Engine start control system

1. An engine start control system for an internal combustion engine of a vehicle, comprising:

a push switch that is pressable by a user to start the engine;

a brake sensor that senses depression of a brake pedal of the vehicle when the user depresses the brake pedal a predetermined distance or greater from an initial point; and

an engine start control unit that controls engine start of the engine, wherein:

the engine start control unit determines that a current operational mode is a normal mode when the brake sensor detects the depression of the brake pedal and is thereby placed in an detected state;

the engine start control unit enables the engine start when the user performs a predetermined normal time push operation on the push switch in the normal mode;

the engine start control unit determines that the current operational mode is a fail-safe mode when the brake sensor does not detect the depression of the brake pedal and is thereby placed in an undetected state;

the engine start control unit enables the engine start when the user performs a predetermined fail-safe push operation on the push switch in the fail-safe mode; and

the fail-safe push operation of the push switch requires an increased work load of the user in comparison to that of the normal time push operation of the push switch.

2. The engine start control system according to claim 1 , wherein:

the vehicle includes a brake booster, which amplifies a depression force applied from the user onto the brake pedal through use of a negative suction pressure of the engine and conducts the increased depression force to a master cylinder; and

the engine start control unit enables the engine start when the user performs the fail-safe push operation on the push switch in the undetected state of the brake sensor, which results from shortage of the depression force of the user for depressing the brake pedal to the predetermined distance because of a reduction in an assist force of the brake booster that is causes by leakage of a remaining negative pressure of the brake booster in a stop state of the engine.

3. The engine start control system according to claim 1 , wherein the engine start control unit enables the engines start when the user performs the fail-safe push operation on the push switch in the undetected state of the brake sensor, which occurs although the brake pedal is depressed the predetermined distance due to a malfunction of the brake sensor.

4. The engine start control system according to claim 3 , wherein:

the brake sensor is a brake switch, which is operated at time of depressing the brake pedal to lit a stop lamp of the vehicle; and

the engine start control unit enables the engine start when the user performs the fail-safe push operation on the push switch in the undetected state of the brake switch, which results from one of:

breaking of a wiring path of the brake switch; and

breaking of a fuse, which is installed in the wiring path of the brake switch.

5. The engine start control system according to claim 1 , wherein:

the push switch includes a plurality of sub-switches, each of which is constructed such that a depressed state and a non-depressed state of the sub-switch correspond to a conducting state and a non-conducting state of the sub-switch;

under the normal mode, the engine start control unit enables the engine start when at least one of the plurality of sub-switches is placed in the conducting state, which indicates the depressed state; and

under the fail-safe mode, the engine start control unit enables the engine start only when all of the plurality of sub-switches are placed in the conducting state, which indicates the depressed state.

6. The engine start control system according to claim 1 , further comprising a diagnostic data storage, which stores a history of the fail-safe push operation as diagnostic data under the fail-safe mode.

7. The engine start control system according to claim 1 , wherein:

under the fail-safe mode, the engine start control unit enables the engine start when the push switch is continuously held in a depressed state for a predetermined period as the fail-safe push operation; and

under the normal mode, the engine start control unit enables the engine start when the push switch is depressed less than the predetermined period.

8. The engine start control system according to claim 1 , wherein under the fail-safe mode, the engine start control unit enables the engine start when the fail-safe push operation is performed on the push switch in a form of a patterned depression operation that implements a predetermined pattern of a depressed period and a non-depressed period of the push switch.

9. The engine start control system according to claim 8 , wherein:

under the normal mode, the engine start control unit enables the engine start when the normal time push operation is performed on the push switch in a form of a single depression operation, in which the push switch is depressed a single time; and

under the fail-safe mode, the engine start control unit enables the engine start when the fail-safe push operation is performed on the push switch in a form of a repeated multiple depression operation, in which the push switch is repeatedly operated a predetermined number of times.

10. The engine start control system according to claim 9 , wherein the fail-safe push operation is executed by alternately implementing:

a repeatedly operating period for repeatedly operating the push switch the predetermined number of times; and

a non-operating period, which is longer than an interval between the operations of the push switch in the repeatedly operating period.

11. The engine start control system according to claim 1 , further comprising a brake-coupled sensor, which detects depression of the brake pedal through a different sensing line that is different from that of the brake sensor when the brake pedal is depressed a preset distance from the initial point, wherein even in the undetected state of the brake sensor, when the brake-coupled sensor senses the depression of the brake pedal, the engine start control unit enables the engine start upon execution of the normal time push operation on the push switch.

12. The engine start control system according to claim 11 , further comprising a diagnostic data storage, which stores a history of the normal time push operation as diagnostic data when the engine start is enabled by the engine start control unit upon execution of the normal time push operation in a detected state of the brake-coupled sensor where the brake-coupled sensor detects the depression of the brake pedal although the brake sensor is in the undetected state.

13. The engine start control system according to claim 11 , wherein the preset distance of the brake pedal, at which the depression of the brake pedal is detected by the brake-coupled sensor, is smaller than the predetermined distance of the brake pedal, at which the depression of the brake pedal is detected by the brake sensor.