JP7477767B2 - Pulley shaft for belt-type continuously variable transmission, belt-type continuously variable transmission, and fixed sheave - Google Patents

Description

This disclosure relates to a pulley shaft used in a belt-type continuously variable transmission, a belt-type continuously variable transmission (CVT) in which the pulley shaft is used, and a fixed sheave used in the pulley shaft.

Belt-type continuously variable transmissions (CVTs) are widely used as transmissions for vehicles such as automobiles and motorcycles. Belt-type continuously variable transmissions are disclosed, for example, in Patent Document 1 (JP 2020-34107 A), Patent Document 2 (JP 2020-26830 A), Patent Document 3 (JP 2020-16293 A), and Patent Document 4 (JP 2018-165529 A). A belt-type continuously variable transmission includes a pair of pulleys (primary pulley, secondary pulley) and a drive belt wound around the pair of pulleys. Each pulley includes a shaft, a fixed sheave fixed to the shaft, and a movable sheave that can slide in the axial direction of the shaft.

JP 2020-34107 A JP 2020-26830 A JP 2020-16293 A JP 2018-165529 A

As disclosed in Patent Documents 1 to 4, the shaft and the fixed sheave are usually formed integrally. A shaft equipped with a fixed sheave is called a "pulley shaft." In a belt-type continuously variable transmission including a pulley shaft, it is necessary to reduce torque transmission loss. If the fixed sheave is formed integrally with the shaft, it is easy to ensure the rigidity of the fixed sheave. If the rigidity of the fixed sheave is high, it is possible to properly clamp the drive belt. As a result, torque transmission loss can be suppressed.

The shaft and fixed sheave are required to have high bending fatigue strength and wear resistance. For this reason, pulley shafts may be subjected to heat treatments such as carburizing and nitriding. When heat treating pulley shafts, multiple pulley shafts are placed on a set of trays or baskets to form one lot. This is called batch processing, in which one lot is loaded into one heat treatment furnace and heat treated once, or continuous furnace processing, in which multiple lots are loaded one at a time and continuously heat treated while being transported.

As mentioned above, a typical pulley shaft has a complex three-dimensional shape, with the shaft and a fixed sheave extending radially of the shaft being integrally formed. This limits the number of pulley shafts that can be loaded in one batch process. As a result, when heat treatment is performed, the productivity of pulley shafts may decrease.

The objective of this disclosure is to provide a pulley shaft that can increase productivity and suppress torque transmission loss even when heat treatment is performed.

The pulley shaft according to the present disclosure comprises:
A pulley shaft for a belt-type continuously variable transmission,
A shaft,
a fixed sheave fixed to the shaft;
The fixed sheave is
a main body member having a conical plate shape, a through hole in a center portion into which the shaft is fitted, and fixed to the shaft;
a support member having a conical plate shape, a through hole in a center portion into which the shaft is fitted, the support member being fixed to the shaft and supporting the main body member;
The body member includes:
A sheave surface that contacts a drive belt of the belt-type continuously variable transmission;
A back surface opposite to the sheave surface,
The support member is
The shaft is disposed on the back surface side of the main body member and is inclined toward the main body member in a cross section including a central axis of the shaft,
The outer diameter of the support member is smaller than the outer diameter of the body member,
The outer peripheral edge of the support member is fixed to the rear surface of the main body member.

The pulley shaft disclosed herein can increase productivity and reduce torque transmission loss even when heat treatment is performed.

FIG. 1 is a cross-sectional view of a belt-type continuously variable transmission according to the present embodiment. FIG. 2 is a cross-sectional view of the pulley device. FIG. 3 is a schematic diagram showing a case where the movable sheave in FIG. 2 slides. FIG. 4 is a cross-sectional view of the pulley shaft in FIG. FIG. 5 is a cross-sectional view of a conventional pulley shaft. FIG. 6 is an image diagram showing the number of conventional pulley shafts that can be loaded into a heat treatment furnace when batch processing is performed in the heat treatment furnace. FIG. 7 is an image diagram showing the number of shafts of this embodiment that can be loaded into a heat treatment furnace having the same capacity as that of FIG. 6 when batch processing is performed in the heat treatment furnace. FIG. 8 is an image diagram showing the number of fixed sieves of this embodiment that can be loaded into a heat treatment furnace having the same capacity as that shown in FIG. 6 when performing batch processing in the heat treatment furnace. FIG. 9 is a cross-sectional view of the fixed sheave of this embodiment. FIG. 10 is a cross-sectional view showing a state in which the fixed sheave of this embodiment is attached to a shaft. FIG. 11 is a schematic diagram for explaining the attachment position of the support member to the main body member in the fixed sheave of this embodiment. FIG. 12 is a schematic diagram showing an example in which the outer peripheral edge of the support member is fixed in a region near 0.8D (D is the outer diameter of the main body member). FIG. 13 is a schematic diagram showing an example in which the outer peripheral edge of the support member is fixed in the vicinity of 0.5D. FIG. 14 is a cross-sectional view of a fixed sheave having a different configuration from that shown in FIG. FIG. 15 is a schematic diagram showing a state in which the fixed sheave shown in FIG. 14 is attached to a shaft. FIG. 16 is a cross-sectional view of a pulley shaft having a different configuration from that shown in FIG. FIG. 17 is a cross-sectional view of a fixed sheave having a different configuration from those in FIGS. FIG. 18 is a schematic diagram showing an example of a fixing means for fixing the main body member and the support member. FIG. 19 is a cross-sectional view of a fixed sheave having a different configuration from those in FIGS. FIG. 20 is a schematic diagram of a pulley shaft assumed in the embodiment. FIG. 21 is a schematic diagram for explaining a finite element model of a pulley shaft. FIG. 22 is a diagram showing the relationship between each position on the contact area and the axial displacement on each pulley shaft, obtained by FEM analysis.

The pulley shaft and the belt type continuously variable transmission according to this embodiment have the following configuration.
[1]
A pulley shaft for a belt-type continuously variable transmission,
A shaft,
a fixed sheave fixed to the shaft;
The fixed sheave is
a main body member having a conical plate shape, a through hole in a center portion into which the shaft is fitted, and fixed to the shaft;
a support member having a conical plate shape, a through hole in a center portion into which the shaft is fitted, the support member being fixed to the shaft and supporting the main body member;
The body member includes:
A sheave surface that contacts a drive belt of the belt-type continuously variable transmission;
A back surface opposite to the sheave surface,
The support member is
The shaft is disposed on the back surface side of the main body member and is inclined toward the main body member in a cross section including a central axis of the shaft,
The outer diameter of the support member is smaller than the outer diameter of the body member,
The outer peripheral edge of the support member is fixed to the back surface of the main body member.
Pulley shaft.

In the pulley shaft of this embodiment, the shaft and the fixed sheave are separate members. Therefore, compared to a pulley shaft in which the fixed sheave and the shaft are integrally molded, the number of pulley shafts that can be treated in one heat treatment can be increased when heat treatment is performed. As a result, the productivity of pulley shafts is increased even when heat treatment is performed.

In addition, in the pulley shaft of this embodiment, the support member supports the main body member at the fixed sheave. As described above, the outer diameter of the support member is smaller than the outer diameter of the main body member. Here, the area of the main body member that is equal to or smaller than the outer diameter of the support member and is supported by the support member is defined as the "inner area," and the area of the main body member that is outside the outer diameter of the support member is defined as the "outer area." The inner area of the main body member has increased rigidity due to support by the support member. On the other hand, the outer area of the main body member has appropriate elasticity.

When the pulley shaft, in which the fixed sheave is integrated with the shaft, rotates (i.e., when driving), the area where the drive belt comes into contact with the sheave surface of the fixed sheave is a range of about 140 to 220° in the circumferential direction. Here, the position on the sheave surface of the fixed sheave where the drive belt begins to come into contact with the sheave surface is defined as the "belt entrance". The position on the sheave surface of the fixed sheave where the drive belt leaves the sheave surface is defined as the "belt exit". In the orbit of the drive belt in contact with the sheave surface, the intermediate position between the belt entrance and belt exit is defined as the "belt winding central position". The belt entrance and belt exit are collectively referred to as the "belt entrance/exit".

During driving, the axial displacement of the fixed sheave is small at the belt entrance and exit, and large at the center of the belt winding. Therefore, during driving, the drive belt is strongly compressed at the belt entrance and exit, and the drive belt is wound around the large diameter side of the fixed sheave (towards the outer edge of the fixed sheave). Meanwhile, at the center of the belt winding, the fixed sheave is more flexible than at the belt entrance and exit. Therefore, the drive belt drops to the small diameter side of the fixed sheave (in the direction of the central axis of the fixed sheave). As a result, the winding diameter of the drive belt changes. The amount of change in the winding diameter corresponds to the amount of slippage of the belt. Therefore, if the amount of change in the winding diameter is large, the slip torque loss in the radial direction of the belt increases, and the torque transmission loss increases.

The amount of change in the winding diameter of the drive belt due to differences in flexure at the belt entrance and exit points and the center of the belt winding position at the fixed sheave described above is more likely to be significant in a pulley shaft in which the fixed sheave and shaft are separated as in the present invention than in a conventional integrated pulley shaft. This is because the fixed sheave is separated and independent from the shaft, so the axial displacement is more likely to change relative to the fixed sheave.

Therefore, in the pulley shaft of this embodiment, as described above, the outer diameter of the support member is made smaller than the outer diameter of the main body member. This allows the support member to support the inside of the outer periphery of the main body member. In this case, the outer region of the main body member has appropriate elasticity. Therefore, during driving, the fixed sheave flexes appropriately not only at the center position of the belt winding, but also at the belt entrance and exit. This makes it possible to suppress the constriction pressure on the drive belt at the belt entrance and exit, and to suppress the variation in axial displacement in the circumferential direction of the fixed sheave. As a result, the amount of change in the winding diameter can be reduced, and torque transmission loss can be suppressed.

[2]
The pulley shaft according to [1],
In a cross section including a central axis of the shaft, the thickness of the body member is smaller than the thickness of the support member.
Pulley shaft.

The pulley shaft [2] allows the outer region of the main body member to bend more appropriately.

[3]
The pulley shaft according to [1] or [2],
When the outer diameter of the main body member is defined as D (mm), the outer peripheral edge portion of the support member is fixed to a region of the back surface of the main body member within a range of 0.5D to 0.8D.
Pulley shaft.

In the pulley shaft of [3], the rigidity of the inner region of the main body member can be ensured while the range of the flexible outer region can be made appropriate.

[4]
[1] - [3] The pulley shaft according to any one of the above,
The support member further comprises:
a boss portion disposed on an inner peripheral edge of the support member;
The boss portion is
The shaft is cylindrical and extends in a direction opposite to the main body member in a cross section including a central axis of the shaft.
The shaft is fitted into a boss portion of the support member.
Pulley shaft.

In the pulley shaft [4], the boss portion can further increase the rigidity of the support member, and as a result, the rigidity of the inner region of the main body member can be further increased.

[5]
The pulley shaft according to [4],
The shaft is
A step portion protruding in a radial direction of the shaft is provided,
The step portion is
a side wall surface facing the end surface of the boss portion of the support member and in contact with the end surface of the boss portion of the support member;
Pulley shaft.

In the pulley shaft of [5], when a force is applied from the drive belt in a direction that widens the groove width of the pulley, the step portion applies a reaction force to the support member against the force from the drive belt. As a result, the support member can effectively support the main body member.

[6]
The pulley shaft according to [4] or [5],
a bearing that supports the shaft rotatably around a central axis of the shaft,
The boss portion of the support member is
The bearing has an outer circumferential surface on which the bearing is placed when the bearing is installed in the belt-type continuously variable transmission.
Pulley shaft.

In the pulley shaft [6], the boss portion of the support member is directly fixed by the bearing. This makes the support member even more firmly fixed. As a result, the rigidity of the support member can be increased, and the rigidity of the inner region of the main body member can be increased.

[7]
[1] - [6] The pulley shaft according to any one of the above,
A recess is formed on the rear surface of the main body member,
The outer peripheral edge portion of the support member is fitted into the recessed portion of the back surface of the main body member.
Pulley shaft.

In the pulley shaft [7], the recess formed on the back surface makes it easy to position the support member relative to the main body member.

[8]
[1] - [7] The pulley shaft according to any one of the above,
The outer peripheral edge of the support member is fixed to the back surface of the main body member by welding,
The body member and the support member are fixed to the shaft by a fixing means other than welding.
Pulley shaft.

In the pulley shaft of [8], the support member is fixed to the main body member by welding, further increasing the rigidity of the inner region of the main body member. On the other hand, welding is not used as a means of fixing the main body member and support member to the shaft. If the support member is welded to the main body member and then welded to the shaft, the main body member or support member may be distorted by the welding heat, and the dimensional accuracy of the shape may decrease. In [8], the means of fixing the main body member and support member to the shaft is a means other than welding, so the dimensional accuracy of the main body member and support member can be maintained.

[9]
A pulley shaft according to any one of [1] to [8],
The body member further comprises:
a boss portion disposed on an inner peripheral edge of the body member;
The boss portion of the main body member is
The shaft has a cylindrical shape and extends from the back surface in a direction opposite to the sheave surface in a cross section including a central axis of the shaft.
The shaft is fitted into the boss portion of the main body member.
Pulley shaft.

In the pulley shaft of [9], the boss portion can further increase the rigidity of the main body member, and as a result, the rigidity of the inner region of the main body member can be further increased.

[10]
[1] to [9], and
A movable sheave that is slidable parallel to the central axis of the shaft;
A drive device that slides the movable sheave parallel to the central axis of the shaft;
a drive belt sandwiched between the sheave surface of the fixed sheave and the sheave surface of the movable sheave,
Belt type continuously variable transmission.

[11]
The fixed sheave according to any one of [1] to [9].

The pulley shaft, belt-type continuously variable transmission, and fixed sheave of this embodiment will be described in detail below with reference to the drawings. The same or corresponding parts in the drawings will be given the same reference numerals and their description will not be repeated.

[Belt-type continuously variable transmission]
FIG. 1 is a cross-sectional view of a belt-type continuously variable transmission of this embodiment. Referring to FIG. 1, the belt-type continuously variable transmission 100 includes a primary pulley device P1 and a secondary pulley device P2. The shaft of the primary pulley device P1 is indirectly connected to a power source (not shown) such as an engine via a gear or the like, and receives torque from the power source. The shaft of the secondary pulley device P2 is indirectly connected to an axle (not shown) that drives a wheel via a well-known gear mechanism (not shown) such as a differential gear. A drive belt B is stretched between the primary pulley device P1 and the secondary pulley device P2. The belt-type continuously variable transmission 100 continuously changes the speed of the driving force (torque) output from the power source and transmits it to the axle.

The configuration of the primary pulley device P1 and the secondary pulley device P2 are substantially the same. In the following description, the primary pulley device P1 and the secondary pulley device P2 are collectively referred to as the "pulley device P." The configuration of the pulley device P is described below.

[Configuration of pulley device P]
2 is a cross-sectional view (longitudinal cross-sectional view) of the pulley device P including the central axis of the shaft. Referring to FIG. 2, the pulley device P includes a pulley shaft 10, a movable sheave 21, a drive device 22 that slides the movable sheave, and bearings 23 and 33.

The pulley shaft 10 comprises a shaft 1 and a fixed sheave 3. When the pulley device P is a primary pulley device P1, the shaft 1 is indirectly connected to a power source. When the pulley device P is a secondary pulley device P2, the shaft 1 is indirectly connected to an axle. The fixed sheave 3 has a conical shape and is fixed to the shaft 1. In other words, the fixed sheave 3 does not slide in the axial direction of the shaft 1, and does not rotate relative to the shaft 1 around the central axis C1 of the shaft 1. The pulley shaft 10 will be described later.

The movable sheave 21 has a conical shape and is disposed opposite the fixed sheave 3. A through hole is formed in the center of the movable sheave 21. The shaft 1 is fitted into the through hole of the movable sheave 21. The movable sheave 21 is supported via a ball spline or the like so as to be slidable parallel to the central axis C1 of the shaft 1. The drive unit 22 slides the movable sheave 21 in the axial direction of the shaft 1. The drive unit 22 is, for example, a hydraulic cylinder. The drive unit 22 may be hydraulic or electric.

Bearing 23 is disposed at one end of shaft 1, and bearing 33 is disposed at the other end of shaft 1. In other words, bearings 23 and 33 are disposed at both ends of shaft 1. Bearings 23 and 33 support shaft 1 so that it can rotate around the central axis C1 of shaft 1.

As described above, the driving device 22 causes the movable sheave 21 to slide in the axial direction of the shaft 1. This causes the distance between the movable sheave 21 and the fixed sheave 3 to vary. Hereinafter, the distance between the movable sheave 21 and the fixed sheave 3 will be referred to as the "groove width." Figure 2 shows the state in which the groove width is at its widest. In this case, the driving belt B is located near the bottom of the groove formed by the movable sheave 21 and the fixed sheave 3 (i.e., near the shaft 1).

In the pulley device P in the state shown in Figure 2, let us assume that the drive device 22 slides the movable sheave 21 toward the fixed sheave 3. In this case, the groove width narrows. As a result, as shown in Figure 3, the drive belt B sandwiched between the movable sheave 21 and the fixed sheave 3 moves radially away from the shaft 1. This causes the winding diameter of the drive belt B to change (become larger), allowing the reduction ratio to be changed steplessly.

[Configuration of pulley shaft 10]
Fig. 4 is a cross-sectional view of the pulley shaft 10 in Fig. 2. Referring to Fig. 4, as described above, the pulley shaft 10 includes the shaft 1 and the fixed sheave 3. The shaft 1 and the fixed sheave 3 are not integrally formed, but are separate members.

In order to improve wear resistance and bending fatigue strength, the surface of the pulley shaft 10 may be subjected to heat treatment. Examples of heat treatment include carburizing and nitriding. The heat treatment of the pulley shaft 10 is usually performed by placing multiple pulley shafts 10 on one tray or one basket in a heat treatment furnace to form one lot. Then, a batch process is performed in which one lot of pulley shafts 10 are loaded into one heat treatment furnace and a single heat treatment is performed, or a continuous furnace process is performed in which multiple lots are prepared and the heat treatment is performed continuously while continuously transporting each lot. Therefore, in order to increase the productivity of the pulley shaft 10, it is preferable to increase the number of pulley shafts that can be stored in one lot as much as possible.

As shown in FIG. 5, in the conventional pulley shaft 200, the shaft 1 and the fixed sheave 300 are integrally formed. Therefore, when performing heat treatment by batch processing on the conventional pulley shaft 200, the number of pulley shafts 200 that can be heat treated by batch processing is limited. FIG. 6 is an image diagram of the number of pulley shafts 200 arranged in one lot (one basket) LT during heat treatment. Referring to FIG. 6, in the case of the conventional pulley shaft 200, the fixed sheave 300 extends in the radial direction of the shaft 1. Therefore, in one lot (one basket) LT, the space between adjacent pulley shafts 200 cannot be sufficiently narrowed and stored, and spaces are generated between the adjacent pulley shafts 200. Therefore, the number that can be treated by one heat treatment is limited.

On the other hand, in the pulley shaft 10 of this embodiment, the shaft 1 and the fixed sheave 3 are separate components. Therefore, as shown in FIG. 7, a large number of shafts 1 can be stored in one lot (one basket) LT of the same capacity as FIG. 6. Similarly, as shown in FIG. 8, a large number of fixed sheaves 3 can be stored in one lot (one basket) LT of the same capacity as FIG. 6. As a result, when heat treated, the pulley shaft 10 of this embodiment can significantly increase productivity compared to the conventional one-piece pulley shaft 200.

In the pulley shaft 10 of this embodiment, the fixed sheave 3 has the following configuration, which can suppress loss in torque transmission. The configuration of the fixed sheave 3 is described in detail below.

[Configuration of fixed sheave 3]
Fig. 9 is a cross-sectional view of the fixed sheave 3 of this embodiment including the central axis C1 of the shaft 1. Referring to Fig. 9, the fixed sheave 3 includes a main body member 31 and a support member 32. The main body member 31, together with the movable sheave 21, serves to sandwich the drive belt B and hold the drive belt B. The support member 32 supports the main body member 31 to increase the rigidity of the inner region 31A of the fixed sheave 3 while maintaining appropriate elasticity of the outer region 31B. The main body member 31 and the support member 32 will be described below.

[Regarding main body member 31]
The main body member 31 is in the shape of a conical plate and has a through hole 31H in the center. The shaft 1 is fitted into the through hole 31H. For example, a spline is formed in the through hole 31H. When viewed from the direction of the central axis C1 of the shaft 1, the main body member 31 is circular. Furthermore, in a cross section including the central axis C1 of the shaft 1, the main body member 31 is plate-shaped and inclined in the opposite direction to the movable sheave 21 from the inner peripheral edge 31IE of the through hole 31H toward the outer peripheral edge 31OE of the main body member 31. In other words, the main body member 31 is a conical (tapered) plate member.

The main body member 31 has a sheave surface 31FS and a back surface 31BS. The sheave surface 31FS is disposed opposite the movable sheave 21 and contacts the drive belt B. The back surface 31BS is the surface opposite the sheave surface 31FS.

[Regarding the support member 32]
The support member 32 is in the form of a conical plate and has a through hole 32H in the center. The shaft 1 is fitted into the through hole 32H. When viewed from the direction of the central axis C1 of the shaft 1, the support member 32 is circular. Furthermore, in a cross section including the central axis C1 of the shaft 1, the support member 32 is plate-shaped and inclined toward the main body member 31. Specifically, in a cross section including the central axis C1 of the shaft 1, the support member 32 is inclined toward the main body member 31 from the inner peripheral edge portion 32IE toward the outer peripheral edge portion 32OE. The support member 32 may be inclined linearly or may be inclined in a curved manner. Also, as shown in FIG. 9, the portion near the outer peripheral edge portion 32OE may be more inclined than the portion near the inner peripheral edge portion 32IE. The end face of the outer peripheral edge portion 32OE of the support member 32 is in contact with the back surface 31BS of the main body member 31, and the outer peripheral edge portion 32OE is fixed to the back surface 31BS.

[Features of fixed sheave 3]
The outer diameter of the support member 32 is smaller than the outer diameter of the main body member 31. Therefore, the outer peripheral edge portion 32OE of the support member 32 is fixed to a back surface portion inside the outer peripheral edge portion 31OE of the main body member 31. Here, the region of the main body member 31 within the outer diameter of the support member 32 (i.e., the region overlapping with the support member 32 when viewed from the central axis C1 direction of the shaft 1) is defined as the inner region 31A, and the region outside the inner region 31A is defined as the outer region 31B. In this case, the rigidity of the inner region 31A is increased by the support of the support member 32. On the other hand, the outer region 31B is not supported by the support member 32. Therefore, the outer region 31B of the main body member 31 has a moderate elasticity.

When the pulley shaft 10 is rotating (i.e., when driven), the area where the drive belt B contacts the sheave surface 31FS of the fixed sheave 3 is in the circumferential direction in a range of approximately 140 to 220°. Here, the position on the sheave surface 31FS where the drive belt B starts to contact the sheave surface 31FS is defined as the "belt entrance". The position on the sheave surface 31FS where the drive belt B leaves the sheave surface 31FS is defined as the "belt exit". In the trajectory of the drive belt B contacting the sheave surface 31FS, the intermediate position between the belt entrance and the belt exit is defined as the "belt winding central position". The belt entrance and belt exit are also collectively referred to as the "belt entrance/exit".

During driving, the axial displacement of the fixed sheave 3 is small at the belt entrance and exit, and large at the center of the belt winding. Therefore, during driving, the drive belt B is strongly compressed at the belt entrance and exit, and the drive belt B is wound around the large diameter side of the fixed sheave 3 (towards the outer periphery of the fixed sheave 3). On the other hand, at the center of the belt winding, the fixed sheave 3 is more flexible than the belt entrance and exit. Therefore, the drive belt B falls towards the small diameter side of the fixed sheave 3 (in the central axial direction of the fixed sheave 3). As a result, the change in the winding diameter of the drive belt B becomes large. The change in the winding diameter corresponds to the amount of slippage of the drive belt B. Therefore, if the change in the winding diameter is large, a radial slip torque loss of the drive belt B occurs, and a torque transmission loss occurs.

The amount of change in the winding diameter of the drive belt B due to the difference in flexure at the belt entrance/exit point and the center of the belt winding position at the fixed sheave 3 described above is more noticeable in the pulley shaft 10 in which the fixed sheave and shaft are separated as in this embodiment than in a conventional integrated pulley shaft. This is because the fixed sheave 3 is separated from the shaft 1, so that axial displacement is more easily applied to the fixed sheave.

Therefore, in the pulley shaft 10, as described above, the outer diameter of the support member 32 is made smaller than the outer diameter of the main body member 31. As a result, the support member 32 supports the main body member 31 on the inside rather than the outer periphery. In this case, the outer region 31B of the main body member 31 has a suitable elasticity. Therefore, during driving, the fixed sheave 3 flexes appropriately not only at the central position of the belt winding, but also at the belt entrance and exit. Therefore, the belt clamping pressure at the belt entrance and exit can be suppressed, and the variation in axial displacement in the circumferential direction of the fixed sheave 3 can be suppressed. As a result, the amount of change in the winding diameter can be reduced, and torque transmission loss can be suppressed.

Preferably, the rigidity of the support member 32 is higher than that of the main body member 31. In this case, the rigidity of the inner region 31A can be further increased. Therefore, even if a force in a direction that widens the groove width of the pulley is applied to the main body member 31 by the drive belt B (that is, a force is applied in a direction in which the main body member 31 falls (inclined direction)), the inner region 31A is less likely to bend. Preferably, as shown in FIG. 10, in a cross section including the central axis C1 of the shaft 1, the thickness T31 of the main body member 31 is thinner than the thickness T32 of the support member 32. In this case, the rigidity of the support member 32 is likely to be higher than that of the main body member 31. Therefore, the flexure of the outer region 31B can be maintained when the drive belt B is clamped while providing a more effective rigidity to the inner region 31A.

As shown in FIG. 10, preferably, the shaft 1 has a step portion 1CO protruding in the radial direction. The step portion 1CO has a side wall surface 1COE that contacts the inner peripheral edge portion 32IE of the support member 32. In this case, the support member 32 is more effectively fixed to the shaft 1.

[Attachment position of outer peripheral edge portion 32OE of support member 32]
The attachment position of the outer peripheral edge 32OE of the support member 32 to the back surface 31BS of the main body member 31 is not particularly limited as long as it is inside the outer peripheral edge 31OE of the main body member 31. As shown in FIG. 11, when the outer diameter of the main body member 31 is defined as D (mm), the outer peripheral edge 32OE of the support member 32 is preferably fixed to an area of the back surface 31BS of the main body member 31 within a range of 0.5D to 0.8D. In this case, the support member 32 can maintain the bending of the outer region 31B when the drive belt B is clamped while providing more effective rigidity to the inner region 31A. FIG. 12 is a schematic diagram showing an example in which the outer peripheral edge 32OE of the support member 32 is fixed in an area near 0.8D, and FIG. 13 is a schematic diagram showing an example in which the outer peripheral edge 32OE of the support member 32 is fixed in an area near 0.5D.

[Other forms of fixed sheave 3]
Fig. 14 is a cross-sectional view of a fixed sheave 3 having a different configuration from that of Fig. 9. Referring to Fig. 14, the support member 32 of the fixed sheave 3 further includes a boss portion 323. The boss portion 323 is disposed on an inner circumferential edge portion 32IE of the support member 32. The boss portion 323 is cylindrical. In a cross section including the central axis C1 of the shaft 1, the boss portion 323 extends from a back surface 32BS of the support member 32 in a direction opposite to the main body member 31.

The inner peripheral surface of the boss portion 323 is connected to the through hole 32H. Figure 15 is a schematic diagram showing the state in which the fixed sheave 3 shown in Figure 14 is attached to the shaft 1. Referring to Figure 15, the shaft 1 is fitted into the boss portion 323.

The support member 32 shown in FIG. 14 has a boss portion 323 that extends in the opposite direction to the main body member 31. This further increases the rigidity of the support member 32. As a result, the rigidity of the inner region 31A of the main body member 31 can be further increased, and torque transmission loss can be suppressed.

Referring to FIG. 15, the shaft 1 further includes a step portion 1CO that protrudes in the radial direction of the shaft. The step portion 1CO includes a side wall surface 1COE. The side wall surface 1COE is annular and is disposed opposite the end surface 323E of the boss portion 323. The side wall surface 1COE is in contact with the end surface 323E of the boss portion 323. Assume that a force F1 that widens the pulley groove width of the drive belt B is applied to the main body member 31. In this case, the step portion 1CO applies a reaction force F2 against the force F1 to the support member 32. Therefore, the support member 32 can support the main body member 31 even more effectively.

Referring to FIG. 16, the boss portion 323 of the support member 32 may further have an outer peripheral surface 323OS on which the bearing 33 is placed when the pulley shaft 10 is assembled into the belt-type continuously variable transmission 100. In this case, the boss portion 323 of the support member 32 is directly fixed to the bearing 33. Therefore, the support member 32 is fixed even more firmly. As a result, the rigidity of the inner region 31A of the main body member 31 can be further increased.

Figure 17 is a cross-sectional view showing another configuration of the fixed sheave 3 different from those in Figures 9, 14, and 16. Referring to Figure 17, a recess 31R is formed in the back surface 31BS of the main body member 31 of the fixed sheave 3. When the back surface 31BS of the main body member 31 is viewed from the direction of the central axis C1 of the shaft 1, the recess 31R is a circular groove.

The recess 31R is used to position the support member 32 relative to the main body member 31. The outer peripheral edge 32OE of the support member 32 is fitted into the recess 31R. This makes it easier to align the position of the support member 32 relative to the main body member 31.

18 is a diagram showing an example of a fixing means for the main body member 31 and the support member 32. The fixing means for the main body member 31 to the shaft 1, the fixing means for the support member 32 to the main body member 31, and the fixing means for the support member 32 to the shaft 1 are not particularly limited. Preferably, as shown in FIG. 18, the outer peripheral edge portion 32OE of the support member 32 is fixed to the main body member 31 by welding 32W. By welding, the support member 32 becomes substantially the same as the state in which it is integrally shaped with the main body member 31. Therefore, the rigidity of the inner region 31A of the main body member 31 is significantly increased. On the other hand, the fixing means for the main body member 31 to the shaft 1 and the fixing means for the support member 32 to the shaft 1 are preferably means other than welding. The fixing means for the main body member 31 to the shaft 1 and the fixing means for the support member 32 to the shaft 1 are, for example, soldering, fixing (fastening) by a screw, fixing using a key or pin, fixing by a spline, etc. If welding is used as the means for fixing the main body member 31 to the shaft 1 and the means for fixing the support member 32 to the shaft 1, the fixed sheave 3 may become distorted after welding due to the effects of welding heat. Therefore, when considering dimensional accuracy, it is preferable to fix the main body member 31 and the support member 32 to the shaft 1 by a fixing means other than welding.

Figure 19 is a cross-sectional view showing another fixed sheave configuration different from those in Figures 9, 14, 16, and 17. In the fixed sheave 3 shown in Figure 19, the main body member 31 has a boss portion 311, as compared to Figure 17.

The boss portion 311 is disposed on the inner peripheral edge portion 31IE of the main body member 31. The boss portion 311 is cylindrical. In a cross section including the central axis C1 of the shaft 1, the boss portion 311 extends from the back surface 31BS of the main body member 31 toward the support member 32. In other words, the boss portion 311 extends in the opposite direction to the sheave surface 31FS of the main body member 31. The inner peripheral surface of the boss portion 311 is connected to the through hole 31H. The shaft 1 is fitted into the boss portion 311.

Like the boss portion 323 of the support member 32, the boss portion 311 of the main body member 31 can also further increase the rigidity of the main body member 31. In other words, the boss portion 311 further increases the rigidity of the inner region 31A of the main body member 31, suppressing torque transmission loss.

Referring to FIG. 19, the shaft 1 may further include a step portion 1CO2 that protrudes in the radial direction of the shaft. The step portion 1CO2 includes a side wall surface 1CO2E, similar to the step portion 1CO. The side wall surface 1CO2E is annular and is disposed opposite the end surface 311E of the boss portion 311. The side wall surface 1CO2E is in contact with the end surface 311E of the boss portion 311. In this case, similar to the step portion 1CO, the step portion 1CO2 applies a reaction force F2 to the main body member 31 against the force F1 in the direction widening the pulley groove width of the drive belt B. This can further increase the rigidity of the main body member 31 and further increase the rigidity of the inner region 31A.

Assuming three types of pulley shafts X to Z shown in Figure 20, an analysis using the finite element method (FEM) was performed to determine the axial displacement of the portion near the outer periphery of the fixed sheave when the drive belt is wrapped around it.

Specifically, pulley shaft X was assumed to be a conventional pulley shaft in which the fixed sheave 300 and shaft 1 are integrated. Pulley shaft Y was assumed to be a pulley shaft in which the fixed sheave 3 and shaft 1 are separate bodies, the fixed sheave 3 includes a main body member 31 and a support member 320, and the outer diameter of the support member 320 is approximately the same as the outer diameter of the main body member 31. Pulley shaft Z was assumed to be a pulley shaft of the present invention in which the fixed sheave 3 and shaft 1 are separate bodies, the fixed sheave 3 includes a main body member 31 and a support member 32, and the outer diameter of the support member 32 is smaller than the outer diameter of the main body member 31.

Figure 21 is a schematic diagram for explaining a finite element model of a pulley shaft. Figure 21 is a view of the pulley shafts X to Z from the sheave surface of the fixed sheave 3 or 300. Referring to Figure 21, the finite element model of the pulley shafts X to Z was a 1/2 axis symmetric model with the line segment L1 that includes the central axis C1 of the sheave surface and extends in the vertical direction as the axis. The same values of Young's modulus and Poisson's ratio were set as the physical property values of the pulley shafts X to Z. A contact area 350 of the drive belt B near the outer periphery of the sheave surface was assumed. Then, the line segment L1 was set to 0°, and attention was paid to the contact area 350 from 0° to 105° around the central axis C1. At each position from 0° to 105° on the contact area 350 when the drive belt B is wound around it, the amount of change in the axial direction from the position (initial position) when the drive belt B is not wound around it was defined as "axial displacement". In addition, if the movable sheave 21 moves in the opposite direction from the initial position (see arrow F in Figure 20), the axial displacement is considered negative (-).

The drive belt B was wrapped around each of the pulley shafts X to Z under the same conditions, and the axial displacement of the contact area 350 was determined by FEM analysis. Note that the static implicit method was used in the FEM analysis.

The results obtained by the above-mentioned FEM analysis are shown in FIG. 22. In FIG. 22, the horizontal axis is the angle (0 to 105°) at the contact area 350, and the vertical axis is the axial displacement. The two-dot chain line in FIG. 22 is the result (axial displacement) of pulley shaft X. The one-dot chain line is the result (axial displacement) of pulley shaft Y. The solid line is the result (axial displacement) of pulley shaft Z. The difference between the maximum and minimum values of the real directional displacement of pulley shaft X was defined as the displacement amount DX. The difference between the maximum and minimum values of the real directional displacement of pulley shaft Y was defined as the displacement amount DY. The difference between the maximum and minimum values of the real directional displacement of pulley shaft Z was defined as the displacement amount DZ. The smaller the displacement amount, the smaller the variation in displacement within the contact area 350, and the smaller the torque transmission loss.

Referring to FIG. 22, the displacement DZ of the pulley shaft Z of the present invention example was smaller than the displacement DY of the pulley shaft Y of the comparative example, and was approximately the same as the displacement DX of the conventional pulley shaft X. Therefore, in the present invention example, even if the fixed sheave 3 is separated from the shaft 1, the torque transmission loss was able to be reduced to the same level as that of the conventional pulley shaft X.

The above describes the embodiments of the present disclosure. However, the above-described embodiments are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiments, and can be implemented by modifying the above-described embodiments as appropriate within the scope of the spirit of the present disclosure.

REFERENCE SIGNS LIST 100 Belt-type continuously variable transmission 1 Shaft 3 Fixed sheave 21 Movable sheave 31 Body member 31FS Sheave surface 31BS Back surface 31H, 32H Through hole 32 Support member 32OE Outer periphery B Drive belt

Claims (8)

A pulley shaft for a belt-type continuously variable transmission,
A shaft,
a fixed sheave fixed to the shaft;
The fixed sheave is
a main body member having a conical plate shape, a through hole in a center portion into which the shaft is fitted, and fixed to the shaft;
a support member having a conical plate shape, a through hole in a center portion into which the shaft is fitted, the support member being fixed to the shaft and supporting the main body member;
The body member includes:
A sheave surface that contacts a drive belt of the belt-type continuously variable transmission;
A back surface opposite to the sheave surface,
The support member is
The shaft is disposed on the back surface side of the main body member and is inclined toward the main body member in a cross section including a central axis of the shaft,
The outer diameter of the support member is smaller than the outer diameter of the body member,
An outer peripheral edge portion of the support member is fixed to the back surface of the main body member,
The support member further comprises:
a boss portion disposed on an inner peripheral edge of the support member;
The boss portion is
The shaft is cylindrical and extends in a direction opposite to the main body member in a cross section including a central axis of the shaft.
the shaft is fitted into the boss portion of the support member,
The pulley shaft further comprises:
a bearing that supports the shaft rotatably around a central axis of the shaft,
The boss portion of the support member is
The bearing has an outer circumferential surface on which the bearing is placed when the bearing is installed in the belt-type continuously variable transmission.
Pulley shaft. 2. The pulley shaft of claim 1,
In a cross section including a central axis of the shaft, the thickness of the body member is smaller than the thickness of the support member.
Pulley shaft. 3. The pulley shaft according to claim 1 or 2,
When the outer diameter of the main body member is defined as D (mm), the outer peripheral edge portion of the support member is fixed to an area of the back surface of the main body member within a range of 0.5D to 0.8D.
Pulley shaft. 2. The pulley shaft of claim 1 ,
The shaft is
A step portion protruding in a radial direction of the shaft is provided,
The step portion is
a side wall surface facing the end surface of the boss portion of the support member and in contact with the end surface of the boss portion of the support member;
Pulley shaft. The pulley shaft according to any one of claims 1 to 4 ,
A recess is formed on the rear surface of the main body member,
The outer peripheral edge portion of the support member is fitted into the recessed portion of the back surface of the main body member.
Pulley shaft. The pulley shaft according to any one of claims 1 to 5 ,
the outer peripheral edge portion of the support member is fixed to the back surface of the main body member by welding,
The body member and the support member are fixed to the shaft by a fixing means other than welding.
Pulley shaft. The pulley shaft according to any one of claims 1 to 6 ,
The body member further comprises:
a boss portion disposed on an inner peripheral edge of the body member;
The boss portion of the main body member is
The shaft is cylindrical and extends from the back surface in a direction opposite to the sheave surface in a cross section including a central axis of the shaft.
The shaft is fitted into the boss portion of the main body member.
Pulley shaft. A pulley shaft according to any one of claims 1 to 7 ;
A movable sheave that is slidable parallel to the central axis of the shaft;
A drive device that slides the movable sheave parallel to the central axis of the shaft;
a drive belt sandwiched between the sheave surface of the fixed sheave and the sheave surface of the movable sheave,
Belt type continuously variable transmission.

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