JPH09287406A - Seal structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of an excessive contact force by moving an end of a seal with a relatively weak force in the case where the end of the seal contacts the shaft in a seal structure of a rotation shaft like, fir example, a steam turbine which has an inside operation fluid, and is applied to a rotation machine which required the seal. SOLUTION: A seal end plate 1 wherein an end is located opposite to an external circumference of the rotation shaft with a clearance is sandwiched between two seal pressing plates 2 and 2, and the seal end plate 1 is held with a pressing force generated with the elastic distortion, and a movement clearance 4 is provided on a seal pressure plate 2 so that the seal end plate 1 can be freely deviated against an excess force at the time of contacting the shaft.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary shaft seal structure applied to a rotary machine, such as a steam turbine, which has an internal working fluid and needs the seal.

[0002]

2. Description of the Related Art A conventional seal structure is shown in FIGS.
5 is a sectional view of the seal structure, FIG. 6 is an axial view showing the conventional seal tip structure, and FIG. 7 is a sectional view showing the conventional seal tip structure.

In these figures, the seal 1 has a half-split structure as shown in FIG. 6, and is embedded in a seal ring 7 shown in FIG.

The seal ring 7 is also attached to the casing 8 having a half-split structure.

Reference numeral 9 denotes a rotary shaft of a rotary machine such as a steam turbine, and the seal 1 is arranged on the outer periphery of the rotary shaft 9 so as to face the rotary shaft 9 and to reduce the clearance between the seal 1 and the rotary machine 9 as much as possible. The leakage of the working fluid of is prevented.

[0006]

However, since the working fluid often has heat, the casing 8 of the rotating machine is thermally deformed.

Further, the rotary shaft 9 is also deformed by the force from the working fluid.

For this reason, if the clearance between the seal 1 and the rotary shaft 9 is set to be narrow, the seal 1 and the rotary shaft 9 contact each other, and the rotary shaft 9 is further deformed by the contact, which causes a problem that a very large vibration is generated.

The pressing force becomes excessive when the seal and the rotating shaft come into contact with each other.

In order to solve the above-mentioned problems of the prior art, the present invention provides the pressing plate with an air gap which can be freely displaced against an excessive force such as when the seal tip plate comes into contact with the rotating shaft, and thereby the excessive contact is caused. It is intended to provide a new seal structure capable of preventing the generation of force.

[0011]

As a structure for achieving the above object, the seal structure of the present invention is a seal structure for preventing the leakage of working steam to the outside from the circumference of a rotating shaft in a rotating machine such as a steam turbine. In, the tip of the seal is sandwiched between two seal pressing plates, the tips of which are opposed to each other with a clearance on the outer circumference of the rotary shaft, and the seal tip plate is held by the pressing force generated by elastic deformation of the seal pressing plates. It is characterized in that the seal pressing plate is provided with a gap that can be freely displaced with respect to an excessive force when the seal tip plate comes into contact with the shaft.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a seal according to a first embodiment of the present invention. In the case of this example, the seal tip plate 1 is sandwiched between the seal pressing plates 2 manufactured by scraping, and the clearance between the pressing plates 2 is slightly smaller than the thickness of the seal tip plate 1.

Therefore, the seal tip plate 1 is pressed by the seal pressing plate 2 to maintain its position by the frictional force.

A moving clearance 4 for the seal tip plate 1 is provided at the rear of the seal tip plate 1, and the seal tip plate 1 can be moved through the clearance 4.

When the seal tip plate 1 comes into contact with the rotary shaft, the reaction force is applied to the seal tip plate, and the reaction force is greater than the frictional force acting on the seal tip plate pressed by the elasticity of the plates sandwiched between the two plates. As the force increases, the seal tip plate moves. This movement eliminates the generation of excessive contact force.

Next, a second embodiment of the present invention will be described with reference to FIG. In the case of this example, the seal pressing plate 2 is separately manufactured, and the intermediate plate 3 having a slightly smaller thickness than the seal tip plate 1 is sandwiched between the seal pressing plates 2 and spot-welded. It has the same function as that of the first embodiment.

FIG. 3 shows a third embodiment of the present invention.
In the case of this example, the vicinity of the tip of the pressing plate 2 of the second example is deformed so that the function as a spring becomes more reliable. This is the pressing plate tip bent portion 5. The case of this example also has the same functions as those of the above examples.

Next, a fourth embodiment of the present invention will be described with reference to FIG. 4, which is an axial view of the seal. In any of the first to third examples, the seal tip plate 1 has a moving clearance 4
However, if the seal gap is large even after the contact between the seal tip plate 1 and the rotating shaft 9 is lost, the leakage of the internal working fluid of the rotating machine is also large. In the case of the example, a spring 6 is installed in the seal moving clearance 4 in order to have a function to restore the proper amount.

[0020]

As described above, according to the seal structure of the present invention, when the tip of the seal comes into contact with the shaft, the tip of the seal moves with a comparatively weak force, and an excessive contact force is not generated. Prevent excessive heat generation.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a seal according to a first exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view of a seal according to a second exemplary embodiment of the present invention.

FIG. 3 is a sectional view of a seal according to a third exemplary embodiment of the present invention.

FIG. 4 is an axial view of a seal according to a fourth exemplary embodiment of the present invention.

FIG. 5 is a sectional view showing a conventional sealing structure.

FIG. 6 is an axial view showing a conventional seal tip structure.

FIG. 7 is a cross-sectional view showing a conventional seal tip structure.

[Explanation of symbols]

 1 Seal tip plate 2 Seal pressing plate 3 Intermediate plate 4 Moving clearance 5 Pressing plate tip bent part 6 Spring

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryosuke Maruta 1-1 1-1 Atsunoura-machi, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard Co., Ltd.

Claims (1)

[Claims] 1. A seal structure for preventing leakage of working steam from the circumference of a rotary shaft in a rotary machine such as a steam turbine to the outside, wherein a seal tip plate is disposed opposite to the outer circumference of the rotary shaft with a gap therebetween. It is sandwiched between two seal pressing plates, and the seal tip plate is held by the pressing force generated by elastic deformation of the seal pressing plates, and freely displaced with respect to an excessive force such as when the seal tip plate contacts the shaft. A seal structure in which a gap that can be formed is provided in the seal pressing plate.