JP4061976B2 - Valve lift adjustment device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a valve lift adjustment device for adjusting a valve lift amount of an intake valve in an internal combustion engine, and in particular, even when a valve lift amount sensor used during an adjustment operation fails, an appropriate air amount is provided. The present invention relates to a valve lift amount adjusting device capable of controlling a valve lift amount so as to be secured.
[0002]
[Prior art]
An invention relating to a valve lift amount adjusting device that takes into account a case where a valve lift amount sensor has failed is disclosed in Japanese Patent Application Laid-Open No. 2000-314329 “Processing device for failure of an operation sensor in a variable valve device of an internal combustion engine”. In this prior art, the operating angle sensor corresponds to a valve lift amount sensor, and when the operating angle sensor fails, the operating angle of the control shaft that controls the valve lift amount is set to the target operating angle at the time of failure. Thereby, even when the valve lift amount sensor is out of order, the retreat travel is enabled.
[0003]
[Problems to be solved by the invention]
However, in this prior art, the countermeasure method when the valve lift sensor breaks down is basically open loop control. Therefore, it is possible to absorb errors caused by component tolerance, variations due to durability deterioration, temperature characteristics, friction variations, etc. However, the error appears as it is in the operating angle of the control result. For this reason, there is a high probability that the evacuation traveling cannot be achieved or an overrun occurs, and the feasibility is poor.
[0004]
[Means for Solving the Problems]
The present invention has been made to solve such a problem. A variable valve lift amount mechanism configured to change the valve lift amount of an intake valve in an internal combustion engine, and a valve lift amount are provided. The valve lift amount sensor to detect and the target value of the valve lift amount is calculated based on the target air amount, and the valve lift amount variable mechanism is driven so that the detected value of the valve lift amount by the valve lift amount sensor matches the target value In the valve lift amount adjusting device including the drive control means, the drive control means fixes the throttle opening and the valve phase and detects the air flow disposed in the intake path when detecting an abnormality of the valve lift amount sensor. Drive the variable valve lift mechanism so that the intake air volume detected by the meter matches the target air volume. It is an feature.
[0005]
When an abnormality of the valve lift amount sensor is detected, a feedback loop for controlling the valve lift amount is formed so that the intake air amount detected by the air flow meter becomes the target air amount. Therefore, the intake air amount converges to the target intake air amount even if there are component tolerances, variations due to durability deterioration, temperature characteristics, friction variations, and the like regarding the components related to valve lift amount adjustment.
[0006]
It is desirable to calculate the target air amount based on the rotational speed of the internal combustion engine and the accelerator position. The current output status of the internal combustion engine can be grasped from the rotational speed, and the driver's intention regarding the output of the internal combustion engine can be grasped from the accelerator position. Therefore, by calculating the target air amount based on the rotation speed and the accelerator position, it is possible to set the target air amount that reflects the current output of the internal combustion engine and the driver's intention.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram showing a configuration of a valve opening / closing device including a valve lift amount adjusting device according to an embodiment of the present invention. The valve opening / closing device 1 employs a direct overhead camshaft system, and includes an exhaust camshaft 2 and an intake camshaft 3 arranged in parallel with each other above a cylinder head (not shown).
[0008]
Timing pulleys 4 and 5 are disposed at one end of each of the camshafts 2 and 3, and the timing pulleys 4 and 5 are connected together by a timing belt 7 together with the crankshaft timing pulley 6.
[0009]
The timing pulley 5 is connected to the intake camshaft 3 via a continuously variable valve timing mechanism 8. The continuously variable valve timing mechanism 8 is a mechanism that optimally adjusts the opening / closing timing of the intake valve 9 according to the operating state. The operation state is determined by an electronic control unit (ECU) 10 that is an engine control computer, and the valve opening / closing timing is controlled based on the result.
[0010]
The intake camshaft 3 is slidable in the axial direction, and a camshaft slide drive unit 11 is provided at one end opposite to the continuously variable valve timing mechanism 8. The camshaft slide drive unit 11 slides the intake camshaft 3 in the axial direction based on a command from the ECU 10.
[0011]
FIG. 2 is a view showing the internal structure of the camshaft slide drive unit 11. The camshaft slide drive unit 11 has a built-in DC motor 20 controlled by the ECU 10, and a gear 21 is fixed to the rotating shaft of the DC motor 20. The gear 21 meshes with the gear 22, and the rotation of the DC motor 20 is transmitted to the gear 22.
[0012]
A cylindrical opening is formed at the center of the gear 22 along the rotation axis, and a spiral groove is formed on the inner wall of the cylindrical opening. A cylindrical body 23 is disposed in the cylindrical opening, and a spiral groove having the same pitch as that of the spiral groove formed on the inner wall of the gear 22 is formed on the outer peripheral wall of the cylindrical body 23. A plurality of spheres are inserted between the spiral grooves formed on the outer wall of the cylindrical body 23 and the inner wall of the gear 22, whereby a ball screw structure is formed between the inner wall of the gear 22 and the outer wall of the cylindrical body 23. Is formed. That is, when the gear 22 is rotated in a state where the rotation of the cylindrical body 23 is stopped, the cylindrical body 23 moves in the rotation axis direction, that is, the stroke direction A.
[0013]
One end of the intake camshaft 3 is connected to one bottom surface of the cylindrical body 23 so as to be axially rotatable. Accordingly, the intake camshaft 3 also moves in the stroke direction A as the cylindrical body 23 moves in the stroke direction A. A stroke sensor core 24 is attached to the other bottom surface of the cylindrical body 23.
[0014]
A core detection unit 25 is disposed at the tip of the stroke sensor core 24. The core detection unit 25 outputs an electrical signal corresponding to the position of the stroke sensor core 24 to the ECU 10 as a stroke sensor value, and constitutes a stroke sensor 26 together with the stroke sensor core 24.
[0015]
FIG. 3 is a view showing the shape of a valve opening / closing cam provided on the intake camshaft 3. As shown in the figure, the valve opening / closing cam 30 is a three-dimensional cam, and the cam profile continuously changes in the axial direction of the intake camshaft 3.
[0016]
Therefore, when the intake camshaft 3 is slid in the axial direction (stroke direction) by the camshaft slide drive unit 11, the cam profile of the portion in contact with the intake valve 9 changes, and the valve lift amount changes.
[0017]
In this way, the intake camshaft 3 that slides in the axial direction, the camshaft slide drive unit 11, and the three-dimensional cam 30 constitute a variable valve lift amount mechanism.
[0018]
Next, the ECU 10 having a function as drive control means of the variable valve lift amount mechanism will be described. In addition to the stroke sensor 26 in the camshaft slide drive unit 11, an accelerator position sensor 13, an engine speed sensor 14, and an air flow meter 15 are connected to the input side of the ECU 10.
[0019]
The accelerator position sensor 13 is a sensor that detects a depression amount (accelerator opening) of an accelerator pedal (not shown). The engine speed sensor 14 is literally a sensor that detects the engine speed. The air flow meter 15 is a sensor that is disposed upstream of the intake path of the engine and detects the intake air amount.
[0020]
Connected to the output side of the ECU 10 are a DC motor 20, a continuously variable valve timing mechanism 8, and a throttle valve 16 in the camshaft slide drive unit 11.
[0021]
FIG. 4 is a flowchart showing an operation related to intake air amount control in the ECU 10 and includes an operation for adjusting the valve lift amount.
[0022]
In step S1, the accelerator opening and the engine speed are acquired based on signals from the accelerator position sensor 13 and the engine speed sensor 14. In step S2, a target air amount is calculated from the accelerator opening and the engine speed detected in step S1. Specifically, the target air amount Gr is calculated by applying the accelerator opening and the engine speed to a map prepared in advance. FIG. 5 is a map (graph) showing an example of the relationship among the accelerator opening, the engine speed, and the target air amount.
[0023]
In step S3, abnormality detection of the stroke sensor 26 is performed. Abnormality detection can be determined from the output voltage value of the sensor, for example. The output of the core detection unit 25 of the stroke sensor 26 is given to the ECU 10 as a voltage signal of 0.5 to 4.5 volts, as in a general sensor. On the other hand, when the output circuit of the sensor is disconnected or short-circuited, the output voltage of the sensor becomes the power supply voltage, that is, 0 volts or 5 volts. Therefore, a failure caused by the disconnection or short-circuit can be detected from the output voltage. Further, even if the output voltage is in the normal range, it is possible to determine that the stroke sensor 26 is abnormal if the same voltage continues for a predetermined time or more.
[0024]
In step S3, when the stroke sensor is normal, that is, when no abnormality is detected, the process proceeds to step S7, and target values for the valve lift amount, the throttle opening, and the valve phase (valve opening / closing timing) are set. Calculate based on the target air volume.
[0025]
When each target value is obtained, the process proceeds to step S8, where each actuator relating to the valve lift amount, the throttle opening degree and the valve phase is driven, and the operation output is matched with the respective target value. As described above, the actuator related to the valve lift amount is a variable valve lift amount mechanism including the intake camshaft 3, the three-dimensional cam 30, and the camshaft slide drive unit 11, and the actuator related to the throttle opening is the throttle valve not shown. The actuator relating to the valve phase, which is a drive mechanism, is a continuously variable valve timing mechanism 8.
[0026]
When the drive control of each actuator is completed in step S8, the process returns to step S1.
[0027]
If an abnormality of the stroke sensor 26 is detected in step S3, the process proceeds to step S4, and each actuator is driven so as to fix the throttle opening and the valve phase to predetermined values.
[0028]
Next, in step S5, the intake air amount is detected based on the signal from the air flow meter 15.
[0029]
In step S6, the camshaft slide drive unit 11 is driven to change the valve lift so that the difference between the intake air amount detected in step S5 and the target air amount calculated in step S2 decreases. When the intake air amount is larger than the target air amount, the camshaft slide drive unit 11 is driven in a direction in which the intake air amount decreases. Conversely, when the intake air amount is smaller than the target air amount, the camshaft slide drive unit 11 is driven in a direction in which the intake air amount increases.
[0030]
Thereafter, the process returns to step S1, and through steps S2, S3, and S4, the intake air amount is detected at step S5, and the valve lift amount is changed at step S6 according to the detection result. In this way, by repeatedly executing Step S1, Step S2, Step S3, Step S4, Step S5, and Step S6, feedback control of the valve lift amount using the intake air amount is executed. As the change amount of the valve lift amount in step S6, an optimal change amount may be appropriately selected based on a technique such as PID control or PID control with dead zone.
[0031]
By the above operation, even if the stroke sensor breaks down, feedback control using the intake air amount is executed, so that the intake air amount can be brought close to the target air amount. In this case, since the open loop control is not performed as in the prior art, there is almost no possibility that the vehicle cannot enter the evacuation traveling state or overrun.
[0032]
In the present embodiment, when an abnormality of the stroke sensor is detected in step S3, the throttle opening and the valve phase are fixed in step S4 in order to control the intake air amount only by the valve lift amount. However, feedback control of the valve lift amount using the intake air amount is possible without fixing the throttle opening and the valve phase. For example, instead of fixing, a method of slowing down the operation can be considered.
[0033]
【The invention's effect】
As described above, according to the valve lift amount adjusting device of the present invention, even when an abnormality of the valve lift amount sensor is detected, the valve lift amount is switched to feedback control using the air flow meter. The minimum required control of the air amount can be reliably maintained, and effective evacuation traveling is possible.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a valve lift adjustment device according to an embodiment of the present invention.
FIG. 2 is a view showing an internal structure of a camshaft slide drive unit 11;
FIG. 3 is a view showing the shape of a valve opening / closing cam provided on the intake camshaft 3;
FIG. 4 is a flowchart showing a control operation of the valve lift adjustment device of the present embodiment.
FIG. 5 is a graph showing an example of a relationship among an accelerator opening, an engine speed, and a target air amount.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Valve opening / closing device, 3 ... Intake cam shaft, 4, 5 ... Timing pulley, 7 ... Timing belt, 8 ... Continuously variable valve timing mechanism, 9 ... Intake valve, 10 ... ECU, 11 ... Cam shaft slide drive part, 13 Accelerator position sensor, 14 Engine speed sensor, 15 Air flow meter, 16 Throttle valve, 20 DC motor, 26 Stroke sensor, 30 Three-dimensional cam.

Claims (2)

A valve lift amount variable mechanism configured to be able to change a valve lift amount of an intake valve in an internal combustion engine, a valve lift amount sensor for detecting the valve lift amount, and a target value of the valve lift amount as target air A valve lift amount adjustment device comprising: a drive control means for driving the variable valve lift amount mechanism so that the detected value of the valve lift amount by the valve lift amount sensor matches the target value. ,
When the drive control means detects an abnormality in the valve lift amount sensor, the drive control means fixes the throttle opening and the valve phase, and the intake air amount detected by the air flow meter disposed in the intake path is the target air amount. The valve lift amount adjusting device is characterized in that the valve lift amount variable mechanism is driven so as to match the above.   The valve lift amount adjusting device according to claim 1, wherein the target air amount is calculated based on a rotational speed and an accelerator position of the internal combustion engine.

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