Control system for internal combustion engines
The control system for internal combustion engines addresses unburned hydrocarbon emissions by prohibiting post-injection during heating and optimizing fuel injection, achieving reduced emissions and improved heating efficiency.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- MITSUBISHI MOTORS CORP
- Filing Date
- 2024-11-08
- Publication Date
- 2026-05-20
AI Technical Summary
Post-injection in internal combustion engines increases the emission of unburned hydrocarbons, particularly when the exhaust gas purification device is being heated or regenerated.
A control system that prohibits post-injection when the heating device is operating and adjusts fuel injection parameters such as after-injection amount and timing to maintain in-cylinder temperature and suppress unburned hydrocarbon emissions.
The system effectively reduces unburned hydrocarbon emissions by prohibiting post-injection during heating, enhances heating performance, and optimizes fuel consumption by adjusting injection stages and intervals.
Smart Images
Figure 2026083679000001_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to a control system for an internal combustion engine.
Background Art
[0002] Conventionally, a control system for an internal combustion engine that performs post-injection has been known (see, for example, Patent Document 1). The control system for the internal combustion engine of Patent Document 1 reduces the injection amount of post-injection according to the wall temperature of the cylinder. Thereby, the control system for the internal combustion engine of Patent Document 1 reduces the fuel adhering to the wall surface and suppresses the generation of unburned hydrocarbons contained in the exhaust gas.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] Post-injection is used to increase the temperature of the exhaust gas purification device and the temperature of the cooling water supplied to the heating device because the exhaust temperature of the internal combustion engine rises. In the control system for the internal combustion engine of Patent Document 1, post-injection is used to increase the temperature of the exhaust gas purification device. However, post-injection increases the emission of unburned hydrocarbons.
[0005] An object of the present disclosure is to provide a control system for an internal combustion engine that can suppress the emission of unburned hydrocarbons.
Means for Solving the Problems
[0006] The control system for an internal combustion engine according to this disclosure is a control system for an internal combustion engine mounted on a vehicle, comprising: a heating device for heating the vehicle; a fuel injection device for performing fuel injection; and a control device for controlling the fuel injection device, wherein the control device performs main injection, after-injection which starts injection after the main injection, and post-injection which starts injection after the after-injection, and prohibits post-injection in the region in which the heating device is operated. [Effects of the Invention]
[0007] According to this disclosure, a control system for an internal combustion engine can be provided that can suppress the emission of unburned hydrocarbons by prohibiting post-injection in the heating region. [Brief explanation of the drawing]
[0008] [Figure 1] A system diagram of a control system for an internal combustion engine according to one embodiment of the present disclosure. [Figure 2] A diagram showing a spray configuration according to one embodiment of the present disclosure. [Figure 3] A flowchart illustrating a control procedure performed by a control device according to one embodiment of the present disclosure. [Modes for carrying out the invention]
[0009] Hereinafter, one embodiment of this disclosure will be described with reference to the drawings.
[0010] As shown in Figure 1, the control system 1 for the internal combustion engine E includes a heating device 2, a fuel injector 4, an exhaust gas purification device 6, an exhaust gas circulation device 8, a control device 10, and an accelerator pedal 12. The control system 1 for the internal combustion engine E is mounted on a vehicle C. In this embodiment, the internal combustion engine E is a four-stroke diesel engine that injects fuel directly into the cylinder N and causes autoignition.
[0011] The heating device 2 is a device that heats the interior of vehicle C. In this embodiment, the heating device 2 has a heat exchanger (not shown). The heating device 2 warms the interior air by exchanging heat between the cooling water of the internal combustion engine E and the interior air using the heat exchanger. In this embodiment, the heating device 2 operates when a switch located inside vehicle C is in the ON position and the interior temperature is lower than the temperature set by the user.
[0012] The fuel injector 4 performs fuel injection to supply fuel to the cylinder N. In this embodiment, the fuel injector 4 is connected to a fuel injection pump P and a pressure accumulator such as a common rail (not shown). The fuel injector 4 is electrically connected to a control device 10, and the injection amount and injection stage are controlled by the control device 10.
[0013] As shown in Figure 2, in this embodiment, the fuel injector 4 injects a main injection MI, an after-injection AI, and a post-injection PI per cycle, with intake, compression, expansion, and exhaust being considered as one cycle. The main injection MI is injected from the compression stroke to the expansion stroke. The main injection MI is the injection that injects the majority of the fuel to be injected per cycle. The after-injection AI is an injection that starts after the main injection MI. The after-injection AI is mainly performed to burn any fuel that was not burned by the main injection MI. The post-injection PI is an injection that starts after the after-injection. The post-injection PI is performed, for example, to raise the temperature of the exhaust gas purification device 6.
[0014] As shown in Figure 1, the exhaust gas purification device 6 is a device that purifies the exhaust gas emitted from the internal combustion engine E. The exhaust gas purification device 6 may include, for example, a diesel particulate filter that captures particulate matter in the exhaust gas, a NOx trap that captures NOx, or a urea selective reduction catalytic system that reduces NOx using urea.
[0015] The exhaust gas recirculation device 8 is a device that recirculates exhaust gas discharged from the internal combustion engine E to the intake air. The exhaust gas recirculation device 8 has an exhaust gas recirculation valve 8a, and the amount of exhaust gas recirculated is adjusted by adjusting the opening degree of the exhaust gas recirculation valve 8a. The exhaust gas recirculation valve 8a is electrically connected to the control device 10, and the opening degree of the valve is controlled. In addition, the exhaust gas in the exhaust gas recirculation device 8 is cooled by passing through an EGR cooler (not shown) before being recirculated to the intake air.
[0016] The control device 10 is electrically connected to the accelerator pedal 12 and obtains the opening degree of the accelerator pedal 12 pressed by the user of vehicle C. The control device 10 determines the requested output Q to be requested from the internal combustion engine E from the opening degree of the accelerator pedal 12. Based on the requested output Q, the control device 10 determines the injection amount and injection mode (e.g., injection stage) of the fuel injector 4 and injects the fuel.
[0017] The control device 10 further determines whether it is necessary to raise the temperature of the exhaust gas purification device 6. For example, the control device 10 may determine that it is necessary to raise the temperature of the exhaust gas purification device 6 if the temperature of the cooling water that cools the internal combustion engine E is below a predetermined temperature (for example, 40°C). Also, if the exhaust gas purification device 6 is a urea selective reduction catalytic system, the control device 10 may determine that it is necessary to raise the temperature of the exhaust gas purification device 6 when injecting urea. If it is necessary to raise the temperature of the exhaust gas purification device 6, the control device 10 may perform post-injection PI.
[0018] The control device 10 further determines whether or not the exhaust gas purification device 6 needs to be regenerated. For example, if the exhaust gas purification device 6 is a diesel particulate filter, the control device 10 may determine that regeneration of the exhaust gas purification device 6 is necessary if the amount of soot accumulated on the diesel particulate filter exceeds a predetermined value. Also, if the exhaust gas purification device 6 is a NOx trap, the control device 10 may determine that regeneration is necessary when the NOx trap has absorbed more than a predetermined amount of NOx. If regeneration of the exhaust gas purification device 6 is necessary, the control device 10 may perform post-injection PI.
[0019] The control device 10 is actually an ECU (Electronic Control Unit) composed of a microcomputer including an arithmetic unit, a memory, an input / output buffer, etc. The control device 10 controls the control system 1 of the internal combustion engine E based on the maps and programs stored in the memory.
[0020] Next, the control procedure executed by the control device 10 will be described using FIG. 3.
[0021] In step S1, the control device 10 executes post-injection PI. As described above, the post-injection PI is executed during warm-up or regeneration of the exhaust gas purification device 6. When the control device 10 executes the post-injection PI, the process proceeds to step S2.
[0022] In step S2, the control device 10 determines whether it is in the heating area. The heating area is the area where the control device 10 operates the heating device 2. The heating area does not necessarily mean that the heating device 2 is actually operating, as long as the heating device 2 can operate. If the control device 10 determines that it is in the heating area (step S2 YES), the process proceeds to step S3. If the control device 10 determines that it is not in the heating area (step S2 NO), the control device 10 returns.
[0023] In step S3, the control device 10 prohibits the post-injection PI. By prohibiting the post-injection PI, the control device 10 suppresses the emission of unburned hydrocarbons. When the control device 10 prohibits the post-injection PI, the process proceeds to step S4.
[0024] In step S4, the control device 10 controls the exhaust gas recirculation valve 8a to reduce the exhaust gas recirculation gas amount (an example of the exhaust gas recirculation amount). The exhaust gas recirculation gas reduces the temperature of the cylinder N. When the in-cylinder temperature T decreases, unburned hydrocarbons are likely to occur. Therefore, the control device 10 reduces the amount of exhaust gas recirculation gas flowing into the cylinder N, suppresses the decrease in the in-cylinder temperature T (see FIG. 2), and suppresses the generation of unburned hydrocarbons. When the control device 10 reduces the exhaust gas recirculation gas amount, the process proceeds to step S5.
[0025] In step S5, the control device 10 increases the injection amount of after-injection AI. When post-injection PI is prohibited, the in-cylinder temperature T and exhaust temperature decrease. The control device 10 suppresses the decrease in in-cylinder temperature T and exhaust temperature by increasing the injection amount of after-injection AI. As a result, the temperature of the coolant in the internal combustion engine E rises, and the heating performance improves. After increasing the injection amount of after-injection AI, the control device 10 proceeds to step S6.
[0026] In step S6, the control device 10 determines whether the load is low or not. The control device 10 may determine that the load is low if the internal combustion engine E is idling or if the mean effective pressure PE, which is an indicator of the pressure in cylinder N, is a low value such as 2 bar. If the control device 10 determines that the load is low (step S6 YES), it proceeds to step S7.
[0027] In step S7, the control device 10 increases the after-interval period. As shown in Figure 2, the after-interval period D is the period between the end of the main injection MI (injection end time) and the start of the after-injection AI. In practice, this timing can be obtained based on the crank angle during one cycle. In this embodiment, the crank angle is 0 degrees at the start of the intake stroke and 720 degrees at the end of the exhaust stroke. By increasing the after-interval period, i.e., bringing the start of the after-injection AI closer to the exhaust stroke, the decrease in cylinder temperature T and exhaust temperature is suppressed. At this time, the after-injection AI with an increased after-interval period serves the roles of both normal after-injection and post-injection. Therefore, the amount of fuel injected is reduced compared to the conventional case where both normal after-injection and post-injection are performed. As a result, the control device 10 can suppress fuel consumption while suppressing the emission of unburned hydrocarbons.
[0028] When increasing the after-interval period, the start time (crank angle at which it starts) of the after-injection AI is preferably the time (crank angle) when the in-cylinder temperature T of the cylinder N is equal to or greater than the combustion limit temperature FT, which is the limit temperature at which the fuel (diesel in this embodiment) ignites. In this embodiment, the combustion limit temperature FT is approximately 520K. The in-cylinder temperature T is highest during the main injection and decreases during the after-interval period. When the after-injection AI is injected, the fuel burns again in the cylinder N, and the in-cylinder temperature T rises. If the start time of the after-injection AI is lower than the combustion limit temperature FT, there is a possibility that the fuel will not ignite and misfire will occur.
[0029] In this embodiment, the control device 10 stores the crank angle during one cycle at which such a combustion limit temperature FT occurs, for each rotation and load of the internal combustion engine E. The control device 10 acquires the in-cylinder temperature T and controls the fuel injector 4 so that after-injection AI is started at a crank angle before the in-cylinder temperature T falls below the combustion limit temperature FT (an example of a predetermined temperature). The start timing may be slightly before or after the time when the combustion limit temperature is reached. The control device 10 may acquire the in-cylinder temperature T from a thermometer (not shown) attached to the cylinder N, or it may be estimated from the exhaust temperature or the like. The control device 10 returns when the after-interval period is increased.
[0030] If the control device 10 determines in step S6 that the load is not low (step S6 NO), the process proceeds to step S8.
[0031] In step S8, the control device 10 determines whether the load is increasing or not. The control device 10 may determine that the load is increasing if the accelerator opening is increasing and the requested output Q is increasing. If the control device 10 determines that the load is increasing (step S8 YES), it proceeds to step S9. If the control device 10 determines that the load is not increasing (step S8 NO), it returns.
[0032] In step S9, the control device 10 advances the start time of the after-injection AI. In this embodiment, the control device 10 advances the start time of the after-injection AI. When the load increases, the injection amount of the main injection MI increases. This causes the in-cylinder temperature T to rise. The control device 10 advances the start time of the after-injection AI, making it more susceptible to receiving thermal energy from the main injection MI, thereby ensuring that the fuel injected by the after-injection AI is burned. This suppresses the generation of unburned hydrocarbons. The control device 10 may shorten the after-interval period as the load increases. This ensures more reliable combustion of the after-injection AI, burning the unburned hydrocarbons generated by the main injection MI with the after-injection AI, and also suppresses the generation of unburned hydrocarbons by the after-injection AI. The control device 10 returns after advancing the disclosure time of the after-injection AI.
[0033] As explained above, the control system 1 of the internal combustion engine E of this disclosure can suppress the generation of unburned hydrocarbons by prohibiting post-injection PI in the heating region. Specifically, the control system 1 prohibits post-injection PI when the region in which the exhaust gas purification device 6 is regenerated or heated overlaps with the heating region. This allows the control system 1 of the internal combustion engine E to suppress the generation of unburned hydrocarbons. The control system 1 of the internal combustion engine E increases the injection amount of after-injection AI by the amount that post-injection PI is prohibited, suppressing the decrease in the in-cylinder temperature T and improving heating performance. Furthermore, the control system 1 of the internal combustion engine E suppresses fuel consumption by lengthening the after-interval period at low loads with low injection amounts. When the load is increasing, the control device 10 shortens the after-interval period to ensure reliable combustion of fuel and suppress unburned hydrocarbons.
[0034] <Other Embodiments> Although embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. In particular, the various modifications described herein can be combined as needed.
[0035] In the above embodiment, examples of post-injection PI were described using heating the exhaust gas purification device 6 and regeneration of the exhaust gas purification device 6, but this disclosure is not limited thereto. Post-injection PI may be injected for other purposes.
[0036] In the above embodiment, an example was described using a fuel injector 4 that injects a main injection MI, an after-injection AI, and a post-injection PI, but the disclosure is not limited thereto. The fuel injector 4 may also inject a pilot injection (not shown) and a pre-injection (not shown) which are initiated before the main injection MI. [Explanation of Symbols]
[0037] 1: Control system, 2: Heating system, 4: Fuel injection system 6: Exhaust purification system, 8: Exhaust circulation system, 10: Control device C: Vehicle, E: Internal combustion engine FT: Flammability limit temperature (an example of a specified temperature) MI: Main injection, AI: After injection, PI: Post injection T: Cylinder temperature
Claims
1. A control system for an internal combustion engine mounted on a vehicle, A heating device for heating the aforementioned vehicle, A fuel injection system that performs fuel injection, A control device for controlling the fuel injection device, Equipped with, The control device performs, by the fuel injection device, a main injection, an after-injection that starts after the main injection, and a post-injection that starts after the after-injection. In the region where the heating device is operated, the post-injection is prohibited. Control system for internal combustion engines.
2. When the control device prohibits the post-injection, it increases the amount of the after-injection. The control system for an internal combustion engine according to claim 1.
3. When the control device prohibits the post-injection, it increases the period from the end of the main injection to the start of the after-injection. The control system for an internal combustion engine according to claim 1.
4. The control device acquires the in-cylinder temperature of the internal combustion engine and sets the start time before the time when the in-cylinder temperature falls below a predetermined temperature. The control system for an internal combustion engine according to claim 3.
5. The control device reduces the period as the load on the internal combustion engine increases. The control system for an internal combustion engine according to claim 3.
6. The system further includes an exhaust circulation device for circulating the exhaust gas of the internal combustion engine, When the control device prohibits post-injection, it reduces the amount of exhaust gas circulated by the exhaust gas circulation device. A control system for an internal combustion engine according to any one of claims 1 to 5.