Electronic stroke sensor for air disc brake

Description

BACKGROUND OF THE INVENTION

[0001] This application is a continuation in part of Application No. 14 / 054,049, filed October 15, 2013, a continuation of Application No. 13 / 162,691, filed June 17, 2011, which claims the benefits of U.S. Patent Application No. 61 / 356,325 filed 18 June 2010

[0002] The present invention relates to an electronic brake stroke control indicator for a vehicle brake. More specifically, the present invention is related to an electronic air brake stroke control indicator for use in heavy duty trucks, transit buses or similar commercial vehicles.

[0003] The miles driven by heavy trucks and passenger buses increase significantly every year. As the size of powered passenger cars has become smaller due to the increase in gasoline prices, it is becoming more and more necessary to ensure the proper operation of the brake actuators and braking systems of these heavy-duty vehicles to give the truck operator every opportunity to avoid losing control. Therefore, various brake actuator stroke monitoring systems have been developed for use in drum brakes, widely used in industrial vehicles.

[0004] However, in heavy duty trucks, such as for example buses, the use of air disc brakes is becoming more and more popular. While extensive basic drum brake monitoring has been achieved, monitoring of additional conditions known to cause unsafe driving conditions, such as for example low brake pad clearance, has not been achieved.

[0005] The prior art uses brake monitoring systems as described in US 2003/0222774 A1. Brake monitoring systems used in air drum brakes are designed to monitor the stroke length of the follower extending from inside the brake actuator chamber. Monitoring enables the user to determine if the brake actuator is functioning properly, is over-travel, or is in a suspended or locked state. Monitoring these conditions by monitoring the follower stroke is possible because the follower of the brake actuator is permanently attached to the drum brake actuator. In the case of an suspended or locked brake, the drum brake actuator is immobilized in the actuated position preventing the return of the push rod to the non-actuated position when the brake pedal is released by the vehicle operator.

[0006] However, the pusher of the disc brake actuator is not permanently attached to the caliper lever arm that actuates the disc brake. Accordingly, when a suspended or locked brake occurs, the lever arm becomes separated from the follower, making the type of monitoring system used in a drum brake not functional with a disc brake. An electronic sensor that monitors the movement of the follower detects that the follower has returned to the non-actuated position and incorrectly detects that the brake is operating normally. Accordingly, it has become necessary to develop a vehicle brake monitoring unit that is capable of identifying and distinguishing an overextension condition from the brake suspension condition of an air disc brake.

SUMMARY OF THE INVENTION

[0007] A vehicle brake control indicator assembly for an air brake includes a brake actuator having a follower extending from within the brake actuator chamber. The follower releasably actuates the caliper arm to move the disc brake to the brake position when the follower is in the extended position and releases the disc brake from the brake position when the follower is placed in the retracted position. The follower comprises a follower shaft and a contact member biased in a telescopic relation to the follower shaft. The clamp lever arm rests on the contact member and counteracts the bias of the contact member, preventing the contact member from slipping telescopically from the follower pin. The sensor is integrated in the assembly near the contact member. A sensor detects the movement of the follower relative to the lever arm and the follower shaft.

[0008] A sensor that is disposed adjacent to the contact member detects differences in transmission along the length of the contact member, which enables the condition of the brake actuator to be determined. For example, a sensor detects when the brake is in normal operation, in the locked condition of the brake, in an over-travel condition, or when out of adjustment. As indicated above, previous attempts to monitor all these conditions for the air brake have been unsuccessful. In particular, prior monitoring devices have not been able to identify the sagging condition of the brake due to the separation of the push rod from the air brake lever arm. This separation is created when the lever arm is locked in the actuated position and the vehicle operator releases the brake pedal, causing the push rod to be pulled into the brake actuator. The telescopic structure of the present invention enables the sensor to detect when the lever arm is locked in the actuated position.

[0009] Another advantage of the present kit according to the invention is its use in a conventional brake caliper without modifying the caliper. Earlier attempts to monitor disc brakes require modifying the brake caliper to determine if the lever arm is locked in the engaged position. By providing an array of sensors near the actuator follower, the inventive assembly has eliminated the need to modify the caliper of the air disc brake system to detect a locked condition of the brake.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Other advantages of the present invention will be readily appreciated as they become better understood by reference to the following detailed description taken in conjunction with the accompanying drawings, in which:

Figure 1 shows a side section of a brake monitoring assembly according to the present invention;

Figure 2a shows a first embodiment of the follower according to the present invention;

Figure 2b shows an alternative embodiment of the follower according to the present invention;

Figure 3 shows an exploded view of the follower according to the present invention;

Figure 4 shows the brake actuator in the extended position in the normal operating condition;

Figure 5 shows a partial section of the brake actuator in an over-travel condition; and

Figure 6 shows a brake actuator according to the present invention in a suspended or locked state.

DETAILED DESCRIPTION OF THE INVENTION

[0011] The brake actuator is shown generally at 10 in Figure 1. The brake actuator 10 includes a brake control indicator assembly 12 for determining whether the brake actuator is operating in a normal or error state, as will be explained further below. The brake cylinder 10 includes a pusher 14 located inside the working chamber 16. One skilled in the art should understand that the working chamber 16 can also be used in conjunction with a secondary chamber or drive spring chamber (not shown), and with various other brake actuator configurations that may be necessary for a given vehicle brake system.

[0012] The working chamber 16 comprises a diaphragm 18 which is fixed between the upper housing member 20 and the lower housing member 22. Therefore, the working chamber 16 is separated by a diaphragm 18 into a pressure side 24 (best seen in Fig. 4) and a return (non-pressurized) side 26 which houses a return spring 28. Pressurized air enters the pressure side 24 of the working chamber 16 through a port 30 of pressurized air, the pressure of which is monitored by a pressure sensor 32. While a pressure sensor 32 is shown near the working chamber 16, the inventors predict that a pressure sensor 32 is located on the pedal valve. (brake pedal) of the vehicle. It should be understood by those skilled in the art that each embodiment also includes a separate pressure sensor (not shown) disposed within the brake pedal to identify the pressure applied by the vehicle operator to the brake pedal. When the operator actuates the brake pedal, compressed air passes through the pressurized air port 30 forcing the diaphragm 18 against the follower 14, causing the follower 14 to come out of the working chamber 16 in a known manner.

[0013] When the vehicle operator depresses the brake pedal, as illustrated above, air pressure enters the pressure side 24 of the working chamber 16 through the pressurized air port 30, pushing the follower 14 out of the working chamber. The lever arm 34 located inside the telltale 36 is rotated by the follower 14 as it protrudes outward, causing the brakes (not shown) of the vehicle to be applied in a known manner. When the vehicle operator releases the pressure from the brake pedal, air is discharged from the pressure side 24 of the working chamber 16, and the return spring 28 pushes the pusher 14 inside the working chamber 16, allowing the lever arm 34 to return to its non-actuated position. It should be understood by those skilled in the art that the control indicator 36 described above is operating in the normal manner.

[0014] Referring now to Figure 2A, the follower 14 includes a contact member 38 that surrounds the follower shaft 40. The contact member 38 forms a tip 41 which rests on the arm 34 of the control indicator lever 36. The follower shaft 40 is received in a tubular hole 42 defined by the contact member 38. A shim 44 is positioned on the base 46 of the tubular hole 42 and is interposed between the stop 48 the follower shaft 40 and the base 46. The shim 44 is provided in multiple thicknesses by which the length of the follower 14 is adjusted to ensure dimensional accuracy between the tip 41 of the contact member 38 and the lever arm 34 as will be seen more clearly below.

[0015] The follower shaft 40 has an elongated bore 50 into which a biasing member 52, shown here as a spring, is disposed. The biasing member 52 is compressed between the floor 53 and the end wall 54 of the elongated opening 50. Therefore, the biasing member 52 provides a biasing force that telescopes the contact member 38 from the follower shaft 40, effectively extending the follower 14.

[0016] The follower shaft 40 has a circumferential groove 56 for receiving a retaining member 58 that is permanently attached to the inner wall 60 of tubular member 42. The retainer 58 slides in an axial direction defined by the follower shaft 40 within the space of the groove 56 The stop 62 prevents the biasing member 52 from separating the contact member 38 from the follower shaft 40 while abutting the retaining member 58. The stop 62 is a spring clip or equivalent positioned in a notch 63 (FIG. 3) in the follower shaft 40.

The sensor member 64 is disposed between the processing chamber 16 and the inspection indicator 36. Inside the sensor member 64 a sensor 66 is provided and sensing access to the contact member 38 is provided, which is provided through an aperture 68 in the sensor member 64. The sensor 66 communicates. via communication line 70 with the controller or central processing unit (CPU) 72. It is envisioned by the inventors that the sensor 66 is in the form of an optical sensor, a magnetic sensor, a mechanical sensor, or an enhanced radio frequency sensor. For the sake of clarity, however, the following description describes an optical sensor, further provided as an infrared sensor. The embodiment uses the OPB733TR Optek optical infrared sensor capable of both transmitting an infrared signal and receiving a reflected infrared signal input. However, those skilled in the art should understand that any of the sensors described above may function. As best shown in Figure 2a, contact member 38 has a non-reflecting surface 74, a semi-reflective surface 76, and a fully reflecting surface 78.

[0018] As best seen in Figure 1, the sealing skirt 80 is sealed to the follower shaft 40 at the upper end and to the sensor member 64 at the opposite end. Therefore, the contact member 38 and the non-reflecting, semi-reflecting and fully reflecting surfaces 74, 76, 78 are protected from environmental contamination which is known to enter the work chamber 16. The second seal 82 seals the sensor member 64 against the control indicator 36 which is fully closed to protect the lever arm 34 from environmental contamination. Therefore, the contact member 38 and the sensor 66 are completely protected from the environment, which prevents the optical sensor 66 and the reflecting surfaces 74, 76, 78 from becoming dirty.

[0019] An alternative embodiment is shown in Figure 2b, where the common elements have the same numbers as the elements disclosed in Figure 2a. In an alternate embodiment, an alternate contact member 84 and line sensor 86 are used. Alternative contact member 84 includes an alternative reflective coating 88 that has a variable reflective surface. The first end 90 of the contact member is more reflective than the second end 92 of the contact member, with a gradual transition therebetween. The sensor detects variations in the amount of reflection by determining the position of the alternative contact member 84, and therefore lever arm 34, as will be more apparent in the description below.

[0020] The sequence of monitoring the brake will now be described. The inventors contemplate that sensor 66 is an infrared sensor that transmits an infrared signal towards contact member 38 which has varying degrees of reflection, as described above, to reflect the infrared signal back towards sensor 66 which in turn signals the controller 72 of degree reflectance via communication lines 70. It will be appreciated by one of skill in the art that other optical sensors may be used, including photoelectric digital lasers, conventional lasers, and their equivalents.

In normal operation, after the brake is released (shown in Figure 1), the optical sensor transmits a light signal towards the non-reflecting surface 74 of contact member 38 without receiving a reflection signal from contact member 38. Pressure applied to the brake as indicated by pressure sensor 32 is less than or equal to about 2 psi (lb / in²). Therefore, no active fault is signaled to the vehicle operator.

[0022] Referring now to Figure 4, pressure is applied to the brake pedal by the operator, causing air to flow into the pressure side 24 of the working chamber 16, which actuates the lever arm 34. As the pusher 14 is pushed out of the work chamber 16 by the diaphragm 18, the sensor 66 is placed near the semi-reflecting surface 76 of the contact member 38. The pressure sensor 32 signals an air pressure greater than or equal to about 2 psi (lb / in.²), signaling the normal operation of the brake actuator 10 as long as sensor 66 detects reflection from the semi-reflective surface 76. The present inventors predict that the semi-reflective surface 76 reflects about thirty percent of the light transmitted from sensor 66. It should be noted that the biasing member 52 remains fully compressed. because the lever arm 34 counteracts the biasing force of the biasing member 52 during the normal, actuated state.

[0023] Figure 5 shows an overtravel condition causing the controller 72 to signal the operator that there is a failure condition. In the over-travel condition, the follower 14 extends out of the work chamber 16 beyond the normal extension length so that the sensor 66 transmits a light signal to the fully reflecting surface 78 and detects total reflection. The brake pressure detected by the pressure sensor 32 is greater than or equal to about 2 psi (lb / in²). Thus, sensor 66 signals the controller to fully bounce at normal operating pressure, which causes the controller to signal an overtravel condition to the operator.

[0024] Figure 6 shows the locked brake condition. The locked brake condition is identified by the controller 72 both when the vehicle is traveling at ground speed and when the vehicle is stationary at ground speed. Under the locked brake condition, air pressure is released on the pressure side 24 of the working chamber 16 causing the return spring 28 to retract the follower 14 into the working chamber 16. However, since the brake is now in the locked state, the lever arm 34 is held in the actuated position causing separation from the contact member 38. As the lever arm 34 no longer counteracts the biasing force of the biasing member, biasing member 52 causes the contact member 38 to telescopically extend. from the shaft 40 of the pusher. Therefore, the sensor 66 now transmits the light signal towards the semi-reflective surface 76 of the contact member 38 as opposed to transmitting the light signal towards the non-reflecting surface 74 which is typical of a normally operating brake. As compressed air has been released from the pressure side 24 of the working chamber 16, the pressure applied to the brake is now less than or equal to about 2 psi (lb / in.²). The combination of semi-reflective surface 76, detected by sensor 66, and low air pressure less than or equal to about 2 psi (lb / in²), causes the controller 72 to indicate the brake locked or suspended condition.

Another defective condition is indicated when the sensor 66 detects a non-reflecting surface 74 when the brake pedal is depressed by the operator, causing the air pressure to be greater than or equal to about 12 psi (lb / in.²). In this case, the controller signals to the operator the faulty state of the actuator.

Controls used in heavy truck applications typically adjust on their own to maintain a constant operating clearance between the brake pads and the rotating disc as the brake pad wears. When functioning properly, the self-adjusting indicator gauge adjusts to maintain a constant ground clearance as the brake pads wear over time. The self-adjusting telltale is known to malfunction and creates an out of adjustment condition when the play between the brake shoes and the rotating disc is less than desired, e.g. less than 6mm. In this situation, normal use of the braking system causes the brake pads to wear faster, generate undesirable heat, resulting in fires or other problems.

[0027] An out-of-adjustment condition or a small brake lining play may be detected by the controller 72. For example, pressure on the brake pedal is applied by the operator causing air to fill the pressure side 24 of the work chamber 16 to activate the lever arm 34. As the pusher 14 is pushed out of the work chamber 16 by the diaphragm 18, the sensor 66 is placed close to the semi-reflective surface 76 of the contact member 38. Pressure sensor 32 signals an air pressure greater than or equal to about 2 psi (lb / in²), indicating normal operation of the brake actuator 10 as long as the sensor 66 detects rebound from the semi-reflecting surface 76. As pressure is still applied to the brake pedal by the operator, the follower and lever 34 are stopped because brake pad play is small due to an out of adjustment condition . Depending on the level of out-of-control condition, the sensor 66 may be located near the transition point between the semi-reflective surface 76 and the non-reflective surface 74. In this position, because normal pressure variations occur, the position of the sensor 66 will oscillate between the semi-reflective surface 76 and the non-reflective surface 74. The combination of the air pressure readings of this swinging and normal air causes controller 72 to indicate an out of control condition. Pressure differences occur even as the operator tries to maintain a constant brake pedal position.

[0028] False positive out of control signals are reduced by triggering out of control in response to a predetermined number of preceding out of control errors in combination with a predetermined number of out of control errors. The pre-error counter is used to detect the number of pendulum changes between the semi-reflecting zone 76 and the non-reflecting zone 74 in the ignition cycle. The down error counter is for detecting the number of down errors in the power cycle of controller 72. In this embodiment, an out-of-control condition is identified after detecting a predetermined number of preceding out-of-control states and a predetermined number of down errors. For example, in one embodiment, two announced out-of-control faults and two out-of-control faults trigger an out of control condition.

As discussed above, instead of the non-reflecting, semi-reflective, and fully reflective surfaces 74, 76, 78, the surfaces include other predetermined characteristics capable of transmitting light to identify the amount of tappet extension 14. For example, in one embodiment, surface 76 is a fully reflective surface, while surfaces 74 and 78 are both non-reflective. In this way, the sensor 66 can provide a binary signal. In such an embodiment, the driver determines that an error condition exists, but additional logic may be used to determine the specific error condition. When the sensor detects a non-reflecting surface 74 or 78 during normal pressures applied to the brake, and the sensor never detects a fully reflecting surface 76, the controller 72 determines that the non-reflecting surface 74 has been detected, and the error is a brake malfunction error. When the sensor detects the reflective surface 76 followed by the non-reflecting surface 74 or 76 during normal pressures applied to the brake, the controller 72 determines that the error condition is either an overtravel condition or an out of control condition. In one embodiment, the overtravel condition and the out of control condition are distinguished by monitoring the return stroke of the follower. If the sensor detects the fully reflecting surface 76 as the pressure drops to the resting pressure, then the controller 72 determines that the non-reflective surface 76 has been detected and the failure is an overtravel fault. If the sensor does not detect a fully reflecting surface 76 when the pressure drops, the controller determines that a non-reflective surface 74 has been detected and the error is an out of control condition.

[0030] The invention has been described in an illustrative manner, and it should be understood that the terminology that has been used is verbal to the description rather than limiting.

[0031] Obviously, numerous modifications and variations of the present invention are possible in light of the foregoing. For example, a hall effect sensor or equivalent may be used in conjunction with a magnet coupled to contact member 38 having a varying degree of magnetism. It is therefore to be understood that the reference numbers herein are for convenience only and should not be limiting in any way, and that the invention may be practiced otherwise than specifically described.

[0032] Further further embodiments are described below to aid the understanding of the invention.

[0033] A first further example describes a method for detecting an error condition of a pneumatic disc brake, the method comprising the steps of: providing a brake actuator having a follower extensible from said brake actuator for actuating a pneumatic disc brake lever arm; monitoring the extension length of said follower from said brake cylinder; monitoring the air pressure of said brake actuator; detecting a fault condition beyond the pneumatic disc brake adjustment based on said monitoring of the follower extension length of said brake cylinder and said air pressure monitoring of said brake cylinder without detecting the condition of the air disc brake. Moreover, said step of monitoring the extension length of said follower can be further determined by detecting the variation of marks provided on said follower. Moreover, the method may further include the step of correlating the air pressure of said brake actuator with a normal activated position and a normal retracted position. Moreover, the method may further include detecting a normal condition by detecting predefined marks on said follower in response to detecting an air pressure correlated with the normal actuated position of said brake actuator. Moreover, the method may further include detecting an overtravel condition by detecting predefined marks on said follower, in response to detecting an air pressure correlated with the normal actuated position of said brake actuator. Also, the method may further include determining whether an error condition is said error condition out of control or said overtravel condition based on said monitoring of the extension length of said follower and said monitoring the air pressure of said brake actuator during the return stroke of said follower. Also, the method may further include detecting a non-operating condition by detecting predefined marks on said follower in response to detecting an air pressure correlated with the normal actuated position of said brake actuator. Also, the method may further include detecting said error condition out of control, may include detecting first predefined marks on said follower in response to detecting air pressure correlated with the normal actuated position of said brake actuator, and detecting second predefined marks on said follower in response to detecting a correlated air pressure. with the normal actuated position of said actuator brake. Further, detecting said error condition out of control may include: detecting a plurality of preceding out-of-control errors, each of which preceding out-of-control errors are detected by detecting a first predefined mark on said follower in response to detecting an air pressure correlated with the normal actuated position of said brake actuator, and detecting a second, different, predefined marks on said follower in response to detecting air pressure correlated with the normal actuated position of said brake actuator; and detecting a plurality of down states, each by detecting predefined marks on said correlated air follower of said actuator in response to detecting a pressure with normal brake actuation pressure; and detecting said plurality of preceding out-of-control errors and said plurality of non-performance errors occurring during the ignition cycle of the vehicle. Also, said step of detecting the changes of said markers may additionally be defined by detecting the changes in the reflectance of said marks. Also, the said step of detecting the change in reflectance of said marks may be further defined by detecting the linear change in reflectance of said marks. Furthermore, said step of detecting a change in reflectance of said markers may be further defined by detecting a plurality of characteristic surfaces of said markers, each surface of which may have different reflectance amounts.

[0034] In another further example, a vehicle brake control indicator assembly is described, comprising: a brake actuator having a pusher slidably protruding from the cavity of said brake actuator, said pusher actuating a lever arm thereby moving the vehicle brake to the actuated position when said pusher is in the extended position and permitting the vehicle brake to be moved to the retracted position when said pusher is in position. located in the retracted position; a pressure sensor for detecting the pressure since the brake pedal is actuated; an optical sensor transmitting a light signal towards the follower and detecting the amount of the reflectance; a controller programmed to determine which of a plurality of error states of said brake actuator occur as a function of an output from said pressure sensor and said optical sensor. Moreover, said controller may correlate air pressure with a magnitude of the reflectance, thereby determining whether said actuator is in a normal state or in an error state.

Also, said push may include markers indicating a normal actuated position, a normal retracted position, and an over-jump position. Also, said controller may determine whether a normal state is present by detecting said amount of reflectance indicative of said normal actuated position, in response to detecting an air pressure correlated with the normal actuated position of said brake actuator. Also, said controller may determine the presence of an overtravel condition by detecting said reflectance magnitude indicative of said overstroke position in response to detecting an air pressure correlated with the normal actuated position of said brake actuator. Moreover, said controller may determine the presence of a non-operating condition by detecting said reflectance quantity indicative of said retracted position in response to detecting an air pressure correlated with the normal actuated position of said brake actuator. Further, said controller may determine the presence of an out-of-control condition by: detecting said reflectance quantity indicative of said normal position in response to detecting an air pressure correlated with the normal actuated position of said brake actuator; and detecting said reflectance amount indicative of said retracted position in response to detecting an air pressure correlated with the normal actuated position of said brake actuator. Also, said controller may be programmed to determine the presence of an out-of-control condition by: detecting a plurality of preceding out-of-control errors, each of the preceding out-of-control errors being detected during brake actuation by: detecting said reflectance magnitude indicative of said normal position in response to pressure detection air correlated with the normal actuated position of said brake actuator; and detecting said reflectance amount indicative of said retracted position in response to detecting an air pressure correlated with the normal actuated position of said brake actuator for a predetermined period of time; and detecting a plurality of non-operating states, each by detecting said reflectance magnitude indicative of said retracted position in response to detecting an air pressure correlated with the normal generated pressure of said brake actuator; and detecting said plurality of preceding out-of-control errors and said plurality of non-performance errors occurring during the ignition cycle of the vehicle. Moreover, said markers showing said normal retracted position and said markers showing said overtravel position may be substantially similar markers. Moreover, said controller may be programmed to distinguish between an overtravel condition and an out-of-control condition by monitoring said amount of reflectance during the return stroke of said follower. Further, said controller may be programmed to distinguish between said overtravel condition and said out-of-control condition by detecting said amount of reflectance indicative of said normal position during said retraction of said follower.

INDIAN HEAD INDUSTRIES, INC.

Proxy:

77P42833PL00

ΕΡ 2 990 683 BI