JP2009085165A - Internal combustion engine controller and pressure control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that it is hard to permit simple and proper handling of such malfunction that pressure inside a delivery pipe 72 excessively increases in an internal combustion engine 10 in which fuel pressure-fed from a fuel pump 44 to be stored in a high-pressure state inside the delivery pipe 72 is injection-fed via a fuel injection valve 20. <P>SOLUTION: When the malfunction has occurred, an injection volume of the fuel injection valve 20 increases and thereby an air-fuel ratio is shifted to a rich side. As a result, a fuel injection volume decreases by means of air-fuel ratio feedback control. A lower limit value, however, is set for valve opening duration of the fuel injection valve 20 and therefore a minimum injection volume is also limited to a lower limit value. When the minimum injection volume increases due to rising of fuel pressure inside the delivery pipe 72, an actual air-fuel ratio becomes richer than a target air-fuel ratio at the time of controlling an idle rotating speed. Hence, the target rotating speed is allowed to increase. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine whose control target is an internal combustion engine to which fuel that is pumped from a fuel pump and stored in a high pressure state in a pressure accumulating vessel is supplied via a fuel injection valve, and pressure control including the control device About the system.

In a cylinder injection internal combustion engine, the fuel in the fuel tank pumped up by the feed pump is pressurized (supplied) to the delivery pipe by the high-pressure fuel pump, and the fuel is stored in a high-pressure state in the delivery pipe. Is injected and supplied to the combustion chamber of the internal combustion engine through the fuel injection valve. At this time, as seen in, for example, Patent Document 1 below, it is also proposed to stop the feed pump when the pressure in the delivery pipe becomes abnormally high. Thereby, the pressure in a delivery pipe can be reduced. Specifically, in the one described in Patent Document 1, when the vehicle is running, the feed pump is turned on / off according to the pressure in the delivery pipe, so that the pressure in the delivery pipe is set to a predetermined value. Control is performed within the pressure region. Further, in the fuel supply system described in Patent Document 1, even when the feed pump is stopped, a small amount of fuel required for idle rotation speed control can be supplied to the delivery pipe by the high-pressure fuel pump. .
Japanese Patent No. 3237567

  In the fuel supply system described above, even when the feed pump is stopped, the pressure inside the delivery pipe can be reliably reduced in the event of an abnormality by adopting a configuration in which a small amount of fuel can be pumped to the delivery pipe by the high-pressure fuel pump. Idle operation is possible while letting it go. However, with such a configuration, the complexity of the configuration and the increase in the number of parts cannot be ignored. Furthermore, in the above, the pressure in the delivery pipe is controlled by turning on and off the feed pump according to the pressure in the delivery pipe when the vehicle is running. Because the pressure fluctuation also increases, when viewed on a microscopic time scale, the fuel injection amount becomes excessive or excessive, and the exhaust characteristics and torque of the internal combustion engine are appropriate. There is also a risk of excessive deviation from the value.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an internal combustion engine in which fuel that is pumped from a fuel pump and stored in a high-pressure state in an accumulator is injected and supplied via a fuel injection valve. Is to provide a control device for an internal combustion engine that can easily and appropriately cope with an abnormality in which the pressure in the pressure accumulating vessel becomes excessively high, and a pressure control system including the control device.

  Hereinafter, means for solving the above-described problems and the effects thereof will be described.

  The invention according to claim 1 is a control device for an internal combustion engine that is controlled by an internal combustion engine in which fuel that is pumped from a fuel pump and stored in a high pressure state in an accumulator is injected via a fuel injection valve. By operating a detecting means for detecting an abnormality in the fuel pump that increases the pressure in the pressure accumulating container, and an actuator for controlling the combustion of the internal combustion engine when the abnormality is detected. Compensating means for compensating for a change caused by the abnormality of the physical quantity correlated with the combustion of fuel is provided.

  In the above invention, since the change in the physical quantity (air-fuel ratio, torque, etc.) is compensated by the compensation means, even when the pressure in the pressure accumulating vessel rises excessively, this can be appropriately dealt with. . In addition, in order to cope with the operation of the actuator for combustion control, it is not necessary to complicate the structure of the fuel pump or the like, and a simple countermeasure can be taken.

  The invention according to claim 2 is the invention according to claim 1, further comprising feedback control means for performing feedback control of the air-fuel ratio of the internal combustion engine to a target air-fuel ratio, wherein the compensation means is the feedback control caused by the abnormality. It is characterized by compensating for a decrease in controllability.

  When an abnormality occurs in which the pressure in the pressure accumulating vessel becomes excessively high, the amount of fuel supplied to the internal combustion engine via the fuel injection valve may increase. When the minimum injection amount of the fuel injection valve increases, a situation may occur in which the actual air-fuel ratio becomes richer than the target air-fuel ratio even when the minimum injection amount is reached, which may reduce the air-fuel ratio feedback controllability. is there. In this regard, in the above-described invention, in order to compensate for a decrease in the controllability of the feedback control, it is possible to suppress the deviation between the actual air-fuel ratio and the target air-fuel ratio, and thus it is possible to suitably suppress the deterioration of the exhaust characteristics. .

  According to a third aspect of the present invention, in the second aspect of the present invention, the compensation means includes a rotational speed increasing means for increasing a target rotational speed during idle rotational speed control of the internal combustion engine when the abnormality is detected. It is characterized by providing.

  When an abnormality occurs in which the pressure in the pressure accumulating vessel becomes excessively high, the amount of fuel supplied to the internal combustion engine via the fuel injection valve may increase. And when the minimum injection quantity of a fuel injection valve increases, there exists a possibility that a torque may increase and, as a result, there exists a possibility that a rotational speed may rise. Here, when the idling rotational speed control is performed, the intake air amount is reduced to suppress the increase in the rotational speed. This is because the actual air-fuel ratio is controlled to be richer than the target air-fuel ratio, and the controllability of the air-fuel ratio is reduced. In this regard, in the above-described invention, by increasing the target rotational speed, the intake air amount can be increased by the idle rotational speed control, and as a result, the controllability of the air-fuel ratio can be recovered.

  According to a fourth aspect of the present invention, in the third aspect of the invention, the rotational speed increasing means gradually increases the target rotational speed.

  In the above-described invention, in order to gradually increase the target rotation speed, it is possible to avoid a situation experienced by the user as much as possible, compared with a case where the target rotation speed is increased at a stroke.

  According to a fifth aspect of the invention, in the third or fourth aspect of the invention, the rotational speed increasing means sets the target rotational speed in accordance with the pressure in the pressure accumulating vessel.

  As the pressure in the pressure accumulating vessel is higher, the minimum injection amount that can be injected from the fuel injection valve tends to increase. For this reason, the target rotational speed required to suppress the difference between the actual air-fuel ratio and the target air-fuel ratio tends to increase as the pressure increases. In the above invention, in view of this point, it is possible to favorably compensate for a decrease in the air-fuel ratio feedback controllability by setting the target rotational speed in accordance with the pressure.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the compensation means suppresses an increase in torque of the internal combustion engine due to the abnormality.

  When an abnormality in which the pressure in the pressure accumulating container becomes excessively high occurs, the amount of fuel injected and supplied to the internal combustion engine via the fuel injection valve increases, and the torque of the internal combustion engine may increase. In this regard, in the above-described invention, it is possible to suitably cope with an abnormality of the fuel pump by suppressing an increase in torque.

  The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the internal combustion engine is a spark ignition internal combustion engine, and the compensation means detects the abnormality, A retarding means for retarding the ignition timing is provided.

  When an abnormality in which the pressure in the pressure accumulating container becomes excessively high occurs, the amount of fuel injected and supplied to the internal combustion engine via the fuel injection valve increases, and the torque of the internal combustion engine may increase. Further, when the minimum injection amount of the fuel injection valve increases, a situation may occur in which the actual air-fuel ratio becomes richer than the target air-fuel ratio even when the minimum injection amount is reached. There is also a risk that the controllability will be reduced.

  Here, when the ignition timing is retarded, the torque of the internal combustion engine decreases, so that the increase in the torque can be suppressed. Further, when the decrease in torque leads to an increase in the intake air amount, the actual air-fuel ratio can be set to the lean side by the retard operation, so that the decrease in controllability of the feedback control can be compensated.

  The invention according to claim 8 is the invention according to claim 7, wherein the retarding means retards the ignition timing in a range where an exhaust temperature of the internal combustion engine is equal to or lower than a predetermined temperature.

  When retarding the ignition timing, the combustion timing shifts to the exhaust stroke side, so the exhaust temperature rises. On the other hand, an excessive increase in the exhaust temperature may lead to a decrease in the reliability of the exhaust system of the internal combustion engine. In the above invention, in view of this point, since the retard operation is performed in a range where the exhaust temperature is equal to or lower than the predetermined temperature, it is possible to suitably avoid a decrease in reliability of the exhaust system.

  The invention according to claim 9 is the invention according to any one of claims 1 to 8, wherein the internal combustion engine is a multi-cylinder internal combustion engine, and the compensation means detects the abnormality when the abnormality is detected. Combustion control is stopped for a part of the cylinders of the internal combustion engine.

  When an abnormality in which the pressure in the pressure accumulating container becomes excessively high occurs, the amount of fuel injected and supplied to the internal combustion engine via the fuel injection valve increases, and the torque of the internal combustion engine may increase. Further, when the minimum injection amount of the fuel injection valve increases, a situation may occur in which the actual air-fuel ratio becomes richer than the target air-fuel ratio even when the minimum injection amount is reached. There is also a risk that the controllability will be reduced.

  Here, if the number of cylinders for which combustion control is performed is reduced, the torque of the internal combustion engine is reduced, so that an increase in the torque can be suppressed. Furthermore, when the decrease in torque leads to an increase in the intake air amount per unit cylinder, the actual air-fuel ratio can be set to the lean side, so that the decrease in controllability of the feedback control can be compensated.

  According to a tenth aspect of the present invention, in the invention according to any one of the first to ninth aspects, the means for depressurizing the pressure in the pressure accumulating vessel increases the pressure in the pressure accumulating vessel exceeding a specified pressure. The pressure in the pressure accumulating vessel is mechanically adjusted to the specified pressure, and the fuel injection valve.

  In the above invention, when the fuel pump is abnormal, the pressure in the pressure accumulating vessel is controlled to the specified pressure. For this reason, it can avoid that the pressure in a pressure accumulation container raises so that the fall of the reliability of a pressure accumulation container may be caused.

  An eleventh aspect of the invention is a pressure control system comprising the control device according to the tenth aspect, the pressure accumulating container, and the fuel pump.

(First embodiment)
Hereinafter, a first embodiment in which a control device for an internal combustion engine according to the present invention is applied to a control device for an in-vehicle gasoline engine will be described with reference to the drawings.

  FIG. 1 shows the system configuration of this embodiment. The illustrated internal combustion engine 10 is a direct injection internal combustion engine. In this embodiment, an eight-cylinder internal combustion engine is assumed, but only one cylinder is shown here for convenience. A spark plug 18 and a fuel injection valve 20 project into the combustion chamber 16 defined by the cylinder block 12 and the piston 14 of the internal combustion engine 10. The combustion chamber 16 communicates with the intake passage 24 by the opening operation of the intake valve 22, whereby fuel is sucked into the combustion chamber 16. On the other hand, the fuel injection valve 20 injects fuel (gasoline fuel) into the combustion chamber 16. The air-fuel mixture in the combustion chamber 16 is combusted by the ignition of the spark plug 18, so that the combustion energy is taken out as the rotational energy of the crankshaft 26. Thereafter, the combustion chamber 16 communicates with the exhaust passage 30 by opening the exhaust valve 28, and the air-fuel mixture subjected to combustion in the combustion chamber 16 is discharged into the exhaust passage 30 as exhaust.

  The fuel injected and supplied into the combustion chamber 16 through the combustion injection valve 20 is stored in the fuel tank 40. The fuel in the fuel tank 40 is pumped up by the electric feed pump 42 and supplied to the fuel pump 44. The fuel pump 44 includes a cylinder 46, a plunger 48 that reciprocates in the cylinder 46, a pressurizing chamber 50 that is defined by the inner peripheral wall surface of the cylinder 46 and the plunger 48, a low-pressure chamber 52, a pressurizing chamber 50, and And a spill valve 54 for communicating and blocking between the low pressure chambers 52.

  In the fuel pump 44 configured as described above, the tappet 60 attached to the lower end of the plunger 48 is pressed against the cam 66 connected to the drive shaft 64 by the spring 62. The drive shaft 64 is mechanically rotated by the rotation of the crankshaft 26 by being mechanically connected directly to the crankshaft 26 or mechanically connected to either the intake camshaft or the exhaust camshaft. Is. On the other hand, the cam 66 has a shape in which the distance between the drive shaft 64 and the outer periphery changes, whereby the plunger 48 reciprocates in the cylinder 46 in synchronization with the rotation of the drive shaft 64. Then, the volume in the pressurizing chamber 50 is changed by the reciprocating motion of the plunger 48.

  Fuel from the feed pump 42 is supplied to the pressurizing chamber 50 through the low-pressure chamber 52 when the spill valve 51 is opened. The low pressure chamber 52 is provided with an electromagnetic solenoid 56 that attracts the spill valve 54 in the valve closing direction, and a spring 58 that applies a force to the spill valve 54 in the valve opening direction. Therefore, when the electromagnetic solenoid 56 is not energized, the spill valve 54 is opened by the spring 58, and when the electromagnetic solenoid 56 is energized, the spill valve 54 is closed by the suction force. The Thus, the spill valve 54 is a normally open type valve element.

  A pressure accumulating container (delivery pipe 72) is connected to the pressurizing chamber 50 through a check valve 74 and a discharge passage 70 to store fuel in a high pressure state and supply the fuel to the fuel injection valve 20 of each cylinder. . The delivery pipe 72 is connected to the fuel tank 40 via a relief valve 76 and a relief passage 78. The relief valve 76 is mechanically opened when the pressure in the delivery pipe 72 increases over a specified pressure (for example, “20 to 30 MPa”), and the pressure in the delivery pipe 72 is mechanically adjusted to the specified pressure. It is a regulator to adjust to. The specified pressure is set to be equal to or lower than an upper limit value that can maintain the reliability of the delivery pipe 72.

  The low pressure chamber 52 and the feed pump 42 are connected to the fuel tank 40 via a relief valve 80 and a relief passage 82. The relief valve 80 is opened when the pressure in the passage between the low pressure chamber 52 and the feed pump 42 becomes equal to or higher than a predetermined value. Thereby, the pressure in the passage between the low pressure chamber 52 and the feed pump 42 is maintained at a predetermined pressure.

  The fuel tank 40 is connected to a canister 92 that collects fuel vapor generated in the fuel tank 40 via a vapor passage 90. The canister 92 includes an adsorbent 92a that adsorbs fuel vapor. The canister 92 includes an atmospheric valve 92b that opens when the pressure in the canister 92 is equal to or higher than a predetermined pressure higher than the atmospheric pressure, and allows excess air in the canister 92 to escape. Further, the canister 92 includes an electronically controlled atmospheric introduction valve 92 c for introducing the atmosphere into the canister 92. The canister 92 is connected to the intake passage 24 via a purge passage 94 and an electronically controlled purge valve 96. According to such a configuration, when the inside of the canister 92 is depressurized by opening the air introduction valve 92 c and the purge valve 96, the fuel vapor adsorbed by the adsorbent 92 a is separated again and is sucked into the intake passage 24. .

  The electronic control unit (ECU 100) is a control unit that controls the internal combustion engine 10. The ECU 100 detects the air-fuel ratio of the combustion chamber 16 based on the fuel pressure sensor 102 that detects the pressure in the delivery pipe 72, the crank angle sensor 104 that detects the rotation angle of the crankshaft 26, and the exhaust component in the exhaust passage 30. The detection values of various sensors such as the fuel ratio sensor 106, the exhaust temperature sensor 108 for detecting the exhaust temperature in the exhaust passage 30 and the air flow meter 110 for detecting the intake air amount are taken in. The ECU 100 controls combustion of the internal combustion engine 10 by operating various actuators such as the ignition plug 18, the fuel injection valve 20, the electromagnetic solenoid 56, the air introduction valve 92c, and the purge valve 96 based on these detected values. Specifically, for example, the basic value FF of the injection amount calculated based on the intake air amount and the rotational speed is feedback-controlled to the target air-fuel ratio (for example, the theoretical air-fuel ratio) from the actual air-fuel ratio detected by the air-fuel ratio sensor 106. For example, air-fuel ratio feedback control for operating the valve opening time of the fuel injection valve 20 is performed by correcting with the feedback correction amount A / FFB. The ECU 100 is electrically connected to a display device 120 that outputs the calculation result as visual information as means for notifying a predetermined calculation result to the outside.

  Here, the operation of the fuel pump 44 by the ECU 100 will be further described with reference to FIG. In the downward stroke of the plunger 48 shown in FIG. 2A, the solenoid solenoid 56 is not energized, and the spill valve 54 is opened. As a result, the fuel pumped up from the fuel tank 40 by the feed pump 42 is sucked into the pressurizing chamber 50. On the other hand, as shown in FIG. 2B, even when the solenoid 48 is not energized during the upward stroke of the plunger 48, the spill valve 54 is opened. For this reason, the fuel in the pressurizing chamber 50 is returned to the fuel tank 40 through the low pressure chamber 52. On the other hand, as shown in FIG. 2C, when the spill valve 54 is closed by energizing the electromagnetic solenoid 56, the fuel in the pressurizing chamber 50 passes through the discharge passage 70 and the delivery pipe 72. Pumped to The ECU 100 determines the energization timing for the electromagnetic solenoid 56 based on the detection value of the fuel pressure sensor 102 so as to control the fuel pressure in the delivery pipe 72 to a predetermined pressure (for example, “5 to 15 Mpa”). Incidentally, the predetermined pressure may be a fixed value during normal operation of the internal combustion engine 10 except during idle rotation speed control.

  By the way, for example, when the energization path of the electromagnetic solenoid 56 is short-circuited with the positive electrode of the battery, the electromagnetic solenoid 56 is always energized. In this case, the spill valve 54 maintains the valve closed state over substantially the entire period of the upward stroke of the plunger 48. However, in the downward stroke of the plunger 48, the spill valve 54 is sucked to the valve opening side due to a decrease in the pressure in the pressurizing chamber 50, and the resultant force of this suction force and the elastic force of the spring 58 is an electromagnetic solenoid. By overcoming the suction force 56, the spill valve 54 opens. For this reason, every time the plunger 48 descends, the fuel is sucked into the pressurizing chamber 50, and the fuel is discharged to the delivery pipe 72 over almost the entire period during which the plunger 48 rises. Therefore, fuel is pumped to the delivery pipe 72 by the substantially maximum discharge capacity of the fuel pump 44, and the pressure may be excessively high. When the amount of fuel equal to or higher than the specified pressure for opening the relief valve 76 is pumped, the fuel pressure in the delivery pipe 72 is mechanically controlled to the specified pressure by the relief valve 76.

  In this state, an excessive amount of fuel is injected beyond the basic value FF depending on the valve opening time of the fuel injection valve 20 corresponding to the basic value FF of the injection amount calculated according to the intake air amount and the rotational speed. There is a risk of being. This is because the injection amount increases as the injection period is longer and as the fuel pressure in the delivery pipe 72 is higher than the fuel pressure in the combustion chamber 16. For this reason, even if it is the same valve opening time, when the fuel pressure in the delivery pipe 72 is excessively high due to the abnormality of the fuel pump 44, the injection amount becomes excessive. In this case, since the actual air-fuel ratio (actual air-fuel ratio) becomes richer than the target air-fuel ratio, the injection amount (or the valve opening time of the fuel injection valve 20) is reduced by the air-fuel ratio feedback control. However, since the fuel injection valve 20 has the minimum value of the valve opening time that can maintain the reliability of the controllability of the injection amount, the lower limit value of the valve opening time is usually set. For this reason, the feedback correction of the valve opening time by the air-fuel ratio feedback control is restricted by the lower limit value of the valve opening time. That is, when the valve opening time reaches the lower limit value, the valve opening time cannot be corrected even when the actual air-fuel ratio is still rich.

  Such a situation is particularly likely to occur in a region where the torque required for the internal combustion engine 10 is small. That is, in this case, since the intake air amount is small, the actual air-fuel ratio tends to be rich if the injection amount is excessive. On the contrary, in the operation region where the required torque is somewhat large, the controllability to the target air-fuel ratio can be maintained. That is, in this case, when the injection amount increases due to the abnormally high pressure of the delivery pipe 72, the generated torque increases, and the intake air amount is reduced according to the torque reduction request from the user. At this time, although the actual air-fuel ratio shifts to the rich side due to the increase in the injection amount or the decrease in the intake air amount, the control to the target air-fuel ratio can be performed by the air-fuel ratio feedback control.

  From the above, there is a concern that the controllability of the air-fuel ratio control at the time of idling may be deteriorated in the case of an abnormality in which the discharge amount of the fuel pump 44 becomes excessive. In other words, in a situation where the pressure in the delivery pipe 72 is controlled by the relief valve 76, the injection amount when the valve opening time of the fuel injection valve 20 is set to the lower limit value is larger than the injection amount normally required by the idle rotation speed control. If it becomes larger, the controllability of the air-fuel ratio control may be reduced.

  Therefore, in the present embodiment, when the abnormality occurs, the ECU 100 performs a process of notifying the user through the display unit 120, while performing a fail-safe process for compensating for a decrease in controllability of the air-fuel ratio feedback control. The operation of the internal combustion engine 10 in accordance with the normal time is maintained, and thus the running performance of the vehicle is maintained.

  FIG. 3 shows a procedure of fail-safe processing according to the present embodiment. This process is repeatedly executed by the ECU 100 at a predetermined cycle, for example.

  In this series of processes, first, in step S10, it is determined whether or not it is during idling speed control. Here, the idle rotational speed control time is when processing for automatically controlling to a target rotational speed capable of stably maintaining the rotational state of the internal combustion engine 10 is performed. In this control, the intake air amount is manipulated to control the actual rotational speed to the target rotational speed. And when it is judged that it is at the time of idle rotation speed control, it transfers to step S12. In step S12, it is determined whether or not there is a closed sticking abnormality in which the spill valve 54 is always closed during the upward stroke of the plunger 48 of the fuel pump 44. This process may be determined to be abnormal when it is determined, for example, that the fuel pressure in the delivery pipe 72 is a specified pressure for opening the relief valve 76 based on the detection value of the fuel pressure sensor 102. . Alternatively, the determination may be made by monitoring the energization state of the electromagnetic solenoid 56.

  If an affirmative determination is made in step S12, opening of the purge valve 96 is prohibited in step S14. This is because it is considered that if the purge valve 96 is opened, enrichment of the air-fuel ratio is promoted even if the air-fuel ratio is likely to be rich because the fuel injection amount is increased at the time of the abnormality. On the other hand, in step S16, it is determined whether or not the actual air-fuel ratio is richer by a predetermined amount α or more than the target air-fuel ratio. This process is for determining whether or not the controllability of the air-fuel ratio feedback control has deteriorated. If a positive determination is made in step S16, the process proceeds to step S18.

  In step S18, it is determined whether or not the target rotational speed is equal to or lower than the upper limit speed β. This process determines whether or not the target rotational speed can be increased. Here, for example, when the vehicle is an automatic transmission vehicle (AT vehicle), the upper limit speed β is set to a value at which the creep torque does not increase excessively. If a positive determination is made in step S18, the process proceeds to step S20. In step S20, the target rotational speed is increased by a predetermined speed γ. This process is a process for compensating for a decrease in controllability of the air-fuel ratio feedback control. That is, since the intake air amount increases as the target rotational speed increases, the actual air-fuel ratio can thereby be shifted to the lean side.

  When a negative determination is made in steps S10, S12, S16, and S18, or when the process of step S20 is completed, this series of processes is temporarily terminated.

  According to such processing, the intake air amount can be increased by increasing the target rotational speed with the upper limit speed β as the upper limit, and consequently the followability of the actual air-fuel ratio to the target air-fuel ratio can be improved. The upper limit speed β is variably set according to the fuel pressure in the delivery pipe 72 (the specified pressure of the relief valve 76). By installing a process (program etc.) that can variably set the upper limit speed β, even if the specified pressure changes according to the specifications of the engine system (specifications of the relief valve 76), it is possible to appropriately handle this Can do. Here, the upper limit speed β is set to increase as the fuel pressure (regulated pressure) in the delivery pipe 72 increases, under the restriction that the torque of the internal combustion engine 10 by idle rotation speed control does not become excessively large. That is, in the case of an AT vehicle, for example, an increase in the target rotational speed first occurs as a shock when shifting to the drive range, but in view of the fact that excessive enrichment causes misfire, the misfire is more than that of the above shock. It is desirable to give priority to avoiding the above. For this reason, the upper limit speed β is increased as the fuel pressure is increased in a range in which the torque at the idle rotation speed is excessive and the operability of the vehicle at the time of creep is not hindered.

  Similarly, the predetermined speed γ is also variably set according to the fuel pressure in the delivery pipe 72. Specifically, the predetermined speed γ is increased as the fuel pressure in the delivery pipe 72 is higher. This is a setting in consideration of the fact that the higher the fuel pressure, the richer the actual air-fuel ratio. Therefore, if the predetermined speed γ is the same regardless of the fuel pressure, the higher the fuel pressure, the longer the follow-up to the target rotational speed is delayed. .

  FIG. 4 shows an aspect of fail-safe processing according to the present embodiment. Specifically, FIG. 4A shows the transition of the operation signal of the fuel pump 44, FIG. 4B shows the transition of the fuel pressure in the delivery pipe 72, and FIG. The transition of the opening command time is shown, FIG. 4D shows the transition of the air-fuel ratio, and FIG. 4E shows the transition of the target rotational speed.

  When the fuel pump 44 is normal, the fuel pressure indicated by the solid line in FIG. 4B follows the target fuel pressure indicated by the one-dot chain line. Here, if an abnormality occurs in which the electromagnetic solenoid 56 of the fuel pump 44 is always energized, the discharge amount of the fuel pump 44 increases, so the fuel pressure rises above the target fuel pressure. At this time, since the injection amount of the fuel injection valve 20 increases, the actual air-fuel ratio indicated by the solid line in FIG. 4D becomes richer than the target air-fuel ratio indicated by the one-dot chain line. When the actual air-fuel ratio becomes rich, the fuel injection valve 20 injection amount and the open command period are reduced by air-fuel ratio feedback control. Thereafter, based on the fact that the fuel pressure becomes equal to or higher than the specified pressure Pth (or based on the fact that the fuel pump 44 is always energized for a predetermined time), an abnormality of the fuel pump 44 is detected at time t1.

  As a result, the target rotation speed increases. For this reason, since it is necessary to increase the torque to increase the actual rotational speed, the intake air amount is increased by the idle rotational speed control, and the actual air-fuel ratio follows the target air-fuel ratio. On the other hand, as shown by a two-dot chain line in FIG. 4 (e), when the target rotational speed increase process is not performed, the actual air-fuel ratio remains rich as shown in FIG. 4 (d). Become.

  According to the embodiment described in detail above, the following effects can be obtained.

  (1) When an abnormality on the side of increasing the pressure in the delivery pipe 72 occurs in the fuel pump 44, a process for compensating for a decrease in controllability of the air-fuel ratio feedback control is performed. As a result, even if the actual air-fuel ratio becomes richer than the target air-fuel ratio due to the increase in the injection amount, the deviation between the actual air-fuel ratio and the target air-fuel ratio can be suppressed, and the exhaust characteristics are thus deteriorated. It can suppress suitably.

  (2) The target rotational speed at the time of idle rotational speed control of the internal combustion engine 10 is increased. As a result, the amount of intake air can be increased, and as a result, the controllability of the air-fuel ratio can be recovered.

  (3) When the fuel pump 44 is abnormal, the target rotational speed is gradually increased. Thereby, compared with the case where it raises at a stretch, the situation experienced by a user as much as possible can be avoided.

  (4) The upper limit speed β of the target rotational speed is set according to the pressure in the delivery pipe 72. Accordingly, the upper limit speed β corresponding to the pressure can be set in consideration of the tendency that the target rotational speed required to suppress the deviation between the actual air-fuel ratio and the target air-fuel ratio increases as the pressure increases. As a result, a decrease in the feedback controllability of the air-fuel ratio can be suitably compensated.

  (5) As a means for reducing the pressure in the delivery pipe 72, in addition to the fuel injection valve 20, when the pressure in the delivery pipe 72 is about to exceed the specified pressure, the pressure is mechanically reduced to the specified pressure. Means to adjust. As a result, it is possible to avoid the pressure in the delivery pipe 72 from rising to the extent that the reliability of the delivery pipe 72 is lowered.

(Second Embodiment)
Hereinafter, the second embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  FIG. 5 shows a procedure of fail-safe processing according to the present embodiment. This process is repeatedly executed by the ECU 100 at a predetermined cycle, for example. In the process shown in FIG. 5, the same step number is attached for convenience to the process corresponding to the process shown in FIG.

  In this series of processes, when the process of step S14 is completed, it is determined in step S22 whether or not the exhaust gas temperature is equal to or lower than the threshold temperature Tth. This process is to determine whether or not the ignition timing can be retarded. Here, the threshold temperature Tth is set according to an upper limit temperature that does not cause a decrease in reliability of the exhaust system including the exhaust passage 30 and the exhaust purification device. If an affirmative determination is made in step S22, it is determined that the ignition timing retarding operation is possible. In step S24, the ignition timing is retarded by a unit amount, and the process returns to step S22. According to such processing, the ignition timing can be retarded in a range in which the exhaust temperature is equal to or lower than a predetermined temperature (<“threshold temperature Tth + unit amount”). Here, the predetermined temperature is set below the upper limit temperature. In view of the concern that abnormal noise (humid noise) may occur in the internal combustion engine 10 by retarding the ignition timing, the exhaust gas temperature is used as a parameter for generating abnormal noise, and when the predetermined temperature is set, Furthermore, you may impose the conditions below the temperature which can suppress generation | occurrence | production of abnormal noise. If a negative determination is made in step S22, the ignition timing can no longer be retarded, and the routine proceeds to step S16.

  By retarding the ignition timing in this way, even if the torque of the internal combustion engine 10 increases due to an increase in the injection amount due to the abnormality of the fuel pump 44, this can be suppressed. Further, in order to increase the target rotational speed so that the actual air-fuel ratio follows the target air-fuel ratio after such processing, the amount of increase in the target rotational speed can be reduced as compared with the first embodiment. That is, since the torque of the internal combustion engine 10 decreases due to the retard of the ignition timing, the amount of intake air necessary to achieve the target rotational speed increases. For this reason, even if the increase amount of the target rotational speed is small, the actual air-fuel ratio can be made the target air-fuel ratio.

  According to this embodiment described above in detail, the following effects can be obtained in addition to the above-described effects of the first embodiment.

  (6) The process which suppresses the increase in the torque of the internal combustion engine 10 resulting from abnormality was performed. Thereby, the abnormality of the fuel pump 44 can be suitably dealt with.

  (7) When abnormality of the fuel pump 44 is detected, the ignition timing is retarded. As a result, it is possible to suppress an increase in torque or to reduce the amount of increase in the target rotational speed for compensating for the decrease in controllability of the air-fuel ratio feedback control.

  (8) The ignition timing is retarded in a range where the exhaust temperature is equal to or lower than the predetermined temperature. Thereby, the fall of the reliability of an exhaust system can be avoided suitably.

(Third embodiment)
Hereinafter, the third embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  FIG. 6 shows a procedure of fail-safe processing according to the present embodiment. This process is repeatedly executed by the ECU 100 at a predetermined cycle, for example. In the process shown in FIG. 6, the same step number is attached for convenience to the process corresponding to the process shown in FIG. 3.

  In this series of processes, when the process of step S14 is completed, the number of cylinders for which combustion control is performed is reduced in step S26. Then, the process proceeds to step S16. Thereby, the average value and the amount of combustion energy of the internal combustion engine 10 per unit period (period of an integral multiple of 4 strokes) can be reduced. For this reason, an increase in the torque of the internal combustion engine 10 due to an increase in the injection amount due to the abnormality of the fuel pump 44 can be suppressed. Further, in order to increase the target rotational speed so that the actual air-fuel ratio follows the target air-fuel ratio after such processing, the amount of increase in the target rotational speed can be reduced as compared with the first embodiment. That is, since the torque of the internal combustion engine 10 is reduced by reducing the number of cylinders for fuel control, the amount of intake air per unit cylinder necessary for achieving the target rotational speed increases. For this reason, even if the increase amount of the target rotational speed is small, the actual air-fuel ratio can be made the target air-fuel ratio.

  According to this embodiment described above in detail, the following effects can be obtained in addition to the above-described effects of the first embodiment.

  (9) When abnormality of the fuel pump 44 is detected, the combustion control is stopped for a part of the cylinders of the internal combustion engine 10. As a result, it is possible to suppress an increase in torque or to reduce the amount of increase in the target rotational speed for compensating for the decrease in controllability of the air-fuel ratio feedback control.

(Other embodiments)
Each of the above embodiments may be modified as follows.

  In the second embodiment, the ignition timing is retarded until the exhaust temperature reaches the threshold temperature Tth, and when the exhaust temperature reaches the threshold temperature Tth, the actual air-fuel ratio is still richer than the target air-fuel ratio. Although the target rotation speed is changed when it is on the side, it is not limited to this. For example, when the fuel pump 44 is abnormal, the ignition timing may be retarded at a stroke to the failsafe ignition timing, and then the ignition timing may be advanced when the exhaust gas temperature reaches the threshold temperature Tth. In this case, after the ignition timing is retarded at once, the process can be shifted to a process of increasing the target rotational speed according to the degree of deviation between the actual air-fuel ratio and the target air-fuel ratio. The target air-fuel ratio can be controlled.

  In the second embodiment, if the actual air-fuel ratio is still richer than the target air-fuel ratio even when the target rotational speed becomes equal to or higher than the upper limit speed β, the number of cylinders that perform combustion control can be reduced. Good. Furthermore, in the second embodiment, the target rotational speed need not be changed. Even in this case, since the torque of the internal combustion engine 10 is reduced by the retard operation of the ignition timing, it is possible to compensate for the increase in torque caused by the abnormality of the fuel pump 44. Furthermore, if the actual rotational speed during idle rotational speed control decreases due to a decrease in torque, the intake air amount is corrected to increase by idle rotational speed control, so the actual air-fuel ratio can be brought closer to the target air-fuel ratio. .

  -In the third embodiment, if the actual air-fuel ratio is still richer than the target air-fuel ratio even if the target rotational speed is equal to or higher than the upper limit speed β, the number of cylinders that perform combustion control is further reduced. May be. In other words, the number of cylinders that perform fuel cut control may be increased. In addition, if the actual air-fuel ratio is still richer than the target air-fuel ratio even when the target rotational speed becomes equal to or higher than the upper limit speed β, the ignition timing may be corrected to be retarded.

  Furthermore, in the third embodiment, the target rotational speed need not be changed. Even in this case, since the torque of the internal combustion engine 10 is reduced by reducing the number of cylinders for which the combustion control is performed, it is possible to compensate for the increase in torque caused by the abnormality of the fuel pump 44. Further, if the actual rotational speed during the idle rotational speed control decreases due to the torque decrease, the intake air amount per unit cylinder is corrected to be increased by the idle rotational speed control, so that the actual air-fuel ratio is brought close to the target air-fuel ratio. Is also possible.

  In the first embodiment, both the ignition timing retarding operation and the combustion control cylinder reduction process may be performed before the target rotational speed is increased. Alternatively, if the actual air-fuel ratio is still richer than the target air-fuel ratio even when the target rotational speed exceeds the upper limit speed β, both the ignition timing retarding operation and the combustion control cylinder reduction process are performed. You may go.

  In each of the above embodiments, the process of gradually increasing the target rotational speed was performed during the idle rotational speed control. Instead of this, the target rotational speed was once increased by the fail-safe process, and then corrected. The target rotation speed may be always stored as a learning value in the memory holding device, and the target rotation speed may be set to the learning value from the beginning every time the idle rotation speed control is shifted. Here, the constant memory holding device is a memory device that always holds the memory regardless of the state of the start switch (main power source of the control device (ECU 100)) of the engine control system. Specifically, there are, for example, a backup RAM in which the power supply state is always maintained regardless of the state of the start switch, and a non-volatile memory such as an EEPROM that always holds a memory regardless of whether power is supplied.

  When the fuel pump 44 is abnormal, a fail-safe process may be performed in which the intake air amount is set as the target intake air amount instead of performing the idle rotation speed control when the torque requested by the user becomes the minimum. Here, the target intake air amount is a feedforward amount for causing the actual air-fuel ratio to follow the target air-fuel ratio. However, after the injection amount becomes the minimum injection amount in the air-fuel ratio feedback control, the target intake air amount may be set as a feedback correction target.

  In each of the above embodiments, when an abnormality occurs in the fuel pump 44, fail-safe processing is performed during idle rotation speed control. In this case, except for the fuel cut control at the time of deceleration, the torque can be continuously adjusted with the torque of the internal combustion engine 10 at the idle rotation speed control as a lower limit, but the torque immediately before the transition to the idle rotation speed control is Since it increases compared with the normal one, the torque adjustable range is lowered. On the other hand, if a means for reducing the number of cylinders used for combustion control or correcting the ignition timing in a higher torque operation region than at the time of idling rotational speed control is provided, torque from the high torque region to the low torque region is provided. Is fully adjustable.

  The fuel pump 44 is not limited to the one having the normally open type spill valve 54. Even in a case having a normally closed spill valve, for example, when the energization path to the solenoid coil is disconnected, the spill valve is closed from the beginning of the ascending stroke of the plunger. For this reason, when the spill valve is mechanically opened due to the negative pressure in the pressurizing chamber 50 during the downward stroke of the plunger, the maximum amount of fuel is discharged each time, and the delivery pipe 72 is abnormal. High pressure. Therefore, the application of the present invention is effective. Furthermore, the fuel pump is not limited to the one provided with the discharge metering valve, but may be provided with the suction metering valve.

  In the above embodiment, the delivery pipe 72 is provided with the relief valve 76 that mechanically controls the delivery pipe 72 to the specified pressure Pth when the pressure inside the delivery pipe 72 exceeds the specified pressure Pth. In addition, a relief valve may be provided in the discharge passage 70 to mechanically control the discharge passage 70 to the specified pressure Pth when the pressure inside the discharge passage 70 exceeds the specified pressure Pth. Furthermore, you may not provide such a relief valve.

  -The number of cylinders of the internal combustion engine may be arbitrarily changed. The invention is not limited to the in-cylinder injection type spark ignition type internal combustion engine. For example, it may be a cylinder ignition type compression ignition type internal combustion engine such as a diesel engine. Even in this case, for example, in a common rail type diesel engine, an increase in torque can be suppressed by reducing the number of cylinders that perform combustion control when the pressure in the common rail becomes an abnormally high pressure.

The figure which shows the system configuration | structure concerning 1st Embodiment. Sectional drawing which shows the suction / discharge operation | movement of the fuel pump concerning the embodiment. The flowchart which shows the process sequence at the time of abnormality of the fuel pump concerning the embodiment. The time chart which shows the air fuel ratio control aspect concerning the embodiment. The flowchart which shows the process sequence at the time of abnormality of the fuel pump concerning 2nd Embodiment. The flowchart which shows the process sequence at the time of abnormality of the fuel pump concerning 3rd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 20 ... Fuel injection valve, 44 ... Fuel pump, 72 ... Delivery pipe, 100 ... ECU (one Embodiment of the control apparatus of an internal combustion engine).

Claims (11)

In a control device for an internal combustion engine that is controlled by an internal combustion engine that is pumped from a fuel pump and stored in a high-pressure state in a pressure accumulating vessel through a fuel injection valve,
Detecting means for detecting that an abnormality on the side of increasing the pressure in the pressure accumulating vessel has occurred in the fuel pump;
Compensating means for compensating for a change caused by the abnormality of a physical quantity correlated with fuel combustion by operating an actuator for combustion control of the internal combustion engine when the abnormality is detected, A control device for an internal combustion engine. Feedback control means for performing feedback control of the air-fuel ratio of the internal combustion engine to a target air-fuel ratio,
2. The control device for an internal combustion engine according to claim 1, wherein the compensation means compensates for a decrease in controllability of the feedback control due to the abnormality.   3. The control apparatus for an internal combustion engine according to claim 2, wherein the compensation means includes a rotational speed increasing means for increasing a target rotational speed during idle rotational speed control of the internal combustion engine when the abnormality is detected. .   4. The control apparatus for an internal combustion engine according to claim 3, wherein the rotation speed increasing means gradually increases the target rotation speed.   5. The control device for an internal combustion engine according to claim 3, wherein the rotation speed increasing means sets the target rotation speed in accordance with a pressure in the pressure accumulating container.   The control device for an internal combustion engine according to claim 1, wherein the compensation unit suppresses an increase in torque of the internal combustion engine due to the abnormality. The internal combustion engine is a spark ignition internal combustion engine,
The control device for an internal combustion engine according to any one of claims 1 to 6, wherein the compensation means includes a retarding means for retarding an ignition timing when the abnormality is detected.   8. The control apparatus for an internal combustion engine according to claim 7, wherein the retarding means retards the ignition timing in a range in which an exhaust temperature of the internal combustion engine is equal to or lower than a predetermined temperature. The internal combustion engine is a multi-cylinder internal combustion engine;
The control device for an internal combustion engine according to any one of claims 1 to 8, wherein, when the abnormality is detected, the compensation means stops combustion control for a part of the cylinders of the internal combustion engine. .   Means for reducing the pressure in the pressure accumulator vessel, mechanically adjusting the pressure in the pressure accumulator vessel to the specified pressure when the pressure in the pressure accumulator vessel is about to exceed a specified pressure; and The control device for an internal combustion engine according to claim 1, comprising a fuel injection valve. A control device according to claim 10;
A pressure control system comprising the pressure accumulating container and the fuel pump.

Images