JP6527709B2 - Metal belt element for continuously variable transmission - Google Patents

Description

  The present invention relates to an element for a metal belt of a continuously variable transmission, and more specifically, suitably reduces stress generated at a neck root portion of the element at the time of driving the metal belt to improve repeated fatigue strength, thereby making the continuously variable transmission The present invention relates to an element for a metal belt of a continuously variable transmission capable of improving the torque transmission capacity and improving the power transmission efficiency of the continuously variable transmission in the vicinity of the overdrive ratio region.

  The metal belt element of the continuously variable transmission, as shown in FIG. 8, includes an element body of a substantially trapezoidal element, and a neck portion having a pair of left and right ring slits into which the metal ring assembly is fitted; And a substantially triangular shaped ear portion formed on the upper portion of the main body via the neck portion. At both end portions in the left-right direction of the element body, a pair of contact surfaces that can contact the V surface of a drive pulley (not shown) and a driven pulley (not shown) are formed. Further, the main surface in contact with the adjacent element is formed on the front side and the rear side in the advancing direction of the element, and an inclined surface is formed on the lower side of the main surface on the front side in the advancing direction ing. Further, in order to connect the elements adjacent to each other in the front and rear sides, a nose portion and a hole portion (FIG. 9B) which can be fitted to each other are formed on the front and rear surfaces of the ear portion. And the saddle surface which supports the inner peripheral surface (inner peripheral surface of the metal ring of innermost periphery) of a metal ring assembly is formed in the lower edge of a ring slit on either side.

  A metal belt consisting of the above metal ring assembly and the above element is wound around a pair of pulleys (drive pulley and driven pulley), both contact surfaces of the element are pressed against the V surface of the pulley, and the contact surfaces The rotational power from the engine is transmitted from the drive pulley to the driven pulley by the frictional force between the belt and the V surface of the pulley. In this manner, when the metal belt rotates, the element is pressed by the V surface of the pulley while the saddle surface is pressed downward by the metal ring assembly. Furthermore, when the element transfers the transmission torque to the drive pulley and the driven pulley, a bending moment in the front-rear direction acts on the element body depending on the transmission direction of the torque. Therefore, stress is concentrated at the neck portion of the element, particularly at the neck root portion (point circle portion in the figure) which is a crossing portion with the saddle surface.

  At the root portion of the neck, an arc concave portion is formed which is smoothly recessed from the side surface of the neck to the saddle surface. The cross-sectional shape of the arc concave portion is constituted by a first arc of curvature radius R1 continuous to the side surface of the neck and a second arc of curvature radius R2 forming the bottom portion continuously to the first arc, the curvature radius R1 being a curvature An element characterized by being larger than the radius R2 is known (see, for example, Patent Document 1).

  An element characterized in that the arc concave portion is constituted by four arcs of curvature radii R1, R2, R3 and R4, and the curvature radius R2 of the second arc forming the bottom portion among these curvature radii is the maximum value. Are known (see, for example, Patent Document 2).

  There is also known an element characterized in that the ratio D / R of the depth D of the arc from the saddle surface to the radius of curvature R is in the range of 0.3 to 0.75 (e.g. See 3).

  On the other hand, it is known that the carbon content (content C%) of the element material has a great influence on the stress concentration at the neck root. It is known to improve the wear resistance and fatigue resistance of an element when the element is made of a steel material having a carbon content (containing C%) of 0.50 to 0.70% (e.g., patent documents See 4).

Patent No. 4766064 Patent No. 3975791 Patent No. 4321119 Patent No. 5594521

The patent documents 1 and 2 are methods for reducing the stress generated at the neck root portion by connecting the saddle surface and the neck side surface with a smooth arc (curved surface). That is, it is a method for reducing the stress generated at the neck root portion by enlarging the curvature radius R of the arc without changing the shape of the entire element.
However, with regard to the stress generated at the root portion of the neck, strength analysis has revealed that the influence of the distance (depth) D from the saddle surface to the lowermost portion of the arc is greater than the curvature radius R. In the above Patent Documents 1 and 2, the distance (D) from the saddle surface to the lowermost part of the arc is not taken into consideration.

As shown in FIG. 9A, in FIG. 10, when stress is generated at the neck root when a downward load is applied on the saddle surface of the element in a state in which the element is restrained, it is determined by strength analysis. Shows the analysis result of. In addition, as shown in FIG. 9 (b), when a load is applied from the hole side to the nose side to the back side that hits the middle position between the saddle surface and the locking edge in the state where the element is restrained. The analysis results are shown when the stress generated at the root of the neck is determined by strength analysis. As apparent from FIGS. 10 (a) and (b) and FIGS. 11 (a) and (b), the occurrence occurs even in the relation of R1 <R2 (R1 / R2 <1) and R3 <R2 (R3 / R2 <1). Stress varies widely at high values. Therefore, it can not be said that the said patent documents 1 and 2 have a big effect regarding reducing the stress of a neck root part.
On the other hand, in the patent document 3, the distance (D) from the saddle surface to the lowermost part of the arc is considered.
However, as is apparent from FIGS. 10C and 11C, it can be seen that high stress is generated at the neck root portion at 0.3 ≦ D / R ≦ 0.75. Therefore, it can not always be said that Patent Document 3 also has a great effect on reducing the stress at the neck root.
Therefore, the present invention has been made in view of the above-mentioned problems of the prior art, and an object thereof is to suitably reduce the stress generated at the neck root portion of the element at the time of driving the metal belt and to improve the repeated fatigue strength. Accordingly, it is possible to provide an element for a metal belt of a continuously variable transmission capable of improving the torque transmission capacity of the continuously variable transmission and improving the power transmission efficiency of the continuously variable transmission in the vicinity of the overdrive ratio region. is there.

In the metal belt element of a continuously variable transmission according to the present invention for achieving the above object, a metal ring assembly in which a plurality of strip-shaped metal rings are laminated aligns the phases and annularly extends along the metal ring assembly. An element for a metal belt of a continuously variable transmission, comprising a plurality of sheets laminated on one another, a saddle surface supporting the metal ring assembly, and a neck portion extending upward from the saddle surface,
A recess recessed toward the saddle surface is formed at a neck root portion where the saddle surface intersects the neck portion, and the recess is formed so as to be connected smoothly to the side surface of the neck and not reach the bottom portion of the recess And a second convex surface (R2) which is smoothly connected to the first curved surface (R1) and which forms the bottom portion, and the second curved surface and the second curved surface. It is composed of an upwardly convex third curved surface (R3) smoothly connected to both sides of the saddle surface,
The radius of curvature increases in the order of the first curved surface (R1), the second curved surface (R2), and the third curved surface (R3), and the depth of the second curved surface with respect to the radius of curvature (R2) of the second curved surface The ratio of D (D) is characterized by a value of 0.3 or less.

  In the above configuration, the neck root portion (corner portion) where the saddle surface intersects the neck portion has a radius of curvature gradually increasing from the neck portion to the saddle surface and the radius of curvature forming the bottom portion is the depth from the saddle surface. The three curved surfaces (arcs) that depend on each other are connected smoothly. That is, the radius of curvature of the first curved surface connected to the neck side surface is R1, the radius of curvature of the second curved surface forming the bottom portion is R2, the radius of curvature of the third curved surface connected to the saddle surface is R3, the second based on the saddle surface Assuming that the depth of the curved surface is D, a neck root portion (corner portion) where the saddle surface intersects the neck portion is formed by the three curved surfaces (arcs) satisfying R1 <R2 <R3 and D / R2 ≦ 0.3. It is configured. In particular, by making the radius of curvature R2 forming the bottom surface portion dependent on the depth D from the saddle surface while sequentially increasing the radius of curvature, it is possible to suitably reduce the stress generated at the neck root portion.

  A second feature of the metal belt element of the continuously variable transmission according to the present invention is that the steel material constituting the element contains at least carbon (C), silicon (Si), manganese (Mn) and chromium (Cr) as additives. And the carbon content (%) is 0.61% or more and 0.71% or less.

  In the above configuration, by using the steel material having the above-mentioned carbon content, in combination with the shape feature of the above-mentioned arc concave portion, it is possible to suitably reduce the stress generated at the neck root portion and to improve the repeated fatigue strength of the element. It becomes possible.

  According to the element of the present invention, the above-mentioned shape characteristic of the neck root portion and the above-mentioned material characteristic of the steel material constituting the element combine to suitably reduce the stress generated at the neck root portion of the element and It is possible to improve the repeated fatigue strength. Further, in the element of the present invention, the distance (D) from the saddle surface to the bottom surface portion is reduced and the stress generated at the neck root portion is reduced, so that the locking edge can be moved to the saddle surface side. As a result, it is possible to reduce torque loss due to slippage between the ring and the saddle surface in the vicinity of the overdrive ratio region, which can contribute to the improvement of the power transmission efficiency of the continuously variable transmission.

It is principal part cross-sectional explanatory drawing which shows the neck root part of the element of this invention. It is a graph which shows an analysis result when stress generated at a neck root part when a downward load is applied on a saddle surface in an element of the present invention is determined by strength analysis. In the element of the present invention, the stress generated at the root of the neck when a load is applied from the hole side to the nose side on the back surface corresponding to the middle position between the saddle surface and the locking edge FIG. It is a graph which shows correlation of steel materials, neck root part shape, and repetition fatigue strength. It is a graph which shows correlation of carbon content, neck root shape, and repetition fatigue strength. It is explanatory drawing which shows the locking edge which concerns on the element of this invention. It is an explanatory view showing the power transmission efficiency concerning the continuously variable transmission which uses the element of the present invention. It is a perspective view which shows the conventional element. It is explanatory drawing which shows the direction of the load added to an element. It is a graph which shows an analysis result when stress generated at a neck root part when a downward load is applied on a saddle surface in a conventional element is determined by strength analysis. In the conventional element, the stress generated at the root of the neck when load is applied from the hole side to the nose side is shown by the strength analysis on the back surface that hits the middle position between the saddle surface and the locking edge. It is a graph. FIG. 6 is an SN diagram for describing “a load corresponding to fatigue strength in a repetition number of 1.0E + 5 times” according to FIGS. 4 and 5;

  Hereinafter, the present invention will be described in more detail by the embodiments shown in the drawings.

FIG. 1 is a cross-sectional view showing the neck root portion of a metal belt element (hereinafter referred to as “element”) 100 of a continuously variable transmission according to the present invention. In addition, FIG.1 (b) is a graph which shows the correlation of each curvature radius R and the depth D. FIG. The symbol D is a depth (distance) from the upper end of the saddle surface to the deepest portion (point) PC, and the symbol W is a distance from the side of the neck to the R start point PE of the saddle surface.
In this element 100, the connecting surface relating to the neck root that smoothly connects the saddle surface and the side surface of the neck gradually increases in radius of curvature from the side surface of the neck to the surface of the saddle and the radius of curvature R2 forming the bottom portion from the saddle surface. Three curved surfaces (arcs) depending on depth D: downward convex curved surfaces (arcs) PA-PB, downward convex curved surfaces (arcs) PB-PD, upward convex curved surfaces (arcs) PD-PE Are connected smoothly. Moreover, although mentioned later for details, as steel materials which constitute this element 100, steel materials whose carbon content (mass%) is 0.61 to 0.71% are used. Here, for convenience of explanation, the curved surface and the arc are used in the same meaning.

  Moreover, "smooth" as used herein means that adjacent curved surfaces (arcs) are connected with the same tangent plane (tangent). Therefore, the center of each arc is determined as the intersection of each normal at both connection points, and the radius of curvature is determined as the distance from the arc center to the connection point. Conversely, when the arc center and curvature radius of each curved surface are known, the straight line connecting the two arc centers becomes the normal, and the position of the connection point is automatically determined by the normal line and the curvature radius. The length of the arc is automatically determined from the position. For example, the positions of the connection points PB and PD of the arc PB-PD are automatically determined by the normal line n2 connecting the arc centers C1 and C2, the normal line n3 connecting the arc centers C2 and C3, and the curvature radius R2. The length of the arc PB-PD is automatically determined from the positions of the connection points PB and PD.

  The arc PA-PB is smoothly connected to the side surface of the neck at the connection point PA and is smoothly connected to the arc PB-PD at the connection point PB which does not reach the deepest portion PC. The arc PA-PB is a downward convex arc having a radius of curvature R1 and an arc center C1 located out of the plane. In addition, since arc PA-PB is tangentially connected to the side surface of the neck and arc PB-PD, it has common tangents L1 and L2, and therefore arc center C1 corresponds to common tangents L1 and L2 at connection points PA and PB. It is obtained as an intersection point of the normals n1 and n2. The height position of the connection point PA, which is the start point of the arc PA-PB, coincides with the saddle surface upper end PF in this embodiment, but the ring (FIG. 8) plate vertically from the saddle surface upper end PF It is desirable to be within half of the thickness, ie within ± 1 / 2Δ.

  The arc PB-PD is smoothly connected to the arc PA-PB at the connection point PB and is formed in a range from the connection point PB including the deepest point PC to the connection point PD, and the arc center C2 is located on the surface and the curvature radius Is a downward convex arc having R 2. Further, since arc PB-PD is tangentially connected to both arc PA-PB and arc PD-PE, it has common tangents L2 and L3, and therefore arc center C2 is common tangent L2 at connection point PB, PD. It is obtained as an intersection point of normals n2 and n3 corresponding to L3. Further, as described later, the depth D from the upper end PF of the saddle surface to the deepest point PC and the radius R2 are mutually dependent, and have a relationship of D / R2 ≦ 0.3.

  The arc PD-PE is smoothly connected to the arc PB-PD at the connection point PD and smoothly connected to the saddle surface at the connection point PE, and is upward convex having an arc center C3 in the plane and a radius of curvature R3. It is a circular arc. Since arc PD-PE is tangentially connected to arc PB-PD and the saddle surface, it has common tangents L3 and L4, so that arc center C3 corresponds to common tangents L3 and L4 at connection points PD and PE. It is determined as the point of intersection of the lines n3 and n4.

  In addition, as the distance W from the neck side to the R start point of the saddle surface increases, the contact surface between the ring and the saddle surface decreases, which adversely affects the ring behavior, so 1.6 to 1.7 mm is desirable .

  For each radius of curvature R1, R2 and R3, as shown in FIG. 1 (b), there is a relationship of R1 <R2 <R3 and at the same time only the radius of curvature R2 depends on the depth D, D / R2 ≦ 0 It has a relationship of .3. Therefore, when the connection point PA and the connection point PE are fixed, when the depth D is determined, the curvature radius R2 is determined from the relationship of D / R2 ≦ 0.3. At the same time, the arc center C2 is also automatically determined (since the arc center C2 is located at a distance R2 from the deepest point PC on the normal line n5 corresponding to the tangent L5 at the deepest point PC). Subsequently, the arc center C1, the radius of curvature R1 and the connection point PB are automatically determined from the relationship of R1 <R2 and the constraint of tangent connection (the arc center is located on the normal line passing the connection point). Similarly, the arc center C3, the radius R3, and the connection point PD are also automatically determined from the relationship of R2 <R3 and the constraint of tangent connection. Thus, in the element 100 of the present invention, the depth D and the curvature radius R2 are determined for the shape of the neck root portion (where the arc PA-PB, arc PB-PD, and arc PD-PE are smoothly connected). Will be determined automatically.

Similarly to FIG. 9 (a), FIG. 2 is an analysis when stress generated at the root of the neck when a downward load is applied on the saddle surface of the element in a state in which the element is restrained is obtained by strength analysis. The results are shown. FIG. 2 (a) shows the case of R1 <R2 <R3 without the constraint of D / R2 ≦ 0.3, and FIG. 2 (b) shows the case of R1 with the constraint of D / R2 ≦ 0.3. The cases of <R2 <R3 are shown.
As apparent from the figure, when there is a constraint condition of D / R2 ≦ 0.3, the maximum stress Smax generated at the neck root portion is further reduced compared to the case without the constraint condition of D / R2 ≦ 0.3. And the variation in stress is also reduced. Although details will be omitted, the value of the radius R2 is necessarily in the range of about 1.0 mm or more from the relationship of D / R2 ≦ 0.3 and R1 <R2 <R3 and the condition of tangential connection at the connection point. It is limited.

As in FIG. 9 (b), FIG. 3 shows the stress generated at the base of the neck when a load is applied from the hole side to the nose side in the neck with the element restrained, by stress analysis. Shows the analysis results of the 3 (a) shows the case of only R1 <R2 <R3 without the constraint of D / R2 ≦ 0.3, and FIG. 3 (b) shows the case of R1 with the constraint of D / R2 ≦ 0.3. The cases of <R2 <R3 are shown.
As apparent from the figure, in the case of the constraint condition of D / R2 ≦ 0.3, the maximum stress Smax generated at the neck root portion is reduced and the variation of the stress is smaller as compared with the case of no constraint condition. ing.

  Thus, as shown in FIG. 2 and FIG. 3, it can be seen that the constraint of D / R2 ≦ 0.3 has a great effect in reducing the stress generated at the neck root.

  By the way, the material characteristic (carbon content: in the range of 0.61 to 0.71%, preferably 0) is added to the above-mentioned shape characteristic (R1 <R2 <R3 and D / R2 ≦ 0.3) relating to the neck root portion. .61 to 0.67%), that is, using a steel material having a carbon content in the above range, the above-mentioned geometrical characteristics (R1 <R2 <R3 and D / R2 ≦ 0.3) In the case of producing the neck root portion, the element has a great effect not only in the stress reduction effect at the neck root portion but also in the improvement of the repeated fatigue strength. Hereinafter, improvement of the repeated fatigue strength according to the present element 100 will be described.

  In FIG. 4, the same quenching and tempering treatment is performed on steel materials A and B with a carbon content [%] of 0.84 and 0.61, respectively, and using these heat-treated steel materials A and B, the neck root (D / R2 = 0.298, 1.0) A total of four types of elements with different part shapes are processed, single unit fatigue tests are performed under the same load conditions as in Fig. 9 (a) or Fig. 9 (b) It is the result of calculating | requiring a figure and calculating | requiring the load corresponded to the fatigue strength in repetition number 1.0E + 5 times, respectively about said 4 types of elements. As used herein, “load equivalent to fatigue strength at a repetition rate of 1.0E + 5 times” refers to the load data of a test body broken at a repetition rate of 1.0E + 5 times or less, as shown in FIG. It is the value S at N = 1.0E + 5 (cycle) in the SN diagram obtained by Further, "the fatigue strength is improved" means that the entire SN chart is shifted upward.

  The steel material B is rich in toughness because the content of the steel material B is smaller than the steel material A, and the 1.0E + 5 times fatigue strength of the material test piece or the like is about 20% or more higher than the steel material A. However, in the shape of the neck root portion of D / R2 = 1.0, when the steel A and the steel B are compared, the improvement in strength is about 5% and the strength difference of the material itself is hardly obtained. This is because the stress concentration at the root of the neck is high and the difference in material strength is almost lost.

  On the other hand, when the result of steel material A and the result of D / R2 = 0.298 of steel material B are compared, the fatigue strength is improved by 50% or more. This is in addition to the effect of alleviating the stress concentration due to the above-mentioned geometric feature (R1 <R2 <R3 and D / R2 ≦ 0.3) in the case of the neck root shape of D / R2 = 0.298 made of steel material B The effect of the material itself is also taken advantage of, which means that the synergistic effect of the shape effect and the material effect results in higher strength.

  As shown in FIG. 4, it can be seen that the improvement of the fatigue strength due to the material effect is different depending on the shape of the neck root portion, that is, the value of D / R 2. Hereinafter, the correlation between the neck root shape and the carbon content [%] will be described.

  In FIG. 5, the steel materials having various carbon contents [%] are subjected to the same quenching and tempering treatment as the above-mentioned FIG. 4, and these heat-treated steel materials are different in neck root shape (D / R2 = 0.298, 0.4 , 1.0), and the same single fatigue test was carried out, respectively, SN graph was obtained, and the load corresponding to the fatigue strength at the repetition number of 1.0E + 5 times was determined for each element.

  When D / R2 = 0.298, in the stress-relaxed neck root shape element, the carbon content [%] becomes maximum strength around 0.6 (0.61 to 0.71), but Above or below, the strength is low. This is considered to be due to the decrease in strength due to insufficient hardness in the region where the carbon content is low, and the decrease in strength due to the decrease in toughness in the region where the carbon content is high. That is, the carbon content [%] which conforms to the above-mentioned topographical features has an optimum value of 0.61 to 0.71, preferably 0.61 to 0.67.

  When D / R2 = 0.4, the fatigue strength gradually increases as the carbon content [%] decreases, but reaches a plateau near 0.65. The material effect is also smaller than the material effect of D / R 2 = 0.298.

  When D / R2 = 1.0, the fatigue strength increases very slowly as the carbon content [%] decreases, but reaches a plateau near 0.6. Regarding the material effect, as described above in FIG. 4, the increase in fatigue strength is about 5%.

FIG. 6 is an explanatory view showing a comparison between the shape of the element of the present invention and the shape of the conventional element.
The depth D of the neck root according to the element of the present invention is smaller than that of the conventional element. This difference (amount of change) can be used as a cutting allowance (moving allowance) for moving the locking edge toward the saddle surface without risk.

  When the locking edge approaches the saddle surface, torque loss due to slippage between the ring and the saddle surface can be reduced near the overdrive (OD) ratio area, as shown in FIG. The power transmission efficiency of the transmission can be suitably improved.

  As described above, according to the element 100 of the present invention, the above-mentioned geometrical characteristics (R1 <R2 <R3 and D / R2 ≦ 0.3) of the neck root portion and the above-mentioned material characteristics (carbon-containing steel material constituting the element) The amount of 0.61 to 0.71%, preferably 0.61 to 0.67%) is combined to suitably reduce the stress generated at the neck root of the element and to improve the cyclic fatigue strength of the element It is possible to This is because, as shown in FIGS. 4 and 5, the fatigue limit and the entire SN diagram are improved. As a result, the torque transmission capacity can be improved without enlarging the size of the element. Further, in the element of the present invention, the distance (D) from the saddle surface to the bottom surface portion is reduced and the stress generated at the neck root portion is reduced, so that the locking edge can be moved to the saddle surface side. As a result, it is possible to reduce torque loss due to slippage between the ring and the saddle surface in the vicinity of the overdrive ratio region, which can contribute to the improvement of the power transmission efficiency of the continuously variable transmission.

100 elements
C1, C2, C3, C4 Arc center
L1, L2, L3, L4, L5 tangent line
n1, n2, n3, n4, n5 normal
PA, PB, PD, PE connection point
PC deepest point
PF saddle top end
PA-PB, PB-PD, PD-PE Curved surface (arc)
R1, R2, R3 Radius of curvature D Distance from the top of the saddle surface to the deepest point (depth)
Distance from W neck side to R start point of saddle surface

Claims (3)

A plurality of strip-shaped metal rings are laminated in an annular pattern along the metal ring assembly by aligning the phases by a plurality of laminated metal ring assemblies, and a saddle surface supporting the metal ring assembly and an upper side from the saddle surface An element for a metal belt of a continuously variable transmission having a neck portion extended to
A recess recessed toward the saddle surface is formed at a neck root portion where the saddle surface intersects the neck portion, and the recess is formed so as to be connected smoothly to the side surface of the neck and not reach the bottom portion of the recess Downward convex first curved surface, and a downward convex second curved surface smoothly connected to the first curved surface and forming the bottom portion, and an upward facing smoothly connected to both the second curved surface and the saddle surface It is composed of a convex third curved surface,
The radius of curvature increases in the order of the first curved surface, the second curved surface, and the third curved surface, and the ratio of the depth of the second curved surface to the radius of curvature of the second curved surface is a value of 0.3 or less An element for a metal belt of a continuously variable transmission characterized by   The steel material constituting the element contains at least carbon (C), silicon (Si), manganese (Mn) and chromium (Cr) as additives, and the content (%) of carbon is 0.61% or more. The element for a metal belt of a continuously variable transmission according to claim 1, characterized in that it is 71% or less. 3. The element for a metal belt of a continuously variable transmission according to claim 1, wherein a depth of the second curved surface is smaller than a distance between a plane including a locking edge and the saddle surface.

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