JP2005036721A - Engine control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent fuel supply shortage from occurring due to the deterioration of a high-pressure fuel pump 21 with the elapse of time in a control device A controlling intake air and fuel according to the operating state of an engine 1. <P>SOLUTION: During the operation of the engine 1, a fuel pressure is feedback-controlled by adjusting the delivery amount of the high-pressure fuel pump 21 by the closing timing (spill angle) of a spill valve 21d (SA4 to SA6). When the advance angle correction amount of a target spill angle from a reference spill angle exceeds a deterioration determination amount α (YES in SA9) with an actual fuel pressure matching a general target fuel pressure (YES in SA8), it is predicted that the fuel supply shortage occurs in a high load area due to the deterioration of a pump, and a target supercharging pressure on a high load side is correctively reduced (SA10) in a supercharging pressure control map to compensate for the shortage of fuel. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an engine control device, and particularly to a fuel pump that supplies high-pressure fuel to a fuel injection valve, such as an in-cylinder direct injection engine, resulting from a shortage of fuel pump discharge due to deterioration over time or the like. It belongs to the technical field of correction control for dealing with defects.

  Conventionally, as a control device for this type of engine, as disclosed in, for example, Patent Document 1, in a direct injection type engine equipped with a supercharger, a fuel requirement is high particularly in a high load region where the supercharger is driven. It is known that an injector having a large nozzle diameter is provided so that a large amount of fuel can be injected in a short period of time in response to an increase in the fuel pressure. In this case, the supercharger is controlled by the controller according to the operating state of the engine.

Further, as disclosed in Patent Document 2, for example, in a direct injection type cylinder engine, according to the operating state of the engine so that a large amount of fuel can be injected in a short time in response to an increase in fuel demand on the high load side. Also known is a fuel supply device in which the fuel pressure of the fuel supplied from the high-pressure fuel pump is increased. In this device, the fuel pressure is controlled to be the target fuel pressure corresponding to the operating state of the engine by feedback correcting the fuel supply amount from the fuel pump based on the signal from the fuel pressure sensor.
Japanese Patent Laid-Open No. 10-274072 JP 2000-249020 A

  By the way, in general, the capacity (discharge capacity) of a pump that supplies high-pressure fuel to an engine fuel injection valve is set as small as possible with a certain margin for the required maximum discharge volume. It is preferable to do. This is to save space and reduce pump drive loss. When the fuel demand is very small, such as during idle operation, a small-capacity pump has better controllability.

  However, the capacity of the fuel pump set in this way may not have much room for the fuel demand of the engine as a result. For example, in the case of an automobile engine, there is a strong demand for space saving and drive loss reduction as described above, and the change in the driving state is large, and the difference between the minimum and maximum fuel demand is quite large. It is difficult to provide a sufficient margin for the maximum discharge amount of the fuel pump. This tendency is particularly remarkable in the case of an engine with a supercharger.

  If the fuel pump capacity does not have much room for the fuel demand of the engine, as the pump capacity decreases due to deterioration over time, etc., for example, at the time of full load operation where the fuel demand becomes the largest. There is a problem in that the shortage of fuel supply occurs and the air-fuel ratio becomes excessively lean, thereby deteriorating emissions. In addition, the shortage of fuel in the full load range may impair the durability reliability of the engine.

  In particular, in the in-cylinder injection engine in which high-pressure fuel is supplied to the fuel injection valve as in the conventional example (Patent Documents 1 and 2), leakage occurs due to deterioration over time in a mechanism portion that delivers high-pressure fuel. Are likely to increase, and the above-mentioned problems are likely to occur.

  The present invention has been made in view of such points, and an object of the present invention is to provide a fuel pump capability over time in a control device that controls intake air and fuel in accordance with the operating state of the engine. The main purpose is to prevent the occurrence of fuel supply shortage due to this.

  In order to achieve the above object, the solution of the present invention maintains the fuel pressure at a substantially target fuel pressure by adjusting the fuel supply amount during operation of the engine, while adjusting the fuel from the initial standard amount. When a decrease in pump capacity is determined based on the degree of deviation, and the occurrence of a shortage of fuel supply is predicted based on this determination result, the target intake air amount is corrected to decrease in advance to meet the shortage.

  Specifically, the invention according to claim 1 includes an operating state detecting unit that detects an operating state of the engine, an intake air amount adjusting unit that adjusts an intake air amount of the engine, and at least the detected engine operating state, An intake air amount control means for controlling the intake air amount adjusting means so as to obtain a preset target intake air amount characteristic; and a fuel pressure detecting means for detecting the fuel pressure of the fuel discharged from the fuel pump and supplied to the fuel injection valve of the engine; A fuel supply amount adjusting means for adjusting a fuel supply amount from the fuel pump to the fuel injection valve; and at least the fuel supply amount adjusting means based on the detected value of the fuel pressure so that the detected value approaches the target fuel pressure. It is premised on an engine control device including a fuel supply amount control means for controlling.

  Then, when the detected value of the fuel pressure substantially matches the target fuel pressure, it is determined how much the operating state of the fuel supply amount adjusting means is deviated from the preset standard state, and the degree of the determined deviation is determined. And a predicting means for predicting that a shortage of fuel supply will occur in a predetermined operating state, and when the occurrence of a shortage of fuel supply is predicted by the predicting means, the target intake air amount characteristic is set to at least the target intake air in the predetermined operating state. And a target intake air amount correcting means for correcting the amount so as to decrease.

  With the above-described configuration, first, during the operation of the engine, the intake air amount adjusting means is controlled so that the target intake air amount characteristic preset according to the operating state or the like is obtained. Further, the fuel supply amount is adjusted by the fuel supply amount adjusting means according to the detected value of the fuel pressure so that the fuel pressure of the fuel discharged from the fuel pump and supplied to the fuel injection valve approaches the target fuel pressure. Then, in such a state that the fuel pressure is maintained at the substantially target fuel pressure, it is determined how much the operating state of the fuel supply amount adjusting means deviates from a preset standard state. That is, in order to maintain the fuel pressure at the target value, the desired amount of fuel supply is required. At this time, if there is no deterioration over time in the performance of the fuel pump, the fuel supply amount adjustment means The operating state should be a standard set in advance. On the other hand, if the pump capacity is reduced due to deterioration over time or the like, the operating state of the fuel supply amount adjusting means should have changed to the fuel increasing side in order to compensate for the decrease in the discharge amount caused by it. The degree of deviation from the standard state represents a decrease in pump capacity.

  Therefore, based on the degree of deviation of the operating state of the fuel supply amount adjusting means, that is, the degree of decrease in the pump capacity, the predicting means may cause insufficient fuel supply in a predetermined operating state such as a high load region where the intake air amount increases. It can be accurately predicted that it will occur. Then, in accordance with the prediction result, the target intake air amount correction means corrects the target intake air amount in the engine so that at least the target intake air amount in the predetermined operating state decreases. Thereby, when the engine actually enters the predetermined operation state, even if the shortage of the fuel supply amount due to the decrease in the capacity of the fuel pump occurs, the intake air amount is reduced to meet the shortage amount. Lean air-fuel ratio is prevented.

  In the invention of claim 2, the intake air amount adjusting means includes a supercharger, the intake air amount control means controls at least the supercharging pressure of the intake air by the supercharger, and the target intake air amount correcting means includes: The target supercharging pressure of the supercharger is corrected. As a result, if a shortage of fuel is predicted when there is a large amount of intake air in an engine with a supercharger, the target supercharging pressure is corrected to match the shortage of that fuel. Even in this state, the intake air amount becomes smaller than the initial (before correction) target air amount, and lean air-fuel ratio is prevented.

  According to a third aspect of the present invention, the intake air amount adjusting means includes an electric throttle valve that is disposed in the intake passage of the engine and is operated by an electric actuator, and the intake air amount control means controls at least the opening of the throttle valve. The target intake air amount correction means corrects at least the target opening of the throttle valve.

  Thus, for example, when controlling the opening of the electric throttle valve based on the operation amount of the accelerator pedal, the engine operating state, etc., if a shortage of fuel is predicted when the intake air amount is large, the shortage of the fuel Since the target opening of the throttle valve is corrected to meet the requirement, even when the engine actually operates with a large intake air amount, the intake air amount becomes smaller than the original (before correction) target air amount, Lean air-fuel ratio is prevented.

  In the invention of claim 4, the target intake air amount correcting means corrects only the target intake air amount corresponding to the high load region in the target intake air amount characteristic of the engine. In this way, even if the capacity of the fuel pump is reduced, the intake air amount set in the original control characteristics is relatively small, and in the low load range and the medium load range where there is no risk of fuel shortage, However, the target intake air amount is not corrected, and therefore the engine output is not reduced by the unnecessary correction of the intake air amount.

  According to a fifth aspect of the present invention, in the engine control device according to any one of the first to fourth aspects, the fuel pressure has decreased at a rate of change greater than or equal to a predetermined value based on the detected value of the fuel pressure by the fuel pressure detecting means. A fuel pressure decrease determining means for determining the intake air amount, and an intake air amount correction control means for controlling the intake air amount adjusting means so as to decrease the intake air amount of the engine in response to the determination of the fuel pressure decrease by the fuel pressure decrease determining means. And

  Thus, for example, even if the engine is in a predetermined operation state with a large intake air amount without correcting the target intake air amount even though the performance of the fuel pump is reduced due to a prediction error, At that time, in response to the determination of sudden decrease in fuel pressure by the fuel pressure decrease determination means, the intake air amount of the engine is immediately decreased by the intake air amount correction control means. As a result, the degree of leaning of the air-fuel ratio due to fuel shortage becomes relatively small, and the period of leaning becomes extremely short.

  According to a sixth aspect of the present invention, the engine control apparatus according to the fifth aspect further comprises an ignition timing correcting means for correcting the ignition timing of the engine to a retarded side in response to the determination of the fuel pressure decrease by the fuel pressure decrease determining means. Shall be provided. As a result, even if the air-fuel ratio becomes lean due to fuel shortage in an operating state with a large intake air amount, knocking can be prevented by retarding the ignition timing by the ignition timing correction means.

  According to a seventh aspect of the present invention, in the same premise configuration as the first aspect of the invention, when the detected value of the fuel pressure by the fuel pressure detecting means substantially coincides with the target fuel pressure, the operating state of the fuel supply amount adjusting means is It is determined how much the standard state set in advance is deviated, and predicting means for predicting that a shortage of fuel supply will occur in a predetermined operating state based on the determined degree of deviation, and the predicting means Based on the target intake air amount correction means for correcting the target intake air amount characteristic so that the target intake air amount decreases in at least the predetermined operating state when the occurrence is predicted, and the detected value of the fuel pressure by the fuel pressure detection means In response to a fuel pressure decrease determination means for determining that the detected value has decreased at a predetermined rate of change, and a fuel pressure decrease determination by the fuel pressure decrease determination means, the ignition timing of the engine is corrected to the retard side. Write, wherein also the fuel supply shortage is predicted by the prediction means, characterized by comprising an ignition timing correcting means not to perform the ignition timing correction according to this.

  According to the above configuration, the same effect as that of the invention according to the first to fourth aspects can be obtained, and, similarly to the invention of the sixth aspect, even if an accidental lean air-fuel ratio is caused, Knocking can be prevented by correcting the ignition timing retardation. On the other hand, since the retard correction of the ignition timing is not performed when the fuel supply shortage is predicted, the fuel consumption is not deteriorated by the retard of the unnecessary ignition timing.

  As described above, according to the engine control apparatus of the first aspect of the present invention, the fuel pressure is reduced before the actual fuel supply shortage due to the deterioration of the fuel pump over time in a predetermined operation state with a large amount of intake air. By determining the degree of decrease in the fuel pump capacity based on the amount of adjustment of the fuel supply by feedback, and by correcting the characteristics of the intake air amount control according to this determination, when the actual operation state with a large intake amount is reached The intake air amount can be reduced to meet the shortage of fuel, and the lean air-fuel ratio can be prevented. That is, it is possible to prevent excessive leaning of the air-fuel ratio due to a decrease in pumping capacity, and to solve problems of emission and durability reliability.

  According to the invention of claim 2, in the engine with a supercharger, the effect of the invention of claim 1 can be obtained by correcting the target supercharging pressure.

  According to the invention of claim 3, in the engine provided with the electric throttle valve, the effect of the invention of claim 1 can be obtained by correcting the target opening of the throttle valve.

  According to the invention of claim 4, by correcting the target intake air amount only in the high load region where fuel shortage may occur, it is possible to prevent the engine output from being lowered due to unnecessary intake air amount correction in the low load region and the middle load region. .

  According to the fifth aspect of the present invention, even if a sudden fuel supply shortage occurs in an operation state with a large amount of intake air due to, for example, a prediction error or a sudden failure, the lean air-fuel ratio is reduced by immediately decreasing the intake air amount. Emissions and reliability problems due to computerization can be minimized.

  According to the invention of claim 6, in addition to the effect of the invention of claim 5, when the air-fuel ratio becomes leaner, reliability can be ensured by preventing knocking by retarding the ignition timing. .

  Further, according to the engine control apparatus of the seventh aspect of the invention, the same effects as those of the first to fourth and sixth aspects of the invention can be obtained, and the fuel consumption can be deteriorated due to the retard of the unnecessary ignition timing. Absent.

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

(Embodiment 1)
FIG. 1 shows the configuration of a multi-cylinder in-cylinder in-cylinder injection engine 1 (not limiting the present invention) according to the present invention. This engine 1 has a cylinder block 3 in which a plurality of cylinders 2, 2,... (Only one is shown) are provided in series, and a cylinder head 4 arranged on the cylinder block 3, and each cylinder 2 A piston 5 is fitted in each of the pistons 5 so as to be able to reciprocate. A combustion chamber 6 is defined between the crown surface of the piston 5 and the lower surface of the cylinder head 4. The reciprocating motion of the piston 5 accompanying the combustion in the combustion chamber 6 is converted to the rotational motion of the crankshaft 8 via the connecting rod 7 and output by the crankshaft 8. The cylinder block 3 includes an electromagnetic crank angle sensor 9 for detecting the rotation angle of the crankshaft 8, a knock sensor 10 for detecting knocking from fluctuations in combustion pressure, and cooling facing the interior of a water jacket (not shown). A water temperature sensor 11 for detecting the temperature of the water (engine water temperature) is provided.

  An intake port 12 and an exhaust port 13 are formed in the cylinder head 4 so as to open toward the ceiling surface of the combustion chamber 6 for each cylinder 2, and a poppet valve is opened and closed to open and close each port opening. The intake and exhaust valves 14 and 15 are respectively arranged. The intake valve 14 and the exhaust valve 15 are opened and operated in synchronism with the rotation of the crankshaft 8 by intake and exhaust camshafts (not shown) supported on the cylinder head 4, respectively. It has become. The intake-side camshaft is provided with a variable phase variable valve mechanism 16 (hereinafter referred to as VVT) that continuously changes the rotational phase with respect to the crankshaft 8 within a predetermined range. The VVT is not limited to the phase variable type and is not essential to the present invention.

  Further, the cylinder head 4 is formed with a through hole along the axis of each cylinder 2 and provided with a spark plug 17. The electrode at the tip of the spark plug 17 is disposed so as to face the combustion chamber 6 from the ceiling surface of the combustion chamber 6, while the base end portion of the spark plug 17 is inserted into the through hole of the cylinder head 4 from above. The cylindrical ignition coil 18 is connected. The ignition coil 18 is integrally provided with an IC igniter 19 for turning on and off the current to the primary side. The ignition coil 18 receives an ignition signal input from an ECU 50 (described later) and receives an ignition signal between electrodes of the ignition plug 17. It is designed to cause a spark discharge.

  Further, the cylinder head 4 is provided with an injector (fuel injection valve) 20 with the injection port facing the intake side peripheral portion of the combustion chamber 6 for each cylinder 2. The injector 20 may be, for example, a known swirl type that injects fuel in a conical shape from a nozzle hole at the front end facing the combustion chamber 6, and may be, for example, a slit type or a multi-hole type. Alternatively, a structure in which the core valve is operated by a piezoelectric element (piezo element type) may be used. The injectors 20 of these cylinders 2 are connected to a fuel supply pipe 22 via fuel distribution pipes (not shown) extending in the cylinder row direction, whereby high-pressure fuel discharged from the high-pressure fuel pump 21 is supplied to each cylinder 2. It is distributed and supplied to the injector 20.

  In the illustrated example, the high-pressure fuel pump 21 is connected to the fuel tank 23 by a fuel passage 24, and the low-pressure fuel pump 25, the low-pressure regulator 26, and the filter 27 are sequentially arranged from the upstream side to the downstream side of the fuel passage 24. Etc. are arranged. The low-pressure fuel pump 25 is arranged so as to be immersed in the fuel in the fuel tank 23, sucks up the fuel and sends it out to the fuel passage 24. The fuel is regulated by a low pressure regulator 26, filtered by a filter 27, supplied to a high pressure fuel pump 21, boosted by the high pressure fuel pump 21, and discharged to a fuel supply pipe 22. The pressure state of the fuel thus discharged and supplied to the injector 20 is detected by a fuel pressure sensor 28 as fuel pressure detecting means disposed in the fuel supply pipe 22 (or fuel distribution pipe). On the other hand, surplus fuel is returned to the low pressure side and is returned to the fuel tank 23 through the return passage 29.

  The schematic structure and operation of the high-pressure fuel pump 21 will be described with reference to FIG. 2. As schematically shown in the figure, the high-pressure fuel pump 21 is driven by an intake side cam of the engine 1 and reciprocates. 21a and a plunger chamber 21b whose volume changes as the plunger 21a reciprocates, and a check valve 21c is provided in a passage connecting the plunger chamber 21b to the fuel supply pipe 22 on the fuel discharge side (high pressure side). On the other hand, a check valve 21d (hereinafter referred to as a spill valve) is also disposed in a passage communicating the plunger chamber 21b with a fuel passage 24 on the fuel suction side (low pressure side). The spill valve 21d is opened and closed by a valve body driven by an electromagnetic solenoid 21e.

  First, in the intake stroke, the electromagnetic solenoid 21e is inactive (off), the spill valve 21d is opened, and fuel is drawn into the plunger chamber 21b from the low pressure side as the plunger 21a is lowered. Thereafter, even when the plunger 21a rises past the bottom dead center, the spill valve 21d remains open until halfway (spill stroke), and fuel flows out (returns) from the plunger chamber 21b to the low pressure side. Then, when the solenoid 21e is energized (on) at a predetermined timing and the spill valve 21d is closed leaving a stroke corresponding to the amount of fuel discharged, the outflow of fuel to the low pressure side is blocked and the plunger chamber 21b When the pressure of the fuel is increased, the check valve 21c on the discharge side is opened and the fuel is discharged.

  In other words, the effective stroke of the plunger 21a in the high-pressure fuel pump 21 changes depending on the closing timing of the spill valve 21d, and the fuel discharge amount (fuel supply amount) is adjusted by changing the closing timing of the spill valve 21d. be able to. Therefore, the spill valve 21d and the electromagnetic solenoid 21e constitute a fuel supply amount adjusting means for adjusting the fuel supply amount to the injector 20.

  As shown in FIG. 1, an intake passage 30 is connected to one side of the engine 1 so as to communicate with the intake port 12 of each cylinder 2. The intake passage 30 supplies air filtered by the air cleaner 31 to the combustion chamber 6 of the engine 1, and the flow rate of air (intake air) sucked into the engine 1 in order from the upstream side to the downstream side. An air flow sensor 32 for detecting the intake air, a compressor 33 driven by a turbine 42 to be described later to compress intake air, an intercooler 34 for cooling the intake air compressed by the compressor 33, and a cross-sectional area of the intake passage 30 is adjusted by a valve body. An electric throttle valve 35 (including a throttle sensor 36 for detecting the position of the valve body) and a surge tank 37 are provided.

  The electric throttle valve 35 is not mechanically connected to an accelerator pedal (not shown). For example, the position of the valve body is changed by an actuator such as a servo motor to adjust the flow rate of intake air (intake air). Amount adjusting means). The surge tank 37 is provided with a boost sensor 38 that detects the pressure in the intake passage 30 downstream of the throttle valve 35. The intake passage 30 on the downstream side of the surge tank 37 is an independent passage branched for each cylinder 2, and the downstream ends of these independent passages communicate with the intake port 12. Each independent passage is provided with an open / close valve 39 (intake flow adjustment valve) for adjusting the strength of the in-cylinder flow, and is opened and closed by an actuator such as a stepping motor.

  On the other hand, an exhaust passage 40 for discharging burned gas (exhaust gas) from the combustion chamber 6 is connected to the other side of the engine 1. The upstream end of the exhaust passage 40 is an exhaust manifold that branches into each cylinder 2 and communicates with the exhaust port 13, and a sensor 41 that detects the oxygen concentration in the exhaust is disposed at a collection portion of the exhaust manifold. ing. Further, a turbine 42 that is rotated by receiving an exhaust flow and a catalytic converter 43 for purifying harmful components in the exhaust gas are disposed in the exhaust passage 40 downstream of the exhaust manifold assembly. Yes.

  The turbine 42 constitutes a turbocharger 45 together with the compressor 33 in the intake passage 30. When the turbine 42 is rotated by the exhaust flow, the compressor 33 that rotates integrally with the turbine 42 compresses the intake air. To supercharge. The turbocharger 45 includes a wastegate passage 46 that bypasses the turbine 42 and distributes exhaust gas from the upstream side of the exhaust passage 40 to the downstream side of the turbine, and a flow rate of exhaust gas that flows through the wastegate passage 46. A wastegate valve 47 for adjusting the pressure is provided.

  Specifically, the valve body of the waste gate valve 47 is urged toward the closing side of the passage 46 by a coil spring (not shown) in the diaphragm 48, and by the supercharging pressure downstream of the turbine 33 guided to the diaphragm 48. It is pressed to the opposite side, and is held by a balance between the pressing force by the supercharging pressure and the urging force of the coil spring. For this reason, when the supercharging pressure reaches a preset target maximum supercharging pressure, the wastegate valve 47 is opened, and a part of the exhaust gas flows through the wastegate passage 46, so that further supercharging is performed. Increase in pressure is suppressed.

  Further, a part of the supercharging pressure guided to the diaphragm 48 is released to the intake passage 30 upstream of the turbine 33 through the electromagnetic solenoid valve 49, and is adjusted by adjusting the opening degree of the electromagnetic solenoid valve 49. The target maximum supercharging pressure of the feeder 45 can be adjusted. In other words, the supercharger 45 of this embodiment is capable of adjusting the maximum supercharging pressure by the wastegate passage 46 and the wastegate valve 47, and is an intake air amount adjusting means for adjusting the intake air amount of the engine 1. Is included. In addition to the above, the turbocharger 45 may be a variable turbo that can change the supercharging efficiency by adjusting the flow area of the intake air led to the turbine 42, for example. The intake air amount can be adjusted by adjusting the supercharging pressure by changing the supercharging efficiency. Further, the supercharger 45 is not limited to a turbocharger but may be a mechanical supercharger.

  Although not shown, the upstream end of the EGR passage that recirculates part of the exhaust to the intake side is branched and connected to a portion of the exhaust passage 40 upstream of the turbine 42. The downstream end of the EGR passage is connected to the surge tank 37, and an electric EGR valve whose opening degree can be adjusted is disposed in the vicinity thereof so that the amount of exhaust gas recirculated through the EGR passage can be adjusted. Yes.

  As schematically shown in FIG. 3, at least an igniter 19, an injector 20, a high-pressure fuel pump 21, an electric throttle valve 35, a supercharger 45, etc. of the engine 1 are provided from an engine control unit 50 (hereinafter referred to as ECU). It is designed to operate in response to the control signal. Further, as shown in the drawing, the ECU 50 receives at least output signals from the crank angle sensor 9, the fuel pressure sensor 28, the air flow sensor 32, the throttle sensor 36, and the like, and further operates an accelerator pedal operation amount (hereinafter referred to as an accelerator pedal). An output signal from an accelerator opening sensor 51 that detects the opening) is input.

  That is, the ECU 50 detects the operating state of the engine 1 (for example, the target load and the engine speed) based on the signal input from the sensor as described above, and in response to this, mainly intake air and fuel to each cylinder 2 are detected. The amount of fuel supplied and the ignition timing for the air-fuel mixture are controlled. For this purpose, the ECU 50 has at least an operation state detection unit 50a that detects the operation state of the engine 1 based on the target load and the engine speed, and a target intake air amount characteristic that is set in advance according to the detected engine operation state. The throttle valve 35 is mainly controlled so as to become the target air-fuel ratio according to a signal from the air flow sensor 32 and the intake air amount control unit 50b that controls the solenoid valve 49 of the VVT 16 and the supercharger 45. A fuel injection control unit 50c that controls the fuel injection amount of the injector 20, an ignition timing control unit 50d that controls the ignition timing of each cylinder 2 according to the detected engine operating state, and a high pressure to maintain the fuel pressure at the target fuel pressure A fuel pressure control unit 50e (fuel supply amount control means) for controlling the fuel discharge amount of the fuel pump 21 includes a software routine (program) It is provided in the form of a beam).

  Here, the control by the fuel pressure control unit 50e will be described. Basically, in synchronism with the timing at which the fuel injection is performed by the injector 20 of each cylinder 2, an amount of fuel necessary for the injection is supplied to the high-pressure fuel pump. By discharging from the fuel tank 21, the average fuel pressure in the fuel supply pipe 22 and the fuel distribution pipe (the pulsation caused by fuel injection smoothed) is maintained at the target fuel pressure. Therefore, in this embodiment, first, the basic discharge amount of fuel from the high-pressure fuel pump 21 is controlled in association with the detected engine operating state or the fuel injection pulse width to the injector 20. . That is, the optimum closing timing of the spill valve 21d corresponding to the effective stroke of the plunger 21a of the high-pressure fuel pump 21 (crank angle position, which corresponds to either the engine operating state or the fuel injection pulse width. The spill angle is determined in advance by experiments or the like, and this is electronically stored in the memory of the ECU 50 as a control map of the spill valve 21d. The reference spill angle is read from the control map based on the engine operating state detected by the operating state detecting unit 50a during the operation of the engine 1 or the fuel injection amount (injection pulse width) determined by the fuel injection control unit 50c. This is the basic control amount.

  In addition, the pressure state of the fuel discharged from the high-pressure fuel pump 21, that is, the fuel pressure in the fuel supply pipe 22 or the fuel distribution pipe is detected by the fuel pressure sensor 28, and this detected value (actual fuel pressure) is fed back to the ECU 50, The basic spill angle control amount is corrected so that the actual fuel pressure approaches the target fuel pressure. That is, if the actual fuel pressure is higher than the target fuel pressure, the spill angle is corrected to the retard side so that the effective stroke of the plunger 21a is reduced. If the actual fuel pressure is lower than the target fuel pressure, the effective stroke of the plunger 21a is increased. The spill angle is corrected to the advance side so that A drive pulse is output to the electromagnetic solenoid 21e that opens and closes the spill valve 21d based on the control amount (hereinafter referred to as a target spill angle) of the spill valve 21d after the feedback correction (see FIG. 2).

  The target fuel pressure is not particularly limited and may be substantially constant regardless of the engine operating state, or may be changed according to the engine operating state. Since the time during which fuel can be injected by the injector 20 is shortened, it is preferable to relatively increase the target fuel pressure so that a large amount of fuel can be injected in a short time. Similarly, the higher the target load, the higher the target fuel pressure. It is preferable to increase the value.

  By the way, the main reason for the feedback correction of the fuel pressure as described above is that the discharge amount of the high-pressure fuel pump 21 varies due to individual differences, and the wear of the sliding part of the component with time and the sealing material mainly. This is because the amount of fuel discharged with respect to the stroke of the plunger 21a gradually decreases due to deterioration of the fuel. That is, as shown in FIG. 4A, the pump discharge amount corresponding to the stroke of the plunger 21a (that is, the spill angle) gradually decreases over a relatively long time from the initial state indicated by the solid line in the figure. As a result, the effective stroke of the plunger 21a necessary for obtaining the required fuel discharge amount is gradually increased, and the spill angle is gradually corrected to the advance side (as indicated by the broken line in the figure). . This is particularly remarkable in a cylinder injection engine that requires high-pressure fuel injection as in this embodiment.

  When the deterioration of the high-pressure fuel pump 21 progresses, as shown by the broken line in FIG. 5B, the maximum fuel demand of the engine 1 is met even in the full discharge state where the stroke of the plunger 21a is completely used. The discharge amount may not be obtained. In this case, for example, at the full load where the supercharging of the intake air by the supercharger 45 is maximized and the fuel demand becomes the largest, the supply of fuel to the intake air is insufficient and the air-fuel ratio becomes leaner than the target value. As a result, there is a risk that the emission reliability will be greatly deteriorated, and the durability reliability of the engine may be impaired due to an excessive increase in the combustion temperature.

  With respect to such a problem, in the engine control apparatus A according to this embodiment, as a characteristic part of the present invention, the fuel discharge amount by the fuel pressure control unit 50e before the fuel demand is still high during the operation of the engine 1. In the state where the fuel pressure is maintained at the target fuel pressure by the above control, the target spill in the control of the high-pressure fuel pump 21 is specifically determined by how much the adjustment amount of the fuel for that purpose deviates from the intended standard value. Based on the advance correction amount of the angle relative to the reference spill angle, the degree of deterioration of the fuel pump 21 with time is detected, and the advance correction amount is indicated by the symbol α in FIG. When it becomes larger than a fixed amount (hereinafter referred to as a deterioration judgment amount) and it is predicted that a fuel supply shortage may occur even in the full discharge state, the predetermined operating state in which the fuel supply shortage is predicted is brought about. The target maximum boost pressure of the response to the supercharger 45 in advance lowered, but was to reduce the amount of intake air in its operating condition.

(Target boost pressure correction)
A control procedure for correcting the target supercharging pressure in accordance with the prediction of insufficient fuel supply as described above will be described below with reference to the flowchart of FIG. The control procedure shown in this flowchart mainly relates to the supercharging pressure and the fuel pressure. In parallel with this, the ECU 50 performs the fuel injection control of the injector 20, the control of the throttle valve 35, and the like.

  In the illustrated flow, in step SA1 after the start, signals from the crank angle sensor 9, the fuel pressure sensor 28, the air flow sensor 32, the throttle sensor 36, the accelerator opening sensor 51, and the like are input, and further temporarily stored in the RAM of the ECU 50. Read stored data. In the subsequent step SA2, the operating state (for example, target load, engine speed, etc.) of the engine 1 is detected, and in the subsequent step SA3, the target maximum supercharging pressure corresponding to the engine operating state is determined. For example, the target maximum supercharging pressure value corresponding to the target load, the engine speed, etc. is determined in advance by experiments or the like, and electronically stored in the memory of the ECU 50 as a supercharging pressure control map. It is sufficient to read from. When a variable turbo or mechanical supercharger is used as the supercharger 45, a target supercharging pressure corresponding to the engine operating state may be determined.

  Subsequently, in step SA4, in this embodiment, the target fuel pressure corresponding to the engine operating state is determined by reading, for example, from the control map therefor, and in step SA5, the reference spill angle of the high-pressure fuel pump 21 corresponding to the engine operating state is determined. Is read from the control map for that purpose, and in step SA6, as described above, the reference spill angle is feedback-corrected based on the detected value of the fuel pressure to determine the target spill angle. For example, the detection value (actual fuel pressure) detected by the fuel pressure sensor 28 is subtracted from the target fuel pressure, the fuel pressure deviation is multiplied by a predetermined control gain to obtain a feedback correction amount, and this is added to the reference spill angle to determine the target spill angle. do it. Further, a map in which a feedback correction amount corresponding to the fuel pressure deviation is set in advance may be provided. In step SA7, the target ignition timing corresponding to the engine operating state is determined by reading from a control map for that purpose, for example.

  In step SA8, it is determined whether or not the absolute value of the fuel pressure deviation is smaller than a predetermined value, that is, whether or not the actual fuel pressure substantially matches the target fuel pressure. On the other hand, if the determination is YES, the process proceeds to Step SA9, and this time, the deviation amount between the target spill angle determined in Step SA7 and the standard spill angle determined in Step SA5, that is, the advance correction of the spill angle. It is determined whether the amount is larger than the deterioration determination amount α (see FIG. 4). That is, that the actual fuel pressure is substantially the target fuel pressure means that the required fuel discharge amount is obtained from the high-pressure fuel pump 21. In this state, the advance correction amount of the spill angle is the high-pressure fuel pump 21. It represents the degree of deterioration.

  Accordingly, when the determination in step SA9 is YES and the advance correction amount of the spill angle is larger than the deterioration determination amount α, it is predicted that there is insufficient fuel supply in a predetermined operation state including at least the full load range. Then, the control map of the supercharging pressure is corrected, and the maximum supercharging pressure in a predetermined operation state is reduced to reduce the intake amount so as to meet the shortage of fuel supply. In step SA11, the electromagnetic solenoid 49 of the supercharger 45 is controlled based on the target maximum boost pressure data read from the corrected boost pressure map, and in step SA12, the target ignition timing is reached. Thus, the igniter 19 is controlled, and then the process returns.

  On the other hand, if the determination in step SA9 is NO and the advance correction amount of the spill angle is equal to or less than the deterioration determination amount α, there is no possibility of insufficient fuel supply, and therefore the correction of the supercharging pressure map is not performed and step SA11 is not performed. In step SA12, the electromagnetic solenoid 49 and the igniter 19 of the supercharger 45 are controlled, and then the process returns.

  In other words, when the advance correction amount of the spill angle (the degree of deviation of the operating state of the fuel supply amount adjusting means from the standard state) is larger than a predetermined value, based on this, the fuel in the predetermined operating state on the high load region side By predicting that supply shortage will occur and correcting the target maximum supercharging pressure in the predetermined operation state in advance, when the engine 1 actually enters the predetermined operation state, the amount of intake air is reduced. It is possible to reduce the air-fuel ratio to the lean side by reducing the supply to meet the shortage of supply.

  Further, in step SA8, which has proceeded after determining that the fuel pressure deviation amount between the actual fuel pressure and the target fuel pressure is greater than or equal to a predetermined value in step SA8, this time, the detected change rate (decrease rate) of the actual fuel pressure is obtained. It is determined whether it is larger than a predetermined rate, that is, whether the fuel pressure is suddenly lowered. If this determination is YES, it is determined that the fuel discharge amount from the high-pressure fuel pump 21 is insufficient because the fuel pressure has abnormally decreased, and the routine proceeds to step SA14 to correct the supercharging pressure control map. Then, the target maximum supercharging pressure in the operating state at that time is greatly reduced, so that the supercharging pressure is immediately reduced to reduce the intake amount to meet the shortage of fuel supply. At this time, the amount of decrease in the supercharging pressure is greater than or equal to that at the time of prediction in step SA10. Further, the target ignition timing is corrected (retarded) to the retard side. Then, the process proceeds to steps SA11 and SA12 to control the solenoid 49 and the igniter 19 of the supercharger 45, and then returns.

  On the other hand, when it is determined NO in step SA13, that is, when the fuel pressure is not rapidly decreased, it is not necessary to immediately decrease the supercharging pressure because the fuel discharge amount is not insufficient. However, since it is determined in step SA8 that the actual fuel pressure has not converged to the target fuel pressure, the pump deterioration determination in step SA9 has not yet been performed at this time, and the high-pressure fuel pump 21 has deteriorated. There is a possibility of progress. Therefore, at this time, in step SA15, the supercharging pressure control map is corrected just in case, and the target supercharging pressure in the predetermined operation state is slightly lowered. At this time, the reduction range of the supercharging pressure is smaller than that at the time of prediction in step SA10. Then, the process proceeds to steps SA11 and SA12, and then returns.

  Step SA2 shown in the flow of FIG. 5 corresponds to the operating state detection unit 50a of the ECU 50 that detects the operating state of the engine 1, and step SA3 is set to a target intake air amount characteristic that is set in advance according to the engine operating state. This corresponds to the control procedure of the intake air amount control unit 50b for controlling the supercharging pressure of the intake air by the supercharger 45. Steps SA4 to SA6 correspond to the fuel pressure control unit 50e that controls the spill valve 21d of the high-pressure fuel pump 21 so that the actual fuel pressure approaches the target fuel pressure.

  The control procedure proceeds from step SA8 to step SA9 in the flow and determines YES. When the actual fuel pressure substantially coincides with the target fuel pressure, the fuel in a predetermined operation state based on the spill angle advance correction amount. Corresponding to the predicting means 50f for predicting that the supply shortage will occur, and step SA10 receives the prediction of the shortage of fuel supply, and the target intake air amount characteristic of the engine 1 is at least the target intake air amount in the predetermined operating state. This corresponds to the target intake air amount correction means 50g that corrects so that the air pressure decreases. In this embodiment, the target intake air amount correction means 50g is configured to reduce the target maximum supercharging pressure only in the predetermined operation state corresponding to the high load range.

  Further, step SA13 of the flow corresponds to the fuel pressure decrease determination means 50h that determines that the actual fuel pressure has decreased at a predetermined rate of change or more, and step SA14 receives the determination of the sudden decrease in fuel pressure, This corresponds to both the intake air amount correction control means 50i for reducing the boost pressure so that the intake air amount decreases, and the ignition timing correction means 50j for correcting the ignition timing to the retard side at that time.

  Therefore, according to the engine control apparatus A according to the first embodiment, the fuel discharge amount from the high-pressure fuel pump 21 is adjusted during operation of the engine 1 to maintain the fuel pressure at a substantially target fuel pressure, and the fuel for that purpose is adjusted. The deterioration of the high-pressure fuel pump 21 is determined based on the adjustment amount, that is, the advance correction amount of the spill angle, and the occurrence of insufficient fuel supply is predicted based on the determination result. It is possible to accurately predict that there will be a shortage of fuel supply in areas.

  And since the control map of the supercharging pressure is corrected in advance according to the prediction result and the target maximum supercharging pressure in the high load range or the like is reduced, the intake air amount is reduced. When operating in a high load range or the like, the intake air amount can be reduced so as to meet the shortage of fuel supply, thereby preventing the air-fuel ratio from becoming lean.

  As a result, it is possible to prevent excessive leaning of the air-fuel ratio in a high load range where fuel supply shortage may occur, and to solve the problems of emission and durability reliability. Since unnecessary correction is not performed in the load and medium load ranges, the engine output does not decrease.

  In addition, even if a sudden fuel shortage occurs due to, for example, a misprediction or a sudden failure, the intake air amount is immediately reduced at this time. Therefore, the emission and reliability of the air-fuel ratio are made leaner. The problem can be minimized and knocking can be prevented by retarding the ignition timing.

(Embodiment 2)
FIG. 6 shows a correction control procedure according to the second embodiment of the present invention. Although not shown, the engine 1 according to the second embodiment does not include the supercharger 45 unlike the first embodiment. In the correction control shown in the drawing, the target supercharging pressure is reduced and corrected. By correcting the target opening degree of the electric throttle valve 35, the intake air amount is reduced to meet the shortage of fuel supply. The overall configuration of the engine 1 and its control system according to the second embodiment is the same as that of the first embodiment except that the supercharger 45 and the associated intercooler 34 are not installed. Hereinafter, the same members are denoted by the same reference numerals, and the description thereof is omitted.

  Then, according to the illustrated flow, the control is performed in the same procedure as that of the first embodiment (see FIG. 5) as a whole, but in step SB3 corresponding to step SA3 of the flow of the first embodiment, the target is set. In step SB10, the target throttle opening is determined instead of the supercharging pressure. Similarly, in the control map for determining the target throttle opening, the set value in the predetermined operation state is corrected so that the throttle opening becomes small. In step SB11, the opening degree of the throttle valve 35 is controlled. Similarly, in steps SB14 and SB15, the target throttle opening is corrected instead of the target boost pressure.

  Therefore, the same operation and effect as those of the first embodiment can be obtained by the engine control apparatus A of the second embodiment.

  In the first and second embodiments, only one of the target supercharging pressure and the target throttle opening is corrected. However, the present invention is not limited to this. For example, the supercharging is performed as in the first embodiment. In the engine 1 provided with the machine 45, the target boost pressure may be corrected and the throttle opening correction as in the second embodiment may be performed together.

  Further, in the case of the engine 1 equipped with the VVT 16 and the intake flow adjustment valve 39 as in the above-described embodiments, they can be used for adjusting the intake air amount. In this case, the intake air amount adjusting means of the present invention includes the VVT 16 and the intake air flow adjusting valve 39.

It is a figure which shows the structure of the engine which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows typically schematic structure and an action | operation of a high pressure fuel pump. It is a block diagram which shows schematic structure of an engine control apparatus. (a) is an explanatory view schematically showing the advance correction of the spill angle corresponding to the deterioration of the pump, and (b) shows a deterioration state in which the maximum fuel demand cannot be satisfied even in the full discharge state. It is a flowchart figure which shows the procedure of correction | amendment of a target supercharging pressure. FIG. 6 is a diagram corresponding to FIG. 5 of Embodiment 2 in which the throttle opening is corrected instead of the supercharging pressure.

Explanation of symbols

A Engine control device 1 Engine 21 High-pressure fuel pump (fuel pump)
21d Spill valve (Fuel supply adjustment means)
21e Solenoid valve (Fuel supply adjustment means)
28 Fuel pressure sensor (fuel pressure detection means)
35 Throttle valve (intake air amount adjusting means)
45 Supercharger (Intake air volume adjusting means)
50a Operation state detection unit (operation state detection means)
50b Intake amount control unit (intake amount control means)
50d Ignition timing control unit (Ignition timing control means)
50e Fuel pressure control unit (fuel supply amount control means)
50f Prediction means 50g Target intake air amount correction means 50h Fuel pressure drop determination means 50i Intake air amount correction control means 50j Ignition timing correction means

Claims (7)

An operating state detecting means for detecting the operating state of the engine;
An intake air amount adjusting means for adjusting the intake air amount of the engine;
An intake air amount control means for controlling the intake air amount adjusting means so as to have a preset target intake air amount characteristic according to at least the detected engine operating state;
Fuel pressure detection means for detecting the fuel pressure of the fuel discharged from the fuel pump and supplied to the fuel injection valve of the engine;
Fuel supply amount adjusting means for adjusting the fuel supply amount from the fuel pump to the fuel injection valve;
Fuel supply amount control means for controlling the fuel supply amount adjusting means based on at least the detected value of the fuel pressure so that the detected value approaches the target fuel pressure;
In an engine control device comprising:
When the detected value of the fuel pressure substantially coincides with the target fuel pressure, it is determined how much the operating state of the fuel supply amount adjusting means deviates from a preset standard state, and based on the determined degree of deviation Predicting means for predicting a shortage of fuel supply in a predetermined operating state;
And a target intake air amount correcting unit that corrects the target intake air amount characteristic so that the target intake air amount decreases at least in the predetermined operation state when occurrence of a shortage of fuel supply is predicted by the predicting unit. Engine control device. The intake air amount adjusting means includes a supercharger,
The intake air amount control means controls at least the supercharging pressure of the intake air by the supercharger,
The engine control apparatus according to claim 1, wherein the target intake air amount correcting means corrects a target supercharging pressure of the supercharger. The intake air amount adjusting means includes an electric throttle valve that is disposed in the intake passage of the engine and is operated by an electric actuator,
The intake air amount control means controls at least the opening of the throttle valve,
2. The engine control apparatus according to claim 1, wherein the target intake air amount correcting means corrects a target opening of the throttle valve.   2. The engine control device according to claim 1, wherein the target intake air amount correcting means is configured to correct only a target intake air amount corresponding to a high load region in the target intake air amount characteristic of the engine. Based on the detected value of the fuel pressure by the fuel pressure detecting means, a fuel pressure lowering determining means for determining that the fuel pressure has decreased at a rate of change of a predetermined value or more
The intake air amount correction control means for controlling the intake air amount adjusting means so as to decrease the intake air amount of the engine in response to the determination of the fuel pressure decrease by the fuel pressure decrease determining means. The engine control device according to any one of 4.   6. The engine control device according to claim 5, further comprising ignition timing correction means for correcting the ignition timing of the engine to the retard side in response to the determination of the fuel pressure decrease by the fuel pressure decrease determination means. Driving state detecting means for detecting the driving state of the engine;
An intake air amount adjusting means for adjusting the intake air amount of the engine;
An intake air amount control means for controlling the intake air amount adjusting means so as to have a preset target intake air amount characteristic in accordance with at least the detected engine operating state;
Fuel pressure detection means for detecting the fuel pressure of the fuel discharged from the fuel pump and supplied to the fuel injection valve of the engine;
Fuel supply amount adjusting means for adjusting the fuel supply amount from the fuel pump to the fuel injection valve;
Fuel supply amount control means for controlling the fuel supply amount adjustment means based on at least the detected value of the fuel pressure so that the detected value approaches the target fuel pressure;
In an engine control device comprising:
When the detected value of the fuel pressure substantially coincides with the target fuel pressure, it is determined how much the operating state of the fuel supply amount adjusting means deviates from a preset standard state, and based on the determined degree of deviation A predicting means for predicting a shortage of fuel supply in a predetermined operating state;
Target intake air amount correction means for correcting the target intake air amount characteristic so that the target intake air amount decreases at least in the predetermined operation state when occurrence of a shortage of fuel supply is predicted by the prediction unit;
Based on the detected value of the fuel pressure by the fuel pressure detecting means, a fuel pressure decrease determining means for determining that the detected value has decreased at a change rate of a predetermined value or more;
In response to the determination of the fuel pressure decrease by the fuel pressure decrease determination means, the ignition timing of the engine is corrected to the retard side. On the other hand, even if the prediction means predicts a shortage of fuel supply, An engine control device comprising: an ignition timing correction means that is not performed.

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