Adjustable volume cylinder for strut

An apparatus, according to an exemplary aspect of the present disclosure includes, among other things, a cylinder defining an internal volume and having a first end and a second end. A piston is received within the cylinder, a rod is coupled to the piston and extends outwardly of the first end, and a cap encloses the second end. The cap is selectively movable relative to the cylinder to vary the internal volume. A method according to an exemplary aspect of the present disclosure includes, among other things, selectively moving an end cap relative to a cylinder body to vary internal volume.

TECHNICAL FIELD

This disclosure relates to an exemplary apparatus and method of providing a cap for a strut that can be used to vary an internal volume of a strut cylinder.

BACKGROUND

Gas struts are used to connect a vehicle panel, such as a liftgate, decklid, tailgate, etc., to a vehicle body structure such that the panel can be moved between open and closed positions. Traditionally, these struts utilize a fixed attachment point geometry, value of mass, and center of gravity of the panel to calculate a pressure that will provide acceptable opening and closing efforts under a typical temperature operating range. If the mass or center of gravity of the panel being raised or lowered changes, the operating efforts are affected accordingly. For example, if the mass of the panel is reduced or the center of gravity is raised on the panel, for a given temperature, the effort to close will increase and the force/speed at which the panel opens will increase. Conversely, if mass is added or the center of gravity lowered, the panel will rise more slowly or require assistance to open, and the panel may not stay open or sag once a full open position is reached.

Vehicle owners often customize their vehicles to include modifications and/or additions to these types of panels such as lights, bike racks, tire kits, etc. These modifications affect the operation of the struts as described above. Further, due to the inconsistency of the modifications between the various add-on providers, the amount of adjustment to gas strut pressures varies significantly, which results in a large number of different strut pressures that would be required to accommodate the different configurations.

SUMMARY

An apparatus according to an exemplary aspect of the present disclosure includes, among other things, a cylinder defining an internal volume and having a first end and a second end. A piston is received within the cylinder, a rod is coupled to the piston and extends outwardly of the first end, and a cap encloses the second end. The cap is selectively movable relative to the cylinder to vary the internal volume.

In a further non-limiting embodiment of the foregoing apparatus, the rod is configured to be connected to one of a vehicle body structure and a panel moveable relative to the vehicle body structure.

In a further non-limiting embodiment of either of the foregoing apparatus, the cap is configured to be connected to the other of the vehicle body structure and the panel.

In a further non-limiting embodiment of any of the foregoing apparatus, the panel comprises a liftgate, decklid or tailgate.

In a further non-limiting embodiment of any of the foregoing apparatus, a seal is between the cap and the second end of the cylinder.

In a further non-limiting embodiment of any of the foregoing apparatus, a threaded connection is between the cap and the cylinder.

In a further non-limiting embodiment of any of the foregoing apparatus, the inner surface of the cap includes a first thread structure and the outer surface of the cylinder includes a second thread structure that directly engages the first thread structure.

In a further non-limiting embodiment of any of the foregoing apparatus, the cylinder is filled with a fluid, and wherein the internal volume is decreased to increase a pressure of the fluid.

In a further non-limiting embodiment of any of the foregoing apparatus, the cylinder is filled with a fluid, and wherein the internal volume is increased to decrease a pressure of the fluid.

In a further non-limiting embodiment of any of the foregoing apparatus, the cap includes an attachment member to be coupled to a movable panel or a fixed vehicle structure.

An apparatus according to another exemplary aspect of the present disclosure includes, among other things, a fixed vehicle structure, a panel moveable relative to the structure, and a cylinder defining an internal volume. The cylinder includes a piston, a rod coupled to the piston and extending outwardly of a first end of the cylinder, and a cap enclosing a second end of the cylinder, wherein the cap is selectively movable to vary the internal volume.

In a further non-limiting embodiment of any of the foregoing apparatus, the cap includes a first attachment member coupled to one of the panel and structure and the rod includes a second attachment member coupled to the other of the panel and structure.

In a further non-limiting embodiment of any of the foregoing apparatus, the cylinder is filled with a fluid, and wherein the internal volume is decreased to increase a pressure of the fluid and is increased to decrease a pressure of the fluid.

In a further non-limiting embodiment of any of the foregoing apparatus, a threaded connection is between the cap and the cylinder.

In a further non-limiting embodiment of any of the foregoing apparatus, a seal is between the cap and the second end of the cylinder.

A method according to another exemplary aspect of the present disclosure includes the steps of, among other things: providing a cylinder body defining an internal volume and having a piston rod extending our from a first end and an end cap enclosing a second end; and selectively moving the end cap relative to the cylinder body to vary the internal volume.

In a further non-limiting embodiment of the foregoing method, the method includes coupling the first end to one of a vehicle structure and moveable panel, coupling the second end to the other of the vehicle structure and moveable panel, and varying the internal volume as needed in response to a change in weight and/or location of a center of gravity of the panel.

In a further non-limiting embodiment of either of the foregoing methods, the method includes threadably connecting the end cap to the cylinder body.

In a further non-limiting embodiment of any of the foregoing methods, the method includes sealing the end cap relative to the cylinder body to prevent fluid from escaping from the cylinder.

In a further non-limiting embodiment of any of the foregoing methods, the method includes filling the cylinder body with a fluid, and adjusting a position of the end cap relative to the cylinder body to decrease the internal volume and increase a pressure of the fluid, and adjusting a position of the end cap relative to the cylinder body to increase the internal volume and decrease the pressure of the fluid.

DETAILED DESCRIPTION

This disclosure details exemplary apparatus and methods of providing a cap for a strut that can be used to vary an internal volume of a strut cylinder to adjust closing/opening efforts of a vehicle panel as needed. These and other features are discussed in greater detail in the following paragraphs of this detailed description.

Gas struts are used to connect a moveable vehicle panel, such as a liftgate, decklid, tailgate, etc., to a vehicle body structure. The struts control movement of the panel as the panel is moved between an open position and a closed position.FIG. 1shows an example of a pick-up truck10having a cargo bed area12that is defined by a pair of side walls14and a moveable panel that comprises a tailgate16that extends between the side walls14. The tailgate16is moveable between a closed position (FIG. 1) and a normal tailgate deployed or open position (FIG. 2). A pair of struts18are used to connect the moveable panel, e.g. the tailgate16, to a fixed vehicle body structure, e.g. the side walls14of the cargo bed area12. The struts18are configured to allow the tailgate16to be pivoted from the closed position to the open position in a controlled manner to provide access to the cargo bed area12.

FIG. 3shows an example of a strut18that incorporates the subject invention, and which can be used to control the movement of the panel shown inFIGS. 1-2. It should be understood that the tailgate16ofFIGS. 1-2is merely one example of a moveable panel, and that the struts18can be used with other panels such as decklids, liftgates, etc.

The strut18includes a cylinder20defining an internal volume22and having a first end24and a second end26. A piston28is received within the cylinder20. A rod30is coupled to the piston28and extends outwardly of the first end24. An end cap32encloses the second end26. The cap32is selectively movable relative to the cylinder20to vary the internal volume22.

The cylinder20has an inner surface34that defines the internal volume22and an external surface36. The piston28slides along the inner surface34as the panel is moved between open and closed positions. The piston28is coupled to the rod30in a known manner and a seal38is provided at the first end24of the cylinder20. The operation of the piston28, rod30and seal38are well known and will not be discussed in greater detail.

The second end26of the cylinder is an open end. The cap32is used to completely enclose this open second end26. In one example, the cap32comprises a cup-shaped component that has an enclosed end40and an open end42(FIG. 4). The cap32has an inner surface44that defines an open internal volume46of the cap32and an outer surface48. The internal volume46of the cap32is added to the internal volume22of the cylinder20to define an overall internal volume for the strut18. A fluid, such as gas for example, is used to fill the internal volume to set a desired pressure for the opening and closing effort. The cap32is selectively moved relative to the cylinder20by a customer or end-user to adjust the overall internal volume to vary the pressure and set a desired open/closing effort.

In one example, a threaded attachment is used between the cap32and the cylinder20. In one example, the external surface36of the cylinder20includes a first threaded structure50(FIG. 3) and the internal surface44of the cap32includes a second threaded structure52(FIG. 4). The cap32is rotated as indicated at54to increase the pressure by decreasing the amount of internal volume46of the cap32that is added to the internal volume22of the cylinder20. As the cap32is rotated in direction54, the cap32moves in an axial direction along the length of the cylinder20to shorten an overall length of the combined cap and cylinder. The cap32is rotated in the opposite direct as indicated at56to decrease the pressure by increasing the amount of internal volume46of the cap32that is added to the internal volume22of the cylinder20. As the cap32is rotated in direction56, the cap32moves in an opposite axial direction along the length of the cylinder20to increase the overall length of the combined cap and cylinder. A threaded attachment is one example of adjusting the position of the cap32relative to the cylinder20, other attachment methods could also be used.

A seal60is included within the cap32to provide a sealed interface at the second end26of the cylinder20. In one example, the seal60is fixed to the second end26of the cylinder20. The seal60can be seated within a groove, for example. As the position of the cap32is adjusted, the seal60slides along the internal surface44of the cap32such that the sealed interface is provided at all adjustment positions.FIG. 3shows the cap32in the fully extended cap position.

The enclosed end40of the cap32includes a first attachment structure62and the rod30includes a second attachment structure64. One of the attachment structures62,64attaches/couples the strut18to the moveable panel and the other structure62,64attaches/couples the strut18to the fixed vehicle structure. Any type of attachment structure can be used at these locations. The operation and composition of these attachment structures are well known and will not be discussed in detail.

The first and second attachment structures62,64remain fixed to the panel/vehicle structure as the panel moves between open and closed positions. The piston28slides within the cylinder20as the rod30extends outwardly of the first end24to extend the length of the strut18as the panel moves to the open position. The rod30retracts back into the cylinder20as the panel moves to the closed position. As discussed above, the position of the cap32is selectively moved relative to the cylinder20to vary the internal volume and adjust the internal pressure as needed in response to a change in weight and/or location of a center of gravity of the panel.

Thus, the subject invention provides a strut cylinder with an adjustable cap on the end opposite of the opening for the piston/rod. This cap includes a seal that can be similar to the seal that seals the rod to the cylinder. Upon tightening the cap, the volume of the cylinder gas chamber is reduced to increase the pressure of the gas in the strut. Conversely, when the cap is loosened, the volume of the cylinder chamber increases and the pressure of the gas would be reduced in the strut. Thus, when a vehicle is equipped with these cylinders, a modification to the mass of center of gravity of a liftgate/tailgate/decklid could be compensated for by tightening or loosening the cap of the gas strut sufficiently to restore proper function of liftgate/tailgate/decklid.

For example, if a tire kit is added to an inner panel of a liftgate, the additional mass mounted low on the gate would cause the liftgate to sag (especially at cold temperatures). To counteract the sagging of the liftgate, the caps of the gas struts could be tightened to reduce the chamber volume and increase the strut pressure to compensate. Conversely, if something is removed from the liftgate such as a trim panel or glass, the liftgate would be hard to close and open with much more force (especially on hot days). To counteract the high closing efforts, the caps on the gas strut can be loosened which would lower the pressure in the strut to compensate.

As such, the subject invention provides an end cap for a strut that can be adjusted to vary the internal volume, and accordingly, the pressure within the cylinder to adjust closing and opening efforts as needed. The advantage of this solution is that there an infinite number of adjustments/modifications can be made to cover a wide range of different struts with different pressures. With an adjustable volume cylinder, the pressure in the cylinder can be tuned to the specific mass and center of gravity required for the specific set of modifications that have been made to the panel. This provides the add-on providers with the capability to tune the cylinder pressure such that the opening/closing efforts are within a reasonable range for the operator. This avoids the requirement for a unique cylinder with a unique pressure for each mass/center of gravity combination. An added benefit of this configuration is that the pressure can be increased as the gas strut wears over time. This would allow adjustments to be made to restore proper function over the course of the gas strut useful life.