Multi-stage turbo supercharging system

A control device for a multi-stage turbo supercharging system, wherein the multi-stage turbo supercharging system comprises:

• a plurality of turbochargers to be driven by exhaust gas of an engine;
• a bypass passage which bypasses a turbocharger from among the plurality of turbochargers, in an intake passage or an exhaust passage of the engine;
• a bypass valve disposed in the bypass passages;
• an EGR passage which brings the exhaust passage and the intake passage into communication;
• and
• an EGR valve disposed in the EGR passage,
• the control device comprising:
• an operation mode selection part configured to select an operation mode from among a plurality of operation modes of the engine;
• a bypass valve opening degree map selection part configured to select at least one bypass valve opening degree map in accordance with the operation mode selected by the operation mode selection part, from among a plurality of bypass valve opening degree maps which represent respective relationships between a plurality of control parameters of the engine and a rotation speed of the engine;
• a bypass valve opening degree determination part configured to determine an opening degree command value for the bypass valve on the basis of the bypass valve opening degree map selected by the bypass valve opening degree map selection part and control parameter information representing the plurality of control parameters;
• and
• a bypass valve opening degree control part configured to control the opening degree of the bypass valve on the basis of the opening degree command value for the bypass valve determined by the bypass valve opening degree determination part,
• wherein the plurality of operation modes include:
• a low EGR operation mode;
• and
• a high EGR operation mode in which an EGR rate representing a ratio of a recirculation flow rate of the exhaust gas to the intake passage via the EGR passage to an intake amount of the engine is greater than that in the low EGR operation mode,
• wherein the plurality of bypass valve opening degree maps include a low EGR map corresponding to the low EGR operation mode and a high EGR map corresponding to the high EGR operation mode, and
• wherein the bypass valve opening degree map selection part is configured to select the low EGR map from the plurality of bypass valve opening degree maps if the low EGR operation mode is selected by the operation mode selection part and select the high EGR map from the plurality of bypass valve opening degree maps if the high EGR operation mode is selected by the operation mode selection part.

An operation control program for a multi-stage turbo supercharging system comprising a plurality of turbochargers to be driven by exhaust gas of an engine;

• a bypass passage which bypasses a turbocharger from among the plurality of turbochargers, in an intake passage or an exhaust passage of the engine;
• and a bypass valve disposed in the bypass passage, the operation control program being configured to cause a computer to:
• select an operation mode from among a plurality of operation modes of the engine;
• select at least one bypass valve opening degree map in accordance with the operation mode, from among a plurality of bypass valve opening degree maps which represent respective relationships between a plurality of control parameters of the engine and an opening degree of the bypass valve;
• determine an opening degree command value for the bypass valve on the basis of the bypass valve opening degree map and control parameter information representing the plurality of control parameters;
• and
• control the opening degree of the bypass valve on the basis of the opening degree command value for the bypass valve,
• wherein the plurality of operation modes include;
• a low EGR operation mode;
• and
• a high EGR operation mode in which an EGR rate representing a ratio of a recirculation flow rate of the exhaust gas to the intake passage via the EGR passage to an intake amount of the engine is greater than that in the low EGR operation mode,
• wherein the plurality of bypass valve opening degree maps include a low EGR map corresponding to the low EGR operation mode and a high EGR map corresponding to the high EGR operation mode, and
• wherein the bypass valve opening degree map selection part is configured to select the low EGR map from the plurality of bypass valve opening degree maps if the low EGR operation mode is selected by the operation mode selection part and select the high EGR map from the plurality of bypass valve opening degree maps if the high EGR operation mode is selected by the operation mode selection part.