Electro-hydraulic variable valve lift apparatus

An electro-hydraulic variable valve lift apparatus includes a housing, a driving cam, a pump piston which forms a main chamber with the housing, reciprocates within the housing according to rotation of the driving cam, and forms hydraulic pressure within the main chamber, a pump piston elastic portion disposed for elastically supporting the pump piston, an oil pressure controller communicating with the main chamber in order to control hydraulic pressure within the main chamber, a hydraulic piston slidably disposed within the housing, includes a first body having a first diameter and a second body having a second diameter larger than the first diameter, and is connected with a valve, and a piston guide disposed between the housing and the hydraulic piston for guiding the hydraulic piston.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2010-0080989 filed in the Korean Intellectual Property Office on Aug. 20, 2010, the entire contents of which application is incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a valve lift apparatus. More particularly, the present invention relates to an electro-hydraulic variable valve lift apparatus for an internal combustion engine.

2. Description of the Related Art

An internal combustion engine generates power by burning fuel in a combustion chamber in air media drawn into the chamber. Intake valves are operated by a camshaft in order to intake the air, and the air is drawn into the combustion chamber while the intake valves are open. In addition, exhaust valves are operated by the camshaft, and a combustion gas is exhausted from the combustion chamber while the exhaust valves are open.

An optimal operation of the intake valves and the exhaust valves depends on a rotation speed of the engine. That is, an optimal lift or optimal opening/closing timing of the valves depends on the rotation speed of the engine. In order to achieve such an optimal valve operation depending on the rotation speed of the engine, various research has been undertaken. For example, a valve for driving a valve is designed having different shapes, a variable valve lift apparatus has variable different lifts depending on an engine speed and so on.

However, since a CVVL (continuous variable valve lift apparatus) which is controlled mechanically, uses a link, eccentric cam a control shaft and so on, so that moment of inertia and accumulated clearance is relatively large, and development of dynamic characteristic of a valve is limited.

Also, each valve is controlled by the same camshaft simultaneously, realizing valve lift is limited.

SUMMARY OF THE INVENTION

Various aspects of the present invention have been made in an effort to provide an electro-hydraulic variable valve lift apparatus which may adjust valve lift according to engine operation condition.

An electro-hydraulic variable valve lift apparatus according to various aspects of the present invention may form ramp profile when a valve is closed so as to reduce valve closing impact.

An electro-hydraulic variable valve lift apparatus according to various aspects of the present invention may be provided with a piston guide so that accurate operation may be realized regardless clearance generated in manufacturing process.

An electro-hydraulic variable valve lift apparatus according to various aspects of the present invention may include a housing, a driving cam, a pump piston which forms a main chamber with the housing, reciprocates within the housing according to rotation of the driving cam, and forms hydraulic pressure within the main chamber, a pump piston elastic portion which is disposed for elastically supporting the pump piston, an oil pressure controller which is communicated with the main chamber in order to control hydraulic pressure within the main chamber, a hydraulic piston which is slidably disposed within the housing, includes a first body having a first diameter and a second body having a second diameter larger than the first diameter, and is connected with a valve, and a piston guide which is disposed between the housing and the hydraulic piston for guiding the hydraulic piston.

The piston guide may be disposed between the first body and the housing, the first body and the housing may form a first auxiliary chamber, and the second body, the housing and the piston guide may form a second auxiliary chamber, wherein the first body may include a first hydraulic line selectively connecting the first auxiliary chamber and the second auxiliary chamber, and a second hydraulic line connecting the first auxiliary chamber and the second auxiliary chamber.

The first hydraulic line may be closed by the piston guide when the valve is closed.

The second body may be provided with a hydraulic pressure valve lash adjuster for adjusting a gap of the valve.

The hydraulic pressure valve lash adjuster may include a low pressure chamber formed in the second body, a lash adjusting hydraulic pressure line formed in the housing, a low pressure chamber hydraulic pressure supply line formed in the second body for connecting the low pressure chamber and the lash adjusting hydraulic pressure line, a lash adjuster housing forming high pressure chamber with the second body and connected with the valve, a lash adjuster spring which is disposed between the lash adjuster housing and the second body and elastically supports the lash adjuster housing, a communicating hole communicating the low pressure chamber with the high pressure chamber, a one-way valve which is disposed within the lash adjuster housing and selectively closes the communicating hole, and a one-way valve spring elastically supporting the one-way valve.

The second body may be provided with a mechanical valve lash adjuster for adjusting a gap of the valve.

A swing arm may be disposed between the driving cam and the pump piston, and the pump piston reciprocates by the swing arm.

The main chamber and the first auxiliary chamber may be communicated with by a hydraulic pump hydraulic pressure line.

Reciprocal motion directions of the pump piston and the hydraulic piston may not be parallel each other.

The first auxiliary chamber and the second auxiliary chamber may be connected by a connecting hydraulic line, and a differential pressure valve may be disposed on the connecting hydraulic line.

The piston guide may be disposed between the second body and the housing, the first body and the housing may form a first auxiliary chamber, and the second body, the housing and the piston guide may form a second auxiliary chamber, wherein the first body may include a first hydraulic line selectively connecting the first auxiliary chamber and the second auxiliary chamber, and a second hydraulic line connecting the first auxiliary chamber and the second auxiliary chamber.

A protrusion portion may be formed in the housing, wherein the first hydraulic line may be closed by protrusion portion when the valve is closed.

The second body may be provided with a hydraulic pressure valve lash adjuster for adjusting a gap of the valve.

The hydraulic pressure valve lash adjuster may include a low pressure chamber formed in the second body, a lash adjusting hydraulic pressure line formed in the housing and the piston guide, a low pressure chamber hydraulic pressure supply line formed in the second body for connecting the low pressure chamber and the lash adjusting hydraulic pressure line, a lash adjuster housing forming high pressure chamber with the second body and connected with the valve, a lash adjuster spring which is disposed between the lash adjuster housing and the second body and elastically supports the lash adjuster housing, a communicating hole communicating the low pressure chamber with the high pressure chamber, a one-way valve which is disposed within the lash adjuster housing and selectively closes the communicating hole, and a one-way valve spring elastically supporting the one-way valve.

The second body may be provided with a mechanical valve lash adjuster for adjusting a gap of the valve.

A swing arm may be disposed between the driving cam and the pump piston, and the pump piston reciprocates by the swing arm.

The main chamber and the first auxiliary chamber may be communicated with by a hydraulic pump hydraulic pressure line.

Reciprocal motion directions of the pump piston and the hydraulic piston may not be parallel each other.

The first auxiliary chamber and the second auxiliary chamber may be connected by a connecting hydraulic line, and a differential pressure valve may be disposed on the connecting hydraulic line.

As described above, an electro-hydraulic variable valve lift apparatus according to various aspects of the present invention may adjust valve lift according to engine operation condition with simple scheme.

An electro-hydraulic variable valve lift apparatus according to various aspects of the present invention may form ramp profile when a valve is closed so as to reduce valve closing impact.

An electro-hydraulic variable valve lift apparatus according to various aspects of the present invention may be provided with a piston guide so that accurate operation may be realized regardless clearance generated in manufacturing process.

DETAILED DESCRIPTION

Referring toFIG. 1toFIG. 6, an electro-hydraulic variable valve lift apparatus according to various embodiments of the present invention includes a housing10, a driving cam20, a pump piston30which forms a main chamber32with the housing10, reciprocates within the housing10according to rotation of the driving cam20, and forms hydraulic pressure within the main chamber32, a pump piston elastic portion34which is disposed for elastically supporting the pump piston30, an oil pressure controller40which is communicated with the main chamber32in order to control hydraulic pressure within the main chamber32, a hydraulic piston50which is slidably disposed within the housing10, includes a first body52having a first diameter and a second body56having a second diameter larger than the first diameter, and is connected with a valve100, and a piston guide60which is disposed between the housing10and the hydraulic piston50for guiding the hydraulic piston50.

The piston guide60is disposed between the first body52and the housing10. The first body52and the housing10form a first auxiliary chamber70, and the second body56, the housing10and the piston guide60form a second auxiliary chamber72. The first body52includes a first hydraulic line54selectively connecting the first auxiliary chamber70and the second auxiliary chamber72, and a second hydraulic line58connecting the first auxiliary chamber70and the second auxiliary chamber72.

The first hydraulic line54is closed by the piston guide60when the valve100is closed.

The second body56is provided with a hydraulic pressure valve lash adjuster (HLA)80for adjusting a gap of the valve100.

The hydraulic pressure valve lash adjuster80includes a low pressure chamber82formed in the second body56, a lash adjusting hydraulic pressure line84formed in the housing10, a low pressure chamber hydraulic pressure supply line86formed in the second body56for connecting the low pressure chamber82and the lash adjusting hydraulic pressure line84, a lash adjuster housing88forming high pressure chamber98with the second body56and connected with the valve100, a lash adjuster spring90which is disposed between the lash adjuster housing88and the second body56and elastically supports the lash adjuster housing88, a communicating hole92communicating the low pressure chamber82with the high pressure chamber98, a one-way valve94which is disposed within the lash adjuster housing88and selectively closes the communicating hole92, and a one-way valve spring96elastically supporting the one-way valve94.

Hereinafter, referring toFIG. 1toFIG. 6, operations of the electro-hydraulic variable valve lift apparatus according to various embodiments of the present invention will be explained.

As shownFIG. 1toFIG. 3, the oil pressure controller40supplies oil to the main chamber32and then closed in high load.

The hydraulic piston50reciprocates according to rotation of the driving cam20and the valve100is opened as shown inFIG. 3.

At the moment of opening the valve100, since the first hydraulic line54is closed by the piston guide60, oil in the first auxiliary chamber70is flows into the auxiliary the second chamber72though the second hydraulic line58. After the first hydraulic line54is opened, the oil in the first auxiliary chamber70is flows into the auxiliary the second chamber72though the second hydraulic line58and the first hydraulic line54.

And thus, when the first hydraulic line54is closed, ramp is formed so that the valve100is opened smoothly. And when the first hydraulic line54is opened, the oil in the first auxiliary chamber70is flows into the auxiliary the second chamber72though the second hydraulic line58and the first hydraulic line54so that normal valve profile is realized.

When the valve100is closed, oil in the second auxiliary chamber72flows into the auxiliary the first chamber70through the first hydraulic line54and the second hydraulic line58, but when the first hydraulic line54is closed by the piston guide60, the oil in the second auxiliary chamber72flows into the auxiliary the first chamber70through the second hydraulic line58.

Thus, when the first hydraulic line54is opened, normal valve profile is realized, however when the first hydraulic line54is closed the oil in the second auxiliary chamber72flows into the auxiliary the first chamber70through the second hydraulic line58to form the ramp, so that the valve100is smoothly closed.

In the high load, ramp profile may be formed according to shape of the cam lobe of the driving cam20by adjusting positions of the hydraulic piston50and not closing the first hydraulic line54.

In the middle load of various embodiments of the present invention, the main chamber32is filled with oil by the oil pressure controller40and then the oil pressure controller40is closed.

When the driving cam20is positioned near “A” as shown inFIG. 1, the oil pressure controller40releases the oil in the main chamber32.

The oil pressure controller40is controlled by an ECU (electronic control unit), and since operations of the oil pressure controller40are not necessary for explaining the present invention and thus description of the operation of the oil pressure controller40will be omitted.

Operations of opening of the valve100are the same as the operations in the high load, and thus detailed explanation will be omitted.

When the valve100is closed, oil in the main chamber32is released through the oil pressure controller40and simultaneously, oil in the second auxiliary chamber72flows into the auxiliary the first chamber70through the first hydraulic line54and the second hydraulic line58. When then the first hydraulic line54is closed by the piston guide60, the oil in the second auxiliary chamber72flows into the auxiliary the first chamber70through the second hydraulic line58.

When the first hydraulic line54is opened, the valve100is closed faster than in the high load. And when the first hydraulic line54is closed, the oil in the second auxiliary chamber72flows into the first auxiliary chamber70through the second hydraulic line58to form a ramp, and thus the valve100is smoothly closed.

That is, as shown inFIG. 2, a period of valve opening in the middle load is shorter than a period of valve opening in the high load.

In the low load of various embodiments of the present invention, the main chamber32is filled with oil by the oil pressure controller40and then the oil pressure controller40is closed. When the driving cam20is positioned near “B” as shown inFIG. 1, the oil pressure controller40releases the oil in the main chamber32.

Before the driving cam20reaches the top position, the oil pressure controller40is opened to release hydraulic pressure within the main chamber32, and thus valve lift is reduced and opening period of the valve100is relatively reduced.

In CDA (cylinder deactivation) mode, the oil pressure controller40is kept in opening state.

Since hydraulic pressure is not supplied to the main chamber32, although the driving cam20rotates, the pump piston30do not moves (lost motion) and the valve100is not opened.

The oil pressure controller40repeats supplying and releasing of the hydraulic pressure according to operation conditions of the engine, and if timing of releasing the hydraulic pressure is controlled, the electro-hydraulic variable valve lift apparatus according to various embodiments of the present invention realizes various valve profiles.

And also, as described above, the electro-hydraulic variable valve lift apparatus according to various embodiments of the present invention may reduce impact of opening and closing of the valve.

Hereinafter, referring toFIG. 3, operations of the hydraulic pressure valve lash adjuster80will be explained.

At the moment the valve100is closed, hydraulic pressure is supplied to the low pressure chamber82through the lash adjusting hydraulic pressure line84and the low pressure chamber hydraulic pressure supply line86.

If a gap is generated between the valve100and a valve seat, hydraulic pressure is supplied from the low pressure chamber82to the high pressure chamber98so as to adjust the gap during the hydraulic piston50reciprocates.

If a gap is in proper range, the one-way valve94closes the communicating hole92by elastic force of the one-way valve spring96and thus the valve100is opened constantly.

The hydraulic pressure valve lash adjuster80may be formed integrally with the second body56, and in this case, scheme of the entire electro-hydraulic variable valve lift apparatus may be simple and numbers of the elements and manufacturing cost may be reduced.

Referring toFIG. 4andFIG. 5, the hydraulic piston50of the electro-hydraulic variable valve lift apparatus of various embodiments of the present invention may realize a variety hydraulic lines forming multistage hydraulic flowing.

That is, as shown inFIG. 5, the first hydraulic line54amay be formed as plural, and one second hydraulic line58amay be formed. Also, the first hydraulic line may be formed as grooves54band54cand the second hydraulic line may be formed as holes58band58c.

And also, the first hydraulic line54a,54b, and54cmay be formed having various length holes or grooves for releasing hydraulic pressure in multistage to form a ramp.

Hereinafter, referring toFIG. 6andFIG. 7, the piston guide of various embodiments of the present invention will be explained.

When the electro-hydraulic variable valve lift apparatus according to various embodiments of the present invention is operated, the pressure within the main chamber32, the first auxiliary chamber70and the second auxiliary chamber72may be about 150 bar.

And thus, precise clearance management is required in manufacturing the electro-hydraulic variable valve lift apparatus.

However, since the hydraulic piston50has two exterior diameters of the first body52and the second body56, high cost for precisely making the hydraulic piston50is required.

But, if the piston guide60is inserted between the housing10and the first body52, the piston guide60may compensates manufacturing clearance even though manufacturing centers of the piston guide60, the housing10and the first body52are not coaxial. That is optimum level of sealing may be possible by self-aligning.

In theFIG. 7, errors of the piston guide60, the housing10and the first body52are exaggerated for better understanding.

Referring toFIG. 8, an electro-hydraulic variable valve lift apparatus according to various embodiments of the present invention includes a housing110, a driving cam120, a pump piston130which forms a main chamber132with the housing110, reciprocates within the housing110according to rotation of the driving cam120, and forms hydraulic pressure within the main chamber132, a pump piston elastic portion134which is disposed for elastically supporting the pump piston130, an oil pressure controller140which is communicated with the main chamber132in order to control hydraulic pressure within the main chamber132, and a hydraulic piston50which is slidably disposed within the housing110, includes a first body152having a first diameter and a second body156having a second diameter larger than the first diameter, and is connected with a valve200.

The piston guide160for guiding the hydraulic piston50is disposed between the second body156and the housing110. The first body152and the housing110form a first auxiliary chamber170. The second body156, the housing110and the piston guide160form a second auxiliary chamber172. The first body152includes a first hydraulic line154selectively connecting the first auxiliary chamber170and the second auxiliary chamber172, and a second hydraulic line158connecting the first auxiliary chamber170and the second auxiliary chamber172.

A protrusion portion111is formed in the housing110and the first hydraulic line152is formed in be closed by the protrusion portion111when the valve200is closed.

The second body156is provided with a hydraulic pressure valve lash adjuster (HLA)180for adjusting a gap of the valve200.

The hydraulic pressure valve lash adjuster180of the illustrated embodiment, similar to that described above, includes a low pressure chamber182formed in the second body156, a lash adjusting hydraulic pressure line184formed in the housing110and the piston guide160, a low pressure chamber hydraulic pressure supply line186formed in the second body156for connecting the low pressure chamber182and the lash adjusting hydraulic pressure line184, a lash adjuster housing188forming high pressure chamber198with the second body156and connected with the valve200, a lash adjuster spring190which is disposed between the lash adjuster housing188and the second body156and elastically supports the lash adjuster housing188, a communicating hole192communicating the low pressure chamber182with the high pressure chamber198, a one-way valve194which is disposed within the lash adjuster housing188and selectively closes the communicating hole192, and a one-way valve spring196elastically supporting the one-way valve194.

The first auxiliary chamber170and the second auxiliary chamber172are connected by a connecting hydraulic line112and a differential pressure valve114is disposed on the connecting hydraulic line112.

The differential pressure valve114may exhaust air within the first auxiliary chamber170and the second auxiliary chamber172and minimize pulsation due to rapid pressure change.

With reference toFIGS. 1-7, an element corresponding to the connecting hydraulic line112and the differential pressure valve114are not described, however it may be provided to the apparatus illustrated therein.

Operations of the electro-hydraulic variable valve lift apparatus according to the illustrated embodiment of the present invention are similar to the operations of the electro-hydraulic variable valve lift apparatus described above, and thus detailed explanation will be omitted.

Referring toFIG. 9, the illustrated electro-hydraulic variable valve lift apparatus according to various embodiments of the present invention, similar to that described above, includes a housing210, a driving cam220, a pump piston230which forms a main chamber232with the housing210, reciprocates within the housing210according to rotation of the driving cam220, and forms hydraulic pressure within the main chamber232, a pump piston elastic portion234which is disposed for elastically supporting the pump piston230, an oil pressure controller240which is communicated with the main chamber232in order to control hydraulic pressure within the main chamber232, and a hydraulic piston250which is slidably disposed within the housing210, includes a first body252having a first diameter and a second body256having a second diameter larger than the first diameter, and is connected with a valve300.

The electro-hydraulic variable valve lift apparatus according to various embodiments of the present invention further includes a first auxiliary chamber270, a second auxiliary chamber272, a first hydraulic line254and the second hydraulic line258.

A piston guide may be disposed to cover the first body252or the second body256similar to the electro-hydraulic variable valve lift apparatus according to the embodiments of the present invention described above.

In various embodiments of the present invention, a mechanical valve lash adjuster280is provided for adjusting a gap of the valve300so as to simplify scheme.

Structure and operation of the mechanical valve lash adjuster280are obvious to a person skilled in the art, so that detailed explanation will be omitted.

Operations of the illustrated electro-hydraulic variable valve lift apparatus are similar to the operations of the electro-hydraulic variable valve lift apparatus described above, and thus detailed explanation will be omitted.

Referring toFIG. 10, the electro-hydraulic variable valve lift apparatus according various embodiments of the present invention, similar to those described above, a housing310, a driving cam320, a pump piston330which forms a main chamber332with the housing310, reciprocates within the housing310according to rotation of the driving cam320, and forms hydraulic pressure within the main chamber332, a pump piston elastic portion334which is disposed for elastically supporting the pump piston330, an oil pressure controller340which is communicated with the main chamber332in order to control hydraulic pressure within the main chamber332, and a hydraulic piston350which is slidably disposed within the housing310, includes a first body352having a first diameter and a second body356having a second diameter larger than the first diameter, and is connected with a valve400.

The electro-hydraulic variable valve lift apparatus according to various embodiments of the present invention further includes a first auxiliary chamber370, a second auxiliary chamber372, a first hydraulic line354and a second hydraulic line358.

A piston guide may be disposed to cover the first body352or the second body356similar to the electro-hydraulic variable valve lift apparatus according to the above described embodiments of the present invention.

A swing arm370is disposed between the driving cam320and the pump piston330for the pump piston330to reciprocate by the swing arm370and a hydraulic pressure valve lash adjuster375or a mechanical valve lash adjuster375may be disposed to an end of the swing arm370.

Operations and scheme of the illustrated electro-hydraulic variable valve lift apparatus are similar to the operations of the electro-hydraulic variable valve lift apparatus described above except for the swing arm370, and thus repeated explanation will be omitted.

Referring toFIG. 11, the illustrated electro-hydraulic variable valve lift apparatus, similar to those described above, includes a housing410, a driving cam420, a pump piston430which forms a main chamber432with the housing410, reciprocates within the housing410according to rotation of the driving cam420, and forms hydraulic pressure within the main chamber432, a pump piston elastic portion434which is disposed for elastically supporting the pump piston430, an oil pressure controller440which is communicated with the main chamber432in order to control hydraulic pressure within the main chamber432, and a hydraulic piston450which is slidably disposed within the housing410, includes a first body452having a first diameter and a second body456having a second diameter larger than the first diameter, and is connected with a valve500.

The electro-hydraulic variable valve lift apparatus according to various embodiments of the present invention further includes a first auxiliary chamber470, a second auxiliary chamber472, a first hydraulic line454and a second hydraulic line458.

The electro-hydraulic variable valve lift apparatus according to various embodiments of the present invention further includes a piston guide460disposed between the first body452and the housing410.

The piston guide460may be disposed between the second body456and the housing410similar to those described above.

In various embodiments of the present invention, a hydraulic pump hydraulic pressure line412is formed between the main chamber432and the first auxiliary chamber470to be communicated with each other.

In this case, since reciprocal motion directions of the pump piston430and the hydraulic piston450do not need to be parallel each other, as shown inFIG. 11, the pump piston430may be vertically mounted to the housing410regardless positions of the driving cam420.

And thus, design freedom of a valve train, a cylinder head and so on may be improved.

The electro-hydraulic variable valve lift apparatus according to various embodiments of the present invention further includes a hydraulic pressure valve lash adjuster480disposed to the second body456for adjusting a gap of the valve400.

The illustrated hydraulic pressure valve lash adjuster480, similar to those described above, includes a low pressure chamber482, a lash adjusting hydraulic pressure line484, a low pressure chamber hydraulic pressure supply line486, a high pressure chamber498, a lash adjuster housing488, a lash adjuster spring490, a communicating hole492, a one-way valve494, and a one-way valve spring496.

Operations and scheme of the illustrated electro-hydraulic variable valve lift apparatus are similar to the operations of the electro-hydraulic variable valve lift apparatus described above, and thus repeated explanation will be omitted.