Dual tube damper and foot valve assembly

Abstract

A dual tube damper and base valve assembly are provided. Generally, a dual tube damper is provided having an inner tube and an outer tube forming a chamber for oil between the inner tube and the outer tube. A piston and rod move within the inner tube in response to driving conditions. A base valve assembly is located between the inner tube and the outer tube. The base valve assembly includes a cylinder end having a first end and a second end. An opening extends through the cylinder end and is in fluid communication between the inner tube and the outer tube. The first end of the base valve assembly defines a sealing surface and an entry disc is mounted adjacent the sealing surface. The sealing surface has a lowered portion. A compression relief valve assembly is positioned adjacent the second end. A gap between the sealing surface and the entry disc allows an additional oil flow path through the base valve assembly when the pressure in the inner tube is low. The gap is gradually closed by the entry disc as the pressure in the inner tube increases.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to dampers, and in particular to vehicle dampers. BACKGROUND

[0002] The most common type of suspension damper used in modern vehicles is a double tube passive hydraulic damper. This type of damper is made of two concentric tubes. The inner tube is the working cylinder in which the piston moves, while the outer tube is the housing and oil reservoir. A fixed hydraulic valve, called the base valve, is located in the lower part of the damper between the two concentric tubes. The base valve controls the oil flow between the cylinder tube and the reservoir chamber when the damper moves.

[0003] In a typical double tube damper, the base valve assembly has a valve body, also called cylinder end, and a pressure relief valve, which controls the oil flow from the inner tube or cylinder tube to the outer tube or reservoir chamber in the compression stroke. Intake discs, present on the opposite sides of the valve body, act as non-return valves, which allow the quick refill of the cylinder tube with oil in the rebound (extension) stroke.

[0004] In a conventional base valve, the intake discs only act as non-return valves. The purpose is to prevent the oil from flowing through the outer port of the cylinder end during damper compression and to enable it to effectively refill the cylinder during extension. The non-return valve can consist of a single intake disc or contain several intake discs. It can also be equipped with an additional spring. The first disc from the cylinder end can be equipped with a slot (fixed orifice).

[0005] The cylinder end is equipped with flat circumferential seats to ensure proper non-return valve sealing during compression. Under the influence of pressure, the intake discs are pressed against them and oil flow is not possible. It is important that, in this case, all the seats are nominally in the same plane.

[0006] Some vehicle applications require high damping forces in the rebound and compression strokes. However, too much damping in compression can negatively affect the isolation of the vehicle body from low amplitude inputs such as slow, small waves on the main road and road particles.

[0007] The base valve of the present invention helps to improve the ride quality and reduce harshness. The variable bleed allows the damping characteristic to be shaped in the initial phase of the compression movement, resulting in a smoother damper operation and improved ride. SUMMARY

[0008] In general, the present application provides a dual tube damper having an outer tube and an inner tube forming a chamber for oil and gas between the inner tube and the outer tube. A piston and rod move within the inner tube in response to driving conditions. A base valve assembly is located between the inner tube and the outer tube. The base valve assembly includes a cylinder end having a first end and a second end. An opening extends through the cylinder end and is in fluid communication between the inner tube and the outer tube. The first end of the base valve assembly defines a sealing surface and an entry disc is mounted adjacent the sealing surface. The sealing surface has a reduced portion. A compression relief valve assembly is positioned adjacent the second end. A gap between the sealing surface and the entry disc allows an additional oil flow path through the base valve assembly when pressure in the inner tube and the outer tube is low. The gap is gradually closed by the entry disc as pressure in the inner tube increases.

[0009] These and other features and advantages of the present application will become more apparent with a detailed description of preferred embodiments. The accompanying drawings are described below. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 is a partial cutaway perspective view of a dual tube damper of the present application.

[0011] Figure 2 is an exploded view of a base valve assembly of the present application.

[0012] Figure 3 is a cross-sectional view of the base valve assembly.

[0013] Figure 4 is an enlarged view of the intermediate seat of the base valve assembly.

[0014] Figure 5 is a cross-sectional view of the base valve assembly.

[0015] Figure 6A is a graph illustrating the relationship of flow rate versus pressure characteristics of the present application.

[0016] Figure 6B is a graph illustrating the relationship of force versus displacement characteristics of a damper including the base valve assembly of the present application. DETAILED DESCRIPTION

[0017] A dual tube damper of the present application having a variable bleed base valve is shown generally at 10. Except for the variable bleed base valve, the dual tube damper shown at 12 is a known damper. It has an outer tube 14 and an inner tube or cylinder tube 16. A piston 18 and rod 20 move within the inner tube in response to driving conditions. A top seal assembly 21 closes the two tubes 14 and 16. A lower mount 22 is shown and it will be understood that an upper mount (not shown) is also provided to mount the dual tube damper within a vehicle.

[0018] Referring Figures 1 to 5 The base valve assembly of the present application is generally shown at 24. The base valve assembly 24 has a cylinder end 26. A compression relief valve assembly 28 including several discs and a bleed disc 30 having slots is mounted adjacent the cylinder end 26. The discs are thick deflection discs and the slots are relatively narrow, which is the standard to provide high damping and good primary ride. A rebound check valve or entry disc 32 is mounted to the opposite side of the cylinder end 26. The entry disc 32 has slots 33 for oil flow. As illustrated, bolts 34 and nuts 36 connect them together to form the base valve assembly 24.

[0019] Referring Figure 3 and Figure 4 The base valve assembly 24 includes windows 38 and 40 and holes 44 and 46. As Figure 5 shown, the windows 38 and 40 and holes 44 and 46 allow oil to flow between the tube 14 and the tube 16. Typically, during a rebound stroke, oil flows through the windows 38 and 40. In a compression stroke, oil flows through the holes 44 and 46.

[0020] The base valve assembly 24 has a surface that generally forms a seat 39, which has an outer seat 41, an inner seat 43, and an intermediate seat 45. The intermediate seat 45 of the base valve assembly 24 has a lowered portion or gap 48 relative to the inner seat 43 and the outer seat 41, such that in an unloaded condition, there is a gap 48 between the seat and the entry disc 32, see Figure 4 . The gap 48 defines a variable orifice.

[0021] As Figure 5 shown, during a rebound stroke, oil flow is generally shown at 50 and flows primarily through the windows 38, 40 by deflecting the entry disc 32. This is conventional base valve operation and the gap 48 has no significant effect on the operation of the damper in a rebound stroke.

[0022] When the damper is compressed, the pressure in the inner tube 16 between the base valve assembly 24 and the piston 18 rises. In effect, oil flows from the compression chamber to the reservoir chamber, as generally shown at 52. The flow path 54 is a conventional flow path and includes flow through the slots 33 of the entry disc 32, the holes 44 and 46 of the cylinder end 26, and the compression relief valve assembly 28. Additionally, oil flows through the gap 48 and then through the windows 38, 40, as shown by the arrows 55. This condition isolates the vehicle from road conditions, such as from rough roads. However, as the pressure differential between the cylinder and the reservoir increases, the entry disc 32 bends toward the gap 48, thereby continuously reducing the gap 48 until the gap 48 is completely closed.

[0023] When the pressure reaches a preset value, the disc of the compression relief valve assembly 28 begins to deflect. If the speed and pressure are low, oil flow 54 occurs only through the orifice disc 30, and the disc of the compression relief valve assembly 28 does not deflect. In this case, the flow 55 has a significant impact on the total flow 52. Therefore, the variable relief effect is most significant for pressures / velocities lower than the opening pressure / velocity of the disc of the compression relief valve assembly 28.

[0024] When using the standard compression relief valve assembly 28 with its narrow slot and numerous thick deflector discs, high damping and good main ride are provided. However, this generally worsens isolation and ride comfort. The disclosed invention provides additional flow through the bottom valve assembly 24 to improve vehicle ride under low-pressure, low-speed conditions. The additional oil flow through the gap 48 occurs at the beginning of the compression stroke and flows at a low speed to improve vehicle smoothness. However, this oil flow path is designed to close as speed or stroke amplitude increases and pressure rises.

[0025] This allows variable oil flow to be released through the bottom valve assembly 24 during the initial phase of damper compression until a certain pressure is achieved in the cylinder. As the pressure increases, the inlet disc 32 gradually deflects toward the intermediate seat 45. The flow rate depends on this pressure, such as... Figure 6A As shown. Figure 6B The effect of the proposed technique on the relationship between damper force and displacement characteristics is shown.

[0026] The intermediate seat 45 of the bottom valve assembly 24, having a lower portion or gap 48 relative to the inner seat 43 and the outer seat 41, provides additional oil flow at low speeds and low pressures for smoother driving. When the dual-tube damper 10 of the present invention is in an unloaded state, i.e., when the pressure is below a predetermined value, a gap 48 exists between the seat and the inlet disc 32. The gap 48 defines a variable orifice to allow additional oil flow to suppress vehicle driving characteristics.

[0027] The foregoing invention has been described in accordance with applicable legal standards. Therefore, this description is exemplary in nature and not restrictive. Variations and modifications to the disclosed embodiments will become apparent to those skilled in the art and do indeed fall within the scope of this invention. Therefore, the legal scope of protection of this invention can only be determined by studying the following claims.

Claims

1. A twin tube damper comprising: an outer tube; an inner tube located within the outer tube forming a chamber between the inner tube and the outer tube; the inner tube and the outer tube configured to contain oil; a piston and rod adapted to move within the inner tube in response to driving conditions; a base valve assembly located between the inner tube and the outer tube, the base valve assembly comprising a cylinder end having a first end and a second end, the base valve assembly having an opening extending through the base valve assembly, the opening in fluid communication between the inner tube and the outer tube, the first end of the cylinder end defining a sealing surface, an entry disc mounted adjacent the sealing surface, and a compression relief valve assembly positioned adjacent the second end, wherein the opening comprises a window and a bore, the entry disc covering the window and the bore, the compression relief valve assembly covering the bore, wherein the entry disc comprises a slot for communicating oil between the inner tube and the outer tube, the slot and the bore positionally corresponding; the sealing surface of the cylinder end having a lowered portion, wherein the sealing surface comprises an outer seat, an inner seat, and an intermediate seat, the intermediate seat lower than the outer seat and the inner seat to define a gap between the sealing surface at the lowered portion and the entry disc; whereby, when pressure in the inner tube is low, the gap allows an additional oil flow path through the base valve assembly, and when pressure in the inner tube increases, the entry disc flexes toward the intermediate seat, thereby progressively closing the gap.

2. The twin tube damper of claim 1, further comprising a top seal enclosing the inner tube and the outer tube.

3. The dual tube damper of claim 2, wherein, the base valve assembly positioned opposite the top seal.

4. The twin tube damper of claim 1, further comprising a fastener connecting the entry disc and the compression relief valve assembly to the cylinder end.

5. The dual-tube damper of claim 1, wherein, the window has a side, and the bore is cylindrical.

6. The dual-tube damper of claim 1, wherein, the compression relief valve assembly comprises a plurality of discs and a bleed disc having a slot.

7. The dual-tube damper of claim 1, wherein, the twin tube damper has a compression stroke, wherein as a pressure differential between the inner tube and the outer tube increases due to movement of the piston, the oil flows through the gap, the entry disc flexes toward the intermediate seat, thereby continuously decreasing the gap until the gap is fully closed.

8. A base valve assembly for installation in a twin tube damper, the base valve assembly comprising: a cylinder end having a first end and a second end, the cylinder end of the base valve assembly having a first end defining a sealing surface, the base valve assembly having an opening extending through the base valve assembly, the opening configured to regulate fluid flow, the first end of the cylinder end defining a sealing surface, an entry disc mounted adjacent the sealing surface, and a compression relief valve assembly positioned adjacent the second end, wherein the opening includes a window and a bore, the entry disc covering the window and the bore, the compression relief valve assembly covering the bore, wherein the entry disc includes a slot configured to pass oil through the base valve assembly, the slot and the bore positionally corresponding; the sealing surface of the base valve assembly having a lowered portion creating a gap, wherein the sealing surface includes an outer seat, an inner seat, and a middle seat, the middle seat being lower than the outer seat and the inner seat to define the gap between the sealing surface at the lowered portion and the entry disc; whereby the gap allows for an additional oil flow path through the base valve assembly, and when pressure adjacent the entry disc increases, the entry disc flexes toward the middle seat, thereby gradually closing the gap.

9. The base valve assembly of claim 8, further comprising fasteners connecting the entry disc and the compression relief valve assembly to the cylinder end.

10. The bottom valve assembly of claim 8, wherein, the window has a side, and the bore is cylindrical.

11. The bottom valve assembly of claim 8, wherein, the dual tube damper having an inner tube and an outer tube, the dual tube damper having a compression stroke, wherein as a pressure differential between the inner tube and the outer tube increases due to movement of a piston, oil flows through the opening and through the gap, the entry disc flexes toward the middle seat, thereby continually decreasing the gap as pressure within the dual tube damper increases until the gap is fully closed.

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