JP7398282B2 - Belt type continuously variable transmission and its manufacturing method - Google Patents

Description

The present invention relates to a belt-type continuously variable transmission constructed by winding an endless metal belt between a pair of pulleys, and a method for manufacturing the same.

Continuously variable transmissions (CVTs), which continuously change a gear ratio using a mechanism other than gears, are used as a transmission means for vehicles and the like. For example, a belt-type continuously variable transmission (belt-type CVT) may be used in a vehicle. This belt-type continuously variable transmission is constructed by winding an endless metal belt between a drive pulley on the driving side and a driven pulley on the driven side. By adjusting the thrust of the drive pulley and the driven pulley, the diameter of the metal belt wound around the drive pulley and driven pulley is changed to continuously change the gear ratio.

In such a belt-type continuously variable transmission, power is transmitted by the frictional force at the contact surface between the drive pulley and the driven pulley (hereinafter simply referred to as "pulley") and the metal belt. Therefore, it is necessary to generate the necessary frictional force on the contact surface between the pulley and the metal belt, and for this purpose, the contact surface of the pulley and the metal belt is polished to an appropriate surface roughness. .

Additionally, lubricating oil is supplied between the pulley and the metal belt to prevent seizure and for cooling, but if there is too much lubricating oil, slippage will occur between the pulley and the metal belt, reducing power transmission efficiency. Therefore, it is necessary to efficiently drain excess lubricating oil. From the viewpoint of ensuring a long durable life, the contact surface between the pulley and the metal belt is required to have high abrasion resistance.

Therefore, Patent Documents 1 and 2 propose a technique in which a large number of minute irregularities are formed on the contact surface of a pulley with a metal belt, and the tips of the minute irregularities are polished to make a flat surface. Further, Patent Document 3 proposes a technique in which a spiral groove is formed by cutting on the contact surface of a pulley with a metal belt, and then final polishing is performed.

Further, Patent Document 4 proposes a technique for providing a plurality of grooves that intersect with each other and have approximately the same width and depth on the contact surface with a large number of elements constituting a metal belt or with elements of a pulley. Patent Document 5 also proposes a technique in which the arithmetic mean roughness and surface hardness of the contact surface of the pulley with the metal belt are each within predetermined values.

Furthermore, in Patent Document 6, in order to ensure the required coefficient of friction and high wear resistance and fatigue strength on the contact surface of the pulley with the metal belt, an area from the surface of the contact surface of the pulley to a predetermined depth is A technique has been proposed in which a surface modified layer is formed by a sonic lapping process and a residual stress of a predetermined value (for example, 1200 MPa) or more is imparted to this surface modified layer.

Japanese Unexamined Patent Publication No. 60-109661 Japanese Patent Application Publication No. 5-010405 Patent No. 2686973 Japanese Unexamined Patent Publication No. 184270/1986 Japanese Patent Application Publication No. 2000-130527 Japanese Patent Application Publication No. 2018-004036

By the way, a metal belt is constructed by connecting a plurality of elements in an annular shape, which are obtained by punching a metal plate material using a die in which a plurality of minute irregularities are formed. Therefore, a large number of minute irregularities are formed on the contact surface of each element with the pulley, but the depth of these minute irregularities becomes shallow, and the contact length (contact area) of each element with the pulley is It grows larger as it deteriorates. Therefore, as the mold deteriorates, the surface pressure of the contact surface of each element with the pulley decreases.

On the other hand, pulleys are made by forging a heat-treated metal material into a predetermined shape by forging, and by subjecting the intermediate molded product formed by the forging process to surface treatments such as cutting and shot blasting. Manufactured through a surface treatment step of forming a large number of minute irregularities on the surface of the product, and a polishing step of removing by polishing the tips of the convex portions of the minute irregularities formed by the surface treatment step to form a flat surface on the minute irregularities. be done. For this reason, the contact surface of the pulley with the metal belt has a surface roughness that provides a predetermined frictional force between the pulley and the metal belt.

However, as mentioned above, as the mold used to mold each element of the metal belt deteriorates, the depth of the minute irregularities formed on the contact surface of each element becomes shallower, so the contact length of each element with the pulley becomes smaller. (contact area) gradually increases. When the contact area of each element with the pulley increases in this way, the surface pressure of the contact surface of each element with the pulley gradually decreases as the mold deteriorates.

Therefore, in order to generate a frictional force that does not cause slip on the contact surface between the pulley and the metal belt, the surface roughness of the contact surface of the pulley must be adjusted according to the decrease in surface pressure on the contact surface due to deterioration of the mold. need to change. Otherwise, a problem arises in that slippage occurs between the pulley and the metal belt due to deterioration of the mold, resulting in a reduction in power transmission efficiency.

One way to solve the above problem is to frequently replace the mold with a new one, but if you replace the mold with a new one frequently, the mold cost will increase and the manufacturing cost will rise. The problem of inviting arises.

Note that Patent Documents 1 to 6 do not disclose a technique for solving problems associated with deterioration of a mold used for molding elements of a metal belt.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to adjust the surface roughness of the contact surface of the pulley according to the deterioration of the mold used for forming the metal belt, and to create a gap between the pulley and the metal belt. Provides a belt-type continuously variable transmission that prevents slippage between the two by ensuring a predetermined frictional force between the two, ensuring high power transmission efficiency and extending the durable life of the mold, and a method for manufacturing the same. It's about doing.

In order to achieve the above object, the present invention is constructed by winding an endless metal belt (6) between a pair of pulleys (3, 5), and the rotation of one of the pulleys (3) is controlled steplessly. In a belt type continuously variable transmission (1) that changes speed and transmits the same to the other pulley (5), the larger the contact area of the metal belt (6) with the pulley (3, 5), the larger the contact area of the metal belt (6) with the pulley (3, 5). It is characterized in that the surface roughness of the contact surfaces (3a, 3b, 5a, 5b) of the pulleys (3, 5) with the metal belt (6) is set to be large.

According to the present invention, the larger the contact area of the element of the metal belt with the pulley, that is, the lower the surface pressure of the pulley of the element due to deterioration due to durability of the mold used for molding the element, the more the element of the pulley By setting the surface roughness of the contact surface to be large, the following effects can be obtained. In other words, if the surface roughness of the contact surface of the pulley increases as the mold deteriorates, the frictional force on the contact surface between the pulley and the element will increase, so even if the pulley surface pressure of the element decreases due to mold deterioration, , slipping of the metal belt is prevented, high power transmission efficiency is ensured, and power is reliably and efficiently transmitted from one pulley to the other pulley via the metal belt.

In addition, even if the mold deteriorates, by adjusting the surface roughness of the contact surface on the pulley side (adjusting in the direction of increasing roughness), the same mold can be used without replacing the mold with a new one. Since it can be used continuously, the durable life of the mold can be extended and it is economical.

In the belt-type continuously variable transmission (1), the surface roughness of the contact surfaces (3a, 3b, 5a, 5b) of the pulleys (3, 5) with the metal belt (6) is adjusted radially outward. You can also set it larger.

Furthermore, in the belt type continuously variable transmission (1), the conical contact surface (3b) of the pulley (3, 5) with the metal belt (6) is arranged on the inner diameter side with respect to the boundary line (M1). is a composite surface with a flat inclined surface (3b1) and a convex curved surface (3b2) on the outer diameter side, and each of the inclined surface (3b1) on the inner diameter side and the convex curved surface (3b2) on the outer diameter side of the composite surface The surface roughness is set larger toward the outside in the radial direction, and the surface roughness at the boundary line (M1) of the convex curved surface (3b2) on the outer diameter side is set to be larger than the surface roughness at the boundary line of the inclined surface (3b1) on the inner diameter side. The surface roughness may be set smaller than the surface roughness at line (M1).

According to the above configuration, the surface pressure acting on the contact surface between the pulley and the metal belt decreases radially outward, so the surface roughness of the pulley contact surface is set to increase radially outward. By doing so, it is possible to always generate a necessary and sufficient frictional force on the contact surface between the pulley and the metal belt to prevent the metal belt from slipping, and it is possible to maintain high power transmission efficiency.

Further, the present invention provides the metal belt (6), which is manufactured by connecting a plurality of elements (6A) obtained by punching a metal plate material with a mold having a plurality of minute irregularities in a ring shape, and The pulleys (3, 5) are formed by a forging process in which a heat-treated metal material is forged into a predetermined shape, and a surface treatment is applied to the intermediate molded product formed by the forging process to form a large number of parts on the surface of the intermediate molded product. a surface treatment step of forming minute irregularities (9), and removing by polishing the convex tips of the minute irregularities (9) formed by the surface treatment step to form a flat surface (9a) on the minute irregularities (9); In the manufacturing method of the belt type continuously variable transmission (1), which is manufactured through a polishing step to form It is characterized by the following.

According to the method for manufacturing a belt-type continuously variable transmission according to the present invention, the surface roughness of the pulley can be increased by shortening the polishing process time in the manufacture of the pulley as the mold deteriorates. Even if the mold deteriorates, it is possible to ensure a necessary and sufficient frictional force between the pulley and the metal belt, prevent slippage of the metal belt, and ensure high power transmission efficiency.

According to the present invention, the surface roughness of the contact surface of the pulley is adjusted in accordance with the deterioration of the mold used for molding the metal belt, and a predetermined frictional force is maintained between the pulley and the metal belt. This has the effect of preventing the occurrence of slippage, ensuring high power transmission efficiency, and extending the durable life of the mold. Further, the present invention has the effect that the surface roughness of the pulley can be accurately changed depending on the size of the contact surface of the element of the metal belt.

1 is a diagram schematically showing the basic configuration of a belt type continuously variable transmission according to the present invention. FIG. 2 is a partial perspective view of a metal belt of the belt-type continuously variable transmission according to the present invention. (a) is a perspective view of a single element constituting a metal belt of a belt-type continuously variable transmission according to the present invention, and (b) is an enlarged detailed view of the X section in (a). FIG. 4 is a partial cross-sectional view showing the shape of the contact surface of the drive pulley and the contact position of the metal belt to the contact surface at each ratio. (a) is a diagram showing minute irregularities formed on the pulley contact surface by surface treatment (shot blasting), and (b) is a diagram showing a state in which the tips of the convex portions of the minute irregularities have been removed by polishing (lapping). It is a figure which shows the durable preload characteristic of a drive pulley. FIG. 6 is a partial cross-sectional view showing the pulley contact length of elements molded by molds A, B, and C having different degrees of deterioration. FIG. 6 is a diagram showing the relationship between the wear amount of elements molded by molds A, B, and C having different degrees of deterioration and the pulley contact length. FIG. 3 is a diagram showing the relationship between the pulley surface roughness and the pulley contact length of the element for maintaining the surface pressure balance between the pulley and the element. FIG. 7 is a diagram showing a method for setting the surface roughness of a pulley (a method for selecting an effective load roughness Rk of a durability preload curve) when an element is molded using molds A, B, and C having different degrees of deterioration.

Embodiments of the present invention will be described below based on the accompanying drawings.

[Configuration and operation of belt type continuously variable transmission]
FIG. 1 is a diagram schematically showing the basic configuration of a belt-type continuously variable transmission according to the present invention, FIG. 2 is a partial perspective view of a metal belt of the belt-type continuously variable transmission, and FIG. 3(a) is a diagram showing the same belt-type continuously variable transmission. A perspective view of a single element constituting a metal belt of a continuously variable transmission, FIG. 3(b) is an enlarged detailed view of the X portion of FIG. 3(a), and FIG. 4 shows the shape of the contact surface of the drive pulley and the contact surface FIG. 3 is a partial cross-sectional view showing contact positions of the metal belt at each ratio.

The belt-type continuously variable transmission 1 shown in FIG. It is constructed by wrapping a belt 6 around it.

Here, the drive shaft 2 and the driven shaft 4 are arranged parallel to each other, and the drive pulley 3 has a fixed sheave (fixed pulley half) 3A fixed to the drive shaft 2 and a fixed sheave (fixed pulley half) 3A fixed to the drive shaft 2. It is configured by arranging a movable sheave (movable pulley half) 3B that is slidable in the axial direction (left-right direction in FIG. 1) and facing each other in the axial direction. An oil chamber S1 is formed on the back side of the movable sheave 3B of the drive pulley 3. Similarly, the driven pulley 5 includes a fixed sheave (fixed pulley half) 5A fixed to the driven shaft 4 and a movable sheave (movable pulley half) 5B that is slidable in the axial direction along the driven shaft 4. The movable sheave 5B is arranged to face each other in the axial direction, and an oil chamber S2 is formed on the back side of the movable sheave 5B.

An electronic control unit (ECU) is installed in an oil chamber S1 formed on the back side of the movable sheave 3B of the drive pulley 3 and an oil chamber S2 formed on the back side of the movable sheave 5B of the driven pulley 5. Oil passages 7 and 8 extending from a hydraulic control unit U2, which is operated in response to a command from U1, are connected to each other.

By the way, the conical slopes of the fixed sheave 3A and the movable sheave 3B of the drive pulley 3 that face each other in the axial direction constitute contact surfaces 3a and 3b with the metal belt 6, respectively. A V groove is formed between them. Similarly, the conical slopes of the fixed sheave 5A and the movable sheave 5B of the driven pulley 5 that face each other in the axial direction constitute contact surfaces 5a and 5b with the metal belt 6, respectively. A V groove is formed between the grooves 5b. A metal belt 6 is wound around the V-groove formed in the drive pulley 3 and the V-groove formed in the driven pulley 5 in a sandwiched manner.

Here, as shown in FIG. 2, the metal belt 6 is configured by connecting a plurality of elements 6A made of metal plates in an annular manner by a pair of endless metal hoops 6B, and each element 6A is 3(a).

By the way, as shown in FIG. 4, for example, the conical contact surface 3b of the movable sheave 3B of the drive pulley 3 has a flat inclined surface 3b1 with an inclination angle θ on the inner diameter side and a flat inclined surface 3b1 on the outer diameter side with the illustrated boundary line M1 as the boundary. The radial side is a composite surface with a convex curved surface 3b2 having a polarity radius r, and correspondingly, the side surface of each element 6A of the metal belt 6 (the surface that contacts the contact surface 3b of the movable sheave 3B) is as shown in FIG. As shown in FIG. 3(b), it is a composite surface having a curved surface 6a on the inner diameter side and a flat inclined surface 6b on the outer diameter side with respect to the boundary line M2. Although not shown, the contact surface 3a of the fixed sheave 3A of the drive pulley 3 and the contact surfaces 5a and 5b of the fixed sheave 5A and movable sheave 5B of the driven pulley 5 are also composite surfaces. Further, the other side surface (the left end surface in FIG. 3(a)) of each element 6A of the metal belt 6 is also a composite surface.

In the belt type continuously variable transmission 1 configured as described above, for example, when the rotation of a drive source such as an engine or an electric motor is input to the drive shaft 2 and the drive shaft 2 is rotationally driven, the drive shaft The rotation of the drive shaft 2 is continuously changed in speed by the action of the belt-type continuously variable transmission 1 and transmitted to the driven shaft 4 via the metal belt 6, and the driven shaft 4 rotates at a predetermined speed.

That is, in the belt-type continuously variable transmission 1, the hydraulic pressure in each oil chamber S1, S2 provided in the drive pulley 3 and the driven pulley 5 is controlled by a hydraulic control unit operated by a command from an electronic control unit (ECU) U1. By being controlled by U2, the gear ratio is adjusted steplessly. Specifically, if the oil pressure in the oil chamber S2 of the driven pulley 5 is increased relative to the oil pressure in the oil chamber S1 of the drive pulley 3, the thrust acting in the axial direction on the movable sheave 5B of the driven pulley 5 ( The pulley thrust force) becomes relatively larger than the thrust force acting on the movable sheave 3B of the drive pulley 3 in the axial direction (pulley thrust force). Therefore, the V-groove width between the fixed sheave 5A and the movable sheave 5B of the driven pulley 5 decreases, and the winding diameter (effective radius) of the metal belt 6 around the driven pulley 5 increases. 3A and the movable sheave 3B increases, and the winding diameter (effective radius) of the metal belt 6 around the drive pulley 3 decreases, the gear ratio of the belt type continuously variable transmission 1 increases. It changes steplessly toward the deceleration (LOW) direction. In this state, the metal belt 6 is at the contact surface 3b of the movable sheave 3B of the drive pulley 3, for example, at the position shown by the broken line in FIG.

Conversely, if the oil pressure in the oil chamber S1 of the drive pulley 3 is increased relative to the oil pressure in the oil chamber S2 of the driven pulley 5, the thrust acting in the axial direction on the movable sheave 3B of the drive pulley 3 (pulley thrust ) is relatively larger than the thrust (pulley thrust) acting on the movable sheave 5B of the driven pulley 5 in the axial direction. Therefore, the width of the V groove between the fixed sheave 3A and the movable sheave 3B of the drive pulley 3 decreases, and the winding diameter (effective radius) of the metal belt 6 around the drive pulley 3 increases. 5A and the movable sheave 5B increases and the winding diameter (effective radius) of the metal belt 6 around the driven pulley 5 decreases, the gear ratio of the belt type continuously variable transmission 1 increases. It changes steplessly toward the speed increasing (HIGH) direction. In this state, the metal belt 6 is at the contact surface 3b of the movable sheave 3B of the drive pulley 3, for example, at the position shown by the chain line in FIG. Further, the position of the metal belt 6 shown by the solid line in FIG. 4 is the position when the belt type continuously variable transmission 1 is between deceleration (LOW) and speed increase (HIGH).

Next, a method of manufacturing the belt type continuously variable transmission 1 configured as above will be explained.

[Manufacturing method of belt type continuously variable transmission]
<Pulley manufacturing method>
The drive pulley 3 and driven pulley 5 (hereinafter simply referred to as "pulleys 3 and 5") that constitute the belt-type continuously variable transmission 1 are manufactured through the following forging process, surface treatment process, and polishing process. Ru.

1) Forging process:
In the forging process, the fixed sheaves 3A, 5A and movable sheaves 3B, 5B of the pulleys 3, 5 are formed by forging carburized or carbonitrided materials of SCM420 to SCM435 (JIS standard) that have been heat treated such as quenching and tempering. An intermediate molded product is obtained by molding into the shape of .

2) Surface treatment process:
In the surface treatment step, the conical contact surfaces (contact surfaces with the metal belt 6) of the intermediate molded products of the fixed sheaves 3A, 5A and the movable sheaves 3B, 5B obtained in the forging step, which is the previous step, are By performing surface treatments such as shot blasting and cutting, countless fine irregularities 9 with a height of 20 μm or more are randomly formed on the contact surface to adjust the friction coefficient, as shown in FIG. 5(a). .

As mentioned above, the surface roughness of the contact surface increases by forming countless minute irregularities 9 on the contact surface of each intermediate molded product by surface treatment such as shot blasting and cutting, and the surface roughness of the contact surface becomes large. The contact surface pressure increases and the coefficient of friction increases. In addition, the contact surfaces of each intermediate molded product are plastically deformed by surface treatments such as shot blasting and cutting, and the hardness of the surfaces is increased by work hardening, and residual stress is imparted to the surfaces of the contact surfaces. The abrasion resistance of The countless minute irregularities 9 improve oil drainage on the contact surface, and prevent the metal belt 6 from slipping due to a large amount of lubricating oil remaining on the contact surface.

3) Polishing process:
In the polishing process, the tips of the convex portions of the countless minute irregularities 9 formed on the contact surface of the intermediate molded product in the previous surface treatment process are removed by a polishing process such as lapping, as shown in FIG. 5(b). By making the tips of the convex portions of the minute irregularities 9 flat surfaces 9a, the fixed sheaves 3A, 5A and the movable sheaves 3B, 5B, which are final products, are manufactured, respectively.

By removing the tips of the convex portions of the minute irregularities 9 formed on the contact surface of the intermediate molded product in the surface treatment process in the polishing process, the area ratio of the flat surface 9a formed at the tip of each convex portion (the total contact surface By setting the ratio of the area of the flat surface 9a to the surface area within a predetermined range, wear on the contact surface is reduced, a large friction coefficient is obtained, and a decrease in the friction coefficient due to secondary wear is avoided. Ru.

Here, the durable preload characteristics of the pulleys 3 and 5 are shown in FIG.

The horizontal axis of Fig. 6 is the load length ratio Mr (%), the vertical axis is the surface roughness R (μm), m in the figure is the load curve, and Rk (μm) on the vertical axis is the effective load roughness ( The amount of wear until the contact surfaces 3a, 3b and 5a, 5b of the pulleys 3, 5 become unusable due to long-term wear (see Fig. 5)), Rpk (μm) is the The cut amount by polishing (see FIG. 5(a)), Rvk (μm), is the oil pool depth.

Here, how to obtain the effective load roughness Rk, the cut amount Rpk, and the oil sump depth Rvk in FIG. 6 will be explained.

A straight line (equivalent straight line) n passing through points a and b such that the difference in load length ratio Mr is 40% on the load curve m shown in Fig. 6 and load length ratio Mr = 0%, 100%. The intersections of the lines s and t passing through the points c and d are respectively points e and f, and the intersections of the cutting level lines s and t with the load curve m are points e and f, and the load curve m and the load length ratio Mr=0%, Let the intersections with 100% be points g and h, respectively.

Then, load length ratio Mr = 0% or higher such that the area of the area surrounded by line segment CG, line segment ce, and curve eg is equal to the area of triangle cei (area of the area indicated by diagonal lines in FIG. 6). Find the point i. In addition, the load length ratio Mr = 100% or above is such that the area of the area surrounded by line segment fd, line segment dh, and curve fh is equal to the area of triangle fdj (area of the area indicated by diagonal lines in FIG. 6). Find the point j. At this time, the difference in cutting level between point c and point d is determined as effective load length Rk, the length of line segment cg is determined as cutting amount Rpk, and the length of line segment dj is determined as oil sump depth Rvk.

<Metal belt manufacturing method>
As described above (see FIG. 2), the metal belt 6 is constructed by connecting a plurality of elements 6A in an annular manner by a pair of endless metal hoops 6B. A metal plate material such as SUJ2 (JIS standard) that has been subjected to heat treatment such as resetting is punched out with a die to form the shape shown in FIG. 3(a). Here, a large number of minute irregularities are formed in the mold, and both left and right sides (contact surfaces with pulleys 3 and 5) of the element 6A, which is formed by punching a metal plate material with this mold, are , a large number of minute irregularities are formed.

By the way, the mold deteriorates over time as it wears down over time. Therefore, as shown in FIG. 7, the height of the convex portions (mountain-shaped protrusions) 10 of minute irregularities formed on the mold gradually decreases due to wear. That is, the height of the convex portion 10 formed in a new mold A is high, but as wear progresses due to durability, the height of the convex portion 10 from mold B to mold C gradually becomes lower.

Therefore, when minute irregularities are formed on the element 6A by a new mold A, the pulley contact length LA of the element 6A (the contact length to the pulleys 3 and 5) is relatively short, and therefore the pulley contact area of the element 6A Since the element 6A is also relatively small, the pulley surface pressure of the element 6A is relatively large.

Then, when the convex portion 10 is worn out by using the mold and its height gradually decreases from mold B to mold C, the pulley contact length LB of the element 6A molded by mold B is The pulley contact length LA of the element 6A molded by mold A is longer than the pulley contact length LA (LB>LA), and therefore the pulley contact area becomes larger, and the pulley surface pressure of the element 6A molded by mold A increases accordingly. It is smaller than the surface pressure.

Similarly, the pulley contact length LC of the element 6A molded by the mold C which has deteriorated the most due to use is longer than the pulley contact length LB of the element 6A molded by the mold B (LC>LB), Therefore, the pulley contact area becomes larger, and the pulley surface pressure becomes smaller than the pulley surface pressure of the element 6A molded by the mold B by that much. That is, the pulley surface pressure of the element 6A gradually decreases in the order of the element 6A molded by the mold A, mold B, and mold C.

FIG. 8 shows the relationship between the wear amount of the element 6A molded by molds A, B, and C and the pulley contact length. The initial wear of the elements 6A molded by the molds A, B, and C ends when the amount of wear reaches a predetermined amount M, and then the wear progresses to steady wear. In this steady wear, the pulley contact length increases in the order of mold A→mold B→mold C for the same amount of wear. Therefore, the pulley surface pressure decreases in this order.

[Features of the present invention]
As mentioned above, the mold used to mold each element 6A of the metal belt 6 deteriorates over time, and the pulley contact length (contact area) of the element 6A molded by the mold gradually increases. When the pulley surface pressure of the element 6A decreases over time, the frictional force at the contact surfaces 3a, 3b and 5a, 5b between the element 6A and the pulleys 3, 5 decreases, causing slip in the metal belt 6, which impedes power transmission. As mentioned above, this leads to a decrease in efficiency.

Therefore, in this embodiment, the larger the contact area of the element 6A of the metal belt 6 with the pulleys 3 and 5, the more the pulley surface of the element 6A is affected by the deterioration due to durability of the mold used for molding the element 6A. The lower the pressure, the greater the surface roughness of the contact surfaces 3a, 3b and 5a, 5b of the pulleys 3, 5 with the element 6A. As described above, when the surface roughness of the contact surfaces 3a, 3b and 5a, 5b of the pulleys 3, 5 is increased as the mold deteriorates, the frictional force between the pulleys 3, 5 and the element 6A is increased. Even if the pulley surface pressure of the element 6A decreases due to deterioration of the mold, slipping of the metal belt 6 is prevented, ensuring high power transmission efficiency, and the drive pulley 3 passes through the metal belt 6 to the driven pulley 5. Power is transmitted reliably and efficiently.

In addition, even if the mold deteriorates, the mold can be replaced with a new one by adjusting the surface roughness of the contact surfaces 3a, 3b and 5a, 5b on the pulleys 3 and 5 side (adjusting in the direction of increasing roughness). Since the same mold can be used continuously without replacing it, the durable life of the mold can be extended, which is economical.

In addition, as a specific method of increasing the surface roughness of the contact surfaces 3a, 3b and 5a, 5b of the pulleys 3, 5, in this embodiment, the more the mold deteriorates, the more the surface roughness of the pulleys 3, 5 is increased. We are trying to shorten the time of the polishing process. In this way, if the time for the polishing process in manufacturing the pulleys 3, 5 is shortened, the minute irregularities 9 formed on the contact surfaces 3a, 3b and 5a, 5b of the pulleys 3, 5 by surface treatment such as shot blasting or cutting can be reduced. The amount of the tip of the convex portion cut by polishing such as lapping in the next step is reduced, and the surface roughness of the contact surfaces 3a, 3b and 5a, 5b of the pulleys 3, 5 becomes large.

Here, FIG. 9 shows the surface roughness of the contact surfaces 3a, 3b and 5a, 5b of the pulleys 3, 5 and the contact length of the element 6A ( As is clear from the figure, in order to maintain the balance of the surface pressure, the pulley contact length of the element 6A becomes longer (the pulley surface pressure decreases due to deterioration of the mold). The more it is necessary to increase the surface roughness of the contact surfaces 3a, 3b and 5a, 5b of the pulleys 3, 5.

10(a) to (c) show how to set the surface roughness of the pulleys 3 and 5 when the element 6A is molded using molds A, B, and C (effective load roughness of the durability preload curve). However, as shown in Fig. 10(a), when molding element 6A using mold A that is new and has little deterioration, the surface roughness of pulleys 3 and 5 should be A relatively small effective load roughness Rk, which is represented by the equivalent curve shown by the solid line in the preload curve, is selected.

As shown in FIG. 10(b), when molding the element 6A using the mold B which has undergone some degree of wear due to deterioration, the surface roughness of the pulleys 3 and 5 is determined by the durability preload curve. A medium effective load roughness Rk is selected, which is larger than the effective load roughness Rk shown in FIG. 10(a), which is represented by the equivalent curve shown by the solid line in the middle.

After that, as shown in FIG. 10(c), when molding element 6A using mold C which has undergone considerable wear due to deterioration, the surface roughness of pulleys 3 and 5 is An effective load roughness Rk is selected that is larger than the effective load roughness Rk shown in FIG. 10(b), which is displayed by the equivalent curve shown by the solid line.

By the way, since the surface pressure acting between the pulleys 3, 5 and the metal belt 6 decreases toward the outside in the radial direction, the surface roughness of the contact surfaces 3a, 3b and 5a, 5b of the pulleys 3, 5 is It is desirable to set it larger toward the outside in the radial direction. By doing this, it is possible to always generate a necessary and sufficient frictional force on the contact surfaces 3a, 3b and 5a, 5b between the pulleys 3, 5 and the metal belt 6, to prevent the metal belt 6 from slipping, and to achieve high power. Transmission efficiency can be ensured.

Further, as in this embodiment, when the contact surfaces 3a, 3b and 5a, 5b of the pulleys 3, 5 are composed of composite surfaces, for example, for the drive pulley 3, the slope of the inner diameter side of the composite surface is The surface roughness of the surface 3b1 and the convex curved surface 3b2 on the outer diameter side (see FIG. 4) is set to be larger toward the outside in the radial direction, and the surface roughness at the boundary line M1 of the convex curved surface 3b2 on the outer diameter side is set to be larger than the inner diameter. It is desirable to set the surface roughness to be smaller than the surface roughness at the boundary line M1 of the side inclined surface 3b1. By doing this, necessary and sufficient frictional force is always generated on the contact surfaces 3a, 3b and 5a, 5b between the pulleys 3, 5 and the metal belt 6, thereby preventing the metal belt 6 from slipping and achieving high power transmission efficiency. can be maintained.

Note that the application of the present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the claims, the technical idea described in the specification, and the drawings.

1 Belt type continuously variable transmission 3 Drive pulley 3A Fixed sheave of drive pulley 3B Movable sheave of drive pulley 3a, 3b Contact surface of drive pulley 3b1 Inclined surface of drive pulley 3b2 Convex curved surface of drive pulley 5 Driven pulley 5A Fixation of driven pulley Sheave 5B Movable sheave of driven pulley 5a, 5b Contact surface of driven pulley 6 Metal belt 6A Element of metal belt 9 Minute unevenness of pulley 9a Flat surface with minute unevenness 10 Convex part of minute unevenness of mold LA to LC Contact length of element M1, M2 Boundary line Rk Effective load roughness Rpk Cut amount Rvk Oil sump depth S1, S2 Oil chamber U1 Electronic control unit U2 Hydraulic control unit

Claims (4)

A belt type continuously variable transmission that is constructed by winding an endless metal belt between a pair of pulleys, and transmits the rotation of one of the pulleys to the other pulley. A method for manufacturing a transmission, the method comprising:
The metal belt is manufactured by connecting a plurality of elements obtained by punching a metal plate material with a mold having a plurality of minute irregularities in a ring shape, and
The pulley includes a forging process in which a heat-treated metal material is forged into a predetermined shape, and a surface treatment is applied to the intermediate molded product formed by the forging process to form a large number of minute irregularities on the surface of the intermediate molded product. A belt type continuously variable transmission manufactured through a surface treatment step of forming a surface, and a polishing step of removing by polishing the tips of the convex portions of the minute irregularities formed by the surface treatment step to form a flat surface on the minute irregularities. In the manufacturing method,
The pulley is manufactured so that as the mold wears out, the surface roughness of the contact surface with the manufactured metal belt increases as the contact area with the manufactured metal belt increases. A manufacturing method for a belt-type continuously variable transmission. The method for manufacturing a belt type continuously variable transmission according to claim 1, wherein the surface roughness of the pulley increases radially outward. The conical contact surface of the pulley with the metal belt is a composite surface with a flat inclined surface on the inner diameter side and a convex curved surface on the outer diameter side with the boundary line as the boundary,
The surface roughness of the inclined surface on the inner diameter side and the convex curved surface on the outer diameter side of the composite surface is increased radially outward, and the surface roughness at the boundary line of the convex curved surface on the outer diameter side is increased. The method for manufacturing a belt type continuously variable transmission according to claim 1 or 2, wherein the surface roughness is made smaller than the surface roughness at the boundary line of the inclined surface on the inner diameter side. The method for manufacturing a belt-type continuously variable transmission according to any one of claims 1 to 3, characterized in that the more the mold deteriorates, the more the time required for the polishing step in manufacturing the pulley is reduced.