JP6390505B2 - Vehicle control device - Google Patents

Description

  The present invention relates to a vehicle control apparatus.

  Patent Document 1 discloses a hybrid vehicle that includes an internal combustion engine and an electric motor as power sources and is provided with an electrically heated catalyst device (EHC; Electrical Heated Catalyst) in an exhaust passage of the internal combustion engine. The electrically heated catalyst device is configured to be able to heat the catalyst carried on the heating element by a heating element that generates heat when held in the exhaust passage and energized.

JP 2013-144473 A

  Since the heat of the heating element is dissipated from the outer peripheral surface, the temperature of the outer peripheral surface of the heating element is lower than the temperature inside the heating element, particularly from the outer peripheral surface of the heating element, slightly inside the outer peripheral surface. A large temperature difference (temperature gradient) occurs in the biased region (outer peripheral region) up to the vicinity of the outer peripheral surface. Since the heating element is held in the exhaust passage and cannot be freely expanded, if a large temperature difference occurs inside the heating element, a large thermal stress may be generated in association therewith, which may cause a crack in the heating element. .

  The internal temperature difference in the outer peripheral region of the heating element is maximized while the temperature of the heating element is raised to the catalyst activation temperature, and tends to increase as the heating rate of the heating element increases. Therefore, it is effective to control the heating rate of the heating element in order to suppress cracks caused by an excessive internal temperature difference in the outer peripheral region of the heating element.

  Here, if the heating element is energized to raise the temperature of the heating element, the heating rate of the heating element can be controlled by controlling the amount of energization so that cracks do not occur in the heating element.

  On the other hand, the temperature of the heating element rises even when the heating element is not energized or is heated by the exhaust heat. For this reason, for example, when the engine required output immediately after the start of the internal combustion engine is large, the exhaust gas also becomes high temperature. Therefore, the catalyst is quickly heated to the activation temperature by the exhaust heat without energizing the heating element. be able to. However, when the catalyst is activated by the exhaust heat in this way, the heating rate of the heating element depends on the engine required output, so that the heating rate of the heating element cannot be controlled and a crack occurs in the heating element. There is a fear.

  Therefore, for example, as in the control device described in Patent Document 1, when the engine required output exceeds a predetermined threshold value, the intake air intake amount is reduced, or excess fuel is supplied without reducing the intake air amount. It is conceivable to reduce the air-fuel ratio by injecting the gas into the exhaust gas so as to reduce the exhaust gas temperature and suppress the generation of cracks in the heating element.

  However, if the intake air amount is reduced and the exhaust temperature is lowered as in the control device described in Patent Document 1, the engine output cannot be changed to the engine required output when the engine required output is large. There is a problem that it decreases.

  On the other hand, when the exhaust gas temperature is lowered by lowering the air-fuel ratio, such a decrease in acceleration performance can be suppressed. However, in Patent Document 1, it is unknown how long the air-fuel ratio is lowered.

  As described above, the internal temperature difference in the outer peripheral region of the heating element becomes the maximum while the temperature of the heating element is raised to the catalyst activation temperature, and thereafter, the temperature difference gradually decreases. Therefore, even after the time when the internal temperature difference in the outer peripheral region of the heating element becomes the maximum, if the air-fuel ratio is lowered and the exhaust temperature is lowered, the fuel is consumed wastefully and the fuel consumption deteriorates. In addition, since the time until the catalyst is activated becomes longer, there is a problem that exhaust emission is also deteriorated.

  The present invention has been made paying attention to such problems, and the temperature difference in the outer peripheral region of the heating element becomes excessive while suppressing deterioration of fuel consumption and exhaust emission without deteriorating the acceleration performance of the vehicle. It aims at suppressing the crack of the heat generating body resulting from it.

  In order to solve the above problems, according to an aspect of the present invention, an internal combustion engine as a power source, a heating element that is held in an exhaust passage of the internal combustion engine and generates heat when energized, and a heating element that carries the heating element A control device that controls a vehicle including the generated catalyst determines whether there is a warm-up request for activating the catalyst based on the temperature of the heating element at the time of starting the engine, and there is a warm-up request When the engine required output is equal to or higher than the exhaust temperature lowering required output determined based on the temperature of the heating element at the time of starting the engine, the catalyst is heated by the exhaust heat without energizing the heating element, and the catalyst is heated by the exhaust heat. Excess fuel for lowering the exhaust gas temperature until the temperature of the heating element heated together exceeds the temperature at which the temperature difference between the outer periphery of the heating element and the outer periphery near the outer periphery becomes maximum. Inject the internal combustion engine Configured to transfer.

  According to this aspect of the present invention, cracks in the heating element due to excessive temperature difference in the outer peripheral region of the heating element are suppressed while suppressing deterioration of fuel consumption and exhaust emission without reducing the acceleration performance of the vehicle. Can be suppressed.

FIG. 1 is a schematic configuration diagram of a vehicle and an electronic control unit that controls the vehicle according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a detailed configuration of the internal combustion engine according to the embodiment of the present invention. FIG. 3 is a diagram illustrating a problem that occurs when the catalyst is activated by exhaust heat without energizing the conductive carrier. FIG. 4 is a flowchart for explaining the control of the internal combustion engine at the time of cold start according to the present embodiment, which is performed by the electronic control unit. FIG. 5 is a table for calculating the exhaust temperature reduction request output based on the initial carrier temperature. FIG. 6 is a time chart for explaining the control operation of the internal combustion engine at the time of cold start according to one embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same reference numerals are assigned to similar components.

  FIG. 1 is a schematic configuration diagram of a vehicle 110 and an electronic control unit 200 that controls the vehicle 110 according to an embodiment of the present invention.

  The vehicle 110 according to the present embodiment includes an internal combustion engine 100, a power split mechanism 40, a first rotating electrical machine 50, a second rotating electrical machine 60, a battery 70, a boost converter 81, a first inverter 82, and a second. An inverter 83, and configured to be able to transmit the power of one or both of the two power sources of the internal combustion engine 100 and the second rotating electrical machine 60 to the wheel drive shaft 112 via the final reduction gear 111. Hybrid vehicle. The vehicle 110 is not limited to a hybrid vehicle, and may be a normal vehicle including only the internal combustion engine 100 as a power source.

  The internal combustion engine 100 includes an engine main body 1, an intake device 20, and an exhaust device 30, and generates power for rotating an output shaft 113 connected to a crankshaft (not shown) of the engine main body 1. . Hereinafter, the detailed configuration of the internal combustion engine 100 will be described with reference to FIG.

  As shown in FIG. 2, the engine body 1 includes a cylinder block 2 and a cylinder head 3 fixed to the upper surface of the cylinder block 2.

  A plurality of cylinders 4 are formed in the cylinder block 2. A piston 5 that reciprocates inside the cylinder 4 in response to combustion pressure is housed inside the cylinder 4. The piston 5 is connected to a crankshaft via a connecting rod, and the reciprocating motion of the piston 5 is converted into rotational motion by the crankshaft. A space defined by the inner wall surface of the cylinder head 3, the inner wall surface of the cylinder 4, and the piston crown surface is a combustion chamber 6.

  The cylinder head 3 includes an intake port 7 that opens to one side surface of the cylinder head 3 and opens to the combustion chamber 6, an exhaust port 8 that opens to the other side surface of the cylinder head 3 and opens to the combustion chamber 6, Is formed.

  The cylinder head 3 includes an intake valve 9 for opening and closing the opening between the combustion chamber 6 and the intake port 7, an exhaust valve 10 for opening and closing the opening between the combustion chamber 6 and the exhaust port 8, and an intake valve 9. An intake camshaft 11 that opens and closes and an exhaust camshaft 12 that opens and closes the exhaust valve 10 are attached. One end of the intake camshaft 11 is provided with a hydraulic variable valve mechanism (not shown) that can set the opening / closing timing of the intake valve 9 to an arbitrary timing.

  Further, the cylinder head 3 has a fuel injection valve 13 for injecting fuel into the combustion chamber 6, and an ignition for igniting the mixture of fuel and air injected from the fuel injection valve 13 in the combustion chamber 6. A plug 14 is attached. The fuel injection valve 13 may be attached so as to inject fuel into the intake port 7.

  The intake device 20 is a device for introducing air into the cylinder 4 through the intake port 7, and includes an air cleaner 21, an intake pipe 22, an intake manifold 23, an air flow meter 211, and an electronically controlled throttle valve. 24.

  The air cleaner 21 removes foreign matters such as sand contained in the air.

  One end of the intake pipe 22 is connected to the air cleaner 21, and the other end is connected to a surge tank 23 a of the intake manifold 23. The intake pipe 22 guides air (intake air) flowing into the intake pipe 22 via the air cleaner 21 to the surge tank 23 a of the intake manifold 23.

  The intake manifold 23 includes a surge tank 23a and a plurality of intake branch pipes 23b branched from the surge tank 23a and connected to the openings of the intake ports 7 formed on the side surface of the cylinder head. The air guided to the surge tank 23a is evenly distributed in each cylinder 4 through the intake branch pipe 23b. Thus, the intake pipe 22, the intake manifold 23 and the intake port 7 form an intake passage for guiding air into each cylinder 4.

  The air flow meter 211 is provided in the intake pipe 22. The air flow meter 211 detects the flow rate of air flowing through the intake pipe 22 (hereinafter referred to as “intake amount”).

  The throttle valve 24 is provided in the intake pipe 22 on the downstream side of the air flow meter 211. The throttle valve 24 is driven by a throttle actuator 25 to change the passage cross-sectional area of the intake pipe 22 continuously or stepwise. By adjusting the opening of the throttle valve 24 (hereinafter referred to as “throttle opening”) by the throttle actuator 25, the amount of intake air taken into each cylinder 4 is adjusted. The throttle opening is detected by the throttle sensor 212.

  The exhaust device 30 is a device for purifying combustion gas generated in the combustion chamber 6 (hereinafter referred to as “exhaust”) and discharging it to the outside air, and includes an exhaust manifold 31, an exhaust pipe 32, and an exhaust temperature sensor. 213 and an electrically heated catalyst device 33.

  The exhaust manifold 31 includes a plurality of exhaust branch pipes 31a connected to the openings of the exhaust ports 8 formed on the side surface of the cylinder head, and a collection pipe 31b that collects the exhaust branch pipes 31a into one. Prepare.

  The exhaust pipe 32 has one end connected to the collecting pipe 31b of the exhaust manifold 31 and the other end opened to the outside air. Exhaust gas discharged from each cylinder 4 through the exhaust port 8 to the exhaust manifold 31 flows through the exhaust pipe 32 and is discharged to the outside air.

  The exhaust temperature sensor 213 is provided in the exhaust pipe 32 upstream of the catalyst device 33 and detects the temperature of the exhaust gas flowing into the catalyst device 33.

  The electrically heated catalyst device 33 includes an outer cylinder 34 attached to the exhaust pipe 32, a conductive carrier 35, a holding mat 36, a pair of electrodes 37, and a carrier temperature sensor 214.

  The outer cylinder 34 is a part for housing the conductive carrier 35 therein, and is typically a case made of a metal such as stainless steel or a non-metal such as ceramic.

The conductive carrier 35 is a carrier formed of a material that generates heat when energized, such as silicon carbide (SiC) or molybdenum disilicide (MoSi ₂ ). The conductive carrier 35 according to the present embodiment is a so-called honeycomb-type carrier in which a plurality of exhaust flow passages are formed along the exhaust flow direction, and a catalyst is supported on the surface of each exhaust flow passage. In this embodiment, the three-way catalyst is supported on the conductive support 35, but the type of catalyst supported on the conductive support 35 is not particularly limited, and desired exhaust purification performance can be obtained from various catalysts. Therefore, a catalyst necessary for the purpose can be appropriately selected and supported.

The holding mat 36 is provided between the outer cylinder 34 and the conductive carrier 35 so as to fill a gap between the outer cylinder 34 and the conductive carrier 35, and the conductive carrier 35 is placed in a predetermined position in the outer cylinder 34. It is a part for holding. The holding mat 36 is made of an electrically insulating material such as alumina (Al ₂ O ₃ ).

  The pair of electrodes 37 are components for applying a voltage to the conductive carrier 35, and are electrically connected to the conductive carrier 35 in a state of being electrically insulated from the outer cylinder 34, respectively. 1, the battery 70 is connected via a voltage adjustment circuit 38 for adjusting the voltage applied to the conductive carrier 35. By applying a voltage to the conductive carrier 35 through the pair of electrodes 37 and supplying electric power to the conductive carrier 35, a current flows through the conductive carrier 35, and the conductive carrier 35 generates heat. The catalyst supported on is heated. The voltage applied to the conductive carrier 35 by the pair of electrodes 37 can be adjusted by controlling the voltage adjustment circuit 38 by the electronic control unit 200. For example, the voltage of the battery 70 can be applied as it is, It is also possible to adjust the voltage to an arbitrary voltage and apply it.

  The carrier temperature sensor 214 is provided in the outer cylinder 34 in the vicinity of the conductive carrier 35 and on the downstream side of the conductive carrier 35, and detects the temperature of the conductive carrier 35.

  Thus, the exhaust port 8, the exhaust manifold 31, the exhaust pipe 32, and the outer cylinder 34 form an exhaust passage through which the exhaust discharged from each cylinder 4 flows.

  In the present embodiment, the non-supercharged gasoline engine as described above has been described as an example of the internal combustion engine 100. However, the present invention is not limited to the above configuration, and the combustion mode, the cylinder arrangement, and the fuel injection mode are described. The configuration of the intake / exhaust system, the configuration of the valve operating mechanism, the presence / absence of a supercharger, the supercharging mode, and the like may be different from those described above.

  Returning to FIG. 1, the power split mechanism 40 divides the power of the internal combustion engine 100 into two systems of power for rotating the wheel drive shaft 112 and power for driving the first rotating electrical machine 50 to regenerate. And a sun gear 41, a ring gear 42, a pinion gear 43, and a planetary carrier 44.

  The sun gear 41 is an external gear and is disposed at the center of the power split mechanism 40. The sun gear 41 is connected to the rotation shaft 53 of the first rotating electrical machine 50.

  The ring gear 42 is an internal gear, and is arranged around the sun gear 41 so as to be concentric with the sun gear 41. The ring gear 42 is connected to the rotating shaft 63 of the second rotating electrical machine 60. Further, a drive gear 114 for transmitting the rotation of the ring gear 42 to the wheel drive shaft 112 via the final reduction gear 111 is integrally attached to the ring gear 42.

  The pinion gear 43 is an external gear, and a plurality of pinion gears 43 are arranged between the sun gear 41 and the ring gear 42 so as to mesh with the sun gear 41 and the ring gear 42.

  The planetary carrier 44 is connected to the output shaft 113 of the internal combustion engine 100 and rotates around the output shaft 113. The planetary carrier 44 is also connected to each pinion gear 43 so that when the planetary carrier 44 rotates, each pinion gear 43 can rotate (revolve) while rotating around the sun gear 41. ing.

  The first rotating electrical machine 50 is, for example, a three-phase AC synchronous motor generator, and is attached to the outer periphery of a rotating shaft 53 connected to the sun gear 41 and a rotor 51 in which a plurality of permanent magnets are embedded in the outer peripheral portion. And a stator 52 around which an exciting coil for generating a rotating magnetic field is wound. The first rotating electrical machine 50 has a function as an electric motor that is driven by power by being supplied with electric power from the battery 70 and a function as a generator that is driven by regeneration by receiving the power of the internal combustion engine 100.

  In the present embodiment, the first rotating electrical machine 50 is mainly used as a generator. When the internal combustion engine 100 is started, the output shaft 113 is rotated and cranked to be used as an electric motor and serve as a starter.

  The second rotating electrical machine 60 is, for example, a three-phase AC synchronous motor generator, and is attached to the outer periphery of the rotating shaft 53 connected to the ring gear 42 and a rotor 61 in which a plurality of permanent magnets are embedded in the outer peripheral portion. And a stator 62 around which an exciting coil for generating a rotating magnetic field is wound. The second rotating electrical machine 60 functions as an electric motor that is driven by power by being supplied with power from the battery 70 and functions as a generator that is driven by regeneration from the wheel drive shaft 112 when the vehicle 110 is decelerated. And having.

  The battery 70 is a chargeable / dischargeable secondary battery such as a nickel / cadmium storage battery, a nickel / hydrogen storage battery, or a lithium ion battery. In the present embodiment, a lithium ion secondary battery having a rated voltage of about 200 V is used as the battery 70. The battery 70 supplies the charging power of the battery 70 to the first rotating electric machine 50 and the second rotating electric machine 60 so that they can be driven by powering, and the first rotating electric machine 50 and the second rotating electric machine 60 The battery 70 is electrically connected to the first rotating electrical machine 50 and the second rotating electrical machine 60 via a boost converter 81 or the like so that the generated power can be charged in the battery 70. The battery 70 also supplies the conductive carrier 35 via the voltage adjustment circuit 38 and the pair of electrodes 37 so that the charging power of the battery 70 can be supplied to the conductive carrier 35 to heat the conductive carrier 35. Electrically connected.

  Further, the battery 70 is configured to be electrically connectable to an external power source via a charge control circuit 71 and a charging lid 72 so that the battery 70 can be charged from an external power source such as a household outlet. The charge control circuit 71 converts an alternating current supplied from an external power source into a direct current based on a control signal from the electronic control unit 200, boosts the input voltage to the battery voltage, and supplies the power of the external power source to the battery 70. It is an electric circuit that can be charged. The battery 70 does not necessarily need to be configured to be able to be charged from an external power source.

  Boost converter 81 boosts the voltage between the terminals of the primary side terminal based on the control signal from electronic control unit 200 and outputs it from the secondary side terminal, and conversely, secondary voltage based on the control signal from electronic control unit 200. An electric circuit capable of stepping down the voltage between the terminals of the side terminals and outputting the voltage from the primary side terminal is provided. The primary side terminal of boost converter 81 is connected to the output terminal of battery 70, and the secondary side terminal is connected to the DC side terminals of first inverter 82 and second inverter 83.

  The first inverter 82 and the second inverter 83 convert a direct current input from the direct current side terminal into an alternating current (three-phase alternating current in the present embodiment) based on a control signal from the electronic control unit 200 to convert the direct current to the alternating current side. Each circuit includes an electric circuit that can output from the terminal and, conversely, convert an alternating current input from the alternating current side terminal into a direct current based on a control signal from the electronic control unit 200 and output the direct current from the direct current side terminal. The DC side terminal of the first inverter 82 is connected to the secondary side terminal of the boost converter 81, and the AC side terminal of the first inverter 82 is connected to the input / output terminal of the first rotating electrical machine 50. The DC side terminal of second inverter 83 is connected to the secondary side terminal of boost converter 81, and the AC side terminal of second inverter 83 is connected to the input / output terminal of second rotating electrical machine 60.

  The electronic control unit 200 is composed of a digital computer and is connected to each other by a bi-directional bus 201. A ROM (read only memory) 202, a RAM (random access memory) 203, a CPU (microprocessor) 204, an input port 205, and an output port 206.

  In addition to the air flow meter 211, the throttle sensor 212, the exhaust temperature sensor 213, and the carrier temperature sensor 214, the input port 205 includes a vehicle speed sensor 215 for detecting the vehicle speed and an SOC sensor for detecting the battery charge amount. An output signal such as 216 is input via each corresponding AD converter 207. Further, the output voltage of the load sensor 217 that generates an output voltage proportional to the amount of depression of the accelerator pedal 220 (hereinafter referred to as “accelerator depression amount”) is input to the input port 205 via the corresponding AD converter 207. The The input port 205 receives an output signal of a crank angle sensor 218 that generates an output pulse every time the crankshaft of the engine body 1 rotates, for example, 15 °, as a signal for calculating the engine rotation speed. As described above, output signals of various sensors necessary for controlling the vehicle 110 are input to the input port 205.

  The output port 206 is connected to the fuel injection valve 13, spark plug 14, throttle actuator 25, voltage adjustment circuit 38, charge control circuit 71, boost converter 81, first inverter 82, and second inverter 83 via a corresponding drive circuit 208. Each control component is electrically connected.

  The electronic control unit 200 controls the vehicle 110 by outputting a control signal for controlling each control component from the output port 206 based on the output signals of various sensors input to the input port 205. Hereinafter, the control of the vehicle 110 performed by the electronic control unit 200 will be described.

  The electronic control unit 200 sets the travel mode of the vehicle 110 based on the battery charge amount. Specifically, when the battery charge amount is larger than a predetermined mode switching charge amount (for example, 25% of the full charge amount), the electronic control unit 200 sets the travel mode of the vehicle 110 to CD (Charge Depleting). Set to mode. The CD mode may be referred to as an EV (Electric Vehicle) mode.

  When the traveling mode of the vehicle 110 is set to the CD mode, the electronic control unit 200 basically powers the second rotating electrical machine 60 using the charging power of the battery 70 with the internal combustion engine 100 stopped. The wheel drive shaft 112 is rotated only by the power of the second rotating electrical machine 60. The electronic control unit 200 exceptionally operates the internal combustion engine 100 when a predetermined engine operating condition is satisfied, and rotates the wheel drive shaft 112 with the power of both the internal combustion engine 100 and the second rotating electrical machine 60.

  The engine operating conditions in the CD mode are set from the viewpoint of ensuring the traveling performance of the vehicle 110 and protecting the parts. For example, when the vehicle speed is a predetermined vehicle speed (for example, 100 km / h) or more, When the vehicle required output set based on the accelerator depression amount and the vehicle speed is greater than or equal to a predetermined output (when sudden acceleration is requested), or when the battery temperature is lower than a predetermined temperature (for example, −10 ° C.) Etc.

  As described above, in the CD mode, the second rotating electrical machine 60 is driven by power using the charging power of the battery 70 preferentially, and at least the power of the second rotating electrical machine 60 is transmitted to the wheel drive shaft 112 to travel the vehicle 110. It is a mode to make it.

  On the other hand, when the battery charge amount is equal to or less than the mode switching charge amount, electronic control unit 200 sets the traveling mode of vehicle 110 to a CS (Charge Sustaining) mode. The CS mode may be referred to as an HV (Hybrid Vehicle) mode.

  When the traveling mode of the vehicle 110 is set to the CS mode, the electronic control unit 200 divides the power of the internal combustion engine 100 into two systems by the power split mechanism 40 and uses one power of the split internal combustion engine 100 as wheels. The first rotary electric machine 50 is regeneratively driven by the other power while being transmitted to the drive shaft 112. Then, basically, the second rotating electrical machine 60 is driven by the power generated by the first rotating electrical machine 50, and the power of the second rotating electrical machine 60 is transmitted to the wheel drive shaft 112 in addition to one power of the internal combustion engine 100. Exceptionally, for example, when the accelerator depression amount is increased and the vehicle required output is equal to or higher than a predetermined output, the generated power of the first rotating electrical machine 50 and the charging power of the battery 70 are ensured to ensure the running performance of the vehicle 110. Thus, the second rotating electrical machine 60 is power-driven, and the power of both the internal combustion engine 100 and the second rotating electrical machine 60 is transmitted to the wheel drive shaft 112.

  As described above, in the CS mode, the internal combustion engine 100 is operated and the second rotating electrical machine 60 is power-driven using the power generated by the first rotating electrical machine 50 with priority, and both the internal combustion engine 100 and the second rotating electrical machine 60 are driven. This is a mode in which the vehicle 110 is driven by transmitting the motive power to the wheel drive shaft 112.

  Thus, in the hybrid vehicle, the internal combustion engine 100 is basically started when the traveling mode is switched from the CD mode to the CS mode. Switching from the CD mode to the CS mode basically depends on the battery charge amount.

  In order for the catalyst device 33 to exhibit the desired exhaust purification performance, it is necessary to raise the temperature of the catalyst supported on the conductive carrier 35 to the activation temperature and activate the catalyst. Therefore, in order to suppress the deterioration of exhaust emission after the engine is started, energization of the conductive carrier 35 is started during the CD mode to start warming up of the catalytic device 33, and before switching to the CS mode, the catalytic device 33 It is desirable to complete the warm-up. Therefore, in the present embodiment, when the battery charge amount decreases to the warm-up start charge amount larger than the mode switching charge amount during the CD mode, energization to the conductive carrier 35 is started to warm up the catalyst device 33. Yes.

  However, as described above, the internal combustion engine 100 may be started even in the CD mode, and before the battery charge amount decreases to the warm-up start charge amount, or the battery charge amount decreases to the warm-up start charge amount. After that, the internal combustion engine 100 may be started before it decreases to the mode switching charge amount. That is, the internal combustion engine 100 may be started before energization of the conductive carrier 35 or during energization.

  Here, for example, when there is a sudden acceleration request during the CD mode and the accelerator depression amount increases and the vehicle request output exceeds a predetermined output, the internal combustion engine 100 is started. "Engine demand output") increases and the exhaust temperature becomes high. Therefore, in such a case, the catalyst can be raised to the activation temperature quickly by the exhaust heat without energizing the conductive carrier 35. Therefore, when the temperature of the catalyst can be raised to the activation temperature early due to exhaust heat, it is not necessary to wastefully consume power by energizing the conductive carrier 35.

  Further, even in the case of a normal vehicle that is not a hybrid vehicle, if there is a sudden acceleration request immediately after the engine is started, the catalyst can be activated at an early activation temperature by exhaust heat even if the conductive carrier 35 is not energized. The temperature can be increased to.

  When the catalyst is activated by the exhaust heat in this way, the temperature of the conductive carrier 35 is increased by heating the conductive carrier 35 by the exhaust heat without energizing the conductive carrier 35. To do. However, when the catalyst is activated by exhaust heat without energizing the conductive carrier 35, the following problems occur.

  FIG. 3 is a diagram illustrating a problem that occurs when the catalyst is activated by exhaust heat without energizing the conductive carrier 35.

  FIG. 3A is a cross-sectional view of the catalyst device 33 when the catalyst device 33 is cut in a direction perpendicular to the exhaust flow direction. FIG. 3B is a diagram showing the transition of the temperature of each part of the conductive carrier 35 when the conductive carrier 35 is heated from the initial temperature corresponding to the outside temperature toward the activation temperature. The solid line in FIG. 3B shows the change in temperature at the center of the conductive carrier 35. The alternate long and short dash line in FIG. 3B shows the transition of the temperature of the outer peripheral surface of the conductive carrier 35 that is in contact with the holding mat 36. The broken line in FIG. 3B shows the transition of the temperature in the vicinity of the outer periphery slightly inside the outer peripheral surface (about 5 mm from the outer peripheral surface). FIG. 3C is a diagram showing the transition of the temperature difference (hereinafter referred to as “internal temperature difference”) ΔT between the outer peripheral surface of the conductive carrier 35 and the vicinity of the outer periphery.

  As shown in FIG. 3B, since the heat of the conductive carrier 35 is radiated from the outer peripheral surface, the temperature of the outer peripheral surface of the conductive carrier 35 is lower than the temperature of the central portion of the conductive carrier 35. In particular, a large temperature difference (temperature gradient) occurs in a biased region (outer peripheral region) from the outer peripheral surface of the heating element to the vicinity of the outer peripheral surface. Since the conductive carrier 35 is held in the exhaust passage and cannot be freely expanded, if a large temperature difference occurs inside the conductive carrier 35, a large thermal stress is generated accordingly, and the conductive carrier 35 is cracked. There is a fear.

  As shown in FIG. 3 (c), the internal temperature difference ΔT in the outer peripheral region of the conductive carrier 35 becomes maximum during the temperature raising of the conductive carrier 35 toward the activation temperature, and gradually thereafter. It gets smaller. The internal temperature difference ΔT tends to increase as the initial temperature of the conductive carrier 35 decreases (as the difference between the initial temperature and the activation temperature increases), and as the heating rate of the conductive carrier 35 increases. is there.

  Therefore, it is effective to control the heating rate of the conductive carrier 35 in order to suppress cracks caused by the excessive internal temperature difference ΔT.

  Here, if the conductive carrier 35 is energized to raise the temperature of the conductive carrier 35, the conductive carrier 35 is controlled so that cracks do not occur in the conductive carrier 35 by controlling the energization amount. The temperature rising rate can be controlled. However, when the catalyst is activated by exhaust heat without energizing the conductive carrier 35, the rate of temperature rise of the conductive carrier 35 depends on the engine required output, so the rate of temperature rise of the conductive carrier 35. There is a possibility that cracks may occur in the conductive support 35 without being controlled.

  Therefore, for example, when the engine required output exceeds a predetermined threshold value, the intake air intake amount is reduced, or the fuel is injected excessively without reducing the intake air intake amount, thereby reducing the air-fuel ratio. It is conceivable that the temperature of the exhaust gas discharged from the main body is lowered to prevent the conductive carrier 35 from cracking. However, if the intake air intake amount is decreased to reduce the exhaust temperature when the engine required output is large, the engine output cannot be made the engine required output and the acceleration performance may be deteriorated.

  On the other hand, when the exhaust temperature is lowered by lowering the air-fuel ratio, such a decrease in acceleration performance can be suppressed, but if the air-fuel ratio is not restored at an appropriate time, the following problems will occur. Arise. That is, as described above, the internal temperature difference ΔT in the outer peripheral region of the conductive carrier 35 is maximized while the temperature of the conductive carrier 35 is raised toward the activation temperature, and gradually decreases thereafter. To go. Therefore, after the time when the internal temperature difference ΔT becomes maximum, that is, after the center temperature of the conductive carrier 35 becomes higher than the temperature at which the internal temperature difference ΔT becomes maximum (hereinafter referred to as “peak temperature”). However, if the exhaust gas temperature is lowered by lowering the air-fuel ratio, the fuel is consumed unnecessarily, the fuel consumption is worsened, and the time until the catalyst is activated is also longer, so the exhaust emission is also worsened.

  Therefore, in this embodiment, when the internal combustion engine 100 is started in a state where the catalyst is not activated and the catalyst is activated by exhaust heat without energizing the conductive carrier 35, acceleration performance, fuel consumption, and exhaust emission are reduced. While suppressing the deterioration, the internal combustion engine 100 is controlled so that cracks in the heating element due to the excessive internal temperature difference ΔT can be suppressed. Hereinafter, control of the internal combustion engine 100 when the internal combustion engine 100 is started in a state where the catalyst is not activated (hereinafter referred to as “during cold start”) will be described.

  FIG. 4 is a flowchart for explaining the control of the internal combustion engine 100 during the cold start according to the present embodiment, which is performed by the electronic control unit 200.

  In step S1, the electronic control unit 200 determines whether or not there is a catalyst warm-up request based on the temperature of the conductive carrier 35 at the time of starting the engine (hereinafter referred to as “initial carrier temperature”). Since the exhaust gas has not yet flowed into the catalyst device 33 when the engine is started, there is no problem even if the temperature detected by the carrier temperature sensor 214 provided in the vicinity of the conductive carrier 35 is regarded as the carrier temperature. Therefore, in the present embodiment, the temperature detected by the carrier temperature sensor 214 when the engine is started is set as the initial carrier temperature. If the initial carrier temperature is lower than the activation temperature, the electronic control unit 200 determines that there is a catalyst warm-up request and proceeds to the process of step S2. On the other hand, if the initial carrier temperature is equal to or higher than the catalyst activation temperature, the electronic control unit 200 determines that there is no catalyst warm-up request and ends the process.

  In step S2, the electronic control unit 200 determines whether or not the initial carrier temperature is equal to or lower than a predetermined exhaust temperature lowering required temperature. The exhaust temperature lowering required temperature is set to an arbitrary temperature higher than the peak temperature (the carrier temperature at which the internal temperature difference ΔT in the outer peripheral region of the conductive carrier 35 is maximized). Such a determination is made because if the initial carrier temperature is already higher than the peak temperature, the conductive carrier 35 will not crack even if the conductive carrier 35 is heated by the exhaust heat. . If the initial carrier temperature is equal to or lower than the exhaust reduction request temperature, the electronic control unit 200 proceeds to the process of step S3. On the other hand, if the initial carrier temperature is higher than the exhaust reduction request temperature, the electronic control unit 200 proceeds to the process of step S9.

  In step S <b> 3, the electronic control unit 200 refers to the table of FIG. 5 and calculates the exhaust temperature reduction request output based on the initial carrier temperature. The exhaust temperature reduction request output is set in advance by experiments or the like. If the engine required output becomes larger than the exhaust temperature reduction required output, when the conductive carrier 35 is heated by the exhaust heat, the internal temperature difference ΔT may become excessive, and the conductive carrier 35 may crack. As shown in FIG. 5, the lower the initial carrier temperature, the smaller the exhaust temperature reduction request output is because the internal temperature difference ΔT when the conductive carrier 35 is heated is lower in the initial carrier temperature. This is because as the time increases (the difference between the initial carrier temperature and the activation temperature increases), the temperature increases.

  In step S4, the electronic control unit 200 determines whether or not the engine request output is equal to or higher than the exhaust temperature reduction request output. If the engine request output is equal to or higher than the exhaust temperature reduction request output, the electronic control unit 200 proceeds to the process of step S5. When the engine required output is equal to or higher than the exhaust temperature reduction required output, the exhaust temperature is sufficiently high, and the catalyst can be activated early by the exhaust heat, so that the conductive carrier 35 is not energized. On the other hand, if the engine required output is less than the exhaust temperature reduction required output, the electronic control unit 200 proceeds to the process of step S9 because there is no possibility of cracking in the conductive carrier 35 even if the exhaust temperature is not reduced.

  In step S5, the electronic control unit 200 determines whether or not the intake air amount has increased to a target intake air amount set based on the engine required output. Specifically, if the intake air amount detected by the air flow meter 211 is equal to or greater than the target intake air amount, the electronic control unit 200 proceeds to the process of step S6. On the other hand, if the intake air amount detected by the air flow meter 211 is less than the target intake air amount, the electronic control unit 200 proceeds to the process of step S9.

  When the engine required output fluctuates, the throttle valve 24 and the variable valve mechanism are driven to control the intake air amount toward the target intake air amount set based on the engine required output. At this time, since there is a delay in operation of the throttle valve 24 and the variable valve mechanism, a time lag occurs until the intake air amount reaches the target intake air amount. Therefore, even if the intake air amount has not increased to the target intake air amount and the flow proceeds to step S7 described later and excessive fuel for lowering the exhaust temperature is injected, fuel is injected more than necessary. As a result, fuel consumption and exhaust emissions deteriorate. Therefore, in the present embodiment, it is determined in step S5 whether or not the intake air amount has increased to the target intake air amount. If the intake air amount has not increased to the target intake air amount, the process proceeds to step S9.

  Thus, in step S5, it is determined whether or not the response delay of the intake system has been eliminated. In particular, in this embodiment, it is determined whether or not the response delay of the intake system has been completely eliminated. For example, it may be determined whether the intake air amount detected by the air flow meter 211 has increased to a predetermined intake air amount that is slightly smaller than the target intake air amount.

In step S <b> 6, the electronic control unit 200 determines whether the carrier temperature exceeds a peak temperature at which the internal temperature difference ΔT in the outer peripheral region of the conductive carrier 35 is maximum. Specifically, the electronic control unit 200 determines whether or not the integrated value GA _sum of the intake air amount after the engine required output becomes equal to or higher than the exhaust temperature decrease required output is equal to or less than a predetermined peak temperature determination threshold GA _peak. .

As described above, the carrier temperature can be accurately detected by the carrier temperature sensor 214 when the engine has not yet flowed into the catalyst device 33, but the carrier temperature sensor 214 can detect the carrier temperature after the exhaust flows. Cannot be detected with high accuracy. Therefore, in the present embodiment, exhaust the integrated value GA _sum of the intake air amount is used as a parameter representing the amount of heat added to the conductive support 35, the integrated value GA _sum of the intake air amount becomes greater than the peak temperature determination threshold GA _peak Sometimes it was determined that the carrier temperature exceeded the peak temperature. In the present embodiment, the peak temperature determination threshold GA _peak is a constant value. However, for example, based on the exhaust temperature detected by the exhaust temperature sensor, for example, the peak temperature determination threshold GA _peak decreases as the exhaust temperature increases. It may be corrected.

If the integrated value GA _sum of the intake air amount is equal to or less than the peak temperature determination threshold GA _peak , the electronic control unit 200 determines that the carrier temperature does not exceed the peak temperature, and proceeds to step S7. On the other hand, if the integrated value GA _sum of the intake air amount exceeds the peak temperature determination threshold GA _peak , the electronic control unit 200 determines that the carrier temperature exceeds the peak temperature, and proceeds to the process of step S8.

  In step S <b> 7, the electronic control unit 200 performs the fuel injection amount increase correction for suppressing the occurrence of cracks due to the excessive internal temperature difference ΔT, and operates the internal combustion engine 100. That is, the electronic control unit 200 operates the internal combustion engine 100 by injecting extra fuel for reducing the exhaust temperature. Specifically, the electronic control unit 200 sets a target intake air amount based on the engine required output, and sets a basic fuel injection amount (injection time) based on the target intake air amount. Then, a value obtained by adding an additional fuel injection amount for lowering the exhaust temperature set based on the target intake air amount to the basic fuel injection amount is set as the target fuel injection amount, and the fuel injection amount becomes the target fuel injection amount. Thus, the fuel injection valve 13 is controlled. Thereby, the temperature of the exhaust gas discharged from the engine body 1 can be lowered without impairing the acceleration performance. In the present embodiment, the basic fuel injection amount is set to an injection amount at which the air-fuel ratio becomes the stoichiometric air-fuel ratio, but it is not necessarily set to an injection amount at which the stoichiometric air-fuel ratio is obtained.

  In step S8, the electronic control unit 200 operates the internal combustion engine 100 without performing at least the fuel injection amount increase correction for suppressing the occurrence of cracks due to the excessive internal temperature difference ΔT. Therefore, the basic fuel injection amount is basically set as the target fuel injection amount, but corrections other than the fuel injection amount increase correction for suppressing the occurrence of cracks are applied to the basic fuel injection amount as necessary. May be.

  In step S9, the electronic control unit 200 determines whether or not the catalyst warm-up has been completed. Whether or not the catalyst has been warmed up can be determined, for example, based on whether the time detected by the exhaust temperature sensor 213 or the carrier temperature sensor 214 is equal to or higher than a predetermined time. . The electronic control unit 200 ends the process if the warming up of the catalyst is completed, and returns to the process of step S4 if completed.

  FIG. 6 is a time chart for explaining the control operation of the internal combustion engine 100 during the cold start according to the present embodiment.

  Assume that at time t1, the accelerator depression amount increases to the maximum depression amount during the CD mode, and the internal combustion engine 100 is started before energization of the conductive carrier 35 is started. Then, the electronic control unit 200 sets the exhaust temperature decrease request output based on the initial carrier temperature, and determines whether or not the engine request output is equal to or higher than the exhaust temperature decrease request output.

  From time t1 to time t2, the engine request output is equal to or higher than the exhaust temperature reduction request output, but the intake air amount has not reached the target intake air amount due to the response delay of the intake system, so the electronic control unit 200 Does not perform at least the fuel injection amount increase correction for suppressing the occurrence of cracks due to the excessive internal temperature difference ΔT, that is, the fuel injection amount increase correction for lowering the exhaust temperature. The engine 100 is operated.

When the intake air amount reaches the target intake air amount at time t2, the electronic control unit 200 causes the internal temperature difference ΔT to become excessive until time 3 when the integrated value GA _sum of the intake air amount exceeds the peak temperature determination threshold GA _peak. The internal combustion engine 100 is operated by performing fuel injection amount increase correction for suppressing the occurrence of cracks. That is, the internal combustion engine 100 is operated by injecting extra fuel for lowering the exhaust temperature.

  After time t3, the internal combustion engine 100 is operated without performing at least the fuel injection amount increase correction for lowering the exhaust gas temperature until the catalyst warm-up is completed.

  According to the present embodiment described above, the electronic control unit 200 that controls the vehicle 110 has a warm-up request for activating the catalyst based on the temperature of the conductive carrier 35 (initial carrier temperature) at the time of starting the engine. In the case where there is a warm-up request, if the engine required output is equal to or higher than the exhaust temperature lowering request output determined based on the temperature of the conductive carrier 35 at the time of starting the engine, the conductive carrier 35 is energized. The temperature of the conductive carrier 35 heated together with the catalyst by the exhaust heat is increased between the outer peripheral portion of the conductive carrier 35 and the outer peripheral vicinity inside the outer peripheral portion. The internal combustion engine 100 is operated by injecting extra fuel for lowering the exhaust temperature until the temperature difference ΔT exceeds the maximum temperature (peak temperature).

  As described above, the internal combustion engine 100 is operated by injecting extra fuel for lowering the exhaust temperature until the temperature of the conductive carrier 35 exceeds the peak temperature. After the time when the internal temperature difference ΔT in the region becomes the maximum, cracks can be prevented from occurring in the conductive carrier 35, and it is possible to suppress unnecessary injection of fuel for lowering the exhaust temperature, The time until the catalyst is activated can also be shortened. Therefore, it is possible to suppress cracks caused by excessive internal temperature difference ΔT in the outer peripheral region of the conductive carrier 35 while suppressing deterioration of fuel consumption and exhaust emission without deteriorating the acceleration performance of the vehicle 110. .

  In addition, the electronic control unit 200 according to the present embodiment takes into account the response delay of the intake system and supplies fuel for lowering the exhaust temperature after the intake amount reaches the target intake amount set based on the engine required output. The internal combustion engine 100 is operated by injecting extra.

  The amount of fuel that is excessively injected to lower the exhaust temperature is set based on the target intake air amount, so that the exhaust air temperature is decreased even though the intake air amount has not increased to the target intake air amount. If excessive fuel is injected, fuel is injected more than necessary, and fuel consumption and exhaust emission deteriorate. Therefore, after the intake air amount reaches the target intake air amount, the fuel consumption and the exhaust emission can be further prevented from deteriorating by operating the internal combustion engine 100 by injecting extra fuel for lowering the exhaust temperature.

  The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

For example, in the above embodiment, whether or not the intake air amount has increased to the target intake air amount in step S5 of FIG. 4 is determined based on whether or not the intake air amount detected by the air flow meter 211 is equal to or greater than the target intake air amount. However, the present invention is not limited to this method, and may be modified as follows, for example. That is, it is determined that the intake air amount has increased to the target intake air amount when the elapsed time after the engine required output becomes larger than the exhaust temperature decrease required output becomes equal to or longer than a predetermined time set in advance. It may be changed. Further, even if the intake air amount integrated value GA _sum becomes equal to or larger than a predetermined threshold value smaller than the peak temperature determination threshold GA _peak , the intake air amount is determined to be increased to the target intake air amount. good. Thus, it can be changed to various determination methods that can determine whether the response delay of the intake system when the engine required output fluctuates has been eliminated.

35 Conductive carrier (heating element)
DESCRIPTION OF SYMBOLS 100 Internal combustion engine 110 Vehicle 200 Electronic control unit (control apparatus)

Claims (2)

An internal combustion engine as a power source;
A heating element that is held in the exhaust passage of the internal combustion engine and generates heat when energized;
A catalyst supported on the heating element;
A vehicle control device comprising:
Based on the temperature of the heating element at the time of engine start, it is determined whether there is a warm-up request for activating the catalyst,
In the case where there is a warm-up request, if the engine required output is equal to or higher than the exhaust temperature lowering request output determined based on the temperature of the heating element at the time of starting the engine, the heating element is not energized and the heat is exhausted. While heating the catalyst,
The exhaust temperature is increased until the temperature of the heating element heated together with the catalyst by the exhaust heat exceeds the peak temperature at which the temperature difference between the outer periphery of the heating element and the outer periphery near the outer periphery is maximum. Operating the internal combustion engine by injecting extra fuel for lowering ,
It is determined that the temperature of the heating element has exceeded the peak temperature when the integrated value of the intake air amount after the engine required output becomes equal to or higher than the exhaust temperature decrease required output is greater than a predetermined peak temperature determination threshold. It is configured to be so that,
Vehicle control device. The peak temperature determination threshold is further reduced as the temperature of the exhaust gas flowing into the heating element is higher.
The vehicle control device according to claim 1.

Images