JP2007057040A - Continuously variable transmission device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuously variable transmission device whose efficiency is prevented from lowering by setting the distance to the working point of a load vector from a toothed ring on a V-pulley to be shorter than 1.3 times as much as a ball pitch circle radius. <P>SOLUTION: The continuously variable transmission device comprises a first shaft 12 rotatably supported on the housing 10, a second shaft 36 rotatably supported on the housing 10, the V-pulley 16 with its variable width supported on the first shaft 12, the ring 30 supported at its outer periphery with both side faces contacting the V-pulley 16, and a mechanism 40 for moving the ring 30 around the second shaft 36. The distance from the working point of the load vector from the ring 30 on the V-pulley 16 to the working point on a bearing is set to be shorter than 1.3 times the ball pitch circle radius of the bearing 18 supporting the V-pulley 16. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a continuously variable transmission used in automobiles and various industrial machines.

Many ideas have been devised for continuously variable transmissions (CVTs). Patent Document 1 describes an example of a traction drive type continuously variable transmission. This continuously variable transmission has a structure in which a pair of pulley members movable in the axial direction sandwich a ring whose teeth are cut on the outer periphery from both sides in the axial direction (see the left side of FIG. 1 and FIG. 2). Torque is transmitted between a first shaft that supports the pulley member and a second shaft that has a gear meshing with the teeth of the ring.
JP 2004-263857 A

  In the device described in Patent Document 1, the support bearing of the V pulley is an angular ball bearing, and the inner ring rotates. And since a ring is pinched | interposed in one place of the radial direction of V pulley, a moment load acts on a support bearing. In this case, it was found that the transmission efficiency decreases when the distance from the point of action of the load vector from the ring to the V pulley to the point of action of the bearing is greater than about 1.3 times the ball pitch circle radius of the support bearing ( (See FIG. 6). In FIG. 6, the horizontal axis represents the pitch circle radius ratio (distance between the load vector and the bearing operating point / pitch circle radius), and the vertical axis represents the transmission efficiency (%).

  A main object of the present invention is to prevent a reduction in transmission efficiency in a continuously variable transmission of the type described in Patent Document 1.

  The continuously variable transmission of the present invention includes a first shaft that is rotatably supported by the housing, a second shaft that is rotatably supported by the housing, and a groove width that is supported by the first shaft is variable. V pulley, a ring that contacts the V pulley on both sides and supported on the outer periphery, and a mechanism for moving the ring around the second axis, and a load vector from the toothed ring to the V pulley The distance from the point of action to the point of action of the bearing is smaller than 1.3 times the ball pitch circle radius of the bearing supporting the V pulley.

  As shown in FIG. 4, by reducing the action point of the load vector from the toothed ring to the V pulley, that is, the distance from the load action point to the bearing action point is less than 1.3 times the pitch circle radius of the ball, The transmission efficiency as shown in FIG. 7 can be obtained, and the reduction of the transmission efficiency as described above with reference to FIG. 6 can be prevented. This reduction in efficiency is estimated from this result because of an increase in bearing torque. That is, it is considered that the contact angle of the ball changes with respect to the phase due to the increase of the moment load, and the torque of the bearing has increased.

  Embodiments of the present invention will be described below with reference to the drawings.

  1 shows a cross section of a continuously variable transmission according to an embodiment of the present invention, and FIG. 2 shows a conceptual diagram of the continuously variable transmission of the present invention. The conventional technology is the same for the conceptual diagram (FIG. 2). As can be understood from these drawings, the continuously variable transmission has a structure in which the ring 30 is sandwiched from both sides in the axial direction by a pair of pulley members 16a and 16b movable in the axial direction. In this embodiment, the ring 30 has teeth such as gears on the outer periphery, and will be hereinafter referred to as a toothed ring.

  In FIG. 1, reference numeral 10 generally indicates a housing. That is, here, the housing is not a single member, but a plurality of members constituting the outer shell of the apparatus as a whole are collectively called a housing. As shown in the figure, two shafts 12 and 36 parallel to each other are rotatably supported in the housing 10 via bearings. These shafts 12 and 36 are in a relationship such that when one axis (12 or 36) is an input shaft, the other axis (36 or 12) is an output shaft.

  The shaft 12 supports a pair of pulley members 16 a and 16 b constituting the V pulley 16. Each pulley member 16a, 16b is composed of a boss portion and a disk portion, and the disk portions face each other to form a V-groove. The disk portion rises in the radial direction from the end of the boss portion. The boss is slidably fitted to the shaft 12 and can be moved in the axial direction of the shaft 12 by a ball spline 14. The structure of the ball spline 14 is a well-known structure in which a ball is interposed between grooves formed in the shaft 12 and the pulley members 16a and 16b.

  FIG. 1 shows a comparison between the prior art and the embodiment of the present invention on the left and right of the center line. The pulley member 16a on the left side of FIG. 1 has a bearing 18a disposed on the outer periphery of the boss portion. The bearing 18a is interposed between the pulley member 18a and the screw shaft 22a and rotatably supports the pulley member 18a. The pulley member 16b on the right side of FIG. 1 has a bearing 18b disposed on the large diameter side of the flange portion. The bearing 18b is interposed between the pulley member 16b and the screw shaft 22b and rotatably supports the pulley member 16b. Because of such a configuration, the bearing 18b has a larger pitch circle diameter than the bearing 18a, and therefore the bearing 18b has a shorter distance from the bearing operating point to the load operating point. Specifically, the same distance is set to less than 1.3 times the pitch circle diameter.

  As shown in FIG. 5, the bearing 18b is a ball bearing that rotates the outer ring. In this case, since the point of action of the bearing is away from the surface of the V pulley, the distance from the load vector is reduced, and the actual moment load is reduced. The size decreases. For this reason, a ball bearing having a smaller pitch circle diameter can be used, and a reduction in torque can be expected, so that transmission efficiency can be improved.

  Note that when a tapered roller bearing is used instead of the ball bearing, the support rigidity of the moment load is remarkably improved, so that the pitch circle need not be increased as described above.

  Each pulley member 16a, 16b is provided with a groove width adjusting mechanism 20. Here, the groove width adjusting mechanism 20 is a ball screw type, and includes screw shafts 22 a and 22 b, a nut 26, and a plurality of balls 28. The screw shafts 22a and 22b have a spiral groove for rolling the ball 28 on the outer periphery, and have a flange 24 with teeth cut on the outer periphery, and are attached to the bosses of the pulley members 16a and 16b via the bearing 18. It is supported rotatably. The nut 26 has a spiral groove for rolling the ball 28 on the inner periphery, and is fixed to the housing 10.

  Similar to a normal ball screw, a ball 28 is interposed between the spiral groove of the screw shafts 22a and 22b and the spiral groove of the nut 26, and the ball 28 circulates along the spiral groove and the screw shafts 22a and 22b. Allows smooth relative rotation and axial movement of the nut 26. In this case, since the nut 26 is fixed, the screw shafts 22a and 22b rotate and move relative to each other in the axial direction. Therefore, when the flange 24 of the screw shafts 22a and 22b is rotated by an external driving means (not shown), the screw shafts 22a and 22b are moved in the axial direction depending on the rotation direction, and the pulley members 16a and 16a are 16b is moved in a direction approaching each other, or the pulley members 16a and 16b are allowed to move in directions away from each other.

  The cross-sectional shape of the side surface of the toothed ring 30 substantially matches the cross-sectional shape of the V groove of the V pulley 16. More specifically, the cross-sectional shape of the side surface of the toothed ring 30 can be a flat surface or a curved surface provided with a secondary curvature. The toothed ring 30 meshes with a gear 34 that is fixed to a shaft 36. The toothed ring 30 has smooth cylindrical guide surfaces 32 on both sides in the axial direction of the teeth that mesh with the teeth of the gear 34, and contacts the guide rollers 42 and 44 at the guide surfaces 32. The guide of the toothed ring 30 employs guide rollers 42 and 44 that roll in contact with the outer peripheral surface of the toothed ring 30 as shown in the figure. A sliding bearing (shoe) that is in sliding contact with the ring 30 may be employed.

  As shown in FIG. 2, in this embodiment, four guide rollers 42, 44 are provided. In FIG. 1, two of them, that is, a pair of discs 42a, 42b arranged on both sides of the gear 34 are shown. A cross section of the guide roller 42 configured and the guide roller 44 appearing in the upper part of the figure is shown. The guide roller 42 is supported so as to be rotatable with respect to the shaft 36. All other guide rollers 44 are rotatably supported by the guide plate 40 via pins 46, respectively. Therefore, the positional relationship between the guide rollers 42 and 44 is fixed. Of these guide rollers 42 and 44, the guide roller 44 appearing at the left end in FIG. 2 also serves to prevent the toothed ring 30 from shaking. The guide plate 40 is coaxially supported by the shaft 36 and is supported by the collar 38 so as to be rotatable.

Since the toothed ring 30 is constrained from the outer periphery by three or more guide rollers 42 and 44, the toothed ring 30 can be rotated without a central axis (centerless roller). The guide rollers 42 and 44 are connected by a guide plate 40, and the rotation center of the toothed ring 30 can be moved around the center O ₁ by turning the guide plate 40. Therefore, the teeth cut on the outer periphery of the toothed ring 30 are always in mesh with the gear 34. If the V pulley 16 and the guide plate 40 are controlled so that there is no gap between the toothed ring 30 and the V pulley 16, the toothed ring 30 moves around the center O _1, whereby The contact point changes, and the speed of the V pulley 16 can be continuously changed with respect to a constant rotation speed of the gear 34. In this way, a so-called CVT is configured.

  When the shaft 12 that supports the V pulley 16 is on the input side, the state in which the toothed ring 30 is pushed in is the deceleration state. If the transmission torque is the same, the clamping force by the V pulley 16 when the toothed ring 30 is pushed in should be increased, and conversely, the contact point between the toothed ring 30 and the V pulley 16 is on the large diameter side. Sometimes it can be small. When considering the bending stress of the V pulley 16 due to the pinching force, this method using the V pulley 16 that can reduce the pinching force at the time of large diameter contact is better than the output.

  When a rotational force is input from the V pulley 16 in the direction indicated by the arrow in FIG. 2, a force F acts on the toothed ring 30 from the V pulley 16, and a force of almost the same magnitude acts from the gear 34. Since the reaction force from the gear 34 acts in a direction to push the toothed ring 30 into the V pulley 16, the contact force automatically increases as the transmission torque increases.

Sectional drawing of continuously variable transmission which shows embodiment (right side) of this invention Conceptual diagram of continuously variable transmission Sectional view of pulley member and support bearing showing conventional technology Sectional drawing of the pulley member and support bearing which show embodiment of this invention Sectional drawing which shows the modification of a pulley member and a support bearing Graph showing the relationship between pitch circle radius ratio and transmission efficiency Graph showing the relationship between pitch circle radius ratio and transmission efficiency

Explanation of symbols

10 housing 12 shaft 14 ball spline 16 V pulley 16a, 14b pulley member P contact portion 18a, 18b bearing 20 groove width adjusting mechanism 22a, 22b screw shaft 24 flange 26 nut 28 ball 30 toothed ring 32 guide surface 34 gear 36 shaft 38 Color 40 Guide plate 42 Guide roller 42a, 42b Side plate 44 Guide roller 46 Pin

Claims (1)

  A first shaft rotatably supported by the housing; a second shaft rotatably supported by the housing; a V pulley having a variable groove width supported by the first shaft; It consists of a ring that contacts the pulley and supported on the outer periphery, and a mechanism for moving the ring around the second axis, from the point of action of the load vector from the toothed ring to the V pulley to the point of action of the bearing Is a continuously variable transmission that is smaller than 1.3 times the ball pitch circle radius of the bearing that supports the V pulley.

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