JP2017198119A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel constitution which can efficiently transmit heat to an internal passage from exhaust emission when introducing the exhaust emission into the internal passage of a cylinder block at a cold start of an internal combustion engine.SOLUTION: In start-time valve-opening control, the value-opening timing of a control valve 22 and a valve-closing period are controlled in order to move heat which is discharged accompanied by the condensation of vapor in exhaust emission flowing in an internal passage 20 to a wall face of the internal passage 20. Concretely, the control valve 22 is opened at timing at which a temperature of exhaust emission flowing in an exhaust passage 14 at an upstream side rather than a branch passage 16 is determined to be higher than a cooling temperature of an internal combustion engine 10. Then, while it is determined that a temperature Tof exhaust emission flowing in a branch passage 18 goes below a dew point after the control valve 22 is opened, the control valve 22 is continued to be opened, and at timing at which the temperature Texceeds the dew point, the control valve 22 is closed.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an internal combustion engine control apparatus, and more particularly to an internal combustion engine control apparatus that controls an internal combustion engine that includes a cylinder block configured to be able to introduce exhaust gas.

  Japanese Patent Laid-Open No. 2004-108256 discloses an internal combustion engine configured to introduce a part of exhaust gas flowing through an exhaust passage of the internal combustion engine into an internal passage formed in a cylinder block of the internal combustion engine when the internal combustion engine is cold-started. An engine control device is disclosed. If a part of the exhaust gas is introduced into the internal passage formed in the cylinder block during the cold start of the internal combustion engine, warming up of the internal combustion engine can be promoted, and friction between the piston and the cylinder wall of the internal combustion engine can be reduced. This can also improve fuel efficiency.

JP 2004-108256 A JP 2001-152960 A

  By the way, the introduction of the exhaust into the internal passage described above is intended to transfer heat to the constituent member by exhaust gas having a temperature higher than that of the constituent member (for example, the cylinder wall) of the cylinder block, and the exhaust introduced into the internal passage. As the flow rate increases, the amount of heat transfer to the constituent member can be increased. However, heat transfer from the exhaust to the internal passage is basically inefficient. In addition, when the internal combustion engine is cold started, it is difficult to obtain high-temperature exhaust in the first place, and the exhaust flow rate is not so high. Therefore, when exhaust gas is introduced into the internal passage of the cylinder block at the time of cold start of the internal combustion engine, it can be said that improvement for realizing efficient heat transfer from the exhaust gas to the internal passage is necessary.

  The present invention has been made in view of the above-described problems, and an object thereof is to efficiently transfer heat from the exhaust to the internal passage when the exhaust is introduced into the internal passage of the cylinder block during a cold start of the internal combustion engine. It is to provide a new configuration that can be performed automatically.

  An internal combustion engine control apparatus according to the present invention includes an internal passage formed in a cylinder block of an internal combustion engine and connected to a first branch passage branched from an exhaust passage of the internal combustion engine, and a downstream side of the first branch passage. A second branch passage branched from the exhaust passage and connected to the internal passage, and a control valve provided in the first branch passage for controlling an inflow of exhaust gas from the first branch passage to the internal passage; And a temperature sensor that is provided in the second branch passage and detects a temperature of exhaust gas flowing through the second branch passage, and is configured to control the internal combustion engine at the time of starting the internal combustion engine, The temperature of the exhaust gas flowing through the exhaust passage upstream of the connecting portion with the first branch passage is higher than the wall surface temperature of the internal passage, and the temperature of the exhaust gas flowing through the second branch passage is the second portion. If below the temperature at which water vapor in the exhaust gas flowing through the passage begins to condense, characterized in that it is composed of the first branch passage to allow the flow of exhaust gas into the internal passage.

  In the control apparatus for an internal combustion engine according to the present invention, when the internal combustion engine is started, the temperature of the exhaust gas immediately after being discharged from the internal combustion engine is higher than the wall surface temperature of the internal passage, and the temperature of the exhaust gas flowing through the second branch passage Is lower than the temperature at which water vapor in the exhaust gas flowing through the second branch passage begins to condense, the inflow of exhaust gas from the first branch passage to the internal passage is permitted. If the temperature of the exhaust gas immediately after being discharged from the internal combustion engine is higher than the wall surface temperature of the internal passage, the wall surface of the internal passage can be warmed by flowing the exhaust gas from the first branch passage into the internal passage. Further, the fact that the temperature of the exhaust gas flowing through the second branch passage is lower than the temperature at which the water vapor in the exhaust gas flowing through the second branch passage begins to condense means that when flowing through the internal passage on the upstream side of the second branch passage, It means that the water vapor in the exhaust is condensed as a result of being cooled by the exhaust coming into contact with the wall surface of the internal passage. Therefore, according to the control apparatus for an internal combustion engine according to the present invention, the heat released along with the condensation of the water vapor in the exhaust flowing through the internal passage can be moved to the wall surface of the internal passage. Even at times, the wall surface of the internal passage can be efficiently heated.

It is a figure explaining the system configuration concerning each embodiment of the present invention. The relationship between the amount of heat transferred from the exhaust to the engine wall when two types of exhaust with different water vapor contents are brought into contact with the engine wall and the temperature of the two types of exhaust after contact with the engine wall is shown. FIG. It is a flowchart which shows an example of the process which ECU30 performs in Embodiment 1 of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
First, Embodiment 1 of the present invention will be described with reference to FIGS.

[Description of system configuration]
FIG. 1 is a diagram illustrating a system configuration according to Embodiment 1 of the present invention. The system shown in FIG. 1 includes an internal combustion engine 10. The internal combustion engine 10 is, for example, an in-line four-cylinder gasoline engine mounted on a vehicle, and an intake passage 12 through which gas (intake) sucked into the internal combustion engine 10 flows and exhaust through which gas (exhaust) discharged from the internal combustion engine 10 flows. And a passage 14. The exhaust passage 14 is branched at two points along the way, a branch passage (first branch passage) 16 is located upstream in the exhaust flow direction, and a branch passage (second branch passage) 18 is located downstream in the same direction. Is located. The branch passages 16 and 18 are connected via an internal passage 20 formed inside the internal combustion engine 10 (more precisely, inside the cylinder block of the internal combustion engine 10). The branch passage 16 is provided with a control valve 22 capable of adjusting the flow rate of the exhaust gas flowing from the branch passage 16 into the internal passage 20. The branch passage 18 is provided with a temperature sensor 24 that detects the temperature T _EX of the exhaust gas flowing through the branch passage 18.

  The system shown in FIG. 1 includes an ECU (Electronic Control Unit) 30 as a control device. The ECU 30 includes, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), and a CPU (Central Processing Unit). The ECU 30 captures and processes signals from various sensors mounted on the vehicle. The various sensors include at least the temperature sensor 24 described above. ECU30 processes the signal of each taken-in sensor, and operates various actuators according to a predetermined control program. The actuator operated by the ECU 30 includes at least the control valve 22 described above.

[Control at start-up by ECU 30]
In the present embodiment, as control during cold start of the internal combustion engine 10 by the ECU 30 shown in FIG. 1, control for opening the control valve 22 (hereinafter also referred to as “start-up valve opening control”) is performed. The arrow shown on the exhaust side of the internal combustion engine 10 shown in FIG. 1 represents the flow of exhaust that occurs when the control valve 22 is opened. As can be seen from this arrow, when the control valve 22 is opened, a part of the exhaust gas from the internal combustion engine 10 is introduced into the branch passage 16, flows from here to the internal passage 20 and the branch passage 18 in this order, and returns to the exhaust passage 14. When the exhaust gas flows through the internal passage 20, if the temperature of the exhaust gas is higher than the temperature of the wall surface of the internal passage 20, heat moves from the exhaust gas to the wall surface. Thereby, the wall surface of the internal passage 20 is warmed, and the cooling water and oil of the internal combustion engine 10 are warmed.

In the start valve opening control, the valve opening timing and the valve opening period of the control valve 22 are controlled so that the heat released along with the condensation of water vapor in the exhaust gas flowing through the internal passage 20 is moved to the wall surface of the internal passage 20. Is done. Specifically, the control valve 22 starts to open at the timing when it is determined that the temperature of the exhaust gas flowing through the exhaust passage 14 upstream of the branch passage 16 is higher than the cooling water temperature of the internal combustion engine 10. Further, after the control valve 22 is opened, the control for opening the control valve 22 to the open side is continued while it is determined that the temperature T _{EX of the} exhaust gas flowing through the branch passage 18 is below the dew point. To increase the amount of heat transferred. Further, the control valve 22 is controlled to the closed side at the timing when it is determined that the temperature T _EX has exceeded the dew point, and the exhaust flow rate is reduced. As a result, the exhaust side can be easily cooled and control can be performed in a state where the temperature T _EX is slightly lower than the dew point. Therefore, the heat of condensation of water vapor can be effectively applied to the wall surface of the internal passage 20 until the control valve 22 is completely closed. Can do. The dew point here means a temperature at which water vapor in the exhaust gas flowing through the branch passage 18 begins to condense.

The temperature of the exhaust gas immediately after being discharged from the internal combustion engine 10, that is, the temperature of the exhaust gas flowing through the exhaust gas passage 14 upstream of the connecting portion with the branch passage 16 is higher than the boiling point of water (about 100 ° C.). The water vapor in the exhaust gas hardly condenses during this flow. When the control valve 22 is opened, as described above, a part of the exhaust from the internal combustion engine 10 is introduced into the branch passage 16 and flows from the internal passage 20 to the branch passage 18 in this order. Therefore, the fact that the temperature T _{EX of the} exhaust gas flowing through the branch passage 18 is below the dew point means that the exhaust gas contacts the wall surface of the internal passage 20 when it flows through the internal passage 20 upstream of the branch passage 18. As a result of being cooled, it means that water vapor in the exhaust is condensed.

Here, when the calorific values of the two types of exhaust having different water vapor contents are compared, the calorific value of the exhaust having a relatively large water vapor content is higher by the latent heat difference of the water vapor. FIG. 2 shows the amount of heat transferred from the exhaust to the engine wall when two types of exhaust having different water vapor contents are brought into contact with the engine wall (specifically, the wall surface of the internal passage 20), and the contact with the engine wall. It is the figure which showed the relationship with the temperature (specifically temperature _TEX ) of the said 2 types of exhaust_gas | exhaustion later. However, the relationship in this figure is based on the premise that the exhaust with only the water vapor content changed is brought into contact with the engine wall. That is, the flow rate of the exhaust to be brought into contact with the engine wall and the temperature of the engine wall before the exhaust contact are set to the same condition.

  As can be seen by comparing the exhaust gas (dry gas) indicated by the solid line in FIG. 2 with the exhaust gas (wet gas) indicated by the broken line, in the temperature range lower than the moisture condensation temperature (about 100 ° C.) of the exhaust gas, The amount of heat that travels increases. The fact that the temperature of the exhaust gas after contact with the engine wall is lower than the moisture condensation temperature means that the exhaust gas is cooled until the water vapor in the exhaust gas is condensed due to the contact with the engine wall. In the temperature range lower than the moisture condensation temperature, the amount of heat that moves from the exhaust to the engine wall is reduced by the amount of heat that moves when the exhaust contacts the engine wall (exhaust gas-engine wall heat transfer heat amount) and the condensation of water vapor. It becomes equal to the sum of the amount of heat released (condensation transfer heat amount of moisture in the exhaust gas).

  Therefore, according to the valve opening control at the time of starting to move the heat released along with the condensation of the water vapor in the exhaust gas flowing through the internal passage 20 to the wall surface of the internal passage 20, it is difficult to obtain high-temperature exhaust gas. Even during the cold start of the internal combustion engine 10 where the flow rate is not so high, the wall surface of the internal passage 20 can be efficiently warmed and the cooling water and oil of the internal combustion engine 10 can be warmed. Therefore, further reduction of friction between the piston and the cylinder wall of the internal combustion engine 10 and improvement of fuel consumption can be realized.

[Specific processing]
FIG. 3 is a flowchart showing an example of processing executed by the ECU 30 in the first embodiment of the present invention. Note that the routine shown in FIG. 3 is repeatedly executed immediately after the internal combustion engine 10 is started.

  In the routine shown in FIG. 3, first, it is determined whether or not the temperature of the heated portion is lower than the temperature of the exhaust gas from the internal combustion engine 10 (step S10). In this step, the ECU 30 estimates the temperature of the heated part (that is, the wall surface of the internal passage 20) using the detected value of the temperature sensor provided at the outlet of the water jacket of the internal combustion engine 10, for example, and estimates the heated object. By comparing the temperature of the part with the detection value of the temperature sensor provided in the exhaust manifold of the internal combustion engine 10, the magnitude relationship between the two is determined. As a result of the determination, when it is determined that the temperature of the heated portion is lower than the temperature of the exhaust (in the case of “YES”), the ECU 30 controls the control valve 22 to open (step S12). On the other hand, if it is determined that this is not the case (in the case of “NO”), it can be determined that heat does not move from the exhaust to the heated portion even if the control valve 22 is opened. To control.

Subsequent to step S12, the ECU 30 determines whether or not the temperature of the exhaust gas after contacting the heated part exceeds the moisture condensation temperature (step S14). In this step, the ECU 30 determines the magnitude relationship between the detected value of the temperature sensor 24 (that is, the temperature T _EX ) and the dew point of the exhaust gas flowing through the branch passage 18 calculated separately. As a result of the determination, when it is determined that the temperature of the exhaust gas after contacting the heated portion exceeds the moisture condensation temperature (in the case of “YES”), the temperature of the wall surface of the internal passage 20 has increased to some extent, Since it can be determined that the water vapor in the exhaust gas flowing through the passage 20 cannot be condensed, the ECU 30 proceeds to step S16 and controls the control valve 22 to the closed side. On the other hand, if it is determined that this is not the case (“NO”), the ECU 30 returns to step S10.

  Following step S16, the ECU 30 determines whether or not the control valve 22 is completely closed (step S18). When it is determined that the control valve 22 is completely closed (in the case of “YES”), the processing by the ECU 30 routine is terminated. On the other hand, if it is determined that this is not the case (“NO”), the ECU 30 returns to step S10.

As described above, according to the routine shown in FIG. 3, when it is determined that the temperature of the heated portion is lower than the temperature of the exhaust, the control valve 22 can be controlled to open. Therefore, since the heat released along with the condensation of water vapor in the exhaust gas flowing through the internal passage 20 can be moved to the wall surface of the internal passage 20, the wall surface of the internal passage 20 can be used even when the internal combustion engine 10 is cold started. It is possible to warm the cooling water and oil of the internal combustion engine 10 efficiently.
Further, according to the routine shown in FIG. 3, when it is determined in step S10 that the temperature of the heated portion exceeds the temperature of the exhaust (in the case of “NO”), the routine proceeds to step S16 and the control valve 22 is closed. Can be controlled. When it is determined in step S10 that the temperature of the heated portion exceeds the temperature of the exhaust, the control valve 22 is controlled to the closed side so that the exhaust side is easily cooled and the temperature T _EX is slightly lower than the dew point. Therefore, the heat of condensation of the water vapor can be effectively applied to the wall surface of the internal passage 20 until the control valve 22 is completely closed. Further, when it is determined in step S10 that the temperature of the heated portion exceeds the temperature of the exhaust, the control valve 22 is controlled to be closed so that the internal combustion engine 10 is restarted after being temporarily stopped. When the temperature of the heated part is higher than the temperature of the exhaust, it is possible to prevent a situation in which the temperature of the heated part is lowered due to low-temperature exhaust and the fuel consumption is deteriorated.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described.
The system according to the present embodiment is based on the configuration described with reference to FIG.

  In the present embodiment, when the valve opening control at the time of starting is being performed, the internal passage 20 is moved to the internal passage 20 based on the operating state of the internal combustion engine 10 (for example, the engine speed and the engine load) and the opening of the control valve 22. The accumulated amount of condensed water generated is estimated in the ECU 30. If the estimated accumulated amount is equal to or greater than the set value, it is confirmed that the exhaust gas temperature and flow rate after the warm-up of the internal combustion engine 10 and immediately after being discharged from the internal combustion engine 10 is equal to or greater than the set value. As a condition, the ECU 30 performs control for temporarily opening the control valve 22 (warm-up water removal control). The temperature of the exhaust gas immediately after being discharged from the internal combustion engine 10 can be obtained from, for example, a detection value of a temperature sensor provided at the outlet of the water jacket of the internal combustion engine 10. The flow rate of the exhaust gas immediately after being discharged from the internal combustion engine 10 can be estimated from, for example, an air flow meter provided at the inlet of the intake passage 12.

  If the start valve opening control described in the first embodiment is performed, condensed water is generated in the internal passage 20. Therefore, if the condensed water generated in the internal passage 20 continues to accumulate, the internal passage 20 may be clogged. Moreover, since acidic components are contained in the exhaust gas, if the condensed water stays in the internal passage 20 for a long time, the condensed water may be acidified to corrode the wall surface of the internal passage 20. In this regard, if the water removal control after warm-up is performed when the temperature and flow rate of the exhaust gas immediately after being discharged from the internal combustion engine 10 are equal to or higher than the set values, the high-temperature exhaust gas introduced into the internal passage 20 causes The accumulated condensed water can be discharged to the branch passage 18 side or evaporated. Therefore, the occurrence of the above-described problems can be suppressed.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described.
The system according to the present embodiment is based on the configuration described with reference to FIG.

In the present embodiment, after the warm-up of the internal combustion engine 10 is completed, when there is a request to maintain the engine temperature at a high temperature, the temperature of the exhaust gas immediately after being discharged from the internal combustion engine 10 is set to a value that is higher than the temperature T _EX. Control that opens the control valve 22 by the ECU 30 (heating control after warm-up) is performed on the condition that the flow rate of the exhaust gas is higher than the set value. The temperature of the exhaust gas immediately after being discharged from the internal combustion engine 10 can be obtained from, for example, a detection value of a temperature sensor provided at the outlet of the water jacket of the internal combustion engine 10. The flow rate of the exhaust gas immediately after being discharged from the internal combustion engine 10 can be estimated from, for example, an air flow meter provided at the inlet of the intake passage 12.

As described in the second embodiment, since the condensed water is accumulated in the internal passage 20, if the condensed water is evaporated by performing the warm-up water removal control, heat is generated from the wall surface of the internal passage 20. Will be taken away. Similarly, in the present embodiment, if heating control is performed after warming up, heat is removed from the wall surface of the internal passage 20 as the condensed water accumulated in the internal passage 20 evaporates. However, the post-warm-up heating control is performed when the temperature of the exhaust gas immediately after being discharged from the internal combustion engine 10 is higher than the set value by the temperature T _EX and the flow rate of the exhaust gas is higher than the set value. Therefore, more heat than the loss due to vaporization of the condensed water can be transferred from the exhaust to the wall surface of the internal passage 20. Therefore, the wall surface of the internal passage 20 can be efficiently warmed to maintain the engine temperature at a high temperature, and fuel efficiency can be improved.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Intake passage 14 Exhaust passage 16, 18 Branch passage 20 Internal passage 22 Control valve 24 Temperature sensor 30 ECU

Claims (1)

An internal passage formed in a cylinder block of the internal combustion engine and connected to a first branch passage branched from the exhaust passage of the internal combustion engine; a branch from the exhaust passage downstream from the first branch passage; and the internal passage A second branch passage connected to the first branch passage, a control valve provided in the first branch passage for controlling an inflow of exhaust gas from the first branch passage to the internal passage, and provided in the second branch passage. A control device for an internal combustion engine configured to control an internal combustion engine comprising: a temperature sensor that detects a temperature of exhaust gas flowing through the second branch passage;
At the start of the internal combustion engine, the temperature of the exhaust gas flowing through the exhaust passage upstream of the connection with the first branch passage is higher than the wall surface temperature of the internal passage, and the second branch passage is When the temperature of the flowing exhaust gas is lower than the temperature at which the water vapor in the exhaust gas flowing through the second branch passage starts to condense, the exhaust gas is allowed to flow into the internal passage from the first branch passage. A control device for an internal combustion engine.

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