JP4753078B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly, to an internal combustion engine having a fuel injection system that pumps fuel to a delivery pipe by a high-pressure fuel pump and injects fuel accumulated in the delivery pipe from a fuel injection valve. The present invention relates to a control device.

  Generally, in a direct-injection internal combustion engine such as a direct-injection gasoline engine or a diesel engine, a fuel injection valve that directly injects fuel into a cylinder is provided for each cylinder, and a delivery pipe that serves as a pressure accumulation pipe for fuel pumped from a high-pressure fuel pump The pressure is accumulated in a high pressure state (sometimes referred to as a common rail), and the accumulated fuel is supplied to each fuel injection valve. Each fuel injection valve is individually controlled to be opened and closed by the control unit. When the fuel injection valve is opened, fuel equal to the fuel pressure (fuel pressure) in the delivery pipe is injected and supplied to the in-cylinder combustion chamber.

  Usually, the high-pressure pump is driven by a crankshaft via a camshaft, and periodically pumps fuel. The fuel pressure value in the delivery pipe is accompanied by pulsation due to the influence of fuel pumping by the high-pressure pump and fuel injection by the fuel injection valve. On the other hand, the fuel pressure value in the delivery pipe is used for various calculation processes including the calculation of the fuel injection amount, but if this value is used directly, control will be hindered due to the influence of pulsation. As for, the value of the annealing fuel pressure obtained by averaging the values of the actual fuel pressure detected by the fuel pressure sensor is used.

  In addition, as a prior art aiming at realizing accurate fuel injection control in consideration of fuel pressure pulsation, for example, as disclosed in Patent Document 1, the amount of fuel supplied into the delivery pipe, the delivery, 2. Description of the Related Art There is known a fuel injection control device for an internal combustion engine that corrects a fuel injection period by predicting a fluctuation amount of fuel pressure in a delivery pipe by increasing / decreasing the amount of fuel discharged from the pipe.

JP 2004-346851 A

  Incidentally, the annealed fuel pressure is naturally a value that deviates from the actual fuel pressure, and if strictly understood, the fuel injection amount deviates from a desired value by this amount of deviation. However, in the past, since the fuel pressure used is in a relatively high pressure range and the volume of the delivery pipe is relatively large, the injection amount deviation has not been regarded as a problem.

  Recently, however, attempts have been made to inject fuel even in the low fuel pressure range in order to expand the dynamic range. Also, in order to shorten the start-up time by increasing the pressure in the delivery pipe at the start-up, the volume of the delivery pipe is increased. Attempts have been made to reduce this. In this case, the ratio of the amount of deviation of the actual fuel pressure with respect to the annealing fuel pressure value becomes large, and the influence of fuel pressure pulsation can never be ignored.

  On the other hand, when the number of fuel injections and the number of fuel pumps during one cycle (720 ° CA) of the internal combustion engine are different, the fuel pressure varies for each fuel injection of each cylinder, resulting in variations in the fuel injection amount between the cylinders. There is also a problem. For example, when performing fuel pumping twice per four fuel injections, fuel injection is performed twice per one fuel pumping, so that the actual fuel pressure between the earlier fuel injection and the subsequent fuel injection is Unlikely, as a result, the injection amount between the cylinders varies. Furthermore, when fuel injection and fuel pumping are irregularly performed asynchronously, for example, when fuel pumping is performed three times per four fuel injections, the actual fuel pressure for each injection varies relatively randomly, and inter-cylinder injection is performed. There is a possibility that the amount variation will be remarkable. In such a case, if the injection amount deviation caused by the fuel pressure deviation is added, the variation in the injection amount between the cylinders will become larger as a result.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is an internal combustion engine capable of suppressing fuel injection amount deviation in individual fuel injection and fuel injection amount variation between cylinders. It is to provide a control device.

  In order to achieve the above object, one aspect of the present invention is a control device for an internal combustion engine that feeds fuel to a delivery pipe with a high-pressure fuel pump and detects a fuel pressure in the delivery pipe with a fuel pressure sensor. Based on the basic fuel injection amount calculation means for calculating the basic fuel injection amount based on the state, and on the basis of the actual fuel pressure detected by the fuel pressure sensor, the smoothed fuel pressure is calculated by averaging the fuel pressure values in the delivery pipe. A first correction value is calculated based on the annealing fuel pressure calculating means, the annealing fuel pressure and the engine operating state, and a second correction value is calculated based on the annealing fuel pressure and the actual fuel pressure. And correction means for correcting the basic fuel injection amount by a correction value and a second correction value.

  According to this aspect of the present invention, in addition to the first correction value calculated based on the annealing fuel pressure and the engine operating state, the basic fuel is also determined by the second correction value calculated based on the annealing fuel pressure and the actual fuel pressure. The injection amount is corrected. Accordingly, the second correction value can be used to correct the fuel injection amount by reflecting the fuel pressure deviation between the smoothed fuel pressure and the actual fuel pressure, thereby reducing the influence of the fuel pressure deviation and the fuel injection quantity deviation caused by the fuel pressure deviation. And variations in the fuel injection amount between cylinders can be suppressed.

  Here, preferably, the correction means calculates the second correction value based on a ratio between the annealed fuel pressure and the actual fuel pressure. Thereby, both fuel pressure gaps can be suitably reflected in correction of the fuel injection amount.

  Further, preferably, the correction means calculates the second correction value based on a square root of a ratio between the annealed fuel pressure and the actual fuel pressure.

  In general, a relationship of Q = C√P (where C is a constant) is established between the flow rate Q and the pressure P. Therefore, by calculating the second correction value based on the square root of the ratio between the annealing fuel pressure and the actual fuel pressure, it is possible to perform accurate correction and effectively suppress the fuel injection amount deviation.

  Preferably, the annealing fuel pressure calculating unit calculates the annealing fuel pressure at a predetermined first timing, the correction unit calculates the first correction value at the first timing, and the first As the smoothed fuel pressure and the actual fuel pressure when calculating the second correction value at a predetermined second timing later than the timing of 1 and before fuel injection, and calculating the second correction value, The annealed fuel pressure calculated at the first timing and the actual fuel pressure detected by the fuel pressure sensor at the second timing are used.

  Depending on the form of the control device of the internal combustion engine, some calculations require a relatively long time to calculate the value of the fuel injection amount to be injected, so some calculations are performed at the fuel injection amount calculation timing immediately before fuel injection. In some cases, the calculation is not in time, and some of the calculations must be executed before the fuel injection amount calculation timing. In addition, since some values used for calculating the fuel injection amount are also used in other processes, the value may be calculated at a timing different from the fuel injection amount calculation timing. This preferable form is suitable when the calculation is performed at such separate timings.

  According to the present invention, it is possible to provide a control device for an internal combustion engine that can suppress a fuel injection amount deviation in individual fuel injections and a fuel injection amount variation between cylinders.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 shows an internal combustion engine control apparatus according to this embodiment. The engine (internal combustion engine) 10 of the present embodiment is a direct-injection multi-cylinder spark ignition engine, and more specifically a 4-cylinder gasoline engine. However, the form of the engine, such as the number of cylinders and fuel, is arbitrary. is there. Although this engine 10 is for vehicles, there is no particular limitation on the use.

  Each cylinder 11 of the engine 10 is provided with an injector 12 as an electromagnetically driven fuel injection valve that directly injects fuel into the cylinder (combustion chamber), and an ignition plug 13 that ignites the air-fuel mixture in the cylinder. Yes. An electronic control unit (hereinafter referred to as ECU) 100 as a control means is provided. The ECU 100 controls the opening and closing of the injector 12 and also controls the ignition by the spark plug 13.

  Fuel is sent to the injector 12 by a fuel supply system 20. The fuel supply system 20 includes a fuel tank 21, a high-pressure fuel pump 30, and a high-pressure fuel line 23 that connects the high-pressure fuel pump 30 and the injector 12. The fuel in the fuel tank 21 is sent to the high-pressure fuel pump 30 by an electric feed pump 24, for example. The fuel pressure, that is, the feed pressure at this time is maintained at a relatively low constant value by the pressure regulator 25, and the value is, for example, about 0.3 MPa (3 atm). A fuel filter 26 is provided at the outlet of the feed pump 24.

  The high-pressure fuel line 23 includes a delivery pipe 27 serving as a pressure accumulation pipe connected in common to the injectors 12 of each cylinder, and a high-pressure fuel pipe 28 connecting the high-pressure fuel pump 30 and the delivery pipe 27. High pressure fuel corresponding to the fuel injection pressure from the injector 12 is accumulated in the high pressure fuel line 23, and the value thereof is, for example, about 5 to 13 MPa (50 to 130 atm). The high-pressure fuel accumulated in the delivery pipe 27 is directly injected from the injector 12 into the combustion chamber when the injector 12 is opened. In the combustion chamber, an air-fuel mixture composed of the fuel and air sent from an intake passage (not shown) is generated. This air-fuel mixture is sparked by the spark plug 13 in the combustion chamber and drives the engine 10. The exhaust gas in the combustion chamber sequentially passes through the exhaust manifold 50 and the exhaust passage 51 and is discharged to the atmosphere, and is purified by the catalyst 52 provided in the exhaust passage 51.

  The high pressure fuel pump 30 pressurizes the low pressure fuel sent from the feed pump 24 and discharges it to the high pressure fuel pipe 28. The high-pressure fuel pump 24 is driven up and down by an inlet-side check valve 31 that mechanically opens and closes a suction passage for low-pressure fuel from the fuel tank 21 and a camshaft 32 driven by the engine, and pressurizes the fuel in the plunger chamber 33. A plunger 34, an outlet-side check valve 35 that mechanically opens and closes a discharge passage connected to the high-pressure fuel pipe 28, and an electromagnetic spill valve 36 that opens and closes an inlet portion of a return passage 37 extending from the plunger chamber 33 to the fuel tank 21. Is provided. When the plunger 34 is lowered, the low pressure fuel pushes the inlet side check valve 31 and flows into the plunger chamber 33. When the electromagnetic spill valve 36 is closed by the ECU 100 at a predetermined timing when the plunger is raised, the fuel in the plunger chamber 33 is pressurized by the subsequent raising of the plunger 34. The pressurized fuel pushes the outlet-side check valve 35 and is pumped to the high-pressure fuel pipe 28. As a result, the fuel pressure (fuel pressure) in the high-pressure fuel line 23 (particularly the delivery pipe 27) is increased, and high-pressure fuel is accumulated in the high-pressure fuel line 23. Backflow to the feed pump 24 side during fuel pumping is prevented by the inlet side check valve 31.

  As shown in FIG. 2, the electromagnetic spill valve 36 is closed and opened by the ECU 100 during the lift (lift) period of the plunger 34 (that is, the period from the bottom dead center BDC to the top dead center TDC). The electromagnetic spill valve 36 is open when on and closed when off. In the present embodiment, the opening timing Vo of the electromagnetic spill valve 36 is fixed at the top dead center TDC, and the closing timing Vc of the electromagnetic spill valve 36 is controlled by the ECU 100, so that the amount of fuel pumped from the high-pressure fuel pump 24 and therefore the delivery are increased. The degree of increase of the fuel pressure in the pipe 27 is controlled. In the illustrated example, since the electromagnetic spill valve 36 is open during the period from the plunger bottom dead center BDC to the closing timing Vc of the electromagnetic spill valve 36, the fuel is not pressurized even when the plunger 34 is raised, and the return passage 37. Is returned to the fuel tank 21. During the period from the closing timing Vc of the electromagnetic spill valve 36 to the opening timing Vo (that is, the plunger top dead center TDC), the electromagnetic spill valve 36 is closed. The check valve 35 is pushed open and discharged to the high-pressure fuel pipe 28. The electromagnetic spill valve 36 is opened while the plunger 34 is lowered.

  The fuel pumping amount becomes maximum when the closing timing Vc of the electromagnetic spill valve 36 coincides with the bottom dead center BDC. This time is assumed to be pump duty D = 100%. As the closing timing Vc is delayed and approaches the opening timing Vo (top dead center TDC), that is, as the pump duty D decreases, the fuel pumping amount decreases. When the closing timing Vc of the electromagnetic spill valve 36 coincides with the opening timing Vo (top dead center TDC), that is, when the pump duty D is 0%, the electromagnetic spill valve 36 is left open without being closed, and the fuel pressure feed amount Becomes zero. At this time, the fuel pressure supply by the high-pressure fuel pump 24 is stopped.

  Returning to FIG. 1, the delivery pipe 27 is provided with a fuel pressure sensor 38 for detecting the internal fuel pressure, and the fuel pressure sensor 38 is connected to the ECU 100. The delivery pipe 27 is provided with a mechanical relief valve 39 as a safety valve. When the fuel pressure in the delivery pipe 27 rises abnormally, the fuel inside the delivery pipe 27 pushes the relief valve 39 open and returns to the fuel tank 21 via the return passage 40. This relief valve 39 is for emergency use only and is not for controlling the pressure in the delivery pipe 27 during normal operation of the engine. In the present embodiment, the fuel pressure in the delivery pipe 27 is reduced by the fuel injection from the injector 12 except for when the relief valve 39 is abnormally opened during normal operation of the engine. The fuel pressure is increased by pumping fuel from the high-pressure fuel pump 30. The average fuel pressure value in the delivery pipe 27 is determined by the balance between the decrease and increase in the fuel pressure, and the fuel pressure in the delivery pipe 27 is pulsated by the decrease and increase in the fuel pressure.

  The engine 10 is provided with various sensors for detecting its operating state, and these sensors are connected to the ECU 100. For example, a water temperature sensor for detecting the temperature of engine cooling water, an air flow meter for detecting the amount of air flowing through the intake passage (intake air amount), a crank angle sensor for detecting the crank angle and thus the engine speed, and an accelerator There is an accelerator opening sensor (indicated by reference numeral 41) for detecting the opening, and an ignition switch operated by the driver. The ECU 100 includes a so-called microcomputer including a CPU, a ROM, a RAM, and the like. The ECU 100 controls, for example, the fuel injection amount, the fuel injection timing, the ignition timing, and the fuel pressure in the delivery pipe 27 (the closing timing of the electromagnetic spill valve 36) based on the output signals of the sensors.

  Next, the contents of the control executed in this embodiment will be described. FIG. 3 shows the change in the fuel pressure value related to the delivery pipe 27 and the execution timing of the arithmetic processing described later. A one-dot chain line ((b) diagram) shows the actual fuel pressure P1, which is a value detected by the fuel pressure sensor 38 itself. A thick solid line ((a) figure) shows the annealing fuel pressure P0. The annealed fuel pressure is a value obtained by averaging the fuel pressure values in the delivery pipe 27, and is calculated based on the actual fuel pressure by a process described later.

  In the illustrated example, fuel injection is performed twice by the high-pressure pump 30 during four fuel injections, that is, during one cycle period (720 ° CA) of the engine. This is a so-called 4-injection 2-pumping configuration. Specifically, as shown in FIG. 1, the camshaft 32 that drives the high-pressure pump 30 makes 1/2 rotation with respect to one rotation of the engine and has two cam peaks. The plunger 34 is pushed up by the cam crest twice. The actual fuel pressure P1 rises at the time of fuel pumping, and the annealing fuel pressure P0 rises accordingly. At the time of fuel injection, the actual fuel pressure P1 falls, and the annealing fuel pressure P0 also falls accordingly. The actual fuel pressure P1 fluctuates or pulsates around the roughly smoothed fuel pressure P0.

  (C) The figure shows the calculation timing of the annealing fuel pressure P0 and the fuel pressure correction coefficient KP described later, that is, the first timing. The first timing is every predetermined time or every crank angle, for example every 20 ° CA. As will be described later, the calculation of the fuel pressure correction coefficient KP includes a map search and is a process that requires a relatively long time. The interval between the first timings is set such that the fuel pressure correction coefficient KP can be calculated.

  (D) The timing for calculating the final fuel injection amount Qfnl as the fuel injection amount to be injected from the injector 12, that is, the second timing is shown in FIG. The second timing is set to a timing immediately before the fuel injection. More specifically, the final fuel injection amount Qfnl is set in time before the fuel injection timing and set to a timing as close to the fuel injection timing as possible. Yes. The interval between the second timings is approximately 180 ° CA, which is longer than the interval between the first timings.

  Next, the content of the calculation process of the annealing fuel pressure P0 and the fuel pressure correction coefficient KP executed at the first timing will be described with reference to FIG. The illustrated routine is repeatedly executed by the ECU 100 every time the first timing arrives. (N) is a value at the time of current processing, and (n-1) is a value at the time of previous processing.

  In step S101, the ECU 100 first acquires the value of the actual fuel pressure P1 (n) detected by the fuel pressure sensor 38 during the current process. Next, in step S102, the ECU 100 determines the difference between these values based on the acquired actual fuel pressure P1 (n) and the smoothed fuel pressure P0 (n-1) calculated in step S104 during the previous process. A fuel pressure fluctuation value ΔP (= P1 (n) −P0 (n−1)) is calculated.

  Next, in step S103, the ECU 100 determines whether or not the fuel pressure fluctuation value ΔP is a value between the predetermined upper limit threshold PH and the predetermined lower limit threshold PL (PL <ΔP <PH). To do. Here, upper limit threshold PH is a positive value, and lower limit threshold PL is a negative value.

  When the fuel pressure fluctuation value ΔP is a value between the upper limit threshold PH and the lower limit threshold PL (S103: YES), the ECU 100 calculates the smoothed fuel pressure P0 (n) at the time of the current processing in step S104: P0 (n) = P0 (n−1) + A × ΔP is calculated. On the other hand, when the fuel pressure fluctuation value ΔP is not a value between the upper limit threshold PH and the lower limit threshold PL (S103: NO), the ECU 100 formulates the smoothed fuel pressure P0 (n) at the time of the current process in step S105. : P0 (n) = P0 (n−1) + B × ΔP. Here, A and B are predetermined annealing constants and have a relationship of A <B.

  When the fuel pressure fluctuation value ΔP is a value between the upper limit threshold PH and the lower limit threshold PL (S103: YES), the current process is performed with respect to the annealed fuel pressure P0 (n-1) at the previous process. This corresponds to a case where the actual fuel pressure P1 (n) at the time deviates only to a small extent. Accordingly, in this case, the fuel pressure fluctuation value ΔP is multiplied by the smaller smoothing constant A, and the annealing fuel pressure at the time of the current processing that changes only to a small extent with respect to the annealing fuel pressure P0 (n−1) at the time of the previous processing. P0 (n) is obtained. On the other hand, when the fuel pressure fluctuation value ΔP is not a value between the upper limit threshold PH and the lower limit threshold PL (S103: NO), this time is compared with the annealed fuel pressure P0 (n−1) at the previous processing. This corresponds to a case where the actual fuel pressure P1 (n) at the time of processing is relatively large. Therefore, in this case, the fuel pressure fluctuation value ΔP is multiplied by the larger smoothing constant B, and the fuel pressure fluctuation P0 at the time of the current process, which fluctuates relatively greatly with respect to the fuel pressure P0 (n−1) at the time of the previous process. (N) is obtained.

  When the calculation of the smoothed fuel pressure P0 (n) during the current process is thus completed, the ECU 100 then calculates a fuel pressure correction coefficient KP as a first correction value in step S106. This fuel pressure correction coefficient KP is calculated based on the smoothed fuel pressure P0 (n) at the time of the current process and the engine operating state. Specifically, ECU 100 calculates fuel pressure correction coefficient KP with reference to a fuel pressure correction coefficient map as shown in FIG. 5 stored in advance. In this fuel pressure correction coefficient map, the relationship between the fuel pressure, the fuel load factor, and the fuel pressure correction coefficient KP is defined. The fuel load factor is a ratio (= Qb / Qbmax) of the current basic fuel injection amount Qb to the maximum value Qbmax of the basic fuel injection amount at a certain engine speed. The basic fuel injection amount Qb is a value stored in the map format in the ECU 100 as a correlation value between the engine speed and the intake air amount. The ECU 100 calculates the basic fuel injection amount Qb based on the detected values of the current engine speed and the intake air amount using the basic fuel injection amount map, and the maximum value Qbmax of the basic fuel injection amount corresponding to the engine rotational speed. And calculate the fuel load factor. The ECU 100 calculates the fuel pressure correction coefficient KP using the fuel pressure correction coefficient map based on the calculated fuel load factor and the smoothed fuel pressure P0 (n) at the time of the current process. This routine is completed.

  As can be seen from this description, the calculation of the fuel pressure correction coefficient KP in step S106 is a process that requires a relatively long time. The value of the annealed fuel pressure P0 (n) calculated here is used to calculate not only the fuel injection amount but also other control amounts. Therefore, regardless of the fuel injection timing, the annealed fuel pressure P0 (n) is periodically calculated at a relatively short time interval.

  Next, the process for calculating the final fuel injection amount Qfnl executed at the second timing described above will be described.

  First, prior to describing the process for calculating the final fuel injection amount Qfnl according to the present invention, the conventional process for calculating the final fuel injection amount Qfnl will be described with reference to FIG. The illustrated routine is repeatedly executed by the ECU 100 every time the second timing arrives.

  First, the ECU 100 calculates a basic fuel injection amount Qb in step S201. The calculation method of the basic fuel injection amount Qb is the same as described above, and is obtained from the outputs of the crank angle sensor and the air flow meter using a basic fuel injection amount map (which may be a function expression) stored in advance in the ECU 100. It is calculated based on the engine speed and the intake air amount.

  Next, in step S202, the ECU 100 acquires the value of the fuel pressure correction coefficient KP calculated at the immediately preceding first timing. For example, as shown in FIG. 3, if the current second timing is T2, the immediately preceding first timing is T1. Thus, the second timing T2 is later than the first timing T1.

  Thereafter, the ECU 100 proceeds to step S203, and calculates the final fuel injection amount Qfnl based on the formula: Qfnl = Qb × KP. That is, the basic fuel injection amount Qb is corrected by a fuel pressure correction coefficient KP that is a function of the annealing fuel pressure P0, and as a result, a final fuel injection amount Qfnl corresponding to the fuel amount to be injected is calculated. This correction is performed in order to correct the deviation between the reference fuel pressure value used in the adaptation stage during engine development and the fuel pressure value during actual operation, and to inject a predetermined amount of fuel.

  In the next step S204, the calculated final fuel injection amount Qfnl is converted into the energization time τ of the injector 12. This routine is thus completed. Although not shown, when the fuel injection timing comes after that, the ECU 100 energizes the injector 12 for a time equal to the energization time τ at the same time, and fuel is injected from the injector 12. As a result, a predetermined amount of fuel that is scheduled in advance should be injected from the injector 12.

  However, in this conventional example, with reference to FIG. 3, the calculated final fuel injection amount Qfnl is a value corrected by the fuel pressure correction coefficient KP based on the smoothed fuel pressure P0x at the first timing T1. On the other hand, at the fuel injection timing Ti, fuel having the fuel pressure value of the actual fuel pressure P1z is injected, and the actual fuel pressure P1z does not coincide with the annealed fuel pressure P0x at the first timing T1, and the fuel pressure deviation dP (= P1z-P0x) has occurred. Accordingly, as a result, the amount of fuel to be injected does not become a predetermined amount, and a fuel injection amount deviation occurs here. The same can be said for other fuel injections.

  Note that this problem can be solved to some extent by calculating the fuel pressure correction coefficient KP using the actual fuel pressure P1y at the second timing T2 instead of the first timing T1, but as described above, the calculation of the fuel pressure correction coefficient KP is relatively difficult. It takes a long time. Therefore, if the fuel pressure correction coefficient KP is calculated at the second timing T2 using the actual fuel pressure P1y at that time, the calculation by the ECU 100 is not in time for fuel injection, or the second timing T2 is set from the fuel injection timing Ti. It must be set at a very short time, and satisfactory results cannot be obtained. Therefore, this method is difficult to adopt.

  Conventionally, since the fuel pressure used is in a relatively high pressure range and the internal volume of the delivery pipe is relatively large, the fuel injection amount deviation has not been a significant problem. Recently, however, attempts have been made to perform fuel injection even in the low fuel pressure range to expand the dynamic range, or to reduce the volume of the delivery pipe in order to shorten the startup time by increasing the pressure in the delivery pipe at the time of startup. Yes. If this happens, the actual fuel pressure will deviate more than the conventional fuel pressure, and there is a concern that the fuel injection amount deviation will increase.

  Further, in the case of performing four injections and two pressures as in the example of FIG. 3, the fuel pressure deviation between the actual fuel pressure and the annealing fuel pressure differs between the two fuel injections per one fuel pressure feed, and as a result, between the cylinders Variation in the injection amount occurs. When a large fuel injection amount deviation is added to this, the variation in the injection amount between the cylinders becomes larger.

  On the other hand, FIG. 7 shows an example of the case where fuel injection and fuel pumping are irregularly performed asynchronously, specifically, the case of performing fuel pumping three times per four fuel injections (four injection three pumping). It is shown. This 4-injection 3-pressure feed has an advantage that the fuel pumping amount can be increased by 1.5 times compared to the above-described 4-injection 2-pressure feed. In this case, when comparing four fuel injections per three fuel pumps, the fuel pressure deviation between the actual fuel pressure and the smoothed fuel pressure varies more randomly than in the case of four fuel injections and two fuel pumps. Therefore, as a result, the injection amount between the cylinders may further vary, and the variation in the injection amount between the cylinders may increase in combination with the large fuel injection amount deviation.

  Therefore, in order to suppress such a deviation in fuel injection amount per fuel injection and a variation in fuel injection amount between cylinders, the present embodiment performs the following calculation process of the final fuel injection amount Qfnl.

  FIG. 8 shows a routine according to the final fuel injection amount calculation process of the present embodiment. The routine shown in the figure is repeatedly executed by the ECU 100 every time the second timing comes. Here, for ease of understanding, the processing at the second timing indicated by T2 in FIG. 3 will be described. The first timing immediately before the second timing T2 is indicated by T1 in FIG.

  First, in step S301, the ECU 100 calculates the basic fuel injection amount Qb as in step S201. Next, in step S302, the ECU 100 obtains the value of the fuel pressure correction coefficient KP calculated at the immediately preceding first timing T1 and the value of the annealed fuel pressure P0 calculated at the immediately preceding first timing T1. .

  Thereafter, the ECU 100 proceeds to step S303, and acquires the value of the actual fuel pressure P1 detected by the fuel pressure sensor 38 at the current second timing T2.

  Next, in step S304, the ECU 100 calculates a fuel pressure deviation correction coefficient KPr, which is a second correction value, based on the acquired annealing fuel pressure P0 and the actual fuel pressure P1. This fuel pressure deviation correction coefficient KPr is calculated based on the equation: KPr = √ (P0 / P1), and as the actual fuel pressure P1 at the second timing T2 deviates greatly from the annealed fuel pressure P0 at the first timing T1, Thus, a fuel pressure deviation correction coefficient KPr deviating greatly from the above can be obtained. When the actual fuel pressure P1 at the second timing T2 becomes larger than the annealed fuel pressure P0 at the first timing T1, a fuel pressure deviation correction coefficient KPr smaller than 1 is obtained, and conversely, the actual fuel pressure P1 at the second timing T2 is When it becomes smaller than the annealing fuel pressure P0 at the first timing T1, a fuel pressure deviation correction coefficient KPr larger than 1 is obtained. As can be seen, the fuel pressure deviation correction coefficient KPr is calculated based on the annealing fuel pressure P0 and the actual fuel pressure P1, more specifically, calculated based on the ratio (P0 / P1) of the annealing fuel pressure P0 and the actual fuel pressure P1, and Specifically, it is calculated based on the square root √ (P0 / P1) of the ratio of the annealing fuel pressure P0 and the actual fuel pressure P1.

  Thereafter, in step S305, the ECU 100 calculates the final fuel injection amount Qfnl based on the formula: Qfnl = Qb × KP × KPr. Thus, the basic fuel injection amount Qb is changed not only from the fuel pressure correction coefficient KP obtained from the annealing fuel pressure P0 at the first timing T1, but from the annealing fuel pressure P0 at the first timing T1 to the actual fuel pressure P1 at the second timing T2. It is also corrected by a fuel pressure deviation correction coefficient KPr that is a value reflecting the amount of fuel pressure deviation.

  According to this correction, the fuel injection amount conventionally given by Qb × KP is further reflected by reflecting the amount of fuel pressure deviation from the smoothed fuel pressure P0 at the first timing T1 to the actual fuel pressure P1 at the second timing T2. It can be corrected. Here, the actual fuel pressure P1 at the second timing T2 does not necessarily coincide with the actual fuel pressure P1 at the fuel injection timing Ti. However, the second timing T2 is still closer to the fuel injection timing Ti than the first timing T1. Nearly, the actual fuel pressure P1 at the second timing T2 is much closer to the actual fuel pressure P1 at the fuel injection timing Ti than the annealed fuel pressure P0 at the first timing T1. Therefore, based on the smoothed fuel pressure P0 at the first timing T1 and the actual fuel pressure P1 at the second timing T2, preferably based on the ratio (P0 / P1), more preferably the square root √ (P0 By correcting the fuel injection amount based on / P1), the influence of the fuel pressure deviation can be reduced as much as possible, and the fuel injection quantity deviation and the inter-cylinder fuel injection quantity variation caused by the fuel pressure deviation can be suppressed.

  In particular, in this embodiment, the fuel injection amount is corrected based on the square root √ (P0 / P1) of the ratio of the annealing fuel pressure P0 at the first timing T1 and the actual fuel pressure P1 at the second timing T2. Yes. This is because a general relationship of Q = C√P (where C is a constant) is established between the flow rate Q and the pressure P. That is, by correcting the fuel injection amount based on the square root √ (P0 / P1) of the ratio of the annealing fuel pressure P0 and the actual fuel pressure P1, accurate correction is performed to significantly suppress the fuel injection amount deviation. Can do.

  Thus, the final fuel injection amount Qfnl obtained in step S305 is a value much closer to the fuel injection amount that has been planned in advance. After calculating the final fuel injection amount Qfnl, the final fuel injection amount Qfnl is converted into the injector energization time τ in step S306, and this routine is terminated. Thereafter, when the fuel injection timing arrives, the ECU 100 energizes the injector 12 for a time equal to the energization time τ and injects fuel from the injector 12. As a result, an amount of fuel that is substantially equal to the amount that has been planned in advance is injected from the injector 12.

  Since the calculation process of this routine is not accompanied by the calculation of the fuel pressure correction coefficient KP and is only a simple four arithmetic operation except for the calculation step (S301) of the basic fuel injection amount Qb, it can be executed in a relatively short time. . Therefore, it can be executed at the same second timing as before, and a sufficiently satisfactory calculation result can be obtained.

  As can be seen from the above description, according to the present embodiment, it is possible to suppress fuel injection amount deviation and inter-cylinder fuel injection amount variation due to fuel pressure deviation. Therefore, accurate fuel injection can be performed even in the low fuel pressure range, and the dynamic range can be expanded. In addition, it is possible to shorten the start-up time by reducing the volume in the delivery pipe and increasing the pressure in the delivery pipe at the start-up. Furthermore, it becomes possible to execute irregular fuel pumping by the high-pressure fuel pump.

  Note that if the calculation speed of the ECU 100 becomes higher, the final fuel injection amount can be calculated by the following method. FIG. 9 shows a routine relating to the final fuel injection amount calculation processing in this case. This routine is also repeatedly executed by the ECU 100 every time the second timing comes. Here, for easy understanding, the processing at the second timing indicated by T2 in FIG. 3 will be described.

  In step S401, the ECU 100 calculates the basic fuel injection amount Qb in the same manner as in step S201. Next, the ECU 100 proceeds to step S402, and acquires the value of the actual fuel pressure P1 detected by the fuel pressure sensor 38 at the current second timing T2.

  Next, in step S403, the ECU 100 uses the basic fuel injection amount Qb calculated in step S401 and the actual fuel pressure P1 acquired in step S402 to directly calculate the fuel pressure correction coefficient KP with reference to the fuel pressure correction coefficient map shown in FIG. Calculate automatically. Here, since the calculation speed of the ECU 100 is sufficiently high, the fuel pressure correction coefficient KP can be calculated in time for the fuel injection at the second timing.

  Thereafter, in step S404, the ECU 100 calculates the final fuel injection amount Qfnl based on the formula: Qfnl = Qb × KP. In step S405, the final fuel injection amount Qfnl is converted into the injector energization time τ, and this routine ends. After that, the injector 12 is energized for the time equal to the energization time τ simultaneously with the arrival of the fuel injection timing, and the fuel is injected as described above. Even in this case, it is possible to execute fuel injection in an amount substantially equal to the amount scheduled in advance, and to suppress fuel injection amount deviation and inter-cylinder fuel injection amount variation.

  Various other embodiments of the present invention are conceivable. For example, in the above embodiment, the second correction value is calculated based on the ratio of the annealing fuel pressure and the actual fuel pressure. Instead, the second correction value is calculated based on the difference between the annealing fuel pressure and the actual fuel pressure. You may make it calculate. Further, instead of calculating the second correction value based on the square root of the ratio between the annealing fuel pressure and the actual fuel pressure, the second correction value may be calculated based on the square root of the difference between the annealing fuel pressure and the actual fuel pressure. . The first and second correction values are not limited to values that are multiplied by the basic fuel injection amount, but may be values that are added to, subtracted, or divided from the basic fuel injection amount. The engine is a spark ignition type internal combustion engine in the above embodiment, but it may be a compression ignition type internal combustion engine, that is, a diesel engine instead. For example, the present invention can be suitably applied to a common rail diesel engine. Further, the engine may be not only a direct injection type but also an intake passage injection type that injects fuel into an intake passage (for example, an intake port). This is because this intake passage injection type engine may also perform high pressure injection. The present invention can also be suitably applied to a so-called dual injection engine having both a direct injection type and an intake passage injection type. Various configurations of the fuel supply system and the high-pressure fuel pump are conceivable.

  As can be seen from the above description, in the present embodiment, the ECU 100 includes the basic fuel injection amount calculating means, the smoothed fuel pressure calculating means, and the correcting means.

  Embodiments of the present invention are not limited to the above-described embodiments, and all modifications, applications, and equivalents included in the spirit of the present invention defined by the claims are included in the present invention. Therefore, the present invention should not be construed as being limited, and can be applied to any other technique belonging to the scope of the idea of the present invention.

1 is a system diagram showing a control device for an internal combustion engine according to the present embodiment. It is a timing chart which shows the opening / closing timing of the plunger lift and electromagnetic spill valve in a high-pressure fuel pump. It is a time chart which shows the change of each fuel pressure value, and the execution timing of each arithmetic processing, and shows the case of 4 injection 2 pressure feeding. It is a flowchart which shows the calculation process of the annealing fuel pressure and fuel pressure correction coefficient which are performed at a 1st timing. A fuel pressure correction coefficient map is shown. It is a flowchart which shows the calculation process of the conventional final fuel injection amount. It is a time chart which shows the change of each fuel pressure value, and the execution timing of each arithmetic processing, and shows the case of 4 injection 3 pressure feed. It is a flowchart which shows the calculation process of the last fuel injection amount of this embodiment. It is a flowchart which shows the calculation process of the last fuel injection amount which concerns on another method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Engine 12 Injector 20 Fuel supply system 23 High pressure fuel line 27 Delivery pipe 28 High pressure fuel pipe 30 High pressure fuel pump 36 Electromagnetic spill valve 38 Fuel pressure sensor 100 Electronic control unit (ECU)
P0 Annealing fuel pressure P1 Actual fuel pressure Qb Basic fuel injection amount Qfnl Final fuel injection amount KP Fuel pressure correction coefficient KPr Fuel pressure deviation correction coefficient T1 First timing T2 Second timing Ti Fuel injection timing

Claims (3)

A control device for an internal combustion engine that pumps fuel to a delivery pipe with a high-pressure fuel pump and detects a fuel pressure in the delivery pipe with a fuel pressure sensor,
Basic fuel injection amount calculating means for calculating a basic fuel injection amount based on the engine operating state;
Based on the actual fuel pressure detected by the fuel pressure sensor, an annealing fuel pressure calculating means for calculating an annealing fuel pressure that is a value obtained by averaging the fuel pressure values in the delivery pipe;
A first correction value is calculated based on the annealing fuel pressure and the engine operating state, and a second correction value is calculated based on the annealing fuel pressure and the actual fuel pressure, and the first correction value and the second correction value are calculated. Correction means for correcting the basic fuel injection amount by a value ,
The annealing fuel pressure calculating means calculates the annealing fuel pressure at a predetermined first timing,
The correction means calculates the first correction value at the first timing, and calculates the second correction value at a predetermined second timing that is later than the first timing and before fuel injection. In addition, the annealing fuel pressure and the actual fuel pressure at the time of calculating the second correction value are detected by the fuel pressure sensor at the annealing fuel pressure calculated at the first timing and at the second timing. An internal combustion engine control device using the actual fuel pressure .   2. The control device for an internal combustion engine according to claim 1, wherein the correction unit calculates the second correction value based on a ratio between the smoothed fuel pressure and the actual fuel pressure.   3. The control device for an internal combustion engine according to claim 2, wherein the correction means calculates the second correction value based on a square root of a ratio between the annealed fuel pressure and the actual fuel pressure.

Images