WO2019226883A1

WO2019226883A1 - Throttle position sensor

Info

Publication number: WO2019226883A1
Application number: PCT/US2019/033726
Authority: WO
Inventors: Martin N. Andersson; Matthew A. Braun; Dale P. KUS; Gerald J. LAMARR, Jr.
Original assignee: Walbro Llc
Priority date: 2018-05-24
Filing date: 2019-05-23
Publication date: 2019-11-28

Abstract

A charge forming device includes a throttle valve having a first position, a second position, a throttle control that is coupled to the throttle valve and has a first position and a second position corresponding to the first and second positions of the throttle valve, and a sensor. The sensor includes at least one sensor element that is coupled to either the throttle control or the throttle valve for movement with that component. The sensor also includes at least one sensor contact that is engaged by the sensor element in at least one position of the throttle valve. The sensor element and sensor contact are electrically within a circuit and the circuit is closed and conductive when the sensor element is engaged with the sensor contact and the circuit is open and not conductive when the sensor element is not engaged with the sensor contact.

Description

THROTTLE POSITION SENSOR

REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Serial No. 62/676,051 filed on May 24, 2018 the entire contents of which are incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to a throttle position sensor.

BACKGROUND

Carburetors and throttle bodies include a throttle valve that is movable between open and closed positions to control fluid flow therethrough. In some applications, it may be desirable to determine the position of the throttle valve in one or more positions of the throttle valve. Rotary position sensors, such as those that utilize magnets and hall effect sensors, require calibration for each carburetor/throttle body, or programming of specific sensor values for the various throttle positions and are relatively complicated and expensive by comparison. Further, adjustments to the throttle valve after the sensor calibration, such as changing the first or second position of the throttle valve, require new calibration of the rotary position sensor.

SUMMARY

In at least some implementations, a charge forming device includes a throttle valve, a throttle control and a sensor. The throttle valve has a first position, a second position and is moveable to and between the first position and second position. The throttle control is coupled to the throttle valve and has a first position and a second position, and when the throttle control is in the first position the throttle valve is in the first position and when the throttle control is in the second position the throttle valve is in the second position. The sensor includes at least one sensor element that is coupled to either the throttle control or the throttle valve for movement with that component. The sensor also includes at least one sensor contact that is engaged by the sensor element in at least one position of the throttle valve. The sensor element and sensor contact are electrically within a circuit and the circuit is closed and conductive when the sensor element is engaged with the sensor contact and the circuit is open and not conductive when the sensor element is not engaged with the sensor contact.

In at least some implementations, the sensor element is a spring that is coupled to the throttle control, and the spring yieldably biases the throttle control to the first position. The throttle control may include a manually movable actuator and a cable that is coupled to the actuator, and the cable may be electrically conductive and the sensor element is coupled to the actuator and arranged to engage the cable in one position of the actuator. The sensor element may be a spring that is coupled to the actuator, and the spring may yieldably bias the actuator to the first position.

In at least some implementations, a body has a bore in which a portion of the throttle valve is received, and the sensor element includes an electrically conductive portion of the throttle valve and the sensor contact is carried by the body. A first sensor element and a second sensor element may be carried by the throttle valve, and a first sensor contact and a second sensor contact may be carried by the body, and the first sensor element may engage the first sensor contact when the throttle valve is in the first position, and the second sensor element may engage the second sensor contact when the throttle valve is in the second position. The first sensor contact may be carried by the body and be adjustable relative to the body to permit adjustment of the first position of the throttle valve. A first resistor may be coupled to the first sensor contact and a second resistor may be coupled to the second sensor contact, and the second resistor may have a different resistance than the first resistor. In at least some implementations, the body is electrically conductive and defines part of the circuit, and the throttle valve engages the body in one or both positions of the throttle valve and the circuit is closed and conductive when the throttle valve engages the body. The body may include a main body and a plate coupled to the main body, both the first sensor contact and the second sensor contact may be defined by or carried by the plate, and the throttle valve may include a throttle valve lever, and the throttle valve lever may engage the first sensor contact in the first position of the throttle valve and the throttle valve lever may engage the second sensor contact in the second position of the throttle valve. The resistance in the circuit may be the same when the first sensor contact is engaged as when the second sensor contact is engaged.

In at least some implementations, both resistors are connected to a wire that is in communicated with a controller, and a conductor is located so that the conductor is engageable by the first sensor element when the throttle valve is in the first position and the conductor is engageable by the second sensor element when the throttle valve is in the second position. The conductor may be coupled to ground via the body.

In at least some implementations, a method of operating an engine, comprising the steps of:

receiving a signal if a throttle valve is in a first position or a second position;

determining if the throttle valve is in the first position or the second; and

determining or adjusting at least one parameter of engine operation as a result of the determination.

In at least some implementations, the throttle valve closes or completes a circuit in either the first position or the second position and the step of receiving a signal includes receiving at a controller a signal or indication of the closed or completed circuit. The circuit may include a first resistance when the throttle valve is in the first position and the circuit includes a second resistance when the throttle valve is in the second position, and the step of determining if the throttle valve is in the first position or the second position may include determining the resistance of the circuit.

In at least some implementations, the method further includes detecting when the throttle valve is moved away from the determined throttle valve position and controlling the engine in accordance with the detected throttle valve movement. In at least some implementations, the step of determining if the throttle valve is in the first position or the second position is based at least in part on the engine speed when the signal is received.

The various features may be utilized in combinations to the extent that such combinations are not mutually exclusive or otherwise contrary to the disclosure herein. The disclosure herein relates to certain implementations but is not intended to limit the innovations to only the particular implementations shown.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of certain embodiments and best mode will be set forth with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a tool including an internal combustion engine and a throttle control;

FIG. 2 is a perspective view of a portion of the tool with an engine cover and part of a handle housing removed to show some internal components;

FIG. 3 is an enlarged, fragmentary view of a portion of the handle housing showing a throttle control trigger in a first position and a throttle position sensing arrangement;

FIG. 4 is a view similar to FIG. 3 showing the trigger in a second position;

FIG. 5 is a view similar to FIG. 3 showing an alternate throttle position sensing arrangement; FIG. 6 is a view similar to FIG. 5 showing the trigger in a second position;

FIG. 7 is a fragmentary perspective view of a charge forming device including a throttle valve and a throttle position sensor, showing the throttle valve in a first or idle position;

FIG. 8 is another fragmentary perspective view of the charge forming device and throttle position sensor;

FIG. 9 is a plan view of a portion of the carburetor showing a throttle valve in a second or wide-open position;

FIG. 10 is a view similar to FIG. 7 showing certain components of the sensing arrangement covered in a sealing material;

FIG. 11 is another view showing the components covered in the sealing material;

FIG. 12 is a perspective view of a carburetor with an electrically conductive member coupled to a plate of the carburetor;

FIG. 13 is a top view of the carburetor with the electrically conductive member removed;

FIG. 14 is a perspective view of a portion of the carburetor showing a throttle valve lever engaged with a second stop surface of or carried by the carburetor;

FIG. 15 is a top view of the carburetor showing a throttle valve lever and a first stop surface of or carried by the carburetor; and

FIG. 16 is a top view of the carburetor with the plate removed and showing a fuel pump diaphragm and electrical isolators coupled to alignment pins of the carburetor body.

DETAILED DESCRIPTION

Referring in more detail to the drawings, FIGS. 1 and 2 illustrate a handheld power tool 10 or product in the form of a grass and weed string trimmer powered by an internal combustion engine 12. Typically, this engine is a light-duty single cylinder two-stroke or four-stroke gasoline powered internal combustion engine. The tool 10 may include a capacitive discharge ignition (CDI) system to control the timing of ignition events in the engine combustion chamber(s). The tool 10 typically does not have any battery supplying an electric current to the ignition system or spark plug coupled to the ignition system or powering a controller (e.g. a microprocessor) associated with the ignition system. Typically, the engine associated with such tools is manually cranked for starting with a recoil rope starter. Of course, other engines may be used, and the tool may include a battery supplying power to the controller or to other components, as desired.

The term“light-duty combustion engine” broadly includes all types of non-automotive combustion engines including two and four-stroke gasoline powered engines used in various devices or products including lawn and garden equipment, lawn mowers, snow blowers, personal watercraft, boats, snowmobiles, motorcycles, all-terrain vehicles, and a variety of handheld power tools including grass and weed trimmers, edgers, chain saws, air blowers, leaf blowers, etc.

A charge forming device 14 with a throttle valve 16 may be provided to control the supply of an air-fuel mixture that is combusted within the engine 12. The device may be a carburetor, or an air intake with a throttle valve (sometimes called a throttle body) controlling air flow into the engine and a fuel injector or other device injecting fuel into either the air flow or engine cylinder of the engine.

As shown in FIGS. 1 and 2, the carburetor includes a throttle valve 16, which may be a rotary barrel or butterfly valve, is connected by a Bowden cable 18 to a manually operable throttle control 20 mounted in a handle housing 22 of the trimmer 10. The throttle control 20 may include an actuator which may be manually movable, called a trigger 24, which is shown as a lever that rotates about a pivot 25 and extends outwardly of the handle housing 22 so that it is accessible by a user of the trimmer 10. The actuator could instead be a rotateable throttle, a button, a sliding member or any other desired component or assembly, as desired. The trigger 24 may be manually moved from an initial or first position (shown in FIG. 3), that may be associated with idle engine operation, to a second position, which may be a fully or wide-open throttle (WOT) position (shown in FIG. 4) which may be associated with high speed or high power engine operation. Movement of the trigger 24 moves a wire 26 of the cable 18 relative to an outer conduit 28 of the cable to move the throttle valve 16 from its idle position toward and to its wide-open position. In at least some implementations, the trigger 24 includes or is coupled to an arm 30 that is in turn coupled to the wire 26 so that movement of the trigger moves the wire.

As shown in FIGS. 3 and 4, a throttle position sensor 32 may be associated with the throttle control 20 to enable detection of at least one position of the throttle control, and hence, at least one position of the throttle valve 16. The sensor 32 may include a sensor element 34 that is coupled to the trigger 24 and moves with the trigger between the first and second position. The sensor element 34 may be electrically conductive and may engage one or more sensor contacts during movement of the throttle control. For example, the sensor element 34 may be spaced from and not engaged with a sensor contact when the throttle control is in the first position and may engage and be electrically coupled to a sensor contact 36 when the throttle control 20 is in the second position. In other implementations, the sensor element may engage a sensor contact when the throttle control is in the first position and/or the second position. Such arrangements may facilitate determination of when the throttle control 20 is in one or both of the first and second positions.

In at least some implementations, a biasing member 40 acts on the trigger 24 and yieldably biases the trigger to the first position so that absent a user displacing the trigger, the trigger is moved or remains in the first position. The biasing member may be a spring 40, and in the implementation shown is a torsion spring having a coil, a first arm 44 extending from the coil and defining a first end of the spring, and a second arm 46 extending from the coil and defining a second end of the spring. One arm of the spring (shown as the first arm 44) may engage the trigger 24, upon actuation of the trigger 24 to or toward the second position, the trigger moves relative to the housing 22, the spring 40 is compressed and the spring force on the trigger increases. As the trigger 24 moves the arm 44 of the spring 40 coupled to the trigger likewise moves.

In at least some implementations, the spring 40 is electrically conductive and may define the sensor element 34, with the first arm 44 engaging or not engaging one or more sensor contacts 36 arranged to be selectively engaged by the first arm at or near either or both of the first and second positions. In some implementations, the spring 40 is part of an electrical circuit that includes or is communicated with a controller 50 that can determine the state or position of the spring 40. As shown in FIG. 3, the second arm 46 of the spring 40 may be coupled to a wire 52 that is in turn coupled to the controller 50 or a circuit that is coupled to the controller. As shown in FIG. 3, the first arm 44 of the spring 40 may be spaced from a sensor contact 36 when the trigger 24 is in the first position such that there is a break in the circuit. This may define the first state of the sensor 32, which is a nonconductive state.

When the trigger 24 is moved to or toward the second position, the first arm 44 engages the sensor contact 36 that, like the second arm 46, is coupled to the controller 50 or a circuit that is coupled to the controller. Engagement of the first arm 44 with the sensor contact 36 then closes or completes the circuit which may include electrical ground to wire 52 to spring 40 to throttle wire 26 to ground. This defines a second state of the sensor 32, which may be a conductive state. In the example shown, the first arm 44 engages the throttle wire 26 of the Bowden cable 18 when the trigger 24 is in the second position, such that the throttle wire 26 defines the sensor contact 36. The throttle wire 26 is grounded and the controller 50 or circuit to which the second arm 46 is coupled via the wire 52 also is grounded, and the throttle wire is then coupled to the controller or circuit through ground.

As shown in FIGS. 5 and 6, an alternate embodiment of a throttle position sensor 60 does not use the throttle wire 26 as a sensor contact. In this sensor 60, another wire 62 may define or be coupled to a sensor contact 64 that is not engaged by the first arm 44 in the first position of the trigger 24 (FIG. 5) and is engaged by the first arm 44 in the second position of the trigger (FIG. 6). While a conductive contact member 64 is shown as being coupled to the additional wire 62, the wire 62 itself could define the sensor contact and be directly engaged by the first arm 44. The additional wire 62 may be grounded or coupled to the controller 50 or circuit like the wire 52 described above. Hence, the circuit is open or not conductive in one position of the trigger 24 and the circuit is closed or conductive in the other position of the trigger. While the embodiments of FIGS. 3-6 show the circuit in the nonconductive state when the trigger 24 is in the first position, and conductive state when the trigger is in the second position, the components could be arranged to reverse those states relative to the trigger positions, as desired.

FIG. 7 shows a carburetor 70 having a rotary barrel type throttle valve 72 with a throttle valve lever 74 coupled to the barrel and to the throttle wire 26. A biasing member, such as a spring 76 may yieldably bias the throttle valve 72 to its idle position. As the trigger 24 is moved, the throttle wire 26 rotates the throttle valve 72 from its idle position toward its wide- open position. When the trigger 24 is released or allowed to return to or toward its first position, the spring 76 acts on the throttle valve lever 74 and rotates the throttle valve 72 back to or toward the idle position.

The idle position of the throttle valve 72 may be defined by engagement of the throttle valve lever 74 with a stop member 78. In the illustrated embodiment, the stop member is defined by an idle stop screw 78 having a threaded shank 80 received within a threaded bore of a support, shown as a projection 82 extending from a cover plate 84 that is coupled to a main body 86 of the carburetor 70. Rotation of the idle stop screw 78 in a first direction advances the screw toward the throttle valve lever 74, and rotation of the screw in the opposite direction retracts the screw away from the throttle valve lever. In FIG. 7, the throttle valve 72 is shown in the idle position with the throttle valve lever 74 engaged with an end of the idle stop screw 78. If, relative to the position shown in FIG. 7, the stop screw 78 were retracted away from the throttle valve lever 74 then the idle position would be further rotated away from the wide-open position and if the stop screw were advanced toward the throttle valve lever then the idle position would be rotationally or angularly closer to the wide-open position.

To enable determination of one or both of the idle and wide-open positions of the throttle valve 72, a throttle position sensor 88 may be provided. The position sensor 88 may include one or more sensor elements carried by or movable with the throttle valve 72, and one or more sensor contacts within a circuit and selectively engageable by a sensor element. In at least some implementations, two sensor elements 90, 92 are carried by the throttle valve lever 74 for movement with the throttle valve lever. In at least some implementations, the two sensor elements 90, 92 are spaced apart and are not electrically coupled together. That is, there is an electrically insulative member between them, which, for example, could be the throttle valve lever 74 itself when it is formed from a material that is insulative or not conductive. In this way, the sensor elements 90, 92 are discrete conductive members (e.g. they are not directly electrically coupled together or electrically communicated with each other) and when one is engaged with a sensor contact the other is not electrically coupled to that sensor contact. Although the sensor elements 90, 92 could be electrically coupled together such as by being formed in the same piece of material.

In at least some implementations, two sensor contacts 94, 96 are provided with a first sensor contact 94 arranged to be engaged by the first sensor element 90 carried by the throttle valve lever 74 and a second sensor contact 96 arranged to be engaged by the second sensor element 92. When one sensor element 90, 92 is engaged with its respective sensor contact 94, 96, the other sensor element is not engaged with its respective sensor contact. The sensor contacts 94, 96 may be arranged in separate circuits such that one circuit is closed and conductive while the other circuit is open or not conductive, and vice versa. In the example shown, the first sensor contact includes the idle stop screw 78 which is electrically conductive.

In at least some implementations, the position sensor 88 includes two resistors 98, 100. A first resistor 98 may be connected to the first sensor contact 94 and a wire 101 that is coupled to or communicated with the controller 50. A second resistor 100 may be connected to the second sensor contact 96 and also to the wire 101. The resistors 98, 100 may be coupled to the wire at a common connection point or location, which may be defined by or include a screw

103 that is threadedly received in the plate 84 or carburetor body 86. To couple the two circuits to ground, a common conductor is provided, shown as a wire or spring 102.

The ground spring 102, in turn, is separately engageable by both the first sensor element 90 (e.g. when the throttle valve 72 is in the first or idle position) and the second sensor element

92 (e.g. when the throttle valve is in the second or wide-open position). The opposite end or a different portion of the spring 102 may be grounded, and in at least one implementation, the spring 102 engages the carburetor body 86 which is in contact with the engine housing via mounting bolts or a separate conductor (e.g. a wire) which completes the ground path to the controller 50. The spring may be yieldable such that it may be flexed when engaged by a sensor element and resilient so that the spring returns to an unflexed state when not engaged by the sensor element. In the example shown, the ground spring 102 has a cantilevered arm 104 engaged by the first sensor element 90 when the throttle valve 72 is in the idle position, and by the second sensor element when the throttle valve is in the wide-open position. So arranged, the first sensor element 90 may engage both the first sensor contact 94 (e.g. the idle stop screw 78) and the arm 104 of ground spring 102 when the throttle valve 72 is in the idle position, as shown in FIG. 7. When the throttle valve is in the second or wide- open position, the second sensor element 92 may engage both the arm 104 of ground spring 102 and the second sensor contact 96 which may be defined by a wire or spring 106 carried by the projection 82 or cover plate 84 spaced from the projection, as desired. This engagement of the throttle valve lever 74/second sensor element 92 with the second sensor contact 96 may define the wide-open position of the throttle valve 72. That is, the rotation of the throttle valve in the direction away from the idle position is limited by engagement of the throttle valve lever 74/second sensor element 92 with the projection 82 or other second sensor contact 96. The resistor 100 may be connected to the spring 106, such as by a solder connection or by a screw that traps a terminal of the resistor and part of the spring against the cover plate 84.

When the first sensor element 90 engages the first sensor contact 94, the position sensor circuit includes the first resistor 98. When second sensor element 92 engages the second sensor contact 96, the position sensing circuit includes the second resistor 100. The different resistances within the circuit in the two states or positions can be determined by the controller 50 which is electrically communicated with the circuit, and thus, the position of the throttle valve 72 in either of the two positions can be positively determined by the controller as a function of the resistance in the circuit.

In addition to determining when the throttle valve 72 is in either of the two positions

(e.g. idle and wide-open), the controller 50 can determine when the throttle valve is not in either position (e.g. the circuit is open or not conductive). This information can be used to control the engine during acceleration, for example, when the controller 50 determines that the throttle valve 72 was in the idle position but was moved away from idle (e.g. when the circuit goes from closed to open), and/or to control deceleration or come-down when the controller determines that the throttle valve was in the wide-open position but has been moved away from the wide-open position. Additionally, the controller 50 can compare engine speed to the position of the throttle valve 72 to make certain determinations regarding engine performance. For example, the engine speed can be checked when the throttle valve 72 is in the idle position to ensure that the engine speed is within a desired speed range. Similar determinations can be made when the throttle valve 72 is in the wide-open position, and in at least some implementations, when the throttle valve is rotated off idle or away from the wide-open position. FIGS. 10 and 11 illustrate certain electrical components, such as the connection points/screws and the resistors, coated or covered with a seal 107 which may be located on the carburetor 70 or elsewhere, such as on a circuit board including the controller 50.

In another implementation of a carburetor 110, as shown in FIGS. 12-16, a portion of the carburetor body 112 that is engaged by a portion of the throttle valve 72 is electrically conductive and defines part of a position sensing arrangement or circuit. The throttle valve 72 may be different than the barrel type valve shown in FIGS. 7-11, and is shown as being a butterfly type valve having a lever 74 coupled to shaft 113 rotatably carried by the body 112. The circuit is closed/conductive when the portion of the carburetor body 112 is engaged by the throttle valve 72 and is open/not conductive when the portion of the carburetor body is not engaged by the throttle valve.

In at least some implementations, the throttle valve lever 74 engages a portion of the carburetor body 112 in two different locations, each of which may define a sensor contact. In at least some implementations, the carburetor includes a body or plate 84 (which may be similar to the plate 84 described above) having a first stop surface or first sensor contactl l6 engaged by the throttle valve lever 74 when the throttle valve 72 is in a first (e.g. idle) position and a second stop surface or second sensor contact 118 (FIG. 14) engaged by the throttle valve lever when the throttle valve is in a second (e.g. wide-open) position. The plate 84 may be fixed to a main body 86 of the carburetor 110, such as by one or more screws, and a gasket and/or diaphragm 122 may be received between the plate 84 and main body 86. The diaphragm 122 may be a fuel pump diaphragm or a fuel metering diaphragm, and may be trapped near or at its periphery between the plate 84 and main body 86, leaving a middle portion that is spaced from the plate 84 and main body 86 that moves relative to the plate 84 and main body 86 in response to pressure differences across the diaphragm 122. The general construction and operation of fuel pump diaphragms and fuel metering diaphragms are known and are not described further herein. The first stop surface 116 may be adjustable, such as a screw (e.g. the idle stop screw 78 threadedly carried by a projection 82 from the plate 84). The second stop surface 118 may be spaced from the screw 78, and may be defined by a surface of the proj ection 82 or elsewhere on the plate 84. Both stop surfaces 116, 118 may be electrically conductive and may be electrically coupled to or part of the plate 84.

As shown in FIG. 12, a wire 130 or other electrically conductive member may be coupled to the plate 84 so that the plate is within an electrical circuit including the wire. In the example shown, the plate 84 is fastened to the main body 86 by a screw 132 having a threaded shank that extends through the plate and is received in a blind threaded bore of the main body, and an enlarged head 134 that overlies part of the plate. The throttle valve lever 74, or other portion(s) of the throttle valve 72 that engage the first and second stop surfaces 116, 118, may also be electrically conductive and part of the circuit. The throttle valve lever 74, or other portion(s) of the throttle valve 72, may act as a switch in the circuit. That is, when the throttle valve lever 74 is engaged with the plate 84, the circuit is complete and conductive, but when the throttle valve lever is not engaged with the plate, the circuit is open and not conductive.

With the wire 130 and circuit current communicated with the plate 84, the plate may be electrically insulated from other components of the carburetor 110, if desired in at least some implementations. To do so, one or more insulators may be provided between the plate 84 and such components. In at least some implementations, insulators are provided between the plate and one or more screws that position and/or mount the plate to the carburetor main body. In the example shown, a washer 136 formed from an electrically insulating material (e.g. plastic) is provided between the head 134 of the screw 132 and a connector 138 of the wire 130 coupled to the plate 84. The connector 138 and/or wire 130 is engaged with or otherwise electrically coupled to the plate 84, while the head 134 of the screw 132 is insulated from the wire/connector by the insulating washer 136. The plate 84 and main body 86 may also include one or more mating alignment features that help to properly orient the plate relative to the main body in assembly. In the example shown, the alignment features are defined by projections 140 extending from the plate 84 that are each received within respective voids (not shown) in the main body 86 although the plate could include the voids and the main body may include the projections, or the plate and main body may have any combination of alignment features. Insulators 144 may be disposed over the projections 140 and received within a void to electrically insulate the projections from the body that includes the voids. This insulates the projections 140 from the main body 86. The diaphragm 122 and any seal or gasket may also be formed from an electrically insulative material and may help to electrically insulate the plate 84 from the adjacent components.

The main body 86 of the carburetor 110 may be electrically coupled or connected to ground via engagement with a grounded component, such as the mounting bolts or screws that couple the carburetor to an engine, or via a wire connected between the main body 86 and ground. The throttle valve 72 is in turn engaged with the main body 86, for example, via the throttle valve shaft 113 or barrel that is carried within a bore formed in the main body 86 for rotation relative to the main body. The throttle valve shaft 113 or barrel may be formed from a conductive material and is coupled to the throttle valve lever 74 which is formed from a conductive material as noted above, to complete the electrical circuit. So arranged, when the throttle valve 72 is in the idle or first position wherein the throttle valve lever 74 engages the first stop surface 116, the circuit is closed and conductive and includes ground, the main body 86, the throttle valve 72 that is engaged with the main body and includes the throttle valve lever 74, the idle stop screw 78 engaged by the throttle valve lever 74, the plate 84 coupled to the idle stop screw, the wire 130 coupled to the plate and the controller 50 which is coupled to the wire 130 (or other component communicated with the wire) and ground. Likewise, when the throttle valve 72 is in the wide-open or second position in which the throttle valve lever 74 engages the second stop surface 118, the circuit is closed and conductive and includes the above components with the exception of the second stop surface in place of the idle stop screw 78. When the throttle valve 72 is not in the first or second positions, the circuit is open and not conductive. The various states of the circuit can be detected or determined by the controller as noted above.

Even without different resistances associated with the first stop surface 116 and second stop surface 118, the system can distinguish a first conductive state associated with the throttle valve 72 in the first position from a second conductive state associated with the throttle valve in the second position. In at least some implementations, the controller 50 receives a signal or data indicative of engine speed and so the controller can determine if the engine speed when the circuit is conductive is indicative of the throttle valve 72 being in the first or second position. Of course, other signals or indicators of engine speed may also be used, for example, timing or other parameter(s) of ignition events which differ between idle and wide-open throttle engine operation.

The determination of throttle position when the circuit is conductive can then be used so that the controller 50 may also detect when the state of the circuit changes. In this way, control operations may be implemented that are associated with, for example, engine acceleration as the throttle valve 72 is moved away from the idle position or engine deceleration as the throttle valve is moved away from the wide-open position, as noted above. Further, with the idle stop screw 78 or other adjustable throttle valve stop being conductive or part of the circuit enables better determination of when the throttle valve 72 is rotated away from idle, in any position of the idle set screw, compared to implementations wherein the stop surface is spaced from the idle stop screw or adjustable stop. As soon as the throttle lever 74 is rotated out of engagement with the idle stop screw 78, the circuit changes from closed to open. If the stop surface is spaced from the idle stop screw, then the opening of the circuit might vary depending upon the position of the idle stop screw. That is, if the first stop surface 116 is located spaced from the idle stop screw, then the throttle valve lever 74 may be rotated some distance away from the idle stop screw before the throttle lever disengages from the first stop surface, delaying the above noted engine acceleration control. Although potentially not as responsive, this arrangement might be acceptable in some implementations, and could be used, as desired.

Further, in at least some implementations, prior to starting the engine to facilitate starting the engine, the throttle valve 72 is rotated away from the idle position to a position between the idle and wide-open positions. A choke valve 145 (a portion of which is shown in FIG. 14, with corresponding shaft and levers shown in FIG. 13), if provided with the carburetor 110, may also be closed before starting the engine to facilitate starting and initial warming up of the engine. The system may determine the position of the choke valve (e.g. with a proximity or other switch, which may include a metal lever on the choke valve shaft engaging a metal component which may include the carburetor body or another component, in the same manner described above with regard to the throttle valve), or the system may determine the state of the circuit including the throttle valve 72 when the engine is initially cranked or started, or both conditions may be determined. This determination(s) indicates that the engine is being started in an off-idle (sometimes called“fast idle”) condition and suitable engine control may be implemented to facilitate starting and warming up the engine. The engine control may include, but is not limited to ignition timing changes, fuel and air mixture changes (e.g. via control of a valve, which may be solenoid actuated) or speed control schemes. In some implementations, the engine drives a tool (e.g. saw blade, trimmer blade or string, etc) through a clutch when the engine speed is above a clutch engagement speed but the clutch prevents movement of the tool when the engine speed is below the clutch engagement speed. When the engine is started with the throttle valve 72 off idle or in the fast idle position, the engine speed may be electronically limited to a speed below the clutch engagement speed to prevent unintended actuation of the tool. After the engine is started, the throttle valve 72 may be actuated by a user (e.g. via the trigger 24) and end up in either the idle or wide-open position, which may be detected by the controller, as noted above. Such a determination may cause a change in the control scheme from one or more schemes associated with engine starting and warm-up to a scheme or schemes associated with normal engine operation, as desired. Of course, other engine control schemes may be used in view of the information of the throttle valve position provided by the systems disclosed herein.

Rotary throttle position sensors, such as those that utilize magnets and hall effect sensors, usually require calibration for each carburetor or programming of specific sensor values for the various throttle positions and are relatively complicated and expensive by comparison. Further, adjustments to the throttle valve after the sensor calibration, such as by moving the idle stop screw, may require new calibration of the rotary position sensor. The systems described above can be self-adjusting, for example where the adjustable idle stop screw provides one of the circuit contact points which automatically changes as the idle position is adjusted without any adjustment or change needed to the circuit or other components.

As noted above, the throttle valve position can be determined in one or more positions with relatively few parts added to an otherwise conventional carburetor. And while primarily described with reference to carburetors, as noted above, the innovations can be applied to a throttle body via which air and fuel are delivered to an engine or via which air is provided for mixing with fuel downstream of the throttle body to determine the position of one or more rotary valves associated therewith. This provides a robust and low-cost solution to a challenging problem. The position sensor or sensing arrangement may be coupled to or responsive to movement of a portion of a device that moves when throttle valve position changes, such as a throttle trigger or the throttle valve itself. Hence, in at least some implementations, the sensing device can be carried by a handle including the trigger or on the carburetor or throttle body itself, as desired. Further, at least some engine operating parameters may be checked or adjusted as a function of the throttle valve position. A signal may be provided when the throttle valve is in either or both of the first and second positions (e.g. idle and wide-open). The signal may include closing or completing a circuit, and the circuit may have a different resistance in the different throttle valve positions, which may enable differentiation between the positions. The engine speed or other operational parameter may also be checked when the circuit is closed (i.e. a signal is received indicative that the throttle valve is in one, or one of the two positions) to aid in determining the throttle valve position. The system can further be used to detect when the throttle valve is moved away from the determined throttle valve position, and an engine parameter may be adjusted or controlled in accordance with the detected throttle valve movement. For example, if it is determined that the throttle valve is moved away from its idle position, the system may operate the engine in a manner to support acceleration (e.g. change fuel supply and/or ignition timing, etc).

It is to be understood that the foregoing description is not a definition of the invention, but is a description of one or more preferred embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. For example, a method having greater, fewer, or different steps than those shown could be used instead. All such embodiments, changes, and modifications are intended to come within the scope of the appended claims.

As used in this specification and claims, the terms“for example,”“for instance,” “e.g.,”“such as,” and“like,” and the verbs“comprising,”“having,”“including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.

Claims

CLAIMS What is claimed is:

1. A charge forming device, comprising:

a throttle valve having a first position, a second position and being moveable to and between the first position and second position;

a throttle control coupled to the throttle valve and having a first position and a second position, and when the throttle control is in the first position the throttle valve is in the first position and when the throttle control is in the second position the throttle valve is in the second position; and

a sensor including at least one sensor element that is coupled to either the throttle control or the throttle valve for movement with that component, and the sensor includes at least one sensor contact that is engaged by the sensor element in at least one position of the throttle valve, and wherein the sensor element and sensor contact are electrically within a circuit and wherein the circuit is closed and conductive when the sensor element is engaged with the sensor contact and the circuit is open and not conductive when the sensor element is not engages with the sensor contact.

2. The device of claim 1 wherein the sensor element is a spring that is coupled to the throttle control, wherein the spring yieldably biases the throttle control to the first position.

3. The device of claim 1 wherein the throttle control includes a manually movable actuator and a cable that is coupled to the actuator, and wherein the cable is electrically conductive and the sensor element is coupled to the actuator and arranged to engage the cable in one position of the actuator.

4. The device of claim 3 wherein the sensor element is a spring that is coupled to the actuator, and wherein the spring yieldably biases the actuator to the first position.

5. The device of claim 1 which also includes a body having a bore in which a portion of the throttle valve is received, and wherein the sensor element includes an electrically conductive portion of the throttle valve and wherein the sensor contact is carried by the body.

6. The device of claim 5 wherein a first sensor element and a second sensor element are carried by the throttle valve, and a first sensor contact and a second sensor contact are carried by the body, and wherein the first sensor element engages the first sensor contact when the throttle valve is in the first position, and the second sensor element engages the second sensor contact when the throttle valve is in the second position.

7. The device of claim 6 wherein the first sensor contact is carried by the body and is adjustable relative to the body to permit adjustment of the first position of the throttle valve.

8. The device of claim 6 wherein a first resistor is coupled to the first sensor contact and a second resistor is coupled to the second sensor contact, and wherein the second resistor has a different resistance than the first resistor.

9. The device of claim 5 wherein the body is electrically conductive and defines part of the circuit, and further wherein the throttle valve engages the body in one or both positions of the throttle valve and the circuit is closed and conductive when the throttle valve engages the body.

10. The device of claim 9 wherein the body includes a main body and a plate coupled to the main body, both the first sensor contact and the second sensor contact are defined by or carried by the plate, and the throttle valve includes a throttle valve lever, and wherein the throttle valve lever engages the first sensor contact in the first position of the throttle valve and the throttle valve lever engages the second sensor contact in the second position of the throttle valve.

11. The device of claim 10 wherein the resistance in the circuit is the same when the first sensor contact is engaged as when the second sensor contact is engaged.

12. The device of claim 8 wherein both resistors are connected to a wire that is in communicated with a controller and wherein a conductor is located so that the conductor is engageable by the first sensor element when the throttle valve is in the first position and the conductor is engageable by the second sensor element when the throttle valve is in the second position.

13. The device of claim 12 wherein the conductor is coupled to ground via the body.

14. A method of operating an engine, comprising the steps of:

determining if the throttle valve is in the first position or the second; and

15. The method of claim 14 wherein the throttle valve closes or completes a circuit in either the first position or the second position and the step of receiving a signal includes receiving at a controller a signal or indication of the closed or completed circuit.

16. The method of claim 14 wherein the circuit includes a first resistance when the throttle valve is in the first position and the circuit includes a second resistance when the throttle valve is in the second position, and wherein the step of determining if the throttle valve is in the first position or the second position includes determining the resistance of the circuit.

17. The method of claim 14 which further includes detecting when the throttle valve is moved away from the determined throttle valve position and controlling the engine in accordance with the detected throttle valve movement.

18. The method of claim 14 wherein the step of determining if the throttle valve is in the first position or the second position is based at least in part on the engine speed when the signal is received.