CONTROL DEVICE AND CONTROL METHOD FOR INTERNAL COMBUSTION ENGINE

• US 20190331083A1
• Filed: 01/02/2019
• Published: 10/31/2019
• Est. Priority Date: 04/27/2018
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: NAKAMURA, Toshifumi, INADA, Takahiko
• Granted Patent: US 10,808,673 B2
• Time in Patent Office: Days
• CPC Class Codes: F02D 35/021 using an ionic current sensor
• CPC Class Codes: F02D 35/027 using knock sensors
• CPC Class Codes: F02P 17/12 Testing characteristics of the spark, ignition voltage or current testing of sparking plugs H01T13/60
• CPC Class Codes: F02P 2017/125 Measuring ionisation of combustion gas, e.g. by using ignition circuits
• CPC Class Codes: F02P 2017/128 for knock detection
• CPC Class Codes: F02P 3/0414 using digital techniques F02P3/0428, F02P3/0442 take precedence
• CPC Class Codes: G01L 23/225 circuit arrangements therefor

Abstract

To provide a control device, of an internal combustion engine, that accurately identifies the combustion state through ion current detection in a wide operation range of the internal combustion engine, without impairing the reliability and the durability of the control device of the internal combustion engine. This internal combustion engine control device includes: an ignition plug having a center electrode and a ground electrode opposed to each other with a gap therebetween; a circulation device for short-circuiting a primary winding to cause a circulation route to enter a conduction state, thereby stopping spark discharge; and an ion-current-detection bias voltage control device for controlling bias voltage for ion current detection. The potential of the center electrode in an ion current detection period is controlled by adjusting the value of the bias voltage and the changing speed of the bias voltage.

Claims

1. An internal combustion engine control device comprising:

an ignition plug having a first electrode and a second electrode which are opposed to each other with a gap therebetween, the ignition plug being for igniting a combustible air-fuel mixture in a combustion chamber;

an ignition device including a primary winding supplied with current from a power supply device and a secondary winding magnetically coupled to the primary winding, the ignition device being for supplying ignition energy to the ignition plug;

an ion current detection device having an ion current detection circuit and an ion-current-detection bias voltage control device, the ion current detection circuit being for detecting, as ion current, ion generated in the combustion chamber as a result of the combustible air-fuel mixture being combusted due to spark discharge caused by the ignition energy, the ion-current-detection bias voltage control device being for controlling bias voltage for ion current detection; and

a circulation device for short-circuiting the primary winding to cause a circulation route to enter a conduction state, thereby stopping the spark discharge, wherein

the ion-current-detection bias voltage control device performs control such that;

the bias voltage is increased such that a potential of the first electrode becomes a positive voltage during a period in which the spark discharge is stopped by the circulation device and ion current is detected; and

the bias voltage is decreased at an end of the period in which the spark discharge is stopped by the circulation device.

2. The internal combustion engine control device according to claim 1, wherein

the ion-current-detection bias voltage control device comprises:

a parallel circuit composed of a capacitor and a Zener diode; and

a short circuit for short-circuiting both ends of the Zener diode.

3. The internal combustion engine control device according to claim 2, wherein

the ion-current-detection bias voltage control device comprises:

a plurality of the Zener diodes which are connected in series to each other and which are connected in parallel to the capacitor; and

the short circuits which are respectively provided for the plurality of the Zener diodes and which each short-circuit both ends of a corresponding one of the Zener diodes.

4. The internal combustion engine control device according to claim 2, wherein

the short circuit comprises a series circuit composed of a resistor and a switch.

5. The internal combustion engine control device according to claim 3, wherein

each short circuit comprises a series circuit composed of a resistor and a switch.

6. The internal combustion engine control device according to claim 2, wherein

the ion-current-detection bias voltage control device controls the bias voltage such that the potential of the first electrode becomes a constant positive voltage during the period in which the spark discharge is stopped by the circulation device and ion current is detected.

7. The internal combustion engine control device according to claim 3, wherein

the ion-current-detection bias voltage control device controls the bias voltage such that the potential of the first electrode becomes a constant positive voltage during the period in which the spark discharge is stopped by the circulation device and ion current is detected.

8. The internal combustion engine control device according to claim 6, wherein

the ion-current-detection bias voltage control device controls a decreasing speed of the bias voltage by use of internal resistance of the short circuit such that the potential of the first electrode becomes a constant positive voltage during the period in which the spark discharge is stopped by the circulation device and ion current is detected.

9. The internal combustion engine control device according to claim 7, wherein

the ion-current-detection bias voltage control device controls a decreasing speed of the bias voltage by use of internal resistance of each short circuit such that the potential of the first electrode becomes a constant positive voltage during the period in which the spark discharge is stopped by the circulation device and ion current is detected.

10. The internal combustion engine control device according to claim 8, wherein

the short circuit is composed of a plurality of sets of a resistor and a switch which are connected in series to each other, the plurality of sets being connected in parallel to each other, and

an internal resistance value of the short circuit is adjusted through combination of conduction states of the plurality of the switches.

11. The internal combustion engine control device according to claim 9, wherein

each short circuit is composed of a plurality of sets of a resistor and a switch which are connected in series to each other, the plurality of sets being connected in parallel to each other, and

an internal resistance value of the short circuit is adjusted through combination of conduction states of the plurality of the switches.

12. The internal combustion engine control device according to claim 2, wherein

the short circuit is configured such that, when the bias voltage is switched to a lower voltage level outside the period in which ion current is detected, an internal resistance value of the short circuit is not less than 20Ω

.

13. The internal combustion engine control device according to claim 12, wherein

the short circuit is configured such that, during the period in which ion current is detected, the internal resistance value of the short circuit is in a range of 50 kΩ

to 500 kΩ

.

14. The internal combustion engine control device according to claim 2, wherein

in an ignition cycle in which the spark discharge stop by the circulation device is not performed among the plurality of ignition cycles, an internal resistance value of the short circuit is 2 kΩ

or less.

15. The internal combustion engine control device according to claim 8, wherein

a time point at which the ion-current-detection bias voltage control device starts the control of the decreasing speed of the bias voltage such that the potential of the first electrode becomes a constant positive voltage is calculated from information of ion current surge that occurs when the spark discharge is stopped.

16. The internal combustion engine control device according to claim 8, wherein

a target value of the decreasing speed of the bias voltage controlled by the ion-current-detection bias voltage control device is calculated from information of voltage across both ends of the primary winding or information of circulation current of the primary winding while the spark discharge is stopped, and the target value is determined for each ignition cycle.

17. The internal combustion engine control device according to claim 1, comprising

a driver circuit having mounted therein a switch for controlling conduction and interruption of current that is supplied from the power supply device to the primary winding, wherein

the ion-current-detection bias voltage control device is built in the driver circuit.

18. A method for controlling an internal combustion engine including:

an ignition plug having a first electrode and a second electrode which are opposed to each other with a gap therebetween, the ignition plug being for igniting a combustible air-fuel mixture in a combustion chamber;

an ignition device including a primary winding supplied with current from a power supply device and a secondary winding magnetically coupled to the primary winding, the ignition device being for supplying ignition energy to the ignition plug;

an ion current detection device having an ion current detection circuit and an ion-current-detection bias voltage control device, the ion current detection circuit being for detecting, as ion current, ion generated in the combustion chamber as a result of the combustible air-fuel mixture being combusted due to spark discharge caused by the ignition energy, the ion-current-detection bias voltage control device being for controlling bias voltage for ion current detection; and

a circulation device for short-circuiting the primary winding to cause a circulation route to enter a conduction state, thereby stopping the spark discharge,

the method comprising the steps of;

supplying ignition energy to the ignition plug to cause spark discharge;

stopping the spark discharge by the circulation device and detecting ion current; and

determining a combustion state on the basis of the detected ion current, and controlling the combustion state, wherein

in the step of detecting the ion current, control is performed such that;

the bias voltage is increased by the ion-current-detection bias voltage control device such that a potential of the first electrode becomes a positive voltage; and

the bias voltage is decreased by the ion-current-detection bias voltage control device at an end of a period in which the spark discharge is stopped by the circulation device.

19. The method for controlling the internal combustion engine according to claim 18, wherein

in the step of detecting the ion current, a decreasing speed of the bias voltage is controlled by the ion-current-detection bias voltage control device such that the potential of the first electrode becomes a constant positive voltage.