KR19980047343A - Overlap variable device of valve timing - Google Patents

Abstract

The present invention relates to an overlap variable device that adjusts the timing of a valve in a DOHC engine. More particularly, the present invention relates to an overlap variable device of valve timing that maximizes the output efficiency of an engine by adjusting the timing of opening and closing of an intake / exhaust valve according to an operating speed of the engine. will be.

According to the present invention, an exhaust cam shaft for operating an exhaust valve and an intake cam shaft for operating an intake valve are separated from each other, and an exhaust cam sprocket and an intake cam sprocket are respectively installed to transmit rotational power from the exhaust cam shaft to the intake cam shaft. In the valve timing apparatus interconnected by a transmission means, the power transmission means 70 is located between the exhaust cam sprocket 50 and the intake cam sprocket 60 so that the intake cam sprocket 60 is rotated by a predetermined angle 70. A plurality of pressing sprockets 80 for pressing the upper side and the lower side, a connecting means 85 for interconnecting and supporting the plurality of pressing sprockets 80, and a driving means for moving the connecting means 85 up and down. It characterized by consisting of 90.

Description

Overlap variable device of valve timing

The present invention relates to an overlap variable device that adjusts the timing of a valve in a DOHC engine. More particularly, the present invention relates to an overlap variable device of valve timing that maximizes the output efficiency of an engine by adjusting the timing of opening and closing of an intake / exhaust valve according to an operating speed of the engine. will be.

As shown in FIG. 1, the DOHC engine includes an intake camshaft 3 that opens and closes the intake valve 1 and an exhaust camshaft 4 that opens and closes the exhaust valve 2. The exhaust valve 2 is opened and closed. The exhaust camshaft 4 is driven by receiving power of a crankshaft, and the intake camshaft 3 is connected to the exhaust camshaft 4 and the belt 7 to receive power.

Here, opening and closing of the intake valve 1 and the exhaust valve 2 at a predetermined time by the intake camshaft 3 and the exhaust camshaft 4 is referred to as valve timing. The intake valve 1 is opened in front of the intake stroke of the piston, i.e., before top dead center, and briefly after the intake stroke, i.e. after bottom dead center. This is to fill the cylinder as many cylinders as possible using the inertia of suction.

Further, the exhaust valve 2 is opened before the exhaust stroke of the piston, i.e., before the bottom dead center, so that the combustion gas is quickly discharged from the combustion chamber and closed immediately after finishing the exhaust stroke and passing over to the intake stroke, i.e., after top dead center. This is to make the emission of combustion gas as perfect as possible.

In particular, there is a time when the intake valve 1 and the exhaust valve 2 open together at the beginning of the intake stroke from the end of the exhaust stroke. This is called an overlap (lap) and is intended to improve the filling efficiency of the mixer while simultaneously releasing the combustion gas.

However, in the conventional D.O.H.C engine, the timing of the valve is constant depending on the rotational speed of the engine, but the time is changed such that the overlap time is short at high speed and relatively long at low speed. In particular, when the high speed rotation, the overlap time is short, there is a problem that the sucked fuel mixture is not able to sufficiently push the explosion gas.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and by adjusting the overlap of the intake camshaft to adjust the overlap according to the load of the engine to increase the fuel consumption efficiency and improve the output in high speed and low speed operation of the engine An overlap variable device of timing is provided.

1 is a partial perspective view showing a valve mechanism in a conventional engine,

Figure 2a is a perspective view showing an overlap variable device of the valve timing according to the present invention,

2b is a front schematic view showing another embodiment of the present invention;

Figure 3a is a front schematic view showing the operating state of the engine low speed of the present invention,

3b is a graph showing an overlap state at low speed of the engine of the present invention;

Figure 4a is a front schematic view showing the operating state of the engine at high speed of the present invention,

Figure 4b is a graph showing the overlap state at the engine high speed of the present invention.

Explanation of symbols for the main parts of the drawings

50: exhaust cam sprocket 60: intake cam sprocket 70: power transmission means

70a: belt 70b: chain 80: push sprocket

82: upper sprocket 84: lower sprocket 85: connecting means

86: central axis 87: connecting shaft 88: bearing

90: drive means 90b: hydraulic pressure providing means 92: rack

94: pinion 96: drive motor

In the valve variable overlap apparatus of the present invention for realizing the above object, an exhaust camshaft for operating an exhaust valve and an intake camshaft for operating an intake valve are separated from each other, and rotational power is applied from the exhaust camshaft to the intake camshaft. In a valve timing apparatus, wherein an exhaust cam sprocket and an intake cam sprocket are respectively installed and interconnected by a power transmission means, the exhaust cam sprocket and the intake cam sprocket are positioned between the exhaust cam sprocket and the intake cam sprocket so that the intake cam sprocket rotates by a predetermined angle. A plurality of pressing sprockets for pressing the upper side and the lower side of the means, a connecting means for connecting and supporting the plurality of pressing sprockets, and a driving means for moving the connecting means up and down.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

The overlap variable apparatus of the valve timing according to the present invention is located between the exhaust cam sprocket 50 and the intake cam sprocket 60 as shown in FIG. 2 so that the intake cam sprocket 60 rotates by a predetermined angle. A plurality of pressing sprockets 80 for pressing the upper and lower sides of the power transmission means 70, connecting means 85 for interconnecting and supporting the plurality of pressing sprockets 80, and the connecting means 85 It consists of a drive means 90 for moving up and down.

The pressing sprocket 80 has an upper sprocket 82 for pressing the upper side of the power transmission means 70 such that the intake cam sprocket 60 rotates counterclockwise by a predetermined angle, and the intake cam sprocket 60. It consists of a lower sprocket 74 for pushing the lower side of the power transmission means 70 so as to rotate clockwise by a predetermined angle.

Here, the pressing sprocket 80 is composed of a pressing roller 80a corresponding to the belt 70a when the power transmission means 70 is formed of the belt 70a as shown in FIG. 2A, and the power When the transmission means 70 is formed of a chain 70b as shown in Fig. 2b, it is composed of a chain gear 80b that meshes with the chain 70b.

The connecting means 85 includes a plurality of central shafts 86 installed at the centers of the plurality of pressing sprockets 80, and a connecting shaft 87 interconnecting the plurality of central shafts, and the central shaft 86 ) And the connection portion of the pressing sprocket 80, it is preferable that the bearing 88 is installed so that the rotation of the pressing sprocket 80 is free.

As shown in FIG. 2B, the driving means 90 is installed at an extension of the connecting shaft 87 and includes hydraulic pressure providing means 90b that vertically moves the connecting shaft 87 by the action of hydraulic pressure.

In another embodiment, the driving means 90 includes a rack 92 formed on the side of the connecting shaft 87, a pinion 94 engaged with the rack 92, and There is also a method comprising a drive motor 96 connected to the pinion 94 to drive the pinion 94.

Referring to the operation of the overlap variable device of the valve timing of the present invention configured as described above are as follows.

Overlaps should be small when the engine is running at low speeds and large at high speeds.

In the engine low speed state, as shown in FIG. 3, the intake cam sprocket 60 is rotated by a predetermined angle α in the counterclockwise direction to reduce the overlap. That is, the pressing sprocket 80 is moved downward by operating the driving means 90 made of the hydraulic pressure providing means 90b or the rack 92 and the pinion 94. The upper sprocket 82 then presses the upper side of the power transmission means 70 such as the belt 70a or the chain 70b.

Therefore, the intake cam sprocket 60 meshed with the power transmission means 70 rotates by receiving the power of the exhaust cam sprocket 50 while being rotated counterclockwise by a predetermined angle α. At this time, as shown in FIG. 3B, the intake timing is delayed to some extent, so that the overlap becomes small.

On the other hand, in the engine high speed state, the driving means 90 is operated in the opposite direction to the above, and the pressing sprocket 80 is moved upward, and the lower sprocket 84 pushes the lower side of the power transmission means 70 upward, thereby causing the intake cam to be inclined. The sprocket 60 is rotated clockwise by a predetermined angle β.

Thus, as shown in FIG. 4B, the intake timing is sucked to some extent and the overlap is increased.

In the variable valve overlap apparatus according to the present invention constructed and acting as described above, the angle of the intake camshaft is changed according to the engine speed, and the overlap is adjusted according to the load of the engine. There is an advantage that this is increased and the output is directed.

That is, the present invention can save fuel by preventing the fuel mixture from escaping between the exhaust valves with a narrow overlap in the low speed state of the engine. In the high speed state of the engine, a wide overlap prevents the explosive gas from remaining in the combustion chamber, thereby reducing the explosive power. Therefore, the present invention results in an increase in fuel efficiency and an increase in engine power.

Claims (8)

An exhaust cam shaft for operating the exhaust valve and an intake cam shaft for operating the intake valve are separated from each other, and an exhaust cam sprocket and an intake cam sprocket are installed to transfer rotational power from the exhaust cam shaft to the intake cam shaft, respectively. In the connected valve timing device, A plurality of push sprockets positioned between the exhaust cam sprocket and the intake cam sprockets to press the upper and lower sides of the power transmission means so that the intake cam sprockets rotate by a predetermined angle, and interconnecting and supporting the plurality of press sprockets. An overlap variable apparatus of a valve timing, characterized in that it comprises a connecting means and a driving means for moving the connecting means up and down. The method of claim 1, The pressing sprocket has an upper sprocket for pressing the upper side of the power transmission means so that the intake cam sprocket rotates counterclockwise by a predetermined angle, and a lower side of the power transmission means so that the intake cam sprocket rotates clockwise by a predetermined angle. Valve timing overlap variable device, characterized in that consisting of a lower sprocket for pushing the. The method of claim 1, And said pressing sprocket is constituted by a chain gear that meshes with said chain when said power transmission means is formed of a chain. The method of claim 1, And the push sprocket is configured as a push pulley corresponding to the belt when the power transmission means is formed as a belt. The method of claim 1, The connecting means is a variable variable valve timing overlap, characterized in that composed of a plurality of central shafts installed in the center of the plurality of pressing sprockets, and a connecting shaft for interconnecting the plurality of central axes. The method of claim 5, The variable variable valve timing overlap, characterized in that the bearing is installed on the connection between the central axis and the pressing sprocket free rotation of the pressing sprocket. The method according to claim 1 or 5, The drive means is provided with an extension portion of the connecting shaft is overlap variable apparatus of the valve timing, characterized in that composed of hydraulic pressure providing means for moving the connecting shaft up and down by the action of the hydraulic pressure. The method of claim 5, And the drive means comprises a rack formed on the side of the connecting shaft, a pinion engaged with the rack, and a drive motor connected to the pinion to drive the pinion.