JP2004324421A - Start control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform appropriate start control even when lock up is not done by a locking mechanism at start of an engine in a valve timing control device having a function of locking relative rotational phase of a cam shaft by the locking mechanism. <P>SOLUTION: A combustion control device can control to vary relative rotational phase of the cam shaft in relation to a crankshaft by hydraulic control of an advancing side pressure chamber and a retarding side pressure chamber. And the relative rotational phase of the cam shaft can be locked at a predetermined intermediate phase by a lock up means using for example a lock pin. At engine start, it is determined whether relative rotational phase is locked at an intermediate phase by a lock determination means. If it is determined that lock up is not done, the lock up means is controlled for locking. Originally, relative rotational phase of the cam shaft is preferably locked at an intermediate phase at start of the engine. Consequently, startability and emission are improved by performing start control of the engine by locking relative rotational phase of the camshaft at an intermediate phase as much as possible when it is determined that lock up is not done. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a valve timing control device for an internal combustion engine.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an internal combustion engine such as an in-vehicle engine may be provided with a variable valve timing mechanism that appropriately changes the valve timing of the engine with the intention of improving output and improving emission (for example, Patent Document 1). Such a variable valve timing mechanism includes, for example, a movable member connected to a camshaft of an internal combustion engine, and an advance side pressure chamber and a retard side pressure chamber provided so as to sandwich the movable member. Then, the relative rotation phase of the camshaft with respect to the crankshaft of the engine is changed to the advance side or the retard side by selectively supplying hydraulic oil to these pressure chambers and moving the movable member by hydraulic pressure. By changing the relative rotation phase of the camshaft in this way, the valve timing of the engine valve in the engine is changed.
[0003]
By the way, at the time of starting the internal combustion engine, the operating oil may be in a state of being released from the pressure chamber, and even if the supply of the operating oil to the pressure chamber is started simultaneously with the start of the engine, sufficient hydraulic pressure is not applied to the movable member. Since it does not act, the relative rotational phase (valve timing) of the camshaft may become the most retarded state due to the reaction force accompanying the opening and closing drive of the engine valve. Therefore, in order to improve the startability of the internal combustion engine, when the valve timing of the engine valve becomes the most retarded state, a valve timing suitable for engine start (hereinafter referred to as start timing) is obtained. It is necessary to set the control range of the valve timing.
[0004]
However, if the control range of the valve timing is set so as to satisfy the above requirements, the control range is narrowed, and it is difficult to optimally control the valve timing over the entire operation range of the internal combustion engine. Therefore, as a technique for suppressing the reduction of the control range of the valve timing while optimizing the valve timing at the time of starting the engine, a valve timing control device provided with a lock mechanism for fixing the relative rotation phase of the cam shaft at the time of starting the engine has been proposed. ing. In such a valve timing control device, when the engine is stopped, the relative rotation phase of the camshaft is locked by a locking mechanism advanced by a predetermined amount from the most retarded state, and when the engine is started thereafter, the operation supplied from the pressure chamber is performed. The locked state of the lock mechanism is maintained based on the oil pressure of the oil. As a result, when the engine is started, the valve timing can be maintained at the start timing, and the startability of the engine can be improved.
[0005]
However, when the internal combustion engine is started without being locked by the lock mechanism for some reason, the following disadvantages cannot be ignored. For example, when the engine is stopped and restarted immediately thereafter, since sufficient hydraulic oil remains in the pressure chamber, hydraulic oil for maintaining the locked state of the lock mechanism is supplied to the pressure chamber. Then, the oil pressure in the pressure chamber immediately rises. As a result, a situation may occur in which the relative rotational phase of the camshaft is significantly deviated from the phase to be locked by the lock mechanism due to the raised oil pressure in the pressure chamber.
[0006]
Further, for example, when the engine is restarted after a long time has elapsed from the stop of the engine, almost no hydraulic oil remains in the pressure chamber, and even if hydraulic oil for holding a lock is supplied, the same pressure chamber is supplied. , The relative rotation phase of the camshaft is changed to the retard side by the reaction force associated with the opening and closing drive of the engine valve, and the phase is out of the phase to be locked by the lock mechanism and becomes the most retarded state .
[0007]
In the valve timing control device having the lock mechanism as described above, if the engine is started without being locked by the lock mechanism, the valve timing greatly deviates from a timing suitable for starting the engine, and Deterioration of sex and emission was inevitable.
[0008]
Therefore, a method has been proposed in which, when the engine is stopped or started, it is determined whether or not the locking by the lock mechanism is performed (hereinafter, also referred to as “lock determination”), and start control is performed according to the determination result. (See, for example, Patent Document 2).
[0009]
[Patent Document 1]
JP-A-11-229828 [Patent Document 2]
Japanese Patent Application Laid-Open No. 2002-161766
[Problems to be solved by the invention]
The position where the relative rotation phase of the camshaft is locked by the lock mechanism is a timing suitable for starting the engine as described above. Therefore, when it is determined by the lock determination that the lock mechanism has not been locked at the time of starting the engine or the like, the locked state is realized if possible rather than starting the engine with the locked state. It is desirable to start the engine from the viewpoint of startability and emission.
[0011]
The present invention has been made in view of the above points, and in a valve timing control device having a function of locking a relative rotation phase of a cam shaft by a lock mechanism, even when the lock by the lock mechanism is not performed at the time of starting the engine. It is intended to perform appropriate start control.
[0012]
[Means for Solving the Problems]
In one aspect of the present invention, a start control device for an internal combustion engine controls a pressure of a working fluid in an advance side pressure chamber and a retard side pressure chamber to thereby control a relative rotational phase of a camshaft with respect to a crankshaft of the internal combustion engine. A lock mechanism for locking the relative rotation phase of the camshaft to an intermediate phase between the most retarded state and the most advanced state, and a locking means for changing the relative rotation phase of the camshaft. A lock determining means for determining whether or not the lock is locked to the intermediate phase, and at the time of starting the internal combustion engine, determining that the lock has not been made despite the lock by the lock means being requested. And control means for controlling the lock means to execute the lock when the lock determination means makes a determination.
[0013]
In the above-described combustion control device, the relative rotation phase of the camshaft with respect to the crankshaft can be variably controlled by hydraulic control of the advance pressure chamber and the retard pressure chamber. Further, the relative rotation phase of the camshaft can be locked at a predetermined intermediate phase by a lock means using, for example, a lock pin. When the engine is started, the lock determination means determines whether or not the relative rotational phase of the camshaft is locked at the intermediate phase. When it is determined that the lock has not been performed, the lock unit is controlled to perform the lock. Originally, it is desirable that the relative rotational phase of the camshaft be locked to the intermediate phase when the engine is started. Therefore, when the engine is not locked, the startability and the emission can be improved by performing the engine start control after locking to the intermediate phase.
[0014]
One aspect of the above-described internal combustion engine start control device includes a temperature detection unit that detects a temperature of the working fluid, and the control unit sets the lock unit only when the temperature of the working fluid is equal to or higher than a predetermined temperature. Control is performed to execute the lock. When the temperature of the working fluid such as the working oil is low, the viscosity of the working fluid is high and the variable valve timing mechanism cannot be operated. Therefore, when it is found that the lock is not made at the time of starting the engine, the temperature of the working fluid such as the working oil is checked, and if the temperature is higher than a predetermined temperature, that is, if the variable valve timing mechanism can be operated, After the locking means is controlled to establish the locked state, the starting of the engine is controlled.
[0015]
One embodiment of the above-described internal combustion engine start control device is a start-up control device that determines whether or not the start environment of the internal combustion engine is good before the determination by the lock determination unit is completed when the internal combustion engine is started. Environment determining means for starting the engine under combustion conditions when the relative rotational phase of the camshaft is in the intermediate phase state when it is determined that the starting environment is good, and determining that the starting environment is not good Combustion control means for controlling the combustion of the engine under the combustion conditions when the relative rotational phase of the camshaft is in the most retarded state when the engine is turned on. At the start of the engine, the lock determining means determines whether or not the relative rotational phase of the camshaft is locked to the intermediate phase. However, until the lock determination is completed, the starting environment of the engine is determined. If the starting environment of the engine is good, combustion of the engine is performed under the combustion conditions in the intermediate phase state, and if the starting environment is not good, combustion of the engine is performed under the combustion conditions in the most retarded state. Do. Thus, even at the stage until the determination of the locked state is completed, appropriate start control can be started, and the startability of the engine can be ensured, and the emission can be improved according to the situation.
[0016]
In one aspect of the start control device for an internal combustion engine, the start environment determining means includes a water temperature sensor for detecting a temperature of a coolant of the internal combustion engine, and the start environment when the water temperature is outside a predetermined cryogenic range. Means for determining that the environment is good and determining that the starting environment is not good when the water temperature is within the extremely low temperature range. If the temperature of the cooling water is extremely low, it is considered that the startability is not good. Therefore, the engine is reliably started according to the combustion condition in the most retarded state.
[0017]
In one aspect of the start control device for an internal combustion engine, after the determination by the lock determination unit is completed, the combustion control unit may determine whether the relative rotation phase of the camshaft is in the intermediate phase state based on the determination result. The combustion of the engine is controlled under either the combustion condition or the combustion condition in the most retarded state. Therefore, after the lock determination is completed, the engine can be started by the optimal combustion control based on the determination result.
[0018]
In one aspect of the above-described internal combustion engine start control device, when the internal combustion engine is started, an injection prohibition unit that prohibits fuel injection in the internal combustion engine until the determination by the lock determination unit is completed is provided. At the start of the engine, the lock determination means determines whether or not the relative rotational phase of the camshaft is locked to the intermediate phase. However, until the lock determination is completed, fuel injection of the engine is prohibited. Thus, fuel injection is prohibited until the state of the relative rotation phase of the camshaft is confirmed, and the emission can be optimized.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[0020]
[Valve timing control device]
A valve timing control device according to an embodiment of the present invention will be described.
[0021]
As shown in FIG. 1, the cylinder block 11a of the internal combustion engine 11 is provided with a piston 12 (only one is shown in FIG. 1) for each cylinder so as to be able to reciprocate. This piston 12 is connected via a connecting rod 13 to a crankshaft 14 which is an output shaft of the internal combustion engine 11.
[0022]
Further, a combustion chamber 16 is provided between the piston 12 and the cylinder head 15 provided at the upper end of the cylinder block 11a. An intake port 17 and an exhaust port 18 that open to the combustion chamber 16 are formed in the cylinder head 15, and the intake port 17 and the exhaust port 18 are connected to an intake passage 19 and an exhaust passage 20, respectively. The intake port 17 and the exhaust port 18 are provided with an intake valve 21 and an exhaust valve 22, respectively. A throttle valve (not shown) is provided in the middle of the intake passage 19, and a bypass passage (not shown) connected to the intake passage 19 on the upstream side and the downstream side of the throttle valve so as to bypass the throttle valve. Is provided. An idle speed control valve (not shown) is provided in the middle of this bypass passage, and the intake air amount during idle operation is adjusted according to the opening degree of the idle speed control valve.
[0023]
An intake camshaft 23 and an exhaust camshaft 24 for opening and closing the intake valve 21 and the exhaust valve 22 are rotatably supported on the cylinder head 15. The rotational force of the crankshaft 14 is transmitted to the camshafts 23 and 24 via a chain 28 and a gear 31 (see FIG. 2). Then, when the intake camshaft 23 rotates, the intake valve 21 is opened and closed via an intake cam (not shown), and the intake port 17 and the combustion chamber 16 are communicated and shut off. When the exhaust camshaft 24 rotates, the exhaust valve 22 is also opened and closed via an exhaust cam (not shown), and the exhaust port 18 and the combustion chamber 16 are communicated and shut off.
[0024]
On the other hand, a fuel injection valve 25 for injecting fuel into the intake port 17 is provided at a downstream end of the intake passage 19. The fuel injection valve 25 injects fuel into the intake port 17 when air in the intake passage 19 is sucked into the combustion chamber 16 during the intake stroke of the internal combustion engine 11 to form a fuel / air mixture. I do.
[0025]
Further, the cylinder head 15 is provided with an ignition plug 26 for igniting the air-fuel mixture filled in the combustion chamber 16. Then, when the air-fuel mixture in the combustion chamber 16 is ignited and the air-fuel mixture burns, the combustion energy causes the piston 12 to reciprocate, the crankshaft 14 to rotate, and the internal combustion engine 11 to be driven. The air-fuel mixture burned in the combustion chamber 16 is sent out to the exhaust passage 20 as exhaust by the rise of the piston 12 during the exhaust stroke of the internal combustion engine 11.
[0026]
Next, a variable valve timing mechanism 30 for varying the valve timing of the intake valve 21 in the internal combustion engine 11 will be described with reference to FIG. As shown in FIG. 2, the variable valve timing mechanism 30 includes the gear 31 and a rotating member 33 fixed to a distal end surface of the intake camshaft 23 by a bolt 32 so as to be integrally rotatable. The gear 31 is rotatable relative to the intake camshaft 23 penetrating through the center thereof.
[0027]
A ring cover 34 provided so as to surround the rotating member 33 is in contact with the front end surface (left side surface in the figure) of the gear 31, and the front end opening of the ring cover 34 is closed by a closing plate 35. . The gear 31, the ring cover 34, and the closing plate 35 are fixed so as to be integrally rotatable by bolts 36. Therefore, the gear 31, the ring cover 34, and the closing plate 35 are relatively rotatable about the axis L of the intake camshaft 23 with respect to the intake camshaft 23 and the rotating member 33.
[0028]
Hydraulic oil is supplied to the variable valve timing mechanism 30 from an advance-side oil passage 37 and a retard-side oil passage 38 formed in the cylinder head 15, the intake camshaft 23, and the like as illustrated. When the variable valve timing mechanism 30 is operated by supplying the hydraulic oil in this manner, the relative rotation phase of the intake camshaft 23 with respect to the crankshaft 14 is changed to the advance side or the retard side, and accordingly, the valve of the intake valve 21 is changed. The timing will also change.
[0029]
The advance side oil passage 37 and the retard side oil passage 38 are connected to an oil control valve (OCV) 40. Further, a supply passage 50 and a discharge passage 51 are connected to the OCV 40. The supply passage 50 is connected to an oil pan 11b provided below the internal combustion engine 11 via an oil pump 52 driven by the rotation of the crankshaft 14, and the discharge passage 51 is directly connected to the oil pan 11b. ing. A temperature sensor 59 for detecting the temperature of the hydraulic oil is attached to the oil pan 11b, and an output signal from the temperature sensor 59 is supplied to the ECU 80.
[0030]
The OCV 40 has a spool 44 having a predetermined number (four in this example) of valve portions 41 and urged in opposite directions by a coil spring 42 and an electromagnetic solenoid 43. In the OCV 40, the position (valve position) of the spool 44 is controlled based on the duty control of the voltage application to the electromagnetic solenoid 43 by an electronic control unit (hereinafter referred to as ECU) 80.
[0031]
That is, when the duty ratio D of the voltage application to the electromagnetic solenoid 43 is set in the range of (50% <D ≦ 100%) by the ECU 80, the spool 44 resists the biasing force of the coil spring 42 on one end side (in the figure). Left). In this state, the advance-side oil passage 37 and the supply passage 50 communicate with each other, and the operating oil in the oil pan 11b is sent out to the advance-side oil passage 37 by the oil pump 52 and the retard-side oil passage The hydraulic oil in the retard-side oil passage 38 is returned to the oil pan 11b through communication between the oil passage 38 and the discharge passage 51.
[0032]
When the duty ratio D of voltage application to the electromagnetic solenoid 43 is set in the range of (0% ≦ D <50%) by the ECU 80, the spool 44 is moved by the urging force of the coil spring 42 to the other end (right side in the figure). Placed in In this state, the retard-side oil passage 38 and the supply passage 50 communicate with each other, and hydraulic oil in the oil pan 11b is sent out to the retard-side oil passage 38 by the oil pump 52, and the advance-side oil passage The hydraulic oil in the advance-side oil passage 37 is returned to the oil pan 11b by the communication between the oil passage 37 and the discharge passage 51.
[0033]
When the duty ratio D of the voltage application to the electromagnetic solenoid 43 is set to 50% by the ECU 80, the spool 44 is moved to the position on the one end side by the balance between the electromagnetic force of the electromagnetic solenoid 43 and the urging force of the coil spring 42. It is arranged at a substantially intermediate position between the end positions. In this state, both the advance-side oil passage 37 and the retard-side oil passage 38 communicate with the supply passage 50, and hydraulic oil is sent out to both of the oil passages 37 and 38.
[0034]
Next, a detailed structure of the rotating member 33 and the ring cover 34 in the variable valve timing mechanism 30 will be described with reference to FIG. As shown in FIG. 3, on the inner peripheral surface 34a of the ring cover 34, four convex portions 34b projecting toward the axis L (see FIG. 2) of the intake camshaft 23 are provided in the circumferential direction of the ring cover 34. It is formed at predetermined intervals. The concave portions 34c are formed at predetermined intervals in the circumferential direction of the ring cover 34 between the convex portions 34b. The rotating member 33 includes four vanes 33a protruding outward so as to be inserted into the respective concave portions 34c from the outer peripheral surface thereof. The space formed by each recess 34c, the gear 31, and the closing plate 35 is partitioned by the vane 33a into an advance pressure chamber 53 and a retard pressure chamber 54. The advance pressure chamber 53 and the retard pressure chamber 54 are positioned so as to sandwich the vane 33 a from both sides in the circumferential direction of the rotating member 33. The advance-side pressure chamber 53 is connected to the advance-side oil passage 37 formed so as to pass through the rotation member 33, and the retard-side pressure chamber 54 is formed to pass through the gear 31. The retarded oil passage 38 is communicated with the engine.
[0035]
In such a variable valve timing mechanism 30, when the duty ratio D of the voltage application to the electromagnetic solenoid 43 of the OCV 40 is set in the range of (50% <D ≦ 100%) by the ECU 80, the advance from the advance side oil passage 37 is performed. The hydraulic oil is supplied to the angular pressure chamber 53, and the hydraulic oil is discharged from the retard pressure chamber 54 via the retard oil passage 38. As a result, the relative movement of each vane 33a in the direction of arrow A causes the rotation member 33 to relatively rotate rightward in the drawing, and changes the relative rotation phase of the intake camshaft 23 with respect to the gear 31 (crankshaft 14). . Incidentally, in the variable valve timing mechanism 30, when the rotation of the crankshaft 14 is transmitted to the gear 31 via the chain 28 and the like, the gear 31 and the intake camshaft 23 both rotate rightward in the drawing. Therefore, when the relative movement of each vane 33a in the direction of the arrow A is performed, the intake camshaft 23 rotates relatively to the advance side with respect to the crankshaft 14, and as a result, the valve timing of the intake valve 21 also advances. I will do it.
[0036]
When the duty ratio D of the voltage application to the electromagnetic solenoid 43 of the OCV 40 is set in the range of (0% ≦ D <50%) by the ECU 80, the hydraulic oil is transferred from the retard oil passage 38 to the retard pressure chamber 54. Is supplied, and hydraulic oil is discharged from the advance side pressure chamber 53 via the advance side oil passage 37. As a result, the relative movement of the vane 33a in the direction opposite to the arrow A causes the rotation member 33 to relatively rotate leftward in the same direction, so that the relative rotational phase of the intake camshaft 23 with respect to the gear 31 (crankshaft 14) becomes Is changed in the opposite direction. In this variable valve timing mechanism 30, in this case, the intake camshaft 23 relatively rotates to the retard side with respect to the crankshaft 14, and as a result, the valve timing of the intake valve 21 also retards.
[0037]
When the duty ratio D of voltage application to the electromagnetic solenoid 43 is set to 50% by the ECU 80, hydraulic oil is supplied from the oil passages 37 and 38 to both the pressure chambers 53 and 54. As a result, the forces acting on the vanes 33a are balanced according to the oil pressures of the pressure chambers 53 and 54, and the relative rotation of the rotating member 33 is stopped. Therefore, in this case, the valve timing of the intake valve 21 is maintained at the current timing.
[0038]
Accordingly, the ECU 80 changes the duty ratio D of the voltage application to the electromagnetic solenoid 43 between 0% and 100% based on the deviation between the actual relative rotation phase of the intake camshaft 23 and the target phase, whereby the advance side pressure is changed. The supply and discharge of the working oil to and from the chamber 53 and the retard pressure chamber 54 are controlled, and the hydraulic pressure in the pressure chambers 53 and 54 is feedback-controlled. By performing feedback control of the hydraulic pressure in the advance pressure chamber 53 and the retard pressure chamber 54 in this manner, it is possible to change the valve timing of the intake valve 21 or to maintain the intake valve 21 in a predetermined state.
[0039]
Here, when the internal combustion engine 11 is started, the operating oil may be released from the advance-side pressure chamber 53 and the retard-side pressure chamber 54 in such a case. Even if the supply of hydraulic oil to 53 and 54 starts, sufficient hydraulic pressure does not act on rotating member 33. Therefore, until a predetermined period elapses from the start of the start of the internal combustion engine 11, the relative rotation phase of the intake camshaft 23 is set to the intermediate phase θ between the most retarded state and the most advanced state by the lock mechanism 60 described later. Lock (hereinafter, also referred to as “intermediate phase lock”). In the present embodiment, the intermediate phase θ is set to a phase suitable for starting the internal combustion engine 11, that is, the valve timing of the intake valve 21 is set to a timing suitable for starting the engine 11 (hereinafter, referred to as a start timing). .
[0040]
Next, a structure for locking the valve timing of the intake valve 21 to the intermediate phase as described above, that is, a structure for locking the relative rotational phase of the intake camshaft 23 with respect to the crankshaft 14, will be described with reference to FIGS. Will be explained.
[0041]
As shown in FIG. 3, the variable valve timing mechanism 30 has a lock for locking the relative rotation phase of the intake camshaft 23 on both the advance side and the retard side when the valve timing is the start timing. A mechanism 60 is provided. The detailed structure of the lock mechanism 60 is shown in FIG. FIG. 4 is a sectional view taken along the line 4-4 in FIG. 3, and shows a state in which the relative rotation phase of the intake camshaft 23 is locked by the lock mechanism 60.
[0042]
As shown in FIG. 4, a housing hole 64 extending in the axial direction of the intake camshaft 23 is formed in one of the vanes 33a. The accommodation hole 64 accommodates a lock pin 62 that can reciprocate in the hole 64 and a coil spring 61 that biases the lock pin 62 toward the gear 31. The gear 31 has a hole 63 into which the tip of the lock pin 62 can be inserted when the gear 31 and the vane 33a are at positions corresponding to the start timing.
[0043]
A flange 62 a is formed on the outer peripheral surface of the lock pin 62, and a cylindrical holding member 65 that fits the lock pin 62 at a position closer to the closing plate 35 than the flange 62 a is provided in the housing hole 64. I have. The advance-side oil chamber 66 is formed by an annular space defined by the holding member 65 and the lock pin 62 in the housing hole 64. The oil chamber 66 is communicated with the advance pressure chamber 53 via a passage 67, and hydraulic oil is supplied from the advance pressure chamber 53. The position of the flange 62 a changes from a position closer to the gear 31 than the opening of the passage 67 to a position closer to the holding member 65 than the opening of the passage 67 with the reciprocation of the lock pin 62. On the other hand, in the hole 63 of the gear 31, a retard-side oil chamber 68 is formed between the bottom of the hole 31 and the tip end surface of the lock pin 62. The oil chamber 68 communicates with the retard pressure chamber 54 via a passage 69, and hydraulic oil is supplied from the retard pressure chamber 54.
[0044]
The lock mechanism 60 controls the relative rotational phase of the intake camshaft 23 in accordance with the pressure of the working oil supplied to the advance pressure chamber 53 and the retard pressure chamber 54, that is, the oil pressure in the pressure chambers 53 and 54. Of the intermediate phase lock and the release of the intermediate phase lock.
[0045]
That is, when the lock pin 62 comes out of the hole 63 and the flange 62 a is located closer to the holding member 65 than the opening of the passage 67 during the operation of the engine (see FIG. 4B), The flange 62 a urges the holding member 65 side by the hydraulic pressure of the chamber 66 or the biasing force urges the distal end of the lock pin 62 toward the closing plate 35 side by the hydraulic pressure of the retard oil chamber 68. The lock pin 62 is maintained in a state of being pulled out of the hole 63 against the urging force of the coil spring 61. At this time, the intermediate phase lock on the advance side and the retard side of the relative rotation phase of the intake camshaft 23 by the lock mechanism 60 is maintained in a released state.
[0046]
On the other hand, when the rotation speed of the crankshaft 14 decreases during the stop process of the internal combustion engine 11, the amount of hydraulic oil sent to each of the pressure chambers 53 and 54 by the oil pump 52 decreases. Therefore, the oil pressure in each of the pressure chambers 53 and 54 decreases, and accordingly the oil pressure in each of the oil chambers 66 and 68 of the lock mechanism 60 also decreases. When these oil pressures decrease to a value at which the lock pin 62 cannot be inserted into the housing hole 64 against the urging force of the coil spring 61, the lock pin 62 is moved by the urging force of the coil spring 61. Try to protrude from In such a state, when the accommodation hole 64 overlaps the hole 63, that is, when the valve timing is the start timing, the lock pin 62 projects and is inserted into the hole 63, and the relative rotation phase of the intake camshaft 23 is set to the middle. Locked in phase.
[0047]
Even if the intermediate phase lock state is not reached when the internal combustion engine 11 is stopped, if the relative rotation phase of the intake camshaft 23 is on the advance side of the intermediate phase θ, the engine 11 is started thereafter. At this time, when the relative rotation phase of the intake camshaft 23 is changed to the retard side by the reaction force accompanying the opening and closing of the intake valve 21 and becomes the intermediate phase θ, the lock pin 62 is inserted into the hole 63 to lock the intermediate phase. Become so.
[0048]
Further, for example, when the relative rotation phase of the intake camshaft 23 fails to be locked at the intermediate phase during the engine stop process, even when the intermediate phase lock state is not established, for example, at the time of subsequent engine startup, If the relative rotation phase of the camshaft 23 is once moved to the advance side from the intermediate phase θ and then gradually moved to the retard side, the lock pin 62 is moved to the hole 63 when the accommodation hole 64 overlaps the hole 63. And an intermediate phase lock state can be established. This control can be specifically realized by the ECU 80 performing duty control of the electromagnetic solenoid 43 of the OCV 40. Hereinafter, the control for controlling the OCV 40 to establish the intermediate phase lock state when the intermediate phase lock state is not established is hereinafter referred to as “intermediate phase lock control”.
[0049]
Further, in a state where the relative rotation phase of the intake camshaft 23 is locked at the intermediate phase by the lock pin 62, the duty ratio D is set to 100%, and the hydraulic oil is supplied only to the advance pressure chamber 53. Then, the flange 62a of the lock pin 62 is urged toward the gear 31 by the oil pressure of the advance side oil chamber 66, and the lock pin 62 is urged toward the hole 63 by the urging force and the urging force of the coil spring 61. Therefore, the state in which the intermediate phase is locked is maintained (this is called "forced intermediate stop").
[0050]
Further, the internal combustion engine 11 is provided with various sensors for detecting the relative rotational phase of the intake camshaft 23 and determining the timing for performing the above-mentioned forced intermediate stop control.
[0051]
That is, as shown in FIG. 1, the cylinder block 11a of the internal combustion engine 11 is provided with a water temperature sensor 55 for detecting the temperature of the cooling water. A crank position sensor 56 for detecting the rotation angle is provided near the crankshaft 14, and a cam position sensor 57 for detecting the rotation angle is provided near the intake camshaft 23. . The output signals of these sensors 55 to 57 are input to the ECU 80. The ECU 80 calculates the actual relative rotational phase of the intake camshaft 23 based on the output signals of the sensors 56 and 57 thus input. Further, the fuel injection valve 25, the spark plug 26, and the OCV 40 are connected to the ECU 80. The ECU 80 outputs drive signals to the fuel injection valve 25, the spark plug 26, and the OCV 40. The ECU 80 includes a CPU, a memory, an input / output port (all are not shown), and the like.
[0052]
[Start control]
As described above, the start control device according to the present invention determines whether or not the intermediate phase is locked by the lock mechanism at the time of starting the engine (lock determination). As a result of the determination, the intermediate phase is not locked. Even if it is known, the intermediate phase lock control is executed so as to realize the intermediate phase locked state, if possible. As a result, the starting control of the engine is performed after establishing the intermediate phase locked state as much as possible, so that the startability and the emission are improved.
[0053]
(First embodiment)
First, a first embodiment of the start control according to the present invention will be described. In the first embodiment, when the lock determination reveals that the relative rotational phase of the intake camshaft 23 is not in the intermediate phase locked state, the intermediate phase locked state is established as much as possible to establish the intermediate phase locked state. Perform control. In this embodiment, at this time, first, the temperature of the hydraulic oil in the variable valve timing mechanism 30 is detected, and if the temperature of the hydraulic oil is equal to or higher than a predetermined temperature, the intermediate phase lock control is executed to execute the intake cam control. The relative rotational phase of the shaft 23 is brought into the intermediate phase locked state. Here, the predetermined temperature of the hydraulic oil is a temperature at which the viscosity of the hydraulic oil becomes sufficiently low to operate the variable valve timing mechanism 30 to change the relative rotational phase of the intake camshaft 23. It can be set to 25 to 30 degrees or more.
[0054]
That is, when the operating oil is at or above the predetermined temperature and the valve timing mechanism 30 can be operated, the intermediate phase lock control is executed to establish the intermediate phase lock state. On the other hand, if the valve timing mechanism 30 cannot be operated because the temperature of the hydraulic oil is low and the viscosity of the hydraulic oil is too high, the intermediate phase lock control cannot be performed. Is executed.
[0055]
In this embodiment, until the completion of the lock determination at the time of starting the engine, the quality of the starting environment of the engine is determined based on the temperature of the cooling water, and the combustion control is performed based on the determination.
[0056]
When the relative rotational phase of the intake camshaft 23 is locked in the intermediate phase by the lock mechanism, the startability of the engine is enhanced. This is because when the intake camshaft 23 is in the intermediate phase locked state, valve overlap occurs, and there is a period in which both the intake valve 21 and the exhaust valve 22 are simultaneously open, so that exhaust is moved to the intake side. This is because the fuel is atomized again.
Therefore, when the intake camshaft 23 is locked in the intermediate phase, it is possible to start the period by using the minimum fuel efficiently, and the emission is improved.
[0057]
On the other hand, when the intake camshaft 23 is not in the intermediate phase locked state, the intake camshaft 23 is normally in the most retarded state, so that more fuel is required to start the engine. Therefore, when the same combustion control as in the intermediate phase locked state is performed under the condition that the startability is poor such as when the cooling water is at a very low temperature, the possibility that the engine will fail to start increases. If the engine fails to start, the fuel is injected again to start the engine, so that the total fuel injection amount eventually increases and the emission deteriorates.
[0058]
Therefore, at the time of starting the engine, until the lock determination is completed, it is determined whether or not the starting environment of the engine is good based on the temperature of the cooling water, that is, whether or not the engine is ready to start. judge. If the temperature of the cooling water falls within the predetermined extremely low temperature range, it is determined that the starting environment is not good, that is, the engine is difficult to start, and the same combustion control as when the intermediate phase lock is not performed. Execute On the other hand, when the temperature of the cooling water does not belong to the predetermined extremely low temperature range, the starting environment is determined to be good, that is, it is determined that the engine is easy to start, and the same as when the intermediate phase lock is performed. Execute combustion control.
[0059]
Specifically, when the coolant temperature is extremely low, the same combustion control is performed as when the intermediate phase is not locked, that is, when the relative rotation phase of the intake camshaft 23 is at the most retarded state. When the intermediate phase lock is not performed, the fuel injection amount is slightly increased compared to the normal case, and the startability control is performed.Therefore, even if the coolant temperature is extremely low, start the engine reliably. Becomes possible. On the other hand, when the temperature of the cooling water is not extremely low, the same combustion control as in the state where the intermediate phase lock is performed is performed. When the intermediate phase is locked, the starting control is performed with the minimum fuel injection amount, so that deterioration of the emission can be prevented. In this way, it is possible to start appropriate start control even during the period until the lock determination is completed.
FIG. 5 shows a flowchart of the engine start control according to the first embodiment. The start control shown in FIG. 5 is executed by the ECU 80 by referring to output signals of various sensors when the engine is started.
[0060]
First, the ECU 80 determines whether an intermediate phase lock request is being made (step S1). Normally, when the engine is started, the ECU 80 sets an intermediate phase lock request and controls the intake camshaft 23 to be locked to the intermediate phase by the lock mechanism. However, after the engine has been successfully started, the intermediate phase lock request is released. For example, when a predetermined time has elapsed after the engine start instruction, or when the engine is actually started and the coolant temperature rises to a predetermined temperature or higher, the ECU 80 determines that the engine has been started and determines that the intermediate phase lock has been completed. Release the request. Therefore, thereafter, the intermediate phase lock request is no longer being issued.
[0061]
If it is in the initial stage of the start control and an intermediate phase lock request is being made (step S1; Yes), the ECU 80 determines whether or not the determination of the locked state is completed (step S2). As described above, for example, the rotation of the crankshaft 14 and the rotation of the intake camshaft 23 are detected by the crank position sensor 56 and the cam position sensor 57, respectively, and the ECU 80 determines the relative rotation phase of the intake camshaft 23. Is calculated.
[0062]
If the determination of the locked state has not been completed yet (step S2: No), the ECU 80 determines whether or not the coolant temperature is a predetermined extremely low temperature based on the output signal of the coolant temperature sensor 55 (step S3). ). The cryogenic temperature range can be set to, for example, -10 ° C or less. When the temperature of the cooling water is in the extremely low temperature range, the startability of the engine deteriorates. Therefore, it is necessary to improve the startability by increasing the fuel injection amount. Therefore, when the coolant temperature is in the extremely low temperature range (step S3: Yes), the ECU 80 performs the oil pressure control as the lock holding control so that the lock pin 62 of the lock mechanism does not come off (step S6), and also performs the intake camshaft. 23 is set to the most retarded state (step S7). On the other hand, if it is determined in step S3 that the coolant temperature is outside the extremely low temperature range, the ECU 80 performs lock holding control (step S8) and sets the state flag of the relative rotational phase of the intake camshaft 23 to an intermediate phase. The state is set (step S9).
[0063]
After the determination of the locked state is completed in step S2, the ECU 80 performs combustion control at the time of starting according to the determination result. That is, if it is in the locked state (Step S4; Yes), the ECU 80 holds the locked state (Step S8) and sets the relative rotation phase of the intake camshaft 23 to the intermediate phase state (Step S9).
[0064]
If it is not in the locked state (Step S4; No), the ECU 80 determines whether the temperature of the hydraulic oil obtained from the temperature sensor 59 attached to the oil pan 11b is higher than a predetermined temperature (Step S5). . When the temperature is high, the viscosity of the hydraulic oil is low, and the variable valve timing mechanism 30 can be operated to execute the intermediate phase lock control. Therefore, the ECU 80 controls the OCV 40 to execute the intermediate phase lock control ( (Step S10), the relative rotational phase of the intake camshaft 23 is set to the intermediate phase state (Step S11).
[0065]
On the other hand, when the temperature of the hydraulic oil is lower than the predetermined temperature (Step S5; No), the viscosity of the hydraulic oil is low and the variable valve timing mechanism 30 cannot be operated, so that the intermediate phase locked state cannot be established. . Therefore, the starting control is performed in the unlocked state. Specifically, the ECU 80 stops the lock holding control for holding the locked state (step S12). When the lock holding control is stopped, the supply of hydraulic oil to the advance side pressure chamber 53 is stopped, and the relative rotational phase of the intake camshaft 23 becomes the most retarded state due to the reaction force accompanying the opening and closing drive of the intake valve 21. Therefore, the ECU 80 sets the relative rotation phase of the intake camshaft 23 to the most retarded state (step S13).
[0066]
Further, when the engine is started and the condition for canceling the intermediate phase lock request as exemplified above is satisfied (Step S1; No), the ECU 80 thereafter executes the normal control of the normal intake camshaft 23 (Step S14). ), The relative rotational position of the intake camshaft 23 is set to the normal control state (step S15). In the normal control, the ECU 80 performs duty control of the OCV 40 to feedback-control the relative rotational phase of the intake camshaft 23 toward the target phase at each time point by hydraulic pressure.
[0067]
Thus, the relative rotation phase of the intake camshaft 23 is set to one of the most retarded state, the intermediate phase state, and the normal control state. After that, the ECU 80 executes the combustion control, that is, the fuel injection amount control, the injection timing control, and the ignition timing control according to these set states. FIG. 6 is a flowchart of the injection amount control, FIG. 7 is a flowchart of the injection timing control, and FIG. 8 is a flowchart of the ignition timing control.
[0068]
First, the injection amount control will be described with reference to FIG. The ECU 80 determines whether or not the relative rotation phase state of the intake camshaft 23 set in the above-described start control is in a normal control state (step S21). The injection amount is calculated (Step S23). If not in the normal control state, the ECU 80 determines whether or not the relative rotation phase of the intake camshaft 23 is in the intermediate phase state (step S22). An appropriate fuel injection amount is calculated in a state where the relative rotational phase of the shaft 23 is locked at the intermediate phase (Step S24). If not in the intermediate phase state, the ECU 80 calculates an appropriate fuel injection amount in the most retarded state, that is, when the relative rotational phase of the intake camshaft 23 is at the most retarded position (step S25). Note that the fuel injection amount calculated in the most retarded state is larger than the fuel injection amount calculated in the intermediate phase state.
[0069]
Next, the injection timing control will be described with reference to FIG. The ECU 80 determines whether or not the relative rotation phase state of the intake camshaft 23 set in the above-described start control is in a normal control state (step S31). The timing is calculated (step S33). If not in the normal control state, the ECU 80 determines whether or not the relative rotation phase of the intake camshaft 23 is in the intermediate phase state (step S32). An appropriate injection timing is calculated in a state where the relative rotational phase of the shaft 23 is locked at the intermediate phase (Step S34). If not in the intermediate phase state, the ECU 80 calculates an injection timing suitable for the most retarded state, that is, when the relative rotational phase of the intake camshaft 23 is at the most retarded position (step S35).
[0070]
Next, the ignition timing control will be described with reference to FIG. The ECU 80 determines whether or not the relative rotation phase state of the intake camshaft 23 set in the above-described start control is a normal control state (step S41). If the relative rotation phase state is the normal control state, appropriate ignition is performed by the normal control. The timing is calculated (step S43). If not in the normal control state, the ECU 80 determines whether or not the relative rotation phase of the intake camshaft 23 is in the intermediate phase state (step S42). An appropriate ignition timing is calculated in a state where the relative rotational phase of the shaft 23 is locked at the intermediate phase (step S44). If not in the intermediate phase state, the ECU 80 calculates an ignition timing suitable for the most retarded state, that is, when the relative rotational phase of the intake camshaft 23 is at the most retarded position (step S45).
[0071]
As described above, in the first embodiment, if it is determined by the lock determination at the time of engine start that the vehicle is not in the intermediate phase lock state, the intermediate phase lock control is executed if possible to establish the intermediate phase lock state. To start control. Originally, it is preferable to execute the start control in the intermediate phase locked state in terms of startability and emission. Therefore, by performing the start control after establishing the intermediate phase locked state as much as possible as in the present invention, the startability and emission can be improved.
[0072]
(Second embodiment)
Next, valve timing control according to a second embodiment will be described. Also in the second embodiment, even if it is found that the engine is not in the intermediate phase lock state by the lock determination at the time of starting the engine, the intermediate phase lock control is executed if possible, and the intermediate phase lock state is established and the start control is performed. . This is the same as in the first embodiment.
[0073]
However, in the first embodiment, in the start control at the time of starting the engine, at the stage before the completion of the lock determination of the relative rotation phase of the intake camshaft 23, the control is performed in accordance with the temperature of the cooling water irrespective of the actual lock. The phase state was set and combustion control was performed. On the other hand, in the present embodiment, the fuel injection is stopped before the lock determination is completed, and after the lock determination is completed, the emission is optimized by performing appropriate combustion control according to the determination result.
[0074]
FIG. 9 shows a flowchart of the start control according to the second embodiment. 9 differs from the first embodiment shown in FIG. 5 only in the processing (steps S55 and S56) when it is determined in step S52 that the determination of the locked state has not been completed.
[0075]
Referring to FIG. 9, first, the ECU 80 determines whether or not a request for the intermediate phase lock is being made (step S51). If the request is being made, the ECU 80 determines whether or not the determination of the locked state is completed (step S51). S52). If the determination of the locked state is not completed (Step S52; No), the ECU 80 performs lock holding control (Step S55), and sets the relative rotation phase of the intake camshaft 23 to an undetermined state (Step S56).
[0076]
When the determination of the locked state is completed (Step S52; Yes), the ECU 80 performs processing according to the determination result. That is, when the lock state is established (Step S53; Yes), lock holding control is performed (Step S57), and the relative rotation phase of the intake camshaft 23 is set to the intermediate phase state (Step S58).
[0077]
If it is not in the locked state (step S53; No), the ECU 80 determines whether the temperature of the hydraulic oil obtained from the temperature sensor 59 attached to the oil pan 11b is higher than a predetermined temperature (step S54). . When the temperature is high, the viscosity of the hydraulic oil is low, and the variable valve timing mechanism 30 can be operated to execute the intermediate phase lock control. Therefore, the ECU 80 controls the OCV 40 to execute the intermediate phase lock control ( (Step S59), the relative rotational phase of the intake camshaft 23 is set to the intermediate phase state (Step S60).
[0078]
On the other hand, when the temperature of the hydraulic oil is lower than the predetermined temperature (Step S54; No), the viscosity of the hydraulic oil is low and the variable valve timing mechanism 30 cannot be operated, so that the intermediate phase locked state cannot be established. . Therefore, the starting control is performed in the unlocked state. Specifically, the ECU 80 stops the lock holding control (step S61), and sets the relative rotation phase of the intake camshaft 23 to the most retarded state (step S62). If the intermediate phase lock is not requested in step S51, normal control is performed (step S63), and the relative rotation phase of the intake camshaft 23 is set to the normal control state (step S64). Thus, the relative rotation phase of the intake camshaft 23 is set to any one of the undetermined state, the intermediate phase state, the most retarded state, and the normal control state.
[0079]
Next, combustion control is performed according to this setting. As an example of the combustion control, a flowchart of the injection amount control is shown in FIG. First, the ECU 80 determines whether the relative rotation phase of the intake camshaft 23 is in the normal control state, and if it is in the normal control state, calculates the fuel injection amount suitable for the normal control state (step S73). ). If it is not in the normal control state, it is determined whether or not it is in the intermediate phase state (step S72). If it is in the intermediate phase state, a fuel injection amount suitable for the intermediate phase state is calculated (step S74). If it is not the intermediate phase state, it is determined whether or not it is in the most retarded state (step S76). If it is in the most retarded state, a fuel injection amount suitable for the most retarded state is calculated (step S76). S75). If it is not in the most retarded state, the relative rotation phase of the intake camshaft 23 is in an undetermined state, so that the fuel injection amount is set to "0" (step S77).
[0080]
As described above, also in the second embodiment, if it is determined by the lock determination at the time of engine start that the vehicle is not in the intermediate phase lock state, the intermediate phase lock control is executed if possible to establish the intermediate phase lock state. To perform start control. Therefore, by performing the start control after establishing the intermediate phase locked state as much as possible as in the present invention, the startability and emission can be improved.
[0081]
【The invention's effect】
As described above, according to the present invention, in the valve timing control device having the mechanism for locking the relative rotation phase of the intake camshaft, when the lock determination at the time of starting the engine reveals that it is not in the intermediate phase locked state. Executes the intermediate phase lock control, if possible, to establish the intermediate phase lock state, and then performs the start control. Originally, it is preferable to execute the start control in the intermediate phase locked state in terms of startability and emission. Therefore, the startability and the emission can be improved by establishing the intermediate phase locked state as much as possible and performing the start control as in the present invention.
[Brief description of the drawings]
FIG. 1 shows a structure of an internal combustion engine to which a valve timing control device according to an embodiment of the present invention is applied.
FIG. 2 shows a mechanism for supplying hydraulic oil to a variable valve timing mechanism according to an embodiment of the present invention.
FIG. 3 is a sectional view showing an internal structure of the variable valve timing mechanism shown in FIG. 2;
FIG. 4 is a sectional view taken along line 4-4 in FIG. 3;
FIG. 5 is a flowchart of a start control according to the first embodiment.
FIG. 6 is a flowchart of fuel injection amount control in the first embodiment.
FIG. 7 is a flowchart of fuel injection timing control in the first embodiment.
FIG. 8 is a flowchart of ignition timing control in the first embodiment.
FIG. 9 is a flowchart of start control according to the second embodiment.
FIG. 10 is a flowchart of a fuel injection amount control in the second embodiment.
[Explanation of symbols]
Reference Signs List 11 internal combustion engine 14 crankshaft 21 intake valve 22 exhaust valve 30 variable valve timing mechanism 40 oil control valve (OCV)
80 Electronic Control Unit (ECU)

Claims (6)

A variable valve timing mechanism that changes the relative rotation phase of the camshaft with respect to the crankshaft of the internal combustion engine by controlling the pressure of the working fluid in the advance pressure chamber and the retard pressure chamber.
Locking means for locking the relative rotation phase of the camshaft to an intermediate phase between the most retarded state and the most advanced state;
Lock determining means for determining whether the relative rotation phase of the camshaft is locked to the intermediate phase by the locking means,
At the time of starting the internal combustion engine, if the lock determination unit determines that the lock has not been made, despite the lock by the lock unit being requested, the lock unit is controlled to lock the lock. And a control means for performing the control. A temperature detection unit configured to detect a temperature of the working fluid,
The control device for an internal combustion engine according to claim 1, wherein the control means controls the lock means to perform the lock only when the temperature of the working fluid is equal to or higher than a predetermined temperature. At the time of starting the internal combustion engine, before the determination by the lock determination unit is completed, a starting environment determining unit that determines whether a starting environment of the internal combustion engine is good,
When the starting environment is determined to be good, the engine is started under the combustion conditions when the relative rotation phase of the camshaft is in the intermediate phase state, and when it is determined that the starting environment is not good, 2. The start control device for an internal combustion engine according to claim 1, further comprising: combustion control means for controlling combustion of the engine under a combustion condition when the relative rotation phase of the camshaft is in the most retarded state. The starting environment determining means,
A water temperature sensor for detecting the temperature of the cooling water of the internal combustion engine,
Means for determining that the starting environment is good when the water temperature is outside a predetermined cryogenic range, and means for determining that the starting environment is not good when the water temperature is within the cryogenic range. The start control device for an internal combustion engine according to claim 3, wherein After the completion of the determination by the lock determination unit, the combustion control unit determines, based on the determination result, combustion conditions when the relative rotational phase of the camshaft is in the intermediate phase state or combustion when the camshaft is in the most retarded state. 5. The start control device for an internal combustion engine according to claim 4, wherein the combustion of the engine is controlled according to one of the conditions. 2. The internal combustion engine according to claim 1, further comprising an injection prohibition unit that prohibits fuel injection in the internal combustion engine until the determination by the lock determination unit is completed when the internal combustion engine is started. Starting control device.

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