JP2009264396A - Power transmission device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power transmission device wherein a pin end face and sheave faces have improved wear resistance. <P>SOLUTION: The end face of a driving pin 14 which contacts a pulley 2 is shaped into a convex face. The cross sections of the sheave faces 2c, 2d of the pulley 2 are shaped so that their curvature radii are smaller at small diameter sides 2f, 2g beyond predetermined diameters than at the large diameter sides. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power transmission device suitable for a continuously variable transmission (CVT) of a vehicle such as an automobile.

  As a continuously variable transmission for an automobile, as shown in FIG. 6, a drive pulley (2) provided on the engine side having a fixed sheave (2a) and a movable sheave (2b), a fixed sheave (3b) and a movable sheave (3a) and a driven pulley (3) provided on the drive wheel side and an endless power transmission chain (1) bridged between the two, and a movable sheave (2b) (3a) by a hydraulic actuator The chain (1) is clamped with hydraulic pressure by moving it toward and away from the fixed sheave (2a) (3b), and this clamping force makes contact between the pulley (2) (3) and the chain (1). It is known that a load is generated and torque is transmitted by the frictional force of the contact portion.

As a power transmission chain, in Patent Document 1, a plurality of links having front and rear insertion portions through which pins are inserted, a front insertion portion of one link, and a rear insertion portion of another link correspond to the chain width direction. A plurality of first pins and a plurality of second pins arranged before and after connecting the links arranged in a row, and the first pin and the second pin are relatively in rolling contact and moved, so that the links can be bent in the longitudinal direction. It has been proposed that both ends of the first pin, which is longer than the second pin, come into contact with the pulley and power is transmitted by frictional force.
JP 2005-233275 A

  In the power transmission chain of Patent Document 1, several first pins are always sandwiched between sheave surfaces, but the pulley diameter (the diameter at which the pin end surface and the sheave surface of the pulley are in contact) is small. When the number is large, the contact surface pressure is relatively high when the number of the pinched is different and the number of the pinched is relatively small. When the contact surface pressure is high, the amount of wear increases on both the pin end surface and the sheave surface.

  An object of the present invention is to provide a power transmission device in which wear resistance of a pin end surface and a sheave surface is improved.

  A power transmission device according to the present invention includes a first pulley having a conical sheave surface, a second pulley having a conical sheave surface, and a power transmission chain spanned between the first and second pulleys. The power transmission chain includes a plurality of links having front and rear insertion portions through which pins are inserted, and links arranged in the chain width direction so that a front insertion portion of one link and a rear insertion portion of another link correspond to each other It has a plurality of first pins and a plurality of second pins arranged before and after connecting each other, and at least one end face of each of the first pins and the second pins is in contact with the pulley and power is transmitted by frictional force. In the power transmission device, the end surface shape of the pin that comes into contact with the pulley is a convex curved surface, and the cross-sectional shape of the sheave surface of each pulley is that the radius of curvature on the smaller diameter side is larger than the predetermined diameter. Smaller It is characterized in.

  In order to make the cross-sectional shape of the sheave surface of each pulley smaller than the radius of curvature on the smaller diameter side than the predetermined diameter, various forms are possible. For example, the cross-sectional shape of the sheave surface of each pulley is The whole may be a concave curve. In this case, the sheave surface of each pulley is a modified surface portion that becomes smaller as the radius of curvature goes to the smaller diameter side. Of course, a part of the straight portion (conical portion) may remain on the large-diameter side portion. The sheave surface cross-sectional shape of each pulley may be a straight or convex curve on the larger diameter side than the predetermined diameter, and a concave curve on the smaller diameter side than the predetermined diameter. In any case, the radius of curvature of each curve forming the sheave surface cross-sectional shape of each pulley is preferably set so that the contact surface pressure does not increase on the small diameter side.

  The end surface shape of the pin that comes into contact with the pulley is a convex curved surface, and is inclined with respect to a surface orthogonal to the axial direction of the pin so as to correspond to the inclined surface of the pulley. The larger diameter side than the predetermined diameter of the sheave surface cross-sectional shape of each pulley may be a straight line (may be a convex curve), or may be a concave curve with a large curvature radius, as in the past. On the smaller diameter side than the predetermined diameter, the end surface shape of the pin that comes into contact with the pulley is a concave curved surface corresponding to the convex curved surface. The radius of curvature of the concave curve is made larger than the radius of curvature of the pin end surface. The convex curved surface of the pin that contacts the pulley may be formed with one radius of curvature, or may be formed with two or more radii of curvature. The concave curve of the sheave surface cross-sectional shape of the pulley may be formed with one radius of curvature regardless of the shape of the convex curved surface of the pin, and two or more (for example, the diameter is reduced toward the smaller diameter side) Etc.) may be formed.

  The concave curve of the sheave surface may be provided on the smaller diameter side from the position corresponding to the gear ratio 1: 1, and provided in a narrower range (for example, a range corresponding to the pin height). May be. The number of pins sandwiched between the sheave surfaces varies depending on the transmission ratio (diameter of the sheave surface), and is the smallest on the drive pulley side in the U / D state or the driven pulley side in the O / D state. If the number of pins sandwiched between the sheave surfaces decreases, the contact surface pressure increases, which is disadvantageous to wear (durability) for both the pins and the pulley, but the number of pins sandwiched between the sheave surfaces is small. Since the sheave surface cross-sectional shape is a concave curve on the pulley small diameter side, the contact area increases and the contact surface pressure decreases, thereby improving the durability of the pin and the pulley.

  In the power transmission chain, at least one of the first pin and the second pin comes into contact with the pulley to transmit power by frictional force. In a chain in which one of the pins contacts the pulley, one of the first pin and the second pin is a pin that contacts the pulley when the chain is used in a continuously variable transmission ( In the following, it is referred to as “first pin” or “drive pin”, and the other is referred to as the pin that does not contact the pulley (interpiece or strip). It is called “interpiece”.

  One of the first pin and the second pin is fixed to the front insertion portion of one link and is movably fitted to the rear insertion portion of the other link, and the other is the front insertion portion of the one link. It is preferable that it is movably fitted in and fixed to a rear insertion portion of another link.

  For example, in a chain, three link rows composed of a plurality of links having the same phase in the width direction are arranged in the traveling direction (front-rear direction) to form one link unit, and the link unit composed of the three rows of link rows in the traveling direction. A plurality of links may be formed, and the number of links included in each link row may be different.

  The pin is fixed to the pin fixing portion by, for example, fitting and fixing the inner edge of the pin fixing portion and the outer peripheral surface of the pin by mechanical press-fitting. Alternatively, shrink fitting or cold fitting may be used. The fitting and fixing is preferably performed at the edges (upper and lower edges) of the portion orthogonal to the length direction of the pin fixing portion. After the fitting and fixing, a pre-tension is applied in the pre-tension applying step, so that an appropriate and residual compressive stress is equally applied to the pin fixing portion (pin press-fitting portion) of the link.

  For example, the link is made of spring steel or carbon tool steel. The material of the link is not limited to spring steel or carbon tool steel, and may of course be other steel such as bearing steel. In the link, the front and rear insertion portions may be independent through holes (links with columns), and the front and rear insertion portions may be one through holes (links without columns). Appropriate steel such as bearing steel is used as the material of the pin.

  For example, the first pin and the second pin are formed as involute curved surfaces in which either one of the contact surfaces is a flat surface and the other contact surface is relatively rollable and movable. Moreover, you may make it each contact surface form a required curved surface for the 1st pin and the 2nd pin.

  In this specification, one end side in the length direction of the link is front and the other end side is rear, but this front and rear are for convenience, and the length direction of the link always coincides with the front and rear direction. It doesn't mean that.

  This power transmission device is suitable for use as a continuously variable transmission for a vehicle such as an automobile.

  In such a continuously variable transmission, each pulley includes a fixed sheave having a conical sheave surface and a movable sheave having a conical sheave surface facing the sheave surface of the fixed sheave. By sandwiching the chain between them and moving the movable sheave by the hydraulic actuator, the distance between sheave surfaces of the continuously variable transmission, that is, the winding radius of the chain is changed.

  According to the power transmission device of the present invention, since the radius of curvature of the cross-sectional shape of the sheave surface is reduced on the pulley small-diameter side where the number of pins sandwiched between the sheave surfaces is reduced, the contact surface pressure is reduced. This improves the wear resistance of the pin and pulley.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, the top and bottom refer to the top and bottom of FIG.

  FIG. 1 shows a part of a power transmission chain used in the power transmission device according to the present invention. The power transmission chain (1) is a front-rear insertion portion (with a predetermined interval in the chain length direction). 12) A plurality of links (11) having (13) and a plurality of drive pins (first pins) (14) and an interpiece for connecting the links (11) arranged in the chain width direction so as to be bendable in the length direction (Second pin) (15). The interpiece (15) is made shorter than the drive pin (14), and both face each other with the interpiece (15) disposed on the front side and the drive pin (14) disposed on the rear side.

  In the chain (1), three link rows composed of a plurality of links having the same phase in the width direction are arranged in the traveling direction (front-rear direction) to form one link unit, and the link unit composed of the three rows of link rows is the traveling direction. Are connected to each other. In this embodiment, one link unit includes a link row having nine links and two link rows having eight links.

  As shown in FIG. 2, the drive pin (14) is wider in the front-rear direction than the interpiece (15). Protruding edges (15a) and (15b) extending toward the drive pin (14) are provided on the upper and lower edges of the interpiece (15). The link (11) includes a front column portion (20) for forming the front shape of the front insertion portion (12) and a rear column portion (22) for forming the rear shape of the rear insertion portion (13). And an intermediate column portion (21) between the front insertion portion (12) and the rear insertion portion (13). The front insertion part (12) of the link (11) includes a drive pin movable part (16) to which the drive pin (14) is movably fitted and an interpiece fixing part (17) to which the interpiece (15) is fixed. The rear insertion portion (13) includes a drive pin fixing portion (18) to which the drive pin (14) is fixed and an interpiece movable portion (19) to which the interpiece (15) is movably fitted.

  When connecting the links (11) aligned in the chain width direction, the links (11) so that the front insertion part (12) of one link (11) and the rear insertion part (13) of the other link (11) correspond to each other ( 11) are overlapped, and the drive pin (14) is fixed to the rear insertion part (13) of one link (11) and movably fitted to the front insertion part (12) of the other link (11). The interpiece (15) is movably fitted to the rear insertion portion (13) of one link (11) and fixed to the front insertion portion (12) of the other link (11). The drive pins (14) and the interpiece (15) are relatively rolled and brought into contact with each other, whereby the links (11) can be bent in the length direction (front-rear direction).

  At the boundary between the drive pin fixing part (18) and the interpiece movable part (19) of the link (11), the upper and lower concave arcuate guide parts (19a) and (19b) of the interpiece movable part (19) are respectively provided. Upper and lower convex arc-shaped holding portions (18a) and (18b) for holding the drive pin (14) fixed to the continuous drive pin fixing portion (18) are provided. Similarly, the boundary between the interpiece fixing part (17) and the drive pin movable part (16) is connected to the upper and lower concave arcuate guide parts (16a) and (16b) of the drive pin movable part (16), respectively. Upper and lower convex arc-shaped holding portions (17a) and (17b) for holding the interpiece (15) fixed to the piece fixing portion (17) are provided.

  The locus of the contact position between the drive pin (14) and the interpiece (15) with respect to the drive pin (14) is an involute of a circle.In this embodiment, the contact surface of the drive pin (14) is The cross section has an involute shape having a base circle of radius Rb and center M, and the contact surface of the interpiece (15) is a flat surface (the cross-sectional shape is a straight line). As a result, when each link (11) moves from the straight portion of the chain (1) to the curved portion or from the curved portion to the straight portion, the drive pin (14) is fixed in the front insertion portion (12). The contact surface of the interpiece (15) moves in the drive pin movable portion (16) while rolling (including a slight sliding contact) with the contact surface of the interpiece (15), and the rear insertion portion (13 ), The interpiece (15) rolls into contact with the contact surface of the drive pin (14) with respect to the drive pin (14) fixed in the interpiece movable part (19) (slight sliding contact) Move). In FIG. 2, the portions indicated by reference signs A and B are lines (dots in the cross section) where the drive pin (14) and the interpiece (15) are in contact with each other in the straight portion of the chain (1). The distance between them is the pitch.

  FIG. 3 shows a first embodiment of a power transmission device according to the present invention, in which the power transmission chain (1) is attached to a V-type pulley type CVT shown in FIG. In the power transmission device, the end face of the interpiece (15) is in contact with the conical sheave surfaces (2c) and (2d) of the fixed sheave (2a) and the movable sheave (2b) of the pulley (2) having the pulley shaft (2e). In such a state, the end surface of the drive pin (14) comes into contact with the conical sheave surfaces (2c) and (2d) of the pulley (2), and power is transmitted by the frictional force generated by this contact.

  As shown in FIG. 3, the end surface (contact surface) shape of the drive pin (14) is a convex curved surface. A curved surface portion (2f) for reducing the contact surface pressure is formed on the small diameter side of the pulley (2). That is, the cross-sectional shape of the sheave surfaces (2c) and (2d) of the pulley (2) is a straight line (cone as a whole) having a predetermined inclination angle (for example, 11 °), as in the past, except for the small diameter side portion. In addition, the small diameter side of the pulley (2) is a curved surface portion (2f), and the cross-sectional shape thereof is a concave curve.

  When the movable sheave (2b) of the drive pulley (2) at the position indicated by the solid line in FIG. 3 is moved toward and away from the fixed sheave (2a), the winding diameter of the drive pulley (2) is as shown in FIG. As indicated by the chain line, it is large when approaching and small when separated. Although not shown in the drawing of the driven pulley (3), when the movable sheave moves in the opposite direction to the movable sheave (2b) of the drive pulley (2) and the winding diameter of the drive pulley (2) increases, the driven pulley (2) When the winding diameter of (3) decreases and the winding diameter of the drive pulley (2) decreases, the winding diameter of the driven pulley (3) increases. As a result, on the basis of the state where the gear ratio is 1: 1 (initial value), the winding diameter of the drive pulley (2) is minimum and the winding diameter of the driven pulley (3) is maximum U / D. An (underdrive) state is obtained, and an O / D (overdrive) state in which the winding diameter of the drive pulley (2) is maximum and the winding diameter of the driven pulley (3) is minimum is obtained.

  The number of drive pins (14) sandwiched between the sheave surfaces (2c) and (2d) varies depending on the gear ratio (diameter of the sheave surface), and the drive pulley (2 in the U / D state in which the winding diameter is minimized) ) Side or the driven pulley (3) side in the O / D state. When the number of drive pins (14) sandwiched between the sheave surfaces (2c) and (2d) decreases, the contact surface pressure increases relatively, both for the drive pins (14) and for the pulleys (2) and (3). This is disadvantageous for wear (durability). The curved surface (2f) on the small diameter side of the pulley (2) (same for the pulley (3)) is intended to improve this wear resistance, and is a drive that is sandwiched between the sheave surfaces (2c) and (2d) By forming this curved surface part (2f) on the small diameter side of the pulley (2) where the number of pins (14) is reduced, the end surface (curved surface) of the drive pin (14) is on the small diameter side of the pulley (2). Then, the cross-sectional shape comes into contact with the curved surface portion (2f) having a concave curve, the contact area increases, and the contact surface pressure decreases. As a result, the wear resistance of both the drive pin (14) and the pulleys (2) and (3) is improved, and the durability of the power transmission device is improved.

  FIG. 4 shows a second embodiment of the power transmission device according to the present invention, and the cross-sectional shapes of the pulleys (2) and (3) are different from those of the first embodiment.

  In the figure, a curved surface portion (2f) similar to that of the first embodiment is formed on the small diameter side of the pulley (2) (the same applies to the pulley (3)), and the curvature of the curved surface portion (2f) is the same. A radius-change curved surface portion (2g) having a radius of curvature that increases as the diameter increases is formed in a portion on the larger diameter side than the curved surface portion (2f) with the radius being minimized.

  According to the second embodiment, the curved surface portion (2f) having the minimum curvature radius on the small-diameter side of the pulley (2) in which the number of drive pins (14) sandwiched between the sheave surfaces (2c) and (2d) is reduced, and Since the modified curved surface portion (2g) is formed, the end surface (curved surface) of the drive pin (14) on the small diameter side of the pulley (2) has a curved surface portion (2f) whose cross-sectional shape is a concave curve and Contact with the modified curved surface portion (2g) increases the contact area and decreases the contact surface pressure. As a result, the wear resistance of both the drive pin (14) and the pulleys (2) and (3) is improved, and the durability of the power transmission device is improved.

  FIG. 5 shows the relationship between the contact diameter and the contact surface pressure between the drive pin (14) and the pulley (2) for the conventional power transmission device and the power transmission device according to the present invention. As shown in the figure, in the conventional power transmission device, the contact surface pressure is relatively small on the large diameter side of the pulley (2) indicated by A, and even if the contact diameter is small, the contact surface pressure is not so much. Although it does not change, the contact surface pressure is relatively large in the part indicated by the arrow in (a), and the contact surface pressure increases rapidly on the small diameter side of the pulley (2) indicated by B, and the pulley indicated by C The contact surface pressure is maximum at the minimum diameter part of (2). Therefore, the wear of the drive pin (14) and the pulleys (2) and (3) becomes relatively large in the small diameter side portions indicated by B and C, which may cause a decrease in wear resistance. In the power transmission device according to the present invention, the radius of curvature of each curve forming the cross-sectional shape of the sheave surface of each pulley (2) is set so that the contact surface pressure does not increase on the small diameter side. Reduces the contact surface pressure at the minimum diameter portion of the pulley (2) indicated by C, and the second embodiment has a small diameter side portion indicated by B and C (portion indicated by an arrow in (b)). By reducing the contact surface pressure, the wear resistance is improved.

  As can be seen from FIG. 5, the cross-sectional shape of the sheave surface of the pulley (2) is not limited to the above, and the radius of curvature of the curve on the smaller diameter side than the predetermined diameter is the curve on the larger diameter side (straight line). Wear resistance can be improved by setting the radius of curvature of each curve so that the contact surface pressure does not increase on the small diameter side.

  In this power transmission chain (1), the required number of drive pins (14) and interpieces (15) are held vertically on an assembly jig, and then one or several links (11) are assembled together. Manufactured by press-fitting. This press-fitting is performed between the upper and lower edges of the drive pin (14) and the interpiece (15) and the upper and lower edges of the drive pin fixing part (18) and the interpiece fixing part (17). The cost is 0.005 mm to 0.1 mm. In this way, tension is applied (pre-tensioned) to the assembled chain (1).

  In the above power transmission chain (1), polygonal vibration occurs due to repeated vertical movement of the pin, which causes noise, but the drive pin (14) and the interpiece (15) are relatively in rolling contact. Because the locus of the contact position between the drive pin (14) and the interpiece (15) with respect to the drive pin (14) is an involute of a circle, both the contact surfaces of the drive pin and the interpiece are Compared with the case of a circular arc surface, vibration can be reduced and noise can be reduced. When used in the CVT, the drive pin (14) and the interpiece (15) are guided by the movable parts (16) and (19) as described above to move in rolling contact. ), The drive pin (14) hardly rotates with respect to the sheave surfaces (2c) and (2d), the friction loss is reduced, and a high power transmission rate is secured.

FIG. 1 is a plan view showing a part of a chain used in the power transmission device according to the present invention. FIG. 2 is an enlarged side view of the main part of FIG. FIG. 3 is a front view showing a first embodiment of the power transmission device according to the present invention. FIG. 4 is a front view showing a second embodiment of the power transmission device according to the present invention. FIG. 5 is a diagram showing the relationship between the contact diameter and the contact surface pressure of the drive pin and the pulley for the conventional power transmission device and the power transmission device according to the present invention. FIG. 6 is a perspective view showing a conventional power transmission device.

Explanation of symbols

(1) Power transmission chain
(2) (3) Pulley
(2a) (3b) Fixed sheave
(2b) (3a) Movable sheave
(2c) (2d) Conical sheave surface
(2f) Curved surface
(2g) Variable surface area
(11) Link
(12) Front insertion part
(13) Rear insertion part
(14) Drive pin (first pin)
(15) Interpiece (2nd pin)

Claims (4)

A first pulley having a conical sheave surface; a second pulley having a conical sheave surface; and a power transmission chain that spans between the first and second pulleys. A plurality of links having front and rear insertion portions through which pins are inserted, and a plurality of links arranged before and after connecting links aligned in the chain width direction so that a front insertion portion of one link and a rear insertion portion of another link correspond to each other. A power transmission device having a first pin and a plurality of second pins, wherein at least one end surface of the first pin and the second pin is in contact with the pulley and power is transmitted by frictional force.
The end surface shape of the pin that contacts the pulley is a convex curved surface, and the sheave surface cross-sectional shape of each pulley is characterized in that the radius of curvature on the smaller diameter side than the predetermined diameter is smaller than the radius of curvature on the larger diameter side. Power transmission device.   2. The power transmission device according to claim 1, wherein the sheave surface cross-sectional shape of each pulley is a concave curve as a whole.   The sheave surface cross-sectional shape of each pulley is a straight or convex curve on the larger diameter side than the predetermined diameter, and a concave curve on the smaller diameter side than the predetermined diameter. Power transmission device.   4. The power transmission device according to claim 1, wherein the curvature radius of each curve is set so that the contact surface pressure does not increase on the small diameter side.

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