Control device for internal combustion engine and control method for internal combustion engine

Abstract

Control device (200) for an internal combustion engine (100), wherein the internal combustion engine (100) comprises the following: a motor body (1); a catalyst device (34) configured in an exhaust gas line of the engine body (1) and comprising an exhaust gas purification catalyst with at least one oxidation function and a microwave absorber contained in a catalyst coating layer (342) formed in a substrate (341); and a microwave transmitter (35) for irradiating the catalyst device (34) with microwaves, wherein the control device (200) is configured such that, if an internal combustion engine start is requested when the temperature of the exhaust gas purification catalyst is lower than a predetermined temperature, it causes the microwave transmitter (35) to irradiate the catalyst device (34) with microwaves and to operate the engine body (1) in such a way that the air-fuel ratio of exhaust gas expelled from the engine body (1) becomes a predetermined lean air-fuel ratio, which is leaner than a stoichiometric air-fuel ratio. the control device (200) is further set up as follows: to calculate a delay time until the combustion engine start is requested; and to cause the microwave transmitter (35) to irradiate the catalyst device (34) with microwaves when the delay time is a predetermined time or less, and when the microwave transmitter (35) is caused to irradiate the catalyst device (34) with microwaves without operating the engine body (1), the specified time is a period of time that allows the temperature of the exhaust gas purification catalyst to be increased to a temperature at which a specified exhaust gas purification performance is achieved in the catalyst device (34), when the engine body (1) is operated in such a way that the air-fuel ratio of the exhaust gas becomes the stoichiometric air-fuel ratio.

Description

Area

[0001] The present invention relates to a control device for an internal combustion engine and a control method for an internal combustion engine. background

[0002] JP 2017-141 803 A discloses an internal combustion engine configured to coat an end face of a catalyst substrate on the upstream side of an exhaust gas with a microwave absorber, enabling this microwave absorber to be irradiated with microwaves. Furthermore, JP 2017-141 803 A discloses a control device for an internal combustion engine that performs a control operation to irradiate the microwave absorber with microwaves before the internal combustion engine is started, to heat the end face of the substrate, and, while the internal combustion engine is starting, to direct a small amount of air to an exhaust duct and use the air, whose temperature increases due to heat exchange as it passes over the end face of the substrate, to heat the substrate as a whole, and to cause the exhaust gas cleaning function to be activated before the internal combustion engine is started.

[0003] Furthermore, US patent 2016 / 0363022A1 discloses an exhaust gas control system comprising a housing, an exhaust gas purification catalyst, and a microwave irradiation device. The microwave irradiation device is configured to irradiate the exhaust gas purification catalyst with microwaves, creating a standing wave with a high magnetic field region and a high electric field region. The exhaust gas purification catalyst comprises a support substrate and a catalytic substance that purifies the exhaust gas. The catalytic substance is arranged on the support substrate. The support substrate comprises a magnetic body region and a dielectric region. The magnetic body region of the support substrate is located in the high magnetic field region within the housing. The dielectric region of the support substrate is located in the high electric field region within the housing.The magnetic body area has a magnetic body that absorbs the microwaves. The dielectric area has a dielectric material that absorbs the microwaves.

[0004] US Patent 5,359,228 A discloses an operating method for a hybrid vehicle that has an electric motor for propelling the vehicle and an internal combustion engine for generating power.

[0005] German patent application DE 10 2016 122 304 A1 discloses a method for heating an electrically heated catalyst in the exhaust system of a motor vehicle with an internal combustion engine. To heat the catalyst before the engine is started, the process involves electrically heating the catalyst before the engine starts, thus enabling efficient exhaust aftertreatment from the outset. Following an electrical preheating phase after the engine starts, the catalyst is further heated by a combined electrical and chemical process involving the exothermic reaction of unburned fuel components on a catalytically active surface of the electrically heated catalyst. The disclosure also relates to a motor vehicle with an internal combustion engine and an exhaust system in which this method is implemented.

[0006] JP H05-49939A discloses that microwave energy is applied to a heating chamber simultaneously with the starting of a gasoline engine, and that the cleaning agent contained in the heating chamber is heated within a short time to a temperature sufficient to decompose hydrocarbons or carbon monoxide. The exhaust gas flows through an exhaust pipe into the heating chamber, and the pollutants contained in the exhaust gas, such as hydrocarbons or carbon monoxide, are removed.

[0007] JP H05-168 950 A discloses a heating material made of a metal oxide, heated by irradiation with an electromagnetic wave, or of a composition containing the metal oxide, supported by a substrate carrying a catalyst. Any conventional substrate for the purification of combustion exhaust gases can be used. This combustion exhaust gas purification catalyst consists of a coating layer, optionally applied to the substrate, the catalyst, and a heating material carried on the coating layer, the cross-sectional structure of which is shown schematically. The coating layer fixes the catalyst to the surface of the substrate and serves to protect the catalyst from heat or toxins.

[0008] Furthermore, DE 100 50 464 A1 discloses an exhaust gas purification unit for an internal combustion engine with a catalyst which has a carrier through which exhaust gas flows and a catalytically active coating on the carrier, wherein the catalyst comprises at least one heating element. Summary

[0009] However, the invention described in the aforementioned JP 2017-141 803 A irradiated the microwave absorber with microwaves to heat the substrate's end face and used the air, whose temperature increases due to heat exchange as it flows past the substrate's end face, to heat the substrate as a whole. This was done to raise the temperature of the exhaust gas purification catalyst within the substrate and activate the exhaust gas purification function. In other words, activating the exhaust gas purification function required raising the substrate's temperature to or above the activation temperature of the exhaust gas purification catalyst. The amount of heat energy required to activate the exhaust gas purification function tended to be large. Consequently, the problem arose that the microwave irradiation time tended to increase, as did the amount of current needed to drive the microwave transmitter.

[0010] The present invention was developed with a focus on such a problem and aims to reduce exhaust emissions while keeping the amount of electricity required to drive the microwave transmitter low.

[0011] The above problem is solved by the subject matter of claims 1 and 10. Advantageous embodiments of the invention are the subject matter of the dependent claims that follow.

[0012] An internal combustion engine according to one aspect of the present disclosure is configured with an engine body, a catalyst device which is configured in an exhaust gas line of the engine body and which has an exhaust gas purification catalyst with at least one oxidation function and a microwave absorber which is contained in a catalyst coating layer which is formed in a substrate, and a microwave transmitter for irradiating the catalyst device with microwaves.Furthermore, a control device for controlling the internal combustion engine is arranged such that, if an internal combustion engine start is requested when the temperature of the exhaust gas purification catalyst is lower than a predetermined temperature, it causes the microwave transmitter to irradiate the catalyst device with microwaves and to operate the engine body in such a way that the air-fuel ratio of exhaust gas expelled from the engine body becomes a predetermined lean air-fuel ratio, which is leaner than the stoichiometric air-fuel ratio.

[0013] Furthermore, according to another aspect of the present disclosure, a control method for an internal combustion engine is designed. The internal combustion engine is designed with an engine body, a catalyst device which is designed in an exhaust pipe of the engine body and which has an exhaust gas purification catalyst with at least one oxidation function and a microwave absorber which is contained in a catalyst coating layer which is formed in a substrate, as well as with a microwave transmitter for irradiating the catalyst device with microwaves.The control procedure causes the microwave transmitter to irradiate the catalyst device with microwaves and operates the engine body in such a way that the air-fuel ratio of exhaust gas expelled from the engine body becomes a predetermined lean air-fuel ratio, which is leaner than a stoichiometric air-fuel ratio if an internal combustion engine start is requested when the temperature of the exhaust gas purification catalyst is lower than a predetermined temperature.

[0014] According to these aspects of the present disclosure, it is possible to reduce exhaust emissions while keeping the amount of electricity required to power the microwave transmitter low. Brief description of the drawing Fig. Figure 1 is a schematic view of a configuration of an internal combustion engine and an electronic control unit for controlling the internal combustion engine according to a first embodiment of the present application. Fig. 2A is a view showing an example of the configuration of a catalyst coating layer. Fig. 2B is a view showing an example of the configuration of a catalyst coating layer. Fig. 2C is a view showing an example of the configuration of a catalyst coating layer. Fig. Figure 3 is a view that shows a relationship between a catalyst temperature and an HC cleaning rate for each air-fuel ratio of exhaust gas flowing into a catalyst. Fig. Figure 4 is a flowchart illustrating a catalyst warm-up control according to the first embodiment of the present application. Fig. Figure 5 is a flowchart that explains an initial warm-up process. Fig. Figure 6 is a flowchart that explains a second warm-up process. Fig. Figure 7 is a timing diagram illustrating the operation of a catalyst warm-up control system according to the first embodiment of the present invention. Fig. Figure 8 is a schematic view of the system of a vehicle according to a second embodiment of the present invention. Fig. Figure 9 is a flowchart illustrating a catalyst warm-up control according to the second embodiment of the present invention. Fig. Figure 10 is a timing diagram illustrating the operation of a catalyst warm-up control according to the second embodiment of the present invention. Fig. Figure 11 is a flowchart illustrating a catalyst warm-up control according to a third embodiment of the present invention. Description of the embodiments

[0015] The following section provides a detailed explanation of embodiments of the present invention with reference to the drawing. It should be noted that similar components are designated with the same reference numerals in the following explanation. First embodiment

[0016] Fig. Figure 1 is a schematic view of a configuration of an internal combustion engine 100 and an electronic control unit 200 for controlling the internal combustion engine 100 according to a first embodiment of the present application.

[0017] The internal combustion engine 100 is designed with an engine body 1, an intake system 20, and an exhaust system 30. The internal combustion engine 100 is, for example, mounted in a vehicle and generates drive power to propel the vehicle.

[0018] The engine body 1 is formed with a cylinder block 2 and a cylinder head 3, which is fixed to an upper surface of the cylinder block 2.

[0019] The cylinder block 2 is configured with a plurality of cylinders 4. Each cylinder 4 contains a piston 5, which experiences combustion pressure and moves back and forth within the cylinder 4. The pistons 5 are connected to a crankshaft (not shown) via connecting rods (not shown). The crankshaft converts the reciprocating motion of the pistons 5 into a rotary motion. The spaces defined by the inner wall surface of the cylinder head 3, the inner wall surfaces of the cylinder 4, and the piston crowns form combustion chambers 6.

[0020] The cylinder head 3 is designed with intake ports 7 that open to one side of the cylinder head 3 and open to the combustion chambers 6, and with exhaust ports 8 that open to the other side of the cylinder head 3 and open to the combustion chambers 6.

[0021] Furthermore, the cylinder head has 3 intake valves 9 attached to it for opening and closing the openings of the combustion chambers 6 and the intake ports 7, exhaust valves 10 for opening and closing the openings of the combustion chambers 6 and the exhaust ports 8, intake camshafts 11 for driving the actuators of the intake valves 9, and exhaust camshafts 12 for driving the exhaust valves 10.

[0022] Furthermore, the cylinder head has 3 fuel injection devices 13 attached to it for injecting fuel into the combustion chambers 6, as well as spark plugs 14 for igniting the fuel-air mixture from the fuel injected by the fuel injection devices 13 and the air in the combustion chamber 6. In the present embodiment, gasoline with a stoichiometric air-fuel ratio of 14.6 is used as fuel, but other fuels can also be used. It should be noted that the fuel injection devices 13 can also be mounted in such a way that they inject fuel into the intake ports 7.

[0023] The intake system 20 is a system for directing air through the intake channels 7 into the interior of the cylinders 4 and is equipped with an air filter 21, an intake pipe 22, an intake manifold 23, a throttle valve 24 with electronic control and an airflow meter 211.

[0024] The air filter 21 removes sand and other foreign particles contained in the air.

[0025] The intake pipe 22 is connected at one end to the air filter 21 and at the other end to an expansion tank 23a of the intake manifold 23. Due to the intake pipe 22, air flowing through the air filter 21 into the interior of the intake pipe 22 (intake or suction) is directed to the expansion tank 23a of the intake manifold 23.

[0026] The intake manifold 23 is equipped with the expansion tank 23a and a plurality of intake pipes 23b, which branch off from the expansion tank 23a and are connected to the openings of the intake ports 7 formed on the side surface of the cylinder head. The air directed to the expansion tank 23a is distributed evenly throughout the interior of the cylinder 4 via the intake pipes 23b. In this way, the intake pipe 22, the intake manifold 23, and the intake ports 7 form intake channels to direct air into the interior of the cylinder 4.

[0027] The throttle valve 24 is integrated into the intake manifold 22. The throttle valve 24 is actuated by a throttle actuator 25 and changes the cross-sectional area of ​​the intake manifold 22 continuously or in stages. By using the throttle actuator 25 to adjust the opening degree of the throttle valve 24 (hereinafter referred to as the "throttle opening degree"), the intake volumes drawn into cylinder 4 are adjusted. The throttle opening degree is detected by a throttle sensor 212.

[0028] The airflow meter 211 is located in the intake pipe 22 on the upstream side of the throttle valve 24. The airflow meter 211 measures the amount of air flowing through the interior of the intake pipe 22 (hereinafter referred to as the "intake quantity").

[0029] The exhaust system 30 is a system for cleaning the combustion gas (exhaust gas) produced in the combustion chambers 6 and for releasing it into the outside air, and is equipped with an exhaust manifold 31, an exhaust pipe 32, an exhaust aftertreatment system 33, an air-fuel ratio sensor 213 and an exhaust gas temperature sensor 214.

[0030] The exhaust manifold 31 is designed with a plurality of exhaust pipes 31a which are connected to openings of exhaust channels 8 which are formed on the side surface of the cylinder head, and is designed with a collector pipe 31b which gathers the exhaust pipes 31a and combines them into one.

[0031] The exhaust pipe 32 is connected at one end to the collector pipe 31b of the exhaust manifold 31 and opens at the other end to the outside air. The exhaust gas, which is expelled from the cylinders 4 through the exhaust ports 8 to the exhaust manifold 31, flows through the exhaust pipe 32 and is expelled to the outside air.

[0032] The exhaust aftertreatment system 33 is equipped with a catalyst 34 and a microwave transmitter 35.

[0033] The catalyst 34 has a substrate 341 which has a plurality of lines running along an exhaust gas flow direction, and a catalyst coating layer 342 (see Fig. 2A to 2C), which is formed on the surface of the same, and is designed in the outlet pipe 32. The catalyst coating layer 342 comprises, as an exhaust gas purification catalyst with at least one oxidation function (oxidation catalyst, three-way catalyst, etc.), an aluminum oxide support (Al2O3), etc., and a precious metal carried on a support such as platinum (Pt), palladium (Pd), rhodium (Rh), etc., and a microwave absorber, such as silicon carbide particles (SiC particles), which absorb microwaves and generate heat.

[0034] By activating the exhaust gas purification function, if an oxidation-type exhaust gas purification catalyst is used, harmful substances in the exhaust gas, such as hydrocarbons (HC) and carbon monoxide (CO), can be removed by oxidation. If a three-way exhaust gas purification catalyst is used, it is possible to remove nitrogen oxides (NOx) in addition to these unburned gases (HC and CO). x ) to reduce to nitrogen (N2) in order to remove them.

[0035] The catalyst coating layer 342 can, for example, be described in Fig. 2A shows that the structure may be formed with a single layer, or with only a single catalyst coating layer 342 formed on the surface of the substrate 341, or it may be, as in Fig. Figure 2B shows a multilayer structure consisting of a plurality of catalyst coating layers 342 formed on the surface of the substrate 341. It should be noted that in the example from Fig. Figure 2B shows a structure with two layers, consisting of an upper layer and a lower layer. Furthermore, in the case of a multilayered structure, as in Fig. 2C shown, it is also possible that only the catalyst coating layer 342, whose temperature is desired to be increased so that it is activated by the heat-generating activity of the microwave absorber (in the example from Fig. 2C the upper catalyst coating layer), that is, the catalyst coating layer 342, in which the exhaust gas purification catalyst is present, which is particularly desired to be activated, contains the microwave absorber.

[0036] In the present embodiment, the catalyst coating layer 342 is as shown in Fig. Figure 2C shows a two-layer structure, and the upper catalyst coating layer is configured to contain the microwave absorber. Furthermore, in the present embodiment, the region of substrate 341 on the upstream side in the direction of exhaust gas flow is configured to contain the microwave absorber.

[0037] In Fig. 1 The microwave transmitter 35 is equipped with a microwave power source 351, a microwave generator 352, a transmission cable 353 and a microwave transmitting antenna 354.

[0038] The microwave power source 351 is electrically connected to the microwave generator 352 and supplies the microwave generator 352 with the current required to generate microwaves. The microwave power source 351 can be a dedicated power source. It can also be the vehicle's battery if the internal combustion engine 100 is installed in a vehicle.

[0039] The microwave generator 352 is driven by the current from the microwave power source 351 and generates microwaves at a predetermined frequency.

[0040] The transmission cable 353 is a cable for transmitting the microwaves generated by the microwave generator 352 to the microwave transmitting antenna 354. One end is connected to the microwave generator, while the other end is connected to the microwave transmitting antenna 354.

[0041] The microwave transmitting antenna 354 is located in the outlet pipe 32, which is positioned on the upstream side in the exhaust gas flow direction from the catalyst 34. The microwave transmitting antenna 354 first irradiates the catalyst 34 with microwaves transmitted via the transmission cable 353. This causes the microwave absorber, which is contained in the catalyst coating layer 342 of the catalyst 34, to generate heat, and the exhaust gas purification catalyst, which is contained in the catalyst coating layer 342, can be directly heated. This makes it possible to efficiently activate the exhaust gas purification function, for example, compared to heating the substrate 341.

[0042] The air-fuel ratio sensor 213 is formed on the collector pipe 31b of the exhaust manifold 31 and detects the air-fuel ratio of the exhaust gas flowing into the first catalyst 34 (hereinafter referred to as "exhaust-air-fuel ratio").

[0043] The exhaust gas temperature sensor 214 is formed in the outlet pipe on the downstream side of the catalyst 34 and detects the temperature Tex of the exhaust gas flowing out of the catalyst 34 (hereinafter referred to as "exhaust gas temperature").

[0044] The electronic control unit 200 has a digital computer and is equipped with components that are interconnected by means of a bidirectional bus 201, such as a ROM (Read Only Memory) 202, RAM (Random Access Memory) 203, CPU (microprocessor) 204, input port 205 and output port 206.

[0045] Input port 205 receives as inputs not only the output signals of the aforementioned airflow meter 211, etc., but also an output signal from an outside air temperature sensor 215 for measuring the outside air temperature To via the corresponding analog-to-digital converters 207. Furthermore, input port 205 receives as input, as a signal for measuring the engine load, the output voltage of a load sensor 217, which generates an output voltage proportional to the degree of depressurization of the accelerator pedal 220 (hereinafter referred to as the "accelerator actuation degree"), via a corresponding analog-to-digital converter 207. Additionally, input port 205 receives as input, as a signal for calculating the engine speed, etc., an output signal from a crankshaft angle sensor 218, which generates an output pulse each time a crankshaft of the engine block 1 rotates, for example, by 15°.In this way, input port 205 receives as input the output signals of the various sensors required for controlling the internal combustion engine 100.

[0046] The output port 206 is connected to the fuel injection devices 13 and other controlled parts via the corresponding control circuits 208.

[0047] The electronic control unit 200 outputs control signals to control the various controlled parts in order to control the internal combustion engine 100 based on the output signals of the various sensors that are entered into the input port 205.

[0048] The electronic control unit 200 controls the internal combustion engine 100 such that the exhaust-air-fuel ratio detected by the air-fuel ratio sensor 213 becomes the target exhaust-air-fuel ratio. In particular, the electronic control unit 200 controls the quantities of fuel injected by the fuel injection devices 13 by means of feedback, based on the exhaust-air-fuel ratio, such that the air-fuel ratio becomes the target exhaust-air-fuel ratio.

[0049] Furthermore, the electronic control unit 200 performs a catalyst warm-up control to warm up the catalyst 33 when the internal combustion engine is cold-started or when it is otherwise necessary to activate the exhaust gas purification function of the catalyst 34.

[0050] As shown in the present embodiment, when the microwave transmitter 35 is configured, it is possible to drive the microwave transmitter 35 to irradiate the catalyst 34 with microwaves from the microwave transmitting antenna 354. This causes the microwave absorber contained in the catalyst coating layer 342 to generate heat and directly heat the exhaust gas purification catalyst contained in the catalyst coating layer 342, thus activating it early. By activating the exhaust gas purification function early, it is possible to reduce exhaust emissions.

[0051] Conversely, when the microwave transmitter 35 is driven, electricity is consumed. The electricity used to drive the microwave transmitter 35 is essentially electricity generated by utilizing the power of the internal combustion engine 100. Therefore, to prevent a deterioration in fuel efficiency, it is desirable to shorten the operating time of the microwave transmitter 35 as much as possible in order to keep the amount of power consumed by the microwave transmitter 35 low, while simultaneously controlling warm-up so that the exhaust gas purification function of the catalytic converter is achieved early.

[0052] Therefore, the inventors conducted intensive studies and learned that it is possible to keep the power consumption of the microwave transmitter 35 low while achieving the exhaust gas purification function early through the exhaust gas purification catalyst by controlling the exhaust air-fuel ratio to a lean air-fuel ratio that is leaner than the stoichiometric air-fuel ratio in order to operate the internal combustion engine 100 while driving the microwave transmitter 35.

[0053] Fig. Figure 3 is a view showing the relationship between the temperature of the exhaust gas purification catalyst in the catalyst 34 (hereinafter referred to as "catalyst temperature") and the cleaning rate of hydrocarbons in the exhaust gas in the catalyst 34 (hereinafter referred to as "HC cleaning rate") for each air-fuel ratio entering the catalyst 34.

[0054] As in Fig. As shown in Figure 3, the catalyst temperature changes at which the HC cleaning rate becomes a predetermined cleaning rate, according to the exhaust gas-air-fuel ratio.In comparison to when the exhaust-air-fuel ratio is controlled to the stoichiometric air-fuel ratio to operate the internal combustion engine 100, specifically the catalyst temperature at which the HC cleaning rate reaches the specified cleaning rate is lower when the exhaust-air-fuel ratio is controlled to a lean air-fuel ratio, which is leaner than the stoichiometric air-fuel ratio to operate the internal combustion engine 100, whereas the catalyst temperature at which the HC cleaning rate reaches the specified cleaning rate is higher when the exhaust-air-fuel ratio is controlled to a rich air-fuel ratio, which is richer than the stoichiometric air-fuel ratio to operate the internal combustion engine 100.

[0055] This means that by controlling the exhaust-air-fuel ratio to a lean air-fuel ratio to operate the internal combustion engine 100, it is possible to lower the catalyst temperature at which HC cleaning (oxidation) becomes possible. Therefore, even when the microwave transmitter 35 is driven to heat the exhaust-cleaning catalyst until the HC cleaning rate reaches a predetermined level, it is possible to shorten the driving time of the microwave transmitter 35 by controlling the exhaust-air-fuel ratio to a lean air-fuel ratio to operate the internal combustion engine 100, compared to controlling the exhaust-air-fuel ratio to a stoichiometric or rich air-fuel ratio to operate the internal combustion engine 100.

[0056] If the catalyst temperature at which the HC cleaning rate assumes a predetermined cleaning rate (for example, 80%) when the exhaust-air-fuel ratio is controlled to a predetermined lean air-fuel ratio to operate the internal combustion engine 100 is designated as the "first catalyst temperature Tth1", and if the catalyst temperature at which the HC cleaning rate assumes a predetermined cleaning rate (for example, 80%) when the exhaust-air-fuel ratio is controlled to the stoichiometric air-fuel ratio to operate the internal combustion engine 100 is designated as the "second catalyst temperature Tth2", then in the present embodiment, as described in Fig. Figure 3 shows the microwave transmitter 35 being driven while the exhaust air-fuel ratio is controlled to the lean air-fuel ratio to operate the internal combustion engine 100 when the catalyst temperature is lower than the first catalyst temperature Tth1.

[0057] When the catalyst temperature reaches the first catalyst temperature Tth1 or higher, microwave transmitter 35 is further ensured to stop, while the exhaust-air-fuel ratio continues to be controlled to the lean air-fuel ratio to operate the internal combustion engine 100. This is because, after the catalyst temperature reaches the first catalyst temperature Tth1, it is possible to clean (oxidize) the HC by a predetermined cleaning rate or higher by controlling the exhaust-air-fuel ratio to the lean air-fuel ratio to operate the internal combustion engine 100, thus making it possible to use the heat of reaction during the cleaning (oxidation) of the HC to raise the catalyst temperature to a second catalyst temperature Tth2.

[0058] After the catalyst temperature has reached the second catalyst temperature Tth2, it will also be possible, even if the exhaust air-fuel ratio is controlled to the stoichiometric air-fuel ratio to control the internal combustion engine 100, to clean the HC by a predetermined cleaning rate or more, so that basically the exhaust air-fuel ratio is controlled to the stoichiometric air-fuel ratio to operate the internal combustion engine 100.

[0059] Fig. Figure 4 is a flowchart to illustrate a catalyst warm-up control according to this embodiment.

[0060] In step S1, the electronic control unit 200 calculates the catalyst temperature Tcat_ini at the start time of the internal combustion engine 100 (hereinafter referred to as the "initial catalyst temperature"). In the present embodiment, the electronic control unit 200 calculates the initial catalyst temperature Tcat_ini based on the catalyst temperature Tcats when the internal combustion engine 100 was stopped at the previous time (hereinafter referred to as the "stop catalyst temperature"), the time that has elapsed since the internal combustion engine 100 was stopped at the previous time (hereinafter referred to as the "engine stop time"), and the ambient air temperature To. The longer the engine stop time, the further the initial catalyst temperature Tcat_ini falls from the stop catalyst temperature Tcats to the ambient air temperature To.

[0061] In step S2, the electronic control unit 200 assesses whether the initial catalyst temperature Tcat_ini is lower than the first catalyst temperature Tth1. If the initial catalyst temperature Tcat_ini is lower than the first catalyst temperature Tth1, the electronic control unit 200 proceeds to the process from step S3. If, on the other hand, the initial catalyst temperature Tcat_ini is equal to or higher than the first catalyst temperature Tth1, the electronic control unit 200 proceeds to the process from step S4.

[0062] In step S3, the electronic control unit 200 performs an initial warm-up process. This initial warm-up process essentially involves operating a lean-burn control system using the microwave transmitter 35 to emit microwaves while the internal combustion engine 100 is operated in such a way that the exhaust-air-fuel ratio assumes the predetermined lean air-fuel ratio. The details of the initial warm-up process will be described later with reference to Fig. 5 described.

[0063] In step S4, the electronic control unit 200 assesses whether the initial catalyst temperature Tcat_ini is lower than the second catalyst temperature Tth2. If the initial catalyst temperature Tcat_ini is lower than the second catalyst temperature Tth2, the electronic control unit 200 proceeds to the process from step S5. If, on the other hand, the initial catalyst temperature Tcat_ini is equal to or greater than the second catalyst temperature Tth2, the electronic control unit 200 determines that catalyst heating is unnecessary and terminates the catalyst heating control.

[0064] In step S5, the electronic control unit 200 performs a second warm-up process. This second warm-up process involves a lean warm-up procedure without causing the microwave transmitter 35 to emit microwaves. The details of the second warm-up process will be described later with reference to Fig. 6 explained.

[0065] Fig. Figure 5 is a flowchart to explain the initial warm-up process.

[0066] In step S31, the electronic control unit 200 starts the microwave transmitter 35, which emits microwaves, starts the internal combustion engine 100 and performs lean control while the internal combustion engine 100 is operating, so that the exhaust-air-fuel ratio assumes a predetermined lean air-fuel ratio during the warm-up control period (for example, 15 to 16 or the like).

[0067] In step S32, the electronic control unit 200 refers to a table, etc., prepared in advance through experiments, etc., and calculates an upper limit tm_th for the time during which the microwave transmitter 35 continues to emit microwaves (hereinafter referred to as the "microwave maximum emission time") based on the initial catalyst temperature Tcat_ini. The microwave maximum emission time tm_th is the time after which it can be determined that the catalyst temperature has reached the initial catalyst temperature Tth1 when the microwave transmitter 35 is caused to emit microwaves while the target air-fuel ratio is adjusted to the lean air-fuel ratio to operate the internal combustion engine 100. The higher the initial catalyst temperature Tcat_ini, the shorter the microwave maximum emission time tm_th.

[0068] In step S33, the electronic control unit 200 reads the actual value Tcat of the catalyst temperature, which is calculated separately from the present process (hereinafter referred to as the "actual catalyst temperature"), and assesses whether the catalyst temperature Tcat is the first catalyst temperature Tth1 or higher. In the present embodiment, the electronic control unit 200 adds the rate of change ΔTcat of the catalyst temperature per unit time to the previous catalyst temperature value Tcatz to calculate the actual catalyst temperature Tcat. It should be noted that the initial value of the previous catalyst temperature value Tcatz becomes the initial catalyst temperature Tcat_ini. Furthermore, the rate of change ΔTcat of the catalyst temperature can be calculated, for example, by calculating the difference in the amount of heat with respect to the catalyst 34 based on the previous catalyst temperature value Tcatz and the exhaust gas temperature Tex.If the actual catalyst temperature Tcat is equal to or greater than the first catalyst temperature Tth1, the electronic control unit 200 proceeds to the process from step S34. If, on the other hand, the actual catalyst temperature Tcat is less than the first catalyst temperature Tth1, the electronic control unit 200 proceeds to the process from step S35.

[0069] In step S34, the electronic control unit 200 causes the microwave transmitter 35 to stop emitting microwaves.

[0070] In step S35, the electronic control unit 200 determines whether the elapsed time tm since the microwave transmitter 35 began emitting microwaves (hereinafter referred to as the "microwave transmission time") is equal to or greater than the maximum microwave transmission time tm_th. If the microwave transmission time tm is equal to or greater than the maximum microwave transmission time tm_th, the electronic control unit 200 proceeds to the operation from step S34 and causes the microwave transmitter 35 to stop emitting microwaves, even if the actual catalyst temperature Tcat is lower than the initial catalyst temperature Tth1. This is because the catalyst temperature can sometimes no longer be calculated accurately, and the actual catalyst temperature Tcat will no longer be equal to or greater than the initial catalyst temperature Tth1, for example, if a fault in the exhaust gas temperature sensor 214 causes the exhaust gas temperature Tex to no longer be measured accurately.This takes such a case into account. Furthermore, the electronic control unit 200 returns to the process from step S33 after a certain waiting period if the microwave transmission time tm is shorter than the microwave maximum transmission time tm_th.

[0071] In step S36, the electronic control unit 200 reads the actual catalyst temperature Tcat and assesses whether it is equal to or greater than the second catalyst temperature Tth2. If it is equal to or greater than the second catalyst temperature Tth2, the electronic control unit 200 proceeds to the process in step S37. Conversely, if the actual catalyst temperature Tcat is less than the second catalyst temperature Tth2, the electronic control unit 200 proceeds to the process in step S38.

[0072] In step S37, the electronic control unit 200 ends the lean control, sets the target exhaust-air-fuel ratio of the internal combustion engine 100 to the target exhaust-air-fuel ratio for the times of normal operation (basically the stoichiometric air-fuel ratio) and ends the first warm-up process.

[0073] In step S38, the electronic control unit 200 assesses whether the continuation time tw of a lean control operation, from the moment the microwave transmitter 35 is instructed to stop emitting microwaves (hereinafter referred to as the "lean control continuation time"), has reached a predetermined upper limit tw_th1 (hereinafter referred to as the "first lean control maximum continuation time") or more. The first lean control maximum continuation time tw_th1 is the time after which it can be determined that the catalyst temperature has reached the second catalyst temperature Tth2 when the lean control operation is performed while the microwave transmitter 35 is not instructed to emit microwaves after the catalyst temperature has been raised to the first catalyst temperature Tth1. In the present embodiment, the first lean control maximum continuation time tw_th1 is set to a pre-defined value.

[0074] If the lean control continuation time tw is greater than or equal to the first lean control maximum continuation time tw_th1, the electronic control unit 200 proceeds to the process from step S37, at which it terminates the lean control, even if the actual catalyst temperature Tcat is lower than the second catalyst temperature Tth2. Furthermore, if the lean control continuation time tw is shorter than the first lean control maximum continuation time tw_th1, the electronic control unit 200 returns to the process from step S36 after waiting a certain period of time.

[0075] Fig. Figure 6 is a flowchart to explain the content of the second warm-up process.

[0076] In step S51, the electronic control unit 200 starts the internal combustion engine 100 without causing the microwave transmitter 35 to emit microwaves, and starts a lean control operation of the internal combustion engine 100, so that the exhaust-air-fuel ratio assumes a predetermined lean air-fuel ratio during the warm-up control (for example, 15 or 16 or the like).

[0077] In step S52, the electronic control unit 200 refers to a table etc. that is prepared in advance by experiments etc. and calculates the upper limit tw_th2 for the continuation time of a lean control in the second warm-up process (hereinafter referred to as the "second lean control maximum continuation time") based on the initial catalyst temperature Tcat_ini.

[0078] The second lean-burn maximum continuation time tw_th2 is the time after which it can be determined that the catalyst temperature has reached the second catalyst temperature Tth2 from the state in which the initial catalyst temperature is Tcat_ini, when lean-burn control is performed without causing microwave transmitter 35 to emit microwaves. The higher the initial catalyst temperature Tcat_ini, the shorter the second lean-burn maximum continuation time tw_th2.

[0079] In step S53, the electronic control unit 200 reads the actual catalyst temperature Tcat and assesses whether it is equal to or greater than the second catalyst temperature Tth2. If it is equal to or greater than the second catalyst temperature Tth2, the electronic control unit 200 proceeds to the process in step S54. Conversely, if the actual catalyst temperature Tcat is less than the second catalyst temperature Tth2, the electronic control unit 200 proceeds to the process in step S55.

[0080] In step S54, the electronic control unit 200 ends the lean control and sets the target exhaust-air-fuel ratio of the internal combustion engine 100 to the target exhaust-air-fuel ratio (basically the stoichiometric air-fuel ratio) for the duration of normal operation and ends the second warm-up process.

[0081] In step S55, the electronic control unit 200 assesses whether the lean control continuation time tw, from the time the second warm-up process was started, is equal to or greater than the second lean control maximum continuation time tw_th2. If the lean control continuation time tw is equal to or greater than the second lean control maximum continuation time tw_th2, the electronic control unit 200 proceeds to the process from step S54 and terminates the lean control, even if the catalyst temperature Tcat is lower than the second catalyst temperature Tth2. Furthermore, if the lean control continuation time tw is shorter than the second lean control maximum continuation time tw_th2, the electronic control unit 200 returns to the process from step S53 after waiting a certain period of time.

[0082] Fig. Figure 7 is a timing diagram illustrating the operation of a catalyst warm-up control according to the present embodiment.

[0083] At time t1, the catalyst warm-up control is started if, for example, the vehicle's start button is switched on and a start of the internal combustion engine 100 is requested. In the Fig. In the example shown, the catalyst temperature at time t1, that is, the initial catalyst temperature Tcat_ini, is lower than the first catalyst temperature Tth1, so the first warm-up process is carried out. That is, the microwave transmitter 35 begins to emit microwaves, the internal combustion engine 100 is started, and a lean-burn control is initiated to operate the internal combustion engine 100 in such a way that the exhaust-air-fuel ratio assumes a predetermined lean air-fuel ratio (for example, 15 or 16 or the like) during the warm-up period.

[0084] As a result, from time t1 the exhaust gas purification catalyst is heated by receiving the exhaust gas heat and the heat emitted by the microwave absorber, so that the catalyst temperature increases.

[0085] At time t2, if the actual catalyst temperature Tcat reaches the first catalyst temperature Tth1, the microwave transmitter 35 stops emitting microwaves, but at time t2 or later the exhaust-air-fuel ratio is adjusted to the lean air-fuel ratio and the internal combustion engine 100 is operated in such a way that the HC is oxidized by a predetermined cleaning rate or more, so that the heat of reaction during oxidation of the HC is used to cause the catalyst temperature to rise even further.

[0086] At time t3, the lean-burn control is terminated and the first warm-up process is completed if the actual catalyst bed temperature Tcat reaches the second catalyst temperature Tth2. At time t3 and thereafter, the target exhaust-air-fuel ratio of the internal combustion engine 100 is essentially set to the target exhaust-air-fuel ratio for normal operating times (as defined in the Fig. 7 shows the stoichiometric air-fuel ratio).

[0087] The internal combustion engine 100 according to the present embodiment described above is configured with an engine body 1, a catalyst 34 (a catalyst device) which is configured in an exhaust gas line of the engine body 1 and which has an exhaust gas purification catalyst with at least one oxidation function and a microwave absorber which is contained in a catalyst coating layer 342 which is formed in a substrate 341, and with a microwave transmitter 35 for irradiating the catalyst 34 with microwaves.Furthermore, an electronic control unit 200 (control device) for controlling the internal combustion engine 100 is arranged such that, if the temperature of the exhaust gas purification catalyst is lower than a predetermined temperature when an internal combustion engine start is requested, the microwave transmitter 35 irradiates the catalyst device 34 with microwaves, and operates the engine body 1 in such a way that the air-fuel ratio of the exhaust gas expelled from the engine body 1 becomes a predetermined lean air-fuel ratio, which is leaner than the stoichiometric air-fuel ratio.In the present embodiment, the predetermined temperature is set to become the temperature of the exhaust gas purification catalyst at which a predetermined exhaust gas purification performance is achieved in the catalyst 34 when the engine body 1 is operated in such a way that the exhaust gas-air-fuel ratio becomes a lean air-fuel ratio, that is, the first catalyst temperature Tth1.

[0088] Therefore, both the exhaust gas heat and the heat generated by the microwave absorber can be used to heat the exhaust gas purification catalyst when the exhaust gas purification catalyst temperature is lower than a predetermined temperature (first catalyst temperature Tth1). In the present embodiment, it is possible to cause the microwave absorber, which is contained in the catalyst coating layer 342, to generate heat and directly heat the exhaust gas purification catalyst contained in the catalyst coating layer 342, thus enabling efficient heating of the exhaust gas purification catalyst and consequently increasing the temperature rise rate of the exhaust gas purification catalyst.

[0089] By operating the engine body 1 in such a way that the exhaust-air-fuel ratio becomes the lean air-fuel ratio, it is furthermore possible, compared to when the engine body 1 is operated in such a way that the exhaust-air-fuel ratio becomes the stoichiometric air-fuel ratio or the rich air-fuel ratio, to reduce the temperature of the exhaust gas purification catalyst at which a predetermined exhaust gas purification performance is achieved in the catalyst 34.

[0090] This means that, according to the present embodiment, it is possible to increase the temperature rise rate of the exhaust gas purification catalyst while simultaneously reducing the temperature of the exhaust gas purification catalyst at which a predetermined exhaust gas purification performance is achieved in the catalyst 34. This makes it possible to reduce exhaust emissions and shorten the time that the microwave transmitter 35 needs to be driven to heat the exhaust gas purification catalyst. Therefore, it is possible to keep the current consumed when driving the microwave transmitter 35 low and to prevent a deterioration in fuel efficiency.

[0091] Furthermore, the electronic control unit 200, according to the present embodiment, is configured such that the microwave transmitter 35 is caused to cease emitting microwaves when the temperature of the exhaust gas purification catalyst reaches a predetermined temperature (first catalyst temperature Tth1) or higher. It is also configured to operate the engine block 1 in such a way that the exhaust gas-air-fuel ratio becomes the stoichiometric air-fuel ratio when the temperature of the exhaust gas purification catalyst is higher than a predetermined temperature (first catalyst temperature Tth1) and is a temperature at which a predetermined exhaust gas purification performance is achieved in the catalyst 34, provided the engine block 1 is operated in such a way that the exhaust gas-air-fuel ratio reaches the stoichiometric air-fuel ratio (i.e., the second catalyst temperature Tth2) or higher.

[0092] In this way it is possible to cause the microwave transmitter 35 to stop emitting microwaves at the time when the temperature of the exhaust gas purification catalyst reaches a temperature at which a predetermined exhaust gas purification performance is achieved in the catalyst 34, thereby reducing exhaust emissions while keeping the amount of electricity consumed during the operation of the microwave transmitter 35 to a minimum.

[0093] Even after the exhaust gas purification catalyst temperature reaches or exceeds the predetermined temperature (first catalyst temperature Tth1), it is still possible to control the exhaust-air-fuel ratio to a lean air-fuel ratio to operate the engine block 1 and thus oxidize the HC in the exhaust gas in the catalyst 34. This allows the heat of reaction to be used at this time to raise the catalyst temperature to the second catalyst temperature Tth2. Once the catalyst temperature reaches or exceeds the second catalyst temperature Tth2, it is further possible to operate the engine block 1 in such a way that the exhaust-air-fuel ratio becomes the stoichiometric air-fuel ratio, thus ensuring combustion stability and output power in the high-load range.

[0094] It should be noted that in the present embodiment, as mentioned above, the predetermined temperature was set to the first catalyst temperature Tth1, but if the predetermined temperature is set to the second catalyst temperature Tth2 and the temperature of the exhaust gas purification catalyst is lower than the second catalyst temperature Tth2, it is also possible, if an internal combustion engine start is requested, to cause the microwave transmitter 35 to irradiate the catalyst 34 with microwaves and for the engine body 1 to be operated in such a way that the air-fuel ratio of the exhaust gas expelled from the engine body 1 becomes a predetermined lean air-fuel ratio, which is leaner than the stoichiometric air-fuel ratio.Furthermore, if the temperature of the exhaust gas purification catalyst becomes the second catalyst temperature Tth2 or more, it is also possible to cause the microwave transmitter 35 to stop emitting microwaves and to operate the engine body 1 in such a way that the exhaust gas-air-fuel ratio becomes the stoichiometric air-fuel ratio.

[0095] In this way it is possible to continue the emission of microwaves even if the temperature of the exhaust gas purification catalyst reaches the first catalyst temperature Tth1 or higher, until it reaches the second catalyst temperature Tth2 or higher, in order to raise the temperature of the exhaust gas purification catalyst to the second catalyst temperature Tth2 earlier than if the emission of microwaves were stopped at the time the temperature of the exhaust gas purification catalyst reaches the first catalyst temperature Tth1 or higher. Second embodiment

[0096] Next, a second embodiment of the present invention will be explained. This embodiment differs from the first embodiment in that the internal combustion engine 100 is mounted in a hybrid vehicle and the microwave transmitter 35 is driven while the vehicle is operating in EV mode to heat the catalyst 34. This difference will be discussed in more detail below.

[0097] Fig. Figure 8 is a schematic system representation of a vehicle according to the present embodiment.

[0098] The vehicle according to the present embodiment is a hybrid vehicle equipped with vehicle propulsion sources formed by an internal combustion engine 100 and an electric motor 300, and with an electronic control unit 200 for controlling the internal combustion engine 100 and the electric motor 300, which is configured to allow the vehicle to be driven using the propulsion power from the internal combustion engine 100 and / or the electric motor 300. The internal combustion engine 100 and the electronic control unit 200 are configured similarly to the first embodiment.

[0099] In the case of such a hybrid vehicle, it is possible, after starting the vehicle, to drive in EV mode, in which the vehicle is essentially driven only by the drive power of the electric motor 300, and to warm up the catalyst 34 while driving in EV mode to reduce exhaust emissions when it later becomes necessary to start the internal combustion engine 100. Therefore, in the present embodiment, the microwave transmitter 35 is driven while the EV mode is active in order to warm up the catalyst 34. The catalyst warm-up control according to the present embodiment is explained below.

[0100] Fig. Figure 9 is a flowchart to illustrate a catalyst warm-up control according to the present embodiment.

[0101] In step S11, the electronic control unit 200 assesses whether the actual catalyst temperature Tcat, while EV mode is active, is lower than the secondary catalyst temperature Tth2. If the actual catalyst temperature Tcat is lower than the secondary catalyst temperature Tth2, the electronic control unit 200 proceeds to the process from step S12. Conversely, if the actual catalyst temperature Tcat is equal to or higher than the secondary catalyst temperature Tth2, the electronic control unit 200 determines that catalyst heating is unnecessary and terminates the catalyst warm-up control.

[0102] It should be noted that the actual catalyst temperature Tcat at the time when the EV mode is started (time of a vehicle start), as in the first embodiment, can be calculated based on the catalyst temperature (stop catalyst temperature) Tcats when the internal combustion engine 100 was stopped at the previous time, the time that has elapsed since the internal combustion engine 100 was stopped at the previous time (engine stop time interval) and the outside air temperature To.Furthermore, the electronic control unit 200 proceeds to the process of step S16, which will be explained later, where the actual catalyst temperature Tcat after stopping the emission of microwaves can be calculated based on the actual catalyst temperature Tcat (which corresponds to the second catalyst temperature Th2) when the emission of microwaves is stopped in step S16, the time elapsed since the emission of microwaves was stopped and the outside air temperature To.

[0103] In step S12, the electronic control unit 200 causes the microwave transmitter 35 to begin emitting microwaves.

[0104] In step S13, the electronic control unit 200 assesses whether an internal combustion engine start is requested. If no internal combustion engine start is requested, the electronic control unit 200 proceeds to the process from step S14. If, on the other hand, an internal combustion engine start is requested, the electronic control unit 200 proceeds to the process from step S17. In the present embodiment, the electronic control unit 200 assesses, for example, that an internal combustion engine start is requested when the battery charge level of the vehicle battery (not shown) falls below a predetermined charge level or when the vehicle's drive power reaches a predetermined drive power or exceeds it.

[0105] In step S14, the electronic control unit 200 calculates the catalyst temperature Tcat1 while it is emitting microwaves. In the present embodiment, the electronic control unit 200 refers to a characteristic map that has been prepared in advance by experiments, etc., and calculates the catalyst temperature Tcat1 while it is emitting microwaves, based on the catalyst temperature when it starts emitting microwaves and the microwave transmission time tm.

[0106] In step S15, the electronic control unit 200 assesses whether the catalyst temperature Tcat1, while emitting microwaves, is equal to or greater than the second catalyst temperature Tth2. If the catalyst temperature Tcat1 is equal to or greater than the second catalyst temperature Tth2 during microwave emission, the electronic control unit 200 proceeds to the process from step S16. Conversely, if the actual catalyst temperature Tcat during microwave emission is lower than the second catalyst temperature Tth2, the electronic control unit 200 returns to the process from step S13 after waiting a certain period of time.

[0107] In step S16, the electronic control unit 200 causes the microwave transmitter 35 to stop emitting microwaves once and continues the process according to the present sequence after waiting a certain time.

[0108] In step S17, the electronic control unit 200 calculates the catalyst temperature Tcat2 when an internal combustion engine start is requested. If an internal combustion engine start is requested while microwaves are being emitted, and the electronic control unit 200 proceeds to step S17, the electronic control unit 200 calculates the catalyst temperature Tcat1 while emitting microwaves as the catalyst temperature Tcat2 when an internal combustion engine start is requested. Conversely, if no microwaves are being emitted and it proceeds to step S17, the electronic control unit 200 calculates the actual catalyst temperature Tcat while EV mode is active in step S11 as the catalyst temperature Tcat2 when an internal combustion engine start is requested.

[0109] In step S18, the electronic control unit 200 assesses whether the catalyst temperature Tcat2 is lower than the initial catalyst temperature Tth1 when an engine start is requested. If the catalyst temperature Tcat2 is lower than the initial catalyst temperature Tth1 when an engine start is requested, the electronic control unit 200 proceeds to the process from step S19. Conversely, if the catalyst temperature Tcat2 is equal to or higher than the initial catalyst temperature Tth1 when an engine start is requested, the electronic control unit 200 proceeds to the process from step S25.

[0110] In step S19, the electronic control unit 200 continues to emit microwaves while causing the internal combustion engine 100 to start, and initiates a lean control to operate the internal combustion engine 100 in such a way that the exhaust air-fuel ratio during the warm-up control period becomes a predetermined lean air-fuel ratio (for example, 15 or 16 or so).

[0111] In step S20, the electronic control unit 200 calculates the maximum microwave emission time tm_th based on the catalyst temperature Tcat2 when an internal combustion engine start is requested. In the present embodiment, the maximum microwave emission time tm_th is the time after which it can be determined that the catalyst temperature has reached the first catalyst temperature Tth1 from the state of catalyst temperature Tcat2 when microwaves are emitted while lean control is being performed.

[0112] In step S21, the electronic control unit 200 assesses whether the microwave transmission time tm is equal to or greater than the maximum microwave transmission time tm_th. If the microwave transmission time tm is equal to or greater than the maximum microwave transmission time tm_th, the electronic control unit 200 proceeds to the process from step S22. If, however, the microwave transmission time tm is shorter than the maximum microwave transmission time tm_th, the electronic control unit 200 repeats the process from step S21 after waiting a certain period of time.

[0113] In step S22, the electronic control unit 200 causes the microwave transmitter 35 to stop emitting microwaves.

[0114] In step S23, the electronic control unit 200 assesses whether the lean-burn control continuation time tw, from the moment it causes the microwave transmitter 35 to stop emitting microwaves, is the first maximum lean-burn control continuation time tw_th1 or more. That is, the first maximum lean-burn control continuation time tw_th1 is, as in the first embodiment, the time after which it can be determined that the catalyst temperature has reached the second catalyst temperature Tth2, if the internal combustion engine 100 is operated in such a way that the exhaust-air-fuel ratio becomes the lean air-fuel ratio, without causing the microwave transmitter 35 to emit microwaves after the catalyst temperature has been raised to the first catalyst temperature Tth1.

[0115] If the lean control continuation time tw is equal to or greater than the first lean control maximum continuation time tw_th1, the electronic control unit 200 proceeds to the operation from step S24. If, on the other hand, the lean control continuation time tw is shorter than the first lean control maximum continuation time tw_th1, the electronic control unit 200 repeats the operation from step S23 after waiting a certain time.

[0116] In step S24, the electronic control unit 200 ends the lean control, sets the target exhaust-air-fuel ratio of the internal combustion engine 100 to the target exhaust-air-fuel ratio for the times of normal operation (basically the stoichiometric air-fuel ratio) and ends the first catalyst warm-up control.

[0117] In step S25, the electronic control unit 200 stops emitting the microwaves, starts the internal combustion engine 100 and starts operating the internal combustion engine 100 with lean control, so that the exhaust-air-fuel ratio assumes a predetermined lean air-fuel ratio during the warm-up control period (for example, 15 to 16 or the like).

[0118] In step S26, the electronic control unit 200 calculates an upper limit tw_th3 of the lean control continuation time (hereinafter referred to as the "third lean control maximum continuation time") based on the catalyst temperature Tcat2 when the combustion engine start is requested.

[0119] The third lean-burn maximum continuation time tw_th3 is the time after which it can be determined that the catalyst temperature has reached the second catalyst temperature Tth2 from the state of catalyst temperature Tcat2, when the internal combustion engine 100 is operated in such a way that the exhaust-air-fuel ratio becomes the lean air-fuel ratio, without causing the microwave transmitter 35 to emit microwaves. The higher the catalyst temperature Tcat2 becomes, the shorter the third lean-burn maximum continuation time tw_th3 becomes when an internal combustion engine start is requested.

[0120] In step S27, the electronic control unit 200 assesses whether the lean control continuation time tw, starting from the moment the microwave transmitter 35 stops emitting microwaves, is equal to or greater than the third maximum lean control continuation time tw_th3. If the lean control continuation time tw is equal to or greater than the third maximum lean control continuation time tw_th3, the electronic control unit 200 proceeds to the operation from step S24. If, on the other hand, the lean control continuation time tw is shorter than the third maximum lean control continuation time tw_th3, the electronic control unit 200 repeats the operation from step S27 after waiting a certain period of time.

[0121] Fig. Figure 10 is a timing diagram illustrating the operation of a catalyst warm-up control according to the present embodiment.

[0122] At time t11, the catalyst warm-up control is started if the vehicle start switch is turned on. In the Fig. In the example shown, no combustion engine start is requested at time t11, so while the combustion engine 100 remains stopped, the drive power of the electric motor 300 is used to start the EV mode. Since the catalyst temperature at time t11, that is, the actual catalyst temperature Tcat, is lower than the second catalyst temperature Tth2 during EV mode, the microwave transmitter 35 starts emitting microwaves.

[0123] If an internal combustion engine start is requested at time t12 while microwaves are being emitted, it is assessed whether the catalyst temperature Tcat2 at the time of the request is lower than the initial catalyst temperature Tth1. In the Fig. In example 10, the catalyst temperature Tcat2 is lower than the first catalyst temperature Tth1 when the internal combustion engine is requested, so that the microwaves continue to be emitted while the internal combustion engine is started and lean control is initiated.

[0124] If, at time t13, the microwave emission time tm is equal to or greater than the maximum microwave emission time tm_th, it is determined that the catalyst temperature has reached the first catalyst temperature Tth1 and microwave emission is stopped. Furthermore, at time t14, if the lean control continuation time tw is equal to or greater than the first maximum lean control continuation time tw_th1, it is determined that the catalyst temperature has reached the second catalyst temperature Tth2 and lean control is terminated.

[0125] According to the present embodiment described above, the electronic control unit 200 is configured such that, when the temperature of the exhaust gas purification catalyst is lower than a second catalyst temperature Tth2 (i.e., a temperature at which a predetermined exhaust gas purification performance is achieved in the catalyst 34 when the engine body 1 is operated in such a way that the exhaust gas-air-fuel ratio becomes the stoichiometric air-fuel ratio) during a drive by the drive power of the electric motor 300, before an internal combustion engine start is requested, it causes the microwave transmitter 35 to irradiate the catalyst 34 (catalyst device) with microwaves.

[0126] Because of this, it is possible to warm up the catalyst 34 before the internal combustion engine 100 is started, so that it is possible to reduce exhaust emissions when it is essentially necessary to start the internal combustion engine 100. Third embodiment

[0127] Next, a third embodiment of the present invention will be explained. This embodiment differs from the first embodiment in that a delay time until the start of the internal combustion engine 100 is predicted, and that the microwave transmitter 35 is caused to begin emitting microwaves when the delay time becomes shorter than a predetermined time. This difference will be discussed in the following explanation.

[0128] Fig. Figure 11 is a flowchart that explains the catalyst warm-up control according to the present embodiment. It should be noted that the flowchart consists of Fig. 11 the process from step S19 and step S21 to step S25 of the second embodiment mentioned above is similar, so further explanation is omitted here.

[0129] In step S31, the electronic control unit 200 assesses whether the actual catalyst temperature Tcat is lower than the second catalyst temperature Tth2. If the actual catalyst temperature Tcat is lower than the second catalyst temperature Tth2, the electronic control unit 200 proceeds to the process from step S32. If, on the other hand, the actual catalyst temperature Tcat is equal to or higher than the second catalyst temperature Tth2, the electronic control unit 200 assesses that catalyst warm-up is unnecessary and terminates the catalyst warm-up control.

[0130] In step S32, the electronic control unit 200 calculates the time span from the current time until the time at which the internal combustion engine 100 is expected to be started, as the delay time t_es until the internal combustion engine 100 is started.

[0131] The delay time t_es is a specific set time, such as the time from when a vehicle door is opened until the internal combustion engine 100 starts, or the time from when a driver is seated in the driver's seat of a vehicle until the internal combustion engine 100 starts. This allows it to be calculated, for example, by detecting when a vehicle door is opened or when the driver is seated. Furthermore, if the electronic control unit 200 is configured to communicate with an external cloud server, it is possible to retrieve data about the host vehicle's past driving information stored on the cloud server and calculate the delay time t_es from this driving information.If the internal combustion engine 100 is installed in a hybrid vehicle, it is also possible to calculate the delay time t_es by predicting the driving load from the driving information of the host vehicle and other vehicles, map information, etc., collected in the cloud server.

[0132] In step S33, the electronic control unit 200 assesses whether the delay time t_es is equal to or less than the warm-up start assessment threshold t_th. The warm-up start assessment threshold t_th is a value that corresponds to the time required to raise the catalyst temperature to the second catalyst temperature Tth2 after the microwave transmitter 35 has been caused to emit microwaves.

[0133] Therefore, if the delay time t_es is equal to or less than the warm-up start evaluation threshold t_th, it is desirable to start emitting microwaves to initiate and warm up the catalyst before the internal combustion engine 100 is expected to start. Therefore, in the present embodiment, the electronic control unit 200 proceeds to the process from step S36, in which it starts emitting microwaves when the delay time t_es is equal to or less than the warm-up start evaluation threshold t_th.

[0134] If, on the other hand, the delay time t_es is greater than the warm-up start evaluation threshold t_th, and there is still some time before the catalyst warms up, then power is to be expected to be wasted unnecessarily if microwaves are emitted from that point onward. Therefore, in the present embodiment, the electronic control unit 200 proceeds to the process from step S34 when the delay time t_es becomes greater than the warm-up start evaluation threshold t_th. Until the delay time t_es becomes less than the warm-up start evaluation threshold t_th, the electronic control unit 200 remains in standby mode without emitting microwaves (i.e., without warming up the catalyst).

[0135] It should be noted that in step S34, it is assessed whether microwaves are being emitted, and if microwaves are being emitted, microwave emission is stopped in step S35 for the following reason: If the delay time t_es becomes the warm-up start assessment threshold t_th or higher, the electronic control unit 200 advances once to step S36, where microwave emission begins. Afterward, the electronic control unit 200 returns from step S37 to step S32, where the delay time t_es is recalculated. At this point, the delay time t_es sometimes changes in one direction and becomes longer. Consequently, the delay time t_es sometimes becomes greater than the warm-up start assessment threshold t_th.

[0136] In step S36, the electronic control unit 200 causes the microwave transmitter 35 to begin emitting microwaves.

[0137] In step S37, the electronic control unit 200 assesses whether the internal combustion engine 100 has actually started. In the present embodiment, the electronic control unit 200 assesses that the internal combustion engine 100 has started when the engine speed reaches a predetermined speed or higher. The electronic control unit 200 proceeds to the process from step S38 if the internal combustion engine 100 has actually started. Conversely, if the internal combustion engine 100 has still not started, the electronic control unit 200 returns to the process from step S32 after waiting a certain time and recalculates the delay time t_es.

[0138] In step S38, the electronic control unit 200 calculates the catalyst temperature Tcat3 for a point at which the internal combustion engine 100 was actually started. In the present embodiment, the electronic control unit 200 calculates the catalyst temperature Tcat3 for a point at which the internal combustion engine 100 was actually started, based on the elapsed time (microwave transmission time) tm from the start of microwave emission in step S36.

[0139] In step S39, the electronic control unit 200 assesses whether the catalyst temperature Tcat3 at a point when the internal combustion engine 100 has actually been started is lower than the initial catalyst temperature Tth1. If the catalyst temperature Tcat3 at a point when the internal combustion engine 100 has actually been started is lower than the initial catalyst temperature Tth1, the electronic control unit 200 proceeds to the process from step S19. Conversely, if the catalyst temperature Tcat3 at a point when the engine is actually started is equal to or higher than the initial catalyst temperature Tth1, the electronic control unit 200 proceeds to the process from step S25.

[0140] In step S40, the electronic control unit 200 calculates the maximum microwave emission time tm_th based on the catalyst temperature Tcat3 when the internal combustion engine 100 is actually started. In the present embodiment, the maximum microwave emission time tm_th is the time after which it can be determined that the catalyst temperature has reached the initial catalyst temperature Tth1 when the microwaves are emitted from a catalyst temperature state Tcat3 during lean-burn operation. It becomes shorter as the catalyst temperature Tcat3 increases when the internal combustion engine 100 is actually started.

[0141] In step S41, the electronic control unit 200 calculates the upper limit of the lean control continuation time (hereinafter referred to as the "fourth lean control maximum continuation time") tw_th4 based on the catalyst temperature Tcat3 when the internal combustion engine 100 is actually started.

[0142] The fourth lean-burn maximum continuation time tw_th4 is the time after which it can be determined that the catalyst temperature has reached the second catalyst temperature Tth2 from the catalyst temperature state Tcat3, when the internal combustion engine 100 is operated in such a way that the exhaust-air-fuel ratio becomes the lean air-fuel ratio, without causing the microwave transmitter 35 to emit microwaves. The fourth lean-burn maximum continuation time tw_th4 becomes shorter the higher the actual catalyst temperature Tcat3 is when a machine is actually started.

[0143] In step S42, the electronic control unit 200 assesses whether the lean control continuation time tw, starting from the moment the microwave transmitter 35 stopped emitting microwaves, is equal to or greater than the fourth maximum lean control continuation time tw_th4. The electronic control unit 200 proceeds to the operation from step S24 if the lean control continuation time tw is equal to or greater than the fourth maximum lean control continuation time tw_th4. However, if the lean control continuation time tw is shorter than the fourth maximum lean control continuation time tw_th4, the electronic control unit 200 repeats the operation from step S42 after waiting a certain period of time.

[0144] According to the present embodiment described above, the electronic control unit 200 is configured to calculate a delay time t_es until the combustion engine start is requested and to cause the microwave transmitter 35 to irradiate the catalyst 34 (catalyst device) with microwaves when the delay time t_es is a predetermined time or less. Furthermore, the predetermined time is defined as the time after which the temperature of the exhaust gas purification catalyst can be raised to a temperature at which a predetermined exhaust gas purification performance is achieved in the catalyst 34 when the engine block 1 is running, such that the exhaust gas-air-fuel ratio becomes stoichiometric in the case where the microwave transmitter 35 is caused to irradiate the catalyst 34 with microwaves without the engine block 1 being run.

[0145] Because of this, it is possible to emit microwaves in such a way that the catalyst 34 is finished heating up at the time when the internal combustion engine 100 is expected to be started, so that it is possible to reduce exhaust emissions while keeping the amount of electricity consumed low when the microwave transmitter 35 is driven.

[0146] Above, embodiments of the present application have been explained, but the embodiments above only show some of the application examples of the present application and are not intended to limit the technical scope of the present application to the specific nature of the embodiments above.

[0147] For example, in the above embodiments, the engine body 1 was operated such that the exhaust air-fuel ratio became a lean air-fuel ratio at the time of the internal combustion engine start-up, but to ensure combustion stability immediately after the internal combustion engine start-up, it is also possible to operate the engine body 1 such that the exhaust air-fuel ratio becomes a rich air-fuel ratio immediately after starting, and then control it to a lean air-fuel ratio.

[0148] If the catalyst warm-up control described in the third embodiment is combined with the catalyst warm-up control described in the second embodiment, it is also possible that the microwave transmitter 35 does not emit the microwaves if the delay time t_es is greater than the warm-up start evaluation threshold t_th (predetermined time), even if the temperature of the exhaust gas purification catalyst is lower than the second catalyst temperature Tth2 during EV mode.

Claims

[1] Control device (200) for an internal combustion engine (100), wherein the internal combustion engine (100) comprises the following: a motor body (1); a catalyst device (34) configured in an exhaust gas line of the engine body (1) and comprising an exhaust gas purification catalyst with at least one oxidation function and a microwave absorber contained in a catalyst coating layer (342) formed in a substrate (341); and a microwave transmitter (35) for irradiating the catalyst device (34) with microwaves, wherein the control device (200) is configured such that, if an internal combustion engine start is requested when the temperature of the exhaust gas purification catalyst is lower than a predetermined temperature, it causes the microwave transmitter (35) to irradiate the catalyst device (34) with microwaves and to operate the engine body (1) in such a way that the air-fuel ratio of exhaust gas expelled from the engine body (1) becomes a predetermined lean air-fuel ratio, which is leaner than a stoichiometric air-fuel ratio. the control device (200) is further set up as follows: to calculate a delay time until the combustion engine start is requested; and to cause the microwave transmitter (35) to irradiate the catalyst device (34) with microwaves when the delay time is a predetermined time or less, and when the microwave transmitter (35) is caused to irradiate the catalyst device (34) with microwaves without operating the engine body (1), the specified time is a period of time that allows the temperature of the exhaust gas purification catalyst to be increased to a temperature at which a specified exhaust gas purification performance is achieved in the catalyst device (34), when the engine body (1) is operated in such a way that the air-fuel ratio of the exhaust gas becomes the stoichiometric air-fuel ratio. [2] Control device (200) for the internal combustion engine (100) according to claim 1, wherein the predetermined temperature is a temperature at which a predetermined exhaust gas purification performance is achieved in the catalyst device (34) when the engine body (1) is operated, such that the air-fuel ratio of exhaust gas becomes the lean air-fuel ratio. [3] Control device (200) for the internal combustion engine (100) according to claim 2, wherein the control device (200) is further configured to cause the microwave transmitter (35) to stop emitting microwaves when the temperature of the exhaust gas purification catalyst reaches the predetermined temperature or more. [4] Control device (200) for the internal combustion engine (100) according to claim 2 or 3, wherein the control device (200) is further configured to operate the engine body (1) in such a way that the air-fuel ratio of the exhaust gas becomes the stoichiometric air-fuel ratio when the temperature of the exhaust gas purification catalyst assumes a higher temperature than the predetermined temperature and a temperature at which a predetermined exhaust gas purification performance is achieved in the catalyst device (34) when the engine body (1) is operated in such a way that the air-fuel ratio of the exhaust gas assumes the stoichiometric air-fuel ratio, or a higher temperature. [5] Control device (200) for the internal combustion engine (100) according to claim 1, wherein the predetermined temperature is a temperature at which a predetermined exhaust gas purification performance is achieved in the catalyst device (34) when the engine body (1) is operated in such a way that the air-fuel ratio of exhaust gas becomes the stoichiometric air-fuel ratio. [6] Control device (200) for the internal combustion engine (100) according to claim 5, wherein the control device (200) is further configured to cause the microwave transmitter (35) to stop emitting microwaves and to operate the engine body (1) in such a way that the air-fuel ratio becomes the stoichiometric air-fuel ratio when the temperature of the exhaust gas purification catalyst reaches the predetermined temperature or more. [7] Control device (200) for the internal combustion engine (100) according to one of claims 1 to 6, wherein the internal combustion engine (100) is installed in a vehicle that is capable of being driven by the power of the internal combustion engine (100) and / or an electric motor (300), and the control device (200) is further configured to cause the microwave transmitter (35) to irradiate the catalyst device (34) with microwaves while the vehicle is being driven by the drive power of the electric motor (300) before the combustion engine start is requested, if the temperature of the exhaust gas purification catalyst is lower than a temperature at which a predetermined exhaust gas purification performance is achieved in the catalyst device (34) when the engine body (1) is operated in such a way that the air-fuel ratio of the exhaust gas becomes the stoichiometric air-fuel ratio. [8] Control device (200) for the internal combustion engine (100) according to claim 7, wherein the control device (200) is further configured as follows: to prevent the microwave transmitter (35) from emitting microwaves if the delay time is longer than the specified time period, even if the temperature of the exhaust gas purification catalyst is lower than a temperature at which a specified exhaust gas purification performance is achieved in the catalyst device (34), when the engine body (1) is operated in such a way that the air-fuel ratio of the exhaust gas becomes the stoichiometric air-fuel ratio. [9] Control device (200) for the internal combustion engine (100) according to one of claims 1 to 8, wherein the microwave absorber is arranged near the exhaust gas purification catalyst which has the oxidation function in the catalyst coating layer (342). [10] Control method for an internal combustion engine (100), wherein the internal combustion engine (100) comprises the following: a motor body (1); a catalyst device (34) configured in an exhaust gas line of the engine body (1) and comprising an exhaust gas purification catalyst with at least one oxidation function and a microwave absorber contained in a catalyst coating layer (342) formed in a substrate (341); and a microwave transmitter (35) for irradiating the catalyst device (34) with microwaves, wherein the tax procedure shows: Causing the microwave transmitter (35) to irradiate the catalyst device (34) with microwaves, and operating the engine body (1) such that an air-fuel ratio of exhaust gas expelled from the engine body (1) becomes a predetermined lean air-fuel ratio, which is leaner than a stoichiometric air-fuel ratio if an internal combustion engine start is requested when a temperature of the exhaust gas purification catalyst is lower than a predetermined temperature; Calculating a delay time until the combustion engine start is requested; and Causing the microwave transmitter (35) to irradiate the catalyst device (34) with microwaves when the delay time is a predetermined time or less, and when the microwave transmitter (35) is caused to irradiate the catalyst device (34) with microwaves without operating the engine body (1), the specified time is a period of time that allows the temperature of the exhaust gas purification catalyst to be increased to a temperature at which a specified exhaust gas purification performance is achieved in the catalyst device (34), when the engine body (1) is operated in such a way that the air-fuel ratio of the exhaust gas becomes the stoichiometric air-fuel ratio.

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