SPECIFICATION

TITLE OF THE INVENTION

ENGINE STARTING DEVICE

BACKGROUND OF THE INVENTION

1. FIELD OF THE INVENTION

The present invention relates to an engine starting device which starts an engine by a starter motor.

2. DESCRIPTION OF THE RELATED ART

In the case of starting an engine, a coil of a starter switch is energized and a fixed contact of the starter switch is close-circuited; and accordingly, electric power is supplied from a vehicular power supply to a starter motor to make the starter motor generate rotational torque, and rotational force of the starter motor is transmitted to an engine crankshaft via an engaged pinion gear and ring gear to make the engine start. At this time, when the starter switch is close-circuited, the starter motor is still in a static state and a counter electromotive voltage is not generated; and therefore, an inrush current of several hundred to one thousand and several hundred amperes flows due to extremely low starter internal resistance. At that time, the vehicular power supply causes a voltage drop in which a terminal voltage lowers due to internal specific resistance.

For this reason, in starting of the engine, there is a problem that an instantaneous interruption is caused in using electrical devices other than a vehicle, for example, a stereo, a navigation system, and an air conditioner due to the voltage drop of the vehicular power supply by the current in starting the starter motor. The instantaneous interruption does not particularly matter in normal starting of the engine; however, in a vehicle or the like equipped with an idling stop function, an instantaneous interruption occurs when restarting is performed after idling stop, and there is a concern that this interruption gives a driver and fellow passengers a feeling of discomfort.

On the other hand, a starter in which the occurrence of an instantaneous interruption is prevented by providing a unit which suppresses an inrush current which flows in starting a starter motor, is known (see Japanese Unexamined Patent Publication No. 2009-287459, referred to as Patent Document 1 hereinafter).

The starter disclosed in Patent Document 1 includes a resistor connected to a motor circuit in series with a main contact, and a second electromagnetic switch which opens and closes an auxiliary contact, the auxiliary contact being connected to the motor circuit in parallel with the resistor. When a time after a first electromagnetic switch is energized until the second electromagnetic switch is energized is referred to as a resistor energization time, the resistor energization time is set so that a maximum value of a current flowing through the motor in energizing the second electromagnetic switch is not higher than a maximum value of a current flowing through the motor in energizing the first electromagnetic switch.

That is, Patent Document 1 discloses the starter in which the resistor energization time is appropriately set and the maximum value of the current flowing through the motor in energizing the second electromagnetic switch is controlled to be not higher than the maximum value of the current flowing through the motor in energizing the first electromagnetic switch; and accordingly, a voltage drop of a battery terminal voltage is stably suppressed and the occurrence of the instantaneous interruption can be prevented.

The above mentioned known art (Patent Document 1) is configured such that the second electromagnetic switch has a timer circuit in order to control the resistor energization time; after the first electromagnetic switch is closed and a suppressed current is applied, the timer circuit which received a signal from an IG switch performs energization to an excitation coil of the second electromagnetic switch after elapsing a predetermined time; and accordingly, the resistor provided in the circuit is short-circuited and a total voltage of the battery is applied to the motor.

However, in the case where the timer circuit is not normally operated from any cause, for example, under the influence of ambient temperature rise, static electricity, or surges; it is conceivable that the excitation coil of the second electromagnetic switch is not energized and the current suppression resistor cannot be short-circuited.

In this case, the starter motor is continued to be energized via the current suppression resistor; and therefore, a value of a current flowing through the motor is small and thus it takes time to start an engine, or it is likely not to be able to start the engine.

In order to deal with this, it is conceivable that when the second electromagnetic switch of the above mentioned known art (Patent Document 1) is set as a normally closed contact (N/C contact) and the timer circuit is normally operated, a drive coil of the second electromagnetic switch is energized, the resistor is energized and the resultant suppressed current is applied, and the resistor energization time is controlled by the timer circuit; and accordingly, the resistor is short-circuited and the total voltage of the battery is applied to the motor. In this case, when the timer circuit is not normally operated by any abnormality, the drive coil of the second electromagnetic switch is not energized; as a result, the current suppression resistor becomes in a normally short-circuited state and a function as the known engine starting device can be maintained, although effects in which the voltage drop of the battery terminal voltage is stably suppressed and the occurrence of an instantaneous interruption is prevented cannot be obtained.

However, in such a circuit configuration, the second electromagnetic switch needs to be first opened from the short-circuited state before the first electromagnetic switch is closed. On the other hand, an opening and closing timing of the second electromagnetic switch can be freely determined by the timer circuit.

Therefore, in the case of a combination in which a time at which the first electromagnetic switch is closed is faster than a time at which the second electromagnetic switch is opened, a short-circuit needs to be made behind the second electromagnetic switch by also controlling a timing at which the first electromagnetic switch is energized; and consequently, a circuit configuration becomes complicated. On the other hand, if a time after the first electromagnetic switch is automatically energized until closing is delayed; it comes out against quick starting that is required for idling stop or the like.

BRIEF SUMMARY OF THE INVENTION

The present invention is implemented to solve the problem in the foregoing known engine starting device, and an object of the present invention is to provide an engine starting device which does not impair a function as the engine starting device and the occurrence of an "instantaneous interruption" caused by lowering of a battery terminal voltage can be prevented by a simple and inexpensive configuration even when the opening and closing of a short-circuiting switch that short-circuits a current suppression resistor cannot be controlled from any cause.

According to the present invention, there is provided an engine starting device which includes a starter switch connected in series between a power supply and a starter motor, a resistor connected in series with the starter switch, a short-circuiting switch which short-circuits the resistor, and a timer circuit which controls opening and closing of the short-circuiting switch. The starter switch is closed, thereby applying a current suppressed via the starter switch and the resistor from the power supply to the starter motor; and the starter switch is closed and then after a delay time is elapsed, the short-circuiting switch is closed to short-circuit the resistor. In the engine starting device, a contact of the short-circuiting switch is a normally closed contact, and the contact of the short-circuiting switch is open-circuited before a contact of the starter switch is close-circuited, and the contact of the short-circuiting switch is close-circuited after the contact of the starter switch is close-circuited.

According to the engine starting device of the present invention, even in the case where the timer circuit is not normally operated from any cause, the short-circuiting switch which short-circuits the resistor is the normally closed contact and accordingly the motor current does not flow through the resistor, whereby a function as the engine starting device is not impaired even when the timer circuit is in an abnormal state.

On the other hand, when the timer circuit is in a normal state, the current suppressed by the resistor is applied to the motor and 2 which starts an engine (not shown in the drawing), a battery 3 serving as a power supply which supplies electric power to the starter motor 2, a starting switch 4 connected to the battery 3 which starts the starter motor 2, a starter switch 5, fixed contacts 5e and 5f connected to the starter motor 2 via contact terminals 5g and 5h of the starter switch 5, a current suppression resistor 6 connected in series with the fixed contacts 5e and 5f, a short-circuiting switch 7 provided to be capable of short-circuiting the current suppression resistor 6 when a request for starting the engine is generated, a timer circuit 8 incorporated in the short-circuiting switch 7 in order to perform energization to a drive coil 7b of the short-circuiting switch 7, and the like.

The starter switch 5 includes the fixed contacts 5e and 5f connected in series between the starter motor 2 and the battery 3, a drive coil 5b which is for driving a movable contact 5i, a holding coil 5c which holds the movable contact 5i at a position coming in contact with the fixed contacts 5e and 5f, and a plunger 5d fixed to the movable contact 5i. The holding coil 5C is connected between the starting switch 4 and a grounding terminal GND.

The short-circuiting switch 7 includes fixed contacts 7e and 7f connected between the starter switch 5 and the starter motor 2; the drive coil 7b which is for driving a movable contact 7i; a plunger 7d fixed to the movable contact 7i; the current suppression resistor 6 in which both terminals are connected between contact terminals 7g and 7h of the short-circuiting switch 7, the current suppression resistor 6 being connected in parallel with the short-circuiting switch 7; and a timer circuit 8 which controls opening and closing between the contact terminals. The drive coil 7b is connected between the timer circuit 8 incorporated in the short-circuiting switch 7 and a grounding terminal GND; and the movable contact: 7i is a normally closed contact held at a position coming in contact with the fixed contacts 7e and 7f.

Next, operation of the thus configured engine starting device according to the preferred embodiment 1 of the present invention will be described.

In FIG. 1 and FIG. 2, first, as a first step of starting the engine, when the starting switch 4 is close-circuited at a request for starting the engine at time Tl, a current begins to be supplied from the battery 3 to the starter motor 2 via the starting switch 4 and the drive coil 5b of the starter switch 5. On the other hand, at the same time as the energization, the request for starting is also inputted to the timer circuit 8 in the short-circuiting switch 7 and the current begins to be supplied to the drive coil 7b.

In this case, by the energization to the drive coil 5b at the request for starting, the movable contact 5i of the starter switch 5 begins to move to the fixed contacts 5e and 5f sides via the plunger 5d and tries so that the starter switch 5 is to be close-circuited.

On the other hand, by the energization to the drive coil 7b at the request for starting, the movable contact 7i of the short-circuiting switch 7 begins to move so as to separate from the fixed contacts 7e and 7f sides via the plunger 7d and tries so that the short-circuiting switch 7 is to be open-circuited.

Times required from the drive coils 5b and 7b of the respective switches 5 and 7 begin to be energized until the respective switches 5 and 7 open and close are determined by magnetic properties of the respective switches, coil specifications, specifications of respective springs (not shown in the drawing) necessary for opening and closing the fixed contacts, andthelike; and the present invention is configured so that the time of opening and closing the starter switch 5 is delayed behind the time of opening and closing the short-circuiting switch 7.

That is, as shown in FIG. 2, at time T2 at which the fixed contacts 7e and 7f of the short-circuiting switch 7 are open-circuited , the fixed contacts 5e and 5f of the starter switch 5 are not close-circuited yet and the starter switch 5a is not close-circuited.

Subsequently, as a second step, the fixed contacts 5e and 5f are close-circuited at time T3; and accordingly, the starter switch 5 is close-circuited. Then, at this time, the holding coil 5c is energized from the battery 3 via the starting switch 4 and the plunger 5d is held at a position where the fixed contacts 5e and 5f are close-circuited. As a result, the closed circuit of the starter switch 5 is maintained.

The starter switch 5 is close-circuited; and accordingly, a current flows from the battery 3 to the starter motor 2 via the current suppression resistor 6. This causes the starter motor 2 to generate rotational torque which makes a pinion gear (not shown in the drawing) coupled to a rotor shaft of the starter motor 2 via an unidirectional clutch move to the ring gear side provided on a crankshaft of the engine and thus the pinion gear is engaged with a ring gear (not shown in the drawing).

At this time, a voltage lower than a total voltage of the battery 3 is applied to the starter motor 2 as shown in FIG. 3 and a current suppressed by the current suppression resistor 6 flows to the starter motor 2; and accordingly, the starter motor 2 rotates at low speed.
When the starter switch 5 is close-circuited, the current flowing from the battery 3 to the drive coil 5b almost disappears and becomes a current which flows from the battery 3 to the close-circuited starter switch 5 and the current suppression resistor 6.

Subsequently, as a third step, the timer circuit 8 is operated then a total voltage of a battery can be applied to the motor at a predetermined timing; a voltage drop of a battery terminal voltage can be stably suppressed; and the occurrence of an "instantaneous interruption" caused by lowering of the battery terminal voltage can be prevented. In addition, energization to a drive coil of the starter switch does not need to be controlled and therefore the engine starting device can be obtained by a simple and inexpensive circuit configuration.

The foregoing and other object, features, and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments and description shown in drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is an electrical circuit diagram of an engine starting device according to a preferred embodiment 1 of the present invention; FIG. 2 is a timing chart related to operation of the engine starting device according to the preferred embodiment 1 of the present invention; and

FIG. 3 is a graph showing current and voltage waveforms according to the preferred embodiment 1 of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Preferred Embodiment 1.

FIG. 1 is an electrical circuit diagram of an engine starting device according to a preferred embodiment 1 of the present invention; and FIG. 2 is a timing chart related to operation of the engine starting device according to the preferred embodiment 1 of the present invention and a lateral axis shows time.

In FIG. 1, an engine starting device 1 includes a starter motor at time T4, that is, a time after a predetermined delay time is elapsed from the time Tl at which the request for starting is given; and the plunger 7d begins to move so that the fixed contacts 7e and 7f of the short-circuiting switch 7 are to be close-circuited. As a result, at time T5 at which a time required for close-circuiting the short-circuiting switch 7 is elapsed from the time T4, the short-circuiting switch 7 connected in parallel with the current suppression resistor 6 is close-circuited. The short-circuiting switch 7 is close-circuited and accordingly the current suppression resistor 6 is short-circuited.

The short-circuiting switch 7 is close-circuited and accordingly a normal starter current is supplied from the battery 3 to the starter motor 2 via the starter switch 5 and the short-circuiting switch 7. At this time, the short-circuiting switch 7 is close-circuited and the current suppression resistor 6 is short-circuited; and therefore, the starter current increases again as shown in FIG. 3. The starter motor 2 is driven by the supplied normal starter current and the resultant rotational force is transmitted to an engine crankshaft via an engaged pinion gear and ring gear to begin starting of the engine; and when a request for starting is terminated at time T6, the starting of the engine is completed at time T7, that is, a time after a time at which the plunger 7d moves is elapsed.

In the first step between the aforementioned times Tl and T2, there are internal specific resistance RB of the battery 3, resistance RP of the drive coil 5b, internal resistance RS of the starter motor 2, andeachwiringresistanceRW inthecircuit. The short-circuiting switch 7 is open-circuited between the times T2 and T3; and therefore, there are the internal specific resistance RB of the battery 3, the resistance RP of the drive coil 5b, a resistance value RSR of the current suppression resistor 6, the internal resistance RS of the starter motor 2, and each wiring resistance RW in the circuit.

The starter switch 5 is close-circuited between the times T3 and T5; and therefore, there are the internal specific resistance RB of the battery 3, the resistance value RSR of the current suppression resistor 6, the internal resistance RS of the starter motor 2, and each wiring resistance RW in the circuit. The short-circuiting switch 7 is close-circuited between the times T5 and T7; and therefore, there are the internal specific resistance RB of the battery 3, the internal resistance RS of the starter motor 2, and each wiring resistance RW in the circuit.

A delay time from the starting switch 4 is close-circuited until the short-circuiting switch 7 is once open-circuited and then close-circuited again and both ends of the current suppression resistor 6 are short-circuited, is determined by a time from the starter switch 5 is close-circuited at the time T3, a current flows to the starter motor 2 via the current suppression resistor 6, and the starter motor 2 begins to rotate until the starter motor 2 reaches a predetermined number of rotation; and the predetermined number of rotation is determined by how far down the voltage drop is allowed to be. That is, if the amount of target voltage drop of the battery may be set large, the delay time can be small; and if the amount of voltage drop has to be set small, the delay time needs to be large. The amount of allowable voltage drop of the battery needs to be within a range which is not made to instantaneously interrupt an in-vehicle electrical device. The delay time and a resistance value of the resistor are set by the internal resistance of the battery, specifications of the starter motor (internal resistance), the wiring resistance, and the target engine.

As described above, according to the engine starting device of the preferred embodiment 1of the present invention, the current suppression resistor 6 located between the battery 3 serving as the power supply and starter motor 2 is first energized at the time T3 that is a time at which the starter motor starts, starting of the starter motor 2 begins at a low current, and the current suppression resistor 6 is made to be short-circuited by the short-circuiting switch 7 after a predetermined delay time is elapsed; and accordingly, a voltage drop of the power supply in beginning to start the engine is suppressed and the occurrence of an "instantaneous interruption" caused by lowering of a battery terminal voltage can be prevented. Furthermore, even when the short-circuiting switch 7 cannot be opened and closed from any cause, the short-circuiting switch 7 is a normally closed contact; and therefore, a function as a normal starter is not impaired.

Incidentally, in the present preferred embodiment 1, the short-circuiting switch 7 is connected between the starter switch 5 and the starter motor 2; however, even when the short-circuiting switch 7 is connected between the battery 3 and the starter switch 5, the same effect can be obtained.

Further, in the preferred embodiment 1, the timer circuit 8 which controls opening and closing of the short-circuiting switch 7 is incorporated in the short-circuiting switch 7; however, the same effect can be obtained even when the starter switch 5 and the short-circuiting switch 7 are totally controlled by an ECU (engine control unit) or the like, or only the short-circuiting switch 7 is controlled.

CLAIMS What is claimed is:

1. An engine starting device comprising:

a power supply (3);

a starter motor (2);

a starter switch (5) connected in series between said power supply (3) and said starter motor (2);

a resistor (6) connected in series with said starter switch;

a short-circuiting switch (7) which short-circuits said resistor; and

a timer circuit (8) which controls opening and closing of said short-circuiting switch,

said starter switch (5) being closed, thereby applying a current suppressed via said starter switch (5) and said resistor (6) from said power supply (3) to said starter motor (2),

said starter switch (5) being closed and then after a delay time being elapsed, said short-circuiting switch (7) being closed to short-circuit said resistor (6),

said short-circuiting switch (7) having a contact serving as a normally closed contact,
said starter switch (5) having a contact,

the contact of said short-circuiting switch (7) being open-circuited before the contact of said starter switch (5) being close-circuited, and

the contact of said short-circuiting switch (7) being close-circuited after the contact of said starter switch (5) being close-circuited.

2. The engine starting device according to claim 1, wherein a time from said short-circuiting switch (7) begins to be energized until the contact is open-circuited is shorter than a time from said starter switch (5) begins to be energized until the contact is close-circuited.

3. The engine starting device according to claim 1 or 2,

wherein said timer circuit (8) which controls the delay time is incorporated in said short-circuiting switch (7).