Description:A PINION GEAR WITH TOOTH CHAMFER ON THE TRANSMITTING FLANK FOR A STARTER MOTOR

FIELD OF THE INVENTION
The present invention generally relates to the field of starter motor for internal combustion (IC) engines, particularly to tooth chamfers on pinion gear for starter motors. More particularly, the present invention relates to tooth chamfer on pinion gear transmitting flank which act as an ‘evading relief’ from oscillating ring gear which becomes a source of vibration and transmitting high shock during collision.

BACKGROUND OF THE INVENTION
In general, an IC engine starter motor of direct engagement type has overrunning clutch assembly (ORC) in which pinion gear is a power transmitting part. The pinion is connected to the ORC with rear end journal portion extending into the clutch inner and therefore contacting multiple rollers according to the quantity of clutch CAMs. Roller springs are placed adjacent to the CAM walls and translate the rollers from transmitting to slipping positions during the starting process. On the front end is the involute spur teeth of pinion when shifted in axial direction engages into the static ring gear of engine and transmit torque to achieve starting. When de energized, the pinion releases from the idling ring gear to its original position. There are two chamfers on the non-transmission side which are used to facilitate engagement.

US5297451 disclosed a drive pinion for an engine starting motor having a lead-in chamfer of the starter pinion defined by a geometry formed by rotating the radial gear tooth involute form through 90 degrees across the end of the tooth. The radius and axis of rotation are selected such that the cam surface is full across the height of the tooth and the cam surface intersects the back side of the tooth at the leading edge of the tooth. Said patent describes the architecture of a lead-in chamfer to avoid non engagements or abutments.

JP3722639B2 provide a starting device for internal combustion engine in which a pinion gear provided to the output shaft of a starter means is engaged to the ring gear of an internal combustion engine, so as to make the engine drivable, the pinion gear is composed of a main gear fixed to an output shaft, and a scissors gear energized to rotate in a specific direction to the main gear by an energizing means. As a result, when the ring gear is driven to rotate by the main gear, a backlash between the ring gear is eliminated by the scissors gear.

US8534145 relates to an engine starting apparatus, together with a one-way clutch, a pinion is pushed toward a ring gear of an engine mounted in a vehicle. The one-way clutch has an idling torque smaller than a torque of the ring gear that tries to turn the pinion when the pinion is pushed to the ring gear. However, the non-transmission side chamfer facilitates the entry of pinion in a coasting ring gear.

DE102017219842 discloses an engine starting device, comprising: an engine generator coupled to a crankshaft of an engine; a starter configured to cause a pinion to mesh with a ring gear provided on the crankshaft when the engine is started, wherein: the engine by simultaneous use of both the engine generator and the starter during an initial starting in which the Engine is started by a start operation by a driver, is cranked; and the engine is cranked by the engine generator when the engine is restarted. However, the chamfer on the non-transmission side is for entry only.

WO2012023393 disclosed an improved engine starter which ensures that a ring gear and a pinion gear are synchronized in phase in an instant the gears are brought into contact with each other even when the gears are mated while the ring gear is rotating. However, the subject chamfer facilitates entry based on the backlash of spline teeth.

WO2012077501A1 disclosed an engine starting device which provides more reliable synchronization and phase alignment at the moment of contact when a pinion gear is forced to engage with a ring gear while the ring gear is rotating, even if there is a difference in the rotational speed of the ring gear or the pinion gear, and minimizes noise, reduction in life due to wear, and delay in startability due to loss of meshing time. However, the chamfer aids pinion to enter the coasting ring gear even the difference between pinion and ring gear speeds are in the order of 300rpm. Two step chamfer on the transmission side is discussed meritoriously after complete engagement of pinion and ring gear.

US20160115934 discloses an internal combustion engine which includes a ring gear having a plurality of ring gear teeth. Each of the plurality of ring gear teeth includes a leading edge surface and a trailing edge surface. A starter motor is mounted to the internal combustion engine. The starter motor includes a pinion gear having a plurality of pinion gear teeth configured and disposed to selectively engage with the plurality of ring gear teeth. Each of the plurality of pinion gear teeth includes a leading edge surface portion and a trailing edge surface portion. The pinion gear is configured and disposed to engage with the ring gear while the ring gear is coasting. At least one of the trailing edge surface of each of the plurality of ring gear teeth and the leading edge surface portion of each of the plurality of pinion gear teeth includes a chamfer.

DE102013213084 provided an engine starting device capable of simply meshing a pinion gear with a ring gear to restart an engine while the ring gear is rotating, regardless of whether the rotation of the ring gear is in a forward or reverse direction, even if there is a large difference in rpm between the ring gear and the pinion gear. A pinion gear of the pinion unit is operable as a single body in the axial direction, and includes a chamfered portion having a curved shape along a tooth surface on a non-torque transmitting surface side and a long length in the axial direction wherein the chamfered portion is provided on an end portion of the tooth surface distal on the gear ring side, on the non-torque transmitting surface side. However, non-transmission side chamfer dimensioning for collision force reduction facilitates entry in a rotating ring gear.

CN102859179 disclosed is a starter system which, given an engine restart request in the middle of stopping the engine, is capable of quickly restarting and of reducing the noise generated when a pinion is engaged with a ring gear of the engine. However, said system having chamfer on both transmission and non-transmission sides to facilitate entry of pinion in a moving ring gear about 80rpm.

WO2013117161 disclosed is a driving gear for a vehicle starter. Each tooth of the driving gear understood a top chamfer formed between a top land and a front end face of the tooth and a side chamfer formed between a non-driving flank and the front end face of the tooth.

JP2002250428 relates to an involute in which at least one of a driving gear and a driven gear slides in an axial direction to engage and disengage. To suppress progress of abrasion of the end faces of teeth in order to improve the durability of an involute gear device, the stating mechanism, and a starter without impairing the engagement of gears by optimizing chamfered widths of tooth flank side chamfered parts of a drive gear and a driven gear, which engage with each other after sliding along an axis, or a combination of the size of chamfered part.

JP2001248710 to prevent the wear of the end faces of teeth and improve the durability of a gear device without impairing the engagement of gears provided a point of crossing a first ridge line between a tooth flank side chamfered portion and an end face of a tooth of a gear and a second ridge line between a tooth tip side chamfered portion and the end face of the tooth is a first intersection.

However, the prior arts have a limitation of overriding the ring gear teeth and cause damage. The impact force due to the collision of pinion and ring gear edges during the de-meshing causing mechanical damage to the inner parts of the gear reduction starter is the problem that persists to be solved. To protect the inner parts of starter against shock load some existing arts would use damper mechanism to absorb it.

Accordingly, there exists a need for a tooth chamfer on pinion gear transmitting flank for starter motors to evade the shock transmitted by the engine ring gear.

OBJECTS OF THE INVENTION
One or more of the problems of the conventional prior arts may be overcome by various embodiments of the system of present invention.

It is the primary object of the present invention to provide a pinion gear with tooth chamfer on the transmitting flank side for starter motors which act as an ‘evading relief’ from oscillating ring gear which becomes a source of vibration and transmitting high shock during collision.

It is another object of the present invention to provide a pinion gear with tooth chamfer on the transmitting flank side which acts as a relief to avoid interference between edges of transmission flank sides of the pinion and ring gear while retraction or up and down motion (compression and exhaust), due to position inaccuracy or vibration in the mounting.

It is another object of the present invention to provide a pinion gear with tooth chamfer on the transmitting flank side to escape the hits from the engine ring gear during retraction or up and down motion and therefore avoiding the breakage of internal parts of starter motor.

It is another object of the present invention to provide a pinion gear with tooth chamfer on the transmitting flank side which is specific for application where the engine back rocking force is huge to cause damage to the starter when the pinion and ring gear are disengaging.

It is another object of the present invention to provide a pinion gear with tooth chamfer on the transmitting flank which is specific for application where, the pinion while retracting from the ring gear will have the edges collide due to position inaccuracy or vibration in the mounting.

It is another object of the present invention, wherein the tooth chamfer on pinion gear transmitting flank avoid collision at edges and therefore shock itself not produced.

SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention, there is provided a pinion gear for a starter motor, comprising:
a plurality of pinion teeth; and
a pinion journal,
wherein each of the pinion teeth having
a transmission flank side;
a non-transmission flank side; and
a lead chamfer and a face chamfer on the non-transmission flank side,
characterized in that, said each of the pinion teeth has a third chamfer on the transmission flank side to evade the shock transmitted by an engine ring gear having a plurality of ring gear teeth, said third tooth chamfer on the transmission flank side dis-engages or retracts without impact during disengagement process,
wherein the pinion gear is connected to a drive assembly of the starter motor with the rear end pinion journal portion extending into clutch inner and therefore contacting multiple rollers of the drive assembly,
wherein when a coil winding in a solenoid switch of the starter motor is de-energized, the pinion gear releases from the idling engine ring gear to its original position and stops rotation by coasting down,
wherein the third tooth chamfer on the transmission flank side acts as an ‘evading relief’ from the oscillating ring gear which becomes a source of vibration and transmitting high shock during collision,
wherein the third tooth chamfer on the transmission flank side acts as a relief to avoid interference between edges of transmission flank sides of the pinion gear and ring gear while retraction or up and down motion and therefore shock itself not produced, and
wherein the third tooth chamfer on the transmission flank side provided to escape the hits from the engine ring gear during retraction or up and down motion and therefore avoiding breakage of internal parts of the starter motor.

It is another aspect of the present invention, wherein the angle of third tooth chamfer on the transmission flank side of the pinion gear depends on the number of teeth and module of the pinion gear.

It is another aspect of the present invention, wherein the angle of third tooth chamfer on the transmission flank side of the pinion gear is 10 degrees.

It is another aspect of the present invention, wherein during engagement, normal dis-engagement and abnormal dis-engagement process, the third tooth chamfer provided on the transmission flank side escapes the hits from the engine ring gear and therefore avoids breakage of internal parts of the starter motor.

BRIEF DESCRIPTION OF DRAWINGS
Figure 1: illustrates a cut section view of a starter.
Figure 2: illustrates a drive assembly or overrunning clutch assembly.
Figure 3: illustrates a cut section view of the Figure 2-drive assembly.
Figure 4: illustrates a pinion gear according to present invention.
Figure 5: illustrates top and front view of third tooth chamfer depicting the angle according to present invention.
Figure 6: illustrates center distance between pinion and ring gear centers according to present invention.
Figure 7: illustrates working of pinion gear -engagement process according to present invention.
Figure 8: illustrates working of pinion gear-normal dis-engagement process according to present invention.
Figure 9: illustrates working of pinion gear-abnormal dis-engagement process according to present invention.
Figure 10: illustrates working of pinion gear wherein tooth chamfer avoids taking hit from ring gear according to present invention.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURES
The present invention as herein described relates to a tooth chamfer on pinion gear transmitting flank side for starter motors which act as an ‘evading relief’ from oscillating ring gear which becomes a source of vibration and transmitting high shock during collision. The tooth chamfer on pinion gear transmitting flank side for starter motors which acts as a relief to avoid interference between edges of transmission flank sides of the pinion and ring gear while retraction or up and down motion (compression and exhaust), due to position inaccuracy or vibration in the mounting.

Referring to Figures 1 to 3, the starter for an internal combustion (IC) engine generally comprises of a DC motor [1]; a solenoid switch [2]; an output shaft [3]; a front bracket [4]; a rear bracket [5]; a drive assembly or overrunning clutch assembly (ORC) [6]; an engaging lever [11] and an engine ring gear [12] having a plurality of ring gear teeth. The drive assembly or overrunning clutch assembly (ORC) [6] comprises of a sleeve [7] with multiple CAM surfaces, multiple rollers [8], multiple roller springs [9] and a pinion gear [10]. The pinion gear is a power transmitting part. Referring to Figure 4, the pinion gear [10] comprises of a plurality of pinion gear teeth [10a], and a pinion journal [10b]. Each pinion gear teeth [10a] having a transmission flank side [10c], and a non-transmission flank side [10d], a lead chamfer [10d1] and a face /top-land chamfer [10d2] on the non-transmission flank side [10d], characterized in that, said each of the pinion teeth [10a] has a third chamfer [10c1] on the transmission flank side [10c] which dis-engages or retracts without impact during disengagement process. The pinion [10] is connected to the drive assembly or overrunning clutch assembly (ORC) [6] with the rear end pinion journal [10b] portion extending into the clutch inner and therefore contacting the multiple rollers [8] according to the quantity of clutch CAMs as depicted in Figures 1 and 2. Referring to Figure 3, the roller springs [9] are placed adjacent to the CAM walls and translate the rollers [8] from transmitting to slipping positions during the starting process. On the front end is the involute spur teeth [10a] of pinion when shifted in axial direction engages into the static ring gear [12] of engine and transmit torque to achieve starting. The inner diameter of the pinion [10] has a bearing [10e] supported by the output shaft [3] to facilitate rotation. The solenoid switch [2] and DC motor [1] are attached to the front bracket [4].

In an embodiment, the third tooth chamfer [10c1] on the transmission flank side [10c] is advantageous under the following condition: The stiffness of a starter mounting flange has an influence on the bending value when the pinion gear [10] retract from the edge surface of the engine ring gear [12]. In this case, the pinon [10] face parallelism is deviated and collides with ring gear edge. The third tooth chamfer [10c1] avoids taking hit from the engine ring gear as depicted in Figure 10.

Referring to Figures 1and 3, the sleeve [7] is configured with a spline in the stem (not shown) which is to mate with an output shaft spline [3a]. The multiple rollers [8] arranged between the sleeve [7] inner CAM surface and pinion journal [10b] outer diameter is to transmit motor torque from the sleeve [7] to the pinion journal [10b]. The roller spring [9] is to position the roller [8] so that the pinion [10] is both connected/disconnected from the sleeve [7] depending upon the transmitting and slipping conditions.

In the solenoid switch [2], when a coil winding [2c] is energized by passing current from a battery, a plunger [2a] along with a hook [2b] is sucked inside and therefore contact points (not shown) are closed, the DC motor [1] starts functioning at this instant by transmitting torque to the output shaft [3] after internal gear reduction unit. In the meantime, when the plunger [2a] is sucked, the engaging lever [11] is also pulled by the hook [2b], causing the engaging lever [11] to rotate with respect to a pivot [12] as center point. In this effect, the drive assembly [6] will axially move on the outer periphery of the output shaft [3] with the aid of the output shaft spline [3a] and engages with the engine ring gear [12]. The pinion gear [10] moves and meshes with the ring gear [12].

When the coil winding [2c] in the solenoid switch [2] is de-energized, the pinion [10] releases from the idling ring gear [12] to its original position. Referring to Figure 4, apart from the existing lead chamfer [10d1] and face /top-land chamfer [10d2] on the non-transmission flank side [10d] of each of the pinion teeth [10a] which are used to facilitate engagement, the third tooth chamfer [10c1] on the transmission flank side [10c] acts as an ‘evading relief ‘from the oscillating ring gear which becomes a source of vibration and transmitting high shock during collision. Also, the third tooth chamfer [10c1] on the transmission flank side [10c] acts as a relief to avoid interference between edges of transmission flank sides of the pinion gear [10] and ring gear [12] while retraction or up and down motion (compression and exhaust), due to position inaccuracy or vibration in the mounting. It is desired to escape the hits from the engine ring gear [12] during the above conditions and therefore avoiding the breakage of internal parts of starter motor.

Some of the primary conditions that are required for the smooth engagement and retraction are a) center distance between flywheel and pinion as depicted in Figure 6, b) parallelism between pinion and ring gear faces.

Working:
Referring to Figures 1 to 4, in the solenoid switch [2], when a coil winding [2c] is energized by passing current from a battery, a plunger [2a] along with a hook [2b] is sucked inside and therefore contact points (not shown) are closed, the DC motor [1] starts functioning at this instant by transmitting torque to the output shaft [3] after internal gear reduction unit. In the meantime, when the plunger [2a] is sucked, the engaging lever [11] is also pulled by the hook [2b], causing the engaging lever [11] to rotate with respect to a pivot [12] as center point. In this effect, the drive assembly [6] will axially move on the outer periphery of output shaft [3] with the aid of an output shaft spline [3a] and engages with the engine ring gear [12].

Engagement process (ring gear in static condition):
Referring to Figure 7,
? During static condition before energization, the gap between the pinion gear [10] and ring gear [12] face is approximately 3mm.
? On energization, the pinion gear [10] moves both axially and rotating anti-clockwise towards the static ring gear [12] and the chamfers [10d1, 10d2] mate to lead the pinion [10] in ring gear teeth gap, the pinion slightly push the ring gear while entry.
? The pinion [10] achieves full travel position and stopped, further no anti-clockwise rotation.
? Transmission flank sides of the pinion gear [10] and ring gear [12] touches and the pinion drives the ring gear engine cranked by starter motor.

Normal dis-engagement process:
Referring to Figure 8,
? The engine was fired and again engagement sides start to touch, the pinion [10] is driven by ring gear [12].
? The solenoid [2] is de-energized and the pinion gear [10] retracts back (ring gear [12] continues to run).
? The pinion gear [10] restored in its original position and stops rotation by coasting down (ring gear continues to run).
Abnormal dis-engagement process:
Referring to Figure 9,
? Fuel cut-off / sporadic firing, the starter is de-energized and the pinion gear [10] is not completely retracted, the ring gear [12] changes rotating direction (clockwise to anti-clockwise) and the transmission edges hit each other creating a collision wherein shock waves were transferred to the starter inner parts and results in breakage.

When the coil winding [2c] in the solenoid switch [2] is de-energized, the pinion [10] releases from the idling ring gear [12] to its original position. According to the present invention, the third tooth chamfer [10c1] on the transmission flank side [10c] engages (act as enabler) without impact. Also, the third tooth chamfer [10c1] on the transmission flank side [10c] acts as a relief to avoid interference between edges of transmission flank sides of the pinion gear [10] and ring gear [12] while retraction or up and down motion (compression and exhaust), due to position inaccuracy or vibration in the mounting. It is desired to escape the hits from the engine ring gear [12] during the above conditions depicted in Figure 10 and therefore avoiding the breakage of internal parts of starter motor.

In an embodiment, the angle of chamfer depends on the number of teeth and module of pinion gear [10]. Referring to Figure 5, in another embodiment, the angle of third tooth chamfer [10c1] is 10 degrees which is deeper and deliberately provided. In another embodiment, the angle of chamfer is such that the cut angle is maintained less than pressure angle of the gear (20°).

Technical advancements:
• The third tooth chamfer on the transmission flank side dis-engages or retracts without impact during disengagement process.
• The third tooth chamfer on the transmitting flank side escapes the hits from the engine ring gear during retraction or up and down motion and therefore avoiding the breakage of internal parts of starter motor.
• The third tooth chamfer on the transmitting flank side avoid collision at edges due to position inaccuracy or vibration in the mounting and therefore shock itself not produced.
, Claims:WE CLAIM:
1. A pinion gear [10] for a starter motor, comprising:
a plurality of pinion teeth [10a]; and
a pinion journal [10b],
wherein each of the pinion teeth [10a] having
a transmission flank side [10c];
a non-transmission flank side [10d]; and
a lead chamfer [10d1] and a face chamfer [10d2] on the non-transmission flank side [10d],
characterized in that, said each of the pinion teeth [10a] has a third chamfer [10c1] on the transmission flank side [10c] to evade the shock transmitted by an engine ring gear [12] having a plurality of ring gear teeth, said third tooth chamfer [10c1] on the transmission flank side [10c] dis-engages or retracts without impact during disengagement process,
wherein the pinion gear [10] is connected to a drive assembly [6] of the starter motor with the rear end pinion journal [10b] portion extending into clutch inner and therefore contacting multiple rollers [8] of the drive assembly [6],
wherein when a coil winding [2c] in a solenoid switch [2] of the starter motor is de-energized, the pinion gear [10] releases from the idling engine ring gear [12] to its original position and stops rotation by coasting down,
wherein the third tooth chamfer [10c1] on the transmission flank side [10c] acts as an ‘evading relief’ from the oscillating ring gear [12] which becomes a source of vibration and transmitting high shock during collision,
wherein the third tooth chamfer [10c1] on the transmission flank side [10c] acts as a relief to avoid interference between edges of transmission flank sides of the pinion gear [10] and ring gear [12] while retraction or up and down motion and therefore shock itself not produced, and
wherein the third tooth chamfer [10c1] on the transmission flank side [10c] provided to escape the hits from the engine ring gear [12] during retraction or up and down motion and therefore avoiding breakage of internal parts of the starter motor.

2. The pinion gear [10] for a starter motor as claimed in claim 1, wherein the angle of third tooth chamfer [10c1] on the transmission flank side [10c] of the pinion gear [10] depends on the number of teeth and module of the pinion gear [10].

3. The pinion gear [10] for a starter motor as claimed in claim 2, wherein the angle of third tooth chamfer [10c1] on the transmission flank side [10c] of the pinion gear [10] is 10 degrees.

4. The pinion gear [10] for a starter motor as claimed in claim 1, wherein during engagement, normal dis-engagement and abnormal dis-engagement process, the third tooth chamfer [10c1] provided on the transmission flank side [10c] escapes the hits from the engine ring gear [12] and therefore avoids breakage of internal parts of the starter motor.