engine includes a cylinder having an exhaust port with an axial extent along the axis of the cylinder structure. An exhaust port valve is mounted adjacent to the exhaust port and is adjustable between a full flow position, in which the exhaust port valve exposes the exhaust port throughout its axial extent, and a restricting position, in which the exhaust port valve restricts the axial extent of the exhaust port. A valve control module is connected to the exhaust port valve and functions to adjust the exhaust port valve between the full flow and restricting positions in response to the cylinder bore gas pressure. At low speeds and low output conditions, the valve is in its restricting position. As the cylinder develops higher pressures at higher speeds and under higher output conditions, the valve control module moves the valve to its full flow position. 
     U.S. Pat. No. 4,986,780, which issued to Sougawa on Jan. 22, 1991, describes a two cycle engine and several embodiments of outboard motors embodying two cycle internal combustion engines which have an exhaust control valve and a decompression control valve that is operated in response to engine operating characteristics to improve performance and to reduce noise. Embodiments are disclosed wherein the control is in response to throttle valve position, engine speed and/or exhaust gas pressure. 
     U.S. Pat. No. 4,829,946, which issued to Boyesen on May 16, 1989, describes an exhaust control valve for a two cycle engine and a process for using the same. The control valve is located within the exhaust passage, seals against the piston, and delays opening of the exhaust passage to the combustion chamber during the expansion stroke of the piston for a preselected number of degrees of rotation of the crankshaft while permitting full opening of the exhaust port during the scavenging cycle. Also disclosed are means for modifying opening of the exhaust valve at high engine speeds to improve scavenging. 
     U.S. Pat. No. 4,723, 514, which issued to Taniuchi on Feb. 9, 1988, describes an exhaust timing control system for a two cycle engine. The system incorporates a pivotally mounted control valve to selectively close the upper portion of an exhaust port in a two cycle engine including a motor coupled with the valve for driving the same. A speed determination means is provided to determine the engine speed relative to a specified value. A drive means rotates the motor in either direction based on the sensing by the speed determination means. A drive current control means detects the magnitude of change of the engine speed and increases or decreases the current supplied to the motor to increase or decrease the speed of change of the control valve. 
     U.S. Pat. No. 4,391,234, which issued to Holzleitner on Jul. 5, 1983, describes an internal combustion engine comprising means for controlling the axial extent of a port in a cylinder. In an engine comprising at least one cylinder having a port and a piston which is reciprocal to open and close the port, the effective axial extent of said port is adapted to be reduced by a restricting member which is movably mounted adjacent to a flow passage which adjoins the port. The restricting member has a restricting edge and is movable to a restricting position in which the restricting edge is substantially flush with the peripheral surface of the cylinder bore. The restricting member defines the exhaust passage on one side thereof adjacent to the exhaust port. In order to improve the cooling of the cylinder and the exhaust gas flow, the restricting member constitutes a hinged member which is pivoted on an axis at that end which is opposite to the restricting edge. 
     U.S. Pat. No. 4,388,894, which issued to Tanaka et al on Jun. 21, 1983, describes a two stroke engine having exhaust timing control valve means. The two stroke has an exhaust port formed in the cylinder wall. At the upper portion of the exhaust port, there is provided a rotary type exhaust timing control valve which is adapted to be actuated by an electric servo motor to control the exhaust timing in accordance with the engine speed. A control circuit is provided for controlling for a power supply to the servo motor in accordance with the engine speed and the position of the valve. A timer switch is provided for providing a power supply to the control circuit for a certain time after the engine ignition switch is turned off so that the valve is moved to the retracted position after the engine is stopped. As the valve is thus moved to the retracted position, carbon deposits on the valve are scraped off by a scraping edge formed in the cylinder. 
     U.S. Pat. No. 4,364,346, which issued to Shiohara on Dec. 21, 1982, describes an exhaust timing device for a two cycle engine. The device, in which a valve member functioning as the upper edge of an exhaust port that opens into the inner circumference of a cylinder is disposed in the upper wall of the exhaust passage from the exhaust port. A valve hole having an elongated cross section is opened in the wall of the exhaust passage in the vicinity of the exhaust port and is formed at the inclination with respect to the axis of the cylinder. The valve member is arranged slidably in the valve hole to that it can be retracted into the valve hole until the leading end portion thereof becomes substantially coextensive with the inner wall surface of the exhaust passage. 
     U.S. Pat. No. 4,341,188, which issued to Nerstrom on Jul. 27, 1982, describes a two cycle internal combustion engine which includes means for varying cylinder port timing. The engine includes an engine block having a cylindrical wall defining a cylinder having a head end, a piston mounted for reciprocative movement in the cylinder, and a passage in the engine block, such as an exhaust passage, a transfer passage, or a crankcase fuel intake passage, terminating at the cylinder wall in a port, such as an exhaust port, a transfer port, or a piston controlled, crankcase fuel intake port, having upper and lower edges. A valve mounted in the passage for movement relative to the port is operable to selectively vary the effective distance of one of the port edges from the cylinder head end and thereby provide the capability of varying the timing of the port opening and/or closing as required to obtain optimum engine performance at different operating conditions. 
     U.S. Pat. No. 4,399,788, which issued to Bostelmann on Aug. 23, 1983, described an internal combustion engine comprising means for controlling the axial extent of an exhaust port in a cylinder. In a two stroke cycle internal combustion engine, cylinder structure has an inside peripheral surface which defines a cylinder bore and is formed with an exhaust port, which has an axial extent along the axis of said cylinder bore and communicates with said exhaust system. A piston is axially reciprocal in said cylinder bore and adapted to open and close said port. A restricting member is mounted in said cylinder structure adjacent to said port and adjustable between a full flow position, in which said restricting member exposes said exhaust port throughout its axial extent, and a restricting position, in which said restricting member restricts the axial extent of said exhaust port. A positioning drive is operatively connected to said restricting member and operable to adjust said restricting member between said full flow and restricting positions. The positioning drive is adapted to be controlled in dependence on the exhaust gas pressure in said exhaust gas system. 
     The above United States patent are hereby explicitly incorporated by reference in the description of the present invention. 
     Exhaust valves are typically provided to allow an engine to operate more efficiently and effectively at low operating speeds even though they are generally tuned for operation at higher speed ranges. When an engine is tuned for its best operation at higher speeds, low speed power is often compromised. This is particularly true for fixed geometry exhaust systems which are commonly used in outboard motor applications. As a result, acceleration performance at lower engine speeds is often less than desired. By providing an exhaust valve, certain advantages can be achieved. For example, exhaust emissions of unburned hydrocarbons can be minimized if the exhaust port size is reduced when the engine is operating at low speeds. Furthermore, the gas dynamic behavior of exhaust systems typically exhibit an expansion wave and a compression wave which arrive at the exhaust port at certain times during each cycle of the engine. By selectively altering the effective cross sectional area of the exhaust conduit of an engine, these expansion and compression waves can be used advantageously instead of occurring deleteriously. These and other advantages of exhaust valves are well known to those skilled in the art. 
     Exhaust valves known in the prior art are typically actuated by exhaust pressure, cylinder pressure, or by stepper motors. The use of exhaust pressure is generally undesirable since it can be affected by outboard motor installation and by boat operating conditions. Cylinder pressure activation is undesirable in many cases because the cylinder pressure can be affected by cylinder combustion quality. The use of a stepper motor is usually prohibitally expensive, especially when it is considered that many engines have multiple cylinders and each cylinder may require an individual stepper motor for these purposes. 
     It would therefore be significantly beneficial if a means for actuating an exhaust valve could be provided without the disadvantages incumbent with exhaust pressure actuation, cylinder pressure actuation, and stepper motor actuation. 
     SUMMARY OF THE INVENTION 
     An exhaust valve control system for an internal combustion engine, principally an outboard motor engine, made in accordance with the present invention comprises a compressor, a controller, an exhaust valve associated with the exhaust conduit of a cylinder of the engine, and a pressure valve. The pressure valve is connected in signal communication with the controller, which can be an engine control module or engine control unit, and is connected in fluid communication with the compressor. The compressor provides actuating pressure for the exhaust valve and this pressure is ported to the exhaust valve through the pressure valve. The controller determines the position of the exhaust valve relative to the exhaust conduit by controlling the pressure valve as a function of at least one operating parameter of the internal combustion engine. The exhaust valve is disposed within the exhaust conduit of a cylinder of the engine and within the exhaust flow stream emanating from the exhaust port of the cylinder and flowing through the exhaust system. 
     The exhaust valve can be a two position valve in which a first position completely opens the exhaust conduit and a second position completely closes the exhaust conduit. Alternatively, the exhaust valve can be movable to any one of a plurality of positions between fully closed and fully opened. 
     The exhaust valve control system of the present invention can further comprise an air rail connected in fluid communication with a compressor and a pressure regulator connected in fluid communication with the air rail to maintain a preselected pressure within the air rail. The system can further comprise an engine speed sensor connected in signal communication with the controller, wherein the controller determines the position of the exhaust valve relative to the exhaust conduit by controlling the pressure valve as a function of an engine speed signal received by the controller from the engine speed sensor. Alternatively, the system can comprise an engine load sensor in which the controller controls the position of the exhaust valve as a function of an engine load signal received from the engine load sensor. 
     The pneumatic circuit of the present invention can further comprise a pressure accumulator connected in fluid communication with the air compressor and, in certain embodiments, between the air compressor and the air rail. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be more fully and completely understood from a reading of the description of the preferred embodiment in conjunction with the drawings, in which: 
     FIG. 1 shows a typical exhaust valve associated with a cylinder of an internal combustion engine; 
     FIG. 2 is a simplified timing diagram showing the opening and closing of exhaust and transfer ports relative to the movement of a piston within a cylinder from top dead center to bottom dead center positions; 
     FIG. 3 shows a first embodiment of the present invention; and 
     FIG. 4 shows an alternative embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Throughout the description of the preferred embodiment of the present invention, like components will be identified by like reference numerals. 
     FIG. 1 is a typical engine with an exhaust valve, such as that disclosed in detail in U.S. Pat. No. 5,873,334, described above. An engine  10  comprises a cylinder  12  in which a piston  14  is slidably disposed for reciprocation within the cylinder  12 . A connecting rod  16  connects the piston  14  to a crankshaft (not shown in FIG.  1 ). A head  18  of the engine  10  defines a combustion chamber  20 . An exhaust passage  24 , or exhaust conduit, intersects the cylinder  12  as shown and a transfer port  28  also intersects the cylinder  12  as shown. An exhaust valve device  30  controls the reciprocal movement of an exhaust valve  32  that can selectively block a portion of the exhaust conduit  24 . The movement of the exhaust valve  32  into a restricting or non restricting position relative to the exhaust conduit  24  is controlled by some force, which can be provided by harnessing the exhaust pressure within the exhaust conduit  24 , cylinder pressure within the cylinder  12 , or by providing an external motive means such as a stepper motor. 
     FIG. 2 is a highly simplified representation of a timing diagram for an internal combustion engine. As the piston rotates from a top dead center (TDC) position within the cylinder  12  to a bottom dead center (BDC) within the cylinder  12 , various important events occur. At some point, such as approximately 92 degrees rotation from top dead center (TDC), as identified by reference numeral  50  in FIG. 2, the exhaust port  24  opens. Then, as the piston  14  continues to move downward within the cylinder  12 , the transfer port opens at point  52 . This can occur at approximately 120 degrees rotation from top dead center (TDC). At some time following the opening of the scavenging port  28 , and as the fuel air mixture is flowing from the crankcase into the cylinder  12  above the piston  14 , an expansion wave returns along the exhaust conduit  24  toward the cylinder  12 . This expansion wave is created by the unsteady action of the exhaust flow through the exhaust system and the shape and size of the exhaust system itself. Although the precise timing of the expansion wave return will vary from one system to another, as a function of many variables, it is desirable that it occur after the scavenging port opens at point  52 . This expansion wave is advantageous because it helps to draw exhaust from the region of the combustion chamber  20  within the cylinder  12 . As the piston reaches its bottom dead center (BDC) position and begins to move upward within the cylinder  12 , it is desirable to have a compression wave to travel along the exhaust conduit  24  toward the cylinder  12  as a natural function of the exhaust gas dynamics generated within the exhaust conduit  24  and the geometry of the exhaust system. This returning pressure pulse, or compression wave, typically occurs prior to the exhaust port  28  being closed by the upwardly moving piston  14 . A return of this compression wave prior to the closing of the exhaust port at point  56  in FIG. 2 can be advantageous because it tends to increase the mass of fresh charge within the cylinder as the exhaust port is closing. This is advantageous because it increases the density of the fuel air mixture within the cylinder and, as a result, the heat release of the subsequent combustion cycle event. The exhaust conduit  24  closes at point  58  as the piston continues toward its top dead center (TDC) position. In a typical application, the scavenging port closes at point  56  at approximately 240 degrees of rotation of the crankcase from top dead center (TDC) and the exhaust closes at approximately 268 degrees after top dead center (TDC). 
     In relative terms, the timing between the expansion wave return and the compression wave return remains generally constant, but these events move away from points  52  and  56 , respectively, in terms of absolute timing when the engine speed is reduced from the tuned condition. In other words, the elapsed time between the expansion wave return and the compression wave return is generally fixed and determined as a function of the exhaust gas temperature (speed of sound) and the geometry of the exhaust system. However, the absolute time between points  52  and  56  can increase significantly at low engine speeds. As a result, the absolute time that elapses between the exhaust port opening at point  50  and the expansion wave return increases at low engine speeds and the absolute time between the compression wave return and the exhaust port opening at point  50  also increase at low engine speeds. As a result, engine efficiency and power production at low engine speeds is reduced. Providing an engine with an exhaust valve can correct these deficiencies at low engine operating speeds. By partially closing the exhaust conduit  24 , the piston will reach the effective upper edge of the exhaust conduit  24  faster during its upward movement within the cylinder  28  than if the exhaust valve  32  is in its upward retracted position. In addition, as the piston  14  moves downward during the power portion of the cycle, the exhaust port will open at a later time because the effective upper edge of the exhaust conduit  24  is lowered relative to the cylinder  12  and the path of the piston  14 . 
     FIG. 3 is a schematic representation of the present invention. In certain outboard motor applications, the internal combustion engine used is provided with a direct fuel injection (DFI) system in which an air compressor  100  is used. The air compressor provides compressed air, through line  102 , to an air rail  106  that is used to pressurize fuel injectors. In a direct fuel injected (DFI) engine, each cylinder is provided with a fuel injector that injects fuel directly into the combustion chamber  20  of the cylinder  12 . A pressure regulator  108  regulates the pressure within the air rail  106  and excess pressurized air is exhausted through line  110  to the atmosphere as represented by reference numeral  114  in FIG.  3 . The present invention makes use of the air compressor and its ability to provide a stream of pressurized air by directing some of that pressurized air, through line  120 , to an inlet  124  of a pressure valve  130 . The pressure valve has a first outlet  132  that is connected in fluid communication with one or more exhaust valves, identified by reference numerals  141 - 143 . The exhaust valves are schematically shown within a dashed box  150  that represents the internal combustion engine of an outboard motor. It should be understood that the precise configuration of the exhaust valves, EV 1 , EV 2 , and EV 3 , is not limiting to the present invention. Any type of exhaust valve that requires an actuating force can be used in conjunction with the present invention which provides the actuating force and control system for the exhaust valves of an internal combustion engine. 
     A second outlet  160  of the pressure valve  130  is connected to an exhaust line  162  that provides an exhaust to the atmosphere, as represented by reference numeral  1   14 . 
     With continued reference to FIG. 3, the pressure valve  130  comprises a piston  170  and an actuating rod  172  that is movable under the force of a solenoid  176 . The piston  170  is shown in a solid line representation at a first position and in a dotted line representation at a second position in FIG.  3 . Movement from the first position to the second position is caused by actuation of the solenoid  176  under the control of a controller  190 , such as an engine control module (ECM). The controller  190  can receive signals from a tachometer  192 , a fuel measurement sensor  194 , or another type of sensor represented by reference numeral  196  and the associated dashed box in FIG.  3 . The precise type of parameter measured and provided to the controller  190  for control of the pressure valve  130  is not limiting to the present invention. It can be a tachometer  192  which measures engine speed, a fuel flow sensor  194 , such as a software routine in the ECM, which monitors the fuel provided to each cylinder of the engine  150 , or any other type of sensor  196 . When in the retracted position, the inlet  124  is blocked and the first and second outlets,  132  and  160 , are connected in fluid communication with each other. This allows the pressure on all of the exhaust valves,  141 - 143 , to be released through the exhaust line  162 . This would place the exhaust valves in their retracted positions in which the exhaust conduits are in a completely opened condition. When the piston  170  is moved toward the right under the force solenoid  176  and the control of the controller  190 , the second outlet  162  is blocked and the first outlet  132  is connected in fluid communication with the inlet  124  to provide pressurized to all of the exhaust valves,  141 - 143 . This actuates the exhaust valves and partially closes the exhaust conduits  24 . 
     In a particularly preferred embodiment of the present invention, a pressure accumulator  200  is provided to prevent undesirable pressure pulses in line  102  when piston  170  is moved from one position to another. 
     With continued reference to FIG. 3, it can be seen that the pressure valve  130  is of the type that can assume either one of two positions. In the first position, the exhaust valves are all fully opened and in the second position they are all fully closed. An alternative arrangement is described below in conjunction with FIG.  4 . 
     In FIG. 4, the compressor  100  is connected to the air rail  106  through line  102  and a regulator is provided to maintain a desired and preselected pressure within the air rail  106 . Excess air is exhausted through line  110  to the atmosphere as represented by reference numeral  114 . In FIG. 4, only one exhaust valve  141  is shown in the outboard motor engine  150  although it should be understood that any number of exhaust valves can be associated with the invention as shown in FIG.  4 . The pressure provided by the compressor  100  is conducted through line  210  and orifice  213  to the exhaust valve  141  and to a variable pressure regulator  214  as shown. The controller  190 , such as an engine control module (ECM) provides a control signal on line  220  to the variable pressure regulator  214  to select a desired pressure in line  210  and in line  230  which directly affects the exhaust valve  141 . In this way, control of the variable pressure regulator  214  can select a pressure in line  230  which can control the position of the exhaust valve  141  to any one of a plurality of positions between fully opened and fully closed. Excess pressure, above that desired in line  210 , is exhausted through line  240  to the atmosphere as represented by reference numeral  114 . 
     It should be understood that the use of a variable pressure regulator  214  can be used in many differently configured pneumatic circuits. The exhaust valves  141  can be connected between the air rail  106  and the atmosphere exhaust  114 , with the air rail  106  being connected between the exhaust values  141  and the compressor  100 . In addition, each exhaust valve  141  could be provided with a position sensor, such as an LVDT, to allow the pressure regulator  214  to be controlled as a function of the desired position and the actual position of each exhaust valve  141 . This type of control loop is within the knowledge of the skilled artisan and won&#39;t be described in the detail herein. 
     The differences between the embodiments shown in FIG.  3  and FIG. 4 relate to the ability of the control system in FIG. 4 to select many different positions for the exhaust valve  141 , whereas the arrangement in FIG. 3 is designed to select either a fully opened or fully closed position of the exhaust valve. 
     Since the compressor  100  is already available on direct fuel injected (DFI) engines, the pressurized air can be provided at no additional cost of manufacturer. The air provides a convenient and available motive force to actuate the exhaust valves, whether the exhaust valves are two position valves or multi-positioned valves. It should be understood that more than one valve may be used on more than one exhaust port in a given cylinder. The valve or valves can be located in a main exhaust passage or can be placed in an auxiliary exhaust port to control passage area and port timing. 
     Although the present invention has been described with particular detail and illustrated to show two particularly preferred embodiments, it should be understood that alternative embodiments are also within its scope.