JP2018128000A - Hollow cam shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a hollow cam shaft lightweight further while securing its strength.SOLUTION: The present invention relates to a hollow cam shaft 20 comprising: a base shaft 21 including a hollow part 10 extending in an axial direction; a journal part 23 and a cam part 22 which are disposed in an intermittent manner in the axial direction of the base shaft 21; and a female screw part 11 which is formed on an inner surface of the hollow part in one end in the axial direction. The hollow part 10 includes: a cross section change part 13 enlarging a cross-sectional area from one end side to the other end side closer to the other end than the female screw part 11; and a large cross section part 16 of which the cross-sectional area is larger than that of the female screw part 11 over the entire area closer to the other end than the cross section change part 13. The large cross section part 16 includes: a plug fitting part 15 which is formed in the other end in the axial direction; and a cross section fixing part 14 which is continued from the cross section change part 13 to the plug fitting part 15 with the same cross section.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hollow camshaft having a hollow portion therein.

  As a camshaft for driving the valve system of an engine, there is a case where a hollow camshaft having a hollow portion extending from one end to the other end in the axial direction is sometimes used for the purpose of weight reduction.

  This hollow camshaft is generally manufactured by a casting method using a core. A core made of a sand mold or the like is arranged in the mold, and after the molten metal is injected and the metal is solidified, the core is removed by shot blasting or the like (for example, see Patent Document 1).

JP 2001-105100 A

  By the way, an internal thread portion for attaching a gear, a sprocket, a pulley, or the like is formed at an axial end portion of the camshaft. The female screw portion is formed on the inner surface of the hollow portion at the end on either side of the axial direction, and a fixing bolt inserted through a gear, a sprocket, a pulley, or the like is screwed into the female screw portion.

  Here, in order to further reduce the weight of the camshaft, when an attempt is made to increase the cross-sectional area of the hollow portion, the screw diameter of the female screw portion formed on the inner surface of the hollow portion also increases accordingly. Since a large stress acts on the female screw portion to transmit rotation, the outer diameter of the camshaft around the female screw portion must be increased in order to ensure strength when the screw diameter of the female screw portion is increased. Don't be. For this reason, even if the cross-sectional area of the hollow portion is increased, it is not always possible to reduce the weight of the camshaft.

  Accordingly, an object of the present invention is to reduce the weight of the hollow camshaft while ensuring its strength.

  In order to solve the above-described problems, the present invention includes a hollow portion extending in the axial direction and a female screw portion formed on an inner surface of one end of the hollow portion in the axial direction, and the hollow portion includes the female screw portion. A cross-sectional area where the cross-sectional area expands from one end side toward the other end side on the other end side, and a large cross-sectional area whose cross-sectional area is larger than that of the female screw portion in the entire area of the other end side than the cross-sectional area change portion. A hollow camshaft equipped with

  Here, the said large cross-sectional part employ | adopts a structure provided with the plug insertion part formed in the other axial end, and the fixed cross-section part which continues in the same cross section from the said cross-section change part to the said plug insertion part. be able to.

  Moreover, the cross-sectional change part can employ | adopt the structure which a cross-sectional area expands in a taper shape.

  In each of these aspects, a plurality of projecting portions projecting in the direction away from the axial center along the axial direction is formed, and the cross-section changing portion is disposed between the opposing end surfaces of the projecting portions adjacent in the axial direction. Can be adopted.

  At this time, the projecting portion is a cam portion that is intermittently disposed along the axial direction, or a flange portion that is disposed on both axial sides of the journal portion that is intermittently disposed along the axial direction. Can be adopted.

  The skirt portion of the end surface of the projecting portion includes a rounded portion that is curved in the axial direction toward the inner side in the radial direction and is connected to the cylindrical surface on the side of the projecting portion at the terminal portion, The structure arrange | positioned between the said termination | terminus parts of the said round parts adjacent to an axial direction is employable.

  Moreover, the cross-sectional change part can employ | adopt the structure which exists in the same axial direction range as the said journal part.

  The present invention relates to a hollow camshaft in which a hollow portion extending from one axial end to the other axial end and a female screw portion is formed on the inner surface of one axial end of the hollow portion, the hollow portion is connected to the other end of the female screw portion. Since the cross-sectional area that increases in cross-sectional area from one end side to the other end side on the side, and a large cross-sectional area that has a larger cross-sectional area than the female screw part in the entire area of the other end side than the cross-sectional change part Further, it is possible to reduce the weight while securing the strength of the hollow camshaft.

It is a longitudinal cross-sectional view of the hollow camshaft which shows one Embodiment of this invention. It is a principal part enlarged view of FIG. (A) (b) is a graph which compares the same embodiment and a prior art example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The hollow camshaft 20 of this embodiment includes a base shaft 21 having a hollow portion 10 extending in the axial direction, a journal portion 23 and a cam portion 22 that are intermittently disposed along the axial direction of the base shaft 21, and an axial direction. And an internal thread portion 11 formed on the inner surface of the hollow portion 10 at one end.

  The hollow portion 10 is formed concentrically with the axis of the base shaft 21 that is a shaft-like member, and is provided in the entire axial length of the base shaft 21 by opening at one end face in the axial direction and the other end face.

  As shown in FIG. 1, five journal portions 23; 23a, 23b, 23c, 23d, and 23e are formed intermittently along the axial direction on the outer surface of the base shaft 21. A cylindrical surface facing the bearing for rotatably supporting the hollow camshaft 20 in the cylinder head of the engine is formed on the outer surface of the journal portion 23. As a bearing structure, a plain bearing is generally used.

  The cam bearings 4; 4a, 4b, 4c, 4d, and 4e in a split state are assigned to the outer surface of the journal portion 23 formed of a cylindrical surface so as to cover the entire circumference of each journal portion 23 around the axis, and through the cam bearing 4 Thus, the hollow camshaft 20 is rotatable about the axis of the cylinder head.

  On both sides in the axial direction of the journal portion 23a located on the most axial end side, flange portions 24 that protrude to the outer diameter side are arranged around the entire circumference of the shaft. On the other side of the journal portion 23 in the axial direction, cam portions 22; 22a, 22b, 22c, and 22d are arranged around the entire circumference of the shaft.

  Each of the flange portion 24 and the cam portion 22 is a protruding portion that protrudes in a direction away from the axis on the outer surface of the base shaft 21. These projecting portions are intermittently arranged along the axial direction, and the end surface w of the projecting portion also functions as a thrust bearing for positioning the cam bearing 4 in the axial direction.

  The required number of cam portions 22 is arranged corresponding to the number of cylinders of the engine. In this embodiment, as shown in FIG. 1, it corresponds to a 4-cylinder engine.

  A cam pulley 5 is fixed to one end in the axial direction of the hollow camshaft 20 via a bolt 3. A timing belt is wound around the cam pulley 5 so that the rotation of the crankshaft is transmitted to the hollow camshaft 20. The hollow camshaft 20 is driven in synchronism with the rotation of the crankshaft. The intake and exhaust valves are driven to open and close by the hollow camshaft 20 via the rocker arm and the like, and the engine is operated.

  In some cases, both the intake and exhaust valves are operated by a single hollow camshaft 20, and both the intake and exhaust valves are operated separately by a plurality of hollow camshafts 20. There is also.

  A female screw portion 11 into which the male screw portion 3 a of the bolt 3 that fixes the cam pulley 5 is screwed is formed on the inner surface of one end in the axial direction of the hollow portion 10.

  Further, the hollow portion 10 is connected to the connecting portion 12 having a cylindrical inner surface adjacent to the other end side in the axial direction of the female screw portion 11, and further to the other end side in the axial direction from the one end side to the other end side. A cross-section changing portion 13 whose area is enlarged, and a large cross-sectional portion 16 having a cross-sectional area larger than that of the female screw portion 11 are provided on the other end side of the cross-section changing portion 13.

  The connecting portion 12 has a circular cross section, and is continuous to one end in the axial direction before the female screw portion 11 is formed on the inner surface of the hollow portion 10. When the female screw portion 11 is formed by tapping from one end in the axial direction, a portion remaining as a cylindrical inner surface without forming a screw groove is the connecting portion 12 in FIG.

  The large cross-sectional portion 16 includes a plug fitting portion 15 formed at the other end in the axial direction, and a constant cross-section portion 14 that continues from the cross-section changing portion 13 to the plug fitting portion 15 in the same cross section.

  A plug is inserted into the plug insertion portion 15 in order to seal the hollow portion 10 that is a lubricating oil passage. The plug insertion portion 15 is usually formed in a larger cross section than the constant cross section 14, but depending on the engine specifications, a case where the cross section is smaller than the constant cross section 14 is also conceivable. However, the plug insertion portion 15 is formed from the inner diameter of the maximum diameter portion of the female screw portion 11, that is, from the bottom portion of the valley between the thread of the female screw portion 11 and the axis of the base shaft 21. It has a relatively larger inner diameter (diameter) than a value obtained by doubling the distance (radius). Thereby, the plug fitting part 15 has a relatively larger cross-sectional area than the female screw part 11.

  The constant cross section 14 is circular in cross section and continues with the same cross section over its entire length. Similarly, the inner diameter (diameter) of the constant section 14 is the inner diameter of the maximum diameter portion of the female screw portion 11, that is, the bottom portion of the valley between the screw thread of the female screw portion 11 and the base shaft 21. It has a relatively larger inner diameter (diameter) than a value obtained by doubling the distance (radius) from the axis. As a result, the constant cross-sectional portion 14 has a relatively larger cross-sectional area than the female screw portion 11.

  The cross-section changing portion 13 has a taper-shaped cross-sectional area that increases from one axial end to the other axial end. The angle α of the taper with respect to the axial direction of the generatrix is preferably more gradual from the viewpoint of suppressing stress concentration, but in particular, the angle α with respect to the axial direction of the taper is preferably 45 ° or less.

  As described above, the hollow portion 10 is located on the other end side with respect to the female screw portion 11, the cross-sectional change portion 13 whose cross-sectional area increases from the one end side toward the other end side, and the other end-side entire region from the cross-section change portion 13. Therefore, the total volume of the hollow portion 10 is increased without increasing the diameter of the female screw portion 11, and the hollow camshaft 20 is increased. Can be reduced in weight. That is, since the diameter of the bolt 3 that fixes the cam pulley 5 is not increased, it is not necessary to increase the thickness of the hollow camshaft 20 in the vicinity of the female screw portion 11, and as a result, the strength of the hollow camshaft 20 is ensured. It is possible to reduce the weight further.

  Moreover, the cross-section change part 13 is arrange | positioned between the end surfaces w and w which the protrusion parts adjacent to an axial direction oppose.

  In this embodiment, as shown in FIG. 2, the cross section changing portion 13 is disposed between the end surface w of the flange portion 24 adjacent to the axial direction and the end surface w of the cam portion 22. In other words, the cross-section changing portion 13 is not overlapped in the axial range where the flange portion 24 and the cam portion 22 that are protruding portions on the outer diameter side are interposed. Thereby, the change of the cross section of the base shaft 21 in the vicinity of the protruding portion where stress tends to concentrate is suppressed, and the strength thereof is increased.

  One end (referred to as the start end) and the other end (referred to as the end) of the cross-section changing portion 13 are preferably arranged on the inner side in the axial direction from the opposing end faces w, w of the projecting portions adjacent in the axial direction. It is desirable that the range of the changing unit 13 is, for example, inside the range indicated by the symbol L1 in FIG.

  Furthermore, it is desirable that the cross-section changing portion 13 is disposed between the end portions of the rounded portion R provided at the skirt portion of the protruding portion adjacent in the axial direction.

  As shown in FIG. 2, the rounded portion R is curved outward in the axial direction toward the inner side in the radial direction at the skirt portion of the end surface w of the protruding portion, and at the terminal portion, the rounded portion R becomes a cylindrical surface on the side of the protruding portion. The shape is connected. That is, the connecting portion between the rounded portion R and the cylindrical surface is a terminal portion of the rounded portion R, and the cross-section changing portion 13 is shown between the terminal portions of the rounded portion R adjacent in the axial direction, for example, L2 in FIG. Arranged inside the range. Thus, the cross-section changing portion 13 is overlapped between the end surfaces w, w of the protruding portions such as the flange portion 24 and the cam portion 22 and the axial range where the rounded portion R of the skirt portion of the protruding portion is interposed. If it is not arranged, further strength can be secured.

  It is desirable that the distance between the start end of the cross-section changing portion 13 and the end face w on the start end side and the distance between the end of the cross-section change portion 13 and the end face w on the end side are as long as possible. As described above, the angle α of the taper with respect to the axial direction is preferably 45 ° or less.

  Moreover, it is desirable that the axial range of the cross-section changing portion 13 includes a midpoint between the opposing end faces w, w of the protruding portions adjacent in the axial direction, and further, the start end of the cross-section changing portion 13 and the start end side thereof. It is desirable that the distance from the end face w and the distance between the start end of the cross-section changing portion 13 and the end face w on the start end side are equal to each other.

  Furthermore, it is desirable that the axial direction range of the cross-section changing portion 13 be arranged so as to avoid the position of the identification protrusion 25 for identifying the type of the hollow camshaft 20 in appearance. Or conversely, it is desirable that the identification protrusion 25 be provided in an axial range different from the axial range of the cross-section changing portion 13.

  In this embodiment, the cross-section changing portion 13 is arranged between the end surface w of the flange portion 24 adjacent in the axial direction and the end surface w of the cam portion 22. The change unit 13 may be set in the same axial range as the journal unit 23. In this case, the cross-section changing portion 13 is disposed between the end surface w of the flange portion 24 adjacent to the axial direction and the end surface w of the flange portion 24, or the cross-section changing portion 13 is arranged in the axial direction. It will be arrange | positioned between the end surface w of the adjacent cam part 22, and the end surface w of the cam part 22. FIG.

  Further, in the case where a projecting portion is provided in addition to the flange portion 24 and the cam portion 22 of the journal portion 23, the cross-section changing portion 13 avoids the projecting portion other than the flange portion 24 and the cam portion 22, and It is desirable to arrange between the end faces w, w of the protrusions adjacent in the direction.

  The hollow camshaft 20 of the present invention is manufactured by a casting method in the same way as a normal camshaft. At the time of casting, a core corresponding to the hollow portion 10 is used, the core is placed in the mold, and after the molten metal is injected and the metal is solidified, the core is removed by shot blasting or the like. Further, the hollow camshaft 20 is completed by processing the journal portion 23, the cam portion 22, the female screw portion 11 and the like.

  The core can have a shape corresponding to the connection portion 12, the cross-section change portion 13, the constant cross-section portion 14 of the large cross-section portion 16, and the plug insertion portion 15, but the plug insertion portion 15 can be processed after casting. You can also

  In this embodiment, the cross-section changing portion 13 is configured such that the cross-sectional area increases in a taper shape from one axial end to the other axial end, and the shape of the taper is linear. The shape of 13 is not limited to this embodiment. For example, the shape of the taper of the cross-section changing portion 13 may be a curved surface in which the generatrix draws an arc. Further, a shape in which the cross-sectional area expands stepwise from one axial end to the other axial end is also possible. However, in any case, it is not preferable to provide a corner portion where stress is concentrated or a corner portion having a sharp ridge line, and the entire cross-sectional change portion 13 and the connection portion 12 or the large cross-section portion 16 It is desirable that the connection points are continuous on the smoothest surface possible.

  FIG. 3 is a graph comparing the performance of the hollow camshaft 20 of the present invention and the conventional hollow camshaft. A line indicated by a chain line in FIG. 1 is a conventional hollow camshaft 20, and a line indicated by a solid line is the hollow camshaft 20 of the present invention.

  FIG. 3 (a) shows a comparison of the cross-section coefficients at each of the sections A, B, C, D, E, F, G, H, and I in FIG. FIG. 3B shows a comparison of the cross-sectional secondary moments at each of the cross sections A, B, C, D, E, F, G, H, and I in FIG. At any point, among the parallel bar graphs, the left bar graph shown in white represents a conventional example, and the right bar graph shown in gray represents an embodiment of the present invention.

  In this invention, since the hollow section 10 is provided with the large cross-sectional portion 16, the volume of the cavity is larger than that of the conventional hollow portion, but almost the same performance is exhibited at any point.

3 Bolt 5 Cam pulley 10 Hollow part 11 Female thread part 12 Connection part 13 Cross section change part 14 Cross section constant part 15 Plug fitting part 16 Large cross section part 20 Hollow camshaft 21 Base shaft 22 Cam part 23 Journal part 24 Flange part 25 For identification Projection w End face R

Claims (7)

A hollow portion extending in the axial direction;
A female screw portion formed on the inner surface of one end in the axial direction of the hollow portion;
With
The hollow part is
A cross-section changing portion whose cross-sectional area expands from one end side to the other end side on the other end side than the female screw portion; and
A large cross-sectional portion having a larger cross-sectional area than the female screw portion in the entire region on the other end side than the cross-sectional change portion,
A hollow camshaft comprising: The large cross section is
A plug insertion portion formed at the other end in the axial direction;
A constant cross-section portion that continues in the same cross-section from the cross-section change portion to the plug insertion portion,
The hollow camshaft according to claim 1, comprising: The hollow camshaft according to claim 1, wherein the cross-sectional change portion has a taper-shaped cross-sectional area. A plurality of protrusions protruding in a direction away from the axis along the axial direction are formed,
The hollow camshaft according to any one of claims 1 to 3, wherein the cross-section changing portion is disposed between opposing end surfaces of the protruding portions adjacent in the axial direction. 5. The projecting portion is a cam portion intermittently disposed along the axial direction or a flange portion disposed on both sides in the axial direction of a journal portion intermittently disposed along the axial direction. The hollow camshaft described. The skirt portion of the end surface of the protruding portion includes a rounded portion that is curved in the axial direction toward the inner side in the radial direction and is connected to the cylindrical surface on the side of the protruding portion at the terminal portion thereof,
The hollow camshaft according to claim 4 or 5, wherein the cross-section changing portion is disposed between the terminal portions of the round portions adjacent in the axial direction. The hollow camshaft according to claim 4 or 5, wherein the cross-section changing portion is in the same axial range as the journal portion.

Images