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Technology

July 2, 1997

5-Link Double Wishbone Rear Suspension Development Objectives

Tokyo, July 2, 1997 --- Suspensions are designed to ensure vehicle stability under any circumstance associated with accelerating, cornering and braking. To properly assume this role and thus avoid any undesirable movement, suspension design needs to be sophisticated. As an uncontested leader in front wheel drive technology, Honda has acquired extensive know how in driving stability. We have been able to determine that further improvements in front wheel drive basic performance required special attention toward the rear suspension.

Carrying less weight than the front wheels and having no role in power transmission, rear wheel movement needs to be much better controlled using a sophisticated rear suspension. Rear body movement also plays an important role in driving comfort. For these two reasons we have developed, using the ß-method analysis, a new 5-link double wishbone rear suspension specially packaged to meet passenger car requirements.

Honda's Rear Suspension Design History

From 1976
Strut Type Suspension:

Honda was one of the first makers to adopt a strut type suspension layout in its mid-class vehicles. This very simple fully independent strut type suspension was incorporated without compromising the front wheel drive layout advantages, ensuring unheard of ride comfort and maneuverability. The use of low-friction dampers and low-compliance bushings allowed for improved ride comfort, road holding and rough terrain drivability.

From 1985
Double Wishbone Suspension:

Honda was one of the first to adopt this new system to cope with the increased performance associated with DOHC engines. This is when the ride improving high mount upper arm layout was first developed. Unequal length lower arms were similarly adopted to restrict brake steer, and improve maneuverability.

From 1989 Matured Double Wishbone Suspension: In order to cope with further power increases associated with VTEC technology, Honda further improved the double wishbone layout. Shock absorbing capability and damper response were upgraded while road noise transmission via the suspension was reduced. This suspension is renowned for combining superior handling and ride comfort.

From 1997
New 5-Link Double Wishbone Suspension:

Honda's innovative 5-link double wishbone suspension features for the first time in the world a Watt link arrangement. The five suspension arms are designed and laid out to provide optimum geometry under all driving situations, thus guaranteeing unprecedented handling and ride levels. A compact in-wheel layout was further adopted to increase cabin space and trunk volume.

New 5-Link Double Wishbone Suspension

Development Process and Achievements

* The 5-Link Double Wishbone Suspension Layout
As shown below, the 3-link and 4-link layouts allow for movement in two or more directions. By comparison, in Honda's new 5-link double wishbone suspension, the fore-and-aft loads are controlled by the trailing and leading arms while lateral loads are controlled by the upper, lower and control arms. The dampers' work load is thus reduced to vertical loads for improved stability and ride. Each suspension arm being located to take loads from one single direction, along the arm's axis, has allowed the use of straighter, lighter arms.

* 5-Link Double Wishbone Suspension with Watt Link Locating Arms
Two arms, one trailing , the other leading, are aligned into a Watt link layout to allow the rear wheel to move along a rearward line when viewed from the side. In more conventional layouts, the wheel travels along a curved plane. Longitudinal loads from the road surface are thus substantially reduced, improving ride characteristics. Finally, with the rear wheel locus angle remaining the same whatever the load, the advantages presented by this layout remain the same under all driving conditions.

Watt Link Locating Arms

* Increased Cabin/Trunk Space:
Wheel housing intrusion into the cabin has been reduced thanks to the Watt link layout and a very compact in-wheel suspension design. All five arms fit within the circumference of the wheel, allowing for increased cabin space and a larger trunk volume.

* Straight Line Characteristics:
The toe change associated with wheel movement is limited and linear. This is accomplished by aligning the virtual axis passing the trailing and lower arm mounting points and the virtual axis passing the leading and upper arm mounting points in parallel. This translates into increased straight line stability, higher rolling resistance and reduced understeer.

* Toe-in Characteristics
Under Cornering
The upper, lower and control arms are arranged to be true to the wheel longitudinal axis, which, coupled with a straight arm design, ensures high stiffness against lateral force. The wheel center to control arm span is longer than the one between the wheel center and the lower arm, allowing a greater displacement of the lower arm bushing to increase toe-in under cornering. This translates into improved handling characteristics and traceability.

Under Braking
The diagonal arrangement of the trailing and leading arms increases toe-in under braking. The control arm on the other hand remains virtually unaffected, further allowing appropriate toe-in control. Handling characteristics are thus maintained even under braking.

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