Vibration isolation mount

Details Vibration isolation mount Vibration isolation mount

1999-06-30

2001-10-16

Graham, Matthew C. (Department: 3613)

Spring devices

Resilient shock or vibration absorber

Having diverse resilient element

C267S293000

Reexamination Certificate

active

06302385

ABSTRACT:

TECHNICAL FIELD
The present invention relates to vibration isolation mounts, and more particularly to isolation mounts useful for mounting an automotive brake system accumulator plate to a vehicle.
BACKGROUND OF THE INVENTION
Hydraulic systems generate vibrations due to the pressure waves traveling through the fluid in the system. Accordingly, it is necessary to isolate components of a hydraulic system to prevent transmission of vibrations to associated support structure. Such vibration isolation is particularly desirable in hydraulic braking systems of automotive vehicles.
Antilock brake systems (“ABS”) are hydraulic braking systems for automotive vehicles that employ modulator units attached to an accumulator plate and include a motor and pumps which transfer fluid pressure from the vehicle wheels during an antilock braking event. A typical antilock brake system (ABS) senses when individual wheels on a vehicle begin to “lock-up” (i.e. cease rotation) during braking, which is an indication that those vehicle wheels are beginning to skid, usually due to adverse road conditions. Vehicle skidding is undesirable in that the vehicle stopping distance is lengthened and vehicle control is lessened. Accordingly, in order to minimize skidding, the ABS modulates hydraulic fluid flow to the vehicle wheel disc brakes that are about to lock up, thereby causing such brakes to alternate between applying and releasing braking pressure in a controlled manner at a high rate. The high rate of braking cycles creates a certain degree of vibration and noise in the ABS components; and such vibrations can be transmitted from the braking system to a vehicle body passenger cabin, especially in braking configurations where the accumulator plate is secured to the body of the vehicle or in close proximity to the passenger cabin. The problem is particularly severe during an ABS braking event, due to the frequency and force with which the flow of the hydraulic fluid is modulated. Such vibrations (and the noise they create) can be annoying and uncomfortable for the vehicle passengers, particularly in larger vehicles employing large hydraulic pumps. Additionally, the vibrations can be detrimental to the mechanical systems in the automobile, contributing to the unreliability and premature failure of these systems. Accordingly, for the above-noted reasons, it is desirable to have a mount for securing an accumulator plate to a vehicle bracket of an automobile which minimizes the vibrations transferred from the accumulator plate to the vehicle bracket, and thus to the vehicle body.
In the past, many attempts have been made to mount hydraulic braking equipment to a vehicle bracket in an automotive application with varying degrees of success. Contributing to the difficulty of the task is the dichotomy of conflicting design constraints which require a relatively “stiff” mount to provide support for the hydraulic equipment and a relatively “loose” mount for improved vibration isolation characteristics. For example, while a standard “stiff” mount (wherein the accumulator plate is bolted directly to the vehicle bracket) would provide plenty of support, it would also transmit an unacceptable amount of vibration to the vehicle bracket, and thus to the vehicle. Conversely, while a relatively “loose” mount, such as one made entirely of rubber, would provide ample vibration damping characteristics, it would unfortunately provide an unacceptably low degree of support for the modulator unit. Additional design constraints, such as the tolerance for movement within the engine compartment due to the presence of other equipment or housings, such as the shock tower, also need to be considered.
One type of prior art mounting which attempted to resolve some of these problems generally consisted of a spool-type collar, a bolt and several elastomeric washers. In this system, the spool-type collar was seated in an aperture in the vehicle bracket and the accumulator plate with the elastomeric washers mounted between the vehicle bracket and the accumlator plate to provide vibration damping characteristics. The bolt was inserted through the collar and tightened with a nut, thereby securing the accumulator plate to the vehicle bracket. While this prior art design allowed for some flexibility of travel for the accumulator plate with respect to the vehicle bracket in the fore/aft direction, it allowed for very little vertical travel, and almost no lateral or “tilt” travel. Accordingly, an unacceptable amount of vibration was transmitted to the passenger compartment. Additionally, these prior art mounts contained several different components that required individual manual installation, thereby adding to the overall assembly costs for the automotive vehicle.
Thus, given the above noted disadvantages of prior art vibration damping mounts, it is desirable to provide an isolation mount for a hydraulic brake system which lessens the transmission of noise and vibrations to a passenger compartment in an automotive vehicle while still adequately supporting hydraulic braking equipment to a bracket.
SUMMARY OF THE INVENTION
The present invention is a vibration isolation mount particularly useful for supporting a brake system accumulator plate on a bracket such that transmission of vibration from the accumulator plate to the bracket is minimized and yet movement of the plate relative to the bracket is restrained. Consequently, the bracket and plate can be mounted adjacent other components without risking damage to such components by contact from the plate. Additionally, the isolation mount of the present invention reduces assembly times and costs by utilizing a bolt/washer assembly which may be preassembled.
In a preferred embodiment of the invention, the isolation mount of the present invention includes a shear mount, a rate washer, a bolt and a nut. The shear mount includes a central bore which retains a spacing collar, an accumulator plate contacting member and a rate washer contacting member, all of which are connected by an annular rib, and at least one rate bump positioned on the accumulator plate contacting member. The rate washer includes a central bore and a raised stack positioned around a periphery of the rate washer. Preferably, over-mold bumps are positioned in the central bore of the rate washer and are used to retain the bolt in the rate washer prior to assembly of the mount.
The mount is installed by seating the shear mount in an aperture in the vehicle bracket with the accumulator plate contacting member facing the inner side of the vehicle bracket and the rate washer contacting member facing the outer side of the vehicle bracket. The rate washer is then positioned on the outer side of the vehicle bracket such that the bolt protrudes through the shear mount central bore and a corresponding aperture on the accumulator plate. The nut is then fastened upon the bolt, thereby urging the accumulator plate inward until the spacing collar contacts the rate washer and the inner side of the accumulator plate. Thus, when the accumulator plate begins to move or vibrate in the fore/aft or lateral (tilt) direction, the rate bumps and the height of the rate washer stack control movement within an acceptable level. Similarly, when the accumulator plate begins to move or vibrate in a vertical direction, the shape and thickness of the annular rib operates to control movement within an acceptable level.
Accordingly, it is an object of the present invention to provide an isolation mount for a hydraulic brake system which minimizes transmission of vibration from the accumulator plate to the support bracket, but prevents excessive gyrations of the accumulator plate; an isolation mount which enables an accumulator plate to be mounted closely adjacent other components without contacting them during operation; and an isolation mount which is inexpensive to manufacture yet robust enough to be employed in automotive applications.


REFERENCES:
patent: 2457058 (1948-12-01), Markowitz
patent: 4858880 (1989-08-01), Durand
patent: 5096153 (1992-03-01), Seeley et a

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