The present invention pertains to work vehicles and, more specifically, to work vehicles that include a park brake.
Typically, work vehicles include a service brake system as well as a park brake system. The park brake may be used in isolation to hold the vehicle at rest in a parked position, or the park brake may be used as a secondary brake in conjunction with the primary service brakes in a situation in which the vehicle needs to stop in a quick or abrupt manner. The park brake may be incorporated into the mechanical transmission of the vehicle. For instance, the park brake may be provided at some location within the power train of the work vehicle, which connects the rotational output of the vehicle's power unit to the drive wheels. Generally, a park brake will include two sets of annular friction plates and an actuator to force the respective plates together in order to retard the movement of a torque-carrying power shaft. The first set of annular friction plates, for example steel plates, may be fixed to the park brake housing such that the first set of plates may move axially but are rotationally fixed. The second set of annular friction plates may be coupled to the torque-carrying power shaft such that the second set of plates rotate along with the shaft. In this regard, the friction between the plates slows the rotation of the power shaft. The plates may be submersed in a lubricant within the park brake housing.
Overtime the secondary brake may become worn or damaged. Generally, the park brake as a secondary brake can only be engaged for a finite number of times to stop a moving vehicle. For example, the application of the secondary brake at a high speed and/or at a high vehicle load can generate heat and cause wear which may damage the park brake. As can be appreciated, it can be advantageous to regularly service and/or replace the secondary brake. For example, vehicle functions may degrade if the secondary brake is worn or damaged. However, an operator or a dealer may not be aware of the condition of the secondary brake.
What is needed in the art is a system and method for estimating the life of a secondary brake.
The present invention provides a system and method for calculating the park brake energy, determining the remaining life of the park brake, and informing an individual of the remaining life of the park brake. The present invention also can inform an individual how much the park brake has been damaged.
The invention in one form is directed to a vehicle including a shaft, a park brake connected to the shaft and configured to retard a rotation of the shaft, and a park brake prognosis system associated with the shaft and the park brake. The park brake prognosis system includes a controller that is configured to calculate a status of the park brake dependent on a park brake energy of at least one engagement of the park brake and a first sensor operably coupled to the controller and the shaft. The first sensor is configured to provide a speed of the shaft. The park brake prognosis system also includes a second sensor operably coupled to the controller and the shaft. The second sensor is configured to provide an instantaneous torque of the shaft.
The invention in another form is directed to a method for estimating a park brake life of a park brake which retards a shaft of a vehicle. The method includes the steps of providing a park brake prognosis system. The park brake prognosis system includes a controller that is configured to calculate a status of the park brake, a first sensor operably coupled to the controller and the shaft, the first sensor is configured to provide a speed of the shaft, and a second sensor operably coupled to the controller and the shaft. The second sensor is configured to provide an instantaneous torque of the shaft. The method includes the further steps of calculating a park brake energy of at least one engagement of the park brake, and calculating the park brake life status dependent on the park brake energy.
The invention in yet another form is directed to a method for estimating a park brake life of a park brake which retards a shaft of a vehicle. The method includes the steps of providing a park brake prognosis system. The park brake prognosis system includes a controller that is configured to calculate a status of the park brake, a first sensor operably coupled to the controller and the shaft, the first sensor is configured to provide a speed of the shaft, and a second sensor operably coupled to the controller and the shaft. The second sensor is configured to provide an instantaneous torque of the shaft. The method includes the further steps of determining by the controller whether the park brake is engaged, calculating by the controller a park brake energy of an engagement of the park brake, calculating by the controller a remaining brake life number dependent on the park brake energy, and determining by the controller whether the remaining brake life number is greater than zero. The method further includes one of repeating the steps of determining whether the park brake is engaged, calculating the park brake energy, calculating the remaining brake life number, and determining whether the remaining brake life number is greater than zero dependent upon the remaining brake life number being greater than zero, or notifying an individual of the status calculated by the controller dependent upon the remaining brake life number not being greater than zero.
An advantage of the present invention is that an individual may be notified of the wear and/or damage of a park brake of a vehicle.
Another advantage of the present invention is that the remaining life of a park brake may be cost-effectively and efficiently calculated as a function of the park brake energy.
For the purpose of illustration, there is shown in the drawings a certain embodiment of the present invention. It should be understood, however, that the invention is not limited to the precise arrangements, dimensions, and instruments shown. Like numerals indicate like elements throughout the drawings. In the drawings:
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates an embodiment, in one form, of the invention and such exemplification is not to be construed as limiting the scope of the invention in any manner.
Referring now to the drawings, and more particularly to
The park brake 28 may include a park brake housing 34, two sets of annular friction plates 36, 38, and an actuator (not shown) which forces the plates 36, 38 to contact one another. The first set of friction plates 36 may be axially moveable but rotationally fixed relative to the park brake housing 34. The second set of friction plates 38 may be coupled to the park brake shaft 30 such that the friction plates 38 rotate along with the shaft 30. The friction plates 36, 38 may be composed of any desired material such that they provide a sufficient friction force to retard the motion of the park brake shaft 30. Additionally, the friction plates 36, 38 may be submersed in a lubricant within the park brake housing 34. It is noted that a park brake engagement may be defined as retarding of the shaft 30, for example, from an initial time when the friction plates 36, 38 first engage with each other till a time when the shaft 30 is completely stopped.
The park brake prognosis system 32 may include a controller 40, one or more speed sensor(s) 42, one or more sensor(s) 44 configured to provide a torque of the shaft 30, and an indicator 46. The park brake prognosis system 32 is configured to calculate the park brake energy, determine a status of the park brake life, or a percent thereof, and inform an operator and/or a dealer of the status of the park brake life so that the park brake may be serviced and/or replaced. The park brake prognosis system 32 determines the remaining park brake life dependent on the park brake energy.
The controller 40 is configured to calculate a status of the park brake 28. The controller 40 may be located on the work vehicle 10 and/or incorporated into the existing control system of the work vehicle 10. The controller 40 may be in the form of a CPU, an ECU, or a processor. The controller 40 may also include a memory 48, which may be preloaded with certain parameters pertaining to the operation of a particular type of park brake. For example, the memory 48 may include a set of values corresponding to the maximum number of engagements that a particular park brake 28 may be desirably used for until service and/or replacement of the park brake 28 is desired. Additionally, the memory 48 may include a set of predetermined values corresponding to any desired or a maximum number of engagements that the park brake 28 may be able to take without getting damaged at a specified park brake energy level.
The speed sensor 42 and the torque sensor 44 may be operably coupled to the controller 40 as well as to the park brake shaft 30. The speed sensor 42 is configured to provide the speed of the brake shaft 30, and the torque sensor 44 is configured to provide the instantaneous torque acting on the brake shaft 30. Either sensor 42, 44 may communicate to the controller 40 via a wired or wireless connection. The speed sensor 42 may be in the form of a known speed sensor, for example, a magnetic speed sensor that couples to the shaft 30 and monitors the speed of the shaft 30. The torque sensor 44 may be in the form of a non-contact sensor or a contact sensor which couples to the shaft 30. For example, the torque sensor 44 may be in the form of a strain gauge or a clamp-on torque cell. Additionally, the sensor 44 may be in the form of a pressure or tracer sensor 44, which is used to calculate the torque of the shaft 30. Thereby, for example, the brake torque information may be obtained by measuring the brake pressure, and then the controller 40 may calculate the instantons brake torque.
The indicator 46 may be operably coupled to the controller 40 and may be configured for notifying an individual, such as an operator or dealer, of the status that is calculated by the controller 40. The indicator 46 may be located within the work vehicle 10. For example, the indicator 46 may be in the form of a visual indicator, such as an indicator light located within the cab of the work vehicle 10. Additionally, the indicator 46 may be integrated as part of a display unit which has a graphic or a display that informs the operator that the park brake 28 should be serviced and/or replaced. Alternatively, the indicator 46 may be located away from the work vehicle 10 such that a dealer of the work vehicle 10 may be notified of the need to replace the park brake 28. For example, an individual, e.g., a dealer, may be wirelessly notified of the status of the park brake 28.
The controller 40 may calculate the total park brake energy for a given engagement (i.e. application) of the park brake 28, as shown in the algorithm below. For example, the controller 40 may calculate the park brake energy over an engagement period which spans from an initial time when the plates 36, 38 first contact each other till the time at which the park brake shaft 30 completely stops rotating. Thereby, the total energy during one park brake application can be calculated as:
E
pb=∫0Tτpb(t)·ω(t)dt
The total park brake energy of a single engagement of the park brake 28 is accumulated from the time the park brake 28 is initially engaged, e.g. t=0, until the time the brake shaft 30 stops rotating. Epb is the total amount of park brake slippage energy generated during one park brake application. τpb (t) is the instantaneous park brake torque which may be provided by the torque sensor 44. ω(t) is the park brake shaft speed which may be provided by the speed sensor 42.
The controller 40 may then determine the remaining brake life number (RBLN) which is dependent on the park brake energy during one or more engagement(s) as calculated above. The controller 40 may then report the status of the park brake 28 if the RBLN approaches a predetermined value. For example, a park brake end of life warning status may be reported when the RBLN value approaches zero, is zero, or falls below zero. With reference to
If the total accumulated energy during a first park brake engagement is E3, then the brake life deterioration number (BLDN) is calculated as:
If the total accumulated energy during a second park brake engagement is E2, then the accumulated BLDN is calculated as:
If energy during a third park brake engagement is less than E1, then the BLDN does not change from the second park brake engagement because no damage is generally done to the park brake 28 at an energy level which is less than E1.
As BLDN increases, RBLN reduces as depicted below:
RBLN=BLDNThreshold−BLDN
The BLDNThreshold may be defined as C4 (e.g. the threshold engagement number at a specified energy level). Thereby, the RBLN may be equal to the value of C4 subtracted by the summation of the number of engagements at distinct energy levels for each individual engagement of the park brake 28 as it is used over the course of its operational life. In other words, the RBLN may be based on the park brake energy E1, E2, E3, E4 and the number of engagements C1, C2, C3, C4. The memory 48 may include the values of the predetermined maximum number of engagements C1, C2, C3, C4, CN that the park brake 28 can take at a given park brake energy level E1, E2, E3, E4, EN until service and/or replacement is desired (
Referring now to
Referring now to
These and other advantages of the present invention will be apparent to those skilled in the art from the foregoing specification. Accordingly, it is to be recognized by those skilled in the art that changes or modifications may be made to the above-described embodiments without departing from the broad inventive concepts of the invention. It is to be understood that this invention is not limited to the particular embodiments described herein, but is intended to include all changes and modifications that are within the scope and spirit of the invention.