Abstract:
A vehicle leveling strut of the type having a direct-acting hydraulic shock absorber provided with a reciprocable piston rod having a dirt shield mounted thereon. A tubular rolling diaphragm member secured at one end to the shock absorber and to the opposite end to the dirt shield and defining therewith a variable volume chamber adapted to be selectively pressurized and de-pressurized for controlling the distance between the sprung and unsprung portions of an associated vehicle. Located interiorly of the pressurizable chamber and concentrically positioned between the shock absorber and fixedly mounted to the dirt shield is a generally tubular support member upon which is mounted at least one pair of electrical coil windings for sensing changes in the electromagnetic field of each coil winding. Associated with the shock absorber axially moving through the tubular support member are means for changing the electromagnetic fields of the coil windings so as to provide a control signal which effects actuation of a pressurized fluid supply source.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to vehicle leveling systems, and more particularly, to a new and improved vehicle leveling device incorporating a novel electronic height sensing apparatus. 
     2. Description of the Related Art 
     Vehicle leveling systems function to maintain a predetermined height relationship between a chassis (sprung portion) of a vehicle and its ground engaging axle assemblies (unsprung vehicle portion). Such systems utilize one or more auxiliary fluid suspension components to supplement the load carrying capacity of the primary vehicle springs. A pressure source is often included in such leveling systems for supplying pressurized fluid to the auxiliary suspension components when a load of predetermined magnitude has been added to the vehicle chassis. Upon such loading, the auxiliary suspension components become operable to supplement the load carrying capacity of the primary springs to return the vehicle chassis to a desired height relationship with respect to the ground engaging axle assembly. When the vehicle load is removed, the primary suspension springs and pressurized auxiliary suspension components co-act to cause the chassis to rise above the desired relationship. When this occurs, the leveling system causes the pressurized fluid to be exhausted from the auxiliary suspension components. 
     To accomplish the aforesaid pressurizing and exhausting of fluid from the auxiliary suspension components, it has been the practice to utilize some type of a height detecting controller. For example, U.S. Pat. No. 4,017,099 discloses an external height detecting controller located remote from vehicle leveling struts of vehicle leveling systems. Such height detecting controllers generally function to vary the attitude or trim height between the ground engaging axle of a vehicle and a vehicle&#39;s chassis. The height detecting controller senses sustained changes in the height relationship between the axle and chassis and controls fluid flow between a suitable source of a pressurized fluid and the suspension struts. Such remotely located controllers have been found to be objectionable because they often require separate factory installation. Additionally, such controllers require accurate positioning and calibration adjustment in order to assure the desired overall operation of the leveling system. 
     While integrated controllers and suspension struts have been proposed in the U.S. Pat. Nos. 3,584,894 and 3,606,375, such devices have been found to be objectionable due to the fact that they were located externally of the suspension struts and thus were subject to the hostile environment that exists in connection with modern automotive vehicles. 
     Aforementioned U.S. Pat. No. 4,017,099 discloses an arrangement by which the height controlling elements are located interiorly of the pressurizing chamber. U.S. Pat. No. 4,141,572 discloses a refinement of the principles set forth in the earlier mentioned patent by which the height sensing elements and their associated electronic circuitry may be conveniently mounted directly upon one peripheral wall portion of the pressurizing chamber of the associated leveling strut. 
     U.S. Pat. Nos. 4,017,099 and 4,141,572 and the present invention are preferably combined with an electrical connector arrangement. The connector is intended to be communicable via a suitable opening or aperture in the suspension strut dirt shield with suitable electrical conductors connected to the associated control system and pressurizing source. Additionally, because a portion of the associated electrical circuitry and height sensing means are supported within the pressurizing chamber, they are protected from the hostile exterior environment. However, aforementioned U.S. Pat. Nos. 4,017,099 and 4,141,572 disclose height sensing control mechanisms utilizing optical height sensing means including a light source and means sensitive to the light source for controlling pressurization of the vehicle leveling strut. Specifically, a pair of light sensitive devices are mounted substantially opposite from a light source upon the interior wall of the dirt shield, or to a support member secured thereto, and are operatively associated such that when the reciprocating shock absorber cylinder blocks the transmission of light from the light source to one or both of the light sensitive devices, an electrical signal is produced to actuate the source of fluid pressure so as to adjust the leveling strut height accordingly. Pre-assembly alignment of the light sensitive devices with the light source so as to direct sufficient light transmission is required. 
     Further methods for sensing the variable location of reciprocating components are disclosed in United Kingdom patent application No. GB 2 163 260 A, as well as U.S. Pat. Nos. 4,502,006 and 4,623,840. These patents disclose methods and apparatuses for sensing the real-time variable position of a reciprocating member. These references are adapted for variable displacement sensing rather than to discrete positional sensing to which the present invention is directed. 
     It is to be noted that the terms &#34;height,&#34; &#34;distance,&#34; &#34;attitude,&#34; etc. and derivatives thereof are used interchangeably herein as well as throughout the automotive art, as referring to the magnitude of spacing between a vehicles sprung and unsprung portions (e.g., between a vehicle frame and its associated axles). It is also to be noted that the term &#34;associated electronic circuitry&#34; used herein is intended to mean wires, conductors (either discrete wires or printed circuits), as well as electronic components per se, either solid state or otherwise or any combinations thereof. Lastly, the vehicle leveling device described herein which incorporates the novel electronic height sensing apparatus encompasses application to either suspension &#34;struts&#34; or &#34;shock absorbers&#34; as utilized in vehicle leveling systems. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is a primary object of the present invention to provide a vehicle leveling strut apparatus incorporating a new and improved height sensing device wherein the height sensing and controlling elements, as well as a portion of the electronic circuitry, are mounted directly within the suspension strut. 
     Another object of the present invention is to provide a new and improved height sensing device adaptable for application in typical leveling systems and which is of relatively simple design, is economical to manufacture, and will have a long and effective operational life. 
     A further object of the height sensing device is to produce a plurality of discrete electrical signals corresponding to the positional location of the shock absorber relative to the height sensing devices as positioned within the leveling strut assembly, wherein said discrete signals eliminate complex signal processor logic systems and calibration requirements necessitated by variable displacement sensing mechanisms. 
     Additionally, it is another object of the present invention to provide a method and apparatus for generating electrical output signals corresponding to a plurality of discrete positional inputs so as to interact with the associated control system and pressurizing source. 
     Specifically, the apparatus according to the present invention encompasses a simplified height sensing device as incorporated into an air adjustable leveling strut. The air adjustable leveling strut consists of a direct acting hydraulic shock absorber, a generally tubular dirt shield coaxially mounted over the piston rod of the shock absorber and a tubular rolling diaphragm member secured to the outer surface of the shock absorber and dirt shield so as to define a sealed pressurizable chamber. Clamping rings are used to secure the diaphragm to its respective surfaces. The height sensing device, consisting of a generally tubular support member, is secured to the inner peripheral surface of the dirt shield within the chamber and axially positioned so as to allow telescopically reciprocating motion of the shock absorber therethrough. Encircling the support member at two distinct positions are two electrical coil windings which are used to generate two electromagnetic fields, the changes in which are delivered to the vehicle&#39;s control module circuitry. An electrical connector is airtightly mounted in an opening through a wall portion of the dirt shield to provide the communicative path between the pair of coil windings and the vehicle control module. The chamber is operatively connected to an external pressurized fluid source actuated by the control circuitry to adjust the vehicular attitude in response to the positional signals generated by the coil windings. 
     According to the method of the present invention, each of the independent coil windings produces an electromagnetic field, the changes in which may be sensed by the control module circuitry of the vehicle. The windings define three discrete signals for sensing positional location of the shock absorber axially reciprocable through the support member on which the windings are maintained. These positions correspond to below, between, and above the longitudinally spaced coil windings. As the shock absorber cylinder moves axially in response to the magnitude of the load carried by the vehicle, the clamping ring securing the diaphragm to the shock absorber cylinder induces a change in the electromagnetic flux of the electromagnetic field associated with either of the first or second coil windings so as to sense one of the three aforementioned positions. This change in the electromagnetic fields signals the control circuit to actuate the fluid pressure source for introducing or exhausting air into the chamber, thereby returning the vehicle to the desired trim height relationship with respect to the ground engaging axle assembly. 
     Accordingly, the present invention senses relative position rather than variable position by utilizing electromagnetic principles. This height sensing device allows for longitudinal spacing of the coil windings at a predefined distance on the support member which corresponds to the specific vehicular application requirements. It is contemplated that a plurality of coil windings may be incorporated into this height sensing device to permit greater positional sensing capabilities whenever required. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various advantages of the present invention will become apparent to one skilled in the art upon reading the following detailed description and by reference to the following drawings in which: 
     FIG. 1 is a schematic representation of an automotive vehicle having the leveling system according to the preferred embodiment of the present invention; 
     FIG. 2 is a side elevational view partially broken away of one of the air adjustable suspension leveling struts of the leveling system shown in FIG. 1, in one of the three height positions according to the preferred embodiment of the invention; 
     FIG. 3 is a side elevational view partially broken away of one of the air adjustable suspension leveling struts of the leveling system shown in FIG. 1 in the second of the three height sensing positions according to the preferred embodiment of the present invention; 
     FIG. 4 is a side elevational view partially broken away of one of the air adjustable suspension leveling struts of the leveling system shown in FIG. 1 in the third of the three height sensing positions according to the preferred embodiment of the present invention; and 
     FIG. 5 is an enlarged pictorial view of the electromagnetic height sensing device incorporated in the air adjustable suspension leveling struts shown in FIGS. 2-4 according to a preferred embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIG. 1, a vehicle leveling system 10 is shown in accordance with a preferred embodiment of the present invention. The vehicle leveling system 10 is shown in operative association with a typical automotive vehicle, which is generally designated by the numeral 12. The vehicle 12 includes a sprung portion or chassis 14 and unsprung or axle portion 16, between which the main or primary suspension springs 18 are located. Generally speaking, the leveling system 10 comprises a pair of auxiliary suspension components or leveling struts 20 and 20&#39; which are adapted to be selectively pressurized and de-pressurized from a suitable source of fluid pressure such as an electrically energized air compressor 22. The compressor 22 is supplied with electrical energy from a conventional 12-volt vehicle battery 24 which is also connected to an electrical control module 26 via an electrical conductor 28. The module 26 is in turn connected to the compressor 22 via a suitable conductor 30, and a suitable fuse 32 may be provided in the electrical circuit connecting the battery 24 with the compressor 22. The compressor 22 is adapted to supply pressurized air to the suspension struts 20 and 20&#39; via conduit 34, control valve mechanism 36, conduit 38, T-fitting 40 and conduits 42 and 44. 
     When the vehicle 12 becomes loaded to a predetermined magnitude, the control module 26 will energize the compressor 22 to increase the pressure in the conduits 34, 38, 42, and 44 and therefore in the leveling struts 20 and 20&#39; connected thereto. The increase in pressure in the leveling struts 20 and 20&#39; cause extension thereof so as to raise the sprung portion 14 of the vehicle 12 to a level or other predetermined attitude. At such time as the vehicle 12 is unloaded, the control module 26 will effect actuation of the control valve 36 such that the leveling struts 20 and 20&#39; will be vented to atmosphere (or elsewhere), whereby the struts 20 and 20&#39; will be compressed or contracted causing the sprung portion 14 of the vehicle 12 to be lowered to some predetermined attitude. 
     As shown in FIG. 2, the leveling strut 20 comprises a direct-acting hydraulic shock absorber 50 having a hydraulic cylinder or housing 52. Extending upwardly from the cylinder 52 is a reciprocable piston rod 54 which is connected at its lower end to a reciprocable piston (not shown) that is reciprocable within the cylinder 52 to dampen relative movement between the sprung and unsprung portions of the vehicle 12. The lower end of the cylinder 52 is provided with a lower end fitting 56 which is adapted to be secured in a conventional manner to the unsprung portion 16 of the vehicle 12, while the upper end of the piston rod 54 is provided with an upper end fitting (not shown) adapted to be secured in a conventional manner to the sprung portion 14 of the vehicle 12. 
     Mounted on and reciprocable with the piston rod 54 is an annular or tubular dirt or dust shield 60 which extends coaxially of the piston rod 54 and is spaced radially outward from the outer periphery of the cylinder 52. The upper end of the dirt shield 60 is provided with a generally inverted cup-shaped end cap 62 that is secured to the piston rod 54 and closes off the upper end of the dirt shield 60. Disposed between the lower end of the dirt shield 60 and the cylinder 52 is a rolling flexible diaphragm member, generally designated by the numeral 64. The diaphragm member 64 is fabricated of a suitable material, such as fabric reinforced rubber, and comprises an inner end portion 66 that is sleeved over the outer periphery of the cylinder 52. 
     The diaphragm member 64 also comprises an outer end portion 68 that is sleeved over the lower end of the dirt shield 60, with the inner and outer portions 66 and 68 being connected by a reversely folded lower portion 70, as illustrated in FIG. 2. The end portions 66 and 68 are secured to the cylinder 52 and dirt shield 60, by suitable clamping rings 72 and 74 respectively. Accordingly, the cylinder 52, dirt shield 60 and diaphragm 64 define a pressurizable chamber 76 which is adapted to be selectively pressurized by fluid, i.e., compressed air or the like, supplied from the compressor 22. A suitable attachment fitting 78 is provided on the dirt shield 60 for securing the adjacent end of the conduit 42 thereto, as will be apparent to those skilled in the art. 
     In accordance with the principles of the present invention, disposed internally of the chamber 76 and radially secured along the lower interior periphery of the dirt shield 60 is the prefabricated height sensing device 100. The height sensing device 100 has a generally tubular support member 80 which is suitable for supporting and locating the below described height sensing components 82 and 84. The tubular support member 80 is disposed concentrically between the cylinder 52 of shock absorber 50 and the dirt shield 60. Encircling the support member 80 is a pair of electrically conductive coil windings 82 and 84. When alternating current is delivered to the coil windings 82 and 84, an electromagnetic field is generated. In accordance with the present invention, the coil windings 82 and 84 encircling the support member 80 are spaced in a manner so as to define three discrete height positions of shock absorber 50 relative to the coil windings 82 and 84 as the shock cylinder 52 axially reciprocates through the support member 80. The three positions correspond to the location of a predefined portion of the shock absorber 50 either below, between or above the coil windings 82 and 84. 
     According to the preferred embodiment, the support member 80 is installed within the chamber 76 in close proximity to the clamping ring 72 which secures diaphragm 64 to the shock cylinder 52. The clamping ring 72 is fabricated from a material capable of producing a change in the electromagnetic field generated by the coil windings 82 and 84 as clamping ring 72 axially passes through the support member 80. The coil windings 82 and 84 are aligned on the support member 80 such that when the clamping ring 72 is positioned between the windings 82 and 84, the control valve 36 remains closed to the atmosphere and the compressor 22 remains de-energized. At such time as the vehicle becomes loaded to a predetermined magnitude causing the dirt shield 60 to move downwardly to the shock absorber 50, the clamping ring 72 will pass through the electromagnetic field generated by the upper coil winding 84 so as to produce a change in the electromagnetic field generated by the coil winding 84. Under these conditions, the control valve 36 is energized causing increased pressurization of the suspension components 20 and 20&#39; to be effected so as to raise the sprung portion 14 of the vehicle 12. 
     When the load on the vehicle 12 is removed, the primary suspension springs 18 will cause the sprung portion 14 of the vehicle 12 to be raised, whereupon the clamping ring 72 will be displaced axially downward relative to the dirt shield 60. When this occurs, the control valve 36 will exhaust the conduit 38 to atmosphere so as to permit lowering of the sprung portion 14 of the vehicle 12. It will be noted that the longitudinal spacing between the coil windings 82 and 84 may be varied in accordance with the desired axial movement between the dirt shield 60 and the clamping ring 72, and that a suitable time delay feature as described in the aforementioned U.S. Pat. No. 4,017,099 may be incorporated in the electric circuitry of the leveling system to prevent premature energization of the compressor 22 and/or control valve 36 during such time as the vehicle transverses relatively irregular road surfaces. 
     With particular reference now to FIGS. 2, 3 and 4, the relative positioning of the clamping ring 72 mounted to shock absorber 50 to the spaced electrical coil windings 82 and 84 mounted on support member 80 is shown in the three height positions. FIG. 4 shows the relative positioning of the components when the vehicle 12 becomes loaded to a predetermined magnitude, such that the clamping ring 72 is axially positioned above upper coil winding 84. FIG. 3 shows the relative positioning of the components when the vehicle 12 is at the desired attitude associated with a predefined vehicular trim height. FIG. 2 represents the relative positioning of the components when the load on the vehicle 12 is removed, whereupon the clamping ring 72 will be positioned below the lower coil winding 82. FIGS. 2 and 4 represent the relative positions immediately following the loading or unloading placed on the sprung portion 14 of the vehicle 12 prior to actuation of the air compressor 22. 
     Referring now to FIG. 5, the height sensing device 100 according to the preferred embodiment of the present invention is shown in greater detail. The generally tubular support member 80 may be fabricated from any material suitable for rigidly supporting electrically conductive coil windings 82 and 84 which encircle its outer peripheral surface. The support member 80 is electrically nonconductive and permits identifiable changes in the electromagnetic field generated by each of the coil windings 82 and 84 when in close proximity thereto. This change in the electromagnetic fields generated by each of the coil windings 82 and 84 is sensed by the control module 26 so as to adjust vehicle height. 
     The support member 80 is fabricated from a rigid plastic material, though other suitable material may be used. The support member 80 may be secured to the inner peripheral wall of the dirt shield 60 by any suitable means so as to maintain its concentric alignment with the reciprocable shock absorber 50. According to the embodiment shown, the lower edge of dirt shield 60 defines an annular shoulder or flange channel 62 within which support member 80 can be easily installed. An electrical connector 92 communicates sensed changes in the electromagnetic field generated by the coil windings 82 and 84 to the control module 26 so as to effect energization of the compressor 22. The electrical connector 92 is airtightly mounted in an opening through a wall portion of dirt shield 60. 
     It will be seen from the foregoing that the present invention provides a leveling system incorporating a simplified height controlling device within the air adjustable leveling strut 20. This invention allows prefabrication of the height sensing device 100 for assembly into a typical air adjustable leveling strut. More importantly, the present invention provides an arrangement by which the height sensing device 100 may be conveniently supported within the associated leveling chamber (dirt shield 60) while eliminating orientation or prearrangement during assembly typical of current height controlling systems. By virtue of the fact that the aforesaid circuitry and height sensing coil windings 82 and 84 are prelocated relative to one another prior to installation, correct operating orientation of these elements is assured so that no subsequent adjustment of their relative position thereof is necessary. Further, if the clamping ring 72 is magnetized, it may be possible to have the coil windings 82 and 84 sense the relative position of the clamping ring 72 without being connected to a source of alternating current. Additionally, the present invention is adaptable to many applications without significantly increasing the assembly time of conventionally assembled leveling struts. Finally, applications of the principles of electromagnetics greatly simplify the operative components incorporated in leveling struts such that the novel height sensing device may be manufactured economically while providing long and effective operational life. 
     While the embodiment presented is directed at air adjustable leveling struts, the utilization of electromagnetics for sensing relative positional displacement is adaptable for application in any suspension component generating multiple positional signals. In particular, it is contemplated that the height sensing apparatus is readily adaptable to damping devices, such as shock absorbers or suspension struts, utilizing air or hydraulics as their primary damping medium. 
     While it will be apparent that the preferred embodiment of the invention disclosed are well calculated to fulfill the objects above stated, it will be appreciated that the invention is acceptable to modification, variation and change without departing from the proper scope of fair meaning of the invention.