JP5262857B2 - In-cylinder direct injection engine controller - Google Patents

Description

  The present invention relates to a control device for an in-cylinder direct injection engine, and particularly to a device for avoiding preignition in a low rotational speed range.

  When regular fuel is used in a high-octane fuel engine, the idle rotation speed is increased when using regular fuel compared to when using high-octane fuel to avoid pre-ignition that occurs when the accelerator pedal is suddenly depressed from the low speed range. By setting the accelerator opening upper limit limiter value to limit the accelerator opening, the auto ignition reaction time is shortened and the volumetric efficiency is reduced when the rotational speed is increased. There is one that avoids pre-ignition that occurs when the accelerator pedal is suddenly depressed (see Patent Document 1).

JP-A-11-182300

  By the way, although it is for pre-ignition avoidance, if the accelerator opening upper limit limiter is set smaller than when using high-octane fuel when using regular fuel, even if the accelerator pedal is depressed from the low speed range, the regular When using fuel, the throttle valve opens more poorly than when using high-octane fuel, resulting in poor operability.

  Therefore, an object of the present invention is to provide an apparatus that can perform pre-ignition avoidance control so that a decrease in engine torque associated with pre-ignition avoidance control is reduced.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

The present invention provides a direct injection in a cylinder provided with a fuel injection valve (21) for directly injecting fuel into a combustion chamber (5) and an ignition plug (14) for igniting an air-fuel mixture formed in the combustion chamber (5). Determination means (42) for determining which of the plurality of cases where the degree of occurrence of pre-ignition is different based on the octane number of the fuel, the environmental conditions, and the operating conditions in the low rotational speed region And a pre-ignition avoidance control means (43) for performing pre-ignition avoidance control so that a decrease in engine torque associated with the pre-ignition avoidance control is reduced in each case, a plurality of cases where the degree of occurrence of the pre-ignition differs, When the octane number is relatively low, when the octane number is relatively high, when the intake air temperature is relatively high, when the water temperature is relatively high Wherein said determination means first determines if the octane number is relatively low.

According to the present invention, in a control apparatus for an in-cylinder direct injection engine that includes a fuel injection valve that directly injects fuel into a cylinder and an ignition plug that ignites an air-fuel mixture formed in a combustion chamber, In this case, it is determined whether the preignition occurrence level is different based on the octane number of the fuel, the environmental conditions, and the operating conditions, and the engine torque reduction associated with the preignition avoidance control is reduced every time the determination is made. In the case where the pre-ignition avoidance control is performed as described above, and when the octane number is relatively low, when the octane number is relatively low, when the octane number is relatively high, when the intake air temperature is relatively high, includes a case where the water temperature is relatively high, the determination means, so first determines if the octane number is relatively low, plague The engine torque drop allowance due to cushion avoidance control can be reduced than in conventional apparatus.

  In addition, since the cases are divided into a plurality of cases where the degree of occurrence of pre-ignition is different, it is possible to perform optimal pre-ignition avoidance control according to each case, and to accurately perform pre-ignition avoidance control. it can.

  Moreover, since it is based on an octane number, environmental conditions, and driving conditions, it is possible to cover almost all cases where pre-ignition tends to occur in a low rotational speed range, and pre-ignition avoidance performance can be improved.

  Furthermore, since the conventional device only determines whether the fuel is a high-octane fuel or a regular fuel, a fuel with an octane number intermediate between the octane number of the high-octane fuel and the regular fuel octane number (intermediate fuel) is used. Although the pre-ignition could not be avoided completely in the low rotation speed range, according to the present invention, the pre-ignition avoidance control is performed based on the octane number, so the low rotation speed range when the intermediate fuel is used. But you can avoid pre-ignition.

It is a schematic block diagram of the control apparatus of the direct injection type engine of 1st Embodiment of this invention. It is a schematic diagram of an engine body. It is the schematic which showed the function of preignition avoidance control with the block. It is a characteristic view which shows the relationship between intake temperature and water temperature, and fuel injection timing. FIG. 6 is a characteristic diagram showing the relationship between intake air temperature / water temperature, intake valve operating angle, and valve lift amount. It is a characteristic view which shows the relationship between intake temperature and water temperature, and intake valve closing timing. It is a characteristic view which shows the relationship between fuel injection timing and ignition timing. It is a characteristic view which shows the relationship between a fuel injection timing and a fuel pressure. It is a flowchart for demonstrating selection and pre-ignition avoidance control method selection. It is the schematic for demonstrating the low octane number time control method. It is the schematic for demonstrating the high octane number time control method. It is the schematic for demonstrating the control method at the time of high intake air temperature. It is the schematic for demonstrating the control method at the time of high water temperature. It is an engine torque characteristic figure for demonstrating the effect of this embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of an in-cylinder direct injection engine control device according to an embodiment of the present invention, and FIG. 2 is a schematic diagram of an engine body. The fuel injection valve 21 is not attached to the intake manifold 3 as shown in FIG. 1, but is attached to the combustion chamber 5 as shown in FIG. Further, the spark plug 14 is not attached to the center of the ceiling of the combustion chamber as shown in FIG. 1, and the fuel injection valve 21 is attached to the ceiling of the combustion chamber as shown in FIG. The spark plug 14 is attached with a slight inclination to a position slightly away from the center position of the ceiling.

  In FIG. 1, air is metered by a throttle valve 23 upstream of the intake collector 2 and supplied to the combustion chamber 5 of the engine 1. As shown in FIG. 2, the fuel is injected from the fuel injection valve 21 (fuel supply means) into the combustion chamber 5 at a predetermined time. The fuel spray from the fuel injection valve 21 forms an air-fuel mixture while being vaporized in the combustion chamber 5, and the gas in the combustion chamber 5 is compressed by the piston 6 after the intake valve 15 is closed. Then, combustion is performed by ignition by the spark plug 14, and the burned gas exits to the exhaust passage 8 when the exhaust valve 16 is opened and is purified by the three-way catalysts 9 and 10 in the exhaust passage 8.

  The throttle valve 23 is driven by a throttle motor 24. Since the torque required by the driver appears in the amount of depression of the accelerator pedal 41 (accelerator opening), the engine controller 31 determines a target torque based on a signal from the accelerator sensor 42, and a target air for realizing this target torque. The amount is determined, and the opening degree of the intake throttle valve 23 is controlled via the throttle motor 24 so that this target air amount is obtained.

  The engine 1 includes a variable valve mechanism (hereinafter referred to as a “VEL mechanism”) 26 configured by a multi-node link mechanism that continuously and variably controls the valve lift amount and the operating angle of the intake valve 15, and the crankshaft 7. And a variable valve timing mechanism (hereinafter referred to as “an intake valve closing timing or an intake valve opening timing”) that continuously and variably controls the rotational phase difference between the intake valve camshaft 25 and the intake valve camshaft 25. VTC mechanism ”) 27. By using the VEL mechanism 26 and the VTC mechanism 27, the valve lift amount and the operating angle of the intake valve 15 and the opening timing IVO and closing timing IVC of the intake valve 15 can be arbitrarily controlled.

  An intake air amount signal from the air flow meter 32, a crank angle signal from the crank angle sensor 33, a cam angle signal from the cam angle sensor 34, a cooling water temperature signal from the water temperature sensor 37, an air-fuel ratio sensor upstream of the catalyst. In an engine controller 31 to which an air-fuel ratio signal from 35 and an oxygen concentration signal from an oxygen concentration sensor (not shown) on the downstream side of the catalyst are input, the fuel injection from the fuel injection valve 21 and the ignition timing by the spark plug 14 are detected. To control. Specifically, in the fuel injection control, the fuel injection amount from the fuel injection valve 21 is controlled so that the air-fuel ratio of the exhaust gas flowing through the three-way catalysts 9 and 10 is within a window centered on the stoichiometric air-fuel ratio. Further, the engine controller 31 performs VEL so as to obtain the valve timing of the intake valve 15 (the intake valve opening timing IVO and the intake valve closing timing IVC), the operating angle of the intake valve 15 and the valve lift amount according to the operating conditions. When the mechanism 26 (operating angle / lift amount varying mechanism) and the VTC mechanism 27 (lift center angle phase varying mechanism) are controlled (normally controlled) and the low rotational speed region, which is an operating condition in which pre-ignition tends to occur, becomes VEL The mechanism 26 and the VTC mechanism 27 are used to perform preignition avoidance control, which will be described later, in preference to the normal control.

  Now, it is known that pre-ignition occurs in a low rotation speed region. The pre-ignition is called pre-ignition, and is a phenomenon (auto-ignition reaction phenomenon) in which the air-fuel mixture in the combustion chamber 5 becomes thermally hot before being ignited by the spark plug 14. Here, before ignition by the spark plug 14, the mixture in the combustion chamber 5 may be ignited by touching a portion where the mixture is thermally high (for example, a spark plug having a high temperature). Since it is not ignition, it is not the preignition handled by the present invention. Combustion due to pre-ignition, unlike a flame generated by ignition by the spark plug 14, is abrupt and generates abnormal noise, which may deteriorate the durability of the engine.

  The conditions under which pre-ignition occurs can be divided into the fuel properties, environmental conditions, and operating conditions of the fuel used, and are summarized as follows.

  <1> For low-octane fuel: There is a relationship between octane number and self-ignitability, and self-ignition is easier when the octane number is low.

<2> When the temperature (intake air temperature, water temperature) is high:
<3> When the temperature in the combustion chamber 5 is high (the compression temperature is high):
<4> When the amount of intake air is large:
<5> When the time during which the fuel is exposed to a high temperature (heat receiving time) is long: Specifically, the heat receiving time is longer in the low rotational speed region than in the high rotational speed region.

  Now, paying attention to the above <1>, pre-ignition that occurs when the accelerator pedal suddenly depresses from the low speed range when regular fuel (low octane fuel) is used in a high-octane fuel (high octane fuel) engine. In order to avoid this, there is a conventional device that mainly performs torque cut control such as controlling the throttle valve 23 to the closed side and reducing the engine torque when using regular fuel, rather than using high-octane fuel. Then, drivability deteriorates due to a decrease in engine torque. That is, the compensation for the engine torque drop is insufficient with the conventional device. In addition, when an octane fuel (intermediate fuel) between the octane number of high-octane fuel and the regular fuel is used, preignition cannot be completely avoided.

  Accordingly, the present invention focuses on both <1> and <2> above, and is any of a plurality of cases in which the degree of pre-ignition occurrence differs in the low rotational speed range based on the octane number of fuel, environmental conditions, and operating conditions. The pre-ignition avoidance control is performed so that the decrease in engine torque associated with the pre-ignition avoidance control is reduced every time it is determined.

  FIG. 3 is a schematic diagram showing the function of pre-ignition avoidance control performed by the engine controller 31 as a block. The octane number estimation block 41, the determination / pre-ignition avoidance control method selection block 42 (determination means), and the pre-ignition avoidance control block 43. (Pre-ignition avoidance control means).

  In the octane number estimation block 41, the octane number of the fuel being used is estimated based on the engine speed, the charging efficiency, the water temperature, the intake air temperature, the equivalence ratio, the knock signal, the fuel pressure, and the fuel injection timing. A known method (for example, see Japanese Patent Application Laid-Open No. 2005-315097) may be used for estimating the octane number. In the present embodiment, eight parameters are used for estimating the octane number, but this is not a limitation.

  A known method (for example, see Japanese Patent Application Laid-Open No. 2006-83804) may be used to calculate the charging efficiency among the eight parameters. The target equivalent ratio TFBYA is used as the equivalent ratio. The target equivalent ratio TFBYA is a value that determines the control air-fuel ratio, and is 1.0 when operating at the stoichiometric air-fuel ratio. Further, at the cold start, the air-fuel ratio becomes larger than 1.0 and is richer than the stoichiometric air-fuel ratio.

  The fuel injection timing is a fuel injection timing when homogeneous combustion is performed. In-cylinder direct injection engines can switch between stratified combustion and homogeneous combustion, and compression stroke injection is performed during stratified combustion and intake stroke injection is performed during homogeneous combustion, but the combustion targeted by the present invention is homogeneous. Therefore, the fuel injection timing is the fuel injection timing during homogeneous combustion. This is because pre-ignition occurs in a low rotational speed region during homogeneous combustion. However, it is not limited to intake stroke injection. Even when compression stroke injection is performed in an in-cylinder direct injection engine, pre-ignition can occur when compression stroke injection is performed in a plurality of times (divided injection is performed), and therefore, the present invention is applicable. Assume that the fuel injection timing is predetermined.

  The knock signal is a signal from the knock sensor 36. The engine speed is detected by a crank angle sensor 33 and a cam angle sensor 34, the water temperature is detected by a water temperature sensor 37, the intake air temperature is detected by an intake air temperature sensor (not shown), and the fuel pressure is detected by a fuel pressure sensor (not shown). The intake air temperature sensor is attached to the position of the air flow meter 32. The fuel in the fuel tank is pumped to the fuel injection valve 21 by the high-pressure fuel pump 22, and the fuel pressure sensor is attached to the fuel supply passage downstream of the high-pressure fuel pump 22.

  In the determination / pre-ignition avoidance control method selection block 42, the degree of pre-ignition differs based on the octane number estimated by the octane number estimation block 41, the water temperature detected by the water temperature sensor 37, and the intake air temperature detected by the intake air temperature sensor. It is determined which of a plurality of cases. Specifically, when the octane number is low (when the octane number is relatively low), when the octane number is high (when the octane number is relatively high), when the intake air temperature is high (when the intake air temperature is relatively high), when the water temperature is high ( It is determined whether the water temperature is relatively high), and the pre-ignition avoidance control method is selected according to the determination result. Here, there are four preignition avoidance control methods. The determination of any of a plurality of cases where the degree of occurrence of pre-ignition is different and the selection of a specific pre-ignition avoidance control method according to the determination result will be described later with reference to the flow of FIG.

  The pre-ignition avoidance control block 43 to which the selection result in the determination / pre-ignition avoidance control method selection block 42 and the octane number, the engine rotation speed, the charging efficiency, the water temperature, the intake air temperature, the equivalence ratio, and the fuel pressure are input are input to the fuel injection timing. (It is abbreviated as “IT” in the figure.) The control and fuel pressure control block 44, the valve timing control block 45, the throttle control block 46, and the ignition timing control block 47, and the fuel injection timing control and fuel pressure control block 44 The fuel injection timing and fuel pressure, the valve timing control block 45, the operating angle and valve lift amount of the intake valve 15 and the closing timing of the intake valve 15, the throttle control block 46 the opening of the throttle valve 23, and the ignition timing control block In 47, the ignition timing is controlled. Here, the fuel injection timing control and the control performed by the fuel pressure control block 44, the valve timing control block 45, and the ignition timing control block 47 are basically open loop control, but only the throttle control block 46 can be feedback controlled. Since this is possible, a feedback control system is configured.

  As described above, six control items for avoiding pre-ignition are fuel injection timing, fuel pressure, intake valve 15 operating angle and valve lift, intake valve 15 closing timing, throttle valve opening, and ignition timing. The selection is based on the characteristics shown in FIGS. Among these, FIGS. 4 to 6 show a method for avoiding pre-ignition in a low rotational speed region, and FIGS. 7 and 8 show methods for compensating for the engine torque that has been lowered to avoid pre-ignition. These will be described in order.

  FIG. 4 shows the relationship between the intake air temperature / water temperature and the fuel injection timing. In the present invention, basically, the pre-ignition is avoided by retarding the fuel injection timing. The reason for retarding the fuel injection timing as the temperature rises to avoid pre-ignition is that if the fuel injection timing is retarded, the time from the fuel injection timing to the ignition timing (that is, the heat receiving time) can be shortened. This is because the mixing of the fuel spray and the air can be prevented from proceeding, thereby avoiding pre-ignition.

  FIG. 5 shows the relationship between the intake air temperature / water temperature, the operating angle of the intake valve 15, and the valve lift. The reason for increasing the operating angle and the valve lift amount of the intake valve 15 as the temperature rises in order to avoid pre-ignition is that if the operating angle and the valve lift amount of the intake valve 15 are increased, the amount of fresh air increases and the combustion chamber 5 This is because the pre-ignition can be avoided. Further, since the intake valve closing timing is retarded by the increase of the operating angle of the intake valve 15 and the valve lift amount and the effective compression ratio is lowered, this also avoids preignition.

  FIG. 6 shows the relationship between the intake air temperature / water temperature and the intake valve closing timing IVC. The reason why the intake valve closing timing IVC is moved away from the bottom dead center as the temperature rises to avoid pre-ignition is that when the intake valve closing timing IVC is moved away from the bottom dead center, the effective compression ratio is lowered and the compression temperature is lowered. This is because preignition can be avoided. As a method of moving the intake valve closing timing IVC away from the bottom dead center, there are a method of moving it to the advance side and a method of moving it to the retard side.

  FIG. 7 shows the relationship between the fuel injection timing and the ignition timing. If the fuel injection timing is retarded in order to avoid pre-ignition, the engine torque will be lower than the state in which the fuel is not retarded. The reason why the ignition timing is advanced as the fuel injection timing is retarded in order to compensate for the torque reduction accompanying the retard of the fuel injection timing is that the combustion speed is increased by the ignition advance and the engine torque is increased.

  FIG. 8 shows the relationship between fuel injection timing and fuel pressure. The reason why the fuel pressure is increased (increased) as the fuel injection timing is retarded is to improve the deterioration of combustion due to the retard of the fuel injection timing. That is, when the fuel injection timing is retarded, the time for mixing the fuel spray and air is shortened, and the combustion state is deteriorated. If the fuel pressure is increased at this time, atomization of the fuel spray is promoted, and the gas flow is generated in the combustion chamber 5 by the fuel spray, so that combustion is facilitated (the combustion state is improved). From this, it is considered that the retarding of the fuel injection timing and the increase of the fuel pressure should be executed at the same time. Therefore, the fuel injection timing control and the fuel pressure control are configured by one block 44 as shown in FIG. Yes.

  FIG. 9 is a flowchart showing the contents performed in the determination / pre-ignition avoidance control method selection block 42 of FIG. This flow is executed only in the low rotation speed range, which is an operating condition in which pre-ignition tends to occur. The engine speed Ne is compared with a predetermined value N1, and if the engine speed Ne is equal to or less than the predetermined value N1, it is determined that the engine speed is in the low speed range. The predetermined value N1 is determined in advance by adaptation.

  In FIG. 9, in step 1, the octane number (estimated by the octane number estimation block 41) and the predetermined value A are compared. The predetermined value A is a value that determines whether or not the octane number is low. Since the octane number of commercially available fuel (gasoline) is generally about 92 to 100, about 95 is set here. Of course, it is not limited to this case. If the octane number is equal to or less than the predetermined value A, it is determined that the low octane number is reached, and the process proceeds to step 4 to select a low octane time control method.

  When the octane number exceeds the predetermined value A, it is determined that the octane number is not low, that is, when the octane number is high, and the process proceeds to Steps 2 and 3 where the intake air temperature detected by the intake air temperature sensor and the predetermined value B are The water temperature detected at 37 is compared with a predetermined value C. The predetermined value B is a value that determines whether or not the intake air temperature is high (specifically, the intake air temperature as in summer in the city), and is about 70 ° C., for example. On the other hand, the predetermined value C is a value that determines whether or not the water temperature is high (specifically, the water temperature just before overheating), and is about 100 ° C., for example.

  If the intake air temperature exceeds the predetermined value B in step 2, it is determined that the intake air temperature is high, and the process proceeds to step 6 to select the high intake air temperature control method. In steps 2 and 3, if the intake air temperature is equal to or lower than the predetermined value B and the water temperature exceeds the predetermined value C, it is determined that the water temperature is high, and the process proceeds to step 7 to select the high water temperature control method.

  If the intake air temperature is equal to or lower than the predetermined value B and the water temperature is equal to or lower than the predetermined value C in Steps 2 and 3, the process proceeds to Step 5 to select the high octane time control method.

  The flow of FIG. 9 is repeatedly executed at regular intervals (for example, every 10 msec) in the low rotation speed region. Assuming that the octane number and intake air temperature (environmental conditions) of the fuel used do not change during a single engine operation, low engine speeds during engine operation after refueling with low-octane fuel (regular fuel or intermediate fuel) The low octane control method is selected in the speed range. In addition, if the engine is operating with high octane fuel (high-octane fuel) at a high intake temperature such as in the summer in the city, the control method at the time of high intake temperature is selected in the low rotation speed range. In addition, if the high load operation is continued in the state of high intake air temperature as in the summer in the city, the high water temperature state will eventually be reached, and then the high water temperature control method is selected when returning to the low rotation speed range. . If none of the above three is selected, the control method with a high octane number is selected in the low rotational speed range.

  The octane number represents the fuel properties, the intake air temperature represents the environmental conditions, and the water temperature represents the operating conditions. It is intended to cover all cases where pre-ignition occurs in a low rotation speed range to determine which of the plurality of cases has different degrees of pre-ignition occurrence based on these. However, if the number of cases is increased too much, the preignition avoidance control becomes complicated. Therefore, here, four cases that are considered to be appropriate are divided.

  The reason why the low octane number is first determined is that the case where there are a lot of control target items for pre-ignition avoidance first. That is, the control object at the time of the low octane number includes the operating angle and valve lift amount of the intake valve 15 and the closing timing of the intake valve, and the VEL mechanism 26 and the VTC mechanism 27 give a command value (target value) from the engine controller 31. Since there is a response delay until the actual value coincides with the command value (target value) after the operation is started, pre-ignition will occur unless the mechanism 26, 27 is given the command value early to operate. Because.

  On the other hand, when the high intake air temperature is compared with the high water temperature, the frequency of the high intake air temperature is high, so it is determined whether the intake air temperature is the second highest. Although there are many items to be controlled at the time of high water temperature as well as at the time of low octane number, it seems that the frequency of high water temperature is low, so it is determined last.

  Next, preignition avoidance control performed by the preignition avoidance control block 43 in the low rotation speed range according to each control method selected in FIG. 9 will be described with reference to FIGS. 10 to 13.

  10 is a low octane number, FIG. 11 is a high octane number, FIG. 12 is a high intake air temperature, FIG. 13 is a fuel injection timing control / fuel pressure control block 44 and valve timing control that constitute a pre-ignition avoidance control block 43 at a high water temperature. The block 45, the throttle control block 46, and the ignition timing control block 47 show how the controlled objects are controlled.

  As shown in FIG. 10, at the time of low octane number, the fuel injection timing control and fuel pressure control block 44 corrects the fuel injection timing IT to the retarding side to avoid preignition, and corrects the fuel injection timing IT to the retard side. Compensate for the accompanying deterioration of combustion by correcting the fuel pressure to the higher side. Preignition is likely to occur when the octane number is low (the degree of preignition is large). In order to lower the compression temperature in the combustion chamber 5, the valve timing control block 45 sets the operating angle and valve lift amount of the intake valve 15. The amount of fresh air in the combustion chamber 5 is increased by correcting to the enlargement side, thereby cooling the inside of the combustion chamber 5 with a large amount of fresh air. In order to lower the actual compression ratio, the valve timing control block 45 corrects (optimizes) the intake valve closing timing IVC away from the bottom dead center to lower the effective compression ratio.

  The deterioration of the combustion state due to the retard side correction of the fuel injection timing IT is compensated for by the fuel pressure up side correction, while the engine torque decreases with the retard side correction of the fuel injection timing IT. Therefore, in order to compensate for the decrease in the engine torque, the ignition timing control block 47 corrects the ignition timing to be advanced according to the retard side correction of the fuel injection timing, and increases the engine torque. Even if the preignition avoidance control is performed by performing the retard side correction of the fuel injection timing IT, the expansion side correction of the operating angle and valve lift amount of the intake valve 15, and the optimization of the intake valve closing timing IVC. When pre-ignition occurs, the pre-ignition is avoided by correcting the throttle valve opening to the closed side by the throttle control block 46. That is, whether or not pre-ignition actually occurs is detected or predicted, and when it is detected or predicted that pre-ignition actually occurs, the throttle valve opening is corrected to the closed side. A method for detecting or predicting whether or not pre-ignition actually occurs is known (see JP-A-2002-339780).

  If the operation when pre-ignition avoidance is not considered is “normal operation”, the optimal target fuel injection timing, target fuel pressure, target operating angle and target valve lift of the intake valve 15, and target intake valve closing during normal operation The timing and the target ignition timing are basically determined in advance using the engine speed and the charging efficiency (corresponding to the engine load) as parameters. For example, when the fuel pressure is increased more than necessary, the driving loss of the high-pressure fuel pump 22 increases and the fuel consumption deteriorates. Therefore, when preignition avoidance is not considered so that a good combustion state can be normally obtained within a range where the fuel consumption does not deteriorate. The target fuel pressure is determined. In “normal operation”, the engine is controlled using the target fuel injection timing, the target fuel pressure, the target operating angle and target valve lift of the intake valve 15, the target intake valve closing timing, and the target ignition timing even in a low rotational speed range. In the present invention, preignition avoidance control is added on the premise that such control during “normal operation” (basic control) is performed. Therefore, as preignition avoidance control, “control during normal operation” is used. The target fuel injection timing, target fuel pressure, intake valve target operating angle and target valve lift amount, target intake valve closing timing and target ignition timing used are corrected as described above to avoid preignition.

  On the other hand, as shown in FIG. 11, preignition is less likely to occur when the octane number is high (the degree of occurrence of preignition is small), so that the fuel injection timing control and fuel pressure control block 44 is on the side of retarding the fuel injection timing IT. By correcting and reducing the heat receiving time of the air-fuel mixture in the combustion chamber 5 (preventing self-ignition), the pre-ignition can be avoided by utilizing the effect of fuel cooling by injecting the fuel at a later timing in the compression process, that is, immediately before ignition. At the same time, the combustion deterioration due to the retard side correction of the fuel injection timing IT is compensated by correcting the fuel pressure to the side that increases the fuel pressure. In other words, the fuel injection at the time of high octane number is compression stroke injection, but this is not for causing stratified combustion, but only for accidental compression stroke injection to avoid preignition. The valve timing control block 45 does not correct the operating angle and valve lift amount of the intake valve 15 and the intake valve closing timing.

  Since the engine torque decreases with the correction of the retarded side of the fuel injection timing IT until just before ignition, the ignition timing control block 47 advances the ignition timing according to the correction of the retarded side of the fuel injection timing in order to compensate for the engine torque decrease. Compensate to the angle side and increase the engine torque. Even if the preignition avoidance control is performed by the retard side correction of the fuel injection timing IT, when preignition occurs, the throttle valve opening is corrected to the close side by the throttle control block 46 as in the case of the low octane number described above. To avoid pre-ignition.

  Next, when the intake air temperature is high, it is considered that the degree of pre-ignition is an intermediate level that is neither large nor small. Since it is not expected to cool the combustion chamber 5 with fresh air at a high intake air temperature, as shown in FIG. 12, the fuel injection timing control and the fuel pressure control block 44 corrects the fuel injection timing IT to the retard side. The valve timing control block 45 corrects (optimizes) the intake valve closing timing IVC away from the bottom dead center, and avoids preignition by lowering the compression temperature.

  The engine torque decreases with the correction of the retarded side of the fuel injection timing IT, so that the ignition timing control block 47 advances the ignition timing in accordance with the correction of the retarded side of the fuel injection timing in order to compensate for the decrease in the engine torque. Correct and increase engine torque. Even if preignition avoidance control is performed by correcting the retard side of the fuel injection timing IT and optimizing the intake valve closing timing IVC, when preignition occurs, the throttle control block 46 controls the throttle as in the case of the low octane number described above. Preignition is avoided by correcting the valve opening to the closed side.

  Next, since the temperature in the combustion chamber 5 is high when the water temperature is high, pre-ignition is likely to occur (the degree of pre-ignition is large) as in the case of the low octane number. Therefore, the same control as in the low octane number is performed. That is, as shown in FIG. 13, the fuel injection timing control and fuel pressure control block 44 corrects the fuel injection timing IT to the retard side to avoid preignition, and the combustion accompanying the retard side correction of the fuel injection timing IT. The deterioration is compensated by correcting the fuel pressure side. Furthermore, in order to lower the compression temperature in the combustion chamber 5, the valve timing control block 45 corrects the operating angle of the intake valve 15 and the valve lift to increase the amount of fresh air in the combustion chamber 5. As a result, the combustion chamber 5 is cooled with a large amount of fresh air. In order to lower the actual compression ratio, the valve timing control block 45 corrects (optimizes) the intake valve closing timing IVC away from the bottom dead center to lower the effective compression ratio.

  The engine torque decreases with the correction of the retarded side of the fuel injection timing IT, so that the ignition timing control block 47 advances the ignition timing in accordance with the correction of the retarded side of the fuel injection timing in order to compensate for the decrease in the engine torque. Correct and increase engine torque. Even if the preignition avoidance control is performed by performing the retard side correction of the fuel injection timing IT, the expansion side correction of the operating angle and valve lift amount of the intake valve 15, and the optimization of the intake valve closing timing IVC. When pre-ignition occurs, the throttle valve opening is corrected to the closing side by the throttle control block 46 as in the case of the low octane number.

  In FIG. 14, since regular fuel is supplied to the high-octane fuel engine, the low octane time control method is selected as the low octane time control method in the flow of FIG. FIG. 11 is an engine torque characteristic diagram in which an experiment confirms what happens to the engine torque when preignition avoidance control is performed as shown in FIG. 10 according to a method. The horizontal axis is the rotational speed in the low rotational speed range.

  In FIG. 14, the thick solid line is an estimate of the engine torque when the throttle valve is fully opened, which would come out if high-octane fuel was used. As the engine speed increases in the low speed range, A → B → C → D is larger.

  When regular fuel is used (when the octane number is low), pre-ignition is likely to occur at a low rotational speed range. When the throttle valve opening is corrected to the closed side in order to avoid the pre-ignition that occurs at this low octane number (that is, in the case of the conventional device), the engine torque changes from E → F → G → D as shown by the thin solid line. Therefore, the torque decrease from the thick solid line is larger at the lower rotational speed side in the entire range of the low rotational speed range.

  On the other hand, when the fuel injection timing IT is corrected to the retard side according to this embodiment instead of correcting the throttle valve opening to the closed side as in the conventional device in order to avoid pre-ignition that occurs in the low rotation speed range, the engine The torque changes from H → I → C → D as shown by the broken line, and even if regular fuel is used in the rotational speed range between CD, there is no torque drop from the thick solid line, and The torque reduction allowance in the rotational speed range between H and C is smaller than in the case of the thin solid line (when the throttle valve opening is corrected to the closing side).

  Furthermore, according to the present embodiment, when the ignition timing is advanced in addition to the retard side correction of the fuel injection timing IT, the engine torque changes from J → B → C → D as indicated by a one-dot chain line. In the rotational speed range between -C and D, even if regular fuel is used, there is no torque reduction from the thick solid line, and there is a small torque reduction only in the rotational speed range between AB.

  Therefore, even if the pre-ignition avoidance control according to the present embodiment is performed in the low rotational speed range when using regular fuel, the torque reduction is not compensated for in the rotational speed range between A and B, that is, when the engine is idling and near idling. Only at speed. A feedback control system is configured for the torque reduction at the time of idling and at a rotational speed close to idling. That is, the torque characteristics between A and B are stored as a table of target torque, the actual engine torque is estimated in the rotation speed range between A and B, and the actual engine torque depends on the rotation speed at that time. The throttle valve opening is feedback controlled so as to match the target torque.

  Thus, according to this embodiment (the invention described in claim 1), the fuel injection valve 21 that directly injects fuel into the combustion chamber 5 and the spark plug 14 that ignites the air-fuel mixture formed in the combustion chamber 5. In a control device for a direct injection engine with a cylinder, it is determined whether it is a plurality of cases where the degree of pre-ignition occurrence differs based on the octane number of fuel, environmental conditions and operating conditions in a low rotational speed range, Since the pre-ignition avoidance control is performed so that the engine torque decrease associated with the pre-ignition avoidance control is reduced every time when the determination is made (see FIGS. 9 to 13), the engine torque decrease allowance associated with the pre-ignition avoidance control is reduced to that of the conventional apparatus. It can be reduced more than the case.

  Further, according to the present embodiment (the invention described in claim 1), the cases are divided into a plurality of cases where the degree of pre-ignition is different (see steps 1 to 3 in FIG. 9). Therefore, it is possible to perform the optimal pre-ignition avoidance control, and to perform the pre-ignition avoidance control with high accuracy.

  Further, according to the present embodiment (the invention described in claim 1), since it is based on the octane number, the intake air temperature (environmental condition), and the water temperature (operating condition) (see steps 1 to 3 in FIG. 9), the low rotation speed It is possible to cover almost all cases where pre-ignition tends to occur in the speed range, and the pre-ignition avoidance performance can be improved.

  Furthermore, since the conventional device only determines whether the fuel is a high-octane fuel or a regular fuel, a fuel with an octane number intermediate between the octane number of the high-octane fuel and the regular fuel octane number (intermediate fuel) is used. Although the pre-ignition could not be completely avoided in the low rotation speed range, according to the present embodiment (the invention described in claim 1), the pre-ignition avoidance control is performed based on the octane number (FIG. 9). Steps 1, 4, 5, FIG. 10, and FIG. 11), pre-ignition can be avoided even in a low rotational speed range when intermediate fuel is used.

  According to the present embodiment (the invention according to claim 2), the VEL mechanism 26 (the operating angle / lift amount variable mechanism capable of continuously expanding and reducing the operating angle and the lift amount of the intake valve) and the VTC mechanism 27 (A lift center angle phase varying mechanism capable of advancing and retarding the phase of the lift center angle of the intake valve), and the preignition avoidance control block 43 (preignition avoidance control means) corrects the fuel injection timing to the retard side, In addition, the operating angle and the valve lift amount of the intake valve 15 are corrected using the VEL mechanism 26 or the intake valve closing timing (the phase of the lift center angle of the intake valve 15) is corrected using the VTC mechanism 27. Since ignition avoidance control is performed (see FIGS. 10 to 13), it is possible to play by correcting the throttle valve opening to the closed side as in the conventional device. Than when performing Nisshon avoidance control, it is possible to suppress the reduction engine torque accompanying the preignition avoidance control.

  According to the present embodiment (the invention described in claim 3), when pre-ignition occurs even if pre-ignition avoidance control is performed, the throttle control block 46 performs the closing side correction of the throttle valve opening (torque cut control). To avoid pre-ignition (see FIGS. 10 to 13). In other words, closing side correction of the throttle valve opening is performed only when pre-ignition occurs even if pre-ignition avoidance control is performed. Can be minimized.

  According to the present embodiment (the invention described in claim 5), the fuel injection timing control and the fuel pressure control block 44 act on the fuel injection valve 21 by the amount that the combustion state deteriorates due to the correction of the fuel injection timing to the retard side. Since the correction is made by correcting the fuel pressure to the up side (rising side) (see FIGS. 10 to 13), even if the fuel injection timing is corrected to the retard side to avoid pre-ignition, the combustion state may deteriorate. Absent.

  According to this embodiment (the invention described in claim 6), the ignition timing control block 47 corrects the amount of decrease in engine torque by correcting the fuel injection timing to the retard side by correcting the ignition timing to the advance side. Since it compensates (refer to FIGS. 10-13), the fall of the engine torque by the retard side correction | amendment of the fuel injection timing for preignition avoidance can be suppressed.

According to the present embodiment (the invention described in claims 7 and 8 ), in a plurality of cases where the degree of occurrence of pre-ignition is different, when the octane number is a low octane number having a predetermined value A or less (when the octane number is relatively low) High octane number when the octane number exceeds a predetermined value A (when the octane number is relatively high) (see step 1 in FIG. 9), and optimal preignition according to each case of low octane number and high octane number Avoidance control control can be performed.

According to the present embodiment (the invention described in claim 9 ), the environmental condition is the intake air temperature, and the intake air temperature is higher than the predetermined value B (intake air) when there are a plurality of pre-ignition occurrence levels. (When the temperature is relatively high) (see step 2 in FIG. 9), optimal pre-ignition avoidance control control according to the high intake air temperature can be performed.

According to the present embodiment (the invention described in claim 10 ), the operation condition is the water temperature, and the water temperature is higher than the predetermined value C when the water temperature is a plurality of different degrees of pre-ignition occurrence (the water temperature is relative). (See step 3 in FIG. 9), it is possible to perform optimal pre-ignition avoidance control control according to the high water temperature.

When the octane number is low (when the octane number is relatively low), preignition is most likely to occur. In this case, if the number of control items for avoiding pre-ignition is increased, it is considered that some actuators have a response delay. For this reason, when the pre-ignition is most likely to occur is determined later in time, the pre-ignition is between the start of the pre-ignition avoidance control and the operation of the actuator until the control item reaches the target. However, according to the present embodiment (the invention described in claim 1 ), in a plurality of cases where the degree of pre-ignition is different, a high octane number (when the octane number is relatively low) is high. Select judgment / preignition avoidance control method, including when octane number (when octane number is relatively high), high intake air temperature (when intake air temperature is relatively high), and high water temperature (when water temperature is relatively high) Since the block 42 (determination means) first determines when the octane number is low (see step 1 in FIG. 9), such a situation can be avoided.

According to this embodiment (the invention described in claim 7 ), the fuel injection timing control and the fuel pressure control block 44 correct the fuel injection timing to the retard side when the octane number is low (when the octane number is relatively low), and The valve timing control block 45 corrects the operating angle of the intake valve 15 and the valve lift amount so as to cool the air-fuel mixture in the combustion chamber 5 by increasing the amount of fresh air in the combustion chamber 5 and actual compression. Since the intake valve closing timing IVC is corrected away from the bottom dead center so that the ratio decreases (see FIG. 10), pre-ignition is achieved by correcting the throttle valve opening to the closing side as in the conventional device when the octane number is low. The engine torque drop associated with preignition avoidance control can be made smaller than when avoidance control is performed.

According to this embodiment (the invention described in claim 8 ), the fuel injection timing control and the fuel pressure control block 44 during the high octane number (when the octane number is relatively high), the heat receiving time of the air-fuel mixture in the combustion chamber 5 Since the fuel injection timing is corrected to the side of retarding until immediately before ignition so that the air-fuel mixture in the combustion chamber 5 is cooled by the fuel injection (see FIG. 11), the throttle valve as in the conventional device is used at the time of high octane number. By correcting the opening to the closed side, it is possible to reduce the engine torque drop associated with the pre-ignition avoidance control as compared with the case where the pre-ignition avoidance control is performed.

According to the present embodiment (the invention described in claim 9 ), the fuel injection timing control and the fuel pressure control block 44 correct the fuel injection timing to the retard side when the intake air temperature is high (when the intake air temperature is relatively high). In addition, since the valve timing control block 45 corrects the intake valve closing timing IVC to the side away from the bottom dead center so that the compression temperature decreases (see FIG. 12), at the time of high intake air temperature, the throttle valve is opened as in the conventional device. By correcting the degree to the closing side, it is possible to reduce the engine torque reduction associated with the pre-ignition avoidance control as compared with the case where the pre-ignition avoidance control is performed.

According to this embodiment (the invention described in claim 10 ), the fuel injection timing control and the fuel pressure control block 44 correct the fuel injection timing to the retard side when the water temperature is high (when the water temperature is relatively high), and The valve timing control block 45 corrects the operating angle of the intake valve 15 and the valve lift amount so as to cool the air-fuel mixture in the combustion chamber 5 by increasing the amount of fresh air in the combustion chamber 5 and actual compression. Since the intake valve closing timing IVC is corrected so as to be away from the bottom dead center so that the ratio decreases (see FIG. 13), pre-ignition can be achieved by correcting the throttle valve opening to the closing side at the time of high water temperature as in the conventional device. The engine torque drop associated with preignition avoidance control can be made smaller than when avoidance control is performed.

DESCRIPTION OF SYMBOLS 1 Engine 14 Spark plug 15 Intake valve 21 Fuel injection valve 26 VEL mechanism (working angle and lift amount variable mechanism)
27 VTC mechanism (lift center angle phase variable mechanism)
31 Engine controller 42 Judgment / pre-ignition avoidance control method selection block (judgment means)
43 Pre-ignition avoidance control block (pre-ignition avoidance control means)

Claims (12)

In a direct injection type engine control device having a fuel injection valve for directly injecting fuel into a combustion chamber and an ignition plug for igniting an air-fuel mixture formed in the combustion chamber,
A determination means for determining which is a plurality of cases where the degree of pre-ignition occurrence is different based on the octane number of fuel, environmental conditions and operating conditions in a low rotational speed range;
Pre-ignition avoidance control means for performing pre-ignition avoidance control so that a decrease in engine torque associated with the pre-ignition avoidance control is reduced every time it is determined ,
When the octane number is relatively low, the octane number is relatively high, the intake air temperature is relatively high, the water temperature is relatively high, in a plurality of cases where the degree of pre-ignition occurrence is different,
The control unit for a direct injection type in-cylinder engine, wherein the determination means first determines a case where the octane number is relatively low . An operating angle / lift amount variable mechanism that can continuously increase and decrease the operating angle and lift amount of the intake valve, and a lift center angle phase variable mechanism that can advance and retard the phase of the lift center angle of the intake valve,
The pre-ignition avoidance control means corrects the fuel injection timing to the retard side and corrects the operating angle and lift amount of the intake valve by using the operating angle / lift amount variable mechanism, or the lift center angle phase variable mechanism. The pre-ignition avoidance control is performed by correcting the phase of the lift center angle of the intake valve using the control device for a direct injection type engine according to claim 1.   3. The control device for a direct injection type engine according to claim 2, wherein when pre-ignition occurs even if the pre-ignition avoidance control is performed, torque cut control is performed to avoid the pre-ignition. 4.   The in-cylinder direct injection engine control device according to claim 3, wherein the torque cut control is control of a throttle valve opening.   3. The cylinder according to claim 2, wherein the amount of deterioration of the combustion state due to the correction to the retard side of the fuel injection timing is compensated by the correction to the increase side of the fuel pressure acting on the fuel injection valve. Control device for internal direct injection engine.   The control of the direct injection type in-cylinder engine according to claim 2, wherein the correction of the fuel injection timing to the retard side compensates for the decrease in the engine torque by the correction of the ignition timing to the advance side. apparatus. In a plurality of cases where the degree of pre-ignition is different, including a case where the octane number is relatively low and a case where the octane number is relatively high,
The pre-ignition avoidance control means corrects the fuel injection timing to the retard side when the octane number is relatively low, and the intake air so that the air-fuel mixture in the combustion chamber is cooled by an increase in the amount of fresh air in the combustion chamber. The cylinder according to claim 2 , wherein the intake valve closing timing is corrected to a side away from the bottom dead center so that the valve operating angle and the valve lift amount are corrected and the actual compression ratio is decreased. Control device for internal direct injection engine. In a plurality of cases where the degree of pre-ignition is different, including a case where the octane number is relatively low and a case where the octane number is relatively high,
The pre-ignition avoidance control means sets the fuel injection timing until immediately before ignition so that the heat receiving time of the air-fuel mixture in the combustion chamber decreases when the octane number is relatively high and the air-fuel mixture in the combustion chamber is cooled by fuel injection. The control apparatus for a direct injection type in-cylinder engine according to claim 2 , wherein correction is performed to the retard side. The environmental condition is intake air temperature,
In a plurality of cases where the degree of pre-ignition is different, including the case where the intake air temperature is relatively high,
The preignition avoidance control means is corrected on the side away the intake valve closing timing as the intake air temperature of the fuel injection timing is corrected to retard side when relatively high, and the compression temperature decreases from bottom dead center The in-cylinder direct injection engine control device according to claim 2 , wherein: The operating condition is water temperature,
In a plurality of cases where the degree of pre-ignition occurrence is different, including the case where the water temperature is relatively high,
The preignition avoidance control means such that said fuel injection timing is corrected to retard side when the water temperature is relatively high, and air-fuel mixture in a combustion chamber in an increase in the air volume of the combustion chamber is cooled intake The cylinder according to claim 2 , wherein the intake valve closing timing is corrected to a side away from the bottom dead center so that the valve operating angle and the valve lift amount are corrected and the actual compression ratio is decreased. Control device for internal direct injection engine.   When the actual engine torque that is reduced by the torque cut control is lower than the engine torque when the pre-ignition avoidance control is not performed, the actual engine torque that is reduced by the torque cut control is the pre-ignition avoidance control. 4. The control device for a direct injection type in-cylinder engine according to claim 3, wherein the throttle valve opening is feedback-controlled so as to coincide with the engine torque when not performed. In a plurality of cases where the degree of pre-ignition is different, including a case where the octane number is relatively low and a case where the octane number is relatively high,
An octane number estimating means for estimating the octane number;
Comparing the estimated octane number and the predetermined value, octane number if there if the octane number is relatively low when it is less than a predetermined value, and in case the octane number is relatively high when the octane number exceeds a predetermined value The in-cylinder direct injection engine control device according to claim 2 , wherein it is determined that there is one.

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