Patent Description:
Document <CIT> discloses a twin-tube hydraulic damper comprising a hydraulic stop assembly comprising a pin inserted into a chamber of a piston and having one end fixed to a base valve assembly and the other end side inserted into the piston rod. The pin has a support flange portion supported by the base valve and a large diameter shaft portion having a constant diameter smaller than that of the support flange portion, and a tapered shaft portion extending in the axial direction from the side opposite to the support flange portion. The orifice in the form of the gap between the small diameter hole of the tip rod and the pin is provided on the lower chamber side in the passage in the rod, having the narrowest passage area when the large-diameter shaft portion is aligned with the small-diameter hole portion in the axial direction, and the widest passage area when the small-diameter shaft portion is aligned with the small-diameter hole portion in the axial direction. The small-diameter hole and the pin change the passage area according to the displacement of the piston rod forming the passage area adjusting mechanism aligning the small diameter hole portion with the axial position of the small diameter shaft portion of the pin to maximize the passage area of the orifice.

Document <CIT> discloses a hydraulic damper, comprising: a main tube filed with working liquid and extending along an axis between an open end and a closed end; a piston assembly slidably disposed inside the main tube, attached to a piston rod that extends outside the hydraulic damper through a sealed piston rod guide located at the open end, dividing the main tube into a rebound chamber and a compression chamber and configured to generate a damping force;a base valve assembly located at the closed end of the compression chamber and configured to control a flow of the working liquid between the compression chamber and a compensation chamber; and at least one compression stop assembly cooperating with a compression valve assembly and comprising a pin disposed slidably within the piston rod and biased to project an activating tip towards the compression chamber to increase damping of said compression valve assembly upon sliding inside the piston rod and to generate an additional damping force with said piston assembly at an end of a compression stroke; wherein said compression valve assembly comprises:at least one deflectable or floating disc covering compression flow passages.

As a compression stop assembly requires space for its operation, it is common to provide this space by decreasing a so called minimum bearing span of a damper that is the distance between a rebound stop and a main piston assembly. However this may exclude implementations of such dampers in suspension systems where piston rod is subjected to side loads (e.g. MacPherson struts), where a sufficient minimum bearing span is crucial for proper operation of the damper. It is thus desirable to reduce the space occupied by the compression stop assembly at the end of the damper compression stroke. Such a space reduction is also beneficial in terms of packaging and handling of the dampers.

It has been the object of the present disclosure to provide a hydraulic damper with a compression stop assembly, which would reduce operational length of the assembly, would be cost efficient and simple in manufacture and assembly, and which would provide versatile tuning properties for shaping the additional damping force.

The present invention provides a hydraulic damper. The hydraulic damper comprises a main tube filed with working liquid and extending along an axis between an open end and a closed end. The hydraulic damper also comprises a piston assembly slidably disposed inside the main tube, attached to a piston rod that extends outside the hydraulic damper through a sealed piston rod guide located at the open end, dividing the main tube into a rebound chamber and a compression chamber and configured to generate a damping force. The hydraulic damper also comprises a base valve assembly located at the closed end of the compression chamber and configured to control a flow of the working liquid between the compression chamber and a compensation chamber. The hydraulic damper also comprises at least one compression stop assembly cooperating with a compression valve assembly and comprising a pin disposed slidably within the piston rod and biased to project an activating tip towards the compression chamber to increase damping of said compression valve assembly upon sliding inside the piston rod and to generate an additional damping force with said piston assembly at an end of a compression stroke. The compression valve assembly comprises: at least one deflectable or floating disc covering compression flow passages and biased by a piston member slidable along said axis and abutting a retaining surface. The compression valve assembly also comprises a pressure chamber having one surface defined by a surface of said piston member abutting said retaining surface. The pin, upon sliding inside the piston rod, facilitates a flow of the working liquid from the compression chamber into said pressure chamber to generate a pressure on said surface of said piston member to increase a biasing load on said at least one deflectable or floating disc.

The present disclosure provides a damper having a compression valve assembly that comprises at least one deflectable or floating disc covering compression flow passages, and biased by a piston member slidable along said axis and normally abutting a retaining surface, and a pressure chamber having one surface defined by a surface of said piston member abutting said retaining surface, wherein said pin, upon sliding inside the piston rod, facilitates a flow of the working liquid from the compression chamber into said pressure chamber to generate a pressure on said surface of said piston member to increase biasing load on said at least one deflectable or floating disc.

In some embodiments, said compression valve assembly comprises at least one spring having a first surface biasing said at least one deflectable or floating disc, and a second surface biasing said piston member.

Therefore, in some embodiments, the piston member compresses the spring and increases its biasing load.

In some embodiments, said compression valve assembly cooperating with said at least one hydraulic compression stop assembly is a compression valve assembly of the piston assembly, and said pressure chamber is additionally defined by a guiding portion fixed on the piston rod, wherein the piston rod has at least one radial channel in fluid communication with said pressure chamber and normally disconnected from the compression chamber by the wall of the pin, wherein the pin has at least one axial channel in fluid communication with the compression chamber having an outlet distal to the activating tip of the pin normally closed by the wall of the piston rod, wherein upon sliding of the pin inside the piston rod along a predetermined distance said at least one axial channel of the pin is in fluid communication with said at least one radial channel of the piston rod to generate pressure on said surface of said piston member.

In some embodiments, said at least one axial channel has a form of a narrowed cross-section of said pin.

In some embodiments, said compression valve assembly cooperating with said at least one hydraulic compression stop assembly is installed within an adapter disposed between the base valve assembly and the compression chamber and comprising an axial opening for a flow of the working liquid through the base valve assembly between the compression chamber and the compensation chamber which is closable by the activating tip of the pin, and said pressure chamber is additionally defined by a guiding portion of said adapter, wherein the adapter has at least one radial channel in fluid communication with said pressure chamber and normally connected with the compression chamber, wherein said compression flow passages are disposed within a valve member fixed between said adapter and the main tube, wherein closing said axial opening by the activating tip and sliding of the pin inside the piston rod along a predetermined distance generates pressure on said surface of said piston member.

In some embodiments, said adapter comprises a number of axial flow passages surrounding said guiding portion, and said valve member has a number of rebound flow passages covered in the compression chamber by at least one deflective or floating intake disk provided with a number of flow passages that allow the working liquid to flow to said compression flow passages during the compression stroke of the damper.

In some embodiments, the pin is biased by a spring disposed within a chamber in the piston rod.

In some embodiments, the pin has an internal axial channel joining the compression chamber with said chamber in the piston rod.

The disclosure shall be described and explained below in connection with the attached drawings on which:.

<FIG> schematically illustrates a fragment of an exemplary vehicle suspension comprising a damper <NUM> of the present disclosure attached to a vehicle chassis <NUM> by means of a top mount <NUM> and a number of screws <NUM> disposed on the periphery of the upper surface of the top mount <NUM>. The top mount <NUM> is connected to a coil spring <NUM> and a piston rod <NUM> of the damper <NUM>. The tube <NUM> of the damper <NUM> is connected to the steering knuckle <NUM> supporting the vehicle wheel <NUM>.

<FIG> presents an embodiment of a twin-tube damper <NUM> according to the present disclosure. The damper <NUM> comprises an external tube <NUM> and a main tube <NUM> filled with viscous working liquid inside of which a movable piston assembly <NUM> is disposed. The piston assembly <NUM> is attached to the piston rod <NUM> led outside the damper <NUM> through a sealed piston rod guide <NUM> by means of a shoulder nut <NUM>. The damper <NUM> is also provided with a base valve assembly <NUM> fixed at the other end of the main tube <NUM>. The piston assembly <NUM> makes a sliding fit with the inner surface of the main tube <NUM> and divides the tube <NUM> into a rebound chamber <NUM> (between the piston assembly <NUM> and the piston rod guide <NUM>) and a compression chamber <NUM> (between the piston assembly <NUM> and the base valve assembly <NUM>). A compensation chamber <NUM> is located at the other side of the base valve assembly <NUM>. A metal rebound stop <NUM> is clenched on a piston rod <NUM> and supports an elastomeric rebound bumper <NUM>. The distance between the rebound bumper <NUM> and the piston assembly <NUM> defines a minimum bearing span <NUM> of the damper <NUM>.

The term "compression" as used herein with reference to particular elements of the damper refers to these elements or parts of elements which are ad-jacent to or face the compression chamber <NUM> or, in a case of the working liquid flow direction, it refers to this flow direction that takes place during the compression stroke of the damper. Similarly the term "rebound" as used in this specification with reference to particular elements of the damper refers to these elements or these parts of particular elements which are adjacent to or face the rebound chamber <NUM> or, in a case of the working liquid flow direction, it refers to this flow direction that takes place during the rebound stroke of the damper.

As shown in <FIG> the piston assembly <NUM> includes a first compression valve assembly <NUM> and a first rebound valve assembly <NUM>. Each of the first com-pression and first rebound valve assemblies <NUM>, <NUM> are configured to control the flow of working liquid passing between the rebound chamber <NUM> and the compression chamber <NUM> while the piston assembly <NUM> is in motion along an axis A and to generate a damping force opposing force applied to the piston rod <NUM> in corresponding compression and rebound directions. Also, the base valve assembly <NUM> includes a second compression valve assembly <NUM> and a second rebound valve assembly <NUM> to control the flow of working liquid passing between the compensation chamber <NUM> and the compression chamber <NUM>, respectively, during rebound and compression stroke of the hydraulic damper <NUM>. As it is well known to those skilled in the art, the valve assemblies <NUM>, <NUM> and <NUM>, <NUM> provide design parameters that may be used to shape desired characteristics of the hydraulic damper <NUM>.

The damper <NUM> is further provided with two compression stop assemblies 8p and 8b to generate an additional damping force at the end of the compression stroke e.g. in order to avoid abrupt stop of the piston assembly <NUM>. An activating component of both compression stop assemblies 8p and 8b is a pin <NUM> disposed slidably within an internal chamber <NUM> of the piston rod <NUM>. The pin <NUM> is biased to project from the piston rod <NUM> towards the compression chamber <NUM> by a spring <NUM> disposed within the internal chamber <NUM>. The pin <NUM> has an internal axial channel <NUM> joining the compression chamber <NUM> with the internal chamber <NUM> to provide venting and lubrication.

The compression stop assembly 8p is installed on the piston assembly <NUM> and cooperates with the first compression valve assembly <NUM> of the piston assembly <NUM>. The first compression valve assembly <NUM> has a spring <NUM> having a first surface biasing four deflectable discs <NUM> covering compression flow passages <NUM> in the body <NUM> of the piston assembly <NUM>. A second surface of the spring <NUM> biases a piston member <NUM> surrounding the piston rod <NUM> and slidable along the axis A. In an inactive state of the compression stop assembly 8p the piston member <NUM> abuts a retaining surface <NUM> of a guiding portion <NUM> fixed on the piston rod <NUM>. The guiding portion <NUM> and the surface of the piston member <NUM> distal to the spring <NUM> define a pressure chamber <NUM>. The piston rod <NUM> is provided with a number of equiangularly spaced radial channels <NUM> that may join the pressure chamber <NUM> with the compression chamber <NUM>, as shall be explained later.

The base compression stop assembly 8b is installed on an adapter <NUM> fixed to the base valve assembly <NUM> and cooperates with a third compression valve assembly <NUM> of the adapter <NUM>. The third compression valve assembly <NUM> has a spring <NUM> having a first surface biasing three deflectable discs <NUM> covering compression flow passages <NUM> in an annular valve member <NUM> fixed between the adapter <NUM> and the main tube <NUM>. A second surface of the spring <NUM> biases a piston member <NUM> surrounding a sleeve member <NUM> and slidable along the axis A. The adapter <NUM> is further provided with a guiding portion <NUM> surrounding the piston member <NUM>. In an inactive state of the base compression stop assembly 8b, the piston member <NUM> abuts a retaining surface <NUM> of the guiding portion <NUM>. The guiding portion <NUM> and the surface of the piston member <NUM> distal to the spring <NUM> define a pressure chamber <NUM>. The adapter <NUM> is provided with a number of equiangularly spaced radial channels <NUM> joining the pressure chamber <NUM> with the compression chamber <NUM>. The sleeve member <NUM> passes through deflectable discs <NUM>, the valve member <NUM>, and an intake disk <NUM> and is fixed to the valve member <NUM> by a securing nut <NUM>. The intake disk <NUM> is provided with a number of flow passages <NUM> that allow the working liquid to flow to the compression flow passages <NUM>. The adapter is provided with an axial opening <NUM>, that allows the working liquid to flow between the compression chamber <NUM> and the compensation chamber <NUM> that may be closed by an activating tip <NUM> of the pin <NUM>, as shall be explained later.

The pin <NUM> has an axial, annular channel <NUM> in fluid communication with the compression chamber <NUM> having an outlet distal to the activating tip <NUM> of the pin <NUM> normally closed by the wall of the piston rod <NUM>. As shown in <FIG> and <FIG>, in an inactive state of the compression stop assembly 8p, during the compression stroke of the damper <NUM>, the axial channel <NUM>, and thus also radial channels <NUM> are closed by the wall of the pin <NUM> and the working liquid flows, as indicated by arrows, from the compression chamber <NUM> to the rebound chamber <NUM> through the first compression valve assembly <NUM> of the piston assembly <NUM>. In this configuration of the piston assembly <NUM> the spring <NUM> has a maximum working length and thus generates a predefined minimum pressure on the stack of deflectable discs <NUM> of the first compression valve assembly <NUM>.

Similarly, as shown in <FIG> and <FIG>, in an inactive state of the base compression stop assembly 8b, during the compression stroke of the damper <NUM>, radial channel <NUM> of the adapter <NUM> is open but the pressure in the pressure chamber <NUM> is not generated, as the working liquid flows, as indicated by arrows, between the compression chamber <NUM> and the compensation chamber <NUM> through a sleeve member <NUM>, the axial opening <NUM> of the adapter <NUM> and the second compression valve assembly <NUM> of the base valve assembly <NUM>.

Each of the compression stop assemblies 8p, 8b cooperates with a corresponding valve assembly <NUM>, <NUM>. The piston compression stop assembly 8p cooperates with the first compression valve assembly <NUM>, and the base compression stop assembly 8b cooperates with the third compression valve assembly <NUM>.

As shown in <FIG>, <FIG> at a certain position of the compression stroke the activating tip <NUM> of the pin <NUM> closes the axial opening <NUM> of the adapter and slides inside the piston rod <NUM> activating both the piston compression stop assembly 8p and the base compression stop assembly 8b.

As shown in <FIG>, in the active state of the compression stop piston assembly 8p the pin <NUM> slides inside the internal chamber <NUM> of the piston rod <NUM> connecting the pressure chamber <NUM> with the compression chamber <NUM> through the axial channel <NUM> of the pin <NUM> and the radial channels <NUM> in the piston rod <NUM>. Increased pressure in the pressure chamber <NUM> forces the piston member <NUM> to slide about the piston rod <NUM> and to compress the spring <NUM>. This increases the reaction of the spring <NUM> and progressively increases the pressure on the stack of deflectable discs <NUM> of the first compression valve assembly <NUM>. Therefore damping force generated by the first compression valve assembly <NUM> of the piston assembly <NUM> progressively increases.

As shown in <FIG>, and <FIG>, in the active state of the base compression stop assembly 8b, the axial opening <NUM> of the adapter <NUM> is closed and the working liquid flows, as indicated by arrows, to the pressure chamber <NUM> through the radial channels <NUM>. Increased pressure in the pressure chamber <NUM> forces the piston member <NUM> to slide about the sleeve member <NUM> and to compress the spring <NUM>. This increases the reaction of the spring <NUM> and progressively increases the pressure on the stack of deflectable discs <NUM> of the third compression valve assembly <NUM>. As indicated by arrows in the active state of the compression stop base valve assembly 8b the working liquid flows from the compression chamber <NUM> to the compensation chamber <NUM> through the flow passages <NUM> in the intake disk <NUM>, compression flow passages <NUM> in the valve member <NUM>, gap between the valve member <NUM> and the stack of deflectable discs <NUM> and finally to the second compression valve assembly <NUM> of the base valve assembly <NUM>, through a number of equiangularly spaced axial flow passages <NUM> surrounding the guiding portion <NUM> of the adapter <NUM>.

As shown in <FIG>, at the onset of the rebound stroke, when the axial opening <NUM> of the adapter <NUM> is closed, the working liquid flows initially from the com-pensation chamber <NUM> to the compression chamber <NUM> through the second rebound valve assembly <NUM> of the base valve assembly <NUM>, then through flow passages <NUM> and finally through a number of equiangularly spaced, radially distal rebound flow passages <NUM> provided in the valve member <NUM>, deflecting the intake disk <NUM>. When the piston assembly <NUM> moves into the rebound chamber <NUM>, the pin <NUM> biased by the spring <NUM> slides outside the piston rod <NUM>, and eventually the activating tip <NUM> opens the axial opening <NUM> in the adapter <NUM>.

Claim 1:
A hydraulic damper (<NUM>), comprising:
a main tube (<NUM>) filed with working liquid and extending along an axis (A) between an open end and a closed end;
a piston assembly (<NUM>) slidably disposed inside the main tube (<NUM>), attached to a piston rod (<NUM>) that extends outside the hydraulic damper (<NUM>) through a sealed piston rod guide (<NUM>) located at the open end, dividing the main tube (<NUM>) into a rebound chamber (<NUM>) and a compression chamber (<NUM>) and configured to generate a damping force;
a base valve assembly (<NUM>) located at the closed end of the compression chamber (<NUM>) and configured to control a flow of the working liquid between the compression chamber (<NUM>) and a compensation chamber (<NUM>); and
at least one compression stop assembly (8p, 8b) cooperating with a compression valve assembly (<NUM>, <NUM>) and comprising a pin (<NUM>) disposed slidably within the piston rod (<NUM>) and biased to project an activating tip (<NUM>) towards the compression chamber (<NUM>) to increase damping of said compression valve assembly (<NUM>, <NUM>) upon sliding inside the piston rod (<NUM>) and to generate an additional damping force with said piston assembly (<NUM>) at an end of a compression stroke;
wherein said compression valve assembly (<NUM>, <NUM>) comprises:
at least one deflectable or floating disc (<NUM>, <NUM>) covering compression flow passages (<NUM>, <NUM>) and biased by a piston member (<NUM>, <NUM>) slidable along said axis (A) and abutting a retaining surface (<NUM>, <NUM>), and
a pressure chamber (<NUM>, <NUM>) having one surface defined by a surface of said piston member (<NUM>, <NUM>) abutting said retaining surface (<NUM>, <NUM>); and
wherein said pin (<NUM>), upon sliding inside the piston rod (<NUM>), facilitates a flow of the working liquid from the compression chamber (<NUM>) into said pressure chamber (<NUM>, <NUM>) to generate a pressure on said surface of said piston member (<NUM>, <NUM>) to increase a biasing load on said at least one deflectable or floating disc (<NUM>, <NUM>).