Abstract:
The invention provides an abrasion detecting probe for a brake pad which does not require insert-moulding and in which production costs are low. 
     A probe  20  is housed in base components  35  and  36,  which are snap-fitted together. In this manner, the terminal  22  can be attached within the base member  21  in a precise predetermined position by the simple operation of joining the base components  35  and  36  together. Therefore, as opposed to a conventional probe, insert-moulding is not required and the probe can be manufactured simply and cheaply. A sleeve  50  may provide an audible brake wear warning.

Description:
TECHNICAL FIELD 
     The present invention relates to an abrasion detecting probe for a brake pad, the probe having a metal terminal inside a synthetic resin base member. 
     BACKGROUND TO THE INVENTION 
     Conventional abrasion detecting probes of this kind include the one described in the JP 6-300064. This type of abrasion detecting probe  1 , shown in FIG. 11 hereof, comprises a pair of electric wires D crimped to a metal terminal  2 , this terminal  2  being insert-moulded inside a synthetic resin base member  3 . The abrasion detecting probe  1  is fixed through a supporting backplate of a brake pad, and when the brake pad attains its abrasion limit as a result of sliding contact with a brake disc, a tip  4  of the probe  1  is worn away together with the brake pad, and the circuit between the two electric wires D is broken. 
     However, because the abrasion detecting probe  1  described above is produced by insert-moulding, position setting of the terminal  2  inside the mould is a troublesome and time-consuming operation which does not allow costs to be reduced. Accurate positioning is essential to ensure that the abrasion limit is set precisely. 
     The present invention has been developed after taking the above problem into consideration, and aims to present an abrasion detecting probe for a brake pad in which insert-moulding is not required and in which production costs can accordingly be reduced. 
     SUMMARY OF THE INVENTION 
     According to the invention there is provided a wear detecting probe for a vehicle brake lining having a backplate and a friction lining thereon, said probe comprising an electrically conducting member adapted for connection to an electrical circuit by input and output connections, said conducting member being housed inside an insulating body and having a bridging portion adjacent one end of said body such that, in use, a braking surface can wear away said bridging portion to separate said conducting member into two, and thereby break an electrical circuit, wherein said body comprises two or more mutually attachable components defining a cavity to house said conducting member. 
     Such a construction avoids the need for insert moulding, and thus lower manufacturing costs can be achieved. 
     The components are typically produced as precision plastic mouldings with a shape suitable for positioning and holding the conducting member with accuracy. 
     Preferably latch means are provided to hold the body components together to avoid rattling, and to avoid separation during transport. The latch means are preferably adapted to pass through the conducting member as an aid to correct location. 
     In a preferred embodiment the probe is surrounded by a protruding sleeve of noise generating material. Such a sleeve gives an audible warning of the approach of the pad abrasion limit. This arrangement permits the friction lining to be replaced before the conducting member is broken, and the probe itself to be inserted into the new friction lining; thus the electrical connections need not be disturbed. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     Other features of the invention will be apparent from the following description of two preferred embodiments shown by way of example only in the accompanying drawings in which: 
     FIG. 1 is a side view showing a braking device of the present invention. 
     FIG. 2 is a side cross-sectional view of a backplate to which an abrasion detecting probe has been attached. 
     FIG. 3 is an exploded view of the abrasion detecting probe. 
     FIG. 4 is an exploded view showing a terminal housed within a housing of a base component. 
     FIG. 5 is an exploded view showing the base components in an attached state. 
     FIG. 6 is a diagonal view showing the abrasion detecting probe in a completed state. 
     FIG. 7 is a cross-sectional view of the abrasion detecting probe in a completed state. 
     FIGS. 8-10 are similar to FIGS. 2,  3  and  6 , and illustrates an outer sleeve for the probe according to a second embodiment of the invention. 
     FIG. 11 is a diagonal view showing a prior art abrasion detecting probe. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     A first embodiment is described with reference to FIGS. 1-7. 
     FIG. 1 shows the components of a braking device. The number  10  in FIG. 1 refers to a brake disc, a pair of backplates  11  and  12  being provided on both sides thereof, brake pads  13  and  14  being provided on the backplates  11  and  12  on the sides thereof facing the disc  10 . The backplates  11  and  12  are moved towards the disc  10  by a mechanism (not shown), and as a result, the brake pads  13  and  14  press against the disc  10  and frictional force halts the rotation of the disc  10 . This is conventional. 
     As shown in FIG. 2, an abrasion detecting probe  20  suitable for use in the present invention is attached by being inserted into a through hole  15  formed in a backplate  12 , the anterior end of the probe  20  protruding into a through hole  17  formed in the brake pad friction material  14 . 
     As shown in FIG. 3, the probe  20  is provided with a terminal  22  made of metal and located within a base member  21  of synthetic resin. The terminal  22  is provided with a pair of foot members  24 , which form a U-shape, joined at the base by a carrier  23  which can be cut off short. The anterior end of each foot member  24  is provided with a crimping member  25  for crimping an electric wire D, each crimping member  25  comprising a protrusion  26  which extends out from the side of the foot member  24  and is folded back above the foot member  24 . Core wires D 1  of the electric wire D are held between the protrusion  26  and the foot member  24  and an electrical connection is established. The core wires D 1  are welded to the terminal  22  in order to further strengthen the connection. Furthermore, the foot members  24  are cranked downwards (as viewed) so that the protrusions  26  of the crimping members  25  do not protrude greatly (upwards in FIG. 3) relative to the terminal  22 . 
     The entire base member  21 , shown in FIG. 6, has a column shape in the direction of a horizontal cross-sectional, and protrudes from the base  12 . A posterior portion  30 , posterior relative to the direction of insertion, having step-shaped protrusions on both sides. As shown in FIG. 2, stepped faces  30 A of the posterior portion  30  make contact with stepped faces  15 A formed in a through hole  15 , thus determining the insertion position of the probe  20 . Further, a groove  32  is formed on an anterior portion  31  of the base member  21  along the direction of the circumference of the outer circumference face. As shown in FIG. 2, after the probe  20  is inserted into the through hole  15  of the base  12 , a clip  33  is installed in the groove  32 , this clip  33  being abutting against the open edge of the through hole  15  on the base  12  and thereby retaining the probe  20  in position. 
     As shown in FIG. 3, the base member  21  is divided along in the horizontal direction into a first base component  35  (the lower part of the base member  21  in FIG. 3) and a second base component  36  (the upper part of the base member  21  in FIG.  3 ). 
     On the first base component  35 , a housing  37  is formed into an attachment face  35 A, this attachment face  35 A joining with the second base component  36 , and the housing  37  housing the terminal  22 . The lower face of the housing  37  is inclined part-way along the face to correspond to the moderate crank-shape of the foot members  24 , the side corresponding to the crimping members  25  being deeper. The anterior side (the lower left side in FIG. 3) of the circumference face of the housing  37  is of a round shape that corresponds to the U-shaped base of the terminal  22 , and the posterior side (the upper right in FIG. 3) widens out on both sides in order to house the sideways-protruding portions of the crimping members  25 . Further, a pair of rounded grooves  38  which pass through to the housing  37  are formed on the posterior end of the first base component  35 , the electric wires D which are attached to the terminal  22  passing to the exterior of the base member  21  through these rounded grooves  38 . In addition, an angular groove  39  which passes through to the housing  37  is formed on the anterior end of the first base component  35 , a connecting member (or bridging portion)  27  which links the carrier  23  and the terminal  22  passing therethrough, the carrier  23  being provided externally with respect to the base member  21 . 
     A pair of position-fixing protrusions  40  are provided along a length-wise direction on the first base component  35 . These position-fixing protrusions  40  protrude from the base face of the first base component  35  towards the second base component  36  and, as shown in FIG. 4, these position-fixing protrusions  40  are located respectively between the anterior end and the base end of the foot members  24  of the terminal  22 . Further, a slit  40 A is formed from the tip towards the base on each position-fixing protrusion  40 . 
     As shown in FIG. 7, a pair of position-fixing holes  41  pass through the second base component  36 , the position-fixing protrusions  40  being inserted through these position-fixing holes  41 , and this insertion fixing the base components  35  and  36  so that they do not move. The inner circumference of each position-fixing hole  41  has a tapered face  42 , this tapered face  42  becoming narrower towards the farther side from the direction of insertion of the position-fixing protrusion  40 . Consequently, the position-fixing protrusions  40  change shape and become narrower in the direction in which the slits  40 A are narrower. As shown in the same figure, a housing  43  is formed on the attachment face of the second base component  36 , this housing  43  housing the crimping members  25  protruding from the housing  37  of the first base component  35 . 
     With the configuration as described above, the operation and effects of the present embodiment are explained. 
     The probe  20  is manufactured in the following manner. The terminal  22  inside the probe  20  is manufactured by a process of punching and folding metal plate. Then, the core wires D 1  of the electric wire D are crimped between the foot members  24  and the protrusions  26  provided on the crimping members  25  of the terminal  22 . Then, the core wires D 1  are welded to the crimping members  25 . 
     In the case of the conventional probe  1  (see FIG.  8 ), the terminal  22  is conveyed to the injection moulding site, and the terminal  22  must be set inside the mould and then insert-moulding carried out. As stated above, this is a troublesome and time-consuming operation which does not allow costs to be reduced. 
     However, the probe  20  of the present embodiment can be produced in the manner described below without having to perform insert-moulding. That is, the first and second base components  35  and  36  of the probe  20  are manufactured by injection moulding separately from the terminal  22 , and are conveyed to the site in which they will be attached to the terminal  22 . At that site, as shown in FIG. 4, the terminal  22  is housed within the housing  37  of the first base component  35 , the attachment faces of the first and second base components  35  and  36  are set facing one another and are then joined together. Then, the position-fixing protrusions  40  enter the position-fixing holes  41 , thus mutually fixing the position of the first and second base components  35  and  36  and attaching them so that they do not move (see FIG.  5 ). At this juncture, the tapered faces  42  provided in the position-fixing holes  41  (see FIG. 7) guide the position-fixing protrusions  40 , so that the slits  40 A in the tips of the position-fixing protrusions  40  change shape and become narrower and, as a result of the outward force exerted by the position-fixing protrusions  40 , the circumferential faces of the position-fixing protrusions  40  and the position-fixing holes  41  fit closely together. This prevents the base components  35  and  36  from rattling. Further, the friction between the position-fixing protrusions  40  and the position-fixing holes  41  maintains the base components  35  and  36  in a joined state. Next, the carrier  23  (see FIG. 5) protruding anteriorly from the base member  21  of the terminal  22  is cut off, and the attachment of the probe  20  is complete (see FIG.  6 ). 
     In this manner, in the probe  20  of the present embodiment, the base components  35  and  36  are joined together in a simple operation which allows the terminal  22  to be attached within the base member  21 . As a result, in comparison to the conventional example in which insert-moulding is required, the probe can be manufactured simply and cheaply. 
     The completed probe  20 , as shown in FIG. 2, is inserted into the through hole  15  of the base  21  of the braking device, and the clip  33  is attached to the groove  32  of the probe  20  by means of a specified tool. The probe  20  is in a fixed state in the base  12  with its tip protruding into the brake pad  14 . In this state, the base components  35  and  36  are maintained reliably in a joined state by the clip  33  and the inner wall of the through hole  15 , and will not separate even if shaken, etc. When the brake pad  14  attains its abrasion limit as a result of sliding contact with the disc  10  (see FIG.  1 ), the tip  27  of the probe  20  is worn away together with the brake pad  14 , the foot members  24  are separated, and the circuit between the two electric wires D is broken, thus allowing the attainment of the abrasion limit to be detected. 
     A second embodiment of the invention is illustrated in FIGS. 8-10, the same parts having common reference numerals. 
     As illustrated a sleeve  50  surrounds the base components  35 , 36 , and maintains them in an attached state. The sleeve  50  is a tight push fit over the components  35 , 36 . As illustrated, the sleeve  50  projects slightly beyond the tip  27  of the terminal  22 , so that as the pad approaches the abrasion limit, the sleeve  50  rubs against the disc. A bracket  52  holds the probe in the brake pad. The sleeve is made of a material, such as metal, which will make a noise as it is worn away; in this way the driver can hear an audible signal that the abrasion limit is about to be reached. 
     The sleeve  50  also has the advantage of preventing separation of the components  35 , 36  during transport from a connector manufacturing location to a brake pad installation location. Furthermore, if the brake pad is replaced when the audible warning is first heard, there is no need to replace the probe itself—the probe can simply be inserted into a replacement brake pad without any disconnection of the electrical wires. If however the tip  27  is worn away, the electrical circuit is broken, thus enabling a signal, such as a warning light, to be indicated to the driver. 
     The present invention is not limited to the embodiments described above with the aid of figures. For example, the possibilities described below also lie within the technical range of the present invention. In addition, the present invention may be embodied in various other ways without deviating from the scope thereof. 
     (1) In the present embodiment, the base member  21  can be divided into two base components  35  and  36 . However, the number of base components into which the base member  21  can be divided is not limited to two. 
     (2) In the present embodiment, tapered faces  42  are formed on the inner circumference of the position-fixing holes  41 . However, it may equally well be the case that tapered faces are formed on the outer circumference of the position-fixing protrusions  40 . 
     (3) The sleeve ( 50 ) may be used to hold the base components  35 , 36  together in the absence of an integral latch.