JPS5912902B2 - mechanical seal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a mechanical seal that prevents fluid from leaking from a shaft that rotates once.

Normally, mechanical seals have a fixed seat ring through which the rotating shaft is inserted, and a driven member that rotates with the rotating shaft slides against it to prevent fluid from leaking from the outer circumferential side to the inner circumferential side of the sliding surface. It has a configuration that prevents

Therefore, in order to improve the sealing effect of the sliding surface, the conventional method is to increase the pressure per unit area of the sliding surface by increasing the pressing force of the driven ring against the seat ring.
Alternatively, countermeasures have been taken, such as selecting materials for both rings that slide into contact to form a robust sealing surface.

However, surface roughness that occurs in sliding contact parts and deformation over time can be avoided after all, especially in harsh conditions where vibrations and temperature changes are applied, such as in mechanical seals applied to compressors of automobile coolers, etc. When used under the hood, fluid leakage is significant and a fundamental improvement in the sealing means has been desired.

Therefore, as a fundamental improvement to this sealing means, the present inventors have already invented a mechanical seal in which a dead-end thread groove with a closed outer end is formed on at least one of the sliding surfaces of the seat ring and the driven ring. A patent application has been filed for this (see Japanese Patent Application No. 52-41838 to Japanese Patent Application Laid-open No. 53-126462, etc.).

The invention according to the above patent application focuses on the fact that radial pressure that can counter leakage flow can be applied to the fluid interposed in the minute gap between the sliding surfaces by using the relative rotation of the sliding surfaces. , characterized in that a thread groove of a desired shape with a closed outer end is provided on at least one of the sliding contact surfaces, and the pump action of the thread groove with the rotation of the driven ring or the thread groove on the driven ring side When grooves are formed, it is believed that leakage can be prevented by the centrifugal force acting on the fluid that enters the thread grooves.

It has been confirmed that a mechanical seal with thread grooves formed in it exhibits an extremely excellent sealing effect in the rotation range above a certain rotation speed of the driven ring. It has become clear that there is a problem with the sealing performance below.

The cause of this was initially thought to be that the effective seal length of the sliding contact area was reduced in the area where the thread grooves existed, but it was also thought that foreign matter could enter between the sliding surfaces caused by the thread grooves, or that this could be caused by this. It has now been revealed that one of the causes is the roughness of the sliding contact surface, or uneven thermal deformation of the driven ring due to the presence of thread grooves.

In other words, the thread grooves draw in abrasion powder generated by sliding contact with the mating material, or dust as they rotate, so these fine powders roughen the sliding surface and create gaps.

In addition, when the driven ring is thermally deformed due to sliding contact, there is a difference in the amount of deformation between the thread groove portion and the flat portion, causing unevenness.
As a result of this unevenness spreading over the entire sliding surface of the driven ring, the sealing performance deteriorates, especially immediately after the driven ring stops.

The present invention has been made based on the above knowledge, and in order to enhance the sealing effect especially under dusty conditions, the present invention has been developed between an inner circumferential groove portion having thread grooves formed on the sliding surface and a flat outer circumferential land portion. ,
It is characterized by an annular groove that defines the two.
Fine particles such as abrasion particles and dust are introduced into this annular groove to eliminate wear and gaps on the sliding surface, and the annular groove prevents uneven thermal deformation of the inner groove from reaching the outer land. This improves the sealing effect under conditions where there are many conditions.

Hereinafter, the present invention will be described in detail with reference to illustrated examples.

FIG. 1 shows a compressor for an automobile cooler as an example of a rotary shaft with such a mechanical seal, where 1 is the rotary shaft of the compressor, and 2 is a rotary shaft 1 whose rotation is restrained by a key 8. 4 is a rotating body rotatable with respect to the casing 5;
When the excitation coil 6 inserted into the space within the rotary body 4 is energized, the rotary body 4 and the coupling body 2 are integrated, and the rotating shaft 1 rotates together with the rotary body 4.

7 is a mechanical seal part that prevents the fluid in the compressor part 8 from leaking toward the rotating shaft 1 side. This sliding contact prevents oil and gas from leaking from the gap between the seat ring 9 and the rotating shaft 1.

11 is a gasket that is in close contact with the rotating shaft 1, 12 is its holder,
13 is a knock ring, and 14 is a spring that applies a pressing force to the driven ring 10 toward the seat ring 9 side.

FIG. 2 is an enlarged view of the mechanical seal portion 7. The knock ring 13 in this figure is constructed as a thick-walled molded product, but the knock ring 13 shown in FIG. 3 is formed by press working. The 13a portion is spot welded to reduce the weight and simplify the overall product.

FIGS. 4A and 4B are a side view and a cross-sectional view of another modified example of the mechanical seal part 7, in which the outer peripheral part of the receiver 12 is formed into a gear shape, and the parts corresponding to the teeth are While the hole is provided, the knock ring 13 is provided with a plurality of claw-like pieces 13b bent in the axial direction.
The claw-like piece 13b is inserted through the hole to prevent the claw-like piece 13b from expanding outward, and the tip end 13c of the claw-like piece 13b is brought into contact with the groove portion of the driven ring 10 to prevent the driven ring 10 from rotating. That's what I do.

FIG. 5 shows the driven ring 10 used in the mechanical seal as described above, in which a plurality of thread grooves 16 are bored in the inner circumferential groove 15 of the sliding surface 10a. An annular groove 1 is formed between the land portion 17 having a flat outer circumference.
8 is drilled.

In order to ensure the radial length of the outer peripheral land portion 17, the annular groove 18 is preferably provided inside the radial intermediate position of the sliding surface 10a.

The mechanism by which the thread groove 16 exerts a sealing effect when the driven ring 10 rotates is that the thread groove 16 scrapes off fluid that attempts to leak through the outer peripheral land portion 17.
crepe), this scraped up fluid flows into the yarn groove 16.
Because the fluid pressure generated by the centrifugal force acting on the fluid inside returns it to the outer peripheral land portion 17 (pump action)
It is believed that.

Therefore, from the point of view of introducing external fluid into the yarn groove 16, it is preferable that the inner end of the yarn groove 16 be opened toward the inner peripheral side of the sliding surface as shown in FIGS. 5A and 5B.

However, even if this is a closed dead-end groove as shown in C and D of the figure, a certain sealing effect can be obtained.

Regarding the inclination angle of the thread groove 16, it is preferable to incline it toward the rear in the rotational movement direction of the sliding surface as shown in FIG. 5, in order to efficiently obtain the above-mentioned pumping action.

However, according to experiments, there is a degree of freedom regarding this angle of inclination, and there is no practical problem even if it is set in the radial direction, or conversely, it is tilted at a certain angle (for example, about 5 degrees) from the radial direction toward the front in the rotational movement direction. A sealing effect was obtained.

This is considered to be because, up to a certain limit angle of inclination of the yarn groove 16, the centrifugal force acting on the fluid in this groove generates a radial pressure capable of counteracting the leakage flow from the sliding surface.

In addition, the width of these thread grooves 16 is about 0.2 to 0.6 mm to obtain a nearly satisfactory sealing effect, and the depth is better to be shallow enough to avoid being buried by wear particles during rotation. According to the paper, a tendency to reduce the number of seals was observed when this distance was reduced to 0.05 m at a time.

Of course, these values may change depending on the number of yarn grooves to be set and the width of the sliding contact area.

The purpose of the annular groove 18 is to retain the dust or abrasion powder drawn in by the thread groove 16 as described above, and to cut off the influence of thermal deformation between the inner circumferential groove part 15 and the outer circumferential land part 17 of the sliding surface 10A. It was drilled in

That is, the dust or abrasion powder reaches the annular groove 18 together with the fluid flow caused by the pump action of the thread groove 16, where part or all of it is retained.

As a result, the amount of these fine particles present on the sliding surfaces is reduced, resulting in less wear and roughness of the surfaces, and at the same time, an increase in the gap between the sliding surfaces due to the presence of fine particles is prevented.

Regarding thermal deformation, the inner circumferential groove portion 15 is
Since the amount of thermal deformation is different between the part and the flat part where this does not exist, unevenness, that is, wave-shaped deformation occurs in the circumferential direction, but the annular groove 18 acts to prevent this deformation from spreading to the outer peripheral land part 17. .

That is, even if the inner circumferential groove portion 15 is deformed into a waveform in the circumferential direction, the outer circumferential land portion 17 remains flat.

Therefore, for these reasons, the sealing effect is particularly improved under dusty conditions.

The width and depth of this annular groove 180 may be set to an appropriate size that does not cause the annular groove to be filled with fine powder such as abrasion powder.

In addition, when the annular groove 18 and the thread groove 16 communicate with each other as shown in FIGS. 5B and 5D, in order to ensure the pumping effect of the thread groove 16, in other words, to prevent the pressure drop inside the thread groove 16 from occurring. In addition, it is preferable to make the volume of the annular groove 18 as small as possible.

Specifically, the width and/or depth of the annular groove 18 is made smaller than that of the thread groove 16.

Of course, the groove shapes of the thread groove 16 and the annular groove 18 may be V-shaped, U-shaped, square, or the like.

Next, the present invention will be explained in detail based on experimental results.

In this experiment, (A) was used as a driven ring on its sliding surface.
: A type with a thread groove 16 and an annular groove 18 as shown in Fig. 5A (B): A type with only a thread groove C) A type with only two annular grooves (D): A flat type without groove Each of these was installed in a compressor under the following conditions, and the leakage amount of the enclosed lubricating oil was measured.

However, the above-mentioned driven rings A, B, and C. For D, a material mainly composed of carbon was used with a surface roughness of 0.4 seconds or less, and the groove depth was 0.2 to 0.3 mm and the width was 0.3 to 0.4 mm (experimental conditions) Compressor : Swash plate compressor Compressor capacity: 148 cc Oil type, oil amount: Refrigerating machine oil 230 cc Rotation speed: 4000 rpm (during operation) Discharge pressure crab 15 kg/i (during operation) 4 kg/cIit (during stop) Suction pressure crab 2 kg/ cr? t (during operation) 4kg/
ff1 (when stopped) Mating material: Cast iron (equivalent to Fc20, rough surface seat ring) 0.73 or less Sliding speed: 4 m/s (4000 rpm) Seat of driven ring: 5 kg/ffl Pressure force on ring Lubricating method: Enclosed Lubricating oil and gas are supplied to the sliding surface in a mist state.

Clean condition: normal environmental condition Dust condition: cement powder in the amount of 100 g/h 2
Spray on the front of the compressor with a pressure of kg/ffl.

The experimental results are shown in the table below.

The amount of leakage is determined by measuring the amount of leakage during 25 hours of operation of the compressor and the amount of leakage for 25 hours when the compressor is stopped, in both clean and dusty conditions, and then summing the same measurements. The measurement was performed four times to measure the total leakage amount for 100 hours each time.

As shown in the above experimental results, when the surrounding environment changes from a clean state to a dusty state, product A of the present invention has a higher rate of increase in leakage than other driven rings B, C, and D both during rotation and when stopped. is small, and its absolute amount is also small.

As mentioned above, the annular groove 18 retains the dust drawn in by the thread groove 16 during rotation, thereby reducing wear and roughness of the sliding surfaces, and also reducing the gap between the sliding surfaces due to the presence of fine powder. This is thought to be because it effectively prevents the increase in the thickness of the yarn, and also effectively prevents the thermal deformation of the waveform in the yarn groove 16 from spreading to the outer peripheral land.

On the other hand, even if the yarn grooves 16 or the annular grooves 18 are formed, if they are formed alone, the amount of leakage, especially in the dusty state, will be significantly increased compared to the product A of the present invention. It is understood that the excellent effects described above can only be obtained by combining the thread groove 16 and the annular groove 18 as in the present invention.

In the embodiment described above, it has been described that the thread groove 16 and the annular groove 18 are formed only on the sliding surface on the driven ring side, but the above action is achieved by the relative rotation between the driven ring and the seat ring. Therefore, it is obvious that they can be provided on the seat ring side, and it is also possible to provide them on both sliding contact surfaces.

As described above, according to the present invention, the simple structure in which the inner circumferential groove part of the sliding surface in which the yarn groove is bored and the outer circumferential land part are defined by an annular groove allows the driven ring to be easily stopped and rotated. An excellent sealing effect can be achieved with this, and this effect is particularly noticeable under dusty conditions.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view showing an example of a rotating shaft with a mechanical seal, Fig. 2 is an enlarged view of the mechanical seal part in Fig. 1, and Figs. 3 and 4 each show a modification of Fig. 2. Figure 5 A, B, C. D is a plan view showing the driven ring according to the present invention, and FIGS. 6 and 7 are cross-sectional views taken along lines VI-VI and -■ in FIGS. 5A and 5D, respectively. DESCRIPTION OF SYMBOLS 1... Rotating shaft, 9... Seat ring, 10... Driven ring, 10a... Sliding surface, 15... Inner circumferential groove part,
16... Thread groove, 17... Outer peripheral land portion, 18...
- Annular groove.

Claims (1)

[Scope of Claims] 1. A seat ring through which the rotating shaft is inserted to form a fixed side member, and a driven ring that rotates together with the rotating shaft and slides into contact with the seat ring to prevent fluid from leaking toward the rotating shaft. In the mechanical seal, an annular groove dividing the sliding surface of at least one of the seat ring and the driven ring into an outer peripheral land portion and an inner peripheral groove portion is formed, and the sliding contact surface is in sliding contact with the inner peripheral groove portion. A mechanical seal characterized in that a plurality of thread grooves are bored from the inside of the surface toward the annular groove. 2. The mechanical seal according to claim 1, wherein the annular groove and the thread groove are non-communicating. 3 Claims [1] in which the annular groove and the yarn groove are in communication
Mechanical seal described in item 1. 4. The mechanical seal according to claim 3, wherein the width and/or depth of the annular groove is smaller than that of the thread groove. 5. The mechanical seal according to any one of claims 1 to 4, wherein the inner end of the thread groove is open toward the inner peripheral side of the sliding surface. 6. The mechanical seal according to any one of Claims 1 and 5, wherein the thread groove is inclined in the radial direction or rearward in the direction of relative movement of the sliding surfaces.