CA1210256A - Fly-wheel device - Google Patents

Fly-wheel device

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Publication number
CA1210256A
CA1210256A CA000449519A CA449519A CA1210256A CA 1210256 A CA1210256 A CA 1210256A CA 000449519 A CA000449519 A CA 000449519A CA 449519 A CA449519 A CA 449519A CA 1210256 A CA1210256 A CA 1210256A
Authority
CA
Canada
Prior art keywords
stack
fly
wheel device
discs
bolt
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA000449519A
Other languages
French (fr)
Inventor
Yasuo Yoshida
Masato Teraoka
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsubishi Electric Corp
Original Assignee
Mitsubishi Electric Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mitsubishi Electric Corp filed Critical Mitsubishi Electric Corp
Priority to CA000449519A priority Critical patent/CA1210256A/en
Application granted granted Critical
Publication of CA1210256A publication Critical patent/CA1210256A/en
Expired legal-status Critical Current

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Abstract

ABSTRACT OF THE DISCLOSURE

A fly-wheel device has a stack of three similar discs axially superposed on one another into a unitary structure by means of several fastening bolts loosely extending at equal angular intervals through axially aligned holes in the discs on a peripheral portion of the stack with associated nuts, each of the fastening bolts being fixed within the aligned holes through annular bushes engaging those surfaces of the intermediate and underlying discs near to a bolt's head at their edge exposed to the aligned holes, each of those portions of the bolts which directly face those discs except for the respective annular bushes having two opposite sides in a radial direction of the stack constricted in its middle and two opposite sides in a circumferential direction of the stack defined by correspond-ing portions of the peripheral surface of the bolt.

Description

~ 5 ~ 1 FLY~WHEEL DEVICE

BACKGROUND OF THE INVENTION
This invention relates to a fly-wheel device, and more particularly to improvements in a fly-wheel device constructed so that electrical energy is converted to inertia energy of a rotary member and when required, t'ne inertia energy is again converted to electrical energy which is, in turn, supplied to a utility line of the power system.
A conventional fly-wheel device of the type referred to has comprised a stack of a plurality of discs having equal thicknesses and axially superposed on one another, and a plurality of fastening bolts axially extending at predetermined equal angular intervals through a peripheral portion of the stack to connect the superposed discs together into a unitary structure, each of the fastening bolts having a cross section uniform axially thereof. The fly-wheel device has been coaxially connected to a rotary shaft of an associated electric generator at one end.
In operation the individual discs of the fly-wheel device are differently raised in temperature tending to have different thermal elongations. The resulting relative movements among the individual discs, however, are restrained by the fastening bolts because each of the fastening bolts has the cross section uniform axially thereof as described above. This has resulted in the disadvantage that a bending stress developed on each of the fastening bolts becomes large as the case may be.

)Z56 Accordingly it is an object of the present inven~ion to provide in the fly-wheel device as described above, an improved fastening bolt having a longitudinal section on at least one predetermined axial portion thereof changed so as to render a restraining force thereof in a radial direction of the stack of the superposed discs weaker than that in a direction perpendicular to the radial direc~ion or a circum-ferential direction thereof.

SUM.~ARY OF THE INVENTION
The present invention provides a fly-wheel device comprising a stack of a plurality of similar discs axially superposed on one another, and a plurality of fastening bolts axially extending at predetermined equal angular intervals through a peripheral portion of the stack to connect the superposed discs together into a unitary structure with associated nuts, each of the fastening bolts having a sectional profile on at least one predetermined axial portion thereof changed so as to render a modulus of section in a radial direction of the stack smaller than that in a circum-ferential direction thereof thereby to weaken a restraining force of each of the fastening bolts in the radial direction of the stack.
In a preferred embodiment of the present invention each of the fastening bolts axially extends through an associated axially aligned holes on the peripheral portion of the stack having an inside diameter somewhat greater than a diameter thereof and fixed within the axially aligned holes through a plurality of annular bushes engaging the surfaces of the respective discs near to a head of the fastening bolt except for the disc contacted by the head of the bolts and at edges exposed to the axially aligned holes, an axial portion of the fastening bolt directly facing at least one predetermined disc except for the associated bush has such a longitudinal sectional profile that a pair of opposite sides of the axial portion perpendicular to the radial direction of the stack are curved concavely toward the central longitudinal plane thereof orthogonal to the radial direction of the stack to be symmetrical with respect to the central longitudinal plane and have a thickness therebetween gradually increased from a minimum in the middle thereof to a maximum at each of axial ends thereof equal to the diameter of the fastening bolt with another pair of opposite sides thereof in a circumferential direction of the stack defined by corresponding portion of the peripheral surface of the fastening bolt.

BRIEF DESCRIPTION OF THE DRAWING
The present invention will become more readily apparent from the following detailed description taken in conjunction with the accompanying drawing in which:
Figure 1 is a longitudinal sectional view of an electric generator comprising a conventional fly-wheel device;
Figure 2 is a fragmental elevational view in an enlarged scale of one of the fastening bolts extending through the fly-wheel device shown in Figure 1 with an adjacent portion of the fly-wheel device illustrated in longitudinal section;

l~lQ256 Figure 3 is a fragmental elevational view in an enlarged scale of one embodiment according to the fastening bolt of the present invention for the fly-wheel device an adjacent portion of which is illustrated in longitudinal section; and Figure 4 is a cross sectional view taken along the line IV-IV of Figure 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT
For a better understanding of the nature of the present invention, a conventional fly-wheel device will now be described in conjunction with Figures 1 and 2. The arrangement illustrated in Figure l comprises a reinforced concrete foundation 10, a circular generator pit 12 disposed in the foundation 10 to open on the surface of the latter, a circular fly-wheel pit 14 smaller in diameter than and disposed under the generater pit 12 within the foundation 10 to be coaxial with the generator bit 12 and open at the bottom of the upper pit 12, and a plurality of ventilating ducts in the form of U's disposed at predetermined equal angular intervals around the lower pit 14 within the foundation 10 and including one end open on the bottom portion of the pit 14 to form an out-let port and other ends opening at the bottom of the upper pit 12 on the peripheral portion to form inlet ports.
The arrangement comprises further an electric generator generally designated by the reference numeral 18 and disposed coaxially within the generator pit 12. More specifically, the electric generator 18 includes a stator 20 turn, supported by a lower bracket 46 fixed to the bottom of the fly-wheel pit 14.
As shown in Figure 1, a plurality of blowers 4g are disposed at the inlet ports of the ventilating ducts 16 one for each duct 16 and a plurality of separate blowers 50 are disposed at predetermined equal angular intervals on the outer surface of the upper bracket 26.
In order to connect the superposed discs 38 together into the unitary structure, usual bolts have been used. As shown best in Figure 2, the fastening bolt 40 has had a diameter or a cross sectlon uniform axially thereof and extended through an associated axially aligned holes 38A in the superposed discs 38 having an inside diameter somewhat larger than the diameter thereof. The fastening bolt 40 is fixed within the axially aligned holes 38A by a plurality of annular bushes 52 engaging those surfaces of the respective discs 38 near to a head of the bolt 40 or the upper surfaces as viewed in Figure 1 except for the disc contacted by the head of the bolt 40 and at their edges exposed to the axially aligned holes 38A. More specifically, the annular bushes 52 are put in annular steps disposed on inner peripheral portions of the upper surfaces as viewed in Figure 2 of the superposed discs 38 to communicate with the axially aligned holes 38A
except for the uppermost disc 38 as viewed in Figure 2.
As described above, the occurrence of different temperature rises on the superposed discs 38 tends -to cause relative movements among the discs 38. However, those relative movements are restrained by the fastening bolts 40 because of the uniform diameter thereof. This has resulted in the disadvantage as described above.

~ 2~ ~

rigidly held by an annular frame 22 with a U-shaped section disposed on the bottom of the generator pit 12 through an annular holding plate. The stator frame 22 is provided on the peripheral wall with a plurality of air coolers 24 located at predetermined equal angular intervals thereon and has an upper leg connected to an upper bracket 26 supported by a plurality of radial arms 28 extending at predetermined equal angular intervals between the bracket 26 and the peripheral wall of the generator pit 12. An upper hollow rotary shaft 30 is journalled by the bracket 26 to extend downward as viewed in Figure 1 and connected to a main hollow rotary shaft 32 which, in turn, extends in the fly-wheel pit 14. A rotor 34 is fixedly secured to the main rotary shaft 32 so as to face the stator 20 through a predetermined annular spacing.
As shown in Figure 1, a fly-wheel device generally designated by the reference numeral 36 is fixedly secured to the lower portion of the main rotary shaft 32 located within the fly-wheel pit 14. The fly-wheel device 36 includes a stack of a plurality of discs 38, in this case, four discs, with a common diameter having suitable equal thicknesses and axially superposed on one another and a plurality of fastening bolts 40 axially extending at prede~ermined equal angular intervals through a peripheral portion of the stack to connect the superposed discs 38 together into a unitary structure with associated nuts.
The lower surface as viewed in Figure 1 of the fly-wheel device 36 is bolted to a thrust collar 42 sub-sequently journalled by a thrust bearing 44 which is, in Lf.'~St~

equal to the diameter of the bolt 40. Another pair of opposite sides of the axial bolt portion C are defined b~
corresponding portion of the peripheral surface of the bolt 40. The axial bolt portion D is identical in longitudinal sectional profile to the axial bolt portion C.
Figure 4 shows the resulting cross sectional profile in the middle of the predetermined axial portion C
of the bolt 40. As shown in Figure 4, the cross sectional profile includes a pair of opposite parallel sides orthogonal to the abovementioned radial direction and a pair of opposite segments of circular defined by corresponding portions of the peripheral surface of the bolt 40.
This is true in the case of the predetermined axial bolt portion D.
Each of the predetermined bolt portions C and D
has such a sectional profile that a modulus of section in the radial direction of the stack is smaller than that in a circumferential direction thereof. 38 ~
A It is assumed that the uppermost disc ~ is different in temperature rise from the next succeeding disc 38C' _~4~ to cause a relative shear ~ therebetween. Under the assumed conditions a bending moment M applied to the fastening bolt 40 may be expressed by M = 6EI~/Q

where E designates a Young's modulus of a material forming the fastening bolt 40, I a second moment of area of the bolt and ~ designates a span shown in Figure 3.
For a large relative shear ~, the bending moment ~f becomes large resulting in a high bending stress developed l~.i!'~'Ji~Sfà

The present invention contemplates to elirninate that disadvantage by provision of a fastening bolts ha-~Jing a specified sectional profile at least one predetermined portion thereof shaped so as to weaken a restraining force thereof exerted on the discs radially thereof.
In Figure 3 wherein like reference numerals designate the components identical to those shown in Figure
2, there is illustrated one embodiment according to the essential part of the fly-wheel device of the present invention. The arrangement illustrated is different from that shown in Figures 1 and 2 only in that in Figure 3, three discs 38B, 38C and 38D having equal thicknesses and equal diameters are axially superposed on one another and the fastening bolt 40 has a specified longitudinal sectional profile on each of two predetermined axial portions thereof, in this case, that portion C extending between the lower end of the annular bush 52 engaged by the second disc 38C and the upper end of the annular bush 52 engaged by the third disc 38D and that portion D extending between the lower end of the latter bush 52 and the lower end of third disc 38D.
The specified longitudinal sectional profile is formed so that a pair of opposite sides of the predetermined bolt portion C perpendicular to a radial-direction of the stack are similarly curved concavely toward of the central longitudinal plane of the bolt 40 orthogonal to a radial direction of the stack to be symmetrical with respect to the central longitudinal plane and have a thickness therebetween gradually lncreased from a minimum in the middle thereof to a maximum at each of axial ends of the axial bolt portion C

;Z5~

on the fastening bolt. However, by forming that the portion C of the bolt applied with the high bending moment or into the cross section shown in Figure 4, the second moment of area I becomes low in the radial direction of the stack.
This results in the alleviation of the bending stress exerted on the fastening bolt.
It has been found that only a single predetermined bolt portion C may have the sectional profile as described above with the satisfactory result.
From the foregoing it is seen that the present invention provides a fly-wheel device comprising a stack of a plurality of similar discs supperposed on one another and a plurality of fastening bolts axially extending at pre-determined equal angular intervals through a peripheral portion of the stack to connect the superposed disc together into a unitary structure with associated nuts, each of the fastening bolts having such a sectional profile on at least one predetermined axial portion thereof so that a modulus of section in a radial direction of the stack is smaller than that in a circumferential direction thereof. Thus the fastening bolt can be easy to be pliantly bent on the predetermined bolt portion. As a result, each of the fastening bolts is applied with a bending stress capable of being effectively alleviated.
While the present invention has been illustrated and described in conjunction with a single preferred embodiment thereof, it is to be understood that numerous changes and modulations may be resorted to without departing from the spirit and scope of the present invention. For ;Z5~i example, any number of fly-wheel discs other than three ¦ discs may be superposed on one another and each of ~he ¦ fastening bolts may have the sectional profiles as described aoove on more than two predetermined portions thereof.

_l

Claims (3)

  1. THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
    PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
    l. A fly-wheel device for storing energy in an electric power generating plant, comprising: a stack of axially superimposed heavy disks; a plurality of fastening bolts axially extending at predetermined equal angular intervals through a peripheral portion of said stack; and a plurality of nuts fastened onto respective ones of said plurality of fastening bolts so as to connect said superimposed disks into a unitary structure, each of said plurality of bolts having a section modulus in the radial direction of said stack which is smaller than the section modulus thereof in the circumferential direc-tion of said stack, at some predetermined locations along the axis thereof, so as to relieve bending stress on each of said plurality of fastening bolts.
  2. 2. A fly-wheel device as in claim 1, wherein said predetermined locations include a pair of predetermined axial portions of each fastening bolt of reduced diameter in the radial direction of said stack, within consecutive ones of said disks.
  3. 3. A fly-wheel device as in claim 1, wherein each fastening bolt includes axial portions having a pair of opposite sides in the radial direction of said stack to be similar and opposite to each other to be symmetrical with respect to the central longitudinal plane and another pair of opposite sides in a circumferential direction of each stack defined by a corres-ponding portion of a peripheral surface of said each fastening bolt.
CA000449519A 1984-03-13 1984-03-13 Fly-wheel device Expired CA1210256A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CA000449519A CA1210256A (en) 1984-03-13 1984-03-13 Fly-wheel device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CA000449519A CA1210256A (en) 1984-03-13 1984-03-13 Fly-wheel device

Publications (1)

Publication Number Publication Date
CA1210256A true CA1210256A (en) 1986-08-26

Family

ID=4127399

Family Applications (1)

Application Number Title Priority Date Filing Date
CA000449519A Expired CA1210256A (en) 1984-03-13 1984-03-13 Fly-wheel device

Country Status (1)

Country Link
CA (1) CA1210256A (en)

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