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EP-4737755-A1 - DETECTING OVERADJUSTMENT OF DRUM BRAKE

EP4737755A1EP 4737755 A1EP4737755 A1EP 4737755A1EP-4737755-A1

Abstract

A computer system (11) comprising processing circuitry (13) configured to: receive a set of indications, including an indication (15) of a torque (T) provided to an S-cam (29) of a drum brake (7), and an indication (17) of an angular displacement (β) of the S-cam (29) resulting from the provided torque (T); determine, based on the set of indications, that the torque (T) is higher than a predefined threshold torque (T TH ) indicating contact between a brake lining (33a-b) of a brake shoe (31a-b) actuated by the S-cam (29) and an inner surface (37) of a brake drum (35), and the angular displacement (β) resulting from the provided torque (T) is less than a predefined threshold angular displacement ((β TH ) expected to result in contact between the brake lining (33a-b) and the inner surface (37) of the brake drum (35); and provide a signal (19) indicating that the drum brake (7) may have been overadjusted.

Inventors

  • WIPPEL, Daniel
  • TRAVAGLIA, Carlos Abilio
  • MIRANDA, EDUARDO

Assignees

  • Volvo Truck Corporation

Dates

Publication Date
20260506
Application Date
20241105

Claims (15)

  1. A computer system (11) comprising processing circuitry (13) configured to: receive a set of indications, including an indication (15) of a torque (T) provided to an S-cam (29) of a drum brake (7), and an indication (17) of an angular displacement (β) of the S-cam (29) resulting from the provided torque (T); determine, based on the set of indications, that the torque (T) is higher than a predefined threshold torque (T TH ) indicating contact between a brake lining (33a-b) of a brake shoe (3 1a-b) actuated by the S-cam (29) and an inner surface (37) of a brake drum (35), and that the angular displacement (β) resulting from the provided torque (T) is less than a predefined threshold angular displacement (β TH ) expected to result in contact between the brake lining (33a-b) and the inner surface (37) of the brake drum (35); and provide a signal (19) indicating potential overadjustment of the drum brake (7).
  2. The computer system (11) of claim 1, wherein the processing circuitry (13) is configured to: compare the torque (T) with the predefined threshold torque (T TH ); and compare the angular displacement (β) with a predefined threshold angular displacement (β TH ).
  3. The computer system (11) of claim 1 or 2, wherein: the indication (15) of the torque (T) provided to the S-cam (29) includes an indication of an air pressure (P) applied to an actuator (21) configured to convert the applied air pressure (P) to the torque (T) provided to the S-cam (29); and the processing circuitry (13) is configured to determine that the torque (T) is higher than the threshold torque (T TH ) indicating contact between the brake lining (33a-b) and the inner surface (37) of the brake drum (35), by determining that the air pressure (P) is higher than a predefined threshold pressure (P TH ) corresponding to the threshold torque (T TH ).
  4. The computer system (11) of claim 3, wherein the processing circuitry (13) is configured to: compare the air pressure (P) with the predefined threshold pressure (P TH ).
  5. The computer system (11) of any of claims 1-4, wherein: the indication (15) of the angular displacement (β) of the S-cam (29) includes a signal from an angular sensor (23) arranged to measure a rotational angle (β) of the S-cam (29); and the processing circuitry (13) is configured to determine that the angular displacement (β) is less than the predefined threshold angular displacement (β TH ) expected to result in contact between the brake lining (33a-b) and the inner surface (37) of the brake drum (35), by determining that the rotational angle (β) of the S-cam is greater than a predefined rotational angle (β TH ).
  6. The computer system (11) of claim 5, wherein the processing circuitry (13) is configured to: compare the rotational angle (β) with the predefined rotational angle (β TH ).
  7. The computer system (11) of claim 6, wherein: the angular sensor (23) is arranged to measure the rotational angle (β) of the S-cam (29) in relation to a reference angular position of the S-cam (29) when no torque is provided to the S-cam (29); and the processing circuitry (13) is configured to determine that the angular displacement (β) is less than the predefined threshold angular displacement (β TH ) expected to result in contact between the brake lining (33a-b) and the inner surface (37) of the brake drum (35), by determining that the rotational angle (β) of the S-cam (β TH ) is greater than a predefined rotational angle (β TH ) in relation to the reference angular position of the S-cam (29).
  8. A braking system (5) comprising: a drum brake (7) including first and second brake shoes (3 1a-b) movable by rotation of an S-cam (29) to push brake linings (33a-b) of the brake shoes (3 1a-b) towards an inner surface (37) of a brake drum (35) of the drum brake (7); a brake actuator (21) controllable to rotate the S-cam (29); a torque indicating arrangement (25) configured to provide an indication (17) of a torque (T) provided to the S-cam (29) of the drum brake (7); an angular displacement indicating arrangement (23) configured to provide an indication (15) of an angular displacement (β) of the S-cam (29); and the computer system (11) of any of claims 1-7 coupled to the torque indicating arrangement (25) and the angular displacement indicating arrangement (23).
  9. The braking system (5) of claim 8, wherein: the brake actuator (21) comprises an air brake chamber (39), a push rod (41) linearly movable by increasing an air pressure (P) in the air brake chamber (39), and a lever arrangement (43) coupled to the push rod (41) and to the S-cam (29) to convert linear movement of the push rod (41) to rotation of the S-cam (29); and the torque indicating arrangement (25) is configured to provide an indication (17) of the air pressure (P) in the air brake chamber (39).
  10. The braking system (5) of claim 8 or 9, wherein: the angular displacement indicating arrangement (23) comprises an angular sensor arranged to measure a rotational angle (β) of the S-cam (29).
  11. A vehicle (1) comprising: at least one vehicle wheel (3); and the braking system (5) of any of claims 8-10.
  12. A computer-implemented method, comprising: receiving (S51) a set of indications, including an indication (15) of a torque (T) provided to an S-cam (29) of a drum brake (7), and an indication (17) of an angular displacement (β) of the S-cam (29) resulting from the provided torque (T); determining (S52), based on the set of indications, that the torque (T) is higher than a threshold torque (T TH ) indicating contact between a brake lining (33a-b) of a brake shoe (31a-b) actuated by the S-cam (29) and an inner surface (37) of a brake drum (35), and the angular displacement (β) resulting from the provided torque (T) is less than a predefined threshold angular displacement (β TH ) expected to result in contact between the brake lining (33a-b) and the inner surface (37) of the brake drum (35); and providing (S53) a signal (19) indicating that the drum brake (7) may have been overadjusted.
  13. The method of claim 12, wherein: the indication (15) of the torque (T) provided to the S-cam (29) includes an indication of an air pressure (P) applied to an actuator (21) configured to convert the applied air pressure (P) to the torque (T) provided to the S-cam (29); and the method comprises determining (S42) that the torque (T) is higher than the threshold torque (T TH ) indicating contact between the brake lining (33a-b) and the inner surface (37) of the brake drum (35), by determining that the air pressure (P) is higher than a predefined threshold pressure (P TH ) corresponding to the threshold torque (T TH ).
  14. The method of claim 12 or 13, wherein: the indication (15) of the angular displacement (β) of the S-cam (29) includes a signal from an angular sensor (23) arranged to measure a rotational angle (β) of the S-cam (29); and the method comprises determining that the angular displacement (β) is less than the predefined threshold angular displacement (β TH ) expected to result in contact between the brake lining (33a-b) and the inner surface (37) of the brake drum (35), by determining that the rotational angle (β) of the S-cam is greater than a predefined rotational angle (β TH ).
  15. A computer program product comprising program code for performing, when executed by the processing circuitry (13) comprised in the computer system (11) of any of claims 1-7, the method of any of claims 12-14.

Description

TECHNICAL FIELD The disclosure relates generally to monitoring of a drum brake. In particular aspects, the disclosure relates to detection of overadjustment of a drum brake. The disclosure can be applied to heavy-duty vehicles, such as trucks, buses, and construction equipment, among other vehicle types. Although the disclosure may be described with respect to a particular vehicle, the disclosure is not restricted to any particular vehicle. BACKGROUND To maintain proper operation of a drum brake over the service life of the brake linings, the starting position of the S-cam may be continuously adjusted. For various reasons, such adjustment may result in insufficient clearance between the brake linings of the brake shoes and the inner surface of the brake drum. This is referred to as "overadjustment, and may result in overheating of the drum brake. It would be desirable to be able to detect overadjustment during operation of the vehicle equipped with the drum brake. SUMMARY According to a first aspect of the disclosure, there is provided a computer system comprising processing circuitry configured to: receive a set of indications, including an indication of a torque provided to an S-cam of a drum brake, and an indication of an angular displacement of the S-cam resulting from the provided torque; determine, based on the set of indications, that the torque is higher than a predefined threshold torque indicating contact between a brake lining of a brake shoe actuated by the S-cam and an inner surface of a brake drum, and the angular displacement resulting from the provided torque is less than a predefined threshold angular displacement expected to result in contact between the brake lining and the inner surface of the brake drum; and provide a signal indicating that the drum brake may have been overadjusted. The first aspect of the disclosure may seek to enable detection of overadjustment of a drum brake during operation of the vehicle equipped with the drum brake. A technical benefit may include that a signal can be provided, to alert an operator that the drum brake needs to be checked, and may need to be adjusted. Hereby, it may be possible to prevent or at least limit overheating of the drum brake. The operator may be, for example, a driver or an autonomous driving system. Examples of the present disclosure may mainly be useful for monitoring drum brakes of the kind with automatic adjustment of the brakes to compensate for wear of the brake linings of the brake shoes. As the brake linings wear out, the starting point for the S-cam (when no brake pressure is applied) may be automatically adjusted towards maintaining a substantially constant pre-defined clearance between the brake linings and the inner surface of the brake drum. If the adjustment does not result in the pre-defined clearance, but a larger clearance, the drum brake can be said to be "underadjusted". The result will be too large brake pedal travel when braking, resulting in longer reaction time. If the adjustment does not result in the pre-defined clearance, but a smaller clearance, the drum brake can be said to be "overadjusted". The result may be that the drum brake becomes more sensitive to, for example, temperature variations. If the brake becomes hot, for example after application of the brakes, the resulting clearance might become so small that there is at least intermittent contact between the brake linings and the inner surface of the brake drum, even when the brake pedal is not actuated. This can lead to more heat, and eventually overheated brakes. Through examples of the present disclosure, this latter situation can be detected, and a signal can be provided indicating that the drum brake may have been overadjusted. Optionally in some examples, including in at least one preferred example, the processing circuitry may be configured to: compare the torque with the predefined threshold torque; and compare the angular displacement with a predefined threshold angular displacement. Optionally in some examples, including in at least one preferred example, the indication of the torque provided to the S-cam may include an indication of an air pressure applied to an actuator configured to convert the applied air pressure to the torque provided to the S-cam; and the processing circuitry may be configured to determine that the torque is higher than the threshold torque indicating contact between the brake lining and the inner surface of the brake drum, by determining that the air pressure is higher than a predefined threshold pressure corresponding to the threshold torque. A technical benefit may include that air pressure is a convenient way of operating drum brakes, which is widely used. It may be relatively easy to determine that the air pressure is higher than a predefined threshold pressure. For example, the air pressure applied to the actuator may be measured, or a command indicative of an air pressure can be used as in indication of the actuall