JP2006118535A - Belt type continuously variable transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a belt type continuously variable transmission constructed to sufficiently satisfy both a high friction coefficient between a pulley and a metal belt and wear resistance. <P>SOLUTION: Surface treatment is applied to a pulley slope PS of at least one of a driving pulley 12 and a driven pulley 22 with hard turning and subsequent shot blasting. A spiral groove formed with hard turning is used as an oil passage for efficiently discharging extra lubricating oil and a number of uneven portions formed on the pulley slope PS with shot blasting are used for increasing a contact area with the metal belt, whereby a friction coefficient against the metal belt 30 is held at a higher value. The hardness of the pulley slope PS is improved by shot blasting and residual compressive stress is additionally imparted thereto, resulting in an increase in the wear resistance of the pulley slope PS. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a belt-type continuously variable transmission configured so that a gear ratio can be changed steplessly by passing a metal belt between two pulleys and changing the groove width of each pulley.

  The belt type continuously variable transmission has a configuration in which a metal belt is stretched between a drive pulley provided on an input-side shaft member and a driven pulley provided on an output-side shaft member. The gear ratio can be changed steplessly by changing the groove width of each of the drive pulley and the driven pulley. Such a belt-type continuously variable transmission can be smoothly changed according to the load state of the prime mover, and is therefore used as a power transmission device for various power machines including automobiles.

  In such a belt type continuously variable transmission, power transmission between the drive and driven pulleys (hereinafter simply referred to as pulleys) and the metal belt is performed by friction on the contact surface between the pulley and the metal belt. Therefore, it is necessary to generate a required frictional force between the pulley slope and the metal belt, and the pulley slope is subjected to a polishing process to obtain an appropriate surface roughness. In addition, lubricating oil for preventing seizure and cooling is supplied between the pulley slope and the metal belt, but if this lubricant is too much, slippage occurs and the coefficient of friction between the pulley slope and the metal belt is increased. Therefore, excess lubricating oil must be discharged efficiently. Furthermore, from the viewpoint of securing the required service life, the pulley slope is also required to have high wear resistance.

As an example of such a belt-type continuously variable transmission, a large number of minute irregularities are formed on a pulley slope, and the tip of the minute irregularities is polished to be processed into a flat surface (see Patent Document 1 and Patent Document 2) and those that perform finish polishing after cutting a spiral groove on a pulley slope (see Patent Document 3 below) are known. Further, on each element or pulley slope constituting the metal belt, a plurality of grooves that intersect with each other and have substantially the same width and depth (see Patent Document 4 below), and arithmetic of the pulley slope Also known is one in which the average roughness and surface hardness are within predetermined values (see Patent Document 5 below).
JP 60-109661 A Japanese Patent Laid-Open No. 5-10405 Japanese Patent No. 2686973 Japanese Patent Laid-Open No. 62-184270 JP 2000-130527 A

  However, the belt-type continuously variable transmissions described in Patent Documents 1 to 3 are expensive because there is a process of polishing the pulley slope, and in the one described in Patent Document 4, the discharge of lubricating oil is efficient. Although often done, the coefficient of friction between the pulley ramp and the metal belt is insufficiently improved. Further, in the belt-type transmission described in Patent Document 5, although the wear resistance of the pulley is improved, the friction coefficient between the pulley slope and the metal belt is insufficient.

  The present invention has been made in view of such problems, and can increase the coefficient of friction between the pulley slope and the metal belt, and can simultaneously improve the wear resistance of the pulley slope. An object of the present invention is to provide a belt-type continuously variable transmission having a simple structure.

  The belt type continuously variable transmission according to the present invention includes a drive pulley provided on an input-side shaft member (for example, the hollow shaft 11 in the embodiment) and an output-side shaft member (for example, the output shaft 20 in the embodiment). ) Having a driven pulley provided above and a metal belt stretched between the pulley slope of the drive pulley and the pulley slope of the driven pulley, and changing the groove width of the drive pulley and the groove width of the driven pulley, respectively. In the belt-type continuously variable transmission configured so that the transmission gear ratio can be changed steplessly, at least one of the drive pulley and the driven pulley is subjected to surface treatment by hard turning treatment and subsequent shot blast treatment. It has been made.

Further, in the belt type continuously variable transmission, when the surface properties of the pulley slope after the shot blasting process are expressed as Ra, the arithmetic average roughness is Ra, the effective load roughness is Rk, and the oil sump depth is Rvk. > 0.7 and Rk / (Rk + Rvk)> 0.7
Is preferably satisfied.

  In the belt-type continuously variable transmission according to the present invention, the pulley inclined surfaces which are the contact surfaces of the drive pulley and the driven pulley with the metal belt are subjected to surface treatment by a hard turning treatment and a shot blast treatment performed thereafter. That is, first, a hard turning process is performed to form a spiral groove on the pulley slope, and the next shot blasting process removes the tip of the spiral groove and forms an infinite number of irregularities on the pulley slope. . The contact area with the metal belt can be efficiently discharged by using the spiral groove formed by the hard turning process as an oil path and the numerous irregularities formed on the pulley slope by the shot blasting process. By increasing this, the coefficient of friction with the metal belt can be maintained at a high value. Further, the hardness of the pulley slope is improved by the shot blasting process, and in addition, the residual compressive stress is given, so that the wear resistance of the pulley slope can be increased. Moreover, since it does not have the process of grind | polishing a pulley slope, manufacturing cost can also be made cheap.

In the surface treatment of such a pulley slope, the surface properties of the pulley slope after the shot blasting are expressed by the equation Ra, where Ra is the arithmetic average roughness, Rk is the effective load roughness, and Rvk is the oil sump depth. > 0.7 and Rk / (Rk + Rvk)> 0.7
By satisfying the above, it is possible to satisfy both the increase of the coefficient of friction between the pulley inclined surface and the metal belt and the improvement of the wear resistance of the pulley inclined surface in an optimum state.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a belt type continuously variable transmission CVT according to an embodiment of the present invention, and FIG. 2 shows a vehicle power transmission device 1 equipped with this belt type continuously variable transmission (hereinafter referred to as a transmission) CVT. Show. This vehicle power transmission device 1 converts the rotational speed and torque of the engine EG with a transmission CVT, and transmits the rotational power of the engine EG to the left and right drive wheels (vehicle front wheels) WL and WR via the differential mechanism 60. have.

  The transmission CVT includes an input shaft 10 and a hollow shaft 11 which are input side members, an output shaft 20 which is an output side member, a drive pulley 12 provided on the hollow shaft 11, a driven pulley 22 provided on the output shaft 20, and The metal belt 30 is stretched between the drive pulley 12 and the driven pulley 22 and is housed in a transmission case (not shown) together with the intermediate shaft 40 and the differential mechanism 60. The input shaft 10 is connected to the crankshaft CS of the engine EG via a coupling mechanism CP, and the hollow shaft 11 is held on the outer peripheral side of the input shaft 10 so as to be rotatable relative to the input shaft 10. A planetary gear mechanism 14 is provided between the hollow shaft 11 and the input shaft 10. An intermediate shaft drive gear 24 and a start clutch 25 are provided on the output shaft 20, and an intermediate shaft driven gear 42 and a final drive gear 44 are provided on the intermediate shaft 40.

  The drive pulley 12 includes a fixed-side drive pulley half 12a fixed on the hollow shaft 11 and a movable-side drive pulley half provided so as not to rotate relative to the hollow shaft 11 and to be movable in the axial direction of the hollow shaft 11. And a pulley side pressure (hydraulic oil pressure) in a cylinder chamber (hydraulic chamber) 13 provided on the side of the movable drive pulley half 12b (right side in FIG. 2). By generating the thrust, the movable drive pulley half 12 b can be moved relative to the cylinder wall 13 a fixed to the hollow shaft 11. That is, the drive pulley 12 is configured to be able to change the groove width (interval between the two drive pulley halves 12a and 12b) in accordance with the applied pulley thrust. Specifically, when the pressure in the cylinder chamber 13 is increased to increase the pulley thrust, the movable drive pulley half 12b approaches the fixed drive pulley half 12a against the tension of the metal belt 30 ( When the groove width of the drive pulley 12 is narrowed (moving to the left in FIG. 2) and the pressure in the cylinder chamber 13 is reduced to reduce the pulley thrust, the movable drive pulley half 12b is attached to the metal belt 30. The groove width of the drive pulley 12 is widened away from the fixed-side drive pulley half 12a by the tension (moved to the right in FIG. 2).

  The driven pulley 22 includes a fixed-side driven pulley half 22a fixed on the output shaft 20 and a movable-side driven pulley half provided so as not to rotate relative to the output shaft 20 and to be movable in the axial direction of the output shaft 20. By generating pulley thrust by applying pulley side pressure to a cylinder chamber (hydraulic chamber) 23 provided on the side of the movable driven pulley half 22b (left side in FIG. 2). The movable driven pulley half 22 b can be moved relative to the cylinder wall 23 a fixed to the output shaft 20. That is, the driven pulley 22 is configured to be able to change the groove width (interval between the drive pulley halves 22a and 22b) in accordance with the applied pulley thrust. Specifically, when the pressure in the cylinder chamber 23 is increased to raise the pulley thrust, the movable driven pulley half 22b approaches the fixed driven pulley half 22a against the tension of the metal belt 30 ( When the groove width of the driven pulley 22 is narrowed (moving to the right in FIG. 2) and the pressure in the cylinder chamber 23 is lowered to reduce the pulley thrust, the movable driven pulley half 22b is moved to the metal belt 30. The groove width of the driven pulley 22 is widened away from the fixed-side driven pulley half 22a by the tension (moved to the left in FIG. 2).

  The planetary gear mechanism 14 includes a sun gear 14 a that rotates integrally with the input shaft 10, a ring gear 14 b that is formed integrally with the hollow shaft 11, and a planetary carrier 14 c that is provided to be rotatable relative to the input shaft 10. The planetary carrier 14c is rotatably supported, and has a plurality of planetary gears 14d that are always meshed with both the sun gear 14a and the ring gear 14b. A forward clutch 15 is provided between the sun gear 14a and the ring gear 14b, and a reverse brake 16 is provided between the planetary carrier 14c and the transmission case. The forward clutch 15 receives a hydraulic operation of a clutch piston (not shown) to connect and release the sun gear 14a and the ring gear 14b, and the reverse brake 16 receives a hydraulic operation of a brake piston (not shown) to receive the planetary carrier 14c and the transmission case. The connection with the member 3 and the release thereof are performed.

  Here, when the forward clutch 15 is engaged (the sun gear 14a and the ring gear 14b are coupled), the sun gear 14a and the ring gear 14b are unable to rotate relative to each other, and the reverse brake 16 is engaged (the planetary carrier 14c and the transmission case on the transmission case). When the member 3 is coupled), the planetary carrier 14c and the transmission case cannot be rotated relative to each other. For this reason, when the forward clutch 15 is engaged with the input shaft 10 rotated (the reverse brake 16 is disengaged), the hollow shaft 11 rotates integrally with the input shaft 10, thereby driving pulleys. 12 rotates in the same direction as the input shaft 10 (this is referred to as forward rotation). At this time, since the sun gear 14a and the ring gear 14b do not rotate relative to each other, the planetary gears 14d rotate (revolve) around the input shaft 10 together with the sun gear 14a and the ring gear 14b without rotating. On the other hand, when the reverse brake 16 is engaged with the input shaft 10 rotated (the forward clutch 15 is disengaged), the sun gear 14a rotates integrally with the input shaft 10, while each planetary gear 14d rotates. Since the ring gear 14b is rotated in the direction opposite to the sun gear 14a, the drive pulley 12 formed integrally with the ring gear 14b via the hollow shaft 11 rotates in the direction opposite to the input shaft 10 (the reverse of this). Direction rotation). When both the forward clutch 15 and the reverse brake 16 are disengaged, only the input shaft 10 and the sun gear 14a integrated therewith rotate, and the rotational power of the engine EG is the hollow shaft 11, that is, the drive pulley. 12 is not transmitted.

  The intermediate shaft drive gear 24 is provided so as to be rotatable relative to the output shaft 20, and the start clutch 25 receives the hydraulic operation of a clutch piston (not shown) to couple and release the output shaft 20 and the intermediate shaft drive gear 24. I do. Here, when the start clutch 25 is engaged (the output shaft 20 and the intermediate shaft drive gear 24 are coupled), the intermediate shaft drive gear 24 cannot rotate relative to the output shaft 20. Therefore, when the start clutch 25 is engaged with the output shaft 20 rotating, the intermediate shaft drive gear 24 rotates together with the output shaft 20 together with the output shaft 20.

  The metal belt 30 spanned between the drive pulley 12 and the driven pulley 22 has a configuration in which a number of metal elements 32 are fitted between two steel bands 31, 31 as shown in FIG. It has become. Each element 32 has both side surfaces 32a and 32a formed in a V shape, and these V-shaped side surfaces are pulley inclined surfaces PS (conical shapes) facing the drive pulley halves 12a and 12b constituting the drive pulley 12. And the metal belt 30 is suitable for both pulleys 12 and 22 so as to be sandwiched between the opposed pulley inclined surfaces PS of the driven pulley halves 22a and 22b constituting the driven pulley 22. By applying a pulley thrust force (which does not slip), the power of the engine EG can be transmitted from the drive pulley 12 to the driven pulley 22.

  The intermediate shaft driven gear 42 and the final drive gear 44 are both fixedly provided on the intermediate shaft 40, and the intermediate shaft driven gear 42 is always meshed with the intermediate shaft drive gear 24 provided on the output shaft 20. Further, the final drive gear 44 is always meshed with a final driven gear 64 fixed to the differential case 61 of the differential mechanism 60.

  The differential mechanism 60 is configured such that a differential mechanism 63 including two differential pinions 62a and 62a and two side gears 62b and 62b is accommodated in a differential case 61. The side gears 62b and 62b include left and right axles. The shafts ASL and ASR are fixed. The left and right axle shafts ASL and ASR are arranged so that the central axes thereof are parallel to the central axis of the intermediate shaft 40, and the differential case 61 rotates with the central axes of the left and right axle shafts ASL and ASR as rotation axes. Supported to be able to. Also, left and right drive wheels WL, WR are attached to the ends of the left and right axle shafts ASL, ASR. Since the final driven gear 64 fixed to the differential case 61 is always meshed with the final drive gear 44 as described above, when the intermediate shaft 40 rotates, the entire differential case 61, together with the left and right axle shafts ASL and ASR, these axles. It rotates around the central axis of shafts ASL and ASR.

  Here, when the rotational power of the engine EG is input to the input shaft 10 in a state where an appropriate pulley thrust without causing the metal belt 30 to slip is applied to each of the drive pulley 12 and the driven pulley 22, the rotational power is Input shaft 10 → drive pulley 12 → metal belt 30 → driven pulley 22 → output shaft 20 is transmitted. The groove width of each of the pulleys 12 and 22 can be changed by increasing or decreasing the pulley thrust of each of the drive pulley 12 and the driven pulley 22, and the winding radius ratio (pulley ratio) of the metal belt 30 to both the pulleys 12 and 22 can be changed. ) Can be changed to achieve smooth stepless shifting.

  Specifically, when control is performed to increase the pulley thrust of the driven pulley 22 and decrease the pulley thrust of the drive pulley 12, the groove width of the driven pulley 22 is narrow and the groove width of the drive pulley 12 is set wide. Therefore, the wrapping radius of the metal belt 30 with respect to the driven pulley 22 is larger than the wrapping radius with respect to the drive pulley 12, and the transmission CVT is in a low ratio state corresponding to low speed running (the rotational speed of the output shaft 20 is the rotational speed of the input shaft 10). A state where the speed is smaller than the speed). Further, when the control is performed so that the pulley thrust of the drive pulley 12 and the pulley thrust of the driven pulley 22 are approximately the same, the groove width of the drive pulley 12 and the groove width of the driven pulley 22 are set to be substantially equal. Therefore, the wrapping radius of the metal belt 30 with respect to the drive pulley 12 and the wrapping radius with respect to the driven pulley 22 are substantially equal, and the transmission CVT is in a medium ratio state corresponding to medium speed running (the rotational speed of the output shaft 20 is the input shaft 10). The rotation speed is almost the same as that of the rotation speed. Further, when control is performed to increase the pulley thrust of the drive pulley 12 and decrease the pulley thrust of the driven pulley 22, the groove width of the drive pulley 12 is set narrow and the groove width of the driven pulley 22 is set wide. The winding radius of the belt 30 with respect to the drive pulley 12 is larger than the winding radius with respect to the driven pulley 22, and the transmission CVT is in a high ratio state corresponding to high speed running (the rotational speed of the output shaft 20 is larger than the rotational speed of the input shaft 10). State).

  When the start clutch 25 is engaged with the rotational power of the engine EG transmitted from the input shaft 10 to the output shaft 20 as described above, the intermediate shaft drive gear 24 rotates integrally with the output shaft 20. The rotational power of the engine EG transmitted to the output shaft 20 is further transmitted from the intermediate shaft drive gear 24 to the intermediate shaft driven gear 42, and the intermediate shaft 40 rotates. As a result, the final drive gear 44 on the intermediate shaft 40 rotates the final driven gear 64, that is, the differential case 61, so that the left and right drive wheels WL, WR are connected via the axle shafts ASL, ASR connected to the left and right side gears 62b, 62b. Is driven. On the other hand, when the start clutch 25 is disengaged, the intermediate shaft drive gear 24 and the output shaft 20 are not connected, and the rotational power of the output shaft 20 is not transmitted to the intermediate shaft drive gear 24. WR is not driven.

  Although the operation of the transmission CVT is as described above, the transmission CVT is characterized by the surface treatment process of each pulley inclined surface PS which is a contact surface with the metal belt 30 of each of the drive pulley 12 and the driven pulley 22. This will be described below.

  The drive pulley 12 and the driven pulley 22 are usually subjected to rough processing of heat-treated carburized steel, and after the entire shape is adjusted by forging or the like, each of the pulley slopes PS in contact with the metal belt 30 is polished. However, in the transmission CVT, each pulley slope PS is not polished after forging or the like, but is subjected to shot blasting after hard turning.

  The reason why the hard turning process is first applied to each pulley slope PS is to form a spiral groove on the pulley slope PS after forging. This is because when the transmission CVT is used, lubricating oil for preventing seizure and cooling is supplied between the pulley inclined surfaces PS of the pulleys 12 and 22 and the elements 32 of the metal belt 30. If the lubricating oil is too much, slipping occurs, so that a thin oil film is stretched on the contact surface between the pulley inclined surface PS and each element 32. For this reason, it is necessary to discharge the excess lubricating oil efficiently, but these spiral grooves function as a discharge oil passage for the excess lubricating oil.

  Further, the shot blasting process is performed on the pulley inclined surface PS after the hard turning process to remove the tip of the spiral groove formed by the hard turning and to add countless minute uneven parts to the pulley inclined surface PS. It is for forming. As described above, the spiral groove formed by the hard turning process can be used as an oil passage to efficiently discharge excess lubricating oil, and the countless uneven parts formed on the pulley slope PS by the shot blasting process can be used to form a metal. By increasing the contact area of the belt 30 with each element 32, the coefficient of friction with the metal belt 30 can be maintained at a high value. Moreover, since the hardness of the pulley inclined surface PS is improved by the shot blasting process and the residual compressive stress is applied, it is possible to increase the wear resistance of the pulley inclined surface PS. In addition, since there is no step of polishing the pulley slope PS, the manufacturing cost can be reduced.

  As described above, by applying the hard turning process and the subsequent shot blasting process to each pulley slope PS, the contact area with the element 32 can be increased and a high friction coefficient can be ensured. From a viewpoint, it is as follows.

  Each graph of FIG. 4 is a graph of a load curve, the horizontal axis of each graph is the load length ratio tp (%), and the vertical axis is the surface roughness R. 4A is a graph of a load curve when neither the hard turning process nor the shot blasting process is performed, and FIG. 4B is a load curve when only the hard turning process is performed and the shot blasting process is not performed. FIG. 4C is a graph of a load curve when the shot blast process is performed after the hard turning process, and FIG. 4D is a load curve when the shot blast process is performed without performing the hard turning process. It is a graph of. Here, when FIG. 4 is viewed in the order of (A) → (B) → (C), the surface roughness is obtained by performing shot blasting after the hard turning process (therefore, an arithmetic average serving as one index of the surface roughness). It can be seen that the roughness Ra) increases. Further, referring to FIG. 4D, when only the shot blasting process is performed without performing the hard turning process, the hard turning process is performed not only when the shot blasting process is performed after the hard turning process. It can be seen that the surface roughness is smaller than when no shot blasting is performed.

  FIG. 5 is a graph of a load curve for explaining how to obtain the effective load roughness and the oil sump depth, which is another index of the surface roughness. A straight line n having the smallest inclination is obtained from the straight lines passing through the two points A and B such that the difference in the value of the load length ratio tp is 40% at the point on the load curve m. Then, the intersections of the straight line n and the load length ratios tp = 0% and 100% are defined as points C and D, respectively, and the intersection of the cutting line s passing through the point D and the load curve m is defined as a point E. And an intersection of the load curve m and the load length ratio tp = 100% is defined as a point F. Then, a point G on tp = 100% is obtained such that the area of the region surrounded by the line segment DE, the line segment DF, and the curve EF is equal to the area of the triangle DEG. At this time, the difference in cutting level between point C and point D is referred to as effective load roughness Rk (μm), and the target surface (here, pulley slope PS) wears until it becomes unusable due to long-term wear. Represents height (depth). The distance between point D and point G is referred to as oil sump depth Rvk (μm), and represents the depth of the oil sump valley.

As described above, the transmission CVT has a surface treatment by the hard turning process and the shot blasting process performed thereafter on the pulley inclined surfaces PS that are in contact with the metal belt 30 in the drive pulley 11 and the driven pulley 22. In addition, a configuration that sufficiently satisfies both the high friction coefficient and the wear resistance between the pulleys 12 and 22 and the metal belt 30 can be obtained. The surface properties are expressed by the formula Ra> 0.7 and Rk / (Rk + Rvk)> 0.7 (1)
If the above condition is satisfied, both the improvement of the coefficient of friction between the pulley slope PS and the metal belt 30 (each element 32) and the improvement of the wear resistance of the pulley slope PS are optimal. Can be satisfied. In the above-described embodiment, the example in which the surface treatment by the hard turning process and the subsequent shot blasting process is performed on the pulley inclined surfaces PS of both the drive pulley 11 and the driven pulley 22 has been described. Of course, even when the surface treatment is applied to at least one of the pulley inclined surfaces PS, the contact area with the metal belt 30 can be increased, and the above effect can be obtained.

  The preferred embodiments of the present invention have been described so far, but the scope of the present invention is not limited to those shown in the above-described embodiments. For example, the operation mode of the drive pulley and the driven pulley constituting the belt type continuously variable transmission to which the present invention is applied is not limited to the hydraulic operation type shown in the above-described embodiment, but is an electric operation type using a motor. May be. Further, in the above-described embodiment, the case where the belt-type continuously variable transmission according to the present invention is applied to a vehicle power transmission device is shown as an example, but the belt-type continuously variable transmission according to the present invention. Can be applied to power transmission devices of other power machines in general.

1 is a cross-sectional view of a belt type continuously variable transmission according to an embodiment of the present invention. It is a skeleton figure which shows the structure of the vehicle power transmission device provided with the said belt-type continuously variable transmission. It is a perspective view which shows a part of metal belt which comprises the said belt-type continuously variable transmission. It is a graph of the load curve which shows a mode that the surface roughness of a pulley slope becomes large by a hard turning process and a shot blasting process. It is a graph of the load curve for demonstrating how to obtain | require effective load roughness and oil sump depth.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle power transmission device 10 Input shaft 11 Hollow shaft (shaft member on the input side)
12 Drive pulley 20 Output shaft (shaft member on the output side)
22 Driven pulley 30 Metal belt 31 Steel band 32 Element CVT Belt type continuously variable transmission PS Pulley slope

Claims (2)

A drive pulley provided on the shaft member on the input side, a driven pulley provided on the shaft member on the output side, and a metal belt stretched between the pulley slope of the drive pulley and the pulley slope of the driven pulley In the belt type continuously variable transmission configured to change the gear ratio steplessly by changing the groove width of the drive pulley and the groove width of the driven pulley,
The belt type continuously variable transmission, wherein the pulley inclined surface of at least one of the drive pulley and the driven pulley is subjected to a surface treatment by a hard turning treatment and a subsequent shot blast treatment. The surface properties of the pulley slope after the shot blasting are expressed by the formula Ra> 0.7 and Rk / (Rk + Rvk) where Ra is the arithmetic average roughness, Rk is the effective load roughness, and Rvk is the oil sump depth. > 0.7
The belt-type continuously variable transmission according to claim 1, wherein:

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