Abstract:
A tone ring assembly for use on a rotatable machine part. The tone ring is able to generate a varying voltage output when rotated at varying speeds. A fixed position magnetic sensor detects this voltage. The tone ring comprises an axially extending main body portion having a plurality of areas able to generate a voltage upon rotation. A retainer having at least one radial flange prevents axial movement of the tone ring and the tone ring includes ribs and spaces on its inside diameter to permit oil to pass therethrough.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to an assembly including a so-called tone ring or exciter ring and a magnetic sensor unit. More particularly, the present invention relates to a portion of a vehicle or other mechanical assembly which is adapted to create a signal of varying voltage output when rotated at varying speeds, with such signal being detected by a pickup or sensor unit with which the rotary part is associated.  
           [0002]    The tone ring preferably has a large plurality of teeth, vanes or lands separated by spaces or grooves therein or can also be a simple cylinder with strips of magnetic rubber molded into it or otherwise fastened to it. Passing the lands or magnets by a fixed sensor at varying speeds creates a speed-varying signal in the sensor and gives an indication of the rotational speed of the shaft with which the tone ring is associated.  
           [0003]    The assembly is primarily intended for vehicles wherein the rotational shaft speed, and particularly variations in the rotational speed of two or more shafts, is sensed for various purposes. These include use in ABS (anti-lock braking systems), differential actuation or control, traction control, all-wheel drive control, vehicle stability and the like. In addition, the invention can be used in other applications, such as sensing the rotational speed of power take-off shafts or other power transmission devices including one or more rotary shafts.  
           [0004]    In the past, tone rings have been fitted onto axle shafts or other rotating members by press fitting them into place like a bearing or seal. This method can be cumbersome at best, and impossible at worst. Other methods of incorporating tone rings on rotary mechanisms involved integrating the tone rings with bearings or with the hubs or with the ring gear, with the tone ring being associated with the rotary part. Because the shaft undergoes deflection in use, and for other reasons, these methods are sometimes not satisfactory, especially where the bearing/ sensor system is too rigid to accommodate such shaft deflection in use.  
           [0005]    Other tone rings or proposals for tone rings involve installing forces that might easily damage the tone ring or sensor. Still others would lack a unitizing feature, wherein means are provided to prevent axial movement of the tone ring beyond certain limits, or where installing a retainer determines the position of the tone ring, at least approximately.  
           [0006]    If a tone ring assembly could be provided which was unitized, as a system approach, it would result in simplified assembly. Likewise, if a tone ring could be made that had mating components installable with low force, especially a construction in which, after installation, the tone ring would grip the shaft more tightly than during initial installation, it would be highly desirable.  
           [0007]    Particularly, if a tone ring assembly were provided which would be associated with a part of the shaft which underwent little or no deflection in use, it would be greatly advantageous. Were these advantages attainable in a design which provided at least one, and preferably several, axial oil passages in use, it would be very desirable.  
           [0008]    It would also be desirable to provide a unitizing retainer in the form of a sleeve with radially inner and outer portions to engage and package a radial flange of the tone ring, or the entire tone ring itself and allow only a limited range of axial movement between flanges of the retainer and tone ring or limited movement of the entire tone ring. Also, this unitizing retainer could be made of one piece in stamped steel or formed in a tough plastic such as Delrin.  
           [0009]    Accordingly, it is an object of the present invention to provide an improved tone ring element able to generate a voltage output by rotation, preferably either in the form of a sleeve having multiple lands, grooves, teeth or magnets for signaling an associated magnetic sensor or pickup as the tone ring lands or magnets rotate past the sensor. By “tone ring” or like words is meant not only a single ring element, but also a plurality of rings, working in concert with sensors connected to or associated with a rotational speed differential computer and feedback mechanism.  
           [0010]    Another object of the invention is to provide a tone ring assembly which is separate from the bearing or seal assembly yet which is associated with an axle shaft supported on such bearings.  
           [0011]    Yet another object of the invention is to provide a tone ring assembly which is sufficiently flexible and positioned such that it is able to accommodate limited axle shaft deflections in use, and also accommodate a limited amount of end play in such shafts.  
           [0012]    Still another object of the invention is to provide a tone ring and retainer which can initially be installed by an ergonomically acceptable force by placing it with an installation tool in place within the axle tube or housing and then sliding the axle shaft through the tone ring with ergonomically desirable forces and just past its functional position in the application to permit an axially inner axle shaft retainer or “C” clip to be installed in a groove in the axle shaft. Thereafter, when the axle shaft is moved just slightly axially outwardly, the clip and the tone ring are centered or aligned axially in place.  
           [0013]    A further object of the invention is to provide a design of tone ring and retainer which can be positioned so as to be in an area of the shaft which undergoes minimum deflection in use.  
           [0014]    A still further object of the invention is to provide a design which is unitized for simple and relatively foolproof assembly.  
           [0015]    An additional object of the invention is to provide a tone ring which, while installing easily, will thereafter use the swell of rubber in reaction to assembly and/or subsequent application lubricant to develop a more firm grip on the shaft.  
           [0016]    Another object of the invention is to provide a design which is compatible with the axle configuration so that there is sufficient axial travel of the axle shaft to enable a retainer or “C” clip to be dropped in place over the axially inner end of the axle shaft, and thereafter, enable the axle shaft to be pulled out a few millimeters to seat the clip, thus loading a thermoplastic or thermoset spacer as the tone ring slides slightly out to a “home” position on the shaft. This spacer can be eliminated if more axial width for retainers is available. It can also be eliminated if the retainer or toner ring flange is made of thermoset or thermoplastic material.  
           [0017]    Yet another object of the invention is to provide a tone ring which lies axially inside the seal and bearing, but is held in position axially by engagement between the opposed flanges of the retainer and the flange of the powdered metal sleeve. It is initially held radially by inner diameter ribs on the tone ring, and thereafter held more firmly in place by lubricant swelling of these radial ribs. The powdered metal flange may be eliminated or the powdered metal tone ring/flange combination may become two or more pieces assembled or molded as an alternate design.  
           [0018]    Still another object of the invention is to provide substantial axial width of the tone ring teeth so the location of the sensor relative to the tone ring accommodates any variation in the stack-up or end play tolerances in the application.  
           [0019]    Another object of the invention is to provide a tone ring that will fit over the smallest machined diameter of an axle shaft, leaving larger respective diameters for accommodating the bearings and the oil seal, respectively and allowing the components to be assembled inside the axle tube.  
           [0020]    A further object of the invention is to provide a tone ring assembly which inherently allows a desired or correct assembly sequence with the axle shaft, the seal, the bearing and the tone ring. The tone ring assembly can also be reused after disassembly in the field.  
           [0021]    A still further object of the invention is to provide a grooved or corrugated outside diameter on the retainer to provide desired passages for oil between the axle tube housing and that of the retainer.  
           [0022]    An additional object of the invention is to provide a tone ring assembly which will allow passage of oil along one, two or several paths through the tone ring and/or around the tone ring.  
           [0023]    The invention achieves these objects and others which are inherent therein by providing an assembly which includes a rotatable tone or exciter ring able to generate a varying voltage output by rotation relative to a magnetic sensor, and ribs on its inner diameter, which includes an optional radial flange, optionally an abutting spacer with radial oil passage spaces, a retainer having at least one radial flange, one or more oil passage features, with the associated sensor being adapted to pick up a speed varying signal as the lands or magnets on the tone ring sleeve pass by the sensor.  
           [0024]    The manner in which these and other objects of the invention are achieved in practice will become more clearly apparent when reference is made to the following detailed description of the preferred embodiments of the present invention set forth by way of example and shown in the accompanying drawings, in which like reference numerals indicate corresponding parts throughout. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]    [0025]FIG. 1 is a perspective view of one form of the tone ring and the retainer showing these parts in their assembled condition, and taken from the axially inner end of the tone ring;  
         [0026]    [0026]FIG. 2 is an exploded fragmentary perspective view of the tone ring assembly of FIG. 1, taken from the axially outer end so as to illustrate the component parts of the retainer, the preferred form of spacer and the various features of these parts and the tone ring;  
         [0027]    [0027]FIG. 3 is an exploded fragmentary perspective view of the tone ring assembly of FIGS. 1 and 2, and showing the retainer in two parts, and the spacer as well as the tone ring from the axially inner end thereof;  
         [0028]    [0028]FIG. 4 is a horizontal sectional view of the tone ring assembly, including the retainer, the spacer and the tone ring in their installed positions within the axle housing and over the axle shaft, and showing the seal and bearings in position encircling the shaft;  
         [0029]    [0029]FIG. 5 is a fragmentary view, with portions broken away, showing an alternate embodiment of the invention; and,  
         [0030]    [0030]FIG. 6 is a fragmentary view, with portions broken away, showing an embodiment of the invention wherein the sensor is positioned over a window or opening in the retainer. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    While the tone ring may be embodied in many applications, including automotive and non-automotive applications such as power take-offs, generators and others, a detailed description of the tone ring or exciter ring assembly and its auxiliary components including the detector or sensor will be given first in an application wherein a vehicle drive axle shaft rotates the tone ring, the sensor is located in a fixed position in the axle tube housing just radially outside or removed from the tone ring surface, and an optional flange on the tone ring holds the ring in a fixed position by reason of contact between the flange and a flange of the retainer, preferably with an optional spacer between the tone ring and the retainer.  
         [0032]    Referring now to the drawings in greater detail, FIGS.  1 - 4  show a tone ring assembly generally designated  10 , preferably located axially inside the wheel bearing within an axle tube housing assembly generally designated  12 , wherein a sensor  14  is held in fixed position within an opening generally designated  16  in the housing assembly  12 .  
         [0033]    The tone ring body, generally designated  18 , includes an axially extending portion  20 , a radial flange  22  defined by axially inner and outer surfaces  24 ,  26  and a radially outermost, stepped surface generally designated  28 . The body generally designated  18  includes a radially outer surface generally designated  30  on the axially extending portion  20 , the axially inner portion of which is defined by alternately radially extending lands  32  and grooves  34 , preferably extending directly purely axially.  
         [0034]    The radial flange  22  has a stepped surface  28 , having a major diameter surface  35  and a minor diameter surface  36  therein for the axial passage of oil. The inside of the tone ring body  18  includes a rubber portion generally designated  38 , and this portion includes a beveled lead-in area  40 . In addition, there are plural axially extending ribs  46 , each of which includes a lead-in area  44 .  
         [0035]    The ribs  46  are spaced apart by axially extending grooves  48 . The ribs  46  snugly engage the outer diameter  49  of the axle shaft shown as  50 , by engaging a portion  52  thereof which is of intermediate size, being slightly larger in diameter than the axially inner portion  53  of the shaft and smaller size than the portion  54  engaging the inside diameter  56  of the bearing generally designated  58 .  
         [0036]    The bearing  58  is shown to include roller elements  60 , and an outer retainer  64 . The actual type of bearing may vary, and, for example, may feature the rollers  60  indirectly engaging the shaft, or being free from a bearing cage or other locator.  
         [0037]    Oil may pass axially through the grooves  48  in the tone ring  18  from the differential (not shown) to the bearings  58  and to the seal generally designated  66 . Although not a necessary part of the invention, the seal  66  is shown typically to include a casing or stamping  68  and a rubber primary lip  70 . The seal is shown with an auxiliary or dirt lip  71  as is typical with vehicle axles, but this is not strictly necessary.  
         [0038]    The tone ring body  18  does not move measurably axially once it is finally installed in the appropriate position over a portion  52  of the shaft  50 . In addition to being held by the friction of the ribs  46 , the body  18  is also held in a final axial position by a tone ring retainer generally designated  75 . Preferably, but not necessarily, the retainer generally designated  75  is made from two components, a thicker gauge radially outer indented casing generally designated  76  and a thinner gauge radially inner casing generally designated  78 .  
         [0039]    The radially inner casing  78  includes an axially extending portion  80  and a radially inwardly extending retaining flange  82 , while the outer casing generally designated  75 , into which the inner, thinner casing  80  is pressed, includes a radially inwardly extending retainer flange  83 , a generally axially extending portion  84  which includes a corrugated exterior surface portion generally designated  88 . Thus, the portion of the casing generally designated  88  includes both raised portions  90  which engage the counterbore  92  and depressed portions  94  which permit axial passage of oil. There are also scalloped cut-outs  97  or relieved areas in the radial flange  83  of the retainer  88 . Thus, oil flow may be inside the body  18 , outside of the retainer  88 , or between the tone ring  18  and the retainer  88 . The result upon final assembly of the components is a U-shaped retainer in cross-section having flanges  82 ,  83  which will prevent undesired axial movement of the tone ring body  18  in either direction.  
         [0040]    Referring now to another preferred element of the invention, a spacer generally designated  96  is shown to be confined between the radial flange  82  of the inner casing  78  and the axially outer surface  26  of the radial flange  22  of the tone ring  18 .  
         [0041]    This spacer  96  includes a continuous inner portion  98  and a plurality of teeth  100  separated by spaces  102 . Preferably, the teeth  100  include beveled end portions  104  and flat, axially inner and outer surfaces  106 ,  108  to facilitate engagement of the radial flange  82  of the radially inner casing  78  and the axially outer surface  26  of the tone ring radial flange  22 .  
         [0042]    The tone ring body  18  may also have a groove  110  or relieved portion adjacent the radial flange  22  to provide extra clearance between the body  18  and the radial flange  83  of the retainer  75 .  
         [0043]    Assembling the tone ring with its mating parts is a fairly straightforward operation. The axle shaft  50  includes a smaller diameter portion  53  throughout most of its length. As the axle shaft  50  approaches its axially outer end, however, the diameter is very slightly enlarged as at  52 , and the axle shaft  50  includes another step lying toward a larger diameter surface  54  terminating before the flange generally designated  57 .  
         [0044]    The sensor generally designated  14  is positioned properly relative to the lands and grooves on the tone ring body  18  at this time or later. Since it does not interfere with the tone ring, it can be inserted at any time. The retainer  75  is then placed in the counterbore  92  with a light press fit, while the tone ring body is held within the retainer. The tone ring is held such that it does not tilt excessively, and thus is positioned to receive the axle. No other means is required to guide the axle shaft into position within the body  18 . Next, the bearing unit  58  is positioned with its outer retainer  64  pressed into its just larger counterbore  95 , and finally, the casing  68  of a seal unit  66  is pressed into the largest counterbore  101 .  
         [0045]    The axle shaft  50  is then inserted gradually until it engages the tone ring  18  on its inner diameter ribs  46 . Then, with the tone ring resisting further inward movement by reason of engagement between the radial flange  83  of the retainer  75  and the tone ring flange surface  24 , the axle shaft  50  is pushed gradually axially inwardly (to the right as shown in FIG. 4) until the innermost end of the axle shaft is positioned to receive a C-clip (not shown) for holding the axle shaft in position. Thereafter, the axle shaft is withdrawn axially a few millimeters so the C-clip is properly engaged and seated in the differential. This moves the tone ring slightly to the left as shown in FIG. 4 and insures that the axially outer surfaces  108  of the spacer teeth  100  will engage the retainer flange, if necessary, sliding the tone ring body  18  slightly axially inwardly relative to the axle shaft and insuring that the body is properly positioned against spacer  96  which is positioned against retainer flange  82 . Thus, the installation is self-aligning and self-centering, which is very desirable. Once the installation is made, another axle shaft may be reinserted in the application by simply pushing it, usually by hand, into place within the tone ring body. Of course, if the original axle shaft were removed, it could be reinserted inside the tone ring.  
         [0046]    The materials from which the tone ring are made are conventional for this application. For example, the tone ring itself may be made from a ferromagnetic powdered metal, which is die-formed then sintered into the desired finished form. Other materials may be used, but powdered metal technology may be preferred by reason of its affording relatively deep, square lands and grooves as well as its cost-effective magnetic properties. Metal embedded in plastic can also be used, including magnetic strips laid out axially, and then covered with an elastomer or a plastic material which is permitted to harden.  
         [0047]    The rubber used to form the ribs  46  and the surrounding material is an EPDM or other suitable elastomer such as so-called Nitrile (NBR), HNBR, FKM, AEM, ACM or other elastomer. Plastics or thermoset materials can also be used as outlined above in another suitable form. The ribs  46  and surrounding portions  40 ,  42  of the elastomer may be coated with a dried PTFE material for lubrication, and the substrate may be made from a thermoplastic or thermoset material. For purposes of lubrication, a wet lubricant such as oil, grease or an ammonium alkyl phosphate may be placed on the ID of the tone ring. Both parts of the retainer are preferably made from mild steel but plastic could also be used.  
         [0048]    The spacer is an insulating, lubricous material such as Delrin or acetal material, but it possibly could be replaced by a low friction coating on the retainer or on the tone ring flanges, or both, or eliminated completely.  
         [0049]    The retainer is fabricated for convenience in two pieces, an inner, thinner piece and an outer, thicker piece, but it could be made in a single piece. The illustrated form has the corrugations in one part of the retainer, which is then combined with a thinner, flat portion to make the radial flanges. The rubber material used in forming the ribs  46  is of the type that will swell in the presence of oil or grease, including oils with extreme pressure additives therein. Consequently, when the tone ring is installed over the axle, it may be located easily, but after the tone ring has been in place for a time, the oil further swells the rubber and the tone ring is held much more firmly in place.  
         [0050]    As alternate designs, one may also provide several other constructions. In one such construction, which would be the simplest of these, and is illustrated in FIG. 5, the tone ring generally designated  18   a  could simply not have the radial flange, which now affords the simplest way for the retainer to insure that the tone ring does not excessively move axially on the shaft during installation. Instead, there is a groove  110   a  in the body  20   a  of the tone ring  18   a , and a flange  82   a  extending into the groove  110   a. In such a construction, the axial extent of the tone ring would be much larger than the axial extent of the retainer in the first embodiment, but the counterbore  92     a  would have the axial flange  80  pressed into it. The sensor  14   a  rests in an opening  16   a . In this way, a unitized construction would also be provided.  
         [0051]    Another alternate construction is shown in FIG. 6. Here, there is no groove or flange, but the retainer  78   b  is allowed to span the entire axial length of the tone ring with both flanges  82   b ,  82   b  thereby confining the body  18   b  against the axial movement. In such a construction, of course, it would be necessary to provide an opening or window  99  in one portion of the retainer so that the sensor  14   b  could function properly.  
         [0052]    As previously indicated, the spacer may be eliminated, and in its place, a lubricous coating could be placed on the face of the radial flange  26  of the body, or on the inner face of the flange  82 , or both. This expedient could be used in the interest of ultimate cost savings, particularly where there would be little or no risk of significant axial movement of the tone ring after installation, that is, during operation. In the further alternative, the spacer could be made of a hard grease block material, thereby being adapted to dissolve after significant contact with the radial flange of the body and the radial flange of the retainer.  
         [0053]    It is important that there be at least one axial oil passage in the assembly, and preferably, several passages. The most advantageous way of providing these passages is to space the tone ring body apart from the axle shaft by a series of shallow ribs, and then also provide passages in the spacer, the retainer, and in the tone ring flange which periodically come into registration to allow the passage of oil through the part. Still further, the outside diameter of the retainer is also preferably provided with a corrugated or like outside diameter to permit the passage of oil around the retainer. These are all useful ways to provide lubrication to the bearings with oil traveling from the differential.  
         [0054]    The simplest application of the tone ring assembly would be for use in controlling speeds of a single shaft, for example, a generator shaft. However, a more typical use of the tone ring and its associated parts is with two wheel drive vehicles, where the feedback from the sensor is sent to a computer which then determines relative velocities of the two axles. For example, such a use would be in ABS systems (anti-lock braking systems), and differential control systems.  
         [0055]    The tone rings are most advantageously used in four wheel drive systems, where the speed of each axle is desired to be governed by a computer having four or more inputs. Thus, the tone rings are useful, not only in various braking systems, but also in traction control systems where front wheel versus rear wheel speeds must be determined instantaneously, and where right versus left wheel speeds may be also measured instantaneously and then corrected, according to the design of the system.  
         [0056]    It will thus be seen that the present invention provides an improved tone ring assembly having a number of advantages and characteristics including those expressly pointed out herein, and others which are inherent in the invention. A few embodiments of the product of the invention, having been shown and described, it is anticipated that variations to the described form of apparatus will occur to those skilled in the art and that such modifications and changes may be made without departing from the spirit of the invention or the scope of the appended claims.