JPH07150908A - Ceramic-made roller - Google Patents

Abstract

PURPOSE:To prevent decrease or disappearance of a chamfering part caused by polishing the end surface of a ceramic-made roller. CONSTITUTION:A lift part 1 is provided on the end surface 3 of a,ceramic-made roller, and the top surface of this lift part 1 is polished, thereby a chamfering part 2 is prevented from invasion of a polishing margin. The positioning in the thrust, direction is made possible by making use of the top surface of the polished lift part 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic roller used for tappets, rocker arms and the like in an internal combustion engine and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, internal combustion engines for automobiles are low in pollution,
Although high performance is required, the internal conditions of the engine tend to be deteriorated due to the increased load on the sliding parts of the rocker arm and tappet. Therefore, for example, as shown in FIG. 10, a ceramic roller 103 is provided at the contact portion between the cam 100 of the overhead camshaft type mechanism and the rocker arm 102 that opens and closes the valve 101, or as shown in FIG. At the contact portion between the cam 100 and the tappet 104 of the mold mechanism, a ceramic roller 103 is provided to improve the contact resistance. The ceramic roller is superior to the metal roller in abrasion resistance and also has an advantage that the number of parts is reduced by eliminating the need for needles and bushes.

The outer peripheral edges of both end surfaces of such a ceramic roller are chamfered in order to prevent galling of parts and members that come into direct contact with the roller and to prevent chipping of the outer peripheral edge itself. Is normal. Also, on the roller end surface,
For example, when a central hole for passing the shaft is formed, the inner peripheral edge of the end face is often chamfered. The chamfered part often has a relatively rough precision, and it may be formed by rough polishing, but the method of forming the chamfered part during powder molding is widely used because it does not require polishing and is effective in reducing man-hours. Has been done.

On the other hand, the inner and outer peripheral surfaces of the roller are pins,
Since it is a portion that comes into contact with a cam or the like, a predetermined accuracy is generally given by polishing. Further, since both end surfaces are portions for contacting with the support fittings of the rocker arm or the like for positioning in the thrust direction, it is usual to grind these end surfaces.

[0005]

By the way, polishing of ceramics is naturally more difficult than that of metal materials due to its abrasion resistance. In order to do this as efficiently as possible, both end faces of the above-mentioned ceramic roller are often simultaneously polished by a double-sided surface grinder.

In this case, as shown in FIG. 12, if both end surfaces are evenly polished by a set amount, the chamfered portions 2 on each end surface also remain uniformly. However, in a double-headed grinder, there may be a difference in the polishing amount on both end faces, and the polishing amount t1 on one end face may be larger than the polishing amount t2 on the other end as shown in FIG. 13, for example. In this case, as shown in an enlarged view in FIG. 14, the width of the chamfered portion 2 remaining on the end face on the side where the amount of polishing is large may be small, or the chamfered portion 2 may disappear in extreme cases. Such a tendency that the chamfered portion disappears becomes more remarkable when the outer peripheral surface of the roller is ground by t3 as shown in FIG.

When the chamfered portion becomes extremely small or disappears due to polishing, it becomes necessary to form a new chamfered portion by post-processing. Such post-processing not only increases the man-hours, but generally the grinding wheel for chamfering is small, and the pressure is concentrated on the tip of the edge part sharpened by polishing, so the grinding wheel surface wears quickly and the grinding wheel replacement frequency is high. It causes a big problem in terms of cost, such as high cost.

An object of the present invention is to make the dimension of the chamfered portion at the peripheral edge of the ceramic roller stable and reduce the processing cost.

[0009]

In order to solve such a problem, according to the present invention, the end surface of the ceramic roller has a raised portion in a region excluding a chamfered portion formed on at least the outer peripheral edge of the end surface. Is characterized by. Here, the expression “at least the outer peripheral edge” is because when the hole is formed in the axial direction of the roller, the outer peripheral edge and the inner peripheral edge exist. Further, although the above-mentioned raised portions are originally provided on both end faces of the roller, a mode in which they are provided only on one end face is also included. Furthermore, the chamfered portion may be a so-called C chamfered portion whose cross section is an inclined straight line, or a so-called R chamfered portion whose cross section is a rounded curve.

The top surface of the raised portion of the ceramic roller as described above is subjected to polishing processing (in the present specification, "polishing" is a broad meaning including grinding) to determine the positioning dimension in the thrust direction. The polishing allowance is equal to or less than the height (protrusion amount) of the raised portion.

As a method for producing such a ceramic roller, the raw material powder is molded into a roller shape so that the chamfered portion at the peripheral edge of the roller and the raised portion are formed, and after firing, the top surface of the raised portion is formed. It can be ground to adjust the thrust dimension. If necessary, the outer peripheral surface and / or the inner peripheral surface of the roller is polished.

[0012]

In the ceramic roller of the present invention, a ridge is formed in advance on the roller end surface that is the positioning portion in the thrust direction, and when the roller end surface is to be polished later, only that ridge is polished. Therefore, the dimensional accuracy in the thrust direction can be improved. Therefore, the chamfered portion formed in advance at least on the outer peripheral edge of the roller is not reduced or lost by the polishing of the roller end surface, and it is possible to avoid an increase in processing man-hours such as performing chamfering again. it can.

Further, in the manufacturing method according to the present invention, the chamfered portion of the roller peripheral edge and the raised portion of the roller end surface are easily formed by molding and firing with a mold, and then the raised portion is ground to improve the dimensional accuracy in the thrust direction. The chamfered part that has been arranged is not affected by the polishing process, and the planned chamfering width is secured.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention will be described below with reference to the drawings. (Example 1) The ceramic roller shown in FIGS.
The raised portions 1 are provided symmetrically with respect to the central cross section on the end faces on both sides thereof. Each of the ridges 1 is formed in an annular shape having a width w concentrically with respect to the center line of the roller, but is located inside the chamfered portions 2 formed on the outer peripheral edges of both ends of the roller by a certain size. However, a step h is formed between the end face 3 and the original end face 3. Note that this roller has a central hole 4
Is formed, and the chamfered portion 5 is also provided on the inner peripheral edge of the center hole 4. Such a ceramic roller is formed into a roller shape including the chamfered portions 2, 5, the central hole 4, and the raised portion 1 from a raw material powder by a predetermined die, and then fired. For this fired product, both end faces of the roller, which are the positioning portion in the thrust direction, are polished by, for example, a double-sided grinder.
The polishing is performed on the top surface of each raised portion 1 with a predetermined polishing amount t.

Here, as a matter of course, in the case where the raised portions 1 on both sides of the roller are actually evenly polished, as shown in FIG.
Even if there is a difference in the polishing amount on both sides of the roller, for example, even if the polishing amount ta on the end surface of the left roller is larger than the polishing amount tb on the right side, only the difference in the reduction amount of the raised portion 1 causes the chamfered portion of the outer peripheral edge. 2 is not affected. Further, since the polishing area of the roller end surface is limited to the top surface of the raised portion 1, the polishing area is small and the processing is easy. When the outer peripheral surface of the roller is subjected to finish polishing, the width of the chamfered portion 2 becomes smaller by that amount, but since the outer peripheral polishing amount tc is predetermined and has little variation, the planned polishing allowance is included. It is sufficient to set the external dimensions.

(Embodiment 2) In the embodiment of FIG. 4, the raised portion 1 on the roller end surface is formed not only from the chamfered portion 2 on the outer peripheral edge but also from the chamfered portion 5 on the inner peripheral edge. In this configuration, the chamfered portion 2 at the outer peripheral edge and the chamfered portion 5 at the inner peripheral edge are not affected by the polishing of the roller end surface (raised portion 1). Further, since the polishing area of the end surface of the roller is further narrowed, the end surface can be processed more easily.

(Embodiments 3 and 4) Here, the shape of the raised portion 1 is not limited to the concentric circular shape as described above, but may be formed radially as shown in FIG. Further, when the chamfered portion is not required at the inner peripheral edge of the roller, a raised portion may be formed so that no step is formed on the inner peripheral edge side as shown in FIGS. Further, the center hole 4 itself may not be formed in the roller.

(Fifth Embodiment) Further, as shown in FIG.
It is also possible to form a plurality of thin protrusions 1 in a concentric circular shape.

Next, an embodiment of the method for manufacturing the above ceramic roller will be described in more detail.

(Example 6) Si ₃ N ₄ powder was the main component, Y ₂ O ₃ -Al ₂ O ₃ based sintering aid and molding binder were added and mixed well, and then pressed by a die press. Powder molding was performed. The obtained molded body was fired to obtain a fired body having a shape as shown in FIG. The fired body has an outer diameter of 40 mm, a center hole having an inner diameter of 15 mm, and a width of 20 mm. In addition, the diameter and height of the raised portion formed on the end surface are 25 mm and 1 mm, respectively.
Is. For comparison, the end surface is not provided with a ridged portion as shown in FIG.
A fired body having the shape shown in 2 was also produced. In each of the fired bodies, the size of the chamfered portion formed on the edge portion on the outer peripheral surface side was C1 mm.

With respect to these fired bodies, the outer peripheral surface of the roller was polished by 0.2 mm, and both end surfaces (protrusions) were polished by a double-sided grinder with a planned polishing amount of 0.3 mm per surface. Then, the outer peripheral surface was subjected to crowning polishing, but finally, barrel polishing may be performed for polishing. When the size of the chamfered portion was measured after the above processing, the following results were obtained.

In the roller of the present invention, the left and right residual chamfering amounts were both C0.8 mm, whereas in the roller of the comparative example, the left side residual chamfering amount was C0.7 mm and the right side was C0.3 mm. That is, it can be seen that the roller of the present invention has a larger residual chamfering amount at any end surface portion.

[Brief description of drawings]

FIG. 1 is a plan view of a ceramic roller according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view taken along line AA of FIG.

FIG. 3 is a view showing an example of a polishing mode for both end faces of the ceramic roller.

FIG. 4 is a plan view of a ceramic roller according to a second embodiment of the present invention.

5 is an enlarged sectional view taken along line BB of FIG.

FIG. 6 is a plan view of a ceramic roller according to a third embodiment of the present invention.

FIG. 7 is a plan view of a ceramic roller according to a fourth embodiment of the present invention.

FIG. 8 is an enlarged cross-sectional view taken along line CC of FIG.

FIG. 9 is a half sectional view of a ceramic roller according to a fifth embodiment of the present invention.

FIG. 10 is a view showing an overhead camshaft type mechanism using a ceramic roller.

FIG. 11 is a view showing an overhead valve type mechanism using a ceramic roller.

FIG. 12 is a diagram illustrating a state where both end surfaces of a conventional ceramic roller are evenly polished.

FIG. 13 is a diagram illustrating a state in which both end surfaces of the conventional ceramic roller are unevenly polished.

FIG. 14 is an enlarged view of the right chamfer in FIG.

FIG. 15 is a view showing a state where the outer periphery of the portion is further polished.

[Explanation of symbols]

 1 Raised part 2 Outer peripheral edge chamfered part 3 Original end face 4 Center hole 5 Inner peripheral edge chamfered part w Height of raised part h Height of raised part

Claims (4)

[Claims] 1. A ceramic roller, wherein a ridge is formed on an end surface of the ceramic roller except a chamfer formed on at least an outer peripheral edge of the end surface. 2. The ceramic roller according to claim 1, wherein a polishing process is applied to a top surface of the raised portion among the end surfaces. 3. A step of molding the raw material powder in the shape of a roller so that chamfered portions are formed on the peripheral edges of both end faces, and raised portions are formed in the regions of both end faces excluding the chamfered portions, respectively. A method of manufacturing a ceramic roller, comprising: a step of firing a molded body; and a step of polishing both end surfaces of the obtained fired body at the top surfaces of the raised portions. 4. The method of manufacturing a ceramic roller according to claim 3, further comprising a step of polishing the peripheral surface of the fired body before or after the polishing step.