JP4227125B2 - Rocker arm and valve mechanism - Google Patents

Description

  The present invention relates to a rocker arm mounted on an internal combustion engine.

The rocker arm plays a role of converting the rotational movement of a valve mechanism in an internal combustion engine, that is, a cam rotating in conjunction with a crankshaft, into a reciprocating movement of the valve shaft of the intake valve or exhaust valve of the internal combustion engine. Such a rocker arm has a roller that is in rolling contact with a camshaft that rotates at a high speed, but the main body that supports the roller is often cast and molded in consideration of durability (the following patents) Reference 1).
JP-A-5-33611

  However, since the cost tends to be high, it has been considered that a metal plate material is pressed and formed as a manufacturing method instead of casting. In that case, the opening to be the roller mounting part is punched out to form the developed shape of the main body part, and then the support wall of the roller mounting part is formed by bending both side edges upward into a U-shape. Can be considered. However, simply doing so has a problem that it is difficult to make a fitting portion with the valve side. That is, the fitting portion on the valve side must be formed in the direction opposite to the bending direction when the support wall is formed, so that the processing is not easy.

  In order to eliminate this, the bending direction of the support wall and the valve fitting portion may be the same direction. That is, conversely to the above, it is conceivable to form the support wall and the roller fitting portion at the same time by bending the developed shape of the main body portion into a downward U-shape. However, even if the support wall is formed by bending downward, it is a constraint that the rocker arm does not interfere with the cylinder head when the rocker arm is assembled to the engine. There is a problem that it is difficult to secure the necessary height dimension.

  Under such circumstances, it is not easy to press the sheet metal material to obtain the rocker arm main body.

  The present invention has been completed based on the above circumstances, and an object of the present invention is to provide a rocker arm that can reduce the manufacturing cost by obtaining the main body of the rocker arm by pressing a plate material. And

As means for achieving the above object, the invention of claim 1 is supported by a pivot of an internal combustion engine so as to be able to swing, and is driven by a cam so as to reciprocate an engine valve in accordance with the swing driving. Provide a rocker arm to drive. The rocker arm includes a roller that is in sliding contact with the cam, a pair of first side walls that support the roller by bending a metal plate upward in a substantially U shape by pressing, and the engine valve. A pair of parallel second side walls having a valve contact portion to be driven, and a width between the first side wall and the second side wall so that the width decreases as the second side wall is approached. And a rocker arm body formed with a pair of third side walls. The engine valve includes: a valve stem; a stem cap that is fitted to the valve stem and has a contact surface that contacts the valve contact portion; and a pair of positioning portions that protrude from the contact surface. Have. The pair of second side walls are formed at a space that can be sandwiched between the pair of positioning portions, and the distance between the opposing surfaces inside the pair of second side walls is smaller than the diameter of the valve stem. It is configured as follows .

According to a second aspect of the present invention, there is provided a valve operating mechanism for an internal combustion engine comprising the rocker arm according to the first aspect and an engine valve. The valve mechanism includes an engine valve and a rocker arm according to claim 1. The engine valve includes: a valve stem; a stem cap that is fitted to the valve stem and has a contact surface that contacts the valve contact portion; and a pair of positioning portions that protrude from the contact surface. Prepare.

<Invention of Claim 1>
According to the first aspect of the present invention, the main body portion of the rocker arm is formed by bending the roller accommodating portion upward. That is, the upward bending process is different from the downward bending process in that there is no restriction condition for avoiding interference with the cylinder head, so that the height dimension of the side wall of the portion supporting the roller can be sufficiently secured. . On the other hand, in view of the fact that positioning with respect to the valve side can no longer be formed in the main body, a positioning portion is formed on the stem side of the valve to maintain the function of preventing the displacement with respect to the valve side.
Thus, according to the first aspect of the present invention, the body portion of the rocker arm is formed by sheet metal working, and a reduction in manufacturing cost can be achieved while ensuring a sufficient support strength for the roller.

<Invention of Claim 2>
According to the second aspect of the present invention, since the positioning portion is formed on the cap that is separate from the stem, only a slight structure needs to be added to the existing structure.

<Embodiment 1>
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an upper part of a cylinder head 1, in which a valve operating device constituted by a pivot 2, a camshaft 3, a valve 4, a valve spring 5 and a rocker arm 6 is provided.

  The rocker arm 6 is in the form of a roller rocker arm 6 having a roller 7, and the roller 7 is in contact with the peripheral surface of the cam of the camshaft. One end of the rocker arm 6 is formed with a swing fulcrum 8 that contacts the upper end of the pivot 2 of the lash adjuster, and the other end is formed with a valve contact portion 10 that engages with the upper end of the valve stem 4A of the valve 4. Has been. Thus, in the valve operating device described above, as the camshaft 3 rotates, the rocker arm 6 swings around the swinging fulcrum 8 and the upper end side of the valve stem 4A is pressed against the valve spring 5 at this time. Then, the valve 4 opens and closes the intake and exhaust ports of the engine at a predetermined timing.

  The rocker arm 6 includes a main body 9 and a roller 7 incorporated in the main body 9. The main body 9 is integrally formed by bending a metal plate with a press. As shown in FIG. 2 and the like, the body 9 is bent upward (in a direction away from the cylinder head) into a substantially U-shaped cross section. Is formed. However, in this embodiment, the main body 9 is formed in a symmetric shape with respect to the central axis in the length direction in plan view.

  Further, the central portion of the main body 9 is a roller accommodating portion 11 for accommodating the roller 7 described above. As shown in FIG. 5, the roller accommodating portion 11 has an opening 12 for projecting a part of the lower side of the roller 7 to the outside. The roller 7 accommodated in the roller accommodating portion 11 is mounted so as to be freely rotatable by a support shaft 19 penetrating between both side walls 11A. In this embodiment, both side walls 11A constituting the roller accommodating portion 11 are formed with a height dimension substantially equal to the diameter of the roller 7 (in FIG. 3, the height dimension is such that the roller end face is slightly exposed vertically). The upper and lower edges are arcuate surfaces that match the circumferential surface of the roller 7. Further, one end side of the main body portion 9 is the above-described swing fulcrum portion 8, which is swelled in a dome shape by drawing so as to be covered with the upper end portion of the pivot 2 in alignment. The receiving convex part 20 is formed. On the other hand, after the width of the valve contact portion 10 is gradually reduced from the roller accommodating portion 11 via the inclined portion 13, both side walls 10A extend so as to be substantially parallel to each other. Further, the upper end surface 10B of both side walls 10A of the valve abutting portion 10 is formed in a descending slope as it goes to the tip, and its lower surface becomes a slight arc surface and comes into contact with the cap 14 described below. Is formed.

  On the other hand, a cap 14 made of metal (SCM415 material is used in this embodiment) is fitted to the upper end of the stem 4A in the valve 4. The cap 14 is formed in a short cylindrical shape that can be almost closely fitted to the valve stem 4A, and a contact surface 16 that can contact the contact surface 15 of the main body 9 of the rocker arm 6 is formed on the upper surface thereof. . In addition, a pair of positioning portions 17 are formed to project at symmetrical positions on the contact surface 16. The outer surfaces of the positioning portions 17 are curved surfaces that are continuous with the outer surface of the base side of the cap 14, but the inner surfaces are formed in planes that face each other in parallel with each other, and both outer surfaces of the valve contact portion 10. The guide surface 18 can be sandwiched in a face-to-face state. By this clamping, positioning between the rocker arm 6 and the valve 4 side is performed in a state where the swing in the width direction is restricted.

  Next, the effect of this embodiment comprised as mentioned above is demonstrated. When producing the main body 9, first, a predetermined position of a metal plate in an unfolded state is punched into a substantially square shape to form a hole for passing the opening 12 and the support shaft 19.

  Next, the plate material in the unfolded state is put on a press die, and both side edges sandwiching the opening 12 by the press die are bent upward. However, the bending at this time is performed over the range corresponding to each from the roller accommodating portion 11 to the valve contact portion 10 except for the portion corresponding to the swing fulcrum portion 8. By this bending process, the main body 9 is formed with a roller accommodating portion 11 by both side walls sandwiching the opening 12, and a valve abutting portion 10 is formed adjacent thereto. Next, the roller 7 is accommodated in the roller accommodating portion 11, and the support shaft 19 is inserted into a hole provided in the side wall of the roller accommodating portion 11 so that the roller 7 is attached in a freely rotatable state.

  On the other hand, the upper surface of the cap 14 is cut to form the positioning portion 17 at a symmetrical position. Thereafter, the cap 14 is fitted to the upper end of the stem 4A of the valve, and the both side wall surfaces of the valve contact portion 10 in the main body portion 9 are clamped by the positioning portions 17 when linked with the rocker arm 6. Thus, the rocker arm 6 is assembled to the upper part of the cylinder head.

  As described above, according to the present embodiment, the positioning portion for the valve stem 4A side is arranged not on the main body 9 side of the rocker arm 6 but on the cap 14 side (positioning portion 17). 9 can be bent upward so that interference with the cylinder head 1 does not cause a problem, so that the side wall 11A portion of the roller accommodating portion 11 can be formed. We can secure what we can.

  The positioning portion 17 can be formed integrally with the valve stem 4A by cutting the upper end of the valve stem 4A or the like. In this embodiment, the positioning portion 17 is formed on the cap 14 which is a separate member from the valve stem 4A. Since it is only necessary to fit the upper end of the stem 4A, only a slight improvement is required to the existing structure.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention, and further, within the scope not departing from the gist of the invention other than the following. Various modifications can be made.

(1) Although a pair of positioning portions 17 are provided in the present embodiment and the valve contact portion 10 of the main body portion 9 is sandwiched between them, the number is not limited.
(2) Moreover, the form of the positioning part 17 is not limited to the sandwiching form, and for example, a protrusion is formed on one side of the lower surface of the cap 14 and the upper end surface of the stem 4A, and a recess is formed on the other side. You may make it do.

Sectional view showing the entire rocker arm Same perspective view Front view Side view Plan view Cross section of cap

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Cylinder head 2 ... Pivot 3 ... Cam shaft 4 ... Valve 4A ... Valve stem 6 ... Rocker arm 7 ... Roller 8 ... Swing fulcrum part 9 ... Main-body part 10 ... Valve contact part 11 ... Roller accommodating part 11A ... Side wall 14 ... Cap 17 ... Positioning part

Claims (2)

A rocker arm that is supported by a pivot of an internal combustion engine so as to be swayable, and is swayed by a cam, and reciprocally drives an engine valve in accordance with the swaying drive,
A roller in sliding contact with the cam;
A metal plate material is bent upward in a substantially U shape by press working, so that a pair of first side walls that support the roller and a parallel abutment that has a valve contact portion that drives the engine valve therebetween. A pair of second side walls and a pair of third side walls formed so as to become narrower toward the second side wall between the first side wall and the second side wall are formed. The rocker arm body,
With
The engine valve is
A valve stem;
A stem cap that is fitted to the valve stem and has a contact surface that contacts the valve contact portion, and a pair of positioning portions that protrude from the contact surface;
Have
The pair of second side walls are formed at an interval that can be sandwiched between the pair of positioning portions, and the distance between the opposing surfaces inside the pair of second side walls is smaller than the diameter of the valve stem. Rocker arm. A valve mechanism for an internal combustion engine,
An engine valve,
A rocker arm according to claim 1;
With
The engine valve is
A valve stem;
A stem cap that is fitted to the valve stem and has a contact surface that contacts the valve contact portion, and a pair of positioning portions that protrude from the contact surface;
A valve mechanism comprising:

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