Abstract:
The dragless brake assembly which can be either hydraulic or electrical incorporates a ballscrew engaged to the inner brake assembly, and an outer brake assembly engaged to a sliding caliper housing, the ballscrew and caliper housing being mechanically engaged to move in directions opposite each other simultaneously between predefined limits for application or release of braking.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application is a continuation in part of U.S. application Ser. No. 09/634,900 filed Aug. 9, 2000 and entitled Electric Brake Caliper, which application claims priority from U.S. Provisional application Ser. No. 60/167,345, filed Nov. 24, 1999. 
     
    
     
       TECHNICAL FIELD  
         [0002]    The present invention relates to dragless automotive braking systems of both the hydraulic and electric type incorporating a sliding brake caliper assembly. More particularly, the dragless brake caliper assembly of the present invention substantially reduces, if not altogether eliminates, brake drag, by incorporating an antirotation ballscrew therein, in place of the typical piston assembly presently used in calipers of the electric and hydraulic type.  
         BACKGROUND OF THE INVENTION  
         [0003]    Heretofore, automotive brake assemblies, both of the hydraulic and electric caliper type, have inherently incorporated drag during braking which decreases fuel economy, shortens the useful life of brake linings, and complicates required brake suspension design to accommodate for the drag created by the assembly.  
           [0004]    Accordingly, there is a need in the industry for a dragless brake caliper assembly, which will overcome shortfalls inherent in the prior art.  
           [0005]    An exemplary brake caliper of the electric type to which the improvement of the subject application applies is disclosed in U.S. application Ser. No. 09/634,900 filed on Aug. 9, 2000 and entitled Electric Brake Caliper, the teachings of which are incorporated herein by reference.  
         SUMMARY OF THE INVENTION  
         [0006]    According to the invention there is provided a brake caliper assembly comprising at least an inner brake assembly mounted to a reciprocable actuating mechanism and an outer brake assembly mounted to a sliding caliper housing, the actuating mechanism and the sliding caliper housing being mechanically engaged in a manner to move opposite each other about a wheel rotor positioned between the brake assemblies, the actuating mechanism comprising a driven ballscrew reciprocating between a predefined home position retracting both brake assemblies and a predefined braking position engaging the assemblies against the rotor. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a perspective view of the brake caliper assembly of the present invention as viewed toward an inner caliper of the assembly;  
         [0008]    [0008]FIG. 2 is a perspective view of the brake caliper assembly of the present invention as viewed toward an outer caliper of the assembly;  
         [0009]    [0009]FIG. 3 is a perspective view of the brake caliper assembly of the present invention as viewed toward a housing of the caliper assembly; and  
         [0010]    [0010]FIG. 4 is a perspective view of the brake caliper assembly of the present invention as viewed toward a mounting bracket thereof.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0011]    The structure proposed herein, which is equally applicable to both electric and hydraulic brake calipers, incorporates an antirotation ballscrew for activation of the caliper within defined limits, which has been found through empirical testing to significantly reduce, if not altogether eliminate brake drag.  
         [0012]    To provide a simple overview of the functionality of a caliper assembly, the following synopsis is provided.  
         [0013]    Various types of brake systems are known for use in automotive vehicles. Such brake systems include, for example, hydraulic brakes, anti-lock brakes and electric brakes. Electric brake systems (also referred to as “brake by wire” systems) utilize caliper mechanisms that incorporate an electric motor for driving a gear assembly positioned within the caliper housing, which, in turn, drives an inner brake pad against a brake rotor disc of a vehicle. A second, outer brake pad mounted to the caliper housing is positioned on an opposite side of the rotor disc. During braking, the inner brake pad is forced against the rotor disc and a resulting reactionary force pulls the outer break pad into engagement with the opposite side of the disc. Engagement of the inner and outer brake pads will slow or stop rotation of the rotor disc, and, in turn, slow the vehicle or hold the vehicle in a fixed position.  
         [0014]    A load sensor is typically positioned to detect the amount of force applied by the inner break pad to the rotor disc. This load sensor is operatively coupled to a mechanism for controlling the position of the caliper housing, and in turn, the force applied by the outer break pad to equalize (or “center”) the force applied by the two brake pads on the rotor disc.  
         [0015]    Such caliper assembly includes at least a brake caliper that comprises a caliper housing having a rotor channel adapted to receive a rotor (such as a rotor disc) therein, where the rotor channel has a first axial surface adapted to seat an outer brake pad thereon. The brake caliper also includes a piston assembly mounted to the housing on an axial side of the rotor channel opposite that of the outer brake pad. The piston assembly includes a piston nut, reciprocatable towards and away from the rotor channel, where the piston nut is adapted to seat an inner brake pad thereon, a driven screw threaded into the piston nut, which axially drives the piston nut towards or away from the rotor disc in the rotor channel.  
         [0016]    As illustrated in FIGS.  1 - 4 , the brake caliper assembly  10  of the present invention which is applicable for use in either an electric or hydraulic braking system includes an inner brake assembly  12  comprising an inner brake pad  14  suitably mounted to an inner brake shoe  16 . The inner brake shoe  16  is suitably fixed to a drive mechanism  18  therefore, which in the preferred embodiment disclosed herein comprises a ball nut  19  of a ball screw  20 . An outer brake assembly  22  comprising a brake pad  24  suitably mounted to an outer brake shoe  26  is suitably attached on the other hand, to a caliper housing  28  via the brake shoe  26 . A caliper bracket  30  is also incorporated into the assembly  10 , the bracket  30  serving as a brake pad guide, and a load transfer mechanism, with the caliper housing  28  being mounted on and reciprocably slidable along a mounting rod  31  of the bracket  30  within predefined limits.  
         [0017]    In operation, during application of the brakes by a driver through brake pedal (not shown) actuation, the inner brake assembly  12  is moved toward outer brake assembly  22  driving brake pad  14  mounted to brake shoe  16  of the assembly  12  against and into an inner rotor face (not shown). Reactionary force, due to mechanical engagement between the ballscrew  20  and the caliper housing  28 , causes the caliper housing  28  to move in a direction opposite that of the ball nut  18 , pulling outer brake assembly  22  attached thereto into an outer rotor face (not shown), with the assemblies  12  and  22  clamping the rotor therebetween and creating desired braking. This scenario, as stated above, is applicable to either hydraulic or electric braking systems.  
         [0018]    Conversely, upon release of the brake pedal by the driver, the brake assemblies  12  and  22  are pulled away from the rotor by opposite action of the drive mechanism  18  and reaction of the caliper housing  28 , creating a clearance between the assemblies  12  and  22  and the rotor sandwiched therebetween.  
         [0019]    In conventional hydraulic brake assemblies, a hydraulic seal around an actuating piston (not shown) thereof is designed to retract the piston from the rotor somewhat, with retraction being dependent on a sliding bracket suspension, the applied force, and the time duration for rubber to contract, as is known.  
         [0020]    In the assembly  10  of the present invention, however, when the ballscrew  20  is incorporated into the assembly  10  in place of the conventional piston assembly, when the inner brake assembly  12  is retracted and reaches a home position against stop  40  on bracket  30 , an axial load is transferred to the caliper housing  28  slidably mounted to the rod  31  of bracket  30 , moving the housing  28  in a direction opposite that of inner brake assembly  12  retraction and thus simultaneously moving the outer brake assembly  22  away from the rotor, in an action opposite that incurred during brake application, creating a clearance between the brake assemblies  12  and  22  and the rotor therebetween, thereby significantly reducing, if not altogether eliminating brake drag.  
         [0021]    Provision of such a clearance between the brake assemblies  12  and  22  and the rotor, as well the degree of clearance created, is understood to be dependent on rotor run out and acceptable predetermined parameters of rotor to pad clearance. The position of the pads  14  and  24  of the assemblies  12  and  22 , respectively, as they relate to position of the rotor therebetween, may be monitored by a motor position encoder (not shown) or alternatively by a position sensor (not shown) which may be located on the ballscrew  20  itself, if required.  
         [0022]    In the assembly  10 , it is understood that predetermined parameters of rotor to pad clearance also take into account wheel speed, with low speeds requiring a greater degree of clearance and high speeds requiring a lesser degree of clearance.  
         [0023]    As described above, the assembly  10  provides a number of advantages, some of which have been described above and others of which are inherent in the invention. Also modifications may be proposed without departing from the teachings herein. Accordingly the scope of the invention is only to be limited as necessitated by the accompanying claims.