JP3981799B2 - Variable valve timing control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a variable valve timing control device that adjusts opening and closing timings of intake valves and exhaust valves of an engine.
[0002]
[Related background]
For example, this type of variable valve timing control device is provided in a timing pulley that is rotationally driven by a crankshaft via a timing belt, and connects a vane rotor disposed therein to a camshaft, and hydraulically moves the vane rotor in an arbitrary direction. , The phase of the vane rotor with respect to the crankshaft, that is, the phase of the camshaft is varied, and as a result, the opening / closing timing of the intake valve and the exhaust valve is adjusted. The target phase angle of the camshaft is set according to the operating state of the engine, and the hydraulic pressure of the variable valve timing control device is controlled so that the actual phase angle detected by the sensor becomes the target phase angle.
[0003]
By the way, in the variable valve timing control apparatus configured as described above, when an installation error of the sensor for detecting the actual phase angle or a detection error of the sensor itself occurs, or when a secular change occurs with the operation. However, the detected actual phase angle includes an error, and the camshaft phase angle is controlled based on the erroneous actual phase angle, so that proper phase control cannot be realized.
[0004]
Therefore, for example, in the variable valve timing control device described in Japanese Patent Application Laid-Open No. 6-299876, the influence of the error described above is eliminated by learning the actual phase angle. That is, in this variable valve timing control device, the target phase angle during idle operation is set to the most retarded position (position where the camshaft is most retarded), so that a predetermined time has elapsed since the start of idle operation. In this case, it is assumed that the actual cam shaft is at the most retarded angle position, and the actual phase angle detected by the sensor at this time is learned.
[0005]
[Problems to be solved by the invention]
However, since the oil pump for supplying hydraulic oil to the variable valve timing control device is driven by the engine, sufficient oil pressure is not generated during idle operation at a low engine speed, and phase control is slowed down. Furthermore, when factors such as aging and contamination are added, there is a possibility that the maximum retarded position will not be reached even after a predetermined time has elapsed. As a result, there is a case where the learning process is performed in a state where the position of the most retarded angle is not reached, and there is a problem in that inappropriate phase control is performed based on the erroneously learned actual phase angle.
[0006]
An object of the present invention is to provide a variable valve timing control device capable of always learning an appropriate actual phase angle and performing cam shaft phase control with high accuracy based on the learned value.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, in the variable valve timing control device that varies the valve timing of at least one of the intake valve and the exhaust valve, the operating state detecting means detects the operating state including at least the engine speed. Real phase angle detection means for detecting the actual phase angle of the camshaft, target phase angle setting means for setting the target phase angle based on the operating state, and the phase of the camshaft so that the actual phase angle is the target phase angle. A phase angle control means for controlling the angle, a reference phase angle learning means for learning the output value of the actual phase angle detection means as a reference phase angle when at least the target phase angle is a predetermined phase angle, and an engine rotational speed of a predetermined value or less And a learning prohibiting means for prohibiting learning of the reference phase angle.
[0008]
Therefore, when the target phase angle is the predetermined phase angle, the output value of the actual phase angle detection means is learned as the reference phase angle by the reference phase angle learning means, and when the engine speed is equal to or less than the predetermined value, that is, the phase In a situation where smooth operation of the angle control means cannot be expected, this learning process is prohibited by the learning prohibition means. As a result, it is possible to prevent the learning process from being executed in a state where the actual phase angle does not reach the predetermined phase angle .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is embodied in a variable valve timing control apparatus for a direct injection engine that directly injects fuel into a combustion chamber will be described.
In the schematic configuration diagram of FIG. 1, reference numeral 1 denotes an in-cylinder in-line four-cylinder gasoline engine for automobiles, and a combustion chamber, an intake device, and the like are designed exclusively for in-cylinder injection. The engine 1 employs a DOHC 4-valve type valve operating mechanism, and timing pulleys 4a and 4b are connected to the front ends of the intake camshaft 3a and the exhaust camshaft 3b provided at the top of the cylinder head 2. The timing pulleys 4 a and 4 b are connected to the crankshaft 6 through a timing belt 5. As the crankshaft 6 rotates, the camshafts 3a and 3b are rotationally driven together with the timing pulleys 4a and 4b, and the intake and exhaust valves 7a and 7b are driven to open and close by the camshafts 3 and 3b.
[0010]
A valve timing variable mechanism 8 as a phase angle control means is provided between the intake camshaft 3a and the intake side timing pulley 4a. The valve timing variable mechanism 8 is connected to an oil pump 9 driven by the engine 1. And an oil control valve (hereinafter referred to as OCV) 10. The variable valve timing mechanism 8 is configured by rotatably providing a vane rotor in a housing provided on the intake side timing pulley 4a and connecting the intake camshaft 3a to the vane rotor. This configuration is well known in, for example, Japanese Patent Laid-Open No. 2000-27609, and therefore will not be described in detail. However, the hydraulic oil supplied from the oil pump 9 is switched and controlled by the OCV 10 and supplied to the variable valve timing mechanism 8. The vane rotor is rotated in an arbitrary direction by hydraulic pressure, and the phase of the cam shaft 3a with respect to the timing pulley 4a, that is, the opening / closing timing of the intake valve 7a can be adjusted. In this variable valve timing mechanism 8, when the OCV 10 is not energized, the hydraulic pressure from the oil pump 9 acts in a direction to retard the vane rotor, and the camshaft 3a is brought to the most retarded position (most retarded position). It has a structure to hold.
[0011]
On the other hand, the cylinder head 2 is provided with an electromagnetic fuel injection valve 12 together with a spark plug 11 for each cylinder, and high-pressure fuel supplied from a fuel pump (not shown) is introduced into the combustion chamber 13 from the fuel injection valve 12. It is designed to be directly injected. An intake port 14 is formed in the cylinder head 2 in a substantially upright direction so as to pass between both the cam shafts 3a and 3b, and the intake air whose flow rate is adjusted by the throttle valve 15 is accompanied by opening of the intake valve 7a. It is introduced into the combustion chamber 13 from the intake port 14. On the other hand, the exhaust port 16 is formed in a substantially horizontal direction as in a normal engine so that the exhaust gas after combustion is discharged from the exhaust port 16 through the exhaust passage 17 when the exhaust valve 7b is opened. It has become.
[0012]
In the vehicle compartment, an input / output device (not shown), a storage device (ROM, RAM, BURAM, etc.) used for storing control programs and control maps, an ECU (engine) equipped with a central processing unit (CPU), a timer counter, etc. Control unit) 21 is installed and performs overall control of the engine 1. On the input side of the ECU 21 are a crank angle sensor 22 as an operating state detection means, a cam angle sensor 23 as an actual phase angle detection means, a throttle sensor 24 for detecting the opening θth of the throttle valve 15, and a coolant temperature Tw of the engine 1. Various sensors such as a water temperature sensor 25 for detecting the water temperature are connected. The crank angle sensor 22 and the cam angle sensor 23 are composed of a timing rotor and a pickup coil, and rotate the timing rotor together with the crankshaft 6 and the camshaft 3a to generate a magnetic field change in the pickup coil by a large number of teeth on the outer periphery. Thus, an AC crank angle signal and a cam angle signal corresponding to the rotation are generated.
[0013]
Further, the above-described OCV 10, spark plug 11, and fuel injection valve 12 are connected to the output side of the ECU 21. The ECU 21 determines the target phase angle, ignition timing, fuel injection amount, and the like of the variable valve timing mechanism based on detection information from each sensor, and drives and controls the OCV 10, the spark plug 11, and the fuel injection valve 12, and the engine. The reference position of the variable valve timing mechanism 8 is learned when 1 is in a predetermined operation state.
[0014]
Next, the phase angle control and learning process executed by the variable valve timing control device for the direct injection engine 1 configured as described above will be described.
The ECU 21 executes the cam phase angle control / learning process routine shown in FIG. 2 at a predetermined control interval, and first, an operation state detection process is executed in step S2. Specifically, input of detection information from the throttle sensor 24, the crank angle sensor 22, etc., and abnormality determination of the sensor based on the detection information are performed. In subsequent step S4, the target phase angle of the variable valve timing mechanism 8 is set. This setting process is performed according to a preset map. For example, the setting process is based on the target average effective pressure Pe (representing the engine load) obtained from the throttle opening θth and the like and the engine rotational speed Ne obtained from the crank angle signal. A target phase angle is set (target phase angle setting means). Next, in step S6, it is determined whether or not the target phase angle is the most retarded position. If YES (affirmative), the process proceeds to step S8 and the energization of the OCV 10 is stopped. Accordingly, the variable valve timing mechanism 8 is thereby actuated to the most retarded position. In subsequent step S10, it is determined whether or not the phase learning condition is satisfied. This phase learning condition is satisfied when the following three kinds of requirements are satisfied continuously for a predetermined time n.
[0015]
a) The OCV is in a non-energized state b) The engine speed Ne is equal to or higher than a preset rotation judgment value N0 c) The cooling water temperature Tw is less than a preset water temperature judgment value T0 where The rotation determination value N0 is a lower limit rotation speed at which the oil pump 9 generates sufficient hydraulic pressure to smoothly operate the variable valve timing mechanism 8, and is set to, for example, 2000 rpm. The water temperature determination value T0 is a hydraulic pressure associated with an increase in oil temperature. This is the upper limit water temperature at which there is no possibility of a decrease (because it can be estimated from the water temperature that is substantially correlated with the oil temperature), and is set to 70 ° C., for example. When the phase learning condition is not satisfied and NO is determined in step S8, the routine is temporarily terminated.
[0016]
When the phase learning condition is satisfied and the determination is YES, the variable valve timing mechanism 8 is considered to be at the most retarded position, and detection information from the crank angle sensor 22 and the cam angle sensor 23 is obtained in step S12. The routine is terminated after inputting and executing the learning process of the reference position in step S14. The contents of the learning process in step S14 are general, for example, as disclosed in Japanese Patent Laid-Open No. Hei 6-299976 described in [Related Background Art], and the crank angle signal and cam angle signal at the most retarded position. And a phase difference as a reference position (reference phase angle learning means). This learning process is performed for each tooth of the timing rotor, that is, for each pulse of the signal. As long as the phase learning condition is satisfied in step S10, the phase difference for each pulse is sequentially learned as the reference position.
[0017]
On the other hand, if NO is determined in step S6 that the target phase angle is not the most retarded position, the process proceeds to step S16 to input detection information from the crank angle sensor 22 and the cam angle sensor 23, and in step S18. Based on the learning value corresponding to the current pulse, the detected phase angle of the camshaft 3a is corrected. Specifically, the actual advance amount of the cam shaft 3a from the reference position is calculated based on the learning value from the phase difference between the crank angle signal and the cam angle signal. Thereafter, in step S20, the duty ratio of the drive signal supplied to the OCV 10 is feedback-controlled so that the corrected phase angle of the camshaft 3a becomes the target phase angle (phase angle control means), and then the routine is terminated.
[0018]
As described above, in the variable valve timing control device of the present embodiment, as a phase learning condition for executing the reference position learning process, not only the OCV 10 in a) is in a non-energized state, but also the engine rotation in b). It is set that the speed Ne is equal to or higher than the rotation determination value N0 and a sufficient oil pressure is secured, and that the cooling water temperature Tw of c) is less than the water temperature determination value T0 and there is no possibility of a decrease in oil pressure.
[0019]
That is, even if the requirement of a) is satisfied and the actual phase is assumed to be controlled to the most retarded position, the requirement of b) and c) is not satisfied (from the oil pump) When the hydraulic pressure is low or the hydraulic pressure is lowered and the operation of the variable valve timing mechanism 8 is slow), the learning process of the reference position is prohibited because the phase learning condition is not satisfied (learning prohibiting means) . Therefore, it is possible to prevent a situation in which the learning process is performed in a state where the actual phase angle does not reach the most retarded angle position, and always obtain an appropriate learned value, and in turn, based on the learned value, the valve timing The phase control of the variable mechanism 8 can be performed with high accuracy.
[0020]
Further, when the oil pressure decreases during the learning process due to deterioration of the valve timing variable mechanism 8 and the difference between the learning values becomes excessive, a failure determination is made and the valve timing variable mechanism 8 is set to the most retarded angle. Although the fail-safe process for fixing the position is performed, the learning process is not executed in the low rotation range that is greatly affected by the decrease in hydraulic pressure as described above, and therefore phase control is continued. Even in such a situation, the engine speed Ne In addition, there is also an advantage that appropriate phase control can be performed in the middle / high rotation range where the hydraulic pressure increases.
[0021]
Furthermore, the learning process is not executed in the situation where the requirements of b) and c) are not satisfied as described above (the situation where sufficient oil pressure is not secured in the low rotation range, the situation where the oil pressure drop occurs at a high oil temperature). In such a situation, it is not necessary to enlarge the pressure receiving area of the vane rotor of the variable valve timing mechanism 8 so that the valve timing variable mechanism 8 can be rotated to the most retarded position, and the variable valve timing mechanism 8 can be made compact.
[0022]
This is the end of the description of the embodiment, but the aspect of the present invention is not limited to this embodiment. For example, in the above-described embodiment, the variable valve timing control device for the direct injection engine 1 is embodied. However, the type of the engine to be applied is not limited to this, for example, a type in which fuel is injected into a normal intake pipe It may be applied to other engines.
[0023]
In the above embodiment, the most retarded angle position is set as the predetermined phase angle for executing the reference position learning process. However, the predetermined phase angle is not limited to this, and is held at the most advanced angle position when the OCV 10 is not energized, for example. When the valve timing variable mechanism 8 is configured as described above, the most advanced angle position may be set as the predetermined phase angle , and the learning process may be executed at this most advanced angle position.
[0024]
Furthermore, in the above embodiment, the valve timing variable mechanism 8 is provided on the intake side to adjust the opening / closing timing of the intake valve 7a. However, the object for adjusting the opening / closing timing may be the exhaust side or the intake / exhaust timing. Both are good.
On the other hand, in the above embodiment, as the phase learning condition, in addition to the original requirement of a), the requirement of c) regarding the cooling water temperature Tw is set together with the requirement of b) regarding the engine rotation speed Ne. A requirement may be eliminated or another requirement may be added.
[0025]
【The invention's effect】
As described above, according to the variable valve timing control device of the first aspect of the invention, the learning process is prohibited in a situation where the engine speed is not more than a predetermined value and the smooth operation of the phase angle control means cannot be expected. Therefore, a situation where the learning process is executed in a state where the actual phase angle does not reach the predetermined phase angle is prevented in advance, and an appropriate learning value is obtained by preventing erroneous learning, and as a result, based on the learning value. The phase control of the camshaft can be performed with high accuracy .
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a variable valve timing control device for a direct injection type engine according to an embodiment.
FIG. 2 is a flowchart showing a cam phase angle control / learning processing routine executed by the ECU.
[Explanation of symbols]
7a Intake valve 7b Exhaust valve 8 Valve timing variable mechanism (phase angle control means)
21 ECU (target phase angle setting means, phase angle control means, reference phase angle learning means, learning prohibition means)
22 Crank angle sensor (operating state detection means)
23 Cam angle sensor (actual phase angle detection means)

Claims (1)

In a variable valve timing control device that varies the valve timing of at least one of an intake valve and an exhaust valve,
Driving state detecting means for detecting a driving state including at least the engine rotation speed;
An actual phase angle detecting means for detecting an actual phase angle of the camshaft;
Target phase angle setting means for setting the target phase angle based on the operating state;
Phase angle control means for controlling the phase angle of the camshaft so that the actual phase angle is the target phase angle;
When at least the target phase angle is a predetermined phase angle, reference phase angle learning means for learning the output value of the actual phase angle detection means as a reference phase angle;
A variable valve timing control apparatus comprising: a learning prohibiting unit that prohibits learning of the reference phase angle when the engine speed is equal to or less than a predetermined value.

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