JP2013122286A - Continuously variable transmission pulley and continuously variable transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a continuously variable transmission pulley suppressing softening when a temperature rises due to heat generation associated with frictional contact with a belt and improving wear resistance of a sheave surface so that it is durable for the use at a high surface pressure.SOLUTION: In a continuously variable transmission pulley with a sheave surface using steel containing at least silicon (Si) and chromium (Cr) and subjected to surface hardening heat treatment and in frictional contact with a continuously variable transmission belt, the Si content is set to 0.35-1.2 mass%, the Cr content is set to 0.30-1.25 mass%, carburizing and quenching and tempering are performed in the surface hardening heat treatment, the surface carbon C content of the sheave surface after the surface hardening heat treatment is set to 0.65-1.0 mass%, and relations of H=160×C+65×Si+30×Cr+455>625 (Hv) are satisfied, where the surface hardness H of the sheave surface after the tempering at the maximum use environment temperature is obtained in terms of Vickers hardness.

Description

  The present invention relates to a pulley for a continuously variable transmission using steel containing at least silicon (Si) and chromium (Cr) and a continuously variable transmission provided with the pulley, and is durable even under a high surface pressure load. The present invention relates to a pulley for a continuously variable transmission and an continuously variable transmission including the pulley.

  The continuously variable transmission includes a continuously variable transmission pulley and a continuously variable transmission belt. Here, the continuously variable transmission pulley includes two sets of an input pulley and an output pulley. On the other hand, the continuously variable transmission belt is an endless belt stretched between an input pulley and an output pulley. The input side pulley and the output side pulley have the continuously variable transmission belt sandwiched between the sheave surfaces from both sides, and the pressing force at this time causes the input side pulley to pass through the continuously variable transmission belt to the output side pulley. Torque is transmitted to

  Currently, there is a demand for improving the fuel efficiency of automobiles from the viewpoint of environmental protection and resource protection, and it is effective to increase the gear ratio range in order to improve the fuel efficiency of a transmission. In the continuously variable transmission, by increasing the pulley diameter, the difference in the winding diameter of the continuously variable transmission belt with respect to the input-side pulley and the output-side pulley can be increased, and the gear ratio range can be increased. . However, when the pulley diameter is increased, the entire continuously variable transmission is increased in size, causing problems such as deterioration in mountability and an increase in weight, thereby reducing the effect of improving fuel efficiency.

  In order to avoid this problem, there is a method of enlarging the speed ratio width by allowing the continuously variable transmission belt to be wound around the inner portion (position closer to the center) of the pulley. In this case, the contact area between the continuously variable transmission belt and the sheave surface is reduced. Therefore, in order to transmit the torque, it is necessary to operate with a higher surface pressure acting between the continuously variable transmission belt and the sheave surface, and a strong durability is required for the sheave surface of the pulley.

  In order to ensure the durability of the sheave surface of the pulley, a high hardness is required on the surface of the sheave surface. Generally, chrome steel or chrome molybdenum steel stipulated in JIS G 4053 is used for carburizing, quenching, and tempering, followed by grinding and shot peening.

  Conventionally, the silicon (Si) content range of chromium steel and chromium molybdenum steel specified in JIS G 4053 has been increased to more than 0.35 and less than 1.0% by mass, and the sheave surface after carbonitriding has been increased. The range of carbon content on the surface is set to 0.65 to 1.40% by mass, and the relationship between the nitrogen content concentration N% of the surface of the sheave surface after carbonitriding and the surface hardness H is expressed as H ≧ −320 × N + 700. Has been proposed (see Patent Document 1).

  In addition, a pulley for continuously variable transmission is proposed in which carburization and shot peening are performed on steel having the same composition as defined in Patent Document 1 and the hardness of the surface of the sheave surface is as high as 800 Hv or more. (See Patent Document 2).

  In addition, carburizing treatment and shot peening were performed on the steel having the same composition defined in Patent Document 1 above, and the relationship between the surface hardness H of the sheave surface and the surface roughness Ra was set to H ≧ 500 × Ra + 650. A pulley for a continuously variable transmission has been proposed (see Patent Document 3).

JP 2009-68608 JP JP 2009-68609 A JP 2009-185321 A

  When a high surface pressure is repeatedly applied from the belt to the sheave surface, the sheave surface of the pulley for the continuously variable transmission is worn with fatigue cracks on the sheave surface of the pulley, and is damaged. Further, the sheave surface generates heat and increases in temperature due to frictional contact with the continuously variable transmission belt during operation, and the sheave surface is softened to promote wear accompanied by fatigue cracks. When the pulley is not in operation, there is no frictional contact with the belt, and the pulley is naturally cooled to lower the temperature. That is, the sheave surface is subjected to a so-called tempering process by heat generation during operation and natural cooling during non-operation.

  On the other hand, in the continuously variable transmission pulleys described in Patent Documents 1, 2, and 3, the relationship between the nitrogen concentration, the compressive residual stress, and the surface roughness including the range of the surface hardness of the sheave surface is shown. In addition to reducing the wear on the sheave surface, the idea of suppressing the softening of the hardness in a high temperature use environment due to frictional heat generation is shown. In addition, as an influencing factor for ensuring wear resistance, each relationship is defined using initial hardness.

That is, in the continuously variable transmission pulleys described in Patent Documents 1, 2, and 3, the respective contents of silicon (Si), chromium (Cr), and carbon (C) after carbonitriding are defined ( Increasing) increases the sheave surface hardness. A technique for increasing the hardness of the sheave surface in the same manner by carbonitriding is also described.
In use, the temperature rises due to heat generated by frictional contact with the belt, and the heat softens the sheave surface. As a result, it is considered that the wear of the sheave surface is promoted, but these are not considered in the conventional literature.

  In the present invention, the idea that it is necessary to suppress the softening of the pulley sheave surface due to heat generated by frictional contact with the belt is the same as in Patent Documents 1, 2, and 3. However, the present invention is a thermal history in the environment of use, and further paying attention to tempering hardness correlated with high temperature hardness, by setting the range of the carbon content after the alloy component of the steel material and the surface hardening heat treatment, We obtained new knowledge that the wear resistance can be improved. The range is different from the range of the pulley for continuously variable transmissions described in Patent Documents 1, 2, and 3.

  The present invention has been made paying attention to the above-mentioned problems, and suppresses softening when the temperature rises due to heat generated by frictional contact with the belt, improves wear resistance of the sheave surface, and is used at a high surface pressure. It is a problem to be solved to provide a continuously variable transmission pulley capable of withstanding the above and a continuously variable transmission including the pulley.

To achieve the above object, the present invention uses a steel containing at least silicon (Si) and chromium (Cr) and subjected to surface hardening heat treatment, and is in frictional contact with a continuously variable transmission belt. In a continuously variable transmission pulley having a surface,
In the steel, the content of the silicon (Si) is set to Si: 0.35 to 1.2% by mass,
The chromium (Cr) content is set to Cr: 0.30 to 1.25% by mass,
The surface hardening heat treatment includes carburizing quenching and tempering,
The content of carbon (C) on the surface of the sheave surface after the surface curing heat treatment is set to C: 0.65 to 1.0% by mass,
The surface hardness of the sheave surface after tempering at the maximum use environment temperature is H in micro Vickers hardness, the carbon (C) content on the surface of the sheave surface is C mass%, and the silicon (Si) content is Si mass%, when the chromium (Cr) content is Cr mass%,
H = 160 × C + 65 × Si + 30 × Cr + 455> 625 (Hv)
It is characterized by satisfying the relationship.

  Sieve surface temperature due to sliding heat generation in continuously variable transmission pulleys where high surface pressure is applied to the sheave surface by making silicon (Si) and chromium (Cr), which have high softening resistance, within the above-mentioned range. Softening of the hardness of the sheave surface due to the rise is suppressed. For this reason, it is possible to suppress the occurrence of fatigue cracks on the sheave surface and to improve the wear resistance of the sheave surface. That is, the continuously variable transmission pulley of the present invention suppresses softening when the temperature rises due to heat generated by frictional contact with the belt, improves the wear resistance of the sheave surface, and can withstand use at high surface pressure. Can be obtained.

It is a perspective view which shows the maximum deceleration state with the continuously variable transmission provided with the pulley for continuously variable transmission of Example 1. FIG. It is an expansion perspective view which shows a part of belt for continuously variable transmission. It is a graph which shows the relationship between silicon (Si) content in chromium which forms the pulley for continuously variable transmission of Example 1, chromium (Cr) content, and maximum use environment temperature tempering hardness, (a) is heat processing. The case where the subsequent carbon (C) content is 0.65% by mass is shown, and (b) shows the case where the carbon (C) content after the heat treatment is 0.8% by mass. It is a graph which shows the relationship between chromium (Cr) content in the steel which forms the pulley for continuously variable transmission of Example 1, and carbon (C) content after heat processing for every silicon (Si) content. It is a table | surface which shows the composition of the steel in the test body for abrasion tests of Example 1, and the test body of a comparative example, carbon content after heat processing, and maximum use environment temperature tempering hardness. It is a table | surface which shows the wear depth after the abrasion test of Example 1 and a comparative example. It is a map figure which shows the result of the abrasion test of Example 1 and a comparative example.

  EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing the continuously variable transmission pulley of this invention and the continuously variable transmission provided with the same is demonstrated based on Example 1 shown in drawing.

[Configuration of continuously variable transmission]
FIG. 1 is a perspective view showing a maximum deceleration state in a continuously variable transmission including a continuously variable transmission pulley according to a first embodiment. FIG. 2 is an enlarged perspective view showing a part of a continuously variable transmission belt. Hereinafter, the structure of the continuously variable transmission provided with the pulley for continuously variable transmission of Example 1 is demonstrated.

  As shown in FIG. 1, the continuously variable transmission M according to the first embodiment includes a continuously variable transmission pulley P and a continuously variable transmission belt V.

  The continuously variable transmission pulley P includes two sets of an input pulley 1 and an output pulley 2. Here, the torque from the engine (not shown) is transmitted to the input pulley 1 through the torque converter and the forward / reverse switching mechanism, and from the output pulley 2 to the reduction gear and drive (not shown) via the continuously variable transmission belt V. It is transmitted to the tire through the shaft. The input-side pulley 1 has a fixed pulley 11 and a slide pulley 12, and the pulley interval is variable in the input shaft direction. The output side pulley 2 has a fixed pulley 21 and a slide pulley 22, and the pulley interval is variable in the output shaft direction. The slide pulleys 12 and 22 generate a pressing force in a direction in which the continuously variable transmission belt V is pinched by piston hydraulic pressure. Furthermore, each pulley 11, 12, 21, 22 has a sheave surface 11a, 12a, 21a, 22a that contacts the continuously variable transmission belt V. In the continuously variable transmission pulley P of the first embodiment, the sheave angle, which is the inclination of each sheave surface 11a, 12a, 21a, 22a, is set to about 11 °, for example.

  The continuously variable transmission belt V is an endless belt stretched between the input side pulley 1 and the output side pulley 2. As shown in FIG. 2, the continuously variable transmission belt V includes a laminated ring 3 in which a large number of annular rings are stacked from inside to outside, and sheave surfaces 11a, 12a, 21a of two sets of pulleys 1, 2 on both sides. , 22b and a plate-like element 4 having a flank surface 4a in contact with it. As shown in FIG. 2, the continuously variable transmission belt V is sandwiched from both sides in saddle grooves 4b, 4b of elements 4,. These multiple elements 4 are combined to form a bundle. When the continuously variable transmission belt V is sandwiched between the fixed pulleys 11 and 21 and the slide pulleys 12 and 22, when the torque is transmitted, the laminated ring 3 generates a force that causes the element 4 to spread in the outer diameter direction. The element 4 supports the pressing force from the two sets of pulleys 1 and 2. The laminated ring 3 is formed by welding a thin plate of the highest strength material equivalent to maraging steel having a thickness of about 0.2 mm to form an annular ring, and laminating a plurality of annular rings having slightly different diameters from inside to outside. Consists of. The element 4 is a punched molded product obtained by punching a steel plate having a thickness of about 2 mm with a punching die.

[Composition range of steel forming pulley for continuously variable transmission]
FIG. 3 is a graph showing the relationship between the silicon (Si) content and the chromium (Cr) content in the steel forming the continuously variable transmission pulley of Example 1 and the maximum operating environment temperature tempering hardness. a) shows an example in which the carbon (C) content after heat treatment is 0.65 mass%, and (b) shows an example in which the carbon (C) content after heat treatment is 0.8 mass%.

  The continuously variable transmission pulley P is made of steel containing at least silicon (Si) and chromium (Cr).

As shown in FIG. 3, the steel has a silicon (Si) content of 0.35 to 1.2 mass% and a chromium (Cr) content of 0.30 to 1.25 mass. Set to the range of%. Further, the carbon (C) content on the surfaces of the sheave surfaces 11a, 12a, 21a, and 22a after the surface hardening heat treatment for performing carburizing and tempering is set in the range of 0.65 to 1.0 mass%. And, the surface hardness of the sheave surfaces 11a, 12a, 21a, 22a after tempering at the maximum use environment temperature is H as micro Vickers hardness, and the surface of the sheave surfaces 11a, 12a, 21a, 22a after heat treatment contains carbon (C). When the amount is C mass%, the silicon (Si) content is Si mass%, and the chromium (Cr) content is Cr mass%, each content of silicon (Si), chromium (Cr), and carbon (C) after heat treatment The amount is set to be within the above range and satisfy the relationship of the following formula (1).
H = 160 × C + 65 × Si + 30 × Cr + 455> 625 (Hv) (1)
Here, the maximum use environment temperature is a temperature set according to the maximum value of the sheave surface temperature that rises due to friction with the continuously variable transmission belt V during use of the continuously variable transmission M.

In FIG. 3, the component position where the same tempering hardness can be obtained is indicated by a straight line with a lower right. And the component range of the steel forming the pulley P for continuously variable transmission has a sheave surface hardness of 625 Hv or more, and the silicon (Si) content and the chromium (Cr) content correspond to the above ranges, respectively. This is an area (area indicated by diagonal lines).
Note that the area corresponding to the change in the content of carbon (C) after the heat treatment changes. When carbon (C) increases after the heat treatment, the corresponding area (area shown by diagonal lines) expands.

The steel component forming the continuously variable transmission pulley P contains one or more of molybdenum (Mo), niobium (Nb), titanium (Ti), nickel (Ni), and boron (B) within the following ranges. May be.
Molybdenum (Mo) content Mo: 0.01 to 0.30 mass%,
Niobium (Nb) Content Nb: 0.005 to 0.2% by mass,
The content of titanium (Ti) is Ti: 0.005 to 0.2% by mass,
The content of nickel (Ni) is Ni: 0.05-3.0 mass%,
The content of boron (B) is B: 0.0005 to 0.005 mass%.

  Silicon (Si) is useful for improving temper softening resistance. The temper softening resistance can be improved by setting the silicon (Si) content to 0.35% by mass or more. However, if the silicon (Si) content is set to more than 1.2% by mass, the toughness may be lowered, and when hot forging is performed at the time of pulley manufacture, the aggressiveness to the mold is increased and the productivity is increased. Worsen. Further, when a gas carburizing treatment is performed as a surface hardening heat treatment, there is a risk of inhibiting the carburizing property. For this reason, silicon (Si) content was set to 0.35-1.2 mass%.

  Chromium (Cr) is an element that improves temper softening resistance, and its content is set to 0.30% by mass or more in combination with the silicon (Si) content. On the other hand, if the chromium (Cr) content is set to more than 1.25% by mass, the workability may be lowered. For this reason, chromium (Cr) content was set to 0.30 to 1.25 mass%.

  Molybdenum (Mo) is an element that improves temper softening resistance, and when contained, improves temper wear resistance. Since the wear resistance is not deteriorated by inclusion, even if it is contained in the range of 0.01 mass% as an inevitable impurity element in the production of steel materials to the upper limit of 0.30 mass% set in JIS steel Good.

  Niobium (Nb) combines with carbon and nitrogen in the steel to form carbonitrides, has a function of suppressing the coarsening of crystal grains in the carburizing process, and exhibits the effect of suppressing a decrease in impact resistance. In order to expect this effect, it is necessary to set the niobium (Nb) content to 0.005 mass% or more. On the other hand, when the niobium (Nb) content exceeds 0.2 mass%, the coarsening suppression effect is saturated. For this reason, the content of niobium (Nb) is set to 0.005 to 0.2% by mass.

  Titanium (Ti) combines with carbon and nitrogen in the steel to form carbonitrides, has the effect of suppressing the coarsening of crystal grains in the carburizing process, and exhibits the effect of suppressing the reduction in impact resistance. In order to expect this effect, it is necessary to set the titanium (Ti) content to 0.005 mass% or more. On the other hand, when the titanium (Ti) content exceeds 0.2% by mass, the effect of suppressing the coarsening of crystal grains is saturated. For this reason, titanium (Ti) content is set to 0.005-0.2 mass%.

  Nickel (Ni) is an effective element for ensuring the hardenability of steel. However, in order to expect this effect, it is necessary to set the nickel (Ni) content to 0.05 mass% or more. On the other hand, if the nickel (Ni) content exceeds 3.0% by mass, the workability is lowered. For this reason, nickel (Ni) content is set to 0.05-3.0 mass%.

  Boron (B) is an effective element for ensuring the hardenability of steel. However, in order to expect this effect, it is necessary to set the boron (B) content to 0.0005 mass% or more. On the other hand, if the boron (B) content exceeds 0.005 mass%, the workability is lowered. Therefore, the boron (B) content is set to 0.0005 to 0.005 mass%.

Here, in carburizing quenching and tempering for determining the hardness of the sheave surface, vacuum carburization (vacuum carburizing) is performed in which the steel product is carburized by heating in a carburizing gas decompressed in a vacuum furnace. It is desirable. When performing a normal gas carburizing process (atmosphere carburizing process), the carburizing property is affected by the silicon (Si) content and the chromium (Cr) content. Therefore, in order to improve the gas carburizing performance, it is necessary to make the silicon (Si) content and the chromium (Cr) content within the optimum ranges.
In order to ensure the carbon (C) content of 0.65 mass% by gas carburizing (atmosphere carburizing), the silicon (Si) content is set to 0.85 mass% or less and the chromium (Cr) content is set. It is desirable to set the amount to 0.8% by mass or less.

  As shown in FIG. 5, steel materials containing different silicon (Si) and chromium (Cr) (Example 1 is steel materials No. 1-19, comparative example is steel materials No. 20-28), and hot forging. Then, machining, vacuum carburizing and quenching treatment, tempering treatment, sheave surface grinding and polishing, shot peening treatment on the sheave surface, and film lapping were performed to produce a pulley P for continuously variable transmission shown in FIG. At this time, the surface roughness of the sheave surface was in the range of 0.15 to 0.2 μm in terms of the calculated average roughness Ra. After producing several pulleys for continuously variable transmissions with the same components and under the same manufacturing conditions, partly used for wear tests, and partly air-tempered for 1 hour at the maximum operating environment temperature. The hardness of the sheave surface was measured. At this time, the carbon content after heat treatment of the sheave surface and the maximum use environment temperature tempering hardness are as shown in FIG.

[Abrasion test]
The continuously variable transmission equipped with the test pulley manufactured as described above was attached to a device capable of arbitrarily changing the input torque, and a wear test was performed. The winding position of the continuously variable transmission belt V is fixed to the small-diameter portion of the sheave surfaces 11a, 12a of the input-side pulley 1 so that the gear ratio becomes the maximum as an operating condition of the pulley, and the input torque and the sheave surfaces 11a, 11a, The sheave surface wear test was conducted with the surface pressure applied to 12a being overloaded.

  The abrasion test was performed by operating for 50 hours under the conditions of an input torque of 300 Nm, an input rotation speed of the input pulley 1 of 6000 rpm, and an oil temperature of 100 ° C. And the stepped depth by the abrasion which arose on the sheave surfaces 11a and 12a of the input side pulley 1 was measured using the shape measuring machine. This step depth is defined as “wear depth”.

  The results are shown in FIGS.

  From this result, it is understood that the wear depth of the sheave surfaces 11a, 12a, 21a, and 22a has a strong correlation with the maximum use environment temperature tempering hardness. That is, the wear depth of the sheave surfaces 11a, 12a, 21a, and 22a tends to decrease due to the increase in the maximum use environment temperature tempering hardness. Therefore, it can be seen that the maximum operating environment temperature tempering hardness needs to be a value larger than 625 Hv in micro Vickers hardness in order to suppress the sheave surface wear amount to a level that does not hinder the function as a continuously variable transmission. .

  Furthermore, this maximum use environment temperature tempering hardness, when carbon (C) content after heat treatment is C mass%, silicon (Si) content is Si mass%, chromium (Cr) content is Cr mass%, It is obtained from the above equation (1). Therefore, the content of each steel composition is set such that the carbon (C) content after heat treatment is set to 0.65 to 1.0 mass%, and the silicon (Si) content is set to 0.35 to 1.2 mass%. It is understood that the chromium (Cr) content must be set to 0.30 to 1.25% by mass and set to a value satisfying the above formula (1).

  That is, in the test pulleys manufactured using the steel materials of the comparative examples (steel materials No. 20 to No. 28), the maximum operating environment temperature tempering hardness is 625 Hv or less. Therefore, when the surface of the sheave surfaces 11a, 12a, 21a, and 22a is tempered due to heat generated by the use of the continuously variable transmission, the sheave surfaces 11a, 12a, 21a, and 22a are softened and worn. It is thought to go forward.

  On the other hand, in the test pulleys manufactured using the steel materials of Example 1 (steel materials No. 1 to No. 19), the maximum operating environment temperature tempering hardness exceeds 625 Hv. For this reason, it is possible to suppress the sheave surface softening when the sheave surfaces 11a, 12a, 21a, and 22a are tempered by friction. As a result, the sheave surfaces 11a, 12a, 21a, and 22a are excellent in wear resistance and can withstand use at high surface pressure, so that it is considered that wear can be suppressed.

[Effect of Example 1]
In the continuously variable transmission pulley and the continuously variable transmission according to the first embodiment, the following effects can be obtained.

(1) Sheave surfaces 11a, 12a, 21a, which are made of steel containing at least silicon (Si) and chromium (Cr) and subjected to surface hardening heat treatment, and which are in frictional contact with the continuously variable transmission belt V. In the continuously variable transmission pulley P provided with 22a, the steel has a content of the silicon (Si) set to Si: 0.35 to 1.2 mass%, and a content of the chromium (Cr). Is set to Cr: 0.30 to 1.25% by mass, and the surface hardening heat treatment is performed by carburizing and tempering, and the surfaces of the sheave surfaces 11a, 12a, 21a, and 22a after the surface hardening heat treatment. The carbon (C) content of C is set to C: 0.65 to 1.0% by mass, and the surface hardness of the sheave surfaces 11a, 12a, 21a, and 22a after tempering at the maximum use environment temperature is micronized. H with Vickers hardness, carbon (C) content on the surface of the sheave surface When the amount is C mass%, the silicon (Si) content is Si mass%, and the chromium (Cr) content is Cr mass%, H = 160 × C + 65 × Si + 30 × Cr + 455> 625 (Hv)
It was set as the structure which satisfies the relationship.
For this reason, it is possible to suppress softening when the temperature rises due to heat generated by frictional contact with the belt V, improve wear resistance of the sheave surfaces 11a, 12a, 21a, and 22a, and endure use at a high surface pressure. Can do.

(2) The maximum use environment temperature is set according to the maximum value of the sheave surface temperature that rises due to friction with the continuously variable transmission belt V during use.
For this reason, in addition to the effect described in the above (1), even if the temperature of the sheave surfaces 11a, 12a, 21a, and 22a is increased by frictional heat, the wear resistance of the sheave surfaces 11a, 12a, 21a, and 22a is surely lowered. Can be prevented.

(3) In the steel, the silicon (Si) content is set to Si: 0.85 mass% or less, and the chromium (Cr) content is set to Cr: 0.8 mass% or less. The carburizing and quenching is configured to be gas carburizing and quenching.
For this reason, in addition to the effects described in (1) or (2) above, the carbon C content on the surfaces of the sheave surfaces 11a, 12a, 21a, and 22a is within a set range in gas carburizing and quenching that is easy to manage the carburizing furnace. And carburizing properties can be ensured.

(4) The steel contains at least one of molybdenum (Mo), niobium (Nb), titanium (Ti), nickel (Ni), and boron (B), and the molybdenum (Mo). The first condition for setting the content of Mo to 0.01 to 0.30% by mass, the second condition for setting the content of niobium (Nb) to Nb: 0.005 to 0.2% by mass The third condition for setting the content of titanium (Ti) to Ti: 0.005 to 0.2 mass%, and the content of nickel (Ni) to Ni: 0.05 to 3.0 mass% The fourth condition is set to satisfy the condition of at least one of the fifth conditions in which the boron (B) content is set to B: 0.0005 to 0.005 mass%.
For this reason, in addition to the effect described in any one of (1) to (3) above, if molybdenum (Mo) is added, temper softening resistance can be improved, and niobium (Nb) or titanium (Ti) can be improved. If added, coarsening of crystal grains can be suppressed, and if nickel (Ni) or boron (B) is contained, hardenability can be ensured.
That is, the wear resistance of the sheave surfaces 11a, 12a, 21a, 22a can be improved by adding an element that satisfies at least one of the above conditions.

(5) A continuously variable transmission belt V, which is provided with a continuously variable transmission pulley P having sheave surfaces 11a, 12a, 21a, 22a that are in frictional contact with the continuously variable transmission belt V. In the transmission M, the continuously variable transmission pulley P is configured as described in (1) or (2) or (3) or (4) above.
For this reason, it is possible to suppress softening when the temperature rises due to heat generated by frictional contact with the belt V, improve wear resistance of the sheave surfaces 11a, 12a, 21a, and 22a, and endure use at a high surface pressure. Can do.

  As mentioned above, although the pulley for continuously variable transmission and the continuously variable transmission of this invention were demonstrated based on Example 1, it is not restricted to this Example 1 about a concrete structure, Claim of Claim Design changes and additions are allowed without departing from the spirit of the invention according to each claim.

  In particular, the maximum use environment temperature is predicted from normal transmission use conditions, for example, the input torque of a continuously variable transmission unit, vehicle, etc., environmental conditions (for example, ambient outside air temperature, etc.), operation conditions (for example, The temperature may be set based on the correlation between the temperature of the climbing road traveling, winding road traveling, sudden acceleration / deceleration during traveling, vehicle weight according to the loading amount, etc.) and the tempering temperature in the manufacturing process.

M continuously variable transmission P continuously variable transmission pulley V continuously variable transmission belt 1 input side pulley 2 output side pulley 11a, 12a, 21a, 22a sheave surface 3 laminated ring 4 element 4a flank surface

Claims (5)

In a pulley for a continuously variable transmission using a steel containing at least silicon (Si) and chromium (Cr) and subjected to surface hardening heat treatment and having a sheave surface in frictional contact with a continuously variable transmission belt ,
In the steel, the content of silicon (Si) is set to Si: 0.35 to 1.2% by mass,
The chromium (Cr) content is set to Cr: 0.30 to 1.25% by mass,
The surface hardening heat treatment includes carburizing quenching and tempering,
The content of carbon (C) on the surface of the sheave surface after the surface hardening heat treatment is set to C: 0.65 to 1.0% by mass,
The surface hardness of the sheave surface after tempering at the maximum use environment temperature is H in micro Vickers hardness, the carbon (C) content on the surface of the sheave surface is C mass%, and the silicon (Si) content is Si mass%, when the chromium (Cr) content is Cr mass%,
H = 160 × C + 65 × Si + 30 × Cr + 455> 625 (Hv)
A pulley for a continuously variable transmission characterized by satisfying the above relationship. In the pulley for continuously variable transmission according to claim 1,
The pulley for a continuously variable transmission, wherein the maximum use environment temperature is set according to a maximum value of a sheave surface temperature that rises due to friction with the continuously variable transmission belt during use. In the pulley for continuously variable transmission according to claim 1 or claim 2,
In the steel, the content of silicon (Si) is set to Si: 0.85 mass% or less,
The chromium Cr content is set to (Cr): 0.8% by mass or less,
The pulley for continuously variable transmission, wherein the carburizing and quenching is gas carburizing and quenching. In the pulley for continuously variable transmission as described in any one of Claims 1-3,
The steel contains at least one of molybdenum (Mo), niobium (Nb), titanium (Ti), nickel (Ni), and boron (B),
A first condition in which the molybdenum (Mo) content is set to Mo: 0.01 to 0.30% by mass;
A second condition in which the content of the niobium (Nb) is set to Nb: 0.005 to 0.2% by mass;
Third condition for setting the content of titanium (Ti) to Ti: 0.005 to 0.2 mass%,
4th condition which sets content of the said nickel (Ni) to Ni: 0.05-3.0 mass%,
A pulley for a continuously variable transmission, characterized in that at least one of the fifth conditions for setting the boron (B) content to B: 0.0005 to 0.005 mass% is satisfied. In a continuously variable transmission comprising a continuously variable transmission pulley having a sheave surface in friction contact with a continuously variable transmission belt,
The continuously variable transmission pulley is a continuously variable transmission pulley according to any one of claims 1 to 4, wherein the continuously variable transmission pulley is the continuously variable transmission pulley.