JP2008095519A - Stop control device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily restart an engine by surely stopping a piston in a desired position in automatic stop of the engine. <P>SOLUTION: In the stop control device for the multi-cylinder four-cycle engine, the engine is automatically stopped when an automatic stop condition set in advance is satisfied, and the engine is restarted by combustion of a stop time expansion stroke cylinder which was in an expansion stroke at least in automatic stop of the engine. The stop control device for the engine is provided with a valve timing control means 50 capable of varying the valve timing of an intake valve 19 of the engine, and the valve timing of the intake valve 19 of the engine is advanced to a predetermined angle by the valve timing control means 50 when the automatic stop condition of the engine is satisfied, and thereby, the piston 13 of the stop time expansion stroke cylinder is stopped in the predetermined position set in advance in automatic stop of the engine. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an engine stop control device, and more particularly to an engine stop control device that automatically stops an engine when idling.

  As an apparatus for automatically stopping the engine as described above, for example, as in an engine control apparatus disclosed in Patent Document 1, the engine is injected and burned in a cylinder in an expansion stroke in a stopped state. Has been developed that can be started immediately.

  In such a control device, particularly when the piston position of the cylinder in the expansion stroke is inappropriate, for example, when the piston position is very close to the bottom dead center, the stroke in which the combustion energy acts on the piston is reduced. The engine may not be able to rotate because it is too short.

In contrast, the engine control device disclosed in Patent Document 1 controls the alternator to adjust the rotational speed of the engine before stopping the engine, thereby bringing the piston stop position of the cylinder to a desired position. It is configured to According to this method, the relationship between the engine speed and the piston stop position is obtained in advance, and the power generation amount of the alternator is adjusted based on this relationship, so that the engine speed is set to the desired position of the piston. By setting the value to a value that can be set to the value, the piston stop position can be set to a desired position to some extent.
JP 2005-282434 A

  However, immediately before the engine is stopped, the pressure in the cylinder in the compression stroke rises due to the inertial force, and the piston is pushed back by the compression reaction force, so that the engine rotates in the reverse direction. The pressure of the engine rises and the engine rotates forward by the compression reaction force. Then, after the reverse rotation and the forward rotation are repeated, the engine is stopped. That is, the stop position of the piston is determined by the balance of the compression reaction force of the compression stroke cylinder and the expansion stroke cylinder, so if the balance of the compression reaction force is lost due to the change of the air amount in each cylinder, the piston stop It may be difficult to set the position to a desired position.

  Conventionally, in a low engine speed range just before the engine stops, in order to secure the amount of air in the cylinder and stabilize combustion, the intake valve is designed to reduce the overlap between the exhaust valve and the valve timing of the intake valve. Many valve timings are set to the retard side. For this reason, when the engine rotates reversely just before the engine is stopped as described above, the intake valve may open and air may flow into the cylinder in the compression stroke. When air flows into the cylinder in the compression stroke in this way, the compression resistance in the cylinder increases, and the balance of the compression reaction force is lost, making it impossible to stop the piston at a desired stop position. There is sex.

  In view of such circumstances, an object of the present invention is to provide an engine stop control device that can reliably stop a piston at a desired position and automatically restart the engine when the engine is automatically stopped.

  According to a first aspect of the present invention for solving the above-described problem, when a preset engine automatic stop condition is satisfied, the engine is automatically stopped and when a preset engine restart condition is satisfied. In addition, in the stop control device of a multi-cylinder four-cycle engine that restarts the engine by combustion in the expansion stroke cylinder at the stop that was in the expansion stroke at least when the engine was automatically stopped, the valve timing of the intake valve of the engine can be changed The valve timing control means, and when the automatic stop condition of the engine is satisfied, the valve timing of the intake valve of the engine is advanced to a predetermined angle by the valve timing control means, The piston of the expansion stroke cylinder at the time of stop is set in advance when the engine is automatically stopped. Is characterized in that the stopping in and predetermined position (claim 1).

  According to the present invention, since the valve timing of the intake valve of the engine is advanced when the automatic engine stop condition is satisfied, the intake valve opens and stops with the reverse rotation of the engine when the engine is automatically stopped. Air can be prevented from flowing into the compression stroke cylinder. That is, it is possible to prevent the piston of the stop expansion stroke cylinder from being stopped at a desired position by increasing the compression resistance of the stop compression stroke cylinder. It becomes possible to restart reliably.

  In the present invention, the valve timing control means may be driven in any way, but it is more effective when used for valve timing control means that is driven using the rotation of the engine as a drive source. 2).

  That is, when the valve timing control means is driven using the rotation of the engine as a drive source, it becomes difficult to instantly drive the valve timing of the intake valve particularly in a low rotation range immediately before the engine stops. Therefore, as described above, if the valve timing of the intake valve is corrected for advance under the condition that the rotational speed is secured as in the case where the automatic engine stop condition is satisfied, the valve timing of the intake valve can be more reliably set. Therefore, it is possible to more reliably suppress the intake valve from opening due to the reverse rotation of the engine immediately before the engine is stopped.

  In the present invention, there is provided a rotation speed control means capable of controlling the rotation speed of the engine, and the rotation speed control means determines the rotation speed of the engine when the automatic engine stop condition is satisfied. It is preferable that the timing control means raises the valve timing to a value that enables correction of the advance angle of the valve timing of the intake valve.

  In this way, the engine speed can be increased to a value at which the advance timing of the valve timing of the intake valve can be corrected by the valve timing control means. Even the valve timing control means driven by the rotation of the valve can sufficiently advance the valve timing of the intake valve. That is, it is possible to more reliably prevent the intake valve from opening during reverse rotation, and it is possible to more reliably restart the engine.

  Further, in the present invention, there is provided valve timing detection means capable of detecting the amount of advancement of the valve timing of the intake valve, and the rotation speed control means is based on a detection result of the valve timing detection means. Is preferably controlled (claim 4).

  In this way, it is possible to optimize the advance amount of the valve timing of the intake valve with a smaller increase in the rotational speed.

  Further, in the present invention, when the engine automatic stop condition is satisfied, the rotation speed control means determines the rotation speed of the engine by the rotation speed necessary for scavenging the inside of the cylinder and the valve timing control means. It is preferable to control the valve timing to a higher rotational speed among the rotational speeds required to correct the advance angle.

  In this way, by increasing the rotational speed by the rotational speed control means, it is possible to scavenge the cylinders of the engine and to advance the valve timing of the intake valve.

  In the present invention, it is preferable that the valve timing control means controls the valve timing of the intake valve of the engine to the most advanced position when the automatic stop condition of the engine is satisfied (Claim 6).

  By controlling the valve timing of the intake valve to the most advanced angle position in this way, it is possible to more reliably prevent the intake valve from opening when the engine rotates reversely during automatic engine stop. it can.

  As described above, according to the present invention, it is possible to prevent the piston from stopping at a position deviated from a desired position when the engine is automatically stopped, thereby reliably restarting the engine. An engine stop control device that can be used can be provided.

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

  1 and 2 show a schematic configuration of a four-cycle spark ignition engine having an engine stop control device according to the present invention. The engine includes an engine main body 1 having a cylinder head 10 and a cylinder block 11 and an ECU 2 for engine control. As shown in FIG. 2, the engine body 1 is provided with four cylinders 12A to 12D. Further, a piston 13 connected to the crankshaft 3 is fitted into each of the cylinders 12A to 12D, so that a combustion chamber 14 is formed thereabove.

  A spark plug 15 is installed at the top of the combustion chamber 14 of each of the cylinders 12 </ b> A to 12 </ b> D such that the plug tip faces the combustion chamber 14. A fuel injection valve 16 that directly injects fuel into the combustion chamber 14 is provided on the side of the combustion chamber 14. This fuel injection valve 16 incorporates a needle valve and a solenoid (not shown), and is driven and opened for a time corresponding to the pulse width of the pulse signal input from the ECU 2, and has an amount corresponding to the valve opening time. The fuel is injected toward the vicinity of the electrode of the spark plug 15.

  In addition, an intake port 17 and an exhaust port 18 that open toward the combustion chamber 14 are provided in the upper portions of the cylinders 12A to 12D. In addition, an intake valve 19 and an exhaust valve 20 are respectively provided at a connection portion between the ports 17 and 18 and the combustion chamber 14. Further, the stop control device of the engine is provided with a valve timing control means 50 capable of changing the opening / closing timing of the intake valve 19, and the opening / closing timing of the intake valve 19 is changed by the valve timing control means 50. It is like that. The valve timing control unit 50 includes a valve timing calculation unit 52 and a valve timing changing unit 51. The valve timing calculation means 52 is provided in the ECU 2 and calculates the opening / closing timing of the intake valve 19. On the other hand, the valve timing changing means 51 changes the opening / closing timing of the intake valve 19 to a predetermined value in accordance with the output signal from the valve timing calculating means 52. Details of the valve timing control means 50 will be described later.

  An intake passage 21 and an exhaust passage 22 are connected to the intake port 17 and the exhaust port 18. As shown in FIG. 2, the downstream side of the intake passage 21 close to the intake port 17 is an independent branch intake passage 21 a corresponding to each cylinder 12 </ b> A to 12 </ b> D, and the upstream end of each branch intake passage 21 a is Each communicates with the surge tank 21b. A common intake passage 21c is provided upstream of the surge tank 21b. The common intake passage 21c is provided with a throttle valve 23 capable of adjusting the amount of air flowing into each of the cylinders 12A to 12D, and an actuator 24 that drives the throttle valve 23. An air flow sensor 25 for detecting the intake flow rate and an intake pressure sensor 26 for detecting the intake pressure are provided on the upstream side and the downstream side of the throttle valve 23, respectively.

  Further, the engine 1 is provided with an intake side camshaft 41 and an exhaust side camshaft 42 for opening and closing the intake valve 19 and the exhaust valve 20 as shown in FIG. The intake camshaft 41 and the exhaust camshaft 42 are connected to an intake cam pulley 43 and an exhaust cam pulley 44, respectively. A timing belt 46 is stretched between the crank pulley 45 fitted to the crankshaft 3 and the cam pulleys 43 and 44, and the rotational force of the crankshaft 3 is transmitted via the timing belt 46 to the cam pulley 43, 44, the camshafts 41 and 42 are rotated synchronously with the crankshaft 3.

  The valve timing changing means 51 is attached to the intake side camshaft 41. Then, the intake side camshaft 41 and the intake side cam pulley 43 are relatively rotated by hydraulic pressure based on the output signal of the valve timing calculation means 52 provided in the ECU 2, and the crankshaft of the intake side camshaft 41 is rotated. 3 is changed, and the opening / closing timing of the intake valve 19 is changed.

  Specifically, as shown in FIG. 4, the valve timing changing means 51 includes a casing 55 that is integrally connected to the intake side cam pulley 43 and a rotor that is rotatably connected to the casing 55. 56. The intake camshaft 41 is connected to the rotor 56 so as to rotate together. The rotor 56 has a plurality of vanes 56 a, and a plurality of pressure receiving chambers 56 b are formed between the rotor 56 and the casing 55 by the vanes 56 a and the protruding wall portions 55 a provided on the casing 55. The pressure receiving chamber 56b communicates with an oil tank 49 through an oil control valve 47 and an oil pump 48 as shown in FIG. The oil control valve 47 is driven based on a signal output from the valve timing calculation means 52, and the hydraulic pressure in the pressure receiving chamber 56b is increased or decreased. When the hydraulic pressure in the pressure receiving chamber 56b changes, the rotor 56 rotates with respect to the casing 55 accordingly. As described above, the intake side camshaft 41 is connected to the rotor 56 so as to rotate integrally. The casing 55 is connected to the intake side cam pulley 43 and thus the crankshaft 3 so as to rotate integrally. When the valve is rotated relative to 55, the valve timing of the intake valve 19 changes.

  Here, the oil pump 48 is connected to the crankshaft 3 and is driven by the rotation of the engine as a drive source. In other words, a piston (not shown) of the oil pump 48 is connected to the crankshaft 3, and the hydraulic oil in the oil tank 49 is pumped by driving the piston as the crankshaft 3 rotates. Yes.

  Further, as shown in FIG. 2, the engine main body 1 is provided with an alternator 28 connected to the crankshaft 3 by a timing belt 46 or the like. The alternator 28 includes a regulator circuit 28a for adjusting the amount of power generation by controlling the current of a field coil (not shown) and adjusting the output voltage, and the control signal from the ECU 2 input to the regulator circuit 28a. Based on the above, control of the amount of power generation corresponding to the electric load of the vehicle, the voltage of the on-vehicle battery, and the like is executed.

  Further, the engine 1 is provided with two crank angle sensors 30 and 31 for detecting the rotation angle of the crankshaft 3, and the engine speed NE is detected based on a detection signal output from one crank angle sensor 30. At the same time, the rotation angle of the crankshaft 3 is detected based on the detection signals out of phase output from both the crank angle sensors 30 and 31. Furthermore, the engine 1 detects a cam angle sensor 32 that detects the rotational position of the intake camshaft 41, a water temperature sensor 33 that detects the coolant temperature, and an accelerator opening corresponding to the driver's accelerator operation amount. An accelerator sensor 34 is provided, and detection signals output from these sensors are input to the ECU 2.

  The ECU 2 performs various calculations based on detection signals from the sensors and outputs control signals for the actuators. For example, the fuel injection amount, injection timing, and ignition timing corresponding to the operating conditions are calculated and a control signal is output to the fuel injection valve 16 and the ignition device 27. Further, the target opening of the throttle valve 23 is calculated according to the operating conditions, and a control signal is output to the actuator 24 so that the opening of the throttle valve 23 becomes the target opening. Further, the ECU 2 automatically stops fuel injection by stopping fuel injection to each of the cylinders 12A to 12D at a predetermined timing when a preset automatic engine stop condition is satisfied, and thereafter The engine is automatically restarted when the restart condition is satisfied, for example, when the driver performs an accelerator operation.

  More specifically, the restart control is performed by first injecting fuel and igniting a stop-time compression stroke cylinder in which the piston 13 is stopped in the middle of the compression stroke when the engine is automatically stopped. Next, a second combustion is performed by injecting and igniting fuel into a stop-time expansion stroke cylinder that is stopped in the middle of the expansion stroke when the engine is automatically stopped. In this restart, the piston 13 is pushed down by the combustion in the compression stroke cylinder at the time of stop, and the crankshaft 3 is slightly rotated in the reverse direction. As a result, the piston 13 of the expansion stroke cylinder at the time of stop is temporarily raised. The air in the stroke cylinder is compressed. If the air in the stop expansion stroke cylinder is compressed in this way, fuel can be injected into the compressed air and ignited to realize the second combustion in the stop expansion stroke cylinder. In this way, the engine is automatically restarted as a result of the forward rotation drive torque being applied to the crankshaft 3.

  In order to properly restart the engine simply by igniting the fuel injected into the stop expansion stroke cylinder without using a restart motor or the like as described above, the combustion obtained in the stop expansion stroke cylinder can be obtained. By securing sufficient energy, the cylinder that reaches the compression top dead center must overcome the compression reaction force and exceed the compression top dead center. That is, it is necessary to secure a predetermined amount of air in the stop-time compression stroke cylinder and to secure a sufficient amount of air in the stop-time expansion stroke cylinder. Specifically, as shown in FIG. 5 and FIG. 6, the piston 13 is slightly lower dead center side than the position where the expansion stroke cylinder at the time of stop is 90 ° CA after the compression top dead center. It is necessary to stop within a predetermined range, for example, an appropriate range R in which the crank angle after compression top dead center is 100 ° to 120 ° CA.

  Here, when the fuel injection is stopped and the engine is automatically stopped as described above, the kinetic energy possessed by the crankshaft 3 or the flywheel is consumed by mechanical loss due to friction or pump work of each cylinder 12A to 12D. As a result, the crankshaft 3 of the engine stops after several revolutions of inertia from the time of stopping fuel injection. For example, in a 4-cylinder, 4-cycle engine, the engine stops after reaching the compression top dead center of about 10 times. Specifically, as shown in FIG. 14, after the time t3 when the fuel injection is stopped, the engine speed Ne temporarily drops and decreases each time the cylinders 12A to 12D reach the compression top dead center. Then, in the cylinder that reaches the compression top dead center after the time when the last compression top dead center is exceeded, the air pressure increases as the piston 13 rises due to the inertial force, and the piston 13 is pushed back by the compression reaction force and cranked. The shaft 3 rotates in the reverse direction. When the air pressure of the expansion stroke cylinder rises due to the reverse rotation of the crankshaft 3, the piston 13 of the expansion stroke cylinder is pushed back to the bottom dead center side according to the compression reaction force, and the crankshaft 3 starts to rotate forward again. In this way, the engine stops after the reverse rotation and forward rotation of the crankshaft 3 are repeated several times.

  Thus, the stop position of the piston 13 when the engine is automatically stopped is determined by the balance of the compression reaction forces in the compression stroke cylinder and the expansion stroke cylinder. Therefore, in order to stop the piston 13 within the appropriate range R suitable for restart when the engine automatically stops, the compression reaction force of the stop expansion stroke cylinder is greater than the compression reaction force of the stop compression stroke cylinder. It is necessary to adjust the intake air flow rate for both cylinders so as to be smaller than a predetermined value.

  Therefore, in the present embodiment, by setting the opening of the throttle valve 23 to a large value at the time of stopping the fuel injection, after a predetermined amount of air is sucked into the stop expansion stroke cylinder and the stop compression stroke cylinder, When the predetermined time has elapsed, the amount of intake air flowing into each cylinder is adjusted by reducing the opening of the throttle valve 23.

  However, in an actual engine, there are individual differences in the shape of the intake port and the branch intake passage, and the behavior of the air flowing through these changes depending on the engine temperature, etc. Variations occur in the intake flow rate sucked into the cylinders 12A to 12D. Therefore, it becomes difficult to keep the stop position of the piston within the appropriate range R only by the opening / closing control of the throttle valve 23.

  In this regard, in the present embodiment, as shown in an example in FIG. 7, when each of the cylinders 12 </ b> A to 12 </ b> D passes the compression top dead center in the process of decreasing the engine speed NE during the automatic engine stop period. It was noted that there is a correlation between the engine speed NE and the stop position of the piston 13. Then, in the process of decreasing the engine speed NE, the engine speed NE is detected every 180 ° CA (when each cylinder passes the compression top dead center), and the power generation amount of the alternator 28 is controlled according to the detection result. As a result, the degree of depression of the engine speed NE is adjusted so that the stop position of the piston 13 when the engine is automatically stopped is within a range close to the appropriate range R.

  FIG. 7 shows the relationship between the engine speed NE for every 180 ° CA and the stop position of the piston 13 when fuel injection is stopped when the engine speed NE is near 800 rpm. Here, as described above, the opening of the throttle valve 23 is reduced when a predetermined time has elapsed after the throttle valve 23 is sufficiently opened when the fuel injection is stopped. The horizontal axis in this figure is the engine speed NE for every 180 ° CA after the fuel injection is stopped, and the vertical axis is the stop position of the piston 13 when the engine is stopped. The numbers in the figure indicate the order in which each cylinder passes through the compression top dead center, counting from the time of automatic engine stop.

  As can be seen from this figure, if the engine speed NE at the time of compression top dead center is within the appropriate speed range (the shaded range), the stop position of the piston 13 is almost within the proper range R suitable for restarting. It becomes possible.

  Therefore, the piston 13 can be stopped within the appropriate range R by adjusting the engine speed NE after the fuel injection is stopped by controlling the power generation amount of the alternator 28 as described above.

  However, when the method of adjusting the engine speed NE by the alternator 28 is carried out with several types of engines, the piston 13 may not be able to be stopped within the appropriate range R in some types of engines. found. As a result of various investigations on this, as a result of the engine reversely rotating until the opening timing of the intake valve 19 immediately before the engine is automatically stopped and the intake valve 19 is opened, air flows into the compression stroke cylinder at the time of stop. Was found to be the cause. That is, even if the drop in the engine speed NE at the time of compression top dead center is adjusted as described above, if the amount of air flows into the stop compression stroke cylinder during the reverse rotation immediately before the automatic stop, The compression reaction force increases, and the piston 13 of the expansion stroke cylinder at the time of stop may not be sufficiently raised. In particular, since the amount of air that flows in varies depending on operating conditions, ambient conditions, and the like, if the intake valve 19 is opened as described above, the piston 13 can be stopped within the appropriate range R even in the same engine. It may become impossible.

  Here, conventionally, under operating conditions where the engine speed NE is low, the valve timing of the intake valve 19 is often controlled to the retard side as shown in FIG. This is because the amount of overlap between the intake valve 19 and the exhaust valve 20 is suppressed and the amount of air in the cylinder is secured in order to stabilize the combustion at the time of low rotation. However, if the valve timing of the intake valve 19 is retarded in this way, the possibility that the intake valve 19 opens during reverse rotation as described above becomes very high.

  Therefore, in the present invention, as shown in FIG. 9, the valve timing of the intake valve 19 is advanced to the most advanced position by the valve timing control means 50 after the automatic engine stop condition is satisfied, and the reverse rotation of the engine is performed. Sometimes the intake valve 19 is prevented from opening.

  In particular, in the present embodiment, the hydraulic pressure of the valve timing changing means 51 is generated by the oil pump 48 that uses the rotation of the engine 1 connected to the crankshaft 3 as a drive source as described above. Therefore, when the engine speed is so low that the automatic engine stop condition is satisfied, the oil pump 48 may not be driven sufficiently and the hydraulic pressure required to change the valve timing may not be obtained. Therefore, in the present embodiment, when the automatic engine stop condition is satisfied, the engine speed is increased until the hydraulic pressure required to advance the valve timing of the intake valve 19 is obtained, and the valve timing is increased. Advancement correction of the valve timing of the intake valve 19 by the changing means 51 is realized.

  The increase in the rotational speed NE and the correction of the valve timing advance of the intake valve 19 as described above are performed by the valve timing control means 50 and the rotational speed control means 60.

  Of the valve timing control means 50, the valve timing calculation means 52 provided in the ECU 2 is for calculating a target advance angle correction amount of the valve timing of the intake valve 19. The valve timing calculation means 52 calculates a target advance angle correction amount for the valve timing of the intake valve 19 based on the deviation between the detected value of the cam angle sensor 32 and the most advanced position, and calculates the valve timing of the intake valve 19 as described above. The required hydraulic pressure that must be supplied to the valve timing changing means 51 in order to advance the target advance angle correction amount is calculated.

  The rotational speed control means 60 is for controlling the engine rotational speed NE to a value necessary for generating the required operating hydraulic pressure by the oil pump 48. In the rotation speed control means 60, first, a target engine rotation speed N1 necessary for realizing the required hydraulic pressure calculated by the valve timing calculation means 52 is calculated. Then, the required injection amount is calculated based on the deviation between the current engine speed NE based on the detection results of the crank angle sensors 30 and 31 and the target speed N1. Here, since the driver feels uncomfortable if the injection amount injected into the engine main body 1 changes suddenly, the required injection amount is actually corrected so that the driver does not feel abnormal. A signal of the required injection amount calculated in this way is output to the fuel injection valve 16. When the engine speed NE reaches the target speed N1, the valve timing of the intake valve 19 is advanced by the valve timing control means 50.

  Further, when the engine is automatically stopped, as described above, the decrease in the engine speed NE after stopping the fuel injection is adjusted by the alternator 28. In order to optimize the decrease in the engine speed NE, the fuel It is preferable to set the engine speed NE immediately before the injection stop, that is, immediately before the engine speed decreases, to a predetermined value N3 (the number of revolutions for alternator control). Therefore, the engine speed NE at the time when the fuel injection is stopped is controlled by the engine speed control means 60 so as to be the alternator control engine speed N3. That is, in the rotation speed control means 60, the injection amount necessary for changing the engine rotation speed NE to the alternator control rotation speed N3 is calculated.

  Furthermore, it is necessary to scavenge the engine 1 when the engine is automatically stopped. Therefore, the engine speed NE is also controlled by the engine speed controller 60 so that the engine speed NE becomes the scavenging engine speed N2, which is the engine speed necessary for scavenging. In other words, the rotational speed control means 60 calculates the injection amount necessary for changing the engine rotational speed NE to the scavenging rotational speed N2.

  Next, a specific control example when the engine is automatically stopped in the present embodiment will be described with reference to FIGS. FIG. 10 is a flowchart showing the first half of the control procedure up to the stop of fuel injection when the engine is automatically stopped. On the other hand, FIG. 11 is a flowchart showing the latter half of the control procedure up to the stop of fuel injection at the time of automatic stop.

  First, it is determined whether or not the engine automatic stop condition is satisfied based on detection signals from various sensors (step S1). Specifically, when the brake operation state continues for a predetermined time and the vehicle speed is equal to or lower than a predetermined value, it is determined that the engine automatic stop condition is satisfied.

  If it is determined that the engine automatic stop condition is satisfied (YES in step S1), the current valve timing of the intake valve 19 is calculated based on the detection signal of the cam angle sensor 32, and the current valve timing and the most advanced A deviation from the angular position, that is, a target advance correction amount is calculated (step S2). Based on this target advance correction amount, the target hydraulic pressure to be supplied to the valve timing changing means 51 is calculated (step S3). Further, a target rotational speed N1 that can realize the calculated target hydraulic pressure is calculated (step S4). Next, the required required injection amount is calculated based on the deviation between the current engine speed NE calculated based on the detection results of the crank angle sensors 30, 31 and the target engine speed N1 (step S5). The pulse width of the injector 16 is gradually increased until the amount reaches the required injection amount, and the engine speed NE is increased to the target speed N1 (step S6).

  Then, it is determined whether or not the engine speed NE has reached the target speed N1 (step S7). If the determination result is YES, the increase in the injection amount is terminated. On the other hand, if the determination result is NO, that is, if the engine speed NE has not reached the target speed N1, steps S5 and S6 are repeated to increase the engine speed NE. After the engine speed NE reaches the target speed N1, the valve timing changing means 51 is driven to advance the valve timing of the intake valve 19 (step S8). Based on the detection result of the cam angle sensor 32, it is determined whether or not the valve timing of the intake valve 19 has been advanced to the most advanced position (step S9). At this time, if this determination result is NO, that is, if the valve timing of the intake valve 19 could not be advanced to the most advanced position, the process returns to step S2 and steps S2 to S9 are performed. To do.

  If the valve timing of the intake valve 19 is corrected to the most advanced angle, then the current engine speed NE is smaller than the scavenging speed N2, or the current engine speed NE is greater than the alternator control speed N3. Is also smaller (step S10). If the determination result is YES, that is, if the current engine speed NE is smaller than either of the engine speeds N2 and N3, the higher of the scavenging engine speed N2 and the alternator control engine speed N3. Is set to the target rotational speed Nt (step S11), and the injection amount is increased (step S12) until the engine rotational speed NE reaches this new target rotational speed Nt (step S13). On the other hand, if the determination result is NO, that is, if the current engine speed NE is greater than any of the engine speeds N2 and N3, scavenging is performed for a predetermined time (step S14).

  Next, it is determined whether or not the current engine speed NE matches the alternator control speed N3 (step S15). If the determination result is NO, the target rotational speed Nt is set as the alternator control rotational speed N3 (step S16), and the injection amount is increased or decreased until the engine rotational speed NE reaches the alternator control rotational speed N3 (step S18). (Step S17). Then, when the engine speed NE becomes the alternator control speed N3, that is, when the determination result is YES, the fuel injection is stopped (step S19).

  Next, an example of control after stopping fuel injection will be described with reference to FIG.

  When the fuel injection is stopped as described above, first, the throttle valve 23 is opened to reach the set opening degree (step S20). Subsequently, it is determined whether or not the engine speed at the top dead center is within an appropriate speed range (step S21).

  If the determination in step S21 is YES, it is further determined whether or not the current engine speed NE is equal to or lower than a predetermined speed (step S22). This predetermined rotational speed is for closing the throttle valve 23 at a timing such that the intake air amount in the stop expansion stroke cylinder is larger than the intake air amount in the stop compression stroke cylinder in consideration of the intake transport delay. For example, it is set in the range of 500 to 600 rpm. If engine speed NE is equal to or lower than this predetermined speed (YES in step S22), throttle valve 23 is closed (step S23). On the other hand, if the engine speed NE is greater than or equal to the predetermined speed, the process returns to step S21.

  On the other hand, when the determination in step S21 is NO, that is, when it is determined that the engine speed NE is out of the appropriate engine speed range, the deviation between the current engine speed NE and the appropriate engine speed is determined. Based on this, the power generation amount of the alternator 28 is calculated (step S24). This power generation amount may be determined from a preset map or the like according to, for example, the engine speed NE, the appropriate rotation speed, and the current power generation amount of the alternator 28. This map increases the power generation amount of the alternator 28 so that the load on the engine body 1 increases when the current engine speed NE is higher than the upper limit of the appropriate engine speed range, while the current engine speed NE is When the engine speed is smaller than the lower limit of the appropriate rotational speed range, the power generation amount is reduced so that the load on the engine body 1 is reduced. In the map, the target value of the power generation amount is set to be large so that the engine speed at the top dead center is near the lower limit of the appropriate speed range.

  Then, the determined power generation amount is generated by the alternator 28 (step S25). By adjusting the load of the engine main body 1 by the power generation operation of the alternator 28, the locus of the rotational speed of the engine main body 1 rotating by inertia is shifted to either the high rotation side or the low rotation side, and gradually becomes the target. Go closer to the trajectory. If the engine speed NE is equal to or lower than the predetermined speed in step S22 (YES), the process proceeds to step S23 and the throttle valve 23 is closed.

  FIG. 14 shows how the engine speed NE changes when the above control is performed.

  This figure shows an automatic stop determination flag that is turned on when the engine automatic stop condition is satisfied, a fuel injection stop flag that is turned on when fuel injection is stopped, the engine speed NE, and the target of the throttle valve 23. The time chart of an opening degree and the valve timing of the intake valve 19 is shown.

  As shown in this figure, first, when the stop determination flag indicating that the automatic stop condition is satisfied is changed from 0 to 1 (OFF to ON) at time t1, the throttle valve 23 has a predetermined opening degree set in advance. And the engine speed NE is controlled by the engine speed control means 60, and the engine speed NE gradually increases. When the engine speed NE rises to the target speed N1 (about 900 rpm in this figure) at time t2, the valve timing of the intake valve 19 is corrected to the most advanced position by the valve timing control means 50. Thereafter, when it is determined that scavenging has been sufficiently performed after a predetermined time has elapsed, the fuel injection stop flag changes from 0 to 1 at time t3, and fuel injection is stopped. At this time, the target opening degree of the throttle valve 23 is reduced. After the fuel injection is stopped (after t3), the engine speed NE decreases while being adjusted by the control of the alternator 28. Accordingly, the driving force of the oil pump 48 is reduced and the valve timing of the intake valve 19 is gradually retarded. Move to the side.

  This figure shows a case where both the scavenging rotation speed N2 and the alternator control rotation speed N3 coincide with the target rotation speed N1 required for the advance timing correction of the valve timing of the intake valve. Accordingly, when the scavenging speed N2 and the alternator control speed N3 are different from the target speed N1, it is preferable to separately control the engine speed NE before stopping the fuel injection as described above.

  In the above-described embodiment, the case has been described in which the valve timing of the intake valve 19 is advanced after the engine speed NE has increased to the predetermined target speed N1, but the control of the engine speed NE and the advance of the valve timing have been described. You may make it perform angle correction simultaneously. FIG. 13 shows a flowchart in the case of such a configuration. In FIG. 13, steps S3 to S7 in FIG. 10 are replaced with steps S33 to S35. That is, as shown in FIG. 10, after calculating the target advance correction amount, the target hydraulic pressure (step S3) and the target rotational speed N1 are calculated (step S4), and the engine rotational speed NE is increased (steps S5 to S7). ) On the other hand, when the engine speed NE reaches the target speed N1, the advance timing of the valve timing is corrected (step S8), whereas the target oil pressure and the target speed are not calculated and the injection amount is increased. Only (step S33), the injection amount is increased to increase the engine speed NE (step S34), and the valve timing of the intake valve 19 is advanced (step S35). The increase in the injection amount is stopped when the valve timing of the intake valve 19 reaches the most advanced position (step S9). In this way, it is not necessary to calculate the target hydraulic pressure or the like, and the calculation load can be further reduced. In addition, the increase in the engine speed NE can be suppressed to the minimum value necessary for the advance correction of the valve timing of the intake valve 19.

  As described above, according to the engine stop control device, when the engine automatic stop condition is satisfied, the valve timing of the intake valve 19 of the engine is advanced, so that when the engine reversely rotates during the automatic stop, It is possible to more reliably suppress the air from flowing into the compression stroke cylinder when the intake valve 19 is opened and stopped. As a result, the piston 13 can be more reliably stopped at a desired position during automatic stop, so that the engine can be reliably restarted by combustion in the expansion stroke cylinder during stop.

  In particular, when the automatic engine stop condition is satisfied, the rotational speed is increased so that the valve timing of the intake valve 19 is advanced, so that the present invention is an oil whose valve timing is driven by the engine rotation as a drive source. Even when used in an engine having a valve timing control means 50 that is changed by driving of the pump 48 or the like, the valve timing of the intake valve 19 can be reliably corrected for advancement.

  Further, if the amount of increase in the engine speed NE is controlled based on the detection result of the cam angle sensor 32, that is, the valve timing detection means, the valve timing of the intake valve 19 is more reliably set to a predetermined advance amount. The advance angle can be corrected.

  Further, if the engine speed NE is increased before the engine is automatically stopped as described above, the engine can be scavenged at the same time. Furthermore, if the valve timing of the intake valve 19 is advanced as described above, there is a possibility that the overlap between the intake valve 19 and the exhaust valve 20 may increase, but as described above, the engine speed NE is increased. If so, a sufficient amount of air flowing into the cylinder can be secured. That is, the combustion can be stabilized while the advance timing of the valve timing of the intake valve 19 is corrected.

  Here, when the automatic stop condition of the engine is satisfied, the engine is set to have a higher rotational speed among the preset rotational speed N2 for scavenging and the target rotational speed N1 for correcting the advance angle of the valve timing of the intake valve. By controlling the rotational speed NE, both the scavenging control and the intake valve advance angle correction control can be reliably and effectively performed.

  The advance amount of the valve timing of the intake valve 19 may be a value that does not cause the intake valve 19 to open due to the reverse rotation of the engine. The valve opening can be suppressed. In particular, when the valve timing control means 50 using the engine rotation as a drive source as described above is used, even when the valve timing of the intake valve 19 shifts to the retarded side due to a decrease in the engine speed NE after the stop of fuel injection. The valve timing can be sufficiently advanced.

  Here, in the above-described embodiment, the case where the valve timing changing unit 51 is a hydraulic device that is driven by oil pumped from the oil pump 48 is shown, but it may be controlled by other motors or the like.

  In the above-described embodiment, when restarting after the engine is automatically stopped, first, the air-fuel mixture in the compression stroke cylinder at the time of stop is combusted and the engine body 1 is slightly rotated in the reverse direction. Although the case where the air-fuel mixture is combusted has been shown, the air-fuel mixture of the stop-time expansion stroke cylinder may be combusted first to realize the restart.

  Further, in the above-described embodiment, the case where the valve timing of the intake valve 19 is corrected to the most advanced position has been described. However, as described above, the advanced position prevents the intake valve 19 from opening during reverse rotation of the engine. If the position is such that the inflow of air is very small even if the valve is opened, it can be set as appropriate.

  In the above embodiment, the value of the target rotational speed N1 is calculated from the target advance correction amount. However, the target rotational speed N1 may be a preset value.

It is a schematic sectional drawing of an engine provided with the stop control device concerning the present invention. It is explanatory drawing which shows the structure of the intake system of the engine shown in FIG. 1, and an exhaust system. It is a side view of the engine shown in FIG. It is a schematic sectional drawing which shows the outline | summary of the valve timing control means provided in the engine shown in FIG. FIG. 2 is an explanatory diagram showing piston stop positions of cylinders that are in an expansion stroke and a compression stroke when the engine shown in FIG. 1 is stopped. FIG. 2 is an explanatory diagram showing an air amount of a cylinder that becomes an expansion stroke and a compression stroke when the engine shown in FIG. 1 is stopped. FIG. 2 is a distribution diagram showing a correlation between an engine speed and a piston stop position when the engine shown in FIG. 1 is stopped. It is explanatory drawing which shows the conventional valve timing of the engine shown in FIG. It is explanatory drawing which shows the valve timing of the engine shown in FIG. It is a flowchart which shows the first half part of the operation | movement until fuel-injection stop among engine automatic stop control. It is a flowchart which shows the latter half part of the operation | movement until fuel-injection stop among engine automatic stop control. It is a flowchart which shows the operation | movement after a fuel injection stop among engine automatic stop control. It is a flowchart which shows other embodiment of operation | movement to fuel-injection stop among engine automatic stop control. It is a time chart which shows change states, such as engine speed at the time of an engine stop.

Explanation of symbols

1 Engine body 2 ECU (automatic stop control means)
3 Crankshaft 13 Piston 16 Fuel Injection Valve 19 Intake Valve 23 Throttle Valve 28 Alternator 32 Cam Angle Sensor (Valve Timing Detection Means)
41 intake side camshaft 48 oil pump 50 valve timing control means 51 valve timing change means 52 valve timing calculation means 60 rotation speed control means

Claims (6)

When the preset automatic engine stop condition is satisfied, the engine is automatically stopped, and when the preset engine restart condition is satisfied, at least the stop in the expansion stroke when the engine is automatically stopped In a stop control device for a multi-cylinder four-cycle engine that restarts the engine by combustion in a time expansion stroke cylinder,
Valve timing control means capable of changing the valve timing of the intake valve of the engine,
By the valve timing control means, when the engine automatic stop condition is satisfied, the valve timing of the intake valve of the engine is advanced to a predetermined angle, so that the piston of the expansion stroke cylinder at the time of stop is adjusted. An engine stop control device for stopping at a predetermined position set in advance when the engine is automatically stopped. The engine stop control device according to claim 1,
An engine stop control device, wherein the valve timing control means is driven using the rotation of the engine as a drive source. The engine stop control device according to claim 2,
A rotation speed control means capable of controlling the rotation speed of the engine;
The rotational speed control means increases the rotational speed of the engine to a value at which the valve timing control means can correct the valve timing of the intake valve when the automatic engine stop condition is satisfied. An engine stop control device characterized by comprising: The engine stop control device according to claim 3,
Valve timing detection means capable of detecting the amount of advancement of the valve timing of the intake valve;
The engine stop control device, wherein the engine speed control means controls the engine speed based on a detection result of the valve timing detection means. The engine stop control device according to claim 3 or 4,
The rotation speed control means advances the valve timing of the intake valve by the rotation speed necessary for scavenging the inside of the cylinder and the valve timing control means when the engine automatic stop condition is satisfied. An engine stop control device characterized by controlling to a higher number of revolutions necessary for angle correction. In the engine stop control device according to any one of claims 1 to 5,
An engine stop control device, wherein the valve timing control means controls the valve timing of the intake valve of the engine to a most advanced position when the automatic engine stop condition is satisfied.

Images