The present invention relates to pneumatic leveling systems and, more particularly, closed pneumatic leveling systems.
Some original equipment manufacturers (“OEMs”) of automotive vehicles offer air suspension leveling systems having more than one vehicle ride or “trim” height. Example trim heights include a “normal” ride height for most driving conditions, a lowered “entry” height for ease of entry and exit from the vehicle, a raised “off-road” height for increased ground clearance, and a slightly lower-than-normal “aero” height for improved fuel economy at higher speeds.
The trend toward multiple trim height suspension systems has brought about the desire for improved response times in changing from one trim height to another, especially when going from a lowered entry position back to normal ride height, and from normal ride height to a lowered Entry position. Air compressors, which provide compressed air to a pneumatic leveling system for changing trim height, are typically driven by DC motors. However, motors that are compatible with the typical OEM automotive requirements of low mass, low electrical current draw and low acoustic noise typically do not generate the air flow rates required to achieve the desired response times (preferably about 10 seconds or less) to change from one trim height to another.
The desire to achieve faster response times has led some OEM's toward several solutions, two of which require the addition of a separate component: an air pressure storage reservoir. An air reservoir can be used in conjunction with a compressor, and can be operated in parallel with the compressor in an “open” mode or in series with the compressor in a “closed” mode.
In the open mode of operation, the air reservoir is charged to a pressure higher than the maximum pressure required for the vehicle's air suspension system, and its air pressure is used in parallel to the output of the compressor to fill at least one air suspension lift device. After each trim height change, the compressor is used to “re-charge” the air reservoir to its original pressure so that it will be ready for the next required use. The source of this re-charge air is usually ambient atmosphere. This may result in relatively long operating times for the compressor (usually on the order of minutes) for each trim height change, which results in objectionable acoustic noise being generated for a corresponding period of time and drives a design requirement for a motor having a high mean time between failure (“MTBF”) rating in order to meet the vehicle's lifetime durability requirements. When air is required to be removed from the air suspension system to lower trim height, air is usually exhausted back into the atmosphere via an exhaust solenoid valve.
In the “closed” mode of operation, the air pressure from the reservoir is used to “pre-charge” the air compressor intake, resulting in pump operation at higher volumetric efficiency (“VE”), higher air flow rates, and faster trim height change response times, usually on the order of seconds. When air needs to be removed from the air suspension system to lower trim height, air flow direction is switched by means of at least one air direction valve, so that the air can be pumped out of the air suspension lift devices back into the air reservoir. In the closed mode of operation, the only air that is required to be added to the system is the air that is required to compensate for any air lost from the system due to system leaks. The air reservoir for a closed mode system does not need to be charged to a pressure higher than the maximum air pressure that will be required by the suspension system (as is the case with the open mode), because its air pressure is not used in parallel with the compressor, but rather is used in series with the compressor to pre-charge the intake side of the compressor. As the air is removed from the reservoir and pumped into the air suspension lift devices to raise the vehicle, the pressure in the reservoir decreases at a rate that is inversely proportional to the volume of the reservoir. Thus, the smaller the reservoir volume, the greater the rate of pressure decrease, and the larger the reservoir volume, the smaller the rate of pressure decrease. Conversely, as air is removed from the air suspension lift devices and pumped into the reservoir to lower the vehicle, the pressure in the reservoir increases at a rate that is inversely proportional to the volume of the reservoir. Volumetric efficiency of the compressor varies, dependent on the pressure in the reservoir. When air is being drawn out of the reservoir to supply the compressor inlet pressure, the VE is directly proportional to the reservoir pressure. When air is being pumped back into the reservoir, the VE is inversely proportional to the reservoir pressure. Thus, for a given system pneumatic volume, the larger the reservoir volume, the less the pressure will change within the reservoir during use, and the more consistent the performance will be for raising and lowering the vehicle trim heights.
Both the open and closed operating modes require the addition of an air reservoir to the vehicle's leveling sub-system. This adds not only mass (which may be significant) and cost, but also adds the considerable complication of finding enough volumetric space on the vehicle having an appropriate geometry for an air reservoir. Packaging space and mass very often come at a premium cost in vehicle designs. Similarly, additional components such as air reservoirs may cause undesireable compromises to be made in leveling system design or leveling system component packaging. Further, the vehicle manufacturer must consider the crashworthiness of the air reservoir, since it is a pressure vessel.
Accordingly, there is a need for an air reservoir for a vehicle pneumatic leveling system that is capable of providing a sufficient capacity of compressed air to facilitate rapid changes in vehicle trim modes, does not unduly add to vehicle weight or cost, and does not compromise the crashworthiness of the vehicle.
One aspect of the present invention provides a suspension system including a pneumatic leveling system adapted to selectively receive and expel a fluid and a spare tire in communication with the leveling system, wherein the spare tire is adapted to provide the fluid to the leveling system.
A second aspect of the present invention provides a pneumatic leveling system including a spare tire, a compressor having an inlet and an outlet, an inlet valve in communication with the compressor inlet, an outlet valve in communication with the compressor outlet, a pneumatic tee for connecting the inlet valve and the outlet valve to the pneumatic leveling system, a reservoir tee for connecting the inlet valve and the outlet valve to the spare tire, and a control unit for controlling the compressor, the inlet valve and the outlet valve, thereby selectively transferring a fluid between the spare tire and the pneumatic leveling system.
Another aspect of the present invention provides a suspension system including a pneumatic leveling system adapted to selectively receive and expel air, a spare tire in communication with the leveling system, wherein the spare tire is adapted to provide air to the leveling system and receive air expelled from the leveling system, and a compressor adapted to facilitate transfer of air between the leveling system and the spare tire.
Other aspects of the present invention will be apparent from the following description, the accompanying drawings and the appended claims.
In the discussion that follows, like numerals are used to identify elements of like structure or function. In addition, the term “reservoir” is understood to encompass all types of air storage structures including, without limitation, accumulators.
A pneumatic adapter, generally designated 4, is shown in
An internal surface 29 of collar 12 may be generally conical to match the external shape of Schrader-type tire valve 34 and has a length L which is adapted to minimize axial misalignment of the collar to the tire valve. Length L may be further adapted to provide adequate support to resist radial motion of pneumatic adapter 4 due to vibration imposed by an attached reservoir hose assembly 3 or an air reservoir 1 (see
With continued reference to
With further reference to
An alternate aspect of pneumatic adapter 4 is depicted in
As illustrated in
Air direction valve 5 of compressor assembly 26 serves as a compressor inlet valve. Inlet valve 5 may be connected to an inlet valve 10a of an air compressor 10. Inlet valve 5 may also be connected to air reservoir 1 via an air reservoir tee 7, reservoir hose 3, and coupling 4. Inlet valve 5 may also be connected to the pneumatic system 9 via a pneumatic tee 8. Compressor assembly 26 may further include an air direction valve 6 that serves as a compressor outlet valve. Outlet valve 6 may be coupled to an outlet valve 10b of air compressor 10. Outlet valve 6 may be connected to air reservoir 1 by an air reservoir tee 7, reservoir hose 3, pneumatic adapter 4, and tire valve coupler 2. Outlet valve 6 may also be connected to the pneumatic system 9 by a pneumatic tee 8.
In operation, control 27 may be manually or automatically signalled by an operator or by conventional sensing means (not shown) to change the trim level of the vehicle. To raise the trim level, control 27 actuates inlet valve 5 while outlet valve 6 is deactuated. Air flows from air reservoir 1 to leveling system 9 as indicated by the solid-line arrows of
An alternate embodiment of the present invention is depicted in
Air direction valve 5 of compressor assembly 26 may serve as a compressor inlet valve. Inlet valve 5 may be coupled to an inlet valve 10a of an air compressor 10. Inlet valve 5 may also be connected to air reservoir 1 by an air reservoir tee 7, reservoir hose 3, coupling 4 and tire valve coupler 2. Inlet valve 5 may further be connected to pneumatic system 9 via a pneumatic tee 8. Compressor assembly 26 may further include an air direction valve 6 that serves as a compressor outlet valve. Outlet valve 6 may be connected to an outlet valve 10b of air compressor 10. Outlet valve 6 may also be connected to air reservoir 1 by an air reservoir tee 7, reservoir hose 3, pneumatic adapter 4 and tire valve coupler 2. Outlet valve 6 may also be connected to the pneumatic system 9 via pneumatic tee 8.
In operation, control 27 may be manually or automatically signalled by an operator or by conventional sensing means (not shown) to change the trim level of the vehicle. To raise the trim level, control 27 actuates both inlet valve 5 and outlet valve 6, thereby displacing their respective solenoids from the positions shown in the drawing. Air flows from air reservoir 1 to leveling system 9 as indicated by the solid-line arrows of
A typical spare tire 25 has an internal pneumatic volume of about 60 to 90 liters, depending upon size, whereas a typical separately-packaged air reservoir may typically be in about the 6 to 14 liter volume range. In terms of control of the trim level, such as between the two functions of raising the vehicle from a lowered position and lowering the vehicle from a raised position, it may be preferable to give higher priority to lowering the vehicle from a raised position, since a lower center of gravity produces a more stable condition in terms of vehicle dynamics.
With reference to
1. More consistent leveling system 9 performance;
2. The potential to reduce the response time required to lower the vehicle, in the case of a multiple trim height suspension system, from one target trim height to a lower target trim height, such as normal to entry mode, or off-road to normal mode;
3. Crashworthiness—adding a separate pressurized air reservoir raises additional crash protection and testing concerns. This concern is eliminated by the present invention, as the crashworthiness of spare tire 25 has already been considered during vehicle design and is not significantly impacted by the present invention;
4. Spare tire pressure—it is not uncommon for the air pressure in spare tire 25 to go unchecked for years. If the owner ever does need the spare, he or she is likely to find it under-inflated. The present invention will maintain spare tire 25 inflation within a predetermined pressure range, and the system may be further adapted to adjust the spare tire to an optimal pressure on manual or automatic command. In a further embodiment of the present invention, the valve stem (not shown) and Schrader-type valve 34 could be removed from wheel 35 (see
5. An alternate embodiment of the present invention comprises a pneumatic leveling system 9 wherein the vehicle owner may lower the pressure of the vehicle's tires to a lower value for off-road use and then use the pneumatic leveling system to re-inflate the tires to a higher pressure for on-road use. If compressor assembly 26 allows compressor 10 to draw air from reservoir 1 instead of atmospheric air, inflation speed is greatly increased while the stress on the compressor is greatly reduced. A small reservoir common in the art, sized for leveling system 9, would provide only a limited “boost” for inflating just the first tire or so. However, the substantial reservoir volume of a full-size spare tire 25 will be of assistance for at least a portion of the four in-service tires of the vehicle, depending on the spare tire pressure and volume;
6. It is less expensive to tool a new double shut-off quick connect tire valve coupler 2, in accordance with an embodiment of the present invention, than it would be to tool a new, uniquely shaped air reservoir and associated mounting hardware. This is a particular advantage for an optional equipment system or a vehicle having a low production volume;
7. The double shut-off feature of the pneumatic connection 4, 2 (
8. The quick-connect feature of the pneumatic connection 4, 2 (
Although the invention is shown and described with respect to certain embodiments, it is obvious that equivalents and modifications will occur to those skilled in the art upon reading and understanding the specification. The present invention includes all such equivalents and modifications and is limited only by the scope of the claims.
This application claims priority from U.S. Provisional Patent App. No. 60/552,317 filed on Mar. 10, 2004, the entire contents of which are incorporated herein by reference.
Number | Date | Country | |
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60552317 | Mar 2004 | US |