US 3798977 A
A pinion for starter gearing having a radially extending concave face, the concave face being formed so that the teeth of said pinion gear are angularly disposed with respect to the transverse plane of said pinion thus protruding outwardly from the engaging end of said pinion. In order to aid a starter drive pinion into mesh with a rotating ring gear the concave face allows the tips of the teeth to protrude from the face of the pinion and therefore easily engage the teeth of the ring gear, thus, bringing the pinion up to synchronous speed with the ring gear more quickly than face-friction alone would accomplish.
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Description (OCR text may contain errors)
United States Patent [1 1 Digby I PINION FOR STARTER GEARING  Inventor: James J. Digby, Elmira, NY.
 Assignee: The Bendix Corporation, Southfield,
 Filed: Apr. 27, 1972 Appl. No.: 249,449
 US. Cl. 74/6, 74/462  Int. Cl. F02n 15/06, Fl6h 55/08  Field of Search 74/6, 7, 7 A, 7 B, 434,
 References Cited UNITED STATES PATENTS 2,947,179 8/1960 Lafitte 74/6 1,329,535 2/1920 McGrath 74/462 FQREIGN PATENTS OR APPLICATIONS Great Britain 74/7 [111 y 3,798,977 [451 Mar. 26,1974
Primary Examiner-Allan D. l-Ierrmann Attorney, Agent, or Firm-Bruce A. Yungman; Raymond J. Eifler; Remy J. VanOphem 5 7] ABSTRACT A pinion for starter gearing having a radially extending concave face, the concave face being formed so that the teeth of said pinion gear are angularly disposed with respect to the transverse plane of said pinion thus protruding outwardly from the engaging end of said pinion. In order to aid a starter drive pinion into mesh with a rotating ring gear the concave face allows the tips of the teeth to protrude from the face of the pinion and therefore easily engage the teeth of the ring gear, thus, bringing the pinion up to synchronous speed with the ring gear more quickly than facefriction alone would accomplish.
1 Claim, 4 Drawing Figures PATENTEnmzs I974 3798377 FIG. I
PRIOR ART PINION FOR STARTER GEARING CROSS REFERENCE TO RELATED CASES This case is related to my commonly assigned copending patent application Ser. No. 249,450 filed Apr. 27, 1972 entitled Indexing Starting Drive, and to my commonly assigned U. S. Pat. No. 3,263,509 issued Aug. 2, 1966.
I. Field of the Invention The present invention relates to the field of starter gearing in general and in particular to that portion of the field of starter gearing which relates to pinion design.
2. Brief Description of the Prior Art Clutches of the general type described herein are well known in the art, with the above mentioned U. S. Pat. No. 3,263,509 being representative of a more advanced design. These types of drives primarily lend themselves to large engine installations, for example,
large volume displacement Diesel Engines. Such a drive is therefore subjected to a hostile working environment including for example extremely high torques and frequent inadvertent starts resulting whenever the driver cannot hear whether or not the engine has started (a condition that often occurs for example on rear engine buses). Attempting to mesh the drive pinion with a ring gear of an engine that is already started and running is obviously a frequent cause of damage to drive pinions and to engine ring gears. This cause of damage to pinion and ring gear can also occur of course in smaller starter drives used for example on automobiles. In starter drives which include overrunning clutches it is desirous to bring the speedof the nonrotating pinion up to the speed of the rotating ring gear where the engine is already started and running as quickly as possible to prevent damage to the pinion and to the drive itself.
One method of preventing damage to the pinion and the ring gear is to point the pinion or the ring gear or both thus preventing chipping of the otherwise blunt engaging teeth whenever they abut. Pointinghowever is of little or no assistance when attempting to mesh a pinion with a rotating ring gear.
SUMMARY OF THE INVENTION It is therefore a primary object of this invention to provide an improved pinion for starter gearing wherein the pinion has a radially extending concave face, the concave face being formed so that the teeth of said pinion gear are angularly disposed relative to the transverse plane of said pinion such that the teeth protrude outwardly from the end of said pinion gear. By allowing the tips of the pinion teeth to protrude from itsradially extending face the pinion teeth easily engage the teeth of the ring gear thus bringing the pinion up to synchronous speed with the ring gear more quickly than facefriction alone would accomplish. When the teeth of the pinion and ring gear are in mesh the starter drive will force the pinion into full engagement allowing it to overrun and therefore prevent damage to the pinion teeth, the ring gear teeth, and the remainder of the starter gearing mechanism.
It is another object of this invention to provide an improved starter drive having a pinion gear which induces mesh with a rotating ring gear in that the pinion gear has teeth which reach beyond its engaging end thereby grabbingthe rotating ring gear and prohibiting abutment of the end faces of the ring gear and pinion gear.
It is still another. object of the present invention to provide an economical reliable engine starter gearing having good torque transmitting characteristics and which has a long service life, and wherein the pinion is characterized by a unique concave engaging face.
Still a further object of this invention is to provide an improved starter drive of the positive shift overrunning dentil clutch type wherein the pinion gear has axially extending teeth provided to assist the pinion gear to mate with a rotating ring gear.
Yet another object'of this invention is to provide an improved pinion for-starter gearing wherein the pinion is configured such that it will be caused to rotate by.
rapid engagement with a rotating ring gear thus bringing the pinion up to synchronous speed with the ring gear more quickly than face friction alone would accomplish.
With the above and other objects in view which will appear as the description proceeds, this invention resides in a novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined in the appended claims, it being understood that such changes in the precise embodiment of the herein disclosed invention may be made as come within the scope of the claims.
BRIEF DESCRIPTION OF THE DRAWING The accompanying drawing illustrates a single example' of a physical embodiment of the invention constructed according-to the best mode so far devised for the-practical application of the principles thereof, and in which:
FIG. 1 is a side elevational view, partly insection and broken away, of the preferred embodiment of my invention showing the'pinion' in abutment with the rotating ring gear the pinion being in its fully indexed or retracted position.
FIG. 2 shows a partial section'ofa pinion gear incorporating" my unique pinion tooth design.
FIG. 3 shows a partial section of a typical prior art pinion design.
FIG. 4 shows an end view of a pinion made according to my invention;
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, there is illustrated a starter drive for an engine generally designated by numeral 10, mounted on a power shaft 12' of a starting motor (not illustrated). The drive includes an axially extending sleeve 14 connected to shaft 12 by straight spline 16 so as to beaxially, but'not rotatively, moveable relative to the shaft. The external surface of the forward or right hand extremity of the sleeve has helical splines 18' formed teeth 82 extending radially therefrom as shown in FIG. 4. Teeth 82 are frusto-conical in cross section with a portion 85 being formed thereon, (called pointing) for the reason described above. Sleeve 28 is secured to sleeve 14 and is slidably supported on a reduced diameterextension of power shaft 12. The pinion gear is adapted for movement into and out of engagement with the engine gear 22. In the illustrated position the teeth of the pinion 26 are shown to be in abuting relationship with the ring gear 22 which for purposes of discussion we will assume is rotating. An annular driven clutch member 30 is integrally formed with the pinion gear as the left-most extension thereof. The driven clutch member is formed to provide an annular or circular recess 32 radially inwardly of the clutch member having its inner extremity defined by sleeve 28. h
The opposing or adjacent faces of the clutch members and are provided with complementing mutually engageable inclined torque transmitting dentil teeth 34 and 36, respectively. The dentils are of the saw-tooth variety to provide a one-way overrunning clutch connection.
A one-piece barrel-shaped housing and shifting collar 38, having a closed and an open end, is slidably supported at its closed end 40 on the external surface of sleeve 14. A lock ring 42 is seated in a notch adjacent the open end of the housing and has sufficient radial length to engage driven clutch member 30 to thereby confine the clutch elements within the housing cavity. It is important to note that the unitary housing 38 provides an axial annular clearance 70 adjacent washer 46.
t The axial dimension of the annular space 70is determined by the axial depth of the dentil teeth 34 and 36. That is, clearance 70 permits driving clutch member 20 to recede and overrun without interference. Housing 38 is of simple design and is therefore more economical to manufacture than prior art casings.
The sleeve 14 is provided with a radial shoulder 44 intermediate its extremities to provide an abutment for a disc or washer 46 slidably journalled on the sleeves. A resiliently yieldable cylinder 48, preferably of an elastically deformable material, such as rubber, is compressively confined between the disc and closed housing end. A resilient spring member 50 is compressively confined between disc 46 and driving clutch member 20 to provide a biasing force, urging the clutches in an engaged position.
Means for moving a starter gear assembly toward or away from the engine gear 22 may comprise the conventional solenoid, air or hydraulic cylinder actuated lever, not illustrated, connected to the shift collar 52 which is connected to the closed end 40 of housing 38.
Means for accomplishing the automatic separation of dentil teeth 34 and 36 are arranged in the annular recess 32 within the driven clutch member 30. An annular thrust washer 54 backed by a loose thrust washer 67 abuts at its outer edge the shoulder 24 of splines 18. The radially inner surface 56 of the thrust washer is inclined or conically formed with respect to the longitudinal axis of the starter gear. A plurality of centrifugal flyweight members are annularly arranged adjacent thrust washer 54, one such flyweight is designated by the numeral 58. Each flyweight has an inclined surface 60 complementary with an abuting surface 56 of the thrust washer. A radial hole 62 is formed in each weight at an intermediate or mid-point closely corresponding with the location of center of gravity of the weight member. A support pin 64 is secured on one end in a radial hole 66 formed in annular driven clutch member 30 and projects radially inwardly therefrom into the hole 62 in the flyweight member. The pin and hole connection restrain the flyweight from movement in either the axial or circumferential direction, while permitting radial movement in response to centrifugal force. it will be noted that sleeve bearing 63 projects into the annular recess 32 and provides a radially-inward stop for the flyweight 58, establishing clearance between flyweight and sleeve 28 to avoid wear or snagging of the moving assembly.
H6. 2 shows a partial section view of the pinion gear (26) which embodies the principles of this invention. The face of the pinion gear (26) and the tooth design is shown in more detail. The free end portion of the tooth (82) has a protrusion (83) which extends axially I outwards from the face The protruding free end portion (83) of the tooth (82) is cut at an angle with respect to the gears face (80) resulting in a tapered surface (84) that extends radially inward from the free end of the protrusion (83) to the face (80) of the gear (26). Extensive testing on the type of drive shown has revealed that the most favorable angle a is about 17". An acceptable angle is an angle less than 30. The angle is formed in pinion 26 by trepanning, although other machining techniques could also be used. Notice that with this design the teeth 82 protrude axially outwardly from the end of the pinion gear such that they will reach out and grab the rotating ring gear 22 (shown in phantom) with their radially outer tip 83. With this design the area of the pinion which is permitted to initially abut the transverse face of the ring gear 22 (i.e., tip 83) is minimized, so that the pinion teeth easily mesh with 82 would abut the left-most engaging surface of the ring gear 22 causing the entire pinion assembly to remain in an abutting relationship with the ring gear. This resulted in milling of the teeth of either the pinion andlor the ring gear causing extensive damage to either or both. The only way pinion 26' could be brought into synchronism with the rotating ring gear 22 was through the face-friction created by the abutting radially extending faces of the teeth of both members.
OPERATION In normal operation, when it is desired to crank the engine, the starter gearing assembly is shifted to the right via a positioning mechanism connected to collar 52 and along the power shaft 12 so that pinion gear 26 engages engine starter gear 22. Shaft 12 is rotated by a starting motor and transmits torque through spline 16 to sleeve 14, from helical splines 18 to driving clutch member 20, driven clutch member 30, pinion 26 to the engine gear 22. As the engine fires and becomes selfoperating, gear 22 will now drive pinion '26 at a speed greater than that of the shaft 12.- Clutch teeth 34 and 36 will slip so that the starting motor is not driven at high engine speeds. This condition has caused severe wear of dentil teeth when overrunning continues for prolonged periods as the relatively heavy clutch engagement spring 50 urges the clutch teeth toward the engaged position while the overrunning cam action between the teeth forces them apart. The centrifugal weight means described above and more fully discussed in U. S. Pat. No. 3,263,509 was added to cause separation of the clutch teeth at a predetermined engine selfoperating speed in order to prevent the dentil teeth from being subjected to long periods of contact while the pinion is overrunning.
The starter gearing shown is further designed to provide an indexing function should the pinion 26 abut one of the teeth of starter gear 22 when being actuated to the right into engagement. In such an event, pinion movement is obstructed by tooth abutment, but the shifting mechanism will continue to shift housing 38 and sleeves l4 and 28. When an abutment occurs pinion and clutch stand still against ring gear 22 while drive sleeves l4 and 28 and case 38 continue to shift rightwardly toward the ring gear. Thus the pinion and clutch members will shift leftwardly relative to sleeve 14. Driving clutch member 20 will be caused to rotate on helical splines 18 which rotation is transmitted to driven clutch member 30 and pinion 26 through the dentil teeth so that the pinion will clear the obstructed tooth on engine gear 22. Note that with my improved pinion design, the angular degree of rotation necessary for the pinion teeth to clear an obstructed tooth of the engine ring gear 22 is greatly reduced since the arcuate area in engagement with a ring gear 22 is only a fraction of the same arcuate area represented by a prior art pinion tooth. As the tooth is cleared spring 50 snaps the pinion and clutch members to the right in the engaged position. Since the amount of time required to index is reduced, the drive engages more rapidly which in turn reduces the time to start the engine.
Should the drive pinion attempt to mesh with the ring gear of an engine that is already started and running however, the pinion will retract all the way on themdexing splines 18 and the ring gear 22 will attempt to force clutch member 30 to overrun clutch member 20. When this condition occurred in the prior ar'tdrives, clutch member 20 was jammed against washer 46 thus preventing the dentils 34 and 36 to separate and overrun. This of course resulted in tooth milling of the pinion 26 and/or the ring gear 22. Since the drive could not overrun in'this position, it was required to bring the armature inertia up to synchronous speed with the ring gear in order to get into mesh and it has been demonstrated that this is extremely difficultif not in fact impossible at engine speeds of over 500 rpm. However, as stated above, the requirement of bringing the pinion up to synchronous speed with the ring gear through facefriction of the abutting teeth faces is virtually eliminated, if such a prior art starter drive were to incorporate a pinion according tothe teachings of my invention. Tests made with my pinion and tooth design have proven its effectiveness in aiding a starter drive to mesh with a rotating ring gear.
The starter gearing mechanism accomplishes all the normal functions of impact cushioning, indexing, overrunning, automatic dentil tooth separation, and in addition provides a pinion gear which aids the starter drive into mesh with both an at-rest and a rotating engine ring gear.
Although but one form of my inventionhas been shown and described in detail it will be understood that changes may be made in the design and arrangement of parts without departing from the spirit of the invention. For example, although the foregoing description pertains to a positive shift starter drive having an overrunning dentil type clutch therein, any type of starter drive incorporating a pinion made according to the teachings of my invention will engage easier and its effectiveness will be correspondingly increased.
I claim: I
1. In combination with the starter drive for an internal combustion engine wherein the rotary motion of a power shaft of a starting motor is transferred to the-engines ring gear through a pinion gear mounted on the power shaft, wherein the improvement comprises:
a pinion gear having a plurality of teeth arranged around the periphery thereof and a' face, .each of the teeth having at the freeend thereof an axial protrusion, extending beyond said face, each of the axial protrusions including a tapered surface that extends radially inward towards said face from the free end portion of the tooth whereby the'axial prowith the of the pinion gear rotating ring gear.