Patent Application
20160376940
The present application claims the benefit of Korean Patent Application No. 10-2015-0091602, filed Jun. 26, 2015, which is incorporated herein by reference in its entirety.
The present disclosure relates generally to a rotation control apparatus of continuous variable valve timing (hereafter, referred to as a CVVT).
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
In general, a CVVT is applied to a vehicle to reduce exhaust gas and improve fuel efficiency and output.
The structure of a common CVVT will be described first with reference to
As shown in
An ECU (Electronic Control Unit) 13 controls valve timing of the cam in accordance with the position of the crank in response to signals from the cam position sensor 11 and the crank position sensor 12 and a control signal from the ECU 13 is sent to an oil flow valve 16 that is supplied with engine oil from an engine oil pump 16, so the cam is rotated.
When the oil control valve 16 allows the cam to rotate in response to a control signal from the ECU 13, the cam position sensor 11 detects the position of the camshaft and feeds it back to the ECU 13 and the ECU 13 estimates the amount of rotation of the cam on the basis of the fed-back position information of the camshaft and transmits a signal for controlling the position of the camshaft back to the oil control valve 16 on the basis of the estimated amount of rotation of the cam. Continuously variable control is performed on valve timing in accordance with this control logic.
On the other hand, in order to smoothly perform the feedback function, a control logic for the oil control valve 16 according to the crank position and the cam position is mapped to the ECU 13. Accordingly, when the mapped position of the camshaft and the cam position detected by the cam position sensor are different, the ECU controls the oil control valve 16, so the rotation of the camshaft is increased/decreased.
A CVVT system improves fuel efficiency by reducing a pumping loss by increasing valve overlap of intake and exhaust valves and a re-combustion effect of non-burned gas is achieved by internal exhaust gas recycling with optimization of the valve overlap, so exhaust gas is reduced.
As shown in
In intermediate phase CVVT, a lock pin on the rotor is locked into a lock pin hole between the advance chamber and the delay chamber while the RPM of an engine is reduced, thereby preparing for later engine start. The action that the lock pin is automatically locked into the lock pin hole when the RPM of an engine is reduced is called ‘self-lock’.
The self-lock is a function that allows a CVVT system to mechanically return to an accurate position without specific adjustment so that operational stability of an engine can be maintained in periods where the CVVT system is not used, that is, when the engine is idling or is started.
However, when the valve timing reaches the most or more retarded position without returning to the intermediate phase, and an engine of a vehicle is idling, a surge tank may not be vacuumized and the internal pressure of the surge tank may increase up to the atmospheric pressure, so the performance of a brake using the vacuum of the surge tank may be deteriorated.
Further, when the valve timing reaches the most retarded position without returning to the intermediate phase, excessive overlap of valve timing may be generated between an intake valve and an exhaust valve, so the operational stability of the engine decreases and vibration of the engine increases, and in some cases, the engine stops.
That is, so-called self-lock of a lock pin in an intermediate phase CVVT may not be automatically performed, so when the rotor and the lock pin are positioned at the most advanced position or the most retarded position, the engine stops and the brake system may not operate because negative pressure is not normally generated.
The foregoing is intended merely to aid in the understanding of the background of the present disclosure, and is not intended to mean that the foregoing is already known to those skilled in the art.
Accordingly, the present disclosure proposes a rotation control apparatus of a CVVT that prevents poor self-lock.
The present disclosure provides, in one embodiment, that by returning to a predetermined intermediate phase position even after a phase is advanced or retarded, a lock pin can be accurately inserted into a lock pin hole.
Additionally, the present disclosure provides, in one embodiment, a specific advanced-angle compensating unit that can compensate torque of a rotor in advancing to solve the problem of ensuring an intermediate phase, because a CVVT can rotate against friction of a valve system while an engine is operated, particularly in advancing the intake.
According to one aspect of the present disclosure, there is provided a rotation control apparatus of a CVVT that includes: an advanced-angle compensating unit disposed at a rotor to always or continuously apply torque in an advancing direction of the rotor between the rotor and a stator, and achieving self-locking of a lock pin; and a stopper locking a side of the advanced-angle compensating unit and releasing the advanced-angle compensating unit after the advanced-angle compensating unit reaches a predetermined position.
The advanced-angle compensating unit may be a bias spring.
The advanced-angle compensating unit may have a first end connected to the rotor and a second end connected to the stator.
The stopper may be inserted in the rotor where the first end of the advanced-angle compensating unit is positioned.
A rotational groove allowing the first end of the advanced-angle compensating unit to rotate within a predetermined range may be formed on the rotor.
The advanced-angle compensating unit may be compressed, when the rotor rotates in a retarding direction, and the advanced-angle compensating unit may increase torque of the rotor with a compressive force when the rotor rotates in the advancing direction, and the locking pin may be continuously locked by a solenoid valve when the rotor rotates in the advancing direction.
Since load of the advanced-angle compensating unit is increased over a cam torque difference from the most retarded state to the self-lock, and since the advanced-angle compensating unit is prevented from rotating by the stopper when the rotor reaches the self-lock position by the advanced-angle compensating unit, it is possible to prevent poor self-lock and ensure more stable operation of the CVVT by ensuring a predetermined accurate intermediate phase.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:
A rotation control apparatus of a CVVT according to exemplary embodiments of the present disclosure is described hereafter with reference to the accompanying drawings.
As shown in the
According to the present disclosure, the advanced-angle compensating unit 500 is disposed at a rotor 100 to always apply torque in an advancing direction of the rotor 100 between the rotor 100 and the stator 300 and achieves self-locking of a lock pin 900.
As shown in
The advanced-angle compensating unit 500 is compressed when the rotor 100 rotates in a retarding direction, and it increases torque of the rotor 100 with its compressive force when the rotor 100 rotates in the advancing direction. Further, when the rotor 100 rotates in the advancing direction, the lock pin 900 is continuously locked by a solenoid valve.
That is, when the rotor 100 rotates in the retarding direction, the advanced-angle compensating unit 500 is wound and keeps an elastic force therein, and when the rotor 100 rotates in the advancing direction, the torque of the rotor 100 is increased by the kept elastic force. Accordingly, it is possible to preclude the problem that rotation in the advancing direction is not smoothly made due to torque of a camshaft and friction force of a valve system, and hence the lock pin 900 may be actuated at any time.
When the rotor 100 rotates in the advancing direction, the torque of the rotor 100 is increased by the advanced-angle compensating unit 500 and the lock pin 900 can be locked into a lock pin hole 910, so it is possible to prevent the problem that an engine stops and a brake system is not operated by poor negative pressure, because an intermediate phase cannot be ensured in the related art.
The elastic force kept in accordance with the length and diameter of the advanced-angle compensating unit 500 is selected at an appropriate level in consideration of the friction force of an engine valve system and the pressure of engine oil, as will be understood by those skilled in the art.
However, when only the advanced-angle compensating unit 500 is provided, theoretically, there is no problem in ensuring an intermediate phase, but it may be difficult to ensure an accurate intermediate phase in actual manufacturing of a vehicle due to differences in engines, parts, cam torque, and the advanced-angle compensating unit 500, so poor self-lock may still result. Accordingly, the stopper 700 is optionally provided, and preferably disposed at a side of the advanced-angle compensating unit 500 to prevent rotation beyond the intermediate phase. The stopper 700 prevents the advanced-angle compensating unit 500 from being further pressed by driving torque of the camshaft after the CVVT ensures an accurate intermediate phase by means of the advanced-angle compensating unit 500, thereby ensuring a predetermined intermediate phase and preventing poor self-lock.
The operation of the rotation control apparatus of a CVVT of the present disclosure having the configuration described above is described with reference to
On the contrary,
That is, by increasing load of the advanced-angle compensating unit 500 over a cam torque difference from the most retarded state to the self-lock, and by stopping the advanced-angle compensating unit 500 with the stopper 700 when a parking position is reached, the CVVT is not further rotated in the advancing direction, so an accurate intermediate phase can be achieved and poor self-lock is prevented.
Therefore, according to the rotation control apparatus of a CVVT, since load of the advanced-angle compensating unit is increased over a cam torque difference from the most retarded state to the self-lock and the advanced-angle compensating unit is prevented from rotating by the stopper when the rotor reaches the self-lock position by the advanced-angle compensating unit, it is possible to prevent poor self-lock and ensure more stable operation of the CVVT by ensuring a predetermined accurate intermediate phase.
Although embodiments of the present disclosure have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the disclosure as disclosed in the accompanying claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1020150091602 | Jun 2015 | KR | national |
