Control device for internal combustion engine

Abstract

A control device for an internal combustion engine which does not require fitting of a feed forward term on an occasion of calculation of a fuel amount to be supplied at a time of temperature raising control is provided. According to the present embodiment, by feed forward control using a steady-state DPF model and a steady-state CCO model, a basic amount (feed forward term) of a fuel amount Q inj that is added from a fuel injector 20 in the temperature raising control can be calculated. Namely, the feed forward term can be calculated without depending on a control map. If the feed forward term can be calculated without depending on the control map, fitting of the feed forward term with use of the controlling map is not required.

1 . A control device for an internal combustion engine, comprising:
 a first purifying device that is provided in an exhaust passage of the internal combustion engine and has an oxidation catalyst function;   a second purifying device that is provided downstream of the first purifying device, in the exhaust passage;   a fuel supply device that supplies fuel to upstream of the first purifying device; and   a control device that controls a temperature of the second purifying device to a target temperature by controlling a fuel supply amount from the fuel supply device,   wherein the control device comprises a first model that is constructed based on a relation of a heat balance established in the first purifying device, and a second model that is constructed based on a relation of a heat balance established in the second purifying device,   the first model and the second model are constructed on a precondition that all of the fuel supplied from the fuel supply device is converted into heat in the first purifying device, and all of the converted heat contributes to raising a temperature of the first purifying device, and   the control device is configured to calculate the temperature of the first purifying device by inputting the target temperature into the second model and calculate the fuel supply amount by inputting the calculated temperature into the first model.   
     
     
         2 . The control device for an internal combustion engine according to  claim 1 ,
 wherein the first model is expressed by expression: (1)
     Q*   inj   =H   v   −1   [K   atm,1st ( T*   1st   −T   atm )+ h   1st   A   1st ( T*   1st   −T   1st,us )]  (1)
 
   wherein Q inj * represents the fuel supply amount that is supplied from the fuel supply device in a predetermined steady state, H v  represents a low heating value of HC, K atm,1st  represents a heat transfer coefficient to an atmosphere in the first purifying device, T 1st * represents a temperature of the first purifying device in a predetermined steady state, T atm  represents an atmospheric temperature, h 1st  represents a heat conversion coefficient per channel unit area of the first purifying device, A 1st  represents a channel area of the first purifying device, and T 1st,us  represents an inlet temperature of the first purifying device;   wherein the second model is expressed by expression: (2),
     T*   1st   =T   ref   2nd −( h   2nd   A   2nd ) −1   [Q   exo,2nd,pm ( T   ref   2nd   ,m   pm )− K   atm,2nd ( T   ref   2nd   −T   atm )]  (2)
 
   wherein T 1st * represents the temperature of the first purifying device in a predetermined steady state, T 2   2nd   ref  represents the target temperature of the second purifying device, h 2nd  represents a heat conversion coefficient per channel unit area of the second purifying device, A 2nd  represents a channel area of the second purifying device, Q exo,2nd,pm  represents a heat flow that moves to the second purifying device by heat generation accompanying PM combustion in an exhaust gas, m pm  represents an accumulation amount of PM, K atm,2nd  represents a heat transfer coefficient to an atmosphere in the second purifying device, and T atm  represents an atmospheric temperature.   
     
     
         3 . The control device for an internal combustion engine according to  claim 1 ,
 wherein the control device is configured to correct a fuel supply amount calculated from the first and the second models by increasing and decreasing the fuel supply amount based on a deviation of an actual temperature of the second purifying device and the target temperature.   
     
     
         4 . The control device for an internal combustion engine according to  claim 1 ,
 wherein the control device is configured to correct the fuel supply amount so that the fuel supply amount is an upper limit value or less, which is set based on an exhaust air-fuel ratio, or less.   
     
     
         5 . The control device for an internal combustion engine according to  claim 1 ,
 wherein the control device is configured to correct the fuel supply amount so that the fuel supply amount is an upper limit value or less, which is set based on an allowable amount of hydrocarbon in the exhaust gas, or less.