GB2309278A

GB2309278A - Accelerator cable vibration damper

Info

Publication number: GB2309278A
Application number: GB9623511A
Authority: GB
Inventors: Charles M Carlstrom
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1996-01-16
Filing date: 1996-11-12
Publication date: 1997-07-23
Anticipated expiration: 2016-11-12
Also published as: GB9623511D0; GB2309278B; DE19654804C2; DE19654804A1

Description

1 ACCELERATOR CABLE VIBRATION DAMPER 2309278 The present invention relates

to vehicles having internal combustion engines employing mechanical linkages between the accelerator pedal and throttle control, and more particularly to a damper for limiting the vibration transferred from the throttle control to the accelerator pedal.

A typical vehicle that uses an internal combustion engine for power employs an accelerator pedal for the operator to control the speed of the engine. The accelerator pedal is typically attached to a throttle body by a mechanical linkage such as an accelerator cable in order to actuate the valve throttle body, which is mounted on the engine.

is A concern which arises due to this mechanical linkage is that vibration from the engine is transmitted through the core wire of the accelerator cable to the accelerator pedal. This causes objectionable pedal vibration (also known as pedal buzz) that the vehicle operator can feel. The pedal vibration is especially a significant concern for many of today's vehicles that employ shorter accelerator cables.

one characteristic of this vibration is that it usually shows up as amplitude spikes at certain combinations of frequency, engine revolutions per minute (RPM) and pedal position (cable load) rather than being constant. By specifically targeting these spikes and minimising the transmitted vibrations for these specific conditions, the operator concern can be minimised.

One way to address this concern is to employ some type of a spring or elastomer as a damper at some point between the throttle body and the accelerator pedal. A factor to consider when attempting to eliminate the vibrations is that as the accelerator pedal is depressed, pedal efforts and corresponding cable loads increase from about zero to a maximum at wide open throttle of typically about fourteen - 2 pounds. Whatever damper is employed then has to take this into account..

For dampers having elastomers with low linear spring rates, which are most effective for damping vibrations at low pedal loads, the deflections that result at high pedal loads will be large, which is unacceptable. Theses large deflections are unacceptable because of lost pedal travel and durability issues that occur with the softer elastomer dampers. High localised deformations (buckling) can cause the material to fatigue, reducing the life of the damper assembly. To reduce the total deflection and increase durability, one may try dampers using elastomers with very high spring rates (high durometer). However, these generally will not effectively reduce vibrations at low pedal efforts. This is also unacceptable considering studies that show that a typical operator spends about 95% of the time within the lower quarter of pedal effort.

one disclosure which attempts to address these concerns is U. S. Patent 4, 800,773 to Nakamura et al. It discloses a damper for an accelerator pedal that uses rubber to isolate the core wire of the accelerator cable from the accelerator pedal. It also recognises that if the elasticity of the damper is too high, then the defection upon depression of the accelerator pedal is too great and if the elasticity of the insulating rubber is too low, then the desired vibration damping effect is not obtained. However, the patent then discloses complex shaped rubber dampers mounted in special housings to damp the vibrations. This type of arrangement is costly and does not lend itself well to simple design chances when adapting.the assembly from one vehicle to another, with its different vibration characteristics that cause different frequency spikes to occur.

It is desirable, then, to have an accelerator pedal vibration damper that will damp out vibrations at low pedal loads while avoiding, too much deflection at high pedal loads and can be tuned to account for amplitude spikes at certain frequencies and pedal loads. The damper should further be inexpensive to produce and easy to modify for different vehicles having differing vibration spikes and pedal loads.

Claims

According to a first aspect of the present invention, there is provided an

accelerator assembly as hereinafter set forth in Claim 1 of the appended claims.

According to two further aspects of the invention, there are provided accelerator assemblies as hereinafter set forth in Claim 8 and Claim 13 of the appended claims.

In its embodiments, the present invention contemplates an accelerator assembly having a frequency tuned damper for isolating, engine vibrations from an accelerator pedal in a vehicle. The accelerator assembly includes an accelerator pedal assembly including the accelerator pedal mounted on an accelerator pedal arm, with the accelerator pedal arm including an opening therethrough. An accelerator core wire has a first and a second end, with the first end operatively engaging the engine and the second end extending through the 2 o pedal arm opening. An end cap receives the second end of the core wire and is secured thereto. The accelerator assembly also includes a first torus shaped elastomeric member located about the core wire, between the end cap and the accelerator pedal arm, for compressing when the pedal arm and cable end cap are biased toward one another.

An advantage of accelerator assembly of the preferred embodiment of the present invention is that the damper assembly is simple, low cost, relatively small in size and low in weight, and durable.

An additional advantage is that the damper provides for a non-linear spring rate due to the shape of the 0-rings, providing adequate damping at low pedal loads while minimising the total deflection at high pedal loads.

A still further advantage is that different vibration spikes associated with different vehicles can be easily - 4 addressed by tuning the damper for the given spikes by changing the size, number and durometer of the 0-rings employed in the damper assembly, by employing several 0rings with different characteristics, several vibration 5 spikes can be addressed by the one damper assembly.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which:- FIG. 1 is a side schematic view of a portion of a vehicle interior in accordance with the present invention; FIG. 2 is an enlarged view of the damper assembly taken from encircled area 2 in FIG. 1 and FIG. 3 is a graph illustrating spring rates for 0-ring -members versus linear spring rates.

Figs. 1 and 2 illustrate a vehicle 10 including a conventional throttle body 12 mounted to a conventional engine 11. An accelerator pedal assembly 14, including a pedal 16 and an accelerator pedal arm 18 are attached to a wall 20 by a pivot joint 22. An accelerator cable 24 extends from the throttle body 12 to near the top of the accelerator pedal arm 18. The accelerator cable 24 includes a core wire 26 that is affixed to a rotational member on the throttle body 12 at one end and affixed to a damper assembly 28 at its other end.

The damper assembly 28 includes a conventional cable end cap 30 that retains the end of the core wire 26, and a cable clip 32, which is affixed near the top of the accelerator pedal arm 18, including a bore 34 through which the core wire 26 passes. A guide 36 is generally T-shaped, with a first leg 38 of the guide 36 in surface contact with the cable end cap 30, and a second leg 40 of the guide 36 extending within a portion of the bore 34 in the cable clip 32. The guide 36 also includes a bore 42 therethrough through which the core wire 26 extends. As an alternate configuration, the guide 36 can be made integral with the cable end cap 30.

Mounted about the second leg 40 are three 0-rings 44, separated by tw6 washers 46, The 0-rings 44 are made of a typical elastomeric material, such as rubber. The 0-rings 44 are typical 0-rings having generally a torus (donut) shape. The damper assembly 28, then, is threaded and free floating on the accelerator cable core wire 26. Tension in the core wire 26 sandwiches the 0-rings 44 between the end of the core wire 26 and the accelerator pedal arm 18. Consequently, as a vehicle operator pushes down on the accelerator pedal 16, the accelerator pedal arm 18 pushes the cable clip 32 toward the cable end cap 30, which is biased toward the throttle body 12; this applies a compression force to the 0-rings 44.

The graph in Fig. 3 illustrates spring rates as they is relate to deflection of a damper for a given force in the general range seen by a core wire 26. The desire is to generally optimise the damper for the range of force under four pounds since this is the most common operating range. In this range, a low linea: spring rate 50 will allow for 20 sufficient deflection to dampen the vibrations, but in the higher force range, the deflection becomes too great. For high linear spring rate 52, the deflection is too small to adequately dampen the vibrations in the low load range even though at higher loads, the deflection does not increase to 25 unacceptable levels.

a Due to the geometry of an 0-ring (a torus shape) its spring rate is nonlinear in compression. This is indicated in Fig. 3 by an example of a possible spring rate 54 for an 0-ring. The non-linear characteristic happens because as the load increases and the 0-ring deforms, the contact area also increases. Thus, at light loads, the contact area is small, creating an effective low spring rate, to give adequate damping at low pedal loads, where the majority of time is spent with vehicle operators; whereas at higher loads, the contact area becomes large, creating a relatively high spring rate to limit the total deflection, with - 6 is correspondingly less localised deformation, increasing the long term durability of the damper assembly 28.

Referring again to Figs. 1 and 2, the operation of the damper assembly 28 will be described. When the engine 11 is operating, it transmits vibrations to the throttle body 12, which, in turn, is the source of vibrations in the core wire 26. As the operator presses on the accelerator pedal 16 tension is created in the core wire 26 since it is biased i the direction of the throttle body 12. In a conventional arrangement, then, these vibrations will transfer from the core wire through to the accelerator pedal.

Here, the vibrations in the core wire 26 transfer to the end cap 0. The vibrations must then pass through the stack-up of the guide leg 38, washers 46 and 0-rings 44 to affect the cable clip 32. As the vibrations attempt to pass through this stack-up, which is now under a compression force, the 0-rings, by elastically deforming, will reduce the vibrations transmitted, thereby isolating the cable clip 32 from the end cap 30. The operator will experience only those vibrations that affect the cable clip 32, since it is affixed to the accelerator pedal arm 18.

Further, the vibrations coming from the engine 11 are not the same for all frequencies of operation and the vibrations transmitted through the core wire 26 are not the same for all cable loads. There tends to be peaks at certain combinations of frequency and cable load for a given vehicle, which will be the most bothersome for the vehicle operator. By determining where these spikes occur, one can choose the proper size and elasticity of 0-rings 44 to maximise the damping effect at these spikes. The configuration of the present invention, in particular, lends itself to targeting multiple spikes (tuning the damper) by the fact that each of the 0-rings in the stack can be chosen with different properties, so each one of the 0-rings targets a different one of the spikes.

7 The cost of this configuration is also minimised by the fact that 0-rings are readily available in many shapes, sizes and hardnesses because they are in very common use as sealing devices in joints. Therefore, a wide variety of 0rings are available off the shelf Tuning the damping for a different vehicle, then, is simplified by the choice of 0rings for that particular application. The number, size and material of the 0-rings can change as needed for the particular vehicle vibration characteristics and pedal loads.

CLAIMS is 1. An accelerator assembly having a frequency tuned damper for isolating engine vibrations from an accelerator pedal in a vehicle, the accelerator assembly comprising:

an accelerator pedal assembly including the accelerator pedal mounted on an accelerator pedal arm, with the accelerator pedal arm including an opening therethrough, an accelerator core wire, having a first and a second end, with the first end operatively engaging the engine and the second end extending through the pedal arm opening, an end cap receiving the second end of the core wire and secured thereto; and a first torus shaped elastomeric member located about the core wire, between the end cap and the accelerator pedal arm, for compressing when the pedal arm and cable end cap are biased toward one another.
2. An accelerator assembly as claimed in claim 1, further including a second torus shaped elastomeric member, located about the core wire adjacent to the first torus shaped member, and a first cylindrical shaped washer, located about the core wire between the first and second torus members.
3. An accelerator assembly as claimed in claim 2, wherein the first and second torus members are made from different durometer material, thereby isolating different ranges of frequencies.
4. An accelerator assembly as claimed in claim 1 or claim 2, further including a third torus shaped elastomeric member, located about the core wire adjacent to the second torus shaped member, and a second cylindrical shaped washer, located about the core wire between the second and third torus members.
5. An accelerator assembly as claimed in any preceding claim; wherein the first torus member is a rubber 0-ring.
6. An accelerator assembly as claimed in any preceding claim, further including a cable clip mounted to the pedal arm about the core wire between the pedal arm and the first torus member.
7. An accelerator assembly as claimed in any preceding claim, further including a T-shaped guide member having a first leg in surface contact with the end cap and a second leg, generally normal to the first leg, having a bore therethrough mounted about the core wire, with the torus member mounted about the second leg of the guide member.
8. An accelerator assembly having a frequency tuned damper for isolating engine vibrations from an accelerator pedal in a vehicle, the accelerator assembly comprising:

an accelerator pedal assembly including the accelerator pedal mounted on an accelerator pedal arm, with the accelerator pedal arm including an opening therethrough; an accelerator core wire, having a first and a second end, with the first end operatively engaging the engine and the second end extending through the pedal arm opening; an end cap receiving the second end of the core wire and secured thereto; a plurality of torus shaped elastomeric members located about the core wire and adjacent to one another, between the end cap and the accelerator pedal arm, for compressing when the pedal arm and cable end cap are biased toward one another. and a plurality of flat cylindrical members, one each respectively interleaved between a pair of adjacent torus members.

- is
9. An accelerator assembly as claimed in claim 8, wherein each of'the plurality of torus members is made from different durometer material, thereby isolating different ranges of frequencies.
10. An accelerator assembly as claimed in claim 8 or 9, further including a cable clip mounted to the pedal arm about the core wire between the pedal arm and one of the torus members.
11. An accelerator assembly as claimed in any of claims 8 to 10, further including a T-shaped guide member having a first leg in surface contact with the end cap and a second leg, generally normal to the first leg, having a bore therethrough mounted about the core wire, with the plurality of torus members and the plurality of flat cylindrical members mounted about the second leg of the guide member.
12. An accelerator assembly as claimed in any of claims 8 to 11, wherein each of the plurality of torus members is a rubber 0-ring.
13. An accelerator assembly having a frequency tuned damper for isolating engine vibrations from an accelerator pedal in a vehicle, the accelerator assembly comprising:

an accelerator pedal assembly including the accelerator pedal mounted on an accelerator pedal arm, with the accelerator pedal arm including an opening therethrough.

an accelerator core wire, having a first and a second end, with the first end operatively engaging the engine and the second end extending through the pedal arm opening, an end cap receiving the second end of the core wire and secured thereto; a pair of rubber 0-rings located about the core wire, between the end cap and the accelerator pedal arm, for compressing when the pedal arm and cable end cap are biased toward one another. and a of 0-rings.

flat cylindrical washer interleaved between the pai
14. An accelerator assembly as claimed in claim 13, further including a cable clip mounted to the pedal arm about the core wire between the pedal arm and a first one of the pair of 0-rings, and a T-shaped guide member having a first leg in surface contact with the end cap and a second leg, generally normal to the first leg, having a bore therethrough mounted about the core wire, with the 0-rings and washer mounted about the second leg of the guide member.
15. An accelerator assembly as claimed in claim 14, wherein the each of the 0-rings are made from different durometer material, thereby isolating different ranges of frequencies.
16. An accelerator assembly constructed, arranged and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.