JP2005330820A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve startability of an internal combustion engine by appropriately performing fuel pressure control for suppressing generation of fuel vapor. <P>SOLUTION: A fuel pump 22 is provided in a fuel tank 21 as a structure of a fuel supply system. A fuel injection valve 13 is connected to the fuel pump 22 via fuel piping 23. Bypass piping 24 connecting the fuel piping 23 and the fuel tank 21 is connected to the fuel piping 23, a fuel pressure control valve 25 is provided in a middle of the bypass piping 24. A pressure sensor 27 for detecting fuel pressure Pf is provided in the fuel piping 23. ECU 30 successively estimates a fuel vapor generation condition in the fuel supply system during the engine stops, and controls fuel pressure in the fuel supply system according to the estimated fuel vapor generation condition. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control device for an internal combustion engine.

  In an internal combustion engine, fuel in a fuel tank is pumped up by a fuel pump in a fuel supply system, and fuel pressure (fuel pressure) in fuel piping is controlled to a predetermined pressure. The fuel of the predetermined pressure is injected and supplied to each cylinder of the internal combustion engine by a fuel injection valve or the like and used for combustion. In such a configuration, when fuel vapor (vapor gas) is generated in the fuel pipe while the internal combustion engine is stopped, the startability of the internal combustion engine is deteriorated. For this reason, techniques for preventing the generation of fuel vapor while the engine is stopped have been proposed.

  For example, Patent Document 1 has a configuration in which a mechanism for holding the fuel pressure in the fuel pipe at a higher pressure than when the engine is operating when the internal combustion engine is stopped is provided. Further, in Patent Document 2, if the coolant temperature is equal to or higher than a predetermined temperature when the ignition switch is turned on, the operation time of the fuel pump is increased.

However, in Patent Document 1, the fuel pressure is uniformly increased by a mechanical configuration after the internal combustion engine is stopped, and it is considered that the increase in pressure is excessive or insufficient. Further, since the above-mentioned Patent Document 2 is intended to increase the fuel pressure after the internal combustion engine is started, there is a disadvantage that the generation of fuel vapor cannot be sufficiently suppressed at the initial start.
Japanese Patent No. 2907976 JP-A-8-61175

  The main object of the present invention is to provide a control device for an internal combustion engine that can appropriately perform fuel pressure control for suppressing the generation of fuel vapor and thus improve the startability of the internal combustion engine. .

  According to the first aspect of the present invention, the generation state of the fuel vapor in the fuel supply system is estimated while the internal combustion engine is stopped, and the fuel pressure in the fuel supply system is controlled according to the estimated generation state of the fuel vapor. In this case, the fuel pressure in the fuel supply system can be controlled without excess or deficiency while suppressing the generation of fuel vapor while the internal combustion engine is stopped. As a result, the fuel pressure control for suppressing the generation of fuel vapor can be appropriately performed, and the startability of the internal combustion engine can be improved.

  Further, in an internal combustion engine having an automatic stop / automatic start function, if fuel vapor is generated while the internal combustion engine is stopped, it is considered that the restart is adversely affected. On the other hand, in the invention according to claim 2, the fuel vapor generation state in the fuel supply system is estimated in a state where the internal combustion engine is automatically stopped, and the fuel supply system is determined according to the estimated fuel vapor generation state. The fuel pressure at is controlled. Therefore, even when the internal combustion engine is restarted after being automatically stopped, the fuel pressure control for suppressing the generation of fuel vapor can be appropriately performed, and thus the startability of the internal combustion engine can be improved.

  Here, as described in claim 3, it is preferable to control the fuel supply system so as to increase the fuel pressure as much fuel vapor is estimated to be generated.

  When the internal combustion engine is started in a state where the fuel piping of the fuel supply system is filled with the high temperature fuel, the high temperature fuel remains in the fuel piping for a while after the startup. Therefore, when the internal combustion engine is started in a state in which the fuel pressure is controlled by the fuel pressure control means, the fuel pressure control state by the fuel pressure control means for a predetermined time after the start of the internal combustion engine. It is good to continue. Thereby, generation | occurrence | production of the fuel vapor | steam immediately after starting of an internal combustion engine can also be suppressed.

  According to the fifth aspect of the present invention, when the fuel pressure controlled by the fuel pressure control means is changed to the engine operating target pressure after the internal combustion engine is started, the fuel pressure is gradually changed with respect to the engine operating target pressure. Let Thereby, the change of the fuel injection amount accompanying the sudden change of the fuel pressure is suppressed, and the deterioration of the exhaust emission accompanying the change of the fuel amount can be suppressed.

  According to the sixth aspect of the present invention, when it is estimated that fuel vapor is generated in the fuel supply system while the internal combustion engine is stopped, the fuel pressure is higher than the fuel pressure that is normally set when the internal combustion engine is automatically stopped. Increase

  When the automatic stop condition is satisfied, the internal combustion engine is automatically stopped, and in a state where fuel vapor is generated during the stop, the fuel pressure is set larger than the fuel pressure when the internal combustion engine is normally set. Thereby, generation | occurrence | production of fuel vapor | steam can be suppressed. Accordingly, it is possible to suppress the startability from deteriorating due to fuel shortage caused by the fuel vapor contained in the fuel injected from the fuel injection valve when the internal combustion engine is started.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. In the present embodiment, an engine control system is constructed for an on-vehicle multi-cylinder gasoline engine. In the control system, an electronic control unit (hereinafter referred to as ECU) is used as a center to control the fuel injection amount and the ignition timing. Control etc. is to be implemented.

  FIG. 1 is a configuration diagram showing an outline of the present control system. In FIG. 1, an intake pipe 11 and an exhaust pipe 12 are connected to the engine 10, and a fuel injection valve 13 is disposed in the intake pipe 11. During operation of the engine 10, an air-fuel mixture is formed by the intake air sucked from the upstream of the intake pipe 11 and the fuel injected from the fuel injection valve 13, and the air-fuel mixture is combusted in the combustion chamber. Then, the exhaust gas after combustion is discharged from the exhaust pipe 12.

  On the other hand, as a configuration of the fuel supply system, a fuel pump 22 is disposed in the fuel tank 21, and a fuel injection valve 13 is connected to the fuel pump 22 via a fuel pipe 23. In this case, the fuel in the fuel tank 21 is pumped up by the operation of the fuel pump 22, and the fuel pressure (fuel pressure Pf) in the fuel pipe 23 is set to a predetermined high pressure state.

  Further, a bypass pipe 24 that connects the fuel pipe 23 and the fuel tank 21 is connected to the fuel pipe 23, and a fuel pressure control valve 25 is provided in the middle of the bypass pipe 24. The fuel pressure control valve 25 is configured to include an electromagnetic solenoid unit 26, and the flow passage area of the bypass pipe 24 is adjusted by controlling the energization state of the electromagnetic solenoid unit 26. At this time, when the fuel pressure control valve 25 is closed by energization of the electromagnetic solenoid section 26, the fuel discharge to the fuel tank 21 through the bypass pipe 24 is restricted, and the fuel pressure in the fuel pipe 23 increases. Further, when the electromagnetic solenoid unit 26 is energized according to a duty signal or the like, the fuel pressure control valve 25 is opened according to the energized state each time, and the fuel pressure in the fuel pipe 23 is lowered by the amount of fuel discharge associated therewith. Thus, the fuel pressure is controlled by the operation of the fuel pressure control valve 25. The fuel pipe 23 is provided with a pressure sensor 27 for detecting the fuel pressure Pf.

  The ECU 30 is configured mainly by a microcomputer including a CPU, ROM, RAM, and the like. In addition to the detection signal of the pressure sensor 27 being input to the ECU 30, a load detection signal, a rotation angle detection signal, a water temperature detection signal, A vehicle speed detection signal, a brake switch signal, and the like are input. The ECU 30 executes various control programs stored in the ROM, thereby controlling the fuel injection amount, the ignition timing, and the like based on the operating state of the engine and the vehicle each time. Further, the ECU 30 sets the target fuel pressure based on the engine operating state and the like each time, and performs the fuel pressure control by the fuel pressure control valve 25 so that the actual fuel pressure Pf (sensor detected fuel pressure) becomes the target fuel pressure.

  Further, the ECU 30 performs idle stop control (engine automatic stop / automatic start control) for the purpose of reducing fuel consumption, reducing exhaust emissions, and reducing noise. In this idle stop control, the engine 10 is automatically stopped and restarted by a vehicle speed detection signal, a brake switch signal, or the like. For example, the engine is automatically stopped when the driver depresses the brake pedal to stop the vehicle, and then the engine is automatically restarted when the driver releases the brake pedal depressing operation. It has become.

  Next, the fuel pressure control procedure at the time of engine stop by idle stop control will be described. FIG. 2 is a flowchart showing a processing procedure of fuel pressure control, and this processing is repeatedly executed by the ECU 30 at a predetermined time period in a state where power is supplied to the ECU 30 via an ignition switch.

  When this processing is started, first, in step S101, it is determined whether or not the engine is currently stopped (during idle stop) by idle stop control. If the engine is idling stop, the process proceeds to step S102, where it is determined whether the fuel pressure Pf detected by the pressure sensor 27 is greater than a predetermined threshold value KP. The threshold value KP is set higher than the target fuel pressure during engine operation, and the generation state of the fuel vapor accompanying the increase in the fuel pressure Pf during idling stop is estimated in step S102.

  If Pf ≦ KP, the process proceeds to step S103, and the target fuel pressure is set to a predetermined value (for example, 4 kPa). However, at this time, it is also possible to variably set the target fuel pressure according to the engine operating state or the like. If Pf> KP, the process proceeds to step S104, and the target fuel pressure is calculated with reference to the water temperature table. The water temperature table is set based on the relationship shown in FIG. 3, for example, and basically the higher the engine water temperature, the higher the target fuel pressure.

  On the other hand, when the idling stop state is released and the engine 10 is restarted, the process proceeds from step S101 to step S105, before the elapsed time tm after the engine restart reaches a predetermined time Kt (for example, several seconds). Or not. If tm <Kt, the process proceeds to step S106, and the target fuel pressure is calculated with reference to the time table. The time table is set so that the fuel pressure Pf is maintained at the fuel pressure while the engine is stopped for a while after the engine is restarted, and then gradually changed with respect to the target pressure during engine operation. The target fuel pressure is reduced one by one. If tm ≧ Kt, the process proceeds to step S107 to set the target fuel pressure to a predetermined value. At this time, the target fuel pressure may be variably set according to the engine operating state or the like. The target fuel pressure in step S107 corresponds to “target pressure during engine operation”.

  The ECU 30 operates the fuel pressure control valve 25 based on the target fuel pressure set as described above, and controls the fuel pressure Pf to the target fuel pressure.

  FIG. 4 is a time chart showing more specifically the flow of fuel pressure control executed as described above. In FIG. 4, the period from timing t1 to t3 is an engine stop period by idle stop control. In the chart, the actual fuel pressure Pf is indicated by a solid line and the target fuel pressure is indicated by a one-dot chain line in the chart portion representing the fuel pressure, and only the solid line is shown when the fuel pressure Pf matches the target fuel pressure.

  Prior to timing t1, the engine 10 is normally operated and fuel injection is also performed. In this case, the fuel pressure Pf is maintained at the target fuel pressure. Thereafter, fuel injection is stopped by idle stop control at timing t1.

  Although the fuel pressure Pf is maintained at the target fuel pressure for a while after the idling stop, the fuel pressure Pf starts to increase with the generation of fuel vapor (vapor gas) in the fuel pipe 23. At timing t2, the fuel pressure Pf reaches the threshold value KP. At this time, the generation state (paper generation amount) of the fuel vapor is determined according to, for example, the engine water temperature, and the target fuel pressure is changed to a set value based on the water temperature table in order to suppress the generation of the fuel vapor. Specifically, the target fuel pressure is set to the higher pressure side as the water temperature is higher.

  After that, at timing t3, the starter motor or the like is driven with the establishment of the restart condition, and the engine 10 is restarted. After t3, the target fuel pressure is held at the set value by the water temperature table for a while. That is, high-temperature fuel remains in the fuel pipe 23 immediately after the engine restart, but generation of fuel vapor after the restart is suppressed by maintaining the fuel pressure in a high pressure state immediately after the engine restart. Thereafter, the target fuel pressure is gradually reduced according to the time table until timing t4 when the predetermined time Kt elapses. Thereby, the change of the fuel injection amount accompanying the sudden change of the fuel pressure is suppressed, and the deterioration of the exhaust emission accompanying the change of the fuel amount can be suppressed. After timing t4, the target fuel pressure is set to a predetermined value.

  According to the embodiment described in detail above, the fuel vapor generation state in the fuel supply system is sequentially estimated while the engine is stopped by the idle stop control, and the target fuel pressure is changed in accordance with the estimated fuel vapor generation state. As a result, the fuel pressure can be controlled without excess or deficiency against the generation of fuel vapor. As a result, the fuel pressure control for suppressing the generation of fuel vapor can be appropriately performed, and the startability of the engine 10 can be improved.

  In addition, this invention is not limited to the content of description of the said embodiment, For example, you may implement as follows.

  In the above embodiment, the fuel pressure control when the engine is stopped by the idle stop control has been described. However, the fuel pressure control is applied when the engine is stopped by an IG key operation or the like. That is, the fuel vapor generation state in the fuel supply system is estimated while the engine is stopped (IG switch = OFF state), and the target fuel pressure is changed according to the estimated fuel vapor generation state. As a result, as described above, the fuel pressure can be controlled without excess or deficiency while suppressing the generation of fuel vapor. However, in such a case, power is supplied to the ECU even after the IG switch is turned off at least until the engine water temperature (or fuel pressure, fuel temperature, etc.) drops to a predetermined level.

  In the above embodiment, the fuel vapor generation state is estimated based on the fuel pressure Pf detected by the pressure sensor 27. Instead of or in addition to this, the fuel temperature, the fuel property (for example, fuel volatility), the fuel pressure Pf The generation state of the fuel vapor may be estimated based on the rate of change, the elapsed time after the engine stops, and the like.

  In the above embodiment, the target fuel pressure is set according to the engine water temperature while the engine is stopped. Instead, the target fuel pressure may be set based on the fuel temperature, fuel properties (for example, fuel volatility), or the like. .

  In the above embodiment, the fuel pressure is maintained in a high pressure state until the predetermined time Kt has elapsed after the engine restart, but instead, for example, until the total fuel injection amount after the engine restart reaches a predetermined amount. You may make it hold | maintain a fuel pressure in a high pressure state in a period. Alternatively, the predetermined time Kt may be changed according to the change rate of the fuel injection amount.

  In the above embodiment, the fuel pressure is controlled by the fuel pressure control valve 25 provided in the bypass pipe 24. However, instead of this configuration, the fuel pressure may be controlled according to the driving state of the fuel pump. Specifically, the fuel pressure is controlled by variably controlling the output torque of the motor built in the fuel pump.

It is a block diagram which shows the outline of the engine control system in embodiment of invention. It is a flowchart which shows a fuel pressure control process. It is a figure which shows the relationship between water temperature and target fuel pressure. It is a time chart which shows the flow of fuel pressure control.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine, 21 ... Fuel tank, 22 ... Fuel pump, 23 ... Fuel piping, 30 ... ECU.

Claims (6)

A fuel supply system for supplying fuel from the fuel tank to a cylinder of the internal combustion engine, and estimating the generation state of the fuel vapor when the internal combustion engine is stopped; and
Fuel pressure control means for controlling the fuel pressure in the fuel supply system in accordance with the generation state of the fuel vapor estimated by the fuel vapor estimation means;
A control apparatus for an internal combustion engine, comprising: Automatic stop / automatic operation that automatically stops the internal combustion engine when a predetermined automatic stop condition is satisfied during operation of the internal combustion engine, and automatically starts the internal combustion engine when a predetermined automatic start condition is satisfied during the automatic stop of the internal combustion engine In the configuration having the start function,
Fuel vapor estimation means for estimating the generation state of fuel vapor in the fuel supply system in a state where the internal combustion engine is automatically stopped;
Fuel pressure control means for controlling the fuel pressure in the fuel supply system in accordance with the generation state of the fuel vapor estimated by the fuel vapor estimation means;
A control apparatus for an internal combustion engine, comprising:   The fuel pressure control means controls the fuel pressure of the fuel supply system to be increased as the fuel vapor estimation means estimates that more fuel vapor is generated in the fuel supply system. The control apparatus for an internal combustion engine according to 1 or 2.   The fuel pressure control state by the fuel pressure control means is continued for a predetermined time after the internal combustion engine is started when the internal combustion engine is started with the fuel pressure control by the fuel pressure control means. The control device for an internal combustion engine according to any one of 1 to 3.   Means for controlling the fuel pressure to the target pressure during engine operation during operation of the internal combustion engine, and when the fuel pressure controlled by the fuel pressure control means is changed to the target pressure during engine operation after the internal combustion engine is started, 5. The control apparatus for an internal combustion engine according to claim 1, wherein the fuel pressure is gradually changed with respect to the target pressure during engine operation.   The fuel pressure control means is normally set in a state where the internal combustion engine is automatically stopped when the fuel vapor estimation means estimates that fuel vapor is generated in the fuel supply system while the internal combustion engine is stopped. 3. The control device for an internal combustion engine according to claim 2, wherein the fuel pressure is made larger than the fuel pressure.

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