Internal combustion engine control device and internal combustion engine control method

Abstract

To solve a problem that conventionally, complex calculations are performed, and there is a need for more simply estimating unburned fuel by using less information.SOLUTION: An internal combustion engine control device is for controlling an internal combustion engine comprising a fuel injection device for injecting fuel, and comprises: a combustion speed detection unit 501 that detects a combustion speed in a cylinder; an unburned fuel level estimation unit 502 that uses the combustion speed to estimate the level of unburned fuel in the cylinder; an allowable value setting unit 503 that sets an allowable value of the level of unburned fuel; and an unburned fuel level adjustment unit 504 that controls the internal combustion engine 1 so that the level of unburned fuel estimated by the unburned fuel level estimation unit 502 becomes equal to or smaller than the allowable value.SELECTED DRAWING: Figure 5

Description

Technical Field

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[0001] The present invention relates to an internal combustion engine control device and an internal combustion engine control method for controlling an internal combustion engine such as a gasoline engine.

Background Art

[0002] In recent years, with the development of environmentally friendly engines, reducing emissions of PN (Particulate Number) and THC (Total Hydro Carbon) generated during engine startup or low-temperature operation has become an issue. The sources of these emissions include fuel adhesion and fuel droplets generated inside the engine cylinder. These are caused by the liquid fuel introduced into the cylinder remaining without evaporating, and are particularly likely to occur during engine startup or operation in a low-temperature environment. In order to reduce the generation of the above substances, several techniques for predicting the amount of fuel adhesion have been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] The techniques described in Patent Documents 1 and 2 estimate the amount of fuel adhesion by complex calculations based on predicted values such as engine operating conditions and the temperature of the cylinder wall surface. They calculate the penetration distance of fuel spray or separate and calculate the fuel mass ratio and the unburned fuel ratio through complex calculations. Therefore, it is difficult to estimate the amount of fuel adhesion in real time during driving of a vehicle. Furthermore, what can be estimated by these techniques is only the fuel adhesion to the inner wall of the cylinder, and the fuel droplets floating in the cylinder are not particularly considered.

[0005] Given the above situation, there was a need for a method that could estimate fuels that did not contribute to combustion more easily using less input information. [Means for solving the problem]

[0006] To solve the above problems, an internal combustion engine control device according to one aspect of the present invention is an internal combustion engine control device that controls an internal combustion engine equipped with a fuel injection device for injecting fuel, comprising: a combustion speed detection unit that detects the combustion speed in a cylinder; an unburned fuel level estimation unit that estimates the level of unburned fuel in a cylinder using the combustion speed; an allowable value setting unit that sets an allowable value for the unburned fuel level; and an unburned fuel level adjustment unit that controls the internal combustion engine so that the unburned fuel level estimated by the unburned fuel level estimation unit is less than or equal to the allowable value. [Effects of the Invention]

[0007] According to at least one aspect of the present invention, it becomes possible to estimate the unburned fuel level more easily and accurately using less input information, and to control the internal combustion engine based on the estimated unburned fuel level. Other issues, configurations, and effects not mentioned above will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic cross-sectional view showing an example of an internal combustion engine. [Figure 2] This diagram shows an example of the hardware configuration of an internal combustion engine control device. [Figure 3] This diagram shows how fuel is sprayed inside an internal combustion engine. [Figure 4] This figure shows an example of the relationship between combustion speed and the amount of unburned fuel, as well as an example of the relationship between the amount of unburned fuel and the air-fuel ratio. [Figure 5] This is a block diagram showing an example configuration and input data for an internal combustion engine control device according to the first embodiment of the present invention. [Figure 6]This figure shows an example of the relationship between combustion speed and unburned fuel level according to the first embodiment of the present invention. [Figure 7] This is a block diagram showing an example configuration and input data for an internal combustion engine control device according to a second embodiment of the present invention. [Figure 8] This figure shows an example of the relationship between the combustion speed and the unburned fuel level before and after correction according to the second embodiment of the present invention. [Figure 9] This is a block diagram showing an example configuration and input data for an internal combustion engine control device according to a third embodiment of the present invention. [Figure 10] This figure shows an example of the relationship between crank angle, fuel injection signal, and unburned fuel amount in the first control example of the fourth embodiment of the present invention. [Figure 11] This figure shows an example of the relationship between the crank angle, fuel injection signal, and unburned fuel amount in multi-stage injection in the first control example of the fourth embodiment of the present invention. [Figure 12] This figure shows an example of the relationship between fuel pressure and unburned fuel amount in a second control example of the fourth embodiment of the present invention. [Figure 13] This figure shows an example of the relationship between crank angle, fuel injection signal, and unburned fuel amount in a third control example of the fourth embodiment of the present invention. [Figure 14] This figure shows an example of the relationship between crank angle, fuel injection signal, unburned fuel amount, and ignition time in multi-stage injection in a third control example of the fourth embodiment of the present invention. [Figure 15] This figure shows an example of the relationship between crank angle and ignition signal, and an example of the relationship between unburned fuel level and pre-ignition count, in a fourth control example of the fourth embodiment of the present invention. [Modes for carrying out the invention]

[0009] Hereinafter, examples of embodiments for carrying out the present invention (hereinafter referred to as "embodiments") will be described with reference to the accompanying drawings. In this specification and the accompanying drawings, the same reference numerals are used for components that are identical or have substantially the same function, and redundant descriptions are omitted.

[0010] <First Embodiment> First, an example of an internal combustion engine will be described with reference to FIG. 1. FIG. 1 is a schematic cross-sectional view showing an example of an internal combustion engine. The internal combustion engine 1 shown in FIG. 1 includes a piston 101, a cylinder 102, and a cylinder head 104. The cylinder head 104 forms a combustion chamber 103 with the crown surface 101P of the piston 101 and the inner wall 109 of the cylinder 102. Further, as an injector (fuel injection device) for fuel injection, it includes at least a direct injection injector 111 or a port injection injector 112, or both. In the present embodiment, an example in which the present invention is applied to a gasoline engine as the internal combustion engine 1 will be described.

[0011] An ignition plug 105 having an electrode 106 for igniting the air-fuel mixture is configured directly above the combustion chamber 103. Air flows into the combustion chamber 103 through an intake port 107 in which an intake valve 113 communicating with the main combustion chamber is opened during the intake stroke. Fuel is sent to the combustion chamber 103 by being atomized by the direct injection injector 111 or the port injection injector 112, or both. The fuel vaporizes in the combustion chamber 103 and mixes with the intake air to form an air-fuel mixture. Then, the air-fuel mixture is compressed by the piston 101, and a main ignition signal is sent to the ignition coil 110 at an appropriate timing. Then, the air-fuel mixture in the combustion chamber 103 is ignited by the ignition plug 105, and the air-fuel mixture in the combustion chamber 103 is burned. As a result, the pressure in the combustion chamber 103 rises and pushes down the piston 101, and the connecting rod 116 rotates the crankshaft 115. The internal combustion engine 1 obtains power by the rotation of the crankshaft 115. The exhaust gas after combustion in the combustion chamber 103 is discharged from the exhaust port 108 to the exhaust pipe when the exhaust valve 114 opens.

[0012] Next, the hardware configuration of the internal combustion engine control device 500 will be described with reference to FIG. 2. FIG. 2 is a block diagram showing an example of the hardware configuration of the internal combustion engine control device 500.

[0013] As shown in FIG. 2, the internal combustion engine control device 500 includes an input circuit 191, an A / D conversion unit 192, a CPU (Central Processing Unit) 193 which is a central processing unit, a ROM (Read Only Memory) 194, a RAM (Random Access Memory) 195, an output circuit 196, and a communication IF 199.

[0014] The CPU 193 expands and executes the program stored in the ROM 194 (an example of a storage unit) in the RAM 195, thereby realizing each function according to the embodiment of the present invention. The CPU 193 is an example of a control device. Note that a processing device such as an MPU (Micro-Processing Unit) may be used instead of the CPU 193.

[0015] The input circuit 191 takes in the signal output from the sensors 210 as an input signal 190. For example, the sensors 210 are an intake air flow rate sensor, a throttle sensor, a water temperature sensor, a crank angle sensor, an intake cam angle sensor, an exhaust cam angle sensor, and the like. When the input signal 190 is an analog signal, the input circuit 191 removes noise components from the input signal 190 and outputs the signal after noise removal to the A / D conversion unit 192.

[0016] The A / D conversion unit 192 converts an analog signal into a digital signal and outputs it to the CPU 193. The CPU 193 takes in the digital signal output from the A / D conversion unit 192 and executes various operations and controls by executing the control logic (program) stored in a storage medium such as the ROM 194.

[0017] The calculation results of the CPU 193 and the conversion results of the A / D conversion unit 192 are temporarily stored in the RAM 195. In this embodiment, a non-volatile memory such as an EEPROM (Electrically Erasable and Programmable Read Only Memory) whose contents can be rewritten may be used as the ROM 194. For example, a program describing algorithms for realizing each function according to the embodiment of the present invention may be stored in the ROM 194 or a non-volatile storage (not shown). In addition, the non-volatile storage (not shown) may store, for example, multiple data acquired from sensors 210, map information corresponding to the unburned fuel curve described later, etc. This non-volatile storage may be a storage medium that can be attached to and detached from the internal combustion engine control device 500, such as a cassette-type SSD (Solid State Drive).

[0018] The calculation results from the CPU 193 are output as a control signal 197 from the output circuit 196 and used to control the actuators 220 to be controlled. Examples of controlled objects include intake valve drive units, exhaust valve drive units, injectors, spark plugs, steering systems, brake systems, power conversion circuits, etc.

[0019] If the input signal 190 is a digital signal, the input signal 190 is sent directly from the input circuit 191 to the CPU 193 via the signal line 198, and the CPU 193 performs the necessary calculations and control operations.

[0020] Communication IF199 consists of communication devices that control communication between other devices. For example, communication IF199 is a communication device that communicates with a wide-area network N (e.g., the Internet), or a communication device that communicates with ECUs and sensors within the vehicle, such as a master ECU (not shown), via CAN (Controller Area Network).

[0021] Figure 3 shows the fuel being sprayed inside the internal combustion engine 1. Normally, when liquid fuel is injected from an injector, the fuel may adhere to the opposing wall while remaining in liquid form. For example, as shown in Figure 3, when a fuel spray 301 is injected into the combustion chamber 103 by a direct injection injector 111, a fuel film 302 is formed on the crown surface 101P of the piston 101 and the inner wall 109 of the cylinder 102. Also, because the fuel spray 301 is at high speed, the impact when it collides with the crown surface 101P of the piston 101 and the inner wall 109 of the cylinder 102 may cause droplets 303 to scatter into the combustion chamber 103. In addition, tip wetting 304 may occur, where fuel droplets remain and adhere around the injection nozzle of the direct injection injector 111.

[0022] When the fuel-air mixture in the combustion chamber 103 is ignited by the spark plug 105, if fuel film 302, droplets 303, or tip wet 304 remain, they burn in a liquid state. At this time, the fuel film 302, droplets 303, and tip wet 304 remaining at the moment the flame reaches them cannot contribute to the output of the internal combustion engine 1 and undergo diffusion combustion separately from the fuel-air mixture. As a result, PN and THC are generated. The same phenomenon occurs when a port injection injector 112 is used. Fuel that could not contribute to the output of the internal combustion engine 1, such as fuel film 302, droplets 303, and tip wet 304, is collectively called "unburned fuel 305".

[0023] To reduce unburned fuel 305, measures such as controlling the shape and length of the fuel spray 301 into the combustion chamber 103 to suppress the formation of a fuel film 302 are being considered. Normally, injection conditions are optimized so that the air-fuel ratio in the combustion chamber 103 of the internal combustion engine 1 reaches the target value. However, in cold starts when the outside temperature is low, the actual air-fuel ratio deviates from the target air-fuel ratio due to poor fuel evaporation in the combustion chamber 103. Other cold starts include restarting the internal combustion engine 1 after a short stop, such as a temporary pause during idling. In these cold starts, unburned fuel usually increases, resulting in not only the generation of large amounts of PN and THC, but also problems such as misfires due to inability to burn. Furthermore, in cold starts, the catalyst and other components are not warmed up, and conventional oxygen sensors and air-fuel ratio sensors are not activated, making accurate measurement by sensors difficult.

[0024] Patent Document 1 introduces a technique for estimating the amount of fuel film 302 in the combustion chamber using a complex calculation formula based on engine operating conditions, fuel injection conditions, engine water temperature, etc. In this technique, estimating the amount of fuel film 302 requires separating the combustion mass ratio and the unburned fuel ratio and performing calculations using a complex mathematical formula, making it difficult to estimate the unburned fuel 305 shown in Figure 3 in real time in an actual vehicle. In addition, the technique described in Patent Document 1 can only estimate the amount of fuel film 302, and cannot estimate the amount of droplets 303 or tip wet 304. Thus, while the relationship between the fuel film 302, the length of the fuel spray 301, the amount of fuel, and the inner wall temperature of the internal combustion engine 1 has been studied, the relationship between the actual combustion state, particularly the combustion speed and the unburned fuel 305, has not been studied. In this specification, combustion speed refers to the time from ignition of the air-fuel mixture until combustion is complete, or the time until the air-fuel mixture reaches a certain fuel mass ratio. The combustion speed is thought to differ depending on the speed at which the flame propagates through the air-fuel mixture.

[0025] Figure 4 shows an example of the relationship between combustion speed and the amount of unburned fuel, as well as an example of the relationship between the amount of unburned fuel and the air-fuel ratio. Here, the relationship between combustion speed and the amount of unburned fuel 401 (upper part of Figure 4) and the relationship between the amount of unburned fuel and the air-fuel ratio in the combustion chamber 103 4011 (lower part of Figure 4) are shown when fuel is injected into the combustion chamber 103 to achieve an ideal air-fuel ratio and burned in the combustion chamber 103. In this invention, in light of the rise of environmentally conscious engines in recent years, we consider injecting fuel to be below the ideal air-fuel ratio. When the target air-fuel ratio, the load of the internal combustion engine 1, and the ignition timing are the same, as shown in Figure 4, the larger the amount of unburned fuel, the greater the difference 407 (deviation) between the target air-fuel ratio and the air-fuel ratio of the actually burned mixture. This is because the laminar flow combustion speed of the fuel changes with the air-fuel ratio.

[0026] Normally, settings such as fuel spray in an internal combustion engine 1 are optimized so that the amount of unburned fuel is below an acceptable value. However, as mentioned above, external factors such as ambient temperature can cause the amount of unburned fuel to exceed the acceptable value (fall outside the acceptable range). The combustion speed when fuel burns is strongly influenced by the fuel's composition, ambient temperature, and ambient pressure. Therefore, if the difference 404 between the reference combustion speed 402 and the actual combustion speed 403 at the target air-fuel ratio, load, and ignition timing is known, the unburned fuel level 405 at that point in combustion, i.e., the difference 407 from the reference value 406 of the air-fuel ratio, can be estimated.

[0027] As a method for detecting combustion speed, a method for accurately detecting the combustion phase from the ignition time by reading the change in output of a crank angle sensor (not shown) is shown, for example, in Japanese Patent Publication No. 2021-161904 (Reference 1). Ignition time is information about the ignition timing (for example, the phase of the crank with top dead center of compression as the base point). By looking at whether the combustion phase is advanced or lagging, it is possible to determine whether the combustion speed is fast or slow. For example, combustion speed can be expressed as the time from the start of combustion until the combustion mass ratio reaches 50% (MFB50).

[0028] Figure 5 is a block diagram showing an example of the configuration and input data of the internal combustion engine control device 500 according to this embodiment. The internal combustion engine control device 500 includes a combustion speed detection unit 501 that detects the combustion speed in the cylinder 102 (combustion chamber 103), an unburned fuel level estimation unit 502 that estimates the unburned fuel level in the cylinder 102 from the combustion speed, an allowable value setting unit 503 that sets an allowable value for the estimated unburned fuel level, and an unburned fuel level adjustment unit 504 that controls the internal combustion engine 1 so that the estimated unburned fuel level is below the allowable value.

[0029] The combustion speed detection unit 501 receives at least variables that significantly affect the combustion speed, such as the target air-fuel ratio (target air-fuel ratio 510), load information 511, ignition time 512, and the detection signal 513 from the crank angle sensor. The load information 511 includes, as an example, the rotational speed of the internal combustion engine 1 (crankshaft 115) and the intake pressure. As shown in the above reference 1, the combustion speed detection unit 501 observes the change in the detection signal 513 from the crank angle sensor and detects the combustion speed. The combustion speed detection unit 501 then outputs the detected combustion speed 514 to the unburned fuel level estimation unit 502.

[0030] The tolerance value setting unit 503 receives at least the target air-fuel ratio 510 and load information 511 as input. The tolerance value setting unit 503 sets an acceptable unburned fuel level (acceptable unburned fuel level 515) based on the target air-fuel ratio 510 and load information 511 input as operating conditions, and outputs it to the unburned fuel level adjustment unit 504. The acceptable unburned fuel level 515 may be set, for example, as a ratio to the fuel injection amount (estimated value) calculated from the target air-fuel ratio 510 and load information 511, or as a ratio to the actual fuel injection amount (measured value). For example, the actual fuel injection amount is the average value of the amount of fuel injected from the injector 520 over an arbitrarily set time range.

[0031] Furthermore, the permissible unburned fuel level 515 may have a storage unit (not shown) that stores it as map information based on the results of simulations or experiments conducted in advance. The storage unit can be, for example, a cache memory, a register, or a form written to a computer program. For example, the map information defines the relationship between the target air-fuel ratio, load information, and the permissible unburned fuel level. By storing the relationships between these items as map information, calculations can be performed at high speed.

[0032] The unburned fuel level estimation unit 502 receives at least the combustion speed 514 detected by the combustion speed detection unit 501, the target air-fuel ratio 510, load information 511, and ignition time 512 as input. The unburned fuel level estimation unit 502 also maintains an unburned fuel curve 601, as shown in Figure 6, which represents the relationship between the combustion speed 514 and the estimated value of the unburned fuel level 516. This unburned fuel curve 601 is set for each combination of the target air-fuel ratio 510, load information 511, and ignition time 512. In Figure 6, the unburned fuel curve 601 is shown as a straight line, but it may actually be a curve.

[0033] Figure 6 shows an example of the relationship between the combustion speed of the air-fuel mixture and the level of unburned fuel. Here, the unburned fuel curve 601 is determined under certain conditions of a target air-fuel ratio 510, load information 511, and ignition time 512. In this case, the reference combustion speed 602 (reference combustion speed) may be the combustion speed when the amount of unburned fuel is 0 and a homogeneous air-fuel mixture is burning, or it may be a value obtained in advance from an experiment in a warmed-up state (when the internal combustion engine 1 is sufficiently warmed up) or from a simulation simulating a warmed-up state.

[0034] For example, the unburned fuel level estimation unit 502 may have a storage unit (not shown) that stores the unburned fuel curve 601 as map information for each target air-fuel ratio 510, load information 511, and ignition time 512. The storage unit may be, for example, a cache memory, a register, or a form written to a computer program. By storing it as map information, the calculation of the unburned fuel level can be performed at high speed.

[0035] The unburned fuel level estimation unit 502 estimates the unburned fuel level by comparing the combustion speed detected by the combustion speed detection unit 501 with the unburned fuel curve 601, which is information showing the relationship between the combustion speed and the unburned fuel level, set in advance from the ignition timing 514, the load of the internal combustion engine 1, and the target air-fuel ratio 510. In this way, the unburned fuel level 516 can be estimated by referring to the unburned fuel curve 601 from the combustion speed 514. This is equivalent to taking the difference between the reference combustion speed 602 and the actual combustion speed 514. In other words, the estimated unburned fuel level 516 reflects this difference in combustion speed 603.

[0036] Here, the unburned fuel level 516 may be defined as the mass of unburned fuel, the ratio of unburned fuel to the amount of injected fuel, or a finite interval obtained by dividing the mass of unburned fuel into segments. For example, the unburned fuel level 516 may be divided into three categories: "high," "moderate (appropriate amount)," and "low," or into five categories: "too much," "slightly too much," "moderate (appropriate amount)," "slightly too little," and "too little." Note that this unburned fuel level 516 is set with all fuel existing in a liquid state, such as the fuel film 302, droplets 303, and tip wet 304 (corresponding to unburned fuel 305).

[0037] The unburned fuel level adjustment unit 504 receives the allowable unburned fuel level 515 and the unburned fuel level 516 as input. If the unburned fuel level 516 exceeds the allowable unburned fuel level 515, the unburned fuel level adjustment unit 504 controls at least one of the injector 520, fuel pump 521, ignition coil 522 (ignition device), and throttle 523 so that the unburned fuel level 516 becomes less than or equal to the allowable unburned fuel level 515. This control reduces the amount of unburned fuel in the combustion chamber 103. The injector 520 corresponds to the direct injection injector and the port injection injector 112. The ignition coil 522 corresponds to the ignition coil 110. Generally, the internal combustion engine control device 500 receives information from sensors 210 indicating the amount the accelerator pedal is pressed and the state of the internal combustion engine 1, and adjusts the final throttle opening of the throttle 523 based on a combination of these.

[0038] Furthermore, the present invention makes it possible to estimate the unburned fuel level even during cold starts when the catalyst is not activated, based on the actual combustion speed 514 and the allowable unburned fuel level 515 set from the operating conditions (target air-fuel ratio 510 and load information 511). Therefore, the present invention can be used to detect unburned fuel during cold starts, which could not be detected before, and can also be used to detect unburned fuel after warming up.

[0039] As described above, in this embodiment, the internal combustion engine control device (internal combustion engine control device 500) that controls an internal combustion engine equipped with a fuel injection device (injector 520) for injecting fuel is configured to include: a combustion speed detection unit (combustion speed detection unit 501) that detects the combustion speed in a cylinder (cylinder 102); an unburned fuel level estimation unit (unburned fuel level estimation unit 502) that estimates the unburned fuel level in the cylinder using the combustion speed; an allowable value setting unit (allowable unburned fuel level setting unit 503) that sets an allowable value for the unburned fuel level (allowable unburned fuel level 515) from the operating conditions or the actual fuel injection amount; and an unburned fuel level adjustment unit (unburned fuel level adjustment unit 504) that controls the internal combustion engine so that the unburned fuel level estimated by the unburned fuel level estimation unit is less than or equal to the allowable value.

[0040] According to the internal combustion engine control device of this embodiment with the above configuration, it is possible to estimate the unburned fuel level more accurately and easily using less input information. Furthermore, this embodiment can adjust (control the internal combustion engine) the estimated unburned fuel level so that it falls below an acceptable value.

[0041] <Second Embodiment> The second embodiment is an example for improving the accuracy of estimating the unburned fuel level compared to the first embodiment.

[0042] An example of the configuration of an internal combustion engine control device according to the second embodiment will be described with reference to Figure 7. Figure 7 is a block diagram showing an example configuration and input data of the internal combustion engine control device 500A according to the second embodiment. The internal combustion engine control device 500A differs from the internal combustion engine control device 500 according to the first embodiment in that it includes an unburned fuel level estimation unit 502A instead of the unburned fuel level estimation unit 502. EGR concentration information 701 of the EGR (Exhaust Gas Recirculation) system (not shown) provided by the internal combustion engine 1 is input to the unburned fuel level estimation unit 502A.

[0043] When fuel burns, the combustion state is strongly influenced by the fuel's composition, the ambient temperature, and the ambient pressure. In addition, in actual engines, exhaust gas (inert gas) is sometimes recirculated into the combustion chamber 103 to dilute the fuel-air mixture before combustion, and the combustion rate is affected by the concentration of the recirculated exhaust gas (hereinafter also referred to as "EGR"). The EGR concentration is defined as the ratio of the amount of exhaust gas recirculated into the cylinder 102 to the volume of the cylinder 102 over a certain period of time.

[0044] Therefore, in combustion with a high EGR concentration, the accuracy of estimating the unburned fuel level may decrease. Thus, it is necessary to input the EGR concentration information 701 into the unburned fuel level estimation unit 502A and correct the dashed unburned fuel curve 601 to a solid unburned fuel curve 801, as shown in Figure 8. Alternatively, the EGR rate may be used instead of the EGR concentration. The EGR rate is defined as the ratio of the recirculated exhaust gas volume to the intake volume of the cylinder 102.

[0045] Figure 8 shows an example of the relationship between the combustion speed and the unburned fuel level before and after correction according to this embodiment. In Figure 8, the horizontal axis represents the combustion speed, and the vertical axis represents the unburned fuel level. When no EGR concentration information 701 is input to the unburned fuel level estimation unit 502A, the unburned fuel level 516 is estimated from the combustion speed 514 using the unburned fuel curve 601. On the other hand, when EGR concentration information 701 is input, the unburned fuel level estimation unit 502A corrects the unburned fuel curve 601 to the unburned fuel curve 801 using the EGR concentration information 701. Then, the unburned fuel level estimation unit 502A can estimate the unburned fuel level 802 corrected using the EGR concentration information 701, compared to the unburned fuel level 516 in the case where there is no EGR concentration information 701.

[0046] As described above, in this embodiment, by inputting EGR concentration information 701 to the unburned fuel level estimation unit 502A, it is possible to estimate the unburned fuel level considering the dilution of the mixture by EGR. As a result, this embodiment can improve the accuracy of unburned fuel level estimation compared to the first embodiment.

[0047] <Third Embodiment> The third embodiment is another example for improving the accuracy of estimating unburned fuel levels compared to the first embodiment.

[0048] An example of the configuration of an internal combustion engine control device according to the third embodiment will be described with reference to Figure 9. Figure 9 is a block diagram showing an example configuration and input data of the internal combustion engine control device 500B according to the third embodiment. The internal combustion engine control device 500B differs from the internal combustion engine control device 500 according to the first embodiment in that it includes an unburned fuel level estimation unit 502B instead of an unburned fuel level estimation unit 502. Correction information 901 is input to the unburned fuel level estimation unit 502B. The EGR concentration information 701 in the second embodiment can be considered a type of correction information 901 in this embodiment.

[0049] For example, the compression ratio of internal combustion engine 1 is expressed as the ratio of the volume of the combustion chamber 103, formed by the crown surface 101P and the inner wall 109 of the piston 101, when the crown surface 101P is at bottom dead center to the volume when the crown surface 101P is at top dead center. The air introduced into the internal combustion engine 1 is compressed at this compression ratio and ignited. The temperature and pressure of the air-fuel mixture at ignition change depending on the compression ratio of the internal combustion engine 1. Therefore, the reference combustion speed 602 will differ depending on the internal combustion engine 1.

[0050] Here, when the unburned fuel level estimation unit 502B estimates the unburned fuel level, if compression ratio information is available as correction information 901, the unburned fuel curve 601 can be corrected according to the compression ratio even if the shape (bore and stroke) of the internal combustion engine 1 changes. As a result, even if the target internal combustion engine 1 changes, the internal combustion engine control device 500B can obtain the optimal unburned fuel curve and estimate the corrected unburned fuel level 902. In addition, environmental information such as intake air temperature or ambient air temperature may be used as correction information 901.

[0051] In this embodiment, by inputting information on the compression ratio of the internal combustion engine 1, or the intake air temperature or ambient air temperature, into the unburned fuel level estimation unit 502B, it is possible to estimate the unburned fuel level considering the compression ratio of the internal combustion engine 1 and environmental information. As a result, this embodiment can improve the accuracy of unburned fuel level estimation compared to the first embodiment.

[0052] <Fourth Embodiment> Here, examples of controlling the amount of unburned fuel by the unburned fuel level adjustment unit 504 according to the first to third embodiments will be explained using Figures 10 to 15. First, a first example of controlling the amount of unburned fuel by the unburned fuel level adjustment unit 504 will be explained using Figures 10 and 11.

[0053] (First control example) Figure 10 shows an example of the relationship between crank angle, fuel injection signal, and unburned fuel amount in the first control example of the fourth embodiment. In Figure 10, the first and second graphs represent the fuel injection signal and unburned fuel amount before controlling the unburned fuel amount, and the third and fourth graphs represent the fuel injection signal and unburned fuel amount after controlling the unburned fuel amount.

[0054] When fuel is injected as indicated by the fuel injection signal 1001, for example, the amount of unburned fuel progresses as shown in the unburned fuel amount 1003 before ignition occurs at the ignition time 1002 (first and second stages of Figure 10). At this time, if the internal combustion engine 1 is cold, the amount of unburned fuel at ignition may increase more than expected. Possible causes of this include the intake air being cold, resulting in poor fuel evaporation, and the inability of droplets 303, etc., generated when the fuel spray 301 collides with the wall surface, to evaporate.

[0055] Therefore, the unburned fuel level adjustment unit 504 controls the fuel injection timing of the injector 520 to advance the timing and corrects the fuel injection signal 1001 to the fuel injection signal 1004 (third stage of Figure 10), thereby securing a longer time leeway for the fuel to evaporate. This promotes the evaporation of the droplet 303 and reduces the amount of unburned fuel at the ignition time 1002, as shown in the unburned fuel amount 1005 (fourth stage of Figure 10). However, in that case, fuel injection starts when the piston 101 is closer to top dead center, which may increase the amount of fuel adhering to the crown surface 101P of the piston 101. For this reason, the fuel pressure may also be adjusted in conjunction with the fuel injection timing. When the fuel pressure is low, the penetration distance of the fuel spray 301 is shortened, so a reduction in the amount of unburned fuel can be expected.

[0056] Figure 11 shows an example of the relationship between crank angle, fuel injection signal, and unburned fuel amount in multi-stage injection in the first control example of the fourth embodiment. In recent years, a technology has been developed to reduce the amount of fuel deposited, such as fuel deposition amount 1103, by generating multiple pulse signals such as fuel injection signal 1101 and injecting fuel in multiple stages in the same combustion cycle. Even with this technology, if the temperature of the inner wall 109 of the cylinder 102 or the intake air temperature is low, the amount of unburned fuel at ignition time 1102 may not be the expected value, as shown in the unburned fuel amount 1103.

[0057] As a countermeasure, for example, the amount of fuel injected in the second stage injection when the crown surface 101P of the piston 101 is close to bottom dead center is increased, as shown in the fuel injection signal 1104 (third stage in Figure 11). In this case, the amount of fuel injected in the first and third stage injections, when the crown surface 101P of the piston 101 is close to top dead center, decreases. As a result, the amount of fuel spray 301 reaching the crown surface 101P decreases, and the amount of fuel deposited can be reduced, as shown in the fuel deposit amount 1105 (fourth stage in Figure 11).

[0058] Furthermore, fuel injection during the compression stroke (for example, a fourth-stage injection not shown) may be newly implemented. In this case, the amount of fuel film 302 adhering to the crown surface 101P of the piston 101 and the amount of droplets 303 generated may increase, but compression will reduce the size of the fuel film 302 and droplets 303 and make them more prone to evaporation.

[0059] Furthermore, the amount of fuel injected during the initial intake stroke (for example, the first injection) may be reduced. This reduces the amount of fuel film 302 adhering to the crown surface 101P of the piston 101 and the droplets 303 that are generated, thereby reducing the amount of fuel adhering.

[0060] Furthermore, the amount of fuel deposited may be controlled by increasing or decreasing the interval between each pulse of the fuel injection signal. In the multi-stage injection described above, the total amount of fuel injected in one combustion cycle basically does not change before and after the change in the fuel injection method.

[0061] (Second control example) Next, a second example of controlling the amount of unburned fuel by the unburned fuel level adjustment unit 504 will be explained using Figure 12. Figure 12 shows an example of the relationship between fuel pressure and unburned fuel amount in the second control example of the fourth embodiment. When the fuel injection pressure by the fuel pump 521 (hereinafter referred to as "fuel pressure") is increased, the atomization of the fuel spray 301 and droplets 303 injected from the injector 520 progresses, and fuel evaporation is promoted. However, since the flight speed of the injected fuel spray 301 also increases, the relationship between fuel pressure and unburned fuel amount may be such that, depending on the arrangement of the injector 520 and the shape of the combustion chamber 103, an increase in fuel pressure leads to an increase in unburned fuel amount, as shown by curve 1201 (upper part of Figure 12).

[0062] Furthermore, when the internal combustion engine 1 is started and the wall temperature inside the combustion chamber 103 is low, once fuel adheres to it, it takes time to evaporate, which may cause the amount of unburned fuel to increase more than expected. As shown in curve 1202 (lower part of Figure 12), which represents the relationship between the fuel pressure of the fuel pump 521 and the amount of unburned fuel during a cold start, the characteristics of the amount of unburned fuel change during a cold start compared to a warm-up. In the example of a cold start shown in the lower part of Figure 12, the amount of unburned fuel increases as the fuel pressure increases compared to a warm-up, and an increasing trend in the amount of unburned fuel can be seen from a fuel pressure even lower than the fuel pressure 1203 at which the amount of unburned fuel is minimal during a warm-up.

[0063] Therefore, during cold-start and warm-up operation, the unburned fuel level adjustment unit 504 controls the fuel pressure of the fuel pump 521, making it possible to bring the amount of unburned fuel closer to the target value.

[0064] (Third control example) Next, a third example of controlling the amount of unburned fuel by the unburned fuel level adjustment unit 504 will be explained using Figures 13 and 14. Figure 13 shows an example of the relationship between crank angle, fuel injection signal, and unburned fuel amount in the third control example of the fourth embodiment. The graphs in the upper and lower parts of Figure 13 are the same as the graphs in the upper and lower parts of Figure 10.

[0065] As explained in Figure 12, during a cold start of the internal combustion engine 1, fuel evaporation is slower than usual, and the amount of unburned fuel is likely to be larger. Therefore, by retarding the ignition time from 1002 to 1301 (upper part of Figure 13), it is possible to secure a sufficient time for fuel evaporation and bring the amount of unburned fuel closer to the target value (lower part of Figure 13).

[0066] Figure 14 shows an example of the relationship between crank angle, fuel injection signal, unburned fuel amount, and ignition time in multi-stage injection in the third control example of the fourth embodiment. The graphs in the upper and lower parts of Figure 14 are the same as the graphs in the upper and lower parts of Figure 11.

[0067] As shown in Figure 14, in the case of multi-stage injection, it is also desirable to retard the ignition time from 1102 to 1401 (upper part of Figure 14). This allows for sufficient time for the fuel to evaporate, similar to the single fuel injection shown in Figure 13, and makes it possible to bring the amount of unburned fuel closer to the target value (lower part of Figure 14).

[0068] (Fourth control example) Next, a fourth example of controlling the amount of unburned fuel by the unburned fuel level adjustment unit 504 will be explained using Figure 15. Figure 15 shows an example of the relationship between crank angle and ignition signal, and an example of the relationship between unburned fuel level and the number of pre-ignitions, in the fourth control example of the fourth embodiment. If the amount of unburned fuel increases too much, there is a risk of misfire during combustion. If misfire occurs, the amount of THC emitted increases. As a countermeasure, a pre-ignition method is effective in which a pre-ignition signal 1502 is output, which performs multiple pre-ignitions by the ignition coil 522 during the intake stroke, as shown in ignition signal 1501, and then the main ignition signal 1503 is output (upper part of Figure 15).

[0069] For example, the number of pre-ignition cycles is varied according to the unburned fuel level based on the pre-ignition cycle curve 1504 (lower part of Figure 15), within a range up to an upper limit of 1505 cycles determined by the performance of the ignition coil 522 and energy consumption limitations. This makes it possible to generate a pre-ignition signal 1502 that includes the optimal number of pre-ignition cycles to reduce THC. In addition, since the temperature of the spark plug 105 also rises due to multiple pre-ignition cycles, it can be expected that the evaporation of fuel present around the electrode 106 of the spark plug 105 will be promoted.

[0070] On the other hand, if the unburned fuel level 516 does not fall below the permissible unburned fuel level 515, especially if no decrease in the unburned fuel level 516 is observed, then, for example, the throttle 523 can be controlled to reduce the amount of air sent to the combustion chamber 103, thereby lowering the rotational speed of the internal combustion engine 1. By lowering the rotational speed, a certain amount of already burned gas can be retained in the high-temperature combustion chamber 103, burning off HC (Hydrocarbon) and reducing PN and THC.

[0071] The first to fourth control examples of unburned fuel amount in this embodiment can be performed individually, or multiple control methods can be implemented in coordination. By implementing multiple control methods in coordination, it is possible to reduce the amount of unburned fuel or the amount of PN and THC generated while offsetting the disadvantages that result from controlling the amount of unburned fuel.

[0072] For example, as shown in Figure 12, increasing the fuel pressure increases the penetration distance of the fuel spray 301, and thus increases the amount of fuel deposited. On the other hand, when the fuel pressure is high, the fuel spray 301 becomes smaller, and even if droplets 303 are generated, they evaporate more easily, thus reducing the amount of fuel deposited. These phenomena associated with increasing fuel pressure are contradictory. Therefore, by combining controls according to the operating conditions at the time, it is possible to change the control of the amount of unburned fuel in many ways. Below, an example of a combination of two control examples is described.

[0073] (1) By increasing the fuel pressure and lengthening the penetration distance of the fuel spray 301, the fuel injection timing is retarded (injection occurs after the crown surface 101P of the piston 101 has lowered). (2) By injecting fuel (retarding the ignition timing) when the crown surface 101P of the piston 101 is lowered, the time until the fuel must complete evaporation is shortened, thus retarding the ignition timing (giving more time for evaporation).

[0074] Furthermore, the first to fourth control examples of the amount of unburned fuel described in this fourth embodiment are just examples, and the control method changes depending on the shape configuration (compression ratio) of the internal combustion engine 1.

[0075] As described above, this embodiment reduces the generation of PN and THC by appropriately controlling the injector 520 (fuel injection device), fuel pump 521, ignition coil 522 (ignition device), and throttle 523 so that the unburned fuel level adjustment unit 504 keeps the unburned fuel level below an acceptable value.

[0076] Furthermore, the control of the amount of unburned fuel in each embodiment may be performed independently for each cylinder. That is, in an internal combustion engine with multiple cylinders, the unburned fuel level adjustment unit 504 controls at least one of the injector 520, fuel pump 521, ignition coil 522 (ignition device), and throttle 523 so that the unburned fuel level 516 for each cylinder is less than or equal to the allowable unburned fuel level 515. This makes it possible to reduce the total emissions of THC and PN from the internal combustion engine with multiple cylinders.

[0077] In the embodiments described above, a gasoline engine was used as an example of an internal combustion engine, but the internal combustion engine may also be a gas engine, diesel engine, or the like.

[0078] Furthermore, the present invention is not limited to the embodiments described above, and it goes without saying that various other applications and modifications can be taken as long as they do not depart from the gist of the invention as described in the claims. For example, the embodiments described above are described in detail and specifically in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those that include all the components described. Also, it is possible to replace a part of the configuration of one embodiment with a component of another embodiment. It is also possible to add a component of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, replace, or delete other components for a part of the configuration of each embodiment.

[0079] Furthermore, some or all of the above configurations, functions, and processing units may be implemented in hardware, for example, by designing them as integrated circuits. Broadly defined processor devices such as FPGAs (Field Programmable Gate Arrays) and ASICs (Application Specific Integrated Circuits) may be used as hardware.

[0080] Furthermore, in the embodiments described above, the control lines and information lines shown are those deemed necessary for explanatory purposes, and not all control lines and information lines are necessarily shown in the actual product. In practice, it can be assumed that almost all components are interconnected. [Explanation of symbols]

[0081] 1…Internal combustion engine, 101…Piston, 101P…Crown, 102…Cylinder, 103…Combustion chamber, 105…Spark plug, 110…Ignition coil, 111…Direct injection injector, 112…Port injection injector, 210…Sensors, 220…Actuators, 301…Fuel spray, 302…Fuel film, 303…Droplet, 304…Tip wet, 305…Unburned fuel, 500, 500A, 500B…Internal combustion engine control device, 501…Combustion speed detection unit, 502, 502A, 502B…Unburned fuel level estimation unit, 503…Allowable value setting unit, 504…Unburned fuel level adjustment unit, 510…Target air-fuel ratio, 511…Load information, 512…Ignition time 513…Detection signal, 514…Combustion rate, 515…Allowable unburned fuel level, 516…Unburned fuel level, 520…Injector, 521…Fuel pump, 522…Ignition coil, 523…Throttle, 601…Unburned fuel curve, 701…EGR concentration information, 801…Unburned fuel curve, 901…Correction information

Claims

1. An internal combustion engine control device that controls an internal combustion engine equipped with a fuel injection device for injecting fuel, A combustion speed detection unit that detects the combustion speed inside the cylinder, An unburned fuel level estimation unit that estimates the level of unburned fuel in the cylinder using the combustion speed, A tolerance value setting unit that sets an allowable value for the unburned fuel level based on operating conditions or the actual fuel injection amount, The system includes an unburned fuel level adjustment unit that controls the internal combustion engine so that the unburned fuel level estimated by the unburned fuel level estimation unit is less than or equal to the allowable value. Internal combustion engine control device.

2. The unburned fuel level estimation unit receives at least the following information: combustion speed, ignition timing, load of the internal combustion engine, and target air-fuel ratio. The internal combustion engine control device according to claim 1.

3. The unburned fuel level estimation unit is further input with information on the concentration of exhaust gas recirculated to the cylinder, and the unburned fuel level estimation unit corrects the estimated result of the unburned fuel level according to the concentration of the recirculated exhaust gas. The internal combustion engine control device according to claim 2.

4. The unburned fuel level estimation unit is further input with information on the compression ratio of the internal combustion engine, and the unburned fuel level estimation unit corrects the estimated result of the unburned fuel level according to the compression ratio. The internal combustion engine control device according to claim 2.

5. The unburned fuel level estimation unit is further input with information on intake air temperature or ambient air temperature, and the unburned fuel level estimation unit corrects the estimated result of the unburned fuel level according to the intake air temperature or ambient air temperature. The internal combustion engine control device according to claim 2.

6. The unburned fuel level estimation unit has a storage unit that stores map information relating the combustion rate and the unburned fuel level. An internal combustion engine control device according to any one of claims 1 to 5.

7. The unburned fuel level estimation unit estimates the unburned fuel level by comparing the combustion speed detected by the combustion speed detection unit with information showing the relationship between the combustion speed and the unburned fuel level, which is set in advance from the ignition timing, the load of the internal combustion engine, and the target air-fuel ratio. The internal combustion engine control device according to claim 2.

8. The combustion speed detection unit receives input from at least the ignition timing, the load of the internal combustion engine, the target air-fuel ratio, and the detection result from the crank angle sensor. The internal combustion engine control device according to claim 1.

9. The permissible value for the unburned fuel level is set using the target air-fuel ratio and the load of the internal combustion engine as operating conditions. The internal combustion engine control device according to claim 1.

10. The tolerance value for the unburned fuel level is set according to the average value of the amount of fuel injected from the fuel injector over an arbitrary set time range. The internal combustion engine control device according to claim 1.

11. The unburned fuel level adjustment unit controls at least one of the fuel injector, fuel pump, ignition system, and throttle so that the unburned fuel level is below the allowable value. The internal combustion engine control device according to claim 1.

12. The aforementioned internal combustion engine is equipped with multiple cylinders, The unburned fuel level adjustment unit controls at least one of the fuel injector, fuel pump, ignition system, or throttle so that the unburned fuel level for each cylinder is below the allowable value. The internal combustion engine control device according to claim 1.

13. An internal combustion engine control method in an internal combustion engine control device that controls an internal combustion engine equipped with a fuel injection device for injecting fuel, A process to detect the combustion speed within the cylinder, A process for estimating the level of unburned fuel in the cylinder using the combustion rate, A process to set an acceptable value for the unburned fuel level based on operating conditions or the actual fuel injection amount, The process includes controlling the internal combustion engine so that the estimated level of unburned fuel is below the permissible value. Internal combustion engine control method.

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