JPH11315909A - Gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the weight of a gear while suppressing reduction of bending rigidity of a web by erecting ribs on the web extending from a boss to a rim. SOLUTION: A plate shaped web 14 is integratedly arranged between a boss 12 and rim 13 of a gear 10. The web 14 is very thinly formed comparing with that of a conventional gear. A plurality of ribs 15 are erected on both surface of the web 14 radially from the boss 12 to the rim 13, in a direction perpendicular to the web 14, namely in an axial direction of a rotary shaft 11. As a result, bending rigidity of a rotary shaft 11 direction of the web 14 is improved, and natural frequency of the gear 10 is increased. Even if the plate thickness of the web 14 is thinned so as to lighten the weight of the gear 10, reduction of vending rigidity of the web 14 can be suppressed. A lightening hole 14a is arranged on the web 14 so as to more lighten the weight.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear provided in, for example, an aircraft jet engine and an accessory gear box (AGB) attached to the jet engine.

[0002]

2. Description of the Related Art Many gears are used as means for transmitting driving force inside a jet engine for an aircraft or an accessory gear box attached to the jet engine. Of these gears, especially large-diameter gears need to be reduced in weight from the viewpoint of being used in jet engines for aircraft.

In order to reduce the weight of the gear, a rim, which is an annular portion provided with teeth on the outer peripheral portion of the gear, and a boss provided between the rim and a boss provided for reinforcement at an edge of a hole into which a shaft is fitted. In general, a method for forming a web having a thickness as small as possible is provided.

By the way, when the weight is reduced by the above-described method, the natural frequency of the gear decreases, and resonance in a low-order mode, which has not been a problem, becomes a concern. There is also a risk that the gear may be broken due to cracks at the joint between the boss and the web.

Here, as a model for explaining a vibration mode generated in a gear, FIG. 3 shows a case where a rotating disk fixed at the center to a shaft is rotated like a gear as a gear.
Among the vibration modes generated in the rotating disk 1, the most dangerous vibration mode that causes the rotating disk 1 to be damaged is that the rotating disk 1 oscillates around the joint with the shaft 2 as shown in the figure. 1 Nodal Diameter Mode
It is.

The one-node-diameter vibration mode is a low-order vibration mode, and often has the lowest natural frequency of the gear. This is considered to cause resonance due to the primary excitation force of the rotation of the rotating shaft and cause deformation of the rotating disk.

[0007] The deformation of the rotating disk in the vibration mode of one-node diameter is bending deformation in which the joint between the rotating disk and the shaft is a fixed end, and when replaced with a gear, the joining of the boss and the web is performed. It is considered that the portion undergoes bending deformation, and if the vibration is repeated, a crack is generated in this portion.

[0008]

In order to suppress the occurrence of a vibration mode having a diameter of one node, one method is as follows.
As shown in FIG. 4 (A), the thickness of the web 4 is increased at the joint between the boss 3 and the web 4 (the portion indicated by the symbol F), the rigidity of the web 4 in the axial direction is increased, and the natural frequency of the gear There is a method of suppressing the occurrence of a vibration mode having a one-node diameter in the practical rotation range of the gear by increasing the gear ratio. However, this causes inconsistency in reducing the weight of the gear.

Therefore, as another method, as shown in FIG. 4B, a vibration damping mechanism called a damper ring 6 is attached to the inner surface of the rim 5, and the vibration is attenuated by friction between the rim 5 and the damper ring 6. Thus, there is a method of suppressing the occurrence of a vibration mode having a diameter of one node. The damper ring 6 is formed by forming a groove in the inner surface of the rim 5 along the circumferential direction, and fitting a ring separate from the rim 5 into this groove. However, in the vibration damping mechanism using the damper ring 6, sliding between the rim 5 and the damper ring 6 is unavoidable, and there is a slight difficulty in durability such as wear of the damper ring 6.

The present invention has been made in view of the above circumstances, and has as its object to reduce the weight of a gear while suppressing a reduction in bending rigidity of a web.

[0011]

As a means for solving the above-mentioned problems, a gear having the following configuration is employed. That is, a gear including a boss attached to a rotating shaft, an annular rim located outside the boss and having teeth formed thereon, and a plate-shaped web provided integrally with the boss and the rim. Then, a rib is erected from the boss to the rim. By erecting the ribs on the web, the bending rigidity of the web increases, and the natural frequency of the gear increases. Therefore, even if the thickness of the web is reduced to reduce the weight of the gear, a reduction in the bending stiffness of the web is suppressed, and it becomes difficult for the gear to exhibit a one-node diameter vibration mode in a practical rotation range.

It is desirable that the rib be provided upright in the direction of the rotation axis. By erecting the ribs toward the rotation axis direction, the bending rigidity of the web is increased in the rotation axis direction.

It is desirable that the ribs are provided radially around the boss and are erected at regular intervals along the circumferential direction of the ribs. By providing the ribs radially, high rigidity is uniformly provided at any position in the circumferential direction of the gear.

Preferably, the web is provided with a hole for lightening between adjacent ribs. If the ribs provide sufficient bending stiffness in the direction of the rotation axis, holes can be formed in the web to reduce the weight of the gears.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a gear according to the present invention will be described with reference to FIGS. As shown in each figure,
The gear 10 includes a boss 12 inserted into the rotating shaft 11, an annular rim 13 arranged concentrically around the outer periphery of the boss 12, and having teeth (not shown) formed on an outer surface thereof; Plate-like web 14 provided integrally between rims 13
It is composed of

The web 14 is formed to be very thin as compared with a conventional gear without ribs.
A plurality of ribs 15 radially extending from the boss 12 to the rim 13 are perpendicular to the web 14, that is, the rotation axis 1.
It stands upright in the axial direction. Each rib 15 is formed radially in seven directions around the axis of the rotating shaft 11. In addition, the web 14 divided by each rib 15
Is formed with a hole 14a for lightening.

In the gear 10 configured as described above, since the ribs 15 are provided, the web 14
Of the gear 10 in the direction of the rotating shaft 11 is increased, and the natural frequency of the gear 10 is increased. Therefore, even though the thickness of the web 14 is reduced to reduce the weight of the gear, the reduction in the bending stiffness of the web 14 is suppressed, and it is difficult for the gear 10 to exhibit a one-node diameter vibration mode in the practical rotation range. Has become.

Therefore, according to the gear 10 configured as described above, it is possible to reduce the weight while suppressing the bending rigidity of the web 14 from decreasing.

Further, since the ribs 15 are provided radially around the boss 12 and are provided at equal intervals along the circumferential direction of the rim 13, the ribs 15 are uniformly high at any position in the circumferential direction of the gear 10. Rigidity is given. This makes it possible to realize a gear that is lightweight and has high bending rigidity of the web 14.

Further, the web 14 is provided with a hole 14a for lightening the space between the adjacent ribs 15, 15. By providing the rib 15, the bending rigidity in the direction of the rotating shaft 11 is sufficiently ensured. In addition, the weight of the gear 10 is further reduced.

The gears shown in FIGS. 1 and 2 show an embodiment of the present invention. The shapes of bosses, rims, webs, and the shapes, numbers, and arrangement positions of the ribs are the same as those of the gears. It can be appropriately changed depending on the size, the number of teeth, the shape, and the like.

[0022]

As described above, the gear according to the present invention has a plate-like shape provided integrally with a boss mounted on a rotating shaft and an annular rim having teeth formed outside the boss. Since the ribs are erected from the boss to the rim on the web, even if the thickness of the web is reduced to reduce the weight of the gear, the reduction in the bending rigidity of the web is suppressed, and the practical use of the gear It becomes difficult to exhibit a vibration mode having a diameter of one node in the rotation range. Thereby, it is possible to reduce the weight of the gear while ensuring sufficient durability by suppressing a decrease in the bending rigidity of the web.

Since the ribs are erected in the direction of the rotation axis, the bending rigidity of the web is increased in the direction of the rotation axis. Thereby, a lightweight and highly durable gear can be realized.

Since the ribs are provided radially around the boss and are provided at equal intervals along the circumferential direction of the rim, high rigidity is provided at any position in the circumferential direction. Thereby, a lightweight and highly durable gear can be realized.

[0025] Since the web is provided with a hole for lightening between adjacent ribs, the weight of the gear can be further reduced.

[Brief description of the drawings]

FIG. 1 is a side view showing an embodiment of a gear according to the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a model diagram for explaining a vibration mode generated in a conventional gear.

4A and 4B are a cross-sectional view and a cross-sectional perspective view illustrating an example of a solution for suppressing a vibration mode in a conventional gear.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Gear 11 Rotation shaft 12 Boss 13 Rim 14 Web 14a Hole 15 Rib

Claims (4)

[Claims] 1. A gear comprising: a boss attached to a rotating shaft; an annular rim having teeth formed outside the boss; and a plate-shaped web provided integrally with the boss and the rim. A gear, wherein a rib is erected from the boss to the rim on the web. 2. The gear according to claim 1, wherein the rib is provided upright toward the rotation axis. 3. The gear according to claim 1, wherein the ribs are provided radially around the boss and are provided at equal intervals along a circumferential direction of the rib. 4. The gear according to claim 1, wherein a hole for lightening the web is provided between the adjacent ribs.