JPH0152605B2 - - Google Patents

Description

[Detailed description of the invention]

A. Purpose of the Invention (1) Industrial Field of Application The present invention provides a metal stepped shaft, in particular, a large diameter portion and a small diameter portion protruding from the end surface of the large diameter portion, the end surface and the outer circumferential surface of the small diameter portion. This invention relates to an improvement in which the outer peripheral surface of the annular fillet portion between the two is formed into a concave curved surface. (2) Prior Art Conventionally, the concave curved surface of the fillet portion is formed to have a constant radius of curvature over its entire axial length. (3) Problems to be Solved by the Invention The reason why the fillet portion is provided with a concave curved surface is to alleviate stress concentration on the fillet portion and improve the mechanical strength of the stepped shaft. Therefore, it is better for the radius of curvature of a concave surface to be as large as possible,
If the radius of curvature of the concave curved surface is kept constant as in the past, the axial length of the fillet section is limited by the bearing that supports the small diameter section, so the radius of curvature of the concave curved surface cannot be significantly increased, and the step There is a problem in that the mechanical strength of the attached shaft cannot be sufficiently improved. An object of the present invention is to provide the stepped shaft that can solve the above problems. B. Structure of the Invention (1) Means for Solving the Problems The present invention provides that the concave curved surface of the fillet portion is
It is characterized by being composed of a first curved surface with a large radius of curvature disposed on the large diameter side, and a second curved surface with a small radius of curvature smoothly continuous with the first curved surface and disposed on the small diameter side. do. (2) Effect In the fillet part, since the first curved surface with a large radius of curvature is provided on the large diameter side where stress concentration is likely to occur, the first curved surface alleviates stress concentration,
The mechanical strength of the stepped shaft can be improved.
Further, since the second curved surface with a small radius of curvature is provided on the small diameter side where stress concentration is less likely to occur, the mechanical strength of the stepped shaft is not impaired in any way. Furthermore, by setting the radius of curvature of both curved surfaces as described above,
Both curved surfaces can be made to continue smoothly and fall within a predetermined range between the large diameter portion and the small diameter portion. (3) Embodiment Figure 1 shows a crankshaft 1 for an internal combustion engine as a stepped shaft.
It consists of a crank arm 3 and a crank pin 4, which are integrally constructed from a metal material. In this case, the crank arm 3 corresponds to the large diameter portion, and the crank main shaft 2 and the crank pin 4 correspond to the small diameter portion. Furthermore, the large diameter shaft portion 2a at the end of the crank main shaft 2 corresponds to the large diameter portion, and the small diameter shaft portion 2b corresponds to the small diameter portion. An annular fillet portion F between both end surfaces of the crank arm 3 and the outer peripheral surfaces of the crank main shaft 2 and crank pin 4, and an annular fillet portion F between the end surface of the large diameter shaft portion 2a and the outer peripheral surface of the small diameter shaft portion 2b of the crank main shaft 2. The outer peripheral surface is formed into a concave curved surface as described below. The concave curved surface 5 in each fillet portion F has approximately the same configuration, so to explain the concave curved surface 5 between the crank arm 3 and the crank main shaft 2, as shown in FIG. It is composed of a first curved surface 5 ₁ and a second curved surface 5 ₁ on the crank main shaft 3 side. The radius of curvature R ₁ of the first curved surface 5 ₁ is set large,
Furthermore, the radius of curvature r ₁ of the second curved surface 5 ₂ is set smaller than the radius of curvature R ₁ of the first curved surface 5 ₁ (that is, R ₁ >
_r1 ). The connecting portion a between both curved surfaces 5 ₁ and 5 ₂ is formed so as to be smoothly continuous without any bending point. Further, a connecting portion b between the end portion of the first curved surface 5 ₁ on the side of the crank arm 3 and the end surface of the crank arm 3 is formed such that the end surface forms a tangential plane to the end portion. Further, the connecting portion c between the end portion of the second curved surface 5 ₂ on the side of the crank spindle 2 and the outer circumferential surface of the crank spindle 2 is formed to have a bending point. In this case, since the crankshaft 2 is supported by the crankcase 7 via the bearing member 6, the axial length of the fillet portion F is limited to fit between the end face of the crank arm 3 and the end face of the bearing member 6 facing it. . In the present invention, as described above, the fillet portion F
Since the concave curved surface 5 is composed of the first and second curved surfaces 5 ₁ and 5 ₂ , and the radius of curvature R ₁ of the first curved surface 5 ₁ is set larger than the second radius of curvature r ₁ , there is a gap between the two end surfaces. Both curved surfaces 5 ₁ and 5 ₂ can be accommodated. In addition, a first curved surface ₅₁ with a large radius of curvature _R1 is provided on the crank arm 3 side where stress concentration is likely to occur, and the end surface of the crank arm 3 is made to form a tangent plane to the terminal end of the first curved surface ₅₁ . Since the first curved surface 5 ₁ and the first curved surface 5 ₁ are formed so that no breaking point occurs at the connecting portion, stress concentration is alleviated by the first curved surface 5 ₁ and the mechanical strength of the crankshaft 1 is improved. Can be done. Even if a bending point occurs at the connection point c between the end of the second curved surface ₅₂ and the outer peripheral surface of the crank spindle 2, stress concentration is unlikely to occur on the second curved surface ₅₂ side, so the bending point Therefore, the mechanical strength of the crankshaft 1 is not impaired. The fillet portion F' shown by the dotted line in FIG. 2 corresponds to the conventional example, and the radius of curvature r' of the concave curved surface 5' is constant, and there is a difference between the radius of curvature R ₁ and r ₁ of the concave curved surface 5 in the present invention. , there is a relationship of R ₁ > r′ > r ₁ . Therefore, in the conventional example, the crank arm 3
Since a concave curved surface 5' with a small radius of curvature r' continues on the end face of the concave surface 5', the mechanical strength of the conventional example is lower than that of the present invention. The table shows examples of metal materials used for the crankshaft 1.

[Table] As this type of metal material, carbon steel and alloy steel with a carbon content of 0.1% by weight or more are used, and cast iron, aluminum alloy, and copper alloy with a tensile strength of 40 kg/mm ² or more are used. used. Carbon steel with a carbon content of 0.1% by weight or more is
Carbon steel A in the table, carbon steels B to D in the table whose hardness can be improved by performing air cooling treatment after hot forging,
This applies to carbon steels for mechanical structures such as JIS S10S to S50C. In addition, alloy steels with a carbon content of 0.1% by weight or more include chromium steels such as JIS SCr415 shown as alloy steel A in the table, JIS SCr435 shown as B in the table, and JIS
This applies to chromium molybdenum steels such as SCM435. Examples of cast irons with a tensile strength of 40 kg/mm ² or more include pearlite malleable cast irons such as JIS FCMP50, which are indicated by cast iron A in the table, and spheroidal graphite cast irons such as JIS FCD55, which are indicated by cast iron B in the table. In addition, examples of aluminum alloys having a tensile strength of 40 Kg/mm ² or more include JIS 2017, which is indicated by high-strength aluminum alloy A in the table, and JIS 7075, which is indicated by alloy B in the table. Furthermore, examples of copper alloys having a tensile strength of 40 Kg/mm ² or more include JIS HB _S C1, indicated by high strength brass A in the table, and JIS HB _S C2, indicated by alloy B, in the table. Next, the roles of typical chemical components in the various metal materials will be described. (a) Regarding carbon steel and alloy steel Carbon increases the hardness of the core of these steels and contributes to surface hardening due to soft nitriding, but when the carbon content is less than 0.1% by weight, this function is lost. unable to perform. Particularly in soft nitriding treatment, if the carbon content is set to 0.1 to 0.5% by weight, a hardened surface layer with excellent mechanical and chemical properties can be obtained. Chromium and aluminum function as nitrocarburizing promoting components. However, in carbon steels B to D added with vanadium, the chromium content is 0.5% by weight.
If the chromium content exceeds 0.5%, the hardening depth increases and the strain relief straightening ability decreases, so the chromium content is set to 0.5% by weight or less. This phenomenon occurs when the aluminum content
This occurs even if the aluminum content exceeds 0.2% by weight, so the aluminum content is set to 0.2% by weight or less. Vanadium is added to the medium carbon steel base,
By applying appropriate air cooling treatment after hot forging, a uniform precipitation hardening phenomenon occurs inside and outside. As a result, it is possible to obtain the same hardness as in the case where the quenching and tempering treatment is performed without performing the quenching and tempering treatment. However, if the vanadium content exceeds 0.3% by weight, the toughness will decrease, so the vanadium content should be 0.3% by weight.
It is set below weight%. When 0.3% by weight or less of one or more chemical components selected from titanium, zircon, niobium + tantalum is added, the strength can be improved due to the precipitation hardening phenomenon caused by the chemical components. However, if the content of the chemical components exceeds 0.3% by weight, the nitrocarburizing property decreases. The matrix can be strengthened by adding 1.5% by weight or more of each of silicon, manganese, copper, molybdenum, tungsten, and cobalt. However, if the content of the chemical components exceeds 1.5% by weight, the nitrocarburizing property decreases. Machinability improves when the content is 0.15% by weight or less for sulfur, 0.3% by weight or less for lead, 0.1% by weight or less for tellurium, and 0.3% by weight or less for selenium, but when each chemical component exceeds the above content, toughness decreases. (b) Regarding aluminum alloys When the chromium content is set to about 0.3% by weight,
It can prevent stress corrosion cracking and improve strength. Copper functions as an age hardening accelerating component, and in order to satisfy the required hardness, it is best to set its content to 4.0 to 4.8% by weight, but on the other hand, machinability is slightly reduced. Magnesium exhibits the effect of preventing stress corrosion cracking, and for this purpose, the magnesium content is preferably set at 2 to 3% by weight. Further, magnesium exhibits the effect of improving hardness, and for this purpose, the magnesium content may be set to about 2% by weight. Zinc functions as an age hardening accelerating component, and maximum hardness can be obtained by setting its content to about 6% by weight. Since the aluminum alloy has a low basic strength, it cannot be subjected to prescribed heat treatment, for example, in the case of JIS 7075.
T6 treatment is applied to improve strength. The above-mentioned copper alloy, ie, high-strength brass, etc., has a strength equivalent to the above-mentioned carbon steel and alloy steel, so it is practical as a metal material for a stepped shaft. The stepped shaft is formed by hot forging the metal material, and can be used as is after being formed, or can be used after being subjected to cold pressing in whole or in part for the purpose of improving strength, etc. Served. When using metal materials such as carbon steel, alloy steel, and cast iron, the pressing force during pressing is
It is set at 200-900Kg/ ^mm2 . Pressure force is 200Kg/
If it is less than mm ² , it is not possible to improve the surface roughness, which is one of the factors for improving strength, while if it is more than 900 kg/mm ² , the life of the pressing tool will be shortened, the pressing surface will peel off, the stepped shaft will bend, etc. This will cause problems. When using metal materials such as the aluminum alloy and steel alloy mentioned above, the pressing force is 100 to 400 Kg/mm ²
is set to If the pressing force is less than 100 kg/ ^mm2 , sufficient Young's modulus and hardness cannot be obtained;
At 400Kg/mm2 or ^more , problems such as bending of the stepped shaft mainly occur. The fillet portion F is generally formed by surface rolling using rollers. Using carbon steels A and B, cast irons A and B, high-strength aluminum alloy B, and high-strength brass B shown in the table above, a crankshaft with a fillet portion F' having a conventional radius of curvature r' and a crankshaft according to the present invention are manufactured. Radius of curvature R ₁ of large and small types,
A crankshaft with a fillet part F having r ₁ was manufactured, and each crankshaft was subjected to a fatigue test using a servohydraulic fatigue tester for repeated bending N = 1 x 10 ⁷ times to determine the fatigue limit of the load level. I asked for The table shows the case of a crankshaft with a conventional fillet part F', and the table shows the case of a crankshaft with a fillet part F' of the present invention.
This applies to crankshafts equipped with In the table, each treatment listed in the heat treatment column was applied to the crankshaft, and the ``implemented'' and ``-'' marks in the cold pressing column correspond to cases where the treatment was applied and not applied, respectively. Furthermore, the strength improvement ratio is based on a reference value of 1.0, which is the case where only the quenching and tempering treatment is applied to a conventional crankshaft made of carbon steel A having a fillet portion F'.

【table】

【table】

[Table] As is clear from the above table, when various conditions are set the same, the crankshaft equipped with the fillet portion F according to the present invention is superior to the crankshaft equipped with the fillet portion F′ of the conventional example. Mechanical strength is improved compared to In this case, it is clear that if a crankshaft made of carbon steel A, B or cast iron A, B is subjected to nitrocarburizing treatment, its mechanical strength will be improved compared to one subjected to quenching and tempering treatment. FIG. 3 shows another embodiment of the present invention, in which the concave curved surface 5 of the fillet portion F is composed of a first curved surface ₅₁ having a large radius of curvature _R2 and a second curved surface ₅₂ having _a small radius of curvature R2. and a connection part c between the end portion of the second curved surface ₅₂ on the crank spindle 2 side and the outer circumferential surface of the crank spindle 2.
is formed such that a plane including the generatrix of the crank main shaft 2 is tangent to the terminal end. Note that the present invention also includes a case where the radius of curvature of the first curved surface ₅₁ gradually decreases from the connecting portion b toward the connecting portion a, and it is sufficient that the radius of curvature of the first curved surface is large as a result. C Effects of the Invention According to the present invention, since the first curved surface with a large radius of curvature is provided on the large diameter side where stress concentration is likely to occur,
This first curved surface can alleviate stress concentration and improve the mechanical strength of the stepped shaft. Furthermore, since the second curved surface with a small radius of curvature is provided on the small diameter portion side where stress concentration is less likely to occur, the mechanical strength of the stepped shaft is not impaired in any way. Furthermore, by setting the radii of curvature of both curved surfaces as described above, both curved surfaces can be smoothly continuous and fit within a predetermined range between the large diameter part and the small diameter part, and no other parts of the stepped shaft will be affected. There is no need to make design changes.

[Brief explanation of drawings]

1 is a front view of an embodiment of the present invention, FIG. 2 is an enlarged sectional view taken in the direction of arrows in FIG. 1, and FIG. 3 is an enlarged sectional view similar to FIG. 2. F...Fillet part, _R1 , _r1 ...Curvature radius, 1...Crankshaft as stepped shaft, 2...Crank main shaft as small diameter part, 3...Crank arm as large diameter part, 5...Concave curved surface, 5 ₁ , 5 ₂ ...first and second curved surfaces.

Claims (1)

[Scope of Claims] 1. A metal comprising a large diameter portion and a small diameter portion protruding from an end surface of the large diameter portion, and an outer circumferential surface of an annular fillet portion between the end surface and the outer circumferential surface of the small diameter portion is formed into a concave curved surface. In the stepped shaft made of raw material, the concave curved surface of the fillet portion is connected to a first curved surface having a large radius of curvature disposed on the large diameter portion side, and a first curved surface smoothly continuous with the first curved surface and disposed on the small diameter portion side. A stepped shaft made of a metal material, characterized in that it is constructed of a second curved surface having a small radius of curvature. 2. The stepped shaft made of a metal material according to claim 1, wherein the metal material is made of carbon steel with a carbon content set to 0.1% by weight or more. 3. The stepped shaft made of a metal material according to claim 1, wherein the metal material is made of alloy steel having a carbon content of 0.1% by weight or more. 4. The stepped shaft made of a metal material according to claim 1, wherein the metal material is made of cast iron having a tensile strength of 40 Kg/mm ² or more. 5. The stepped shaft made of a metal material according to claim 1, wherein the metal material is made of an aluminum alloy having a tensile strength of 40 Kg/mm ² or more. 6. The stepped shaft made of a metal material according to claim 1, wherein the metal member is made of a copper alloy having a tensile strength of 40 Kg/mm ² or more.