Patent Description:
Chinese Publication <CIT> and <CIT> concern wheel hubs including particular motor and brake arrangements. Other non-U. publications that may be of interest are Chinese Publication <CIT>, <CIT>, <CIT>, <CIT> and <CIT>, and <CIT>. <CIT>, <CIT>, <CIT>and <CIT>may all be of interest as well.

A drum brake assembly such as that mentioned above requires an extended drum that reaches from the outboard surface of the wheel hub, inboard over the electric drive motor, and further inboard to interface with the drum brake, located on the inboard side of the motor. In such an arrangement, the extended drum length could cause a loss of torsional rigidity in the drum, potentially causing poor braking performance and noise issues. The multiple key features of the extended length drum provided according to the present invention engage with mating slot features of the electric motor rotor and serve to support the center of the circumferential portion of the extended length drum. This engagement of the key and slot features provides both torsional and radial stiffness, which should improve braking performance, address noise issues, and allow for a lighter weight drum than would be required without these features.

The invention concerns a brake drum and electric motor engagement assembly according to claim <NUM>, a brake drum according to claim <NUM> and a process of producing a brake drum and electric motor engagement assembly according to claim <NUM>. The brake drum and electric motor engagement assembly for a vehicle includes a wheel hub mounted for rotation around a wheel spindle, an electric motor unit having an electric motor rotor, an electric motor stator, and power electronics, a brake drum, and a reinforcing ring. The electric motor rotor includes a web portion configured to partially enclose the remainder of the electric motor unit and terminate in a circumferentially extending rim. The brake drum defines an engagement surface for drum brake linings, and has an outboard end securable to the wheel hub, an open inboard end, and a circumferential wall extending between the outboard and inboard ends and surrounding the engagement surface. The reinforcing ring interlocks the circumferentially extending rim of the web portion and the circumferential wall of the brake drum, and is secured to the circumferentially extending rim and to the circumferential wall of the brake drum at a location that is disposed axially between the rim of the web portion and the engagement surface of the brake drum.

The assembly can include keys projecting into slots to interlock the circumferentially extending rim and the circumferential wall of the brake drum. The keys could be defined on the brake drum and project radially inwardly, while the slots could be defined in the reinforcing ring and project radially inwardly. In one construction, the keys are disposed adjacent to openings distributed around the circumferential perimeter of the brake drum, with the openings providing for ventilation of the brake drum and discharge of dust. The assembly can further include a support for brake shoes having the drum brake linings, and a dust guard mounted in the support plate inboard of the engagement surface. Each of the keys can be disposed between a pair of adjacent openings distributed around the circumferential perimeter of the brake drum. The invention additionally concerns a brake drum assembly per se, as well as a process of producing a brake drum and electric motor engagement assembly.

Referring initially to <FIG>, the wheel-end brake drum and electric motor brake or engagement assembly illustrated is mounted to an axle tube <NUM> having an inboard section <NUM> interconnected at a step <NUM> to a reduced diameter outboard section <NUM>. An attachment flange <NUM> is shown as welded or otherwise secured to the inboard axle tube section <NUM>. By way of bolts <NUM> passing through aligned holes <NUM> and <NUM> (<FIG>), a support, here formed by a drum brake support plate <NUM>, is securely attached to the flange <NUM> and the axle tube <NUM>. A pair of drum brake shoes <NUM> having linings <NUM> are pivotally secured by way of at least one post <NUM> to the support plate <NUM> in typical fashion. A dust guard <NUM> is mountable to the support plate <NUM> by suitable fasteners <NUM> to minimize passage of liquid and road debris into the illustrated assembly as well as discharge of brake dust produced during braking out of the assembly and onto a vehicle exterior. Upon operation of an actuator <NUM> (<FIG> and <FIG>), a cam <NUM> (<FIG>) is rotated in the conventional way to displace adjacent ends of the shoes <NUM> away from one another against the action of a return spring <NUM>, causing the shoes <NUM> to pivot around the post <NUM> and forcing the linings <NUM> into contact with an inner circumferential friction surface <NUM> of a brake drum <NUM>, described below. Attachment of the return spring to the brake shoes <NUM> is best visible in <FIG>.

Suitable cables <NUM>, passing through openings in the flange <NUM> and/or the support plate <NUM>, permit communication of relevant vehicle controls (not shown) and a vehicle battery (not shown) with a schematically represented electric motor rotor, stator, and power electronics unit <NUM>. By way of a sleeve <NUM>, press fit, keyed to, or otherwise affixed to the rotor of the unit <NUM>, and a splined fitting <NUM> secured to the outboard section <NUM> of the axle tube <NUM>, the stator and power electronics portions of the unit <NUM> (not individually shown) are rigidly secured to the outboard section <NUM> of the axle tube <NUM>, while the rotor of the unit <NUM> (not individually shown) is rotatable relative to the stator and power electronics portions of the unit <NUM>. The splined fitting <NUM> is received within the sleeve <NUM>, such that both the sleeve <NUM> and the splined fitting <NUM> are disposed axially with respect to the tube <NUM> between the reduced diameter outboard axle section <NUM> and an outer wheel spindle <NUM>.

A wheel hub <NUM> is mounted by way of bearings <NUM> for rotation relative to the spindle <NUM>. Inner bearing races <NUM> are defined on the exterior of a tubular bearing race insert <NUM> received over, extending around, and secured in any suitable manner to the spindle <NUM>. Outer bearing races <NUM> respectively corresponding to the inner bearing races <NUM> mentioned are defined by suitably formed or machined surfaces on the wheel hub <NUM>. The wheel hub <NUM> shown is a unitary cast or machined element including a hollow stem <NUM>, a protective cap <NUM>, and a flange <NUM>, extending at least partly around the wheel hub <NUM> and located between the stem <NUM> and the cap <NUM>. Threaded bolts <NUM>, passing through aligned holes in the wheel hub flange <NUM> and a mounting flange <NUM> (<FIG>) at the outboard end of the brake drum <NUM>, are used, along with nuts received on the bolts <NUM>, to secure the brake drum <NUM> and the wheel hub <NUM> together. The bolts <NUM> are also used to secure a wheel rim (not shown) to the wheel hub <NUM>, with the mounting flange <NUM> of the drum <NUM> then being sandwiched between the wheel rim and the hub <NUM>. A schematically illustrated split ring <NUM>, receivable in a groove (not shown) circumferentially formed in the interior surface of the cap <NUM> of the wheel hub, can engage a dust blocking annular wall <NUM> formed on the insert <NUM> to retain the insert in proper axial position relative to the wheel hub <NUM> and the spindle <NUM>. A dust seal <NUM> (<FIG>) is also provided between the axially interior end of the stem <NUM> and the spindle <NUM>. The seal <NUM> and the annular wall <NUM> serve to minimize effects of road debris and dust generated during vehicle braking on the bearings <NUM>.

Referring now to <FIG>, it will be seen that the drum <NUM> includes a large diameter inboard section <NUM>, a small diameter outboard section <NUM> indicated in <FIG>, an intermediate section <NUM> between the inboard and outboard drum sections <NUM> and <NUM>, as well as tapered transition sections <NUM> and <NUM> respectively located between the inboard and intermediate drum sections <NUM> and <NUM> and the outboard and intermediate drum sections <NUM> and <NUM>. A portion of the interior wall surface of the large diameter inboard section <NUM> forms the friction surface <NUM> engaged during braking by the brake linings <NUM>. The inboard drum section <NUM> is shown as having a circumferentially extending reinforcing rib or bulge <NUM> extending around an end of the drum opposite the mounting flange <NUM>. The rib or bulge <NUM> provides added strength to the drum <NUM>, which might be required, as the elongated configuration of the drum <NUM> could possibly compromise torsional drum rigidity.

The rotor of the schematically represented electric motor rotor, stator, and power electronics unit <NUM> of the electric motor is secured to or formed together with a rotor section <NUM> including a substantially U-shaped web portion <NUM>. The web portion <NUM> is configured to partially enclose the remainder of the unit <NUM>. The rotor section <NUM> is rigidly secured in a particular manner to be described to the brake drum <NUM> so that the rotor section <NUM> rotates together with the drum. A suitable bearing/seal arrangement (not indicated) may be mounted between the web portion <NUM> and the sleeve <NUM> to enable relative rotation and to limit passage of any contaminants. In addition to partially enclosing the unit <NUM> of the electric motor, the web portion <NUM> extends axially with respect to the tube <NUM> inboard beyond the unit <NUM>, defining an enlarged mounting rim <NUM> extending circumferentially around the inboard axial end of the web portion <NUM>. A reinforcing ring <NUM> is secured by screws or other suitable fasteners <NUM> to the axial end surface of the rim <NUM>, as best seen in <FIG> and <FIG>.

As shown in <FIG>, openings <NUM>, referred to as key slots, are provided on each side of multiple keys <NUM>, integrally formed with and distributed around the circumferential perimeter wall of the brake drum <NUM>. Air is permitted to enter into the arrangement shown through the key slots <NUM>. Air entering through the key slots <NUM> performs cooling and, to a certain extent, entrains dust generated during braking. The key slots <NUM> are located in pairs on opposite sides each of the keys <NUM>. As most clearly illustrated in the enlarged portions of <FIG> and <FIG>, these keys <NUM> project inward radially relative to the brake drum and are received in corresponding radial recesses or slots <NUM> provided in the reinforcing ring <NUM> secured to the end surface of the rim <NUM>. By having the keys <NUM> received in the recesses or slots <NUM> of the ring <NUM> as described, the brake drum <NUM> and the web portion <NUM> of the rotor section <NUM> are locked together for rotation, so that the brake drum <NUM> and the rotor section <NUM>, and thus the brake drum and the rotor of the schematically represented unit <NUM>, rotate together.

The extended length brake drum <NUM> is particularly suitable for use with a wheel end electric drive motor on a commercial vehicle. The drum <NUM> extends from an outboard mounting face on a wheel hub, here defined by the mounting flange <NUM>, over the electric drive motor unit <NUM>, and incorporates an inboard portion, here formed by the large diameter inboard section <NUM>, that provides the friction surface <NUM>. The drum projects axially inwardly beyond the plate <NUM>, which forms a support for the drum brake located inboard of the electric motor. In the circumferential area of the drum that passes over the electric drive motor, the multiple key features engaging with the key slots <NUM> included in the overall rotor arrangement of the motor serve to support the extended length drum, both torsionally and radially, thereby improving braking performance, addressing noise issues, and allowing for a lighter weight drum.

The vehicle brake drum and electric motor engagement assembly described thus includes the wheel hub <NUM> mounted for rotation around a wheel spindle <NUM> and an electric motor unit <NUM>, having an electric motor rotor, an electric motor stator, and power electronics (not individually shown), with the rotor of the unit <NUM> configured to include a web portion <NUM> partially enclosing the remainder of the electric motor unit <NUM> and terminating in a circumferentially extending rim <NUM>. The brake drum <NUM> defines an engagement surface <NUM> for the drum brake linings <NUM>, and has an outboard end, defining the flange <NUM>, securable to the wheel hub <NUM> by way of the bolts <NUM>. The brake drum also includes an open inboard end, partly covered over by the dust guard <NUM>, and a circumferential wall, including drum sections <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, extending between the outboard and inboard ends and surrounding the engagement surface <NUM>. By way of the keys <NUM> and the slots or recesses <NUM>, the reinforcing ring <NUM> interlocks the circumferentially extending rim <NUM> of the web portion <NUM> and the circumferential wall of the brake drum <NUM>. The reinforcing ring <NUM> is secured, by way of fasteners <NUM> (<FIG>) or in any other suitable manner, to the circumferentially extending rim <NUM> and to the circumferential wall of the brake drum <NUM> at a location, best seen in <FIG>, disposed axially between the rim <NUM> of the web portion <NUM> and the engagement surface <NUM> of the brake drum <NUM>.

Claim 1:
A brake drum and electric motor engagement assembly for a vehicle, comprising:
a wheel hub (<NUM>) mounted for rotation around a wheel spindle (<NUM>),
an electric motor unit (<NUM>) having an electric motor rotor, an electric motor stator, and power electronics, the electric motor rotor including a web portion (<NUM>) configured to partially enclose the remainder of the electric motor unit (<NUM>) and terminate in a circumferentially extending rim (<NUM>),
a brake drum (<NUM>) defining an engagement surface (<NUM>) for drum brake linings (<NUM>), the brake drum (<NUM>) having an outboard end securable to the wheel hub (<NUM>), an open inboard end, and a circumferential wall extending between the outboard and inboard ends and surrounding the engagement surface (<NUM>),
characterized by
a reinforcing ring (<NUM>) interlocking the circumferentially extending rim (<NUM>) of the web portion (<NUM>) and the circumferential wall of the brake drum (<NUM>), the reinforcing ring (<NUM>) being secured to the circumferentially extending rim (<NUM>) and to the circumferential wall of the brake drum (<NUM>),
wherein the reinforcing ring (<NUM>) is secured to the circumferential wall of the brake drum (<NUM>) at a location disposed axially between the rim (<NUM>) of the web portion (<NUM>) and the engagement surface (<NUM>) of the brake drum (<NUM>).