Patent Application
20060230875
1. Field of the Invention
The subject invention relates to a vehicle foot pedal assembly having an electronic control with a hysteresis generating structure incorporated therein.
2. Description of the Prior Art
Foot pedal assemblies are used to mechanically control various vehicle functions including the engine and brakes, for example. The foot pedal assemblies usually include a pedal arm mounted to the vehicle body with a series of linkages and levers connecting the pedal arm to an associated device, i.e., carburetor, fuel injector, controller, brake drum, brake housing, clutch housing or the like. Drivers are accustomed to certain application and release pressures on a pedal arm and have become accustomed to a resistance force of the pedal arm as well as a rate of withdrawal as applied pressure is relaxed.
Typically, the pedal arm pressure required when advancing an accelerator pedal, for example, is greater than that required to maintain a fixed position. This difference is often referred to as a hysteresis effect. This effect is important in maintaining the pedal arm in position while driving at a relatively constant speed or for continuous braking. The pressure which must be applied in accelerating, for example, is easily borne but if the back pressure of an accelerator spring produced the same effect during the time it was required to retain or maintain speed, it would soon become uncomfortable for the driver to maintain a relatively constant speed. The hysteresis effect provides relief and lessens the load required to maintain a setting of the pedal arm. Yet there is still force to cause reverse pedal action when the applied pressure is removed.
An improvement in the automotive industry relating to foot pedal assemblies is the use of drive-by-wire systems. Drive-by-wire systems allow the control of the vehicle engine or brakes, for example, without the need for a direct mechanical connection between the pedal arms and the engine or brakes. A drive-by-wire system utilizes electronic or electrical means for controlling the vehicle system, i.e., the engine throttle or vehicle brakes, without the need for a direct mechanical linkage to the engine or brakes.
In the drive-by-wire systems, it is important that the pedal arm provide the customary feel and performance of a mechanical linkage. The foot pedal assemblies should function responsively to driver input and should provide non-fatiguing resistance. Drive-by-wire foot pedals therefore typically have a hysteresis mechanism that replicate the customary feel and performance of an ordinary pedal with a direct mechanical linkage. The hysteresis mechanism replicates the mechanical linkage by creating a frictional force that resists the pivotal movement of the pedal arm. The hysteresis mechanism typically utilizes a spring and braking means to create the fictional resistance. Drive-by-wire systems for vehicle engines with this type of arrangement for a hysteresis mechanism are well known in the art and one such example is U.S. Pat. No. 5,408,899.
An improved drive-by-wire system with a hysteresis mechanism is U.S. Pat. No. 6,575,053 and is assigned to the assignee of the subject invention. The '053 patent provides a pedal assembly having a hysteresis mechanism providing a pair of brake shoes biased into the housing to resist movement of the pedal arm.
The invention provides for a pedal assembly including a housing having two inner surfaces, a pedal arm, and a hysteresis mechanism. The pedal arm is pivotally connected to the housing for movement between and parallel to the inner surfaces of the housing and the hysteresis mechanism responds to reaction forces between the pedal arm and the inner surfaces of the housing to provide a resistance to the pivotal movement of the pedal arm. The hysteresis mechanism includes a first brake element and a second brake element movable relative to one another along a braking axis extending between the inner surfaces of the housing. Each brake element presents a brake shoe that frictionally engages the inner surface of the housing. The brake elements include a pair of parallel ramps spaced from one another along the braking axis, and offset from one another laterally in a direction transverse to the braking axis. The pair of ramps of one brake element are in sliding engagement with the pair of ramps of the other brake element to move the brake elements relative to one another along the braking axis in response to the reaction forces causing the sliding movement between the ramps of the brake elements. Stated another way, the brake elements include coacting ramps in sliding engagement to move the brake elements relative to one another along the braking axis in response to the reaction forces causing sliding movement along the ramps. One of the brake elements could include a pair of fingers flanking one of the ramps for nesting and guiding the other brake element.
Accordingly, the subject invention sets forth an improved alternative design over the prior art hysteresis mechanisms.
Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
Referring to the Figures wherein like numerals indicate like or corresponding parts throughout the several views, a pedal assembly is generally shown at 10 in
The pedal assembly 10 includes a housing 20, presenting two spaced apart inner surfaces 22. The housing 20 pivotally supports a pedal arm 24 having a first end 26 and a second end 28. The first end 26 is disposed within the housing 20 when the pedal arm 24 is mounted to the housing 20. A pedal pad 21 is mounted to the second end 28 of the pedal arm 24. At least a portion of the pedal arm 24 pivots between and parallel to the inner surfaces 22 of the housing 20. A cover 40 is mounted to the housing 20 to substantially encapsulate the first end 26 of the pedal arm 24 within the housing 20. The cover 40 is attached to the housing 20 by a snap tab 42 and is additionally secured to the housing 20 by a fastener 44, i.e., a rivet, or by other adequate methods. A coil spring 38 reacts between the first end 26 of the pedal arm 24 and the cover 40 to continuously bias the pedal arm 24 into a rest or idle position.
The pedal assembly 10 includes a hysteresis mechanism 30 mounted on the pedal arm 24 that is responsive to reaction forces between the pedal arm 24 and the inner surfaces 22 of the housing 20. The hysteresis mechanism 30 is disposed between the first end 26 of the pedal arm 24 and the spring 38 to provide resistance to the pivotal movement of the pedal arm 24 relative to the housing 20. The hysteresis mechanism 30 simulates the variable force or hysteresis effect to duplicate the pedal performance and driver feel of an ordinary foot pedal having a direct mechanical linkage.
Referring also to
As shown in
Referring also to
The pair of ramps 46 of each of the brake elements 32, 34 includes a root ramp 48 and a distal ramp 50, as shown in
Each of the brake elements 32, 34 includes a finger 52, 54, 56 extending from the next adjacent root ramp 48 and parallel to the braking axis (B). The distal ramps 50 are disposed on the ends of the respective fingers 52, 54, 56 of the braking elements 32, 34. The fingers 52, 54, 56 of the brake elements 32, 34 are disposed in side-by-side relationship in a transverse direction along the braking axis (B) for sliding relative to one another as the root ramps 48 engage the distal ramps 50 of the respective brake elements 32.
One of the brake elements 32, 34 includes a pair of fingers 52, 54 flanking one of the ramps 46 for nesting and guiding the other brake element 32, 34. Specifically, the first brake element 32 includes the pair of fingers 52, 54 that are parallel with the braking axis (B) and spaced in a transverse direction from the braking axis (B). The first brake element 32 further includes one of the ramps 46 disposed between the pair of fingers 52, 54 along the braking axis (B). More specifically, the first brake element 32 includes a first finger 52 and a second finger 54 spaced and parallel to the first finger 52. The second brake element 34 includes a single finger 56 that is nestled between the pair of fingers 52, 54 of the first brake element 32. The single finger 56 of the second brake element 34 defines one of the ramps 46 that engages with one of the ramps 46 of the first brake element 32 in a sliding movement along the braking axis (B) in response to the reaction force. In addition one of the brake elements 32, 34 includes a spring seat 60.
The single finger 56 of the second brake element 34 is preferably disposed between the first finger 52 and the second finger 54 of the first brake element 32. The single finger 56 further includes a tab portion 57 that is a raised to provide a slight interference fit between the single finger 56 and the first and second fingers 52, 54 of the first brake element 32. The second brake element 34 further includes one of the root ramps 48 on each side of the single finger 56. The pair of root ramps 48 on the second brake element 34 engages the distal ramps 50 on the first finger 52 and on the second finger 54 of the first brake element 32. The first brake element 32 includes a root ramp 48 between the first finger 52 and the second finger 54 to engage with the distal ramp 50 on the single finger 56 of the second brake element 34.
The first brake element 32 further includes a flange 58 extending from the brake shoe 36 and underlying the flange 58 are the first finger 52 and the second finger 54. The flange 58 includes the spring seat 60 which engages the coil spring 38.
The hysteresis mechanism 30 further incorporates a slide guide interconnecting the second brake element 34 to the first end 26 of the pedal arm 24. The slide guide supports the second brake element 34 on the pedal arm 24 and allows the second brake element 34 to move relative to the pedal arm 24 parallel with the braking axis (B). The slide guide includes a post 64 extending from the second brake element 34, as shown in
It should be appreciated that the hysteresis mechanism 30 can include a pair of coil springs 38, as shown in
Obviously, many modifications and variations of the present invention are possible in light of the above teachings. The invention may be practiced otherwise than as specifically described within the scope of the appended claims, wherein that which is prior art is antecedent to the novelty set forth in the “characterized by” clause. The novelty is meant to be particularly and distinctly recited in the “characterized by” clause whereas the antecedent recitations merely set forth the old and well-known combination in which the invention resides. These antecedent recitations should be interpreted to cover any combination in which the incentive novelty exercises its utility. In addition, the reference numerals in the claims are merely for convenience and are not to be read in any way as limiting.
