Control device for internal combustion engine

Patent metadata

Field	Value
Publication number	US-9976497-B2
Application number	US-201415113241-A
Country	US
Kind code	B2
Filing date	Dec 16, 2014
Priority date	Jan 23, 2014
Publication date	May 22, 2018
Grant date	May 22, 2018

Abstract

In an internal combustion engine an air-fuel ratio is switched between at least two target values without generating torque fluctuations, while a deterioration in fuel consumption performance and exhaust performance is suppressed. When a condition for switching a combustion mode from stoichiometric combustion to lean combustion and a condition that the amount of change in a target torque is less than or equal to a predetermined value are satisfied, a target EGR rate is increased towards an EGR limit prior to switching the target air-fuel ratio. The target air-fuel ratio is maintained at the stoichiometric air-fuel ratio until the target EGR rate reaches the EGR limit, and in response to the target EGR rate reaching the EGR limit, the target air-fuel ratio is changed towards a lean air-fuel ratio.

First claim

The invention claimed is:

1. A control device for an internal combustion engine that is configured to be capable of selecting operation according to a first air-fuel ratio and operation according to a second air-fuel ratio that is leaner than the first air-fuel ratio, comprising:
first means for, in a case where a condition for switching an operation mode from the operation according to the first air-fuel ratio to the operation according to the second air-fuel ratio is satisfied, controlling the internal combustion engine so as to increase an EGR rate in a continuous manner up to a switching-time target EGR rate; and
second means for, in a case where the condition is satisfied, controlling the internal combustion engine so as to maintain an air-fuel ratio at the first air-fuel ratio until the EGR rate reaches the switching-time target EGR rate, and in response to the EGR rate reaching the switching-time target EGR rate, to cause the air-fuel ratio to change in a continuous manner from the first air-fuel ratio towards the second air-fuel ratio.

2. The control device for an internal combustion engine according to claim 1 , wherein the first means comprises means for controlling the internal combustion engine so that, in response to a gas-fuel ratio reaching an equal value to a value of the second air-fuel ratio, the internal combustion engine causes the EGR rate to decrease in a continuous manner from the switching-time target EGR rate while maintaining the gas-fuel ratio at the value of the second air-fuel ratio.

3. The control device for an internal combustion engine according to claim 1 , wherein:
the second means comprises:
target air-fuel ratio switching means for switching a target air-fuel ratio from the first air-fuel ratio to the second air-fuel ratio in response to the condition being satisfied,
target air amount calculation means for back-calculating a target air amount for achieving a target torque based on the target air-fuel ratio from the target torque,
first actuator control means for determining an operation amount of a first actuator that changes an amount of air that is drawn into a cylinder based on the target air amount, and operating the first actuator in accordance with the operation amount, and
second actuator control means for determining a fuel supply amount based on the target air-fuel ratio, and operating a second actuator that supplies fuel into a cylinder in accordance with the fuel supply amount; and
the target air-fuel ratio switching means is configured so as to, in a case where the condition is satisfied, maintain the target air-fuel ratio at the first air-fuel ratio until the EGR rate reaches the switching-time target EGR rate, and to cause the target air-fuel ratio to change in a continuous manner from the first air-fuel ratio towards the second air-fuel ratio in response to the EGR rate reaching the switching-time target EGR rate.

4. The control device for an internal combustion engine according to claim 3 , wherein:
the first means comprises:
target EGR rate calculation means for calculating a target EGR rate in accordance with an operating condition of the internal combustion engine, and
third actuator control means for determining an operation amount of a third actuator that adjusts the EGR rate based on the target EGR rate, and operating the third actuator in accordance with the operation amount; and
the target EGR rate calculation means is configured so as to increase the target EGR rate in a continuous manner up to the switching-time target EGR rate in response to the condition being satisfied.

5. The control device for an internal combustion engine according to claim 4 , wherein:
the target EGR rate calculation means is configured so as to decrease the target EGR rate in a continuous manner from the switching-time target EGR rate in response to a gas-fuel ratio reaching an equal value to the second air-fuel ratio; and
the target air-fuel ratio switching means is configured so as to, in response to the gas-fuel ratio reaching an equal value to the second air-fuel ratio, change the target air-fuel ratio within a range from the first air-fuel ratio to the second air-fuel ratio so that the gas-fuel ratio is maintained at the second air-fuel ratio.

6. The control device for an internal combustion engine according to claim 1 , wherein the switching-time target EGR rate is an EGR rate that corresponds to an EGR limit.

7. The control device for an internal combustion engine according to claim 1 , further comprising restriction means for restricting control by the first means in a case where a condition that an amount of change in a target torque is equal to or less than a predetermined value is not satisfied.

8. A control device for an internal combustion engine that is configured to be capable of selecting operation according to a first air-fuel ratio and operation according to a second air-fuel ratio that is leaner than the first air-fuel ratio, comprising an engine controller programmed to:
in a case where a condition for switching an operation mode from the operation according to the first air-fuel ratio to the operation according to the second air-fuel ratio is satisfied, control the internal combustion engine so as to increase an EGR rate in a continuous manner up to a switching-time target EGR rate; and
in a case where the condition is satisfied, control the internal combustion engine so as to maintain an air-fuel ratio at the first air-fuel ratio until the EGR rate reaches the switching-time target EGR rate, and in response to the EGR rate reaching the switching-time target EGR rate, to cause the air-fuel ratio to change in a continuous manner from the first air-fuel ratio towards the second air-fuel ratio.

Assignees

• Toyota Motor Co Ltd

Inventors

• Matsumoto Yosuke
• Adachi Noriyasu

Classifications

• F02D2250/36

  Control for minimising NOx emissions · CPC title

• F02D41/307

  to avoid torque shocks · CPC title

• F02M26/53

  using electric actuators, e.g. solenoids · CPC title

• F02M26/51

  EGR valves combined with other devices, e.g. with intake valves or compressors (combined with intake air throttles F02M26/64) · CPC title

• Y02T10/47

  Cross-Sectional Technologies · mapped topic