JPH0212354Y2 - - Google Patents

Description

[Detailed description of the invention] [Purpose of the invention] 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.

Normally, the seat ring and the driven ring, which are the sliding members of a mechanical seal, 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 structural countermeasures for 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.
A configuration in which an external actuator that controls the surface pressure is driven based on information from the sensor is conceivable, but this is not only expensive but also increases the size of the device, making it impractical. Ta.

In view of the above points, the present invention has been made with the aim of obtaining the same effect as the automatic surface pressure control mechanism using a combination of the temperature sensor and actuator using a shape memory alloy.

[Structure of the idea]

To achieve this objective, the present invention uses a spring made of a shape memory alloy and a spring whose one end is in constant pressure contact with the non-sliding surface side of the driven ring as an elastic means for pressing the driven ring toward the seat ring. shape memory treatment in two directions, such that it expands under low temperature conditions and one end presses against the non-sliding surface side of the driven ring, and contracts under high temperature conditions and its free length is equal to or less than the installation length under low temperature conditions. These springs are arranged alternately in the circumferential direction.

Shape memory alloys such as TiNi alloys have different crystal phases above and below a certain transition (transformation) temperature, and the transition proceeds by non-diffusion martensitic transformation. Among these types of alloys, those with unidirectional shape memory memorize a certain shape and then deform it, the deformation is canceled by simply heating it above the transition temperature, and the memory is restored. It returns to its original shape, but
Even if the temperature is lowered to below the transition temperature again, the shape of the deformed state will not be achieved. On the other hand, those with bidirectional (omnidirectional) shape memory characteristics,
The shape can be memorized in the flow temperature regions on the high temperature side and the low temperature side of the transition temperature, and reversible repeatable operation characteristics in two directions can be obtained. Note that the transition temperature of the shape memory alloy can be adjusted by various additive elements.

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 presses the driven ring against the seat ring together with the spring that is always in pressure contact with the non-sliding surface side of the driven ring. However, when the ambient temperature becomes high, the free length of the shape memory alloy spring will change when installed under low temperature conditions. Since the driven ring is compressed to a length smaller than the length of the driven ring, the driven ring is pressed only by the spring that is always in pressure contact with the non-sliding surface side of the driven ring. Therefore, on the sliding surface of the driven ring, undulations that form liquid pools are generated due to the decrease in surface pressure in the area corresponding to the shape memory alloy spring, and the lubricity between the sliding surface and the seat ring is significantly improved. , the amount of heat generated by sliding is reduced and the heat is efficiently removed. When the ambient temperature drops to the low temperature range, the shape memory alloy spring expands and comes into pressure contact with the driven ring again, returning the sliding surface pressure to its normal state.

〔Example〕

Hereinafter, a preferred embodiment of the present invention will be described based on FIGS. 1 and 2.

11 is a non-rotating seat ring that is airtightly supported and fixed on the inner periphery of the housing 12 via an O-ring 13; 14 is a non-rotating seat ring that is airtightly supported and fixed on the outer periphery of a rotating shaft 15 that is loosely inserted through the housing 12 via an O-ring 16; Shape-memory alloy coil springs 18a are held by collars 17 which are externally inserted into the stepped portion of the rotating shaft 15, and are alternately and equidistantly arranged in the circumferential direction. The driven member is elastically biased in the axial direction by metal coil springs 18b (see FIG. 3), rotates together with the rotating shaft 15 by transmitting torque through the knock pins 19, and slides into the seat ring 11. It's a ring.

Under normal low-temperature conditions, the coil spring 18a made of a shape memory alloy such as a TiNi-based alloy has one end located on the rear surface opposite to the sliding surface of the driven ring 14.
4'', and under high temperature conditions exceeding the transition temperature, its free length is equal to or less than the installation length l (distance between the back surface of driven ring 14 and the contact portion with collar 17) under low temperature conditions. Processing is being done.

According to the above configuration, at low temperatures below the transition temperature, the shape memory alloy coil spring 18a and the general metal coil spring 18b have the same spring constant, but the sliding between the seat ring 11 and the driven ring 14 When the shape-memory alloy coil spring 18a transforms and contracts when it reaches a high temperature state that exceeds the transition temperature due to heat generation due to movement, it no longer exerts a spring action on the driven ring 14, so that the sliding of both rings 11 and 14 is prevented. The surface pressure of surfaces 11' and 14' is reduced as a whole. Also, of the sliding surface 14' of the driven ring 14, the metal coil spring 1
A relatively large surface pressure is maintained near the portion 14'b corresponding to the shape memory alloy coil spring 18a, while the portion 14'a corresponding to the shape memory alloy coil spring 18a
Since the surface pressure on the seat ring 11 is decreasing, slight waviness occurs in the sliding surface 14' in the circumferential direction as shown by the broken line in FIG. An oil pool is formed between the two parts and the lubrication condition improves, and the amount of heat generated by sliding decreases. Note that when the temperature reaches a low temperature below the transition temperature due to a decrease in calorific value, the shape memory alloy coil spring 18a expands again, and both rings 11,
14 returns to its original sliding state.

[Effect of idea]

As is clear from the above explanation, the surface pressure automatic control type mechanical seal of the present invention uses springs that have a constant biasing force and shape memory alloy springs arranged alternately in the circumferential direction as means for elastically biasing the driven ring. When the ambient temperature rises due to dynamic heat generation, the load on the shape memory alloy spring is released, the surface pressure on the sliding surface automatically decreases, and undulations that become liquid pools are formed on the sliding surface. Since the structure is designed to increase lubricity, it is possible to prevent wear and tear such as acceleration of wear due to heat on the sliding surfaces, generation of thermal cracks, seizure between sliding surfaces, and foaming phenomena, which can prevent equipment from increasing in size. It has the feature of being able to obtain the same effect as an automatic surface pressure control mechanism using a temperature detection sensor and actuator without any noise.
Its practical value is extremely high.

[Brief explanation of drawings]

The drawings show an embodiment of the automatic surface pressure control type mechanical seal according to the present invention, and FIG. 1 is a sectional view of the main part, and FIG. 2 is an explanatory diagram of the arrangement of a coil spring. 11... Seat ring, 11', 14'... Sliding surface, 12... Housing, 14... Driven ring,
15... Rotating shaft, 18a... Shape memory alloy coil spring, 18b... General metal 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 loosely passed 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 spring whose one end is always in pressure contact with the non-sliding surface side of the driven ring, and a spring made of a shape memory alloy that expands under low temperature conditions and whose one end is in pressure contact with the non-sliding surface of the driven ring. Springs that are pressed against the non-sliding surface side and undergo shape memory treatment in two directions that contract under high temperature conditions and have a free length equal to or less than the installation length under low temperature conditions are arranged alternately in the circumferential direction. A mechanical seal with automatic surface pressure control.