JPS60238234A - Manufacturing method of pulley for belt driving type stepless transmission - Google Patents

Abstract

PURPOSE:To give compressive residual stress to a sliding surface of a pulley and thereby aim at a distinct improvement in its service life, by machining a surface- hardenable steel material into a pulley form, hardening it through heat treatment, grinding it, and shot-peening it with fine steel balls being above the specified hardness each. CONSTITUTION:CrMo alloyed steel equivalent to SCM2 is machined into a pulley form at the input or output side for a belt driving type stepless transmission, then, this rough section is hardened and annealed, besides heat treatment, and ground up into a final form as a pulley. And, using cast steel balls of Hv 600- 800 in hardness by way of example, shot-peening treatment takes place under the treatment condition of 0.3-0.35mm. in arc height and more than 95% in coverage. Thus, in each sliding surface of both pulleys 1 and 2, a hardness drop of up to about 0.1mm. in depth from a surface to be produced by grinding and a drop in compressive residual stress are harder than the hardness by hardening, annealing and heat treatment owing to shot-peening treatment using cast steel balls and, what is more, the compressive residual stress also can be made higher than the state of hardening, annealing and heat treatment.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for manufacturing a pulley for a belt-driven continuously variable transmission. Machining and hardening heat treatment to make pulleys into pulley shapes from steel parts.

A pulley for a belt-driven continuously variable transmission that is manufactured using a process consisting of grinding and shot peening on the sliding surface of the pulley, which imparts compressive residual stress to the sliding surface of the pulley and extends its service life. It depends on the manufacturing method.

[Prior art]

Continuously variable transmissions can continuously control the gear ratio of the transmission, making full use of the characteristics of the engine and improving exhaust gas and fuel efficiency.

In general, continuously variable transmissions are classified into fluid type, mechanical type, electric type, etc., but fluid type and mechanical type are mostly used for vehicles, and among them, hydraulic drive.

Heald drive, fluid torque converter is the main one.

As shown in FIGS. 1 and 2, the transmission section of the belt-driven continuously variable transmission consists of an input pulley 1 and an output pulley 1, which can vary the diameter of the belt 3 by means of a hydraulic mechanism (not shown). It consists of a pulley 2 on the side and a belt 3 that transmits the power of the pulley 1 on the input side to the pulley 2 on the output side.

Furthermore, the heald 3 is connected to the input side pulley 1. A hoop 5 formed by layering a plurality of endless metal bands hung like a belt between the output side pulleys 2, and the input side pulley 1. It has a hoop groove opened opposite to the sliding surface of the output side boo U2, and is capable of sliding in the width direction of the hoop 5 through this hoop groove, and has a large number of continuously arranged hoop grooves. Block 4 and its hoop groove 5~
A hoop 5 made of 15 endless metal strips stacked in a layered manner is fitted into the hoop 5.

Boo I of block 4 used for belt 3
A surface unevenness is formed on the end face 4a of the block that comes into sliding contact with the block IJI, 2 in order to adjust the relative coefficient of friction between the block 4 and the sliding surface of the block IJI, 2.

Now, in the belt-driven continuously variable transmission, the block 4 used in the heald 3 is pressed against the pulley 1 on the input side and transmits torque to the pulley 2 on the output side. If the coefficient of friction relative to the sliding surface is low, there is a problem in that the belt 3 slips.

The slivers of the belt 3 not only reduce transmission efficiency, but also cause damage to the heald 3 and pulley 1.2, such as scuffing.

On the other hand, if the relative coefficient of friction between the block end face 4a and the sliding surfaces of the pulleys 1 and 2 is too high, not only will smooth gear changes not be possible and the vehicle will vibrate or make abnormal noises. There is a problem that the service life of the belt 3 and pulley 1.2 is reduced.

By the way, the pulley 1.2, which is the transmission part of the belt-driven continuously variable transmission, is usually made of a steel member that has been quench-hardened by heat treatment.

Then, as described above, the block end face 4a and the pulley 1.2
It is necessary to ensure a reliable torque transmission function by setting the relative friction coefficient with the sliding surface of the block within an appropriate range.As a countermeasure for this, conventionally, the block end face 4a is shot blasted. , the block end face 4a is formed into a surface roughness with a surface roughness of 10 to 40μ as shown in FIG. Attempts have been made to adjust the relative coefficient of friction (for example, Japanese Patent Application No. 58-23419).

However, when the block end face 4a is subjected to shot blasting treatment as described above, the block end face 4a
It has been confirmed that damage accompanied by surface fatigue occurs in pulley 1.a and pulley 1.2, causing rapid wear.

The reason for this is that when the block end face 4a is still shot blasted, the surface unevenness of the block end face 4a has a sharp shape as shown in Fig. 3. This is thought to be due to the occurrence of

As a countermeasure for this, it has been revealed that the most effective method is to provide a smooth portion at the tip of the uneven surface of the block end face 4a to reduce the contact stress. As a method for manufacturing a transmission block, a method for stably forming such a smooth portion on the end face 4a of the block has already been proposed as another invention.

Conventionally, the pulley 1.2 is made of alloy steel, which is quenched and hardened by heat treatment.

However, the pulley l is in sliding contact with the block end face 4a.

The sliding surface of pulley 1.2 is usually finished by grinding in order to ensure accuracy, and when it is finished by grinding in the final manufacturing process of pulley 1.2, the front surface near the surface of pulley 1.2 is The problem is that the compressive residual stress imparted to the surfaces of the pulleys 1 and 2 due to heat treatment during the process is eliminated by the grinding finish, which reduces the crank resistance (pisoching resistance) on the sliding surfaces of the pulleys 1 and 2. was there.

That is, as shown in FIG. 4, the ground pulleys 1 and 2 are
On the sliding surface of It is understood that the situation is decreasing.

[Purpose of the invention]

The present invention was made in order to solve the problems of the prior art as described above, and the manufacturing process of a pulley for a belt-driven continuously variable transmission includes machining of a steel member into a pulley shape.
The belt-driven type is manufactured using a process consisting of hardening heat treatment, grinding, and shot peening treatment on the sliding surface of the pulley, which increases the service life by applying compressive residual stress to the sliding surface of the pulley. The object of the present invention is to provide a method for manufacturing a pulley for a continuously variable transmission.

[Structure of the invention]

According to the present invention, such a purpose is achieved by moving the input pulley from the input pulley to the output pulley in a belt-driven continuously variable transmission.
The pulleys on the input and output sides slide on the end faces of a large number of blocks arranged in series so that they can slide on a hoop formed by stacking a plurality of endless metal strips suspended like a belt. A method for manufacturing a pulley for a belt-driven continuously variable transmission that transmits torque by being pressed against a surface, the pulley being used on the input or output side of a heald-driven continuously variable transmission using a surface-hardened steel member. A step of machining the pulley into the shape; a hardening heat treatment step of hardening the surface portion of the pulley; a step of grinding the pulley;
This is achieved by a method for manufacturing a pulley for a belt-driven continuously variable transmission, which is characterized by comprising the step of shot peening using 0 or more hard steel balls.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings.

In this example, the material is JIS standard SCM2.
A comparable material (CrMo alloy steel) is machined into the shape of an input or output pulley for a belt-driven continuously variable transmission, and then the rough shape material machined into this pulley shape is quenched and quenched. After heat treatment, it was ground to the final shape of the pulley.

Then, using a cast steel ball with hardness Hv600-800, arc height: 0.3-0.35m, coverage: 9
Shot peening treatment was performed under treatment conditions of 5% or more.

FIG. 4 shows the hardness distribution and residual stress distribution from the surface on the sliding surface of the pulley manufactured in this manner.

As is clear from Fig. 4, the conventional boot I with a grinding finish
In the sliding surface of JI, 2, the hardness decreased from the surface to a depth of around 0°1fi, and the residual stress of -40 kg/mm' (compressive) that had been formed by the quenching and tempering heat treatment decreased the hardness. In contrast, the pulley 1 for a belt-driven continuously variable transmission manufactured by the method of the present invention
, 2, the reduction in hardness and compressive residual stress to a depth of 0.1fi from the surface caused by the grinding process can be reduced by quenching and tempering by shot peening treatment using steel balls on the cast steel part. It is harder than that obtained by heat treatment, and the compressive residual stress can also be made higher than in the quenched and tempered heat treated state.

In particular, it is understood that the pulley for a belt-driven continuously variable transmission manufactured by the method of the present invention has the highest hardness and compressive residual stress at a depth of about 0.05 m below the surface.

The pulley for a belt-driven continuously variable transmission of the present invention manufactured as described above and the pulley for a belt-driven continuously variable transmission manufactured by the conventional method as a comparative product were used for a belt-driven continuously variable transmission. Assembly, rotation speed i 3500 rpm
, input torque; 16 Kg-m.

Gear ratio; 2. A 150 hour durability test was conducted under the following conditions.

The test results are shown in FIG.

As is clear from the test results, pulleys for belt-driven continuously variable transmissions manufactured by the conventional method have significant wear associated with fatigue, whereas pulleys for belt-driven continuously variable transmissions manufactured by the method of the present invention In the pulley, not only was the amount of wear reduced to 1/3 to 1/7 compared to conventional pulleys, but no progressive damage such as cracks or scuffing was observed on the pulley surface.

This effect is due to the fact that the maximum Hertzian stress occurs at a depth of about 0.01 to 0.02 m below the surface when the uneven surface shape of the block end comes into sliding contact with the sliding surface of the pulley. It seems that durability was improved by increasing hardness and compressive residual stress.

The location where this maximum Hertzian stress occurs is 0.01 to 0.0 mm below the surface.
02 m is also estimated from the fact that the crank generated in a conventional pulley matches that depth.

[Function and effect of the invention]

As is clear from the above, according to the method for manufacturing a pulley for a belt-driven continuously variable transmission according to the present invention, the manufacturing process of the pulley for a belt-driven continuously variable transmission can be changed from a steel member to a pulley shape. By manufacturing through a process consisting of mechanical processing, hardening heat treatment, grinding, and shoulder/nod peening treatment on the sliding surface of the pulley, compressive residual stress is applied to the sliding surface of the pulley, thereby extending the service life. There is an advantage that it can be done.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of a transmission section of a belt-driven continuously variable transmission. FIG. 2 is a perspective view showing how the hoop and block are assembled. FIG. 3 is a diagram showing the surface unevenness of the end face of the block. FIG. 4 is a diagram showing the hardness and residual stress distribution of pulleys manufactured by the method of the present invention and the conventional method. FIG. 5 is a diagram showing the durability test results of pulleys for belt-driven continuously variable transmissions manufactured by the method of the present invention and the conventional method. 1-・-111 Pulley at the input end. 2---One output side pulley. 3-------belt. 4・------Block. 4a--Block end face. 5------- Hoop. Figure 8; ``rrrn'' clothing mm (a) (b)

Claims (1)

[Claims] 1. A hoop formed by stacking a plurality of endless metal bands hung like a belt from an input pulley to an output pulley in a belt-driven continuously variable transmission. A method for manufacturing a pulley for a belt-driven continuously variable transmission, in which the block end faces of a large number of blocks arranged in series so as to be slidable are pressed against the sliding surfaces of input and output side bobbles to transmit torque. a step of machining a surface-hardenable steel member into the shape of the input or output side pulley for a belt-driven continuously variable transmission; and a hardening heat treatment step of hardening at least a surface portion of the pulley. and a step of grinding and finishing the pulley, and grinding the sliding surface of the pulley that the block end surface comes into sliding contact with to Hv70.
A method for manufacturing a pulley for a belt-driven continuously variable transmission, the method comprising the step of subjecting the method to shot peening using hard steel balls of 0 or more.