Patent Publication Number: US-9429107-B2

Title: Solenoid autochoke for an engine

Description:
BACKGROUND 
     The present invention relates to an engine starting system for an internal combustion engine. More particularly, the invention relates to an automatic choke system for a small engine. 
     Internal combustion engines typically include a system or mechanism, such as a carburetor with a choke valve, to regulate the air/fuel mixture to the engine. The choke valve reduces the airflow through the carburetor to enrich the air/fuel mixture. When starting the engine, it is typically desirable to provide a rich air/fuel mixture. When initially starting an engine in cold engine temperature conditions, it may be desirable to keep the choke closed for an extended period of time. 
     SUMMARY 
     One embodiment of the invention relates to a choke system for an internal combustion engine including a carburetor having an air intake, a choke valve disposed in the air intake, and a choke lever coupled to the choke valve, wherein the choke valve is movable between a closed position and an open position, a mechanical linkage coupled to the choke lever, and a solenoid attached to the carburetor and coupled to the mechanical linkage so activation of the solenoid moves the choke valve, wherein the solenoid is activated in response to activation of a starter system of an internal combustion engine, thereby moving the choke valve via the mechanical linkage to the closed position. 
     Another embodiment of the invention relates to an engine starting system including a battery, a starter motor electrically coupled to the battery, a starter switch electrically coupled between the battery and the starter motor, an ignition actuator configured to close the starter switch when the ignition actuator is in a start position, a carburetor having an air intake and a choke valve disposed in the air intake, and an automatic choke mechanism coupled to the choke valve, the automatic choke mechanism comprising a solenoid electrically coupled to the starter switch and mechanically coupled to the choke valve, wherein the solenoid includes a plunger moveable in a direction parallel to a flow of air through the air intake between an extended position and a refracted position, and wherein the plunger moves to the retracted position to close the choke valve when the starter switch is closed and moves to the extended position to open the choke valve when the starter switch is open. 
     Another embodiment of the invention relates to a method for adjusting the position of a choke valve including providing a choke valve in the air passage of a carburetor, providing a linkage external to the carburetor and coupled to the choke valve, providing an automatic choke mechanism electrically coupled to a starting system for an engine, the automatic choke mechanism comprising a solenoid coupled to the linkage and oriented parallel to the air passage, and energizing the solenoid upon activation of the starting system, thereby rotating the linkage and closing the choke valve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will become more fully understood from the following detailed description, taken in conjunction with the accompanying figures. 
         FIG. 1  is an exploded view of an internal combustion engine including a choke override, in accordance with an exemplary embodiment. 
         FIG. 2  is a schematic diagram of a starter system for an internal combustion engine. 
         FIG. 3  is an isometric view of an air intake assembly for the internal combustion engine of  FIG. 1 . 
         FIG. 4  is an isometric view of the carburetor for the air intake assembly of  FIG. 3 . 
         FIG. 5A  is an isometric view of the air intake assembly of  FIG. 3  with the choke open. 
         FIG. 5B  is a top view of the air intake assembly of  FIG. 3  with the choke open. 
         FIG. 6A  is an isometric view of the air intake assembly of  FIG. 3  with the choke closed by an automatic choke mechanism. 
         FIG. 6B  is a top view of the air intake assembly of  FIG. 3  with the choke closed by the automatic choke mechanism. 
         FIG. 7A  is an isometric view of the air intake assembly of  FIG. 3  with the choke closed by a manual choke mechanism. 
         FIG. 7B  is a top view of the air intake assembly of  FIG. 3  with the choke closed by the manual choke mechanism. 
         FIG. 8  is a schematic diagram of a starter system for an internal combustion engine, according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Before turning to the figures, which illustrate the exemplary embodiments in detail, it should be understood that the present application is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology is for the purpose of description only and should not be regarded as limiting. 
     Referring to  FIG. 1 , in an exemplary embodiment, an engine  20  is a small, single cylinder, gasoline-powered, four-stroke cycle internal combustion engine. However a broad range of engines may benefit from the teachings disclosed herein. In some embodiments, the engine  20  is vertically shafted (as shown in  FIG. 1 ), while in other embodiments, the engine may be horizontally shafted. In some contemplated embodiments, the engine may include two or more cylinders or may have a two-stroke cycle. In one embodiment, the engine is configured to power a riding lawn mower. In other embodiments, the engine  20  may be configured to power a broad range of equipment, including walk behind lawn mowers, pressure washers, electric generators, snow throwers, and other outdoor power equipment. In contemplated embodiments, the engine  20  may be gasoline-powered or otherwise fueled. The engine  20  includes a cover  22  and a cylinder head  24  that are fastened to an cylinder block  26  of the engine  20 . 
     As shown schematically in  FIG. 2 , the engine  20  is coupled to a starting system  30  with a battery  32 , a starter motor  36  powered by the battery  32 , a operator input such as an ignition actuator or keyswitch  34 , and a starter switch or solenoid  38 . The battery  32  provides stored electrical energy to operate the starting system  30  and may be configured to provide electrical energy to other systems of a vehicle powered by the engine  20 . According to an exemplary embodiment, the battery is a 12-volt battery (e.g., a lead acid battery). In some embodiments, the keyswitch  34  has a stop position, a run position, and a start position. An operator starts the engine  20  by turning the keyswitch  34  to a start position. This, in turn, closes the starter solenoid  38  to electrically couple the starter motor  36  to the battery  32 . The starter motor  36  draws power from the battery  32  and is configured to turn the crankshaft of the engine  20  to start the engine  20 . Once the engine  20  is running, the operator may turn the keyswitch  34  to the run position, opening the starter solenoid  38  to decouple the starter motor  36  from the battery  32 . In some embodiments, the ignition actuator  34  is a pushbutton, switch, or other appropriate user input device. 
     Referring to  FIG. 3 , the engine  20  further includes an air intake assembly  40  with an intake manifold  42  coupled to a carburetor  50 . The engine  20  draws an air/fuel mixture into the engine  20  via the air intake assembly  40 . Air is directed to the air intake assembly  40  (e.g., through an air filter), where it is mixed with a fuel (e.g., gasoline) in the carburetor  50 . The air/fuel mixture is then directed through the intake manifold  42  to the cylinder block  26 , where it is combusted in an internal combustion chamber that may be formed from a cylinder and a piston, a plurality of pistons, a cylinder head, a valve, a plurality of valves and the like. According to an exemplary embodiment, the carburetor  50  is coupled to an automatic choke mechanism  70  and a manual choke mechanism  80 . The automatic choke mechanism  70  and the manual choke mechanism  80  act to adjust carburetor  50  to provide a preferred air-to-fuel ratio in a variety of operational conditions. 
     The air flow rate through the air cleaner and the air intake assembly may be in part governed by a controller (not shown), such as a computer, with a processor, memory, and/or stored instructions. For example, the controller may activate a super- or turbo-charger compressor fan, based upon the stored instructions (e.g., a logic module), to draw an increased air flow through the air system. Such a controller may also operate other features and components of an engine, such as a timing of valves in a combustion chamber, and the like. 
     Referring to  FIG. 4 , the carburetor  50  mixes fuel from a fuel input  52  with air for combustion in the engine  20 . The carburetor  50  includes a throttle valve with a throttle lever arm (not shown) and a choke valve  54  (e.g., choke plate). The choke valve  54  is a butterfly valve that rotates about a shaft  56  in an air inlet passage  58  to control the amount of air drawn into the carburetor  50  and the ratio of air to fuel mixed in the carburetor  50 . In an open position, as shown in  FIG. 4 , the choke valve  54  is oriented generally parallel to the flow of air through the inlet passage  58 , thereby increasing the air flow into the carburetor  50  to provide a leaner air/fuel mixture to the engine  20 . In a closed position (as shown in  FIGS. 6A-7B ), the choke valve  54  is oriented generally perpendicular to the flow of air through the inlet passage  58 , thereby reducing the air flow into the carburetor  50  to provide a richer air/fuel mixture to the engine  20 . In an exemplary embodiment, the choke valve  54  is biased to the open position by a biasing member, such as a torsion spring (not shown). 
     Referring still to  FIG. 4 , the choke valve shaft  56  is coupled to a choke lever  60  mounted to the exterior of the carburetor  50 . According to an exemplary embodiment, the choke lever  60  is coupled via a linkage  62  to the automatic choke mechanism  70  and the manual choke mechanism  80 . The automatic choke mechanism  70  and the manual choke mechanism  80  adjust the carburetor  50  by acting on the choke lever  60  through the linkage  62  to adjust the position of the choke valve  54  in the inlet passage  58 . The linkage  62  coupling the automatic choke mechanism  70  and the manual choke mechanism  80  to the choke lever  60  is formed by a single lever rotating about a pivot point  63 . A first end  64  of the linkage  62  includes a slot  65  that engages a peg  61  (e.g., protrusion, nub, extension, etc.) of the choke lever  60 . A second end  66  of the linkage  62  includes a first opening  67  by which the automatic choke mechanism  70  is coupled to the linkage  62  and a second opening  68  by which the manual choke mechanism  80  is coupled to the linkage  62 . The single member linkage  62  simplifies the mechanical connection between the choke lever  60  and the choke mechanisms  70  and  80 , reducing the potential for stacked tolerance issues and providing a more precise and responsive movement of the choke lever  60  in response to input from the automatic choke mechanism  70  or the manual choke mechanism  80 . 
     Referring now to  FIGS. 5A-7B , the air intake assembly  40  is shown in several modes of operation.  FIGS. 5A and 5B  depict the air intake assembly  40  when the engine  20  is at rest with the choke valve  54  in the open position. 
       FIGS. 6A and 6B  depict the air intake assembly  40  when the engine  20  is being started with the starting system  30 . The automatic choke mechanism  70  is utilized to automatically engage the choke to enrich the air/fuel mixture and facilitate the starting of the engine  20  and disengage the choke at an appropriate point to keep the engine  20  from stumbling or stalling after it has started. In an exemplary embodiment, the automatic choke mechanism includes a solenoid  72  that is electrically coupled to the starting system  30  and mechanically coupled to the air intake assembly  40 , for example, via a pinned connection to the first opening  67  of the linkage  62 . In some embodiments, the solenoid  72  includes a plunger  73  (e.g., a linear actuator, a post, etc. biased to a normally extended position. In different embodiments, the shape of the plunger  73  may vary. In some embodiments, the solenoid  72  is a rotary solenoid. The solenoid  72  is attached to the carburetor  50  and, in some embodiments, may also be attached to the air intake manifold  42  proximate to the carburetor  50 . This provides for a relatively small, compact assembly of the solenoid  72  and carburetor  50  which keeps the overall size of the engine  20  substantially the same as an engine without the automatic choke mechanism  70 . This is advantageous because it reduces the design constraints or changes necessary to use the engine  20  with the automatic choke mechanism  70  in a commercial product (e.g., lawn mower, snow thrower, generator, pressure washer, etc.). 
     As shown in  FIG. 2 , the solenoid  72  is electrically coupled to the starting system  30  through the starter motor  36 . The solenoid  72  is electrically coupled in series with the starter motor  36 . In some embodiments, a thermal switch (e.g., thermal switch  74  shown in  FIG. 8  and discussed below) is electrically coupled in series between the solenoid  72  and the starter motor  36 . The thermal switch is configured to open when subjected to a threshold temperature, thereby breaking the circuit and cutting power to the solenoid  72 . In some embodiments, the thermal switch is located on or near the engine block to detect the threshold engine temperature. The threshold engine temperature may be, for example, 110° F. By cutting power to the solenoid  72  at the threshold engine temperature, the thermal switch deactivates the automatic choke mechanism  70  when the engine  20  is already warm enough to not require automatic choking for a warm restart. The solenoid  72  may be coupled to the starter motor  36  with an existing wire harness and no additional inputs or wire harnesses are needed. When the operator starts the engine  20  by turning the keyswitch  34 , the starter solenoid  38  closes to electrically couple the solenoid  72  to the battery  32  such that the battery  32  energizes the solenoid  72 . When energized by the battery  32 , the plunger  73  of the solenoid  72  moves from its extended, rest position to a retracted position. In some embodiments, the solenoid  72  activates at a voltage (e.g., approximately 5V) that is less than the voltage (e.g., an operational voltage) drawn by the starter motor  36  (e.g., approximately 7.5V). When the starter solenoid  38  closes, the solenoid  72  is therefore activated before the starter motor  36 . The plunger  73  of the solenoid  72  is positioned along and travels in a direction parallel to the flow of air through the carburetor  50  (i.e., parallel to the longitudinal axis of the air inlet passage  58 ). In other embodiments, the plunger  73  does not travel in a direction parallel to the flow of air through the carburetor  50 . Because the end of the plunger  73  is coupled to the first opening  67  in the linkage, the retraction of the plunger  73  rotates the linkage  62  about the pivot point  63 . The rotation of the linkage  62  forces the peg  61  to move along the slot  65 , causing the choke valve  54  to rotate in the air inlet passage  58  to the closed position. In the closed position, the choke valve  54  reduces the air flow into the carburetor  50  to provide a richer air/fuel mixture when the engine  20  is started. 
     Once the engine  20  has started and the operator moves the keyswitch  34  from the starting position to the run position, the starter motor  36  begins to ramp down. As the starter motor  36  runs down from full speed to a stop, a voltage continues to be applied to the solenoid  72 . The automatic choke mechanism  70  therefore continue to hold the choke valve  54  in the closed position for a short period (e.g., approximately 0.4 seconds) after the engine  20  has started and the starter motor  36  is disengaged. This short period of time prolongs the amount of time the engine  20  is choked, which can be advantageous for some engines, particularly when starting the engine in cold weather. When the starter motor  36  stops turning and a voltage is no longer applied to the solenoid  72 , the biasing member returns the choke valve  54  to the open position. 
     The voltage provided to the solenoid  72  by starting system  30  is limited by the capacity of the battery  32  and the voltage needed to turn the starter motor  36 . The starting system  30  is configured to provide the solenoid  72  a voltage that is sufficient to actuate the solenoid  72  to overcome the biasing force urging the choke valve  54  to the open position. By orienting the plunger  73  of the solenoid  72  parallel to the flow of air through the carburetor  50  and coupling the post to the choke valve  54  with a single linkage or lever  62 , allows the stroke of the plunger  73  to be minimized while delivering sufficient force to the linkage  62  to close the choke valve  54 . The force delivered by the solenoid  72  is limited by two primary factors, the voltage applied to the solenoid  72 , which is itself limited by the battery  32  and other draws on the battery  32 , and the length of the stroke of the plunger  73 . Using the mechanical advantage provided by the single linkage  62  allows the stroke of the plunger  73  to be optimized relative to the voltage available from the battery  32  to ensure that the solenoid  72  closes the choke valve  54  when the starting system  30  is activated. 
     Referring to  FIG. 8 , an alternative starting system  130  is illustrated. Except for the differences discussed below, the starting system  130  is similar to the starting system  30 . In starting system  130 , the solenoid  72  is electrically coupled in parallel with the starter motor  36 . When the ignition actuator  34  is moved to the start position, the starter solenoid  38  is energized. The high voltage side of the starter solenoid  38  conducts power to the starter motor  36  to start the starter motor  36 . The low voltage side of the starter solenoid  38  is electrically coupled to the solenoid  72  of the autochoke mechanism  70  so that the solenoid  72  is energized when the starter solenoid  38  is energized. Thermal switch  74  is electrically coupled in series between the starter solenoid  38  and the solenoid  72  and configured to break the circuit and cut power to the solenoid  72  when exposed to a threshold engine temperature. Diode  76  is electrically coupled in parallel with the solenoid  72 . Diode  76  prevents remanence or the magnetization of the housing or other components of the solenoid  72  that may occur due to repeated cycling of the solenoid  72 . In some embodiments, the diode  76  is incorporated into the wiring harness coupled to the solenoid  72 . When the ignition actuator  34  is moved out of the start position (e.g., to the run position), the starter solenoid  38  is de-energized and the solenoid  72  is de-energized. In this way, the solenoid  72  of starting system  130  is de-energized in response to the ignition actuator, not the in response to the starter motor  36  like the solenoid  72  of starting system  30 . Accordingly, starting system  130  does not provide the extra “short period” of choke provide by starting system  30 . This can be advantageous for engines that are particularly sensitive to choke. 
     The location of the pivot point  63  closer to the second end  66  than to the first end  64  and the sliding connection between the peg  61  of the choke lever  60  and slot  65  of the linkage  62  provides a mechanical advantage. The stroke length of the plunger  73  of the solenoid  72  may therefore be minimized while still rotating the choke lever  60  a sufficient amount to move the choke valve  54  from the open position to the closed position. A minimal stroke length for the plunger  73  increases the amount of force that may be applied to the linkage  62  by the solenoid  72 . In an exemplary embodiment, the stroke length of the plunger  73  is between 5 mm and 8 mm. In a preferred embodiment, the stroke length of the plunger  73  is between 6.2 mm and 6.3 mm. In other embodiments, the plunger  73  may have a stroke length of less than 5 mm or more than 8 mm. 
       FIGS. 7A and 7B  depict the air intake assembly  40  with the manual choke mechanism  80  utilized to close the choke valve  54  independently of the starting system  30 . In some scenarios (e.g., in cold operating environments below approximately 40° F.), the automatic choke mechanism  70  may disengage too quickly, causing the air/fuel mixture to lean out prematurely and making it difficult to start the engine  20 . The manual choke mechanism  80  allows an operator to adjust the position of the choke valve  54  to obtain a desired fuel/air mixture. The manual choke mechanism  80  is mounted to a bracket  82  (as shown in  FIG. 3 ) coupled to the engine  20  and includes a button or slide  84 , a first link or member  86 , and a second link or member  88 . 
     The slide  84  may be moved along a slot or track  83  in the bracket (as shown in  FIG. 3 ) by an operator. The slide  84  is fixed to a rack gear  90  that engages a pinion gear  92  on the first link  86 . Movement of the slide  84  along the track  83  rotates the first link  86  through the rack and pinion interface, bringing a tab or contact  94  on the first link  86  into contact with an end of the second link  88 . Further movement of the slide  84  along the track  83  causes further rotation of the first link  86 , which pushes against the second link  88 , as shown in  FIG. 7A . A manual input device (e.g., a lever, handle, etc.) is coupled to the manual choke mechanism  80  (e.g., by a Bowden cable) to provide a means for the user or operator to actuate or move the manual choke mechanism  80  (e.g., by moving the slide  84 ). According to an exemplary embodiment, the second link  88  is a bent wire member. Because the end of the second link  88  is coupled to the second opening  68  in the linkage  62  (e.g., by a hooked end of the second link  88 ), the movement of the second link  88  rotates the linkage  62  about the pivot point  63 . The rotation of the linkage  62 , in turn, moves the choke valve  54  within the air inlet passage  58  as described above in relation to the automatic choke mechanism  70 . The operator may therefore move the choke valve  54  to any position between a fully open position and a fully closed position utilizing the manual choke mechanism  80  to achieve a desired air/fuel mixture. 
     The manual choke mechanism  80  may be biased towards the default position shown in  FIGS. 3, 5A, and 6A  by a member such as a spring (e.g., compression spring, tension spring, torsion spring, etc.) or another biasing device coupled to a component of the manual choke mechanism  80 . According to an exemplary embodiment, the manual choke mechanism  80  includes a tension spring (not shown) coupled between an arm  96  of the first link  86  and the bracket  82 . By biasing the manual choke mechanism  80  towards the default position, the second link  88  is automatically disengaged from the first link  86  unless the operator is utilizing the manual choke mechanism  80  and applying a force to the slide  84  to overcome the biasing force. The disengagement of the first link  86  from the second link  88  allows the linkage  62  and the second link  88  to move independently without moving the rest of the manual choke mechanism  80  (e.g., when the linkage  62  is moved by the automatic choke mechanism  70 ). 
     The construction and arrangements of the choke mechanism, as shown in the various exemplary embodiments, are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. Some elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present invention.