VARIABLE VALVE LIFT APPARATUS

Abstract

A variable valve lift apparatus including an inner tappet, an outer tappet surrounding and slidably contacting the inner tappet, and a latching pin slidably inserted into the inner tappet so as to implement a high lift and a low lift by selectively joining the inner tappet and the outer tappet may include a stopper partially inserted into the outer tappet and spaced apart from the latching pin in a movement direction of the latching pin so as to limit movement of the latching pin, and forming a latching pin joining groove in the outer tappet to selectively receive the latching pin, wherein the stopper partially projects to the outside of the outer tappet and is slidably engaged to a cylinder head groove formed to a cylinder head bore to prevent the variable valve lift apparatus from being rotated.

Description

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No. 10-2010-0095559 filed in the Korean Intellectual Property Office on Sep. 30, 2010, the entire contents of which is incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a variable valve lift apparatus, and more particularly, to a variable valve lift apparatus with a stopper that is inserted into an outer tappet to limit movement of a latching pin and projects to the outside of the outer tappet and slides in a cylinder head groove to prevent the variable valve lift apparatus from being rotated.

2. Description of Related Art

In general, an internal combustion engine receives fuel and air in a combustion chamber and combusts the fuel and air to form power. An intake valve is actuated by driving a cam shaft at the time of suctioning air and air is suctioned into the combustion chamber while the intake valve is opened. Further, an exhaust valve is actuated by driving the cam shaft and air is discharged from the combustion chamber while the exhaust valve is opened.

However, an optimal operation of the intake valve/exhaust valve depends on a rotational velocity of an engine. That is, an appropriate lift or valve opening/closing time depends on the rotational velocity of the engine. As such, in order to implement the appropriate valve operation depending on the rotational velocity of the engine, a variable valve lift (VVL) apparatus in which a cam driving the valve is designed to have a plurality of shapes or the valve is implemented to operate in different lifts depending on the number of rotations of the engine has been researched.

FIG. 9 is a cross-sectional view of a variable tappet in a high lift mode of a known variable valve lift apparatus and FIG. 10 is a cross-sectional view of a variable tappet in a low lift mode of a known variable valve lift apparatus.

First, in the high lift mode, oil pressure is supplied to a hydraulic chamber 240 formed in an outer tappet 100 and a plunger 350 pushes a latching pin 310 by the supplied oil pressure. Therefore, as shown in FIG. 9, the latching pin 310 is inserted into a latching pin joining groove 340 and an inner tappet 200 and the outer tappet 100 are joined to each other.

In this case, a high cam 12 is joined to a cam shaft 10, such that the high cam 12 presses the outer tappet 100 by rotation of the cam shaft 10, and as a result, the outer tappet 100 and the inner tappet 200 integrally move up and down. That is, high lift is executed by rotational movement of the high cam 12.

On the contrary, in the low lift mode, the oil pressure of the hydraulic chamber 240 formed in the outer tappet 100 is released and the latching pin 310 moves with being separated from the latching pin joining groove 340 by a restoring force of a return spring 330, as shown in FIG. 10. The inner tappet 200 and the outer tappet 100 are separated from each other by the movement of the latching pin 310 and independently move. In this case, a latching pin supporting pin 320 supports the return spring 330 and is inserted into the inner tappet 200.

The valve is opened and closed by the inner tappet 200 that reciprocates by rotation of a low cam 14 joined to the cam shaft 10 and the outer tappet 100 merely moves up and down by a lost motion spring 500 (see FIG. 4) depending on the rotation of the high cam 12 and has no influence on the opening and closing of the valve.

However, if the cams 12 and 14 and surfaces of the tappets 100 and 200 of the variable valve lift apparatus do not coincide with each other, respectively, the variable tappets 100 and 200 rotate, and as a result, the engine is damaged.

Further, since a working fluid can be supplied only when positions of a supply hole of the working fluid actuating the variable valve lift apparatus and a working fluid supplying hole of a bore of a cylinder head coincide with each other, an additional rotation preventing device for preventing rotation of the entire variable valve lift apparatus is required.

The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing a variable valve lift apparatus with a stopper capable of limiting movement of a latching pin while allowing cams and tappet surfaces of the variable valve lift apparatus to coincide with each other by preventing the variable valve lift apparatus from being rotated.

A variable valve lift apparatus including an inner tappet, an outer tappet surrounding and slidably contacting the inner tappet, and a latching pin slidably inserted into the inner tappet so as to implement a high lift and a low lift by selectively joining the inner tappet and the outer tappet, may include a stopper partially inserted into the outer tappet and spaced apart from the latching pin in a movement direction of the latching pin so as to limit movement of the latching pin, and forming a latching pin joining groove in the outer tappet to selectively receive the latching pin, wherein the stopper partially projects to the outside of the outer tappet and may be slidably engaged to a cylinder head groove formed to a cylinder head bore to prevent the variable valve lift apparatus from being rotated.

The stopper may include an insertion portion having substantially the same diameter as the latching pin and being inserted into the outer tappet to limit the movement of the latching pin, and a projection portion projecting from the insertion portion to the outside of the outer tappet and having a shape to be slidably inserted into the cylinder head groove in order to prevent the variable valve lift apparatus from being rotated.

The projection portion may have a semi-spherical shape which may be slidable while contacting the cylinder head groove.

The projection portion may have a semi-cylindrical shape formed in a movement direction of the outer tappet and slides while contacting the cylinder head groove.

A through-hole may be formed in the stopper and fluid-connected to the latching pin joining groove to smoothly discharge oil pressure supplied to actuate the latching pin.

The insertion portion may have a cylindrical shape having the same radius as the latching pin.

According to the exemplary embodiments of the present invention, it is possible to prevent an engine from being damaged by internally limiting a movement distance of a latching pin and externally preventing a variable valve lift apparatus from being rotated, make supply of a working fluid smooth, and save a manufacturing cost because an additional rotation preventing device does not need to be processed in a tappet skirt part.

The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of a variable tappet according to an exemplary embodiment of the present invention.

FIG. 2 is a plan view of a variable tappet according to an exemplary embodiment of the present invention.

FIG. 3 is a perspective view of a state in which inner and outer tappets are partially cut according to an exemplary embodiment of the present invention.

FIG. 4 show a use state diagram before and after a variable valve lift apparatus according to an exemplary embodiment of the present invention is joined to a cylinder head and an enlarged diagram of a principal part.

FIG. 5 is a perspective view of a variable tappet according to various exemplary embodiments of the present invention.

FIG. 6A to 6D are a perspective view, a plan view, a side view, and a front view of a stopper according to various exemplary embodiments of the present invention.

FIG. 7 is a perspective view of a variable tappet according to various exemplary embodiments of the present invention.

FIGS. 8A to 8D are a perspective view, a plan view, a side view, and a front view of a variable tappet according to various exemplary embodiments of the present invention.

FIG. 9 is a cross-sectional view of a variable tappet in a high lift mode of a known variable valve lift apparatus.

FIG. 10 is a cross-sectional view of a variable tappet in a low lift mode of a known variable valve lift apparatus.

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.

In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown.

FIG. 1 is a longitudinal cross-sectional view of a variable tappet of a state in which a stopper is joined to the variable tappet according to an exemplary embodiment of the present invention and FIG. 2 is a plan view of a variable tappet according to an exemplary embodiment of the present invention.

FIG. 3 is a perspective view of a state in which inner and outer tappets are partially cut according to an exemplary embodiment of the present invention, FIG. 4 is a use state diagram before and after a variable valve lift apparatus according to an exemplary embodiment of the present invention is joined to a cylinder head, FIG. 5 is a perspective view of a variable tappet according to a first exemplary embodiment of the present invention, and FIG. 6A to 6D are a perspective view, a plan view, a side view, and a front view of a stopper according to a first exemplary embodiment of the present invention.

First, referring to FIGS. 1 to 6A to 6D, a stopper 400 that is provided to be spaced apart from a latching pin 310 at one upper side of an outer tappet 100 in a movement direction of the latching pin 310 is provided in the outer tappet 100. In the above description, the latching pin 310 may be partially a hollow body and have a cylindrical shape. A latching pin supporting pin 320 limiting movement of the latching pin 310 while penetrating the latching pin 310 is joined to an inner tappet 200. A return spring 330 that restores the latching pin 310 to an original state when oil pressure is released, while contacting the latching pin supporting pin 320, is inserted into the latching pin 310.

Referring to FIGS. 4 and 5, the stopper 400 includes an insertion portion 410 having the same shape as the latching pin 310 to limit horizontal movement of the latching pin 310 and a projection portion 420 having a similar shape to a plan cross section of a groove 110 to slide while projecting to the outside of the outer tappet 100 and contacting an inner circumference of the groove 110 of a cylinder head. The insertion portion 410 may be a cylindrical shape having the same radius as the latching pin 310.

An exemplary embodiment of the present invention will hereinafter be described in more detail with reference to the accompanying drawings.

In the variable valve lift apparatus, an auxiliary latching pin 370 pushes the latching pin 310 by oil pressure supplied at the time when the oil pressure is supplied through a hydraulic chamber 360 and the latching pin 310 in the inner tappet 200 moves to one inner side of the outer tappet 100, such that the inner tappet 200 and the outer tappet 100 are joined to each other. In this case, a distance in which the latching pin 310 can move is limited to a movement limiting distance A.

As such, the latching pin 310 selectively joins the outer tappet 100 and the inner tappet 200 while moving in a horizontal direction in order to control a valve lift, thereby implementing a high lift or a low lift. In this case, when the supplied oil pressure is excessively large, the latching pin 310 may move excessively. In order to prevent the excessive movement of the latching pin 310, the latching pin 310 should move only within the movement limiting distance A in which the latching pin 310 can move. In the exemplary embodiment of the present invention, the stopper 400 serves to such a function. Further, the projection portion 420 that projects to the outside of the outer tappet 100 is engaged in the groove 110, and as a result, the variable valve lift apparatus may move up and down without rotating. Therefore, since surfaces of the inner and outer tappets 100 and 200 coincide with a high cam 12 and a low cam 12 in a rotational direction, it is possible to prevent an engine from being damaged.

FIG. 4 shows a use state diagram showing a state in which the stopper 400 according to the exemplary embodiment of the present invention is positioned in a cylinder head groove with being partially exposed to the outer tappet 100 and an enlarged diagram of a principal part. A left side of FIG. 5 shows a state in which a tappet is inserted into a bore of a known cylinder head and a right side of FIG. 5 shows a state in which the stopper 400 according to the exemplary embodiment of the present invention is inserted into the cylinder head groove 110. Further, the enlarged diagram of the principal part shows a state in which the stopper 400 is engaged in the cylinder head groove 110.

The projection portion 420 of the stopper 400 should have a structure to slide on an inner circumference of the cylinder head groove in order to prevent the variable valve lift apparatus from being rotated. That is, when a plan cross section of the inner circumference of the cylinder head groove 110 has a semi-spherical shape, a plan cross section of the projection portion 420 should also have the semi-spherical shape.

Therefore, in the first exemplary embodiment of the present invention, as shown in FIG. 6B, the plan cross section of the projection portion 420 may have the semi-spherical shape. Further, since the projection portion 420 should slide on the inner circumference of the cylinder head groove 110, the projection portion 420 may have a semi-cylindrical shape that is long in a vertical direction which is a movement direction, as shown in FIGS. 5 and 6. In addition, a through-hole 430 is formed at the center of the stopper 400 by passing through the insertion portion 410 and the projection portion 420. The formation of the through-hole 430 is to easily discharge the oil pressure after actuating the latching pin 310 to the outside.

A second exemplary embodiment is shown in FIGS. 7 and 8A to 8D. According to the second exemplary embodiment, a projection portion 460 may have a semi-spherical shape. In this case, an insertion portion 450 has a cylindrical shape as shown in FIG. 7, and since the insertion portion 450 has a through-hole 470 formed at the center thereof as described in the first exemplary embodiment, the insertion portion 450 has a structure to easily discharge preused oil pressure. When the stopper 400 is manufactured as described in the second exemplary embodiment, the stopper 400 can be more easily manufactured than the stopper 400 in the first exemplary embodiment.

As described above, it is possible to limit excessive horizontal movement of the latching pin 310 by the insertion portions 410 and 450 having the cylindrical shape, which are inserted into the outer tappet 100 and prevent the variable valve lift apparatus from being rotated by the projection portions 420 and 460 that project to the outside of the outer tappet 100. It is possible to make supply of a working fluid smooth by allowing positions of a working fluid supplying hole and a supplying hole on a surface of a cylinder head bore 120 to coincide with each other as the variable valve lift apparatus is prevented from being rotated. Further, rotation surfaces of the high cam 12 and the low cam 14 of the variable valve lift apparatus coincide with the surfaces of the outer tappet 100 and the inner tappet 200, respectively, thereby preventing the engine from being damaged.

For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “lower”, “inner” and “outer” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.

Claims

1. A variable valve lift apparatus including an inner tappet, an outer tappet surrounding and slidably contacting the inner tappet, and a latching pin slidably inserted into the inner tappet so as to implement a high lift and a low lift by selectively joining the inner tappet and the outer tappet, the apparatus comprising:

a stopper partially inserted into the outer tappet and spaced apart from the latching pin in a movement direction of the latching pin so as to limit movement of the latching pin, and forming a latching pin joining groove in the outer tappet to selectively receive the latching pin,

wherein the stopper partially projects to the outside of the outer tappet and is slidably engaged to a cylinder head groove formed to a cylinder head bore to prevent the variable valve lift apparatus from being rotated.

2. The apparatus of claim 1, wherein the stopper includes:

an insertion portion having substantially the same diameter as the latching pin and being inserted into the outer tappet to limit the movement of the latching pin; and

a projection portion projecting from the insertion portion to the outside of the outer tappet and having a shape to be slidably inserted into the cylinder head groove in order to prevent the variable valve lift apparatus from being rotated.

3. The apparatus of claim 2, wherein the projection portion has a semi-spherical shape which is slidable while contacting the cylinder head groove.

4. The apparatus of claim 2, wherein the projection portion has a semi-cylindrical shape formed in a movement direction of the outer tappet and slides while contacting the cylinder head groove.

5. The apparatus of claim 2, wherein a through-hole is formed in the stopper and fluid-connected to the latching pin joining groove to smoothly discharge oil pressure supplied to actuate the latching pin.

6. The apparatus of claim 2, wherein the insertion portion has a cylindrical shape having the same radius as the latching pin.