JP2747537B2 - Camshaft - Google Patents

Description

The present invention relates to camshafts.

"Prior art" As a camshaft manufactured by fitting a separate cam to the outer periphery of a shaft, the following is conventionally known.

A plurality of key grooves extending in the axial direction are formed on the outer periphery of the shaft, and a key ridge is formed on the inner surface of the shaft hole of the cam, and the key groove is engaged with the key ridge to attach the cam to the shaft. These gaps are filled with a wax and fixed.

After passing the hollow shaft through the shaft hole of the cam and positioning the cam, the cam fixing portion of the hollow shaft is expanded to fix the cam.

After positioning all the cams as before, the hollow shaft is expanded over its entire length and all the cams are fixed simultaneously.

[Problems to be Solved by the Invention] However, in the above-described camshaft, high dimensional accuracy is required for the relative position between the key groove of the shaft and the key ridge of the cam. There are drawbacks in that it is troublesome, hinders improvement in productivity, and costs a great deal.

Also, with the above-described camshaft, the cam fixing work is troublesome, the production cost is high, and a large stress is permanently applied to the cam. Difficult to use with
From this point, there is a problem that the production cost is high.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems of the related art, and can extremely easily perform an assembling operation of a shaft and a cam, extremely increase a fixing force of a cam to a shaft, and further increase the production of an assembly. It is an object of the present invention to provide a camshaft with high performance and low cost.

"Means for solving the problem" The present invention has been made to achieve the above object,
First, in the camshaft according to the first aspect of the present invention, a large number of circumferentially extending grooves and ridges protruding around these grooves are formed at the cam fixing portion on the outer peripheral surface, and the amount of protrusion of these ridges is determined by press-fitting of the cam. One or more shafts having a shaft that is relatively small on the front side in the direction and a shaft hole having a larger diameter than the main body of the shaft, and a plurality of key projections extending in the axial direction are formed on the inner surface of the shaft hole. The cam is fixed by press-fitting the cam fixing portion of the shaft into the shaft hole of the cam and forming a key groove in the ridge portion of the shaft with the key ridge of the shaft hole. Features.

The camshaft according to the second aspect of the present invention is different from the first aspect in that the interval between the ridges formed on the shaft is relatively large on the front side in the cam press-fitting direction. Points.

Further, in the camshaft according to the third aspect of the present invention, the cross-sectional shape of each ridge formed on the shaft has a triangular or trapezoidal shape in which the base angle in the front side in the press-fitting direction of the cam is smaller than the base angle in the rear side. Is different from the first term.

"Operation" With this camshaft, the cam can be fixed at any angle position simply by press-fitting the cam into the shaft, so it is easy to increase the positional accuracy between the cam and the shaft, and the key ridge of the cam is formed by itself. The fixing force is extremely large because it is fitted into the key groove in close contact. Further, since a large stress is not applied to the cam after press-fitting, a cam made of a low-cost sintered body can be used with high reliability.

Further, when the protrusion amount of the ridge of the shaft is relatively small on the front side in the press-fitting direction of the cam, first, at the start of press-fitting, the axis of the cam and the shaft center of the shaft are matched by the ridge having a small protrusion amount. The effect is obtained, and concentricity between the cam and the shaft is enhanced, so that the positional accuracy can be improved. Further, since the key groove is formed from the ridge having the smaller protrusion amount, the force required for press-fitting is initially small and gradually increases, so that the press-fitting operation can be performed smoothly.

Further, when the interval between the ridges formed on the shaft is relatively increased on the front side in the press-fitting direction of the cam, the density of the ridges per unit press-fit length is small in the initial stage of the press-fitting. It is small and press-fitting work can be performed smoothly as described above.

Furthermore, when the cross-sectional shape of each of the ridges is a triangle or trapezoid whose base angle on the front side in the press-fitting direction of the cam is smaller than that on the rear side, the press-fitting of these ridges during the press-in operation. A sliding force is generated on the key ridge along the inclined surface on the front side in the direction, and the effect of aligning the axis of the cam with the shaft is obtained, so that the concentricity thereof can be improved. At the same time, since the base angle on the rear side is large, the ridge has a tendency to slightly fall to the rear side when the cam is press-fitted, whereby the contact area between the key ridge and the key groove can be increased, and the fixing strength can be improved.

"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.

In the figure, reference numeral 1 denotes a hollow metal shaft, and a sintered body cam 2 (only one is shown) having a predetermined angle is fixed to each cam fixing portion 1A of the shaft 1 so as to be separated from each other.

Prior to the cam fixing, a large number of grooves 3 are spirally or concentrically rolled in the circumferential direction at the cam fixing point 1A of the shaft 1 as shown in FIG. The climax is ridge 4. In particular, in this example, the groove 3 is formed shallow on both sides in the axial direction of the shaft 1 and deep at the center, so that the protrusion amount of the ridge 4 is small on both sides.
It is large at the center. The amount of protrusion of these ridges 4 is
The maximum outer diameter D2 at the center is 101 of the outer diameter D1 of the shaft body 1B.
It is desirable to be about 110%. 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 decreases.

On the other hand, as shown in FIG. 2, the cam 2 has a shaft hole 2A having an inner diameter D3 larger than the diameter D1 of the shaft main body 1B.
Is formed, and on the inner surface of the shaft hole 2A,
Key ridges 5 extending in the axial direction are formed at equal intervals in the circumferential direction (eight in this case). The cross section of the key ridge 5 has a rectangular shape having an edge, and the protrusion amount is such that the inner diameter D4 at the vertex surface of the key ridge 5 is larger than the shaft outer diameter D1 and smaller than the maximum outer diameter D2 of the ridge 4. The relationship between the dimensions is summarized as follows.

D1 ≦ D4 ≦ D2 ≦ D3 The width and the cross-sectional shape of the ridge 4 are such that when the cam 2 is pressed into the shaft 1, the ridge 4 is satisfactorily cut by the key ridge 5 to form the key groove 6. It is necessary to consider that the ridge 4 does not fall down and collapse on the rear side in the press-fitting direction.

When the cam 2 is fixed to the shaft 1, the rolling of the groove 3 and the ridge 4 and the press-fitting of the cam 2 are alternately repeated in order from the cam fixing portion 1A at one end of the shaft 1.
Then, as shown in FIG. 4, each key ridge 5 of the cam 2 is
First, the axial position is corrected while slightly shaving off the upper end of the ridge 4 on the front side with a small amount of protrusion, and then the key 2 is advanced to the ridge 4 with a large amount of protrusion while notching the key groove 6. Fixed. The camshaft can be used even when the press-fitting is completed. However, in order to further enhance the strength and reliability, the gap between the cam 2 and the shaft 1 is filled with a brazing agent, or the cam 2 and the shaft are filled. 1
May be spot-welded.

In the camshaft having the above-described configuration, the cam 2 can be fixed at an arbitrary angular position only by press-fitting the cam 2 into the shaft 1, so that the assembling work is extremely easy and time-consuming, and the productivity is enhanced. Manufacturing costs can be reduced. Further, since the key ridge 5 of the cam 2 is fitted into the key groove 6 cut out by itself in close contact, the fixing force is extremely large, and
There is no backlash and high positional accuracy can be easily realized. Furthermore, since no large stress is applied to the cam 2 after the press-fitting, a low cost and high dimensional accuracy cam made of a sintered body can be used, and from this point, cost reduction and high accuracy can be achieved.

Further, in the first embodiment, since the protrusion amount of the ridge 4 formed on the shaft 1 is relatively smaller than the central portion at both ends in the press-fitting direction of the cam 2, as described above, when the press-fitting is started. The effect of matching the axis of the cam 2 with the axis of the shaft 1 can be obtained by the ridge 4 having a small amount of protrusion, and the concentricity can be enhanced to improve the positional accuracy. Further, since the key groove 6 is formed from the protrusion 4 having the smaller protrusion amount, the force required for press-fitting is small at first, gradually increases, and then becomes small again at the end of press-fitting, so that the press-fitting work is performed smoothly and safely. I can do it. Further, in this example, since the amount of protrusion of the ridge 4 of the shaft 1 is small at both ends, there is an advantage that the cam 1 may be press-fitted from either the front or rear side due to the assembly process.

Next, FIG. 5 shows the camshaft (before the cam is fixed) of the second embodiment according to the first aspect of the present invention. In this example, the amount of protrusion of the ridge 4 formed on the shaft 1 is It is characterized in that it gradually decreases from the center in the press-fitting direction toward the front side. In this example, the same effect as in the first embodiment can be obtained.

Next, FIG. 6 shows an embodiment of a camshaft according to the second aspect of the present invention. In this embodiment, the interval (pitch) P between the ridges 4 of the shaft 1 extends from the front side to the rear side in the cam press-fitting direction. It is formed so as to become gradually smaller. The width and the amount of protrusion of each ridge 4 are fixed, and only the width of the groove 3 is changed.

According to this example, since the density of the ridges 4 per unit press-fitting length is small on the front side, the press-fitting required immediately after the start of press-fitting is relatively small, and the press-fitting operation can be performed smoothly and safely.

Next, FIG. 7 shows an embodiment according to the third aspect of the present invention. In this embodiment, the cross-sectional shape of the ridge 4 of the shaft 1 (the outer peripheral surface of the main body 1B as a reference surface) is determined by press-fitting the cam. The base angle α on the front side in the direction is smaller than the base angle β on the rear side in a triangular or trapezoidal shape. Specifically, when the base angle α is about 45 to 60 ° and the base angle β is 70 to 85 °,
The effects described later become significant. Other conditions may be the same as those in the above embodiments.

In this example, at the time of press-fitting of the cam 2, when the key ridge 5 of the cam hits the front inclined surface 4 </ b> A of the ridge 4, a slight slippage occurs between them, and the axial center of the cam 5 and the shaft 1. Since the matching effect is obtained, the concentricity can be improved. At the same time, since the rear base angle β is large, the ridge 4 has a tendency to slightly fall rearward while being cut into the key ridge 5, thereby increasing the contact area between the key ridge 5 and the key groove (6). As a result, the fixing strength of the cam 2 can be improved.

In addition, the present invention is not limited to the above embodiments, and the effects can be further enhanced by combining the components of each embodiment to form a decoding type.

[Effects of the Invention] As described above, according to the camshaft according to the present invention, the cam can be fixed at an arbitrary angular position only by press-fitting the cam into the shaft, so that the assembling work is extremely easy and time-consuming. The productivity is increased, and the manufacturing cost is reduced accordingly. Further, since the key ridge of the cam fits into the notched key groove in a close contact state, the fixing force is extremely large, there is no backlash, and high positional accuracy can be easily realized. Further, since a large stress is not applied to the cam after press-fitting, a low cost and high dimensional accuracy cam made of a sintered body can be used, and from this point, cost reduction and high accuracy can be achieved.

Further, in the camshaft according to the first aspect of the present invention,
Since the amount of protrusion of the ridge formed on the shaft is relatively small on the front side in the press-fitting direction of the cam, the effect of matching the axis of the cam with the axis of the shaft with the ridge having a small amount of protrusion at the start of press-fitting. Is obtained, and concentricity between the cam and the shaft is increased to improve the positional accuracy. Further, since the key groove is formed from the ridge having the smaller protrusion amount, the force required for press-fitting is initially small and gradually increases, so that the press-fitting operation can be performed smoothly and safely.

Further, according to the camshaft according to the second aspect of the present invention, since the density of the ridges per unit press-in length is small on the front side, the initial press-in force is relatively small, and the press-in operation is smooth as in the first section. It can be done safely.

Further, in the camshaft according to the third aspect of the present invention, when the key ridge of the cam hits the front inclined surface of the ridge of the shaft at the time of press-fitting of the cam, a slight slip occurs between them, and the cam and the shaft Therefore, the concentricity can be improved. At the same time, since the base angle on the rear side is large, the ridge has a tendency to slightly fall to the rear side while being cut into a key ridge, thereby increasing the contact area between the key ridge and the key groove, and securing the cam. Improvement can be achieved.

[Brief description of the drawings]

1 and 2 are a longitudinal sectional view and a transverse sectional view showing a first embodiment of a camshaft according to the present invention. FIGS. 3 and 4 are longitudinal sectional views showing an assembled state of the same embodiment. 5
FIGS. 7 to 9 are longitudinal sectional views showing second to fourth embodiments of the present invention, respectively. 1 ... shaft, 1A ... cam fixing point, 1B ... shaft body, 2 ... sintered cam, 2A ... shaft hole, 3 ...
... Shaft groove, 4 ... Shaft ridge, 5 ... Key ridge, 6 ... Key groove, D1 ... Outer diameter of shaft body, D2 ...
… Maximum outer diameter of the ridge, D3 …… Inner diameter of the shaft hole, D4 …… Inner diameter between the opposing key ridges, α …… Front base angle of the ridge, β
…… the outer base angle of the ridge, P …… The ridge spacing.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Teruyoshi Tanase 3-1 Koganecho, Niigata City, Niigata Pref. Niigata Works, Mitsubishi Metals Corporation (56) References 55-1294 (JP, A) JP-A-59-140911 (JP, A) JP-A-59-206605 (JP, A) JP-A-60-33302 (JP, A) JP-A-60-129264 (JP, A A) JP-A-63-297707 (JP, A) U.S. Pat. No. 2,279,954 (US, A) German publication 3522020 (DE, A1)

Claims (3)

(57) [Claims] A large number of grooves extending in the circumferential direction and ridges protruding around these grooves are formed in the cam fixing portion on the outer peripheral surface, and the protrusion amounts of these ridges are relatively small on the front side in the cam press-fitting direction. A shaft having a larger diameter than the main body of the shaft, and one or more cams formed with a plurality of key projections extending in the axial direction on the inner surface of the shaft hole. A camshaft characterized in that the cam is fixed by press-fitting a cam fixing portion of the shaft into the shaft hole and forming a key groove in a ridge portion of the shaft with a key ridge of the shaft hole. 2. A plurality of grooves extending in the circumferential direction and ridges protruding around these grooves are formed in the cam fixing portion on the outer peripheral surface, and the interval between these ridges is relatively large on the front side in the cam press-fitting direction. A shaft having a larger diameter than the main body of the shaft, and one or more cams formed with a plurality of key projections extending in the axial direction on the inner surface of the shaft hole. A camshaft characterized in that the cam is fixed by press-fitting a cam fixing portion of the shaft into the shaft hole and forming a key groove in a ridge portion of the shaft with a key ridge of the shaft hole. 3. A plurality of grooves extending in the circumferential direction and ridges protruding around these grooves are formed in a cam fixing portion on the outer peripheral surface, and the cross-sectional shape of each of the ridges is the bottom on the front side in the press-fitting direction of the cam. A shaft having a triangular or trapezoidal shape whose angle is smaller than the base angle on the rear side; and a plurality of key protrusions having a shaft hole having a larger diameter than the main body of the shaft, and extending in an axial direction on an inner surface of the shaft hole. A cam fixing portion of the shaft is press-fitted into a shaft hole of the cam, and a key groove is formed in a ridge portion of the shaft with a key ridge of the shaft hole. A camshaft having a fixed cam.