JP4572797B2 - V-belt type continuously variable transmission pulley disk and manufacturing method thereof - Google Patents

Description

  The present invention relates to a disk for a V-belt type continuously variable transmission pulley and a manufacturing method thereof.

  Existing transmissions for automobiles such as manual transmissions and automatic transmissions that have been widely used so far, either manually or automatically using hydraulic pressure, usually switch gears according to vehicle speed by switching gears of 3 to 5 stages. Is what you do. For this reason, conventional transmissions inevitably involve a transmission loss of driving force as the gears are switched.

  In recent years, V belt type continuously variable transmissions (hereinafter, referred to in this specification) are one of the means for responding to the reduction in fuel consumption that is strongly demanded from the viewpoint of environmental problems, energy problems, and costs for automobiles. Simply abbreviated as “CVT (Continuously Variable Transmission)”.

  FIG. 1 and FIG. 2 are explanatory diagrams schematically showing the principle of continuously variable transmission performed by CVT 1, FIG. 1 shows a low speed, and FIG. 2 shows a high speed. FIGS. 1 (a) and 2 (a) are perspective views schematically showing the entire configuration of the CVT 1 in a partially broken state. FIGS. 1 (b) and 2 (b) are FIGS. ) And FIG. 2 (a) are views taken in the direction of arrow A, and FIGS. 1 (c) and 2 (c) are views taken in the direction of arrow B in FIGS. 1 (a) and 2 (a).

  As shown in FIGS. 1 and 2, the CVT 1 has two conical discs arranged so as to be movable in the axial direction (the white arrow direction in FIG. 1 (a) and the arrow direction in FIG. 1 (b)). A pair of parallelly arranged pulleys (pulleys) 2 and 3 having V-shaped grooves formed by 2a and 2b, 3a and 3b and connected to the drive side or the engine side, and V-shaped grooves of the pulleys 2 and 3 And a V-belt (continuously variable transmission belt) 4 spanning the belt. As shown in FIGS. 1 and 2, the actual working diameters of pulleys 2 and 3 that match the width of the V-belt 4 by controlling the axial intervals of the disks 2 a and 2 b, 3 a and 3 b having inclined surfaces according to the vehicle speed, respectively. Is continuously changed (see FIG. 1 (b), FIG. 2 (b), FIG. 1 (c), FIG. 2 (c)), and a gear ratio of about 2.5 to 0.5 is obtained steplessly. It is done. Therefore, if the CVT 1 is mounted on an automobile, the transmission ratio can be continuously changed in a stepless manner, so that transmission loss of driving force can be suppressed as much as possible, thereby improving fuel efficiency. For this reason, CVT1 tends to be actively installed in recently developed automobiles as one of the technologies for promoting fuel efficiency reduction of automobiles.

  The V-belt 4 constituting the CVT 1 transmits power between the pulleys 2 and 3 while changing the gear ratio steplessly, so that it has not only high strength but also high reliability. Is required to have excellent ductility and fatigue characteristics that can sufficiently withstand bending and unbending, and excellent wear resistance against contact with the pulleys 2 and 3. Therefore, as shown in FIG. 3, the V-belt 4 is composed of two metal rings 5 and 6 and a number of special-shaped metal elements (belt pieces) 7 fitted between them. Is done.

  On the other hand, of the disks 2a and 2b, 3a and 3b with which the V-belt 4 abuts, the disks 2a and 3a are inclined surfaces 8 with which the V-belt 4 abuts as shown in FIGS. 1 (a) and 2 (a). And a shaft portion 10 connected to the sheave portion 9. The sheave portion 9 and the shaft portion 10 are integrally manufactured from the material stage. That is, the disks 2a and 3a are made of a round steel material made of alloy steel for mechanical structure such as JIS standard SCr420 or SCM420, and hot forging, cutting, carburizing and quenching (surface hardening treatment), tempering at 200 ° C. or less, cutting Further, by polishing as necessary, the abrasion resistance required for the sheave portion 9 and the bending fatigue strength and rolling fatigue life required for the shaft portion 10 were satisfied.

  Until now, this CVT has been mounted mainly on vehicles equipped with an engine with a relatively small displacement of, for example, 2000 cc class or less. However, there is an increasing demand for further weight reduction and downsizing.

  In addition, there is a request for reducing the manufacturing cost for CVT. That is, the final product shapes of the disks 2a and 3a including the sheave portion 9 and the shaft portion 10 are extremely complicated as shown in FIGS. 1 (a) and 2 (a). For this reason, the hot forging in the manufacturing process of the disks 2a and 3a cannot be roughly molded to a state close to the final product shape. For this reason, after hot forging, cutting such as drilling and rough turning must be performed to a considerable extent, and the cost required for cutting is extremely high, which is a major factor in increasing the manufacturing cost of CVT1. . In other words, in order to significantly reduce the manufacturing cost of the CVT 1, it is indispensable to omit or significantly reduce the cutting that is inevitably performed after hot forging of the disks 2a and 3a.

  In addition, if the amount of strain generated by heating in this carburizing and quenching (surface hardening treatment) after cutting is large, cutting must be performed again to ensure proper dimensional accuracy, and the formed surface hardening treatment layer Cutting requires a large amount of man-hours, and it is also necessary to increase the depth of the surface-hardened layer to be formed in anticipation of cutting off part of this surface-hardened layer. In some cases, the processing time becomes longer.

  For this reason, not only can the disks 2a and 3a be forged to a state close to the final product shape, cutting can be omitted or significantly reduced, but the amount of distortion generated by heating during the surface hardening treatment is also small. Requested.

Many proposals have been made so far regarding such a CVT and its pulley disk.
For example, Patent Document 1, the contact surface of the V-belt of the fixed pulley and the movable pulley, so that the friction coefficient mu ₂ friction coefficient mu ₁ and the large diameter portion of the smaller diameter portion satisfies mu _1> mu ₂ relationship By forming at least the large diameter part of the fixed pulley and the movable pulley with a material having good heat conduction, it is possible to increase the thrust, prevent the V belt from slipping and biting, and increase the heat dissipation effect. It is disclosed that it can be done. In Patent Document 1, the sheave portion of the disk is divided into a large diameter portion and a small diameter portion, each of which is made of a different material, but the shaft portion is provided integrally with the small diameter sheave portion.

Further, in Patent Document 2, in the CVT pulley, the surface roughness of the conical sheave surface in frictional contact with the V-belt is 0.1 μm or more and 0.5 μm or less in terms of the center line average roughness Ra. There is disclosed a CVT pulley in which the wear resistance of the sheave surface is improved by setting the surface hardness of the surface to 850 Hv or more in terms of micro Vickers hardness. The CVT pulley disk is formed by integrally forming a sheave portion and a shaft portion, which have been subjected to hot forging and carburizing quenching and tempering using alloy steel for machine structure.
Japanese Examined Patent Publication No. 3-61858 JP 2000-130527 A

  However, the invention disclosed in Patent Document 1 requires that at least the large-diameter portion of the pulley be made of a material having good heat conduction (in the embodiment, an aluminum alloy), as shown in the embodiment. In this case, the small-diameter sheave portion and the shaft portion are integrally manufactured by hot forging. Therefore, as described above, after hot forging, cutting such as drilling or rough turning must be performed to a considerable extent, and according to the present invention, cutting can not be omitted or reduced. In addition, aluminum alloy is inferior in wear resistance compared to surface-treated steel, so it fully satisfies the wear resistance required for the sheave part, the bending fatigue strength and rolling fatigue life required for the shaft part. It is also difficult to do. For this reason, according to the present invention, it is difficult to reduce the weight and size of the CVT and to reduce the manufacturing cost.

  In the invention disclosed in Patent Document 2, since the entire disk is carburized and quenched, the amount of distortion due to heat treatment increases, and a large number of man-hours are required for cutting after carburizing and quenching. In the present invention, since the bending fatigue strength and rolling fatigue life of the shaft portion of the CVT pulley disk are not considered at all, it is difficult to reduce the weight and size of the pulley.

  As described above, according to any of the inventions disclosed in Patent Document 1 and Patent Document 2, hot forging in the manufacturing process of the disks 2a and 3a cannot be roughly molded to a state close to the final product shape, and thereafter In addition, since cutting such as drilling and rough turning must be performed to a considerable extent, the cost required for cutting is extremely high. In addition, according to these inventions, since the amount of distortion due to heat treatment cannot be suppressed, it is necessary to perform cutting work to ensure dimensional accuracy after heat treatment, and from this point of view, an increase in manufacturing cost is inevitable.

  Furthermore, these inventions also do not provide a CVT pulley disk having good wear resistance on the sheave surface, bending fatigue strength of the shaft portion, and rolling fatigue life.

  As described above, most of CVT pulley discs are made of JIS standard SCr420, SCM420, etc. after cutting the steel steel for mechanical structure into a predetermined length and then hot forging the conical sheave and shaft. After the parts are roughly molded integrally, they are manufactured through steps of cutting, carburizing and quenching, tempering at 200 ° C. or lower, cutting, and polishing as necessary.

The present inventors, without being bound by this conventional manufacturing process, have satisfied the CVT pulley disk at a low price and sufficiently satisfy all of the wear resistance of the sheave portion, the bending fatigue strength of the shaft portion, and the rolling fatigue life. We intensively studied the means that can be manufactured. as a result,
(I) The surface of the CVT pulley disk, which has been manufactured by integrating the sheave part and the shaft part so far, after molding the first part forming the sheave part and the second part forming the shaft part. If the first part and the second part are combined and integrated after being subjected to the curing process, it is possible to roughly mold to a state close to the final product shape by forging. , The cutting work that has been performed after forging can be omitted or greatly reduced,

(Ii) As described above, since the first part and the second part are subjected to surface hardening treatment after the first part and the second part are molded and combined, the simplified and compact size is achieved. The surface hardening treatment is performed with the dimensionalized shape, the amount of distortion generated by the surface hardening treatment can be reduced, and thereby the cutting work performed after the surface hardening treatment can be omitted or greatly reduced; and (iii) Optimize the surface hardening treatment applied to the first component and the second component, specifically, the first component is subjected to carburizing or carbonitriding, and the second component is induction-hardened. Can further reduce the amount of strain generated by the surface hardening treatment, and sufficiently provide all of the wear resistance required for the sheave part and the bending fatigue strength and rolling fatigue life required for the shaft part. And knowledge to be able to foot. The present invention is based on these important findings.

In the present invention, a first part forming a sheave part having an inclined surface with which the V-belt abuts and a second part forming a shaft part connected to the sheave part are respectively molded and surface-hardened. Thereafter, the first part and the second part are combined and integrated to produce a CVT pulley disk including a sheave part and a shaft part, and the base material part of the first part is C: 0. 1% or more and 0.3% or less (in this specification, “%” means “mass%” unless otherwise specified), and the second part is C: 0.4% or more. The surface hardening treatment for the first component is a carburizing treatment or carbonitriding treatment, and the surface hardening treatment for the second component is an induction hardening treatment. Of disc for CVT pulley It is a production method.

  In the manufacturing method of the disk for a CVT pulley according to the present invention, the second part is combined with the first part at the same time as the molding process or after the molding process and before the combination with the second part. It is desirable to form a through hole.

  In these CVT pulley disc manufacturing methods according to the present invention, it is desirable that the molding of the first component and / or the second component is forging. In this case, it is desirable that forging is cold forging or warm forging.

From another viewpoint, the present invention provides a first component that forms a sheave portion in which a carburized layer or a carbonitriding layer is formed on an inclined surface with which the V-belt abuts, and an induction-hardened layer that is connected to the sheave portion. The second part different from the first part is integrated into the shaft part formed with C, and the base material part of the first part is C: 0.1% or more and 0.3% The V-belt continuously variable transmission pulley disk is characterized in that it is made of the following steel, and the second part is made of C: 0.4% to 1.0% steel .

  In this specification, “hot” means a temperature range exceeding 750 ° C., “warm” means a temperature range of 750 ° C. or lower and 300 ° C. or higher, and “cold” means less than 300 ° C. It means temperature range.

  According to the present invention, the base material part of the first part forming the sheave part is, for example, a cutting of a round steel material having a C content of 0.1% or more and 0.3% or less → cold forging or warm forging ( Shaft through-hole formation) → Cutting → Carburizing and quenching (surface hardening treatment) → Tempering as necessary → Cutting → Polishing as necessary, or cutting of round steel material → Cold forging or warm forging → Shaft It is manufactured through a process of through-hole formation, cutting → carburizing and quenching (surface hardening treatment) → tempering as necessary → cutting → polishing as necessary. On the other hand, the second part forming the shaft portion is, for example, cutting of a round steel material having a C content of 0.4% to 1.0% → cold forging or warm forging → cutting → high frequency quenching (surface hardening treatment) ) → Tempering if necessary → Cutting → Manufacturing through a process of polishing if necessary.

The first part and the second part thus manufactured are surface hardened on the inclined surface with which the V-belt abuts by integrating the shaft part through the through-hole and combining them as appropriate. A CVT in which a first part forming a sheave part formed with a layer and a second part different from the first part forming a shaft part formed with a surface hardened layer connected to the sheave part are integrated A pulley disk is provided.

  According to the present invention, it is possible to roughly mold the first part forming the sheave part and the second part forming the shaft part to a state close to the final product shape by molding such as forging. The cutting process performed after the molding process can be omitted or greatly reduced, and the manufacturing cost of the CVT pulley can be greatly reduced.

  Further, according to the present invention, the first component and the second component are subjected to surface hardening treatment after the first component and the second component are molded and combined, respectively, so that simplification and downsizing are achieved. The surface hardening treatment will be performed with the measured dimensions and shape, the amount of distortion generated by the surface hardening treatment can be further reduced, cutting after the surface hardening treatment can be omitted or greatly reduced, and carburizing and quenching can be performed as the surface hardening treatment. In this case, since the processing time can be shortened, the manufacturing cost of the CVT disk can also be reduced in this respect.

  Further, according to the present invention, the surface hardening treatment to be applied to the first component and the second component respectively is optimized. Specifically, the first component is subjected to carburizing treatment or carbonitriding treatment and the second component. By subjecting parts to induction hardening, the amount of distortion generated by surface hardening can be further suppressed, and the wear resistance required for the sheave part, the bending fatigue strength and rolling required for the shaft part. All of fatigue life can be fully satisfied.

  For this reason, according to the present invention, the manufacturing cost of CVT can be significantly reduced, and the weight and size of CVT itself can be reduced. Furthermore, it can be expected that the CVT will be mounted on a vehicle equipped with an engine having a higher output and a higher torque than a vehicle on which the CVT has been mounted so far.

BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the CVT pulley disk and the manufacturing method thereof according to the present invention will be described in detail below with reference to the accompanying drawings.
As described above, most of the disks for CVT pulleys are roughly formed by integrally forming the sheave part and the shaft part by hot forging after cutting a steel round alloy steel for mechanical structure such as JIS standard SCr420 or SCM420. After that, it has been manufactured by processes of cutting, carburizing and quenching (surface hardening treatment), tempering at 200 ° C. or lower, cutting, and polishing as necessary.

  Here, in order to promote the installation of CVT in automobiles by reducing costs, the cutting after hot forging and the cutting after surface hardening treatment, which are the main causes of cost increase, are omitted or significantly reduced. There is a need to.

  In addition, in order to reduce the weight and size of the pulley, it is necessary to maintain both excellent wear resistance of the sheave surface and excellent bending fatigue strength and rolling fatigue life of the shaft portion at a high level. .

  Therefore, the present inventors have characteristics equivalent to or better than those of a V-belt CVT pulley carburized and hardened into an alloy steel for machine structure, that is, wear resistance of the sheave surface, bending fatigue strength of the shaft portion, and rolling fatigue life. As a result of intensive investigation and research on means capable of omitting or reducing the cutting process after the surface hardening treatment after hot forging and after the surface hardening treatment, the findings (a) to (g) listed below are as follows: )

(A) Since the shape of the disk for the CVT pulley is complicated, it is impossible to roughly form the shape close to the final product shape even if the sheave portion and the shaft portion are integrally forged. It is necessary to perform a considerable amount of cutting such as rough turning. On the other hand, since the first part forming the sheave part and the second part forming the shaft part are separately manufactured by forging, rough forming can be performed by forging to a state close to the final product shape. Most of the cutting can be omitted or greatly reduced.

(B) Surface hardening for each of the first part forming the sheave part and the second part forming the shaft part as compared with the case where the surface hardening process is performed on the disk for the CVT pulley in which the sheave part and the shaft part are integrated. When the treatment is performed, the surface hardening treatment is performed with a simplified and miniaturized size and shape, and the amount of distortion after the heat treatment can be suppressed to a small value.
(C) Since the shaft portion of the disk subjected to induction hardening as the surface hardening treatment only needs to heat only the surface layer of the shaft portion as compared with the shaft portion of the disk subjected to carburizing and quenching, the heat treatment distortion is small.

(D) Carburized and hardened case-hardened steel has excellent wear resistance, but is inferior in bending fatigue strength and rolling fatigue life compared to induction-hardened medium carbon steel.
(E) In the case of induction hardening, compared to carburizing and quenching, since the heating is performed for a short time, the growth of crystal grains is suppressed and an abnormal oxide layer on the surface is not generated. Further, since only the surface layer is heated, compressive residual stress is generated in the surface layer portion. Moreover, it has the characteristic that the depth of the hardened layer by induction hardening is large. For this reason, induction-hardened medium carbon steel is superior in bending fatigue strength and rolling fatigue life compared to carburized and quenched case-hardened steel.

(F) The first part and the second part that have been subjected to forging and surface hardening treatment are made to pass through the shaft part of the second part through a through hole formed in the first part, for example, press-fitting, baking It can be integrated by fitting and fixing by well known means such as a spline. Forming the through hole in the first part is easy and desirable at the same time as the molding process (forging), that is, plastic processing, but after the molding process and before combining with the second part, the molding process is performed. You may make it carry out separately by different machining.

(G) Further, when hot forging is performed on the first part and the second part, oxide scale is generated and decarburized, and most of the surfaces of the first part and the second part are cut. Need to be done. Therefore, forging of the first part and the second part is preferably performed by cold forging or warm forging at a lower temperature than hot forging because cutting after forging can be omitted or significantly reduced.

Next, a method for manufacturing a continuously variable transmission pulley disk according to the present embodiment will be described.
In the present embodiment, the continuously variable transmission pulley disk is manufactured through the first to third steps described below, so the first to third steps will be sequentially described.
(First step)
In the present embodiment, steel is used as the material. Hereinafter, the composition of the base material part of the steel material used in the present embodiment, that is, a part manufactured by molding and surface hardening treatment will be described.
C: Base material part of first part; 0.1% or more and 0.3% or less, second part; 0.4% or more and 1.0% or less

  The C content in the base material portion of the first part forming the sheave portion 9 in FIGS. 1 and 2 is preferably 0.1% or more and 0.3% or less. C can ensure the core strength of the parts when carburized or carbonitrided and quenched by containing 0.1% or more. However, when the C content exceeds 0.3%, carburizing and quenching or carburizing is performed. The heat treatment distortion when nitriding and quenching becomes too large, and a large number of man-hours are required for cutting. Therefore, it is desirable that the C content of the base material portion of the first part is 0.1% or more and 0.3% or less.

  On the other hand, the C content of the second component forming the shaft portion 10 in FIGS. 1 and 2 is desirably 0.4% or more and 1.0% or less. When C is contained in an amount of 0.4% or more, the hardness of the surface layer of the second part when induction-quenched can be ensured, and excellent bending fatigue strength and rolling fatigue life can be obtained. If it exceeds 1.0%, the amount of retained austenite in the induction-quenched portion is excessively increased, so that the hardness decreases, and the bending fatigue strength and rolling fatigue life decrease. Therefore, the C content of the second part is desirably 0.4% or more and 1.0% or less.

  The chemical composition other than the base material portion of the first part and the C of the second part is not particularly limited, and is a chemistry that can ensure both the characteristics required in the final product and the industrial productivity. What is necessary is just a composition. Hereinafter, composition examples other than the base material portion of the first part and C of the second part will be exemplified.

Si: 0.1% or more and 1.5% or less Si is contained in an amount of 0.1% or more, so that it has the effect of improving hardenability and temper softening resistance, so wear resistance, bending fatigue strength, and rolling fatigue life. It is an effective element for enhancing However, if the Si content exceeds 1.5%, not only the effect of increasing wear resistance, bending fatigue strength and rolling fatigue life is saturated, but also machinability is greatly reduced. Therefore, the Si content is preferably 0.1% or more and 1.5% or less.

Mn: 0.2% or more and 1.5% or less Mn is effective in enhancing wear resistance, bending fatigue strength and rolling fatigue life because it has the effect of improving hardenability by containing 0.2% or more. Element. However, if the Mn content exceeds 1.5%, not only the effect of increasing wear resistance, bending fatigue strength and rolling fatigue life is saturated, but also machinability is greatly reduced. Therefore, the Mn content is preferably 0.2% or more and 1.5% or less.

S: 0.005% or more and 0.08% or less S contains 0.005% or more, so that it combines with Mn to form MnS, thereby improving the machinability. However, if the S content exceeds 0.08%, the bending fatigue strength and rolling fatigue life are greatly reduced due to coarse MnS. Therefore, the S content is preferably 0.005% or more and 0.08% or less.

Cu: 0.05% or more and 1.0% or less Cu is effective in enhancing wear resistance, bending fatigue strength and rolling fatigue life because it has the effect of improving hardenability by containing 0.05% or more. Element. However, if the Cu content exceeds 1.0%, not only the effect of increasing wear resistance, bending fatigue strength and rolling fatigue life is saturated, but also hot workability is lowered. Therefore, the Cu content is preferably 0.05% or more and 1.0% or less.

Ni: 0.2% or more and 2.0% or less Ni is effective in enhancing wear resistance, bending fatigue strength and rolling fatigue life because it has an effect of improving hardenability by containing 0.2% or more. Element. However, if the Ni content exceeds 2.0%, the effect of increasing the wear resistance, bending fatigue strength and rolling fatigue life is saturated and the cost is increased. Therefore, the Ni content is preferably 0.2% or more and 2.0% or less.

Cr: 0.1% or more and 2.0% or less Cr is contained in an amount of 0.1% or more, and has the effect of increasing hardenability and tempering softening resistance. Therefore, it has wear resistance, bending fatigue strength, and rolling fatigue life. It is an effective element to enhance. However, if the Cr content exceeds 2.0%, not only the effect of increasing wear resistance, bending fatigue strength and rolling fatigue life is saturated, but also machinability is greatly reduced. Therefore, the Cr content is preferably 0.1% or more and 2.0% or less.

Mo: 0.05% or more and 1.0% or less Mo contains 0.05% or more, and has the effect of increasing hardenability and tempering softening resistance. Therefore, it has wear resistance, bending fatigue strength and rolling fatigue life. It is an effective element to enhance. However, if the Mo content exceeds 1.0%, not only the effect of increasing wear resistance, bending fatigue strength and rolling fatigue life is saturated, but also machinability is greatly reduced. Therefore, the Mo content is preferably 0.05% or more and 1.0% or less.

Nb: 0.01% or more and 0.1% or less When Nb is contained in an amount of 0.01% or more, it is easy to form NbC, NbN, Nb (C, N) by combining with C and N. It is effective for grain refinement and has the effect of increasing bending fatigue strength and rolling fatigue life. However, if the Nb content exceeds 0.1%, coarse NbC and Nb (C, N) are easily formed, so that bending fatigue strength and rolling fatigue life are reduced. Therefore, the Nb content is preferably 0.01% or more and 0.1% or less.

V: 0.02% or more and 0.3% or less V is contained in an amount of 0.02% or more, so that it easily combines with C and N to form VN and VC. It is effective in improving the bending fatigue strength and rolling fatigue life. However, if the V content exceeds 0.3%, the machinability is greatly deteriorated. Therefore, the V content is preferably 0.02% or more and 0.3% or less.

Ti: 0.01% or more and 0.2% or less Ti is contained in an amount of 0.01% or more to form TiC, Ti (C, N), TiN by combining with C and N, and crystal grains in the quenched portion. It is effective for miniaturization and has the effect of increasing bending fatigue strength and rolling fatigue life. However, if the Ti content exceeds 0.2%, it becomes easy to form coarse TiN, so that the bending fatigue strength and the rolling fatigue life are lowered. Therefore, the Ti content is preferably 0.01% or more and 0.2% or less.

Al: 0.005% or more and 0.05% or less Al contains 0.005% or more, and has a deoxidizing action, and is easily combined with N to form AlN. It is effective and has the effect of increasing bending fatigue strength and rolling fatigue life. However, when the Al content exceeds 0.05%, coarse oxide inclusions are easily formed, so that the bending fatigue strength and the rolling fatigue life are lowered. Therefore, the Al content is preferably 0.005% or more and 0.05% or less.

B: 0.0003% or more and 0.005% or less B is effective for enhancing wear resistance, bending fatigue strength, and rolling fatigue life because it has an effect of improving hardenability by containing 0.0003% or more. Element. However, if the B content exceeds 0.005%, a coarse B compound is easily formed, so that the bending fatigue strength and the rolling fatigue life are reduced. Therefore, the B content is preferably 0.0003% or more and 0.005% or less.

Rare earth elements: 0.0003% or more and 0.005% or less Rare earth elements contain 0.0003% or more, so that sulfides are easily formed, and are not stretched by hot rolling or hot forging like MnS. It is an element effective for increasing the bending fatigue strength and rolling fatigue life in order to reduce the major axis of the object. However, if the rare earth element content exceeds 0.005%, it becomes easy to form coarse oxide inclusions containing rare earth elements, so that the bending fatigue strength and the rolling fatigue life are lowered. Therefore, the rare earth element content is preferably 0.0003% or more and 0.005% or less.

Ca: 0.0003% or more and 0.005% or less Ca is contained by 0.0003% or more, so that it is easy to form a sulfide and does not stretch by hot rolling or hot forging like MnS. It is an element effective for increasing the bending fatigue strength and rolling fatigue life in order to reduce the major axis. However, when the Ca content exceeds 0.005%, coarse oxide inclusions containing Ca are easily formed, so that bending fatigue strength and rolling fatigue life are reduced. Therefore, the Ca content is preferably 0.0003% or more and 0.005% or less.

Te: 0.003% or more and 0.01% or less Te contains 0.003% or more so that it is easy to form a sulfide, and unlike MnS, it is not stretched by hot rolling or hot forging. It is an element effective for increasing the bending fatigue strength and rolling fatigue life in order to reduce the major axis. However, since Te sulfide has a low melting point, hot workability deteriorates when the Te content exceeds 0.01%. Therefore, the Te content is preferably 0.003% or more and 0.01% or less.

N: 0.005% or more and 0.025% or less N is easy to form AlN, NbN, VN, TiN by combining with Al, Nb, V, Ti, and is effective for refining the crystal grains in the quenched portion. It has the effect of increasing fatigue strength and rolling fatigue life. However, when the N content exceeds 0.025%, coarse AlN, NbN, VN, and TiN are easily formed, so that the bending fatigue strength and the rolling fatigue life are lowered. Therefore, the N content is preferably 0.005% or more and 0.025% or less.

P: 0.05% or less P is an element that easily segregates at the grain boundaries and embrittles the grain boundaries. When the P content exceeds 0.05%, wear resistance, bending fatigue strength, and rolling fatigue life Reduce. Therefore, the P content is preferably 0.05% or less.

O: 0.003% or less O is likely to combine with Al to form hard oxide inclusions, and reduce wear resistance, bending fatigue strength, and rolling fatigue life. Particularly when the O content exceeds 0.003%, the wear resistance, bending fatigue strength, and rolling fatigue life are significantly reduced. Therefore, the O content is preferably 0.003% or less. In addition, although it is desirable to reduce O content as an impurity element as much as possible, it is more preferable to reduce to about 0.001% when the cost in steelmaking is considered.

The remainder other than the above is substantially Fe.
In the present embodiment, a first part that forms a sheave portion having an inclined surface with which the continuously variable transmission belt abuts by performing molding using a steel material having the above-described steel composition, preferably a round steel material, A second part forming a shaft portion connected to the sheave portion is manufactured.

  It is desirable that the molding process in the first step is forging. The first part forming the sheave part 9 in FIGS. 1 and 2 and the second part forming the shaft part 10 in FIGS. 1 and 2 are both simple shapes. It can be roughly molded to a shape very close to the final product shape. For this reason, cutting after forging can be omitted or greatly reduced.

  In the present embodiment, the through-hole for penetrating the shaft portion of the second component is formed in the center of the first component by the molding process in the first step, so the through-hole is simply provided. be able to. However, considering the capacity and load of the processing machine used for the molding process, it is not formed by this molding process, but after the molding process and before being combined with the second part, it is penetrated separately by a different machining process than the molding process. A hole may be formed.

  Forging is preferable to hot forging forging in a temperature range of 750 ° C. or lower and 300 ° C. or higher, or cold forging forging in a temperature range of less than 300 ° C., rather than hot forging forging in a temperature range exceeding 750 ° C. . When hot forging is performed, oxide scale is generated or decarburized on the surface of the first part or the second part, and it is necessary to cut most of the surface of the first part or the second part after forging. On the other hand, the forging of the first part or the second part is performed at a lower temperature than that of the hot forging to produce the cold forging or the warm forging. This is because generation of oxide scale and decarburization in can be prevented, so that cutting after forging can be omitted or greatly reduced.

  As described above, in the first process, since the first part and the second part are both simple shapes, rough shape to a shape close to the final product shape is obtained by warm forging or cold forging in the first process. Can be molded. For this reason, cutting after forging can be omitted or greatly reduced.

(Second step)
In the second step performed subsequent to the first step described above, the surface hardening treatment is applied to the first component and the second component, respectively, before combining the first component and the second component manufactured by forging. Apply. At this time, in the present embodiment, compared with the case where the surface hardening treatment is performed on the conventional CVT pulley disk in which the sheave portion 9 and the shaft portion 10 are integrally formed, the first component constituting the sheave portion 9 and Since the second part constituting the shaft portion 10 is individually subjected to the surface hardening process, the shape of the part to be subjected to the surface hardening process is simple, so that it can be easily cooled axisymmetrically and the surface hardening process is performed. The size of the component is reduced, and the variation in temperature depending on the location during cooling is reduced, whereby the amount of distortion of each of the first component and the second component after the surface hardening process can be suppressed to a small level.

  In this case, it is desirable to use a carburizing process or a carbonitriding process as the surface hardening process for the first part, and it is desirable to use an induction hardening process as the surface hardening process for the second part.

  That is, since the shaft portion 10 subjected to induction hardening as the surface hardening treatment is heated only in its surface layer as compared with the shaft portion 10 subjected to carburizing hardening, the amount of distortion due to the surface hardening treatment is small. Become.

Although carburized and hardened case-hardened steel has excellent wear resistance, it has poor bending fatigue strength and rolling fatigue life compared to induction-hardened medium carbon steel.
On the other hand, the bending fatigue strength and rolling fatigue life of induction-hardened medium carbon steel are improved compared to carburized and quenched case-hardened steel. Since the time is short, the growth of crystal grains is suppressed, (B) the surface is not heated due to the short heating time, and (C) only the surface layer is heated. And (D) the depth of the hardened layer by induction hardening is a factor.

  For this reason, it is desirable to use a carburizing process or a carbonitriding process as the surface hardening process for the first part forming the sheave portion 9 that requires wear resistance, while bending fatigue strength and rolling fatigue life are required. It is desirable to use induction hardening as the surface hardening process for the second component forming the shaft portion 10.

  After this, both the first part and the second part are tempered as necessary, and if there is a slight amount of distortion, they are subjected to slight cutting, and further as necessary. Polishing for giving a predetermined surface roughness is performed.

  In this way, the base material portion of the first part forming the sheave portion 9 is a cut of a round steel material having a C content of 0.1% to 0.3% → cold forging or warm forging (shaft Through hole formation) → Cutting (minimal) → Carburizing and quenching (surface hardening treatment) → Tempering as necessary → Cutting (minimal) → Polishing as necessary, or cutting of round steel material → Cold forging or temperature It is manufactured through the steps of intermediate forging, shaft through-hole formation, cutting (minimum), carburizing and quenching (surface hardening treatment), tempering if necessary, cutting (minimum), and polishing if necessary.

On the other hand, the second part constituting the shaft portion 10 is a cutting of a round steel material having a C content of 0.4% or more and 1.0% or less → cold forging or warm forging → cutting (very small) → high frequency quenching ( (Surface hardening treatment) → Tempered as necessary → Cutting (very small) → If necessary, it is manufactured through a process of polishing.
(Third step)
The first component and the second component that have finished the surface hardening process in the second step described above, the shaft portion of the second component is passed through the through hole formed in the first component, for example, press-fitting, They are integrated by shrink-fitting or by fixing and combining them by well-known and conventional means such as splines.

  In this way, the first part forming the sheave portion 9 in which the carburized layer or the carbonitriding layer is formed on the inclined surface with which the V-belt abuts, and the induction-hardened layer connected to the sheave portion 9 are formed. A second part different from the first part forming the shaft part 10 is integrated, and a through hole for penetrating the shaft part 10 in the second part is formed in the first part. The disc for the CVT pulley of this embodiment is manufactured.

  The material of the first part constituting the CVT pulley disk of this embodiment is C: 0.1% or more and 0.3% or less of steel, and the material of the second part is C: 0.4%. More than 1.0% steel.

  Thus, according to the present embodiment, the first part forming the sheave part 9 and the second part forming the shaft part 10 are roughly molded to a state close to the final product shape by warm forging or cold forging. Therefore, it is possible to omit or greatly reduce the cutting process that has been inevitably performed after forging so far, and thus the manufacturing cost of the disk for the CVT pulley can be greatly reduced.

  In addition, when forming the through hole for penetrating the shaft in the first part after cold forging or warm forging, machining is performed after forging, but the number of steps required for this machining is small. Therefore, also in this case, it is possible to fully enjoy the benefits of omission of cutting after forging or a significant reduction.

  In addition, according to the present embodiment, after the first part and the second part are warm forged or cold forged, respectively, and before being combined with each other, the first part and the second part are respectively surfaced. Since the curing process is performed, the surface curing process is performed with a simplified and miniaturized size and shape, the amount of distortion generated by the surface curing process can be suppressed, and the cutting process that must be performed after the surface curing process is omitted. Alternatively, it can be significantly reduced, and when carburizing and quenching is performed as a surface hardening treatment, the treatment time can be shortened, so that the manufacturing cost of the CVT pulley disk can also be reduced from this point.

  Furthermore, according to the present embodiment, the surface hardening treatment applied to the first component and the second component is optimized, specifically, the carburizing treatment or carbonitriding treatment is performed on the first component. In addition, by subjecting the second part to induction hardening, the amount of strain generated by the surface hardening treatment can be further suppressed, and the wear resistance required for the sheave portion and the bending fatigue required for the shaft portion All of strength and rolling fatigue life can be fully satisfied.

  Therefore, according to the present invention, the manufacturing cost of the CVT pulley disk can be greatly reduced, and the CVT itself can be reduced in weight and size. Furthermore, it can be expected that the CVT will be mounted on a vehicle equipped with an engine having a higher output and a higher torque than a vehicle on which the CVT has been mounted so far.

Furthermore, the present invention will be described more specifically with reference to examples.
Steels a and b having the chemical composition shown in Table 1 were melted in a 180 kg vacuum melting furnace and cast into an ingot. An ingot made of steels a and b was heated at 1250 ° C. for 30 minutes, and then hot forged at a finishing temperature of 950 ° C. or higher to obtain steel bars having a diameter of 20 mm and 65 mm. After these steel bars were allowed to cool to room temperature, they were further heated at 925 ° C. for 1 hour and then allowed to cool to room temperature.

  Ono-type rotation with a 20mm diameter steel bar made of steel a, with a parallel part diameter of 8mm, length of 25mm, and a R1 notch formed in the center of the parallel part, with a shoulder radius of 24mm. A bending fatigue test piece was cut out. The Ono type rotating bending fatigue test piece was subjected to carburizing and quenching and low temperature tempering under the conditions shown in the graph of FIG. In addition, the code | symbol Cp in the graph of FIG. 4 means a carbon potential.

  On the other hand, an Ono-type rotary bending fatigue test piece having the same dimensions was cut out from a steel bar made of steel b having a diameter of 20 mm by cutting. This Ono-type rotating bending fatigue test piece is induction-hardened under the conditions that the maximum heating temperature is 950 to 1000 ° C. and the curing depth (meaning effective hardened layer depth, hereinafter the same) is about 2 mm at the notch bottom. After tempering at 170 ° C. for 1 hour using a heat treatment furnace, a rotating bending fatigue test was conducted.

In the rotating bending fatigue test, seven test pieces were used per steel type, and the maximum stress that was not broken in 10 ⁷ times was defined as the fatigue strength.
As a result of the rotating bending fatigue test, the fatigue limit of the steel a subjected to carburizing and quenching was 550 MPa, whereas the fatigue strength of the steel b subjected to induction hardening was 720 MPa. Therefore, it turns out that rotation bending fatigue strength can be improved significantly by changing the heat processing of the shaft part 10 of the disk for CVT pulleys from carburizing quenching to induction quenching like this invention.

  Next, a test piece having a diameter of 60 mm and a thickness of 5 mm was produced from a steel bar made of steel a having a diameter of 65 mm by cutting. This test piece was carburized and quenched and tempered under the conditions shown in the graph of FIG. 4, and then the surface was polished to a mirror surface to prepare a test piece. And the rolling fatigue test was done using this test piece.

  On the other hand, test pieces having the same dimensions were produced from a steel bar made of steel b having a diameter of 65 mm by cutting. This test piece was induction-quenched under the conditions that the maximum heating temperature was 950 to 1000 ° C. and the curing depth was about 2 mm, and further tempered at 170 ° C. for 1 hour using a normal heat treatment furnace, and then the surface was mirror-finished A test piece was prepared by polishing. And the rolling fatigue test was done using this test piece.

The rolling fatigue test was carried out using a thrust type rolling fatigue tester, using No. 60 spindle oil as the lubricating oil, under a load condition of a Hertz maximum contact stress of 540 kgf / mm ² and a rotational speed of 1200 rpm.

  Ten test pieces per steel type were used for the rolling fatigue test. The rolling fatigue life is plotted on a Weibull probability paper with the rolling fatigue life of each of the 10 test pieces for each condition plotted on the vertical axis and the cumulative failure probability on the horizontal axis, and the rolling fatigue life on the horizontal axis. A straight line was drawn to determine the rolling fatigue life (hereinafter referred to as “L30 life”) at which the cumulative frequency failure probability was 30%.

As a result, the L30 life of the steel a subjected to carburizing and quenching was 2.2 × 10 ⁷ times, whereas the L30 life of the steel b subjected to induction hardening was 4.9 × 10 ⁷ times. Therefore, it can be seen that the rolling fatigue life can be significantly improved by changing the heat treatment of the shaft portion 10 from carburizing quenching to induction quenching as in the present invention.

  Next, after heating a steel bar having a diameter of 65 mm made of steel a or steel b at 1250 ° C. for 30 minutes, the hot forging is finished at a finishing temperature of 950 ° C. or higher, and the cross-sectional shape and dimensions shown in FIG. mm, and then allowed to cool to room temperature, further heated at 925 ° C. for 1 hour, and then allowed to cool to room temperature.

Carburizing and quenching and low-temperature tempering were performed on each of five parts 11, 12, and 13 produced from steel a under the conditions shown in the graph of FIG.
On the other hand, induction hardening is performed on the part 12 made of steel b under the conditions that the maximum heating temperature is 950 to 1000 ° C. and the hardening depth is about 2 mm, and further tempering is performed at 170 ° C. for 1 hour using a normal heat treatment furnace. It was.

  The component 11 simulates a conventional CVT pulley disk in which the sheave portion 9 and the shaft portion 10 are integrally formed. The part 12 simulates the second part of the present invention that forms the shaft 10, and the part 13 simulates the first part of the present invention that forms the sheave 9.

  For each of five parts 11 and 12 made from steel a subjected to carburizing and quenching and low temperature tempering, and five parts 12 made from steel b, V-shaped rollers having a width of 5 mm are provided below both ends of the shaft portion 10. The shaft portion 10 is rotated and the shaft portion 10 is rotated, and the amount of deflection (maximum height-maximum height) at the central portion in the longitudinal direction of the shaft 10 is measured by a normal method. It was calculated as the amount of shaft runout.

  Further, as shown in FIG. 6, each of five parts 11 or 13 made from steel a subjected to carburizing and quenching and low-temperature tempering is placed on a V-shaped roller 14 having a width of 5 mm, and the part 11 or 13 is rotated. Then, the shake amount (maximum height-maximum height) at a position 10 mm inside from the outer periphery was measured, and the average value of the five shake amounts was obtained as the surface shake amount of the component.

  The axial shake amount and the face shake amount thus obtained are shown together in Table 2.

  As can be seen from Table 2, by dividing the part 11 into the parts 12 and 13, both the amount of shaft runout and the amount of runout are reduced even when the same carburizing and quenching is performed. It can also be seen from Table 2 that the amount of shaft run-out decreases by changing the heat treatment method for the component 13 from carburizing quenching to induction quenching.

  Therefore, after the CVT pulley disc is molded separately into the first part forming the sheave part 9 and the second part forming the shaft part 10, the first part is subjected to carburizing and quenching and the second part is formed. It can be seen that the amount of distortion that inevitably occurs with the surface hardening treatment can be greatly suppressed by combining the first component and the second component after induction hardening.

  From the above results, it can be seen that the CVT disk according to the present invention not only has an excellent bending fatigue strength and rolling fatigue life, but also has a small amount of distortion caused by the surface hardening treatment.

  Steels a and b having the chemical compositions shown in Table 3 were melted and continuously cast in a 70-ton converter, and then 180 mm square billets were obtained by split rolling in the usual manner. The billet was heated at 1250 ° C. for 30 minutes and then hot-rolled at a finishing temperature of 950 ° C. or higher to obtain a steel bar having a diameter of 65 mm. A part of the steel bar having a diameter of 65 mm was heated at 760 ° C. for 2 hours, then cooled to 670 ° C. at a cooling rate of 10 ° C./hour, and then allowed to cool to room temperature. In addition, the steel bar before performing this heat processing is described as steel a and b, and the steel bar which performed the heat processing mentioned above about this steel bar a and b is described as a and b.

  Three types of columnar test pieces of diameter 60 mm and length 282 mm, diameter 60 mm and length 220 mm, diameter 60 mm and length 74 mm by machining from steel bars a, b, a-s and b-s with a diameter of 65 mm Was cut out. These three types of cylindrical test pieces are expressed as test piece X, test piece Y, and test Z in the order of length.

Production of the part 15 shown in FIG. 7 from the test piece X, production of the part 16 shown in FIG. 7 from the test piece Z, and production of the part 17 shown in FIG.
The component 15 simulates a conventional CVT pulley disk in which the sheave portion 9 and the shaft portion 10 are integrally formed. Further, the part 16 simulates the second part of the present invention that forms the shaft 10, and the part 17 simulates the first part of the present invention that forms the sheave 9.

  As a result of forging under the conditions shown in Table 4, the shape is good by dividing the first part and the second part as shown in Table 4 and performing the forging temperature in the warm region or the cold region. It can be seen that molding can be performed in a state where there is little generation of scale and no decarburization.

  Since it can be molded in such a state, drilling, rough turning, and cutting of the first part and the second part of the cutting can be omitted or greatly reduced.

  Each part produced in test numbers 1, 5, 6 and 9 in Table 4 was heat-treated under the conditions shown in FIG. Moreover, induction hardening was performed on the parts produced by test number 8 in Table 4 under conditions that the maximum heating temperature was 950 to 1000 ° C. and the curing depth was about 2 mm, and further, 170 ° C. for 1 hour using a normal heat treatment furnace. Tempering was performed.

  Among the parts subjected to the above heat treatment, the parts produced by test numbers 5 and 6 and the parts produced by test numbers 8 and 9 are the same as the position of the sheave portion of part A shown in FIG. They were integrated by being combined and penetrated and fixed. The penetration and fixation were performed by press-fitting.

  3 parts produced by the above procedure, that is, the part produced by test number 1, the part produced by test numbers 5 and 6, integrated by passing through and fixed, produced by test numbers 8 and 9 The parts integrated by penetrating and fixing the parts are hereinafter referred to as parts α, β, and γ, respectively.

  The parts α, β, and γ are mounted on a V-shaped roller having a width of 5 mm arranged below both ends of the shaft portion, and the parts α, β, and γ are rotated, and the amount of deflection at the central portion in the longitudinal direction of the shaft ( (Maximum height-maximum height) was measured by an ordinary method, and the amount of deflection was determined as the amount of shaft runout of the component. Further, the components α, β, and γ are mounted on a V-shaped roller 18 having a width of 5 mm as shown in FIG. 9, and the components α, β, and γ are rotated, and the deflection amount (maximum height) is 10 mm inside from the outer periphery. (Height-maximum height) was measured, and the amount of deflection was determined as the amount of surface deflection of the component.

  The axial shake amount and the face shake amount measured in this way are shown together in Table 5.

  As can be seen from Table 5, by converting the integral part 15 in FIG. 7 into a separate piece from the parts 16 and 17, both the amount of shaft runout and the amount of runout are reduced even when the same carburizing and quenching is performed. .

Further, as shown in Table 5, it can be seen that the amount of shaft runout is further reduced by changing the heat treatment method of the component 16 from carburizing quenching to induction quenching.
Therefore, after the CVT pulley disk is divided into the first component 17 and the second component 16, the surface hardening treatment suitable for each is performed, and then the second component is passed through the first component. It is understood that it is effective to integrate by fixing

FIG. 1 is an explanatory view schematically showing the principle of continuously variable transmission at low speed by CVT, and FIG. 1A is a perspective view showing the entire configuration of CVT in a partially broken state, FIG. FIG. 1B is a view taken in the direction of arrow A in FIG. 1A, and FIG. 1C is a view taken in the direction of arrow B in FIG. FIG. 2 is an explanatory view schematically showing the principle that CVT is performed at a high speed by CVT, and FIG. 2A is a perspective view schematically showing the entire configuration of CVT in a partially broken state. FIG. 2B is a view as viewed from an arrow A in FIG. 2A, and FIG. 2C is a view as viewed from an arrow B in FIG. It is explanatory drawing which shows the structure of V belt. It is a graph which shows the conditions of carburizing quenching and low temperature tempering in Example 1. FIG. 3 is an explanatory diagram showing the shape of each component in Example 1. FIG. 3 is an explanatory diagram conceptually showing a method of measuring a surface blur amount in Example 1. It is explanatory drawing which shows the shape of each component in Example 2. FIG. It is a graph which shows the conditions of carburizing quenching and low temperature tempering in Example 2. FIG. 6 is an explanatory diagram conceptually showing a method of measuring the amount of surface blur in Example 2.

Explanation of symbols

1 V belt type continuously variable transmission (CVT)
2, 3 pulley
2a and 2b, 3a and 3b Disc 4 Continuously variable transmission belt (V belt)
5, 6 Ring 7 Element (belt piece)
8 Inclined surface 9 Sheave part 10 Shaft part 11, 15 Conventional CVT pulley disk 12, 16 Second part 13, 17 in the present invention First part in the present invention

Claims (5)

After manufacturing a first part forming a sheave part having an inclined surface with which the continuously variable transmission belt abuts and a second part forming a shaft part connected to the sheave part by molding and surface hardening treatment, respectively. Manufacturing a disk for a V-belt type continuously variable transmission pulley including the sheave part and the shaft part by combining and integrating the first part and the second part ; The base material part of the part is made of steel of C: 0.1 to 0.3% by mass, the second part is made of steel of C: 0.4 to 1.0% by mass, and For the V-belt continuously variable transmission pulley, the surface hardening treatment for one part is carburizing or carbonitriding, and the surface hardening treatment for the second part is induction hardening . Disc manufacturing method.   The through-hole for combining the second part with the first part is formed simultaneously with the molding process or after the molding process and before combining with the second part. A method of manufacturing a disk for a V-belt type continuously variable transmission pulley as described. The method for manufacturing a disk for a V-belt type continuously variable transmission pulley according to claim 1 or 2, wherein the molding of the first part and / or the second part is forging. The method of manufacturing a disk for a V-belt type continuously variable transmission pulley according to claim 3 , wherein the forging is warm forging or cold forging. A first part that forms a sheave portion in which a carburized layer or a carbonitriding layer is formed on an inclined surface with which the continuously variable transmission belt abuts, and a shaft portion in which an induction-hardened layer that is connected to the sheave portion is formed. The second part different from the first part is integrated , and the base material part of the first part is made of steel of C: 0.1 to 0.3% by mass. The second part is made of C: 0.4 to 1.0% by mass of steel, and is a disk for a V-belt type continuously variable transmission pulley.

Images