Abstract:
A brake caliper assembly includes opposing brake shoes positioned on substantially opposing inner surfaces of a dual-disk rotor, wherein said assembly comprises an internal actuator circumferentially arranged between radially inner and outer portions of the rotor, the actuator having an inner surface facing an inboard rotor inner surface and an outer surface facing an outboard rotor inner surface; a plurality of pistons integral to the actuator and displaceable therein by pressurized fluid supplied to the actuator; a first brake shoe mounted to the actuator inner surface and displaceable by the plurality of pistons to engage the inboard rotor inner surface; a pair of pins mounted on the actuator to slide for purposes of transferring a reactionary load; and a second brake shoe mounted to the actuator outer surface and driven by the reactionary load into the outboard rotor inner surface.

Description:
BACKGROUND 
       [0001]    The disclosure is directed generally to a hydraulic brake caliper assembly, and more particularly to a hydraulic brake caliper assembly being circumferentially located between a dual-disk rotor including brake pads internally applied on the dual-disk rotor. 
         [0002]    Automotive vehicle wheel disc brakes rely upon the friction of opposing brake pads gripping a rotor to slow a vehicle such as a car or truck. Conventional brake caliper assemblies cause the brake pads located on opposite sides of a single rotor to apply a braking force against the rotor to generate a braking torque. A piston is supported by the brake caliper assembly and is in contact with the inner brake pad. A stationary member (i.e., caliper bridge) of the brake caliper assembly is positioned proximate to but does not contact the rotor and holds the pads. The caliper bridge thickness is limited by the wheel inside diameter. The stationary member further includes a forward bridge and a rear bridge that each span the outer circumference of the rotor from inboard to outboard. During braking, the inner brake pad is forced against the rotor and a resulting reactionary force pulls the outer brake pad into engagement with the opposite side of the rotor. 
         [0003]    In order to determine the maximum deflection of a pad support structure (i.e., bridge deflection or rotor deflection) and the corresponding brake fluid displacement, a variety of finite element analysis computer dynamic models of hydraulic brake systems simulating different caliper geometry (i.e., externally applied on a single-disk rotor or internally applied on a dual-disk rotor) having a fixed clamping force as an input are created. Elimination of the caliper bridge geometry and its associated deflection, as well as dual-disk rotor deflection management, provides opportunities to enhance a wide range of system parameters such as increased brake pedal stiffness, decreased brake fluid displacement and decreased brake apply pressure. 
       SUMMARY 
       [0004]    According to one aspect, a brake caliper assembly includes opposing brake shoes positioned on substantially opposing inner surfaces of a dual-disk rotor, wherein said assembly comprises an internal actuator circumferentially arranged between radially inner and outer portions of the rotor, the actuator having an inner surface facing the inboard rotor inner surface, and an outer surface facing the outboard rotor inner surface; a plurality of pistons integral to the actuator displaceable by pressurized fluid supplied to the actuator; a first brake shoe mounted to the actuator inner surface and displaceable by the pistons into the inboard rotor inner surface; a pair of pins mounted on the actuator allowing the actuator to slide for purposes of transferring a reactionary load; and a second brake shoe mounted to the actuator outer surface and driven by the reactionary load into the outboard rotor inner surface. 
         [0005]    In another aspect, the brake caliper assembly also includes apparatus for reducing the rotor displacement. 
         [0006]    In another aspect, the brake caliper assembly also includes apparatus for transmitting increasing braking force torque to the rotor, as well as transmitting increasing braking force torque to an associated vehicle axle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawings will be provided by the Office upon request and payment of the necessary fee. 
           [0008]      FIG. 1  is a front perspective, inboard view of one aspect of the disclosed internal brake caliper assembly; 
           [0009]      FIG. 2  is a front perspective view of an internal actuator assembly for the internal brake caliper assembly shown in  FIG. 1 ; 
           [0010]      FIG. 3  is a front perspective view of a brake shoe and lining assembly mounted onto the internal actuator assembly of  FIG. 2 ; 
           [0011]      FIG. 4  is a rear perspective view of the brake shoe and lining assembly of  FIG. 3 ; 
           [0012]      FIG. 5  is a front perspective, inboard view of the internal brake caliper assembly of  FIG. 1 ; 
           [0013]      FIG. 6  is a front perspective, inboard view of the dual rotor assembly of  FIG. 5 ; 
           [0014]      FIG. 7  is a front perspective, inboard view of the internal actuator circumferentially located between the dual-disk rotor of the internal brake caliper assembly of  FIG. 5 ; 
           [0015]      FIG. 8  is a front perspective view of the internal brake caliper assembly of  FIG. 5 , shown without the dual rotor assembly; 
           [0016]      FIG. 9  is an illustration calculated by finite element analysis showing the maximum Von Mises stress for one aspect of the disclosed internal brake caliper assembly; 
           [0017]      FIG. 10  is an illustration calculated by finite element analysis showing the maximum displacement between the rotors for one aspect of the disclosed internal brake caliper assembly; 
           [0018]      FIG. 11  is an illustration calculated by finite element analysis showing the maximum Von Mises stress for a conventional hydraulic brake caliper; and 
           [0019]      FIG. 12  is an illustration calculated by finite element analysis showing the maximum displacement of the caliper bridge for a conventional hydraulic brake caliper. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    As shown in  FIG. 1 , a brake caliper assembly, generally denoted  10 , may include a central mounting face  12  for mounting the assembly  10  on an associated vehicle drive member (not shown), such as a spindle or vehicle axle. The mounting face  12  may be provided with a central pilot aperture  14  in which the spindle hub or the like may be closely received and a plurality of circumferentially spaced-apart fastener apertures  16  in which fasteners (not shown) may be received to mount the assembly  10  on an associated drive mechanism (not shown) in a conventional manner. The brake caliper assembly  10  further includes a peripheral section (also referred to as a dual rotor), generally denoted  20 , an actuator assembly, generally denoted  30 , and a shoe and lining assembly, generally denoted  40 . 
         [0021]    As illustrated in  FIG. 6 , the dual rotor  20  may include a pair of annular braking plates including an outboard braking plate  22  and an inboard braking plate  24 , disposed in a spaced-apart relationship. The dual rotor  20  further includes a central hub  29  disposed in an axial direction between the braking plates  22 ,  24  and through which the vehicle axle (not shown) may be closely received. The first braking plate  22  preferably extends radially from the central mounting face  12 . The outboard and inboard braking plates  22 ,  24  have substantially the same radial dimension and thickness, although alternatively, the braking plates may be of a different radial and/or thickness dimensions. 
         [0022]    As shown in  FIG. 6 , each braking plate  22 ,  24  has a respective inner surface  21 ,  23 . The inner surfaces  21 ,  23  may face each other. Braking plates  22 ,  24  may include outer surfaces  25 ,  26 , respectively. A flat, annular braking surface  27  may be disposed on the inner surface  21  of the first braking plate  22 , and a flat, annular braking surface  28  may be disposed on the inner surface  23  of the second braking plate  24 . The braking surfaces  21 ,  23  may be disposed in a parallel relationship for contact with the brake pads (not shown). 
         [0023]    The tangential direction of the resulting compressive clamping or braking force onto the inner braking surfaces  27 ,  28  of the braking plates  22 ,  24 , respectively is shown by the arrow F, as illustrated in  FIG. 8 . Likewise, the radial distance from the central pilot aperture  14  to the braking surfaces  27 ,  28  is shown by the arrow R, as illustrated in  FIG. 8 . It is well known to those skilled in the art, that braking torque is the product of the resulting compressive clamping force and the radial distance, and consequently, the torque may be increased by an increase in the force, by an increase in the radial distance, or combinations thereof. 
         [0024]    As illustrated in  FIG. 2 , an actuator  30  includes a pair of notches  38  located in the radially extending side walls of the actuator below a pair of pin bores  36 , where each side wall contains a single notch  38  and a single pin bore  36 . A plurality of piston assemblies  31  (see  FIG. 2 ) may be received in the plurality of piston cylinder bores  34 . A single hydraulic opening  32  is provided for the piston bores  34  and is located on the uppermost surface of the actuator assembly  30 . Alternatively, two hydraulic openings may be provided, one for bleeding purposes and the other for connection to a source of brake fluid actuating pressure such as a master cylinder (not shown). The brake fluid actuating pressure will drive the multiple pistons (not shown) into the outer braking pad  42  (see  FIGS. 3 and 4 ) which is driven into an inner braking surface  27  of the outboard braking plate  22 . 
         [0025]    As shown in  FIG. 4 , the actuator  30  ( FIG. 3 ) includes a shoe and lining assembly  40  having a pair of outer braking surfaces  42 ,  44  oriented facing the braking surfaces disposed on the inner surfaces  27 ,  28 , respectively (see  FIG. 6 ). As shown in  FIG. 3 , notches  38  and base portions  39  immediately below the notches on the actuator  30  have two functions. First, the notches  38  receive pins  41  (see  FIG. 1 ) that allow the actuator  30  to slide in order to transfer the reactionary loads to the opposite inner disk surface  28 . Second, once the pads  42 ,  44  are in full contact with both inside disk surfaces  27 ,  28  the braking torque is transferred through the notches  38  to the caliper bracket  33  (see  FIG. 5 ) to the knuckle  35 , and to an associated vehicle axle (not shown). The base portions  39  support the caliper bracket  33  and generally retard circumferential deflection by the caliper bracket  33  from the forces associated with the braking torque. It should be noted that the steering knuckle  35  is the pivot point of the steering system. On vehicles with conventional suspension systems, the spindle of steering knuckle  35  locates and supports the inner and outer wheel bearings (not shown). 
         [0026]    With the embodiments described, the resulting clamping force applied to the dual rotor braking plates  22 ,  24  will only result in a small deflection of the dual rotor braking plates  22 ,  24 , compared to a conventional hydraulic caliper where there is substantial caliper bridge deflection. Both outer rotor surfaces  25 ,  26  (see  FIG. 6 ) are exposed directly and entirely to ambient airflow resulting in an increased heat dissipation. The outer rotor  25 ,  26  surface area available for convective heat transfer may be about twice the single-rotor surface area typically used with conventional brakes. The dual rotor assembly  20  preferably may be cast as a unitary, one-piece rotor, although separate components may be cast and assembled to achieve the finished dual rotor assembly  20 . 
         [0027]    With the embodiments of this disclosure, the need for a caliper bridge may be eliminated, which provides increased brake pedal stiffness and reduced brake response time. Further advantages include an increase in available rotor surface area inside the rotor to increase heat dissipation as well as allow adequate space for multiple pistons. Use of multiple pistons with smaller diameters will generate more braking torque but should also be more responsive (i.e., reduced brake response time) due to the elimination of bridge deflection. The multiple pistons preferably are spaced around the dual disk rotor  20  to increase brake shoe surface area, thereby reducing shoe wear and applying force to the rotor uniformly to reduce shoe taper wear. The specific number of pistons selected for implementation into the actuator assembly  30  can be variable and application dependent. 
         [0028]    During braking, actuator assembly  30  sandwiched between braking plates  22 ,  24 , urges the piston head against the back of the brake shoe and lining assembly  40 , in particular the inner brake shoe  42 , and urges the friction material of the shoe against the braking surface  27  of the outboard braking plate  22 . The reactionary force on the actuator assembly  30  causes the actuator to slide on pins  41  within a channel formed by the region comprising the notches  38  and the caliper bracket  33  which forces the outer brake shoe  44  into the inner brake surface  28  of the inboard braking plate  24 , thereby generating a clamping force or braking force against the braking plates  22 ,  24  which acts to slow the driven vehicle. 
         [0029]    Conversely, upon release of the brake pedal, the brake shoe and lining assembly  40  are pulled away from the braking plates  22 ,  24  by opposite action of the actuator assembly  30 , creating a clearance between the braking plates  22 ,  24  and the actuator assembly  30  sandwiched therebetween, thereby significantly reducing, if not altogether eliminating brake drag. Provision of such a clearance between the actuator assembly  30  and the braking plates  22 ,  24  as well as the degree of clearance created, is understood to be dependent on rotor braking plate  22 ,  24  run out and acceptable predetermined parameters of braking plates  22 ,  24  to brake shoe  42 ,  44  clearance. In conventional hydraulic brake assemblies, a hydraulic seal around an actuating piston thereof is designed to retract the piston from the rotor somewhat, with retraction being dependent on parameters known by those skilled in the art. 
         [0030]    The following non-limiting examples enable certain aspects of the disclosure to be more clearly understood. Other examples are left to the artisan. 
       EXAMPLE 1 
     Conventional Hydraulic Brake System 
       [0031]    A conventional hydraulic brake system (not shown) was tested in simulation using a validated vehicle simulation model. U.S. Pat. No. 6,668,983 to Drennen et al., discloses the operation and assembly of a conventional hydraulic brake caliper having opposing brake pads positioned on opposite sides of a rotor and is incorporated herein by reference. The tests included a simulated 7,000 lb. clamping force placed on both sides of a single rotor by a conventional caliper assembly. The finite element analysis results were presented as Von Mises stress, and maximum displacement. The Von Mises stress is a useful quantitative measurement of tensile loading for a material of construction. As the artisan well knows, a lower tensile loading placed on the rotor material enhances the ability of the rotor material to transmit braking force torque applied by the brake calipers through the caliper assembly and to the vehicle axle. The inside diameter of the wheel is disposed directly above the caliper bridge, thereby limiting the allowable bridge thickness and consequently, the allowable dimensions for the caliper assembly. It is well known by those in the art, that a thinner bridge significantly increases the maximum displacement of the bridge, and conversely, reduces the stiffness of the brake pedal. Said another way, brake pedal stiffness may be characterized as a low displacement in a braking system. A low displacement is highly desirable in a brake system, as less displacement translates into a shorter response time for the braking system. As the piston and piston bore is a component of the caliper assembly, the piston bore size is limited for the same reasons as the bridge thickness detailed above. 
         [0032]    In Example 1, one piston element having a bore diameter of 52 mm and operating with a 2,000 psi hydraulic pressure generated a 0.037 inch displacement in the caliper bridge, as illustrated in  FIG. 10  at point  70 . Said another way, for the piston to move 0.037 inches requires 111 mm 3  hydraulic fluid displacement from the master cylinder, which results in a delayed response time for the conventional hydraulic braking system. The Von Mises stress result was 60,000 psi, as illustrated in  FIG. 9  at point  60 . 
       EXAMPLE 2 
     Internal Brake Caliper Assembly 
       [0033]    An internal brake caliper assembly (shown in  FIG. 1 ) was tested in simulation using the validated vehicle simulation model, as in Example 1. The tests included a simulated 7,000 lb. clamping force placed on the inner surfaces of a dual rotor by an internal caliper assembly. The finite element analysis results were presented as Von Mises stress, and maximum displacement. The internal brake caliper assembly did not include a caliper bridge and consequently did not suffer from the thickness limitations of said bridge. Furthermore, the pistons and pistons bores are components of the actuator assembly, and consequently do not suffer from the piston bore size limitations of the caliper assembly of Example 1. 
         [0034]    In Example 2, four piston elements, each having a bore diameter of 38 mm and operating with a 1,000 psi hydraulic pressure generated a 0.012 inch displacement in the rotor braking plates (i.e., rotor coning), as illustrated in  FIG. 12  at point  90 . Said another way, for the pistons to move 0.012 inches requires 54 mm 3  hydraulic fluid displacement from the master cylinder, which results in approximately one-half the delayed response time for the internal brake caliper assembly, as compared to Example 1. The Von Mises stress result was 16,000 psi, as illustrated in  FIG. 11  at point  80 , which enables the internal brake caliper assembly to transmit an additional 44,000 psi of braking torque, as compared to Example 1. 
         [0035]    Having described the disclosure in detail and by reference to specific embodiments thereof, it will be apparent that numerous variations and modifications are possible without departing from the spirit and scope of the disclosure as defined by the following claims.