JP2003041955A - Reference position learning system for variable valve mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a degradation in detection accuracy due to output dispersion of an operating angle sensor for detecting an operating angle of a control shaft, in a variable valve mechanism for continuously varying a valve lift and a valve operating angle of an engine valve by varying the operating angle of the control shaft. SOLUTION: If any condition is met out of an off position of an ignition switch, a start-up, an engine stall and a target operating angle equal to a minimal angle (S3), the target operating angle is set smaller than the minimal operating angle (S5) to abut the control shaft in a minimal operating angle position. In the state, a mean value of outputs of the operating angle sensor is learned as an output corresponding to the minimal operating angle position (S6 to S8), and the sensor output used for detection of the operating angle is corrected according to the learning result (S9).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve mechanism for continuously changing a valve lift amount and a valve working angle of an engine valve according to a working angle of a control shaft, and a sensor corresponding to a reference position of the control shaft. A device for learning output.

[0002]

2. Description of the Related Art Conventionally, there is known a variable valve mechanism having a structure in which a valve lift amount and a valve operating angle of an intake valve / exhaust valve are continuously changed (JP 2001-012A).
262). The variable valve mechanism includes a drive shaft that rotates in synchronization with a crankshaft, a drive cam fixed to the drive shaft, a swing cam that swings to open and close an intake valve, and one end of the drive cam side. And a control shaft having a control cam for changing the attitude of the transmission mechanism, and an actuator for rotating the control shaft.

The actuator is feedback-controlled so that the actual operating angle of the control shaft detected by the operating angle sensor matches the target operating angle corresponding to the required valve opening characteristic.

[0004]

By the way, a potentiometer or the like is used as the working angle sensor. However, since the correlation between the sensor output and the actual working angle varies due to mechanical and electrical variations, the sensor output is changed. There is a possibility that the accuracy of the feedback control of the operating angle based on this may be deteriorated, and the desired valve lift amount and valve operating angle may not be accurately controlled.

The present invention has been made in view of the above problems, and the actual operating angle can be accurately detected even if the correlation between the sensor output and the actual operating angle varies. The aim is to be able to precisely control the quantity and the valve operating angle.

[0006]

Therefore, the invention according to claim 1 is to open and close an intake valve by swinging a drive shaft that rotates in synchronization with a crank shaft, a drive cam fixed to the drive shaft, and the like. A rocking cam, a transmission mechanism having one end linked to the drive cam side and the other end linked to the swing cam side, and a control shaft having a control cam for changing the posture of the transmission mechanism.
In a variable valve mechanism configured to include an actuator that rotates the control shaft, the actuator is controlled to abut the control shaft at a minimum angular position or a maximum angular position in a rotatable range, and at this time, The output of the operating angle sensor is learned as a reference position output, and the operating angle is detected from the output of the operating angle sensor based on the reference position output.

According to this structure, when the actuator is controlled to abut the minimum angular position or the maximum angular position, the sensor output at that time is used as a reference corresponding to the minimum operating angle or the maximum operating angle (reference position). The position output value is learned, the sensor output is discriminated based on the reference position output, and the operating angle is detected. According to a second aspect of the invention, the control shaft is abutted against the minimum angular position or the maximum angular position of the rotatable range by setting the target operating angle exceeding the rotatable range of the control shaft.

According to this structure, the control shaft is abutted against the minimum angular position or the maximum angular position of the rotatable range by setting the target operating angle that requires the control shaft to rotate beyond the rotatable range. In the invention according to claim 3, when the target operating angle based on the engine operating condition is the minimum angular position or the maximum angular position, a target operating angle smaller than the minimum angle or larger than the maximum angle is set. And

According to such a configuration, when there is a demand for controlling the operating angle to the minimum angle or the maximum angle from the engine operating conditions, the target depending on the operating conditions should be set so that the control shaft is surely brought into contact with the minimum angular position or the maximum angular position. If is the minimum angle, the target is changed to a smaller value, and if the target under operating conditions is the maximum angle, the target is changed to a larger value. Claim 4
In the invention described above, when the ignition switch of the engine is turned off, the target operating angle smaller than the minimum angle or larger than the maximum angle is set.

According to this structure, the control shaft is abutted at the minimum angular position or the maximum angular position by giving a target exceeding the rotatable range in a state where the engine ignition switch is turned off and the engine is stopped. According to the invention of claim 5, when the engine is started, a target operating angle smaller than the minimum angle or larger than the maximum angle is set.

According to this structure, at the time of starting the engine, the control shaft is abutted against the minimum angular position or the maximum angular position by giving a target exceeding the rotatable range. In the invention according to claim 6, the target operating angle smaller than the minimum angle or larger than the maximum angle is set immediately after the engine is stopped. With this configuration, when the engine is stopped due to the ignition switch being turned off, or when the engine is stopped, such as when a so-called engine stall occurs, the control shaft is abutted at the minimum angular position or the maximum angular position by giving a target that exceeds the rotatable range.

[0012]

According to the first aspect of the present invention, the intermediate angle is detected based on the sensor output in the state where the operating angle of the control shaft is actually estimated to be minimum or maximum. Even if the correlation between the sensor output and the actual operating angle varies due to mechanical and electrical variations of the sensor,
There is an effect that the actual operating angle can be accurately detected from the sensor output, and thus the valve lift amount and the valve operating angle of the engine valve can be accurately controlled.

According to the second aspect of the invention, there is an effect that the control axis can be reliably abutted against the minimum angular position or the maximum angular position, and the reference position output can be learned with high accuracy. According to the invention described in claims 3 to 6, the operating angle of the control shaft is forcibly abutted against the minimum angular position or the maximum angular position without affecting the drivability of the engine, and the sensor output corresponding to the reference position is output. There is an effect that can be learned regularly.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show a variable valve mechanism VEL of an internal combustion engine for a vehicle according to an embodiment, which is a mechanism for continuously changing a valve lift amount and a valve operating angle of two intake valves provided for each cylinder. Is.

It is obvious that a variable valve mechanism having a structure for driving the exhaust valve may be used. The variable valve mechanism VEL shown in FIGS. 1 to 3 includes a pair of intake valves 12, 12
A hollow cam shaft 13 (driving shaft) rotatably supported by a cam bearing 14 of the cylinder head 11, and the cam shaft 1
Two eccentric cams 15, 1 which are rotary cams pivotally supported by 3
5 (driving cam), a control shaft 16 rotatably supported by the same cam bearing 14 above the cam shaft 13, and a pair swingably supported by the control shaft 16 via the control cam 17. Rocker arms 18 and 18 and respective intake valves 12 and 12
Is provided with a pair of independent rocking cams 20 and 20 arranged via valve lifters 19 and 19, respectively.

The eccentric cams 15 and 15 and the rocker arm 1
8 and 18 are linked by link arms 25 and 25, and rocker arms 18 and 18 and swing cams 20 and 20 are linked by link members 26 and 26. The rocker arms 18, 18, the link arms 25, 25,
The link members 26, 26 form a transmission mechanism.

The eccentric cam 15 is, as shown in FIG.
A cam body 15a having a substantially ring shape and having a small diameter, and a flange portion 15b integrally provided on an outer end surface of the cam body 15a.
The cam shaft insertion hole 15c is formed so as to penetrate in the inner axial direction, and the shaft center X of the cam body 15a is eccentric from the shaft center Y of the cam shaft 13 by a predetermined amount. Further, the eccentric cam 15 is press-fitted and fixed to the cam shaft 13 on both outer sides which do not interfere with the valve lifter 19 through the cam shaft insertion holes 15c, and the outer peripheral surface 1 of the cam body 15a.
5d have the same cam profile.

As shown in FIG. 3, the rocker arm 18 is bent in a substantially crank shape, and a central base portion 18a is rotatably supported by the control cam 17. In addition, a pin hole 18d into which a pin 21 that is connected to the tip of the link arm 25 is press-fitted is formed through one end 18b protruding from the outer end of the base 18a, while an inner end of the base 18a is formed. Each of the link members 26 is attached to the other end portion 18c protrudingly provided in the portion.
Is formed with a pin hole 18e into which a pin 28 that is to be connected to one end portion 26a of FIG.

The control cam 17 has a cylindrical shape and is fixed to the outer periphery of the control shaft 16, and the position of the shaft center P1 is eccentric from the shaft center P2 of the control shaft 16 by α as shown in FIG. The swing cam 20 has a substantially horizontal U-shape as shown in FIGS. 1, 5, and 6, and the cam shaft 13 is fitted and inserted into a substantially annular base end portion 22 to be rotatably supported. Support hole 2
2a is formed so as to penetrate, and a pin hole 23a is formed so as to penetrate through the end portion 23 of the rocker arm 18 located on the other end portion 18c side.

On the lower surface of the swing cam 20, the base end portion 2 is provided.
A base circular surface 24a on the second side and a cam surface 24b extending in an arc shape from the base circular surface 24a to the end edge of the end portion 23 are formed,
The base circular surface 24a and the cam surface 24b come into contact with predetermined positions on the upper surface of each valve lifter 19 according to the swing position of the swing cam 20. That is, as seen from the valve lift characteristics shown in FIG. 7, as shown in FIG. 1, the predetermined angle range θ1 of the base circle surface 24a becomes the base circle section, and the predetermined angle range θ2 from the base circle section θ1 of the cam surface 24b. A so-called ramp section is set, and further, a predetermined angle range θ3 from the ramp section θ2 of the cam surface 24b is set to be a lift section.

The link arm 25 is provided with an annular base portion 25a and a projecting end 25b protruding at a predetermined position on the outer peripheral surface of the base portion 25a, and the eccentric cam 15 is provided at the center of the base portion 25a. A fitting hole 25c for rotatably fitting is formed on the outer peripheral surface of the cam body 15a, while a pin hole 25d through which the pin 21 is rotatably inserted is formed at the protruding end 25b.

Further, the link member 26 is formed in a straight line of a predetermined length, and the other ends 26a and 26b of the circular shape are the other end 18c of the rocker arm 18 and the end 23 of the rocking cam 20, respectively. Each pin 2 press-fitted into the pin holes 18d, 23a
Pin insertion holes 26 through which the ends of 8, 29 are rotatably inserted
c and 26d are formed through. In addition, each pin 21,2
Snap rings 30, 3 for restricting axial movement of the link arm 25 and the link member 26 are provided at one end of
1, 32 are provided.

The control shaft 16 has a D provided at one end.
An actuator 101 such as a C servo motor drives the control shaft 16 to rotate within a predetermined rotation angle range between a minimum angular position and a maximum angular position defined by a stopper.
The valve lift amount and the valve working angle of the intake valve 12 are continuously changed by changing the working angle of the actuator 101 by the actuator 101, and the valve working angle is changed smaller as the valve lift amount decreases. (See FIG. 8).

When the valve lift amount and the valve operating angle are reduced, as shown in FIGS. 5A and 5B, the axis P2 of the control shaft 16 is lower than the axis P1 of the control cam 17. When the control shaft 16 is rotated so that the valve lift amount and the valve operating angle are increased,
As shown in FIGS. 6A and 6B, the axis P of the control shaft 16
2 rotates the control shaft 16 so that the shaft center P1 of the control cam 17 is located higher than the shaft center P1.

The actuator 101 is controlled based on a drive signal from the control unit 102, as shown in FIG. The control unit 102 includes an engine load sensor 103 and an engine speed sensor 10
4 and the output from the operating angle sensor 105 that detects the operating angle of the control shaft 16.

In the control unit 102, the target operating angle calculating section 106 calculates the target operating angle of the control shaft 16 in accordance with the engine operating conditions such as the engine load and the engine speed, while the operating angle detecting section 107. Detects the actual operating angle of the control shaft 16 based on the output of the operating angle sensor 105, and the drive circuit 108 outputs a drive signal to the actuator 101 according to the deviation between the target operating angle and the actual operating angle. Feedback control.

The operating angle sensor 105 is, for example, a potentiometer type sensor, and as shown in FIG.
In the control range of the operating angle of the control shaft 16 (minimum value MIN to maximum value MAX), the output voltage increases and changes in proportion to the increasing change of the operating angle.
Then, the process of converting the sensor output voltage into the data of the operating angle is performed according to the correlation shown by the solid line in FIG.

Here, the sensor output voltage corresponding to the operating angle of the control shaft 16 may shift as a whole as shown by the dotted line in FIG. 10 due to sensor variations, and the reference characteristic (shown by the solid line in FIG. 10). If the sensor output voltage is converted into the operating angle based on the above, the operating angle will be erroneously detected. Therefore, a reference position output learning unit 109 for learning the shift amount is provided, and the processing contents of the reference position output learning unit 109 will be described in detail below with reference to the flowchart of FIG. 11.

In step S1, it is determined whether or not a failure such as disconnection or short-circuit of the operating angle sensor 105 has been diagnosed. If no failure such as disconnection or short-circuiting has occurred in the operating angle sensor 105, step S2 is performed. Go to. In step S2, it is determined whether or not the voltage VB of the battery that is the power source of the operating angle sensor 105 is equal to or higher than a predetermined voltage.

If the voltage VB is equal to or higher than the predetermined voltage, the process proceeds to step S3, and the ignition switch 110 is turned off.
Time, starting, engine stall, or whether the target operating angle based on engine operating conditions is at the minimum angular position. In step S3, turn the ignition switch O
When it is determined that the target operating angle based on the engine operating condition is at the minimum angular position during FF, starting, engine stall, the process proceeds to step S4, and all the conditions of step S1 to step S3 are satisfied. It is discriminated whether or not the continued time is longer than a predetermined time.

If it is determined in step S4 that the operation will continue for a predetermined time or longer, the process proceeds to step S5, and a target operating angle smaller than the minimum angular position is set. By setting the target operating angle smaller than the minimum angular position as described above, the control shaft 16 is abutted against the minimum angular position defined by the stopper.

In step S6, the output voltage of the working angle sensor 105 is sequentially read, and the average value of the voltages read so far is calculated. In step S7, it is determined whether or not the number of samples in the average value calculation is equal to or larger than a predetermined number, and the process of step S6 is repeated until the number of samples is equal to or larger than the predetermined number. When the output voltages of a predetermined number or more are averaged, the process proceeds from step S7 to step S8, and the average value is learned as the reference position output which is the sensor output value corresponding to the minimum angular position.

As shown in FIG. 10, the operating angle sensor 105
The output voltage is set to 0.5 V at the minimum angular position, and the output voltage is converted into the operating angle based on the initial setting. Therefore, for example, if the sensor output voltage with respect to the operating angle shifts in the increasing direction as a whole and a voltage higher than 0.5 V is output at the minimum angular position, it is actually the minimum angular position. A larger operating angle will be detected.

Therefore, in step S9, the result obtained by subtracting the reference position output from 0.5 V which is the initial setting output of the minimum angular position is set as the correction value of the output voltage, and the output voltage is converted into the working angle. In addition, the result of adding the correction value to the actual output voltage is converted into the working angle.
For example, if the reference position output is 1.0V,
-0.5V is set as the correction value, and the value obtained by subtracting 0.5V from the sensor output voltage is converted into the working angle. As a result, the sensor output characteristic used for detecting the working angle is shown in FIG. It will be corrected to the characteristic shown by the solid line.

In the above embodiment, the control shaft 16 is abutted against the minimum angular position by setting the target operating angle smaller than the minimum angular position, but by setting the target operating angle larger than the maximum angular position. The control shaft 16 may be abutted against the maximum angular position. In this case, in step S3, it is determined whether or not the target operating angle according to the operating condition is the maximum angular position, and in step S9, the maximum angle is determined. The difference between the initial setting output (4.5 V) corresponding to the position and the reference position output learned as corresponding to the maximum angular position is set as the correction value.

Further, in the above embodiment, the working angle sensor is of potentiometer type, but it is obvious that it may be a sensor which detects the working angle by other methods.

[Brief description of drawings]

FIG. 1 is a sectional view showing a variable valve mechanism according to an embodiment of the present invention (a sectional view taken along the line AA in FIG. 2).

FIG. 2 is a side view of the variable valve mechanism.

FIG. 3 is a plan view of the variable valve mechanism.

FIG. 4 is a perspective view showing an eccentric cam used in the variable valve mechanism.

FIG. 5 is a cross-sectional view showing a function of the variable valve mechanism at a low lift (cross-sectional view taken along the line BB in FIG. 2).

FIG. 6 is a cross-sectional view (cross-sectional view taken along the line BB in FIG. 2) showing the action of the variable valve mechanism during high lift.

FIG. 7 is a valve lift characteristic diagram corresponding to a base end surface and a cam surface of a swing cam in the variable valve mechanism.

FIG. 8 is a characteristic diagram of valve timing and valve lift of the variable valve mechanism.

FIG. 9 is a block diagram showing a control system of the variable valve mechanism.

FIG. 10 is a diagram showing the output characteristics of the operating angle sensor of the variable valve mechanism.

FIG. 11 is a flowchart showing learning of a reference position output of an operating angle sensor in the variable valve mechanism.

[Explanation of symbols]

12 ... Intake valve 13 ... Cam shaft 15 ... Eccentric cam 16 ... Control axis 17 ... Control cam 18 ... Rocker Arm 20 ... Swing cam 25 ... Link arm 101 ... Actuator 102 ... Control unit 103 ... Engine load sensor 104 ... Engine speed sensor 105 ... Working angle sensor 106 ... Target operating angle calculation unit 107 ... Working angle detector 108 ... Driving circuit 109 ... Reference position output learning unit 110 ... Ignition switch

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3G018 AB05 BA19 CA07 DA03 DA04                       DA09 DA10 DA12 DA19 DA66                       EA21 EA22 EA35 FA01 FA06                       FA07 FA08 FA09 GA02                 3G092 AA11 DA05 EA03 EA04 EA10                       EB06 EC05 FA06 FA48 GA01                       GA10 HA13Z HE01Z

Claims (6)

[Claims] 1. A drive shaft that rotates in synchronization with a crankshaft, a drive cam fixed to the drive shaft, a swing cam that swings to open and close an intake valve, and a drive cam side at one end. A transmission mechanism that is linked to the rocking cam side at the other end, a control shaft having a control cam that changes the posture of the transmission mechanism, an actuator that rotates the control shaft, and an operating angle of the control shaft. In a variable valve mechanism configured to include an operating angle sensor that generates a corresponding output, the actuator is controlled to bring the control shaft into contact with the minimum angular position or the maximum angular position of the rotatable range. A reference position learning of a variable valve mechanism, wherein the output of the operating angle sensor is learned as a reference position output, and the operating angle is detected from the output of the operating angle sensor based on the reference position output. Location. 2. The variable according to claim 1, wherein the control shaft is abutted against the minimum angular position or the maximum angular position of the rotatable range by setting a target operating angle exceeding the rotatable range of the control shaft. Reference position learning device for valve mechanism. 3. A target operating angle smaller than the minimum angle or larger than the maximum angle is set when the target operating angle based on the engine operating condition is the minimum angular position or the maximum angular position. The reference position learning device for the variable valve mechanism according to claim 2. 4. The reference position of the variable valve mechanism according to claim 2, wherein when the ignition switch of the engine is turned off, a target operating angle smaller than the minimum angle or larger than the maximum angle is set. Learning device. 5. The reference position learning device for a variable valve mechanism according to claim 2, wherein a target operating angle smaller than the minimum angle or larger than the maximum angle is set when the engine is started. 6. The reference position learning device for a variable valve mechanism according to claim 2, wherein a target operating angle smaller than the minimum angle or larger than the maximum angle is set immediately after the engine is stopped.