JPH07113385B2 - One way clutch - Google Patents

Description

TECHNICAL FIELD The present invention relates to a one-way clutch using a sprag.

[Prior Art] One-way clutches that use sprags for one-way rotation transmission are widely used. There are two types of sprags, disengagement type (Fig. 1) and engagement type (Fig. 2). There are two types, and each is determined by the behavior of the sprag when the outer ring rotates.

In the former disengagement type sprag, when the center of gravity G of the sprag 1 is on the left side of the normal line at the contact point A of the outer ring 2 in FIG.
The sprag 1 separates from the raceway surface of the inner ring 4 by rotating clockwise around the contact point A against the spring force F of the inner ring 4.

As described above, the disengagement type sprag 1 has an advantage that the wear of the sprag 1 when the outer ring 2 idles at high speed can be reduced.

Further, in the engagement type sprag 11, the center of gravity G of the sprag 11 is a contact point A with the outer ring 2 of the sprag 11 in FIG.
When it is on the right side of the normal line in, the centrifugal force C acts and a force to rotate the sprag 11 counterclockwise around the contact A is generated, and when the sprag 11 rotates counterclockwise, the sprag height increases. As the inner ring 4 and sprag 11
Come into contact with.

Therefore, the engagement type sprag 11 is used when the one-way clutch needs to be engaged while the outer ring 2 is rotating at high speed.

For this reason, the engagement type sprag 11 is always in contact with the inner ring raceway surface by the ribbon spring 3 in a slipping state, and therefore, depending on conditions such as lubrication conditions, surface roughness of the inner ring raceway surface and the sprag cam surface, There is a problem that the inner ring raceway surface 4 and the cam surface of the sprag 11 are worn and peeled and the life is short.

It is well known that the surface roughness of the cam surface and the inner ring raceway surface of the sprag 11 is an important factor, and conventionally, the finish of the cam surface and the inner ring raceway surface of the sprag is as smooth as possible. It was thought that it would be better to make it the surface, but normally the finished surface of the cam surface is tumbler finish and Rmax.
A contact surface of 2 to 4 μm cannot be said to be good.

Therefore, in the engagement type sprag 11, it is strongly desired to develop means for preventing wear and damage on the cam surface and the inner ring raceway surface and improving durability.

[Object of the Invention]

The present invention has been made to solve the above problems, and the contact portion between the cam surface of the sprag and the inner ring raceway surface is in a considerably strict boundary lubrication region and is locally in a metal contact state. A long-life one-way clutch that is used under conditions where surface damage is likely to occur, gives the sprag's cam surface a good surface condition for the formation of an oil film on the contact surface, and is compatible with both the surface roughness of the mating inner ring raceway. The purpose is to provide.

[Means for Solving the Problems]

In order to solve the above problems, the present invention provides a one-way clutch using a sprag, in which a large number of independent minute concave recesses are randomly formed on the outer surface of the sprag, and the surface roughness of the sprag outer surface is formed. When the width is measured in the circumferential direction in the width direction and displayed as a parameter RMS, the ratio RMS (L) / RMS (C) of the surface roughness RMS (L) in the width direction and the surface roughness RMS (C) in the circumferential direction is obtained. ) Is an average value of 1.0 or less, and the surface roughness parameter SK value is also an average value of -1.6 or less in both the width direction and the circumferential direction.

[Action]

The outer surface of the sprag contacting the inner ring raceway surface is formed into a random minute rough surface, and the finished surface roughness parameter RMS of this minute rough surface is obtained in the width direction (L) and the circumferential direction (C), and the ratio RMS
(L) / RMS (C) is 1.0 or less, and parameter S
Since the K value was set to -1.6 or less in both the width direction and the circumferential direction, the oil film formation rate on the sprag cam surface was improved, a sufficient oil film thickness was secured to suppress metal contact at the contact part, and the surface roughness of the mating inner ring raceway surface was improved. Regardless of the age, peeling damage or wear does not occur on the cam surface of the sprag, and the long life of the one-way clutch can be obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 2 to 7 of the accompanying drawings.

As shown in FIG. 2, in the one-way clutch using the sprag 11, the cam surface of the sprag 11 is formed on the minute rough surface 11a in a random direction, and this minute rough surface 11a shows the surface roughness of the cam surface. When the width direction and the circumferential direction are obtained and displayed as parameters RMS, the average value of the ratio RMS (L) / RMS (C) of the width direction surface roughness RMS (L) and the circumferential direction surface roughness RMS (C) 1.
The value of the surface roughness parameter SK is not more than 0, and the average value is not more than -1.6 in both the axial direction and the circumferential direction.

In the surface processing for obtaining the rough surface condition of the cam surface as described above, a desired finished surface can be obtained by special barrel polishing.

Here, the parameter RMS is the curve f (x) from the center line.
Is the square root value obtained by integrating the squares of the deviations up to the measurement length 1 section and averaging in that section, which is also known as root mean square roughness. The RMS can be obtained by numerical calculation from the cross-sectional curve and the roughness curve that have been recorded enlarged.

Width direction surface roughness RMS (L) → Roughness measured by moving the stylus of the roughness gauge in the roller width direction Circumferential surface roughness RMS (C) → Move the stylus in the circumferential direction as above Roughness measured RMS (L) / RMS (C) means the shape and directionality of the depression, and when the depression is oriented in the width direction, the value of RMS is such that the roughness in the width direction becomes smaller, The roughness in the circumferential direction, which is measured transversely to the depression, is large. Therefore, when RMS (L) / RMS (C) has an average value of 1.0 or less as in the present invention,
The depressions tend to be oriented in the width direction on average.

Regarding the surface shape and oil film formation in sliding contact, it is known that the processing in which grinds remain in the width direction is superior to ordinary cylindrical grinding, and the recess of the present invention having the major axis in the width direction, The oil film forming ability is excellent.

The parameter SK value refers to the degree of distortion (SKEWNESS) of the distribution curve of the surface roughness, and is a statistic that is a standard for knowing the asymmetry of the uneven distribution. For a symmetrical distribution such as Gaussian distribution, SK
The value is close to 0, negative when the convex and concave parts are removed,
In the opposite case, it takes a positive value.

The SK value can be controlled by selecting the rotational speed of the centrifugal barrel polishing machine, the processing time, the work input amount, the type and size (grain size) of the polishing agent, and the type and size of the chip described above. The value is an average value −1 in both the width direction and the circumferential direction.
The reason for setting it to 6 or less is that there are few dents that become oil reservoirs, there is little oil leakage in the sliding direction and the perpendicular direction even when compressed, it is excellent in oil film molding, regardless of whether the finish surface roughness of the mating surface is good or not. The oil film formation is good, the metal contact rate is small, and it has the effect of minimizing surface damage.

By reducing the metal contact ratio of the contact portion, surface damage of the sprag cam surface, peeling, abnormal wear from the peeling, and peeling can be prevented, and damage during idling can be prevented to improve durability.

The effect of forming an oil film on the outer surface of the sprag according to the present invention is clear even in comparison with a normal tumbler plug described below.

RM on the outer surface of conventional sprags and inventive sprags
The result of the distribution measurement data of the SK value of S is shown in FIG. 3, and FIG. 4 shows the result of the measurement of the finish roughness of the outer surface of the sprag of the present invention.

Next, the result of the life test using the conventional sprag and the sprag of the present invention will be described.

The contents of the outer diameter surface of the sprag used in the test are shown in Table 1, the test results are shown in Table 2, and FIG. 5 shows the roughness of the mating inner ring raceway surface.

The test results are shown in Table 1, and in the case where the finished surface roughness of the outer surface of the sprag is in the range of Rmax1 to 4 μm, the conventional sprag is peeled and wear is advanced in 100 hours.

On the other hand, the sprag of the present invention has no abnormality for 600 hours against the inner ring raceway surface having Rmax of 2 to 4 μm, has extremely excellent durability, and proves that the oil film is sufficiently formed. It should be noted that there is no difference between the inner ring raceway surfaces in which both of them are in a familiar state in which the projections of the surface roughness are slightly removed.

The oil film formation rate by this test is as shown in FIG. 6 and FIG. 7, and the oil film formation rate of the finished surface of the test sprag of the present invention is about 20% at the start of operation as compared with the conventional test sprag. The formation rate is improved.

In addition, the number of idling 6.3 × 10 ⁵ (7000 rpm × 1.5 _H = 7000 × 90 =
It was confirmed that an oil film was formed almost completely at 6.3 × 10 ⁵ ).

Although data is omitted here, it is also effective in reducing wear and preventing an increase in the sliding friction coefficient at the sliding contact point between the sprag outer surface and the inner ring raceway surface.

Even in the disengagement type sprag 1, when the lubrication condition is poor and the idling is performed at a low speed, the sprag 1 is not separated from the raceway surface of the inner ring 4 and is therefore easily damaged by the surface. By subjecting the surface of the present invention to the surface treatment, the same effect as that of the engagement type sprag can be exhibited.

〔effect〕

As described above, according to the present invention, on the outer surface of the sprag,
Since independent minute dents are formed randomly, the minute dents supply oil to the contact area as an oil reservoir, and are excellent in forming an oil film.The oil film formation status is good regardless of the roughness of the finished surface of the inner ring raceway of the partner. Good, low metal contact rate and effective in minimizing surface damage. Therefore, the durability of the one-way clutch using the sprag can be significantly improved.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a one-way clutch using a disengagement type sprag, FIG. 2 is a longitudinal sectional view of a one-way clutch using an engagement type sprag, and FIG.
FIG. 4 is a graph showing distribution measurement data of RMS and SK values, FIG. 4 is a schematic view showing a finished surface condition of a sprag in the one-way clutch of the present invention, and FIG. 5 is an explanatory view showing roughness of a mating inner ring raceway surface, 6 and 7 are graphs showing the oil film formation rate. 1, 11 ...... Sprag, 2 ... Outer ring, 3 ... Ribbon spring, 4 ... Inner ring, 11a ... Slightly rough surface.

Claims (1)

[Claims] 1. A one-way clutch using a sprag, in which innumerable minute recessed dents are formed independently on the outer surface of the sprag at random, and the surface roughness of the sprag outer surface is measured in the width direction and the circumferential direction. Parameters for each
When displayed in RMS, the ratio RMS (L) / RMS (C) of the surface roughness RMS (L) in the width direction to the surface roughness RMS (C) in the circumferential direction is an average value of 1.0.
The one-way clutch is characterized in that the surface roughness parameter SK value is equal to or less than the average value −1.6 both in the width direction and the circumferential direction.