JP2002372114A - Frictional continuously variable transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control axial pressurizing force of a contact part of a traction drive according to load torque, to eliminate post working such as cutting/ grinding, to required shorten working time, and to improve product yield, operation stability and efficiency. SOLUTION: In this frictional continuously variable transmission, carriers 25a and 25b are moved in the axial directions of input/output shafts 21 and 22 by a speed change mechanism 32, a contact part of a double cone 26, a sun roller 23 and an outer ring 24 is displaced, and continuously variable transmission is performed. Pressurizing cams 30 and 31 in which cam surfaces for imparting pressure contact force to the double cone 26 after changing pressure contact force according to input shaft torque and transmitting rotary torque are formed oppositely to the axial directions of the input/output shafts 21 and 22 are interposed into either one of at least between the sun roller 23 and a high speed shaft or between the outer ring 24 and a low speed shaft. The cam surfaces of the pressurizing cams 30 and 31 are made of cold forging working surfaces.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frictionless continuously variable transmission, and more particularly, to a traction drive type continuously variable transmission used for an industrial machine or a vehicle transmission.

[0002]

2. Description of the Related Art A traction drive is a kind of friction transmission device, and power is transmitted through an oil film formed between two surfaces having a smooth surface. Such a traction drive has the following features. (1) Vibration and noise levels are lower than gears. (2) Continuously Variable Transmissi
on, CVT).

[0003] A continuously variable transmission can be realized by changing the radius of rotation (the distance from the rotation axis to the contact portion with another power transmission member) of the power transmission member constituting the traction drive. Various types of traction drive type continuously variable transmissions have been developed according to the method of changing the turning radius, and a typical one is a cone type CVT.

FIG. 7 shows an example of a cone type CVT. A high-speed shaft 2 and a low-speed shaft 3 are arranged coaxially in a casing 1 via an angular ball bearing 4, a radial ball bearing 5, and a needle bearing 6, and a sun roller having a rolling surface 7a at an end of the high-speed shaft 2. 7 are formed. An outer ring 8 having a rolling surface 8a on its inner peripheral surface is attached to an end of the low-speed shaft 3. In FIG. 7, the outer ring 8
And the low-speed shaft 3 are shown separately, but they may be integrally formed. Double cones 9 are arranged between the sun roller 7 and the outer ring 8 at equal intervals in the circumferential direction and rotatably. The double cone 9 has two conical surfaces 9a and 9b, which are rolling surfaces, and the conical surfaces 9a and 9b
, Respectively, is in pressure contact with the sun roller 7 and the outer ring 8. When this cone type CVT is used as a speed reducer, the high speed shaft 2 is used as an input shaft and the low speed shaft 3 is used as an output shaft.

A shaft 9 for rotatably supporting the double cone 9
The rotation of the carrier 10 holding c at equal intervals in the circumferential direction about the axis of the input / output shafts 2 and 3 is restricted. That is,
The double cone 9 is restricted from revolving around the axis of the input and output shafts 2 and 3, and can only rotate around the axis of the shaft 9c. In this case, the gear ratio e (= high-speed shaft speed / low-speed shaft speed) is given by the following equation. e = bd / ac where a is the radius of rotation from the axis of the sun roller 7 to the contact portion with the double cone 9, b is the radius of rotation from the axis of the double cone 9 to the contact portion with the sun roller 7, and c is the double radius. The radius of rotation from the axis of the cone 9 to the contact portion with the outer ring 8, d is the radius of rotation of the double cone 9 from the axis of the outer ring 8.
Is the radius of rotation up to the contact area.

Referring to FIG. 8, the mechanism of shifting the cone type CVT will be described. The double cone 9 has a conical generatrix 9 a ′ in contact with the sun roller 7 and a conical generatrix 9 b ′ in contact with the outer ring 8.
Are formed in parallel. Therefore, as shown in FIG. 8, the double cone 9 can move along the cone generating lines 9a 'and 9b'. When the double cone 9 moves, the turning radii b and c in the above equation continuously change, so that the gear ratio e becomes continuously variable. In the cone type CVT, the carrier 10 supporting the double cone 9 is used.
Is driven by a pinion gear 13 attached to a speed change shaft 12, whereby the carrier 10 is moved in the direction of the input / output axis to change the speed. In FIG. 7, reference numeral 1a denotes a lubricating oil supply path, and 1b denotes a lubricating oil discharge path. Both of them are formed at the end of the casing 1 and lubricate a bearing portion and a friction contact portion.

[0007]

In a cone type CVT using a traction drive, a contact portion between the sun roller 7 and the double cone 9 and a contact portion between the double cone 9 and the outer ring 8 transmit power through an oil film. For,
A large normal force is required. In the case of FIG. 8, since the taper angle θ is given to the cone generating lines 9a ′ and 9b ′ of the double cone 9 with respect to the axes of the input and output shafts 2 and 3, the contact portion between the sun roller 7 and the double cone 9 and Double cone 9
By applying a pressing force in the axial direction of the input / output shafts 2 and 3 to the contact portion between the motor and the outer ring 8, normal forces F ₁ and F ₂ required for power transmission are generated. Therefore, in the cone type CVT shown in FIG. 7, an axial force by a spring 14 is applied to the low speed shaft 3 via the radial ball bearing 5.
At this time, as the pressing force in the axial direction of the input and output shafts 2 and 3 is increased, the normal force generated at the contact portion is increased. Since the loss increases, the efficiency is reduced. This is because when the normal force is applied to the contact portion by a constant pressurizing method as in the case of the spring 14 in FIG. 7, the spring force is set according to the maximum load. Means that In order to minimize such a decrease in transmission efficiency, it is necessary to control the axial pressing force of the contact portion according to the load torque. As one of the solutions, transmission of the rotational torque is required. A pressing cam having a cam surface formed to face the input / output shaft in the axial direction is provided at least between the sun roller 7 and the high-speed shaft 2 or between the outer ring 8 and the low-speed shaft 3. It is effective to intervene.

[0008] As shown in FIG. 6A, the above-mentioned pressure cam is usually formed from a rod-shaped material (for example, carburized steel) by hot forging into a shape close to the final product, and then machined by cutting or the like. Processing, heat treatment, and then a finishing method, a rolling method and the like, a solid material formed into a rod shape,
Alternatively, it is manufactured by a processing method or the like in which a rod-shaped hollow material is finished by cutting such as cutting.

However, in the forming by hot forging, the size and shape change due to cooling shrinkage after forming is large, and an abnormal structure or an oxide film is generated on the material surface by heating. Machine processing is required. Also,
Even when there is no formation of an abnormal structure or an oxide film, machining is indispensable because burrs are not removed and the surface roughness of the material is not good. Poor surface roughness has an adverse effect on the operating accuracy of the pressure cam and destabilizes the normal force generated at each contact that transmits the rotational torque, causing deterioration in operating stability and efficiency. . In addition, a machining method of finishing a bar-shaped material other than hot forging by cutting such as by shaving not only requires a longer time required for machining but also lowers the yield, which is not desirable in terms of cost.

Therefore, the present invention can control the axial pressing force at the contact portion between the double cone of the cone type CVT and the sun roller and the outer ring in accordance with the load torque, and can perform post-processing such as cutting and grinding. The object of the present invention is to reduce the time required for machining, improve the product yield, and improve the operation stability and efficiency.

[0011]

As a technical means for achieving the above object, a friction type continuously variable transmission according to the present invention comprises a high-speed shaft and a low-speed shaft rotatably and coaxially arranged on a casing. A sun roller connected to the high-speed shaft and having an outer peripheral surface as a rolling surface; an outer ring connected to the low-speed shaft and having an inner peripheral surface as a rolling surface; and a coaxial core disposed with the sun roller and the outer ring. A carrier that is movable in the axial direction on the shaft center by the transmission mechanism, and is held rotatably via a rotating shaft at circumferentially equally spaced positions of the carrier, the rolling surface of the sun roller and A plurality of double cones that are pressed between the rolling surfaces of the outer ring to transmit rotational torque, and one of the high-speed shaft and the low-speed shaft is used as an input shaft, and the other is used as an output shaft, and input and output is performed by the transmission mechanism. Rotation around axis By moving the regulated carrier in the axial direction of the input / output shaft, the contact portion of the sun roller and the outer ring with respect to the double cone is displaced, so that the rotational speed of the output shaft with respect to the rotational speed of the input shaft changes steplessly. In the continuously variable transmission, a pressure contact force to the double cone is applied while being changed in accordance with a transmission torque transmitted from the input shaft to the output shaft, and a cam surface for transmitting a rotational torque is provided. A pressure cam formed to face the output shaft in the axial direction is interposed between at least one of the sun roller and the high-speed shaft or between the outer ring and the low-speed shaft, and The cam surface is formed by a cold forging surface.

According to the above configuration, the axial pressing force of the contact portion between the double cone of the cone-type CVT and the sun roller and the outer ring can be controlled in accordance with the load torque, and moreover, after forming by cold forging. Since the pressure cam has a small change in size and shape due to cooling shrinkage, cutting and grinding, which is indispensable in hot forging, can be omitted, and the required processing time can be reduced. Further, according to the forming of the pressure cam by cold forging, not only is there no abnormal metal structure or oxide film formed after hot forging, but also the surface finish (surface roughness) is good. Further, compared to a pressure cam formed by cutting such as shaving, the required processing time can be reduced, and the product yield can be improved.

By forming one of the opposed cam surfaces of the pressure cam integrally with the sun roller or the outer ring, the number of parts can be reduced.

Further, the power transmission surface serving as a contact portion between the double roller and the sun roller or the outer ring cold-forged integrally with the pressure cam is a finished surface to further transmit the rotational torque. It can be performed smoothly. The finished surface is a surface that has been finished by grinding, polishing, or the like.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional side view showing an embodiment of a friction-type continuously variable transmission according to the present invention, in which an upper half shows a state at a maximum speed ratio and a lower half shows a state at a minimum speed ratio.

In FIG. 1, 21 is a high-speed axis, 22 is a low-speed axis, 23 is a sun roller, 24 is an outer ring, 25a,
25b is a carrier, 26 is a double cone, 27 is a rotating shaft, 28 is a high speed side support cam, 29 is a low speed side support cam, 30 is a high speed side press cam, 31 is a low speed side press cam,
Reference numeral 32 denotes a speed change mechanism.

The high-speed shaft 21 is rotatably supported by a part 33 of the casing via an angular ball bearing 34. The low-speed shaft 22 is rotatably supported by a part of the casing via a bearing (not shown) so as to be coaxially opposed to the high-speed shaft 21. At the opposite end of the high-speed shaft 21 and the low-speed shaft 22, an axial concave portion 21a and a small-diameter convex portion 22a are formed so as to face each other, and these are rotatable coaxially via a needle bearing 35. Are combined.

The sun roller 23 is rotatably supported on the outer peripheral surface of an end portion of the high-speed shaft 21 so as to be movable in the axial direction, and has a conical rolling surface 23a on the outer peripheral surface. Outer ring 2
4 is rotatably supported by a cylindrical support portion 29a on the outer peripheral portion of the low-speed side support cam 29 so as to be freely rotatable in the axial direction, and has a conical rolling surface 24a on the inner peripheral surface.

The carriers 25a and 25b support both ends of the rotation shaft 27 of the double cone 26. One of the carriers 25a and 25b is rotatably movable in the axial direction on a peripheral surface near the tip of the low-speed shaft 22 via a needle bearing 36. The other is supported by a part 33 of the casing movably in the axial direction of the high-speed shaft 21.

The double cone 26 has two conical surfaces 26 a and 26 b which are in pressure contact with the rolling surface 23 a of the sun roller 23 and the rolling surface 24 a of the outer ring 24, and the carriers 25 a and 25 b A plurality (three or more) are arranged at equally spaced positions in the circumferential direction. The conical generatrix of the two conical surfaces 26a and 26b pressed against the rolling surface 23a of the sun roller 23 and the rolling surface 24a of the outer ring 24 are formed parallel to each other, and the high-speed shaft 2
1 and the low-speed shaft 22 are configured to intersect at a small angle.

The rotation shaft 27 supports the double cone 26 rotatably and movably in the axial direction, and has both ends fixed to carriers 25a and 25b. The axis of the rotation shaft 27 is arranged to intersect the axis of the high-speed shaft 21 and the low-speed shaft 22 at a predetermined angle (for example, 45 °).

The high-speed support cam 28 is mounted on the high-speed shaft 21 so as to rotate integrally with the sun roller 23 via a key 37 so as not to move in the axial direction. . The low-speed side support cam 29 is opposed to the outer ring 24 on the low-speed shaft 22 in the axial direction.
2 is mounted so as to rotate integrally via a key 38 so as not to move in the axial direction.

The high-speed pressing cam 30 is composed of a cam surface 30a, 30b formed on an axially facing surface of the sun roller 23 and the high-speed support cam 28, and a steel ball interposed between the two cam surfaces 30a, 30b. The ball 30c is provided for transmitting rotational torque between the high-speed shaft 21 and the sun roller 23 and for pressing the sun roller 23 against the double cone 26. The cam surfaces 30a, 30
"b" is formed at equal intervals in the circumferential direction between the sun roller 23 and the high-speed support cam 28, and has a V-shaped groove.

The low speed side pressing cam 31 is
Surfaces 31a and 31b formed on an axially opposed surface of the low speed side support cam 29 and a ball 31c made of a steel ball interposed between the two cam surfaces 31a and 31b. 24 and the outer ring 24 is double-cone 26
It is arranged to be pressed against. The cam surface 31
The a and 31b are formed at equal circumferential positions of the outer ring 24 and the low-speed side support cam 29, and have a V-groove shape.

The transmission mechanism 32 includes a rack 32a formed in a part of the carrier 25b, a pinion gear 32b meshing with the rack 32a, and a transmission shaft 3 having the pinion gear 32b fixed thereto.
The speed change shaft 32c is rotatably mounted on a part of the casing.

As shown in FIG. 1, the pressurizing cams 30 and 31 are installed not only on both sides of the high speed shaft 21 and the low speed 22 but also on one of them. . 2 shows a case where the pressing cam 30 is installed only on the high-speed shaft 21 side, and FIG. 3 shows a case where the pressing cam 31 is installed only on the low-speed shaft 22 side. 1 to 3,
The support cams 28 and 29 are a high-speed shaft 21 and a low-speed shaft 22.
Although it is separate from the above, it can also be manufactured integrally.

When the pressure cams 30 and 31 are not loaded, the outer rings 24 as shown in FIG.
Alternatively, the balls 30c and 31c are held between the sun roller 23 and the support cams 28 and 29 so that the gap in the axial direction is minimized. However, when the load is applied, as shown in FIG. The rotational torque is transmitted by increasing the axial gap in accordance with the torque, and the axial pressing force depending on the transmitted torque acts on the outer ring 24 and the sun roller 23 as a pressure contact force on the double cone 26, and each contact portion , A normal force corresponding to the load torque is generated. Therefore, the pressure generating mechanism by the pressure cams 30 and 31 is as follows.
Compared with a constant pressure mechanism using a spring, an axial pressing force corresponding to the load torque can be generated at each of the contact portions,
In particular, it is possible to improve the transmission efficiency at low load torque and extend the life of the continuously variable transmission. Note that a roller may be used instead of the ball.

It is also possible to transmit the rotational torque and apply the axial pressing force by using face cams 30 'and 31' as shown in FIGS. 5A and 5B. However, these face cams 30 ', 31' have cam surfaces 30a ', 30b', 3
Because of the high sliding friction resistance of 1a ', 31b', there is a hysteresis between the load torque and the axial pressing force generated by the pressing cams 30 ', 31'. Such hysteresis causes the normal force acting on the contact portion of the traction member to change with the operation of the transmission, and may adversely affect the operation stability. Therefore, when the face cams 30 'and 31' are employed, dimensional accuracy and surface roughness accuracy are more strictly required.

According to the present invention, the pressure cams 30, 31, 3
0 ′, 31 ′ are formed by cold forging, and their cam surfaces 30a ′,
30b ', 31a', and 31b 'are formed by cold forging surfaces so that post-processing such as cutting and grinding can be omitted.

FIG. 6B is an explanatory view of a process of cold forging according to the present invention, in which a material (for example, carburized steel) is cold forged and heat-treated to obtain a finished product. In this case, the cold forging is performed by the sun roller 23, the outer ring 24, and the support cam 2 constituting the pressure cams 30, 31, 30 ', 31'.
8, 29, which are formed by cold forging from a material shape suitable for each to a final product shape, and the cam surfaces 30a 'of the pressure cams 30, 31, 30', 31 'formed by the cold forging. , 30b ', 31a', and 31b 'are heat-treated without performing machining such as cutting and grinding after cold forging to complete products. That is, in the case of cold forging, since the change in size and shape after forming is small, machining such as cutting which is indispensable in hot forging can be omitted. Further, not only an abnormal structure and an oxide film such as hot forging are not formed, but also the surface finish is good. Furthermore, compared to a processing method of manufacturing only by cutting such as shaving, the yield can be improved and the required processing time can be reduced. The rolling surface 23a of the sun roller 23 and the rolling surface 24a of the outer ring 24 that come into contact with the double cone 26 are subjected to finishing such as polishing after heat treatment, if necessary.

The configuration of this embodiment is as described above. Next, the operation will be described with reference to FIG. For example, when used as a reduction gear, the high-speed shaft 21 becomes an input shaft, and the low-speed shaft 22 becomes an output shaft. Therefore, the rotational torque of the high-speed shaft 21 is transmitted from the high-speed support cam 28 to the sun roller 23 via the high-speed pressing cam 30, transmitted from the sun roller 23 to the outer ring 24 via the double cone 26, and further transmitted to the outer ring 24. From the low-speed support cam 29 to the low-speed shaft 22 via the low-speed pressure cam 31. During this time, the speed of the double cone 26 is reduced at a predetermined speed reduction ratio, that is, e = bd / ac. The reduction ratio e is the speed change shaft 32 c of the speed change mechanism 32.
, The carrier 25b, the rotation shaft 27, the carrier 25a, and the double cone 26 are moved in the axial direction of the high-speed shaft 21 and the low-speed shaft 22 via the pinion gear 32b and the rack 32a, so that the sun roller 23 and the outer roller It is appropriately changed by changing the contact position of the ring 24 with the double cone 26.

In the high-pressure side pressing cam 30 and the low-speed side pressing cam 31, the load state shown in FIG. 4B is changed from the unloaded state shown in FIG. 4A to the sun roller 23 and the outer ring. An axial force Fa corresponding to the load torque acts on 24, the axial gap increases from L ₁ to L ₂ , and a contact portion between the sun roller 23 and the double cone 26 and a contact portion between the outer ring 24 and the double cone 26. Sufficient normal force can be applied.

While the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, but can be variously modified. For example, as shown in FIG. 2 or FIG. Alternatively, the pressing cam may be provided only on one of the high-speed shaft 21 side and the low-speed shaft 22 side. Further, the pressing cam may be a face cam as shown in FIGS.

[0034]

According to the present invention, the axial pressing force at the contact portion between the double cone of the cone type CVT and the sun roller and the outer ring can be controlled in accordance with the load torque. By forming the cam surface of the pressurizing cam by cold forging, which is a pressurizing method that can improve performance, transmission efficiency, and life, cutting and grinding, which is indispensable for hot forging, can be omitted. The required time can be reduced. In addition, according to the forming of the pressure cam by cold forging, not only is there no abnormal metal structure or oxide film formed after hot forging, but also the surface finish (surface roughness)
Is also good. Furthermore, compared to a pressure cam formed by cutting such as shaving, the required processing time can be reduced,
Product yield is improved.

By forming one of the opposed cam surfaces of the pressure cam integrally with the sun roller or the outer ring, the number of parts can be reduced.

Further, the power transmission surface serving as a contact portion of the sun roller or the outer ring with the double cone, which is cold forged integrally with the pressure cam, is a finished work surface to further transmit the rotational torque. It can be performed smoothly.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view showing a first embodiment of a friction type continuously variable transmission according to the present invention, in which an upper half shows a state at a maximum speed ratio and a lower half shows a state at a minimum speed ratio. Is shown.

FIG. 2 is a longitudinal sectional side view showing a friction type continuously variable transmission according to a second embodiment of the present invention, in which an upper half shows a state at a maximum speed ratio and a lower half shows a state at a minimum speed ratio. Is shown.

FIG. 3 is a vertical sectional side view showing a third embodiment of the friction type continuously variable transmission according to the present invention, in which an upper half shows a state at a maximum speed ratio, and a lower half shows a state at a minimum speed ratio. Is shown.

FIG. 4 is an enlarged explanatory view of a main part showing a state where a pressure cam is not loaded and a state where a pressure cam is loaded.

FIGS. 5A and 5B are schematic perspective views of two types of face cams.

FIG. 6A is an explanatory view of a hot forging step of a pressure cam,
(B) is an explanatory view of a cold forging step of the pressure cam.

FIG. 7 is a longitudinal sectional side view showing an example of a conventional friction type continuously variable transmission.

FIG. 8 is an operation explanatory view of a main part of the friction type continuously variable transmission.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 High-speed shaft 22 Low-speed shaft 23 Sun roller 24 Outer ring 25a, 25b Carrier 26 Double cone 27 Self-rotating shaft 28 High-speed side support cam 29 Low-speed side support cam 30 High-speed side press cam 31 Low-speed side press cam 32 Transmission mechanism 33 Casing

Continuation of the front page F term (reference) 3J051 AA03 BA05 BB04 BC03 BD02 BE05 CB05 DA01 EA06 EB02 EB04 ED01 FA01 FA07

Claims (3)

[Claims] A high-speed shaft and a low-speed shaft rotatably arranged on a coaxial center in a casing; a sun roller connected to the high-speed shaft and having an outer peripheral surface as a rolling surface; and a sun roller connected to the low-speed shaft. An outer ring having a circumferential surface as a rolling surface, a carrier disposed coaxially with the sun roller and the outer ring, and capable of moving in the axial direction on the axis by a transmission mechanism, and a circumferential direction of the carrier. A plurality of double cones which are rotatably held at equal intervals via respective rotation shafts and which are pressed against the rolling surface of the sun roller and the rolling surface of the outer ring to transmit rotational torque, and And the low-speed shaft is used as an input shaft and the other is used as an output shaft, and the carrier whose rotation around the input / output shaft is restricted by the transmission mechanism is moved in the axial direction of the input / output shaft, thereby forming a pair with the double cone. In the friction type continuously variable transmission in which the rotation speed of the output shaft with respect to the rotation speed of the input shaft is changed steplessly by displacing the contact portion between the sun roller and the outer ring, the pressure contact force to the double cone is output from the input shaft. It is applied by changing according to the transmission torque transmitted to the shaft,
And, a pressing cam formed with a cam surface for transmitting the rotational torque facing in the axial direction of the input / output shaft, at least between the sun roller and the high-speed shaft or between the outer ring and the low-speed shaft. A friction type continuously variable transmission, wherein the frictional stepless transmission is interposed in any one of the pressure cams and the cam surface of the pressure cam is formed by a cold forging surface. 2. The friction type continuously variable transmission according to claim 1, wherein one of the opposing cam surfaces of the pressure cam is formed integrally with the sun roller or the outer ring. 3. The friction-type continuously variable transmission according to claim 2, wherein the power transmission surface of the sun roller or the outer ring, which is a contact portion with the double cone, is a finishing surface.