Patent Publication Number: US-2022235834-A1

Title: Brake drum system for a wheel of a vehicle

Description:
TECHNICAL FIELD 
     The invention relates to a brake drum system for a wheel of a vehicle. The invention also relates to a vehicle comprising such a brake drum system. 
     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. 
     BACKGROUND 
     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&#39;s point of view, such steering wheel vibrations may cause irritation. 
     U.S. Pat. No. 3,027,980 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 U.S. Pat. No. 3,027,980 presents a solution to concentrically aligning brake drums, it would be desirable to simplify the alignment process. 
     SUMMARY 
     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  1 . Thus, according to the first aspect of the invention, there is provided a brake drum system for a wheel of a vehicle, comprising
         a brake drum rotatable with the wheel, the brake drum having an inner surface adapted to receive a friction-generating lining when a driver applies the brakes of the vehicle,   a wheel end hub adapted to be located radially between a drive axle of the vehicle and the brake drum, and   a substantially circular spring element 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, wherein the spring element has an outer surface adapted to be pressed against the brake drum and an inner surface adapted to be pressed against the wheel end hub.       

     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, may suitably be 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 360°. 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:
         metal,   plastic,   rubber, and   composite material.       

     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. 
     Further advantages and advantageous features of the invention are disclosed in the following description and in the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples. 
       In the drawings: 
         FIG. 1  is a schematic illustration of a vehicle, in accordance with at least one exemplary embodiment of the invention, 
         FIG. 2  is a general illustration, partly in cross-section, of a brake drum mounted on a wheel end hub, 
         FIGS. 3 a -3 d    illustrate a brake drum system, and a spring element for use in the brake drum system, in accordance with at least one exemplary embodiment of the invention, 
         FIGS. 4 a -4 d    illustrate a brake drum system, and a spring element for use in the brake drum system, in accordance with at least another exemplary embodiment of the invention, 
         FIGS. 5 a -5 d    illustrate a brake drum system, and a spring element for use in the brake drum system, in accordance with at least yet another exemplary embodiment of the invention, and 
         FIGS. 6 a -6 d    illustrate a brake drum system, and a spring element for use in the brake drum system, in accordance with at least still another exemplary embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION 
       FIG. 1  is a schematic illustration of a vehicle  2 , in accordance with at least one exemplary embodiment of the invention. Although the vehicle  2  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  4  in which a driver may operate the vehicle. The vehicle comprises a number of road wheels  6 , 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  4  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. 1 ) connected to the road wheels  6 . 
       FIG. 2  is a general illustration, partly in cross-section, of a brake drum  10  mounted on a wheel end hub  12 . The wheel end hub  12  has a central axle-receiving portion  14  for receiving a drive axle (not shown) of a vehicle. A drum-receiving flange portion  16  of the wheel end hub  12  projects radially from the central portion  14 . The flange portion  16  is provided with a plurality of studs  18  for mating with corresponding holes  20  in a flange portion  22  of the brake drum  10 . The brake drum  10  has an inner surface  24  adapted to receive a friction-generating lining (not shown) when a driver applies the brakes of the vehicle. The flange  22  of the brake drum  10  has a pilot surface  26  facing radially inwardly. The flange portion  16  of the wheel end hub  12  comprises axially projecting pilot portions  28 , having pilot surfaces  30  facing radially outwardly. The pilot surfaces  26 ,  30  of the brake drum  10  and the wheel end hub  12  are provided for aligning the brake drum  10  with the wheel end hub  12 . 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. 
       FIGS. 3 a -3 d    illustrate a brake drum system  100 , and a spring element  102  for use in the brake drum system  100 , in accordance with at least one exemplary embodiment of the invention.  FIG. 3 a    illustrates the spring element  102  for use in the brake drum system  100 .  FIG. 3 b    is a detailed view illustrating a cross-section of the spring element  102 .  FIG. 3 c    illustrates, partly in cross-section, the spring element  102  mounted and clamped between the brake drum  110  and the wheel end hub  112 .  FIG. 3 d    illustrates, in a cross-sectional view, the spring element  102  mounted and clamped between the brake drum  110  and the wheel end hub  112 . 
     As shown in  FIG. 3 b   , the brake drum  110  has an has an inner surface  124  adapted to receive a friction-generating lining (not shown) when a driver applies the brakes of the vehicle. 
     As best seen in  FIG. 3 a   , the spring element  102  is substantially circular, and as best seen in  FIG. 3 b   , the spring element  102  has an outer surface  140  adapted to be pressed against the brake drum  110  and an inner surface  142  adapted to be pressed against the wheel end hub  112 . When clamped between the brake drum  110  and the wheel end hub  112 , the spring element  102  provides a radially directed spring force. The spring element  102  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. 3 b   , the spring element comprises a plurality of discrete portions  150 . These discrete portions  150 , on the outer surface  140  of the spring element  102 , configured to be in contact with the brake drum  110  for providing said radially directed spring force when the system  100  has been assembled. The discrete portions  150  are separated from each other and distributed along the circular circumferential direction of the spring element  102 . The discrete portions  150  may suitably be clamped between pilot surfaces  126 ,  130  of the brake drum  110  and the wheel end hub  112 , respectively, such as illustrated in  FIGS. 3 c    and  3   d.    
     Turning back to  FIGS. 3 a  and 3 b   , the discrete portions  150  have a wing-shaped profile. The discrete portions (profiled portions) bulge radially outwardly. When applied in the brake drum system  100 , the bulge  152  of the profile will be spaced from the wheel end hub  112 , and will be pressed against the brake drum  110 . The void space underneath the bulge  152  allows brake drum  110  to press/compress the bulge  152  radially inwardly towards the wheel end hub  152 . The resiliency and the bias of the spring element  102  will cause the bulge  152  to urge towards its original shape, i.e. providing a radial outwardly directed force onto the brake drum  110 . Since the discrete portions  150  and the bulges  152  are distributed around the circumference of the spring element  102 , the brake drum  110  will be subjected to such a force in several radial directions, thereby aligning the brake drum  110  properly. The discrete portions  150  in  FIGS. 3 a -3 d    (and in other embodiments disclosed herein) are suitably equidistantly distributed along the spring element  102 . 
     As best seen in  FIG. 3 b   , the spring element  102  has two lateral edges  154 ,  156 . One of the lateral sides  154  of the spring element  102  is formed by a radially outwardly projecting ledge  158 . The lateral sides  154 ,  156  of the spring element  102  are separated from each other in the axial direction of the spring element  102 . When the drum brake system  100  has been assembled, the projecting ledge  158  is clamped between radially extending wall portions  160 ,  162  of the brake drum  110  and the wheel end hub  112 , respectively. This is best seen in  FIG. 3 d   . The ledge  158  functions as a stop in order to reduce the risk of the spring element  102  falling off the wheel end hub  112 . Thus, as can be seen in  FIG. 3 d   , the spring element  102  will be clamped between the pilot surfaces  126 ,  130  of the brake drum  110  and the wheel end hub  112 , and will also be clamped between radially extending wall portions  160 ,  162  of the brake drum  110  and the wheel end hub  112 . The discrete portions  150  of the spring element  102  will thus be clamped in the radial direction, while the ledge  158  will be clamped in the axial direction. 
       FIGS. 4 a -4 d    illustrate a brake drum system  200 , and a spring element  202  for use in the brake drum system  200 , in accordance with at least another exemplary embodiment of the invention.  FIG. 4 a    illustrates the spring element  202  for use in the brake drum system  200 .  FIG. 4 b    is a detailed view illustrating a cross-section of the spring element  202 .  FIG. 4 c    illustrates, partly in cross-section, the spring element  202  mounted and clamped between the brake drum  210  and the wheel end hub  212 .  FIG. 4 d    illustrates, in a cross-sectional view, the spring element  202  mounted and clamped between the brake drum  210  and the wheel end hub  212 . 
     The spring element  202  shown in  FIGS. 4 a -4 d    has a ledge  258  similarly to the spring element  202  in  FIGS. 3 a   - 3   d,  and provides the corresponding stopping function, improving the keeping of the spring element  202  in place. Furthermore, the spring element  202  shown in  FIGS. 4 a -4 d    may either form an open ring or a closed ring. 
     Unlike  FIGS. 3 a   - 3   d,  the spring element  202  shown in  FIGS. 4 a -4 d    does not have such discrete profiled portions (cf. reference numeral  150  in  FIG. 3 ). Instead, the spring element  202  in  FIGS. 4 a -4 d    has a substantially constant profiled cross-section. The profiled cross-section is U-shaped, wherein the legs  270 ,  272  of the U-shape are adapted to be pressed against the wheel end hub  212  and the interconnecting bridge  274  (bulge) of the U-shape is adapted to be pressed against the brake drum  210 . The legs  270 ,  272  of the U-shape are separated from each other in the axial direction of the substantially circular spring element  202 . Thus, one leg  270  extends from the interconnecting bridge  274  of the U-shape towards the lateral side  254  having the ledge  258 , while the other leg  272  extends towards the opposite lateral side  256 . As best seen in  FIG. 4 d   , there is a void space  276  underneath the interconnecting bridge  274  of the U-shaped profile allowing the brake drum  210  to radially press/compress the interconnecting bridge  274  towards the wheel end hub  212 . The interconnecting bridge  274  of the U-shaped profile will thus be biased towards recovering its original shape and exert a radially directed counterforce on the brake drum  210 . 
       FIGS. 5 a -5 d    illustrate a brake drum system  300 , and a spring element  302  for use in the brake drum system  300 , in accordance with at least yet another exemplary embodiment of the invention.  FIG. 5 a    illustrates the spring element  302  for use in the brake drum system  300 .  FIG. 5 b    is a detailed view illustrating a cross-section of the spring element  302 .  FIG. 5 c    illustrates, partly in cross-section, the spring element  302  mounted and clamped between the brake drum  310  and the wheel end hub  312 .  FIG. 5 d    illustrates, in a cross-sectional view, the spring element  302  mounted and clamped between the brake drum  310  and the wheel end hub  312 . 
     Although the spring element  302  shown in  FIGS. 5 a -5 d    does not have a ledge at a lateral side as in the embodiments illustrated in  FIGS. 2 a -2 d  and 3 a   - 3   d,  it should be understood that in other exemplary embodiments, the spring element  302  shown in  FIGS. 5 a -5 d    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. 2 a -2 d  and 3 a -3 d    by removing the ledge. 
     As best seen in  FIGS. 5 a  and 5 b   , the spring element  302  comprises a plurality of profiled portions  350  for providing the radially directed spring force to the brake drum  310 , each profiled portion  350  having a profile bulging radially outwardly against the brake drum  310  and being spaced from the wheel end hub  312  when the system  300  has been assembled (see  FIGS. 5 c  and 5 d   ). The profile is U-shaped, wherein the legs  370 ,  372  of the U-shape are adapted to be pressed against the wheel end hub  312  and the interconnecting bridge  374  of the U-shape is adapted to be pressed against the brake drum  310 . The legs  370 ,  372  of the U-shaped profile are separated from each other in the circumferential direction of the spring element  302 . The spring element  302  is provided with a plurality of central slits  378  extending and being distributed in the circumferential direction, wherein the U-shaped profile is configured as U-shaped bulges  380 ,  382  provided on either side of each slit  378 , whereby under the inner surface of the spring element an open space  384  extends across the spring element  302  from one lateral side  354  to the other lateral side  356  of the spring element  302  when the system  300  has been assembled. 
       FIGS. 6 a -6 d    illustrate a brake drum system  400 , and a spring element  402  for use in the brake drum system  400 , in accordance with at least still another exemplary embodiment of the invention.  FIG. 6 a    illustrates the spring element  402  for use in the brake drum system  400 .  FIG. 6 b    is a detailed view illustrating a cross-section of the spring element  402 .  FIG. 6 c    illustrates, partly in cross-section, the spring element  402  mounted and clamped between the brake drum  410  and the wheel end hub  412 .  FIG. 6 d    illustrates, in a cross-sectional view, the spring element  402  mounted and clamped between the brake drum  410  and the wheel end hub  412 . 
     Although the spring element  402  shown in  FIGS. 6 a -6 d    does not have a ledge at a lateral side as in the embodiments illustrated in  FIGS. 2 a -2 d  and 3 a   - 3   d,  it should be understood that in other exemplary embodiments, the spring element  402  shown in  FIGS. 6 a -6 d    may be modified to include such a ledge at a lateral side of the spring element. 
     As best seen in  FIG. 6 b   , the spring element  402  comprises a plurality of pairs  450  of discrete portions  480 , 482 , suitably equidistantly distributed along the circumference of the spring element  402 . Each pair  450  of discrete portions comprises a discrete portion  480 ,  482  on either side of a slot  478 , wherein each discrete portion  480 ,  482  in such a pair  450  of discrete portions project radially outwardly and towards a centre of the slot  478 . In other words, in each pair  450 , one  480  of the discrete portions extends in one axial direction towards the centre of the slot  478 , while the other one  482  of the discrete portions extends in the opposite axial direction towards the centre of the slot  478 . The oblique extension (due to both radial and axial extension) of the discrete portions  480 ,  482  provide for good resiliency. Thus, when clamped between the brake drum  410  and the wheel end hub  412 , suitably between the pilot surfaces  426 ,  430  (see in particular  FIG. 6 d   ) of the brake drum  410  and the wheel end hub  412 , the discrete portions  480  will be pressed radially inwardly towards the slot  478 . The resiliency of the discrete portions  480 ,  482  will provide a counterforce directed radially outwardly on the brake drum  410 , thus supporting a proper alignment of the brake drum  410  relative to the wheel end hub  412 . 
     As can be seen in the different embodiments shown in  FIGS. 3 d , 4 d , 5 d  and 6 d   , 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. 
     It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.