JP2008298174A - Mechanical fuse and connecting structure of power transmission system including the mechanical fuse - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mechanical fuse that can be used stably for a long period of time without rupture even when load fluctuates to some extent, and a connecting structure of a power transmission system including the mechanical fuse. <P>SOLUTION: The mechanical fuse is made of a titanium alloy and the fatigue limit ratio thereof is equal to or higher than 0.7. The mechanical fuse is a shear bolt arranged at a connecting portion provided in the power transmission system. In the connecting structure of the power transmission system including the mechanical fuse, flange portions respectively provided on a drive side and a driven side are connected to each other via the shear bolt that is the mechanical fuse. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a mechanical fuse provided to cut off power transmission when an overload occurs in a power transmission device and to ensure the safety of the device, and a connection structure of a power transmission system including the mechanical fuse.

The mechanical fuse is set between a driving side and a driven side (for example, a driving shaft and a driven shaft) in a power transmission device that transmits rotational power on the driving side to the driven side. And if a large differential occurs between the driving side and the driven side while the rotational power is being transmitted, the power transmission is forcibly interrupted by the breakage of itself, and this causes the overload torque to be This is to prevent locks and destruction caused by spreading.
There are various forms of mechanical fuses, such as shear pins, shear bolts, and shear plates.

  Such a mechanical fuse is required to have a characteristic of reliably breaking when a predetermined excessive torque is applied. On the other hand, in normal use conditions, it is desired that there will be no breakage over a long period of time even if there is some torque fluctuation. Therefore, a material having a large fatigue limit ratio (a fatigue limit / tensile strength) is desired.

As a conventionally proposed iron-based alloy mechanical fuse, a mechanical fuse made of an iron-based sintered alloy has been proposed (for example, see Patent Document 1).
JP 2002-168267 A

However, the one described in Patent Document 1 has a fatigue limit ratio of 0.5 or less, and when it is used for a long period of time, if there is a load fluctuation and it exceeds the fatigue limit, there's a possibility that. If the mechanical fuse breaks under normal use conditions rather than overloading, it may be a great damage depending on the power transmission device in which the mechanical fuse is used.
Therefore, there is a demand for a mechanical fuse that can be used stably for a long period of time without breaking even if the steady load varies somewhat.

  The present invention has been made to solve such a problem, and is a mechanical fuse that can be used stably for a long period of time without breaking even if the load fluctuates somewhat. The power transmission system coupling structure including the mechanical fuse The purpose is to obtain.

(1) The mechanical fuse according to the present invention is made of a titanium alloy and has a fatigue limit ratio of 0.7 or more.

(2) Further, in the above (1), the mechanical fuse is a shear bolt installed in a connecting portion provided in a power transmission system.

(3) A power transmission system coupling structure according to the present invention is a power transmission system coupling structure having the mechanical fuse described in (2) above, and is provided on each of the drive side and the driven side. The parts are connected via a shear bolt that is the mechanical fuse.

  Since the mechanical fuse according to the present invention is made of a titanium alloy and has a fatigue limit ratio of 0.7 or more, even if the load fluctuates somewhat, it can be used stably for a long time without breaking.

[Embodiment 1]
The mechanical fuse is installed between the drive side and the driven side (for example, the drive shaft and the driven shaft) in various power transmission systems. In this embodiment, the mechanical fuse is used as a power transmission system in rolling equipment. I will explain.
In addition, as a form of the mechanical fuse, there are a shear bolt, a shear pin, a shear plate, and the like. In this embodiment, a shear bolt will be described as an example.

FIG. 1 is an explanatory diagram for explaining an outline of a power transmission system of a rolling facility provided with a mechanical fuse according to an embodiment of the present invention.
The power transmission system of the rolling equipment includes a motor 1 as a driving device, a speed reducer 3 connected to the rotation shaft of the motor 1, a lead spindle 7 connected at one end to the output shaft of the speed reducer 3 via a joint member 5, A pinion stand 9 connected to the other end of the lead spindle 7, a universal joint spindle 11 provided on the output shaft side of the pinion stand 9, and a work roll 13 connected to the universal joint spindle 11 are provided.
The shear bolt 19 is installed as a connecting member that connects the flange portion 15 of the joint member 5 connected to the output shaft of the speed reducer 3 and the flange portion 17 of the lead spindle 7 (see FIG. 2 described later).

2 is an enlarged cross-sectional view of a portion A surrounded by a square in FIG. 1, FIG. 3 is a cross-sectional view taken along line AA in FIG. 2, and FIG. 4 is a cross-sectional view taken along line BB in FIG. Hereinafter, the structure of the connecting portion including the shear bolt 19 according to the present embodiment will be described with reference to FIGS.
The structure of the connecting portion according to the present embodiment includes a joint member 5 having a flange portion 15, a lead spindle 7 having a flange portion 17 in contact with the flange portion 15, and eight shear bolts inserted between the flanges. 19, a fall prevention plate 21 attached to the joint member 5, a presser bolt 23 that attaches the fall prevention plate 21 to the joint member 5, and a positioning pin 25 that determines the position of the fall prevention plate 21 are constituent members.
Hereinafter, each component will be described in detail.

<Fitting member>
The joint member 5 is formed of a cylindrical body having a gear 27 formed on the inner surface thereof, and has a flange portion 15 for connecting to the joint member 5 at one end thereof. An output shaft 29 of the speed reducer 3 is inserted in the cylinder. A plurality (24 in this example) of bolt holes 31 are formed in the flange portion 15.

<Lead spindle>
The lead spindle 7 is formed of a cylindrical body, and a flange portion 17 connected to a flange portion 15 of the joint member 5 via a shear bolt 19 is formed at an end portion. In the flange portion 17, 24 bolt holes 32 are formed as in the flange portion 15 of the joint member 5.

<Sherbolt>
The shear bolt 19 is inserted through the bolt holes 31 and 32 of the flange portion 15 of the joint member 5 and the flange portion 17 of the lead spindle 7 to connect the two.
5 is a cross-sectional view taken along the line CC in FIG. As shown in FIG. 5, the shear bolt 19 is composed of a hexagonal bolt, and a notch 33 having a narrow groove shape is formed in the circumferential direction at the axial center of the main body. When the shear bolt 19 is installed, the notch 33 coincides with the contact surface of the flange portions 15 and 17.

The shear bolt 19 is made of a titanium alloy, and its fatigue limit ratio is 0.9.
Table 1 shows an example of chemical components of a titanium alloy that is a material of the shear bolt 19. The shear bolt 19 is formed by machining after titanium forging shown in Table 1 is hot forged at a heating temperature of 850 ° C. and annealed at 720 ° C.

FIG. 6 is a graph showing the fatigue characteristics of the titanium alloy according to the present embodiment, where the vertical axis indicates the maximum stress and the horizontal axis indicates the number of repetitions.
The fatigue characteristics were evaluated by the method of JIS Z2274, and the fatigue limit ratio was determined from the fatigue limit and the tensile strength.
As shown in FIG. 6, the fatigue limit ratio of the titanium alloy that is the material of the shear bolt 19 of the present embodiment is 0.9. FIG. 7 is a diagram comparing the fatigue limit ratios of the titanium alloy of the present embodiment and the general steel material (SCM440). As shown in FIG. 7, the fatigue limit ratio of the titanium alloy of the present embodiment is extremely large compared to general steel materials, which means that it will not break even if fluctuating torque acts after long-term use. This means that stable use is possible.

<Fall prevention plate>
The fall prevention plate 21 is a member for preventing the driven-side joint member 5 from falling when the shear bolt 19 is broken and the connection by the shear bolt 19 is broken.
The fall prevention plate 21 includes an attachment portion 35 made of an arcuate plate material, and a support portion 37 formed by bending the outer periphery of the attachment portion 35 in a direction perpendicular to the attachment portion 35. The mounting portion 35 is provided with three bolt holes. A presser bolt 23 for attaching the fall prevention plate 21 to the joint member 5 is inserted into the bolt holes at both ends, and the fall is prevented in the middle bolt hole. Positioning pins 25 for temporarily fixing the plate 21 to the joint member 5 are inserted.

The fall prevention plate 21 is configured such that the support portion 37 supports the flange portion 17 of the lead spindle 7 in the installed state.
In this example, four drop prevention plates 21 are provided, but the number is not limited.

<Presser bolt>
The presser bolt 23 is a bolt for fixing the fall prevention plate 21 to the joint member 5, and is set to a length that does not extend beyond the flange portion 15 of the joint member 5 in the attached state, as shown in FIG. 2. ing.

<Positioning pin>
The positioning pin 25 is a member for temporarily fixing the fall prevention plate 21 to the joint member 5, and is set to a length that does not extend beyond the flange portion 15 of the joint member 5 in the mounted state, similarly to the presser bolt 23. ing.

The operation of the drive system having the structure of the connecting portion configured as described above will be described.
In a normal use state, the driving force of the motor 1 is transmitted to the work roll 13 via the speed reducer 3, the shear bolt 19, the lead spindle 7, the pinion stand 9 and the universal spindle 11. At that time, the fatigue limit ratio of the shear bolt 19 is 0.9, and its value is very high compared to the conventional one, so even if there is some torque fluctuation exceeding the steady torque in the long-term use state, No breakage occurs unless the torque exceeds 90% of the breakage torque.
Since it is usually not considered that the fluctuating torque exceeds 90% of the breaking torque, the shear bolt 19 can be used semipermanently unless the breaking torque acts.

This is compared to the fact that the shear limit ratio of the shear bolt 19 made of a normal iron-based metal is about 0.3 to 0.5 and breaks when it exceeds 30% to 50% of the breaking torque in a long-term use state. Then, such a breakage disappears, and the effect is very large considering the damage of the equipment and the like. For example, as shown in the present embodiment, in a power transmission system in rolling equipment, if the shear bolt 19 is broken due to torque fluctuation, the steel plate being rolled becomes unusable as a product, and the damage is significant. become.
In this respect, according to the present embodiment, such a situation does not occur, so that the equipment can be used stably, and the effect is great.

  Further, even if it is used for a long time, it will not break unless 90% of the torque is applied to the breaking torque, so that it can be used for power transmission of a drive system having a large torque fluctuation in a normal use state. . For this reason, the object apparatus which can be used increases and it can be used for various uses.

As described above, in this embodiment, a shear bolt made of a titanium alloy and having a fatigue limit ratio of 0.9 is used. It can be used stably.
It can also be used for power transmission systems with large torque fluctuations.

  In the above embodiment, the shear bolt is taken as an example of the mechanical fuse, but the present invention is not limited to this, and is formed of a titanium alloy having a fatigue limit ratio of 0.7 or more. For example, shear pins and shear plates are also included.

It is explanatory drawing explaining the outline | summary of the power transmission system of the rolling installation which installed the mechanical fuse which concerns on one embodiment of this invention. It is an axial sectional view of the connecting part in FIG. It is arrow AA sectional drawing of FIG. It is arrow BB sectional drawing of FIG. FIG. 4 is a sectional view taken along the line CC in FIG. 3. It is the graph which showed the fatigue characteristic of the titanium alloy which concerns on this Embodiment. It is a graph which shows the comparison of the fatigue characteristic of the titanium alloy which concerns on this Embodiment, and the fatigue characteristic of a general iron-type material. It is explanatory drawing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor 3 Reduction gear 5 Joint member 7 Lead spindle 9 Pinion stand 11 Universal joint spindle 13 Work roll 15, 17 Flange part 19 Shear bolt 21 Fall prevention plate

Claims (3)

A mechanical fuse made of a titanium alloy and having a fatigue limit ratio of 0.7 or more. The mechanical fuse according to claim 1, wherein the mechanical fuse is a shear bolt installed in a connecting portion provided in a power transmission system. It is the connection structure of the power transmission system which has the mechanical fuse of Claim 2, Comprising: The flange part provided in each of a drive side and a driven side is connected via the shear bolt which is the said mechanical fuse. Power transmission system connection structure characterized by

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