JP2003120790A - Cam piece - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cam piece of an assembly type cam shaft preventing generation of cracking when a pipe inserted into a base circle of the cam piece is developed. SOLUTION: This cam piece comprises a cam nose part 11 and a cam base part 12. The cam base part 12 has the base circle 13 having space for the pipe to be a shaft to be inserted. In an inner circumferential surface of the base circle 13, a cut 21 is provided, having space continuous from the cam circle 13 in the direction of the cam nose part 11 as well as recessed parts 14 provided at a constant interval to be a rotation stopper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cam piece for an assembled cam shaft.

[0002]

2. Description of the Related Art Assembled camshafts have heretofore been manufactured by a casting method or a forging method, which is also referred to as a cam lobe.
The camshaft is formed integrally with the camshaft, but a campiece is separately manufactured by a sintering method, etc., and the shaft is joined to the camshaft to form a camshaft, which reduces the manufacturing cost and weight. It is developed for the purpose of planning.

In this method of manufacturing the assembly type cam shaft, for example, a hollow cam piece in which a cam nose portion and a base circle are integrally formed of a sintered alloy is manufactured, and a pipe fitted to the inner circumference of the base circle of the cam piece is formed in the base circle. After being inserted into, the pipe is bulged by a pipe expansion method such as bulge processing or mandrel processing, and the pipe is joined to the cam piece.

However, such an assembled camshaft has a problem that a large force is applied to the cam piece from the inside when the pipe inserted into the base circle is expanded, so that a crack is generated.

In order to solve such a problem, for example, in Japanese Unexamined Patent Publication No. 10-339110, a cam piece is heat-treated so that the hardness of the inner peripheral portion is lower than the surface hardness of the outer peripheral portion thereof. It is disclosed that the generation of cracks is prevented by receiving the stress at the time of expanding the shaft at the inner peripheral portion having a low hardness.

Further, in Japanese Unexamined Patent Publication No. 6-106267, the cam piece is not formed by a sintering method but is formed by a hollow member having a substantially uniform thickness, and the position of a rotation stop provided on the inner peripheral portion of the base circle is determined by the base circle. It is disclosed that the stress is prevented from concentrating on the rotation stopping portion and the generation of cracks is prevented by providing the portion except the circular portion having different curvature.

[0007]

However, in the former method disclosed in Japanese Unexamined Patent Publication No. 10-339110, the cam piece must have a double structure with different hardness, which results in complicated heat treatment steps. Since it is necessary, there is a problem that the manufacturing cost reduction effect, which is one of the main purposes of the assembled camshaft, is impaired.

Further, in JP-A-6-106267, since the cam piece is made of a hollow material having a substantially uniform wall thickness, cracks may occur in portions other than the rotation stopper, and in particular, When this method is applied to the sintering method, the cam nose portion also has the same thickness as the base circle, and therefore the cam nose portion may be cracked by the force applied when the pipe is expanded.

Therefore, an object of the present invention is to provide a cam piece for an assembly type camshaft, which can prevent cracks from occurring when expanding a pipe inserted into the base circle of the cam piece without increasing the manufacturing cost. Is to provide.

[0010]

The object of the present invention is achieved by the following constitutions.

(1) A base circle having a cam nose portion and a cam base portion, which is formed in the cam base portion and has a hole into which a pipe serving as a shaft is inserted; and a base circle inner peripheral surface of the hole portion. Has a recess and a notch formed continuously from the inner peripheral surface of the hole of the base circle, and the notch has a distance from the tip to the outer peripheral surface of the base circle to the outer peripheral surface of the hole of the base circle. A cam piece characterized by being formed longer than the shortest part to the surface.

(2) The notch is characterized in that the tip is arcuate.

(3) The notch has a rectangular tip.

(4) The notch is V-shaped.

(5) The opening width of the notch is the same as the opening width of the recess, and the notches are provided at equal intervals on the inner peripheral surface of the hole of the base circle together with the plurality of recesses. It is characterized by being.

(6) The opening width of the notch is smaller than the opening width of the recess.

(7) The notch is provided at a position different from an arrangement interval of the plurality of recesses.

(8) The cam piece is manufactured by a sintering method.

[0019]

The present invention has the following effects for each claim.

According to the first aspect of the present invention, by providing the notch in the base circle, when the pipe is expanded after being inserted into the base circle, the distance from the inner peripheral surface to the outer peripheral surface of the hole of the base circle. It is possible to prevent the occurrence of cracks by relieving the stress concentration in the portion where the length becomes shortest. Further, by providing the notch, the weight of the cam piece can be reduced accordingly.

According to the second aspect of the present invention, since the notch tip has an arc shape, the notch is formed by a gentle shape, so that the strength of the entire cam piece can be increased. In particular, when the cam piece is formed by the sintering method, since there is no corner portion, the stability of the formed product at the time of forming the sintered alloy before sintering is good.

According to the third aspect of the present invention, since the notch tip has a rectangular shape, dimensional control is easy.

According to the fourth aspect of the present invention, since the notch is V-shaped, stress concentration is likely to occur in the notch, and a sufficient stress relaxation effect can be provided with a small notch. .

According to the fifth aspect of the present invention, the opening width of the notch is set to be the same as the opening width of the recess, and the recesses are arranged at equal intervals on the inner peripheral surface of the hole of the base circle. Thus, the cutout itself can be provided with a function as a recess for the rotation stopper, and the reduction of the contact area between the pipe and the base circle due to the provision of the cutout can be eliminated.

According to the sixth aspect of the present invention, since the opening width of the notch is smaller than the opening width of the recess, the contact area between the pipe and the inner circumferential surface of the base circle hole is reduced by providing the notch. Can be minimized.

According to the seventh aspect of the present invention, the opening width of the notch is made smaller than the opening width of the recess so as to be arranged at a position different from the arrangement interval of the plurality of recesses. 9. The present invention according to claim 8, wherein even when the pipe cannot be provided at the installation position, the reduction of the contact area between the pipe and the inner peripheral surface of the hole of the base circle due to the provision of the notch can be suppressed to the necessary minimum. In this case, since the cam piece is manufactured by the sintering method, the cutout can be saved to save the sintered alloy.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a drawing showing a cam piece of an assembling type cam shaft according to a first embodiment of the present invention, as seen from an inserting direction of a pipe serving as a shaft.

The cam piece 1 is manufactured by a sintering method using a sintered alloy, and includes a cam nose portion 11 and a cam base portion 12.

The cam base portion 12 has a base circle 13 having a hole for inserting a pipe serving as a shaft. On the inner peripheral surface of the hole of the base circle 13, there are provided seven recesses 14 which serve as rotation stoppers, and a notch 21 having a continuous space from the base circle 13 toward the cam nose portion 11.

The notch 21 functions as one of the rotation stoppers together with the recesses 14, and as will be described later, is for alleviating the stress concentration in each recess 14 when the pipes are expanded at the time of pipe joining. .

The notches 21 are installed at equal intervals along with the recesses 14 installed on the inner peripheral surface of the hole of the base circle 13.

The opening width A of the notch 21 is the same as the opening width U of the recess 14. Also, the depth B of the cut 21
Is deeper than the depth W of the recess 14 and the cut 1
The distance C from the tip of the space to the outer peripheral surface (referred to as a remaining portion) C by 2 is the shortest in the distance from the inner peripheral surface of the hole of the base circle 13 to the outer peripheral surface, here from the tip of the concave portion 14. It is made longer than the distance (referred to as the shortest part) X to the outer peripheral surface.

The condition of the notch 21 is that the opening width is made the same as that of the recess 14 so that the area of the portion expanded during pipe expansion does not change from that of the recess 14.
This is to prevent generation of unnecessary force or change in outer diameter. This is because when the opening width is too large, the lack of strength occurs due to the provision of the notch, and the contact area between the pipe and the inner peripheral surface of the base circle hole decreases, which reduces the joint strength between the pipe and base circle. Therefore, the opening width of the notch 21 is the same as the opening width of the recess 14.

Further, the opening width of the notch 21 is set to the recess 14
If the mandrel is used when expanding the tube, the width will be the same as that of
The mandrel used in the above can be used as it is.

The cutting depth B is made deeper than the recess depth W because if the cutting depth is shallower than the recess, it will not function as a rotation stopper. On the other hand, the reason why the remaining portion C is made longer than the shortest portion X is that the stress is concentrated on the portion where the notch 21 is provided, so if the remaining portion B is the shortest portion X.
If the length is shorter, the portion provided with the notch 21 may be damaged, which is not preferable.

The shape of the notch 21 is such that the end is arcuate. By thus forming the arcuate end portions, in the sintering method, it is difficult to cause molding cracks when the pre-sintered molded product is taken out of the mold after filling the sintered alloy with the mold. be able to.

FIG. 2 is a schematic view showing a step of joining a cam piece thus provided with a notch and a pipe serving as a shaft. Here, as an example of a method for joining the cam piece 1 and the pipe 51, a method using a mandrel 52 as shown is shown.

In the method using the mandrel 52, the cam piece 1 is inserted into the pipe 51 and then the cam piece 1 is inserted into the pipe 5.
1 to a predetermined position. Then, the mandrel 52 is inserted into the pipe 51. Mandrel 52 at this time
The corner portions of are aligned with the recesses 14 and the notches 21 provided in the cam piece 1.

With the insertion of the mandrel 52, the mandrel 5
The corner portion 2 expands the pipe 51, a part of the expanded pipe 51 is fitted in the recess 14 and the notch 21, and the cam piece 1 and the pipe 51 are joined.

Incidentally, such a cam piece 1 and pipe 5
In addition to using a mandrel, bulging by hydraulic pressure or pneumatic pressure may be used for the joining of No. 1.

Next, with respect to the cam piece having the cutout of the first embodiment and the conventional cam piece having no cutout, the result of simulating the stress applied to the cam piece when the above-mentioned mandrel processing is performed. Will be explained.

FIG. 3 is a schematic view showing the result of stress simulation in the conventional cam piece, and FIG. 4 is the first diagram.
FIG. 6 is a schematic diagram showing a result of stress simulation in the cam piece according to the embodiment. 3 and 4 show only half of the cam piece so that the inside of the base circle of the cam piece can be seen.

First, in the conventional cam piece shown in FIG. 3, as a result of simulation, a large stress is applied to the portion where the distance from the tip to the outer periphery of each recess 14 is shortest due to the insertion of the mandrel. . In FIG. 3, the color of this portion is darkened and a strong stress is applied.

On the other hand, in the cam piece according to the present embodiment shown in FIG. 4, the stress is concentrated on the notch 21 so that the stress is dispersed over the entire cam piece and is made uniform, so that the recess 14 is formed. The stress that had been applied to it has been relieved.
In FIG. 4, as compared with FIG. 3 described above, it is shown that the color of the concave portion 14 becomes lighter and the stress is relieved. Since the remaining portion of the notch 21 where the stress is concentrated is the portion where the distance from the inner peripheral surface to the outer peripheral surface is the longest in the cam piece, no crack is generated due to this stress concentration.

As described above, also from the result of the simulation, by providing the notch in the cam piece as in the first embodiment, the distance from the inner peripheral surface to the outer peripheral surface of the hole portion has been short so far, and cracks are generated during pipe expansion. It can be understood that the stress in the concave portion, which may have been caused, can be relaxed.

Since the stress in the concave portion can be relieved in this way, a relatively inexpensive alloy material may be used as the sintered alloy material for forming the cam piece, which results in further cost reduction. A reduction effect can be expected.

Further, by providing the notch in the cam piece, the weight of the notch becomes lighter, and the weight of the cam piece can be reduced. Further, in the case of the sintering method, the material can be saved by the amount of the notch, which can contribute to the reduction of the material cost.

Further, since the notch is continuous from the space of the base circle, it is not necessary to use a special mold in which a plurality of shapes are separated. You can

Although one embodiment to which the present invention is applied has been described above, the notch shape in the present invention can be various shapes. Therefore, in the following, embodiments having different notch shapes will be described.

(Second Embodiment) FIG. 5 is a view showing a cam piece according to a second embodiment.

In the second embodiment, the shape of the notch 22 provided in the cam piece 2 is such that the notch tip has a rectangular shape and the entire notch has a substantially rectangular shape as shown in the figure. is there. The other configurations are the same as those of the above-described embodiment, in particular, the size of the notch 22 has the same opening width as the opening width of the recess 14, and the depth of the notch is deeper than the recess 14. Moreover, the remaining portion is made longer than the shortest portion.

As described above, the cam piece 2 provided with the rectangular notch 22 can relieve the stress concentration in the recess 14 at the time of pipe expansion, as in the first embodiment described above, and the notch 22 can be formed. Since the shape is rectangular, it is easy to control the dimensions and manufacture of the mold used for sintering.

(Third Embodiment) FIG. 6 is a view showing a cam piece according to a third embodiment.

In the third embodiment, the notch 23 provided in the cam piece 3 is V-shaped as shown in the drawing. The other configurations are the same as those of the above-described embodiment, and in particular, the size of the notch 23 has the same opening width as the opening width of the recess 14, and the depth of the notch is
The depth is deeper than the recess and the remaining portion is longer than the shortest portion.

As described above, since the cam piece 1 provided with the V-shaped notch 23 has a small tip shape, the entire stress is likely to be concentrated on this portion, and the first embodiment and the second embodiment described above are easy to concentrate. The smaller notch as compared with the embodiment can exert a stress relaxation effect on the recess 14.

(Fourth Embodiment) FIG. 7 is a view showing a cam piece according to a fourth embodiment.

In the fourth embodiment, as shown in the figure,
The cam piece 4 is provided with two notches 24a and 24b.

The notches 24a and 24b are provided at positions different from the recess 14 of the rotation stopper. The opening width D may be equal to or smaller than the opening width U of the concave portion 14, and does not necessarily have to be the same as in the above-described first to third embodiments. On the other hand, the depth E of the notch is deeper than the depth of the recess 14, and the remaining portion is longer than the shortest portion.

This is because both of the two cutouts 24a and 24b do not function as rotation stoppers, so that the opening width does not necessarily have to match the opening width of the recess. In this case, if the opening width is large, the contact area between the pipe and the inner circumferential surface of the base circle is small, and the joint strength between the pipe and the base circle is reduced. Therefore, it is preferable to make it as small as possible. Although the lower limit of the opening width of the notch is very small and is not particularly limited, it is defined by the limit of the opening width that can be produced by the die used for sintering.

On the other hand, if the depth of the notch is too shallow, there is no effect. On the contrary, if the notch is so deep that the remaining portion is shorter than the shortest portion, the strength of this portion becomes insufficient, which is not preferable.

Two cutouts 24a and 24b are provided.
Must be provided in the same shape at the target position with respect to the center line T passing through the tip of the cam nose portion 11. This is because if the two cutouts 24a and 24b have different installation positions or shapes, the symmetry of the cam is lost and the balance is deteriorated, so that the cutout cannot be used as a camshaft.

As described above, even if two notches are provided, the stress concentration on the recess 14 can be alleviated as in the first to third embodiments.

Although the notches 24a and 24b shown in FIG. 7 have a circular arc-shaped tip, they may be rectangular or V-shaped instead.

(Fifth Embodiment) FIG. 8 is a view showing a cam piece according to a fifth embodiment.

This cam piece 5 has a recess 14 for stopping rotation.
Is different from each of the above-described embodiments, and is provided so as to be symmetrical with respect to the center line T passing through the tip of the cam nose portion 11, and the notch 25 is provided on the center line T. There is.

The notches 24a and 24b are provided at positions different from the recess 14 of the rotation stopper. The opening width D has only to be the same as or smaller than the opening width W of the concave portion 14, and does not necessarily have to be the same as in the above-described first to third embodiments. On the other hand, the depth of the notch is deeper than the recess and the remaining portion is longer than the shortest portion.

In this case, since the notch 25 does not have a function as a rotation stopper, its opening width does not necessarily have to match the opening width of the recess. However, as in the above-described fourth embodiment, when the opening width is large, the contact area between the pipe and the inner circumferential surface of the base circle hole portion is small, and the joint strength between the pipe and the base circle is reduced. The opening width is preferably smaller than the opening width of the recess 14.

On the other hand, the depth of the notch is set to be deeper than the concave portion 14 and the remaining portion is longer than the shortest portion, as in each of the above-described embodiments.

As described above, when the concave portion 14 serving as the rotation stop is provided at a position different from the center line passing through the tip of the cam nose portion, one notch 25 is provided to provide the above-mentioned first to first Similar to the fourth embodiment, the recess 14
The stress concentration on the

Although the notch 25 shown in FIG. 8 has a circular arc-shaped tip, it may be rectangular or V-shaped instead.

(Sixth Embodiment) FIG. 9 is a view showing a cam piece according to the sixth embodiment.

This cam piece 6 is provided so that the position of the concave portion 14 as the rotation stop is symmetrical with respect to the center line T passing through the tip of the cam nose portion 11, as in the case of the fifth embodiment described above. And two notches 2
6a and 26b together with the recess 14 in the base circle 1
The holes are provided on the inner peripheral surface of the hole 3 at equal intervals.

Since the notches 26a and 26b also have a function as rotation stoppers as in the first embodiment described above, the opening width thereof is the same as the opening width of the recess 14. The depth of the notch is deeper than the recess and
The remaining part is made longer than the shortest part. Also,
The two notches 26a and 26b are used for the cam nose portion 1
The same shape is provided at a target position with respect to the center line T passing through the tip of 1.

As described above, when the position of the recess 14 serving as the rotation stopper is different from the center line passing through the tip of the cam nose portion, the notches 26a and 26b are provided so as to be equally spaced with the recess 14. As a result, stress concentration on the recess 14 can be relaxed, as in the first to fifth embodiments described above.

Note that the notches 26a and 26b shown in FIG. 9 have a circular arc-shaped tip, but instead of this, they may be rectangular or V-shaped.

[Brief description of drawings]

FIG. 1 is a drawing showing a cam piece according to a first preferred embodiment of the present invention.

FIG. 2 is a schematic view showing a step of joining the cam piece and the pipe in the first embodiment.

FIG. 3 is a schematic diagram showing a result of stress simulation in a conventional cam piece.

FIG. 4 is a schematic diagram showing a result of stress simulation in the cam piece according to the first embodiment.

FIG. 5 is a drawing showing a cam piece according to a second preferred embodiment of the present invention.

FIG. 6 is a view showing a cam piece according to a third embodiment of the present invention.

FIG. 7 is a drawing showing a cam piece according to a fourth embodiment of the present invention.

FIG. 8 is a drawing showing a cam piece according to a fifth embodiment of the present invention.

FIG. 9 is a drawing showing a cam piece according to a sixth embodiment of the present invention.

[Explanation of symbols]

1, 2, 3, 4, 5, 6 cam pieces 11 Cam nose part 12 Cam base 13 base circle 14 recess 21 notches 51 pipes 52 Mandrel

Claims (8)

[Claims] 1. A base circle having a cam nose portion and a cam base portion, the base circle having a hole formed in the cam base portion and into which a pipe serving as a shaft is inserted; and a base circle formed on an inner peripheral surface of the hole of the base circle. The recess has a notch formed continuously from the inner peripheral surface of the hole of the base circle, and the notch has a distance from the tip to the outer peripheral surface of the hole of the base circle to the outer peripheral surface of the hole. The cam piece is characterized by being formed longer than the shortest distance to. 2. The cam piece according to claim 1, wherein the notch has an arcuate tip. 3. The cam piece according to claim 1, wherein the notch has a rectangular tip end. 4. The cam piece according to claim 1, wherein the notch has a V shape. 5. The opening width of the notch is the same as the opening width of the recess, and the notches are provided along with the plurality of recesses at equal intervals on the inner peripheral surface of the hole of the base circle. The cam piece according to any one of claims 1 to 4, characterized in that 6. The cam piece according to claim 1, wherein an opening width of the cutout is smaller than an opening width of the recess. 7. The cam piece according to claim 6, wherein the notch is provided at a position different from an arrangement interval of the plurality of recesses. 8. The cam piece according to claim 1, wherein the cam piece is manufactured by a sintering method.