JP2004100540A - Rocker arm - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rocker arm made by sheet metal pressing which can prevent the single contact of a valve to a valve receiving part without performing an after working. <P>SOLUTION: This rocker arm 1 is rocked by a cam 2 to operate the valve 3 of an internal combustion engine 3. An arm body 4 is a press worked product having a pair of opposed side walls 5 and a connecting wall 6 for mutually connecting both the opposed side walls 5, which is formed by bending one sheet material into a substantially U-shaped cross sectional shape. The arm body 4 is mounted with a roller 10 rockably supported by either one longitudinal end or the middle and rolled in contact with the cam 2. The part of the connecting wall 6 at the other longitudinal end of the arm body 4 is formed into a valve receiving part 8 to abut on the valve 3. The valve contact surface of the valve receiving part 8 has a protruding curved cross sectional shape. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rocker arm that opens and closes a valve provided in a cylinder head by swinging a cam in an internal combustion engine.
[0002]
[Prior art and problems to be solved by the invention]
As this type of conventional rocker arm, a precision cast product, an inexpensive and light weighted one by press work, and the like have been developed, and in particular, a substantially U-shaped press work rocker arm has become the mainstream. The rocker arm is classified into an end pivot type and a center pivot type depending on the position of the swing fulcrum. Both types have a valve receiving portion at the other end. In the end pivot type, a pivot portion is formed at one end of the arm body, a roller that is in rolling contact with the cam is provided in the middle, and a valve receiving portion is provided at the other end. The center pivot type is supported in a swingable manner in the middle of the arm body, a roller that is in rolling contact with a cam is provided at one end, and a valve receiving portion is provided at the other end.
[0003]
As a function of the rocker arm, the accuracy of the parallelism between the swing center and the valve receiving part is important. If the accuracy is poor, the valve comes into contact with the valve receiving portion, causing problems such as early breakage and early wear.
Forging and casting rocker arm products have poor dimensional accuracy and roughness accuracy, and therefore, post-processing such as polishing is performed to ensure a predetermined accuracy.
The press-worked rocker arm is advantageous in that it is inexpensive and can be reduced in weight, but it is difficult to ensure the accuracy that satisfies the parallelism by the press work. If countermeasures are taken and post-processing is performed in the same manner as cast products and forged products, the cost will increase despite the low cost of folding and pressing.
[0004]
The object of the present invention is to eliminate such problems, and even in the case of press working, the valve does not come into contact with the valve receiving portion without performing post-processing, and premature breakage or early wear occurs. It is providing the rocker arm which can prevent.
[0005]
[Means for Solving the Problems]
The present invention relates to a rocker arm that is driven to swing by a cam to operate a valve of an internal combustion engine, and is a single U-shaped cross-sectional plate having a pair of opposed side walls and a connecting wall that connects the opposed side walls. An arm body bent from the side. This arm body is constructed as follows.
The arm body is supported so as to be swingable at one of the longitudinal end and the middle, and on the other hand, a roller that is in rolling contact with the cam is attached. A portion of the connecting wall at the other end in the longitudinal direction of the arm body serves as a valve receiving portion that contacts the valve. The cross-sectional shape of the valve contact surface of the valve receiving portion is a convex curve.
Thus, if the cross-sectional shape of the valve contact surface is a convex curve, the valve will hit the valve contact surface of the convex curve even if there is some error in the parallelism between the swing center of the arm body and the valve receiving portion. Therefore, it will not be a piece. Therefore, occurrence of early breakage or early wear can be prevented, and deterioration of the function of the rocker arm can be prevented. Further, since it is not necessary to ensure the accuracy of the valve receiving portion by post-processing, a low-cost rocker arm can be obtained.
[0006]
The convex curve having the cross-sectional shape of the valve contact surface may be an arc shape or a logarithmic function curve in a range excluding the vicinity of both edge portions of the connecting wall. In the case of an arc shape, the radius of curvature of the arc may be in the range of 30 to 300 mm, for example. In the case of a logarithmic function curve, for example, the drop amount from the apex to the end of the logarithmic function curve may be 0.03 mm or less.
When the curvature radius of the convex curve of the valve contact surface is small or the drop amount is large, the contact surface pressure increases and premature wear may occur due to point contact. For this reason, the radius of curvature is preferably 30 mm or more in the case of an arc shape, and the drop amount is preferably 0.03 mm or less in the case of a logarithmic function curve. In the case of an arc shape, if the radius of curvature exceeds 300 mm, the anti-contact effect due to the arc shape hardly occurs. The range in which the convex curve is an arc or logarithmic curve is defined as the range excluding the vicinity of both edges of the connecting wall. This is because the bulb is not in contact with both ends and it is not necessary to have a convex curve shape.
[0007]
The material of the arm body is preferably made of a steel plate, and in particular, a material using carburized steel as a material and subjected to carburizing heat treatment as heat treatment is preferable. When carburized heat treatment is performed as carburized steel, the required strength, surface hardness, etc. against wear and the like can be obtained with simple processing, and a rocker arm having excellent durability can be manufactured at low cost.
[0008]
The plate thickness of the valve receiving portion may be thicker than the plate thickness of other portions of the arm body. Since the valve receiving part is in a state close to point contact with the valve, it is necessary to ensure the strength, but by making the plate thickness of the valve receiving part thicker than other parts, the thickness of other parts is wasted. The required strength can be ensured without increasing the thickness, which is preferable from the viewpoint of saving the amount of material used and reducing the weight.
[0009]
Further, in the present invention, the pivot part has a screw hole to be attached with a male screw part in the connecting wall portion at the other end of the arm body, and the pivot part has a screw hole on the opposite surface in the vicinity of the screw hole. You may form the partial screw threadedly engaged with the said external thread part following the said screw hole. In this case, it becomes an end pivot type in which the arm body is swingably supported around the tip of the pivot part. The pivot part is screwed in to adjust the opening / closing amount of the valve.
In the arm main body made of sheet metal press, the plate thickness is reduced for weight reduction, so it is difficult to secure a sufficient depth of the screw hole for screwing the male screw portion of the pivot part. However, as described above, by forming a partial screw on the opposite side wall of the substantially U-shaped arm main body, the male screw portion of the pivot part can be screwed over the partial screw from the screw hole of the connecting wall, The part of the opposite side wall can also be used for the female thread for mounting the pivot part. Therefore, the strength of screwing is ensured, and the mounting strength of the pivot part can be ensured while maintaining the weight reduction of the arm body.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to FIGS. The rocker arm 1 is mounted on an internal combustion engine and is driven to swing by a cam 2 to operate a valve 3 of a cylinder head. The rocker arm 1 is made of a sheet metal press product, and is an end pivot type supported at one end by a pivot receiving seat 26 so as to be swingable. The arm body 4 of the rocker arm 1 is provided with an adjustment screw 7 as a pivot part at one end, and the adjustment screw 7 is provided with a pivot portion 7b supported by the pivot receiving seat 26 at the tip of the male screw portion 7a. Yes. The pivot portion 7b has a spherical shape. At the other end of the arm body 4, a valve receiving portion 8 that abuts on the operation shaft portion 3 a that can move up and down of the valve 3 is provided, and a roller 10 that is in rolling contact with the cam 2 is attached in the middle of the length direction. . The operation shaft portion 3a of the valve 3 is provided with a valve body (not shown) at the lower end and is urged upward by a valve spring 3b.
[0011]
As shown in FIG. 2, the arm body 4 has a substantially U-shaped cross-sectional shape composed of a pair of parallel opposing side walls 5 and a connecting wall 6 that connects the upper edges of the opposing side walls 5. The sheet metal is bent and formed by press working. The connecting wall 6 is on the upper surface side, that is, the side opposite to the valve 3. In other words, the arm body 4 has a substantially inverted U-shaped cross section. The side surface shape of the arm main body 4 is substantially linear in this embodiment, but may be, for example, a curved shape. The connecting wall 6 of the arm body 4 is provided in the remaining range excluding the intermediate portion in the longitudinal direction, and the intermediate portion is formed in a window 11 from which a part of the roller 10 protrudes. The portion on the one end side of the window 11 is the adjustment screw mounting portion 9, and the portion on the other end side is the valve receiving portion 8.
[0012]
A screw hole 12 that is an attachment hole for the adjustment screw 7 is provided in a portion of the connecting wall 6 that becomes the adjustment screw attachment portion 9, and a male screw portion 7 a of the adjustment screw 7 projects upward in the screw hole 12. Screwed. The adjustment screw 7 is fixed to the arm body 4 by tightening a nut 13 into a portion protruding from the screw hole 12.
[0013]
The roller 10 in FIG. 1 is rotatably supported by a roller support hole 16 provided in the opposite side wall 5 of the arm body 4 via a support shaft 19. Both sides of the support shaft 19 are fitted and fixed to the roller support holes 16.
For example, as shown in FIG. 3A, the roller 10 has a double structure of an inner roller 10a and an outer roller 10b, a contact surface between the inner diameter surface of the inner roller 10a and the support shaft 19, and an outer surface of the inner roller 10a. The sliding surfaces between the radial surface and the inner diameter surface of the outer roller 10b are bearing surfaces that are in sliding contact with each other. In addition to this, as shown in FIG. 3B, the roller 10 may be composed of an outer ring of a rolling bearing. In the example of the figure, a roller bearing in which a rolling element 20 made of a roller is interposed between the inner diameter surface of the roller 10 and the support shaft 19 is provided. 3A is a double roller type, and FIG. 3B is a rolling type. In the case of sliding contact, as shown in FIG. 3C, the roller 10 is composed of a single part. It may be a single roller type.
[0014]
An example of the material of the arm body 4 in FIGS. 1 and 2 is a steel material such as case-hardened steel (for example, SCM415), which is tempered after carburizing and quenching. The effective curing depth is, for example, 0.4 to 1.5 mm, and preferably 0.4 to 0.9 mm.
[0015]
FIG. 4 shows an enlarged view of a cross section taken along arrow IV-IV in FIG. As shown in the figure, the cross-sectional shape of the valve contact surface of the valve receiving portion 8 composed of the connecting wall 6 at the other end in the longitudinal direction of the arm body 4 (the cross-sectional shape in the direction perpendicular to the arm body length direction) It is a convex curve. Specifically, the convex curve, which is the cross-sectional shape of the valve contact surface, has an arc shape in a range excluding the vicinity of both edge portions of the connecting wall 6. The radius of curvature R of the arc varies depending on the width dimension of the rocker arm 1, but is preferably in the range of 30 to 300 mm.
[0016]
In addition, the convex curve may be a logarithmic function curve in a range excluding the vicinity of both edges of the connecting wall 6 as shown in FIG. Although this logarithmic function curve varies depending on the width dimension of the rocker arm 1, it is desirable that the drop amount from the apex to the end of the logarithmic function curve be 0.03 mm or less.
[0017]
According to the rocker arm 1 having this configuration, since the cross-sectional shape of the valve contact surface of the valve receiving portion 8 is a convex curve, there is a slight error in the parallelism between the swing center of the arm body 4 and the valve receiving portion 8. Even if there is, there is no contact between the bulb 3 and the bulb contact surface of the convex curve. Therefore, the occurrence of early breakage or early wear can be prevented, and the function deterioration of the rocker arm 1 can be prevented. In addition, since it is not necessary to ensure the accuracy of the valve receiving portion 8 by post-processing, the convex curve of the valve contact surface of the valve receiving portion 8 that can be used as a low-cost rocker arm 1 by taking advantage of the features made of sheet metal press. If the radius of curvature R of the arc is too small, the valve 3 tends to be in point contact with the valve receiving portion 8 and the contact surface pressure becomes high, and premature wear may occur. By setting it to a range of 30 mm or more, early wear can be prevented. If the curvature radius R exceeds 300 mm, the effect of preventing one-sided contact due to the convex curved surface cannot be sufficiently obtained, which is not preferable. Further, when the valve contact surface is a logarithmic curve as shown in FIG. 5, if the drop amount is too large, the valve 3 tends to be in point contact with the valve receiving portion 8, and the contact surface pressure becomes high, resulting in early wear. Although it may occur, premature wear can be prevented by setting the drop amount within the range of 0.03 mm or less.
[0018]
FIG. 6 shows an embodiment corresponding to the second invention. In this embodiment, in the first embodiment shown in FIGS. 1 to 5, the thickness of the connecting wall 6 is made thicker than the thickness of the other part of the arm body 4. FIG. 6A shows an example in which the cross-sectional shape of the valve contact surface of the valve receiving portion 8 is an arc shape having a radius of curvature R in the range of 30 to 300 mm as in the case of FIG. FIG. 6B shows the cross-sectional shape of the valve contact surface of the valve receiving portion 8 in a logarithmic form in which the drop amount from the apex to the end of the logarithmic function curve is 0.03 mm or less, as in FIG. An example of a function curve is shown.
[0019]
Since the valve receiving portion 8 is in a state close to point contact with the valve 3, it is necessary to ensure strength, but by making the plate thickness of the valve receiving portion 8 thicker than other portions as in this embodiment, The required strength can be ensured without unnecessarily increasing the thickness of the other portions, which is preferable in terms of saving the amount of material used and reducing the weight.
[0020]
7 to 9 show still another embodiment of the present invention. In this embodiment, in the first embodiment shown in FIGS. 1 to 5, the male screw portion 7 a of the adjustment screw 7 is screwed onto the opposing surfaces of the opposing side walls 5 on both sides in the vicinity of the screw hole 12 of the arm body 4. The partial screw 12 b is formed following the screw hole 12. In the arm body 4, at least the dimension L between the opposite side walls 5 on both sides in the vicinity of the screw hole 12 is set to be a dimension that is narrower than the hole diameter of the screw hole 12. In this embodiment, the end of the arm body 4 on the side where the screw hole 12 is formed is processed into a narrow portion 4a, and the screw hole 12 and the partial screw 12b are provided in the narrow portion 4a. The arm body 4 may have the same width as the narrow portion 4a over the entire length instead of forming the local narrow portion 4a. The adjustment screw 7 is screwed into a female screw portion including the screw hole 12 and the partial screw 12b of the arm main body 4, and a nut 13 is screwed into the male screw portion 7a protruding upward from the arm main body 4 as in the first embodiment. Yes. Other configurations in this embodiment are the same as those in the first embodiment.
[0021]
When the partial screws 12b are formed to face each other in this way, the adjustment screw 7 can be screwed over the partial screw 12b from the screw hole 12 of the connecting wall 6 of the arm body 4, and the portion of the opposing side wall 5 is also an adjustment screw. 7 can be used as the female screw for attachment, and the strength of screwing is ensured. Therefore, the strength of the screwing and the strength of the periphery of the screw hole 12 for attaching the adjusting screw 7 are ensured without increasing the thickness of the arm body 4.
[0022]
10 and 11 show still another embodiment of the present invention. This embodiment shows an example applied to a center pivot type. This rocker arm 1A is also mounted on the internal combustion engine and is driven to swing by a cam 2A to operate the valve 3A of the cylinder head. The arm body 4A is swingably supported by a support shaft 24 in the middle in the longitudinal direction, a roller 10A that is in rolling contact with the cam 2A is attached to one end, and the other end is a valve receiving portion 8A. The valve receiving portion 8A receives the operation shaft portion 3Aa that can be moved up and down of the valve 3A. The operation shaft portion 3Aa of the valve 3A is provided with a valve body (not shown) at the lower end, and is lifted and biased by a valve spring 3Ab.
[0023]
As shown in FIG. 11, the arm main body 4A has a substantially U-shaped cross section formed by a pair of parallel opposing side walls 5A and a connecting wall 6A connecting the upper edges of the opposing side walls 5A. It is formed by bending from a sheet metal such as press by pressing. The connecting wall 6A is on the upper surface side, that is, the side opposite to the valve 3A. The side surface shape of the arm main body 4A is substantially linear in this embodiment, but may be, for example, a curved shape. The connecting wall 6A of the arm body 4A is provided over the remaining substantially entire length except for the attachment side end of the roller 10A. The portion on the other end side of the connecting wall 6A is the valve receiving portion 8A. A swing fulcrum hole 22 is provided in the opposite side wall 5A on both sides of the arm body 4A, and a support shaft 24 is fitted through the bush 25 over the swing fulcrum hole 22 on both sides. The roller 10A is rotatably supported by a roller support hole 16A provided in the opposing side wall 6A of the arm body 4A via a support shaft 19A. Both ends of the support shaft 19A are fitted and fixed in the roller support holes 16A. As the roller 10A, for example, those having various configurations described above with reference to FIGS.
[0024]
The cross-sectional shape of the valve contact surface of the valve receiving portion 8A is a convex curve, and as a specific example of the convex curve, an arc shape is used in the range excluding the vicinity of both edges of the connecting wall 6A, or both edges of the connecting wall 6A The logarithmic function curve is the same as in the first embodiment except in the range excluding the vicinity of the portion.
Thus, even when applied to a center pivot type rocker arm, various effects such as prevention of one-sided contact can be obtained by making the cross-sectional shape of the valve contact surface of the valve receiving portion 8A into a convex curve.
[0025]
【The invention's effect】
The rocker arm according to the present invention has an arm body that is bent from one plate material into a substantially U-shaped cross-sectional shape including a pair of opposing side walls and a connecting wall that connects the opposing side walls, and the longitudinal direction of the arm body Since the cross-sectional shape of the valve contact surface of the valve receiving portion is a convex curve in the case where the connecting wall portion at the other end of the valve is the valve receiving portion, the valve receiving portion is not subjected to post-processing, so that the valve Can be prevented from coming into contact with each other, and premature breakage and premature wear can be prevented. In addition, since it is not necessary to ensure the accuracy of the valve receiving portion by post-processing, a low-cost rocker arm utilizing the features of a press-made rocker arm can be obtained.
[Brief description of the drawings]
FIG. 1 is a side view of a rocker arm according to a first embodiment of the present invention.
2A is a view taken along the line AA in FIG. 1, and FIG. 2B is a schematic perspective view of the arm body.
FIGS. 3A to 3C are explanatory diagrams of examples of rollers in the first embodiment, respectively. FIGS.
4 is an example of a cross section of a valve receiving portion shown as an enlarged cross-sectional view taken along the line IV-IV in FIG. 2 (B).
FIG. 5 is another example of a cross section of the valve receiving portion shown as an enlarged cross-sectional view taken along the line IV-IV in FIG.
FIGS. 6A and 6B are cross-sectional views showing still another example of the valve receiving portion, respectively.
FIG. 7 is a perspective view of an arm body according to still another embodiment of the present invention.
8A is a front view of an end portion of the rocker arm on an adjuster screw side, and FIG. 8B is a cross-sectional view of the same.
9A is a cross-sectional view of a screw hole forming portion of the arm main body, and FIG. 9B is a bottom view showing the vicinity of the end of the arm main body on the screw hole forming side.
FIG. 10 is a side view of a rocker arm according to still another embodiment of the present invention.
FIG. 11 is a schematic perspective view of the arm main body.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Rocker arm 2 ... Cam 3 ... Valve 4 ... Arm main body 5 ... Opposite side wall 6 ... Connection wall 7 ... Adjustment screw (pivot part)
7a ... male screw portion 8 ... valve receiving portion 10 ... roller 12 ... screw hole 12b ... partial screw 1A ... rocker arm 2A ... cam 3A ... valve 4A ... arm body 5A ... opposing side wall 6A ... connecting wall 8A ... valve receiving portion 10A ... roller

Claims (8)

In a rocker arm that is driven to swing by a cam and operates a valve of an internal combustion engine,
It has an arm body bent from a single plate material into a substantially U-shaped cross-sectional shape composed of a pair of opposing side walls and a connecting wall that connects these opposing side walls. A roller that is supported so as to be swingable on one side and that is in contact with the cam on the other side is attached, and the connecting wall portion at the other end in the longitudinal direction of the arm body serves as a valve receiving portion that contacts the valve. The rocker arm is characterized in that the cross-sectional shape of the valve contact surface of the valve receiving portion is a convex curve. The rocker arm according to claim 1, wherein the convex curve having a cross-sectional shape of the valve contact surface is arcuate in a range excluding the vicinity of both edges of the connection wall. The rocker arm according to claim 1, wherein the convex curve having a cross-sectional shape of the valve contact surface is a logarithmic function curve in a range excluding the vicinity of both edges of the connection wall. The rocker arm according to claim 2, wherein a radius of curvature of the arc that forms the convex curve is in a range of 30 to 300 mm. 4. The rocker arm according to claim 3, wherein the logarithmic function curve as the convex curve has a drop amount of 0.03 mm or less from the apex to the end of the logarithmic function curve. 6. The rocker arm according to claim 1, wherein the arm body uses carburized steel as a material and is subjected to carburizing heat treatment as heat treatment. 7. The rocker arm according to claim 1, wherein a plate thickness of the valve receiving portion is made thicker than a plate thickness of other portions of the arm body. 8. The opposing surface of the opposing side wall according to claim 1, wherein the connecting wall at the other end of the arm body has a screw hole to which the pivot part is attached by a male screw portion, and the opposing side wall in the vicinity of the screw hole. And a rocker arm in which a partial screw threadedly engaged with the male screw portion of the pivot part is formed following the screw hole.

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