Claims:I / WE CLAIM:

1. A rotating machine, comprises:
a drive pinion comprises a plurality of teeth each having a drive face flank (3), a driven face flank (4) and a top land face (1);
the drive face flank (3) is chamfered between the drive face flank (3) and front side face (2) with a tolerance angle of 40° to 45° degrees to improve the engagement behavior and the drive face (5) is chamfered between the drive face flank (3) and front side face (2) with a tolerance angle of 30° to 35° degrees.

2. The rotating machine as claimed in claim 1, wherein the teeth extend radially outwards from a root circle of the toothing.

3. The rotating machine as claimed in claim 1, wherein the drive pinion is displaced axially to engage in the ring gear of the internal combustion engine. , Description:FIELD OF THE INVENTION:

The present invention generally relates to ring gear in a starter motor attached to an internal combustion engine. More particularly, the present invention relates to dual entry chamfer for drive face of pinion gear with increased durability and reduced noise.

BACKGROUND:

Starter motor for an internal combustion engine, includes a shaft rotated by the electric motor of the starter motor, and supporting a pinion assembly having a pinion gear wheel engageable, in use, with a ring gear of the associated internal combustion engine. The gear of the starter motor engages with internal combustion engine, in order to crank it.

German Patent Application number 102010038443 to Stefan Tumback entitled “Asymmetrical toothing” discloses a sprocket tooth whose thickness is asymmetrical, in particular reduced or enlarged on one or both sides. However, such a tooth profile is only partially optimized from the point of view of noise.

On the other hand, for an axial penetration distance of the pinion between two teeth of the given ring, the driving ratio is not constant. It can go from two points of contact between the pinion and the crown to a single point of contact. This passage from two points of contact to a point of contact will generate an impact which causes noise and compromises the durability of the pinion.

Also, it is known from PCT patent application 2017203156, about the starter with a pinion having at least one profiled tooth. It does not disclose about the flank compression and the occurring tooth root stresses in the root circle of the individual teeth both in the region of the reduced tooth thickness in the tooth root and the tooth flank which can compromise the durability of the pinion. Helix angle of the driven face is between 5o and 45o. The surface of the section in the second plane (P2) being greater than the surface of the section in the fourth plane (P4) which is itself greater than the area of the section in the third plane (P3). The gear teeth are all profiled teeth having same involute profile at the other end as well.

It is known from the prior art that the teeth of the drive pinion should have a bevel on an end side of the drive pinion in order to facilitate the engagement of the drive pinion in the ring gear of the internal combustion engine. The area of the end side is reduced by the bevel, and therefore the probability that two teeth bear on one another by their end sides is reduced. Nevertheless, jamming of the drive pinion with the ring gear of the internal combustion engine can occur, with the result that increased wear is caused.

In order to overcome the aforementioned drawbacks, the present invention proposes a dual entry chamfer for drive face of pinion gear without compromise on reduced tooth thickness in the tooth root and the tooth flank so that the durability of pinion gear will improve. Further, maintaining a situation in which two pairs of teeth come into contact with one another simultaneously can be avoided so that we can achieve constant driving ratio. Consequently, the risk of jamming between the drive pinion and the ring gear of the internal combustion engine is reduced, as a result, the wear and noise can be reduced overall.

OBJECTS OF THE INVENTION:

The primary object of the present invention is to provide a better engagement behavior of the drive pinion to the ring gear of the internal combustion engine.

Another object of the present invention is to provide a dual entry chamfer for drive face of pinion gear to improve durability and achieve constant driving ratio.

Yet another object of the present invention is to optimize the noise behavior of the toothing.
Still another object of the present invention is to reduce force value at initial contact with flywheel with dual chamfer provided on pinion gear.

SUMMARY:

To achieve the aforementioned objectives, the present invention discloses a dual entry chamfer for drive face of pinion gear without compromise on reduced tooth thickness in the tooth root and the tooth flank so that the durability of pinion gear will improve.

According to present invention, the starter motor engages the ring gear of the internal combustion engine with pinion gear, comprising a tooting which consists of drive face flank, a driven face flank and a top land face.

In order to improve the engagement behavior, it is proposed that a drive face flank is chamfered between the drive face flank and front side face with a tolerance angle of 40° to 45° degrees, and the drive face is chamfered between the drive face flank and front side face with a tolerance angle of 30° to 35° degrees.
The present invention relates to teeth of the drive pinion being provided with an additional chamfer on the drive face flank. According to the invention, chamfers are formed on an end side of the drive pinion, wherein two chamfers are providing on a drive face, the first chamfer on drive face chamfer is formed between the drive face and the front end face with tolerance angle of 40° to 45°deg, and second chamfer on the drive face is formed between the drive face and front end with tolerance angle of 30° to 35° deg. As a result, a situation in which two pairs of teeth come into contact with one another simultaneously can be avoided. Consequently, the risk of jamming between the drive pinion and the ring gear of the internal combustion engine is reduced and as a result the wear and noise can be reduced.
Advantageously, the peak force can be splitted into two segments, i.e., in the first force with first entry chamfer of pinion and second force is the second entry chamfer of pinion gear. Further, shock force exerted by pinion on flywheel is reduced; damage to pinion gear as well as flywheel is reduced; noise level is reduced and involves easy manufacturing process.

The objective and advantages of the present invention will become more evident from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS:

The objective of the present invention will now be described in more detail with reference to the accompanying drawings, in which:

FIG. 1 shows the dual entry chamfer for starter motor pinion gear according to present invention;

FIG. 2 illustrates surface section of different planes; and

FIGS. 3(a) and 3(b) show the pinion gear with single entry chamfer and pinion gear with dual entry chamfer respectively.

REFERENCE NUMERALS:

1 – top land
2 – Front side face
3 – drive face flank
4 – driven face flank
5 – drive flank
101 – first plane
102 – second plane
103 – third plane

DETAILED DESCRIPTION OF THE INVENTION:

The present invention discloses a dual entry chamfer for drive face of pinion gear without compromise on reduced tooth thickness in the tooth root and the tooth flank so that the durability of pinion gear will improve.

The starter motor for an internal combustion engine (i.e., rotating machine) is used for engaging the ring gear of the internal combustion engine with pinion gear comprising a tooting which consists of drive face flank (3), a driven face flank (4) and a top land (1) as shown in FIG. 1.

In order to improve the engagement behavior, it is proposed that a drive face flank is chamfered between the drive face flank and front side face with a tolerance angle of 40° to 45° degrees, and the drive face is chamfered between the drive face flank and front side face with a tolerance angle of 30° to 35° degrees.

In an embodiment, in order to improve the engagement behavior, it is proposed that a top land (1) is chamfered between the top land (1) and front side face (2), a drive face flank (3) is chamfered between the drive face flank (3) with tolerance angle of 35 to 45 deg and the front side face (2), and drive flank (5) is chamfered between the drive face flank (3) and the drive flank (5) with tolerance angle of 50 to 55 deg.

From the above cutting chamfer angles, the surface of the section in the first plane (P1 or 101) being greater than the surface of the section in the third plane (P3 or 103) which is greater than the surface of the section in the second plane (P2 or 102) as shown in FIG. 2.
P1> P3>P2
According to present invention, it is proposed to form a dual entry chamfer for drive face of pinion gear without compromise on reduced tooth thickness in the tooth root and the tooth flank so that the durability of pinion gear will improve. Maintain a situation in which two pairs of teeth come into contact with one another simultaneously can be avoided so that we can achieve constant driving ratio. Consequently, the risk of jamming between the drive pinion and the ring gear of the internal combustion engine is reduced, as a result, the wear and noise can be reduced overall.

In accordance with the present invention, the drive pinion of the starter motor for engaging in a ring gear of the internal combustion engine is provided, in order to drive the engine. Such drive pinions have a toothing which comprises a plurality of teeth which each have a drive face flank, a driven face flank and a top surface. Here, the teeth extend radially outwards from a root circle of the toothing. Such drive pinions are used in starters motor to start the internal combustion engine. Here, for starting, the drive pinion is usually displaced axially in order to engage in the ring gear of the internal combustion engine. A problem with this procedure is that the drive pinion can engage in the ring gear only when it is correctly oriented with the teeth of the ring gear. If, for example, two teeth are situated over one another, the end sides of the drive pinion and of the ring gear each come into contact with one another such that the drive pinion cannot engage in the ring gear.

The present invention provides an improved embodiment of a drive pinion for better engagement behavior of the drive pinion to the ring gear of the internal combustion engine. This is achieved by providing different entry chamfer to pinion gear as described below.

The present invention relates to teeth of the drive pinion being provided with an additional chamfer on the drive face flank. According to the invention, chamfers are formed on an end side of the drive pinion, wherein two chamfers are providing on a drive face, the first chamfer on drive face chamfer is formed between the drive face and the front end face with tolerance angle of 40° to 45°deg, and second chamfer on the drive face is formed between the drive face and front end with tolerance angle of 30° to 35° deg. As a result, a situation in which two pairs of teeth come into contact with one another simultaneously can be avoided. Consequently, the risk of jamming between the drive pinion and the ring gear of the internal combustion engine is reduced and as a result the wear and noise can be reduced.

In the present invention, the impact force or hitting force exerted by the pinion gear on to the ring rear can be split into two segments i.e. The first impact force will be in first entry chamfer of pinion and second impact force will be in with second entry chamfer of pinion gear. The splitting of impact forces will have less impact when compared to direct impact with one chamfer. As a result, the stress induced in the root circle and in the region of the reduced tooth thickness can be reduced. These two points of contact will generate less impact force compared to single point of contact on the ring gear and pinion gear. So, it will reduce the noise. As a result, the durability of the pinion gear and ring gear increases. Further, the constant driving ratio or minimized driving ratio can be achieved.

In the existing design, the peak contact force of pinion with flywheel generated at single point of time only because of single entry chamfer. In the new design, the peak force is split into two segments i.e., in the first force with first entry chamfer of pinion and second force is the second entry chamfer of the pinion gear. The new design reduces the shock force exerted by pinion on flywheel. Damage to flywheel and noise level is reduced with the new design.

Further, FIGS. 3(a) and 3(b) illustrate the geometric consideration of pinion gear, where current design of pinion gear with single entry chamfer is provided in FIG. 3(a) and the new design of pinion gear with dual chamfer is provided in FIG. 3(b)

The advantages of the present invention include, but not limited to: (i) Smooth engagement with ring gear; (ii) Noise level of the toothing will reduce; (iii) The gear tooth axial rebound force will reduce; (iv) Durability of the ring gear will increase and (v) Ease of manufacturing

While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The invention should therefore not be limited by the above described embodiment, method, and examples, but by all embodiments and methods within the scope of the invention as claimed.