JPS60260738A - Planetary gear - Google Patents

Abstract

PURPOSE:To increase the efficiency of power transmiting operation in a planetary gear constructed such that disks and rings both having the equal diameter to a pitch circle are arranged at both sides of a gear by forming a planetary gear with swelling boss parts at both sides thereof and having the planetary disk supported by the swelling boss parts. CONSTITUTION:A planetary gear mechanism consists of a central sun gear 1, a plurality of planetary gears 2 which surround said sun gear, an externally mounted internal gear 3 placed in the most external position, and a carrier 4 which axially supports the planetary gears 2. In the above planetary gear mechanism, each of the planetary gears 2 consists of both a planetary gear 6 having swelling boss parts 20 at both sides thereof, and planetary disks 7 and 7 which are disposed at both sides of said gear 6, has the same external diameter as that of a pitch circle and has a circumferential projection 23 having the same width as that of said boss parts 20. The internal gear 3 consists of an externally disposed gear 8 and externally-disposed rings 9 which are disposed at both sides thereof and has the same internal diameter as that of the pitch circle. The carrier 4 consists of a pair of carrier pieces 10 and 11 so as to have the planetary gears 2 supported from both sides thereof by a planetary gear shaft 5.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a planetary gear device having a structure in which a disk and a ring equal to a pitch circle are attached to both sides of a gear.

A planetary gear device in which a disk or ring having the same diameter as the pitch circle is provided on both sides of the planetary gear and the outer shell internal gear is already known (Japanese Patent Publication No. 17111/1983).

FIG. 6 shows a sectional view of such a planetary gear device. This includes a sun gear 31, a planetary gear 32, and an outer shell internal gear 33.
, a carrier 34 that pivotally supports a planetary gear.

The planetary gear 32 includes a flexible ring-shaped planetary gear 36 and planetary discs 37 located on both sides of the ring-shaped planetary gear 36 and supporting the planetary gear 36. The outer shell internal gear 33 consists of a central outer shell gear 38 and outer shell rings 39 provided on both sides thereof.

The planetary disk 37 and the outer shell ring roll along the pitch circle (2). The force in the radial direction, such as the centrifugal direction, is the planetary disk 37
is directly transmitted by the outer shell ring 39 and the carrier 34
Eccentric movements of can be prevented. Torque is planetary gear 36
, is transmitted by the outer shell gear 38. Since the radial direction is not affected by the meshing of the gears, the accuracy of the gears,
The carrier division accuracy is not strict. In this way, the requirement for strict consistency of meshing conditions, which is an inherent difficulty of planetary gear devices, can be alleviated.

However, the planetary gear 36 does not come into contact with the planetary shaft 35, but is supported by a boss portion 40 that bulges inwardly of the planetary disk 37. This is because the gear is not constrained and the tips of the teeth are easily bent, making it easier to achieve alignment conditions.

The inventor has realized that such a planetary gear arrangement, in which the planetary gears are indirectly supported, still has drawbacks. Although such a device is supposed to generate less heat and mesh smoothly, when used for a long time, the back surface of the planetary gear, that is, the part that contacts the inwardly bulging boss portion 40 of the disk 37, wears out considerably. That's a thing. What's more, it sometimes generated considerable heat while driving.

The present inventor considered the cause of wear at the contact portion between the planetary gear and the disk.

Ideally, the planetary discs 37 have a size equal to the pitch circle, the outer shell ring 39 has an inner diameter equal to the pitch circle of the outer shell internal gear, and all planetary discs are always attached to the outer shell ring. They should be in contact. Therefore, the planetary disc and the planetary gear rotate together as one, and no slippage occurs between them.

However, since there are dimensional errors in the ring and disc, clearance must be maintained between them in order for them to roll smoothly. The pitch circle of the planetary disk is slightly smaller than its pitch circle, and the outer shell ring is slightly larger than the pitch circle of the outer shell gear.

Further, a clearance is also provided between the planetary shaft 35 and the through hole 41 of the planetary disk 37.

Regarding the gear 36 and the disk 37 that constitute the planetary gear 32, the rotation of the gear 36 is accurate because the gears mesh. , but the rotation of the disk 37 involves uncertainty. The force that rotates the disc 3γ at the same speed as the gear is the contact friction force F1 between the disc 37 and the outer shell ring 39, and the disc 37 and the gear 36.
This is caused by the contact friction force F2 with

On the other hand, there is also a force that suppresses the rotation of the disk 37.

This is the frictional force F3 between the planetary shaft 35 and the through hole 41.

If the rotational frictional force (F10F2) is larger than the braking frictional force F3, the disc rotates at a constant speed together with the gear. F1+
If F2 is smaller than the braking frictional force F3, the disk 37 is restrained by the planetary shaft 35 and does not rotate.

It is sufficient if F 1 + F 2 > F 3 (1) is always satisfied, but since these forces are all frictional forces, they fluctuate rapidly, so this is not always the case.

Due to the clearance of the disk, outer shell ring, planetary shaft, etc., not all of the planetary disk is always in contact with the outer shell ring 39. For the disk that is separated from the outer shell ring, it becomes Fl-0. In such a case, it is easy to write F 1 + F 2 < F 3 (2).

Then, the disk 37 gets stuck on the planetary shaft and does not rotate, causing significant slippage at the contact surface between the disk and the gear, which generates heat.
This causes the contact surfaces to wear out.

Unfortunately, Fl is unrelated to the force applied to the planetary axis, but F2. F3 is the normal force f between the planetary axis and the disk
is proportional to. In other words, it is proportional to the transmitted torque. This is quite large. If the coefficient of friction between the planetary shaft and the disk through hole is μ, the frictional forces F2 and F3 can be written as p2=μIf(3) F3=μf(4). Since the frictional force F1 due to the contact between the outer shell ring and the disc is not proportional to the transmitted torque, if μ>μI, there is a high possibility that the braking frictional force F3 will be dominant. As the transmitted torque increases, the slippage between the planetary disk and the planetary gear increases, and heat generation also increases. This is because the frictional force applied to the sliding surface is proportional to the torque as shown in equation (3). The transmission torque T is related to the normal force f between the planetary shaft and the disk by T2N t R (5), where the number of planetary gears is N1 and the distance between the planetary shaft and the center of the sun gear is k.

Then, it seems that it would be better to make the connection between the disc and the gear tighter. This is because μ'>μ, the frictional force F2 between the disc and the gear becomes larger than the other two forces Fl and F3, and inequality (1) is always satisfied.

Although it is true that the disk and gear are integrated (7), there are other difficulties. This is because a strong frictional braking force is generated between the disk and the outer shell ring 38.

The disk is slightly smaller than the pitch circle of the planet gear, and the shell ring 38 is larger than the pitch circle of the shell gear.

Therefore, if the disc rolls in contact with the outer shell gear, it must rotate somewhat faster than the planetary gear. However, if the disk and gear are closely integrated, they cannot rotate independently, and this acts as a braking force for the planetary gear. This braking force reduces the power transmission efficiency of the entire planetary gear system.

Ultimately, the most desirable combination is one in which the planetary discs and planetary gears constituting the planetary gear are combined with relative slippage, but it is better to have less slippage and a smaller frictional force F2.

The present invention has been made in response to such demands.

In the present invention, instead of making the boss part of the disk bulge, the boss part of the gear is made to bulge out on both sides, and the disk is supported by this bulge part.

Hereinafter, the structure (8) of the present invention will be explained with reference to drawings showing embodiments. We will explain in detail its composition, action, and effects.

FIG. 1 is a partially cutaway front view of a planetary gear device according to an embodiment of the present invention, FIG. 2 is a partially cutaway rear view, and FIG. 3 is an XOY sectional view of FIG. 1.

The planetary gear device consists of a central sun gear 1, a plurality of planetary gears 2 surrounding the sun gear, an outermost internal gear 3, and a carrier 4 that pivotally supports the planetary gears.

The planetary gear 2 consists of a central planetary gear 6 equipped with teeth, and planetary disks 7 provided on both sides of this and having an outer diameter equal to the pitch circle of the planetary gear 6, both of which are connected to the carrier 4 by the planetary shaft 5. Rotatably supported.

The outer shell internal gear 3 includes a central outer shell gear 8 provided with teeth,
It consists of outer shell rings 9 provided on both sides of this and having an inner diameter equal to the pitch circle of the outer shell gear 8.

Here, the planetary disk 7 and the outer shell ring 9 are said to have an outer diameter and an inner diameter that are equal to the pitch circles of the planetary gear and the outer shell gear, respectively.
Of course, I took appropriate rear balance.

Since the planetary gear 2 is supported by the planetary shaft 5 from both sides, the A carrier 10 and the B carrier 1 are in the form of a disc.
It is made by combining 1.

The sun gear 1 has a sun shaft hole 12, and the carrier 4 has a carrier shaft hole 13 formed in a shape that prevents rotation, and an input/output shaft (not shown) is mounted thereon.

In this example, the A carrier 10 and the B carrier 11 have the A raised part 14 and the B raised part 15 formed in advance.
The protrusion 16 of No. 4 is fitted into the fitting hole 17 of the B raised portion 15 and fixed with an adhesive 18. The protrusion 16 may be extended and welded on the outside. This applies when the carrier is plastic, but when it is metal, the A and B carriers are connected using rivets, bolts, etc. A casing (
(not shown) mounting hole 19. ...... is the perforation.

FIG. 4 is an enlarged sectional view of only the planetary gear 2.

The planetary gear 6 is thin near the outer periphery and bulges out on both sides near the boss portion. A gear through hole 21 and a disk through hole 22 through which the planet shaft 5 passes are bored in the center of the planet gear 6 and the planet disk 7. Let V be the radius of the planetary shaft 5, the radius of the T1 gear through hole 21, and the radius of the U1 disc through hole 22.

The planetary disk 7 is provided with an inward circumferential protrusion 23 that protrudes inward near the outer periphery. The bulging boss portion 21 of the gear portion and the inward circumferential protrusion 23 of the disc 7 have the same width, and the bulging boss portion 21 has the same width as the inward peripheral protrusion 23 of the disc 7
It enters into a space S partitioned by an inward circumferential protrusion 23.

Therefore, the disc 7 and the gear 6 can be assembled together with almost no gap in dimension. When combined, the inward contact surface 25 of the stepped portion of the disc 7 and the outward contact surface 26 of the shoulder portion of the gear 6 are
They exert radial forces on each other.

Let X be the radius of the contact surface 25 of the inward circumferential protrusion 23 of the disc 7. Let Y be the radius of the contact surface 26 of the bulging boss portion 20 of the gear 6.

If you look at only one side, the cross-sectional shapes of gear 6 and disc 7 are as follows.
It has an inverted "L" shape.

The tooth width W of the gear 6, the protrusion width D of the bulging boss portion, and the thickness K of the disk 7 near the boss are arbitrary. Also, the height Q of the notch with respect to the pitch radius P of the gear 6.

The height k of the bulging boss portion and the radius V of the through hole 21 are also determined appropriately.

Furthermore, the following inequality holds between the planetary shaft radius T, the gear through hole radius U, the disk through hole radius V, the disk contact surface radius X, and the gear contact surface radius Y.

0<(UV)<(X-Y)<(UT) (a) Regarding the planetary shaft, the maximum deviation amount of the planetary gear 6 is (UT).

With respect to the planetary axis, the maximum deviation of the planetary disk γ is (V-T
).

If there is no planetary shaft, the maximum relative deviation between the planetary disk 7 and the planetary gear 6 is (XY).

Although the disc 7 does not move in the radial direction, the gear 6 moves in the radial direction and may strongly bite into the outer shell internal gear 3 and the sun gear 1. To prevent this, (X-Y)<(U-
T) (7).

The disk 7 and the gear 6 can move in the circumferential direction until they come into contact with the planetary shaft 5. In order for the gear 6 to always be able to directly transmit force to the planetary shaft 5 by movement in the circumferential direction, it is sufficient if 0<(UV)<(X-Y) (8). If gear 6 is offset in the circumferential direction,
In other words, under normal circumstances, almost no force is applied to the disk 7.

The operation and effect of the above configuration will be explained.

This planetary gear device can be used as a speed reducer or a speed increaser, and torque is transmitted from the sun gear 1 through the planetary gear 6, outer shell gear 8, carrier 4, and gears. Radial vibration of the carrier and radial movement of the planetary gear due to centrifugal force are suppressed by the planetary disk 7 and the outer shell ring 9, thereby maintaining a suitable rotational state.

Since the planetary gear 6 and the planetary disk T are not fixed, they can rotate relative to each other. Therefore, even if the planetary disk 7 is smaller than the pitch circle by an amount of tolerance and has a rotational speed slower than the planetary gear 6, this slight delay is corrected by the relative rotation and does not interfere with the rotational movement of the planetary gear. In this respect, it is superior to those in which the gear and disc are integrated.

Compared to a case where the planetary gear is indirectly supported by a disc, the frictional force F2 at the contact surfaces 25 and 26 between the planetary disc and the gear is small, and the deviation itself is also small. This is because the planetary gear 6 is directly supported by the planetary shaft 5. Normal force f between the planetary shaft 5 and the planetary gear 2 resulting from the torque T applied to the carrier
(Equation (5)) is applied directly only to the planetary gear 6 without passing through the disk 7.

FIG. 5 is a schematic diagram showing the force relationship of the planetary gears of the present invention.

The planetary gear 6 receives a force of f/2 in the same direction from the sun gear 1 and the outer shell gear 8, and receives an opposite force of f from the planetary shaft 5. This h is offset from the planetary axis.

However, since there is an appropriate rear balance Z between the contact surfaces 25 and 26, the planetary disk 7 receives almost no force from the gear. Therefore, the planetary disk 7 is not strongly pressed against the planetary shaft 5, and the frictional force F3 between the disk and the shaft is small. Frictional force F2. Both Fa and torque are small and do not increase in proportion to torque T.

On the other hand, the frictional force F1 between the planetary disk 7 and the outer shell ring 9 is
As long as the two are in contact, it's pretty big.

Therefore, in many cases F1+F2>Fa, the rotational force (F1+F2) exceeds the braking force (Fa), and the disk rotates at approximately the same speed as the gear.

Therefore, the presence of the disk does not impair the rotational movement of the planetary gear and does not reduce efficiency. The frictional force F2 between the disc and the gear is small and there is little slippage, so there is little heat generation. Even after many years of use, the gear contact surface 26 and the disc contact surface 25 hardly wear out. Conversely, since the need for lubrication is reduced, maintenance efforts are also reduced. Of course, the frictional force F4 between the planetary gear and the planetary shaft is large in proportion to the torque T, but this has nothing to do with the contact between the disk and the gear.

Furthermore, the radius U of the through hole in the planetary gear 6 and the radius ■ of the through hole in the disk 7 can be determined independently, and since ■ is made slightly smaller than U, the effect of suppressing eccentric motion by the disk can be prevented. It is possible to compensate for misalignment between the planetary gear, sun gear, and outer shell gear. If the planetary gear 6 is eccentric in the diametrical direction and strongly meshes with the outer shell internal gear 3 and the sun gear 1, the efficiency will drop significantly, but the contact surfaces 25 and 26 of the gear 6 and the disc 7 will come into contact first, Since the eccentricity of the planetary gear 6 is prevented, jamming does not occur and a decrease in efficiency is prevented. In this way, it is a useful invention.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway front view of a planetary gear device according to an embodiment of the present invention. Figure 2 is a partially cutaway rear view of the same item. FIG. 3 is an XOY sectional view in FIG. 1. Figure 4 is an exploded enlarged sectional view of only the planetary gear. FIG. 5 is a schematic diagram showing the force relationship of planetary gears in the configuration of the present invention. FIG. 6 is a sectional view of a known planetary gear device. FIG. 7 is a schematic diagram showing the force relationship of the planetary gears in the device of FIG. 6. 1... Sun gear 2... Planet gear 3... Outer shell internal gear 4... Carrier 5... Planet shaft 6... ... Planet gear 7 ... Planet disk 8 ... Outer shell gear 9 ... Outer ring 10 ... A carrier 11 ... ...B carrier 20...Bulging boss portion 21...Gear through hole 22...Disc through hole 23...Inward circumferential protrusion 24... ...Rolling surface 25...Contact surface 26...Contact surface Fl...Frictional force F2 between the planetary disk and the outer shell ring
...Frictional force F3 between the planetary disk and the planetary gear...
...Frictional force f between the planetary disk and the planetary shaft ...Normal force T generated between the planetary gear and the disk or planetary shaft ...Carrier torque N ...Planet Number of gears Inventor Shoji Igaku Etsuo Kazufujimori Patent applicant Matex Co., Ltd.

Claims (1)

[Scope of Claims] A sun gear 1, an appropriate number of planetary gears 2 surrounding and meshing with the sun gear 1, an outer shell internal gear 3 surrounding the planetary gear 2 and meshing with it, and a planetary gear 2. ...... as the planetary shaft 5. ...
In a planetary gear device including a carrier 4 pivotally supported by..., the planetary gear 2 includes a planetary gear 6 having a bulged boss portion 20 on both sides, and a planetary gear 6 provided on both sides of the planetary gear 6 with an outer diameter equal to a pitch circle. The outer shell internal gear 3 is composed of a combination of planetary disks 1, 1 having a diameter and an inward circumferential protrusion 23 having the same width as the bulging boss portion 20 near the outer periphery. It consists of an outer shell ring 9 with an inner diameter equal to the pitch circle provided on both sides of the outer shell gear 8, the radius of the through hole 21 of the planetary gear 6 is U, the radius of the through hole 22 of the planetary disk 7 is 2, and the planetary circle is If the radius of the contact surface 25 of the inward circumferential protrusion 23 of the plate 7 is X, the radius of the outward contact surface 26 of the bulging boss portion 20 of the planetary gear 6 is Y, and the radius of the planetary shaft 5 is T, then (1) A planetary gear device characterized in that 0<(U-V)<(X-Y)<(UT).