Internal combustion engine control apparatus

Abstract

To inhibit a PM exhaust volume from increasing even in a state where condensed water remains in a filter.SOLUTION: An internal combustion engine control apparatus controls an internal combustion engine equipped with a filter in an exhaust pipe connected to an engine body, the filter for capturing PM. The control apparatus includes: a condensed water residual determination part for determining whether condensed water remains in the filter; and an output suppress control part. In a case where the condensed water residual determination part determines that the condensed water remains in the filter, the output suppress control part suppresses an output of the engine body more than in a case where no condensed water remains in the filter. The condensed water residual determination part determines that the condensed water remains in the filter when a temperature of exhaust gas passing through the filter is lower than a given threshold related to the temperature of the exhaust gas.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a control device for an internal combustion engine. [Background technology]

[0002] Conventionally, internal combustion engines have been known that are provided with a filter in an exhaust passage of the engine to capture particulate matter (PM) in the exhaust. Condensed water can accumulate on such filters. For example, Patent Document 1 proposes using an electric heater to raise the temperature of the filter on which condensed water has accumulated, thereby evaporating the condensed water. Patent Document 1 claims that evaporating the condensed water can suppress an increase in back pressure caused by condensed water accumulation on the filter, thereby maintaining good drivability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-81979 Summary of the Invention [Problem to be solved by the invention]

[0004] Meanwhile, the inventors of the present application have discovered a new finding regarding the relationship between condensed water in a filter and the PM capture efficiency. Based on this finding, if condensed water remains on the filter, the PM capture efficiency of the filter decreases. If the PM capture efficiency of the filter decreases, the amount of PM released into the atmosphere increases. Patent Document 1 aims to avoid an increase in back pressure due to condensed water, and does not address the decrease in the PM capture efficiency.

[0005] Therefore, an object of the invention disclosed in this specification is to suppress an increase in the amount of PM emitted even when condensed water remains on the filter. [Means for solving the problem]

[0006] The above-mentioned object is achieved by a control device for an internal combustion engine in which a filter for capturing PM is provided in an exhaust pipe connected to the engine body, the control device including: a condensed water remaining determination unit that determines whether condensed water remains in the filter; and an output suppression control unit that suppresses the output of the engine body when the condensed water remaining determination unit determines that condensed water remains in the filter, compared to when no condensed water remains in the filter.

[0007] The condensed water remaining determination unit may be configured to determine that condensed water remains in the filter when the temperature of the exhaust gas that has passed through the filter is lower than a predetermined threshold value related to the temperature of the exhaust gas.

[0008] The condensed water remaining determination unit may include a condensed water occurrence determination unit that determines whether condensed water has occurred in the filter.

[0009] The condensed water remaining determination unit may determine that the condensed water remains in the filter when the amount of intake air into the engine body is less than a predetermined threshold value related to the amount of intake air. [Effects of the Invention]

[0010] The invention disclosed in this specification can suppress an increase in the amount of PM emitted even when condensed water remains on the filter. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing an internal combustion engine in which a control device according to an embodiment is incorporated. [Figure 2] Fig. 2A is a flowchart showing an example of control according to an embodiment. Fig. 2B is a flowchart showing detailed processing for determining whether condensed water remains. Fig. 2C is a flowchart showing detailed processing for determining whether condensed water in the GPF has disappeared. [Figure 3]FIG. 3 is a flowchart showing another example of determining whether the condensed water in the GPF has disappeared. [Figure 4] FIG. 4 is a diagram showing an example of a map for suppressing the output of an internal combustion engine. [Figure 5] FIG. 5 is a time chart illustrating the changes in each value that occur with the control of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0013] (Embodiment) [Internal combustion engine] The internal combustion engine 100 includes an intake pipe 11 and an exhaust pipe 14 connected to an engine body 10. An air flow meter 12 and a throttle valve 13 are provided in the intake pipe 11. A first catalyst 15 and a second catalyst 16 are provided in the exhaust pipe 14, in this order from the side closest to the engine body 10. The internal combustion engine 100 also includes an ECU (Electronic Control Unit) 50 that functions as a control device. The internal combustion engine 100 is mounted on a vehicle. The vehicle may be a hybrid vehicle. In this case, the internal combustion engine 100 is combined with a motor and a battery (not shown) to form a hybrid system.

[0014] The engine body 10 can use fuel containing hydrocarbons. The engine body 10 in this embodiment is a gasoline engine that uses gasoline as fuel. The engine body 10 can also be a diesel engine that uses diesel as fuel. In the internal combustion engine 100, water (H2O) is produced by burning fuel that contains hydrocarbons. The produced water can be cooled and become condensed water.

[0015] The air flow meter 12 detects the amount of intake air flowing through the intake pipe 11 and sent to the engine body 10. The throttle valve 13 adjusts the amount of intake air sent to the engine body 10.

[0016] The first catalyst 15 is a three-way catalyst. However, the first catalyst 15 is not essential. The internal combustion engine 100 may also be configured in a manner in which the first catalyst 15 is omitted.

[0017] The second catalyst 16 is a GPF (Gasoline Particulate Filter). If the engine body 10 is a diesel engine, a DPF (Diesel Particulate Filter) is provided instead of a GPF. The GPF and DPF are filters that capture PM emitted from the engine body 10 and reduce the PN (Particulate Number) released into the atmosphere. PN is the number of PM.

[0018] Coolant circulates within the engine body 10. The engine body 10 is provided with a water temperature sensor 17 that detects the temperature of the coolant.

[0019] An exhaust gas temperature sensor 18 is provided downstream of the second catalyst 16 in the exhaust pipe 14. The exhaust gas temperature sensor 18 detects the temperature of the exhaust gas (outlet gas) that passes through the second catalyst 16 and is discharged from the second catalyst 16. The exhaust gas temperature sensor 18 calculates the temperature T outGPF The exhaust gas temperature sensor 18 may be provided in the second catalyst 16 itself, instead of downstream of the second catalyst 16. In this case, the temperature T outGPF The detected value of the exhaust gas temperature sensor 18 may be multiplied by a coefficient previously obtained through an experiment or the like so as to obtain the above equation.

[0020] The ECU 50 includes a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), a storage device, etc. The ECU 50 executes programs stored in the ROM and the storage device to control the internal combustion engine 100. An accelerator opening sensor 20 (not shown) that detects the opening of an accelerator is electrically connected to the ECU 50. Although a description thereof will be omitted here, in addition to the accelerator opening sensor 20, many other sensors for controlling the internal combustion engine 100 are connected to the ECU 50.

[0021] The ECU 50 functions as a condensed water remaining determination unit 51 and an output suppression control unit 52. The condensed water remaining determination unit 51 determines whether or not condensed water remains in the second catalyst 16. The condensed water remaining determination unit 51 may include a condensed water occurrence determination unit 51a and a condensed water disappearance determination unit 51b.

[0022] The condensed water occurrence determination unit 51a is electrically connected to the outside air temperature sensor 19. The condensed water occurrence determination unit 51a determines whether or not condensed water has occurred using the detection value of the outside air temperature sensor 19. The condensed water occurrence determination unit 51a determines that condensed water has occurred when the outside air temperature detected by the outside air temperature sensor 19 falls below a preset threshold, for example, 10 degrees.

[0023] The condensation water occurrence determination unit 51a may be configured to be electrically connected to the water temperature sensor 17 instead of the outside air temperature sensor 19. In this case, whether or not condensation water has occurred is determined using the detection value of the water temperature sensor 17. The condensation water occurrence determination unit 51a determines that condensation water has occurred when the water temperature falls below a preset threshold value.

[0024] The condensed water occurrence determination unit 51a may determine whether or not condensed water has occurred using both the detection value of the outside air temperature sensor 19 and the detection value of the water temperature sensor 17. The condensed water occurrence determination unit 51a may also use other parameters that are correlated with the water temperature.

[0025] The condensed water disappearance determination unit 51b is electrically connected to the exhaust gas temperature sensor 18. The condensed water disappearance determination unit 51b determines whether or not the condensed water has disappeared by using the detected value of the exhaust gas temperature sensor 18. The condensed water disappearance determination unit 51b determines whether or not the condensed water has disappeared by using the detected value of the exhaust gas temperature sensor 18. outGPF When the temperature T is equal to or greater than a predetermined threshold T, it can be determined that the condensed water has disappeared. The threshold T can be set to the condensed water vaporization temperature. Thus, the condensed water disappearance determination unit 51b determines whether the temperature T outGPF When it is determined that the temperature T is equal to or greater than the threshold value T, it is determined that the condensed water in the second catalyst 16 has disappeared. outGPF is equal to or greater than the threshold value T, the condensed water has reached its vaporization temperature and is considered to have evaporated. outGPF If is lower than the threshold value T, it is determined that condensed water remains.

[0026] The condensed water disappearance determining unit 51b may be configured to electrically connect the air flow meter 12 instead of the exhaust temperature sensor 18. In this case, it is determined whether or not the condensed water has disappeared using the detected value of the air flow meter 12. That is, the condensed water disappearance determining unit 51b determines whether or not the condensed water has disappeared based on the intake air amount G detected by the air flow meter 12. in is equal to or greater than a preset threshold value G, the condensed water is determined to have disappeared. The intake air amount can be used as a parameter for evaluating the load on the engine body 10. The load on the engine body 10 is correlated with the amount of heat generated by the engine body 10. The greater the amount of heat generated by the engine body 10, the higher the temperature of the second catalyst 16 becomes, and the easier it is for the condensed water in the second catalyst 16 to evaporate. Therefore, it is possible to determine whether the condensed water has evaporated and disappeared based on the intake air amount. The condensed water disappearance determination unit 51b uses the intake air amount G in If the difference is less than a preset threshold G, it is determined that condensed water remains.

[0027] The condensed water remaining determination unit 51 may be configured in a manner that omits the condensed water generation determination unit 51a. If the condensed water generation determination unit 51a determines that condensed water has not been generated, the condensed water remaining determination unit 51 can determine that no condensed water remains in the second catalyst 16 at that point. On the other hand, even if the condensed water generation determination unit 51a is not provided, if the condensed water disappearance determination unit 51b determines that the condensed water in the second catalyst 16 has disappeared, the condensed water remaining determination unit 51 can determine that no condensed water remains in the second catalyst 16. In other words, the condensed water disappearance determination unit 51b determines whether the condensed water has disappeared, and thereby the condensed water remaining determination unit 51 can determine whether condensed water remains in the second catalyst 16.

[0028] When the condensed water remaining determination unit 51 determines that condensed water remains in the second catalyst 16, the output reduction control unit 52 reduces the output of the engine body 10 compared to when condensed water does not remain in the second catalyst 16. The throttle valve 13 is electrically connected to the output reduction control unit 52. When the condensed water remaining determination unit 51 determines that condensed water remains in the second catalyst 16, the output reduction control unit 52 limits the opening degree of the throttle valve 13. When the amount of intake air supplied to the engine body 10 increases, the output of the engine body 10 increases. Accordingly, the PN discharged from the engine body 10 increases. When the output of the engine body 10 is reduced, the PN in the engine body 10 is reduced. In other words, when condensed water remains in the second catalyst 16, the output reduction control unit 52 reduces the amount of PM generated.

[0029] [Output suppression control] The output suppression control in the embodiment will be described with reference to FIGS. 2A to 4. FIG.

[0030] In step S1, the ECU 50 determines whether the engine required output is greater than 0. That is, the ECU 50 determines whether the internal combustion engine 100 is operating. This is because output reduction control is unnecessary if the internal combustion engine 100 is not operating. If the ECU 50 makes a positive determination (Yes determination) in step S1, the ECU 50 proceeds to step S2. If the ECU 50 makes a negative determination (No determination) in step S1, the ECU 50 proceeds to step S4. In step S4, the ECU 50 turns off the output reduction request flag.

[0031] In step S2, the ECU 50 determines whether condensed water remains in the second catalyst 16. This determination is made by the condensed water remaining determination unit 51. FIG. 2B illustrates the details of the processing in step S2 in more detail. The processing in step S2 includes steps S21 and S22. In step S21, the condensed water remaining determination unit 51 determines whether condensed water has occurred in the second catalyst 16. This determination is made by the condensed water occurrence determination unit 51a. The condensed water occurrence determination unit 51a determines that condensed water has occurred (positive determination) if there is a history of the detection value of the outside air temperature sensor 19 being below a preset threshold value after the internal combustion engine 100 was last stopped. If the ECU 50 makes a positive determination in step S21, the process proceeds to step S22. If the ECU 50 makes a negative determination in step S21, the process proceeds to step S4. As described above, if the condensed water occurrence determination unit 51a is omitted, step S21 is omitted. In this case, the ECU 50 proceeds from step S1 to step S22.

[0032] In step S22, the ECU 50 determines whether the condensed water in the second catalyst 16 has disappeared. This determination is made by the condensed water disappearance determination unit 51b. FIG. 2C illustrates the details of the process in step S22 in more detail. The process in step S22 includes steps S221 and S222. In step S221, the condensed water disappearance determination unit 51b determines whether the temperature T outGPF In step S222, the condensed water disappearance determining unit 51b obtains the temperature T outGPFis lower than a threshold value T. The threshold value T is set in advance as the temperature at which condensed water vaporizes and evaporates. If the ECU 50 makes a positive determination in step S222, the process proceeds to step S3. If the ECU 50 makes a negative determination in step S222, the process proceeds to step S4.

[0033] The process of step S22 may include steps S221' and S222' illustrated in Fig. 3. These steps are adopted instead of steps S221 and S222. Steps S221' and S222' are performed by adjusting the temperature T outGPF Instead, the intake air volume G in In step S221', the condensed water disappearance determining unit 51b determines whether the condensed water has disappeared or not by calculating the intake air amount G in In step S222', the condensed water disappearance determining unit 51b obtains the intake air amount G in is smaller than a threshold value G. The threshold value G is preset as an intake air amount that can provide the heat required for vaporizing the condensed water. If the ECU 50 determines affirmatively in step S222', the process proceeds to step S3. If the ECU 50 determines negatively in step S222', the process proceeds to step S4.

[0034] In step S3, the ECU 50 turns on the output reduction request flag. In step S5, which is executed following step S3, the output reduction control unit 52 determines whether the output reduction request flag is on. If the output reduction control unit 52 makes a positive determination in step S5, the process proceeds to step S6. If the output reduction control unit 52 makes a negative determination in step S5, the process repeats the process from step S1.

[0035] In step S6, the output suppression control unit 52 determines the upper limit output P out Set the upper limit output P out is set based on the map shown in FIG. 4. The horizontal axis of the map shown in FIG. 4 represents the temperature T outGPF The vertical axis is the upper limit of the engine output P outIn Figure 4, the temperature of the outgoing gas T outGPF is drawn with a solid line. The map shown in FIG. 4 is the map used when going through the steps shown in FIG. 2C. The threshold value T is set to 100 degrees, which is the boiling point of condensed water. The temperature of the outlet gas T outGPF When the temperature of the exit gas T is lower than 100°C, outGPF In the map shown in FIG. 4, the output of the engine body 10 is suppressed compared to when the temperature T outGPF When is lower than 100 degrees, the upper limit output P out is set to approximately 18 kW. For this reason, even if the required output of the engine body 10 calculated based on the manner in which the driver of the vehicle depresses the accelerator pedal is higher than 18 kW, the output of the engine body 10 is limited to 18 kW. This suppresses PN in the engine body 10. For this reason, even if the second catalyst 16 is in a state in which it is difficult to capture PM due to condensed water, PN released into the atmosphere is suppressed.

[0036] In the map shown in FIG. 4, the upper limit output P out The upper limit output P out As shown by the dashed line in FIG. 4, outGPF The vehicle speed may be gradually changed depending on the vehicle speed. This improves the drivability of the vehicle.

[0037] [effect] The effect of the embodiment will be described with reference to the time chart shown in FIG.

[0038] In FIG. 5, the transition of each value in the embodiment is depicted by a solid line. The transition of each value in the comparative example is depicted by a dashed line. The comparative example has the same hardware configuration as the internal combustion engine 100 of the embodiment, but differs from the embodiment in that output suppression control is not performed. In FIG. 5, the accelerator opening, engine output, GPF outlet gas temperature (temperature T outGPF), and the ON / OFF status of the output suppression request flag are shown. Furthermore, FIG. 5 shows the PN at the engine body 10 and the PN downstream of the second catalyst 16 (GPF). In FIG. 5, the PN at the engine body 10 and the PN downstream of the second catalyst 16 are drawn on the same vertical axis for convenience of drawing. However, in reality, the PN downstream of the second catalyst 16 is less than the PN at the engine body 10. Even if condensed water remains on the second catalyst 16 and its PM collection capacity is reduced, a certain amount of PM is collected by the second catalyst 16. Therefore, the PN downstream of the second catalyst 16 is less than the PN at the engine body 10.

[0039] Time t1 is the time when the internal combustion engine 100 starts. The ECU 50 starts the output reduction control from time t1. Accordingly, the output reduction request flag is switched from OFF to ON (see step S3 in FIG. 2A). As illustrated in FIG. 5, at time t2, the PN from the engine main body 10 and the PN downstream of the second catalyst 16 momentarily rise. This is because the amount of fuel injection is increased in order to start the internal combustion engine 100.

[0040] At time t3, the accelerator opening increases. Accordingly, in the comparative example, the engine output increases. As the engine output increases, the PN from the engine body 10 increases. The PN from the engine body 10 has a correlation with the engine output. Therefore, the PN is shown as a PN corresponding to the engine output. Furthermore, in the comparative example, as the engine output increases, the temperature T outGPF As a result, at time t4, the temperature T outGPF reaches the condensed water vaporization temperature. As a result, the PN downstream of the second catalyst 16 decreases from time t4 to time t5. The period from time t4 to time t5 is considered to be a period during which the condensed water gradually evaporates and the PM trapping function of the second catalyst 16 is restored. In the comparative example, the PM trapping function of the second catalyst 16 is restored after time t5.

[0041] In contrast to this, in the embodiment, the engine output is suppressed even though the accelerator opening degree increases at time t3. This is because the output suppression request flag is ON and the upper limit output P out This is because the PN in the engine body 10 is suppressed low (see step S6 in FIG. 2A). In the embodiment, the engine output is suppressed, and therefore the PN in the engine body 10 is suppressed. Furthermore, since the PN itself in the engine body 10 is suppressed, the PN downstream of the second catalyst 16 is also suppressed. In other words, despite the presence of condensed water on the second catalyst 16, the PN downstream of the second catalyst 16 is suppressed. Note that if the vehicle is a hybrid vehicle, the power equivalent to the suppressed engine output can be compensated for by, for example, the output of a motor.

[0042] In this embodiment, the engine output is suppressed. outGPF The rate of increase in temperature T outGPF The temperature T reaches the condensed water vaporization temperature at time t6. outGPF When the temperature T reaches the condensed water vaporization temperature, i.e., the threshold value T, the output suppression request flag is switched from ON to OFF (see step S4 in FIG. 2A). Then, the engine output suppression caused by the presence of condensed water is released. outGPF After time t6, converges to the same value as in the comparative example indicated by the dashed line.

[0043] When the output suppression request flag is switched to OFF, engine output according to the accelerator opening is permitted. Accordingly, the PN in the engine body 10 increases from time t6 to time t7. However, the PM trapping function of the second catalyst 16 has been restored at time t6. Therefore, the PN downstream of the second catalyst 16 converges to the value when the second catalyst 16 was performing the intended PM trapping function.

[0044] The PN on the downstream side of the second catalyst 16 in this embodiment can be reduced by the amount shown by hatching in FIG. 5 compared to the comparative example.

[0045] As described above, according to this embodiment, even when condensed water remains on the second catalyst 16, an increase in the amount of PM emitted can be suppressed.

[0046] The above-described embodiments are merely examples for implementing the present invention, and the present invention is not limited to these. Various modifications of these embodiments are within the scope of the present invention. Furthermore, it is obvious from the above description that various other embodiments are possible within the scope of the present invention. [Explanation of symbols]

[0047] 10 engine body, 12 air flow meter, 13 throttle valve, 16 second catalyst, 17 water temperature sensor, 18 exhaust temperature sensor, 19 outside air temperature sensor, 50 ECU, 51 condensed water remaining determination unit, 51a condensed water occurrence determination unit, 51b condensed water disappearance determination unit, 52 output suppression control unit

Claims

1. A control device for an internal combustion engine in which a filter for collecting PM is provided in an exhaust pipe connected to an engine body, a condensed water remaining determination unit that determines whether condensed water remains in the filter; an output suppression control unit that, when the condensed water remaining determination unit determines that the condensed water remains in the filter, suppresses the output of the engine body compared to when the condensed water does not remain in the filter; A control device for an internal combustion engine, comprising:

2. the condensed water remaining determination unit determines that the condensed water remains in the filter when the temperature of the exhaust gas that has passed through the filter is lower than a predetermined threshold value related to the temperature of the exhaust gas. The control device for an internal combustion engine according to claim 1.

3. the condensed water remaining determination unit includes a condensed water occurrence determination unit that determines whether condensed water has occurred in the filter. The control device for an internal combustion engine according to claim 1.

4. the condensed water remaining determination unit determines that the condensed water remains in the filter when an intake air amount of the engine body is less than a predetermined threshold value related to the intake air amount. The control device for an internal combustion engine according to claim 1.

Images