Claims:We claim,
1. A metallic starter relay (1) for a motor vehicle, connected to the power source, ignition switch and the starter motor of the said vehicle; wherein the said starter relay (1) comprises of;
a metallic cup (2), a stop plate (3), a bottom plate (4), a bobbin (5), a harness (6) with coupler, a coil (7), a MS plate (8), a plunger (9), a plunger spring (10), two fixed contacts (11), a moving contact (12), a contact spring (13), a head cover (14), two small O-rings (15), two plain washers (16), two serrated washers (17), two hex nuts (18) and two serrated nuts (19); and is characterized in that;
the coil (7) is wound around the bobbin (5);
the said coil (7) and the said bobbin (5) are placed inside the
metallic cup (2);
the stop plate (3) is placed inside the metallic cup (2);
the plunger spring (10) is wound around the plunger (9);
the said plunger spring (10) and the said plunger (9) are placed in
the hollow circular space of the said bobbin (5) such that the
bobbin (5), the plunger (9) and the plunger spring (10) are axially
parallel to each other;
the moving contact (12) and the two fixed contacts (11) are placed
above the said plunger (9) and MS plate (8) such that the moving
contact (12) is not permanently bound to the plunger (9);
the head cover (14) is placed above the moving contact (12) and
the fixed contacts (11); and wherein;
the said fixed contacts (11) are stationary at their respective
locations while the said moving contact (12) is capable of moving
vertically in the space between the said fixed contacts (11);
the contact spring (13) is in contact with the moving contact (12)
such that it moves the moving contact (12) back and forth as per the
change of state of the starter relay (1);
the plunger (9) is pulled downwards due to the magnetic force
generated when the coil (7) is energized;
the plunger spring (10) and the contact spring (13) work opposite to
each other leading to requirement of a smaller magnetic force to
pull the plunger (9) downwards, thus reducing the amount of coil (7)
required; and wherein
the said relay (1) has functionally two modes - ON mode and an
OFF mode;
the moving contact (12) and the fixed contacts (11) do not have a
physical connection when the relay is in OFF mode;
a physical connection between the moving contact (12) and the
fixed contacts (11) is established when the relay is in ON mode;
the contact force, depends only on the contact spring (13) after
establishment of a physical contact between the moving contact
(12) and the fixed contacts (11);
the contact force is independent of input voltage; and
the said starter relay has a low component count, is simple in
design and is cost effective.

2.The metallic starter relay (1) as claimed in claim 1, wherein an electric current flows through the coil (7) of the said starter relay (1) when the ignition switch of the vehicle is pressed thereby energizing the coil (7) of the said starter relay (1).

3.The metallic starter relay (1) as claimed in claim 1, wherein the energizing of coil (7) leads to generation of a magnetic field, creating a magnetic force to pull the said plunger (9) downwards.

4.The metallic starter relay (1) as claimed in claim 1, wherein the displacement of the said plunger (9) downwards establishes a physical contact between the fixed contacts (11) and the moving contact (12), leading to completion of circuit, actuation of starter motor and cranking of engine.

5.The metallic starter relay (1) as claimed in claim 1, wherein the de-energizing of coil (7) leads to displacement of the plunger back to its initial location thereby disestablishing the physical contact between the fixed contacts (11) and the moving contact (12), resulting in breaking of circuit, stopping of starter motor and stopping of cranking operation of the engine.

6.The metallic starter relay (1) as claimed in claim 1, wherein the plunger spring (10) is compressed when the contact spring (13) is expanded, and the plunger spring (10) is expanded when the contact spring (13) is compressed.

7.The metallic starter relay (1) as claimed in claim 1, wherein in the OFF mode the plunger (9) keeps the moving contact (12) away from the fixed contacts (11) and the contact spring in a compressed state.

8.The metallic starter relay (1) as claimed in claim 1, wherein in the ON mode, the plunger (9) is pulled downwards by the magnetic force generated by the energized coil (7), thereby expanding the contact spring (13) and compressing the plunger spring (10).

9.The metallic starter relay (1) as claimed in claim 1, wherein the stop plate (3) is made of steel and the bobbin (5) is made of a temperature tolerant, heat dissipating and strong material such as but not limited to plastic.

10.The metallic starter relay (1) as claimed in claim 1, wherein the coil (7) is made of an electrically conductive material such as but not limited to copper, and wherein the plunger spring (10) and the contact spring (13) are made of but not limited to a strong material such as steel.

11.The metallic starter relay (1) as claimed in claim 1, wherein the fixed contacts (11) and the moving contact (12) are made of an electrically conductive material such as but not limited to copper. , Description:FIELD OF THE INVENTION:

The present invention relates to a metallic starter relay for motor vehicles. The present invention particularly relates to an improved metallic starter relay which has a less component count, is cost effective, and is less complex in design and operation.

BACKGROUND:

A starter relay refers to an electrical device used in the starting system of a motor vehicle. A typical starter relay used in motor vehicles is an electromagnetically controlled device which helps in either completing an electric circuit or breaking an electric circuit. The said circuit is typically completed or broken by opening and closing of electrical contacts. The completion or breaking of a circuit by means of a starter relay affects the operation of other devices in the same or another electrical circuit.

A conventional starter relay typically establishes an electrical connection between the ignition key/switch of a motor vehicle, the battery, the starter motor and the engine. The starter relay uses a small ignition switch current to close the much heavy-duty starter circuit. When the ignition switch of the motor vehicle is turned ON, a battery DC voltage draws through the coil of the starter relay and results in establishment of connection between the battery and the starter motor of the vehicle. This in turn helps in cranking of the engine and hence starting of the vehicle.

A typical starter relay used in motor vehicles may include fixed contacts, movable contacts, a conductive coil and a plunger. When the ignition switch is turned ON, a connection between the starter relay and the power source (battery of the vehicle) is established. This causes a small amount of current to flow through the coil of the starter relay. The flux of current through the coil also generates a magnetic field around it i.e. the flux of current energizes the coil thus turning it into an electromagnet. The magnetism of the coil activates movement of the plunger - attracting it to close the circuit. When the connection between the coil and the battery of the vehicle is disconnected, the coil de-energizes and loses its magnetism. The loss of magnetism of the coil repels the plunger and hence opens the circuit. Thus, the movement of plunger by induction of magnetism affects the switching between the fixed and moving contacts and hence controls the switching on or switching off of the electric circuit.

While such kind of starter relays are widely used in motor vehicles, the conventional ones currently available in the market have certain limitations. Firstly, the design of the existing starter relays is fairly complex, involving a large number of individual components which have to function in co-ordination with each other. This not only makes the overall operation of these starter relays complicated but also adds up to the manufacturing cost, thus making these relays less favourable in terms of operation and economics.

Secondly, in most of the relays available in the market, the movable contact is bound with the plunger assembly. This makes the operation of the relay more complex and variable. Thirdly, in these relays, an important parameter i.e. the contact force between the movable contacts and the fixed contacts depends on a lot of other factors such as the contact spring, plunger, plunger brush, plunger riveting height and magnetic force, thus introducing a lot of variation in the functioning of the relays. Additionally, since the contact force is a resultant of multiple forces, chances of contact chatter/bounce with slightest mismatch of forces are pretty high. Further, due to dependency on multiple other forces, the contact force may also at times result into welding of contacts on their positions.

Fourthly, in these relays, the contact force also depends on input voltage. Due to this, the chances of reduction in contact force are very high when the battery is low. Furthermore, in these relays, gradual reduction of contact force when the power is switched off, leads to a stronger arc formation.

Therefore, there is a need for an improved starter relay to eliminate or ameliorate the above limitations of the existing starter relays in the market.

Prior art:
KR20150131138A discloses a starter motor which includes a stationary field, an armature rotatable relative to a fixed field, an armature shaft coupled to the armature, and an armature shaft slidably disposed on the armature shaft and a motor portion having a pinion gear rotatably fixed to the armature. The starter motor also includes a solenoid mounted on the motor section. This solenoid includes a plunger mechanically connected to the pinion gear.

US 6,965,172 B2 discloses a starter for cranking an internal combustion engine is mainly composed of an electric motor and a magnetic switch having a battery bolt connected to an on-board battery and a motor bolt connected to the electric motor. When the magnetic switch is closed, electric power is supplied to the electric motor to thereby generate a rotational torque for cranking the engine. One end of a motor terminal is electrically connected to the motor bolt, and the other end is led into a motor casing through a rubber insulator supported on the motor casing. The motor terminal includes one or more curved portions having resiliency, and they are positioned between the rubber insulator and the motor bolt. Water penetration into the motor casing is prevented by the rubber insulator, and the vibration of the motor terminal is alleviated by resiliency of the curved portions.

OBJECTS OF THE INVENTION:

An object of the present invention is to provide a starter relay for motor vehicles which is more cost effective than the starter relays currently available in the market.

Another object of the present invention is to provide a starter relay for motor vehicles which has a less component count and hence simple in design and operation.

Yet another object of the present invention is to provide a starter relay for motor vehicles which has a self aligning moving contact.

Yet another object of the present invention is to provide a starter relay for motor vehicles wherein the contact force depends only on the contact spring after establishment of physical contact between the fixed contacts and the moving contact.

Yet another object of the present invention is to provide a starter relay for motor vehicles wherein the contact force is independent of the input voltage after establishment of physical contact between the fixed contacts and the moving contact.

Yet another object of the present invention is to provide a starter relay for motor vehicles which enables faster arc quenching, in case if there is any, and wherein the fixed and the moving contacts do not weld in on position.

Yet another object of the present invention is to provide a starter relay for motor vehicles which has a significantly less requirement of magnetic force, and hence the amount of coil used, as compared to the starter relays currently available in the market.

SUMMARY:

The present invention relates to a metallic starter relay for motor vehicles. The metallic starter relay of the present invention primarily comprises of a metallic cup, a stop plate, a bottom plate, a bobbin, a harness with coupler, a coil, a MS plate, a plunger, a plunger spring, two fixed contacts, a moving contact, a contact spring, a head cover, two small O-rings, two plain washers, two serrated washers, two hex nuts and two serrated nuts.

In one aspect, the plunger spring is wound around the plunger and the entire plunger assembly is placed inside the metallic cup. Unlike the conventional metallic starter relays, the moving contact of the starter relay of the present invention is not permanently bound with the plunger.

In another aspect, the fixed contacts and the moving contact of the metallic starter relay are arranged such that the fixed contacts stay stationary at their location while the moving contact moves vertically in the space between the two fixed contacts. The fixed contacts and the moving contacts do not have a permanent attachment between them. The force between the fixed contacts and the moving contact is referred to as the contact force.

In yet another aspect, when the coil of the starter relay is energized, the plunger is pulled downwards due to the magnetic field generated around the coil, and a physical contact is established between the fixed contacts and the moving contact, thereby completing the electrical circuit. The completion of the electrical circuit leads to actuation of the starter motor of the vehicle and consequential cranking of the engine.

In yet another aspect, when the coil of the starter relay is de-energized, the plunger relocates back to its original position. In the process of relocation to its initial location, the plunger pushes the moving contact to its initial location thereby breaking the physical contact between the fixed contacts and the moving contact. This leads to breaking of the electrical circuit, thereby stopping the starter motor. This eventually leads to stopping of the cranking operation of the engine.

In yet another aspect, the metallic starter relay of the present invention is designed such that it has a low component count than the conventional starter relays in the market and is simple in design. The said starter relay is designed such that the plunger spring and the contact spring work opposite to each other, as a result of which the net magnetic force required to pull the plunger downwards is less. This, further results into reduction in the amount of coil required for operation of the starter relay thereby bringing down its design and operational cost and making it more cost effective.

In yet another aspect, the metallic starter relay of the present invention is designed such that the contact force, defined as the force between the fixed contacts and moving contacts; depends only on the contact spring and is independent of input voltage, once a physical contact is established between the fixed contacts and the moving contact. This design also leads to fast arc quenching, if there occurs any.

BRIEF DESCRIPTION OF DRAWINGS:

FIG. 1 illustrates the external view of the starter relay.

FIG. 2 illustrates the exploded view of the starter relay.

FIG. 3 illustrates the cross sectional view of the stater relay in “ON” and “OFF” mode.

FIG. 4 illustrates the coil assembly.

FIG. 5 illustrates the plunger with the plunger spring wound around it.

FIG. 6 illustrates the moving contact with the contact spring.

FIG. 7 illustrates the fixed contacts.

FIG. 8 illustrates the top view of the head cover.

FIG. 9 illustrates the bottom view of the head cover displaying a displaced contact spring and moving contact.

FIG. 10 illustrates the exemplary heights and gaps between different components of the starter relay in OFF mode, just before touch condition and in ON mode.

DETAILED DESCRIPTION OF DRAWINGS:

Before the present invention is described, it is to be understood that this invention is not limited to methodologies described, as these may vary as per the person skilled in the art. It is also to be understood that the terminology used in the description is for the purpose of describing the particular embodiments only and is not intended to limit the scope of the present invention. Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. Various embodiments of the present invention are described below. It is, however noted that the present invention is not limited to these embodiments, but rather the intention is that modifications those are apparent are also included.

The present invention relates to a metallic starter relay used in motor vehicles. The metallic starter relay of the present invention has a low constructional component count and is simple in design and operation. FIG. 1 illustrates the exterior view of the metallic starter relay (1). The metallic starter relay (1), as illustrated in FIG. 2, comprises of a metallic cup (2), a stop plate (3), a bottom plate (4), a bobbin (5), a harness (6) with coupler, a coil (7), a MS plate (8), a plunger (9), a plunger spring (10), two fixed contacts (11), a moving contact (12), a contact spring (13), a head cover (14), two small O-rings (15), two plain washers (16), two serrated washers (17), two hex nuts (18) and two serrated nuts (19). The individual components of the starter relay are as illustrated in FIG. 4 to FIG. 9.

The metallic starter relay (1) is further connected to the power source (battery of the vehicle; not shown in drawings) and the starter motor (not shown in drawings) of the vehicle. An electric current passes through the metallic starter relay (1) when the ignition switch (not shown in drawings) of the vehicle is pressed. The completion of the electric circuit of the metallic starter relay (1) leads to the actuation of starter motor thereby leading to cranking of engine. The actual working of the metallic starter relay (1) shall be explained in the description to follow.

In a preferred embodiment of the present invention, the metallic cup (2) is the lowermost part of the starter relay (1). The coil (7) is wound around the bobbin (5). The coil (7) and the bobbin (5) are placed inside the metallic cup (2). The bobbin (5) is circular in shape and has a hollow circular space at its centre. The plunger spring (10) is wound around the plunger (9). The plunger (9) and the plunger spring (10) are placed in the hollow circular space of the bobbin (5). In other words, the spring used between the bobbin (5) and the plunger (9) is referred to as the plunger spring (10). The bobbin (5) and the plunger (9) with the plunger spring (10) are placed axially parallel to each other. The stop plate (3) is placed inside the metallic cup (2).

The plunger (9) has an upper protruding part which rests on the MS plate (8). Placed above the plunger (9) is the moving contact (12). Two fixed contacts (11) are also placed above the plunger (9). The upper part of the plunger (9) is in contact with the lower part of the moving contact (12) when the starter relay (1) is in “OFF” mode. However, in the “ON” mode, an air gap is generated between the upper part of the plunger (9) and the lower part of the moving contact (12). The moving contact (12) and the fixed contacts (11) are not in contact with each other in the “OFF” mode of the starter relay (1) while a physical contact is established between the moving contact (12) and the fixed contacts (11) in the “ON” mode.

In another embodiment, the arrangement of the fixed contacts (11) and the moving contact (12) is such that the two fixed contacts (11) remain stationary and the moving contact (12) moves between them in a vertical direction. The spring used between the moving contact (12) and the head cover (14) is referred to as the contact spring (13). The contact spring (13) moves the moving contact (12) back and forth as per the change of state of the starter relay (1) from ON to OFF, and OFF to ON. The plunger spring (10) and the contact spring (13) work opposite to each other i.e. when the plunger spring (10) is compressed the contact spring (13) is expanded and vice versa. The head cover (14) is placed above the moving contact (12) and the fixed contacts (11).

In another embodiment as shown in FIG. 3, which illustrates the cross sectional view of the starter relay (1) in ON and OFF mode, the starter relay (1) has functionally two modes namely an ON mode and an OFF mode. In an event wherein the ignition switch of the vehicle is pressed in order to start the engine, a certain amount of battery voltage is applied to the coil (7) of the starter relay (1). The applied voltage results into flow of a DC current through the coil (7) of the starter relay (1). As per the law of electromagnetic induction, with the flow of the current, a magnetic field is also generated around the coil (7), thereby energizing the coil (7) of the relay (1). The so generated magnetic field pulls the plunger (9) of the starter relay (1), also resulting in compression of of the plunger spring (10) and storage of energy sufficient to break the established contacts when the coil (7) of the starter relay (1) is de-energized. The total force required to pull the plunger (9) downwards is referred to as the net magnetic force.

The plunger (9) in its initial state i.e OFF mode of the starter relay (1), keeps the moving contact (12) away from the the fixed contacts (11) and the contact spring (13) in a compressed state. However, as soon as the plunger (9) starts to move because of the generated magnetic field of the coil (7), the moving contact (12) also starts moving under the force exerted by the contact spring (13) and hits the fixed contacts (11). This movement of moving contact (12) towards the fixed contacts (11) establishes a physical contact between the moving contact (12) and the two fixed contacts (11). Consequentially, due to completion of the electric circuit, the electric current flows through the starter relay (1) to the starter motor. The actuation of the starter motor further results into cranking of the engine of the motor vehicle. The force between the fixed contacts and the moving contact is referred to as the contact force.

On the other hand, in an event wherein the ignition switch is released, the electric circuit through the starter relay (1) coil breaks. The reduction of electric current flowing through the coil (7) leads to hence collapse of the generated magnetic field eventually. In such an event, the force exerted by the magnetic field on the plunger (9) is reduced and the plunger spring (10) releases the plunger (9), thereby trying to maintain a steady state. However, the then shifted moving contact (12) comes in the way of the plunger (9). Due to the strong force generated by the plunger spring (10), the plunger (9) moves the moving contact (12) back to its initial position. In this process, the moving contact (12) loses its physical contact with the fixed contacts (11) leading to breaking of the electric circuit. This, consequentially stops the current flowing through the starter motor thereby stopping it. This further leads to termination of the cranking operation of the engine.

Functionality wise, all the components of the starter relay (1) serve at least one specific purpose. The metallic cup (2) and stop plate (3) provide a closed high permeability path to magnetic flux and generate magnetic force sufficient to pull the plunger (9) even at minimum applied voltage. Mechanically, the metallic cup (2) and the stop plate (3) hold the coil assembly (20), as shown in FIG. 4, intact. The bobbin (5) acts as a base to house the windings of the coil (7). The harness (6) gives supply to the coil (7) offering least resistance and provides a strong base for connection between thin wires of the winding and coupler supplying energy to the coil (7) from outside. The coil (7) generates sufficient magnetic force using the electrical energy supplied to the coil (7) at minimum voltage and produces minimum heat losses.

The plunger spring (10) keeps the moving contact (12) away from fixed contacts (11) against the force of contact spring (13) when the relay (1) is OFF and stores energy when the relay (1) is energized and the plunger (9) is pulled under the influence of the magnetic field. The plunger spring (10) helps keeping the contact open in de-energized condition so that the contacts do not inadvertently touch each other under the influence of external vibrations and shock. The plunger spring (10) also helps in ensuring that the moving contact (12) positively moves to the OFF position when the relay (1) is in OFF mode. On the other hand the contact spring (13) provides the pressure necessary to achieve good contact between the fixed contacts (11) and the moving contact (12) for ensuring a low temperature rise at the contact point.

Further, the moving contact (12) and the fixed contacts (11) provide a least resistance path to current flowing through the starter relay (1), from the power source to the starter motor of the vehicle. The head cover (14) keeps the moving contact (12) and the fixed contacts (11) intact at defined positions. It also helps in proper termination of wires coming from the power source and the starter motor. This termination of wires is facilitated with the help of nuts and washers fixed on the fixed contacts. These include two small O-rings (15), two plain washers (16), two serrated washers (17), two hex nuts (18) and two serrated nuts (20). Further, the head cover (14) also provides grooves for fitting with the metallic cup (2). Furthermore, the head cover (14) also provides a proper weather proofing to the complete assembly for the head cover (14) fits perfectly into the metallic cup (2) and is sealed with an epoxy resin.

According to a preferred embodiment, an important aspect of the starter relay (1) of the present invention is that due to the opposite working of the plunger spring (10) and the contact spring (13), less magnetic force is required to pull the plunger (9) downwards. In conventional starter relays, the plunger spring and the contact spring work in a similar manner i.e. when the plunger spring is expanded, the contact spring is also expanded and when the plunger spring is compressed, the contact spring is also compressed. This necessitates a greater magnetic force for pulling the plunger downwards.

On the other hand, the plunger spring (10) and the contact spring (13) of the starter relay (1) of the present invention work opposite to each other i.e. when the plunger spring (10) is expanded, the contact spring (13) is compressed and when the plunger spring (10) is compressed, the contact spring (13) is expanded. Due to this, the magnetic force required to pull down the plunger (9) is lesser. This in turn reduces the amount of coil (7) to be used in the starter relay (1) thereby bringing down the cost of the starter relay (1), making it more economic as well. The above concept is explained by means of FIG. 10 and the following example.

Example:
As illustrated in FIG. 10, in OFF mode, the contact spring force (A) at a height of 8.50mm is 750g and the plunger spring force (B) at a height of 9.00mm is 950g. Hence the resultant spring force is (B) - (A) = 950g - 750g = 200g. Hence, in OFF mode, the net magnetic force required to pull the plunger is again (B) - (A) = 200g. At this stage, the gap between the fixed contacts (11) and the moving contact (12) is 1.20mm and the gap between the lower part of the plunger (9) and the bottom of the metallic cup (2) is 1.80mm.

In just before contact condition, the contact spring force (C) at a height of 9.68mm is 635g and the plunger spring force (D) at a height of 7.82mm is 1020g. Hence the resultant spring force in this case is (D) - (C) = 1020g - 635g = 385g. Hence, in just before contact condition, the net magnetic force required to pull the plunger is (D) - (C) = 385g. At this stage, the gap between the fixed contacts (11) and the moving contact (12) is reduced to 0.02mm and the gap between the lower part of the plunger (9) and the bottom of the metallic cup (2) is reduced to 0.62mm.

In ON mode, the contact spring force (E) at a height of 9.70mm is 630g and the plunger spring force (F) at a height of 7.40mm is 1080g. In ON mode, there is no direct contact between the plunger and any of the contacts. Hence, in OFF mode, the net magnetic force required to pull the plunger is simply the force (F) = 1080g. At this stage, the fixed contacts (11) and the moving contact (12) are in physical contact with each other with a zero gap in between, while an air gap of about 0.40mm is generated between the upper part of the plunger (9) and the lower part of the moving contact (12). The gap between the the lower part of the plunger (9) and the bottom of the metallic cup (2) is further reduced to 0.20mm in the ON mode.

In order to assess the overall performance of the starter relay (1), multiple assessment tests were performed including a general performance test, electrical life/ endurance test, continuous ON test, functional test on vehicle, and vehicle road endurance test. The starter relay (1) of the present invention completed all the tests successfully. The starter relay could successfully complete 1,00,000 cycles of endurance test (repeated operation test). The starter relay (1) could fit successfully fit onto the desired motor vehicle and cranked the vehicle 100 times. With the starter relay (1) mounted on the desired motor vehicle, the vehicle could successfully run 1,00,000 km with the relay (1) performing consistently well throughout. It is to be noted that the overall performance of the starter relay is not limited to the above numbers and that the numbers may increase on prolonged assessment of the starter relay (1).

While considerable emphasis has been placed herein on the specific elements of the preferred embodiment, it will be appreciated that many alterations can be made and that many modifications can be made in preferred embodiment without departing from the principles of the invention. These and other changes in the preferred embodiments of the invention will be 5 apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.