JP2015040490A - Control device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cancel preignition effectively if the preignition occurs at a low-speed and high-load state.SOLUTION: A control device of an engine includes: a preignition detection means for detecting occurrence of preignition in a combustion chamber; and a fuel adhesion suppression means for suppressing fuel adhesion to a liner in the combustion chamber. If the preignition detection means detects the occurrence of preignition, the fuel adhesion suppression means suppresses fuel adhesion to the liner and thereby avoids preignition. The preignition detection means is a non-resonance type knock sensor and detects the occurrence of preignition by detecting oscillation larger than that of knocking. If the preignition detection means detects the occurrence of preignition, the fuel adhesion suppression means increases a temperature of an engine coolant and thereby suppresses fuel adhesion to the liner.

Description

  The present invention relates to an engine control device that suppresses the occurrence of pre-ignition.

  Conventionally, in a gasoline engine, the compression ratio is generally set to about 10 to 12. However, in recent years, development of high compression ratio engines that improve thermal efficiency and further improve fuel efficiency by further increasing the compression ratio has been underway.

  In a high compression ratio engine, as the compression ratio is set higher, and in an engine equipped with a supercharger, as the supercharging pressure is set higher, a low rotation high load region or a low rotation high supercharging region. However, a self-ignition phenomenon (hereinafter referred to as pre-ignition) that has not occurred in the prior art is likely to occur.

  Preignition is a phenomenon in which fuel burns before ignition by a spark plug.

  When pre-ignition occurs, a rapid pressure rise occurs in the combustion chamber, and the shock wave collides with the inner wall of the piston or cylinder. Due to this collision, the temperature in the cylinder further increases, and the engine cannot exhibit a predetermined performance. For this reason, it is necessary to take measures to prevent pre-ignition.

  In addition to the pre-ignition, there is knocking as a self-ignition phenomenon of fuel in the combustion chamber. Knocking is caused by spontaneous ignition of the unburned mixture (end gas) before normal combustion occurs due to the high temperature and high pressure of the mixture of fuel and air during the combustion process.

  As a technique for distinguishing whether the phenomenon occurring in the combustion chamber is pre-ignition or knocking, for example, there are those described in Patent Documents 1 and 2.

JP 2011-226473 A JP 2011-214447 A

  In the techniques described in Patent Documents 1 and 2, as measures for avoiding the occurrence of pre-ignition at the time of high rotation and high load, the richness of the air-fuel ratio, the delay of the closing timing of the intake valve, the injection timing of some fuels The retardation is performed step by step. However, there is no disclosure about pre-ignition avoidance measures at low rotation and high load.

  Accordingly, an object of the present invention is to quickly eliminate pre-ignition when pre-ignition occurs at low rotation and high load.

  In order to solve the above-described problems, the present invention includes pre-ignition detection means for detecting the occurrence of pre-ignition in the combustion chamber, and fuel adhesion suppression means for suppressing fuel adhering to the liner in the combustion chamber. When the pre-ignition detection means detects the occurrence of pre-ignition, the fuel adhesion suppressing means avoids the pre-ignition by suppressing the fuel from adhering to the liner. The device was adopted.

  In the above configuration, if a non-resonant knock sensor is used as the pre-ignition detection means, the non-resonant knock sensor detects vibration exceeding a predetermined threshold, that is, vibration exceeding the vibration level of knocking. Thus, occurrence of pre-ignition can be detected.

  If a cooling water adjusting device that controls the temperature of engine cooling water is employed as the fuel adhesion suppressing means, when the pre-ignition detecting means detects the occurrence of pre-ignition, the cooling water adjusting device By increasing the temperature of the cooling water, the adhesion of fuel to the liner can be suppressed.

  Further, if a tumble flow generating means for generating a tumble flow in the combustion chamber is employed as the fuel adhesion suppressing means, when the pre-ignition detecting means detects the occurrence of pre-ignition, the tumble flow generating means By reinforcing the internal flow, it is possible to suppress the adhesion of fuel to the liner.

  In addition, if fuel injection pressure control means for adjusting the fuel injection pressure is employed as the fuel adhesion suppression means, when the pre-ignition detection means detects the occurrence of pre-ignition, the fuel injection pressure control means By weakening the fuel injection pressure, the adhesion of fuel to the liner can be suppressed.

  If fuel injection timing control means for adjusting the fuel injection timing is adopted as the fuel adhesion suppression means, when the pre-ignition detection means detects the occurrence of pre-ignition, the fuel injection timing control means By retarding the injection timing, it is possible to suppress the adhesion of fuel to the liner.

  In this invention, when the pre-ignition detection means detects the occurrence of pre-ignition, the fuel adhesion suppressing means suppresses the fuel from adhering to the liner in the combustion chamber, so that the pre-ignition can be quickly eliminated. .

  In addition, pre-ignition at low rotation and high load is accompanied by vibration that is stronger than vibration that occurs at the time of knocking. Therefore, a non-resonant knock sensor is used as the pre-ignition detection means to detect vibration exceeding a predetermined threshold. Thus, the occurrence of pre-ignition can be promptly detected.

It is a principal part enlarged front view which shows the structure of the engine and engine control apparatus of one Embodiment of this invention. It is a flowchart which shows control of the engine of the embodiment. It is a graph which shows the generation | occurrence | production area | region of the preignition at the time of low rotation high load. It is a graph which shows the waveform of the vibration when knocking occurs. It is a graph which shows the waveform of the vibration when preignition occurs. It is a map figure of target water temperature. It is a graph of a water temperature correction value. It is a graph of water temperature correction time. It is a graph of a water temperature correction value.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. This embodiment is a control device for a four-cycle gasoline engine for automobiles. FIG. 1 shows the main part of the combustion chamber 3 in one cylinder provided in the engine and the configuration of the engine control device. In these drawings, only members and means directly related to the present invention are shown, and other members and the like are not shown.

  As shown in FIG. 1, a piston 2 is accommodated in a cylinder 1 of the engine. A combustion chamber 3 is formed by the inner wall surface of the cylinder 1 and the top surface of the piston 2. The inner wall surface of the cylinder 1 is formed by a cylindrical liner 3 a press-fitted into the cylinder 1, and smoothly slides with the piston ring on the outer periphery of the piston 2.

  In addition, the cylinder 1 is disposed with an intake port 5 that guides the air-fuel mixture to the combustion chamber 3, an exhaust port 7 that sends exhaust gas from the combustion chamber 3, and downward from the cylinder head along the cylinder axis direction of the cylinder. A spark plug 4 and the like are provided.

  Although only one cylinder 1 is shown in the drawing, the engine may be a single cylinder or a multi-cylinder having a plurality of cylinders 1.

  The intake port 5 is provided with a port injection valve 9 as a fuel injection device that injects fuel into the intake port 5. The port injection valve 9 injects fuel into the intake air in the flow path of the intake port 5 to form an air-fuel mixture. The cylinder 1 is provided with a direct injection valve 10 as an in-cylinder fuel injection device that directly injects fuel into the combustion chamber 3.

  The intake port 5 is provided with an intake valve 6 that opens and closes an opening to the combustion chamber 3. The exhaust port 7 is provided with an exhaust valve 8 that opens and closes an opening to the combustion chamber 3.

  Since these intake valve 6 and exhaust valve 8 are connected to a camshaft provided on the cylinder head side via a valve lifter, the intake port 5 and the exhaust port 7 are opened and closed at a predetermined timing by the rotation of the camshaft. . Power is transmitted to the camshaft by connecting a sprocket provided on the camshaft side and a sprocket provided on the crankshaft side by a timing chain or the like.

  The intake valve 6, exhaust valve 8, spark plug 4, port injection valve 9, direct injection valve 10 and other devices necessary for the operation of the engine are controlled by the electronic control unit 20 through cables. Controlled by means. In this embodiment, a part of the computer of the electronic control unit is used as engine control means.

  This engine includes preignition detection means s for detecting that preignition has occurred in the combustion chamber 3. In this embodiment, a non-resonant knock sensor 11 that can detect the vibration of the cylinder block is employed as the pre-ignition detection means s.

  The non-resonant knock sensor 11 is fixed to a cylinder block or the like and has a function of converting vibration into voltage by a built-in piezoelectric element. Since it is a non-resonant type, it is not limited to the vibration at the time of knocking, and can deal with a wide range of vibration frequencies and vibration levels including at the time of pre-ignition. Based on the voltage value output from the non-resonant knock sensor 11, the numerical value of the vibration level and the presence or absence of occurrence of knocking or pre-ignition can be detected and determined.

  Preignition is accompanied by a vibration that is stronger than the vibration that occurs during knocking. In particular, at low rotation and high load, the pre-ignition is accompanied by vibration that is considerably stronger than the vibration that occurs during knocking. For this reason, when the non-resonant knock sensor 11 detects a vibration exceeding a predetermined threshold, that is, the vibration level of knocking, it can be determined that the vibration is not due to knocking but due to pre-ignition. The occurrence of pre-ignition can be detected.

  The threshold value may be set to a value higher than the maximum vibration intensity that can occur during knocking. When the generated vibration exceeds the threshold value, it can be detected that the phenomenon occurring in the combustion chamber 3 is not knocking but pre-ignition.

  Whether the detected vibration is due to knocking or pre-ignition can be determined by the vibration determination means 24 provided in the electronic control unit 20. Further, this determination may be performed by the non-resonant knock sensor 11 itself.

  In addition, the engine includes fuel adhesion suppressing means that suppresses fuel adhering to the liner 3 a in the combustion chamber 3. In this embodiment, a cooling water adjusting device 12 that controls the temperature of engine cooling water is employed as the fuel adhesion suppressing means. The cooling water adjustment device 12 may be, for example, an electric thermostat that can freely control the temperature of the cooling water by adjusting the flow rate of the cooling water to the radiator, or adjust the amount of the cooling water that is sent to the radiator. By doing so, an electric water pump or the like that can freely control the temperature of the cooling water may be used.

  An adhesion suppression control means 21 for controlling the fuel adhesion suppression means is provided in the computer of the electronic control unit 20. In this embodiment, the adhesion suppression control means 21 issues an operation command to the electric thermostat, the electric water pump or the like through a cable or the like.

  The engine information acquisition means 22 provided in the electronic control unit 20 acquires information on the temperature of the cooling water necessary for control, engine speed, load information, etc. from the engine, and controls the information by the adhesion suppression control means 21. It is utilized for. Further, the engine information acquisition unit 22 acquires information from the non-resonant knock sensor 11 and the vibration determination unit 24, particularly information on whether knocking or pre-ignition has occurred.

  When the pre-ignition detection means s detects the occurrence of pre-ignition, and the engine information acquisition means 22 acquires information about the occurrence of pre-ignition, the adhesion suppression control means 21 causes the cooling water so that the temperature of the engine cooling water increases. The adjustment device 12 is controlled.

  If the temperature of the cooling water rises, the temperature of the cylinder 1 and its inner liner 3a will rise and fuel vaporization will be promoted, so that the fuel will be prevented from adhering to the liner 3a.

  If the amount of fuel adhering to the liner 3a is reduced, it is considered that oil scattering from the liner is less likely to occur, and preignition can be effectively avoided. That is, the pre-ignition that has already occurred can be quickly eliminated.

  The engine control method will be described with reference to the flowchart of FIG. 2 and the map diagrams and graphs shown in FIGS.

  As shown in FIG. 2, first, the engine speed and load are read. Reading of information is performed by the engine information acquisition means 22 of the electronic control unit 20 (see step S1 in the figure).

  Based on the read engine speed and load information, it is determined whether or not the current operating state is the pre-ignition generation region p at the time of low rotation and high load shown in the shaded portion in the upper left of FIG. The pre-ignition generation region p is a region where pre-ignition peculiar to low rotation and high load is likely to occur, and this information is stored in the electronic control unit 20 in advance. The determination is performed by the driving status determination means 23 provided in the electronic control unit 20 (see step S2 in the figure). In the case of an engine equipped with a supercharger, a region where pre-ignition peculiar to low rotation and high supercharging is likely to occur corresponds to the pre-ignition generation region p.

  If the current driving situation is not in the pre-ignition generation region p, the driving is continued as it is. If the current driving situation is in the pre-ignition generation region p, there is a high possibility that pre-ignition will occur, and the process proceeds to step S3.

  In step S3, the numerical value of the voltage or vibration output from the non-resonant knock sensor 11 as the pre-ignition detection means s (hereinafter, the output information from the pre-ignition detection means s is referred to as “knock sensor output”). It is determined whether or not it is equal to or greater than a first predetermined value (hereinafter referred to as “predetermined value 1”) which is a preset threshold value.

  When the knock sensor output is less than the predetermined value 1, it is determined that neither knocking nor pre-ignition has occurred, and the operation is continued as it is. If the knock sensor output is greater than or equal to the predetermined value 1, it is determined that knocking or pre-ignition has occurred, and the process proceeds to step S4.

  In step S4, it is determined whether or not the knock sensor output is equal to or greater than a second predetermined value (hereinafter referred to as “predetermined value 2”) which is a preset threshold value.

  If the knock sensor output is less than the predetermined value 2, it is determined that pre-ignition has not occurred and knocking has occurred, and the process proceeds to step S6. In step S6, normal knock control, such as retarding the ignition timing, that is, knock avoidance control performed during normal operation is performed. If knocking disappears, normal operation continues.

  If the output vibration value is greater than or equal to the predetermined value 2, it is determined that knocking has not occurred and pre-ignition has occurred, and the process proceeds to step S5. In step S5, pre-ignition avoidance control, that is, the following pre-ignition avoidance control is performed.

  In this embodiment, since the cooling water adjusting device 12 that controls the temperature of the engine cooling water is adopted as the fuel adhesion suppressing means, the adhesion suppressing control means 21 is used as the cooling water adjusting device 12 as preignition avoidance control. Control to reduce the amount of water passing through and raise the temperature of the cooling water. Specifically, the control is to increase the operating temperature of the electric thermostat (the lowest set temperature that allows the flow of the cooling water) or to limit the discharge amount of the electric water pump.

  As a result, the temperature of the cylinder 1 and the liner 3a in the cylinder 1 increase along with the temperature of the cooling water, and fuel vaporization is promoted. By promoting the vaporization, the fuel is suppressed from adhering to the liner 3a, and the preignition is eliminated. If pre-ignition is resolved, normal operation is continued.

  Note that the predetermined value 1 can be determined based on the magnitude of vibration generated at the time of knocking. As the predetermined value 1, for example, as shown in FIG. 4, it is possible to set the magnitude of steady vibration generated at the time of knocking, or the average value of vibration. That is, the predetermined value 1 is a numerical value that can be determined that knocking has occurred if the detected vibration is equal to or greater than the predetermined value 1.

  The predetermined value 2 can be determined based on the magnitude of vibration generated during pre-ignition. As the predetermined value 2, for example, as shown in the center of FIG. 5, a numerical value between a numerical value of vibration that occurs at the time of pre-ignition that projects higher than the vibration at the time of knocking and a maximum value of vibration that can occur at the time of knocking It can be. The protruding waveform with a large amplitude shown in the center of FIG. 5 is due to pre-ignition, and the small amplitude waveforms on both sides are due to knocking. That is, the predetermined value 2 is a numerical value that can be determined that at least pre-ignition has occurred if the detected vibration is equal to or greater than the predetermined value 2.

  Here, when controlling the water temperature with an electric thermostat or the like, the water temperature is usually set to be lower as the load becomes higher, for example, for the purpose of avoiding knocking as shown in the map diagram of FIG. The

  In this invention, as shown in FIG. 7, the temperature of the cooling water is set to be higher as the knock sensor output becomes larger, that is, as the pre-ignition degree becomes larger. The vertical axis | shaft of FIG. 7 shows the numerical value of the set water temperature, ie, a water temperature correction value. The horizontal axis is “knock sensor output−predetermined value 1”, but may be “knock sensor output−predetermined value 2”. As shown in the graph, since the water temperature that can be set naturally has an upper limit, even if the knock sensor output becomes larger than a certain value, the temperature rise is limited at a certain upper limit temperature.

  FIG. 8 is a map of the water temperature rise time correction. The vertical axis in FIG. 8 indicates the set duration of the water temperature correction, that is, the water temperature correction time. The point that the horizontal axis is “knock sensor output−predetermined value 1” is the same. The water temperature correction time, that is, the time to increase the water temperature is normally about several tens of seconds. Therefore, the longer the knock sensor output, that is, the greater the preignition level, the longer the water temperature correction time is set. .

  FIG. 9 shows a change in the water temperature after the water temperature correction is continued, that is, after the water temperature rise time has ended. The vertical axis | shaft of FIG. 9 shows the numerical value of the set water temperature, ie, a water temperature correction value. The horizontal axis is the elapsed time. As shown in the graph, when the water temperature rise time is over, the water temperature is gradually returned to the normal target water temperature.

  In the above embodiment, the cooling water adjusting device 12 that controls the temperature of the cooling water of the engine is employed as the fuel adhesion suppressing means. However, the fuel adhesion suppressing means has a function of suppressing the adhesion of fuel to the liner 3a. The following means may be adopted.

  For example, a tumble flow generating means for generating a tumble flow that is a swirling flow in the vertical direction connecting the cylinder head side and the crankshaft side may be adopted as the fuel adhesion suppressing means in the combustion chamber 3.

  The tumble flow generating means may be, for example, a tumble control valve that is provided at the opening of the intake port 5 to the combustion chamber 3 and guides the air flow from the intake port 5 to the combustion chamber 3 toward the crankshaft. Good. The tumble control valve opens and closes an intake passage provided in a portion of the intake port 5 other than the opening to the combustion chamber 3, and is tumbled into the combustion chamber 3 by an airflow introduced from the intake passage. It may generate a flow. The adhesion suppression control means 21 of the electronic control unit 20 can issue an operation command to the tumble control valve through a cable or the like.

  When the pre-ignition detecting means s detects the occurrence of pre-ignition, the tumble flow generating means enhances the in-cylinder flow by generating a tumble flow in the combustion chamber 3. By enhancing the in-cylinder flow, the adhesion of fuel to the liner 3a can be suppressed.

  Further, fuel injection pressure control means for adjusting the fuel injection pressure may be employed as the fuel adhesion suppressing means. The fuel injection pressure control means may adjust the injection amount of the port injection valve 9 but desirably controls the direct injection valve 10 that directly injects fuel into the combustion chamber 3.

  When the pre-ignition detection means s detects the occurrence of pre-ignition, the fuel injection pressure control means weakens the fuel injection pressure. As a result, the penetrating force that the fuel tries to go straight by the initial speed at the time of injection is reduced, and the adhesion of fuel to the liner 3a can be suppressed.

  Further, a fuel injection timing control means for adjusting the fuel injection timing may be employed as the fuel adhesion suppressing means. Similarly, the fuel injection timing control means may adjust the injection timing of the port injection valve 9 but preferably controls the direct injection valve 10.

  When the pre-ignition detection means s detects the occurrence of pre-ignition, the fuel injection timing control means can suppress the fuel from adhering to the liner 3a by retarding the fuel injection timing. This is because by delaying the fuel injection timing, the fuel that hits the top surface of the piston 2 increases and the fuel that hits the liner 3a decreases.

  In this embodiment, a vibration sensor, particularly a non-resonant knock sensor, is used as the pre-ignition detection means s. However, other vibration sensors that can detect vibration during pre-ignition may be used. Further, instead of the vibration sensor, an in-cylinder pressure sensor that can detect the pressure in the combustion chamber 3, an ion current sensor that can detect the occurrence of flame in the combustion chamber 3, or the like may be used.

  In the prior art disclosed in Patent Documents 1 and 2, the ignition timing is used when the maximum value of the vibration intensity generated in the cylinder exceeds a predetermined threshold value using an in-cylinder pressure sensor or a vibration sensor. The pre-ignition and the knocking are distinguished depending on whether or not the vibration intensity is reduced by the retardation.

  In addition to the in-cylinder pressure sensor and vibration sensor, the above conventional technology uses an ion current sensor that detects a flame generated by the combustion of fuel, which is different from that at the time of normal combustion or occurrence of knocking. The timing of flame occurrence was detected, and preignition and knocking were distinguished.

  According to the present invention, since the non-resonant knock sensor 11 is employed as the pre-ignition detection means s, pre-ignition and knocking can be instantaneously distinguished during low speed and high load operation. In other words, smooth and speedy control is possible compared to the above-described technique in which the reaction is differentiated after waiting for the reaction after the ignition timing is retarded.

  Further, if a non-resonant type knock sensor is used as the pre-ignition detection means s, the detection of knocking and the detection of pre-ignition can be performed by the same sensor. For this reason, compared with the said technique which used the ion current sensor separately from the cylinder pressure sensor and the vibration sensor, the simplification and cost reduction of an apparatus are possible.

1 Cylinder 2 Piston 3 Combustion chamber 4 Spark plug 5 Intake port 6 Intake valve 7 Exhaust port 8 Exhaust valve 9 Fuel injection device (port injection valve)
10 In-cylinder fuel injection device (direct injection valve)
11 Non-resonant knock sensor 12 Cooling water adjusting device 20 Electronic control unit (Electronic Control Unit)
21 Adhesion suppression control means 22 Engine information acquisition means 23 Operating condition discrimination means 24 Vibration discrimination means s Pre-ignition detection means

Claims (8)

Pre-ignition detection means for detecting that pre-ignition has occurred in the combustion chamber;
Fuel adhesion suppressing means for suppressing fuel adhering to the liner in the combustion chamber,
When the pre-ignition detection unit detects the occurrence of pre-ignition, the fuel adhesion suppressing unit avoids the pre-ignition by suppressing the fuel from adhering to the liner. . The pre-ignition detection means is a non-resonant knock sensor;
The engine control device according to claim 1, wherein the non-resonant knock sensor detects the occurrence of pre-ignition by detecting vibration exceeding a predetermined threshold value. The fuel adhesion suppression means is a coolant adjustment device that controls the temperature of engine coolant.
When the pre-ignition detection means detects the occurrence of pre-ignition, the cooling water adjusting device suppresses the adhesion of fuel to the liner by increasing the temperature of engine cooling water. Item 3. The engine control device according to Item 1 or 2.   The engine control device according to claim 3, wherein the cooling water adjusting device is set such that the temperature of the cooling water increases as the degree of pre-ignition increases.   5. The engine control device according to claim 3, wherein the cooling water adjusting device is set so that the time for increasing the temperature of the cooling water becomes longer as the degree of pre-ignition becomes larger.   The fuel adhesion suppressing means is a tumble flow generating means for generating a tumble flow in the combustion chamber. When the pre-ignition detecting means detects the occurrence of pre-ignition, the tumble flow generating means enhances in-cylinder flow. The engine control apparatus according to claim 1, wherein adhesion of fuel to the liner is suppressed.   The fuel adhesion suppressing means is a fuel injection pressure control means for adjusting a fuel injection pressure, and when the pre-ignition detection means detects the occurrence of pre-ignition, the fuel injection pressure control means 3. The engine control device according to claim 1, wherein adhesion of fuel to the liner is suppressed by weakening the pressure. 4.   The fuel adhesion suppressing means is a fuel injection timing control means for adjusting the fuel injection timing, and when the preignition detection means detects the occurrence of preignition, the fuel injection timing control means 3. The engine control device according to claim 1, wherein fuel is prevented from adhering to the liner by retarding the angle.

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