Unpowered pedal assist device and vehicular clutch assembly including the same

Embodiments of an unpowered pedal assist device are provided for use in conjunction with a vehicular control pedal movable between a non-depressed position and a depressed position. In one embodiment, the unpowered pedal assist device includes a multi-bar linkage and at least one resilient element coupled to the multi-bar linkage. The multi-bar linkage is configured to be coupled to the vehicular control pedal and, when so coupled to move from a start position to a finish position as the vehicular control pedal moves from the non-depressed position to the depressed position. The at least one resilient element is configured to bias the multi-bar linkage: (i) toward the start position over an initial range of travel of the vehicular control pedal, and (ii) toward the finish position over a primary range of travel of the vehicular control pedal.

TECHNICAL FIELD

The following disclosure relates generally to vehicular clutch assemblies and, more particularly, to embodiments of an unpowered pedal assist device suitable for use in conjunction with a clutch assembly or other vehicular control pedal assembly.

BACKGROUND

Vehicular clutch assemblies are well-known devices for selectively disengaging an automatic or manual transmission from a vehicle's internal combustion engine during operation of the engine. One of the most common types of vehicular clutch assemblies includes a clutch disc, a pressure plate, a diaphragm spring (also referred to as a “plate spring”), and a thrust bearing (also referred to as a “throw-out bearing”). The clutch disc, pressure plate, and diaphragm spring are slidably mounted around the transmission input shaft and rotate in conjunction therewith. The thrust bearing is also slidably mounted around the transmission input shaft, but generally remains stationary as the input shaft rotates. The clutch assembly normally resides in an engaged position wherein the clutch disc frictionally engages a flywheel driven by the engine resulting in rotation of the clutch disc, pressure plate, diaphragm spring, and the transmission input shaft. To disengage the clutch assembly, the thrust bearing is pressed against the diaphragm spring, which urges the pressure plate and the clutch disc to move away from, and therefore frictionally disengage from, the engine-driven flywheel. When the clutch assembly is moved into the disengaged position, the rotation of the clutch disc, the pressure plate, the diaphragm spring, and the transmission input shaft is slowed or halted to facilitate transmission gear changes. In the case of a manual transmission, disengagement of the clutch assembly is typically controlled by a driver-actuated clutch pedal, which is mechanically linked to the thrust bearing by one or more intervening structures (e.g., a clutch lever and/or a hydraulic system).

The phrase “clutch pedal apply force” is commonly utilized to describe the force that a driver must apply to depress the clutch pedal. The clutch pedal apply force varies over the clutch pedal's range of travel and typically peaks near disengagement of the clutch assembly. For many drivers, such as those with arthritic knees, utilizing a clutch pedal that requires relatively high clutch pedal apply forces can be uncomfortable. Driver discomfort is especially problematic in high horsepower platforms wherein the peak apply force tends to be relatively high (e.g., approaching or exceeding approximately 130 Newton). A limited number of powered and unpowered pedal assist devices have been implemented in some vehicles (e.g., semi-trailer trucks) to lower the driver-required apply force over a portion or over the entirety of the clutch pedal's range of travel. However, in the case of powered pedal assist devices, such assist devices tend to be relatively complex, costly to implement, and often exhibit a noticeable lag between driver actuation of the clutch pedal and the generation of the assist force. Furthermore, in the case of certain proposed unpowered pedal assist devices, the assist device may bias the clutch pedal toward the depressed position over the pedal's initial range of travel, which may result in undesirable wear between clutch assembly components (e.g., the thrust bearing and the spinning diaphragm spring). Finally, in the case of both powered and conventional unpowered pedal assist devices, such devices are often incorporated directly into the clutch assembly (e.g., integrally formed as part of the clutch pedal lever) and are consequently impractical to retrofit to an existing clutch assembly.

There thus exists an ongoing need to provide embodiments of an unpowered pedal assist device for use in conjunction with a clutch assembly (or other vehicular control pedal assembly) that significantly reduces clutch pedal apply forces, that is relatively inexpensive to implement, that is reliable, and that exhibits substantially zero lag between driver actuation of the clutch pedal and generation of the assist force. It would be desirable if embodiments of such an unpowered pedal assist device were amenable to aftermarket installation on existing vehicles. It would further be desirable if such an assist device would initially bias the clutch pedal toward the non-depressed position to ensure that, after being depressed, the clutch pedal returns to the non-depressed or upright position to minimize wear between clutch assembly components. Finally, it would be desirable to provide embodiments of a clutch assembly including such an unpowered pedal assist device. Other desirable features and characteristics of the present invention will become apparent from the subsequent Detailed Description and the appended Claims, taken in conjunction with the accompanying Drawings and this Background.

BRIEF SUMMARY

Embodiments of an unpowered pedal assist device are provided for use in conjunction with a vehicular control pedal movable between a non-depressed position and a depressed position. In one embodiment, the unpowered pedal assist device includes a multi-bar linkage and at least one resilient element coupled to the multi-bar linkage. The multi-bar linkage is configured to be coupled to the vehicular control pedal and, when so coupled, to move from a start position to a finish position as the vehicular control pedal moves from the non-depressed position to the depressed position. The at least one resilient element is configured to bias the multi-bar linkage: (i) toward the start position over an initial range of travel of the vehicular control pedal, and (ii) toward the finish position over a primary range of travel of the vehicular control pedal.

Embodiments of a vehicular clutch assembly are also provided. In one embodiment, the vehicular clutch assembly includes an unpowered pedal assist device and a clutch pedal movable between a non-depressed position and a depressed position. The unpowered pedal assist device includes a four bar linkage and at least one resilient element coupled to the four bar linkage. The four bar linkage is mechanically linked to the clutch pedal and configured to move in conjunction therewith between a start position and a finish position corresponding to the non-depressed position and the depressed position, respectively. The at least one resilient element biases the four bar linkage: (i) toward the start position over an initial range of travel of the clutch pedal to bias the clutch pedal toward the non-depressed position, and (ii) toward the finish position over a primary range of travel of the clutch pedal to bias the clutch pedal toward the depressed position.

DETAILED DESCRIPTION

The following Detailed Description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding Background or the following Detailed Description. Although primarily described below in the context of a vehicular clutch assembly, it is emphasized that embodiments of the unpowered pedal assist device are suitable for use in conjunction with other types of vehicular control pedal assemblies including, for example, brake pedal assemblies. As appearing herein, the phrase “resilient element” is utilized to indicate a structural element or assemblage of structural elements, such as a spring or an elastic band, that is inherently biased to return to an original position or state when deformed or otherwise displaced from the original position or state.

FIGS. 1 and 2are functional diagrams of a vehicular powertrain10(partially shown) and an unpowered pedal assist device12in accordance with an exemplary embodiment. Powertrain10includes an internal combustion engine14, a clutch assembly16, and a manual transmission18having an output shaft20. Clutch assembly16includes a clutch pedal22(e.g., a lever arm and a foot plate), a clutch housing24, and various additional components (e.g., a clutch disc, a pressure plate, a diaphragm spring, a thrust bearing, etc.) that are well-known within the automotive industry and not shown inFIGS. 1 and 2for clarity. In the simplified example illustrated inFIGS. 1 and 2, clutch pedal22is mounted directly to clutch housing24; however, in actual implementations of clutch assembly16, one or more intervening structural elements (e.g., one or more additional levers and/or a hydraulic system) will typically be connected between clutch pedal22and clutch housing24. As depicted inFIG. 1, clutch pedal22normally resides in an upright or non-depressed position, which corresponds to the engaged position of clutch assembly16. As indicated inFIG. 2, clutch pedal22can be depressed by a driver to rotate clutch pedal22into a depressed position, disengage clutch assembly16, and permit a driver to change the gear ratio of manual transmission18.

A driver will typically use his or her foot to depress clutch pedal22and move clutch pedal22from the non-depressed position shown inFIG. 1toward the fully depressed position shown inFIG. 2. However, in certain cases, such as when a disabled driver lacks full usage of his or her legs or feet, a driver may move clutch pedal from the non-depressed position to the depressed position utilizing a different manual control, such as a hand-actuated lever mounted near the vehicle's steering wheel. For at least this reason, the term “pedal,” the phrase “clutch pedal,” the phrase “vehicular control pedal,” and like terms and phrases are utilized herein in a broad sense to encompass any manually-actuated control (e.g., a clutch pedal, a hand-actuated lever deployed aboard a passenger vehicle, a hand-actuated lever deployed aboard a motorcycle, etc.) that can be utilized by a driver selectively disengage a vehicular clutch assembly, such as clutch assembly16shown inFIGS. 1 and 2. In addition, embodiments of unpowered pedal assist device12can also be utilized in conjunction with other types of vehicular control pedals, such as brake pedals. Thus, as appearing herein, the phrase “unpowered pedal assist device” and similar phrases are utilized to denote embodiments of a device that assists a driver in the actuation of a clutch pedal, a brake pedal, or any other vehicular control pedal as previously defined.

To transmit the force output of unpowered pedal assist device12to vehicular clutch assembly16, device12is conveniently mechanically linked to clutch assembly16by one or more rigid links. For example, as shown inFIGS. 1 and 2, unpowered pedal assist device12may be mechanically connected to clutch assembly16by a force apply rod30, which is pivotally coupled between an output member of unpowered pedal assist device12(e.g., grounded link44described below in conjunction withFIGS. 3-5) and the lever of clutch pedal22. This example notwithstanding, unpowered pedal assist device12can be mechanically linked to clutch pedal22, or any other component of clutch assembly16, utilizing any number and type of intervening structural elements that cooperate to effectively transmit the force assist output of unpowered pedal assist device12to clutch assembly16. In addition, unpowered pedal assist device12can be mounted in any desired orientation in three dimensional space. For example, in one specific embodiment, unpowered pedal assist device12can be transversely mounted under a vehicle's dashboard and mechanically linked to clutch pedal22utilizing a bell crank assembly.

In the exemplary embodiment illustrated inFIGS. 1 and 2, and in contrast to certain other pedal assist devices, unpowered pedal assist device12is not integrated into clutch assembly16; e.g., the four bar linkage described below and included within assist device12is structurally separate and remotely located from clutch pedal22. A vehicle can thus be equipped with unpowered pedal assist device12during original manufacture or, instead, subsequently equipped with assist device12via aftermarket installation. In this latter case, unpowered pedal assist device12can be mounted at least partially beneath the driver's seat and connected to clutch pedal22utilizing an elongated rigid link, such as force apply rod30shown inFIGS. 1 and 2. Notably, the force output profile of unpowered pedal assist device12can be customized to complement the resistance characteristics of the clutch assembly included within a particular vehicle and/or to accord with driver preferences. The force output profile of unpowered pedal assist device12can be adjusted by altering the angle at which unpowered pedal assist device12is connected to clutch pedal22(indicated inFIGS. 1 and 2by double-headed arrow33) and/or by altering various structural parameters of assist device12(e.g., spring constants, lever lengths, location of pivot joints, etc.), as described more fully below.

FIGS. 3-5are plan views of unpowered pedal assist device12including a four bar linkage32and a plurality of resilient elements34,36,38in accordance with an exemplary implementation of assist device12. Four bar linkage32is movable from a start position (shown inFIG. 3), through an intermediate or “over-center” position (shown inFIG. 4), and to a finish position (shown inFIG. 5). As indicated above, and as described more fully below, four bar linkage32is mechanically linked to clutch pedal22by force apply rod30when unpowered pedal assist device12is installed within a vehicle. When four bar linkage32is mechanically linked to clutch pedal22in this manner, the start position (FIG. 3) and the finish position (FIG. 5) of four bar linkage32correspond to the non-depressed position (FIG. 1) and the fully depressed position (FIG. 2) of clutch pedal22, respectively. Thus, as clutch pedal22normally resides in the non-depressed position (FIG. 1), four bar linkage32will normally reside in the start position (FIG. 3); and movement of clutch pedal22into the fully depressed position (FIG. 2) will result in corresponding movement of four bar linkage32into the finish position (FIG. 5).

Four bar linkage32includes a frame link42(also commonly referred to as a “fixed link” or a “ground link”), a first grounded link44, a second grounded link46, and a coupler link48. Coupler link48is pivotally coupled between an upper end portion50of first grounded link44and an intermediate portion52of second grounded link46. The lower end portion54of first grounded link44is, in turn, pivotally coupled to frame link42at a first location; and the lower end portion56of second grounded link46is pivotally coupled to frame link42at a second location longitudinally spaced from the first location. Finally, first grounded link44is pivotally coupled to a first end of force apply rod30, the opposing end of which is coupled to the lever arm of clutch pedal22(FIGS. 1 and 2) as previously described. Notably, in the exemplary embodiment illustrated inFIGS. 3-5, force apply rod30is not directly connected to the main body of first grounded link44; instead, force apply rod30is connected to an output arm58of first grounded link44, which is rigidly joined to and angularly offset from the main body of grounded link44throughout the range of motion of grounded link44. Output arm58changes the ratio of mechanical advantage of four bar linkage32over its initial range of motion to the mechanical advantage at the end of the range of motion toward the finish position and, therefore, adjusts the rate at which the assist force builds early in travel and the rate of force decay after peak assist force is created by the unpowered pedal assist device12. The angle between the main body of grounded link44and output arm58can be increased or decreased, as desired, to adjust the force assist profile of unpowered pedal assist device12to accord with driver preferences and/or to complement the resistance characteristics of a particular clutch assembly. The foregoing notwithstanding, grounded link44may not include an output arm in alternative embodiments, and force apply rod30may be pivotally joined directly to the main body of grounded link44(e.g., to a central portion of grounded link44).

In the exemplary embodiment illustrated inFIGS. 3-5, resilient elements34,36,38include a main spring34, a return spring36, and a soft stop spring38. Main spring34assumes the form of a helical extension spring, which is coupled between a generalized static mounting structure60and an upper end portion62of grounded link46. During operation of assist device12, main spring34biases grounded link46to rotate in a first rotational direction (counterclockwise in the illustrated orientation). Return spring36likewise assumes the form of a helical extension spring, which is coupled between a generalized static mounting structure64and an intermediate portion of coupler link48. During operation of assist device12, return spring36biases coupler link48to rotate in the first rotational direction. Finally, soft stop spring38assumes the form of a helical compression spring, which is mounted to a mounting structure66projecting from frame link42and positioned to be compressed by grounded link44when four bar linkage32is in the start position (FIG. 3). Thus, in the start position (FIG. 3), four bar linkage32biases grounded link44to rotate in the first rotational direction and, more generally, biases four bar linkage32toward the over-center position (FIG. 4). The foregoing notwithstanding, the manner in which springs34,36, and38are interconnected with four bar linkage32will inevitably vary amongst different embodiments; e.g., return spring36may be connected to grounded link44in alternative embodiments and/or soft stop spring38may be positioned to be compressed by coupler link48in the start position (FIG. 3). In further embodiments, one or more of springs34,36, and38may be omitted or replaced by a different type of resilient element; e.g., in alternative embodiments, main spring34and/or return spring36may be replaced by an elastic band or by a torsion spring disposed around a pivot joint of linkage32.

Static mounting structures60and64will typically remain stationary during operation of unpowered pedal assist device12, although the possibility that structures60and64may be repositioned by a driver or a technician when assist device12is not in use is by no means precluded. Static mounting structures60and64may assume the form of a base member or any other structural member that is rigidly mounted to the vehicle chassis, the driver's seat, the vehicle's dashboard, the passenger compartment floor, or the like. Fixed link42will likewise remain stationary as four bar linkage32moves between start (FIG. 3) and finish (FIG. 5) position and, more specifically, as links44,46, and48change relative orientation from a first orientation (i.e., the orientation shown inFIG. 3) to a second orientation (i.e., the orientation shown inFIG. 5). The relative spatial positioning of fixed link42, static mounting structure60, and static mounting structure64will thus typically remain fixed during normal operation of unpowered pedal assist device12.

When four bar linkage32moves into the over-center position shown inFIG. 4, grounded link44and coupler link48rotate into linear alignment (i.e., the longitudinal axes of links44and48become parallel) and effectively act as a brace between grounded link46and frame link42. Consequently, when four bar linkage32is in the over-center position (FIG. 4), main spring34exerts little to no bias force on four bar linkage32. In all other positions, main spring34biases four bar linkage32toward either the start position (FIG. 3) or the finish position (FIG. 5). In particular, when four bar linkage32is between the start position (FIG. 3) and the over-center position (FIG. 4), main spring34biases four bar linkage32toward the start position (FIG. 3), and force apply rod30exerts a pulling force on clutch pedal22biasing pedal22toward the non-depressed position (indicated inFIG. 1by arrow26). Conversely, when four bar linkage32is between the over-center position (FIG. 4) and the finish position (FIG. 5), main spring34biases four bar linkage32toward the finish position (FIG. 5), and force apply rod30exerts a pushing force on clutch pedal22biasing pedal22toward the fully depressed position (indicated inFIG. 2by arrow28). Return spring36, by comparison, biases four bar linkage32toward the start position (FIG. 3) throughout the range of motion of linkage32. Consequently, after four bar linkage32has moved into the finish position (FIG. 5), return spring36helps to return four bar linkage32to the start position (FIG. 3) and to prevent a lock-out condition as four bar linkage32rotates through the over-center position (FIG. 4). As a result of the above-described structural arrangement, unpowered pedal assist device12provides a unique, bi-directional force assist output profile over the range of travel of clutch pedal22, as described more fully below in conjunction withFIG. 6.

FIG. 6is a graph of pedal travel (horizontal axis) versus force (vertical axis) illustrating: (i) the pedal apply forces required to depress exemplary clutch pedal22(FIGS. 1 and 2) when unpowered pedal assist device12is not coupled to clutch pedal22(referred to herein as the “unassisted pedal apply force profile” and shown inFIG. 6at70), (ii) the force assist output profile generated by unpowered pedal assist device12over the range of travel of exemplary clutch pedal22(shown inFIG. 6at72), and (iii) the pedal apply force required to depress clutch pedal22when assist device12is coupled thereto (referred to herein as the “assisted pedal apply force profile” and shown inFIG. 6at74). In addition,FIG. 6graphically expresses the pedal release force profile of clutch pedal22; i.e., the maximum force that can be applied to clutch pedal22and still allow pedal22to return to the non-depressed position (FIG. 1) after being depressed (shown inFIG. 6at76). The force profiles and values graphically illustrated inFIG. 6and described below are, of course, provided by way of non-limiting examples only and will vary amongst different embodiments of unpowered pedal assist device12and clutch assembly16.

In the exemplary embodiment illustrated inFIG. 6, unassisted pedal apply force profile70has a relatively gentle slope over an initial range of travel of clutch pedal22(e.g., approximately 0-20 millimeters). During this initial range of travel, which is commonly referred to as the “pedal free play zone,” the thrust bearing of clutch assembly16moves toward, but does not engage the diaphragm spring. Next, over a second range of travel (e.g., approximately 20-55 millimeters), unassisted pedal apply force profile70has a relatively steep slope, which generally corresponds to the deflection of the diaphragm spring and the disengagement of clutch assembly16. At the end of the second range of travel, unassisted pedal apply force profile70peaks in magnitude (referred to here as the “unassisted peak apply force”) as clutch assembly16moves into a fully disengaged position. In the illustrated example, the unassisted peak apply force of clutch pedal22is approximately 130 Newton. Lastly, over a final range of travel (e.g., approximately 55-100 millimeters), unassisted pedal apply force profile70has a gradual, negative slope, which generally corresponds to further deflection of the diaphragm spring after disengagement of clutch assembly16.

As shown inFIG. 6, the exemplary force assist output profile72of unpowered pedal assist device12is negative over an initial range of travel of clutch pedal22(e.g., approximately 0-20 millimeters). More specifically, the assist force provided by unpowered pedal assist device12is approximately −20 Newton when clutch pedal22is initially displaced from the non-depressed position (FIG. 1) and increases relatively rapidly to approximately 0 Newton after pedal22has traveled approximately 20 millimeters. When coupled to clutch pedal22, assist device12thus biases clutch pedal22toward the non-depressed position (FIG. 1) over the initial range of travel. In this manner, unpowered pedal assist device12helps to ensure that, when clutch assembly16is in the engaged position (FIG. 1), frictional wear of the internal components of clutch assembly16(e.g., the thrust bearing and the diaphragm plate) is minimized or eliminated. Furthermore, by rapidly reducing the negative assist force to zero over the initial range of motion of clutch pedal22, and specifically over the pedal free play zone, unpowered pedal assist device12only marginally increases the driver effort required to initially depress clutch pedal22.

Exemplary force assist output profile72of unpowered pedal assist device12is positive over the remaining range of travel of clutch pedal22(referred to herein as the pedal's “primary range of travel”; approximately 20-100 millimeters in the illustrated example). More specifically, force assist output profile72is slightly greater than approximately 0 Newton after pedal22has traveled approximately 20 millimeters, increases to a peak assist force of approximately 70 Newton after pedal22has traveled approximately 65 millimeters, and then gradually decreases to approximately 55 Newton after pedal22has traveled approximately 100 millimeters. Unpowered pedal assist device12thus provides a force assist output profile having a first average slope over an initial range of travel of clutch pedal22(e.g., approximately 0-70 millimeters in the illustrated example) and having a second average slope, which is negative and less than the first average slope, over a subsequent range of travel of clutch pedal22(e.g., approximately 70-100 millimeter in the illustrated example).

Considering force assist output profile72shown inFIG. 6, it should be appreciated that, when coupled to clutch pedal22, unpowered pedal assist device12significantly reduces the force required by a driver to depress clutch pedal22over its primary range of travel (e.g., approximately 20-100 millimeters). This may be more fully appreciated by comparing unassisted pedal apply force profile70of clutch pedal22to assisted pedal apply force profile74, as further shown inFIG. 6. As can be seen, when coupled to clutch pedal22, unpowered pedal assist device12reduces the peak apply force required by a driver to further depress clutch pedal22by more than half, from approximately 130 Newton to approximately 55 Newton. In addition, force assist output profile72does not surpass pedal force release profile76of clutch pedal22over the range of travel of pedal22; consequently, assist device12will not interfere with the normal return of clutch pedal22to the non-depressed position (FIG. 1) when the driver-applied force is removed.

The foregoing has thus provided at least one exemplary embodiment of an unpowered pedal assist device for use in conjunction with a vehicular clutch assembly (or other vehicular control pedal assembly) that significantly reduces the force required by a driver to depress a clutch pedal (or other control pedal) to increase driver comfort, especially in the context of high performance or high horsepower platforms. Notably, the above-described exemplary assist device initially biases the clutch pedal toward the non-depressed position to ensure that, after being depressed, the clutch pedal returns to the non-depressed or upright position to minimize wear between clutch assembly components. In addition, the above-described exemplary assist device is relatively inexpensive to implement, reliable, and exhibits substantially zero lag between driver actuation of the clutch pedal and generation of the assist force. Furthermore, in the above-described exemplary embodiment, the unpowered pedal assist device is not directly integrated into the vehicular clutch assembly (e.g., four bar linkage32is formed independently of and remotely located from clutch pedal22, as shown inFIGS. 1-5); consequently, the above-described assist device is well-suited for aftermarket installation on existing vehicles. Although, in the foregoing example, the unpowered pedal assist device employed a four bar linkage, the unpowered pedal assist device may include other types of movable linkages having a different number of links (e.g., five or more links) in further embodiments. For this reason, the phrase “multi-bar linkage” may be utilized herein to encompass movable linkages including three or more bar links capable of moving between a start position and a finish position to produce a force assist output profile as previously described.

While at least one exemplary embodiment has been presented in the foregoing Detailed Description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing Detailed Description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set-forth in the appended Claims. Furthermore, as appearing in the appended Claims, the term “connected” is utilized in a relative sense to indicate that a first named element is more directly coupled to a second named element than to any other structural element recited in a given claim and in any claims from which the given claim depends. The term “connected,” then, does not preclude the possibility of intervening structural elements. For example, in the context of claim that positively recites the features of link A, link B, and link C, the statement “link A is connected to link B” indicates that link A is coupled more directly to link B than to link C.