JP2011196426A - Belt for continuously variable transmission and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt for a continuously variable transmission capable of improving belt durability and reliability, by preventing an element from being damaged by pulleys.SOLUTION: This belt V for the continuously variable transmission includes a laminated ring 3 and the element 4 having flank surfaces 4a on both sides. The element 4 is formed by alternately arranging a crest part 41 contacting via an oil film with the pulleys 1 and 2 and a groove part 42 for discharging lubricating oil in the pulley peripheral direction, in the pulley radial direction on the flank surfaces 4a and 4a on both sides, and a low hardness area part T set in a hardness value lower than a hardness value of an element base part 4x, is formed in a predetermined range toward the groove part 42 from a top part 41a of the crest part 41.

Description

  The present invention relates to a continuously variable transmission belt that is stretched around a pulley in a continuously variable transmission and a method for manufacturing the same.

  Conventionally, in a continuously variable transmission belt configured by sandwiching two sets of laminated rings from both sides into saddle grooves of a plurality of elements arranged in series, on the flank surface of the element that contacts the sheave surface of the pulley. In addition, there is known one in which a peak portion that contacts the sheave surface via an oil film and a groove portion for discharging lubricating oil are formed (for example, see Patent Document 1).

JP 2009-270696 JP

However, in the conventional continuously variable transmission belt, the hardness of the entire element is constant, and the hardness is the same from the base portion to the top portion even in the peak portion formed on the flank surface. For this reason, when the flank surface of the element and the sheave surface of the pulley contact each other, the flank surface is not easily worn, and it takes time until the initial wear is completed.
On the other hand, when the flank surface of the element and the sheave surface of the pulley come into contact with each other, the flank surface receives contact surface pressure, and shear stress is generated inside. This shear stress damages the sheave surface of the pulley when it exceeds a certain threshold value.
Therefore, if the flank surface is not easily worn, the shear stress generated inside the flank surface becomes excessive, and the damage accumulated on the sheave surface of the pulley increases. If the same belt running radius is repeatedly used in a state where the accumulated damage on the sheave surface is large, a step may occur on the sheave surface due to this. Furthermore, there is a problem that if the element is caught in this step at the time of shifting, an excessive stress acts on the element and the element may be damaged.

  The present invention has been made paying attention to the above problems, and provides a continuously variable transmission belt capable of preventing an element from being damaged by a pulley and improving belt durability reliability, and a manufacturing method thereof. The purpose is to do.

In order to achieve the above object, in the continuously variable transmission belt of the present invention, a laminated ring in which a large number of annular rings are stacked from the inside to the outside, and elements having flank surfaces that contact the sheave surfaces of the pulleys on both sides are provided. 2 sets of the above-mentioned laminated rings are constructed by sandwiching them from both sides into the saddle grooves of the elements arranged in series, and when transmitting torque between the 2 sets of pulleys, the elements are arranged in the outer diameter direction. The laminated ring supports the force of spreading, and the element supports the pressing force from the two sets of pulleys.
The element is formed by alternately arranging, on the flank surfaces on both sides, a peak portion that contacts the sheave surface of the pulley via an oil film, and a groove portion that discharges lubricating oil in the circumferential direction of the pulley, in the pulley radial direction,
A low hardness region portion set to a hardness value lower than the hardness value of the element base portion was formed in a predetermined range from the top portion of the peak portion toward the groove portion.

  Therefore, in the continuously variable transmission belt of the present invention, the low hardness region portion is formed in a predetermined range from the top portion of the ridge portion formed on the flank surface of the element toward the groove portion. The hardness value near the top (tip portion) decreases. As a result, when the flank surface comes into contact with the sheave surface of the pulley, the wear of the ridges is promoted and the initial wear is completed in a short time, thereby suppressing damage accumulation on the sheave surface. The sheave surface damage accumulation suppression action prevents the sheave surface from being stepped even when the same belt running radius is used, and the element does not get caught during shifting. As a result, the element can be prevented from being damaged by the pulley, and the belt durability reliability can be improved.

It is a perspective view which shows two sets of pulleys of the maximum deceleration state with the belt-type continuously variable transmission to which the belt for continuously variable transmission of Example 1 is applied. FIG. 3 is an enlarged perspective view showing a part of the continuously variable transmission belt according to the first embodiment. 1 shows elements that are constituent elements of a continuously variable transmission belt of Example 1, (a) shows an element front view, (b) shows an element side view, and (c) shows an element shown in FIG. 3 (a). An enlarged view of the flank portion F is shown. It is an enlarged view which shows the flank surface before the lapping of the element which is a component of the belt for continuously variable transmission of Example 1. FIG. It is an enlarged view which shows the flank surface after the lapping of the element which is a component of the belt for continuously variable transmission of Example 1. FIG. It is a figure which shows the relationship characteristic between the groove ratio of the element which is a component of the belt for continuously variable transmission, a punching die lifetime, and the intensity | strength of a peak part. It is a figure which shows what wrote the pulley damage threshold value and the oil discharge property NG area | region to the relational characteristic of the flat ratio of the element which is a component of the continuously variable transmission belt, and groove pitch. 3 is a flowchart illustrating a method for manufacturing an element that is a component of the continuously variable transmission belt according to the first embodiment. It is explanatory drawing which shows a punching process, (a) shows a raw material conveyance procedure, (b) shows a raw material setting procedure, (c) shows a raw material shearing procedure. It is explanatory drawing which shows a punching element, (a) shows the whole perspective view, (b) shows the front view of a flank part. It is a principal part enlarged view which shows the high frequency induction heating procedure in a tempering heat treatment process. It is a figure which shows the relational characteristic of the height of the peak part of a continuously variable transmission belt, and lapping elapsed time. FIG. 5 is a diagram showing an oil discharge NG region, a mold life NG region, and a peak strength NG region written in the relational characteristic between the flat ratio of the element, which is a component of the continuously variable transmission belt, and the groove pitch. It is a figure which shows what wrote the damage limit value in the relational characteristic of the hardness of the element which is a component of the belt for continuously variable transmission of Example 1, and the damage degree for every pulley hardness.

  Hereinafter, the best mode for realizing a continuously variable transmission belt according to the present invention will be described based on Example 1 shown in the drawings.

First, the configuration will be described.
FIG. 1 is a perspective view showing two sets of pulleys in a maximum deceleration state in a belt-type continuously variable transmission to which a continuously variable transmission belt according to a first embodiment is applied. FIG. 2 is an enlarged perspective view illustrating a part of the continuously variable transmission belt according to the first embodiment. 3A and 3B show elements that are components of the continuously variable transmission belt according to the first embodiment. FIG. 3A is a front view of the element, FIG. 3B is a side view of the element, and FIG. The enlarged view of the element flank part F of a) is shown.

  The continuously variable transmission belt V according to the first embodiment is stretched between the input-side pulley 1 and the output-side pulley 2 as shown in FIG. 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. Then, the slide pulleys 12 and 22 generate a pressing force in the direction of pinching the belt by the 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 pulleys 11, 12, 21, and 22 of the first embodiment, the sheave angle that is the inclination of the sheave surfaces 11a, 12a, 21a, and 22a is set to about 11 °, for example.

  As shown in FIG. 2, the continuously variable transmission belt V includes a laminated ring (endless band) 3 in which a large number of annular rings are stacked from inside to outside, and sheave surfaces 11a of two sets of pulleys 1 and 2 on both sides. And a plate-like element 4 having a flank surface 4a in contact with 12a, 21a, 22a.

  As shown in FIG. 2, the continuously variable transmission belt V includes two sets of laminated rings 3, 3 on both sides of the saddle grooves 4b, 4b of the elements 4,. And is configured by bundling these many elements 4. Then, when torque is transmitted with the continuously variable transmission belt V sandwiched between the two sets of pulleys 1 and 2, the laminated ring 3 supports the force that the element 4 tries to spread in the outer diameter direction. The element 4 supports the pressing force from the pulleys 1 and 2.

  Laminated ring 3 is made by welding a thin plate of the highest strength material equivalent to maraging steel with a thickness of about 0.2 mm to form an annular ring, and laminating a plurality of annular rings with slightly different diameters from inside to outside in layers. Constitute.

  The element 4 is a punched molded product obtained by punching a steel plate (material) having a thickness of about 2 mm with a punching die. As shown in FIG. 3A, the element 4 includes flank surfaces 4a and 4a, saddle grooves 4b and 4b, a neck portion 4c, a nose portion 4d, ear portions 4e and 4e, and a hole portion 4f. And a rocking edge portion 4g.

  The flank surfaces 4a and 4a are formed at positions on both sides of the element in contact with the sheave surfaces 11a, 12a, 21a and 22a of the pulleys 1 and 2. The saddle grooves 4b and 4b are formed at the element inner position where the two pairs of laminated rings 3 and 3 are sandwiched from both sides. The neck portion 4c is formed at the center position of the element sandwiched between the saddle grooves 4b and 4b. The nose portion 4d is formed to protrude in the belt traveling direction at the upper portion of the element front position. The ear portions 4e and 4e are formed extending from the nose portion 4d in the element width direction. The hole portion 4f is formed below the element back surface position corresponding to the set position of the nose portion 4d. The locking edge portion 4g is formed in the width direction at the element front surface position having the flank surfaces 4a, 4a.

  The flank surfaces 4a and 4a of the element 4 are in contact with the sheave surfaces 11a, 12a, 21a and 22a of the two sets of pulleys 1 and 2 through an oil film, as shown in FIGS. The crest portions 41 and the groove portions 42 for discharging the lubricating oil in the pulley circumferential direction are alternately arranged at equal pitches in the pulley radial direction.

  FIG. 4 is an enlarged view showing a flank surface of the element, which is a component of the continuously variable transmission belt according to the first embodiment, before wrapping. FIG. 5 is an enlarged view showing a flank surface of the element, which is a component of the continuously variable transmission belt according to the first embodiment, after lapping. FIG. 6 is a graph showing the relationship between the groove ratio of the element, which is a component of the continuously variable transmission belt, the punching die life, and the strength of the crest. FIG. 7 is a diagram showing a pulley damage threshold value and an oil dischargeability NG region written in the relational characteristic between the flat ratio of the element, which is a constituent element of the continuously variable transmission belt, and the groove pitch.

  The element 4 has a groove ratio, which is a ratio of the groove width to the sum of the peak width and the groove width of the peak portion 41 and the groove portion 42, before wrapping (rubbing) the flank surface 4a and the sheave surfaces 11a, 12a, 21a, 22a. In FIG. 5, the die strength of the punching die is ensured, and the peak strength of the peak portion 41 is set within a range. Further, the element 4 has a flat ratio, which is a ratio of the peak width of the peak portion 41 and the groove portion 42 and the total width of the groove widths, before the wrapping of the flank surface 4a and the sheave surfaces 11a, 12a, 21a, 22a and the wrapping. Later, it is set to a range that is equal to or greater than the pulley damage threshold and that ensures oil discharge.

Here, the “mountain width” is the width in the mountain groove alignment direction (left and right direction in FIGS. 4 and 5) at the top 41 a of the mountain portion 41, and the “groove width” is the mountain groove alignment at the open end of the groove portion 42. The width in the direction (left and right in FIGS. 4 and 5). The flat ratio is calculated by the following formula (1), and the groove ratio is calculated by the following formula (2).
Flat ratio = mount width / (mount width + groove width) (1)
Groove ratio = groove width / (mountain width + groove width) (2)

  “Before wrapping” refers to a state before the element 4 and the pulleys 1 and 2 are lapped (rubbed together), which is a so-called new state.

  Further, “after lapping” means a state in which the progress of wear of the element 4 caused by lapping (rubbing) between the element 4 and the pulleys 1 and 2 is settled, that is, a state in which the initial wear has been completed. The initial wear is settled from the time when the components contained in the lubricating oil combine to form a protective film and the amount of wear becomes the same as that of the protective film. The wear after this initial wear is referred to herein as wear over time. This aging wear progresses in proportion to the wrapping elapsed time (proportional to the travel distance), but it is known that the progress is extremely slow.

  Also, “the mold strength of the punching die is ensured” means that the punching die life can be maintained for a necessary period, that is, the die life is equal to or greater than a set threshold (die life threshold). “Setting the groove ratio within a range in which the mold strength of the mold is ensured” means that the groove ratio is set to a value equal to or greater than the groove ratio (α in FIG. 6) at which the life of the punching mold becomes the mold life threshold. That is. Note that the “necessary period” is set, for example, from a period in which the number of punched molded products (elements in this case) that can suppress an increase in unit price can be manufactured.

  Further, “the peak strength of the peak portion 41 is ensured” means that the peak portion 41 has a strength (rigidity) that can withstand punching, that is, the peak strength is equal to or higher than a set threshold (peak strength threshold). “The groove ratio is set in a range in which the peak strength of the peak portion 41 is ensured” means that the groove has a value equal to or less than the groove ratio (β in FIG. 6) at which the strength of the peak portion 41 becomes the peak strength threshold. Is to set the ratio.

  Further, the “pulley damage threshold” is a limit flat ratio that can allow damage (pulley damage) accumulated on the sheave surfaces 11a, 12a, 21a, and 22a of the pulleys 1 and 2. Here, the higher the flat ratio, the larger the contact area between the pulley and the element, so the pulley damage is proportional to the flat ratio. “Set the flat ratio above the pulley damage threshold” is to set the flat ratio to a value above the pulley damage threshold.

  “Oil drainability is ensured” means that the element 4 and the pulleys 1 and 2 are not fluid lubricated, and the peak points determined by the flat ratio and groove pitch (points A and B shown in FIG. 7). Is not in the oil dischargeable NG area (dot area in FIG. 7). “Setting the flat ratio in a range where oil dischargeability is ensured” means setting the flat ratio to a value determined by a mountain-shaped point not located in the oil dischargeability NG region. That is, for example, when the flat ratio is set to a value (A1) determined when the mountain-shaped point is located at the point A, the flat ratio is set in a range in which oil discharge performance is ensured. Further, when the flat ratio is set to a value (B1) determined when the mountain-shaped point is positioned at the B point, the flat ratio is not set within a range in which the oil discharge performance is ensured.

  Thereby, in the element 4 before lapping shown in FIG. 4, the groove ratio is set in the range of α to β in FIG. 6, and the flat ratio meets or exceeds the pulley damage threshold value in FIG. It is set to a value determined by a mountain-shaped point that is not located at.

  Further, in the element 4 after lapping shown in FIG. 5, the flat ratio is set to a value determined by a mountain shape point not located in the oil dischargeability NG region in FIG. Since the flat ratio is increased by lapping, if the flat ratio before lapping is equal to or greater than the pulley damage threshold, the flat ratio after lapping is also equal to or greater than the pulley damage threshold.

  Further, the element 4 has a predetermined range from the top 41a of the peak portion 41 toward the groove 42, and here, the flat ratio before and after the wrapping of the flank surface 4a and the sheave surfaces 11a, 12a, 21a, and 22a ensures oil discharge performance. The low hardness region T is formed in a range that is worn by initial wear due to lapping of the flank surface 4a and the sheave surfaces 11a, 12a, 21a, and 22a and that can ensure oil drainage when wear with time occurs. ing.

  The low hardness region portion T is a region set to a hardness value lower than the hardness value of the element base portion 4x, and the hardness value of the low hardness region portion T is the sheave surface 11a of the pulleys 1 and 2 in contact with the peak portion 41. , 12a, 21a, 22a is set to a value lower than the hardness value. Here, the element base portion 4x is a portion located at an element inner position with respect to the flank surface 4a in which the peak portion 41 and the groove portion 42 are formed, and is a so-called element general portion.

  In the element 4 of Example 1, the hardness value of the low hardness region portion T is set to 58 HRC, for example, and the hardness value of the element base portion 4x is set to 60 HRC.

  Moreover, in the element 4 of Example 1, the low hardness area | region part T is formed between the peak part 41a of the peak part 41 to the position where the flat ratio after lapping becomes the maximum in the range which ensures oil discharge property. ing. At this time, the height of the peak portion 41 before lapping is set to 30 μm, for example, and the height H of the low hardness region portion T (depth from the top portion 41a of the peak portion 41 toward the groove portion 42) H depends on the initial wear. Set to 20 μm for wear. That is, even if the low hardness region T having a height of 20 μm is worn out by the initial wear from the peak 41 of 30 μm, the peak 41 remains about 10 μm, so that oil drainage is ensured even if wear with time occurs.

  Next, a method for manufacturing the continuously variable transmission belt V according to the first embodiment will be described.

  FIG. 8 is a flowchart illustrating a method of manufacturing an element that is a component of the continuously variable transmission belt according to the first embodiment. FIG. 9 is an explanatory diagram showing a punching process, where (a) shows a material conveying procedure, (b) shows a material setting procedure, and (c) shows a material shearing procedure. FIG. 10 is an explanatory view showing a punching element, where (a) shows an overall perspective view and (b) shows a front view of a flank portion. FIG. 11 is an enlarged view of a main part showing a high-frequency induction heating procedure in the tempering heat treatment step. Hereinafter, each step of FIG. 8 will be described.

  In step S1, the outline of the element 4 is punched out from the steel plate material W by fine blanking by the press working apparatus 100 shown in FIGS. 9A to 9C, and at the same time, the ridge 41 and the groove 42 are formed. The process proceeds to S2. That is, this step S1 corresponds to a punching process.

  Here, the press working apparatus 100 includes a female die 101, a male punch 102, a plate presser 103 disposed at a position facing the die 101, and a plate receiver 104 disposed at a position facing the punch 102. Have. The press working apparatus 100 shears and punches the steel sheet material W by the relative movement of the die 101 and the punch 102. The fine blanking process is a method of punching by controlling the material flow in the sheared portion of the steel sheet material W to be punched. That is, the die 101 and punch 102 having extremely small clearance, the plate presser 103 having a knife-edge-shaped V-ring and the plate holder 104 generate high compressive stress inside the steel plate material W, and increase the ductility of the steel plate material W. In this way, the occurrence of cracks is prevented, and a shear surface without breakage is obtained.

  In the material conveying procedure (step S11) in step S1, as shown in FIG. 9 (a), the steel plate material W is conveyed to the press working apparatus 100 from the direction perpendicular to the punching direction (shear direction) (horizontal direction). To do.

  In the material setting procedure in step S1 (step S12), as shown in FIG. 9B, the steel plate material W conveyed to the press working apparatus 100 in the material conveying procedure is restrained by closing the punch 102 and the plate holder 104. To do. At this time, hydraulic pressure is applied to the plate holder 103 and the plate holder 104, and a knife-edge V ring (not shown) formed on the plate holder 103 is driven into the steel plate material W. And the steel plate material W which is going to spread in the direction perpendicular to the punching direction (horizontal direction) is pressed down to increase the compressive stress of the steel plate material W to be punched.

  In the material shearing procedure in step S1 (step S13), as shown in FIG. 9C, the element outline is punched out from the steel plate material W constrained in the material setting procedure by fine blanking to form the punching element E. . At this time, the positions of the punch 102 and the plate holder 104 are fixed, and the die 101 and the plate presser 103 are lowered. As a result, the relative positions of the die 101 and the punch 102 are shifted to form a shear plane. A peak portion 41 and a groove portion 42 are carved at a position corresponding to the flank surface 4a in the shear surface. Thereafter, the restriction by the die 101, the punch 102, the plate presser 103, and the plate support 104 is released, and the punching element E is discharged.

  Therefore, a ridge 41 and a groove 42 extending in the thickness direction are formed on the flank surfaces E1 on both sides of the punching element E shown in FIG. 10A (see FIG. 10B).

  In step S2, the punching element E formed in step S1 is locally heated using the coil C shown in FIG. 11, and tempering heat treatment processing, here, annealing is performed to provide the low hardness region T, and the element 4 is formed. To do. That is, this step S2 corresponds to a tempering heat treatment step.

  In the high-frequency induction heating procedure (step S21) in step S2, as shown in FIG. 11, a high-frequency current is passed through the coil C arranged along the flank surface E1 of the punching element E, thereby electromagnetically moving the punching element E side. An induced current is generated. The Joule heat generated by the electromagnetic induction current heats a predetermined range from the top 41 a of the peak 41 toward the groove 42. That is, local heating is performed only in a predetermined range from the top 41 a of the peak 41 toward the groove 42 by high frequency induction heating. At this time, since the coil C is disposed along the flank surface E1 of the punching element E, local heating is performed only in the vicinity of the top 41a of the peak 41 from the direction facing the flank surface E1. Here, masking to the non-heated part is unnecessary.

  In the cooling removal procedure (step S22) in step S2, the punching element E that has been locally heated by the high frequency induction heating procedure is cooled (cooled), the internal strain of the heated portion is removed, and the tissue is softened. The hardness value of the low hardness region T changes from, for example, 60 HRC to 58 HRC by the high frequency induction heating procedure and the cooling procedure.

Next, the operation will be described.
First, “the problem of the belt for the continuously variable transmission of the comparative example” will be described, and subsequently, the effects of the belt for the continuously variable transmission of the first embodiment will be described as “the element damage preventing action by promoting the element wear”, “oil The description will be divided into “transmission torque maintenance action by ensuring discharge”, “mold life improvement and mountain strength ensuring action”, and “characteristic action in manufacturing method”.

[Problems of the belt for the continuously variable transmission of the comparative example]
The element of the belt V for the continuously variable transmission of the comparative example has an oil film on the flank surface that comes into contact with the sheave surface in order to achieve both the oil drainability and the contact area when contacting the sheave surface of the pulley. And a groove portion for discharging the lubricating oil.
Here, the element is formed by punching a steel plate material by fine blanking, but the ridge and the groove are formed on the flank surface simultaneously with the punching of the element outline. That is, the peak portion and the groove portion are formed on the flank surface by punching the steel plate material with a punching die having irregularities according to the shapes of the peak portion and the groove portion. At this time, in order to maintain the life of the punching die, the base of the convex portion of the die is thick (thick). Therefore, the peak portion has a trapezoidal shape whose base side is thicker than the top side, while the groove portion has a trapezoidal shape whose bottom side is narrower than the open end side.
In such a ridge and groove shape, the contact area when the flank surface and the pulley sheave surface contact each other is not constant depending on the wear state of the flank surface, and the contact area gradually increases as wear progresses. That is, the peak width of the peak part contacting the pulley sheave surface gradually increases due to wear, and the flat ratio, which is the ratio of the peak width to the total width of the peak width and the groove width, and the groove width, increases.

  By the way, when the flank surface of the element comes into contact with the sheave surface of the pulley, the flank surface receives contact surface pressure. At this time, as the contact area of the flank surface is smaller, the surface pressure is concentrated and the shear stress generated in the flank surface is increased. In addition, the larger the contact area at this time, the smaller the surface pressure is leveled on the entire contact surface, and the smaller the shear stress.

However, in the element of the comparative example, the hardness of the entire element was constant, and the hardness was constant from the base portion to the top portion even in the peak portion formed on the flank surface. For this reason, the flank surface is less likely to be worn, and the degree of damage generated on the pulley sheave surface when the shear stress exceeds a certain threshold value is increased.
That is, since the flank surface is difficult to wear, it takes time until the initial wear region wears out as shown in FIG. 12, that is, the initial wear end of the flank surface takes time, and it takes time to expand the contact area. For this reason, the total damage accumulated on the sheave surface is increased, and the pulley sheave surface is greatly damaged.

When the damage on the pulley sheave surface becomes excessive, a step is generated on the sheave surface. When the element moves while keeping contact with the pulley at the time of shifting, the element is caught by this step, and the smooth movement of the element may be hindered. Furthermore, due to this influence, excessive stress was generated in the element, and it was considered that the element was damaged.
In particular, at the initial stage of wrapping (rubbing) between the flank surface and the sheave surface, since the surface roughness shape of both is large, the shear stress generated in the element increases, and the damage received by the sheave surface accordingly increases.

  Therefore, it has been desired to secure a contact area on the flank surface of the element so that the shear stress generated in the flank surface from the beginning of lapping does not exceed a certain threshold.

However, in order to ensure the contact area of the flank surface, it is necessary to make the base of the convex portion thin (small) in the punching die for punching the element. That is, in order to secure the contact area, the peak width of the peak portion formed on the flank surface must be increased to some extent, and the groove width of the groove portion must be relatively reduced. However, the groove width corresponds to the root of the convex portion of the punching die.
Therefore, when the contact area of the flank surface is enlarged and the rigidity of the punching die forming the groove becomes severe, the die life is reduced, and as a result, the product (element) unit price is increased. It is possible. Therefore, there is a limit in securing the contact area of the flank surface.

[Element damage prevention by promoting element wear]
In the continuously variable transmission belt V according to the first embodiment, the hardness is lower than the hardness value of the element base 4x within a predetermined range from the top 41a of the peak 41 formed on the flank 4a on both sides of the element 4 to the groove 42. A low hardness region T set to a value is formed.

  For this reason, the hardness of the top part 41a vicinity of the peak part 41 which contacts the sheave surface 11a, 12a, 21a, 22a of the pulleys 1 and 2 can be reduced, and the sheave surface 11a, 12a, 21a, 22a and the peak part 41 Increased hardness difference.

  As a result, when the sheave surfaces 11a, 12a, 21a, and 22a come into contact with the peak portion 41, the wear of the peak portion 41 is promoted, and the initial wear end time at which the initial wear region wears out as shown in FIG. 12 is t1. Become. The initial wear end time t1 is shorter than the initial wear end time t2 in the element of the comparative example. In the element 4 of Example 1, the peak hardness is shorter than the element having a constant peak hardness (the element of the comparative example). The contact area can be expanded over time. As the contact area increases, the contact surface pressure is leveled over the entire area, and the total damage accumulated on the sheave surface does not increase, thereby reducing damage.

As described above, since the damage accumulated on the sheave surfaces 11a, 12a, 21a, and 22a is suppressed, no step is generated on the sheave surfaces 11a, 12a, 21a, and 22a. Therefore, the smooth movement of the element 4 is not hindered by the step, and no excessive stress is generated in the element, and damage to the element can be prevented.
Furthermore, even when a constant belt running radius in the pulleys 1 and 2 is intensively used at the initial stage of lapping between the flank surface 4a of the element 4 and the sheave surfaces 11a, 12a, 21a and 22a of the pulleys 1 and 2, No step is caused by the damage of the sheave surfaces 11a, 12a, 21a, 22a.

  Further, simultaneously with the end of initial wear and expansion of the contact area in a short time due to accelerated wear of the crest 41, the surface roughness of the sheave surfaces 11a, 12a, 21a, 22a can be leveled in a short time, and the sheave surface Damage caused to 11a, 12a, 21a, and 22a can be further reduced.

  In particular, in the element 4 of the first embodiment, the low hardness region portion T is worn by initial wear due to the wrapping of the flank surface 4a and the sheave surfaces 11a, 12a, 21a, and 22a, and oil drainability is ensured when wear with time occurs. The range is set as possible.

  For this reason, as shown in FIG. 12, the initial wear region of the peak portion 41 can be worn out in a shorter time (here, time t1) than the element of the comparative example, and the initial wear is completed in a relatively short time. Can be made. Thereby, the damage accumulated on the sheave surfaces 11a, 12a, 21a, 22a can be further suppressed. Further, the hardness of the portion where wear with time occurs is equivalent to that of the element base 4x, and the wear with time progresses at the same speed as the element of the comparative example.

  Further, in the continuously variable transmission belt V of Example 1, the hardness value of the low hardness region portion T is set to 58HRC, and the hardness value of the low hardness region portion T is set to a value lower than the hardness values of the pulleys 1 and 2. Has been.

  For this reason, the low hardness region portion T is easily easily worn, and the wear of the peak portion 41 can be further promoted to complete the initial wear in a short time.

[Transmission torque maintenance by ensuring oil drainage]
In the continuously variable transmission belt V according to the first embodiment, the low hardness region T is set within a range in which the flat ratio of the flank surface 4a and the sheave surfaces 11a, 12a, 21a, and 22a before and after wrapping ensures oil discharge. is doing.

  For this reason, the flat ratio in the flank surface 4a before lapping shown in FIG. 4 is set to a value determined by a mountain shape point not located in the oil draining NG region in FIG. 7, and oil drainability at the initial stage of lapping can be ensured. As a result, the lubricating oil discharge function is not impaired, and fluid lubrication between the element 4 and the pulleys 1 and 2 does not occur. Therefore, it is possible to prevent the friction coefficient from being lowered, promote smooth wear of the peak 41, and maintain the transmission torque.

  Further, the flat ratio in the flank surface 4a after lapping shown in FIG. 5 is set to a value determined by a mountain shape point not located in the oil dischargeability NG region in FIG. Accordingly, even after the wrapping is sufficiently performed and the low hardness region portion T where the hardness value is low and the wear is promoted is worn away and the contact area is enlarged, the oil discharge property can be ensured. Thereby, even after the contact area is expanded due to wear of the ridges 41, the lubricating oil discharge function is not impaired. Therefore, there is no fluid lubrication between the element 4 and the pulleys 1 and 2, and a reduction in the friction coefficient can be prevented and the transmission torque can be maintained.

[Improves mold life and secures peak strength]
In the continuously variable transmission belt V of the first embodiment, the element 4 is a punched molded product in which a peak portion 41 and a groove portion 42 are formed by punching a steel plate material with a punching die (die 101, punch 102). The groove ratio, which is the ratio of the groove width to the total width of the ridges 41 and the grooves 42 before the wrapping of the flank surface 4a and the sheave surfaces 11a, 12a, 21a, 22a, is determined by the punching die. The mold strength is ensured and the peak strength of the peak portion 41 is set in a range that is ensured.

  Thus, before lapping (new condition), the groove width of the groove portion 42 is large enough to ensure the mold strength of the punching mold and ensure the mold life to the necessary extent. On the other hand, the crest width of the crest portion 41 has a strength that can be punched, and does not hinder the punching of the element 4. Therefore, the initial shape of the element 4 after punching is a shape having a low flat ratio and a long mold life while maintaining the strength at which the peak portion 41 can be punched. That is, it is possible to achieve both improvement of the mold life and securing of peak strength.

That is, in the continuously variable transmission belt V according to the first embodiment, as shown in FIG. 13, the peak shape points determined by the flat ratio and the groove pitch before wrapping (new state) are the mold life NG region and the peak strength NG region. It exists in the area | region (point A) from which it deviated from. The flat ratio at this time is not less than the pulley damage line but is relatively low.
When the low hardness region T is worn away by the initial wear due to the wrapping of the element 4 and the pulleys 1 and 2, the contact area of the element 4 is expanded and the flat ratio is increased. Therefore, the mountain shape point moves to the A ′ point. At this time, since the oil discharging property is ensured before and after the wrapping, the point A ′ does not enter the oil discharging property NG region.

  Thus, in the continuously variable transmission belt V according to the first embodiment, the mold life and the mountain strength at the time of manufacture are ensured, and at the same time, the wear of the mountain portion 41 is accelerated, the initial wear is completed in a short time, and the contact area is expanded. It is possible to suppress surface damage → prevent element damage → improve belt durability reliability.

"Characteristic effects in manufacturing methods"
In order to manufacture the element 4 that is a component of the continuously variable transmission belt V of the first embodiment, the punching element E is formed by fine blanking in the punching step (step S1), and then tempering heat treatment is performed. By the process (step S2), the low hardness region portion T is formed by tempering heat treatment by local heating from the direction facing the flank surface E1.

  At this time, the peak portion 41 and the groove portion 42 are formed simultaneously with punching the outline of the element 4. The tempering heat treatment is an annealing treatment here, and is performed by local heating from the direction facing the flank surface E1 of the punching element E. Thereby, adjustment of a heating range can be performed easily and hardness can be softened only in the aimed range.

In particular, the first embodiment has a high-frequency induction heating procedure for performing local heating by high-frequency induction heating that is heated by electromagnetic induction current generated by flowing a high-frequency current through the coil C disposed along the flank surface 4a.
Therefore, the adjustment of the heating depth can be facilitated and the processing time can be shortened. Furthermore, since the coil C is disposed along the flank surface 4a, the coil shape becomes simple. Therefore, the electromagnetic induction current (eddy current) becomes constant and uniform heating can be performed.

Next, the effect will be described.
In the continuously variable transmission belt V according to the first embodiment, the following effects can be obtained.

(1) a laminated ring 3 in which a large number of annular rings are stacked from the inside to the outside, and an element 4 having flank surfaces 4a that contact the sheave surfaces 11a, 12a, 21a, and 22a of the pulleys 1 and 2 on both sides, Two sets of the laminated rings 3, 3 are sandwiched between the saddle grooves 4b, 4b of the elements 4,... Arranged in series, and are sandwiched between the two sets of pulleys 1, 2. In the belt V for continuously variable transmission, the element 4 supports the force that the element 4 tries to spread in the outer diameter direction when the torque is transmitted, and the element 4 supports the pressing force from the two pulleys 1 and 2. 4 is a ridge 41 that contacts the sheave surfaces 11a, 12a, 21a, and 22a of the pulleys 1 and 2 via oil films on the flank surfaces 4a on both sides, and a groove that discharges lubricating oil in the circumferential direction of the pulleys 1 and 2. 42 in the pulley radial direction A configuration in which the low hardness region T is set to a hardness value lower than the hardness value of the element base portion 4x in a predetermined range from the top portion 41a of the peak portion 41 toward the groove portion 42. did.
For this reason, it is possible to prevent the element from being damaged by the pulley, and to improve the belt durability reliability.

(2) The low hardness region T has a flat ratio that is a ratio of the crest width of the crest portion 41 and the crevice portion 42 to the total width of the crest portions 42, and the flank surface 4a and the sheave surfaces 11a, 12a. , 21a, and 22a before and after lapping, the oil drainability is set within a range to be secured.
For this reason, in addition to the effect described in (1) above, before and after the wrapping, it is possible to always ensure oil drainage, prevent a reduction in the friction coefficient, and maintain the transmission torque.

(3) The element 4 is a punched molded product obtained by punching a material (steel plate material W) with a punching die (die 101, punch 102) to form the ridge 41 and the groove 42. The groove ratio, which is the ratio of the groove width to the sum of the crest width and groove width of the groove portion 42, is determined by the punching dies 101, 102 before lapping the flank surface 4a and the sheave surfaces 11a, 12a, 21a, 22a. The mold strength is set to a range in which the peak strength of the peak portion 41 is ensured.
For this reason, in addition to the effect described in the above (2), the element 4 has a shape with a low flat ratio before lapping, and the mold life can be improved.

(4) The hardness value of the low hardness region T is set to a value lower than the hardness value of the sheave surfaces 11a, 12a, 21a, 22a of the pulleys 1 and 2 in contact with the peak 41.
For this reason, in addition to the effects described in (1) to (3) above, the wear of the element 4 can be surely promoted and the occurrence of element damage can be prevented.

(5) The low hardness region portion T is set within a range where the flank surface 4a and the sheave surfaces 11a, 12a, 21a, and 22a are worn away by initial wear due to lapping and oil drainability can be secured when wear with time occurs. It was set as the structure to do.
For this reason, in addition to the effects described in (1) to (4) above, the initial wear can be completed in a short time, and damage accumulated on the sheave surfaces 11a, 12a, 21a, and 22a can be further suppressed.

(6) Peak portions 41 that contact the flank surfaces 4a on both sides of the element 4 with the sheave surfaces 11a, 12a, 21a, 22a of the pulleys 1 and 2 through an oil film, and lubricating oil in the circumferential direction of the pulleys 1 and 2 In the manufacturing method of the continuously variable transmission belt V that forms the discharging groove portion 42, the tempering heat treatment by local heating from the direction facing the flank surface 4a leads to the groove portion 42 from the top portion 41a of the peak portion 41. Further, a tempering heat treatment step (step S2) for forming a low hardness region T set to a hardness value lower than the hardness value of the element base 4x is set in a predetermined range.
For this reason, when manufacturing the continuously variable transmission belt V in which the ridge portions 41 and the groove portions 42 are formed on the flank surfaces 4a on both sides of the element 4, the heating range can be easily adjusted, and the low hardness region portion T can be formed in an appropriate range.

(7) The tempering heat treatment step (step S2) has a high frequency induction heating procedure (step S21) for performing local heating by high frequency induction heating.
For this reason, in addition to the effect described in the above (6), the heating depth can be easily adjusted and the processing time can be shortened during the tempering heat treatment of the element 4.

(8) The high frequency induction heating procedure (step S21) is configured to heat by the electromagnetic induction current generated by flowing a high frequency current through the coil C arranged along the flank surface 4a.
For this reason, in addition to the effect described in (7) above, when the element 4 is subjected to high-frequency induction heating, the coil shape can be simplified, and the electromagnetic induction current (eddy current) can be made constant and uniform heating can be performed.

(9) In the tempering heat treatment step (step S2), the contour of the element 4 is punched out by fine blanking processing in which the flow of the material in the shearing part is controlled and punched with high precision. It was set as the structure performed after the punching process to form (step S1).
For this reason, in addition to the effects described in (6) to (8) above, when the element 4 is tempered, the deformation of the part to be tempered can be prevented and the low hardness region T can be formed appropriately. .

  While the belt for continuously variable transmission and the manufacturing method thereof according to the present invention have been described based on the first embodiment, the specific configuration is not limited to this embodiment, and each claim of the claims Design changes and additions are permitted without departing from the spirit of the invention according to the paragraph.

  In Example 1, the hardness value of the low hardness region portion T is set to 58 HRC, and the hardness value of the element base portion 4x is set to 60 HRC. However, these hardness values are not limited to the above values, and may be arbitrarily set according to the material, peak width / groove width size, groove pitch, and the like. As shown in FIG. 14, the degree of pulley damage is higher as the element hardness value is higher (larger) regardless of the pulley hardness value. Therefore, the hardness value of the sheave surfaces 11a, 12a, 21a, and 22a of the pulleys 1 and 2 that are in contact with the peak portion 41 is determined if the low hardness region T is a hardness value that does not exceed the pulley damage limit value γ. May be set to a lower value, and may be set to a higher value as the hardness value of the pulleys (sheave surfaces 11a, 12a, 21a, 22a) is higher.

  As a result, the hardness value of the low hardness region portion T varies according to the hardness value of the pulleys 1 and 2, and the element hardness can be made as high as possible, thereby improving the durability reliability of the continuously variable transmission belt V. Further efforts can be made. Further, the difference in hardness is constant regardless of the hardness of the pulleys 1 and 2, and the wear amount of the element can be easily managed.

  In the tempering heat treatment step in Example 1, local heating is performed by high-frequency induction heating, but the heating method is not limited to this, and may be laser heating, resistance heating, infrared heating, or the like.

  In the first embodiment, an example of a continuously variable transmission belt applied to a belt type continuously variable transmission of an engine vehicle is shown. However, the present invention is not limited to a continuously variable vehicle mounted on another vehicle such as a hybrid or an electric vehicle. The present invention can also be applied to a transmission belt.

V Belt for continuously variable transmission 1 Input pulley 11 Fixed pulley 12 Slide pulley 11a, 12a Sheave surface 2 Output pulley 21 Fixed pulley 22 Slide pulley 21a, 22a Sheave surface 3 Laminated ring 4 Element 4a Flank surface 41 Mountain portion 41a Top portion 42 Groove 4x Element base T Low hardness area

Claims (9)

A laminated ring in which a large number of annular rings are stacked from the inside to the outside, and elements having flank surfaces that contact the sheave surfaces of the pulleys on both sides,
Two sets of the above-mentioned laminated rings are configured by being sandwiched from both sides in the saddle grooves of the elements arranged in series, and when the torque is transmitted between the two sets of pulleys, the elements expand in the outer diameter direction. In the belt for continuously variable transmission, the laminating ring supports the force to try, and the element supports the pressing force from two sets of pulleys.
The element is formed by alternately arranging, on the flank surfaces on both sides, a peak portion that contacts the sheave surface of the pulley via an oil film, and a groove portion that discharges lubricating oil in the circumferential direction of the pulley, in the pulley radial direction,
A belt for continuously variable transmission, wherein a low hardness region portion set to a hardness value lower than a hardness value of an element base portion is formed in a predetermined range from the top portion of the peak portion toward the groove portion. The continuously variable transmission belt according to claim 1,
The low hardness region portion has a flat ratio that is a ratio of the crest width and the crest width of the crest portion and the crest width to the total width of the groove portion, and ensures oil discharge before and after lapping of the flank surface and the sheave surface. A belt for continuously variable transmission, characterized in that it is set within a range to be used. In the belt for continuously variable transmission according to claim 2,
The element is a punched molded product in which a material is punched by a punching die to form the ridge and the groove,
The groove ratio, which is the ratio of the groove width to the total width of the peak width and the groove width of the groove portion, and the groove width is secured before the flank surface and the sheave surface are wrapped, and the die strength of the punching die is ensured. The belt for continuously variable transmissions is set in a range in which the peak strength of the peak portion is ensured. In the belt for continuously variable transmission as described in any one of Claims 1-3,
The continuously variable transmission belt according to claim 1, wherein a hardness value of the low hardness region portion is set to be lower than a hardness value of a sheave surface of a pulley contacting the peak portion. In the belt for continuously variable transmission as described in any one of Claims 1-4,
The belt for continuously variable transmission, wherein the low hardness region portion is set in a range that can be worn out by initial wear due to lapping of the flank surface and the sheave surface and that can ensure oil drainage when wear with time occurs. . In the method for manufacturing a continuously variable transmission belt, on the flank surfaces on both sides of the element, a peak portion that contacts the sheave surface of the pulley via an oil film and a groove portion that discharges lubricating oil in the circumferential direction of the pulley are formed.
By a tempering heat treatment by local heating from the direction facing the flank surface, a low hardness region portion set at a hardness value lower than the hardness value of the element base portion in a predetermined range from the top of the peak portion toward the groove portion. A method of manufacturing a belt for continuously variable transmission, comprising a tempering heat treatment step to be formed. In the manufacturing method of the belt for continuously variable transmission according to claim 6,
The tempering heat treatment step includes a high frequency induction heating procedure for performing local heating by high frequency induction heating. In the method for manufacturing a continuously variable transmission belt according to claim 7,
The high frequency induction heating procedure is a method of manufacturing a belt for continuously variable transmission, wherein heating is performed by electromagnetic induction current generated by flowing high frequency current through a coil disposed along the flank surface. In the method for manufacturing a continuously variable transmission belt according to any one of claims 6 to 8,
The tempering heat treatment step is performed after the punching step of forming the ridges and the grooves at the same time as punching the outline of the element by fine blanking processing that performs punching of the material in the sheared portion with high accuracy. A method for manufacturing a continuously variable transmission belt.

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