JP2012145005A - Degradation suppressing control device for exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately protect an exhaust emission control system while suppressing degradation in fuel economy.SOLUTION: A degradation suppression control device for an exhaust emission control device is applied to a system which includes: a catalyst 17 as the exhaust emission control device in an exhaust path of an engine 10; and a cooling device 30 for the engine 10. The degradation suppression control device includes an ECU 50 which determines whether the exhaust temperature is within a predetermined high temperature range where the catalyst 17 may degrade by the exhaust heat. When the exhaust temperature is determined to be in the predetermined range, the degradation suppression control device carries out a cooling improving process of improving an engine cooling performance of the engine cooling device 30 as a cooling device, and also carries out an ignition advance process of advancing an ignition timing of the engine 10 after starting the cooling improving process.

Description

  The present invention relates to an exhaust purification device deterioration suppression control device, and more particularly to a technique for suppressing deterioration of an exhaust purification device provided in an exhaust passage of an engine due to high-temperature exhaust.

  Conventionally, in the high-load operation region of the engine, fuel increase (high load increase) is performed in order to suppress deterioration of the exhaust purification device due to an increase in exhaust temperature, or the recirculation amount (EGR) of exhaust to the intake system Etc.) (for example, refer to Patent Document 1). In Patent Document 1, when the temperature of the catalyst as the exhaust purification device is higher than a predetermined temperature, the exhaust gas recirculation amount is increased, and then the catalyst bed temperature is higher than the predetermined temperature even after the predetermined time elapses. It is disclosed to perform fuel increase.

Japanese Patent No. 2869903

  However, when the exhaust purification device is configured to suppress deterioration of the exhaust purification device by increasing the exhaust gas recirculation amount, the increase of the exhaust gas recirculation amount may be limited in a situation where the exhaust gas is likely to become hot, such as during high-load operation. is there. In this case, there is a possibility that the exhaust purification device cannot be protected. On the other hand, the increase in fuel is relatively limited even during high-load operation, and is considered effective as a process for protecting the exhaust purification device.

  However, in recent years, with the tightening of regulations, durability required for exhaust emission control devices has become more severe. In addition, from the viewpoint of fuel consumption, it is conceivable that protection of the exhaust emission control device by increasing the amount of fuel is limited. On the other hand, the frequency of high-load operation is increasing due to engine supercharging downsizing, running mode (US06 mode), and the like, and deterioration of the exhaust purification device due to high-temperature exhaust gas is likely to occur. For this reason, development of a new technology for protecting the exhaust purification device is desired.

  The present invention has been made in order to solve the above problems, and has as its main object to provide a deterioration suppression control device for an exhaust purification device that can appropriately protect the exhaust purification device while suppressing deterioration in fuel consumption. To do.

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

  The deterioration suppression control device for an exhaust purification device of the present invention is applied to a system including an engine, an exhaust purification device provided in an exhaust passage of the engine, and a cooling device for cooling the engine. According to the first aspect of the present invention, there is provided a deterioration determination means for determining whether or not the exhaust gas temperature is in a predetermined high temperature range in which the exhaust purification device may be deteriorated by exhaust heat, and the exhaust gas is exhausted by the deterioration determination means. When it is determined that the temperature is within the predetermined high temperature range, a cooling control unit that performs a cooling improvement process that improves engine cooling performance of the cooling device; and after the start of the cooling improvement process by the cooling control unit, And an ignition advance means for advancing the ignition timing.

  In short, in this configuration, when the exhaust gas is at a high temperature, the engine cooling performance can be improved to improve the engine knock resistance, thereby enabling the ignition advance. Further, the exhaust gas temperature can be lowered by performing the ignition advance. Furthermore, according to the present inventors, by increasing the engine cooling performance, it is possible to reduce the engine operating region in which the amount of fuel is increased to suppress deterioration of the exhaust purification device or the like (see FIG. 3). In other words, by improving the engine cooling performance at the exhaust temperature, for example, the opportunity for increasing the fuel to suppress the deterioration of the exhaust purification device due to exhaust heat, for example, or the amount of fuel used for increasing the fuel is reduced. You can make it. Therefore, according to the present invention, it is possible to appropriately protect the exhaust purification device while suppressing deterioration in fuel consumption.

  According to a second aspect of the present invention, there is provided a reduction determination means for determining that the cylinder temperature of the engine has dropped after the start of the cooling improvement processing, and the ignition advance means has the cylinder temperature lowered by the reduction determination means. After it is determined that the ignition timing has been reached, the ignition timing is advanced.

  There is a delay time from the start of the operation of the cooling device to improve the cooling performance of the engine until the engine is cooled to such an extent that the effect of improving the knocking resistance of the engine can be obtained. In view of this, by adopting the above configuration, it is possible to suppress the occurrence of knocking when performing the ignition advance. The determination of the decrease in the cylinder temperature may be performed, for example, by detecting the temperature of the cylinder head or the cylinder block, or may be performed by detecting the temperature of the engine cooling water. Moreover, you may perform based on the elapsed time after starting a cooling improvement process.

  In the third aspect of the present invention, a maximum torque operation region that can be controlled at the maximum torque ignition timing at which the torque is maximum is determined as the engine operation region, and the engine operation state after the start of the cooling improvement process is the maximum operation region. Means for determining whether or not the engine is in a torque operation region, and the ignition advance means determines the ignition timing when the engine operation state after the start of the cooling improvement processing is in the maximum torque operation region. Advance the ignition timing.

  In an engine, there are an MBT operation region in which the ignition timing can be controlled by the maximum torque ignition timing (MBT ignition timing) at which the torque is maximum, and a trace knock operation region in which the ignition timing is controlled to advance to the knock generation limit (see FIG. 2). In the above configuration, when the current engine operating state belongs to the MBT operating region, the ignition timing is set to the MBT ignition timing in order to prioritize the reduction of the fuel increase over the torque when the ignition advance is performed by the ignition advance means. More advanced angle. At this time, the ignition timing may be determined in consideration of the balance between the deterioration in fuel consumption due to the excessive advance angle of the ignition timing and the improvement in fuel efficiency due to engine cooling and the ignition advance angle.

In the invention according to claim 4, the ignition advance means sets the ignition timing as the maximum torque ignition timing when the exhaust gas temperature is lower than a predetermined determination temperature set in the predetermined high temperature range, and the predetermined determination When the temperature is higher than the temperature, the ignition timing is advanced from the maximum torque ignition timing.
That is, in this configuration, when the exhaust gas temperature is in the predetermined high temperature range, the ignition timing is over-advanced with respect to the MBT ignition timing when the possibility of deterioration of the exhaust purification device is particularly high. In this case, it can be selected according to the environment of the exhaust purification device whether priority is given to improving the fuel efficiency or protection of the exhaust purification device from the exhaust heat.

  The present invention may be applied to an apparatus including a fuel increase means for increasing the fuel in at least a part of the predetermined high temperature region, as in the fifth aspect of the present invention. In order to suppress deterioration of the exhaust emission control device due to exhaust heat, the fuel increase may be performed at a high exhaust temperature. However, there is a concern that the fuel consumption deteriorates due to the fuel increase. In this regard, according to the present invention, since the cooling improvement process and the ignition advance angle are performed in a predetermined high temperature range, the opportunity for increasing the fuel and the amount of fuel used for increasing the fuel can be reduced.

  In the configuration including the fuel increasing means, the temperature for detecting the exhaust temperature after the start of the cooling improvement process by the cooling control means and the ignition advance by the ignition advance means as in the invention according to claim 6. And a fuel increasing unit that detects fuel when the exhaust temperature detected by the temperature detecting unit reaches a second temperature that is higher than a first temperature that is predetermined as a start temperature of the cooling improvement process. It is recommended to increase the amount. According to the configuration of the sixth aspect, by performing the cooling improvement process and the ignition advance before performing the fuel increase for suppressing the deterioration of the exhaust purification device, the opportunity for the fuel increase can be reduced as much as possible. As a result, it is possible to suppress as much as possible the deterioration of the fuel consumption due to the fuel increase.

  Further, as a configuration including the fuel increase means, as in the invention according to claim 7, when the fuel increase by the fuel increase means is performed, the cooling control means is performed together with the fuel increase or after the fuel increase is performed. It is also possible to adopt a configuration in which the cooling enhancement process by the ignition advance and the ignition advance by the ignition advance means are performed. In suppressing the deterioration of the exhaust emission control device due to the exhaust heat, the latter is considered to be more effective than the former in the case of the cooling improvement process and the ignition advance angle and the case of the fuel increase. Therefore, as described above, when the exhaust gas is at a high temperature, the fuel increase is first performed, and the cooling improvement process and the ignition advance are performed together with the fuel increase or after the fuel increase. Can be obtained as early as possible.

  In the invention according to claim 8, the cooling device includes first cooling means for cooling the cylinder block of the engine and second cooling means for cooling the cylinder head, and the cooling control means includes the deterioration determining means. When it is determined that the exhaust temperature is in the predetermined high temperature range, the cooling performance of the cylinder head by the second cooling means is improved.

  Some engine cooling systems have different cooling performances between the engine cylinder head and the cylinder block. While applying the present invention to such an engine cooling system and adopting a configuration that actively cools the cylinder head of the engine as a cooling improvement process, cooling is suppressed while suppressing an increase in mechanical loss due to cooling of the cylinder block. It is possible to more suitably improve the knocking resistance by the improvement process.

  In the invention according to claim 9, the cooling performance of the cooling device is variable, and the cooling control means cools the engine with the cooling performance according to the exhaust temperature.

  When the cooling performance of the engine is improved, it is possible that the knocking resistance can be improved, but the cooling loss is increased, or the power for improving the engine cooling performance is required in the cooling device. In view of this, as in this configuration, by changing the cooling performance of the engine by the cooling device according to the exhaust temperature, it is possible to achieve both suppression of deterioration of the exhaust purification device due to exhaust heat and suppression of increase in cooling loss. Can be planned.

The block diagram which shows the outline | summary of an engine control system. The figure which shows an ignition timing characteristic. The figure which shows the relationship between engine cooling performance and OT increase area | region. The flowchart which shows the process sequence of the catalyst deterioration suppression process of 1st Embodiment. The subroutine which shows the process sequence of a 2nd ignition advance process. The figure which shows the specific aspect of the catalyst deterioration suppression process of 1st Embodiment, and shows the case where exhaust temperature falls by the 1st cooling improvement process and the 1st ignition advance process. The specific aspect of the catalyst deterioration suppression process of 1st Embodiment is shown, and the case where fuel increase correction | amendment is implemented after the start of a 2nd cooling improvement process and a 2nd ignition advance process is shown. The flowchart which shows the process sequence of the catalyst deterioration suppression process of 2nd Embodiment. The figure which shows the specific aspect of the catalyst deterioration suppression process of 2nd Embodiment. The block diagram which shows the outline of the engine control system of other embodiment. The block diagram which shows the outline of the engine control system of other embodiment. The block diagram which shows the outline of the engine control system of other embodiment. The block diagram which shows the outline of the engine control system of other embodiment.

(First embodiment)
Hereinafter, a first embodiment in which the present invention is embodied in a vehicle equipped with a spark ignition type multi-cylinder gasoline engine will be described with reference to the drawings. FIG. 1 is a configuration diagram showing an outline of an engine control system equipped with an exhaust emission control device deterioration suppressing device according to the present invention.

  In FIG. 1, an engine 10 is, for example, a four-cylinder engine, and includes a throttle valve 11 as an air amount adjusting unit that adjusts an intake air amount into the cylinder, an injector 12 as a fuel injection unit that injects and supplies fuel, and a cylinder. An igniter (not shown) is provided as ignition means for generating ignition sparks in the spark plug 13 provided for each. The engine 10 may be an intake port injection type in which the injector 12 is provided in the vicinity of the intake port, or may be a direct injection type provided in the cylinder head 14 of each cylinder.

  The exhaust pipe 15 of the engine 10 is provided with an exhaust temperature sensor 16 for detecting the temperature of the exhaust, and a catalyst 17 as an exhaust purification device is provided on the downstream side of the exhaust temperature sensor 16. The catalyst 17 is, for example, a three-way catalyst, and purifies harmful components and the like in the exhaust when the exhaust passes.

  Next, the configuration of the engine cooling system 30 as a cooling device for the engine 10 will be described.

  A water jacket 31 is formed inside the cylinder block 18 and the cylinder head 14 of the engine 10. Cooling water is circulated and supplied to the water jacket 31 so that the engine 10 is cooled. In this embodiment, the water jacket 31 is provided with a block-side path 31A as a first cooling means for cooling the cylinder block 18 and a head-side path 31B as a second cooling means for cooling the cylinder head 14.

  A circulation path 33 made of cooling water piping or the like is connected to the block side path 31A, and a circulation path 34 made of cooling water piping or the like is connected to the head side path 31B. Among these, the circulation path 34 on the cylinder head 14 side is provided with an on-off valve 35 capable of adjusting the flow rate of the cooling water passing through the circulation path 34. The two circulation paths 33 and 34 are connected on the inlet side (upstream side) of the engine 10, and a water pump 36 for circulating the cooling water is provided on the upstream side of the connection point. The water pump 36 is, for example, a mechanical pump that is driven as the engine 10 rotates.

  In each of the circulation paths 33 and 34, in the vicinity of the outlet side of the engine 10, a water temperature sensor 32a for detecting the temperature (cooling water temperature) of the cooling water in the block side path 31A and the cooling water temperature in the head side path 31B are detected. A water temperature sensor 32b is provided. Further, the two circulation paths 33 and 34 are connected on the outlet side (downstream side) of the engine 10 and are branched again in two directions on the downstream side of the connection portion.

  A heater core 38 is provided in one of the branched circulation paths 37. Air conditioning air is sent to the heater core 38 from a blower fan (not shown). When the air conditioning air passes through the heater core 38 or its vicinity, the air conditioning air is heated by heat received from the heater core 38, and Supplied in the passenger compartment. The cooling water that has passed through the heater core 38 or the vicinity thereof is returned to the engine 10 via the circulation path 37 again.

  The other of the branched circulation paths 39 is further branched in two directions, and a radiator 41 as an atmospheric heat radiation portion is provided in one of the circulation paths 39A. In the radiator 41, heat dissipation is promoted by a radiator fan (not shown). The branched circulation paths 39 and 39A are connected again on the downstream side of the radiator 41, and a thermostat 42 that changes the flow path of the cooling water by operating according to the cooling water temperature is provided at the connection portion. ing. If the cooling water is at a low temperature (below the thermostat operating temperature), the cooling water is prevented from flowing into the radiator 41 and is circulated in the circulation path without being dissipated by the radiator 41. For example, before the warm-up of the engine 10 is completed (during warm-up operation), the cooling water flowing into the radiator 41 is blocked by the thermostat 42, thereby suppressing the cooling (cooling) of the cooling water in the radiator 41. Is done. Further, when the cooling water reaches a high temperature (above the thermostat operating temperature), the cooling water is allowed to flow into the radiator 41 by the thermostat 42 and circulates in the circulation path while being radiated by the radiator 41. Thereby, the cooling water is maintained at an appropriate temperature (for example, about 80 ° C.) under the engine operating condition. The thermostat 42 can be opened and closed by a drive signal. In the present embodiment, the flow rate of the cooling water to the radiator 41 increases as the thermostat opening increases.

  In the present embodiment, an opening / closing valve 43 capable of changing the distribution ratio (flow rate ratio) of the cooling water flow rate to each circulation path is provided at a branching portion branched in two directions of the circulation paths 37 and 39. Yes. For example, when a heating request is generated in the passenger compartment, the heating request is satisfied by changing the opening of the on-off valve 43 to the side where the flow rate ratio to the circulation path 37 is increased. On the other hand, when the cooling water reaches a high temperature (for example, the thermostat operating temperature or higher), the opening of the on-off valve 43 is changed to the side where the flow rate ratio to the circulation path 39 is increased, thereby promoting the heat radiation of the cooling water in the radiator 41. Let However, the on-off valve 43 is not necessarily required, and a configuration without the on-off valve 43 may be employed.

  The present control system includes an ECU (electronic control unit) 50 that forms the center of engine control, and the ECU 50 performs various controls relating to the operation of the engine 10. That is, as is well known, the ECU 50 is configured mainly by a microcomputer including a CPU, ROM, RAM, and the like, and executes various control programs stored in the ROM, thereby performing various controls of the engine 10 according to the engine operating state. To implement. In the present system, as an operation state detection means for detecting the engine operation state, a rotation speed sensor 51 that detects an engine rotation speed, a load sensor 52 that detects an engine load such as an intake air amount and an intake pipe negative pressure, and the like are provided. The detection signals from the sensors 51 and 52 and the water temperature sensors 32a and 32b described above are appropriately input to the ECU 50.

  The ECU 50 receives detection signals from the various sensors described above, and performs air amount adjustment control by the throttle valve 11, fuel injection control by the injector 12, ignition timing control by the igniter, and the like based on the various detection signals. . The various controls described above are basically performed on the basis of conformity data and the like so that the engine 10 has the highest efficiency (maximum fuel consumption) in each engine operation state. For example, for ignition timing control, the knock generation limit is not exceeded so as to be as close as possible to the MBT ignition timing (MBT: Minimum Advance for Best Torque), which is the ignition timing at which the torque is maximum in the current engine operating state. Set each time.

  FIG. 2 is a diagram showing ignition timing characteristics. In the engine 10, the relationship between the MBT ignition timing and the knock generation limit (trace knock ignition timing) differs depending on the engine operating state. Specifically, as shown in FIG. 2, an MBT operation region S1 in which the MBT ignition timing is retarded from the trace knock ignition timing, and a TK operation region in which the MBT ignition timing is advanced from the TK ignition timing. There is S2. In these two operation areas S1 and S2, the low load side is the MBT operation area S1 and the high load side is the TK operation area S2 with respect to the boundary line L1. Moreover, about MBT driving | operation area | region S1, the area | region has spread to the high load side, so that engine rotational speed becomes high. When the output torque of the engine 10 is maximized, the ECU 50 sets the target ignition timing to the MBT ignition timing in the MBT operation region S1, and sets the target ignition timing to the trace knock ignition timing in the TK operation region S2.

  For fuel injection control, for example, the basic fuel injection amount is calculated based on the intake air amount, and the post-startup increase correction, warm-up increase correction, and high load increase correction (OT increase correction) are calculated for the basic fuel injection amount. ) And other corrections. In detail about the OT increase correction, when the exhaust temperature rises to a predetermined catalyst deterioration temperature (for example, 850 ° C.), the fuel increase corresponding to the rotational speed and load of the engine 10 is performed in order to reduce the exhaust temperature.

  Here, it is desirable that the amount of fuel increase and the amount of fuel for suppressing catalyst deterioration due to high-temperature exhaust be as small as possible from the viewpoint of improving fuel efficiency. Therefore, in this embodiment, by improving the engine cooling performance, the knocking resistance is improved and the ignition advance is possible, and the OT increase region in which the OT increase correction is performed is reduced (the excess air ratio λ = 1), the cooling performance of the engine 10 is improved by changing the operation mode of the engine cooling system 30 in a predetermined high temperature range where the catalyst may be deteriorated due to exhaust heat. After that, the ignition timing of the engine 10 is advanced.

  The change in the OT increase region due to the improvement of the engine cooling performance will be described in detail with reference to FIG. FIG. 3 is a diagram showing the relationship between the cooling performance of the engine 10 and the OT increase region. In the figure, boundary lines L1 and L1 ′ are boundary lines between the MBT operation region S1 and the TK operation region S2, and boundary lines L3 and L3 ′ are λ = 1 operation region and OT increase region where OT increase correction is not performed. Is the boundary line. Among these, L1 and L3 indicate before the engine cooling performance is improved, and L1 'and L3' indicate after the engine cooling performance is improved. Further, OT-MBT indicates an engine operation region in which OT increase is performed in the MBT operation region S1, and OT-TK indicates an engine operation region in which OT increase is performed in the TK operation region S2.

  As shown in FIG. 3, the OT increase correction is performed in an engine operating region with high engine speed and high load. Here, when the cooling performance of the engine 10 is improved, as shown in FIG. 3, the boundary line between the λ = 1 operating region and the OT increasing region moves from L3 to L3 ′. That is, the λ = 1 operation region is increased and the OT increase region is decreased. Thereby, the frequency of performing the OT increase correction is reduced, and the amount of fuel used for suppressing thermal deterioration of the catalyst 17 can be reduced.

  Furthermore, when the engine cooling performance is improved, as shown in FIG. 3, the boundary line L1 between the MBT operation region S1 and the TK operation region S2 moves to the high load side and becomes L1 '. That is, the MBT operation area S1 becomes larger and the TK operation area S2 becomes smaller. Thereby, the opportunity which controls ignition timing with MBT ignition timing can be increased, and the fuel consumption reduction effect is acquired.

  Next, the catalyst deterioration suppressing process of this embodiment will be described. FIG. 4 is a flowchart showing a processing procedure for catalyst deterioration suppression processing. This process is executed by the ECU 50 at predetermined intervals.

  In FIG. 4, in step S101, it is determined whether or not the exhaust gas temperature Tex is higher than the first determination value T1. Here, the first determination value T1 is set to a value lower than the catalyst deterioration temperature by a predetermined temperature α, and is set to 800 ° C., for example. The exhaust gas temperature Tex may be an actual measurement value detected by the exhaust gas temperature sensor 16 or an estimated temperature calculated based on the engine operating state (engine speed, engine load, etc.). Alternatively, it may be a predicted temperature after a predetermined time calculated based on a measured value and a temperature gradient by the exhaust temperature sensor 16, or may be any one of a measured value, estimated temperature, and predicted temperature of the catalyst bed temperature instead of the exhaust temperature. . In the present embodiment, the first determination value T1 corresponds to the “first temperature”, and the temperature range higher than the first determination value T1 corresponds to the “predetermined high temperature range”.

When step S101 is YES, it progresses to step S102 and it is determined whether the 2nd flag F2 is ON. If the second flag F2 is not ON, the process proceeds to step S103, and the first cooling improvement process is performed to improve the cooling performance of the engine 10. The first cooling improvement process is to cool the engine 10 in a mode lower than the maximum cooling performance. Specifically,
Increase the opening of the on-off valve 35 and increase the coolant flow rate in the head side path 31B by ΔQ1. Increase the opening of the thermostat 42 by ΔL1 and increase the coolant flow to the radiator 41 side. We are going to carry out. Here, ΔQ1 is set in a range in which the coolant flow rate in the head-side path 31B is not maximized, and ΔL1 is set in a range in which the thermostat 42 is not at the maximum opening degree Lmx. Further, when increasing the coolant flow rate toward the head side path 31B or the radiator 41 side, the opening degree of the on-off valve 43 may be changed to the side where the flow rate of the circulation path 39 is increased.

  In a succeeding step S104, it is determined whether or not the cylinder temperature of the engine 10 has decreased. Here, it is determined whether or not the coolant temperature (engine outlet temperature) detected by the water temperature sensor 32b is equal to or lower than the determination value TW1. Note that the cylinder temperature decrease determination may be performed by determining whether or not the amount of decrease in the coolant temperature exceeds a predetermined value, or the elapsed time after the start of the first cooling improvement process is set to a predetermined time. You may perform by determining whether it exceeded. Further, when a pressure sensor for detecting the internal pressure of the path is provided in the head side path 31B or the circulation path, the determination may be made based on the detection value of the pressure sensor. At this time, when the engine cooling performance is not sufficiently obtained, the radiator fan may be further operated.

  When step S104 is YES, it progresses to step S105 and a 1st ignition advance process is implemented. Specifically, using the engine operation region map after improving the engine cooling performance (for example, the map of FIG. 3), if the current engine operation state belongs to the TK operation region, the target ignition timing is set to trace knock ignition. In the case where it belongs to the MBT operation region, the target ignition timing is set as the MBT ignition timing. Note that the ignition timing control to the target ignition timing is executed by a separate routine (not shown). In step S105, the first flag F1 is turned on.

  In step S106, two conditions are (1) that the exhaust temperature Tex is higher than the first determination value T1 for a determination time Time1 or more, and (2) the exhaust temperature Tex is higher than the second determination value T2. It is determined whether or not both are established. Here, the second determination value T2 is set to a temperature (for example, the catalyst deterioration temperature or the vicinity thereof) higher than the first determination value T1. The second determination value T2 corresponds to “predetermined determination temperature”. In step S106, whether or not the conditions (1) and (2) are satisfied is determined. However, only one of the conditions may be determined. When step S106 is YES, it progresses to step S107, turns on the 2nd flag F2, and once complete | finishes this routine.

If the second flag F2 is ON and the exhaust temperature Tex is higher than the first determination value T1, steps S101 and S102 are YES, and the process proceeds to step S108, where the second cooling improvement process is performed. The second cooling improvement process is different from the first cooling improvement process in that the engine cooling by the cooling system 30 is performed with the maximum cooling capacity. In particular,
The maximum opening degree of the on-off valve 35 is set to the maximum cooling water flow rate in the head-side path 31B. Do either.

  In a succeeding step S109, it is determined whether or not the cylinder temperature of the engine 10 is lowered by the second cooling improvement process. Here, for example, is it determined whether or not the cooling water temperature detected by the water temperature sensor 32b is equal to or less than the determination value TW2 (TW2 <TW1). The determination value TW2 may be the same temperature as the determination value TW1.

  When step S109 is YES, it progresses to step S110 and implements 2nd ignition advance processing. In the second ignition advance processing, the engine operation region map after improving the cooling performance is used, and depending on whether the current engine operation state belongs to the TK operation region or the MBT operation region, It is switched whether the same mode as the first ignition advance processing is used.

  FIG. 5 is a subroutine showing a processing procedure of the second ignition advance processing. In FIG. 5, in step S41, it is determined whether or not the current engine operation state belongs to the MBT operation region. When step S41 is NO, that is, when it belongs to the TK operation region, the routine proceeds to step S42, and this routine is terminated with the target ignition timing as the trace knock ignition timing. On the other hand, if it belongs to the MBT operation region, step S41 becomes YES, the process proceeds to step S43, and this routine is ended with the target ignition timing set to the advance side of the MBT ignition timing.

  Returning to the description of FIG. 4, in step S111, it is determined whether or not a state in which the exhaust temperature Tex is higher than the second determination value T2 (corresponding to “second temperature”) continues for the determination time Time2 or more. If YES, the process proceeds to step S112, and fuel increase correction (OT increase correction) for catalyst protection is performed on the basic fuel injection amount. The fuel correction amount is set based on the engine operating state. Specifically, the fuel correction amount is increased as the engine rotational speed is higher or the engine load is larger. In this fuel increase correction, the fuel increase can be reduced as much as possible by the cooling improvement process and the ignition advance angle before the correction. In step S112, the third flag F3 is turned on.

  When the exhaust temperature Tex becomes equal to or lower than the first determination value T1, step S101 becomes NO and the process proceeds to step S113. In step S113, it is determined whether or not the third flag F3 is turned on. If step S113 is YES, the process proceeds to step S114, the OT increase correction is stopped, and the third flag F3 is turned off. In the following step S115, it is determined whether or not the first flag F1 is ON. If F1 = ON, the process proceeds to step S116, and the cooling performance reduction process and the ignition delay are performed. Here, as the cooling performance reduction process, for example, when the exhaust temperature Tex becomes equal to or lower than the first determination value T1 by the first cooling improvement process and the first ignition advance process, for example, the cooling water flow rate of the head side path 31B is changed. A process of reducing the amount by ΔQ3, a process of reducing the opening of the thermostat 42 by ΔL3, and the like are performed. At this time, ΔQ3 may be smaller than ΔQ1, and ΔL3 may be smaller than ΔL1. When the exhaust temperature Tex becomes equal to or lower than the first determination value T1 after the start of the second cooling improvement process and the second ignition advance process, for example, the cooling water flow rate in the head side path 31B is set to ΔQ4 (> ΔQ3). ), The process of reducing the opening of the thermostat 42 by ΔL4 (> ΔL3), and the like. In step S116, the first flag F1 and the second flag F2 are turned off, and this routine ends.

  Next, a specific aspect of the catalyst deterioration suppressing process will be described with reference to the time charts of FIGS. FIG. 6 shows a case where the exhaust temperature Tex becomes equal to or lower than the first determination value T1 by the first cooling improvement process and the first ignition advance process, and FIG. 7 shows the second cooling improvement process and the second ignition advance process. After the start of this, the case where the fuel increase correction is further performed is shown. In the figure, (a) shows the change in the accelerator opening, (b) shows the change in the exhaust temperature Tex, (c) shows the change in the coolant flow rate in the head side path 31B, and (d) shows the engine outlet. (E) shows the change of the ignition timing, (f) shows the change of the fuel increase amount by the fuel increase correction, and (g) shows the change of the first flag F1. Shows the transition. In FIG. 7, (h) shows the transition of the second flag F2, and (i) shows the transition of the third flag F3.

  In FIG. 6, when the accelerator pedal is depressed at the timing t11, the ignition timing is retarded to suppress the occurrence of knocking, and the coolant flow rate of the engine 10 is increased. Further, the exhaust temperature Tex of the engine 10 increases due to the large accelerator opening. When the exhaust temperature Tex exceeds the first determination value T1, at the timing t12, the opening degree of the on-off valve 35 is changed to the larger side, and the coolant flow rate in the head side path 31B is further increased by ΔQ1 (first). 1 cooling improvement process). Further, when the engine outlet temperature becomes equal to or lower than the determination value TW1 as the cooling water flow rate increases, the ignition advance is performed at the timing t13, and the first flag F1 is turned on. At this time, when the engine operation state belongs to the TK operation region, the angle is advanced to the trace knock ignition timing, and when it belongs to the MBT operation region, the angle is advanced to the MBT ignition timing (first ignition advance processing). .

  When the above-described cooling improvement processing and ignition advance are not performed, the exhaust temperature Tex continues to rise as indicated by the alternate long and short dash line in FIG. 6B, but the cooling improvement processing and ignition advance are performed. As shown by the solid line, the exhaust gas temperature Tex starts to decrease. When the exhaust gas temperature Tex becomes equal to or lower than the first determination value T1 at timing t14, the coolant flow rate in the head side path 31B is reduced by ΔQ3 (<ΔQ1) and the ignition delay is performed. Thereby, the exhaust gas temperature Tex is maintained in the vicinity of the first determination value T1.

  Next, the case of FIG. 7 will be described. In FIG. 7, when the exhaust gas temperature Tex rises and exceeds the first determination value T1 as the accelerator pedal is depressed at the timing t21, the opening degree of the on-off valve 35 is changed to the larger side at the timing t22. Then, the coolant flow rate in the head-side path 31B is increased by ΔQ1 (first cooling improvement process). When the engine outlet temperature becomes equal to or lower than the determination value TW1 as the cooling water flow rate increases, the ignition timing is advanced at the timing t23. At this time, when the engine operation state belongs to the TK operation region, the angle is advanced to the trace knock ignition timing, and when it belongs to the MBT operation region, the angle is advanced to the MBT ignition timing (first ignition advance processing). .

  Also in the first cooling improvement process and the first ignition advance process, the exhaust temperature Tex continues to rise, the state where the exhaust temperature Tex is higher than the first determination value T1 continues for the determination time Time1 and the second determination value T2 is set. If it exceeds the state, the opening / closing valve 35 is fully opened at the timing t24, and the cooling water flow rate in the head side path 31B is set to the maximum flow rate Qmx (second cooling improvement process). Further, the ignition timing is further advanced at timing t25 when the engine outlet temperature becomes equal to or lower than the determination value TW2. At this time, when the engine operation state belongs to the TK operation region, the angle is advanced to the trace knock ignition timing, and when it belongs to the MBT operation region, the engine is over-advanced beyond the MBT ignition timing (second ignition advance). Corner processing).

  If the exhaust temperature Tex does not decrease even by the second cooling improvement process and the second ignition advance process, and the state higher than the second determination value T2 continues for the determination time Time2 or more, the basic fuel injection amount after the timing t26. The fuel increase correction is performed on the fuel cell. As a result, the exhaust gas temperature Tex decreases and becomes equal to or lower than the second determination value T2. In the present embodiment, the fuel increase correction is stopped when the exhaust gas temperature Tex becomes equal to or lower than the first determination value T1. However, the exhaust temperature at which the fuel increase correction is stopped is arbitrary.

  Here, when the cooling improvement process and the ignition advance are not performed, the fuel increase correction is performed when the exhaust temperature Tex exceeds the second determination value T2 at the timing t23A and the determination time Time2 has elapsed from the timing t23. The On the other hand, in the present embodiment, the execution period of the fuel increase correction can be shortened as much as possible (the opportunity for implementation is reduced as much as possible) by performing the cooling improvement process and the ignition advance.

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

  It is determined whether or not the exhaust gas temperature is higher than the first determination value T1, and if the exhaust gas temperature is higher than the first determination value T1, it is assumed that the exhaust gas is in a predetermined high temperature range where the catalyst 17 may be deteriorated due to exhaust heat. Since the cooling improvement process for improving the cooling performance of the engine 10 is performed and the ignition advance process for advancing the ignition timing of the engine 10 is performed after the start of the cooling improvement process, the exhaust temperature is lowered. Can be made. As a result, the opportunity for performing the OT increase correction can be reduced, and the amount of fuel used for the OT increase correction can be reduced. Therefore, it is possible to appropriately protect the catalyst 17 while suppressing deterioration in fuel consumption.

  After the start of the cooling improvement process, it is determined whether or not the cylinder temperature of the engine 10 has decreased, and the ignition timing is advanced after it is determined that the cylinder temperature has decreased. The ignition advance can be performed in consideration of the delay time until the engine 10 is cooled to such an extent that the effect of improving the knocking resistance of the engine 10 is obtained. Generation | occurrence | production can be suppressed.

  In the second ignition advance processing, when it is determined that the engine operating state after the start of the second cooling improvement processing is in the MBT operation region, the ignition timing is advanced from the MBT ignition timing. Depending on the circumstances of the environment where the fuel is exposed, priority can be given to reducing the increase in fuel over torque. Further, when it is determined that the engine operating state after the start of the cooling improvement process is in the MBT operation region, the target ignition timing is set as the MBT ignition timing in the first ignition advance process, and the target ignition timing is set in the second ignition advance process. Since the ignition timing is set to be more advanced than the MBT ignition timing, it is possible to switch according to the environment of the catalyst 17 whether priority is given to improving fuel efficiency or protection of the catalyst 17 from exhaust heat.

  When the exhaust temperature after the start of the execution of the second cooling improvement process and the second ignition advance process is detected, the exhaust temperature is higher than the second determination value T2, and the state continues for a predetermined time Time2 or more, the OT increase amount Since the correction is performed, deterioration of the catalyst 17 due to exhaust heat can be suitably suppressed. In particular, in this configuration, since the cooling improvement process and the ignition advance are performed before the fuel increase for suppressing the deterioration of the catalyst 17 is performed, the opportunity for the fuel increase can be reduced as much as possible. It is possible to suppress as much as possible the deterioration of the fuel consumption due to the fuel increase.

  The water jacket 31 includes a block-side path 31A for cooling the cylinder block 18 and a head-side path 31B for cooling the cylinder head 14, and increases the cooling water flow rate in the head-side path 31B as cooling improvement processing. Therefore, the cylinder head 14 can be actively cooled at the time of high exhaust temperature. Thereby, it is possible to more appropriately improve the knocking resistance by the cooling improvement process while suppressing the increase in the mechanical loss due to the cooling of the cylinder block 18.

  Since the engine 10 is cooled by the cooling performance corresponding to the exhaust temperature, more specifically, the engine 10 is cooled by the cooling performance different between the first cooling improvement process and the second cooling improvement process. Suppression of catalyst deterioration due to heat and suppression of increase in cooling loss can be performed in a balanced manner.

(Second Embodiment)
Next, a second embodiment of the present invention will be described focusing on differences from the first embodiment. In the first embodiment, the fuel increase correction is performed when the exhaust temperature does not decrease to the predetermined temperature even when the cooling improvement process and the ignition advance angle are performed. However, in the present embodiment, the exhaust temperature exceeds the predetermined temperature. In such a case, first, the fuel increase correction is performed, and at the same time as the fuel increase correction, a cooling improvement process and an ignition advance are performed. This point is different from the first embodiment. Hereinafter, the catalyst deterioration suppressing process of the present embodiment will be described with reference to FIGS.

  FIG. 8 is a flowchart showing a processing procedure of the catalyst deterioration suppressing process of the present embodiment. This process is executed by the ECU 50 at predetermined intervals.

  In FIG. 8, in step S301, it is determined whether or not the exhaust gas temperature Tex is higher than the third determination value T3. The third determination value T3 is set at or near the catalyst deterioration temperature, and is set at 850 ° C., for example. When step S301 is YES, the process proceeds to step S302, and OT increase correction is performed on the basic fuel injection amount. At this time, for example, the fuel correction amount is increased as the engine rotational speed is higher or the engine load is larger. In step S302, the fourth flag F4 is turned on.

In a succeeding step S303, a cooling improvement process is performed. here,
Increase the opening of the on-off valve 35 to increase the cooling water flow rate in the head side path 31B by ΔQ11. Increase the opening of the thermostat 42 by ΔL11 to increase the cooling water flow rate to the radiator 41 side. We are going to carry out. Here, ΔQ11 and ΔL1 are set to a very small amount.

  In a succeeding step S304, it is determined whether or not the cylinder temperature of the engine 10 has decreased due to the cooling improvement process. Here, for example, it is determined whether or not the cooling water temperature (engine outlet temperature) detected by the water temperature sensor 32b is equal to or lower than the determination value TW1. When step S304 is YES, the process proceeds to step S305, and the target ignition timing is advanced by a predetermined angle Δθ. In this advance angle control, the engine operation region map after the start of the cooling improvement process is used. When the current engine operation state belongs to the TK operation region, the ignition timing is advanced to the limit of the trace knock ignition timing, and the MBT When belonging to the operation region, the ignition timing is advanced with the MBT ignition timing as a limit. When the engine operation state belongs to the MBT operation region, the angle may be further advanced than the MBT ignition timing.

  In step S306, it is determined whether or not the exhaust temperature Tex is lower than a fourth determination value T4 (for example, T4 <T3). If step S306 is NO, this routine is once ended. Then, the processes in steps S301 to S306 are repeatedly executed until the exhaust temperature Tex becomes lower than the fourth determination value T4. When step S306 becomes YES, the process proceeds to step S307, the fifth flag F5 is turned on, and the process is temporarily terminated. To do.

  When the exhaust temperature Tex becomes equal to or lower than the third determination value T3, step S301 is NO and the process proceeds to step S308. In step S308, it is determined whether or not the fifth flag F5 is ON. If F5 = ON, the process proceeds to step S309, and the fuel increase due to the OT increase correction is decreased. In step S310, it is determined whether the exhaust temperature Tex is lower than a fifth determination value T5 (for example, T5 <T4). If step S310 is YES, the process proceeds to step S311 to stop the OT increase correction, Cooling performance reduction processing and ignition retardation are performed. Further, the fourth flag F4 and the fifth flag F5 are turned off, and this routine is finished.

  Next, a specific aspect of the catalyst deterioration suppressing process of the present embodiment will be described using the time chart of FIG. In the figure, (a) shows the change in the accelerator opening, (b) shows the change in the exhaust temperature Tex, (c) shows the change in the coolant flow rate in the head side path 31B, and (d) shows the engine outlet. (E) shows the transition of the ignition timing, (f) shows the transition of the fuel increase amount by the fuel increase correction, (g) shows the transition of the fourth flag F4, (h) The transition of the fifth flag F5 is shown. In addition, the dashed-dotted line of (b) shows the case where a catalyst deterioration suppression process is not implemented, and a continuous line shows the case where a catalyst deterioration suppression process is implemented.

  In FIG. 9, when the accelerator pedal is depressed at the timing t31 and the exhaust temperature Tex of the engine 10 rises and exceeds the third determination value T3, the fuel increase correction is started at the timing t32 and the fourth flag F4 is turned on. The At the subsequent timing t33, the opening degree of the on-off valve 35 is changed to a larger side, and the cooling water flow rate in the head side path 31B is increased by ΔQ11 (cooling improvement process). When the engine outlet temperature becomes equal to or lower than the determination value TW3 with the increase in the coolant flow rate, the ignition is advanced by a predetermined angle Δθ at the timing t34. The cooling water flow rate is increased by ΔQ11 until the exhaust temperature Tex becomes lower than the fourth determination value T4, the ignition timing is advanced by Δθ, and when the exhaust temperature Tex eventually becomes equal to or lower than the fourth determination value T4, the timing is reached. At t35, the fifth flag F5 is turned on and the fuel increase amount is decreased. Thereby, the exhaust gas temperature Tex is maintained near the fourth determination value T4.

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

  Regarding the fuel increase, considering that the immediate effect of suppressing the catalyst deterioration is high, when the exhaust temperature exceeds the third determination value T3, the OT increase correction is performed, and the cooling improvement process is performed along with the OT increase correction. In addition, since the ignition advance is implemented, the effect of suppressing the deterioration of the catalyst 17 can be obtained quickly. Further, the fuel amount for OT increase correction can be reduced.

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

  In the above-described embodiment, the ignition advance is performed after it is determined that the cylinder temperature of the engine 10 has decreased after the start of the cooling improvement process. It is also possible to adopt a configuration in which the ignition advance is advanced before the determination of the decrease in the ignition.

  As the cooling improvement processing, the configuration including the means for increasing the cooling water flow rate of the head side path 31B is included, but the configuration including the means for increasing the cooling water flow rates of both the head side path 31B and the block side path 31A may be adopted. Good.

  The water jacket 31 is provided with two paths, a head side path 31B for cooling the cylinder head 14 of the engine 10 and a block side path 31A for cooling the cylinder block 18, but as shown in FIG. The path 131 may be used.

  As the cooling improvement process, the configuration in which the cooling water flow rate in the head side path 31B is increased and the cooling water flow rate to the radiator 41 is increased is exemplified. However, the cooling improvement processing is not limited thereto. It is good also as a structure which makes it an electric pump which can adjust flow volume, and increases the cooling water flow rate of the circulation paths 33 and 34 by controlling this electric pump. Or it is good also as a structure which operates a radiator fan.

  In the above embodiment, the opening / closing valve 35 is provided in the circulation path 34 and the cooling water flow rate in the head side path 31B is adjusted by controlling the opening degree of the opening / closing valve 35. However, the opening / closing valve 35 may not be provided. . In this case, the flow path cross-sectional areas of the circulation paths 33 and 34 may be different. Specifically, the flow path cross-sectional area of the circulation path 34 is made larger than that of the circulation path 33 (for example, 7: 3 or 8). : 2) The flow rate of the head side path 31B may be larger than that of the block side path 31A.

  In an engine equipped with a variable valve mechanism that can change the valve timing of at least one of the intake valve and the exhaust valve, the valve timing is changed together with the cooling improvement process as a process for suppressing catalyst deterioration due to exhaust heat. Thus, a process for increasing the internal EGR amount is performed, and then the ignition advance is performed. When the internal EGR amount is increased, the ignition timing can be further advanced by improving the knocking resistance, and as a result, the exhaust temperature can be further lowered. The internal EGR amount can be increased by, for example, opening the intake valve early or closing the exhaust valve late.

  As shown in FIG. 11, in an engine having an EGR passage 61 that connects the exhaust pipe 15 and the intake pipe of the engine 10 and recirculates a part of the exhaust gas to the intake system of the engine 10, to suppress catalyst deterioration due to exhaust heat. In addition to the cooling improvement process, the process of increasing the exhaust gas recirculation amount (external EGR amount) may be performed, and then the ignition advance may be performed. In this case, as the external EGR amount increases, the anti-knocking property is improved, whereby the ignition advance amount can be further increased. Further, for example, as shown in FIG. 11, the EGR passage 61 is provided with an EGR cooler 62 as a heat exchanger, and when the engine cooling performance is improved, the cooling performance of the EGR cooler 62 is improved to further increase the external EGR amount. It may be increased.

  In the configuration for improving the cooling performance of the cylinder head 14 of the engine 10, the engine intake system side is cooled more than the engine exhaust system side. By further cooling the intake side that is effective in suppressing knocking, the ignition advance amount can be increased, and the exhaust temperature can be further decreased.

  -As shown in FIG. 12, you may apply this invention to the structure by which the heater core 38 and the radiator 41 are arrange | positioned in the middle of the circulation path which connects the exit side of the engine 10, and an inlet side. In this case, in a state where the inflow of cooling water to the radiator 41 side is permitted by the thermostat 42, the engine cooling water that has passed through the engine 10 flows into the radiator 41 through the heater core 38.

  Exhaust cooling means for directly cooling the exhaust is provided, and the exhaust cooling means is used to cool the exhaust together with the cooling improvement process and the ignition advance angle. At this time, for example, as shown in FIG. 13, the engine coolant is circulated so that the engine exhaust system side is cooled rather than the engine intake system side. Specifically, as shown in FIGS. 13A and 13B, the engine coolant is circulated from the exhaust side to the intake side in the head side path 31B. Further, as shown in FIG. 13C, an intake side path 63A and an exhaust side path 63B are separately provided as head side paths, so that the coolant flow rate in the exhaust side path 63B is larger than that in the intake side path 63A. You may comprise a side path. Alternatively, as shown in FIG. 13D, a cooling passage 65 for directly cooling the exhaust pipe or the exhaust manifold with engine cooling water may be provided.

  DESCRIPTION OF SYMBOLS 10 ... Engine, 12 ... Injector, 13 ... Spark plug, 14 ... Cylinder head, 15 ... Exhaust pipe, 17 ... Catalyst (exhaust gas purification device), 18 ... Cylinder block, 30 ... Engine cooling system (cooling device), 31 ... Water Jacket, 31A ... Block side path (first cooling means), 31B ... Head side path (second cooling means), 33, 34, 37, 39 ... circulation path, 50 ... ECU (degradation judgment means, cooling control means, ignition) Advance angle means, decrease determination means, fuel increase means, temperature detection means).

Claims (9)

Applied to a system comprising an engine, an exhaust purification device provided in an exhaust passage of the engine, and a cooling device for cooling the engine;
Deterioration determining means for determining whether or not the exhaust temperature is in a predetermined high temperature range where there is a risk of deterioration of the exhaust purification device due to exhaust heat;
Cooling control means for performing a cooling improvement process for improving the engine cooling performance of the cooling device when the deterioration determining means determines that the exhaust temperature is in the predetermined high temperature range;
Ignition advance means for advancing the ignition timing of the engine after the start of the cooling improvement process by the cooling control means;
A deterioration suppression control device for an exhaust emission control device. A decrease determination means for determining that the cylinder temperature of the engine has decreased after the start of the cooling improvement process;
The deterioration suppression control device for an exhaust emission control device according to claim 1, wherein the ignition advance means advances the ignition timing after it is determined by the decrease determination means that the cylinder temperature has decreased. As the engine operating range, a maximum torque operating range that can be controlled at the maximum torque ignition timing that maximizes the torque is determined,
Means for determining whether or not the engine operating state after the start of the cooling improvement process is in the maximum torque operating region;
The ignition timing advance means advances the ignition timing with respect to the maximum torque ignition timing when the engine operating state after the start of the cooling improvement process is in the maximum torque operating region. Deterioration suppression control device for exhaust purification device.   The ignition advance means sets the ignition timing as the maximum torque ignition timing when the exhaust gas temperature is lower than a predetermined determination temperature set in the predetermined high temperature range, and sets the ignition timing when the exhaust temperature is higher than the predetermined determination temperature. The deterioration suppression control device for an exhaust emission control device according to claim 3, wherein the deterioration angle control device is advanced from the maximum torque ignition timing.   The deterioration suppression control device for an exhaust emission control device according to any one of claims 1 to 4, further comprising a fuel increase unit that increases the fuel in at least a part of the predetermined high temperature range. A temperature detecting means for detecting an exhaust temperature after the start of execution of the cooling improvement processing by the cooling control means and the ignition advance by the ignition advance means;
The fuel increasing means increases the fuel when the exhaust temperature detected by the temperature detecting means reaches a second temperature higher than a first temperature predetermined as a starting temperature of the cooling improvement process. Item 6. A deterioration suppression control device for an exhaust purification device according to Item 5.   6. When performing fuel increase by the fuel increase means, cooling improvement processing by the cooling control means and ignition advance by the ignition advance means are performed together with or after the fuel increase. Deterioration suppression control device for exhaust gas purification device. The cooling device includes first cooling means for cooling the cylinder block of the engine, and second cooling means for cooling the cylinder head,
The cooling control means improves the cooling performance of the cylinder head by the second cooling means when the exhaust gas temperature is judged to be in the predetermined high temperature range by the deterioration judgment means. The deterioration suppression control device for the exhaust emission control device according to Item. The cooling device has variable engine cooling performance,
The deterioration control device for an exhaust gas purification apparatus according to any one of claims 1 to 8, wherein the cooling control means cools the engine with a cooling performance corresponding to an exhaust gas temperature.

Images