JP2022074885A - Internal combustion engine control apparatus - Google Patents

Abstract

To provide an internal combustion engine control apparatus capable of suppressing exhaustion of NOx while securing a good sporty sound.SOLUTION: An internal combustion engine control apparatus configured to control the ignition timing, fuel injection amount, intake air volume and air-fuel ratio of an internal combustion engine incorporated in a vehicle, executes: torque-down control for retarding ignition timing by decreasing a fuel injection amount and an intake air volume while controlling an air-fuel ratio toward a lean side than a theoretical air-fuel ratio when shifting from an accelerator On to accelerator Off; and exhaust noise control for further retarding the ignition timing to a post-upper dead point between a compression stroke and an expansion stroke so that a combustion of an air-fuel mixture continues until an exhaust valve of the internal combustion engine starts opening next.SELECTED DRAWING: Figure 2

Description

The present invention relates to a control device for an internal combustion engine.

Patent Document 1 describes an operation of increasing the opening degree of the throttle valve to increase the output torque of the engine and a retardation of the ignition timing to reduce the output torque of the engine when the shift down due to the accelerator off is performed. It is disclosed that the operation is executed at the same time and the increase amount of the output torque is set to be larger than the decrease amount of the output torque in this case. As a result, it is possible to effectively generate the intake sound of the intake officer and the combustion sound in the combustion chamber without causing a feeling of popping out of the vehicle, and to obtain a good sports sound.

Japanese Unexamined Patent Publication No. 2009-103065

It is desired to suppress NOx emissions while ensuring the above-mentioned good sports sound.

Therefore, an object of the present invention is to provide a control device for an internal combustion engine that can suppress NOx emissions while ensuring good sports sound.

The above purpose is the air-fuel ratio when the accelerator is changed from the accelerator on to the accelerator off in the control device of the internal combustion engine that controls the ignition timing, the fuel injection amount, the intake air amount, and the air-fuel ratio of the internal combustion engine mounted on the vehicle. Is controlled to be leaner than the stoichiometric air-fuel ratio, torque down control is executed to reduce the fuel injection amount and intake air amount to retard the ignition timing, and then the exhaust valve of the internal combustion engine starts to open. This can be achieved by a control device of an internal combustion engine that performs exhaust noise control that further retards the ignition timing until after the top dead point between the compression stroke and the expansion stroke so that the combustion of the air-fuel mixture continues until.

According to the present invention, it is possible to provide a control device for an internal combustion engine that can suppress NOx emissions while ensuring good sports sound.

FIG. 1 is a schematic diagram showing a schematic configuration of an internal combustion engine. FIG. 2 is a timing chart showing an example of control executed by the ECU. FIG. 3 is a graph showing the relationship between the valve opening timing of the intake valve and the exhaust valve and the ignition timing. FIG. 4A is a graph showing the relationship between the exhaust sound level and the excess air ratio, and FIG. 4B is a graph showing the relationship between the exhaust sound level and the ignition timing. FIG. 5 is a flowchart showing an example of the control executed by the ECU. FIG. 6 is a flowchart showing an example of the control executed by the ECU. FIG. 7 is a timing chart showing a modified example of the control executed by the ECU.

FIG. 1 is a schematic diagram showing a schematic configuration of an internal combustion engine 10. As shown in FIG. 1, air is sucked into the combustion chamber 11 of the internal combustion engine 10 through the intake passage 12 by opening the intake valve 22, and the fuel injection valve 13 is directed toward the port of the intake passage 12. The injected fuel is supplied. When the spark plug 14 ignites the air-fuel mixture composed of the intake air and the injected fuel, the air-fuel mixture burns, the piston 15 reciprocates, and the crankshaft 16 of the internal combustion engine 10 rotates. When the exhaust valve 23 is opened, the air-fuel mixture after combustion is sent out from the combustion chamber 11 of the internal combustion engine 10 to the exhaust passage 17 as exhaust gas.

The exhaust gas passing through the exhaust passage 17 is purified by the catalyst 20 provided in the exhaust passage 17. Specifically, the catalyst 20 is a three-way catalyst, and is released to the outside after purifying harmful components such as HC, CO, and NOx in the exhaust gas. This three-way catalyst has an oxygen storage function in order to effectively remove the above three components in the exhaust gas. This oxygen storage function is provided to the three-way catalyst, and the fuel injection amount of the fuel injection valve 13 is controlled so that the oxygen concentration in the catalyst atmosphere converges to the value at the time of combustion of the air-fuel mixture at the theoretical air-fuel ratio. The original catalyst can effectively purify the three components such as NOx, HC, and CO in the exhaust. Further, an air-fuel ratio sensor 21 that outputs a signal based on the oxygen concentration in the exhaust gas is provided in the upstream portion of the catalyst in the exhaust passage 17.

In addition, instead of the above-mentioned three-way catalyst, an oxidation catalyst, a NOx storage reduction catalyst, or the like may be used. The oxidation catalyst oxidizes NOx, CO, etc. in the exhaust gas. The NOx occluded reduction catalyst occludes NOx in the exhaust in a lean atmosphere, and when a reducing agent such as HC or CO is supplied from the upstream, releases the stored NOx and reacts with the reducing agent to cause NOx. Is reduced to NH ₃ and N ₂ .

The ECU (Electronic Control Unit) 30 is a CPU (Central Processing Unit) that executes various arithmetic processes related to various controls, a ROM (Read Only Memory) that stores programs and data necessary for the arithmetic, and a central processing unit. It is equipped with a RAM (Random Access Memory) for temporarily storing calculation results, an input port and an output port for inputting and outputting signals to and from the outside.

Various sensors are connected to the input port of the ECU 30. As such sensors, for example, an accelerator opening sensor 31 that detects the opening degree of the accelerator pedal 18 and a throttle sensor 32 that detects the opening degree of the throttle valve 19 provided in the intake passage 12 are provided. .. In addition, an air amount sensor 34 for detecting the intake air amount, a crank sensor 35 for detecting the rotation speed of the crankshaft 16, an ignition switch 36 operated at the start and stop of the operation of the internal combustion engine 10, and the like are also provided.

The ECU 30 grasps the rotation speed and the load of the internal combustion engine 10 based on the output signals of various sensors. The ECU 30 outputs a command signal to various drive circuits connected to the output port according to the operating state thus grasped. The controls performed by the ECU 30 in this way include throttle control for adjusting the opening degree of the throttle valve 19, fuel injection control for adjusting the injection amount of the fuel injection valve 13, and ignition timing for adjusting the ignition timing of the spark plug 14. Control is mentioned. The ECU 30 is an example of a control device for the internal combustion engine 10.

The ECU 30 executes torque down control when it detects accelerator off from accelerator on, and further executes exhaust sound control when a predetermined condition is satisfied. FIG. 2 is a timing chart showing an example of the control executed by the ECU 30. FIG. 2 shows the state of the accelerator, the transition of the intake air amount and the fuel injection amount, the presence / absence of the fuel cut signal, the presence / absence of the execution of the exhaust sound control, and the transition of the ignition timing. When the accelerator opening decreases at time t1 and the accelerator opening becomes zero at time t2, the air-fuel ratio becomes higher than the theoretical air-fuel ratio while the intake air amount and fuel injection amount gradually decrease from time t1. It is controlled to the lean side, and the ignition timing is gradually controlled to the retard side. In this way, torque down control during deceleration is executed.

In the torque down control, the throttle valve 19 is controlled so that the intake air amount gradually decreases regardless of the opening degree of the accelerator pedal 18. Further, the opening degree of the throttle valve 19 in the exhaust sound control may be controlled to be the same as the opening degree during idle operation, or may be controlled to be slightly more open than the opening degree during idle operation. Alternatively, the control may be performed slightly on the closed side. The fuel injection amount in the exhaust sound control may be controlled to be the same as the injection amount in the idle operation, may be slightly larger than the injection amount in the idle operation, or may be slightly smaller.

When the fuel cut signal is switched from off to on at time t3, the exhaust sound control is executed. The ignition timing immediately before the exhaust sound control is executed is set to θa. In the exhaust sound control, the intake air amount is controlled to be the intake air amount during idle operation, and the ignition timing is set between the compression stroke and the expansion stroke while the fuel injection is continued with a minute injection amount. The angle is significantly retarded to θb after the point. In this embodiment, the ignition timing θb is set to, for example, ATDC (After Top Dead Center) 20 °.

FIG. 3 is a graph showing the relationship between the valve opening timings of the intake valve 22 and the exhaust valve 23 and the ignition timings θa and θb. In FIG. 3, the horizontal axis indicates the crank angle, and the vertical axis indicates the valve lift amount. By setting the ignition timing θb significantly retarded from the ignition timing θa, the combustion speed of the air-fuel mixture decreases. As a result, the combustion of the air-fuel mixture can be continued until the exhaust valve 23 is opened near the bottom dead center of the exhaust stroke. As a result, when the exhaust valve 23 is opened, the combustion sound of the air-fuel mixture can be propagated as the exhaust sound in the exhaust passage 17, and a good sports sound can be obtained. Therefore, for example, it can contribute to improving the commercial value of a high-performance sports car. In the example of FIG. 3, the ignition timing θa is set before the top dead center between the compression stroke and the expansion stroke, but specifically, θa is set to the ignition timing set during normal idle operation. Then, depending on the amount of intake air, for example, the BTDC (Before Top Dead Center) is set within the range of 45 ° to 0 ° or the BTDC of 10 ° to 0 °.

Further, as described above, since the combustion extinguishing speed of the air-fuel mixture is lowered by the exhaust sound control, the temperature of the internal combustion engine 10 is lowered, and the amount of NOx in the exhaust gas discharged from the combustion chamber 11 is sufficiently suppressed. Further, since the air-fuel ratio is controlled lean, the HC can be sufficiently purified by the catalyst 20.

Next, as shown in FIG. 2, the exhaust sound control is stopped at the time t4 when a predetermined time has elapsed since the exhaust sound control was executed, the ignition timing θa is set, the fuel injection is stopped, and the original fuel cut is executed. do. If the rotation speed of the internal combustion engine 10 becomes equal to or less than the return rotation speed during the execution of the fuel cut, the ECU 30 restarts the fuel injection by the fuel injection valve 13.

As described above, since the injection of a minute amount of fuel is continued during the execution of the exhaust sound control, the decrease in the exhaust temperature is suppressed, the decrease in the temperature of the catalyst 20 is also suppressed, and the exhaust purification performance can be maintained. Further, when the internal combustion engine 10 is equipped with a supercharger, the exhaust sound control is executed during deceleration, so that the decrease in the rotation speed of the supercharger can be suppressed, and thereby after returning to the normal operation. Turbo lag can be suppressed.

Next, the relationship between the exhaust noise level and the excess air rate will be described. FIG. 4A is a graph showing the relationship between the exhaust noise level and the air excess rate λ. In FIG. 4A, the vertical axis indicates the level of exhaust noise, and the horizontal axis indicates the excess air ratio λ. The air-fuel ratio λ can be expressed by the air-fuel ratio / stoichiometric air-fuel ratio, and the larger it is, the leaner it is. As shown in FIG. 4A, the exhaust sound level peaks in the range where the excess air ratio λ is larger than 1. By appropriately controlling the excess air ratio λ at the time of executing the exhaust sound control in this way, a more effective sports sound can be produced.

Next, the relationship between the combustion noise level of the exhaust gas and the ignition timing will be described. FIG. 4B is a graph showing the relationship between the exhaust noise level and the ignition timing. In FIG. 4B, the vertical axis indicates the exhaust sound level, and the horizontal axis indicates the ignition timing. The more the ignition timing is retarded, the higher the level of exhaust noise. It is considered that this is because the more the ignition timing is retarded, the longer the time during which the combustion of the air-fuel mixture continues during the valve opening period of the exhaust valve 23 becomes longer. By appropriately controlling the ignition timing at the time of executing the exhaust sound control in this way, a more effective sports sound can be produced.

Next, the control executed by the ECU 30 will be described. 5 and 6 are flowcharts showing an example of the control executed by the ECU 30. First, it is determined whether or not the accelerator is turned on and off based on the accelerator opening sensor 31 (step S11). For example, in the timing chart shown in FIG. 2, it is determined as Yes in the process of step S11 at time t2.

In the case of Yes in step S11, it is determined whether or not the temperature of the catalyst 20 is within a predetermined range (step S12). For example, if the temperature of the catalyst 20 is higher than this range and the exhaust sound control is executed, the temperature of the catalyst 20 may become excessively high. The process of step S12 is executed in order to suppress such a problem. The temperature of the catalyst 20 may be detected by a sensor or estimated by another known method.

In the case of Yes in step S12, it is determined whether or not the rotation speed of the internal combustion engine 10 is within a predetermined range (step S13). For example, when the rotation speed is low, the amount of intake air also decreases, but in this case, if the ignition timing is retarded, a misfire may occur, and if the exhaust sound control is executed when the rotation speed is low, the driver may feel uncomfortable. Because there is sex. The rotation speed of the internal combustion engine 10 is calculated based on the detection value of the crank sensor 35.

If Yes in step S13, the execution of the exhaust sound control is permitted (step S14), and the exhaust sound control execution time T is set (step S15). The exhaust sound control execution time T is determined based on a map stored in advance in the ROM of the ECU 30. This map defines, for example, the exhaust sound control execution time T based on the rotation speed and the load of the internal combustion engine 10. The exhaust sound control execution time T specified in the map is set to a time in which the temperature of the catalyst 20 becomes equal to or less than the allowable upper limit temperature even if the exhaust sound control is executed by an experiment in advance. For example, when the operating state of the internal combustion engine 10 is high rotation and high load, the temperature of the catalyst 20 is in a relatively high state, so that the exhaust sound control execution time T is set to a relatively short time.

If No in any of steps S12 and S13 described above, exhaust sound control is prohibited (step S16).

If No in step S11, it is determined whether or not exhaust sound control is permitted as shown in FIG. 6 (step S21). For example, after the time t2 in FIG. 2, it is determined as No in step S11. Further, for example, even when the accelerator is turned off and the accelerator is turned on, it is determined as No in step S11. If No in step S21, this control ends.

The case of Yes in step S21 is, for example, a case where exhaust sound control is permitted in step S14 described above. In this case, it is determined whether or not the preprocessing for executing the exhaust sound control is completed (step S22). Specifically, it is determined whether or not the preprocessing for executing the fuel cut is completed during the lockup, and whether or not the torque down is completed in the case of the lockup off state. The pre-processing for executing the fuel cut is, for example, a process for suppressing a torque shock when the lock-up state is switched off from the lock-up state before the fuel cut is executed. In the determination of whether or not the torque reduction is completed, it is determined whether or not the torque of the internal combustion engine 10 has decreased to a predetermined value due to the deceleration. The lockup state means that the lockup clutch of the torque converter is in the engaged state, and the lockup off means the state in which the engaged state is released.

Whether or not a predetermined time has elapsed since the exhaust sound control was permitted or when it was detected that the accelerator was switched from on to off, instead of determining whether or not the preprocessing was completed in step S22 described above. May be determined. That is, it may be considered that the above-mentioned pretreatment has been completed when the predetermined time has elapsed.

If No in step S22, the exhaust sound control is not executed and the standby state is entered (step S23). If Yes in step S22, exhaust noise control is executed (step S24).

Next, it is determined whether or not the accelerator off is detected (step S25). In the case of Yes in step S25, it is determined whether or not the temperature of the catalyst 20 is within a predetermined range (step S26). In the case of Yes in step S26, it is determined whether or not the exhaust sound control duration is equal to or longer than the exhaust sound control execution time T described above (step S27). If No in step S27, this control is terminated. That is, the exhaust sound control is continued. If No in any of steps S25 and S26, or if Yes in step S27, the exhaust sound control is terminated (step S28). As a result, the exhaust sound control ends even when the accelerator pedal 18 is depressed while the exhaust sound control is being executed, or when the temperature of the catalyst 20 rises excessively.

FIG. 7 is a timing chart showing a modified example of the control executed by the ECU 30. When the accelerator opening decreases at time t1 and the accelerator turns off at time t2, the fuel cut signal is turned on and the fuel injection amount is controlled to zero. That is, the fuel cut is executed. When the exhaust sound control is executed at time t3 during the fuel cut, a minute fuel injection is started, the ignition timing θb is set, and the angle is significantly retarded. When the exhaust sound control ends at time t4, the fuel cut is continued. By executing the fuel cut immediately after the accelerator is turned off in this way, a feeling of deceleration can be ensured. For example, when the diameter of the throttle valve 19 is large, or when the volume of the intake system after the throttle valve 19 is large, it takes time for the intake air amount to sufficiently decrease during deceleration, and the feeling of deceleration may decrease. There is sex. This modification is suitable for such a case. In addition, since the exhaust sound control is executed after the intake air amount decreases to some extent after the fuel cut is executed, it is possible to produce the exhaust sound while ensuring a feeling of deceleration at an early stage, and the sportiness of the vehicle is made more effective. It can be directed.

In the above embodiment, the ignition timing θb in the exhaust sound control is set to ATDC 20 °, but the ignition timing is not limited to this, and if the combustion of the air-fuel mixture is continued when the exhaust valve 23 is opened, for example, ATDC 17 ° to The ignition timing may be between 23 ° and ATDC 15 ° to 25 °.

Further, in the above embodiment, an example applied to the internal combustion engine 10 for a vehicle has been described, but the vehicle may be, for example, a so-called hybrid vehicle, a motorcycle, or the like. Further, the fuel injection valve 13 of the internal combustion engine 10 is not limited to the port injection valve, but may be an internal combustion engine provided with an in-cylinder injection valve, and the port injection valve and the in-cylinder injection valve. It may be an internal combustion engine provided with both of the above.

Although the examples of the present invention have been described in detail above, the present invention is not limited to such specific examples, and various modifications and variations are made within the scope of the gist of the present invention described in the claims. It can be changed.

10 Internal combustion engine 12 Intake passage 13 Fuel injection valve 14 Spark plug 17 Exhaust passage 18 Accelerator pedal 19 Throttle valve 20 Catalyst 30 ECU (Internal combustion engine control device)

Claims (1)

In an internal combustion engine control device that controls the ignition timing, fuel injection amount, intake air amount, and air-fuel ratio of an internal combustion engine mounted on a vehicle.
When shifting from accelerator on to accelerator off, torque down control is executed to delay the ignition timing by reducing the fuel injection amount and intake air amount while controlling the air-fuel ratio to the lean side of the theoretical air-fuel ratio, and then Exhaust sound control is executed to further retard the ignition timing until after the top dead center between the compression stroke and the expansion stroke so that the combustion of the air-fuel mixture continues until the exhaust valve of the internal combustion engine starts to open. Internal combustion engine control device.

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