Engine equipment

Abstract

To start a fuel increase in an engine to suppress overheating of a catalyst at more appropriate timing.SOLUTION: An engine device comprises an engine that has a combustion chamber, an exhaust port, an exhaust manifold, and an exhaust pipe, and outputs power using a hydrocarbon-based fuel, a catalyst attached to the engine's exhaust pipe, and a control unit that performs a fuel increase in the engine to suppress overheating of the catalyst from when a start condition is met until an end condition is met. The control unit assumes that the catalyst is in a non-deteriorated state and estimates the temperature of the catalyst as a first temperature on the basis of a number of parameters including an inlet gas temperature of the catalyst, the heating value of combustion of hydrocarbon in the catalyst, and the heating value of oxidation-reduction reaction in the catalyst. The start condition is that the first temperature reaches or exceeds a first predetermined temperature.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] This disclosure relates to an engine device.

Background Art

[0002] Conventionally, as this type of engine device, there has been proposed one that estimates the temperature of exhaust gas discharged from the combustion chamber of the engine and flowing through the exhaust port when fuel injection and ignition of the engine are performed (see, for example, Patent Document 1). In this engine device, in the case of stoichiometry, the temperature of the exhaust gas is estimated based on the first thermal energy based on the combustion gas temperature, the combustion gas amount, and the combustion gas specific heat. In the case of lean, the temperature of the exhaust gas is estimated based on the first thermal energy and the second thermal energy based on the air temperature, the excess air amount with respect to stoichiometry, and the air specific heat. In the case of rich, the temperature of the exhaust gas is estimated based on the first thermal energy and the third thermal energy based on the fuel temperature, the excess fuel amount with respect to stoichiometry, the fuel specific heat, and the latent heat of fuel evaporation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such an engine device, when the catalyst attached to the exhaust pipe of the engine becomes relatively high in temperature, in order to suppress overheating of the catalyst, the fuel amount of the engine is increased, and thus it is required to start this at a more appropriate timing. The main object of the engine device of this disclosure is to start increasing the fuel amount of the engine for suppressing overheating of the catalyst at a more appropriate timing.

Means for Solving the Problems

[0005] <000003> The engine device of this disclosure employs the following means to achieve the main objective described above. The engine device of this disclosure comprises an engine having a combustion chamber, an exhaust port, an exhaust manifold, and an exhaust pipe, and outputting power using a hydrocarbon-based fuel; a catalyst attached to the exhaust pipe; and a control device that increases the amount of fuel supplied to the engine to suppress overheating of the catalyst from the time a start condition is met until a termination condition is met, wherein the control device assumes that the catalyst is in an undegraded state and estimates the temperature of the catalyst as a first temperature based on a plurality of parameters including the inlet gas temperature of the catalyst, the amount of heat generated by the combustion of hydrocarbons in the catalyst, and the amount of heat generated by the oxidation-reduction reaction in the catalyst, and the start condition is the condition in which the first temperature reaches or exceeds a first predetermined temperature.

[0006] In the engine system of this disclosure, assuming that the catalyst is in an undegraded state, the catalyst temperature is estimated as a first temperature based on multiple parameters including the catalyst's inlet gas temperature, the heat generated by the combustion of hydrocarbons in the catalyst, and the heat generated by the oxidation-reduction reaction in the catalyst. The starting condition is when the first temperature reaches or exceeds a first predetermined temperature. By estimating the first temperature assuming that the catalyst is in an undegraded state, the first temperature is higher than when the first temperature is estimated assuming that the catalyst is in a degraded state, allowing the engine's fuel injection to suppress catalyst overheating to be started at a more appropriate timing. As a result, catalyst overheating can be suppressed more effectively. Here, "undegraded state" means a state in which there is no degradation (a state in which the degree of degradation is below a predetermined level), and examples include a new state or a state after break-in.

[0007] In the engine device of this disclosure, the control device assumes that the catalyst is in an undegraded state and the air-fuel ratio is stoichiometric, and estimates the temperature of the catalyst as the second temperature without using the amount of heat generated by the oxidation-reduction reaction in the catalyst from among the plurality of parameters, and the termination condition may be the condition in which the second temperature falls below the second predetermined temperature, which is less than or equal to the first predetermined temperature.

[0008] In the engine device of the present disclosure, the control device may estimate the first and second temperatures using the amount of heat transferred between the exhaust gas passing through the exhaust manifold and the exhaust manifold, and the amount of heat transferred between the inlet gas of the catalyst and the catalyst. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of the engine device 10 according to the embodiment of the present disclosure. [Figure 2] This is a processing block diagram for the first method, 100A. [Figure 3] This is a processing block diagram for the first method, 100A. [Figure 4] This is a processing block diagram for the second method, 100B. [Figure 5] This is a processing block diagram for the second method, 100B. [Figure 6] This is a flowchart showing an example of a processing routine. [Modes for carrying out the invention]

[0010] Embodiments of this disclosure will be described with reference to the drawings. Figure 1 is a schematic diagram of the engine device 10 according to an embodiment of this disclosure. As shown in the figure, the engine device 10 of the embodiment comprises an engine 12 and an electronic control unit (hereinafter referred to as "ECU") 70. The engine device 10 is installed, for example, in an engine-powered vehicle that runs using power from the engine 12, or in a hybrid vehicle that has an engine 12 in addition to a motor.

[0011] Engine 12 is configured as a multi-cylinder internal combustion engine that outputs power through four strokes: intake, compression, expansion (explosive combustion), and exhaust, using hydrocarbon (HC) fuels such as gasoline or diesel. Engine 12 has a port injection valve 27p that injects fuel into the intake port 26p and an in-cylinder injection valve 27d that injects fuel into the combustion chamber 29, and can be operated in port injection mode, in-cylinder injection mode, or shared injection mode. In port injection mode, air cleaned by the air cleaner 22 is drawn into the intake manifold 23, passes through the throttle valve 24, and then through the surge tank 25, intake manifold 26m, and intake port 26p in that order, while fuel is injected from the port injection valve 27p to mix the air and fuel. This mixture is drawn into the combustion chamber 29 via the intake valve 28 and explodes and burns due to an electric spark from the spark plug 30, and the reciprocating motion of the piston 32 pushed down by the energy from the explosive combustion is converted into rotational motion of the crankshaft 14. In the in-cylinder injection mode, air is drawn into the combustion chamber 29, similar to the port injection mode, and fuel is injected from the in-cylinder injection valve 27d in one or multiple bursts during the intake and compression strokes. This fuel is then explosively combusted by an electric spark from the spark plug 30 to obtain rotational motion of the crankshaft 14. In the shared injection mode, fuel is injected from the port injection valve 27p when air is drawn into the combustion chamber 29, and also from the in-cylinder injection valve 27d in one or multiple bursts during the intake and compression strokes. This fuel is then explosively combusted by an electric spark from the spark plug 30 to obtain rotational motion of the crankshaft 14. The exhaust gas (exhaust gas) discharged from the combustion chamber 29 through the exhaust valve 33, exhaust port 34p, and exhaust manifold 34m to the exhaust pipe 35 is then discharged to the outside air via the purification device 36 and PM filter 37. The purification device 36 has a catalyst (three-way catalyst) 36a that purifies harmful components such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) in the exhaust gas. The PM filter 37 collects particulate matter (PM) such as soot in the exhaust gas. Alternatively, a four-way catalyst that combines the purification function of the three-way catalyst with the collection function for particulate matter may be used instead of the PM filter 37.

[0012] The ECU70 is a microcomputer equipped with a CPU, ROM, RAM, flash memory, input / output ports, and communication ports, as well as various drive circuits and various logic ICs. The ECU70 receives input from the crank position sensor 14a, which provides the rotational position (crank angle θcr) of the crankshaft 14 of the engine 12, and from the water temperature sensor 15, which provides the temperature of the coolant in the engine 12 (coolant temperature Tw). The ECU70 also receives input from the cam position sensor 16, which provides the rotational position (cam angles θci, θco) of the intake camshaft that opens and closes the intake valve 28 and the exhaust camshaft that opens and closes the exhaust valve 33. The ECU70 also receives input from the airflow meter 23a and temperature sensor 23t, respectively, which are mounted upstream of the throttle valve 24 in the intake manifold 23, which provide the intake air volume Qa and intake air temperature Ta, from the airflow meter 23a and temperature sensor 23t, respectively, which provide the position of the throttle valve 24 (throttle opening TH) from the throttle position sensor 24a, and from the pressure sensor 25a mounted on the surge tank 25, which provides the surge pressure Ps. The ECU70 also receives input from the front air-fuel ratio AF1 and rear air-fuel ratio AF2 from the front air-fuel ratio sensor 37a and rear air-fuel ratio sensor 37b, which are installed upstream of the exhaust pipe 35 purification device 36 and between the purification device 36 and the PM filter 36, respectively, as well as the differential pressure ΔP (the differential pressure between the upstream and downstream sides) across the PM filter 36 from the differential pressure sensor 36a.

[0013] The ECU 70 outputs control signals to the throttle valve 24, port injection valve 27p, in-cylinder injection valve 27d, and spark plug 30 of the engine 12. The ECU 70 calculates the rotational speed Ne of the engine 12 based on the crank angle θcr, and calculates the load ratio KL of the engine 12 based on the intake air volume Qa and the rotational speed Ne of the engine 12. The load ratio KL is defined as the ratio of the volume of air actually inhaled in one cycle to the stroke volume per cycle of the engine 12. The ECU 70 estimates the exhaust (exhaust gas) flow velocity Vg from the combustion chamber 29 based on the rotational speed Ne of the engine 12.

[0014] The ECU70 controls the operation of the engine 12 (intake air volume control, fuel injection control, and ignition control) based on the target load ratio KL* of the engine 12, which is determined by the accelerator opening and vehicle speed. For intake air volume control, the ECU70 controls the throttle valve 24 by setting the target opening TH* of the throttle valve 24 so that the load ratio KL becomes the target load ratio KL*. For fuel injection control, the ECU70 sets the injection ratio Rp,Rd (Rp+Rd=1) based on the rotational speed Ne and load ratio KL of the engine 12, and sets the total target injection amount Qf* as the product of the basic injection amount based on the load ratio KL and the correction coefficient for air-fuel ratio feedback control to ensure that the front air-fuel ratio AF1 becomes the target air-fuel ratio AF*. The ECU70 controls the port injection valve 27p and the in-cylinder injection valve 27d by setting the target injection amounts Qfp* and Qfd* of the port injection valve 27p and the in-cylinder injection valve 27d as the product of the injection ratio Rp,Rd and the total target injection amount Qf*. In ignition control, the target ignition timing Ti* of the spark plug 30 is set based on the engine speed Ne and target load ratio KL* of the engine 12, and the spark plug 30 is controlled accordingly.

[0015] Next, the operation of the engine device 10 of the embodiment, in particular, the estimation of the temperature of the leading edge of the catalyst 36a by the first and second methods 100A and 100B will be described. Hereinafter, the temperatures of the leading edge of the catalyst 36a obtained by the first and second methods 100A and 100B will be collectively referred to as temperature Tcf, or as temperature Tcf1 and Tcf2, respectively. The first method 100A estimates the temperature Tcf1 of the leading edge of the catalyst 36a by considering the effects of the air-fuel ratio of the combustion chamber 29 and catalyst 36a, as well as the oxidation-reduction reaction in catalyst 36a, whereas the second method 100B estimates the temperature Tcf2 of the leading edge of catalyst 36a by assuming that the air-fuel ratio is stoichiometric and without considering these effects. Thus, the first and second methods 100A and 100B differ from each other in that they estimate the temperature Tcf2 of the leading edge of catalyst 36a by assuming that the air-fuel ratio is stoichiometric.

[0016] Figures 2 and 3 are processing block diagrams for the first method 100A, and Figures 4 and 5 are processing block diagrams for the second method 100B. These will be explained in order below. In the processing units of the first and second methods 100A and 100B, the air-fuel ratio of the combustion chamber 29 and catalyst 36a may be determined using the front air-fuel ratio AF1, or an estimated air-fuel ratio based on the intake air amount Qa and the total fuel injection amount of the port injection valve 27p and the in-cylinder injection valve 27d may be used.

[0017] The first method 100A will now be explained. As shown in Figures 2 and 3, the processing block of the first method 100A has processing units 110 to 320. Processing unit 110 estimates the combustion chamber outlet temperature Teccs by applying the rotational speed Ne and load factor KL to a map that has been predetermined by experiments and analyses as the relationship between rotational speed Ne, load factor KL, and the combustion chamber outlet temperature Teccs when the engine 12 is assumed to be in a steady state. Here, the steady state of the engine 12 is when the air-fuel ratio in the combustion chamber 29 is stoichiometric and the ignition timing is at the optimal ignition timing (MBT: Minimum spark advance for Best Torque). In this map, the combustion chamber outlet temperature Teccs is determined to be higher as the rotational speed Ne increases and as the load factor KL increases.

[0018] The processing unit 112 applies the rotational speed Ne, load factor KL, and ignition retardation amount to a map predetermined by experiments and analyses, which shows the relationship between rotational speed Ne, load factor KL, ignition retardation amount, and temperature rise due to retardation, to estimate the temperature rise due to retardation. Here, the ignition retardation amount is the amount of retardation relative to the optimal ignition timing. The temperature rise due to retardation is the increase in the outlet gas temperature of the combustion chamber 29 based on the ignition retardation amount. In this map, the temperature rise due to retardation is determined to increase as rotational speed Ne increases, load factor KL increases, and ignition retardation amount increases. The processing unit 114 calculates the first temperature T1 by adding the temperature rise due to retardation obtained by the processing unit 112 to the outlet gas temperature Tecgs of the combustion chamber 29 obtained by the processing unit 110.

[0019] The processing unit 120 estimates the product of the amount of unburned fuel and the fuel temperature as the heat amount of the unburned fuel. Here, the amount of unburned fuel is estimated within a range of 0 or more based on the intake air amount Qa and the total fuel injection amount of the port injection valve 27p and the in-cylinder injection valve 27d. The processing unit 122 estimates the product of the amount of unburned fuel and a coefficient as the heat of vaporization amount of the unburned fuel. Here, the coefficient is determined in advance by experiments, analysis, or the like. The processing unit 124 calculates, as the second temperature T2, a value obtained by adding the temperature conversion value (value converted into a temperature change amount) of the heat amount of the unburned fuel obtained by the processing unit 120 to the first temperature T1 obtained by the processing unit 114 and then subtracting the temperature conversion value of the heat of vaporization amount of the unburned fuel obtained by the processing unit 122.

[0020] The processing unit 130 estimates, as the temperature of the air passing through the combustion chamber 29, a value obtained by adding the product of the temperature of the exhaust port 34p and the temperature influence coefficient to the coolant temperature Tw. Here, based on the fact that the temperature of the exhaust port 34p is substantially equal to the temperature Tem of the exhaust manifold 34m, the temperature (previous Tem) of the exhaust manifold 34m obtained by the processing unit 202 last time is used as the temperature of the exhaust port 34p. The temperature influence coefficient is obtained by applying the exhaust gas flow rate Vg to a map determined in advance by experiments, analysis, or the like as the relationship between the exhaust gas flow rate Vg and the temperature influence coefficient to derive the temperature influence coefficient. In this map, the temperature influence coefficient is determined such that it becomes larger as the exhaust gas flow rate Vg is lower.

[0021] The processing unit 132 estimates the product of the temperature of the air passing through the combustion chamber 29 obtained by the processing unit 130 and the excess air amount as the heat amount of the excess air. Here, the excess air amount is estimated within a range of 0 or more based on the intake air amount Qa and the total fuel injection amount of the port injection valve 27p and the in-cylinder injection valve 27d. The processing unit 134 calculates, as the third temperature T3, a value obtained by adding the temperature conversion value of the heat amount of the excess air obtained by the processing unit 132 to the first temperature T1 obtained by the processing unit 114.

[0022] When the air-fuel ratio in the combustion chamber 29 is rich, the processing unit 140 estimates the second temperature T2 obtained by the processing unit 124 as the exhaust gas temperature Tecgo of the combustion chamber 29, corresponding to the operating state of the engine 22 (air-fuel ratio and ignition retardation amount in the combustion chamber 29). On the other hand, when the air-fuel ratio in the combustion chamber 29 is lean, the processing unit 140 estimates the third temperature T3 obtained by the processing unit 134 as the exhaust gas temperature Tecgo of the combustion chamber 29.

[0023] The processing unit 150 applies the combustion chamber 29 outlet temperature Tecgo and the exhaust gas flow velocity Vg to a map predetermined by experiments and analyses, which shows the relationship between the combustion chamber 29 outlet temperature Tecgo, the exhaust gas flow velocity Vg, and the reaction rate Rexhc of unburned HC at the exhaust port 34p, exhaust manifold 34m, and exhaust pipe 35, obtained by the processing unit 140, to estimate the reaction rate Rexhc of unburned HC. Here, the reaction rate Rexhc of unburned HC at the exhaust port 34p, exhaust manifold 34m, and exhaust pipe 35 is the proportion of unburned HC contained in the exhaust gas from the combustion chamber 29 that burns at the exhaust port 34p, exhaust manifold 34m, and exhaust pipe 35. In this map, the reaction rate Rexhc of unburned HC is set to increase as the combustion chamber 29 outlet temperature Tecgo increases and the exhaust gas flow velocity Vg decreases.

[0024] The processing unit 160 estimates the amount of unburned HC at low water temperatures as the product of the temperature difference between the coolant temperature Tw and the reference water temperature and the HC increase coefficient at low water temperatures. Here, low water temperature refers to the time when the coolant temperature Tw is lower than the reference water temperature. As the reference water temperature, for example, the temperature at which the engine 12 is determined to be warmed up is used. The HC increase coefficient at low water temperatures is predetermined by experiments or analyses. Note that the amount of unburned HC at low water temperatures is set to 0 if the coolant temperature Tw is equal to or higher than the reference water temperature. The processing unit 162 estimates the amount of unburned HC due to ignition retardation as the product of the ignition retardation amount and the sensitivity coefficient. Here, the amount of unburned HC due to ignition retardation is the amount of unburned HC based on the ignition retardation amount. The sensitivity coefficient is predetermined by experiments or analyses. The processing unit 164 calculates the amount of unburned HC as the sum of the amount of unburned HC at low water temperature obtained by the processing unit 160 and the amount of unburned HC due to the ignition timing retardation effect obtained by the processing unit 162. The processing unit 166 estimates the maximum value of the heat generation of unburned HC, Qexhcmax, as the product of the amount of unburned HC obtained by the processing unit 164 and the heat generation coefficient. Here, the heat generation coefficient is predetermined by experiments or analyses.

[0025] The processing unit 170 calculates the product of the reaction rate of unburned HC, Rexhc, obtained by the processing unit 150, and the maximum calorific value of unburned HC, Qexhcmax, obtained by the processing unit 166, as the calorific value of unburned HC. The processing unit 180 calculates the output gas temperature of exhaust port 34p, Tepg, by adding the temperature-converted value of the calorific value of unburned HC obtained by the processing unit 170 to the output gas temperature of combustion chamber 29, Tecgo, obtained by the processing unit 140.

[0026] The processing unit 200 estimates the amount of heat transferred from the exhaust gas passing through the exhaust manifold 34m to the exhaust manifold 34m as the product of the exhaust gas outlet temperature Tepg obtained by the processing unit 180, the heat transfer coefficient, and the heat transfer ratio. Here, the heat transfer coefficient is predetermined by experiment or analysis. The heat transfer ratio is obtained by applying the exhaust gas flow velocity Vg to a map predetermined by experiment or analysis as the relationship between the exhaust gas flow velocity Vg and the heat transfer coefficient, and deriving the heat transfer coefficient. The processing unit 202 estimates the temperature of the exhaust manifold 34m, Tem, as the value obtained by the processing unit 200 by adding the amount of heat transferred from the exhaust gas passing through the exhaust manifold 34m to the exhaust manifold 34m (previous Tem) obtained by the processing unit 202.

[0027] The processing unit 204 estimates the exhaust manifold 34m's outlet gas temperature Tempg (catalyst 36a's inlet gas temperature) as the product of the first temperature difference ΔT1 obtained by the processing unit 200 and the heat transfer amount from the exhaust gas passing through the exhaust manifold 34m to the exhaust manifold 34m, obtained by the processing unit 200, from the exhaust port 34p's outlet gas temperature Tempg (catalyst 36a's inlet gas temperature) obtained by the processing unit 180. The processing unit 210 estimates the first temperature difference ΔT1 as the product of the first temperature difference ΔT1 obtained by the processing unit 210 and the heat transfer coefficient, which represents the heat transfer amount from the exhaust manifold 34m's outlet gas temperature Tempg (catalyst 36a's inlet gas temperature) obtained by the processing unit 204 and the temperature difference at the front end of the catalyst 36a, obtained by the processing unit 320. The processing unit 212 estimates the heat transfer amount from the exhaust gas at the exhaust manifold 34m (catalyst 36a's inlet gas) to the front end of the catalyst 36a as the product of the first temperature difference ΔT1 obtained by the processing unit 210 and the heat transfer coefficient. Here, the heat transfer coefficient is predetermined by experimentation or analysis.

[0028] The processing unit 220 estimates the second temperature difference ΔT2 by subtracting the temperature of the central part of the catalyst 36a (previously obtained by a separate process (not shown)) from the temperature of the front end of the catalyst 36a (previously obtained by the processing unit 320 (previously obtained Tcf). The method for estimating the temperature Tcc of the central part of the catalyst 36a will be described later. The processing unit 222 estimates the amount of heat transferred from the front end of the catalyst 36a to the central part of the catalyst 36a by subtracting the amount of heat transferred from the front end of the catalyst 36a to the central part of the catalyst 36a (obtained by the processing unit 222) from the amount of heat transferred from the exhaust gas of the exhaust manifold 34m (inlet gas of the catalyst 36a) to the front end of the catalyst 36a (obtained by the processing unit 212).

[0029] The processing unit 240 estimates the temperature Tccs at the center of the catalyst 36a by applying the rotational speed Ne and load factor KL to a map predetermined by experiments and analyses, which represents the relationship between rotational speed Ne, load factor KL, and the temperature Tccs at the center of the catalyst 36a when the engine 12 is in a steady state. In this map, the temperature Tccs at the center of the catalyst 36a is determined to increase as the rotational speed Ne increases and the load factor KL increases. The processing unit 242 calculates the third temperature difference ΔT3 by subtracting the exhaust gas temperature Tecgs of the combustion chamber 29 obtained by the processing unit 110 from the temperature Tccs at the center of the catalyst 36a obtained by the processing unit 240.

[0030] The processing unit 250 subtracts the reaction rate of unburned HC, Rexhc, obtained by the processing unit 150, from the value 1. The processing unit 252 estimates the product of the maximum value of unburned HC heat output Qexhcmax obtained by the processing unit 166 and the value (1-Rexhc) obtained by the processing unit 250 as the heat output of unburned (unreacted) HC in the exhaust port 34p, exhaust manifold 34m, and exhaust pipe 35. The processing unit 260 estimates the sum of the third temperature difference ΔT3 obtained by the processing unit 242 and the heat output of unreacted HC in the exhaust port 34p, exhaust manifold 34m, and exhaust pipe 35 obtained by the processing unit 252 as the heat output of HC combustion in the entire catalyst 36a.

[0031] The processing unit 270 applies the previous temperature of the catalyst 36a front end (previous Tcf) and the exhaust gas flow rate Vg to a map predetermined by experiments and analyses, which shows the relationship between the temperature of the catalyst 36a front end (previous Tcf) obtained by the processing unit 320 in the previous test, the exhaust gas flow rate Vg, and the reaction rate Rcfhc of unburned HC at the catalyst 36a front end, in order to estimate the reaction rate Rcfhc of unburned HC. Here, the reaction rate Rcfhc of unburned HC at the catalyst 36a front end is the proportion of HC that burns at the catalyst 36a front end out of the unburned HC contained in the inlet gas of the catalyst 36a. In this map, the reaction rate Rcfhc of unburned HC is determined to increase as the previous temperature of the catalyst 36a front end (previous Tcf) increases and as the exhaust gas flow rate Vg decreases. The processing unit 280 estimates the amount of heat generated by HC combustion at the leading end of catalyst 36a as the product of the amount of heat generated by HC combustion at the entire catalyst 36a obtained by the processing unit 260 and the reaction rate Rcfhc of unburned HC at the leading end of catalyst 36a obtained by the processing unit 270.

[0032] The processing unit 290 estimates the amount of fuel burned at the front end of catalyst 36a by dividing the change in the oxygen storage capacity (OSA) of catalyst 36a, ΔOSA, by the product of the stoichiometric air-fuel ratio and the oxygen content in the air. Here, the change in the oxygen storage capacity of catalyst 36a, ΔOSA, is estimated as the current value of the oxygen storage capacity of catalyst 36a minus the previous value. The oxygen storage capacity of catalyst 36a is estimated as the previous oxygen storage capacity of catalyst 34a plus a correction value. The correction value is estimated based on the air-fuel ratio within catalyst 36a, the reaction rate of catalyst 36a as a whole, and the exhaust gas flow velocity Vg. The reaction rate of unburned HC in catalyst 36a as a whole is estimated in the same way as the reaction rate of unburned HC at the front end of catalyst 36a, Rcfhc. The processing unit 292 estimates the total heat of combustion (total reaction heat) for the reduction reaction (HC combustion with oxygen release) at the front end of the catalyst 36a as calculated by the product of the amount of fuel burned at the front end of the catalyst 36a obtained by the processing unit 290 and the amount of heat of combustion per unit of fuel (e.g., 1g). Here, the amount of heat of fuel combustion is predetermined by experiments or analysis. The processing unit 294 estimates the heat of combustion (reaction heat) for the reduction reaction (oxygen release) at the front end of the catalyst 36a as calculated by the product of the total heat of combustion for the reduction reaction at the front end of the catalyst 36a obtained by the processing unit 292 and the reaction rate Rcfhc of unburned HC at the front end of the catalyst 36a obtained by the processing unit 270.

[0033] The processing unit 300 estimates the change in the oxygen storage capacity ΔOSA of catalyst 36a by the oxygen storage capacity (OSC) of catalyst 36a as the percentage change in oxygen storage capacity relative to the maximum oxygen storage capacity of catalyst 36a. The oxygen storage capacity of catalyst 36a is predetermined by experiments or analysis. The processing unit 302 estimates the total heat generated by the oxidation reaction (oxygen adsorption) of catalyst 36a as the total heat of reaction, calculated by the product of the percentage change in oxygen storage capacity relative to the maximum oxygen storage capacity of catalyst 36a obtained by the processing unit 300 and the temperature rise of catalyst 36a when the oxygen storage capacity (OSC) of catalyst 36a changes. Here, the temperature rise of catalyst 36a when the oxygen storage capacity of catalyst 36a changes is predetermined by experiments or analysis. The processing unit 304 estimates the heat of the oxidation reaction (oxygen adsorption) at the leading end of catalyst 36a as the heat of the oxidation reaction (heat of reaction) obtained by processing unit 304 by the product of the total heat of the oxidation reaction in the entire catalyst 36a obtained by processing unit 302 and the reaction rate Rcfhc of unburned HC at the leading end of catalyst 36a obtained by processing unit 270.

[0034] When the air-fuel ratio in catalyst 36a is rich, the processing unit 310 estimates the amount of heat generated by the reduction reaction at the front end of catalyst 36a, obtained by the processing unit 294, as the amount of heat generated by the oxidation-reduction reaction at the front end of catalyst 36a. On the other hand, when the air-fuel ratio in catalyst 36a is lean, the processing unit 304 estimates the amount of heat generated by the oxidation reaction at the front end of catalyst 36a, obtained by the processing unit 304, as the amount of heat generated by the oxidation-reduction reaction at the front end of catalyst 36a. The processing unit 320 estimates the temperature Tcf at the front end of catalyst 36a as the sum of the exhaust gas temperature Temg (inlet gas temperature of catalyst 36a) of the exhaust manifold 34m obtained by the processing unit 204, the temperature-converted value of the change in heat at the front end of catalyst 36a obtained by the processing unit 230, the temperature-converted value of the amount of heat generated by HC combustion at the front end of catalyst 36a obtained by the processing unit 280, and the temperature-converted value of the amount of heat generated by the oxidation-reduction reaction at the front end of catalyst 36a obtained by the processing unit 310.

[0035] As described above, in the process of estimating the temperature Tcf at the front end of catalyst 36a, the processing unit 220 uses the temperature of the central part of catalyst 36a (previous Tcc) obtained in the previous step. Here, the temperature Tcc at the central part of catalyst 36a can be estimated in the same way as the temperature Tcf at the front end of catalyst 36a. However, the following processing needs to be changed (reinterpreted) for the processing block diagram of the first method 100A in Figures 2 and 3. For processing unit 210, the process is changed from subtracting the temperature of the front end of catalyst 36a (previous Tcf) obtained in the previous step from the exhaust gas temperature Temg (inlet gas temperature of catalyst 36a) of the exhaust manifold 34m to subtracting the temperature of the central part of catalyst 36a (previous Tcc) obtained in the previous step from the temperature Tcf at the front end of catalyst 36a. For processing unit 212, the process is changed from estimating the amount of heat transferred from the exhaust gas (inlet gas of catalyst 36a) of the exhaust manifold 34m to the front end of catalyst 36a to estimating the amount of heat transferred from the front end of catalyst 36a to the central part of catalyst 36a. Although the gas emitted from the front end of catalyst 36a also contains heat, the amount of heat transferred between the components (between the front end of catalyst 36a and the central part of catalyst 36a) is sufficiently small (minute), so in this embodiment, it is not considered (negligible).

[0036] For processing unit 220, the process is changed from subtracting the temperature of the central part of catalyst 36a (previously obtained Tcc) from the temperature of the front part of catalyst 36a (previously obtained Tcf) obtained previously to subtracting the temperature of the rear end of catalyst 36a (previously obtained Tcr) from the temperature of the central part of catalyst 36a (previously obtained Tcc) obtained previously. Note that the temperature Tcr of the rear end of catalyst 36a can be estimated in the same way as the temperature Tcf of the front end of catalyst 36a and the temperature Tcc of the central part of catalyst 36a. For processing unit 222, the process is changed from estimating the amount of heat transferred from the front end of catalyst 36a to the central part of catalyst 36a to estimating the amount of heat transferred from the central part of catalyst 36a to the rear end of catalyst 36a. For processing unit 230, the process is changed from estimating the amount of heat change at the front end of catalyst 36a to estimating the amount of heat change at the central part of catalyst 36a. The processing unit 270 is changed from estimating the reaction rate Rcfhc of unburned HC at the leading end of catalyst 36a to estimating the reaction rate Rcchc of unburned HC at the central part of catalyst 36a. The processing unit 320 is changed from estimating the temperature Tcf at the leading end of catalyst 36a to estimating the temperature Tcf at the central part of catalyst 36a.

[0037] Next, we will explain the second method 100B. As shown in Figures 4 and 5, the processing block of the second method 100B differs from the processing block of the first method 100A shown in Figures 2 and 3 in that the processing units 120-140 and 290-310 are removed, and the processing unit 320 is replaced with processing unit 320B. This is because, as mentioned above, in estimating the temperature Tcf at the front end of the catalyst 36a, the first method 100A considers the effects of the air-fuel ratio of the combustion chamber 29 and catalyst 36a, as well as the oxidation-reduction reaction in catalyst 36a, whereas the second method 100B assumes that the air-fuel ratio is stoichiometric and does not consider these effects.

[0038] In the second method 100B, the first temperature T1 obtained by the processing unit 114 is estimated as the exhaust gas temperature Tecgo of the combustion chamber 29 according to the operating conditions of the engine 12 (ignition retardation amount, and the air-fuel ratio in the combustion chamber 29 is assumed to be stoichiometric). Furthermore, in the processing unit 320B, the exhaust gas temperature Temg (inlet gas temperature of the catalyst 36a) of the exhaust manifold 34m obtained by the processing unit 204 is added to the temperature-converted value of the change in heat quantity at the front end of the catalyst 36a obtained by the processing unit 230 and the temperature-converted value of the calorific value of HC combustion at the front end of the catalyst 36a obtained by the processing unit 280, and this value is estimated as the temperature Tcf at the front end of the catalyst 36a.

[0039] In this embodiment, among the first and second methods, the processing units 240 and 270 (twenty frames in Figure 5), the oxygen storage capacity (OSC) of the catalyst 36a, and the temperature rise of the catalyst 36a when the oxygen storage capacity of the catalyst 36a changes (both underlined) were adapted assuming that the catalyst 36a was in an undegraded state. Here, "undegraded state" means a state in which there is no degradation (a state in which the degree of degradation is below a predetermined level), and examples include a new state or a state after break-in has been completed.

[0040] In the processing unit 240, the relationship (map) between the rotational speed Ne, the load factor KL, and the temperature Tccs at the center of the catalyst 36a was determined so that the temperature Tccs at the center of the catalyst 36a is higher than when the catalyst 36a is assumed to be in a degraded state. In the processing unit 270, the relationship (map) between the previous temperature at the front of the catalyst 36a (previous Tcf), the exhaust gas flow velocity Vg, and the reaction rate Rcfhc of unburned HC is determined so that the reaction rate Rcfhc of unburned HC is higher than when the catalyst 36a is assumed to be in a degraded state. The oxygen storage capacity of the catalyst 36a and the temperature rise of the catalyst 36a when the oxygen storage capacity (OSC) of the catalyst 36a changes were set to higher values ​​than when the catalyst 36a is assumed to be in a degraded state.

[0041] From these observations, the temperatures Tcf1 and Tcf2 at the front end of the catalyst 36a obtained by the first and second methods 100A and 100B are higher than those obtained when the catalyst 36a is assumed to be in a degraded state. Furthermore, when the air-fuel ratio of the combustion chamber 29 is rich or lean, the temperature of the exhaust gas from the combustion chamber 29 decreases compared to the stoichiometric case due to excess fuel and air. For this reason, the exhaust gas temperature Tecgo of the combustion chamber 29 obtained by the first method 100A is lower than the exhaust gas temperature Tecgo of the combustion chamber 29 obtained by the second method 100B, and the temperature Tcf1 at the front end of the catalyst 36a obtained by the first method 100A is lower than the temperature Tcf2 at the front end of the catalyst 36a obtained by the second method 100B.

[0042] Next, the start and end of the fuel enrichment (OT (Over Temperature) enrichment) of the engine 12 to suppress overheating of the catalyst 36a will be explained. In OT enrichment, the amount of fuel enrichment is set based on the temperature Tcf2 at the front end of the catalyst 36a obtained by the second method 100B (assuming that the air-fuel ratio in the combustion chamber 29 is stoichiometric) and used for fuel injection control. Figure 6 is a flowchart of an example of a processing routine executed by the ECU 70. This routine is executed repeatedly. When this routine is executed, the ECU 70 first inputs the temperatures Tcf1 and Tcf2 at the front end of the catalyst 36a estimated by the first and second methods (step S100), and determines whether or not OT enrichment is in progress (step S110).

[0043] If it is determined in step S110 that OT is not being increased, it is determined whether the temperature Tcf1 at the front end of catalyst 36a obtained by the first method 100A is equal to or greater than the threshold Tcfst (step S120). Here, the threshold Tcfst is a threshold used to determine whether or not to start increasing the amount of OT, and is predetermined by experiments or analyses. If it is determined that the temperature Tcf1 at the front end of catalyst 36a is less than the threshold Tcfst, this routine is terminated without starting to increase the amount of OT. On the other hand, if it is determined that the temperature Tcf1 at the front end of catalyst 36a is equal to or greater than the threshold Tcfst, the OT is increased (step S130) and this routine is terminated.

[0044] As described above, the temperature Tcf1 at the front end of catalyst 36a obtained by the first method 100A (assuming catalyst 36a is in an undegraded state) is higher than the temperature Tcf1 at the front end of catalyst 36a obtained by assuming catalyst 36a is in a degraded state. Therefore, by using the temperature Tcf1 at the front end of catalyst 36a obtained by assuming catalyst 36a is in an undegraded state as the determination for the start of OT enrichment, OT enrichment can be started at a more appropriate timing, and overheating of catalyst 36a can be suppressed more effectively. Note that when OT enrichment is performed, the air-fuel ratio in the combustion chamber 29 tends to become richer compared to when OT enrichment is not performed.

[0045] If it is determined in step S110 that OT is being increased, it is determined whether the temperature Tcf2 at the front end of catalyst 36a obtained by the second method 100B is less than the threshold Tcfsp (step S140). Here, the threshold Tcfsp is a threshold used to determine whether or not to terminate OT increase, and is predetermined by experiments or analyses as a value less than or equal to the threshold Tcfst. If it is determined that the temperature Tcf2 at the front end of catalyst 36a is greater than or equal to the threshold Tcfsp, OT increase is continued and this routine is terminated. On the other hand, if it is determined that the temperature Tcf2 at the front end of catalyst 36a is less than the threshold Tcfsp, OT increase is terminated (step S150) and this routine is terminated.

[0046] As described above, the temperature Tcf2 at the front end of the catalyst 36a obtained by the second method 100B (assuming that the catalyst 36a is in an undegraded state and the air-fuel ratio in the combustion chamber 29 is stoichiometric) is higher than the temperature Tcf1 at the front end of the catalyst 36a obtained by the first method 100A (assuming that the catalyst 36a is in an undegraded state and based on the air-fuel ratio in the combustion chamber 29), and also higher than the temperatures Tcf1 and Tcf2 at the front end of the catalyst 36a obtained by assuming that the catalyst 36a is in a degraded state. Furthermore, as described above, in OT enrichment, the fuel enrichment amount is set based on the temperature Tcf2 at the front end of the catalyst 36a obtained by the second method 100B and used for fuel injection control. From these points, by using the temperature Tcf2 at the front end of the catalyst 36a obtained by assuming that the catalyst 36a is in an undegraded state and the air-fuel ratio in the combustion chamber 29 as the determination of the end of OT enrichment, OT enrichment can be terminated at a more appropriate timing, and overheating of the catalyst 36a can be suppressed more effectively.

[0047] In the engine device 10 of this embodiment described above, the temperature Tcf1 at the front end of the catalyst 36a obtained by the first method 100A (assuming the catalyst 36a is in an undegraded state and based on the air-fuel ratio of the combustion chamber 29) is used to determine the start of OT enrichment. This allows OT enrichment to be started at a more appropriate timing, and overheating of the catalyst 36a can be suppressed more effectively. Furthermore, the temperature Tcf2 at the front end of the catalyst 36a obtained by the second method 100B (assuming the catalyst 36a is in an undegraded state and the air-fuel ratio of the combustion chamber 29 is stoichiometric) is used to determine the end of OT enrichment. This allows OT enrichment to be terminated at a more appropriate timing, and overheating of the catalyst 36a can be suppressed more effectively.

[0048] In the above-described embodiment, the temperature Tcf1 at the front end of the catalyst 36a obtained by the first method 100A was used to determine the start of OT increase, and the temperature Tcf2 at the rear end of the catalyst 36a obtained by the second method 100B was used to determine the end of OT increase. However, the temperature Tcf1 at the front end of the catalyst 36a obtained by the first method 100A may also be used for both the start and end of OT increase. Furthermore, in the above-described embodiment, the temperature Tcf at the front end of the catalyst 36a was estimated and used for the start and end of OT increase, but the temperature of the entire catalyst 36a may also be estimated and used for the start and end of OT increase.

[0049] In the embodiments described above, although not explained, the processing unit 114 may add the temperature rise amount due to functional afterburning, or the processing unit 164 may add the amount of unburned HC due to functional afterburning. Examples of functional afterburning effects include the effects of dithering and scavenging.

[0050] In the embodiments described above, the engine 12 is equipped with port injection valves 27p and in-cylinder injection valves 27d, but it may be equipped with only one of these. Also, in the embodiments described above, the engine 12 is not equipped with a supercharger (turbocharger or supercharger), but it may be equipped with a supercharger.

[0051] While embodiments for implementing this disclosure have been described above, this disclosure is not limited in any way to these embodiments, and can of course be implemented in various forms without departing from the gist of this disclosure. [Industrial applicability]

[0052] This disclosure can be used in industries such as the manufacturing of engine equipment. [Explanation of symbols]

[0053] 10 Engine unit, 12 engine, 36a catalytic converter, 70 ECU.

Claims

1. An engine system comprising: an engine having a combustion chamber, an exhaust port, an exhaust manifold, and an exhaust pipe, and outputting power using a hydrocarbon-based fuel; a catalyst attached to the exhaust pipe; and a control device that increases the fuel supply to the engine to suppress overheating of the catalyst from the time the start condition is met until the end condition is met, The control device assumes that the catalyst is in an undegraded state and estimates the temperature of the catalyst as a first temperature based on a plurality of parameters including the input gas temperature of the catalyst, the amount of heat generated by the combustion of hydrocarbons in the catalyst, and the amount of heat generated by the oxidation-reduction reaction in the catalyst. The aforementioned starting condition is the condition in which the first temperature reaches or exceeds a first predetermined temperature. Engine unit.

2. The engine device according to claim 1, The control device estimates the first temperature using the amount of heat transferred between the exhaust gas passing through the exhaust manifold and the exhaust manifold, and the amount of heat transferred between the inlet gas of the catalyst and the catalyst. Engine unit.

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