Patent Description:
Shock absorbers are used in vehicles to assist the vehicle in adapting to different driving conditions due to irregularities in the road, such as bumps, potholes, and other road surface anomalies. Shock absorbers are also used to assist a vehicle in traveling over more extreme conditions such as off-road driving.

In conditions such as off-road driving, the irregularities can be severe and may cause a standard shock absorber to bottom out, i.e. abruptly reaching their maximum compression, producing a jarring impact. In order to overcome this deficiency shock absorbers with jounce control have been developed. A jounce control shock absorber provides an elevated damping force when the shock approaches the bottoming out condition. However, known jounce control systems are limited in their effectiveness due to the fact that such system only provide one stage of an elevated damping force.

Document <CIT> discloses a gas spring with a cylinder and a piston. The piston splits the inner space of cylinder into a first working chamber and a second working chamber. The piston has a piston rod attached to one side, which is guided out of the cylinder by a sealing and guide package. In the second working chamber, a damping piston is disposed, which can be moved in an end damping range of cylinder. In the end damping range, a tracking spring is attached to the damping piston, which applies a small force to it in the direction of the piston. The damping piston has a recess cavity, in which the piston can be accommodated. The damping piston also has a guide opening. In the guide opening there is a slide gate, which can be moved in the direction of the end damping range. A pressure spring is arranged between the bottom of the guide opening and the slide gate, which applies a spring force to the slide gate.

The invention is directed to a multistage damping system that implements a novel and unobvious jounce control shock absorber in the form of a jounce control shock absorber with multistage jounce control.

The present invention provides a multistage damping system with an elongated housing containing a damping medium, an axially moveable primary piston assembly arranged in the housing comprising a primary piston and a valve assembly, and an axially moveable secondary piston assembly. The axially moveable secondary piston has an orifice disposed in a location to engage the valve assembly when the primary piston assembly is moved in a compressive direction beyond a particular compressive movement distance. When the valve assembly engages the orifice, it regulates the flow of damping medium to provide a greater compressive damping force when said primary piston assembly and said secondary piston assembly are moved beyond the particular compressive movement distance. The invention includes an axially moveable tertiary piston assembly having a recessed cavity formed therein with the secondary piston assembly disposed therein.

A more complete understanding of the present disclosure may be realized by reference to the accompanying drawing in which:.

The illustrative embodiments are described more fully by the Figures and detailed description. The inventions may, however, be embodied in various forms and are not limited to specific embodiments described in the Figures and detailed description.

The invention is directed to a shock absorber comprised in a multistage damping system advantageously for use with a vehicle suspension. The shock absorber increases the damping force when there is significant travel of the vehicle suspension. In particular, as the suspension reaches a bottoming out condition during compression, the damping force of the shock absorber increases. The present invention provides unique and novel mechanisms for increasing the damping force depending on the position of the shock absorber during compression so as to significantly reduce or avoid a bottoming out condition. As discussed below, the shock absorber of the present invention sequentially increases the damping force using a multistage jounce control configuration.

For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. The following illustrates the principles of the disclosure. It will thus be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the disclosure and are included within its spirit and scope.

All examples and conditional language recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the disclosure and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions.

<FIG> shows a cross-sectional perspective view of an exemplary shock absorber <NUM> in accordance with the present invention. The shock absorber <NUM> comprises an elongated housing <NUM> with a first piston <NUM> coupled to piston rod <NUM> forming a primary piston assembly. First piston <NUM> is slidably received within the inner diameter of elongated housing <NUM>. First piston <NUM> separates the internal volume of housing <NUM> into a primary compression volume <NUM> located between piston <NUM> and the distal end of the shock absorber and a rebound volume <NUM> located between piston <NUM> and the proximal end of the shock absorber.

First piston <NUM> includes valves <NUM> and <NUM>. Valve <NUM> permits the damping medium to flow from the compression volume <NUM> to the rebound volume <NUM>. Valve <NUM> permits fluid to flow from the rebound volume <NUM> to the compression volume <NUM>. The distal end of first piston <NUM> comprises a piston rod valve assembly <NUM> that engages second piston <NUM> as the piston rod <NUM> moves in the compressive direction. The piston rod valve assembly <NUM> controls the flow of the damping medium through apertures in the second piston <NUM> and flask <NUM>. For the reasons discussed below, the flask <NUM> is alternatively referred to as third piston <NUM>.

Also disposed within housing <NUM> are a flask <NUM> and cup <NUM>, which house second <NUM> piston and third <NUM> piston, respectively. Disposed within flask <NUM> is second piston <NUM>. Second piston <NUM> is slidably received within the inner diameter of flask <NUM>. Second piston <NUM> forms a second compression volume <NUM> between second piston <NUM> and the distal end of flask <NUM>. Second piston <NUM> comprises at least one aperture <NUM> through which the damping medium may flow as the second piston <NUM> moves in the compressive direction.

Also disposed within flask <NUM> is a first return spring <NUM>. In the dipicted embodiment, first return spring <NUM> is a conical spring that reduces to the thickness of the wire diameter upon compression. However, it should be understood by one having ordinary skill in the art, that other types of springs are useable for first return spring <NUM> including, for example, wave springs, Belleville springs, and the like that are known in the art. The first return spring <NUM> provides an expansive force on second piston <NUM> and returns the second piston <NUM> to its initial position when the piston rod <NUM> moves in the expansive direction.

Flask <NUM> is disposed at least partially in cup <NUM>. Flask <NUM> is slidably received within the inner diameter of cup <NUM> and acts as a third piston. Flask <NUM> forms a third compression volume <NUM> between flask <NUM> and the distal end of cup <NUM>. The distal end of flask <NUM> comprises an aperture <NUM> through which the damping medium may flow as the third piston <NUM> moves in the compressive direction. Cup <NUM> may be formed integral with the housing. Also disposed within cup <NUM> is a second return spring <NUM>.

In the depicted embodiment in <FIG>, second return spring <NUM> is a conical spring that reduces to the thickness of the wire diameter upon compression. As with the first return spring <NUM>, alternative spring types are useable for the second return spring <NUM>. The second return spring <NUM> provides an expansive force on flask <NUM> and returns the third piston <NUM> to its initial position when the piston rod <NUM> moves in the expansive direction.

The shock absorber <NUM> also includes a second cylinder <NUM> in communication with the main tube <NUM>. The second cylinder <NUM> includes a reserve piston <NUM> that separates gas reservoir <NUM> from damping medium chamber <NUM>. A flow path <NUM> permits the damping medium to flow between the primary compression chamber and the damping medium chamber <NUM>.

<FIG> provide a cross-sectional view of the shock absorber <NUM> of <FIG> and illustrate the characteristics of the shock absorber during a compression cycle. <FIG> provides a chart illustrating the compression damping force versus distance provided by shock absorber <NUM> as the shock absorber moves through the three compression stages discussed below.

As shown in <FIG>, initially, during a first compression stage of shock absorber <NUM>, piston rod <NUM> and first piston <NUM> are moved in the compressive direction, i.e. the distal direction, over a first distance and provide a first compression damping force <NUM> (shown in <FIG>). During the first compression stage the valve <NUM> regulates flow of the damping medium from the compression volume <NUM> to the rebound volume <NUM> as depicted by flow arrows <NUM>. This causes the size of the compression volume <NUM> to be reduced and the rebound volume <NUM> to enlarge. The first compression stage continues until the piston rod valve assembly <NUM> engages second piston <NUM>.

As shown in <FIG>, when the first piston assembly compresses beyond the first distance, the piston rod valve assembly <NUM> will engage second piston <NUM> and the assembly <NUM> covers the at least one aperture <NUM> of second piston <NUM>. The piston rod valve assembly <NUM> communicates with the aperture <NUM> of second piston <NUM> and controls the flow of the damping medium through the aperture <NUM> as depicted by flow arrows <NUM>. After engagement, as the piston rod <NUM> begins to move in the compressive direction over a second distance, a second compression stage begins. During the second compression stage, the combination of the piston rod valve assembly <NUM> with the second piston <NUM> provides a second compression damping force <NUM> that is greater than the first compression damping force <NUM> (shown in <FIG>).

During the second compression stage the piston rod valve assembly <NUM> permits the damping medium to flow from the second compression volume <NUM> to the primary compression volume <NUM>. This causes the size of the second compression volume <NUM> to be reduced. The second compression stage continues until the second piston rod reaches the distal end of flask <NUM>.

When the second piston <NUM> reaches the distal end of flask <NUM>, flask <NUM> acting as the third piston begins to move in the compressive direction over a third distance. This provides the beginning of a third compression stage. During the third compression stage, the piston rod valve assembly <NUM> controls the flow of the damping medium from the third compression volume <NUM> through the aperture <NUM> at the distal end of flask <NUM>. This causes the size of the third compression volume <NUM> to be reduced. The combination of the piston rod valve assembly with the flask <NUM> provides a third compression damping force <NUM> that is greater that the first compression damping force <NUM> and second compression damping force <NUM> (shown in <FIG>).

It should be readily understood that selection of the dimensions for the housing and valves configurations enable a shock designer to change the corresponding damping forces provided. The damping forces useable for a particular automotive or other application are determined based upon, for example, the weight of the vehicle, type of suspension and intended application. Exemplary ranges for damping forces for first, second and third compression damping forces include, for example, <NUM> kN - <NUM> kN, <NUM> kN - <NUM> kN, and <NUM> kN - <NUM> kN, respectively.

Likewise, exemplary ranges for the first, second and third compression distances from full compression include for example, <NUM> - <NUM>, <NUM> - <NUM> and <NUM> - <NUM>, respectively. The damping force for each compression stage is chosen by optimizing or altering the components of the shock absorber described herein. For instance, the damping force can be controlled by the valve disc selection in pistons <NUM> and <NUM>. Also, the damping force in the third zone can be controlled by modifying the internal diameters of the flask <NUM> and cup <NUM>. The engagement point of the second piston <NUM> to piston rod valve assembly <NUM> or the engagement point of the second piston <NUM> to the distal end of flask <NUM> can be used to alter damping force timing.

While the invention has been described in based on the above example, those skilled in the art will recognize that the invention is not limited to this particular embodiment. The above description points out the fundamental novel features of the invention as applied to a preferred embodiment.

For example, it is expressly intended that all combinations of those elements which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.

Further, while the example shown above employed a single aperture <NUM>, <NUM> in the second piston <NUM> and third piston <NUM>, it should be readily apparent to one skilled in the art, that a shock absorber in accordance with the invention may alternatively employ, for example, second <NUM> and third <NUM> pistons with multiple apertures that permit the damping medium to flow out of a compression volume.

Claim 1:
A multistage damping system comprising:
- an elongated housing (<NUM>) containing a damping medium;
- an axially moveable primary piston assembly arranged in the housing comprising a primary piston (<NUM>) and a valve assembly (<NUM>,<NUM>);
- an axially moveable secondary piston assembly (<NUM>) having an orifice (<NUM>) disposed in a location to engage said valve assembly when said primary piston assembly is moved in a compressive direction beyond a particular compressive movement distance, wherein said valve assembly once engaged with said orifice regulates the flow of damping medium to provide a greater compressive damping force when said primary piston assembly and said secondary piston assembly are moved beyond said particular compressive movement distance; and
- an axially moveable tertiary piston assembly (<NUM>) having a recessed cavity formed therein,
wherein said secondary piston assembly is disposed within said recessed cavity; characterized in a second housing (<NUM>),
wherein the tertiary piston assembly is disposed and moveable within the second housing, and wherein the second housing is formed integral with the elongated housing, and
further comprising a first restoration spring (<NUM>) disposed in the recessed cavity and
configured to provide an expansive force on the secondary piston assembly.