JP5262532B2 - Diesel engine automatic stop device and diesel engine control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic stop device for a diesel engine 10 improved in restarting performance of the engine 10, and a control method for the same. <P>SOLUTION: This control method includes: a step of stopping fuel supply when an automatic stop condition is satisfied; a step of keeping both an intake valve 26 and an exhaust valve 27 in a closed state simultaneously with the fuel supply stop or immediately after the fuel supply stop; a step of completely stopping the diesel engine 10 through the fuel supply stop and the closing of the intake valve 26 and the exhaust valve 27; and a step of restarting the engine 10 by restarting the fuel supply when a restarting condition is satisfied. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a diesel engine automatic stop device that automatically stops a diesel engine when a predetermined automatic stop condition is satisfied, and restarts the diesel engine when a predetermined restart condition is satisfied, and It belongs to the technical field related to control methods.

Conventionally, for the purpose of reducing fuel consumption and suppressing CO ₂ emission, the engine is automatically stopped when a predetermined automatic stop condition such as idling is satisfied. In order to automatically stop the engine, it is necessary to restart the engine. However, it is required to perform the restart reliably and promptly.

  Here, in the case of a diesel engine, a glow plug is provided for warming the intake air and improving the ignitability of fuel when the engine is cold. In order to prevent deterioration of fuel ignitability due to a decrease in internal temperature, the inside of the cylinder is heated by the glow plug, thereby improving the restartability of the engine.

On the other hand, in recent years, there has been known a valve drive means for driving the intake valve and the exhaust valve independently by an actuator regardless of the rotational position of the crankshaft, and controlling the operation of the valve drive means. ing. By controlling the operation of such valve driving means, the operating state of the intake valve, that is, the opening degree (lift amount) of the intake valve and the valve opening period can be freely controlled. For example, in the intake stroke or the exhaust stroke It is also possible to make it fully closed.
JP 2004-176469 A

  As in the conventional example, in the method of heating the inside of the cylinder with the glow plug in order to improve the restartability of the engine, the power consumption of the glow plug is large. There is a problem in that the power supplied to the load is reduced, and it is preferable not to use the glow plug as much as possible.

  The present invention has been made in view of such a point, and an object of the present invention is to provide an automatic stop device for a diesel engine with improved restartability of the engine and a control method therefor.

  According to one aspect of the present invention, the control method is a control method for a diesel engine that is operated by controlling operating states of an intake valve and an exhaust valve of a cylinder and controlling fuel supply to the cylinder.

In this control method, the fuel supply to the cylinder is stopped when a predetermined automatic stop condition is satisfied, and the intake valve and the exhaust valve of the cylinder are both closed simultaneously with or immediately after the fuel supply stop. And the step of stopping the diesel engine after stopping the fuel supply and closing the intake valve and the exhaust valve, and supplying the fuel to the cylinder when a predetermined restart condition is satisfied. by resuming, and a step of restarting the Dee cell engine wherein stopped.

  According to this configuration, when the predetermined automatic stop condition is satisfied and the fuel supply to the cylinder is stopped, the process proceeds to an engine stop process until the diesel engine reaches a complete stop.

  In this engine stop process, both the intake valve and the exhaust valve of the cylinder are closed simultaneously with or immediately after the fuel supply is stopped. As a result, new air is not newly sucked into the cylinder from the intake side of the diesel engine, and a decrease in the in-cylinder temperature is suppressed.

  Further, by closing the intake valve and the exhaust valve, only a small amount of air is compressed in the cylinder, and the stop vibration caused by the compression of the air in the cylinder during the engine stop process is suppressed.

  Thus, when a predetermined restart condition is satisfied and the diesel engine that has been stopped by restarting the fuel supply to the cylinder is restarted, the decrease in the in-cylinder temperature is suppressed. Improves.

The control method includes at least the in a particular cylinder to be compressed stroke when the diesel engine is stopped, further Ru comprising a step of performing suction by the suction stroke of the stop just before.

  As described above, when the diesel engine is stopped with the intake valve and the exhaust valve closed, the next time the engine is restarted, air is first taken into the cylinder, and then compressed to expand the expansion stroke. There is a delay in starting the diesel engine.

  Therefore, in the specific cylinder that is in the compression stroke when the diesel engine is stopped, intake is performed in the intake stroke immediately before the stop, so that the specific cylinder is in the cylinder when the engine is stopped, in other words, when the engine is restarted. It will be in the state which put air in. For this reason, when the engine is restarted, it is possible to compress the air in the specific cylinder and shift to the expansion stroke, and the diesel engine is started quickly.

  The step of performing the intake may be performed by closing the intake valve of the specific cylinder and opening the exhaust valve.

  In the engine stop process, the exhaust side temperature of the diesel engine is higher than that on the intake side due to the exhaust heat until then. Therefore, when intake is performed in the intake stroke immediately before the stop in the specific cylinder, the in-cylinder temperature is increased by performing intake from the exhaust side of the diesel engine by closing the intake valve and opening the exhaust valve of the specific cylinder. . As a result, the restartability of the diesel engine is further improved.

  The control method may further include a step of performing intake in an intake stroke after the restart condition is satisfied and fuel supply to the cylinder is restarted in cylinders other than the specific cylinder.

  That is, for a cylinder that does not take air into the cylinder before the engine is stopped, intake may be performed in the intake stroke when the engine is restarted.

  The step of performing the intake may be performed by exhaust side suction control for intake from the exhaust side of the diesel engine by closing the intake valve of the cylinder and opening the exhaust valve.

  As described above, the in-cylinder temperature is increased by performing intake from the exhaust side of the diesel engine. As a result, the restartability of the diesel engine is improved.

  The exhaust side suction control is performed after the fuel supply is resumed until the rotational speed of the diesel engine reaches a predetermined rotational speed, and after the rotational speed reaches the predetermined rotational speed, the intake valve is controlled in the intake stroke. Ordinary control for intake from the intake side of the diesel engine may be performed by opening and closing the exhaust valve.

  The exhaust side suction control is performed in the first intake stroke after resumption of the fuel supply. In the second and subsequent intake strokes, the intake valve of the diesel engine is opened by opening the intake valve and closing the exhaust valve in the intake stroke. It is also possible to perform normal control for inhaling air.

  Since combustion gas is discharged to the exhaust side after the restart of the diesel engine is started, switching to intake air from the intake side at a predetermined timing is desirable for improving engine startability.

  The control method may further include a step of supplying secondary air to an exhaust side of the diesel engine in the engine stop process.

  By doing so, as described above, when intake is performed from the exhaust side of the diesel engine, air having a high oxygen concentration is drawn into the cylinder. As a result, fuel ignitability is improved and engine startability is enhanced.

  The supply of the secondary air is preferably started after both the intake valve and the exhaust valve of each cylinder are closed.

  By doing so, the secondary air supplied to the exhaust side is suppressed from flowing downstream to the exhaust side, and the secondary air stays near the exhaust valve. As a result, when the exhaust valve is opened during the intake stroke, air containing a large amount of the secondary air is sucked into the cylinder.

According to another aspect of the present invention, an automatic stop device for a diesel engine includes at least one cylinder provided with an intake valve and an exhaust valve, controls an operating state of the intake valve and the exhaust valve, and supplies the cylinder to the cylinder. A diesel engine operated by controlling the fuel supply of the engine, and automatically stopping the diesel engine by stopping the fuel supply to the cylinder when a predetermined automatic stop condition is satisfied, and a predetermined restart condition An automatic stop / restart control means for restarting the diesel engine by resuming the fuel supply to the cylinder when the condition is established, a valve driving means for driving the intake valve and the exhaust valve of the cylinder, and the valve Valve operation control means for controlling operating states of the intake valve and the exhaust valve by the drive means, and the valve operation control means comprises the automatic stop. - simultaneously or immediately thereafter the fuel supply stop to the cylinder by the restart control means holds in both closed and the intake and exhaust valves of the cylinders, at least, compressed when the diesel engine is stopped In the specific cylinder that becomes the stroke, intake is performed in the intake stroke immediately before the stop .

  According to this configuration, as described above, by closing both the intake valve and the exhaust valve of the cylinder simultaneously with or immediately after the stop of the fuel supply in the engine stop process, the decrease in the in-cylinder temperature is suppressed, and the engine Restartability is improved.

  As described above, according to the present invention, in the process of stopping the engine, the decrease in the cylinder temperature can be suppressed by closing both the intake valve and the exhaust valve of the cylinder simultaneously with or immediately after the stop of the fuel supply. As a result, the restartability of the diesel engine can be improved. Further, the stop vibration during the engine stop process can be suppressed by closing the intake valve and the exhaust valve.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the following description of the preferred embodiment is merely illustrative in nature, and is not intended to limit the present invention, its application, or its use.

  FIG. 1 shows a schematic configuration of a four-cycle diesel engine 10 (hereinafter simply referred to as an engine 10) provided with an automatic stop device according to Embodiment 1 of the present invention. In the present embodiment, an example in which the engine 10 is mounted on a vehicle connected to a manual transmission is shown.

Referring to FIG. 1, the engine 10 includes a cylinder head 11 and a cylinder block 12. In the cylinder head 11 and the cylinder block 12, four cylinders 14A to 14D are arranged in series in order from the front side of the engine. A piston 16 connected to the crankshaft 15 by a connecting rod (not shown) is fitted inside each of the cylinders 14A to 14D. A cavity 16 a that partitions the combustion chamber 17 together with the cylinder head 11 is formed in the piston 16. The pistons 16 provided in the cylinders 14A to 14D are configured to move up and down with the rotation of the crankshaft 15 with a predetermined phase difference. Here, in the engine 10 that is a four-cylinder four-cycle engine, each of the cylinders 14A to 14D performs a cycle including intake, compression, expansion, and exhaust strokes with a predetermined phase difference. The numbering cylinder 14A, the numbering cylinder 14C, the numbering cylinder 14D, and the numbering cylinder 14B are configured so as to be performed with a phase difference of 180 ° (180 ° CA) in crank order.

  The cylinder head 11 is provided with a glow plug 18 for each of the cylinders 14 </ b> A to 14 </ b> D disposed so that the plug tip faces the combustion chamber 17. The cylinder head 11 is provided with a fuel injection valve 19 for each of the cylinders 14A to 14D. The fuel injection valve 19 has a branch pipe 21 provided for each of the cylinders 14A to 14D with respect to the common rail 20 that stores and distributes fuel in a high pressure state higher than the valve opening pressure (injection pressure) of the fuel injection valve 19. Are connected to each other. Each fuel injection valve 19 opens the fuel passage by electromagnetic force when energized to open the true valve of the injection nozzle by fuel pressure, and burns high-pressure fuel supplied from the common rail 20 from a plurality of injection holes at the tip of the injection nozzle. Direct injection is supplied into the cylinders 14 </ b> A to 14 </ b> D toward the cavity 16 a of the piston 16 that defines the chamber 17. In the present embodiment, a fuel pressure sensor SW <b> 1 for detecting fuel pressure is provided on the common rail 20. The fuel injection amount of the fuel injection valve 19 is controlled by the energization time. A common rail 20 that supplies fuel to the fuel injection valve 19 is connected to a fuel supply pump 23 via a high-pressure fuel supply pipe 22.

  In addition, the cylinder head 11 is provided with an intake port 24 and an exhaust port 25 that open toward the combustion chamber 17 at the upper part of each of the cylinders 14A to 14D. In addition, an intake valve 26 and an exhaust valve 27 are respectively provided at a connection portion between the ports 24 and 25 and the combustion chamber 17.

  The intake valve 26 is driven to open and close by an electromagnetic intake valve drive means 26A. Similarly, the exhaust valve 27 is also driven to open and close by an electromagnetic exhaust valve drive means 27. Both the intake valve 26 and the exhaust valve 27 are not mechanically linked to the crankshaft 15, and are opened and closed by the operation of the valve driving means 26A and 27A regardless of the rotational position of the crankshaft 15. . That is, when the intake valve drive means 26A is demagnetized, the intake valve 26 is closed by a return spring (not shown), while when the intake valve drive means 26A is excited, the intake valve 26 resists the return spring. The valve is opened. Similarly, when the exhaust valve driving means 27A is demagnetized, the exhaust valve 27 is closed by a return spring (not shown), while when the exhaust valve driving means 27A is excited, the exhaust valve 27 resists the return spring. The valve is then opened. In the present embodiment, the exciting force of the intake valve driving means 26A can be adjusted stepwise or steplessly, and thereby the opening degree (lift amount) of the intake valve 26 can be changed. That is, the opening degree of the intake valve 26 is changed according to the engine speed and the engine load. On the other hand, the exhaust valve driving means 27A is operated ON / OFF, and the opening degree of the exhaust valve 27 is set to be always constant. Note that the opening degree of both the intake valve 26 and the exhaust valve 27 may be changed, or may be set so as to be always constant.

  The opening time of the intake valve 26 is determined in advance corresponding to the opening of the intake valve 26, and becomes longer as the opening is larger. In this case, regardless of the opening degree (lift amount) of the intake valve 26, the valve opening start timing with respect to the crank angle is uniform, while the valve closing completion timing is as the opening degree of the intake valve 26 decreases. It is preferable to be faster. As a result, the pumping loss can be reduced. The opening time of the intake valve 26 may be constant regardless of the opening degree of the intake valve 26.

  The valve driving means 26A and 27A are operated in response to a command from an intake / exhaust valve operation control unit 103 of the engine control unit 100, which will be described later, and the intake / exhaust valve operation control unit 103 provides valve drive means. The operating states of the intake valve 26 and the exhaust valve 27 by 26A and 27A are controlled. Thus, the intake / exhaust valve operation control unit 103 constitutes the valve operation control means of the present invention.

  An intake passage 28 and an exhaust passage 29 are connected to the intake port 24 and the exhaust port 25, respectively. The downstream portion of the intake passage 28 is a branched intake passage 28a branched for each of the cylinders 14A to 14D, and the upstream end of each branched intake passage 28a communicates with the surge tank 28b. A common intake passage 28c is provided on the upstream side of the surge tank 28b. Although schematically shown in FIG. 1, the common intake passage 28c includes an air flow sensor SW2 that detects an intake flow amount, an intake pressure sensor SW3 that detects intake pressure, and an intake temperature sensor SW4 that detects intake temperature. Is provided.

  The upstream portion of the exhaust passage 29 is a branched exhaust passage that branches into the cylinders 14A to 14D.

  The engine 10 is provided with an alternator 32 connected to the crankshaft 15 by a timing belt or the like. The alternator 32 includes a regulator circuit 33 that adjusts the amount of power generation by adjusting the output voltage by controlling the current of a field coil (not shown), and is controlled by the engine control unit 100 that is input to the regulator circuit 33. Based on the signal, control of the amount of power generation corresponding to the electric load of the vehicle, the voltage of the vehicle-mounted battery, and the like is executed.

  Further, the engine 10 is provided with a starter motor 34 for starting the engine 10. The starter motor 34 has a motor body 34a and a pinion gear 34b. The pinion gear 34b reciprocates on the output shaft of the motor body 34a in a state where relative rotation is impossible. The crankshaft 15 is provided with a ring gear 35 fixed to a flywheel (not shown) concentrically with respect to the center of rotation. When the starter motor 34 is used to restart the engine 10, the pinion gear 34b moves to a predetermined meshing position and meshes with the ring gear 35, so that the crankshaft 15 is driven to rotate. It has become.

  Further, the engine 10 is provided with two crank angle sensors SW5 and SW6 for detecting the rotation angle of the crankshaft 15, and the engine rotation speed is based on a detection signal (pulse signal) output from one crank angle sensor SW5. Is detected, and the rotation angle of the crankshaft 15 is detected on the basis of detection signals out of phase output from the crank angle sensors SW5 and SW6. Further, the engine 10 is operated by a water temperature sensor SW7 for detecting a coolant temperature, an accelerator opening sensor SW8 for detecting an accelerator opening corresponding to an operation amount of the accelerator pedal 36 of the vehicle, and an operation of a brake pedal 37 of the vehicle. A brake pedal sensor SW9 for detection is provided.

  Further, the engine 10 is provided with an exhaust gas recirculation device 40. The exhaust gas recirculation device 40 includes an EGR passage 41 that circulates part of the exhaust gas from the exhaust passage 29 to the intake passage 28, and an EGR valve 42 provided in the middle of the EGR passage 41. The EGR valve 42 is controlled to be opened and closed by an EGR control unit 106 of the engine control unit 100 described below.

  Further, the engine 10 is provided with a secondary air supply device 5 that supplies air into the exhaust passage 29. The secondary air supply device 5 includes, in the exhaust passage 29, a secondary air supply passage 51 communicating with the vicinity of the exhaust port 25, and an electric pump 52 provided in the middle of the secondary air supply passage 51. By driving and controlling the electric pump 52 by a secondary air control unit 107 of the engine control unit 100 described later, air is supplied in the vicinity of the exhaust port 25 to the exhaust valve 27 in the exhaust passage 29 as necessary. It is like that.

  In the present embodiment, no intake throttle valve is provided in the intake passage 28, and the intake valve 26 plays the same role as the intake throttle valve.

  Operation of the engine 10 is controlled by the engine control unit 100.

  The engine control unit 100 includes a CPU, a memory, a counter timer group, an interface, and a microprocessor having a path connecting these units. Based on detection signals from input elements such as the sensors SW1 to SW9, While performing various calculations, it outputs control signals for the actuators such as the fuel injection valve 19, the starter motor 34, and the glow plug 18. For example, the fuel injection amount and injection timing corresponding to the operating conditions are calculated, and a control signal is output to the fuel injection valve 19 and the like. Further, a target value of the opening degree (lift amount) of the intake valve 26 is calculated in accordance with the operating state of the engine 10 (engine speed and engine load), and a control signal is set so that the opening degree becomes this target value. Output to the intake valve driving means 26A.

  The engine control unit 100 includes a driving state determination unit 101 that determines the driving state of the vehicle, a fuel injection control unit 102 that controls fuel injection of the engine 10 based on the determination of the driving state determination unit 101, and the valve drive. An intake / exhaust valve operation control unit 103 that controls the operation of the means 26A, 27A, a starter control unit 104 that drives and controls the starter motor 34 of the engine 10 when a restart condition is established based on the determination of the operating state determination unit 101; The glow plug control unit 105 that controls the glow plug 18 and the EGR control unit 106 that drives and controls the EGR valve 42 of the exhaust gas recirculation device 40 are logically configured.

  The operating state determination unit 101 includes a fuel pressure sensor SW1, an air flow sensor SW2, an intake pressure sensor SW3, an intake air temperature sensor SW4, a crank angle sensor SW5, SW6, a water temperature sensor SW7, an accelerator opening sensor SW8, a brake pedal sensor SW9, and the like. This is a module for determining whether or not the automatic stop condition or restart condition of the engine 10 is satisfied or canceled based on the sensor signal and whether or not the operating state of the engine 10 is in a low-load operating state. In addition to this, the operation state determination unit 101 determines various operation states such as the fuel pressure, the stop position of the piston 16, the in-cylinder temperature, or whether the engine 10 is rotating forward. The operating state determination unit 101 also determines the stop position of the piston 16 when the engine 10 is automatically stopped, and sets an appropriate stop position SA at which the piston 16 should stop. In the present embodiment, the appropriate stop position SA of the compression stroke cylinder at the time of stop (cylinder that becomes the compression stroke when the automatic stop of the engine 10 is completed) is, by default, 120 ° CA before compression top dead center to 100 ° before compression top dead center. Set to the range of CA. As will be described later, in a diesel engine, it is necessary to inject fuel into the compression stroke cylinder at the time of stop, and to drive the piston 16 by the starter motor 34 so that the air-fuel mixture is self-ignited in the cylinder into which the fuel has been injected. Therefore, it is preferable that the piston 16 is stopped on the bottom dead center side. On the other hand, when the piston 16 is in the vicinity of the bottom dead center, the drive time of the starter motor 34 becomes long. Therefore, in order to achieve both reliable self-ignition and shortening of the drive time of the starter motor 34, the compression is increased by default. It is set in a range from 120 ° CA before the dead center to 100 ° CA before the compression top dead center. However, when the in-cylinder temperature is high, the effective compression ratio of the stop compression stroke cylinder can be set small, so that the appropriate stop position SA is corrected to the top dead center side by the in-cylinder temperature. ing. The in-cylinder temperature is configured to be estimated based on data stored in advance in a memory. In the present embodiment, the driving state determination unit 101 receives a detection signal from a sensor (not shown) so as to be able to determine ON / OFF of the brake pedal 37 of the vehicle, vehicle speed, and the like.

  The fuel injection control unit 102 sets a fuel injection amount and a fuel injection timing corresponding to an appropriate air-fuel ratio of the engine 10 based on the determination of the operating state determination unit 101, and based on the setting, the fuel injection valve 19 Is a module for controlling the driving of

  The intake / exhaust valve operation control unit 103 calculates a target value of the opening degree (lift amount) of the intake valve 26 based on the determination of the operating state determination unit 101, and the target value and both crank angle sensors SW5, SW6. This is a module for controlling the operation of the valve drive means 26A, 27A according to the rotation angle of the crankshaft 15 detected by the above.

  The starter control unit 104 is a module that outputs a control signal to the starter motor 34 when the engine 10 is started to drive the starter motor 34.

  The glow plug control unit 105 drives the glow plug 18 when the piston 16 of the stop compression stroke cylinder is on the top dead center side with respect to the appropriate stop position SA when the engine is cold or the engine is restarted. It is a module that controls

  The EGR control unit 106 is a module that improves combustion stability by opening the EGR valve 42 in a predetermined partial load operation region.

  The secondary air control unit 107 supplies air into the exhaust passage 29 through the secondary air supply passage 51 by driving the electric pump 52 during the engine stop process during which the engine 10 is automatically stopped. Thus, the module improves the restartability of the engine 10.

  The engine control unit 100 automatically stops the engine 10 when a predetermined automatic stop condition is satisfied, and restarts the engine 10 that has been automatically stopped when a predetermined restart condition is satisfied. It constitutes restart control means. A control example of the automatic stop control and restart control of the engine 10 in the engine control apparatus 100 will be described.

  FIG. 2 is a flowchart including automatic stop control and restart control according to the present embodiment, and FIG. 3 is a timing chart showing operating states of the intake valve 26 and the exhaust valve 27 based on the control example of FIG.

  Referring to FIG. 2, engine control unit 100 waits for a preset automatic engine stop condition to be satisfied (step S21). Specifically, when the operating state of the brake pedal 37 continues for a predetermined time and the vehicle speed is equal to or lower than a predetermined value (that is, when the idling operation state of the engine 10 is assumed to continue for a predetermined time), It is determined that the automatic stop condition for engine 10 is satisfied.

  If it is determined in step S21 that the automatic stop condition is satisfied, the fuel supply from the fuel injection valve 19 is stopped (step S22), and the process proceeds to the engine stop process. The engine control unit 100 (intake / exhaust valve operation control unit 103) fully closes the intake valve 26 and the exhaust valve 27 in the full stroke of each cylinder 14A to 14D (step S23). That is, the intake valve 26 is fully closed even during the intake stroke, and the exhaust valve 27 is fully closed also during the exhaust stroke. Thereby, the fall of the in-cylinder temperature due to the fresh intake of fresh air into each of the cylinders 14A to 14D can be suppressed. Further, by closing the intake valve 26 and the exhaust valve 27, very little air is compressed in each of the cylinders 14A to 14D, and the stop vibration caused by the compression of the air in the cylinders 14A to 14D when the engine is stopped is suppressed. can do. This step S23 is executed simultaneously with or immediately after step S22.

  In subsequent step S <b> 24, the engine control unit 100 (secondary air control unit 107) drives the electric pump 52 to supply secondary air into the exhaust passage 29. Thus, by supplying the secondary air after closing the intake valve 26 and the exhaust valve 27 of each cylinder 14A to 14D, the supplied secondary air flows downstream of the exhaust passage 29 by the exhaust flow. The secondary air can be retained in the vicinity of the exhaust port 25 to the exhaust valve 27. The supply of secondary air stops after a predetermined time has elapsed.

  Then, with the cylinders 14A to 14D being closed, the stop position of the engine 10 is predicted based on detection signals and the like of the crank angle sensors SW5 and SW6 (step S25).

  Then, based on the predicted stop position of the engine 10, for the cylinders that are in the compression stroke when the engine 10 is stopped, the process proceeds from step S26 to step S27, while for the other cylinders, the process proceeds to step S211. Transition.

  In step S27, the stop-time compression stroke cylinder sucks air from the exhaust side by opening the exhaust valve 27 and closing the intake valve 26 during the intake stroke immediately before engine stop. In FIG. 3, the second cylinder corresponds to a compression stroke cylinder at the time of stop, and the exhaust valve 27 is opened during the intake stroke immediately before the engine is stopped (timing t2 in FIG. 3). Here, in step S24, since secondary air is supplied to the exhaust side, the secondary air is included and air heated by the exhaust heat on the exhaust side is sucked into the cylinder. . In step S28, the engine 10 is stopped.

  In contrast, the cylinders other than the stop-time compression stroke cylinder, that is, the stop-time intake stroke cylinder, the stop-time exhaust stroke cylinder, and the stop-time expansion stroke cylinder are stopped as they are (step S211; step S28). And S211 are the same step).

  After the engine 10 is automatically stopped, it waits for the restart condition to be satisfied (step S29 and step S212). When the restart condition is satisfied, air in the stop compression stroke cylinder is sucked in advance from the exhaust side. Therefore, the starter controller 104 drives the starter motor 34 to compress the air in the cylinder. As a result, the in-cylinder temperature rises, and the fuel injection control unit 102 drives and controls the fuel injection valve 19 so that fuel is injected into the cylinder at a predetermined timing and the process proceeds to the expansion stroke. Thus, the compression stroke cylinder at the time of stop is shifted to normal control as it is after the restart condition is satisfied (step S210).

  On the other hand, the intake stroke cylinder at stop (1st cylinder in the example of FIG. 3), the exhaust stroke cylinder at stop (3rd cylinder in the example of FIG. 3), and the expansion stroke cylinder at stop (4th cylinder in the example of FIG. 3). Takes in air from the exhaust side by opening the exhaust valve 27 and closing the intake valve 26 during the first intake stroke. Thus, the compression stroke is shifted to the expansion stroke.

  In addition, the cylinders other than the stop-time compression stroke cylinder also shift to the normal control (step S210). With this, in these cylinders, the intake valve 26 is opened and the exhaust valve 27 is opened in the second and subsequent intake strokes. By closing, fresh air is inhaled from the intake side (not shown in FIG. 3). Then, the engine 10 is restarted.

  Therefore, in the present embodiment, in the automatic stop control in the engine control unit 100, the cylinders 14A to 14A to 14C are immediately or immediately after the automatic stop condition of the engine 10 is established and the fuel supply to the engine 10 is stopped. Since the intake valve 26 and the exhaust valve 27 of 14D are closed, it is possible to suppress a decrease in the in-cylinder temperature due to new intake of fresh air. Further, it is possible to suppress stop vibration that occurs due to the compression of air in the cylinders 14A to 14D when the engine is stopped.

  As described above, the intake valve 26 and the exhaust valve 27 of each cylinder 14A to 14D are closed until the engine 10 is actually stopped after the automatic stop condition of the engine 10 is satisfied, but the compression is performed when the engine 10 is stopped. With respect to the cylinder serving as the stroke cylinder, intake is performed during the intake stroke immediately before the cylinder is stopped. Thus, when the engine 10 is restarted, the air in the compression stroke cylinder is compressed, whereby the engine 10 can be started by self-ignition from the cylinder, and the engine 10 is started quickly.

  In addition, the compression stroke cylinder at the time of stopping opens the exhaust valve 27 and takes in air from the exhaust side during the intake stroke, so that the air warmed on the exhaust side can be taken into the cylinder, and the in-cylinder temperature Rises and the engine 10 is reliably started.

  Furthermore, since the secondary air is supplied to the exhaust side by the secondary air supply device 5, a large amount of oxygen is sucked into the compression stroke cylinder at the time of stop, and the startability of the engine 10 can be further improved. it can.

  On the other hand, for the cylinders other than the compression stroke cylinder at the time of stop, after the restart condition of the engine 10 is satisfied, by taking in air from the exhaust side in the first intake stroke, as described above, warmed air (including secondary air) ) Is sucked into the cylinder, and the startability of the engine 10 is improved.

  In addition, in the second and subsequent intake strokes, fresh air is sucked into the cylinder by inhaling fresh air from the intake side. For example, when the accelerator pedal 36 is depressed, the vehicle is accelerated. Even when a request is made, it becomes possible to quickly respond to the request.

  In the control described above, for cylinders other than the compression stroke cylinder at the time of stop, intake is performed from the exhaust side in the first intake stroke, and intake is performed from the intake side in the second and subsequent intake strokes. Based on the number of revolutions, before the engine speed reached the predetermined speed or higher, intake from the exhaust side (that is, exhaust side suction control), and the engine speed became the predetermined speed (for example, idle speed) or higher. After that, intake may be performed from the intake side (that is, normal control). By doing so, it becomes possible to shift to normal control at an early stage, and for example, it is possible to quickly respond to an acceleration request.

  The present invention can be applied not only to a four-cylinder diesel engine but also to a diesel engine having a plurality of cylinders such as six cylinders and eight cylinders.

  The present invention can improve the restartability of a diesel engine after an automatic stop, and thus is useful, for example, as an automatic stop device and control method for a diesel engine mounted on a vehicle.

It is a schematic block diagram which shows the engine provided with the automatic stop apparatus which concerns on this invention. It is a flowchart which shows the automatic stop control and restart control in an engine control apparatus. It is a timing chart which shows the operating state of an intake valve and an exhaust valve in an engine stop and a restart process.

Explanation of symbols

10 Diesel engine 14A-14D Cylinder 26 Intake valve 26A Intake valve drive means (valve drive means)
27 Exhaust valve 27A Exhaust valve drive means (valve drive means)
100 Engine control device (automatic stop / restart control means)
103 Intake / exhaust valve operation control section (valve operation control means)

Claims (9)

A control method for a diesel engine that is operated by controlling operating states of an intake valve and an exhaust valve of a cylinder and controlling fuel supply to the cylinder,
Shifting to an engine stop process to automatically stop the diesel engine by stopping fuel supply to the cylinder when a predetermined automatic stop condition is satisfied;
Holding both the intake valve and the exhaust valve of the cylinder in a closed state simultaneously with or immediately after the fuel supply stop in the engine stop process;
A step of completely stopping the diesel engine through the stop of the fuel supply and the closing of the intake valve and the exhaust valve;
Restarting the stopped diesel engine by restarting fuel supply to the cylinder when a predetermined restart condition is satisfied;
And a step of performing intake in the intake stroke immediately before the stop in the specific cylinder that is in the compression stroke when the diesel engine is stopped . The control method according to claim 1 ,
The step of performing the intake is a control method performed by closing an intake valve of the specific cylinder and opening an exhaust valve. The control method according to claim 1 or 2 ,
A control method further comprising the step of performing intake in an intake stroke after the restart condition is satisfied and fuel supply to the cylinder is restarted in cylinders other than the specific cylinder. The control method according to claim 3 , wherein
The step of performing the intake is a control method by exhaust side suction control for intake from the exhaust side of the diesel engine by closing the intake valve of the cylinder and opening the exhaust valve. The control method according to claim 4 , wherein
The exhaust side suction control is performed until the rotational speed of the diesel engine reaches a predetermined rotational speed after restarting the fuel supply,
A control method for performing normal control of intake from the intake side of the diesel engine by opening an intake valve and closing an exhaust valve in the intake stroke after the rotation speed reaches a predetermined rotation speed. The control method according to claim 4 , wherein
The exhaust side suction control is performed in the first intake stroke after resumption of the fuel supply. In the second and subsequent intake strokes, the intake valve of the diesel engine is opened by opening the intake valve and closing the exhaust valve in the intake stroke. A control method that performs normal control of inhaling air. The control method according to claim 2 or 4 ,
A control method further comprising a step of supplying secondary air to an exhaust side of the diesel engine in the engine stop process. The control method according to claim 7 ,
The secondary air supply is started after both the intake valve and the exhaust valve of each cylinder are closed. A diesel engine that includes at least one cylinder provided with an intake valve and an exhaust valve, controls the operating state of the intake valve and the exhaust valve, and is operated by controlling fuel supply to the cylinder;
Automatically stopping the diesel engine by stopping fuel supply to the cylinder when a predetermined automatic stop condition is satisfied, and restarting fuel supply to the cylinder when a predetermined restart condition is satisfied Automatic stop / restart control means for restarting the diesel engine by
Valve driving means for driving the intake valve and the exhaust valve of the cylinder;
Valve operation control means for controlling operating states of the intake valve and the exhaust valve by the valve drive means, and
The valve operation control means holds both the intake valve and the exhaust valve of the cylinder in a closed state simultaneously with or immediately after the fuel supply stop to the cylinder by the automatic stop / restart control means , and at least An automatic stop device for a diesel engine that performs intake in an intake stroke immediately before the stop in a specific cylinder that is in a compression stroke when the diesel engine is stopped .

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