JP2004011532A - Valve lift regulator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valve lift regulator capable of performing feedback control even when a valve lift sensor is failed. <P>SOLUTION: This valve lift regulator comprises valve lift variable mechanisms 3 and 11, a valve lift sensor 26 to detect the valve lift, and a drive control means 10 to drive the valve lift variable mechanisms so that a target valve lift value is calculated based on the target air volume, and the detected valve lift value by the valve lift sensor is agreed with the target value. The drive control means 10 drives the valve lift variable mechanisms 3 and 11 so that the intake air volume detected by an air flow meter 15 placed in an intake passage is agreed with the target air volume if any abnormality of the valve lift sensor 26 is detected. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a valve lift adjustment device that adjusts a valve lift amount of an intake valve in an internal combustion engine.In particular, even when a valve lift amount sensor used during an adjustment operation fails, an appropriate air amount is adjusted. The present invention relates to a valve lift adjusting device capable of controlling a valve lift so as to secure the valve lift.
[0002]
[Prior art]
An invention relating to a valve lift adjusting device that takes into consideration the case where a valve lift sensor has failed is disclosed in Japanese Patent Laid-Open Publication No. 2000-314329, entitled "Processing device for operation sensor failure in variable valve operating device of internal combustion engine". In this prior art, the operating angle sensor corresponds to the valve lift 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 fails, the limp-home running is enabled.
[0003]
[Problems to be solved by the invention]
However, according to this conventional technique, when a valve lift amount sensor fails, a method for coping with the failure is basically open loop control, so that errors caused by component tolerances, variations due to durability deterioration, temperature characteristics, friction variations, and the like can be absorbed. Instead, the error appears as it is in the operation angle of the control result. For this reason, there is a high probability that the vehicle will not be able to perform the limp-home run or will lead to an overrun, and the feasibility has been poor.
[0004]
[Means for Solving the Problems]
The present invention has been made to solve such a problem, and a valve lift variable mechanism configured to be able to change a valve lift of an intake valve in an internal combustion engine, and a valve lift are disclosed. Calculates the valve lift amount sensor to be detected and the target value of the valve lift amount based on the target air amount, and drives 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. And a drive control means for controlling the amount of intake air detected by an air flow meter disposed in the intake path when the abnormality of the valve lift sensor is detected. The variable valve lift mechanism is driven to match the amount.
[0005]
When an abnormality of the valve lift sensor is detected, a feedback loop for controlling the valve lift 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 is a component tolerance, a variation due to durability deterioration, a temperature characteristic, a friction variation, etc., for the components related to the valve lift adjustment.
[0006]
It is desirable that the target air amount is calculated based on the rotation speed and the accelerator position of the internal combustion engine. The current output state of the internal combustion engine can be grasped from the rotation speed, and the driver's intention regarding the internal combustion engine output 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 reflecting the current output of the internal combustion engine and the driver's intention.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a diagram showing a configuration of a valve opening / closing device including a valve lift adjusting device according to an embodiment of the present invention. The valve opening / closing device 1 employs a direct type 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 to a crankshaft timing pulley 6 by a timing belt 7.
[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 operation state. The determination of the operating state is performed in an electronic control unit (ECU) 10 which 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 diagram 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 a 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 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 rotatably connected to one bottom surface of the cylindrical body 23. Therefore, as the cylinder 23 moves in the stroke direction A, the intake camshaft 3 also 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 arranged ahead of the stroke sensor core 24. The core detector 25 outputs an electric signal corresponding to the position of the stroke sensor core 24 to the ECU 10 as a stroke sensor value, and forms a stroke sensor 26 together with the stroke sensor core 24.
[0015]
FIG. 3 is a diagram showing a 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 changes continuously 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 changes.
[0017]
As described above, the intake camshaft 3, the camshaft slide drive unit 11, and the three-dimensional cam 30 that slide in the axial direction constitute a variable valve lift mechanism.
[0018]
Next, the ECU 10 having a function as drive control means of the variable valve lift mechanism will be described. On the input side of the ECU 10, an accelerator position sensor 13, an engine speed sensor 14, and an air flow meter 15 are connected in addition to the stroke sensor 26 in the camshaft slide drive unit 11.
[0019]
The accelerator position sensor 13 is a sensor that detects the amount of depression of an accelerator pedal (accelerator opening degree) not shown. The engine speed sensor 14 is a sensor that literally 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 amount of intake air.
[0020]
A DC motor 20, a continuously variable valve timing mechanism 8, and a throttle valve 16 in the camshaft slide drive unit 11 are connected to the output side of the ECU 10.
[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 a valve lift amount.
[0022]
In step S1, the accelerator opening and the engine speed are acquired based on the 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 prepared map. 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. The abnormality detection can be determined, for example, from the output voltage value of the sensor. The output of the core detection unit 25 of the stroke sensor 26 is supplied to the ECU 10 as a voltage signal of 0.5 volt to 4.5 volt, similarly to a general sensor. On the other hand, if the output circuit of this sensor is disconnected or short-circuited, the output voltage of the sensor becomes the power supply voltage, that is, 0 volts or 5 volts, so that a failure due to disconnection or short-circuit can be detected from the output voltage. Further, even if the output voltage is within the normal range, if the same voltage continues for a predetermined time or more, it is possible to determine that the stroke sensor 26 is abnormal.
[0024]
If the stroke sensor is normal in step S3, that is, if no abnormality is detected, the process proceeds to step S7, where target values for the valve lift, the throttle opening, and the valve phase (valve opening / closing timing) are set. It is calculated based on the target air amount.
[0025]
When each target value is obtained, the process proceeds to step S8, in which each actuator relating to the valve lift, the throttle opening, and the valve phase is driven, and the operation output is made to coincide with each target value. The actuator related to the valve lift is a valve lift variable mechanism including the intake camshaft 3, the three-dimensional cam 30, and the camshaft slide drive unit 11 as described above, and the actuator related to the throttle opening is a throttle valve not shown. The actuator that is the driving mechanism and relates to the valve phase is the 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 that the throttle opening and the valve phase are fixed at predetermined values.
[0028]
Next, in step S5, the intake air amount is detected based on a signal from the air flow meter 15.
[0029]
In step S6, the camshaft slide drive unit 11 is driven to change the valve lift amount 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, passes through steps S2, S3, and S4, detects the intake air amount in step S5, and changes the valve lift amount in step S6 according to the detection result. In this way, by repeatedly executing steps S1, S2, S3, S4, S5, and S6, feedback control of the valve lift amount using the intake air amount is performed. As the change amount of the valve lift amount in step S6, an optimum change amount may be appropriately selected based on a method such as PID control or PID control with a dead zone.
[0031]
By the above operation, even if the stroke sensor fails, the feedback control using the intake air amount is executed, so that the intake air amount can be made closer to the target air amount. In this case, since it is not the open loop control as in the related art, there is almost no possibility that the vehicle will be in a limp-home state or an overrun state.
[0032]
In this 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 adjustment device of the present invention, even when an abnormality of the valve lift sensor is detected, the valve lift is switched to feedback control using the air flow meter, so The minimum necessary control of the air amount can be reliably maintained, and effective limp-home running is possible.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a valve lift adjusting device according to an embodiment of the present invention.
FIG. 2 is a diagram showing an internal structure of a camshaft slide drive unit 11;
FIG. 3 is a view showing a shape of a valve opening / closing cam provided on an intake camshaft 3;
FIG. 4 is a flowchart showing a control operation of the valve lift adjusting device according to the 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 camshaft, 4, 5 ... Timing pulley, 7 ... Timing belt, 8 ... Continuously variable valve timing mechanism, 9 ... Intake valve, 10 ... ECU, 11 ... Camshaft 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 variable mechanism configured to be able to change a valve lift of an intake valve in an internal combustion engine, a valve lift sensor for detecting the valve lift, and a target air value for the valve lift. And a drive control means for driving the variable valve lift mechanism so that the value detected by the valve lift sensor matches the target value. ,
The drive control means, when detecting an abnormality of the valve lift amount sensor, adjusts the valve lift amount variable mechanism so that an intake air amount detected by an air flow meter arranged in an intake path matches the target air amount. And a valve lift adjusting device for driving the valve lift. The valve lift adjustment device according to claim 1, wherein the target air amount is calculated based on a rotation speed and an accelerator position of the internal combustion engine.

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