Patent Application
20070131491
The subject invention relates to a brake lining wear sensor that includes a body supporting a sensor wire positioned between adjacent lining blocks, wherein the brake lining wear sensor generates a warning signal to indicate when vehicle brake linings should be replaced.
Brake lining wear sensors are used to indicate that brake linings have worn to a level where the brake linings should be replaced. There are many different types of brake lining wear sensors including electrical sensors and purely mechanical sensors. One type of mechanical sensor generates an audible squeaking noise that indicates linings should be replaced. These types of sensors are disadvantageous for heavy vehicle applications as audible noise is difficult to hear during vehicle operation. Another type of mechanical sensor requires constant visual checking at each pad location. This is tedious and time consuming.
These types of mechanical sensors are not preferred because operators may not perform visual inspections in a timely manner. This can result in the brake linings wearing down too far, and potentially exposing rivets that hold the brake linings to an associated support plate. If the rivets are exposed, they could contact and damage the rotating brake drum.
Electrical sensors have also been used for brake lining wear sensors. These types of sensors are often complicated and are used to continuously monitor and calculate wear of the brake lining material at multiple, different, wear levels. These types of sensors are also often embedded within brake lining material, which increases cost and assembly time of an associated brake shoe assembly.
Thus, there is a need for a simplified electrical brake lining wear sensor that is low cost and can be easily installed, as well as overcoming the other identified deficiencies of the prior art.
A brake lining wear sensor includes a body that is secured to a support plate between adjacent brake lining blocks. The body includes a bore extending from a first end to a second end that receives a sensor wire. The sensor wire includes a single looped portion that extends outwardly from an end face of the second end, and which is positioned at a predefined maximum lining wear limit. When the single looped portion is broken due to contact with a rotating brake component, a warning signal is communicated to an operator to indicate that the predefined maximum lining wear limit has been reached. The body is preferably formed from a thermoplastic material such that further contact between the brake lining wear sensor and the rotating brake component, after the single looped portion has been broken, does not damage the rotating brake component.
The support plate includes an opening formed within a gap between adjacent lining blocks. The thermoplastic body is received within the opening such that the first end extends outwardly from one side of the support plate and the second end extends outwardly from an opposite side of the support plate. The second end comprises an enlarged head that includes a slot that extends inward into the central bore such that the enlarged head is separated into first and second head portions. The first end includes a threaded portion that engages a nut to clamp the support plate between the enlarged head and the nut. Also, when the nut is threaded onto the first end, the sensor wire is clamped within the slot between the first and second head portions to position the single looped portion at the predefined maximum lining wear limit.
The subject invention provides a simple, low-cost brake lining wear sensor that is easily installed into a brake assembly, and which can be easily incorporated into existing vehicle electronic control systems. These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.
A drum brake 10 includes brake shoes 12 that selectively engage a rotating brake drum 14 in response to a braking request. Each brake shoe 12 includes a plate 16 that supports a brake lining 18. The brake lining 18 is preferably formed as a plurality of brake lining blocks 18a, 18b that are spaced apart from each other along the plate 16.
The brake lining 18 includes a lining surface 20 that engages an inner surface 22 of the brake drum 14 during each braking actuation. An actuator A is used to move the brake shoes 12 into engagement with the brake drum 14. Any type of actuator A could be used to actuate the brake shoes 12, such as a cam, hydraulic cylinder, etc., for example. Contact between the brake lining 18 and the brake drum 14 results in wear of the brake lining 18. As the brake lining 18 wears, the thickness of brake lining material decreases.
The brake shoes 12 need to be replaced before the brake linings 18 wear out. Typically each brake lining block 18a, 18b is attached to the plate 16 with a plurality of rivets 24 (schematically shown in
In order to avoid damaging the brake drum 14 and to notify an operator when the brake linings 18 have worn to a predetermined maximum brake lining wear level limit, the drum brake 10 includes a brake lining wear sensor 30 that is attached to the plate 16 of each brake shoe 12.
When the brake linings 18 have worn to the predetermined maximum brake lining wear level the brake lining wear sensor 30 generates a signal 32 that is transmitted or otherwise communicated to an electronic control unit (ECU) 34. The ECU 34 then generates a warning signal 36 that is communicated to the operator by a warning indicator 38, such as a lamp, display screen, alarm beep, etc.
The brake lining wear sensor 30 is shown in greater detail in
A nut 54 is threaded onto the threaded outer surface 48 to attach the brake lining wear sensor 30 to the plate 16. A spring washer 56 is positioned between the plate 16 and the nut 54 (see
The sensor wire 42 is inserted through a bore 60 that is formed within the body 40. The sensor wire 42 includes a single looped portion 62 that extends outwardly beyond an end face 64 of the enlarged head portion 52, as shown in
Once the single looped portion 62 is broken the brake drum 14 will continue to contact the brake lining wear sensor 30. The body 40 is preferably formed from a thermoplastic material such that contact between the body 40 and the inner surface 22 of the brake drum 14 will not result in damage to the brake drum 14. Preferably, the body 40 is formed as a single piece by a molding process.
As shown in
As shown in
As shown in
When the brake lining wear sensor 30 is inserted through the opening 80, the first portion 46 of the body 40 extends outwardly from one side 84 of the plate 16, and the second portion 50 extends outwardly from an opposite side 86 of the plate. The body portion includes a flanged area 88 that transitions from the first portion 46 into the enlarged head portion 52. The flanged area 88 is generally received within the opening 80 of the plate 16 such that a bottom end surface 90 of the enlarged head portion 52 abuts directly against the plate 16. When the nut 54 is tightened onto the threaded outer surface 48, the enlarged head portion 52 is securely held in place against the plate 16.
Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
