JP2009092001A - Control device for internal combustion engine, control method, program for materializing method, and record medium recording program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve fuel consumption efficiency without dropping exhaust emission control performance of a catalyst in restart of an internal combustion engine controlled to temporarily stop during vehicle travel. <P>SOLUTION: ECU executes a program including a step S110 for judging whether estimated temperature TSC of a first catalyst purifying exhaust gas of an engine is higher than lower limit temperature T(1) or not, a step S112 for judging whether estimated temperature TUF of a second catalyst provided at a downstream of the first catalyst is higher than lower limit temperature T(2) or not, a step S114 for continuing temporary stop of the engine when TSC is higher than T(1) (Yes in S110) and TUF is higher than T(2) (Yes in S112), and a step S116 for restarting the engine when TSC is lower than T(1) (No in S110) or TUF is lower than T(2) (No in S112). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to control of an internal combustion engine mounted on a vehicle, and more particularly to control of an internal combustion engine that is controlled to be temporarily stopped while the vehicle is running.

  Hybrid vehicles using an engine and a motor as power sources have been put into practical use. In such a hybrid vehicle, for the purpose of air environment conservation and fuel consumption efficiency improvement, the engine is temporarily stopped according to the traveling state of the vehicle, and the vehicle is driven only by the motor. On the other hand, the exhaust system of the engine is provided with a catalytic converter that purifies harmful substances (HC, CO, NOx, etc.) contained in the exhaust gas. In order to activate and effectively operate the catalyst in the catalytic converter, it is necessary to heat the catalyst to a considerably high temperature (for example, around 700 ° C.), but the temperature of the catalyst is higher (for example, around 850 ° C.). ), The catalyst function deteriorates. While the hybrid vehicle is running, if the engine is temporarily stopped as described above, the flow of the exhaust gas passing through the catalyst is interrupted, and the cooling action of the catalyst by the exhaust gas is reduced. In addition, the temperature of the catalyst may increase for a while immediately after the engine is stopped due to reaction heat caused by unburned components already present in the catalytic converter when the engine is stopped. Therefore, there is a possibility of deteriorating the catalyst function. A technique for solving such a problem is disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-299400 (Patent Document 1).

  Japanese Patent Laid-Open No. 2005-299400 (Patent Document 1) discloses that, in a vehicle in which an internal combustion engine is stopped and restarted, the state of the catalyst resulting from the operation history is reflected in the control so that the high temperature of the catalyst after restarting. A technique for effectively suppressing deterioration is disclosed. The vehicle stop and start device disclosed in this publication includes first stop means for stopping the internal combustion engine when a predetermined first stop condition is satisfied, and a predetermined second stop different from the first stop condition. And second stop means for stopping the internal combustion engine when a second stop condition is satisfied that includes a condition that the catalyst temperature is equal to or higher than a predetermined value and that the amount of gas passing through the catalyst is less than a predetermined value. And a restarting means for restarting the internal combustion engine when a predetermined restart condition is satisfied after the internal combustion engine is stopped. The stop start device includes a storage means for storing a signal to that effect when there is a stop by the second stop means, and an oxygen amount reducing means for reducing the amount of oxygen in the intake air mixture of the internal combustion engine. The restarting means reduces the oxygen amount to the oxygen amount reducing means upon restarting when a signal is stored in the storage means.

According to the vehicle stop / start device disclosed in this publication, when the second stop condition including that the catalyst temperature is equal to or higher than a predetermined value and the amount of gas passing through the catalyst is lower than the predetermined value is satisfied, The stop means stops the internal combustion engine, and in that case, the storage means stores a signal to that effect. Then, when the signal is stored in the storage unit, the restart unit causes the oxygen amount reduction unit to decrease the oxygen amount when restarting. If there is a stop by the second stop means, the catalyst temperature is relatively high, and conditions other than the temperature such as the amount of unburned components in the catalytic converter are considered to be in a state where the catalyst is likely to overheat. By reducing the amount of oxygen at the time of restart when there is a stop by the second stop means, the state of the catalyst resulting from the operation history can be reflected in the control. As a result, high temperature deterioration of the catalyst after restart can be effectively suppressed.
JP-A-2005-299400

  By the way, when the engine is temporarily stopped while the hybrid vehicle is traveling, the flow of the high-temperature exhaust gas passing through the catalyst is interrupted and the cooling of the catalyst by the traveling wind is continued. Therefore, if the engine is stopped for a long time, the fuel efficiency can be improved, but the temperature of the catalyst is excessively lowered, and the exhaust gas purification action of the catalyst may not be effective when the engine is restarted. However, Patent Document 1 discloses a technique for suppressing high-temperature deterioration of the catalyst after restarting the internal combustion engine. However, both improvement in fuel efficiency and suppression of reduction in exhaust purification performance during restart of the internal combustion engine are achieved. No mention is made of technology to do.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a catalyst for restarting an internal combustion engine in an internal combustion engine controlled to be temporarily stopped while the vehicle is running. It is to provide a control device, a control method, a program for realizing the method, and a recording medium on which the program is recorded, which can improve the fuel consumption efficiency without deteriorating the exhaust gas purification performance.

  A control device according to a first aspect controls an internal combustion engine in which exhaust gas is purified by at least one catalyst. The internal combustion engine is controlled so as to be temporarily stopped while the vehicle is traveling. The control device is configured to estimate the temperature of the catalyst based on the state of the vehicle, and when the internal combustion engine is controlled to be temporarily stopped, the estimated temperature is the exhaust gas purification of the catalyst. The internal combustion engine is temporarily stopped when it is higher than a predetermined temperature related performance, and is restarted when the estimated temperature is lower than the predetermined temperature. Control means for controlling. The control method according to the sixth invention has the same requirements as the control device according to the first invention.

  According to the first or sixth invention, based on the state of the vehicle (for example, the rotational speed of the internal combustion engine, the cooling water temperature of the internal combustion engine, the intake air amount, the intake air temperature, the stop time of the internal combustion engine, the vehicle speed, etc.) The temperature of the catalyst that purifies the exhaust of the internal combustion engine is estimated. When the internal combustion engine is controlled to be temporarily stopped and the estimated catalyst temperature is higher than a predetermined temperature related to the exhaust gas purification performance of the catalyst, the internal combustion engine is temporarily stopped. If it continues and is below a predetermined temperature, the internal combustion engine is restarted. In this way, for example, the temporary stop time of the internal combustion engine can be ensured to the maximum while maintaining the catalyst temperature at or above the temperature necessary for activating the catalyst. Therefore, it is possible to improve the fuel consumption efficiency without reducing the exhaust gas purification performance of the catalyst when the internal combustion engine is restarted. As a result, in an internal combustion engine that is controlled so as to be temporarily stopped while the vehicle is running, it is possible to improve the fuel consumption efficiency without reducing the exhaust purification performance of the catalyst when the internal combustion engine is restarted. A control device and a control method can be provided.

  In the control device according to the second invention, in addition to the configuration of the first invention, the predetermined temperature is a lower limit temperature of the catalyst that exhibits exhaust purification performance required for the vehicle. The control method according to the seventh invention has the same requirements as the control device according to the second invention.

  According to the second or seventh aspect of the invention, the internal combustion engine is temporarily stopped until the estimated temperature of the catalyst is lowered to the lower limit temperature of the catalyst that exhibits the exhaust purification performance required for the vehicle. Therefore, it is possible to maximize the fuel consumption efficiency while ensuring the minimum catalyst exhaust purification performance.

  In the control device according to the third aspect of the invention, in addition to the configuration of the first or second aspect, the estimating means includes the vehicle speed, the rotational speed of the internal combustion engine, and the cooling water of the internal combustion engine during operation of the internal combustion engine. A means for estimating the temperature of the catalyst based on the temperature, the amount of air sucked into the internal combustion engine and the temperature of the air sucked, and the internal combustion engine is controlled to be temporarily stopped; And means for correcting the estimated temperature of the catalyst during operation of the internal combustion engine based on at least one of the stop time of the internal combustion engine and the speed of the vehicle. The control method according to the eighth invention has the same requirements as the control device according to the third invention.

  According to the third or eighth aspect of the present invention, the catalyst is cooled by the traveling wind while the vehicle is traveling, regardless of the operating state of the internal combustion engine. Further, during the operation of the internal combustion engine, the catalyst is heated or cooled by the exhaust gas. Therefore, during operation of the internal combustion engine, the speed of the vehicle having a correlation with the flow rate of the traveling wind, the rotation speed of the internal combustion engine having a correlation with the exhaust temperature, the temperature of the cooling water of the internal combustion engine, the air sucked into the internal combustion engine The temperature of the catalyst is estimated based on at least one of the amount of air taken into the internal combustion engine that has a correlation with the temperature of the exhaust gas and the exhaust gas flow rate. As a result, the temperature of the catalyst during operation of the internal combustion engine can be accurately estimated. On the other hand, during the temporary stop of the internal combustion engine, the flow of exhaust gas is interrupted and the cooling of the catalyst by the traveling wind is continued, so the temperature of the catalyst decreases with time. Therefore, when the internal combustion engine is controlled to be temporarily stopped, at least one of the vehicle speed correlated with the stop time of the internal combustion engine where the cooling by the traveling wind continues and the flow rate of the traveling wind is correlated. Based on this, the temperature of the catalyst estimated during operation of the internal combustion engine is corrected. Thereby, when the internal combustion engine is temporarily stopped, the temperature of the catalyst can be accurately estimated.

  In the control device according to the fourth invention, in addition to the configuration of any one of the first to third inventions, the vehicle includes an upstream catalyst and a downstream catalyst. The estimation means includes means for estimating the temperature of the upstream catalyst and means for estimating the temperature of the downstream catalyst. When the temperature of the upstream catalyst is higher than a predetermined temperature related to the exhaust purification performance of the upstream catalyst, the control means determines that the temperature of the downstream catalyst is a predetermined temperature related to the exhaust purification performance of the downstream catalyst. Means for continuing the temporary stop in at least any of the higher cases. The control method according to the ninth aspect has the same requirements as the control device according to the fourth aspect.

  According to the fourth or ninth invention, the vehicle is provided with the upstream catalyst and the downstream catalyst, and the temperature of the upstream catalyst and the temperature of the downstream catalyst are estimated. When the temperature of the upstream catalyst is higher than the predetermined temperature related to the exhaust purification performance of the upstream catalyst, the temperature of the downstream catalyst is higher than the predetermined temperature related to the exhaust purification performance of the downstream catalyst. In at least one of the cases, the internal combustion engine is temporarily stopped. In this way, for example, emphasizing fuel consumption efficiency, continuing the temporary stop of the internal combustion engine until the temperature of both catalysts decreases to the lower limit temperature, emphasizing the reliability of exhaust purification performance, The internal combustion engine can be restarted when the temperature of one catalyst falls to the lower limit temperature.

  In the control device according to the fifth invention, in addition to the configuration of any one of the first to third inventions, the vehicle includes an upstream catalyst and a downstream catalyst. The estimation means includes means for estimating the temperature of the upstream catalyst. The control means includes means for continuing the temporary stop when the temperature of the upstream catalyst is higher than a predetermined temperature related to the exhaust gas purification performance of the upstream catalyst. The control method according to the tenth invention has the same requirements as the control device according to the fifth invention.

  According to the fifth or tenth aspect of the invention, the vehicle includes the upstream catalyst and the downstream catalyst. The temperature of the upstream catalyst is more susceptible to exhaust than the downstream catalyst. Therefore, when the temperature of the catalyst is estimated from the exhaust gas temperature or the flow rate, the temperature of the upstream catalyst can be estimated more accurately than the downstream catalyst. Therefore, the temperature of the upstream catalyst is estimated, and when the temperature of the upstream catalyst is higher than a predetermined temperature related to the exhaust gas purification performance of the upstream catalyst, the internal combustion engine is temporarily stopped. In this way, the internal combustion engine is temporarily stopped until the temperature of the upstream catalyst decreases to the lower limit temperature, and it is not necessary to estimate the downstream catalyst temperature. Therefore, it is possible to achieve both reduction of exhaust purification performance and improvement of fuel consumption efficiency while reducing costs.

  In the program according to the eleventh invention, a computer is caused to execute the control method according to any of the sixth to tenth inventions. A recording medium according to a twelfth aspect of the invention is a medium in which a computer-readable program for causing a computer to execute the control method according to any of the sixth to tenth aspects of the invention is recorded.

  According to the eleventh or twelfth invention, the control method according to any of the sixth to tenth inventions can be realized using a computer (which may be general purpose or dedicated).

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  A hybrid vehicle 10 equipped with a control device according to the present embodiment will be described with reference to FIG. The vehicle to which the present invention can be applied is not limited to the hybrid vehicle 10 shown in FIG. 1 as long as the engine is temporarily stopped while the vehicle is running, and may be a vehicle having another aspect. .

  Hybrid vehicle 10 includes an engine 100 and motor generators 300A, 300B (MG (1) 300A, MG (2) 300B). In the following, for convenience of explanation, MG (1) 300A and MG (2) 300B are also referred to as motor generator 300 when they are described without being distinguished. Regenerative braking is performed when motor generator 300 functions as a generator. When motor generator 300 functions as a generator, the kinetic energy of the vehicle is converted into electric energy, a regenerative braking force (regenerative brake) is generated, and the vehicle is decelerated.

  In addition to this, the hybrid vehicle 10 includes a speed reducer 14 that transmits power generated by the engine 100 and the motor generator 300 to the drive wheels 12, and transmits driving of the drive wheels 12 to the engine 100 and the motor generator 300. , Power split mechanism 200 that distributes the power generated by engine 100 to output shaft 212 and MG (1) 300A, travel battery 310 that charges power for driving motor generator 300, and travel battery 310 Inverter 330 that performs current control while converting direct current and alternating current of motor generator 300, engine ECU 406 that controls the operating state of engine 100, motor generator 300, inverter 330, and battery for traveling according to the state of hybrid vehicle 10 Control charge / discharge status of 310 To include a MG_ECU402, and mutually managing and controlling engine ECU406 and MG_ECU402 like, the HV_ECU404 for controlling the entire hybrid system such hybrid vehicle 10 can travel most efficiently.

  A boost converter 320 is provided between the traveling battery 310 and the inverter 330. Since the rated voltage of traveling battery 310 is lower than the rated voltage of motor generator 300, when power is supplied from traveling battery 310 to motor generator 300, boost converter 320 boosts the power.

  In FIG. 1, each ECU is configured separately, but may be configured as an ECU in which two or more ECUs are integrated. For example, as shown by a dotted line in FIG. 1, an example is an ECU 400 in which MG_ECU 402 and HV_ECU 404 are integrated. In the following description, MG_ECU 402 and HV_ECU 404 are described as ECU 400 without distinction.

  The ECU 400 includes an engine ECU 406, a vehicle speed sensor, an accelerator opening sensor, a brake stroke sensor, a throttle opening sensor, an MG (1) rotation speed sensor, an MG (2) rotation speed sensor, and an engine rotation speed sensor (all not shown). ), And a signal from the monitoring unit 340 is input.

  The vehicle speed sensor detects the vehicle speed V from the rotation speed of the drive shaft 16 and transmits a signal representing the detection result to the ECU 400.

  The accelerator opening sensor detects an accelerator pedal opening (accelerator opening) ACC, and transmits a signal representing the detection result to ECU 400.

  The brake stroke sensor detects a brake pedal stroke (brake stroke) BS and transmits a signal representing the detection result to ECU 400.

  The throttle opening sensor detects the opening of the throttle valve (throttle opening) used for adjusting the amount of air taken into engine 100 and transmits a signal representing the detection result to ECU 400.

  MG (1) rotation speed sensor detects rotation speed NM (1) of MG (1) 300A, and transmits a signal representing the detection result to ECU 400.

  The MG (2) rotational speed sensor detects the rotational speed NM (2) of MG (2) 300B and transmits a signal representing the detection result to ECU 400.

  The engine rotational speed sensor is connected to engine ECU 406, detects the rotational speed (engine rotational speed) NE of the output shaft (crankshaft) of engine 100, and transmits a signal representing the detection result to ECU 400 via engine ECU 406. .

  The monitoring unit 340 is connected to the traveling battery 310 and monitors the state of the traveling battery 310. The monitoring unit 340 includes a voltage sensor, a current sensor, and a temperature sensor (all not shown) provided in the traveling battery 310, a voltage value between terminals of the traveling battery 310, and a charge / discharge current value of the traveling battery 310. Information such as (battery current value) I and temperature (battery temperature) TB of the traveling battery 310 is input. The monitoring unit 340 calculates the remaining capacity of the traveling battery 310 based on information such as the battery current value I and the battery temperature TB.

  ECU 400 is sent from engine ECU 406, vehicle speed sensor, accelerator opening sensor, brake stroke sensor, throttle opening sensor, MG (1) rotation speed sensor, MG (2) rotation speed sensor, monitoring unit 340, engine rotation speed sensor, and the like. Based on the received signal, a map and a program stored in a ROM (Read Only Memory), the devices are controlled so that the hybrid vehicle 10 is in a desired traveling state.

  Further, ECU 400 temporarily stops engine 100 in accordance with the traveling state of hybrid vehicle 10 to improve fuel consumption efficiency during traveling of hybrid vehicle 10, and the hybrid is generated by the power of motor generator 300 alone. Control for causing the vehicle 10 to travel (hereinafter also referred to as engine intermittent stop control) is executed.

  The engine 100 according to the present embodiment will be described with reference to FIG. Engine 100 includes an intake pipe 110 and an exhaust pipe 120.

  In the engine 100, air drawn from an air cleaner (not shown) flows through the intake pipe 110 and is introduced into the combustion chamber 102 of the engine 100. The intake air amount KL is adjusted by the opening of the throttle valve 114 (throttle opening). The throttle opening is controlled by a throttle motor 112 that operates based on a signal from the engine ECU 406.

  The fuel is stored in a fuel tank (not shown), and injected from the injector 104 into the combustion chamber 102 by a fuel pump (not shown). An air-fuel mixture of air introduced from the intake pipe 110 and fuel injected from the injector 104 is ignited and burned using an ignition coil 106 controlled by a control signal from the engine ECU 406.

  The exhaust gas after the air-fuel mixture burns is discharged to the atmosphere through the first catalyst 130 and the second catalyst 140 provided in the middle of the exhaust pipe 120.

  The first catalyst 130 is provided close to the combustion chamber 102 on the upstream side of the exhaust pipe 120, and the second catalyst 140 is provided on the lower side of the floor panel on the downstream side of the first catalyst 130. The first catalyst 130 and the second catalyst 140 are three-way catalysts that purify harmful substances such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) contained in the exhaust gas. The first catalyst 130 and the second catalyst 140 carry a noble metal based on alumina and added with platinum, palladium, and rhodium, and perform oxidation reaction of hydrocarbon and carbon monoxide and reduction reaction of nitrogen oxide. It can be done at the same time.

  The first catalyst 130 and the second catalyst 140 have different temperatures depending on the positions where they are arranged, the difference in heat generation energy, the amount of heat release, and the like.

  In order to activate the first catalyst 130 and the second catalyst 140 to exhibit the exhaust purification performance required for the hybrid vehicle 10, it is necessary to heat each catalyst to a predetermined temperature or higher. The predetermined temperature described above is different between the first catalyst 130 and the second catalyst 140 due to a difference in the amount of noble metal supported therein.

  The first catalyst 130 is provided upstream of the exhaust pipe 120 and close to the combustion chamber 102, so that the first catalyst 130 is heated and activated earlier than the second catalyst 140. Therefore, when the engine 100 is started, even if the second catalyst 140 is not yet activated, the exhaust gas is appropriately purified by the first catalyst 130.

  Engine ECU 406 receives signals from engine water temperature sensor 108, air flow meter 116, intake air temperature sensor 118, air-fuel ratio sensor 122, and oxygen sensor 124.

  Engine water temperature sensor 108 detects the temperature (engine water temperature) TE of cooling water flowing in a water jacket formed in engine 100 and transmits a signal representing the detection result to engine ECU 406.

  The air flow meter 116 is provided in the intake pipe 110 upstream of the throttle valve 114, and detects the amount of intake air (intake air quantity) KL introduced into the combustion chamber 102 of the engine 100 via the intake pipe 110. Then, a signal representing the detection result is transmitted to engine ECU 406.

  The intake air temperature sensor 118 is provided in the intake pipe 110 upstream of the throttle valve 114 and determines the temperature (intake air temperature) TA of intake air introduced into the combustion chamber 102 of the engine 100 via the intake pipe 110. A signal representing the detection result is transmitted to engine ECU 406.

  Air-fuel ratio sensor 122 is provided in exhaust pipe 120 between engine 100 and first catalyst 130, detects the ratio of air to fuel in the exhaust gas, and transmits a signal representing the detection result to engine ECU 406.

  The oxygen sensor 124 is provided in the exhaust pipe 120 between the first catalyst 130 and the second catalyst 140, detects the oxygen concentration in the exhaust gas, and transmits a signal representing the detection result to the engine ECU 406.

  Engine ECU 406 transmits signals sent from engine water temperature sensor 108, air flow meter 116, intake air temperature sensor 118, air-fuel ratio sensor 122, oxygen sensor 124, and the like to ECU 400 and a control signal sent from ECU 400. Thus, the engine 100 is controlled so that the engine 100 is in a desired operation state.

  For example, the engine ECU 406 controls the injector 104 based on signals from each sensor so that the proper fuel injection timing and fuel injection amount are obtained. At this time, the fuel injection timing and the fuel injection amount are feedback-controlled based on the signals from the air-fuel ratio sensor 122 and the oxygen sensor 124 so that the air-fuel ratio becomes an appropriate value. Further, the engine ECU 406 controls the ignition coil 106 so as to achieve an appropriate ignition timing or controls the throttle motor 112 so as to achieve an appropriate throttle opening based on signals from the respective sensors.

  When the engine 100 is temporarily stopped by the engine intermittent stop control while the hybrid vehicle 10 equipped with the control device according to the present embodiment is running, the high-temperature exhaust gas that passes through the first catalyst 130 and the second catalyst 140. The flow stops. Further, since the hybrid vehicle 10 is traveling, the cooling of the first catalyst 130 and the second catalyst 14 by the traveling wind is continued. Therefore, if the engine 100 is stopped for a long time, the fuel efficiency can be improved. On the other hand, the temperature of the first catalyst 130 and the second catalyst 140 is excessively lowered, and the first catalyst 130 and the second catalyst 130 are restarted when the engine 100 is restarted. The case where the exhaust gas purification action of the catalyst of the catalyst 140 does not act effectively can be considered.

  In order to suppress this problem, in the control device according to the present embodiment, the temperature of first catalyst 130 and the temperature of second catalyst 140 are estimated based on the state of hybrid vehicle 10, and these estimated temperatures are used. Based on the determination result, it is determined whether to stop the engine 100 temporarily by the intermittent engine stop control or to restart the engine 100, and the engine 100 is controlled based on the determination result.

  With reference to FIG. 3, a functional block diagram of the control device according to the present embodiment will be described. As shown in FIG. 3, the control device includes an engine control unit 410, an engine stop time detection unit 420, and a catalyst temperature estimation unit 430.

  The engine control unit 410 is based on the vehicle speed V, the accelerator opening ACC, the engine water temperature TE, and the estimated temperature TSC of the first catalyst 130 and the estimated temperature TUF of the second catalyst 140 transmitted from the catalyst temperature estimation unit 430. An engine control (stop / start) signal is output to engine 100 via engine ECU 406 and also output to engine stop time detector 420.

  Based on a signal from engine control unit 410, engine stop time detection unit 420 detects an elapsed time after the engine stop signal is output (hereinafter also referred to as engine stop time).

  Based on the engine water temperature TE, the intake air temperature TA, the engine speed NE, the intake air amount KL, the vehicle speed V, and the engine stop time from the engine stop time detection unit 420, the catalyst temperature estimation unit 430 is based on the first catalyst 130. The estimated temperature TSC and the estimated temperature TUF of the second catalyst 140 are calculated.

  The control device according to the present embodiment having such a functional block can be read from a CPU (Central Processing Unit) and a memory and a memory included in the ECU 400 even with hardware mainly composed of a digital circuit or an analog circuit. It can also be realized by software mainly composed of programs that are issued and executed by the CPU. In general, it is said that it is advantageous in terms of operation speed when realized by hardware, and advantageous in terms of design change when realized by software. Below, the case where a control apparatus is implement | achieved as software is demonstrated. Note that a recording medium on which such a program is recorded is also an embodiment of the present invention.

  With reference to FIG. 4, a control structure of a program executed by ECU 400 serving as a control device according to the present embodiment when engine 100 is temporarily stopped while hybrid vehicle 10 is traveling will be described. Note that this program is repeatedly executed at a predetermined cycle time.

  In step (hereinafter step is abbreviated as S) 100, ECU 400 determines whether or not vehicle speed V is higher than a predetermined vehicle speed V (0). If it is higher than the predetermined vehicle speed V (0) (YES in S100), the process proceeds to S116. Otherwise (NO in S100), the process proceeds to S102.

  In S102, ECU 400 determines whether or not accelerator opening ACC is larger than a predetermined opening A (0). If it is larger than predetermined opening degree A (0) (YES in S102), the process proceeds to S116. Otherwise (NO in S102), the process proceeds to S104.

  In S104, ECU 400 determines whether engine water temperature TE is higher than a predetermined temperature T (0) or not. If it is higher than a predetermined temperature T (0) (YES in S104), the process proceeds to S106. Otherwise (NO in S104), the process proceeds to S116.

  In S106, ECU 400 reads estimated temperature TSC of first catalyst 130 stored in the internal memory of ECU 400. A method for calculating the estimated temperature TSC of the first catalyst 130 will be described later.

  In S108, ECU 400 reads estimated temperature TUF of second catalyst 140 stored in the internal memory of ECU 400. A method for calculating the estimated temperature TUF of the second catalyst 140 will be described later.

  In S110, ECU 400 determines whether or not estimated temperature TSC of first catalyst 130 is higher than a predetermined lower limit temperature T (1). Here, the predetermined lower limit temperature T (1) is the lower limit temperature of the first catalyst 130 that exhibits the exhaust purification performance required for the hybrid vehicle 10. The predetermined lower limit temperature T (1) is not limited to this. If it is higher than predetermined lower limit temperature T (1) (YES in S110), the process proceeds to S112. Otherwise (NO in S110), the process proceeds to S116.

  In S112, ECU 400 determines whether or not estimated temperature TUF of second catalyst 140 is higher than a predetermined lower limit temperature T (2). Here, the predetermined lower limit temperature T (2) is the lower limit temperature of the second catalyst 140 that exhibits the exhaust purification performance required for the hybrid vehicle 10. The predetermined lower limit temperature T (2) is not limited to this. If it is higher than a predetermined lower limit temperature T (2) (YES in S112), the process proceeds to S114. Otherwise (NO in S112), the process proceeds to S114.

  In S114, ECU 400 outputs a control signal for continuing temporary stop of engine 100 to engine 100 via engine ECU 406.

  In S116, ECU 400 outputs a control signal for starting engine 100 to engine 100 via engine ECU 406.

  With reference to FIG. 5, a control structure of a program executed when ECU 400 as the control device according to the present embodiment calculates estimated temperature TSC of first catalyst 130 and estimated temperature TUF of second catalyst 140 will be described. . Note that this program is repeatedly executed at a predetermined cycle time.

  In S200, ECU 400 determines whether or not engine 100 is temporarily stopped while hybrid vehicle 10 is traveling. If paused (YES in S200), the process proceeds to S210. Otherwise (NO in S200), the process proceeds to S202.

  In S202, ECU 400 detects engine speed NE, intake air amount KL, engine water temperature TE, intake air temperature TA, and vehicle speed V.

  In S204, ECU 400 calculates estimated temperature TSC of first catalyst 130. The ECU 400 determines the estimated temperature of the first catalyst 130 based on, for example, a map that uses at least one of the engine speed NE, the integrated amount of the intake air amount KL, the engine water temperature TE, the intake air temperature TA, and the vehicle speed V as parameters. Calculate TSC.

  In S206, ECU 400 calculates estimated temperature TUF of second catalyst 140. ECU 400 calculates estimated temperature TUF of second catalyst 140 based on, for example, a map that uses at least one of engine speed NE, intake air amount KL, engine water temperature TE, intake air temperature TA, and vehicle speed V as parameters. To do.

  In S208, ECU 400 stores estimated temperature TSC of first catalyst 130 and estimated temperature TUF of second catalyst 140 in a memory inside ECU 400.

  In S210, ECU 400 detects the engine stop time and vehicle speed V. In S212, ECU 400 corrects estimated temperature TSC of first catalyst 130 based on at least one of engine stop time and vehicle speed V. For example, ECU 400 corrects estimated temperature TSC of first catalyst 130 to a lower value when the engine stop time is long than when it is short, and when vehicle speed V is high and when it is low.

  In S214, ECU 400 corrects estimated temperature TUF of second catalyst 140 based on engine stop time and vehicle speed V. For example, ECU 400 corrects estimated temperature TUF of second catalyst 140 to a lower value when the engine stop time is longer than when it is short, and when vehicle speed V is high and when it is low.

  An operation of engine 100 controlled by ECU 400 that is the control device according to the present embodiment based on the above-described structure and flowchart will be described.

  As shown in FIG. 6, it is assumed that the accelerator opening degree ACC is reduced to substantially zero at time t (1) and the engine 100 is temporarily stopped by the intermittent engine stop control.

  During operation of engine 100 until time t (1) (NO in S200), engine speed NE, intake air amount KL, engine water temperature TE, intake air temperature TA, and vehicle speed V are detected (S202). Based on these pieces of information, the estimated temperature TSC of the first catalyst 130 and the estimated temperature TUF of the second catalyst 140 are calculated (S204, S206). As described above, the first catalyst is based on the engine speed NE, the intake air amount KL, the engine water temperature TE, the intake air temperature TA, and the vehicle speed V that are correlated with the flow rate of the traveling wind, which are correlated with the exhaust gas temperature. Since the estimated temperature TSC of 130 and the estimated temperature TUF of the second catalyst 140 are calculated, the temperatures of the first catalyst 130 and the second catalyst 140 during operation of the engine 100 can be accurately estimated. In this case, as shown in FIG. 6, the estimated temperature TSC of the first catalyst 130 and the estimated temperature of the second catalyst 140 are taken into consideration that the first catalyst 130 and the second catalyst 140 are heated by the high-temperature exhaust gas. The TUF is calculated to increase. The estimated temperature TSC of the first catalyst 130 and the estimated temperature TUF of the second catalyst 140 calculated in this way are stored in a memory inside the ECU 400 (S208).

  After time t (1), engine 100 is temporarily stopped (YES in S200), the flow of exhaust gas is interrupted, and cooling of each catalyst by running wind is continued. For this reason, the temperature of each catalyst decreases as the engine stop time elapses. Therefore, the estimated temperature TSC of the first catalyst 130 and the estimated temperature TUF of the second catalyst 140 are corrected based on the engine stop time and the vehicle speed V (S212, S214). Thus, during the temporary stop of the engine 100, the estimated temperature TSC and the second temperature of the first catalyst 130 are based on the vehicle speed V that is correlated with the engine stop time during which cooling by the traveling wind continues and the flow rate of the traveling wind. The estimated temperature TUF of the catalyst 140 is corrected. Therefore, the temperature of each catalyst can be accurately estimated even when engine 100 is temporarily stopped. In this case, as shown in FIG. 6, the estimated temperature TSC of the first catalyst 130 and the estimated temperature TUF of the second catalyst 140 are corrected so as to decrease according to the engine stop time.

  Thereafter, until time t (2) when the estimated temperature TSC of the first catalyst 130 decreases to the lower limit temperature T (1) of the first catalyst 130 that exhibits the exhaust purification performance required for the hybrid vehicle 10 (at S110). YES, YES at S112), engine 100 is temporarily stopped (S114). Therefore, it is possible to maximize the fuel consumption efficiency while ensuring the minimum catalyst exhaust purification performance.

  When estimated temperature TSC of first catalyst 130 decreases to lower limit temperature T (1) at time t (2) (NO in S110), engine 100 is restarted (S116). As a result, the first catalyst 130 is again heated by the exhaust gas. Therefore, the estimated temperature TSC of the first catalyst 130 can be maintained higher than the lower limit temperature T (1), and the exhaust purification performance of the first catalyst 130 can be ensured.

  Since engine 100 is restarted when estimated temperature TSC of first catalyst 130 decreases to lower limit temperature T (1), estimated temperature TUF of second catalyst 140 is lower limit temperature as shown in FIG. A state higher than T (2) is maintained. Therefore, the reliability of the exhaust purification performance can be improved.

  As described above, according to the control device according to the present embodiment, when the engine is temporarily stopped by the engine intermittent stop control, the catalyst temperature is estimated, and the estimated catalyst temperature is required for the vehicle. The engine is temporarily stopped until the temperature reaches a lower limit temperature that exhibits exhaust purification performance, and the engine is restarted when the lower limit temperature is reached. Therefore, the engine stop time can be ensured to the maximum while maintaining the exhaust purification performance of the catalyst. As a result, the fuel consumption efficiency can be improved without degrading the exhaust gas purification performance of the catalyst when the engine is restarted.

  In the present embodiment, an example has been described in which engine 100 is restarted when either estimated temperature TSC of first catalyst 130 or estimated temperature TUF of second catalyst 140 decreases to the lower limit temperature. For example, the engine 100 may be restarted when both the estimated temperature TSC of the first catalyst 130 and the estimated temperature TUF of the second catalyst 140 are lowered to the lower limit temperature. In this way, the fuel consumption efficiency can be further improved by extending the engine stop time, and the other catalyst is activated even if the temperature falls below the temperature at which one catalyst is activated. The minimum purification performance can be ensured.

<First Modification>
In the above-described embodiment, only the estimated temperature TSC of the first catalyst 130 may be calculated, and stop or start of the engine 100 may be controlled based on only the estimated temperature TSC of the first catalyst 130. Thus, the engine 100 is temporarily stopped until the estimated temperature TSC of the first catalyst 130 decreases to the lower limit temperature T (1), and it is not necessary to calculate the estimated temperature TUF of the second catalyst 140. Therefore, the cost and processing load can be reduced.

  Note that the first catalyst 130 is provided upstream of the exhaust pipe 120 and close to the combustion chamber 102, so that the first catalyst 130 is heated and activated earlier than the second catalyst 140, and the exhaust when the engine 100 is started is activated. Gas can be purified properly. Furthermore, since the first catalyst 130 is more susceptible to the exhaust gas than the second catalyst 140, the estimated temperature TSC of the first catalyst 130 is higher when the temperature of the catalyst is estimated based on the exhaust gas temperature or flow rate. The estimated temperature TUF of the second catalyst 140 can be estimated with higher accuracy.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a figure which shows the structure of the vehicle by which the control apparatus which concerns on embodiment of this invention is mounted. It is a figure which shows the structure of the engine mounted in the vehicle which concerns on embodiment of this invention. It is a functional block diagram of a control device concerning an embodiment of the invention. It is a flowchart (the 1) which shows the control structure of ECU which is a control apparatus which concerns on embodiment of this invention. It is a flowchart (the 2) which shows the control structure of ECU which is a control apparatus which concerns on embodiment of this invention. It is a timing chart which shows the driving | running state of the engine controlled by the control apparatus which concerns on embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Hybrid vehicle, 12 Drive wheel, 14 Reducer, 16 Drive shaft, 100 Engine, 102 Combustion chamber, 104 Injector, 106 Ignition coil, 108 Engine water temperature sensor, 110 Intake pipe, 112 Throttle motor, 114 Throttle valve, 116 Air flow meter 118, intake air temperature sensor, 120 exhaust pipe, 122 air-fuel ratio sensor, 124 oxygen sensor, 130 first catalyst, 140 second catalyst, 200 power split mechanism, 212 output shaft, 300, 300A, 300B motor generator, 310 for running Battery, 320 Boost converter, 330 Inverter, 340 Monitoring unit, 410 Engine control unit, 420 Engine stop time detection unit, 430 Catalyst temperature estimation unit, 400 ECU, 402 MG ECU, 404 HV_ECU, 406 engine ECU.

Claims (12)

A control device for an internal combustion engine in which exhaust gas is purified by at least one catalyst, wherein the internal combustion engine is controlled to be temporarily stopped while the vehicle is running,
The controller is
Estimating means for estimating the temperature of the catalyst based on the state of the vehicle;
When the internal combustion engine is controlled to be temporarily stopped, the internal combustion engine is temporarily stopped if the estimated temperature is higher than a predetermined temperature related to the exhaust gas purification performance of the catalyst. And a control means for controlling the internal combustion engine so as to restart the internal combustion engine when the estimated temperature is lower than the predetermined temperature.   The control device according to claim 1, wherein the predetermined temperature is a lower limit temperature of the catalyst that exhibits exhaust purification performance required for the vehicle. The estimation means includes
During operation of the internal combustion engine, at least one of the speed of the vehicle, the rotational speed of the internal combustion engine, the temperature of cooling water of the internal combustion engine, the amount of air sucked into the internal combustion engine, and the temperature of the sucked air And means for estimating the temperature of the catalyst,
When the internal combustion engine is controlled to be temporarily stopped, the catalyst estimated during operation of the internal combustion engine based on at least one of the stop time of the internal combustion engine and the speed of the vehicle The control device according to claim 1, further comprising means for correcting the temperature. The vehicle includes an upstream catalyst and a downstream catalyst,
The estimation means includes
Means for estimating the temperature of the upstream catalyst;
Means for estimating the temperature of the downstream catalyst,
When the temperature of the upstream catalyst is higher than a predetermined temperature related to the exhaust purification performance of the upstream catalyst, the control means relates to the exhaust purification performance of the downstream catalyst. The control device according to any one of claims 1 to 3, comprising means for continuing the temporary stop in at least one of cases where the temperature is higher than a predetermined temperature. The vehicle includes an upstream catalyst and a downstream catalyst,
The estimating means includes means for estimating a temperature of the upstream catalyst;
The control means includes means for continuing the temporary stop when the temperature of the upstream catalyst is higher than a predetermined temperature related to exhaust purification performance of the upstream catalyst. The control apparatus in any one of -3. An internal combustion engine control method in which exhaust gas is purified by at least one catalyst, wherein the internal combustion engine is controlled to be temporarily stopped during vehicle travel,
The control method is:
An estimation step of estimating the temperature of the catalyst based on the state of the vehicle;
When the internal combustion engine is controlled to be temporarily stopped, the internal combustion engine is temporarily stopped if the estimated temperature is higher than a predetermined temperature related to the exhaust gas purification performance of the catalyst. And a control step of controlling the internal combustion engine to restart the internal combustion engine when the estimated temperature is lower than the predetermined temperature.   The control method according to claim 6, wherein the predetermined temperature is a lower limit temperature of the catalyst that exhibits exhaust purification performance required for the vehicle. The estimation step includes
During operation of the internal combustion engine, at least one of the speed of the vehicle, the rotational speed of the internal combustion engine, the temperature of cooling water of the internal combustion engine, the amount of air sucked into the internal combustion engine, and the temperature of the sucked air Estimating the temperature of the catalyst based on
When the internal combustion engine is controlled to be temporarily stopped, the catalyst estimated during operation of the internal combustion engine based on at least one of the stop time of the internal combustion engine and the speed of the vehicle The control method according to claim 6, further comprising a step of correcting the temperature. The vehicle includes an upstream catalyst and a downstream catalyst,
The estimation step includes
Estimating the temperature of the upstream catalyst;
Estimating the temperature of the downstream catalyst,
In the control step, when the temperature of the upstream catalyst is higher than a predetermined temperature related to the exhaust purification performance of the upstream catalyst, the temperature of the downstream catalyst relates to the exhaust purification performance of the downstream catalyst. The control method according to any one of claims 6 to 8, comprising a step of continuing the temporary stop in at least any case when the temperature is higher than a predetermined temperature. The vehicle includes an upstream catalyst and a downstream catalyst,
The estimating step includes estimating a temperature of the upstream catalyst;
The control step includes a step of continuing the temporary stop when a temperature of the upstream catalyst is higher than a predetermined temperature related to an exhaust purification performance of the upstream catalyst. The control method in any one of.   The program for making a computer perform the control method in any one of Claims 6-10.   The recording medium which recorded the program for making a computer perform the control method in any one of Claims 6-10 so that computer reading was possible.

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