JP2008240634A - Valve gear of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valve gear of an engine having high durability, equally distributing input to a pair of engine valves from a rocker arm. <P>SOLUTION: This valve gear of the engine has valve springs 5 respectively energizing the pair of engine valves 2 installed on a cylinder head 1 of the engine in the closing direction, a bridge member 8 arranged to be bridged between head parts of both engine valves 2, the rocker arm 10 rockingly supported by the cylinder head 1 via a rocker shaft 9 and opening both engine valves 2, 3 by pressing a pressure receiving surface 20 formed in an intermediate part of the bridge member 8 by a rocking end part, and a camshaft 6 driving this rocker arm 10 to the opening side of the engine valves 2, 3. A roller 11 rolling on the pressure receiving surface 20 of the bridge member 8 in response to rocking of this rocker arm 10, is supported by the rocker arm 10. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a valve operating apparatus for an engine, and in particular, a valve spring that biases a pair of engine valves attached to an engine cylinder head in a closing direction and a bridge between the heads of both engine valves. A bridge member provided, and a rocker arm that is swingably supported by a cylinder head via a rocker shaft, and that opens both engine valves by pressing a pressure receiving surface formed at an intermediate portion of the bridge member by a swing end portion; The present invention relates to an improvement in a thing provided with a cam shaft for driving the rocker arm to the opening side of an engine valve.

Such a valve operating apparatus for an engine is already known as disclosed in Patent Document 1.
Japanese Utility Model Publication No. 59-100905

  In such engine valve gears, in general, when the bridge member is pressed from the rocker arm, the guide member such as a dedicated guide shaft or engine valve stem is opened so that the engine valve opens while moving parallel to the engine valve. An inevitable sliding gap exists between the guide member and the bridge member supported by the rod.

  By the way, in the conventional valve gear, since the pressing surface formed on the rocking end of the rocker arm is brought into contact with the flat pressure receiving surface of the bridge member, the pressure receiving of the bridge member accompanying the rocking of the rocker arm. The surface and the pressure receiving surface of the rocker arm move while tilting, causing a shift. Such a phenomenon greatly moves the pressing point of the rocker arm against the pressure receiving surface of the bridge member. Therefore, when the input from one rocker arm is distributed to the pair of engine valves by the bridge member, the distribution arm of the bridge member in two directions is arranged. The effective length of the input changes, making it difficult to distribute the input evenly. In addition, if the rocker arm pressing surface moves on the pressure receiving surface of the bridge member and the displacement occurs, the frictional force generated by the displacement adds a large side thrust to the bridge member. Or the frictional resistance of the sliding part between the guide part such as the stem part of the engine valve is increased, and the wear of the sliding part is also accelerated.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a valve operating device for an engine capable of evenly distributing input from a rocker arm to a pair of engine valves and having high durability. To do.

  In order to achieve the above object, the present invention is arranged so that a pair of engine valves attached to a cylinder head of an engine are urged in a closing direction and bridged between the heads of both engine valves. And a rocker arm that is swingably supported by a cylinder head via a rocker shaft, and that opens both engine valves by pressing a pressure receiving surface formed at an intermediate portion of the bridge member by a rocking end. In a valve operating apparatus for an engine having a camshaft for driving the rocker arm to the opening side of the engine valve, the first is to support a roller that rolls on the pressure receiving surface as the rocker arm swings. It is characterized by. The engine valves correspond to intake valves 2 and 2 and exhaust valves 3 and 3 which will be described later.

  In addition to the first feature, the present invention has a second feature that the rocker shaft is disposed obliquely with respect to the arrangement direction line of both engine valves.

  According to the first feature of the present invention, when the rocker arm is swung in the opening direction of the engine valve by the driving force from the cam shaft, the roller supported by the rocker arm presses the pressure receiving surface of the bridge member. The bridge member is lowered and the pair of intake valves are opened against the urging force of the valve spring. At that time, the roller rolls the pressure receiving surface of the bridge member to the minimum, so that the contact state between the roller and the pressure receiving surface does not always change to the line contact state regardless of the change in the rocker arm swing angle, and the rocker arm swings. As a result, the change in the pressure point on the pressure-receiving surface of the roller, that is, the pressure point on the bridge member of the rocker arm, can be suppressed very little, and therefore the effective length of the distribution arm in the two directions of the bridge member hardly changes. It is possible to equalize the valve opening lift amount for both intake valves while ensuring a substantially equal distribution of the input to the intake valves and equalizing the loads of both valve springs. Further, the rolling of the roller with respect to the pressure receiving surface can avoid side thrust from being applied to the bridge member from the rocker arm, and the increase in sliding resistance with the guide shaft 16 of the bridge member 8 can be suppressed. Combined with a substantially uniform distribution of the input to the valve, the durability of the valve operating device can be improved.

  According to the second feature of the present invention, the rocker shaft is brought as close as possible to the center of the combustion chamber of the engine, so that the valve operating device can be made compact. The input from the rocker arm to the pair of intake valves can be evenly distributed.

  Embodiments of the present invention will be described below based on one embodiment of the present invention shown in the accompanying drawings.

  FIG. 1 is a perspective view of a valve operating apparatus for a diesel engine according to an embodiment of the present invention, FIG. 2 is a view taken in the direction of arrow 2 in FIG. 1, and FIG.

  First, in FIG. 1, a cylinder head 1 of a diesel engine has a pair of intake and exhaust ports (both not shown) in which a pair of intake valves 2 and 2 and exhaust valves 3 and 3 open to the combustion chamber 1a. Is provided. Reference numerals 4 and 4 denote valve gears for opening and closing the intake valves 2 and 2 and the exhaust valves 3 and 3, respectively, and their configurations are basically the same. The valve gear 4 on the side of the valves 2 and 2 will be described below.

  The pair of intake valves 2 and 2 are umbrella-shaped, and are arranged with the valve stems 2a and 2a in parallel. The valve gear 4 rotates on the valve stems 2a and 2a of the intake valves 2 and 2 so as to urge the valve stems 2a and 2a in the valve closing direction, and on the engine body below the cylinder head 1. A camshaft 6 that is freely supported and driven with a reduction ratio of one half from a crankshaft (not shown), and a tappet that is supported by the engine body so as to be raised and lowered and is operated by an intake cam 6i on the camshaft 6. 17, a push rod 7 that extends upward with its lower end abutted against the tappet 17, a bridge member 8 that is bridged between the heads of the valve stems 2 a and 2 a of the intake valves 2 and 2, and the cylinder head 1 The rocker shaft 10 is supported by the rocker shaft 9 so as to be swingable, and is configured by a rocker arm 10 that interlocks and connects the upper end portion of the push rod 7 and the bridge member 8. A roller 18 that can relatively roll on the outer peripheral surface of the intake cam 6 i is pivotally supported at the lower end of the tappet 17. The upper and lower end portions of the push rod 7 are formed at spherical end portions 12, 12, and spherical concave portions 13, 14 with which they swing so as to swing are formed at the tappet 17 and the rocker arm 10, respectively.

  As shown in FIGS. 1 to 3, the bridge member 8 integrally has a boss 8 a that protrudes downward in the center in the longitudinal direction, and this boss 8 a is connected to them at the center position of both intake valves 2 and 2. A guide shaft 16 fixed to the cylinder head 1 in parallel is supported so as to be movable up and down. An adjustment bolt 15 for securing simultaneous contact between the bridge member 8 and both valve stems 2a and 2a heads is attached to one end portion of the bridge member 8.

  Further, on the upper surface of the bridge member 8, a flat pressure receiving surface 20 is formed so as to protrude at a position corresponding to the midpoint between the intake valves 2 and 2. On the other hand, a roller 11 that can roll on the pressure receiving surface 20 is pivotally supported at the end of the rocker arm 10 opposite to the push rod 7. That is, a pair of left and right support arms 21, 21 are formed at the end of the push rod 7, and the roller 11 is disposed between the support arms 21, 21 and the support arms 21, 21. It is supported rotatably on the pivot 22 supported by. The pivot 22 is arranged in parallel with the rocker shaft 9.

  The rocker shaft 9 is disposed obliquely with respect to the arrangement direction line A of both intake valves 2 and 2. Such an arrangement of the rocker shaft 9 and the intake valves 2 and 2 makes the rocker shaft 9 as close as possible to the central portion of the combustion chamber 1a, and can contribute to the compactness of the valve operating device 4.

  The camshaft 6 is formed with an intake cam 6i and an exhaust cam 6e with a journal 23 supported by the engine body interposed therebetween.

  Next, the operation of this embodiment will be described.

  In the intake stroke of the engine, when the intake cam 6i pushes up the push rod 7 via the tappet 17, the rocker arm 10 swings around the rocker shaft 9 and lowers the roller 11, so that the roller 11 moves the pressure receiving surface 20 down. The bridge member 8 is pushed down to open both intake valves 2 and 2 against the urging force of the valve springs 5 and 5. At this time, the bridge member 8 that is in contact with the heads of both intake valves 2 and 2 is lowered along the guide shaft 16, so that both intake valves 2 and 2 can be opened simultaneously.

  In particular, the roller 11 supported on the rocker arm 10 by the pivot 22 parallel to the rocker shaft 9 presses the flat pressure receiving surface 20 of the bridge member 8, so that the roller 11 is changed according to the change in the rocking angle of the rocker arm 10. The pressure receiving surface 20 rolls to the minimum. This is because the rocker arm 10 swings because the contact state between the roller 11 and the pressure receiving surface does not always change to the line contact state regardless of the rocking angle of the rocker arm 10. This means that the displacement of the pressure point on the pressure receiving surface 20 of the roller 11, that is, the displacement of the pressure point on the bridge member 8 of the rocker arm 10 is extremely small. Therefore, despite the fact that the rocker shaft 9 is disposed obliquely with respect to the arrangement direction line A of the two intake valves 2 and 2, the effective length of the distribution arm in the two directions of the bridge member hardly changes, and the rocker arm The substantially equal distribution of the input from 10 to the pair of intake valves 2 and 2 can be ensured, and the load on both valve springs 5 and 5 can be equalized.

  Further, by rolling the roller 11 with respect to the pressure receiving surface 20, it is possible to avoid the side thrust from being applied to the bridge member 8 from the rocker arm 10, and to suppress an increase in sliding resistance with the guide shaft 16 of the bridge member 8. In combination with the substantially equal distribution of the input to the pair of intake valves 2, 2, the durability of the valve gear 4 can be improved.

  The present invention is not limited to the above embodiment, and various design changes can be made without departing from the scope of the invention. For example, the present invention can be applied to an electric ignition engine. Further, the push rod 7 can be eliminated, and the present invention can also be applied to a valve operating apparatus in which the end of the rocker arm 10 is directly pushed by the cam shaft 6. Further, the bridge member 8 can be configured such that the guide shaft 16 is eliminated and the valve stem 2 a can be used as a guide portion of the bridge member 8.

The perspective view of the valve operating apparatus of the diesel engine which concerns on the Example of this invention. FIG. FIG. 3 is a sectional view taken along line 3-3 in FIG. 2.

Explanation of symbols

A ... Arrangement direction line of engine valve 1 ... Cylinder head 2 ... Engine valve (intake valve)
3 .... Engine valve (exhaust valve)
4 .... Valve operating device 6 ... Cam shaft 8 ... Bridge member 9 ... Rocker shaft 10 ... Rocker arm 11 ... Roller 20 ... Pressure receiving surface

Claims (2)

A valve spring (5, 5) for urging a pair of engine valves (2, 2, 3 and 3) attached to the cylinder head (1) of the engine in the closing direction, and both engine valves (2, 2; 3, 3) A bridge member (8) disposed so as to be bridged between the heads, and a cylinder head (1) supported by a rocker shaft (9) so as to be swingable. A rocker arm (10) that opens both engine valves (2, 2; 3, 3) by pressing a pressure receiving surface (20) formed in an intermediate portion of the member (8), and this rocker arm (10) is connected to the engine valve (2 , 2; 3, 3) and a camshaft (6) driven on the open side of the engine,
A valve operating apparatus for an engine, characterized in that a roller (11) that rolls on the pressure receiving surface (20) as the rocker arm (10) swings is pivotally supported on the rocker arm (10). The valve gear for an engine according to claim 1,
A valve operating apparatus for an engine, characterized in that the rocker shaft (9) is disposed obliquely with respect to the arrangement direction line (A) of both engine valves (2, 2; 3, 3).

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