JP5257087B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and in particular, an exhaust cooling structure including cooling means for cooling exhaust flowing into a catalyst with a refrigerant, and inflow control means capable of controlling the inflow of refrigerant to the cooling means. And an internal combustion engine control apparatus that controls an internal combustion engine in which automatic stop control and automatic restart control are performed.

  Conventionally, a technique for cooling exhaust gas flowing into a catalyst with a refrigerant is known. As such a technique, for example, a technique of cooling an exhaust manifold with cooling water of an internal combustion engine is disclosed in Patent Document 1. In addition, as a technique considered to be related to the present invention, a technique for changing the ratio of the cooling medium supplied to the cooling unit according to the engine operating state is disclosed in Patent Document 2. Specifically, this technique is a technique for changing the ratio of each cooling medium supplied to a plurality of cooling units.

JP-A-6-241044 JP 2007-132313 A

  By the way, the catalyst exhibits suitable purification performance when it is within the active temperature range. On the other hand, it is preferable to dispose the catalyst close to the internal combustion engine in order to activate the catalyst early. However, when the catalyst is arranged close to the internal combustion engine, the catalyst function is deteriorated such as deterioration of the catalyst due to overheating or deterioration of exhaust purification performance at the time of engine high load operation, and as a result, the exhaust emission may be deteriorated. is there. In this regard, it has been considered that the exhaust gas flowing into the catalyst is cooled by a refrigerant. According to this, it becomes possible to achieve both early activation of the catalyst by the close arrangement and prevention of deterioration of the function of the catalyst due to overheating.

  On the other hand, in recent years, hybrid vehicles and vehicles capable of performing eco-run control have been put into practical use in order to achieve high fuel efficiency. In these vehicles, high fuel efficiency can be realized by performing automatic stop control and automatic restart control of the internal combustion engine under predetermined conditions. Specifically, for example, automatic stop control is performed instead of idling when the vehicle is stopped, and automatic restart control is performed when the vehicle starts, thereby eliminating the consumption of fuel consumed by idling and realizing high fuel efficiency performance. . The technology for cooling the exhaust gas flowing into the catalyst with a refrigerant can also be applied to these vehicles.

  However, in these vehicles to which such technology is applied, when the automatic stop control of the internal combustion engine is performed, the amount of heat received by the refrigerant (for example, the amount of heat received from the exhaust or when the refrigerant is cooling water of the internal combustion engine). Further, since the amount of heat received from the internal combustion engine is reduced, the cooling performance of the refrigerant is enhanced. For this reason, in these vehicles, when exhaust gas is cooled with a refrigerant in accordance with the subsequent automatic restart control, the exhaust gas is significantly cooled, so that moisture contained in the exhaust gas may be condensed. The condensed moisture reaches the catalyst by scattering and delays the activation of the catalyst that is in an inactive state or the catalyst that has become inactive as a result of the loss of the exhaust flow during automatic stop control. There was a problem in that there was a risk of causing deterioration. The heater used for heating receives heat from the cooling water of the internal combustion engine that has received heat. When the cooling water of the internal combustion engine is used as a refrigerant, the cooling performance is enhanced by automatic stop control, and thus the heater performance is impaired. There was also a problem in that there was a possibility of being.

  Therefore, the present invention has been made in view of the above problems, and even when the automatic stop control of the internal combustion engine is performed, the moisture is prevented or suppressed from being condensed by cooling the exhaust with the refrigerant thereafter. An object of the present invention is to provide a control device for an internal combustion engine that can improve catalyst warm-up performance and heater performance.

  The present invention for solving the above-mentioned problems is an exhaust cooling structure comprising cooling means for cooling the exhaust flowing into the catalyst with a refrigerant, and an inflow control means capable of controlling the inflow of the refrigerant to the cooling means. And a control device for an internal combustion engine that controls an internal combustion engine for which automatic stop control is performed, the detection means detecting the temperature of the refrigerant flowing through the cooling means, and the temperature detected by the detection means A control means for controlling the inflow control means to prohibit the inflow of the refrigerant to the cooling means or to reduce the inflow amount of the refrigerant to the cooling means when the internal combustion engine is automatically And setting means for increasing the predetermined value when the stop control is performed.

  According to the present invention, even when the automatic stop control of the internal combustion engine is performed, the water is prevented or suppressed from being condensed by cooling the exhaust with the refrigerant, and the catalyst warm-up property and the heater performance are improved. Can be improved.

It is a figure which shows ECU1 typically with each structure concerned. It is a figure which shows typically the specific structure of ECU1. It is a figure which shows operation | movement of ECU1 with a flowchart. It is a figure which shows operation | movement of ECU1 when the automatic stop control of the internal combustion engine 50 is started by a flowchart.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram schematically showing an internal combustion engine control device according to the present embodiment realized by an ECU (Electronic Control Unit) 1 together with related components such as an internal combustion engine 50. The internal combustion engine 50 is provided with an exhaust system 10 and a cooling system 20. The exhaust system 10 includes a water-cooled exhaust manifold 11, a catalyst 12, and an exhaust pipe 13. The water-cooled exhaust manifold 11 joins the exhaust discharged from each cylinder of the internal combustion engine 50. Exhaust gas flowing through the water-cooled exhaust manifold 11 flows into the catalyst 12 through the exhaust pipe 13.

The cooling system 20 includes a water pump 21, a first valve 22, a second valve 23, a heater 24, a reserve tank 25, a radiator 26, a thermostat 27, and a bypass pipe 28. An internal combustion engine 50 and a water-cooled exhaust manifold 11 are incorporated in the cooling system 20. The water pump 21 is an electric water pump and pumps cooling water. Cooling water discharged from the water pump 21 flows through a water jacket (not shown) provided in the internal combustion engine 50 and is discharged from the internal combustion engine 50.

  Cooling water discharged from the internal combustion engine 50 flows into the water-cooled exhaust manifold 11 via the first valve 22. In the present embodiment, the first valve 22 specifically adjusts the inflow ratio between the amount of cooling water flowing into the water-cooled exhaust manifold 11 and the amount of cooling water flowing into the bypass pipe 28 under the control of the ECU 1. Thus, the flow rate adjusting valve can control the inflow of the cooling water to the water-cooled exhaust manifold 11. The water-cooled exhaust manifold 11 has a structure for circulating a refrigerant around each of the plurality of exhaust pipes 111, and the cooling water that has flowed into the water-cooled exhaust manifold 11 flows into the catalyst 12 by cooling each of the plurality of exhaust pipes 111. Cool the exhaust. In this embodiment, the cooling water of the internal combustion engine 50 corresponds to the refrigerant, the water-cooled exhaust manifold 11 corresponds to the cooling means, and the first valve 22 corresponds to the inflow control means. In this embodiment, the water-cooled exhaust manifold 11 and the first valve 22 are provided in the internal combustion engine 50 as an exhaust cooling structure.

  The cooling water discharged from the water-cooled exhaust manifold 11 reaches the second valve 23. The second valve 23 is a switching valve capable of switching the coolant flow path under the control of the ECU 1. Specifically, the second valve 23 is provided so that the flow path can be switched between a flow path through which cooling water flows through the heater 24 for heating and a flow path through which cooling water does not flow through the heater 24. The flow path through which the cooling water flows to the heater 24 is connected to the flow path where the cooling water does not flow to the heater 24 on the downstream side of the heater 24. After the merging, these distribution paths are further branched into a distribution path for circulating cooling water to the water pump 11, a distribution path for circulating cooling water to the reserve tank 25, and a distribution path for circulating cooling water to the radiator 26, respectively. ing. Cooling water flowing through the reserve tank 25 and the radiator 26 is guided to the water pump 11 via the thermostat 27. The water-cooled exhaust manifold 11 is provided with a water temperature sensor 71, and the catalyst 12 is provided with an exhaust temperature sensor 72.

  FIG. 2 is a diagram schematically showing a specific configuration of the ECU 1. The ECU 1 includes a microcomputer including a CPU 2, a ROM 3, a RAM 4, and the like, and input / output circuits 5 and 6. The CPU 2, ROM 3, RAM 4, and input / output circuits 5 and 6 are connected to each other via a bus 7. The ECU 1 is mainly configured to control the internal combustion engine 50. Specifically, the ECU 1 is configured to control a fuel injection valve of the internal combustion engine 50 (not shown), for example. In addition, the ECU 1 is configured to control the first and second valves 22 and 23. The first and second valves 22 and 23 are electrically connected to the ECU 1 as control targets.

  Various sensors such as a water temperature sensor 71, an exhaust temperature sensor 72, a crank angle sensor 73, and an air flow meter 74 are electrically connected to the ECU 1. The temperature THW of the cooling water flowing through the water-cooled exhaust manifold 11 is based on the output of the water temperature sensor 71, the temperature of the exhaust gas flowing through the catalyst 12 is based on the output of the exhaust temperature sensor 72, and the rotational speed NE of the internal combustion engine 50 is the crank angle sensor 73. The intake air amount GA of the internal combustion engine 50 is detected by the ECU 1 based on the output of the air flow meter 74.

  The ROM 3 is configured to store programs, map data, and the like in which various processes executed by the CPU 2 are described. When the CPU 2 executes processing while using the temporary storage area of the RAM 4 as necessary based on the program stored in the ROM 3, the ECU 1 has various control means, determination means, detection means, calculation means, and the like. To be realized. In this regard, the ECU 1 functionally realizes an eco-run control means for automatically stopping and automatically restarting the internal combustion engine 50 under predetermined conditions, for example. The automatic stop control is performed when the vehicle is stopped, for example, and the automatic restart control is performed when the vehicle is started, for example. It should be noted that whether or not the vehicle is stopped or whether or not the vehicle is starting may be determined by a known technique, and therefore detailed description thereof is omitted here.

  Further, the ECU 1 detects, for example, the temperature of the cooling water flowing through the water-cooled exhaust manifold 11 (water temperature THW), and the cooling water to the water-cooled exhaust manifold 11 when the water temperature THW detected by the detection means is less than a predetermined value L. The control means for controlling the first valve 22 to reduce the inflow amount of the engine and the setting means for increasing the predetermined value L when the internal combustion engine 50 is controlled to be automatically stopped are functionally realized. Further, in the ECU 1, for example, a control unit that controls the second valve 23 is functionally realized. For example, when the water temperature THW is lower than the predetermined value L, the control means for controlling the second valve 23 switches the second valve 23 so as to switch the flow path of the cooling water to the flow path that does not flow the cooling water to the heater 24. It is realized to control.

  The control means for controlling the first valve 22 described above further controls the first valve 22 so that the cooling water does not flow through the water-cooled exhaust manifold 11 when the water temperature THW is less than a predetermined value L, for example, The amount of cooling water to the water-cooled exhaust manifold 11 is adjusted according to the bed temperature of 12, and the first valve 22 is controlled so that the bed temperature of the catalyst 12 becomes the target value N, or the water-cooled exhaust manifold 11 of the water-cooled exhaust manifold 11 is controlled according to the water temperature THW. The first valve 22 is controlled by adjusting the amount of cooling water so that the water temperature THW falls within a predetermined range.

  Next, the operation of the ECU 1 will be described using the flowchart shown in FIG. This flowchart is started when the internal combustion engine 50 is started, and is repeatedly executed at very short intervals during the operation of the internal combustion engine 50. The ECU 1 determines whether or not the water temperature THW is less than the lower limit value (step S11). In this embodiment, the lower limit value is a predetermined value L, and the lower limit value can be set to 60 ° C., for example. If an affirmative determination is made in step S11, the ECU 1 controls the second valve 23 in step S12 to switch the cooling water flow path to a flow path that does not flow the cooling water to the heater 24 (the heater 24 of the second valve 23). Side closed). Thereby, since it is possible to prevent the cooling water from radiating heat with the heater 24, the warm-up property of the cooling water can be improved.

  In step S13 following step S12, the ECU 1 controls the first valve 22 to decrease the inflow amount of the cooling water to the water-cooled exhaust manifold 11 by a predetermined degree (reduction of the first valve 22 on the water-cooled exhaust manifold 11 side). After step S13, this flowchart is temporarily terminated. Thereafter, when the water temperature THW is lower than the lower limit value, the processes shown in steps S11 to S13 are repeatedly executed every time the flowchart is restarted. As a result, the first valve 22 is controlled so as to reduce the amount of cooling water flowing into the water-cooled exhaust manifold 11 when cold, and further to prohibit the inflow of cooling water into the water-cooled exhaust manifold 11. . As a result, the cooling water can be prevented from receiving heat from the exhaust with the water-cooled exhaust manifold 11, so that the exhaust temperature can be increased and the warm-up performance of the catalyst 12 can be improved.

  On the other hand, if the water temperature THW is equal to or higher than the lower limit value, a negative determination is made in step S11 when this flowchart is restarted. At this time, the ECU 1 controls the second valve 23 in step S14, and switches the flow path of the cooling water to the flow path for flowing the cooling water to the heater 24 (opening the heater 24 side of the second valve 23). Thereby, the heater 24 can receive heat from the cooling water. Subsequently, the ECU 1 determines whether or not the water temperature THW is higher than the upper limit value (step S15). If the determination is affirmative, the ECU 1 controls the first valve 22 in step S16 to increase the amount of cooling water flowing into the water-cooled exhaust manifold 11 by a predetermined degree (increase in the water-cooled exhaust manifold 11 side of the first valve 22). . After step S16, this flowchart is temporarily terminated.

  Thereafter, when the water temperature THW is higher than the upper limit value, the processes shown in steps S11 and S14 to S16 are repeatedly executed every time the flowchart is restarted. Thus, the first valve 22 is controlled so as to increase the amount of cooling water flowing into the water-cooled exhaust manifold 11 and further to prohibit the cooling water from flowing into the bypass pipe 28. That is, in the process shown in step S13 following the affirmative determination in step S11 and the process shown in step S16 following the negative determination in step S11, the first valve 22 changes the cooling water amount of the water-cooled exhaust manifold 11 according to the water temperature THW. The water temperature THW is adjusted so as to be within a predetermined range. Thereby, generation | occurrence | production of the condensed water by cooling of exhaust can be prevented or suppressed, and the improvement of the performance of the heater 24 and catalyst warm-up property can be aimed at. Thereby, overheating of the catalyst 12 due to insufficient cooling of the exhaust gas can be prevented or suppressed, and as a result, deterioration of the function of the catalyst 12 and deterioration of exhaust emission can be prevented or suppressed.

  Thereafter, if the water temperature THW becomes equal to or lower than the upper limit value when the present flowchart is resumed, a negative determination is made in step S15. At this time, the ECU 1 determines whether or not the bed temperature of the catalyst 12 is lower than the target value (step S17). The bed temperature of the catalyst 12 can be detected, for example, based on the output of a temperature sensor that directly detects the bed temperature of the catalyst 12. However, the detection is not limited to this, and the detection may be performed by estimating the bed temperature of the catalyst 12 based on various parameters such as the exhaust gas temperature. The target value can be set to 400 ° C., for example. However, the present invention is not limited to this, and the target value may be set as a range having a predetermined width, for example.

  If it is affirmation determination by step S17, it will progress to step S13. As a result, exhaust cooling is prevented or suppressed, so that warm-up of the catalyst 12 can be promoted, and as a result, deterioration of exhaust emission can be prevented or suppressed. On the other hand, if a negative determination is made in step S17, the ECU 1 determines whether or not the bed temperature of the catalyst 12 is higher than the target value (step S18). If the determination is negative, it is determined that the bed temperature of the catalyst 12 is the target value. In this case, this flowchart is temporarily terminated. On the other hand, if a positive determination is made in step S18, the process proceeds to step S16. Thereby, since cooling of exhaust gas is promoted, the bed temperature of the catalyst 12 can be lowered, and as a result, deterioration of exhaust emission can be prevented or suppressed.

  Instead of controlling the first valve 22 to control the first valve 22 so that the cooling water does not flow through the water-cooled exhaust manifold 11 when the water temperature THW is lower than the predetermined value L, the control means for controlling the first valve 22 is used. The first valve 22 is controlled so as to improve the performance of the heater 24 by adjusting the amount of cooling water to the water-cooled exhaust manifold 11 according to the operating state (here, the rotational speed NE and the intake air amount GA) and the water temperature THW. It can also be realized. Controlling in this way, for example, without providing the second valve 23 and the bypass pipe 28, the first valve 22 is a flow rate adjustment valve capable of adjusting the amount of cooling water flowing into the water-cooled exhaust manifold 11, This is particularly effective when the cooling path is configured so that cooling water flows from the water-cooled exhaust manifold 11 into the heater 24.

  Here, when the operating state of the internal combustion engine 50 (here, the rotational speed NE and the intake air amount GA) is constant and the flow rate of the cooling water is constant, the increase width ΔT of the water temperature THW is substantially constant. In this regard, the conventional setting of the flow rate of the cooling water assumes that the water temperature THW is high, for example, so that the increase width ΔT does not cause the cooling water to boil according to the operating state of the internal combustion engine 50. Has been done. However, in this setting, for example, when the increase width ΔT is 10 ° C. in a certain operation state, the increase width ΔT is 10 ° C. in the same operation state even when the water temperature THW is low. Specifically, for example, when the water temperature THW is 25 ° C., the water temperature THW is suppressed to 35 ° C. That is, in such a setting, when the water temperature THW is low, the amount of heat received by the heater 24 is limited to be low.

  On the other hand, when the control means for controlling the first valve 22 is configured as described above, in step S13, the ECU 1 determines the water-cooled exhaust manifold 11 according to the rotational speed NE, the intake air amount GA, and the water temperature THW. The first valve 22 is controlled so as to improve the performance of the heater 24 by adjusting the amount of cooling water to the heater. In this case, the ECU 1 specifically sets the map data in which the inflow amount of the cooling water to the water-cooled exhaust manifold 11 is set in advance according to the rotational speed NE, the intake air amount GA, and the water temperature THW based on the result of the bench test. The first valve 22 is controlled with reference to FIG. Thereby, since the amount of heat received by the heater 24 can be increased, the performance of the heater 24 can be improved. The map data described above can be stored in the ROM in advance. In this case, the processes shown in steps S12 and S14 may be omitted.

  Next, the operation of the ECU 1 when the automatic stop control of the internal combustion engine 50 is started will be described using the flowchart shown in FIG. This flowchart is started when the internal combustion engine 50 is started, and is repeatedly executed at very short intervals during the operation of the internal combustion engine 50. The ECU 1 determines whether or not automatic stop control has been started (step S21). Whether or not the automatic stop control is started can be determined, for example, by determining whether or not a predetermined condition for executing the automatic stop control is satisfied. If a negative determination is made in step S21, this flowchart is temporarily ended. On the other hand, if an affirmative determination is made in step S21, the ECU 1 executes a process of increasing the predetermined value L (step S22). In this step, for example, the predetermined value L, which was 60 ° C., can be changed to 70 ° C.

  Thereby, the lower limit value of step S11 in the flowchart shown in FIG. 3 is increased. As a result, even if the cooling performance of the cooling water increases due to the decrease in the amount of heat received, the amount of cooling water flowing into the water-cooled exhaust manifold 11 remains until the water temperature THW reaches 70 ° C. Further, since the inflow of the cooling water to the water-cooled exhaust manifold 11 is prohibited, the cooling of the exhaust gas by the cooling water having improved cooling performance is prevented or suppressed. For this reason, it is possible to prevent or suppress the condensation of moisture contained in the exhaust gas, and even if moisture is condensed, it is possible to easily evaporate the condensed moisture by increasing the predetermined value L. it can.

For this reason, the condensed water reaches the catalyst 12 due to scattering, and the catalyst 12 which is in an inactive state or the catalyst 12 which has become inactive as a result of the exhaust gas being circulated during the automatic stop control is activated. Can be prevented or suppressed. Further, the exhaust temperature can be increased by increasing the predetermined value L. That is, the catalyst warm-up property can be improved by these. In addition, it is possible to prevent the cooling water having an improved cooling performance from flowing into the heater 24 and to increase the warm-up property of the cooling water by increasing the predetermined value L, so that the heater performance can be improved. .
As described above, even when the automatic stop control of the internal combustion engine 50 is performed, the ECU 1 prevents or suppresses the condensation of moisture due to the cooling of the exhaust gas by the cooling water, and also warms up the catalyst and the heater performance. Can be improved.

The embodiment described above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention.
For example, in the above-described embodiment, the case where the internal combustion engine 50 on which the eco-run control is performed is an internal combustion engine, but the internal combustion engine may be an internal combustion engine mounted on a hybrid vehicle, for example.

  Further, for example, in the above-described embodiment, the case where the water-cooled exhaust manifold 11 is the cooling means has been described in detail. However, the specific configuration of the cooling exhaust manifold 11 is not necessarily limited to this, and all or a part of the exhaust manifold is cooled by the refrigerant. Other suitable configurations that can be used. The cooling means may be, for example, a flow path forming portion that forms a flow path for circulating a coolant such as cooling water around the exhaust port of the internal combustion engine.

Further, for example, in the above-described embodiment, the case where the first valve 22 that is a flow rate adjusting valve is the inflow control means has been described in detail. However, the inflow control means is not necessarily limited to this, and the inflow of the refrigerant to the cooling means is controlled. In this case, it may be realized by a shut-off valve that permits or blocks the inflow of the refrigerant. Further, the inflow control means may be , for example, an electric pump provided exclusively for the cooling means.

  The detection means, the control means, and the setting means are rationally realized mainly by the ECU 1 that controls the internal combustion engine 50. For example, other electronic control devices, hardware such as dedicated electronic circuits, and combinations thereof It may be realized by. In this regard, the control device for an internal combustion engine of the present invention may be realized by, for example, a plurality of electronic control devices, hardware such as electronic circuits, or a combination of electronic control devices and hardware such as electronic circuits. Similarly, various means functionally realized by the control device for an internal combustion engine of the present invention include a plurality of electronic control devices, hardware such as electronic circuits, and a combination of electronic control devices and hardware such as electronic circuits. It may be realized with.

1 ECU
DESCRIPTION OF SYMBOLS 10 Exhaust system 11 Water-cooled exhaust manifold 12 Catalyst 13 Exhaust pipe 20 Cooling system 21 Water pump 22 1st valve 23 2nd valve 24 Heater 25 Reserve tank 26 Radiator 27 Thermostat 28 Bypass pipe 50 Internal combustion engine 71 Water temperature sensor 72 Exhaust temperature sensor 73 Crank angle sensor 74 Air flow meter

Claims (1)

An exhaust cooling structure is provided that includes a cooling unit that cools the exhaust gas flowing into the catalyst with a refrigerant, and an inflow control unit that can control the inflow of the refrigerant into the cooling unit. A control device for an internal combustion engine that controls an internal combustion engine for which start control is performed,
Detecting means for detecting the temperature of the refrigerant flowing through the cooling means;
Control for controlling the inflow control means so as to prohibit the inflow of the refrigerant into the cooling means or reduce the inflow amount of the refrigerant into the cooling means when the temperature detected by the detecting means is less than a predetermined value. Means,
A control device for an internal combustion engine, comprising: setting means for increasing the predetermined value when the internal combustion engine is controlled to be automatically stopped.

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