Patent Application
20060130808
1. Field of the Invention
The present invention relates to small internal combustion engines of the type used with lawnmowers, lawn tractors, other utility implements, and in sport vehicles, for example. In particular, the present invention relates to speed control mechanisms for such engines.
2. Description of the Related Art
Small internal combustion engines typically include a carburetor which supplies an air/fuel mixture to one or more combustion chambers of the engine for combustion to drive the piston(s) and the crankshaft of the engine. The engine speed is typically regulated by a throttle valve disposed within the intake passage of the carburetor, which is movable between a substantially closed position corresponding to the engine being stopped or the engine running at a low or idle speed, and a substantially open position, corresponding to the engine running at its running speed.
Many small internal combustion engines also include a governor for maintaining a desired running speed of the engine, including a mechanical governor mechanism disposed within the crankcase and driven from the crankshaft. The governor mechanism may include one or more flyweights movable responsive to engine speed, which actuate a governor arm with the crankcase and a governor lever disposed externally of the crankcase. The governor lever is linked to the throttle valve of the carburetor. In operation, when the engine speed falls below a desired running speed, such as when a load is imposed upon the engine, the governor operates to further open the throttle valve of the carburetor to increase the engine speed. When the engine speed increases beyond a desired running speed, such as when a load is removed from the engine, the governor operates to further close the throttle valve of the carburetor to decrease the engine speed.
Many small internal combustion engines also include a speed control mechanism which is operable by an operator to set the running speed of the engine. The speed control mechanism includes a speed control lever which may be disposed either near the engine itself, or on the handle of an implement with which the engine is used. The speed control lever is movable between stop, idle, and various running speed positions, for example, to set the engine speed. When the speed control lever is disposed in the stop position, the throttle valve of the carburetor is substantially fully closed. When the speed control lever is disposed in the idle position, the throttle valve of the carburetor is slightly open to maintain a low engine running speed. When the speed control lever is moved through the various running speed positions toward a high speed position, the throttle valve is progressively opened to provide progressively higher engine running speeds. When the throttle lever is positioned to establish a desired running speed, that running speed is maintained by the governor responsive to engine load in the manner described above.
One disadvantage of the foregoing speed control arrangement is that if a load is imposed upon the engine, such as by a lawnmower encountering tall grass or a snow thrower encountering deep or heavy snow, for example, there is often a time lag between the imposition of the load and decrease in engine speed, and the response of the governor to correct for the underspeed and bring the engine speed back up to the desired running speed. Conversely, when a load is removed from the engine, there is often a time lag between the removal of the load and increase in engine speed, and the response of the governor to correct for the overspeed and bring the engine speed back down to the desired running speed. Notably, even if the operator anticipates the variation in load which is imposed upon the engine, the operator cannot easily vary the engine speed, but must wait for the governor to correct the engine speed after the load is imposed or after the load is removed.
What is needed is a speed control mechanism for small internal combustion engines which is an improvement over the foregoing.
The present invention provides a secondary engine speed control mechanism for small internal combustion engines, including an operator control which is manually operable to override an engine running speed which is set by the engine's primary speed control mechanism and governed by the governor. The secondary speed control mechanism may be selectively actuated by the operator in anticipation of an increased engine load to provide a temporary increase or “boost” to engine speed above the set, governed engine running speed. The secondary speed control mechanism may include an operator actuated, trigger-type mechanism located on the handle of an implement with which the engine is used.
In one embodiment, the engine includes a primary speed control mechanism which operates through linkage including the governor lever for setting a desired, set and governed engine running speed, and a second speed control mechanism for allowing the operator to override the set running speed to temporarily increase the engine speed. The secondary speed control mechanism includes a cable-actuated lever which engages a throttle actuation lever of the primary speed control mechanism to move the throttle valve of the carburetor to its fully open position via the primary speed control linkage.
In another embodiment, the engine includes a primary speed control mechanism connected to the governor lever of the engine for allowing the operator to set a desired, set and governed running speed of the engine, and a secondary speed control mechanism which is independently attached to the governor lever to allow the operator to override the primary speed control mechanism to temporarily increase the running speed of the engine. The second speed control mechanism includes an actuator device mounted to the engine housing, including a translatable, cable-actuated plunger connected to the governor lever via a spring link to rotate the governor lever and move the throttle valve of the carburetor to its fully open position.
Each of the embodiments disclosed herein advantageously allow the operator of a small internal combustion engine to manually override a set and governed running speed of the engine to provide a quick increase or “boost” to the engine speed above the set and governed running speed, such as when the operator anticipates an increased engine load. For example, an operator of a snow thrower with which the engine is used may temporarily increase the engine speed when encountering thick or heavy snow, or an operator using a lawnmower with which the engine is used may temporarily increase the engine speed when encountering thick or tall grass.
In one form thereof, the present invention provides an internal combustion engine, including an engine housing including a rotatably driven crankshaft supported therein; a carburetor including an intake passage with a throttle valve therein, the throttle valve positionable between a substantially closed position, a substantially open position, and a fully open position; a primary speed control mechanism including a first operator control element mechanically linked to the throttle valve, the first operator control element movable to selectively position the throttle valve between the substantially closed and the substantially open positions; and a secondary speed control mechanism including a second operator control element mechanically linked to the throttle valve, the second operator control element movable to selectively position the throttle valve between the substantially open and the fully open positions.
In another form thereof, the present invention provides an internal combustion engine, including a crankcase; a cylinder block attached to the crankcase; a crankshaft rotatably supported by the crankcase; a carburetor including an intake passage with a throttle valve, the throttle valve rotatable within the intake passage between a substantially closed position, a substantially open position, and a fully open position; a primary speed control mechanism including a first operator control element connected to the throttle valve via mechanical linkage, the first operator control element movable to selectively position the throttle valve between the substantially closed and the substantially open positions; and speed control override means for actuating at least some components of the mechanical linkage to selectively position the throttle valve between the substantially open and the fully open positions.
In a further form thereof, the present invention provides an internal combustion engine, including an engine housing including a crankcase and a cylinder block; a crankshaft rotatably supported by the crankcase; a carburetor including an intake passage with a throttle valve therein; a governor mechanism driven from the crankshaft, including a governor arm disposed externally of the engine housing and mechanically linked to the throttle valve, the governor arm and the throttle valve positionable between a first position in which the throttle valve is substantially closed, a second position in which the throttle valve is substantially open, and a third position in which the throttle valve is fully open; a primary speed control mechanism including a first operator control element mechanically linked to the governor arm by primary linkage, the first operator control element movable to selectively position the governor arm and throttle valve between the first and second positions; and a secondary speed control mechanism including a second operator control element mechanically linked to an actuator by secondary linkage, the second operator control element movable to engage the actuator with the primary speed control mechanism to selectively position the governor arm and throttle valve between the second and third positions.
In a still further form thereof, the present invention provides an internal combustion engine, including an engine housing including a crankcase and a cylinder block; a crankshaft rotatably supported by the crankcase; a carburetor including an intake passage with a throttle valve therein; a governor mechanism driven from the crankshaft, including a governor arm disposed externally of the engine housing and mechanically linked to the throttle valve, the governor arm and the throttle valve positionable between a first position in which the throttle valve is substantially closed, a second position in which the throttle valve is substantially open, and a third position in which the throttle valve is fully open; a primary speed control mechanism including a first user control element mechanically linked to the governor arm, the first operator control element movable to selectively position the governor arm and the throttle valve between the first and second positions; and a secondary speed control mechanism including a second user control element mechanically linked to the governor arm independently of the primary speed control mechanism, the second operator control element movable to selectively position the governor arm and the throttle valve between the second and third positions.
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate preferred embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention any manner.
Referring to
Engine 10 includes a carburetor 20 connected to engine 10 in fluid communication with the combustion chamber(s) of the engine cylinder(s) to supply an air/fuel combustion mixture to engine 10 for combustion. Carburetor 20 generally includes an intake air passage or throat 22 extending therethrough from and inlet end 24 of carburetor 20 to an outlet end 26 of carburetor 20 which is in communication with combustion chamber(s) of the engine cylinder(s). Carburetor 20 additionally includes a venturi section 28 within throat 22 at which fuel from fuel bowl 30 of carburetor 20 is drawn into the stream of intake air which passes through throat 22 in a known manner to form an air/fuel combustion mixture. Carburetor 22 additionally includes a throttle valve 32 rotatably mounted within throat 22. Optionally, carburetor 22 may additionally include a rotatable choke valve (not shown) upstream of throttle valve 32, which is operable in a conventional manner to selectively provide an enriched air/fuel mixture to aid in cold starts of engine 10.
Engine 10 additionally includes a governor device for regulating and/or maintaining a set running speed of engine 10 in the manner described in further detail below. The governor device of engine 10 is similar to those disclosed in U.S. Pat. Nos. 4,517,942 and 5,163,401, assigned to the assignee of the present invention, the disclosures of which are expressly incorporated herein by reference. The governor device includes a governor mechanism 34 disposed within crankcase 12 and including governor gear 36 rotatably mounted upon shaft 38 and driven from drive gear 40 of crankshaft 16. Alternatively, governor gear 36 could be driven from a camshaft or countershaft (not shown) of engine 10. Two or more flyweights 42 are pivotally mounted to governor gear 36, and engage a spool 44 for translating spool 44 upon shaft 38. A governor arm 46 is rotatably mounted within crankcase 12, and includes paddle 48 in engagement with spool 44, and an outer end which extends externally of crankcase 12 and is attached to governor lever 50. In operation, flyweights 42 pivot under centrifugal force responsive the speed of engine 10, thereby translating spool 44 to rotate governor arm 46 and governor lever 50 in the manner described below. For clarity, the foregoing components of governor mechanism 34 are only shown in
Still referring to
Primary speed control lever 60 includes handle 66, which may be made of a suitable plastic, for example, for grasping by an operator to rotate primary speed control lever 60, and additionally includes adjustment screw 68 for limiting the rotational movement of throttle actuator lever 62 to set a minimum high engine running speed. Throttle actuator lever 62 includes a first end 70 extending generally upwardly, and an opposite, second end 72 extending generally downwardly. Second end 72 is connected to a lower or central portion of governor lever 50 via link 74, and the upper end of governor lever 50 is connected via link 75 to crank arm 76 of carburetor 20, which is in turn connected via a rotatable shaft to throttle valve 32 of carburetor 20.
Engine 10 additionally includes a secondary speed control mechanism 78 for overriding a set, governed high engine running speed of primary speed control mechanism 60 in the manner described below. Secondary speed control mechanism 78 includes secondary speed control lever 80 including a lower end 82 pivotally mounted to mount plate 54, and an upper end 84. A translatable, Bowden-type cable 86 is secured at one end thereof to a central portion of secondary speed control lever 80, and at its opposite end is secured to an operator-controlled trigger mechanism 88 which includes trigger handle or bail 90 pivotally mounted to handle 18 of the implement with which engine 10 is used. Cable 86 is covered by sleeve 92 which is secured at its opposite ends to a first clamp 94 mounted to mount plate 54, and second clamp 96 mounted to handle 18 of the implement. Adjustable stop screw 98 is provided on mount plate 54 to limit rotational movement of secondary speed control lever 80.
Referring to
After the engine starts, the operator moves primary speed control lever 60 upwardly or counterclockwise from the idle position to a desired engine running speed position, which is shown in
In this condition, the high engine running speed is maintained by the governor device as follows. For example, when a load is placed upon engine 10, such as by the implement contacting thick snow or tall grass when engine 10 is used in a snow thrower or lawnmower application, respectively, the engine speed decreases, and flyweights 42 of governor mechanism 34 rotate inwardly with respect to one another, allowing translation of spool 44 and rotating governor arm 46 and governor lever 50 slightly in a clockwise direction from the position of governor lever 50 which is shown in solid lines in
Notwithstanding the operation of the governor device, there may be circumstances wherein the operator wishes to quickly increase or “boost” the speed of engine 10 beyond the high engine running speed which is set by primary speed control mechanism 52, such as when the operator anticipates an increased load which may be imposed upon engine 10. In particular, the operator may desire to increase the engine speed before the load is imposed upon engine 10 so that the operator need not wait for the governor to correct for an engine underspeed caused by the increased load. For example, when operating engine 10 in a snow thrower application, the operator may anticipate encountering thick snow and desire to quickly increase the engine speed above the set high engine running speed to a maximum speed to accommodate the increased load. In another example, an operator of a lawnmower including engine 10 may anticipate encountering tall or thick grass, and may desire to quickly increase the running speed of engine 10 above the set high engine running speed to a maximum speed to accommodate the increased load.
When the operator desires to increase the engine speed above the set high engine running speed, the operator actuates trigger handle 90 of trigger mechanism 88 to rotate same from the position shown in
In this manner, secondary speed control mechanism 78 is manually operable to override the governor and primary speed control mechanism 52 for temporarily increasing the running speed of engine 10. Release of trigger handle 90 by the operator returns secondary speed control lever 80, throttle acutator lever 62, governor lever 50, and the rest of the associated linkage to the position shown in
A secondary speed control mechanism according to a second embodiment of the present invention is shown in
Referring to
Referring to
Referring to
Referring to
While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
