KR20020012606A - Ivt component - Google Patents

Abstract

Infinitely variable transmission components include input disks and output disks. Each disc is provided with travel path (s) of the input disc and the output disc opposite each other. The roller has a surface that engages the travel path and the position of the power roller relative to the disk can be varied to change the transmission ratio between the disks. One or more discs or power rollers can be made from PM M62 type steel.

Description

Infinitely Variable Transmission Parts {IVT COMPONENT}

Such transmission parts are known from EP-0462637A. In this application, a continuously variable transmission CVT is disclosed in which a belt is wound between two pulleys having a variable effective diameter. At least one contact surface of the pulley in contact with the belt is covered with a layer realized through powder metallurgy techniques. This layer starts from the base pulley and is formed during the later stages of the manufacturing process. The operating state of the continuously variable transmission indicates that the contact pressure between the belt and the pulley is relatively low. This operation is generally dry, ie without lubricant.

The present invention relates to an infinitely variable transmission (IVT) component. Hereinafter, the infinitely variable transmission is a toroidal type infinitely variable transmission, and more specifically, it should be understood as an infinitely variable transmission disk or roller. The contact surface of each disk and roller is subjected to a large contact load in the presence of lubricant. For roller bearings, the contact pressure is very high between the circumferential surface of the power roller and the raceway of the disk. In the absence of a lubricating film, static load requirements as well as high contact fatigue strength requirements are established.

It has been found that typical rolling bearing steels do not meet these requirements.

The present invention relates to a transmission component made of high alloy steel of the powder metallurgical type.

1 shows an example of an infinitely variable transmission.

2 shows a comparative graph of contact stress.

3 shows a comparison graph of blunt notch toughness.

It is an object of the present invention to provide a component having excellent properties which makes it particularly suitable for infinitely variable transmissions and power roller components.

According to the present invention, this object is realized because the transmission component comprises a disk or roller of an infinitely variable transmission of the toroidal type, which is integrally molded through powder metallurgy technology.

It should be understood that integrally molded consists entirely of powder metallurgy materials. This is in contrast to that of EP-0462637, in which only a layer of powder metallurgy material is provided. By only integrally manufacturing the disk and more preferably the infinitely variable transmission component such as the power roller, it is possible to realize a sufficient useful life in the state of high contact fatigue load.

As mentioned above, the present invention is particularly used for producing power rollers of infinitely variable transmissions.

A more specific composition of the steel used for the infinitely variable transmission parts is as follows.

C: 0.75-1.85 weight%

Si: 0.10-0.45 weight%

Mn: 0.15-0.50 weight%

Cr: 3.50-4.50 wt%

Mo: 4.00-11.00 weight%

V: 0.90-5.25 weight%

W: 0.10-13.00 weight%

According to a preferred embodiment of the present invention, PM M62 type steel with the following composition is used.

C: 1.25-1.35 weight%

Si: 0.15-0.4 wt%

Mn: 0.15-0.40 weight%

Cr: 3.50-4.25 weight%

Mo: 10.00-11.00 weight%

V: 1.80-2.20 wt%

W: 5.75-6.75 weight%

Although the cost of manufacturing these types of steels is considerably higher than that of conventional rolling bearing steels such as ASTM A295, their properties make them more suitable for CVT / IVT disc and power roller parts than conventional rolling bearing steels. With proper treatment, very high surface hardness of PM M62 steel products can be realized. However, unlike typical steels made to have very high hardness, the toughness of the core material of PM M62 does not decrease. This means that the toughness / hardness ratio is significantly higher than conventional martensitic hardened ASTM A295 52100 rolling bearing steel.

Powder metallurgical steel can be produced by any method known in the art. In one example, the following steps are made.

Vacuum induction melting and refining step for powder metallurgical steel composition,

Atomization step of nitrogen gas powder,

Grading and canning steps of the powder,

Hot constant pressure compression stage,

Hot forging step.

Other economical plastic molding techniques are also included.

Preferably, the powder metallurgy high alloy steel should be subjected to a secondary hardening treatment. Preferably, this is achieved by austenitizing at 1205 ± 5 ° C for 5 to 10 minutes, followed by quenching and tempering of gas, oil, or brine at about 550 ° C. In the above-mentioned preferred embodiment in which M62 steel is used, the hardness is as high as 67 HRC which exhibits high temperature properties.

The invention will be described in detail with reference to the accompanying drawings.

1 shows an example of CVT / IVT. The most common embodiments of CVT / IVT include an input disk 1 connected to an engine output shaft and an opposing output disk 2 connected to a drive chain or additional gearbox part of an automobile or other article, such as an automobile or the like. It should be driven by variable transmission ratio. There are a number of power rollers 3 between these disks. This power roller 3 can be journaled to any shaft, the axis of which is indicated by reference numeral 4 . This shaft can rotate in the direction of the arrow 5. Through the rotation of the other rollers in the direction of the arrow 5, the transmission ratio between the input disk and the output disk changes. As shown in Fig. 1, the power roller 3 is engaged with the input disk near the center line, while the output disk is engaged away from this center line. It is pressure that causes the circumferential surface of the power roller to be tightened to the travel path 8 of the input disk and the travel path 9 of the output disk, respectively. This tightening force is schematically indicated by the arrow 10. The CVT / IVT shown in FIG. 1 is also known as 'Torotrak Infinitely Variable Transmission (Torotrak IVT)'. Other means are also used in the art, but in all embodiments, it is essential that at least three power rollers be installed to vary the transmission ratio between the input disk and the output disk by tilting slightly according to the arrow 5. It has been found that this structure can provide 15% increased efficiency over conventional automatic transmissions. Unlike rolling bearings, there is no lubrication between adjacent parts of this structure.

The circumferential surface of each power roller as well as the travel paths 8 and 9 are subjected to significant loads. Perhaps this is one of the reasons why this technique is not generally accepted so far. For example, the maximum contact stress between the circumferential surface of the power roller and its associated travel path is so high as to be 4 GPa. This is much higher than the contact pressure found in ordinary rolling bearings. In addition, tilting in accordance with the arrow 5 results in the sliding of the roller relative to the disk. Such slippage is absent in rolling bearings. Reportedly, repeated cracking stresses result in fatigue cracking and fracture. The disk area in the circle 11 is particularly susceptible to damage. This means that the combined rolling contact fatigue strength and fatigue failure strength of the friction surface (traveling path) should be improved. Below, a very brief load summary of some parts of the CVT / IVT is given.

Infinity variable transmission parts Characteristic Breaking mode Output Disc-Spine Connection Torsional Load of Spline Radius Structural fatigue crack Input disk that abuts the power roller via a sliding friction fluid Up to 3.5 GPa contact pressure * Rolling contact fatigue failure * Surface fatigue * Structural load to promote contact fatigue Power roller Up to 3.5 GPa contact pressure * Rolling contact fatigue fracture * Surface fatigue Effective tightening force across disc and power roller by hydraulic piston Bending structural stress * Structural fatigue cracking Drive disk via chain sprocket Bending force of output drive Bending fatigue crack Disc and power roller High temperature (up to 120 ° C) and structural stress Growth and axial clearance increase Disc and power roller Vibration load Accelerated Structural Fatigue Cracks

2 shows the rolling contact fatigue life at different contact stresses. Conventional rolling bearing steel ASTM A295 521009 (dashed line) is compared with steel according to PM M62 (solid line) according to the invention. Cycle recovery L50 is one million stress cycles.

3 shows the hardness for blunt notch toughness. Advantage dashed line shows 52100 steel, and ■ PM M62. It is clear from this figure that despite the very high hardness of the PM M62 steel (67 HRC), the blunt notch toughness is on par with the standard martensite 52100 rolling bearing steel.

Powder metallurgical steel, more specifically M62 composition, can be used to reduce the size of the disk and power roller of CVT / IVT at the same torque output.

Although the invention has been described above in connection with M62 steel as a preferred embodiment, other metallurgical high alloy steels can be used in CVT / IVT and are within the protection scope of the invention.

Claims (5)

10. A transmission component comprising a powder metallurgical type high alloy steel, the component comprising a disk or roller of a toroidal type infinitely variable transmission integrally molded through powder metallurgy technology. The method of claim 1, wherein the steel is C: 0.75-1.85 weight% Si: 0.10-0.45 weight% Mn: 0.15-0.50 weight% Cr: 3.50-4.50 wt% Mo: 4.00-11.00 weight% V: 0.90-5.25 weight% W: 0.10-13.00 weight% Transmission part that includes a. The transmission component according to claim 1 or 2, comprising M62 type steel. The transmission component according to any one of the preceding claims, comprising a disk. The transmission component according to any one of the preceding claims, comprising a power roller.