JP2724516B2 - Tappet manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a tappet used in an internal combustion engine.

[Prior Art] In recent years, the oil lubrication conditions of an internal combustion engine have been becoming severer with higher performance, maintenance-free operation, and EGR. In response to this demand, attempts have been made to ceramicize the sliding portion of the tappet that slides with the cam.

Generally, in the tappet manufacturing process, metal and ceramic members are joined by mechanical joining represented by shrink fitting and chemical joining represented by brazing. In shrink fitting, the shape of the ceramic member is complicated. Therefore, the method using brazing is effective.

On the other hand, the sliding surface of the tappet is raised several μm to several tens of μm higher than the outer edge to make the middle part of the tappet gentle to avoid contact with the sliding surface of other parts. Is formed.

Therefore, as a method of forming crowning on a sliding surface of ceramic, a method of polishing with a diamond grindstone has been used.

In JP-A-63-225728, the sliding surface of the base metal is
A method is disclosed in which a ceramic having a lower coefficient of thermal expansion than a base metal is thermally joined and, at the same time, the crowning is formed by cooling and shrinking the joint.

[Problem to be Solved by the Invention] However, providing a crowning, which is a cubic curved surface, on the surface of the ceramic member by polishing requires cost and time.

In the method disclosed in JP-A-63-225728, it is very difficult to accurately control the atmosphere and temperature during heating and cooling, and it is a method that utilizes the physical properties of the material itself. Therefore, the dimensional accuracy is poor.

An object of the present invention is to provide an inexpensive method with high dimensional accuracy in a method of forming crowning on a ceramic sliding surface of a tappet.

[Means for Solving the Problems] The means is to apply a load to a ceramic sliding surface after brazing in a tappet obtained by brazing a ceramic member forming a sliding surface and a base metal forming a main body. A crowning is provided on the ceramic sliding surface.

Here, the ceramic member includes all materials having excellent sliding characteristics, such as silicon nitride, zirconia, alumina, carbide, and cermet.

Known brazing methods include metallizing the surface of the ceramic and then brazing with a metal braze such as silver braze or aluminum braze, or directly joining the base metal with a silver braze containing active metals such as titanium and zirconium. It is performed by the method described above.

The load can be applied by any means, but to apply the load to the outer edge of the ceramic sliding surface, the outer diameter is approximately the same as the outer diameter of the ceramic sliding surface. It is good to add from the vertical direction.

"Action" The effect is that the base metal below the outer edge of the loaded ceramic sliding surface undergoes plastic deformation due to the load, and the ceramic sliding surface brazed to the base metal also deforms. , Resulting in a crowning shape.

"Example" The manufacturing method of the present invention will be described with reference to FIG.

First, an alumina-yttria-based sintering aid and a forming binder are added to 90% by weight of silicon nitride powder, and a ceramic to be a sliding surface is formed into a disk shape by a die press. Then, it is fired in a nitrogen atmosphere and the end face is lapped and polished to make it flat,
A ceramic disk 1a of 33 mm × 2 mm thickness was obtained.

Next, the base metal 1b was machined after forging SNCM630. Its shape and size are T-shaped in cross section in the axial direction, axial length 70 mm, diameter of brazing surface with ceramic sliding surface 33
mm and a thickness of 3 mm and a diameter of 18 mm at the end face opposite to the brazing face.

The ingot-copper-silver-titanium-based brazing material was interposed between the above components, and the mixture was held at 790 ° C. for 30 minutes in a vacuum. The crowning of the surface of the ceramic (1a) of the tappet 1 was measured by a surface roughness meter and found to be 5 μm.

Then, place the tappet 1 on the lower base 4 with the ceramic sliding surface 1a.
On the autograph 3 via the ring 2
A load of 5000 kgf was applied at a speed of 0.5 mm / min. The above-mentioned ring has an outer diameter of 35 mm, an inner diameter of 25 mm, and a thickness of 10 mm as shown in FIG.
The ring 2 manufactured by D-11 was used. The surface of the ceramic 1a after applying a load is 40 μm due to the plastic deformation of the underlying base metal 1b.
Was crowned.

Similarly, as a result of applying a load of 3000 kgf, a crowning of 30 μm was generated, and a correlation was recognized between the load and the generated crowning, and it was found that any crowning could be obtained.

Each of the above 40 μm crowning and 30 μm crowning tappets was assembled into a 10,000 cc V8 cylinder diesel engine, and the durability was evaluated at 2500 rpm under a full load of 200 hours. After the endurance, no abnormality was observed in the ceramic, and the amount of crowning did not change at all.

[Effect] According to the manufacturing method of the present invention, crowning can be provided on the ceramic sliding surface of the tappet at a low cost and with high dimensional accuracy.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 2 shows a ring used in the embodiment of the present invention. 1 ... tappet, 1a ... ceramic, 1b ... metal substrate,
2 ... Ring, 3 ... Autograph, 4 ... Lower stand

Claims (1)

(57) [Claims] In a method of manufacturing a tappet, a ceramic member forming a sliding surface and a base metal forming a main body are brazed and joined, by applying a load to the ceramic sliding surface after brazing. A method for producing a tappet, comprising providing a crowning on a surface.