Intake air amount control apparatus for vehicle engine and method thereof

1. An intake air amount control apparatus for a vehicle engine provided with a brake booster for assuring a master vacuum negative pressure by using a negative pressure of said engine, comprising:

an intake valve;

a variable valve mechanism which varies a lift amount of said intake valve;

an intake throttle valve disposed on an upstream side of said intake valve;

an actuator opening/closing said intake throttle valve;

an operating condition detector detecting operating conditions of said engine; and

a control unit that receives detection signals from said operating condition detector and also outputs control signals to said variable valve mechanism and said actuator,

wherein said control unit diagnoses whether or not said variable valve mechanism is failed, and

controls an intake air flow amount of said engine by controlling the lift amount of said intake valve and also controls an intake negative pressure of said engine to be constant by controlling an opening degree of said intake throttle valve, when said variable valve mechanism is normal, while

stops the driving of said variable valve mechanism and controls the opening of said intake throttle valve to control the intake air flow amount of said engine, and also, restricts the opening degree of said intake throttle valve for controlling said intake air flow amount to an upper limit value or a value less than the upper limit value, when said variable valve mechanism is failed.

2. An intake air amount control apparatus for a vehicle engine according to claim 1 ,

wherein said operating condition detector includes an intake pressure sensor detecting an intake pressure of said engine, and

said control unit sets said upper limit value based on the intake pressure detected by said intake pressure sensor.

3. An intake air amount control apparatus for a vehicle engine according to claim 2 ,

wherein said control unit sets said upper limit value to a smaller value as the intake pressure approaches the atmospheric pressure.

4. An intake air amount control apparatus for a vehicle engine according to claim 1 ,

wherein said operating condition detector includes a rotation speed sensor detecting a rotation speed of said engine, and

said control unit executes the processing of restricting the opening degree of said intake throttle valve to said upper limit value, when the rotation speed of said engine detected by said rotation speed sensor is equal to or larger than a threshold.

5. An intake air amount control apparatus for a vehicle engine according to claim 1 ,

wherein said operating condition detector includes an intake pressure sensor detecting an intake pressure of said engine, and

said control unit executes the processing of restricting the opening degree of said intake throttle valve to said upper limit value, when the intake pressure detected by said intake pressure sensor is equal to or larger than a threshold.

6. An intake air amount control apparatus for a vehicle engine according to claim 1 ,

wherein said operating condition detector includes an intake pressure sensor detecting an intake pressure of said engine and a rotation speed sensor detecting a rotation speed of said engine, and

said control unit executes the processing of restricting the opening degree of said intake throttle valve to said upper limit value, when the rotation speed of said engine detected by said rotation speed sensor is equal to or larger than a threshold, and also the intake pressure detected by said intake pressure sensor is equal to or larger than a threshold.

7. An intake air amount control apparatus for a vehicle engine according to claim 6 ,

wherein said control unit sets said upper limit value based on the intake pressure detected by said intake pressure sensor.

8. An intake air amount control apparatus for a vehicle engine according to claim 1 ,

wherein said control unit feedback controls said variable valve mechanism based on a target valve lift amount, and when a state where a deviation between said target valve lift amount and an actual valve lift amount is equal to or larger than a predetermined value stays for a predetermined period of time, judges that said variable valve mechanism is failed.

9. An intake air amount control apparatus for a vehicle engine according to claim 1 ,

wherein said variable valve mechanism varies the lift amount and an operating angle of said intake valve, and

said intake air amount control apparatus further comprises a variable valve timing mechanism which varies a center phase of the operating angle of said intake valve.

10. An intake air amount control apparatus for a vehicle engine provided with a brake booster for assuring a master vacuum negative pressure by using a negative pressure of said engine, comprising:

an intake valve;

variable valve means for varying a lift amount of said intake valve;

an intake throttle valve disposed on the upstream side of said intake valve;

drive means for opening/closing said intake throttle valve;

operating condition detecting means for detecting operating conditions of said engine;

diagnosis means for diagnosing whether or not said variable valve mechanism is failed;

first control means for controlling an intake air flow amount of said engine by controlling the lift amount of said intake valve and also controlling an intake negative pressure of said engine to be constant by controlling an opening degree of said intake throttle valve, when said variable valve mechanism is normal; and

second control means for stopping the driving of said variable valve mechanism and controlling the opening degree of said intake throttle valve to control the intake air flow amount of said engine, and also, restricting the opening of said intake throttle valve for controlling said intake air flow amount to an upper limit value or a value less than the upper limit value, when said variable valve mechanism is failed.

11. An intake air amount control method for a vehicle engine provided with a brake booster for assuring a master vacuum negative pressure by using a negative pressure of said engine, a variable valve mechanism which varies a lift amount of an intake valve and an actuator opening/closing an intake throttle valve disposed on the upstream side of said intake valve, comprising the steps of:

diagnosing whether or not said variable valve mechanism is failed;

controlling an intake air flow amount of said engine by controlling the lift amount of said intake valve, when said variable valve mechanism is normal;

controlling an intake negative pressure of said engine to be constant by controlling an opening degree of said intake throttle valve, when said variable valve mechanism is normal;

stopping the driving of said variable valve mechanism, when said variable valve mechanism is failed;

controlling the opening degree of said intake throttle valve to control the intake air flow amount of said engine, when said variable valve mechanism is failed; and

restricting the opening degree of said intake throttle valve for controlling said intake air flow amount to an upper limit value or a value less than the upper limit value.

12. An intake air amount control method for a vehicle engine according to claim 11 , further comprising the steps of:

detecting an intake pressure of said engine, and

setting said upper limit value based on said intake pressure.

13. An intake air amount control method for a vehicle engine according to claim 12 ,

wherein said step of setting the upper limit value based on said intake pressure;

sets said upper limit value to a smaller value as said intake pressure approaches the atmospheric pressure.

14. An intake air amount control method for a vehicle engine according to claim 11 ,

wherein said step of restricting the opening degree of said intake throttle valve to the upper limit value or a value less than the upper limit value comprises the steps of:

detecting a rotation speed of said engine; and

restricting the opening degree of said intake throttle valve to said upper limit value, when said rotation speed of said engine is equal to or larger than a threshold.

15. An intake air amount control method for a vehicle engine according to claim 11 ,

wherein said step of restricting the opening of said intake throttle valve to the upper limit value or a value less than the upper limit value comprises the steps of:

detecting an intake pressure of said engine; and

restricting the opening degree of said intake throttle valve to said upper limit value, when said intake pressure is equal to or larger than a threshold.

16. An intake air amount control method for a vehicle engine according to claim 11 ,

wherein said step of restricting the opening of said intake throttle valve to the upper limit value or a value less than the upper limit value comprises the steps of:

detecting an intake pressure of said engine;

detecting a rotation speed of said engine; and

restricting the opening degree of said intake throttle valve to said upper limit value, when said rotation speed of said engine is equal to or larger than a threshold, and also said intake pressure is equal to or larger than a threshold.

17. An intake air amount control method for a vehicle engine according to claim 16 , further comprising the steps of:

detecting the intake pressure of said engine; and

setting said upper limit value based on said intake pressure.

18. An intake air amount control method for a vehicle engine according to claim 11 , further comprising the step of;

feedback controlling said variable valve mechanism based on a target valve lift amount,

wherein said step of diagnosing whether or not said variable valve mechanism is failed, comprises the steps of:

computing a deviation between said target valve lift amount and an actual valve lift amount;

judging whether or not said deviation is equal to or larger than a predetermined value;

measuring the duration in which said deviation is equal to or larger than the predetermined value; and

judging that said variable valve mechanism is failed, when said duration reaches or exceeds a predetermined period of time.