JP2002180856A - Variable valve timing control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable valve timing control device for an engine, capable of executing learning processing of a phase angle while preventing the worsening of fuel consumption due to an increase in load of an oil pump. SOLUTION: In fuel cut during deceleration of a vehicle (YES in Step S12), a variable valve timing mechanism is controlled to be at a maximum phase lag position (Step S14) and learning processing of the phase angle is executed (from Step S18 on). At this time, the engine is reverse driven by the inertia of the vehicle and fuel supply is originally stopped, and so an increase in load of the oil pump with the operation of the variable valve timing mechanism gives no increase in fuel consumption.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve timing control device for adjusting the opening and closing timing of an intake valve and an exhaust valve of an engine.

[0002]

2. Description of the Related Art For example, a variable valve timing control device of this type is provided on a timing pulley that is rotationally driven by a crankshaft via a timing belt, and connects a vane rotor disposed inside to a camshaft to control the hydraulic pressure. By rotating 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 of the camshaft becomes the target phase angle.

[0003] The actual phase angle of the camshaft is detected by a crank angle sensor and a cam angle sensor. These sensors rotate a timing rotor together with the crankshaft and the camshaft.
A magnetic field change is caused in the pickup coil by the teeth on the outer periphery, and an AC crank angle signal or a cam angle signal corresponding to the rotation is obtained. Since the actual phase angle of the camshaft is detected as the phase difference between the pulses of the crank angle signal and the cam angle signal, the actual phase angle is directly affected by the processing error of the timing rotor teeth and the mounting error of the pickup coil. Become.

Therefore, the variable valve timing device described in JP-A-6-299876 or JP-A-11-229914 executes a learning process of comparing the detected pulse phase difference with a reference phase difference. The detected phase difference is corrected based on the learning result. Since this learning process must always be performed at the same phase angle (that is, the most retarded position or the most advanced position at both ends of the phase stroke),
For example, Japanese Unexamined Patent Publication No. 6-299876 discloses that the idle-side camshaft is controlled to the most retarded position in order to stabilize the rotation during the idling operation. When the time has elapsed, the learning process is performed on the assumption that the actual camshaft is at the most retarded position.

However, the application of the above technique is not limited to the phase control for the camshaft on the intake side, and cannot be applied to an engine controlled to a position other than the most retarded position during idling operation. For example, in an engine for a hybrid vehicle, the phase of a camshaft on the intake side is further delayed at the time of starting than at the time of idling for the purpose of reducing motor torque required for starting and decompression for reducing vibration during cranking. Since the control is performed on the corner side, the control is not performed at the most retarded position during the idling operation, and as a result, the above technique cannot be applied. In other words, the above technique cannot be applied to an engine that is not controlled to the most retarded position during idling operation for some purpose.

Therefore, in order to always learn in the same phase without being limited to the type of intake / exhaust or the type of engine, the conventional variable valve timing control apparatus actively proactively controls the most retarded position or the most retarded position during operation of the engine. The learning process was performed after changing the phase angle to the advanced position.

[0007]

However, since the oil pressure for rotating the vane rotor uses oil from an oil pump for lubricating the engine, the load on the oil pump is temporarily changed when the phase angle is changed. Increases,
Accordingly, the fuel consumption of the engine increases. That is, in addition to the original phase angle control, if the phase angle is changed during the learning process as described above, there is a problem that the frequency of increasing the load on the oil pump increases, which eventually leads to deterioration of fuel efficiency.

It is an object of the present invention to provide a variable valve timing control device for an engine that can execute a learning process of a phase angle while preventing deterioration of fuel efficiency due to an increase in the load on an oil pump.

[0009]

In order to achieve the above object, according to the present invention, a valve timing is continuously changed by changing a rotation phase of a camshaft with respect to a crankshaft based on a hydraulic pressure of a pump driven by an engine. A variable valve timing mechanism for stopping the supply of fuel to the engine during deceleration of the vehicle; and a variable valve timing mechanism for driving the camshaft to the most retarded position or the most retarded position when the fuel cut means operates. Phase angle control means for controlling to an advanced position, and when the camshaft is at the most retarded position or the most advanced position by the phase angle control means, the rotational phase difference of the camshaft with respect to the crankshaft is set to a predetermined reference value. A learning means for learning the rotational phase difference between the camshaft and the crankshaft by comparison is provided.

Therefore, during fuel cut when fuel supply to the engine is stopped during vehicle deceleration, the camshaft is controlled to the most retarded position or the most advanced position, and the rotational phase difference between the camshaft and the crankshaft is controlled. Learning is performed. Since the engine at this time is driven in reverse by the inertia of the vehicle and the fuel supply is originally stopped, even if the load on the oil pump increases due to the operation of the variable valve timing mechanism, the fuel consumption increases. There is no.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a variable valve timing control apparatus for a direct injection type engine which injects fuel directly into a combustion chamber will be described below. In the schematic diagram of FIG. 1, reference numeral 1 denotes an in-cylinder injection type in-line
It is a cylinder gasoline engine, and the combustion chamber and intake device are designed exclusively for in-cylinder injection. DOHC for Engine 1
A four-valve type valve operating mechanism is adopted, and timing pulleys 4a and 4b are connected to front ends of an intake camshaft 3a and an exhaust camshaft 3b provided on an upper portion of the cylinder head 2, respectively. , 4b are connected to a crankshaft 6 via a timing belt 5. As the crankshaft 6 rotates, the camshafts 3a and 3b are driven to rotate together with the timing pulleys 4a and 4b, and the camshafts 3 and 3b open and close the intake valve 7a and the exhaust valve 7b.

A variable valve timing mechanism 8 is provided between the intake camshaft 3a and the intake-side timing pulley 4a. The variable valve timing mechanism 8 is connected to a lubrication oil pump 9 driven by the engine 1. It is connected via an oil control valve (hereinafter referred to as OCV) 10. The variable valve timing mechanism 8 is configured such that a vane rotor is rotatably provided in a housing provided on a timing pulley 4a on the intake side, and the intake camshaft 3a is connected to the vane rotor. This configuration is publicly known, for example, in Japanese Patent Application Laid-Open No. 2000-27609, and will not be described in detail. However, the operating oil supplied from the oil pump 9 is switched and controlled by the OCV 10 and supplied to the variable valve timing mechanism 8. By rotating the vane rotor in an arbitrary direction by hydraulic pressure, 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.

On the other hand, an electromagnetic fuel injection valve 12 is attached to the cylinder head 2 together with an ignition plug 11 for each cylinder, and high-pressure fuel supplied from a fuel pump (not shown) is supplied from the fuel injection valve 12 to the combustion chamber. 13 is directly injected. An intake port 14 is formed in the cylinder head 2 in a substantially upright direction so as to pass through between the two camshafts 3a and 3b. The intake air whose flow rate is adjusted by the throttle valve 15 is opened with the opening of the intake valve 7a. The air is introduced from the intake port 14 into the combustion chamber 13. On the other hand, the exhaust port 16 is formed in a substantially horizontal direction similarly to a normal engine, and the exhaust gas after combustion is exhausted by the exhaust port 16 with the opening of the exhaust valve 7b.
Through the exhaust passage 17.

An ECU (not shown) provided with an input / output device (not shown), storage devices (ROM, RAM, etc.) for storing control programs and control maps, a central processing unit (CPU), a timer counter, and the like. Engine control unit)
21 are provided to perform comprehensive control of the engine 1. On the input side of the ECU 21, a crank angle sensor 22,
Various sensors such as a cam angle sensor 23, a throttle sensor 24 for detecting the opening degree θth of the throttle valve 15, and a water temperature sensor 25 for detecting the cooling water temperature Tw of the engine 1 are connected. The output side of the ECU 21 is connected to the O
The CV 10, the spark plug 11, and the fuel injection valve 12 are connected.

The crank angle sensor 22 and the cam angle sensor 23 are composed of a timing rotor and a pickup coil. The timing rotor is rotated together with the crankshaft 6 and the camshaft 3a, and a plurality of teeth on the outer periphery form the pickup coil. A magnetic field change is generated to generate an AC crank angle signal or a cam angle signal according to the rotation.

The ECU 21 executes the ignition timing control by the spark plug 11 and the fuel injection control by the fuel injection valve 12 based on the detection information from each sensor, and also executes the OCV control.
10 is driven to perform the phase angle control of the intake camshaft 3a by the variable valve timing mechanism 8. In these controls, information detected by the crank angle sensor 22 and the camshaft sensor 23 includes, for example, calculation of the engine rotation speed Ne, determination of a reference position for determining fuel injection timing and ignition timing, and phase angle of the intake camshaft 3a. Is used for the determination of

The ECU 21 performs a fuel cut when the vehicle is decelerated by the driver's operation of turning off the accelerator and the engine speed Ne is within a predetermined range (fuel cut means). The phase angle learning process of the mechanism 8 is executed. The learning process of the phase angle will be described in detail with reference to the flowcharts shown in FIGS. 2 and 3 and the time chart shown in FIG.

The ECU 21 executes the phase angle learning routine of FIGS. 2 and 3 at a predetermined control interval, and first determines in step S2 whether learning of the phase angle is necessary. Specifically, when the phase error learning value θerrL described later is stored in the backup memory of the storage device, and the phase error learning value θerrL has been updated after the engine is started, the learning process has already been performed. Is determined to be NO (No). In this case, the ECU 21 determines in step S
4, the time T1 from the fall of the pulse of the cam angle sensor 23 to the fall of the pulse of the crank angle sensor 22 is measured as shown in FIG. Find the phase angle θ1.

Θ1 = T1 / sgt180T × 180 (1) where sgt180T is 180 ° at the current engine speed.
This is the time required for CA. In the following step S6, the following equation
According to (2), the corrected phase angle θ0 is calculated using the phase error learning value θerrL stored in the backup memory, and the routine ends. Then, based on the obtained corrected phase angle θ0, the phase angle control of the variable valve timing mechanism 8 is executed by another routine.

Θ0 = θ1 + θerrL (2) On the other hand, in step S2, if the phase error learning value θerrL is not stored in the backup memory, or even if the phase error learning value θerrL is stored, the engine is started. If it has not been updated later, it is determined that learning is required, and a determination of YES (affirmation) is made. In this case, the process proceeds to step S8 to determine whether or not the engine speed Ne is within a predetermined range (NeA <Ne <NeB). At step S10, the cooling water temperature Tw is within the predetermined range (TwA).
It is determined whether or not <Tw <TwB). Step S8
If the result of the determination is NO, the rotational fluctuation of the engine 1 is large,
If the determination in step S10 is NO and the engine 1 is not in a hot state, the process proceeds to step S4.

If both the judgments in step S8 and step S10 are YES, the flow shifts to step S12 to judge whether or not a predetermined time Ta has elapsed from the start of the fuel cut and the start of the fuel cut. Sometimes said step S
Move to 4. If the determination in step S12 is YES, the process proceeds to step S14, and a command is issued to set the phase angle of the variable valve timing mechanism 8 to the most retarded position (phase angle control means). Based on this command, the actual phase angle is moved to the most retarded position by another routine. In the following step S16, the ECU 21 determines whether or not a predetermined time Tb has elapsed from the command and the command is still being continued. If the determination is NO, the process proceeds to step S4.

If the determination in step S16 is YES, it is considered that the movement to the most retarded position is completed, and step S1 is performed.
8, the time T1 from the fall of the pulse of the cam angle sensor 23 to the fall of the pulse of the crank angle sensor 22 is measured in the same manner as in step S4. In the following step S20, the phase error measurement value θerrM is obtained as an angle conversion value according to the following equation (3).

ΘerrM = (T 1 −T 0) / sgt 180 T × 180 (3) where T 0 is a reference time of the most retarded position, and is a detection error of the crank angle sensor 22 and the cam angle sensor 23 (timing rotor This value is based on the assumption that there is no machining error of the tooth and the mounting error of the pickup coil. As shown in FIG. 4, when the intake camshaft 3a is shifted to the advance side with respect to the crankshaft 6, a time T1 longer than the reference time T0 is measured, and the phase error measurement value θe
rrM is calculated as a positive value. Conversely, when the intake camshaft 3a is shifted to the retard side, a time T1 shorter than the reference time T0 is measured, and the phase error measurement value θerrM is a negative value. Is calculated as

In the following step S22, the obtained phase error measurement value θerrM and the previous phase error calculation value θerrC (n−
Based on (1), the current phase error calculation value θerrC (n) is calculated according to the following equation (4). θerrC (n) = (1−K) × θerrM + K × θerrC (n−1) (4) where K is a filter gain set to 1.0 or less. The processing of steps S18 to S22 is repeated to improve the accuracy of the phase error calculation value θerrC (n). In the subsequent step S24, until the number of times of calculation N reaches the predetermined value N0, it is stored in the backup memory in step S26. After the phase error learning value θerrL is set to 0, the process proceeds to step S4. Accordingly, in step S6 in this case, the detected phase angle θ1 is used as it is as the corrected phase angle θ0.
It will be.

On the other hand, when the number N of times of calculation of the phase error calculation value θerrC (n) reaches the predetermined value N0, the determination in step S24 becomes Y.
When ES is reached, the phase error calculation value θerrC (n) at that point is stored in the backup memory as the phase error learning value θerrL in step S28 (learning means), and then the process proceeds to step S4. Therefore, hereafter, step S6
Then, the calculation process of the corrected phase angle θ0 based on the phase error learning value θerrL is performed according to the above equation (2).

The above learning process is performed for each tooth of the timing rotor, that is, for each pulse of the signal. As long as the conditions for executing the learning process in step S12 are satisfied, the phase error learning value θerrL for each pulse is backed up. Stored in memory sequentially. As described above, in the variable valve timing control device of the engine 1 of the present embodiment, the learning process of the phase angle is executed by controlling the intake camshaft 3a to the most retarded position during the fuel cut at the time of vehicle deceleration. . In other words, the engine 1 at this time is reversely driven by the inertia of the vehicle,
Since the fuel supply is originally stopped, even if the load on the oil pump 9 increases due to the operation of the variable valve timing mechanism 8, the fuel consumption does not increase at all. As a result, even if the learning process is frequently performed, it is possible to reliably prevent the fuel consumption from being deteriorated due to the execution of the learning process.

Further, since the learning process is executed after the phase angle is positively controlled to the most retarded position, for example, Japanese Patent Application Laid-Open No. H10-163702 utilizes the fact that the intake camshaft becomes the most retarded position during idling operation. As in the prior art described in JP-A-6-299876, the phase control is limited to the intake camshaft,
There is no limitation to the engine controlled to the most retarded position during the idling operation. Therefore, the learning process can be performed without being limited to the type of intake / exhaust gas or the type of engine, and the applicable range can be greatly expanded.

Further, changing the phase angle set by the original phase angle control to the most retarded position or the most advanced position for the learning process requires a phase angle optimum for the operating state of the engine 1. If the learning process is performed during the operation of the engine as in the variable valve timing control device described as a conventional example, the drivability is degraded. On the other hand, in the present embodiment, since the learning process is performed during the fuel cut that does not affect the drivability, good drivability can be maintained.

Further, since the engine 1 during the learning process is maintained at least at the rotation speed at which the fuel cut is returned, the oil pump 9 generates a sufficiently high oil pressure as compared with, for example, the idle operation. Therefore, the variable valve timing mechanism 8 quickly and reliably moves to the most retarded position without causing an operation failure due to insufficient hydraulic pressure, and has the effect of always learning an accurate phase error learning value θerrL.

Although the embodiment has been described above, aspects of the present invention are not limited to this embodiment. For example, in the above-described embodiment, the variable valve timing control device for the in-cylinder injection type engine 1 is embodied. However, the type of the engine to be applied is not limited to this, and for example, a type in which fuel is injected into a normal intake pipe. You may apply to the engine of.

In the above embodiment, the vane type variable valve timing mechanism 8 is provided. However, if the phase of the camshafts 3a and 3b with respect to the crankshaft 6 can be changed,
The format is not limited. Therefore, for example, a helical variable valve timing mechanism that changes the phase of the cam shafts 3a, 3b with respect to the timing pulleys 4a, 4b by shifting the helical gear in the axial direction of the cam shafts 3a, 3b may be provided.

Further, in the above embodiment, the variable valve timing mechanism 8 is provided on the intake side to adjust the opening / closing timing of the intake valve 7a. However, the target for adjusting the opening / closing timing may be the exhaust side, or Both air intake and exhaust may be used. Further, in the above-described embodiment, the learning process is performed by controlling the phase angle to the most retarded position. However, the learning process may be performed after controlling the phase angle to the most advanced position.

[0033]

As described above, according to the variable valve timing control apparatus for an engine of the present invention, it is possible to prevent the fuel consumption from being deteriorated due to the increase in the load on the oil pump, and to execute the phase angle learning process. it can.

[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 of an embodiment.

FIG. 2 is a flowchart illustrating a phase angle learning routine executed by an ECU.

FIG. 3 is a flowchart illustrating a phase angle learning routine executed by an ECU.

FIG. 4 is a time chart showing a state of generation of a crank angle pulse and a cam angle pulse.

[Explanation of symbols]

Reference Signs List 1 engine 3a intake camshaft 6 crankshaft 8 variable valve timing mechanism 9 oil pump 21 ECU (fuel cut means, phase angle control means, learning means)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 43/00 301 F02D 43/00 301Z 45/00 340 45/00 340D (72) Inventor Kazuhiro Ipponi Tokyo 3-33-8 Shiba, Minato-ku, Tokyo F-term in Mitsubishi Motors Corporation (Reference) 3G084 BA13 BA23 CA06 DA02 DA04 EA05 EB08 EB16 EB20 EC02 FA10 FA17 FA20 FA38 FA39 3G092 AA01 AA06 AA11 AB02 BB10 DA01 DA02 DA08 DC03 DE01Y EA15 EA22 EA25 EB05 EC05 EC06 EC10 FA24 GA15 GB08 HA06Z HA13X HA13Z HB02X HB02Z 3G301 HA01 HA04 HA19 JA02 KA16 LA01 LA07 LB04 LB13 MA11 MA24 NA07 NA09 NC02 ND22 ND25 ND45 NE11 NE12 NE17 NE19 PA11Z PEBZAPE03A08

Claims (1)

[Claims] A variable valve timing mechanism for continuously changing a valve timing by changing a rotation phase of a camshaft with respect to a crankshaft based on a hydraulic pressure of a pump driven by the engine; Fuel cut means for stopping the supply of fuel to the fuel cut means, phase angle control means for driving the variable valve timing mechanism to control the camshaft to the most retarded position or the most advanced position when the fuel cut means is operated, When the camshaft is at the most retarded position or the most advanced position by the phase angle control means, the camshaft and the crankshaft are compared by comparing the rotational phase difference of the camshaft with respect to the crankshaft with a predetermined reference value. A variable valve timing control device for an engine, comprising: learning means for learning a rotational phase difference from a shaft.