KR20200009311A - Control method of continuous variable valve timing system - Google Patents

Abstract

According to the present invention, a control method of a continuous variable valve timing system determines whether a locking control for locking a rotor to a reference position on a cam phaser of the continuous variable valve timing system is executed, monitors an actual position of the rotor to determine whether the rotor is locked when the locking control is executed, and if it is determined that the locking of the rotor is not performed, stops the locking control and executes a holding control of keeping the rotor at the reference position.

Description

CONTROL METHOD OF CONTINUOUS VARIABLE VALVE TIMING SYSTEM}

The present invention relates to a control method of a continuous variable valve timing system, and more particularly, to a control method of a continuous variable valve timing system capable of preventing the occurrence of RPM drop and starting off after locking control.

Recently, in response to high demands for fuel economy improvement, emission reduction, low speed torque increase and output improvement, the continuously variable valve timing system in which the engine intake / exhaust valve opening and closing time can be optimally controlled according to the engine revolutions. System or Camshaft Phaser System (CVVT) is needed to improve performance.

An example of achieving the performance improvement requirement of the continuous variable valve timing system by improving the system responsiveness and expanding the cam operating area is a middle phase continuous variable valve timing system (hereinafter, referred to as a middle phase CVVT).

In particular, the mid-phase CVVT is an engine applying a solenoid valve (for example, an oil-flow control valve (OCV)) for switching flow paths by moving a spool (or plunger), and applying PWM pulse width modulation duty (DUTY). The position control is executed by the ECU (Electronic Control Unit), and when the position control is executed, the cam position is controlled at the intermediate position (parking) rather than the most angular (intake) and most advanced (exhaust) position, so that the system response compared to the CVVT. Faster sex and wider cam area.

Therefore, in the mid-phase CVVT, the fuel efficiency is improved by reducing the pumping loss by increasing the valve overlap of the intake / exhaust valve, and the emission reduction is further improved by the internal EGR through the optimization of the valve overlap according to the engine conditions. In addition, by improving the volumetric efficiency by optimizing the intake valve timing according to the engine conditions, the effect of increasing the low speed torque and output is further enhanced.

After the control of the intermediate phase CVVT, the locking control by the lock pin is executed when the intermediate phase CVVT reaches the unused area (stopping condition such as the idle state of the vehicle).

As shown in FIG. 1, when the intermediate phase CVVT reaches the unused area (see section D, which is the unused impact of the accelerator pedal), when locking is not normally performed due to a hardware (physical) failure of the medium phase CVVT, As illustrated in FIG. 1, the actual cam position (see line A) may be excessively advanced (or perceived) from the target cam position (see line B). This may cause an RPM drop (C-line section) or engine stall. E line of FIG. 1 is a line which shows an accelerator pedal signal, and F line of FIG. 1 is a line which shows engine RPM.

When starting off occurs due to the RPM drop or engine stall, it is difficult to determine the cause, and it is not possible to prevent problems such as starting off because it is not checked whether the lock is actually locked by the locking pin after the locking control. In addition, since the locking control is repeatedly performed after the aforementioned problem occurs, the same problem repeatedly occurs.

The matters described in this Background section are intended to enhance the understanding of the background of the invention, and may include matters not previously known to those of ordinary skill in the art.

The present invention has been made in view of the above, and an object of the present invention is to provide a control method of a continuously variable valve timing system that can prevent the occurrence of RPM drop and starting off after locking control.

The control method of the continuous variable valve timing system according to the present invention for achieving the above object,

On the cam phaser of the continuously variable valve timing system, it is determined whether the locking control for locking the rotor to the reference position is performed.

When the locking control is executed, the actual position of the rotor is monitored to determine whether the rotor is locked,

If it is determined that the rotor is not locked, the locking control is stopped and at the same time, the holding control for holding the rotor at the reference position is executed.

It is determined whether the locking control is executed if the vehicle is stopped when the continuous variable valve timing system is activated.

The actual position of the rotor is monitored by a cam sensor, and a difference value between the reference position and the actual position of the rotor is calculated. If the difference value is larger than a set value, the failure detection counter is increased by a set increase rate.

If the fault detection counter is larger than the reference counter, a fault code indicating that locking of the rotor is not normally performed is stored.

The locking control is terminated in accordance with the stored fault code, and a holding control for holding the rotor at a reference position is executed.

The oil control valve is controlled in accordance with the PWM duty cycle corresponding to the holding signal to execute the holding control.

If the stored fault code is maintained, the locking control is terminated in the corresponding stop condition and the subsequent stop condition, and the holding control is executed.

Locking control for locking the rotor to a reference position in the corresponding driving cycle is prohibited according to the stored fault code.

According to the present invention, it is determined whether locking is performed after the locking control, and if it is determined that the locking is bad, stopping the locking control and performing the holding control can prevent the occurrence of the RPM drop and the start-off. Improve the maintainability against hardware locking failure of the timing system.

1 is a graph showing a cam position, an RPM, an accelerator pedal signal, and the like when the locking phase is controlled by a lock pin when the intermediate phase CVVT reaches an unused region.
2 is a diagram illustrating one embodiment of a continuously variable valve timing system.
3 is a flowchart illustrating a control method of a continuously variable valve timing system according to an exemplary embodiment of the present invention.

Hereinafter, some embodiments of the present invention will be described in detail through exemplary drawings. In adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used to refer to the same components as much as possible, even if displayed on different drawings. In addition, in describing the embodiments of the present invention, when it is determined that the detailed description of the related well-known configuration or function interferes with the understanding of the embodiments of the present invention, the detailed description thereof will be omitted.

In describing the components of the embodiment of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are only for distinguishing the components from other components, and the nature, order or order of the components are not limited by the terms. In addition, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art, and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

Referring to FIG. 2, the continuously variable valve timing system 1 includes a cam shaft 5, a cam phaser 10 installed on a cam sprocket 6 of the cam shaft 5, and an oil pan 22. It may include an oil control valve 20 for adjusting the flow direction of the oil supplied to the cam phaser 10 from).

The cam phaser 10 can be configured to switch the phase between the crankshaft of the engine and the camshaft 5, whereby the rotational phase of the cam fixed to the camshaft 5 is changed so that the intake valve And / or opening and closing of the exhaust valve can be adjusted.

The cam phaser 10 may include a housing 11 and a rotor 12 housed within the housing 11.

The housing 11 may have a plurality of cavities 14. The rotor 12 may have a plurality of vanes 13, with each vane 13 extending radially from the rotor 12. The cam shaft 5 is coupled to the rotor 12 such that the cam shaft 5 and the rotor 12 can rotate together in the same direction. Each vane 13 may be disposed in each cavity 14, and each vane 13 in which the advance chamber 25 and the perceptual chamber 26 are located inside each cavity 14 in each cavity 14. It can be defined by.

A locking circuit (not shown) having a locking pin 15, a locking groove (not shown), and a spring (not shown) may be disposed between the rotor 12 and the housing 11, and the locking pin 15 is locked. The rotor 12 may be locked or unlocked to the housing 11 by being engaged or released in the groove (not shown). The locking pin 15 is movably installed in the vanes 13 of the rotor 12, and a locking groove (not shown) may be provided in the housing 11. The spring (not shown) may be configured to forcibly push the locking pin 15 toward the locking groove (not shown).

The oil control valve 20 may be configured to supply oil to the locking circuit having the advance chamber 25, the perception chamber 26, and the locking pin 15 in the housing 11. When oil is supplied to the advance chamber 25 by the oil control valve 20, each vane 23 of the rotor 12 moves to the set advance position, thereby allowing the operation of the variable valve timing system 1 to be operated at right angles. Can be carried out, and when oil is supplied to the tectonic chamber 26 by the oil control valve 20, each vane 23 of the rotor 12 is moved to the set tectonic position, so that the perception of the continuously variable valve timing system 1 Retarded operation may be performed. When oil is supplied to or discharged from the advance chamber 25 and the perception chamber 26 at an appropriate ratio by the oil control valve 20, each vane 23 of the rotor 12 is maintained at a set position so that the variable valve timing system is maintained. The holding operation of (1) can be executed.

Meanwhile, according to an embodiment of the present invention, the continuous variable valve timing system 1 may be a middle phase continuous variable valve timing system (hereinafter, referred to as 'middle phase CVVT'), and an intermediate phase The CVVT is a solenoid valve (for example, an oil-flow control valve (OCV)) that converts a plurality of flow paths by moving a spool (or plunger), and an ECU of an engine that applies PWM pulse width modulation duty (DUTY). Position control is executed by (Electronic Control Unit), and when the position control is executed, the cam position is controlled at the intermediate position (parking) instead of the lowest (intake) and most advanced (exhaust) position, so that the system responsiveness It is faster and the cam area is widened. Accordingly, when oil is properly distributed to the advance chamber 25 and the perceptual chamber 26 by the oil control valve 20, each vane 23 of the rotor 12 is set to an intermediate position between the most advanced and most perceptual positions. (mid position or intermediate phase angle position).

When the oil is discharged from the locking circuit by the oil control valve 20, the locking pin 15 may be coupled to the locking groove (not shown) by the spring, so that each vane 13 of the rotor 12 is By locking at the set reference position, a locking operation of the continuously variable valve timing system 1 can be executed. When oil is supplied to the locking circuit side, the locking pin 15 can be released from the locking groove (not shown), so that each vane 13 of the rotor 12 can be unlocked.

The oil control valve 20 can be a directional control valve with a linear solenoid, restoring spring and spool valve. The oil control valve 20 may be controlled by the ECU 30, and the ECU 30 may include a processor and a memory. The ECU 30 may be configured to receive signals from various sensors and to send signals to each device of the engine.

ECU 30 according to an embodiment of the present invention may be a microprocessor-based controller. The ECU 30 may include a microprocessor or central processing unit, read only memory (ROM), random access memory (RAM), electrically programmable read only memory (EPROM), high speed clokc, and the like. The ECU 30 may be configured to control or manage the overall operation of the oil control valve 20 in association with driving of the engine.

The ECU 30 may include a processor 31 and a memory 32, and the processor 31 receives control instructions stored in the memory 32, and transmits a control instruction to the oil control valve 20. instructions) can be programmed to transmit. The memory 32 includes data such as a hard disk drive, a solid-state drive, a server, a volatile media, a non-volatile media, and the like. It may be a data store.

The ECU 30 may be configured to control the oil control valve 20 according to a set PWM duty cycle. The ECU 30 may have different PWM duty values according to the perceptual operation, the advance operation, the holding operation, the locking operation, and the like of the continuous variable valve timing system 1.

An oil pump 21 is connected to the oil control valve 20, and oil may be supplied to the oil control valve 20 by the oil pump 21. Then, a cam sensor 9 for detecting the angle of the cam shaft 5 may be installed. In addition, an oil pressure sensor (not shown) may be installed in the flow path of the oil so as to detect the oil pressure.

3 is a flowchart illustrating a control method of a continuously variable valve timing system according to an exemplary embodiment of the present invention.

The ECU 30 determines whether the control of the continuously variable valve timing system 1 is activated (S1). If the control of the continuously variable valve timing system 1 is not activated, the failure detection counter is initialized (S2).

After the control of the continuously variable valve timing system 1 is activated, if the vehicle is in a stopping condition such as an idle state (that is, when the unused area of the continuously variable valve timing system 1 is reached), the ECU 30 continuously changes the variable. It is determined whether the locking control of the valve timing system 1 is executed (S3). Locking control of the continuously variable valve timing system 1 is such that when the ECU 30 transmits a locking signal to the oil control valve 20, the oil control valve 20 is discharged from the locking circuit having the locking pin 15. When the locking pin 15 is coupled to the locking groove by the spring, the rotor 12 of the cam phaser 10 is locked to the reference position R.

If the locking control of the continuously variable valve timing system 1 is not executed, the failure detection counter is initialized (S2).

When the locking control of the continuously variable valve timing system 1 is executed, the cam sensor 9 detects the rotation angle of the cam shaft 5 to monitor the current position of the rotor 12 (S4).

The ECU 30 calculates a difference value RC between the reference position R and the current position C of the rotor 12 according to the execution of the locking control, and the ECU 30 calculates the difference value RC described above. It is judged whether it is larger than this set value T1 (S5). Here, the set value T1 may be a reference value for determining whether the rotor 12 is locked.

If the above-described difference value RC is not larger than the first set value T1 (that is, the rotor 12 is determined to be locked near the reference position R), the failure detection counter DC is initialized ( S2).

If the difference value RC between the reference position R of the rotor 12 and the current position C of the rotor 12 is larger than the first set value T1 (that is, the rotor 12 is the reference position R). If it is determined that the lock has not been locked in the vicinity of), the ECU 30 increases the failure detection counter DC by a set increase rate (for example, 1 unit) (S6).

The ECU 30 determines whether the increased failure detection counter DC is larger than the reference counter T2 (S7). Here, the reference counter T2 may be a reference value for determining whether a failure occurs.

If the increased fault detection counter DC is larger than the reference counter T2, the ECU 30 may transmit a fault code (or service code) to the memory of the ECU 30 indicating that the locking of the rotor 12 is not normally performed. Save (S8).

According to the fault code stored in the memory 32 of the ECU 30, the ECU 30 terminates the locking control of the continuously variable valve timing system 1 and executes the holding control of the continuously variable valve timing system 1. (S9). In the holding control of the continuously variable valve timing system 1, when the ECU 30 transmits a holding signal to the oil control valve 20, the oil control valve 20 may be controlled according to a PWM duty cycle corresponding to the holding signal. By the duty control of the oil control valve 20, oil is distributed to the advance chamber 25 and the tectonic chamber 26 of the housing 11 of the cam phaser 10 at a predetermined ratio, thereby providing the cam phaser 10. Refers to the control that keeps the rotor 12 at the reference position.

In this way, when the fault code is stored in the memory 32 of the ECU 30 and the fault code stored in the memory 32 is not released, the continuous variable valve timing system 1 is maintained not only in the corresponding stop condition but also in the subsequent stop condition. And the locking control of the continuous variable valve timing system 1 are executed.

In addition, the ECU 30 may control the oil control valve 20 to prohibit locking control of locking the rotor 12 to the reference position R in a corresponding driving cycle according to the fault code stored in the memory 32. Control (S10).

As described above, the present invention can determine whether the locking after the locking control, and if it is determined that the locking is bad, stops the locking control and performs the holding control to prevent the occurrence of RPM drop and starting off, etc. Improved serviceability against hardware locking failures of the continuously variable valve timing system.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art may make various modifications and changes without departing from the essential characteristics of the present invention.

Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

1: Continuously variable valve timing system 5: Camshaft
6: Cam Sprocket 9: Cam Sensor
10: Cam Phaser 11: Housing
12: Rotor 13: Bain
14: Cavity 15: Locking Pin
20: oil control valve 21: oil pump
22: oil pan 25: advance chamber
26: Tectonic Chamber 30: ECU

Claims (8)

On the cam phaser of the continuously variable valve timing system, it is determined whether the locking control for locking the rotor to the reference position is performed.
When the locking control is executed, the actual position of the rotor is monitored to determine whether the rotor is locked,
And if it is determined that the locking of the rotor is not performed, stopping the locking control and simultaneously holding control for holding the rotor at a reference position. The method according to claim 1,
And controlling whether the locking control is executed if the vehicle is stopped after activation of the continuously variable valve timing system. The method according to claim 1,
Monitoring the actual position of the rotor by a cam sensor, calculating a difference value between the reference position and the actual position of the rotor,
And if the difference is greater than the set value, increase the failure detection counter by a predetermined increase rate. The method according to claim 3,
The control method of the continuous variable valve timing system for storing a failure code indicating that the locking of the rotor is not normally performed when the failure detection counter is larger than the reference counter. The method according to claim 4,
And a holding control for ending the locking control according to the stored fault code and holding the rotor at a reference position. The method according to claim 4,
A control method of a continuous variable valve timing system for performing the holding control by controlling an oil control valve according to a PWM duty cycle corresponding to a holding signal. The method according to claim 4,
And if the stored fault code is maintained, terminating the locking control in a corresponding stop condition and a subsequent stop condition and executing a holding control. The method according to claim 3,
The control method of the continuous variable valve timing system for prohibiting the locking control of locking the rotor to the reference position in the driving cycle in accordance with the stored fault code.

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