JPS5853612A - Tappet - Google Patents

Abstract

PURPOSE:To improve resistance to pitching and resistance to scuffing in such a way that sliding member made of Co base sintered alloy which contains carbide is arranged on the surface of a cam contacting part, and Fe base sintered alloy is arranged between the sliding member and the tappet body. CONSTITUTION:A tappet is integrated by a cam contacting part 2 which forms a sliding surface 35 to a cam 5, and a tappet body 1, and further the cam contacting part 2 is formed by a sliding member 3 in which the cam contacting part 2 forms the sliding surface 35, and an intermediate member 4. The tappet body 1 forms a barrel part 16 which slides with a tappet guide 6, and a washer 17 which slides with a push rod 7. The barrel part 16 and the washer 17 are not involved in the particular surface pressure and impact in the event of comparing with the cam contacting part 2, and resistance to wear is not required. Thus, resistance to pitching and resistance to scuffing can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a valve train tappet that follows the camshaft of an internal combustion engine. Traditionally, chilled castings, alloy steels, and carbonitrided steels have been used, and they have also been subjected to surface coatings such as Cr metal spraying, and heat treatments such as hardening and nitriding. With the increase in output, tappets made of sintered alloys or composite material tappets of sintered alloys, cast iron, and steel are attracting attention. The reason for this is that the sintered alloy not only has excellent formability, but also improves lubricity due to the presence of pores and improves wear resistance due to the presence of hard fine particles.

However, sintered alloys made by solid-phase sintering of ordinary iron-based alloy powders have a large amount of pores, and the pores act as structural notches, making them suitable for tappets and other objects with high sliding surface pressure. Cam followers and cams are prone to cracks, cracks, and chips due to fatigue on the sliding surfaces, which causes wear called pitting.

To prevent such pitting, it is effective to reduce the amount of pores in the sintered alloy and improve the strength of the sintered alloy. Tappets that have achieved composite structure and high strength by bonding, or tappets that have a solid phase sintered alloy surface densified and the amount of pores adjusted as in Utility Model Application No. 169607/1983 and No. 83607/1983 Proposed.

Although this composite tappet made by liquid phase sintering has excellent bonding with the base metal and the strength of the sintered alloy itself, it has poor lubrication conditions when the sliding mating material, the cam, is made of chill casting or carburized steel. In engines under high load, soft nitriding treatment is applied to the surface to prevent metal-to-metal fusion wear called scuffing from occurring. In general, sliding members provided with a nitrocarburized layer are sufficiently effective for those with a relatively low surface pressure (such as piston rings), but in tappets used under high surface pressure, the nitrocarburizing Softening occurs at the bottom of the nitrided diffusion layer, making pitting more likely to occur. That is, a hard nitride compound layer is formed on the surface of the sliding surface, and a diffusion layer is formed below it, and the layer from the sliding surface to about 0.5 mm is hardened, but on the contrary, the layer below that is in a tempered state. It becomes soft. In particular, in the case of liquid phase sintered alloys for tappets, which are high-alloyed and have a high density, if it is attempted to provide a soft-nitrided layer to the required depth (usually 02 mm), a long processing time is required and the tendency for softening is significant.

This is the same problem with tappets made of densified solid-phase sintered alloys; it is not possible to achieve both scuffing resistance and pitting resistance by simply adjusting the amount of surface pores in the sintered alloys or heat-treating them. I can't get a satisfactory tappet.

The object of the present invention is to provide a tappet which is excellent in both the above-mentioned scuffing resistance and pitting resistance, and is also excellent in productivity, and will be described in detail below.

First, the gist of the present invention lies in a tappet having the following three constituent features.

(1) A cam abutting part is provided on the sliding part of the tappet body made of cast iron or steel with the cam.

(2) A sliding member made of a Co-based sintered alloy containing 15 to 40% by weight of carbide is disposed on the surface of the cam contact portion.

(3) F between the sliding member of the cam contact part and the tappet body
Arrange e-based sintered alloy.

An embodiment of the tappet of the present invention is shown in FIG. 1 and will be described with reference to FIG.

The tappet is a cam contact portion 2 that forms a sliding surface 35 with the cam 5.
The cam contact portion 2 is further formed by a sliding member 3 forming a sliding surface 35 and an intermediate member 4. The tappet body 1 includes a body portion 16 that slides on the tappet guide 6 and a seat portion 17 that slides on the bushing rod 7.
○This body part 16 and seat part 17 do not have special surface pressure or impact when compared with the cam contact part 2, and do not have strict requirements for wear resistance, so they are hardened to the tappet body 1. This provides sufficient wear resistance.

On the other hand, a Co-based sintered alloy containing carbide, which has excellent scuffing resistance and pitting resistance, is used for the sliding member 3 that slides on the cam 5, and the tappet body 1 and the sliding member 3 are connected to each other. By arranging the intermediate member 4 to support the tappet 3, the tappet main body 1, the intermediate member 4, and the sliding member 3 are firmly connected, and sufficient strength as a tappet can be obtained.

The reason why a CO-based sintered alloy is used for the sliding member 3 that forms this sliding surface 35 is as follows.Firstly, regarding the scuffing resistance, the Co-based sintered alloy of the present invention is resistant to carbide particles and Co-based This is achieved by having a synergistic effect of the alloy base. That is, W, Cy, 'l'i, Nb
The carbide has a significantly high hardness of HV1500 or more, and because it is dispersed throughout the matrix, it creates a bearing effect between sliding surfaces and contributes to lubricity and wear resistance. However, if it is less than 15% by weight, the amount of carbide particles is too small and the above effect is not achieved, and if it exceeds 40% by weight, the amount of base supporting the carbide particles is too small compared to the carbide particles, resulting in the strength of the sintered alloy. Not only does it become brittle and prone to pitching, but
The hardness is too high for the mating material, the cam, and causes significant wear, so it must be selected in a range of 15 to 40% by weight. On the other hand, since the base of the sliding member is formed of a Co-based alloy, it is a completely different material from the cam, which is generally cast iron, steel, or an iron-based sintered alloy. It is difficult to cause interfusion, and the possibility of scuff ink generation is extremely low. Furthermore, Co-based alloys have a lower melting point than Fe-based alloys, and generate a large amount of liquid phase at the liquidus temperature of the intermediate member Fe-based sintered alloy (described later), improving the sintered alloy density and reducing pores. The strength after completion of sintering is high and the pitting resistance is also excellent.

The sintered alloy used for such sliding members is WX as a carbide.
Crs'rt and Nb are selected because they have excellent sliding conditions, but in practice it is desirable to select them in a range of 25 to 35% by weight to satisfy wear resistance and strength. In addition to these carbides, the sintered alloy also contains C in weight%.
1.0~4.0%, Cr6~18%, W2~10ch,
It is desirable that the remaining component composition be substantially CO. Cr
, Co-Cr-W- as well as strengthening base organization for W.
Although the fine carbides of C are mentioned above, Cr less than 64, W
If it is less than 2%, the effect is small, Cr18%, W10%
Since the base becomes brittle if Cr exceeds 6~
18%, W2 to 10% is preferable. O or C lowers the melting temperature of the Co-based alloy and acts as a carbide forming element, but if it is less than C1.04, it has no effect and 4.0% If the amount exceeds 1.0 to 40, the amount of carbide becomes large and becomes brittle, so it is preferable to choose between 1.0 and 40. At the same time, it is integrated with the Co-based sintered alloy that is the sliding member. C, which is a sliding member before and after sintering.
It also has the effect of supporting the o-based sintered alloy. That is, the CO-based sintered alloy as described above is impractical because the raw materials are extremely expensive, but if you try to overlay or thermally spray it, a large amount of material is required for overlaying, Thermal spraying is unfeasible because it tends to peel off easily. In contrast, in the present invention, the CO-based sintered alloy constituting the sliding member and the Fe-based sintered alloy supporting it are sintered from a composite green compact in which powder is laminated before sintering. It becomes possible to significantly reduce the amount of CO-based sintered alloy. That is, the second
This is because a powder compact is formed as shown in Figures (a) to (a).

Figure 2 (a) shows the state where the die D is raised and the Fe-based sintered alloy powder F is filled, which is the same as before. Only the upper part of the powder F is compacted by the punch U, then the die D is lowered to the compacted height, the feeder A for the CO-based sintered alloy powder C is set, and then the die D is raised and the powder C is Fill it. (The state shown in FIG. 2 (c)) Therefore, the powder C is filled with a uniform thickness even if it is thin in the height direction. The subsequent process is the same as before, as shown in Figure 2), lower the upper bunch U and lower the die D at the same time, compact the same amount of powder from the upper and lower punches U and L, then lower the die D and take out the green compact. 0 In the powder compact formed in this way, the powder C and the powder F are strongly pressed together, so by making the powder F relatively thick, even if the powder C is thin, the powder compact can be easily removed when taken out. It will not be damaged due to spring back force or handling during post-processing.

This green compact is assembled with a separately prepared tappet body and sintered at a temperature at which the Fe-based sintered alloy forms a liquid phase.

Through this liquid phase sintering, the amount of pores existing in the Fe-based sintered alloy is reduced and a high-density sintered alloy is obtained, and at the same time as the liquid phase is generated, elements in the sintered alloy are diffused into the tappet body. progresses, and metallurgical diffusion bonding is achieved between the tappet body and the Fe-based sintered alloy. At the same time, metallurgical diffusion bonding to the Fe-based sintered alloy has been achieved with the Co-based sintered alloy, which has a lower liquid phase generation temperature than the Fe-based sintered alloy, and after completion of sintering, these three components are completely combined.

Such a Fe-based sintered alloy needs to support the Co-based sintered alloy even after sintering is completed, so it must have excellent strength and rigidity. Therefore, in weight%, cl, 5 to 4.0 chi, (P
0.2 to 0.2 or more of one or more of the following:
An alloy containing 5.0% and 1.0 to 5.0% of Cu is desirable. P N B N Sl is added in small amounts to lower the liquidus temperature, but if it is less than 0.24, it has no effect, and if it exceeds 5.0, the base becomes brittle, so it is added in the range of 0.2 to 5. Selected at .0%. C is added to adjust the matrix structure and lower the liquid phase generation temperature, but it is added at 1.5
Below 1, the amount of tuyurite in the base is large and the rigidity is low.
If it exceeds 4.0%, the cementite becomes too large and becomes brittle, so the content is selected between 1.5 and 4.0%. Further, Cu is added to strengthen the base, but it is preferably less than 1.0 Cu. The reason for this is that in normal engines, the taper 7), which receives surface pressure and makes sliding contact, has a surface of 0.1 to 0.6
The stress is most concentrated near the in, and if the strength of this part is low, it will cause pitting. However, in the present invention, the Co-based sintered alloy and the Fe-based sintered alloy are metallurgically bonded by diffusion bonding. Therefore, this joint is the strongest layer.

That is, there are no carbide particles in the CO-based sintered alloy, and F
A bonding layer formed by diffusing Co, Cr, W, etc. into an e-based sintered alloy achieves a base strength greater than that of a Fe-based sintered alloy. Therefore, the thickness of the Co-based sintered alloy is 0.1 to 1.
By selecting within the range of O1m, the effect of pitting resistance can be further improved. In addition, when trying to obtain such a thin sintered alloy layer, it is necessary to mix vaporizable powder or liquid with the Co-based sintered alloy powder and fill it onto the Fe-based sintered alloy powder in order to increase the apparent amount of powder. In some cases, a two-layer green compact may be formed by coating or coating. Also, in normal engines that are not particularly harsh on pitching, C.
.

The base sintered alloy can sufficiently withstand even relatively thick walls of about 05 to 1.5 tttx.

In addition, in order to prevent misalignment in the sintering furnace, as shown in FIG. It is also possible.

As described above, the tappet of the present invention not only has excellent scuffing resistance and pitting resistance, but is also easy to manufacture.The following are the test results of the tappet manufactured as follows.

As CO-based sintered alloys, WC powder, CrC powder and Co
- Mix C-W alloy powder and C powder, and mix Fe-P-C powder, C powder, and Cu powder to prepare Fe-based sintered alloy.
After filling the layer, it was press-formed at 6t/crl, and combined with the tappet body made of SCM type steel in a cyclic atmosphere of 1240
After sintering at ℃, quenching and tempering were performed and the final dimensions were processed to obtain the following tappet.

(Co-based sintered alloy) - Sliding member component weight%, WC8.1%, Cr C20.3%, Cr
12.2%, W5.5%, C3.0%, balance C.

Wall thickness (126111N surface hardness H%/650 density 8
．． 21 (Fe-based sintered alloy) - Intermediate member component weight %, C3.4%, PO, 6%, Si 1.1
%, Cu 3.2%, remaining Fe Wall thickness 2.611N Middle part hardness HV200 Density 7.5
I (dimensions) Sliding part outer diameter ff30, weight 150g (Test equipment) The above tappet is assembled with a camshaft, the rotation speed is changed by a transmission directly connected to the electric motor, and the load is changed by a spring force applied to the tappet.

(Comparison tappet) Component weight %, C2,8'L SiO, 67%, Po,
45%, Ni 1.1%, Cr t2.8%, Mo
1.2'%, residual Fe liquid phase sintered alloy composite tappet surface 2 hardness) (V2O3 density 7.51 (mate material camshaft) component weight%, TC3.2%, Si 2.2%, Mn
0.8%, NiO, 3%, Cr 1.2%, Mo
0.4'%, surface hardness HR after quenching with residual Fe
C54 (Test 1. Scuffing test) The rotation speed is 2000r9" and the load is 10kl every 5 minutes?
Increase the load step by step to determine the load that causes scuffing.

(Test 2. Pitching test) The rotation speed was set to 1000 rpm, and the load was increased in 25 kg increments to reach the pitching limit load after 10 cycles.

(Test results) Unit: kg As is clear from these experimental results, the Tamisoto of the present invention has excellent pitting resistance and scuffing resistance at the same time, and is suitable for high-load, high-speed engines, as well as for harsh engines with poor lubrication conditions. It is durable enough.

[Brief explanation of drawings]

FIG. 1: A sectional view of an embodiment of the tappet of the present invention. FIG. 2: A sectional view showing the manufacture of the tappet of the present invention. FIG. 3; sectional view of another embodiment of the present invention. Explanation of numbers 1: Tappet body 2: Cam contact part 3: Sliding member 4: Intermediate member patent applicant Nippon Pisto/S/G Co., Ltd.

Claims (6)

[Claims] (1) In a tappet in which a cam contact part 2 made of a different material is arranged on the sliding contact part of a tappet body 1 made of cast iron or steel with the cam, the surface of the cam contact part is coated with carbide with a weight of 15 ~
A sliding member 3 made of a Co-based sintered alloy containing 40% Co is disposed between the sliding member 3 and the tappet body 1, and liquid-phase sintered F
A tappet characterized by having an intermediate member 4 made of e-based sintered alloy. (2) The sliding member 3 is (WN Cr N Tiz
Nb) A total of 2 tons of one or more types of carbides35
It is a CO-based sintered alloy containing % by weight, and the thickness is 0.1~
1. Tappet described in Patent Paragraph 1 characterized by being intoxicated (3) The sliding member 3 has (W, Cr, Tt
Nb) A total of 2 tons of one or more types of carbides3
0%, C 1.0-4.0%, Cr6-18%, W2-
A tappet according to claim 1, characterized in that the tappet consists of 10% and the balance substantially of Co. (4) The intermediate member 4 is C1,θ~4D% in terms of weight
, (P% B% St) 02
~50%, Cu 1.0~5.0%, remaining substantially F
The tappet according to claim 1, characterized in that the tappet is made of e. (5) The tappet according to claim 1, wherein the sliding member 3 and the intermediate member 4 are sintered from a composite green compact obtained by laminating powders of each of the sliding members 3 and the intermediate member 4. (6) The tappet main body 1 and the intermediate member 4 are connected to the intermediate member 4.
The tappet according to claim 1, characterized in that it is metallurgically bonded by diffusion of elements therein.