Abstract:
A pinion adjustable assembly for steering mechanisms for automotive vehicles, a pinion-rack set incorporated in a pinion housing and a tubular cylindrical bushing with free angular displacement that is positioned inside the housing and is coupled to an angular positioning nut. The said bushing has an eccentric inner wall with regard to outer wall surface surrounding a pinion housing. Angular displacement of said bushing by angular movement changes its eccentricity to allow the pinion to move relative to the rack bar for overcoming wearing out effect on teeth.

Description:
RELATED APPLICATION 
     The present invention claims priority based on Argentina Patent Application Serial No. P99/01/01670, filed Apr. 12, 1999 and P99/01/02911, filed Jun. 17, 1999 
     FIELD OF THE INVENTION 
     The present invention relates generally to a steering mechanism assembly for automotive vehicles, and more particularly to rack and pinion steering mechanisms. 
     BACKGROUND OF THE INVENTION 
     An important requirement for steering mechanisms for automotive vehicles, particularly pinion-rack bar power-assisted mechanisms, is offering stable steering means with precise movement between a pinion and a rack bar. This may be accomplished by providing a proper gear teeth assembly with proper contact points. This is achieved by mounting the components within established limits of tolerances. Sometimes, the tolerances vary out of established limits during the manufacturing process and to create an undesirable clearance between the gear teeth. Commonly, the correction usually involves additional complicated and time-consuming operations. 
     Moreover, the steering gear teeth are subject to wear over the life of the vehicle. The wear may adversely affect the assembly relationship since clearance between the teeth creates undesirable noises and improper alignment of vehicle relative to the steering wheel. 
     Undesirable operation of pinion-and-rack bar set is obtained when teeth are worn out. Wear is created by axial stresses present in the articulations of the steering housings. These stresses tend to urge the rack into a position distant from and out of proper assembly with the pinion. Thus, these stresses create a force opposed to maintaining the pinion and rack bar teeth in tight engagement. 
     The above cited teeth clearance is usually solved or compensated for by applying a force to a pinion roller bearing and rack bar and dampening by using an adjustment washer and pushing spring to urge the pinion and rack bar together for a proper assembly relationship. 
     Proper alignment and adjustment during manufacturing process of this mechanism, as well as wear corrections of the assembly between pinion and rack bar, is difficult in the prior known method. 
     Also, the source of the problem is hard to determine and sometimes requires the replacement of the complete steering unit. 
     It would therefore be desirable to improve the assembly relationship between teeth of said pinion-and-rack set. More particularly, it would be desirable to provide an adjustable assembly between the teeth for reducing bothersome noises and the above-mention knocking effects. 
     SUMMARY OF THE INVENTION 
     One object of the present invention is to improve the above cited pinion-rack bar mechanisms to enable adjustment of the relative position of teeth gears of the pinion-and-rack bar assembly in a fast and easy manner. 
     Another object of the present invention is to provide a novel pinion assembly of a steering mechanism that allows a periodical adjustment of pinion-rack bar assembly relationship so that the rotational movement of steering wheel is converted into reciprocal linear movement of rack which results in reduced effort with reduced steering. 
     Another object of the present invention is to provide a steering mechanism that allows selectively adjustable assembly of pinion-rack bar set inside a pinion casing integral to rack bar casing. The angular shifting of the mechanism avoids an excessive clearance in the pinion-rack bar assembly and allows a radial placement of the pinion for a proper transmission movement. Improper variations of the pinion clearance act against a uniform assembly relationship. 
     In one aspect of the invention, a tubular sleeve or bushing is positioned inside the casing that is fixed to rack bar casing. The cylindrical outer surface of the bushing is concentric and coaxial to the pinion casing. The inner surface of the bushing is eccentric. The tubular sleeve or bushing is capable of being radially moved in response to angular shifting of the bushing inside the casing to achieve a proper positioning of pinion and rack bar teeth by adjusting the eccentricity of the bushing outer surface relative to the pinion. 
     In another aspect of the invention, a tubular sleeve or bushing having an outer surface eccentric with regard to a rack casing has an upper end flange for manually or mechanically varying its outer eccentricity. It is also provided with an inner end nut for fixing it in a proper position against the casing. At the same time the rack is engaged to the pinion, an outer elastic buckling seal for resting against the inner concentric surface of the tubular sleeve or bushing absorbs eccentricity differences of the bushing when it is rotated for compensating for preloading the pinion and for assembly differences and for maintaining the rack in contact against the concentric inner surface. 
     One feature of the present invention is to provide improvements in steering mechanism casings offering the possibility of positioning the pinion by a simple angular displacement of a tubular sleeve or bushing when excessive clearance in the assembly relationship is detected due to teeth wear effects or manufacturing assembly failures. 
     The present invention is related to improvements in a steering mechanism casing for obtaining a proper adjustment in the assembly relationship between pinion and rack bar of the mechanism. In order to achieve the goal, a novel assembly with new improved characteristics is proposed for the pinion inside the casing. By using the proposed invention the pinion may be fixed to the torque bar of vehicle&#39;s steering column in an assembly relationship with the rack bar. 
     This assembly allows a selective regulation of pinion axial positioning with regard to the rack bar and in response to teeth improper clearance generated by deficient adjustment during assembly of the casing or by a functional wear effect on the assembled means, thus compensating assembly differences and avoiding undesirable pounding effects on steering command during driving. 
     The adjustment is achieved by incorporating a bushing or sleeve telescopically assembled inside the casing and fixed to the rack bar casing with free angular clearance. The bushing has an upper flange for resting on the upper edge of the rack, and an outer thread in its lower edge for a roller nut against the lower edge for fixing the bushing in a proper position. 
     The bushing or tubular sleeve has a cylindrical outer surface coaxial to the rack inner surface, and an inner surface eccentric with regard to the outer surface of the bushing that delimits a movement area of a tubular retention and torsional supporting rack for the torque bar (pinion) end of vehicle&#39;s steering column. 
     The lower end of the tubular rack is held or retained against a bushing or sleeve by a “seeger” type washer which avoids axial movements of the rack but allows angular displacements of same in response to torsional loading leaving the rack in contact to the eccentric surface of the bushing through end resilient buckling washers which allow a frictional contact with the surface. 
     By unscrewing the lower retention nut of the bushing an angular displacement of bushing is allowed and therefore the eccentricity of bushing inner surface could be varied transversely with regard to the axis of same, generating a repositioning movement of torque bar axis as well as a pinion approaching to rack bar thus obtaining a desired adjustment of teeth clearance. 
     Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 represents a general plan view of a pinion-rack bar mechanism of a power-assisted steering incorporating the improvements of the present invention. 
     FIG. 2 represents a schematic cross-section showing the assembly of the present invention. 
     FIG. 3 shows another schematically sectional view of FIG. 1 showing bushing eccentricity as well as the functional relationship with regard to tubular rack of torque bar end including the pinion. 
     FIG. 4 shows a schematic plan view of an alternative embodiment of a power steering mechanism for automotive vehicles incorporating the novel assembly of the present invention. 
     FIG. 5 shows a schematically longitudinal section view of the proposed assembly of FIG. 4 inside a casing housing of the mechanism. 
     FIG. 6 shows a transverse cross-sectional view of FIG. 5 showing bushing eccentricity. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is described with respect to a power steering mechanism. Those skilled in the art would recognize the present invention is applicable to various rack and pinion steering systems such as electric, manual, electrohydraulic, and hydraulic. 
     As illustrated in FIGS. 1-3, the improvements proposed by the present invention comprise a steering mechanism incorporated in a casing (c) (see FIG. 1) comprising as is already known in the art a rack bar casing  1  and a pinion casing  2  that is traversely arranged with regard to the casing  1  where rack bar  3  is mounted in relation with pinion  4  integral with a pinion shaft or torque bar  5 . The torque bar  5  may be used to drive valve means  6  of steering column in a hydraulic application. These components are not described in detail as they are known in the steering mechanisms art. 
     In accordance with the present invention, pinion casing  2  includes an assembly for adjusting teeth assembly relationship of rack bar  2  and pinion  4  as is clearly shown in FIGS. 2 and 3. 
     The teeth assembly is defined by a tubular sleeve or bushing  7  telescopically arranged in the pinion casing  2  for allowing angular displacement of the bushing with regard to the inner surface of casing  2 . 
     The tubular sleeve or bushing  7  includes an outer cylindrical surface  7 ′ concentrically and coaxially arranged with regard to casing  2 , and an inner surface  7 ″ eccentrically arranged with regard to outer surface  7 ′. This bushing  7  has a variable thickness wall as is clearly shown in FIG.  3 . 
     The bushing  7  also has an upper holding flange  8  against upper edge  2 ′ of casing  2  and a lower projecting end portion  9  which is projected from inner edge  2 ″ of casing  2  that includes a thread  10  for screwing in a fixing nut  11  of bushing  7  against the lower edge  2 ″ of rack  2 . Thus, this nut  11  allows fastening the bushing  7  in an angular desired position. 
     Inside bushing  7  a pinion housing  12  is concentrically arranged with regard to cylindrical lower surface  7 ″ which in turn is concentrically arranged with regard to outer surface  7 ′. The pinion housing  12  is fastened to torque bar  5  through its upper end including a bearing  13  in its lower end for torque bar end  5 , that is fastened by a nut  14  so that the bearing  13  absorbs torsional stresses when the steering mechanism is driven by rotational movements of vehicle&#39;s steering wheel. 
     Pinion housing  12  is fastened against bearing lower end by a “seeger” type washer  14  having annular ridges  12 ′- 12 ″ with annular grooves  15  for respective square-cross section elastic buckling seals or rings  16   b  permanently rested against eccentric cylindrical inner surface  7 ″ of bushing  7 . Rings  16  help preload the pinion assembly with a force during assembly. 
     Regulation of between-teeth clearance of rack bar  3  and pinion  4  is achieved as follows: nut  11  is unscrewed so that bushing  7  is freed. Using upper flange  8 , bushing  7  may be angularly moved (rotated) provoking a positioning movement of eccentric cylindrical inner surface  7 ″ from a first position relative to casing  2  (See FIG.  3 ). The positioning movement produces a corresponding radial movement (to a second position) in the pinion housing  12  which is fastened to torque bar  5  to vary the assembly relationship of pinion teeth with regard to rack bar teeth. 
     As can be appreciated from the attached figures, the assembly regulation is produced by varying the eccentricity of inner surface  7 ″ of bushing  7  provoking the radial repositioning of the pinion housing  12 . 
     Referring now to FIGS. 4-6, an alternative embodiment of the present invention is illustrated. 
     In accordance with the attached drawings, particularly with reference to FIG. 4, a steering mechanism (m) is shown which comprises a rack bar casing  100  where the rack bar  200  is assembled, in relation with a pinion (not illustrated) of a powering cylinder feeding by conduits from valve related to a vehicle&#39;s steering column through a torque bar  600 . The torque bar  600  includes a pinion  700  assembled inside casing housing  800  which forms an integral part of the rack bar casing  100  and having an aperture  900  through which pinion  700  and rack bar  200  are assembled. 
     In accordance with the present alternative embodiment of the present invention, inside casing housing  100  a cylindrical tubular bushing  110  is concentrically assembled that is projected from upper flange  100 ′ of casing housing  100  and which is related to a rotating dragging nut  111  for dragging bushing  110 . The “dragging” action is achieved by manually driving the nut  111 . 
     Bushing  110  has a cylindrical lateral surface  110 ′ with a free rotating contact against inner surface  100 ″ of casing  100  and an inner surface  110 ″ eccentric with regard to the bushing axis (e). 
     Inside the bushing  110  is freely mounted a portion  112 ′ of piece  112  which includes supporting racks  113  and  114  for torque bar  106  formed by bushing  115  and bearing  116 , supported on rubber rings  117  and  118  of proper hardness in seats  119  and  120  of piece  112  leaving pinion  107  arranged between seats  119 - 120 . Casing wall  110  and piece  112  having apertures  121 - 122  coincident with aperture  109  of housing wall  100 , for relating pinion  107  and rack bar  102 . 
     The way in which pinion  700  is regulated is by screwing or unscrewing nut  111  which in turn determines a radial variation of inner surface  110 ′ eccentricity of bushing  110  producing a radial movement of piece  112  approaching pinion  107  to rack bar  102  in order to achieve a proper assembly relationship between them when an excessive clearance between teeth is detected. 
     Moreover, rings  117  and  118  are made of elastic buckling material to absorb differences between pinion  700  and rack bar  200  to reduce noises and pounding usually found in this kind of mechanisms. 
     While particular embodiments of the invention have been shown and described, numerous variations alternate embodiments will occur to those skilled in the art. Accordingly, it is intended that the invention be limited only in terms of the appended claims.