Drum brake assembly and wear sensor arrangement

Abstract

A drum brake assembly includes first and second brake pad assemblies and a wear sensor device. A wear sensor device includes a sleeve, a plunger, and a sensor. The sleeve is coupled to the first brake pad assembly. The plunger is coupled to the second brake pad assembly. A sensor provides a signal indicative of a position of the plunger relative to the sleeve.

Description

Technical Field

[0001] The present invention relates to a drum brake assembly and a device for sensing friction material wear of a brake pad assembly of the drum brake assembly. background

[0003] A drum brake assembly and a brake pad sensor are disclosed in US Pat. No. 6,360,850.

[0004] Overview

[0005] The present invention relates to a drum brake assembly. The drum brake assembly includes a first brake pad assembly, a second brake pad assembly and a wear sensor device. The wear sensor device includes a sleeve, a plunger and a sensor. The plunger is coupled to the first brake pad assembly. The sleeve is coupled to the second brake pad assembly. The plunger is movable relative to the sleeve. The sensor provides a signal indicating the position of the plunger relative to the sleeve.

[0006] The sleeve may include a sleeve hole. The plunger may be at least partially disposed within the sleeve hole. The sensor may be disposed on the sleeve. The plunger may move relative to the sensor. For example, when the first brake pad assembly and the second brake pad assembly are actuated away from each other, the plunger may move relative to the sleeve. When the first brake pad assembly and the second brake pad assembly are retracted toward each other, the plunger does not move relative to the sleeve.

[0007] The wear sensor device may further include a first mounting member. The first mounting member may extend from the first brake pad assembly. The first mounting member may further include a first mounting member hole. The plunger may extend through the first mounting member hole.

[0008] The plunger may include an enlarged head. The enlarged head may be sized to not pass through the first mounting member hole. The enlarged head may engage with a side of the first mounting member that faces away from the sleeve.

[0009] The plunger may extend along the wear sensor device axis. An enlarged head may be provided at a first end of the plunger. The second mounting member aperture may be positioned axially between the enlarged head and the sleeve.

[0010] The plunger may further include a core. The core may be received in the sleeve bore. The signal generated by the sensor may indicate a position of the core relative to the sensor.

[0011] The core may further include a body. The first arm and the second arm may extend from the body. The first pad and the second pad may extend from the first arm and the second arm respectively. The first pad and the second pad may engage the sleeve. The body and the first arm and the second arm may not contact the sleeve.

[0012] The gap may extend between the first pad and the second pad. The gap may extend between the first arm and the second arm. The first arm and the second arm may bias the first pad and the second pad against the sleeve, respectively. The first pad may further include a material detectable by the sensor. The sensor may include a linear variable differential transformer.

[0013] The wear sensor device may further include a second mounting member. The second mounting member may couple the sleeve to the second brake pad assembly. The sleeve may have a free end. The free end may be arranged opposite to the second mounting member. As the thickness of the friction material of the first brake pad assembly decreases, the core may be positioned closer to the free end of the sleeve.

[0014] The drum brake assembly may further include a camshaft. The camshaft may rotate about a camshaft axis to actuate the first brake pad assembly and the second brake pad assembly. The camshaft axis may intersect the wear sensor device.

[0015] The drum brake assembly may further include a first cam roller and a second cam roller. The first cam roller and the second cam roller may engage the first brake pad assembly and the second brake pad assembly, respectively. The camshaft may further include a cam. The cam may engage the first cam roller and the second cam roller. The wear sensor device may extend across the cam. The wear sensor device may extend across the first cam roller and the second cam roller. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a perspective view of an example of a drum brake assembly and a brake drum.

[0017] Figure 2 yes Figure 1 Another perspective view of an example of a drum brake assembly and a wear sensor device, with the brake drum omitted for clarity.

[0018] Figure 3 yes Figure 2 A perspective view of the wear sensor device shown.

[0019] Figure 4 is an exploded view of the wear sensor assembly.

[0020] Figure 5 is a perspective view of an example of a core of a wear sensor device.

[0021] Figures 6 to 8 is a simplified side view showing a wear sensor device and a brake pad assembly in a first position, a second position, and a third position, wherein the friction material of the brake pad assembly is unworn, partially worn, and nearly fully worn, respectively. DETAILED DESCRIPTION

[0022] As required, detailed embodiments of the present invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely examples of the present invention that may be implemented in various and alternative forms. The drawings are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but merely as a representative basis for teaching those skilled in the art to employ the present invention in various ways.

[0023] It should also be understood that, although the terms first, second, etc. are used in some cases herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of the various embodiments described, the first element can be referred to as the second element, and similarly, the second element can be referred to as the first element. Both the first element and the second element are elements, but they are not the same element.

[0024] The terms used in the description of the various embodiments described are only for the purpose of describing specific embodiments, and are not intended to be limiting. As used in the description of the various embodiments described and the appended claims, the singular forms "one", "a kind of" and "the" are intended to also include plural forms, unless the context clearly indicates otherwise. It should also be understood that, as used herein, the term "and / or" refers to and encompasses any and all possible combinations of one or more listed related items. It should be further understood that, when used in this specification, the terms "comprising", "comprising", "including" and / or "including" indicate the presence of the narrated features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or their groups.

[0025] refer to Figure 1 , an example of a drum brake assembly 10 is shown. The drum brake assembly 10 may be provided for a vehicle, such as a truck, a bus, farm equipment, mining equipment, a transport or armed vehicle, or a cargo loading device for a land, air, or marine vessel. In one or more embodiments, the vehicle may include or may be a trailer for transporting cargo.

[0026] The drum brake assembly 10 is configured to brake or slow the rotation of a wheel. The drum brake assembly 10 is associated with a brake drum 20. In some configurations, the drum brake assembly 10 includes a brake spider 22, at least one brake pad assembly 24, one or more anchor pins 26, one or more cam rollers 28, and a camshaft 30. The drum brake assembly 10 also includes a wear sensor device 32.

[0027] The brake drum 20 surrounds the brake pad assembly 24 and may surround the brake support frame 22. The brake drum 20 may be fixedly mounted to the wheel hub and may rotate with the wheel hub about an axis 40. The wheel may be mounted to the wheel hub and may rotate with the wheel hub and the brake drum 20 about the axis 40. Thus, the brake drum 20 may rotate relative to the brake support frame 22 and the brake pad assembly 24 about the axis 40.

[0028] The brake support bracket 22 helps to mount the drum brake assembly 10 to a structural member of the vehicle. For example, the brake support bracket 22 can be fixedly mounted to a steering knuckle or an axle housing. The brake support bracket 22 can be disposed inside the brake drum 20 and can support an anchor pin 26 and a camshaft 30.

[0029] One or more brake pad assemblies 24 are configured to engage the inner surface of the brake drum 20 facing the axis 40 to slow the rotation of the wheel hub about the axis 40. In the illustrated configuration, two brake pad assemblies 24 are shown disposed generally opposite to each other. For ease of reference, these brake pad assemblies are referred to as first brake pad assemblies 24 and second brake pad assemblies 24. The brake pad assemblies 24 are movable relative to the brake support frame 22 and may partially surround the brake support frame 22. As shown in FIG. Figure 2 As best shown, the brake pad assembly 24 may include a brake shoe 50 and a friction material 52 .

[0030] The brake shoe 50 is a structural member of the brake pad assembly 24. The brake shoe 50 can be pivotally mounted to the brake support frame 22 via the anchor pin 26 at a first end. In this way, the brake shoe 50 can pivot or rotate about the anchor pin axis 60. The anchor pin axis 60 can be arranged to be substantially parallel to the axis 40. As used herein, the term "substantially parallel" means the same as parallel or very close to parallel, and includes features or axes within ±3° of parallel to each other. In at least one configuration, the brake shoe 50 includes a workbench 70 and at least one web 72.

[0031] The table 70 supports the friction material 52. The table 70 can be configured as an arcuately extending plate. In at least one configuration, the table 70 can include a first table side and a second table side 82.

[0032] The first table side 80 faces the friction material 52 and can engage or contact the friction material 52. As such, the first table side 80 can face away from the web 72.

[0033] The second table side 82 can be disposed opposite the first table side 80. Thus, the second table side 82 can face away from the friction material 52 and can face the web 72. In at least one configuration, the second table side 82 can be disposed substantially parallel to the first table side 80.

[0034] The brake shoe 50 may be provided with at least one web 72. In the illustrated configuration, each brake shoe 50 is provided with two webs 72. The web 72 extends from the table 70 and may be fixedly coupled to the table 70. For example, the web 72 may extend from the second table side 82 in a direction extending away from the first table side 80 and may be welded to or otherwise fixedly coupled to the table 70. The webs 72 may be spaced apart from one another and may facilitate mounting the brake pad assembly 24 to other components of the drum brake assembly 10. For example, a first recess may be provided at a first end of the web 72 and may receive the anchor pin 26. A second recess may be provided at a second end of the web 72 and may receive the cam roller 28 supported by the camshaft 30.

[0035] The friction material 52 (which may also be referred to as a brake lining) is disposed on the table 70. The friction material 52 may extend from the first table side 80 in a direction extending away from the second table side 82. In this way, the friction material 52 is oriented to face the inner surface of the brake drum 20. The friction material 52 may engage the inner surface of the brake drum 20 during friction braking or when the drum brake assembly 10 provides a braking torque. When friction braking is not applied, the friction material 52 may be spaced apart from the brake drum 20. The friction material 52 may be fixedly attached to the table 70 in any suitable manner. For example, the friction material 52 may be fixedly attached to the table 70 by fasteners (such as rivets).

[0036] The anchor pin 26 is mounted to the brake support frame 22 and supports the corresponding brake pad assembly 24. In some configurations, the anchor pin 26 is fixedly positioned relative to the brake support frame 22. The anchor pin 26 can be received in the first recess of the web 72 of the corresponding brake pad assembly 24 so that the brake shoe 50 can pivot or rotate about the anchor pin axis 60. For example, when the brake shoe 50 is actuated by the camshaft 30, the brake pad assembly 24 can pivot or rotate relative to the anchor pin 26 about the outer surface or outer circumference of the anchor pin 26. It is also contemplated that the anchor pin 26 can be rotatably disposed on the brake support frame 22, in which case the brake shoe 50 can pivot or rotate with the anchor pin 26 about the anchor pin axis 60.

[0037] The cam roller 28 extends between the brake pad assembly 24 and the camshaft 30. In this way, the cam roller 28 supports the corresponding brake pad assembly 24 on the camshaft 30. The cam roller 28 can be received in the second recess of the web 72 of the corresponding brake pad assembly 24 so that the brake shoe 50 can pivot or rotate about the cam roller axis 90. The cam roller axis 90 can be arranged to be substantially parallel to the axis 40 and the corresponding anchor pin axis 60. For example, when the brake shoe 50 is actuated by the camshaft 30, the brake pad assembly 24 can pivot or rotate relative to the cam roller 28.

[0038] The camshaft 30 is configured to actuate the brake pad assembly 24. The camshaft 30 may have any suitable configuration. For example, the camshaft 30 may include a shaft 100 and a cam 102.

[0039] The shaft 100 is rotatable about a camshaft axis 110. In some configurations, the shaft 100 is rotatably supported on the brake support bracket 22.

[0040] The cam 102 extends from the shaft 100. For example, the cam 102 can protrude or extend away from the camshaft axis 110 and the shaft 100. The cam 102 can be fixedly disposed on the shaft 100 or formed integrally with the shaft. In this way, the shaft 100 and the cam 102 can rotate together about the camshaft axis 110. In some configurations, the cam 102 is configured to engage the S-shaped cam of the cam roller 28.

[0041] The rotation of the camshaft 30 about the camshaft axis 110 in a first direction (e.g., from Figure 2 Rotation of the camshaft 30 about the camshaft axis 110 in a second direction opposite to the first direction may allow the cam rollers 28, 28 and the brake pad assemblies 24, 24 to retract or move toward each other and toward the camshaft axis 110 and disengage the inner surface of the brake drum 20. The camshaft 30 may be rotated by an actuator known to those skilled in the art. As shown in FIG. Figures 6 to 8 As best shown in , the camshaft axis 110 may intersect the wear sensor device 32 .

[0042] refer to Figures 2 to 4The wear sensor device 32 is configured to provide a signal indicative of a wear state of the friction material 52 of at least one brake pad assembly 24. The wear sensor device 32 may be disposed adjacent to the camshaft 30. For example, the wear sensor device 32 may extend across the camshaft 30 and the first cam roller 28 and the second cam roller 28, as in Figures 6 to 8 In this configuration, the camshaft axis 110 and the cam roller axes 90, 90 may intersect the wear sensor device 32. In some configurations and as shown in reference Figure 3 and Figure 4 As best shown, the wear sensor assembly 32 includes a first mount 120 , a second mount 122 , a sleeve 124 , a plunger 126 , and a sensor 128 .

[0043] The first mount 120 facilitates mounting the plunger 126 to a brake pad assembly, such as the first brake pad assembly 24. For example, the first mount 120 can be coupled to the brake shoe 50 of the first brake pad assembly 24. In some configurations, the first mount 120 can be coupled to the web 72 of the brake shoe 50. For example, the first mount 120 can be received in a hole in the web 72 or can be coupled to the web 72 in any suitable manner, such as with fasteners, adhesives, threaded connections, etc. The first mount 120 can be rotated relative to the brake shoe 50 or fixed to the brake shoe 50. In some configurations, the first mount 120 includes or defines a first mount hole 130.

[0044] The first mounting hole 130 may be a through hole in the first mounting member 120. The first mounting hole 130 may extend along a wear sensor device axis 140. The wear sensor device axis 140 may be disposed substantially perpendicular to the axis 40, the anchor pin axis 60, the camshaft axis 110, or a combination thereof. The term "substantially perpendicular" is used herein to refer to features or axes that are the same as or very close to perpendicular to perpendicular, and includes features within ±3° of perpendicular to each other. The plunger 126 may extend through the first mounting hole 130.

[0045] The second mount 122 facilitates mounting the sleeve 124 to a brake pad assembly, such as the second brake pad assembly 24. For example, the second mount 122 can be coupled to the brake shoe 50 of the second brake pad assembly 24. In some configurations, the second mount 122 can be coupled to the web 72 of the brake shoe 50. For example, the second mount 122 can be received in a hole in the web 72 or can be coupled to the web 72 in any suitable manner, such as with fasteners, adhesives, threaded connections, etc. The second mount 122 can be rotatable relative to the brake shoe 50 or fixed to the brake shoe 50. It is contemplated that the second mount 122 and the sleeve 124 can be integrally formed.

[0046] The sleeve 124 is coupled to a brake pad assembly 24 (e.g., the second brake pad assembly 24). Additionally, the sleeve 124 is separate from the first brake pad assembly 24. As such, the sleeve 124 can move with the second brake pad assembly 24 and can move relative to the first brake pad assembly 24. In some configurations, the sleeve 124 includes a first end 150, a second end 152, and a sleeve bore 154.

[0047] The first end 150 is a free or distal end of the sleeve 124 that can be separated from the second brake pad assembly 24. For example, the first end 150 can be disposed opposite the second mount 122. In some configurations, the first end 150 can be disposed adjacent to the first brake pad assembly 24 or can extend above the first brake pad assembly.

[0048] The second end 152 is disposed opposite to the first end 150. For example, the second end may be disposed adjacent to the second mount 122.

[0049] The sleeve hole 154 can extend from the first end 150 toward the second end 152 or to the second end. The sleeve hole 154 can be disposed along the wear sensor device axis 140 and can be centered about the wear sensor device axis. The inner side of the sleeve 124 facing the wear sensor device axis 140 at least partially defines the sleeve hole 154. In some configurations, the sleeve hole 154 has a substantially constant diameter.

[0050] The plunger 126 is coupled to the brake pad assembly 24 (e.g., the first brake pad assembly 24). In this way, the sleeve 124 and the plunger 126 can be coupled to different brake pad assemblies. The plunger 126 can move with the first brake pad assembly 24 and can move relative to the sleeve 124. For example, the plunger 126 can move relative to the sleeve 124 (e.g., along the wear sensor device axis 140). The plunger 126 can be at least partially received within the sleeve bore 154 or disposed within the sleeve bore and can move or slide relative to the sleeve 124 in the sleeve bore 154. The plunger 126 can move relative to the sensor 128. In some configurations, the plunger 126 includes a core 160 and a connecting rod 162.

[0051] Main references Figure 3 and Figure 4 , the core 160 is received in the sleeve bore 154 and can move or slide relative to the sleeve 124 along the wear sensor device axis 140. For example, the core 160 can be received in the sleeve bore 154 and can be positioned between the first end 150 and the second end 152 of the sleeve 124. In some configurations and as Figure 5As best shown in FIG. 1 , the core 160 includes a body 170 , a first arm 172 , a second arm 174 , a first backing block 176 , and a second backing block 178 .

[0052] The body 170 can be received inside the sleeve hole 154. The body 170 can be spaced apart from the sleeve 124 and can not contact the sleeve. For example, the body 170 can have a generally cylindrical configuration having a smaller diameter than the sleeve hole 154. The body 170 is coupled to the connecting rod 162. The body 170 can be coupled to the connecting rod 162 in any suitable manner, such as by being integrally formed with the connecting rod 162 or fastened to the connecting rod such as by using a male connection, a female connection, a fastener, an adhesive, etc. In the configuration shown, the body 170 has an orifice 180 to which the connecting rod 162 can be coupled. The orifice 180 can be arranged in an orientation different from the orientation shown. For example, the orifice 180 can be arranged along or substantially parallel to the wear sensor device axis 140.

[0053] The first arm 172 extends from the body 170. For example, the first arm 172 can extend from the body 170 in a direction extending away from the connecting rod 162. The first arm 172 can extend from the body 170 to the first pad 176. The first arm 172 can be spaced apart from the sleeve 124 and can not contact the sleeve. In some configurations, the first arm 172 can be configured to bias or hold the first pad 176 against the sleeve 124.

[0054] The second arm 174 extends from the body 170. For example, the second arm 174 can extend from the body 170 in a direction extending away from the connecting rod 162. The second arm 174 can extend from the body to the second pad 178. The second arm 174 can be spaced apart from the sleeve 124 and can not contact the sleeve. In some configurations, the second arm 174 can be configured to bias or hold the second pad 178 against the sleeve 124.

[0055] The first pad 176 extends from the first arm 172. For example, the first pad 176 can extend from an end of the first arm 172 that is disposed opposite the body 170. The first pad 176 can contact or engage the sleeve 124. In some configurations, the first pad 176 extends farther from the wear sensor device axis 140 than the first arm 172, and the first pad engages or contacts the inside of the sleeve 124. In this configuration, the first pad 176 can have an arcuate surface 190 that faces away from the wear sensor device axis 140 and engages or contacts the inside of the sleeve 124. The first pad 176 can be spaced apart from the second pad 178.

[0056] The second pad 178 extends from the second arm 174. For example, the second pad 178 can extend from an end of the second arm 174 that is disposed opposite the body 170. The second pad 178 can contact or engage the sleeve 124. In some configurations, the second pad 178 extends farther from the wear sensor device axis 140 than the second arm 174, and the second pad engages or contacts the inside of the sleeve 124. In this configuration, the second pad 178 can have an arcuate surface 192 that faces away from the wear sensor device axis 140 and engages or contacts the inside of the sleeve 124.

[0057] At least one of the first liner block 176 and the second liner block 178 can include a material 194 that can be detected by the sensor 128. In some configurations, the material 194 is encapsulated inside the liner block. For example, the material 194 can be a metal or metal alloy, such as a ferrous material. The material 194 can be encapsulated inside a non-ferrous material, such as a polymer that can be made of the associated liner block. It is contemplated that the core 160 can be made of a non-ferrous material other than the material 194, thereby allowing the position of the core 160 to be more accurately measured or determined.

[0058] The gap 200 may be disposed between the first arm 172 and the second arm 174 and between the first pad 176 and the second pad 178, or extend between the first arm 172 and the second arm 174 and between the first pad 176 and the second pad 178. The gap 200 may permit the first arm 172 and the second arm 174 to bend or flex relative to the sleeve 124. For example, the gap 200 may permit the first arm 172 and the second arm 174 to bend or flex toward each other when the first pad 176 and the second pad 178 are inserted into the sleeve hole 154. Thus, the first arm 172 and the second arm 174 may bias the first pad 176 and the second pad 178 away from the wear sensor device axis 140 and toward the inner side of the sleeve 124. For example, the first arm 172 and the second arm 174 can bias the first pad 176 and the second pad 178 in opposite directions and push the first arm 172 and the second arm 174 to apply force against the sleeve 124 in opposite directions, which can allow the body 170 to remain in a stationary position relative to the sleeve 124 when insufficient force is applied to the body 170 via the connecting rod 162, as will be discussed in more detail below.

[0059] Main references Figure 3 and Figure 4The connecting rod 162 helps couple the core 160 to the first mount 120. The connecting rod 162 or a portion thereof can extend along the wear sensor device axis 140 and can be spaced apart from the sleeve 124. In some configurations, the connecting rod 162 extends from the body 170. For example, the connecting rod 162 can be connected to the aperture 180. It is also contemplated that the connecting rod 162 can be integrally formed with the body 170 and the aperture 180 can be omitted. In some configurations, the connecting rod 162 includes an enlarged head 210.

[0060] The enlarged head 210 facilitates connecting the connecting rod 162 to the first mount 120. The enlarged head 210 can be disposed at or near the end of the plunger 126. For example, the enlarged head 210 can be disposed at or near the end of the connecting rod 162. The enlarged head 210 can have a larger diameter than the first mount hole 130, or the enlarged head can be otherwise sized or shaped to not pass through the first mount hole 130. The enlarged head 210 can engage with a first side of the first mount 120 that faces away from the sleeve 124. In this way, the first mount hole 130 can be axially positioned or positioned along the wear sensor device axis 140 between the enlarged head 210 and the sleeve 124.

[0061] The sensor 128 is configured to provide a signal indicating the position of the plunger 126 relative to the sleeve 124. In some configurations, the sensor 128 is disposed on the sleeve 124. For example, the sensor 128 can be disposed outside the sleeve 124, inside the sleeve 124, or can be encapsulated in the sleeve 124. The signal generated by the sensor 128 can indicate the position of the core 160 relative to the sensor 128. The sensor 128 can be of any suitable type. For example, the sensor 128 can be a proximity sensor, a linear displacement sensor (such as a linear variable differential transformer), etc. For simplicity, an electrical connector or wiring harness that can extend from the sensor 128 to a data bus, a controller, or a control module is not shown.

[0062] refer to Figures 6 to 8 , the operation of the wear sensor device 32 will now be described in more detail. In these figures, a portion of the first brake pad assembly 24 and the second brake pad assembly 24 located near the wear sensor device 32 are shown, and the camshaft 30 and other background components of the drum brake assembly 10 are omitted for clarity.

[0063] exist Figure 6, the brake pad assemblies 24, 24 are shown with new or unworn friction material 52. In addition, the brake pad assemblies 24, 24 are extended so that the friction material 52 engages the brake drum 20. The core 160 is positioned in the sleeve bore 154 near the end of the sensor 128 that is disposed farthest from the first end 150 of the sleeve 124. The sensor 128 provides a signal indicative of the position of the material 194 of the core 160, and therefore the position of the plunger 126 relative to the sleeve 124. The signal can be correlated to a position indicating new or unworn friction material 52.

[0064] As the friction material 52 wears, the camshaft 30 may move the first and second brake pad assemblies 24, 24 further away from the camshaft axis 110 as the camshaft 30 rotates to move the brake pad assemblies 24, 24 against the brake drum 20. Thus, the extension of the brake pad assemblies 24, 24 may exert a force on the enlarged head 210, which may actuate the plunger 126 relative to the sleeve 124 and move the core 160 closer to the first end 150 of the sleeve 124. More specifically, as the brake pad assemblies 24, 24 extend, the first mount 120 may engage the enlarged head 210 and exert a force against the enlarged head, which may move the core 160 along the wear sensor device axis 140 and closer to the first end 150 of the sleeve 124 as the thickness of the friction material 52 of at least one of the brake pad assemblies 24 decreases. Thus, the plunger 126 may move relative to the sleeve 124 when the first brake pad assembly 24 and the second brake pad assembly 24 are actuated away from each other.

[0065] exist Figure 7 In FIG. 1 , the brake pad assemblies 24, 24 are shown with partially worn friction material 52. In addition, the brake pad assemblies 24, 24 are extended so that the friction material 52 engages the brake drum 20. Thus, the distance between the camshaft axis 110 and each cam roller axis 90 is Figure 7 In Figure 6 In the larger. Figure 6 Compared to the position shown in FIG. 1 , the core 160 is positioned in the sleeve bore 154 closer to the end of the sensor 128 that is disposed closest to the first end 150 of the sleeve 124. The sensor 128 provides a signal indicative of the position of the material 194, and therefore the position of the plunger 126 relative to the sleeve 124, which is different from the signal corresponding to the position of the plunger 126. Figure 6 The signal associated with the position shown. The signal at this position may be associated with the friction material 52 being partially worn (eg, approximately half worn or 50% worn).

[0066] exist Figure 8In FIG. 1 , the brake pad assemblies 24, 24 are shown with the friction material 52 almost completely worn away. In addition, the brake pad assemblies 24, 24 are extended so that the friction material 52 engages the brake drum 20. Thus, the distance between the camshaft axis 110 and each cam roller axis 90 is Figure 8 In Figure 7 In the larger. Figure 7 Compared to the position shown in FIG. 1 , the core 160 is positioned in the sleeve bore 154 closer to the end of the sensor 128 that is disposed closest to the first end 150 of the sleeve 124. The sensor 128 provides a signal indicative of the position of the material 194, and therefore the position of the plunger 126 relative to the sleeve 124, which is different from the signal corresponding to the position of the plunger 126. Figure 6 and Figure 7 A signal associated with the position shown. A signal at this position may be associated with the friction material 52 being almost completely worn, and therefore indicates that the brake pad assembly 24 should be serviced or replaced.

[0067] When the brake pad assembly is Figures 6 to 8 When the first and second brake pad assemblies 24, 24 are retracted, the plunger 126 can maintain its position in the sleeve 124. For example, when the brake pad assemblies 24, 24 are retracted, the biasing force applied by the first pad 176 and the second pad 178 can keep the core 160 in a stationary position relative to the sleeve 124. More specifically, the first and second brake pad assemblies 24, 24 can move toward the camshaft axis 110 when retracted, and the sleeve 124 can move toward the camshaft axis 110 with the second brake pad assembly 24, but the plunger 126 may not move relative to the sleeve 124 because the connecting rod 162 can extend further through the first mount hole 130 when the first brake pad assembly 24 is retracted. Therefore, the enlarged head 210 can disengage the first mount 120 and move axially away from the first mount. Therefore, when the first and second brake pad assemblies 24, 24 are retracted toward each other, the plunger 126 does not move relative to the sleeve 124.

[0068] The signal from the sensor 128 may be wirelessly or electronically transmitted to a controller, which in turn may communicate with the vehicle operator. For example, when the signal indicates that the brake pad assembly is almost completely worn, a visual signal, an audible signal, a tactile signal, or a combination thereof may be provided to the vehicle operator.

[0069] The drum brake assembly and wear sensor device as described above can allow the wear state of the friction material of the brake pad assembly to be monitored continuously or electronically. Therefore, the wear state can be monitored and transmitted to the vehicle operator or the vehicle maintenance management system without the need for manual inspection or manual measurement of the thickness of the friction material, which may be difficult to reach and difficult to visually inspect. The wear sensor device can be compatible with drum brake assemblies manufactured by different manufacturers. The wear sensor device can be easier to package than a sensor that detects the rotation or rotation angle of the camshaft. In addition, the wear sensor device can provide a more stable signal or a more accurate signal than a sensor that detects the rotation of the camshaft. For example, the wear sensor device can directly measure the actuation distance or linear movement of the brake pad assembly relative to each other, and maintain a stationary position when the brake pad assembly is not actuated, so that a continuous signal or a signal with less fluctuation can be provided.

[0070] Although exemplary embodiments are described above, these embodiments are not intended to describe all possible forms of the present invention. On the contrary, the words used in this specification are descriptive rather than restrictive, and it should be understood that various changes can be made without departing from the spirit and scope of the present invention. Additionally, the features of various implemented embodiments can be combined to form other embodiments of the present invention.

Claims

1. A drum brake assembly, comprising: a first brake pad assembly and a second brake pad assembly; as well as A wear sensor device, the wear sensor device comprising: a plunger coupled to the first brake pad assembly; a sleeve coupled to the second brake pad assembly, wherein the plunger is movable relative to the sleeve; and A sensor provides a signal indicative of a position of the plunger relative to the sleeve.

2. The drum brake assembly of claim 1, wherein: The sensor is disposed on the sleeve, and the plunger is movable relative to the sensor.

3. The drum brake assembly of claim 1, wherein: The sleeve further includes a sleeve bore, and the plunger is at least partially disposed within the sleeve bore.

4. The drum brake assembly of claim 1, wherein: The plunger is movable relative to the sleeve when the first brake pad assembly and the second brake pad assembly are actuated away from each other.

5. The drum brake assembly of claim 1, wherein: The plunger does not move relative to the sleeve when the first brake pad assembly and the second brake pad assembly are retracted toward each other.

6. The drum brake assembly of claim 1, wherein: The wear sensor arrangement further includes a first mount extending from the first brake pad assembly, wherein the first mount further includes a first mount aperture, and the plunger extends through the first mount aperture.

7. The drum brake assembly of claim 6, wherein: The plunger further includes an enlarged head sized not to pass through the first mount aperture, wherein the enlarged head is engageable with a side of the first mount facing away from the sleeve.

8. The drum brake assembly of claim 7, wherein: The plunger extends along a wear sensor device axis, the enlarged head is disposed at a first end of the plunger, and the first mount aperture is positioned axially between the enlarged head and the sleeve.

9. The drum brake assembly of claim 1, wherein: The sleeve further includes a sleeve bore, the plunger further includes a core, the core is received in the sleeve bore, and the signal generated by the sensor indicates a position of the core relative to the sensor.

10. The drum brake assembly of claim 9, wherein: The core further includes a body, first and second arms extending from the body, and first and second pads extending from the first and second arms, respectively, wherein the first and second pads engage the sleeve.

11. The drum brake assembly of claim 10, wherein: The body and the first and second arms do not contact the sleeve.

12. The drum brake assembly of claim 10, wherein: A gap extends between the first backing block and the second backing block.

13. The drum brake assembly of claim 12, wherein: The gap extends between the first arm and the second arm.

14. The drum brake assembly of claim 10, wherein: The first arm and the second arm bias the first pad and the second pad, respectively, against the sleeve.

15. The drum brake assembly of claim 10, wherein: The first backing block further includes a material detectable by the sensor.

16. The drum brake assembly of claim 6, wherein: The plunger further includes a core received within the sleeve, the wear sensor device further includes a second mount coupling the sleeve to the second brake pad assembly, and the sleeve further includes a free end disposed opposite the second mount, wherein the core is positioned closer to the free end of the sleeve as the thickness of the friction material of the first brake pad assembly decreases.

17. The drum brake assembly of claim 1, wherein: The sensor includes a linear variable differential transformer.

18. The drum brake assembly of claim 1, wherein: The drum brake assembly further includes a camshaft rotatable about a camshaft axis to actuate the first brake pad assembly and the second brake pad assembly, wherein the camshaft axis intersects the wear sensor device.

19. The drum brake assembly of claim 1, further comprising first and second cam rollers and a camshaft, the first and second cam rollers engaging the first and second brake pad assemblies, respectively, the camshaft being rotatable about a camshaft axis to actuate the first and second brake pad assemblies, wherein: The camshaft further includes a cam engaging the first cam roller and the second cam roller, and the wear sensor device extends across the cam.

20. The drum brake assembly of claim 19, wherein: The wear sensor device extends across the first cam roller and the second cam roller.

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