CN117703559A - Unlocking control method of middle locking type variable valve timing system - Google Patents

Abstract

The invention discloses an unlocking control method of an intermediate locking type variable valve timing system, which comprises the following steps of S1: after an unlocking instruction is acquired and an unlocking condition is met, S2 is entered; s2: acquiring a current duty ratio, controlling the current duty ratio t1 time in an open loop manner, acquiring the current phase of a cam shaft in real time, and adjusting the current phase to a target phase if the phase difference between the current phase and the initial phase is greater than or equal to a deviation threshold value, wherein the unlocking is successful; otherwise, the unlocking is unsuccessful, and S3 is entered; s3: the current duty cycle is adjusted to a first duty cycle t2 time; s4: adjusting the time of a current duty ratio t3 according to an oscillation auxiliary unlocking rule, acquiring a current phase in real time, and if the phase difference is greater than or equal to a deviation threshold value, successfully unlocking, performing closed-loop control on the current duty ratio, and adjusting the current phase to a target phase; otherwise, the unlocking is unsuccessful, and a fault code is reported. The unlocking time under normal conditions can be shortened, the overshoot amplitude is reduced, and the phenomenon of unlocking failure is reduced.

Description

Unlocking control method of middle locking type variable valve timing system

Technical Field

The invention belongs to the technical field of engines, and particularly relates to an unlocking control method of an intermediate locking type variable valve timing system.

Background

In modern engines, variable valve timing (Variable Valve Timing, VVT) technology is commonly used in order to meet both fuel consumption and performance requirements. CO for various countries with global warming ₂ Emissions are increasingly demanding, and hybrid engines have become a trend in automotive internal combustion engines. Naturally aspirated hybrid engine to reduce CO ₂ The emission commonly adopts an Atkinson cycle (Atkinson cycle) with a large intake cam wrap angle, the Atkinson cycle requires that the intake valve is closed greatly, and the intake valve is closed late, which is unfavorable for cold starting of the engine. Therefore, the middle locking type VVT with a larger adjusting range and the requirements of cold start emission and idle speed stability of the engine can be met, and the middle locking type VVT starts to be applied to the hybrid engine of each large main engine plant.

The patent publication CN110410168B describes an intermediate locking VVT control system and method that includes a 3-position 4-way oil control (Oil Control Valve, OCV) valve and an oil switching (Oil Switching Valve, OSV) valve, with the lock pin oil passage being independently controllable, with high system cost and complexity. The unlocking control strategy is to open loop control the OCV valve firstly and then open the OSV valve for unlocking, if the open loop control is not performed again after unlocking, the control strategy does not show that the unlocking control method has better improvement effect on the unlocking condition. Therefore, the unlocking method using the intermediate locking VVT control system may not be unlocked.

Therefore, an intermediate locking VVT system may be provided, which has a 4-position 5-way OCV valve, and has a lock pin control oil path integrated into the OCV valve, which saves an OSV valve compared with the aforementioned patent, effectively reduces the cost of parts and control complexity, and the basic structure of the OCV valve and the control oil path are as shown in fig. 1, and the intermediate locking VVT system receives a duty ratio signal from an electronic control unit through the electromagnet 300, generates an axial electromagnetic force, and further controls the valve core 210 to move in a direction away from or close to the electromagnet 300 in an axial direction relative to the valve body 220. The duty ratio is different, the electromagnetic force is different, the moving distance of the valve core 210 is different, and the working mode of the middle locking VVT system is different. As shown in fig. 2 a-2 d, the control oil paths in different working modes of the middle locking VVT system are different in movement distance of the valve core 210, and the oil paths inside the OCV valve 200 after being fed from the oil inlet P are also different, so that the oil feeding and discharging paths leading to the advance oil chamber a, the retard oil chamber B and the locking oil chamber L can be switched, and the rotation direction of the rotor 500 and the unlocking/locking state of the lock pin 700 can be determined. Two oil chambers of an advance oil chamber A and a retard oil chamber B are respectively arranged on two sides of the locking position, when the VVT system is unlocked, oil flows into the advance oil chamber A and the locking oil chamber L from two oil inlets P at the same time, the oil pressure of the advance oil chamber A pushes the rotor 500 to rotate clockwise, and the engine oil of the locking oil chamber L pushes the lock pin 700 to lift and unlock.

At present, the VVT system is generally controlled to unlock through open loop control of the duty ratio, but the duty ratio of the unlocking requirement is different under different conditions, and when the flow is large and the flow is fast under the condition of high oil pressure, the high back pressure of the lock pin 700 or the side leaning of the rotor 500 is easily caused, so that the excessive tangential force is caused to cause unsuccessful unlocking.

In order to ensure successful unlocking, the duty ratio during open-loop unlocking can be increased and the open-loop control time can be prolonged, but the unlocking time is too long, and the overshoot can be too large, so that the use requirement of the intermediate locking type VVT system in the transient process can not be met.

Disclosure of Invention

The invention aims to solve the problem that an intermediate locking type variable valve timing system adopting a 4-bit 5-way OCV valve cannot unlock or has overlarge overshoot after unlocking. The invention provides an unlocking control method of an intermediate locking type variable valve timing system, which can shorten the unlocking time under normal conditions, reduce the overshoot range and greatly reduce the phenomenon of unlocking, thereby reducing the failure rate of an engine.

In order to solve the above technical problems, an embodiment of the present invention discloses an unlocking control method for an intermediate locking type variable valve timing system, the intermediate locking type variable valve timing system including a 4-position 5-way engine oil control valve, the unlocking control method including:

s1: acquiring an unlocking instruction and the current phase of a cam shaft, and judging whether an unlocking condition is met or not according to the current phase;

if it is determined that the unlock condition is satisfied, the process proceeds to step S2.

S2: acquiring a current duty ratio, performing open-loop control on the current duty ratio, and maintaining t1 time; acquiring the current phase of the cam shaft in real time in t1, and judging whether unlocking is successful or not according to the comparison result of the current phase of the cam shaft and the initial assembly phase; if the phase difference between the current phase and the initial loading phase is larger than or equal to the deviation threshold value, judging that the unlocking is successful, performing closed-loop control on the current duty ratio, and adjusting the current phase to the target phase; if the phase difference between the current phase and the initial loading phase is smaller than the deviation threshold, the unlocking is judged to be unsuccessful, and the step S3 is carried out.

S3: the current duty cycle is adjusted to the first duty cycle and maintained for a time t 2.

S4: adjusting the current duty ratio according to an oscillation auxiliary unlocking rule, maintaining t3 time, acquiring the current phase of the cam shaft in real time in the t3 time, and judging whether the unlocking is successful or not according to the comparison result of the current phase of the cam shaft and the initial assembly phase; if the phase difference between the current phase and the initial loading phase is larger than or equal to the deviation threshold value, judging that the unlocking is successful, performing closed-loop control on the current duty ratio, and adjusting the current phase to the target phase; if the phase difference between the current phase and the initial loading phase is smaller than the deviation threshold value, judging that unlocking is unsuccessful, and reporting a fault code;

wherein, adjust current duty cycle according to concussion auxiliary unlocking rule includes:

s41: adjusting the current duty cycle to a second duty cycle and maintaining for t4 time, and then executing step S42; wherein the second duty cycle is greater than the first duty cycle;

s42: then the current duty ratio is adjusted to the third duty ratio and maintained for t5 time, and then the step S41 is continuously executed; wherein the third duty cycle is less than the second duty cycle, and the t3 time is greater than or equal to the sum of all t4 times and all t5 times.

By adopting the technical scheme, after the unlocking instruction is acquired and the unlocking condition is met, the current duty ratio is acquired, the current duty ratio is subjected to open loop control and is maintained for t1 time, the current phase of the cam shaft is acquired in real time in the process of open loop control (within the time of t 1), and the current phase of the cam shaft is acquired by the methodJudging whether unlocking is successful or not according to the comparison result of the current phase of the camshaft and the initial loading phase, judging that unlocking is successful if the phase difference between the current phase and the initial loading position is larger than or equal to the deviation threshold value, performing closed-loop control on the current duty ratio, and adjusting the current phase to the target phase. Compared with the conventional open-loop unlocking strategy, the method shortens the unlocking time under normal conditions, reduces the overshoot amplitude, brings better driving feeling and fuel economy to customers, and reduces CO ₂ Discharge amount.

Further, if the phase difference between the current phase and the initial loading position is smaller than the deviation threshold in the open loop control process, judging that unlocking is unsuccessful, adjusting the current duty ratio to the first duty ratio and maintaining t2 time, and then adjusting the current duty ratio according to the oscillation auxiliary unlocking rule and maintaining t3 time. The oscillation auxiliary unlocking rule comprises the steps of firstly adjusting the current duty cycle to a second duty cycle (high duty cycle) and maintaining t4 time, wherein the second duty cycle is larger than the first duty cycle, then adjusting the current duty cycle to a third duty cycle (low duty cycle) and maintaining t5 time, wherein the third duty cycle is smaller than the second duty cycle, so that the current duty cycle is adjusted circularly, and the t3 time is larger than or equal to the sum of all t4 times and all t5 times. The method is equivalent to the condition that the current phase of the cam shaft is adjusted left and right, and unlocking is unsuccessful due to locking of the lock pin by the side. In the process of adjusting the current duty ratio according to the oscillation auxiliary unlocking rule (within the time t 3), acquiring the current phase of the cam shaft in real time, judging that the unlocking is successful if the phase difference between the current phase and the initial installation position is greater than or equal to a deviation threshold value, performing closed-loop control on the current duty ratio, and adjusting the current phase to a target phase; if the phase difference between the current phase and the initial installation position is smaller than the deviation threshold value, judging that the unlocking is unsuccessful, reporting a fault code, and reminding a user to check. Therefore, the phenomenon that the middle locking type variable valve timing system adopting the 4-position 5-way OCV valve is not unlocked is greatly reduced, the failure rate of the engine is reduced, and a large number of after-sale detection and maintenance costs of customers are saved.

According to another embodiment of the present invention, in the unlocking control method of the intermediate locking type variable valve timing system disclosed in the embodiment of the present invention, in step S1, determining whether the unlocking condition is satisfied according to the current phase includes: if the current phase is in the initial loading phase, judging that the unlocking condition is met; otherwise, judging that the unlocking condition is not satisfied.

By adopting the technical scheme, the unlocking condition is judged to be met only when the current phase is in the initial installation phase, namely, in the preset locking position, and if the unlocking condition is not judged to be met, the subsequent open-loop control unlocking can be performed when the current phase is in the preset locking position.

According to another embodiment of the present invention, in the unlocking control method of the intermediate locking type variable valve timing system disclosed in the embodiment of the present invention, in step S1, the time t1 is 0.1S.

According to another embodiment of the present invention, the unlocking control method of the intermediate locking type variable valve timing system disclosed in the embodiment of the present invention has a deviation threshold of 3 ° CA in step S2 and step S4.

According to another embodiment of the present invention, in the unlocking control method of the intermediate locking type variable valve timing system disclosed in the embodiment of the present invention, in step S3, the first duty ratio is 10%, and the time t2 is 0.2S to 0.5S.

According to another embodiment of the present invention, the unlocking control method of the intermediate locking type variable valve timing system according to embodiment 6 of the present invention as set forth in claim 1, in step S4, the time t3 is 1S.

According to another embodiment of the present invention, in the unlocking control method of the intermediate locking type variable valve timing system disclosed in the embodiment of the present invention, in step S41, the second duty ratio is 90%.

According to another embodiment of the present invention, in the unlocking control method of the intermediate locking type variable valve timing system disclosed in the embodiment of the present invention, in step S41, the time t4 is 0.1S.

According to another embodiment of the present invention, in the unlocking control method of the intermediate locking type variable valve timing system disclosed in the embodiment of the present invention, in step S42, the third duty ratio is 35%.

According to another embodiment of the present invention, in the unlocking control method of the intermediate locking type variable valve timing system disclosed in the embodiment of the present invention, in step S42, the time t5 is 0.1S.

The beneficial effects of the invention are as follows:

the invention provides an unlocking control method of an intermediate locking type variable valve timing system, which comprises the steps of obtaining a current duty ratio after an unlocking instruction is obtained and an unlocking condition is met, carrying out open loop control on the current duty ratio, maintaining t1 time, obtaining the current phase of a cam shaft in real time in the process of open loop control (within the t1 time), judging whether unlocking is successful according to the comparison result of the current phase and the initial loading phase of the cam shaft, judging that unlocking is successful if the phase difference between the current phase and the initial loading position is greater than or equal to a deviation threshold value, carrying out closed loop control on the current duty ratio, and regulating the current phase to a target phase. Compared with an open-loop unlocking strategy, the method shortens the unlocking time under normal conditions, reduces the overshoot amplitude, brings better driving feeling and fuel economy to customers, and reduces CO ₂ Discharge amount.

Further, if the phase difference between the current phase and the initial loading position is smaller than a deviation threshold in the open loop control process, judging that unlocking is unsuccessful, adjusting the current duty cycle to a first duty cycle and maintaining t2 time, then adjusting the current duty cycle according to an oscillation auxiliary unlocking rule and maintaining t3 time, wherein the oscillation auxiliary unlocking rule comprises the steps of firstly adjusting the current duty cycle to a second duty cycle and maintaining t4 time, then adjusting the current duty cycle to a third duty cycle and maintaining t5 time, and circularly adjusting the current duty cycle; the second duty ratio is larger than the first duty ratio and larger than the third duty ratio, and the time t3 is larger than or equal to the sum of all the time t4 and all the time t5, which is equivalent to the condition that the current phase of the cam shaft is adjusted left and right to prevent the unlocking failure caused by the locking of the lock pin by side. And in the process of adjusting the current duty ratio according to the oscillation auxiliary unlocking rule (within the time t 3), acquiring the current phase of the cam shaft in real time, judging that the unlocking is successful if the phase difference between the current phase and the initial installation position is greater than or equal to a deviation threshold value, performing closed-loop control on the current duty ratio, and adjusting the current phase to a target phase. If the phase difference between the current phase and the initial installation position is smaller than the deviation threshold value, judging that the unlocking is unsuccessful, reporting a fault code, and reminding a user to check. Therefore, the phenomenon that the middle locking type variable valve timing system adopting the 4-position 5-way OCV valve is not unlocked is greatly reduced, the failure rate of the engine is reduced, and a large number of after-sale detection and maintenance costs of customers are saved.

Drawings

FIG. 1 is a schematic diagram of an intermediate lock-up variable valve timing system and a camshaft according to an embodiment of the present invention;

FIG. 2a is a schematic diagram of a control oil passage and a lock pin position of an intermediate lock-up type variable valve timing system in a lock-down mode according to an embodiment of the present invention;

FIG. 2b is a schematic diagram of the control oil passage and the lock pin position of the intermediate lock-up type variable valve timing system in the advance adjustment mode according to the embodiment of the present invention;

FIG. 2c is a schematic diagram of the control oil passage and lock pin position of the intermediate locked variable valve timing system in the unlock/phase hold mode according to an embodiment of the present invention;

FIG. 2d is a schematic diagram of the control oil passage and the lock pin position of the intermediate lock-up type variable valve timing system in the retard mode according to the embodiment of the present invention;

FIG. 3 is a flow chart of an unlock control method of an intermediate lock-up type variable valve timing system according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of an open-loop unlocking of an intermediate-locking variable valve timing system according to an embodiment of the present invention;

fig. 5 is a schematic diagram of an unlock control method of an intermediate lock-up type variable valve timing system according to an embodiment of the present invention.

Reference numerals illustrate:

100: a cam shaft; 200: an OCV valve; 210: a valve core; 220: a valve body; 300: an electromagnet; 400: a harness joint; 500: a rotor; 600: a sprocket; 700: a locking pin; 800: a latch slot; 900: a back cover plate; a: an oil advance chamber; b: a retard oil chamber; p: an oil inlet; l: locking the oil cavity; t: and an oil discharge port.

Detailed Description

Further advantages and effects of the present invention will become apparent to those skilled in the art from the disclosure of the present specification, by describing the embodiments of the present invention with specific examples. While the description of the invention will be described in connection with the preferred embodiments, it is not intended to limit the inventive features to the implementation. Rather, the purpose of the invention described in connection with the embodiments is to cover other alternatives or modifications, which may be extended by the claims based on the invention. The following description contains many specific details for the purpose of providing a thorough understanding of the present invention. The invention may be practiced without these specific details. Furthermore, some specific details are omitted from the description in order to avoid obscuring the invention. It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.

It should be noted that in this specification, like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.

In the description of the present embodiment, it should be noted that the azimuth or positional relationship indicated by the terms "upper", "lower", "inner", "bottom", etc. are based on the azimuth or positional relationship shown in the drawings, or the azimuth or positional relationship in which the inventive product is conventionally put in use, are merely for convenience of describing the present invention and simplifying the description, and are not indicative or implying that the apparatus or element to be referred to must have a specific azimuth, be configured and operated in a specific azimuth, and therefore should not be construed as limiting the present invention.

The terms "first," "second," and the like are used merely to distinguish between descriptions and are not to be construed as indicating or implying relative importance.

In the description of the present embodiment, it should also be noted that, unless explicitly specified and limited otherwise, the terms "disposed," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present embodiment can be understood in a specific case by those of ordinary skill in the art.

For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

The embodiment of the present invention discloses an intermediate locking type variable valve timing system, which includes a 4-position 5-way OCV valve 200, an electromagnet 300, a rotor 500, a sprocket 600, and a rear cover 900 thereof, as shown in fig. 1. Wherein, rotor 500 is fixed with 4-position 5-way OCV valve 200, 4-position 5-way OCV valve 200 and rotor 500 are fixed on camshaft 100, sprocket 600 and back plate 900 are fixed connection, and sprocket 600's inside has the oil pocket, and rotor 500 is located the oil pocket inside. Sprocket 600 is in driving connection with the crankshaft of the engine via a transmission (chain). The power transmission mode is as follows: once the engine crankshaft rotates, rotational force is transmitted to the sprocket 600 through the transmission, and the rotor 500 is rotated about its axis by the oil pressure of the oil chamber, and the camshaft 100 is rotated in parallel, and the cam provided on the camshaft 100 pushes down the intake valve or the exhaust valve to open the valve.

And the 4-position 5-way OCV valve 200 includes a valve body 220, a spool 210 movable in an axial direction thereof with respect to the valve body 220, and an electromagnet 300 is disposed opposite to one end of the spool 210. The electromagnet 300 is connected to an electronic control unit (Electronic Control Unit, ECU) through a harness connector 400, receives a pulse width modulation (Pulse Width Modulation, PWM) duty cycle signal from the electronic control unit, generates an axial electromagnetic force, and further controls the valve core 210 to move in a direction away from or toward the electromagnet 300 in an axial direction relative to the valve body 220. The larger the duty ratio is, the larger the electromagnetic force is, and the larger the moving distance of the spool 210 is.

The control oil passages in the different operation modes of the intermediate lock-up type variable valve timing system are shown in fig. 2a to 2 d. As shown in fig. 2a to 2d, the OCV valve 200 has two oil inlets P, an oil drain L, and a plurality of internal oil passages, and the intermediate locking type variable valve timing system further includes a lock pin 700, a lock pin groove 800, and a plurality of oil chambers. The plurality of oil chambers comprise an advance oil chamber A, a retard oil chamber B and a locking oil chamber L. The latch groove 800 is located on a side of the back plate 900 near the rotor 500 and communicates with the locking oil chamber L. The rotor 500 is provided with a locking pin hole through which one end of the locking pin 700 passes and the other end of which is engaged with the locking pin groove 800. The duty ratio is different, the moving distance of the valve core 210 is different, and the internal oil passage through the OCV valve 200 after the oil is fed from the oil inlet P is also different, so that the oil feeding and discharging paths to the advance oil chamber a, the retard oil chamber B and the lock oil chamber L can be switched, and the rotation direction of the rotor 500 and the unlock/lock state of the lock pin 700 are determined, wherein the lock pin 700 is in the lock state when the lock pin 700 is located in the lock pin groove 800.

As shown in fig. 2a, in the lock-down mode, the spool 210 of the OCV valve 200 is at the initial position, at which the oil entering the OCV valve 200 from the oil inlet P is not led to the advance oil chamber a, the retard oil chamber B, and the lock-up oil chamber L, and the oil of the lock-up oil chamber L is discharged from the oil discharge port T, the lock pin 700 is in the locked state, at which the rotor 500 cannot rotate relative to the sprocket 600, and this mode is generally at the engine start time.

As shown in fig. 2B, when the PWM duty ratio increases, the spool 210 moves inward (to the right), and enters the advance regulation mode, at this time, the oil entering the OCV valve 200 from the oil inlet P is led to the advance oil chamber a, the lock oil chamber L, and the oil of the retard oil chamber B is discharged from the oil discharge port T, so that the lock pin 700 can be maintained in a lifted state (moved upward), and the rotor 500 can rotate clockwise about its axis with respect to the sprocket 600, thereby regulating the camshaft 100 in the advance direction.

As shown in fig. 2c, when the PWM duty ratio continues to increase, the spool 210 continues to move inward (to the right), and enters an unlock/phase hold mode, at which time the oil entering the OCV valve 200 from the oil inlet P is only led to the lock oil chamber L, pushing the lock pin 700 to lift or always hold in a lifted state, the rotor 500 cannot rotate relative to the sprocket 600, and the phase of the camshaft 100 is not adjusted.

As shown in fig. 2d, when the PWM duty ratio increases again, the valve core 210 moves further inward (right), and the oil entering the OCV valve 200 from the oil inlet P is led to the retard oil chamber B and the lock oil chamber L, and the oil in the advance oil chamber a is discharged from the oil discharge port T, so that the lock pin 700 can be maintained in a lifted state, and the rotor 500 can rotate counterclockwise about its axis relative to the sprocket 600, thereby adjusting the camshaft 100 in the retard direction.

That is, the operation mode of the intermediate locking type variable valve timing system, that is, the moving position of the valve spool 210, may be controlled by the duty ratio given to the electromagnet 300 by the electronic control unit, thereby controlling the phase of the camshaft 100.

Ideally, the duty ratio in the unlock/phase hold mode is required to be used when the intermediate locking type variable valve timing system is unlocked, but the valve element 210 of the OCV valve 200 is gradually pushed in from the lock-down mode to the unlock/phase hold mode, and inevitably undergoes the advance adjustment mode, which means that the advance oil chamber a with a short period of VVT is filled with oil, and in the high pressure mode of the engine, the more the engine oil amount entering the advance oil chamber a, the more easily the lock pin 700 is brought to the side, i.e., the right side of the lock pin 700 abuts against the lock pin groove 800, so that the oil pressure at the bottom of the lock pin 700 cannot overcome the friction force generated by the shear force of the lock pin 700, and thus cannot be unlocked. In addition, due to variations in the manufacturing consistency of the parts (variations in the electromagnetic force profile of the electromagnet 300, tolerances in the return spring force of the spool 210, etc.), even given the same duty cycle, there is some variation in the actual position of the spool 210 of the OCV valve 200, resulting in a variation in the actual operation mode from the intended one.

In order to solve the risk of unlocking caused by the side leaning of the lock pin 700 under high oil pressure and consider part deviation, a duty ratio slightly larger than the current duty ratio (reaching a hysteresis adjustment duty ratio interval) is generally set, so that in the initial stage of the unlocking process, the hysteresis oil cavity B of the middle locking type variable valve timing system can enter some engine oil, and the rotor 500 is pushed to swing reversely, so that the lock pin 700 does not lean on the side, and the lock pin 700 is lifted and unlocked more easily.

However, the duty ratio given by the electronic control unit is controlled by an open loop and the control time is fixed, so that a large margin is generally provided for the open loop time to ensure that enough time is available for unlocking, which means that after the lock pin 700 is unlocked at the rear end of the open loop time, a certain time delay exists for the oil cavity B to be still supplied with oil, so that the rotor 500 is pushed to adjust in the hysteresis direction, and thus the intermediate locking type variable valve timing system is smoothly unlocked in the open loop time, but the phase is overtuned in the hysteresis direction. If the open-loop time is prolonged, which means that more engine oil is fed to the retard oil chamber B, the overshoot of the intermediate lock-up type variable valve timing system is greater.

In order to solve the above technical problems, as shown in fig. 3, an embodiment of the present invention discloses an unlocking control method of an intermediate locking type variable valve timing system, including:

s1: acquiring an unlocking instruction and the current phase of a cam shaft, and judging whether an unlocking condition is met or not according to the current phase; if it is determined that the unlock condition is satisfied, the process proceeds to step S2.

In a specific embodiment, in step S1, determining whether the unlocking condition is satisfied according to the current phase includes: if the current phase is in the initial loading phase, judging that the unlocking condition is met; otherwise, judging that the unlocking condition is not satisfied.

In the present embodiment, when it is determined that the unlock condition is satisfied, the present phase is required to be the initial charge phase, and the intermediate lock-up type variable valve timing system enabling condition is required to be satisfied. Generally, if the current rotational speed of the engine is greater than the idle rotational speed and the current oil temperature is within the range of-10 ℃ to 130 ℃, then it is determined that the VVT enabling condition is satisfied.

It should be noted that, acquiring the current phase of the camshaft includes: an Electronic Control Unit (ECU) reads a phase sensor signal on the camshaft and calculates a current phase of the camshaft from the phase sensor signal. The initial phase refers to the theoretical initial lock-up phase, i.e., the position of the camshaft immediately after the engine is started. The engine is just started, the rotating speed and the oil temperature do not reach the enabling conditions of the middle locking type variable valve timing system, at the moment, the camshaft is fixed at the initial phase position and cannot be adjusted, the phase position of the camshaft is required to be determined and preset according to the test results in combination with combustion stability, emission and oil consumption when the engine is just started, and the engine is stored in an Electronic Control Unit (ECU).

S2: acquiring a current duty ratio, performing open-loop control on the current duty ratio, and maintaining t1 time; acquiring the current phase of the cam shaft in real time in t1, and judging whether unlocking is successful or not according to the comparison result of the current phase of the cam shaft and the initial assembly phase; if the phase difference between the current phase and the initial loading phase is larger than or equal to the deviation threshold value, judging that the unlocking is successful, performing closed-loop control on the current duty ratio, and adjusting the current phase to the target phase. If the phase difference between the current phase and the initial loading phase is smaller than the deviation threshold, the unlocking is judged to be unsuccessful, and the step S3 is carried out. In one embodiment, in step S1, the time t1 is 0.1S. In a specific embodiment, in step S1, the deviation threshold is 3 ° CA.

The current duty cycle means that the electromagnet receives a PWM duty cycle signal from the electronic control unit. According to the current duty ratio electromagnet, axial electromagnetic force can be generated, and then the pushing amount of the valve core inwards along the axial direction is controlled, so that the oil inlet and discharge paths of an advance oil cavity, a retard oil cavity and a locking oil cavity can be switched, the rotation direction of a rotor and the unlocking/locking state of a lock pin are determined, the working mode of the middle locking type variable valve timing system is switched, and the current phase of a cam shaft can be further controlled. I.e. the current phase of the camshaft can be adjusted by adjusting the current duty cycle.

In this embodiment, as shown in fig. 4, the open loop control of the current duty ratio means: the electronic control unit gives the electromagnet a fixed duty ratio (unlocking duty ratio), the electromagnet can act according to the fixed duty ratio to push the valve core, the working mode of the middle locking type variable valve timing system is switched, and the current phase of the cam shaft is adjusted. The fixed duty ratio is preset according to the oil temperature calibration of the engine, and the engine needs to be given according to a real-time oil temperature lookup table when unlocking is executed each time.

Closed loop control of the current duty cycle refers to: PID closed-loop control is performed, namely, the electronic control unit gives the electromagnet a duty ratio which is adjusted in real time according to the difference between a target phase and an actual phase preset according to working conditions, and the electromagnet acts according to the duty ratio which is adjusted in real time to push the valve core, so that the current phase of the camshaft is adjusted.

Adjusting the current phase to a target phase among the target phases refers to a target position of a camshaft of the intermediate lock-up type variable valve timing system under different conditions in engine operation. The target position is determined by a combination of fuel consumption, emissions, performance, combustion stability, responsiveness, smoothness, temperature, altitude, etc., and is usually determined by computer aided engineering (computer aided engineering, CAE) calculation and testing and preset in the ECU.

S3: as shown in fig. 5, the current duty cycle is adjusted to the first duty cycle and maintained for a time t 2. In a specific embodiment, in step S3, the first duty cycle is 10% and the time t2 ranges from 0.2S to 0.5S. The purpose of this is to keep the lock pin still in the locked state, facilitating the step S4.

In this embodiment, the time t2 may be any one of 0.2s, 0.3s, 0.4s, and 0.5s, or may be other time between 0.2s and 0.5s, which is not particularly limited, and may be set by those skilled in the art according to actual situations.

S4: as shown in fig. 5, the current duty ratio is adjusted according to the oscillation auxiliary unlocking rule and is maintained for t3 time, the current phase of the cam shaft is obtained in real time in the t3 time, and whether the unlocking is successful is judged according to the comparison result of the current phase of the cam shaft and the initial assembly phase; if the phase difference between the current phase and the initial loading phase is larger than or equal to the deviation threshold value, judging that the unlocking is successful, performing closed-loop control on the current duty ratio, and adjusting the current phase to the target phase; if the phase difference between the current phase and the initial loading phase is smaller than the deviation threshold value, judging that the unlocking is unsuccessful, and reporting a fault code. In one embodiment, the time t3 is 1s. In one embodiment, the deviation threshold in step S4 is 3 ° CA.

Wherein, adjust current duty cycle according to concussion auxiliary unlocking rule includes:

s41: adjusting the current duty cycle to a second duty cycle and maintaining for t4 time, and then executing step S42; wherein the second duty cycle is greater than the first duty cycle. In one embodiment, the second duty cycle is 90% and the t4 time is 0.1s.

S42: then the current duty ratio is adjusted to the third duty ratio and maintained for t5 time, and then the step S41 is continuously executed; wherein the third duty cycle is less than the second duty cycle, and the t3 time is greater than or equal to the sum of all t4 times and all t5 times. In one embodiment, the third duty cycle is 35% and the t5 time is 0.1s.

In the present embodiment, the second duty ratio is 90%, which is a high duty ratio, and the third duty ratio is 35%, which is a low duty ratio. the time t3 is 1s, the time t4 and the time t5 are both 0.1s, namely the high-low duty ratio is alternately not more than 5 times in the oscillation auxiliary unlocking rule. The current duty ratio is adjusted according to the oscillation auxiliary unlocking rule, so that the risk of unlocking caused by the side leaning of the lock pin 700 is avoided.

In this embodiment, the longest operation time in step S4 is the sum of time t3 and all the judging times for judging whether the unlocking is successful in real time according to the comparison result of the current phase and the initial assembly phase of the camshaft, and if the longest operation time in step S4 reaches time t6, it is still judged that the unlocking is unsuccessful, a fault code is reported. In one embodiment, time t6 ranges from 2s to 3s. In addition, if fault codes are reported in two continuous driving cycles, the instrument panel is lighted, and a customer needs to be reminded to enter the station for detection, wherein the complete process of completing ignition, running and flameout of the automobile is called a driving cycle.

By adopting the technical scheme, after the unlocking instruction is acquired and the unlocking condition is met, the current duty ratio is acquired, the current duty ratio is subjected to open loop control and is maintained for t1 time, the current phase of the cam shaft is acquired in real time in the process of open loop control (within the time of t 1), whether the unlocking is successful is judged according to the comparison result of the current phase and the initial loading phase of the cam shaft, if the phase difference between the current phase and the initial loading position is greater than or equal to the deviation threshold value, the unlocking is judged to be successful, the current duty ratio is subjected to closed loop control, and the current phase is regulated to the targetPhase position. Compared with an open-loop unlocking strategy, the method shortens the unlocking time under normal conditions, reduces the overshoot amplitude, brings better driving feeling and fuel economy to customers, and reduces CO ₂ Discharge amount.

Further, if the phase difference between the current phase and the initial loading position is smaller than a deviation threshold in the open loop control process, judging that unlocking is unsuccessful, adjusting the current duty cycle to a first duty cycle and maintaining t2 time, then adjusting the current duty cycle according to an oscillation auxiliary unlocking rule and maintaining t3 time, wherein the oscillation auxiliary unlocking rule comprises the steps of adjusting the current duty cycle to a second duty cycle and maintaining t4 time, and then adjusting the current duty cycle to a third duty cycle and maintaining t5 time, and circularly adjusting the current duty cycle; the second duty ratio is greater than the first duty ratio and greater than the third duty ratio, and the time t3 is greater than the sum of all the time t4 and all the time t5, which is equivalent to adjusting the current phase of the camshaft left and right (the rotor 500 swings due to the oil pressure difference between the advance oil chamber A and the retard oil chamber B), so as to prevent the unsuccessful unlocking caused by the locking of the lock pin by edge. In the process of adjusting the current duty ratio according to the oscillation auxiliary unlocking rule (within the time t 3), acquiring the current phase of the cam shaft in real time, judging that the unlocking is successful if the phase difference between the current phase and the initial installation position is greater than or equal to a deviation threshold value, performing closed-loop control on the current duty ratio, and adjusting the current phase to a target phase; if the phase difference between the current phase and the initial installation position is smaller than the deviation threshold value, judging that the unlocking is unsuccessful, reporting a fault code, and reminding a user to check. Therefore, the phenomenon that the middle locking type variable valve timing system adopting the 3-position 4-way OCV valve is not unlocked is greatly reduced, the failure rate of the engine is reduced, and a large number of after-sale detection and maintenance costs of customers are saved.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing is a further detailed description of the invention with reference to specific embodiments, and it is not intended to limit the practice of the invention to those descriptions. Various changes in form and detail may be made therein by those skilled in the art, including a few simple inferences or alternatives, without departing from the spirit and scope of the present invention.

Claims (10)

1. An unlock control method of an intermediate lock-up type variable valve timing system, characterized in that the intermediate lock-up type variable valve timing system includes a 4-position 5-way engine oil control valve, the unlock control method comprising:

s1: acquiring an unlocking instruction and a current phase of a cam shaft, and judging whether an unlocking condition is met or not according to the current phase;

if the unlocking condition is judged to be met, the step S2 is carried out;

s2: acquiring a current duty ratio, performing open-loop control on the current duty ratio, and maintaining t1 time; acquiring the current phase of the cam shaft in real time in the time t1, and judging whether unlocking is successful or not according to the comparison result of the current phase of the cam shaft and the initial assembly phase;

if the phase difference between the current phase and the initial installation phase is greater than or equal to a deviation threshold value, judging that unlocking is successful, performing closed-loop control on the current duty ratio, and adjusting the current phase to a target phase;

if the phase difference between the current phase and the initial assembly phase is smaller than a deviation threshold, judging that unlocking is unsuccessful, and entering step S3;

s3: adjusting the current duty cycle to a first duty cycle and maintaining for a t2 time;

s4: adjusting the current duty ratio according to an oscillation auxiliary unlocking rule, maintaining t3 time, acquiring the current phase of the cam shaft in real time in the t3 time, and judging whether unlocking is successful or not according to the comparison result of the current phase of the cam shaft and the initial assembly phase;

if the phase difference between the current phase and the initial loading phase is greater than or equal to the deviation threshold, judging that unlocking is successful, performing closed-loop control on the current duty ratio, and adjusting the current phase to the target phase;

if the phase difference between the current phase and the initial assembly phase is smaller than the deviation threshold, judging that unlocking is unsuccessful, and reporting a fault code;

wherein, adjusting the current duty cycle according to the oscillation auxiliary unlocking rule includes:

s41: adjusting the current duty cycle to a second duty cycle and maintaining for t4 time, and then executing step S42; wherein the second duty cycle is greater than the first duty cycle;

s42: adjusting the current duty cycle to a third duty cycle and maintaining for t5 time, and then continuing to execute the step S41; wherein the third duty cycle is less than the second duty cycle; the t3 time is greater than or equal to the sum of all the t4 times and all the t5 times.

2. The unlock control method of an intermediate locking type variable valve timing system according to claim 1, characterized in that in said step S1, determining whether an unlock condition is satisfied according to said current phase includes: if the current phase is in the initial loading phase, judging that the unlocking condition is met; otherwise, judging that the unlocking condition is not satisfied.

3. The unlock control method of an intermediate locking type variable valve timing system according to claim 1, characterized in that in said step S1, said t1 time is 0.1S.

4. The unlock control method of an intermediate locking type variable valve timing system according to claim 1, characterized in that in said step S2 and said step S4, said deviation threshold is 3 ° CA.

5. The unlock control method of an intermediate lock-up type variable valve timing system according to claim 1, characterized in that in said step S3, said first duty ratio is 10%, and said time t2 is in the range of 0.2S to 0.5S.

6. The unlock control method of an intermediate locking type variable valve timing system according to claim 1, characterized in that in said step S4, said t3 time is 1S.

7. The unlock control method of an intermediate locking type variable valve timing system according to claim 1, characterized in that in said step S41, said second duty ratio is 90%.

8. The unlock control method of the intermediate locking type variable valve timing system according to claim 1, characterized in that in said step S41, said t4 time is 0.1S.

9. The unlock control method of an intermediate locking type variable valve timing system according to claim 1, characterized in that in said step S42, said third duty ratio is 35%.

10. The unlock control method of the intermediate locking type variable valve timing system according to any one of claims 1 to 9, characterized in that in said step S42, said t5 time is 0.1S.