JPH01310129A - Support device for bearing receiving radial load - Google Patents

Abstract

PURPOSE:To avoid the proceeding of breakage by supporting a bearing with a plurality of flexibly deformable beams after the buckling of a bearing support member to convert it to a flexible structure so that it follows the displacement due to the circular motion defining the radius of the bearing support member. CONSTITUTION:When moving blades of a fan are scattered to give a large radial load to a bearing 1, the intermediate portion of connecting portions 5 in two spots of a conical bearing support member 3 is buckled so that a large radial load is avoided from being applied to a main body side strength member through bolt connecting portion 2. Also, after the buckling of the support member 3, the bearing 1 is supported with a plurality of cylindrical pipes 6 or flexible deformable beams 4-1, 4-2... so that the rotational frequency of primary danger of a shaft system including a bearing support device becomes lower than the rotational frequency of running of a rotary system. Thus, only smaller radial load is applied to the bearing 1, while the rotation is continued stably. Next, after the buckling of the support member 3, the possibility of breakage also exists. However, since the bending rigidity of individual beams in the independent beams 4-1, 4-2... or cylindrical pipes 6 is low, the occurrence of breakage can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is applied to the fan rotating part of a high-bypass turbofan for aircraft, the propeller part of a turboprop (including an advanced turboprop), or the radial part of other industrial turbomachinery. The present invention relates to a support device for a bearing that receives a load.

[Conventional technology]

As shown in FIG. 5, a conventional high-bypass turbofan engine fan for an aircraft includes a long rotor blade 10 that is similar to a propeller. When this is viewed as a turbomachine, its boss ratio is very small, and therefore it is dimensionally difficult to attach a large number of rotor blades 1O to a disk or the like on the rotating shaft side. For this reason, the number of fan moving blades must be reduced. On the other hand, the tip side of the rotor blade requires a blade cross-sectional shape with a large chord, so the rotor blade is designed to widen from the true root side toward the blade tip, with each blade being heavily overlapped. I have no choice but to.

The relative velocity of the tips of the rotor blades to the air should be set as high as the hydrodynamic limit allowed in relation to normal "walls," and the design should be the smallest and lightest to meet the required output. It's normal.

For this reason, if a large bird collides with an aircraft while it is in flight, the tip of one rotor blade may break off and be scattered, leaving only the root of the blade. The whirling load due to unbalance is (rotation angle ratio) 2, and the magnitude of this load tends to increase in engines with a large bypass ratio.

Engines for passenger aircraft tend to be designed with higher bypass ratios than conventional ones in order to improve fuel economy, so when fan rotor blades fly off, the unbalanced swinging load tends to be large.

In addition, the above-mentioned ducted fans (with fan cowl), unducted fans (without fan cowl), and new types of aero engines called advanced turboprops have ultra-bypass ratios that are significantly higher than conventional ones. It is becoming increasingly important to have a lightweight structure that can withstand the swinging load caused by the unbalance of flying blades.

Considering the fatigue phenomenon of structural materials due to such huge whirling loads (for stationary structures such as bearing support devices, this is a "rotating load" in which the direction of the load rotates), it is important to consider the allowable stress of the material. Since it has to be set low, it is not possible to design a large number of aero engines unless there is some kind of design ingenuity.

FIG. 6 is an explanatory diagram showing a state when the fan rotor blades are scattered.

FIG. 6(a) shows a case where the fan section is rotating at a rotational speed lower than the primary critical speed of the rotating system. Since the radius of the center of gravity G of the fan rotating part from the center of rotation A gradually increases after the rotor blades are scattered, the centrifugal load increases, and accordingly, a large radial load is applied to the bearings that support the rotating system.

FIG. 6(b) shows a case where the fan section is rotating at a rotation speed higher than the primary critical speed of the rotation system. The center of gravity G of the fan rotating part after the rotor blades are scattered is the center of rotation between the physical rotation center A' and the geometric center A of the fan rotating part (which coincides with the center of rotation of the fan rotor blades before they are scattered). Since the rotor can continue to rotate stably at this position, the centrifugal load does not increase significantly as in the case of FIG. 6(a).

The critical rotational speed of a rotating system is determined by the size and distribution pattern of the mass distributed on the rotating shaft, as well as the characteristics of the deflection of the shaft system. The deflection of the shaft system is determined by the rigidity of the shaft itself and its distribution pattern, as well as the rigidity of the bearing support device that supports the rotating shaft. Therefore, the shaft system (
(including the bearing support system) is designed so that the next critical rotational speed is higher, and when the rotor blades fly off, the huge centrifugal load is used to intentionally break a part of the bearing support system. Alternatively, by buckling and changing the spring constant, the critical rotational speed of the primary shaft system can be lowered below the operating rotational speed, thereby avoiding the risk of exposing related parts to huge whirling loads.

The idea is that by designing the shaft system from the beginning so that the primary critical rotational speed is lower than the operating rotational speed range, it is possible to avoid processes that are difficult to control, such as breaking or buckling parts of the bearing support device. However, if such a weak (easily bent) shaft system (including the bearing support system) is adopted, the shaft system may become damaged in the transitional stage until the state shown in Figure 6(b) is reached after the rotor blades fly off. This is not a realistic solution because a large bending phenomenon occurs.

Due to the above background, in order to avoid applying a huge centrifugal load due to the unbalance of the rotating body after the rotor blades fly off to structural members such as the engine, a part of the bearing support device is intentionally buckled/plastically deformed. There are also ways to do this.

However, in this case, since it includes elements that are difficult to handle such as buckling/plastic deformation, the results will vary, and the buckling/plastic deformation part will be removed before the rotating part stops. There are uncertainties such as there is a risk that the material will be damaged due to hp and deformation, and that it will eventually break.

[Problem to be solved by the invention]

As mentioned in the prior art section above, when a bearing support device is made to undergo buckling/plastic deformation, (1) cracks occur at an early stage when plastic deformation begins under heavy load; The crack spreads over the entire cross section of the strength member, causing it to break prematurely.

(2) It undergoes repeated plastic deformation and eventually breaks from that part.

It is possible that However, in any of the above cases, the function of holding the rotating side close to its normal position is lost, which is not preferable.

The present invention attempts to solve these problems.

[Means to solve the problem]

In the present invention, in a bearing support device, (1) a bearing support member provided around a rotating shaft having a cylindrical, conical, or box shape having necessary rigidity; (2) bearing support members each having both ends thereof; It has a plurality of flexible and easily deformable beams that are fixed to the body and rearranged like a splint, and that are independent of each other.

[For production]

As explained in FIG. 6(a), when the rotational speed of the rotating shaft is lower than the primary critical frequency of the rotating system, the bearing support device must have enough rigidity to withstand the centrifugal force due to unbalance. In the present invention, since the bearing support member has the necessary rigidity, the bearing support member can withstand centrifugal force due to unbalance within a certain limit.

However, if the centrifugal force exceeds this limit, the highly rigid bearing support member will buckle.

After the highly rigid bearing support member in the bearing support device buckles in this way, the bearing is supported by multiple beams that are flexible and easily deformed, resulting in the primary dangerous rotation of the shaft system including the bearing support device. The result is that the number falls below the operating speed of the rotary shaft.

Therefore, as explained with reference to FIG. 6(b), since the rotating system rotates around the part close to the center of gravity, the axis after flying off the rotor blade rotates in a circle with a constant radius around the center of rotation, i.e. The bearing support device also performs circular motion with a defined radius, but in the present invention, after the bearing support member buckles, the bearing is supported by a plurality of flexible beams that are easily deformed, and Because the structure is converted to
The radius of the bearing support device can be made to follow the displacement due to the defined circular motion, and the bearing support device can be prevented from further damage.

〔Example〕

A first embodiment of the present invention is shown in FIGS. 1 and 2. In this embodiment, the present invention is applied to the part labeled "bearing support device" that supports the bearing closest to the rotating part of the fan rotor blade in FIG.

In Figures 1 and 2, 1 is a bearing that supports the rotating part of the fan, 3 is a conical bearing support member having the necessary rigidity, one end of which supports the bearing 1, and the other end with bolts. A joint 2 is formed and attached to a main strength member of the engine, not shown. 4 is a plurality of mutually independent beam portions 4-1.4-2.4-3. It is a splint having an overall conical shape as shown in FIG. The beam portions 4-1.4-2.4-3 extend in the axial direction of the rotating shaft and are spaced apart from each other, and both ends thereof come together to form annular end portions 4', 4''. .

The same end portion 4-2.4-3 is an annular protrusion 3-1. provided inside the bearing support member 3. , 3-2 and 5 are connected by welding, brazing, or other means.

The beam portions 4-1.4-2.4-3 are constructed to be flexible and easily deformable, and are arranged at intervals from each other to form independent splint-like beams. is forming.

A second embodiment of the present invention is shown in FIGS. 3 and 4. Similarly to the above-mentioned embodiments, this embodiment also applies the present invention to the part marked as "E bearing support device" in Fig. 5, and the bearing 1, coupling part 2, and bearing support member 3 are This embodiment has the same configuration as the embodiment of -. In this embodiment, a portion corresponding to the splint of the first embodiment is constituted by a plurality of flexible and easily deformable circular tubes 6. A plurality of circular tubes 6 are arranged in an annular shape around the rotating shaft at intervals from each other, and both ends thereof are inserted into holes of annular protrusions 3-1 and 3-2 formed inside the bearing support member 3. It is inserted and connected to the bearing support member 3 by means of welding, brazing, etc. at a portion indicated by the reference numeral 5, forming a plurality of beams arranged like mutually independent splints. Further, the plurality of circular tubes 6 are configured to be flexible and easily deformable.

7. Both embodiments are constructed as described above, so when a huge radial load is applied to the bearing 1 due to the fan rotor blades flying off, the two joints of the conical bearing support member 3 The middle part of 5 is buckled.

This prevents a huge radial load from being applied to the strength member on the main body side through the bolt joint 2. Further, after the bearing support member 3 buckles, the bearing 1 is formed into a flexible and easily deformable beam, that is, a double-R beam M4 1, 4 2.
4 3... or supported by multiple circular tubes 6, the primary dangerous rotational speed of the shaft system including the bearing support device will fall below the operating rotational speed of the rotating system, and as a result, As explained with reference to FIG. 6(b), stable rotation is continued while only a smaller radial load is applied to the bearing 1.

Even after the bearing support part 3 buckles, plastic deformation is applied to the buckled part with a delay due to the large moment of inertia and high rotational speed of the rotating body, and there is a risk that it will eventually break. However, the beam part 4-1゜4-2.4-3...
...Or, since the circular tubes 6 are each independent and the bending rigidity of each beam is low, such a rupture occurs because it can respond to externally forced displacement with not very high stress. This can be prevented.

Moreover, even if a crack occurs in a part of the bearing support member 3 at an early stage after buckling and propagates to the entire circumference, the beam portion 4-1.4-2.4-3. Or, since the plurality of circular tubes 6 are separate members from the bearing support member 3, they are not affected by this.

Furthermore, even if a crack occurs in any of the beam parts 4-1.4-2.4-3... or the plurality of circular pipes 6, each of them is independent. As described above, the cracks do not propagate to adjacent parts, and each of the above embodiments can prevent the spread of an accident due to unexpected breakage after buckling of the bearing support member.

In the above embodiments, a conical bearing support member is shown, but in the present invention, a suitable bearing support member such as a cylindrical shape, a box shape, etc. that surrounds the rotating shaft may be adopted. I can do it.

In addition, although the present invention has been mainly described in relation to a bearing support device for a fan rotating part of an aircraft bypass turbofan, the present invention is not limited to this, but is applicable to a propeller part of an aircraft turboprop or a wide range of other applications. It can be applied to bearing support devices for industrial turbomachinery.

〔Effect of the invention〕

As explained above, the following effects are produced by the present invention.

(1) When a radial load of a predetermined value or more is applied to the bearing, the bearing support member buckles, thereby preventing the large radial load from being transmitted to other parts.

(2) When the bearing support member buckles, the bearing is supported by a flexible and easily deformable beam, and the spring constant changes. As a result, the primary critical rotational speed of the shaft system including the bearing support device decreases, and the rotating shaft The rotation speed drops below the operating speed. For this reason, the center of gravity of the rotating part is located midway between the rotation center of physical motion (rotating shaft axis center) and the geometric center of the rotating part, and stable rotation is continued. The heart rotates in a circle with a constant radius around the geometric center of the rotating part.

Furthermore, in the present invention, since the bearing is supported by a flexible and easily deformable beam, the bearing support device according to the present invention can follow the displacement due to the circular motion with the defined radius.

(3) Even if a crack occurs in a part of the bearing support member after buckling, this crack will not be transmitted to a separate beam.

(4) Even if a crack occurs in any of the beams, since each beam is independent, the crack will not propagate to adjacent beams.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a first embodiment of the present invention, FIG. 2 is a perspective view of the main parts of the above embodiment, FIG. 3 is a longitudinal sectional view of a second embodiment of the invention, The figure is a sectional view taken along the line A-A in Figure 3, Figure 5 is an explanatory diagram of a bearing support device for a conventional aircraft bypass turbo fan, and Figure 6 is a rotational state when a part of the fan rotor blade is blown off. This is an explanatory diagram of . 1... Bearing, 2... Bolt joint part 13
... Bearing support member 2 4 ... Splint member. 6...Circular tube. Agent: Patent Attorney Akigai Sakama (2 people) Figure 2

Claims (1)

[Claims] Consisting of a bearing support member that surrounds the rotating shaft and has the necessary rigidity, and a plurality of flexible and easily deformable beams that are independent of each other and are arranged like a splint, with each end fixed to the bearing support member. A support device for a bearing that receives a radial load, characterized by: