Patent Publication Number: US-6662554-B2

Title: Adjustable restriction muffler system for a combine

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to harvesting apparatus, such as combines, and particularly to a muffler system for such combines that effectively increases engine horsepower in operation. 
     BACKGROUND OF THE INVENTION 
     Agricultural combines, such as disclosed in U.S. Pat. No. 6,257,977 are used to harvest crops in the field. However, there are times when such combines must be transported or driven on roads to reach the field or to return from the field. Some regulatory bodies have established noise restrictions for utility vehicles that travel on public roads. The “drive-by noise limitations” imposed by TueV and other European regulatory agencies are stringent. As the engine size and power level requirements increase, it becomes more difficult to meet these restrictions. 
     One source of noise emanating from a vehicle is the exhaust noise. Exhaust noise is usually attenuated by a muffler on the exhaust pipe. Normally, the noise attenuation capability of a muffler is directly proportional to its flow restriction. Flow restriction is typically measured as back pressure. Increased exhaust noise attenuation typically results in increased back pressure at the engine exhaust manifold which limits the available power from the engine. 
     Increased exhaust back pressure typically results in decreased available engine power, decreased fuel economy and possibly decreased turbocharger durability. 
     The present inventors have recognized that maximum power requirement for a combine does not occur in a road transport situation where the drive-by noise regulation must be restricted. The maximum power requirement occurs in the field. For transport on the road, the power requirement would be less than three quarters of the maximum rated power, the engine speed can be reduced, and the corresponding exhaust flows are much less than maximum flows. The present inventors have recognized that a muffler can be sized to meet these limited exhaust flows for noise attenuation requirements for road transport, but that such muffler would be too restrictive for full power operation in the field. 
     The present inventors have recognized that it would be desirable to develop a muffler system that reduces noise to acceptable levels during road transport, without imposing excessive back pressure limitations on the engine when operated in the field. 
     SUMMARY OF THE INVENTION 
     The present invention provides a bypass for an exhaust system for a utility vehicle, such as a combine, that, when substantially closed, would provide maximum noise attenuation for road transport, i.e., relatively high back pressure, and then, when substantially open, would provide a reduced flow restriction, i.e., relatively low back pressure, for full power, field operation. 
     The invention provides a bypass flow path in an exhaust pipe located upstream of a primary muffler. A diaphragm can be provided to manipulate a damper which acts to close the exhaust flow to the primary muffler and open the bypass to an exhaust pipe to effectively bypass the primary muffler, for field use of the utility vehicle. The system can be configured to entirely bypass the primary muffler and entirely route exhaust gases through the bypass or can be a system which bypasses a portion of the flow to effectively reduce back pressure while still maintaining some flow through the primary muffler. This would reduce the level of noise while still reducing back pressure to some extent. Additionally, the system could be configured to bypass exhaust gas from the primary, more restrictive muffler, to allow flow either entirely or proportionally to a less restrictive secondary muffler. Alternatively, the system could be configured such that the secondary muffler is not necessarily less restrictive, but the combined flow path through both primary and secondary mufflers is significantly less restrictive than through the primary muffler alone. 
     The amount of flow directed through the bypass would be dependent on the damper position. The damper position can be controlled by a diaphragm subject to positive air pressure delivered through an air line from the intake manifold of the engine, the air pressure being dependent on engine load for a turbocharged engine. Alternately, for a normally aspirated engine, intake manifold vacuum could be used to move the diaphragm. A solenoid valve can be inserted in the air line for more precise control. The solenoid valve can be controlled by a controller, preferably an electronic control unit of the vehicle. The degree of modulation of the damper could be controlled by the electronic control unit to be proportional to power requirements of the combine. When power requirements are low, all of the exhaust gases can be passed through the primary muffler. When power requirements are increased, progressively increasing amounts of exhaust gases can be bypassed by the opening of the damper, through the bypass flow path. Thus, even in the field where road noise restrictions are not applicable, a maximum amount of noise attenuation is achieved corresponding to the power demand. 
     The positioning of the damper can be undertaken in different ways. For example, the damper can be manually positioned by a lever and push/pull cable located in the vehicle cab and extending to the damper. Alternately, a solenoid valve can be signal connected to a manual selection switch and supplied with pressurized air, or vacuum, to manually control air pressure on the diaphragm that is connected to the damper. Alternately, the damper could be spring loaded to urge the bypass closed but which would be urged open by increasing back pressure. Alternately, an electrical switch could be triggered by an operator to open the bypass damper by use of a motorized screw thread actuator or stepper motor. 
     The bypass system could be electronically deactivated when the combine is placed in a higher gear used only for road travel, i.e., forcing all exhaust gas through the primary muffler. This would ensure compliance with road noise restrictions. 
     Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram of a muffler system according to the present invention, shown with the damper in a road transport position. 
     FIG. 2 is a schematic diagram of a muffler system according to the present invention, shown with the damper in a full power field position. 
     FIG. 3 is a schematic diagram of a further embodiment muffler system according to the present invention that uses a manual mechanism to effect exhaust bypass of the primary muffler. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While this invention is susceptible of embodiment in many different forms, there are shown in the drawings, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated. 
     FIG. 1 illustrates an engine  50  connected to an exhaust pipe  54  which connects to a valve station  56 . The valve station  56  is connected to two outlets, a first outlet  60  which is connected to a muffler pipe  62  and a second connection  66  connected to a bypass pipe  70 . The muffler pipe  62  is connected to a first muffler  72  connected to a first tail pipe  74 . 
     The bypass pipe  70  can be connected to a second muffler  76  that is connected to a second tail pipe  80 . The second muffler  76  can be a less restricted muffler for passing a substantial amount of the total exhaust flow at lower back pressure than the first muffler  62 , or could be more or less restrictive than the first muffler wherein the passing of the total exhaust gas through both mufflers results in a decreased back pressure during field use of the combine. Alternatively, the second muffler  76  can be eliminated entirely and the bypass pipe  70  can be connected to, or formed integral with, the tail pipe  80 . 
     Within the valve station  56  is a moveable damper  84 . The damper is pivotal about a pivot point  86 . In the position shown in FIG. 1, the damper is in a position such that all of the exhaust flows through the first muffler  72 . The damper is connected to an actuator rod  90  that is connected to a diaphragm  94 . The diaphragm is in pressure communication with a control air line  104 . The control air line  104  is connected to a pressurized air intake manifold  110  which delivers combustion air into the internal combustion engine  50 . As boost pressure in the intake manifold  110  increases, the damper is proportionally opened to bypass an amount of exhaust gas to the outlet  66  of the station  56 . The exhaust back pressure would thus be reduced during high power demand. 
     A solenoid valve  106  can be connected in the control air line  104 . The solenoid valve can be signal connected to a controller, such as a microprocessor based electronic control unit. Such controllers are associated with the combine transmission and control engine speed and transmission power output to the wheels. Such controllers are used to optimize vehicular efficiency. The controller can progressively open the bypass as power demand is made on the combine in the field. 
     Alternatively, the solenoid valve can be controlled manually by an operator activated electrical switch that opens or closes the solenoid valve. 
     FIG. 2 illustrates the system of FIG. 1 with the damper moved to close the exhaust pathway through the muffler and to open the bypass pathway. In this exhaust configuration, the exhaust system would be less restrictive and would result in more available horsepower from the engine when operated in the field where noise restrictions are not as important compared to operation during road transport. 
     FIG. 3 illustrates an alternate embodiment wherein a manual push-pull cable  202  is connected to an operator controlled handle or lever  204 . The cable  202  is connected to a bell crank  208 , the bell crank pivoted at a point  210  to the combine body. An opposite end of the bell crank is connected to the actuator rod  90 . Pushing or pulling the handle  204  would close or open the bypass outlet  66 . 
     From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.