JP2010025088A - Automatic stop control method and automatic stop device for diesel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a temperature drop in a combustion chamber caused by suction air by giving a load to a diesel engine through driving of a fuel pump when the diesel engine is to be stopped automatically and enhance the restarting performance of the diesel engine by force-feeding the fuel to a fuel rail by the fuel pump with securing a fuel pressure required to make restarting of the engine in the fuel rail. <P>SOLUTION: When the diesel engine is to be stopped automatically, the fuel is force-fed to the fuel rail of the diesel engine by the fuel pump after the automatic stop conditions are established, and the fuel pump is driven by the driving force of the diesel engine so that the fed fuel pressure becomes higher than the fuel pressure to be supplied to the fuel rail when the engine is idling. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a diesel engine automatic stop technology for automatically stopping a diesel engine when a predetermined automatic stop condition is satisfied.

  In recent years, in vehicles such as automobiles equipped with diesel engines, predetermined automatic stop conditions have been established for the purpose of improving fuel economy and reducing exhaust gas (for example, when the vehicle speed is substantially zero, the brake pedal is set to be longer than a certain time). Technology that automatically stops the diesel engine when it is continuously stepped on), when the diesel engine is automatically stopped and then restarted, the restart must be performed reliably and promptly, That is, it is required to improve the restartability of the diesel engine.

  On the other hand, in a diesel engine having an injector that directly injects fuel into its combustion chamber, when the diesel engine is operating, the fuel pump is driven by the driving force of the diesel engine to pump the fuel to the fuel rail. The high-pressure fuel inside is supplied from the fuel rail to the injector. When the diesel engine is automatically stopped, the fuel is first cut into the combustion chamber. Usually, the output is stopped so that the fuel pump does not pump the fuel to the fuel rail together with the fuel cut.

Here, in Patent Document 1, after an automatic engine stop condition is satisfied, a lock-up clutch is engaged, or an alternator is driven by the driving force of the engine to apply a load to the engine to stop the engine. A technique for reducing the amount of idling in is disclosed.
JP 2003-214210 A

  When the diesel engine is automatically stopped, first the fuel is cut into the combustion chamber. During the engine stop process after this fuel cut until the diesel engine is completely stopped, the temperature of the combustion chamber is reduced by the intake air that is not used for combustion. descend. When the idling amount in the engine stop process is increased, the temperature drop of the combustion chamber due to the intake air that increases with the increase is disadvantageous in increasing the restartability of the diesel engine. With the technique described in Patent Document 1, this point can be improved.

  However, in the prior art including the technique of Patent Document 1, when the diesel engine is automatically stopped, the output of the fuel pump is usually stopped together with the fuel cut so that the fuel pump does not pump the fuel to the fuel rail. Therefore, it is difficult to secure the fuel pressure necessary for the fuel injection from the injector to the combustion chamber in the fuel rail, that is, to ensure the operational reliability of the fuel rail when the engine is restarted. This is an obstacle to improving the restartability of the diesel engine.

  In particular, when the diesel engine is automatically stopped, the automatic stop condition is normally established when the diesel engine is idling or transitioning to the idling operation, the fuel pump is stopped together with the fuel cut, and when the engine is idling, The fuel pressure in the fuel rail becomes lower than the fuel pressure in the fuel rail when the engine is not operated during idle operation due to a request by the engine control. In general, the fuel pressure in the fuel rail exceeds the predetermined high pressure. There is a relief valve that adjusts so that the fuel pressure in the fuel rail will gradually leak from the relief valve and decrease after the engine is stopped. It is difficult to leave.

  The purpose of the present invention is to drive the fuel pump when the diesel engine is automatically stopped, thereby applying a load to the diesel engine and reducing the idling amount during the engine stop process to suppress the temperature drop of the combustion chamber due to intake air. In addition, the fuel pressure is supplied to the fuel rail by the fuel pump, so that the fuel pressure necessary for reliably injecting fuel from the injector to the combustion chamber is ensured in the fuel rail when the engine is restarted. That is, it is to provide a diesel engine automatic stop technology that can ensure the operation reliability of the fuel rail in engine restart and thereby improve the restartability of the diesel engine.

  The invention “the diesel engine automatic stop control method” is the diesel engine automatic stop control method in which the diesel engine is automatically stopped when a predetermined automatic stop condition is satisfied. The fuel pump is controlled to be driven by the driving force of the diesel engine so that the pressure becomes higher than the fuel pressure supplied during idling operation of the diesel engine.

  Here, in the first aspect of the invention, after the automatic stop condition is satisfied, the fuel pump is driven by the driving force of the diesel engine so that the fuel pressure is increased to the maximum allowable pressure (the second aspect of the invention). In the invention of claim 1 or 2, after the automatic stop condition is satisfied, the fuel pump may be driven and controlled so that its output becomes maximum (invention of claim 3).

  According to a fourth aspect of the present invention, there is provided a diesel engine automatic stop device that automatically stops the diesel engine when a predetermined automatic stop condition is satisfied, and is driven by the driving force of the diesel engine. A fuel pump capable of pumping fuel to the fuel rail, a relief valve that adjusts the fuel pressure in the fuel rail so as not to exceed a predetermined high pressure, and after the automatic stop condition is satisfied, And an automatic stop control means for driving and controlling the fuel pump so as to be higher than the fuel pressure supplied to the fuel rail during operation.

  According to the automatic stop control method for a diesel engine according to claim 1, when the diesel engine is automatically stopped, after the automatic stop condition is established, the fuel pressure is higher than the fuel pressure supplied during the idling operation of the diesel engine. Since the fuel pump is controlled so as to be driven by the driving force of the diesel engine, first, by driving the fuel pump, a load is applied to the diesel engine, and the idling amount in the process of stopping the engine is reduced, so that the combustion chamber by intake air In order to ensure that the fuel pressure is higher than the fuel pressure supplied during idle operation of the diesel engine, and to ensure that fuel is injected from the injector into the combustion chamber when the engine is restarted. Ensure the required fuel pressure, that is, ensure the operational reliability when restarting the engine. It is possible to increase the restarting of the diesel engine.

  According to the automatic stop control method for a diesel engine according to claim 2, the fuel pump is driven by the driving force of the diesel engine so that the fuel pressure is increased to an allowable maximum pressure after the automatic stop condition is satisfied. The fuel pressure necessary for restarting the engine can be reliably ensured while preventing malfunction and failure of the equipment.

  According to the diesel engine automatic stop control method of claim 3, since the fuel pump is driven and controlled so that the output thereof is maximized after the automatic stop condition is established, the fuel pressure is made as high as possible, and the diesel engine by the fuel pump is used. Thus, the temperature drop of the combustion chamber due to the intake air can be reliably suppressed.

  According to the diesel engine automatic stop device of the fourth aspect, the fuel pump is driven by the driving force of the diesel engine and can pump fuel to the fuel rail of the diesel engine, so that the fuel pressure in the fuel rail does not exceed a predetermined high pressure. Relief valve to be adjusted and automatic stop control means, especially after the automatic stop condition is established, the fuel pressure in the fuel rail is higher than the fuel pressure supplied to the fuel rail when the diesel engine is idling. Thus, since the fuel pump is driven and controlled, the same effect as in the first aspect can be obtained.

  In addition, the relief valve increases the reliability of the fuel rail, and after the engine is stopped, the fuel pressure in the fuel rail gradually leaks and decreases from the relief valve. By pumping the fuel, it is possible to secure the fuel pressure in the fuel rail necessary for reliably performing fuel injection from the injector to the combustion chamber when the engine is restarted.

  The diesel engine automatic stop technology of the present invention automatically stops the diesel engine when a predetermined automatic stop condition is satisfied. After the automatic stop condition is satisfied, the fuel pump pumps fuel to the fuel rail of the diesel engine. Then, the fuel pump is controlled to be driven by the driving force of the diesel engine so that the fuel pressure becomes higher than the fuel pressure supplied to the fuel rail during the idling operation of the diesel engine.

  FIG. 1 shows a schematic configuration of a diesel engine 1 (hereinafter referred to as an engine 1) mounted on a vehicle (automobile) and equipment related to the engine 1 and its automatic stop device 2. FIG. 1 shows a schematic configuration of a fuel supply device 30 that supplies fuel. The engine 1 is, for example, a 4-cylinder 4-cycle diesel engine 1.

  As shown in FIG. 1, the engine 1 includes a cylinder head 3 and a cylinder block 4, and the cylinder head 3 and the cylinder block 4 form four cylinders 5 in series. A piston 7 connected to the crankshaft 6 by a connecting rod (not shown) is inserted into each cylinder 5, and a combustion chamber 8 is formed above the piston 7 in each cylinder 5. The pistons 7 of the plurality of cylinders 5 move up and down with the rotation of the crankshaft 6 with a predetermined phase difference, and intake, compression, expansion, and exhaust processes are sequentially performed in each cylinder 5.

  The cylinder head 3 includes, for each cylinder 5, an intake port 10 and an exhaust port 11 facing the combustion chamber 8, an intake valve 12 and an exhaust valve 13 that open and close the intake port 10 and the exhaust port 11, respectively, and a piston in the combustion chamber 8. An injector 31 for directly injecting fuel is provided toward a cavity 7 a formed at the upper end portion of 7. An intake passage 15 and an exhaust passage 16 each having an intake flow rate adjustment control valve 14 are connected to the intake port 10 and the exhaust port 11, respectively. The intake passage 15 and the exhaust passage 16 pass a part of the exhaust gas from the exhaust passage 16. In order to recirculate to the intake passage 15, a recirculation passage 18 having an open / close control valve 17 is connected.

  The mechanism for opening and closing the intake valve 12 and the exhaust valve 13 is not shown in the figure, but is driven through a cam mechanism linked to the crankshaft 6 or without being linked to the crankshaft 6. A valve that independently drives the intake valve 12 and the exhaust valve 13 with an electromagnetic actuator is employed.

  The engine 1 is provided with an alternator 20 that is connected by a timing belt or the like and is driven by the driving force of the engine 1 to generate electric power, and a starter 21 for starting the engine 1. The starter 21 meshes with a ring gear 22 whose pinion 20a is fixed to a flywheel (not shown). 23 is a brake pedal, and 24 is an accelerator pedal.

  As shown in FIGS. 1 and 2, the fuel supply device 30 includes the injector 31, the fuel rail 32 connected to the injector 31, and the fuel pressure in the fuel rail 32 does not exceed a predetermined high pressure (for example, 280 MPa). And a fuel pump 35 driven by the driving force of the engine 1 and capable of pumping fuel in the fuel tank 34 to the fuel rail 32. When the fuel is supplied from the fuel rail 32 to the plurality of injectors 31 and the fuel injection passages are opened in the injectors 31, the high-pressure fuel is opened to the combustion chamber 8 through the injection holes.

  The fuel pump 35 includes a pump cylinder 40, a pump piston 41 that reciprocates in the pump cylinder 40, a cam 42 that drives the pump piston 41, a spill valve 43 that is an electromagnetic control valve provided on the fuel suction side, And a check valve 44 provided on the fuel intake / discharge side. The fuel tank 34 and the spill valve 43 are connected by a pipe 45. The pipe 45 has a low-pressure pump 46 for feeding the fuel in the fuel tank 34 to the spill valve 43, and a filter 47 for cleaning the fuel. Is provided.

  A return line 45a branched from the filter 47 and reaching the fuel tank 34 is connected to the line 45, and a regulator 48 for maintaining the fuel pressure in the line 45 below a predetermined low pressure is provided on the return line 45a. ing. Further, the fuel rail 32 and the conduit 45 are connected by a reflux conduit 45b, and a relief valve 33 is provided in the reflux conduit 45b. That is, when the fuel pressure in the fuel rail 32 exceeds a predetermined high pressure, the relief valve The valve 33 is opened, and the fuel is refluxed from the reflux line 45b to the line 45.

  The spill valve 43 includes a valve body 50, a spring 51 that urges the valve body 50 toward the valve closing side, and a solenoid 52 that drives the valve body 50 toward the valve opening side. In synchronization with the movement, the solenoid 52 is turned on and off to open and close the valve body 50, and when the pump piston 41 retreats when the valve body 50 is open, the pump cylinder 40 passes through the spill valve 43 from the pipe 45. When the pump piston 41 protrudes when the fuel is sucked into the valve body 50 and the valve body 50 is closed, the fuel on the pump cylinder 40 side is pressurized, and the check valve 44 is opened to be pumped to the fuel rail 32.

  In this fuel supply device 30, an ECU 60 (engine control unit 60) detects, by a pressure sensor 61, an injector driver 31 a that drives a plurality of injectors 31, a spill valve 43 (solenoid 52) of a fuel pump 35, and a low-pressure pump 46. In addition to the detection information of the fuel pressure in the fuel rail 32, the control is performed based on the detection information such as the intake air temperature, the intake air amount, and the engine speed detected by the sensors 62 to 64.

  In this case, the opening / closing timing of the valve body 50 is changed by the control of the solenoid 52 of the spill valve 43, whereby the output of the fuel pump 35 (that is, the pressure of the fuel) is changed. The fuel pressure inside is adjusted. The fuel pressure in the fuel rail 32 when the engine 1 is in idle operation is adjusted to be lower than the fuel pressure in the fuel rail 32 when the engine 1 is in operation other than during idle operation.

  The automatic stop device 2 of the engine 1 automatically stops the engine 1 when a predetermined automatic stop condition is satisfied (for example, when the brake pedal 23 is continuously depressed for a certain time or more when the vehicle speed is substantially zero). After the engine 1 is automatically stopped, the engine 1 is restarted when a predetermined restart condition is satisfied (for example, when the accelerator pedal 24 is depressed).

  The automatic stop device 2 of the engine 1 includes a fuel supply device 30 (an injector 31, a relief valve 33, a fuel pump 35) and the like, and also includes switches / sensors 61, 65, 66, and an ECU 60. When the detection signals from the switches / sensors 61, 65, 66 are received and the automatic stop condition is satisfied, the injector 31 (injector driver 31a), the fuel pump 35 (spill valve 43), and the like are controlled, and the engine 1 Is automatically stopped. In the switches and sensors, 65 is a vehicle speed sensor, and 66 is a brake pedal switch for detecting that the brake pedal 23 is operated. The engine 1 is provided with other various switches and sensors necessary for the control, but is omitted.

  The ECU 60 is composed of a computer having a CPU, a ROM, a RAM, and the like. After the automatic stop condition is established, the fuel pump 35 pumps the fuel to the fuel rail 32, and the fuel pressure is applied to the fuel rail 32 when the engine 1 is idling. An automatic stop control unit 60a (automatic stop control means 60a) that controls the fuel pump 35 to be driven by the driving force of the engine 1 so as to be higher than the supplied fuel pressure is provided.

  Next, the automatic stop control (automatic stop control method) of the engine 1 executed by the ECU 60 will be described in detail. A program for executing this automatic stop control is stored in the ECU 60 computer ROM or the like.

  As shown in FIG. 3, this automatic stop control is executed when an ignition switch (not shown) is turned on and the engine 1 is operating. First, whether or not the automatic stop condition of the engine 1 is satisfied, For example, based on signals from the vehicle speed sensor 65 and the brake pedal switch 66, it is determined whether or not the brake pedal 23 has been depressed for a predetermined time or longer when the vehicle speed is substantially zero (S1). S1; If No, return.

  In the case of S1; Yes, the injector 31 is controlled so as not to inject fuel into the combustion chamber 8, a fuel cut (S2) to the combustion chamber 8 is performed, and then the fuel pump 35 is driven by the driving force of the engine 1. The spill valve 43 (solenoid 52) of the fuel pump 35 is controlled so as to be driven to pump fuel to the fuel rail 32 and raise the fuel pressure in the fuel rail 32 (S3). At this time, the fuel pump 35 is driven and controlled so as to adjust the opening and closing timing of the valve body 50 of the spill valve 43 so that the output (that is, the pressure of the fuel) becomes maximum.

  Next, it is determined whether or not the fuel pressure in the fuel rail 32 detected by the pressure sensor 61 is equal to or higher than an allowable maximum pressure (for example, 260 MPa) (S4), and the process waits until S4; Yes. Then, when S4 is Yes, the valve body 50 of the spill valve 43 is held open so that the fuel pump 35 is controlled to stop outputting so as not to pump fuel to the fuel rail 32 (S5), and the process ends. . However, when the engine 1 is completely stopped by S4; Yes, this control is also terminated when the engine 1 is stopped.

According to the automatic stop control method of the engine 1 and the automatic stop device 2, the following effects are obtained.
When the engine 1 is automatically stopped, after the automatic stop condition is satisfied, the fuel pump 35 pumps the fuel to the fuel rail 32, and the fuel pressure becomes higher than the fuel pressure supplied to the fuel rail 32 when the engine 1 is idling. Thus, since the fuel pump 35 is controlled to be driven by the driving force of the engine 1, first, by driving the fuel pump 35, a load is applied to the engine 1 to reduce the idling amount in the stopping process of the engine 1. Thus, the temperature drop of the combustion chamber 8 due to the intake air can be suppressed.

  Here, when the engine 1 is automatically stopped, the automatic stop condition is normally established when the engine 1 is in an idle operation or when the engine 1 is shifted to the idle state, and the output of the fuel pump 35 is stopped together with the fuel cut. During operation, the fuel pressure in the fuel rail 32 becomes lower than the fuel pressure in the fuel rail 32 when the engine 1 is in an operation other than the idling operation due to a request by the engine control. The fuel pressure supplied to the fuel rail 32 during idling of the engine 1 can be made higher.

  When the engine 1 is automatically stopped, fuel is supplied to the fuel rail 32 by the fuel pump 35 so that the fuel pressure in the fuel rail 32 is higher than the fuel pressure supplied to the fuel rail 32 when the engine 1 is idling. By pumping, when the engine 1 is restarted, the fuel pressure necessary for reliably injecting fuel from the injector 31 to the combustion chamber 8 is secured in the fuel rail 32, that is, the engine 1 is restarted. Therefore, the operation reliability of the fuel rail 32 can be ensured, and the restartability of the engine 1 can be improved.

  In addition, after the automatic stop condition is satisfied, the fuel pump 35 is driven by the driving force of the engine 1 so that the fuel pressure supplied to the fuel rail 32 is increased to the allowable maximum pressure. The fuel pressure necessary for restarting the engine 1 can be reliably ensured in the fuel rail 32 after preventing the failure. Further, since the fuel pump 35 is driven and controlled so that the output thereof is maximized after the automatic stop condition is satisfied, the fuel pressure supplied to the fuel rail 32 can be made as high as possible. Thus, the temperature drop of the combustion chamber 8 due to the intake air can be reliably suppressed.

  As a modification of the above embodiment, S4 and S5 may be omitted in the automatic stop control (automatic stop control method) of the engine 1 shown in FIG. That is, in S3, the spill valve 43 (solenoid 52) of the fuel pump 35 is driven so that the fuel pump 35 is driven by the driving force of the engine 1 to pump the fuel to the fuel rail 32 and raise the fuel pressure in the fuel rail 32. This state may be continued until the engine 1 is completely stopped. Here, the relief valve 33 functions so that the fuel pressure in the fuel rail 32 does not rise too much, and compensation is made so that the fuel pressure in the fuel rail 32 does not exceed a predetermined high pressure.

  In addition, in the range which does not deviate from the meaning of the present invention, various modifications can be added in addition to the above disclosure, and the present invention can be applied to various automobiles and various vehicles other than automobiles. It can be applied to technology that automatically stops the engine.

It is a schematic block diagram of the apparatus relevant to a diesel engine and its automatic stop apparatus. It is a schematic block diagram of the fuel supply apparatus containing an automatic stop apparatus. It is a flowchart of engine automatic stop control.

Explanation of symbols

1 Diesel Engine 2 Automatic Stop Device 8 Combustion Chamber 32 Fuel Rail 33 Relief Valve 35 Fuel Pump 60 ECU (Engine Control Unit)

Claims (4)

In a diesel engine automatic stop control method for automatically stopping a diesel engine when a predetermined automatic stop condition is satisfied,
After the automatic stop condition is established, the diesel engine is controlled so that the fuel pump is driven by the driving force of the diesel engine so that the fuel pressure becomes higher than the fuel pressure supplied during the idling operation of the diesel engine. Automatic stop control method.   2. The diesel engine automatic stop control method according to claim 1, wherein after the automatic stop condition is satisfied, the fuel pump is driven by the driving force of the diesel engine so that the fuel pressure increases to an allowable maximum pressure.   3. The diesel engine automatic stop control method according to claim 1, wherein after the automatic stop condition is satisfied, drive control of the fuel pump is performed so as to maximize the output of the fuel pump. In a diesel engine automatic stop device that automatically stops the diesel engine when a predetermined automatic stop condition is satisfied,
A fuel pump driven by the driving force of the diesel engine and capable of pumping fuel to the fuel rail of the diesel engine;
A relief valve that adjusts the fuel pressure in the fuel rail so as not to exceed a predetermined high pressure;
Automatic stop control means for driving and controlling the fuel pump so that the fuel pressure is higher than the fuel pressure supplied to the fuel rail during idle operation of the diesel engine after the automatic stop condition is satisfied;
A diesel engine automatic stop device characterized by comprising: