Patent Description:
In at least one embodiment a brake assembly is provided. The brake assembly
according to the invention includes a brake caliper, a tappet, a piston, and a wear adjuster mechanism. The tappet is moveable along an axis with respect to the brake caliper. The tappet is adapted to engage a brake pad assembly. The tappet has an inner thread. The piston is rotatable about the axis and is at least partially received in the tappet. The piston has an outer thread that mates with the inner thread. The wear adjuster mechanism is at least partially received inside the piston. The wear adjuster mechanism includes a shaft and a wrap spring. The shaft is rotatable about the axis. The wrap spring is received inside the piston and encircles the shaft. The wrap spring engages the piston and the shaft. The wrap spring is configured to slip with respect to the piston but not slip with respect to the shaft when the wrap spring is rotated in a first rotational direction. The wrap spring is configured to slip with respect to the shaft but not slip with respect to the piston when the wrap spring is rotated in a second rotational direction. The first rotational direction is disposed opposite the second rotational direction.

The wrap spring may contact the piston and the shaft. A first amount of surface area of the wrap spring that contacts the piston may be greater than a second amount of surface area of the wrap spring that contacts the shaft.

The piston may have a piston hub. The piston hub may be disposed opposite the outer thread. The piston hub may protrude toward the axis. The wrap spring may engage the piston hub.

The piston may have a piston wall. The piston wall may be disposed opposite the outer thread. The piston wall may protrude farther toward the axis than the piston hub. The wrap spring may engage the piston wall.

The brake assembly may include a first bearing assembly. The first bearing assembly may be disposed inside the piston. The first bearing assembly may rotatably support the piston with respect to the shaft. The wrap spring may extend from the first bearing assembly.

The piston may have a first piston end and a second piston end disposed opposite the first piston end. The piston hub may be spaced apart from the first piston end. The piston hub may be spaced apart from the second piston end. The piston hub may extend from the piston wall toward the first piston end.

The shaft may have a shaft hub. The shaft hub may protrude away from the axis. The wrap spring may engage the shaft hub. The shaft hub may extend from the first bearing assembly. The shaft hub may be axially offset from the piston hub such that the piston hub does not encircle the shaft hub.

The shaft may have a first shaft end and a second shaft end. The second shaft end may be disposed opposite the first shaft end. The shaft hub may be spaced apart from the first shaft end and the second shaft end.

The shaft may have an intermediate shaft surface. The intermediate shaft surface may face away from the axis. The shaft hub may extend farther away from the axis than the intermediate shaft surface extends from the axis. The intermediate shaft surface may extend from the shaft hub toward the second piston end. The wrap spring may encircle the intermediate shaft surface. The wrap spring may be spaced apart from the intermediate shaft surface. The piston hub may encircle the intermediate shaft surface. The piston hub may be spaced apart from the intermediate shaft surface.

The brake assembly may include a second bearing assembly. The second bearing assembly may be disposed inside a yoke. The second bearing assembly may rotatably support the shaft with respect to the yoke. The wrap spring may be the only component that is positioned between the piston and the shaft that is axially positioned between the first bearing assembly and the yoke and that is positioned closer to the axis than the piston and farther from the axis than the shaft.

In at least one embodiment a method of controlling a brake assembly is provided. The method includes rotating a shaft in a first rotational direction about an axis. The shaft is disposed inside of a piston that is rotatable about the axis and that is received in a tappet. The tappet is moveable along the axis with respect to a brake caliper and is adapted to engage a brake pad assembly. The tappet and the piston have mating inner and outer threads, respectively. A wrap spring is received inside the piston and engages the piston and the shaft. The wrap spring engages the piston and the shaft. Rotating the shaft and the first rotational direction may tighten the wrap spring against the shaft such that the wrap spring does not slip with respect to the shaft and such that the wrap spring slips with respect to the piston when sufficient torque is applied to the shaft in the first rotational direction.

The method may include rotating the shaft in a second rotational direction that is disposed opposite the second rotational direction. Rotating the shaft in the second rotational direction tightens the wrap spring against the piston such that the wrap spring does not slip with respect to the piston and such that the wrap spring slips with respect to the shaft when sufficient torque is applied to the shaft in the second rotational direction.

The wrap spring slips with respect to the piston when a first amount of torque is applied in the first rotational direction. The wrap spring slips with respect to the shaft when a second amount of torque is applied in the second rotational direction. The second amount of torque is less than the first amount of torque.

As required, detailed embodiments of the present invention are disclosed herein. It is to be understood that the disclosed embodiments are merely exemplary and that various and alternative forms are possible. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ embodiments according to the invention.

It will also be understood that, although the terms first, second, etc. are, in some instances, used herein to describe various elements, these elements should not be limited by these terms. For example, a first element could be termed a second element, and similarly a second element could be termed a first element without departing from the scope of the various described embodiments. The first element and the second element are both elements, but they are not the same element.

The terminology used in the description of the various described embodiments is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various described embodiments and the appended claims, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms "includes," "including," "comprises," and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Referring to <FIG>, an example of a brake assembly <NUM> is shown. The brake assembly <NUM> may be provided as part of a vehicle, such as a motor vehicle like a truck, bus, farm equipment, military transport or weaponry vehicle, or cargo loading equipment for land, air, or marine vessels.

The brake assembly <NUM> is configured as a disc brake. In at least one configuration, the brake assembly <NUM> includes a brake carrier <NUM>, a brake caliper <NUM>, a pair of brake pad assemblies <NUM>, and optionally a retainer bracket <NUM>. Referring primarily to <FIG> and <FIG>, the brake assembly <NUM> includes components that may facilitate movement of the brake pad assemblies <NUM>, such as a tappet <NUM>, a piston <NUM>, and a wear adjuster mechanism <NUM>, and may include a brake actuator <NUM>, an operating shaft <NUM>, a yoke <NUM>, a tappet <NUM>, a piston <NUM>, a wear adjuster mechanism <NUM>, a retraction spring <NUM>, or combinations thereof. In addition, the brake assembly <NUM> may include a sensor assembly <NUM> that may be in communication with a controller <NUM>. The brake assembly <NUM> will primarily be described below with a configuration that has one tappet and piston; however, it is contemplated that the brake assembly <NUM> may be provided with multiple tappets and/or pistons.

Referring to <FIG>, the brake carrier <NUM> facilitates mounting of the brake assembly <NUM> to the vehicle. The brake carrier <NUM> may be fixedly mounted to a vehicle component. For example, the brake carrier <NUM> may be directly or indirectly mounted to an axle assembly or a steering knuckle. The brake carrier <NUM> may receive and support the brake pad assemblies <NUM> in a manner that permits the brake pad assemblies <NUM> to move along an axis toward and away from a brake rotor <NUM> while inhibiting rotation of the brake pad assemblies <NUM> about the axis. The brake carrier <NUM> may include a rotor opening that may receive the brake rotor <NUM>. As such, the brake carrier <NUM> may straddle the brake rotor <NUM> and help position the brake pad assemblies <NUM> on opposite sides of the brake rotor <NUM>.

Referring to <FIG> and <FIG>, the brake caliper <NUM> is moveably disposed on the brake carrier <NUM>. The brake caliper <NUM> receives various components of the brake assembly <NUM>. In addition, the brake caliper <NUM> facilitates positioning of the brake pad assemblies <NUM> with respect to the brake rotor <NUM> to facilitate braking of the vehicle. In at least one configuration, the brake caliper <NUM> may include a caliper housing <NUM> and a caliper bridge <NUM>.

The caliper housing <NUM> is moveably disposed on the brake carrier <NUM>. For example, the caliper housing <NUM> may be slidably disposed on a pair of guide pins that may be fixedly disposed on the brake carrier <NUM>. As is best shown in <FIG>, the caliper housing <NUM> may facilitate mounting of the brake actuator <NUM> and may define a cavity <NUM> and an opening <NUM>.

The cavity <NUM> may receive or partially receive various components that facilitate movement of the brake pad assemblies <NUM>, such as the operating shaft <NUM>, yoke <NUM>, tappet <NUM>, piston <NUM>, wear adjuster mechanism <NUM> and retraction springs <NUM>. The cavity <NUM> may have an aperture that may face toward the brake rotor <NUM> and that may be at least partially enclosed by a cover plate <NUM> that may be fixedly mounted to the caliper housing <NUM>, such as with fasteners like bolts.

The opening <NUM> may extend from the cavity <NUM>. For instance, the opening <NUM> may extend through a back side of the caliper housing <NUM> that may face away from the brake rotor <NUM>. In at least one configuration, a shaft of the brake actuator <NUM> may extend through the opening <NUM> to facilitate actuation of the operating shaft <NUM>. The opening <NUM> may be disposed above an axis <NUM>.

Referring to <FIG> and <FIG>, the caliper bridge <NUM> may be integrally formed with or may be fixedly disposed on the caliper housing <NUM>. For example, the caliper bridge <NUM> may be generally C-shaped and may be coupled to the caliper housing <NUM> with one or more fasteners, such as bolts. In at least one configuration, the caliper bridge <NUM> may cooperate with the caliper housing <NUM> to at least partially define an opening <NUM> that may facilitate insertion and removal of the brake pad assemblies <NUM>.

Referring to <FIG>, a pair of brake pad assemblies <NUM> are configured to be received in and supported by the brake carrier <NUM>. The brake pad assemblies <NUM> may be disposed on opposite sides of the brake rotor <NUM> and may be engageable with the brake rotor <NUM> to slow rotation of the brake rotor <NUM> and an associated wheel about a brake rotor axis of rotation <NUM>. The brake rotor axis of rotation <NUM> may be offset from and may extend substantially parallel to the axis <NUM>. One brake pad assembly <NUM> may be positioned between the caliper housing <NUM> and the brake rotor <NUM> and may be referred to as an inboard brake pad assembly <NUM>. The brake pad assembly <NUM> located on the opposite side of the brake rotor <NUM> may be positioned between the caliper bridge <NUM> and the brake rotor <NUM> and may be referred to as an outboard brake pad assembly <NUM>. Each brake pad assembly <NUM> may include a backplate <NUM> and friction material <NUM>.

The backplate <NUM> is a structural member of a brake pad assembly <NUM>. The backplate <NUM> may be configured as a generally flat plate and may be made of any suitable material, such as metal or a metal alloy. As is best shown in <FIG>, a side of the backplate <NUM> that faces away from the friction material <NUM> may engage or contact the tappet <NUM>.

The friction material <NUM> is disposed on a side of the backplate <NUM> that faces toward the brake rotor <NUM>. The friction material <NUM> may contact the brake rotor <NUM> during vehicle braking.

Referring to <FIG>, the retainer bracket <NUM> may be removably mounted to the brake caliper <NUM>. For example, the retainer bracket <NUM> may extend across the brake pad assemblies <NUM> and the opening <NUM> in the brake caliper <NUM> to help retain the brake pad assemblies <NUM> in the brake carrier <NUM> when the retainer bracket <NUM> is secured to the brake caliper <NUM>. Conversely, the retainer bracket <NUM> may be detached from or removed from the brake caliper <NUM> to permit removal of the brake pad assemblies <NUM> or installation of the brake pad assemblies <NUM> via the opening <NUM>.

Referring to <FIG>, the brake actuator <NUM> is configured to provide force to actuate the brake pad assemblies <NUM>. The brake actuator <NUM> may be mounted to the brake caliper <NUM>. In at least one configuration, the brake actuator <NUM> may be mounted to the back side of the caliper housing <NUM> and may have a brake actuator shaft that may extend through the opening <NUM> in the caliper housing <NUM>. The brake actuator shaft may engage the operating shaft <NUM> and may be moveable to rotate the operating shaft <NUM>.

Referring to <FIG>, <FIG>, and <FIG>, the operating shaft <NUM> may transmit force from the brake actuator <NUM> other moveable components of the brake assembly <NUM>. In at least one configuration, the operating shaft <NUM> may generally be configured like an inverted "Y" and may include a lever <NUM>, at least one cam <NUM>, and a tab <NUM>.

Referring to <FIG>, the lever <NUM> may extend from the cams <NUM> toward the opening <NUM>. The lever <NUM> may have a pocket that may receive an end of the brake actuator shaft.

Referring to <FIG> and <FIG>, the cams <NUM> may be spaced apart from each other such that a gap <NUM> is provided between the cams <NUM>. In at least one configuration, the cams <NUM> may have mirror symmetry with respect to each other. In at least one configuration, a cam <NUM> may include a concave recess <NUM> and a convex surface <NUM>.

Referring to <FIG>, the concave recess <NUM> may receive a corresponding roller <NUM>. The roller <NUM> may be supported by a corresponding arcuate surface in the cavity <NUM> of the caliper housing <NUM> and may be rotatable about a roller axis of rotation <NUM>, which is best shown in <FIG>.

Referring to <FIG>, the convex surface <NUM> may be disposed opposite the concave recess <NUM>. The convex surface <NUM> may engage a corresponding set of roller bearings <NUM> that may be disposed between the convex surface <NUM> and the yoke <NUM>. The rollers <NUM> and roller bearings <NUM> may facilitate rotation of the operating shaft <NUM> about an axis of rotation.

Referring to <FIG> and <FIG>, a tab <NUM> may extend from at least one of the cams <NUM> into the gap <NUM>. A ball pin <NUM> may be fixedly mounted to the tab <NUM> and may extend toward the wear adjuster mechanism <NUM> as will be discussed in more detail below. In at least one configuration, the ball pin <NUM> may have a generally spherical or rounded ball at its distal end.

Referring to <FIG>, the yoke <NUM> is disposed between the operating shaft <NUM> and the piston <NUM>. In at least one configuration, the yoke <NUM> may include a concave surface <NUM>, an engagement surface <NUM>, a through hole <NUM>, and a ring <NUM>.

Referring primarily to <FIG>, the concave surface <NUM> may face toward the operating shaft <NUM> and may engage the roller bearings <NUM>.

The engagement surface <NUM> may be disposed opposite the concave surface <NUM>. The engagement surface <NUM> may engage or contact the piston <NUM>.

The through hole <NUM> may receive at least a portion of the wear adjuster mechanism <NUM>. In at least one configuration, such as a configuration having a single piston <NUM>, the through hole <NUM> may be disposed proximate the center of the yoke <NUM> and may extend around the axis <NUM>.

The ring <NUM> may encircle a portion of the through hole <NUM>. The ring <NUM> may protrude from the engagement surface <NUM> in a direction that extends away from the concave surface <NUM>. The ring <NUM> may be encircled by an may engage the piston <NUM>.

Referring primarily to <FIG> and <FIG>, the tappet <NUM> is moveable along the axis <NUM> with respect to the caliper housing <NUM>. The brake carrier <NUM> may inhibit or prevent the tappet <NUM> from rotating about the axis <NUM>. The tappet <NUM> may protrude away from the cavity <NUM> of the caliper housing <NUM> and may have a generally hollow body that includes an inner thread <NUM> and an engagement face <NUM>.

The inner thread <NUM> may face toward the axis <NUM> and may extend around the axis <NUM>.

The engagement face <NUM> may face away from the cavity <NUM>. The engagement face <NUM> may engage or contact the inboard brake pad assembly <NUM>. For example, the engagement face <NUM> may engage or contact a side of the backplate <NUM> that may be disposed opposite the friction material <NUM>.

Referring to <FIG>, <FIG>, and <FIG>, the piston <NUM> is at least partially received inside the tappet <NUM>. The piston is rotatable about the axis <NUM>. In addition, the piston <NUM> may be moveable along the axis <NUM>. In at least one configuration, the piston <NUM> may have a hollow tubular configuration that may extend from a first piston end <NUM> to a second piston end <NUM>. As is best shown in <FIG>, the piston <NUM> includes an outer thread <NUM> and may include, a piston hub <NUM>, a piston wall <NUM>, and optionally an end cap <NUM>.

The first piston end <NUM> may face away from the yoke <NUM> and may face toward the closed end of the tappet <NUM>. As such, the first piston end <NUM> may face toward the left from the perspective shown in <FIG>.

The second piston end <NUM> may be disposed opposite the first piston end <NUM>. As such, the second piston end <NUM> may face toward the yoke <NUM>, or to the right from the perspective shown in <FIG>. The second piston end <NUM> may engage or contact the engagement surface <NUM> of the yoke <NUM>.

The outer thread <NUM> may face away from the axis <NUM> and may extend around the axis <NUM>. The outer thread <NUM> mates with the inner thread <NUM> of the tappet <NUM>. As such, the tappet <NUM> and the piston <NUM> have mating threads.

The piston hub <NUM> may be disposed opposite the outer thread <NUM>. As such, the piston hub <NUM> may face toward the axis <NUM>. In addition, the piston hub <NUM> may protrude toward the axis <NUM> or extend farther toward the axis <NUM> than an adjacent inside surface or inside circumferential surface of the piston <NUM>. The piston hub <NUM> may be axially positioned or positioned with respect to the axis <NUM> between the first piston end <NUM> and the second piston end <NUM>. For instance, the piston hub <NUM> may be spaced apart from the first piston end <NUM>, the second piston end <NUM>, or both. The piston hub <NUM> may engage a wrap spring <NUM> of the wear adjuster mechanism <NUM> as will be discussed in more detail below.

The piston wall <NUM>, if provided, may be disposed opposite the outer thread <NUM>. The piston wall <NUM> may protrude toward the axis <NUM>. For example the piston wall <NUM> may protrude farther toward the axis <NUM> than the piston hub <NUM> but may be spaced apart from a shaft <NUM> of the wear adjuster mechanism <NUM>. In at least one configuration, the piston hub <NUM> may extend from the piston wall <NUM> toward the first piston end <NUM> or to the left from the perspective shown. In the configuration shown, the piston wall <NUM> extends substantially perpendicular to the axis <NUM>. The piston wall <NUM>, if provided, may help position and constrain axial movement of a wrap spring <NUM> of the wear adjuster mechanism <NUM>. For instance, the wrap spring <NUM> may engage the piston wall <NUM>. However, it is contemplated that the piston wall <NUM> may be omitted and that the wrap spring <NUM> may engage another component, such as the yoke <NUM>. Optionally, the piston wall <NUM> may include a hook portion <NUM> that may extend away from the yoke <NUM> and generally toward the first piston end <NUM>. The hook portion <NUM> may help position the wrap spring <NUM> or receive a coil of the wrap spring <NUM> to help center the wrap spring <NUM> with respect to the axis <NUM>.

Referring to <FIG>, <FIG>, and <FIG>, the end cap <NUM>, if provided, may be disposed at an end of the piston <NUM> that may face toward the brake pad assembly <NUM> and the tappet <NUM>. The end cap <NUM> may be integrally formed with the body of the piston <NUM> or may be provided as a separate component. In the configuration shown, the end cap <NUM> is provided as a separate component that may be received in the hollow body of the piston <NUM>. The end cap <NUM> may be fixed to the piston <NUM> such that the piston <NUM> is not rotatable with respect to the end cap <NUM>.

Referring to <FIG>, the wear adjuster mechanism <NUM> is configured to maintain a desired running clearance between the brake pad assemblies <NUM> and the brake rotor <NUM> when the brake pad assemblies <NUM> are retracted. As an overview, the wear adjuster mechanism <NUM> may include a bidirectional wrap spring that may permit the axial position of a brake pad assembly along the axis <NUM> to be adjusted or move closer to the brake rotor <NUM> in response to wear of the friction material <NUM>. The wear adjuster mechanism <NUM> is at least partially received inside the piston <NUM>. In at least one configuration and as is best shown with reference to <FIG>, <FIG>, and <FIG>, the wear adjuster mechanism <NUM> includes a shaft <NUM>, a wrap spring <NUM>, a first bearing assembly <NUM>, and a second bearing assembly <NUM>.

The shaft <NUM> may be at least partially received in the cavity <NUM> of the caliper housing <NUM>. The shaft <NUM> may be disposed in the through hole <NUM> of the yoke <NUM> and inside the hole or cavity of the piston <NUM>. In addition, the shaft <NUM> may be spaced apart from the yoke <NUM> and the piston <NUM>. The shaft <NUM> may extend from a first shaft end <NUM> to a second shaft end <NUM>. The shaft <NUM> may be rotatable about the axis <NUM> and may define a shaft cavity <NUM>, a ball pin engagement feature <NUM>, a shaft hub <NUM>, and an intermediate shaft surface <NUM>.

Referring primarily to <FIG> and <FIG>, the first shaft end <NUM> may face away from the yoke <NUM> and may face toward the closed end of the tappet <NUM>. As such, the first shaft end <NUM> may face toward the left from the perspective shown in <FIG>.

The second shaft end <NUM> may be disposed opposite the first shaft end <NUM>. As such, the second shaft end <NUM> may face toward the yoke <NUM>, or to the right from the perspective shown in <FIG>.

The shaft cavity <NUM> may extend along the axis <NUM>. In at least one configuration, the shaft cavity <NUM> may be configured as a through hole that may extend along the axis <NUM> from the first shaft end <NUM> to the second shaft end <NUM>. A portion of the shaft cavity <NUM> that may be received inside the yoke <NUM> may have a larger diameter than a portion of the shaft cavity <NUM> that may be received inside the piston <NUM>.

Referring primarily to <FIG>, the ball pin engagement feature <NUM> may be configured to engage the ball pin <NUM>. The ball pin engagement feature <NUM> may be disposed proximate the second shaft end <NUM> and may be offset from the axis <NUM>. In the configuration shown, the ball pin engagement feature <NUM> is configured as a recess that may receive the ball pin <NUM>. The ball pin <NUM> may extend at an angle with respect to the axis <NUM> such that rotation of the operating shaft <NUM> may cause the ball pin <NUM> to engage a side or surface of the ball pin engagement feature <NUM> in a manner that may rotate the shaft <NUM> about the axis <NUM>. It is also contemplated that the ball pin engagement feature <NUM> may have a male configuration and the ball pin <NUM> may have a female configuration in other configurations.

Referring primarily to <FIG> and <FIG>, the shaft hub <NUM> may face away from the axis <NUM>. In addition, the shaft hub <NUM> may protrude away from the axis <NUM> or extend farther away from the axis <NUM> than an adjacent outside surface or outside circumferential surface of the shaft <NUM>. The shaft hub <NUM> may be axially positioned or positioned with respect to the axis <NUM> between the first shaft end <NUM> and the second shaft end <NUM>. For instance, the shaft hub <NUM> may be spaced apart from the first shaft end <NUM>, the second shaft end <NUM>, or both. The shaft hub <NUM> may be axially offset from the piston hub <NUM> such that the piston hub <NUM> does not encircle the shaft hub <NUM>. The shaft hub <NUM> may extend from the first bearing assembly <NUM> in a direction that extends toward the second shaft end <NUM>. The wrap spring <NUM> engages the shaft hub <NUM>.

The intermediate shaft surface <NUM> may face away from the axis <NUM>. As such, the intermediate shaft surface <NUM> may be an outside circumferential surface of the shaft <NUM>. The intermediate shaft surface <NUM> may be disposed closer to the axis <NUM> than the shaft hub <NUM> is disposed to the axis <NUM>. The intermediate shaft surface <NUM> may extend from the shaft hub <NUM> toward the second shaft end <NUM>. The intermediate shaft surface <NUM> may extend axially from an end of the shaft hub <NUM> toward the second shaft end <NUM>. The piston hub <NUM> and the wrap spring <NUM> may encircle the intermediate shaft surface <NUM>. In addition, the piston <NUM> and the wrap spring <NUM> may be spaced apart from the intermediate shaft surface <NUM>.

The wrap spring <NUM> controls relative rotation of the piston <NUM> and the shaft <NUM>. The wrap spring <NUM> is received inside the piston <NUM> and encircles or coils around the shaft <NUM>. In addition, the wrap spring <NUM> is configured to engage or contact the piston <NUM> and the shaft <NUM>. For instance, the wrap spring <NUM> may engage or contact the piston hub <NUM> of the piston <NUM> and the shaft hub <NUM> of the shaft <NUM>. The wrap spring <NUM> may extend axially between the first bearing assembly <NUM> and the second bearing assembly <NUM>. For instance, the wrap spring <NUM> may extend from the first bearing assembly <NUM> to the piston wall <NUM>. The wrap spring <NUM> may encircle the intermediate shaft surface <NUM> but may be spaced apart from the intermediate shaft surface <NUM>. In at least one configuration, the wrap spring <NUM> may not be received inside the through hole <NUM> or ring <NUM> of the yoke <NUM>.

Referring to <FIG>, the wrap spring <NUM> may be the only component that is positioned between the piston <NUM> and the shaft <NUM> in the region that extends axially from the first bearing assembly <NUM> to the yoke <NUM>. For instance, the wrap spring <NUM> may be the only component or moveable component that is axially positioned between the first bearing assembly <NUM> and the yoke <NUM> and that is radially positioned closer to the axis <NUM> than the piston <NUM> and farther from the axis <NUM> than the shaft <NUM>. As such, the present invention may provide a simpler design than other wear adjuster mechanisms and may not include additional wear adjuster mechanism components such as a drum, disc pack, spacer, additional biasing member or spring, or combinations thereof. The wrap spring <NUM> may be the only component that engages the piston hub <NUM> and the shaft hub <NUM>.

The amount of surface area of the wrap spring <NUM> that contacts the piston <NUM> may differ from the amount of surface area of the wrap spring <NUM> that contacts the shaft <NUM>. For instance, a first amount of surface area of the wrap spring <NUM> may contact the piston <NUM> while a second amount of surface area may contact the shaft <NUM>. The first amount of surface area of the wrap spring <NUM> that contacts the piston <NUM> may be greater than the second amount surface area that contacts the shaft <NUM>. This is represented in <FIG> and <FIG> by the greater number of coils of the wrap spring <NUM> that engage the piston hub <NUM> as compared to the shaft hub <NUM>. This surface area difference may help provide different slip torques between the wrap spring <NUM> and the piston hub <NUM> and between the wrap spring <NUM> and the shaft hub <NUM> as will be discussed in more detail below. The wrap spring <NUM> is illustrated with a circular cross section but it is contemplated that a different cross section may be provided, such as a square cross section.

Rotation of the shaft <NUM> in a first rotational direction may exert force on the wrap spring <NUM> that causes the wrap spring <NUM> to tighten against the shaft hub <NUM> to resist or inhibit slipping between the wrap spring <NUM> and the shaft <NUM>. Rotation of the shaft <NUM> in a second rotational direction that is opposite the first rotational direction may exert force that causes the wrap spring <NUM> to tighten against the piston hub <NUM> to resist or inhibit slipping between the wrap spring <NUM> and the piston <NUM>.

Referring to <FIG>, <FIG>, and <FIG>, the first bearing assembly <NUM> may rotatably support the piston <NUM> and the shaft <NUM>. For instance, the first bearing assembly <NUM> may rotatably support the piston <NUM> with respect to the shaft <NUM>. The first bearing assembly <NUM> may be disposed proximate the first shaft end <NUM> and may encircle the shaft <NUM>. For instance, the first bearing assembly <NUM> may extend around the shaft <NUM> and may be received inside the piston <NUM>. As such, the first bearing assembly <NUM> may extend between the shaft <NUM> and the inner surface of the piston <NUM>.

The second bearing assembly <NUM> may rotatably support the shaft <NUM>. The second bearing assembly <NUM> may be disposed proximate the second shaft end <NUM> and may encircle the shaft <NUM>. For instance, the second bearing assembly <NUM> may extend around the shaft <NUM> and may be received inside the through hole <NUM> of the yoke <NUM>. As such, the second bearing assembly <NUM> may extend between the shaft <NUM> and the yoke <NUM>.

Referring to <FIG>, at least one retraction spring <NUM> may be provided to facilitate retraction of the brake pad assemblies <NUM>. In the configuration shown, a pair of retraction springs <NUM> are provided. The retraction springs <NUM> may be received in the cavity <NUM> of the caliper housing <NUM> and may extend from the yoke <NUM> to the cover plate <NUM>. The retraction springs <NUM> may be configured to actuate the yoke <NUM> away from the cover plate <NUM> since the cover plate <NUM> is fixed to the caliper housing <NUM>. As such, the retraction springs <NUM> may urge the yoke <NUM> to move along the axis <NUM> in a direction that extends away from the brake rotor <NUM> and the cover plate <NUM>.

Referring primarily to <FIG>, the sensor assembly <NUM> may be received inside the shaft <NUM>. For example, at least a portion of the sensor assembly <NUM> may be received inside the shaft cavity <NUM>. The sensor assembly <NUM> may provide a signal that may be indicative of rotation of the shaft <NUM> about the axis <NUM>.

Referring to <FIG>, the controller <NUM> may monitor and control operation of the brake assembly <NUM>. For instance, the controller <NUM> may monitor and control operation of the brake actuator <NUM>. The controller <NUM> may be of any suitable type, such as a multiprocessor-based controller. The controller <NUM> may also process signals or data from various input devices, such as the sensor assembly <NUM> and one or more input devices, such as a brake pedal sensor or another sensor that may trigger braking of the vehicle, such as an adaptive cruise control system or a proximity sensor that may detect an object or obstruction in front of the direction of travel of the vehicle.

Referring to <FIG>, operation of the brake assembly <NUM> will now be described in more detail. As an overview, the brake assembly <NUM> may start in a retracted state in which braking of the vehicle is not requested. As such, the brake pad assemblies <NUM> may be retracted away from the brake rotor <NUM> and components of the brake assembly <NUM> may be positioned as shown.

In response to a vehicle braking command, such as may be provided by an input device, the controller <NUM> may initiate braking of the vehicle. The controller <NUM> may operate the brake actuator <NUM> to extend the brake actuator shaft, thereby rotating the operating shaft <NUM> about its axis of rotation in a first direction or a counterclockwise direction from the perspective shown. Rotation of the operating shaft <NUM> may move the yoke <NUM>, tappet <NUM>, piston <NUM>, wear adjuster mechanism <NUM>, and the inboard brake pad assembly <NUM> that is disposed adjacent to the tappet <NUM> along the axis <NUM> toward the brake rotor <NUM>, or to the left from the perspective shown. Movement of the yoke <NUM> toward the brake rotor <NUM> may compress the retraction springs <NUM>. In addition, rotation of the operating shaft <NUM> may cause the ball pin <NUM> to engage the ball pin engagement feature <NUM> of the shaft <NUM>, which may provide torque that rotates the shaft <NUM> about the axis <NUM>. Once the inboard brake pad assembly <NUM> contacts the brake rotor <NUM>, a reaction force may then move the brake caliper <NUM> with respect to the brake carrier <NUM> to actuate the outboard brake pad assembly <NUM> that is disposed between the brake rotor <NUM> and the caliper bridge <NUM> into engagement with an opposite side of the brake rotor <NUM> to help slow rotation of the brake rotor <NUM> and an associated vehicle wheel. Retracting the brake actuator shaft may allow the operating shaft <NUM> to rotate about its axis of rotation in a clockwise direction from the perspective shown, which in turn may allow the actuation sequence to proceed in reverse under the biasing force of the retraction springs <NUM>.

Rotation of the operating shaft <NUM> may or may not result in adjustment of the running clearance between the brake pad assembly <NUM> and the brake rotor <NUM>. For example, rotation of the operating shaft <NUM> in the first direction about its axis of rotation may operate the wear adjuster mechanism <NUM> to extend the tappet <NUM> closer to the brake rotor <NUM> with respect to the piston <NUM> when the operating shaft <NUM> and the ball pin <NUM> rotate the shaft <NUM> in a first rotational direction about the axis <NUM> before the inboard brake pad assembly <NUM> contacts the brake rotor <NUM>. As such, the shaft <NUM> and the wrap spring <NUM> may rotate together about the axis <NUM> in the first rotational direction and the wrap spring <NUM> may tighten against the shaft <NUM> to inhibit the wrap spring <NUM> from slipping with respect to the shaft <NUM>. Rotation of the wrap spring <NUM> may cause the piston <NUM> to rotate about the axis <NUM> in the first rotational direction due to the friction between the wrap spring <NUM> and the piston hub <NUM>. Rotation of the piston <NUM> may extend the tappet <NUM> (i.e., extend the tappet <NUM> farther away from the yoke <NUM> and closer to the brake rotor <NUM>) due to relative rotation of the outer thread <NUM> of the piston <NUM> and the inner thread <NUM> of the tappet <NUM>. For example, rotation of the piston <NUM> may cause the tappet <NUM> to extend when the inboard brake pad assembly <NUM> has not contacted the brake rotor <NUM> due to operation of the mating threads and because the tappet <NUM> is inhibited from rotating about the axis <NUM> by the brake carrier <NUM> (i.e., the brake carrier <NUM> prevents the inboard brake pad assembly <NUM> and thus the tappet <NUM> from merely rotating with the piston <NUM>). An example of extension of the tappet <NUM> to reduce the running clearance is shown in <FIG>.

Referring to <FIG>, extension of the tappet <NUM> with respect to the piston <NUM> may stop when the inboard brake pad assembly <NUM> contacts the brake rotor <NUM>. For example, the torque required to rotate the piston <NUM> increases substantially when the inboard brake pad assembly <NUM> contacts the brake rotor <NUM> even when the brake actuator <NUM> continues to rotate the operating shaft <NUM> and hence continues to rotate the shaft <NUM>. As a result, the torque exerted in the first rotational direction becomes sufficient to cause the wrap spring <NUM> and the piston <NUM> to slip with respect to each other, thereby permitting rotation of the shaft <NUM> and the wrap spring <NUM> to rotate with respect to the piston <NUM>.

The wear adjuster mechanism <NUM> may operate to hold the tappet <NUM> in its adjusted position when the brake pad assemblies <NUM> are retracted. For example, when the brake actuator <NUM> is retracted the operating shaft <NUM> may rotate in a second direction that is disposed opposite the first direction, or clockwise from the perspective shown. The ball pin <NUM> may then rotate the shaft <NUM> in the opposite direction or in a second rotational direction about the axis <NUM> and back toward its previous rotational position. Rotation of the shaft <NUM> in the second rotational direction loosens the wrap spring <NUM> from the shaft hub <NUM> and tightens the wrap spring <NUM> against the piston hub <NUM>. As a result, the wrap spring <NUM> may inhibit rotation of the piston <NUM> about the axis <NUM> (and hence inhibit relative rotation between the piston <NUM> and the tappet <NUM>) while the wrap spring <NUM> may slip with respect to the shaft hub <NUM>, thereby allowing the shaft <NUM> to rotate about the axis <NUM> in the second rotational direction with respect to the wrap spring <NUM> and back to its previous position.

Rotation of the operating shaft <NUM> may not result in adjustment of the running clearance between the brake pad assembly <NUM> and the brake rotor <NUM> when the inboard brake pad assembly <NUM> contacts the brake rotor <NUM> before the operating shaft <NUM> and the ball pin <NUM> rotate the shaft <NUM> about the axis <NUM>. As previously discussed, the torque required to rotate the piston <NUM> increases substantially when the inboard brake pad assembly <NUM> contacts the brake rotor <NUM>. As a result, the wrap spring <NUM> and the shaft <NUM> may slip with respect to each other as the operating shaft <NUM> rotates in the first direction, thereby permitting rotation of the shaft <NUM> with respect to the piston <NUM> while rotation of the piston <NUM> is opposed by the tappet <NUM> reacting against the brake rotor <NUM>. Thus, the wear adjuster mechanism <NUM> may operate to hold the tappet <NUM> in its current position with respect to the piston <NUM> when the brake pad assemblies <NUM> are retracted.

It is noted that in <FIG> and <FIG> there is little visible movement of the wrap spring <NUM> since at least one coil of the wrap spring <NUM> remains engaged with the piston hub <NUM> and at least one coil of the wrap spring <NUM> remains engaged with the shaft hub <NUM> when the wrap spring is rotated in both the first rotational direction and the second rotational direction.

In summary, the wrap spring <NUM> is configured to slip with respect to the piston <NUM> but not with respect to the shaft <NUM> when the wrap spring <NUM> is rotated and a first rotational direction about the axis <NUM>. However, the wrap spring <NUM> may slip with respect to the piston <NUM> when sufficient torque is applied to the shaft <NUM> in the first rotational direction. This sufficient torque at which slip occurs with respect to the piston <NUM> is designated a first amount of torque. Conversely, the wrap spring <NUM> is configured to slip with respect to the shaft <NUM> but not with respect to the piston <NUM> when the wrap spring <NUM> is rotated in the second rotational direction about the axis <NUM>. However, the wrap spring <NUM> may slip with respect to the shaft <NUM> when sufficient torque is applied in the second rotational direction. The sufficient torque at which slip occurs with respect to the shaft <NUM> is designated a second amount of torque. The first amount of torque may be greater than the second amount of torque. For instance, the first amount of torque may be two or more times greater than the second amount of torque. Thus, the slip torque between the wrap spring <NUM> and the piston hub <NUM> may be greater than the slip torque between the wrap spring and the shaft hub <NUM>.

The brake assembly and method of control as discussed above may allow a wrap spring to bidirectionally control torque transmission, which results in a simpler wear adjustment mechanism design with fewer parts, lower cost, and easier assembly. For instance, the present invention may use one wrap spring to control torque in both rotational directions rather than different mechanisms to control torque in each rotational direction, such as a multi-plate clutch and a spring. The present invention allows different slip torques to be provided between a piston and a shaft and allows these slip torques to be provided in different rotational directions. In addition, use of a bidirectional wrap spring may provide a high torque-to-size ratio, provide accurate and repeatable torque transmission, have lower power consumption, and provide a long life. Additionally, a wrap spring may also be configured to apply a bearing preload against one or more bearing assemblies of the wear adjustment mechanism, thereby helping avoid spinning of the bearing assembly and improving bearing life.

Claim 1:
A brake assembly (<NUM>) comprising:
a brake caliper (<NUM>);
a tappet (<NUM>) that is moveable along an axis (<NUM>) with respect to the brake caliper (<NUM>) and that is adapted to engage a brake pad assembly (<NUM>), wherein the tappet (<NUM>) has an inner thread (<NUM>);
a piston (<NUM>) that is rotatable about the axis (<NUM>) and is at least partially received in the tappet (<NUM>), wherein the piston (<NUM>) has an outer thread (<NUM>) that mates with the inner thread (<NUM>); and
a wear adjuster mechanism (<NUM>) that is at least partially received inside the piston (<NUM>), wherein the wear adjuster mechanism (<NUM>) includes:
a shaft (<NUM>) that is rotatable about the axis (<NUM>); and
a wrap spring (<NUM>) that is received inside the piston (<NUM>) and that encircles the shaft (<NUM>), wherein the wrap spring (<NUM>) engages the piston (<NUM>) and the shaft (<NUM>), the wrap spring (<NUM>) is configured to slip with respect to the piston (<NUM>) but not slip with respect to the shaft (<NUM>) when the wrap spring (<NUM>) is rotated about the axis (<NUM>) in a first rotational direction, and the wrap spring (<NUM>) is configured to slip with respect to the shaft (<NUM>) but not slip with respect to the piston (<NUM>) when the wrap spring (<NUM>) is rotated about the axis (<NUM>) in a second rotational direction that is disposed opposite the first rotational direction.