Claims:We claim,
1. An optimized solenoid assembly with hybrid engagement system for automotive starters in internal combustion engines, comprising of:
atleast a starter motor (1);
atleast a solenoid body/ switch (2) comprising of atleast a solenoid with a coil arrangement around an iron core and housing a set of heavy metal contacts (8, 9), wherein the solenoid functions as a magnetic solenoid switch;
atleast a pinion (3);
atleast a flywheel ring gear (4);
atleast a plunger (5) placed outside the solenoid body (2), wherein the solenoid moves the plunger (5), causing the pinion (3) gear to engage with the engine’s flywheel ring gear (4);
atleast an inner and an outer engagement spring (6, 7) to split the plunger (5) and the pinion (3) when required, wherein the engagement springs (6, 7) are positioned in a plunger operating rod (13),

wherein the solenoid coil arrangement comprises of pull-in (11) and hold-on (10) coils, wherein the pull-in winding comprises a lower-resistance aluminium wire, and the hold-on winding comprises a copper wire with same number of turns as that of the pull-in coil, wherein the hold-on coil (10) surrounds the pull-in coil (11),

Wherein the current from the starter motor (1) is transferred to the engine through the pinion (3) which is engaged with the ring gear (4) of the engine flywheel through the solenoid switch (2), wherein the solenoid switch in response to a cranking signal of the engine, shifts the plunger (5) which simultaneously moves the pinion (3) towards the ring gear (4) and closes the contacts (8, 9), thereby applying full system voltage to the starter motor (1),

wherein when there is an obstruction to the pinion (3) travel due to abutment with ring gear (4) teeth face, a soft engagement by the solenoid switch (2) enables rotation of the pinion (3) to engage with the ring gear (4) even before the contacts (8, 9) close,

wherein when the soft engagement cannot overcome the obstruction, the engagement springs (6, 7) enable separation of the plunger (5) from the plunger operating rod (13), allowing the plunger (5) to close the contacts (8, 9) and thus enabling the starter motor (1) to operate with full power and enabling full rotation of the pinion (3) to engage with the ring gear (4) by compressing the engagement springs (6, 7).

2. The optimized solenoid assembly with hybrid engagement system for automotive starters as claimed in claim 1, wherein the plunger reaches its end of travel, and pushes the heavy solenoid metal contacts together with a copper contact plate, letting battery current flow to the starter motor (1).

3. The optimized solenoid assembly with hybrid engagement system for automotive starters as claimed in claim 1, wherein the soft engagement enables the soft rotation of the pinion (3) even before the contacts (8, 9) close thereby aiding the pinion (3) to slip into the ring gear (4) and achieve meshing through the solenoid switch.

4. The optimized solenoid assembly with hybrid engagement system for automotive starters as claimed in claim 1, wherein when the cranking signal is sensed, even before the contacts (8, 9) are closed, winding in the solenoid switch (2) is configured to provide a low voltage to the starter motor (1) which in turn develops a mild torque to rotate the starter motor (1) and pinion (3) by overcoming friction between the pinion (3) and ring gear (4), wherein said torque before contacts (8, 9) closure is lesser than the full torque of the starter motor (1).

5. The optimized solenoid assembly with hybrid engagement system for automotive starters as claimed in claim 1, wherein during the soft engagement, the pinion (3) is configured such that it indexes through the ring gear (4) in case of obstruction.

6. The optimized solenoid assembly with hybrid engagement system for automotive starters as claimed in claim 1, wherein the pinion (3) reaches a position where there is no obstruction, the energy stored in a plunger return spring (14) pushes the pinion (3) to engage with the ring gear (4).

7. The optimized solenoid assembly with hybrid engagement system for automotive starters as claimed in claim 1, wherein the engagement springs (6, 7) do not compress when there is no obstruction to the pinion (3) travel.

8. The optimized solenoid assembly with hybrid engagement system for automotive starters as claimed in claim 1, wherein the hybrid engagement system with both soft engagement and the engagement springs (6, 7) mechanisms ensure smooth engagement of the pinion (3) with the ring gear (4).

9. The optimized solenoid assembly with hybrid engagement system for automotive starters as claimed in claim 1, wherein the closing of an ignition switch of the vehicle energizes both the pull-in coil (11) and the hold-on coil, wherein the current flowing through the pull-in coil (11) reaches the electric motor (1), applying limited power to the electric motor (1), and resulting in low torque turning of the pinion (3) gear.

10. The optimized solenoid assembly with hybrid engagement system for automotive starters as claimed in claim 1, wherein energization of the pull-in coil (11) and hold-on coil (10) moves the solenoid shaft or plunger (5) in an axial direction which in turn moves a shift lever (12) attached to the end of the plunger (5) and pushes the pinion (3) gear toward engagement with the engine ring gear (4).

11. The optimized solenoid assembly with hybrid engagement system for automotive starters as claimed in claim 1, wherein the pull-in coil (11) and the hold-on coil (10) are configured such that the electromagnetic forces of the two coils cancel each other upon opening of the ignition switch of the vehicle, and the return spring (14) forces the plunger (5) back to its original un-energized position.
, Description:Field of Invention
The present invention relates generally to the field of internal combustion Engines. More specifically, the present disclosure relates to solenoid switch assembly in starters for internal combustion engines resulting in superior performance of starters.

Background of the Invention
Generally, a solenoid assembly in electric starter motors comprises of a cylindrically and uniformly wound coil which is used as an electromagnet to convert electric energy to mechanical energy. The solenoid assembly has two main functions, where they pull a plunger in to move a drive pinion gear out and further close a heavy-duty contact switch and control a starter circuit in the starter motors.
There are typically four Terminals on a heavy-duty starter solenoid. The two smaller ones are the “SOL” terminal, which is energized by a key switch or through a starter/ solenoid relay, and the “GND” terminal, which supplies the ground to the solenoid. The two larger terminals are: “BAT” which is for the main Battery positive cable and a STA terminal that sends current from the solenoid to the motor. Sometimes the grounding wire isn’t needed as the solenoid may be grounded internally (Body Grounded).
The starter solenoid has two sets of wire windings namely Pull-in coil and Hold on coil wrapped around a moveable iron core and a pair of metal contacts The pull-in and the hold-on windings get energized to pull the solenoid plunger in against an arrangement of spring pressure. The pull-in winding uses a copper wire. And hold-on winding uses a copper wire with number of turns that is same as that of the pull-in coil. Hold-on coil surrounds the pull-in coil. Pull-in winding will create a strong magnetic field that is needed to overcome the initial spring pressure. Also, low resistance coil enables the starter motor to rotate at a reduced speed during engagement which in turn reduces the effect of pinion and engine flywheel ring gear milling (soft engagement with CNC proof design). If the pull-in winding stayed energized, it would overheat because of the higher current flow. When the plunger is pulled in, it will also connect the two contacts with a heavy copper contact plate. This will allow current to flow from the main battery cable into the starter motor where it starts heading to ground through the field coils, brushes, and armature. The hold-on winding will have its own ground and stay energized as long as the “SOL” terminal gets power from a key switch or start relay. The pull-in coil is also energized from the SOL terminal, but it gets its ground ultimately from the starter motor ground. Once the solenoid contact plate starts allowing the current flow to the starter motor, the pull-in coil’s ground turns into a positive part of the circuit. As the pull-in coil has a positive voltage on each end of its winding, there is no potential difference and, therefore, current stops flowing through the coil. The use of two coils namely pull-in and hold-on reduces the power consumption. But solenoid becomes expensive if both windings are of copper and requires more turns to achieve the required force to satisfy the performance requirements. Further, there are obstructions caused to the pinion travel due to abutment with ring gear of the engine. Such obstructions result in wear of ring gears and reduced performance of the engine. So, it is required to have an optimized design which can meet the operating requirements at reduced cost. There exist many prior arts showing various starter solenoids designs to optimize performance.
Chinese patent application CN101892934B discloses a system for controlling a starter, the starter includes a pinion shiftable between an engagement position and a disengagement position. The starter includes an actuator configured to shift the pinion from the disengagement position to the engagement position when energized, and a motor configured to rotate the pinion when energized. The system includes a control circuit, a first switch unit configured to switch between energization and deenergization of the actuator under control of the control circuit, and a second switch unit configured to switch between energization and deenergization of the motor under control of the control circuit. The first switch unit and the second switch unit are individually arranged. The second switch unit includes a first relay configured to switch between energization and deenergization of the motor under control of the control circuit, and a second relay configured to control activation of the first relay.

European patent application EP2093786B1 relates to a solenoid switch which has an improved arrangement of a resistor that is used to limit electric current supplied to a starter motor. the solenoid switch includes a pair of main contacts, a pair of auxiliary contacts, and a resistor. The main contacts are connected in parallel with the auxiliary contacts in an electric circuit of the starter for supplying electric power from a battery to the motor. The resistor is connected in series with the auxiliary contacts in the electric circuit. During a starting operation, only the auxiliary contacts are closed in the first stage to supply limited current, which is limited by the resistor, to the motor. Consequently, the motor is energized to rotate at a low speed, facilitating establishment of an engagement between a pinion of the starter and a ring gear of the engine. As soon as the engagement between the pinion and the ring gear has been established, the main contacts are closed in the second stage to apply the full voltage of the battery to the motor, causing the motor to rotate at a high speed.

US patent US4958097 relates to a starter motor, for use with an internal combustion engine, comprising an electric motor, a shaft rotated by the motor and carrying a pinion assembly, a solenoid spaced from said shaft and including an armature movable from a rest position towards an operative position by energization of an electromagnet winding of the solenoid, and, a lever assembly mounted for pivotal movement about an axis passing between the solenoid and said shaft. The lever assembly links the armature of said solenoid and said pinion assembly such that movement of the armature is transmitted to the pinion assembly to move the pinion assembly axially on said shaft from a rest position towards an operative position, and comprises a rigid element supported for pivotal movement about said axis and a resilient element carried by said rigid element and coupled at one end to said armature. The end of the lever assembly remote from said solenoid is coupled to said pinion assembly, and said resilient element includes a region shaped to flex torsionally in the event of operative movement of said solenoid armature without corresponding movement of the pinion assembly, said region being prestressed during construction of the lever assembly in such a direction that the torsional stressing of said region would be increased by said movement of the solenoid armature relative to the pinion assembly.

Though the prior art serve its intended purposes, they aim at only controlling the starter using control circuits, and further the solenoid switches use components such as resistor to limit electric current supplied to a starter motor. The existing methods further use lever assembly links of solenoid for coupling the solenoid assembly with the pinion assembly. Hence there exists a need for improved solenoid assembly that proves to be cost-effective and results in enhanced performance of the starters.

The present invention provides a value-added solenoid assembly design which comprises of pull-in coil of aluminium wire and hold-on coil of copper wire with same number of turns where hold-on coil surrounds the pull-in coil and a spring arrangement enabling the hybrid engagement system. This not only reduces cost but also reduces the solenoid assembly weight by a significant amount. The present invention also discloses a hybrid mechanism comprising of both soft engagement and engagement springs mechanisms which ensures smooth engagement of pinion with ring gear of the engine, in case of any obstructions in the travel of the pinion.

According to the present invention, when the obstruction caused to the pinion travel due to abutment with ring gear of the engine is strong, the engagement springs enable separation of the plunger from the plunger operating rod, allowing the plunger to close the contacts thus enabling the starter motor to operate with full power. The hybrid engagement system with both soft engagement and engagement spring mechanisms ensures smooth engagement of pinion with ring gear.

Objects of the Invention:
The main object of the present invention is to provide an optimized solenoid assembly with hybrid engagement system for automotive starters in internal combustion engines and thereby enabling improved performance of the starters.

The primary object of the present invention is to provide an optimized solenoid assembly with aluminium pull-in coil and copper hold-on coil which has similar number of turns as that of the pull-in coil.
It is another object of the present invention to provide an optimized solenoid assembly with hybrid engagement system for automotive starters wherein the hold-on coil surrounds the pull-in coil and a spring arrangement.
Still another object of the present invention is to provide an optimized solenoid assembly enabling soft rotation of a pinion abutting a ring gear of the engine, thereby enhancing the durability of the ring gear.
It is another object of the present invention to provide an optimized solenoid assembly with hybrid engagement system by providing engagement springs mechanism to enhance the durability of the ring gear when the soft rotation of the pinion cannot overcome the obstruction of pinion movement.
It is another object of the present invention to provide an optimized solenoid assembly with hybrid engagement system for automotive starters wherein the hybrid engagement system with both soft engagement and engagement spring mechanisms ensures successful engagement of the pinion with the ring gear of the engine, thereby reducing ring gear wear rate.
It is another object of the present invention to provide an optimized solenoid assembly with hybrid engagement system for automotive starters which is cost effective and reduces power consumption.
SUMMARY OF THE INVENTION

The present invention discloses an optimized solenoid assembly with hybrid engagement system for automotive starters in internal combustion engines. The starter with hybrid engagement system comprises of a starter motor, a solenoid comprising a a coil arrangement around an iron core, a pinion, a ring gear, a plunger and an inner and outer engagement spring to split the plunger and the operating rod and a pair of contacts made of copper. The solenoid housed in the solenoid body functions as a powerful electromagnet switch also known as a solenoid switch, activates the starter motor of the internal combustion engine. The solenoid body also houses a set of heavy metal/electric contacts.

In the preferred embodiment of the present invention, the solenoid coil arrangement comprises of two sets of coils: pull-in and hold-on coils, wherein the pull-in winding comprises a lower-resistance aluminium wire, a bigger gauge wire
to let more current flow through it. And hold-on winding comprises a copper wire with same number of turns as that of the pull-in coil.

Wherein, the coil windings generate the magnetic force to draw the plunger down the solenoid core when current flows through them. When the plunger reaches its end of travel, it pushes the heavy solenoid metal contacts together with the copper contact plate, letting battery current flow to the starter motor. The solenoid moves the plunger, causing the starter pinion gear to engage the engine’s flywheel ring gear through a lever mechanism. The pinion gear of the starter engages with the ring gear (flywheel) and does the rotating of the crankshaft of the engine.

In the preferred embodiment of the present invention, the engagement springs are positioned in a plunger operating rod. Power from the starter motor is transferred to the engine through the pinion which is engaged with the ring gear of the engine flywheel through the solenoid switch only at the time of cranking of the engine. The solenoid switch, preferably magnetic solenoid switch in response to the cranking signal, shifts the plunger which simultaneously moves the pinion towards the ring gear and closes contacts, thereby applying full system voltage to the starter motor and causes said starter motor to rotate the pinion and eventually rotates the ring gear.

In the preferred embodiment of the present invention, when there is an obstruction to the pinion travel due to abutment with ring gear teeth face, soft engagement by the solenoid switch enables rotation of the pinion to engage with the ring gear even before the closure of the contacts. When the cranking signal is sensed, even before the contacts are closed, winding in the solenoid switch is configured to provide a low voltage to the starter motor. The low voltage causes current flow through the starter motor, which in turn develops a mild torque to rotate the starter motor and pinion by overcoming friction between the pinion and ring gear, said torque before contacts closure is lesser than the full torque of the starter motor. The solenoid switch which enables the soft rotation of pinion even before contacts closure thereby aiding the pinion to slip into the ring gear and achieve meshing is known as soft engagement. During soft engagement, the pinion is configured such that it indexes through the ring gear in case of obstruction and hence reduces ring gear wear rate, thereby enhancing the durability of the ring gear.

In the preferred embodiment of the present invention, wherein there is an obstruction to the pinion travel which is strong enough such that it cannot be overcome by the soft rotation/ engagement, the engagement springs enable separation of the plunger from the plunger operating rod, allowing the plunger to close the contacts enabling the starter motor to operate with full power/ current and hence results in full rotation of the pinion to engage with the ring gear by compressing the engagement springs and allowing the contacts to close. The engagement springs preload is such that it does not compress when there is no obstruction to the pinion travel. Once the pinion reaches a position where there is no obstruction, the energy stored in the plunger return spring pushes the pinion to engage with the ring gear.

In the preferred embodiment of the present invention, the hybrid engagement system with both soft engagement and engagement springs mechanisms ensure successful engagement of the pinion with ring gear.

Other features and advantages of embodiments will be apparent from the accompanying drawings and from the detailed description that follows.
Brief Description of the Drawings
Figure 1 represents the sectional view of the solenoid assembly in the starter of an internal combustion engine in accordance with an embodiment of the present invention.
Figure 2 represents connection scheme of the solenoid winding in the starter motor according to the present invention.
While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the invention.
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concept of the term appropriately to describe its own invention in the best way. The present invention should be construed as meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined. Therefore, the embodiments described in this specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, it should be understood that equivalents and modifications are possible.
Detailed Description of the Invention with Respect to the Drawings
The present invention as embodied by "Optimized solenoid assembly with hybrid engagement system for automotive starters in internal combustion engines" succinctly fulfils the above-mentioned need(s) in the art. The present invention has objective(s) arising as a result of the above-mentioned need(s), said objective(s) being enumerated below. In as much as the objective(s) of the present invention are enumerated, it will be obvious to a person skilled in the art that, the enumerated objective(s) are not exhaustive of the present invention in its entirety, and are enclosed solely for the purpose of illustration. Further, the present invention encloses within its scope and purview, any structural alternative(s) and/or any functional equivalent(s) even though, such structural alternative(s) and/or any functional equivalent(s) are not mentioned explicitly herein or elsewhere, in the present disclosure. The present invention therefore encompasses also, any improvisation(s)/ modification(s) applied to the structural alternative(s)/functional alternative(s) within its scope and purview. The present invention may be embodied in other specific form(s) without departing from the essential attributes thereof.
Throughout this specification, the use of the word "comprise" and variations such as "comprises" and "comprising" may imply the inclusion of an element or elements not specifically recited.
The present invention discloses an optimized solenoid assembly with hybrid engagement system for automotive starters in internal combustion engines. As seen in figure 1, the starter with optimized solenoid assembly and hybrid engagement system comprises of at least one starter motor (1) , a solenoid body/ switch (2) comprising of a solenoid with a coil arrangement around an iron core, atleast a pinion (3), atleast one ring gear (4), atleast a plunger (5); and an inner and outer engagement spring (6, 7) to split the plunger (5) and the pinion (3) when required and a contact plate made of copper.

The solenoid housed in the solenoid body functions as a powerful electromagnet switch also known as a solenoid switch, and also activates the starter motor (1) of the internal combustion engine. The solenoid body further houses a set of heavy metal/electric contacts (8, 9).

In the preferred embodiment of the present invention as seen in figure 2, the solenoid coil arrangement comprises of two sets of coils: pull-in (11) and hold-on coils, wherein the pull-in winding comprises a lower-resistance aluminium wire, a bigger gauge wire to let more current flow through it. And hold-on winding comprises a copper wire with same number of turns as that of the pull-in coil, wherein the hold-on coil (10)surrounds the pull-in coil.

In the preferred embodiment of the present invention the hold on coil is provided close to the solenoid body resulting in better heat dissipation.

Wherein, the coil windings generate the magnetic force to draw the plunger (5) down the solenoid core when current flows through them. When the plunger (5) reaches its end of travel, it pushes the heavy solenoid metal contacts (8, 9) together with the copper contact plate, letting battery current flow to the starter motor (1).

The solenoid assembly also consists of terminals on one side to bring current to the assembly, while the other end of the assembly contains the plunger (5) protrusion. One of the terminals connects to an ignition switch of the vehicle. The solenoid is controlled by a control circuit, which links it to the ignition switch.

The solenoid moves the plunger (5), causing the starter pinion (3) gear to engage the engine’s flywheel ring gear (4). As the solenoid coils pull in the plunger, a shift lever (12) attached to the end of the plunger pushes out the starter pinion (3) gear. This movement meshes the small pinion (3) gear with the larger engine flywheel ring gear.

Wherein the flywheel is a large gear ring that is connected to the rear of a crankshaft of the engine. The flywheel rim has teeth on the surface. The ring gear (4) of the starter solenoid engages with the flywheel and does the rotating of the crankshaft of the engine. The starter is used to rotate crankshaft of the internal combustion engine.

The pinion (3) gear is connected to the starter motor (1), which cranks the engine through the flywheel. When the ignition switch is released, the magnetic force is reduced, and the holding coil releases the plunger. The starter solenoid contacts open, cutting battery power from the starter motor (1).

In the preferred embodiment of the present invention, the engagement springs (6, 7) is positioned in a plunger operating rod (13). Current from the starter motor (1) is transferred to the engine through the pinion (3) which is engaged with the ring gear (4) of the engine flywheel through the solenoid switch (2) only at the time of cranking of the engine. The solenoid switch, preferably magnetic solenoid switch (2) in response to the cranking signal, shifts the plunger (5) which in turn simultaneously moves the pinion (3) towards the ring gear (4) and closes contacts (8, 9), thereby applying full system voltage to the starter motor (1) and causes said starter motor (1) to rotate the pinion (3) and eventually the ring gear (4). The teeth of the ring gear are driven by the pinion (3) of the starter motor (1). The pinion (3) engages the ring gear (4) during starting and once the engine is running the pinion (3) withdraws.

In the preferred embodiment of the present invention, when there is an obstruction to the pinion (3) travel due to abutment with ring gear (4) teeth face, soft engagement by the solenoid switch (2) enables rotation of the pinion (3) to engage with the ring gear (4) even before the closure of the contacts (8, 9). When the cranking signal of the engine is sensed, even before the contacts (8, 9) are closed, winding in the solenoid switch (2) is configured to provide a low voltage to the starter motor (1). The low voltage causes current flow through the starter motor (1), which in turn develops a mild torque to rotate the starter motor (1) and pinion (3) by overcoming friction between the pinion (3) and ring gear (4), and said torque before contacts (8, 9) closure is lesser than the full torque of the starter motor (1). The solenoid switch (2) which enables the soft rotation of pinion (3) even before contacts (8, 9) closure thereby aiding the pinion (3) to slip into the ring gear (4) and achieve meshing is known as soft engagement. The pinion is retained in mesh until the solenoid switch (2) is released, when a spring (14) returns the pinion. During soft engagement, the pinion (3) is configured such that it indexes through the ring gear (4) in case of obstruction and hence reduces ring gear wear rate, thereby enhancing the durability of the ring gear.

In the preferred embodiment of the present invention, wherein there is an obstruction to the pinion (3) travel which is strong enough such that it cannot be overcome by the soft rotation of the pinion (3), the engagement springs (6, 7) enable separation of the plunger (5) from the plunger operating rod (13), allowing the plunger (5) to close the contacts (8, 9) and enabling the starter motor (1) to operate with full power. Thus, it results in full rotation of the pinion (3) to engage with the ring gear (4) by compressing the engagement springs (6, 7) and allowing the contacts (8, 9) to close. The engagement springs (6, 7) preload is such that it does not compress when there is no obstruction to the pinion (3) travel. When there is an obstruction during rotation of the pinion (3), the engagement springs (6, 7) compress thereby allowing the plunger (5) in aiding closure with contacts (8, 9) and rotating the starter motor (1) with full power. The starter motor (1) overcomes the friction between pinion (3) teeth and ring gear teeth when it attains the full power and causes the pinion (3) to rotate. Once the pinion (3) reaches a position where there is no obstruction, the energy stored in the plunger return spring (14) pushes the pinion (3) to engage with the ring gear (4). Wherein the plunger return spring (14) is placed outside the solenoid body (2).

Thus, when there is obstruction of pinion (3) travel due to abutment with ring gear (4) teeth face, the soft rotation ensures to engage with the ring gear (4). When the obstruction is strong, the engagement springs (6, 7) come into action allowing the contacts (8, 9) to close. Since the engagement by the springs (6, 7) mechanism is enabled only when the soft rotation of the pinion (3) cannot overcome the obstruction, the wearing out of ring gear (4) teeth entry region is reduced, thereby enhancing the durability of the ring gear (4).

In the preferred embodiment of the present invention, the hybrid engagement system with both soft engagement and engagement springs (6, 7) mechanisms ensure successful engagement as per requirement. Starters with a hybrid engagement system, such as that of FIG. 1, typically include the coil arrangement with two distinct coils - the pull-in coil (11) and the hold on coil. During operation of the starter, the closing of the ignition switch (typically upon the operator turning a key of the vehicle) energizes both the pull-in coil (11) and the hold-on coil. Current flowing through the pull-in coil (11) at this time also reaches the electric motor (1), applying limited power to the electric motor (1), and resulting in low torque turning of the pinion gear. Energization of the pull-in coil (11) and hold-on coil (10)moves the solenoid shaft or plunger (5) in an axial direction. The axial movement of the solenoid plunger (5) moves the shift lever (12) and biases the pinion gear (2) toward engagement with the engine ring gear(3). Once the solenoid plunger reaches the plunger stop, the set of metal contacts (8, 9) is closed, thereby delivering full power to the electrical motor (1). Closing of the electrical contacts effectively short circuits the pull-in coil (11), eliminating unwanted heat generated by the pull-in coil (11). However, when the pull-in coil (11) is shorted, the hold-on coil (10)provides sufficient electromagnetic force to hold the plunger (5) in place and maintain the electrical contacts in a closed position, thus allowing the delivery of full power to continue to the electric motor (1). The fully powered electric motor (1) drives the pinion (3) gear, resulting in rotation of the engine ring gear (4), and thereby cranking the vehicle’s engine.

After the engine fires (i.e., vehicle starts), the operator of the vehicle opens the ignition switch. The electrical circuit of the starter motor (1) assembly is configured such that opening of the ignition switch causes current to flow through the hold-on coil (10)and the pull-in coil in opposite directions. The pull-in coil (11) and the hold-on coil (10)are configured such that the electromagnetic forces of the two coils cancel each other upon opening of the ignition switch, and the return spring (14) forces the plunger (5) back to its original un-energized position. As a result, the metal contacts that connected the electric motor (1) to the source of electrical power are opened, and the electric motor (1) is de-energized.

EXAMPLE 1
The present invention provides an optimized solenoid assembly with hybrid engagement system for automotive starters in internal combustion engines, comprising of: a starter motor (1), a solenoid body (2) comprising of a solenoid with a coil arrangement around an iron core, a pinion (3), a ring gear (4), a plunger (5); and an inner and outer engagement spring (6, 7) to split the plunger (5) and the pinion (3) when required and a contact plate made of copper. The solenoid housed in the solenoid body also known as a solenoid switch, activates the starter motor (1) of the internal combustion engine. The solenoid body also houses a set of heavy metal contacts (8, 9). The solenoid coil arrangement comprises of two sets of coils: pull in (11) and hold on coils, wherein the pull-in winding comprises a lower-resistance aluminium wire which is a bigger gauge wire to let more current flow through it. And the hold-on winding comprises a copper wire with same number of turns as that of the pull-in coil, wherein the hold-on coil (10)surrounds the pull-in coil and a spring arrangement enabling the hybrid engagement system. Wherein, the coil windings generate the magnetic force to draw the plunger down the solenoid core when current flows through them. When the plunger (5) reaches its end of travel, it pushes the heavy solenoid metal contacts (8, 9) together with the copper contact plate, letting battery current flow to the starter motor (1). This hybrid engagement system using aluminium wire in pull-in (Series) winding and copper in hold-on (shunt) winding mechanism not only reduces cost but also reduces the starter solenoid weight by a significant amount, thus achieving optimum performance.

EXAMPLE 2
The present invention provides an optimized solenoid assembly with hybrid engagement system for automotive starters in internal combustion engines, comprising of: a starter motor (1), a solenoid body (2) comprising of a solenoid with a coil arrangement around an iron core, a pinion (3), a ring gear (4), a plunger (5); and an inner and outer engagement spring (6, 7) to split the plunger (5) and the pinion (3) when required and a contact plate made of copper. The solenoid housed in the solenoid body also known as a solenoid switch, activates the starter motor (1) of the internal combustion engine. The solenoid body also houses a set of heavy metal contacts (8, 9). The solenoid coil arrangement comprises of two sets of coils: pull in and hold on coils, wherein the pull-in winding comprises a lower-resistance aluminium wire which is a bigger gauge wire to let more current flow through it. And the hold-on winding comprises a copper wire with same number of turns as that of the pull-in coil, wherein the hold-on coil (10)surrounds the pull-in coil and a spring arrangement enabling the hybrid engagement system. Further, the solenoid moves the plunger (5), causing the starter pinion (3) gear to engage the engine’s flywheel ring gear (4). As the solenoid coils pull in the plunger, a shift lever (12) attached to the end of the plunger (5) pushes out the starter pinion (3) gear. This movement meshes the pinion (3) gear with the larger engine flywheel ring gear (4).

When there is an obstruction to the pinion (3) travel due to abutment with ring gear (4) teeth face, soft engagement by the solenoid switch (2) enables rotation of the pinion (3) to engage with the ring gear (4) even before the contacts (8, 9) close. When the cranking signal of the engine is sensed, even before the contacts (8, 9) are closed, winding in the solenoid switch (2) is configured to provide a low voltage to the starter motor (1). The low voltage causes current flow through the starter motor (1), which in turn develops a mild torque to rotate the starter motor (1) and pinion (3) by overcoming friction between the pinion (3) and ring gear (4), and said torque before contacts (8, 9) closure is lesser than the full torque of the starter motor (1). The solenoid switch (2) enables the soft rotation of pinion (3) even before the closure of the metal contacts (8, 9) thereby aiding the pinion (3) to slip into the ring gear (4) and achieve meshing which is known as soft engagement. During soft engagement, the pinion (3) is configured such that it indexes through the ring gear (4) in case of obstruction and hence reduces ring gear wear rate, thereby enhancing the durability of the ring gear (4).

EXAMPLE 3
The present invention provides an optimized solenoid assembly with hybrid engagement system for automotive starters in internal combustion engines, comprising of: a starter motor (1), a solenoid body (2) comprising of a solenoid with a coil arrangement around an iron core, a pinion (3), a ring gear (4), a plunger (5); and an inner and outer engagement spring (6, 7) to split the plunger (5) and the pinion (3) when required and a contact plate made of copper. The solenoid housed in the solenoid body also known as a solenoid switch, activates the starter motor (1) of the internal combustion engine. The solenoid body also houses a set of heavy metal contacts (8, 9). The solenoid coil arrangement comprises of two sets of coils: pull in (11) and hold on coils, wherein the pull-in winding comprises a lower-resistance aluminium wire which is a bigger gauge wire to let more current flow through it. And the hold-on winding comprises a copper wire with same number of turns as that of the pull-in coil, wherein the hold-on coil (10)surrounds the pull-in coil (11) and a spring arrangement enabling the hybrid engagement system. Further, the solenoid moves the plunger (5), causing the starter pinion (3) gear to engage the engine’s flywheel ring gear (4). As the solenoid coils pull in the plunger (5), a shift lever (12) attached to the end of the plunger pushes out the starter pinion (3) gear. This movement meshes the small pinion (3) gear with the larger engine flywheel ring gear. When there is an obstruction to the pinion (3) travel which is strong enough such that it cannot be overcome by the soft rotation/ engagement of the pinion, the engagement springs (6, 7) enable separation of the plunger (5) from the plunger operating rod (13), allowing the plunger (5) to close the contacts (8, 9) and enabling the starter motor (1) to operate with full power. Thus, it results in full rotation of the pinion (3) to engage with the ring gear (4) by compressing the engagement spring (6, 7) and allowing the contacts (8, 9) to close.

Thus, when there is an obstruction of pinion (3) travel due to abutment with ring gear (4) teeth face, the soft rotation of the pinion ensures to engage with the ring gear (4). When the obstruction is strong, the engagement springs (6, 7) come into action allowing the metal contacts (8, 9) to close. Since the engagement by the springs (6, 7) mechanism is enabled only when the soft rotation of the pinion (3) cannot overcome the obstruction, the wearing out of ring gear (4) teeth entry region is reduced, thereby enhancing the durability of the ring gear (4). The hybrid engagement system with both soft engagement and the engagement springs (6, 7) mechanisms ensures successful engagement as per requirement. This hybrid engagement system using aluminium wire in pull-in (Series) winding and copper in hold-on (shunt) winding mechanism not only reduces cost but also reduces the starter solenoid weight by a significant amount, thus achieving optimum performance.

Although the proposed concept has been described as a way of example with reference to various models, it is not limited to the disclosed embodiment and that alternative designs could be constructed without deviating from the scope of invention as defined above.
It will be apparent to a person skilled in the art that the above description is for illustrative purposes only and should not be considered as limiting. Various modifications, additions, alterations, and improvements without deviating from the scope of the invention may be made by a person skilled in the art.