JPH02150543A - Camshaft - Google Patents

Abstract

PURPOSE: To fix a cam in an optional angular position and to increase cam fixing strength by forming circumferential grooves and projection bars in a cam fixing part in a shaft and forming a key projection bar with a small projection quantity on a press-in direction front side on a shaft hole inside face of the cam. CONSTITUTION: In the cam fixing part of a shaft 1, grooves 3 extending in the circumference direction and projection bars 4 are formed, and on the shaft hole inside face of a cam 2, a key projection bar 6 with a relatively small projection quantity on the press-in direction front side is formed. Consequently, the cam 2 can be fixed in an optional angular position only by forcibly fitting it to the shaft 1, and positional precision between the cam 2 and the shaft 1 can be increased easily. In addition, in a press-in process, the projection bar 4 in the shaft 1 is slightly cut by the front end part of the key projection bar 6, and then, a key groove is formed with the notched part pressed by means of a projection increasing part, so that the cam 2 is fixed with proper stress applied to the fitting face. Therefore, cam fixing strength can be increased.

Description

[Detailed description of the invention] "Industrial application field" The present invention relates to a camshaft.

"Prior Art" The following camshafts are conventionally known, which are manufactured by fitting a separate cam to the outer periphery of the shaft.

■ A plurality of key grooves extending in the axial direction are formed on the outer circumference of the shaft, and a key protrusion is formed on the inner surface of the shaft hole of the cam.The cam is attached to the shaft by combining these key grooves and key protrusions. , These gaps are filled with wax and fixed.

■ Pass the hollow shaft through the shaft hole of the cam, position the cam, and then bulge the cam fixing part of the hollow shaft to fix the cam.

(2) After positioning all the cams in the same manner as (2) above, expand the hollow shaft over the entire length l, and fix all the cams at the same time.

[Problem to be Solved by the Invention] However, in the camshaft of item (2) above, high dimensional accuracy is required for the relative position of the key groove of the shaft and the key protrusion of the cam, so it is difficult to form these key grooves and the key protrusion. This method is time-consuming, hinders productivity improvement, and is costly.

In addition, with the camshafts described in ■ and ■, the cam fixing work is time-consuming and production costs are high, and the cams are permanently subjected to large stress, so sintered cams, which are cheaper to manufacture, are less durable and reliable. This makes it difficult to use, and this also raises the problem of high production costs.

[Means for Solving the Problems] The present invention has been made to solve the above problems, and firstly, the camshaft according to the first aspect of the present invention has a groove extending in the circumferential direction at the cam fixing location on the outer circumferential surface. A shaft is formed with protrusions that rise around these grooves, and a shaft hole having a larger diameter than the main body of the shaft is formed. The cam is composed of one or more cams each having a plurality of key protrusions with a relatively small protrusion amount, and the cam fixing part of the shaft is press-fitted into the shaft hole of the cam, and the key protrusion of the shaft hole is used to lock the shaft. A feature is that the cam is fixed by forming a keyway in the protrusion.

The camshaft according to the second aspect of the present invention is characterized in that a plurality of key protrusions extending in the axial direction and having a triangular or semicircular cross-sectional shape are formed on the inner surface of the shaft hole of the cam. This is the difference from Section 1.

Furthermore, the camshaft according to @3 of the present invention has a first feature that a plurality of key protrusions are formed on the inner surface of the shaft hole of the cam, extending in the axial direction and having a width that is relatively small on the front side in the shaft press-fitting direction. This is the difference in item 7.

``Function'' With this camshaft, the cam can be fixed at any angular position simply by press-fitting the cam into the shaft, making it easy to improve the positional accuracy of the cam and shaft. Because it fits tightly into the formed keyway, the fixing force is extremely high. Further, since no large stress is applied to the cam after press-fitting, a cam made of an inexpensive sintered body can also be used with high reliability.

Furthermore, in the camshaft according to the first aspect of the present invention, since the amount of protrusion of the key protrusion is relatively small on the front side in the shaft press-fitting direction, when press-fitting, the front end of the key protrusion first touches the protrusion of the shaft. After making a small notch, a key groove is formed by compressing this notch at a portion where the amount of protrusion gradually increases, and an appropriate stress is applied to the mating surface of the key protrusion and key groove. Since the shaft and the cam can be fixed in place, the cam fixing strength can be further increased compared to the case where the protrusion amount of the key protrusion is constant in the longitudinal direction.

Further, as in the second aspect of the present invention, the cross-sectional shape of the key protrusion may be changed to 3.
When the key protrusion has a square or semicircular shape, the key protrusion does not have a plane parallel to the shaft surface, so even though the cross-sectional area of the key protrusion is relatively small compared to cases where the key protrusion has a rectangular cross section, etc. The entire surface of the key protrusion that comes into contact with the key groove effectively generates an anti-slip force, thereby increasing the anti-slip force between the cam and the shaft.

Furthermore, when the radius of the key protrusion is made relatively small on the front side in the press-fitting direction as in the third aspect of the present invention, the width of the key protrusion increases as the press-fitting progresses, and both sides of the key protrusion increase in width on both sides of the keyway. Since the surface is compressed, the cam and shaft can be fixed while applying appropriate stress to them, and the strength of fixing them can be increased.

Embodiment FIGS. 1 and 2 are a longitudinal sectional view and a transverse sectional view showing an embodiment of a camshaft according to the first aspect of the present invention.

Reference numeral 1 in the drawing denotes a hollow metal shaft, and sintered body cams 2 (only one is shown) are fixed at predetermined angles to each cam fixing location IA of the shaft 1 at a distance from each other.

At the cam fixing point IA, as shown in FIG. 3, prior to fixing the cam, a large number of grooves 3 are rolled in the circumferential direction in a spiral or concentric manner, thereby increasing the gap between the grooves 3 and creating a protrusion. Article 4.

The outer diameter D2 of these protrusions 4 is the outer diameter D of the shaft main body IB.
It is desirable that it be about 101 to 110% of 1. If it is smaller than this range, sufficient cam fixing strength cannot be obtained, and if it is larger than this range, smooth press-fitting becomes difficult and the positional accuracy of the cam 2 decreases.

On the other hand, as shown in FIG. 2, the cam 2 is formed with a shaft hole 5 in the axial direction having an inner diameter D3 larger than the outer diameter D1 of the shaft body portion IB.

On the inner surface of the shaft hole 5, key protrusions 6 extending in the axial direction are formed at equal intervals in the circumferential direction (eight in this case), and the cross section of the key protrusions 6 is rectangular with edges.

The amount of protrusion of these key protrusions 6 is gradually increased from the front side (left side in FIG. 1) to the rear side (right side in FIG. 1) in the press-fitting direction of the shaft 1, and the inner diameter of the apex surface 6A at the rear end is D4,
If the inner diameter at the front end is D5, the following relationship is satisfied.

D1≦04(D5(D2≦D3) The difference between D5 and D4 is determined by the dimensions of each part so that after the cam 2 is press-fitted and fixed, the key protrusion 6 and the key groove 7 (described later) abut with appropriate stress. On the other hand, the radius and cross-sectional shape of the protrusion 4 are set such that when the cam 2 is press-fitted into the shaft l, the protrusion 4 can be cut and deformed under pressure by the key protrusion 6. It should be considered that

To fix the cam 2 to the shaft 1, the rolling of the groove 3 and the protrusion 4 and the press-fitting of the cam 2 are alternately repeated starting from the cam fixing part IA at one end of the shaft l. Then,
As shown in FIG. 3, each key protrusion 6 of the cam 2 sequentially forms small notches in the protrusion 4 at its front end edge, and then presses and deforms this at the apex surface 6A, and finally the key groove 7 , and the cam 2 is fixed. Although this camshaft can be used even after press-fitting is completed, in order to further increase the strength and reliability, the gap between cam 2 and shaft 1 may be filled with brazing agent, or the gap between cam 2 and shaft 1 may be filled with brazing agent. 1
It is also possible to spot weld.

With the camshaft having the above configuration, the cam 2 can be fixed at any angular position simply by press-fitting the cam 2 into the shaft 1, so the assembly work is extremely easy and requires no effort.
Productivity can be increased and manufacturing costs can be reduced accordingly. Also,
Since the key protrusion 6 of the cam 2 tightly fits into the key groove 7 cut by itself, the fixing force is extremely large, there is no rattling at all, and high positional accuracy can be easily achieved. Furthermore, since conventional press-fit camshafts do not apply any large stress to the cam 2 after press-fitting, it is possible to use a cam 2 made of a sintered body with low cost and high dimensional accuracy. Cost reduction and high precision can be achieved.

In addition, in this example, since the amount of protrusion of the key protrusion 6 increases from the front side to the rear side in the shaft press-fitting direction, an appropriate stress is applied to the fitting surface of the key protrusion 6 and the key groove 7 as described above. The shaft 1 and the cam 2 can be fixed in the same state, and the fixing strength of the cam 2 can be further increased compared to the case where the protrusion amount of the key protrusion 6 is constant in the longitudinal direction. Furthermore, after the protrusion 4 is made small by the key protrusion 6, it is compressed and deformed at the apex surface 6A, so the force required for press-fitting is relatively small, and the effect of aligning the axis of the cam 2 is achieved, resulting in fixation. It also has the advantage of improving accuracy.

In the above embodiment, the protrusion amount of the key protrusion 6 gradually increases toward the rear side, but as shown in FIG. Alternatively, the same effect can be obtained by chamfering only the front end of the key protrusion 6 to form an inclined surface 6C as shown in FIG.

Next, FIG. 6 shows an embodiment related to the second item of the present invention,
In this example, the cross-sectional shape of the key protrusion lO is an isosceles triangular shape that is approximately a regular triangle.

The amount of protrusion of the key protrusion 10 is equal across the entire length, or is relatively small on the front side in the press-fitting direction as in each of the embodiments described above, and the dimensional conditions are the same as in the embodiments described above.

In this example, since the key protrusion 10 does not have a plane parallel to the outer circumferential surface of the shaft 1, it comes into contact with the keyway 7 even though its cross-sectional area is relatively small compared to the case where the cross-section is rectangular. The entire surface of the key protrusion 10 in contact effectively produces an anti-slip force, and the anti-slip force between the cam 2 and the shaft 1 can be increased.

Also, when press-fitting, the key protrusion 10 becomes a triangular blade and the protrusion 4
Since the cutting progresses forward, the escape of chips is better than in the case of a rectangular cross section, and the pressing force can be reduced.

Note that even if the key protrusion 11 has a semicircular cross-sectional shape as shown in FIG. 7, the same effect as the camshaft shown in FIG. 6 can be obtained.

Next, FIG. 8 is a plan view showing the inner surface of the shaft hole 5 in an embodiment related to the third aspect of the present invention, and in this example, the cross section of the key protrusion 12 on the front side in the shaft press-fitting direction is an equilateral triangle. It has a shape 2, and its width gradually increases toward the rear, and the cross section on the rear side is trapezoidal. key protrusion 1
The amount of protrusion of No. 2 is approximately constant or slightly larger on the rear side, and the dimensional conditions are the same as in the previous embodiment.

According to this example, when press-fitting the shaft 1 into the cam 2, first a small notch is formed in the protrusion 4 of the shaft l at the front end of each key protrusion 12, and then the width of both sides of this notch is gradually increased. Since the key groove 7 is formed by pushing apart with the key protrusion 12, the cam 2 and the shaft 1 can be fixed while applying stress to the mating surfaces of the key protrusion 12 and the key groove 7, thereby increasing their fixing strength. Can be done.

Note that the cross-sectional shape of the key protrusion 12 is not limited to a triangle or trapezoid, but may also be semicircular or rectangular, and the width of the key protrusion 12 does not gradually change over the entire length, but rather changes from the front in the press-fitting direction. It may also have a shape in which only the sides are narrowed. Furthermore, both the width and the amount of protrusion of the key protrusion 12 may be relatively small on the front side in the press-fitting direction.

Furthermore, in the camshaft of the present invention, the cam 2 may have a double structure, and the inner layer of the cam including the key protrusion may be made of a harder material than the outer layer. The strength of the key protrusion can be improved, and the strength of fixing the cam can be increased. At the same time, if the hardness of the key protrusion is increased, the cutting efficiency of the protrusion 4 by the key protrusion is high when the cam 2 is press-fitted into the shaft 1, and the press-fitting operation can be easily performed.

"Effects of the Invention" As explained above, according to the camshaft of the present invention, the cam can be fixed at any angular position simply by press-fitting the cam onto the shaft, making assembly work extremely easy and time-consuming. First, productivity can be increased and manufacturing costs can be reduced accordingly. In addition, since the key protrusion of the cam tightly fits into the key groove cut out by itself, the fixing force is extremely large, there is no wobbling, and high positional accuracy can be easily achieved. Furthermore, since no large stress is applied to the cam after press-fitting, it is possible to use a cam made of a sintered body at low cost and with high dimensional accuracy, and from this point of view as well, cost reduction and high precision can be achieved.

In addition, in the camshaft according to the first aspect of the present invention, since the amount of protrusion of the key protrusion is relatively small on the front side in the shaft press-fitting direction, when press-fitting, the front end of the key protrusion first pushes the shaft. After making a small cut out of the protrusion, a key groove was formed by compressing this notch at a portion where the amount of protrusion gradually increased, and an appropriate stress was applied to the mating surface of the key protrusion and key groove. Since the shaft and cam can be fixed in their original state,
The fixing strength of the cam can be further increased compared to the case where the protrusion amount of the key protrusion is constant in the longitudinal direction.

Further, as in the second aspect of the present invention, the cross-sectional shape of the key protrusion may be changed to 3.
When the key protrusion has a square or semicircular shape, the key protrusion does not have a plane parallel to the shaft surface, so compared to a case where the key protrusion has a rectangular cross section, the cross-sectional area is relatively small. First, the entire surface of the key protrusion that comes into contact with the keyway effectively generates an anti-slip force, thereby increasing the anti-slip force between the cam and the shaft.

Furthermore, when the width of the key protrusion is made relatively small on the front side in the press-fitting direction as in the third aspect of the present invention, the width of the key protrusion increases as the press-fitting progresses, and both sides of the key protrusion are formed on both sides of the keyway. Since the surface is compressed, the cam and shaft can be fixed while applying appropriate stress to them, and the strength of fixing them can be increased.

[Brief explanation of the drawing]

1 and 2 are a vertical cross-sectional view and a cross-sectional view of a camshaft according to item 1 of the present invention, FIG. 3 is a vertical cross-sectional view showing the manufacturing process of the camshaft, and FIGS. 4 and 5 6 and 7 are longitudinal cross-sectional views showing a modified example of the key protrusion of the same embodiment, respectively, FIGS. It is an explanatory view showing the key protrusion in the example of item 3 of the invention. 1...Shaft, IB...Body part, 3...Groove, 5...Shaft hole, 7...Keyway, 1A...Cam fixing point, 2...Sintered body cam , 4... Shaft protrusion, 6... Key protrusion, 10.11.12... Key protrusion.

Claims (3)

[Claims] (1) A shaft having grooves extending in the circumferential direction and protrusions raised around these grooves formed at the cam fixing location on the outer circumferential surface, and a shaft hole having a larger diameter than the main body of the shaft; The inner surface of the shaft hole is composed of one or more cams each having a plurality of key protrusions extending in the axial direction and having a relatively small protruding amount on the front side in the shaft press-fitting direction, and the shaft is inserted into the shaft hole of the cam. A camshaft characterized in that the cam is fixed by press-fitting the cam fixing point of the shaft hole and forming a key groove in the shaft protrusion with a key protrusion of the shaft hole. (2) A shaft having grooves extending in the circumferential direction and a large number of protrusions raised around these grooves formed at the cam fixing location on the outer circumferential surface, and a shaft hole having a larger diameter than the main body of the shaft,
The shaft hole is composed of one or more cams each having a plurality of key protrusions extending in the axial direction and having a triangular or semicircular cross-sectional shape formed on the inner surface of the shaft hole. A camshaft characterized in that the cam is fixed by press-fitting the cam fixing point and forming a keyway in the shaft protrusion with a key protrusion of the shaft hole. (3) a shaft having grooves extending in the circumferential direction and a large number of protrusions raised around these grooves formed at the cam fixing location on the outer circumferential surface; and a shaft hole having a larger diameter than the main body of the shaft;
The inner surface of the shaft hole is composed of one or more cams having a plurality of key protrusions extending in the axial direction and whose width is relatively small on the front side in the shaft press-fitting direction. A camshaft characterized in that the cam is fixed by press-fitting the cam fixing point and forming a keyway in the shaft protrusion with a key protrusion of the shaft hole.