JP2005188286A - Valve lift control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To excellently perform learning processing with a lift quantity as a minimum value VLmin, without impairing combustion stability, while widely securing a lift operable range by sufficiently reducing the minimum value VLmin of a valve lift quantity. <P>SOLUTION: This valve lift control device has a lift variable mechanism 1 capable of varying the valve lift quantity of an intake valve, and performs the learning processing of the valve lift quantity (Step 7), by operating the lift variable mechanism so that the valve lift quantity becomes the minimum value VLmin, when realizing a predetermined learning permitting condition corresponding to the combustion stability (Step 2), in vehicle deceleration causing a fuel cut (Step 1). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a valve lift control device for an internal combustion engine provided with a variable lift mechanism that varies at least one of a valve lift amount and an operating angle of an intake valve or an exhaust valve.

  As a mechanism for changing the valve timing of the intake valve of the internal combustion engine, a phase variable mechanism for changing the phase of the camshaft with respect to the crank angle is known. Patent Document 1 discloses a technique for performing the phase learning process with the phase of the camshaft as the most retarded angle or the most advanced angle during vehicle deceleration accompanied by a fuel cut. By performing the learning process during the fuel cut in this way, the fuel consumption is not increased along with the learning process.

Patent Document 2 previously proposed by the present applicant discloses a variable lift / operating angle mechanism capable of continuously changing both the valve lift amount and the operating angle as a variable lift mechanism. By variably controlling the valve lift amount according to the engine operating state by such a variable lift mechanism, it is possible to improve both fuel consumption and output.
JP 2002-180856 A JP-A-11-107725

  In such a variable lift mechanism, a valve lift amount learning process and a correction process are preferably performed so as to absorb deterioration with time and various errors. This learning process is performed by operating the lift variable mechanism to the mechanical minimum or maximum value of the lift variable range, preferably the minimum value with low reaction force from the valve operating system and low loss. For example, in the case where an angle sensor, a lift sensor, or the like for detecting the valve lift amount is provided and the closed loop control is performed based on the output of the sensor, the control that can use the mechanical minimum value of the valve lift amount as the control target value. It is set to a value (for example, about 1 mm) lower than the minimum value (for example, about 1.5 mm), and a learning value is calculated with respect to the reference position of the sensor corresponding to this mechanical lift minimum value.

  However, when the operable range of the valve lift amount is widened so that the valve lift amount can be widely changed according to the engine operating state, the minimum lift amount is, for example, the minimum lift of about 1 mm, and the intake air amount is Since it becomes extremely small, stable combustion of the internal combustion mechanism may not be established. Note that even if the phase is changed by the above-described variable phase mechanism, the intake air amount does not change so that combustion of the internal combustion engine is no longer established as in the variable lift mechanism. Even when the vehicle is decelerated with fuel cut, if the valve lift is set to the mechanical minimum value, there is a possibility that the combustion stability after release of the fuel cut cannot be ensured.

  The present invention has been made in view of such a problem, and after ensuring a wide operable range of the valve lift amount or the operating angle by sufficiently reducing the minimum value of the valve lift amount or the operating angle, It is an object of the present invention to provide a novel valve lift control device for an internal combustion engine that can satisfactorily perform learning processing or correction processing of a valve lift amount or operating angle operated by a variable lift mechanism without impairing combustion stability. Yes.

  A variable lift mechanism that varies at least one of the valve lift amount or operating angle of the intake valve or exhaust valve, fuel cut means for cutting the fuel of the internal combustion engine during vehicle deceleration, and predetermined learning corresponding to combustion stability Learning permission condition determining means for determining whether the permission condition is satisfied. When the fuel cut is in progress and the learning permission condition is satisfied, the lift variable mechanism is operated so that the valve lift amount or the operating angle becomes the minimum value. Perform correction processing.

  According to the present invention, the valve lift amount is operated by operating the variable lift mechanism so that the valve lift amount or the operating angle becomes the minimum value only during fuel cut and when the learning permission condition is satisfied. Alternatively, an operation angle learning process or a correction process is performed. In other words, even when the fuel is being cut, if the learning permission condition is not satisfied, the learning / correction process for minimizing the valve lift amount or the operating angle is prohibited. Therefore, by making the minimum value of the valve lift or operating angle mechanically small enough to ensure a substantially wide range of lift operation, good learning / correction processing without compromising combustion stability Can be done.

  Hereinafter, an embodiment in which a valve lift control device for an internal combustion engine according to the present invention is applied to an intake valve of a spark ignition type gasoline internal combustion engine for an automobile will be described.

  FIG. 1 is an explanatory diagram showing a variable valve mechanism that changes the operating characteristics of an intake valve of an internal combustion engine. Each cylinder is provided with a pair of intake valves 11, and a drive shaft 2 that rotates in conjunction with the crankshaft is disposed above the valve lifter 10 of the intake valves 11. The variable valve mechanism includes a lift / operating angle variable mechanism (VEL) 1 as a variable lift mechanism capable of continuously and continuously changing the valve lift amount and operating angle of the intake valve, and the operating angle of the intake valve. And a phase variable mechanism 21 for advancing or retarding the center phase with respect to the crank angle.

  The lift / operating angle variable mechanism 1 has been previously proposed by the applicant of the present invention. However, since it has been publicly known, for example, in Japanese Patent Application Laid-Open No. 11-107725, only the outline thereof will be described. The variable lift / operating angle mechanism 1 includes a control shaft 12, a control eccentric shaft portion 18 provided eccentric to the control shaft 12, a rocker arm 6 fitted to the control eccentric shaft portion 18 so as to be swingable, and a drive. A drive eccentric shaft portion 3 provided eccentric to the shaft 2, a swing cam 9 slidably fitted to the drive shaft 2, and a ring-shaped first connecting the drive eccentric shaft portion 3 and one end of the rocker arm 6. One link 4 and a second link 8 that links the other end of the rocker arm 6 and the tip of the swing cam 9 are provided. Similarly to the drive shaft 2, the control shaft 12 is rotatably supported by an engine fixing element such as a cylinder block, and the rotation angle position is changed and held by the operating angle actuator 13 via the worm gear 15. The first link 4 is rotatably fitted to the circular outer periphery of the drive eccentric shaft portion 3. One end of the rocker arm 6 and the tip of the first link 4 are rotatably connected by a first connecting pin 5. The other end of the rocker arm 6 and one end of the second link 8 are rotatably connected by a second connecting pin 7. The other end of the second link 8 and the tip of the swing cam 9 are rotatably connected by a third connecting pin 17.

  When the drive shaft 2 rotates in conjunction with the crankshaft, the rocker arm 6 swings through the drive eccentric shaft portion 3 and the first link 4, and the rocking motion of the rocker arm 6 swings through the second link 8. The oscillation cam 9 is oscillated by being transmitted to the cam 9. When the swing cam 9 that swings comes into contact with and presses the valve lifter 10 provided above the intake valve 11, the intake valve 11 opens and closes against the valve spring reaction force. When the rotational position of the control shaft 12 is changed by the operating angle actuator 13, the center position of the control eccentric shaft portion 18 that is the swing fulcrum of the rocker arm 6 changes. As a result, the swing range of the swing cam 9 is changed, and the valve lift amount of the intake valve 11 (with the center phase of the operating angle of the intake valve 11 with respect to the crank angle (rotational position of the crankshaft) remains substantially constant. Both the maximum lift) and the operating angle change continuously and steplessly. The control state of the lift / operating angle variable mechanism 1 is detected by a control shaft sensor (lift sensor) 14 that is an angle sensor that responds to the rotational position of the control shaft 12.

  Such a variable lift / operating angle mechanism 1 has the following specific effects in addition to being able to continuously change both the valve lift amount and the operating angle of the intake valve 11. Since many of the connecting parts of each link element are in surface contact, lubrication is easy and reliability and durability are excellent. Since there is no need to use an urging means such as a return spring, the structure is simple, the loss is small, and the reliability and durability are excellent. The drive shaft 2 and the swing cam 9 can be arranged at substantially the same positions as the cam shaft and fixed cam of the existing direct acting valve system, and the layout is greatly increased compared to the internal combustion engine of the direct acting valve system. It can be easily applied without changing.

  The phase variable mechanism 21 includes a sprocket 22 provided at the front end of the drive shaft 2 and a phase actuator 23 that relatively rotates the sprocket 22 and the drive shaft 2 within a predetermined angle range. . The sprocket 22 rotates around an axis in synchronization with the crankshaft via a timing chain or timing belt (not shown). The phase actuator 23 is composed of, for example, a rotary actuator such as a hydraulic type or an electromagnetic type, and operates according to a control signal from an engine control unit 19 described later. By the action of the phase actuator 23, the sprocket 22 and the drive shaft 2 rotate relatively, and the center phase (opening / closing timing) of the operating angle of the intake valve 11 with respect to the crank angle is retarded / advanced. That is, the lift characteristic curve itself does not change, and the whole advances or retards. This change can also be obtained continuously. The control state of the phase variable mechanism 21 is detected by the drive shaft sensor 16 that responds to the rotational position of the drive shaft 2.

  FIG. 2 is a system configuration diagram of the intake system of the internal combustion engine. An electronically controlled throttle (valve) 27 that opens and closes the intake passage 25 is provided upstream of the collector 26 in the intake passage 25. In this internal combustion engine, the intake air supplied to the combustion chamber 28 of the cylinder is controlled by combining the throttle 27, the lift / operating angle variable mechanism 1 and the phase variable mechanism 21 described above. Yes. That is, the engine control unit 19 detects the vehicle speed detected by the vehicle speed sensor 30, the gear ratio of the continuously variable transmission 31, the accelerator signal detected by the accelerator opening sensor 32, and the engine speed detected and calculated by the rotational speed sensor 33. ON of the brake switch 38 that detects the speed (the number of revolutions), the engine coolant temperature detected by the water temperature sensor 36, the intake pressure of the intake passage 25 in the intake manifold detected by the pressure sensor 37, and whether the brake pedal is depressed. Based on input signals representing various engine operating conditions such as the / OFF signal, the rotational position of the drive shaft 2 detected by the drive shaft sensor 16, and the rotational position of the control shaft 12 detected by the control shaft sensor 14. 27, output a command signal to the operating angle actuator 13 and the phase actuator 23, Torr 27, controls the operation of the lift operating angle varying mechanism 1 and variable phase mechanism 21. The control of the lift / working angle variable mechanism 1 and the phase variable mechanism 21 is not limited to closed loop control based on the detection signals of the sensors 14 and 16, but may be simply open loop control according to the operating conditions. As is well known, the engine control unit 19 outputs a control signal to the spark plug 34 and the fuel injector 35 based on the engine operating state, and controls the ignition timing, the fuel injection amount, and the fuel injection timing. The continuously variable transmission 31 can change the gear ratio continuously and continuously, and a belt type or a toroidal type is known, and a description thereof is omitted here.

  Next, learning control of the valve lift amount according to one embodiment of the present invention will be described with reference to FIGS. In this embodiment, the variable lift mechanism 1 is operated so that the valve lift amount becomes the mechanical minimum value only when the vehicle is decelerated with fuel cut and a predetermined learning permission condition is satisfied. A learning process of the valve lift detected by the control axis sensor 14 is performed. 3 and 4 are flowcharts showing a control routine that is repeatedly executed at predetermined intervals by the engine control unit 19, and FIG. 5 is a time chart at the time of deceleration fuel cut when the learning control according to the present embodiment is applied. It is.

  Referring to FIG. 3, in step (denoted as S in the figure) 1, it is determined whether the vehicle is decelerating with a fuel cut, that is, whether the fuel is being decelerated. For example, as shown in FIG. 5, when the accelerator opening becomes 0 (zero) while the vehicle speed is higher than 0, the fuel cut flag FCUT is set to 1 after a predetermined period. As a result, the fuel cut is executed by another routine (not shown), and the fuel supply by the fuel injector 35 is stopped.

  In step 2, it is determined whether the learning permission flag FGS is 0 (zero). The learning permission flag FGS is set to 1 when a predetermined learning permission condition is satisfied by a determination routine of FIG. 4 described later, and is reset to 0 when the learning permission condition is not satisfied.

  In step 3, it is determined whether the learning end flag FGE is set to 1. This learning end flag FGE is set to 1 when the learning process is executed in step 7 to be described later. Further, the learning end flag FGE is reset to 0 when the driving state other than the deceleration fuel cut is entered so that the learning process is not repeatedly performed during one deceleration fuel cut operation (step 8).

  In step 4, it is determined whether or not the control axis sensor 14 as the lift amount detecting means is abnormal. This abnormality determination is performed based on, for example, a comparison between a signal output from the control axis sensor 14 and a predetermined value.

  The learning permission condition is satisfied during the deceleration fuel cut (FGS = 1), the learning process is not yet performed during the current fuel cut (FGE = 0), and the lift sensor (control axis sensor) Only when 14 is normal, the learning process of steps 5 to 7 is performed. In other cases, the process proceeds to Step 9 where the valve lift amount is operated and controlled toward the normal target value. In this embodiment, in order to secure a wide operable range of the valve lift amount, the mechanical minimum value VLmin is the minimum value of the control range used as the actual control target value, that is, the control minimum value VLs (for example, 1.5 mm), for example, a minimal lift of about 1 mm where the intake air amount is extremely small or substantially 0 (zero). In other words, as shown in FIG. 5, in consideration of combustion stability, the target value during the normal fuel cut without performing the learning process is set to the above-described value VLs that is higher than the mechanical minimum value VLmin.

  In step 5, a command signal corresponding to the minimum value VLmin is output to the operating angle actuator 23, and the lift / operating angle variable mechanism 1 is operated toward the minimum value VLmin. In step 6, it is determined whether the valve lift amount has reached the minimum value VLmin. This determination is made based on, for example, the amount of intake air detected by an air flow meter or the like, or is simply determined based on whether a predetermined period has elapsed. T1 in FIG. 5 corresponds to the timing at which the determination in step 6 is switched to affirmative and the process proceeds to step 7.

  In step 7, a valve lift amount learning process is executed. That is, the detection value for the minimum position, which is the reference position of the lift sensor 14, is calculated by comparing the detection signal of the control axis sensor 14 that is the lift sensor with the reference value corresponding to the preset minimum value VLmin. And store it in the backup memory. This learning value is reflected on, for example, subsequent detection values of the control axis sensor 14.

  FIG. 4 is a routine for determining the plurality of (eight in this example) learning permission conditions described above. In step 11, it is determined whether the brake switch 38 is OFF, that is, whether the brake pedal is released. In step 12, it is determined whether the engine speed is larger than a predetermined value (for example, 1200 rpm). In step 13, it is determined whether the cooling water temperature is higher than a predetermined value (for example, 70 ° C.). In step 14, it is determined whether the vehicle speed is greater than a predetermined value (for example, 20 km / h). In step 15, it is determined whether the reduction speed of the engine speed (engine speed) is smaller than a predetermined value (for example, 200 rpm / 100 ms). In step 16, it is determined whether the transmission ratio of the transmission 31 is smaller than a predetermined value (for example, 1.2). In step 17, it is determined whether the intake pressure, that is, the intake depth is lower than a predetermined value (for example, -65 kpa). In step 18, it is determined whether the center phase of the operating angle of the intake valve operated by the phase variable mechanism 21 is the most retarded phase.

  When all of the learning permission conditions in the above steps 11 to 18 are satisfied, there is no risk of engine stall (misfire) even if the valve lift amount is set to the minimum value VLmin in accordance with the learning process, and the intended combustion stability is reduced. If it is determined that the learning permission condition can be secured, the process proceeds to step 19 where the learning permission flag FGS indicating that the learning permission condition is satisfied is set to 1. If any of the learning permission conditions in steps 11 to 18 is not satisfied, the process proceeds to step 20, and if the lift amount is set to the minimum value VLmin in accordance with the learning process, it is determined that the combustion stability after the release of the fuel cut cannot be secured well Then, the learning flag FGS is reset to 0.

  According to the present embodiment as described above, the valve lift mechanism 1 is operated so that the valve lift amount becomes the minimum value VLmin only when the fuel is cut and the learning permission condition is satisfied, and the valve lift The amount learning process is performed. In other words, even when the fuel is being cut, if the learning permission condition is not satisfied, the learning process for setting the valve lift amount to the minimum value VLmin is prohibited. Accordingly, the minimum value VLmin of the valve lift amount is set to a minimum value of, for example, about 1 mm, and the valve lift amount learning process is satisfactorily performed without sacrificing combustion stability while ensuring a sufficiently wide range of valve lift operation. Can do.

  As described above, the present invention has been described based on specific examples. However, the present invention is not limited to the above-described examples, and the following (A) to (C) can be made without departing from the spirit of the present invention. ) And various modifications and changes.

  (A) In the above embodiment, the value calculated in step 7 is stored in the backup memory as a learning value. However, this value may be stored in the temporary memory as a correction value.

  (B) In the above embodiment, the angle sensor 14 for detecting the angular position of the control shaft is used as the lift sensor for detecting the valve lift amount. However, the present invention is not limited to this. It may be a sensor to detect.

  (C) The lift sensor may be omitted mainly for the sake of simplification, and the lift variable mechanism may be subjected to open loop control. In this case, the learning value (or correction value) calculated in step 7 may be reflected in the command value of the operating angle actuator 13.

  (D) Although the present invention is applied to the intake valve in the above embodiment, it can also be applied to the exhaust valve. In the above embodiment, the learning / correction control is performed on the valve lift amount. However, the learning / correction control may be performed on the operating angle.

  The technical ideas that can be grasped from the above explanation are listed below.

  (1) A variable lift mechanism 1 that makes at least one of the valve lift amount or the operating angle of the intake valve 11 or the exhaust valve variable, fuel cut means for cutting fuel in the internal combustion engine during vehicle deceleration, and combustion stability Learning permission condition determination means (steps 11 to 18) for determining whether or not a corresponding predetermined learning permission condition is satisfied; and when the fuel permission is cut and the learning permission condition is satisfied, the valve lift amount or The variable lift mechanism 1 is operated so that the operating angle becomes the minimum value VLmin (step 5), and learning means (step 7) for performing learning processing or correction processing of the valve lift amount or operating angle is provided.

  (2) During the fuel cut and when the learning permission condition is not satisfied, the lift variable mechanism 1 is operated so that the valve lift amount or the operating angle becomes a value VLs larger than the minimum value VLmin. (Step 9, FIG. 5).

  (3) The variable lift mechanism 1 includes a control shaft 12, an actuator 13 that changes and holds the rotational position of the control shaft 12, a control eccentric shaft portion 18 that is provided eccentric to the control shaft 12, and the control eccentricity. A rocker arm 6 slidably fitted to the shaft 18, a swing cam 9 slidably fitted to the drive shaft 2 that rotates in conjunction with the crankshaft, and opens and closes the intake valve 11 or the exhaust valve; A drive eccentric shaft portion 3 provided eccentric to the drive shaft 2, a first link 4 linking the drive eccentric shaft portion 3 and one end of the rocker arm 6, the other end of the rocker arm 6, and the swing cam 9 And a second link 8 that links the tip.

(4) The learning permission condition includes at least one of the following conditions.
・ The brake switch is OFF (step 11).
The engine speed is greater than a predetermined value (step 12),
The engine coolant temperature is greater than a predetermined value (step 13),
The vehicle speed is greater than a predetermined value (step 14),
-Decreasing speed of the engine speed is smaller than a predetermined value (step 15),
The transmission gear ratio is less than a predetermined value (step 16),
The intake pressure is smaller than a predetermined value (step 17),
A phase variable mechanism 21 that varies the center phase of the intake valve operating angle with respect to the crank angle is provided, and the center phase is the most retarded angle (step 18).

  (5) It has a lift sensor (control shaft sensor 14) for detecting the valve lift amount, and the learning means performs a correction process or a learning process for the reference position of the lift sensor corresponding to the minimum value VLmin of the valve lift amount. Perform (Step 7).

  (6) When an abnormality of the lift sensor is detected, the operation of the learning means is prohibited (step 4).

The perspective view which shows the lift and the working angle variable mechanism which is an example of a variable lift mechanism. 1 is a system configuration diagram of an intake system of an internal combustion engine to which a valve lift control device according to an embodiment of the present invention is applied. The flowchart which shows the flow of the learning control which concerns on a present Example. Learning permission condition judgment routine. Time chart when the vehicle is decelerated with fuel cut.

Explanation of symbols

1. Lift / operating angle variable mechanism (lift variable mechanism)
DESCRIPTION OF SYMBOLS 2 ... Drive shaft 3 ... Drive eccentric shaft part 4 ... 1st link 6 ... Rocker arm 8 ... 2nd link 9 ... Swing cam 12 ... Control shaft 13 ... Actuation angle actuator 14 ... Control shaft sensor (lift sensor)
18 ... Control eccentric shaft part 19 ... Engine control unit 21 ... Phase variable mechanism

Claims (6)

A variable lift mechanism that varies at least one of a valve lift amount or an operating angle of the intake valve or the exhaust valve;
Fuel cutting means for cutting the fuel of the internal combustion engine during vehicle deceleration;
Learning permission condition determining means for determining whether a predetermined learning permission condition corresponding to the combustion stability is satisfied;
Learning the valve lift amount or operating angle by operating the variable lift mechanism so that the valve lift amount or operating angle becomes the minimum value during the fuel cut and when the learning permission condition is satisfied. Learning means for performing processing or correction processing;
A valve lift control device for an internal combustion engine.   2. The variable lift mechanism according to claim 1, wherein the lift variable mechanism is operated such that the valve lift amount or the operating angle is larger than a minimum value when the fuel cut is in progress and the learning permission condition is not satisfied. The valve lift control device for an internal combustion engine.   The variable lift mechanism includes a control shaft, an actuator that changes and holds the rotational position of the control shaft, a control eccentric shaft portion that is eccentrically provided on the control shaft, and a swingable fit on the control eccentric shaft portion. A rocker arm, a swinging cam that swingably engages with a drive shaft that rotates in conjunction with the crankshaft, and opens and closes an intake valve or an exhaust valve, and a drive eccentric shaft portion that is eccentrically provided on the drive shaft The first link that links the drive eccentric shaft portion and one end of the rocker arm, and the second link that links the other end of the rocker arm and the tip of the swing cam. A valve lift control device for an internal combustion engine. The valve lift control device / brake switch of the internal combustion engine according to any one of claims 1 to 3, wherein the learning permission condition includes at least one of the following conditions:
・ The engine speed is larger than the specified value.
・ The engine coolant temperature is higher than the specified value.
・ Vehicle speed is higher than the specified value.
-Decrease speed of engine rotation speed is smaller than the predetermined value,
・ The transmission gear ratio is smaller than the specified value.
・ Intake pressure is smaller than the specified value,
A phase variable mechanism that varies the center phase of the intake valve operating angle with respect to the crank angle is provided, and the center phase is the most retarded angle. A lift sensor for detecting the valve lift amount;
The valve lift control device for an internal combustion engine according to any one of claims 1 to 4, wherein the learning means performs correction processing or learning processing of a reference position of a lift sensor corresponding to the minimum value of the valve lift amount. 6. The valve lift control device for an internal combustion engine according to claim 5, wherein when the abnormality of the lift sensor is detected, the operation of the learning means is prohibited.

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