JP7405722B2 - shaft seal - Google Patents

Description

The present invention relates to a shaft seal for a rotating shaft, and particularly to a shaft seal for a rotating shaft of a scroll compressor for an on-vehicle air conditioner.

A seal member is used in the compressor to prevent leakage of refrigerant and refrigerator oil. For example, in a scroll compressor that includes a compression mechanism that combines a fixed scroll and a movable scroll that rotates relative to the fixed scroll, a shaft seal is attached to a rotating shaft that drives the compression mechanism.

Lip seals such as those disclosed in Patent Documents 1 and 2 have been disclosed as shaft seals. For example, a lip seal disclosed in Patent Document 1 is shown in FIG. As shown in FIG. 6, the lip seal 21 has inner seal portions 25, 26, and 27 that contact the outer circumferential surface of the drive shaft 22 in a cross-sectional view along the axial direction of the drive shaft 22. Furthermore, the lip seal 21 has a first seal lip L1 and a second seal lip L2 in which the inner peripheral seal parts 25 and 26 are located on the inner side in the drive shaft direction of the housing 24 than the fixing parts 28 and 29 to the shaft hole 23 side. The inner circumferential seal portion 27 has a structure including a third seal lip L3 located on the outer side in the drive shaft direction of the housing 24 than the fixing portion 30 to the shaft hole 23 side. Since a space S capable of holding lubricating oil is formed between the second seal lip L2 and the third seal lip L3, the lubricating oil held in this space S causes the second seal lip L2 and the third seal lip to Abrasion of L3 is prevented and sealing performance is ensured. In Patent Document 1, the inclination angle θ of the second seal lip L2 with respect to the outer circumferential surface of the drive shaft 22 is approximately 30°, but the relationship between θ and rotational torque is not studied.

FIG. 7 shows the lip seal of Patent Document 2. As shown in FIG. 7, the lip seal 31 is installed between the housing 32 and the rotating shaft 33, and is formed by the seal lip portion 35 of the first seal element 34 and the seal lip portion 37 of the second seal element 36. The fluid (refrigerant and refrigerating machine oil) in the fluid storage chamber R is prevented from leaking to the low pressure side A. The first seal element 34 is made of synthetic rubber, and the second seal element 36 is made of synthetic resin such as tetrafluoroethylene (PTFE) resin. When the rotating shaft is stationary, the seal lip portion 35 of the first sealing element 34 comes into elastic contact with the rotating shaft 33 to prevent fluid leakage. Further, during rotation, fluid slightly leaking from the first seal element 34 is sealed by the seal lip portion 37 of the second seal element 36. Patent Document 2 does not mention the inclination angle of the first seal element 35 with respect to the outer peripheral surface of the rotating shaft.

Japanese Patent Application Publication No. 2018-17161 Patent No. 2847277

Patent Documents 1 and 2 do not consider how the rotational torque and sealing performance will change when the inclination angle of the seal lip with respect to the outer circumferential surface of the rotating shaft and the length of the seal lip in cross-sectional view are changed. Moreover, the lip seals of Patent Documents 1 and 2 have a complicated shape composed of an annular metal core material and a plurality of seal lips made of resin or rubber, which may result in high cost.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a shaft seal having a substantially U-shaped cross section that can reduce rotational torque and has excellent sealing performance.

The shaft seal of the present invention is an annular shaft seal that tightly seals the sealing fluid on the outer circumferential surface of a rotating shaft, and the gap between the rotating shaft and the housing in which the shaft seal is mounted is reduced by the shaft seal. The shaft seal is divided into a high pressure side and a low pressure side, and the shaft seal is an injection molded body having a substantially U-shaped cross section in the axial direction, and a seal lip portion extending toward the high pressure side and sliding on the rotating shaft; an outer lip portion provided on the outer diameter side of the seal lip portion, the seal lip portion has an inclination angle of 5° to 20° with respect to the outer circumferential surface of the rotating shaft, and the shaft seal has an axial direction. The seal lip portion has a length of 2.0 mm to 6.5 mm when viewed in cross section. The "angle of inclination of the seal lip portion" in the present invention refers to the angle at which the seal lip portion is inclined with respect to the outer circumferential surface of the rotating shaft when the shaft seal is attached to the rotating shaft.

The shaft seal is characterized in that it is made of a resin composition or a thermoplastic elastomer composition.

The shaft seal is used in a scroll compressor equipped with a compression mechanism that combines a fixed scroll and a movable scroll that orbits with respect to the fixed scroll, and the rotating shaft is a rotating shaft that drives the compression mechanism. characterized by something.

The scroll compressor is a scroll compressor for an on-vehicle air conditioner.

The sealing fluid is characterized in that it contains oil.

The shaft seal of the present invention has a substantially U-shaped cross-sectional view in the axial direction, and includes a seal lip portion that extends toward the high pressure side and slides on the rotating shaft, and a seal lip portion that is provided on the outer diameter side of the seal lip portion. Since the seal lip has an inclination angle of 5° to 20° with respect to the outer circumferential surface of the rotating shaft, it is possible to exert an appropriate tension force on the rotating shaft, reduce rotational torque, and Excellent sealing properties. Furthermore, in the axial cross-sectional view of the shaft seal, the seal lip portion has a length of 2.0 mm to 6.5 mm, and since the seal lip portion has a certain length, the tension force of the seal lip portion against the rotating shaft is reduced. It is smaller and contributes further to lower torque.

Since the shaft seal is made of a resin composition or a thermoplastic elastomer composition, it does not require a metal core material, and is highly economical.

FIG. 2 is a diagram showing an example of the shaft seal of the present invention attached to a rotating shaft. FIG. 2 is an enlarged cross-sectional view of the shaft seal of FIG. 1 in a state before installation. FIG. 6 is a diagram showing another example of the shaft seal of the present invention attached to a rotating shaft. FIG. 2 is a schematic cross-sectional view showing a compression mechanism section of a scroll compressor. FIG. 3 is a schematic diagram of a rotational torque measurement test. FIG. 2 is a diagram showing the configuration of a conventional shaft seal. FIG. 2 is a diagram showing the configuration of a conventional shaft seal.

A compressor to which the shaft seal of the present invention is applied will be explained based on FIG. 1. FIG. 1 shows an axial cross-sectional view of a shaft seal mounted on a rotating shaft. As shown in FIG. 1, the shaft seal 1 is an annular member having a substantially U-shaped cross section in the axial direction. The seal also has an outer lip portion 3 provided on the outer diameter side. The sealing lip portion 2 and the outer lip portion 3 each extend from the proximal end portion 4. A concave groove 5 is formed by the seal lip portion 2, the outer lip portion 3, and the base end portion 4. The housing 7 is provided with an insertion hole 7a through which the rotating shaft 6 is inserted, and an annular groove 8 is provided around the insertion hole 7a. The shaft seal 1 is mounted in this annular groove 8, and as the rotating shaft 6 rotates about the axis O, the seal lip portion 2 slides on the rotating shaft 6.

In FIG. 1, the shaft seal 1 is installed in the annular groove 8 such that the seal lip portion 2 and the outer lip portion 3 each extend toward the high pressure side H. In this case, the groove 5 side corresponds to the high pressure side H, and the rear surface 4a side of the base end 4 corresponds to the low pressure side L. In the installed state, the vicinity of the tip of the outer lip 3 of the shaft seal 1 contacts the side wall 8a of the annular groove 8, and the vicinity of the tip of the seal lip 2 contacts the outer peripheral surface of the rotating shaft 6. Further, the back surface 4a of the base end portion 4 is in close contact with the bottom wall 8b of the annular groove 8. On the other hand, spaces are formed between the outer lip portion 3 and the side wall 8a and between the seal lip portion 2 and the rotating shaft 6, respectively.

The present inventors have determined the inclination angle α of the seal lip portion 2 with respect to the outer circumferential surface of the rotating shaft 6 and the lip length L 2 of the seal lip in a cross-sectional view for a shaft seal 1 having a simple structure and a substantially U _- shape. We have discovered that by optimizing it, we can achieve lower torque and lower leakage. Specifically, the shaft seal 1 is characterized in that the inclination angle α of the seal lip portion 2 is 5° to 20°, and the lip length L ₂ of the seal lip portion 2 is 2.0 mm to 6.5 mm. It is said that If the inclination angle α is less than 5°, the seal lip portion 2 and the rotating shaft 6 become close to parallel, and fluid leakage is likely to occur. On the other hand, when the inclination angle α becomes larger than 20°, the tension force of the seal lip portion 2 against the rotating shaft 6 becomes high, and thus the rotational torque becomes large. The angle of inclination α is preferably between 10° and 20°.

Furthermore, if the lip length _L2 is shorter than 2.0 mm, the seal lip portion 2 will be difficult to bend and the tension force will be high, which may increase the rotational torque. On the other hand, as the lip length _L2 becomes longer, the space for incorporating the shaft seal becomes larger, so it is set to 6.5 mm or less. The preferred range of lip length L ₂ is 4.2 mm to 6.5 mm.

Each dimension of the shaft seal 1 will be explained with reference to FIG. 2. FIG. 2 shows the shaft seal in a state (free state) before being attached to the housing. In the shaft seal 1, the seal lip portion 2 and the outer lip portion 3 are formed so as to be inclined in a direction in which the tip portions 2a and 3a are separated from each other. In the present invention, the inner diameter dimension d of the shaft seal 1 refers to the minimum inner diameter dimension of the shaft seal 1. In FIG. 2, the inner diameter dimension d indicates the distance between the opposing tip portions 2a of the seal lip portions 2. On the other hand, the maximum inner diameter dimension d _max of the shaft seal 1 is the maximum distance between the opposing base ends 4, and in FIG. 2, the distance between the inner edges of the back surface 4a. In addition, in FIG. 2, the inner circumferential surface of the shaft seal 1 is formed so as to continuously decrease in diameter from the back surface 4a to the tip end 2a, and the outer circumferential surface of the shaft seal 1 is formed to continuously decrease in diameter from the back surface 4a to the tip end 3a. It is formed to expand in diameter.

The seal lip portion 2 has a predetermined lip length _L2 on its outer peripheral surface. As shown in FIG. ₂ , the lip length L2 is the length of a straight line from the corner of the bottom surface 4b of the shaft seal 1 (seal lip portion 2 side) to the apex on the outer diameter side of the tip portion 2a of the seal lip portion 2. It is. Further, in FIG. 2, the back surface 4a and the bottom surface 4b are formed of flat surfaces that are substantially parallel to a surface perpendicular to the axis of the shaft seal 1. This facilitates close contact with the bottom wall 8b of the annular groove 8 (see FIG. 1). Note that the lip length _L2 is the same length in the free state of the shaft seal in FIG. 2 and in the mounted state in FIG. 1.

Further, the outer lip portion 3 has a predetermined lip length _L3 on its inner peripheral surface. As shown in FIG. 2, the lip length _L3 is the length of a straight line from the corner of the bottom surface 4b of the shaft seal 1 (outer lip part 3 side) to the apex of the tip part 3a of the outer lip part 3 on the inner diameter side. It is. Note that the lip length L ₃ of the outer lip portion 3 is preferably longer than the lip length L ₂ of the seal lip portion 2 .

The thickness t ₂ of the seal lip portion 2 is preferably 0.3 mm to 1 mm. Further, when the thickness t ₂ changes from the proximal end side to the distal end side, it is preferable to change it within a range of 0.3 mm to 1 mm. If the thickness _t2 is less than 0.3 mm, short shots are likely to occur during injection molding. Moreover, if the thickness _t2 exceeds 1 mm, the tension force of the seal lip portion 2 against the rotating shaft becomes high, and there is a possibility that the rotational torque becomes large. The thickness t ₂ is more preferably 0.3 mm to 0.6 mm. Furthermore, from another point of view, as shown in FIG. 2, it is preferable that the thickness _t2 of the seal lip portion 2 is smaller than the thickness t3 of the outer lip portion ₃ . When the thickness t ₂ is larger than the thickness t ₃ , the tension force of the outer lip portion 3 on the housing 7 is smaller than the tension force of the seal lip portion 2 on the rotating shaft 6 , and the side wall of the outer lip portion 3 and the housing 7 is There is a possibility that sliding may occur between the holder and the holder 8a.

Returning to FIG. 1, the seal lip portion 2 of the shaft seal 1 is in close contact with the outer circumferential surface of the rotating shaft 6, thereby preventing fluid on the high pressure side H from leaking to the low pressure side L. Examples of the fluid include a refrigerant, oil, a mixture of refrigerant and oil, and the like. In order to ensure the sealing performance of the shaft seal, it is necessary to make the inner diameter dimension d (see FIG. 2) of the shaft seal 1 before installation smaller than the outer diameter dimension D of the rotating shaft 6. That is, when the shaft seal 1 is assembled into the rotating shaft 6, the shaft seal 1 needs to have an interference margin.

The relationship between the inner diameter dimension d of the shaft seal 1 before the rotation shaft 6 is assembled, the outer diameter dimension D of the rotation shaft 6, and the interference margin (Dd) of the rotation shaft 6 is (Dd)/D=0. 005 to 0.06, more preferably (Dd)/D=0.01 to 0.02. By setting the dimensional ratio between the outer diameter dimension D of the rotating shaft 6 and the interference (D-d) at the tip of the seal lip that contacts the rotating shaft 6 within a predetermined range, sealing performance can be maintained without impairing sealing performance. , rotational torque can be further reduced.

Furthermore, in order to reduce rotational torque, it is preferable that a space be formed between the seal lip portion 2 and the rotating shaft 6, as shown in FIG. In this case, the base end portion 4 is not in contact with the rotating shaft 6 in the attached state. Furthermore, in terms of dimensions, it is preferable that D<d _max (see FIG. 2).

The outer diameter dimension D of the rotating shaft 6 is not particularly limited, but is, for example, about 10 mm to 50 mm. Furthermore, the size of the tightening margin (Dd) is not particularly limited, but is, for example, about 0.1 mm to 3 mm.

Note that the shaft seal of the present invention is not limited to the form shown in FIG. For example, although the seal lip portion 2 is formed in a straight line in FIG. 1, the seal lip portion may be formed in a curved shape as shown in FIG. In the case of FIG. 3, the inclination angle α is the angle between the tangent to the seal lip portion 2 (indicated by a broken line) at the contact point between the seal lip portion 2 and the rotary shaft 6 and the outer circumferential surface of the rotary shaft 6. The lip length _L2 of the seal lip portion 2 is the length of the straight line explained in FIG. Further, the shaft seal may be provided with a lip portion other than the seal lip portion and the outer lip portion (for example, a dust lip that slides on the rotating shaft).

In the compressor shown in FIG. 1, a compression mechanism section is provided on the high-pressure side H of the housing 7. The compression mechanism may be of any type as long as the fluid is compressed by rotation of a rotating shaft, and a scroll type, swash plate type, or the like can be adopted. For example, in the case of a scroll type, the compression mechanism is configured by combining a fixed scroll and a movable scroll that rotates relative to the fixed scroll.

FIG. 4 shows a partial cross-sectional view of the scroll-type compression mechanism. As shown in FIG. 4, the compression mechanism section 9 includes a fixed rotor 11 having a base plate 11a and a fixed scroll blade 11b standing upright on the surface thereof, and a movable rotor having a base plate 12a and a movable scroll blade 12b standing upright on the surface of the base plate 11a. 12. A fixed rotor 11 and a movable rotor 12 are eccentrically engaged with each other, and a compression chamber 10 is formed between them. The movable rotor 12 is directly or indirectly connected to the above-mentioned rotating shaft, and as the movable rotor 12 revolves around the axis of the fixed rotor 11, the compression chamber 10 moves toward the center of the spiral shape. The fluid is compressed. The compressed fluid is discharged from the discharge pipe through the discharge port 13 in the center of the movable rotor 12, and flows out into the refrigeration cycle. Then, the fluid of the refrigeration cycle (such as refrigerant gas) is introduced into the compression chamber 10 via the suction port (not shown).

The shaft seal of the present invention is an injection molded product and is made of a resin composition or a thermoplastic elastomer composition. The injection molded article preferably has a flexural modulus of 200 MPa to 2400 MPa as measured in accordance with ASTM D790. If the bending elastic modulus is less than 200 MPa, there is a risk that it will be easily worn and the sealing performance will deteriorate. Furthermore, when the bending elastic modulus exceeds 2400 MPa, the tension force of the shaft seal against the rotating shaft becomes high, which may result in high torque. The flexural modulus of the resin composition forming the shaft seal of the present invention, measured in accordance with ASTM D790, is preferably 200 MPa to 1800 MPa, more preferably 400 MPa to 1800 MPa.

In the resin composition, the main component resin (base resin) is not limited, and includes polyamide (PA) resin, polyphenylene sulfide (PPS) resin, polyetheretherketone (PEEK) resin, and polyamideimide (PAI) resin. , polytetrafluoroethylene (PTFE) resin, tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA) resin, tetrafluoroethylene-hexafluoropropylene copolymer (FEP) resin, ethylene-tetrafluoroethylene copolymer ( ETFE) resin, vinylidene fluoride resin, liquid crystal polymer, polyethersulfone resin, polysulfone resin, polyphenylsulfone resin, polyarylate resin, polyetherimide resin, polyimide resin, polyester resin, etc. can be used.

Among the above resins, it is preferable to use PA resin, PFA resin, FEP resin, ETFE resin, and vinylidene fluoride resin, which have excellent heat resistance, chemical resistance, and flexibility, and are injection moldable. Since these resins have excellent chemical resistance and oil resistance, they are suitable, for example, for shaft seals of rotating shafts of compressors used in the presence of fluids containing refrigerants and refrigerator oil.

In the thermoplastic elastomer composition, the elastomer that is the main component is not limited, and polyolefin elastomers, polyester elastomers, polyamide elastomers, and the like can be used. From the viewpoint of heat resistance and chemical resistance, polyester elastomers are particularly preferred. The polyester elastomer includes a hard segment and a soft segment, and the hard segment uses a polyester unit, and the soft segment uses a polyether unit or a polyester unit. The polyester elastomer is a polyester-polyether type or polyester-polyester type multi-block copolymer.

A solid lubricant such as PTFE resin, graphite, molybdenum disulfide, etc. can be blended into the above resin composition and thermoplastic elastomer composition for the purpose of improving friction and wear characteristics.

PTFE resin is a solid lubricant and can reduce the coefficient of dynamic friction of a molded article of a resin composition or a thermoplastic elastomer composition. As the PTFE resin, any of molding powder produced by suspension polymerization, fine powder produced by emulsion polymerization, and recycled PTFE may be employed. In order to stabilize the fluidity of the resin composition, it is preferable to use recycled PTFE, which is difficult to form fibers due to shearing during injection molding and is difficult to increase melt viscosity. Recycled PTFE refers to heat-treated (heat history-added) powder, powder that has been irradiated with γ-rays, electron beams, or the like. For example, molding powder or fine powder that has been heat treated, powder that has been further irradiated with gamma rays or electron beams, powder that has been ground into molded molding powder or fine powder, and powder that has been subsequently irradiated with gamma rays or electron beams. There are types such as irradiated powder, molding powder, or fine powder irradiated with gamma rays or electron beams.

Commercially available PTFE resins that can be used in the present invention include Kitamura Co., Ltd.: KTL-610, KTL-450, KTL-350, KTL-8N, KT-400H, Mitsui Chemours Fluoro Products Co., Ltd.: Teflon (registered) Trademark) 7-J, TLP-10, manufactured by AGC Corporation: Fluon G163, L150J, L169J, L170J, L172J, L173J, manufactured by Daikin Industries, Ltd.: Polyflon M-15, LeBron L-5, manufactured by 3M Japan Corporation: Examples include Dyneon TF9205 and TF9207. It may also be a PTFE resin modified with a perfluoroalkyl ether group, a fluoroalkyl group, or another side chain group having fluoroalkyl. Among the above, PTFE resins irradiated with gamma rays or electron beams are manufactured by Kitamura Co., Ltd.: KTL-610, KTL-450, KTL-350, KTL-8N, and manufactured by AGC Corporation: Fluon L169J, L170J, L172J. , L173J, etc.

Graphite is a solid lubricant and can reduce the coefficient of dynamic friction of a molded article of a resin composition or a thermoplastic elastomer composition. As the graphite, either natural graphite or artificial graphite may be used. Examples of natural graphite include ACP manufactured by Nippon Graphite Industries Co., Ltd.; examples of artificial graphite include KS-6, KS-25, and KS-44 manufactured by Imerys GC Japan Co., Ltd.

The blending amount of the solid lubricant is preferably 1% to 40% by volume, more preferably 1% to 20% by volume, and more preferably 10% to 20% by volume based on 100% by volume of the resin composition or thermoplastic elastomer composition. Volume % is more preferred. If it exceeds 40% by volume, the elongation properties of the resin composition or thermoplastic elastomer composition may deteriorate, and cracks may occur when the shaft seal is assembled into the rotating shaft.

In addition, to the extent that the effects of the present invention are not impaired, the resin composition or the thermoplastic elastomer composition may be added with fibrous reinforcing materials such as carbon fiber, glass fiber, or aramid fiber, spherical fillers such as spherical silica, or scale-like materials such as mica. Reinforcements, sliding reinforcements such as calcium phosphate and calcium sulfate, and microfiber reinforcements such as potassium titanate whiskers may also be used. Colorants such as carbon black and iron oxide can also be added. These can be blended alone or in combination.

The shaft seal of the present invention can be used in a scroll compressor for an on-vehicle air conditioner. The scroll compressor may be belt-driven using engine power or motor-driven without using engine power. Further, the shaft seal of the present invention can be used not only for compressors.

The shaft seal of the present invention is molded by injection molding using a general injection molding machine for thermoplastic resin. The materials constituting the resin composition or the thermoplastic elastomer composition are mixed, if necessary, using a Henschel mixer, a ball mixer, a ribbon blender, etc., and then mixed using a melt extruder such as a twin-screw kneading extruder. By melt-kneading, pellets for molding can be obtained. Note that the filler may be introduced by side feeding when melt-kneading with a twin-screw extruder or the like. Using this molding pellet, a shaft seal is molded by injection molding.

Examples 1 to 7, Comparative Examples 1 to 4
A resin composition containing 20% by volume of PTFE resin (50% particle size: 20 μm) as a solid lubricant, with the remainder being polyamide 66 resin (viscosity: 150ml/g) was prepared using a twin-screw kneading extruder and pelletized. It became. The viscosity number was measured using a sulfuric acid solution in accordance with ISO 307. A shaft seal was obtained by injection molding using the obtained pellets. The shaft seals were shaped as shown in FIG. 1, and as shown in Table 1, 11 types of shaft seals (inner diameter d: 19.88 mm) with different inclination angle α and lip length _L2 of the seal lip portion were fabricated. The bending elastic modulus of the resin composition forming these shaft seals was 2200 MPa as measured in accordance with ASTM D790.

<Rotational torque test>
A rotational torque test was conducted under the following conditions using the rotational torque testing machine shown in FIG. 5, and the rotational torque and oil leak amount were measured. The outer diameter dimension D of the rotating shaft was 20 mm, and the interference (Dd) between the shaft seal and the rotating shaft was 0.12 mm in diameter, and (Dd)/D=0.006.
<Test conditions>
Rotating shaft: Material S45C
Rotation speed: 7500min ^-1
Hydraulic pressure: 0.3MPa
Oil temperature: 40℃
Refrigerating machine oil: Polyalkylene glycol oil Test time: 60 minutes

As shown in FIG. 5, the housing of the testing machine 14 is constructed by assembling an outer housing 17 and an inner housing 18. At the mating surfaces of these housings, an O-ring 19 is placed in the outer circumferential groove of the inner housing 18 to prevent refrigerating machine oil from leaking from the mating surfaces. The shaft seal 15 is in close contact with the rotating shaft 16 and comes into sliding contact with the outer peripheral surface of the rotating shaft 16 as the rotating shaft 16 rotates. Refrigerating machine oil was pumped and supplied to the space inside the housing. As shown in FIG. 5, the refrigerating machine oil flows in through the inflow path 17b, passes through the housing interior space, and flows out through the outflow path 17c. The oil leak amount is based on the amount of refrigerating machine oil leaking from between the rotating shaft 16 and the insertion hole 17a, and represents the average value for 50 to 60 minutes after the start of the test. Furthermore, the rotational torque indicates the average value for 50 to 60 minutes after the start of the test. The results are shown in Table 1.

As shown in Table 1, when comparing the results for the inclination angle α=20°, when the lip length L ₂ =2.2 mm to 6.5 mm (Examples 1 to 5), the rotational torque is 0.07 to While the torque was low at 0.11 N・m, in the case of lip length L ₂ = 1.2 mm (Comparative Example 1), the rotational torque was 0.16 N・m, which was a relatively high torque. became. In examining the inclination angle α, a significant increase in the amount of oil leakage was observed when α=3° (Comparative Example 3). In addition, when α=30° and 45° (Comparative Example 2 and Comparative Example 4), the rotational torque is 0.15N・m and 0.17N・m, and as the inclination angle α increases, the rotational torque increases. It was done. On the other hand, when α=5° and 10° (Examples 6 to 7), low torque and low leakage were exhibited.

Next, the composition of the resin composition was changed and the rotational torque and sealing performance were evaluated.

Examples 8-14
The raw materials for the resin compositions used in each example are listed below.
(1) ETFE Resin AGC Co., Ltd.: Fluon C-88AXMP
(2) PFA resin Daikin Industries, Ltd.: Neoflon AP202
(3) Polyphenylene sulfide (PPS) resin DIC Corporation: FZ-2100
(4) Carbon fiber (average fiber length: 150 μm)
(5) Graphite (50% particle size: 20 μm)
(6) PTFE resin (50% particle size: 20 μm)

Using raw materials (1) to (6), resin compositions shown in Examples 8 to 14 in Table 2 were produced using a twin-screw kneading extruder and pelletized. A shaft seal having a cross-sectional shape shown in FIG. 1 and a molded body for bending tests were obtained by injection molding using the obtained pellets.

<Bending test>
A bending test was conducted in accordance with ASTM D790, and the bending modulus was measured.

<Rotational torque test>
A rotational torque test was conducted under the above test conditions using the rotational torque testing machine shown in FIG. 5, and the rotational torque and oil leak amount were measured. In Examples 8 to 13, the dimensions of the rotating shaft and shaft seal of the rotating torque testing machine are as follows: outer diameter of the rotating shaft D = 20.5 mm, inner diameter of the shaft seal d = 20 mm, and interference (D-d). = 0.5 mm, (Dd)/D = 0.024. Further, in Example 14, the outer diameter dimension D of the rotating shaft is 20 mm, the inner diameter dimension d of the shaft seal is 19.9 mm, the tightening margin (D-d) is 0.1 mm, and (D-d)/D is 0. It was set as 005.

As shown in Table 2, the shaft seals of Examples 8 to 14 had flexural modulus in the range of 200 MPa to 2400 MPa, and exhibited low torque and low oil leakage. From the results in Table 2, a rough correlation was seen between the magnitude of the bending elastic modulus and the magnitude of the rotational torque. Furthermore, in examining the size ratio (Dd)/D, it was found that as (Dd)/D became smaller, the torque decreased (Example 9, Example 14).

As described above, in the present invention, low torque and low leakage are achieved by optimizing the inclination angle and lip length of the seal lip with respect to the outer circumferential surface of the rotating shaft. Further, by combining the above structure with a preferable composition of the resin composition, it is possible to further reduce torque and leakage.

Since the shaft seal of the present invention can reduce rotational torque and has excellent sealing properties, it can be widely used as a shaft seal that seals sealing fluid while slidingly contacting the outer peripheral surface of a rotating shaft. In particular, it is suitable as a shaft seal for a rotating shaft that rotates the compression mechanism of a scroll-type refrigerant compressor for an on-vehicle air conditioner.

1, 1' Shaft seal 2 Seal lip portion 3 Outer lip portion 4 Base end portion 5 Concave groove 6 Rotating shaft 7 Housing 8 Annular groove 9 Compression mechanism portion 10 Compression chamber 11 Fixed rotor 12 Movable rotor 13 Discharge port 14 Testing machine 15 Shaft Seal 16 Rotating shaft 17 Outer housing 18 Inner housing 19 O-ring

Claims (7)

An annular shaft seal that seals the sealing fluid by closely contacting the outer peripheral surface of the rotating shaft,
A gap between the rotating shaft and a housing in which the shaft seal is mounted is divided into a high pressure side and a low pressure side by the shaft seal,
The shaft seal is an injection molded body having a substantially U-shaped cross-sectional view in the axial direction, and includes a seal lip portion that extends toward the high-pressure side and slides on the rotating shaft, and a seal lip portion that extends toward the high-pressure side and slides on the rotating shaft, and a seal lip portion that extends toward the high-pressure side and slides on the rotating shaft. and an outer lip provided in the
The inclination angle of the seal lip portion with respect to the outer peripheral surface of the rotating shaft is 5° to 20°,
In an axial cross-sectional view of the shaft seal, the seal lip portion has a length of 2.0 mm to 6.5 mm,
A shaft seal characterized in that the injection molded product has a bending elastic modulus of 200 MPa to 2400 MPa as measured in accordance with ASTM D790 . The shaft seal according to claim 1, wherein the shaft seal is made of a resin composition or a thermoplastic elastomer composition. The shaft seal is used in a scroll compressor equipped with a compression mechanism that combines a fixed scroll and a movable scroll that orbits with respect to the fixed scroll, and the rotating shaft is a rotating shaft that drives the compression mechanism. The shaft seal according to claim 1 or claim 2, characterized in that: The shaft seal according to claim 3, wherein the scroll compressor is a scroll compressor for an on-vehicle air conditioner. The shaft seal according to any one of claims 1 to 4, wherein the sealing fluid contains oil. The relationship between the inner diameter dimension d of the shaft seal before incorporating the rotating shaft, the outer diameter dimension D of the rotating shaft, and the interference (Dd) of the rotating shaft is (Dd)/ The shaft seal according to claim 1, wherein D=0.005 to 0.06. The shaft seal according to claim 1, wherein the seal lip portion has a thickness of 0.3 mm to 1 mm.

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