JP2011247166A - Engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly purify exhaust discharged from an engine.SOLUTION: This vehicle control system is applied to a hybrid vehicle using an engine 10 and a motor 28 as power sources. The motor 28 functions as a starter of the engine 10. A hybrid ECU 60 determines whether or not an idle condition is established which brings an engine idle state that an engine output shaft 25 is brought into a rotating state under a combustion stop state of the engine 10 associated with engine stop. When the idle condition is determined to be established, an EGR valve 24 used as a supply restricting means for restricting the supply of air from the engine 10 to a catalyst 22 is controlled to the air supply restricting state in the engine idle state.

Description

  The present invention relates to an engine control device, and more particularly, to an engine control device for appropriately controlling the oxygen adsorption amount of a catalyst in an engine aftertreatment device that purifies exhaust by an exhaust purification catalyst that adsorbs or releases oxygen. Is.

  Conventionally, a three-way catalyst is known as a catalyst for purifying HC, CO and NOx contained in engine exhaust. The three-way catalyst is disposed in the exhaust system, and purifies HC, CO, and NOx in the exhaust by performing adsorption and release of oxygen according to the amount of oxygen in the exhaust. That is, when the air-fuel ratio of the exhaust is leaner than the stoichiometric air-fuel ratio, NOx is reduced by the oxygen adsorption capacity of the catalyst, and when it is rich, oxygen adsorbed on the catalyst is released into the exhaust. As a result, HC and CO are oxidized.

  By the way, in so-called idle stop vehicles and hybrid vehicles, the engine is automatically stopped and restarted repeatedly. At the time of engine restart, the engine output shaft is rotated by a starter or an electric motor (motor) before starting combustion. The engine is idle. In this engine idling state, air introduced from the intake system is supplied to the catalyst, and oxygen in the supplied air is adsorbed by the three-way catalyst, so that the oxygen adsorption amount of the catalyst becomes excessive. Conceivable. In this excessive oxygen adsorption state, there is a possibility that NOx reduction by the catalyst cannot be properly performed at the time of engine start.

  A method for eliminating the excessive oxygen adsorption state of the catalyst at the time of starting the engine and performing NOx reduction appropriately has been proposed (see, for example, Patent Document 1). Patent Document 1 pays attention to the fact that the amount of O2 storage of the catalyst before the start of engine combustion at the start of the engine differs depending on whether the catalyst is in a new state or in a deteriorated state. It is disclosed that the fuel injection amount at the time is variable. That is, in Patent Document 1, when increasing the amount of fuel at the start of the engine, an amount of fuel (HC) corresponding to the catalyst state is injected so that oxygen adsorbed on the catalyst is released from the catalyst. This eliminates the excessive oxygen adsorption state of the catalyst.

JP 2008-190477 A

  However, in Patent Document 1, in order to reduce the oxygen adsorption amount of the catalyst, it is necessary to inject an amount of fuel commensurate with the oxygen adsorbed on the catalyst when the engine is idling. In particular, the amount of O2 storage increases. If the catalyst is easy to be new, there is a concern that the fuel consumption may be deteriorated or the emission of HC may be increased before the catalyst is warmed up, resulting in a worse emission.

  The present invention has been made in order to solve the above-described problems, and a main object of the present invention is to provide an engine control device capable of appropriately purifying exhaust gas discharged from the engine.

  The present invention employs the following means in order to solve the above problems.

  The present invention is applied to a system including an engine, an engine starter, and an exhaust purification catalyst that is disposed in an exhaust passage of the engine and adsorbs or releases oxygen. The present invention relates to an engine control device that restarts the engine by rotating the output shaft of the engine by the starter. The invention according to claim 1 is a condition for determining whether or not an idling condition for achieving an idling engine condition in which the output shaft rotates in a state where the engine is stopped when the engine is stopped is satisfied. A supply restricting means for restricting the supply of air from the engine to the exhaust purification catalyst when it is determined by the determining means and the condition determining means that the idling condition is satisfied; And a restriction control means for controlling to a supply restriction state.

  In short, when the engine is stopped or when the engine is restarted after the engine is stopped, specifically, the period from the engine stop request until the engine rotation stops, During the rotation period, the engine output shaft may be in a rotated state (idle state) when the engine is in a combustion stop state. In the idling state of the engine, air (fresh air) introduced into the engine flows into the exhaust passage as it is, and air is supplied to the exhaust purification catalyst. In such a case, it is conceivable that oxygen contained in the air is adsorbed by the catalyst, and as a result, the catalyst is in an excessively adsorbed state of oxygen (for example, an oxygen saturated state). In such a state of excessive oxygen adsorption, the exhaust purification performance of the catalyst is not properly exhibited at the next combustion restart of the engine, that is, the catalyst cannot take oxygen from the NOx in the exhaust, and the NOx purification is not performed. Proper implementation may not be possible.

  In view of this point, in the present invention, by restricting the supply of air to the catalyst in the idling state of the engine, it is avoided that oxygen is adsorbed excessively on the catalyst. As a result, NOx reduction can be properly performed at the time of next combustion restart of the engine, and exhaust purification can be appropriately performed.

  Before starting combustion of the engine at the restart after the engine is stopped, air is introduced into the engine by the rotation of the engine output shaft by the starter, and the introduced air is supplied to the catalyst. Therefore, as in the invention described in claim 2, it is preferable to start the rotation of the engine output shaft by the starting device after the supply restricting means is in a state of restricting the supply of air to the catalyst. By so doing, it is possible to limit the supply of air to the catalyst from the beginning of the rotation of the engine output shaft by the starter, and to suitably suppress the oxygen adsorption of the catalyst.

  According to a third aspect of the present invention, the engine is automatically stopped when a predetermined stop condition is satisfied, and the restart request is issued when a predetermined restart condition is satisfied after the stop condition is satisfied. In the engine control device that performs engine restart as a thing, when the stop condition is satisfied, it is determined that the idling condition is satisfied, and the restart condition is satisfied after it is determined that the stop condition is satisfied. Accordingly, the supply restriction means is controlled to the air supply restriction state in a period before the combustion of the engine is restarted. According to this configuration, the supply of air to the catalyst is restricted during the period from the engine stop request until the engine rotation stops and the period when the engine output shaft is rotated by the starter in response to the restart request after the engine stop. Thus, oxygen adsorption of the catalyst can be suppressed in a series of engine stop / restart flows.

  In a so-called hybrid vehicle in which the traveling motor also functions as a starting device and the engine and the traveling motor are the power sources, the engine output shaft is rotated by the starting device when the engine is started in order to increase engine operating efficiency. After performing until the speed is stabilized, specifically, after performing cranking to an engine rotational speed (for example, 1000 to 2000 rpm) higher than the engine idle rotational speed (for example, 700 rpm), and then restarting the combustion of the engine There is. In this case, since the combustion is resumed after waiting for the engine rotation speed to stabilize, it is considered that the engine is kept idle for a long time, and as a result, the catalyst tends to be in an oxygen-rich state.

  Therefore, as in the invention described in claim 4, in addition to the engine, the invention is applied to a vehicle including a travel motor as a power source, and the travel motor functions as the starting device. State determination means for determining that the rotational speed of the engine has become stable at a predetermined rotational speed during a rotation execution period of the output shaft by the starter in response to a restart request, and the rotation by the state determination means Restart control means for restarting combustion of the engine after it has been determined that the speed has become stable, and supply of air to the catalyst in the period before restarting combustion upon engine restart By limiting this, it is possible to suitably obtain an effect that oxygen can be prevented from being excessively adsorbed on the catalyst.

  In so-called hybrid vehicles that use an engine and a motor as power sources, there are two types of engine restart requests, one based on a vehicle travel request and the other based on a charge request for a power storage device. Among these, when the engine restart request is based on the vehicle travel request, it is considered that there is a need to start the engine as quickly and reliably as possible compared to the charge request because of the travel priority.

  In view of this, the invention according to claim 5 is applied to a vehicle including a generator that generates electric power by rotation of the output shaft and a power storage device that can exchange electric power with the generator. The condition determination means determines whether the establishment of the idling condition is due to the restart request due to a charge request of the power storage device or the restart request due to a vehicle travel request. The restriction control means determines that the supply restriction means is in the air supply restriction state when the condition determination means determines that the establishment of the idling condition is the restart request due to the charge request. And when it is determined that the restart request is due to the vehicle travel request, the supply restriction unit is controlled so that the supply of air is not restricted. By doing so, it is possible to achieve a good balance between ensuring the startability of the engine and ensuring the catalyst performance in accordance with the request for engine restart.

  According to a sixth aspect of the present invention, an EGR passage connecting the upstream side of the exhaust purification catalyst and the intake system of the engine in the exhaust passage, and an exhaust gas of the engine which is disposed in the EGR passage and recirculates to the intake system. In a system including an EGR valve that adjusts the amount of recirculation to be performed, the supply restriction means is the EGR valve, and when it is determined that the idle rotation condition is satisfied, the EGR valve is disposed on the side that increases the recirculation amount. Control. By controlling the EGR valve to increase the recirculation amount, at least a part of the air flowing from the engine to the catalyst is returned to the intake side. Thereby, the amount of air supplied to the catalyst can be reduced, and the oxygen adsorption of the catalyst is suppressed.

  Alternatively, as in the invention described in claim 7, a flow rate adjustment valve for adjusting the flow rate of air from the engine to the exhaust purification catalyst is disposed upstream of the exhaust purification catalyst in the exhaust passage, The supply restricting unit may be the flow rate adjusting valve, and when it is determined that the idling condition is satisfied, the flow rate adjusting valve may be controlled to reduce the air flow rate.

  In particular, when the flow adjustment valve is arranged upstream of the exhaust purification catalyst in the exhaust passage and upstream of the connection portion between the EGR passage and the exhaust passage, and the idling condition is satisfied, in addition to the flow adjustment valve, The EGR valve may be controlled. That is, when the engine is idling, the flow rate adjustment valve is controlled to reduce the air flow rate to the catalyst, and the EGR valve is controlled to increase the recirculation amount. According to this configuration, the supply of air to the catalyst can be limited by the flow rate adjustment valve, and the pressure increase in the exhaust passage due to the supply limitation can be suppressed by the EGR valve. Therefore, when restricting the supply of air to the catalyst, it is possible to reduce the load on the starting device as compared with the control by the flow rate adjusting valve alone.

The block diagram which shows the whole vehicle control system outline. The time chart which shows transition of the opening degree of EGR valve, and O2 storage amount. The flowchart which shows the process sequence at the time of an engine stop request | requirement. The flowchart which shows the process sequence at the time of an engine restart request | requirement. The time chart which shows the specific aspect of the engine control of 2nd Embodiment. The flowchart which shows the process sequence at the time of the engine restart request | requirement of 2nd Embodiment. The block diagram which shows the whole vehicle control system outline of 3rd Embodiment. The time chart which shows the specific aspect of the engine control of 3rd Embodiment. The flowchart which shows the process sequence at the time of the engine restart request | requirement of 3rd Embodiment.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. This embodiment is embodied in a control device of a vehicle control system in a hybrid vehicle that uses an engine and a motor as power sources. In the control system, an engine electronic control unit (engine ECU) and a hybrid electronic control unit (hybrid ECU) are provided. Then, fuel injection amount control and ignition timing control in the engine are performed using the engine ECU as a center, and the entire system of the vehicle is controlled using the hybrid ECU as a center. FIG. 1 is a block diagram showing the overall outline of the control system.

  In FIG. 1, an intake pipe 11 and an exhaust pipe 12 are connected to the engine 10, and the intake pipe 11 is provided with a throttle valve 13 for adjusting the amount of intake air into the cylinder. The throttle valve 13 is an air amount adjusting means that is electrically opened and closed by a throttle actuator 14 made of a motor or the like. The throttle actuator 14 has a built-in throttle sensor for detecting the opening of the throttle valve 13 (throttle opening).

  The engine 10 includes an injector 15 as fuel injection means for injecting and supplying fuel to each cylinder of the engine 10, and an igniter (ignition device) 17 as ignition means for generating an ignition spark in a spark plug 16 provided for each cylinder. And an intake valve 18 and an exhaust valve 19 as passage opening / closing means disposed in the intake port and the exhaust port, respectively. The intake valve 18 and the exhaust valve 19 are of a mechanical drive type that opens and closes as the output shaft 25 of the engine 10 rotates.

  In the present embodiment, an intake port injection type engine is adopted, and the injector 15 is provided in the vicinity of the intake port. Instead, a direct injection type engine is adopted, and the injector 15 is provided for each cylinder. It is good also as a structure provided in a cylinder head etc.

  The exhaust pipe 12 is provided with an A / F sensor 21 as an oxygen concentration sensor for detecting the oxygen concentration in the exhaust gas. In the exhaust pipe 12, a catalyst 22 as an exhaust purification device is provided on the downstream side of the A / F sensor 21.

  The catalyst 22 is, for example, a three-way catalyst, and purifies harmful components and the like in the exhaust when the exhaust passes. Specifically, the catalyst 22 has a function of adsorbing oxygen in a lean atmosphere (O2 storage function), and releases the adsorbed oxygen by being exposed to a rich atmosphere after the lean atmosphere. When the air-fuel ratio of the exhaust is leaner than the stoichiometric air-fuel ratio, the catalyst 22 reduces the NOx in the exhaust by the O2 storage function, and when it is rich, the adsorbed oxygen is put into the exhaust. By releasing, HC and CO in the exhaust are oxidized.

  In addition, the present system is provided with an EGR device (exhaust gas recirculation device) that introduces a part of the exhaust gas into the intake system as EGR gas. That is, an EGR pipe 23 having one end connected to the throttle valve downstream side of the intake pipe 11 and the other end connected to the upstream side of the catalyst 22 of the exhaust pipe 12 is provided between the intake pipe 11 and the exhaust pipe 12. In the middle of the EGR pipe 23, an electromagnetic EGR valve 24 is provided. In this case, the EGR recirculation amount is adjusted to increase or decrease by adjusting the opening degree of the EGR valve 24.

  A power distribution device 26 using planetary gears is connected to the output shaft 25 of the engine 10. A motor 28 that can be driven as an electric motor and a generator is connected to the power distribution device 26 via a gear shaft 27, and wheels (drive wheels) 33 are connected via a gear shaft 29, a differential gear 31, and a drive shaft 32. Is connected. Thereby, the engine 10 and the motor 28 can output power to the same drive shaft 32.

  The motor 28 is connected to the high voltage battery 35 via the inverter 34. When the motor 28 is driven as a generator, the electric power generated by the motor 28 is converted from alternating current to direct current by the inverter 34 and then charged to the high voltage battery 35. On the other hand, when the motor 28 is driven as an electric motor, the electric power from the high voltage battery 35 is supplied to the motor 28 via the inverter 34. The remaining capacity (SOC) of the high voltage battery 35 is calculated based on the charge / discharge current detected by the current sensor 36.

  As is well known, the engine ECU 50 and the hybrid ECU 60 are configured mainly by a microcomputer (hereinafter referred to as a microcomputer) including a CPU, a ROM, a RAM, and the like, and by executing various control programs stored in the ROM, Implement various controls related to vehicle drive.

  Specifically, the engine ECU 50 operates the engine 10 such as a crank angle sensor 37 that outputs a rectangular crank angle signal for each predetermined crank angle of the engine 10 and a cooling water temperature sensor 38 that detects the temperature of engine cooling water. Detection signals from various sensors for detecting the state are input, and the fuel injection amount, ignition timing, and the like are calculated based on these various signals to control the drive of the injector 15 and the ignition device 17. Engine ECU 50 is electrically connected to hybrid ECU 60 and controls engine 10 based on a control signal from hybrid ECU 60.

  The hybrid ECU 60 receives detection signals from the ignition switch 39, the current sensor 36, and various sensors that detect various types of information related to vehicle operation, and controls the driving of the motor 28, the inverter 34, and the like based on these various signals. Further, the hybrid ECU 60 exchanges various control signals and data with the engine ECU 50 to control the engine 10 and the motor 28 in a vehicle travel mode in consideration of the fuel efficiency of the engine 10 or to perform idle stop control. .

  For details on the control in the vehicle travel mode, for example, in a region where the fuel efficiency of the engine 10 is poor, such as when the vehicle starts or travels at a low load, the engine 10 is stopped (combustion stopped), and the power of the motor 28 is Only the wheel 33 is rotated. Further, when the vehicle is traveling at a medium load, the wheel 33 is basically rotated by the power of the engine 10, and if the engine power alone cannot output a desired amount of power, such as during vehicle acceleration or high load traveling, the engine 10 is started, and the wheels 33 are rotated by the power of the engine 10 and the motor 28. Further, even when the remaining capacity (SOC) of the high-voltage battery 35 becomes equal to or less than a predetermined amount during the running of the motor, the engine 10 is started, whereby the high-voltage battery 35 is charged.

  Next, idle stop control will be described in detail. In general, the idle stop control is to automatically stop the engine 10 when a predetermined idle stop condition is satisfied during the idling operation of the engine 10 and to restart the engine 10 when a predetermined idle restart condition is satisfied thereafter. is there. The idle stop condition includes, for example, at least one of an accelerator operation amount becoming zero, a brake pedal depressing operation being performed, a vehicle speed being reduced to a predetermined value or less, and the like. Further, the idle restart condition includes at least one of an accelerator operation performed when the engine is stopped and a brake pedal being released.

  In the case where the engine 10 is started when the combustion of the engine 10 is stopped, the system uses the motor 28 as a starting device. That is, the electric power stored in the high voltage battery 35 is supplied to the motor 28 via the inverter 34, and the output shaft 25 of the engine 10 is rotated (cranking is performed) by the power of the motor 28 output thereby. Thereafter, combustion of the engine 10 is started.

  Regarding the cranking by the motor 28, in this embodiment, in particular, the rotation of the engine output shaft 25 by the motor 28 is performed until the engine rotation speed is stabilized. Specifically, from the idle rotation speed of the engine 10 (for example, 700 rpm). The motor 28 rotates the engine output shaft 25 while the combustion of the engine 10 is stopped until the engine rotation speed is stabilized at a motor start rotation speed NEa (for example, 1000 to 2000 rpm) which is a higher engine rotation speed. That is, when starting the engine, the engine output shaft 25 is rotated by the motor 28 in the low rotation range where the engine operation efficiency is not so good in order to increase the engine operation efficiency, and the engine rotation speed increases to the motor start rotation speed NEa. In addition, after becoming stable at the rotational speed NEa, the combustion of the engine 10 is restarted so as to switch from the rotation by the motor 28 to the rotation by the combustion of the engine 10. In this case, it is significant in that the vibration of the vehicle at the time of starting the engine can be suppressed by starting the combustion of the engine 10 after quickly passing through the resonance rotational speed range (for example, 400 to 500 rpm) of the vehicle. Further, it is significant that the initial fuel injection and ignition can be performed with the air flow rate relatively high in the engine 10 and the engine 10 can be reliably started with a smaller amount of fuel.

  The motor start rotational speed NEa is also a rotational speed higher than a so-called starter motor cranking rotational speed (for example, 200 rpm).

  By the way, when the engine 10 is automatically stopped and restarted when the idle stop control or the vehicle travel mode is switched, if the engine is stopped, the combustion of the engine 10 is stopped and then the rotation of the engine output shaft 25 is stopped. If the engine is restarted, the engine output shaft 25 is rotated in the combustion stop state of the engine 10 during the period from the start of rotation of the output shaft 25 by the motor 28 to the restart of combustion. The state, that is, the state in which the engine 10 is idled. In this engine idling state, the air introduced into the intake pipe 11 flows into the exhaust pipe 12 via the cylinder and is further supplied to the catalyst 22. In this case, the catalyst 22 is exposed to a lean atmosphere, and oxygen contained in the air is adsorbed by the catalyst 22. That is, the oxygen adsorption amount (O2 storage amount) of the catalyst 22 is not maintained in a neutral state where both the oxidation of HC and CO and the reduction of NOx can be properly performed, and the oxygen adsorption amount may become excessive. Conceivable. In such an excessive oxygen adsorption state, when the combustion of the engine 10 is restarted next time, the catalyst 22 cannot take oxygen from the NOx in the exhaust gas, and as a result, there is a possibility that the NOx purification cannot be performed properly.

  In particular, in the present system, when cranking the engine 10, the engine rotational speed is increased to a relatively high motor start rotational speed NEa (1000 to 2000 rpm), and after waiting for the engine 10 to stabilize at the rotational speed NEa, Resume combustion. Therefore, it can be considered that the time during which the engine 10 is kept idle is long, and the catalyst is likely to be in an oxygen-rich state. Further, since the motor starting rotational speed NEa is relatively high, the flow rate of air in the idling state of the engine is increased, and as a result, the amount of air (oxygen amount) sent to the catalyst 22 is increased. It is thought that the state of excessive oxygen adsorption tends to occur.

  Therefore, in the present embodiment, it is determined whether or not the idling condition for achieving the idling engine condition in which the engine output shaft 25 is rotated in the combustion stop condition of the engine 10 accompanying the engine stop is satisfied, and the idling condition is satisfied. When it is determined that the rotation condition is satisfied, the supply of air from the engine 10 to the catalyst 22 is restricted in the engine idling state.

  Specifically, in the present embodiment, when the EGR valve 24 is used as a supply restriction unit that restricts the supply of air from the engine to the exhaust purification catalyst, and the idling condition is satisfied, here, the engine 10 is requested to stop. If there is, the EGR valve 24 is switched from the closed state to the opened state, more specifically, the fully closed state is switched to the fully opened state. Thus, the supply of air to the catalyst 22 is limited during the period from the engine stop request until the engine rotation stops and the period during which the engine output shaft is rotated by the starter in response to the restart request after the engine stop. Then, before resuming combustion of the engine 10, the EGR valve 24 is switched to the closed state (fully closed), and the restriction on the supply of air to the catalyst 22 is released.

  FIG. 2 is a time chart showing changes in the opening degree of the EGR valve 24 and the O2 storage amount during a period from when the engine 10 is requested to stop until the combustion of the engine 10 is restarted in response to the restart request. In the figure, (a) shows the engine speed, (b) shows combustion / combustion of the engine 10, (c) shows the opening of the EGR valve, and (d) shows the transition of the O2 storage amount of the catalyst 22. Further, in the drawing, the solid line indicates a case where the supply of air to the catalyst 22 is restricted when the engine 10 is idling, and the alternate long and short dash line indicates a case where the supply of air to the catalyst 22 is not restricted.

  In this embodiment, as shown by the solid line in FIG. 2, when there is a request to stop the engine 10 during engine operation, EGR is performed at a timing t12 after a predetermined delay time TA has elapsed from the request timing t11. The valve 24 is switched from the fully closed state to the fully open state. Here, the delay time TA is defined as the time required for exhaust remaining in the exhaust pipe 12 in the cylinder and upstream of the catalyst 22 to be discharged to the downstream side of the catalyst 22.

  During the operation stop period of the engine 10 after the engine stop request, the fully opened state of the EGR valve 24 is maintained as it is. When there is a restart request in this engine operation stop state, cranking of the engine 10 by the motor 28 is started at the request timing t14, and the engine speed NE is increased. Then, the engine rotational speed NE reaches a motor start rotational speed NEa (1000 to 2000 rpm in the present embodiment) that is higher than the idle rotational speed, and the engine 10 is kept in a stable state for a predetermined time at the rotational speed NEa. Then, the EGR valve 24 is switched to the closed state at timing t15. Further, fuel injection and ignition of the engine 10 are resumed at a timing t16 after a predetermined time TB has elapsed from the switching timing t15.

  The predetermined time TB is determined based on the time required for the actual opening of the EGR valve 24 to reach the fully closed opening after the signal for making the EGR valve 24 fully closed is output. That is, in this embodiment, fuel injection and ignition are restarted after the EGR valve 24 is fully closed.

  When the EGR valve 24 is opened when the engine is idling (in the case of a solid line), compared to the configuration in which the EGR valve 24 is kept closed (in the case of a one-dot chain line), The amount of air to be supplied is reduced, thereby suppressing an increase in the amount of O 2 storage of the catalyst 22. That is, when the combustion of the engine 10 is restarted, the O2 storage amount of the catalyst 22 can be set to an appropriate amount, and as a result, the reduction of HC, CO, and NOx in the exhaust gas is properly performed from the beginning of the combustion of the engine 10. It becomes possible to do.

  Next, the engine control processing procedure of this system will be described with reference to the flowcharts of FIGS. Here, FIG. 3 is a flowchart showing a processing procedure when there is a request for stopping the engine 10, and FIG. 4 is a flowchart showing a processing procedure when there is a request for restarting the engine 10 after the engine stop request. It is. These processes are executed by the hybrid ECU 60 at predetermined intervals.

  In FIG. 3, first, in step S11, it is determined whether or not a stop request for the engine 10 has been made. The stop request includes one that accompanies establishment of an idle stop condition, one that accompanies switching of the vehicle travel mode, and the like. If there is a stop request, the process proceeds to step S12 to stop fuel injection and ignition.

  In step S13, it is determined whether or not the delay time TA has elapsed from the timing of the engine stop request. Then, the process proceeds to step S14 on condition that the delay time TA has elapsed, the EGR valve 24 is switched from the fully closed state to the fully open state, and this process is terminated.

  Next, processing when there is a restart request for the engine 10 after the engine is stopped will be described with reference to FIG. In FIG. 4, first, in step S21, it is determined whether or not there has been a restart request for the engine 10 after the engine is stopped. As a restart request, a request accompanying establishment of an idle restart condition, a request accompanying switching of the vehicle travel mode, specifically, a request accompanying charging of the high voltage battery 35 during motor travel, a request for acceleration of the vehicle, And those associated with vehicle travel requests such as high-speed travel requests. And when there exists an engine restart request | requirement, it progresses to step S22.

  In step S22, energization of the motor 28 is started and cranking of the engine 10 is started. In step S23, it is determined whether or not the engine rotation speed is stable at the motor start rotation speed NEa. If it is determined that the engine rotation speed is maintained near the motor start rotation speed NEa for a predetermined time and the engine rotation speed is stable at the motor start rotation speed NEa, the process proceeds to step S24, where the EGR valve 24 Is switched from the fully open state to the fully closed state. Thereafter, in step S25, after the EGR valve 24 is switched to fully closed, fuel injection and ignition are started at a timing when a predetermined time has elapsed.

  According to the embodiment described in detail above, the following excellent effects can be obtained.

  It is determined whether or not an idling condition for achieving an engine idling state in which the engine output shaft 25 is rotated in the combustion stop state of the engine 10 due to the engine stop is met, and it is judged that the idling condition is met. In this case, since the supply of air from the engine 10 to the catalyst 22 is restricted in the idling state of the engine, it is possible to avoid excessive adsorption of oxygen on the catalyst 22. As a result, when the combustion of the engine 10 is resumed for the next time, NOx reduction can be properly performed, and thus exhaust purification can be appropriately performed.

  In addition, since the air supply from the engine 10 to the catalyst 22 is restricted in the idling state of the engine, the amount of oxygen adsorbed by the catalyst 22 compared to the case where the air supply restriction to the catalyst 22 is not performed. Can be reduced. Therefore, when starting the engine and before starting combustion, it is not necessary to supply the fuel (HC) for making the catalyst 22 neutral, or even if necessary, the amount of fuel can be reduced as much as possible.

  When the engine is restarted, the engine 10 is cranked by the motor 28 after the air supply to the catalyst 22 is restricted. Therefore, the air supply restriction to the catalyst 22 is restricted. It can be implemented from the beginning of the ranking.

  When there is an engine stop request, the air supply restriction to the catalyst 22 is started assuming that the engine idling condition is satisfied, and then the air supply restriction state is changed for a period until the combustion of the engine 10 is restarted. Since the structure is maintained, oxygen adsorption of the catalyst 22 can be suppressed in a series of engine stop / restart flows.

  In the cranking of the engine 10, in the configuration in which the engine speed is increased to a relatively high motor start speed NEa and the engine 10 is restarted after waiting for the engine speed to stabilize at the speed NEa, the engine 10 is empty. It is considered that the time for which the catalyst 22 is held in the rotating state becomes long, and the catalyst 22 is likely to be in an excessive oxygen state. By applying the present invention to such a configuration, it is possible to suitably obtain an effect that exhaust gas purification can be appropriately performed.

  At least a part of the air flowing from the engine 10 to the catalyst 22 is configured by limiting the air supply to the catalyst 22 by the EGR valve 24 and opening the EGR valve 24 when the engine idling condition is satisfied. Can be returned to the intake side. Therefore, in the system having the EGR device, the oxygen adsorption of the catalyst 22 in the idling state of the engine can be suppressed without adding a new configuration.

(Second Embodiment)
Next, the second embodiment of the present invention will be described focusing on the differences from the first embodiment described above. In the above embodiment, when there is an engine stop request, the EGR valve 24 is switched to the fully open state as if the engine idling condition is satisfied, but this configuration is changed in this embodiment. That is, in the present embodiment, when there is a restart request for the engine 10 after the engine is stopped, the EGR valve 24 is switched to the fully open state assuming that the engine idling condition is satisfied.

  FIG. 5 is a time chart showing a specific mode of engine control of the present embodiment. In the figure, (a) shows engine speed, (b) shows combustion / combustion stop of the engine 10, (c) shows drive / drive stop of the motor 28, and (d) shows changes in the opening degree of the EGR valve 24, respectively. . Moreover, in (d), a dashed-dotted line has shown transition of the target opening degree of the EGR valve 24, and the continuous line has shown transition of actual opening degree.

  In FIG. 5, after the engine stop request, the target opening degree of the EGR valve 24 is set to the fully closed opening degree. When the engine 10 is requested to restart after the engine is stopped, the target opening of the EGR valve 24 is changed from the fully closed position to the fully opened position at the request timing t21. Thereby, the EGR valve 24 is switched to the fully open state.

  Subsequently, the drive of the motor 28 is started at a timing t22 after the required switching time TC has elapsed from the request timing t21. Here, the required switching time TC is determined based on the time required for the EGR valve 24 to be fully opened after the target opening of the EGR valve 24 is changed to the fully opened opening, and is longer than the required time. As a value. That is, in the present embodiment, the engine output shaft 25 is rotated (cranked) by the motor 28 after the EGR valve 24 is fully opened.

  When the engine rotation speed NE reaches the motor start rotation speed NEa (1000 to 2000 rpm in the present embodiment) with the cranking of the engine 10 and the engine 10 is kept stable for a predetermined time at the rotation speed NEa, the timing is reached. At t23, the target opening of the EGR valve 24 is changed to the fully closed opening. Thereby, the EGR valve 24 is switched to the fully closed state. Further, fuel injection and ignition of the engine 10 are resumed at timing t24 after the EGR valve 24 is switched to the fully closed state.

  Next, the engine control processing procedure when the engine is restarted according to this embodiment will be described with reference to the flowchart of FIG. This process is executed by the hybrid ECU 60 at predetermined intervals. In addition, about the same process as FIG. 4 in the said 1st Embodiment, the same step number as FIG. 4 is attached | subjected and the description is abbreviate | omitted.

  In FIG. 6, first, in step S31, it is determined whether or not there is a request for restarting the engine 10 after the engine is stopped, that is, in step S32 if there is the request. The EGR valve 24 is switched to the fully open state.

  In a succeeding step S33, it is determined whether or not the motor 28 is permitted to rotate, that is, whether or not the air flow from the upstream side to the downstream side of the catalyst 22 is permitted. Here, whether or not the time required from when the target opening of the EGR valve 24 is changed to the fully opened position until the EGR valve 24 is fully opened (required switching time TC) has elapsed from the restart request timing. Determine. When it is determined that the required switching time TC has elapsed from the restart request timing, the process proceeds to step S34, where the rotation of the motor 28 is started and the engine 10 is cranked. Thereafter, in steps S35 to S37, the same processing as that in steps S23 to S25 of FIG. 4 is executed, and this processing is terminated.

  Also in the second embodiment described in detail above, it is possible to avoid excessive oxygen adsorption on the catalyst 22 as in the first embodiment. As a result, NOx reduction can be properly performed at the time of next combustion restart of the engine, and exhaust purification can be appropriately performed.

  In particular, when the engine 10 is requested to be restarted after the engine is stopped, the EGR valve 24 is switched to the open state because the engine idling condition is satisfied, and the opening degree of the EGR valve 24 is set to the target opening degree. Since the driving of the motor 28 is started after reaching the above, the amount of air supplied to the catalyst 22 during the cranking period can be made as small as possible.

(Third embodiment)
Next, a third embodiment of the present invention will be described focusing on differences from the first embodiment and the second embodiment described above. In the above embodiment, the supply restriction means is the EGR valve 24, and the air supply to the catalyst 22 is restricted in the engine idling state by changing the opening degree of the EGR valve 24 when the engine idling condition is satisfied. Although the configuration is adopted, this configuration is changed in the present embodiment. That is, in the present embodiment, a control valve that adjusts the exhaust gas flow rate is disposed in the exhaust passage on the upstream side of the catalyst 22 and on the downstream side of the connection portion with the EGR pipe 23 in the exhaust passage. When the engine idling condition is satisfied, the air supply to the catalyst 22 is limited in the engine idling state by controlling the opening degree of the control valve.

  FIG. 7 is a configuration diagram showing an overall outline of the present control system. In FIG. 7, the hybrid system such as the motor 28 is not shown.

  As shown in FIG. 7, a catalyst 22 is disposed in the exhaust pipe 12, and an exhaust system and an intake system are connected by an EGR pipe 23 on the upstream side of the catalyst 22. Further, the exhaust pipe 12 is provided with a shutter valve 41 that changes the flow path cross-sectional area in accordance with opening and closing on the upstream side of the catalyst 22 and downstream of the connection portion with the EGR pipe 23. The shutter valve 41 is a flow rate adjusting means that is electrically opened and closed by an actuator 42 made of a motor or the like. In the open state of the shutter valve 41, the flow of air to the catalyst 22 is allowed, and the flow of air to the catalyst 22 is restricted by switching to the closed state.

  In this embodiment, when there is an engine restart request, by switching the opening and closing of the shutter valve 41, specifically, by switching the shutter valve 41 from a fully open state to a fully closed or almost fully closed state. The air supply to the catalyst 22 is restricted when the engine 10 is idling.

  Here, when the shutter valve 41 is switched to the fully closed or almost fully closed state, the pressure on the upstream side of the shutter valve 41 is increased, and the driving load of the motor 28 may be increased. In this case, the power consumption of the motor 28 may increase, or the engine rotation speed may not be stabilized at the motor start rotation speed (1000 to 2000 rpm in this embodiment).

  Therefore, in this embodiment, when the engine idling condition is satisfied, the shutter valve 41 is fully closed in the idling state, and the EGR valve 24 is opened (fully opened in the present embodiment). As a result, the supply of air to the catalyst 22 is restricted by the fully closed state or almost fully closed state of the shutter valve 41, and the pressure increase on the upstream side of the shutter valve 41 is suppressed by the open state of the EGR valve 24. 28 is prevented from increasing.

  In addition, the opening degree of the EGR valve 24 in the engine idling state may be an intermediate opening degree in addition to the full opening degree.

  A specific aspect of engine control according to this embodiment will be described with reference to the time chart of FIG. In the figure, (a) is the engine speed, (b) is the combustion / combustion stop of the engine 10, (c) is the drive / drive stop of the motor 28, (d) is the opening of the EGR valve 24, (e) is The transition of the opening degree of the shutter valve 41 is shown respectively. Further, in (d) and (e), the alternate long and short dash line indicates the transition of the target opening, and the solid line indicates the transition of the actual opening.

  In FIG. 8, when the engine 10 is requested to restart after the engine is stopped, the target opening of the EGR valve 24 is changed to the fully opened position at the request timing t31, and the target opening of the shutter valve 41 is fully closed and opened. Change in degrees. Thereby, the EGR valve 24 is switched to the fully open state, and the shutter valve 41 is switched to the fully closed state.

  After the EGR valve 24 is fully opened and the shutter valve 41 is fully closed, the rotation of the motor 28 is started at the timing t32 and cranking of the engine 10 is started. That is, the engine output shaft 25 is rotated (cranked) by the motor 28 after the EGR valve 24 is fully opened and the shutter valve 41 is fully closed.

  As the engine 10 is cranked, the engine speed NE reaches a motor start speed NEa (for example, 1000 to 2000 rpm), and the engine 10 is kept stable for a predetermined time at the speed NEa. Thus, the target opening of the EGR valve 24 is changed to a fully closed opening, and the target opening of the shutter valve 41 is changed to a fully opened opening. Thereby, the EGR valve 24 is switched to the fully closed state, and the shutter valve 41 is switched to the fully opened state. Further, fuel injection and ignition of the engine 10 are resumed at timing t34 after switching between opening and closing of the EGR valve 24 and the shutter valve 41.

  Next, the engine control processing procedure when the engine is restarted according to this embodiment will be described with reference to the flowchart of FIG. This process is executed by the hybrid ECU 60 at predetermined intervals. In addition, about the same process as FIG. 6 in the said 2nd Embodiment, the same step number as FIG. 6 is attached | subjected and the description is abbreviate | omitted.

  In FIG. 9, first, in step S41, the same process as in step S31 of FIG. 6 is executed. When a restart request is made after the engine is stopped, in step S42, the shutter valve 41 is fully closed and the EGR valve 24 is fully opened. Put it in a state.

  In steps S43 to S45, the same processing as in steps S33 to S35 of FIG. 6 is executed, and when the engine rotation speed becomes stable, in step S46, the shutter valve 41 is fully opened and the EGR valve 24 is fully closed. Put it in a state. Thereafter, in step S47, the same process as in step S37 is executed, and this process is terminated.

  Also in the third embodiment described in detail above, it is possible to avoid that oxygen is adsorbed excessively on the catalyst 22 as in the first embodiment. As a result, NOx reduction can be properly performed at the time of next combustion restart of the engine, and exhaust purification can be appropriately performed.

  In particular, since the EGR valve 24 is controlled in addition to the shutter valve 41 when the idling condition is satisfied, the supply of air to the catalyst 22 can be restricted by the shutter valve 41, and the exhaust due to the restriction of the supply. The pressure increase in the passage can be suppressed by the EGR valve 24. Therefore, when the air supply to the catalyst 22 is restricted, the load on the motor 28 can be reduced as compared with the control by the shutter valve 41 alone.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be implemented as follows, for example.

  Switching whether or not to restrict the supply of air to the catalyst 22 in the engine idling state, depending on whether the restart request after the engine is stopped is a request for charging the high voltage battery 35 or a vehicle travel request . When there is a vehicle travel request, specifically, when the engine 10 is restarted when the idle restart condition is satisfied, or when the motor 10 travels while the motor travels, the engine 10 is restarted according to a vehicle acceleration request or a high-speed travel request. In this case, it is desirable to start combustion without waiting for the engine rotation speed to stabilize at the motor start rotation speed NEa, in order to give priority to running performance. Here, when the combustion is restarted without waiting for the engine rotation speed to stabilize, the time during which the engine 10 is idling is short and the amount of air supplied to the catalyst 22 is not so large. It is thought that there is no need to implement the supply restrictions in the first place. Therefore, when the engine restart request is due to a charge request, the air supply restriction to the catalyst 22 in the engine idling state is performed, whereas when the engine restart request is due to a vehicle travel request, the air supply restriction is performed. The configuration is not implemented. By so doing, it is possible to achieve a proper balance between NOx purification optimization and traveling performance.

  In the third embodiment, the EGR valve 24 is not controlled to be opened when the engine is idling. That is, in the engine idling state, the shutter valve 41 is switched from the opened state to the closed state, and the EGR valve 24 is maintained in the opened state. Even in this case, the supply of air to the catalyst 22 is restricted by the shutter valve 41, and the amount of O 2 storage of the catalyst 22 can be optimized.

  In the above embodiment, the case where the engine 10 is stopped in response to the engine stop request and then the engine is restarted when the restart request is made is described. However, the engine 10 is switched in accordance with the switching of the IG switch 39 to OFF. Can be applied to the case where the engine 10 is warmed up and restarted when the IG switch 39 is turned on. In this case, it is assumed that the engine idling condition is, for example, that the IG switch 39 is switched off and that the switch 39 is switched on within a predetermined time from the off switching. In this case, when the IG switch 39 is turned off, the EGR valve 24 is kept closed. When the IG switch is turned on within a predetermined time from the IG switch off switching timing, the EGR valve 24 is switched to the open state by the main relay of the hybrid ECU 60, for example, and the engine 10 is closed in that state. Make a ranking.

  Alternatively, the engine idling condition may be that the IG switch 39 is switched off. In this case, the valve opening state of the EGR valve 24 is continued for a predetermined valve opening allowable time from the switching timing. Note that the open state of the EGR valve 24 is maintained, for example, by a main relay of the hybrid ECU 60. When there is an engine restart request within the valve opening allowable time and the cranking of the engine 10 is started, the valve opening state of the EGR valve 24 is maintained during the cranking period, and then fuel injection and ignition are performed. Before starting, the EGR valve 24 is switched to the closed state.

  -About at least one of the EGR valve 24 and the shutter valve 41, the opening degree in the engine idling state is made variable. For example, the O2 storage amount of the catalyst 22 is estimated based on the output of the air-fuel ratio sensor, and the opening degree of the EGR valve 24 or the shutter valve 41 is set according to the estimated O2 storage amount. At this time, the larger the estimated amount of O2 storage, the larger the opening of the EGR valve 24 and the smaller the opening of the shutter valve 41.

  A configuration in which the supply of air to the catalyst 22 in the engine idling state is restricted after the engine stop request until the next engine restart request, and the supply restriction is not performed after the restart request. To do.

  Although the EGR valve 24 and the shutter valve 41 provided in the exhaust pipe 12 are used as the supply restriction unit that restricts the supply of air to the catalyst 22, the supply restriction unit is not limited thereto. For example, a branch pipe branched from the exhaust pipe 12 is provided on the upstream side of the catalyst 22 with respect to the exhaust pipe 12 in which the catalyst 22 is disposed, and an open / close valve is provided in the branch pipe. Then, in the engine idling state, the on-off valve of the branch pipe is switched to the flow rate increasing side (valve opening side). Even in this case, the amount of air supplied to the catalyst 22 can be reduced, and the O2 storage amount of the catalyst 22 when the engine is started can be suppressed.

  In the first embodiment, the opening timing of the EGR valve 24 is changed to the timing t12 after the delay time TA has elapsed from the engine automatic stop request timing t11, and the timing immediately after the request timing t11. It is good.

  In the second and third embodiments, the rotation start timing (t22, t32) of the motor 28 may be the engine restart request timing (t21, t31).

  In the above embodiment, the configuration in which the motor 28 as a power source of the vehicle is used as the starting device of the engine 10 has been described. However, a configuration including a starter motor as the starting device may be applied to the present invention. In this configuration, before starting combustion when the engine is restarted, the engine speed is increased to the cranking speed (for example, 200 rpm) by the starter motor, and after that increase, the engine 10 is idle until the combustion is restarted. It will be in the state. Therefore, by restricting the supply of air to the catalyst 22 in the idling state, it is possible to suppress the catalyst 22 from being in an excessive oxygen state, and it is possible to appropriately perform NOx purification.

  The present invention is applied to a configuration in which only the engine 10 having an idle stop function is provided as a power source and a starter motor is provided as a starting device. In this configuration, the engine 10 is repeatedly stopped and automatically restarted by the idling stop function, so that the engine 10 is frequently in an idling state, whereby air is supplied to the catalyst 22 in the idling state. Because it is possible.

  In the above embodiment, the present invention is applied to a hybrid vehicle in which the engine 10 is connected to the motor 28 via the power distribution device 26, but the configuration of the hybrid vehicle is not limited to this. For example, the engine 10 and the motor 28 may be directly connected, or the engine 10 and the motor 28 may output power to different drive shafts. Moreover, the structure provided with the engine 10, the 1st motor as an electric motor, and the 2nd motor as a generator may be sufficient. Furthermore, the engine 10 is not limited to a gasoline engine, and may be a diesel engine.

  DESCRIPTION OF SYMBOLS 10 ... Engine, 22 ... Catalyst, 23 ... EGR piping, 24 ... EGR valve (supply restricting means), 25 ... Engine output shaft, 28 ... Motor (traveling motor, generator), 35 ... High voltage battery (power storage device), 41 ... Shutter valve (supply restriction means), 50 ... Engine ECU, 60 ... Hybrid ECU (Condition determination means, restriction control means, restart control means, requested content determination means)

Claims (7)

The present invention is applied to a system including an engine, an engine starter, and an exhaust purification catalyst that is disposed in an exhaust passage of the engine and adsorbs or releases oxygen. When the engine is requested to restart after the engine is stopped In the engine control device for restarting the engine by rotating the output shaft of the engine by the starter,
Condition determining means for determining whether or not an idling condition for achieving an engine idling state in which the output shaft rotates in the engine combustion stop state accompanying engine stop is satisfied;
Supply restriction means for restricting the supply of air from the engine to the exhaust purification catalyst when the condition determination means determines that the idling condition is satisfied, in an air supply restriction state in the engine idling state Limit control means to control,
An engine control device comprising:   The engine control device according to claim 1, wherein the start of the rotation of the output shaft is started after the supply control device is controlled to the air supply control state by the control device. Engine control that automatically stops the engine when a predetermined stop condition is satisfied, and restarts the engine on the assumption that the restart request is made when the predetermined restart condition is satisfied after the stop condition is satisfied In the device
The condition determination means determines that the idle rotation condition is satisfied when the stop condition is satisfied,
The restriction control means is a period from the time when the condition determination means determines that the stop condition is satisfied to a time before restarting combustion of the engine with the satisfaction of the restart condition. The engine control device according to claim 1, wherein the engine control device is controlled to be in the air supply restriction state. In addition to the engine, it is applied to a vehicle equipped with a motor for driving as a power source,
The traveling motor functions as the starting device;
State determination means for determining that the rotation speed of the engine has become stable at a predetermined rotation speed during the rotation execution period of the output shaft by the starter in response to the restart request;
Restart control means for restarting combustion of the engine after it is determined by the state determination means that the rotational speed is in a stable state,
The restriction control means controls the supply restriction means to the air supply restriction state during a period before the combustion is resumed by the restart control means when the engine is restarted in response to the restart request. Item 4. The engine control device according to any one of Items 1 to 3. Applied to a vehicle comprising a generator that generates electric power by rotating the output shaft, and a power storage device capable of exchanging electric power with the generator;
The generator functions as the starting device;
The condition determining means determines whether the establishment of the idling condition is due to the restart request due to a charge request of the power storage device or the restart request due to a vehicle travel request,
The restriction control means controls the supply restriction means to the air supply restriction state when the condition determination means determines that the establishment of the idling condition is the restart request due to the charge request. The engine control device according to claim 4, wherein when it is determined that the restart request is due to the vehicle travel request, the supply restriction unit is controlled so that the supply of air is not restricted. An EGR passage connecting the upstream side of the exhaust purification catalyst and the intake system of the engine in the exhaust passage; an EGR valve disposed in the EGR passage for adjusting a recirculation amount for returning the exhaust of the engine to the intake system; Applied to a system comprising
The supply limiting means is the EGR valve;
The engine control apparatus according to any one of claims 1 to 5, wherein the limit control unit controls the EGR valve to increase the recirculation amount when it is determined that the idling condition is satisfied. . A flow rate adjusting valve for adjusting a flow rate of air from the engine to the exhaust purification catalyst is disposed upstream of the exhaust purification catalyst in the exhaust passage;
The supply restriction means is the flow rate adjustment valve;
The engine according to any one of claims 1 to 6, wherein, when it is determined that the idling condition is satisfied, the restriction control unit controls the flow rate adjustment valve to reduce the flow rate of the air. Control device.

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