Camshaft rotation sensor mounting arrangement

Abstract

The present invention relates to a sensor mounting arrangement for a drum brake assembly of a heavy duty vehicle, comprising a sensor assembly mounted on a cam tube of the drum brake assembly. The cam tube is formed with an opening. The sensor assembly comprises a detector disposed at least partially in or adjacent to the opening of the cam tube and a target disposed about an outer surface of a cam shaft of the drum brake assembly.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 220,133, filed on July 9, 2021. Technical Field

[0003] This invention generally relates to braking system technology for heavy-duty vehicles. Specifically, it relates to braking systems for heavy-duty vehicles using drum brakes. More specifically, it relates to a sensor mounting arrangement for measuring camshaft rotation and total camshaft rotation during braking using sensors at least partially mounted within the cam tube of the drum brake system, thereby providing a robust, accurate sensor mounting arrangement with minimal impact on the assembly and maintenance of the braking system. Background Technology

[0004] The use of braking systems on heavy-duty vehicles is well-known. For clarity and convenience, the term "heavy-duty vehicle" as used herein is understood to include trucks, tractor-trailers or semi-trailers, trailers, and the like. Common types of braking systems used on heavy-duty vehicles typically include disc brake systems and drum brake systems.

[0005] Drum braking systems are typically integrated into a wheel axle / suspension system and usually include a brake drum mounted on the hub of a wheel-end assembly rotatably mounted on the outer end of the wheel axle. The brake drum typically includes a pair of brake shoes housed within it. Each brake shoe has sacrificial, high-friction brake pads mounted on a metal backing plate or shoe mount, radially spaced from the inner braking surface of the brake drum. An S-shaped cam on the outer end of the camshaft assembly attached to the drum braking system engages with a pair of rollers, each roller connected to one end of a corresponding brake shoe. Drum braking systems may also include a slack adjuster attached to the inner splined end of the camshaft.

[0006] When the driver of a heavy-duty vehicle depresses the brakes, compressed air is supplied from an air source (such as a compressor and / or air tank) through air ducts or lines to the brake chambers, as is well known. The brake chambers convert air pressure into mechanical force, pushing a pushrod. The pushrod then moves the slack adjuster, causing the camshaft and S-cam to rotate, forcing the brake pads against the inner brake surface of the brake drum, thereby generating friction to slow or stop the heavy-duty vehicle. Once the driver releases the brakes, the camshaft and the S-cam rotate back, re-establishing the radial clearance between the brake pads and the inner brake surface of the brake drum. As the brake pads wear, the slack adjuster maintains a preset distance or gap between the brake pads and the inner brake surface of the brake drum.

[0007] To prevent potential safety hazards and ensure timely maintenance of the drum brake system components at each wheel end, existing sensor mounting arrangements are employed. More specifically, since camshaft rotation is proportional to the pushrod stroke generated by the brake chamber, existing sensor mounting arrangements typically utilize external components added to the splined end of the camshaft or to the S-cam, external components attached to the slack adjuster, or external components located within the slack adjuster to measure camshaft rotation.

[0008] However, existing sensor mounting arrangements have drawbacks, shortcomings, and limitations. Specifically, many manufacturers have designed existing sensor mounting arrangements by integrating proprietary sensors into their slack adjusters. While third-party sensors are available, they are typically only compatible with specific commercial slack adjuster styles or can only be directly attached to S-cams, modified inner ends of camshafts, wheel axles, or other components of the suspension system. More specifically, these existing sensor mounting arrangements are often located in areas that may be subject to impact damage; areas that may interfere with the assembly, disassembly, and / or maintenance of drum braking systems and heavy-duty vehicles, or increase their complexity; and / or areas that may expose the sensors to environmental conditions such as extreme temperatures, which could negatively impact the accuracy and lifespan of the sensors. Furthermore, some existing sensor mounting arrangements have limited functionality. Specifically, some existing sensor mounting arrangements can indicate the stroke length of the pushrod generated by the brake chamber but lack the ability to predict the wear limit of the brake pads or the available lift of the S-cam. Summary of the Invention

[0009] Therefore, there is a need in the art for a sensor mounting arrangement that is separate from and compatible with any commercially available slack adjuster; that can accurately monitor camshaft rotation during braking, as well as total camshaft rotation during camshaft indexing to compensate for brake pad wear; that is positioned away from potential shock damage and environmental exposure; and that does not interfere with the maintenance and assembly of drum braking systems, nor add to their complexity.

[0010] The object of the present invention includes providing a sensor mounting arrangement structure that is separate from and compatible with any commercially available relaxation regulator.

[0011] Another object of the present invention is to provide a sensor mounting arrangement structure that accurately monitors camshaft rotation during braking as well as total camshaft rotation during indexing and brake pad wear.

[0012] Another object of the present invention is to provide a sensor mounting arrangement structure that is protected from potential impact damage and is not exposed to environmental conditions.

[0013] Another object of the present invention is to provide a sensor mounting arrangement structure that does not interfere with the maintenance and assembly of the drum braking system, nor does it increase its complexity.

[0014] These objectives and advantages are achieved through a sensor mounting arrangement for a drum brake assembly used in heavy-duty vehicles, the arrangement comprising a sensor assembly mounted on a cam tube of the drum brake assembly. The cam tube has an opening. The sensor assembly includes a detector at least partially disposed in or near the opening of the cam tube and a target disposed around the outer surface of the camshaft of the drum brake assembly. Attached Figure Description

[0015] Preferred embodiments of the invention illustrate the best mode by which the applicant would consider applying the principles of the invention. These preferred embodiments are set forth in the following description and illustrated in the accompanying drawings, and are particularly expressly pointed out and set forth in the appended claims.

[0016] Figure 1 It is a partial perspective view of a drum brake assembly integrated into the wheel axle / suspension system;

[0017] Figure 2 yes Figure 1 The partial perspective view of the drum brake assembly shown shows the brake drum removed and the camshaft disposed within the cam tube.

[0018] Figure 3A yes Figure 1-2 The cross-sectional schematic diagram of the drum brake assembly shown shows the inner surface of the brake drum as a dashed circle, and the rotational position of the S-shaped cam when the new brake shoe with extended service life brake pads is in the folded position.

[0019] Figure 3B yes Figure 1-2 The diagram shows a cross-sectional view of the drum brake assembly, with the inner surface of the brake drum shown as a dashed circle, and the rotational position of the S-shaped cam when a new brake shoe with a standard service life brake pad is in the folded position.

[0020] Figure 3C yes Figure 3A The schematic cross-sectional view of the drum brake assembly shown illustrates the rotational position of the S-shaped cam as the new brake shoe with extended service life brake pads undergoes clearance adjustment.

[0021] Figure 3D yes Figure 3B The cross-sectional schematic diagram of the drum brake assembly shown illustrates the rotational position of the S-shaped cam as a new brake shoe with standard service life brake pads undergoes clearance adjustment.

[0022] Figure 3E yes Figure 3A and Figure 3C The cross-sectional schematic diagram of the drum brake assembly shown illustrates the rotational position of the S-shaped cam when a new brake shoe with extended service life brake pads is in a worn state.

[0023] Figure 3F yes Figure 3B and Figure 3D The cross-sectional schematic diagram of the drum brake assembly shown illustrates the rotational position of the S-shaped cam when a new brake shoe with a standard service life brake pad is in a worn state.

[0024] Figure 3G yes Figure 3A , Figure 3C and Figure 3E The cross-sectional schematic diagram of the drum brake assembly shown illustrates the rotational position of the S-cam when the new brake shoe with extended service life brake pads approaches flipping or the S-cam flips.

[0025] Figure 3H yes Figure 3B , Figure 3D and Figure 3F The cross-sectional schematic diagram of the drum brake assembly shown illustrates the rotational position of the S-cam when a new brake shoe with standard service life brake pads approaches flipping or the S-cam flips.

[0026] Figure 4 This is a partial perspective view of a drum brake assembly according to the invention, which is integrated into a wheel axle / suspension system and includes an exemplary embodiment of a camshaft rotation sensor mounting arrangement.

[0027] Figure 5 yes Figure 4 The partial sectional perspective view of the drum brake assembly shown illustrates the removal of the brake drum and the cross-section of the camshaft.

[0028] Figure 6 It is installed on the cam tube Figure 4-5 The exemplary embodiment shown is a cross-sectional front view of the sensor mounting arrangement structure;

[0029] Figure 7 yes Figure 4-6 The exemplary embodiment shown is a partially sectional perspective view of the sensor mounting arrangement, illustrating a variant of the sensor assembly utilizing the Hall effect sensor.

[0030] Figure 8 yes Figure 4-6 The exemplary embodiment shown is a partially sectional front view of the sensor mounting arrangement structure, illustrating a variant of the sensor assembly utilizing an inductive sensor;

[0031] Figure 9 yes Figure 4-6 The exemplary embodiment shown is a partially sectional perspective view of the sensor mounting arrangement structure, illustrating a variant of the sensor assembly utilizing an eddy current sensor.

[0032] Figure 10 yes Figure 9 The exemplary embodiment shown is a partially sectional front view of the sensor mounting arrangement, illustrating a sensor assembly using an optional target and housing;

[0033] Figure 11 yes Figure 10 The exemplary embodiment shown is a partially sectional front view of the sensor mounting arrangement, illustrating an optional target positioned around an optional camshaft;

[0034] Figure 12 yes Figure 9 The exemplary embodiment shown is a partially sectional front view of the sensor mounting arrangement, illustrating the detector in an optional position relative to the cam tube; and

[0035] Figure 13 yes Figure 9 The exemplary embodiment shown is a partially sectional front view of the sensor mounting arrangement, illustrating different optional positions of the detector relative to the cam tube.

[0036] Similar symbols indicate similar parts throughout the text. Detailed Implementation

[0037] To better understand the sensor mounting arrangement structure and its operating environment of the present invention, a drum brake assembly 10 (partially shown) is shown mounted on the axle 12 (not shown) of the wheel axle / suspension system (not shown) of a heavy-duty vehicle (not shown). Figure 1-2 ).

[0038] The axle 12 includes a central tube 14 having a pair of axially opposite ends, and a corresponding spindle 18 (only one shown in the figure) is rigidly connected to the corresponding end of the central tube by any suitable method (e.g., welding). A pair of wheel end assemblies 16 (only one shown in the figure) having corresponding hubs 26 (only one shown in the figure) are rotatably mounted on the corresponding spindle 18.

[0039] The drum brake assembly 10 includes a brake support structure or brake spider 34 and a brake drum 30. As is known, the brake spider 34 is rigidly mounted on the center tube 14 of the axle 12, adjacent to the hub 26 of the wheel end assembly 16. The brake drum 30 is typically integrally cast from gray iron and includes an inner brake surface 31. As is known, a mounting flange 29 extends radially inward from the outer end of the brake drum 30 and includes a plurality of openings 28 for receiving corresponding interference-fit studs 24 of the hub 26 for mounting the brake drum.

[0040] The drum brake assembly 10 also includes a pair of brake shoes 32. As is known, each brake shoe 32 has a brake lining 33, which is generally formed of a friction material and has a convex outer surface for engaging the inner surface 31 of the brake drum 30. As is known, one end of each brake shoe 32 remains against a corresponding roller 40, which contacts an actuator or S-shaped cam 38 that is in contact with the camshaft 36 of the drum brake assembly 10. Figure 2 The outer end is integrally molded or attached.

[0041] The camshaft 36 is rotatably mounted within the cam tube 42 via a pair of camshaft bushings 45 located at opposite axial ends of the cam tube. The cam tube 42 is connected to the cam tube support 44 via friction. Figure 1 (Only one shown) The friction cam tube support holds the cam tube in place axially and circumferentially, subsequently connecting the cam tube to axle 12 or other components of the axle / suspension system. The slack adjuster 50 is located on the inner spline end 35 of the camshaft 36. Figure 2 The slack adjuster 50 is also connected to the brake chamber 54 via a push rod 56. The slack adjuster 50 maintains a distance between the inner surface 31 of the brake drum 30 and the brake pads 33 of the brake shoes 32, ensuring that the brake pads do not contact or drag against the inner surface of the brake drum when the drum brake assembly 10 is not actuated. The slack adjuster 50 also maintains a distance between the inner surface 31 of the brake drum 30 and the brake pads 33 such that this distance is not excessive, which could cause the brake pads to detach from the brake drum during actuation of the drum actuator assembly 10 due to excessive travel of the push rod 56.

[0042] During operation, when the drum brake assembly 10 is actuated, air pressurizes the air chamber 54, generating a proportional force. This proportional force is transmitted by the push rod 56 and acts on the slack adjuster 50, producing torque around the slack adjuster and causing it to rotate, which in turn causes the camshaft 36 to rotate. The S-shaped cam 38 rotates with the camshaft 36 and engages with the roller 40, forcing the roller and brake shoe 32 to move radially outward, causing the brake pad 33 to contact the inner surface 31 of the brake drum 30, thereby generating friction and slowing down or stopping the heavy-duty vehicle. The rotational displacement of the slack adjuster 50 and the camshaft 36 continues until the deflection caused by the rotational force reaches equilibrium. As is known, when the actuation of the drum brake assembly 10 stops, the camshaft 36 rotates back, causing the brake shoe 32 to move radially inward inside the inner surface 31.

[0043] As is known, the rotational displacement of the slack adjuster 50 causes the camshaft 36 to rotate, such that the camshaft rotation is approximately proportional to the stroke of the pushrod 56 generated by the air chamber 54. Therefore, determining and predicting the rotation of the camshaft 36 can be used to determine and / or predict the actual stroke of the pushrod 56 during brake assembly 10 actuation and the available stroke of the pushrod. This is important because the stroke of the pushrod 56 and consequently the rotation of the camshaft 36 are influenced by a number of factors, including the air pressure in the air chamber 54, the stiffness of the components in the drum brake assembly 10, the thermal expansion of the brake drum 30, and the initial operating clearance between the brake pads 33 of the brake shoes 32 and the inner surface 31 of the brake drum when the brake assembly is not actuated. For the drum brake assembly 10, the air chamber 54 typically has a maximum stroke capacity of approximately 3 inches for the pushrod 56. Once the pushrod 56 has traveled within approximately 0.5 inches of its maximum stroke, the force generated by the air chamber 54 becomes inefficient, thus losing all efficiency at maximum stroke. Therefore, determining and predicting the actual travel of the push rod 56 during the actuation of the drum brake assembly 10, and determining whether the brake assembly is approaching the limit of its usable travel, is crucial to ensuring that the air chamber 54 can generate sufficient air pressure to produce adequate braking effect. Furthermore, the relative travel between multiple brake assemblies 10 in a common air system control loop (not shown) can be compared to detect undesirable variations in travel at the same air pressure within the respective air chambers 54, which may indicate a malfunction in the brake drum 30.

[0044] Determining and predicting the rotation of the camshaft 36 also determines and / or predicts the position of the roller 40 along the S-shaped cam 38. Specifically, as is known, when the brake pads 33 of the brake shoes 32 and / or the inner surface 31 of the brake drum 30 wear, the manual and / or automatic slack adjuster 50 will gradually rotate the camshaft 36, thereby rotating the S-shaped cam 38, causing the roller 40 to gradually move and position along the surface of the S-shaped cam. The position of the roller 40 also varies depending on the thickness of the brake pads 33. For example, two different thicknesses of brake pads 33 are typically used with the brake backing plate 34 and the S-shaped cam 38: a standard service life model and a thicker extended service life model. Therefore, once the slack adjuster 50 has established the operating clearance between the new, cold brake pads 33 and the inner surface 31 of the brake drum 30, the roller 40 can be positioned at different locations along the S-shaped cam 38 depending on whether a standard or extended service life model brake pad is being used. More specifically, the standard service life model of the brake pad 33 will position the roller 40 further along the S-shaped cam 38, thus closer to the end of the S-shaped cam than the extended service life model.

[0045] Therefore, special reference Figure 3A -H, new, cold, standard service life, and extended service life brake pads 33 may cause the approximate rotation angle α of the camshaft 36 relative to the zero starting point of the S-shaped cam 38 to differ, respectively as follows: Figure 3B and 3A The best view is shown in the diagram. More specifically, the camshaft 36 can rotate approximately 29 degrees in new, cold, standard service, and extended service brake pads 33, respectively. Figure 3D ) and 17 degrees ( Figure 3C The angle α is adjusted to the operating clearance position, but this can vary depending on the manufacturing of the components of the drum brake assembly 10. Heating and expansion of the brake drum 30 may cause deflection of other components of the drum brake assembly 10, thereby increasing the rotation of the camshaft 36 during operation. At the end of its service life, the cold standard service life and extended service life brake pads 33 may cause the approximate rotation angle α of the camshaft 36 relative to the zero starting point of the S-shaped cam 38 to reach approximately 143 degrees ( ). Figure 3F ) and 153 degrees ( Figure 3E (This continues) until the brake pads make contact with the inner surface 31 of the brake drum 30. Figure 3GAs best illustrated in section -H, in both standard-life and extended-life brake pads 33, when roller 40 reaches the end of S-cam 38, the approximate rotation angle α of camshaft 36 relative to the zero starting point of S-cam 36 is approximately 168 degrees. Therefore, at the end of the service life of both standard-life and extended-life brake pads 33, roller 40 may be at different angles, but still relatively close to the end of S-cam 38. The positioning of roller 40 near the end of S-cam 38 is also affected by significant thermal expansion of brake drum 30 due to overheating and / or normal or excessive wear of the inner surface 31 of brake pads 33 and / or brake drum, and generally indicates the need for replacement of brake pads and / or brake drum. To prevent the roller 40 from potentially overshooting the end of the S-cam 38 and falling into the groove on the back side of the S-cam (commonly referred to as S-cam flipping), which could lead to malfunction of the drum brake assembly 10, it is advantageous to issue a notification or warning when the roller approaches the end of the S-cam, preferably when the rotation angle α of the camshaft 36 is less than 168 degrees. To allow time for scheduling routine maintenance of the drum brake assembly 10, it is also advantageous to provide notification that the service life of the brake shoes 32, brake pads 33, and / or brake drum 30 is nearing its end, for standard or extended service life models of brake pads, when the rotation angle α of the camshaft 36 is less than 143 degrees or 153 degrees, respectively. Therefore, to determine whether the drum brake assembly 10 requires maintenance and to provide notification, it is desirable to be able to determine and / or predict the amount of rotation of the camshaft 36 during the actuation of the drum brake assembly 10, the relative rotation of the camshafts between the brake assemblies, and the total rotation of the camshaft indexed by the slack adjuster 50 during adjustment.

[0046] Furthermore, the determination and / or prediction of the rotation of the camshaft 36 can be combined with the synchronous acquisition of pressure data from the air chamber 54 using a microprocessor, central electronic module, or electronic control unit (ECU) (not shown) to enable a more accurate prediction of the end-of-life time of the brake shoes 32, brake linings 33, and / or brake drum 30. This allows for less conservative notification times and prevents premature maintenance of the drum brake assembly 10. Specifically, the combination of low actuation pressure in the air chamber 54 and the rotation angle α of the camshaft 36 generally improves the accuracy of the prediction. More specifically, the low actuation pressure in the air chamber 54 and the rotation angle α of the camshaft 36 can be combined with the time between actuation events of the drum brake assembly 10 to determine the temperature of the brake drum 30. This further refines the end-of-life prediction and improves its accuracy by utilizing simple kinematic modeling of the brake shoes 32, brake linings 33, and brake drum.

[0047] Prior art sensor mounting arrangements (not shown) have been used to determine and / or predict the rotation of camshaft 36, thereby determining and / or predicting the stroke of pushrod 56. However, prior art sensor mounting arrangements have drawbacks, shortcomings, and limitations. Specifically, many manufacturers have designed prior art sensor mounting arrangements by integrating proprietary sensors into specific styles of slack adjusters 50. While third-party sensors can be used, these typically only work with specific models of slack adjusters 50 available on the market, or are only suitable for direct attachment to the splined end 35 of the S-cam 38 or a modified camshaft 36, axle 12, or other components of the axle / suspension system. More specifically, prior art sensor mounting arrangements are typically located in areas that may be subject to impact damage; areas that typically interfere with or increase the complexity of assembling, disassembling, and maintaining the drum brake assembly 10; and / or areas that may expose the sensors to environmental conditions such as extreme temperatures, which may negatively impact the accuracy and lifespan of the sensors. Furthermore, some existing sensor mounting arrangements have limited functionality, meaning that the sensing device may only indicate the stroke length of the push rod 56 generated by the air chamber 54, but cannot predict the wear limit of the brake pad 33 or the available lift of the S-shaped cam 38. According to the present invention, the camshaft rotation sensor mounting arrangement overcomes the shortcomings, defects, and limitations of existing sensor mounting arrangements.

[0048] Camshaft rotation sensor mounting arrangement structure 70 according to an exemplary embodiment of the present invention Figure 4-11 It can be used with any suitable brake assembly, such as drum brake assembly 10, as described above.

[0049] Specifically, according to an important aspect of the present invention, the sensor mounting arrangement structure 70 includes a housing or protective housing 73 and a sensor assembly 72. Figure 6 The housing 73 can have any suitable shape, such as a cuboid, cylindrical, or similar shape, and can be formed from any suitable material (e.g., metal or composite material) using any suitable method (e.g., stamping). The housing 73 can be disposed outside the cam tube 42 by any suitable means such as welding, threaded engagement, fasteners, etc., and is at least partially mounted on the cam tube. Specifically, the housing 73 may include an opening 75 ( Figure 6The opening 75 aligns with the opening 43 formed on the outer surface of the cam tube 42 and extending to the inner surface of the cam tube. The opening 43 can be located at any suitable axial position along the cam tube 42, but is preferably located on the cam tube at a position between the S-shaped cam 38 and the splined end 35 of the camshaft 36. The opening 75 of the housing 73 can engage, for example, with the opening 43 of the cam tube 42 via a threaded connection, forming an interface between the housing and the cam tube. A seal (not shown) may be formed around the interface to prevent water, chemicals, and / or debris from entering the cam tube 42 and / or the housing 73. The housing 73 may be disposed on the cam tube 42 and adjacent to the wheel axle / suspension system 5, such that the cam tube and the wheel axle / suspension system provide protection against potential impact damage and debris. The housing 73 may be disposed on or at least partially encapsulate the sensor assembly 72 and / or other electronic and / or mechanical components, such as a wireless transmitter (not shown), an ECU (not shown), a battery (not shown), an energy harvesting device (not shown), or similar devices, to protect the sensor assembly and / or other components from water, chemicals, debris, environmental conditions, and impact. Furthermore, mounting the housing 73 on the cam tube 42 allows the sensor assembly 72 and other electronic and / or mechanical components to be positioned away from and protected from the heat-generating areas (such as the brake drum 30 and brake shoes 32) of the drum brake assembly 10.

[0050] The sensor assembly 72 may also include a positioner 74 that extends axially from the housing 73 along the cam tube 42, parallel to the center tube 14 of the wheel axle 12, and engages with an opening on the cam tube support 44. The engagement between the positioner 74 and the cam tube support 44 determines the rotational position of the cam tube 42 relative to the centerline of the drum brake assembly 10 between the center of the camshaft 36 and the center of the brake drum 30. Alternatively, the cam tube 42 may be welded to a mounting flange (not shown) for attachment to the brake backing plate 34. In this configuration, the mounting flange has only a single orientation relative to the brake backing plate 34, making it easy to determine the rotational position of the cam tube 42 during welding, thus eliminating the need for the positioner 74.

[0051] According to another important aspect of the invention, the sensor assembly 72 includes a detector 76 ( Figure 6 The detector is disposed, or at least partially disposed, in the cam tube 42 adjacent to the opening 75 of the housing 73, and oriented to the zero starting point of the S-shaped cam 38. As is known, the zero starting point of the S-shaped cam 38 is the position of the camshaft 36 when the roller 40 is located at the narrowest point between the two halves of the S-shaped head of the S-shaped cam. The detector 76 can use any suitable type of sensor or sensing device, such as a Hall effect sensor. Figure 7 ), sensing sensor ( Figure 8), eddy current sensor ( Figure 9-13 The detector 76 may be equipped with an anisotropic magnetoresistive sensor (not shown) or similar device, and may be positioned such that the detector is aligned with the centerline between the camshaft 36 and the brake drum 30, or may be positioned perpendicular to the centerline between the camshaft 36 and the brake drum. The detector 76 may be configured to communicate electronically with an ECU (not shown) via wired or wireless communication, the ECU being configured to receive electronic signals. Specifically, the detector 76 may include a wired connection (not shown) utilizing a two-wire or three-wire connection. More specifically, the detector 76 may use a two-wire connection, with the first wire for power supply and the second wire for ground, and the electronic signal transmitted wirelessly. Alternatively, the detector 76 may employ a three-wire connection, with the first wire for power supply, the second wire for ground, and the third wire for transmitting the electronic signal. In this configuration, the third wire for transmitting the electronic signal may be directly or indirectly connected to the ECU, such that the third wire can be connected to an antenna or transmitter for wireless transmission to the ECU or a receiver communicating electronically with the ECU, to prevent interruption of electronic communication due to signal interference from components of the heavily loaded vehicle that may block or limit signal transmission in the vicinity of the drum brake assembly 10.

[0052] It is conceivable that the electrical and / or electronic components of sensor assembly 72, such as detector 76, could use a battery (not shown) as a power source. However, since the actuation signal of drum brake assembly 10 is typically transmitted over a short actuation period of unknown duration, wireless transmission typically requires continuous monitoring, thus necessitating continuous power consumption. Therefore, using wireless transmission could potentially deplete the battery of detector 76 and / or other components of sensor assembly 72. Therefore, sensor mounting arrangement 70 may also include an energy harvesting device (not shown) electronically connected to sensor assembly 72 and at least partially encapsulated in housing 73. The energy harvesting device can provide and maintain sensor assembly 72 at an acceptable voltage and provide current to the battery and maintain battery charge. It is also conceivable to connect an external charging cable (not shown) to sensor assembly 72 to maintain battery charging or otherwise power components of the sensor assembly (e.g., detector 76).

[0053] According to another important aspect of the invention, the sensor assembly 72 further includes at least one target 78 (partially shown) arranged around and at least partially surrounding the camshaft 36. More specifically, the target 78 may be positioned on the surface of the camshaft 36 at any suitable axial location along the camshaft, for example, approximately at the midpoint between the S-shaped cam 38 and the inner spline end 35, or more preferably at the midpoint between the camshaft bushings 45. The target 78 may be disposed within a recess 37 formed radially inward of the outer surface of the camshaft 36 and circumferentially around the outer surface of the camshaft 36. The recess 37 may have any suitable size and depth, but is preferably formed to be about 1.0 inch wide and about 0.12 inches deep. Depending on the type of detector 76 used in the sensor assembly 72, the use of multiple targets 78 may also be considered. In this configuration, the targets 78 may have substantially the same configuration and may be oriented such that the targets are circumferentially spaced about 180 degrees apart around the camshaft 36. Therefore, multiple targets 78 will be positioned circumferentially so that the corresponding zero starting point of the S-shaped cam 38 will be correct regardless of which roller 40 is associated with which recess of the S-shaped cam 38.

[0054] The sensor assembly 72 of the camshaft rotation sensor mounting structure 70 can have various configurations. Figure 7 The diagram shows one such variation of using a Hall effect sensor as sensor component 72a.

[0055] The sensor assembly 72a includes a tubular or annular target 78a disposed within a recess 37 of the camshaft 36. The target 78a may be formed or composed at least partially of a magnetic material (e.g., an ferrous metal), and is circumferentially spaced around the target and thus around the camshaft 36. Because the magnetic material is integrated into the target 78a in a circumferentially spaced manner, the sensor assembly 72a does not require an ECU (not shown) to record the zero starting point of the S-shaped cam 38. Therefore, power loss to the ECU or the sensor assembly 72a does not cause the zero starting point to be reset or lost. The configuration of the target 78a also allows the target to be pre-positioned as a sub-assembly on the camshaft 36 prior to the final assembly of the drum brake assembly 10, thereby simplifying the installation and maintenance of the brake assembly. For example, the target 78a may be composed of a magnetic material suspended in a circumferentially spaced stretchable elastomer. This construction of the target 78a allows the target to stretch or expand radially during assembly and be positioned around the groove 37 of the camshaft 36, then relax to engage with the camshaft within the groove. Alternatively, the target 78a can be formed as a pair of flexible plastic split rings or two-piece rings in which magnetic material can be suspended in a circumferentially spaced arrangement. Thus, during assembly, the split or two-piece rings of the target 78a can open or separate, be positioned around the camshaft 36 and within the groove 37, and then snap together or join together. Any suitable adhesive can also be used to fix the target 78a in the correct orientation around the camshaft 36 relative to the zero starting point of the S-shaped cam 38. Additionally, the target 78a can be formed with a timing brake (not shown) to allow the target to be oriented relative to the zero starting point of the S-shaped cam 38.

[0056] The sensor assembly 72a also includes a Hall effect sensor or detector 76a incorporating a Hall element that responds to the magnetic field generated by the target 78a, thereby determining the actual rotation angle α of the camshaft 36 relative to the zero starting point of the S-shaped cam 38. During operation, once the drum brake assembly 10 is actuated, the camshaft 36 rotates, causing the target 78a to rotate, thus altering the distribution of the magnetic material on the target near the detector 76a. Consequently, the Hall voltage generated by the detector 76a changes, allowing determination of the rotation angle α of the camshaft 36 relative to the zero starting point of the S-shaped cam 38 during actuation, and the total rotation angle of the camshaft after indexing through the relaxation adjuster 50, taking into account the loss of the brake pads 33.

[0057] Therefore, according to the present invention, the exemplary embodiment of the camshaft rotation sensor mounting arrangement 70 provides a housing 73 and a sensor assembly 72a, which are separate from and can be used with any commercially available slack adjuster 50, positioned away from potential shock damage and environmental exposure, and do not hinder or increase the complexity of maintenance and assembly of the drum brake assembly 10. It also provides a detector 76a and a target 78a, which are at least partially disposed within the cam tube 42, to accurately monitor the rotation of the camshaft 36 during brake assembly actuation and the total rotation of the camshaft after indexing by the slack adjuster, taking into account the wear of the brake pads 33.

[0058] Figure 8 Another sensor assembly 72b is shown in the exemplary embodiment of the camshaft mounting arrangement 70 according to the present invention, and this sensor assembly will be described below.

[0059] The sensor assembly 72b includes a ring-shaped flexible sensor or detector 76b and a tubular or ring-shaped target 78b. The detector 76b may be at least partially disposed within the housing 73 and formed by a series of wires arranged in a suitable pattern (e.g., a crisscrossing grid), these wires being placed on or embedded in a flexible plastic membrane disposed within the cam tube 42. The detector 76b may at least partially surround the camshaft 36, extend at least 160 degrees around the camshaft, and may be radially spaced outward from the camshaft by a certain distance.

[0060] The target 78b may be formed as a curved substrate having a combination of conductive materials (e.g., metals) and non-conductive materials (e.g., plastics) arranged in circumferential segments. The target 78b may be disposed within a recess 37 around a camshaft 36 and at least partially surround and / or engage the camshaft 36, such that the detector 76b is radially close to the target. It is contemplated that the sensor assembly 72b may also include a pad (not shown) formed of any suitable flexible and / or elastic material (e.g., rubber, closed-cell foam, rubber with a pressure relief bag, or similar material), disposed between the detector 76b and the inner surface of the cam tube 42 to provide contact pressure and maintain radial proximity between the detector and the target 78b.

[0061] During assembly, detector 76b can be at least partially disposed within cam tube 42. The flexible plastic membrane of detector 76b can be configured such that the inner diameter of the detector is smaller than the outer diameter of camshaft 36 and / or target 78b. Once target 78b is positioned and seated within the groove 37 of camshaft 36, camshaft can be inserted into cam tube 42, causing detector 76b to bend outward or move radially outward. Thus, detector 76b allows camshaft 36 to be mounted within cam tube 42 while providing appropriate contact pressure between detector and target 78b.

[0062] During operation, when the drum brake assembly 10 is actuated, the camshaft 36 rotates, causing the target 78b to rotate. The rotation of the target 78b causes conductive and non-conductive materials on the target to pass under the detector 76b, inducing a current that varies with the rotation of the camshaft 36 and is converted into an electrical signal. Therefore, the sensor assembly 72b can accurately determine the rotation angle α of the camshaft 36 relative to the zero starting point of the S-shaped cam 38 based on the change in current and the signal generated by the detector 76b. It is also possible for the sensor assembly 72b to employ a pair of detectors 76b arranged axially adjacent or side-by-side. In this arrangement, each detector 76b is associated with a separate target 78b positioned around the camshaft 36, such that the conductive material of one target is circumferentially spaced apart from the conductive material of the other target by a predetermined distance. Therefore, this configuration allows the sensor assembly 72b to use a larger detector arc surface without affecting the mounting of the camshaft 36 and / or the orientation of the S-shaped cam 38 relative to the roller 40, thus allowing the camshaft with the S-shaped cam 38 to be mounted in any suitable orientation.

[0063] Therefore, according to the present invention, the exemplary embodiment of the camshaft rotation sensor mounting arrangement 70 provides a housing 73 and a sensor arrangement 72b, which are separate from and can be used with any commercially available slack adjuster 50, are positioned away from potential shock damage and environmental exposure, and do not hinder or increase the complexity of maintenance and assembly of the drum brake assembly 10, while providing a detector 76b and a target 78b, which are at least partially disposed within the cam tube 42, to accurately monitor the rotation of the camshaft 36 during brake assembly actuation and the total rotation of the camshaft after indexing by the slack adjuster, taking into account the wear of the brake pads 33.

[0064] Figure 9 Another sensor assembly 72c is shown in the exemplary embodiment of the camshaft mounting arrangement 70 according to the present invention, and the sensor assembly will be described below.

[0065] The sensor assembly 72c includes an eddy current sensor or detector 76c, which is at least partially disposed within the housing 73 and at least partially disposed within the cam tube 42. More specifically, the detector 76c may extend partially into the cam tube 42, for example, through aligned openings 75, 43 of the housing 73 and the cam tube, respectively, and extend into the cam tube. It is also contemplated that the detector 76c be disposed within an optional housing 73c. Figure 10 ), and is at least partially disposed within the cam tube 42.

[0066] Alternatively, the detector 76c could be entirely housed within the housing 73, adjacent to the opening 43 of the cam tube 42. In this configuration, particularly with reference to... Figure 12 The detector 76c may be enclosed within a portion of the housing 73, which extends through the opening 43 and into the cam tube 42. The portion of the housing 73 may be inserted between the detector 76c and the cam tube 42 to prevent the detector from being affected by pressurized grease within the cam tube without affecting its operation. A seal 82 may be at least partially disposed within the opening 43 at the interface between the housing 73 and the opening using any suitable method (e.g., an interference fit) to prevent pressurized grease from flowing out of the cam tube and to prevent the ingress of water, chemicals, and / or debris. The seal 82 may be made of any suitable material (e.g., an elastomer) and have any suitable shape (e.g., a cylinder) to form an interference fit between the opening 43, the housing 73, and the seal, thereby preventing pressurized grease from flowing out of the cam tube 42 and / or preventing the ingress of water, chemicals, and / or debris into the cam tube 42.

[0067] Alternatively, refer to the specific details. Figure 13 The detector 76c can be disposed within the housing 73, adjacent to the opening 43 of the cam tube 42. In this configuration, the seal 82 can be formed as a plug that engages with the cam tube 42, is disposed in the opening 43 with an interference fit, and is inserted between the detector 76c and the camshaft 36. The seal 82 not only prevents water, chemicals, and / or debris from entering the cam tube 42, but also protects the detector 76c from potential detachment or damage caused by pressurized grease flowing from the cam tube into the housing 73.

[0068] The sensor assembly 72c also includes a target 78c disposed around the camshaft 36 and at least partially surrounding the camshaft 36 within a recess 37. The target 78c may be formed with an annular shape having a variable axial width W. More specifically, the target 78c may be formed with any suitable axial profile or shape, such as a triangle or similar shape, such that the axial width W varies around the circumference of the target. Alternatively, the target 78c may have a pair of axial profiles, such as... Figure 9As best shown, the corresponding axial widths W and X vary around the circumference of the target and camshaft 36 in an arrangement spaced approximately 180 degrees circumferentially. The target 78c can be made of any suitable conductive material (e.g., metal) and disposed within the recess 37 of the camshaft 36 by any suitable means (e.g., press fit). It is conceivable that the target 78c can be coupled to another camshaft 36c having a shoulder 39 formed thereon. Figure 11 This is used in conjunction with the camshaft 36c and is positioned around the camshaft 36c. In this configuration, the target 78c can be positioned around the camshaft 36c and rest against the shoulder 39. Alternatively, the target 78c can be made of a flat conductive material and molded or shaped within the groove 37 around the camshaft 36c, so that the two ends of the target can be connected by any suitable method, such as crimping.

[0069] During operation, when the drum brake assembly 10 is actuated, the camshaft 36 or camshaft 36c rotates, causing the target 78c to rotate. When the target 78c rotates, the axial width W of the target adjacent to or clearly visible to the detector 76c changes, generating eddies that vary in relation to the axial width. This allows the sensor assembly 72c to accurately determine the rotation angle α of the camshafts 36 and 36c relative to the zero starting point of the S-shaped cam 38.

[0070] Therefore, according to the present invention, the exemplary embodiment of the camshaft rotation sensor mounting arrangement 70 provides a housing 73 and a sensor arrangement 72c, which is separate from and can be used with any commercially available slack adjuster 50, positioned away from potential shock damage and environmental exposure, and does not hinder or increase the complexity of maintenance and assembly of the drum brake assembly 10. It also provides a detector 76c and a target 78c, which are at least partially disposed within the cam tube 42, and can accurately monitor the rotation of the camshafts 36, 36c during brake assembly actuation and the total rotation of the camshaft after indexing by the slack adjuster, taking into account the wear of the brake pads 33.

[0071] Without altering the overall concept or operation of the invention, it is conceivable that any portion of the sensor assembly 72 housed within the cam tube 42 be positioned along the cam tube at different axial positions between the S-shaped cam 38 and the spline end 35, or have an orientation different from that shown and described. It is also conceivable that the camshaft rotation sensor mounting arrangement 70 of the invention can employ any type of sensor technology known in the art, such as anisotropic magnetoresistive, variable resistor, potentiometer, etc., without altering the overall concept or operation of the invention. It is also conceivable that the camshaft rotation sensor mounting arrangement 70 of the invention be completely housed within the cam tube 42 without altering the overall concept or operation of the invention. It is conceivable that the camshaft rotation sensor mounting arrangement 70 of the invention can be used in the braking system of a heavy-duty vehicle having more than one axle and / or one or more wheels on each wheel-end assembly, without altering the overall concept or operation of the invention. It is also conceivable that the camshaft rotation sensor mounting arrangement 70 can be used in all types of heavy-duty vehicle drum braking systems without altering the overall concept or operation of the invention.

[0072] It is conceivable that different arrangements and materials may be used in addition to the illustrated and described camshaft rotation sensor mounting arrangement 70 without altering the overall concept or operation of the invention. Other methods and assembly sequences may also be considered for assembling or mounting the sensor assembly 72, cam tube 42, and camshafts 36, 36c without changing the overall concept or operation of the invention.

[0073] Therefore, the camshaft rotation sensor mounting arrangement structure 70 of the present invention is simplified; it provides an effective, safe, inexpensive and efficient structure and method, achieving all the listed objectives; it eliminates the difficulties encountered in the sensor mounting arrangement structure in the prior art; and it solves the problems existing in the prior art and achieves new results.

[0074] In the foregoing description, certain terms have been used for the sake of brevity, clarity, and understanding; however, no unnecessary limitations are implied except as required by the prior art, since these terms are used for descriptive purposes and are intended to be broadly interpreted. Furthermore, the description and illustration of the invention are merely exemplary, and the scope of the invention is not limited to the exact details shown or described.

[0075] The following are now described: the features, discoveries, and principles of the invention; the use and installation method of the camshaft rotation sensor mounting arrangement structure of the invention; the features of the construction, arrangement, and method steps; and the advantageous, new, and useful results obtained; new and useful structures, devices, elements, arrangements, processes, components, and combinations are set forth in the appended claims.

Claims

1. A sensor mounting arrangement structure for a drum brake assembly of a heavy-duty vehicle, the sensor mounting arrangement structure comprising: A sensor assembly mounted on a cam tube of the drum brake assembly, the cam tube having an opening; The sensor assembly includes a detector and a target; The detector is at least partially disposed in or adjacent to the opening of the cam tube, and includes a Hall effect element near the target; and The target includes a stretchable elastomer and is disposed around the outer surface of the camshaft of the drum brake assembly, the stretchable elastomer having a magnetic material formed in an annular shape; The magnetic material is suspended in the elastomer and distributed around the target in a circumferentially spaced arrangement.

2. A sensor mounting arrangement structure for a drum brake assembly of a heavy-duty vehicle, the sensor mounting arrangement structure comprising: A sensor assembly mounted on a cam tube of the drum brake assembly, the cam tube having an opening; The sensor assembly includes a housing, a detector, a target, and a seal, the housing being connected to the cam tube; The housing engages with the opening of the cam tube and forms an interface with the opening of the cam tube; The detector includes an eddy current sensor near the target, the detector being at least partially disposed in or adjacent to the opening of the cam tube, and at least partially disposed within the housing; The seal is formed around the interface to prevent water, chemicals, and debris from entering the housing and the cam tube; and The target is made of a conductive material and has an annular shape. The axial width of its axial profile varies around the circumference of the target. The target is positioned around the outer surface of the camshaft of the drum brake assembly.

3. The sensor mounting arrangement structure according to claim 2, wherein the target has a pair of axial profiles; Each of the pair of axial profiles is circumferentially spaced 180 degrees around the camshaft, and each of the pair of axial profiles has a corresponding axial width that varies circumferentially around the camshaft.

4. A sensor mounting arrangement structure for a drum brake assembly of a heavy-duty vehicle, the sensor mounting arrangement structure comprising: A sensor assembly mounted on a cam tube of the drum brake assembly, the cam tube having an opening; The sensor assembly includes a detector, a target, and a flexible pad; The detector includes a sensing sensor located near the target, and the detector is at least partially disposed in or adjacent to the opening of the cam tube; The sensing sensor includes wires arranged on a flexible membrane that at least partially surrounds the target; The target includes a curved base having a combination of conductive and non-conductive materials arranged in circumferential segments around the target, the target being disposed around the outer surface of the camshaft of the drum brake assembly; and The flexible pad is disposed between the cam tube and the flexible membrane of the detector to provide contact pressure to the detector in order to keep the detector and the target close together.

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