Patent Application
20070193400
The present invention relates to clutch pedal mechanisms for vehicles.
A vehicle with a manually shiftable transmission typically has a clutch pedal mechanism that operates a clutch to selectively decouple the engine from the transmission during shift events. The clutch pedal mechanism includes a clutch lever member pivoted on a mount or on a similar stationary support member. The clutch lever member has two end positions, one of which corresponds to the engaged state of the clutch, while the other corresponds to the disengaged state of the clutch. A past-dead-center or over-center spring may be provided that acts on the clutch lever member. The overcenter spring exerts a force on the clutch lever member when the clutch lever member is positioned between an intermediate or dead-center position and the end position corresponding to a disengaged clutch state, such that the force is directed towards this end position. This overcenter spring is effective in reducing the clutch pedal force required by the operator to disengage the clutch.
Systems for reducing the pedal force during the clutch disengagement process are known. The basic premise is to reduce to a reasonable level the amount of pedal force that must be applied to the clutch lever member during clutch disengagement, since the necessary force is quite large due to the necessarily high contact pressure of clutches for modern high-powered engines. The overcenter spring is effective in reducing operator fatigue in stop-and-go traffic conditions. The overcenter spring is typically tuned for a very low pedal effort, this may be undesirable for a performance style of driving, such as closed course driving
Accordingly, provided is a clutch pedal mechanism having a clutch lever member pivotably connected at one end to a mounting member. The clutch lever member has a first position corresponding to an engaged clutch condition, a second position corresponding to an disengaged clutch condition, and a third position intermediate of the first and second position. A plurality of springs are pivotably connected to the clutch lever member and are operable to reduce the force required to displace the clutch lever member from the third position to the second position. At least one of the plurality of springs is selectively detachable from the clutch lever member such that the force required to displace the clutch lever member from the third position to the second position may be selectively increased over the force required when all of the plurality of springs are attached.
The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.
In
The pedal force, indicated at F, applied to the clutch lever member 12 is transmitted hydraulically to the clutch. For this purpose, a hydraulic cylinder 20 is secured to the pedal mount 12 at attachment points 22 and 24. A hydraulic piston, not shown, is reciprocally movable within the hydraulic cylinder 20 in the direction of arrow 26. The piston is connected with a piston rod 28 that is pivotably connected to the clutch lever member 12 at a pivot point 30.
A first pair of spring guides 32 and 32′ are pivoted at attachment points 34 and 34′, respectively, on an angular projection 36 of the hydraulic cylinder 20. A second pair of spring guides 38 and 38′ articulate with the clutch lever member 12 approximately in the lower third of the clutch lever member 12 at attachment points 40 and 40′, respectively. The spring guides 32, 38 and 32′, 38′ are designed and mounted in such a way that they can move relative to each other in the direction of their (congruent) longitudinal axes. The spring guides 32 and 40 hold a spring 42, while the spring guides 32′ and 40′ hold a spring 42′. In the clutch pedal mechanism 10, the springs 42 and 42′ act as overcenter springs, which reduce the pedal force required to depress the clutch lever member 12, thereby disengaging the clutch. The springs 42 and 42′ are preferably helical coil compression springs; however, those skilled in the art will recognize that other springs may be used such as elastomeric members. Additionally, torsional springs may be used while remaining within the scope of that which is claimed. The overcenter points of springs 42 and 42′ need not coincide.
The springs 42 and 42′ are most strongly stressed at the dead-center position B. Nevertheless, the reducing force at position B is approximately equal to zero, since the spring attachment points at 34, 34′ and 40, 40′ and the center of rotation at pivot point 14 of the clutch lever member 12 all lie on a generally straight line. Therefore, there is little or no resultant lever arm and thus little or no resultant moment from the force of the compression springs 42 and 42′. The clutch lever member 12 at position C creates a resultant lever arm for the force of the compression springs 42 and 42′, so that a moment is applied to the clutch lever member 12 in the direction of clutch disengagement. However, when the clutch lever member 12 moves toward position A, a lever arm develops in such a way that the moment resulting from the force of the compression springs 42 and 42′ and the lever arm 12 amplifies the pedal operating force, thereby allowing the clutch lever member 12 to seat securely in the undepressed state at position A. In both cases, the compression springs 42 and 42′ relax from the dead center position B of the clutch lever member 12, shown in
Referring now to
The curve 44 illustrates the force exerted on the clutch lever member 12 by both springs 42 and 42′. The present invention provides that one of the springs 42 and 42′ can be selectively detached, such as by unbolting, or otherwise rendered nonfunctional within the clutch pedal mechanism 10. The curve 46 illustrates the force exerted on the clutch lever member 12 by one of the springs 42 and 42′. By removing one of the springs 42 and 42′, the pedal force F required to depress the clutch lever member 12 is increased as the clutch lever member 12 moves from position B to position C. This is desirable when operating the vehicle in a performance-oriented fashion, such as closed course driving. The clutch pedal mechanism 10 may be returned to the two spring configuration when the operator wishes to have a lower pedal force F, such as when driving in stop-and-go traffic.
While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.
