Patent Description:
The invention can be applied in heavy-duty vehicles, such as trucks, buses and construction equipment. Although the invention will be described with respect to a truck, the invention is not restricted to this particular vehicle, but may also be used in other vehicles such as cars.

Vehicle brakes are available in various configurations. One type of vehicle brake is a disc brake, in which a brake disc rotating with the road wheel axle is pinched between brake pads to slow down the rotation of the brake disc. Another type of vehicle brake is a drum brake, in which a brake drum is connected to a rotating wheel end hub of a roadwheel, and a friction-generating lining (e.g. provided on brake shoes) is pressed against an inner surface of the brake drum to slow down the rotation of the brake drum. With respect to drum brakes, it is a challenge to correctly align the brake drum when mounting it on the wheel end hub. An incorrect alignment may cause eccentric drum rotation, which in turn may result in steering wheel vibrations when a driver activates the brakes (for example by pressing a brake pedal). From a driver's point of view, such steering wheel vibrations may cause irritation.

<CIT> discloses a solution to concentrically aligning a brake drum with a wheel end hub. A bevelled ring is provided between the brake drum and the wheel end hub. The bevelled ring is pressed in an axial direction into indirect contact with the brake drum and wheel end hub under the action of a nut and washer. Thus, the nut has to be adequately tightened so that the applied axial force is turned into radial force by the bevelled ring for accomplishing proper alignment. Although <CIT> presents a solution to concentrically aligning brake drums, it would be desirable to simplify the alignment process.

An object of the invention is to provide a brake drum system which allows for a simplified alignment between a brake drum and a wheel end hub.

According to a first aspect of the invention, the object is achieved by a brake drum system for a wheel of a vehicle, in accordance with claim <NUM>. Thus, according to the first aspect of the invention, there is provided a brake drum system for a wheel of a vehicle, comprising.

By the provision of a brake drum system which comprises a radially pressing spring element a simple aligning process is achieved. Thus, the invention is based on the insight that by using a substantially circular spring element, a radial aligning force may inherently be present in the spring element itself. This will retain the geometrical centre axis of the brake drum in its position during mounting. The spring element, or at least parts of it, is radially compressed when it is clamped between the brake drum and the wheel end hub, thus urging to expand in the radial direction. In the mounted state of the system, the brake drum, the substantially circular spring element and the wheel end hub are concentrically arranged relative to each other.

The various directions of extensions of the components of the brake drum system may be described based on a cylindrical r, Θ, z - coordinate system, wherein the coordinate r defines the radial direction, the coordinate Θ defines the circumferential/angular direction and the coordinate z defines the axial direction. Thus, according to the invention, in an assembled state of the brake drum system, following the r-direction, the spring element is located radially outside of the wheel end hub, and the brake drum is located radially outside of the spring element. When the vehicle is in motion, e.g. is driven on a road, the rotational motion of the brake drum is in the θ-direction.

The brake drum and the wheel end hub may suitably comprise respective pilot surfaces for piloting the brake drum onto the wheel end hub, when the brake drum is in the process of becoming mounted to the wheel end hub in the axial direction. A pilot surface of the brake drum may suitably face radially inwardly, while a pilot surface of the wheel end hub may suitably face radially outwardly. The spring element may suitably be clamped between the pilot surfaces of the brake drum and the wheel end hub. Suitably the pilot surface of the brake drum may be profiled to conform with or at least partly conform with a cross-sectional profile of the spring element.

According to at least one exemplary embodiment, the spring element has the form of an open ring with two end portions facing each other. This is advantageous since an spring element in the form of an open ring is oftentimes easies to manufacture than a spring element in the form of a closed ring. However, it should be understood that, in at least some exemplary embodiments, the brake drum system may comprise a spring element in the form of a closed ring, instead of an open ring. With respect to the exemplary embodiments in which the spring element is in the form of an open ring having two end portions facing each other, there are different conceivable configurations for how they face each other. In at least some exemplary embodiments, the two end portions may face each other in the circumferential direction, i.e. the θ-direction. In other exemplary embodiments, the two end portions may be overlapping such that the open ring extends slightly more than <NUM>°. In such case, one of the end portions may be located radially outside of the other end portion, thus facing each other in the r-direction. In such an overlapping configuration, each individual end portion may suitably be thinner than the major portion of the ring, so that the thickness at the overlap substantially corresponds to the thickness at the major portion of the ring.

According to at least one exemplary embodiment, discrete portions of the outer surface of the spring element are in contact with the brake drum for providing said radially directed spring force when the system has been assembled, wherein the discrete portions are separated from each other and distributed along the circular circumferential direction of the spring element. By providing discrete portions along the circumference of the spring element, i.e. along the θ-direction, an efficient spring effect is created in different radial directions, thereby improving the concentric alignment. In at least some exemplary embodiments, the discrete portions may suitably be symmetrically distributed around the spring element. In at least some exemplary embodiments, the discrete portions may be resilient, wherein they become compressed when the spring element is clamped between the brake drum and the wheel end hub. Such compressed discrete portion may urge to return to a non-compressed state, i.e. each discrete portion pressing the brake drum in a respective radial direction. The number of discrete portions may be different in different exemplary embodiments. For instance, the number of discrete portions may be three, four, five, six, seven, eight, nine, ten, eleven, twelve, or even more.

According to at least one exemplary embodiment, the spring element comprises a plurality of profiled portions for providing said radially directed spring force, each profiled portion having a profile bulging radially outwardly against the brake drum and being spaced from the wheel end hub when the system has been assembled. By providing radially bulging profiled portion an efficient spring effect is created in different radial directions, thereby improving the concentric alignment. Suitably, the profiled portions are resilient so that when the brake drum is mounted in order to clamp the spring element, the profiled portions become pressed towards the wheel end hub, whereby the profiled portions will exert a radially outwardly directed counterforce against the brake drum. The profiled portions may in at least some exemplary embodiments form part of or comprise the above-mentioned discrete portions.

According to at least one exemplary embodiment, said profile is U-shaped, the legs of the U-shape being adapted to be pressed against the wheel end hub and the interconnecting bridge of the U-shape being adapted to be pressed against the brake drum. By having a U-shaped profile the bridge of the U-shape may be pressed downwardly because of the clamping force, and the bridge will thus provide a counterforce striving to push the brake drum in a radially outwards direction.

According to at least one exemplary embodiment, the legs of the U-shaped profile are separated from each other in the circumferential direction of the spring element. This allows a simple production of a spring element with U-shaped profiled portions. Furthermore, it allows a large variation of possible U-shaped configurations. Thus, because of the separation of the legs in the circumferential direction, it is possible to choose a large interconnecting bridge between the legs, if desired. If the separation is in the axial direction, the width of the spring element is a limiting factor for designing the interconnecting bridge of the U-shaped profile.

Nevertheless, an axial separation of the legs of a U-shaped profile may also be conceivable. This is reflected in at least one exemplary embodiment, according to which the spring element has a substantially constant profiled cross-section, wherein said profiled cross-section is U-shaped, the legs of the U-shape being adapted to be pressed against the wheel end hub and the interconnecting bridge of the U-shape being adapted to be pressed against the brake drum, wherein the legs of the U-shape are separated from each other in the axial direction of the circular spring element. This is advantageous it is simple to manufacture a circular ring with a constant cross-section.

According to at least one exemplary embodiment, the spring element is provided with a plurality of central slits extending and being distributed in the circumferential direction, wherein U-shaped bulges are provided on either side of each slit, whereby under the inner surface of the spring element an open space extends across the spring element from one lateral side to the other lateral side of the spring element when the system has been assembled. By providing a central slit, an improved resiliency of the U-shaped bulges is obtainable.

According to at least one exemplary embodiment, the spring element comprises a plurality of raised wings forming said profiled portions, the wings being distributed along the circumference of the spring element and being adapted to be pressed against the brake drum. By designing the profiled portions as raised wings, a good resiliency is obtainable.

According to at least one exemplary embodiment, said discrete portions comprise a plurality of pairs of discrete portions, each pair of discrete portions comprising a discrete portion on either side of a slot, wherein each discrete portion in such a pair of discrete portions project radially outwardly and towards a centre of the slot. By having such raised discrete portions, they will become pressed downwardly when the spring element is clamped between the brake drum and the wheel end hub, and will thus exert a an radially outwardly directed counterforce on the brake drum.

According to at least one exemplary embodiment, one of the lateral sides of the spring element is formed by a radially outwardly projecting ledge. This is advantageous since the ledge may function as a stop, preventing the spring element to accidently slide off the wheel end hub. In some exemplary embodiments, the ledge may, for instance, extend into a slit in one of (or both of) the brake drum and the wheel end hub. In other exemplary embodiments, it may be clamped between the brake drum and the wheel end hub, such as for instance reflected in the following exemplary embodiment.

According to at least one exemplary embodiment, when the system has been assembled, the projecting ledge is clamped between radially extending wall portions of the brake drum and the wheel end hub. By clamping the ledge between radially extending wall portions a firm fixation of the spring element is obtainable.

According to at least one exemplary embodiment, the spring element is made of one or more materials selected from the group consisting of:.

The above mentioned materials may provide the desired resiliency of the spring element. Furthermore, it should be understood that in some exemplary embodiment, the entire spring element may be resilient, such as radially compressible and biased to return to its original shape/size by radial expansion. In other exemplary embodiments, only portions, such as discrete portions are resilient and be biased to return to their original shape by radial expansion after having been compressed. In yet other exemplary embodiments, the discrete portions (such as profiled portions) and other portions of the spring element may both be resilient and biased to return to their original shape.

According to a second aspect of the invention, the object is achieved by a vehicle comprising a brake drum system according to the first aspect, including any embodiments thereof.

<FIG> is a schematic illustration of a vehicle <NUM>, in accordance with at least one exemplary embodiment of the invention. Although the vehicle <NUM> is illustrated in the form of a truck, other types of vehicles, such as busses, construction equipment, trailers or passenger cars may be provided in accordance with the invention.

The truck (vehicle) comprises a cab <NUM> in which a driver may operate the vehicle. The vehicle comprises a number of road wheels <NUM>, herein illustrated as three pairs of wheels, however in other embodiments there may be a different number of wheels, such as two pairs, four pairs or more. In the cab <NUM> a driver may press a brake pedal with his/her foot in order to activate the brake or brakes. Activation of the brake causes friction-generating linings (such as on multiple brake shoes) to be pressed against an inner surface of a brake drum (not illustrated in <FIG>) connected to the road wheels <NUM>.

<FIG> is a general illustration, partly in cross-section, of a brake drum <NUM> mounted on a wheel end hub <NUM>. The wheel end hub <NUM> has a central axle-receiving portion <NUM> for receiving a drive axle (not shown) of a vehicle. A drum-receiving flange portion <NUM> of the wheel end hub <NUM> projects radially from the central portion <NUM>. The flange portion <NUM> is provided with a plurality of studs <NUM> for mating with corresponding holes <NUM> in a flange portion <NUM> of the brake drum <NUM>. The brake drum <NUM> has an inner surface <NUM> adapted to receive a friction-generating lining (not shown) when a driver applies the brakes of the vehicle. The flange <NUM> of the brake drum <NUM> has a pilot surface <NUM> facing radially inwardly. The flange portion <NUM> of the wheel end hub <NUM> comprises axially projecting pilot portions <NUM>, having pilot surfaces <NUM> facing radially outwardly. The pilot surfaces <NUM>, <NUM> of the brake drum <NUM> and the wheel end hub <NUM> are provided for aligning the brake drum <NUM> with the wheel end hub <NUM>. It is nevertheless a challenge to achieve a correct alignment.

The inventors of the present invention have solved the alignment problem by providing a brake drum system in which a spring element is clamped between a brake drum and a wheel end hub, wherein the spring element exerts a radially directed force onto the brake drum for proper alignment. Some exemplary embodiments will be discussed in the following.

<FIG> illustrate a brake drum system <NUM>, and a spring element <NUM> for use in the brake drum system <NUM>, in accordance with at least one exemplary embodiment of the invention. <FIG> illustrates the spring element <NUM> for use in the brake drum system <NUM>. <FIG> is a detailed view illustrating a cross-section of the spring element <NUM>. <FIG> illustrates, partly in cross-section, the spring element <NUM> mounted and clamped between the brake drum <NUM> and the wheel end hub <NUM>. <FIG> illustrates, in a cross-sectional view, the spring element <NUM> mounted and clamped between the brake drum <NUM> and the wheel end hub <NUM>.

As shown in <FIG>, the brake drum <NUM> has an has an inner surface <NUM> adapted to receive a friction-generating lining (not shown) when a driver applies the brakes of the vehicle.

As best seen in <FIG>, the spring element <NUM> is substantially circular, and as best seen in <FIG>, the spring element <NUM> has an outer surface <NUM> adapted to be pressed against the brake drum <NUM> and an inner surface <NUM> adapted to be pressed against the wheel end hub <NUM>. When clamped between the brake drum <NUM> and the wheel end hub <NUM>, the spring element <NUM> provides a radially directed spring force. The spring element <NUM> may have the form of an open ring with two end portions facing each other, or it may have the form of a closed ring without any end portions.

As best seen in <FIG>, the spring element comprises a plurality of discrete portions <NUM>. These discrete portions <NUM>, on the outer surface <NUM> of the spring element <NUM>, configured to be in contact with the brake drum <NUM> for providing said radially directed spring force when the system <NUM> has been assembled. The discrete portions <NUM> are separated from each other and distributed along the circular circumferential direction of the spring element <NUM>. The discrete portions <NUM> may suitably be clamped between pilot surfaces <NUM>, <NUM> of the brake drum <NUM> and the wheel end hub <NUM>, respectively, such as illustrated in <FIG> and <FIG>.

Turning back to <FIG>, the discrete portions <NUM> have a wing-shaped profile. The discrete portions (profiled portions) bulge radially outwardly. When applied in the brake drum system <NUM>, the bulge <NUM> of the profile will be spaced from the wheel end hub <NUM>, and will be pressed against the brake drum <NUM>. The void space underneath the bulge <NUM> allows brake drum <NUM> to press/compress the bulge <NUM> radially inwardly towards the wheel end hub <NUM>. The resiliency and the bias of the spring element <NUM> will cause the bulge <NUM> to urge towards its original shape, i.e. providing a radial outwardly directed force onto the brake drum <NUM>. Since the discrete portions <NUM> and the bulges <NUM> are distributed around the circumference of the spring element <NUM>, the brake drum <NUM> will be subjected to such a force in several radial directions, thereby aligning the brake drum <NUM> properly. The discrete portions <NUM> in <FIG> (and in other embodiments disclosed herein) are suitably equidistantly distributed along the spring element <NUM>.

As best seen in <FIG>, the spring element <NUM> has two lateral edges <NUM>, <NUM>. One of the lateral sides <NUM> of the spring element <NUM> is formed by a radially outwardly projecting ledge <NUM>. The lateral sides <NUM>, <NUM> of the spring element <NUM> are separated from each other in the axial direction of the spring element <NUM>. When the drum brake system <NUM> has been assembled, the projecting ledge <NUM> is clamped between radially extending wall portions <NUM>, <NUM> of the brake drum <NUM> and the wheel end hub <NUM>, respectively. This is best seen in <FIG>. The ledge <NUM> functions as a stop in order to reduce the risk of the spring element <NUM> falling off the wheel end hub <NUM>. Thus, as can be seen in <FIG>, the spring element <NUM> will be clamped between the pilot surfaces <NUM>, <NUM> of the brake drum <NUM> and the wheel end hub <NUM>, and will also be clamped between radially extending wall portions <NUM>, <NUM> of the brake drum <NUM> and the wheel end hub <NUM>. The discrete portions <NUM> of the spring element <NUM> will thus be clamped in the radial direction, while the ledge <NUM> will be clamped in the axial direction.

<FIG> illustrate a brake drum system <NUM>, and a spring element <NUM> for use in the brake drum system <NUM>, in accordance with at least another exemplary embodiment of the invention. <FIG> illustrates the spring element <NUM> for use in the brake drum system <NUM>. <FIG> is a detailed view illustrating a cross-section of the spring element <NUM>. <FIG> illustrates, partly in cross-section, the spring element <NUM> mounted and clamped between the brake drum <NUM> and the wheel end hub <NUM>. <FIG> illustrates, in a cross-sectional view, the spring element <NUM> mounted and clamped between the brake drum <NUM> and the wheel end hub <NUM>.

The spring element <NUM> shown in <FIG> has a ledge <NUM> similarly to the spring element <NUM> in <FIG>, and provides the corresponding stopping function, improving the keeping of the spring element <NUM> in place. Furthermore, the spring element <NUM> shown in <FIG> may either form an open ring or a closed ring.

Unlike <FIG>, the spring element <NUM> shown in <FIG> does not have such discrete profiled portions (cf. reference numeral <NUM> in <FIG>). Instead, the spring element <NUM> in <FIG> has a substantially constant profiled cross-section. The profiled cross-section is U-shaped, wherein the legs <NUM>, <NUM> of the U-shape are adapted to be pressed against the wheel end hub <NUM> and the interconnecting bridge <NUM> (bulge) of the U-shape is adapted to be pressed against the brake drum <NUM>. The legs <NUM>, <NUM> of the U-shape are separated from each other in the axial direction of the substantially circular spring element <NUM>. Thus, one leg <NUM> extends from the interconnecting bridge <NUM> of the U-shape towards the lateral side <NUM> having the ledge <NUM>, while the other leg <NUM> extends towards the opposite lateral side <NUM>. As best seen in <FIG>, there is a void space <NUM> underneath the interconnecting bridge <NUM> of the U-shaped profile allowing the brake drum <NUM> to radially press/compress the interconnecting bridge <NUM> towards the wheel end hub <NUM>. The interconnecting bridge <NUM> of the U-shaped profile will thus be biased towards recovering its original shape and exert a radially directed counterforce on the brake drum <NUM>.

<FIG> illustrate a brake drum system <NUM>, and a spring element <NUM> for use in the brake drum system <NUM>, in accordance with at least yet another exemplary embodiment of the invention. <FIG> illustrates the spring element <NUM> for use in the brake drum system <NUM>. <FIG> is a detailed view illustrating a cross-section of the spring element <NUM>. <FIG> illustrates, partly in cross-section, the spring element <NUM> mounted and clamped between the brake drum <NUM> and the wheel end hub <NUM>. <FIG> illustrates, in a cross-sectional view, the spring element <NUM> mounted and clamped between the brake drum <NUM> and the wheel end hub <NUM>.

Although the spring element <NUM> shown in <FIG> does not have a ledge at a lateral side as in the embodiments illustrated in Figs. 2a-2d and <FIG>, it should be understood that in other exemplary embodiments, the spring element <NUM> shown in <FIG> may be modified to include such a ledge at a lateral side of the spring element. Conversely, it is conceivable, at least in some exemplary embodiments, to modify the spring element illustrated in Figs. 2a-2d and <FIG> by removing the ledge.

As best seen in <FIG>, the spring element <NUM> comprises a plurality of profiled portions <NUM> for providing the radially directed spring force to the brake drum <NUM>, each profiled portion <NUM> having a profile bulging radially outwardly against the brake drum <NUM> and being spaced from the wheel end hub <NUM> when the system <NUM> has been assembled (see <FIG> and <FIG>). The profile is U-shaped, wherein the legs <NUM>, <NUM> of the U-shape are adapted to be pressed against the wheel end hub <NUM> and the interconnecting bridge <NUM> of the U-shape is adapted to be pressed against the brake drum <NUM>. The legs <NUM>, <NUM> of the U-shaped profile are separated from each other in the circumferential direction of the spring element <NUM>. The spring element <NUM> is provided with a plurality of central slits <NUM> extending and being distributed in the circumferential direction, wherein the U-shaped profile is configured as U-shaped bulges <NUM>, <NUM> provided on either side of each slit <NUM>, whereby under the inner surface of the spring element an open space <NUM> extends across the spring element <NUM> from one lateral side <NUM> to the other lateral side <NUM> of the spring element <NUM> when the system <NUM> has been assembled.

<FIG> illustrate a brake drum system <NUM>, and a spring element <NUM> for use in the brake drum system <NUM>, in accordance with at least still another exemplary embodiment of the invention. <FIG> illustrates the spring element <NUM> for use in the brake drum system <NUM>. <FIG> is a detailed view illustrating a cross-section of the spring element <NUM>. <FIG> illustrates, partly in cross-section, the spring element <NUM> mounted and clamped between the brake drum <NUM> and the wheel end hub <NUM>. <FIG> illustrates, in a cross-sectional view, the spring element <NUM> mounted and clamped between the brake drum <NUM> and the wheel end hub <NUM>.

Although the spring element <NUM> shown in <FIG> does not have a ledge at a lateral side as in the embodiments illustrated in Figs. 2a-2d and <FIG>, it should be understood that in other exemplary embodiments, the spring element <NUM> shown in <FIG> may be modified to include such a ledge at a lateral side of the spring element.

As best seen in <FIG>, the spring element <NUM> comprises a plurality of pairs <NUM> of discrete portions <NUM>,<NUM>, suitably equidistantly distributed along the circumference of the spring element <NUM>. Each pair <NUM> of discrete portions comprises a discrete portion <NUM>, <NUM> on either side of a slot <NUM>, wherein each discrete portion <NUM>, <NUM> in such a pair <NUM> of discrete portions project radially outwardly and towards a centre of the slot <NUM>. In other words, in each pair <NUM>, one <NUM> of the discrete portions extends in one axial direction towards the centre of the slot <NUM>, while the other one <NUM> of the discrete portions extends in the opposite axial direction towards the centre of the slot <NUM>. The oblique extension (due to both radial and axial extension) of the discrete portions <NUM>, <NUM> provide for good resiliency. Thus, when clamped between the brake drum <NUM> and the wheel end hub <NUM>, suitably between the pilot surfaces <NUM>, <NUM> (see in particular <FIG>) of the brake drum <NUM> and the wheel end hub <NUM>, the discrete portions <NUM> will be pressed radially inwardly towards the slot <NUM>. The resiliency of the discrete portions <NUM>, <NUM> will provide a counterforce directed radially outwardly on the brake drum <NUM>, thus supporting a proper alignment of the brake drum <NUM> relative to the wheel end hub <NUM>.

As can be seen in the different embodiments shown in <FIG>, <FIG>, <FIG> and <FIG>, respectively, the cross-sectional profile of the pilot surface of the brake drum may suitably conform with, or at least partly conform with a cross-sectional profile of the spring element, including the cross-sectional profile of the above discussed discrete portions of the spring element.

Claim 1:
A brake drum system (<NUM>, <NUM>, <NUM>, <NUM>) for a wheel (<NUM>) of a vehicle (<NUM>), comprising
- a brake drum (<NUM>, <NUM>, <NUM>, <NUM>) rotatable with the wheel, the brake drum having an inner surface (<NUM>) adapted to receive a friction-generating lining when a driver applies the brakes of the vehicle,
- a wheel end hub (<NUM>, <NUM>, <NUM>, <NUM>) adapted to be located radially between a drive axle of the vehicle and the brake drum,
characterized by a substantially circular spring element (<NUM>, <NUM>, <NUM>, <NUM>) for concentrically aligning the brake drum with the wheel end hub, the spring element being adapted to be clamped between the brake drum and the wheel end hub for providing a radially directed spring force, and the spring element, or at least parts of it, being radially compressed when it is clamped between the brake drum and the wheel end hub, thus urging to expand in the radial direction, wherein the spring element has an outer surface (<NUM>) adapted to be pressed against the brake drum and an inner surface (<NUM>) adapted to be pressed against the wheel end hub.