JPH02223609A - Manufacture of rocker arm - Google Patents

Abstract

PURPOSE:To prevent an occurrence of a crack or the like at both front and rear end parts of a sliper surface by forming beforehand a prescribed, chamfered part at both front and rear end parts in the sliding direction of a slipper surface of a ceramic tip and forming the slipper surface to the surface roughness whose value is smaller than the prescribed one. CONSTITUTION:A chamfered part 21, whose degree of chamfering is about C1 is formed at both front and rear ends in the sliding direction of a slipper surface 2 of a tip 1 made of ceramics, while the surface roughness of the slipper surface 2 is finished to Rmax=1mum superior. The tip 1 is set in a tip inserting part of a die casting mound 3 in such a manner that the slipper surface abuts on a cavity surface 31. Then, aluminium, molten metal is poured by pressure into a cavity space 32 for internal chill of the tip 1. After this, a mould opening rocker arm 4 is taken out. With this contrivance, the consistency between both front and rear end parts of the sipper surface and the corner parts of the cavity surface is improved, and consequently the rocker arm is hardly caught on the cavity surface when the rocker arm is taken out of the die mould. Therefore, casting defects such as a crack or a corner breakage at both front and rear end parts of the slipper surface scarecely occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing a rocker arm, and particularly to a method for manufacturing a rocker arm in which a ceramic chip is cast by die-casting.

(Prior Art) Conventionally, as a manufacturing method for a rocker arm for an automobile engine, an iron-based chip made of a wear-resistant sintered alloy is brought into contact with the cavity surface of a die-casting mold, and then the die-casting mold is heated. Inject molten metal into the cavity space under pressure,
A method of casting iron-based chips using a die-casting method is known.

However, with the increase in engine output in recent years, the surface pressure applied to the slipper surface of the rocker arm has tended to increase. For this reason, as shown in Japanese Patent Application Laid-Open No. 59-39909, a method of manufacturing a rocker arm has been proposed in which a ceramic chip made of silicon nitride or the like is cast in place of the iron chip by die casting.

(Problem to be Solved by the Invention) However, when ceramic chips are cast using the conventional die-casting method, the slipper surface of the ceramic chip does not fit well with the cavity surface of the die-casting mold.
Local bending stress is applied to the slipper surface of the ceramic chip during pressure pouring, or the slipper surface gets caught on the cavity surface when removing the rocker arm from the die casting mold after pressure pouring. Coupled with the fact that the front and rear ends in the sliding direction are thin, there is a problem in that cracks, chips, etc. occur at the front and rear ends of the slipper surface of the ceramic chip.

In view of the above, an object of the present invention is to prevent the above-mentioned cracks from occurring at the front and rear ends of a ceramic chip.

(Means for Solving the Problems) In order to achieve the above object, the present invention forms predetermined chamfered portions in advance at the front and rear ends of the slipper surface of the ceramic chip in the sliding direction, and The surface roughness is kept below a predetermined value.

Specifically, the solution purchased by the present invention is to form a chamfered portion or a rounded portion of approximately 1C or more on the front and rear ends of the slipper surface of the ceramic chip that comes into sliding contact with the cam portion in the sliding direction, and to The surface roughness of the surface is Rmax-1
The ceramic chip is formed to a thickness of .mu.m or less, and then the ceramic chip is cast into the ceramic chip using a die-casting method.

(Function) With the above configuration, a chamfered portion or a rounded portion of approximately 1C or more is formed at the front and rear ends of the slipper surface of the ceramic chip, so that the front and rear ends of the slipper surface and the cavity surface of the die-casting mold are In addition, the contact area between the ceramic chip and the cavity surface is reduced, making it difficult for the ceramic chip to get caught on the cavity surface when the rocker arm is removed from the die-casting mold.

In addition, since the surface roughness of the slipper surface is formed to Rmax-1μm or less, the unevenness formed on the slipper surface is reduced, making it difficult to apply local bending stress to the slipper surface during pressurized pouring. , the friction force when removing the rocker arm from the die-casting mold is reduced, and the mechanical stress generated on the ceramic chip is reduced.

(Example) Hereinafter, a first embodiment of the present invention will be described based on the drawings.

The method for manufacturing a rocker arm according to the first embodiment is as follows:
As shown in Figures (A) and (B), a chamfered portion 21 of approximately 1C or more is formed at the front and rear ends of the slipper surface 2 of the ceramic chip 1 in the sliding direction, and a chamfered portion 21 of approximately 1C or more is formed on the slipper surface 2 of the ceramic chip 1. The surface roughness of 2 is Rmax −
After that, as shown in FIG. 2, the ceramic chip 1 is set in the chip insert part of the die-casting mold 3 so that the slipper surface 2 is in contact with the cavity surface 31, and then the die-casting mold 3 is Molten aluminum is injected under pressure into the cavity space 32 of the mold, a ceramic chip 1 is cast into the mold by die-casting, the mold is opened, and then an aluminum rocker arm 4 as shown in FIG. 3 is taken out using an eject bin. .

The ceramic chip 1 described above is manufactured as follows.

First, ceramic powder containing silicon nitride as a main component is filled into a mold having a shape corresponding to the chamfered portion 21, and then pressurized with a press to form a compression molded body. Next, this compression molded body is temporarily After firing, the ceramic chip 1 is obtained by main firing. In addition, the slipper surface 2 of the ceramic chip 1
In place of the chamfered portion 21, a rounded portion of about 1C may be formed at the front and rear ends of.

The reason why the rounded portion 21 or rounded portion of about 1 C is formed in the ceramic chip 1 as described above is as follows.

That is, as shown in FIGS. 7(a) and 7(b), the front and rear ends of the slipper surface 2 of the ceramic chip 1 are not provided with a chamfered portion or a rounded portion, or even if they are formed, the chamfered portion or the rounded portion is not formed. If the size is smaller than about 1C, the front and rear ends of the slipper surface 2 of the ceramic chip 1 and the corners of the cavity surface 31 of the die-casting mold 3 will not match well, and the die-casting mold will not fit properly after pouring. When taking out the aluminum rocker arm 4 from the mold 3, the ceramic chip 1 tends to get caught on the cavity surface 31 of the die-casting mold 3.

However, if chamfered portions 21 or rounded portions are formed at the front and rear ends of the slipper surface 2 of the ceramic chip 1, the front and rear ends of the slipper surface 2 of the ceramic chip 1 and the cavity surface 31 of the die-casting mold 3 are separated. Since there is a gap between the slipper surface 2 and the corner, it is difficult to apply local bending stress even when pressure is applied during pressurized pouring, so cracks and chipping of wood ends are difficult to occur at the front and rear ends of the slipper surface 2. In addition, ceramic chip 1
Since the contact surface between the aluminum rocker arm 4 and the cavity surface 31 is reduced, it becomes difficult for the ceramic chip 1 to get caught on the cavity surface 31 of the die-casting mold 3 when the aluminum rocker arm 4 is removed. Cracks and wood chips are less likely to occur in the parts.

Next, the slipper surface 2 of the ceramic chip 1 after main sintering
is barrel-ground to have a surface roughness of RIIax-1 μm or less. The reason for doing this is as follows.

That is, when the surface roughness of the slipper surface 2 of the ceramic chip 1 is rougher than Rmax -1 μm, unevenness exists on the slipper surface 2, so that local bending stress is generated on the slipper surface 2 during pressurized pouring. Furthermore, since the frictional force when removing the aluminum rocker arm 4 from the die-casting mold 3 after pouring becomes large, the mechanical stress applied to the ceramic chip is large.

However, the surface roughness of the slipper surface 2 is Ra + ax −1
If the thickness is less than μm, almost no unevenness will be formed on the slipper surface 2, so that it will be difficult to apply local bending stress to the slipper surface 2 during pressurized pouring, and cracks will occur at the front and rear ends of the slipper surface 2. It becomes less likely to occur. In addition, since the frictional force when taking out the aluminum rocker arm 4 from the die-casting mold 3 after pouring is reduced, the mechanical stress applied to the ceramic chip 1 is reduced, which also reduces the front and rear ends of the slipper surface 2. Cracks are less likely to occur in the parts.

A specific example of the first embodiment will be described below.

First, a 1C chamfer 21 is formed on the front and rear ends of the slipper surface 2 of the ceramic chip 1 in the sliding direction, and the surface roughness of the slipper surface 2 of the ceramic chip 1 is set to R11ax -0,6 to 0. It was formed to have a thickness of 9 μm.

Next, after setting the ceramic chip 1 in the chip insert part of the die-casting mold 3, 680°C ADClo aluminum alloy molten metal is injected under pressure into the cavity space 32 of the die-casting mold 3 for 5 to 6 seconds. Afterwards, the die-casting mold 3 was opened, and the aluminum rocker arm 4 was taken out from the die-casting mold 3.

Next, after deburring this aluminum spout/lock arm 4, the presence or absence of cracks on the slipper surface 2 was investigated by fluorescence flaw detection. As a result, no cracks were found, and when 30 other aluminum rocker arms 4 manufactured by the same method were similarly investigated, no cracks were found.

A comparative example conducted for comparison with the specific example described above will be described below.

First, a radiused portion of 0.5R is formed at the front and rear ends of the slipper surface 2 of the ceramic chip 1 in the sliding direction, and the surface roughness of the slipper surface 2 of the ceramic chip 1 is set to Rmax-1,3~ It was formed to have a thickness of 1°9 μm.

Next, the ceramic chip 1 was die-cast under the same conditions as in the specific example to obtain an aluminum rocker arm, and then the aluminum rocker arm 4 was deburred. Thirty aluminum rocker arms 4 were manufactured using this method, and each was examined for the presence or absence of cracks on the slipper surface 2 using fluorescent flaw detection. Cracks had occurred at the front and rear ends.

A second embodiment of the present invention will be described below.

First, a ceramic chip 1 whose main component is silicon nitride, where neither the chamfered portion 21 nor the rounded portion described above is formed on the slipper surface 2, and whose slip surface 2 is not ground is prepared.
After setting the slipper surface 2 in the chip insert part of the die-casting mold 3 so that it is in contact with the cavity 1lili31, aluminum melt is injected under pressure into the cavity space 32 of the die-casting mold 3, and the ceramic chip 1 is die-casted. After casting and opening the mold, the aluminum rocker arm 4 is taken out using an eject bin.

Next, after trimming, shot blasting is performed to remove burrs around the ceramic chip 1, and then the rocker shaft portion, HLA portion, oil hole portion, etc. of the aluminum rocker arm 4 are machined.

Thereafter, as shown in FIG. 4, the slipper surface 2 of the ceramic chip 1 is ground using a diamond grindstone 5.

In this way, by grinding the slipper surface 2 of the ceramic chip 1 after casting the ceramic chip 1, when machining the body of the aluminum rocker arm 4 using the slipper surface 2 of the ceramic chip 1 as a reference, This is advantageous because the accuracy errors that occur can be avoided.

In this case, the following conditions are preferable for grinding the slipper surface 2 of the ceramic chip 1. That is, a 5D600# diamond grinding wheel 5 was used, a water-soluble grinding fluid was used, and the grinding speed was 0.4 mm/
A method of performing rough grinding with a depth of cut of 0.25 mm/2 passes or less, followed by medium grinding with a depth of cut of 15 μm/2 passes or less, and then finish grinding with a depth of cut of 5 μm/2 passes or less. is preferred.

In this case, the reason for performing medium grinding after rough grinding is that the slipper surface 2 will be stripped off due to rough grinding, and the cam part of the sliding contact will be easily damaged, and there is a concern that fine cracks and racks will occur on the slipper surface 2. This is to prevent these problems. The depth of cut for medium grinding is 20 μm/2.
As mentioned above, a depth of cut of 15 μm/2 or less is preferable, and the depth of cut for finish grinding is 10 μm/2, as the removal condition due to rough grinding cannot be sufficiently improved with a pass level.
Since a good ground surface cannot be obtained with a pass or so, a 5 μm/2 bus is preferable as mentioned above, and the grinding speed is 0.
．． If the speed is about 8 mm/sec, grinding scratches will be created on the slipper surface 2, so as mentioned above, the speed is preferably 0.4 mm/sec or less.

In addition, as a grinding method, the slipper surface 2 is swung in the direction shown by the arrow A, that is, in the front and back direction of the sliding contact direction, with the rocker shaft hole 41 as the axis, on the diamond grindstone 5 rotating the aluminum mouth/grind arm 4. Don't let it come into contact with you.

However, when the slipper surface 2 is ground in this manner, the side edges 22 of the slipper surface 2 become rough and rough, and if the operation is performed in this state, the edge load of the ceramic chip 1 causes the slipper surface 2 to become rough. There is a risk that chipping of the wood end may occur at the side end portion of the cam, or local wear may occur on the cam portion, which is the mating member.

Therefore, in order to remove the edges generated at the side edges of the slipper surface 2, as shown in FIG. 5 and FIG. 100-300 for part 22
Perform chamfering in μm. In this case, for chamfer 2, the above-mentioned amount is preferable because if it is too large, the chip contact length will be shortened and the surface pressure will increase.

In addition, instead of chamfering with the diamond whetstone 6, PV
Edges may be ground on both side ends 22 of the slipper surface 2 using an A grindstone.

As in this second embodiment, after machining the body of the aluminum rocker arm 4, it is made of ceramic.

By grinding the slipper surface 2 of the aluminum tip 1, an aluminum rocker arm 4 of the desired shape is obtained, and the slipper surface 2 has a surface shape that is good in terms of sliding characteristics, so wear resistance can be ensured. . Moreover, the chamfering process can effectively prevent wood chipping at the side end portion of the ceramic chip 1 and local wear of the cam portion, which is a mating member.

A specific example of the second embodiment will be described below.

First, a ceramic chip 1 in which a chamfered part and a radiused part are not formed on the slipper surface 2 and whose slip surface 2 is not ground is cast by a die-casting method, and then
After trimming, shot blasting and deburring, the main body of the aluminum rocker arm 4 was machined.

Next, the slipper surface 2 of the ceramic chip 1 is 5D6
Using diamond grinding wheel 5 with 00# and 3100 rotations, grinding speed 0.4 mm/sec, depth of cut = 0.25 mm/2
The grinding process was performed in the following order: rough grinding of the bus, medium grinding with a depth of cut fi of 15 μm, and finish grinding with a depth of cut of 5 μm. after that,
Both ends 2 of the slipper surface 2 of the ceramic chip 1 are cut using a 230# air grinder diamond grindstone 6.
2 was chamfered to about 120 μm.

As a result, the surface roughness of the slipper surface 2 of the ceramic chip 1 was Rmax-0.8 μm, and when the slipper surface 2 was observed by SEM, there was no occurrence of peeling or cracking, and the surface condition was good. Obtained.

(Effects of the Invention) As explained above, according to the method for manufacturing a rocker arm according to the present invention, a chamfered portion or a rounded portion of approximately 1C or more is formed at the front and rear ends of the slipper surface of the ceramic chip. This improves the alignment between the edges and the corners of the cavity surface of the die-casting mold, and makes it difficult for the ceramic chip to get caught on the cavity surface when removing the rocker arm from the die-casting mold, preventing cracks at the front and rear ends of the slipper surface. It is difficult to cause cracks such as wood chips and chipping of wood ends.

In addition, since the surface roughness of the slipper surface is formed to be approximately Rmax - 1 μm or less, the local bending stress applied to the slipper surface during pressurized pouring and the mechanical stress when removing the rocker arm from the die-casting mold are reduced. Cracks and cracks such as chipped wood edges are less likely to occur at the front and rear ends of the slipper surface.

[Brief explanation of the drawing]

1 to 3 show a method of manufacturing a rocker arm according to a first embodiment of the present invention, FIG. 1(A) is a side view of a ceramic chip, and FIG. 1(B) is a side view of a ceramic chip. 2 is a sectional view showing the state in which the ceramic chip is set, FIG. 3 is a side view of the aluminum rocker arm obtained by this method, and FIGS. 4 to 6.
The figure shows a method for manufacturing a rocker arm according to a second embodiment of the present invention, FIG. 4 is a side view showing the process of grinding the slip surface of a ceramic chip, and FIGS. 5 and 6 are chamfering of the slip surface. Front view showing the process, Figure 7 (a) and (
B) is a side view and a front view showing a ceramic chip in a conventional rocker arm manufacturing method. 1... Ceramic chip 2... Slipper surface 3... Die casting mold 4... Aluminum rocker arm 21... Chamfered portion Fig. 4 Fig. 7 Fig. 1... Ceramic chip 2...・Slipper surface 3... Die-casting mold 4... Aluminum rocker arm 21... Chamfered part

Claims (1)

[Claims] (1) A chamfer or radius of about 1C or more is formed on the front and rear ends of the slipper surface of the ceramic chip that makes sliding contact with the cam part in the sliding direction, and the surface roughness of the slipper surface is set to Rmax=1 μm or less and then,
A method for manufacturing a rocker arm, comprising casting the ceramic chip by a die-casting method.