Double path mount for cab suspension with tilting function

A cab mounting assembly attaches a cab to a chassis of a vehicle at the point of rotation of the cab when the cab is tilted. The cab mounting assembly provides two paths for the forces acting between the cab and the chassis. The static forces are supported by a bearing assembly which includes a relatively hard elastomeric member. The dynamic forces are supported by an elastomeric mount which includes a relatively soft elastomeric member. The elastomeric mount is attached to the bearing assembly and to a shock absorber. The bearing assembly is attached to the elastomeric mount and to an air spring assembly.

FIELD

The present disclosure relates to a cab suspension system typically used in large trucks and other vehicles. More particularly, the present disclosure relates to a mount located at the tilting point of the cab which includes a double path mounting system for isolating the cab.

BACKGROUND

In order to provide comfort for large vehicle operators and reduce driving fatigue experienced by operators of larger vehicles, the operator's cab is suspended utilizing a vibration isolation device and a shock absorption device between the vehicle's chassis and the vehicle's cab which reduces the shock, vibration and consequent pounding the operator experiences during operation of the vehicle. Additionally, the continued application of vibration and shock forces to the cab results in structural damage which ultimately increases the costs associated with maintenance.

The load carried by a large vehicle is supported by the vehicle's frame which is resiliently carried by the vehicle's suspension springs and the vehicle's shock absorbers supported by the vehicle's wheels. Suspension springs typically have a high rate of stiffness which makes the ride more jarring on the operator of the vehicle. To dampen the vibration and shock transmitted to the cab, cab suspension systems have been developed utilizing cab mounting systems that include cab hydraulic shock absorbers and cab air springs to reduce the jounce and rebound movements of the cab with respect to the vehicle's frame.

These cab hydraulic shock absorbers and cab air springs can be mounted at both the front and rear ends of the cab. Typically, a cab is tilted by rotating around a pair of cab air springs and cab hydraulic shock absorbers which are located at the front of the vehicle. The front mounting cab hydraulic shock absorbers and cab air springs often need some type of a bearing to enable the rotational movement during the tilting of the cab. This rotational movement requirement makes it difficult from a design point of view to adequately isolate the cab from the frame.

SUMMARY

The present disclosure provides a cab mounting assembly which is designed for the mounting of the cab at the position where the cab rotates when it tilts. The cab mounting assembly of the present disclosure provides a double path for the loading on the cab mounting assembly such that the dynamic load is uncoupled from the static load. This uncoupling of the two loads allows for the design optimization of both paths to optimally isolate both the static loading and the dynamic loading.

DETAILED DESCRIPTION

Referring now to the figures where like reference numerals designate like or similar components in the various views, there is illustrated inFIG. 1a vehicle which incorporates the cab mounting assembly in accordance with the present disclosure and which is designated generally by the reference numeral10. Vehicle10comprises a cab12, a front suspension14and a rear suspension16.

Front suspension14comprises a pair of longitudinal oscillating arms20mounted to oscillate about a common transverse axis22generally perpendicular to a vertical longitudinal plane of vehicle10. The free ends of oscillating arms20are connected to a transverse torsion bar24. A pair of supports26are rotatably mounted on torsion bar24. Supports26are rigidly connected to the structure of cab12allowing cab12to rotate about the axis of torsion bar24. This allows the raising of cab12by means of rotating about the axis of torsion bar24when it is necessary to gain access to an engine set underneath cab12for maintenance operations. A pair of cab mounting assemblies30are disposed between the free ends of oscillating arms20and the chassis of vehicle10. Rear suspension16comprises a pair of spring damper assemblies32which are attached to the chassis of vehicle10and to cab12through a pair of oscillating arms34.

Referring now toFIG. 2, cab mounting assembly30is illustrated in greater detail. Cab mounting assembly30comprises a shock absorber40, an air spring assembly42and a double path top mount44. Shock absorber40is a dual-tube shock absorber which comprises a pressure tube54, a piston assembly56, a piston rod58, a reserve tube60and a base valve assembly62.

Pressure tube54defines a working chamber64. Piston assembly56slidingly engages pressure tube54and is disposed within working chamber64. Piston rod58is adapted to be attached to piston assembly56and it extends out of working chamber64through one end of pressure tube54and air spring assembly42to be attached to double path top mount44which is attached to cab12. Reserve tube60surrounds pressure tube54to define a reserve chamber66. Base valve assembly62is attached to pressure tube54to control fluid flow between working chamber64and reserve chamber66. The end of reserve tube60opposite to piston rod58is adapted to be attached to the chassis of vehicle10.

Because piston rod58only extends through one portion of working chamber64, movement of piston assembly56causes a different amount of fluid flow in the portion of working chamber64above and below piston assembly56. This difference in fluid flow is known as the “rod volume” and it flows through base valve assembly62. During a compression movement, fluid will flow from below piston assembly56to above piston assembly56through valving in piston assembly56. The “rod volume” of fluid will flow from working chamber64through valving in base valve assembly62and into reserve chamber66. The flow of fluid through the valving in base valve assembly62during a compression stroke defines the damping characteristics for shock absorber40. During an extension stroke, fluid will flow from above piston assembly56to below piston assembly56through valving in piston assembly56. The “rod volume” of fluid will flow from reserve chamber66through valving in base valve assembly62and into working chamber64. The flow of fluid through the valving in piston assembly56during an extension stroke will determine the damping characteristics for shock absorber40.

Air spring assembly42comprises an upper mount70, a lower mount72and a spring sleeve74. Upper mount70mates with double path top mount44. Upper mount70sealingly mates with piston rod58of shock absorber40. A dynamic air seal76seals the interface between air spring assembly42and piston rod58of shock absorber40. Lower mount72is sealingly attached to shock absorber40and acts as a piston for air spring assembly42. Spring sleeve74sealingly engages upper mount70and lower mount72to define a sealed chamber78. An inlet80extends through lower mount72and is utilized to insert pressurized fluid, preferably air into sealed chamber78.

Referring now toFIG. 3, double path top mount44comprises a bracket82, a bearing assembly84, and an elastomeric mount86. Bracket82is secured to and interfaces with upper mount70of air spring assembly42. Bracket82comprises an upright portion88which interfaces with bearing assembly84, an annular portion90extending generally perpendicular to upright portion88and which interfaces with upper mount70of air spring assembly42and an annular portion92extending generally perpendicular to annular portion90and which extends around upper mount70of air spring assembly42.

Bearing assembly84comprises an outer metal94, an inner metal96and an elastomeric member98disposed between outer metal94and inner metal96. Outer metal94is attached to upright portion88of bracket82by being press fit into a pair of holes100defines by upright portion88of bracket82. While outer metal94is illustrated as being press fit into holes100of upright portion88, outer metal94can be attached to upright portion88by any other means known in the art. The ends of outer metal94are rolled over as illustrated at102to encapsulate elastomeric member98. Inner metal96is illustrated as a tubular member defining a through hole104and an arcuate center section106. While inner metal96is illustrated having through hole104and arcuate central section106, other inner metal configurations known in the art can be utilized in bearing assembly84. Through hole104accepts a fastener which secures double path top mount44to cab12. The interface between inner metal96and elastomeric member98defines a bearing which allows elastomeric member98to rotate around inner metal96to allow for the tilting of cab12. Elastomeric member98can be manufactured from a self lubricating elastomer to provide for the rotation of elastomeric member98around inner metal96. Other alternatives for elastomeric member98include, but are not limited to, a plastic bearing bushing or a DU bushing. Elastomeric member98is preferably manufactured from a relatively hard elastomeric material in order to enable it to withstand and isolate the static and dynamic loading applied to dual path top mount44.

Elastomeric mount86comprises a piston rod mount110, an outer metal112, an inner metal114and an elastomeric member116disposed between outer metal112and inner metal114. Piston rod mount110comprises a piston rod interface118which is threadingly received on piston rod58or otherwise attached to piston rod58and an annular ring120which is attached to piston rod interface118. Outer metal112is attached to annular ring120by being press fit or otherwise secured within annular ring120. Inner metal114is a tubular member which is press fit over or otherwise secured to outer metal94of bearing assembly84. Elastomeric member116is disposed between outer metal112and inner metal114. Elastomeric member116is only loaded by the dynamic loads and therefore it can be manufactured from a relatively soft elastomeric material to provide improved Noise Vibration and Harshness (NVH) characteristics as opposed to the harder elastomeric material of elastomeric member98of bearing assembly84.

During operation, the static loads are transferred through bearing assembly84to bracket82and then to air spring assembly42. The relatively hard elastomeric material for elastomeric member98of bearing assembly84transfers the static loading between bearing assembly84and bracket82. The dynamic (damping) forces are transferred by piston rod58, through dynamic air seal76and through elastomeric mount86to bearing assembly84. The relative soft elastomeric material for elastomeric member116provides improved NVH characteristics for the dynamic loading and creates a barrier for the high frequency vibrations.

Dynamic air seal76allows for the movement of piston rod58of shock absorber40with respect to upper mount70of air spring assembly42. Dynamic air seal76comprises a rigid outer member130, a rigid inner member132and an elastomeric member134disposed between rigid outer member130and rigid inner member132. Dynamic air seal76provides a seal for sealed chamber78as well as allowing for the movement of piston rod58separate from upper mount70of air spring assembly42to permit the proper isolation by elastomeric mount86.