Land vehicles – Wheeled – Running gear
Reexamination Certificate
2002-05-16
2004-10-26
Carone, Michael J. (Department: 3641)
Land vehicles
Wheeled
Running gear
C280S124154, C280S124146
Reexamination Certificate
active
06808193
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a wheel suspension with a wheel-guiding strut which has a helical compression spring, a suspension arm, and a shock absorber, and which is connected on the one hand to the body and on the other to the wheel, wherein the helical compression spring is preferably made such that it at least partially compensates for reaction forces on the shock absorber.
2. Description of the Related Art
In wheel suspensions of the type fundamentally under consideration here, often also called a MacPherson wheel suspension, the upper suspension arm which is present in otherwise conventional wheel suspensions is replaced by a long-stroke strut (see Lueger
Lexikon der Technik
, vol. 12
Lexikon der Fahrzeugtechnik,
1967 Deutsche Verlags-Anstalt GmbH, page 425).
In wheel suspensions of the type underlying the invention, the helical compression spring can be located concentrically to the axis of the shock absorber. Here the entire reaction force, which occurs on the upper support point and therefore on the body, must be accommodated by the piston rod of the shock absorber. This creates considerable friction forces on the piston of the shock absorber and results in bucking spring deflection and rebound.
To reduce the reaction forces acting on the piston rod of the shock absorber, the helical compression spring has traditionally been installed in the strut such that the line of action of the spring force of the helical compression spring forms an acute angle with the shock absorber axis. Ideally, the angle between the line of action of the spring force of the helical compression spring and the shock absorber axis would have to correspond to the angle between the line of supporting action and the shock absorber axis. Therefore, in the normally loaded state, the piston rod of the shock absorber would be largely free of reaction forces. Reaction forces would only occur during the normally loaded state in the event of spring deflection or rebound. However, the angle between the line of action of the spring force of the helical compression spring and the shock absorber axis generally can only be smaller than the angle between the line of supporting action and the shock absorber axis, since the shock absorber axis must be able to pass through the helical compression spring and the wheel must have sufficient freedom of motion.
Due to the continuous widening of the tires and the associated displacement of the wheel rise point to the outside, increased angles necessarily occur between the line of supporting action and the shock absorber axis, thereby preventing the preferred arrangement described above from eliminating reaction forces on the piston rod.
For these reasons, the helical compression spring cannot be set as obliquely with reference to the shock absorber axis as would be desirable. Therefore, the line of action of the spring force is shifted relative to the center line of the spring by slanting one or both of the end turns, by thickening the end turns, by slanting the spring plate, or by combinations of the aforementioned measures. This results in the line of action of the spring force on the lower end of the helical compression spring being farther to the outside than the center line of the spring while the line of action of the spring force and the center line of the spring on the upper end of the helical compression spring passes through the support point.
Since the attainable angle between the line of action of the spring force and the shock absorber axis is still too large to eliminate the reaction forces on the piston rod of the shock absorber, the helical compression spring has been configured such that it compensates at least partially for the reaction forces which occur on the shock absorber. German patent 1 505 616 discloses a wheel suspension of the type under consideration with a helical compression spring with a spring center line in the unloaded state which is roughly C-shaped. Furthermore, German patent 37 43 450 (which corresponds to U.S. Pat. No. 4,903,985) and European patent 0 319 651 disclose a wheel suspension of the type under consideration with a helical compression spring with a spring center line in the unloaded state which is roughly S-shaped.
More specifically, German patent 37 43 450 and U.S. Pat. No. 4,903,985 describe the aforementioned problem of reaction forces acting on the shock absorber or on the piston rod of the shock absorber. German patent 37 43 450 and U.S. Pat. No. 4,903,985 also disclose a helical compression spring with a roughly C-shaped spring center line in the unloaded state. Moreover, German patent 37 43 450 and U.S. Pat. No. 4,903,985 disclose a helical compression spring with a roughly S-shaped spring center line in the unloaded state. Wheel suspensions which use the teaching of German patent 37 43 450 and U.S. Pat. No. 4,903,985 and which also have a helical compression spring with a roughly S-shaped spring center line in the unloaded state have already proven themselves millions of times and are becoming increasingly important.
It was stated initially that the invention relates to a wheel suspension which includes a helical compression spring which is configured such that it at least partially compensates for reaction forces which occur on the shock absorber. The helical compression spring may be of the types described above including the helical compression spring with a roughly C-shaped or S-shaped spring center line in the unloaded state. On one hand, in helical compression springs, the spring center lines are of course not physically present; only the individual spring turns or only the totality of the spring turns are physically present. On the other hand, there is no known definition for the spring center lines of helical compression springs. Therefore it will be described below how the spring center lines of helical compression springs can be determined and what is needed when referencing the spring center lines of helical compression springs.
One process for determining the spring center lines of helical compression springs is to first construct the envelop jacket of the helical compression spring and then equate the center line of the envelop jacket to the center line of the spring. This process can be used at best to a limited degree; it fails especially wherever there are spring turns with a changing turn diameter. Another process for determining the spring center line of helical compression springs is characterized in that the center points of the spring turns are determined from the arithmetic mean of the turn points and that the connection of the center points of the spring turns determined in this way represents the center line of the spring. Finally, the spring center line of the helical compression springs can be determined by the projections of the individual spring turns being examined in one plane, by the center point of each spring turn being assumed to be the center point of a circle which has approached the spring turn, and by the center points of the spring turns which have been obtained in this way being connected to one another.
When reference is made to the spring center lines of the helical compression springs, what matters is the importance of the spring center lines for the lines of action of the spring force of the helical compression springs. If a helical compression spring has a straight spring center line, the line of action of the spring force which is of course always a straight line coincides with the center line of the spring. In a helical compression spring with a roughly C-shaped spring center line in the unloaded state, the line of action of the spring force when in the installed state is shifted relative to the center line of the spring, which runs straight in the installed state (compare FIG. 5 of German patent 37 43 450). Conversely, for a helical compression spring with a roughly S-shaped spring center line in the unloaded state, it applies that in the installed state the line of action of the spring force runs at an acute an
Brandt Robert
Kobelev Vladimir
Lebioda Michael
Neubrand Jorg
Carone Michael J.
Muhr und Bender
Nixon & Peabody LLP
Safran David S.
Thomson M
LandOfFree
Wheel suspension does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Wheel suspension, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Wheel suspension will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3306465