JPH0241392Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to shaft sealing technology for the rotating shaft of equipment.
More specifically, it is an object of the present invention to provide a mechanical seal in which sliding surface pressure is automatically controlled in accordance with temperature changes due to sliding heat generation and the like.

[Conventional technology]

BACKGROUND ART Conventionally, a seat ring and a driven ring, which are sliding members of a mechanical seal, usually generate heat due to sliding motion between the two, and their temperature increases. When both rings become hot, wear and tear such as accelerated wear on the sliding surfaces, occurrence of thermal cracking due to thermal imbalance, fusion between the sliding surfaces, and foaming inside the sliding material is likely to occur. It is no exaggeration to say that most of the conventional preventive measures against this problem belong to measures to reduce temperature rise through flushing, etc., use of heat-resistant materials, and improvement of thermal shock resistance. As a technology to control the sliding surface pressure as the temperature of the material increases, for example, a temperature detection sensor is built into the mechanical seal, and an external actuator that controls the surface pressure is driven based on information from the sensor. However, it is not only expensive but also increases the size of the device, making it difficult to put it into practical use.

[The problem that the idea aims to solve]

In view of the above points, the present invention has a simple structure and, like the automatic surface pressure control mechanism using a combination of a temperature sensor and an actuator, reduces surface pressure at high temperatures to prevent overheating. This was done as a challenge.

[Means to solve the problem]

In order to solve the above-mentioned problems, the surface pressure automatic control type mechanical seal according to the present invention uses an elastic means that biases a non-rotating driven ring toward a rotating seat ring to seal between the housing and the driven ring. A metal bellows is attached and constantly energizes the driven ring, and the inner circumference of the bellows is made of a shape memory alloy, which expands under low temperature conditions and presses both ends to the end fittings at both ends of the bellows. A spring is provided with shape memory processing in two directions so that the free length thereof is approximately equal to the distance between the facing surfaces of both end fittings when contracted under certain conditions.

[Effect]

In the present invention, the shape memory alloy spring has shape memory in two directions, and if the ambient temperature, which is heated due to the sliding heat generation between the driven ring and the seat ring, is within a certain low temperature range, it will retain its shape. The memory alloy spring, together with the metal bellows, presses the driven ring against the seat ring through end fitting, but when the ambient temperature rises above a predetermined value, the shape memory alloy spring's free length extends to both ends of the bellows. Since it contracts to a length approximately equal to the distance between the facing surfaces of the fitting, the pressure on the driven ring is performed only by the spring force of the bellows, and therefore the sliding surface pressure between the driven ring and the seat ring is reduced. The amount of heat generated by sliding decreases. When the ambient temperature drops to the low temperature range, the shape memory alloy spring expands and comes into pressure contact with both end fittings again, returning the sliding surface pressure to its normal state.

〔Example〕

Hereinafter, the present invention will be explained with reference to an illustrated embodiment.

In the figure, 1 is a seat ring that is fitted and fixed to the outer circumferential step 2' of a rotating shaft 2 loosely inserted into the inner periphery of the housing, and rotates together with the rotating shaft 2; 3 is a seat ring that is attached to the inner periphery of the housing 4 via a metal bellows 7 It is a non-rotating driven ring that is airtightly and elastically supported on the The metal bellows 7 airtightly fits and supports the driven ring 3 within the inner circumferential step 5' of the end fitting 5 at its front end, and also fits and supports the driven ring 3 into the housing 4 at the end fitting 6 at its rear end. It is airtightly fitted and fixed to the circumferential surface, and is appropriately compressed in the axial direction to constantly keep the driven ring 3 in contact with the seat ring 1.
It presses and urges.

A coil spring 8 made of a shape memory alloy is attached to the inner periphery of the metal bellows 7, and both ends thereof are in contact with the opposing end surfaces of the end fittings 5 and 6. This shape memory alloy coil spring 8
under low temperature conditions, it expands and comes into pressure contact with both end fittings 5, 6, and under high temperature conditions exceeding a predetermined temperature, it contracts and its free length becomes the distance l between the opposing surfaces of both end fittings 5, 6. Shape memory processing is performed in two directions that are approximately equivalent to .

According to this embodiment, in a low temperature atmosphere below the transition temperature of the shape memory alloy constituting the coil spring 8, the free length of the coil spring 8 is large and the coil spring 8 is in pressure contact with both end fittings 5, 6. The driven ring 3 is pressed against the seat ring 1 by the spring force of both the metal bellows 7 and the coil spring 8.
When a high-temperature atmosphere exceeding the transition temperature is brought about due to the heat generated by sliding with the coil spring 8, the free length of the coil spring 8 is approximately equal to the distance l between the opposing surfaces of the end fittings 5 and 6 due to the phase transformation of the shape memory alloy. Since the driven ring 3 shrinks to the same length and has almost no spring action on the driven ring 3, the driven ring 3
is pressed against the seat ring 1 only by the metal bellows 7. Therefore, both rings 1,
The sliding surface pressure on sliding surfaces 1' and 3' of No. 3 decreases,
A thick lubricating liquid film is formed and the amount of heat generated is also reduced.

In addition, the shape memory alloy coil spring 8 is
As mentioned above, shape memory is performed in two directions, so if the temperature becomes lower than the transition temperature due to a decrease in the amount of heat generated by sliding, the shape memory alloy coil spring 8 will revert to the shape on the low temperature side. It transforms and expands, and the spring force on the driven ring 3 is restored, so the sliding surface pressure increases and sealing performance is improved.

[Effect of idea]

As described above, according to the present invention, when the temperature rise due to sliding heat is within the normal range, both the metal bellows and the shape memory alloy spring press the driven ring against the seat ring, so good sealing performance is achieved. If the temperature rise exceeds the normal range, the load on the shape memory alloy spring is automatically reduced and only the metal bellows presses the driven ring, reducing the amount of heat generated by sliding. It is possible to prevent the acceleration of wear due to overheating of the sliding surfaces, occurrence of thermal cracks, seizure between sliding surfaces, and foaming phenomena, etc., without increasing the size and complexity of the equipment. This provides the same effect as using an automatic surface pressure control mechanism using a temperature detection sensor and actuator.

[Brief explanation of the drawing]

The drawing is a half-cut sectional view showing an embodiment of the automatic surface pressure control type mechanical seal of the present invention. 1...Seat ring, 1', 3'...Sliding surface, 2
... Rotating shaft, 3 ... Driven ring, 4 ... Housing, 7 ... Metal bellows, 8 ... Shape memory alloy coil spring.

Claims (1)

[Scope of utility model registration request] A mechanical seal that seals the fluid inside the device by a seat ring and a driven ring that are placed between a housing and a rotating shaft inserted through the inner periphery of the housing, and that slide and rotate in close contact with each other. The elastic means for biasing toward the seat ring includes a metal bellows that is sealed between the housing and the non-rotating driven ring and constantly biases the driven ring, and a shape memory alloy metal bellows on the inner periphery of the bellows. Under low temperature conditions, it expands and both ends press into contact with the end fittings at both ends of the bellows, and under high temperature conditions exceeding a predetermined temperature, it contracts and its free length becomes approximately equal to the distance between the opposing surfaces of both end fittings. A mechanical seal with automatic surface pressure control, characterized by a spring that has been subjected to shape memory treatment in two directions.