JP2007198236A - Reference position learning device for movable member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent drop of learning accuracy due to deformation of a sensor mounting part when sensor output corresponding to a stopper position defining the minimum lift position in a variable valve gear continuously changing lift of an engine valve by driving and rotating a control shaft. <P>SOLUTION: When a learning condition of the minimum lift position is satisfied, inertia force at a time of butting on a stopper is reduced to prevent deformation of the sensor mounting part by gradually changing target lift toward the minimum lift and changing angle of the control shaft to make the target lift follow actual lift. When the control shaft rotates to angles nearly equivalent to the maximum lift and sensor output is stable, sensor output at that time is learned as output equivalent to the minimum lift position. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a movable member reference position learning device that learns a reference position of a movable member that is moved by an actuator, and more particularly, to a reference position learning device that is suitable for a variable valve mechanism that varies an opening characteristic of an engine valve.

In Patent Document 1, in a variable valve mechanism that continuously varies the valve lift amount and operating angle of an engine valve by rotating a control shaft with an actuator, the valve lift amount and operation during deceleration fuel cut are disclosed. A device that controls the actuator so that the angle becomes the minimum value, and learns the output of the sensor that detects the angular position of the control shaft when it is determined that the valve lift amount / operating angle is the minimum value Is disclosed.
JP 2005-188286 A

By the way, in learning of the minimum lift position, the control shaft is rotated toward the stopper that determines the minimum lift position, and the sensor output in the state where the stopper is in contact is learned.
However, due to the inertial force according to the angular velocity when the control shaft is rotated toward the stopper, the sensor mounting part bends when the stopper hits, causing a deviation in the sensor output, and learning the minimum lift position. There was a problem that the accuracy decreased.

  The present invention has been made in view of the above problems, and an object of the present invention is to suppress a decrease in learning accuracy due to bending of a sensor mounting portion when learning a stopper abutting position.

Therefore, the invention according to claim 1 includes a sensor that outputs a signal according to the position of the movable member that is moved by the actuator, in order to learn the output of the sensor at a reference position where the movement of the movable member is regulated by the stopper. When operating the actuator to move the movable member toward the reference position, the operation speed of the movable member is set to a predetermined speed or less.
According to this configuration, in order to learn the reference position, when the movable member is moved toward the abutting position (reference position) of the stopper by operating the actuator, the moving speed of the movable member is set to a predetermined speed or less.

Therefore, the inertial force when the movable member moves toward the stopper's abutting position can be reduced, and the bending of the sensor mounting portion when the movable member hits the stopper can be prevented, thereby preventing the learning accuracy from being lowered due to the bending. it can.
The invention described in claim 2 is characterized in that the operation speed of the movable member is set to a predetermined speed or less by limiting the change in the target position of the movable member.

According to this configuration, when the movable member is moved from the position other than the reference position to the reference position and the movable member is moved toward the reference position, the change of the target position is limited, so that the target position becomes the reference position. The speed that changes to the position is decreased, and the speed at which the movable member moves toward the reference position is set to a predetermined speed or less.
Therefore, by operating the actuator based on the target position, the operation speed of the movable member is slowed down, and it is possible to prevent the sensor mounting portion from being bent when it hits the stopper.

The invention according to claim 3 is characterized in that the operation amount of the actuator is feed-forward controlled so that the operation speed of the movable member is lower than a predetermined speed.
According to this configuration, the operation speed of the movable member when moving toward the reference position is set to a predetermined speed or less by feedforward control of the operation amount of the actuator.
Therefore, the feedforward control of the operation amount of the actuator can reduce the operation speed of the movable member and prevent the sensor attachment portion from being bent when it hits the stopper.

Embodiments of the present invention will be described below.
FIG. 1 is a system configuration diagram of a vehicle engine in the embodiment.
In FIG. 1, an intake pipe 102 of an engine (gasoline internal combustion engine) 101 is provided with an electronic control throttle 104 that opens and closes a throttle valve 103 b by a throttle motor 103 a, and the electronic control throttle 104 and the intake valve 105 are interposed therebetween. Then, air is sucked into the combustion chamber 106.

Further, an electromagnetic fuel injection valve 131 is provided in the intake port 130 upstream of the intake valve 105 of each cylinder, and the fuel injection valve 131 is an injection pulse of an injection pulse signal sent from an engine control unit 114 described later. An amount of fuel (gasoline) proportional to the width (valve opening time) is injected.
The air-fuel mixture formed in the combustion chamber 106 is ignited and burned by spark ignition by a spark plug (not shown).

The combustion exhaust in the combustion chamber 106 is discharged through the exhaust valve 107, purified by the front catalyst 108 and the rear catalyst 109, and then released into the atmosphere.
The exhaust valve 107 is driven to open and close by a cam 111 provided on the exhaust camshaft 110 while maintaining a constant valve lift, valve operating angle, and valve timing.
On the other hand, on the intake valve 105 side, a variable valve event and lift (VEL) mechanism 112 and a variable valve timing control (VTC) mechanism 113 are provided as variable valve mechanisms that vary the opening characteristics of the intake valve 105.

The VEL mechanism 112 is a mechanism that continuously varies the valve lift amount of the intake valve 105 together with the operating angle. The VTC mechanism 113 changes the rotation phase of the intake side drive shaft with respect to the crankshaft, thereby changing the intake valve 105. This is a mechanism for continuously varying the center phase of the valve operating angle.
As the VTC mechanism 113, for example, a vane supported by the intake side drive shaft is included in a casing supported by a cam sprocket, so that an advance hydraulic chamber and a retard hydraulic chamber are provided on both sides of the vane. By changing the relative angle of the vane with respect to the cam sprocket and changing the rotation phase of the intake side drive shaft with respect to the crankshaft by controlling the supply and discharge of hydraulic pressure to the advance side hydraulic chamber and the retard side hydraulic chamber Use a mechanism.

  The engine control unit 114 incorporating the microcomputer sets the fuel injection amount, the ignition timing, the target intake air amount, and the target intake negative pressure by arithmetic processing according to a program stored in advance, and fuel injection based on these. Control signals are output to the valve 131, the power transistor for the ignition coil, the electronic control throttle 104, the VEL mechanism 112, and the VTC mechanism 113.

In this embodiment, the electronic control throttle 104 is provided mainly for generating intake negative pressure, and the intake air amount of the engine 101 is changed by changing the opening characteristics of the intake valve 105 by the VEL mechanism 112 and the VTC mechanism 113. Be controlled.
The engine control unit 114 includes an air flow meter 115 for detecting the intake air amount of the engine 101, an accelerator pedal sensor 116 for detecting the depression amount (opening degree) of an accelerator pedal operated by a vehicle driver, and a reference for the crankshaft 120. A crank angle sensor 117 that outputs a crank angle signal for each rotational position, a throttle sensor 118 that detects the opening TVO of the throttle valve 103b, a water temperature sensor 119 that detects the cooling water temperature of the engine 101, and a reference for an intake drive shaft 3 to be described later A cam sensor 132 that outputs a cam signal for each rotational position and a detection signal from an intake pressure sensor 133 that detects an intake manifold pressure (intake pressure) downstream of the throttle valve 103b and upstream of the intake valve 105 are input.

FIG. 2 is a perspective view showing the structure of the VEL mechanism 112.
In the engine 101 of the embodiment, a pair of intake valves 105 are provided in each cylinder, and an intake drive shaft 3 that is rotationally driven by the crankshaft 120 rotates along the cylinder row direction above the intake valves 105. Supported as possible.
A swing cam 4 that contacts the valve lifter 105a of the intake valve 105 and opens and closes the intake valve 105 is fitted on the intake drive shaft 3 so as to be relatively rotatable.

A VEL mechanism 112 is provided between the intake drive shaft 3 and the swing cam 4 for continuously changing the operating angle and valve lift amount of the intake valve 105.
A VTC mechanism 113 that continuously changes the center phase of the operating angle of the intake valve 105 by changing the rotational phase of the intake drive shaft 3 with respect to the crankshaft 120 is provided at one end of the intake drive shaft 3. It is arranged.

  As shown in FIGS. 2 and 3, the VEL mechanism 112 includes a circular drive cam 11 that is eccentrically fixed to the intake drive shaft 3 and a ring-shaped link that is externally fitted to the drive cam 11 so as to be relatively rotatable. 12, a control shaft 13 extending in the cylinder row direction substantially parallel to the intake drive shaft 3, a circular control cam 14 eccentrically fixed to the control shaft 13, and a relative rotation with the control cam 14 The rocker arm 15 has one end connected to the tip of the ring-shaped link 12 and a rod-shaped link 16 connected to the other end of the rocker arm 15 and the swing cam 4.

The control shaft 13 is rotationally driven by a motor 17 via a gear train 18, and corresponds to a preset minimum lift position by a stopper 13a provided integrally with the control shaft 13 coming into contact with the fixed side. Further rotation to the lift amount decreasing side is restricted at the angular position.
In the present embodiment, the control shaft 13 corresponds to a movable member, and the motor 17 corresponds to an actuator. Moreover, it can be set as the structure provided with the stopper which determines the maximum lift position with the stopper which determines the minimum lift position.

With the above configuration, when the intake drive shaft 3 rotates in conjunction with the crankshaft 120, the ring-shaped link 12 moves substantially in translation through the drive cam 11, and the rocker arm 15 swings around the axis of the control cam 14. Then, the swing cam 4 swings through the rod-shaped link 16 and the intake valve 105 is driven to open and close.
Further, by driving and controlling the motor 17 to change the rotation angle of the control shaft 13, the axial center position of the control cam 14 serving as the rocking center of the rocker arm 15 changes and the posture of the rocking cam 4 changes. .

As a result, the operating angle of the intake valve 105 and the valve lift amount continuously change while the central phase of the operating angle of the intake valve 105 remains substantially constant.
A detection signal from an angle sensor 133 that detects the rotation angle of the control shaft 13 is input to the engine control unit 114, and the control shaft 13 is rotated to a target angle position corresponding to a target lift amount. Based on the detection result of the angle sensor 133, the direction and magnitude of the current of the motor 17 are feedback-controlled.

In the VEL mechanism 112 of the present embodiment, since the reaction force for opening and closing the valve acts in the decreasing direction of the lift amount, a motor torque against the reaction force is always required in order to maintain the increase state of the lift amount.
The angle sensor 133 is a non-contact type rotation angle sensor. For example, as disclosed in Japanese Patent Application Laid-Open No. 2003-194580, a magnet attached to an end of the control shaft 13 and an outer peripheral surface of the magnet. It is a sensor that comprises a magnetoelectric conversion means arranged to face each other and detects a change in magnetic flux accompanying the rotation of the control shaft 13.

However, the angle sensor 133 is not limited to a non-contact type sensor, and may be a contact type angle sensor using a potentiometer, for example.
By the way, in the control of the VEL mechanism 112, the actual lift amount is detected by detecting the actual rotation angle of the control shaft 13, and the motor 17 is feedback-controlled so as to match the target lift amount.

Therefore, if there is a deviation in the correlation between the output of the angle sensor 133 and the angle of the control shaft 13, the actual lift amount (control shaft angle) is erroneously detected, and the control accuracy to the target lift amount decreases.
Therefore, in the present embodiment, the engine control unit 114 learns the detection output of the angle sensor 133 at the minimum lift position (reference position) of the control shaft 13 with which the stopper 13a contacts the fixed side, and the angle sensor 133 The correlation between the detection output and the angular position of the control shaft 13 is calibrated.

The flowchart of FIG. 4 shows the details of the minimum lift position learning by the engine control unit 114. Note that the routine shown in the flowchart of FIG. 4 is executed by interruption every predetermined time.
In the flowchart of FIG. 4, first, in step S11, it is determined whether or not a learning condition for the minimum lift position is satisfied.

The learning condition needs to be an operation condition that can forcibly minimize the lift amount of the intake valve 105. For example, the learning permission condition is that the engine is decelerated or when the engine is stopped. And
When the learning condition is satisfied, the process proceeds to step S12, where the target lift amount used for feedback control of the VEL mechanism 112 is gradually decreased and the VEL mechanism 112 is feedback-controlled based on the gradually decreased target lift amount. (See FIG. 5).

The decreasing rate of change in the target lift amount is set to a predetermined speed or less.
When the control shaft 13 is rotated toward the abutting position of the stopper 13a, if the angular velocity of the control shaft 13 is fast, the attachment portion of the angle sensor 133 (magnet) bends when the stopper 13a abuts due to the inertial force, There is a possibility of changing the sensor output.

Here, when the target lift amount is changed stepwise to the minimum lift amount based on the establishment of the learning condition, the control shaft 13 is rotated at a high angular velocity to follow this, and in a state having a large inertia force. There is a possibility that the stopper 13a will come into contact, and the mounting portion of the angle sensor 133 (magnet) will be greatly bent to greatly change the sensor output.
Therefore, the target lift amount is set so that the angular velocity of the control shaft 13 is equal to or less than the maximum allowable angular velocity (predetermined velocity) at the time of learning so that the change in sensor output exceeding the allowable level does not occur due to the occurrence of bending due to the inertia force. It regulates change.

When the target lift amount is gradually decreased and decreased toward the contact position of the stopper 13a as described above, in step S13, it is determined whether or not the detection output of the angle sensor 133 is substantially constant for a predetermined time or more. Thus, it is determined whether or not the stopper 13a is in contact and the rotation of the control shaft 13 is stopped.
If the change in the detection output of the angle sensor 133 does not stop, it is determined that the stopper 13a has not been hit yet, the learning process in step S14 is not performed, and the decrease in the target lift amount is continued.

On the other hand, if it is determined in step S13 that the detection output of the angle sensor 133 is substantially constant for a predetermined time or more, it is determined that the stopper 13a is actually abutted and the rotation of the control shaft 13 is stopped. Then, the process proceeds to step S14.
In step S14, the detection output of the angle sensor 133 at that time is learned as an output corresponding to the minimum lift position, and the correlation between the sensor output and the lift amount (the angle of the control shaft 13) is rewritten. Based on the correlation, the sensor output is converted into lift amount (angle of the control shaft 13) data and used for feedback control.

When rewriting the correlation between the sensor output and the lift amount (the angle of the control shaft 13), for example, the overall correlation can be shifted by the amount of deviation of the sensor output corresponding to the minimum lift amount. Further, instead of rewriting the correlation between the sensor output and the lift amount, a correction value for correcting the sensor output or the lift amount (angle of the control shaft 13) can be learned.
According to the above embodiment, in order to learn the minimum lift position, when the control shaft 13 is rotated to the position where the stopper 13a hits, the change in the target lift amount (target angle of the control shaft 13) is set to a predetermined speed or less. The angular velocity (operation speed) of the control shaft 13 is lowered.

Accordingly, the inertial force when the control shaft 13 rotates toward the minimum lift position can be reduced. As a result, when the stopper 13a hits, the attachment portion of the angle sensor 133 bends and the sensor output changes. And the learning accuracy of the minimum lift position can be maintained.
When the stopper is also provided on the maximum lift side, the sensor output at the maximum lift position can be learned in the same manner as in the above embodiment by changing the direction of change of the target lift amount.

Further, the target lift amount may be gradually changed toward the minimum lift position or the maximum lift position after the target lift amount is changed stepwise to the minimum lift position or the vicinity of the maximum lift position where the stopper 13a abuts. In addition, the changing speed of the target lift amount can be gradually reduced.
Further, by changing the gain in the feedback control based on the target lift amount, the angular velocity when the control shaft 13 rotates toward the position where the stopper 13a abuts can be reduced.

The flowchart of FIG. 6 shows a second embodiment of minimum lift position learning by the engine control unit 114.
In the second embodiment, the control method for rotating the control shaft 13 toward the minimum lift position (reference position) is different from the first embodiment shown in the flowchart of FIG.
In the flowchart of FIG. 6, in step S21, it is determined whether the learning condition is satisfied, as in step S11.

If the learning condition is satisfied, the process proceeds to step S22.
In step S22, feed forward control is performed to reduce the operation amount (current) of the motor 17 which is an actuator for rotating the control shaft 13 of the VEL mechanism 112 by a predetermined amount every predetermined period, and toward the minimum lift position. The control shaft 13 is rotated.
As described above, in the VEL mechanism 112 of the present embodiment, the valve opening / closing reaction force works in the direction of decreasing the lift amount. Therefore, in order to maintain the lift amount increasing state, the motor torque against the reaction force is increased. Required.

Accordingly, when the current of the motor 17 (current in the direction of generating the motor torque acting on the lift increasing side) is gradually decreased, the valve reaction force becomes dominant with respect to the motor torque, and the lift amount decreases. Thus, the control shaft 13 is rotated.
The period and step change amount when changing the operation amount (current) of the motor 17 are controlled so that the inertia force causes a deflection when the stopper 13a hits, and the sensor output does not change beyond an allowable level. The angular velocity of the shaft 13 is set to be equal to or less than the maximum allowable angular velocity (predetermined velocity) at the time of learning.

In step S23, it is determined whether or not the detection output of the angle sensor 133 is substantially constant for a predetermined time or more, thereby determining whether or not the stopper 13a is in contact and the rotation of the control shaft 13 is stopped.
If it is determined in step S23 that the detection output of the angle sensor 133 is substantially constant for a predetermined time or more, it is determined that the stopper 13a is actually hitting and the rotation of the control shaft 13 is stopped. Proceed to S24.

In step S24, the detection output of the angle sensor 133 at that time is learned as an output corresponding to the minimum lift position, and the correlation between the sensor output and the lift amount (angle of the control shaft 13) is rewritten, or the sensor output or A correction value for correcting the lift amount (angle of the control shaft 13) is learned.
In the above embodiment, the control shaft 13 of the VEL mechanism 112 as the movable member is configured to learn the position where the control shaft 13 abuts on the stopper. However, the movable member is not limited to the control shaft 13, and the movable member The present invention may be configured to move linearly, and it is apparent that the present invention can be widely applied to a system including a movable member that is moved by an actuator and whose movement is restricted by a stopper, and a sensor that detects the position of the movable member. It is.

Here, technical ideas other than the claims that can be grasped from the above embodiment will be described together with effects.
(A) In the movable member reference position learning device according to any one of claims 1 to 3,
The movable member is
It is included in a variable valve mechanism that varies the opening characteristic of an engine valve of an internal combustion engine, and is a control shaft that continuously changes the opening characteristic by changing its rotation angle with an actuator.
A movable member reference position learning device comprising an angle sensor for detecting a rotation angle of the control shaft as the sensor.

According to this configuration, the sensor output at the position where the rotation of the control shaft is restricted by the stopper can be learned with high accuracy by slowing the angular velocity when the control shaft rotates to the reference position. The control accuracy of the valve opening characteristics can be improved.
(B) In the movable member reference position learning device according to claim (a),
The variable valve mechanism is a mechanism that makes at least the lift amount of the engine valve variable,
The rotation of the control shaft is regulated by a stopper on the minimum lift amount side,
A reference position learning device for a movable member, wherein the sensor output at the minimum lift amount position is learned.

According to such a configuration, by learning the sensor output corresponding to the minimum lift position of the engine valve, the detection accuracy of the rotation angle of the control shaft, in other words, the lift amount of the engine valve, is improved based on the minimum lift position. .
(C) In the movable member reference position learning device according to any one of claims 1 to 3,
A movable member reference position learning device, wherein when the output of the sensor is substantially constant for a predetermined time or more, it is determined that the movable member is positioned at a reference position regulated by a stopper.

  According to such a configuration, it is possible to accurately learn the sensor output at the position where the movable member is regulated by the stopper by accurately determining the abutting state of the stopper from the state where the output of the sensor is constant.

The system diagram of the vehicle engine in the embodiment. The perspective view which shows the detail of the VEL mechanism in embodiment. Sectional drawing which shows the operating angle change mechanism of the said VEL mechanism. The flowchart which shows 1st Embodiment of the minimum lift position learning. The time chart which shows the change characteristic of the target angle and real angle of the control axis in the said 1st Embodiment. The flowchart which shows 2nd Embodiment of the minimum lift position learning.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 3 ... Intake drive shaft, 13 ... Control shaft, 13a ... Stopper, 17 ... Motor, 101 ... Engine, 104 ... Electronically controlled throttle, 105 ... Intake valve, 112 ... VEL mechanism, 113 ... VTC mechanism, 114 ... Engine control unit, 116 ... Accelerator pedal sensor, 117 ... Crank angle sensor, 120 ... Crankshaft, 132 ... Cam sensor, 133 ... Angle sensor

Claims (3)

A sensor that outputs a signal corresponding to the position of the movable member that is moved by the actuator;
A movable member reference position learning device that learns the output of the sensor at a reference position where movement of the movable member is regulated by a stopper,
In order to learn the output of the sensor at the reference position, when the movable member is moved toward the reference position by operating the actuator, the operation speed of the movable member is set to a predetermined speed or less. A reference position learning device for a movable member. The reference position learning device for a movable member according to claim 1, wherein an operation speed of the movable member is set to a predetermined speed or less by restricting a change in a target position of the movable member. The reference position learning device for a movable member according to claim 1, wherein the operation amount of the actuator is feedforward controlled so that the operation speed of the movable member is lower than a predetermined speed.

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